GB2530761A

GB2530761A - Fuel injection equipment

Info

Publication number: GB2530761A
Application number: GB1417308.2A
Authority: GB
Inventors: Philip Dingle
Original assignee: Delphi International Operations Luxembourg SARL
Current assignee: Delphi International Operations Luxembourg SARL
Priority date: 2014-10-01
Filing date: 2014-10-01
Publication date: 2016-04-06
Also published as: GB201417308D0

Abstract

A fuel injection method adapted to control the fuel injection equipment 12 of an internal combustion engine 10, the equipment being provided with direct in-cylinder fuel injectors 46, 64. Each cylinder 14 of the engine is fuelled by a first fuel injector 46 and also by a second fuel injector 64. The method comprises a first strategy (102, figs 2-6) for controlling the first injectors 46 and a second strategy (104, figs 2-6) for controlling the second injectors 64. Each strategy comprises the steps of commanding pressure, opening time and duration, the first strategy being different from the second strategy. Some of these differences may be: different pressures within the first and second injectors; they can open at different times deepening upon the angular position of the crankshaft; the duration of opening maybe different. There may be a control module for controlling the fuel injection equipment, there can be a first and second control module controlling the first and second control strategy respectively. When fuelling a plurality of cylinders the first injectors may belong to a first set of injectors and the second injectors may belong to a second set of injectors.

Description

Fuel Injection Equipment

TECHNICAL FIELD

The present invention relates to a method to control fuel inj ection equipment having two or more injectors per cylinder of an internal combustion engine. The invention also relates to a control unit implementing the method, and to fuel injection equipment provided with said control unit, and to an engine provided with the fUel equipment.

BACKGROUNJ OF THE INVENTION

Internal combustion engines, either compression ignition or spark ignition, having two inj ectors per cylinder are known. The past few decades have seen the development of engines with a single injector per cylinder, and those engines are now meeting today's standards in levels of exhaust gas emissions. To achieve these low emission levels, the injector is substantially axially mounted in the cylinder and, high pressure pumping and fuel injection equipment such as direct injection "common rail" systems have been developed enabling injection into the cylinders of fuel at pressures of 2000 bars, 2500 bars and even 3000 bars.

Consequently, the side injection engines of the prior art with a single side mounted injector do not readily meet the required emissions standards and, the advantages of the two-injectors-per-cylinder type engines remain theoretical, as said engines have not benefited from recent developments in fuel injection equipment.

SUMMARY OF TIlE INVENTION

Accordingly, it is an object of the present invention to resolve, at least partially, the above mentioned problems in providing a fuel injection method adapted to control the fuel injection equipment of an internal combustion engine.

The fuel injection equipment is provided with direct in-cylinder fuel injectors, commuting between an open position, where fuel injection occurs and, a closed position, where fuel injection is prohibited. Furthermore, each cylinder of the engine is fuelled by a first fuel injector and also by a second fuel injector.

The method comprises a first strategy for controlling the first injectors, the first strategy comprising the steps of a) commanding the first fuel pressure level HP within the first injectors, b) commanding the first opening time of each of the first inj ectors relative to crankshaft angular position of each of the first injectors, c) commanding the first opening duration of the first injectors.

The method further comprises a second strategy for controlling the second injectors, the second strategy comprising the steps of: d) commanding the second fuel pressure level HP within the second injectors, e) commanding the second opening time of each of the second injectors relative to crankshaft angular position of each of the second injectors, 0 commanding the second opening duration of the second injectors, the first strategy and the second strategy being different.

Particularly, the steps a) and d) can be different, the first high pressure of the fuel injected by the first injectors and the second high pressure of the fuel injected by the second injectors being different.

Also, the steps b) and e) can be different so, during a combustion cycle, within each cylinder the opening time of the first injector and the opening time of the second injector are different, the fuel injection of the first injector and the fuel injection of the second injector starting at a different moment relative to crankshaft angular position.

Also, the steps c) and 1) can be different so, during a combustion cycle, within each cylinder the opening duration of the first injector and the opening duration of the second injector are different, the fuel injection of the first injector and the fuel injection of the second injector lasting for different durations.

The invention also extends to a control module for controlling a fuel injection equipment according to a method as detailed above.

The control module can comprise a single electronic control unit or alternatively, can comprise a first electronic control unit able to execute the first strategy and, a second control unit able to execute the second strategy.

The invention further extends to fuel injection equipment for an internal combustion engine having a plurality of cylinders, each of which being able to be fuelled by a first injector belonging to a first set of injectors and also by a second injector belonging to a second set of injectors, the fuel injection equipment being controlled by a control module having one or two electronic control units as previously mentioned.

Also, the injectors of the first set may be different from the injectors of the second set, the difference enabling the first injector to achieve a different commuting time, faster or slower, between the open and the closed position than the second injector.

Furthermore, the injectors of the first set and the injectors of the second set may provide different spray pattern and/or different hydraulic flow values. This can be achieved thanks to specific nozzle geometry, number of spray holes, orientation of the spray holes or via any other means differentiating the injectors of the first set from the injectors of the second set.

Also, the injectors of the first set may be different from the injectors of the second set, the difference enabling the first injector to operate with a first fuel and the second injector to operate with a second fuel different from the first fuel.

Also, the inj ectors of at least one of the first or second set of inj ectors can be provided with an internal reservoir able to withstand high pressure fuel so that said set of injectors constitutes a rail-less distributed reservoir fhel injection system.

More particularly, both the first and second set of injectors constitute rail-less distributed reservoir systems.

The fuel injection equipment can comprise a first common rail reservoir fluidly connected to the injectors of the first set and, a second common rail reservoir fluidly connected to the injectors of the second set ofinjectors.

The fuel injection equipment can further be provided with a first high pressure pump delivering fuel to the first set of injectors and also with a second high pressure pump delivering fuel to the second set of injectors.

The invention further extends to an internal combustion engine provided with a fuel injection equipment as described above.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is now described by way of example with reference to the accompanying drawings in which: Figure 1 is a schematic view of an engine provided with a first embodiment of twin-thel injection equipment as per the invention.

Figure 2, 3, 4, 5 and 6 are five graphs representing five injection methods of the equipment of figure 1.

Figure 7 is an alternative embodiment to the first embodiment of figure 1.

Figures 8 and 9 are partial axial section of an opposed piston engine provided with a third embodiment of twin-equipment as per the invention.

Figure 10 is an axial section of an engine having a piston reaching the top dead center position, the engine being provided with a fourth alternative of a twin-equipment as per the invention.

Figure 11 is a graph representing an injection method particularly adapted to the engine of figure to.

Figure 12 is a schematic view of an engine provided with a fifth embodiment of twin-friel injection equipment as per the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Figure 1 is a schematic representation of a first embodiment of an internal combustion engine 10 having three cylinders 14 provided with a fuel injection equipment t2. The skilled person will understand that said three-cylinder engine is just an example with no intention to limit the invention to such type of engines.

The fuel injection equipment 12, so-called "twin fuel injection equipment" 12, comprises a first half system or hemi-equipment 16 and a second half system or hemi-equipment 18, the two hemi-equipment's 16, 18, sharing a common low pressure supply line 20 going from a low pressure fuel tank 22 to an inlet T- junction 28 and comprising a low pressure pump 24 and a fuel filter 26. the hemi-equipment's divide after the inlet T-junction 28.

The first hemi-equipment 16, represented on the top of figure 1, comprises, from the inlet T-junction 28, a first low pressure inlet line 30 extending to a first

S

inlet valve 32 arranged on the inlet of a first high pressure pump module 34 that is actuated by a rotating cam 36. From the outlet of the first high pressure pump 34 extends a first high pressure supply line 38 connected to a first high pressure common-rail reservoir 40 that has a well-known elongated tubular shape at an S extremity of which is arranged a first pressure sensor 42. To the first common rail are fluidly connected in parallel a first set 44 of three first injectors 46.

Obviously, the set of injectors 44 comprises as many injectors 46 as there are cylinders 14. Each first injector 46 is laterally arranged on one of the cylinder 14 so that, when the injectors open, fbel injection occurs and each first injector 46 will inj ect a first chordal spray of fuel that, in the non-limiting example of the figure, is represented substantially radial relative to the axis of displacement of the piston within the cylinder 14. The first hemi-equipment 16 further comprises a first return drain 48, to which is connected the three first inj ectors 46, said first return drain 48 leading back to the low pressure tank 22, IS As can be observed on the figure, the second hemi-equipment 18 is similar to the first hemi-equipment and symmetrically arranged on the engine 10. The second hemi-equipment 18 comprises, from the inlet T-junction 28, a second low pressure inlet line 50 extending to a second inlet valve 52 arranged on the inlet of a second high pressure pump module 54 that is actuated by the same rotating cam 36. From the outlet of the second high pressure pump 54 extends a second high pressure supply line 56 connected to a second high pressure common-rail reservoir 58 that has the same elongated tubular shape as the first common rail 40.

At an extremity of the second common-rail 58 is arranged a second pressure sensor 60, To the second common rail 58 is fluidly connected in parallel a second set 62 of three injectors 64, each second injector 46 being laterally arranged on one of the cylinder 14, diagonally opposed to the first inj ector 46, so that, when fuel injection occurs, each second injector 64 injects a second chordal spray of fuel that in the non-limiting example of the figure is represented substantially radial relative to the axis of displacement of the piston within the cylinder 14 and that is in the opposite direction as the spray from the first injector 46, The second hemi-equipment 18 further comprises a second return drain 66, to which is connected the three second injectors 64, said second return drain 66 leading back to the low pressure tank 22.

As can be seen, the two high pressure pumps 34, 54, are actuated by the same cam 36. Alternatively to this constmction, the two pumps could be individually actuated by distinct cams or by any other actuation means known in the art.

S The twin equipment 12 is operated by a control module 67 electrically connected to the inlet valves 32, 52, to the pressure sensors 42, 60, and to all the injectors 46, 64, the system control unit 67 being able to run the steps of a controlling method 100 commanding the operation of the twin-equipment 12.

The control module 67 comprises a first electronic control unit 68 for controlling the operation of the first hemi-equipment 16 and a second electronic control unit 69 controlling the operation of the second hemi-equipment 18, Alternatively, the control module 67 may comprise a single electronic control unit controlling both hemi-equipment' s 16, 18.

In a first embodiment of this engine 10 and twin-equipment 12, the first and IS second hemi-equipment's 16, 18, are identical still, the steps of the controlling method 100 are divided in a first set of steps constituting a first strategy 102 for operating the first hemi-equipment 16 and, a second set of steps constituting a second strategy 104 for operating the second hemi-equipment 18.

As known in the domain of internal combustion engines provided with direct fuel injection equipment, an injector opens and sprays several times when a piston of the engine reaches or leaves the top dead centre position. For instance, five or seven injection events can occur at each combustion cycle of the piston, said inj ection events often being different from each other in terms of opening time or opening duration.

The present twin-equipment 12 can advantageously enable to easily manage these distinct injection events thanks to the first strategy 102 being different from the second strategy 104.

The figures 2, 3, 4, 5 and 6 provide illustrative examples of distinct first and second strategies 102, 104, which are plotted on x-y graphs where the x axis is the Time and, they axis represents the open/close state of the injector.

The first strategy 102 is the upper plot and, the second strategy 104 is the lower plot. The plots are simplified examples that do not provide details or values, but in a more notional representation provide a general shape enabling comparison between strategies. In each graph, the Time scale is common to both first 102 and second 104 strategies, thus enabling direct comparison between the plots arid, the injector state scale is binary and limited to a base level, identifying when the nozzle is closed preventing fUel injection and, a high level, identifying when the nozzle is open enabling an injection event.

In the first example of figure 2 illustrating a particular engine operating condition, the first hemi-equipment 16 operates at a first high pressure HP] lower than the second high pressure HP2 at which the second hemi-equipment 18 operates. The method 100 commands to the first injector 46 two short pilot injection events EP done at the first high pressure HP1 before the piston reaches the top dead centre position then, to the second injector 64, a main injection event EM done at the second high pressure FIP2, said main event EM being longer in duration and, finally, a late post injection event EL done when the piston has left the top dead centre position is commanded to the first injector 46 and is done at the first high pressure HPI.

An advantage of this first method 100 is to optimize the hemi-equipment at two different high pressure levels HP1, HP2, and therefore eliminate the limitation of a single rail pressure level as is the case in a single rail system.

In the second example of figure 3, showing a different engine operating condition, both hemi-equipment's 102, 104, may operate at the same rail pressure level if desired and, consequently the twin equipment 12 previously described could be simplified by being provided with a single high pressure pump delivering high pressure fuel to both first 40 and second 58 common-rails. The method 100 commands, prior to the main event EM, a train of alternate short pilot events EP with closer time spacing as could be achieved by a single injector, so the pilot events EP alternate between the first injector 46 and the second injector 64. This second method 100 could be advantageously implemented by using certain conventional hydraulic servo injectors that may be limited in response time.

In the third example of figure 4 both hemi-equipment's 102, 104, may also operate at the same rail pressure but the rate of heat released during combustion is modified by staggering the start and end of the main injection event EM between the two injectors, Although figure 4 represents a strategy ofinjection with a single event per inj ector, said strategy can be utilized for multiple inj ections from one or both injectors in this general way to also influence the rate of heat release during combustion.

In the fourth example of figure 5, the first injector 46 and the second injector 64 are identical and individually have a capacity to deliver half of the friel quantity normally delivered in single injector equipment. As long as the engine 10 operates at half load, or below, the first injector 46 operates alone. This phase is represented on the left portion of the graph, and, as soon as the half load is surpassed, both injectors cooperate and contribute to the injection events.

In an alternative to the fourth example, illustrated in figure 6, below half load of the engine, the main injection event EM, instead of being provided solely by the first injector 46, could alternate between the first 46 and the second 64 injector and, therefore the durability of the engine could be improved.

A second embodiment of the twin equipment 12 is represented in figure 7 and can also support the strategies presented. Instead of having common-rail reservoirs, the hemi-equipment' s 16, 18, are provided with inj ectors 46, 64, having distributed reservoirs. Each injector 46, 64, has an internal capacity to contain an appropriate volume, for instance 10 cm5 of high pressure fuel. In such an embodiment, the injectors 46, 64, are interconnected by high pressure pipes 70 as in a daisy chain. Also, each injector may be provided with an individual pressure sensor for instance as described in patent US7552717. Several alternative architectures of such rail-less equipment's are known in the art.

To further support the execution of the strategies, the twin-equipment 12 can benefit from distinguishing its hemi-equipment's 16, 18, and specializing its hardware in a particular role.

For instance, in the case of the first strategy of figure 2, the twin equipment 2 could be provided with a first high pressure pump 34 supplying less pressure than the second high pressure pump 54 and also with, first injectors 46 enabling slower commutation or switching time between open and closed positions and, second injectors 64 supporting the higher pressure and the faster switch time.

Figures 8 and 9 illustrate the case of a third embodiment of a twin-fuel injection equipment 12 provided on an opposed piston engine. These engines could benefit from a twin-equipment 12 as per the invention. In particular, as illustrated on figure 8, the first injector 46, on the top of figures 8 and 9, provides an initial spray early during the compression stroke directed down the bore, said spray promoting premixed air/fuel combustion while the second injector, having a nozzle geometry arranged for chordal focused injection opens when the pistons are near the top dead centre, this second inj ection event promoting ignition and diffusion combustion.

Figures 10 and 11 illustrate another engine 10 provided with a fourth embodiment of a twin-fbel injection equipment 12, Figure lOis an axial section of a piston in a cylinder and, figure 11 is the graph of an example injection strategy.

The first 46 and second 64 injectors are arranged on the top of the cylinder 14, the two injectors being diagonally opposed. The respective injector axis are at an angle of approximately 200 with the main axis of the cylinder N but, this angle value is provided for illustration and clarity purposes while other values are of course possible. Also, as indicated on figure 10, the injectors have their respective fuel spray inj ected at different angles X and Y. As is represented on the figure, both injectors are designed so their respective fuel sprays are oriented along a spray direction that is almost perpendicular to the cylinder axis, in order to ensure an optimum penetration of the fuel spray within the combustion chamber. Furthermore, the crown of the piston is illustrated with a conventional toroidal bowl for receiving said thel sprays. To accommodate such non-symmetrical injection events, the injector's nozzles are provided with spray holes arranged on a limited angular sector of the nozzle tip and, the injector itself is arranged in the engine head so said angular sector is oriented in a non-limiting way as a chord across the combustion chamber, however the spray target for injector 46 relative to the injector axis and illustrated as angle "X" in figure 10 is different from that of injector 64, therefore the angle at which the spray or sprays departs the nozzle of injector 46 is greater than that of injector 64 where the comparable angle is illustrated as From an injection strategy stand point, the first injector4ô, on the left of the figure, injects the early pilot event EP and late event EL when the piston is approaching or departing TDC respectively, while the second injector 64, to the right in the figure injects the main event EM when the piston is near the top dead centre position. Although given these distinctive roles, the twin-equipment 12 can as well execute the strategies as previously illustrated in figures 2 to 6.

Figure 12 illustrates a fifth embodiment of twin-injection equipment 12, said equipment being arranged on a hi-fuel engine 10. The hi-fUel engine 10 consumes distinct fuels under different operation conditions and, this is conveniently managed due to the twin-injection equipment 12 having a first hemi-equipment 16 operating with first fuel F] and the second hemi-equipment 18 operating with a second fuel F2.

In the bi-fuel twin-equipment U shown in figure 10 the hemi-equipment have no common low pressure line 20 and no common return drain. Each hemi-equipment has its own low pressure line with its own low pressure reservoir 22, 23, low pressure pump, fuel filter and connecting hoses. Each hemi-equipment can be a common-rail type equipment, as represented on the figure 12, or similarly to figure 7 a rail-less type equipment with distributed reservoir inside each injector.

Figure 12 should also be taken as applying to dual-fuel engines in which two distinctly different fuels are injected into the combustion chamber 14 during the same combustion event and consumed by the engine. For example, fUel tank 22 may contain, and thus injection equipment 16 will inject a fuel of low reactivity such as methane, gasoline, ammonia, or ethanol, while fuel taiik 23 may contain, and thus injection equipment 18 will inject a fuel of high reactivity such as diesel fuel or dimethyl ether.

For clarity purposes, the description made is limited to two injectors per cylinder while three injectors, or even more, can be implemented without difficuhies in using the same teachings.

The following list of references has been utilized in the description: engine 12 twin fuel injection equipment 14 cylinder of the engine 16 first hemi-equipment 18 second hemi-equipment common low pressure supply line 22 low pressure fuel tank 23 low pressure fuel tank 24 low pressure pump 26 ftiel filter 28 inlet T-junction first low pressure inlet line 32 first inlet flow control valve 34 first high pressure pump module 36 pumping cam 38 first high pressure supply line first common rail 42 first rail pressure sensor 44 first set of injectors 46 inj ector within first set 48 first return drain second low pressure inlet line 52 second inlet flow control valve 54 second high pressure pump module 56 second high pressure supply line 58 second common rail second rail pressure sensor 62 second set of inj ectors 64 inj ector within second set 66 second return drain 67 control module 68 first electronic control unit 69 second electronic control unit high pressure pipe method 102 first injection strategy 104 second injection strategy LP Low level of pressure HP high level of pressure HP1 first high pressure HP2 second high pressure EP pilot injection event EL late post inj ection event EM main injection event Fl first fuel [2 second ffie

Claims

CLAIMSL A fuel injection method (100) adapted to control the fuel injection equipment (12) of an internal combustion engine (10), the fuel injection equipment (12) being provided with direct in-cylinder fuel injectors (46, 64) commuting between an open position, where fuel injection occurs and, a closed position, where fuel injection is prohibited; each cylinder (14) of the engine (10) being fuelled by a first fuel injector (46) and also by a second fuel injector (64), characterized in that the method (100) comprises a first strategy (102) for controlling the first injectors (46), the first strategy (102) comprising the steps of: a) commanding the first fuel pressure level (HP 1) within the first injectors (46), b) commanding the first opening time of each of the first injectors relative to crankshaft angular position of each of the first injectors (46), c) commanding the first opening duration of the first injectors (46) and, the method (100) further comprises a second strategy (104) for controlling the second injectors (64), the second strategy (104) comprising the steps of: d) commanding the second fuel pressure level (HP2) within the second injectors (64), e) commanding the second opening time of each of the second injectors relative to crankshaft angular position of each of the second injectors (64), 1) commanding the second opening duration of the second injectors (64), the first strategy and the second strategy being different.
2. A method (100) as claimed in the preceding claim wherein the steps a) and d) are different, the first high pressure (HP I) of the fuel injected by the first injectors (46) and the second high pressure (HP2) of the fuel injected by the second injectors (64) being different.
3, A method (100) as claimed in any one of the preceding claims wherein the steps b) and e) are different so, during a combustion cycle, within each cylinder (14) the opening time of the first injector (46) and the opening time of the second injector (64) are different, the fuel injection of the first injector (46) and the fuel injection of the second injector (64) starting at a different moment relative to crankshaft angular position.
4. A method (100) as claimed in anyone of the preceding claims wherein the steps c) and I') are different so, during a combustion cycle, within each cylinder (14) the opening duration of the first injector (46) and the opening duration of the second injector (64) are different, the thel injection of the first injector (46) and the fuel injection of the second injector (64) lasting for different durations.
5, A control module (67) for controlling a fuel injection equipment (12) according to a method (00) as claimed in anyone of the preceding claims.
6. A control module (67) as claimed in claim 5, comprising a first electronic control unit (68) able to execute the first strategy (102) and, a second control unit (69) able to execute the second strategy (104).
7. A friel inj ection equipment (t2) for an internal combustion engine (10) having a plurality of cylinders (14), each of which being able to be fuelled by a first injector (46) belonging to a first set (44) of injectors and also by a second injector (64) belonging to a second set (62) of injectors, the fuel injection equipment (12) being controlled by a control module (67) as claimed in anyone of the claims 5 or 6.
8. A fuel injection equipment (t2) as claimed in claim 7 wherein the injectors (46) of the first set (44) are different from the injectors (64) of the second set (62), the difference enabling the first injector (46) to a faster commuting time between the open and the closed position than the second injector (64).
9. A fuel injection equipment (12) as claimed in anyone of the claims 7 or 8 wherein the injectors (46) of the first set (44) are different from the injectors (64) of the second set (62), the difference enabling the first injector (46) to operate with a first fuel (Fl) and the second injector (64) to operate with a second fuel (F2) different from the first fuel (Fl).
10. A the! injection equipment (12) as claimed in anyone of the claims 7 to 9 wherein the injectors (46) of the first set (44) and the injectors (64) of the second set (62), provide different spray patterns.S
11. A fuel injection equipment (12) as claimed in anyone of the claims 7 to 10 wherein the injectors (46) of the first set (44) and the injectors (64) of the second set (62), provide different hydraulic flow values.
12. A fuel injection equipment (t2) as claimed in anyone of the claims 7 to wherein the injectors of at least one of the first (44) or second set (62) of injectors are provided with an internal reservoir able to withstand high pressure fuel (HP) so that said set of injectors constitutes a rail-less distributed reservoir fuel injection system.
13. A fuel injection equipment (12) as set in claim 12 wherein both the first and second set of injectors constitute rail-less distributed reservoir systems.
14, A fuel injection equipment (12) as claimed in anyone of the claims 7 to II further comprising a first common rail reservoir (40) fluidly connected to the injectors (46) of the first set (44) and, a second common rail reservoir (58) fluidly connected to the injectors (64) of the second set ofinjectors (62).
15. A fuel injection equipment (t2) as claimed in anyone of the claims 7 to t4 further provided with a first high pressure pump (34) delivering fuel to the first set (44) ofinjectors and also with a second high pressure pump (54) delivering fuel to the second set (62) of injectors.

16, An internal combustion engine (10) provided with a fuel injection equipment (12) as claimed in anyone of the claims 7 to 15.