JP5344312B2 - Abnormality diagnosis device for fuel supply system of internal combustion engine - Google Patents

Description

  The present invention relates to an abnormality diagnosis device for a fuel supply system of an internal combustion engine that supplies fuel discharged from a low pressure pump to a high pressure pump and supplies fuel discharged from the 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. For this reason, in a cylinder injection engine, fuel pumped up from a fuel tank by an electric low-pressure pump is supplied to a high-pressure pump driven by the camshaft of the engine, and high-pressure fuel discharged from the high-pressure pump is injected into the fuel. It is trying to pump to the valve.

  Generally, in-cylinder injection engines are provided with a fuel pressure sensor that detects a fuel pressure (fuel pressure) in a high-pressure fuel system that supplies high-pressure fuel from a high-pressure pump to a fuel injection valve. The discharge amount of the high-pressure pump is feedback-controlled so that the fuel pressure of the fuel becomes equal to the target fuel pressure.

  As such a fuel supply system abnormality diagnosis technique, for example, as described in Patent Document 1 (Japanese Patent No. 3958839), the low pressure pump is operated while the high pressure pump is stopped (the engine is stopped). Make the fuel pressure in the high-pressure fuel system equal to the fuel pressure in the low-pressure fuel system, and diagnose the abnormality of the low-pressure fuel system based on the fuel pressure in the high-pressure fuel system (= fuel pressure in the low-pressure fuel system) detected by the fuel pressure sensor in this state. There is something to do.

Japanese Patent No. 3958839 (second page, etc.)

  However, in the technique of Patent Document 1 described above, an abnormality in the low-pressure fuel system occurs when the low-pressure pump is operated while the high-pressure pump is stopped (while the engine is stopped) and the fuel pressure in the high-pressure fuel system is equal to the fuel pressure in the low-pressure fuel system. Since the diagnosis is performed, the abnormality diagnosis of the low-pressure fuel system cannot be performed while the high-pressure pump is operating. Moreover, immediately after the high-pressure pump is stopped, the fuel pressure in the high-pressure fuel system is still higher than the fuel pressure in the low-pressure fuel system. Therefore, after the high-pressure pump is stopped, the fuel pressure in the high-pressure fuel system drops to near the fuel pressure in the low-pressure fuel system. It is necessary to wait until the low-pressure fuel system abnormality is diagnosed. For this reason, the execution frequency of the abnormality diagnosis of the low-pressure fuel system cannot be made very high, and when the abnormality of the low-pressure fuel system occurs, the abnormality may not be detected early.

  Therefore, the problem to be solved by the present invention is that it is possible to perform abnormality diagnosis of the low-pressure fuel system during operation of the high-pressure pump, and to detect the abnormality early when a low-pressure fuel system abnormality occurs. An object of the present invention is to provide an abnormality diagnosis device for a fuel supply system of an internal combustion engine.

  In order to solve the above-mentioned problem, the invention according to claim 1 is directed to a fuel supply for an internal combustion engine that supplies fuel discharged from a low-pressure pump to a high-pressure pump and supplies fuel discharged from the high-pressure pump to a fuel injection valve. A fuel pressure detecting means for detecting fuel pressure (hereinafter referred to as “fuel pressure”) in the high pressure fuel system that is applied to the system and supplying fuel from the high pressure pump to the fuel injection valve; and in the high pressure fuel system detected by the fuel pressure detecting means An abnormality diagnosis device for a fuel supply system of an internal combustion engine having a high-pressure side fuel pressure feedback control for performing high-pressure side fuel pressure feedback control to feedback-control a high-pressure pump so that the fuel pressure matches a target fuel pressure. The low-pressure pump discharge amount forced change control for forcibly changing the discharge amount of the low-pressure pump is executed, and the low-pressure pump discharge amount forced change control is executed. Based on the control state of the high pressure side fuel pressure feedback control when, is obtained by a structure in which a diagnosis means for determining the presence or absence of an abnormality in the low-pressure fuel system that supplies fuel from the low pressure pump to the high pressure pump.

  If the low pressure pump discharge amount forced change control that forcibly changes the discharge amount of the low pressure pump during execution of the high pressure side fuel pressure feedback control, the fuel pressure in the high pressure fuel system changes accordingly, and the high pressure side fuel pressure feedback control Control state (for example, feedback correction value, etc.) changes, but when the low-pressure fuel system (for example, low-pressure pump) is abnormal, the control state of the high-pressure side fuel pressure feedback control is different from that when the low-pressure fuel system is normal. come. Therefore, by monitoring the control state of the high-pressure side fuel pressure feedback control when the low-pressure pump discharge amount forced change control is executed during the execution of the high-pressure side fuel pressure feedback control, it is possible to accurately determine whether there is an abnormality in the low-pressure fuel system. it can. In this way, the abnormality diagnosis of the low-pressure fuel system can be performed during the operation of the high-pressure pump, so that the frequency of executing the abnormality diagnosis of the low-pressure fuel system can be sufficiently increased, and an abnormality of the low-pressure fuel system occurs. In such a case, the abnormality can be detected at an early stage.

  In this case, it is preferable to forcibly increase or decrease the discharge amount of the low pressure pump during the low pressure pump discharge amount forced change control. For example, if the change in the control state of the high-pressure side fuel pressure feedback control is small despite the low-pressure pump discharge amount forced change control for forcibly increasing the discharge amount of the low-pressure pump, For example, it can be determined that the fuel pressure supplied from the low-pressure pump to the high-pressure pump does not increase normally. On the other hand, when the change in the control state of the high-pressure side fuel pressure feedback control is small despite the execution of the low-pressure pump discharge amount forced change control for forcibly reducing the discharge amount of the low-pressure pump, an abnormality in the low-pressure fuel system ( For example, it can be determined that there is a fuel pressure increase abnormality in which the fuel pressure supplied from the low pressure pump to the high pressure pump does not drop normally.

  By the way, if the fuel pressure in the high-pressure fuel system (fuel pressure supplied to the fuel injection valve) changes too much due to the forced change control of the low-pressure pump discharge amount, the fuel injection control accuracy may deteriorate and exhaust emissions may deteriorate. .

  Therefore, as described in claim 3, the control amount of the high-pressure pump may be corrected in advance so as to suppress the fuel pressure change in the high-pressure fuel system generated by the low-pressure pump discharge amount forced change control. In this way, it is possible to suppress a change in the fuel pressure in the high-pressure fuel system due to the forced change control of the discharge amount of the low-pressure pump, thereby preventing the deterioration of the fuel injection control accuracy and the deterioration of the exhaust emission. Can do.

  Further, as in claim 4, there is provided fail-safe control means for reducing the discharge amount of the low-pressure pump from the normal time (when the low-pressure fuel system is normal) when the abnormality diagnosis means determines that there is an abnormality in the low-pressure fuel system. It is good also as a structure provided. In this way, it is possible to prevent the fuel pressure in the low-pressure fuel system or the high-pressure fuel system from becoming abnormally high due to an abnormality in the low-pressure fuel system.

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 flowchart for explaining the flow of processing of the abnormality diagnosis routine of the first embodiment. FIG. 3 is a flowchart for explaining the flow of processing of the fail-safe control routine. FIG. 4 is a flowchart for explaining the flow of processing of the abnormality diagnosis routine of the second embodiment. FIG. 5 is a flowchart for explaining the flow of processing of the abnormality diagnosis routine of the third embodiment. FIG. 6 is a flowchart for explaining the flow of processing of the abnormality diagnosis routine of the fourth 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 low-pressure pump 12 may use a pump that can continuously change the discharge amount by duty-controlling the drive voltage, or the discharge amount may be changed to a plurality of levels (for example, 3) by switching the drive voltage to a plurality of levels. A pump that can be switched to a stage) may be used.

  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.

  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. The delivery pipe 30 is provided with a relief valve 33, and a discharge port of the relief valve 33 is connected to the fuel tank 11 (or the low-pressure side fuel pipe 13) via a relief pipe 34.

  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) to thereby determine the fuel injection amount of the fuel injection valve 31 according to the engine operating state. The ignition timing of a spark plug (not shown) is controlled.

  At that time, the ECU 38 executes a fuel pressure control routine (not shown), thereby functioning as a fuel pressure control means in the claims, and according to the engine operating state (for example, engine speed, engine load, etc.). The target fuel pressure is calculated from a map or the like, the fuel pressure F / B correction value is calculated so that the fuel pressure in the high-pressure fuel system detected by the fuel pressure sensor 32 matches the target fuel pressure, and this fuel pressure F / B correction value is used. High-pressure side fuel pressure F / B control for correcting the discharge amount of the high-pressure pump 14 (energization timing of the fuel pressure control valve 23) is executed. Here, “F / B” means “feedback” (hereinafter the same).

  Further, the ECU 38 functions as an abnormality diagnosis means in the scope of claims by executing an abnormality diagnosis routine shown in FIG. 2 to be described later, and controls the discharge amount of the low pressure pump 12 during execution of the high pressure side fuel pressure F / B control. A low pressure pump discharge amount forced change control for forcibly changing (for example, increasing) is executed, and a control state of the high pressure side fuel pressure F / B control when the low pressure pump discharge amount forced change control is executed (for example, fuel pressure F / B correction) Value) to determine whether there is an abnormality in the low-pressure fuel system (for example, the low-pressure pump 12, the fuel pipe 13, the pressure regulator 15, the control system of the low-pressure pump 12).

  When low-pressure pump discharge amount forced change control is performed to forcibly change (for example, increase) the discharge amount of the low-pressure pump 12 during execution of the high-pressure side fuel pressure F / B control, the fuel pressure in the high-pressure fuel system changes accordingly. Then, the control state of the high pressure side fuel pressure F / B control (for example, the fuel pressure F / B correction value) changes. At this time, when the low pressure fuel system is abnormal, the control state of the high pressure side fuel pressure F / B control is the low pressure fuel system. It will be different from the normal time. Therefore, if the control state of the high-pressure side fuel pressure F / B control when the low-pressure pump discharge amount forced change control is executed during execution of the high-pressure side fuel pressure F / B control, the presence or absence of abnormality in the low-pressure fuel system can be accurately detected. Can be determined.

Further, the ECU 38 executes a fail-safe control routine shown in FIG. 3 to be described later, thereby functioning as a fail-safe control means in the scope of claims. It is determined by the abnormality diagnosis routine shown in FIG. 2 that there is an abnormality in the low-pressure fuel system. In this case, the discharge amount of the low-pressure pump 12 is smaller than that at normal time (when the low-pressure fuel system is normal). Fail-safe control to be reduced to (value).
The processing contents of the abnormality diagnosis routine of FIG. 2 and the fail safe control routine of FIG. 3 executed by the ECU 38 will be described below.

[Abnormal diagnosis routine]
The abnormality diagnosis routine shown in FIG. 2 is repeatedly executed at a predetermined cycle while the ECU 38 is powered on. When this routine is started, first, in step 101, it is determined whether or not the high-pressure side fuel pressure F / B control is being executed, and if it is determined that the high-pressure side fuel pressure F / B control is not being executed. In this case, the routine is terminated without executing the processing from step 102 onward.

  On the other hand, if it is determined in step 101 that the high-pressure side fuel pressure F / B control is being executed, the processing after step 102 is executed as follows. First, in step 102, whether or not the fuel pressure in the high-pressure fuel system detected by the fuel pressure sensor 32 is stable is determined, for example, by the amount of change in the fuel pressure in the high-pressure fuel system (for example, the difference between the previous value and the current value). Judgment is made based on whether or not it is within a predetermined range.

  If it is determined in step 102 that the fuel pressure in the high-pressure fuel system is stable, the process proceeds to step 103, and after storing the fuel pressure F / B correction value before execution of the low-pressure pump discharge amount forced change control, step Proceeding to 104, low-pressure pump discharge amount forced change control for forcibly increasing the discharge amount of the low-pressure pump 12 by a predetermined amount is executed.

  After this, the routine proceeds to step 105, where the fuel pressure F / B correction value during execution of the low pressure pump discharge amount forced change control is stored, and then proceeds to step 106, where fuel pressure F / B before execution of the low pressure pump discharge amount forced change control. The absolute value of the deviation between the correction value and the fuel pressure F / B correction value during execution of the low pressure pump discharge amount forced change control is calculated as the change amount of the fuel pressure F / B correction value.

  Thereafter, the routine proceeds to step 107, where it is determined whether or not the change amount of the fuel pressure F / B correction value is larger than the abnormality determination value. If it is determined in step 107 that the change amount of the fuel pressure F / B correction value is larger than the abnormality determination value, the process proceeds to step 108 and the low-pressure fuel system (for example, the low-pressure pump 12, the fuel pipe 13, the pressure regulator). 15, the control system of the low-pressure pump 12) is determined to be normal (normal), the abnormal flag is maintained OFF, and this routine is terminated.

  On the other hand, if it is determined in step 107 that the change amount of the fuel pressure F / B correction value is equal to or less than the abnormality determination value, the low pressure pump discharge amount forcibly increasing the discharge amount of the low pressure pump 12. In spite of execution of the forced change control, the change amount of the fuel pressure F / B correction value is small, so the process proceeds to step 109, where the low pressure fuel system abnormality (for example, the fuel pressure supplied from the low pressure pump 12 to the high pressure pump 14 is normal). It is determined that there is a fuel pressure drop abnormality that does not rise), the abnormality flag is set to ON, a warning lamp (not shown) provided on the driver's seat instrument panel is turned on, or the driver's seat instrument panel Is displayed on a warning display unit (not shown) to warn the driver, and the abnormality information (abnormal code, etc.) can be rewritten in a backup RAM (not shown) of the ECU 38 or the like. Running abnormality processing such as stored in the volatile memory (rewritable memory that holds stored data even during ECU38 power off), the routine ends.

[Fail-safe control routine]
The fail safe control routine shown in FIG. 3 is repeatedly executed at a predetermined cycle while the ECU 38 is powered on. When this routine is started, first, at step 201, it is determined whether or not the low-pressure fuel system is abnormal based on the abnormality diagnosis result of the abnormality diagnosis routine of FIG.
If it is determined in step 201 that the low-pressure fuel system is not abnormal (normal), the routine ends without performing the process of step 202.

  On the other hand, if it is determined in step 201 that the low-pressure fuel system is abnormal, the process proceeds to step 202, where the discharge amount of the low-pressure pump 12 is less than that for normal operation (when the low-pressure fuel system is normal). Fail-safe control is performed to reduce the discharge amount to a lower discharge amount (for example, a lower limit value of a discharge amount at which the engine 11 can be operated or a value slightly larger than that).

  In the first embodiment described above, the low pressure pump discharge amount forced change control for forcibly increasing the discharge amount of the low pressure pump 12 is executed during the execution of the high pressure side fuel pressure F / B control. Since the presence or absence of an abnormality in the low-pressure fuel system is determined based on the amount of change in the fuel pressure F / B correction value of the high-pressure side fuel pressure F / B control when the control is executed, the low-pressure fuel during operation of the high-pressure pump 14 is determined. System abnormality diagnosis can be performed, the frequency of low-pressure fuel system abnormality diagnosis can be sufficiently increased, and when a low-pressure fuel system abnormality occurs, the abnormality can be detected early .

  In the first embodiment, when it is determined that there is an abnormality in the low-pressure fuel system, the discharge amount of the low-pressure pump 12 is reduced to a discharge amount for fail-safe that is smaller than normal (when the low-pressure fuel system is normal). Since fail-safe control is executed, it is possible to prevent the fuel pressure in the low-pressure fuel system or the high-pressure fuel system from becoming abnormally high due to an abnormality in the low-pressure fuel system.

  Next, Embodiment 2 of the present invention will be described with reference to FIG. 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 first embodiment, the discharge amount of the low-pressure pump 12 is forcibly increased during the low-pressure pump discharge amount forced change control. In the second embodiment, the abnormality diagnosis routine of FIG. By executing, the discharge amount of the low-pressure pump 12 is forcibly decreased during the forced change control of the low-pressure pump discharge amount. The routine of FIG. 4 is obtained by changing the process of step 104 of the routine of FIG. 2 described in the first embodiment to the process of step 104a, and the processes of other steps are the same as those of FIG.

  Further, the ECU 38 executes the fail-safe control routine of FIG. 3 described above, and when the abnormality diagnosis routine of FIG. 4 determines that there is an abnormality in the low-pressure fuel system, the ECU 38 reduces the discharge amount of the low-pressure pump 12 from the normal time. Fail-safe control is performed to reduce the discharge amount for fail-safe.

Hereinafter, the processing contents of the abnormality diagnosis routine of FIG. 4 executed by the ECU 38 in the second embodiment will be described. In this routine, if it is determined that the fuel pressure in the high-pressure fuel system is stable during execution of the high-pressure side fuel pressure F / B control, the fuel pressure F / B correction value before execution of the low-pressure pump discharge amount forced change control is calculated. Store (steps 101-103).
Thereafter, the process proceeds to step 104a, and low-pressure pump discharge amount forced change control for forcibly reducing the discharge amount of the low-pressure pump 12 by a predetermined amount is executed.

Thereafter, after storing the fuel pressure F / B correction value during execution of the low pressure pump discharge amount forced change control, the absolute value of the deviation between the fuel pressure F / B correction value before and during execution of the low pressure pump discharge amount forced change control is stored. Is calculated as the change amount of the fuel pressure F / B correction value, and it is determined whether or not the change amount of the fuel pressure F / B correction value is larger than the abnormality determination value (steps 105 to 107).
As a result, when it is determined that the change amount of the fuel pressure F / B correction value is larger than the abnormality determination value, it is determined that there is no abnormality (normal) in the low-pressure fuel system (step 108).

  On the other hand, when it is determined that the change amount of the fuel pressure F / B correction value is equal to or less than the abnormality determination value, the low pressure pump discharge amount forced change control for forcibly reducing the discharge amount of the low pressure pump 12 is executed. Nevertheless, since the change amount of the fuel pressure F / B correction value is small, it is determined that there is an abnormality in the low-pressure fuel system (for example, an abnormality in fuel pressure increase in which the fuel pressure supplied from the low-pressure pump 12 to the high-pressure pump 14 does not drop normally). (Step 109).

  In the second embodiment described above, the low-pressure pump discharge amount forced change control for forcibly reducing the discharge amount of the low-pressure pump 12 is executed during the execution of the high-pressure side fuel pressure F / B control. Since the presence or absence of abnormality of the low-pressure fuel system is determined based on the amount of change in the fuel pressure F / B correction value of the high-pressure side fuel pressure F / B control when the control is executed, the same effect as in the first embodiment is obtained. Can be obtained.

  Next, Embodiment 3 of the present invention will be described with reference to FIG. 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 third embodiment, the ECU 38 executes an abnormality diagnosis routine of FIG. 5 described later, thereby forcibly increasing the discharge amount of the low-pressure pump 12 during execution of the high-pressure side fuel pressure F / B control. When executing the change control, the discharge amount of the high-pressure pump 14 (the energization timing of the fuel pressure control valve 23) is corrected in advance in a direction to suppress the increase in the fuel pressure in the high-pressure fuel system generated by the low-pressure pump discharge amount forced change control. Fuel pressure F / F correction is executed. Here, “F / F” means “feed forward” (the same applies hereinafter).

  Further, the ECU 38 executes the fail-safe control routine of FIG. 3 described above, and when the abnormality diagnosis routine of FIG. 5 determines that there is an abnormality in the low-pressure fuel system, the ECU 38 reduces the discharge amount of the low-pressure pump 12 from the normal time. Fail-safe control is performed to reduce the discharge amount for fail-safe.

  Hereinafter, the processing content of the abnormality diagnosis routine of FIG. 5 executed by the ECU 38 in the third embodiment will be described. In this routine, if it is determined that the fuel pressure in the high-pressure fuel system is stable during execution of the high-pressure side fuel pressure F / B control, the fuel pressure F / B correction value before execution of the low-pressure pump discharge amount forced change control is calculated. Store (steps 301-303).

  Thereafter, the process proceeds to step 304, and after executing low pressure pump discharge amount forced change control for forcibly increasing the discharge amount of the low pressure pump 12 by a predetermined amount, the process proceeds to step 305 and is generated by the low pressure pump discharge amount forced change control. Fuel pressure F / F correction for correcting the discharge amount of the high-pressure pump 14 (energization timing of the fuel pressure control valve 23) in advance in a direction to suppress the increase in fuel pressure in the high-pressure fuel system is executed. In this fuel pressure F / F correction, the fuel pressure in the high-pressure fuel system is reduced (that is, the discharge amount of the high-pressure pump 14 is reduced) by the fuel pressure increase in the high-pressure fuel system generated by the low-pressure pump discharge amount forced change control. A fuel pressure F / F correction value is calculated, and the discharge amount of the high-pressure pump 14 (energization timing of the fuel pressure control valve 23) is corrected using the fuel pressure F / F correction value.

  Thereafter, the process proceeds to step 306, and after storing the fuel pressure F / B correction value during execution of the low pressure pump discharge amount forced change control, the process proceeds to step 307, where the fuel pressure F / B before execution of the low pressure pump discharge amount forced change control is executed. The absolute value of the deviation between the correction value and the fuel pressure F / B correction value during execution of the low pressure pump discharge amount forced change control is calculated as the change amount of the fuel pressure F / B correction value.

  Thereafter, the process proceeds to step 308, where it is determined whether or not the change amount of the fuel pressure F / B correction value is smaller than the abnormality determination value. If it is determined in step 308 that the change amount of the fuel pressure F / B correction value is smaller than the abnormality determination value, the process proceeds to step 309 to determine that there is no abnormality (normal) in the low-pressure fuel system.

  On the other hand, if it is determined in step 308 that the amount of change in the fuel pressure F / B correction value is greater than or equal to the abnormality determination value, the discharge amount of the low pressure pump forcibly increasing the discharge amount of the low pressure pump 12. When executing the forced change control, the fuel pressure F / F correction for correcting the discharge amount of the high pressure pump 14 in advance in a direction to suppress the increase in the fuel pressure in the high pressure fuel system generated by the low pressure pump discharge amount forced change control is executed. Nevertheless, since the change amount of the fuel pressure F / B correction value is large, the process proceeds to step 310, and the low-pressure fuel system abnormality (for example, the fuel pressure lowering abnormality in which the fuel pressure supplied from the low-pressure pump 12 to the high-pressure pump 14 does not rise normally) Judge that there is.

  In the third embodiment described above, when the low-pressure pump discharge amount forced change control for forcibly increasing the discharge amount of the low-pressure pump 12 is executed, the low-pressure pump discharge amount forced change control in the high-pressure fuel system generated by the low-pressure pump discharge amount forced change control is executed. Since the fuel pressure F / F correction for correcting the discharge amount of the high pressure pump 14 (energization timing of the fuel pressure control valve 23) in advance in the direction of suppressing the increase in the fuel pressure is executed, the high pressure fuel system by the low pressure pump discharge amount forced change control The change in the fuel pressure can be suppressed, thereby preventing the fuel injection control accuracy from being lowered and the exhaust emission from being deteriorated.

  Next, Embodiment 4 of the present invention will be described with reference to FIG. However, description of substantially the same parts as in the third embodiment will be omitted or simplified, and different parts from the third embodiment will be mainly described.

  In the fourth embodiment, the ECU 38 executes an abnormality diagnosis routine shown in FIG. 6 to be described later, thereby forcibly reducing the discharge amount of the low-pressure pump 12 during the execution of the high-pressure side fuel pressure F / B control. When the change control is executed, the discharge amount of the high-pressure pump 14 (energization timing of the fuel pressure control valve 23) is corrected in advance so as to suppress the fuel pressure drop in the high-pressure fuel system generated by the low-pressure pump discharge amount forced change control. Fuel pressure F / F correction is executed. The routine of FIG. 6 is obtained by changing the processing of steps 304 and 305 of the routine of FIG. 5 described in the third embodiment to the processing of steps 304a and 305a. The processing of other steps is the same as that of FIG. It is.

  Further, the ECU 38 executes the fail-safe control routine of FIG. 3 described above, and when it is determined by the abnormality diagnosis routine of FIG. 6 that there is an abnormality in the low-pressure fuel system, the discharge amount of the low-pressure pump 12 is increased from the normal time. Fail-safe control is performed to reduce the discharge amount for fail-safe.

  Hereinafter, the processing contents of the abnormality diagnosis routine of FIG. 6 executed by the ECU 38 in the fourth embodiment will be described. In this routine, if it is determined that the fuel pressure in the high-pressure fuel system is stable during execution of the high-pressure side fuel pressure F / B control, the fuel pressure F / B correction value before execution of the low-pressure pump discharge amount forced change control is calculated. Store (steps 301-303).

  Thereafter, the process proceeds to step 304a, and after executing low pressure pump discharge amount forced change control for forcibly reducing the discharge amount of the low pressure pump 12 by a predetermined amount, the process proceeds to step 305a and is generated by the low pressure pump discharge amount forced change control. Fuel pressure F / F correction for correcting the discharge amount of the high pressure pump 14 (energization timing of the fuel pressure control valve 23) in advance in a direction to suppress the fuel pressure drop in the high pressure fuel system is executed. In this fuel pressure F / F correction, the fuel pressure in the high-pressure fuel system is increased by the amount of fuel pressure decrease in the high-pressure fuel system generated by the low-pressure pump discharge amount forced change control (that is, the discharge amount of the high-pressure pump 14 is increased). A fuel pressure F / F correction value is calculated, and the discharge amount of the high-pressure pump 14 (energization timing of the fuel pressure control valve 23) is corrected using the fuel pressure F / F correction value.

After this, after storing the fuel pressure F / B correction value during execution of the low pressure pump discharge amount forced change control, the absolute value of the deviation of the fuel pressure F / B correction value during execution before execution of the low pressure pump discharge amount forced change control Is calculated as the change amount of the fuel pressure F / B correction value, and it is determined whether or not the change amount of the fuel pressure F / B correction value is smaller than the abnormality determination value (steps 306 to 308).
As a result, when it is determined that the change amount of the fuel pressure F / B correction value is smaller than the abnormality determination value, it is determined that there is no abnormality (normal) in the low-pressure fuel system (step 309).

  On the other hand, when it is determined that the amount of change in the fuel pressure F / B correction value is greater than or equal to the abnormality determination value, low-pressure pump discharge amount forced change control that forcibly decreases the discharge amount of the low-pressure pump 12 is executed. When performing the fuel pressure F / F correction for correcting the discharge amount of the high-pressure pump 14 in a direction to suppress the decrease in the fuel pressure in the high-pressure fuel system generated by the low-pressure pump discharge amount forced change control, Since the change amount of the fuel pressure F / B correction value is large, it is determined that there is an abnormality in the low-pressure fuel system (for example, a fuel pressure decrease abnormality in which the fuel pressure supplied from the low-pressure pump 12 to the high-pressure pump 14 does not decrease normally) (step 310).

  In the fourth embodiment described above, when the low-pressure pump discharge amount forced change control for forcibly reducing the discharge amount of the low-pressure pump 12 is executed, the low-pressure pump discharge amount forced change control generates the internal pressure of the high-pressure fuel system. Since the fuel pressure F / F correction for correcting the discharge amount of the high-pressure pump 14 (the energization timing of the fuel pressure control valve 23) in advance in the direction of suppressing the decrease in the fuel pressure is performed, substantially the same effect as the third embodiment can be obtained. Can do.

  In each of the first to fourth embodiments, the presence / absence of abnormality of the low-pressure fuel system is determined based on the fuel pressure F / B correction value of the high-pressure side fuel pressure F / B control. The presence or absence of an abnormality in the low-pressure fuel system is determined based on the control amount of the high-pressure pump 14 corrected using the fuel pressure F / B correction value of the high-pressure side fuel pressure F / B control (for example, the energization timing of the fuel pressure control valve 23). You may do it.

  Further, in each of the first to fourth embodiments, the present invention is applied to the fuel supply system of the direct injection type engine. However, the present invention is not limited to this, and if the fuel supply system includes a low pressure pump and a high pressure pump, the intake air The present invention may be applied to a fuel supply system of a port injection type engine or a dual injection type engine fuel supply system including both a fuel injection valve for intake port injection and a fuel injection valve for in-cylinder injection. .

  In addition, the present invention can be implemented with various modifications within a range not departing from the gist, such as appropriately changing the configuration of the fuel supply system.

  DESCRIPTION OF SYMBOLS 11 ... Fuel tank, 12 ... Low pressure pump, 13 ... Fuel piping, 14 ... High pressure pump, 15 ... Pressure regulator, 23 ... Fuel pressure control valve, 29 ... High pressure fuel piping, 30 ... Delivery pipe, 31 ... Fuel injection valve, 32 ... Fuel pressure sensor (fuel pressure detection means), 38 ECU (fuel pressure control means, abnormality diagnosis means, fail safe control means)

Claims (4)

The present invention is applied to a fuel supply system of an internal combustion engine that supplies fuel discharged from a low-pressure pump to a high-pressure pump and supplies fuel discharged from the high-pressure pump to a fuel injection valve. Fuel is supplied from the high-pressure pump to the fuel injection valve. A fuel pressure detecting means for detecting the pressure of the fuel in the high pressure fuel system to be supplied (hereinafter referred to as “fuel pressure”), and the high pressure pump so that the fuel pressure in the high pressure fuel system detected by the fuel pressure detecting means matches the target fuel pressure. In an abnormality diagnosis device for a fuel supply system of an internal combustion engine, comprising a fuel pressure control means for executing high pressure side fuel pressure feedback control for feedback control,
During the execution of the high pressure side fuel pressure feedback control, the low pressure pump discharge amount forced change control for forcibly changing the discharge amount of the low pressure pump is executed, and the high pressure side fuel pressure when the low pressure pump discharge amount forced change control is executed A fuel supply system for an internal combustion engine, comprising: an abnormality diagnosing unit that determines whether there is an abnormality in a low-pressure fuel system that supplies fuel from the low-pressure pump to the high-pressure pump based on a control state of feedback control Abnormality diagnosis device.   2. The fuel supply system abnormality of the internal combustion engine according to claim 1, wherein the abnormality diagnosis unit forcibly increases or decreases a discharge amount of the low-pressure pump during the low-pressure pump discharge amount forced change control. Diagnostic device.   2. The abnormality diagnosing means includes means for correcting a control amount of the high pressure pump in advance in a direction to suppress a change in fuel pressure in the high pressure fuel system generated by the forced change control of the low pressure pump discharge amount. Or the abnormality diagnosis apparatus of the fuel supply system of the internal combustion engine of 2.   The fail-safe control means for reducing the discharge amount of the low-pressure pump as compared with the normal time when the abnormality diagnosis means determines that there is an abnormality in the low-pressure fuel system. An abnormality diagnosis device for a fuel supply system of an internal combustion engine according to any one of the above.

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