Abnormality diagnostic device for engine fuel system

Abstract

To achieve both suppression of engine malfunctions and more accurate determination of a fault in a high fuel pressure pump.SOLUTION: A controller 10: upon determining that a relief valve 25 is open at start of an engine E, stops the engine E while deferring determination of whether or not there is a failure in a high fuel pressure pump 23; waits for a predetermined period of time from the engine stopping until the relief valve 25 closes, and then, restarts the engine E; and upon determining again that the relief valve 25 is open at restart of the engine, determines that a failure has occurred in the high fuel pressure pump 23.SELECTED DRAWING: Figure 7

Description

[Technical field]

[0001] The present disclosure relates to an engine fuel system abnormality diagnosis device. [Background technology]

[0002] For example, Patent Document 1 discloses a relief valve opening determination device. This valve opening determination device includes a high fuel pressure pump (fuel pump) that pressurizes and discharges fuel, a pressure sensor that detects the pressure of the high-pressure fuel in a pressure accumulator, and a relief valve that opens when the fuel pressure rises to a predetermined valve opening pressure.

[0003] The valve open determination device according to Patent Document 1, when it is determined that the pressure detected by the pressure sensor has risen to the valve open pressure, acquires a pressure drop parameter indicating the slope of the pressure drop after the detected pressure changes from an increase to a decrease or a correlation value thereof. The valve open determination device determines that the relief valve is in an open state based on the acquired pressure drop parameter. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2019-052609 A Summary of the Invention [Problem to be solved by the invention]

[0005] As described in the above-mentioned Patent Document 1, it is known to determine that a failure has occurred in the high fuel pressure pump, for example, in its discharge system, by determining that the relief valve is in an open state.

[0006] However, depending on the engine configuration, the volume of the fuel system related to the high fuel pressure pump is small, making it easier for the fuel pressure to increase. In addition, when the engine is stopped, the fuel temperature rises, which may lead to an increase in fuel pressure.

[0007] It has now been discovered that the aforementioned factors, combined with vibration of the relief valve caused by the engine's starting system, may cause the relief valve to open during engine start-up, and this opening is not due to a failure of the high fuel pressure pump.

[0008] The opening of the relief valve at the time of starting not only leads to malfunction of the engine, but also leads to an erroneous determination of a fault in the high fuel pressure pump, as described above, which is inconvenient.

[0009] The present disclosure has been made in consideration of the above points, and has an object to simultaneously suppress engine malfunctions and more accurately determine a fault in the high fuel pressure pump. [Means for solving the problem]

[0010] The present disclosure relates to a fuel system abnormality diagnosis device for an engine, the fuel system abnormality diagnosis device comprising: a high fuel pressure pump connected to a drive shaft of an engine and pressurizing and discharging fuel, a fuel pipe through which the high-pressure fuel discharged from the high fuel pressure pump flows, an injector connected to the fuel pipe and injecting the high-pressure fuel, a mechanical relief valve that opens when the fuel pressure in the fuel pipe rises to a predetermined valve opening pressure and closes when the fuel pressure in the fuel pipe falls to a predetermined valve closing pressure, a fuel pressure sensor that detects the pressure of the fuel discharged from the high fuel pressure pump in the fuel pipe, and a controller that determines whether the fuel pressure can reach the valve opening pressure based on the fuel pressure detected by the fuel pressure sensor, and the controller determines that the relief valve is open when the fuel pressure in the fuel pipe falls below a predetermined first threshold after it is determined that the fuel pressure in the fuel pipe can reach the valve opening pressure, and determines whether the high fuel pressure pump has a malfunction based on the determination result.

[0011] According to the present disclosure, when the controller determines that the relief valve is open upon starting the engine, it stops the engine while deferring determination of the presence or absence of a malfunction, and restarts the engine after waiting for a predetermined period of time from the engine stop to wait for the relief valve to close, and when the controller determines again that the relief valve is open upon restarting the engine, it determines that a malfunction has occurred in the high fuel pressure pump.

[0012] According to the above configuration, when the controller determines that the relief valve is open when starting the engine, the controller stops the engine, waits for the engine to be stopped, and then restarts the engine. This makes it possible to wait for the relief valve to be closed before restarting the engine, thereby making it possible to suppress malfunctions of the engine.

[0013] Furthermore, with the above-mentioned configuration, if the controller again determines that the relief valve is open when the engine is restarted, it determines that some kind of failure has occurred in the high fuel pressure pump. This makes it possible to more accurately determine a failure in the high fuel pressure pump without erroneously determining that the valve is open due to a rise in fuel temperature, vibration from a starting device, etc.

[0014] The engine may be a single cylinder engine, and the controller may increase the engine speed to a normal speed by a starting device when starting and restarting the engine.

[0015] According to the above configuration, since the engine is a single cylinder engine, the overall volume of the fuel supply system is compact compared to a multi-cylinder engine. In this case, the fuel pressure is relatively likely to increase, and this, combined with factors such as an increase in fuel temperature, can easily lead to high fuel pressure. For this reason, accurate fault determination as described above is particularly effective.

[0016] The engine may be an engine that is not connected to the drive wheels of the vehicle and is dedicated to generating electricity.

[0017] According to the above configuration, since the engine is dedicated to generating electricity, the overall volume of the fuel supply system is compact compared to engines used for driving vehicles. In this case, the fuel pressure tends to increase relatively easily, and this, combined with factors such as an increase in fuel temperature, can easily lead to high fuel pressure. For this reason, accurate failure determination as described above is particularly effective.

[0018] In addition, since the engine is dedicated to generating electricity, even if start-up is retried, the effect on the driving feeling can be minimized as compared to an engine used to run a vehicle.

[0019] In addition, a pressure value that is less than the valve opening pressure and greater than or equal to the first threshold value may be set as a second threshold value, and the controller may determine that the fuel pressure in the fuel pipe may reach the valve opening pressure when the fuel pressure exceeds the second threshold value while the engine speed is increasing upon starting or restarting the engine.

[0020] The above configuration contributes to more accurate fault determination of the high fuel pressure pump. Effect of the Invention

[0021] As described above, according to the present disclosure, it is possible to both suppress engine malfunctions and more accurately determine a fault in the high fuel pressure pump. [Brief description of the drawings]

[0022] [Figure 1] FIG. 1 is a diagram illustrating a vehicle equipped with an engine. [Diagram 2] FIG. 2 is a diagram illustrating a schematic configuration of the engine. [Diagram 3] FIG. 3 is a functional block diagram illustrating the configuration of the engine fuel system abnormality diagnosis device. [Figure 4] FIG. 4 is a flowchart illustrating a process related to the driving force control of the vehicle. [Diagram 5]FIG. 5 is a flowchart illustrating an example of an engine start process, a process for determining whether the relief valve is open, and a process for determining a failure based on the result of the process.

[0023] [Figure 6] FIG. 6 is a flowchart illustrating a process related to the valve open determination. [Figure 7] FIG. 7 is a flowchart illustrating a process related to retrying the valve open determination. [Figure 8] FIG. 8 is a diagram showing a schematic transition of the fuel pressure during the determination of whether the relief valve is open. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] Hereinafter, an embodiment of the present disclosure will be described. Note that the following description is an example. Fig. 1 is a diagram illustrating a vehicle 100 equipped with an engine E. Fig. 2 is a diagram illustrating a schematic configuration of the engine E. Fig. 3 is a functional block diagram illustrating a configuration of a fuel system abnormality diagnosis device 1 for the engine E.

[0025] (Overall composition) The vehicle 100 is a so-called series hybrid vehicle. The vehicle 100 includes a drive device P and a controller 10. The drive device P includes an electric drive unit 110 for driving the vehicle 100 using electric power, and an engine E for generating electricity. The controller 10 is electrically connected to the drive device P and controls each function of the drive device P.

[0026] The electric drive unit 110 has a motor 111, a reducer 112, and a generator 113. The motor 111 operates by receiving electric power. The reducer 112 reduces the output of the motor 111. The generator 113 generates electricity to be supplied to the motor 111.

[0027] Here, the generator 113 is a starter generator that combines a starting device and a power generator. The generator 113 functions as a starting device that starts the engine E, and also functions as a power generator that receives power from the engine E and generates electricity. As shown in Fig. 3 described later, the engine E starts operation by injecting high-pressure fuel from the injector 3 by the fuel supply system 2 and igniting the fuel by the spark plug 4.

[0028] The engine E is a single cylinder engine. For example, the engine E is a rotary engine with one rotor. Although details will be described later, when starting and restarting the engine E, the controller 10 increases the engine speed to a normal speed by using the generator 113 as a starting device. The "normal speed" here refers to a speed range suitable for generating electricity by the engine E.

[0029] The engine E is an engine dedicated to generating electricity, which is not connected to the drive wheels 101 (here, the front wheels) of the vehicle 100. That is, the power for propelling the vehicle 100 is generated by the motor 111. The power generated by the motor 111 is changed in speed by the reduction gear 112, and then transmitted to the drive wheels 101 (here, the front wheels) via a differential device.

[0030] The vehicle 100 includes a battery B. The battery B is charged with electricity generated by a generator 113 via a power generation inverter. The battery B converts the electricity stored therein by a motor inverter and outputs the converted electricity to the motor 111.

[0031] (Engine outline) 2, the engine E according to this embodiment includes a fuel supply system 2 for injecting fuel for generating electricity from an injector 3, and a controller 10. In addition to the injector 3 described above, the fuel supply system 2 includes a fuel tank 21, a low fuel pressure pump 22, a high fuel pressure pump 23, a fuel pipe 24, and a relief valve 25.

[0032] Here, the fuel pipe 24 has a low-pressure side pipe 24a, a high-pressure side pipe 24b, and a bypass pipe 24c. The low-pressure side pipe 24a connects the low fuel pressure pump 22 and the high fuel pressure pump 23. The high-pressure side pipe 24b connects the high fuel pressure pump 23 and the injector 3. The bypass pipe 24c bypasses the high fuel pressure pump 23 and connects the high-pressure side pipe 24b and the low-pressure side pipe 24a.

[0033] The fuel tank 21 stores fuel for generating electricity. The fuel tank 21 is disposed inside the vehicle 100.

[0034] The low fuel pressure pump 22 draws in fuel from the fuel tank 21, pressurizes it, and then discharges it. The low fuel pressure pump 22 is disposed inside the fuel tank 21. The low fuel pressure pump 22 is operated by receiving electric power from, for example, a battery B. The fuel discharged from the low fuel pressure pump 22 is supplied to the high fuel pressure pump 23 via a low pressure side pipe 24a.

[0035] The high fuel pressure pump 23 is connected to the drive shaft E1 of the engine E and configured to pressurize and discharge fuel. Specifically, the high fuel pressure pump 23 has a pressure chamber 23a, a spill valve 23b, a plunger 23c, and a discharge valve 23d.

[0036] The pressure chamber 23a receives fuel from the low-pressure side pipe 24a. The fuel inlet of the pressure chamber 23a is opened and closed by the spill valve 23b. The pressure chamber 23a discharges the fuel to the high-pressure side pipe 24b. The fuel outlet of the pressure chamber 23a is opened and closed by the discharge valve 23d. The pressure chamber 23a can also be called a "plunger chamber."

[0037] The spill valve 23b is a solenoid valve electrically connected to the controller 10. The closing timing of the spill valve 23b, and therefore the amount of fuel supplied to the pressure chamber 23a, are controlled by a control signal input from the controller 10 to the spill valve 23b.

[0038] The plunger 23c changes the pressure in the pressure chamber 23a. The plunger 23c is connected to a cam 23e. This cam 23e is connected to a drive shaft E1 of the engine E and rotates according to the rotation speed of the engine E (engine speed). As the cam 23e rotates, the plunger 23c repeatedly moves down and up. As the plunger 23c moves, the fuel in the pressure chamber 23a is pressurized.

[0039] The discharge valve 23d is a check valve. When the discharge valve 23d opens the outlet, the fuel pressurized by the plunger 23c is discharged from the pressure chamber 23a to the high-pressure side pipe 24b. The discharge valve 23d prevents the fuel from flowing back from the high-pressure side pipe 24b to the pressure chamber 23a. The discharge valve 23d can also be called a "check valve."

[0040] The mechanism of high-pressure fuel discharge will now be described.

[0041] The high fuel pressure pump 23 opens the spill valve 23b during the downward stroke of the plunger 23c, and draws fuel into the pressure chamber 23a from the low pressure side. Thereafter, the spill valve 23b is open at the beginning of the stroke when the plunger 23c rises, so the fuel drawn into the pressure chamber 23a flows out to the low pressure side at the beginning of the upward stroke (the fuel returns). Thereafter, when the spill valve 23b is closed at a timing appropriate for the amount of fuel discharged, the outflow of fuel to the low pressure side is blocked, the fuel in the pressure chamber 23a is pressurized, and the discharge side check valve (non-return valve 23d) is opened to discharge the fuel. At the timing when high pressure fuel is discharged, the spill valve 23b is closed. The high-pressure side pipe 24b of the fuel pipe 24 passes the high-pressure fuel discharged from the high fuel pressure pump 23. The injector 3 that injects the high-pressure fuel is connected to the high-pressure side pipe 24b. As described above, the engine E according to this embodiment is a single-cylinder engine. Therefore, only one injector 3 is connected to the high-pressure side pipe 24b.

[0042] 2, the bypass pipe 24c of the fuel pipe 24 has an upstream end connected to the high-pressure side pipe 24b and a downstream end connected to the low-pressure side pipe 24a, bypassing the high fuel pressure pump 23. A relief valve 25 is provided in the bypass pipe 24c.

[0043] Specifically, the relief valve 25 according to this embodiment is a mechanical relief valve that opens when the fuel pressure in the high-pressure side pipe 24b rises to a predetermined valve opening pressure and closes when the fuel pressure drops to a predetermined valve closing pressure. When the relief valve 25 opens, the high-pressure fuel in the high-pressure side pipe 24b returns to the low-pressure side pipe 24a through the bypass pipe 24c, and the fuel pressure in the high-pressure side pipe 24b drops.

[0044] Further, the high pressure side pipe 24b is provided with a fuel pressure sensor 11. This fuel pressure sensor 11 is configured to detect the pressure of the fuel in the high pressure side pipe 24b discharged from the high fuel pressure pump 23. A detection signal of the fuel pressure sensor 11 is sent to the controller 10. Note that the fuel pressure sensor 11 may detect the fuel pressure in the injector 3, or may detect the fuel pressure in the bypass pipe 24c on the upstream side of the relief valve 25 (the inlet side of the bypass pipe 24c). Note that the output upper limit Pl of the fuel pressure sensor 11 may be equal to or lower than the valve opening pressure of the relief valve 25, for example, as shown in FIG. 8.

[0045] (Vehicle control system) 3 is a functional block diagram illustrating the configuration of a fuel system abnormality diagnosis device 1 for an engine E. The fuel system abnormality diagnosis device 1 includes a fuel pressure sensor 11, a fuel supply system 2 for the engine E, an injector 3, and an ignition plug 4, and a controller 10.

[0046] The controller 10 is a microcomputer having a CPU, a ROM, a RAM, an input / output bus, etc. The controller 10 may be a combination of multiple modules, such as a module for a battery, a module for controlling the entire power train, a module for the motor 111, a module for the generator 113, and a module for the engine E.

[0047] In addition to the detection signal of the fuel pressure sensor 11, the controller 10 receives detection signals from a voltage sensor 12 and a current sensor 13 of the battery B, detection signals from an accelerator opening sensor 14 and a vehicle speed sensor 15 of the vehicle 100, and a detection signal from an engine revolution sensor 16 that detects the rotation speed of the engine E.

[0048] The controller 10 inputs control signals to the actuators constituting the vehicle 100 based on detection signals input from various sensors. Targets to which the control signals are input include the electric drive unit 110, the fuel supply system 2 of the engine E, the injector 3, and the spark plug 4. The controller 10 controls the running of the vehicle 100 by inputting control signals to these actuators.

[0049] These sensors and actuators are each connected to the controller 10 via a communication path 5. The communication path 5 transmits and receives signals between the respective sensors and actuators and the controller 10. For example, a controller area network (CAN) may be adopted as the communication protocol in the communication path 5.

[0050] For example, when controlling the driving force of the vehicle 100, the controller 10 executes the process shown in Fig. 4. Fig. 4 is a flowchart illustrating the process related to the driving force control of the vehicle 100.

[0051] First, in step S1 of Fig. 4, the controller 10 judges whether or not the vehicle 100 is in a start-up state (Ready ON?) The controller 10 repeats the judgment in step S1 until this judgment becomes YES.

[0052] In the following step S2, the controller 10 determines the SOC of the battery B based on the detection signals of the voltage sensor 12 and the current sensor 13. In addition, in this step S2, the controller 10 also reads a power generation prohibition flag, which will be described later.

[0053] In the next step S3, the controller 10 calculates the required driving force of the motor 111 based on the detection signals of the accelerator opening sensor 14 and the vehicle speed sensor 15. Note that the power generation prohibition flag may be read in this step S3 or in the following step S4. The order of steps S2 and S3 may be interchanged.

[0054] In the next step S4, the controller 10 calculates the amount of electric power required by the motor 111 based on the SOC calculated in step S2 and the required driving force calculated in step S3, and determines based on the calculation result whether or not power generation by the engine E is required. If this determination is NO (i.e., if operation of the engine E is not required), the controller 10 skips steps S5 and S6 described below and advances the control process to step S7.

[0055] On the other hand, if the determination in step S4 is YES (that is, if operation of the engine E is required), the controller 10 advances the control process to step S5.

[0056] In step S5, the controller 10 determines whether or not power generation by the engine E is permitted (power generation permitted?) based on the power generation prohibition flag read in step S3. If the power generation prohibition flag is 0, the controller 10 determines that power generation by the engine E is permitted. If the power generation prohibition flag is 1, the controller 10 determines that power generation by the engine E is prohibited. If the determination in step S5 is NO (i.e., if power generation by the engine E is prohibited), the controller 10 skips step S6 and advances the control process to step S7.

[0057] In this embodiment, when a failure occurs in the fuel supply system 2 of the engine E, particularly in the high fuel pressure pump 23 thereof, the generation of power by the engine E is prohibited.

[0058] On the other hand, if the determination in step S5 is YES (that is, if power generation by the engine E is not prohibited), the controller 10 advances the control process to step S6.

[0059] In the next step S6, the controller 10 calculates the required amount of power generation of the generator 113, and calculates the required engine driving force of the engine E so as to realize the required amount of power generation. Thereafter, the controller 10 drives the engine E based on these calculation results. The controller 10 determines a target fuel pressure of the high-pressure fuel in the fuel supply system 2 based on the required engine driving force of the engine E, and determines the closing timing of the spill valve 23b, etc. so as to realize the target fuel pressure. The controller 10 operates each part of the high fuel pressure pump 23 based on the thus determined closing timing, etc. In this way, the engine E is driven.

[0060] In the next step S7, the controller 10 inputs control signals to actuators such as the motor 111 to drive them so as to realize the required driving force calculated in step S3.

[0061] (Fuel system abnormality diagnosis processing) Next, the process related to the abnormality diagnosis of the fuel system (particularly, the failure judgment of the fuel supply system 2) will be described in detail with reference to Fig. 5 to Fig. 8. Here, Fig. 5 is a flowchart illustrating the process related to the start process of the engine E, the open valve judgment of the relief valve 25, and the failure judgment based on the judgment result. Fig. 6 is a flowchart illustrating the process related to the open valve judgment, and Fig. 7 is a flowchart illustrating the process related to the retry of the open valve judgment.

[0062] Additionally, Fig. 8 is a diagram showing a schematic diagram of a transition of the fuel pressure in the valve opening determination of the relief valve 25. Note that the horizontal axis of Fig. 8 indicates time, and the vertical axis of Fig. 8 indicates the magnitude of the fuel pressure.

[0063] First, in step S101 in Fig. 5, the controller 10 judges whether or not both the condition that the power generation of the engine E is requested and the condition that the power generation of the engine E is not prohibited are satisfied. This judgment is equivalent to judging whether or not the conditions for proceeding to step S6 via steps S4 and S25 in the flow in Fig. 4 are satisfied.

[0064] If the determination in step S101 is NO, the controller 10 returns to the determination in step S101. If the determination in step S101 is YES, the controller 10 advances the control process to step S102. The controller 10 repeats the determination in step S101 until the determination in the same step is YES.

[0065] In step S102, the controller 10 executes a start process for the engine E. Specifically, the controller 10 starts the engine E by the generator 113 as a starter, and increases the engine speed toward a normal speed. The plunger 23c starts to operate when the engine E is started, and the spill valve 23b is operated around the start of the operation, whereby high-pressure fuel is discharged to the high-pressure side pipe 24b based on the discharge mechanism described above. After the engine speed has been increased, the controller 10 discharges high-pressure fuel from the injector 3 and ignites the high-pressure fuel by the spark plug 4, thereby starting the operation of the engine E.

[0066] Before starting the operation of the engine E, the controller 10 executes the process of step S103 following step S102. The process of step S103 is started in synchronization with the start of the engine E, for example.

[0067] Specifically, the controller 10 starts counting by the first timer 10a in step S103. This count time corresponds to the elapsed time from when the engine E has started to be started.

[0068] In the following step S104, the controller 10 records the value of the fuel pressure at the time when the first timer 10a starts counting (that is, the time when the engine E starts to be started) based on the detection signal of the fuel pressure sensor 11.

[0069] In the following step S105, the controller 10 determines whether or not the relief valve 25 is opened. More specifically, in step S105, the controller 10 determines, based on the fuel pressure detected by the fuel pressure sensor 11, whether or not the fuel pressure can reach the valve opening pressure Po of the relief valve 25.

[0070] Furthermore, in step S105, the controller 10 determines that the relief valve 25 is open when the fuel pressure on the high-pressure side in the fuel pipe 24 falls below a predetermined first threshold value P1 after it is determined that the fuel pressure can reach the valve opening pressure Po.

[0071] Specifically, in step S105, the flow shown in Fig. 6 is executed. In this flow, first, in step S201, detection signals of various sensors are read. The detection signals read in step S201 include, for example, the detection signal of the engine revolution sensor 16 and the detection signal of the fuel pressure sensor 11.

[0072] In the following step S202, the controller 10 determines whether or not the drive shaft E1 of the engine E is rotating as a result of the generator 113 starting the engine E, for example.

[0073] Here, the fact that the drive shaft E1 is rotating means that it can be determined that the plunger 23c of the high fuel pressure pump 23 is operating. In this case, if the spill valve 23b of the high fuel pressure pump 23 is malfunctioning, it can be determined that there is a possibility that a large amount of high-pressure fuel will be discharged from the high fuel pressure pump 23, and as a result, the relief valve 25 will open. On the other hand, if the drive shaft E1 is not rotating, it can be determined that the high fuel pressure pump 23 is not operating in the first place, and there is no possibility that the relief valve 25 will open.

[0074] Therefore, if the determination in step S202 is YES, the controller 10 determines that the relief valve 25 can be opened, and proceeds to step S203. On the other hand, if the determination in step S202 is NO, it determines that there is no possibility that the relief valve 25 can be opened, and returns from the flow shown in Fig. 6. In the latter case, the controller 10 determines that "the relief valve 25 is not open."

[0075] Next, in step S203, the controller 10 determines whether or not the fuel pressure detected by the fuel pressure sensor 11 has exceeded a predetermined second threshold value P2. The second threshold value P2 is equal to or less than the valve opening pressure of the relief valve 25 and the output upper limit Pl of the fuel pressure sensor 11, and may be equal to or greater than a first threshold value P1 described later (see FIG. 8).

[0076] In other words, the processing of step S203, when the fuel pressure crosses and exceeds the second threshold value P2 while the engine speed is increasing during starting or restarting of the engine E, the controller 10 determines that the fuel pressure in the fuel pipe 24, particularly in the high-pressure side pipe 24b, may reach the valve opening pressure.

[0077] If the determination in step S203 is YES, the controller 10 advances the control process to step S204. In this step S204, the controller 10 sets an experience flag to 1, which indicates that the controller 10 has experienced that the fuel pressure has exceeded the second threshold value P2 when starting or restarting the engine E. For example, the value of this experience flag is reset to zero every time the engine E is started. After that, the controller 10 advances the control process to step S205.

[0078] On the other hand, if the determination in step S203 is NO, the controller 10 skips step S204 and advances the control process to step S205.

[0079] In step S205, the controller 10 judges whether or not the experience flag is 1, and if the judgement is YES, the control process proceeds to step S206, and if the judgement is NO, the control process returns to step S202.

[0080] In other words, as long as the engine E is rotating, if the fuel pressure exceeds the second threshold value P2 even once, the control process proceeds from step S205 to step S206. On the other hand, as long as the fuel pressure does not exceed the second threshold value P2, the control process does not proceed from step S205 to step S206.

[0081] In step S206, the controller 10 determines whether the fuel pressure detected by the fuel pressure sensor 11 has fallen below a predetermined first threshold value P1. The first threshold value P1 may be a value that is less than the valve opening pressure of the relief valve 25 and the output upper limit Pl of the fuel pressure sensor 11, and is also less than the above-mentioned first threshold value P1.

[0082] If the determination in step S206 is YES, the controller 10 advances the control process to step S207. In step S207, the controller 10 starts counting the time by the second timer 10b. This count time corresponds to the elapsed time since the fuel pressure fell below the first threshold value P1.

[0083] On the other hand, if the determination in step S206 is NO, the controller 10 returns the control process from step S206 to step S202.

[0084] Then, in step S208, the controller 10 determines that the fuel pressure detected by the fuel pressure sensor 11 has become equal to or lower than a third threshold value P3, which is lower than the target fuel pressure of the high-pressure fuel, within a predetermined first period T1 from the start of counting by the second timer 10b, and that the fuel pressure has maintained this state after becoming equal to or lower than the third threshold value P3 until a predetermined second period T2 (>first period T1) from the start of counting by the second timer 10b (see FIG. 8).

[0085] Here, the first period T1 is shorter than the third and fourth periods described below. The first period T1 may be, for example, 120 ms or more and 240 ms or less, more specifically, 150 ms or more and 210 ms or less. On the other hand, the second period T2 is longer than the first period T1 and shorter than the third and fourth periods. The second period T2 may be, for example, 400 ms or more and 800 ms or less, more specifically, 500 ms or more and 700 ms or less (see FIG. 8).

[0086] If both conditions of step S208 are satisfied, the controller 10 determines that "the relief valve 25 is open (relief valve: open)" (step S209). On the other hand, if at least one of the conditions of step S208 is not satisfied, the controller 10 determines that "the relief valve 25 is not open (relief valve: closed)" (step S210).

[0087] Next, the flow returns from the flow shown in Fig. 6 to the flow of Fig. 5. Then, in the processing after step S106, if it is determined in step S105 that the relief valve 25 is opened, the controller 10 determines whether or not a malfunction has occurred in the high fuel pressure pump 23 based on the determination result.

[0088] Specifically, in step S106 following step S105, the controller 10 determines whether the relief valve 25 is open (relief present?). If this determination is NO, the controller 10 advances the control process to step S112 to determine that no failure has occurred in the high fuel pressure pump 23. In the following step S113, the controller 10 assigns 0 to the power generation prohibition flag.

[0089] On the other hand, if the determination in step S106 is YES, the controller 10 advances the control process to step S108, and determines the retry condition for the relief determination illustrated in step S105 and FIG.

[0090] After that, in the subsequent steps S107 to S115, if the controller 10 determines that the relief valve 25 is open when the engine E is started, the controller 10 reserves the determination of the presence or absence of a malfunction and stops the engine E, and waits for a predetermined third period from the stop of the engine E to wait for the relief valve 25 to close, and then restarts the engine E. Then, if the controller 10 again determines that the relief valve 25 is open when the engine E is restarted, the controller 10 determines that a malfunction has occurred in the high fuel pressure pump 23.

[0091] Specifically, in step S107, the flow shown in Fig. 7 is executed. In this flow, first, in step S301, detection signals of various sensors are read in. The detection signals read in step S301 include, for example, the count by the first timer 10a and the detection signal of the fuel pressure sensor 11.

[0092] In the next step S302, the controller 10 judges whether or not the fuel pressure at the time of engine start recorded in step S104 in Fig. 5 is equal to or greater than a predetermined third threshold value P3. The third threshold value P3 may be, for example, a value equal to or greater than the first threshold value P1 and equal to or less than the output upper limit Pl of the fuel pressure sensor 11 (see Fig. 8). The judgment in step S302 is not essential.

[0093] If the determination in step S302 is YES, it can be determined that the relief valve 25 has opened because the fuel pressure was high to a certain extent at the time of starting. In this case, since it is considered possible that the relief valve 25 has opened due to a factor described below, that is, there is no malfunction in the fuel supply system 2, the controller 10 advances the control process to step S303 to establish the retry condition.

[0094] On the other hand, if the determination in step S302 is NO, it can be determined that the relief valve 25 has opened even though the fuel pressure is not very high at the time of starting. In this case, the controller 10 determines that the relief valve 25 has opened due to an event other than the factors described below, that is, that some kind of failure has occurred in the fuel supply system 2, and therefore advances the control process to step S305. In this case, the controller 10 ends the flow in FIG. 7 without satisfying the retry condition.

[0095] In step S303, the controller 10 determines whether or not the count time of the first timer 10a (the time elapsed since the start of the engine E) counted from step S103 in Fig. 5 is less than a predetermined fourth period. This fourth period may be set to about the time required to start the engine E. The fourth period may be set to, for example, 3 seconds or more and 7 seconds or less, more specifically, 4 seconds or more and 6 seconds or less.

[0096] If the determination in step S303 is YES, it can be determined that this is the first start before the retry. In this case, the controller 10 advances the control process to step S304 to retry the relief determination in step S105. The controller 10 determines in step S304 that the retry condition is met.

[0097] On the other hand, if the determination in step S303 is NO, it can be determined that it is time for restart after retry. In this case, the controller 10 advances the control process to step S305 so as not to repeatedly retry the relief determination. The controller 10 determines in step S305 that the retry condition is not satisfied.

[0098] Returning from the flow of Fig. 7 to the flow of Fig. 5, the controller 10 advances the control process to step S108. In step S108, the controller 10 determines whether or not a retry condition is met.

[0099] If the determination in step S108 is YES (if the retry condition is established), the controller 10 advances the control process to step S109 to suspend the determination of the presence or absence of a malfunction and temporarily stop the engine E.

[0100] On the other hand, if the determination in step S108 is NO (if the retry condition is not satisfied), the controller 10 determines that a failure has occurred in the high fuel pressure pump and advances the control process to step S114. In the following step S115, the controller 10 assigns 1 to the power generation prohibition flag.

[0101] In step S109, the controller 10 stops the starting of the engine E. Specifically, the controller 10 stops the ignition of the spark plug 4 and stops the fuel injection from the injector 3. This also stops the drive of the high fuel pressure pump 23.

[0102] In the next step S110, the controller 10 waits for a predetermined third period after starting and stopping the engine E without restarting it. If no failure occurs in the high fuel pressure pump 23, this waiting period reduces the fuel pressure and closes the relief valve 25. The length of the third period is equal to the fourth period in this embodiment. The third period may be set to, for example, 3 seconds or more and 7 seconds or less, more specifically, 4 seconds or more and 6 seconds or less.

[0103] In the following step S111, the controller 10 restarts (start retry) the engine E. Specifically, the controller 10 restarts the fuel injection from the injector 3 and restarts the ignition of the spark plug 4. This also restarts the drive of the high fuel pressure pump 23.

[0104] When the process of step S111 is completed, the controller 10 returns the control process to step S104. In step S104 after the restart, the value of the fuel pressure at the time of the restart is recorded.

[0105] After that, let us assume that the determination in step S106 becomes YES again. This situation corresponds to a situation in which the relief valve 25 is detected to be open again during restart. In this case, because of waiting in step S109 before the retry, the determination in step S303 in FIG. 7 becomes NO in step S107 after the retry. As a result, if the relief valve 25 is detected to be open again during the start retry, it can be determined that some kind of failure has occurred in the high fuel pressure pump 23.

[0106] As described above, according to this embodiment, when it is determined that the relief valve 25 is open when starting the engine E, the controller 10 stops the engine E, waits, and then restarts it (see steps S106 to S111 in FIG. 5). This allows the engine E to be restarted after waiting for the relief valve 25 to close, thereby preventing malfunction of the engine E.

[0107] 5, steps S106 to S108, and as illustrated in FIG 7, the controller 10 determines that a malfunction has occurred in the high fuel pressure pump 23 (e.g., the spill valve 23b) if it is determined again that the relief valve 25 is open when the engine E is restarted. This makes it possible to more accurately determine a malfunction of the high fuel pressure pump 23 without erroneously determining that the valve is open due to a rise in fuel temperature, vibration from the generator 113, etc.

[0108] As shown in Fig. 2, engine E is a single cylinder engine equipped with one injector 3, so the overall volume of the fuel supply system is compact compared to a multi-cylinder engine. In this case, the fuel pressure tends to increase relatively easily, and this, combined with factors such as an increase in fuel temperature, can easily lead to high fuel pressure. For this reason, accurate failure determination as described above is particularly effective.

[0109] As shown in Fig. 1, the engine E is dedicated to generating electricity, so the overall volume of the fuel supply system is compact compared to an engine for driving a vehicle. In this case, the fuel pressure tends to increase relatively easily, and this, combined with factors such as an increase in fuel temperature, can easily lead to high fuel pressure. For this reason, accurate failure determination as described above is particularly effective.

[0110] In addition, since the engine E is dedicated to generating electricity, even if start-up is retried, the effect on the driving feeling can be minimized as compared to an engine E used for propelling the vehicle. [Explanation of symbols]

[0111] 100 vehicles 101 Drive wheel 110 Electric drive unit 113 Generator (starting device) E-Engine E1 Drive shaft 1. Fuel system abnormality diagnosis device 2. Fuel supply system 23 High fuel pressure pump 23b Spill valve 24b High pressure side piping (fuel piping) 25 Relief valve 3. Injector 10 Controller 11 Fuel pressure sensor Po opening pressure P1 First threshold P2 Second threshold

Claims

1. A high-pressure fuel pump that is connected to a drive shaft of the engine and pressurizes and discharges fuel; a fuel pipe for circulating the high-pressure fuel discharged from the high fuel pressure pump; an injector connected to the fuel pipe for injecting high-pressure fuel; a mechanical relief valve that opens when the fuel pressure in the fuel pipe rises to a predetermined valve opening pressure and closes when the fuel pressure in the fuel pipe falls to a predetermined valve closing pressure; a fuel pressure sensor for detecting the pressure of the fuel discharged from the high fuel pressure pump in the fuel pipe; a controller that determines whether or not the fuel pressure detected by the fuel pressure sensor can reach the valve opening pressure, the controller determines that the relief valve is opened when the fuel pressure in the fuel pipe falls below a predetermined first threshold value after it is determined that the fuel pressure can reach the valve opening pressure, and determines whether or not a malfunction has occurred in the high fuel pressure pump based on the determination result; The controller: when it is determined that the relief valve is open when starting the engine, the engine is stopped while suspending the determination of the presence or absence of a malfunction, and the engine is restarted after waiting for a predetermined period from the engine stop to wait for the relief valve to close; If it is determined that the relief valve is again open upon restarting the engine, it is determined that a fault has occurred in the high fuel pressure pump.

2. An engine fuel system abnormality diagnosis device comprising:

2. 2. The engine fuel system abnormality diagnosis device according to claim 1, The engine is a single cylinder engine, The controller increases the engine speed to a normal speed by a starting device when starting and restarting the engine.

2. An engine fuel system abnormality diagnosis device comprising:

3. 3. The engine fuel system abnormality diagnosis device according to claim 2, The engine is an engine that is not connected to the drive wheels of the vehicle and is dedicated to generating electricity.

2. An engine fuel system abnormality diagnosis device comprising:

4. 3. The engine fuel system abnormality diagnosis device according to claim 2, A pressure value that is equal to or lower than the valve opening pressure and equal to or higher than the first threshold value is defined as a second threshold value. The controller determines that the fuel pressure in the fuel pipe may reach the valve opening pressure when the fuel pressure exceeds the second threshold value while the engine speed is increasing upon starting or restarting the engine.

2. An engine fuel system abnormality diagnosis device comprising:

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