JP2010053741A - Diagnostic device of fuel supply system of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a diagnostic device avoiding or restraining the continuation of operation in a failure state, by highly accurately diagnosing abnormality of fuel pressure due to a failure of a fuel supply system. <P>SOLUTION: When an air-fuel ratio feedback correction factor sticks to a lower limit value, the air-fuel ratio is a rich tendency and an electric current of a fuel pump is higher than usual, a closing fixation of a pressure regulator for adjusting the fuel pressure is presumed. When the closing fixation is presumed in traveling, the operation is continued by reducing impression voltage in the fuel pump, and when a key switch is turned off once, restarting of an internal combustion engine is prohibited. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a diagnostic apparatus that determines whether there is an abnormality in a fuel supply system that pumps fuel by a fuel pump to a fuel injection device of an internal combustion engine.

In Patent Document 1, in a fuel supply system that feedback-controls the drive voltage of a fuel pump so that the fuel pressure detected by a fuel pressure sensor is maintained at a predetermined pressure, a required fuel amount of the internal combustion engine and a feedback correction value of the drive voltage are disclosed. Based on the above, it is disclosed to detect an abnormality in the fuel supply path.
JP 2006-161675 A

By the way, as a fuel supply system using a fuel pump, a mechanical pressure regulator is provided in the middle of the piping, and when the fuel pressure exceeds a set pressure, the pressure regulator opens to relieve the fuel in the fuel piping. Thus, there is a system for keeping the fuel pressure at the set pressure.
In the above system, for example, if the pressure regulator is stuck in the closed state and does not open even if the fuel pressure exceeds the set pressure, the adjustment of the fuel pressure becomes impossible and the fuel pressure rises abnormally. End up.

However, a relief valve that relieves the fuel in the fuel pipe when the fuel pressure becomes abnormal is generally provided separately from the pressure regulator. Therefore, if the pressure regulator is stuck in the closed state, the pressure regulator The fuel pressure is maintained at the valve opening pressure of the relief valve that is higher than the valve opening pressure of the regulator.
At this time, although the fuel pressure becomes higher than the target pressure and the amount of fuel injected from the fuel injection valve per unit time increases, the injection amount is decreased and corrected by air-fuel ratio feedback control. Since the richness is prevented, the drivability does not change greatly, and the operation may continue as it is.

In such a case, the fuel pressure in the fuel pipe is higher than the target pressure during normal operation. Therefore, fuel leaks from the joints of the fuel pipe and the load on the fuel pump increases, causing the fuel pump to overheat. However, there is a possibility that problems such as failure of the fuel pump may occur.
The present invention has been made in view of the above problems, and provides a diagnostic device capable of accurately diagnosing an abnormality in fuel pressure due to a failure in a fuel supply system, and thus avoiding or suppressing continuation of operation in a failure state. The purpose is to provide.

  Therefore, in the present invention, the presence or absence of abnormality in the fuel supply system is determined from the control state of the fuel pump and the air-fuel ratio control state in the internal combustion engine.

According to the above invention, the air-fuel ratio control state in the internal combustion engine, in other words, whether the base air-fuel ratio of the internal combustion engine tends to be rich or lean, and simultaneously detects the control state of the fuel pump, thereby The level of fuel pressure can be estimated.
For this reason, even if the actual air-fuel ratio is controlled so as not to impair the drivability, it is determined whether or not the deviation in the base air-fuel ratio is due to an abnormality in the fuel supply system. It is possible to accurately diagnose abnormality in the fuel supply system.

Embodiments of the present invention will be described below.
FIG. 1 is a system diagram showing a fuel supply system of an internal combustion engine for a vehicle in a first embodiment of the present invention.
In FIG. 1, a fuel injection valve 1 is a fuel injection device installed in an intake port of each cylinder of an internal combustion engine 2 mounted on a vehicle, and the internal combustion engine 2 is a port injection internal combustion engine.

Each fuel injection valve 1 is connected to a fuel gallery pipe 3, and supplies the fuel in the fuel gallery pipe 3 to the internal combustion engine 2.
The fuel gallery pipe 3 is connected to the other end of the fuel pipe 5 whose one end is connected to the discharge port of the fuel pump 4.
The fuel pump 4 is fixed inside the fuel tank 10 that stores the fuel of the internal combustion engine 2, sucks the fuel in the fuel tank 10 from the suction port 4 a, and faces the fuel gallery pipe 3 (fuel injection valve 1). Pump.

The fuel filter 6 is provided so as to cover the suction port 4a of the fuel pump 4, so that the fuel pump 4 does not suck in dust or the like mixed in the fuel.
As described above, one end of the fuel pipe 5 is connected to the discharge port of the fuel pump 4 and extends through the upper wall of the fuel tank 10 to the fuel gallery pipe 3. One end of a return pipe 7 is connected to the portion of the fuel pipe 5 that is disposed, and the other end of the return pipe 7 is opened in the fuel tank 10.

A pressure regulator 8 for opening and closing the return pipe 7 is interposed in the middle of the return pipe 7.
When the pressure of the fuel in the fuel pipe 5 exceeds a set pressure (target pressure) (when the pressure difference between the fuel pressure in the fuel pipe 5 and the reference pressure exceeds the set pressure), the pressure regulator 8 ) When the pressure of the fuel in the fuel pipe 5 is equal to or lower than a set pressure (target pressure) (when the pressure difference between the fuel pressure in the fuel pipe 5 and the reference pressure is equal to or lower than the set pressure). ) Is a mechanical valve mechanism that maintains the closed state.

When the pressure regulator 8 is opened and the fuel in the fuel pipe 5 is relieved into the fuel tank 10, the fuel pressure in the fuel pipe 5 decreases.
Therefore, when the pressure of the fuel in the fuel pipe 5 exceeds a set pressure (when the differential pressure between the fuel pressure in the fuel pipe 5 and the reference pressure exceeds a threshold value), the pressure regulator 8 is opened. Thus, the fuel pressure in the fuel pipe 5 is prevented from exceeding the set pressure, and as a result, the fuel pressure in the fuel pipe 5 (fuel supply pressure to the fuel injection valve 1) is It will be held near the set pressure.

As a result, the fuel injection amount per unit valve opening time of the fuel injection valve 1 is maintained at a constant value, and the fuel injection valve 1 injects an amount of fuel proportional to the valve opening time.
Further, when the pressure in the fuel pipe 5 exceeds an allowable maximum pressure higher than the set pressure (target pressure) in the pressure regulator 8, the fuel in the fuel pipe 5 is relieved into the fuel tank 10. A relief valve 9 is provided at a portion of the fuel pipe 5 provided in the fuel tank 10.

The relief valve 9 can be installed in the fuel pump 4.
The set pressure (target pressure) in the pressure regulator 8 is about 350 kPa, for example, and the valve opening pressure of the relief valve 9 is set to about 700 kPa, for example.
If the pressure regulator 8 is fixed in a closed state, for example, and the pressure of the fuel in the fuel pipe 5 exceeds the set pressure, and the pressure regulator 8 does not open, the fuel pressure exceeds the set pressure.

However, when the relief valve 9 operates normally, if the fuel pressure in the fuel pipe 5 exceeds the allowable maximum pressure, the relief valve 9 opens and the fuel is relieved. The pressure is prevented from rising beyond the maximum allowable pressure.
Detection signals from various sensors are input to an electronic control unit (ECU) 11 that controls fuel injection by the fuel injection valve 1, and a valve opening drive pulse signal that is output to the fuel injection valve 1 based on the detection signals. The pulse width (injection time, fuel injection amount) is calculated.

The various sensors include an air flow sensor 12 that detects the intake air flow rate QA of the internal combustion engine 2, a crank angle sensor 13 that outputs a pulse signal CA corresponding to the rotation of the crankshaft of the internal combustion engine 2, and an exhaust pipe in the internal combustion engine 2. An air-fuel ratio sensor 14 that outputs an air-fuel ratio signal AF based on the oxygen concentration is provided.
The electronic control unit 11 determines the basic injection pulse width (basic fuel injection) from the intake air flow rate QA detected by the air flow sensor 12 and the engine speed NE calculated based on the pulse signal CA from the crank angle sensor 13. Amount) TP (TP = K * QA / NE: K is a constant) is calculated.

In addition, the electronic control unit 11 uses an air-fuel ratio feedback correction coefficient KAF for correcting the basic injection pulse width TP as an actual air-fuel ratio detected by the air-fuel ratio sensor 14 and a target air-fuel ratio (for example, a theoretical air-fuel ratio). ) And proportional / integral / differential action based on the deviation.
By correcting the basic injection pulse width TP with the air / fuel ratio feedback correction coefficient KAF (air / fuel ratio correction value), air / fuel ratio feedback control is performed to bring the actual air / fuel ratio of the internal combustion engine 2 closer to the target air / fuel ratio.

The electronic control unit 11 corrects the basic injection pulse width TP with the air-fuel ratio feedback correction coefficient KAF or the like to determine a final fuel injection pulse width (fuel injection amount) TI.
Then, the valve opening drive pulse signal having the pulse width TI is output to each fuel injection valve 1 in accordance with the intake stroke of each cylinder.

The fuel pump 4 is an electric pump that rotationally drives the pump with a motor, and operates using the battery VB as a power source.
The battery VB is connected to the fuel pump 4 (motor) via a power supply relay 21 and a drive circuit 22 built in the electronic control unit 11, and further detects a drive current of the fuel pump 4 (motor). A current detection circuit 23 is provided in the electronic control unit 11.

The electronic control unit 11 includes a microcomputer (CPU) 24, and the microcomputer (CPU) 24 outputs a control signal to the drive circuit 22, and a duty ratio for energization control of the fuel pump 4 by the drive circuit 22. The applied voltage to the fuel pump 4 is controlled by adjusting the (on-time ratio).
Furthermore, information on the drive current value detected by the current detection circuit 23 is input to the microcomputer (CPU) 24.

The electronic control unit 11 has an arithmetic processing function for diagnosing the presence or absence of an abnormality in the fuel supply system including the fuel pump 4, the pressure regulator 8, the fuel pipe 5, and the like.
The routine shown in the flowcharts of FIGS. 2 and 3 shows the abnormality diagnosis process.

Note that the abnormality diagnosis process described below is executed on the assumption that there is no abnormality in various sensors such as the current detection circuit 23 and the airflow sensor 12.
In step S101, the energization control to the fuel pump 4 is normally performed.
The normal energization control is, for example, a process of determining the on-duty of the fuel pump 4 (motor) according to the engine load TP and the engine speed NE, in other words, according to the fuel consumption of the internal combustion engine 2. In this process, the applied voltage (discharge amount) of the fuel pump 4 is controlled.

However, a constant voltage can be applied to the fuel pump 4.
In step S102, the air-fuel ratio feedback correction coefficient KAF (air-fuel ratio correction value) is stuck to the upper limit value (increase determination criterion) (KAF = upper limit value) or the lower limit value (increase determination criterion). Whether the value is within the variable range between the upper limit value and the lower limit value (lower limit value <KAF <upper limit value).

The initial value of the air-fuel ratio feedback correction coefficient KAF (air-fuel ratio correction value) is 1.0, the fuel injection amount (injection pulse width) is increased and corrected when KAF> 1.0, and the fuel injection is performed when KAF <1.0. The amount (injection pulse width) is corrected to decrease.
Accordingly, if the actual air-fuel ratio is leaner than the target air-fuel ratio, the air-fuel ratio is corrected by increasing the air-fuel ratio feedback correction coefficient KAF (air-fuel ratio correction value) above 1.0 to increase the fuel injection amount. If the actual air-fuel ratio is richer than the target air-fuel ratio, the fuel injection amount is corrected to decrease by reducing the air-fuel ratio feedback correction coefficient KAF (air-fuel ratio correction value) below 1.0. To make the air-fuel ratio lean.

The upper limit value is a value that defines the upper limit of the variable range of the air-fuel ratio feedback correction coefficient KAF (air-fuel ratio correction value). Even if the actual air-fuel ratio is leaner than the target, the air-fuel ratio feedback correction is performed. The coefficient KAF does not exceed the upper limit value.
The lower limit value is a value that defines the lower limit of the variable range of the air-fuel ratio feedback correction coefficient KAF (air-fuel ratio correction value), and even if the actual air-fuel ratio is richer than the target, the air-fuel ratio feedback correction is performed. The coefficient KAF is limited not to be set to a value lower than the lower limit value, and the air-fuel ratio feedback correction coefficient KAF (air-fuel ratio correction value) is changed within a variable range including an initial value sandwiched between the upper limit value and the lower limit value. The

  Here, in the determination of step S102, instead of determining whether or not the air-fuel ratio feedback correction coefficient KAF (air-fuel ratio correction value) is stuck to the upper and lower limit values, the air-fuel ratio feedback correction coefficient KAF (air-fuel ratio) (Correction value) is configured to determine whether the increase threshold (> 1.0) is exceeded or less than the decrease threshold (<1.0), and the increase threshold is smaller than the upper limit. And the decrease side threshold value can be set to a value larger than the lower limit value.

  However, the upper and lower limit values and the increase / decrease side threshold (increase side determination criterion / decrease side determination criterion) are the variation of the adjustment pressure by the pressure regulator 8, the injection amount variation of the fuel injection valve 1, and the air flow sensor 12. When the air-fuel ratio variation caused by detection variation is absorbed, the air-fuel ratio feedback correction coefficient KAF (air-fuel ratio correction value) is not reached, and the fuel supply system, the fuel injection valve 1 and the injection amount calculation When an abnormality occurs in various sensors used for the air-fuel ratio, and an air-fuel ratio change exceeding the normal variation range occurs, the air-fuel ratio feedback correction coefficient KAF (air-fuel ratio correction value) is set to a value that can be reached. To do.

  The value of the air-fuel ratio feedback correction coefficient KAF is learned as an air-fuel ratio learning correction value for each engine operating region, and the injection pulse width is corrected with the air-fuel ratio learning correction value and the air-fuel ratio feedback correction coefficient KAF. When it is possible to perform correction near the target air-fuel ratio without correction by the air-fuel ratio feedback correction coefficient KAF, a correction level that combines the air-fuel ratio learning correction value or the air-fuel ratio feedback correction coefficient KAF and the air-fuel ratio learning correction value is Then, it is determined whether or not the threshold value is exceeded.

In step S102, the air-fuel ratio feedback correction coefficient KAF (air-fuel ratio correction value) is a value within a variable region sandwiched between an upper limit value and a lower limit value (or within a normal region sandwiched between increase / decrease side thresholds). If it is determined that there is no abnormality, it is determined that there is no abnormality in the fuel supply system, the process proceeds to step S103, and the normal control of the fuel pump 4 is continued as it is.
On the other hand, when it is determined that the air-fuel ratio feedback correction coefficient KAF (air-fuel ratio correction value) is stuck to the lower limit value (below the reduction-side threshold value), that is, when the reduction correction state exceeds the criterion. The process proceeds to step S104.

When the state where the air-fuel ratio feedback correction coefficient KAF (air-fuel ratio correction value) is stuck to the lower limit value (below the decrease side threshold value) continues for the reference time or longer, the process proceeds to step S104. Thus, a temporary change in the air-fuel ratio feedback correction coefficient KAF (air-fuel ratio correction value) can be prevented from being determined as an abnormality in the fuel supply system.
In step S104, it is determined whether the current (pump load) of the fuel pump 4 is higher than the maximum current determination value.

The maximum current judgment value is based on the current at the maximum fuel pressure PMAX when the fuel pressure is adjusted by the pressure regulator 8 in consideration of variations in pressure regulation of the pressure regulator 8 and variations in fuel pipe pressure loss. And the higher the power supply voltage of the fuel pump 4, that is, the battery voltage, the higher the value is set (see FIG. 4).
In FIG. 4, the pressure regulator 8 adjusts the maximum fuel pressure when the intersection γ1 between the vertical line α1 passing through the maximum fuel pressure PMAX and the straight line β rising to 12V is a power supply voltage of 12V. In this case, the maximum current determination value SLMAX is shown. As the power supply voltage of the fuel pump 4 is higher, the straight line β moves in parallel to the side where the current increases, and the maximum current determination value SLMAX also increases.

In other words, when the fuel pressure is normally adjusted by the pressure regulator 8, the current of the fuel pump 4 does not exceed the maximum current determination value SLMAX, and the current of the fuel pump 4 (pump load) is the maximum current. When the determination value SLMAX (maximum value) is exceeded, it can be estimated that the fuel pressure is higher than the normal range.
Therefore, if it is determined in step S104 that the current (pump load) of the fuel pump 4 at that time exceeds the maximum current determination value SLMAX, the fuel pressure exceeds the set pressure of the pressure regulator 8 and is abnormally high. It is estimated that

That is, an abnormal state in which the fuel pressure is abnormally high can be detected without directly detecting the fuel pressure with the fuel pressure sensor.
In addition, since it is determined in step S102 that the air-fuel ratio tends to be enriched earlier, the fuel pressure has increased due to the failure of the pressure regulator 8 to be closed, so that the fuel injection valve 1 per unit time It is estimated that the injection amount is larger than when the pressure regulator 8 is normal.

  On the other hand, if it is determined in step S104 that the current (pump load) of the fuel pump 4 at that time is equal to or less than the maximum current determination value SLMAX, the air-fuel ratio tends to become rich, but the pressure regulator 8 Since it is determined that there is no abnormality in at least the fuel supply system because the pressure has been adjusted to the normal pressure, the process proceeds to step S105, and the normal control of the fuel pump 4 is continued as it is.

If it is determined in step S104 that the current (pump load) of the fuel pump 4 at that time exceeds the maximum current determination value SLMAX, the process proceeds to step S106, and the fuel supply system (pressure regulator 8) is abnormal (abnormal). The warning lamp 31 is lit to warn the vehicle driver of the high pressure state.
As a result, the driver can know that an abnormality has occurred in the fuel supply system, can recognize the cause when a fail-safe process is performed after that, and can take measures such as stopping the vehicle. Will be able to.

Further, in the next step S107, it is determined based on the vehicle speed VSP detected by the vehicle speed sensor 32 whether or not the vehicle is traveling.
When the vehicle speed VSP is approximately 0 km / h and the vehicle is stopped (when the vehicle is in a fast idle state after the internal combustion engine 2 is started), the process proceeds to step S108, and a control signal for controlling energization of the fuel pump 4 is displayed. The duty ratio is set to zero, the power supply (voltage application) to the fuel pump 4 is forcibly cut off, and the operation of the fuel pump 4 is stopped.

When the operation of the fuel pump 4 is stopped, the fuel pressure is reduced to a set pressure or lower, and even if the fuel injection valve 1 is opened, fuel corresponding to the intake air amount cannot be injected, and normal Since the ignition combustion cannot be performed, the internal combustion engine 2 is stopped.
Here, the power supply (voltage application) to the fuel pump 4 can be forcibly cut off, and at the same time, the valve opening drive and ignition of the fuel injection valve 1 can be forcibly stopped.

Furthermore, in the next step S109, the restart (fuel injection / ignition) of the internal combustion engine 2 is prohibited.
The restart prohibition measure is preferably not released until some maintenance is performed, and the restart prohibition device is released by inputting an external release signal to the electronic control unit 11 or the like. Can be made.

As described above, when the operation of the fuel pump 4 is stopped and the internal combustion engine 2 is stopped, it is possible to prevent the fuel pump 4 from being continuously driven while the pressure in the fuel pipe is excessively high. Further, it is possible to avoid or suppress the fuel leakage from the joint portion of the fuel pipe, the overheating of the fuel pump and the like.
Since the fuel supply system of the present embodiment is provided with the relief valve 9, even if the pressure regulator 8 does not open (is stuck closed), the fuel pressure rises above the opening pressure of the relief valve 9. However, as described above, if it is determined that the fuel pressure is higher than that during the pressure regulation by the pressure regulator 8 and the operation of the fuel pump 4 is stopped, the fuel pump 4 is kept at a high fuel pressure. It is possible to prevent the drive from continuing.

On the other hand, if the power supply to the fuel pump 4 is cut off and the internal combustion engine 2 is forcibly stopped while the vehicle is running (after starting to run the vehicle from the fast idle state), it is contrary to the driver's driving intention. Since it will move, it is not preferable.
Therefore, if it is determined in step S107 that the vehicle speed VSP is not zero and the vehicle is running (after starting to run the vehicle from the fast idle state), the process proceeds to step S110 to apply the fuel pump 4 By executing the process of forcibly reducing the voltage, the fuel pressure is reduced while the operation of the internal combustion engine 2 is continued.

In step S111, after the key switch is turned off, a setting for prohibiting restart of the internal combustion engine 2 is performed.
This restart prohibition measure is preferably not released until some maintenance is performed.
Therefore, if a failure occurs in the pressure regulator 8 after running the vehicle, the operation of the internal combustion engine 2 is continued while the process for forcibly reducing the voltage applied to the fuel pump 4 is executed, and the vehicle is stopped. When the key switch is turned off, restart is prohibited, and re-running with the pressure regulator 8 in a failed state is avoided.

  The applied voltage lowering process in step S110 may be a process of reducing the duty ratio of the control signal for controlling the energization of the fuel pump 4 by a constant value or a fixed ratio, or the air-fuel ratio feedback correction coefficient KAF ( Processing for feedback control of the duty ratio of the control signal for controlling the energization of the fuel pump 4 may be performed so that the air-fuel ratio correction value approaches the initial value.

  Further, when it is determined that the fuel supply system (pressure regulator 8) is abnormal while the vehicle is stopped (fast idle state), the internal combustion engine 2 is controlled by forcibly reducing the voltage applied to the fuel pump 4. Alternatively, the fuel pump 4 may be driven at a duty ratio (voltage) lower than normal from the start of the operation of the fuel pump 4, instead of not prohibiting the restart. can do.

  Furthermore, when the applied voltage of the fuel pump 4 is lowered, it is possible to limit the load (intake air amount) of the internal combustion engine 2 at the same time. Specifically, in an engine equipped with an electronically controlled throttle that opens and closes a throttle valve with a motor, the maximum opening of the electronically controlled throttle is set smaller than usual, and the throttle opening is changed only in a low opening range. To.

The above processing is performed when it is determined in step S102 that the air-fuel ratio feedback correction coefficient KAF (air-fuel ratio correction value) is stuck to the lower limit value (below the decrease-side threshold value). This is processing when the fuel ratio tends to be rich.
If it is determined in step S102 that the air-fuel ratio feedback correction coefficient KAF (air-fuel ratio correction value) is stuck to the upper limit (exceeding the increase side threshold) and the base air-fuel ratio is a lean air-fuel ratio, When the increase correction state exceeds the determination criterion, the process proceeds to step S112.

When the state where the air-fuel ratio feedback correction coefficient KAF (air-fuel ratio correction value) is stuck to the upper limit (exceeding the increase side threshold) continues for the reference time or longer, the process proceeds to step S112. Thus, a temporary increase in the air-fuel ratio feedback correction coefficient KAF (air-fuel ratio correction value) can be prevented from being determined as an abnormality in the fuel supply system.
In step S112, it is determined whether the current (pump load) of the fuel pump 4 is lower than the minimum current determination value.

The minimum current judgment value is based on the current at the minimum fuel pressure PMIN when the fuel pressure is adjusted by the pressure regulator 8 in consideration of variations in pressure regulation of the pressure regulator 8 and variations in fuel pipe pressure loss. And the higher the power supply voltage of the fuel pump 4, that is, the battery voltage, the higher the value is set (see FIG. 4).
In FIG. 4, when the intersection γ2 between the vertical line α2 passing through the minimum fuel pressure PMIN and the straight line β rising to 12V is a power supply voltage of 12V, the pressure regulator 8 regulates the minimum fuel pressure. Current level, that is, the minimum current judgment value SLMIN, and the higher the power supply voltage of the fuel pump 4, the more the straight line β moves in parallel to the higher current.

In other words, when the fuel pressure is normally adjusted by the pressure regulator 8, the current of the fuel pump 4 does not fall below the minimum current determination value SLMIN, and the current of the fuel pump 4 does not exceed the minimum current determination value SLMIN. When it is lower, it can be estimated that the fuel pressure is lower than the normal range.
That is, when the pressure regulator 8 is normally regulated, the current (pump load) of the fuel pump 4 changes between the maximum current determination value SLMAX and the minimum current determination value SLMIN, and the fuel pump 4 is out of the region sandwiched between the maximum current determination value SLMAX and the minimum current determination value SLMIN, the pressure regulator 8 is not normally regulating, and the fuel pressure is normal (the pressure regulator 8 Therefore, if it is determined in step S112 that the current (pump load) of the fuel pump 4 is lower than the minimum current determination value SLMIN, the fuel pressure is It is estimated that the air / fuel ratio is abnormally low, and it is determined that the air-fuel ratio tends to become leaner in the determination in step S102. Therefore, the fuel injection pressure per unit valve opening time of the fuel injection valve 1 is smaller than normal because the fuel pressure is lowered due to fuel leakage due to breakage of the fuel piping or the pressure regulator 8 open fixing failure. Presumed.

As described above, it is possible to detect an abnormal state in which the fuel pressure is abnormally low without directly detecting the fuel pressure with the fuel pressure sensor, and furthermore, the occurrence of fuel leakage is estimated because the air-fuel ratio is leaner. it can.
On the other hand, if it is determined in step S112 that the current (pump load) of the fuel pump 4 is equal to or greater than the minimum current determination value SLMIN (SLMAX ≧ pump current ≧ SLMIN), the air-fuel ratio tends to become leaner. However, it is determined that there is no abnormality in at least the fuel supply system (pressure regulator 8) because the pressure is regulated to normal pressure by the pressure regulator 8, and the routine proceeds to step S113, where the normal control of the fuel pump 4 is performed. Continue as it is.

If it is determined in step S112 that the current (pump load) of the fuel pump 4 at that time is below the minimum current determination value SLMIN, the process proceeds to step S114, where the fuel supply system is abnormal (low-pressure abnormality / leakage occurrence). The warning lamp 31 is turned on to warn the driver of the vehicle.
Further, in the next step S115, it is determined based on the vehicle speed VSP detected by the vehicle speed sensor 32 whether or not the vehicle is traveling.

When the vehicle speed VSP is approximately 0 km / h and the vehicle is stopped (when the vehicle is in a fast idle state after the internal combustion engine 2 is started), the process proceeds to step S116, and a control signal for controlling energization of the fuel pump 4 is displayed. The duty ratio is set to zero, the power supply (voltage application) to the fuel pump 4 is forcibly cut off, and the operation of the fuel pump 4 is stopped.
When the operation of the fuel pump 4 stops, the fuel pressure further decreases, and even if the fuel injection valve 1 is opened, fuel corresponding to the intake air amount cannot be injected, and normal ignition combustion cannot be performed. Therefore, the internal combustion engine 2 is stopped.

Here, the power supply (voltage application) to the fuel pump 4 can be forcibly cut off, and at the same time, the valve opening drive and ignition of the fuel injection valve 1 can be forcibly stopped.
Further, in the next step S117, restart (fuel injection / ignition) of the internal combustion engine 2 is prohibited.
The restart prohibition measure is preferably not released until some maintenance is performed, and the restart prohibition device is released by inputting an external release signal to the electronic control unit 11 or the like. Can be made.

As described above, if the operation of the fuel pump 4 is stopped and the internal combustion engine 2 is stopped, the operation of the internal combustion engine 2 is continued in a state where fuel leakage from the fuel pipe is occurring. Can be prevented.
On the other hand, if it is determined in step S115 that the vehicle speed VSP is not zero and the vehicle is traveling (after starting to travel the vehicle from the fast idle state), the process proceeds to step S118 to Then, voice guidance or a warning message for prompting to stop the vehicle and stop the internal combustion engine 2 (turn off the key switch) is performed.

In the next step S119, the operation is performed by forcibly stopping the internal combustion engine 2 when the operation of the internal combustion engine 2 is continued when a certain time has elapsed from the warning of the operation stop. Prevent the driver from continuing the operation without performing the operation in accordance with the warning.
Further, in step S120, a setting for prohibiting restart of the internal combustion engine 2 is performed.

This restart prohibition measure is preferably not released until some maintenance is performed.
In the above embodiment, the pressure regulator 8 is disposed in the fuel tank 10 as shown in FIG. 1, but as shown in FIG. 5, the fuel is introduced into the fuel tank 10 from the downstream side of the fuel gallery pipe 3. A return pipe 41 is provided, and a pressure regulator 42 can be interposed in the middle of the return pipe 41 and outside the fuel tank 10.

As shown in FIG. 5, the abnormality diagnosis process shown in the flowcharts of FIGS. 2 and 3 can be applied to the fuel supply system in which the pressure regulator 42 is disposed outside the fuel tank 10 as it is.
Next, an embodiment for a fuel supply system that supplies fuel to an in-cylinder direct injection internal combustion engine in which the fuel injection valve directly injects fuel into the combustion chamber (in-cylinder) of the internal combustion engine will be described.

FIG. 6 is a view showing a fuel supply system in a direct injection type internal combustion engine.
The fuel injection valve 51 is a fuel injection device installed so as to inject fuel directly into the combustion chamber (inside the cylinder) of each cylinder of the in-cylinder direct injection internal combustion engine 52.
Each fuel injection valve 51 is connected to a fuel gallery pipe 53 and directly injects high-pressure fuel in the fuel gallery pipe 53 into each combustion chamber (cylinder) of the internal combustion engine 52.

The fuel gallery pipe 53 is supplied with fuel pressurized by a high-pressure pump (engine-driven fuel pump) 54 via a high-pressure fuel pipe 55.
The high-pressure pump 54 is an engine-driven plunger pump that pressurizes and discharges fuel by a piston 54 a that reciprocates by a cam 54 b provided on a cam shaft of the internal combustion engine 52.

The high-pressure pump 54 is supplied with fuel discharged from a low-pressure pump (electric fuel pump) 56 through a low-pressure fuel pipe 57.
The suction port 54c of the high-pressure pump 54 is provided with an electromagnetic valve 58 for opening and closing the suction port 54c. By controlling the opening period of the solenoid valve 58 variably, the discharge pressure of the high-pressure pump 54 is controlled. It can be controlled.

The low-pressure pump 56 is an electric pump, and is fixed inside a fuel tank 59 that stores the fuel of the internal combustion engine 52. The fuel in the fuel tank 59 is sucked from the suction port 56a and is pumped toward the high-pressure pump 54. To do.
The fuel filter 56b is provided so as to cover the suction port 56a of the low-pressure pump 56, so that the low-pressure pump 56 does not suck in dust or the like mixed in the fuel.

One end of the low-pressure fuel pipe 57 is connected to the discharge port of the low-pressure pump 56 and extends through the upper wall of the fuel tank 59 to the high-pressure pump 58, but the low-pressure fuel pipe 57 is disposed in the fuel tank 59. One end of a return pipe 60 is connected to the fuel pipe 57, and the other end of the return pipe 60 is opened in the fuel tank 59.
Further, a pressure regulator 61 for opening and closing the return pipe 60 is interposed in the middle of the return pipe 60.

The pressure regulator 61 opens when the fuel pressure in the low-pressure fuel pipe 57 (low-pressure system) exceeds a set pressure (target pressure), and the fuel pressure in the low-pressure fuel pipe 57 is set to a set pressure ( This is a mechanical valve mechanism that holds the valve closed state when the pressure is equal to or lower than the target pressure.
When the pressure regulator 61 is opened and the fuel in the low-pressure fuel pipe 57 is relieved in the fuel tank 59, the fuel pressure in the low-pressure fuel pipe 57 decreases.

Therefore, when the pressure of the fuel in the low-pressure fuel pipe 57 exceeds the set pressure, the pressure regulator 61 is opened to prevent the fuel pressure in the low-pressure fuel pipe 57 from exceeding the set pressure. As a result, the pressure of the fuel in the low-pressure fuel pipe 57 is maintained near the set pressure.
As a result, a constant pressure of fuel can be supplied to the high-pressure pump 58, and the discharge period of the high-pressure pump 58, that is, the supply of fuel to the fuel injection valve 51 is controlled by variably controlling the open period of the electromagnetic valve 58. The pressure can be controlled with high accuracy.

Further, when the pressure in the low-pressure fuel pipe 57 exceeds the allowable maximum pressure higher than the set pressure (target pressure) in the pressure regulator 61, the valve is opened, and the fuel in the low-pressure fuel pipe 57 is fed into the fuel tank 59. A relief valve 62 for relief is provided at a portion of the low-pressure fuel pipe 57 disposed in the fuel tank 59.
The relief valve 62 can be installed in the fuel pump 56.

  A high-pressure relief pipe 63 that connects the downstream side of the fuel gallery pipe 53 and the inside of the fuel tank 59 is provided, and the pressure in the fuel gallery pipe 53 (high-pressure system) is provided in the middle of the high-pressure relief pipe 63. Is provided with a high-pressure relief valve 64 that opens when the pressure exceeds a limit pressure (allowable maximum pressure of the high-pressure system) higher than the target supply pressure of fuel to the fuel injection valve 51.

Detection signals from various sensors are input to an electronic control unit (ECU) 71 that controls fuel injection by the fuel injection valve 51, and a valve opening drive pulse signal that is output to the fuel injection valve 51 based on the detection signals. The pulse width (fuel injection amount) is calculated.
The various sensors include an air flow sensor 72 that detects the intake air flow rate QA of the internal combustion engine 52, a crank angle sensor 73 that outputs a pulse signal CA corresponding to the rotation of the crankshaft of the internal combustion engine 52, and an exhaust pipe of the internal combustion engine 52. An air-fuel ratio sensor 74 that outputs an air-fuel ratio signal AF based on the oxygen concentration, a pressure sensor 75 that detects the fuel pressure in the fuel gallery pipe 53, and the like are provided.

The electronic control unit 71 calculates the basic injection pulse width TP (TP) from the intake air flow rate QA detected by the airflow sensor 72 and the engine rotational speed NE calculated based on the pulse signal CA from the crank angle sensor 73. = K * QA / NE: K is a constant).
Further, the electronic control unit 71 sets an air-fuel ratio feedback correction coefficient KAF for correcting the basic injection pulse width TP, an actual air-fuel ratio detected by the air-fuel ratio sensor 74, and a target air-fuel ratio (for example, theoretical air-fuel ratio). Set by proportional / integral / derivative operation based on deviation from (fuel ratio).

By correcting the basic injection pulse width TP with the air-fuel ratio feedback correction coefficient KAF (air-fuel ratio correction value), air-fuel ratio feedback control is performed to bring the actual air-fuel ratio of the internal combustion engine 52 closer to the target air-fuel ratio.
The electronic control unit 71 corrects the basic injection pulse width TP with the air-fuel ratio feedback correction coefficient KAF or the like to determine a final fuel injection pulse width TI.

Then, the valve opening drive pulse signal having the pulse width TI is output to each fuel injection valve 1 in accordance with the intake stroke or compression stroke of each cylinder.
The low-pressure pump 56 is an electric pump that rotationally drives the pump with a motor, and operates using the battery VB as a power source.
The battery VB is connected to the low-pressure pump 56 (motor) via a power supply relay 81 and a drive circuit 82 built in the electronic control unit 71, and further detects the drive current of the low-pressure pump 56 (motor). A current detection circuit 83 is provided in the electronic control unit 71.

The electronic control unit 71 includes a microcomputer (CPU) 84, and the microcomputer (CPU) 84 outputs a control signal to the drive circuit 82, and the drive circuit 82 uses the duty ratio (on time) of the low-pressure pump 56. The voltage applied to the low-pressure pump 56 is controlled by adjusting the ratio.
Furthermore, information on the drive current value detected by the current detection circuit 83 is input to the microcomputer (CPU) 84.

The electronic control unit 71 (microcomputer 84) receives the output of the pressure sensor 75, and the fuel pressure in the fuel gallery pipe 53 detected by the pressure sensor 75 approaches the set pressure (target pressure). In addition, the open period of the electromagnetic valve 58 is feedback-controlled.
The electronic control unit 11 has an arithmetic processing function for diagnosing the presence or absence of abnormality in the fuel supply system including the low pressure pump 56, the pressure regulator 61, the low pressure fuel pipe 57, and the electromagnetic valve 58.

The routines shown in the flowcharts of FIGS. 7 to 9 show processing for abnormality diagnosis in the fuel supply system of the direct injection type internal combustion engine 52 shown in FIG.
In step S201, power supply control to the low pressure pump 56 is normally performed.
The normal energization control is, for example, a process of determining the on-duty of the low-pressure pump 56 (motor) according to the engine load TP and the engine speed NE, in other words, according to the fuel consumption of the internal combustion engine 52. In this process, the applied voltage (discharge amount) of the low-pressure pump 56 is controlled.

However, it can be configured to apply a constant voltage to the low-pressure pump 56.
In step S202, the air-fuel ratio feedback correction coefficient KAF (air-fuel ratio correction value) is stuck to the upper limit value (increase determination criterion) (KAF = upper limit value) or the lower limit value (increase determination criterion). Whether the value is within the variable range between the upper limit value and the lower limit value (lower limit value <KAF <upper limit value).

The initial value of the air-fuel ratio feedback correction coefficient KAF (air-fuel ratio correction value) is 1.0, the fuel injection amount (injection pulse width) is increased and corrected when KAF> 1.0, and the fuel injection is performed when KAF <1.0. The amount (injection pulse width) is corrected to decrease.
Accordingly, if the actual air-fuel ratio is leaner than the target air-fuel ratio, the air-fuel ratio is corrected by increasing the air-fuel ratio feedback correction coefficient KAF (air-fuel ratio correction value) above 1.0 to increase the fuel injection amount. If the actual air-fuel ratio is richer than the target air-fuel ratio, the fuel injection amount is corrected to decrease by reducing the air-fuel ratio feedback correction coefficient KAF (air-fuel ratio correction value) below 1.0. To make the air-fuel ratio lean.

The upper limit value is a value that defines the upper limit of the variable range of the air-fuel ratio feedback correction coefficient KAF (air-fuel ratio correction value). Even if the actual air-fuel ratio is leaner than the target, the air-fuel ratio feedback correction is performed. The coefficient KAF does not exceed the upper limit value.
The lower limit value is a value that defines the lower limit of the variable range of the air-fuel ratio feedback correction coefficient KAF (air-fuel ratio correction value), and even if the actual air-fuel ratio is richer than the target, the air-fuel ratio feedback correction is performed. The coefficient KAF is limited not to be set to a value lower than the lower limit value, and the air-fuel ratio feedback correction coefficient KAF (air-fuel ratio correction value) is changed within a variable range including an initial value sandwiched between the upper limit value and the lower limit value. The

  Here, in the determination of step S202, instead of determining whether or not the air-fuel ratio feedback correction coefficient KAF (air-fuel ratio correction value) is stuck to the upper and lower limit values, the air-fuel ratio feedback correction coefficient KAF (air-fuel ratio) (Correction value) is configured to determine whether the increase threshold (> 1.0) is exceeded or less than the decrease threshold (<1.0), and the increase threshold is smaller than the upper limit. And the decrease side threshold value can be set to a value larger than the lower limit value.

  However, the upper and lower limit values and the increase / decrease-side threshold (increase-side determination criterion / decrease-side determination criterion) are the variations in the adjustment pressure by the pressure regulator 61, the injection amount variation of the fuel injection valve 51, and the air flow sensor 72. When the air-fuel ratio variation caused by detection variation is absorbed, the air-fuel ratio feedback correction coefficient KAF (air-fuel ratio correction value) is not reached, and the fuel supply system, the fuel injection valve 51, and the injection amount calculation When an abnormality occurs in various sensors used for the air-fuel ratio, and an air-fuel ratio change exceeding the normal variation range occurs, the air-fuel ratio feedback correction coefficient KAF (air-fuel ratio correction value) is set to a value that can be reached. To do.

  The value of the air-fuel ratio feedback correction coefficient KAF is learned as an air-fuel ratio learning correction value for each engine operating region, and the injection pulse width is corrected with the air-fuel ratio learning correction value and the air-fuel ratio feedback correction coefficient KAF. When it is possible to perform correction near the target air-fuel ratio without correction by the air-fuel ratio feedback correction coefficient KAF, a correction level that combines the air-fuel ratio learning correction value or the air-fuel ratio feedback correction coefficient KAF and the air-fuel ratio learning correction value is Then, it is determined whether or not the threshold value is exceeded.

In step S202, the air-fuel ratio feedback correction coefficient KAF (air-fuel ratio correction value) is a value within a variable region sandwiched between an upper limit value and a lower limit value (or within a normal region sandwiched between increase / decrease side thresholds). If it is determined that there is no abnormality in the fuel supply system, the process proceeds to step S203, and the normal control of the low-pressure pump 56 is continued as it is.
On the other hand, when it is determined that the air-fuel ratio feedback correction coefficient KAF (air-fuel ratio correction value) is stuck to the lower limit value (below the reduction-side threshold value), that is, when the reduction correction state exceeds the criterion. The process proceeds to step S204.

When the state where the air-fuel ratio feedback correction coefficient KAF (air-fuel ratio correction value) is stuck to the lower limit value (below the decrease side threshold value) continues for the reference time or longer, the process proceeds to step S204. Thus, a temporary change in the air-fuel ratio feedback correction coefficient KAF (air-fuel ratio correction value) can be prevented from being determined as an abnormality in the fuel supply system.
In step S204, it is determined whether or not the current (pump load) of the low-pressure pump 56 is higher than the maximum current determination value.

  The maximum current judgment value is the maximum fuel pressure when the fuel pressure in the low-pressure fuel pipe 57 is adjusted by the pressure regulator 61 in consideration of the pressure regulation fluctuation of the pressure regulator 61 and the pressure loss fluctuation of the fuel pipe. The current is set based on the current during PMAX, and the higher the power supply voltage of the low-pressure pump 56, that is, the battery voltage, the higher the value is set (see FIG. 4).

  In FIG. 4, when the intersection γ1 between the vertical line α1 passing through the maximum fuel pressure PMAX and the straight line β rising to 12V is a power supply voltage of 12V, the pressure regulator 61 adjusts the maximum fuel pressure. In this case, the maximum current determination value SLMAX is shown. As the power supply voltage of the low-pressure pump 56 is higher, the straight line β moves in parallel to the side where the current increases, and the maximum current determination value SLMAX also increases.

In other words, when the fuel pressure is normally adjusted by the pressure regulator 61, the current of the low-pressure pump 56 does not exceed the maximum current determination value SLMAX, and the current of the low-pressure pump 56 does not exceed the maximum current determination value SLMAX ( If the maximum value is exceeded, it can be estimated that the fuel pressure is higher than the normal range.
Therefore, when it is determined in step S204 that the current (pump load) of the low pressure pump 56 at that time exceeds the maximum current determination value SLMAX, the fuel pressure of the low pressure system is reduced due to the closed fixing failure of the pressure regulator 61. It is estimated that the pressure exceeds the set pressure of the pressure regulator 61 and is abnormally high.

  Further, since it is determined in step S202 that the air-fuel ratio tends to be rich, the fuel pressure in the low-pressure system (in the low-pressure fuel pipe 57) is higher than the set pressure due to the closed adhering failure of the pressure regulator 8. Therefore, it is estimated that the fuel pressure in the high-pressure fuel pipe 55 cannot be controlled near the target pressure by controlling the electromagnetic valve 58, and the fuel pressure in the high-pressure system is also higher than the target pressure.

  On the other hand, if it is determined in step S204 that the current (pump load) of the low-pressure pump 56 at that time is equal to or smaller than the maximum current determination value SLMAX, the air-fuel ratio tends to become rich, but the pressure regulator 8 Since the pressure is adjusted to normal pressure (set pressure) and it is determined that there is no abnormality in at least the low pressure system, the process proceeds to step S205, and the normal control of the low pressure pump 56 is continued as it is.

If it is determined in step S204 that the current (pump load) of the low-pressure pump 56 at that time exceeds the maximum current determination value SLMAX, the process proceeds to step S206, and the fuel supply system (pressure regulator 61) is abnormal (high pressure). In order to warn the driver of the abnormality), the warning lamp 31 is turned on.
As a result, the driver can know that an abnormality has occurred in the fuel supply system, can recognize the cause when a fail-safe process is performed after that, and can take measures such as stopping the vehicle. Will be able to.

Further, in the next step S207, it is determined based on the vehicle speed VSP detected by the vehicle speed sensor 76 whether or not the vehicle is traveling.
When the vehicle speed VSP is 0 km / h and the vehicle is stopped (when the vehicle is in the first idle state after the internal combustion engine 52 is started), the routine proceeds to step S208 and the duty of the control signal for controlling the energization of the low-pressure pump 56 is reached. The ratio is set to zero, the power supply (voltage application) to the low-pressure pump 56 is forcibly cut off, and the operation of the fuel pump 4 is stopped.

Here, the power supply (voltage application) to the low-pressure pump 56 is forcibly cut off, and at the same time, the valve opening drive and ignition of the fuel injection valve 51 can be forcibly stopped.
Further, in the next step S209, restart of the internal combustion engine 52 (fuel injection / ignition) is prohibited.
The restart prohibition measure is preferably not released until some maintenance is performed, and the restart prohibition device is released by inputting an external release signal to the electronic control unit 71. Can be made.

As described above, if the operation of the low-pressure pump 56 is stopped and the internal combustion engine 52 is stopped, it is possible to prevent the operation from being continued while the pressure in the low-pressure fuel pipe is excessively high. Pump overheating can be avoided.
Since the fuel supply system of the present embodiment is provided with relief valves 62 and 64, even if the pressure regulator 61 does not open (becomes closed and stuck), the fuel pressure of the low-pressure system and the high-pressure system is reduced. Although the pressure does not rise above the valve opening pressure of 62, 64, as described above, it is determined that the fuel pressure is higher than that during normal pressure adjustment by the pressure regulator 61, and the operation of the low pressure pump 56 is stopped. By doing so, it is possible to prevent the operation from being continued with a high fuel pressure.

On the other hand, if the power supply to the low-pressure pump 56 is shut off and the internal combustion engine 52 is stopped while the vehicle is running (after starting to run the vehicle from the fast idle state), the vehicle may be decelerated unintentionally. This is not preferable.
Therefore, if it is determined in step S207 that the vehicle speed VSP is not zero and the vehicle is traveling (after starting to travel from the first idle state), the process proceeds to step S210, and the application of the low-pressure pump 56 is performed. By executing the process of forcibly decreasing the voltage, the fuel pressure is decreased while the operation of the internal combustion engine 52 is continued.

In step S211, after the key switch is turned off, a setting for prohibiting restart of the internal combustion engine 52 is performed.
This restart prohibition measure is preferably not released until some maintenance is performed.
Therefore, if a failure occurs in the pressure regulator 61 after running the vehicle, the operation of the internal combustion engine 52 is continued while the process for forcibly reducing the voltage applied to the low-pressure pump 56 is executed, and the vehicle is stopped. When the key switch is turned off, restart is prohibited, and re-running with the pressure regulator 61 in a failed state is avoided.

  The applied voltage lowering process in step S210 may be a process of reducing the duty ratio of the control signal for controlling the energization of the low-pressure pump 56 by a constant value or a constant ratio, or the air-fuel ratio feedback correction coefficient KAF ( A process of feedback-controlling the duty ratio of the control signal for controlling the energization of the low-pressure pump 56 may be performed so that the air-fuel ratio correction value) approaches the initial value.

  Further, even when it is determined that the fuel supply system (pressure regulator 61) is abnormal while the vehicle is stopped (fast idle state), the internal combustion engine 52 is controlled by forcibly reducing the voltage applied to the low-pressure pump 56. The low-pressure pump 56 may be driven at a duty ratio (voltage) lower than usual from the start of the operation of the low-pressure pump 56 instead of not stopping the restart. can do.

  Further, when the applied voltage of the low-pressure pump 56 is lowered, it is possible to limit the load (intake air amount) of the internal combustion engine 52 at the same time. Specifically, in an engine equipped with an electronically controlled throttle that opens and closes a throttle valve with a motor, the maximum opening of the electronically controlled throttle is set smaller than usual, and the throttle opening is changed only in a low opening range. To.

If it is determined in step S202 that the air-fuel ratio feedback correction coefficient KAF (air-fuel ratio correction value) is stuck to the lower limit value (below the decrease-side threshold value), in other words, This is processing when the fuel ratio tends to be rich.
Note that the base air-fuel ratio indicates an air-fuel ratio when correction is not performed to bring the air-fuel ratio closer to the target air-fuel ratio.

If it is determined in step S202 that the air-fuel ratio feedback correction coefficient KAF (air-fuel ratio correction value) is stuck to the upper limit (exceeding the increase side threshold), and the base air-fuel ratio is a lean air-fuel ratio, that is, When the increase correction state exceeds the determination criterion, the processing after step S212 and the processing after step S221 are executed in parallel.
It should be noted that when the air-fuel ratio feedback correction coefficient KAF (air-fuel ratio correction value) is stuck to the upper limit value (exceeding the increase side threshold value) continues for a reference time or longer, step S212 and step By proceeding to S221, it is possible to prevent a temporary increase in the air-fuel ratio feedback correction coefficient KAF (air-fuel ratio correction value) from being determined as an abnormality in the fuel supply system.

In step S212, it is determined whether or not the current (pump load) of the low-pressure pump 56 is lower than the minimum current determination value.
The minimum current judgment value is based on the current at the minimum fuel pressure PMIN in a state where the fuel pressure is adjusted by the pressure regulator 61 in consideration of variations in pressure regulation of the pressure regulator 61 and variations in pressure loss of the fuel piping. And the higher the power supply voltage of the low-pressure pump 56, that is, the battery voltage, the higher the value is set (see FIG. 4).

In FIG. 4, when the intersection γ2 between the vertical line α2 passing through the minimum fuel pressure PMAX and the straight line β rising to 12V is a power supply voltage of 12V, the pressure regulator 61 regulates the minimum fuel pressure. Current level, that is, the minimum current determination value SLMIN, and the higher the power supply voltage of the low-pressure pump 56, the more the straight line β moves in parallel to the higher current side.
In other words, when the fuel pressure is normally adjusted by the pressure regulator 61, the current of the low pressure pump 56 does not fall below the minimum current determination value SLMIN, and the current of the low pressure pump 56 does not exceed the minimum current determination value SLMIN. If it is lower, it can be estimated that the fuel pressure of the low-pressure system is lower than the normal range.

  That is, when the pressure regulator 61 is normally regulated, the current (pump load) of the low-pressure pump 56 changes between the maximum current determination value SLMAX and the minimum current determination value SLMIN, and the low-pressure pump When the current of 56 deviates from the region sandwiched between the maximum current determination value SLMAX and the minimum current determination value SLMIN, the pressure regulator 61 is not normally regulating, and the low-pressure fuel pressure is normal (pressure It can be estimated that the pressure is higher or lower than the set pressure of the regulator 8.

Therefore, when it is determined in step S212 that the current (pump load) of the low-pressure pump 56 is lower than the minimum current determination value SLMIN, the fuel pressure in the low-pressure fuel pipe 57 is abnormally low. It is estimated to be.
However, since it is determined that the air-fuel ratio tends to become leaner in the determination of step S202, the low pressure fuel pipe 57 is caused by fuel leakage due to damage of the fuel pipe or an open fixing failure of the pressure regulator 61. It is estimated that the pressure inside the high-pressure fuel pipe 55 has fallen without being controlled to the target pressure because the fuel pressure at is lower than the set pressure.

  On the other hand, if it is determined in step S212 that the current (pump load) of the low-pressure pump 56 at that time is equal to or greater than the minimum current determination value SLMIN, the pressure regulator 61 tends to make the air-fuel ratio lean. Since it is determined that there is no abnormality in at least the low-pressure fuel supply system because the pressure is adjusted to normal pressure, the process proceeds to step S213, and the normal control of the low-pressure pump 56 is continued as it is.

If it is determined in step S212 that the current (pump load) of the low-pressure pump 56 is lower than the minimum current determination value SLMIN, the process proceeds to step S214, where the fuel supply system is abnormal (low-pressure abnormality / leak occurrence). The warning lamp 31 is turned on to warn the driver of the vehicle.
Further, in the next step S215, it is determined based on the vehicle speed VSP detected by the vehicle speed sensor 76 whether or not the vehicle is traveling.

  When the vehicle speed VSP is 0 km / h and the vehicle is stopped (when the vehicle is in the fast idle state after the internal combustion engine 52 is started), the routine proceeds to step S216 and the duty of the control signal for controlling the energization of the low-pressure pump 56 is reached. By setting the ratio to zero and shutting off the power supply to the low-pressure pump 56, the fuel supply to the high-pressure pump 54 is stopped, the fuel injection is disabled, and the internal combustion engine 52 is forcibly stopped.

Here, the power supply (voltage application) to the low-pressure pump 56 is forcibly cut off, and at the same time, the valve opening drive and ignition of the fuel injection valve 51 can be forcibly stopped.
Further, in the next step S217, restart (fuel injection / ignition) of the internal combustion engine 52 is prohibited.
The restart prohibition measure is preferably not released until some maintenance is performed, and the restart prohibition device is released by inputting an external release signal to the electronic control unit 71. Can be made.

As described above, if the operation of the low-pressure pump 56 is stopped and the internal combustion engine 52 is stopped, it is possible to prevent the operation from being continued in a state where the fuel leaks from the fuel pipe.
On the other hand, if it is determined in step S215 that the vehicle speed VSP is not zero and the vehicle is traveling (after starting to travel the vehicle from the fast idle state), the process proceeds to step S218 to Then, voice guidance or a warning message that prompts the user to stop the vehicle and stop the internal combustion engine 52 (turn off the key switch) is displayed.

In the next step S219, when the operation of the internal combustion engine 52 is continued when a predetermined time has elapsed since the warning of the operation stop, a process for forcibly stopping the internal combustion engine 52 is executed. Prevent the driver from continuing the operation without performing the operation in accordance with the warning.
Further, in step S220, a setting for prohibiting restart of the internal combustion engine 52 is performed.

This restart prohibition measure is preferably not released until some maintenance is performed.
On the other hand, in step S221, it is determined whether or not the current (pump load) of the low-pressure pump 56 at that time is equal to or less than the maximum current determination value SLMAX.
If it is determined that the current (pump load) of the low-pressure pump 56 is equal to or less than the maximum current determination value SLMAX, the air-fuel ratio tends to become lean, but the pressure regulator 61 adjusts the pressure to normal pressure. Since it is determined that there is at least no abnormality in the low-pressure fuel supply system, the process proceeds to step S222, and the normal control of the low-pressure pump 56 is continued as it is.

If it is determined in step S221 that the current (pump load) of the low-pressure pump 56 exceeds the maximum current determination value SLMAX, the fuel pressure in the low-pressure fuel pipe 57 is set by the pressure regulator 61 being closed and fixed. It is estimated that the pressure is higher than the pressure.
Further, it is determined that the air-fuel ratio of the internal combustion engine 52 tends to become lean. When the fuel pressure of the low-pressure system is higher than normal, but the air-fuel ratio is lean, the electromagnetic valve 58 There is a possibility of closed adhesion.

That is, when the solenoid valve 58 is closed and fixed, even if the low-pressure fuel pressure is high, the fuel supply to the high-pressure pump 54 is not performed. The air-fuel ratio becomes lean and the air-fuel ratio feedback correction coefficient KAF (air-fuel ratio correction value) sticks to the upper limit (exceeds the increase-side threshold).
Therefore, when it is determined in step S221 that the current (pump load) of the low-pressure pump 56 at that time exceeds the maximum current determination value SLMAX, it is estimated that the pressure regulator 61 and the electromagnetic valve 58 are closed and closed. Proceed to step S223.

In step S223, the warning lamp 31 is lit to warn the driver of the vehicle of an abnormality in the fuel supply system (abnormal increase in pressure in the low pressure system and abnormality in injection failure).
Further, in the next step S224, it is determined based on the vehicle speed VSP detected by the vehicle speed sensor 76 whether or not the vehicle is traveling.
When the vehicle speed VSP is 0 km / h and the vehicle is stopped (when the vehicle is in the first idle state after the internal combustion engine 52 is started), the routine proceeds to step S225 and the duty of the control signal for controlling the energization of the low-pressure pump 56 is reached. By setting the ratio to zero and shutting off the power supply to the low-pressure pump 56, the fuel supply to the high-pressure pump 54 is stopped, the fuel injection is disabled, and the internal combustion engine 52 is forcibly stopped.

Here, the power supply (voltage application) to the low-pressure pump 56 is forcibly cut off, and at the same time, the valve opening drive and ignition of the fuel injection valve 51 can be forcibly stopped.
Further, in the next step S226, restart (fuel injection / ignition) of the internal combustion engine 52 is prohibited.
The restart prohibition measure is preferably not released until some maintenance is performed, and the restart prohibition device is released by inputting an external release signal to the electronic control unit 71. Can be made.

As described above, if the operation of the low-pressure pump 56 is stopped and the internal combustion engine 52 is stopped, the operation in a state where the pressure in the low-pressure system is abnormally high can be promptly terminated. Exhaust temperature rise due to over lean can be suppressed / avoided to protect exhaust system components (air-fuel ratio sensor, catalyst, etc.).
On the other hand, if it is determined in step S224 that the vehicle speed VSP is not zero and the vehicle is traveling (after starting to travel the vehicle from the fast idle state), the process proceeds to step S227 to Then, voice guidance or a warning message that prompts the user to stop the vehicle and stop the internal combustion engine 52 (turn off the key switch) is displayed.

  In the next step S228, the operation is performed by forcibly stopping the internal combustion engine 52 when the operation of the internal combustion engine 52 is continued when a certain time has elapsed from the warning of the operation stop. The operation is continued without the operator performing an operation in accordance with the warning, in other words, the low pressure system is prevented from being left in a high pressure state and an air-fuel ratio over lean state.

Further, in step S229, a setting for prohibiting restart of the internal combustion engine 52 is performed.
This restart prohibition measure is preferably not released until some maintenance is performed.
In the above embodiment, the fuel pump 4 and the low-pressure pump 56 that are electric pumps are arranged in the fuel tank, but may be arranged outside the fuel tank.

  Further, the pressure regulators 9, 42, 61 may be electromagnetic valves that are electronically controlled in addition to mechanical valve mechanisms. Further, the pressure regulators 9, 42, 61 are not equipped with pressure regulators, and are electrically driven so that the fuel pressure approaches the target pressure. A fuel supply system configured to control the discharge amount (applied voltage) of the fuel pump may be used.

1 is a system diagram of a fuel supply system of a port injection type internal combustion engine in an embodiment of the present invention. It is a flowchart which shows the diagnostic process applied to the fuel supply system of FIG. It is a flowchart which shows the diagnostic process applied to the fuel supply system of FIG. It is a diagram for demonstrating the characteristic of the determination criterion of the electric current used for the said diagnostic process. It is a system diagram which shows another example of the fuel supply system which can apply the diagnostic process of FIG. 1 is a system diagram of a fuel supply system of a direct injection type internal combustion engine in an embodiment of the present invention. It is a flowchart which shows the diagnostic process applied to the fuel supply system of FIG. It is a flowchart which shows the diagnostic process applied to the fuel supply system of FIG. It is a flowchart which shows the diagnostic process applied to the fuel supply system of FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Fuel injection valve (fuel injection apparatus), 2 ... Internal combustion engine, 3 ... Fuel gallery pipe, 4 ... Fuel pump, 5 ... Fuel tank, 8, 42, 61 ... Pressure regulator, 9 ... Relief valve, 10 ... Fuel tank , 11 ... Electronic control unit (ECU), 12, 72 ... Air flow sensor, 13, 73 ... Crank angle sensor, 14, 74 ... Air-fuel ratio sensor, 32, 76 ... Vehicle speed sensor, 23 ... Current detection circuit, 54 ... High pressure pump 56 ... Low pressure pump

Claims (5)

A fuel supply system diagnostic device for pumping fuel by a fuel pump to a fuel injection device of an internal combustion engine,
A diagnostic apparatus for a fuel supply system of an internal combustion engine that determines whether or not there is an abnormality in the fuel supply system from a control state of the fuel pump and an air-fuel ratio control state of the internal combustion engine.   The fuel pump is an electric fuel pump, and an air-fuel ratio correction value for correcting the fuel injection amount of the fuel injection device is feedback-controlled so that the air-fuel ratio of the internal combustion engine approaches a target air-fuel ratio, 2. The diagnostic apparatus for a fuel supply system of an internal combustion engine according to claim 1, wherein whether or not there is an abnormality in the fuel supply system is determined from the drive current of the fuel pump and the air-fuel ratio correction value.   The abnormality in the fuel supply system is determined when the driving current of the electric fuel pump is larger than a threshold value and the air-fuel ratio correction value is in a reduction correction state exceeding a determination criterion. 3. A diagnostic apparatus for a fuel supply system of an internal combustion engine according to 2.   The abnormality of the fuel supply system is determined when the driving current of the electric fuel pump is smaller than a threshold value and the air-fuel ratio correction value is in an increase correction state exceeding a determination criterion. 3. A diagnostic apparatus for a fuel supply system of an internal combustion engine according to 2.   5. The fuel supply of the internal combustion engine according to claim 2, wherein when an abnormality of the fuel supply system is determined, a voltage applied to the electric fuel pump is limited to be small. System diagnostic device.

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