JPH0842403A - Exhaust gas recirculation trouble diagnoser - Google Patents

Abstract

PURPOSE:To secure an exhaust gas recirculation trouble diagnoser that prevents any erroneous judgment due to an engine misfire from occurring. CONSTITUTION:An exhaust gas recirculation control valve 31 is set up in an exhaust gas recirculation passage 30 connecting both intake and exhaust passages 2 and 11 of an engine 1, while an intake pipe pressure sensor 3 detecting the extent of pressure in this intake passage is installed there. A control circuit 10 forcibly closes the exhaust gas recirculation control valve during this EGR control valve opening (during the execution of exhaust gas recirculation), and when a difference in the intake pipe pressure in front and in the rear of the valve closing detected by the intake pipe pressure sensor is smaller than the specified value it so judges that abnormality with the valve is produced there. In addition, this control circuit 10 judges whether there is an engine misfire or not from a variation in engine speed, and when this misfire is detected, any execution of an exhaust gas recirculation trouble diagnosis is prohibited.

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 device for an internal combustion engine, and more particularly to an exhaust gas recirculation abnormality diagnosis device for determining whether or not there is an abnormality in exhaust gas recirculation.

[0002]

2. Description of the Related Art An exhaust passage and an intake passage of an internal combustion engine are connected by an exhaust gas recirculation passage (EGR passage), and an EGR passage is opened by an exhaust gas recirculation control valve (EGR control valve) provided in this EGR passage. There is known an exhaust gas recirculation apparatus for an internal combustion engine, which controls exhaust gas recirculation from an exhaust system to an intake system.

[0003] In the engine provided with an exhaust gas recirculation system, by refluxing the low exhaust gas oxygen concentration, it decreases the engine combustion temperature amount of the NO _X in the exhaust gas (nitrogen oxides) reduction in the intake system To be done. Further, during light load operation in which the throttle valve opening decreases, exhaust gas recirculation is performed to increase the intake pipe pressure, so that pumping loss of the engine can be reduced.

However, if an abnormality occurs in the exhaust gas recirculation device as described above, a problem will occur. For example, EGR
If the exhaust gas recirculation in operating conditions should be performed recirculation original exhaust gas by malfunction of the control valve is such not performed, there is a problem such as increase in the pumping loss increased and institutions of the NO _X in the exhaust gas . On the contrary, if exhaust gas recirculation is performed during light load operation where exhaust gas recirculation is not originally performed due to poor closing of the EGR control valve, misfire may occur due to deterioration of combustion state and engine rotation may become unstable. There arises a problem that exhaust properties deteriorate.

However, even if such an abnormality occurs, the engine operation can be carried out without any trouble, and therefore the driver may continue to operate for a long period of time without noticing the abnormality in the exhaust gas recirculation. In order to prevent such a situation, an exhaust gas recirculation abnormality diagnosis device has been devised which judges whether or not there is an abnormality in the exhaust gas recirculation device and informs the driver.

An example of such an exhaust gas recirculation abnormality diagnosing device is disclosed in Japanese Patent Laid-Open No. 4-27750. In the abnormality diagnosis device described in the publication, the differential pressure between the intake pipe pressure when the exhaust gas recirculation is performed and the intake pipe pressure when the exhaust gas recirculation is stopped during the engine low load steady operation is equal to or less than a predetermined value. In this case, it is determined that an abnormality has occurred in the exhaust gas recirculation.

When exhaust gas recirculation is carried out, a part of the engine exhaust gas is recirculated to the downstream side of the throttle valve of the intake system.
The intake pipe pressure increases as compared with the case where exhaust gas recirculation is not performed. Therefore, if the intake pipe pressure does not differ by more than a predetermined value due to the presence or absence of exhaust gas recirculation, it is considered that the EGR control valve remains open or closed due to malfunction.

The device disclosed in the above publication reexhausts the exhaust gas during a low load operation in which the intake pipe pressure is low to a certain extent and the change in the intake pipe pressure due to the presence or absence of exhaust gas recirculation is large, and during steady operation in which the intake pipe pressure varies little. The presence / absence of exhaust gas recirculation abnormality is determined based on whether or not the intake pipe pressure change exceeds a predetermined value depending on the presence / absence of circulation.

[0009]

However, as described above, when a problem occurs when the abnormality of the exhaust gas recirculation is judged from the change in the intake pipe pressure caused by the presence or absence of the exhaust gas recirculation during the low load steady operation as described above. There is. For example, when the engine misfires, the intake pipe pressure fluctuates, but whether the change in the intake pipe pressure due to the presence or absence of exhaust gas recirculation reaches a predetermined value as in the device of the above publication. When the abnormality of the EGR control valve is determined by the above, an erroneous determination may occur due to intake pipe pressure fluctuation caused by engine misfire.

That is, since the measured value of the intake pipe pressure when the exhaust gas recirculation is stopped has a larger variation than usual at the time of misfire, depending on the measured measured value of the intake pipe pressure, the exhaust gas may be normal even if the EGR control valve is operating normally. The decrease in intake pipe pressure when recirculation is stopped may be reduced, and a normal EGR control valve may be erroneously determined to be abnormal. Further, when the EGR control valve is defectively closed, the difference in intake pipe pressure between when the EGR control valve is opened and when it is closed is small. If the intake pipe pressure fluctuates,
Depending on the measured value of the intake pipe pressure, the intake pipe pressure drop apparently increased when the EGR control valve was closed, resulting in valve closing failure E
The GR control valve may be erroneously determined to be normal.

In view of the above problems, it is an object of the present invention to provide an exhaust gas recirculation abnormality diagnosis device capable of preventing erroneous determination due to engine misfire and accurately determining abnormality of the exhaust gas recirculation system. .

[0012]

According to the present invention, there are provided an exhaust gas recirculation means for recirculating a part of exhaust gas of an internal combustion engine to an intake system, and an intake pressure detection means for detecting an engine intake pipe pressure. Exhaust comprising: an exhaust gas recirculation means for determining whether there is an abnormality in exhaust gas recirculation based on an intake pipe pressure when exhaust gas recirculation is performed and an intake pipe pressure when exhaust gas recirculation is stopped. In the gas recirculation abnormality diagnosis device,
Exhaust gas recirculation abnormality diagnosis, characterized by comprising: misfire detection means for detecting engine misfire; and prohibition means for prohibiting the judgment by the judgment means when engine misfire is detected by the misfire detection means. A device is provided.

[0013]

The operation of the determination means is based on the intake pipe pressure when the exhaust gas recirculation is performed and the intake pipe pressure when the exhaust gas recirculation is stopped.
For example, when the change in the intake pipe pressure due to the presence or absence of exhaust gas recirculation is smaller than a predetermined value, it is determined that the exhaust gas recirculation is abnormal. Further, the misfire detection means detects that the engine has misfired, for example, based on a change in the engine speed.
When it is detected that the engine has misfired, the prohibiting means prohibits the determining means from determining whether or not there is an exhaust gas recirculation abnormality.

[0014]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a diagram showing an overall schematic configuration of a vehicle internal combustion engine to which the present invention is applied. In FIG. 1, 1 is an internal combustion engine body, 2 is an intake passage, 11 is an exhaust passage, and 3 is an analog voltage corresponding to a pressure (intake pipe pressure) in a surge tank 13 provided in the intake passage. It is an intake pipe pressure sensor. This output signal is input to the A / D converter 101 with a built-in multiplexer of the control circuit 10.

On the crankshaft (not shown) of the engine 1, a reference position detecting pulse signal is generated for each compression top dead center (for each crankshaft rotation angle of 720 °) of a specific cylinder (for example, the first cylinder). Crank angle sensor 5 and crankshaft rotation angle 30 °
A crank angle sensor 6 for generating a crank angle detection pulse signal is provided for each of them. The crank angle sensors 5 and 6 are provided with, for example, a gear attached to the end of the crankshaft and a pickup including a proximity sensor arranged to face the tooth surface of the gear, and the teeth of the gear pass through a position facing the pickup. A pulse signal is output every time the pulse signal is output. The pulse signals of the crank angle sensors 5 and 6 are supplied to the input / output interface 102 of the control circuit 10, of which the output of the crank angle sensor 6 is the CPU 103.
It is supplied to the interrupt terminal of.

Further, the intake passage 2 is provided with a fuel injection valve 7 for supplying pressurized fuel from the fuel supply system to the intake port for each cylinder. Further, the intake passage 2 is provided with a throttle valve 16 having an opening degree according to the operation amount of a driver's accelerator pedal 21, and further, the throttle valve 16 has an opening degree according to the opening degree of the throttle valve 16. A throttle opening sensor 17 that generates a voltage signal is provided. The output of this throttle opening sensor is the A / D converter 1
01 is input.

In FIG. 1, reference numeral 30 denotes an exhaust gas recirculation passage (EGR passage) which connects the exhaust passage 11 and the surge tank 13 of the intake passage 2. EGR passage 30
An exhaust gas recirculation control valve (EGR control valve) 31 that controls the amount of exhaust gas that flows back from the exhaust passage 11 to the intake passage 2 through this passage is provided in the. Reference numeral 32 is an actuator of an appropriate type such as a negative pressure actuator or a step motor that controls the operation of the EGR control valve 31. The actuator 32 opens and closes the EGR control valve 31 in response to a control signal from the control circuit 10 to control execution of exhaust gas recirculation.

The water jacket 8 of the cylinder block of the engine body 1 is provided with a water temperature sensor 9 for detecting the temperature of the cooling water. The water temperature sensor 9 generates an electric signal of analog voltage according to the temperature of the cooling water. This output is also supplied to the A / D converter 101. Control circuit 1
0 is configured as a microcomputer, for example,
A / D converter 101, input / output interface 102,
In addition to the CPU 103, a ROM 104, a RAM 105, a backup RAM 106, a clock generation circuit 107, etc. are provided.

The control circuit 10 detects the fluctuation of the engine speed in this embodiment in addition to the basic control for controlling the fuel injection and the ignition timing of the engine 1 based on the intake pipe pressure and the engine speed. Misfire detection operation to detect the presence or absence of engine misfire and EG
Exhaust gas recirculation control that controls the opening and closing of the R valve 31 to control exhaust gas recirculation to the engine, and EG under predetermined operating conditions.
The R control valve is opened / closed, and an abnormality determination operation for determining the presence / absence of exhaust gas recirculation abnormality is performed based on the change in the intake pipe pressure due to the opening / closing.

The pressure data from the intake pipe pressure sensor 3, the throttle opening data from the throttle opening sensor 17, and the cooling water temperature data from the water temperature sensor 9 are A / D converted for a predetermined time period or a predetermined crank angle. It is fetched by a routine and stored in a predetermined area of the RAM 105. In addition, as will be described later, the intake pipe pressure is calculated as an average value PM for every fixed time by a time interruption routine that is separately executed.
Is calculated and similarly stored in a predetermined area of the RAM 105.

That is, the intake pipe pressure data, throttle opening data, and cooling water temperature data in the RAM 105 are updated every predetermined time. Further, the rotation speed data is 30 ° CA of the crank angle sensor 6 based on the pulse signal of the crank angle sensor 6 and the clock signal of the clock 107.
RAM1 is calculated by interruption for each (crank angle)
05 is stored in a predetermined area.

Next, the exhaust gas recirculation control of this embodiment will be described. In the present embodiment, the control circuit 10 causes the actuator 32 to open the EGR control valve 31 to perform exhaust gas recirculation when the following conditions are satisfied. The engine cooling water temperature must be above a specified value (eg 65 ° C). The engine load must be below the specified value on the high load side.

The engine load is not less than a predetermined value on the light load side. In the above conditions, if exhaust gas recirculation is performed before engine warm-up is completed, the warm-up may be delayed due to deterioration of the combustion state.Therefore, exhaust gas re-circulation has completed engine warm-up. This is done only when it is judged. Further, the above conditions are for securing the engine output by prohibiting the exhaust gas recirculation during the engine high load operation that originally requires the output, because the engine output decreases when the exhaust gas recirculation is performed. .

The above conditions are for preventing the occurrence of misfire due to deterioration of the combustion state under light load. In this embodiment, the intake pipe pressure P is set as a parameter indicating the engine load.
M and engine speed N are used, PM and N are
The engine load condition is determined by whether or not it is within a predetermined range corresponding to the area. Further, the control circuit 10 opens and closes the EGR control valve 31 under a predetermined operating condition as described later,
Based on the change in the intake pipe pressure at this time, it is determined whether or not the exhaust gas recirculation is abnormal. That is, when the exhaust gas recirculation is performed, the exhaust gas is recirculated to the intake passage 2 through the EGR passage 30, so that the intake pipe pressure rises as compared with the case where the exhaust gas recirculation is not performed. Therefore, if the exhaust gas recirculation is normally performed, the intake pipe pressure changes as the EGR control valve 31 opens and closes. Therefore, EGR
When the change in the intake pipe pressure due to the opening / closing of the control valve 31 is less than or equal to a predetermined value, it can be determined that an abnormality in the exhaust gas recirculation system such as a malfunction of the EGR control valve 31 has occurred.

However, since the intake pipe pressure fluctuates when the engine misfires as described above, the exhaust gas recirculation abnormality is detected based on the intake pipe pressure change accompanying the opening and closing of the EGR control valve 31 as described above. Misjudgment may occur if the presence or absence is judged. The reason why the intake pipe pressure fluctuates when a misfire occurs in the engine is as follows.

That is, in a steady operation in which the engine is not misfired, the variation in the intake air amount among the cylinders is relatively small, and the intake pipe pressure in the surge tank 13 is relatively stable. This is because the force that sucks in air during the intake stroke of each cylinder is determined by the rotational torque of the crankshaft, that is, the explosive force of the other cylinders that are in the explosion stroke during the intake stroke of a cylinder, but when there is no misfire in the engine. Since the variation of the explosive force among the cylinders is relatively small, the force of sucking air in the intake stroke of each cylinder is also averaged, and the fluctuation of the intake pipe pressure is relatively small.

On the other hand, when a misfire occurs in the engine, the explosive force does not occur in the misfiring cylinder, so that the cylinder that is in the intake stroke at the time of the explosive stroke of the misfiring cylinder has a reduced force for sucking air, and the intake air amount of each cylinder. Variation becomes large. Therefore, the intake pipe pressure fluctuates according to the variation in the intake air amount. Therefore, the EGR control valve 31
If the presence / absence of an exhaust gas recirculation abnormality is determined based on the change in the intake pipe pressure due to opening / closing, the erroneous determination occurs as described above.

In the present embodiment, it is judged whether or not there is a misfire in the engine based on the change in the engine speed, in addition to the change in the intake pipe pressure. By prohibiting the determination of the presence or absence of circulation abnormality, an erroneous determination is prevented. FIG. 2 is a flow chart for explaining the abnormality determination operation. This routine is executed by the control circuit 10 at regular time intervals.

When the routine starts in FIG.
At step 201, throttle opening TH and intake pipe pressure P
Each data of M (average value) and engine speed N is stored in the RAM 105.
Read from. Next, at step 203, it is judged if the operating condition of the engine is in the region where the exhaust gas recirculation should be carried out.
The routine is ended as it is without performing the abnormality diagnosis of the exhaust gas recirculation in step 205 and thereafter. That is, in the present embodiment, the exhaust gas recirculation abnormality diagnosis is performed only in the exhaust gas recirculation execution region.

If exhaust gas recirculation is currently being performed in step 203, it is determined in step 205 whether or not the abnormality diagnosis execution condition is satisfied. Here, the execution condition of the abnormality diagnosis in the present embodiment is that the engine operating condition is stable (that is, the operating state in which the fluctuations of the intake air amount pressure PM and the throttle opening TH are small).
The intake pipe pressure PM and the engine speed N are within predetermined ranges (that is, operating conditions that do not cause a large change in the engine output even when the EGR control valve 31 is opened / closed for abnormality diagnosis). The abnormality diagnosis execution timing (for example, a predetermined time has elapsed since the previous abnormality diagnosis was executed).

If any of the above conditions is not satisfied, the routine ends without performing abnormality diagnosis, and only if all of the above conditions are satisfied, step 20 is performed.
7 and below are executed. In step 207, the flag FM
It is determined whether the value of IS is 1 or not. Here, the flag FM
IS is a misfire flag set by a misfire detection routine (not shown) which is separately executed by the control circuit 10.
MIS = 1 means that a misfire is currently detected in the engine, and FMIS = 0 means that no misfire is detected.

In this embodiment, the presence or absence of misfire is detected in the misfire detection routine based on the fluctuation of the engine speed. That is, the control circuit 10 obtains the time interval of the pulse signal input from the crank angle sensor 6 every 30 ° of the crank rotation angle by a misfire detection routine (not shown) that is separately executed, and determines the engine rotation speed in the explosion stroke of a certain cylinder. , The crankshaft rotation pulse signal time intervals corresponding to 90 ° and 120 ° after the top dead center (TDC) of a certain cylinder are the same as those of other cylinders at the same time. It is judged that a misfire has occurred when the value becomes larger than a certain ratio by a certain ratio or more.

When a misfire occurs in a cylinder, no torque is generated in that cylinder during the explosion stroke. Therefore, in the range of the crank rotation angle corresponding to the explosion stroke of the misfire cylinder, the crankshaft rotation speed is lower than that of the other cylinders. . In the present embodiment, the control circuit 10 determines that a misfire has occurred by detecting the decrease in the crankshaft rotation speed in the explosion stroke of each cylinder as described above, and it is determined that a misfire has occurred in one of the cylinders. In this case, the value of the misfire flag FMIS is set to 1.

The misfire detection method applicable to the present invention is not limited to the above-mentioned fluctuation in the number of revolutions, and other methods can be used. For example, in an engine equipped with a combustion pressure sensor that detects the combustion pressure in the combustion chamber, the combustion pressure of each cylinder during the explosion stroke is monitored, and it is determined that misfire has occurred when this combustion pressure is below a predetermined value. You may

When it is determined in step 207 that FMIS = 1, that is, misfire has occurred, step 2
The routine is terminated without executing the abnormality diagnosis subroutine of 09, and the abnormality diagnosis subroutine of step 209 is executed only when FMIS = 0, that is, when the engine does not misfire. As a result, the execution of the abnormality diagnosis sub-routine is prohibited when the engine is misfired, so that it is possible to prevent an erroneous determination of the presence or absence of the exhaust gas recirculation abnormality due to the engine misfire.

Next, the abnormality diagnosis subroutine executed in step 209 of FIG. 2 will be described with reference to the flowchart of FIG. In this subroutine, it is determined that the exhaust gas recirculation is abnormal when the difference between the intake pipe pressures when the exhaust gas recirculation is performed and when the exhaust gas recirculation is stopped is smaller than a predetermined value.

That is, the subroutine starts in FIG.
Then, in step 301, it is determined whether the value of the flag F is 1 or not.
Is determined, where the flag F indicates that exhaust gas recirculation is being performed.
Intake pipe pressure PM in_ONIndicating whether or not the measurement of
It is a lag, and F = 1 means that the measurement is finished.
ing. In step 301, F ≠ 1, that is, exhaust gas re-
Intake pipe pressure PM during circulation_ONMeasurement is not completed
In this case, the process proceeds to step 303 and step 201 in FIG.
The intake pipe pressure (average value) PM read in _ONAs
It is stored in the RAM 105. In step 203 of FIG.
As described above, in this embodiment, the exhaust gas recirculation execution region
Step 303 is executed to execute the abnormality diagnosis only in
When the EGR control valve 31 is opened, the EGR control valve 31 is open.

[0038] By the above, after storing the PM _ON, the flag F indicating the measurement end of the PM _ON at step 305 is set to 1, then in step 307, the actuator 32 is actuated to force the EGR control valve 31 Fully close and end the subroutine. As a result, in this subroutine execution, PM _ON is stored in the RAM 105, the EGR control valve 31 is fully closed, and the flag F is set to 1.

When this subroutine is executed next in this state, F = 1 is satisfied in step 301, so step 309 is executed next, and the intake pipe pressure PM at this time is executed.
Is stored in the RAM 105 as the intake pipe pressure PM _OFF when the EGR control valve 31 is closed (when the exhaust gas recirculation is stopped).
In step 311, the difference between the previously measured intake pipe pressure PM _ON during execution of exhaust gas recirculation and the intake pipe pressure PM _OFF measured during exhaust gas recirculation stop measured this time is a predetermined value ΔPM.
Whether or not it is determined, and if this pressure difference is smaller than the predetermined value, the abnormality flag FEG is set to 1 in step 313, and an alarm (not shown) indicating an abnormality in exhaust gas recirculation in step 315. Is lit.

In step 311, PM _ON- PM _OFF
If ≧ ΔPM, the abnormality flag FEG is reset (= 0) in step 317. Also, step 31
After completion of 5 or 317, in step 319, the value of the flag FEG set as described above is stored in the backup RAM 106 of the control circuit 10 in preparation for the next maintenance and inspection, and then in step 321, the EGR control valve 31 is opened. Then, in step 323, the value of the PM _ON measurement end flag F is reset in preparation for the next abnormality diagnosis execution (=
0) and then this subroutine is terminated.

In the above subroutine, the exhaust gas recirculation abnormality diagnosis is performed in the state where the engine misfire does not occur, so it is possible to accurately determine the presence or absence of the exhaust gas recirculation abnormality from the change in the intake pipe pressure due to the opening / closing of the EGR control valve 31. Can be determined. In the above embodiment, the EG
The presence or absence of exhaust gas recirculation abnormality is determined by forcibly closing the R control valve, but the present invention is not limited to this, and, for example, a region where exhaust gas recirculation is not performed. The exhaust gas recirculation abnormality diagnosis similar to that in the above-described embodiment may be performed by forcibly opening the EGR control valve and calculating the difference in intake pipe pressure before and after opening.

[0042]

According to the exhaust gas recirculation abnormality diagnosis device of the present invention, when the engine misfires, the exhaust gas recirculation abnormality diagnosis based on the intake pipe pressure change depending on whether the exhaust gas recirculation is performed or not is prohibited. By doing so, it is possible to prevent erroneous determination due to engine misfire and to accurately determine the presence or absence of exhaust gas recirculation abnormality.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an overall configuration of an internal combustion engine to which an exhaust gas recirculation abnormality diagnosis device of the present invention is applied.

FIG. 2 is a flow chart showing an exhaust gas recirculation abnormality diagnosis routine of the embodiment of FIG.

FIG. 3 is a flowchart showing an abnormality diagnosis subroutine executed in step 209 of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Internal combustion engine main body 2 ... Intake passage 3 ... Intake pipe pressure sensor 5, 6 ... Crank angle sensor 10 ... Control circuit 11 ... Exhaust passage 30 ... Exhaust gas recirculation passage 31 ... Exhaust gas recirculation control valve

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location G01M 15/00 Z

Claims (1)

[Claims] 1. An exhaust gas recirculation means comprising: an exhaust gas recirculation means for recirculating a part of exhaust gas of an internal combustion engine to an intake system; and an intake pressure detection means for detecting an engine intake pipe pressure. In an exhaust gas recirculation abnormality diagnosis device equipped with a determination means for determining whether or not there is an abnormality in exhaust gas recirculation based on the intake pipe pressure when recirculation is performed and the intake pipe pressure when exhaust gas recirculation is stopped, An exhaust gas recirculation abnormality diagnosis device comprising: a misfire detecting means for detecting a misfire; and a prohibiting means for prohibiting the judgment by the judging means when the misfire detecting means detects a misfire of the engine.