JPH01163450A - Diagnosis device for exhaust gas recirculating device for internal combustion engine - Google Patents

Abstract

PURPOSE:To perform reliable diagnosis of an exhaust gas recirculating device without erroneous decision, by a method wherein, when an air-fuel ratio learning high land correction factor is below a given value, diagnosis is prohibited. CONSTITUTION:A microcomputer 50 performs diagnosis of an exhaust gas recirculating device as well as control of an fuel injection amount. From an intake air flow rate detected by an airflow meter 3 and the number of revolutions of an internal combustion engine 1 detected by a number of revolutions sensor 56, an air amount per one stroke of an engine is calculated, and when it exceeds a lower limit value and is below an upper limit value, an air-fuel ratio learning high land correction factor for control of an air-fuel ratio is inputted. When the air-fuel ratio learning high land factor is below a given value, reset is made so that diagnosis is prohibited. Thus, only when diagnosis is prohibited and an atmospheric pressure is not so low and reliably accurate diagnosis is effected, diagnosis is executed during lowering of an atmospheric pressure, e.g. during running on a high land.

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.

2. Description of the Related 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, 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 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 realizing this, resulting in air pollution. arise. 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, fault warning devices have already been proposed which are configured to notify the user that exhaust gas recirculation is no longer being performed due to a fault in the exhaust gas recirculation device, and to provide an incentive for repairs. For example,
This method is disclosed in Japanese Utility Model Publication No. 52-9471 and Japanese Utility Model Application No. 50-67220, and was also proposed in Utility Model Application No. 163288-1980 filed by the same applicant as the present applicant.

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 recirculation device is malfunctioning as the exhaust gas is not flowing through the exhaust gas recirculation passage. The E is configured so that the amount of intake air per stroke is determined from the amount of intake air and the rotational speed, and fuel supply is controlled based on this.
In an FI type internal combustion engine, when the intake air amount is within a predetermined value, exhaust gas recirculation should be performed, but if the atmospheric pressure changes due to high altitude driving etc. Since the intake pipe pressure also fluctuates, the conditions under which exhaust gas recirculation should be performed may not be properly determined, and there is a risk that failure diagnosis of the exhaust gas recirculation device may not be performed correctly.

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 amount of intake air per stroke of the engine is detected from the intake air flow rate and rotational speed of the internal combustion engine, and the intake air amount is within a predetermined value. When the exhaust gas recirculation is supposed to be carried out, the diagnosis device of the exhaust gas recirculation system of the internal combustion engine determines whether or not the exhaust gas recirculation is actually being carried out. Diagram of an exhaust gas recirculation device, characterized in that it is provided with an air-fuel ratio learning high-altitude correction coefficient for fuel ratio control, and is configured to prohibit diagnosis when the air-fuel ratio learning high-altitude correction coefficient is less than a predetermined value. Accomplished by gnostic devices.

Note that air-fuel ratio learning for air-fuel ratio control may be performed according to a well-known method, and if a detailed explanation is required,
Please refer to JP-A-60-50249 and JP-A-60-53635.

Effects and Effects of the Invention According to the above-described configuration, diagnosis is prohibited when the atmospheric pressure drops such as when driving at high altitudes, where there is a risk that diagnosis may not be performed again, and the diagnosis is reliably accurate even when the atmospheric pressure is not so low. Diagnosis is performed only when it can be performed, thereby ensuring accurate diagnosis.

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
Air is drawn into the combustion chamber 7 through an air cleaner 2, an air flow meter 3, an intake pipe 5 having a throttle valve 4, and an intake manifold 6, and fuel is injected and supplied from a fuel injector 8, and the burned gas, that is, the exhaust gas is discharged to the exhaust manifold 9.

The fuel injection amount control of the fuel injector 8 is performed by a microcomputer 50, which will be described later, in a manner including high altitude correction (atmospheric pressure compensation).

The exhaust manifold 9 is provided with an exhaust gas intake port 10 for exhaust gas recirculation, and the intake manifold 6 is provided with an exhaust gas injection port 11. are connected to each other in communication by a conduit 12 for exhaust gas recirculation, an exhaust gas recirculation control valve 20 and a conduit 13.

The exhaust gas recirculation control valve 20 has an inlet boat 21 and an outlet boat 22, the inlet boat 21 is connected in communication with the exhaust gas intake port 10 by a conduit 12, and the outlet boat 22 is connected in communication with the exhaust gas intake port 10 by a conduit 13. It is communicatively connected to port 11.

The exhaust gas recirculation control valve 20 has a valve port 23 and a valve element 24.
The valve boat 23 is opened and closed by a valve element 24 and its opening degree 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 is pushed down by the spring force of a compression coil spring 28 to push the valve boat 23 when a negative pressure greater than a predetermined value, for example, −70 mmHg, is not introduced into the diaphragm chamber 27. When the diaphragm chamber 27 is closed and a negative pressure larger than a predetermined value is introduced into the diaphragm chamber 27, the valve boat 23 rises against the spring force of the compression coil spring 28 in response to the negative pressure 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 outlet provided in the intake pipe 5 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. It is communicatively connected to the boat 34. 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 open position, and is located downstream of the throttle valve 4 when the throttle valve 4 is opened beyond a relatively small predetermined opening. It is located on the side.

The negative pressure control valve 30 has a valve element 36 that opens and closes the valve port 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. 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 port 23 of the exhaust gas recirculation control valve 2o 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 27 of the exhaust gas recirculation control valve 20 so as to keep the exhaust gas pressure in the pressure chamber 43 almost constant, in other words, adjust the opening degree of the valve port 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 always kept substantially constant.

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 above-described configuration, the exhaust gas recirculation control valve 20 applies a negative pressure greater than a predetermined value to the conduit 29, for example -70 mmH.
When a negative pressure greater than g is applied and the temperature of the cooling water of the internal combustion engine 1 is at a predetermined value, for example, 60°C or higher, and the temperature-sensitive valve 32 is open, the valve is opened and the exhaust gas is re-circulated at a flow rate corresponding to the amount of opening of the valve. A cycle takes place.

In the figure, 50 indicates a microcomputer that performs fuel injection amount control and 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 port 53, and an output port 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, and the air flow meter 3 receives information regarding the intake air flow rate. Information regarding the temperature of the conduit 10 is obtained from the temperature sensor 59 provided in the
The 02 sensor 61 attached to the exhaust manifold 9 provides information regarding the oxygen concentration in the exhaust gas, and based on this information, the fuel injection amount is controlled, and the exhaust gas is controlled according to the flowchart shown in FIG. A diagnosis is made to see if the recirculation device is operating normally, and when it is determined that the exhaust gas recirculation device is not operating normally, an indicator lamp 58 is turned on.

In the fuel injection amount control, Q/N is calculated from the engine rotation speed N detected by the rotation speed sensor 56 and the intake air flow mQ detected by the air flow meter 3, and the basic fuel injection amount Tp is determined based on this. , determining a warm-up correction coefficient Ktw based on the cooling water temperature Tv detected by the water temperature sensor 57;
The air-fuel ratio correction coefficient is determined based on the air-fuel ratio signal from the 02 sensor 61, and the air-fuel ratio learning high altitude correction coefficient FGHAC is determined by learning control based on the air-fuel ratio correction coefficient Kf'. This is performed by determining the fuel injection time by calculating the ff1Tp and the various correction coefficients Ktv, Kf', and FGHAC mentioned above, and this control may be performed according to a conventionally known general method. The air-fuel ratio learning high altitude correction coefficient FGHAC is a numerical value that decreases as the atmospheric pressure decreases, as shown in FIG.

Next, the operation of the diagnosis 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. A determination is made as to whether or not there is one.

When the indicator lamp 58 is on, it has already been determined that the exhaust gas recirculation system is abnormal, and at this time the process is reset. On the other hand, when the indicator lamp 58 is not on, the process proceeds to step 12.

In step 12, it is determined whether the cooling water temperature Tv detected by the water temperature sensor 57 is equal to or higher than a predetermined 1Tvset, for example, 60°C. TV
>, Twset, the process proceeds to step 14; otherwise, it is the time when exhaust gas recirculation is not performed and is reset.

In step 14, the intake air WQ/N equivalent to the engine stroke is calculated from the intake air flow EmQ detected by the air flow meter 3 and the rotation speed N of the internal combustion engine 1 detected by the rotation speed sensor 56. Then, it is determined whether Q/N is greater than or equal to a predetermined lower limit value Q/N mln. If (Q/N)>(Q/Nm1n), the process proceeds to step 16, otherwise it is reset.

In step 16, it is determined whether the intake air mQ/N equivalent to one stroke of the engine is less than or equal to a predetermined upper limit value Q/NWaX. (Q/N) < (Q/N
nax ), it is determined that the exhaust gas recirculation operation region is present, and in this case, the process proceeds to step 18.
Otherwise it will be reset.

In step 18, the air-fuel ratio learning high altitude correction coefficient FGHAC for air-fuel ratio control is loaded. After step 18, the process proceeds to step 20.

In step 20, the air-fuel ratio learning high altitude correction coefficient FGH is
It is determined whether AC is greater than or equal to a predetermined value Hset. When FGHAC>Hset,
This is the time when the atmospheric pressure is above a predetermined value and the diagnosis can be performed accurately. In this case, the process proceeds to step 22 to execute the diagnosis, and if not, the diagnosis is reset to be prohibited.

In step 22, it is determined whether the exhaust gas recirculation passage temperature Tegr detected by the temperature sensor 59 is equal to or lower than a predetermined value T set. T
If egr < T set, the process proceeds to step 24, otherwise it is reset.

In step 24, the time elapsed after the determination of YES is made in step 16, that is, the time since the exhaust gas recirculation operation region is determined, that is, the EGR time Cegr, is calculated from the count value etc. . After step 24, the process proceeds to step 26.

In step 26, it is determined whether the EGR time Cegr is longer than a predetermined determination time Cset. When Cegr > Cset, it is determined that the exhaust gas recirculation device is malfunctioning and the process proceeds to step 28.
Otherwise it will be reset.

In step 28, the indicator lamp 58 is turned on, that is, turned on.

By performing the diagnosis of the exhaust gas recirculation device according to the flowchart as described above, the exhaust gas recirculation operation range is accurately detected regardless of changes in atmospheric pressure, and the diagnosis of the exhaust gas recirculation device can avoid erroneous judgments. It will definitely be done without having to do it.

[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 FIG. 3 is a graph showing the air-fuel ratio learning high altitude correction coefficient characteristics with respect to atmospheric pressure. DESCRIPTION OF SYMBOLS 1... Internal combustion engine, 2... Air cleaner, 3... Airf 0-meter, 4... Throttle valve, 5...
intake pipe. 6...Intake manifold, 7...Combustion chamber, 8...
Fuel injector, 9...Exhaust manifold, 10.
...Exhaust gas intake boat, 11...Exhaust gas injection boat, 12.13...Conduit, 20...Exhaust gas recirculation control valve. 21... Inlet port, 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 sensitive valve, 3
3... Conduit. 34...Intake pipe negative pressure take-out boat, 35...Valve boat. 36... Valve element, 37... Diaphragm, 38...
・Atmospheric release chamber, 39...Diaphragm chamber, 40...
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, 5
7...Water temperature sensor, 58...Indicator lamp,
59...Temperature sensor, 61...02 sensor patent applicant Toyota Motor Corporation representative
Patent Attorney Masaki Akashi Figure 3 1M GHAC (Voluntary) Procedural Amendment December 29, 1988

Claims (1)

[Claims] The intake air amount per engine stroke is detected from the intake air flow rate and rotational speed of the internal combustion engine, and when the intake air amount is within a predetermined value, it is determined that exhaust gas recirculation is to be performed. In the diagnosis device of the exhaust gas recirculation system of the internal combustion engine that determines whether or not the air-fuel ratio learning high-altitude correction is actually being performed, an air-fuel ratio learning high-altitude correction coefficient for air-fuel ratio control of the internal combustion engine is given, and the air-fuel ratio learning high-altitude correction is A diagnosis device for an exhaust gas recirculation device, characterized in that the diagnosis device is configured to prohibit diagnosis when a coefficient is less than a predetermined value.