Abnormality diagnosis device for fuel pressure sensor

Abstract

To provide an abnormality diagnostic device of a fuel pressure sensor in which misdiagnosis is suppressed.SOLUTION: An abnormality diagnosis device for a fuel pressure sensor, which is applied to an engine system of a vehicle and performs abnormality diagnosis of the fuel pressure sensor based on a detection value of the fuel pressure sensor after an ignition is turned off, wherein the abnormality diagnosis is executed when a temperature of cooling water of the engine becomes equal to or lower than a predetermined temperature before a predetermined time elapses after the ignition is turned off.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to an abnormality diagnosis device for a fuel pressure sensor. [Background technology]

[0002] A vehicle engine system is equipped with a fuel pressure sensor that detects the fuel pressure in a high-pressure fuel passage to which fuel pressurized by a high-pressure pump is supplied. After the ignition is turned off, the temperature of the fuel in the high-pressure fuel passage drops, which in turn reduces the fuel pressure in the high-pressure fuel passage. A method for diagnosing an abnormality in the fuel pressure sensor is known, in which the fuel pressure sensor's detection value after the ignition is turned off indicates a drop in fuel pressure (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2020-148199 Summary of the Invention [Problem to be solved by the invention]

[0004] In some engine systems, a check valve is provided in the high-pressure fuel passage to allow fuel to pass from the high-pressure pump to the direct injection valve but restrict fuel from passing from the direct injection valve to the high-pressure pump. Because of the presence of such a check valve, the fuel pressure may rise again after a temporary drop due to, for example, a change in outside air temperature after the ignition is turned off. If an abnormality diagnosis of the fuel pressure sensor is performed when the fuel pressure rises in this way, the fuel pressure sensor may be erroneously diagnosed as abnormal even though it is actually normal.

[0005] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide an abnormality diagnosis device for a fuel pressure sensor that is capable of suppressing erroneous diagnosis. [Means for solving the problem]

[0006] The object is to provide an engine, an in-cylinder injection valve that directly injects fuel into a cylinder of the engine, a port injection valve that injects fuel into an intake port of the engine, a low-pressure pump that pressurizes fuel, a low-pressure fuel passage that supplies the fuel pressurized by the low-pressure pump to the port injection valve, a high-pressure pump that further pressurizes the fuel supplied from the low-pressure fuel passage, a high-pressure fuel passage that branches off from the low-pressure fuel passage and supplies the fuel pressurized by the high-pressure pump to the in-cylinder injection valve, and a fuel pump that is disposed in the high-pressure fuel passage and allows fuel to pass from the high-pressure pump side to the in-cylinder injection valve side but does not allow fuel to pass from the in-cylinder injection valve side to the This can be achieved by a fuel pressure sensor abnormality diagnosis device that is applied to a vehicle engine system that is equipped with a check valve that restricts the passage of fuel to the high-pressure pump side, a fuel pressure sensor that detects the fuel pressure on the in-cylinder injection valve side of the check valve in the high-pressure fuel passage, and a water temperature sensor that detects the temperature of the engine coolant, and that performs abnormality diagnosis of the fuel pressure sensor based on the detection value of the fuel pressure sensor after the ignition is turned off, and that performs the abnormality diagnosis if the temperature of the engine coolant falls below a predetermined temperature before a predetermined time has elapsed since the ignition was turned off. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide an abnormality diagnosis device for a fuel pressure sensor in which erroneous diagnosis is suppressed. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a schematic configuration diagram of an engine system according to an embodiment of the present invention; [Figure 2] 4 is a flowchart illustrating an example of abnormality diagnosis control for a fuel pressure sensor. [Figure 3] 10 is a timing chart showing the transition of fuel pressure in the high-pressure delivery pipe when abnormality diagnosis of the fuel pressure sensor is not performed and is discontinued. DETAILED DESCRIPTION OF THE INVENTION

[0009] [Engine system overview] 1 is a schematic diagram of an engine system 1 of this embodiment. The engine system 1 includes an engine 10 and an ECU (Electronic Control Unit) 40 that controls the engine 10. The engine 10 is a spark-ignition inline four-cylinder engine equipped with a cylinder group 11 including cylinders 111 to 114 arranged in series, a direct injection valve group 37, and a port injection valve group 27. The ECU 40 is an example of an abnormality diagnosis device for a fuel pressure sensor.

[0010] The in-cylinder injection valve group 37 includes in-cylinder injection valves 371 to 374 that inject fuel into the cylinders 111 to 114, respectively. The port injection valve group 27 includes port injection valves 271 to 274 that inject fuel into the intake ports 13 that communicate with the cylinders 111 to 114, respectively. Each of the in-cylinder injection valve group 37 and the port injection valve group 27 is an electromagnetically driven open / close valve.

[0011] The engine 10 is formed with an intake passage 12 having a plurality of intake ports 13 corresponding to each of the cylinder groups 11, and an exhaust passage having a plurality of exhaust ports (not shown). Each of the cylinder groups 11 houses a piston (not shown) to define a combustion chamber. The combustion chamber is opened and closed by an intake valve and an exhaust valve. The engine 10 is also equipped with a spark plug (not shown). The engine 10 is also equipped with a crankshaft 14 linked to the plurality of pistons, and an intake camshaft 15 linked to the crankshaft 14 to drive the intake valve. The engine is also equipped with a crank angle sensor 14a that detects the rotation angle of the crankshaft 14, and an air flow meter 12a that detects the amount of intake air Ga introduced into the intake passage 12.

[0012] The engine system 1 includes a fuel tank 21, a low-pressure fuel pump 22, a pressure regulator 23, a low-pressure fuel pipe 25, a low-pressure delivery pipe 26, and a fuel pressure sensor 28. The fuel tank 21 stores gasoline as fuel. The low-pressure fuel pump 22 pressurizes the fuel and discharges it into the low-pressure fuel pipe 25. The pressure regulator 23 adjusts the pressure of the fuel discharged into the low-pressure fuel pipe 25 to a preset low-pressure supply pressure. The drive of the low-pressure fuel pump 22 is controlled by the ECU 40.

[0013] The low-pressure fuel pipe 25 and the low-pressure delivery pipe 26 supply the fuel discharged from the low-pressure fuel pump 22 to the port injection valve group 27. The fuel is pressurized to a predetermined pressure level by the low-pressure fuel pump 22 and adjusted to a low-pressure supply pressure by the pressure regulator 23, and is introduced into the low-pressure delivery pipe 26 via the low-pressure fuel pipe 25. The low-pressure fuel pipe 25 and the low-pressure delivery pipe 26 are an example of a low-pressure fuel passage.

[0014] The port injection valve group 27 is connected to a low-pressure delivery pipe 26 and injects fuel into the intake ports 13 corresponding to the respective cylinder groups 11. A fuel pressure sensor 28 detects the fuel pressure value in the low-pressure delivery pipe 26.

[0015] The engine system 1 includes a high-pressure fuel pump 31, a high-pressure fuel pipe 35, a high-pressure delivery pipe 36, and a fuel pressure sensor 38. The high-pressure fuel pump 31 draws fuel from a branch pipe 25a branched from the low-pressure fuel pipe 25, and pressurizes the fuel to a high-pressure level higher than the supply pressure level from the low-pressure fuel pump 22. The branch pipe 25a is provided with a pulsation damper 29 that suppresses fuel pressure pulsation within the branch pipe 25a.

[0016] Specifically, the high-pressure fuel pump 31 includes a pump housing 31h, a plunger 31p slidable within the pump housing 31h, and a pressurization chamber 31a defined between the pump housing 31h and the plunger 31p. The volume of the pressurization chamber 31a changes in response to the displacement of the plunger 31p. With the solenoid valve 32 open, fuel pressurized by the low-pressure fuel pump 22 is introduced into the pressurization chamber 31a via the branch pipe 25a. The fuel in the pressurization chamber 31a is pressurized to a high pressure by the plunger 31p and discharged into the high-pressure fuel pipe 35.

[0017] A pump cam 19 that drives a plunger 31p is attached to the intake camshaft 15 of the engine 10. The high-pressure fuel pump 31 has a follower lifter 31f that is raised and lowered by the pump cam 19, and a pump spring 31g that urges the follower lifter 31f toward the pump cam 19. The plunger 31p is linked to the follower lifter 31f, and rises and falls together with the follower lifter 31f.

[0018] A solenoid valve 32 is provided at a fuel inlet port of the pressurization chamber 31a of the high-pressure fuel pump 31. The solenoid valve 32 has a valve element 32v, a coil 32c that drives the valve element 32v, and a spring 32k that constantly biases the valve element 32v in an open direction. The supply of electricity to the coil 32c is controlled by the ECU 40. When the coil 32c is energized, the valve element 32v blocks communication between the branch pipe 25a of the low-pressure fuel pipe 25 and the pressurization chamber 31a against the biasing force of the spring 32k. When the coil 32c is not energized, the valve element 32v is maintained in an open state by the biasing force of the spring 32k.

[0019] A spring-loaded check valve 34 is provided in the high-pressure fuel pipe 35 between the high-pressure fuel pump 31 and the in-cylinder injection valve group 37. The check valve 34 opens when the fuel pressure in the high-pressure fuel pump 31 becomes higher than the fuel pressure in the high-pressure fuel pipe 35 by a predetermined amount.

[0020] During the intake stroke of the high-pressure fuel pump 31, the solenoid valve 32 opens and the plunger 31p descends, allowing fuel to be supplied from the branch pipe 25a of the low-pressure fuel pipe 25 to the pressurization chamber 31a. During the pressurization stroke, the solenoid valve 32 closes and the plunger 31p ascends, reducing the volume of the pressurization chamber 31a and increasing the pressure of the fuel in the pressurization chamber 31a. During the discharge stroke, when the force due to the fuel pressure in the pressurization chamber 31a exceeds the biasing force of the check valve 34 spring, the check valve 34 opens and the pressurized fuel is supplied to the high-pressure fuel pipe 35 and the high-pressure delivery pipe 36. As described above, the elevation of the plunger 31p is achieved by the rotation of the pump cam 19, which is linked to the crankshaft 14 via the intake camshaft 15. Therefore, the high-pressure fuel pump 31 is driven in conjunction with the crankshaft 14.

[0021] High-pressure fuel pressurized by the high-pressure fuel pump 31 is accumulated in the high-pressure delivery pipe 36 via the high-pressure fuel piping 35. The high-pressure fuel piping 35 and the high-pressure delivery pipe 36 supply high-pressure fuel from the high-pressure fuel pump 31 to the in-cylinder injection valves 371 to 374. The high-pressure fuel piping 35 and the high-pressure delivery pipe 36 are an example of a high-pressure fuel passage.

[0022] Direct injection valve group 37 injects high-pressure fuel directly into each of cylinders 111 to 114 in a predetermined sequence from within high-pressure delivery pipe . Fuel pressure sensor detects the fuel pressure within high-pressure delivery pipe .

[0023] The ECU 40 includes a CPU (Central Processing Unit), a ROM (Read Only Memory), and a RAM (Random Access Memory). The ECU 40 executes abnormality diagnosis control of a fuel pressure sensor 38 (described later) based on information from sensors and information previously stored in the ROM, in accordance with a control program previously stored in the ROM. The ECU 40 is electrically connected to an accelerator operation amount sensor 41 for detecting an accelerator operation amount Acc, an ignition switch 42 for detecting whether the ignition is ON or OFF, a water temperature sensor 43 for detecting the temperature of the coolant for the engine 10, and the above-mentioned fuel pressure sensors 28 and 38.

[0024] The ECU 40 determines the fuel injection allocation ratio between the in-cylinder injection valve group 37 and the port injection valve group 27 based on the rotational speed NE of the engine 10 and the accelerator depression amount Acc. Next, the ECU 40 calculates a target injection amount Qdt for each of the in-cylinder injection valves 371-374 and a target fuel pressure Pdt, which is a target value of the fuel pressure in the high-pressure delivery pipe 36 when fuel is injected from each of the in-cylinder injection valves 371-374, based on the allocation ratio, the rotational speed NE, and the accelerator depression amount Acc. Next, the ECU 40 calculates an injection time Fdi, which is the execution time of the fuel injection for each of the in-cylinder injection valves 371-374, based on the target injection amount Qdt and the target fuel pressure Pdt. The ECU 40 energizes the in-cylinder injection valves 371, 373, 374, and 372 in that order at predetermined crank angle intervals for the calculated injection time Fdi. In this way, the fuel injection amount of each of the direct injection valves 371 to 374 is controlled to the target injection amount Qdt.

[0025] Similarly, based on the above-mentioned sharing ratio, the engine speed NE, and the accelerator depression amount Acc, the ECU 40 calculates the target injection amount Qpt for each of the port injection valves 271-274 and the target fuel pressure Ppt, which is the target value of the fuel pressure in the low-pressure delivery pipe 26 when fuel is injected from each of the port injection valves 271-274. Next, based on the target injection amount Qpt and the target fuel pressure Ppt, the ECU 40 calculates the injection time Fpi, which is the execution time of the fuel injection for each of the port injection valves 271-274. The ECU 40 energizes the port injection valves 271, 273, 274, and 272 in that order at predetermined crank angle intervals for the calculated injection time Fpi. In this way, the fuel injection amount of each of the port injection valves 271-274 is controlled to the target injection amount Qpt.

[0026] [Fuel pressure sensor 38 abnormality diagnosis] During the soak period after the ignition is turned off, if the detection value of the fuel pressure sensor 38 indicates approximately zero, the ECU 40 diagnoses that the fuel pressure sensor 38 is normal, and if the detection value of the fuel pressure sensor 38 indicates anything other than that, the ECU 40 diagnoses that the fuel pressure sensor 38 is abnormal.

[0027] 2 is a flowchart illustrating an example of abnormality diagnosis control for the fuel pressure sensor 38. The ECU 40 determines whether the ignition is off (step S1). If the answer is No in step S1, this control ends. If the answer is Yes in step S1, the ECU 40 determines whether a predetermined time A has elapsed since the ignition was turned off (step S2). The predetermined time A is set to the minimum time during which it is considered that the fuel pressure in the high-pressure delivery pipe 36 may increase after the ignition was turned off. This is because if too much time has elapsed since the ignition was turned off, the fuel pressure may increase due to changes in the outside air temperature.

[0028] If the answer is No in step S2, the ECU 40 determines whether the temperature of the coolant of the engine 10 is equal to or lower than a predetermined temperature B (step S3). The predetermined temperature B is set to the maximum temperature of the coolant at which the fuel pressure in the high-pressure delivery pipe 36 is considered to have sufficiently decreased since the ignition was turned off. If the coolant temperature has not decreased sufficiently even after a long period of time has passed, the environment is such that the coolant temperature is unlikely to decrease, and further waiting is not expected to result in a temperature decrease, and the coolant temperature may actually increase. The predetermined temperature B is a temperature lower than the temperature indicating that the warm-up of the engine 10 is complete. Note that the predetermined temperature B may be set to a lower value as the fuel pressure indicated by the detection value of the fuel pressure sensor 38 when the ignition was turned off increases. If the answer is No in step S3, this control ends. That is, if the answer is Yes in step S1 and No in steps S2 and S3, this control is repeatedly executed.

[0029] If step S3 is Yes, the ECU 40 performs an abnormality diagnosis on the fuel pressure sensor 38 (step S4). Specifically, it is determined whether the detection value of the fuel pressure sensor 38 indicates approximately zero. If the detection value indicates approximately zero, the fuel pressure sensor 38 is diagnosed as normal, and otherwise, it is diagnosed as abnormal. If step S2 is Yes, the ECU 40 stops performing an abnormality diagnosis on the fuel pressure sensor 38 (step S5). That is, if the coolant temperature has not dropped to or below a predetermined temperature B by the time the elapsed time since the ignition was turned off reaches a predetermined time A, the abnormality diagnosis on the fuel pressure sensor 38 is not performed. Note that the ECU 40 may obtain the detection value of the fuel pressure sensor 38 at the time when step S2 is Yes, and not perform the abnormality diagnosis by not outputting a diagnostic result based on that detection value.

[0030] 3 is a timing chart showing the change in fuel pressure in the high-pressure delivery pipe 36 when an abnormality diagnosis of the fuel pressure sensor 38 is not performed and is canceled. In addition to the fuel pressure in the high-pressure delivery pipe 36, FIG. 3 also shows the changes in engine speed, ambient temperature, and water temperature. When the ignition is turned off at night, the engine speed drops to zero, and the fuel pressure and water temperature begin to drop, along with the ambient temperature (time t1). After that, the fuel pressure in the high-pressure delivery pipe 36 drops to 0 MPa (time t2), but the fuel pressure does not become negative. This is because, when the fuel pressure in the high-pressure delivery pipe 36 attempts to become negative, the check valve 34 opens, allowing fuel to be supplied from the low-pressure fuel pipe 25 through the branch pipe 25a into the high-pressure fuel pipe 35 and the high-pressure delivery pipe 36.

[0031] When a predetermined time A has elapsed since the ignition was turned off, the water temperature is higher than the predetermined temperature B, and therefore the execution of the abnormality diagnosis is stopped (time t3). When night turns to day (time t4), the outside air temperature begins to rise, and the fuel pressure in the high-pressure delivery pipe 36 begins to increase (time t5). For example, if an abnormality diagnosis of the fuel pressure sensor 38 is executed while the fuel pressure in the high-pressure delivery pipe 36 is increasing, an erroneous diagnosis may be made. As night approaches, the outside air temperature begins to drop again, and the fuel pressure and water temperature begin to drop again, and the fuel pressure again becomes 0 MPa (time t6). By stopping the abnormality diagnosis of the fuel pressure sensor 38 in such a case, an erroneous diagnosis is prevented.

[0032] The fuel pressure sensor abnormality diagnostic device has been described above as being applied to a vehicle engine system 1, but the invention is not limited to this. For example, the fuel pressure sensor abnormality diagnostic device can be applied to any device that uses an engine as a power source, and can also be applied to engine systems mounted on so-called hybrid vehicles, motorcycles, etc.

[0033] Although the embodiments of the present invention have been described in detail above, the present invention is not limited to such specific embodiments, and various modifications and variations are possible within the scope of the gist of the present invention as defined in the claims. [Explanation of symbols]

[0034] 1 Engine System 10 Engine 22 Low-pressure fuel pump 25 Low-pressure fuel piping (low-pressure fuel passage) 26 Low-pressure delivery pipe (low-pressure fuel passage) 27 port injection valve group 271~274 Port injection valve 38 Fuel pressure sensor 31 High-pressure fuel pump 35 High-pressure fuel piping (high-pressure fuel passage) 36 High-pressure delivery pipe (high-pressure fuel passage) 37 In-cylinder injection valve group 371~374 In-cylinder injection valve 40 ECU (abnormality diagnosis device, execution unit, cancellation unit) 42 Ignition switch 43 Water temperature sensor

Claims

[Claim 1] a low-pressure pump that pressurizes fuel; a low-pressure fuel passage that supplies the fuel pressurized by the low-pressure pump to the port injection valve; a high-pressure pump that further pressurizes the fuel supplied from the low-pressure fuel passage; a high-pressure fuel passage that branches off from the low-pressure fuel passage and supplies the fuel pressurized by the high-pressure pump to the in-cylinder injection valve; a check valve that is disposed in the high-pressure fuel passage and allows fuel to pass from the high-pressure pump side to the in-cylinder injection valve but restricts fuel from passing from the in-cylinder injection valve side to the high-pressure pump side; a fuel pressure sensor that detects the fuel pressure on the in-cylinder injection valve side of the high-pressure fuel passage relative to the check valve; and a water temperature sensor that detects the temperature of cooling water for the engine, The abnormality diagnosis device for a fuel pressure sensor executes the abnormality diagnosis when the temperature of the engine cooling water falls below a predetermined temperature before a predetermined time has elapsed since the ignition was turned off.

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