CN117846800A

CN117846800A - Method of controlling a fuel injection system

Info

Publication number: CN117846800A
Application number: CN202311280980.0A
Authority: CN
Inventors: 阿曼多·斯皮齐里; 里卡多·马里亚内洛; 卢卡·曼奇尼; 斯特凡诺·彼得雷基亚; 米歇尔·佩特龙
Original assignee: Marilyn Europe
Current assignee: Marilyn Europe
Priority date: 2022-10-06
Filing date: 2023-10-07
Publication date: 2024-04-09
Also published as: EP4350139A1; IT202200020604A1

Abstract

A method of controlling a fuel injection system (1) for an internal combustion engine provided with a fuel pump (4). The fuel pump (4) has: a pump chamber (14); a piston (15) mounted to slide within the pump chamber (14); an inlet conduit (17) ending in the pump chamber (14) and provided with an inlet valve (18); an output conduit (19) starting from the pump chamber (14) and provided with an output valve (20); and a flow regulating device (6) coupled to the inlet valve (18) and controllable to prevent or allow the inlet valve (18) to close when the fuel pressure inside the pump chamber (14) exceeds the fuel pressure in the inlet conduit (17). The control method comprises the following steps: detecting when the internal combustion engine is stopped; and after the internal combustion engine has stopped, controlling the flow regulating means (6) to allow the inlet valve (18) to close.

Description

Method of controlling a fuel injection system

Cross Reference to Related Applications

The present patent application claims priority from italian patent application No. 102022000020604 filed at month 10 and 6 of 2022, the entire disclosure of which is incorporated herein by reference.

Technical Field

The present invention relates to a method of controlling a fuel injection system; preferably, the direct injection system is for a spark ignition internal combustion engine, and is therefore powered by gasoline or similar fuel.

Background

The direct injection system comprises a plurality of injectors, a "common rail" supplying the injectors with pressurized fuel, a high pressure fuel pump supplying the fuel to the common rail via a high pressure supply conduit and provided with a flow regulating device, and a control unit driving the flow regulating device to keep the fuel pressure in the common rail equal to a desired value, which typically varies over time depending on the operating conditions of the engine.

The high-pressure fuel pump described in patent application EP2236809A1 comprises: the fuel pump includes a main body, a pump chamber formed in the main body and having a piston reciprocally sliding therein, an inlet conduit regulated by an inlet valve to supply low-pressure fuel inside the pump chamber, and an output conduit regulated by an output valve to supply high-pressure fuel outside the pump chamber to a common rail.

Modern vehicles typically implement a "start and stop" system to reduce fuel consumption during urban use, typically automatically stopping and starting the internal combustion engine when the vehicle is stopped due to a red light (typically the internal combustion engine remains stopped for tens of seconds or even minutes). In order to be able to restart the combustion engine quickly and regularly, it is preferable that the fuel pressure in the common rail remains substantially unchanged during a stop of the combustion engine (which also requires stopping of the high-pressure fuel pump driven by the engine shaft of the combustion engine). Therefore, it is necessary to minimize all fuel leakage that leads to a loss of fuel in the common rail, thereby minimizing a decrease in fuel pressure in the common rail.

The main causes of common rail fuel leakage are related to poor sealing of the output valve of the high-pressure fuel pump and poor sealing of the relief valve of the high-pressure fuel pump. In order to reduce the leakage of fuel through the outlet valve and the pressure reducing valve, it is suggested to improve the structural characteristics of the valves, modify their shape, increase their machining accuracy, and use higher performance materials. In any case, these solutions add significant cost to the high pressure fuel pump.

Patent applications EP2187038A1 and DE102008042371A1 describe a high-pressure fuel pump for an internal combustion engine. When the internal combustion engine is stopped (turned off), the fuel pump is controlled to reduce the fuel pressure in the high-pressure supply system.

Disclosure of Invention

An object of the present invention is to provide a control method of a fuel injection system that reduces fuel leakage through an output valve of a high-pressure fuel pump and a pressure reducing valve of the high-pressure fuel pump when an internal combustion engine is stopped, and at the same time, is easy to implement quickly.

According to the present invention, there is provided a method of controlling a fuel injection system according to what is set forth in the appended claims.

The claims describe preferred embodiments of the invention, which form an integral part of the present description.

Drawings

The invention will now be described with reference to the accompanying drawings, which illustrate non-limiting embodiments of the invention, wherein:

FIG. 1 is a schematic illustration with details of a common rail direct fuel injection system for an internal combustion engine removed for clarity;

FIG. 2 is a longitudinal cross-sectional view of a high pressure fuel pump of the injection system of FIG. 1;

FIG. 3 is a plan view of a deformable strip of the inlet valve of the high pressure fuel pump of FIG. 2; and

fig. 4 is a longitudinal cross-sectional view of a variation of the high-pressure fuel pump of fig. 2.

Detailed Description

In fig. 1, reference numeral 1 generally designates a common rail direct fuel injection system for an internal combustion engine.

The direct injection system 1 comprises a plurality of injectors 2, a common rail 3 supplying pressurized fuel to the injectors 2, a high-pressure pump 4 supplying fuel to the common rail 3 via a supply conduit 5 and provided with a flow regulating device 6, a control unit 7 maintaining the fuel pressure inside the common rail 3 equal to a desired value, which typically varies with time according to the operating conditions of the internal combustion engine; and a low-pressure fuel pump 8 that supplies fuel from a tank 9 to the high-pressure pump 4 via a supply conduit 10.

The control unit 7 is coupled to the flow rate adjustment device 6 to control the flow rate of the high-pressure pump 4 so as to supply the common rail 3 with the amount of fuel required to have a desired pressure value inside the common rail 3 at a time. Specifically, the control unit 7 adjusts the flow rate of the high-pressure pump 4 via feedback control using the fuel pressure value inside the common rail 3 (detected by the pressure sensor 11 in real time) as a feedback variable.

According to the illustration of fig. 2, the high-pressure pump 4 comprises a body 12 having a longitudinal axis 13 and defining internally a cylindrical pump chamber 14. Inside the pump chamber 14, a piston 15 is mounted for sliding movement by a reciprocating motion along the longitudinal axis 13, determining a cyclic variation of the volume of the pump chamber 14. The smaller part of the piston 15 is coupled to a spring 16, which tends to push the piston 15 towards the maximum volume position of the pump chamber 14, on the one hand, and the smaller part of the piston 15 is coupled to a cam (not shown), which is rotated by the engine shaft of the internal combustion engine to cyclically move the piston 15 upwards, compressing the spring 16.

An inlet conduit 17 regulated by an inlet valve 18 arranged at the pump chamber 14 starts from one side wall of the pump chamber 14. The inlet valve 18 is normally controlled under pressure and, without external intervention, the inlet valve 18 is closed when the fuel pressure in the pump chamber 14 is greater than the fuel pressure in the inlet conduit 17 and the inlet valve 18 is opened when the fuel pressure in the pump chamber 14 is less than the fuel pressure in the inlet conduit 17. The flow regulating device 6 is mechanically coupled to an inlet valve 18 to allow the control unit 7 to keep the inlet valve 18 open when necessary during the pumping step of the piston 15, so that fuel can flow out of the pump chamber 14 through the inlet conduit 17.

An output conduit 19 regulated by a one-way output valve 20 (also referred to as an "OC-outlet shut-off valve") begins at the side wall of the pump chamber 14 and begins at the opposite side of the inlet conduit 17, the one-way output valve 20 being disposed at the pump chamber 14 and allowing fuel only to flow out of the pump chamber 14. The output valve 20 is controlled under pressure and opens when the fuel pressure in the pump chamber 14 is greater than the fuel pressure in the inlet conduit 19 and closes when the fuel pressure in the pump chamber 14 is less than the fuel pressure in the output conduit 19.

The inlet conduit 17 is regulated by an inlet valve 18 (arranged at the pump chamber 14) and extends partially inside the body 12. A damping device 21 (compensator) is arranged along the inlet conduit 17 (upstream of the inlet valve 18), which damping device 21 is fixed to the body 12 of the high-pressure pump 14 and has the function of reducing the amount of pulsation of the fuel flow and thus of the oscillation of the fuel pressure in the low-pressure branch.

The flow regulating device 6 comprises a control lever 22 coupled to the inlet valve 18 and movable between a passive position allowing the inlet valve 18 to close and an active position not allowing the inlet valve 18 to close. The flow regulating device 6 further comprises an electromagnetic actuator 23 coupled to the control lever 22 for moving the control lever 22 between the active and passive positions.

According to the illustration of fig. 2, the electromagnetic actuator 23 comprises a spring 24 and an electromagnet 25, the spring 24 holding the control lever 22 in the active position, the electromagnet 25 being designed to magnetically attract a ferromagnetic anchor 26 integral with the control lever 22, so as to overcome the elastic force generated by the spring 24, to move the control lever 22 into the passive position. When the electromagnet 25 is excited, the control lever 22 is withdrawn to the passive position, and the communication between the inlet conduit 7 and the pump chamber 4 can be interrupted by the closure of the inlet valve 18. Together, the control rod 22 and the anchor 26 form a moving device for the flow regulating means 6, the flow regulating means 6 being axially movable between an active position and a passive position under the control of the electromagnetic actuator 23.

According to the illustration of fig. 2, the inlet valve 18 comprises a disc 27 and a flexible sheet 28, the disc 27 having a series of feed holes through which the fuel can flow, the flexible sheet 28 having a circular shape (better illustrated in fig. 3), the flexible sheet 28 resting on the base of the disc 27, closing the passage through the feed holes. The inlet valve 18 is normally controlled under pressure and without external intervention (i.e. intervention of the flow regulating means 6) the inlet valve 18 is closed when the fuel pressure in the pump chamber 14 is greater than the fuel pressure in the inlet conduit 17 and the inlet valve 18 is opened when the fuel pressure in the pump chamber 14 is less than the fuel pressure in the inlet conduit 17. In particular, as the fuel flows to the pumping chamber 14, the tabs 28 deform away from the disk 27 under the thrust of the fuel, allowing the fuel to pass through the feed holes. Conversely, when fuel flows from the pumping chamber 14, the tabs 28 press against the discs 27 to seal the feed holes, thereby preventing fuel from passing through the feed holes. In the active position, the lever 22 pushes the tab 28 centrally, preventing the tab 28 from adhering to the disk 27, thus preventing the tab 28 from sealing the feed aperture. Conversely, in the passive position, the lever 22 is relatively far from the tab 28, allowing the tab 28 to be attached to the disk 27 and thus allowing the tab 28 to seal the feed aperture.

According to the figures 2 and 4, in the body 12 and below the pump chamber 14, the housing seat 29 is formed in a cylindrical shape, the diameter of which is greater than that of the pump chamber 14, and houses the guide bush 30 of the piston 15, the guide bush 30 basically having the function of guiding the axial alternate sliding of the piston 15. The guide bush 30 is made of a material having a suitable hardness and surface finish to facilitate axial sliding of the piston 15.

The guide bush 30 has a tubular shape and has a central through hole 31 inside which the piston 15 is accommodated so as to slide. The central bore 31 of the guide bush 30, in which the piston 15 is arranged, and the piston 15 are machined very precisely in order to minimize the mechanical play (i.e. the distance) that exists between the central bore 31 of the guide bush 30 and the piston 15 (in order to limit as much as possible the leakage of fuel along the piston 15), but in any case such mechanical play cannot be completely eliminated (obviously this is indispensable for allowing the piston 15 to slide inside the guide bush 30).

According to the embodiment shown in fig. 4, a sealing gasket 32 is interposed between the piston 15 and the central hole 31 of the guide bush 30, which has the function of further limiting the leakage of fuel along the piston 15. The sealing gasket 32 has a certain elasticity so as to be elastically deformable (in particular radially pressed against the inner surface of the central hole 31 of the guide bush 30). The sealing gasket 32 is preferably made of a low coefficient of friction material, for example, the sealing gasket 32 may be made of a material based on PTFE (polytetrafluoroethylene, also commercially known as) Is made of a material which may be loaded with glass or graphite.

According to the preferred embodiment shown in the drawings, the piston 15 has an annular throat which accommodates a sealing gasket 32. In other words, the annular throat constitutes a location for receiving the sealing washer 32 such that the sealing washer 32 cannot move axially relative to the piston 15.

According to a preferred embodiment, there is also a one-way pressure relief valve (also referred to as "PRV-relief valve") that allows fuel to flow only inside the pump chamber 14 through the output conduit 19 and may be integrated with the output valve 20. The function of the relief valve is to allow fuel release in case the fuel pressure in the common rail 3 (i.e. downstream of the output valve 20) exceeds a maximum value established during the design phase (for example, in case of an error in the check performed by the control unit 7 or in case of a failure of the injector 2 connected to the common rail 3). In other words, the relief valve is calibrated to automatically open when the pressure jump at its end becomes greater than the threshold established during the design phase, thereby preventing the fuel pressure in the common rail 3 from exceeding the maximum established during the design phase.

As is clear from the above, the flow regulating device 6 acts only on the inlet valve 18 and has no effect on the outlet valve 20. In other words, the inlet valve 18 is completely separate and independent from the outlet valve 20.

In use, the control unit 7 detects when the internal combustion engine is stopped (turned off) and immediately after the internal combustion engine has stopped (i.e. without any significant delay) controls the flow regulating device 6 to allow the inlet valve 18 to close (i.e. it activates the electromagnetic actuator 23 to move the control lever 22 from the normal active position assumed by the thrust of the spring 24 to the passive position allowing the inlet valve 18 to close).

The control unit 7 preferably continues to control the flow regulating means 6 so that the inlet valve 18 can be closed for a predetermined amount of time (typically lasting 1 to 5 seconds). In other words, the control unit 7 keeps the electromagnetic actuator 23 activated to keep the control lever 22 in the passive position to allow the inlet valve 18 to close for a predetermined amount of time.

Once the internal combustion engine is stopped (as a result, the piston 15 stops all its alternating sliding movements), the fuel pressure in the pump chamber 14 becomes equal to the fuel pressure in the inlet conduit 17, and therefore the pressure difference between the output valve 20 and the relief valve becomes very high, causing fuel to leak through the output valve 20 and the relief valve (i.e., high-pressure fuel in the output conduit 19 leaks through the output valve 20 and the relief valve, into the pump chamber 14). At the same time as the internal combustion engine is shut down (i.e. immediately after the internal combustion engine has stopped), the control unit 7 controls the flow regulating device 6 to allow the inlet valve 18 to close, the inlet valve 18 spontaneously closing when the pressure in the pump chamber 14 increases (due to the high-pressure fuel leaking through the output valve 20 and the relief valve), because the fuel pressure in the pump chamber 14 has become greater than the fuel pressure in the inlet conduit 17. Once the inlet valve 18 has been closed (because the flow regulating device 6 has allowed it to close), the fuel pressure in the pump chamber 14 gradually (but more slowly) increases due to the continued (but more and more decreasing) leakage of fuel through the outlet valve 20 and the pressure relief valve. After a relatively short time (even less than one second, or in any case a few seconds), the fuel pressure in the pump chamber 14 reaches a value in order to keep the inlet valve 18 closed, irrespective of the action of the flow regulating device 6. In other words, the flow regulating device 6 is able to prevent the inlet valve 18 from closing when the fuel pressure in the pump chamber 14 is only slightly (minimally) higher than the fuel pressure in the inlet conduit 17, but the flow regulating device 6 is unable to reopen the inlet valve 18 when the fuel pressure in the pump chamber 14 is substantially higher than the fuel pressure in the inlet conduit 17.

In other words, at a time when the internal combustion engine has stopped without significant delay, the control unit 7 controls the flow regulating device 6 to allow the inlet valve 18 to close while keeping the output valve 20 fully closed (i.e., without causing the output valve 20 to open, even partially open) so as to minimize the fuel flowing out of the pump chamber 14 through the inlet valve 18 and the fuel flowing into the pump chamber 14 through the output valve 20 from a time when the internal combustion engine has stopped without significant delay. In this way, a decrease in fuel pressure in the output conduit 19 and downstream of the pump chamber 14 is minimized.

Combinations between the embodiments described herein may be made without departing from the scope of the invention.

The control method described above has many advantages.

First, the above control method can significantly reduce the leakage of fuel through the output valve 20 and the pressure reducing valve when the internal combustion engine is stopped (turned off). This result is that, because the inlet valve 18 is allowed to close when the internal combustion engine is stopped (closed), fuel that initially flows through the output valve 20 and the pressure relief valve remains in the pump chamber 14, thereby increasing the fuel pressure inside the pump chamber 14 and thus significantly reducing the pressure differential between the output valve 20 and the pressure relief valve. Of course, the pressure difference between the output valve 20 and the pressure reducing valve is reduced (almost eliminated), and as a result, leakage of fuel through the output valve 20 and the pressure reducing valve is reduced (almost eliminated).

The above-described control method is more effective when the sealing gasket 32 is included, which makes it possible to minimize fuel leakage from the pump chamber 14 and through the gap between the guide bush 30 and the piston 15.

The implementation costs of the above-described control method are substantially zero, since only a small part of the code has to be added to the software of the control unit 7.

The control method described above can also be applied to the already marketed injection system 1 via a simple update of the software of the control method 7.

List of reference numerals:

1 spray system

2 ejector

3 common rail

4 high-pressure fuel pump

5 supply conduit

6 adjusting device

7 control unit

8 low pressure fuel pump

9 boxes

10 supply conduit

11 pressure sensor

12 main body

13 longitudinal axis

14 pump chambers

15 piston

16 spring

17 inlet conduit

18 inlet valve

19 output catheter

20 output valve

21 damping device

22 control lever

23 electromagnetic actuator

24 spring

25 electromagnet

26 anchor

27 dish

28 sheets

29 containing seat

30 guide bushing

31 centre hole

32 sealing gasket

Claims

1. A method of controlling a fuel injection system (1) for an internal combustion engine provided with a fuel pump (4), the fuel pump (4) comprising: a pump chamber (14); a piston (15) mounted to slide within the pump chamber (14); an inlet conduit (17) ending in the pump chamber (14) and provided with an inlet valve (18); an output conduit (19) starting from the pump chamber (14) and provided with an output valve (20); and a flow regulating device (6) coupled to the inlet valve (18) and controllable to prevent or allow the inlet valve (18) to close when the fuel pressure inside the pump chamber (14) exceeds the fuel pressure in the inlet conduit (17);

the control method includes the steps of detecting when the internal combustion engine is stopped;

the control method is characterized in that the control method comprises the further steps of: the flow regulating means (6) is controlled at a time when the internal combustion engine has stopped without significant delay to allow the inlet valve (18) to close while keeping the outlet valve (20) fully closed to minimize fuel flowing out of the pump chamber (14) through the inlet valve (18) and fuel flowing into the pump chamber (14) through the outlet valve (20) from a time when the internal combustion engine has stopped without significant delay.

2. The control method according to claim 1, comprising the further step of: the flow regulating means (6) is continuously controlled to allow the inlet valve (18) to close for a predetermined amount of time.

3. The control method of claim 2, wherein the predetermined amount of time ranges from 1 second to 5 seconds.

4. A control method according to claim 1, wherein the flow regulating means (6) is controlled to allow the inlet valve (18) to close immediately after the internal combustion engine has stopped.

5. A control method according to claim 1, wherein the flow regulating means (6) acts only on the inlet valve (18) and has no effect on the outlet valve (20).

6. The control method according to claim 1, wherein the inlet valve (18) is completely separate and independent from the outlet valve (20).

7. A control method according to claim 1, wherein the flow regulating means (6) is controlled to allow the inlet valve (18) to close while keeping the outlet valve (20) fully closed, at a time when the combustion engine has stopped without significant delay, so as to minimize a reduction in fuel pressure in the outlet conduit (19) and downstream of the pump chamber (14).

8. The control method according to claim 1, wherein:

after the internal combustion engine has stopped, the fuel pressure in the pump chamber (14) increases due to the high-pressure fuel leaking through the output valve (20), and the inlet valve (18) spontaneously closes because the fuel pressure in the pump chamber (14) becomes greater than the fuel pressure in the inlet conduit (17);

once the inlet valve (18) has been closed, the fuel pressure in the pump chamber (14) increases gradually and more slowly due to a constant but decreasing leakage of fuel through the output valve (20) as the flow regulating means (6) has allowed the inlet valve (18) to close;

at some point, the fuel pressure in the pump chamber (14) reaches a value that allows it to keep the inlet valve (18) closed, regardless of the action of the flow regulating device (6).

9. The control method according to any one of claims 1 to 8, wherein the flow regulating device (6) comprises a control lever (22) coupled to the inlet valve (18) and movable between a passive position in which the control lever allows the inlet valve (18) to close and an active position in which the control lever does not allow the inlet valve (18) to close.

10. The control method according to claim 9, wherein the flow regulating device (6) comprises an electromagnetic actuator (23) coupled to the control lever (22) to move the control lever (22) between the active position and the passive position.

11. Control method according to claim 10, wherein the electromagnetic actuator (23) comprises a spring (24) holding the control lever (22) in the active position and an electromagnet (25) designed to overcome the spring force generated by the spring (24) to move the control lever (22) to the passive position.

12. A control method according to claim 9, wherein the inlet valve (18) comprises a disc (27) having a series of feed-through holes through which fuel can flow; and a flexible sheet (28) having a circular shape, the flexible sheet abutting against the base of the disc (27) so as to close the passage through the feed hole, and the flexible sheet being coupled to the control lever (22) of the flow regulating device (6).

13. The control method according to any one of claims 1 to 8, wherein the fuel pump (4) includes:

a housing seat (29) defined in the main body (12) below the pump chamber (14);

a guide bush (30) housed in the housing seat (29) and provided with a central hole (31) in which the piston (15) is slidingly arranged; and

and a sealing gasket (32) interposed between the piston (15) and the central hole (31) of the guide bush (30).

14. A control method according to any one of claims 1 to 8, wherein the fuel pump (4) comprises a one-way pressure relief valve which only allows fuel to flow into the pump chamber (14) through the output conduit (19).