JPH1162716A - Emission gas reflux controller for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately and speedily judge abnormality of an emission gas reflux control valve by judging it based on a difference between a detected value by a means for detecting an actual opening when driven with the emission gas reflux control valve entirely closed and a detected value by the means for detecting the actual opening when driven with the emission gas reflux control valve fully opened. SOLUTION: An ECU 15 controls a three way switching valve 14 in accordance with an operating status of an internal combustion engine 1 and controls an opening of an EGR valve 30 with a negative pressure for a driving source, when an operating status of an engine is judged to be in an EGR execution area by output signals from various sensors. In this case, a target opening corresponding to an engine speed and a load is calculated, and a target duty ratio corresponding to the target opening is calculated. An actual opening d detected by a lift sensor 21 and the target opening are also compared, and a duty ratio is compensated so as to make the difference zero. A difference of the opening between when a EGR valve is fully opened and when it is completely closed is found, and if the difference is less than a movement amount of a valve shaft 24 moved from an entirely closed position to a fully opened position when the EGR valve 18 is normal, the EGR valve 18 is judged abnormal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas recirculation control device for recirculating exhaust gas flowing through an exhaust system of an internal combustion engine to an intake system, and more particularly to a technique for detecting an abnormality of the exhaust gas recirculation control device.

[0002]

2. Description of the Related Art In an internal combustion engine, when an air-fuel mixture having a low fuel concentration and an excessive amount of oxygen, that is, a so-called lean air-fuel mixture is burned, a large amount of nitrogen oxides NO _X is contained in the exhaust gas, and the exhaust emission deteriorates. It is known to invite. In particular, as the combustion speed of the mixture increases in the combustion chamber of the internal combustion engine,
Alternatively, the higher the combustion temperature of the air-fuel mixture, the more NO _X is contained in the exhaust gas.

On the other hand, the exhaust gas discharged from an internal combustion engine, steam H ₂ O or carbon dioxide CO in addition of the NO _X described above
It contains a large amount of inert gas such as ₂ . Since this inert gas does not burn itself to become a heat source and has the property of absorbing heat, when the exhaust gas is contained in the air-fuel mixture, the combustion speed and the combustion temperature in the combustion chamber are reduced. Can be.

Therefore, the exhaust passage and the intake passage of the internal combustion engine are communicated with each other through an exhaust gas recirculation passage, and a part of the exhaust gas flowing through the exhaust passage is caused to flow into the intake passage, so that the exhaust gas is contained in the air-fuel mixture and the combustion is performed. 2. Description of the Related Art Exhaust gas recirculation control devices for reducing the combustion speed and combustion temperature in a room have become widespread.

[0005] If the mixture contains excessive exhaust gas, the combustion speed and the combustion temperature in the combustion chamber are unduly reduced, the output characteristics of the engine are deteriorated, and carbon monoxide CO, hydrocarbon HC and the like are deteriorated. Of the unburned gas components in the exhaust gas. For this reason, in the exhaust gas recirculation control device, an exhaust gas recirculation control valve for controlling the flow rate of the exhaust gas recirculation passage is provided, and the exhaust gas recirculation control valve is controlled so as to realize an exhaust gas recirculation amount according to an operation state of the internal combustion engine. I have.

[0006] In such an exhaust gas recirculation control device, if the exhaust gas recirculation control valve is stuck or a foreign object is caught, a desired amount of exhaust gas recirculation cannot be realized, resulting in deterioration of exhaust emission. Therefore, it is necessary to accurately detect the abnormality of the exhaust gas recirculation control valve.

As a technique for detecting an abnormality of the exhaust gas recirculation control valve, there is known an exhaust gas recirculation system for an internal combustion engine described in Japanese Patent Application Laid-Open No. 6-299912. This exhaust gas recirculation device includes an opening sensor that detects the actual opening of the exhaust gas recirculation control valve, and determines the actual opening detected by the opening sensor and the opening required of the exhaust gas recirculation control valve. In comparison, while the difference between the actual opening and the required opening is equal to or less than a predetermined level, it is determined that the error is caused by a change with time of the opening sensor or the like. It is determined that the control valve is abnormal.

That is, the exhaust gas recirculation device is a device that reliably detects only an essential abnormality without detecting a characteristic change with time that does not significantly affect exhaust emission as an abnormality.

[0009]

Incidentally, since the operating state of the internal combustion engine changes every moment, the required opening degree of the exhaust gas recirculation control valve also changes correspondingly. In such a transient state, there is very little chance that the required opening and the actual opening coincide with each other even in a normal state. It is necessary to set the error relatively wide, and there is a problem that the accuracy of abnormality detection is reduced.

In response to such a problem, when the internal combustion engine is in a fuel cut state such as during deceleration, the exhaust gas recirculation control valve is controlled so that the required opening degree is temporarily maintained. And a method of comparing the required opening degree with the required opening degree.

However, in the above-described method, the execution time of the abnormality determination processing is limited to the time of execution of the deceleration fuel cut, so that the number of times of execution of the abnormality determination processing is reduced. In this case, it takes time from the occurrence of the abnormality to the detection of the abnormality. During that time, the recirculation flow rate of the exhaust gas cannot be set to a desired flow rate, which may lead to deterioration of the engine output, deterioration of the exhaust emission, and the like.

The present invention has been made in view of the above-described problems, and provides a technique capable of accurately and promptly detecting an abnormality of an exhaust gas recirculation control valve. It is intended to prevent deterioration of exhaust emission.

[0013]

The present invention employs the following means in order to solve the above-mentioned problems. That is,
An exhaust gas recirculation control device for an internal combustion engine according to the present invention includes an exhaust gas recirculation control valve for controlling an exhaust gas flow rate in an exhaust gas recirculation passage connecting an exhaust gas passage and an intake passage of the internal combustion engine, and an actual opening of the exhaust gas recirculation control valve. And an actuation means for driving the exhaust gas recirculation control valve such that the actual opening detected by the actual opening detection means coincides with a desired target opening. An exhaust gas recirculation control device for the engine, wherein the drive means drives the exhaust gas recirculation control valve to make the exhaust gas recirculation control valve fully closed, a detection value of the actual opening degree detection means, and the driving means controls the exhaust gas recirculation control valve. An abnormality determining unit is provided for determining an abnormality of the exhaust gas recirculation control valve based on a difference between the actual opening degree detecting unit and a detection value of the actual opening degree detecting unit when driven to a fully open state.

In the exhaust gas recirculation control device for an internal combustion engine configured as described above, the exhaust gas recirculation control valve is fully opened and fully closed relatively frequently, and the exhaust gas recirculation control valve is fully opened and fully closed. Based on the inventor's finding that the state is maintained even temporarily.

That is, if the exhaust gas recirculation control valve is frequently opened and closed, the abnormality judging means is also frequently subjected to abnormality judgment processing. Time is reduced.

Further, in the exhaust gas recirculation control device, it may take some time from the start of driving by the driving means to the actual operation of the exhaust gas recirculation control valve, that is, a so-called response delay of the exhaust gas recirculation control valve may occur. When the exhaust gas recirculation control valve is fully opened and fully closed, the full open drive state and the fully closed drive state are temporarily held. Therefore, the actual opening degree detection means determines whether the exhaust gas recirculation control valve is actually fully opened and fully closed. The actual opening at the time when the operation is completed (when the operation is completed to achieve the target opening) can be detected.

As a result, the abnormality judging means judges the abnormality of the exhaust gas recirculation control valve based on the accurate actual opening, and the accuracy of the abnormality judgment is improved. Incidentally, in the exhaust gas recirculation control valve, the opening amount from fully closed to fully open may vary even in a normal state due to an initial tolerance of component parts and the like. In such a case, the abnormality determining means collects a predetermined number of the detection values of the actual opening degree detecting means when the driving means drives the exhaust gas recirculation control valve to fully close the exhaust gas recirculation control valve, and the driving means Collects a predetermined number of detection values of the actual opening detection means when the exhaust gas recirculation control valve is driven to the fully opened state,
These detected values may be statistically processed to calculate the difference in the opening degree between the fully opened state and the fully closed state.

In such a configuration, since the actual opening degree at the time of fully closing and at the time of full opening is statistically processed, the variation of the opening amount from the fully closed state to the fully opened state is suppressed.
The determination process can be performed without considering the initial tolerance and the like of the exhaust gas recirculation control valve.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an exhaust gas recirculation control device for an internal combustion engine according to the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing a schematic configuration of an internal combustion engine to which the present invention is applied. The internal combustion engine shown in FIG. 1 is a four-cycle four-cylinder internal combustion engine 1. An intake branch pipe 2 and an exhaust branch pipe 9 are connected to the internal combustion engine 1. The intake branch pipe 2 is connected to a surge tank 3. The surge tank 3 is connected to an air cleaner box 5 via an intake pipe 4. The intake branch pipe 2, surge tank 3, and intake pipe 4 implement an intake passage according to the present invention.

Subsequently, the intake pipe 4 is provided with a throttle valve 34 for adjusting the flow rate of intake air flowing through the intake pipe 4 in conjunction with an accelerator pedal (not shown). An idle switch 36 that outputs an ON signal when the valve 34 is fully closed and outputs an OFF signal when the valve 34 is not fully closed is attached. Further, an air flow meter 16 that outputs an electric signal corresponding to the mass of the intake air flowing through the intake pipe 4 is attached to the intake pipe 4, and the surge tank 3 is provided with an air flow meter corresponding to the pressure in the surge tank 3. A vacuum sensor 20 that outputs an electric signal is attached.

Next, fuel injection valves 7a, 7b, 7c, 7d (hereinafter collectively referred to as fuel injection valves 7) are attached to the respective branch pipes of the intake branch pipe 2, and these fuel injection valves 7 ,
Connected to fuel distribution pipe 6. The fuel distribution pipe 6 is provided with fuel injected from a fuel pump (not shown) to each fuel injection valve 7.
Distribute to

Further, the fuel injection valve 7 includes a drive circuit 8
a, 8b, 8c, 8d (hereinafter collectively referred to as drive circuit 8)
The valve is opened when a drive current from the drive circuit 8 is applied, and the fuel supplied from the fuel distribution pipe 6 is injected into the intake branch pipe 2.

The exhaust branch pipe 9 is connected to an exhaust pipe 10. In the middle of the exhaust pipe 10, components such as NO _X , HC, and CO contained in exhaust gas discharged from the internal combustion engine 1. An exhaust purification catalyst 11 for purifying the exhaust gas is provided. The exhaust branch pipe 9 and the exhaust pipe 10 realize an exhaust passage according to the present invention.

An air-fuel ratio sensor 12 that outputs a current corresponding to the air-fuel ratio of the exhaust gas flowing through the exhaust pipe 10 is attached to the exhaust pipe 10 upstream of the exhaust purification catalyst 11.

Further, an exhaust gas recirculation passage 30 is connected to the exhaust branch pipe 9. The exhaust gas recirculation passage 30 is connected to the surge tank 3, and can recirculate a part of the exhaust gas flowing in the exhaust branch pipe 9 to the surge tank 3. An exhaust gas recirculation control valve (EGR valve) 18 for adjusting the amount of exhaust gas flowing in the exhaust gas recirculation passage 30 is provided in the exhaust pipe flow passage 30.

The EGR valve 18 is, as shown in FIG.
An EGR valve main body 22 is provided, and a sensor unit 21 for detecting an opening degree of the EGR valve main body 22 is provided. First, the EGR valve main body 22 has two spaces 3 inside the EGR valve main body 22.
A diaphragm 23 having a peripheral edge fixed to a side wall in the EGR valve main body 22 is provided so as to be divided into 6, 37. Further, the EGR valve main body 22 is
2 and shaft 2 penetrating through diaphragm 23 in the axial direction
4 is held back and forth.

The shaft 24 is connected to the diaphragm 2
3 and moves forward and backward in conjunction with the reciprocating operation of the diaphragm 23. The tip of the shaft 24 is located in the exhaust gas recirculation passage 30, and a valve body 25 is attached to the end thereof. The valve body 25 shuts off the exhaust gas recirculation passage 30 when the shaft 24 advances, and conducts the exhaust gas recirculation passage 30 when the shaft 24 retreats.

Here, of the space portions 36 and 37, the space portion 36 located on the base end side of the shaft 24 is adapted to allow the shaft 24 to advance, that is, the valve body 25.
A spring 26 for biasing the diaphragm 23 to shut off the exhaust gas recirculation passage 30 is provided.

Further, the space 36 is provided with a negative pressure passage 38.
Is connected to a three-way switching valve (VSV) 14. In addition to the negative pressure passage 38, an intake negative pressure passage 33 and an atmospheric pressure passage 39 are connected to the VSV 14. The intake negative pressure passage 33 is connected to the intake pipe 4 downstream of the throttle valve 34, and reduces the intake pipe negative pressure generated in the intake pipe 4 to the V
Lead to SV14. In the middle of the intake negative pressure passage 33, a pressure regulating valve 13 for adjusting the intake pipe negative pressure introduced from the intake pipe 4 to the intake negative pressure passage 33 to a constant pressure is provided. On the other hand, the atmospheric pressure passage 39 has an open end in the atmosphere and guides the atmospheric pressure to the VSV 14.

Here, the VSV 14 establishes conduction between the negative pressure passage 38 and the intake negative pressure passage 33 (blockage of the atmospheric pressure passage 39) and conduction between the negative pressure passage 38 and the atmospheric pressure passage 39 (the And a solenoid 14b for driving the valve body 14a.

The solenoid 14b is connected to the negative pressure passage 3
8 and a drive pulse signal having a duty ratio corresponding to the ratio of the conduction time of the intake negative pressure passage 33 and the conduction time of the negative pressure passage 38 and the atmospheric pressure passage 39, the driving pulse signal is applied. The valve body 14a is driven to alternately switch between conduction of the negative pressure passage 38 and the intake negative pressure passage 33 and conduction of the negative pressure passage 38 and the atmospheric pressure passage 39.

When a drive pulse signal having a duty ratio of 100% is applied, the solenoid 14b conducts between the negative pressure passage 38 and the intake negative pressure passage 33 (when the atmospheric pressure passage 39 is closed). State) is maintained, and when a drive pulse signal having a duty ratio of 0% is applied, the conduction state between the negative pressure passage 38 and the atmospheric pressure passage 39 (the intake negative pressure) is maintained. The valve element 14a is driven to maintain the closed state of the passage 33).

Then, a drive pulse signal having a duty ratio: 100% is applied to the VSV 14, and the intake negative pressure passage 3
When the conduction state of the negative pressure passage 3 and the negative pressure passage 38 is maintained, the negative pressure of the intake pipe generated in the surge tank 3 is reduced by the pressure regulating valve 13.
Via the VSV 14 and the space 36 in the EGR valve body 22
Will be introduced. At this time, if the negative pressure of the space 36 is larger than the urging force of the spring 26, the diaphragm 23 is sucked toward the space 36 as shown in FIG. The space 3
6 and retreats the valve body 25 to the fully open position.

On the other hand, when a drive pulse signal having a duty ratio of 0% is applied to the VSV 14 and the conduction state of the atmospheric pressure passage 39 and the negative pressure passage 38 is maintained, the driving pulse signal is introduced from the open end of the atmospheric pressure passage 39. VSV14
Through the EGR valve main body 22 into the space 36.
At this time, since the negative pressure of the space 36 is reduced, the dial flam 23 is urged toward the space 37 by the spring 26 as shown in FIG. Advances to the space 37 side,
The valve body 25 is moved to the fully closed position.

Next, the sensor unit 21 of the EGR valve 18
Includes a cover 21c attached to the EGR valve main body 22 so as to cover a base end of the shaft 24 protruding from the EGR valve main body 22. The cover 21c includes a variable resistance part 21b and a brush 21a that moves with the shaft 24 while being in contact with the variable resistance part 21b.

The variable resistance section 21b is connected to a positive terminal of a battery (not shown), and a current from the battery flows to the brush 21a via the variable resistance section 21b. And the shaft 24
The brush 21a and the variable resistance part 21b
When the contact position with the brush changes, the resistance value of the variable resistance portion 21b changes, and the variable resistance portion 21b
The value of the current flowing to a changes.

As a result, the current value output from the brush 21a changes according to the amount of movement of the shaft 24, in other words, the amount of opening of the valve body 25. As described above, the sensor section 21 detects the opening degree of the EGR valve 18, and realizes the actual opening degree detecting means according to the present invention. Hereinafter, the sensor unit 21 is referred to as a lift sensor 21.

Returning now to FIG. 1, the internal combustion engine 1
The crankshaft (not shown) has a predetermined angle (for example, 30 degrees).
Degree) Each time it rotates, a crank position sensor 17 that outputs an electric signal and a water temperature sensor 19 that outputs an electric signal corresponding to the temperature of the cooling water are attached.

The crank position sensor 1
7, the water temperature sensor 19, the idle switch 36, the air flow meter 16, the vacuum sensor 20, the air-fuel ratio sensor 12, and the lift sensor 21 are each connected to an electronic control unit (Electric Control Unit) for engine control via electric wiring. : ECU) 15, and output signals of the respective sensors are input to the ECU 15.

The ECU 15 determines the operating state of the internal combustion engine 1 using the output signals from the sensors described above as parameters, and performs various controls such as fuel injection control and exhaust gas recirculation control according to the operating state. The EGR valve abnormality determination control, which is the gist, is executed.

Here, as shown in FIG. 4, the ECU 15 is connected to a CP which is interconnected by a bidirectional bus 41.
U42, a ROM 43, a RAM 44, an input port 45, and an output port 46.
And an A / D converter (A / D) 47 connected to the A / D converter.

The input port 45 receives signals from the crank position sensor 17 and the idle switch 36, and transmits these signals to the CPU 42 or the RAM 44. Further, the input port 45 outputs signals from the air-fuel ratio sensor 12, the air flow meter 16, the water temperature sensor 19, the vacuum sensor 20, and the lift sensor 21 to A.
/ D converter 47 and input these signals to C
The data is transmitted to the PU 42 or the RAM 44.

The output port 46 outputs a control signal from the CPU 42 to the drive circuit 8 or the VSV 14. The ROM 43 is used for a fuel injection amount control routine for determining a fuel injection amount of each fuel injection valve 7, a fuel injection timing control routine for determining a fuel injection timing of each fuel injection valve 7, and control of the VSV 14. An application program such as a VSV control routine for determining a duty ratio to be used or an EGR abnormality determination routine for determining an abnormality of the EGR valve 18 and various control maps are stored.

The control map includes, for example, a fuel injection amount control map showing the relationship between the operating state of the internal combustion engine 1 and the fuel injection amount, and a fuel injection timing control showing the relationship between the operating state of the internal combustion engine 1 and the fuel injection timing. A map, an EGR valve control map showing the relationship between the operating state of the internal combustion engine 1 and the target opening of the EGR valve 18, or a VSV control map showing the relationship between the target opening of the EGR valve 18 and the duty ratio for controlling the VSV 14 It is.

Subsequently, the RAM 44 stores output signals from the respective sensors, calculation results of the CPU 42, and the like. The calculation result is, for example, an engine speed calculated from an output signal of the crank position sensor 17. The output signal from each sensor, the calculation result of the CPU 42, and the like are updated each time the crank position sensor 17 outputs a signal.

The CPU 42 operates according to an application program stored in the ROM 43,
The operating state of the internal combustion engine 1 is determined from the output signals of the sensors stored in the AM 44, and the fuel injection amount, the fuel injection timing, the target opening of the EGR valve 18, or the VSV 14 control is determined from the operating state and each control map. Calculate the duty ratio and so on. Then, the CPU 42 controls the drive circuit 8 and the VSV 14 according to the calculated fuel injection amount, fuel injection timing, target opening, and VSV 14 control duty ratio.

When the operating state of the internal combustion engine 1 is in the execution region of the exhaust gas recirculation process, the CPU 42
The control of the SV 14 is performed. Specifically, the CPU 42
(1) A predetermined time has passed since the start of the internal combustion engine 1, (2) the temperature of the cooling water is higher than a predetermined temperature, (3)
Conditions such as that the engine speed is lower than a predetermined speed, (4) the idle switch is off, (5) the intake pipe negative pressure is higher than a predetermined value, and (6) the engine load is higher than a predetermined value. It is determined whether or not all the conditions are satisfied, and these (1) to (6)
When all the conditions are satisfied, it is determined that the operating state of the internal combustion engine 1 is in the execution region of the exhaust gas recirculation process.

When the operating state of the internal combustion engine 1 is in the execution region of the exhaust gas recirculation process, the CPU 42 accesses the EGR valve control map in the ROM 43 and calculates the target opening corresponding to the engine speed, the engine load, and the like. I do. Next, CPU4
2 accesses the VSV control map of the ROM 43 and calculates a duty ratio corresponding to the target opening.

Then, the CPU 42 applies a drive pulse having a pulse width corresponding to the duty ratio to the VSV 14 via the output port 46. that time,
The CPU 42 compares the actual opening detected by the lift sensor 21 with the target opening, and corrects the duty ratio so that the deviation between the actual opening and the target opening becomes zero. Do. Thus, the CPU
42 and the application program in the ROM 43 and the VS
V14 implements the driving means according to the present invention.

Further, the CPU 42 sets the E
The abnormality of the GR valve 18 is determined. At that time, the CPU 42
When it is determined whether or not the operating state of the internal combustion engine 1 is in the non-execution region of the exhaust gas recirculation process, and when it is determined that the operation state of the internal combustion engine 1 is in the non-execution region of the exhaust gas recirculation process,
The output signal of the lift sensor 21 is input. And CP
U42 stores the output signal in the RAM 44 as the actual opening degree when the EGR valve 18 is fully closed.

The non-execution region of the exhaust gas recirculation process can be exemplified, for example, when the internal combustion engine 1 is idling or decelerating. In the present embodiment, when the internal combustion engine 1 is idling. It is assumed that the actual opening degree when fully closed is detected.

Subsequently, the CPU 42 determines that the operating state of the internal combustion engine 1 is in the execution region of the exhaust gas recirculation process, and that the EG
When the R valve 18 is fully opened, the output signal of the lift sensor 21 (actual opening at full opening) is input, and the actual opening at full opening and the actual opening at full closing stored in the RAM 44 are stored. Are compared to determine whether the EGR valve 18 is abnormal.

Here, as shown in FIG.
Assuming that the movement amount of the shaft 24 (valve element 25) from the fully closed state to the fully opened state in the normal state is MO, when a foreign matter is caught in the EGR valve 18, the shaft 2 is moved from the fully closed state to the fully open state.
As shown in FIG. 6, the amount by which the valve element 4 (valve element 25) moves is a value (Mng) smaller than the MO. That is, EGR
The difference between the actual opening of the valve 18 when it is fully opened and the actual opening of the valve 18 when it is fully closed is determined. If this difference is less than the movement amount MO, it can be determined that the EGR valve 18 is abnormal.

However, according to the above-described determination method, when the output characteristics of the lift sensor 21 change due to the aging of the lift sensor 21 and the EGR valve main body 22, the EGR valve 18
Is operating normally, the EGR valve 18 is determined to be abnormal.

Further, since the components such as the lift sensor 21 and the EGR valve body 22 have an initial tolerance, the opening amount from fully open to fully closed may vary even in a normal state. Accordingly, in the present embodiment, a reference value: α is set in consideration of the change with time and the initial tolerance, and the CPU 42 determines the actual opening degree when the EGR valve 18 is fully closed and the actual opening degree when the EGR valve 18 is fully opened. When the difference is less than the reference value: α, the EGR valve 18 is determined to be abnormal. Thus, the CPU 42
Executes the application program in the ROM 43, thereby realizing the abnormality determining means according to the present invention.

The operation and effect of this embodiment will be described below. The CPU 42 is provided at predetermined time intervals (for example, each time the crank position sensor 17 outputs a signal).
Then, an EGR abnormality determination routine as shown in FIG. 7 is executed. In this EGR abnormality determination routine, the CPU 42
Accesses the RAM 44 in S701 to determine whether or not the output signal of the idle switch 36 is an ON signal, that is, whether or not the internal combustion engine 1 is in an idle state.

If it is determined in S701 that the internal combustion engine 1 is in an idle state, the CPU 42 proceeds to S709.
Then, the output signal of the lift sensor 21 is input. Then, the CPU 42 stores the output signal in the RAM 44 as the actual opening degree L0 when the EGR valve 18 is fully closed.

On the other hand, if it is determined in S701 that the internal combustion engine 1 is not in the idle state, the CPU 42
Proceed to S702. In S702, the CPU 42
Accesses the RAM 44, the engine speed of the internal combustion engine 1, the output signal of the water temperature sensor 19 (temperature of the cooling water), the output signal of the air flow meter 16 (the amount of intake air), and the output signal of the vacuum sensor 20 (the intake pipe load). Pressure) is read out.
Then, the CPU 42 determines whether or not each of the output signals satisfies the execution condition of the exhaust gas recirculation process, that is, whether the internal combustion engine 1
It is determined whether or not the operation state is in the execution region of the exhaust gas recirculation processing.

If it is determined in S702 that the operating state of the internal combustion engine 1 is in the execution range of the exhaust gas recirculation process, the CPU 42 proceeds to S703. And CPU
42 is the VSV at the present time in S703.
14 It is determined whether or not the duty ratio for control is 100%, that is, whether or not the EGR valve 18 is driven to the fully open state.

If it is determined in S703 that the EGR valve 18 is being driven to the fully open state, the CPU 42
Proceeds to S704. Then, in the above S704,
The CPU 42 determines that the output signal (intake air amount: GN) of the air flow meter 16 stored in the RAM 44 is a predetermined value: GN
Determine if it is less than one.

That is, in order to drive the EGR valve 18 fully open, an intake pipe negative pressure equal to or more than a certain value is required. The intake pipe negative pressure increases as the intake air amount of the internal combustion engine 1 decreases, so that the intake air negative pressure increases. If the amount: GN is less than the predetermined value: GN1, it can be estimated that the intake pipe negative pressure at that time is a negative pressure sufficient to fully open the EGR valve 18. In step S704, an output signal (intake pipe negative pressure) of the vacuum sensor 20 may be used instead of the intake air amount.

In S704, the intake air amount: GN is smaller than the predetermined value: GN1, and the EGR valve 1
8 is determined to be capable of being fully driven, the CPU 42
Proceeds to S705. In S705, the CPU 42
Represents the output signal of the lift sensor 21 at that time,
The degree of opening of the EGR valve 18 when it is fully opened is input as L1.

Subsequently, the CPU 42 proceeds to S706,
The fully-closed opening: L0 stored in the RAM 44 is read out, and the fully-closed opening: L0 is subtracted from the fully-opened opening: L1 input in step S705. Opening amount difference: L is calculated.

Then, the CPU 42 proceeds to S707,
It is determined whether or not the difference: L is less than the reference value: α, and if it is determined that the difference: L is less than the reference value: α,
Proceeding to 708, it is determined that the EGR valve 18 is abnormal.

When the abnormality of the EGR valve 18 is determined as described above, the CPU 42 may turn on a warning lamp or the like on an instrument panel arranged in the cabin of the vehicle to call the driver's attention.

On the other hand, in S707, the difference: L
Is greater than or equal to the reference value: α,
42 determines that the EGR valve 18 is normal. In this case, the CPU 42 continuously performs the exhaust gas recirculation process.

In the above-described embodiment, in the EGR valve using the intake pipe negative pressure as a drive source, the target opening and the actual opening are likely to coincide with each other, and the EGR valve at the time of full opening and full closing which occurs relatively frequently. By performing the abnormality determination based on the difference between the actual opening degrees, the accuracy of the abnormality determination is improved and the frequency of the abnormality determination is increased.

Therefore, according to the present embodiment, the abnormality of the EGR valve can be detected accurately and early, and the deterioration of the exhaust emission due to the abnormality of the EGR valve is prevented. <Other embodiments> Hereinafter, other embodiments of the exhaust gas recirculation control device for an internal combustion engine according to the present invention will be described with reference to the drawings. Here, a configuration different from the above-described embodiment will be described, and a description of the same configuration will be omitted.

In the present embodiment, the CPU 42
A predetermined number of actual opening degrees when the valve 18 is fully opened and a predetermined number of actual opening degrees when the valve 18 is fully closed are collected and statistically processed. Is calculated, and the abnormality of the EGR valve 18 is determined based on the difference between the two average values.

In this case, the CPU 42 of the ECU 15
It has a first counter for counting the number of actual openings when the GR valve 18 is fully opened, and a second counter for counting the number of actual openings when the EGR valve 18 is fully closed. Although not shown, the first and second counters can be realized by a register or the like constituting the CPU 42.

Each time the CPU 42 detects the fully open state of the EGR valve 18, the CPU 42 increments the value of the first counter by one, and simultaneously outputs the output signal of the lift sensor 21 at that time to the actual opening degree at the time of full opening: R as Lk
Store it in AM44. As a result of repeating this process,
When the value of the first counter reaches a predetermined value: K, that is, when K actual openings when the EGR valve 18 is fully opened are collected, the CPU 42 calculates an average value of the K actual openings: ΣLk
/ K is calculated.

On the other hand, every time the CPU 42 detects the fully closed state of the EGR valve 18, the CPU 42 increments the value of the second counter by one, and simultaneously outputs the output signal of the lift sensor 21 at that time when the EGR valve 18 is fully opened. Degree: R as L'i
Store it in AM44. As a result of repeating this process,
When the value of the second counter reaches a predetermined value: I, that is, when I actual openings when the EGR valve 18 is fully closed are collected, the CPU 42 calculates the average value of the I actual openings. : ΣL '
Calculate i / I.

Then, the average value of the actual opening at the time of full opening: ΔLk
After calculating / K and the average value of the actual opening degree when fully closed: ΣL'i / I, the CPU 42 calculates the average value of the actual opening degree when fully opened: Σ
The average value of the actual opening degree at the time of full closing: ΣL'i / I is subtracted from Lk / K, and the difference in the opening degree between the fully opening state and the fully closing state: L (= ΣLk /
K−ΣL′i / I) is calculated. And the CPU 42
Is the EGR valve 1 if the difference L is less than the reference value β.
8 is determined to be abnormal, and if the difference L is equal to or greater than the reference value β, it is determined that the EGR valve 18 is normal.

The difference between the actual opening of the EGR valve 18 when it is fully opened and the actual opening of the EGR valve 18 when the EGR valve 18 is fully closed, L, is obtained by using the statistical processing described above.
Therefore, the reference value β can be set to a value that takes into account only the aging of the lift sensor 21 and the EGR valve body 22.

The other configuration is the same as that of the above-described embodiment, and the description is omitted. Hereinafter, the operation and effects according to the present embodiment will be described. CPU 42 of ECU 15
Executes an EGR abnormality determination routine as shown in FIG. 8 every predetermined time. In this EGR abnormality determination routine, the CPU 42 resets (= 0) the values of the first and second counters: i, k in S801.

Subsequently, the CPU 42 proceeds to S802,
The output signal of the idle switch 36 stored in the RAM 44 is read, and whether or not the output signal is an ON signal
That is, it is determined whether or not the internal combustion engine 1 is in an idle state.

If it is determined in step S802 that the internal combustion engine 1 is in the idle state, the CPU 42 proceeds to step S812.
Then, the value of the second counter: i is incremented by one.

Subsequently, the CPU 42 proceeds to S813,
The output signal of the lift sensor 21 at that time is input. Then, the CPU 42 stores the output signal in the RAM 44 as the actual opening degree L′ i when the EGR valve 18 is fully closed.

On the other hand, when it is determined in S802 that the internal combustion engine 1 is not in the idle state, the CPU 42
Proceed to 803 and access the RAM 44 to access the internal combustion engine 1
, The output signal of the water temperature sensor 19 (the temperature of the cooling water), the output signal of the air flow meter 16 (the amount of intake air), and the output signal of the vacuum sensor 20 (the negative pressure of the intake pipe).
And so on. Then, the CPU 42 determines whether or not each of the output signals satisfies an execution condition of the exhaust gas recirculation process, that is, whether or not the operation state of the internal combustion engine 1 is in an execution region of the exhaust gas recirculation process.

If the CPU 42 determines in step S803 that the operating state of the internal combustion engine 1 is within the execution range of the exhaust gas recirculation process, the CPU 42 proceeds to step S804. And CPU4
2 determines in S804 whether or not the current duty ratio for VSV14 control is 100%, that is, whether or not the EGR valve 18 is driven to the fully open state.

If it is determined in S804 that the EGR valve 18 is being driven to the fully open state, the CPU 42
Proceeds to S805, and determines whether or not the output signal (intake air amount: GN) of the air flow meter 16 stored in the RAM 44 is less than a predetermined value: GN1.

At S805, the intake air amount:
If GN is less than the predetermined value: GN1, the CPU 42
It is determined that the GR valve 18 can be fully opened, and the process proceeds to S806. In S806, the CPU 42 increments the counter value: k of the first counter by one.

Subsequently, the CPU 42 proceeds to S807,
The output signal of the lift sensor 21 at that time is expressed as EG
Opening degree of R valve 18 when fully opened: Input as Lk, RAM4
4 in a predetermined area.

Next, in S808, the CPU 42 determines whether or not the counter value i of the first counter is equal to or more than the predetermined number I and the counter value k of the second counter is equal to or more than the predetermined number K. That is, it is determined whether or not K or more actual opening degrees when fully opened and I or more actual opening degrees when fully closed are collected.

In step S808, if the counter value of the first counter: i is smaller than the predetermined number: I, or the counter value: k of the second counter is smaller than the predetermined number: K,
The PU 42 determines that the counter value of the first counter: i is equal to or more than the predetermined number: I and the counter value of the second counter is:
Until k becomes equal to or larger than the predetermined number: K, the above-described processing after S802 is repeatedly executed.

If it is determined in step S808 that the counter value i of the first counter is equal to or larger than the predetermined number I, and the counter value k of the second counter is equal to or larger than the predetermined number K, the CPU 42 Proceeds to S809.

In step S809, the CPU 42 first accesses the RAM 44 and reads out K actual opening degrees L1 to LK and I actual opening degrees L'1 to L'I. Subsequently, the CPU 42 determines the K actual opening degrees (L1 to L1).
LK) average value: ΔLk / K and the I actual opening (L ′)
1 to L′ I): ΣL′i / I is calculated. Further, the CPU 42 subtracts the average value: ΣL'i / I from the average value: ΣLk / K, and calculates a difference L between the actual opening degree when fully opened and the actual opening degree when fully closed: L. calculate.

Subsequently, the CPU 42 proceeds to S810,
The CPU 42 determines whether or not the difference: L calculated in S809 is less than the reference value: β. If it is determined in S810 that the difference: L is less than the reference value: β, the CPU 42 determines whether the difference: L is less than the reference value: β.
Proceeding to 811, it is determined that the EGR valve 18 is abnormal.
On the other hand, if it is determined in S810 that the difference: L is equal to or larger than the reference value: β, the CPU 42 proceeds to S814,
It is determined that the EGR valve 18 is normal.

As described above, according to the present embodiment, the opening amount between the fully opened state and the fully closed state is obtained from the average value of the actual opening degree at the time of full opening and the average value of the actual opening degree at the time of fully closing. E to find the difference
The reference value: β can be set without considering the initial tolerance of the GR valve 18 and the like, and the accuracy of the abnormality determination can be further improved.

[0091]

The exhaust gas recirculation control device for an internal combustion engine according to the present invention is based on the difference in the actual opening between the fully open drive and the fully closed drive which occurs relatively frequently when driving the exhaust gas recirculation control valve. Since the abnormality of the exhaust gas recirculation control valve is determined, the chance of the abnormality determination processing increases, and the abnormality of the exhaust gas recirculation control valve can be detected early.

Further, when the exhaust gas recirculation control valve is fully opened and fully closed, the driving means is often driven to temporarily hold the fully open state and the fully closed state. Even if a delay occurs, the actual opening detection means can detect the actual opening when the exhaust gas recirculation control valve actually performs the full opening operation and the full closing operation. As a result, the abnormality determination means makes the abnormality determination based on the accurate actual opening, and the determination accuracy can be improved.

Therefore, according to the present invention, the abnormality of the exhaust gas recirculation control valve can be accurately and promptly detected.
It is possible to suppress the deterioration of the exhaust emission due to the abnormality of the exhaust gas recirculation control valve.

[Brief description of the drawings]

FIG. 1 is a diagram showing a schematic configuration of an internal combustion engine to which an exhaust gas recirculation control device for an internal combustion engine according to the present invention is applied;

FIG. 2 is a diagram showing a configuration of an exhaust gas recirculation control mechanism.

FIG. 3 is a diagram illustrating the operation of an exhaust gas recirculation control mechanism.

FIG. 4 is a diagram showing an internal configuration of an ECU.

5A is a diagram showing a fully closed state of the EGR valve in a normal state, and FIG. 5B is a diagram showing a fully opened state of the EGR valve in a normal state.

FIG. 6A is a diagram showing a fully closed state of the EGR valve at the time of abnormality, and FIG. 6B is a diagram showing a fully open state of the EGR valve at the time of abnormality.

FIG. 7 is a flowchart showing an EGR abnormality determination routine;

FIG. 8 is a flowchart illustrating an EGR abnormality determination routine according to another embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Internal combustion engine 2 ... Intake branch pipe 3 ... Surge tank 4 ... Intake pipe 9 ... Exhaust branch pipe 10 ... Exhaust pipe 13 ... Pressure regulating valve 14 VSV 15 ECU 18 EGR valve 21 Lift sensor (actual opening detection means) 21a Brush 21b Variable resistor 21c Cover 30 Exhaust recirculation passage

Claims (2)

[Claims] An exhaust gas recirculation control valve for controlling an exhaust gas flow rate of an exhaust gas recirculation passage connecting an exhaust gas passage and an intake air passage of an internal combustion engine, and an actual opening detection for detecting an actual opening of the exhaust gas recirculation control valve Means for driving the exhaust gas recirculation control valve so that the actual opening detected by the actual opening detecting means coincides with a desired target opening. A detection value of the actual opening degree detecting means when the driving means drives the exhaust gas recirculation control valve to the fully closed state, and a detection value of the actual opening degree detecting means when the driving means drives the exhaust gas recirculation control valve to the fully open state. An exhaust gas recirculation control device for an internal combustion engine, comprising: abnormality judgment means for judging an abnormality of the exhaust gas recirculation control valve based on a difference from a value detected by the actual opening degree detecting device. 2. The abnormality judging means collects a predetermined number of values detected by the actual opening degree detecting means when the driving means drives the exhaust gas recirculation control valve so as to bring the exhaust gas recirculation control valve into a fully closed state. Collects a predetermined number of detected values of the actual opening detecting means when the exhaust gas recirculation control valve is driven to the fully opened state, and statistically processes these detected values to determine the opening amount between the fully opened state and the fully closed state. 2. The exhaust gas recirculation control device for an internal combustion engine according to claim 1, wherein the difference is calculated.