JPH0275748A - Self diagnosis device of exhaust gas re-circulating device - Google Patents

Abstract

PURPOSE:To prevent change of operatability of a malfunctioned internal combustion engine and increase of concentration of poisonous element in exhaust gas by forcibly opening an EGR valve at the time of fuel supply stoppage when self-diagnosis of an exhaust gas re-circulating device is performed. CONSTITUTION:When a vehicle is driven, and a condition for stopping of fuel supply at the time of deceleration is established at a CPU 51, it is judged whether the condition is a fuel supply stopping delay period until the start of the fuel supply stopping or not. When the answer is NO, it is judged whether the fuel supplying stoppage at the time pf deceleration is carried out or not. When the fuel supply stoppage is carried out, electricity is applied to a solenoid control valve 45, a port a is connected to a port c, and a comparative large negative pressure in an intake pipe of a surge tank 3 is introduced in a diaphragm chamber 27 of an EGR valve 20 to forcibly open the EGR valve. An intake pipe pressure detected by an intake pipe pressure sensor 58 is taken both at the time that the EGR valve is forcibly opened and not opened. The malfunction of the EGR device is judged when the difference between the intake pipe pressure is a specified value or smaller.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a self-diagnosis device 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. .

[Prior Art] When exhaust gas recirculation is no longer performed due to a failure of the exhaust gas recirculation device, it is necessary to check whether the exhaust gas recirculation device is operating normally in order to inform the user of this fact and provide an opportunity for repair. Various self-diagnosis devices have been proposed to date. As one of these self-diagnosis devices, the exhaust gas recirculation control valve is forcibly opened and closed, and based on changes in the amount of intake air at this time, it is diagnosed whether the exhaust gas recirculation device is operating normally. A self-diagnosis device that performs this is known, and is disclosed in, for example, Japanese Patent Laid-Open No. 62-51747.

[Problems to be Solved by the Invention] In the self-diagnosis device for the exhaust gas recirculation device as described above, as shown in Japanese Utility Model Publication No. 52-9471, Diagnosis is more accurate than a self-diagnosis device that diagnoses whether the exhaust gas recirculation system is operating normally, but it is possible to diagnose whether the exhaust gas recirculation system is operating normally or not. The exhaust gas recirculation control valve is forcibly driven to open and close in the state in which the exhaust gas recirculation is forcibly turned on and off.
The amount of intake air changes, and the air-fuel ratio of the air-fuel mixture supplied to the internal combustion engine changes accordingly. This may cause the output torque of the internal combustion engine to fluctuate and cause a vehicle surge, and the concentration of harmful components such as HC and Co5Nox in the exhaust gas will increase. In particular, while exhaust gas recirculation is forcibly stopped, the Nox concentration in the exhaust gas increases.

SUMMARY OF THE INVENTION An object of the present invention is to provide a self-diagnosis device for an exhaust gas recirculation device that performs accurate diagnosis without adversely affecting the operability and exhaust gas performance of an internal combustion engine.

[Means for Solving the Problems] According to the present invention, the above object is to provide a fuel supply stop determination means for determining whether or not fuel supply is stopped, and a fuel supply stop determination means to determine whether or not the fuel supply is stopped. an exhaust gas recirculation forced start means for forcibly opening the exhaust gas recirculation control valve when it is determined that the exhaust gas recirculation control valve is open; an intake pipe pressure detection means for detecting the intake pipe pressure; and an intake pipe pressure detection means for detecting the intake pipe pressure. The intake pipe pressure detected by the means is captured by the exhaust gas recirculation forced start means when the exhaust gas recirculation control valve is forcibly opened and when it is not, and the intake pipe pressure is incorporated at these two times. This is achieved by a self-diagnosis device for an exhaust gas recirculation device, which has a determining means for determining that the exhaust gas recirculation device is malfunctioning when the difference between the intake pipe pressures is less than a predetermined value.

[Operations and Effects of the Invention] According to the configuration as described above, forcibly driving the exhaust gas recirculation control valve to open does not cause a change in the air-fuel ratio of the air-fuel mixture. Since this is performed when the fuel supply is stopped, the operability of the internal combustion engine will not change even if the exhaust gas recirculation control valve is forcibly opened for fault diagnosis and exhaust gas recirculation is started. It also does not increase the concentration of harmful components in exhaust gas.

The fuel supply may be stopped during deceleration, and in this case, the exhaust gas recirculation control valve is forced to open during deceleration, so the change in intake pipe pressure due to this is larger than during other operations. As a result, failure diagnosis based on this pressure difference can be performed more reliably than in the past.

[Example] The present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 shows an embodiment of an exhaust gas recirculation device incorporating a diagnosis device according to the invention.

In the figure, 1 indicates an internal combustion engine, and the internal combustion engine is
Air is drawn into the combustion chamber 5 through the throttle valve 2, surge tank 3, and intake manifold 4, fuel is injected and supplied from the fuel injector 61, and burned gas, that is, exhaust gas, is discharged to the exhaust manifold 6. ing.

The exhaust manifold 6 is provided with an exhaust gas intake boat 7 for exhaust gas recirculation, and the intake manifold 3 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 port 22, the inlet boat 21 being connected in communication with the exhaust gas intake boat 7 by a conduit 9, and the outlet port 2
2 is connected to the exhaust gas injection boat 8 by a conduit 1o. The exhaust gas recirculation control valve 20 is connected to the valve boat 23
and a valve element 24, and the valve boat 23 has a valve element 2.
4, and the degree of opening is controlled to control the exhaust gas recirculation flow rate. The valve element 24 is connected to a diaphragm 26 of a diaphragm device 25, and when a negative pressure greater than a predetermined value is not introduced into the diaphragm chamber 27, the valve element 24 is pushed down by the spring force of a compression coil spring 28 to close the valve boat 23, and the diaphragm When a negative pressure greater than a predetermined value is introduced into the chamber 27, the pressure rises in response to the negative pressure against the spring force of the compression coil spring 28.
The valve boat 23 is opened.

The diaphragm chamber 27 of the exhaust gas recirculation control valve 20 takes out negative pressure from the intake pipe through two conduits, an electromagnetic switching valve 45, a conduit 31, a temperature-sensitive valve 32, a conduit 33, and a negative pressure control valve 30 for back pressure control. It is communicatively connected to the boat 34. The intake pipe negative pressure take-out boat 34 is connected to the throttle valve 2 as shown in the figure.
When the throttle valve 2 is in the fully open position, it is located on the upstream side thereof, and when the throttle valve 2 is opened beyond a relatively small first predetermined opening degree, it is located on the downstream side thereof.

The negative pressure control valve 30 for back pressure control has a valve element 36 for opening and closing the valve boat 35 and a diaphragm 37 supporting the valve element. An open atmospheric release chamber 38 and a pressure chamber 39 are defined on the lower side, and the diaphragm acts as a compression coil spring when pressure (positive pressure) higher than a predetermined value is not introduced into the pressure chamber 39. 40 moves the valve element 36 away from the valve boat 35 to open the valve boat. On the other hand, when pressure above a predetermined value is introduced into the pressure chamber 39, the valve element 36 resists the action of the compression coil spring 40. In the figure, the valve element 36 is moved upward in the figure to a position where the valve element 36 is brought into contact with the valve boat 35 and the valve boat is closed.

The pressure chamber 39 of the negative pressure control valve 30 is connected by a conduit 41 to a back pressure chamber 43 between the valve boat 23 of the exhaust gas recirculation control valve 20 and an orifice 42 provided on the downstream side thereof. The exhaust gas pressure in the back pressure chamber is introduced.

Further, the diaphragm chamber 38 of the negative pressure control valve 30 is connected to an intake pipe negative pressure take-out boat 47 through a conduit 46 . The intake pipe negative pressure take-out boat 47 is as shown in the figure.
When the throttle valve 2 is in the fully closed position, it is located on the upstream side thereof, and when the throttle valve 2 is opened to a second predetermined opening degree or more that is larger than the first predetermined opening degree, it is located on the downstream side thereof. It is set up as follows.

The temperature-sensitive valve 32 is sensitive to the temperature of the cooling water of the internal combustion engine 1, and closes to cut off communication between the conduits 31 and 33 during the warm-up process when the temperature of the cooling water is below a predetermined value, for example, 60°C. However, when the cooling water temperature is above a predetermined value, communication between the conduits 31 and 33 is established.

The electromagnetic switching valve 45 has a boat C in addition to boat a to which the conduit 29 is connected and boat b to which the conduit 31 is connected.
It is communicatively connected to an intake pipe negative pressure take-out boat 49 provided in the intake pipe. When the electromagnetic switching valve 45 is energized, boat A is communicatively connected to boat C instead of boat B, whereas when it is not energized, boat A is communicatively connected to boat B instead of boat C.

Therefore, when the electromagnetic switching valve 45 is energized,
The conduit 29 is connected to an intake pipe negative pressure extraction boat 49 provided in the surge tank 3, and the intake pipe negative pressure is guided to the diaphragm chamber 27 of the exhaust gas recirculation control valve 20 regardless of the opening degree of the throttle valve 2. It becomes like this. Solenoid switching valve 45
The microcomputer 50 is configured to energize it.

According to the above configuration, when the electromagnetic switching valve 45 is not energized, the intake pipe negative pressure appearing on the intake pipe negative pressure extraction boat 34 is regulated by the negative pressure control valve 30, and the exhaust gas recirculation control is performed. The exhaust gas is guided into the diaphragm chamber 27 of the valve 20, and the exhaust gas is recirculated with a typical control characteristic, that is, when the throttle valve 2 is in the fully closed position, the exhaust gas recirculation control valve 20 is driven closed; On the other hand, solenoid switching valve 4
5 is energized, intake pipe negative pressure is introduced into the diaphragm chamber 27 from the intake pipe negative pressure extraction boat 49 regardless of the opening degree of the throttle valve 2, that is, even if the throttle valve 2 is in the fully closed position. As a result, the exhaust gas recirculation control valve 20 is forced to open.

The microcomputer 50 has a general structure, and includes a central processing unit (CPU) 51, a memory 52,
It has an input boat 53 and an output boat 54, and a rotation speed sensor 56 provided in a distributor 55 of the internal combustion engine 1 receives information regarding the rotation speed of the internal combustion engine 1, and a water temperature sensor 57 receives information regarding the temperature of the cooling water of the internal combustion engine 1. Information about
Information regarding the intake pipe pressure from the intake pipe pressure sensor 58,
Information regarding whether or not the throttle valve 2 is in the fully closed position is provided by the throttle switch 59, and based on this information, a fuel injection time control signal is output to the fuel injector 61, and an ignition timing control signal is output to the igniter 62. Furthermore, according to the flowchart shown in Figure 2, a diagnosis is made to determine whether the exhaust gas recirculation system is operating normally, and if it is determined that the exhaust gas recirculation system is not operating normally, the indicator The lamp 60 is turned on.

Next, the operation of the diagnosis apparatus according to the present invention will be explained with reference to the flowchart shown in FIG.

In the first step 10, the flag F_dny is 1
A determination is made as to whether this is the case. The flag Fdly is a flag set in the fuel supply stop control routine shown in Fig. 5, and the flag Fdly is a flag that is set in the fuel supply stop control routine shown in Fig. 5.The flag Fdly is a flag that is set in the fuel supply stop control routine shown in FIG. This flag is set to 1 during the stop delay period, and when the flag Fdly is 1, that is, during the fuel supply stop delay period, the process proceeds to step 12; otherwise, the process proceeds to step 14.

In step 12, information regarding the intake pipe pressure PM detected by the intake pipe pressure sensor 58 is acquired, and this information is used as the intake pipe pressure PMoff' when the exhaust gas recirculation is stopped.
It is done to memorize it as.

During the fuel supply stop delay engine when the flag F dly is 1, the fuel cut condition during deceleration is satisfied, and at this time, due to the general exhaust gas recirculation characteristics, the exhaust gas recirculation control valve 2o is Atmospheric pressure is introduced into the diaphragm chamber 27 and the valve is driven to close, and if the exhaust gas recirculation control valve 2o is not malfunctioning, this is the time when the valve is closed and exhaust gas recirculation is not being performed. The intake pipe pressure PM at this time is equal to the intake pipe pressure P when exhaust gas recirculation is stopped.
Mof'f'. Note that the intake pipe pressure PM detected by the intake pipe pressure sensor 58 is taken in by a time interrupt routine as shown in FIG.

In step 14, it is determined whether the flag F cut is 1 or not. The flag F cut is a flag set in the fuel supply stop control routine shown in FIG. 5, and is set to 1 while the fuel supply stop during deceleration is executed (started).

When the flag Fcut is not 1, it is assumed that the fuel supply is not stopped during deceleration and the process proceeds to step 30. On the other hand, when the flag Fcut is 1, that is, when the fuel supply is stopped during deceleration, the process proceeds to step 16.

In step 16, the electromagnetic control valve 45 is energized. As a result, boat a of the electromagnetic switching valve 45 is connected to boat C instead of boat B. By connecting the boat a of the electromagnetic switching valve 45 to the boat c, a relatively large intake pipe negative pressure appearing on the intake pipe negative pressure extraction boat 49 of the surge tank 3 is transferred to the exhaust gas recirculation control valve 2.
0 into the diaphragm chamber 27, and the exhaust gas recirculation control valve 20 is forced to open. After step 16, the process advances to step 18.

In step 18, it is determined whether a predetermined diagnostic delay time has elapsed. The diagnosis delay time is measured by a timer that starts when the electromagnetic switching valve 45 is energized, and when a predetermined period of time has elapsed since the electromagnetic switching valve 45 was energized, it is determined that the diagnosis delay time has elapsed and the process proceeds to step 20. Proceed to. This diagnosis delay time is the exhaust gas recirculation control valve 2.
It is sufficient that the time required for opening the valve under normal operation at 0 is determined according to the time required to open the valve.

In step 20, the intake pipe pressure PM detected by the intake pipe pressure sensor 58 is taken in and stored as the intake pipe pressure PMon when exhaust gas recirculation is executed. After step 20, the process proceeds to step 22.

In step 22, the intake pipe pressure PMof'f' when the exhaust gas recirculation is stopped, stored in step 12, is subtracted from the intake pipe pressure PMon when the exhaust gas recirculation is executed to obtain the differential pressure ΔPM of the intake pipe pressure. is calculated. After step 22, the process proceeds to step 24.

In step 24, it is determined whether the differential pressure ΔPM of the intake pipe pressure is larger than a predetermined value PMset. If the exhaust gas recirculation control valve 20 is in a state where it can operate normally, the exhaust gas recirculation control valve 20 should be opened by the forced valve opening drive in step 16, but even if this is not the case, For example, the intake pipe pressure PMon should be larger than the predetermined value PMset when viewed as a positive pressure than the intake pipe pressure PMorr, so ΔP M > P Ms
If it is, the exhaust gas recirculation control valve 20 is not malfunctioning, and the process proceeds to step 26. If not, the exhaust gas recirculation control valve 20 is not opened normally even if it is forced to open. At this time, it is assumed that the exhaust gas recirculation control valve 20 is out of order, and the process proceeds to step 28. Note that even in a failure state where the exhaust gas recirculation control valve 20 is stuck in the open state, ΔP M > P Mse
t is not established, and the process proceeds to step 28 for failure determination.

In step 26, the EGR diagnosis flag F is set to 0.

In step 28, the EGR diagnosis flag F is set to 1. When the flag is F-1, it means that the exhaust gas recirculation valve 20 is out of order, and the indicator lamp 60 is turned on.

In step 30, in order to complete the self-diagnosis, the power supply to the electromagnetic switching valve 45 is stopped, that is, the forced opening drive of the exhaust gas recirculation control valve 20 is canceled.

FIG. 4 shows the characteristics of the intake pipe pressure with respect to the throttle opening when exhaust gas recirculation is being performed and when it is not being performed. Since the differential pressure ΔPM of the intake pipe pressure between when exhaust gas recirculation is performed and when it is not performed becomes large when the throttle opening is small, as mentioned above, fuel supply is stopped during deceleration. In other words, when the throttle opening is 0 (idle opening), the failure diagnosis of the exhaust gas recirculation device is performed based on this differential pressure ΔPM, which makes this failure diagnosis more reliable.

FIG. 5 shows a fuel supply stop control routine during deceleration. In this control routine, the throttle switch 5
9 is on, that is, the throttle valve 2 is in the fully closed position, and the internal combustion engine 1 is detected by the rotation speed sensor 56.
When the rotational speed of the engine is equal to or higher than the first predetermined value Ne5et+, it is assumed that the fuel cut condition during deceleration has been met, and the flag Fdly is first set to 1, and when a predetermined fuel supply stop delay time has elapsed, the flag Fdly is set to 0. Then, the fuel supply stop flag F cut is set to 1.

Even if the throttle switch 59 is on, the engine speed N
When e is less than or equal to the second predetermined value N eset2 which is lower than the first predetermined value N eset+, both the flag F dny and the flag F cut are set to 0 in order to resume fuel supply.
will be carried out.

FIG. 6 shows a routine for calculating the fuel injection time. When the flag F cut is 1, it means that the fuel supply is stopped during deceleration, and the fuel injection time TAU is set to 0, whereas the flag F cut is 1. If not, the fuel injection amount TAU is calculated in accordance with intake pipe pressure, engine speed, cooling water temperature, etc. during normal fuel supply.

By performing control according to the flowchart ``t'' above, the self-diagnosis of the exhaust gas recirculation system is performed by forcibly opening the exhaust gas recirculation control valve 20 when fuel supply is stopped during deceleration when fuel supply is not performed. This is done by driving.

As a result, even if the exhaust gas recirculation control valve is forcibly opened and exhaust gas recirculation is started for fault diagnosis of the exhaust gas recirculation control device, the operability of the internal combustion engine will not change. Moreover, the concentration of harmful components in the exhaust gas does not increase.

In addition, during deceleration, the exhaust gas recirculation control valve 20 is forced to open due to the relatively large intake pipe negative pressure.
It can also be expected that the sticking of the exhaust gas recirculation control valve 20 will be eliminated.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram showing one embodiment of an exhaust gas recirculation device incorporating a self-diagnosis device according to the present invention, and FIG. 2 shows the operation of the self-diagnosis device for an exhaust gas recirculation device according to the present invention. Flowchart, FIG. 3 is a flowchart showing a time interrupt A/D conversion routine for acquiring intake pipe negative pressure information, and FIG. FIG. 5 is a flow chart showing an example of a fuel supply stop control routine during deceleration, and FIG. 6 is a flow chart showing an example of a fuel injection calculation routine. 1... Internal combustion engine, 2... Throttle valve, 3...
・Surge tank, 4...Intake manifold, 5...
combustion chamber. 6...Exhaust manifold, 7...Exhaust gas intake boat. 8... Exhaust gas injection boat, 9.10... Conduit, 2
0... Exhaust gas recirculation control valve, 21... Inlet boat, 22... Outlet port, 23... Valve boat, 24...
...Valve element. 25...Diaphragm device, 26...Diaphragm. 27...Diaphragm chamber, 28...Compression coil spring. 29... Conduit, 30... Negative pressure control valve, 31... Conduit, 32... Temperature sensing valve, 34... Intake pipe negative pressure take-out boat, 35... Valve boat, 36...・Valve element, 37...
・Diaphragm.

Claims (1)

[Claims] a fuel supply stop determination means for determining whether or not the fuel supply is stopped; and when the fuel supply stop determination means determines that the fuel supply is stopped, the exhaust gas recirculation control valve is forcibly opened. A driven exhaust gas recirculation forced start means, an intake pipe pressure detection means for detecting intake pipe pressure, and an exhaust gas recirculation forced start means that detects the intake pipe pressure detected by the intake pipe pressure detection means. If the difference in the built-in intake pipe pressure between the two times when the circulation control valve is forcibly opened and when it is not is less than a predetermined value, the exhaust gas recirculation system is malfunctioning. A self-diagnosis device for an exhaust gas recirculation device, comprising a determination means for determining that an exhaust gas recirculation device exists.