EP4069959A1 - Hydraulic control system for a variable compression ratio engine - Google Patents

Hydraulic control system for a variable compression ratio engine

Info

Publication number
EP4069959A1
EP4069959A1 EP20841973.9A EP20841973A EP4069959A1 EP 4069959 A1 EP4069959 A1 EP 4069959A1 EP 20841973 A EP20841973 A EP 20841973A EP 4069959 A1 EP4069959 A1 EP 4069959A1
Authority
EP
European Patent Office
Prior art keywords
hydraulic
hydraulic control
engine
chambers
control system
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP20841973.9A
Other languages
German (de)
French (fr)
Inventor
René Pierre BERTHEAU
Sylvain Bigot
Xavier CHEMIN
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
MCE5 Development SA
Original Assignee
MCE5 Development SA
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by MCE5 Development SA filed Critical MCE5 Development SA
Publication of EP4069959A1 publication Critical patent/EP4069959A1/en
Withdrawn legal-status Critical Current

Links

Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D15/00—Varying compression ratio
    • F02D15/02—Varying compression ratio by alteration or displacement of piston stroke
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02B—INTERNAL-COMBUSTION PISTON ENGINES; COMBUSTION ENGINES IN GENERAL
    • F02B75/00—Other engines
    • F02B75/04—Engines with variable distances between pistons at top dead-centre positions and cylinder heads
    • F02B75/045—Engines with variable distances between pistons at top dead-centre positions and cylinder heads by means of a variable connecting rod length
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02B—INTERNAL-COMBUSTION PISTON ENGINES; COMBUSTION ENGINES IN GENERAL
    • F02B75/00—Other engines
    • F02B75/04—Engines with variable distances between pistons at top dead-centre positions and cylinder heads
    • F02B75/048—Engines with variable distances between pistons at top dead-centre positions and cylinder heads by means of a variable crank stroke length

Definitions

  • the present invention relates to the field of variable compression ratio engines. It relates in particular to a hydraulic system for controlling said rate, supplied by the engine lubrication circuit, which system is provided with an independent means of pressurizing the oil ensuring an average hydraulic pressure in the hydraulic control circuit constantly greater than engine lubrication pressure during engine operation.
  • Variable compression ratio engines are known in which the said rate control system, operating individually for each combustion cylinder, is based on a hydraulic cylinder.
  • the continuous rate VCRi engine developed by the applicant, and the so-called two-rate connecting rod systems developed in particular by the FEV or AVL companies.
  • VCRi engine operates at pressures of up to 300 bars, while two-rate connecting rod systems can operate at pressures of up to more than 2000 bars.
  • Oil is a compressible fluid, especially since it is loaded with gas (engine oil is conventionally aerated between 5% and 30% depending on the operating conditions).
  • This elasticity measured by the isostatic modulus of elasticity (otherwise called bulk modulus), results in a modification of the position of the control cylinder as a function of the force applied, which causes oscillations in the system, leading to an amplification of the forces by dynamic effect, and adversely affects the precision desired for the control of the compression ratio.
  • the company FEV (“2-step variable compression ratio System development & industrialization”, 2 nd International FEV ConfInter, Feb 7-8, 2019) proposes to use a special distributor to ensure the pressure increase in the hydraulic chamber of the control system, by pumping effect.
  • a rate change which will result in the opening of the distributor, will drop the pressure in the control system to the supply pressure (lubrication circuit): this implies that the module of The isostatic elasticity of the oil will not be optimal at least for a few cycles, which may lead to temporary overloads of the kinematics (amplification phenomena due to shocks).
  • Document JP2003 / 322036 proposes a mechanism for a variable compression ratio engine comprising electrical means for controlling the control shaft in rotation and a hydraulic holding means making it possible to reduce the forces applied to the control means and avoiding to supply them continuously with energy.
  • Document FR2914951 proposes an electro-hydraulic device for controlling a closed loop of a control cylinder for an engine with a variable compression ratio.
  • the present invention provides an alternative solution to those of the state of the art, remedying all or part of the aforementioned drawbacks. It relates in particular to a hydraulic control system comprising a control cylinder and a hydraulic control circuit, and the architecture of which makes it possible to increase the average pressure in the hydraulic chambers of the control cylinder to values greater than the lubrication pressure. , and typically greater than 20 bars, and to maintain said average pressure during changes in the compression ratio of the engine.
  • the invention relates to a hydraulic control system for a variable compression ratio engine comprising:
  • control cylinder comprising a piston and a body in which two hydraulic chambers of equivalent sections are defined on either side of the piston, said piston being able to move in the body to control the compression ratio of the engine
  • a hydraulic control circuit comprising at least one conduit connecting the two hydraulic chambers to one another, and a controlled fluidic distribution device to establish or block fluidic communication between said chambers,
  • the hydraulic control system is remarkable in that:
  • the hydraulic control circuit comprises:
  • the control cylinder comprises a return device tending to bring said cylinder to a length corresponding to a maximum compression ratio of the engine.
  • the hydraulic control system makes it possible to supply the hydraulic control circuit by means of a low pressure oil supply, typically connected to the engine lubrication circuit (low pressure, between 2 and 6 bars for example. ), thanks to the conduit connecting at least one of the hydraulic chambers and a low pressure oil supply. It also makes it possible to increase the average pressure in the hydraulic chambers of the control cylinder to values greater than the lubrication pressure, and typically greater than 20 bars, due to the presence of the first non-return valve which allows the rewashing of the hydraulic circuit when the combustion and / or inertia forces applied to the jack sequentially cause pressure drops in the chamber connected to the supply.
  • the hydraulic control system makes it possible to maintain this average pressure, typically greater than 20 bars, in the hydraulic chambers, during the rate change operation.
  • the presence of the first regwashing non-return valve prevents the hydraulic control circuit from dropping down to low supply pressure, by isolating it from said supply whatever the operating conditions of the engine.
  • the rate change linked to the displacement of the piston in the body of the control cylinder, is defined by the controlled fluid distribution device which manages the circulation and transfer of oil from one chamber to the other, and thus the piston position. The accuracy of the rate setting is thus improved because the hydraulic control system operates in pressure ranges above the stabilization pressure of the bulk module.
  • the hydraulic control system according to the invention makes it possible to regulate the average pressure in the hydraulic chambers and it allows the effective attainment of the variable compression ratios between minimum rate and maximum rate, as well as an effective rate change, that is to say with a good dynamic, between minimum rate and maximum rate, or vice versa.
  • the pipe fitted with the relief valve connects the oil discharge and the chamber, among the two hydraulic chambers, which is not subjected to combustion forces from the engine,
  • the return device is placed in the chamber, among the two hydraulic chambers, which undergoes combustion forces from the engine,
  • the hydraulic control circuit is carried by the body of the control cylinder;
  • the controlled fluid distribution device is actuated by an electrical control circuit
  • the controlled fluid distribution device is actuated by a hydraulic control circuit
  • the fluidic distribution device comprises a two-position controlled shutter, one position of which blocks the fluidic communication between the two chambers and the other position allows fluidic communication between the two chambers, in both directions of circulation;
  • the hydraulic control circuit comprises at least two conduits connecting the two hydraulic chambers to each other, and in which the fluid distribution device comprises two controlled two-position shutters and two oriented valves, a first shutter and a first oriented valve being carried by a first duct, to block or allow the circulation of oil from the first chamber to the second chamber, and a second shutter and a second oriented valve being carried by a second duct, to block or allow the circulation of oil from the second bedroom to the first bedroom;
  • Each controlled shutter is arranged along a transverse axis, normal to a longitudinal axis of displacement of the piston in the body of the control cylinder;
  • the piston of the control cylinder is intended to be connected to a return member of a movable coupling of the engine, and the body of the control cylinder is intended to be connected to a fixed part of the engine.
  • Figure 1 shows a curve relating the isostatic modulus of elasticity of oils to pressure
  • Figure 2 shows a block diagram of a hydraulic control system according to a first embodiment, according to the invention
  • Figures 3a and 3b respectively show a block diagram of a hydraulic control system according to a second embodiment, according to the invention, and various options for the rest position of the fluid distribution device in a hydraulic control system according to the second embodiment;
  • Figures 4a and 4b show curves illustrating the operation of a control system according to the state of the art, with pressure drop at each rate change and respectively without and with oil backwashing of the hydraulic control system;
  • Figures 6a, 6b, 6c, 6d, 6e show a particular example of implementation of the hydraulic control system, according to the second embodiment of the invention.
  • FIG. 7 shows a mobile coupling and a system for controlling the variable compression ratio in an engine according to the state of the art
  • Figure 8 shows a side view of a mobile coupling and a hydraulic control system of a variable compression ratio engine, said system being in accordance with the invention.
  • the present invention relates to a hydraulic control system 3 for a variable compression ratio engine, two embodiments of which are illustrated respectively in FIG. 2 and in FIG. 3a.
  • the control system 3 comprises a control cylinder 30 comprising a piston 30a and a body 30b in which two hydraulic chambers 31, 32 of equivalent sections are defined on either side of the piston 30a.
  • a control cylinder 30 comprising a piston 30a and a body 30b in which two hydraulic chambers 31, 32 of equivalent sections are defined on either side of the piston 30a.
  • Figures 2 and 3a are schematic and do not illustrate the equivalent nature of the sections of the two chambers 31, 32.
  • Said piston 30a is able to move in the body 30b, which modifies the length of the cylinder and defines (or in other words, controls) the compression ratio of the engine.
  • control system 3 could be integrated into a connecting rod of variable length, directly connected to the combustion piston and to the crankshaft of an engine with variable combustion rate. It can also be integrated into a VCRi type control jack. Finally, as will be described in more detail in one example below, such a control system 3 can be integrated into a VC-T type engine (for “variable compression - turbo”) described in document EP2787196.
  • the hydraulic control system 3 also comprises a hydraulic control circuit 37 whose role is in particular to supply the hydraulic chambers 31, 32 of the control cylinder 30 with oil and to manage the transfer of oil from one chamber to 1 '. other.
  • the hydraulic control circuit 37 comprises at least one conduit 37a, 37b, 37c connecting the two hydraulic chambers 31, 32 to one another. Subsequently, this or these conduits 37a, 37b, 37c will be called transfer conduits 37a, 37b, 37c because they allow the circulation of oil from one chamber 31, 32 to the other.
  • the hydraulic control circuit 37 also comprises a fluidic distribution device 371a, 372 disposed on said (at least one) transfer duct 37a, 37b, 37c, between the two hydraulic chambers 31, 32.
  • the fluidic distribution device 371a, 372 is controlled to establish or block a fluidic communication between said chambers 31, 32; in other words, said device 371a, 372 is controlled to open or close the duct (s) 37a, 37b, 37c connecting the two chambers 31, 32.
  • the transfer conduits 37a, 37b, 37c and the fluid distribution device 371a, 372 make it possible to manage the transfer of oil from one hydraulic chamber 31, 32 to the other, and thus to modify the length of the control cylinder 30. , corresponding to a modification of the engine compression ratio.
  • the hydraulic control circuit 37 also comprises at least one conduit 37d connecting at least one of the hydraulic chambers 31, 32 to a supply of oil 60 at low pressure.
  • a first non-return valve 373 is arranged on said conduit 37d: it only allows the passage of oil from the oil supply 60 to the hydraulic chamber 31, 32, when the pressure in said hydraulic chamber drops below the oil supply pressure. In practice, the oil pressure from the supply 60 is between 2 and 6 bars. Because pipe 37d and the first non-return valve 373 allow the hydraulic circuit to be rewashed with oil 37, they may be called respectively subsequently, rewashing duct 37d and rewashing valve 373.
  • the regwashing duct 37d and the regwashing valve 373 are arranged between the oil supply 60 and that of the two hydraulic chambers 32 which is not subjected to the combustion forces of the engine.
  • the forces generated by the combustion being greater than those generated by the inertias, the hydraulic chamber 32 will see the greatest depression and the lowest instantaneous pressure, thus improving the regavage.
  • the hydraulic control circuit 37 makes it possible to increase the average pressure in the hydraulic chambers 31, 32 of the control cylinder 30 to values greater than the lubrication pressure (low pressure), and typically greater than 20 bars, or even greater than 30. bars. This is made possible by the presence of the rewash valve 373 which allows the introduction of oil into the hydraulic control circuit 37, when the combustion and / or inertia forces applied to the cylinder 30 sequentially cause drops of pressure in the chamber connected to the supply.
  • the hydraulic control circuit 37 makes it possible to maintain this average pressure, typically greater than 20 bars, in the hydraulic chambers 31, 32, during the rate change operation.
  • the regavage valve 373 prevents the hydraulic control circuit 37 from falling back to the low supply pressure, by isolating it from said supply, whatever the operating conditions of the engine.
  • the rate change, linked to the movement of the piston 30a in the control cylinder 30, is defined by the piloted fluid distribution device 371a, 372 which manages the circulation and transfer of oil from a chamber towards the other, and thus the position of the piston 30a in the body 30b of the control cylinder 30.
  • FIG. 4a illustrates the operation of a hydraulic control system close to the state of the art, that is to say undergoing a loss of power. pressure during compression ratio changes; in FIG. 4a, the system does not have an oil regeneration function, while in FIG. 4b, the system is provided with it.
  • FIG. 5 illustrates the operation of a hydraulic control system according to the present invention, not undergoing a loss of pressure during changes in compression ratio and comprising a function of rewashing the hydraulic chambers 31, 32 with oil.
  • the engine In both cases, the engine is operating under conditions of 1000 revolutions per minute and having a maximum pressure in the combustion cylinder of 32 bars.
  • the average pressure in the hydraulic chambers is calculated over an engine cycle (0.12 s).
  • the rate setpoint is defined as follows: +1 requests an increase in the compression ratio, 0 requests a fixed rate, -1 requests a decrease in the compression ratio.
  • the average pressure in the hydraulic chambers always remains below 10 bars.
  • the actual compression ratio obtained oscillates very strongly, typically by more than two points, which makes servo-control impossible.
  • the average pressure in the hydraulic chambers can reach values greater than 20 bars in a certain control phase but drop with each change in compression ratio.
  • the actual compression ratio obtained oscillates strongly, and takes time to stabilize, which makes the control difficult.
  • the average pressure in the hydraulic chambers 31, 32 increases during the first engine cycles and remains greater than 20 bars, or even greater than 30 bars, during the compression ratio change operations.
  • the compression rate obtained is much more stable (no or few oscillations) and precise.
  • the hydraulic control system 3 according to the invention therefore shows very good performance, even on a very lightly loaded operating point (low engine speed, idling).
  • the hydraulic control circuit 37 further comprises at least one conduit 37e connecting at least one of the hydraulic chambers 31, 32 to an oil outlet 70.
  • a second non-return valve 374 is disposed on said conduit 37e and allows the drain to be drained. hydraulic control circuit 37 when the pressure in said hydraulic chamber 31, 32 exceeds a determined maximum pressure due to the combustion forces and / or inertia of the engine applying to the cylinder (30).
  • the 37th duct and the second non-return valve 374 may respectively be named subsequently, 37th drain duct and 374 drain valve. They make it possible to prevent the average pressure in the hydraulic chambers 31, 32 from being too high and that 'it imposes complex sealing solutions in the control cylinder 30.
  • the hydraulic control system 3 could nevertheless operate with a hydraulic control circuit 37 devoid of drain pipe 37e and drain valve 374: the particularity of having hydraulic chambers 31,32 of equivalent sections allows the piloting and the 'servo-control of the system 3, regardless of the average pressure in the chambers 31,32.
  • This average pressure would increase to a stabilization level corresponding to the stopping of the regavage function (i.e. when the instantaneous pressure in the hydraulic chamber (s) 31.32 connected to the oil supply 60 via the pipe 37d and the rewash valve 373 no longer goes below the supply pressure).
  • the stabilized average pressure could be high, typically greater than 500 bars and would require a seal adapted to the maximum instantaneous pressure levels attainable in the hydraulic chambers 31, 32.
  • the hydraulic control circuit 37 is carried by the body 30b of the control cylinder 30.
  • the conduits 37a, 37b, 37c, 37d, 37e are formed by drilling in said body 30b; the fluid distribution device 371a, 372 and the first and second non-return valves 373,374 are integrated in the body 30b.
  • the oil supply 60 is external to the control cylinder 30, it is typically connected to the engine lubrication circuit.
  • the control cylinder 30 comprises a return device 34, tending to bring said cylinder 30 to a length corresponding to the maximum compression ratio. Note that depending on the location of the control cylinder 30 in the engine, the maximum compression ratio may correspond to its minimum or maximum length.
  • the control jack 30 At low speed, the combustion forces exerted on the control cylinder 30 (tending to bring the system to minimum rate) are greater than the inertia forces (tending to bring the system to maximum rate). Because of the equivalent sections, the control jack 30 therefore has an easier time going to its position corresponding to minimum rate than to its position corresponding to maximum rate, because there is potentially more effort to do so.
  • the return device 34 makes it possible to exert an additional effort (in addition to the inertia forces) to increase the speed of change of length of the jack 30 towards the maximum rate and thus not to penalize fuel consumption and pollution emissions. . As illustrated in the examples of Figures 2 and 3a, the return device 34 is arranged in the hydraulic chamber 31 which is subjected to the combustion forces of the engine.
  • the hydraulic control system 3 therefore allows the effective attainment of the variable compression ratios between the minimum rate and the maximum rate, as well as an effective rate change, that is to say. say with a good dynamic, between minimum rate and maximum rate, and vice versa.
  • the return device 34 (for example a spring) is typically sized to return the control cylinder 30 from the position (length) corresponding to a minimum compression ratio to the position corresponding to a maximum compression ratio, in less than 2 seconds. , under engine speed conditions of about 1000 revolutions per minute. This dimensioning takes into account the pre-load and the stiffness of the return device 34, in line with the calibration of the pressure drop of (or des) transfer conduits 37a, 37b, 37c connecting the two hydraulic chambers 31, 32 together. Of course, the return device 34 must also allow the rate change to the minimum compression ratio, by the combustion forces, with an acceptable dynamic, typically in less than 0.5 to 0.8 seconds, under conditions. engine speed to approximately 1000 revolutions per minute (rpm).
  • a hydraulic control system 3 designed for an engine with variable compression ratio (100), of the type illustrated in FIG. 8, and the kinematics of which leads to a maximum force at l end of the control cylinder 30 of 31kN at 1500rpm for a pressure in the combustion cylinder of 120bar, and 10kN for a combustion pressure of 55bar. At 5500rpm, these forces become 40kN for a combustion pressure of 120bar, and 15kN for a combustion pressure of 55bar.
  • the diameter of the piston 30a is chosen at 47mm to limit the pressure in the control cylinder 30 to the maximum force.
  • the spring 34 has a preload of 200N, and a stiffness of 50N / mm.
  • a calibrated orifice of 2mm between the two hydraulic chambers 31, 32, located on the transfer duct 37c allows, in this configuration, a speed of variation from the maximum rate to the minimum rate of 0.35s at 1500rpm, and of 0.17s at 5500rpm.
  • a calibrated 1mm orifice, located on duct 37c, allows a rate variation speed of 0.84s at 1500rpm, and 0.53s at 5500rpm.
  • the configuration described previously leads to a rate of rise from the minimum rate to the maximum rate of 1.13s at 1500 rpm, and from 0.37s to 5500 rpm, while a 1mm orifice, located on duct 37b, allows a speed of variation from the minimum rate to the maximum rate of 1.9s at 1500rpm and of 0.67s at 5500rpm.
  • the fluidic distribution device 371a comprises a two-position controlled shutter, one position of which blocks the fluidic communication between the two chambers 31, 32 and the other position allows the fluidic communication between the two rooms 31,32, in both directions of circulation.
  • This first embodiment is based on synchronous operation of the hydraulic control system 3, that is to say that the control of the fluidic distribution device 371a must be synchronized with the engine cycles.
  • the control of the fluidic distribution device 371a must be synchronized with the engine cycles.
  • the piston 30a to move the piston 30a towards the maximum length of the cylinder 30 (corresponding for example to a minimum compression ratio)
  • the reverse principle must be implemented to move the piston 30a towards the minimum length of the cylinder 30 (corresponding for example to a maximum compression ratio
  • the controlled fluidic distribution device 371a must be compatible with a very short switching time, typically 1 ms.
  • An electro-hydraulic shutter directly installed in the body of the cylinder 30b, could fulfill this function and would require a wired connection between the mobile cylinder 30 and a fixed motor control.
  • a purely hydraulic fluid distribution device, as illustrated in FIG. 2, can also be envisaged. In this case, it is necessary to take into account a time delay for the actuation of the device 371a, due to the oil duct connecting the pilot part 80 of said device.
  • the hydraulic control circuit 37 comprises at least two transfer conduits 37b, 37c connecting the two hydraulic chambers 31, 32 to one another.
  • the fluidic distribution device 372 comprises two piloted shutters 372b, 372c with two positions, and two oriented valves 372b ', 372c'.
  • This second embodiment is based on an asynchronous operation of the hydraulic control system 3, that is to say that the control of the fluidic distribution device 372 is independent of the engine cycles.
  • the first shutter 372b allows fluid communication between the chambers 31, 32, while the second shutter 372c blocks fluid communication.
  • the combustion and / or inertia forces tend to increase the pressure in the upper chamber 31, an oil transfer takes place from the upper chamber 31 to the lower chamber 32; the progressive filling (with the alternation of the engine cycles) of the lower chamber 32 and the progressive emptying of the upper chamber
  • the second shutter 372c is placed in a position allowing fluid communication between the chambers 31, 32, while the first obturator 372b is placed in a position blocking fluid communication. It is thus only possible to transfer oil from the lower chamber 32 to the upper chamber 31; the progressive filling (with the alternation of the engine cycles) of the upper chamber 31 and the progressive emptying of the lower chamber
  • each shutter 372b, 372c at rest can be chosen in different ways, according to the preferred strategy in failure of the pilot circuit 80.
  • the two shutters 372b, 372c at rest block all fluid communication, which freezes the compression ratio at its value in the event of failure of the pilot circuit 80.
  • the shutter 372b in its rest position allows fluid communication from the lower chamber 32 to the upper chamber 31, while the shutter 372c, in its rest position, blocks fluid communication in the reverse direction.
  • the length of the control cylinder 30 will gradually vary towards its minimum length. If this minimum length corresponds for example to a maximum compression ratio, this option ensures the best performance and the best efficiency of the engine, limiting the pollution caused, but this reduces the range of use of the engine (limitation in speed and / or in charge).
  • the shutter 372c in its rest position allows fluid communication from the upper chamber 31 to the lower chamber 32, while the shutter 372b, in its rest position, blocks fluid communication in the reverse direction.
  • the length of the control cylinder 30 will gradually vary towards its maximum length. If this maximum length corresponds for example to a minimum compression ratio, this option makes it possible to maintain the performance of the engine (no limitation in speed and / or load) but reduces its efficiency and its output which increases the pollution produced by the engine. engine.
  • control circuit 80 the role of which is to control the fluid distribution device 371a, 372 of the control system 3, two variants are proposed.
  • the controlled fluid distribution device 371a, 372 is actuated by an external electrical control circuit.
  • an electric wire must connect a fixed part of the motor, in which the electrical control circuit is located, and the fluid distribution device 371a, 372 preferably integrated into the control cylinder 30, which constitutes a movable part in the motor. .
  • the controlled fluid distribution device 371a, 372 (which is included in the hydraulic control circuit 37) is actuated by a hydraulic circuit. control 80.
  • the fluid distribution device 371a, 372 is tilted from a pass position to a blocking position (and vice versa) by means of the pressure of a fluid issuing from said hydraulic control circuit 80
  • This fluid can be water, gas or oil.
  • the first and second embodiments of the invention presented respectively in Figures 2 and 3a illustrate a hydraulic control circuit 80 essentially external to the control cylinder 30.
  • At least one fluidic channel 81 connects the fluidic distribution device 371a, 372 to the pilot circuit 80.
  • the latter may for example comprise an electrically actuated pilot valve 82 making it possible to deliver a fluid pressure in the fluidic channel 81 or to block the arrival of fluid in said channel 81, in order to switch the fluidic distribution device 371a, 372 respectively in one or the other of its positions.
  • the pilot valve 82 is connected to the engine lubrication circuit, the fluid is then low pressure oil.
  • the fluidic distribution device 371a, 372 can be controlled, therefore actuated, directly by the fluid pressure coming from the pilot circuit 80: it will then be necessary for the fluidic channel 81 to allow direct communication between the pilot fluid and said device 371a, 372.
  • the fluidic distribution device 371a, 372 could be actuated mechanically, by a force exerted by a mechanical actuating element, the latter being moved by the fluid pressure coming from the pilot circuit 80.
  • each controlled shutter 371a, 372b, 372c of the fluid distribution device 371a, 372 is arranged along a transverse axis T, normal to a longitudinal axis L of displacement of the piston 30a in the body 30b of the control cylinder 30.
  • a shutter 371a, 372b, 372c may for example be formed by a linear hydraulic slide whose central axis is parallel to the transverse axis T. This orientation avoids the shutter 371a, 372b, 372c to undergo the inertia and / or combustion forces applied to the control cylinder 30, forces which could interfere with the control forces necessary for actuating the shutters.
  • FIGS. 6a to 6e A particular example of the implementation of the hydraulic control system 3 will now be described, with reference to FIGS. 6a to 6e.
  • This example is based on the second embodiment previously described, that is to say involving a fluid distribution device 372 comprising two piloted shutters 372b, 372c and two oriented valves 372b ', 372c'. It is also based on controlling the fluid distribution device 372 by mechanical actuation.
  • control cylinder 30 with its piston 30a movable in the body 30b.
  • the piston 30a is extended by a foot 30a 'extending beyond the body 30b according to a longitudinal axis L, and capable of establishing a pivot connection with a mobile element of the engine.
  • a first chamber 31 and a second chamber 32 are defined in the body 30b of the control cylinder 30, on either side of the piston 30a which incorporates seals.
  • the first chamber 31 (or upper chamber) is called a “high pressure chamber” because it takes up the combustion forces; in contrast, the second chamber 32 (or lower chamber) is called a “low pressure chamber”.
  • the respective filling and emptying of the first 31 and of the second 32 chambers modify the length of the control cylinder 30.
  • the body 30b of the control cylinder 30 comprises two coaxial side bearings 35 of transverse axis T normal to the longitudinal axis L (FIG. 6b).
  • These lateral bearings 35 are intended to establish a pivot connection with a part of the engine (either fixed integral with the engine block, or mobile, depending on the configuration of integration of the hydraulic control system 3 in the engine).
  • the lateral position of said bearings 35 makes it possible to compact the control cylinder 30 with respect to a conventional cylinder with the connection points at the ends, thus limiting the bulk in the engine block.
  • each lateral bearing 35 has a shoulder 35a to ensure the positioning of the jack 30, along the transverse axis T, in the engine.
  • the control cylinder 30 comprises a spacer 52 attached to each side bearing 35 and intended to be integral with the above-mentioned part of the motor (FIG. 6c).
  • the connection between the side bearings 35 and the added spacers 52 allows the oscillating movement of the control cylinder 30 necessary for the operation of the control system 3 in the engine 100.
  • each added spacer 52 has a cylindrical internal housing, for this purpose. accommodate a side bearing 35.
  • the outer casing of the spacer 52 may also be cylindrical. It may nevertheless be advantageous to provide an ovoid outer casing to block any movement of the rotation of the spacer 52 vis-à-vis the part of the engine to which it is fixed.
  • the control cylinder 30 comprises a shouldered ring 53 interposed between each side bearing 35 and its attached spacer 51, to limit the friction associated with the oscillation movement of the control cylinder 30 and to partially take up the combustion forces as well as those of inertia undergone by said jack 30.
  • the fluidic distribution device 372 of the hydraulic control circuit 37 comprises a first hydraulic spool 372b and a second hydraulic spool 372c, respectively housed in the first lateral bearing 35 and the second lateral bearing 35 of the cylinder 30 (FIG. 6d).
  • the two drawers are arranged along the transverse axis T, coaxially with the side bearings 35.
  • a movement along the transverse axis T of the first hydraulic spool 372b makes it possible for example to establish a circulation of oil (shown diagrammatically by the black arrows in FIG. 6d) from the first chamber 31 to the second chamber 32, via first passages 37b arranged in the body 30b of the jack 30.
  • the movement of the first slide 372b places the first passages 37b leading to the two chambers 31, 32 in communication, and a first non-return valve 372b 'is arranged on said first passages 37b , allowing only a circulation of fluid from the first chamber 31 to the second chamber 32 (FIG. 6e, (i), (ii)).
  • a displacement of the second hydraulic spool 372c makes it possible to establish an oil circulation of the second chamber 32 to the first chamber 31, via second passages 37c arranged in the body 30b.
  • the movement of the second slide 372c places the second passages 37c leading to the two chambers 31, 32 in communication, and a second non-return valve 372c 'is disposed on said second passages 37c, allowing only a circulation of fluid from the second chamber 32 to the first chamber 31.
  • the system 3 implements a hydraulic pilot circuit 80.
  • the pilot circuit 80 is supplied with a pressurized fluid (for example, oil) coming from the part of the valve. motor to which the body 30b is connected.
  • each hydraulic slide 372b, 372c is intended to be in contact via a ball 803 with a pilot piston 801,802 carried by the attached spacer 52 (FIG. 6c (ii), FIG. 6d).
  • Each pilot piston 801,802 can be moved by the oil pressure (shown schematically by the white arrows in FIG. 6e) in the pilot circuit 80, to induce the displacement of the associated hydraulic spool 372b, 372c.
  • the oil from this circuit 80 is conveyed via conduits 81 to an internal housing of each attached spacer 52, which housing accommodates the pilot piston 801,802.
  • the mechanical contact between the pilot piston 801,802 and the hydraulic spool 372b, 372c is provided by a ball 803, which is capable of accommodating the oscillation of the jack 30 relative to the other connecting parts of the engine, including in particular relative to the pilot piston 801.802.
  • This configuration provides a simple and robust solution for the external piloting of the hydraulic control circuit 37 of the system 3.
  • the hydraulic control circuit 37 comprises at least one bore 37d and a rewash valve 373, between an oil supply and the lower chamber 32 (FIG. 6e (i), (iii)).
  • Regwash valve 373 is configured so as to allow circulation of oil from the oil supply to the second chamber 32, when the pressure in said chamber 32 is lower than the supply pressure.
  • the hydraulic control circuit 37 comprises at least one bore 37e and a relief valve 374 between the second hydraulic chamber 32 and the outside of the cylinder 30, so as to evacuate oil from the control circuit 37, when the pressure in said chamber 32 exceeds a determined maximum pressure.
  • a relief valve 374 whose opening pressure is greater than 200 bars or 300 bars, to avoid the implementation of complex sealing solutions in the hydraulic control system 3.
  • the hydraulic control system 3, and in particular the system 3 according to the aforementioned example of implementation, is particularly suitable for integration into a variable compression ratio engine of the VCT type.
  • VCT motor an implementation of which according to the state of the art is illustrated in FIG. 7, comprises two distinct groups of components:
  • the control system 2 integrating the control rods 20, the eccentric shaft 22, the levers 23,25, the rod 24 and the electric control means 26.
  • the hydraulic control system 3 can replace the aforementioned control system 2, as illustrated in FIG. 8.
  • the piston 30a of the control cylinder 30 is intended to be connected, via its foot 30a 'to a return member of a movable coupling of the engine, and the body 30b of the control cylinder 30 is intended to be connected to a fixed part 51 of the engine.
  • the hydraulic control system 3 for an engine with variable compression ratio, comprises one or more control ram (s) as described above.
  • the mobile coupling 1 of the VCT-type engine 100, integrating the combustion pistons 10, the main connecting rods 11, the return members 12 and the crankshaft 13 can remain unchanged as well as the upper part of the engine.
  • the shape of the control jacks 30 is designed to fit into the current size of the engine, thus avoiding increasing the center distance of the engine 100.

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Abstract

The invention relates to a hydraulic control system (3) for a variable compression ratio engine, comprising: - a control cylinder (30) comprising a piston (30a), a body (30b) in which two hydraulic chambers (31, 32) with equivalent sections are defined on either side of the piston (30a) and a return device (34) arranged in one of the chambers (31), - a hydraulic control circuit (37) comprising: - at least one duct (37b, 37c) connecting the two chambers (31,32) to each other, and a controlled fluid discharging device (372) for establishing or blocking a fluid communication between the chambers, - at least one duct (37d) connecting one of the chambers (32) to a low-pressure oil supply (60), and a refill valve (373), - at least one duct (37e) connecting an oil outlet (70) to at least one of the chambers (32), and a relief valve (374).

Description

SYSTEME HYDRAULIQUE DE COMMANDE POUR UN MOTEUR A TAUX DE HYDRAULIC CONTROL SYSTEM FOR A RATE MOTOR
COMPRESSION VARIABLE VARIABLE COMPRESSION
DOMAINE DE L' INVENTION FIELD OF THE INVENTION
La présente invention concerne le domaine des moteurs à taux de compression variable. Elle concerne en particulier un système hydraulique de commande dudit taux, alimenté par le circuit de lubrification du moteur, lequel système est muni d'un moyen autonome de pressurisation de l'huile assurant une pression hydraulique moyenne dans le circuit hydraulique de commande constamment supérieure à la pression de lubrification du moteur au cours du fonctionnement du moteur. The present invention relates to the field of variable compression ratio engines. It relates in particular to a hydraulic system for controlling said rate, supplied by the engine lubrication circuit, which system is provided with an independent means of pressurizing the oil ensuring an average hydraulic pressure in the hydraulic control circuit constantly greater than engine lubrication pressure during engine operation.
ARRIERE PLAN TECHNOLOGIQUE DE L' INVENTION TECHNOLOGICAL BACKGROUND OF THE INVENTION
On connaît les moteurs à taux de compression variable dont le système de commande dudit taux, opérant individuellement pour chaque cylindre de combustion, est basé sur un vérin hydraulique. Par exemple, le moteur VCRi à taux continu, développé par la demanderesse, et les systèmes dits de bielle bi-taux développés notamment par les sociétés FEV ou AVL. Variable compression ratio engines are known in which the said rate control system, operating individually for each combustion cylinder, is based on a hydraulic cylinder. For example, the continuous rate VCRi engine, developed by the applicant, and the so-called two-rate connecting rod systems developed in particular by the FEV or AVL companies.
L'avantage connu d'utiliser un système hydraulique pour commander le taux est qu'il est possible de transférer des efforts importants sur des encombrements réduits au travers de la pression hydraulique. Ainsi, un moteur VCRi opère à des pressions pouvant aller jusqu'à 300 bars, tandis que les systèmes de bielle bi-taux peuvent opérer à des pressions allant jusqu'à plus de 2000 bars. The known advantage of using a hydraulic system to control the rate is that it is possible to transfer significant forces over small dimensions through the hydraulic pressure. Thus, a VCRi engine operates at pressures of up to 300 bars, while two-rate connecting rod systems can operate at pressures of up to more than 2000 bars.
Le système de transmission de puissance de tout moteur est soumis à des efforts alternatifs. Cette alternance d'efforts s'applique naturellement au système de commande hydraulique, qui va subir des efforts allant d'une pression maximale, définie habituellement par la pression de combustion maximale rencontrée, à une pression minimale, définie par les efforts d'inertie rencontrés au point mort haut. The power transmission system of any engine is subjected to alternating forces. This alternation of forces naturally applies to the hydraulic control system, which will be subjected to forces ranging from a maximum pressure, defined usually by the maximum combustion pressure encountered, at a minimum pressure, defined by the inertia forces encountered at top dead center.
L'huile est un fluide compressible, d'autant plus qu'il est chargé en gaz (une huile moteur est classiquement aérée entre 5% et 30% en fonction des conditions de fonctionnement). Cette élasticité, mesurée par le module d'élasticité isostatique (autrement appelé module de bulk) , se traduit par une modification de la position du vérin de commande en fonction de l'effort appliqué, ce qui entraine des oscillations dans le système, conduit à une amplification des efforts par effet dynamique, et nuit à la précision souhaitée pour la commande du taux de compression. Pour minimiser ces effets négatifs, il est souhaitable d'utiliser les huiles les moins souples possible, c'est-à-dire ayant le module de bulk le plus élevé possible. Oil is a compressible fluid, especially since it is loaded with gas (engine oil is conventionally aerated between 5% and 30% depending on the operating conditions). This elasticity, measured by the isostatic modulus of elasticity (otherwise called bulk modulus), results in a modification of the position of the control cylinder as a function of the force applied, which causes oscillations in the system, leading to an amplification of the forces by dynamic effect, and adversely affects the precision desired for the control of the compression ratio. To minimize these negative effects, it is desirable to use the least flexible oils possible, that is to say having the highest possible bulk modulus.
Il est connu (voir la courbe en figure 1) que le module de bulk (KE) d'une huile (a,b,c,d,e) augmente avec la pression (p), puis se stabilise à partir d'un certain niveau de pression. On a donc intérêt, pour améliorer la précision du réglage de taux, à opérer dans des gammes de pressions qui se situent au- dessus de la pression de stabilisation du module de bulk, soit environ 30 bars pour de l'huile moteur. It is known (see the curve in figure 1) that the bulk modulus (K E ) of an oil (a, b, c, d, e) increases with pressure (p), then stabilizes from a certain level of pressure. It is therefore advantageous, in order to improve the accuracy of the rate adjustment, to operate in pressure ranges which are located above the stabilization pressure of the bulk module, ie approximately 30 bars for engine oil.
Pour des raisons économiques, on souhaite en général utiliser le circuit de lubrification du moteur pour assurer une mise en pression du système de commande ; or, celui-ci opère à des pressions de 2 à 6 bars, bien en-dessous de la pression de stabilisation du module d'élasticité isostatique. Pour gagner en précision, et limiter les amplifications dynamiques des efforts subis par le système de commande, il est donc nécessaire d'augmenter la pression d'huile dans ledit système. Le document WO2018/158539 propose d'ajouter une pompe hydraulique sur le circuit basse pression pour augmenter la pression moyenne dans le système de commande au-delà de la pression de stabilisation du module de bulk de l'huile, ainsi qu'un clapet entre la sortie de la pompe hydraulique et le système de commande, permettant d'augmenter encore cette pression en fonction des conditions d'utilisation du moteur. For economic reasons, it is generally desired to use the engine lubrication circuit to pressurize the control system; however, this operates at pressures of 2 to 6 bars, well below the pressure for stabilizing the isostatic modulus of elasticity. To gain in precision, and to limit the dynamic amplifications of the forces undergone by the control system, it is therefore necessary to increase the oil pressure in said system. Document WO2018 / 158539 proposes to add a hydraulic pump on the low pressure circuit to increase the average pressure in the control system beyond the stabilization pressure of the oil bulk module, as well as a valve between the output of the hydraulic pump and the control system, making it possible to further increase this pressure according to the conditions of use of the engine.
La société FEV (« 2-step variable compression ratio System development & industrialization », 2nd International FEV Conférence, Fev 7-8, 2019) propose d'utiliser un distributeur particulier permettant d'assurer l'augmentation de pression dans la chambre hydraulique du système de commande, par effet de pompage. Dans une telle configuration, un changement de taux, qui va se traduire par l'ouverture du distributeur, va faire chuter la pression dans le système de commande à la pression d'alimentation (circuit de lubrification) : cela implique que le module d'élasticité isostatique de l'huile ne sera pas optimal au moins pendant quelques cycles, pouvant conduire à des surcharges temporaires de la cinématique (phénomènes d'amplification dus à des chocs). The company FEV (“2-step variable compression ratio System development & industrialization”, 2 nd International FEV Conférence, Feb 7-8, 2019) proposes to use a special distributor to ensure the pressure increase in the hydraulic chamber of the control system, by pumping effect. In such a configuration, a rate change, which will result in the opening of the distributor, will drop the pressure in the control system to the supply pressure (lubrication circuit): this implies that the module of The isostatic elasticity of the oil will not be optimal at least for a few cycles, which may lead to temporary overloads of the kinematics (amplification phenomena due to shocks).
Le document JP2003/322036 propose un mécanisme pour moteur à taux de compression variable comprenant des moyens électriques de pilotage en rotation de l'arbre de commande et un moyen hydraulique de maintien permettant de diminuer les efforts s'appliquant sur les moyens de pilotage et évitant d'alimenter continûment en énergie ces derniers. Document JP2003 / 322036 proposes a mechanism for a variable compression ratio engine comprising electrical means for controlling the control shaft in rotation and a hydraulic holding means making it possible to reduce the forces applied to the control means and avoiding to supply them continuously with energy.
Le document FR2914951 propose un dispositif électrohydraulique de pilotage en boucle fermée d'un vérin de commande d'un moteur à taux de compression variable. Document FR2914951 proposes an electro-hydraulic device for controlling a closed loop of a control cylinder for an engine with a variable compression ratio.
OBJET DE L' INVENTION OBJECT OF THE INVENTION
La présente invention propose une solution alternative à celles de l'état de la technique, remédiant à tout ou partie des inconvénients précités. Elle concerne en particulier un système de commande hydraulique comprenant un vérin de commande et un circuit hydraulique de commande, et dont l'architecture permet d'augmenter la pression moyenne dans les chambres hydrauliques du vérin de commande à des valeurs supérieures à la pression de lubrification, et typiquement supérieures à 20 bars, et de maintenir ladite pression moyenne lors des changements de taux de compression du moteur. The present invention provides an alternative solution to those of the state of the art, remedying all or part of the aforementioned drawbacks. It relates in particular to a hydraulic control system comprising a control cylinder and a hydraulic control circuit, and the architecture of which makes it possible to increase the average pressure in the hydraulic chambers of the control cylinder to values greater than the lubrication pressure. , and typically greater than 20 bars, and to maintain said average pressure during changes in the compression ratio of the engine.
BREVE DESCRIPTION DE L' INVENTION BRIEF DESCRIPTION OF THE INVENTION
L'invention concerne un système de commande hydraulique pour un moteur à taux de compression variable comprenant : The invention relates to a hydraulic control system for a variable compression ratio engine comprising:
- un vérin de commande comportant un piston et un corps dans lequel deux chambres hydrauliques de sections équivalentes sont définies de part et d'autre du piston, ledit piston étant apte à se déplacer dans le corps pour commander le taux de compression du moteur, - a control cylinder comprising a piston and a body in which two hydraulic chambers of equivalent sections are defined on either side of the piston, said piston being able to move in the body to control the compression ratio of the engine,
- un circuit hydraulique de commande comportant au moins un conduit reliant les deux chambres hydrauliques entre elles, et un dispositif de distribution fluidique piloté pour établir ou bloquer une communication fluidique entre lesdites chambres, a hydraulic control circuit comprising at least one conduit connecting the two hydraulic chambers to one another, and a controlled fluidic distribution device to establish or block fluidic communication between said chambers,
Le système de commande hydraulique est remarquable en ce que :The hydraulic control system is remarkable in that:
- le circuit hydraulique de commande comporte : - the hydraulic control circuit comprises:
* au moins un conduit reliant au moins une des chambres hydrauliques et une alimentation d'huile à basse pression, et un premier clapet anti-retour, pour regaver le circuit hydraulique de commande lorsque la pression dans ladite chambre hydraulique passe en-deçà de ladite basse pression, du fait des efforts de combustion et/ou d'inertie du moteur s'appliquant au vérin,* at least one conduit connecting at least one of the hydraulic chambers and a low pressure oil supply, and a first non-return valve, for rewashing the hydraulic control circuit when the pressure in said hydraulic chamber falls below said low pressure, due to combustion forces and / or engine inertia applied to the cylinder,
* au moins un conduit reliant une évacuation d'huile et au moins une des chambres hydrauliques, et un clapet de décharge pour vidanger le circuit hydraulique de commande lorsque la pression dans ladite chambre hydraulique excède une pression maximale déterminée, * at least one pipe connecting an oil outlet and at least one of the hydraulic chambers, and a relief valve to drain the hydraulic control circuit when the pressure in said hydraulic chamber exceeds a determined maximum pressure,
- le vérin de commande comprend un dispositif de rappel tendant à ramener ledit vérin à une longueur correspondant à un taux de compression maximum du moteur. - The control cylinder comprises a return device tending to bring said cylinder to a length corresponding to a maximum compression ratio of the engine.
Le système hydraulique de commande selon l'invention permet d'alimenter le circuit hydraulique de commande au moyen d'une alimentation d'huile à basse pression, typiquement reliée au circuit de lubrification du moteur (basse pression, entre 2 et 6 bars par exemple), grâce au conduit reliant au moins une des chambres hydrauliques et une alimentation d'huile à basse pression. Il permet aussi d'augmenter la pression moyenne dans les chambres hydrauliques du vérin de commande à des valeurs supérieures à la pression de lubrification, et typiquement supérieures à 20 bars, du fait de la présence du premier clapet anti-retour qui autorise le regavage du circuit hydraulique lorsque les efforts de combustion et/ou d'inertie s'appliquant au vérin provoquent séquentiellement des chutes de pression dans la chambre reliée à l'alimentation. The hydraulic control system according to the invention makes it possible to supply the hydraulic control circuit by means of a low pressure oil supply, typically connected to the engine lubrication circuit (low pressure, between 2 and 6 bars for example. ), thanks to the conduit connecting at least one of the hydraulic chambers and a low pressure oil supply. It also makes it possible to increase the average pressure in the hydraulic chambers of the control cylinder to values greater than the lubrication pressure, and typically greater than 20 bars, due to the presence of the first non-return valve which allows the rewashing of the hydraulic circuit when the combustion and / or inertia forces applied to the jack sequentially cause pressure drops in the chamber connected to the supply.
Le système hydraulique de commande selon l'invention permet de conserver cette pression moyenne, typiquement supérieures à 20 bars, dans les chambres hydrauliques, lors de l'opération de changement de taux. En effet, la présence du premier clapet anti-retour de regavage, empêche le circuit hydraulique de commande de redescendre à la basse pression d'alimentation, en l'isolant de ladite alimentation quelles que soient les conditions de fonctionnement du moteur. Et le changement de taux, lié au déplacement du piston dans le corps du vérin de commande, est défini par le dispositif de distribution fluidique piloté qui gère la circulation et le transfert d'huile d'une chambre vers l'autre, et ainsi la position du piston. La précision du réglage de taux est ainsi améliorée car le système de commande hydraulique opère dans des gammes de pressions se situant au-dessus de la pression de stabilisation du module de bulk. The hydraulic control system according to the invention makes it possible to maintain this average pressure, typically greater than 20 bars, in the hydraulic chambers, during the rate change operation. In fact, the presence of the first regwashing non-return valve prevents the hydraulic control circuit from dropping down to low supply pressure, by isolating it from said supply whatever the operating conditions of the engine. And the rate change, linked to the displacement of the piston in the body of the control cylinder, is defined by the controlled fluid distribution device which manages the circulation and transfer of oil from one chamber to the other, and thus the piston position. The accuracy of the rate setting is thus improved because the hydraulic control system operates in pressure ranges above the stabilization pressure of the bulk module.
De plus, le système hydraulique de commande selon l'invention permet de réguler la pression moyenne dans les chambres hydrauliques et il autorise l'atteinte effective des taux de compression variables entre taux minimum et taux maximum, ainsi qu'un changement de taux efficace, c'est-à-dire avec une bonne dynamique, entre taux minimum et taux maximum, ou vice versa. In addition, the hydraulic control system according to the invention makes it possible to regulate the average pressure in the hydraulic chambers and it allows the effective attainment of the variable compression ratios between minimum rate and maximum rate, as well as an effective rate change, that is to say with a good dynamic, between minimum rate and maximum rate, or vice versa.
Selon d'autres caractéristiques avantageuses et non limitatives de l'invention, prises seules ou selon toute combinaison techniquement réalisable : According to other advantageous and non-limiting characteristics of the invention, taken alone or in any technically feasible combination:
- le conduit muni du clapet de décharge relie l'évacuation d'huile et la chambre, parmi les deux chambres hydrauliques, qui ne subit pas des efforts de combustion du moteur, - the pipe fitted with the relief valve connects the oil discharge and the chamber, among the two hydraulic chambers, which is not subjected to combustion forces from the engine,
- le dispositif de rappel est disposé dans la chambre, parmi les deux chambres hydrauliques, qui subit des efforts de combustion du moteur, - the return device is placed in the chamber, among the two hydraulic chambers, which undergoes combustion forces from the engine,
- le circuit hydraulique de commande est porté par le corps du vérin de commande ; - the hydraulic control circuit is carried by the body of the control cylinder;
- le dispositif de distribution fluidique piloté est actionné par un circuit électrique de pilotage ; - The controlled fluid distribution device is actuated by an electrical control circuit;
- le dispositif de distribution fluidique piloté est actionné par un circuit hydraulique de pilotage ; - the controlled fluid distribution device is actuated by a hydraulic control circuit;
- le dispositif de distribution fluidique comprend un obturateur piloté à deux positions, dont une position bloque la communication fluidique entre les deux chambres et l'autre position autorise la communication fluidique entre les deux chambres, dans les deux sens de circulation ; - le circuit hydraulique de commande comporte au moins deux conduits reliant les deux chambres hydrauliques entre elles, et dans lequel le dispositif de distribution fluidique comprend deux obturateurs pilotés à deux positions et deux clapets orientés, un premier obturateur et un premier clapet orienté étant portés par un premier conduit, pour bloquer ou autoriser la circulation d'huile de la première chambre vers la deuxième chambre, et un deuxième obturateur et un deuxième clapet orienté étant portés par un deuxième conduit, pour bloquer ou autoriser la circulation d'huile de la deuxième chambre vers la première chambre ; the fluidic distribution device comprises a two-position controlled shutter, one position of which blocks the fluidic communication between the two chambers and the other position allows fluidic communication between the two chambers, in both directions of circulation; - The hydraulic control circuit comprises at least two conduits connecting the two hydraulic chambers to each other, and in which the fluid distribution device comprises two controlled two-position shutters and two oriented valves, a first shutter and a first oriented valve being carried by a first duct, to block or allow the circulation of oil from the first chamber to the second chamber, and a second shutter and a second oriented valve being carried by a second duct, to block or allow the circulation of oil from the second bedroom to the first bedroom;
- chaque obturateur piloté est disposé selon un axe transverse, normal à un axe longitudinal de déplacement du piston dans le corps du vérin de commande ; - Each controlled shutter is arranged along a transverse axis, normal to a longitudinal axis of displacement of the piston in the body of the control cylinder;
- le piston du vérin de commande est destiné à être relié à un organe de renvoi d'un attelage mobile du moteur, et le corps du vérin de commande est destiné à être relié à une partie fixe du moteur. - The piston of the control cylinder is intended to be connected to a return member of a movable coupling of the engine, and the body of the control cylinder is intended to be connected to a fixed part of the engine.
BREVE DESCRIPTION DES FIGURES BRIEF DESCRIPTION OF THE FIGURES
D'autres caractéristiques et avantages de l'invention ressortiront de la description détaillée de l'invention qui va suivre en référence aux figures annexées sur lesquelles : Other characteristics and advantages of the invention will emerge from the detailed description of the invention which will follow with reference to the appended figures in which:
• La figure 1 présente une courbe reliant le module d'élasticité isostatique d'huiles à la pression ; • Figure 1 shows a curve relating the isostatic modulus of elasticity of oils to pressure;
• La figure 2 présente un schéma de principe d'un système de commande hydraulique selon un premier mode de réalisation, conforme à l'invention ; • Figure 2 shows a block diagram of a hydraulic control system according to a first embodiment, according to the invention;
• Les figures 3a et 3b présentent respectivement un schéma de principe d'un système de commande hydraulique selon un deuxième mode de réalisation, conforme à l'invention, et différentes options pour la position au repos du dispositif de distribution fluidique dans une système de commande hydraulique selon le deuxième mode de réalisation ; • Figures 3a and 3b respectively show a block diagram of a hydraulic control system according to a second embodiment, according to the invention, and various options for the rest position of the fluid distribution device in a hydraulic control system according to the second embodiment;
• Les figures 4a et 4b présentent des courbes illustrant le fonctionnement d'un système de commande selon l'état de la technique, avec chute de pression à chaque changement de taux et respectivement sans et avec regavage en huile du système de commande hydraulique ; • Figures 4a and 4b show curves illustrating the operation of a control system according to the state of the art, with pressure drop at each rate change and respectively without and with oil backwashing of the hydraulic control system;
• La figure 5 présente des courbes illustrant le fonctionnement d'un système de commande conforme à la présente invention ; • Figure 5 presents curves illustrating the operation of a control system according to the present invention;
• Les figures 6a, 6b, 6c, 6d, 6e présentent un exemple particulier de mise en œuvre du système de commande hydraulique, conforme au deuxième mode de réalisation de l'invention ; • Figures 6a, 6b, 6c, 6d, 6e show a particular example of implementation of the hydraulic control system, according to the second embodiment of the invention;
• La figure 7 présente un attelage mobile et un système de commande du taux de compression variable dans un moteur selon l'état de la technique ; FIG. 7 shows a mobile coupling and a system for controlling the variable compression ratio in an engine according to the state of the art;
• La figure 8 présente une vue de côté d'un attelage mobile et d'un système de commande hydraulique d'un moteur à taux de compression variable, ledit système étant conforme à l'invention. • Figure 8 shows a side view of a mobile coupling and a hydraulic control system of a variable compression ratio engine, said system being in accordance with the invention.
DESCRIPTION DETAILLEE DE L' INVENTION DETAILED DESCRIPTION OF THE INVENTION
Dans la partie descriptive, les mêmes références sur les figures pourront être utilisées pour des éléments de même type ou de même fonction. Certaines figures sont des représentations schématiques qui, dans un objectif de lisibilité, ne sont pas nécessairement à l'échelle et ne reflètent pas nécessairement toutes les contraintes pratiques de mise en œuvre. In the descriptive part, the same references in the figures may be used for elements of the same type or the same function. Some figures are schematic representations which, for the sake of readability, are not necessarily to scale and do not necessarily reflect all the practical constraints of implementation.
La présente invention concerne un système de commande hydraulique 3 pour un moteur à taux de compression variable dont deux modes de réalisation sont illustrés respectivement en figure 2 et en figure 3a. The present invention relates to a hydraulic control system 3 for a variable compression ratio engine, two embodiments of which are illustrated respectively in FIG. 2 and in FIG. 3a.
Le système de commande 3 selon l'invention comprend un vérin de commande 30 comportant un piston 30a et un corps 30b dans lequel deux chambres hydrauliques 31,32 de sections équivalentes sont définies de part et d'autre du piston 30a. Notons que les figures 2 et 3a sont schématiques et n'illustrent pas le caractère équivalent des sections des deux chambres 31,32. Ledit piston 30a est apte à se déplacer dans le corps 30b, ce qui modifie la longueur du vérin et définit (ou en d'autres termes, commande) le taux de compression du moteur. The control system 3 according to the invention comprises a control cylinder 30 comprising a piston 30a and a body 30b in which two hydraulic chambers 31, 32 of equivalent sections are defined on either side of the piston 30a. Note that Figures 2 and 3a are schematic and do not illustrate the equivalent nature of the sections of the two chambers 31, 32. Said piston 30a is able to move in the body 30b, which modifies the length of the cylinder and defines (or in other words, controls) the compression ratio of the engine.
On comprend qu'un tel système de commande 3 pourra être intégré dans une bielle de longueur variable, directement reliée au piston de combustion et au vilebrequin d'un moteur à taux de combustion variable. Il pourra également être intégré à un vérin de commande de type VCRi. Enfin, comme cela sera décrit plus en détail dans un exemple par la suite, un tel système de commande 3 pourra être intégré à un moteur de type VC-T (pour « variable compression - turbo ») décrit dans le document EP2787196. It will be understood that such a control system 3 could be integrated into a connecting rod of variable length, directly connected to the combustion piston and to the crankshaft of an engine with variable combustion rate. It can also be integrated into a VCRi type control jack. Finally, as will be described in more detail in one example below, such a control system 3 can be integrated into a VC-T type engine (for “variable compression - turbo”) described in document EP2787196.
Le système de commande hydraulique 3 comprend également un circuit hydraulique de commande 37 dont le rôle est notamment d'alimenter les chambres hydrauliques 31,32 du vérin de commande 30 en huile et de gérer le transfert d'huile d'une chambre à 1'autre. Pour cela, le circuit hydraulique de commande 37 comprend au moins un conduit 37a,37b,37c reliant les deux chambres hydrauliques 31,32 entre elles. Par la suite, ce ou ces conduits 37a,37b,37c seront appelés conduits de transfert 37a,37b,37c car ils permettent la circulation d'huile d'une chambre 31,32 à l'autre. Le circuit hydraulique de commande 37 comprend également un dispositif de distribution fluidique 371a,372 disposé sur ledit (au moins un) conduit de transfert 37a,37b,37c, entre les deux chambres hydrauliques 31,32. Le dispositif de distribution fluidique 371a,372 est piloté pour établir ou bloquer une communication fluidique entre lesdites chambres 31,32 ; en d'autres termes, ledit dispositif 371a,372 est piloté pour ouvrir ou obturer le (ou les) conduit (s) 37a,37b,37c reliant les deux chambres 31,32. Cela sous-entend la présence d'un circuit de pilotage 80, relié au dispositif de distribution fluidique 371a,372 ; ledit circuit 80 sera décrit plus loin. Les conduits de transfert 37a,37b,37c et le dispositif de distribution fluidique 371a,372 permettent de gérer le transfert d'huile d'une chambre hydraulique 31,32 à l'autre, et ainsi de modifier la longueur du vérin de commande 30, correspondant à une modification du taux de compression du moteur. The hydraulic control system 3 also comprises a hydraulic control circuit 37 whose role is in particular to supply the hydraulic chambers 31, 32 of the control cylinder 30 with oil and to manage the transfer of oil from one chamber to 1 '. other. For this, the hydraulic control circuit 37 comprises at least one conduit 37a, 37b, 37c connecting the two hydraulic chambers 31, 32 to one another. Subsequently, this or these conduits 37a, 37b, 37c will be called transfer conduits 37a, 37b, 37c because they allow the circulation of oil from one chamber 31, 32 to the other. The hydraulic control circuit 37 also comprises a fluidic distribution device 371a, 372 disposed on said (at least one) transfer duct 37a, 37b, 37c, between the two hydraulic chambers 31, 32. The fluidic distribution device 371a, 372 is controlled to establish or block a fluidic communication between said chambers 31, 32; in other words, said device 371a, 372 is controlled to open or close the duct (s) 37a, 37b, 37c connecting the two chambers 31, 32. This implies the presence of a pilot circuit 80, connected to the fluid distribution device 371a, 372; said circuit 80 will be described later. The transfer conduits 37a, 37b, 37c and the fluid distribution device 371a, 372 make it possible to manage the transfer of oil from one hydraulic chamber 31, 32 to the other, and thus to modify the length of the control cylinder 30. , corresponding to a modification of the engine compression ratio.
Le circuit hydraulique de commande 37 comprend également au moins un conduit 37d reliant au moins une des chambres hydrauliques 31,32 à une alimentation d'huile 60 à basse pression. Un premier clapet anti-retour 373 est disposé sur ledit conduit 37d : il autorise uniquement le passage d'huile de l'alimentation d'huile 60 vers la chambre hydraulique 31,32, lorsque la pression dans ladite chambre hydraulique passe en- deçà de la pression d'alimentation d'huile. En pratique, la pression d'huile issue de l'alimentation 60 est comprise entre 2 et 6 bars. Parce que le conduit 37d et le premier clapet anti retour 373 permettent de regaver en huile le circuit hydraulique de commande 37, ils pourront être respectivement nommés par la suite, conduit de regavage 37d et clapet de regavage 373. The hydraulic control circuit 37 also comprises at least one conduit 37d connecting at least one of the hydraulic chambers 31, 32 to a supply of oil 60 at low pressure. A first non-return valve 373 is arranged on said conduit 37d: it only allows the passage of oil from the oil supply 60 to the hydraulic chamber 31, 32, when the pressure in said hydraulic chamber drops below the oil supply pressure. In practice, the oil pressure from the supply 60 is between 2 and 6 bars. Because pipe 37d and the first non-return valve 373 allow the hydraulic circuit to be rewashed with oil 37, they may be called respectively subsequently, rewashing duct 37d and rewashing valve 373.
Avantageusement, comme le vérin de commande 30 du système 3 selon l'invention est destiné à subir les efforts d'inertie et de combustion du moteur, le conduit de regavage 37d et le clapet de regavage 373 sont disposés entre l'alimentation en huile 60 et celle des deux chambres hydrauliques 32 qui ne subit pas les efforts de combustion du moteur. Les efforts générés par la combustion étant supérieurs à ceux générés par les inerties, la chambre hydraulique 32 verra la plus grande dépression et la pression instantanée la plus basse, améliorant ainsi le regavage. Advantageously, as the control cylinder 30 of the system 3 according to the invention is intended to undergo the inertia and combustion forces of the engine, the regwashing duct 37d and the regwashing valve 373 are arranged between the oil supply 60 and that of the two hydraulic chambers 32 which is not subjected to the combustion forces of the engine. The forces generated by the combustion being greater than those generated by the inertias, the hydraulic chamber 32 will see the greatest depression and the lowest instantaneous pressure, thus improving the regavage.
Le circuit hydraulique de commande 37 permet d'augmenter la pression moyenne dans les chambres hydrauliques 31,32 du vérin de commande 30 à des valeurs supérieures à la pression de lubrification (basse pression), et typiquement supérieures à 20 bars, voire supérieures à 30 bars. Cela est rendu possible par la présence du clapet de regavage 373 qui autorise l'introduction d'huile dans le circuit hydraulique de commande 37, lorsque les efforts de combustion et/ou d'inertie s'appliquant au vérin 30 provoquent séquentiellement des chutes de pression dans la chambre reliée à l'alimentation. The hydraulic control circuit 37 makes it possible to increase the average pressure in the hydraulic chambers 31, 32 of the control cylinder 30 to values greater than the lubrication pressure (low pressure), and typically greater than 20 bars, or even greater than 30. bars. This is made possible by the presence of the rewash valve 373 which allows the introduction of oil into the hydraulic control circuit 37, when the combustion and / or inertia forces applied to the cylinder 30 sequentially cause drops of pressure in the chamber connected to the supply.
De plus, le circuit hydraulique de commande 37 selon l'invention permet de conserver cette pression moyenne typiquement supérieure à 20 bars, dans les chambres hydrauliques 31,32, lors de l'opération de changement de taux. En effet, le clapet de regavage 373 empêche le circuit hydraulique de commande 37 de redescendre à la basse pression d'alimentation, en l'isolant de ladite alimentation, quelles que soient les conditions de fonctionnement du moteur. Et le changement de taux, lié au déplacement du piston 30a dans le vérin de commande 30, est défini par le dispositif de distribution fluidique piloté 371a,372 qui gère la circulation et le transfert d'huile d'une chambre vers l'autre, et ainsi la position du piston 30a dans le corps 30b vérin de commande 30. In addition, the hydraulic control circuit 37 according to the invention makes it possible to maintain this average pressure, typically greater than 20 bars, in the hydraulic chambers 31, 32, during the rate change operation. In fact, the regavage valve 373 prevents the hydraulic control circuit 37 from falling back to the low supply pressure, by isolating it from said supply, whatever the operating conditions of the engine. And the rate change, linked to the movement of the piston 30a in the control cylinder 30, is defined by the piloted fluid distribution device 371a, 372 which manages the circulation and transfer of oil from a chamber towards the other, and thus the position of the piston 30a in the body 30b of the control cylinder 30.
La précision du réglage de la longueur du vérin de commande 30, et donc la précision de réglage du taux de compression, sont améliorées car le système de commande hydraulique 3 opère dans des gammes de pression moyenne se situant au-dessus de la pression de stabilisation du module de bulk. Cela apparaît clairement par comparaison des courbes des figures 4a, 4b et 5. Les figures 4a, 4b illustrent le fonctionnement d'un système de commande hydraulique proche de l'état de la technique, c'est-à-dire subissant une perte de pression lors des changements de taux de compression ; sur la figure 4a, le système est dépourvu de fonction de regavage en huile, alors que sur la figure 4b, le système en est pourvu. La figure 5 illustre le fonctionnement d'un système de commande hydraulique conforme à la présente invention, ne subissant pas de perte de pression lors des changements de taux de compression et comprenant une fonction de regavage en huile des chambres hydrauliques 31,32. The precision of the adjustment of the length of the control cylinder 30, and therefore the precision of adjustment of the compression ratio, is improved because the hydraulic control system 3 operates in ranges of medium pressure lying above the stabilization pressure. of the bulk module. This appears clearly by comparing the curves of Figures 4a, 4b and 5. Figures 4a, 4b illustrate the operation of a hydraulic control system close to the state of the art, that is to say undergoing a loss of power. pressure during compression ratio changes; in FIG. 4a, the system does not have an oil regeneration function, while in FIG. 4b, the system is provided with it. FIG. 5 illustrates the operation of a hydraulic control system according to the present invention, not undergoing a loss of pressure during changes in compression ratio and comprising a function of rewashing the hydraulic chambers 31, 32 with oil.
Dans les deux cas, on se place dans des conditions de régime moteur à 1000 tours par minute et présentant une pression maximale dans le cylindre de combustion de 32 bars. La pression moyenne dans les chambres hydrauliques est calculée sur un cycle moteur (0,12 s). La consigne de taux est définie de la manière suivante : +1 demande une augmentation du taux de compression, 0 demande un taux fixe, -1 demande une diminution du taux de compression. In both cases, the engine is operating under conditions of 1000 revolutions per minute and having a maximum pressure in the combustion cylinder of 32 bars. The average pressure in the hydraulic chambers is calculated over an engine cycle (0.12 s). The rate setpoint is defined as follows: +1 requests an increase in the compression ratio, 0 requests a fixed rate, -1 requests a decrease in the compression ratio.
Sur la figure 4a, la pression moyenne dans les chambres hydrauliques reste toujours inférieure à 10 bars. Pour une consigne définie, le taux de compression réel obtenu oscille très fortement, typiquement de plus de deux points, ce qui rend un asservissement impossible. Sur la figure 4b, la pression moyenne dans les chambres hydrauliques peut atteindre des valeurs supérieures à 20 bars dans certaine phase de commande mais chute à chaque changement de taux de compression. Là encore, pour une consigne définie, le taux de compression réel obtenu oscille fortement, et met du temps à se stabiliser ce qui rend l'asservissement difficile. In FIG. 4a, the average pressure in the hydraulic chambers always remains below 10 bars. For a defined setpoint, the actual compression ratio obtained oscillates very strongly, typically by more than two points, which makes servo-control impossible. In figure 4b, the average pressure in the hydraulic chambers can reach values greater than 20 bars in a certain control phase but drop with each change in compression ratio. Here again, for a defined setpoint, the actual compression ratio obtained oscillates strongly, and takes time to stabilize, which makes the control difficult.
Sur la figure 5, la pression moyenne dans les chambres hydrauliques 31,32 augmente au cours des premiers cycles moteur et demeure supérieure à 20 bars, voire supérieure à 30 bars, lors des opérations de changement de taux de compression. Pour la même consigne de taux que précédemment, le taux de compression obtenu est beaucoup plus stable (pas ou peu d'oscillations) et précis. Le système de commande hydraulique 3 selon l'invention montre donc de très bonnes performances, même sur un point de fonctionnement très peu chargé (faible régime moteur, ralenti). In FIG. 5, the average pressure in the hydraulic chambers 31, 32 increases during the first engine cycles and remains greater than 20 bars, or even greater than 30 bars, during the compression ratio change operations. For the same rate setpoint as previously, the compression rate obtained is much more stable (no or few oscillations) and precise. The hydraulic control system 3 according to the invention therefore shows very good performance, even on a very lightly loaded operating point (low engine speed, idling).
L'observation est similaire quand on se place dans des conditions de régime moteur plus élevées, typiquement à 4000 tours par minute, avec une pression maximale dans le cylindre de combustion de 67 bars. The observation is similar when one places oneself in higher engine speed conditions, typically at 4000 revolutions per minute, with a maximum pressure in the combustion cylinder of 67 bars.
Le circuit hydraulique de commande 37 comprend en outre au moins un conduit 37e reliant au moins une des chambres hydrauliques 31,32 à une évacuation d'huile 70. Un deuxième clapet anti-retour 374 est disposé sur ledit conduit 37e et permet de vidanger le circuit hydraulique de commande 37 lorsque la pression dans ladite chambre hydraulique 31,32 excède une pression maximale déterminée du fait des efforts de combustion et/ou d'inertie du moteur s'appliquant au vérin (30). Le conduit 37e et le deuxième clapet anti-retour 374 pourront respectivement être nommés par la suite, conduit de vidange 37e et clapet de vidange 374. Ils permettent d'éviter que la pression moyenne dans les chambres hydrauliques 31,32 soit trop élevée et qu'elle impose des solutions complexes d'étanchéité dans le vérin de commande 30. En d'autres termes, ils permettent de réguler la pression moyenne dans les chambres hydrauliques 31,32. Il est favorable de relier le conduit de vidange 37e à la chambre hydraulique 32 qui ne subit pas les efforts de combustion du moteur (comme cela est illustré sur les exemples des figures 2 et 3a), pour une meilleure régulation de la pression moyenne car les surpressions dans ladite chambre 32 sont moins élevées que celles dans la chambre 31 subissant les efforts de combustion. The hydraulic control circuit 37 further comprises at least one conduit 37e connecting at least one of the hydraulic chambers 31, 32 to an oil outlet 70. A second non-return valve 374 is disposed on said conduit 37e and allows the drain to be drained. hydraulic control circuit 37 when the pressure in said hydraulic chamber 31, 32 exceeds a determined maximum pressure due to the combustion forces and / or inertia of the engine applying to the cylinder (30). The 37th duct and the second non-return valve 374 may respectively be named subsequently, 37th drain duct and 374 drain valve. They make it possible to prevent the average pressure in the hydraulic chambers 31, 32 from being too high and that 'it imposes complex sealing solutions in the control cylinder 30. In other words, they make it possible to regulate the average pressure in the hydraulic chambers 31.32. It is favorable to connect the drain pipe 37e to the hydraulic chamber 32 which is not subjected to the combustion forces of the engine (as illustrated in the examples of FIGS. 2 and 3a), for better regulation of the average pressure because the overpressures in said chamber 32 are lower than those in chamber 31 undergoing combustion forces.
Notons que le système de commande hydraulique 3 pourrait néanmoins fonctionner avec un circuit hydraulique de commande 37 dépourvu de conduit de vidange 37e et de clapet de vidange 374 : la particularité d'avoir des chambres hydrauliques 31,32 de sections équivalentes permet le pilotage et l'asservissement du système 3, quelle que soit la pression moyenne dans les chambres 31,32. Cette pression moyenne augmenterait jusqu'à un niveau de stabilisation correspondant à l'arrêt de la fonction de regavage (c'est-à-dire lorsque la pression instantanée dans la (ou les) chambre (s) hydraulique (s) 31,32 reliée (s) à l'alimentation d'huile 60 via le conduit 37d et le clapet de regavage 373 ne passe plus en dessous de la pression d'alimentation). Cependant, selon les points de fonctionnement, la pression moyenne stabilisée pourrait être élevée, typiquement supérieure à 500 bars et nécessiterait une étanchéité adaptée aux niveaux de pression instantanée maximum atteignables dans les chambres hydrauliques 31,32. Note that the hydraulic control system 3 could nevertheless operate with a hydraulic control circuit 37 devoid of drain pipe 37e and drain valve 374: the particularity of having hydraulic chambers 31,32 of equivalent sections allows the piloting and the 'servo-control of the system 3, regardless of the average pressure in the chambers 31,32. This average pressure would increase to a stabilization level corresponding to the stopping of the regavage function (i.e. when the instantaneous pressure in the hydraulic chamber (s) 31.32 connected to the oil supply 60 via the pipe 37d and the rewash valve 373 no longer goes below the supply pressure). However, depending on the operating points, the stabilized average pressure could be high, typically greater than 500 bars and would require a seal adapted to the maximum instantaneous pressure levels attainable in the hydraulic chambers 31, 32.
Avantageusement, le circuit hydraulique de commande 37 est porté par le corps 30b du vérin de commande 30. En pratique les conduits 37a,37b,37c,37d,37e sont aménagés par perçage dans ledit corps 30b ; le dispositif de distribution fluidique 371a,372 et les premier et deuxième clapets anti-retour 373,374 sont intégrés dans le corps 30b. L'alimentation en huile 60 est extérieure au vérin de commande 30, elle est typiquement reliée au circuit de lubrification du moteur. Enfin, le vérin de commande 30 comprend un dispositif de rappel 34, tendant à ramener ledit vérin 30 à une longueur correspondant au taux de compression maximum. Notons qu'en fonction de l'implantation du vérin de commande 30 dans le moteur, le taux de compression maximum pourra correspondre à sa longueur minimale ou maximale. A faible régime, les efforts de combustion exercés sur le vérin de commande 30 (tendant à amener le système à taux minimum) sont supérieurs aux efforts d'inertie (tendant à amener le système à taux maximum). Du fait des sections équivalentes, le vérin de commande 30 a donc plus de facilité à aller dans sa position correspondant à taux minimum que dans sa position correspondant à taux maximum, car il y a potentiellement plus d'effort pour le faire. Le dispositif de rappel 34 permet d'exercer un effort supplémentaire (en plus des efforts d'inertie) pour accroitre la rapidité de changement de longueur du vérin 30 vers le taux maximum et ainsi ne pas pénaliser la consommation de carburant et les émissions de pollution. Comme illustré sur les exemples des figures 2 et 3a, le dispositif de rappel 34 est disposé dans la chambre hydraulique 31 qui subit les efforts de combustion du moteur. Advantageously, the hydraulic control circuit 37 is carried by the body 30b of the control cylinder 30. In practice, the conduits 37a, 37b, 37c, 37d, 37e are formed by drilling in said body 30b; the fluid distribution device 371a, 372 and the first and second non-return valves 373,374 are integrated in the body 30b. The oil supply 60 is external to the control cylinder 30, it is typically connected to the engine lubrication circuit. Finally, the control cylinder 30 comprises a return device 34, tending to bring said cylinder 30 to a length corresponding to the maximum compression ratio. Note that depending on the location of the control cylinder 30 in the engine, the maximum compression ratio may correspond to its minimum or maximum length. At low speed, the combustion forces exerted on the control cylinder 30 (tending to bring the system to minimum rate) are greater than the inertia forces (tending to bring the system to maximum rate). Because of the equivalent sections, the control jack 30 therefore has an easier time going to its position corresponding to minimum rate than to its position corresponding to maximum rate, because there is potentially more effort to do so. The return device 34 makes it possible to exert an additional effort (in addition to the inertia forces) to increase the speed of change of length of the jack 30 towards the maximum rate and thus not to penalize fuel consumption and pollution emissions. . As illustrated in the examples of Figures 2 and 3a, the return device 34 is arranged in the hydraulic chamber 31 which is subjected to the combustion forces of the engine.
Grâce au dispositif de rappel 34, le système de commande hydraulique 3 selon l'invention autorise donc l'atteinte effective des taux de compression variables entre taux minimum et taux maximum, ainsi qu'un changement de taux efficace, c'est- à-dire avec une bonne dynamique, entre taux minimum et taux maximum, et vice versa. Thanks to the return device 34, the hydraulic control system 3 according to the invention therefore allows the effective attainment of the variable compression ratios between the minimum rate and the maximum rate, as well as an effective rate change, that is to say. say with a good dynamic, between minimum rate and maximum rate, and vice versa.
Le dispositif de rappel 34 (par exemple un ressort) est typiquement dimensionné pour ramener le vérin de commande 30 de la position (longueur) correspondant à un taux de compression minimum à la position correspondant à un taux de compression maximum, en moins de 2 secondes, dans des conditions de régime moteur à environ 1000 tours par minute. Ce dimensionnement prend en compte la pré-charge et la raideur du dispositif de rappel 34, en adéquation avec le calibrage de perte de charge du (ou des) conduits de transfert 37a,37b,37c reliant les deux chambres hydrauliques 31,32 entre elles. Bien sûr, le dispositif de rappel 34 doit par ailleurs autoriser le changement de taux vers le taux de compression minimum, par les efforts de combustion, avec une dynamique acceptable, typiquement en moins de 0,5 à 0,8 secondes, dans des conditions de régime moteur à environ 1000 tours par minute (tpm). The return device 34 (for example a spring) is typically sized to return the control cylinder 30 from the position (length) corresponding to a minimum compression ratio to the position corresponding to a maximum compression ratio, in less than 2 seconds. , under engine speed conditions of about 1000 revolutions per minute. This dimensioning takes into account the pre-load and the stiffness of the return device 34, in line with the calibration of the pressure drop of (or des) transfer conduits 37a, 37b, 37c connecting the two hydraulic chambers 31, 32 together. Of course, the return device 34 must also allow the rate change to the minimum compression ratio, by the combustion forces, with an acceptable dynamic, typically in less than 0.5 to 0.8 seconds, under conditions. engine speed to approximately 1000 revolutions per minute (rpm).
A titre d'exemple, si l'on considère un système de commande hydraulique 3, conçu pour un moteur à taux de compression variable (100), du type illustré à la figure 8, et dont la cinématique conduit à un effort maximum à l'extrémité du vérin de commande 30 de 31kN à 1500tpm pour une pression dans le cylindre de combustion de 120bar, et de lOkN pour une pression de combustion de 55bar. A 5500tpm, ces efforts deviennent 40kN pour une pression de combustion de 120bar, et 15kN pour une pression de combustion de 55bar. Le diamètre du piston 30a est choisi à 47mm pour limiter la pression dans le vérin de commande 30 à l'effort maximum. Pour assurer un rappel en position de taux de compression maximum à faible régime, le ressort 34 présente une précharge de 200N, et une raideur de 50N/mm. By way of example, if we consider a hydraulic control system 3, designed for an engine with variable compression ratio (100), of the type illustrated in FIG. 8, and the kinematics of which leads to a maximum force at l end of the control cylinder 30 of 31kN at 1500rpm for a pressure in the combustion cylinder of 120bar, and 10kN for a combustion pressure of 55bar. At 5500rpm, these forces become 40kN for a combustion pressure of 120bar, and 15kN for a combustion pressure of 55bar. The diameter of the piston 30a is chosen at 47mm to limit the pressure in the control cylinder 30 to the maximum force. To ensure a return to the position of maximum compression ratio at low speed, the spring 34 has a preload of 200N, and a stiffness of 50N / mm.
Un orifice calibré de 2mm entre les deux chambres hydrauliques 31,32, situé sur le conduit de transfert 37c permet, dans cette configuration, une vitesse de variation du taux maximum au taux minimum de 0.35s à 1500tpm, et de 0.17s à 5500tpm. Un orifice calibré de 1mm, situé sur le conduit 37c, permet une vitesse de variation de taux de 0.84s à 1500tpm, et 0.53s à 5500tpm. A calibrated orifice of 2mm between the two hydraulic chambers 31, 32, located on the transfer duct 37c allows, in this configuration, a speed of variation from the maximum rate to the minimum rate of 0.35s at 1500rpm, and of 0.17s at 5500rpm. A calibrated 1mm orifice, located on duct 37c, allows a rate variation speed of 0.84s at 1500rpm, and 0.53s at 5500rpm.
Pour changer le taux du taux de compression minimum vers le taux de compression maximum, la configuration décrite précédemment, avec un orifice de 2mm situé sur le conduit de transfert 37b, mène à une vitesse de remontée du taux minimum au taux maximum de 1.13s à 1500 tpm, et de 0.37s à 5500 tpm, tandis qu'un orifice de 1mm, situé sur le conduit 37b, permet une vitesse de variation du taux minimum au taux maximum de 1.9s à 1500tpm et de 0.67s à 5500tpm. To change the ratio from the minimum compression ratio to the maximum compression ratio, the configuration described previously, with a 2mm orifice located on the transfer duct 37b, leads to a rate of rise from the minimum rate to the maximum rate of 1.13s at 1500 rpm, and from 0.37s to 5500 rpm, while a 1mm orifice, located on duct 37b, allows a speed of variation from the minimum rate to the maximum rate of 1.9s at 1500rpm and of 0.67s at 5500rpm.
Cet exemple illustre l'impact de la configuration du circuit hydraulique 37 sur la dynamique du système de commande 3. On peut noter que l'augmentation de la raideur du ressort 34, ou de sa précharge, aurait conduit à des écarts différents entre les temps de changement de taux à bas régime et à haut régime, et aurait également nécessité d'autres diamètres d'orifice calibré sur les conduits 37a,37b,37c dans le circuit hydraulique 37. This example illustrates the impact of the configuration of the hydraulic circuit 37 on the dynamics of the control system 3. It can be noted that the increase in the stiffness of the spring 34, or of its preload, would have led to different differences between the times. rate change at low speed and at high speed, and would also have required other calibrated orifice diameters on the conduits 37a, 37b, 37c in the hydraulic circuit 37.
Selon le premier mode de réalisation illustré sur la figure 2, le dispositif de distribution fluidique 371a comprend un obturateur piloté à deux positions, dont une position bloque la communication fluidique entre les deux chambres 31,32 et l'autre position autorise la communication fluidique entre les deux chambres 31,32, dans les deux sens de circulation. According to the first embodiment illustrated in FIG. 2, the fluidic distribution device 371a comprises a two-position controlled shutter, one position of which blocks the fluidic communication between the two chambers 31, 32 and the other position allows the fluidic communication between the two rooms 31,32, in both directions of circulation.
Ce premier mode de réalisation est basé sur un fonctionnement synchrone du système de commande hydraulique 3, c'est-à-dire que le pilotage du dispositif de distribution fluidique 371a doit être synchronisé avec les cycles moteur. Par exemple, pour déplacer le piston 30a vers la longueur maximale du vérin 30 (correspondant par exemple à un taux de compression minimum), il est nécessaire d'autoriser la communication fluidique entre les chambres 31,32 lorsque les efforts de combustion et/ou d'inertie tendent à augmenter la pression dans la première chambre 31 (ou chambre supérieure sur la figure 2), ce qui provoquera un transfert d'huile de la première chambre 31 vers la deuxième chambre 32 (ou chambre inférieure) ; il est séquentiellement nécessaire de bloquer la communication fluidique entre les chambres 31,32 lorsque les efforts de combustion et/ou d'inertie tendent à augmenter la pression dans la chambre inférieure 32, de manière à éviter de transférer de l'huile de la chambre inférieure 32 vers la chambre supérieure 31. Le principe inverse doit être mis en œuvre pour déplacer le piston 30a vers la longueur minimale du vérin 30 (correspondant par exemple à un taux de compression maximum du moteur). This first embodiment is based on synchronous operation of the hydraulic control system 3, that is to say that the control of the fluidic distribution device 371a must be synchronized with the engine cycles. For example, to move the piston 30a towards the maximum length of the cylinder 30 (corresponding for example to a minimum compression ratio), it is necessary to allow fluid communication between the chambers 31, 32 when the combustion forces and / or inertia tend to increase the pressure in the first chamber 31 (or upper chamber in Figure 2), which will cause oil transfer from the first chamber 31 to the second chamber 32 (or lower chamber); it is sequentially necessary to block the fluid communication between the chambers 31, 32 when the combustion and / or inertia forces tend to increase the pressure in the lower chamber 32, so as to avoid transferring oil from the chamber lower 32 to the upper chamber 31. The reverse principle must be implemented to move the piston 30a towards the minimum length of the cylinder 30 (corresponding for example to a maximum compression ratio of the engine).
Dans ce premier mode de réalisation, le dispositif de distribution fluidique piloté 371a doit être compatible avec un temps de commutation très court, typiquement 1 ms. Un obturateur électrohydraulique, directement implanté dans le corps du vérin 30b, pourrait remplir cette fonction et requerrait une connexion filaire entre le vérin 30 mobile et un contrôle moteur fixe. Un dispositif de distribution fluidique purement hydraulique, comme illustré sur la figure 2, est également envisageable. Dans ce cas, il faut prendre en compte un retard temporel pour 1'actionnement du dispositif 371a, du fait du conduit d'huile reliant la partie pilotage 80 dudit dispositif. In this first embodiment, the controlled fluidic distribution device 371a must be compatible with a very short switching time, typically 1 ms. An electro-hydraulic shutter, directly installed in the body of the cylinder 30b, could fulfill this function and would require a wired connection between the mobile cylinder 30 and a fixed motor control. A purely hydraulic fluid distribution device, as illustrated in FIG. 2, can also be envisaged. In this case, it is necessary to take into account a time delay for the actuation of the device 371a, due to the oil duct connecting the pilot part 80 of said device.
Selon le deuxième mode de réalisation illustré sur la figure 3a, le circuit hydraulique de commande 37 comporte au moins deux conduits de transfert 37b,37c reliant les deux chambres hydrauliques 31,32 entre elles. Le dispositif de distribution fluidique 372 comprend deux obturateurs pilotés 372b,372c à deux positions, et deux clapets orientés 372b',372c'. Un premier obturateur 372b et un premier clapet orienté 372b' sont portés par un premier conduit de transfert 37b, pour bloquer ou autoriser la circulation d'huile de la deuxième chambre 32 (ou chambre inférieure sur la figure 3) vers la première chambre 31 (ou chambre supérieure). Un deuxième obturateur 372c et un deuxième clapet orienté 372c' sont portés par un deuxième conduit de transfert 37c, pour bloquer ou autoriser la circulation d'huile de la première chambre 31 vers la deuxième chambre 32. Dans ce mode de réalisation, il peut être intéressant de calibrer la perte de charge de chaque conduit reliant les deux chambres hydrauliques de manière à gérer la vitesse de déplacement du vérin de commande 30. According to the second embodiment illustrated in FIG. 3a, the hydraulic control circuit 37 comprises at least two transfer conduits 37b, 37c connecting the two hydraulic chambers 31, 32 to one another. The fluidic distribution device 372 comprises two piloted shutters 372b, 372c with two positions, and two oriented valves 372b ', 372c'. A first shutter 372b and a first oriented valve 372b 'are carried by a first transfer duct 37b, to block or allow the circulation of oil from the second chamber 32 (or lower chamber in FIG. 3) to the first chamber 31 ( or superior room). A second shutter 372c and a second oriented valve 372c 'are carried by a second transfer duct 37c, to block or allow the circulation of oil from the first chamber 31 to the second chamber 32. In this embodiment, it can be interesting to calibrate the pressure drop of each duct connecting the two hydraulic chambers so as to manage the speed of movement of the control cylinder 30.
Ce deuxième mode de réalisation est basé sur un fonctionnement asynchrone du système de commande hydraulique 3, c'est-à-dire que le pilotage du dispositif de distribution fluidique 372 est indépendant des cycles moteur. This second embodiment is based on an asynchronous operation of the hydraulic control system 3, that is to say that the control of the fluidic distribution device 372 is independent of the engine cycles.
Par exemple, pour déplacer le piston 30a vers la longueur maximale du vérin 30 (correspondant par exemple à un taux de compression minimum du moteur), le premier obturateur 372b autorise la communication fluidique entre les chambres 31,32, alors que le deuxième obturateur 372c bloque la communication fluidique. Ainsi, lorsque les efforts de combustion et/ou d'inertie tendent à augmenter la pression dans la chambre supérieure 31, un transfert d'huile s'opère de la chambre supérieure 31 vers la chambre inférieure 32 ; le remplissage progressif (avec l'alternance des cycles moteur) de la chambre inférieure 32 et le vidage progressif de la chambre supérieureFor example, to move the piston 30a towards the maximum length of the cylinder 30 (corresponding for example to a minimum compression ratio of the engine), the first shutter 372b allows fluid communication between the chambers 31, 32, while the second shutter 372c blocks fluid communication. Thus, when the combustion and / or inertia forces tend to increase the pressure in the upper chamber 31, an oil transfer takes place from the upper chamber 31 to the lower chamber 32; the progressive filling (with the alternation of the engine cycles) of the lower chamber 32 and the progressive emptying of the upper chamber
31 donnent lieu au déplacement du piston 30a, vers la longueur maximale du vérin de commande 30. 31 give rise to the displacement of the piston 30a, towards the maximum length of the control cylinder 30.
Pour déplacer le piston 30a vers la longueur minimale du vérin 30 (correspondant par exemple à un taux de compression maximum du moteur), le deuxième obturateur 372c est placé dans une position autorisant la communication fluidique entre les chambres 31,32, alors que le premier obturateur 372b est placé dans une position bloquant la communication fluidique. Il ne peut ainsi s'opérer un transfert d'huile que de la chambre inférieure 32 vers la chambre supérieure 31 ; le remplissage progressif (avec l'alternance des cycles moteur) de la chambre supérieure 31 et le vidage progressif de la chambre inférieureTo move the piston 30a towards the minimum length of the cylinder 30 (corresponding for example to a maximum compression ratio of the engine), the second shutter 372c is placed in a position allowing fluid communication between the chambers 31, 32, while the first obturator 372b is placed in a position blocking fluid communication. It is thus only possible to transfer oil from the lower chamber 32 to the upper chamber 31; the progressive filling (with the alternation of the engine cycles) of the upper chamber 31 and the progressive emptying of the lower chamber
32 donnent lieu au déplacement du piston 30a, vers la longueur minimale du vérin de commande 30. 32 give rise to the displacement of the piston 30a, towards the minimum length of the control cylinder 30.
Dans ce deuxième mode de réalisation de l'invention, la position de chaque obturateur 372b,372c au repos (c'est-à-dire sans actionnement par le circuit de pilotage 80) peut être choisie de différentes manières, selon la stratégie privilégiée en cas de défaillance du circuit de pilotage 80. Selon une première option (figure 3b (i)), les deux obturateurs 372b,372c au repos bloquent toute communication fluidique, ce qui fige le taux de compression à sa valeur en cas de défaillance du circuit de pilotage 80. In this second embodiment of the invention, the position of each shutter 372b, 372c at rest (that is to say without actuation by the control circuit 80) can be chosen in different ways, according to the preferred strategy in failure of the pilot circuit 80. According to a first option (FIG. 3b (i)), the two shutters 372b, 372c at rest block all fluid communication, which freezes the compression ratio at its value in the event of failure of the pilot circuit 80.
Selon une deuxième option (figure 3b (ii)), l'obturateur 372b dans sa position au repos autorise la communication fluidique de la chambre inférieure 32 vers la chambre supérieure 31, alors que l'obturateur 372c, dans sa position au repos, bloque la communication fluidique dans le sens inverse. En cas de défaillance du circuit de pilotage 80, la longueur du vérin de commande 30 va progressivement varier vers sa longueur minimale. Si cette longueur minimale correspond par exemple à un taux de compression maximum, cette option assure le meilleur rendement et la meilleure efficacité du moteur, limitant la pollution occasionnée, mais cela réduit la plage d'utilisation du moteur (limitation en régime et/ou en charge). According to a second option (Figure 3b (ii)), the shutter 372b in its rest position allows fluid communication from the lower chamber 32 to the upper chamber 31, while the shutter 372c, in its rest position, blocks fluid communication in the reverse direction. In the event of failure of the control circuit 80, the length of the control cylinder 30 will gradually vary towards its minimum length. If this minimum length corresponds for example to a maximum compression ratio, this option ensures the best performance and the best efficiency of the engine, limiting the pollution caused, but this reduces the range of use of the engine (limitation in speed and / or in charge).
Selon une troisième option (figure 3b (iii)), l'obturateur 372c dans sa position au repos autorise la communication fluidique de la chambre supérieure 31 vers la chambre inférieure 32, alors que l'obturateur 372b, dans sa position au repos, bloque la communication fluidique dans le sens inverse. En cas de défaillance du circuit de pilotage 80, la longueur du vérin de commande 30 va progressivement varier vers sa longueur maximale. Si cette longueur maximale correspond par exemple à un taux de compression minimum, cette option permet de conserver les performances du moteur (pas de limitation en régime et/ou en charge) mais réduit son efficacité et son rendement ce qui augmente la pollution produite par le moteur. According to a third option (Figure 3b (iii)), the shutter 372c in its rest position allows fluid communication from the upper chamber 31 to the lower chamber 32, while the shutter 372b, in its rest position, blocks fluid communication in the reverse direction. In the event of failure of the control circuit 80, the length of the control cylinder 30 will gradually vary towards its maximum length. If this maximum length corresponds for example to a minimum compression ratio, this option makes it possible to maintain the performance of the engine (no limitation in speed and / or load) but reduces its efficiency and its output which increases the pollution produced by the engine. engine.
Revenant à la description du circuit de pilotage 80 dont le rôle est de piloter le dispositif de distribution fluidique 371a,372 du système de commande 3, deux variantes sont proposées. Returning to the description of the control circuit 80, the role of which is to control the fluid distribution device 371a, 372 of the control system 3, two variants are proposed.
Selon une première variante du système de commande hydraulique 3 s'appliquant à tout mode de réalisation de l'invention, le dispositif de distribution fluidique 371a,372 piloté est actionné par un circuit électrique de pilotage externe. Dans ce cas, un fil électrique doit relier une partie fixe du moteur, dans laquelle est implanté le circuit électrique de pilotage, et le dispositif de distribution fluidique 371a,372 préférentiellement intégré au vérin de commande 30, qui constitue une partie mobile dans le moteur. According to a first variant of the hydraulic control system 3 applying to any embodiment of the invention, the controlled fluid distribution device 371a, 372 is actuated by an external electrical control circuit. In this case, an electric wire must connect a fixed part of the motor, in which the electrical control circuit is located, and the fluid distribution device 371a, 372 preferably integrated into the control cylinder 30, which constitutes a movable part in the motor. .
Selon une deuxième variante du système de commande hydraulique 3 s'appliquant à tout mode de réalisation de l'invention, le dispositif de distribution fluidique 371a,372 piloté (qui est inclus dans le circuit hydraulique de commande 37) est actionné par un circuit hydraulique de pilotage 80. En d'autres termes, le dispositif de distribution fluidique 371a,372 est basculé d'une position passante à une position bloquante (et vice versa) au moyen de la pression d'un fluide issu dudit circuit hydraulique de pilotage 80. Ce fluide peut être de l'eau, du gaz ou de l'huile. According to a second variant of the hydraulic control system 3 applying to any embodiment of the invention, the controlled fluid distribution device 371a, 372 (which is included in the hydraulic control circuit 37) is actuated by a hydraulic circuit. control 80. In other words, the fluid distribution device 371a, 372 is tilted from a pass position to a blocking position (and vice versa) by means of the pressure of a fluid issuing from said hydraulic control circuit 80 This fluid can be water, gas or oil.
Les premier et deuxième modes de réalisation de l'invention présentés respectivement sur les figures 2 et 3a illustrent un circuit hydraulique de pilotage 80 essentiellement externe au vérin de commande 30. Au moins un canal fluidique 81 relie le dispositif de distribution fluidique 371a,372 au circuit de pilotage 80. Ce dernier peut par exemple comporter un distributeur de pilotage 82 actionné électriquement permettant de délivrer une pression de fluide dans le canal fluidique 81 ou de bloquer l'arrivée de fluide dans ledit canal 81, pour basculer le dispositif de distribution fluidique 371a,372 respectivement dans une ou l'autre de ses positions. The first and second embodiments of the invention presented respectively in Figures 2 and 3a illustrate a hydraulic control circuit 80 essentially external to the control cylinder 30. At least one fluidic channel 81 connects the fluidic distribution device 371a, 372 to the pilot circuit 80. The latter may for example comprise an electrically actuated pilot valve 82 making it possible to deliver a fluid pressure in the fluidic channel 81 or to block the arrival of fluid in said channel 81, in order to switch the fluidic distribution device 371a, 372 respectively in one or the other of its positions.
Avantageusement, le distributeur de pilotage 82 est raccordé au circuit de lubrification du moteur, le fluide est alors de l'huile à basse pression. Advantageously, the pilot valve 82 is connected to the engine lubrication circuit, the fluid is then low pressure oil.
Notons que le dispositif de distribution fluidique 371a,372 pourra être piloté, donc actionné, directement par la pression de fluide issue du circuit de pilotage 80 : il faudra alors que le canal fluidique 81 permette la communication directe entre le fluide de pilotage et ledit dispositif 371a,372. Alternativement, le dispositif de distribution fluidique 371a,372 pourra être actionné mécaniquement, par une force exercée par un élément mécanique d'actionnement, ce dernier étant déplacé par la pression de fluide issue du circuit de pilotage 80. Note that the fluidic distribution device 371a, 372 can be controlled, therefore actuated, directly by the fluid pressure coming from the pilot circuit 80: it will then be necessary for the fluidic channel 81 to allow direct communication between the pilot fluid and said device 371a, 372. Alternatively, the fluidic distribution device 371a, 372 could be actuated mechanically, by a force exerted by a mechanical actuating element, the latter being moved by the fluid pressure coming from the pilot circuit 80.
De manière avantageuse, dans la deuxième variante du système de commande hydraulique 3, chaque obturateur piloté 371a,372b,372c du dispositif de distribution fluidique 371a,372 est disposé selon un axe transverse T, normal à un axe longitudinal L de déplacement du piston 30a dans le corps 30b du vérin de commande 30. Un obturateur 371a,372b,372c pourra par exemple être formé par un tiroir hydraulique linéaire dont l'axe central est parallèle à l'axe transverse T. Cette orientation évite à l'obturateur 371a,372b,372c de subir les efforts d'inertie et/ou de combustion s'appliquant au vérin de commande 30, efforts qui pourraient venir parasiter les efforts de commande nécessaires à 1'actionnement des obturateurs. Advantageously, in the second variant of the hydraulic control system 3, each controlled shutter 371a, 372b, 372c of the fluid distribution device 371a, 372 is arranged along a transverse axis T, normal to a longitudinal axis L of displacement of the piston 30a in the body 30b of the control cylinder 30. A shutter 371a, 372b, 372c may for example be formed by a linear hydraulic slide whose central axis is parallel to the transverse axis T. This orientation avoids the shutter 371a, 372b, 372c to undergo the inertia and / or combustion forces applied to the control cylinder 30, forces which could interfere with the control forces necessary for actuating the shutters.
Un exemple particulier de mise en œuvre du système de commande hydraulique 3 va maintenant être décrit, en référence aux figures 6a à 6e. Cet exemple est basé sur le deuxième mode de réalisation précédemment décrit, c'est-à-dire impliquant un dispositif de distribution fluidique 372 comprenant deux obturateurs pilotés 372b,372c et deux clapets orientés 372b',372c'. Il est également basé sur un pilotage du dispositif de distribution fluidique 372 par actionnement mécanique. A particular example of the implementation of the hydraulic control system 3 will now be described, with reference to FIGS. 6a to 6e. This example is based on the second embodiment previously described, that is to say involving a fluid distribution device 372 comprising two piloted shutters 372b, 372c and two oriented valves 372b ', 372c'. It is also based on controlling the fluid distribution device 372 by mechanical actuation.
On retrouve sur la figure 6a le vérin de commande 30, avec son piston 30a mobile dans le corps 30b. Le piston 30a est prolongé par un pied 30a' s'étendant au-delà du corps 30b selon un axe longitudinal L, et susceptible d'établir une liaison pivot avec un élément mobile du moteur. We find in Figure 6a the control cylinder 30, with its piston 30a movable in the body 30b. The piston 30a is extended by a foot 30a 'extending beyond the body 30b according to a longitudinal axis L, and capable of establishing a pivot connection with a mobile element of the engine.
Une première chambre 31 et une deuxième chambre 32 sont définies dans le corps 30b du vérin de commande 30, de part et d'autre du piston 30a qui intègre des étanchéités. La première chambre 31 (ou chambre supérieure) est nommée « chambre haute pression » car reprenant les efforts de combustion ; par opposition, la deuxième chambre 32 (ou chambre inférieure) est appelée « chambre basse pression ». Le remplissage et le vidage respectifs de la première 31 et de la deuxième 32 chambres modifient la longueur du vérin de commande 30. A first chamber 31 and a second chamber 32 are defined in the body 30b of the control cylinder 30, on either side of the piston 30a which incorporates seals. The first chamber 31 (or upper chamber) is called a “high pressure chamber” because it takes up the combustion forces; in contrast, the second chamber 32 (or lower chamber) is called a “low pressure chamber”. The respective filling and emptying of the first 31 and of the second 32 chambers modify the length of the control cylinder 30.
Le corps 30b du vérin de commande 30 comprend deux paliers latéraux 35 coaxiaux d'axe transverse T normal à l'axe longitudinal L (figure 6b). Ces paliers latéraux 35 sont destinés à établir un liaison pivot avec une partie du moteur (soit fixe solidaire du bloc moteur, soit mobile, selon la configuration d'intégration du système de commande hydraulique 3 dans le moteur). La position latérale desdits paliers 35 permet de compacter le vérin de commande 30 par rapport à un vérin classique avec les points de liaison aux extrémités, limitant ainsi l'encombrement dans le bloc moteur. Avantageusement, chaque palier latéral 35 présente un épaulement 35a pour assurer le positionnement du vérin 30, selon l'axe transverse T, dans le moteur. The body 30b of the control cylinder 30 comprises two coaxial side bearings 35 of transverse axis T normal to the longitudinal axis L (FIG. 6b). These lateral bearings 35 are intended to establish a pivot connection with a part of the engine (either fixed integral with the engine block, or mobile, depending on the configuration of integration of the hydraulic control system 3 in the engine). The lateral position of said bearings 35 makes it possible to compact the control cylinder 30 with respect to a conventional cylinder with the connection points at the ends, thus limiting the bulk in the engine block. Advantageously, each lateral bearing 35 has a shoulder 35a to ensure the positioning of the jack 30, along the transverse axis T, in the engine.
Le vérin de commande 30 comprend une entretoise 52 rapportée sur chaque palier latéral 35 et destinée à être solidaire de la partie du moteur susmentionnée (figure 6c). La liaison entre les paliers latéraux 35 et les entretoises rapportées 52 autorise le mouvement d'oscillation du vérin de commande 30 nécessaire au fonctionnement du système de commande 3 dans le moteur 100. Pour cela, chaque entretoise rapportée 52 présente un logement interne cylindrique, pour accueillir un palier latéral 35. L'enveloppe externe de l'entretoise 52 pourra également être cylindrique. Il peut néanmoins être avantageux de prévoir une enveloppe externe ovoïde pour bloquer tout mouvement de la rotation de l'entretoise 52 vis-à-vis de la partie du moteur à laquelle elle est fixée. On peut aussi prévoir que le logement interne accueillant un palier latéral 35 soit excentré par rapport à l'axe central de l'enveloppe externe de l'entretoise rapportée 52, qui sera choisie dans ce cas cylindrique ou ovoïde : cela procure également une fonction anti-rotation. The control cylinder 30 comprises a spacer 52 attached to each side bearing 35 and intended to be integral with the above-mentioned part of the motor (FIG. 6c). The connection between the side bearings 35 and the added spacers 52 allows the oscillating movement of the control cylinder 30 necessary for the operation of the control system 3 in the engine 100. For this, each added spacer 52 has a cylindrical internal housing, for this purpose. accommodate a side bearing 35. The outer casing of the spacer 52 may also be cylindrical. It may nevertheless be advantageous to provide an ovoid outer casing to block any movement of the rotation of the spacer 52 vis-à-vis the part of the engine to which it is fixed. Provision can also be made for the internal housing accommodating a lateral bearing 35 to be eccentric with respect to the central axis of the outer casing of the attached spacer 52, which will be chosen in this case cylindrical or ovoid: this also provides an anti-corrosion function. -rotation.
Le vérin de commande 30 comprend une bague épaulée 53 intercalée entre chaque palier latéral 35 et son entretoise rapportée 51, pour limiter les frottements liés au mouvement d'oscillation du vérin de commande 30 et pour reprendre partiellement les efforts de combustion ainsi que ceux d'inertie subis par ledit vérin 30. The control cylinder 30 comprises a shouldered ring 53 interposed between each side bearing 35 and its attached spacer 51, to limit the friction associated with the oscillation movement of the control cylinder 30 and to partially take up the combustion forces as well as those of inertia undergone by said jack 30.
Le dispositif de distribution fluidique 372 du circuit hydraulique de commande 37 comprend un premier tiroir hydraulique 372b et un deuxième tiroir hydraulique 372c, respectivement logés dans le premier palier latéral 35 et le deuxième palier latéral 35 du vérin 30 (figure 6d). Préférentiellement, les deux tiroirs sont disposés selon l'axe transversal T, coaxialement avec les paliers latéraux 35. The fluidic distribution device 372 of the hydraulic control circuit 37 comprises a first hydraulic spool 372b and a second hydraulic spool 372c, respectively housed in the first lateral bearing 35 and the second lateral bearing 35 of the cylinder 30 (FIG. 6d). Preferably, the two drawers are arranged along the transverse axis T, coaxially with the side bearings 35.
Un déplacement selon l'axe transversal T du premier tiroir hydraulique 372b permet par exemple d'établir une circulation d'huile (schématisée par les flèches noires sur la figure 6d) de la première chambre 31 vers la deuxième chambre 32, via des premiers passages 37b aménagés dans le corps 30b du vérin 30. En pratique, le déplacement du premier tiroir 372b met en communication les premiers passages 37b menant aux deux chambres 31,32, et un premier clapet anti-retour 372b' est disposé sur lesdits premiers passages 37b, autorisant uniquement une circulation de fluide de la première chambre 31 vers la deuxième chambre 32 (figure 6e, (i), (ii)). A movement along the transverse axis T of the first hydraulic spool 372b makes it possible for example to establish a circulation of oil (shown diagrammatically by the black arrows in FIG. 6d) from the first chamber 31 to the second chamber 32, via first passages 37b arranged in the body 30b of the jack 30. In practice, the movement of the first slide 372b places the first passages 37b leading to the two chambers 31, 32 in communication, and a first non-return valve 372b 'is arranged on said first passages 37b , allowing only a circulation of fluid from the first chamber 31 to the second chamber 32 (FIG. 6e, (i), (ii)).
Un déplacement du deuxième tiroir hydraulique 372c permet d'établir une circulation d'huile de la deuxième chambre 32 vers la première chambre 31, via des deuxièmes passages 37c aménagés dans le corps 30b. En pratique, le déplacement du deuxième tiroir 372c met en communication les deuxièmes passages 37c menant aux deux chambres 31,32, et un deuxième clapet anti retour 372c' est disposé sur lesdits deuxièmes passages 37c, autorisant uniquement une circulation de fluide de la deuxième chambre 32 vers la première chambre 31. A displacement of the second hydraulic spool 372c makes it possible to establish an oil circulation of the second chamber 32 to the first chamber 31, via second passages 37c arranged in the body 30b. In practice, the movement of the second slide 372c places the second passages 37c leading to the two chambers 31, 32 in communication, and a second non-return valve 372c 'is disposed on said second passages 37c, allowing only a circulation of fluid from the second chamber 32 to the first chamber 31.
Pour générer le déplacement des tiroirs hydrauliques 372b,372c, le système 3 met en œuvre un circuit hydraulique de pilotage 80. Le circuit de pilotage 80 est alimenté par un fluide sous pression (par exemple, de l'huile) venant de la partie du moteur à laquelle le corps 30b est relié. To generate the displacement of the hydraulic spools 372b, 372c, the system 3 implements a hydraulic pilot circuit 80. The pilot circuit 80 is supplied with a pressurized fluid (for example, oil) coming from the part of the valve. motor to which the body 30b is connected.
Dans l'exemple illustré en figure 6d, l'actionnement des tiroirs hydrauliques 372b,372c est opéré par voie mécanique. Une telle option peut être avantageuse en ce qu'elle évite une gestion parfois complexe de l'étanchéité entre parties fixe et mobile ou entre deux parties mobiles dans le moteur. Pour cela, chaque tiroir hydraulique 372b,372c est destiné à être en contact via une bille 803 avec un piston de pilotage 801,802 porté par l'entretoise rapportée 52 (figure 6c (ii), figure 6d). In the example illustrated in FIG. 6d, the actuation of the hydraulic spools 372b, 372c is effected mechanically. Such an option can be advantageous in that it avoids sometimes complex management of the seal between fixed and mobile parts or between two mobile parts in the engine. For this, each hydraulic slide 372b, 372c is intended to be in contact via a ball 803 with a pilot piston 801,802 carried by the attached spacer 52 (FIG. 6c (ii), FIG. 6d).
Chaque piston de pilotage 801,802 peut être déplacé par la pression d'huile (schématisée par les flèches blanches sur la figure 6e) dans le circuit de pilotage 80, pour induire le déplacement du tiroir hydraulique 372b,372c associé. L'huile de ce circuit 80 est acheminée via des conduits 81 jusqu'à un logement interne de chaque entretoise rapportée 52, lequel logement accueille le piston de pilotage 801,802. Each pilot piston 801,802 can be moved by the oil pressure (shown schematically by the white arrows in FIG. 6e) in the pilot circuit 80, to induce the displacement of the associated hydraulic spool 372b, 372c. The oil from this circuit 80 is conveyed via conduits 81 to an internal housing of each attached spacer 52, which housing accommodates the pilot piston 801,802.
Le contact mécanique entre le piston de pilotage 801,802 et le tiroir hydraulique 372b,372c est assuré par une bille 803, qui est capable d'accommoder l'oscillation du vérin 30 par rapport aux autres parties en liaison du moteur, dont notamment par rapport au piston de pilotage 801,802. Cette configuration apporte une solution simple et robuste de pilotage externe du circuit hydraulique de commande 37 du système 3. The mechanical contact between the pilot piston 801,802 and the hydraulic spool 372b, 372c is provided by a ball 803, which is capable of accommodating the oscillation of the jack 30 relative to the other connecting parts of the engine, including in particular relative to the pilot piston 801.802. This configuration provides a simple and robust solution for the external piloting of the hydraulic control circuit 37 of the system 3.
Le circuit hydraulique de commande 37 comporte au moins un perçage 37d et un clapet de regavage 373, entre une alimentation d'huile et la chambre inférieure 32 (figure 6e (i), (iii)). Le clapet de regavage 373 est configuré de manière à autoriser une circulation d'huile depuis l'alimentation d'huile vers la deuxième chambre 32, lorsque la pression dans ladite chambre 32 est inférieure à la pression d'alimentation. The hydraulic control circuit 37 comprises at least one bore 37d and a rewash valve 373, between an oil supply and the lower chamber 32 (FIG. 6e (i), (iii)). Regwash valve 373 is configured so as to allow circulation of oil from the oil supply to the second chamber 32, when the pressure in said chamber 32 is lower than the supply pressure.
Le circuit hydraulique de commande 37 comporte au moins un perçage 37e et un clapet de décharge 374 entre la deuxième chambre hydraulique 32 et l'extérieur du vérin 30, de manière à évacuer de l'huile du circuit de commande 37, lorsque la pression dans ladite chambre 32 excède une pression maximale déterminée. On pourra par exemple choisir un clapet de décharge 374 dont la pression d'ouverture est supérieure à 200 bars ou 300 bars, pour éviter la mise en œuvre de solutions complexes d'étanchéité dans le système hydraulique de commande 3. The hydraulic control circuit 37 comprises at least one bore 37e and a relief valve 374 between the second hydraulic chamber 32 and the outside of the cylinder 30, so as to evacuate oil from the control circuit 37, when the pressure in said chamber 32 exceeds a determined maximum pressure. For example, it is possible to choose a relief valve 374 whose opening pressure is greater than 200 bars or 300 bars, to avoid the implementation of complex sealing solutions in the hydraulic control system 3.
Le système de commande hydraulique 3, et en particulier le système 3 selon l'exemple de mise en œuvre précité est particulièrement adapté à une intégration dans un moteur à taux de compression variable de type VCT. The hydraulic control system 3, and in particular the system 3 according to the aforementioned example of implementation, is particularly suitable for integration into a variable compression ratio engine of the VCT type.
Ce type de moteur VCT, dont une mise en œuvre selon l'état de la technique est illustrée en figure 7, comprend deux groupes distincts de composants : This type of VCT motor, an implementation of which according to the state of the art is illustrated in FIG. 7, comprises two distinct groups of components:
• L'attelage mobile 1 intégrant les pistons de combustion 10, les bielles principales 11, les organes de renvoi 12 et le vilebrequin 13, • The mobile coupling 1 integrating the combustion pistons 10, the main connecting rods 11, the return members 12 and the crankshaft 13,
• Le système de commande 2 intégrant les bielles de commande 20, l'arbre à excentriques 22, les leviers 23,25, la biellette 24 et le moyen de pilotage électrique 26. Le système de commande hydraulique 3 selon l'invention peut remplacer le système de commande précité 2, comme illustré sur la figure 8. Dans cette utilisation, le piston 30a du vérin de commande 30 est destiné à être relié, via son pied 30a' à un organe de renvoi d'un attelage mobile du moteur, et le corps 30b du vérin de commande 30 est destiné à être relié à une partie fixe 51 du moteur. • The control system 2 integrating the control rods 20, the eccentric shaft 22, the levers 23,25, the rod 24 and the electric control means 26. The hydraulic control system 3 according to the invention can replace the aforementioned control system 2, as illustrated in FIG. 8. In this use, the piston 30a of the control cylinder 30 is intended to be connected, via its foot 30a 'to a return member of a movable coupling of the engine, and the body 30b of the control cylinder 30 is intended to be connected to a fixed part 51 of the engine.
Le système de commande hydraulique 3 conforme à la présente invention, pour un moteur à taux de compression variable, comprend un ou plusieurs vérin (s) de commande 30 tel(s) que précédemment décrit(s). L'attelage mobile 1 du moteur 100 de type VCT, intégrant les pistons de combustion 10, les bielles principales 11, les organes de renvoi 12 et le vilebrequin 13 peut rester inchangé ainsi que la partie supérieure du moteur. La forme des vérins de commande 30 est conçue pour s'intégrer dans l'encombrement actuel du moteur, évitant ainsi d'augmenter l'entraxe du moteur 100. The hydraulic control system 3 according to the present invention, for an engine with variable compression ratio, comprises one or more control ram (s) as described above. The mobile coupling 1 of the VCT-type engine 100, integrating the combustion pistons 10, the main connecting rods 11, the return members 12 and the crankshaft 13 can remain unchanged as well as the upper part of the engine. The shape of the control jacks 30 is designed to fit into the current size of the engine, thus avoiding increasing the center distance of the engine 100.
Bien entendu, l'invention n'est pas limitée aux modes de réalisation et aux exemples décrits, et on peut y apporter des variantes de réalisation sans sortir du cadre de l'invention tel que défini par les revendications. Of course, the invention is not limited to the embodiments and to the examples described, and variant embodiments can be provided without departing from the scope of the invention as defined by the claims.

Claims

REVENDICATIONS
1. Système de commande hydraulique (3) pour un moteur à taux de compression variable (100) comprenant : 1. Hydraulic control system (3) for a variable compression ratio engine (100) comprising:
- un vérin de commande (30) comportant un piston (30a) et un corps (30b) dans lequel deux chambres hydrauliques (31,32) de sections équivalentes sont définies de part et d'autre du piston (30a), ledit piston (30a) étant apte à se déplacer dans le corps (30b) pour commander le taux de compression du moteur, - a control cylinder (30) comprising a piston (30a) and a body (30b) in which two hydraulic chambers (31,32) of equivalent sections are defined on either side of the piston (30a), said piston ( 30a) being able to move in the body (30b) to control the compression ratio of the engine,
- un circuit hydraulique de commande (37) comportant :- a hydraulic control circuit (37) comprising:
* au moins un conduit (37a,37b,37c) reliant les deux chambres hydrauliques (31,32) entre elles, et un dispositif de distribution fluidique (371a,372) piloté pour établir ou bloquer une communication fluidique entre lesdites chambres (31,32), le système de commande hydraulique (3) étant caractérisé en ce que : * at least one conduit (37a, 37b, 37c) connecting the two hydraulic chambers (31,32) to each other, and a fluid distribution device (371a, 372) controlled to establish or block fluid communication between said chambers (31, 32), the hydraulic control system (3) being characterized in that:
- le circuit hydraulique de commande (37) comporte: - the hydraulic control circuit (37) comprises:
* au moins un conduit (37d) reliant au moins une des chambres hydrauliques (32) et une alimentation d'huile (60) à basse pression, soit entre 2 et 6 bars, et un premier clapet anti-retour (373) pour regaver le circuit hydraulique de commande (37) lorsque la pression dans ladite chambre hydraulique (32) passe en-deçà de ladite basse pression du fait des efforts de combustion et/ou d'inertie du moteur s'appliquant au vérin (30), * at least one conduit (37d) connecting at least one of the hydraulic chambers (32) and an oil supply (60) at low pressure, ie between 2 and 6 bars, and a first non-return valve (373) for rewashing the hydraulic control circuit (37) when the pressure in said hydraulic chamber (32) falls below said low pressure due to combustion forces and / or inertia of the engine applying to the cylinder (30),
* au moins un conduit (37e) reliant au moins une des chambres hydrauliques (32) et une évacuation d'huile (70), et un clapet de décharge (374), pour vidanger le circuit hydraulique de commande (37) lorsque la pression dans ladite chambre hydraulique (32) excède une pression maximale déterminée, * at least one conduit (37e) connecting at least one of the hydraulic chambers (32) and an oil outlet (70), and a relief valve (374), to drain the hydraulic control circuit (37) when the pressure in said hydraulic chamber (32) exceeds a determined maximum pressure,
- le vérin de commande (30) comprend un dispositif de rappel (34) tendant à ramener ledit vérin (30) à une longueur correspondant à un taux de compression maximum du moteur. - the control cylinder (30) comprises a return device (34) tending to reduce said cylinder (30) to a length corresponding to a maximum compression ratio of the engine.
2. Système de commande hydraulique (3) selon la revendication précédente, dans lequel le conduit (37e) muni du clapet de décharge (374) relie l'évacuation d'huile (70) et la chambre (32), parmi les deux chambres hydrauliques, qui ne subit pas des efforts de combustion du moteur. 2. Hydraulic control system (3) according to the preceding claim, wherein the conduit (37e) provided with the relief valve (374) connects the oil discharge (70) and the chamber (32), among the two chambers. hydraulic, which is not subjected to the combustion forces of the engine.
3. Système de commande hydraulique (3) selon l'une des revendications précédentes, dans lequel le dispositif de rappel (34) est disposé dans la chambre (31), parmi les deux chambres hydrauliques, qui subit des efforts de combustion du moteur. 3. Hydraulic control system (3) according to one of the preceding claims, wherein the return device (34) is disposed in the chamber (31), among the two hydraulic chambers, which undergoes combustion forces of the engine.
4. Système de commande hydraulique (3) selon l'une des revendications précédentes, dans lequel le circuit hydraulique de commande (37) est porté par le corps (30b) du vérin de commande (30). 4. Hydraulic control system (3) according to one of the preceding claims, wherein the hydraulic control circuit (37) is carried by the body (30b) of the control cylinder (30).
5. Système de commande hydraulique (3) selon l'une des revendications précédentes, dans lequel le dispositif de distribution fluidique piloté (371a, 372) est actionné par un circuit électrique de pilotage. 5. Hydraulic control system (3) according to one of the preceding claims, wherein the controlled fluid distribution device (371a, 372) is actuated by an electrical control circuit.
6. Système de commande hydraulique (3) selon l'une des revendications 1 à 4, dans lequel le dispositif de distribution fluidique piloté (371a, 372) est actionné par un circuit hydraulique de pilotage (80). 6. Hydraulic control system (3) according to one of claims 1 to 4, wherein the controlled fluid distribution device (371a, 372) is actuated by a hydraulic control circuit (80).
7. Système de commande hydraulique (3) selon l'une des revendications précédentes, dans lequel le dispositif de distribution fluidique (371a) comprend un obturateur piloté à deux positions, dont une position bloque la communication fluidique entre les deux chambres (31,32) et l'autre position autorise la communication fluidique entre les deux chambres (31,32), dans les deux sens de circulation. 7. Hydraulic control system (3) according to one of the preceding claims, wherein the fluid distribution device (371a) comprises a two-position piloted shutter, one position of which blocks communication. fluidic between the two chambers (31,32) and the other position allows fluid communication between the two chambers (31,32), in both directions of circulation.
8. Système de commande hydraulique (3) selon l'une des revendications 1 à 6, dans lequel le circuit hydraulique de commande (37) comporte au moins deux conduits (37b,37c) reliant les deux chambres hydrauliques (31,32) entre elles, et dans lequel le dispositif de distribution fluidique (372) comprend deux obturateurs pilotés (372b,372c) à deux positions et deux clapets orientés (372b',372c'), un premier obturateur (372b) et un premier clapet orienté (372b') étant portés par un premier conduit (37b), pour bloquer ou autoriser la circulation d'huile de la première chambre (31) vers la deuxième chambre (32), et un deuxième obturateur (372c) et un deuxième clapet orienté (372c') étant portés par un deuxième conduit (37c), pour bloquer ou autoriser la circulation d'huile de la deuxième chambre (32) vers la première chambre (31). 8. Hydraulic control system (3) according to one of claims 1 to 6, wherein the hydraulic control circuit (37) comprises at least two conduits (37b, 37c) connecting the two hydraulic chambers (31,32) between them, and in which the fluid distribution device (372) comprises two piloted shutters (372b, 372c) with two positions and two oriented valves (372b ', 372c'), a first shutter (372b) and a first oriented valve (372b ') being carried by a first duct (37b), to block or allow the circulation of oil from the first chamber (31) to the second chamber (32), and a second shutter (372c) and a second oriented valve (372c ') being carried by a second duct (37c), to block or allow the circulation of oil from the second chamber (32) to the first chamber (31).
9. Système de commande hydraulique (3) selon l'une des deux revendications précédentes, dans lequel chaque obturateur piloté (371a,372b,372c) est disposé selon un axe transverse (T), normal à un axe longitudinal (L) de déplacement du piston (30a) dans le corps (30b) du vérin de commande (30). 9. Hydraulic control system (3) according to one of the two preceding claims, wherein each controlled shutter (371a, 372b, 372c) is arranged along a transverse axis (T), normal to a longitudinal axis (L) of displacement. of the piston (30a) in the body (30b) of the control cylinder (30).
10. Système de commande hydraulique (3) selon l'une des revendications précédentes, dans lequel : 10. Hydraulic control system (3) according to one of the preceding claims, wherein:
* le piston (30a) du vérin de commande (30) est destiné à être relié à un organe de renvoi (12) d'un attelage mobile (1) du moteur (100), et * the piston (30a) of the control cylinder (30) is intended to be connected to a return member (12) of a movable coupling (1) of the engine (100), and
* le corps (30b) du vérin de commande (30) est destiné à être relié à une partie fixe (51) du moteur (100). * the body (30b) of the control cylinder (30) is intended to be connected to a fixed part (51) of the engine (100).
EP20841973.9A 2019-12-05 2020-12-04 Hydraulic control system for a variable compression ratio engine Withdrawn EP4069959A1 (en)

Applications Claiming Priority (2)

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FR1913798A FR3104209B1 (en) 2019-12-05 2019-12-05 hydraulic control system for a variable compression ratio engine
PCT/FR2020/052280 WO2021111088A1 (en) 2019-12-05 2020-12-04 Hydraulic control system for a variable compression ratio engine

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FR3104209A1 (en) 2021-06-11
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FR3104209B1 (en) 2022-06-03
CN114930006A (en) 2022-08-19

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