JP7586009B2 - Fuel pressure sensor abnormality diagnosis device - Google Patents

Description

The present invention relates to a fuel pressure sensor abnormality diagnosis device.

There is a known fuel supply system that includes a high-pressure pump with a pressurizing chamber that pressurizes fuel supplied from a fuel tank, a pressure accumulator that stores the fuel discharged from the pressurizing chamber, a fuel injection valve that directly injects the fuel in the pressure accumulator into a cylinder of an internal combustion engine, a relief valve that is provided downstream of the pressurizing chamber of the high-pressure pump and opens to return fuel to the pressurizing chamber when the fuel pressure from the pressure accumulator reaches a predetermined valve opening pressure, and a fuel pressure sensor that detects the fuel pressure in the pressure accumulator (see, for example, Patent Document 1).

JP 2017-193226 A

The fuel in the accumulator vessel may be pressurized to the opening pressure of the relief valve, and the presence or absence of an abnormality in the fuel pressure sensor may be diagnosed based on whether the output value of the fuel pressure sensor at that time is within a normal range. In this case, the relief valve opens when the valve body of the relief valve moves away from the valve seat against the biasing member, and then the valve body seats on the valve seat due to the biasing force of the biasing member, closing the relief valve.

Here, in order to shorten the diagnosis time, it is conceivable to increase the fuel pressure in the accumulator vessel to the valve opening pressure in a short time. However, in this case, the fuel that has been increased in pressure in a short time may cause the valve disc to move significantly away from the valve seat, which may increase the biasing force of the biasing member, and the valve disc may then collide with the valve seat due to the biasing force of the biasing member, causing abnormal noise.

The present invention aims to provide a fuel pressure sensor abnormality diagnosis device that reduces diagnostic time while suppressing abnormal noise.

The above object is achieved by applying the above object to a fuel supply system including a high-pressure pump having a pressurizing chamber that pressurizes fuel supplied from a fuel tank, a pressure accumulator that stores fuel discharged from the pressurizing chamber, a fuel injection valve that directly injects the fuel in the pressure accumulator into a cylinder of an internal combustion engine, and a relief valve that is provided downstream of the pressurizing chamber of the high-pressure pump and has a valve body that moves away from a valve seat against the biasing force of a biasing member when the fuel pressure from the pressure accumulator side is higher than a predetermined valve opening pressure to return fuel to the pressurizing chamber, and that closes when the fuel pressure from the pressure accumulator side falls below the valve opening pressure by the valve body seating on the valve seat in accordance with the biasing force of the biasing member, and a fuel pressure sensor that detects the fuel pressure in the pressure accumulator, In a fuel pressure sensor abnormality diagnosis device that diagnoses the presence or absence of an abnormality in the fuel pressure sensor based on whether or not the pressure is within a normal range , a diagnosis start condition for the fuel pressure sensor is established when the internal combustion engine's speed, load, cooling water temperature, and oil temperature are each within a predetermined range and a predetermined time or more has elapsed since the previous diagnosis of the presence or absence of an abnormality in the fuel pressure sensor, and when the fuel pressure sensor diagnosis start condition is established, a first control unit that controls a command discharge amount to the high-pressure pump to a first discharge amount when the fuel pressure in the pressure accumulator vessel is less than a predetermined pressure that is lower than the valve opening pressure, and a second control unit that controls the command discharge amount to a second discharge amount less than the first discharge amount when the fuel pressure in the pressure accumulator vessel is from equal to or higher than the predetermined pressure to the valve opening pressure.

The device may include a calculation unit that calculates an initial value of the second discharge amount corresponding to the target pressure increase rate based on an actual pressure increase rate, which is the actual pressure increase rate of the fuel in the pressure accumulator vessel when the commanded discharge amount is controlled to the first discharge amount, and the second control unit may control the commanded discharge amount to the initial value of the second discharge amount when the fuel pressure in the pressure accumulator vessel becomes equal to or higher than the predetermined pressure.

The first discharge amount may be the maximum value of the instructed discharge amount that can be instructed to the high-pressure pump.

The fuel supply system may include a low-pressure pump that pressurizes and supplies fuel from the fuel tank to the pressurized chamber, and the predetermined pressure may be equal to or greater than an intermediate value between the pressure of the fuel pressurized by the low-pressure pump and the valve opening pressure.

The present invention provides a fuel pressure sensor abnormality diagnosis device that reduces diagnostic time and suppresses abnormal noise.

FIG. 1 is a schematic diagram of a fuel supply system. FIG. 2A is a schematic diagram of a relief valve, and FIGS. 2B and 2C are explanatory diagrams of the action of force when the relief valve is opened. FIG. 3 is a timing chart showing the transition of the fuel pressure in the high-pressure delivery pipe during execution of the abnormality diagnosis control of the fuel pressure sensor. FIG. 4 is a flowchart showing an example of the abnormality diagnosis control of the fuel pressure sensor executed by the ECU. FIG. 5 is a flowchart showing an example of a method for calculating the initial value of the ejection amount.

[General configuration of fuel supply system]
1 is a schematic diagram of a fuel supply system 1. The fuel supply system 1 includes an engine 10, a fuel tank 21, a low-pressure pump 22, a low-pressure pipe 25, a low-pressure delivery pipe 26, a high-pressure delivery pipe 36, fuel pressure sensors 28 and 38, a fuel temperature sensor 39, a high-pressure pump 40, and an ECU (Electronic Control Unit) 5. The fuel supply system 1 is mounted on, for example, a vehicle that uses the engine 10 as a power source for running, but is not limited to this.

Engine 10 is a spark-ignition, four-cylinder gasoline engine equipped with in-cylinder injection valves 37 that inject fuel into each cylinder, and port injection valves 27 that inject fuel into each intake port. Engine 10 also has a camshaft 15 that drives the intake or exhaust valves in conjunction with a crankshaft that is linked to multiple pistons.

The fuel tank 21 stores gasoline as fuel. The low-pressure pump 22 pressurizes the fuel and discharges it into the low-pressure pipe 25. The fuel discharged into the low-pressure pipe 25 is supplied to the port injection valve 27 via the low-pressure delivery pipe 26, and is also supplied to the high-pressure pump 40 via a branch pipe 25a branching off from the low-pressure pipe 25.

The high-pressure pump 40 pressurizes the fuel supplied from the branch pipe 25a and discharges it into the high-pressure delivery pipe 36. The fuel pressurized by the high-pressure pump 40 is supplied to the in-cylinder injection valve 37 via the high-pressure delivery pipe 36. The high-pressure delivery pipe 36 is an example of a pressure accumulator.

The fuel pressure sensors 28 and 38 detect the fuel pressure in the low pressure delivery pipe 26 and the high pressure delivery pipe 36, respectively. The fuel temperature sensor 39 detects the temperature of the fuel in the high pressure delivery pipe 36. The ECU 5 acquires the detection values of the fuel pressure sensors 28 and 38 and the fuel temperature sensor 39.

The ECU 5 includes a CPU (Central Processing Unit), a RAM (Random Access Memory), a ROM (Read Only Memory), and a rewritable non-volatile memory, and the CPU executes a program stored in the ROM to perform abnormality diagnosis control of the fuel pressure sensor 38, which will be described later. The abnormality diagnosis control of the fuel pressure sensor 38 is performed by a first control unit, a second control unit, and a calculation unit, which are functionally realized by the CPU, ROM, RAM, and non-volatile memory. Details will be described later.

The ECU 5 also changes the in-cylinder injection rate, which is the ratio of the amount of fuel injected from the in-cylinder injection valve 37 to the total amount of fuel injection, depending on the operating range of the engine 10. For example, when the operating range of the engine 10 is in the low load range, the in-cylinder injection rate is set to 0%, when in the high load range, it is set to 100%, and when in the medium load range, it is set to an intermediate value.

[General configuration of high pressure pump]
The high-pressure pump 40 will now be described. The high-pressure pump 40 includes a cylinder 41, a plunger 42, a pressurizing chamber 43, a suction passage 45, a discharge passage 47, a relief passage 49, a suction valve 50, a discharge valve 60, and a relief valve 70.

The plunger 42 reciprocates within the cylinder 41 in conjunction with the drive of the engine 10. In detail, the plunger 42 is biased by a spring toward the cam CP that rotates together with the camshaft 15, and reciprocates within the cylinder 41 as the cam CP rotates.

The pressurized chamber 43 is defined by the cylinder 41 and the plunger 42. When the plunger 42 rises, the volume of the pressurized chamber 43 decreases, and when the plunger 42 descends, the volume of the pressurized chamber 43 increases.

The suction passage 45 connects the branch pipe 25a branched from the low pressure pipe 25 to the pressurized chamber 43. The suction passage 45 is provided with a pulsation damper 44 that suppresses fuel pressure pulsation. The relief passage 49 connects the pressurized chamber 43 to the high pressure delivery pipe 36. The discharge passage 47 connects the relief passage 49 on the pressurized chamber 43 side of the discharge valve 60 to the relief passage 49 on the high pressure delivery pipe 36 side of the discharge valve 60. In other words, the discharge passage 47 bypasses the relief valve 70.

The suction valve 50 is provided on the fuel inlet side of the pressurized chamber 43, and is an electromagnetically driven on-off valve that switches the communication state between the suction passage 45 and the pressurized chamber 43. The suction valve 50 has a valve body 51, a coil 55 that drives the valve body 51, and a spring 53 that constantly biases the valve body 51 in the open direction. The flow of electricity through the coil 55 is controlled by the ECU 5. When the coil 55 is energized, the valve body 51 cuts off the suction passage 45 and the pressurized chamber 43 against the biasing force of the spring 53. When the coil 55 is not energized, the valve body 51 is maintained in an open state by the biasing force of the spring 53.

The discharge valve 60 is provided on the discharge passage 47 and is a check valve that allows fuel to flow from the pressurized chamber 43 to the high-pressure delivery pipe 36 but prevents fuel from flowing in the opposite direction. Specifically, the discharge valve 60 opens when the fuel pressure in the pressurized chamber 43 becomes higher than the fuel pressure in the high-pressure delivery pipe 36 by a predetermined amount.

During the intake stroke of the high-pressure pump 40, the intake valve 50 opens and the plunger 42 descends, filling the pressurized chamber 43 with fuel from the branch pipe 25a through the intake passage 45. During the pressurized stroke, the intake valve 50 closes and the volume of the pressurized chamber 43 decreases as the plunger 42 ascends, pressurizing the fuel in the pressurized chamber 43. During the discharge stroke, when the force of the fuel pressure acting on the discharge valve 60 from the pressurized chamber 43 side becomes greater due to the force of the fuel pressure acting on the discharge valve 60 from the high-pressure delivery pipe 36 side and the spring force of the discharge valve 60, the discharge valve 60 opens and the pressurized fuel is supplied to the high-pressure delivery pipe 36.

The relief valve 70 is a check valve that is provided on the relief passage 49 and allows fuel to flow from the high-pressure delivery pipe 36 to the pressurized chamber 43 but prevents fuel from flowing in the opposite direction. The relief valve 70 opens when the fuel pressure in the high-pressure delivery pipe 36 rises excessively to the extent that abnormalities may occur in the high-pressure delivery pipe 36 or the in-cylinder injection valve 37, thereby preventing these abnormalities from occurring.

[General Configuration of Relief Valve]
2A is a schematic diagram of the relief valve 70. The relief valve 70 includes a valve body 71, a valve seat 73, and a spring 75. The valve body 71 is spherical. The valve seat 73 has a hole 73a formed therein and is located closer to the high-pressure delivery pipe 36 than the valve body 71. The spring 75 is an example of a biasing member that biases the valve body 71 so that the valve body 71 seats on the valve seat 73 and closes the hole 73a. The discharge valve 60 has a similar structure to the relief valve 70.

2B and 2C are explanatory diagrams of the action of forces when the relief valve 70 is open. FIG. 2B shows forces F1 to F3 acting on the valve body 71. Forces F1 and F2 are forces that act in the direction in which the valve body 71 moves toward the valve seat 73, i.e., in the closing direction of the relief valve 70. Force F3 is a force that acts in the direction in which the valve body 71 moves away from the valve seat 73, i.e., in the opening direction of the relief valve 70. Force F1 is the biasing force that the valve body 71 receives from the spring 75. Force F2 is a force that the valve body 71 receives from the fuel pressure in the relief passage 49 on the pressurizing chamber 43 side of the relief valve 70. Force F3 is a force that the valve body 71 receives from the fuel pressure in the relief passage 49 on the high-pressure delivery pipe 36 side. Force F2 increases as the rotation speed of the low-pressure pump 22 increases. The force F3 repeatedly increases and decreases between a maximum value and a minimum value depending on the stroke of the high-pressure pump 40. This is because the fuel in the relief passage 49 on the pressurization chamber 43 side of the relief valve 70 is sucked into the pressurization chamber 43 during the intake stroke and discharged to the relief valve 70 side during the pressurization stroke and discharge stroke.

When the fuel pressure in the high-pressure delivery pipe 36 has not risen excessively as described above, forces F1 to F3 act on the valve body 71 as shown in FIG. 2B, and the relationship (F1 + F2) > F3 is established, so the relief valve 70 remains closed.

When the fuel pressure in the high-pressure delivery pipe 36 increases and (F1 + F2) < F3 is reached as shown in FIG. 2C, the valve body 71 moves away from the valve seat 73 against the force F1 of the spring 75, and fuel in the relief passage 49 flows from the high-pressure delivery pipe 36 side to the pressurized chamber 43 side through the hole 73a. As a result, F2 = F3 is reached, and the valve body 71 seats on the valve seat 73 again due to the force F1, and the relief valve 70 closes.

Here, because force F1 is the biasing force of spring 75, the greater the compression amount of spring 75, the greater force F1. Therefore, the greater the magnitude of force F3 relative to force F2 at the moment when valve body 71 leaves valve seat 73, the greater the compression amount of spring 75 after valve body 71 leaves valve seat 73, and the greater force F1. For this reason, if the compression amount of spring 75 is large and force F1 is large, there is a risk of a collision sound being generated when valve body 71 subsequently sits on valve seat 73.

The above situation may occur during the execution of abnormality diagnosis control of the fuel pressure sensor 38. In the abnormality diagnosis control of the fuel pressure sensor 38, when the diagnosis condition is satisfied, the fuel in the high-pressure delivery pipe 36 is pressurized to the valve opening pressure at which the relief valve 70 opens, and the fuel pressure sensor 38 is diagnosed as normal or abnormal based on whether the fuel pressure detected by the fuel pressure sensor 38 at that time is within the normal range. Here, in order to shorten the time required to pressurize the fuel in the high-pressure delivery pipe 36 to the valve opening pressure and complete the diagnosis in a short time, it is considered to increase the pressure rise speed of the fuel in the high-pressure delivery pipe 36 as much as possible. If the pressure rise speed of the fuel in the high-pressure delivery pipe 36 is fast, as described above, the collision sound when the valve body 71 collides with the valve seat 73 when the relief valve 70 opens and closes again increases. For example, when the fuel supply system 1 is mounted on a vehicle, the collision sound may be recognized as an abnormal sound by the driver when the vehicle is in an idling state.

[Fuel pressure sensor abnormality diagnosis control]
Therefore, the ECU 5 executes abnormality diagnosis control of the fuel pressure sensor 38 as follows. Fig. 3 is a timing chart showing the transition of the fuel pressure in the high-pressure delivery pipe 36 during execution of abnormality diagnosis control of the fuel pressure sensor 38. When abnormality diagnosis control is started from time t1, the fuel pressure is increased at a pressure increase speed V1 until it reaches pressure P1. Pressure P1 is an example of a predetermined pressure. When the fuel pressure is increased to pressure P1 at time t2, the fuel pressure is gradually increased to pressure P2 at a pressure increase speed V2 slower than the pressure increase speed V1. Pressure P2 is the valve opening pressure of the relief valve 70. When the fuel pressure is increased to pressure P2 at time t3, the relief valve 70 repeatedly opens and closes, so that the fuel pressure repeatedly rises and falls near pressure P2, and in this state, it is diagnosed whether the fuel pressure detected by the fuel pressure sensor 38 is within a normal range or not. In this way, the fuel pressure is increased to pressure P1 at a fast pressure increase rate V1, thereby shortening the diagnosis time, and the fuel pressure is increased from pressure P1 to pressure P2 at a slow pressure increase rate V2, thereby suppressing abnormal noise when the relief valve 70 is opened and closed.

From the viewpoint of shortening the diagnosis time, it is preferable that the pressure increase speed V2 is as fast as possible within a range in which abnormal noises generated when the relief valve 70 is opened and closed can be suppressed. From the viewpoint of shortening the diagnosis time, it is preferable that the pressure P1 is close to the pressure P2. For example, it is preferable that the pressure P1 is equal to or higher than the intermediate pressure between the fuel pressure applied by the low-pressure pump 22 and the pressure P2. However, if the pressure P1 is too close to the pressure P2, when the fuel pressure reaches the pressure P1, the pressure increase speed may reach the pressure P2 before it decreases from the pressure increase speed V1 to the pressure increase speed V2, and abnormal noises generated when the relief valve 70 is opened and closed may not be suppressed. Therefore, it is preferable that the pressure P1 is far enough away from the pressure P2 that the pressure increase speed can be decreased from the pressure increase speed V1 to the pressure increase speed V2. From the viewpoint of suppressing abnormal noises, it is preferable that the pressure increase speed V2 is slow, but it is not necessary to completely suppress the abnormal noises described above. For example, when the fuel supply system 1 is installed in a vehicle, the driving sound of the engine 10 prevents the driver from noticing abnormal noise to a certain extent, so the boost speed V2 may be fast as long as it is within a range that can suppress the abnormal noise to a level that is not noticeable to the driver.

Next, an example of the abnormality diagnosis control of the fuel pressure sensor 38 executed by the ECU 5 will be described. FIG. 4 is a flowchart showing an example of the abnormality diagnosis control of the fuel pressure sensor 38 executed by the ECU 5. The ECU 5 repeatedly executes this control at predetermined time intervals while the ignition is on.

The ECU 5 determines whether or not the diagnosis start condition for the fuel pressure sensor 38 is satisfied (step S1). The diagnosis start condition is, for example, that the engine speed, engine load, engine coolant temperature, and engine oil temperature are within a predetermined range, and that a predetermined time or more has passed since the previous execution of abnormality diagnosis control for the fuel pressure sensor 38. If the result in step S1 is No, this control is terminated.

If the answer is Yes in step S1, the ECU 5 sets the in-cylinder injection rate to 0% and sets the target fuel pressure in the high-pressure delivery pipe 36 to pressure P2, which is the opening pressure of the relief valve 70 (step S2). The ECU 5 sets the instructed discharge amount to the high-pressure pump 40 to discharge amount E1 (step S3). Although not necessarily limited to this, the discharge amount E1 is a fixed value, and it is preferable that it is the maximum value of the discharge amount that can be instructed to the high-pressure pump 40. Next, the ECU 5 determines whether the detected fuel pressure by the fuel pressure sensor 38 indicates pressure P1 or more (step S4). If the answer is No in step S4, the process of step S3 is continued. That is, while the detected fuel pressure is less than pressure P1, the instructed discharge amount to the high-pressure pump 40 is set to the maximum discharge amount E1, so that the fuel in the high-pressure delivery pipe 36 can be boosted in a short time at the above-mentioned boost speed V1. Step S3 is an example of the process executed by the first control unit.

If step S4 is Yes, the discharge amount of the high-pressure pump 40 is set to a discharge amount E2 smaller than the discharge amount E1, and the discharge amount E2 is feedback-controlled (step S5). Since the instructed discharge amount to the high-pressure pump 40 is set to a discharge amount E2 smaller than the discharge amount E1, the fuel in the high-pressure delivery pipe 36 can be gradually boosted at the above-mentioned boost speed V2, and abnormal noise caused by the opening and closing of the relief valve 70 can be suppressed. The feedback control of the discharge amount E2 is described in detail later, but the discharge amount E2 is variably set so that the boost width U2, which is the amount of increase in fuel pressure in the fuel pressure sensor 38 due to one fuel discharge from the high-pressure pump 40, converges to a predetermined target value. Step S5 is an example of a process executed by the second control unit.

Next, the ECU 5 determines whether the relief valve 70 has opened or closed (step S6). Specifically, if the detection value of the fuel pressure sensor 38 repeatedly increases and decreases in synchronization with the discharge of fuel from the high-pressure pump 40, it is determined that the relief valve 70 is opening and closing, and if the detection value of the fuel pressure sensor 38 is constant or increases at a constant rate, it is determined that the relief valve 70 remains closed.

If the answer is No in step S6, the ECU 5 determines whether a predetermined time has elapsed since the answer was No in step S6 (step S7). The predetermined time is, for example, several seconds. If the answer is No in step S7, that is, until the predetermined time has elapsed since the answer was No in step S6, the processing of step S5 is continued.

If the answer is Yes in step S6 or Yes in step S7, the ECU 5 performs an abnormality diagnosis of the fuel pressure sensor 38 based on whether the detected fuel pressure is within the normal range as described above, specifically, whether the detected fuel pressure is equal to or less than the lower threshold value α and equal to or less than the upper threshold value β (>α) (step S8). The lower threshold value α is a value that is smaller than the pressure P2, which is the opening pressure of the relief valve 70, by a predetermined margin. The upper threshold value β is a value that is larger than the pressure P2 by a predetermined margin.

If the answer is Yes in step S8, the ECU 5 diagnoses that the fuel pressure sensor 38 is normal (step S9). If the answer is No in step S8, the ECU 5 diagnoses that the fuel pressure sensor 38 is abnormal (step S10).

Next, a method for calculating the initial value e2 of the discharge amount E2 will be described. FIG. 5 is a flow chart showing an example of a method for calculating the initial value e2 of the discharge amount E2. The ECU 5 determines whether or not fuel boosting by abnormality diagnosis control has started (step S11). If the answer is No in step S11, this control ends. If the answer is Yes in step S11, the ECU 5 calculates the discharge start timing of the high-pressure pump 40 for boosting (step S12). Specifically, the timing of switching between the open and closed states of the intake valve 50 is calculated based on the phase of the cam CP of the camshaft 15 and the discharge amount E1, and the discharge start timing of the high-pressure pump 40 is calculated based on this timing. The discharge start timing of the high-pressure pump 40 is, in detail, the timing at which fuel is discharged from the pressurizing chamber 43 of the high-pressure pump 40.

Next, the ECU 5 calculates the fuel pressure propagation arrival timing at which the fuel pressure reaches the fuel pressure sensor 38 from the pressurizing chamber 43 of the high-pressure pump 40 via the discharge passage 47 and the high-pressure delivery pipe 36 (step S13). Here, the propagation time T required for the fuel pressure to reach the fuel pressure sensor 38 from the pressurizing chamber 43 via the discharge passage 47 and the high-pressure delivery pipe 36 can be calculated using the following relational expression (Equation 1).
T=L/(G/ρ) ^1/2 ...(1)
"L" is the length [cm] of the piping from the pressurized chamber 43 through the discharge passage 47 and the high-pressure delivery pipe 36 to the fuel pressure sensor 38. "G" is the bulk modulus of the fuel [dyn/ ^cm2 ]. "ρ" is the density of the fuel [g/ ^cm3 ]. The bulk modulus is calculated based on the fuel pressure and fuel temperature. The fuel density is calculated based on the fuel temperature. The fuel pressure and fuel temperature are detected based on the fuel pressure sensor 38 and the fuel temperature sensor 39, respectively.

The fuel propagation arrival timing is calculated based on the propagation time T calculated in this manner. Specifically, the fuel propagation arrival timing can be calculated by adding the propagation time T to the discharge start timing calculated in step S12.

The ECU 5 calculates the fuel pressure rise width U1 detected by the fuel pressure sensor 38 at the fuel pressure propagation arrival timing calculated in step S13 (step S14). Specifically, the amount of increase in fuel pressure detected by the fuel pressure sensor 38 before and after the fuel pressure propagation arrival timing is calculated as the pressure rise width U1. The pressure rise width U1 corresponds to the discharge amount E1. That is, when the command discharge amount is set to the discharge amount E1 and fuel is discharged from the pressurizing chamber 43, the pressure rise width U1 corresponds to the amount of increase in fuel pressure at the fuel pressure sensor 38 when the fuel pressure is propagated to the fuel pressure sensor 38 due to the discharged fuel. In this way, by calculating the amount of increase in fuel detected by the fuel pressure sensor 38 at the fuel pressure propagation arrival timing as the pressure rise width U1, it is possible to accurately calculate the pressure rise width U1 corresponding to the discharge amount E1 with noise and the like removed.

Next, the ECU 5 calculates the boost width U1 calculated as described above each time fuel is discharged from the pressurized chamber 43, and calculates the average value AU1 of these values (step S15). By calculating the average value AU1, it is possible to more accurately calculate the boost width corresponding to the discharge amount E1.

Next, the ECU 5 determines whether the fuel pressure detected by the fuel pressure sensor 38 is equal to or greater than pressure P1 (step S16). If the answer is No in step S16, the process continues from step S12 onwards.

If the answer is Yes in step S16, an initial value e2 of the discharge amount E2 is calculated (step S17). Specifically, the initial value e2 is calculated based on the following equation (3) which is calculated from the following ratio equation (2) showing the relationship between the command discharge amount and the boost amount.
e2:TU2=E1:AU1...(2)
e2=(E1×TU2)/AU1...(3)
"TU2" is a target value of the boost width corresponding to the discharge amount E2, and is determined in advance to a degree that can suppress the generation of abnormal noise caused by the opening and closing of the relief valve 70. Although the target boost width TU2 is not limited to this, it is preferable that it is as large as possible within a range that can suppress the generation of abnormal noise. This is because the diagnosis time can be further shortened. Step S17 is an example of a process executed by the calculation unit.

The commanded discharge amount to the high-pressure pump 40 is set to the initial value e2 calculated in this manner, and the ECU 5 feedback-controls the discharge amount E2 so that the boost width U2 detected by the fuel pressure sensor 38 is maintained at the target boost width TU2. Even when the commanded discharge amount is set to the initial value e2 or the discharge amount E2, the boost width U2 corresponding to the discharge amount E2 is calculated in a manner similar to steps S12 and S13 described above, and the discharge amount E2 is feedback-controlled. In this manner, feedback-controlling the discharge amount E2 so that the actual boost width becomes the target boost width TU2 can effectively suppress the generation of abnormal noise associated with the opening and closing of the relief valve 70.

Although the embodiments of the present invention have been described in detail above, the present invention is not limited to these specific embodiments, and various modifications and variations are possible within the scope of the gist of the present invention as described in the claims.

1 Fuel supply system 5 ECU (fuel pressure sensor abnormality diagnosis device, first control unit, second control unit)
10. Engine (internal combustion engine)
15 Camshaft 21 Fuel tank 22 Low pressure pump 25 Low pressure pipe 25a Branch pipe 26 Low pressure delivery pipe 27 Port injection valve 28, 38 Fuel pressure sensor 39 Fuel temperature sensor 36 High pressure delivery pipe (accumulator)
37 In-cylinder injection valve 40 High-pressure pump 41 Cylinder 42 Plunger 43 Pressurizing chamber 47 Discharge passage 49 Relief passage 50 Suction valve 60 Discharge valve 70 Relief valve 71 Valve body 73 Valve seat 73a Hole 75 Spring (biasing member)
CP Cam

Claims (5)

a high-pressure pump having a pressurizing chamber for pressurizing fuel supplied from a fuel tank;
a pressure accumulator vessel that accumulates the fuel discharged from the pressurizing chamber;
a fuel injection valve that directly injects the fuel in the pressure accumulator into a cylinder of an internal combustion engine;
a relief valve that is provided downstream of the pressurizing chamber of the high-pressure pump, and that opens when the fuel pressure from the pressure accumulator container side is higher than a predetermined valve opening pressure by moving a valve body away from a valve seat against the biasing force of a biasing member to return fuel to the pressurizing chamber, and closes when the fuel pressure from the pressure accumulator container side falls below the valve opening pressure by seating the valve body on the valve seat in accordance with the biasing force of the biasing member;
a fuel pressure sensor for detecting a fuel pressure in the pressure accumulator;
a fuel pressure sensor abnormality diagnosis device that diagnoses whether or not the fuel pressure sensor is abnormal based on whether or not the fuel pressure detected by the fuel pressure sensor when the relief valve is open is within a normal range,
a diagnosis start condition for the fuel pressure sensor is satisfied when the rotation speed, load, coolant temperature, and oil temperature of the internal combustion engine are each within a predetermined range, and a predetermined time or more has elapsed since the previous diagnosis of the presence or absence of an abnormality in the fuel pressure sensor was performed;
a first control unit that controls an instructed discharge amount of the high-pressure pump to a first discharge amount when the fuel pressure in the pressure accumulator container is less than a predetermined pressure that is lower than the valve opening pressure when a diagnosis start condition of the fuel pressure sensor is established;
and a second control unit that controls the instructed discharge amount to a second discharge amount that is less than the first discharge amount when the fuel pressure in the pressure accumulator vessel is from equal to or higher than the predetermined pressure to the valve opening pressure. The fuel pressure sensor abnormality diagnosis device of claim 1, wherein the second control unit feedback controls the second discharge amount so that the fuel in the pressure accumulator vessel is pressurized at a predetermined target pressure increase rate. a calculation unit that calculates an initial value of the second discharge amount corresponding to the target pressure rise rate based on an actual pressure rise rate that is an actual pressure rise rate of the fuel in the pressure accumulator vessel when the command discharge amount is controlled to the first discharge amount,
3. The fuel pressure sensor abnormality diagnosis device according to claim 2, wherein the second control unit controls the instructed discharge amount to an initial value of the second discharge amount when the fuel pressure in the pressure accumulator container becomes equal to or higher than the predetermined pressure. The fuel pressure sensor abnormality diagnosis device according to any one of claims 1 to 3, wherein the first discharge amount is the maximum value of the commanded discharge amount that can be commanded to the high-pressure pump. the fuel supply system includes a low-pressure pump that pressurizes and supplies fuel from the fuel tank to the pressurized chamber,
5. The fuel pressure sensor abnormality diagnosis device according to claim 1, wherein the predetermined pressure is equal to or greater than an intermediate value between the pressure of the fuel pressurized by the low pressure pump and the valve opening pressure.

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