JP4223083B2 - Engine control device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention employs an electronic throttle control system that operates a throttle valve by a throttle actuator, and when performing a failure diagnosis on a diagnosis target, determines a diagnosis condition based on an engine operating state, and when the diagnosis condition is satisfied, More particularly, the present invention relates to an engine control device that can reliably and quickly perform a failure diagnosis on a diagnosis target by continuously diagnosing a diagnosis condition based on an engine operating state.
[0002]
[Prior art]
Conventionally, instead of directly connecting the accelerator pedal and the throttle valve installed in the intake system of the engine with a wire, the accelerator operation amount of the driver, such as the amount of depression of the accelerator pedal, is detected by an accelerator sensor, and a stepping motor or DC An electronic throttle control system in which a throttle valve is operated by a throttle actuator composed of a servo motor or the like is employed (see Japanese Patent Laid-Open Nos. 7-77088 and 7-158492).
[0003]
In this type of electronic throttle control system, the output signal of the accelerator sensor and the output signal of the throttle opening sensor that detects the actual opening of the throttle valve are input to the control device, and the accelerator detected by the accelerator sensor is detected. The target throttle opening is set based on the operation amount. Based on the target throttle opening and the actual throttle opening of the throttle valve detected by the throttle opening sensor, a control amount for the throttle actuator is set, 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 degree by the throttle valve matches the target throttle opening degree.
[0004]
In parallel with this, in the engine control system, output signals from various sensors that detect the engine operating state are input to the control device, and fuel injection is performed based on the engine operating state data detected by these various sensors. The engine control such as fuel injection control and ignition timing control is performed by setting the amount, ignition timing, and the like, and outputting a drive signal based on this to actuators such as an injector and an igniter.
[0005]
Here, when a sensor for detecting an engine operating state or an actuator to be controlled fails, engine controllability is remarkably deteriorated, and exhaust emission is deteriorated or an engine is adversely affected.
[0006]
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, consistency of various input data input from these sensors, or This is done by judging the consistency of the output data for each actuator, and when a failure occurs, the failure is reported by turning on an alarm lamp or the like.
[0007]
Therefore, since the control device performs failure diagnosis for various sensors and actuators by judging the consistency of various input / output data, the on-board failure diagnosis by the control device is performed while the driver is driving freely. Therefore, the failure diagnosis for the diagnosis target is performed only under a certain operating condition, that is, only when the diagnosis condition based on the predetermined engine operating state is satisfied.
[0008]
Here, in the failure diagnosis for the diagnosis target sensor, the diagnosis condition is determined based on the engine operating state detected by the other sensor, the diagnosis condition is satisfied, and the output value of the sensor to be diagnosed is set at this time A value outside the range indicates a value that cannot normally be obtained in this engine operating state, and when this state continues for a predetermined time, a failure of the sensor to be diagnosed is diagnosed.
[0009]
That is, when an abnormal state of the sensor output value continues for a predetermined time, a failure is diagnosed to prevent erroneous diagnosis due to a temporary sudden change in the sensor output value caused by a disturbance or the like.
[0010]
In the failure diagnosis for the actuators, the diagnosis condition is determined based on the engine operation state detected by various sensors, the diagnosis condition is satisfied, and the abnormal state of the drain voltage for the actuator to be diagnosed at this time is predetermined. When a certain number of times, that is, for a predetermined time, is continued, the failure of the diagnosis target actuator is diagnosed.
[0011]
[Problems to be solved by the invention]
However, when the electronic throttle control system is employed, the accelerator operation amount changes due to the driver's accelerator operation, and the actual throttle opening of the throttle valve is set to the target throttle opening set based on the accelerator operation amount. Since the control amount for the throttle actuator is set so as to coincide with each other and the throttle valve is operated via the throttle actuator, the engine operating state changes accordingly.
[0012]
Therefore, when performing failure diagnosis, the engine operating state cannot be maintained at the predetermined engine operating state corresponding to the diagnosis condition for the predetermined time period that gives the duration of the abnormal state, or the engine operating state itself is the diagnosis condition. It does not agree, and the failure diagnosis for the diagnosis target is delayed, or the failure diagnosis is not performed.
[0013]
As a result, even if a failure occurs, the failure cannot be determined by the on-board failure diagnosis, and the failure is not notified. Therefore, the operation is continued with the failure occurring, leading to deterioration of exhaust emissions and adverse effects on the engine. There is an inconvenience.
[0014]
In view of the above circumstances, the present invention provides an engine control device that can reliably and quickly perform a failure diagnosis for a diagnosis target in an engine that employs an electronic throttle control system by reliably continuing diagnosis conditions according to engine operating conditions. The purpose is to provide.
[0015]
[Means for Solving the Problems]
  In order to achieve the above object, according to the first aspect of the present invention, the control amount for the throttle actuator is set based on the accelerator operation amount of the driver, and the throttle valve is operated by the throttle actuator to control the opening degree of the throttle valve. As well asSensors or actuators provided in the engine control system are to be diagnosedIn the engine control device that performs failure diagnosis, as shown in the basic configuration diagram of FIG. 1, the diagnosis condition is determined based on the engine operation state,the aboveDiagnostic means for performing a failure diagnosis for the diagnosis target, and when the failure diagnosis is not executed, a target throttle opening for the throttle valve is set based on the accelerator operation amount, and during the execution of the failure diagnosis,The difference between the accelerator operation amount at the start of diagnosis and the current accelerator operation amount is compared with a predetermined value, and when the difference is less than the predetermined value, the actual throttle opening at the start of diagnosis is set as the target throttle opening, and the difference When the value exceeds a predetermined value, the target throttle opening is set based on the current accelerator operation amount.A target throttle opening setting means, and a 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 are provided.
[0016]
  According to a second aspect of the present invention, in the first aspect of the invention, the diagnostic means is a diagnostic object.And notThe diagnosis condition is determined based on the engine operating state detected by the sensor.SensorOutput value or diagnosis target fromActuatorWhen a state in which the output value for the output is abnormal is continued for a predetermined time, it is diagnosed as a failure to be diagnosed and the failure is reported.KnowIt is characterized by that.
[0017]
According to a third aspect of the present invention, in the first or second aspect of the present invention, the accelerator operation amount is an accelerator opening indicating an amount of depression of an accelerator pedal.
[0018]
  That is, in the first aspect of the invention, the diagnosis condition is determined based on the engine operating state, and when the diagnosis condition is satisfied,Sensors or actuators provided in the engine control system are to be diagnosedPerform fault diagnosis. Then, the execution of the failure diagnosis is determined, and when the failure diagnosis is not executed, the target throttle opening for the throttle valve is set based on the accelerator operation amount by the driver, while during the failure diagnosis execution period,The difference between the accelerator operation amount at the start of diagnosis and the current accelerator operation amount is compared with a predetermined value, and when the difference falls below the predetermined value, the actual throttle opening at the start of diagnosis is set as the target throttle opening, and the difference is When the predetermined value is exceeded, the target throttle opening is set based on the current accelerator operation amount.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 fault diagnosis for the diagnosis target due to the establishment of the diagnosis condition,When the difference between the accelerator operation amount at the start of diagnosis and the current accelerator operation amount is less than a predetermined value, the target throttle opening set to the throttle opening when the diagnosis condition is satisfied and the actual throttle opening of the throttle valve The throttle valve is actuated via the throttle actuator so that the two are consistent, and the diagnosis condition based on the engine operating state is reliably maintained regardless of the driver's accelerator operation, so that the failure diagnosis for the diagnosis target can be performed reliably and quickly. Can be performed. On the other hand, when the difference between the accelerator operation amount at the start of diagnosis and the current accelerator operation amount exceeds a predetermined value, the target throttle opening set based on the current accelerator operation amount is adopted, and normal throttle control is performed. To secure the required engine output by the driver's accelerator operation..
[0019]
  Further, in the invention according to claim 2, when performing a failure diagnosis on the diagnosis target, the diagnosis targetAnd notDiagnosis conditions are determined based on the engine operating state detected by the sensor. And if the diagnostic conditions are met,SensorOutput value or diagnosis target fromActuatorWhen the output value for the is abnormal value continues for a predetermined time, diagnose the failure of the diagnosis target and report the failureThe
[0020]
In that case, in the invention described in claim 3, the accelerator opening indicating the depression amount of the accelerator pedal is adopted as the accelerator operation amount.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
[0022]
First, a schematic configuration of the engine employed in the present embodiment will be described based on FIG. In the figure, reference numeral 1 denotes an engine for a vehicle such as an automobile. In the figure, a horizontally opposed four-cylinder gasoline engine is shown. Cylinder heads 2 are provided in both the left and right banks of the cylinder block 1a of the engine 1, and each cylinder head 2 is formed with an intake port 2a and an exhaust port 2b corresponding to each cylinder.
[0023]
In the intake system of the engine 1, an intake manifold 3 is communicated with each intake port 2a, and a throttle chamber 5 is communicated with the intake manifold 3 via an air chamber 4 in which intake passages of the 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 an air intake chamber 8.
[0024]
The throttle chamber 5 is provided with a throttle valve 5a. The throttle valve 5a is not mechanically connected to the accelerator pedal 9 shown in FIG. 6, and employs an electronic throttle control system. The throttle valve 5a is rotated by a throttle actuator 10 provided therein, and is throttled by the throttle valve 5a. The opening degree, that is, the intake air flow rate (throttle passage air flow rate) passing through the throttle valve 5a is controlled.
[0025]
In the present embodiment, the throttle actuator 10 is composed of a stepping motor, and operates according to a drive signal output from an electronic control device 40 described later, thereby rotating the throttle valve 5a to a predetermined opening. In the present embodiment, the throttle valve 5a is rotated in the valve opening direction by the forward rotation operation of the stepping motor constituting the throttle actuator 10, and the throttle valve 5a is rotated in the valve closing direction by the reverse rotation operation of the stepping motor. .
[0026]
The intake pipe 6 is connected to a bypass passage 11 that bypasses the throttle valve 5a. The amount of bypass air flowing through the bypass passage 11 is adjusted to the bypass passage 11 according to the valve opening degree at the time of idling. An idle speed control valve (ISC valve) 12 for controlling the speed is provided. Further, an injector 13 is disposed immediately upstream of the intake port 2a of each cylinder of the intake manifold 3.
[0027]
On the other hand, a spark plug 15 that exposes the discharge electrode at the tip to the combustion chamber is attached to each cylinder of the cylinder head 2, and an igniter is connected to the spark plug 15 via an ignition coil 16 disposed for each cylinder. 17 is connected.
[0028]
Further, as an exhaust system of the engine 1, an exhaust pipe 19 is connected to a collecting portion of an exhaust manifold 18 communicating with each exhaust port 2 b of the cylinder head 2, and a catalytic converter 20 is interposed in the exhaust pipe 19 so that the muffler 21 is communicated.
[0029]
Next, sensors for detecting the engine operating state will be described.
[0030]
As shown in FIG. 6, an accelerator sensor 22 composed of a potentiometer or the like is attached to the support portion 9 a of the accelerator pedal 9 in order to detect the accelerator opening indicating the depression amount of the accelerator pedal 9 as the accelerator operation amount by the driver. Has been.
[0031]
Further, a thermal intake air amount sensor 23 using a hot wire or a hot film is provided immediately downstream of the air cleaner 7 of the intake pipe 6. Further, a throttle valve 5 a provided in the throttle chamber 5 is connected to a throttle valve 5 a. 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 connected. Further, an intake pipe pressure sensor 25 for detecting the intake pipe pressure downstream of the throttle valve 5a as an absolute pressure is communicated with the air chamber 4.
[0032]
Further, a knock sensor 26 is attached to the cylinder block 1a of the engine 1, and a cooling water temperature sensor 28 is exposed to a cooling water passage 27 communicating with the left and right banks of the cylinder block 1a.
[0033]
An O 2 sensor 29 for detecting the oxygen concentration in the exhaust gas is disposed upstream of the catalytic converter 20.
[0034]
In addition, a crank angle sensor 32 made of an electromagnetic pickup or the like is provided on the outer periphery of a crank rotor 31 that is axially attached to the crankshaft 30 of the engine 1, and is further connected to a camshaft 33 that rotates 1/2 with respect to the crankshaft 30. A cylinder discriminating sensor 35 made up of an electromagnetic pickup or the like is provided on the cam rotor 34 provided.
[0035]
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 determining a cylinder is formed on the outer periphery of the cam rotor 34. As the engine is operated, the crankshaft 30 and the camshaft 33 are rotated, and accordingly, the crank rotor 31 and the cam rotor 34 are rotated. Each projection of the crank rotor 31 is detected by the crank angle sensor 32, and the crank angle is detected. A crank pulse corresponding to a predetermined crank angle is outputted from the sensor 32, a cylinder discrimination projection of the cam rotor 34 is detected by the cylinder discrimination sensor 35, and a cylinder discrimination pulse is outputted from the cylinder discrimination sensor 35.
[0036]
Then, in an electronic control unit 40 (see FIG. 7), which will be described later, the engine speed NE is calculated based on the input interval time of the crank pulse output from the crank angle sensor 32, and from the cylinder discrimination sensor 35. Based on the cylinder discrimination pulse and the pattern of the combustion stroke order of each cylinder (for example, # 1 cylinder → # 3 cylinder → # 2 cylinder → # 4 cylinder), cylinder discrimination such as a fuel injection target cylinder and an ignition target cylinder is performed. Do.
[0037]
Engines such as throttle control, fuel injection control, ignition timing control, idle speed control, etc., calculation of control amounts for actuators such as the throttle actuator 10, injector 13, spark plug 15, ISC valve 12, and output of control signals. The control is performed by an electronic control unit (ECU) 40 shown in FIG.
[0038]
The ECU 40 is composed mainly of a microcomputer in which a CPU 41, a ROM 42, a RAM 43, a backup RAM 44, a counter / timer group 45, and an I / O interface 46 are connected to each other via a bus line, and supplies stabilized power to each part. Peripheral circuits such as a constant voltage circuit 47, a drive circuit 48 connected to the I / O interface 46, a throttle actuator drive circuit 49, and an A / D converter 50 are incorporated.
[0039]
The counter / timer group 45 includes a free-run counter, various counters such as a cylinder discrimination sensor signal (cylinder discrimination pulse) input counter, a fuel injection timer, an ignition timer, and a periodic interrupt for generating a periodic interrupt. Various timers such as interrupt timer, crank angle sensor signal (crank pulse) input interval timing timer, and watchdog timer for system abnormality monitoring are collectively referred to for convenience. Various other software counters / timers Is used.
[0040]
The constant voltage circuit 47 is connected to the battery 52 via a first relay contact of a power relay 51 having two relay contacts. The relay coil of the power relay 51 is connected to the battery 52 via an ignition switch 53. It is connected. The constant voltage circuit 47 is directly connected to the battery 52. When the ignition switch 53 is turned on and the contact of the power relay 51 is closed, power is supplied to each part of the ECU 40, while the ignition switch 53 is supplied. Regardless of whether the power is on or off, backup power is always supplied to the backup RAM 44. A power line for supplying power from the battery 52 to each actuator is connected to the second relay contact of the power relay 51.
[0041]
The input port of the I / O interface 46 includes an idle switch 24b, a knock sensor 26, a crank angle sensor 32, a cylinder discrimination sensor 35, a vehicle speed sensor 36 for detecting the vehicle speed, and a starter switch 37 for detecting the engine start state. Further, the accelerator sensor 22, the intake air amount sensor 23, the throttle opening sensor 24a, the intake pipe pressure sensor 25, the cooling water temperature sensor 28, and the O2 sensor 29 are connected via the A / D converter 50. And the battery voltage VB is input and monitored.
[0042]
On the other hand, at the output port of the I / O interface 46, the ISC valve 12, the injector 13, and an alarm lamp 38 that is arranged on an instrument panel (not shown) and displays various alarms in a concentrated manner are provided via the drive circuit 48. Further, the throttle actuator 10 is connected via the throttle actuator drive circuit 49, and the igniter 17 is connected.
[0043]
As is well known, the throttle actuator drive circuit 49 is composed of an H bridge circuit and the like, and a pulse width modulation signal (hereinafter referred to as “PWM signal”) output from the I / O interface 46 is used in the H bridge circuit. The switching element is chopper-controlled, a drive current is output to the stepping motor constituting the throttle actuator 10, and the rotation direction of the stepping motor is determined by the phase switching signal.
[0044]
Further, 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, the ECU 40 is connected to the ECU 40 by the serial monitor 60. I / O data, and failure data including a later-described intake air amount sensor NG flag FAFNG indicating failure of the intake air amount sensor system stored in the backup RAM 44 by the self-diagnosis function of the ECU 40, and trouble data indicating failure contents It can be read and diagnosed. Further, the serial monitor 60 can be used to initially set (clear) the trouble data.
[0045]
The trouble data diagnosis and initial set by the serial monitor 60 are described in detail in Japanese Patent Publication No. 7-76730 by the present applicant.
[0046]
In the CPU 41, in accordance with a control program stored in the ROM 42, the detection signals from the sensors and switches inputted through the I / O interface 46, the battery voltage, etc. are processed, and various data stored in the RAM 43, Based on various learning value data stored in the backup RAM 44, fixed data stored in the ROM 42, etc., the control amount for the throttle actuator 10, the fuel injection amount, the ignition timing, the duty ratio of the drive signal for the ISC valve 12, etc. Calculation is performed, and engine control such as throttle control, fuel injection control, ignition timing control, idle speed control is performed.
[0047]
In such an engine control system, the ECU 40 performs failure diagnosis on each sensor and each actuator by on-board failure diagnosis.
[0048]
That is, the diagnosis condition is determined based on the engine operating state, and when the diagnosis condition is satisfied, a failure diagnosis for the diagnosis target is performed. Then, the execution of the failure diagnosis is determined, and when the failure diagnosis is not executed, the target throttle opening THVTGT for the throttle valve 5a is set based on the accelerator opening ALPH representing the accelerator operation amount by the driver, 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. Then, the control amount for the throttle actuator 10 that operates the throttle valve 5a is set based on the target throttle opening THVTGT and the actual throttle opening THV by the throttle valve 5a.
[0049]
As a result, during the period of execution of the failure diagnosis for the diagnosis target due to the establishment of the diagnosis condition, 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 activated. The throttle valve 5a is operated via the throttle actuator 10 so that the throttle opening THV matches the target throttle opening THVTGT. As a result, the state in which the diagnosis condition is established according to the engine operating state is reliably continued, and the failure diagnosis for the diagnosis target can be performed reliably and promptly.
[0050]
More specifically, when performing failure diagnosis on a diagnosis target, the diagnosis condition is determined based on the engine operating state detected by a sensor excluding the diagnosis target. When the output value from the sensor to be diagnosed or the output value for the actuator to be diagnosed shows an abnormal value continues for a predetermined time under the established diagnosis condition, the diagnosis object is diagnosed as a failure. Notify the failure. Further, when setting the target throttle opening THVTGT, the difference between the diagnosis start accelerator opening ALPHDIAGST representing the accelerator operation amount at the start of diagnosis and the current accelerator opening ALPH is compared with a predetermined value during the execution of the failure diagnosis. . When the difference is smaller 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 can be performed regardless of the driver's accelerator operation. The degree THV is maintained at the throttle opening at the start of diagnosis when the diagnosis condition is satisfied, and the diagnosis condition according to the engine operating state is reliably continued.
[0051]
On the other hand, when the difference between the accelerator opening ALPHDIAGST at the start of diagnosis and the current accelerator opening ALPH exceeds a predetermined value, the target throttle opening THVTGT set based on the current accelerator opening ALPH by the driver's accelerator operation. By adopting, the normal throttle control is restored, and the required engine output by the driver's accelerator operation is ensured.
[0052]
That is, the ECU 40 implements the functions of the diagnostic unit, target throttle opening setting unit, and control amount setting unit according to the present invention.
[0053]
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.
[0054]
Hereinafter, the control process according to the present invention executed by the ECU 40 will be described with reference to the flowcharts shown in FIGS.
[0055]
First, when the ignition switch 53 is turned on and the ECU 40 is turned on, the system is initialized, and the flags and counters except for trouble data and various learning values stored in the backup RAM 44 are initialized. It becomes. When the starter switch 37 is turned on and the engine 1 is started, for each crank pulse input from the crank angle sensor 32, the engine speed NE is calculated based on the crank pulse input interval time, and from the cylinder discrimination sensor 35. Cylinder discrimination is performed by inputting a cylinder discrimination pulse. The cylinder discrimination result is reflected in fuel injection control, ignition timing control, etc., although not described in detail here.
[0056]
Then, after the system initialization, the failure diagnosis routine shown in FIG. 2 is executed every predetermined period (for example, 10 msec), and the failure diagnosis for the intake air amount sensor 23 is performed.
[0057]
In this failure diagnosis routine, first, in steps S1 to S4, it is determined whether or not a diagnosis condition is satisfied based on the engine operating state detected by each sensor excluding the intake air amount sensor 23 to be diagnosed.
[0058]
  In the present embodiment, the engine speed NE and the actual throttle opening of the throttle valve 5a.THVWhen the engine operating state due to the intake pipe pressure P downstream of the throttle valve 5a is within a preset range, it is determined that the diagnosis condition is satisfied, and based on the output value (output voltage) VQ of the intake air amount sensor 23 Then, failure diagnosis for the intake air amount sensor 23 is performed.
[0059]
  Therefore, in step S1, the crank angle sensor 32 that detects the crank angle that is the base for calculating the engine speed NE, the throttle opening sensor 24a that detects the actual throttle opening, and the intake pipe pressure P are detected. It is determined whether both intake pipe pressure sensors 25 are normal. That is,Self-diagnosis function of ECU40The crank angle sensor 32, the throttle opening sensor 24a, and the intake pipe pressure sensor 25 for detecting the engine operating state for judging the diagnosis condition with reference to the failure diagnosis result for each of the sensors 32, 24a, 25 diagnosed by the It is determined whether all of the above are normal.
[0060]
Here, when any of these sensors 32, 24a, 25 for detecting the engine operating condition for determining the diagnosis condition is abnormal, the diagnosis condition cannot be determined. At this time, the failure diagnosis for the intake air amount sensor 23 is performed. Doing so leads to misdiagnosis. Therefore, at this time, without performing failure diagnosis on the intake air amount sensor 23, the routine jumps from step S1 to step S13, and clears the count value TM of the diagnosis timer that measures the duration of the abnormal state of the intake air amount sensor 23. (TM ← 0), exit the routine.
[0061]
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 in steps S2 to S4, the current engine speed NE and the throttle opening sensor 24a are used. The actual throttle opening THV 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 set to the lower limit values NEL, ALPHAL, PL, and Compare with the upper limit values NEH, ALPHH, and PH.
[0062]
When any of the engine speed NE, the actual throttle opening THV, and the intake pipe pressure P is outside the range of the lower limit values NEL, ALPHAL, PL and the upper limit values NEH, ALPHAH, PH, the diagnosis condition is not satisfied. It is determined that the routine is established, and the routine is exited from the corresponding step through step S13 without performing failure diagnosis on the intake air amount sensor 23.
[0063]
  In steps S2 to S4, NEL ≦ NE ≦ NEH and ALPHA ≦THV≦ ALPHH, and PL ≦ P ≦ PH, and engine speed NE, actual throttle opening THV, and intake pipe pressure P are all regions with lower limit values NEL, ALPHAL, PL, and upper limit values NEH, ALPHAH, PH If it is within the range, it is determined that the diagnosis 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, and this intake air amount sensor output value VQ Is compared with the lower limit value VQL and the upper limit value VQH, which determine the failure of the intake air amount sensor 23.
[0064]
  That is, engine speed NE, actual throttle openingTHVBy determining the consistency of the output value VQ of the intake air amount sensor 23 with respect to the intake pipe pressure P, a failure diagnosis for the intake air amount sensor 23 is performed.
[0065]
  Here, when the engine speed NE is in a predetermined range of the engine operating state (NEL ≦ NE ≦ NEH), the throttle valve 5a is opened to a predetermined opening range (ALPH ≦THV≦ ALPHH), and engine speed NE and throttle opening within this predetermined rangeTHVWhen the intake pipe pressure P downstream of the throttle valve 5a shows a value within a predetermined range (PL ≦ P ≦ PH), the intake air amount sensor output value VQ isOutput value range that can normally be taken (output value range that can be taken if the intake air amount sensor 23 is in a normal state)When it deviates from the above, it is possible to diagnose a failure of the intake air amount sensor system.
[0066]
Therefore, the above lower limit values NEL, ALPHAL, PL, VQL, and upper limit values NEH, ALPHAH, PH, VQH are optimum values of the upper limit value and the lower limit value by simulation or experiment in advance based on their consistency. The value is obtained and stored in ROM 42 as fixed data.
[0067]
In step S5, when VQL <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 normal. In step S6, the intake air amount sensor NG flag FAFNG indicating a failure in the intake air amount sensor system stored as trouble data in the backup RAM 44 is cleared (FAFNG ← 0), and a predetermined alarm lamp 38 is set. The routine is exited through the above step S13 without displaying the malfunction of the intake air amount sensor system due to the blinking of the code.
[0068]
On the other hand, in step S5, when VQL ≧ VQ or VQ ≧ VQL and the output value VQ of the intake air amount sensor 23 deviates from the normal range of the lower limit value VQL and the upper limit value VQH and indicates an abnormal value, the process proceeds to step S7. The process proceeds to step S7 and subsequent steps to determine the duration of the abnormal state, and when the abnormal state continues for a predetermined time, it is diagnosed as a malfunction of the intake air amount sensor system.
[0069]
In step S7, the count value TM of the diagnostic timer that measures the duration of the abnormal state of the intake air amount sensor system is referred to, and when the diagnosis of TM = 0 is started, that is, at the first time of abnormality diagnosis of the intake air amount sensor system, Proceed to step S8.
[0070]
Then, in step S8, the current accelerator opening ALPH by the accelerator sensor 22 is read out, and this accelerator opening ALPH is stored as a diagnosis starting accelerator opening ALPHDIAGST at a predetermined address in the RAM 43 (ALPHDIAGST ← ALPH), and subsequent step S9. Thus, the current actual throttle opening THV by the throttle opening sensor 24a is stored as a throttle opening THVDIAGST at the start of diagnosis in a predetermined address of the RAM 43 (THVDIAGST ← THV), and the process proceeds to step S10.
[0071]
In step S7, TM ≠ 0, and when the routine is executed for the second and subsequent times after the abnormality diagnosis is started, the process jumps from step S7 to step S10.
[0072]
In step S10, the count value TM of the diagnostic timer is counted up (TM ← TM + 1), and in step S11, the count value TM of the diagnostic timer is determined to determine the duration of the abnormal state of the intake air amount sensor system. For comparison with the set value TMDIAG.
[0073]
The set value TMDIAG prevents erroneous diagnosis due to the temporary abnormal output value VQ of the intake air amount sensor 23 due to the influence of disturbance or the like, and determines that the intake air amount sensor system is surely broken. The appropriate time value is obtained in advance by simulation or experiment and stored in the ROM 42 as fixed data.
[0074]
If TM ≦ TMDIAG and the continuation time 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 is exited as it is because the failure is not confirmed.
[0075]
On the other hand, when TM> TMDIAG in step S11 and 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, all the diagnostic conditions in steps S1 to S4 are satisfied. When the output value VQ of the intake air amount sensor 23 shows a value that cannot normally be obtained and remains out of the normal range for a predetermined time, the intake air amount sensor 23 itself fails or the intake air amount The failure of the intake air amount sensor system due to disconnection or short of the connector or harness between the sensor 23 and the ECU 40 is determined, and the process proceeds to step S12.
[0076]
In step S12, the intake air amount sensor NG flag FAFNG indicating a failure in the intake air amount sensor system is set (FAFNG ← 1), and the blinking length, the number of blinks in a predetermined period, or a predetermined blink by a combination thereof. The code blinks the alarm lamp 38 to notify the malfunction of the intake air amount sensor system. In preparation for the next diagnosis, the count value TM of the diagnosis timer is cleared in step S13, and the routine is exited.
[0077]
As a result, when a failure occurs in the intake / intake air amount sensor system, the warning lamp 38 is notified by blinking, and the driver can easily determine the failure.
[0078]
Further, when troubleshooting at a service factory such as a dealer, the serial monitor 60 is connected via the external connection connector 55, so that the trouble data by the intake air amount sensor NG flag FAFNG in the ECU 40 is read by the serial monitor 60. Therefore, it is possible to accurately determine the failure of the intake air amount sensor system.
[0079]
Then, after repairing the relevant part, the intake air amount sensor NG flag FAFNG is cleared by the serial monitor 60. In the present embodiment, after repairing the relevant part, even if the intake air amount sensor NG flag FAFNG is not cleared by the serial monitor 60, if the intake air amount sensor system returns to a normal state, the failure diagnosis is performed. In the routine, the intake air amount sensor NG flag FAFNG is cleared.
[0080]
On the other hand, in parallel with the failure diagnosis routine, the throttle control routine shown in FIG. 3 is executed every predetermined period (for example, 10 msec) to determine whether or not the above-described failure diagnosis is performed. The target throttle opening THVTTG for the throttle valve 5a is set based on the accelerator opening ALPH by 22, and the target throttle opening THVTGT is set by the throttle opening THVDIAGST at the start of diagnosis during the failure diagnosis execution period. A control amount for the throttle actuator 10 that operates the throttle valve 5a is set in accordance with a deviation ΔTH of the actual throttle opening THV of the throttle valve 5a with respect to the target throttle opening THVTGT, and a drive signal based on the control amount is set as a throttle actuator. 10, the throttle valve 5 a is operated by the throttle actuator 10, and feedback control is performed so that the actual throttle opening THV of the throttle valve 5 a matches the target throttle opening THVTGT.
[0081]
Next, the throttle control routine of FIG. 3 will be described.
[0082]
In this throttle control routine, first, in step S21, the accelerator opening ALPH by the accelerator sensor 22 is read, and a target for the throttle valve 5a is referred to with reference to the target throttle opening table with interpolation calculation based on the accelerator opening ALPH. Set the throttle opening THVTGT.
[0083]
In the target throttle opening table, the appropriate 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. These values are obtained in advance by simulation or experiment, set as a table having the appropriate throttle opening as the target throttle opening and 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 corresponding to the actual opening of the throttle valve 5a suitable for the accelerator operation amount of the driver.
[0084]
An example of this target throttle opening table is shown in step S21. As shown in step S21, the target throttle opening THVTGT is in an increasing function relationship with the accelerator opening ALPH. For this reason, instead of the target throttle opening table, the target throttle opening THVTGT may be set by a functional expression based on the accelerator opening ALPH.
[0085]
Next, the process proceeds to step S22, and it is determined whether or not failure diagnosis is currently being executed by referring to the count value TM of the diagnosis timer obtained by the above-described failure diagnosis routine.
[0086]
When TM = 0, the continuation time of the abnormal state of the intake air amount sensor system is not timed, and when failure diagnosis is not executed, the routine jumps to step S25 and is detected based on the output value of the throttle opening sensor 24a. The current actual throttle opening THV of the throttle valve 5a is read, and the actual throttle opening THV is subtracted from the target throttle opening THVTGT to calculate a deviation ΔTH of the actual throttle opening THV with respect to the target throttle opening THVTGT ( ΔTH ← THVTGT−THV).
[0087]
In step S26, the control amount table stored in the ROM 42 is referred to based on the deviation ΔTH, and the throttle actuator control amount DACT for determining the control amount for the throttle actuator 10 is set.
[0088]
Here, as is well known, the throttle actuator control amount DACT is set according to the magnitude relationship of the actual throttle opening THV with respect to the target throttle opening THVTGT and the magnitude of the deviation ΔTH.
[0089]
That is, as shown in FIG. 4, when the deviation ΔTH of the actual throttle opening THV with respect to the target throttle opening THVTTG is a negative value, the actual throttle opening THV is larger than the target throttle opening THVTGT, and according to the deviation ΔTH. An appropriate throttle actuator control amount DACT is set so that the step position of the stepping motor constituting the throttle actuator 10 is decreased by a predetermined number of steps and the throttle valve 5a is closed by a predetermined angle by the reverse rotation of the throttle actuator 10.
[0090]
At this time, as the actual throttle opening THV is larger than the target throttle opening THVTGT and the deviation ΔTH is more negative, the number of steps to reversely rotate the step motor is set to the negative side, and the throttle by the throttle actuator 10 The valve closing speed of the valve 5a is increased so that the actual throttle opening THV of the throttle valve 5a can be converged to the target throttle opening at an early stage. Then, as the actual throttle opening THV approaches the target throttle opening THVTGT, the number of steps for determining the change amount of the step position in the minus direction by the step motor is reduced, and the closing speed of the throttle valve 5a by the throttle actuator 10 is decreased. Let This prevents overshoot or undershoot of the actual throttle opening THV with respect to the target throttle opening THVTGT, improves the convergence of the throttle valve 5a with respect to the target throttle opening THVTTG by the throttle actuator 10, and stabilizes the control. It becomes possible to plan.
[0091]
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 the throttle actuator 10 is configured according to this deviation ΔTH. An appropriate throttle actuator control amount DACT is set to increase the step position of the stepping motor by a predetermined number of steps and open the throttle valve 5a by a predetermined angle by forward rotation of the throttle actuator 10.
[0092]
At this time, as the actual throttle opening THV is larger than the target throttle opening THVTGT and the deviation is larger on the plus side, the number of steps for forward rotation of the step motor is increased, and the throttle by the throttle actuator 10 is increased. The valve opening speed of the valve 5a is increased so that the actual throttle opening THV of the throttle valve 5a can be converged to the target throttle opening at an early stage. Then, as the actual throttle opening THV approaches the target throttle opening THVTGT, the increase step number for determining the step position change amount by the step motor is decreased, and the closing speed of the throttle valve 5a by the throttle actuator 10 is decreased. The overshoot or undershoot of the actual throttle opening THV with respect to the target throttle opening THVTTG is prevented, the convergence of the throttle valve 5a with respect to the target throttle opening THVTGT by the throttle actuator 10 is improved, and the control is stabilized.
[0093]
As shown in FIG. 4, in the present embodiment, when the deviation ΔTH is −1 deg to 1 deg, the dead zone is set by setting the number of steps for changing the step position of the stepping motor constituting the throttle actuator 10 to 0, By stopping the stepping motor at the current step position, the throttle valve 5a is held at the current throttle opening without opening and closing, thereby preventing hunting.
[0094]
In step S27, the throttle actuator control amount DACT is set, and the routine is exited.
[0095]
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 drive circuit 49, and the stepping motor of the stepping motor constituting the throttle actuator 10 by the phase switching signal is output. A rotation direction is determined, and a drive current is output from the throttle actuator drive circuit 49 to the stepping motor.
[0096]
As a result, the throttle valve 5a is actuated by driving of the stepping motor constituting the throttle actuator 10, and when the failure diagnosis is not executed, the actual throttle opening THV of the throttle valve 5a represents the accelerator opening representing the driver's accelerator operation amount. Feedback control is performed so as to follow the target throttle opening THVTTGT set based on ALPH, and the throttle opening air flow rate is adjusted to an appropriate throttle opening that obtains an engine output request according to the accelerator operation amount of the driver.
[0097]
On the other hand, in step S22, TM ≠ 0 and the duration time of the abnormal state of the intake air amount sensor system is measured, and the process proceeds to step S23 during the fault diagnosis execution period.
[0098]
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 | ALPHDIAGST-ALPH | of the difference between the accelerator opening ALPHDIAGST at the start of diagnosis and the current accelerator opening ALPH is set to the set value. Compared with ΔALPHS, a change in the accelerator operation amount from the start of diagnosis to the present due to an abnormal state of the intake air amount sensor system is determined.
[0099]
The set value ΔALPHS determines the change in the accelerator operation amount by the driver from the start of diagnosis, and when the change in the accelerator opening ALPH indicating the driver's accelerator operation amount is small, regardless of the driver's accelerator operation, By maintaining the actual throttle opening THV of the throttle valve 5a at the throttle opening at the start of diagnosis, priority is given to continuing diagnosis conditions for the intake air amount sensor system, and when the change in the accelerator opening ALPH is large, the driver's The target throttle opening THVTGT set based on the accelerator opening ALPH representing the accelerator operation amount is adopted, and the actual throttle opening THV of the throttle valve 5a is controlled by the throttle actuator 10 in accordance with the driver's accelerator operation. This is to give priority to the accelerator operation by, by simulation or experiment in advance Seek positive, are those memory as fixed data in the ROM 42.
[0100]
And, | ALPHDIAGST−ALPH | <ΔALPHS, the absolute value of the difference between the diagnosis starting accelerator operation amount ALPHDIAGST representing the accelerator operation amount at the start of diagnosis and the current accelerator opening ALPH is a predetermined value based on the set value ΔALPHS. If it falls below, the process proceeds to step S24, where 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 throttle opening at diagnosis start corresponding to the actual throttle opening at the start of diagnosis. Reset by THVDIAGST (THVTGT ← THVDIAGST).
[0101]
Then, the process proceeds to step S25, and the current actual throttle opening THV is subtracted from the target throttle opening THNTGT newly set in step S24 to calculate a deviation ΔTH of the actual throttle opening THV with respect to the target throttle opening THVTGT. Further, in steps S26 and S27, referring to the control amount table based on the deviation ΔTH, a throttle actuator control amount DACT for determining a control amount for the throttle actuator 10 is set, and the control amount DACT is set to execute a routine. Exit.
[0102]
As a result, during the failure diagnosis execution period, when the absolute value of the difference between the diagnosis start accelerator opening ALPHDIAGST indicating the accelerator operation amount at the start of diagnosis and the current accelerator opening ALPH is below the set value ΔALPHS, the target throttle The opening THVTGT is reset by the diagnosis opening throttle opening THVDIAGST corresponding to the actual throttle opening at the start of diagnosis. Then, the stepping motor constituting the throttle actuator 10 is driven according to the deviation ΔTH of the current actual throttle opening THV with respect to the target throttle opening THVTGT, and the throttle valve 5a is operated by the driving of the stepping motor. The actual throttle opening THV is feedback-controlled so as to maintain the throttle opening THVDIAGST at the start of diagnosis.
[0103]
Accordingly, when the change in the amount of accelerator operation by the driver is relatively small during the execution of the failure diagnosis, the actual throttle opening THV by the throttle valve 5a is a diagnosis that satisfies the diagnosis condition, regardless of the driver's accelerator operation. By maintaining the throttle opening at the start time THVDIAGST, the state in which the diagnosis condition is established according to the engine operating state is reliably maintained, and the failure diagnosis for the intake air amount sensor 23 can be performed reliably and promptly.
[0104]
As a result, in an engine that employs an electronic throttle control system, it is possible to increase the diagnosis frequency in the market (under the usage conditions of the user) and expand the diagnosis possible area, and to perform highly accurate diagnosis. Become.
[0105]
And since it becomes possible to perform failure diagnosis for the intake air amount sensor 23 reliably and quickly, when a failure occurs in the intake air amount sensor system, on-board failure diagnosis by executing the above-described failure diagnosis routine, It is possible to reliably determine and notify the malfunction of the intake air amount sensor system, prevent the vehicle from continuing to run while the intake air amount sensor system is malfunctioning, and reduce exhaust emissions due to the malfunction of the intake air amount sensor. It is possible to prevent secondary problems such as harmful effects on the engine.
[0106]
On the other hand, in step S23, when | ALPHDIAGST−ALPH | ≧ ΔALPHS and the absolute value of the difference between the accelerator opening ALPHDIAGST at the start of diagnosis and the current accelerator opening ALPH is equal to or greater than a predetermined value by the set value ΔALPHS, Jump to step S25.
[0107]
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 current actual throttle opening THV is subtracted from the target throttle opening THV. Then, the deviation ΔTH of the actual throttle opening THV with respect to the target throttle opening THVTGT is calculated, and the throttle actuator control amount DACT is set by referring to the control amount table based on the deviation ΔTH in steps S26 and S27. Then, the control amount DACT is set and the routine is exited.
[0108]
Therefore, even when the failure diagnosis is being performed, when the change in the accelerator opening ALPH due to the driver's accelerator operation is large, the target throttle opening that is set based on the current accelerator opening ALPH that represents the driver's accelerator operation amount is displayed. By adopting the degree THVTGT and controlling the actual throttle opening THV of the throttle valve 5a by the throttle actuator 10 according to the driver's accelerator operation, the accelerator operation by the driver is prioritized, and the normal throttle control is restored. It is possible to ensure the required engine output by the driver's accelerator operation.
[0109]
If the engine operating state changes 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 described above are not satisfied, When the count of the duration of the abnormal state of the intake air amount sensor system is stopped and the count value TM of the diagnostic timer is cleared (step S13 in FIG. 2), the next time the throttle control routine is executed, step S22 is executed. From step S25, normal throttle control is continued by the target throttle opening THVTGT set based on the current accelerator opening ALPH.
[0110]
In this embodiment, the failure diagnosis for the intake air amount sensor has been described as the diagnosis target. However, the present invention is not limited to this, and the diagnosis target may be a sensor other than the intake air amount sensor or an actuator. Of course.
[0111]
In this embodiment, the accelerator opening is adopted as the accelerator operation amount of the driver. However, the present invention is not limited to this, and the present invention can be applied as long as it represents the accelerator operation amount. .
[0112]
Further, the accelerator operation can be applied to automatic operation control by operating with a control device such as a microcomputer. In this case, the driver includes not only personnel but also the control device.
[0113]
Further, in this embodiment, a stepping motor type throttle actuator is used as the throttle actuator, but 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.
[0114]
【The invention's effect】
  As described above, according to the first aspect of the present invention, the diagnosis condition is determined based on the engine operating state, and when the diagnosis condition is satisfied,Sensors or actuators provided in the engine control system are to be diagnosedPerform fault diagnosis. Then, the execution of the failure diagnosis is judged, and when the failure diagnosis is not executed, the target throttle opening for the throttle valve is set based on the accelerator operation amount by the driver, and the target throttle opening and the actual throttle opening are set. Since the control amount for the throttle actuator that operates the throttle valve is set based on this, the required engine output by the driver's accelerator operation is ensured. On the other hand, during the fault diagnosis execution period,The difference between the accelerator operation amount at the start of diagnosis and the current accelerator operation amount is compared with a predetermined value, and if the difference is less than the predetermined value, the target throttle opening is set to the actual throttle opening at the start of diagnosis. When the change in the accelerator operation amount by the driver is relatively small during the diagnosis execution period, the actual throttle opening by the throttle valve is the throttle opening at the start of diagnosis when the diagnosis condition is satisfied, regardless of the driver's accelerator operation. The diagnosis condition according to the engine operating state is reliably maintained and the failure diagnosis for the diagnosis target can be performed reliably and promptly. In addition, this makes it possible to expand the diagnosis possible area by increasing the frequency of diagnosis in the market (under the use condition of the user) in an engine employing an electronic throttle control system..
[0115]
  According to the invention described in claim 2, when performing a failure diagnosis on a diagnosis target, the diagnosis targetAnd notDiagnosis conditions are determined based on the engine operating state detected by the sensor. And if the diagnostic conditions are met,SensorOutput value or diagnosis target fromActuatorWhen a state in which the output value for the value indicates an abnormal value continues for a predetermined time, the failure is diagnosed and the failure is notified.SoThis has the effect of making a highly accurate diagnosis.
[0116]
Furthermore, since the failure diagnosis for the diagnosis target can be performed reliably and promptly, when a failure occurs in the diagnosis target, it becomes possible to reliably determine and notify the diagnosis target failure by the on-board failure diagnosis, Accordingly, it is possible to prevent the diagnosis target from continuing to operate and to prevent secondary problems such as deterioration of exhaust emissions and harmful effects on the engine due to the failure of the diagnosis target.
[0118]
  According to invention of Claim 3, said Claim 1 or Claim2In addition to the effects of the invention described above, an effect that the present invention can be easily applied to engine control of a vehicle engine by adopting an accelerator opening indicating an amount of depression of an accelerator pedal as the accelerator operation amount. Have
[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 deviation of an actual throttle opening with respect to a target throttle opening and an operation relationship of a stepping motor.
FIG. 5 is an overall schematic diagram of the engine.
FIG. 6 is a side view of an accelerator pedal.
FIG. 7 is a circuit configuration diagram of an electronic control system.
[Explanation of symbols]
1 engine
5a Throttle valve
10 Throttle actuator
Accelerator sensor
23 Intake air volume sensor (diagnostic object)
24a Throttle opening sensor (Sensor excluding diagnosis target)
25 Intake pipe pressure sensor (Sensor excluding diagnosis target)
32 Crank angle sensor (Sensor excluding diagnosis target)
40 Electronic control device (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 condition)
P Intake pipe pressure (engine operating condition)
THVTGT Target throttle opening
THV actual throttle opening (engine operation state)
DACT Throttle actuator control amount (control amount for throttle actuator)
VQ intake air volume sensor output value (output value for diagnosis)
TMDIAG setting value (predetermined time)
ALPHDIAGST Accelerator opening at diagnosis start (accelerator operation amount at diagnosis start)
ΔALPHS setting value (predetermined value)
THVDIAGST Throttle opening at diagnosis start (actual throttle opening at diagnosis start)

Claims (3)

The control amount for the throttle actuator is set based on the accelerator operation amount of the driver, and the throttle valve is operated by the throttle actuator to control the opening of the throttle valve, and the sensor or actuator provided in the engine control system is diagnosed. In the engine control device that performs failure diagnosis as a target ,
Determining a diagnostic condition on the basis of the engine operating condition, when the establishment of diagnosis condition, a diagnosis unit for performing fault diagnosis of the diagnosis object,
When failure diagnosis is not performed, the target throttle opening for the throttle valve is set based on the accelerator operation amount. During the failure diagnosis execution period, the difference between the accelerator operation amount at the start of diagnosis and the current accelerator operation amount is calculated. When the difference is less than the predetermined value, the actual throttle opening at the start of diagnosis is set as the target throttle opening, and when the difference is greater than or equal to the predetermined value, based on the current accelerator operation amount Target throttle opening setting means for setting the target throttle opening;
A control apparatus for an engine, comprising: a 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. The diagnosis means determines a diagnosis condition based on an engine operating state detected by a sensor not to be diagnosed, and outputs an output value from a sensor to be diagnosed or an output to an actuator to be diagnosed when the diagnosis condition is satisfied. when the value is a state indicating an error value has continued for a predetermined time, the control device for an engine according to claim 1, wherein the multi-address known to Rukoto fault diagnose a failure of the diagnostic object.   The engine control apparatus according to claim 1 or 2, wherein the accelerator operation amount is an accelerator opening degree indicating an amount of depression of an accelerator pedal.

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