JP2019060315A - Valve opening discrimination device for relief valve - Google Patents

Abstract

To provide a valve opening discrimination device for a relief valve capable of properly discriminating that the relief valve is being opened.SOLUTION: An ECU 90 is applied to a fuel injection system 10 comprising a relief valve 80 which is opened by increasing a fuel pressure to a predetermined valve opening pressure and closed by decreasing the fuel pressure to a predetermined valve closing pressure at a lower pressure side of the valve opening pressure in such a valve opening state. In a case where it is discriminated that a detected pressure is increased to the valve opening pressure of the relief valve 80, the ECU 90 calculates a fluctuation range indicating fuel pressure fluctuation inside of a delivery pipe 60. Based on a result of comparison between the calculated fluctuation range and a predetermined range discrimination value, it is discriminated that the relief valve is in the valve opening state.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an apparatus for determining that a relief valve of a fuel injection system is open.

  Patent Document 1 discloses a fuel injection system including a fuel pump for pressurizing and discharging fuel, a pressure accumulation container for storing high pressure fuel discharged from the fuel pump, and a fuel injection valve for injecting high pressure fuel in the pressure accumulation container. Is disclosed.

  In the fuel injection system, a relief valve is provided between the fuel pump and the pressure accumulation container, which opens when the fuel pressure is higher than a predetermined value. In an abnormal state in which the pressure in the pressure accumulation container becomes higher than a predetermined value, the pressure in the pressure accumulation container is reduced by opening the relief valve.

Patent No. 3610894 gazette

  The failure of the fuel pump may cause a full discharge abnormality in which the discharge amount of the fuel pump is the maximum discharge amount. The full discharge abnormality is caused, for example, by the failure of the metering valve that controls the discharge amount of the fuel pump. When the full discharge abnormality occurs, the fuel pressure in the pressure accumulation container becomes larger than a predetermined value, and the relief valve is opened.

  Here, it is conceivable to provide a pressure sensor for detecting the fuel pressure in the pressure accumulation container, and to determine the valve open state in which the relief valve is open based on the detection value of the pressure sensor. However, when the relief valve is opened, the fuel pressure in the pressure accumulation container is lower than when the relief valve is opened. Therefore, when the valve opening state of the relief valve is determined from the detection value of the pressure sensor, there is a possibility that the relief valve may be erroneously determined to be closed even if the relief valve is in the valve opening state.

  This invention is made in view of the said subject, The main objective is to provide the valve open determination apparatus of the relief valve which can determine appropriately that a relief valve is valve-opening. .

  In order to solve the above-mentioned problems, in the relief valve opening determination device according to the present invention, a fuel pump driven by rotation of a drive shaft of an internal combustion engine to discharge fuel from high pressure and discharged from the fuel pump A pressure accumulation container for storing high pressure fuel, a fuel injection valve for injecting high pressure fuel in the pressure accumulation container, a pressure sensor for detecting a detection pressure in the pressure accumulation container, the pressure accumulation container or the fuel pump to the pressure accumulation container The relief valve is provided in the high-pressure piping of the valve and is opened as the internal fuel pressure becomes abnormally high, and the relief valve is opened when the fuel pressure rises to a predetermined valve opening pressure, and the valve opening The present invention is applied to a fuel injection system which is closed when the fuel pressure is decreased to a predetermined valve closing pressure lower than the valve opening pressure in the state. The valve opening determination device determines whether the detected pressure detected by the pressure sensor has risen to the valve opening pressure, and when it is determined that the detected pressure has risen to the valve opening pressure, An open unit that determines that the relief valve is in an open state based on an acquisition unit that acquires a fluctuation range indicating the fluctuation of the detection pressure, and a comparison result of the acquired fluctuation range and a predetermined width determination value. And a valve determination unit.

  When the relief valve is opened due to a full discharge abnormality of the fuel pump, both a fuel pressure increase due to the fuel discharge by the fuel pump and a fuel pressure decrease due to the relief valve being open occur. Therefore, the fuel pressure fluctuation occurs in the pressure accumulation container, and this fuel pressure fluctuation is more than the fuel pressure fluctuation caused by the fuel pressure increase accompanying the fuel discharge in the state where the relief valve is closed and the fuel pressure decrease accompanying the fuel injection by the fuel injection valve. growing. In this respect, in the above configuration, when it is determined that the detected pressure has increased to the valve opening pressure, a fluctuation range indicating fluctuation of the detected pressure is acquired. Then, based on the comparison result of the acquired fluctuation range and the predetermined width determination value, it is determined that the relief valve is in the open state. In this case, the valve open state and the valve closed state of the relief valve can be clearly distinguished by the comparison result of the fluctuation range and the width determination value, and the valve open state of the relief valve can be properly determined.

The block diagram of a fuel supply system. The figure which demonstrates the fuel pressure change in the delivery pipe. The flowchart which demonstrates valve-opening determination processing. The figure explaining the relationship between each conditions and rise time judgment value. The figure explaining the relationship between each conditions and width judgment value. The timing chart explaining the effect | action of this embodiment.

First Embodiment
Hereinafter, a fuel injection system to which the valve open determination device for a relief valve according to the first embodiment is applied will be described with reference to the drawings. In FIG. 1, a 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 houses 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 the present embodiment, since the engine 100 is a direct injection type of direct injection type, the injectors 62 for injecting fuel are provided for each cylinder, and the cylinder head of the engine 100 is provided with an ignition for each cylinder. A plug is attached, and the mixture in the cylinder is ignited by spark discharge of the spark plug.

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

  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 an accumulator, and the injector 62 corresponds to a fuel injection valve.

  Inside the fuel tank 18 is provided a low pressure pump 20 that sucks in fuel and pressurizes it before discharging it. The outlet of the low pressure pump 20 is in communication with the low pressure side pipe 22. The pressure of the fuel discharged by the low pressure pump 20 is regulated by a regulator or the like. Further, a fuel temperature sensor 16 for detecting a fuel temperature is provided inside the fuel tank 18. Further, inside the fuel tank 18, an alcohol concentration sensor 17 for detecting an alcohol concentration which is a fuel property is provided. The fuel temperature sensor 16 and the alcohol concentration sensor 17 are connected to the ECU 90, and output detected values 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 pressure chamber 42 are formed in the cylinder body 32 of the high pressure pump 30. The low pressure chamber 40 is in communication with the low pressure side pipe 22 and stores the 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 adjusted by a control signal from the ECU 90.

  The pressure chamber 42 is provided with a plunger 34 for changing the pressure in the pressure chamber 42 by reciprocating operation. The end of the plunger 34 opposite to the pressure 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 for discharging the fuel pressurized in the pressurizing chamber 42. The discharge port of the discharge valve 38 is in communication with the high pressure side pipe 44 connected to the delivery pipe 60. The discharge valve 38 is a check valve that allows fuel to flow from the pressure chamber 42 to the high pressure side pipe 44. When the fuel pressure in the pressure chamber 42 becomes equal to or higher than a predetermined discharge pressure, the discharge valve 38 is opened.

  The fuel in the low pressure chamber 40 is drawn into the pressurizing chamber 42 by the metering valve 36 being opened and the plunger 34 decreasing from the top dead center to the bottom dead center. The metering valve 36 is in the open state, and the plunger 34 rises from the bottom dead center to 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. . Then, the metering valve 36 is closed, and the rising of the plunger 34 is continued, whereby the fuel in the pressurizing chamber 42 is pressurized. When the fuel pressure of the pressure chamber 42 becomes equal to or higher than the discharge pressure, the discharge of fuel by the discharge valve 38 is performed.

  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. The delivery pipe 60 is in communication with an injector 62 for injecting fuel.

  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 rises 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 opening 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. When the relief valve 80 is opened, the fuel in the high pressure side pipe 44 is returned 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 set to be lower than, for example, the pressure resistance (rail pressure resistance) before the delivery pipe 60 is deteriorated.

  The delivery pipe 60 is provided with a pressure sensor 82 for detecting the fuel pressure of the delivery pipe 60. The pressure sensor 82 is connected to the ECU 90, and outputs the 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 performs feedback control of the discharge amount of the high-pressure pump 30 based on the deviation between the target fuel pressure, which is the target value of the fuel pressure in the delivery pipe 60, and the detected pressure Pm (detected pressure) detected by the pressure sensor 82. Specifically, the discharge amount of the discharge valve 38 is controlled by controlling the open period of the metering valve 36 provided in the high pressure pump 30 according to the target fuel pressure.

  In the fuel injection system 10 configured as described above, the relief valve 80 is opened when the fuel pressure in the delivery pipe 60 rises to an abnormal high pressure (opening pressure) that causes the relief valve 80 to open. Fuel pressure decreases. FIG. 2A is a timing chart showing the transition of the fuel pressure change in the delivery pipe 60. As shown in FIG.

  As shown in FIG. 2A, before time t1, the high pressure pump 30 does not break down, and the discharge amount of the high pressure pump 30 is controlled so that the fuel pressure of the delivery pipe 60 becomes a value close to the target fuel pressure. . As shown in FIG. 2 (b), before time t 1, the fuel pressure in the delivery pipe 60 is reduced by the repetition of the fuel pressure increase accompanying the fuel discharge by the high pressure pump 30 and the fuel pressure decrease accompanying the fuel injection by the injector 62. The target fuel pressure is maintained.

  It is assumed that the high pressure pump 30 has a full discharge abnormality in which the high pressure pump 30 discharges at the maximum discharge amount due to the failure of the high pressure pump 30 immediately before time t1. The amount of one discharge from the high pressure pump 30 exceeds the amount of fuel injection of the injector 62 once, and the fuel pressure in the delivery pipe 60 is increased each 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 the open state. When the relief valve 80 is in the open state, the fuel in the high pressure side pipe 44 is returned to the low pressure chamber 40 through the return pipe 45, and the fuel pressure of the delivery pipe 60 is lowered at time t3.

  The relief valve 80 maintains an open state until the fuel pressure becomes a valve closing pressure lower than the valve opening pressure P 1. Therefore, after the relief valve 80 is opened, the fuel pressure in the delivery pipe 60 continues to decrease. Therefore, the fuel pressure in the delivery pipe 60 has a value lower than the valve opening pressure P1 of the relief valve 80. On the other hand, even in the closed state of the relief valve 80, the fuel pressure decrease occurs due to the limitation of the fuel discharge amount by the feedback control. Therefore, it is difficult to distinguish whether the relief valve 80 is in the open state or in the closed state from the detected pressure Pm.

  After the delivery pipe 60 has an abnormally high pressure, the relief valve 80 is opened, which causes both a rise in fuel pressure associated with fuel discharge by the high pressure pump 30 and a decrease in fuel pressure associated with the open valve state of the relief valve 80. Fuel pressure fluctuation occurs in the delivery pipe 60 (FIG. 2 (c)). The fuel pressure fluctuation in the valve open state of the relief valve 80 is larger than the fuel pressure fluctuation in the valve closed state. Therefore, in the open state of the relief valve 80, the fluctuation width W2 (FIG. 2 (c)) showing the fuel pressure fluctuation in the delivery pipe 60 shows the fluctuation width W1 (FIG. 2 (b)) showing the fuel pressure fluctuation in the valve closed state. It becomes bigger than).

  In the present embodiment, the fuel pressure fluctuation in the delivery pipe 60 is acquired as a fluctuation width, and the valve opening state and the valve closing state of the relief valve 80 are determined based on the acquired fluctuation width. Specifically, the ECU 90 determines that the fuel pressure in the delivery pipe 60 has risen to the valve opening pressure of the relief valve 80, and based on the comparison result of the fluctuation width after judgment and a predetermined width judgment value, relief. Determine that the valve is open.

  Next, the process of determining whether the relief valve 80 is open, 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 in a predetermined cycle.

  In step S11, it is determined whether the detected pressure Pm has risen to a high pressure abnormal state in which the relief valve 80 is opened. In the present embodiment, the detected pressure Pm is compared with the valve opening pressure P1 of the relief valve 80. Step S11 corresponds to a fuel pressure determination unit.

  If the detected pressure Pm is larger than the valve opening pressure P1, the process proceeds to step S12. In step S12, an abnormality determination value TH1 for determining the time during which the detected pressure Pm is maintained at a value larger than the valve opening pressure P1 is set. In the present embodiment, the abnormality determination value TH1 is set based on various conditions that affect the fuel pressure change. Specifically, the engine rotational speed Ne detected by the rotational angle sensor 13, the fuel injection amount Q indicating the fuel injection amount per injection of the injector 62, and the fuel temperature sensor as various conditions affecting the fuel pressure change The fuel temperature Temp measured by 16 and the fuel property which shows alcohol concentration ALC contained in a fuel are used.

  FIG. 4 is a diagram for explaining the relationship between the various conditions and the abnormality determination value TH1. FIG. 4A is a graph in which the horizontal axis is the engine rotational speed Ne and the vertical axis is the abnormality determination value TH1. FIG. 4B is a graph in which the horizontal axis is the fuel injection amount Q and the vertical axis is the abnormality determination value TH1. FIG. 4C is a graph in which the horizontal axis is the fuel temperature Temp and the vertical axis is the abnormality determination value TH1. FIG. 4D is a graph in which the abscissa represents the alcohol concentration ALC, and the ordinate represents the abnormality determination value TH1.

  As the engine rotation speed Ne is smaller, the frequency of fuel injection of the injector 62 is lower, so the delivery pipe 60 is more likely to be maintained in the high pressure abnormal state. Therefore, as shown in FIG. 4A, the abnormality determination value TH1 is set to a larger value as the engine rotation speed Ne is lower.

  As the fuel injection amount Q is smaller, the amount of decrease in fuel pressure in one fuel injection becomes smaller, and the delivery pipe 60 is more likely to be maintained in the high pressure abnormal state. Therefore, as shown in FIG. 4B, as the fuel injection amount Q is smaller, the abnormality determination value TH1 is set to a larger value.

  The higher the fuel temperature Temp, the lower the bulk modulus of the fuel, and the easier it is for the delivery pipe 60 to be maintained in a high pressure abnormal state. Therefore, as shown in FIG. 4C, as the fuel temperature Temp is higher, the abnormality determination value TH1 is set to a larger value.

  The lower the concentration of alcohol contained in the fuel, the lower the bulk modulus of the fuel, and the easier it is for the delivery pipe 60 to be maintained in a high pressure abnormal state. Therefore, as shown in FIG. 4D, the abnormality determination value TH1 is set to a larger value as the alcohol concentration is lower.

  The influence on the fuel pressure change is that the engine rotation speed Ne and the fuel injection amount Q become higher than the fuel temperature Temp and the alcohol concentration ALC. Therefore, in the present embodiment, the weighting of the abnormality determination value TH1 in the engine rotation speed Ne and the fuel injection amount Q is increased, and the weighting of the abnormality determination value TH1 in the fuel temperature Temp and the alcohol concentration ALC is reduced.

  In step S13, the abnormality determination counter Co1 is increased. The abnormality determination counter Co1 is a value that measures the time during which the detected pressure Pm continues to have a value larger than the valve opening pressure P1. In step S11, if the detected pressure Pm is less than the valve opening pressure P1, the process proceeds to step S14, and the abnormality determination counter Co1 is reset to zero.

  In step S15, it is determined whether the waiting time counter Co2 is 0 or more. The waiting time counter Co2 has an initial value of zero. If the waiting time counter Co2 is an initial value, a negative determination is made in step S15, and the process proceeds to step S16.

  In step S16, the abnormality determination counter Co1 is compared with the abnormality determination value TH1 set in step S12. If it is determined that the abnormality determination counter Co1 is equal to or less than the abnormality determination value TH1, the process of FIG. 3 is temporarily ended. Then, in the next processing, if the detected pressure Pm is a value larger than the valve opening pressure P1, the abnormality determination counter Co1 is increased in step S13.

  On the other hand, if it is determined in step S16 that the abnormality determination counter Co1 has a value larger than the abnormality determination value TH1, since the delivery pipe 60 is in the high pressure abnormality state, the process proceeds to step S17.

  In step S17, the waiting time counter Co2 is increased. In a period in which the fuel pressure in the delivery pipe 60 decreases, the fuel pressure fluctuation may increase even when the relief valve 80 is closed. Therefore, the ECU 90 detects the detection pressure Pm after the elapse of a predetermined waiting time as the convergence fuel pressure in the delivery pipe 60 after determining that the detection pressure Pm has increased to the valve opening pressure P1. Specifically, the waiting time counter Co2 counts the time until the fuel pressure in the delivery pipe 60 converges.

  In step S18, it is determined whether the waiting time counter Co2 is larger than the convergence determination value TH2. The convergence determination value TH2 indicates the time required for the fuel pressure in the delivery pipe 60 to decrease from the valve opening pressure P1 to the convergence fuel pressure. For example, the convergence determination value TH2 may be changed in accordance with the fuel temperature or the fuel pressure property. If the waiting time counter Co2 is equal to or less than the convergence determination value TH2, the process of FIG. 3 is once ended. In this case, the waiting time counter Co2 is increased in the process of the next step S17.

  If it is determined in step S18 that the waiting time counter Co2 is larger than the convergence determination value TH2, then the process proceeds to step S19, assuming that the fuel pressure in the delivery pipe 60 has converged.

  In step S19, the fluctuation width W of the fuel pressure in the delivery pipe 60 is calculated based on the detected pressure Pm. In the present embodiment, the maximum value and the minimum value within the fluctuation period of the detected pressure Pm according to the engine rotational speed Ne are acquired, and the value obtained by subtracting the minimum value from the acquired maximum value is calculated as the fluctuation width W. Do. For example, a value obtained by subtracting the minimum value from the maximum value of the detection pressure Pm within the fluctuation period may be calculated a plurality of times, and the average value of the calculated values may be calculated as the fluctuation width W. Step S19 corresponds to an acquisition unit.

  In step S20, a width determination value TH3 for determining the fluctuation range W is set. In the present embodiment, the width determination value TH3 is set based on the estimated fluctuation range of the fuel pressure when it is assumed that the relief valve 80 is closed. When the relief valve 80 is in the closed state, the change state of the fuel pressure in the delivery pipe 60 differs depending on various conditions. Therefore, the width determination value TH3 is set in consideration of various conditions that affect the change mode of the fuel pressure. Specifically, the engine speed Ne, the fuel injection amount Q, the fuel temperature Temp, and the fuel property (alcohol concentration ALC) are set as the various conditions, and the width determination value TH3 is set.

  FIG. 5 is a diagram for explaining the relationship between various conditions and the width determination value TH3. FIG. 5A is a graph in which the horizontal axis is the engine rotational speed Ne and the vertical axis is the width determination value TH3. FIG. 5B is a graph in which the fuel injection amount Q is used and the vertical axis is used as the width determination value TH3. FIG. 5C is a graph in which the horizontal axis is the fuel temperature Temp and the vertical axis is the width determination value TH3. FIG. 5D is a graph in which the abscissa represents the alcohol concentration ALC and the ordinate represents the width determination value TH3.

  When pulsation occurs in the delivery pipe 60, the fluctuation range (variation width) is maximum at a predetermined rotation speed N1. Therefore, as shown in FIG. 5A, the width determination value TH3 is set according to the engine rotation speed Ne so that the fluctuation range at the rotation speed N1 is maximized.

  As the fuel injection amount Q of the injector 62 is larger, the amount of decrease in fuel pressure in the delivery pipe 60 accompanying fuel consumption of the injector 62 is larger, and the convergent fuel pressure is lower. As the convergent fuel pressure in the delivery pipe 60 is lower, the fuel injection rate indicating the fuel injection amount per unit time is smaller, and the fluctuation range of the fuel is smaller. Therefore, as shown in FIG. 5 (b), the width determination value TH3 is set to a smaller value as the fuel injection amount Q is larger.

  The higher the fuel temperature Temp of the delivery pipe 60, the lower the bulk elastic coefficient of the fuel, and the lower the value of the discharge fuel pressure of the fuel discharged by the high-pressure pump 30. The lower the discharge fuel pressure, the smaller the fluctuation produced in the fuel. Therefore, as shown in FIG. 5C, the width determination value TH3 is set to a smaller value as the fuel temperature Temp is higher.

  The lower the alcohol concentration ALC contained in the fuel, the lower the bulk modulus of elasticity of the fuel, and the lower the value of the discharge fuel pressure of the fuel discharged by the high-pressure pump 30. Therefore, as shown in FIG. 5 (d), the width determination value TH3 is set to a smaller value as the alcohol concentration ALC is lower.

  The influence on the fuel pressure change is that the engine rotation speed Ne and the fuel injection amount Q become higher than the fuel temperature Temp and the alcohol concentration ALC. Therefore, in the present embodiment, when setting the width determination value TH3, the weighting for the engine speed Ne and the fuel injection amount Q for the width determination value TH3 is higher than the weighting for the fuel temperature Temp and the alcohol concentration ALC for the width determination value TH3. doing.

  Returning to FIG. 3, in steps S21 to S25, the relief valve 80 is determined to be open using the comparison result of the fluctuation range W calculated in step S19 and the width determination value TH3. Steps S21 to S25 correspond to the valve opening determination unit.

  First, in step S21, it is determined whether the fluctuation range W calculated in step S19 is larger than the width determination value TH3 set in step S20. If the fluctuation range W is larger than the width determination value TH3, the process proceeds to step S22, and the valve opening determination counter Co3 is increased. The valve opening determination counter Co3 is a value for measuring a time during which the fluctuation range W is larger than the width determination value TH3. On the other hand, if the fluctuation range W is equal to or less than the width determination value TH3, the process proceeds to step S21, and the valve opening determination counter Co3 is reset to zero.

  In step S24, it is determined whether the valve opening determination counter Co3 is larger than the time determination value TH4. If the valve opening determination counter Co3 is larger than the time determination value TH4, the process proceeds to step S25, and it is determined that the relief valve 80 is in the open state. On the other hand, if the valve opening determination counter Co3 is equal to or less than the time determination value TH4, the process of FIG. 3 is temporarily ended without determining the valve opening state of the relief valve 80.

  Next, the operation according to the present embodiment will be described using FIG.

  FIG. 6 is a time chart showing the valve opening determination process. FIG. 6 shows the change of the fuel pressure in the idling state in which the engine rotational speed Ne is kept constant.

  It is assumed that the high pressure pump 30 has a failure 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. Further, with the full discharge abnormality of the high pressure pump 30, the fluctuation range in the delivery pipe 60 also becomes large.

  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 TH1, whereby the high pressure abnormality state of the delivery pipe 60 is determined. Therefore, the measurement of the waiting time counter Co2 is started.

  The fuel pressure in the delivery pipe 60 decreases with the opening state of the relief valve 80, and then the fuel pressure converges to the convergent fuel pressure. In FIG. 6, at time t24, the waiting time counter Co2 becomes larger than the convergence determination value TH2, and measurement of a fluctuation range indicating fuel pressure fluctuation in the delivery pipe 60 is started.

  Even after time t24, the fluctuation range continues to be larger than the width determination value TH3, and the valve opening determination counter Co3 is increased. Then, the valve open determination counter Co3 becomes larger than the time determination value TH4, whereby the valve open state of the relief valve 80 is determined.

  The following effects are achieved in the embodiment described above.

  When the ECU 90 determines that the detected pressure has risen to the valve opening pressure P1 of the relief valve 80, the relief valve is based on the comparison result of the fluctuation width W indicating the fluctuation of the detected pressure Pm and the width judgment value TH3. It was determined that 80 was in the open state. In this case, the valve open state and the valve closed state of the relief valve 80 can be clearly distinguished by the comparison result of the fluctuation range W and the width determination value TH3, and the valve open state of the relief valve 80 is properly determined. be able to.

  The ECU 90 sets the width determination value TH3 based on the engine rotation speed Ne. In this case, the width determination value TH3 can be set according to the fluctuation tendency of the fuel pressure accompanying the engine rotation speed Ne, and the accuracy of the opening determination of the relief valve 80 can be enhanced.

  The ECU 90 sets the width determination value TH3 based on the fuel injection amount Q by the injector 62. In this case, the width determination value TH3 can be set according to the fluctuation tendency of the fuel pressure caused by the fuel injection amount Q by the injector 62, and the accuracy of the opening determination of the relief valve 80 can be enhanced.

  The ECU 90 sets the width determination value TH3 based on the fuel temperature Temp of the delivery pipe 60. In this case, the width determination value TH3 can be set according to the fluctuation tendency of the fuel pressure accompanying the fuel temperature Temp, and the accuracy of the opening determination of the relief valve 80 can be enhanced.

  The ECU 90 sets the width determination value TH3 based on the alcohol concentration ALC of the fuel. In this case, the width determination value TH3 can be set according to the fluctuation tendency of the fuel pressure accompanying the alcohol concentration ALC of the fuel, and the accuracy of the opening determination of the relief valve 80 can be enhanced.

  The ECU 90 acquires the fluctuation width W after the detection pressure Pm converges when it is determined that the detection pressure Pm of the delivery pipe 60 has increased to the valve opening pressure P1. Then, based on the acquired fluctuation range W, it is determined that the relief valve 80 is in the open state. In this case, the relief valve 80 can be determined to be open during a period in which the difference in fuel pressure fluctuation is large between the valve opening state and the valve closing state of the relief valve 80. As a result, it is possible to enhance the accuracy of the valve open determination of the relief valve 80.

(Other embodiments)
In step S21 of FIG. 3, when the ECU 90 determines that the fluctuation range W is larger than the width determination value TH3, the ECU 90 may proceed to step S25 to perform the valve open determination.

  In step S20, at least one of the engine rotation speed Ne and the fuel injection amount Q may be used as the conditions for setting the width determination value TH3.

  The relief valve 80 may be provided in the delivery pipe 60.

  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, 100 ... Engine.

Claims (6)

A fuel pump (30) driven by rotation of a drive shaft (12) of an internal combustion engine (100) to discharge the fuel under high pressure; an accumulator container (60) for storing high pressure fuel discharged from the fuel pump; In a fuel injection valve (62) for injecting high pressure fuel in a pressure accumulation container, a pressure sensor (82) for detecting the fuel pressure in the pressure accumulation container, the pressure accumulation container, or high pressure piping from the fuel pump to the pressure accumulation container Equipped with a relief valve (80) that opens when the internal fuel pressure becomes abnormally high.
The relief valve is opened when the fuel pressure is increased to a predetermined valve opening pressure, and is closed when the fuel pressure is decreased to a predetermined valve closing pressure lower than the valve opening pressure in the valve opening state. Applied to fuel injection systems that are
A fuel pressure determination unit that determines that the detected pressure detected by the pressure sensor has increased to the valve opening pressure;
An acquisition unit that acquires a fluctuation range indicating a fluctuation of the detection pressure when it is determined that the detection pressure has increased to the valve opening pressure;
A valve opening determination unit that determines that the relief valve is in the open state based on the comparison result of the acquired fluctuation range and a predetermined width determination value;
Relief valve opening determination device comprising:   The relief valve opening determination device according to claim 1, wherein the width determination value is set based on a rotational speed of the internal combustion engine.   The relief valve opening determination device according to claim 1, wherein the width determination value is set based on a fuel injection amount of the fuel injection valve.   The relief valve opening determination device according to any one of claims 1 to 3, wherein the width determination value is set based on a fuel temperature of the pressure accumulation container.   The relief valve opening determination device according to any one of claims 1 to 4, wherein the width determination value is set based on an alcohol concentration contained in the fuel. The acquisition unit acquires the fluctuation range after the detection pressure converges when it is determined that the detection pressure has increased to the valve opening pressure.
The relief valve according to any one of claims 1 to 5, wherein the valve open determination unit determines that the relief valve is in an open state based on the fluctuation range after the detection pressure converges. Valve opening judgment device.