JPH0925852A - Fail safe device for engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an engine fail safe device capable of preventing the occurrence of a secondary failure during the failed opening of an exhaust return control valve. SOLUTION: An engine fail safe device is provided with an opening failure diagnosing means (e) for diagnosing the failed opening time of an exhaust return control valve (d) greatly exceeding a target value and a fail safe control means (f) for controlling the output of an engine during failed opening. Thus, even when the lighting of an alarm lamp is not noticed, the generation of a primary failure caused by over heating due to high temperature exhaust gas and a deterioration in an engine main body performance are prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a failsafe device for an engine equipped with an exhaust gas recirculation device.

[0002]

2. Description of the Related Art An exhaust gas recirculation device provided in an automobile engine or the like for preventing air pollution recirculates a part of exhaust gas, which is inactive according to operating conditions, to an intake system. Conventionally, a device for diagnosing whether an exhaust gas recirculation control valve or the like is operating normally has been proposed.

A fail-safe device for an exhaust gas recirculation device disclosed in, for example, Japanese Patent Laid-Open No. 3-138444 has a sensor for detecting the temperature of the exhaust gas recirculation passage, and the temperature of the exhaust gas recirculation passage rises due to exhaust heat during exhaust gas recirculation. When the temperature of the exhaust gas recirculation passage is higher than the reference value when the exhaust gas recirculation is stopped, the exhaust gas recirculation control valve remains open and the exhaust gas recirculation amount becomes excessive. It has become.

When it is diagnosed that there is an open failure, a warning light or the like is activated to notify the driver of this.

[0005]

However, the driver does not notice this even if the warning light or the like is operated at the time of an open failure in which the exhaust gas recirculation control valve remains open and the exhaust gas recirculation amount becomes excessive. When driving to generate high output,
There was a concern that the exhaust gas recirculation control valve would be overheated by the high temperature exhaust gas.

It is an object of the present invention to provide a fail safe device for an engine, which focuses on the above problems and prevents a secondary failure from occurring when the exhaust gas recirculation control valve fails to open.

[0007]

A fail-safe device for an engine according to claim 1 operates an exhaust gas recirculation passage c connecting an exhaust passage a and an intake passage b, and an exhaust gas recirculation passage c, as shown in FIG. An exhaust gas recirculation control valve d that opens and closes according to the state,
In the engine including, the exhaust recirculation control valve d is opened larger than a target value. An open failure diagnosis means e for diagnosing an open failure.
And a fail-safe control means f for limiting the output of the engine when the open failure occurs.

According to a second aspect of the present invention, in the engine of the first aspect, the failsafe control device includes a failsafe control means for limiting the engine speed to a predetermined value or less when the open failure occurs.

According to a third aspect of the present invention, there is provided an engine fail-safe device according to the first aspect, further comprising fail-safe control means for limiting the fuel supply amount of the engine to a predetermined value or less when the open failure occurs.

According to a fourth aspect of the present invention, in the engine fail-safe device of the first aspect, the EGR gas temperature downstream of the exhaust gas recirculation control valve in the exhaust gas recirculation passage is detected. EGR gas temperature detection means,
An open-failure diagnosing means for diagnosing an open-failure in which the exhaust gas recirculation control valve opens more than a target value when the exhaust EGR gas temperature is higher than a predetermined value when the exhaust gas recirculation control valve is closed.

[0011]

In the fail-safe device for an engine according to claim 1, the driver turns on a warning light or the like when an open failure occurs in which the exhaust gas recirculation control valve d remains open and the exhaust gas recirculation amount becomes excessive. Even if not noticed, avoiding the operation of generating a high output in the engine, the exhaust gas recirculation control valve d is overheated by the high temperature exhaust gas to cause a secondary failure, or the performance of the engine body deteriorates. Can be prevented.

In the engine fail-safe device according to the second aspect of the present invention, by limiting the engine speed to a predetermined value or less at the time of an open failure, it is possible to avoid the operation of generating a high output of the engine, and It is possible to prevent the exhaust gas recirculation control valve d from being overheated by the exhaust gas to cause a secondary failure or deteriorate the performance of the engine body.

In the engine fail-safe device according to a third aspect of the present invention, by limiting the fuel supply amount of the engine to a predetermined value or less at the time of opening failure, it is possible to avoid the operation of generating a high output of the engine, It is possible to prevent the exhaust gas recirculation control valve d from being overheated by the high-temperature exhaust gas to cause a secondary failure or to deteriorate the performance of the engine body.

In the failsafe device for an engine according to claim 4, EGR detected when the exhaust gas recirculation control valve is closed.
By determining whether or not the gas temperature is higher than the predetermined value, it is possible to accurately diagnose the open failure when the exhaust gas recirculation control valve opens larger than the target value during operation.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the accompanying drawings.

As shown in FIG. 1, the engine 1 sucks intake air (mixture) into the cylinder from the intake passage 2 as the intake valve is opened, compresses the intake air with a piston, and uses the spark plug 6 Exhaust gas is discharged to the exhaust passage 3 as the exhaust valve is opened by igniting and burning, and each of these steps is continuously repeated.

An injector 7 for injecting fuel into an intake port and a throttle valve 8 for restricting intake air in association with an accelerator pedal are provided in the middle of the intake passage 2, and an air flow meter for detecting the intake air amount is provided upstream thereof. 9 is provided.

A three-way catalyst 10 is installed in the middle of the exhaust passage 3 to oxidize HC and CO in the exhaust gas and NOx.
Reduce.

In the control unit 12, the intake air amount Q detected by the air flow meter 9, the idle switch signal SW, the engine speed Ne detected by the engine speed sensor 13, and the cooling water temperature sensor 14 are detected. By inputting the cooling water temperature Tw and the like, the basic fuel injection amount Tp is calculated according to the operating state and the ignition timing is calculated.

The control unit 12 outputs the output VO ₂ according to the oxygen concentration in the exhaust gas detected by the O ₂ sensor 15.
Is input to feedback control the fuel injection amount from the injector 7 so that the air-fuel mixture has the stoichiometric air-fuel ratio, and the conversion efficiency of the three-way catalyst 10 is maintained at the maximum.

An exhaust gas recirculation passage 4 that connects the intake passage 2 and the exhaust passage 3 is provided, and an exhaust gas recirculation control valve 5 that opens and closes the exhaust gas recirculation passage 4 is provided in the middle of the exhaust gas recirculation passage 4.

A step motor 16 is used as an actuator for driving the exhaust gas recirculation control valve 5.

As shown in FIG. 12, the step motor 16
Is the coil 17 fixed to the casing side, and the coil 17
Has a rotor 18 rotatably supported inside, and the rod 28 moves in the axial direction according to the rotation angle of the rotor 18, and the valve body 19 acts on the displacement of the rod 28 via the urging force of the return spring 20. The opening area of the exhaust gas recirculation passage 4 is changed accordingly.

A water jacket 22 for circulating engine cooling water is formed in the casing 21. The cooling water circulating in the water jacket 22 carries away the heat of the casing 21 heated by the EGR gas, so that the step motor 16 and the like are not overheated.

The step motor 16 changes its rotation angle stepwise by applying a predetermined pulse signal to the coil 17, and has a structure in which the rotor 18 makes one rotation at a predetermined number of steps.

The control unit 12 responds to the intake air amount Q detected by the air flow meter 9, the engine speed Ne detected by the engine speed sensor 13, the cooling water temperature TW detected by the cooling water temperature sensor 14, and the like. The target value of the exhaust gas recirculation amount is determined in advance, the target exhaust gas recirculation amount that meets the current operating conditions is obtained by referring to this target value map, and this target exhaust gas recirculation amount is converted into a control command value. A pulse signal is output to the motor 16.

In this way, the exhaust gas recirculation control valve 5 is opened according to the operating condition, and a part of the exhaust gas which is inactive is sucked into the intake passage 2.
The maximum temperature at the time of combustion is lowered by recirculating to N
Reduces the production of Ox.

By the way, for example, a malfunction of the step motor 16 occurs, or a stick in which the valve body 19 is fixed by carbon, rust, or the like occurs, and the valve body 19 remains open, resulting in an excessive exhaust gas recirculation amount. There is a possibility that an open failure will occur.

Although the exhaust recirculation control valve 5 is provided with a return spring 20, the return spring 2
0 has a function of causing the valve body 19 to follow the rod 28, and the valve body 19 cannot be forcibly closed when a failure of the step motor 16 occurs.

When an operation for producing a high output is performed in the engine 1 in the state where an open failure occurs in which the valve body 19 remains open in this way, the exhaust gas recirculation control valve 5 is overheated by the high temperature exhaust gas and the secondary There is a possibility of causing a failure or degrading the performance of the engine body 1.

In response to this, the present invention determines whether or not an open failure has occurred in which the opening degree of the exhaust gas recirculation control valve 5 is larger than a target value, and when it is determined that the open failure has occurred,
The warning light 24 is turned on to inform the driver of this, and fail-safe control for limiting the output of the engine 1 is performed.

EGR gas temperature sensor 2 for detecting the temperature TEGR downstream of the exhaust gas recirculation control valve 5 in the exhaust gas recirculation passage 4.
5 are provided.

The flowchart of FIG. 3 shows a control program executed by the control unit 12 for diagnosing an open failure, which is executed at regular intervals.

First, in step 1, the cooling water temperature T at the time of starting
W is greater than or equal to a predetermined value TWIEH (for example, 35 ° C),
The EGR gas temperature TEGRINT at the time of starting is a predetermined value TEG.
It is determined whether it is RJ3 or more.

If these starting conditions are met,
Proceeding to step 2, the engine speed Ne is the predetermined value N1.
(For example, 400 rpm) or more, and the cooling water temperature TW is TWEJL (for example, −10 ° C.) ≦ TW <TWEJH
The exhaust gas recirculation control valve 5 is closed (for example, 50 ° C.) and the operating condition in which the diagnostic condition is satisfied is the predetermined time EG.
It is determined whether ROPD (for example, 60 seconds) or more has elapsed.

The operating state in which the diagnostic conditions are satisfied is the predetermined time E
When it is determined that more than GROPD has elapsed, the routine proceeds to step 3, where the EGR gas temperature TEGR and the EG at start
The difference in R gas temperature TEGRINT is a predetermined value TEGRONG
(For example, 28 ° C) or more is determined.

EGR gas temperature TEGR and EGR at starting
When it is determined that the difference in the gas temperature TEGRING is lower than the predetermined value TEGRONG, the routine proceeds to step 4, where it is determined that the exhaust gas recirculation control valve 5 is normally closed.

On the other hand, the difference between the EGR gas temperature TEGR and the EGR gas temperature TEGRINT at the start is a predetermined value TEGRO.
When it is determined that it is more than NG, the routine proceeds to step 5, where it is determined that the exhaust gas recirculation control valve 5 is not normally closed, the warning lamp 24 is turned on at step 6, and the routine proceeds to step 7 to be described later. Engine 1 with fail-safe control
Limit the output of

The flow chart of FIG. 4 shows a fail-safe control program executed by the control unit 12 for limiting the output of the engine 1 at the time of an open failure, which is executed at regular intervals.

First, in steps 11 and 12, it is determined that the engine 1 is rotating and the starter switch for starting the engine 1 is OFF, and then step 1
The routine proceeds to step 3 and it is judged whether or not the open failure has been diagnosed by the above routine.

When it is diagnosed that the open failure has occurred, the routine proceeds to step 14 and a control for stopping the fuel injection from the injector 7 is performed at the time of high engine speed Ne where the engine speed Ne rises above a predetermined value (for example, 2800 rpm). To do.

As another embodiment, step 14
In the above, the control for stopping the fuel injection from the injector 7 may be performed during the high load operation in which the basic fuel injection amount Tp increases above a predetermined value.

As a result, when an open failure occurs in which the exhaust gas recirculation control valve 5 remains open, even if the driver does not notice that the warning lamp 24 is lit, the engine 1 is operated to generate a high output. This can be avoided, and the exhaust gas recirculation control valve 5 can be prevented from being overheated by the high-temperature exhaust gas to cause a secondary failure or to deteriorate the performance of the engine 1.

Next, the embodiment shown in FIG. 5 will be described.

A diaphragm type exhaust gas recirculation control valve 5 is provided in the exhaust gas recirculation passage 4. Exhaust gas recirculation control valve 5
The valve opens against the return spring 19 as the negative pressure introduced into the diaphragm chamber 38 becomes stronger. As the opening degree of the exhaust gas recirculation control valve 5 increases, the amount of exhaust gas recirculated to the intake passage 2 via the exhaust gas recirculation passage 4 increases.

A BPT negative pressure passage 54 that connects the diaphragm chamber 38 of the exhaust gas recirculation control valve 5 and the VC port 48 of the intake passage 2 is provided, and the diaphragm chamber 38 of the exhaust gas recirculation control valve 5 is connected via the BPT negative pressure passage 54. A BPT valve 36 is provided for appropriately diluting the negative pressure introduced into the valve with the atmospheric pressure.

The VC port 48 is the intake throttle valve 8
Intake throttle valve 8 in the idle position near the
Is located on the upstream side of the tip of the valve and opens to the intake passage 2. At the VC port 48, atmospheric pressure is generated during idling,
Negative pressure is generated in the low and medium load range.

The BPT valve 36 has its diaphragm chamber 41 communicated between the exhaust gas recirculation control valve 5 of the exhaust gas recirculation passage 4 and the orifice 43 through the EGR gas pressure passage 44, and the EGR gas pressure P ₂ of the exhaust gas recirculation passage 4 is communicated. Is being guided.

The BPT valve 36 is connected to the E of the exhaust gas recirculation passage 4.
As the GR gas pressure P ₂ rises, its opening becomes smaller, that is, the degree to which the negative pressure introduced to the exhaust gas recirculation control valve 5 is diluted with atmospheric pressure becomes smaller, and the exhaust gas recirculation control valve 5 opens. And the EGR gas pressure P _{2 in} the exhaust gas recirculation passage 4 is increased.
Feedback control is performed to keep constant.

Thus, the EGR of the exhaust gas recirculation passage 4 is performed.
When the gas pressure P ₂ is kept constant, the differential pressure between the exhaust pressure P ₁ in the P ₂ and the exhaust passage 3, an exhaust gas recirculation amount recirculated through the orifice 43 is proportional to the exhaust pressure P _1. Since the exhaust pressure P ₁ has a correlation with the intake air amount of the engine, the exhaust gas recirculation amount increases as the intake air amount increases, so that the exhaust gas recirculation rate is kept substantially constant.

Exhaust pressure control (BPT) system in which the exhaust gas recirculation amount is adjusted via the BPT valve 36 according to operating conditions, and intake negative pressure control in which the exhaust gas recirculation amount is adjusted by the intake negative pressure without the BPT valve 36. In order to switch the (VC) system, a VC negative pressure passage 50 that connects the diaphragm chamber 38 of the exhaust gas recirculation control valve 5 and the VC port 48 of the intake passage 2 is provided, and the VC negative pressure passage 50 has a first solenoid valve 51. And the second solenoid valve 52 are respectively interposed.

The first solenoid valve 51 has a VC negative pressure passage 50 with respect to the diaphragm chamber 38 of the exhaust gas recirculation control valve 5.
And the BPT negative pressure passage 54 are connected to each other.

The second solenoid valve 52 closes the VC negative pressure passage 50 at a position where the VC negative pressure passage 50 communicates with the atmosphere release port 53, a position where the VC negative pressure passage 50 and the atmosphere release port 53 communicate with each other. Further, it has a position where the communication between the atmospheric pressure dilution passage 56 and the BPT negative pressure passage 54 is cut off.

The control unit 40 switches the positions of the first and second solenoid valves 51 and 52 from the detected values of the engine speed Ne, the load, the cooling water temperature, etc. according to the contents of a preset map, and controls the exhaust pressure. Switches between the (BPT) system and the suction negative pressure control (VC) system. As a result, the degree of freedom in setting the exhaust gas recirculation rate can be expanded, and while it is possible to ensure engine operating stability, it is possible to reduce fuel consumption and to effectively suppress NOx emissions.

By the way, for example, the first solenoid valve 5
1. The malfunction of the second solenoid valve 52 occurs, or the stick that the valve body 39 is fixed by carbon, rust, etc. occurs, and the valve body 39 remains open and the exhaust gas recirculation amount becomes excessive. Failure may occur.

When the engine is operated to generate a high output in the state where an open failure occurs in which the valve element 39 remains open, the exhaust gas recirculation control valve 5 is overheated by the high temperature exhaust gas and a secondary failure occurs. May occur or the performance of the engine body 1 may deteriorate.

In response to this, the present invention is directed to the exhaust gas recirculation passage 4
The EGR gas temperature sensor 25 for detecting the temperature TEGR on the downstream side of the exhaust gas recirculation control valve 5 is provided.
Based on GR, it is determined whether or not there is an open failure in which the opening degree of the exhaust gas recirculation control valve 5 is larger than a target value. When it is determined that an open failure has occurred, a warning light is turned on and the driver is informed. In addition to notifying this, fail-safe control that limits the output of the engine is performed.

As a result, when an open failure occurs in which the exhaust gas recirculation control valve 5 remains open, even if the driver does not notice the lighting of the warning light, the operation that causes the engine to generate a high output is performed. By avoiding this, it is possible to prevent the exhaust gas recirculation control valve 5 from being overheated by the high-temperature exhaust gas to cause a secondary failure or to deteriorate the performance of the engine body.

[0059]

As described above, in the failsafe device for an engine according to the first aspect of the present invention, when an open failure occurs in which the exhaust gas recirculation control valve remains open, failsafe control for limiting the output of the engine is performed. Even if the driver does not notice the lighting of the warning light etc. by the configuration that is performed, it is possible to avoid the operation that causes the engine to generate a high output, and the exhaust gas recirculation control valve is overheated by the high temperature exhaust gas to cause a secondary failure. It is possible to prevent the engine from causing a deterioration in the performance of the engine body.

A failsafe device for an engine according to a second aspect of the present invention has a configuration in which the engine speed is limited to a predetermined value or less when the exhaust gas recirculation control valve remains open and a failure occurs. It is possible to avoid driving.

In the engine fail-safe device according to the third aspect of the present invention, a high output is generated in the engine by limiting the fuel supply amount of the engine to a predetermined value or less when the exhaust gas recirculation control valve remains open. It is possible to avoid performing the driving that causes it.

A failsafe device for an engine according to a fourth aspect of the present invention determines whether the detected EGR gas temperature is higher than a predetermined value when the exhaust gas recirculation control valve is closed, and determines that the exhaust gas recirculation control valve is higher than a target value during operation. It is possible to accurately diagnose when the open failure is wide open.

[Brief description of drawings]

FIG. 1 is a system diagram showing an embodiment of the present invention.

FIG. 2 is a sectional view of the exhaust gas recirculation control valve.

FIG. 3 is a flowchart showing the control contents for diagnosing the open failure.

FIG. 4 is a flowchart showing the contents of fail-safe control.

FIG. 5 is a system diagram showing another embodiment.

FIG. 6 is a claim correspondence diagram showing the invention according to claim 1;

[Explanation of symbols]

 a exhaust path b intake path c exhaust gas recirculation path d exhaust gas recirculation control valve e failure diagnosis means f fail-safe control means 1 engine 2 intake path 3 exhaust path 4 exhaust gas recirculation path 5 exhaust gas recirculation control valve 6 spark plug 7 fuel injection valve 12 Control Unit 13 Rotation Speed Sensor 17 Step Motor 26 EGR Gas Temperature Sensor 36 BPT Valve 38 Diaphragm Chamber 40 Control Unit 41 Diaphragm Chamber 43 Orifice 44 EGR Gas Pressure Passage 50 VC Negative Pressure Passage 51 First Solenoid Valve 52 Second Solenoid Valve 54 BPT negative pressure passage 56 Atmospheric pressure dilution passage

Claims (4)

[Claims] 1. An engine having an exhaust gas recirculation passage that connects an exhaust gas passage and an intake air passage, and an exhaust gas recirculation control valve that opens and closes the exhaust gas recirculation passage according to operating conditions. An engine fail-safe device comprising: an open-fault diagnosis means for diagnosing a failure; and a fail-safe control means for limiting an engine output when the open-failure occurs. 2. The failsafe device for an engine according to claim 1, further comprising failsafe control means for limiting an engine speed to a predetermined value or less when the open failure occurs. 3. The failsafe device for an engine according to claim 1, further comprising failsafe control means for limiting the fuel supply amount of the engine to a predetermined value or less when the open failure occurs. 4. An EGR gas temperature detecting means for detecting an EGR gas temperature on a downstream side of an exhaust gas recirculation control valve in an exhaust gas recirculation passage, and an exhaust gas during an operation in which the EGR gas temperature detected when the exhaust gas recirculation control valve is closed is higher than a predetermined value. The fail-safe device for an engine according to any one of claims 1 to 3, further comprising: open-failure diagnosing means for diagnosing an open-failure in which the recirculation control valve opens larger than a target value.