JP2013068127A - Internal combustion engine control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an internal combustion engine control device, capable of performing failure diagnosis of a fuel pressure sensor during operation of the internal combustion engine.SOLUTION: An internal combustion engine includes: a fuel pump; a relief valve opened when a fuel pressure by the fuel pump exceeds an upper limit pressure and relieving the fuel discharged by the fuel pump in a fuel tank; and a fuel pressure sensor detecting the fuel pressure by the fuel pump. An engine control module determines the presence of air-fuel ratio abnormality, and starts failure diagnosis of the fuel pressure sensor when the air-fuel ratio abnormality occurs. In the failure diagnosis of the fuel pressure sensor, the fuel pressure is raised to a valve opening pressure of the relief valve, by setting a driving duty of the fuel pump to a diagnosis duty, and the presence of a failure of the fuel pressure sensor is determined on the basis of whether the fuel pressure sensor detects the vicinity of the valve opening pressure at that time.

Description

  The present invention relates to a control device that outputs an operation amount of a fuel pump according to a detection value of a fuel pressure sensor.

  In Patent Document 1, after the ignition switch is turned off, based on the behavior of the fuel pressure when the pressure reducing valve is opened, a provisional diagnosis is made as to whether or not the pressure reducing valve is abnormal. Disclosed is a fuel injection control device that determines that the fuel pressure sensor is normal and determines the temporary diagnosis result of the pressure reducing valve as the final diagnosis result when the fuel pressure detected by Has been.

JP 2007-1000062 A

By the way, when the failure diagnosis of the fuel pressure sensor is performed when the ignition switch is turned off, that is, when the internal combustion engine is stopped, even if the abnormality occurs in the fuel pressure sensor during the operation of the internal combustion engine, the abnormality is not detected until the internal combustion engine is stopped. Cannot detect the occurrence of
For this reason, even if an abnormality occurs in the fuel pressure sensor during operation of the internal combustion engine, it is not possible to take measures against the abnormality.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a control device for an internal combustion engine capable of diagnosing abnormality of a fuel pressure sensor during operation of the internal combustion engine.

  Therefore, the present invention changes the operation amount of the fuel pump in the direction of increasing the fuel supply pressure by the fuel pump for diagnosis of the fuel pressure sensor, and based on the detected value of the fuel pressure sensor at this time, the fuel pressure Judgment of sensor failure.

  According to the above invention, the fuel pressure sensor can be diagnosed during operation of the internal combustion engine, and when an abnormality occurs in the fuel pressure sensor, it is possible to detect such abnormality with a good response and implement countermeasures.

1 is a system diagram of an engine in an embodiment of the present invention. It is a flowchart which shows an air fuel ratio abnormality diagnosis in embodiment of this invention. It is a flowchart which shows the failure diagnosis of the fuel pressure sensor made to raise to the valve opening pressure of a relief valve in embodiment of this invention. 4 is a time chart showing changes in an air-fuel ratio feedback correction coefficient, a duty, and a detected value FUPR at the time of failure diagnosis in FIG. 3. It is a flowchart which shows the failure diagnosis of the fuel pressure sensor which performs feed forward control based on the target fuel pressure for diagnosis in embodiment of this invention. 6 is a time chart showing changes in an air-fuel ratio feedback correction coefficient, a duty, and a detected value FUPR at the time of failure diagnosis in FIG. 5. It is a flowchart which shows the failure diagnosis of the fuel pressure sensor which performs feedback control based on the target fuel pressure for diagnosis in embodiment of this invention. 8 is a time chart showing changes in the air-fuel ratio feedback correction coefficient, duty, and detection value FUPR at the time of failure diagnosis in FIG.

Embodiments of the present invention will be described below.
FIG. 1 is a system diagram of a vehicle engine including a control device according to the present invention.
An engine (internal combustion engine) 1 shown in FIG. 1 includes a fuel injection valve 3 in an intake passage 2, and the fuel injection valve 3 injects fuel toward an intake valve 4.

The fuel injected by the fuel injection valve 3 is sucked into the combustion chamber 5 together with air through the intake valve 4 and ignited and burned by spark ignition by the spark plug 6. The combustion gas in the combustion chamber 5 is discharged to the exhaust passage 8 through the exhaust valve 7.
An electronically controlled throttle 10 that is opened and closed by a throttle motor 9 is disposed upstream of the portion of the intake passage 2 where the fuel injection valve 3 is disposed, and the intake air of the engine 1 is determined by the opening degree of the electronically controlled throttle 10. Adjust the amount.

The engine 1 also includes a fuel supply device 13 that supplies the fuel in the fuel tank 11 to the fuel injection valve 3 (engine 1) by the fuel pump 12.
The fuel supply device 13 includes a fuel tank 11, a fuel pump 12, a fuel gallery pipe 14, a fuel supply pipe 15, and a fuel filter 16.
The fuel pump 12 is an electric fluid pump that rotationally drives a pump impeller with a motor, and is disposed in the fuel tank 11.

The fuel pump 12 opens when a check valve (a check valve) 12a for preventing a reverse flow of discharged fuel and a discharge pressure (fuel supply pressure) of the fuel pump 12 exceeds an upper limit pressure, A relief valve 12b for relieving the fuel discharged by the fuel pump 12 into the fuel tank 11 is incorporated.
Note that the check valve (check valve) 12 a and the relief valve 12 b can be provided in the fuel supply pipe 15 separately from the fuel pump 12.

One end of the fuel supply pipe 15 is connected to the discharge port of the fuel pump 12, and the other end of the fuel supply pipe 15 is connected to the fuel gallery pipe 14.
A fuel filter 16 for filtering fuel is provided in a portion located in the fuel tank 11 in the middle of the fuel supply pipe 15.
A fuel injection valve 3 for each cylinder is connected to the fuel gallery pipe 14.
An ECM (engine control module) 31 including a computer is provided as an engine control unit that controls fuel injection by the fuel injection valve 3, ignition by the spark plug 6, opening of the electronic control throttle 10, and the like.

Further, as a fuel pump control unit for driving the fuel pump 12, an FPCM (fuel pump control module) 30 including a computer is provided.
The ECM 31 and the FPCM 30 are configured to be able to communicate with each other, and signals indicating the duty ratio and frequency in the PWM control of the fuel pump 12 are transmitted from the ECM 31 to the FPCM 30, and diagnosis is performed from the FPCM 30 to the ECM 31. Information etc. are transmitted.
Note that the ECM 31 can also have the function as the FPCM 30.

The ECM 31 includes a fuel pressure sensor 33 that detects a fuel pressure FUPR in the fuel gallery pipe 14, that is, a fuel supply pressure by the fuel pump 12, an accelerator opening sensor 34 that detects an accelerator pedal depression amount ACC (not shown), and an engine 1 According to the air flow sensor 35 for detecting the intake air flow rate QA, the rotation sensor 36 for detecting the rotational speed NE of the engine 1, the water temperature sensor 37 for detecting the cooling water temperature TW (engine temperature) of the engine 1, and the oxygen concentration in the engine exhaust Then, a detection signal from an air-fuel ratio sensor 38 for detecting the air-fuel ratio of the combustion mixture of the engine 1 is input.
Then, the ECM 31 controls the fuel injection amount and injection timing by the fuel injection valve 3, the ignition timing by the ignition plug 6, the opening degree of the electronic control throttle 10, and the like based on the detection signals of the various sensors described above.

The ECM 31 calculates the fuel injection amount by the fuel injection valve 3 as follows.
First, the intake air flow rate QA is detected based on the output signal of the air flow sensor 35, and the engine rotation speed NE is detected based on the output signal of the rotation sensor 36. Based on the intake air flow rate QA and the engine rotation speed NE, the fuel is detected. The basic injection pulse width TP (basic fuel injection amount) corresponding to when the supply pressure is the reference pressure is calculated.

Further, a correction coefficient for coping with a change in the injection amount per unit time is calculated based on the fuel pressure detected by the fuel pressure sensor 33, and the fuel injection amount is calculated during cold operation based on the cooling water temperature TW detected by the water temperature sensor 37. A correction coefficient for increasing the amount is calculated, and various correction coefficients for correcting the basic injection pulse width TP, such as a correction coefficient for bringing the air-fuel ratio detected by the air-fuel ratio sensor 38 closer to the target air-fuel ratio, are calculated. .
Then, the basic fuel injection pulse width TP is corrected with various correction coefficients to calculate the final fuel injection pulse width TI, and the injection pulse signal of the fuel injection pulse width TI is supplied to the fuel injection valve 3 at the injection timing in each cylinder. Output.

Further, the ECM 31 sets the target value TGFUPR of the fuel pressure FUPR based on the operating conditions (engine load, engine speed, engine temperature, etc.) of the engine 1, and the detected fuel pressure FUPR based on the output of the fuel pressure sensor 33 is the target value. The duty ratio (operation amount) in the PWM control of the fuel pump 12 is determined so as to approach TGFUPR.
Further, the ECM 31 has a function of performing a failure diagnosis of the fuel pressure sensor 33 during operation of the engine 1 as software.

If the fuel pressure sensor 33 fails and an error occurs between the actual fuel pressure and the detected value FUPR, the amount of fuel injected according to the fuel injection pulse width TI corrected based on the detected value FUPR and the target air-fuel ratio A deviation from the fuel amount occurs, and the air-fuel ratio deviates from the target air-fuel ratio.
Here, the air-fuel ratio shift also occurs due to factors other than the failure of the fuel pressure sensor 33. However, if the fuel pressure sensor 33 fails, an air-fuel ratio shift occurs. Therefore, the ECM 31 detects the occurrence of the air-fuel ratio shift. In addition, it is set so as to determine whether or not the cause is due to the failure of the fuel pressure sensor 33, and the failure diagnosis will be described in detail below.

The flowchart of FIG. 2 shows a routine in which the ignition switch (engine switch) is turned on and interrupted at a constant time period during the operation of the engine 1 to determine whether or not an air-fuel ratio deviation has occurred.
First, in step S101, the output of the air-fuel ratio sensor 38 is read.

In step S102, an air-fuel ratio feedback correction coefficient LAMBDA (air-fuel ratio) for correcting the basic injection pulse width TP so that the actual air-fuel ratio detected based on the output of the air-fuel ratio sensor 38 read in step S101 approaches the target air-fuel ratio. (Operation amount) is calculated.
In step S103, it is determined whether or not the air-fuel ratio feedback correction coefficient LAMBDA is a value included in the normal determination region in the convergence state of the air-fuel ratio feedback correction coefficient LAMBDA.

Here, the normal determination region corresponds to an allowable deviation range of the air-fuel ratio that occurs due to manufacturing variations of parts, and the air-fuel ratio feedback correction coefficient LAMBDA deviates from the normal determination region when the fuel pressure sensor 33 fails. In addition, the normality determination area is set in advance.
For example, when the initial value of the air-fuel ratio feedback correction coefficient LAMBDA is 1.0 and the air-fuel ratio feedback correction coefficient LAMBDA is the initial value, if the basic injection pulse width TP is not substantially corrected, A region having a constant width and a region having a constant width on the minus side are set as normal determination regions.

If it is determined in step S103 that the air-fuel ratio feedback correction coefficient LAMBDA is within the normal determination range, in other words, if the air-fuel ratio deviation is within the allowable range, the process proceeds to step S104 where the fuel pressure sensor 33 is normal. Is determined.
On the other hand, if it is determined that the air-fuel ratio feedback correction coefficient LAMBDA is out of the normal determination range and the air-fuel ratio deviation exceeds the allowable level, the process proceeds to step S105, where the air-fuel ratio feedback correction coefficient LAMBDA is out of the normal determination range. The time duration TCON that is out of the range is measured.

In step S106, it is determined whether or not the duration time TCON has reached the determination time TSL. That is, even if the air-fuel ratio feedback correction coefficient LAMBDA deviates from the determination region, if this is a transient phenomenon, the air-fuel ratio deviation is temporary because it is different from the air-fuel ratio deviation due to the failure of the fuel pressure sensor 33. Is determined based on a comparison between the duration TCON and the determination time TSL.
If the duration time TCON is less than the determination time TSL, the air-fuel ratio deviation is in an abnormal state where the air-fuel ratio deviation occurs, but the air-fuel ratio deviation may be transient, so step S107. , The air-fuel ratio abnormality is determined, and the failure diagnosis of the fuel pressure sensor 33 is not performed.

On the other hand, when the duration TCON reaches the determination time TSL, the air-fuel ratio shift is not temporary, and the air-fuel ratio may be continuously shifted due to the failure of the fuel pressure sensor 33. Proceeding to step S108, the diagnosis execution flag fFSDIA is set to 1 to instruct execution of the failure diagnosis of the fuel pressure sensor 33.
The initial value of the diagnosis execution flag fFSDIA is 0. As will be described later, when the diagnosis execution flag fFSDIA is set to 1, failure diagnosis of the fuel pressure sensor 33 is performed.

Here, when an air-fuel ratio abnormality is judged, operation in a high-rotation and high-load range is prohibited by limiting the maximum opening of the throttle opening, etc., and the exhaust temperature is excessive due to lean air-fuel ratio due to fuel shortage It can be suppressed that the height is increased.
The flowchart of FIG. 3 shows a diagnostic routine of the fuel pressure sensor 33 that is executed when the ignition switch (engine switch) is on and interrupted at a fixed time period during the operation of the engine 1.

First, in step S201, the value of the diagnosis execution flag fFSDIA is read.
In the next step S202, it is determined whether or not the failure diagnosis of the fuel pressure sensor 33 is to be performed by determining whether or not the diagnosis execution flag fFSDIA is 1.
If 0 is set in the diagnosis execution flag fFSDIA, it is determined that it is not necessary to perform a failure diagnosis of the fuel pressure sensor 33, and this routine is terminated as it is.

On the other hand, when 1 is set in the diagnosis execution flag fFSDIA, the process proceeds to step S203 in order to perform a failure diagnosis of the fuel pressure sensor 33.
In step S203, the duty (operation amount) in the PWM control of the fuel pump 12 is switched from the duty set based on the detected value FUPR and the target pressure TGFUPR to 100% stored in advance as the diagnostic duty, and held. Thus, the fuel pump 12 is driven with the maximum power (maximum voltage), and the fuel pressure rises above the target value TGFUPR at that time, and reaches the valve opening pressure RVP of the relief valve 12b.
The target value TGFUPR is variably set in accordance with the engine operating conditions in a fuel pressure region less than the valve opening pressure RVP.

When the fuel supply pressure (discharge pressure) by the fuel pump 12 rises to the valve opening pressure RVP of the relief valve 12b, the relief valve 12b is opened, and the fuel pressure is prevented from rising beyond the valve opening pressure RVP. Therefore, when the duty in PWM control of the fuel pump 12 is switched to the duty for diagnosis, the fuel pressure near the valve opening pressure RVP is held after the actual fuel pressure rises up to the valve opening pressure RVP.
In other words, the diagnostic duty is preset as a duty at which the actual fuel pressure rises to the valve opening pressure RVP.

However, the duty for diagnosis is not limited to 100%, and a value of less than 100% can be set in advance as long as the actual fuel pressure is reliably increased to the valve opening pressure RVP of the relief valve 12b. .
In addition, when the duty is switched to the diagnostic duty, in order to suppress the occurrence of an air-fuel ratio shift due to a sudden change in fuel pressure, the duty may be gradually increased from the duty before the diagnosis toward the diagnostic duty. Preferably, the duty can be increased and changed so as to change the fuel pressure along the reference response.

In addition, the condition for performing the diagnosis by switching the drive duty of the fuel pump 12 to the duty for diagnosis can be limited to a preset engine operation region (for example, a region specified by the engine load and the engine speed).
Further, by switching to the diagnostic duty, the actual fuel pressure becomes close to the valve opening pressure RVP of the relief valve 12b. Therefore, in the correction according to the fuel pressure of the fuel injection pulse width, the fuel pressure is corrected to be the valve opening pressure RVP. Can be performed.

In step S204, after switching to the diagnostic duty, the fuel pressure FUPR detected based on the output of the fuel pressure sensor 33 after the fuel pressure corresponding to the diagnostic duty, that is, the response delay time estimated to reach the valve opening pressure RVP has elapsed. Is read.
Then, in the next step S205, it is determined whether or not the detected value FUPR read in step S204 is included in the normal determination region of the detected fuel pressure value including the valve opening pressure RVP of the relief valve 12b.

The normality determination region means that the fuel pressure sensor 33 is normal under the condition that the relief valve 12b is opened even if there is a variation in the valve opening pressure RVP of the relief valve 12b or a variation in the output of the fuel pressure sensor 33. A detection value area that can be determined is set in advance.
In other words, the fuel pressure when the duty is the diagnostic duty holds the valve opening pressure RVP of the relief valve 12b, but the actual valve opening pressure RVP has an error from the design value. In addition, since the correlation between the actual fuel pressure in the fuel pressure sensor 33 and the detected output varies from sensor to sensor, the output of the fuel pressure sensor 33 when the relief valve 12b is open is within a certain range even if the fuel pressure sensor 33 is normal. It becomes the value in.

Here, the output range of the fuel pressure sensor 33 can be specified in advance based on the variation range of the valve opening pressure RVP, the variation range of the output characteristics of the fuel pressure sensor 33, and the like, so that the normal determination region is based on the normal output range. Is set.
Therefore, if the detected value FUPR at that time is within the normality determination region, the fuel pressure sensor 33 can determine that the output is in a normal state corresponding to the valve opening pressure RVP that is the actual fuel pressure, and is empty. It can be estimated that the abnormality in the fuel ratio is caused by other than the fuel pressure sensor 33. On the other hand, if the detected value FUPR at that time is out of the normal determination region, it can be estimated that the detected value FUPR does not indicate the original value because the fuel pressure sensor 33 is abnormal.

Note that the normality determination region can be variably set in accordance with the properties of the fuel used at that time (heavy and light, the mixing ratio of alcohol to gasoline, etc.).
For example, the pump discharge flow rate and the relief flow rate from the relief valve 12b become different due to the difference in viscosity depending on the fuel properties, and thus the fuel pressure in the opened state of the relief valve 12b varies.
Therefore, the correlation between the fuel property and the fuel pressure variation is obtained in advance, and in the case of the fuel property that the fuel pressure variation becomes large, the normality determination area is expanded, and conversely, in the case of the fuel property that the fuel pressure variation becomes small, Reduce the normality judgment area.

If it is determined in step S205 that the detected value FUPR at that time is within the normal determination region, the process proceeds to step S206, and it is determined that the fuel pressure sensor 33 is normal. If it is determined that the fuel pressure sensor 33 is normal, the abnormality of the air-fuel ratio is caused by an abnormality of a device other than the fuel pressure sensor 33 such as the fuel injection valve 3 and the air flow sensor 35.
On the other hand, if the detected value FUPR at that time is out of the normal determination region, the process proceeds to step S207, and it is determined that the fuel pressure sensor 33 is abnormal. That is, since the detected value FUPR of the fuel pressure sensor 33 is different from the actual fuel pressure, the fuel injection pulse width is corrected based on the detected value FUPR of the fuel pressure sensor 33. As a result, the fuel amount required for forming the target air-fuel ratio is reduced. Therefore, it is determined that the actual fuel injection amount has become excessive or insufficient, and that the actual air-fuel ratio has shifted from the target air-fuel ratio.

If it is determined whether the fuel pressure sensor 33 is normal or abnormal, the process further proceeds to step S208, and the diagnosis execution flag fFSDIA is reset to zero.
If it is determined that the fuel pressure sensor 33 is normal, the calculation of the drive duty of the fuel pump 12 based on the detection value FUPR of the fuel pressure sensor 33 and the fuel injection pulse width based on the detection value FUPR of the fuel pressure sensor 33 are performed. Continue the correction calculation.

  On the other hand, when it is determined that the fuel pressure sensor 33 is abnormal, an alarm for notifying the occurrence of the abnormality is issued, the calculation of the drive duty of the fuel pump 12 based on the detection value FUPR of the fuel pressure sensor 33, and the fuel pressure sensor 33 The fuel injection pulse width correction calculation based on the detected value FUPR is prohibited, or the driving duty of the fuel pump 12 is fixed to a preset duty for sensor abnormality, and the fuel pressure corresponding to the duty is considered to be Then, carry out fail-safe processing such as correcting the fuel injection pulse width.

FIG. 4 shows an example of changes in the air-fuel ratio food back correction coefficient, duty, and detected value FUPR at the time of failure diagnosis of the fuel pressure sensor 33.
As shown in FIG. 4, when the fuel injection pulse width is corrected based on an erroneous detection value FUPR due to an abnormality in the fuel pressure sensor 33, the air-fuel ratio deviates from the target air-fuel ratio and attempts to absorb such air-fuel ratio deviation. The air-fuel ratio feedback correction coefficient is changed. When the air-fuel ratio deviation is large and the air-fuel ratio feedback correction coefficient changes beyond the normal determination range (allowable range), it is determined that there is a possibility that the fuel pressure sensor 33 has failed, and the drive duty of the fuel pump 12 is set. By increasing to the diagnostic duty, the actual fuel pressure is increased to the valve opening pressure RVP of the relief valve 12.

Here, since the actual fuel pressure becomes the valve opening pressure RVP of the relief valve 12 by switching to the diagnostic duty, if the fuel pressure sensor 33 is normal, the detected value FUPR of the fuel pressure sensor 33 is the valve opening pressure. When the value is in the vicinity of RVP and the detected value FUPR of the fuel pressure sensor 33 is not a value in the vicinity of the valve opening pressure RVP, it is determined that the fuel pressure sensor 33 is in an abnormal state detecting a value different from the actual fuel pressure. To do.
That is, when the supply pressure exceeds the valve opening pressure RVP of the relief valve 12, the relief valve 12 opens, so that the actual maximum fuel pressure is the valve opening pressure RVP. Therefore, even if the operation amount corresponding to the supply pressure exceeding the valve opening pressure RVP is given to the fuel pump 12, the actual fuel pressure is maintained in the vicinity of the valve opening pressure RVP. At this time, the fuel pressure sensor 33 is operated at the valve opening pressure RVP. If the fuel pressure near the RVP is detected, the fuel pressure sensor 33 is normal, and if the detected value of the fuel pressure sensor 33 is not the fuel pressure near the valve opening pressure RVP, the detected value and the actual value are different. Therefore, it can be determined that the fuel pressure sensor 33 has failed.

According to the failure diagnosis of the fuel pressure sensor 33 described above, the diagnosis can be performed during the operation of the engine 1, so that the abnormality is promptly detected and the process proceeds to the fail-safe process. Deterioration of drivability can be suppressed as small as possible.
If the failure diagnosis of the fuel pressure sensor 33 cannot be performed during the operation of the engine 1, for example, when correcting the fuel injection pulse width based on the detection value of the fuel pressure sensor, the correction is performed improperly, the fuel injection amount, Furthermore, an error occurs in the air-fuel ratio, and the operability, exhaust properties, and fuel consumption performance of the internal combustion engine are deteriorated. However, since the failure diagnosis of the fuel pressure sensor 33 described above can be performed during the operation of the engine 1, a failure is caused. By promptly shifting to the safe process, it is possible to suppress the occurrence of errors in the fuel injection amount and the air-fuel ratio, and it is possible to suppress the decrease in drivability, exhaust properties, and fuel consumption performance of the internal combustion engine.
In addition, since the failure diagnosis of the fuel pressure sensor 33 is performed when an abnormality in the air-fuel ratio occurs, the fuel pressure sensor 33 can be diagnosed under conditions that may cause an abnormality. In a state where there is no abnormality, it is possible to prevent unnecessary diagnostic processing from being performed, and it is possible to suppress power consumption and pump noise increase associated with the diagnosis.

In the diagnosis of the fuel pressure sensor 33, the operation amount of the fuel pump 12 is changed to increase the fuel pressure to the valve opening pressure RVP of the relief valve 12b. Therefore, the actual fuel pressure at the time of diagnosis is not used by the output of the fuel pressure sensor 33. The fuel pressure can be controlled to a known fuel pressure, and by comparing this known fuel pressure with the detected value FUPR of the fuel pressure sensor 33, an abnormality in the fuel pressure sensor 33 can be diagnosed with high accuracy.
Further, since the actual fuel pressure is controlled to the known valve opening pressure RVP of the relief valve 12b at the time of diagnosis, the fuel injection pulse width is corrected based on the valve opening pressure RVP in the correction of the fuel injection pulse width according to the fuel supply pressure. By correcting this, the air-fuel ratio shift can be reduced.
Further, in the diagnosis, the fuel pressure is set to the valve opening pressure RVP which is the maximum pressure, so that deterioration of combustibility due to insufficient fuel pressure can be suppressed.

By the way, in the failure diagnosis of the fuel pressure sensor 33 described above, the fuel pressure is increased to the valve opening pressure RVP of the relief valve 12b at the time of diagnosis, but the diagnosis can be performed by increasing the fuel pressure to be lower than the valve opening pressure RVP. This will be specifically described below.
The failure diagnosis described below can also be applied to a fuel supply apparatus that does not include the relief valve 12b.

The flowchart of FIG. 5 shows a diagnostic routine of the fuel pressure sensor 33 that is executed when the ignition switch (engine switch) is on and interrupted at a fixed time period during the operation of the engine 1.
First, in step S301, the value of the diagnosis execution flag fFSDIA set in the routine shown in the flowchart of FIG. 2 is read.

In the next step S302, it is determined whether or not a failure diagnosis of the fuel pressure sensor 33 is to be performed by determining whether or not the diagnosis execution flag fFSDIA is 1.
If 0 is set in the diagnosis execution flag fFSDIA, it is determined that it is not necessary to perform a failure diagnosis of the fuel pressure sensor 33, and this routine is terminated as it is.

On the other hand, if the diagnosis execution flag fFSDIA is set to 1, the process proceeds to step S303 in order to perform a failure diagnosis of the fuel pressure sensor 33.
In step S303, control (feedback correction) for correcting the drive duty of the fuel pump 12 based on the detected value FUPR of the fuel pressure sensor 33 is prohibited, and the valve opening pressure of the relief valve 12b is higher than the target fuel pressure TGFUPR at that time. The fuel pump 12 is driven at a feed forward control duty FFDUTY (diagnostic duty) corresponding to the target fuel pressure TGPLAB for diagnosis lower than RVP.

In other words, the feedforward control duty FFDUTY is a duty (amount of operation) that is expected when the actual fuel pressure becomes the target fuel pressure TGPLAB for diagnosis, and the fuel pressure sensor 33 may be abnormal. Without using the value FUPR, the actual fuel pressure is increased to the target fuel pressure TGPRAB by feed forward control.
Here, the target fuel pressure TGFUPR is gradually increased to the target fuel pressure TGPRAB for diagnosis, or the increase change of the duty is regulated to suppress the actual fuel pressure from rapidly increasing and causing an air-fuel ratio shift. Is preferred.

In step S304, the detection value FUPR of the fuel pressure sensor 33 is read after a delay time that is expected to increase from the actual fuel pressure to the target fuel pressure TGPRAB after the feed forward control duty FFDUTY is given.
In step S305, it is determined whether or not the detection value FUPR read in step S304 is included in the normal determination region of the detection result including the target fuel pressure TGPRAB.

Even if the feed forward control duty FFDUTY, which is expected to obtain the target fuel pressure TGPLAB, is given to the fuel pump 12, the actual fuel pressure may cause an error with respect to the target fuel pressure TGPLAB depending on variations in the fuel pump 12 and the fuel properties. Because the output of the fuel pressure sensor 33 varies, even if the fuel pressure sensor 33 is normal, the detected value FUPR when the feed forward control duty FFDUTY is given to the fuel pump 12 does not match the target fuel pressure TGPLAB and shows variation. become.
Therefore, a range in which the detected value FUPR varies in a normal state of the fuel pressure sensor 33 is set in advance as the normality determination range.

Therefore, if the detected value FUPR at that time is within the normality determination region, it can be estimated that the fuel pressure sensor 33 is normal and the air-fuel ratio abnormality is caused by something other than the fuel pressure sensor 33. Conversely, the detection at that time When the value FUPR is out of the normal determination region, it can be estimated that the detected value FUPR does not indicate the original value because the fuel pressure sensor 33 is abnormal.
As described above, the actual fuel pressure when the feedforward control duty FFDUTY is given to the fuel pump 12 changes according to the properties of the fuel used at that time (heavy and light, the mixing ratio of alcohol to gasoline, etc.). The width of the normal determination region can be made variable according to the fuel properties.

If it is determined in step S305 that the detected value FUPR at that time is within the normal determination region, the process proceeds to step S306, where it is determined that the fuel pressure sensor 33 is normal. If it is determined that the fuel pressure sensor 33 is normal, the abnormality of the air-fuel ratio is caused by an abnormality of a device other than the fuel pressure sensor 33 such as the fuel injection valve 3 and the air flow sensor 35.
On the other hand, if the detected value FUPR at that time is out of the normal determination region, the process proceeds to step S307, and it is determined that the fuel pressure sensor 33 is abnormal.

That is, since the detected value FUPR of the fuel pressure sensor 33 is different from the actual fuel pressure, the fuel injection pulse width is corrected based on the detected value FUPR of the fuel pressure sensor 33. As a result, the fuel amount required for forming the target air-fuel ratio is reduced. Therefore, it is determined that the actual fuel injection amount has become excessive or insufficient, and that the actual air-fuel ratio has shifted from the target air-fuel ratio.
When it is determined whether the fuel pressure sensor 33 is normal or abnormal, the process further proceeds to step S308, and the diagnosis execution flag fFSDIA is reset to zero.

If it is determined that the fuel pressure sensor 33 is normal, the calculation of the drive duty of the fuel pump 12 based on the detection value FUPR of the fuel pressure sensor 33 and the fuel injection pulse width based on the detection value FUPR of the fuel pressure sensor 33 are performed. Continue the correction calculation.
On the other hand, when it is determined that the fuel pressure sensor 33 is abnormal, an alarm for notifying the occurrence of the abnormality is issued, the calculation of the drive duty of the fuel pump 12 based on the detection value FUPR of the fuel pressure sensor 33, and the fuel pressure sensor 33 The fuel injection pulse width correction calculation based on the detected value FUPR is prohibited, or the driving duty of the fuel pump 12 is fixed to a preset duty for sensor abnormality, and the fuel pressure corresponding to the duty is considered to be Perform fail-safe processing such as setting the fuel injection pulse width.

FIG. 6 shows an example of changes in the air-fuel ratio food back correction coefficient, duty, and detected value FUPR at the time of failure diagnosis of the fuel pressure sensor 33.
As shown in FIG. 6, when the fuel injection pulse width is corrected based on an erroneous detection value FUPR due to an abnormality in the fuel pressure sensor 33, the air-fuel ratio deviates from the target air-fuel ratio and tries to absorb such an air-fuel ratio deviation. The air-fuel ratio feedback correction coefficient is changed. When the air-fuel ratio deviation is large and the air-fuel ratio feedback correction coefficient changes beyond the normal determination range (allowable range), it is determined that there is a possibility that the fuel pressure sensor 33 has failed, and the drive duty of the fuel pump 12 is The feedback control is stopped, and the fuel pressure is raised to higher than normal by the feed forward control.

  Here, since the actual fuel pressure is close to the target fuel pressure for diagnosis by feedforward control, if the fuel pressure sensor 33 is normal, the detected value FUPR of the fuel pressure sensor 33 is close to the target fuel pressure for diagnosis. When the detected value FUPR of the fuel pressure sensor 33 is not a value near the target fuel pressure for diagnosis, it is determined that the fuel pressure sensor 33 is in an abnormal state in which a value different from the actual fuel pressure is detected. .

According to the failure diagnosis of the fuel pressure sensor 33 described above, the diagnosis can be performed while the engine 1 is in operation. Therefore, the abnormality is promptly detected and the process shifts to the fail-safe process, and deterioration of the exhaust property and driving performance of the engine 1 is as much as possible. Can be kept small.
In addition, since the failure diagnosis of the fuel pressure sensor 33 is performed when an abnormality in the air-fuel ratio occurs, the fuel pressure sensor 33 can be diagnosed under conditions that may cause an abnormality. In a state where there is no abnormality, it is possible to prevent unnecessary diagnostic processing from being performed, and it is possible to suppress power consumption and pump noise increase associated with the diagnosis.

In addition, when the failure diagnosis is started based on the abnormality of the air-fuel ratio, the fuel pressure is made higher than that before the failure diagnosis (normal time), so that the air-fuel ratio deviation margin due to the variation of the fuel injection valve 3 and the like can be reduced, and It is possible to suppress the actual fuel pressure from falling below the target fuel pressure, and to suppress deterioration in combustibility due to insufficient fuel pressure.
Here, the failure diagnosis of the fuel pressure sensor 33 can be performed while feedback control of the drive duty of the fuel pump 12 based on the detection value FUPR of the fuel pressure sensor 33, which will be specifically described below.

The routine shown in the flowchart of FIG. 7 is a diagnostic routine for the fuel pressure sensor 33 that is executed when the ignition switch (engine switch) is on and interrupted at a constant time period during the operation of the engine 1.
Note that the failure diagnosis shown in the flowchart of FIG. 7 can also be applied to a fuel supply apparatus that does not include the relief valve 12b.

First, in step S401, the value of the diagnosis execution flag fFSDIA set in the routine shown in the flowchart of FIG. 2 is read.
In the next step S402, it is determined whether or not a failure diagnosis of the fuel pressure sensor 33 is to be performed by determining whether or not the diagnosis execution flag fFSDIA is 1.

If 0 is set in the diagnosis execution flag fFSDIA, it is determined that it is not necessary to perform a failure diagnosis of the fuel pressure sensor 33, and this routine is terminated as it is.
On the other hand, if the diagnosis execution flag fFSDIA is set to 1, the process proceeds to step S403 in order to perform a failure diagnosis of the fuel pressure sensor 33.

In step S403, the target fuel pressure TGFUPR is set to a target fuel pressure TGPLAB for diagnosis that is higher than the target fuel pressure TGFUPR before starting diagnosis and lower than the valve opening pressure RVP of the relief valve 12b.
Then, the feedforward control duty (basic duty) FFDUTY where the target fuel pressure TGPRAB is expected to be substantially obtained is calculated, and the detected value FUPR is set to the target fuel pressure TGPRAB based on the deviation between the detected value FUPR of the fuel pressure sensor 33 and the target fuel pressure TGPRAB. The feedback control duty (correction duty) FBDUTY to be close to is calculated, and the fuel pump 12 is PWM-controlled using the sum of the feedforward control duty FFDUTY and the feedback control duty FBDUTY as the final control duty.
Note that the change in the feedback control duty FBDUTY is set in advance and limited to a variable range.

In step S404, after the feedback control for bringing the detected value FUPR of the fuel pressure sensor 33 closer to the target fuel pressure TGPRAB has converged, that is, after the feedback control duty (correction duty) becomes substantially constant, the feedback control duty FBDUTY is within the normal determination region. It is determined whether or not.
By controlling the fuel pump 12 with the feedforward control duty (basic duty) FFDUTY, the actual fuel pressure is controlled in the vicinity of the target fuel pressure TGPRAB, so that the fuel pressure sensor 33 is normal and an output substantially corresponding to the actual fuel pressure is output. If this occurs, the duty correction by the feedback control duty FBDUTY calculated based on the detection value FUPR of the fuel pressure sensor 33 is limited to a relatively small level necessary to absorb various variations. The feedback control duty (correction duty) FBDUTY converges in a relatively narrow range centered on the initial value.

On the other hand, when an abnormality occurs in the fuel pressure sensor 33 and an output corresponding to a fuel pressure different from the actual fuel pressure in the vicinity of the target fuel pressure TGPRAB is generated, the detected value FUPR away from the target fuel pressure TGPRAB is brought closer to the target fuel pressure TGPRAB. The feedback control duty FBDUTY is changed. As a result, the duty correction by the feedback control duty FBDUTY is larger than that in the normal state, and changes outside the convergence range in the normal state.
Therefore, when the fuel pressure sensor 33 is normal, a normality determination region is set in advance based on the duty correction amount by the feedback control duty FBDUTY required to absorb various variations, and if the fuel pressure sensor 33 is normal, feedback is performed. When the control duty FBDUTY is changed within the normal determination range and the feedback control duty FBDUTY is outside the normal determination range, the fuel pressure different from the actual fuel pressure is detected due to the abnormality of the fuel pressure sensor 33. It can be determined that the correction request by FBDUTY has been expanded.

The normal determination region of the feedback control duty FBDUTY is a variable range of the feedback control duty FBDUTY for absorbing the fuel pressure error when the fuel pump 12 is controlled with the feedforward control duty FFDUTY. The fuel pressure error is the fuel pump 12 Therefore, the normal determination region can be determined based on these error factors, and the normal determination region can be set variably according to the fuel property at that time. it can.
If it is determined in step S404 that the feedback control duty FBDUTY is within the normal determination region, the process proceeds to step S405, where it is determined that the fuel pressure sensor 33 is normal. If it is determined that the fuel pressure sensor 33 is normal, the abnormality of the air-fuel ratio is caused by an abnormality of a device other than the fuel pressure sensor 33 such as the fuel injection valve 3 and the air flow sensor 35.

On the other hand, if it is determined in step S404 that the feedback control duty FBDUTY is outside the normal determination range, the process proceeds to step S406, where it is determined that the fuel pressure sensor 33 is abnormal. That is, since the detected value FUPR of the fuel pressure sensor 33 is different from the actual fuel pressure, the fuel injection pulse width is corrected based on the detected value FUPR of the fuel pressure sensor 33. As a result, the fuel amount required for forming the target air-fuel ratio is reduced. Therefore, it is determined that the actual fuel injection amount has become excessive or insufficient, and that the actual air-fuel ratio has shifted from the target air-fuel ratio.
When the normality / abnormality of the fuel pressure sensor 33 is determined, the process further proceeds to step S407, and the diagnosis execution flag fFSDIA is reset to zero.

If it is determined that the fuel pressure sensor 33 is normal, the calculation of the drive duty of the fuel pump 12 based on the detection value FUPR of the fuel pressure sensor 33 and the fuel injection pulse width based on the detection value FUPR of the fuel pressure sensor 33 are performed. Continue the correction calculation.
On the other hand, when it is determined that the fuel pressure sensor 33 is abnormal, an alarm for notifying the occurrence of the abnormality is issued, the calculation of the drive duty of the fuel pump 12 based on the detection value FUPR of the fuel pressure sensor 33, and the fuel pressure sensor 33 The fuel injection pulse width correction calculation based on the detected value FUPR is prohibited, or the driving duty of the fuel pump 12 is fixed to a preset duty for sensor abnormality, and the fuel pressure corresponding to the duty is considered to be Perform fail-safe processing such as setting the fuel injection pulse width.

FIG. 8 shows an example of changes in the air-fuel ratio food back correction coefficient, duty, and detected value FUPR at the time of failure diagnosis of the fuel pressure sensor 33.
As shown in FIG. 8, when the fuel injection pulse width is corrected based on an erroneous detection value FUPR due to an abnormality in the fuel pressure sensor 33, the air-fuel ratio deviates from the target air-fuel ratio and attempts to absorb such air-fuel ratio deviation. The air-fuel ratio feedback correction coefficient is changed. When the air-fuel ratio deviation is large and the air-fuel ratio feedback correction coefficient changes beyond the normal determination range (allowable range), it is determined that there is a possibility that the fuel pressure sensor 33 has failed, and the drive duty of the fuel pump 12 is Increase the target fuel pressure in feedback control.

  Here, since the actual fuel pressure is in the vicinity of the target fuel pressure for diagnosis by feedforward control, if the fuel pressure sensor 33 is normal, the fuel pressure sensor 33 has a fuel pressure in the vicinity of the target fuel pressure for diagnosis that is the actual fuel pressure. , And the feedback control duty FBDUTY holds a value near the initial value. On the other hand, when an abnormality occurs in the fuel pressure sensor 33 and the fuel pressure sensor 33 detects a fuel pressure that is different from the target fuel pressure for diagnosis that is the actual fuel pressure, the fuel pressure sensor 33 tries to bring the detected value different from the actual fuel pressure closer to the target. As a result of changing the feedback control duty FBDUTY, the feedback control duty FBDUTY becomes a value away from the initial value, so that the abnormal state of the fuel pressure sensor 33 can be determined from the value of the feedback control duty FBDUTY.

According to the failure diagnosis of the fuel pressure sensor 33 described above, since the diagnosis can be performed during the operation of the engine 1, the abnormality is promptly detected and the process proceeds to the fail-safe process, and deterioration of the exhaust property and the drivability of the engine 1 is made possible. Can be kept small.
In addition, since the failure diagnosis of the fuel pressure sensor 33 is performed when an abnormality in the air-fuel ratio occurs, the fuel pressure sensor 33 can be diagnosed under conditions that may cause an abnormality. In a state where there is no abnormality, it is possible to prevent unnecessary diagnostic processing from being performed, and it is possible to suppress power consumption and pump noise increase associated with the diagnosis.

Further, in the failure diagnosis, as in the case where diagnosis is not performed, the calculation of the feedforward control duty FFDUTY based on the target fuel pressure TGFUPR and the calculation of the feedback control duty FBDUTY based on the target fuel pressure TGFUPR and the detected value FUPR by the fuel pressure sensor 33 Therefore, the control change for diagnosis can be reduced.
Further, since the feedback control of the fuel pressure is continued during the diagnosis, if the fuel pressure sensor 33 is normal, the control accuracy of the fuel pressure can be maintained even during the diagnosis, and the occurrence of the air-fuel ratio shift can be suppressed.
Further, by increasing the target fuel pressure at the time of diagnosis, it is possible to suppress the actual fuel pressure from falling below the fuel pressure required under the operating conditions at that time due to the abnormality of the fuel pressure sensor 33, and it is possible to suppress the deterioration of combustibility.

Although the preferred embodiments have been specifically described above, it is obvious that those skilled in the art can take various modifications.
For example, instead of making a failure diagnosis of the fuel pressure sensor 33 on the condition that an air-fuel ratio shift has occurred, a failure diagnosis of the fuel pressure sensor 33 is performed when the operating conditions of the engine 1 correspond to preset diagnosis execution conditions. Can be performed.

In addition, the fuel pressure sensor 33 can be disposed in the fuel supply pipe 15, and the fuel pump 12 supplies fuel to the engine-driven high-pressure fuel pump and supplies fuel from the high-pressure fuel pump to the fuel injection valve. In the apparatus, the present invention can also be applied to failure diagnosis of a fuel pressure sensor that detects the supply pressure of fuel to the high-pressure fuel pump by the fuel pump 12.
Also, the presence or absence of an air-fuel ratio deviation is determined from the detected value of the air-fuel ratio sensor 38 in the stopped state of the air-fuel ratio feedback control for correcting the fuel injection pulse width based on the detection result of the air-fuel ratio sensor 38. Can be diagnosed.
Further, when the detection value of the fuel pressure sensor 33 continues to be out of the normal determination region, the abnormality determination of the fuel pressure sensor 33 can be performed.

Here, technical ideas other than the claims that can be grasped from the above embodiment will be described together with effects.
(B) A configuration for correcting the injection pulse width of the fuel injection valve based on the detection value of the fuel pressure sensor,
The presence or absence of a failure in the fuel pressure sensor is determined by changing an operation amount of the fuel pump in a direction to increase the supply pressure when a deviation of an actual air fuel ratio from a target air fuel ratio exceeds an allowable range. The control apparatus for an internal combustion engine according to claim 1.

According to the above invention, since the injection pulse width of the fuel injection valve is corrected based on the detected value of the fuel pressure sensor, an error occurs in the fuel injection amount due to an error in the detected value of the fuel pressure sensor, and the air-fuel ratio deviates from the target air-fuel ratio. The occurrence of the air-fuel ratio deviation may be caused by the failure of the fuel pressure sensor. On the other hand, if the air-fuel ratio deviation does not occur, it can be estimated that the fuel pressure sensor is normal. When the air-fuel ratio deviation exceeds the allowable range, the fuel pressure sensor is diagnosed.
Thereby, it can suppress performing a diagnosis, although a fuel pressure sensor is normal.

(B) Based on whether or not the detected value of the fuel pressure sensor is within a normal determination region corresponding to the change in the operation amount, it is determined whether or not there is a failure in the fuel pressure sensor;
The control device for an internal combustion engine according to claim 1, wherein the normality determination region is variably set in accordance with fuel properties.

  According to the above invention, the fuel pressure actually obtained varies with respect to the amount of operation of the fuel pump depending on the fuel properties (height and lightness of the fuel, differences in viscosity, etc.), so the normal judgment range of the fuel pressure detection value according to the fuel properties Is set to suppress misdiagnosis of a difference in fuel pressure due to a difference in fuel properties as a failure of the fuel pressure sensor.

(C) Based on whether or not the fuel pressure sensor detects the supply pressure corresponding to the diagnostic operation amount by increasing and changing the operation amount of the fuel pump to a preset diagnostic operation amount. The control device for an internal combustion engine according to claim 1, wherein presence or absence of a failure in the fuel pressure sensor is determined.

  According to the above invention, since the actual supply pressure when the operation amount for diagnosis is given to the fuel pump becomes a value substantially corresponding to the operation amount for diagnosis, the fuel pressure sensor at that time uses the operation amount for diagnosis. Whether or not the fuel pressure sensor is normal is diagnosed based on whether or not a supply pressure substantially corresponding to the above is detected.

(D) Increasing and changing the target value of the supply pressure toward the target value for diagnosis, the feedforward operation amount corresponding to the target value for diagnosis, and detection of the target value for diagnosis and the fuel pressure sensor Controlling the fuel pump with a feedback manipulated variable based on the value;
The control apparatus for an internal combustion engine according to claim 1, wherein the presence or absence of a failure in the fuel pressure sensor is determined based on the feedback operation amount.

According to the above invention, by supplying the feedforward operation amount to the fuel pump, the actual supply pressure becomes close to the target value for diagnosis, and the feedback operation amount is the difference between the detected value of the fuel pressure sensor and the target value for diagnosis. Is set to be reduced.
Therefore, if the fuel pressure sensor is normal, the fuel pressure near the target value for diagnosis is detected when the feedforward operation amount is given to the fuel pump, and the fuel pressure difference to be absorbed by the feedback operation amount is relatively small. On the other hand, if the fuel pressure sensor is faulty and the detected value is different from the target value for diagnosis, the apparent fuel pressure difference to be absorbed by the feedback manipulated variable will be larger than normal, so feedback correction Based on the amount of fuel, failure diagnosis of the fuel pressure sensor can be performed.

  DESCRIPTION OF SYMBOLS 1 ... Engine (internal combustion engine), 2 ... Intake passage, 3 ... Fuel injection valve, 4 ... Intake valve, 12 ... Fuel pump, 12b ... Relief valve, 31 ... ECM (engine control module), 33 ... Fuel pressure sensor

Claims (2)

A control device that is applied to an internal combustion engine that includes a fuel pump and a fuel pressure sensor that detects a fuel supply pressure by the fuel pump, and that outputs an operation amount of the fuel pump according to a detection value of the fuel pressure sensor. ,
For the diagnosis of the fuel pressure sensor, the operation amount of the fuel pump is changed in the direction of increasing the supply pressure, and based on the detected value of the fuel pressure sensor at this time, the presence or absence of a failure in the fuel pressure sensor is determined. Control device for internal combustion engine. The internal combustion engine includes a relief valve that opens and relieves fuel when the supply pressure exceeds a valve opening pressure;
The operation amount of the fuel pump is changed to an operation amount corresponding to a supply pressure exceeding the valve opening pressure, and the presence or absence of a failure in the fuel pressure sensor is determined based on a detection value of the fuel pressure sensor at this time. Item 2. A control device for an internal combustion engine according to Item 1.