JP2019039408A - Valve opening determining device of relief valve - Google Patents

Abstract

To provide a valve opening determining device of a relief valve which properly determines that the relief valve is opened.SOLUTION: An ECU 90 feedback-controls the discharge amount of a high-pressure pump 30, on the basis of a deviation between a target fuel pressure in a delivery pipe 60 and an actual fuel pressure detected by a pressure sensor 82. Also, the ECU 90 sets the target fuel pressure at a predetermined target value at valve opening, when it is determined that the actual fuel pressure rises to valve opening pressure. Then, on the basis of the followability of the actual fuel pressure to the set target value at valve opening, it is determined that a relief valve 80 is in a valve opening state.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a relief valve opening determination device.

  Patent Document 1 discloses a fuel injection system that includes a fuel pump that discharges fuel at a high pressure, a pressure accumulation container that stores high-pressure fuel discharged from the fuel pump, and a fuel injection valve that injects high-pressure fuel in the pressure accumulation container. Is disclosed. Further, in the fuel injection system, the discharge amount of the fuel pump is feedback-controlled so that the fuel pressure that is the fuel pressure in the pressure accumulating vessel becomes the target fuel pressure.

  In the fuel injection system, a relief valve that opens when the fuel pressure is higher than a predetermined value is provided between the fuel pump and the pressure accumulating vessel. In an abnormal state where the pressure in the pressure accumulating vessel is higher than a predetermined value, the pressure accumulating vessel is depressurized by opening the relief valve.

Japanese Patent No. 3610894

  Due to the failure of the fuel pump, there may be a full discharge abnormality in which the discharge amount of the fuel pump is maintained at the maximum discharge amount. The full discharge abnormality occurs, for example, due to a failure of a metering valve that controls the discharge amount of the fuel pump. When the full discharge abnormality occurs, the fuel pressure in the pressure accumulating container becomes larger than a predetermined value, so that the relief valve is opened.

  Here, it is conceivable that a pressure sensor for detecting the fuel pressure in the pressure accumulating vessel is provided, and a valve opening state in which the relief valve is open is determined based on a detection value of the pressure sensor. However, after the relief valve is opened, the pressure accumulating vessel is depressurized, and the fuel pressure in the pressure accumulating vessel may decrease to near the target fuel pressure. In such a case, if the open state of the relief valve is determined based on the detection value of the pressure sensor, it may be erroneously determined that the relief valve is closed even if the relief valve is open.

  The present invention has been made in view of the above problems, and a main object thereof is to provide a relief valve opening determination device that can appropriately determine that a relief valve is open. .

  In order to solve the above-described problems, a relief valve opening determination device according to the present invention is driven by rotation of a drive shaft of an internal combustion engine to increase the pressure of fuel to be discharged, and a high pressure discharged from the fuel pump. A pressure accumulating container for storing fuel, a fuel injection valve for injecting high-pressure fuel in the pressure accumulating container, a pressure sensor for detecting an actual fuel pressure in the pressure accumulating container, the pressure accumulating container, or the fuel pump to the pressure accumulating container The present invention is applied to a fuel injection system provided with a relief valve that is provided in a high-pressure side pipe and opens when the internal fuel pressure becomes abnormally high. The relief valve opens when the fuel pressure increases to a predetermined valve opening pressure, and closes when the fuel pressure decreases to a predetermined valve closing pressure lower than the valve opening pressure in the valve open state. I speak. The relief valve opening determination device is a pump that feedback-controls the discharge amount of the fuel pump based on a deviation between a target fuel pressure, which is a target value of the fuel pressure in the pressure accumulator, and an actual fuel pressure detected by the pressure sensor A control unit, a fuel pressure determining unit that determines that the actual fuel pressure has increased to the valve opening pressure, and a target valve opening of the target fuel pressure when it is determined that the actual fuel pressure has increased to the valve opening pressure. And a valve opening determination for determining that the relief valve is in an open state based on a followability of the actual fuel pressure with respect to the valve opening target value set by the setting unit. A section.

  For example, when the relief valve is opened due to a full discharge abnormality of the fuel pump, the fuel pressure in the pressure accumulating container is lowered while the relief valve is opened, and eventually converges to a predetermined fuel pressure. The convergence of the fuel pressure due to the opened state of the relief valve is caused by the balance between the discharge amount of the fuel pump and the reduced pressure amount by the relief valve when the full discharge is abnormal.

  In this regard, in the above configuration, when it is determined that the actual fuel pressure has increased to the valve opening pressure, the target fuel pressure is set to a predetermined valve opening target value. As described above, the target fuel pressure of the fuel pressure feedback control is intentionally set taking into consideration that the fuel pressure is balanced between the pump discharge amount and the pressure reduction amount by the relief valve after the relief valve is opened. Therefore, it can be clarified that the fuel pressure cannot follow the target fuel pressure due to the relief valve being opened. Thereby, it can be determined appropriately that the relief valve is open.

The block diagram of a fuel supply system. The timing chart explaining the fuel pressure change in a delivery pipe. The flowchart explaining valve opening determination processing. The flowchart explaining the process of step S11 in detail. The figure explaining the relationship between various conditions and a rising time determination value. The figure explaining the relationship between various conditions and the valve opening target value. The flowchart which shows the process of step S17 in detail. The figure explaining the fuel-injection timing of an injector. The timing chart explaining the effect | action of this embodiment. The figure explaining the relationship between the engine speed Ne and the fuel pressure after convergence. The figure explaining the valve opening target value according to engine speed Ne. The flowchart explaining the valve opening determination process which concerns on 2nd Embodiment.

(First embodiment)
Hereinafter, a fuel injection system to which a relief valve opening determination device according to a first embodiment is applied will be described with reference to the drawings. In FIG. 1, the fuel injection system 10 is applied to a four-cylinder engine 100 (corresponding to an internal combustion engine).

  Each cylinder of the cylinder block 110 accommodates a piston connected to the drive shaft 12. Each cylinder is connected to an intake pipe through which inflow air flows through an intake port, and is connected to an exhaust pipe through which exhaust gas is exhausted through an exhaust port.

  In this embodiment, since engine 100 is an in-cylinder injection type (direct injection type), an injector 62 for injecting fuel is provided for each cylinder. In addition, a cylinder head of engine 100 is ignited for each cylinder. A plug is attached, and the air-fuel mixture in the cylinder is ignited by spark discharge of the spark plug.

  A rotation angle sensor 13 that outputs a pulse signal each time the drive shaft 12 rotates at a predetermined crank angle is attached to the outer peripheral side of the drive shaft 12. Based on the crank angle signal from the rotation angle sensor 13, the crank angle and the engine rotation speed Ne are detected.

  The fuel injection system 10 includes a fuel tank 18, a high-pressure pump 30, a delivery pipe 60, and an ECU 90 in addition to the injector 62. The high-pressure pump 30 corresponds to a fuel pump, the delivery pipe 60 corresponds to a pressure accumulating container, and the injector 62 corresponds to a fuel injection valve.

  Inside the fuel tank 18 is provided a low-pressure pump 20 that sucks and pressurizes the fuel and discharges it. The outlet of the low pressure pump 20 communicates with the low pressure side pipe 22. The pressure of the fuel discharged by the low pressure pump 20 is adjusted by a regulator or the like. A fuel temperature sensor 16 for detecting the fuel temperature is provided inside the fuel tank 18. Further, an alcohol concentration sensor 17 for detecting an alcohol concentration that is a fuel property is provided inside the fuel tank 18. The fuel temperature sensor 16 and the alcohol concentration sensor 17 are connected to the ECU 90 and output a detection value to the ECU 90.

  The high pressure pump 30 increases the pressure of the fuel supplied from the low pressure side pipe 22 and discharges it to the high pressure side pipe 44. In the present embodiment, the high-pressure pump 30 corresponds to a fuel pump.

  A low pressure chamber 40 and a pressurizing chamber 42 are formed in the cylinder body 32 of the high pressure pump 30. The low pressure chamber 40 communicates with the low pressure side pipe 22 and stores fuel supplied through the low pressure side pipe 22. A metering valve 36 is provided in a passage where the low pressure chamber 40 and the pressurizing chamber 42 communicate with each other. The metering valve 36 is connected to the ECU 90, and the amount of fuel supplied from the low pressure chamber 40 to the pressurizing chamber 42 is controlled by a control signal from the ECU 90.

  The pressurizing chamber 42 is provided with a plunger 34 that changes the pressure in the pressurizing chamber 42 by a reciprocating operation. An end of the plunger 34 opposite to the pressurizing chamber 42 is connected to the cam 14. The cam 14 is connected to the drive shaft 12 of the engine 100, and the rotational speed of the cam 14 changes according to the engine rotational speed Ne. The plunger 34 reciprocates between the top dead center and the bottom dead center by the rotation of the cam 14.

  The pressurizing chamber 42 is provided with a discharge valve 38 that discharges fuel pressurized in the pressurizing chamber 42. The discharge port of the discharge valve 38 communicates with a high-pressure side pipe 44 that is connected to the delivery pipe 60. The discharge valve 38 is a check valve that allows fuel to flow from the pressurizing chamber 42 to the high-pressure side pipe 44, and is opened when the fuel pressure in the pressurizing chamber 42 exceeds a predetermined discharge pressure.

  The metering valve 36 is opened, and the plunger 34 is lowered from the top dead center toward the bottom dead center, whereby the fuel in the low pressure chamber 40 is sucked into the pressurizing chamber 42. Hereinafter, the stroke in which the fuel in the low pressure chamber 40 is sucked into the pressurizing chamber 42 is referred to as a suction stroke. The metering valve 36 is in the open state, and the plunger 34 is raised from the bottom dead center toward the top dead center, whereby the fuel in the pressurizing chamber 42 is returned to the low pressure chamber 40 via the metering valve 36. . Hereinafter, the stroke in which the fuel in the pressurizing chamber 42 is returned to the low-pressure chamber 40 is referred to as a return stroke. Then, the metering valve 36 is closed, and the plunger 34 continues to rise, so that the fuel in the pressurizing chamber 42 is pressurized. When the fuel pressure in the pressurizing chamber 42 is equal to or higher than the discharge pressure, the discharge valve 38 discharges the fuel. Hereinafter, the stroke in which the fuel in the pressurizing chamber 42 is pressurized to the discharge pressure is referred to as a discharge stroke.

  The delivery pipe 60 communicating with the high-pressure side pipe 44 stores the fuel discharged by the high-pressure pump 30 in a pressurized state. An injector 62 for injecting fuel communicates with the delivery pipe 60.

  The high-pressure side pipe 44 is provided with a relief valve 80 that depressurizes the fuel in the delivery pipe 60. The relief valve 80 opens when the fuel pressure increases to a predetermined valve opening pressure, and closes when the fuel pressure decreases to a predetermined valve closing pressure lower than the valve opening pressure in the valve open state.

  The inlet side of the relief valve 80 communicates with the high pressure side pipe 44, and the outlet side communicates with the low pressure chamber 40 through the return pipe 45. By opening the relief valve 80, the fuel in the high-pressure side pipe 44 returns to the low-pressure chamber 40 through the relief valve 80, and the delivery pipe 60 is depressurized. The valve opening pressure for opening the relief valve 80 is determined to be lower than the pressure resistance (rail pressure resistance) before the delivery pipe 60 deteriorates, for example. The valve opening pressure corresponds to an abnormally high pressure.

  The delivery pipe 60 is provided with a pressure sensor 82 that detects the fuel pressure of the delivery pipe 60. The pressure sensor 82 is connected to the ECU 90 and outputs a detected fuel pressure (hereinafter referred to as a detected pressure Pm) to the ECU 90. The pressure sensor 82 may detect the fuel pressure in the high-pressure side pipe 44 or the fuel pressure in the injector 62.

  The ECU 90 is a microcomputer including a CPU, a ROM, a RAM, a drive circuit, an input / output interface, and the like. The ECU 90 feedback-controls the discharge amount of the high-pressure pump 30 based on the deviation between the target fuel pressure that is the target value of the fuel pressure in the delivery pipe 60 and the detected pressure Pm (actual fuel pressure) detected by the pressure sensor 82. Specifically, the discharge amount of the discharge valve 38 is controlled by controlling the valve opening period of the metering valve 36 provided in the high-pressure pump 30 according to the target fuel pressure. Therefore, the ECU 90 corresponds to a pump control unit.

  Further, the ECU 90 can switch between a compression stroke injection for injecting fuel into the injector 62 during the compression stroke of the engine 100 and an intake stroke injection for injecting fuel into the injector 62 during the intake stroke. In the compression stroke injection, the ECU 90 sets an injection timing SOI indicating the timing at which the injector 62 injects fuel to the compression stroke. On the other hand, in the intake stroke injection, the ECU 90 sets the injection timing SOI to the intake stroke. In the present embodiment, the intake stroke of the high-pressure pump 30 is synchronized with the compression stroke of the engine 100, and the discharge stroke is synchronized with the intake stroke of the engine.

  In the fuel injection system 10 having the above-described configuration, when the fuel pressure in the delivery pipe 60 rises to an abnormally high pressure (valve opening pressure) that opens the relief valve 80, the relief valve 80 is opened so that the delivery pipe 60 is Reduce pressure. FIG. 2 is a timing chart for explaining a change in fuel pressure in the delivery pipe 60.

  Before time t1, the discharge amount of the high-pressure pump 30 is controlled so that the high-pressure pump 30 has not failed and the fuel pressure of the delivery pipe 60 is close to the target fuel pressure Tf. It is assumed that the high pressure pump 30 fails immediately before time t1, resulting in a full discharge abnormality in which the high pressure pump 30 discharges with the maximum discharge amount. A single discharge amount from the high-pressure pump 30 exceeds a single injection amount of the injector 62, and the fuel pressure in the delivery pipe 60 increases every time the high-pressure pump 30 discharges.

  At time t2, the fuel pressure reaches the valve opening pressure P1 of the relief valve 80, and the relief valve 80 is in an open state. By opening the relief valve 80, the fuel in the high-pressure side pipe 44 returns to the low-pressure chamber 40 through the return pipe 45, and the fuel pressure in the delivery pipe 60 decreases at time t3.

  Since the relief valve 80 maintains the valve open state until the fuel pressure becomes a valve closing pressure lower than the valve opening pressure P1, the fuel pressure in the delivery pipe 60 continues to decrease after the relief valve 80 is opened. In the fuel pressure change indicated by the broken line in FIG. 2, for example, the fuel pressure at time t4 is higher than the target fuel pressure Tf, and the difference from the target fuel pressure Tf is also large. Therefore, the ECU 90 can determine that the relief valve 80 is in the open state based on the difference between the detected pressure Pm detected by the pressure sensor 82 and the target fuel pressure Tf.

  On the other hand, in the fuel pressure change shown by the solid line in FIG. 2, the difference between the fuel pressure at time t4 and the target fuel pressure Tf is smaller than the difference in the fuel pressure change shown by the broken line. In this case, from the difference between the detected pressure Pm and the target fuel pressure Tf, whether the fuel pressure of the delivery pipe 60 has decreased to the target fuel pressure Tf due to the feedback control functioning, or the relief valve 80 continues to open. It is difficult to distinguish whether the fuel pressure has decreased to the target fuel pressure Tf.

  In a state where the fuel pressure is converged by feedback control, the discharge amount of the high-pressure pump 30 is controlled so that the fuel pressure set by the target fuel pressure Tf is obtained. Therefore, by changing the target fuel pressure Tf, the convergent fuel pressure changes so as to follow the changed target fuel pressure Tf. That is, in a state where the relief valve is closed and the fuel pressure is converged by feedback control, it can be said that the followability of the converged fuel pressure with respect to the change of the target fuel pressure Tf is high.

  On the other hand, in a state where the fuel pressure has converged by continuing the open state of the relief valve 80, the fuel pressure converges to a predetermined value by balancing the discharge amount from the high-pressure pump 30 and the pressure reduction amount by the relief valve 80. Yes. Therefore, even if the target fuel pressure Tf is changed, the fuel pressure does not change so as to follow the target fuel pressure Tf. That is, in a state where the fuel pressure is converged by continuing the opened state of the relief valve 80, it can be said that the followability of the fuel pressure with respect to the change of the target fuel pressure Tf is low.

  In the present embodiment, in a situation where the fuel pressure in the delivery pipe 60 has converged, it is determined that the relief valve 80 is in the open state by using the followability of the fuel pressure with respect to the change in the target fuel pressure Tf. It was. Specifically, when the ECU 90 determines that the fuel pressure of the delivery pipe 60 has increased to the valve opening pressure, the target value at the time of valve opening indicates a target fuel pressure Tf that is different from the convergence value of the fuel pressure in the delivery pipe 60. Set to. Then, the ECU 90 determines the followability of the fuel pressure with respect to the valve opening target value. When the followability of the fuel pressure with respect to the valve opening target value is high, the ECU 90 determines that the relief valve 80 is closed. On the other hand, when the followability of the fuel pressure with respect to the valve opening target value is low, the ECU 90 determines that the relief valve 80 is in the valve open state.

  Next, the opening determination process of the relief valve 80, which is performed by the ECU 90, will be described with reference to FIG. The valve opening determination process shown in FIG. 3 is repeatedly executed by the ECU 90 at a predetermined cycle.

  In step S11, it is determined whether or not the detected pressure Pm has reached a high-pressure abnormal state in which the relief valve 80 is opened. In the present embodiment, step S11 corresponds to a fuel pressure determination unit.

  FIG. 4 is a flowchart for explaining the process of step S11 in detail. In step S21, the detected pressure Pm is compared with the high pressure side determination value TH1. In the present embodiment, the high-pressure side determination value TH1 is set to the valve opening pressure of the relief valve 80.

  If the detected pressure Pm is larger than the high-pressure side determination value TH1, the process proceeds to step S22. In step S22, an abnormality determination value TH2 for determining a duration time during which the detected pressure Pm is larger than the high pressure side determination value TH1 is set. In the present embodiment, the abnormality determination value TH2 is set based on various conditions that affect the change in fuel pressure. Specifically, as various conditions that affect the change in fuel pressure, the engine rotation speed Ne detected by the rotation angle sensor 13, the fuel injection amount Q indicating the injection amount per injection of the injector 62, and the fuel temperature sensor 19 The fuel temperature Temp measured by the above and the fuel property indicating the alcohol concentration ALC contained in the fuel are used.

  FIG. 5 is a diagram for explaining the relationship between various conditions and the abnormality determination value TH2. FIG. 5A is a graph in which the horizontal axis is the engine rotation speed Ne and the vertical axis is the abnormality determination value TH2. FIG. 5B is a graph in which the horizontal axis represents the fuel injection amount Q and the vertical axis represents the abnormality determination value TH2. FIG. 5C is a graph in which the horizontal axis is the fuel temperature Temp and the vertical axis is the abnormality determination value TH2. FIG. 5D is a graph in which the horizontal axis represents the alcohol concentration ALC and the vertical axis represents the abnormality determination value TH2.

  As the engine speed Ne increases, the fuel injection frequency of the injector 62 and the discharge frequency of the high-pressure pump 30 increase, so that the change in the fuel pressure increases and the fuel pressure easily changes. Therefore, as shown in FIG. 5 (a), the detected pressure Pm is less likely to be maintained at a value higher than the high-pressure side determination value TH1 as the engine rotational speed Ne increases, and thus the abnormality determination value TH2 is set to a small value. The

  The greater the fuel injection amount Q, the greater the fuel pressure reduction rate. Therefore, as shown in FIG. 5B, as the fuel injection amount Q increases, the detected pressure Pm is less likely to be maintained at a value higher than the high-pressure side determination value TH1, and therefore the abnormality determination value TH2 is set to a small value. The

  The lower the fuel temperature Temp, the higher the bulk modulus of the fuel, so the fuel pressure tends to decrease. Therefore, as shown in FIG. 5C, as the fuel temperature Temp becomes higher, the detected pressure Pm is less likely to be maintained at a value higher than the high-pressure side determination value TH1, and thus the abnormality determination value TH2 is set to a large value. .

  The higher the alcohol concentration contained in the fuel, the higher the bulk modulus of the fuel, so the fuel pressure tends to decrease. Therefore, as shown in FIG. 5D, the higher the alcohol concentration is, the more difficult it is to maintain the detected pressure Pm at a value higher than the high-pressure side determination value TH1, so the abnormality determination value TH2 is set to a small value.

  The influence on the fuel pressure change is that the engine speed Ne and the fuel injection amount Q are higher than the fuel temperature Temp and the alcohol concentration ALC. Therefore, in the present embodiment, the weighting of the abnormality determination value TH2 in the engine rotation speed Ne and the fuel injection amount Q is increased, and the weighting of the abnormality determination value TH2 in the fuel temperature Temp and the alcohol concentration ALC is decreased.

  In step S23, the abnormality determination counter Co1 is incremented. The abnormality determination counter Co1 is a value for measuring the time during which the detected pressure Pm is maintained at a value larger than the high pressure side determination value TH1. In step S21, if the detected pressure Pm is equal to or lower than the high pressure side determination value TH1, the process proceeds to step S24, and the abnormality determination counter Co1 is reset to zero.

  In step S25, the abnormality determination counter Co1 is compared with the abnormality determination value TH2 set in step S22. By continuing the time during which the detected pressure Pm is larger than the high-pressure side determination value TH1, the increase of the abnormality determination counter Co1 is also continued. If the abnormality determination counter Co1 is equal to or less than the abnormality determination value TH2, the process proceeds to step S12 in FIG. On the other hand, if it is determined in step S25 that the abnormality determination counter Co1 is greater than the abnormality determination value TH2, the process proceeds to step S26, where it is determined that the delivery pipe 60 is in a high pressure abnormality state.

  Returning to FIG. 3, in step S12, if it is determined in step S11 that the high-pressure abnormal state has been determined, the process proceeds to step S13. On the other hand, if determination of a high voltage | pressure abnormal condition is not performed, it will progress to step S14.

  The amount of discharge from the high-pressure pump 30 and the amount of pressure reduction by the relief valve 80 are not balanced until the fuel pressure converges after the relief valve 80 is opened due to the delivery pipe 60 becoming in a high-pressure abnormal state. Therefore, the fluctuation of the detection pressure Pm becomes larger than the fluctuation in the state where the detection pressure Pm is converged. There is a possibility that the followability of the fuel pressure with respect to the target value at the time of valve opening may be erroneously determined due to the fluctuation of the detection pressure Pm. Therefore, in steps S13 to S15, the valve opening determination of the relief valve 80 is performed after the elapse of a predetermined waiting time after determining the high pressure abnormality state.

  First, in step S13, the post-determination counter Co2 is incremented. The post-judgment counter Co2 is a value for measuring the time required for the fuel pressure to converge after the fuel pressure starts to decrease. When the process proceeds to step S14, the post-determination counter Co2 is reset to zero.

  In step S15, it is determined whether or not the fuel pressure of the delivery pipe 60 has converged. Specifically, when the after-determination counter Co2 is larger than the convergence time TH3, it is determined that the fuel pressure has converged. The convergence time TH3 is the time required for the fuel pressure to converge after the fuel pressure changes from rising to falling. For example, the convergence time TH3 is determined according to the properties of the fuel. If the post-judgment counter Co2 is equal to or less than the convergence time TH3, the fuel pressure of the delivery pipe 60 has not converged, and the process of FIG.

  If the post-determination counter Co2 is larger than the convergence time TH3, the process proceeds to step S16. In step S16, a valve opening target value V1 is set as the target fuel pressure. In the present embodiment, the valve opening target value V1 is set to a value higher than a value assumed as the fuel pressure after convergence in the delivery pipe 60. Specifically, since the fuel pressure after convergence changes according to various conditions for changing the fuel pressure, the target value V1 at the time of valve opening is set in consideration of these various conditions. Specifically, the valve opening target value V1 is set in consideration of the engine speed Ne, the fuel injection amount Q, the fuel temperature Temp, and the properties of the fuel (alcohol concentration ALC). Step S16 corresponds to a setting unit.

  FIG. 6 is a diagram for explaining the relationship between various conditions and the valve opening target value V1. FIG. 6A is a graph in which the horizontal axis is the engine rotational speed Ne and the vertical axis is the valve opening target value V1. FIG. 6B is a graph in which the fuel injection amount Q is set and the vertical axis is the valve opening target value V1. FIG. 6C is a graph in which the horizontal axis is the fuel temperature Temp and the vertical axis is the valve opening target value V1. FIG. 6D is a graph in which the horizontal axis represents the alcohol concentration ALC and the vertical axis represents the valve opening target value V1.

  As the engine rotation speed Ne increases, the discharge frequency of the high-pressure pump 30 increases and the fuel pressure is less likely to decrease. Therefore, as shown in FIG. 6 (a), the higher the engine speed Ne, the higher the fuel pressure in the delivery pipe 60. Therefore, the valve opening target value V1 is set to a larger value.

  As the fuel injection amount Q is larger, the fuel pressure is reduced more easily, so that the fuel pressure is easily lowered. Therefore, as shown in FIG. 6B, the fuel pressure in the delivery pipe 60 becomes lower as the fuel injection amount becomes larger, so the valve opening target value V1 is set to a smaller value.

  The lower the fuel temperature Temp, the higher the bulk modulus of the fuel, and the higher the fuel pressure. Therefore, as shown in FIG. 6C, the higher the fuel temperature Temp, the lower the fuel pressure in the delivery pipe 60, so the valve opening target value V1 is set to a smaller value.

  The higher the concentration of alcohol contained in the fuel, the higher the bulk modulus of the fuel, and thus the higher the fuel pressure. Therefore, as shown in FIG. 6 (d), the higher the alcohol concentration, the lower the fuel pressure in the delivery pipe 60. Therefore, the valve opening target value V1 is set to a larger value.

  The influence on the fuel pressure change is that the engine speed Ne and the fuel injection amount Q are higher than the fuel temperature Temp and the alcohol concentration ALC. Therefore, in this embodiment, the weighting for the valve opening target value V1 at the engine speed Ne and the fuel injection amount Q is set higher than the weighting for the valve opening target value V1 at the fuel temperature Temp and the alcohol concentration ALC.

  Returning to FIG. 3, in step S <b> 17, the target fuel pressure is set to the valve opening target value set in step S <b> 16, thereby performing the valve opening determination of the relief valve 80. Therefore, in the process of step S17, the followability of the detected pressure Pm after convergence with respect to the valve opening target value is determined. Step S17 corresponds to the valve opening determination unit.

  FIG. 7 is a flowchart showing in detail the process of step S17. In step S40, the valve opening target value V1 set in step S16 is set as the target fuel pressure Tf. In this embodiment, every time the process of FIG. 3 is repeatedly performed, the valve-opening target value V1 is set in step S40. Therefore, the valve-opening target value V1 set as the target fuel pressure Tf is filtered. So-called annealing treatment is applied.

  In step S41, the current detected pressure Pm of the delivery pipe 60 is acquired. In this embodiment, it is determined in step S15 that the fuel pressure in the delivery pipe 60 has converged, and the detected pressure Pm acquired in step S41 is the fuel pressure after convergence.

  In steps S42 to S46, the followability of the detected pressure Pm with respect to the valve opening target value is determined based on the fuel pressure deviation ΔPm between the target fuel pressure Tf and the detected pressure Pm.

  First, in step S42, the fuel pressure deviation ΔPm, which is the difference between the valve opening target value V1 set in step S41 and the detected pressure Pm, is compared with the deviation determination value TH4. In the present embodiment, the absolute value of the difference between the valve opening target value V1 and the detected pressure Pm is defined as the fuel pressure deviation ΔPm. The deviation determination value TH4 may be determined according to an error between the detected pressure Pm and the target fuel pressure when the detected pressure Pm is controlled to the target fuel pressure by feedback control, for example.

  If the fuel pressure deviation ΔPm is larger than the deviation determination value TH4, the process proceeds to step S43, and the valve opening determination counter Co3 is increased. The valve opening determination counter Co3 is a value for measuring the time during which the fuel pressure deviation ΔPm continues and is greater than the deviation determination value TH4. If the fuel pressure deviation ΔPm is equal to or smaller than the deviation determination value TH4, the process proceeds to step S44, and the valve opening determination counter Co3 is reset to zero.

  In step S45, it is determined whether or not the valve opening determination counter Co3 is larger than the time determination value TH5. The time determination value TH5 indicates a time during which the fuel pressure deviation ΔPm continues to be larger than the deviation determination value TH4. Therefore, when the valve opening determination counter Co3 is larger than the time determination value TH5, it can be determined that the detected pressure Pm has not approached the target fuel pressure Tf and the followability of the fuel pressure with respect to the valve opening target value is low.

  In step S46, it is determined that the relief valve 80 is open. Then, returning to FIG. 3, the process proceeds to step S18. On the other hand, if the valve opening determination counter Co3 is equal to or smaller than the time determination value TH5, the process proceeds to step S18 without determining that the relief valve 80 is in the valve open state.

  In steps S18 and S19, the injection timing SOI of the injector 62 is changed depending on whether the relief valve 80 is in the open state or in the closed state. When the suction stroke and the discharge stroke of the high-pressure pump 30 are compared, the fuel pressure of the delivery pipe 60 becomes lower than the discharge stroke in the suction stroke because the discharge valve 38 does not discharge fuel. Further, when the fuel injection of the injector 62 is performed so as to overlap with the suction stroke, the fuel pressure of the delivery pipe 60 is greatly reduced as compared with the case where the fuel injection is not performed. Therefore, if fuel injection is performed in the intake stroke after the fuel pressure has converged, the fuel pressure is reduced to the valve closing pressure, and the relief valve 80 may be changed from the open state to the closed state.

  When the relief valve 80 is closed, the fuel pressure of the delivery pipe 60 starts to rise again. The increase in the fuel pressure is continued until the fuel pressure rises to the valve opening pressure of the relief valve 80, and the fuel pressure rises again when the relief valve 80 is opened. Therefore, the fuel pressure is repeatedly increased and decreased in the delivery pipe 60, and the pressure change in a short period increases. As a result, there is a risk of promoting deterioration from the high-pressure side pipe 44 to the delivery pipe 60. Therefore, when the open state of the relief valve 80 is determined, the relief timing 80 is prevented from being closed again by changing the injection timing SOI from the intake stroke to the discharge stroke.

  FIG. 8 is a diagram for explaining each stroke of the high-pressure pump 30. FIG. 8 shows the relationship between each stroke (intake stroke D1, return stroke D2, and discharge stroke D3) of the high-pressure pump 30 and the injection timing SOI of the injector 62. The injection timing SOI when the relief valve 80 is determined to be closed is indicated by a broken line, and the injection timing SOI when the relief valve 80 is determined to be open is indicated by a solid line.

  First, in step S18, when it is determined in step S17 that the relief valve 80 is open, the process proceeds to step S19. In step S19, the injection timing SOI is changed from the suction stroke of the high-pressure pump 30 to the discharge stroke. In the present embodiment, the injection timing SOI is changed by changing the injection of the injector 62 from the compression stroke injection to the intake stroke injection.

  Step S19 corresponds to a timing setting unit. Then, when the process of step S19 ends, the process of FIG. 3 is temporarily ended. On the other hand, if it is determined in step S18 that the relief valve 80 is in a closed state, the processing in FIG.

  FIG. 9 is a time chart showing the opening determination of the relief valve of the present embodiment. FIG. 9 shows a change in fuel pressure in an idling state where the engine rotation speed Ne is kept constant.

  It is assumed that the high-pressure pump 30 has failed before time t21 and the high-pressure pump 30 has a full discharge abnormality. Therefore, the fuel pressure in the delivery pipe 60 starts to rise. When the fuel pressure of the delivery pipe 60 exceeds the valve opening pressure P1 at time t22, the relief valve 80 is opened. At time t23, the abnormality determination counter Co1 becomes larger than the abnormality determination value TH2, whereby the high pressure abnormality state of the delivery pipe 60 is determined. Thereafter, the time until the detection pressure Pm converges is measured by the post-determination counter Co2.

  At time t24, the post-determination counter Co2 becomes larger than the convergence time TH3, and it is determined that the fuel pressure has converged. For this reason, the target fuel pressure Tf is set to the valve opening target value V1, and the followability of the detected pressure Pm with respect to the valve opening target value V1 is determined.

  In FIG. 9, even after time t25, the fuel pressure deviation ΔPm, which is the difference between the detected pressure Pm and the valve opening target value V1, continues to increase, and the valve opening determination counter Co3 increases. At time t26, the valve opening determination counter Co3 becomes larger than the time determination value TH5. Therefore, at time t26, it is determined that the relief valve 80 is open.

  The embodiment described above has the following effects.

  The ECU 90 sets the valve opening target value to the target fuel pressure when it is determined that the detected pressure has increased to the valve opening pressure. And based on the followability of the detected pressure with respect to the set valve-opening target value, it is determined that the relief valve 80 is in the valve open state. In this case, after the relief valve 80 is opened, the target fuel pressure for feedback control is intentionally set taking into account that the fuel pressure is balanced between the pump discharge amount and the pressure reduction amount by the relief valve 80. Therefore, it can be clarified that the fuel pressure cannot follow the target fuel pressure due to the relief valve 80 being in the open state. Thereby, it can be determined appropriately that the relief valve is open.

  The ECU 90 sets the valve opening target value to a larger value as the engine speed Ne is larger. In this case, the target value at the time of valve opening can be set according to the convergence tendency of the fuel pressure accompanying the engine rotation speed Ne, and it can be appropriately determined that the relief valve 80 is in the valve open state.

  The ECU 90 sets the valve opening target value to a smaller value as the fuel injection amount increases. In this case, it is possible to set a valve opening target value in consideration of the fuel injection amount, and to improve the accuracy of the relief valve opening determination.

  The ECU 90 sets the valve opening target value to a smaller value as the fuel temperature increases. In this case, it is possible to set the valve opening target value in consideration of the fuel temperature, and it is possible to improve the accuracy of the valve opening determination of the relief valve 80.

  The ECU 90 sets the valve opening target value to a larger value as the alcohol concentration of the fuel becomes higher. In this case, the target value at the time of valve opening can be set in consideration of the concentration of alcohol contained in the fuel, and the accuracy of the valve opening determination of the relief valve 80 can be improved.

  The ECU 90 determines that the relief valve 80 is in an open state based on the followability of the detected pressure after a lapse of a predetermined waiting time after determining that the detected pressure has increased to the valve opening pressure. did. In this case, erroneous determination of the valve opening state can be suppressed by determining the followability with respect to the target value at the time of valve opening in a state where the variation in the detected pressure is small.

  The ECU 90 determines that the injection timing of the injector 62 is set from the suction stroke of the high-pressure pump 30 to the discharge stroke after determining that the relief valve 80 is in the open state. In this case, it is possible to prevent the fuel pressure in the delivery pipe 60 from repeatedly increasing and decreasing, and to prevent deterioration from being promoted from the high-pressure side pipe 44 to the delivery pipe 60.

(Second Embodiment)
In the second embodiment, a description will be given focusing on a configuration different from the first embodiment. In addition, the location which attached | subjected the same code | symbol shows the same location, and the description is not repeated.

  Also in the second embodiment, the ECU 90 sets a target fuel pressure that is different from the convergence value of the fuel pressure in the delivery pipe 60, and determines the opening state of the relief valve 80 based on the followability of the fuel pressure with respect to the set target fuel pressure.

  FIG. 10 is a diagram for explaining the relationship between the engine rotational speed Ne and the fuel pressure after convergence in the delivery pipe 60 in a state where the relief valve 80 is open, and the horizontal axis is the engine rotational speed Ne. It is a graph which makes the vertical axis | shaft the fuel pressure after convergence. The fuel pressure range defined by the upper limit value P2 and the lower limit value P3 indicates the fuel pressure range that is assumed when fuel discharge by the high-pressure pump 30 is normal. The ECU 90 sets the target fuel pressure within the fuel pressure range.

  Also in this embodiment, the valve opening target value used for the valve opening determination of the relief valve 80 is set to a higher value as the engine speed Ne is larger. Since the target fuel pressure cannot be set higher than the upper limit value P2, when the valve opening target value is set to a value higher than the fuel pressure after convergence, the target fuel pressure converges from the valve opening target value in a region where the engine speed Ne is high. The fuel pressure difference up to the fuel pressure becomes smaller. Further, since the target fuel pressure cannot be set to a value lower than the lower limit value P3, when the target value at valve opening is set to a value lower than the fuel pressure after convergence, the target value at valve opening is set in a region where the engine rotational speed Ne is low. The fuel pressure difference from to the convergent fuel pressure becomes smaller. When the fuel pressure difference from the target value at the time of valve opening to the convergent fuel pressure is small, it may be assumed that the valve opening determination of the relief valve 80 cannot be performed properly.

  Further, for example, when the relief valve 80 is in a closed state, if the valve opening target value is set to the upper limit value P2 of the fuel pressure range or the lower limit value P3 of the fuel pressure range, the discharge performance of the high pressure pump 30 In some cases, the fuel pressure cannot follow the valve opening target value.

  Therefore, in the present embodiment, when the engine rotational speed Ne is higher than a predetermined rotational speed, the valve opening target value is set lower than the value assumed as the fuel pressure at the time of convergence. In FIG. 11, the convergent fuel pressure V2 considered to converge when the relief valve 80 is in the open state is indicated by a broken line. Further, the speed determination value TH6 is indicated by a one-dot chain line, and the region of the engine rotation speed Ne lower than the speed determination value TH6 is defined as a low speed rotation region A1, and the region of the engine rotation speed Ne higher than the speed determination value TH6 is rotated at high speed. It is set as area A2. For example, the speed determination value TH6 is determined on the lower rotation side than the engine rotation speed Ne corresponding to the upper limit value P2 in FIG.

  The valve opening target value V3 in the low speed rotation region A1 is set to a value higher than the convergent fuel pressure V2 considered to converge when the relief valve 80 is in the valve open state. Further, the valve opening target value V4 in the high speed rotation region A2 is set to a value lower than the convergent fuel pressure V2.

  FIG. 12 is a flowchart for explaining a valve opening determination process according to the second embodiment. The process shown in FIG. 12 is repeatedly performed by the ECU 90 at a predetermined cycle.

  If it is determined in step S15 that the post-determination counter Co2 is greater than the convergence time TH3 and the detected pressure Pm has converged, the process proceeds to step S51. In step S51, it is determined whether or not the engine rotation speed Ne is in a high rotation state. Specifically, the engine speed Ne is compared with a speed determination value TH6.

  If it is determined that the engine speed Ne is greater than the speed determination value TH6, the process proceeds to step S52. On the other hand, if it is determined that the engine speed Ne is equal to or less than the speed determination value TH6, the process proceeds to step S54.

  In step S52, the valve opening target value V4 is set. On the other hand, in step S54, the valve opening target value V3 is set.

  In step S53, the valve opening target value V4 set in step S52 is set to the target fuel pressure, so that the relief valve 80 is determined to be opened. In step S55, the valve opening target value V3 set in step S54 is set to the target fuel pressure, so that the relief valve 80 is determined to be opened.

  The embodiment described above has the following effects.

  The ECU 90 sets the target fuel pressure to a valve opening target value lower than the convergent fuel pressure if the engine rotational speed Ne is in the low speed rotation range. On the other hand, if the engine rotation speed Ne is in the high speed rotation range, the target fuel pressure is set to a valve opening target value higher than the convergent fuel pressure. In this case, the difference between the target value at the time of valve opening and the convergent fuel pressure is prevented from becoming small, and the valve opening state of the relief valve 80 can be properly determined.

(Other embodiments)
You may change the said embodiment as follows, for example.

  In steps S16, S52, and S54, as various conditions for setting the valve opening target value, at least one of the engine speed Ne, the fuel injection amount Q, the fuel temperature, and the fuel property may be used.

  DESCRIPTION OF SYMBOLS 10 ... Fuel injection system, 12 ... Drive shaft, 30 ... High pressure pump, 60 ... Delivery pipe, 62 ... Injector, 80 ... Relief valve, 82 ... Pressure sensor.

Claims (8)

A fuel pump (30) driven by rotation of the drive shaft (12) of the internal combustion engine (100) to discharge the fuel at a high pressure; a pressure accumulating container (60) for storing high-pressure fuel discharged from the fuel pump; A fuel injection valve (62) for injecting high-pressure fuel in the pressure accumulator, a pressure sensor (82) for detecting an actual fuel pressure in the pressure accumulator, and a high-pressure side pipe from the pressure accumulator or the fuel pump to the pressure accumulator (44) provided with a relief valve (80) that opens when the internal fuel pressure becomes abnormally high,
The relief valve opens when the fuel pressure increases to a predetermined valve opening pressure, and closes when the fuel pressure decreases to a predetermined valve closing pressure lower than the valve opening pressure in the valve open state. Applied to the fuel injection system,
A pump control unit that feedback-controls the discharge amount of the fuel pump based on a deviation between a target fuel pressure that is a target value of the fuel pressure in the pressure accumulator and the actual fuel pressure detected by the pressure sensor;
A fuel pressure determination unit that determines that the actual fuel pressure has increased to the valve opening pressure;
When it is determined that the actual fuel pressure has increased to the valve opening pressure, a setting unit that sets the target fuel pressure to a predetermined valve opening target value;
A valve opening determining unit that determines that the relief valve is in an open state based on the followability of the actual fuel pressure with respect to the valve opening target value set by the setting unit;
A relief valve opening determination device comprising:   2. The relief valve opening determination device according to claim 1, wherein the setting unit sets the valve opening target value to a larger value as the rotation speed of the internal combustion engine is higher.   3. The relief valve opening determination device according to claim 1, wherein the setting unit sets the valve opening target value to a smaller value as the injection amount of the fuel injection valve per unit time is larger.   The relief valve opening determination device according to any one of claims 1 to 3, wherein the setting unit sets the valve opening target value to a smaller value as the fuel temperature is higher.   The relief valve opening determination device according to any one of claims 1 to 4, wherein the setting unit sets the valve opening target value to a larger value as the concentration of alcohol contained in the fuel is higher. The setting unit
In a rotational range where the rotational speed of the internal combustion engine is higher than a predetermined rotational speed, the target value at the time of valve opening is considered to converge when the fuel pump is driven and the relief valve is in the valve open state. Set the fuel pressure lower than the converged fuel pressure,
6. The valve opening target value is set to a fuel pressure higher than the convergent fuel pressure in a rotational range where the rotational speed of the internal combustion engine is lower than the predetermined rotational speed. The opening determination apparatus of the relief valve as described.   The valve opening determination unit is configured to open the relief valve based on the followability of the actual fuel pressure after a lapse of a predetermined waiting time after it is determined that the actual fuel pressure has increased to the valve opening pressure. The valve opening determination device for a relief valve according to any one of claims 1 to 6, wherein the determination is made. A timing setting unit for setting an injection timing of the fuel injection valve to any one of an intake stroke for sucking fuel by the fuel pump and a discharge stroke for discharging fuel;
The timing setting unit sets an injection timing of the fuel injection valve to a discharge stroke of the fuel pump when the valve opening determination unit determines that the relief valve is in an open state. The valve open determination apparatus of the relief valve as described in any one of -7.

Images