Control device of internal combustion engine

A fuel cut failsafe function monitoring section of a microcomputer sets a fuel cut failsafe function diagnosis period in a period, in which an operation of an engine is stopped (e.g., a period before engine start), and sends a fuel cut failsafe execution command signal to a fuel cut failsafe execution section of an abnormality monitoring device during the fuel cut failsafe function diagnosis period. Thus, the fuel cut failsafe execution section is caused to output a fuel cut failsafe signal to an injector driver to stop an operation of the injector driver. The fuel cut failsafe function monitoring section monitors an output level of a disablement port of the injector driver at the time, thereby performing abnormality diagnosis of a fuel cut failsafe function.

CROSS REFERENCE TO RELATED APPLICATION

This application is based on and incorporates herein by reference Japanese Patent Application No. 2007-305242 filed on Nov. 27, 2007.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a control device of an internal combustion engine that monitors an operating state of a microcomputer controlling at least a fuel injection device and that activates a fuel cut failsafe function when an abnormality in the microcomputer is detected.

2. Description of Related Art

A control device of this kind for an internal combustion engine is described in Patent document 1 (PCT application Japanese translation No. H4-500846), for example. The control device compulsorily activates a fuel cut failsafe function when deceleration fuel cut (i.e., fuel cut during deceleration) is performed during running of a vehicle and monitors an operation state of the fuel cut failsafe function. Thus, the control device aims to perform abnormality diagnosis of the fuel cut failsafe function without affecting drivability during the running of the vehicle.

However, since the control device described in above Patent document 1 performs the abnormality diagnosis of the fuel cut failsafe function during the deceleration fuel cut period in the running of the vehicle, the vehicle runs in a state where the abnormality diagnosis of the fuel cut failsafe function is not performed during a period since the running of the vehicle is started until the deceleration fuel cut is performed. Therefore, the vehicle running is performed without detecting the abnormality even if the fuel cut failsafe function is abnormal during the period since the running of the vehicle is started until the deceleration fuel cut is performed.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a control device of an internal combustion engine capable of performing abnormality diagnosis of a fuel cut failsafe function before a driver starts running of a vehicle, thereby avoiding the running of the vehicle in a state where the fuel cut failsafe function is abnormal.

According to an aspect of the present invention, a control device of an internal combustion engine has a microcomputer and an abnormality monitoring device. The microcomputer controls at least a fuel injection device of the internal combustion engine. The abnormality monitoring device monitors an operation state of the microcomputer and activates a fuel cut failsafe function by outputting a fuel cut failsafe signal to the fuel injection device to compulsorily stop fuel injection of cylinders when the abnormality monitoring device detects an abnormality in the microcomputer. The microcomputer has a fuel cut failsafe function monitoring section that sets a fuel cut failsafe function diagnosis period in a period in which an operation of the internal combustion engine is stopped, that causes the abnormality monitoring device to output the fuel cut failsafe signal to the fuel injection device during the fuel cut failsafe function diagnosis period, and that monitors a signal state of an operation state monitoring port of the fuel injection device at the time, thereby performing abnormality diagnosis of the fuel cut failsafe function. With such the construction, the abnormality diagnosis of the fuel cut failsafe function can be performed before the driver starts running of the vehicle. Accordingly, the running of the vehicle in a state where the fuel cut failsafe function is abnormal can be avoided.

According to the present invention, the fuel cut failsafe function diagnosis period may be set arbitrarily in the period in which the operation of the internal combustion engine is stopped. Therefore, for example, the fuel cut failsafe function diagnosis period may be set in a period in which a main relay of a power supply circuit is maintained at an ON state for a while after the internal combustion engine stops (i.e., an ON period of the main relay after the stop of the internal combustion engine).

However, if an engine stoppage time lengthens when the fuel cut failsafe function diagnosis period is set in the ON period of the main relay after the stop of the internal combustion engine, there is a possibility that an abnormality is caused in the fuel cut failsafe function by some causes during the stoppage of the internal combustion engine.

Therefore, according to another aspect of the present invention, the fuel cut failsafe function monitoring section sets the fuel cut failsafe function diagnosis period in a period since a switching-on operation (i.e., ON operation) of an ignition switch of the internal combustion engine is performed until start of the internal combustion engine is commenced. Thus, even if the abnormality is caused in the fuel cut failsafe function by some causes during the stoppage of the internal combustion engine, the abnormality in the fuel cut failsafe function can be detected in the period since the ON operation of the ignition switch is performed until the start of the internal combustion engine is commenced after the occurrence of the abnormality. Accordingly, the running of the vehicle in a state where the fuel cut failsafe function is abnormal can be surely avoided.

According to another aspect of the present invention, the fuel cut failsafe function monitoring section directs the abnormality monitoring device to output the fuel cut failsafe signal during the fuel cut failsafe function diagnosis period, thereby causing the abnormality monitoring device to output the fuel cut failsafe signal to the fuel injection device. With such the construction, the abnormality monitoring device can be caused to output the fuel cut failsafe signal to the fuel injection device by simple processing.

In the case where the microcomputer has a test execution section for testing an operation of the microcomputer, according to yet another aspect of the present invention, the fuel cut failsafe function monitoring section causes the test execution section to output an abnormal test result to the abnormality monitoring device during the fuel cut failsafe function diagnosis period to provide a state where the abnormality monitoring device detects the abnormality in the microcomputer, thereby causing the abnormality monitoring device to output the fuel cut failsafe signal to the fuel injection device. With such the construction, it can be additionally determined whether both of the test execution section of the microcomputer and an abnormality determination section of the abnormality monitoring device function normally when performing the abnormality diagnosis of the fuel cut failsafe function.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

Hereafter, two embodiments of the present invention will be described with reference to the drawings.

A first embodiment of the present invention will be described below with reference toFIGS. 1 to 3. First, an entire system configuration will be explained with reference toFIG. 1.

A microcomputer11(CPU) has functions of an engine control section13controlling a fuel injection device12and the like, an engine control monitoring section14monitoring an operation state of the engine control section13, a test execution section15testing an operation of the microcomputer11, a fuel cut failsafe function monitoring section16performing an abnormality diagnosis of a fuel cut failsafe function, and the like. The microcomputer11realizes the functions with various programs stored in ROM (not shown). The engine control section13may control at least one of an electronic throttle device, a variable valve device, an EGR device and the like of an engine (an internal combustion engine, not shown) in addition to the fuel injection device12, for example.

The fuel injection device12consists of an injector driver17, into which an injection signal is inputted from the engine control section13, and injectors18of respective cylinders driven by the injector driver17. The single injector driver17drives the injectors18of all the cylinders.

An abnormality monitoring device21has functions of an abnormality determination section22that monitors an operation state of the microcomputer11and determines existence/nonexistence of an abnormality in the microcomputer11, a fuel cut failsafe execution section23that activates a fuel cut failsafe function by outputting a fuel cut failsafe signal to the injector driver17for compulsorily stopping the fuel injection of the cylinders when the abnormality determination section22detects the abnormality in the microcomputer11, and the like. The abnormality monitoring device21may be constituted of an abnormality monitoring IC or may be constituted of a microcomputer (CPU) separate from the microcomputer11.

In the present embodiment, the fuel cut failsafe function monitoring section16of the microcomputer11sets a fuel cut failsafe function diagnosis period in a period, in which operation of the engine is stopped. The fuel cut failsafe function monitoring section16outputs a fuel cut failsafe execution command signal to the fuel cut failsafe execution section23of the abnormality monitoring device21during the fuel cut failsafe function diagnosis period. Thus, the fuel cut failsafe function monitoring section16causes the fuel cut failsafe execution section23to output a fuel cut failsafe signal to the injector driver17to stop the operation of the injector driver17. The fuel cut failsafe function monitoring section16monitors an output level of a disablement port (an operation state monitoring port) indicating an operation state of the injector driver17at the time. Thus, the fuel cut failsafe function monitoring section16performs abnormality diagnosis of the fuel cut failsafe function.

According to the present invention, the fuel cut failsafe function diagnosis period may be set arbitrarily in the period, in which the operation of the engine is stopped. Therefore, for example, the fuel cut failsafe function diagnosis period may be set in a period, in which a main relay of a power supply circuit (not shown) is maintained at an ON state for a while after the engine stops (i.e., an ON period of the main relay after the engine stop).

However, if an engine stoppage time lengthens when the fuel cut failsafe function diagnosis period is set in the ON period of the main relay after the engine stop, there is a possibility that an abnormality is caused in the fuel cut failsafe function by some causes during the engine stoppage.

Therefore, in the first embodiment, the fuel cut failsafe function diagnosis period is set in a period since ON operation (i.e., switching-on operation) of an ignition switch (not shown) is performed until engine start is commenced. Thus, even if the abnormality is caused in the fuel cut failsafe function by some causes during the engine stoppage, the abnormality in the fuel cut failsafe function can be detected in the period since the ON operation of the ignition switch is performed until the engine start is commenced after the occurrence of the abnormality.

The above-described abnormality diagnosis of the fuel cut failsafe function according to the first embodiment is performed by the microcomputer11as follows according to a fuel cut failsafe function abnormality diagnosis program shown inFIG. 2. The program is executed in a predetermined cycle during an ON period of a power supply to the microcomputer11(i.e., during the ON period of the main relay of the power supply circuit).

If the program is started, first in S101(S means “Step”), it is determined whether an IG flag is ON, which indicates an ON state of the ignition switch. If the IG flag is OFF, which indicates an OFF state of the ignition switch, it is determined that the abnormality diagnosis of the fuel cut failsafe function is prohibited, and the program is ended without executing subsequent processing.

If it is determined in S101that the IG flag is ON, the process proceeds to S102, in which it is determined whether the current state is before the engine start. If the current state is not before the engine start, it is determined that the abnormality diagnosis of the fuel cut failsafe function is prohibited, and the program is ended without executing subsequent processing.

If both of S101and S102are YES, it is determined that the current state is in the fuel cut failsafe function diagnosis period in which the abnormality diagnosis of the fuel cut failsafe function is permitted, and the process proceeds to S103. In S103, a fuel cut failsafe function monitoring execution flag is set to ON to activate the fuel cut failsafe function monitoring section16.

Then, the process proceeds to S104, in which a fuel cut failsafe execution flag is set to ON to cause the fuel cut failsafe function monitoring section16to send a fuel cut failsafe execution command signal to the fuel cut failsafe execution section23of the abnormality monitoring device21. Thus, the fuel cut failsafe execution section23is caused to output a fuel cut failsafe signal to the injector driver17to stop the operation of the injector driver17. The fuel cut failsafe function monitoring section16monitors the output level of the disablement port of the injector driver17at the time.

When the fuel cut failsafe function is normal, the output level of the disablement port becomes H level, and a disablement flag is set to ON. When the fuel cut failsafe function is abnormal, the output level of the disablement port is not changed from L level, and the disablement flag is maintained at OFF.

In following S105, it is determined whether the fuel cut failsafe function is normal based on whether the disablement flag is ON. When the disablement flag is ON, it is determined that the fuel cut failsafe function is normal, and an abnormality flag is maintained at OFF in S106. When the disablement flag is OFF, it is determined that the fuel cut failsafe function is abnormal, and the abnormality flag is set to ON in S107.

If the abnormality flag is maintained at OFF when the abnormality diagnosis of the fuel cut failsafe function ends, the start of the engine (i.e., energization to a starter) is permitted promptly. If the abnormality flag is set at ON when the abnormality diagnosis of the fuel cut failsafe function ends, the start of the engine is prohibited.

A time chart ofFIG. 3shows an execution example of the above-described fuel cut failsafe function abnormality diagnosis program ofFIG. 2. As shown inFIG. 3, the fuel cut failsafe function monitoring execution flag (FAILSAFE FUNCTION MONITORING FLAG inFIG. 3) and the fuel cut failsafe execution flag (FAILSAFE EXECUTION FLAG inFIG. 3) are set to ON respectively immediately after the driver performs the ON operation of the ignition switch and the IG flag is switched from OFF to ON. Thus, the fuel cut failsafe function monitoring section16sends the fuel cut failsafe execution command signal to the fuel cut failsafe execution section23of the abnormality monitoring device21, thereby performing the abnormality diagnosis of the fuel cut failsafe function.

Thus, the fuel cut failsafe execution section23of the abnormality monitoring device21outputs the fuel cut failsafe signal to the injector driver17to stop the operation of the injector driver17. The output level of the disablement port of the injector driver17at the time is read into the microcomputer11. If the fuel cut failsafe function is normal, the output level of the disablement port is at the H level, and the disablement flag is set to ON. If the fuel cut failsafe function is abnormal, the output level of the disablement port does not change from the L level, and the disablement flag is maintained at OFF. Using the relationship, it is determined whether the fuel cut failsafe function is normal based on whether the disablement flag is ON.

If it is determined that the fuel cut failsafe function is normal as the result, a start permission state is established promptly. If the driver performs the starting operation in this state, a starter (not shown) is energized promptly and the engine is started.

According to the above-described first embodiment, the fuel cut failsafe function diagnosis period is set in the period (the period before the engine start), in which the operation of the engine is stopped. The fuel cut failsafe execution command signal is sent to the fuel cut failsafe execution section23of the abnormality monitoring device21during the fuel cut failsafe function diagnosis period. Thus, the fuel cut failsafe execution section23is caused to output the fuel cut failsafe signal to the injector driver17. The output level of the disablement port of the injector driver17at the time is monitored. Thus, the abnormality diagnosis of the fuel cut failsafe function is performed. Accordingly, the abnormality diagnosis of the fuel cut failsafe function can be performed before the driver starts running of the vehicle. As a result, the running of the vehicle in a state where the fuel cut failsafe function is abnormal can be avoided.

Moreover, according to the first embodiment, the abnormality diagnosis of the fuel cut failsafe function is performed in the period since the ON operation of the ignition switch is performed until the engine start is commenced. Accordingly, even when the abnormality is caused in the fuel cut failsafe function by some causes during the engine stoppage, the abnormality in the fuel cut failsafe function can be detected in the period since the ON operation of the ignition switch is performed until the engine start is commenced after the occurrence of the abnormality. Accordingly, the running of the vehicle in the state where the fuel cut failsafe function is abnormal can be surely avoided.

The fuel cut failsafe execution section23of the abnormality monitoring device21outputs the fuel cut failsafe signal to the injector driver17to stop the operation of the injector driver17. Accordingly, the fuel cut failsafe of all the cylinders can be checked at the same time, thereby quickly performing the abnormality diagnosis of the fuel cut failsafe function.

Next, the second embodiment of the present invention will be explained.

In the above-described first embodiment, the fuel cut failsafe function monitoring section16of the microcomputer11sends the fuel cut failsafe execution command signal to the fuel cut failsafe execution section23of the abnormality monitoring device21during the fuel cut failsafe function diagnosis period. Thus, the fuel cut failsafe execution section23is caused to output the fuel cut failsafe signal to the injector driver17to perform the abnormality diagnosis of the fuel cut failsafe function.

The second embodiment of the present invention shown inFIGS. 4 and 5uses the test execution section15of the microcomputer11. That is, the fuel cut failsafe function monitoring section16of the microcomputer11according to the second embodiment causes the test execution section15to send an abnormal test result to the abnormality determination section22of the abnormality monitoring device21during the fuel cut failsafe function diagnosis period, providing a state where the abnormality determination section22detects the abnormality in the microcomputer11. Thus, the fuel cut failsafe execution section23of the abnormality monitoring device21is caused to output the fuel cut failsafe signal to the injector driver17. The other construction is the same as the first embodiment (shown inFIG. 1).

The above-described abnormality diagnosis of the fuel cut failsafe function according to the second embodiment is performed by the microcomputer11as follows according to a fuel cut failsafe function abnormality diagnosis program shown inFIG. 4. The program is executed in a predetermined cycle during the ON period of the power supply to the microcomputer11.

If the program is started, first in S201, it is determined whether the IG flag is ON, which indicates ON state of the ignition switch. If the IG flag is OFF, which indicates the OFF state of the ignition switch, it is determined that the abnormality diagnosis of the fuel cut failsafe function is prohibited, and the program is ended without executing subsequent processing.

If it is determined in S201that the IG flag is ON, the process proceeds to S202, in which it is determined whether the current state is before the engine start. If the current state is not before the engine start, it is determined that the abnormality diagnosis of the fuel cut failsafe function is prohibited, and the program is ended without executing subsequent processing.

If both of S201and S202are YES, it is determined that the current state is in the fuel cut failsafe function diagnosis period, in which the abnormality diagnosis of the fuel cut failsafe function is permitted, and the process proceeds to S203. In S203, the fuel cut failsafe function monitoring execution flag is set to ON to activate the fuel cut failsafe function monitoring section16.

Then, the process proceeds to S204, in which an abnormal test result is calculated in the test execution section15, and the abnormal test result is sent to the abnormality determination section22of the abnormality monitoring device21. Then, the process proceeds to S205, in which the abnormality determination section22determines whether the test result is abnormal. If it is determined that the test result is not abnormal, the program is ended without performing subsequent processing.

If it is determined in S205that the test result is abnormal, the process proceeds to S206, in which a computer abnormality determination flag is set to ON, which indicates the abnormality in the microcomputer11. In following S207, the fuel cut failsafe execution flag is set to ON to cause the abnormality determination section22to send the fuel cut failsafe function execution command signal to the fuel cut failsafe execution section23. Thus, the fuel cut failsafe execution section23is caused to output the fuel cut failsafe signal to the injector driver17to stop the operation of the injector driver17. The fuel cut failsafe function monitoring section16monitors the output level of the disablement port of the injector driver17at the time.

When the fuel cut failsafe function is normal, the output level of the disablement port becomes H level, and the disablement flag is set to ON. When the fuel cut failsafe function is abnormal, the output level of the disablement port does not change from L level, and the disablement flag is maintained at OFF.

In following S208, it is determined whether the fuel cut failsafe function is normal based on whether the disablement flag is ON. When the disablement flag is ON, it is determined that the fuel cut failsafe function is normal, and the abnormality flag is maintained at OFF in S209. When the disablement flag is OFF, it is determined that the fuel cut failsafe function is abnormal, and the abnormality flag is set to ON in S210. If the abnormality flag is set to ON, the start of the engine (energization to the starter) is prohibited.

A time chart ofFIG. 5shows an execution example of the above-described fuel cut failsafe function abnormality diagnosis program ofFIG. 4. As shown inFIG. 5, the fuel cut failsafe function monitoring execution flag (FAILSAFE FUNCTION MONITORING FLAG inFIG. 5), the computer abnormality determination flag and the fuel cut failsafe execution flag (FAILSAFE EXECUTION FLAG inFIG. 5) are set to ON respectively immediately after the IG flag is switched from OFF to ON through the ON operation of the ignition switch. Thus, the test execution section15of the microcomputer11sends the abnormal test result to the abnormality determination section22of the abnormality monitoring device21to provide a state where the abnormality determination section22detects the abnormality in the microcomputer11. Thus, the fuel cut failsafe execution section23of the abnormality monitoring device21is caused to output the fuel cut failsafe signal to stop the operation of the injector driver17. Thus, the abnormality diagnosis of the fuel cut failsafe function is performed, and it is determined whether the fuel cut failsafe function is normal based on whether the disablement flag is ON. If it is determined that the fuel cut failsafe function is normal as the result, a start permission state is established promptly. If the driver performs the starting operation in this state, the starter (not shown) is energized promptly and the engine is started.

According to the above-described second embodiment, the test execution section15of the microcomputer11sends the abnormal test result to the abnormality determination section22of the abnormality monitoring device21to provide the state where the abnormality determination section22detects the abnormality in the microcomputer11. Thus, the fuel cut failsafe execution section23of the abnormality monitoring device21is caused to output the fuel cut failsafe signal. Therefore, the second embodiment exerts an effect of additionally enabling determination of whether both of the test execution section15of the microcomputer11and the abnormality determination section22of the abnormality monitoring device21function normally when performing the abnormality diagnosis of the fuel cut failsafe function.

According to the fuel cut failsafe function abnormality diagnosis programs ofFIGS. 2 and 4, the abnormality diagnosis of the fuel cut failsafe function is performed in the period since the ON operation of the ignition switch is performed until the engine start is commenced. The period for performing the abnormality diagnosis may be set arbitrarily in the period, in which the operation of the engine is stopped. Therefore for example, the abnormality diagnosis of the fuel cut failsafe function may be performed in a period, in which the main relay of the power supply circuit (not shown) is maintained at the ON state for a while after the engine stops (i.e., an ON period of the main relay after the engine stop).