JPH1136924A - Control device for engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To surely and rapidly carry out fault diagnosis for an item to be diagnosed in an engine using an electronic throttle control system, by surly continuing diagnosing terms in accordance with an engine condition. SOLUTION: Diagnosing terms are determined in accordance with an operating condition of an engine, and if the diagnosing terms are satisfied, fault diagnosis is carried out for an item to be diagnosed. Further, a desired throttle opening degree THVTGT for a throttle valve is set with reference to a table in accordance with an accelerator opening degree ALPH indicating a degree of manipulation upon an accelerator by a driver (S21). Further, the fault diagnosis is carried out (S22), and when the fault diagnosis is not carried out, the above-mentioned desired throttle opening degree THVTGT which has been set in accordance with the accelerator opening degree ALPH is used. Meanwhile, during execution of the fault diagnosis, a desired throttle opening degree THVTGT is reset in accordance with an actual throttle opening degree THVDIAGST upon initiation of the fault diagnosis (S24). Further, a control value DACT for a throttle valve actuator for actuating the throttle valve is set in accordance with a deviation ΔTH between the desired throttle opening degree THVTGT and a present actual opening degree of the throttle valve (S25 to S27).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention employs an electronic throttle control system that operates a throttle valve by a throttle actuator, and determines a diagnosis condition based on an engine operating state when performing a failure diagnosis on a diagnosis target. More specifically, the present invention relates to an engine control device that performs a failure diagnosis on a diagnosis target when a diagnosis condition is satisfied. More specifically, it is possible to reliably and quickly perform a failure diagnosis on a diagnosis target by reliably continuing a diagnosis condition based on an engine operating state. The present invention relates to an engine control device.

[0002]

2. Description of the Related Art Conventionally, instead of directly connecting an accelerator pedal and a throttle valve provided in an intake system of an engine by a wire, an accelerator operation amount such as an accelerator pedal depression amount is detected by an accelerator sensor. An electronic throttle control system in which a throttle valve is actuated by a throttle actuator including a stepping motor, a DC servo motor, and the like is employed (Japanese Patent Laid-Open No. 7-7).
7088, JP-A-7-158492, etc.).

In this type of electronic throttle control system, an output signal of the accelerator sensor and an output signal of a throttle opening sensor for detecting the actual opening of the throttle valve are input to a control device and detected by the accelerator sensor. The target throttle opening is set based on the operated accelerator operation amount. A control amount for the throttle actuator is set based on the target throttle opening and the actual throttle opening of the throttle valve detected by the throttle opening sensor, and a drive signal based on the control amount is output to the throttle actuator. In general, the throttle valve is operated by a throttle actuator, and feedback control is performed so that the actual throttle opening by the throttle valve coincides with the target throttle opening.

[0004] In parallel with this, in the engine control system, output signals from various sensors for detecting the engine operating state are input to the control device, and based on the engine operating state data detected by these various sensors. A fuel injection amount, an ignition timing, and the like are set, and a driving signal based on the fuel injection amount and an ignition timing are output to actuators such as an injector and an igniter to perform engine control such as fuel injection control and ignition timing control.

[0005] Here, if a sensor for detecting the operating state of the engine or an actuator to be controlled breaks down, the controllability of the engine is remarkably deteriorated, and the exhaust emission is deteriorated and the engine is adversely affected.

For this reason, the control device has a self-diagnosis function and performs on-board failure diagnosis, and performs failure diagnosis on various sensors and various actuators by matching various input data input from these sensors. sex,
Alternatively, it is performed by determining the consistency of the output data for each actuator, and when a failure occurs, the failure is notified by lighting an alarm lamp or the like.

[0007] Therefore, the control device performs a failure diagnosis on various sensors and various actuators by judging the consistency of various input / output data. Therefore, the on-board failure diagnosis by the control device can be freely performed by a driver. During driving, only under certain operating conditions, that is, only when diagnostic conditions based on a predetermined engine operating state are satisfied,
Failure diagnosis is performed on the diagnosis target.

Here, the failure diagnosis for the sensor to be diagnosed is performed by judging a diagnostic condition based on an engine operating state detected by another sensor, and when the diagnostic condition is satisfied and the output of the sensor to be diagnosed at this time is determined. The value is out of the set range and indicates a value which cannot be normally taken in this engine operating state. When this state continues for a predetermined time, it is determined that the sensor to be diagnosed has failed.

That is, when the abnormal state of the sensor output value continues for a predetermined period of time, it is diagnosed as a failure to prevent erroneous diagnosis due to a temporary sudden change in the sensor output value due to disturbance or the like.

In the failure diagnosis for the actuators, a diagnosis condition is determined based on an engine operating state detected by various sensors, and the diagnosis condition is satisfied. When the state has continued for a predetermined number of times, that is, for a predetermined time, it is determined that the actuator to be diagnosed has failed.

[0011]

However, when the above-mentioned electronic throttle control system is adopted, the accelerator operation amount changes according to the accelerator operation by the driver, and the target throttle opening set based on the accelerator operation amount is set. The control amount for the throttle actuator is set so that the actual throttle opening of the throttle valve coincides with each other, and the throttle valve is operated via the throttle actuator. Accordingly, the engine operating state changes accordingly.

Therefore, when performing the failure diagnosis, the engine operation state cannot be maintained at the predetermined engine operation state corresponding to the diagnosis condition during the above-mentioned predetermined time for giving the duration of the abnormal state, or the engine operation state itself is not changed. Failure to meet the diagnostic conditions, delaying the failure diagnosis for the diagnosis target, or
This causes inconvenience that failure diagnosis is not performed.

As a result, even if a failure occurs, the failure cannot be determined by the on-board failure diagnosis and the failure is not reported, so that the operation is continued with the failure, and the exhaust emission deteriorates and the engine is adversely affected. And so on.

The present invention has been made in view of the above circumstances, and in an engine employing an electronic throttle control system, an engine capable of reliably continuing a diagnosis condition based on an engine operation state and performing a failure diagnosis for a diagnosis target reliably and promptly. It is an object of the present invention to provide a control device.

[0015]

According to a first aspect of the present invention, a control amount for a throttle actuator is set based on a driver's accelerator operation amount, and a throttle valve is operated by the throttle actuator. Control the throttle valve opening to determine the diagnosis condition based on the engine operating state when performing a failure diagnosis on the diagnosis target, and when the diagnosis condition is satisfied, perform the failure diagnosis on the diagnosis target. In the control device,
As shown in the basic configuration diagram of FIG. 1, a diagnosing means for judging a diagnostic condition based on an engine operating state and performing a fault diagnosis on a diagnosis target when the diagnostic condition is satisfied; Set the target throttle opening for the throttle valve based on the amount and set the target throttle opening to a value corresponding to the throttle opening when the diagnosis condition is satisfied during the execution of the failure diagnosis. Means, and control amount setting means for setting a control amount for the throttle actuator based on the target throttle opening and the actual throttle opening by the throttle valve.

According to a second aspect of the present invention, in the first aspect of the present invention, the diagnostic means determines a diagnostic condition based on an engine operating state detected by a sensor excluding a diagnostic target. When a state in which the output value from the diagnosis target or the output value of the diagnosis target indicates an abnormal value continues for a predetermined time, the diagnosis target is diagnosed as a failure and the failure is notified, and the target throttle opening degree setting means includes: During the execution of the failure diagnosis, the difference between the accelerator operation amount at the start of the diagnosis and the current accelerator operation amount is compared with a predetermined value, and when the difference is smaller than the predetermined value, the target throttle opening is measured at the start of the diagnosis. The throttle opening is set to a value corresponding to the throttle opening, and when the difference is equal to or greater than a predetermined value, the target throttle opening set based on the current accelerator operation amount is adopted.

According to a third aspect of the present invention, in the first or second aspect, the accelerator operation amount is an accelerator opening indicating an amount of depression of an accelerator pedal.

That is, according to the first aspect of the present invention, a diagnosis condition is determined based on an engine operating state, and when the diagnosis condition is satisfied, a failure diagnosis is performed on a diagnosis target. And
Judging the execution of the failure diagnosis, and when not performing the failure diagnosis,
The target throttle opening for the throttle valve is set based on the accelerator operation amount by the driver, while the target throttle opening is set to a value corresponding to the throttle opening when the diagnosis condition is satisfied during the execution of the failure diagnosis. Set. Then, the control amount for the throttle actuator that operates the throttle valve is set based on the target throttle opening and the actual throttle opening by the throttle valve. Therefore, during the execution period of the failure diagnosis for the diagnosis target due to the establishment of the diagnosis condition, the target throttle opening is set to a value corresponding to the throttle opening when the diagnosis condition is established, and the actual throttle opening of the throttle valve is set. However, the throttle valve is operated via the throttle actuator so as to match the target throttle opening. As a result, the state of satisfaction of the diagnosis condition based on the engine operating state is reliably continued, and the failure diagnosis for the diagnosis target can be performed reliably and quickly.

According to the second aspect of the present invention, when performing a failure diagnosis on a diagnosis target, a diagnosis condition is determined based on an engine operating state detected by a sensor excluding the diagnosis target. Then, when a state in which the output value from the diagnosis target or the output value to the diagnosis target indicates an abnormal value continues for a predetermined time under the satisfaction of the diagnosis condition, the failure is diagnosed as the diagnosis target and the failure is notified. Further, when setting the target throttle opening, during the failure diagnosis execution period, the difference between the accelerator operation amount at the start of the diagnosis and the current accelerator operation amount is compared with a predetermined value. When the difference is smaller than the predetermined value, the target throttle opening is set to a value corresponding to the actual throttle opening at the start of the diagnosis, so that the diagnosis condition based on the engine operating state can be reliably obtained regardless of the accelerator operation by the driver. To continue. On the other hand, when the difference between the accelerator operation amount at the start of diagnosis and the current accelerator operation amount is equal to or greater than a predetermined value, the target throttle opening set based on the current accelerator operation amount is employed to perform normal throttle control. And the required engine output by the driver's accelerator operation is secured.

In this case, according to the third aspect of the present invention, an accelerator opening indicating the amount of depression of an accelerator pedal is adopted as the accelerator operation amount.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

First, a schematic configuration of an engine employed in the present embodiment will be described with reference to FIG. In the figure, reference numeral 1 denotes an engine for a vehicle such as an automobile, and in the figure, a horizontally opposed four-cylinder gasoline engine is shown. Cylinder heads 2 are provided in both left and right banks of a cylinder block 1a of the engine 1, respectively. An intake port 2a and an exhaust port 2b are formed in each cylinder head 2 corresponding to each cylinder.

In the intake system of the engine 1, an intake manifold 3 communicates with each intake port 2a, and a throttle chamber 5 communicates with the intake manifold 3 via an air chamber 4 in which intake passages of respective cylinders are gathered. . An air cleaner 7 is attached to the upstream side of the throttle chamber 5 via an intake pipe 6, and the air cleaner 7 is communicated with the air intake chamber 8.

The throttle chamber 5 is provided with a throttle valve 5a. This throttle valve 5
a, which is not mechanically connected to the accelerator pedal 9 shown in FIG. 6 but employs an electronic throttle control system, is rotated by a throttle actuator 10 attached thereto, and has a throttle opening degree by a throttle valve 5a; That is, the flow rate of intake air passing through the throttle valve 5a (flow rate of air passing through the throttle) is controlled.

In the present embodiment, the throttle actuator 10 is constituted by a stepping motor, and operates according to a drive signal output from an electronic control unit 40 described later to rotate the throttle valve 5a to a predetermined opening. . In this embodiment, the throttle valve 5a rotates in the valve opening direction by the forward rotation of the stepping motor constituting the throttle actuator 10, and the throttle valve 5a rotates in the valve closing direction by the reverse rotation of the stepping motor. .

The intake pipe 6 has a throttle valve 5
a bypass passage 11 is connected to the bypass passage 11 and an idle speed control valve (an idle speed control valve) that controls the idle speed by adjusting the amount of bypass air flowing through the bypass passage 11 according to the valve opening during idling. An ISC valve 12 is interposed. Further, an injector 13 is disposed immediately upstream of the intake port 2a of each cylinder of the intake manifold 3.

On the other hand, for each cylinder of the cylinder head 2, a spark plug 15 exposing a discharge electrode at the tip to the combustion chamber is provided.
The ignition plug 15 is connected to an igniter 17 via an ignition coil 16 provided for each cylinder.

As an exhaust system of the engine 1, an exhaust pipe 19 is connected to a collection portion of an exhaust manifold 18 communicating with each exhaust port 2b of the cylinder head 2, and a catalytic converter 20 is interposed in the exhaust pipe 19. And is communicated with the muffler 21.

Next, sensors for detecting the operating state of the engine will be described.

As shown in FIG. 6, the accelerator pedal 9
Of the accelerator operation amount by the driver on the support portion 9a of
An accelerator sensor 22 composed of a potentiometer or the like is provided in order to detect an accelerator opening indicating the amount of depression of the accelerator pedal 9.

Further, a thermal intake air amount sensor 23 using a hot wire or a hot film is interposed immediately downstream of the air cleaner 7 in the intake pipe 6, and further a throttle provided in the throttle chamber 5 is provided. For the valve 5a,
A throttle sensor 24 having a built-in throttle opening sensor 24a that outputs a voltage value corresponding to the actual throttle opening of the throttle valve 5a and an idle switch 24b that is turned on when the throttle valve 5a is fully closed is provided in series. Further, an intake pipe pressure sensor 25 that detects the intake pipe pressure downstream of the throttle valve 5a as an absolute pressure is connected to the air chamber 4.

Further, the cylinder block 1a of the engine 1
A knock sensor 26 is mounted on the cooling water passage 2 which communicates the left and right banks of the cylinder block 1a.
7, a cooling water temperature sensor 28 is provided.

An O2 sensor 29 for detecting the oxygen concentration in the exhaust gas is provided upstream of the catalytic converter 20.

The crankshaft 30 of the engine 1
A crank angle sensor 32 composed of an electromagnetic pickup or the like is provided on the outer periphery of a crank rotor 31 that is axially mounted on
A cylinder discriminating sensor 35 composed of an electromagnetic pickup or the like is provided opposite to a cam rotor 34 connected to a camshaft 33 that makes a half rotation with respect to the crankshaft 30.

A projection for detecting a crank angle is formed on the outer periphery of the crank rotor 31 at every predetermined crank angle, and a projection for discriminating the cylinder is formed on the outer periphery of the cam rotor 34. Then, the crankshaft 30 and the camshaft 33 rotate with the operation of the engine, and the crank rotor 31 and the cam rotor 34 rotate with the rotation of the crankshaft 30, and each projection of the crank rotor 31 is detected by the crank angle sensor 32. A crank pulse corresponding to a predetermined crank angle is output from the sensor 32,
The cylinder discrimination projection of the cam rotor 34 is detected by the cylinder discrimination sensor 35, and the cylinder discrimination sensor 35
Output a cylinder discrimination pulse.

Then, an electronic control unit 40 described later (FIG. 7)
), The engine speed NE is calculated based on the input interval time of the crank pulse output from the crank angle sensor 32, and the cylinder discrimination pulse from the cylinder discrimination sensor 35 and the combustion stroke order of each cylinder are calculated. (For example,
Based on the pattern of # 1 cylinder → # 3 cylinder → # 2 cylinder → # 4 cylinder), cylinder discrimination such as fuel injection target cylinder and ignition target cylinder is performed.

Calculation of control amounts for actuators such as the throttle actuator 10, injector 13, ignition plug 15, ISC valve 12, etc., output of control signals,
That is, engine control such as throttle control, fuel injection control, ignition timing control, and idle speed control is performed by an electronic control unit (ECU) 40 shown in FIG.

The ECU 40 includes a CPU 41, a ROM 4
2, RAM 43, backup RAM 44, counter
A timer group 45 and an I / O interface 46 are mainly configured by a microcomputer connected to each other via a bus line, and are connected to the constant voltage circuit 47 for supplying a stabilized power to each unit, and to the I / O interface 46. And a peripheral circuit such as a drive circuit 48, a throttle actuator drive circuit 49, and an A / D converter 50.

The counter / timer group 45 generates various counters such as a free-run counter, a counter for counting the input of a cylinder discrimination sensor signal (cylinder discrimination pulse), a fuel injection timer, an ignition timer, and a periodic interrupt. Timers, such as a timer for periodic interrupts, a timer for measuring an input interval of a crank angle sensor signal (crank pulse), and a watchdog timer for monitoring system abnormalities, are collectively referred to for convenience. A counter timer is used.

The constant voltage circuit 47 is connected to a battery 52 via a first relay contact of a power supply relay 51 having two circuit relay contacts, and a relay coil of the power supply relay 51 is connected to the battery 52 by an ignition switch 53.
Connected through. The constant voltage circuit 47
Is connected directly to the battery 52. When the ignition switch 53 is turned on and the contact point of the power supply relay 51 is closed, power is supplied to each part of the ECU 40, regardless of whether the ignition switch 53 is on or off. The backup power is always supplied to the backup RAM 44. A power supply line for supplying power from the battery 52 to each actuator is connected to a second relay contact of the power supply relay 51.

The input port of the I / O interface 46 includes an idle switch 24b, a knock sensor 2
6, a crank angle sensor 32, a cylinder discrimination sensor 35, a vehicle speed sensor 36 for detecting a vehicle speed, and a starter switch 37 for detecting an engine start state,
Further, through the A / D converter 50, an accelerator sensor 22, an intake air amount sensor 23, a throttle opening sensor 2
4a, the intake pipe pressure sensor 25, the coolant temperature sensor 28, and the O2 sensor 29 are connected, and the battery voltage VB
Is input and monitored.

On the other hand, the ISC valve 12 and the injector 1 are connected to the output port of the I / O interface 46.
An alarm lamp 38, which is arranged on an instrument panel (not shown) and collectively displays various alarms, is connected via the drive circuit 48, and further connected to the throttle actuator 10 via the throttle actuator drive circuit 49. And an igniter 17 is connected.

The above-mentioned throttle actuator drive circuit 4
9 is composed of an H bridge circuit and the like, as is well known.
A switching element in the H-bridge circuit is chopper-controlled by a pulse width modulation signal (hereinafter, referred to as a “PWM signal”) output from the I / O interface 46, and outputs a drive current to a stepping motor constituting the throttle actuator 10. In addition, the rotation direction of the stepping motor is determined by the phase switching signal.

An external connection connector 55 is connected to the I / O interface 46. By connecting a serial monitor (portable failure diagnosis device) 60 to the external connection connector 55, a serial monitor is provided. 60, the input / output data in the ECU 40 and the ECU
The self-diagnosis function of the backup RAM 44
A failed portion including an intake air amount sensor NG flag FAFNG, which will be described later, indicating a failure of the intake air amount sensor system stored in
Trouble data indicating the content of the failure is read out to enable diagnosis. Further, the serial monitor 60 allows the trouble data to be initially set (cleared).

The diagnosis of trouble data by the serial monitor 60 and the initial set are described in detail in Japanese Patent Publication No. 7-76730 by the present applicant.

In accordance with the control program stored in the ROM 42, the CPU 41 processes the detection signals from the sensors and switches, which are input via the I / O interface 46, the battery voltage, and the like, and stores them in the RAM 43. Based on various data, various learning value data stored in the backup RAM 44, fixed data stored in the ROM 42, and the like, a control amount for the throttle actuator 10, a fuel injection amount, an ignition timing, IS
The duty ratio of the drive signal for the C valve 12 is calculated, and the like.
It performs engine control such as throttle control, fuel injection control, ignition timing control, and idle speed control.

In such an engine control system, EC
In U40, a failure diagnosis for each of the above-described sensors and actuators is performed by on-board failure diagnosis.

That is, a diagnosis condition is determined based on the engine operating state, and when the diagnosis condition is satisfied, a failure diagnosis is performed on the diagnosis target. When the failure diagnosis is not performed, the target throttle opening THVTGT for the throttle valve 5a is set based on the accelerator opening ALPH indicating the accelerator operation amount by the driver when the failure diagnosis is not performed. During the execution period, the target throttle opening THVTGT is set to a value corresponding to the throttle opening when the diagnosis condition is satisfied. And the throttle valve 5a
Is set on the basis of the target throttle opening THVTGT and the actual throttle opening THV by the throttle valve 5a.

Thus, during the execution of the failure diagnosis for the object to be diagnosed due to the establishment of the diagnostic condition, the target throttle opening THVTGT is set to a value corresponding to the throttle opening when the diagnostic condition is established, and the throttle valve is set. The actual throttle opening THV of 5a is the target throttle opening TH.
The throttle valve 5a is operated via the throttle actuator 10 so as to coincide with VTGT. As a result, the state of satisfaction of the diagnosis condition based on the engine operating state is reliably continued, and it is possible to perform the failure diagnosis for the diagnosis target reliably and promptly.

More specifically, when performing a fault diagnosis on a diagnosis target, a diagnosis condition is determined based on an engine operating state detected by a sensor excluding the diagnosis target. Then, when the output value from the sensor to be diagnosed or the output value to the actuator to be diagnosed shows an abnormal value for a predetermined time under the satisfaction of the diagnostic condition,
The failure is diagnosed as the diagnosis target and the failure is notified. Also, when setting the target throttle opening THVTGT, the difference between the accelerator opening ALPHDIAGST at the start of diagnosis indicating the accelerator operation amount at the start of the diagnosis and the current accelerator opening ALPH during the execution of the failure diagnosis is compared with a predetermined value. . When the difference is less than the predetermined value, the target throttle opening THVTGT is set to a value corresponding to the actual throttle opening at the start of diagnosis, so that the actual throttle opening by the throttle valve 5a is performed regardless of the accelerator operation by the driver. The degree THV is maintained at the throttle opening at the start of the diagnosis when the diagnosis condition is satisfied, and the diagnosis condition based on the engine operating state is reliably continued.

On the other hand, the accelerator opening ALPHDI at the start of diagnosis
When the difference between the AGST and the current accelerator opening ALPH is equal to or greater than a predetermined value, the target throttle opening THVTGT set based on the current accelerator opening ALPH by the driver's accelerator operation is employed to obtain a normal throttle opening THVTGT. Return to throttle control and secure the required engine output from the driver's accelerator operation.

That is, the ECU 40 realizes the functions of the diagnostic means, the target throttle opening setting means, and the control amount setting means according to the present invention.

In the present embodiment, a case where a failure diagnosis is performed on the intake air amount sensor 23 will be described as an example of a diagnosis target.

Hereinafter, the control processing according to the present invention executed by the ECU 40 will be described with reference to the flowcharts shown in FIGS.

First, the ignition switch 53 is turned on.
Then, when the power is supplied to the ECU 40, the system is initialized, and each flag and each counter are initialized except for trouble data and data such as various learning values stored in the backup RAM 44. And
When the starter switch 37 is turned on and the engine 1 is started, every time a crank pulse is input from the crank angle sensor 32, the engine speed NE is calculated based on the input interval time of the crank pulse, and the cylinder discrimination from the cylinder discrimination sensor 35 is performed. Cylinder discrimination is performed by pulse input. Although not described in detail here, the cylinder discrimination result is reflected in fuel injection control, ignition timing control, and the like.

After system initialization, FIG.
The failure diagnosis routine shown in FIG.
This is executed for each c), and a failure diagnosis for the intake air amount sensor 23 is performed.

In this failure diagnosis routine, first,
In steps S1 to S4, the intake air amount sensor 2 to be diagnosed
It is determined whether or not the diagnostic condition is satisfied based on the engine operating state detected by each of the sensors except 3.

In this embodiment, the engine speed NE,
The actual throttle opening ALPH of the throttle valve 5a, and
When the engine operating state based on the intake pipe pressure P downstream of the throttle valve 5a is within a preset range, it is determined that the diagnostic condition is satisfied, and the intake air amount sensor 23 determines the intake condition based on the output value (output voltage) VQ. The failure diagnosis for the air amount sensor 23 is performed.

Therefore, in step S1, a crank angle sensor 32 for detecting a crank angle serving as a base when calculating the engine speed NE, a throttle opening sensor 24a for detecting an actual throttle opening, and an intake pipe pressure P It is determined whether both of the intake pipe pressure sensors 25 for detecting the pressure are normal. That is, the crank angle sensor 32 for detecting an engine operating state for judging a diagnosis condition is referred to by referring to a failure diagnosis result for each of the sensors 32, 24a and 25 diagnosed by another failure diagnosis routine not shown, and a throttle opening. It is determined whether all of the sensor 24a and the intake pipe pressure sensor 25 are normal.

Here, these sensors 32, 24a, and 2 for detecting the engine operating state that determines the diagnostic conditions are used.
When any one of 5 is abnormal, the diagnosis condition cannot be determined,
At this time, if a failure diagnosis is performed for the intake air amount sensor 23, an erroneous diagnosis is caused. Therefore, at this time, the failure diagnosis for the intake air amount sensor 23 is not performed, and step S1 is performed.
From step S13 to step S13.
Clears the count value TM of the diagnosis timer for measuring the duration of the abnormal state (TM ← 0), and exits the routine.

On the other hand, when all of the crank angle sensor 32, the throttle opening sensor 24a, and the intake pipe pressure sensor 25 are normal, the process proceeds to step S2, and at steps S2 to S4, the current engine speed NE and the throttle opening are respectively determined. The actual throttle opening THV by the sensor 24a and the intake pipe pressure P by the intake pipe pressure sensor 25 are read, and the engine speed NE, the actual throttle opening THV, and the intake pipe pressure P are read.
Is compared with the lower limit values NEL, ALPHL, PL and the upper limit values NEH, ALPHH, PH which determine the diagnostic conditions.

Then, any one of the engine speed NE, the actual throttle opening THV, and the intake pipe pressure P is changed to the lower limit value NEL, ALPHL, PL and the upper limit value NEH, ALPH.
If it is out of the range of H and PH, it is determined that the diagnosis condition is not satisfied, and the routine exits from the corresponding step through the above step S13 without performing a failure diagnosis on the intake air amount sensor 23.

In steps S2 to S4, NEL
≤ NE ≤ NEH and ALPHL ≤ ALPH ≤ ALPH
H, and PL ≦ P ≦ PH, the engine speed NE, the actual throttle opening THV, and the intake pipe pressure P are all lower limit values NEL, ALPHL, PL, and upper limit values NEH, ALPHH,
When it is within the range of PH, it is determined that the diagnostic condition is satisfied, and the process proceeds to step S5, where the output value (output voltage) VQ of the intake air amount sensor 23 is read out, and the output value VQ of the intake air amount sensor is converted Lower limit value VQL that determines the normal range of
And the upper limit value VQH to determine a failure in the intake air amount sensor 23.

That is, the failure diagnosis for the intake air amount sensor 23 is performed by determining the consistency of the output value VQ of the intake air amount sensor 23 with respect to the engine speed NE, the actual throttle opening ALPH, and the intake pipe pressure P.

Here, when the engine speed NE is in the predetermined range of the engine operating state (NEL ≦ NE ≦ NEH), the throttle valve 5a is opened in the predetermined opening range (ALP).
HL ≦ ALPH ≦ ALPHH), and when the intake pipe pressure P downstream of the throttle valve 5a indicates a value in a predetermined range corresponding to the engine speed NE and the throttle opening ALPH in the predetermined range (PL ≦ P .Ltoreq.PH), when the intake air amount sensor output value VQ deviates from a normal output value range when the intake air amount sensor 23 is in a normal state, diagnosing a failure of the intake air amount sensor system. Can be.

Therefore, the lower limit values NEL, ALPHL,
PL, VQL and upper limit values NEH, ALPHH, PH, VQH
The optimal values of the upper limit and the lower limit are determined in advance by simulation or experiment based on the consistency, and are stored in the ROM 42 as fixed data.

Then, in the above step S5, VQL <
When VQ <VQH and the output value VQ of the intake air amount sensor 23 is within the range defined by the lower limit value VQL and the upper limit value VQH that define the normal range, the intake air amount sensor system is determined to be normal, and the process proceeds to step S6. Proceed to backup RAM 44
In addition to clearing the intake air amount sensor NG flag FAFNG indicating a failure of the intake air amount sensor system stored as trouble data at (FAFNG ← 0), the alarm lamp 38 flashes a predetermined code to indicate the failure of the intake air amount sensor system. Without performing the routine, the process exits the routine through the step S13.

On the other hand, in step S5, VQL ≧
When VQ or VQ ≧ VQL and the output value VQ of the intake air amount sensor 23 deviates from the normal range defined by the lower limit value VQL and the upper limit value VQH and indicates an abnormal value, the process proceeds to step S7.
By the processing after step S7, the duration of the abnormal state is determined, and when the abnormal state continues for a predetermined time, it is diagnosed that the intake air amount sensor system has failed.

At step S7, the count value T of the diagnostic timer for measuring the duration of the abnormal state of the intake air amount sensor system is measured.
Referring to M, at the start of the diagnosis of TM = 0, that is, at the first time of the abnormality diagnosis of the intake air amount sensor system, the process proceeds to step S8.

Then, in step S8, the accelerator sensor 2
2, the accelerator opening ALPH is read out, and the accelerator opening ALPH is read at the start of the diagnosis.
PHDIAGST is stored in a predetermined address of the RAM 43 (ALPHDIAGST ← ALPH), and in the following step S9, the current actual throttle opening THV by the throttle opening sensor 24a is stored in a predetermined address of the RAM 43 as a throttle opening THVDIAGST at the start of diagnosis. (THVDIAG
(ST ← THV), and proceeds to step S10.

In step S7, TM ≠ 0, and the routine jumps from step S7 to step S10 when executing the second and subsequent routines after the start of the abnormality diagnosis.

Then, in step S10, the count value TM of the diagnostic timer is counted up (TM ← TM + 1),
In the following step S11, the count value TM of the diagnostic timer
Is compared with a set value TMDIAG for determining the duration of the abnormal state of the intake air amount sensor system.

The above set value TMDIAG prevents erroneous diagnosis due to the output value VQ of the intake air amount sensor 23 temporarily showing an abnormal value due to disturbance or the like, and ensures that the intake air amount sensor system fails. An appropriate value is determined in advance by simulation or experiment, and is stored in the ROM 42 as fixed data.

If TM ≦ TMDIAG and the duration of the abnormal state of the intake air amount sensor system has not reached the predetermined time determined by the set value TMDIAG, the routine exits as it is because the failure has not been determined.

On the other hand, in step S11, TM> T
In the MDIAG, when the continuation time of the abnormal state of the intake air amount sensor system reaches a predetermined time determined by the set value TMDIAG, that is, when the diagnostic conditions of steps S1 to S4 are all satisfied, the intake air Output value V of quantity sensor 23
When Q is a value that cannot be normally taken and deviates from the normal range for a predetermined period of time, a failure of the intake air amount sensor 23 itself, a disconnection of the connector or the harness between the intake air amount sensor 23 and the ECU 40, a short circuit, etc. Is determined as failure of the intake air amount sensor system due to the above, and the process proceeds to step S12.

In step S12, an intake air amount sensor NG flag FAFNG indicating a failure of the intake air amount sensor system is set (FAFNG ← 1), and the length of blinking, the number of blinking in a predetermined period, or a combination thereof is determined. The alarm lamp 38 flashes with a predetermined flashing code to notify a failure of the intake air amount sensor system. Then, in preparation for the next diagnosis, in step S13, the count value TM of the diagnosis timer is set.
And exit the routine.

As a result, when a failure occurs in the intake / intake air amount sensor system, the alarm lamp 38 blinks to notify the driver, and the driver can easily determine the failure.

Further, at the time of troubleshooting at a service factory such as a dealer, by connecting the serial monitor 60 via the external connection connector 55, the serial monitor 60 allows trouble data by the intake air amount sensor NG flag FAFNG in the ECU 40 to be obtained. And read
A failure of the intake air amount sensor system can be accurately determined.

Then, after repairing the corresponding portion, the serial monitor 60 controls the intake air amount sensor NG flag FAF.
Clear NG. In this embodiment, if the intake air amount sensor system returns to a normal state without repairing the corresponding portion and clearing the intake air amount sensor NG flag FAFNG by the serial monitor 60, the failure diagnosis is performed. In the routine, the intake air amount sensor NG flag FAFNG is cleared.

On the other hand, in parallel with the above-mentioned failure diagnosis routine,
The throttle control routine shown in FIG. 3 is executed at predetermined intervals (for example, every 10 msec) to determine the execution of the above-described failure diagnosis.
Throttle valve 5 based on accelerator opening ALPH
The target throttle opening THVTGT is set for the target throttle opening THVDIAGST during the execution of the failure diagnosis.
Set TGT. Then, the control amount for the throttle actuator 10 for operating the throttle valve 5a is changed to the throttle valve 5 for the target throttle opening THVTGT.
a is set in accordance with the deviation ΔTH of the actual throttle opening THV, and a drive signal based on the control amount is output to the throttle actuator 10 so that the throttle actuator 1
0 activates the throttle valve 5a,
The actual throttle opening THV of a is equal to the target throttle opening TH.
Feedback control is performed so as to match VTGT.

Next, the throttle control routine of FIG. 3 will be described.

In this throttle control routine,
First, in step S21, the accelerator opening ALPH by the accelerator sensor 22 is read, and the accelerator opening ALP is read.
The target throttle opening THVTGT for the throttle valve 5a is set with reference to the target throttle opening table with interpolation calculation based on H.

The target throttle opening degree table indicates that the throttle opening of the throttle valve 5a corresponding to the amount of air passing through the throttle for obtaining the engine output is obtained for each accelerator opening ALPH indicating the driver's accelerator operation amount, that is, the engine output request. The opening is obtained in advance by simulation or experiment, and the appropriate throttle opening is set as a target throttle opening, set as a table using the accelerator opening ALPH as a parameter, and stored in a series of addresses in the ROM 42. . That is, the target throttle opening THVTGT is set in accordance with the actual opening of the throttle valve 5a appropriate to the accelerator operation amount of the driver.

An example of the target throttle opening table is shown in step S21. As shown in step S21, the target throttle opening THVTGT is equal to the accelerator opening A
LPH has an increasing function relationship. Therefore, instead of the target throttle opening table, the target throttle opening THVTGT may be set by a function formula based on the accelerator opening ALPH.

Next, the routine proceeds to step S22, where it is determined whether or not the failure diagnosis is currently being performed by referring to the count value TM of the diagnosis timer in the above-described failure diagnosis routine.

Then, when TM = 0, the duration of the abnormal state of the intake air amount sensor system is not measured, and when the failure diagnosis is not executed, the process jumps to step S25 to output the output value of the throttle opening sensor 24a. The actual throttle opening THV of the throttle valve 5a detected based on the actual throttle opening THV is read out, and the actual throttle opening THV is subtracted from the target throttle opening THVTGT to obtain a deviation ΔTH of the actual throttle opening THV from the target throttle opening THVTGT. Calculate (ΔTH ← THVTGT-THV).

Then, in step S26, the deviation ΔTH
The throttle actuator control amount DACT that determines the control amount for the throttle actuator 10 is set with reference to the control amount table stored in the ROM 42 based on the above.

Here, the throttle actuator control amount DACT is, as is well known, the target throttle opening TH.
It is set in accordance with the magnitude relationship of the actual throttle opening THV with respect to VTGT, and the magnitude of the deviation ΔTH.

That is, as shown in FIG. 4, when the deviation ΔTH of the actual throttle opening THV with respect to the target throttle opening THVTGT is a negative value, the actual throttle opening THV is larger than the target throttle opening THVTGT.
In accordance with the deviation ΔTH, the throttle actuator 1
0, the step position of the stepping motor is reduced by a predetermined number of steps.
An appropriate throttle actuator control amount DACT is set so that the throttle valve 5a is closed at a predetermined angle by the reverse rotation of.

At this time, the target throttle opening THV
The actual throttle opening THV is larger than TGT, and the deviation Δ
As TH becomes more negative, the number of steps for reversely operating the step motor is made more negative, the closing speed of the throttle valve 5a by the throttle actuator 10 is increased, and the actual throttle opening THV of the throttle valve 5a is earlier. Can converge to the target throttle opening. Then, as the actual throttle opening THV approaches the target throttle opening THVTGT, the number of steps for determining the amount of change in the step position in the minus direction by the step motor is reduced, and the throttle actuator 1
0, the valve closing speed of the throttle valve 5a is reduced. As a result, overshoot or undershoot of the actual throttle opening THV with respect to the target throttle opening THVTGT is prevented, and the target throttle opening THVTGT of the throttle valve 5a by the throttle actuator 10 is prevented.
Can be improved, and control can be stabilized.

On the other hand, when the deviation ΔTH of the actual throttle opening THV with respect to the target throttle opening THVTGT is a positive value, the actual throttle opening THV is smaller than the target throttle opening THVTGT, and according to this deviation ΔTH,
The step position of the stepping motor constituting the throttle actuator 10 is increased by a predetermined number of steps, and an appropriate throttle actuator control amount DACT for opening the throttle valve 5a by a predetermined angle by the forward rotation of the throttle actuator 10 is set.

At this time, the target throttle opening THV
As the actual throttle opening THV is larger than TGT and the deviation is larger on the positive side, the number of steps for rotating the step motor forward is increased, and the opening speed of the throttle valve 5a by the throttle actuator 10 is increased. ,
It is possible to converge the actual throttle opening THV of the throttle valve 5a to the target throttle opening at an early stage. The actual throttle opening THV is equal to the target throttle opening T.
As the value approaches HVTGT, the number of increments for determining the amount of change of the step position by the step motor is made small, and the closing speed of the throttle valve 5a by the throttle actuator 10 is decreased, so that the target throttle opening TH
The overshoot or undershoot of the actual throttle opening THV with respect to VTGT is prevented, the convergence of the throttle valve 5a with the target throttle opening THVTGT by the throttle actuator 10 is improved, and control is stabilized.

As shown in FIG. 4, in the present embodiment, when the deviation ΔTH is between −1 deg and 1 deg, the number of steps for changing the step position of the stepping motor constituting the throttle actuator 10 is set to 0 to set the dead zone. By setting and stopping the stepping motor at the current step position, the throttle valve 5a is maintained at the current throttle opening without opening and closing, thereby preventing hunting.

Then, in step S27, the throttle actuator control amount DACT is set, and the routine exits.

By setting the throttle actuator control amount DACT, a PWM signal and a phase switching signal corresponding to the throttle actuator control amount DACT are output to the throttle actuator driving circuit 49, and the throttle actuator 10 is constituted by the phase switching signal. The rotation direction of the stepping motor is determined, and a driving current is output from the throttle actuator driving circuit 49 to the stepping motor.

As a result, the throttle actuator 10
The throttle valve 5a is actuated by the driving of the stepping motor, and when the failure diagnosis is not executed, the actual throttle opening THV of the throttle valve 5a is set based on the accelerator opening ALPH representing the accelerator operation amount of the driver. Feedback control is performed so as to follow the target throttle opening THVTGT, and the throttle opening is controlled to an appropriate throttle opening that obtains a throttle passing air flow rate that meets the engine output demand based on the accelerator operation amount of the driver.

On the other hand, in step S22, TM ≠
At 0, the continuation time of the abnormal state of the intake air amount sensor system is measured, and the process proceeds to step S23 during the execution period of the failure diagnosis.

In step S23, the accelerator opening ALPHDIAGST at the start of diagnosis by the above-described failure diagnosis routine is read, and the absolute value | ALPHDI of the difference between the accelerator opening ALPHDIAGST at the start of diagnosis and the current accelerator opening ALPH is read.
AGST-ALPH | is compared with the set value ΔALPHS to determine a change in the accelerator operation amount from the start of diagnosis due to an abnormal state of the intake air amount sensor system to the present.

The set value ΔALPHS is used to determine the change in the accelerator operation amount by the driver from the start of the diagnosis, and when the change in the accelerator opening ALPH indicating the accelerator operation amount of the driver is small, the set value ΔALPHS is used for the accelerator operation by the driver. Regardless,
By maintaining the actual throttle opening THV of the throttle valve 5a at the throttle opening at the start of diagnosis, continuation of the diagnostic conditions for the intake air amount sensor system is prioritized, and the accelerator opening A
When the change in LPH is large, the target throttle opening THVTGT set based on the accelerator opening ALPH representing the accelerator operation amount of the driver is adopted, and the throttle actuator 5 is activated by the throttle actuator 10 according to the driver's accelerator operation. This is for controlling the throttle opening THV to give priority to the accelerator operation by the driver.
This is stored as fixed data in M42.

Then, | ALPHDIAGST-ALPH | <
The absolute value of the difference between the accelerator operation amount ALPHDIAGST at the start of diagnosis, which represents the accelerator operation amount at the start of diagnosis, and the current accelerator opening ALPH is represented by ΔALPHS.
If it is less than the predetermined value determined by HS, the process proceeds to step S24, in which the throttle opening THVDIAGST at the start of diagnosis by the above-described failure diagnosis routine is read, and the target throttle opening THVTGT is set to the diagnosis corresponding to the actual throttle opening at the start of diagnosis. It is reset by the throttle opening THVDIAGST at the start (THVTGT ← THVDIAGST).

Then, the process proceeds to step S25, where the target throttle opening THNT newly set in step S24 is set.
The actual throttle opening THV is subtracted from the target actual throttle opening THVTGT by subtracting the current actual throttle opening THV from GT.
The deviation ΔTH of the HV is calculated, and the above steps S26 and S27 are further performed.
Then, a throttle actuator control amount DACT that determines a control amount for the throttle actuator 10 is set with reference to the control amount table based on the deviation ΔTH, the control amount DACT is set, and the routine exits.

As a result, during the execution of the failure diagnosis, the accelerator opening ALPHDIAGST at the start of diagnosis indicating the accelerator operation amount at the start of diagnosis and the current accelerator opening ALPH
When the absolute value of the difference between the target throttle opening and the target throttle opening THVTGT is smaller than the set value ΔALPHS, the target throttle opening THVTGT corresponds to the actual throttle opening at the start of diagnosis.
Reset by VDIAGST. Then, the current actual throttle opening T with respect to the target throttle opening THVTGT
Throttle actuator 1 according to HV deviation ΔTH
The throttle valve 5a is operated by the drive of the stepping motor, and the actual throttle opening THV of the throttle valve 5a is feedback-controlled so as to maintain the throttle opening THVDIAGST at the start of diagnosis.

Therefore, during the execution of the failure diagnosis,
When the change in the accelerator operation amount by the driver is relatively small, the actual throttle opening THV by the throttle valve 5a is maintained at the throttle opening THVDIAGST at the start of the diagnosis when the diagnosis condition is satisfied, regardless of the accelerator operation by the driver. As a result, the state of satisfaction of the diagnosis condition based on the engine operating state is reliably continued, and the failure diagnosis for the intake air amount sensor 23 can be performed reliably and promptly.

As a result, in the engine employing the electronic throttle control system, the diagnosis frequency in the market (under the use condition of the user) can be increased and the diagnosable area can be expanded, and the diagnosis can be performed with high accuracy. Becomes possible.

Since the failure diagnosis for the intake air amount sensor 23 can be performed reliably and promptly, when a failure occurs in the intake air amount sensor system, the on-board failure by executing the above-described failure diagnosis routine is performed. The diagnosis makes it possible to reliably determine and notify the failure of the intake air amount sensor system, prevent the vehicle from continuing to run while the intake air amount sensor system has failed, and exhaust emissions due to the failure of the intake air amount sensor. It is possible to prevent secondary problems such as deterioration of the engine and adverse effects on the engine.

On the other hand, in step S23, | AL
If PHDIAGST−ALPH | ≧ ΔALPHS, the accelerator opening ALPHDIAGST at the start of diagnosis and the current accelerator opening AL
When the absolute value of the difference from the PH is equal to or more than a predetermined value based on the set value ΔALPHS, the process jumps to step S25.

In step S21, the target throttle opening THVTGT set based on the current accelerator opening ALPH by the driver's accelerator operation is adopted, and the target actual throttle opening THV is calculated from the target throttle opening THV. Is subtracted to obtain the target throttle opening THV.
A deviation ΔTH of the actual throttle opening THV with respect to TGT is calculated, and in steps S26 and S27, a throttle actuator control amount DACT is set by referring to the control amount table based on the deviation ΔTH, and the control amount DACT is calculated. Set and exit the routine.

Therefore, even when the failure diagnosis is being executed, if the change in the accelerator opening ALPH due to the accelerator operation by the driver is large, the setting is made based on the current accelerator opening ALPH representing the accelerator operation amount of the driver. By adopting the target throttle opening THVTGT, and controlling the actual throttle opening THV of the throttle valve 5a by the throttle actuator 10 according to the accelerator operation of the driver, the accelerator operation by the driver is prioritized and the normal throttle control is performed. Then, it is possible to secure the required engine output by the driver's accelerator operation.

When the engine operation state changes in accordance with the change in the actual throttle opening THV of the throttle valve 5a due to the return to the normal throttle control, and the diagnosis conditions in steps S2 to S4 of the failure diagnosis routine are not satisfied. In the meantime, the counting of the duration of the abnormal state of the intake air amount sensor system is stopped and the count value TM of the diagnosis timer is cleared (step S13 in FIG. 2). Then, the routine jumps from step S22 to step S25, and normal throttle control is continued with the target throttle opening THVTGT set based on the current accelerator opening ALPH.

In this embodiment, the failure diagnosis for the intake air amount sensor has been described as a diagnosis target.
The present invention is not limited to this, and it goes without saying that the diagnosis target may be a sensor other than the intake air amount sensor or an actuator.

In this embodiment, the accelerator opening is used as the accelerator operation amount of the driver.
The present invention is not limited to this, and the present invention can be applied as long as it represents an accelerator operation amount.

It is also possible to apply the automatic operation control by operating the accelerator operation with a control device including a microcomputer or the like. In this case, the driver includes not only the personnel but also the control device.

Further, in this embodiment, a stepping motor type throttle actuator is used as the throttle actuator. However, the present invention is not limited to this, and a servo motor type throttle actuator, a hydraulic motor type throttle actuator or the like may be used. Good.

[0114]

As described above, according to the first aspect of the present invention, a diagnosis condition is determined based on an engine operating state, and when the diagnosis condition is satisfied, a failure diagnosis is performed on a diagnosis target. Then, it is determined that the failure diagnosis is to be performed, and when the failure diagnosis is not performed, the target throttle opening for the throttle valve is set based on the accelerator operation amount by the driver,
Since the control amount for the throttle actuator that operates the throttle valve is set based on the target throttle opening and the actual throttle opening, the required engine output by the driver's accelerator operation is ensured. On the other hand, during the execution of the failure diagnosis, the target throttle opening is set to a value corresponding to the throttle opening when the diagnosis condition is satisfied, and the throttle valve is opened based on the target throttle opening and the actual throttle opening. The target throttle opening is set to a value corresponding to the throttle opening when the diagnosis condition is satisfied during the period of executing the failure diagnosis for the diagnosis target based on the satisfaction of the diagnosis condition because the control amount for the operating throttle actuator is set. Then, the throttle valve is operated via the throttle actuator so that the actual throttle opening of the throttle valve matches the target throttle opening. Therefore, in the engine adopting the electronic throttle control system, the condition for the diagnosis condition to be satisfied by the operating state of the engine is reliably maintained, and the failure diagnosis for the diagnosis target can be performed reliably and promptly.

According to the second aspect of the present invention, when performing a failure diagnosis on a diagnosis target, a diagnosis condition is determined based on an engine operating state detected by a sensor excluding the diagnosis target. Then, when a state in which the output value from the diagnosis target or the output value to the diagnosis target indicates an abnormal value continues for a predetermined time under the satisfaction of the diagnosis condition, the failure is diagnosed as the diagnosis target and the failure is notified. Further, when setting the target throttle opening, during the failure diagnosis execution period, the difference between the accelerator operation amount at the start of the diagnosis and the current accelerator operation amount is compared with a predetermined value. When the difference is smaller than the predetermined value, the target throttle opening is set to a value corresponding to the actual throttle opening at the start of the diagnosis. When the change in the accelerator operation amount by the driver is relatively small, the actual throttle opening by the throttle valve is maintained at the throttle opening at the start of the diagnosis when the diagnosis condition is satisfied, regardless of the accelerator operation by the driver. Therefore, the state of satisfaction of the diagnosis condition based on the engine operating state is reliably continued, and the failure diagnosis for the diagnosis target can be performed reliably and quickly. In addition, this makes it possible to increase the diagnosis frequency in the market (under the use condition of the user) and expand the diagnosable area in the engine employing the electronic throttle control system,
This has the effect that highly accurate diagnosis can be performed.

Further, since the failure diagnosis can be performed reliably and quickly for the diagnosis target, when a failure has occurred in the diagnosis target, it is possible to reliably determine and notify the failure of the diagnosis target by the on-board failure diagnosis. This makes it possible to prevent the diagnosis target from continuing to operate with a failure, and to prevent secondary problems such as deterioration of exhaust emission and adverse effects on the engine due to the failure of the diagnosis target.

When the difference between the accelerator operation amount at the start of diagnosis and the current accelerator operation amount is equal to or larger than a predetermined value during the failure diagnosis execution period, the target throttle opening set based on the current accelerator operation amount is set. Therefore, even when the failure diagnosis is being performed, when the change in the accelerator operation amount by the driver is large, it is possible to give priority to the accelerator operation by the driver and to return to the normal throttle control. This has an effect that the required engine output by the driver's accelerator operation can be secured.

According to the third aspect of the present invention, in addition to the effects of the first or third aspect of the present invention, an accelerator opening indicating an amount of depression of an accelerator pedal is employed as the accelerator operation amount. The present invention has an effect that the present invention can be easily applied to engine control of a vehicle engine.

[Brief description of the drawings]

FIG. 1 is a basic configuration diagram of the present invention.

FIG. 2 is a flowchart of a failure diagnosis routine;

FIG. 3 is a flowchart of a throttle control routine.

FIG. 4 is an explanatory diagram showing a relationship between a deviation of an actual throttle opening from a target throttle opening and an operation of a stepping motor.

FIG. 5 is an overall schematic diagram of an engine.

FIG. 6 is a side view of the accelerator pedal.

FIG. 7 is a circuit configuration diagram of an electronic control system.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Engine 5a Throttle valve 10 Throttle actuator 22 Accelerator sensor 23 Intake air amount sensor (Diagnosis target) 24a Throttle opening sensor (Sensor excluding diagnosis target) 25 Intake pipe pressure sensor (Sensor excluding diagnosis target) 32 Crank angle sensor (Diagnosis) Sensors excluding target) 40 Electronic control unit (diagnosis means, target throttle opening setting means, control amount setting means) ALPH accelerator opening (accelerator operation amount; current accelerator operation amount) NE engine speed (engine operating state) P Intake pipe pressure (engine operating state) THVTGT Target throttle opening THV actual throttle opening (engine operating state) DACT Throttle actuator control amount (control amount for throttle actuator) VQ Intake air amount sensor output value (output value of diagnosis target) TMDIAG Setting (Predetermined time) ALPHDIAGST diagnosis start accelerator opening (accelerator operation amount at the time of diagnosis start) DerutaALPHS setpoint (predetermined value) THVDIAGST diagnosis start throttle opening (actual throttle opening at the start of the diagnosis)

Claims (3)

[Claims] A throttle valve control amount is set based on a driver's accelerator operation amount, a throttle valve is operated by the throttle actuator to control an opening of the throttle valve, and a failure diagnosis is performed for a diagnosis target. When performing the diagnosis, the diagnosis condition is determined based on the engine operation state, and when the diagnosis condition is satisfied, in the engine control device that performs a failure diagnosis on the diagnosis target, the diagnosis condition is determined based on the engine operation state, and the diagnosis condition is determined. A diagnosis means for performing a failure diagnosis on the diagnosis target when the condition is satisfied; and a target throttle opening degree for the throttle valve based on the accelerator operation amount when the failure diagnosis is not performed;
During the execution of the failure diagnosis, target throttle opening setting means for setting the target throttle opening to a value corresponding to the throttle opening when the diagnosis condition is satisfied; actual throttle opening by the target throttle opening and the throttle valve. A control amount setting unit for setting a control amount for the throttle actuator based on the degree. 2. The diagnostic means judges a diagnostic condition based on an engine operating state detected by a sensor excluding a diagnostic object, and, when the diagnostic condition is satisfied, an output value from the diagnostic object or an output value for the diagnostic object. When the state indicating an abnormal value continues for a predetermined time, the target throttle opening setting means diagnoses the failure as the diagnosis target and reports the failure. During the execution of the failure diagnosis, the accelerator operation at the start of the diagnosis is performed. The difference between the amount and the current accelerator operation amount is compared with a predetermined value, and when the difference is smaller than the predetermined value, the target throttle opening is set to a value corresponding to the actual throttle opening at the start of diagnosis, and the difference is set to a predetermined value. 2. The engine control device according to claim 1, wherein a target throttle opening set based on a current accelerator operation amount is adopted when the value exceeds the value. 3. The engine control device according to claim 1, wherein the accelerator operation amount is an accelerator opening indicating a depression amount of an accelerator pedal.