fuel supply unit

Abstract

To provide a fuel supply device capable of determining whether a fuel pressure sensor is normal or not when the operation of an internal combustion engine is stopped.SOLUTION: When the operation of an internal combustion engine is stopped, a processing circuit 71 of a fuel supply device 20 opens a relief valve 52 by increasing the fuel pressure in a high-pressure delivery pipe 30 until the fuel pressure reaches or exceeds a specified pressure prior to stopping the operation of the internal combustion engine. After the fuel pressure in the high-pressure delivery pipe 30 begins to decrease due to the relief valve 52 being opened, the processing circuit 71 determines whether a fuel pressure sensor 62 is normal or not on the basis of the comparison result between the delivery fuel pressure and a fuel pressure determination value.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a fuel supply device having a function of determining whether a fuel pressure sensor for detecting the pressure of fuel supplied to a fuel injection valve of an internal combustion engine is normal or not.

Background Art

[0002] Patent Document 1 discloses an example of a fuel supply device including a fuel injection valve, a delivery pipe, a fuel pump, and a fuel pressure sensor. The fuel pump pressurizes fuel and pumps it into the delivery pipe. A fuel injection valve is connected to the delivery pipe. Then, the fuel injection valve injects the fuel supplied from the delivery pipe. The fuel pressure sensor detects the fuel pressure in the delivery pipe.

[0003] The above fuel supply device has a function of determining whether the fuel pressure sensor is abnormal or not. Specifically, when at least one of the conditions that the duration of the operation stop of the internal combustion engine is equal to or longer than a predetermined time and the temperature of the cooling water of the internal combustion engine is equal to or lower than a predetermined temperature is satisfied, the device determines whether the fuel pressure sensor is abnormal or not based on the comparison result between the detected value of the fuel pressure sensor and a predetermined threshold value.

Prior Art Documents

Patent Documents

[0004]

Patent Document Ⅰ

Summary of the Invention

Problems to be Solved by the Invention

[0005] When starting the internal combustion engine, if the duration of the operation stop has not reached the predetermined time and the temperature of the cooling water is higher than the predetermined temperature, the above determination cannot be carried out.

Means for Solving the Problems

[0006] A fuel supply device to solve the above problems is a device that supplies fuel to an internal combustion engine. The fuel supply device includes a fuel injection valve that injects fuel to be supplied to the internal combustion engine, a delivery pipe that stores the fuel supplied to the fuel injection valve, a fuel pump that pressurizes the fuel and pumps it into the delivery pipe, a relief valve that opens to allow fuel to flow out of the delivery pipe when the fuel pressure in the delivery pipe exceeds a specified pressure, and a fuel pressure sensor that detects the fuel pressure in the delivery pipe. A fuel tank for storing fuel, a supply channel which is a passage for fuel supplied from the fuel tank to the fuel pump, a feed pump which pumps fuel from the fuel tank and discharges the fuel into the supply channel, and a feed pressure sensor which detects the pressure of the fuel discharged from the feed pump into the supply channel. It comprises a processing circuit and a fuel pressure detection value obtained from the output signal of the fuel pressure sensor. The fuel pressure detected by the feed pressure sensor is used as the fuel pressure determination value. In this case, the processing circuit, when the operation of the internal combustion engine is stopped, opens the relief valve by increasing the fuel pressure in the delivery pipe until the fuel pressure in the delivery pipe exceeds the specified pressure, prior to the stopping of the operation of the internal combustion engine. When it is determined that the relief valve has opened, the fuel pump is stopped from pressurizing the fuel. If the detected fuel pressure value falls below the determined fuel pressure value before a predetermined time elapses from the time the fuel pump stops pressurizing the fuel, the fuel pressure sensor is determined to be normal. If the detected fuel pressure value does not fall below the determined fuel pressure value even after the elapsed time has exceeded the predetermined time, the fuel pressure sensor is determined to be abnormal. Execute this.

[0007] The inventors of this case have obtained the following findings from various experiments: When the relief valve is opened by increasing the fuel pressure in the delivery pipe to a specified pressure, the fuel pressure in the delivery pipe decreases to a level equivalent to the pressure of the fuel supplied to the fuel pump before the relief valve closes.

[0008] The above-mentioned abnormality detection device forcibly opens the relief valve by increasing the fuel pressure in the delivery pipe to a specified pressure prior to stopping the operation of the internal combustion engine. Then, after the fuel pressure in the delivery pipe begins to decrease due to the opening of the relief valve, the abnormality detection device determines whether the fuel pressure sensor is functioning normally based on the comparison result between the detected fuel pressure value and the determined fuel pressure value. In this way, the abnormality detection device can determine whether the fuel pressure sensor is functioning normally when the operation of the internal combustion engine is stopped. [Brief explanation of the drawing]

[0009] [Figure 1]Figure 1 is a schematic diagram showing the general configuration of a fuel supply device according to an embodiment, and the general configuration of an internal combustion engine to which fuel is supplied from the fuel supply device. [Figure 2] Figure 2 is a diagram showing the fuel supply system of Figure 1. [Figure 3] Figure 3 is a graph showing the characteristics of the relief valve in the fuel supply system shown in Figure 1. [Figure 4] Figure 4 is a flowchart showing the sensor determination process performed by the processing circuit of the fuel supply device shown in Figure 1. [Modes for carrying out the invention]

[0010] An embodiment of the fuel supply system will be described below with reference to Figures 1 to 4. Figure 1 shows an internal combustion engine 10 mounted on a vehicle and a fuel supply device 20 that supplies fuel to the internal combustion engine 10.

[0011] <Internal Combustion Engine> The internal combustion engine 10 has multiple cylinders 11. Figure 1 shows only one of the multiple cylinders 11. Each of the multiple cylinders 11 houses a piston 12 that is capable of reciprocating motion, and each piston 12 partitions a combustion chamber 13. In the multiple combustion chambers 13, a mixture of fuel and air is burned. Each of the multiple combustion chambers 13 is connected to an intake passage 14 and an exhaust passage 15. The intake passage 14 is the passage through which air flows to be introduced into the multiple combustion chambers 13. The intake passage 14 is equipped with a throttle valve 16 that adjusts the amount of intake air introduced from the intake passage 14 into the combustion chamber 13. The exhaust passage 15 is the passage through which exhaust gas generated in the multiple combustion chambers 13 is discharged.

[0012] <Fuel supply device> As shown in Figure 1, the fuel supply device 20 includes a fuel tank 21 and fuel injectors that inject fuel to be supplied to the internal combustion engine 10. The fuel tank 21 stores the fuel to be supplied to the internal combustion engine 10. The fuel supply device 20 includes a port injector 22 and an in-cylinder injector 23 as fuel injectors. One port injector 22 and one in-cylinder injector 23 are provided for each cylinder 11. The port injector 22 injects fuel into the portion of the intake passage 14 downstream of the throttle valve 16. The in-cylinder injector 23 injects fuel into the combustion chamber 13.

[0013] As shown in Figure 2, the fuel supply device 20 includes a feed pump 25, a supply passage 26, a high-pressure fuel pump 28, a pressurized passage 29, a high-pressure delivery pipe 30, and a relief mechanism 31. The feed pump 25 is an electrically operated pump that draws fuel from the fuel tank 21 and discharges the fuel into the supply passage 26. The supply passage 26 is the passage for fuel supplied to the high-pressure fuel pump 28. A pulsation damper 27 is provided in the supply passage 26. The pulsation damper 27 reduces the pulsation of the fuel flowing through the supply passage 26. The fuel flowing through the supply passage 26 is supplied to the high-pressure fuel pump 28 via the pulsation damper 27.

[0014] The high-pressure fuel pump 28 pressurizes the fuel supplied from the supply passage 26 and discharges it into the pressurized passage 29. The pressurized passage 29 is a passage that guides the fuel discharged from the high-pressure fuel pump 28 to the high-pressure delivery pipe 30. In other words, the high-pressure fuel pump 28 pressurizes the fuel and delivers it to the high-pressure delivery pipe 30. Multiple in-cylinder injection valves 23 are connected to the high-pressure delivery pipe 30. In other words, the high-pressure delivery pipe 30 stores the fuel supplied to the multiple in-cylinder injection valves 23. The relief mechanism 31 has the function of releasing the fuel inside the high-pressure delivery pipe 30 to the outside of the high-pressure delivery pipe 30. The configuration of the high-pressure fuel pump 28 and the relief mechanism 31 will be described later.

[0015] The fuel supply device 20 includes a branch passage 33 and a low-pressure delivery pipe 34. The branch passage 33 is a passage for guiding a portion of the fuel flowing through the supply passage 26 to the low-pressure delivery pipe 34. Specifically, the branch passage 33 is connected to the portion of the supply passage 26 downstream of the pulsation damper 27. Multiple port injection valves 22 are connected to the low-pressure delivery pipe 34. In other words, the low-pressure delivery pipe 34 stores the fuel supplied to the multiple port injection valves 22.

[0016] <High-pressure fuel pump> The high-pressure fuel pump 28 comprises a cylinder 41, a plunger 42, a check valve 43, and a solenoid spill valve 44. The plunger 42 is installed inside the cylinder 41 in a manner that allows it to reciprocate. Specifically, the plunger 42 reciprocates within the cylinder 41 as a cam 18, which rotates integrally with the camshaft 17 of the internal combustion engine 10, rotates. Within the cylinder 41, the plunger 42 partitions a pressurizing chamber 45. The high-pressure fuel pump 28 pressurizes the fuel supplied via the supply passage 26 in the pressurizing chamber 45. The check valve 43 is installed in the passage connecting the pressurizing chamber 45 and the pumping passage 29. The check valve 43 prevents backflow of fuel from the pumping passage 29 to the pressurizing chamber 45 by closing the valve when the fuel pressure in the pressurizing chamber 45 is lower than the fuel pressure in the pumping passage 29. On the other hand, the check valve 43 opens when the fuel pressure in the pressurizing chamber 45 is higher than the fuel pressure in the pressurizing passage 29, thereby allowing fuel to flow out from the pressurizing chamber 45 to the pressurizing passage 29. The electromagnetic spill valve 44 opens and closes in response to the energization, switching between a state in which fuel flow between the supply passage 26 and the pressurizing chamber 45 is permitted and a state in which such flow is blocked.

[0017] The fuel pressurization operation of the high-pressure fuel pump 28 will now be explained. In the high-pressure fuel pump 28, the volume of the pressurizing chamber 45 changes in accordance with the reciprocating motion of the plunger 42 in the cylinder 41. Hereafter, the movement of the plunger 42 in the direction that expands the volume of the pressurizing chamber 45 will be referred to as "downward movement of the plunger 42," and the movement of the plunger 42 in the direction that decreases the volume of the pressurizing chamber 45 will be referred to as "upward movement of the plunger 42."

[0018] When the plunger 42 descends with the electromagnetic spill valve 44 open, the volume of the pressure chamber 45 expands, causing fuel to flow from the supply passage 26 into the pressure chamber 45. If the electromagnetic spill valve 44 remains open even after the plunger 42 changes from descending to ascending, the fuel in the pressure chamber 45 is pushed back into the supply passage 26. When the electromagnetic spill valve 44 closes during the ascent of the plunger 42 and remains closed until the plunger 42 changes from ascending to descending, the volume of the pressure chamber 45 decreases as the plunger 42 ascends, thereby pressurizing the fuel in the pressure chamber 45. When the fuel pressure in the pressure chamber 45 exceeds the fuel pressure in the pressure feed passage 29, the check valve 43 opens, and the fuel in the pressure chamber 45 is sent out to the pressure feed passage 29. Thus, the high-pressure fuel pump 28 pressurizes the fuel supplied from the supply passage 26 and sends it out to the pressure feed passage 29 for each reciprocation of the plunger 42. Note that the fuel pressure in the high-pressure delivery pipe 30 is adjusted by changing the closing timing of the electromagnetic spill valve 44 during the ascent of the plunger 42.

[0019] <Relief mechanism> The relief mechanism 31 includes a relief passage 51 and a relief valve 52. The relief passage 51 bypasses the high-pressure fuel pump 28 and connects the pressure feed passage 29 and the supply passage 26. That is, the first end of the relief passage 51 is connected to the pressure feed passage 29, while the second end of the relief passage 51 is connected to the pulsation damper 27 of the supply passage 26.

[0020] The relief valve 52 opens to allow the fuel in the high-pressure delivery pipe 30 to flow out when the fuel pressure in the high-pressure delivery pipe 30 becomes equal to or higher than the specified pressure PDL. Specifically, the relief valve 52 is installed in the relief passage 51. The relief valve 52 has a valve seat 53, a valve body 54, and a valve spring 55. When the valve body 54 is pressed against the valve seat 53 by the biasing force of the valve spring 55, the relief valve 52 is closed. When the relief valve 52 is closed, the flow of fuel in the relief passage 51 is restricted.

[0021] The fuel pressure in the high-pressure delivery pipe 30 acts to move the valve body 54 away from the valve seat 53. When the fuel pressure in the high-pressure delivery pipe 30 is less than the specified pressure PDL, the relief valve 52 remains closed. As a result, the flow of fuel in the high-pressure delivery pipe 30 to the supply passage 26 via the relief passage 51 is restricted. On the other hand, when the fuel pressure in the high-pressure delivery pipe 30 exceeds the specified pressure PDL, the valve body 54 is displaced away from the valve seat 53 against the biasing force of the valve spring 55. That is, the relief valve 52 opens. As a result, the fuel in the high-pressure delivery pipe 30 flows out to the supply passage 26 via the relief passage 51.

[0022] Figure 3 illustrates the characteristics of the relief valve 52. The fuel pressure range RPD in Figure 3 is the range of fuel pressure set when the internal combustion engine 10 is in operation. As shown in Figure 3, the relief valve 52 is designed so that the specified pressure PDL is higher than the upper limit PDA of the fuel pressure range RPD. Therefore, the relief valve 52 will not open while the internal combustion engine 10 is in operation. In addition, the fuel pressure range RPD is set so that the lower limit PDB is higher than the feed pressure. The feed pressure is the pressure of the fuel discharged from the feed pump 25 into the supply passage 26.

[0023] The high-pressure fuel pump 28 can raise the fuel pressure in the high-pressure delivery pipe 30 above the upper limit PDA of the fuel pressure range RPD. When the fuel pressure in the high-pressure delivery pipe 30 exceeds the specified pressure PDL, the valve body 54 moves away from the valve seat 53, causing the relief valve 52 to open. As a result, the fuel in the high-pressure delivery pipe 30 flows out through the relief valve 52 into the supply passage 26, causing the fuel pressure in the high-pressure delivery pipe 30 to decrease. When the fuel pressure in the high-pressure delivery pipe 30 decreases, the valve body 54 moves closer to the valve seat 53 due to the biasing force of the valve spring 55. Then, when the valve body 54 seats on the valve seat 53, the relief valve 52 closes.

[0024] The inventors of this case have conducted various experiments and obtained the following findings. Specifically, when the relief valve 52 is opened by increasing the fuel pressure in the high-pressure delivery pipe 30 to a specified pressure PDL, the relief valve 52 does not immediately close even if the fuel pressure in the high-pressure delivery pipe 30 falls below the specified pressure PDL due to the outflow of fuel through the relief valve 52. In other words, once the relief valve 52 opens, it remains open for a while. Therefore, before the relief valve 52 closes, the fuel pressure in the high-pressure delivery pipe 30 drops to a level equivalent to the fuel pressure in the supply passage 26.

[0025] <Detection system for fuel supply device> As shown in Figure 2, the fuel supply device 20 includes a feed pressure sensor 61 and a fuel pressure sensor 62 as detection systems. The various sensors 61 and 62 output signals corresponding to the detection results to the control device 70, which will be described later. The feed pressure sensor 61 detects the pressure of the fuel discharged from the feed pump 25 into the supply passage 26. For example, the feed pressure sensor 61 is installed in the low-pressure delivery pipe 34. The fuel pressure sensor 62 detects the fuel pressure in the high-pressure delivery pipe 30. The fuel pressure based on the output signal of the feed pressure sensor 61 is called "feed pressure PFS". The fuel pressure based on the output signal of the fuel pressure sensor 62 is called "delivery fuel pressure PDS". In this embodiment, the delivery fuel pressure PDS corresponds to the "fuel pressure detection value".

[0026] <Control device for fuel supply system> As shown in Figure 2, the fuel supply system 20 includes a control device 70 that controls the fuel pressure in the high-pressure delivery pipe 30 and the fuel pressure in the low-pressure delivery pipe 34. The control device 70 has a processing circuit 71. For example, the processing circuit 71 is an electronic control device. In this case, the processing circuit 71 has a CPU 72 and a memory 73. The memory 73 stores a control program executed by the CPU 72. By executing the control program, the CPU 72 controls the feed pump 25 and the solenoid spill valve 44.

[0027] The processing circuit 71 determines whether the fuel pressure sensor 62 is functioning correctly when the operation of the internal combustion engine 10 is stopped. Specifically, prior to the stopping of the operation of the internal combustion engine 10, the processing circuit 71 opens the relief valve 52 by increasing the fuel pressure in the high-pressure delivery pipe 30 until the fuel pressure is equal to or greater than the specified pressure PDL. Then, after the fuel pressure in the high-pressure delivery pipe 30 begins to decrease due to the opening of the relief valve 52, the processing circuit 71 determines whether the fuel pressure sensor 62 is functioning correctly based on the comparison result between the delivery fuel pressure PDS and the fuel pressure determination value.

[0028] <Sensor detection process> Referring to Figures 3 and 4, the sensor determination process performed by the processing circuit 71 will be described. The sensor determination process is a series of processes to determine whether or not the fuel pressure sensor 62 is functioning correctly. Figure 4 shows a flowchart illustrating the sensor determination process. While the internal combustion engine 10 is in operation, the processing circuit 71 repeatedly performs the sensor determination process.

[0029] As shown in Figure 4, in step S11, the processing circuit 71 sets a value corresponding to the feed pressure PFS as the fuel pressure determination value PDth. The fuel pressure determination value PDth is a threshold value that serves as a criterion for determining whether the fuel pressure sensor 62 is functioning correctly or not. The processing circuit 71 sets a larger value as the fuel pressure determination value PDth the higher the feed pressure PFS at that time. The fuel pressure in the supply passage 26 to which the relief passage 51 is connected is approximately equal to the fuel pressure in the low-pressure delivery pipe 34. Therefore, the processing circuit 71 can set a value equivalent to the fuel pressure in the supply passage 26 as the fuel pressure determination value PDth. For example, a pressure slightly higher than the fuel pressure in the supply passage 26 may be set as the fuel pressure determination value PDth.

[0030] In the next step, S13, the processing circuit 71 determines whether or not there is a request to stop the operation of the internal combustion engine 10. The processing circuit 71 determines that there is a request to stop operation, for example, when the vehicle's driving switch is turned off. If the processing circuit 71 determines that there is a request to stop operation (S13: YES), it proceeds to step S15. On the other hand, if the processing circuit 71 determines that there is no request to stop operation (S13: NO), it terminates the current sensor determination process.

[0031] In step S15, prior to stopping the operation of the internal combustion engine 10, the processing circuit 71 starts increasing the fuel pressure in the high-pressure delivery pipe 30. Specifically, the processing circuit 71 increases the fuel discharge amount of the high-pressure fuel pump 28 by advancing the closing timing of the electromagnetic spill valve 44 while the plunger 42 is rising.

[0032] In step S17, the processing circuit 71 determines whether the relief valve 52 has opened by increasing the fuel pressure in the high-pressure delivery pipe 30. When the relief valve 52 opens due to an increase in the fuel pressure in the high-pressure delivery pipe 30, the fuel pressure in the high-pressure delivery pipe 30 drops sharply, causing the delivery fuel pressure PDS to drop sharply. Therefore, the processing circuit 71 can determine that the relief valve 52 has opened if the delivery fuel pressure PDS has increased and then started to drop. If the processing circuit 71 determines that the relief valve 52 has not opened (S17: NO), it repeats the determination in step S17 until it can determine that the relief valve 52 has opened. On the other hand, if the processing circuit 71 determines that the relief valve 52 has opened (S17: YES), it proceeds to step S19.

[0033] In step S19, the processing circuit 71 stops pressurizing the fuel by the high-pressure fuel pump 28. For example, the processing circuit 71 keeps the solenoid spill valve 44 open by stopping the power supply to the solenoid spill valve 44. In step S21, the processing circuit 71 permits the internal combustion engine 10 to stop operating.

[0034] In the next step S23, the processing circuit 71 determines whether the elapsed time since the fuel pressurization by the high-pressure fuel pump 28 was stopped has reached a predetermined time TMth. As described above, when the relief valve 52 opens by raising the fuel pressure in the high-pressure delivery pipe 30 to a specified pressure PDL or higher, the relief valve 52 does not close for a while. The time from when the relief valve 52 opens until it closes can be estimated from the specifications of the fuel supply device 20. Therefore, a time slightly longer than the estimated time from when the relief valve 52 opens until it closes is set in advance as the predetermined time TMth.

[0035] If the processing circuit 71 determines that the elapsed time has not exceeded the predetermined time TMth (S23: NO), it proceeds to step S25. In step S25, the processing circuit 71 determines whether the delivery fuel pressure PDS is less than or equal to the fuel pressure determination value PDth. If the delivery fuel pressure PDS is higher than the fuel pressure determination value PDth (S25: NO), the processing circuit 71 returns to step S23. On the other hand, if the delivery fuel pressure PDS is less than or equal to the fuel pressure determination value PDth (S25: YES), the processing circuit 71 proceeds to step S27.

[0036] In step S27, the processing circuit 71 determines that the fuel pressure sensor 62 is functioning normally. Specifically, the processing circuit 71 determines that the fuel pressure sensor 62 is functioning normally if the delivery fuel pressure PDS falls below the fuel pressure determination value PDth before the elapsed time reaches a predetermined time TMth. After that, the processing circuit 71 terminates the sensor determination process.

[0037] On the other hand, if the processing circuit 71 determines in step S23 that the elapsed time is longer than the predetermined time TMth (YES), it proceeds to step S29. In step S29, the processing circuit 71 determines that the fuel pressure sensor 62 is not functioning correctly. That is, if the delivery fuel pressure PDS does not fall below the fuel pressure determination value PDth even after the elapsed time has become longer than the predetermined time TMth, the processing circuit 71 determines that the fuel pressure sensor 62 is not functioning correctly. After that, the processing circuit 71 terminates the sensor determination process.

[0038] <Mechanism and Effects> The operation of the fuel supply device 20 will be explained with reference to Figure 3. At timing t1 while the internal combustion engine 10 is operating, a request to stop the operation of the internal combustion engine 10 is input to the processing circuit 71. In response, prior to stopping the operation, the processing circuit 71 increases the fuel pressure in the high-pressure delivery pipe 30 using the high-pressure fuel pump 28. As a result, the delivery fuel pressure PDS increases, as shown by the solid line in Figure 3. Consequently, the delivery fuel pressure PDS becomes higher than the upper limit PDA of the fuel pressure range RPD. At timing t2, when the fuel pressure in the high-pressure delivery pipe 30 becomes equal to or higher than the specified pressure PDL, the relief valve 52 opens. As a result, the fuel in the high-pressure delivery pipe 30 flows out through the relief passage 51, causing the fuel pressure in the high-pressure delivery pipe 30 to drop sharply. The processing circuit 71 can determine that the relief valve 52 has opened by monitoring the change in the delivery fuel pressure PDS.

[0039] When the relief valve 52 is forcibly opened in this manner, the relief valve 52 remains open for a period of time. As a result, fuel continues to flow out of the high-pressure delivery pipe 30, and the fuel pressure in the high-pressure delivery pipe 30 drops to a level equivalent to the fuel pressure in the supply passage 26.

[0040] In the fuel supply device 20, a value corresponding to the fuel pressure in the supply passage 26 is set as the fuel pressure determination value PDth. Therefore, if the fuel pressure sensor 62 is functioning correctly, opening the relief valve 52 will reduce the delivery fuel pressure PDS to below the fuel pressure determination value PDth. On the other hand, if the fuel pressure sensor 62 is not functioning correctly, opening the relief valve 52 may not reduce the delivery fuel pressure PDS to below the fuel pressure determination value PDth.

[0041] Therefore, after the relief valve 52 opens and the fuel pressure in the high-pressure delivery pipe 30 begins to decrease, the fuel supply device 20 determines whether the fuel pressure sensor 62 is functioning normally based on the comparison result between the delivery fuel pressure PDS and the fuel pressure determination value PDth.

[0042] As described above, when the relief valve 52 is opened and then closed, the actual fuel pressure in the high-pressure delivery pipe 30 becomes approximately equal to the fuel pressure in the supply passage 26. Therefore, if the fuel pressure sensor 62 is functioning correctly, the delivery fuel pressure PDS will be less than or equal to the fuel pressure determination value PDth. Consequently, the processing circuit 71 determines that the fuel pressure sensor 62 is functioning correctly when the delivery fuel pressure PDS is less than or equal to the fuel pressure determination value PDth. On the other hand, if the delivery fuel pressure PDS does not become less than or equal to the fuel pressure determination value PDth, there is a possibility that a discrepancy exists between the delivery fuel pressure PDS and the actual fuel pressure in the high-pressure delivery pipe 30. Therefore, the processing circuit 71 determines that the fuel pressure sensor 62 is not functioning correctly when the delivery fuel pressure PDS does not become less than or equal to the fuel pressure determination value PDth.

[0043] In this embodiment, the following effects can be obtained. (1) In recent years, in order to improve the exhaust characteristics of internal combustion engines, it has been considered to raise the upper limit PDA of the fuel pressure range RPD. When the upper limit PDA is raised, the relief valve 52 is designed so that the specified pressure PDL is raised so that the relief valve 52 does not open during operation of the internal combustion engine.

[0044] Conventionally, when determining an abnormality in the fuel pressure sensor 62, the fuel pressure in the high-pressure delivery pipe 30 is not intentionally increased when the internal combustion engine 10 is stopped. That is, while the engine is stopped, the fuel pressure in the high-pressure delivery pipe 30 increases due to heat absorption from the internal combustion engine 10. When the fuel pressure reaches the specified pressure PDL due to this increase in fuel pressure associated with heat absorption, fuel flows out of the high-pressure delivery pipe 30 through the small gap between the valve seat 53 and the valve body 54 of the relief valve 52. As a result, the fuel pressure in the high-pressure delivery pipe 30 gradually decreases. After a predetermined time has elapsed since the engine was stopped, the fuel pressure in the high-pressure delivery pipe 30 decreases to the level equivalent to the fuel pressure in the supply passage 26. Therefore, when the internal combustion engine 10 is started again, the fuel pressure sensor 62 is determined to be normal or not by comparing the delivery fuel pressure PDS with the fuel pressure determination value.

[0045] However, as mentioned above, if the specified pressure PDL is set too high, the fuel pressure in the high-pressure delivery pipe 30 may not increase to the specified pressure PDL while the internal combustion engine 10 is stopped. In this case, there is a risk that almost no fuel will flow out of the high-pressure delivery pipe 30 while the engine is stopped. As a result, it becomes impossible to determine whether the fuel pressure sensor 62 is functioning correctly or not.

[0046] In this embodiment, when the operation of the internal combustion engine 10 is stopped, the relief valve 52 is forcibly opened by increasing the fuel pressure in the high-pressure delivery pipe 30. Therefore, when the operation of the internal combustion engine 10 is stopped, the fuel pressure in the high-pressure delivery pipe 30 can be reduced to a level equivalent to the fuel pressure in the supply passage 26. Thus, the fuel supply device 20 can determine whether the fuel pressure sensor 62 is functioning correctly when the operation of the internal combustion engine 10 is stopped.

[0047] (2) The processing circuit 71 sets the fuel pressure determination value PDth to a value that is larger the higher the fuel pressure in the supply passage 26. Therefore, the fuel supply device 20 can suppress variations in the accuracy of the fuel pressure sensor 62 in determining whether or not the fuel pressure sensor is normal, depending on the magnitude of the fuel pressure in the supply passage 26 when the operation of the internal combustion engine 10 is stopped.

[0048] (3) In the fuel supply device 20, the relief passage 51 is connected to the supply passage 26. Therefore, the fuel supply device 20 can reduce the fuel pressure in the high-pressure delivery pipe 30 to a level equivalent to the fuel pressure in the supply passage 26 by opening the relief valve 52.

[0049] Now, let's consider the case where the relief passage is connected to the pressurizing chamber 45 instead of the supply passage 26. In this case, when the high-pressure fuel pump 28 pressurizes the fuel, it will pressurize the fuel in the pressurizing chamber 45 and the relief passage. In contrast, in the fuel supply device 20 described above, since the relief passage 51 is not connected to the pressurizing chamber 45, the fuel in the relief passage 51 does not need to be pressurized when the high-pressure fuel pump 28 pressurizes the fuel. As a result, the high-pressure fuel pump 28 can efficiently increase the fuel pressure in the high-pressure delivery pipe 30.

[0050] <Example of changes> The above embodiment can be implemented with the following modifications. The above embodiment and the following modifications can be combined with each other to the extent that they do not contradict each other technically.

[0051] The relief channel may be connected to the pressurizing chamber 45 of the high-pressure fuel pump 28, rather than to the supply channel 26. The fuel pressure judgment value PDth may be fixed to a pre-set value.

[0052] The high-pressure fuel pump 28 does not have to be an engine-driven pump as shown in Figure 2, as long as it can increase the fuel pressure in the high-pressure delivery pipe 30. For example, the high-pressure fuel pump 28 may be a pump that reciprocates a plunger 42 in a cylinder 41 by the operation of an electric actuator.

[0053] The fuel supply device may maintain the fuel pressure in the supply passage 26 at a predetermined fuel pressure. In this case, it is preferable that the fuel pressure determination value PDth be maintained at a value corresponding to the predetermined fuel pressure. The processing circuit 71 is not limited to one that includes a CPU and ROM and executes software processing. In other words, the processing circuit 71 may have any of the following configurations: (a), (b), or (c).

[0054] (a) The processing circuit 71 includes one or more processors that perform various processes according to a computer program. The processor includes a CPU and memory such as RAM and ROM. The memory stores program code or instructions configured to cause the CPU to perform the processes. The memory, i.e., computer-readable media, includes any available media that can be accessed by a general-purpose or dedicated computer.

[0055] (b) The processing circuit 71 includes one or more dedicated hardware circuits that perform various processes. Examples of dedicated hardware circuits include application-specific integrated circuits, i.e., ASICs or FPGAs. ASIC is an abbreviation for "Application Specific Integrated Circuit," and FPGA is an abbreviation for "Field Programmable Gate Array."

[0056] (c) The processing circuit 71 includes a processor that executes a portion of the various processes according to a computer program, and a dedicated hardware circuit that executes the remaining processes among the various processes. [Explanation of Symbols]

[0057] 10...Internal combustion engine, 20...Fuel supply system, 21...Fuel tank, 23...In-cylinder injection valve, 25...Feed pump, 26...Supply passage, 28...High-pressure fuel pump, 29...Pressure delivery passage, 30...High-pressure delivery pipe, 51...Relief passage, 52...Relief valve, 62...Fuel pressure sensor, 71...Processing circuit.

Claims

1. A fuel supply device that supplies fuel to an internal combustion engine, A fuel injector that injects fuel to be supplied to the internal combustion engine, A delivery pipe for storing fuel to be supplied to the fuel injection valve, A fuel pump that pressurizes fuel and pumps it to the delivery pipe, A relief valve that opens when the fuel pressure in the delivery pipe exceeds a specified pressure, allowing fuel to flow out of the delivery pipe, A fuel pressure sensor for detecting the fuel pressure in the delivery pipe, A fuel tank for storing fuel, A supply path which is a flow path for fuel supplied from the fuel tank to the fuel pump, A feed pump that draws fuel from the fuel tank and discharges the fuel into the supply channel, A feed pressure sensor for detecting the pressure of fuel discharged from the feed pump into the supply channel, A processing circuit is provided, When the fuel pressure in the delivery pipe based on the output signal of the fuel pressure sensor is taken as the fuel pressure detection value, and the fuel pressure detected by the feed pressure sensor is taken as the fuel pressure determination value, The aforementioned processing circuit is When the operation of the aforementioned internal combustion engine is stopped, Prior to stopping the operation of the internal combustion engine, the relief valve is opened by increasing the fuel pressure in the delivery pipe until the fuel pressure in the delivery pipe exceeds the specified pressure, When it is determined that the relief valve has opened, the fuel pump will stop pressurizing the fuel. If the detected fuel pressure value falls below the determined fuel pressure value before the elapsed time from the point when the fuel pump stops pressurizing the fuel reaches a predetermined time, the system determines that the fuel pressure sensor is functioning correctly. If the elapsed time exceeds the predetermined time but the detected fuel pressure value does not fall below the determined fuel pressure value, the system determines that the fuel pressure sensor is not functioning correctly. Fuel supply device.

2. A pressurized flow path which is a flow path that guides the fuel discharged from the fuel pump to the delivery pipe, The system includes a relief passage that bypasses the fuel pump and connects the pressurized passage and the supply passage, The relief valve is installed in the relief channel. The fuel supply device according to claim 1.

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