JPS63192943A - Diagnosis device for exhaust gas recirculation apparatus in internal combustion engine - Google Patents

Abstract

PURPOSE:To make it possible to precisely diagnose an exhaust gas recirculation apparatus by judging that the exhaust gas recirculation apparatus fails when the temperature of an exhaust gas recirculation passage is below a predetermined value even though the count value by a counter exceeds a predetermined value. CONSTITUTION:A microcomputer 50 receives detection signals from a rotational speed sensor 56 provided in a distributor 55 in an internal combustion engine 1, a water temperature sensor 57, an intake pipe pressure sensor 58, a temperature sensor 59 disposed in an exhaust gas recirculation conduit 10, and therefore, judges whether or not an exhaust gas recirculation apparatus normally operates. In this arrangement, it is determined that the operation of the engine falls when a detection signal from the temperature sensor 59 is below a predetermined value and the engine rotational speed in a range in which exhaust gas recirculation is carried out, and therefore, the count-up is made by the counter. Further, when the count value by the counter exceeds a predetermined value, it is judged that the exhaust gas recirculation apparatus fails.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a 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.

Conventional Technology In internal combustion engines used in vehicles such as automobiles, various methods have been used to incorporate exhaust gas recirculation devices that recirculate exhaust gas in order to reduce NOx in the exhaust gas. ing. This type of exhaust gas recirculation device is disclosed in, for example, Japanese Utility Model Application No. 54-121116 and Japanese Patent Application Publication No. 58-88450.
No., Japanese Patent Publication No. 60-24303, etc.

Exhaust gas recirculation devices generally include an exhaust gas recirculation control valve for controlling the flow rate of exhaust gas recirculation, a negative pressure control valve for controlling back pressure, a temperature-sensitive valve, etc., and failure of these components may occur. In this case, there is a possibility that the internal combustion engine may be operated in a state where exhaust gas recirculation is not performed and NOx in the exhaust gas is not reduced. Even if exhaust gas recirculation is no longer performed due to a malfunction, 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 being aware of this, resulting in air pollution problems. . Furthermore, if exhaust gas recirculation is not performed within a predetermined operating range, there is a risk that knocking will occur, and fuel efficiency may deteriorate due to bomb loss caused by the intake air of the internal combustion engine itself.

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 is shown, for example, in Japanese Utility Model Application Publication No. 49-64623.

Problems to be Solved by the Invention Fault diagnosis of the exhaust gas recirculation device is performed by checking whether the temperature of the exhaust gas recirculation passage is above a predetermined value under conditions where exhaust gas recirculation should be performed. In other words, when the temperature is below a predetermined value, it may be determined that the exhaust gas is not flowing through the exhaust gas recirculation passage and that the exhaust gas recirculation device is malfunctioning. The actual temperature of the circulation passage changes as the exhaust gas recirculation is repeatedly executed and stopped, so it is difficult to accurately detect whether or not exhaust gas is flowing through the exhaust gas recirculation passage based only on the high or low temperature. It is difficult to diagnose the failure of the exhaust gas recirculation system by simply determining the temperature of the exhaust gas recirculation passage under conditions where exhaust gas recirculation is performed, but this cannot be done correctly. There is a risk.

SUMMARY OF THE INVENTION An object of the present invention is to provide an improved diagnosis system for an exhaust gas recirculation system that solves the above-mentioned problems.

Means for Solving the Problems According to the present invention, the above-mentioned objects include a temperature detection means for detecting the temperature of the exhaust gas recirculation passage, and a temperature detected by the temperature detection means is below a predetermined value. a determination means for determining whether or not the temperature is below a predetermined value, and an exhaust gas recirculation operation for detecting whether or not the operation range is in which exhaust gas recirculation is performed when the temperature is determined to be below a predetermined value by the determination means. When the exhaust gas recirculation operation range detection means and the exhaust gas recirculation operation range detection means detect that the operation range is in which exhaust gas recirculation is performed, the count is increased, and when it is detected that the exhaust gas recirculation is not in the operation range, the operation range is counted down. This is achieved by a diagnosis device for an exhaust gas recirculation device that has a counter and a determining means that determines that the exhaust gas recirculation device is malfunctioning when the counter value of the counter is greater than or equal to a predetermined value.

In other words, the exhaust gas recirculation operation range detecting means detects exhaust gas recirculation based on the intake air flow rate, intake pipe pressure, a combination of these and the engine speed, and a combination of these and the engine cooling water temperature. It is sufficient that the device detects the operating range in which exhaust gas recirculation is performed when the device is operating normally, and the detection items may be determined according to the exhaust gas recirculation control characteristics.

Effects and Effects of the Invention According to the above-described configuration, when the count value of the counter is greater than or equal to a predetermined value, if the exhaust gas recirculation device is operating normally, the temperature of the exhaust gas recirculation passage is ensured to be sufficient. If the temperature in the exhaust gas recirculation passage is below a predetermined value, it is determined that the exhaust gas recirculation system is malfunctioning, and accurate diagnosis is performed based on this. It becomes like this.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will now be described in detail by way of embodiments 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
Combustion chamber 5 via throttle valve 4 and intake manifold 3
The air-fuel mixture is sucked into the exhaust manifold 6, and burned gas, that is, exhaust gas, is discharged to the exhaust manifold 6.

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 in communication to the exhaust gas injection boat 8 by a conduit 10; The exhaust gas recirculation control valve 20 is connected to the valve boat 2
3 and a valve element 24, the valve boat 23 is opened and closed by the valve element 24 and its opening degree is controlled to control the exhaust gas recirculation flow rate. The valve element 24 is
connected to the diaphragm 26 of the diaphragm device 25;
When a negative pressure greater than a predetermined value (for example, -7C)+mHg is not introduced into the diaphragm chamber 27, the spring force of the compression coil spring 28 pushes down and closes the valve port 23, and a negative pressure greater than the predetermined value is introduced into the diaphragm chamber 27. When the valve boat 23 is opened, the valve boat 23 rises in response to the negative pressure against the spring force of the compression coil spring 28 and opens the valve boat 23.

The diaphragm chamber 27 of the exhaust gas recirculation control valve 20 is connected to an intake pipe negative pressure extraction boat 34 via a conduit 29, a negative pressure control valve 30 for controlling back pressure, a conduit 31, a temperature-sensitive valve 32, and a conduit 33. There is. As shown in the figure, the intake pipe negative pressure take-out boat 34 is located upstream of the throttle valve 4 when the throttle valve 4 is in the fully closed position, and is located upstream of the throttle valve 4 when the throttle valve 4 is opened beyond a relatively small predetermined opening. It is provided to be located on the downstream side.

The negative pressure control 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 port 35 to open the valve port, and when pressure above a predetermined value is introduced into the diaphragm chamber 39, the valve moves upward in the figure against the action of the compression coil spring 40. Displacing the valve element 36 to the valve port 35
The valve boat is located in a position where the valve boat is brought into contact with the valve boat and the valve boat is closed.

The diaphragm chamber 39 of the negative pressure control valve 30 is connected by a conduit 41 to a pressure chamber 4 between the valve boat 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 control valve 30 and the orifice 42 as described above is a well-known back pressure control mechanism, and in the exhaust gas recirculation operating range where intake pipe negative pressure is applied to the exhaust gas recirculation control valve 20. , adjust the negative pressure supplied to the diaphragm chamber 20 of the exhaust gas recirculation control valve 20 so as to keep the exhaust gas pressure in the pressure chamber 43 substantially constant; in other words, adjust the opening degree of the valve boat 23; As a result, the ratio of the exhaust gas recirculation flow rate to the intake air flow rate, that is, the EGR rate, is kept almost constant at all times.

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.

According to the configuration as described above, the exhaust gas recirculation control valve 20 applies a negative pressure to the conduit 29 that is greater than a predetermined value, for example -70 mg+.
When a negative pressure greater than Hg acts and the temperature of the cooling water of the internal combustion engine 1 is at a predetermined value, for example 60°C or higher, the temperature-sensitive valve 32 opens, and the exhaust gas is discharged at a flow rate corresponding to the amount of opening of the valve. Recirculation takes place.

In the figure, 50 indicates a microcomputer that performs diagnosis of the exhaust gas recirculation system. The microcomputer 50 has a general structure and includes a central processing unit (CPU) 51, a memory 52, an input boat 53, and an output boat 54. The number sensor 56 receives information regarding the rotational speed of the internal combustion engine 1 , the water temperature sensor 57 receives information regarding the temperature of the cooling water of the internal combustion engine 1 , the intake pipe pressure sensor 58 receives information regarding the intake pipe pressure, and the exhaust gas recirculation conduit 10 receives information regarding the intake pipe pressure from the intake pipe pressure sensor 58 . Information regarding the temperature of the conduit 10 is provided from a temperature sensor 59 provided in the middle of the pipe, and based on this information, the exhaust gas recirculation device operates normally according to the flowcharts shown in FIGS. 2 and 3. When it is determined that the exhaust gas recirculation system is not operating normally, an indicator lamp 62 is turned on.

Note that the temperature sensor 59 may be a sensor that detects the temperature of the outer wall of the conduit 10, and may have lower heat resistance and corrosion resistance than a sensor that comes into direct contact with the exhaust gas.

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

The EGR diagnosis routine shown in FIG. 2 is executed as an interrupt routine at predetermined time intervals, and in the first step 10, the exhaust gas recirculation passage temperature Tegr is read from the temperature sensor 59. Next, proceed to step 12.

In step 12, the exhaust gas recirculation passage temperature Tegr detected by the temperature sensor 59 is determined to be the determination temperature Tsθt.
A determination is made as to whether or not it is higher than that. Tθgr≧TSe
When T is t, exhaust gas recirculation is being performed, and at this time, it is assumed that the condition is normal and the process proceeds to step 32. On the other hand, when Tegr≧T set is not established, exhaust gas recirculation is not being performed. In this case, step 1
Proceed to step 4.

In step 14, the intake pipe pressure Pl is read from the intake pipe pressure sensor 58, and the engine rotation speed Ne is read from the rotation speed sensor 56, and the process then proceeds to step 16.

In step 16, it is determined whether the intake pipe pressure P1 detected by the intake pipe pressure sensor 58 is greater than or equal to P1set1 and less than or equal to P1set2, which is greater than this. If P 1set+≦P1≦P 1set2, the process proceeds to step 18; otherwise, the process proceeds to step 22.

In step 18, the rotation speed Ne of the internal combustion engine 1 detected by the rotation speed sensor 56 is set to a predetermined value N.
For example, it is determined whether or not the speed is 1600 rpm or more. When Ne≧NEISθt, the process proceeds to step 20, and when No≧N eset does not hold, the process proceeds to step 22.

In step 20, the count value C of the counter is incremented by a predetermined value α, and then the process proceeds to step 24.

In step 22, the count value C of the counter is decremented by a predetermined value β, and then the process proceeds to step 26.

In step 24, it is determined whether the count value C of the counter has reached a predetermined value Cset. Predetermined value C
set is determined according to the required diagnosis sensitivity, and when C>Cset, the process proceeds to step 30.

In step 26, it is determined whether the count value C of the counter is 0 or more. When C>□0 is not satisfied, the process proceeds to step 28, and in step 28, the count value C is set to 0.

In step 30, the indicator lamp 62 is turned on based on the failure determination. The lighting of this indicator lamp 62 allows the user to know that a failure has occurred in the exhaust gas recirculation system.

In step 32, the indicator lamp 62 is turned off based on the normality determination. This is when the exhaust gas recirculation system is operating normally.

3 and 4 show the relationship between the wall temperature of the exhaust gas recirculation conduit and the count value C of the counter due to exhaust gas recirculation. Figure 3 shows the state when exhaust gas recirculation continues for more than a predetermined time and the count value C on the counter is simply incremented, and Figure 4 shows the on/off state of exhaust gas recirculation. is repeated and the count value of the counter changes up and down.

By diagnosing the exhaust gas recirculation system according to the flowchart described above, the exhaust gas recirculation pipe can be maintained regardless of the complicated temperature changes in the exhaust gas recirculation pipe that occur when the exhaust gas recirculation is turned on and off. Reliable diagnosis without erroneous judgments can be performed from simple temperature judgments.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing one embodiment of an exhaust gas recirculation device incorporating a diagnosis device according to the present invention;
FIG. 2 is a flowchart showing the operation of the diagnosis device according to the present invention, and FIGS. 3 and 4 are graphs showing the relationship between the wall temperature of the exhaust gas recirculation conduit and the count value of the counter due to exhaust gas recirculation. .・1... Internal combustion engine, 3... Intake manifold, 4...
... Throttle valve, 5... Combustion chamber, 6... Exhaust manifold, 7... Exhaust gas intake boat, 8...
Exhaust gas injection boat, 9.10... conduit, 20...
Exhaust gas recirculation control valve, 21...inlet port, 22.
...Exit 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-sensitive valve, 33 ... Conduit, 34 ... Intake pipe negative pressure take-out boat, 35 ... Valve port, 36 ... Valve element,
37...Diaphragm. 38...Atmospheric release chamber, 39...Diaphragm chamber, 4
0... Compression coil spring, 41... Conduit, 42...
Orifice, 43...pressure chamber, 50...microcomputer. 51... Central processing unit, 52... Memory, 53
...Input port, 54...Output port, 55...
Distributor, 56... Rotation speed sensor, 57...
・・Water temperature sensor, 58・・Intake pipe pressure sensor, 59・
...Temperature sensor, 62...Indicator lamp Patent applicant Toyota Motor Corporation representative
Patent Attorney Masatake AkashiFigure 3Figure 4

Claims (1)

[Claims] temperature detection means for detecting the temperature of the exhaust gas recirculation passage; determination means for determining whether the temperature detected by the temperature detection means is below a predetermined value; If it is determined that the exhaust gas is recirculated, the exhaust gas recirculation operation range detection means detects whether or not the exhaust gas recirculation is performed. a counter that counts up when it is detected to be in an operating range where exhaust gas recirculation is to be carried out and counts down when it is detected that it is not in an operating range where exhaust gas recirculation is to be carried out; and an exhaust gas recirculation device when the counter value of the counter is equal to or higher than a predetermined value. 1. A diagnosis device for an exhaust gas recirculation device, comprising: determination means for determining that the exhaust gas recirculation device is malfunctioning.