JP5370685B2 - Failure diagnosis device for fuel supply system of direct injection internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To diagnose a failure of a relief valve during the operation of a high pressure pump. <P>SOLUTION: When a failure diagnosis execution condition of the prescribed relief valve 33 is satisfied at the start of an engine or during the drive of the engine, target fuel pressure Pftg in a high pressure fuel system is set higher than relief pressure Pfrl, and fuel-pressure forcible rise control for controlling the high pressure pump 14 is performed so as to make fuel pressure Pf in the high pressure fuel system reach the target fuel pressure Pftg. After the lapse of a prescribed standby period KT1 after the fuel pressure Pf in the high pressure fuel system reaches the relief pressure Pfrl by the fuel-pressure forcible rise control, the fuel pressure Pf in the high pressure fuel system is acquired as determination fuel pressure Pf2, and when the determination fuel1 prescribed Pf2 is determined to be lower than failure determination fuel pressure KPf, it is determined that the relief valve 33 has no failure (normal). However, when the determination fuel pressure Pf2 is not lower than the failure determination fuel pressure KPf, it is determined that there is a failure of the relief valve 33 (for example, closed valve adhesion failure that the relief valve 33 is firmly adhered in a closed-valve state). <P>COPYRIGHT: (C)2012,JPO&amp;INPIT

Description

  The present invention relates to a failure diagnosis device for a fuel supply system of a direct injection internal combustion engine that supplies high-pressure fuel discharged from a high-pressure pump to a fuel injection valve.

  An in-cylinder injection engine that directly injects fuel into a cylinder has a shorter time from injection to combustion and sufficient time to atomize the injected fuel compared to an intake port injection engine that injects fuel into an intake port. Therefore, it is necessary to atomize the injected fuel by increasing the injection pressure. Therefore, in a cylinder injection engine, the fuel pumped up from the fuel tank by the electric low-pressure pump is supplied to a high-pressure pump (for example, driven by the camshaft of the engine), and the high-pressure fuel discharged from this high-pressure pump Is pumped to the fuel injection valve.

  In such a fuel injection system for an in-cylinder injection engine, for example, as described in Patent Document 1 (Japanese Patent Laid-Open No. 2002-256943), high-pressure fuel is supplied from a high-pressure pump to a fuel injection valve. In order to prevent the fuel pressure (fuel pressure) in the high-pressure fuel system from becoming excessively high, a relief valve is provided at a predetermined location (for example, a delivery pipe) of the high-pressure fuel system so that the fuel pressure in the high-pressure fuel system is at a predetermined relief pressure. In some cases, when the pressure becomes higher, the relief valve opens to return the fuel in the high-pressure fuel system to the low-pressure fuel system, thereby reducing the fuel pressure in the high-pressure fuel system.

  Furthermore, in the technique of Patent Document 1, the difference (fuel pressure reduction allowance) between the fuel pressure immediately after the engine is stopped and the fuel pressure after a predetermined time has elapsed since the engine stop is calculated, and the fuel pressure reduction allowance is calculated as a predetermined failure judgment value (reference value). If it is greater than the allowance for lowering fuel pressure, it is determined that there is a relief valve failure (a failure that causes a foreign object to become incompletely closed).

JP 2002-256943 A

  However, since the technique of Patent Document 1 performs failure diagnosis of the relief valve based on the fuel pressure after the engine is stopped (that is, after the high pressure pump is stopped), the failure diagnosis of the relief valve is performed during the operation of the high pressure pump. Can not do. For this reason, even if a relief valve failure occurs during operation of the high-pressure pump, there is a drawback that the failure cannot be detected during operation of the high-pressure pump (that is, during engine operation). Further, this method has a drawback that even if a failure of the incomplete closing of the relief valve can be detected, a state where the relief valve is stuck on the closed side cannot be detected.

  Accordingly, an object of the present invention is to provide a failure diagnosis device for a fuel supply system of a direct injection internal combustion engine capable of performing failure diagnosis of a relief valve during operation of a high pressure pump.

In order to solve the above problems, the invention according to claim 1 is applied to a fuel supply system of a direct injection internal combustion engine that supplies high-pressure fuel discharged from a high-pressure pump to a fuel injection valve. Provided with a relief valve that opens to lower the fuel pressure in the high-pressure fuel system when the fuel pressure (hereinafter referred to as “fuel pressure”) in the high-pressure fuel system that supplies fuel to the injection valve becomes higher than a predetermined relief pressure In the in-cylinder internal combustion engine fuel supply system failure diagnosis device, the target fuel pressure in the high-pressure fuel system is set to a pressure higher than the relief pressure, and the fuel pressure in the high-pressure fuel system is set to the target fuel pressure. run the fuel pressure force increase control for controlling the pump, after the fuel pressure in the high pressure fuel system has passed the predetermined standby time from reaching the relief pressure by the fuel pressure force increase control, the fuel pressure to a predetermined high-pressure fuel system Compared to impaired judgment fuel pressure includes determining failure diagnosis means the presence or absence of a failure of the relief valve, the failure diagnosing means is higher by a first predetermined value than the relief pressure to the target fuel pressure during the fuel pressure force increase control And setting the failure determination fuel pressure to a pressure higher by a second predetermined value than the relief pressure, and setting the first predetermined value to a value larger than the second predetermined value. It is a feature.

  When the fuel pressure forced increase control is performed to control the high pressure pump so that the fuel pressure in the high pressure fuel system becomes a target fuel pressure higher than the relief pressure, the fuel pressure in the high pressure fuel system moves toward the target fuel pressure (pressure higher than the relief pressure). However, the behavior after the fuel pressure in the high-pressure fuel system reaches the relief pressure differs depending on whether the relief valve is normal or failure. Therefore, by monitoring the fuel pressure in the high-pressure fuel system after the fuel pressure in the high-pressure fuel system reaches the relief pressure by the fuel pressure forced increase control, it is possible to determine whether or not the relief valve has failed. In this way, since the failure diagnosis of the relief valve can be performed during the operation of the high-pressure pump, even if a failure of the relief valve occurs during the operation of the high-pressure pump, the failure is determined as the operation of the high-pressure pump. Can be detected in.

The present invention relates to a relief valve that compares a fuel pressure in a high-pressure fuel system with a predetermined failure determination fuel pressure after a predetermined waiting period has elapsed after the fuel pressure in the high-pressure fuel system has reached a relief pressure by fuel pressure forced increase control. The first feature is to determine whether or not there is a failure .

  When the fuel pressure forced increase control is executed, the fuel pressure in the high-pressure fuel system increases toward the target fuel pressure (pressure higher than the relief pressure). At that time, if the relief valve functions normally, after the fuel pressure in the high-pressure fuel system reaches the relief pressure, the fuel pressure in the high-pressure fuel system is maintained near the relief pressure, but if the relief valve opens normally. If a failure that does not occur (for example, a closed failure that closes when the relief valve is closed) occurs, after the fuel pressure in the high-pressure fuel system reaches the relief pressure, it is near the target fuel pressure that is higher than the relief pressure. The fuel pressure in the high-pressure fuel system rises to Therefore, after the fuel pressure in the high-pressure fuel system reaches the relief pressure by the fuel pressure forced increase control, a predetermined waiting period (for example, when the fuel pressure in the high-pressure fuel system rises to the vicinity of the target fuel pressure when the relief valve closes and closes) If the fuel pressure in the high-pressure fuel system is compared with a predetermined failure determination fuel pressure after the necessary period has elapsed, it is possible to accurately determine whether there is a failure in the relief valve.

Furthermore, the present invention sets the target fuel pressure at the time of forced fuel pressure increase control to a pressure that is higher than the relief pressure by a first predetermined value (= relief pressure + first predetermined value), and sets the failure determination fuel pressure from the relief pressure. also set to a higher pressure by a second predetermined value (= relief pressure + second predetermined value), the second setting means sets the first predetermined value to a value larger than the second predetermined value . In this way, the failure determination fuel pressure can be set between the target fuel pressure and the relief pressure during the fuel pressure forced increase control.

Further, as in claim 2 , the first predetermined value and the second predetermined value may be set based on at least one of a valve opening characteristic of the relief valve and a design specification of the high pressure fuel system, respectively. good. In this way, the target fuel pressure (= relief pressure + first predetermined value) and the failure determination fuel pressure (= relief pressure + second predetermined value) at the time of forced increase control of the fuel pressure are respectively calculated as the valve opening characteristics of the relief valve, It can be set to an appropriate value in consideration of the design specifications (for example, pressure resistance performance) of the high pressure fuel system.

Further, as in claim 3 , the standby period may be set according to the rotational speed of the internal combustion engine. In this way, the discharge performance of the high-pressure pump changes according to the rotational speed of the internal combustion engine, which is necessary, for example, until the fuel pressure in the high-pressure fuel system rises to the vicinity of the target fuel pressure when the relief valve is closed and stuck. Corresponding to the change of the period, the standby period can be changed, and the standby period can be set to an appropriate value. Thereby, it is possible to avoid the standby period from becoming unnecessarily long and complete the failure diagnosis of the relief valve at an early stage.

Further, as described in claim 4 , if the fuel pressure in the high-pressure fuel system does not reach the relief pressure even after a predetermined permissible period has elapsed since the start of the fuel pressure forced increase control, the fuel pressure forced increase control is terminated. You may make it do. In other words, the high-pressure fuel is used even though a predetermined permissible period (for example, a period slightly longer than the period required for the fuel pressure in the high-pressure fuel system to rise to the relief pressure) has elapsed since the fuel pressure forced increase control was started. If the fuel pressure in the system does not reach the relief pressure, it is determined that there is a possibility that some abnormality has occurred in the high-pressure pump, the control system of the high-pressure pump, etc., and the fuel pressure forced increase control is terminated. In this way, it is possible to prevent the fuel pressure forced increase control from being continued unnecessarily for a long time.

In this case, as in claim 5 , the allowable period may be set according to the fuel pressure in the high-pressure fuel system at the start of the forced fuel pressure increase control and the rotational speed of the internal combustion engine. In this way, the fuel pressure in the high-pressure fuel system rises to the relief pressure according to the fuel pressure in the high-pressure fuel system at the start of the fuel pressure forced increase control and the rotational speed of the internal combustion engine (discharge performance of the high-pressure pump). The permissible period can be changed corresponding to the change in the period required for the time period, and the permissible period can be set to an appropriate value.

Further, as in claim 6 , the allowable period may be corrected according to the coolant temperature of the internal combustion engine at the start of the forced fuel pressure increase control. In this way, the discharge performance of the high-pressure pump changes according to the cooling water temperature of the internal combustion engine at the start of the fuel pressure forced increase control, and the period required for the fuel pressure in the high-pressure fuel system to rise to the relief pressure changes. Corresponding to this, the allowable period can be appropriately corrected.

  According to the present invention, the relief valve failure diagnosis may be executed every time the internal combustion engine is operated. However, if the frequency of the relief valve failure diagnosis becomes too high, the relief valve opening associated with the forced fuel pressure increase control is performed. / The frequency of repeated valve closing operations may become too high, which may reduce the durable life of the relief valve.

Therefore, as in claim 7 , when the number of operations of the internal combustion engine since the previous execution of the failure diagnosis of the relief valve reaches a predetermined number, the failure diagnosis of the next relief valve may be permitted. . In this way, it is possible to moderately suppress the frequency of execution of the failure diagnosis of the relief valve, and moderately suppress the frequency of execution of the repeated opening / closing operation of the relief valve associated with the forced increase control of the fuel pressure. It is possible to prevent a decrease in the durable life.

Further, as described in claim 8 , when the vehicle is switched to a predetermined check mode for vehicle inspection, the relief valve failure diagnosis may be permitted. That is, during normal operation of the internal combustion engine, the relief valve failure diagnosis is prohibited, and when the dealer switches to the check mode for vehicle inspection, the relief valve failure diagnosis is permitted. Even in this case, it is possible to suppress the frequency of execution of the relief valve failure diagnosis, and to suppress the frequency of repeated relief valve opening / closing operations associated with the forced fuel pressure increase control. A decrease can be prevented.

Further, as described in claim 9 , when the failure diagnosis of the relief valve is executed when the internal combustion engine is started, the fuel injection of the fuel injection valve may be stopped until the failure diagnosis of the relief valve is completed. In this way, when the failure diagnosis of the relief valve is executed at the start of the internal combustion engine, the fuel pressure is forcibly increased in a state where the fuel injection of the fuel injection valve is stopped (that is, the fuel in the high-pressure fuel system is not consumed). Since the control can be executed, the fuel pressure in the high-pressure fuel system can be quickly increased by the fuel pressure forced increase control, and the failure diagnosis of the relief valve can be completed early.
According to a tenth aspect of the present invention, a fuel return passage may be provided that returns the fuel in the high-pressure fuel system to the high-pressure pump.

FIG. 1 is a diagram showing a schematic configuration of a fuel supply system for a direct injection engine according to Embodiment 1 of the present invention. FIG. 2 is a time chart for explaining an execution example when the failure diagnosis of the relief valve of the first embodiment is executed at the time of normal engine start. FIG. 3 is a time chart illustrating an execution example when the failure diagnosis of the relief valve of the first embodiment is executed at the time of engine restart after complete warm-up. FIG. 4 is a time chart for explaining an execution example when the failure diagnosis of the relief valve of the first embodiment is executed during engine operation. FIG. 5 is a flowchart for explaining the processing flow of the relief valve failure diagnosis routine of the first embodiment. FIG. 6 is a diagram conceptually showing an example of the map of the allowable period KT2. FIG. 7 is a diagram conceptually illustrating an example of a table of the correction coefficient α. FIG. 8 is a diagram conceptually showing an example of the table of the standby period KT1. FIG. 9 is a time chart for explaining an execution example when the failure diagnosis of the relief valve of the second embodiment is executed during engine operation. FIG. 10 is a flowchart for explaining the flow of processing of the relief valve failure diagnosis routine of the second embodiment. FIG. 11 is a diagram conceptually showing an example of the table of the determination period KT3. FIG. 12 is a diagram conceptually illustrating an example of the failure determination value ΔKPf table. FIG. 13 is a diagram showing a schematic configuration of a fuel supply system for a direct injection engine according to another embodiment.

  Hereinafter, some embodiments embodying the mode for carrying out the present invention will be described.

A first embodiment of the present invention will be described with reference to FIGS.
First, a schematic configuration of the entire fuel supply system of an in-cylinder injection engine (internal combustion engine) will be described with reference to FIG.

  A low pressure pump 12 that pumps up the fuel is installed in the fuel tank 11 that stores the fuel. The low-pressure pump 12 is driven by an electric motor (not shown) that uses a battery (not shown) as a power source. The fuel discharged from the low pressure pump 12 is supplied to the high pressure pump 14 through the fuel pipe 13. A pressure regulator 15 is connected to the fuel pipe 13, and the pressure regulator 15 regulates the discharge pressure of the low-pressure pump 12 (fuel supply pressure to the high-pressure pump 14) to a predetermined pressure. Is returned to the fuel tank 11 by the fuel return pipe 16.

  The high-pressure pump 14 is a piston pump that reciprocates a piston 19 in a cylindrical pump chamber 18 and sucks / discharges fuel. The piston 19 rotates by a cam 21 fitted to a camshaft 20 of the engine. Driven by. For example, a double mountain cam having two cam peaks may be used as the cam 21, but the cam 21 is not limited to this, and a three mountain cam having three cam peaks and a four mountain cam having four cam peaks are used. May be used. Further, the driving method of the high-pressure pump 14 is not limited to the method driven by the cam shaft 20.

  A fuel pressure control valve 23 is provided on the suction port 22 side of the high-pressure pump 14. The fuel pressure control valve 23 is a normally open type electromagnetic valve, and includes a valve body 24 that opens and closes the suction port 22, a spring 25 that urges the valve body 24 in the valve opening direction, and a valve body 24 in the valve closing direction. And a solenoid 26 that is electromagnetically driven.

  During the suction stroke of the high-pressure pump 14 (when the piston 19 is lowered), the fuel pressure control valve 23 is opened and fuel is sucked into the pump chamber 18, and during the discharge stroke of the high-pressure pump 14 (when the piston 19 is raised). By controlling the valve closing period of the fuel pressure control valve 23 (the crank angle section in the valve closing state from the valve closing start time to the top dead center of the piston 19), the discharge amount of the high pressure pump 14 is controlled to control the fuel pressure (discharge). Pressure).

  That is, when increasing the fuel pressure, the valve closing start timing (energization timing) of the fuel pressure control valve 23 is advanced, thereby extending the valve closing period of the fuel pressure control valve 23 and increasing the discharge amount of the high pressure pump 14. Conversely, when lowering the fuel pressure, the valve closing start timing (energization timing) of the fuel pressure control valve 23 is retarded, thereby shortening the valve closing period of the fuel pressure control valve 23 and reducing the discharge amount of the high-pressure pump 14. .

  On the other hand, a check valve 28 for preventing the backflow of discharged fuel is provided on the discharge port 27 side of the high-pressure pump 14. The fuel discharged from the high-pressure pump 14 is sent to the delivery pipe 30 through the high-pressure fuel pipe 29, and the high-pressure fuel is distributed from the delivery pipe 30 to the fuel injection valve 31 attached to each cylinder of the engine. The delivery pipe 30 (or the high-pressure fuel pipe 29) is provided with a fuel pressure sensor 32 (fuel pressure detection means) that detects the fuel pressure (fuel pressure) in the high-pressure fuel system such as the high-pressure fuel pipe 29 and the delivery pipe 30.

  In order to prevent the fuel pressure in the high-pressure fuel system from becoming excessively high, the delivery pipe 30 is provided with a relief valve 33, and the discharge port of the relief valve 33 is connected to the fuel tank 11 via the relief pipe 34. (Or the fuel pipe 13 on the low pressure side). Further, a branch pipe 35 branched from the relief pipe 34 is connected to the pump chamber 18 of the high-pressure pump 14. When the fuel pressure in the high-pressure fuel system becomes higher than a predetermined relief pressure Pfrl, the relief valve 33 opens and the fuel in the high-pressure fuel system passes through the relief pipe 34 and the fuel tank 11 (or the low-pressure side fuel pipe 13). ) Or the pump chamber 18, the fuel pressure Pf in the high-pressure fuel system decreases, and the relief valve 33 closes when the fuel pressure Pf in the high-pressure fuel system falls below the relief pressure Pfrl. Yes.

  Further, the engine is provided with an air flow meter 36 for detecting the amount of intake air and a crank angle sensor 37 for outputting a pulse signal at every predetermined crank angle in synchronization with rotation of a crankshaft (not shown). Based on the output signal of the crank angle sensor 37, the crank angle and the engine speed are detected.

  Outputs of these various sensors are input to an electronic control circuit (hereinafter referred to as “ECU”) 38. The ECU 38 is mainly composed of a microcomputer, and executes various engine control programs stored in a built-in ROM (storage medium), so that the fuel injection amount and the ignition timing are determined according to the engine operating state. The throttle opening (intake air amount) and the like are controlled.

  At that time, the ECU 38 calculates the target fuel pressure Pftg based on the engine operating state (for example, engine speed, engine load, etc.) using a map or the like, and uses the fuel pressure Pf in the high-pressure fuel system detected by the fuel pressure sensor 32 as the target fuel pressure Pftg. The fuel pressure feedback control is executed to feedback control the discharge amount of the high-pressure pump 14 (the energization timing of the fuel pressure control valve 23) so as to match the above.

  In addition, the ECU 38 executes a relief valve failure diagnosis routine shown in FIG. 5 to be described later, so that when a predetermined failure diagnosis execution condition for the relief valve 33 is satisfied during engine start-up or engine operation, The target fuel pressure Pftg is set to a pressure higher than the relief pressure Pfrl, and the fuel pressure forced increase control for controlling the high pressure pump 14 is executed so that the fuel pressure Pf in the high pressure fuel system becomes the target fuel pressure Pftg. After a predetermined waiting period KT1 has elapsed after the fuel pressure Pf in the high-pressure fuel system has reached the relief pressure Pfrl, the fuel pressure Pf in the high-pressure fuel system is compared with a predetermined failure determination fuel pressure KPf and a failure of the relief valve 33 occurs. The presence or absence of is determined.

  When the fuel pressure forcibly increasing control for controlling the high pressure pump 14 is performed so that the fuel pressure Pf in the high pressure fuel system becomes a target fuel pressure Pftg higher than the relief pressure Pfrl, the fuel pressure Pf in the high pressure fuel system becomes the target fuel pressure Pftg (relief pressure Pfrl). In this case, the fuel pressure Pf in the high-pressure fuel system after the fuel pressure Pf in the high-pressure fuel system reaches the relief pressure Pfrl when the relief valve 33 is normal and when the failure occurs. Behave differently.

  For example, as shown by solid lines in FIGS. 2 to 4, if the relief valve 33 functions normally, the fuel pressure Pf in the high-pressure fuel system reaches the relief pressure Pfrl after the fuel pressure Pf in the high-pressure fuel system reaches the relief pressure Pfrl. Although it is maintained in the vicinity of Pfrl, as shown by broken lines in FIGS. 2 to 4, if the relief valve 33 does not open normally (for example, a closed valve fixing failure in which the relief valve 33 is fixed in a closed state). If this occurs, after the fuel pressure Pf in the high-pressure fuel system reaches the relief pressure Pfrl, the fuel pressure Pf in the high-pressure fuel system rises to near the target fuel pressure Pftg that is higher than the relief pressure Pfrl. Therefore, after the fuel pressure Pf in the high-pressure fuel system reaches the relief pressure Pfrl by the fuel pressure forced increase control, a predetermined waiting period KT1 (for example, the fuel pressure Pf in the high-pressure fuel system at the time when the relief valve 33 is stuck closed becomes the target fuel pressure Pftg). If the fuel pressure Pf in the high-pressure fuel system is compared with a predetermined failure determination fuel pressure KPf after a lapse of a necessary period until it rises in the vicinity, the presence or absence of the failure of the relief valve 33 can be accurately determined.

  In this case, the target fuel pressure Pftg at the time of forced fuel pressure increase control is set to a pressure (= relief pressure Pfrl + first predetermined value P1) higher than the relief pressure Pfrl by the first predetermined value P1, and the failure determination fuel pressure KPf is set. A pressure higher than the relief pressure Pfrl by a second predetermined value P2 (= relief pressure Pfrl + second predetermined value P2) is set, and the first predetermined value P1 is set to a value larger than the second predetermined value P2. Thus, the failure determination fuel pressure KPf is set between the target fuel pressure Pftg and the relief pressure Pfrl at the time of forced fuel pressure increase control.

  Here, the first predetermined value P1 and the second predetermined value P2 are based on the valve opening characteristics of the relief valve 33 and the design specifications of the high pressure fuel system (for example, the pressure resistance performance of the high pressure fuel pipe 29 and the delivery pipe 30), respectively. Thus, the target fuel pressure Pftg (= relief pressure Pfrl + first predetermined value P1) and failure determination fuel pressure KPf (= relief pressure Pfrl + second predetermined value P2) at the time of forced increase control of the fuel pressure are respectively relieved. The valve 33 is set to an appropriate value in consideration of the valve opening characteristics, the design specifications of the high pressure fuel system, and the like.

  The processing contents of the relief valve failure diagnosis routine of FIG. 5 executed by the ECU 38 in the first embodiment will be described below.

  The relief valve failure diagnosis routine shown in FIG. 5 is repeatedly executed at a predetermined cycle while the ECU 38 is turned on, and serves as failure diagnosis means in the claims. When this routine is started, first, at step 101, it is determined whether or not a predetermined failure diagnosis execution condition for the relief valve 33 is satisfied. Here, the failure diagnosis execution condition of the relief valve 33 is to satisfy all of the following conditions (1) to (3), for example.

(1) The fuel pressure sensor 32 and the high pressure pump 14 are normal.
(2) The engine is starting or the engine is in steady operation
(3) The number of times the engine has been operated since the previous failure diagnosis of the relief valve 33 has reached a predetermined number (for example, 3 times). Note that the above condition (2) is simply that the engine is started. It's also good. Alternatively, it may simply be “being in steady engine operation”.

  If all the above conditions (1) to (3) are satisfied, the failure diagnosis execution condition for the relief valve 33 is satisfied, but there is a condition that does not satisfy any one of the above conditions (1) to (3). In this case, the failure diagnosis execution condition for the relief valve 33 is not satisfied. The failure diagnosis execution condition of the relief valve 33 is not limited to the above conditions (1) to (3), and may be changed as appropriate.

  If it is determined in step 101 that the failure diagnosis execution condition for the relief valve 33 is not satisfied, this routine is terminated without executing the processing from step 102 onward.

  On the other hand, if it is determined in step 101 that the failure diagnosis execution condition for the relief valve 33 is satisfied, the processing after step 102 is executed as follows.

  First, in step 102, it is determined whether or not the engine is being started (before starting is completed). If it is determined that the engine is being started, the process proceeds to step 103 and fuel injection of the fuel injection valve 31 is stopped. However, if it is determined that the engine is not being started (that is, the engine is running after the engine is started), the fuel injection of the fuel injection valve 31 is continued.

  Thereafter, the routine proceeds to step 104, where the target fuel pressure Pftg in the high pressure fuel system is set to a pressure (= relief pressure Pfrl + first predetermined value P1) higher than the relief pressure Pfrl by the first predetermined value P1. Fuel pressure forcible increase control for controlling the discharge amount of the high-pressure pump 14 is executed so that the fuel pressure Pf in the fuel system becomes the target fuel pressure Pftg. In this fuel pressure forced increase control, for example, the discharge amount of the high-pressure pump 14 (the energization timing of the fuel pressure control valve 23) may be controlled by a control amount that is set in advance to achieve the target fuel pressure Pftg. Alternatively, the discharge amount of the high-pressure pump 14 (the energization timing of the fuel pressure control valve 23) may be feedback-controlled so that the fuel pressure Pf in the high-pressure fuel system detected by the fuel pressure sensor 32 matches the target fuel pressure Pftg.

  Thereafter, the routine proceeds to step 105, where it is determined whether or not an elapsed period T2 from the start of the fuel pressure forced increase control is within a predetermined allowable period KT2. Here, the allowable period KT2 is set to a period slightly longer than a period necessary for the fuel pressure Pf in the high-pressure fuel system to rise to the relief pressure Pfrl, for example. The elapsed period T2 and the allowable period KT2 may be set by time (msec or the like) or may be set by crank angle (° C. A).

  In this case, referring to the map of the allowable period KT2 shown in FIG. 6, the allowable period KT2 corresponding to the fuel pressure Pf1 in the high-pressure fuel system at the start of the fuel pressure forced increase control and the engine rotational speed Ne is calculated. Referring to the table of the correction coefficient α shown in FIG. 7, after calculating the correction coefficient α according to the engine coolant temperature THW at the start of the fuel pressure forced increase control, the allowable period KT2 is corrected by this correction coefficient α and finally A permissible period KT2 is obtained.

  The map of the allowable period KT2 in FIG. 6 indicates that the fuel pressure Pf in the high-pressure fuel system at the start of the fuel pressure forced increase control and the fuel pressure Pf in the high-pressure fuel system according to the engine speed Ne (discharge performance of the high-pressure pump 14). Considering that the period required to increase to the relief pressure Pfrl changes, for example, the allowable period KT2 becomes longer as the fuel pressure Pf1 in the high-pressure fuel system at the start of the forced fuel pressure increase control becomes lower, and the engine speed Ne. The allowable period KT2 is set to be shorter as the value becomes higher. The map of the allowable period KT2 is created in advance based on test data, design data, etc., and is stored in the ROM of the ECU 38.

  In the table of the correction coefficient α in FIG. 7, the discharge performance of the high-pressure pump 14 changes according to the cooling water temperature THW at the start of the fuel pressure forced increase control, and the fuel pressure Pf1 in the high-pressure fuel system rises to the relief pressure Pfrl. For example, the correction coefficient α is set to be larger and the allowable period KT2 is longer as the coolant temperature THW at the start of the fuel pressure forced increase control is lower. The table of the correction coefficient α is created in advance based on test data, design data, and the like, and is stored in the ROM of the ECU 38.

  If it is determined in step 105 that the elapsed period T2 from the start of the fuel pressure forced increase control is within the allowable period KT2, the process proceeds to step 106, where the fuel pressure Pf in the high-pressure fuel system detected by the fuel pressure sensor 32 is determined. It is determined whether or not the pressure is equal to or higher than the relief pressure Pfrl. If it is determined that the fuel pressure Pf in the high-pressure fuel system is lower than the relief pressure Pfrl, the process returns to step 105.

  Thereafter, if it is determined in step 105 that the elapsed time T2 from the start of the fuel pressure forced increase control exceeds the allowable period KT2, that is, the allowable period KT2 has elapsed since the start of the fuel pressure forced increase control. Regardless, if the fuel pressure Pf in the high pressure fuel system does not reach the relief pressure Pfrl, it is determined that there may be some abnormality in the high pressure pump 14, the control system of the high pressure pump 14, etc. Proceeding to 111, the fuel pressure forced increase control is terminated, and normal control (for example, normal fuel pressure feedback control or fuel injection control) is executed. In this case, failure diagnosis of the relief valve 33 is not executed.

  On the other hand, if it is determined in step 106 that the fuel pressure Pf in the high pressure fuel system is equal to or higher than the relief pressure Pfrl, that is, before the permissible period KT2 elapses after the fuel pressure forced increase control is started, When the fuel pressure Pf of the fuel reaches the relief pressure Pfrl, the routine proceeds to step 107, and whether or not the elapsed period T1 after the fuel pressure Pf in the high-pressure fuel system reaches the relief pressure Pfrl is equal to or longer than the predetermined standby period KT1. Determine whether. Here, the standby period KT1 is set to a period necessary for the fuel pressure Pf in the high-pressure fuel system to rise to the vicinity of the target fuel pressure Pftg, for example, when the relief valve 33 is stuck closed. The elapsed period T1 and the standby period KT1 may be set by time (msec or the like), or may be set by crank angle (° C. A).

  In this case, the standby period KT1 corresponding to the engine speed Ne is calculated with reference to the table of the standby period KT1 shown in FIG. The table of the waiting period KT1 in FIG. 8 shows that the discharge performance of the high-pressure pump 14 changes according to the engine speed Ne, and the fuel pressure Pf in the high-pressure fuel system becomes Pftg near the target fuel pressure when the relief valve 33 is stuck closed. Considering that the period required until the engine speed increases, for example, the standby period KT1 is set shorter as the engine speed Ne increases. The table of the waiting period KT1 is created in advance based on test data, design data, and the like, and is stored in the ROM of the ECU 38.

  If it is determined in step 107 that the elapsed time T1 after the fuel pressure Pf in the high-pressure fuel system reaches the relief pressure Pfrl is equal to or longer than the standby period KT1, that is, the fuel pressure Pf in the high-pressure fuel system is the relief pressure. When it is determined that the standby period KT1 has elapsed since reaching Pfrl, the routine proceeds to step 108, where the fuel pressure Pf in the high-pressure fuel system detected by the fuel pressure sensor 32 is acquired as the determination fuel pressure Pf2, and then the routine proceeds to step 109. Then, it is determined whether the determination fuel pressure Pf2 is lower than a predetermined failure determination fuel pressure KPf (= relief pressure Pfrl + second predetermined value P2).

  If it is determined at step 109 that the determination fuel pressure Pf2 is lower than the failure determination fuel pressure KPf, the routine proceeds to step 110, where it is determined that there is no failure (normal) of the relief valve 33 and the abnormality flag is kept OFF. Thereafter, the process proceeds to step 111 where the fuel pressure forced increase control is terminated and normal control (for example, normal fuel pressure feedback control or fuel injection control) is executed.

  On the other hand, when it is determined in step 109 that the determination fuel pressure Pf2 is equal to or higher than the failure determination fuel pressure KPf, the process proceeds to step 112, and the failure of the relief valve 33 (for example, the relief valve 33 is in the closed state). It is determined that there is a malfunction (fixing failure of the closed valve), the abnormality flag is set to ON, a warning lamp (not shown) provided on the instrument panel of the driver's seat is turned on, or the instrument of the driver's seat is turned on. A warning is displayed on a warning display section (not shown) of the panel to warn the driver, and the abnormal information (abnormal code, etc.) is rewritable nonvolatile memory (ECU 38) such as a backup RAM (not shown) of the ECU 38. Stored in a rewritable memory that retains stored data even when the power is off.

  Thereafter, the process proceeds to step 113, where fail-safe processing is executed. In this fail-safe process, for example, the fuel pressure control valve 23 of the high-pressure pump 14 is maintained in an open state (energization off state), and the fuel discharge operation of the high-pressure pump 14 is stopped. Alternatively, the engine is stopped and the operation of the high-pressure pump 14 is stopped.

  An execution example of the failure diagnosis of the relief valve 33 of the first embodiment described above will be described with reference to time charts of FIGS. Here, FIG. 2 shows an example of execution when the failure diagnosis of the relief valve 33 is executed during normal engine start, and FIG. 3 shows the case where the failure diagnosis of the relief valve 33 is executed when the engine is restarted after complete warm-up. FIG. 4 shows an execution example when failure diagnosis of the relief valve 33 is executed during engine operation.

  In any of the cases shown in FIGS. 2 to 4, the forced fuel pressure increase control is executed when the failure diagnosis execution condition for the relief valve 33 is satisfied. In this fuel pressure forced increase control, the target fuel pressure Pftg is set to a pressure higher than the relief pressure Pfrl by a first predetermined value P1 (= relief pressure Pfrl + first predetermined value P1), and the fuel pressure Pf in the high-pressure fuel system is set. The high pressure pump 14 is controlled so that the fuel pressure becomes the target fuel pressure Pftg. If the failure diagnosis execution condition is satisfied at the time of engine start (before the start is completed) (in the case of FIG. 2 or FIG. 3), the fuel injection of the fuel injection valve 31 is stopped until the failure diagnosis of the relief valve 33 is completed. However, when the failure diagnosis execution condition is satisfied during engine operation (in the case of FIG. 4), the fuel injection of the fuel injection valve 31 is continued.

  Thereafter, the fuel pressure Pf in the high-pressure fuel system is reduced to the relief pressure Pfrl before the allowable period KT2 elapses from the time t1 when the fuel pressure forced increase control is actually started (the time when the control amount of the high-pressure pump 14 is actually changed). When the fuel pressure Pf in the high-pressure fuel system reaches the relief pressure Pfrl, the fuel pressure Pf in the high-pressure fuel system is acquired as the judgment fuel pressure Pf2 at the time t3 when the standby period KT1 has elapsed from the time t2 when the fuel pressure Pf in the high-pressure fuel system reaches the relief pressure Pfrl. This determination fuel pressure Pf2 is compared with a failure determination fuel pressure KPf (= relief pressure Pfrl + second predetermined value P2).

  As a result, when it is determined that the determination fuel pressure Pf2 is lower than the failure determination fuel pressure KPf, it is determined that there is no failure (normal) of the relief valve 33, but the determination fuel pressure Pf2 is greater than or equal to the failure determination fuel pressure KPf. When the determination is made, it is determined that there is a failure of the relief valve 33 (for example, a closed valve fixing failure in which the relief valve 33 is fixed in a closed state), and the fuel discharge operation of the high pressure pump 14 is stopped (or the engine To stop the operation of the high-pressure pump 14).

  If the fuel pressure Pf in the high-pressure fuel system does not reach the relief pressure Pfrl even though the allowable period KT2 has elapsed from the time t1 when the fuel pressure forced increase control is actually started, the high-pressure pump 14 or the high-pressure pump 14 14 determines that there is a possibility that some abnormality has occurred in the control system 14 and the like, and terminates the fuel pressure forced increase control. In this case, failure diagnosis of the relief valve 33 is not executed.

  In the first embodiment described above, the target fuel pressure Pftg in the high-pressure fuel system is set to a pressure higher than the relief pressure Pfrl, and the high-pressure pump 14 is controlled so that the fuel pressure Pf in the high-pressure fuel system becomes the target fuel pressure Pftg. The fuel pressure forced increase control is executed, and after the predetermined standby period KT1 has elapsed after the fuel pressure Pf in the high pressure fuel system reaches the relief pressure Pfrl by this fuel pressure forced increase control, the fuel pressure Pf in the high pressure fuel system is set to a predetermined value. Therefore, the failure diagnosis of the relief valve 33 can be performed during the operation of the high-pressure pump 14. For this reason, even if a failure of the relief valve 33 occurs during the operation of the high-pressure pump 14, the failure can be detected during the operation of the high-pressure pump 14.

  In the first embodiment, since the standby period KT1 is set according to the engine rotational speed Ne, the discharge performance of the high-pressure pump 14 changes according to the engine rotational speed Ne, for example, the relief valve 33 is closed. The waiting period KT1 can be changed in response to the change of the period required for the fuel pressure Pf in the high-pressure fuel system to rise to Pftg near the target fuel pressure at the time of valve sticking failure, and the waiting period KT1 is set to an appropriate value. Can be set. As a result, it is possible to avoid the standby period KT1 from becoming unnecessarily long and complete the failure diagnosis of the relief valve 33 at an early stage.

  Further, in the first embodiment, the high pressure pump is used when the fuel pressure Pf in the high pressure fuel system does not reach the relief pressure Pfrl even though the predetermined allowable period KT2 has elapsed since the start of the fuel pressure forced increase control. 14 and the control system of the high-pressure pump 14 and the like, and it is determined that there is a possibility that some abnormality has occurred, so that the fuel pressure forced increase control is terminated, so that the fuel pressure forced increase control is continued unnecessarily for a long time. This can be prevented beforehand.

  In the first embodiment, the allowable period KT2 is set according to the fuel pressure Pf1 in the high-pressure fuel system at the start of the fuel pressure forced increase control and the engine speed Ne. Corresponding to the change in the time required for the fuel pressure Pf in the high pressure fuel system to rise to the relief pressure Pfrl according to the fuel pressure Pf1 in the high pressure fuel system and the engine speed Ne (discharge performance of the high pressure pump 14) Thus, the allowable period KT2 can be changed, and the allowable period KT2 can be set to an appropriate value.

  Further, in the first embodiment, since the allowable period KT2 is corrected according to the cooling water temperature THW at the start of the fuel pressure forced increase control, the discharge of the high pressure pump 14 according to the cooling water temperature THW at the start of the fuel pressure forced increase control. The permissible period KT2 can be appropriately corrected in response to the change in the period required for the fuel pressure Pf1 in the high-pressure fuel system to rise to the relief pressure Pfrl due to the change in performance.

  Further, in the first embodiment, the fact that the number of engine operations since the previous execution of the failure diagnosis of the relief valve 33 has reached a predetermined number of times is set as one of the failure diagnosis execution conditions of the relief valve 33. Since the failure diagnosis of the next relief valve 33 is permitted when the number of engine operations since the previous execution of the failure diagnosis of 33 has reached a predetermined number of times, the frequency of execution of the failure diagnosis of the relief valve 33 is moderate. Therefore, it is possible to moderately reduce the frequency of the repeated opening / closing operation of the relief valve 33 associated with the forced increase control of the fuel pressure, and to prevent the durability life of the relief valve 33 from being lowered.

  In the first embodiment, when the failure diagnosis of the relief valve 33 is executed when the engine is started, the fuel injection of the fuel injection valve 31 is stopped until the failure diagnosis of the relief valve 33 is completed. When failure diagnosis of the relief valve 33 is sometimes executed, the forced fuel pressure increase control can be executed in a state where the fuel injection of the fuel injection valve 31 is stopped (that is, a state where fuel in the high-pressure fuel system is not consumed). Thus, the fuel pressure Pf in the high-pressure fuel system can be quickly raised by the fuel pressure forced increase control, and the failure diagnosis of the relief valve 33 can be completed early.

  Next, a second embodiment of the present invention will be described with reference to FIGS. However, description of substantially the same parts as those in the first embodiment will be omitted or simplified, and different parts from the first embodiment will be mainly described.

  In the second embodiment, the ECU 38 executes a relief valve failure diagnosis routine shown in FIG. 10 to be described later, so that a predetermined waiting period KT1 after the fuel pressure Pf in the high-pressure fuel system reaches the relief pressure Pfrl by the fuel pressure forced increase control. After a lapse of time, a fluctuation amount (amplitude) ΔPf of the fuel pressure in the high-pressure fuel system within a predetermined judgment period KT3 is calculated, and this fluctuation amount ΔPf of the fuel pressure is compared with a predetermined failure judgment value ΔKPf. Determine if there is a failure.

  When the fuel pressure forced increase control is executed, the fuel pressure Pf in the high-pressure fuel system increases toward the target fuel pressure Pftg (pressure higher than the relief pressure Pfrl). At this time, for example, as shown by a solid line in FIG. 9, if the relief valve 33 functions normally, after the fuel pressure Pf in the high-pressure fuel system reaches the relief pressure Pfrl, the relief valve 33 is opened / closed. Repeatedly, the fuel pressure Pf in the high-pressure fuel system fluctuates (vibrates) in the vicinity of the relief pressure Pfrl. However, as shown by the broken line in FIG. 9, if the relief valve 33 does not open normally (for example, the relief valve 33 is If the valve is stuck in the closed state, the fuel pressure Pf reaches the relief pressure Pfrl, and then reaches the target fuel pressure Pftg higher than the relief pressure Pfrl. The fuel pressure Pf in the fuel tank rises and is substantially stabilized near the target fuel pressure Pftg (Note that during fuel injection, the fuel pressure Pf in the high-pressure fuel system fluctuates relatively small for each fuel injection). Therefore, after the fuel pressure Pf in the high-pressure fuel system reaches the relief pressure Pfrl by the fuel pressure forced increase control, a predetermined waiting period KT1 (for example, the fuel pressure Pf in the high-pressure fuel system at the time when the relief valve 33 is stuck closed becomes the target fuel pressure Pftg). If the amount of fluctuation (amplitude) ΔPf of the fuel pressure in the high-pressure fuel system within a predetermined determination period KT3 is compared with a predetermined failure determination value ΔKPf after a lapse of a necessary period until it rises in the vicinity, the relief valve 33 It is possible to accurately determine whether or not there is a failure.

  The routine of FIG. 10 is obtained by changing the processing of steps 108 and 109 of the routine of FIG. 5 described in the first embodiment to the processing of steps 108a and 109a, and the processing of each other step is the same as FIG. It is.

  The processing contents of the relief valve failure diagnosis routine of FIG. 10 executed by the ECU 38 in the second embodiment will be described below. In this routine, when the failure diagnosis execution condition for the relief valve 33 is satisfied, the target fuel pressure Pftg in the high-pressure fuel system is set to a pressure higher than the relief pressure Pfrl, and the fuel pressure Pf in the high-pressure fuel system is set to the target fuel pressure Pftg. The fuel pressure forced increase control for controlling the discharge amount of the high-pressure pump 14 is executed (steps 101 to 104).

  Thereafter, if the fuel pressure Pf in the high-pressure fuel system reaches the relief pressure Pfrl before the allowable period KT2 elapses after the fuel pressure forced increase control is started, the fuel pressure Pf in the high-pressure fuel system becomes the relief pressure Pfrl. It is determined whether or not the elapsed period T1 after reaching the period is equal to or longer than the waiting period KT1 (steps 105 to 107).

  Thereafter, when it is determined that the elapsed time T1 after the fuel pressure Pf in the high-pressure fuel system reaches the relief pressure Pfrl is equal to or longer than the standby period KT1, that is, the fuel pressure Pf in the high-pressure fuel system is set to the relief pressure Pfrl. When it is determined that the standby period KT1 has elapsed since the arrival, the routine proceeds to step 108a, where the fluctuation amount ΔPf of the fuel pressure in the high-pressure fuel system within the predetermined determination period KT3 is calculated. Here, the determination period KT3 is set to, for example, the minimum period in which the fuel pressure fluctuation amount ΔPf in the high-pressure fuel system can be calculated. The determination period KT1 may be set by time (msec or the like), or may be set by crank angle (° C. A).

  In this case, the determination period KT3 corresponding to the engine speed Ne is calculated with reference to the determination period KT3 table shown in FIG. The table of the determination period KT3 in FIG. 11 takes into account that the fluctuation cycle of the fuel pressure Pf in the high-pressure fuel system changes according to the engine speed Ne, for example, the determination period KT3 increases as the engine speed Ne increases. It is set to be shorter. The determination period KT3 table is created in advance based on test data, design data, and the like, and is stored in the ROM of the ECU 38.

  Further, the fluctuation amount ΔPf of the fuel pressure in the high-pressure fuel system in the determination period KT3 is, for example, the difference between the maximum value and the minimum value of the fuel pressure Pf in the high-pressure fuel system in the determination period KT3. Is calculated as a fluctuation amount ΔPf. Alternatively, the difference between the average value of the peak value of the fuel pressure Pf and the average value of the bottom value (or the average value of the difference between the peak value and the bottom value) in the high-pressure fuel system within the judgment period KT3 is calculated in the high-pressure fuel system. The fuel pressure fluctuation amount ΔPf may be calculated.

  Thereafter, the routine proceeds to step 109a, where it is determined whether or not the fuel pressure fluctuation amount ΔPf in the high-pressure fuel system within the determination period KT3 is larger than a predetermined failure determination value ΔKPf. In this case, the failure determination value ΔKPf corresponding to the engine rotational speed Ne is calculated with reference to the failure determination value ΔKPf table shown in FIG. In the table of failure judgment value ΔKPf in FIG. 12, the discharge performance of the high-pressure pump 14 changes according to the engine rotational speed Ne, and the fluctuation amount (amplitude) of the fuel pressure in the high-pressure fuel system due to the relief valve 33 being opened / closed. ) In consideration of the change in ΔPf, for example, the failure determination value ΔKPf is set to increase as the engine speed Ne increases. The table of the failure determination value ΔKPf is created in advance based on test data, design data, and the like, and is stored in the ROM of the ECU 38.

  If it is determined in step 109a that the fluctuation amount ΔPf of the fuel pressure in the high-pressure fuel system is larger than the failure determination value ΔKPf, it is determined that there is no failure (normal) in the relief valve 33, and then the fuel pressure forced increase control is performed. After completing, normal control is executed (steps 110 and 111).

  On the other hand, when it is determined in step 109a that the fuel pressure fluctuation amount ΔPf in the high-pressure fuel system is equal to or less than the failure determination value ΔKPf, the relief valve 33 has failed (for example, the relief valve 33 is closed). After it is determined that there is a valve-closing sticking failure that is stuck at), fail-safe processing is executed (steps 112 and 113).

  In the second embodiment described above, after the predetermined standby period KT1 has elapsed after the fuel pressure Pf in the high-pressure fuel system has reached the relief pressure Pfrl by the fuel pressure forced increase control, the high-pressure fuel system in the predetermined determination period KT3 has elapsed. The fuel pressure fluctuation amount (amplitude) ΔPf is calculated, and the fuel pressure fluctuation amount ΔPf is compared with a predetermined failure judgment value ΔKPf to determine whether or not the relief valve 33 has failed. Failure diagnosis of the relief valve 33 can be performed during operation, and substantially the same effect as in the first embodiment can be obtained.

  In the second embodiment, the determination period KT3 is set according to the engine speed Ne when calculating the fuel pressure fluctuation amount ΔPf in the high-pressure fuel system in the determination period KT3. According to Ne, the determination period KT3 can be changed in response to the change of the fluctuation cycle of the fuel pressure Pf in the high-pressure fuel system, and the determination period KT3 can be changed to an appropriate value (for example, the fluctuation of the fuel pressure in the high-pressure fuel system). The amount ΔPf can be set to a minimum period during which calculation is possible.

  Further, in the second embodiment, since the failure determination value ΔKPf is set according to the engine speed Ne, the discharge performance of the high-pressure pump 14 changes according to the engine speed Ne, and the relief valve 33 is opened. The failure judgment value ΔKPf can be changed in response to the change (amplitude) ΔPf of the fuel pressure in the high-pressure fuel system due to the valve / valve closing, and the failure judgment value ΔKPf can be set to an appropriate value. it can.

  In the first and second embodiments, the failure diagnosis of the next relief valve 33 is permitted when the number of engine operations after the previous execution of the failure diagnosis of the relief valve 33 has reached a predetermined number. However, the present invention is not limited to this. For example, when the travel time, travel distance, etc. since the previous failure diagnosis of the relief valve 33 has reached a predetermined value, the failure diagnosis of the next relief valve 33 is permitted. Anyway. Alternatively, the failure diagnosis of the relief valve 33 is prohibited during normal engine operation, and the failure diagnosis of the relief valve 33 is permitted when the dealer or the like switches to the check mode for vehicle inspection. Also good. Even in this case, it is possible to suppress the frequency of execution of failure diagnosis of the relief valve 33, and to suppress the frequency of execution of the repeated opening / closing operation of the relief valve 33 associated with the fuel pressure forced increase control. It is possible to prevent a decrease in durability life. However, if the durable life of the relief valve 33 is not a problem, failure diagnosis of the relief valve 33 may be permitted every time the engine is operated.

  In the first and second embodiments, the fuel pressure Pf in the high-pressure fuel system after a predetermined waiting period KT1 has elapsed after the fuel pressure Pf in the high-pressure fuel system reaches the relief pressure Pfrl by the fuel pressure forced increase control. Although the presence or absence of failure of the relief valve 33 is determined based on the variation amount ΔPf of the fuel pressure, the failure determination method is not limited to this, and may be changed as appropriate. For example, high pressure fuel is controlled by fuel pressure forced increase control. The increase amount of the fuel pressure Pf in the high-pressure fuel system within a predetermined period after the fuel pressure Pf in the system reaches the relief pressure Pfrl is compared with a failure determination value to determine whether or not the relief valve 33 has failed, Alternatively, the difference between the fuel pressure Pf in the high-pressure fuel system and the target fuel pressure Pftg after the predetermined period has elapsed after the fuel pressure Pf in the high-pressure fuel system reaches the relief pressure Pfrl by the fuel pressure forced increase control (or the high-pressure fuel system). Inside fuel pressure The difference between Pf and the relief pressure Pfrl) may be compared with a failure determination value to determine whether or not the relief valve 33 has failed.

  In the first and second embodiments, as shown in FIG. 1, the present invention is applied to a system in which a relief valve 33 is provided separately from the high-pressure pump 14 (a system in which the relief valve 33 is provided in the delivery pipe 30). However, the present invention is not limited to this, and the configuration of the fuel supply system may be appropriately changed. For example, as shown in FIG. 13, a system in which a relief valve 33 is integrally provided in the high pressure pump 14 (in the high pressure pump 14 The present invention may be applied to a system in which a fuel return passage 39 for returning the fuel in the high-pressure fuel pipe 29 to the pump chamber 18 is integrally provided, and a relief valve 33 is provided in the middle of the fuel return passage 39).

  DESCRIPTION OF SYMBOLS 11 ... Fuel tank, 12 ... Low pressure pump, 14 ... High pressure pump, 18 ... Pump chamber, 19 ... Piston, 22 ... Suction port, 23 ... Fuel pressure control valve, 27 ... Discharge port, 29 ... High pressure fuel piping, 30 ... Delivery pipe , 31 ... Fuel injection valve, 32 ... Fuel pressure sensor, 33 ... Relief valve, 34 ... Relief piping, 38 ... ECU (failure diagnosis means)

Claims (10)

Fuel pressure in a high-pressure fuel system that is applied to a fuel supply system of a direct injection internal combustion engine that supplies high-pressure fuel discharged from a high-pressure pump to a fuel injection valve, and that supplies fuel from the high-pressure pump to the fuel injection valve Failure of a fuel supply system of a direct injection internal combustion engine provided with a relief valve that opens when the fuel pressure (hereinafter referred to as “fuel pressure”) becomes higher than a predetermined relief pressure and reduces the fuel pressure in the high-pressure fuel system In the diagnostic device,
A target fuel pressure in the high-pressure fuel system is set to a pressure higher than the relief pressure, and a fuel pressure forced increase control is performed to control the high-pressure pump so that the fuel pressure in the high-pressure fuel system becomes the target fuel pressure, The fuel pressure in the high-pressure fuel system is compared with a predetermined failure determination fuel pressure after a predetermined standby period has elapsed after the fuel pressure in the high-pressure fuel system reaches the relief pressure by the fuel pressure forced increase control. Provided with a failure diagnosis means for determining the presence or absence of a valve failure ,
The failure diagnosis means sets the target fuel pressure during the fuel pressure forced increase control to a pressure higher by a first predetermined value than the relief pressure, and sets the failure determination fuel pressure by a second predetermined value above the relief pressure. A failure diagnosis device for a fuel supply system of a direct injection internal combustion engine , wherein the pressure is set to a high pressure and the first predetermined value is set to a value larger than the second predetermined value . The failure diagnosis means sets the first predetermined value and the second predetermined value based on at least one of a valve opening characteristic of the relief valve and a design specification of the high-pressure fuel system, respectively. The failure diagnosis device for a fuel supply system of a direct injection internal combustion engine according to claim 1 . The failure diagnosis device for a fuel supply system for a direct injection internal combustion engine according to claim 1 or 2 , wherein the failure diagnosis means sets the standby period according to the rotational speed of the internal combustion engine. If the fuel pressure in the high-pressure fuel system does not reach the relief pressure even after a predetermined allowable period has elapsed since the start of the fuel pressure forced increase control, the failure diagnosis means performs the fuel pressure forced increase control. The failure diagnosis apparatus for a fuel supply system for a direct injection internal combustion engine according to any one of claims 1 to 3 , wherein the apparatus is terminated. 5. The cylinder according to claim 4 , wherein the failure diagnosis unit sets the allowable period according to a fuel pressure in the high-pressure fuel system at the start of the fuel pressure forced increase control and a rotation speed of the internal combustion engine. A failure diagnosis device for a fuel supply system of an internal injection internal combustion engine. 6. The fuel supply system for a direct injection internal combustion engine according to claim 5 , wherein the failure diagnosis unit corrects the permissible period according to a cooling water temperature of the internal combustion engine at the start of the fuel pressure forced increase control. Fault diagnosis device. The failure diagnosis means permits a failure diagnosis of the next relief valve when the number of operations of the internal combustion engine after a previous execution of the failure diagnosis of the relief valve reaches a predetermined number. A failure diagnosis apparatus for a fuel supply system for a direct injection internal combustion engine according to any one of claims 1 to 6 . The in-cylinder according to any one of claims 1 to 7 , wherein the failure diagnosis unit permits failure diagnosis of the relief valve when the vehicle is switched to a predetermined check mode for vehicle inspection. A failure diagnosis device for a fuel supply system of an injection internal combustion engine. The failure diagnosis means stops fuel injection of the fuel injection valve until the failure diagnosis of the relief valve is completed when the failure diagnosis of the relief valve is executed when the internal combustion engine is started. A failure diagnosis apparatus for a fuel supply system for a direct injection internal combustion engine according to any one of 1 to 8 . 10. A failure diagnosis of a fuel supply system for a direct injection internal combustion engine according to claim 1, further comprising a fuel return passage for returning the fuel in the high pressure fuel system into the high pressure pump. apparatus.

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