JP3533997B2 - Failure diagnosis device for intake flow control valve - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a failure diagnosis device for an intake flow control valve that changes the flow state of gas in a combustion chamber of an internal combustion engine.

[0002]

2. Description of the Related Art Conventionally, for example, in an internal combustion engine which directly injects fuel into a combustion chamber, an intake flow control valve for causing a gas flow is provided in the combustion chamber in order to obtain a favorable combustion of an air-fuel mixture. It has been known. Such an intake flow control valve is provided in the intake passage of the internal combustion engine. Then, by controlling the intake flow control valve, the flow state of the gas generated in the combustion chamber changes, and the degree of diffusion of the injected fuel with respect to the air changes. Therefore, by controlling the intake flow control valve in accordance with the engine operating state and making the gas flow state in the combustion chamber appropriate for the engine operating state, good combustion of the air-fuel mixture in the combustion chamber can be achieved. You will get it.

In an internal combustion engine that controls the intake flow control valve in order to obtain good combustion in this way, the combustion state is greatly affected by a failure of the intake flow control valve, and therefore, among various failure diagnoses in the internal combustion engine, Fault diagnosis of the intake flow control valve is particularly important. As a device for diagnosing the failure of the intake flow control valve, for example, Japanese Patent Laid-Open No. 8-2
The failure diagnosis device described in Japanese Patent No. 00116 is known.

An internal combustion engine to which the failure diagnosing device described in the publication is applied has an intake flow control valve which is opened and closed by driving a motor. Then, by controlling the opening degree of the intake flow control valve by driving the motor based on the opening degree command value obtained based on the engine operating state, the flow state of the gas generated in the combustion chamber is suitable for the engine operating state. To be done. Further, the failure diagnosis device described in the publication includes an opening sensor that detects an actual opening of the intake flow control valve, and an opening command value obtained based on an engine operating state to control the intake flow control valve. And the actual opening obtained based on the detection signal from the opening sensor are compared. Then, based on the fact that the difference between the opening degree command value and the actual opening degree becomes excessively large, it is accurately determined that the intake flow control valve has a failure.

[0005]

By the way, in recent years, instead of the intake flow control valve driven by the motor, an intake flow control valve driven by a negative pressure type actuator is adopted, thereby reducing the cost of the internal combustion engine. Is being considered. Here, the negative pressure type actuator operates based on the negative pressure generated in the intake passage, and the operation of the actuator causes the intake flow control valve to change between the valve opening position and the valve closing position. However, even if an intake flow control valve driven by such a negative pressure type actuator is adopted, if an opening sensor for detecting the actual opening of the intake flow control valve is provided for the above-mentioned failure diagnosis, the The cost increase by that amount cannot be ignored.

The present invention has been made in view of the above circumstances, and an object thereof is to perform a failure diagnosis without providing a special sensor such as an opening sensor for detecting the opening of the intake flow control valve. An object of the present invention is to provide a failure diagnosis device for an intake flow control valve that can be performed.

[0007]

[Means for Solving the Problems] Means for achieving the above-mentioned objects and their effects will be described below. In order to achieve the above object, in the invention according to claim 1, it is provided in the intake passage of the internal combustion engine, and is controlled between the valve opening position and the valve closing position based on the engine operating state, so that In the failure diagnosis device for the intake flow control valve that causes gas flow, when deterioration of the combustion state of the internal combustion engine is detected, from the engine control state suitable for the state where the intake flow control valve is in one valve position, Changing means for changing the control state of the internal combustion engine to an engine control state suitable for the state where the intake flow control valve is at the other valve position, and the combustion state of the internal combustion engine after changing the engine control state by the changing means. And a diagnostic means for diagnosing that a failure has occurred in the intake flow control valve based on the fact that deterioration of the internal combustion engine is not detected.
Depending on the engine operating condition, the combustion method can be either homogeneous combustion or stratified combustion.
Switching between baking and firing, the changing means is
Deterioration of the combustion state was detected during stratified charge combustion operation of the fuel engine
At this time, switching the combustion method from stratified combustion to homogeneous combustion
And

When a failure occurs in the intake flow control valve that can be switched between the open position and the closed position, the intake flow control valve is no longer controlled to a valve position suitable for the engine operating state, so The generated gas flow state becomes unsuitable for the engine operating state, and the combustion state of the internal combustion engine deteriorates.
When the deterioration of the combustion state of the internal combustion engine is detected, from the engine control state suitable for the state in which the intake flow control valve is located at the valve position (open valve position or valve closed position) based on the engine operating condition at that time, The control state of the internal combustion engine is changed to the engine control state suitable for the state where the intake flow control valve is located at the other valve position. When the intake flow control valve is not controlled to the valve position suitable for the engine operating state due to a failure, the combustion state is recovered by changing the engine control state as described above. According to this configuration, after the engine control state is changed, if the combustion state is recovered and the deterioration of the combustion state is not detected, it is determined that the intake flow control valve has a failure. It is possible to diagnose the failure of the intake flow control valve without providing a special sensor such as an opening sensor that detects the opening of the intake flow control valve, and to reduce the cost of the internal combustion engine by the amount of the sensor. You can

[0009]

In the above internal combustion engine, when the internal combustion engine is required to have a high engine output at high rotation and high loads, homogeneous combustion is performed in which an air-fuel mixture in which fuel is evenly mixed with air is combusted. In addition, when the internal combustion engine does not require a very high output when the engine is running at low speed and low load, fuel is collected around the spark plug to increase the fuel concentration around the plug and improve the ignitability, and to improve the average air-fuel ratio of the mixture as a whole. Stratified combustion is performed in which the value can be made leaner than the stoichiometric air-fuel ratio. During this stratified charge combustion operation, since it is necessary to collect the fuel around the spark plug as described above, it is easily affected by the flow state of gas in the combustion chamber, and the intake flow control valve fails and the valve position is incorrect. If appropriate, it will have a great adverse effect on the combustion state. On the other hand, during the homogeneous combustion operation, since the air-fuel mixture in which the fuel is evenly mixed with the air is burned, it is less affected by the flow state of the gas in the combustion chamber. Therefore, during the stratified charge combustion operation of the internal combustion engine, when the intake flow control valve is in an inappropriate valve position due to a failure, the gas flow state in the combustion chamber becomes unsuitable for the stratified charge combustion and the combustion state deteriorates. To do. When the deterioration of the combustion state of the internal combustion engine is detected, the combustion system of the internal combustion engine is switched from stratified combustion to homogeneous combustion, and the engine control state is changed.
When the intake flow control valve is in a valve position (open position or closed position) inappropriate for stratified charge combustion due to a failure, the stratified charge combustion operation is switched to the homogeneous combustion operation that is less susceptible to the gas flow state as described above. As a result, the combustion state of the internal combustion engine is restored. According to this configuration, after the combustion mode is switched, if the combustion state is recovered and the deterioration of the combustion state is not detected, it is determined that the intake flow control valve has a failure. It is possible to diagnose the failure of the intake flow control valve without providing a special sensor such as an opening sensor that detects the opening of the intake flow control valve, and to reduce the cost of the internal combustion engine by the amount of the sensor. You can

According to a second aspect of the invention, in the first aspect of the invention, the changing means is in an engine operating state in which the intake flow control valve is in a valve position for weakening the flow of the gas while stratified charge combustion is performed. Therefore, when the deterioration of the combustion mode in the internal combustion engine is detected, the combustion method is switched from the stratified combustion to the homogeneous combustion.

In the stratified charge combustion operation of the internal combustion engine, when the intake flow control valve is in the valve position for strengthening the gas flow due to a failure and the intake flow control valve is in the inappropriate valve position, The flow of gas in the combustion chamber is stronger than the proper state and is unsuitable for stratified combustion, and the combustion state deteriorates. When the deterioration of the combustion state of the internal combustion engine is detected, the combustion system is switched to the homogeneous combustion that is less likely to be affected by the gas flow state in the combustion chamber. According to this configuration, after the combustion method is switched, if the combustion state is recovered and the deterioration of the combustion state is not detected, this causes a failure of the intake flow control valve, thereby increasing the gas flow at the valve position. It is possible to judge that sticking has occurred.

According to the third aspect of the invention, the intake air of the internal combustion engine is
It is installed in the passage to open and close the valve based on engine operating conditions.
Controlled between the valve position and gas in the combustion chamber
Diagnostic device for intake flow control valve
When the deterioration of the combustion state of the internal combustion engine is detected,
Engine control suitable for the state where the intake flow control valve is in one valve position
From the control state, the same intake flow control valve is in the other valve position
Change the control state of the internal combustion engine to the engine control state suitable for
Changing means for changing the engine control state by the changing means.
After the change, the deterioration of the combustion state of the internal combustion engine shall not be detected.
On the basis of the fact that a failure has occurred in the intake flow control valve.
The internal combustion engine switches the combustion method between homogeneous combustion and stratified combustion according to the engine operating state, and the changing means performs homogeneous combustion and the intake air. When the deterioration of the combustion state in the internal combustion engine is detected in the engine operating state in which the flow control valve is in the valve position that strengthens the flow of the gas, the ignition timing of the engine is set to the intake flow control valve to change the flow of the gas. It was decided to switch to a time suitable for the state of the valve position to be weakened.

In the above internal combustion engine, when the internal combustion engine is required to have a high engine output at a high rotation speed and a high load, homogeneous combustion is performed in which a mixture of fuel and air is uniformly mixed. In addition, when the internal combustion engine does not require a very high output when the engine is running at low speed and low load, fuel is collected around the spark plug to increase the fuel concentration around the plug and improve the ignitability, and to improve the average air-fuel ratio of the mixture as a whole. Stratified combustion is performed in which the value can be made leaner than the stoichiometric air-fuel ratio. During the homogeneous combustion operation, since the combustion speed of the air-fuel mixture changes according to the flow state of the gas in the combustion chamber, the ignition timing of the internal combustion engine varies depending on the valve position of the intake flow control valve in order to obtain good combustion. Will be controlled.
During homogeneous combustion operation of the internal combustion engine, when the intake flow control valve is in a valve position that weakens the gas flow due to a failure and the intake flow control valve is in an inappropriate valve position, the gas flow in the combustion chamber is It is weaker than the proper state, and the diffusion of fuel to the air is not properly performed, and the combustion state deteriorates. When the deterioration of the combustion state of this internal combustion engine is detected,
The ignition timing of the internal combustion engine is suitable for the state where the intake flow control valve is in the valve position where the gas flow is strengthened, and from the timing when the intake flow control valve is in the valve position where the gas flow is weakened. Is switched to. According to this configuration, after the ignition timing is switched, if the combustion state is recovered and the deterioration of the combustion state is not detected, this causes a failure of the intake flow control valve to weaken the gas flow at the valve position. It is possible to judge that sticking has occurred.

According to the invention described in claim 4 , the intake air of the internal combustion engine
It is installed in the passage to open and close the valve based on engine operating conditions.
Controlled between the valve position and gas in the combustion chamber
Diagnostic device for intake flow control valve
When the deterioration of the combustion state of the internal combustion engine is detected,
Engine control suitable for the state where the intake flow control valve is in one valve position
From the control state, the same intake flow control valve is in the other valve position
Change the control state of the internal combustion engine to the engine control state suitable for
Changing means for changing the engine control state by the changing means.
After the change, the deterioration of the combustion state of the internal combustion engine shall not be detected.
On the basis of the fact that a failure has occurred in the intake flow control valve.
Diagnostic means for performing a diagnosis , the internal combustion engine is for switching the combustion method according to the engine operating state, the changing means, the engine control state to be changed when the deterioration of the combustion state of the internal combustion engine is detected The target of change is changed for each combustion method.

According to this configuration, the engine control state is changed for the purpose of diagnosing the failure of the intake flow control valve. However, the failure of the intake flow control valve is diagnosed by making the change target appropriate for the combustion system. Can be done accurately.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment in which the present invention is applied to an in-line four-cylinder direct injection gasoline engine for automobiles will be described below with reference to FIG.
~ It demonstrates according to FIG.

As shown in FIG. 1, the engine 11 is provided with a total of four pistons 12 (only one is shown in FIG. 1) provided in each cylinder block 11a for reciprocating movement in each cylinder. . On the heads of these pistons 12,
The depression 12a necessary to execute the stratified combustion is formed. Further, these pistons 12 are connected to a crankshaft 14 which is an output shaft via a connecting rod 13. The reciprocating movement of the piston 12 is converted into the rotation of the crankshaft 14 by the connecting rod 13.

A signal rotor 14a is attached to the crankshaft 14. This signal rotor 14
A plurality of protrusions 14b are provided on the outer peripheral portion of a at equal angles around the axis of the crankshaft 14. A crank position sensor 14c is provided on the side of the signal rotor 14a. Then, the crankshaft 14 rotates, and the protrusions 14b of the signal rotor 14a sequentially pass by the side of the crank position sensor 14c, so that the sensor 14c detects a pulsed state corresponding to the passage of the protrusions 14b. The signal will be output.

The cylinder block 11a includes an engine 1
A water temperature sensor 11b that detects the cooling water temperature of No. 1 and a knock sensor 11c that detects knocking based on the vibration generated in the cylinder block 11a are provided. Further, the cylinder head 15 is provided on the upper end of the cylinder block 11a.
Is provided, and a combustion chamber 16 is provided between the cylinder head 15 and the piston 12. In the combustion chamber 16, a pair of intake ports 17a and 17b provided in the cylinder head 15 and a pair of exhaust ports 18a and 1b are also provided.
8b is in communication (in FIG. 1, one intake port 17
b and the exhaust port 18b are only shown). This intake port 1
An intake valve 19 and an exhaust valve 20 are provided at 7a and 17b and exhaust ports 18a and 18b, respectively.

On the other hand, the cylinder head 15 rotatably supports an intake camshaft 21 and an exhaust camshaft 22 for opening and closing the intake valve 19 and the exhaust valve 20. The intake and exhaust camshafts 21 and 22 are connected to the crankshaft 14 via a timing belt, a gear (both not shown), etc., and the rotation of the crankshaft 14 is transmitted by the belt, the gear, etc. . Then, when the intake camshaft 21 rotates, the intake valve 19 is opened / closed, and the intake ports 17a and 17b and the combustion chamber 16 are communicated / blocked. When the exhaust camshaft 22 rotates, the exhaust valve 20 is opened and closed to drive the exhaust ports 18a and 18b.
And the combustion chamber 16 are communicated / interrupted.

Further, in the cylinder head 15, a cam position sensor 21b for detecting a projection 21a provided on the outer peripheral surface of the intake cam shaft 21 and outputting a detection signal is provided on the side of the intake cam shaft 21. . Then, when the intake camshaft 21 rotates, the same shaft 2
The first projection 21a passes by the side of the cam position sensor 21b. In this state, the cam position sensor 21b outputs a detection signal at predetermined intervals in response to the passage of the protrusion 21a.

The intake port 17a, 17b and the exhaust port 18a, 18b have an intake pipe 30 and an exhaust pipe 3, respectively.
1 is connected. The intake pipe 30 and the intake ports 17a and 17b form an intake passage 32, and the exhaust pipe 31 and the exhaust ports 18a and 18b form an exhaust passage 33.
Has become.

A throttle valve 23 is provided upstream of the intake passage 32. This throttle valve 23
Is a throttle motor 2 including a direct current (DC) motor
It is rotated by the drive of 4 and the opening degree is adjusted. The opening of the throttle valve 23 is detected by the throttle position sensor 44.

The drive of the throttle motor 24 is controlled based on the depression amount of the accelerator pedal 25 (accelerator depression amount) provided inside the vehicle. That is, when the driver of the automobile depresses the accelerator pedal 25, the accelerator depression amount is detected by the accelerator position sensor 26, and the throttle motor 24 is drive-controlled based on the detection signal of the sensor 26. By adjusting the opening degree of the throttle valve 23 based on the drive control of the throttle motor 24, the air flow area of the intake passage 32 is changed and the amount of air taken into the combustion chamber 16 is adjusted.

In the intake passage 32, the throttle valve 2
A vacuum sensor 36 for detecting the pressure in the passage 32 is provided in a portion located on the downstream side of 3. Then, the vacuum sensor 36 outputs a detection signal corresponding to the detected pressure in the intake passage 32.

The cylinder head 15 has a combustion chamber 1
6, a fuel injection valve 40 for injecting and supplying fuel into the combustion chamber 1
An ignition plug 41 for igniting a mixture of fuel and air with which the interior of the fuel cell 6 is filled is provided. The ignition timing of the mixture by the spark plug 41 is adjusted by an igniter 41a provided above the spark plug 41.

When the fuel is injected from the fuel injection valve 40 into the combustion chamber 16, the fuel is mixed with the air sucked into the combustion chamber 16 through the intake passage 32, and the combustion chamber 1
Within 6, a mixture of air and fuel is formed. Further, the air-fuel mixture in the combustion chamber 16 is ignited by the ignition plug 41 and burned, and the air-fuel mixture after combustion is sent to the exhaust passage 33 as exhaust gas.

Next, the structure of the intake system in the engine 11 will be described in detail with reference to FIG. As shown in FIG. 2, a surge tank 34 is provided in the middle of the intake pipe 30, and the intake passage 32 passes through the surge tank 34. The intake passage 32 branches into two upstream of the surge tank 34, and then into four corresponding to the cylinders of the engine 11 downstream of the surge tank 34. A swirl control valve (SCV) 48 for changing the flow state of gas in the combustion chamber 16 is provided in a portion of the intake passage 32 corresponding to the intake port 17a.

The SCV 48 has a rod 5 extending from an actuator 49 which uses a negative pressure generated in the intake passage 32 as an operation source.
The rod 50 is connected to 0 and opens and closes between the valve opening position and the valve closing position by the expansion and contraction of the rod 50 based on the operation of the actuator 49. When the SCV 48 is open, the combustion chamber 1 is discharged from both the intake port 17a and the intake port 17b.
6 is supplied with air, and when the SCV 48 is closed, air is supplied into the combustion chamber 16 only from the intake port 17b. The opening / closing operation of the SCV 48 is performed to adjust the strength of gas flow (swirl) in the combustion chamber 16.

That is, when the SCV is closed, the intake port 17b extending away from the center M of the combustion chamber.
The air is supplied to the combustion chamber 16 from only the swirl in the combustion chamber 16 by the air supply.
It becomes stronger than when V48 is opened and air is supplied from both intake ports 17a and 17b into the combustion chamber 16. Therefore,
By opening / closing the SCV 48 between the valve opening position and the valve closing position, the strength of the swirl generated in the combustion chamber 16 is adjusted.

Here, the actuator 49 for opening and closing the SCV 48 and the structure for operating the actuator 49 will be described in detail. Actuator 4
In FIG. 9, the inside of the housing 51 is divided into an atmosphere chamber 53 and a negative pressure chamber 54 by a diaphragm 52 having elasticity. Further, in the actuator 49, the rod 50 is connected to the diaphragm 52, and the negative pressure chamber 54
Is provided with a coil spring 55 having elasticity in the extension / contraction direction of the rod 50. The coil spring 55 normally causes the rod 50 to extend and the SCV 48
Is held in an open state, that is, a state in which it is located in the valve opening position.

In the actuator 49, the atmosphere chamber 53 communicates with the outside of the housing 51, and the negative pressure chamber 54 communicates with the vacuum tank 57 via the negative pressure passage 58. In this way, the vacuum tank 57, to which the negative pressure passage 58 is connected, communicates with the downstream side of the throttle valve 23 in the intake passage 32 of the engine 11 via the suction passage 59.

The suction passage 59 is provided with a check valve 59a for preventing backflow of intake air from the intake passage 32 to the vacuum tank 57. The check valve 59a is opened and closed by the pressure difference between the intake passage 32 and the vacuum tank 57, and is opened only when the pressure in the intake passage 32 becomes a value on the vacuum side of the pressure in the vacuum tank 57. It will be. By the opening / closing operation of the check valve 59a, the pressure in the vacuum tank 57 is controlled to a value closer to the vacuum side than the pressure in the intake passage 32.

A vacuum switching valve (VSV) 61 is provided in the negative pressure passage 58.
The VSV 61 includes an electromagnetic solenoid (not shown). Then, by controlling the voltage application to the electromagnetic solenoid, the VSV 61 is opened and closed so that the negative pressure chamber 54 and the vacuum tank 57 are connected and disconnected.

Therefore, when the VSV 61 is opened and the negative pressure chamber 54 and the vacuum tank 57 communicate with each other while the negative pressure generated in the intake passage 32 during operation of the engine 11 is accumulated in the vacuum tank 57, Air is sucked from the negative pressure chamber 54 to the vacuum tank 57 side based on the negative pressure in the tank 57. When air is sucked from the negative pressure chamber 54 in this way, the diaphragm 52 moves to the coil spring 55.
Is displaced in the direction of contracting. Due to the displacement of the diaphragm 52, the rod 50 contracts to close the SCV 48, that is, the SCV 48 is positioned at the valve closing position.

Next, the electrical configuration of the fault diagnosis device for performing the fault diagnosis of the SCV 34 will be described with reference to FIG. This failure diagnosis device includes an electronic control unit (hereinafter referred to as “ECU”) 92 for controlling the operating state of the engine 11, such as fuel injection amount control, fuel injection timing control, ignition timing control, and throttle opening degree control. ing. This EC
The U92 is configured as an arithmetic logic operation circuit including a ROM 93, a CPU 94, a RAM 95, a backup RAM 96, and the like.

Here, the ROM 93 is a memory in which various control programs and maps referred to when executing these various control programs are stored, and the CPU 94 is an R memory.
The arithmetic processing is executed based on various control programs and maps stored in the OM 93. RAM95 is a CPU
The backup RAM 9 is a memory for temporarily storing the calculation result of 94, data input from each sensor, and the like.
Reference numeral 6 is a non-volatile memory that stores data to be saved when the engine 11 is stopped. And ROM9
3, CPU94, RAM95 and backup RAM9
6 are connected to each other via a bus 97, and are also connected to an external input circuit 98 and an external output circuit 99.

The external input circuit 98 includes a water temperature sensor 11
b, knock sensor 11c, crank position sensor 1
4c, a cam position sensor 21b, an accelerator position sensor 26, a vacuum sensor 36, a throttle position sensor 44, etc. are connected. On the other hand, the external output circuit 99 is connected to the throttle motor 24, the fuel injection valve 40, the igniter 41a, the VSV 61, and the like.

The ECU 92 having such a configuration switches the combustion system between "stratified combustion" and "homogeneous combustion" according to the operating state of the engine 11. That is, the ECU 92
Calculates the engine speed NE based on the detection signal from the crank position sensor 14c. Further, the ECU 92
Calculates the intake pressure PM based on the detection signal from the vacuum sensor 36 and the accelerator depression amount ACCP based on the detection signal from the accelerator position sensor. Then, the intake pressure PM or the accelerator depression amount ACC
A basic fuel injection amount Qbse, which is a value corresponding to the engine load, is calculated based on P and the engine speed NE.

The ECU 92 switches the combustion mode of the engine 11 based on the basic fuel injection amount Qbse and the engine speed NE. For example, "homogeneous combustion" is performed when the operating state of the engine 11 is in the high rotation and high load region, and "stratified combustion" is performed when it is in the low rotation and low load region. In this way, the combustion method is changed by increasing the engine output by setting the air-fuel ratio of the air-fuel mixture to a value on the rich side at high rotation and high load where high output is required, and at low rotation and low load that does not require too high output. This is because sometimes the air-fuel ratio is set to a lean value to improve fuel efficiency.

When the combustion system of the engine 11 is "homogeneous combustion", the ECU 92 calculates the basic fuel injection amount Qbse based on the intake pressure PM and the engine speed NE. Then, the fuel injection valve 40 is drive-controlled to inject into the combustion chamber 16 an amount of fuel corresponding to the final fuel injection amount Qfin obtained from the basic fuel injection amount Qbse during the intake stroke of the engine 11. In the air-fuel mixture formed in the combustion chamber 16 based on such fuel injection, the fuel is evenly mixed with the air, and the air-fuel ratio thereof is the theoretical air-fuel ratio or a value on the rich side of the theoretical air-fuel ratio. become. When controlling the air-fuel ratio of the air-fuel mixture to the stoichiometric air-fuel ratio, the ECU 9
2 performs feedback correction of the fuel injection amount based on the oxygen concentration in the exhaust gas.

Further, the ECU 92 controls the accelerator depression amount AC.
The target throttle opening TAt is calculated based on the CP and the engine speed NE, and the throttle motor is moved so that the actual throttle opening TAr calculated based on the detection signal from the throttle position sensor 44 approaches the target throttle opening TAt. 24 is controlled. In addition, the ECU 9
2 calculates a target ignition timing by referring to a map based on the intake pressure PM and the engine speed NE, and drives and controls the igniter 41a based on the target ignition timing. By controlling the throttle opening and the ignition timing as described above, the throttle opening and the ignition timing are suitable for "homogeneous combustion".

When the combustion system of the engine 11 is "stratified combustion", the ECU 92 calculates the basic fuel injection amount Qbse based on the accelerator depression amount ACCP and the engine speed NE. Then, the fuel injection valve 40 is drive-controlled to inject and supply an amount of fuel corresponding to the final fuel injection amount Qfin obtained from the basic fuel injection amount Qbse during the compression stroke of the engine 11. The air-fuel ratio of the air-fuel mixture formed in the combustion chamber 16 by such fuel injection is set to a value leaner than the air-fuel ratio at the time of "homogeneous combustion".

Further, the ECU 92 controls the basic fuel injection amount Qbs.
The target throttle opening TAt is calculated based on e and the engine speed NE, and the throttle motor 24 is drive-controlled so that the actual throttle opening TAr approaches the target throttle opening TAt. Further, the ECU 92 calculates a target ignition timing by referring to a map based on the engine operating state such as the basic fuel injection amount Qbse and the engine speed NE, and drives and controls the igniter 41a based on the target ignition timing.
By controlling the throttle opening and the ignition timing as described above, these throttle opening and the ignition timing become suitable for "stratified combustion".

During the above "stratified combustion", the engine 1
The fuel injected from the fuel injection valve 40 during the compression stroke of No. 1 enters the recess 12 a (FIG. 1) provided in the head of the piston 12, and the movement of the piston 12 causes the spark plug 4 to move.
Collected around 1. By collecting the fuel around the spark plug 41 in this way, even if the average air-fuel ratio of the entire air-fuel mixture in the combustion chamber 16 is made larger than that in the “homogeneous combustion”,
The air-fuel ratio of the air-fuel mixture around the plug 41 is set to be suitable for ignition, and a good air-fuel mixture is ignited. Further, in order to make the average air-fuel ratio of the entire air-fuel mixture in the combustion chamber 16 larger than that at the time of "homogeneous combustion", the throttle opening is controlled to the open side and the intake air amount is increased. The pumping loss of 11 is reduced.

Next, the control of the SCV 48 for adjusting the gas flow state (swirl strength) in the combustion chamber 16 will be described. The ECU 92 determines the engine speed N
E, actual throttle opening TAr, and water temperature sensor 11
Based on the cooling water temperature of the engine 11 detected by b, the VSV 61 is drive-controlled to open / close the SCV 48. The ECU 92 normally closes the VSV 61 to disconnect the negative pressure chamber 54 of the actuator 49 from the vacuum tank 57. As a result, the actuator 49 is deactivated and the SCV 48 is kept open, and the swirl generated in the combustion chamber 16 is weakened.

When the throttle opening TAr and the engine speed NE are located in the operating region where the SCV 48 should be closed, a command to close the SCV 48 is issued. Based on the close command of the SCV 48, the ECU 92 causes the VSV
61 is opened to connect the negative pressure chamber 54 of the actuator 49 to the vacuum tank 57. As a result, the actuator 49 operates to close the SCV 48, and the swirl generated in the combustion chamber 16 becomes stronger.

The operating range of the engine 11 in which the SCV 48 closing command is issued is shown in FIGS. 4 (a) and 4 (b).
FIG. 4A shows the operating region of the engine 11 in which the SCV 48 is requested to be closed when the cooling water temperature of the engine 11 is low (for example, less than 80 ° C.). Further, FIG. 4B shows an operating region of the engine 11 in which a request for closing the SCV 48 is made when the cooling water temperature of the engine 11 is high (for example, 80 ° C. or higher). The throttle opening TA is shown in the shaded area in these figures.
When r and engine speed NE are located, SCV48
Will be issued.

As is apparent from FIG. 4A, when the cooling water temperature is low, the SCV 48 is closed and the swirl is strengthened except when the engine 11 is in the high rotation and high load state. Further, as is apparent from FIG. 4B, when the cooling water temperature is high, except when the engine 11 is in the low rotation low load state or the high rotation high load state, that is, the engine 11 is in the low rotation high load state or the high rotation high load state. When the rotating load is low, SC
V48 is closed and the swirl is strengthened.

Therefore, when the cooling water temperature is high,
During the stratified charge combustion operation of the engine 11, the SCV 48 is opened to weaken the swirl. This is because the fuel is designed to easily collect around the spark plug 41 when the swirl in the combustion chamber 16 is weak. On the other hand, during the homogeneous combustion operation of the engine 11 in the state where the cooling water temperature is high, the SCV 48 is controlled to either the valve opening position or the valve closing position according to the engine load (throttle opening TAr) and the engine speed NE. The swirl strength is adjusted. By controlling the SCV 48 in this way, the SCV 48 is unnecessarily closed while forming the air-fuel mixture in which the fuel is appropriately diffused into the air by the swirl and good combustion is obtained during the homogeneous combustion operation. It is possible to suppress an increase in pumping loss.

When the strength of the swirl is adjusted by opening and closing the SCV 48 as described above, the engine control amount used for controlling the operation of the engine 11 according to the strength of the swirl, for example, the optimum value of the target ignition timing. Also changes. Therefore, the ECU 92 switches the map for calculating the engine control amount such as the target ignition timing according to the open / close state of the SCV 48. That is, for example, as a map for calculating the target ignition timing, the SCV 48 is in the open state (weak swirl).
There are two types, one suitable for when the SCV 48 is closed and one suitable for when the SCV 48 is in the closed valve state (strong swirl). Then, from the above two types of maps, SCV
A map used for calculating the target ignition timing is selected according to the valve positions of 48. In this way, by selecting the map for calculating the engine control amount such as the target ignition timing according to the valve position of the SCV 48, the engine control of the ignition timing etc. can be performed regardless of the swirl strength based on the valve position of the SCV 48. The operation of the engine 11 can be suitably controlled by setting the amount to be appropriate.

At the target ignition timing, the target ignition timing calculated from the map corresponding to the opening of the SCV 48 (weak swirl) under the same engine condition is the valve closing of the SCV 48. The value is on the advance side of the target ignition timing calculated from the map corresponding to the time (strong swirl). This is because when the SCV 48 is in the valve open position and the swirl is weak, the degree of diffusion of the fuel in the combustion chamber 16 into the air becomes small and the combustion speed of the air-fuel mixture becomes slow, so that the ignition plug 41 ignites the air-fuel mixture. The reason is that it is necessary to carry out at an early stage.

In the engine 11 provided with the SCV 48, if the swirl strength becomes improper due to the failure of the SCV 48, the combustion of the air-fuel mixture will be adversely affected. For this reason, for example, a sensor for detecting the valve position (opening degree) of the SCV 48 may be provided and the SCV 48 may be diagnosed based on a detection signal from the sensor.
The cost increase will not be ignored.

Therefore, in the present embodiment, when a misfire due to the deterioration of the combustion state occurs in the engine 11, the SCV4
If 8 is in the stratified charge combustion operation when the cooling water temperature is high, which should be the valve open state, the combustion method is switched to the homogeneous combustion operation which is the engine control state suitable for the valve closing of the SCV 48, and the engine control state is changed. . When the SCV 48 is not in the open valve position during the stratified charge combustion operation when the cooling water temperature is high due to a failure, the swirl strength in the combustion chamber 16 is not suitable for the “stratified combustion”, and the ignition plug 41 is ignited at the same time. It becomes difficult to allow an air-fuel mixture having an air-fuel ratio suitable for ignition to exist around 41, and the combustion state deteriorates. In such a state, when the combustion system is switched from "stratified combustion" to "homogeneous combustion" as described above, the combustion state is recovered and misfire does not occur. This is because during "homogeneous combustion",
This is because the air-fuel mixture in which the fuel is evenly mixed with the air is combusted, and thus the influence of the strength of the swirl in the combustion chamber 16 is less likely to occur. Therefore, when a misfire occurs during the stratified charge combustion operation at high cooling water temperature, the combustion method is switched from "stratified combustion" to "homogeneous combustion", and the misfire does not occur based on this switching.
Then, it is judged that there is a failure such as being stuck in the valve closing position.

On the other hand, in the case where the engine 11 is in the homogeneous combustion operation and the operating condition of the engine 11 is in the operation region where the SCV 48 should be closed (strong swirl), when a misfire occurs in a predetermined cylinder. Changes the engine control state of the engine 11 to a timing suitable for opening the SCV 48 (weak swirl) to change the engine control state. During the homogeneous combustion operation, the degree of diffusion of the fuel into the air changes according to the strength of the swirl and the combustion speed of the air-fuel mixture changes, so the ignition timing is controlled according to the valve position of the SCV 48. Therefore, when the engine 11 is in the homogeneous combustion operation and the operating state of the engine 11 is in the operating region where the SCV 48 should be closed, if the SCV 48 is not in the closed valve state (strong swirl) due to a failure, the swirl in the combustion chamber 16 is more than appropriate. It becomes weak, the fuel is not properly diffused into the air in the combustion chamber 16, the combustion state deteriorates, and misfire occurs in a predetermined cylinder. Further, at this time, the ignition timing is controlled to a timing suitable for closing the valve of the SCV 48 (strong swirl), but in reality, due to a failure of the SCV 48, the swirl becomes weaker than an appropriate value and the combustion speed becomes slow. Therefore, the controlled ignition timing is later than appropriate. In this situation, when the ignition timing is switched to a timing suitable for opening the SCV 48 (weak swirl) as described above, the ignition timing advances and the swirl is weak and the combustion speed is slow. Then, the mixture is ignited, and knocking does not occur as the ignition timing advances. Therefore, when the homogeneous combustion operation is being performed and the operating state of the engine 11 is in the operating region where the SCV 48 should be closed, after switching the ignition timing as described above in response to the occurrence of misfire, if there is no knocking, the SCV 48 is set. It is determined that a failure such as sticking at the valve opening position has occurred.

As described above, when misfire occurs in the engine 11 due to deterioration of the combustion state, from the engine control state (combustion system, ignition timing) suitable for the valve position of the SCV 48 according to the engine operating state at that time, Whether the SCV48 has a failure based on whether or not the engine control state is changed to a state suitable for the other valve position of the SCV48 and whether the deterioration of the combustion state such as misfire or knocking disappears after the change. It can be judged whether or not. Therefore, a failure of the SCV 48 can be diagnosed without providing an opening sensor, etc.
The cost increase of 1 can be suppressed.

Next, when the SCV 48 is stuck at the valve closing position, for example, when the SCV 48 should originally be at the valve opening position, a failure (hereinafter referred to as a closing failure) to stop the valve being located at the valve opening position is determined. The procedure will be described with reference to FIG. FIG. 5 is a flowchart showing a closed failure determination routine for determining the above failure. This closed failure determination routine is executed by the ECU 92 by, for example, a time interruption at every predetermined time.

In the closed failure judgment routine, it is judged by the processing of steps S101 to S103 whether or not a misfire has occurred during the stratified charge combustion operation at a high cooling water temperature.
If the same misfire occurs, step S104,
By the process of S105, the stratified misfire flag F1 for determining whether or not a misfire has occurred in the engine operating state is set to "1", and a homogeneous combustion request is made. A homogeneous combustion operation is performed in response to such a homogeneous combustion request, and at this time, it is determined whether or not a misfire has occurred by the processing of steps S107 to S109, and the SCV 48 is closed based on whether or not the misfire has occurred. A determination is made as to whether a failure has occurred.

In the closed failure determination routine, the ECU 92
Is the water temperature sensor 11b as the process of step S101.
It is determined whether or not the cooling water temperature of the engine 11 obtained based on the detection signal from is high temperature (for example, 80 ° C. or higher). Then, if the cooling water temperature is low (less than 80 ° C.), the closing failure determination routine is temporarily terminated, and if the cooling water temperature is high (80 ° C. or higher), the process proceeds to step S102. EC
U92 judges whether or not stratified charge combustion operation is currently in progress,
If the stratified charge combustion operation is in progress, the process proceeds to step S103.

The ECU 92 executes the process of step S103 based on the detection signals from the crank position sensor 14c and the cam position sensor 21b.
It is determined whether or not a misfire has occurred in a predetermined cylinder in 1. Then, if no misfire has occurred, this closed failure determination routine is once ended, and if a misfire has occurred, the routine proceeds to step S104. An example of such a situation where misfire occurs is when the SCV 48 is out of order.

Normally, in the stratified charge combustion operation when the cooling water temperature is high, the SCV 48 is in the valve open state (weak swirl), but due to a failure, the SCV 48 is not in the valve open state and is stuck in the valve closed position (close failure). When it occurs, the swirl strength in the combustion chamber 16 becomes unsuitable for "stratified combustion". As a result, it becomes difficult to make an air-fuel ratio suitable for ignition around the ignition plug 41 when the ignition plug 41 is ignited, and the combustion state deteriorates to cause misfire.

The ECU 92 stores "1" as the stratified misfire flag F1 in a predetermined area of the RAM 95 in the process of step S104, issues a homogeneous combustion request in the process of the following step S105, and then once ends the closed failure determination routine. To do. When a homogeneous combustion request is made as described above, even if the current combustion method is "stratified combustion", it is switched to "homogeneous combustion", and "homogeneous combustion" is performed in the engine operating area where "stratified combustion" is performed. Will be performed.

When "homogeneous combustion" is performed in response to the homogeneous combustion request in this way, it is determined in step S102 that the stratified charge combustion operation is not in progress, and the process proceeds to step S106. As the processing of step S106, the ECU 92 is switched to "homogeneous combustion" based on whether or not the stratification misfire flag F1 is "1", that is, when misfire has occurred during the stratification combustion operation at a high cooling water temperature. It is determined whether it is in the state. Then, in the processing of step S106,
If the determination is negative (NO), the closed failure determination routine is temporarily terminated, and if the determination is positive (YES), the process proceeds to step S107.

As the processing of step S107, the ECU 92 determines whether or not a misfire has occurred in a predetermined cylinder based on the detection signals from the crank position sensor 14c and the cam position sensor 21b. Whether or not there is a misfire at this time can determine whether or not the above-mentioned misfire during the stratified charge combustion operation at the high cooling water temperature is due to the closing failure of the SCV 48. That is, when the close failure of the SCV 48 occurs, if the combustion method is switched to “homogeneous combustion” which is less susceptible to the swirl in the combustion chamber 16 in response to the homogeneous combustion request in the process of step S105, the combustion is performed. The condition recovers and the misfire does not occur.

Therefore, in the process of step S107, it is determined that no misfire has occurred,
It is possible to judge that the SCV 48 has a closed failure. When no misfire has occurred in the process of step S107 and it is determined that the SCV 48 has a closing failure, the ECU 92 sets "1" as the closing failure flag Fc in the backup RAM 9 in the processing of step S109.
After storing in a predetermined area of 6, the process proceeds to step S110.
When the closed failure flag Fc is set to "1" as described above, E
The CU 92 lights up a warning light provided on, for example, an instrument panel of an automobile to notify the driver that the SCV 48 has a closed failure.

On the other hand, when it is determined that the misfire has occurred in the process of step S107 and the misfire during the stratified charge combustion operation at the high temperature of the cooling water is not due to the closing failure of the SCV 48, the ECU 92 causes the step to be performed. After stopping the homogeneous combustion request in the process of S108, the process proceeds to step S110.
In the process of step S110, the ECU 92 stores "0" as a stratified misfire flag F1 in a predetermined area of the RAM 95, and then temporarily ends this closed failure determination routine.

Next, when the SCV 48 is stuck at the valve opening position, for example, when the SCV 48 should originally be at the valve closing position, the failure (hereinafter referred to as the valve opening failure) at which the SCV 48 is not located at the valve closing position is determined. The procedure will be described with reference to FIG. FIG. 6 is a flowchart showing an open failure determination routine for determining the above failure. This open failure determination routine is executed by the ECU 92 by, for example, a time interruption at every predetermined time.

In the open failure determination routine, it is determined by the processing of steps S201 to S204 whether or not a misfire has occurred during the homogeneous combustion at the time when the cooling water temperature is high and the SCV 48 closing command is issued. To be done. When the same misfire occurs, steps S206 to S2
By the processing of 08, the ignition timing is changed to a timing suitable when the SCV 48 is in the valve opening position, and it is determined whether or not the SCV 48 has an open failure based on the determination of knocking in this state. Done.

In the open failure judgment routine, the ECU 92
Determines whether the cooling water temperature of the engine 11 is high (for example, 80 ° C. or higher) as the process of step S201, and determines whether the homogeneous combustion operation is being performed as the process of step S202. Further, the ECU 92 executes step S
As a process of 203, it is determined whether or not the SCV 48 closing command is issued, and as a process of step S204, it is determined whether a misfire has occurred.

Then, the above steps S201 to S204
If NO is determined by any one of the determination processes,
U92 once ends this open failure determination routine. In addition, in all the processes of steps S201 to S204, Y
If it is determined to be ES, the process proceeds to step S205. In this way, the situation where the process proceeds to step S205 is S
There may be a case where a failure has occurred in the CV48.

When the SCV 48 has a failure (open failure) that is stuck at the valve opening position, for example, when the SCV 48 is commanded to be closed during the homogeneous combustion operation at high cooling water temperature, The swirl in 16 becomes weaker than appropriate. As a result, the degree of diffusion of the fuel into the air in the combustion chamber 16 decreases, the combustion state of the air-fuel mixture deteriorates, and misfire occurs in a predetermined cylinder.
Further, at this time, the ignition timing is controlled to a timing suitable for the time when the SCV 48 is closed (strong swirl).
Due to the open failure of V48, the swirl becomes weaker than the proper value and the combustion speed becomes slow. Therefore, the controlled ignition timing is later than appropriate.

Then, in the process of step S205, the ECU 92 sets RA to "1" as the open failure diagnosis end flag F2.
It is determined whether or not it is stored in the predetermined area of M95.
The open failure diagnosis end flag F2 is set in step S described later.
Whether the diagnosis of the open failure of the SCV 48 performed by the processing of 206 to S208 has already been completed, that is, the engine 11
It is for determining whether or not the open failure has been diagnosed even once after the start of. The open failure diagnosis end flag F2 is "1" in the processing of step S209 after the open failure diagnosis processing of steps S206 to S208 is performed.
Will be said. Further, the open failure diagnosis end flag F2
Is set to "0" every time the engine 11 is stopped.

In the process of step S205, if the open failure diagnosis end flag F2 is "1 (completed)", the open failure diagnosis routine is temporarily ended and the open failure diagnosis end flag F2 is set to "0 (not completed). End) ”, the process proceeds to step S206. As the processing of step S206, the ECU 92 changes the ignition timing of the engine 11 to a timing suitable for opening the SCV 48. That is, the map used for calculating the target ignition timing is switched from the one for closing the SCV 48 to the one for closing the valve, and the igniter 41a is drive-controlled based on the target ignition timing calculated from this map. Then, the ignition timing of the engine 11 is controlled to the advance side.

Subsequently, the ECU 92 determines whether or not knocking has occurred based on the detection signal from the knock sensor 11c as the processing of step S207. Whether or not knocking occurs at this time can determine whether or not the misfire is due to an SCV open failure. That is, SCV
When the open failure of 48 occurs, when the ignition timing is controlled to a timing suitable for opening the SCV 48 by the processing of step S206, the combustion state of the air-fuel mixture is recovered, and
No knocking occurs.

Therefore, in the process of step S207, it can be determined that the SCV 48 has an open failure based on the determination that knocking has not occurred. When it is determined that knocking has not occurred in the process of step S207 and the SCV has an open failure, the ECU 92 causes the ECU 92 to execute step S208.
After storing "1" as the open failure flag Fo in the predetermined area of the backup RAM 96 by the processing of step S209,
Proceed to. When the open failure flag Fo is set to "1" as described above, the ECU 92 lights up a warning light provided on, for example, an instrument panel of an automobile to notify the driver that an open failure of the SCV 48 has occurred. .

On the other hand, if knocking has occurred in the process of step S207 and it is determined that the misfire is not due to an open failure of the SCV 48, step S2
Go to 09. The ECU 92 stores "1" in a predetermined area of the RAM 95 as the open failure diagnosis end flag F2 in the processing of step S209, and then temporarily ends this open failure diagnosis routine. When the open failure diagnosis end flag F2 is set to "1" in this way, the above-described step S2 is performed until the engine 11 is stopped and the open failure diagnosis end flag F2 becomes "0".
No is determined in the processing of 05, and steps S206 to S2
The processing for diagnosing the open failure of the SCV 48 at 08 will not be performed.

According to the present embodiment in which the processing described in detail above is performed, the following effects can be obtained. (1) When a misfire due to deterioration of the combustion state occurs in the engine 11 during the stratified charge combustion operation when the cooling water temperature is high and the SCV 48 should originally be in the open state, the engine control state is suitable for closing the SCV 48. The combustion method is switched to the homogeneous combustion operation, and the engine control state is changed. When the SCV 48 is not in the open position during the stratified charge combustion operation when the cooling water temperature is high due to the closing failure, the swirl strength in the combustion chamber 16 becomes unsuitable for the “stratified combustion” and the ignition plug 41 causes the same. It becomes difficult for the air-fuel mixture having an air-fuel ratio suitable for ignition to exist around the plug 41, and the combustion state deteriorates. In such a state, when the combustion system is switched from "stratified combustion" to "homogeneous combustion" as described above, the combustion state is recovered and misfire does not occur. Therefore, based on the fact that misfire does not occur due to switching from "stratified combustion" to "homogeneous combustion", SC
It is possible to judge that a failure (close failure) such as being stuck to the valve closing position at V48 has occurred. Thus S
By performing the close failure diagnosis of the CV48, it is possible to diagnose the close failure of the SCV48 without providing a special sensor such as an opening sensor for detecting the opening of the SCV48.
It is possible to suppress an increase in the cost of the engine 11 due to the provision of the above sensor.

(2) During homogeneous combustion operation of the engine 11, when the operating state of the engine 11 is in an operating region where the SCV 48 should be closed (strong swirl), a misfire occurs in a predetermined cylinder. The ignition timing is switched to a timing suitable for the opening of the SCV 48 (weak swirl) as the engine control state of the engine 11, and the engine control state is changed. During the homogeneous combustion operation as described above, S
If the SCV 48 is not in the valve closed state (strong swirl) due to the opening failure in the engine operating state where the close command of the CV 48 is issued, the swirl in the combustion chamber 16 becomes weaker than appropriate, and the air in the combustion chamber 16 The fuel is not properly diffused into the cylinder, the combustion state deteriorates, and misfire occurs in a predetermined cylinder. Further, at this time, the ignition timing is controlled to a timing suitable for closing the valve of the SCV 48 (strong swirl), but in reality, the swirl becomes weaker than appropriate due to the open failure of the SCV 48, and the combustion speed becomes slow. Therefore, the controlled ignition timing is later than appropriate. In this situation, when the ignition timing is switched to a timing suitable for opening the SCV 48 (weak swirl) as described above, the ignition timing advances and the swirl is weak and the combustion speed is slow. Then, the mixture is ignited, and knocking does not occur as the ignition timing advances. Therefore, based on the fact that knocking does not occur after the ignition timing is switched as described above in response to the occurrence of misfire when the engine 11 is in the operating region where the SCV 48 should be closed during the homogeneous combustion operation. It is possible to judge that a failure (open failure) such as the SCV 48 being stuck at the valve opening position has occurred. By performing the open failure diagnosis of the SCV 48 in this manner, the SCV 48 can be opened without a special sensor such as an opening sensor for detecting the opening of the SCV 48.
The open failure of the V48 can be diagnosed, and the cost increase of the engine 11 due to the provision of the sensor can be suppressed.

(3) SCV when the combustion method of the engine 11 is "stratified combustion" and "homogeneous combustion"
The engine control state change targets (combustion method, ignition timing) that are changed to perform the 48 failure diagnosis are different. Therefore, the target of change of the engine control state can be made appropriate according to the combustion system, and the failure diagnosis of the SCV 48 can be accurately performed even in the engine 11 in which the combustion system is switched.

The present embodiment can be modified as follows, for example. In the present embodiment, in order to determine whether there is an open failure in the SCV 48, the presence or absence of knocking after switching the ignition timing to the timing corresponding to the opening of the SCV 48 is diagnosed. Not limited to. For example, the presence or absence of the open failure in the SCV 48 may be determined based on whether or not the misfire in the predetermined cylinder due to the open failure of the SCV 48 has been recovered. Further, the presence or absence of the open failure in the SCV 48 may be determined based on whether or not the exhaust temperature has become an appropriate temperature after switching the ignition timing. That is, when the SCV 48 has an open failure and the ignition timing is the timing corresponding to the valve closing of the SCV 48, the ignition timing becomes a state that is later than appropriate and the exhaust temperature becomes higher than the appropriate value. After the switching of the ignition timing, if the SCV 48 has an open failure, the ignition timing becomes a proper timing and the exhaust temperature becomes a proper value. Therefore, it is possible to determine whether or not the open failure of the SCV 48 has occurred, based on whether or not the exhaust temperature after switching the ignition timing is an appropriate value.

In the present embodiment, the present invention is applied to the engine 11 in which the SCV 48 is opened and the swirl is weakened during the stratified charge combustion operation at a high cooling water temperature. The present invention may be applied to an engine in which the SCV 48 is closed and the swirl is strengthened during the stratified charge combustion operation. In this case, when misfire occurs during stratified charge combustion operation at high cooling water temperature, the combustion method is switched from "stratified combustion" to "homogeneous combustion", and the misfire does not occur due to this homogeneous combustion operation. , SCV48
It is possible to judge that a failure has occurred in the.

In the present embodiment, the combustion method and the ignition timing are exemplified as the change targets of the engine control state that are changed in order to judge the failure of the SCV 48. However, these change targets of the engine control state are not necessarily the above two types. There is no need to limit it to.

In this embodiment, the swirl becomes strong when the SCV 48 is closed, and the swirl becomes weak when the SCV 48 is opened. However, the present invention is not limited to this. That is, instead of this, SCV48
An intake system structure in which the swirl becomes weak when the SCV 48 is closed and becomes strong when the SCV 48 is opened may be adopted.

[0085]

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an entire engine to which an SCV failure diagnosis device according to the present embodiment is applied.

FIG. 2 is a plan sectional view showing a structure of an intake system in the engine.

FIG. 3 is a block diagram showing an electrical configuration of the failure diagnosis device.

FIG. 4 is a diagram showing an operating region of an engine in which an SCV closing command is issued.

FIG. 5 is a flowchart showing a procedure for determining a closing failure.

FIG. 6 is a flowchart showing a procedure for determining an open failure.

[Explanation of symbols]

11 ... Engine, 11c ... Knock sensor, 14c ... Crank position sensor, 21b ... Cam position sensor, 23 ... Throttle valve, 24 ... Throttle motor, 32 ... Intake passage, 40 ... Fuel injection valve, 41 ... Spark plug, 41a ... Igniter, 44 ... Throttle position sensor, 48 ... Swirl control valve (SC
V), 49 ... Actuator, 57 ... Vacuum tank, 58 ... Negative pressure passage, 59 ... Suction passage, 61 ... VSV,
92 ... Electronic control unit (ECU).

Continuation of front page (51) Int.Cl. ⁷ Identification code FI F02D 43/00 301 F02D 43/00 301B 301E 301U 45/00 345 45/00 345A 368 368Z F02P 5/15 F02P 5/15 L

Claims (4)

(57) [Claims] 1. An intake flow control valve provided in an intake passage of an internal combustion engine for changing a flow state of gas in a combustion chamber by being controlled between an open position and a closed position based on an engine operating state. In the failure diagnosis device, when the deterioration of the combustion state of the internal combustion engine is detected, the intake flow control valve is changed from the engine control state suitable for the state in which the intake flow control valve is in one valve position to the other valve position. Change means for changing the control state of the internal combustion engine to an engine control state suitable for a certain state, and after the change of the engine control state by the changing means, deterioration of the combustion state of the internal combustion engine is not detected and a diagnostic means for performing diagnosis to the effect that a failure in the flow control valve has occurred, the internal combustion engine, the homogeneous combustion mode in accordance with the engine operating condition
Switching between combustion and stratified charge combustion, and the changing means changes the combustion state during stratified charge combustion operation of the internal combustion engine.
When the deterioration of the combustion is detected, the combustion method is changed from stratified combustion to homogeneous.
A failure diagnosis device for an intake flow control valve, which is characterized by switching to combustion . 2. The failure diagnosis device for an intake air flow control valve according to claim 1, wherein the changing means performs stratified combustion and the intake air
Engine with a flow control valve in a valve position that weakens the flow of the gas
In operating condition, deterioration of combustion mode in internal combustion engine is detected.
When the engine is turned on, the failure diagnosis device for the intake flow control valve is characterized in that the combustion system is switched from stratified combustion to homogeneous combustion. 3. An engine operating in an intake passage of an internal combustion engine.
It is controlled between the open and closed positions based on the condition.
Intake flow control that changes the flow state of gas in the combustion chamber by
When the deterioration of the combustion state of the internal combustion engine is detected in the control valve failure diagnosis device, the intake air
Engine control condition suitable for the flow control valve in one valve position
From the state, it is suitable for the state where the intake flow control valve is in the other valve position.
Change the control state of the internal combustion engine to the controlled engine control state
Changing means and an internal combustion engine after changing the engine control state by the changing means
Based on the fact that the deterioration of the combustion state of
A diagnostic hand that diagnoses that a malfunction has occurred in the air flow control valve.
The internal combustion engine has a homogeneous combustion method according to engine operating conditions.
Combustion and stratified charge combustion are switched, and the changing means performs combustion in an internal combustion engine in an engine operating state in which homogeneous combustion is performed and the intake flow control valve is in a valve position that strengthens the flow of the gas. When the deterioration of the state is detected, the intake flow control valve sets the ignition timing of the engine to the above.
To a time suitable for the valve position that weakens the gas flow
A failure diagnosis device for an intake flow control valve, characterized by being switched between. 4. An engine operating in an intake passage of an internal combustion engine.
It is controlled between the open and closed positions based on the condition.
Intake flow control that changes the flow state of gas in the combustion chamber by
When the deterioration of the combustion state of the internal combustion engine is detected in the control valve failure diagnosis device, the intake air
Engine control condition suitable for the flow control valve in one valve position
From the state, it is suitable for the state where the intake flow control valve is in the other valve position.
Change the control state of the internal combustion engine to the controlled engine control state
Changing means and an internal combustion engine after changing the engine control state by the changing means
Based on the fact that the deterioration of the combustion state of
A diagnostic hand that diagnoses that a malfunction has occurred in the air flow control valve.
And a stage, the internal combustion engine is for Switching Operation <br/> changing the combustion method according to the engine operating condition, said changing means detects the deterioration of the combustion state of the internal combustion engine
The target of changing the engine control state, which is changed at each time, for each combustion method
A failure diagnosis device for an intake flow control valve, which is different .