GB1599553A - Regulating system for driving means more particularly a hydrostatic travelling drive - Google Patents
Regulating system for driving means more particularly a hydrostatic travelling drive Download PDFInfo
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- GB1599553A GB1599553A GB889/78A GB88978A GB1599553A GB 1599553 A GB1599553 A GB 1599553A GB 889/78 A GB889/78 A GB 889/78A GB 88978 A GB88978 A GB 88978A GB 1599553 A GB1599553 A GB 1599553A
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- control
- restrictor
- prime mover
- pressure
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- 230000001105 regulatory effect Effects 0.000 title claims description 33
- 230000002706 hydrostatic effect Effects 0.000 title claims description 31
- 230000005540 biological transmission Effects 0.000 claims description 43
- 230000000670 limiting effect Effects 0.000 claims description 28
- 230000036961 partial effect Effects 0.000 claims description 13
- 230000002829 reductive effect Effects 0.000 claims description 10
- 230000033228 biological regulation Effects 0.000 claims description 9
- 230000007246 mechanism Effects 0.000 claims description 8
- 238000011144 upstream manufacturing Methods 0.000 claims description 6
- 230000001419 dependent effect Effects 0.000 claims description 3
- 230000004048 modification Effects 0.000 claims description 3
- 238000012986 modification Methods 0.000 claims description 3
- 230000003247 decreasing effect Effects 0.000 claims description 2
- 239000000446 fuel Substances 0.000 description 12
- 238000002347 injection Methods 0.000 description 11
- 239000007924 injection Substances 0.000 description 11
- 230000001276 controlling effect Effects 0.000 description 4
- 239000000243 solution Substances 0.000 description 4
- 238000010586 diagram Methods 0.000 description 3
- 230000009467 reduction Effects 0.000 description 3
- 238000002485 combustion reaction Methods 0.000 description 2
- 238000010276 construction Methods 0.000 description 2
- 238000000034 method Methods 0.000 description 2
- 102100021277 Beta-secretase 2 Human genes 0.000 description 1
- 101710150190 Beta-secretase 2 Proteins 0.000 description 1
- 238000010521 absorption reaction Methods 0.000 description 1
- 230000004075 alteration Effects 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 230000006378 damage Effects 0.000 description 1
- 230000003467 diminishing effect Effects 0.000 description 1
- 238000006073 displacement reaction Methods 0.000 description 1
- 239000012530 fluid Substances 0.000 description 1
- 230000006698 induction Effects 0.000 description 1
- 230000002441 reversible effect Effects 0.000 description 1
- 230000000630 rising effect Effects 0.000 description 1
- 230000007704 transition Effects 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60W—CONJOINT CONTROL OF VEHICLE SUB-UNITS OF DIFFERENT TYPE OR DIFFERENT FUNCTION; CONTROL SYSTEMS SPECIALLY ADAPTED FOR HYBRID VEHICLES; ROAD VEHICLE DRIVE CONTROL SYSTEMS FOR PURPOSES NOT RELATED TO THE CONTROL OF A PARTICULAR SUB-UNIT
- B60W10/00—Conjoint control of vehicle sub-units of different type or different function
- B60W10/04—Conjoint control of vehicle sub-units of different type or different function including control of propulsion units
- B60W10/06—Conjoint control of vehicle sub-units of different type or different function including control of propulsion units including control of combustion engines
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60W—CONJOINT CONTROL OF VEHICLE SUB-UNITS OF DIFFERENT TYPE OR DIFFERENT FUNCTION; CONTROL SYSTEMS SPECIALLY ADAPTED FOR HYBRID VEHICLES; ROAD VEHICLE DRIVE CONTROL SYSTEMS FOR PURPOSES NOT RELATED TO THE CONTROL OF A PARTICULAR SUB-UNIT
- B60W10/00—Conjoint control of vehicle sub-units of different type or different function
- B60W10/04—Conjoint control of vehicle sub-units of different type or different function including control of propulsion units
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60W—CONJOINT CONTROL OF VEHICLE SUB-UNITS OF DIFFERENT TYPE OR DIFFERENT FUNCTION; CONTROL SYSTEMS SPECIALLY ADAPTED FOR HYBRID VEHICLES; ROAD VEHICLE DRIVE CONTROL SYSTEMS FOR PURPOSES NOT RELATED TO THE CONTROL OF A PARTICULAR SUB-UNIT
- B60W10/00—Conjoint control of vehicle sub-units of different type or different function
- B60W10/10—Conjoint control of vehicle sub-units of different type or different function including control of change-speed gearings
- B60W10/101—Infinitely variable gearings
- B60W10/103—Infinitely variable gearings of fluid type
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60W—CONJOINT CONTROL OF VEHICLE SUB-UNITS OF DIFFERENT TYPE OR DIFFERENT FUNCTION; CONTROL SYSTEMS SPECIALLY ADAPTED FOR HYBRID VEHICLES; ROAD VEHICLE DRIVE CONTROL SYSTEMS FOR PURPOSES NOT RELATED TO THE CONTROL OF A PARTICULAR SUB-UNIT
- B60W10/00—Conjoint control of vehicle sub-units of different type or different function
- B60W10/10—Conjoint control of vehicle sub-units of different type or different function including control of change-speed gearings
- B60W10/11—Stepped gearings
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60W—CONJOINT CONTROL OF VEHICLE SUB-UNITS OF DIFFERENT TYPE OR DIFFERENT FUNCTION; CONTROL SYSTEMS SPECIALLY ADAPTED FOR HYBRID VEHICLES; ROAD VEHICLE DRIVE CONTROL SYSTEMS FOR PURPOSES NOT RELATED TO THE CONTROL OF A PARTICULAR SUB-UNIT
- B60W30/00—Purposes of road vehicle drive control systems not related to the control of a particular sub-unit, e.g. of systems using conjoint control of vehicle sub-units
- B60W30/18—Propelling the vehicle
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16H—GEARING
- F16H61/00—Control functions within control units of change-speed- or reversing-gearings for conveying rotary motion ; Control of exclusively fluid gearing, friction gearing, gearings with endless flexible members or other particular types of gearing
- F16H61/38—Control of exclusively fluid gearing
- F16H61/40—Control of exclusively fluid gearing hydrostatic
- F16H61/42—Control of exclusively fluid gearing hydrostatic involving adjustment of a pump or motor with adjustable output or capacity
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16H—GEARING
- F16H61/00—Control functions within control units of change-speed- or reversing-gearings for conveying rotary motion ; Control of exclusively fluid gearing, friction gearing, gearings with endless flexible members or other particular types of gearing
- F16H61/38—Control of exclusively fluid gearing
- F16H61/40—Control of exclusively fluid gearing hydrostatic
- F16H61/42—Control of exclusively fluid gearing hydrostatic involving adjustment of a pump or motor with adjustable output or capacity
- F16H61/433—Pump capacity control by fluid pressure control means
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16H—GEARING
- F16H61/00—Control functions within control units of change-speed- or reversing-gearings for conveying rotary motion ; Control of exclusively fluid gearing, friction gearing, gearings with endless flexible members or other particular types of gearing
- F16H61/38—Control of exclusively fluid gearing
- F16H61/40—Control of exclusively fluid gearing hydrostatic
- F16H61/46—Automatic regulation in accordance with output requirements
- F16H61/465—Automatic regulation in accordance with output requirements for achieving a target input speed
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- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Chemical & Material Sciences (AREA)
- Combustion & Propulsion (AREA)
- General Engineering & Computer Science (AREA)
- Transportation (AREA)
- Automation & Control Theory (AREA)
- Physics & Mathematics (AREA)
- Fluid Mechanics (AREA)
- Control Of Fluid Gearings (AREA)
Description
(54) REGULATING SYSTEM FOR DRIVING MEANS,
MORE PARTICULARLY A HYDROSTATIC
TRAVELLING DRIVE
(71) We, SAUER GETRIEBE KG, a West
German Company, of Krokamp 35, 2350 Neumiinster 6, West Germany, do hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- The invention relates to a control system for driving means, with a prime mover and a hydrostatic transmission in which the transmission ratio of the hydrostatic transmission is coupled to the rotational speed of the prime mover. The term regulating system in the present case is to cover regulating systems and/or control systems.
Known embodiments of hydrostatic travelling transmissions are in use in which the transmission ratio of the hydrostatic transmission is controlled in dependence on the rotational speed of the prime mover.
Irrespective of differences in construction known hydromechanical regulating systems operate in accordance with the basic principle described below:
Primary adjustment (hydraulic pump adjustment) of the hydrostatic transmission (in a closed circuit) is obtained by means of a final control cylinder which is driven by a differential control pressure, performs a final control motion and thus alters the displacement of the hydraulic pump which is associated with the transmission. The delivery of a control pump, driven at the prime mover speed or a speed proportional thereto and having a constant delivery rate, is conducted through a restrictor in order to obtain the differential control pressure. The differential pressure produced across the said restrictor is approximately proportional to the square of the prime mover speed.
This differential pressure is used as the control signal for adjusting the hydraulic pump so that the transmission ratio of the hydrostatic transmission is linked to the rotational speed of the prime mover.
The operator of a vehicle influences the prime mover by actuating a driving pedal.
In carburettor engines the driving pedal acts on the throttle flap of the induction manifold. The rotational speed of the prime mover will then be defined by the position of the throttle flap and the loading torque.
In engines with fuel injection the driving pedal acts on an injection device. -More particularly, the regulating rod of an injection pump and therefore the set speed of a centrifugal governor of the injection pump is adjusted in diesel engines. So long as the load moment is less than the limiting moment for the given speed the regulator will maintain a constant speed of the prime mover within the speed regulating span, namely by varying the injection rate. If the load moment exceeds the limiting moment (this applies to carburettor engines and to fuel injection engines) the engine speed will drop. The prime mover will then be "held back" and in an extreme case it will be "stalled".
Adapting the power requirements of the vehicle to the capacity of the prime mover (limiting load regulation) is normally performed in a hydrostatic transmission by the displaced volume of the hydraulic pump associated with the hydrostatic transmission being reduced as the working pressure increases (rising hydraulic motor torque) so that a constant torque of the hydraulic pump shaft is maintained. Experience has shown that optimum utilization of the available prime mover power is not possible with this kind of control over the entire working range of the travelling drive. Partranges with insufficient utilization of the power alternate with ranges of excessive engine hold-back (this again results in insufficient utilization of the available power). Particularly unfavourable conditions occur if the prime mover is required to drive additional loads such as hydraulic power pumps, large fans, power take-off shafts and the like in addition to the load which comprises more particularly the hydrostatic transmission and the vehicle since the power consumption of such supplementary loads is not covered by the regulating system of the travelling drive.
The known art discloses problem solutions (German Offenlegungschrift 24 27 112, German Auslegeschrift 23 63 335) in which the driving pedal additionally alters the setting value of a driving restrictor (restrictor cross-section, spring prestress) in order to improve the limiting load regulating conditions. With this procedure the proportionally which exists between the prime mover speed and the differential control pressure and therefore the transmission ratio is altered in dependence on the position of the driving pedal. In another known problem solution (German
Offenlegungsschrift 24 59 800) an additional control signal is obtained from the limiting load moment of a diesel engine (for example position of the piston of the injection pump) which said signal additionally acts on the position of the hydraulic pump (displaced volume) and therefore on the transmission ratio. Another known circuit ("Hydrostatikantriebe:Grenzlast- und Sekundärregelung" by Bahde, published in "Fluid", April 1973, more particularly page 78, Figure 8) makes use of a mechanical centrifugal governor which acts on an element of the hydraulic control system in the sense of reducing the differential control pressure for the hydraulic pump of the hydrostatic transmission if the engine hold-back becomes excessive so that the load on the prime mover is relieved. The known art also discloses electrohydraulic regulating systems (Moog system,
Application 109, brochure published 1975) in which the rotational speed of the prime mover and the transmission ratio is linked by electrical means. In this case only the rotational speed of the prime mover is the input signal for regulating the limiting load so that power matching between the prime mover, the travelling drive and supplementary loads is better than would be possible with hydromechanical regulating systems.
In addition to the previously-mentioned disadvantages all known regulating systems have a tendency to instability in the transition zone between partial load regulation (in diesel engines the working range of the injection pump governor) and limiting load regulation (adjustment of the hydraulic pump of the hydrostatic transmission).
The deceleration characteristics of known travelling drives are unsatisfactory if power is suppled to the drive via its output shaft, for example when travelling downhill.
If the power supplied in this manner exceeds the deceleration power of the prime mover at its maximum permissible speed the latter will rise excessively, a feature which may lead to the destruction of the prime mover. The operator can prevent "overspeeding" of the prime mover by operating the "inching pedal" (which also has additional functions) and thus prevent a reduction of the volume displaced by the hydraulic pump. The regulating system does not act in the correct sense in this case. The supply of power to the output shaft (deceleration operation) in most known systems causes adjustment of the hydrostatic transmission in the sense of increasing over loading of the prime mover, i.e. exceeding its deceleration capacity due to the linking between the rotational speed of the prime mover and the transmission ratio.
According to the present invention there is provided a propulsion mechanism comprising a prime mover, a hydrostatic transmission and a control system therefor that receives an input signal, the control system including means for generating a reference signal dependent upon prime mover speed, and the input signal, said reference signal being used to derive at least one control signal for the prime mover, and at least one control signal for the hydrostatic transmission in accordance with the operational state of the propulsion mechanism, overloading of the prime mover being prevented by limiting load regulation through adjustment of the transmission ratio.
Driving means in the form of a travelling drive are substantially subject to four operating states which can be described as follows, by reference to the prime mover.
Limiting Load Range
The transmission ratio of the hydrostatic transmission must be adjusted by limiting load regulation so that its required input power is adapted to the maximum available power of the prime mover which is offered to the travelling drive.
Partial Load Range
Partial load regulation must adapt the prime mover output to the power required by the hydrostatic transmission which is lower in this operating state than the maximum available power of the prime mover.
Normal Deceleration Range
Power flows from the output to the prime mover (pusher operation in vehicles). The power supplied to the prime mover is less than its maximum possible deceleration power (where appropriate taking into account the power absorbed by supplementary loads).
Emergency Deceleration Range
The power transmitted by the output to the hydraulic motor of the transmission is greater than the maximum deceleration power of the prime mover (risk of overspeeding). Part of the power must be absorbed by additional elements of the transmission (deceleration restrictor, bypass restrictor. and/or (controllable) supplementary loads of the prime mover).
The regulating system according to the invention recognizes the operating state of the travelling drive from processing of the input signal and the speed signal of the prime mover and produces control signals for the final control elements for the purpose of:
Influencing the prime mover (in internal combustion engines: fuel supply, rotational speed, throttle flap position),
Influencing the displaced volume of the hydraulic pump,
Influencing the displaced volume of the hydraulic motor,
Influencing the efficiency of the transmission, for example by increasing the deceleration power through raising the hydraulic losses (deceleration restrictor) and/or of the volumetric losses (bypass restrictor leading to the hydraulic motor) and
Influencing the power absorption (or where appropriate delivery) of supplementary loads (operating systems such as hydraulic power means, take-off shaft, fan, water pumps and the like which are driven by the prime mover parallel with the travelling drive)
so that optimum characteristics of the travelling drive are obtained for each operating state.
Further advantages, features and fields of application of the present invention are disclosed in the description hereinbelow given by way of example only at embodiments in conjunction with the figures of the accompanying drawings in which:
Figure 1 is a basic circuit of known control systems for a travelling drive with hydrostatic transmission,
Figure 2 is a basic diagram of the control system of the invention for a travelling drive with a hydrostatic transmission,
Figures 3a, b are circuits of embodiments, modified with respect to those in Figure. 2 and relating to the element group of the control system of the invention for producing the reference signal,
Figure 4 is a circuit of another embodiment of the element group of the control system of the invention for producing the reference signal,
Figures 5a, b, c, d show a practical embodiment in longitudinal section of the element group for producing the reference signal with different circuit modifications, and
Figure 6 is a graph differential control pressures plotted against the control oil flow with different operating ranges of the travelling drive.
Figure 1 shows a basic diagram of known control systems for a travelling drive with a hydrostatic transmission. The travelling drive comprises a prime mover 1 in the form of an internal combustion engine, usually a diesel engine, and a hydrostatic transmission with a hydraulic pump 2 and a hydraulic motor 3. The hydraulic pump and where appropriate the hydraulic motor are variable. The prime mover 1 drives the hydraulic pump 2 the delivery of which drives the hydraulic motor 3 in a closed circuit which in turn drives a load 4, for example the vehicle. A final control cylinder 5 for adjusting the hydraulic pump 2 is controlled by a differential pressure
Ap2. The adjusting direction of the hydraulic pump 2 and therefore the direction of rotation of the hydraulic motor 3 is defined by means of a directional valve 6. A control pump 7, driven at the speed of the prime mover, delivers a control oil flow q, which is proportional to the rotational speed of the prime mover 1 and produces across a restrictor 8 the differential pressure Ap2 which is required for controlling the final control cylinder 5. The said differential pressure is approximately proportional to the square of the prime mover speed. The prior art discloses solutions in which the differential pressure across the restrictor 8 is boosted by hydraulic means (pressure booster) and the output signal of the pressure booster is utilized for controlling the final control cylinder 5. This enables the differential pressure across the restrictor 8 to be kept small.
The prestressing force of a spring (= speed set point) of a centrifugal governor 10 associated with an injection pump 11 of the diesel engine 1 is generally set by means of a driving pedal 9. The injection pump 11 supplies the diesel engine 1 with the maximum amount of fuel until the prestressing force of the spring, preselected by means of the driving pedal 9, is compensated by the centrifugal forces exerted by the flywheel weights of the centrifugal governor. This regulation maintains the rotational speed of the diesel engine 1 at a constant value defined by the driving pedal 9 for as long as the diesel engine 1 is not overloaded.
A differential control pressure Ap2, which adjusts the hydraulic pump 2 by means of the final control cylinder 5 in dependence on the rotational speed of the diesel engine 1 is produced by means of the control pump 7 in dependence on the speed of the diesel engine 1 which is preselected by means of the driving pedal 9.
A control signal which pivots the hydraulic pump 2 in the reverse direction, i.e. to reduce its swept volume, is obtained from the high pressure of the hydrostatic circuit in known solutions of the problem in order to prevent overloading of the diesel
engine (exceeding the maximum prime
mover torque). To this end the internal
forces which act on the swashplate of a hydraulic pump are used in the simplest embodiment.
The differential control pressure Ap2 across the restrictor 8 can be reduced with a constant rotational speed of the control pump 7 by means of an inching restrictor 12 which can be mechanically or hydraulically actuated by means of an inching pedal 31.
This causes the hydraulic pump 2 to be pivoted back (its swept volume is reduced), the rotational speed of the hydraulic motor 3 is reduced and the travelling speed of the vehicle is therefore also reduced.
The prime mover, in this case the diesel engine, normally also drives supplementary loads in addition to the vehicle (hydrostatic transmission 2, 3 and load 4). In the system according to Fig. 1 the power consumption of the supplementary loads 13 is not influenced by the regulating system nor is the regulating system influenced by the magnitude of the power absorbed by the supplementary loads.
Figure 2 shows a basic circuit diagram of the regulating system according to the invention for a travelling drive with a hydrostatic transmission. Substantially, the travelling drive comprises three element groups 14, 15 and 16. The elements in the power circuit, i.e. the prime mover 1, the hydraulic pump 2, the hydraulic motor 3, the load 4, the supplementary loads 13, the bypass restrictor 36, the deceleration restrictor 18 are combined as element group 14. The element group 15 comprises the final control elements which are adapted to adjust the elements in the power circuit to the extent to which these are adjustable. A final control cylinder 19 adjusts the supply of fuel to the prime mover 1, the final control cylinder 5 (associated with the directional valve 6) adjusts the hydraulic pump 2, a final control cylinder 20 (which is associated with a supplementary valve 21) adjusts the hydraulic motor 3, a final control cylinder 22 adjusts the bypass restrictor 36, a final control cylinder 23 adjusts a deceleration restrictor 18 and a final control cylinder 24 adjusts a control restrictor 25 which, in cooperation with a fixed restrictor 26, produces a differential control pressure.
The element group 16 comprises the elements which generate the reference signal Apl in dependence on the rotational speed of the prime mover 1 (the control pump 7) and in dependence on the position of the driving pedal 9a, i.e. an adjustable restrictor 17 which is actuated by the driving pedal 9, an adjustable restrictor 27 which is actuated by a final control cylinder 28, an adjustable restrictor 29 which is actuated by a final control cylinder 30 and the constant travelling restrictor 8 across which is generated the differential control pressure Ap2 for controlling the final control cylinder 5 of the hydraulic pump 2.
If the element groups 15 and 16 are regarded as an integral unit the said control unit will generate control signals Yl-YE for the elements of the power circuit in dependence on the prime mover speed and in dependence on the position of the driving pedal (and in addition in dependence on the position of the inching pedal 31 which actuates the inching restrictor 12).
The control signal Yl influences the prime mover 1;
The control signal Y2 influences the hydraulic pump 2;
The control signal Y3 influences the
hydraulic motor 3;
The control signal Y4 influences the bypass restrictor 36;
The control signal Y, influences the deceleration restrictor 18;
The control signal Y6 influences, where appropriate, adjustable supplementary loads 13.
In dependence on the incoming signals (control oil flow Q, of the control pump 7, position of the travelling pedal 9a) and in dependence on the set points which are programmed in the elements 8, 27 and 28, 29 and 30, 19, 5, 22, 23, 20, 24 with 25 and 26 of the control unit, the control unit 15, 16 detects the operating range in which the travelling drive operates and generates the control signals Y1-Y6 for adjustment of the power circuit elements in the correct direction so as to achieve optimum operating characteristics.
The operation of the regulating system for the travelling drive according to Fig. 2 will now be described in sequence for idling and starting as well as for the ranges covering partial load, limiting load, normal deceleration and emergency deceleration.
Idling
In idling the restrictor 17 is set to a small restrictor cross-section when the travelling pedal 9a is not actuated. The control oil flow Q7, which is delivered by the control pump 7 at the idling speed of the prime mover 1, produces a differential control pressure Ap1 across the restrictor 17 which is sufficient to allow the spool of the control cylinder 19 to move fully into the limiting position against the force exerted by the prestressed spring so that a minimum amount of fuel is suppled to the prime mover 1. To this end the final control cylinder 19 acts directly or via the centrifugal governor 10 on the injection pump 11. The directional valve 6 is in the middle position so that no differential control pressure Ap2 can be built up across the final control cylinder 5. The hydraulic pump 2 is therefore in the zero position (the displaced volume is equal to zero) and despite rotation of the pump shaft no oil flow is delivered to the hydraulic motor 3. At this moment the restrictor 27 is closed because the differential control pressure Ap1 does not overcome the prestress exerted by the spring of the final control cylinder 28. Due to the final control cylinder 30 being biased the restrictor 29 is closed by the differential control pressure Ap1.
Starting
To start, the directional valve 6 is actuated in accordance with the desired travelling direction. The driving pedal 9a is then actuated so that the cross-section of the restrictor 17 is enlarged and the differential control pressure Apl is reduced.
The restrictor 29 is opened (its cross-section is enlarged), the differential control pressure Ap2 across the restrictor 8 diminishes and the hydraulic pump 2 is unable to pivot. Due to the diminishing differential control pressure pl across the restrictor 17 the prestressed spring moves the piston of the cylinder 19 towards the starting position thus increasing the amount of fuel for the prime mover 1 whose rotational speed therefore increases. As the speed increases the delivery rate of the control oil flow Q, of the control pump 7 also increases. The differential control pressure Ap1 across the restrictor 17 again increases and the differential control pressure Apz across the parallel connection of the restrictors 8 and 29 increases so that the hydraulic pump 2 begins to pivot. The restrictor 29 closes as the speed increases further and the differential control pressure Apl continues to increase.
The differential control pressure Ap2 continues to increase and the hydraulic pump 2 is pivoted further. During this phase the final control cylinders 20, 22, 23 and 24 are normally in the starting position. The bypass restrictor 36 is closed, the deceleration restrictor 18 is open and the hydraulic motor 3 is at its maximum pivoting angle, i.e. it is set to its maximum displaced volume.
Partial Load Range
If the travelling drive operates in the partial load range after starting a prime mover speed corresponding to the position of the travelling pedal 9a is maintained by the final control cylinder 19 reducing the supply of fuel due to the increasing differential control pressure pl and vice versa in the event of a tendency to increase the rotational speed. The restrictors 27 and 29 and the bypass restrictor 36 are closed in the partial load range. The deceleration restrictor is open and the hydraulic motor 3 advantageously is set to a small pivoting angle (=small displaced volume, high speed, low torque) due to the final control cylinder 20 being biased with the differential control pressure pl following the preceding changeover of the supplementary valve 21.
The restrictor 25 is kept open by the final control cylinder 24 so that a differential control pressure is built up across the restrictor 26 to control a supplementary load for the purpose of absorbing power.
For example, at low speeds of the hydraulic pump 2 or of the prime mover 1 the hydraulic motor 3 should remain set to a large pivoting angle. The purpose of the supplementary valve 21 is to prevent adjustment of the hydraulic motor 1 over specific speed range of the prime mover 1.
Limiting Load Range
The speed of the prime mover 1 drops below the value called for by the travelling pedal 9a on changing into the limiting load range. The differential control pressure bp, drops and as a first reaction the fuel supplied to the prime mover 1 is increased by a corresponding adjustment of the final control cylinder 19. When the maximum supply of fuel is set (final control cylinder 19 in the zero position) and the specified speed is not maintained the prestressed spring will move the piston of the final control cylinder 30 so that the restrictor 29 is open. The differential control pressure p2 across the parallel connection of the restrictors 8 and 29 diminishes and the final control cylinder 5 resets the hydraulic pump 2 to a smaller pivoting angle, i.e. to a lower displaced volume. The hydraulic pump delivery rate will then diminish (with the speed remaining approximately constant) and the power consumed by the hydraulic pump is reduced. In the limiting load range the hydraulic motor 3 is advantageously set to a large pivoting angle (final control cylinder 20 in the spring-defined zero position).
However, it can also be set to a small angle or in intermediate positions over at least part of the limiting load range. Therestrictor 25 is closed as the differential control pressure pl diminishes. The pressure upstream of the restrictor 26 therefore drops. The power absorbed by the supplementary load which is controlled by this pressure therefore diminishes. In this operating phase the bypass restrictor 36 is closed and the deceleration restrictor 18 is open.
Normal Deceleration Range
The travelling drive changes into the normal deceleration range by sufficiently retracting the position of the travelling pedal 9a. The cross-section of the restrictor 17 diminishes, the differential control pressure p, increases and the final control cylinder 19 reduces the supply of fuel to the prime mover 1. If the restrictor 29 was open (limiting load range) the final control cylinder 30 will close this restrictor as the differential control pressure pl increases.
The rotational speed of the prime mover 1 drops because of the reduced supply of fuel.
The differential pressure p2 across the restrictor 8 diminishes and the hydraulic pump 2 is set by the spring-centred final control cylinder 5 to a smaller pivoting angle. The bypass restrictor 36 is closed, the deceleration restrictor 18 is open and operation of the supplementary valve 21 causes the hydraulic motor 3 to move over a large pivoting angle into the spring-defined starting position.
Emergency Deceleration Range
If the deceleration capacity of the prime mover 1 is insufficient, for example when travelling downhill or if the travelling pedal is rapidly retracted, the speed of the prime mover will increase beyond the predefined maximum value (=maximum idling speed).
The speed would increase until the deceleration power of the prime mover 1 is equal to the power supplied to the output shaft. This operating state is not possible in technical terms because the speed of the prime mover in deceleration operation may rise only slightly above the maximum idling speed and the deceleration power thus defined amounts to only approximately 300/, of the maximum input power.
If there is a risk of an excessive increase in the speed of the prime mover the differential control pressure pl across the restrictor 17 will rise. The prestressing force of the spring associated with tthe final control cylinder 28 will be overcome and the restrictor 27 will open. Since the
restrictor 27 is arranged parallel with the
restrictor 8 the differential pressure Ap2 will drop as a result of which the hydraulic pump is set to a smaller pivoting angle and with the high pressure remaining constant there is a reduction of the pump shaft torque which is suppled by the prime mover.
If the reduction of the hydraulic pump pivoting angle is insufficient for maintaining the loading moment of the prime mover 1 within permissible limits it will be necessary to reduce the differential operating pressure (the high pressure) which acts on the hydraulic pump. The bypass restrictor 36 and the deceleration restrictor 18 are inserted to this end into the power circuit and it is possible for either only the restrictor 36 or only the restrictor 18 or both to be present. With an increasing rotational speed of the prime mover 1 the control oil flow q7 and therefore the differential control pressure pl increases. The bypass restrictor 36 opens or the deceleration restrictor 18 closes as the spring prestress force in the final control cylinders 22 and/or 23 is overcome. Opening of the bypass restrictor 36 permits part of the delivery flow of the hydraulic motor 3 (deceleration operation) not being absorbed by the hydraulic pump. The said part returns via the bypass restrictor 36 under the differential operating pressure of the hydraulic motor 3 to the input of the motor and produces hydraulic power which is then converted into heat in the bypass restrictor.
Closing of the deceleration restrictor 18 reduces part of the differential operating pressure of the hydraulic motor 3 across the deceleration restrictor 18 so that hydraulic power is again converted into heat. Both devices (bypass restrictor 36 and/or deceleration restrictor 18) take over part of the deceleration power and therefor reduce the power transmitted by the hydraulic pump 2 to the prime mover 1 thus preventing the prime mover deceleration power being exceeded and at the same time ensuring maximum utilization of the prime mover deceleration power.
To increase the power which can be absorbed in deceleration operation by the travelling drive the differential control pressure for controllable supplementary loads can be increased additionally with the aid of the final control cylinder 24 and the control signal Y3, the elements 20, 21 are omitted) do not contain any bypass restrictor 36 (no control signal Y4, the elements 22, 36 are omitted), do not contain any deceleration restrictor 18 (no control signal Y5, the elements 18, 23 are omitted) and do not contain any means for generating a differential control pressure for controlling supplementary loads (no control signal Ya, the elements 24, 25, 26 are omitted).
Two modified embodiments 16a and 16b of the element group 16 are shown in
Figures 3a and b.
The element group 16a of Figure 3a is provided with a three-way flow regulating valve 32 which replaces the restrictor 17 in the element group 16 of Figure 2 and is operated by the travelling pedal 9b and precedes the restrictor 8. The differential control pressure åpl in this embodiment of the regulating system is produced as a pressure drop across a restrictor 33. For as long as the prime mover speed and therefore the control oil flow Q, is smaller than the set value on the three-way flow regulating valve 32 defined by the traveling pedal 9b no oil will be discharged through the restrictor 33. The differential control pressure åpl is zero. The restrictor 29 is open and maintains the differential control pressure åp2 across the parallel connection of restrictors 29 and 8 at a low value. The hydraulic pump 2 pivots into a small pivoting angle. The restrictor 27 is closed.
on reaching the rotational speed demanded by the position of the travelling pedal 9b and when slightly exceeding this speed part of the control oil flow Q7 supplied to the threeway flow regulating valve 32 is discharged via the restrictor 33 and the control oil flow through the restrictor 8, which generates the differential control pressure Ap2, remains constant despite the increase in the rotational speed of the prime mover 1. This results in a differential control pressure åp1 which biases the final control cylinder 30 to close the restrictor 29. The differential control pressure åp2 increases, the hydraulic pump 2 pivots to a larger displaced volume and even if the speed of the prime mover 1 is increased it will remain at the displaced volume that was reached when the restrictor 29 was set to minimum cross-section (zero where appropriate) and the restrictor 27 was not then open. A twoway flow regulating valve with a pressure limiting valve can be inserted into the bypass in place of the three-way flow regulating valve 32. The operation of the element group 16a in all other respects corresponds to that of the element group 16 of Fig. 2. Its operating characteristic differs because of the manner in which the differential control pressures åp, and Ap2 are generated differently from the manner of the element group 16.
In place of the three-way flow regulating valve 32 of Figure 3a the element group 16b of Figure 3b is provided with a restrictor 34 which is actuated by the travelling pedal 9c
When the set pressure of a pressure valve 37 is exceeded part of the control oil flow Q7 will flow through the pressure valve 37 and through a restrictor 35 to the reservoir. In dependence on the operating state of the vehicle drive, i.e. the rotational speed of the prime mover 1 relative to the setting of the restrictor 34 a differential control pressure Asp1, is obtained from the pressures upstream of the restrictor 35 and of the restrictor 8 to act on the final control cylinders 28, 30, 20, 22, 23 and 24. The element group 16b fulfils the same function as the element group 16 of Figure 2.
However, it has a different characteristic.
Figure 4 shows another embodiment 16c of the element group 16 of Fig. 2. The adjustable restrictor 17 in the element group
16c is replaced by a constant orifice restrictor 17a and the prestress of the springs in the final control cylinders 19a, 28a and 30a is altered by means of the travelling pedal 9d. The differential control pressure åpl in the element groups 16, 16a, and 16b was adapted to the prestress of the springs associated with the final control
cylinders 19, 28, 30, 20, 22, 23, 24 by altering the settings of the restrictors, flow regulating valves and pressure valves but in the element group 16c the prestress of the springs associated with the final control cylinders
19a, 28a, 30a (and where appropriate, but not shown, of the final control cylinders 20a, 22a, 23a, 24a) is adapted to the differential control pressure across the restrictor 17a, which said pressure appears
across the restrictor 17a at a specific control oil flowrate, i.e. at a specific prime mover speed. The elements 38, 39, 40 permit any
desired alteration of the proportionality between the position of the travelling pedal 9d and the prestress of the springs in the final control cylinders 19a, 28a and 30a. In an embodiment of suitable construction the springs of the final control cylinders 19a, 28a and 30a can be combined into a single spring system.
Figure Sa shows a practical embodiment of a control block 41 which performs the functions or part of the functions of the elements associated with the element group
16 for generating the reference signal.
Figure Sa illustrates the circuit of the control block 41 corresponding to the element group 16b of Figure 3b. The elements 8, 35, 27, 29 of Figure 3b correspond to the elements 8a, 35a, 27a and 29a of Figure Sa. The spring of the final control cylinder 28 corresponds to the spring 43 and the spring of the final control cylinder 30 corresponds to the spring 42 of
Fig. Sa. The control block 41 operates as follows:
A main cone 46 is in its open position when the control oil flow Q7 of the control pump 7 is lower than the control oil flow which corresponds to the required prime mover speed. The cross-section of the restrictor 29a is large and the differential control pressure Ap, is small. With an increasing prime mover speed and an increasing control oil flow rate of the control pump 7 the pressure upstream of the restrictor 34 rises. The pressure valve 37 opens and control oil flows via the restrictor 35a in a spool 47 to the reservoir. Pressure is built up upstream of the restrictor 35a so that the differential pressure åpl generated between the two connections 48 and 49 of the control block 41 is such that the main cone 46 is moved into the closed position against the force exerted by the spring 42.
The cross-section of the restrictor 29a is closed. Only the cross-section of the restrictor 8a is available to the flow of control oil so that the differential control pressure Ap, increases. If the rotational speed of the prime mover 1 and therefore that of the control pump 7 increase still further the differential control pressure åpl will rise and the spool 47 will move against the spring 43 so that the cross-section of the restrictor 27a is opened. Accordingly, the differential control pressure åp2 is reduced.
It is possible and can be convenient to integrate the separate pressure valve 37 into the control block 41.
Figures. Sb-Sd show circuit variations of the control block 41. Figure 5b corresponds to Figure 3a and Figure Sd corresponds to
Figure 2 with the inclusion of a pressure valve 45. Figure Sc shows a further circuit modification with a flow regulating valve 44.
Figure 6 is a graph of the differential control pressures åpl and Ap, plotted against the control oil flow Q, over the partial load range, limiting load range, normal load range and emergency deceleration range.
WHAT WE CLAIM IS:- 1. A propulsion mechanism comprising a prime mover, a hydrostatic transmission and a control system therefor that receives an input signal, the control system including means for generating a reference signal dependent upon prime mover speed, and the input signal, said reference signal being used to derive at least one control signal for the prime mover, and at least one control signal for the hydrostatic transmission in accordance with the operational state of the propulsion mechanism, overloading of the prime mover being prevented by limiting load regulation through adjustment of the transmission ratio.
2. The control system according to Claim
1, characterized in that the input signal acts on an adjustable element in a hydraulic control circuit and in conjunction with a signal, which depends on the rotational speed of the prime mover, generates the reference signal in the form of a differential pressure.
3. The control system according to Claim 2, characterized in that the adjustable element in the hydraulic control circuit is a restrictor.
4. The control system according to Claim 2, characterized in that the adjustable element in the hydraulic control circuit is a three-way flow regulating valve or a twoway flow regulating valve with a pressure limiting valve.
5. The control system according to any of the Claims 1 to 4, characterized in that the input signal influences the prestress of final control elements for adjusting elements in the hydraulic control circuit and where appropriate for influencing elements in the controlled condition.
6. The control system according to any of the Claims 1 to 5, characterized in that limiting load signals, partial load signals and deceleration load signals are derived from the reference signal in accordance with the operating state of the propulsion mechanism.
7. The control system according to Claim 6, characterized in that in the limiting load range a control signal for a final control element is derived from the reference signal to increase the output power of the prime mover and/or a control signal for a final control element is derived from altering (increasing or decreasing) the displaced volume of the hydraulic pump and/or a control signal is obtained for a final control element for altering the displaced volume of the hydraulic motor and/or control signals are obtained for final control elements to reduce the power consumption of the load and/or of the supplementary loads.
8. The control system according to Claim 6, characterized in that in the partial load range a control signal is derived from the reference signal for a final control element to reduce the output power of the prime mover and/or a control signal is derived for a final control element for increasing the displaced volume of the hydraulic pump and/or a control signal is derived for a final control element for setting the displaced volume of the hydraulic motor and/or control signals are derived for final control elements to increase the power consumption of the load and/or of the supplementary loads.
9. The control system according to Claim
**WARNING** end of DESC field may overlap start of CLMS **.
Claims (13)
1. A propulsion mechanism comprising a prime mover, a hydrostatic transmission and a control system therefor that receives an input signal, the control system including means for generating a reference signal dependent upon prime mover speed, and the input signal, said reference signal being used to derive at least one control signal for the prime mover, and at least one control signal for the hydrostatic transmission in accordance with the operational state of the propulsion mechanism, overloading of the prime mover being prevented by limiting load regulation through adjustment of the transmission ratio.
2. The control system according to Claim
1, characterized in that the input signal acts on an adjustable element in a hydraulic control circuit and in conjunction with a signal, which depends on the rotational speed of the prime mover, generates the reference signal in the form of a differential pressure.
3. The control system according to Claim 2, characterized in that the adjustable element in the hydraulic control circuit is a restrictor.
4. The control system according to Claim 2, characterized in that the adjustable element in the hydraulic control circuit is a three-way flow regulating valve or a twoway flow regulating valve with a pressure limiting valve.
5. The control system according to any of the Claims 1 to 4, characterized in that the input signal influences the prestress of final control elements for adjusting elements in the hydraulic control circuit and where appropriate for influencing elements in the controlled condition.
6. The control system according to any of the Claims 1 to 5, characterized in that limiting load signals, partial load signals and deceleration load signals are derived from the reference signal in accordance with the operating state of the propulsion mechanism.
7. The control system according to Claim 6, characterized in that in the limiting load range a control signal for a final control element is derived from the reference signal to increase the output power of the prime mover and/or a control signal for a final control element is derived from altering (increasing or decreasing) the displaced volume of the hydraulic pump and/or a control signal is obtained for a final control element for altering the displaced volume of the hydraulic motor and/or control signals are obtained for final control elements to reduce the power consumption of the load and/or of the supplementary loads.
8. The control system according to Claim 6, characterized in that in the partial load range a control signal is derived from the reference signal for a final control element to reduce the output power of the prime mover and/or a control signal is derived for a final control element for increasing the displaced volume of the hydraulic pump and/or a control signal is derived for a final control element for setting the displaced volume of the hydraulic motor and/or control signals are derived for final control elements to increase the power consumption of the load and/or of the supplementary loads.
9. The control system according to Claim
6, characterized in that in the deceleration load range a control signal is derived from the reference signal for a final control element to maximize the deceleration power of the prime mover and/or a control signal is derived for a final control element to reduce the displaced volume of the hydraulic pump and/or a control signal is derived for a final control element to reduce the hydromechanical efficiency of the hydrostatic transmission and/or control signal is derived for a final control element for reducing the volumetric efficiency of the hydrostatic transmission.
10. A control system constructed and arranged substantially as described herein and shown in Figure 2 of the accompanying drawings.
11. A control system constructed and arranged substantially as described herein and shown in Figures 3a, 3b. of the accompanying drawings.
12. A control system constructed and arranged substantially as described herein and shown in Figure 4 of the accompanying drawings.
13. A control system constructed and arranged substantially as described herein and shown in Figures 5a, 5b, Sc and Sd of the accompanying drawings.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE2700803A DE2700803C2 (en) | 1977-01-11 | 1977-01-11 | Control system for a drive device |
| DE19772715400 DE2715400A1 (en) | 1977-04-06 | 1977-04-06 | Control circuit for automatic transmission - with hydraulic logic to select gear change mode |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| GB1599553A true GB1599553A (en) | 1981-10-07 |
Family
ID=25771443
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB889/78A Expired GB1599553A (en) | 1977-01-11 | 1978-01-10 | Regulating system for driving means more particularly a hydrostatic travelling drive |
Country Status (3)
| Country | Link |
|---|---|
| FR (1) | FR2393208A1 (en) |
| GB (1) | GB1599553A (en) |
| IT (1) | IT1091735B (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2275761A (en) * | 1993-03-05 | 1994-09-07 | Linde Ag | Improvements in braking vehicles with hydrostatic drive |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4282711A (en) * | 1979-07-26 | 1981-08-11 | Deere & Company | Hydrostatic transmission control system |
Family Cites Families (12)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3127745A (en) * | 1962-07-05 | 1964-04-07 | New York Air Brake Co | Hydrostatic transmission |
| US3214911A (en) * | 1963-06-04 | 1965-11-02 | Dowty Hydraulics Units Ltd | Hydraulic apparatus |
| DE2001701C3 (en) * | 1970-01-15 | 1979-04-05 | Linde Ag, 6200 Wiesbaden | Setting device for the remote control of a continuously adjustable hydrostatic transmission |
| US3636705A (en) * | 1970-09-14 | 1972-01-25 | Clark Equipment Co | Automatic control system for hydrostatic drive |
| US3932991A (en) * | 1973-07-23 | 1976-01-20 | Robert Cecil Clerk | Hydrostatic transmission control system |
| DE2363335C3 (en) * | 1973-12-19 | 1978-06-29 | Hydromatik Gmbh, 7900 Ulm | Control device for a drive unit consisting of an internal combustion engine and a continuously adjustable hydrostatic transmission |
| DE2363762C2 (en) * | 1973-12-21 | 1985-11-21 | Linde Ag, 6200 Wiesbaden | Control device for a hydrostatic motor vehicle transmission |
| DE2449464A1 (en) * | 1974-10-19 | 1976-05-06 | Kloeckner Humboldt Deutz Ag | HYDROSTATIC VEHICLE TRANSMISSION |
| DE2451204A1 (en) * | 1974-10-29 | 1976-05-20 | Kloeckner Humboldt Deutz Ag | CONTROL DEVICE FOR A DRIVE UNIT FORMED FROM A COMBUSTION ENGINE AND A HYDROSTATIC TRANSMISSION |
| DE2541398A1 (en) * | 1975-09-17 | 1977-03-31 | Orenstein & Koppel Ag | CONTROL DEVICE FOR A HYDROSTATIC TRAVEL DRIVE, IN PARTICULAR FOR FORKLIFT TRUCKS |
| US4017216A (en) * | 1976-03-15 | 1977-04-12 | Caterpillar Tractor Co. | Variable underspeed system linkage |
| DE2648094A1 (en) * | 1976-10-23 | 1978-04-27 | Bosch Gmbh Robert | CONTROL DEVICE FOR A HYDROSTATIC TRANSMISSION |
-
1978
- 1978-01-10 IT IT19121/78A patent/IT1091735B/en active
- 1978-01-10 GB GB889/78A patent/GB1599553A/en not_active Expired
- 1978-01-11 FR FR7800689A patent/FR2393208A1/en not_active Withdrawn
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2275761A (en) * | 1993-03-05 | 1994-09-07 | Linde Ag | Improvements in braking vehicles with hydrostatic drive |
| GB2275761B (en) * | 1993-03-05 | 1996-03-20 | Linde Ag | Improvements in vehicles with hydrostatic drive |
Also Published As
| Publication number | Publication date |
|---|---|
| IT1091735B (en) | 1985-07-06 |
| IT7819121A0 (en) | 1978-01-10 |
| FR2393208A1 (en) | 1978-12-29 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PS | Patent sealed [section 19, patents act 1949] | ||
| PCNP | Patent ceased through non-payment of renewal fee |