JPH0278765A - Self-diagnostic method for exhaust gas recycling device of internal combustion engine - Google Patents

Abstract

PURPOSE:To accurately diagnose troubles by continuing operation of an internal combustion engine even after OFF of the engine key switch, and judging troubles in an exhaust gas recycling device when the operating condition of the internal combustion engine does not change in spite of execution of increasing opening control of an exhaust gas recycling control valve. CONSTITUTION:When a key switch 56 is off, an exhaust gas recycling control valve 20 is fully opened by an exhaust gas recycling control device 62 through a step motor 33. At this time, if the step motor 33 is troubled or a sticking trouble is generated in a valve element 24, stall of an internal combustion engine is not generated, as the exhaust gas recycling control valve 20 can not be fully opened. Hereby, when the speed of the internal combustion engine 1 detected with an engine speed sensor 51 is not same as the predetermined value 0 or near to 0 or lower than it, the internal combustion engine 1 is continued to operate, and the trouble of the exhaust gas recycling control device 62 is judged.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a self-diagnosis method for diagnosing whether or not an exhaust gas recirculation device of an internal combustion engine used in a vehicle such as an automobile is operating normally. It depends.

[Prior Art] Exhaust gas recirculation devices incorporated in internal combustion engines used in vehicles such as automobiles generally include an exhaust gas recirculation control valve for controlling the flow rate of exhaust gas recirculation and a negative pressure control valve for controlling back pressure. ,
It contains temperature-sensitive valves, etc., and if a failure occurs in these components, exhaust gas recirculation will no longer occur and the N in the exhaust gas will be reduced.
There is a possibility that the internal combustion engine will be operated in a state where Ox is not reduced. Even if exhaust gas recirculation is no longer performed due to a failure, the internal combustion engine will continue to operate without any problems, so there is a risk that the driver will continue to operate the engine for a long period of time without noticing this, resulting in the problem of air pollution.

In view of the above-mentioned problems, a failure warning system has already been proposed which is configured to notify the user of the failure of the exhaust gas recirculation system and provide an incentive for repairs. This means, for example,
Utility Model Publication No. 52-9471, JP-A-55-123345, JP-A-62-71363, JP-A-62-51747
This is shown in each publication of the issue.

[Problems to be Solved by the Invention] Conventionally known failure warning devices determine failure of the exhaust gas recirculation device based on the temperature of the exhaust gas recirculation passage and the opening amount of the exhaust gas recirculation control valve. Therefore, a sensor for detecting temperature and valve opening amount, a switch, and a signal input circuit from these are required. This results in higher costs, and the structure becomes more complex as the number of parts increases, increasing the possibility that the failure warning device itself will fail.

As shown in Japanese Unexamined Patent Publication No. 62-51747, the exhaust gas recirculation control valve is controlled to be forced open or closed, and the opening of the exhaust gas recirculation control valve is controlled by the change in the amount of intake air at this time. When checking the valve or valve closing to determine a failure, in electronically controlled fuel injection internal combustion engines, the intake air amount may be detected by an intake air amount sensor installed for fuel control. , does not require special senna species. However, since this failure determination is performed during normal steady running, large engine torque fluctuations occur during steady running, and the concentration of harmful components in the exhaust gas increases. In other words, if the exhaust gas recirculation control valve is forced to open, the engine torque will be reduced, causing a temporary but significant deterioration in vehicle drivability, and there is a risk that unburned components in the exhaust gas will increase. be. In addition, if the exhaust gas recirculation control valve is forced to close, the engine torque will fluctuate, and the
There is a risk that the NOx concentration of

In view of the above-mentioned problems, the present invention provides accurate failure diagnosis without requiring the addition of new parts, deteriorating vehicle drivability, or increasing the concentration of harmful components in exhaust gas. The aim is to provide a new type of self-diagnosis method.

[Means for Solving the Problem] According to the present invention, the above-mentioned object is to continue operating the internal combustion engine even after the engine key switch is turned off when the internal combustion engine is stopped, and to maintain this state. Control is performed to increase the opening amount of the exhaust gas recirculation control valve at This is achieved by a self-diagnosis method for an exhaust gas recirculation device of an internal combustion engine, which is characterized in that it is determined that the exhaust gas recirculation device is malfunctioning when the operating state of the engine does not change.

Changes in the internal combustion engine may be found by engine speed, intake air amount, intake pipe pressure, and the like.

[Operations and Effects of the Invention] Since the self-diagnosis method according to the present invention is performed when the internal combustion engine is stopped, even if the output torque of the internal combustion engine decreases due to the exhaust gas recirculation control valve being forcibly opened, Even if an engine stall occurs, the drivability of the vehicle is not affected. Also, when the engine is stopped, it is equivalent to idling, so
At this time, even if the concentration of unburned components in the exhaust gas increases due to the forced opening of the exhaust gas recirculation control valve, the concentration of unburned components does not increase dramatically because the amount of fuel itself is small.

〔Example〕

The invention will now be described in detail by way of example embodiments with reference to the accompanying drawings.

FIG. 1 shows an example of a control device used to carry out the self-diagnosis method for an exhaust gas recirculation device according to the present invention. In FIG. 1, 1 indicates an internal combustion engine, which takes in air through a throttle valve 2, a surge tank 4, and an intake manifold 5, and injects fuel such as gasoline through a fuel injection valve 12. A mixture of fuel and air is ignited by a spark plug 13, and burned gas, that is, exhaust gas, is discharged to an exhaust manifold 6.

The exhaust manifold 6 is provided with an exhaust gas intake boat 7 for exhaust gas recirculation, and the surge tank 4 is provided with an exhaust gas injection boat 8. are connected to each other by a conduit 9 for exhaust gas recirculation, an exhaust gas recirculation control valve 20 and a conduit 10.

The exhaust gas recirculation control valve 20 has an inlet boat 21 and an outlet boat 22, the inlet boat 21 being connected in communication with the exhaust gas intake boat 7 by a conduit 9, and the outlet boat 2
2 is connected in communication to the exhaust gas injection boat 8 by a conduit 10. The exhaust gas recirculation control valve 20 has a valve boat 23 and a valve element 24, and the valve boat 23 has a valve element 24.
The opening degree is controlled to control the exhaust gas recirculation flow rate. The valve element 24 is
It is connected to a step motor 33 and is driven to open and close by the step motor 33.

The fuel injection valve 12 is controlled by a fuel injection control device 60, the spark plug 13 is controlled by an ignition control device 61, and the step motor 3 is controlled by a fuel injection control device 60.
3 are operated and controlled by an exhaust gas recirculation control device 60, and a fuel injection control device 60, an ignition control device 61, and an exhaust gas recirculation control device 62 are supplied with current from a battery 57 in response to opening and closing of a main relay 58. , are adapted to operate based on control signals from a common microcomputer 50.

The microcomputer 50 transmits information regarding the rotation speed of the internal combustion engine 1 from the rotation speed sensor 51 to the intake pipe pressure sensor 5.
2, information regarding the intake pipe pressure and atmospheric pressure, information regarding the intake air temperature from the intake air temperature sensor 53, information regarding the throttle opening of the throttle valve 2 from the throttle opening sensor 54, and information regarding the throttle opening of the throttle valve 2 from the cooling water temperature sensor 55. Information regarding the temperature of the cooling water and information regarding the opening/closing of the switch are given from the key switch 56, and based on these information, a control signal regarding the fuel injection amount and a control signal regarding the advance angle of the ignition timing are sent to the exhaust gas recirculation flow rate. It outputs control signals for control to the control devices 60, 61, and 62, respectively, performs failure diagnosis of the exhaust gas recirculation device according to the flowchart shown in FIG. 2, and controls the lighting of the indicator lamp 63. It is supposed to be done.

Next, an embodiment of the self-diagnosis method for an exhaust gas recirculation device according to the present invention will be described with reference to the flowchart shown in FIG.

When the key switch 56 is closed when starting the internal combustion engine 1, that is, when the key switch 56 is turned on, step 1o is first executed.

In step 10, the main relay 58 is closed, that is, turned on. Closing of main relay 58 causes fuel injection control device 60. Each of the ignition control device 61 and the exhaust gas recirculation control device 62 is energized, and a starter (not shown) is energized to start the internal combustion engine 1.

After step 10, proceed to step 2o.

In step 20, it is determined whether flag F is 1 or not. This flag F is stored in the non-volatile memory of the micro combinator 50, and the flag F-1 is when the exhaust gas recirculation device has already been diagnosed as having failed, and in this case, the process proceeds to step 30.

In step 30, the indicator lamp 63 is turned on. The lighting of the indicator lamp 63 allows the driver to know that the exhaust gas recirculation system is out of order.

In step 20, if the flag is not F-1, the process advances to step 40.

In step 40, it is determined whether the key switch 56 is opened, that is, whether the key switch 56 is in the OFF state. When the key switch 56 is in the OFF state, it means that the internal combustion engine 1 is stopped, and in this case, the process advances to step 50.

In step 50, a control signal for fully opening the exhaust gas recirculation control valve 20 is output to the exhaust gas recirculation control device 62.

As a result, the exhaust gas recirculation control device 62 supplies a current or an electric signal to the step motor 33 to fully open the exhaust gas recirculation control valve 2o. At this time, if the step motor 33 is not malfunctioning and is operating normally, and the valve element 24 of the exhaust gas recirculation control valve 20 is not stuck, the valve element 24 will move fully open and the exhaust gas The recirculation control valve 20 becomes fully open.

When the engine is stopped, it is in idle operation, so if the exhaust gas recirculation control valve 20 is fully opened at this time, the exhaust gas will be recirculated with a large flow rate, and the internal combustion engine 1 will stall due to a misfire. On the other hand, if the step motor 33 is malfunctioning or the valve element 24 is stuck, the exhaust gas recirculation will not be possible even if the step motor 33 is given a current or electrical signal to fully open the exhaust gas recirculation control valve 2o. The circulation control valve 20 maintains a fully open state or a state close to it, and since this does not become a fully open state, the internal combustion engine 1
does not cause stall.

After step 50, proceed to step 60;
In this case, hold control is performed to keep the exhaust gas recirculation control valve 20 fully open for a predetermined period of time.

After step 60, the process proceeds to step 70.

In step 70, it is determined whether the rotation speed Ne of the internal combustion engine 1 detected by the rotation speed sensor 51 is equal to or less than a predetermined value N eset of 0 or close to 0. It will be done.

When Ne≦N eset, exhaust gas recirculation control valve 2
This is when the internal combustion engine 1 stalls due to full throttle.
At this time, it is assumed that the exhaust gas recirculation device is operating normally, and the process proceeds to step 90, whereas Ne≦N eset
When this is not the case, the internal combustion engine 1 has not stalled and continues to operate even though the exhaust gas recirculation control valve 20 has been fully opened, and in this case, the exhaust gas recirculation control device is not activated. It is assumed that the device is out of order and the process proceeds to step 80.

In step 80, flag F is set to 1. Since this flag F is stored in the nonvolatile memory of the microcomputer 50, it is saved even after power supply to the microcomputer 50 is stopped. As a result, when the internal combustion engine 1 is restarted, the indicator lamp 63 is turned on based on the determination of the flag F-1.

After step 80, the process proceeds to step 90. Step 90
In this case, the exhaust gas recirculation control valve 20 is installed for restarting.
Control is performed to fully open the valve.

After step 90, the process proceeds to step 100.

In step 100, main relay 58 is turned off. By turning off the main relay 58, even if the internal combustion engine 1 is still operating at this time, the fuel supply and ignition are stopped, so that the internal combustion engine 1 is turned off.
operation will be stopped.

FIG. 3 shows the opening/closing timing of the key switch, the main relay, and the exhaust gas recirculation control valve during self-diagnosis of the exhaust gas recirculation system performed in the manner described above.

FIG. 4 shows another example of a control device used to carry out the self-diagnosis method for an exhaust gas recirculation device according to the present invention.

In this embodiment, the valve element 24 of the exhaust gas recirculation control valve 20 is connected to a diaphragm 26 of a diaphragm device 25, and a diaphragm chamber 271; 28 to close the valve boat 23, and when a negative pressure greater than a predetermined value is introduced into the diaphragm chamber 27, it rises against the spring force of the compression coil spring 28 in response to the negative pressure. The valve boat 23 is opened.

The diaphragm chamber 27 of the exhaust gas recirculation control valve 20 is connected via a conduit 29, a negative pressure adjustment valve 30 for controlling back pressure, and a conduit 31 to an intake pipe negative pressure take-out boat 32 provided in the surge tank. . As shown in the figure, the intake pipe negative pressure extraction boat 32 is provided downstream of the throttle valve 2, and is always subjected to intake pipe negative pressure.

The negative pressure regulating valve 30 has a valve element 36 that opens and closes the valve boat 35 and a diaphragm 37 supporting the valve element. A chamber 38 and a diaphragm chamber 39 are defined on the lower side, and the diaphragm closes the valve by the action of a compression coil spring 40 when pressure (positive pressure) higher than a predetermined value is not introduced into the diaphragm chamber 39. Element 3
6 is separated from the valve boat 35 to open the valve boat, and when a pressure higher than a predetermined value is introduced into the diaphragm chamber 39, it moves upward in the figure against the action of the compression coil spring 40. Displace the valve element 36 from the valve boat 35
The valve port is located in a position where the valve port is closed by contacting the valve port.

The diaphragm chamber 39 of the negative pressure regulating valve 30 is connected by a conduit 41 to a pressure chamber 4 between the valve port 23 of the exhaust gas recirculation control valve 20 and an orifice 42 provided on the downstream side thereof.
3, and the exhaust gas pressure in the pressure chamber is introduced.

The structure consisting of the negative pressure regulating valve 30 and the orifice 42 as described above is a well-known back pressure control mechanism, and the diaphragm of the exhaust gas recirculation control valve 20 keeps the exhaust gas pressure in the pressure chamber 43 almost constant at all times. The negative pressure supplied to the chamber 20 is adjusted, in other words, the opening degree of the valve boat 23 is adjusted, thereby maintaining the ratio of the exhaust gas recirculation flow rate to the intake air kfA, that is, the EGR rate, almost constant at all times. It looks like this.

The atmosphere opening chamber 38 of the negative pressure regulating valve 30 is connected to an intake pipe negative pressure take-out boat 46 through a conduit 47 . The intake pipe negative pressure extraction boat 46 is located upstream of the throttle valve 2 when the opening is below a predetermined opening, and is located downstream of the throttle valve 2 when the opening is above the predetermined opening to remove the intake pipe negative pressure. It is now being influenced by

In this embodiment, the intake pipe negative pressure appearing in the intake pipe negative pressure take-off boat 46 in response to f5 of the throttle valve 2 is supplied to the atmosphere opening chamber 38 of the negative pressure regulating valve 30, thereby achieving medium load operation. At times, the EGR rate will increase.

A negative pressure switching valve 45 is provided in the middle of the conduit 29.

The negative pressure switching valve (VSV) 45 is configured as an electromagnetically actuated three-way switching valve, and is connected to a port a connected to the diaphragm chamber 27, a negative pressure boat b connected to the negative pressure regulating valve 34, and the atmosphere. When energized, that is, in the on state, port a is disconnected from the atmospheric pressure boat C and connected to negative pressure boat B, whereas when not energized, that is, When in the off state, port a is disconnected from negative pressure boat b and connected to atmospheric pressure boat C. Current is selectively supplied to the negative pressure switching valve 45 from a battery 57 via a main relay 58 and a switch 64 whose opening and closing are controlled by a microcomputer 50.

In this embodiment as well, failure diagnosis of the exhaust gas recirculation system is performed according to the flowchart as shown in FIG. In this case, the control to fully open the exhaust gas recirculation control valve 20 is to close the switch 64 and close the negative pressure switching valve 45.
This is done by connecting port a of , to negative pressure boat b. In this fault diagnosis, the exhaust gas recirculation control valve 20
In addition to the failure diagnosis of the negative pressure switching valve 45, the failure diagnosis of the negative pressure switching valve 45 is also performed.

FIG. 5 shows another embodiment of the self-diagnosis method for an exhaust gas recirculation device according to the present invention. In this embodiment, steps 42 and 44 are provided between steps 40 and 50, and when the exhaust gas recirculation control valve is fully opened, the internal combustion engine is under conditions that will inevitably stall. Self-diagnosis is performed by fully opening the exhaust gas recirculation control valve only when the exhaust gas recirculation control valve is fully opened, thereby more reliably avoiding erroneous failure determinations.

The self-diagnosis execution determination routine at step 42 is shown in FIG. In this routine, the coolant temperature Tv detected by the coolant temperature sensor 55 reaches the first predetermined value T.
vset+, for example, at 80°C or higher and at the second predetermined value T
wset2, for example, the temperature is 100° C. or less, the throttle valve 2 is fully closed, and the engine rotation speed Ne detected by the rotation speed sensor 51 is set to a predetermined value Neset2, for example, 900 rp.
11 or less, the vehicle interior air conditioner is off, and the vehicle speed detected by the vehicle speed sensor 65 is at the predetermined value VSet%.
For example, the intake pipe absolute pressure P detected by the intake pipe pressure sensor 52 is 0 kIl/h or less, that is, when the vehicle is stopped.
1m is the predetermined value PImset, for example 30011111
1 gA bs or less for a predetermined period of time determined by the set value Cset of the count value C of the counter, for example 1 gA bs or less.
If the duration continues for more than a second, the flag Fdla is set to 1 to allow execution of the self-diagnosis; otherwise, the count value C of the counter is reset to 0, and Fdla is set to 0 to prevent the self-diagnosis from being executed. .

In step 44 of the self-diagnosis routine, the flag F determined in the self-diagnosis execution determination routine as described above is
When dia is 1, the process proceeds to step 50 so that self-diagnosis is started; otherwise, the process proceeds to step 100 so that the self-diagnosis is not executed, and the main relay is turned off.

Therefore, in this case, when the engine is stopped and the driver depresses the accelerator pedal and turns off the key, the exhaust gas recirculation control valve is fully opened and the engine stalls. Self-diagnosis of the exhaust gas recirculation system based on whether As a result, it is possible to avoid erroneously determining that the exhaust gas recirculation control valve is malfunctioning even though the exhaust gas recirculation control valve is in a state where it can operate normally.

Note that the self-diagnosis execution determination routine in step 42 may be performed in advance before the key switch is turned off. In this case, it is only necessary to determine that the predetermined operating state has continued for a predetermined period of time before the key switch is turned off. It is no longer necessary to wait for a long time.

That is, in this embodiment, when the key switch is off, the exhaust gas recirculation control is activated under conditions in which the internal combustion engine may not stall even if the exhaust gas recirculation control valve is fully opened. If the self-diagnosis by fully opening the valve is not performed and the engine is quickly stopped by turning off the main relay, and the exhaust gas recirculation control valve is fully opened, the exhaust gas recirculation control valve will be activated only when the internal combustion engine inevitably stalls. Self-diagnosis will be carried out by fully opening the engine.

FIG. 7 shows another example of a control device used to carry out the self-diagnosis method for an exhaust gas recirculation device according to the present invention. In addition, in Fig. 7, the parts corresponding to Fig. 1 are shown in Fig. 1.
They are indicated by the same reference numerals as those in the figures. In this embodiment, an auxiliary intake passage 48 is provided to bypass the throttle valve 2 for controlling the idle speed (idle rotational speed). Auxiliary intake passage 48
There is an electromagnetically actuated idle speed control valve (IS) in the middle of the
CV) 49 is provided. The operation of the idle speed control valve 49 is controlled by an idle speed control device 66, and the idle speed control device 66 is supplied with current from a battery 57 according to the opening and closing of a main relay 58, and operates based on a control signal from a microcomputer 50. It looks like this.

8 to 14 show one embodiment of a self-diagnosis method and an accompanying internal combustion engine control method according to the present invention in the exhaust gas recirculation system shown in FIG. 7.

FIG. 8 shows a main routine for controlling the operation of an internal combustion engine, including a self-diagnosis method for an exhaust gas recirculation system according to the present invention. Step 200 is an internal combustion engine control processing step when the key switch 56, which is the ignition switch of the internal combustion engine, is in the on state, and in this step, the interrupt routine shown in FIG. 13, ignition timing calculation processing using an interrupt routine as shown in FIG. 14,
Exhaust gas recirculation control is performed using an interrupt routine as shown in FIG.

This step also includes a flag XE, which indicates that the exhaust gas recirculation system is abnormal, as shown in Figure 9.
Determine whether GRF is 1 or not, and
When this is the case, the process includes a process indicating that the exhaust gas recirculation device is abnormal, for example, a display process step of turning on the indicator lamp 63.

After step 200, the process advances to step 210, in which it is determined whether 115W is on, that is, whether the key switch 56 is on. When the key switch 56 is on, the process returns to step 200, and when the key switch 56 is off, that is, when the engine is stopped, the process proceeds to step 220.

In step 220, the LL signal indicating the fully closed throttle is sent from the throttle opening sensor 54 to the rotation speed sensor 51.
The rotation speed NE of the internal combustion engine 1 is read from the vehicle speed sensor 65, the vehicle speed SPD is read from the vehicle speed sensor 65, and the current exhaust gas recirculation control valve 20 is read.
The amount of electricity supplied to the step motor 33 is read as the actual opening signal R3TEP of the exhaust gas recirculation control valve 20. After step 220, the process proceeds to step 230.

Steps 230 to 260 are steps for determining whether or not the exhaust gas recirculation system is in a condition that allows it to perform self-diagnosis based on the signal read in step 220. Valve 2 is in the fully open position, the engine speed is equivalent to the idle speed,
Only when the vehicle speed is substantially O and the actual opening degree of the exhaust gas recirculation control valve 20 is 0, that is, when all the conditions that it is fully open, proceed to step 260; otherwise, proceed to step 270. and skip step 280 and perform step 2
Step 90 is performed.

In step 270, the flag Xl5CFB for permitting idle speed control is set to 0 to prohibit idle speed control.

This prohibition of idle speed control is to avoid misdiagnosis due to fluctuations in intake pipe pressure caused by idle speed control in the next exhaust gas recirculation abnormality diagnosis process. be. Step 270
Next, the process proceeds to step 280.

In step 280, exhaust gas recirculation abnormality diagnosis processing is executed according to the exhaust gas recirculation abnormality diagnosis routine shown in FIG.

After step 280, the process proceeds to step 290, where control of fuel injection and ignition timing is ended. Step 290 is followed by step 30
Go to 0.

In step 300, main relay 58 is turned off. This causes the internal combustion engine 1 to stop.

FIG. 10 shows an abnormality diagnosis processing routine for the exhaust gas recirculation device. In step 291, the current intake pipe pressure PIM detected by the intake pipe pressure sensor 52 is converted into the intake pipe pressure PM before the forced opening of the exhaust gas recirculation control valve 20.
It is taken in as O. After step 291, the process advances to step 292.

In step 292, the valve opening instruction signal TSTEP of the exhaust gas recirculation control valve 20 is set to α. α
is set as an opening degree that causes an increase in intake pipe pressure by a predetermined amount or more if the exhaust gas recirculation control valve 20 opens while the internal combustion engine is in an idling state. This α may be determined according to the intake pipe pressure characteristics as shown in FIG.

After step 292, the process advances to step 293.

In step 293, it is determined whether the actual opening signal RSTEP of the exhaust gas recirculation control valve 20 has reached α. When RSTEP-α is not reached, this step is repeatedly executed, and when RSTEP-α is reached, the process proceeds to step 294.

In step 294, the current intake pipe pressure PIM detected by the intake pipe pressure sensor 52 is taken in as the intake pipe pressure PME after the exhaust gas recirculation control valve 20 is forcibly opened. Step 294 is followed by step 295
Proceed to.

In step 295, the intake pipe pressure PME after forced valve opening
The difference ΔLPM between the intake pipe pressure PMO and the intake pipe pressure PMO before forced valve opening is calculated. Step 295 is followed by step 2
Proceed to 96.

In step 296, it is determined whether the difference in intake pipe pressure DLPM is greater than or equal to a predetermined value A. DLPM＞
A is the time when the exhaust gas recirculation control valve 20 is actually opened, and at this time, the abnormality diagnosis processing routine for the exhaust gas recirculation device is completed without executing step 297, and the DLPM >A means that the exhaust gas recirculation control valve 20 does not open by the predetermined amount α, and in this case, the process advances to step 297.

In step 297, a flag XEGRF indicating that the exhaust gas recirculation system is abnormal is set to 1. By setting the flag XEGRF to 1 in this step, when the engine is restarted, the indicator lamp 63 is activated according to the flowchart shown in FIG.
This is done to indicate to the driver that there is an abnormality in the exhaust gas recirculation system.

FIG. 11 shows the exhaust gas recirculation control routine under normal operating conditions. In step 400, it is determined whether the abnormality flag XEGRF is 0 or not. When it is not XEGRF-0, it means that the exhaust gas recirculation device is malfunctioning, and in this case, this control routine ends immediately to prohibit exhaust gas recirculation control, whereas when it is XEGRF-0, the step Proceed to 402.

In step 402, the current exhaust gas recirculation control valve opening command value TSTEP and the current actual opening value RSTEP are read. After step 402, the process advances to step 404.

In step 404, it is determined whether the opening instruction value TSTEP and the actual opening value RSTEP are equal. T
If STEP-RSTEP, the process advances to step 406; otherwise, the process advances to step 408.

In step 406, the actual opening value RSTEP is held at the current value.

In step 408, it is determined whether the opening degree command value TSTEP is larger than the actual opening value RSTEP. T
When STEP>RSTEP, the process proceeds to step 410; otherwise, the process proceeds to step 412.

In step 410, the actual opening value RSTEP is increased by one count.

In step 412, the actual opening value RSTEP is decreased by one count.

By executing the above-described control routine, when the exhaust gas recirculation device is not abnormal, the opening degree of the exhaust gas recirculation control valve 20 is controlled to an appropriate opening degree according to the opening degree instruction value.

FIG. 12 shows the idle speed control routine. In step 420, the idle speed control valve 4
9 opening instruction value Tl5C5 and idle speed control valve 4
The actual opening value RISCS found from the amount of control electricity applied to the valve is read. Step 42
After 0, the process proceeds to step 422.

In step 422, it is determined whether the idle speed control permission flag Xl5CFB is 1 or not. When Xl5CFB-1, that is, when idle speed control is permitted, the process proceeds to step 424; otherwise, when it is prohibited, the process proceeds to step 426.

In step 424, it is determined whether the opening instruction value Tl5C8 and the actual opening value RISCS are equal. T
If it is 15CS-RISCS, the process proceeds to step 426; otherwise, the process proceeds to step 428.

In step 426, the actual opening value RISC3 is held at the current value.

In step 428, it is determined whether the opening degree instruction value Tl5C8 is larger than the actual opening degree value RISC8. T
If l5CS>RISCS, the process proceeds to step 430; otherwise, the process proceeds to step 432.

In step 430, the actual opening value RISC9 is increased by one count.

In step 432, the actual opening value RISC8 is decreased by one count.

As a result, when idle speed control is permitted, the opening degree of the idle speed control valve 49 is controlled according to the opening degree command value Tl5CS, and when it is prohibited, the current opening degree is maintained.

FIG. 13 shows the fuel injection time calculation routine. In step 460, the basic fuel injection time TP is determined from a data table based on the intake pipe pressure detected by the intake pipe pressure sensor 52 and the engine speed detected by the rotation speed sensor 51. After step 460, the process proceeds to step 462.

In step 462, it is determined whether the abnormality flag X EG RF of the exhaust gas recirculation system is 0 or not. When the flag is XEGRF-0, it means that the exhaust gas recirculation device is operating normally, and in this case, the process advances to step 464. If not, that is, when the exhaust gas recirculation device is abnormal, the fuel injection time is The process advances to step 466 to prohibit the EGR correction from being performed.

In step 464, the EGR correction coefficient FEGR for the fuel injection time is found from the data table based on the engine speed and intake pipe pressure, and the EGR correction for the basic fuel injection time is performed by multiplying this by the basic fuel injection time TP. be exposed.

After step 464, the process proceeds to step 466.

In step 466, the fuel injection time TAU is calculated by multiplying the basic fuel type injection time TP by another fuel correction coefficient F based on the engine cooling water temperature, intake air temperature, etc.

FIG. 14 shows the ignition timing calculation routine. At step 470, the basic ignition timing ABASE is determined from a data table based on intake pipe pressure and engine speed. Step 470 is followed by step 472
Proceed to.

In step 472, it is determined whether the abnormality flag XEGRF of the exhaust gas recirculation system is 0 or not. When XEGRF-0, that is, when the exhaust gas recirculation device is normal, proceed to step 474; otherwise,
In other words, if the exhaust gas recirculation system is abnormal, the ignition timing E
The process advances to step 476 to prohibit GR correction from being performed.

In step 474, an EGR correction value AEG for ignition timing is determined from a data table based on engine speed and intake pipe pressure.
EGR correction of the basic ignition timing is performed by calling R and dividing this by the basic ignition timing ABASE. Step 4
After 74, the process proceeds to step 476.

In step 476, another ignition timing correction value AAD is added to the basic ignition timing ABASE, and the actual ignition timing AOP is
is determined.

Although the present invention has been described in detail with respect to specific embodiments above, the present invention is not limited to these, and it is understood that various embodiments can be made within the scope of the present invention. It will be clear to those skilled in the art.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram showing one embodiment of a control device used to implement the self-diagnosis method for an exhaust gas recirculation device according to the present invention, and FIG. 2 is a self-diagnosis method for an exhaust gas recirculation device according to the present invention. FIG. 3 is a time chart showing the opening/closing timing of the key switch, main relay, and exhaust gas recirculation control valve when implementing the self-diagnosis method for the exhaust gas recirculation device according to the present invention. , FIG. 4 is a schematic configuration diagram showing another embodiment of a control device used for carrying out the self-diagnosis method for an exhaust gas recirculation device according to the present invention, and FIG. A flowchart showing another embodiment of the self-diagnosis method, FIG. 6 is a flowchart showing an example of the self-diagnosis execution determination routine shown in FIG. 5 and used in the embodiment, and FIG. A schematic configuration diagram showing another example of a control device used to carry out the self-diagnosis method for a recirculation device, FIG. A flowchart showing the routine, FIG. 9 is a flowchart showing a part of the internal combustion engine control processing steps, and FIG.
Fig. 0 is a flowchart showing the abnormality diagnosis routine of the exhaust gas recirculation device, Fig. 11 is a flowchart showing the control routine of the exhaust gas recirculation device, Fig. 12 is a flowchart showing the idle speed control routine, and Fig. 13 is a flowchart showing the fuel injection control routine. Flowchart showing time calculation routine, 14th
15 is a flowchart showing the ignition timing calculation routine, and FIG. 15 is a graph showing the relationship between the opening degree of the exhaust gas recirculation control valve and the intake pipe pressure during idling operation. DESCRIPTION OF SYMBOLS 1... Internal combustion engine, 2... Throttle valve, 4... Surge tank, 5... Intake manifold, 6... Exhaust manifold, 7... Exhaust gas intake boat, 8...
Exhaust gas recirculation injection boat, 9.1o... conduit, 12
...Fuel injection valve, 13...Spark plug, 20...
Exhaust gas recirculation control valve, 21... Inlet boat, 22.
...Exit boat. 23... Valve boat, 24... Valve element, 25... Diaphragm device, 26... Diaphragm, 27...
Diaphragm chamber, 28... Compression coil spring, 29...
- Conduit, 30... Negative pressure regulating valve, 31... Conduit, 32
...Intake pipe negative pressure take-out boat, 33...Step motor, 35...Valve port, 36...Valve element, 37...
Diaphragm, 38... Atmospheric release chamber, 39... Diaphragm chamber, 40... Compression coil spring, 41... Conduit, 42... Orifice. 43...Pressure chamber, 45...Negative pressure switching valve, 46...
Intake pipe negative pressure extraction port, 47... Conduit, 48... Auxiliary intake passage, 49... Idle speed control valve, 50
... Microcomputer, 51 ... Rotation speed sensor, 52 ... Intake pipe pressure sensor, 53 ... Intake air temperature sensor, 54 ... Throttle opening degree, 55 ... Cooling water temperature sensor, 56. ...Key switch, 57...Battery, 58...Main relay, 60...Fuel injection control device, 61...Ignition control device, 62...Exhaust gas recirculation control device, 63... Indicator lamp, 64・
...Switch, 65...Vehicle speed sensor, 66...Idle speed control device Applicant: Toyota Motor Corporation Representative Patent Attorney Masatake AkashiFigure 2 ← Reluctance or L! :IR Figure 9↓

Claims (1)

[Claims] Even after the engine key switch is turned off when the internal combustion engine is stopped, the internal combustion engine continues to operate, and in this state the exhaust gas recirculation control valve is controlled to increase its opening amount, reducing the amount of exhaust gas. Detecting whether the operating state of the internal combustion engine has changed due to execution of control to increase the opening amount of the recirculation control valve;
A self-diagnosis method for an exhaust gas recirculation device of an internal combustion engine, characterized in that the exhaust gas recirculation device is determined to be malfunctioning when the operating state of the internal combustion engine does not change.