JPH0830451B2 - Diagnostic device for exhaust gas recirculation system of internal combustion engine - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a diagnostic device for diagnosing whether an exhaust gas recirculation device for an internal combustion engine used in a vehicle such as an automobile is operating normally.

BACKGROUND ART An exhaust gas recirculation device incorporated in an internal combustion engine used in a vehicle such as an automobile generally has an exhaust gas recirculation control valve for exhaust gas recirculation flow rate control, a negative pressure control valve for back pressure control, If a malfunction occurs in these components, including the temperature valve, exhaust gas recirculation will not be performed, and there is a risk that the internal combustion engine will be operated in a state where NO _{X in} the exhaust gas is not reduced. is there. Even if exhaust gas recirculation is not performed due to a failure, the internal combustion engine operates without failure, so the driver may not notice this and may operate for a long period of time, which causes the problem of air pollution. Occurs. If exhaust gas recirculation is not performed within a predetermined operating range, knocking may occur, and fuel consumption may deteriorate due to pump loss due to intake of the internal combustion engine itself.

In view of the above-mentioned problems, there has already been proposed a failure alarm device configured to inform the user of this when exhaust gas recirculation is stopped due to a failure of the exhaust gas recirculation device and to motivate the repair. And this is, for example,
It is disclosed in the official gazettes of Japanese Utility Model Publication No. 52-9471 and Japanese Utility Model Publication No. 50-67220, and the application by the same applicant of the present application is
It is also proposed in No. 60-163288.

Problems to be Solved by the Invention A failure diagnosis of the exhaust gas recirculation device is performed by checking whether or not the temperature of the exhaust gas recirculation passage is equal to or higher than a predetermined value under the condition that the exhaust gas recirculation should be performed. That is, it may be determined that the exhaust gas recirculation device is out of order because the exhaust gas does not flow through the exhaust gas recirculation passage when the temperature is equal to or lower than a predetermined value, but in particular, The intake air amount per stroke was found from the intake air amount and the number of revolutions, and the fuel supply was controlled based on this.
In an EFI internal combustion engine, if it is time to perform exhaust gas recirculation when the intake air amount is within a predetermined value, it is accompanied by a change in atmospheric pressure due to running at high altitude. Since the intake pipe pressure also fluctuates, the state in which the exhaust gas recirculation should be performed cannot be properly found, and the failure diagnosis of the exhaust gas recirculation device, that is, the diagnosis may not be performed correctly.

Also, since the exhaust gas recirculation system has a considerable heat capacity,
The temperature of the exhaust gas recirculation system is detected by the temperature sensor, and when the detected temperature is higher than the specified value, it is judged that the exhaust gas recirculation device is operating normally.The exhaust gas recirculation device is diagnosed. In this case, the internal combustion engine itself has already reached the warm-up state, the intake air amount per one stroke of the engine is within a certain range, and the atmospheric pressure is higher than a predetermined atmospheric pressure. Even after the exhaust gas recirculation is started, the exhaust gas recirculation system naturally has a considerable heat capacity, and the initial state at which the diagnosis is started changes greatly. Until the period elapses, the value detected by the temperature sensor cannot always correctly indicate whether the exhaust gas recirculation system is operating normally, and even if it is temporary, the exhaust gas recirculation system does not become normal. Works There is a possibility that mistakenly diagnosed as failure in spite of there.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an improved exhaust gas recirculation device diagnosis system which solves the above problems.

According to the present invention, the exhaust gas recirculation system operates normally when the temperature of the exhaust gas recirculation system of the internal combustion engine is detected and the detected temperature is equal to or higher than a predetermined value. The exhaust gas recirculation system of the internal combustion engine is determined to be a diagnosis device, and at least the intake air amount per engine stroke determined from the cooling water temperature of the internal combustion engine, the intake air flow rate of the internal combustion engine, and the rotational speed The information of the atmospheric pressure is given, and the diagnosis of the exhaust gas recirculation device is performed until the predetermined time elapses from the moment when the operating state of the internal combustion engine is judged to have entered the exhaust gas recirculation region based on these information. It is achieved by the diagnosis device of the exhaust gas recirculation device, which is characterized in that

It should be noted that the air-fuel ratio learning for air-fuel ratio control may be performed according to a well-known method, and if detailed explanation is required for this, see JP-A-60-50249 and JP-A-60-53635. I want to be done.

ACTION AND EFFECT OF THE INVENTION As described above, the predetermined time elapses from the moment when it is determined that the operating state of the internal combustion engine has entered the exhaust gas recirculation region based on at least the engine cooling water temperature, the intake air amount per engine stroke, and the atmospheric pressure. Until then, the exhaust gas recirculation system will not be diagnosed, so that even if the exhaust gas recirculation system does not break down, the failure of the exhaust gas recirculation system will be alarmed. As a result, it is possible to avoid giving the driver an extra discomfort.

Example Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 shows one embodiment of an exhaust gas recirculation device incorporating a diagnosis device according to the present invention. In the drawing, reference numeral 1 denotes an internal combustion engine, which sucks air into a 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. Further, fuel is injected and supplied from the fuel injector 8, and burned gas, that is, exhaust gas is discharged to the exhaust manifold 9. The control of the fuel injection amount of the fuel injector 8 is performed by a microcomputer 50 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, respectively, and the exhaust gas intake port 10 and the exhaust gas injection port 11 are provided. Are connected to each other by an exhaust gas recirculation conduit 12, an exhaust gas recirculation control valve 20 and a conduit 13.

Exhaust gas recirculation control valve 20 has inlet port 21 and outlet port
And the inlet port 21 is communicatively connected to the exhaust gas intake port 10 by a conduit 12 and the outlet port 22 is a conduit.
It is connected to the exhaust gas injection port 11 by means of 13. The exhaust gas recirculation control valve 20 has a valve port 23 and a valve element 24. The valve port 23 is opened and closed by the valve element 24 and the opening degree is controlled to control the exhaust gas recirculation flow rate. ing. The valve element 24 is connected to the diaphragm 26 of the diaphragm device 25 and has a predetermined value in the diaphragm chamber 27.
For example, when a negative pressure larger than −70 mmHg is not introduced, it is pushed down by the spring force of the compression coil spring 28 to close the valve port 23, and when a negative pressure larger than a predetermined value is introduced into the diaphragm chamber 27, the negative pressure is set. Accordingly, the compression coil spring 28 rises against the spring force to open the valve port 23.

The diaphragm chamber 27 of the exhaust gas recirculation control valve 20 is connected to a conduit
29, negative pressure control valve for back pressure control 30, conduit 31, temperature sensing valve 32, conduit
Intake pipe negative pressure extraction port 34 provided in the intake pipe 5 via 33
Connected to. As shown in the drawing, the intake pipe negative pressure extraction port 34 is located on the upstream side when the throttle valve 4 is in the fully closed position, and downstream thereof when the throttle valve 4 is opened at a relatively small predetermined opening or more. It is provided to be located on the side.

The negative pressure control valve 30 has a valve element 36 for opening and closing the valve port 35 and a diaphragm 37 carrying the valve element, and the diaphragm 37 is open to the atmosphere open to the atmosphere on the upper side in the figure. A chamber 38 and a diaphragm chamber 39 on the lower side are respectively defined, and the diaphragm is operated by a compression coil spring 40 when a pressure (positive pressure) higher than a predetermined value is not introduced into the diaphragm chamber 39. The element 36 is located at a position where the valve port 35 is separated from the valve port 35 and the valve port is opened. On the other hand, when a pressure higher than a predetermined value is introduced into the diaphragm chamber 39, the element is moved upward against the action of the compression coil spring 40. Is displaced to bring the valve element 36 into contact with the valve port 35 so that the valve port is in a closed position.

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

The structure including 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 region where the intake pipe negative pressure is given to the exhaust gas recirculation control valve 20, , The negative pressure supplied to the diaphragm chamber 27 of the exhaust gas recirculation control valve 20 is adjusted so that the exhaust gas pressure in the pressure chamber 43 is always kept substantially constant, in other words, the opening degree of the valve port 23 is adjusted, 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 is closed during the warm-up process in which the temperature of the cooling water is a predetermined value, for example, 60 ° C. or less, to cut off the communication between the conduits 31 and 33. On the other hand, when the cooling water temperature is equal to or higher than the predetermined value, the communication between the conduits 31 and 33 is established.

According to the configuration as described above, the exhaust gas recirculation control valve 20 acts on the conduit 29 with a negative pressure larger than a predetermined value, for example, a negative pressure larger than -70 mmHg, and the cooling water temperature of the internal combustion engine 1 reaches a predetermined value.
For example, when the temperature sensitive valve 32 is open at 60 ° C or higher, it opens.
Exhaust gas recirculation is performed at a flow rate according to the valve opening amount.

In the figure, reference numeral 50 denotes a microcomputer for controlling the fuel injection amount and for diagnosing the exhaust gas recirculation device. The microcomputer 50 has a general structure and includes a central processing unit (CPU) 51 and a memory 52.
, An input port 53, an output port 54, and a rotation speed sensor 56 provided in the distributor 55 of the internal combustion engine 1.
More information on the number of revolutions of the internal combustion engine 1 is obtained from the water temperature sensor 57.
The information about the temperature of the cooling water of the internal combustion engine 1, the information about the intake air flow rate from the air flow meter 3, the information about the temperature of the conduit 13 from the temperature sensor 59 provided on the way of the exhaust gas recirculation conduit 13, Information concerning the oxygen concentration in the exhaust gas is given from the O ₂ sensor 61 attached to the manifold 9, the fuel injection amount is controlled based on this information, and the exhaust gas is controlled in accordance with the flow chart shown in FIG. A diagnosis is made as to whether or not the recirculation device is operating normally, and when it is determined that the exhaust gas recirculation device is not operating normally, the indicator lamp 58 is turned on.

In the fuel injection amount control, Q / N is calculated from the engine speed N detected by the speed sensor 56 and the intake air flow rate Q detected by the air flow meter 3, and the basic fuel injection amount Tp is determined based on this. , The warm-up correction coefficient Ktw is determined based on the cooling water temperature Tw detected by the water temperature sensor 57, and the O ₂ sensor 61
Determine the air-fuel ratio correction coefficient Kf based on the air-fuel ratio signal from
Further, the learning control based on the air-fuel ratio correction coefficient Kf determines the air-fuel ratio learning highland correction coefficient FGHAC, and the basic fuel injection amount T
The fuel injection time is determined by calculating p and the above-described various correction coefficients Ktw, Kf, and FGHAC, and this control may be performed according to a generally known conventional method. Air-fuel ratio learning High altitude correction factor 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 described with reference to the flow chart 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, it is judged whether the indicator lamp 58 is in the ON state, that is, whether it is already lit or not. Be seen. When the indicator lamp 58 is in the on state, it is already judged that the exhaust gas recirculation device is abnormal and is reset at this time, while when the indicator lamp 58 is not in the on state, the routine proceeds to step 12.

In step 12, the cooling water temperature Tw detected by the water temperature sensor 57 is a predetermined value Twset which is corrected in advance, for example, 60.
It is determined whether or not the temperature is equal to or higher than ° C. When Tw> Twset, the routine proceeds to step 14, and when not, it is reset when exhaust gas recirculation is not performed.

In step 14, the intake air amount Q / N corresponding to one stroke of the engine is calculated from the intake air flow rate Q 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. The Q / N is a predetermined lower limit value Q / Nm
It is determined whether or not it is in or more. (Q / N)> (Q / N
min), go to step 16, otherwise reset.

In step 16, it is determined whether or not the intake air amount Q / N corresponding to one stroke of the engine is equal to or less than a predetermined upper limit value Q / Nmax. When (Q / N) <(Q / Nmax), it is determined that it is in the exhaust gas recirculation operation range. At this time, the routine proceeds to step 18, otherwise it is reset.

In step 18, the intake of the air-fuel ratio learning highland correction coefficient FGHAC for air-fuel ratio control is performed. After step 18, the process proceeds to step 20.

At step 20, the air-fuel ratio learning highland correction factor FGHAC
Is determined to be equal to or greater than a predetermined value Hset set in advance. When FGHAC> Hset, the atmospheric pressure is equal to or higher than the predetermined value, and the diagnosis can be performed accurately. At this time, proceed to Step 22 to execute the diagnosis, otherwise, the diagnosis is prohibited. It is reset as much as possible.

In step 22, the exhaust gas recirculation passage temperature Tegr detected by the temperature sensor 59 is set to a predetermined value Ts.
Whether or not it is equal to or less than et is determined. If Tegr <Tset, proceed to step 24, otherwise reset.

In step 24, the time after the determination in step 16 is YES, that is, the time from when it is determined to be in the exhaust gas recirculation operation range, that is, the EGR time Cegr is calculated from the count value or the like. . Step 24 is followed by Step 26
Go to.

At step 26, it is judged if the EGR time Cegr is longer than a predetermined judgment time Cset. Cegr
When it is> Cset, it is determined that the exhaust gas recirculation device is out of order, and the process proceeds to step 28, otherwise it is 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 above-mentioned flowchart, the exhaust gas recirculation operation region is accurately detected regardless of the change in atmospheric pressure, and the diagnosis of the exhaust gas recirculation device is erroneously determined. It will surely be done without doing it.

[Brief description of drawings]

FIG. 1 is a schematic view showing an embodiment of an exhaust gas recirculation device incorporating a diagnosis device according to the present invention,
FIG. 2 is a flow chart showing the operation of the diagnosis device according to the present invention, and FIG. 3 is a graph showing the air-fuel ratio learning highland correction coefficient characteristic with respect to atmospheric pressure. 1 …… Internal combustion engine, 2 …… Air cleaner, 3 …… Air flow meter, 4 …… Throttle valve, 5 …… Intake pipe, 6 …… Intake manifold, 7 …… Combustion chamber, 8 …… Fuel injector, 9 ……
Exhaust manifold, 10 …… Exhaust gas intake port, 11 …… Exhaust gas injection port, 12, 13 …… Conduit. 20 …… Exhaust gas recirculation control valve, 21 …… Inlet port, 22 …… Outlet port, 23 ......
Valve port, 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 extraction port, 35
…… Valve port, 36 …… Valve element, 37 …… Diaphragm, 38…
… Atmosphere open 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, 57 ... Water temperature sensor, 58 ... Indicator lamp, 59 ... Temperature sensor, 61
...... O ₂ sensor

Claims (1)

[Claims] 1. An exhaust gas recirculation system for an internal combustion engine, which detects the temperature of an exhaust gas recirculation system of an internal combustion engine and judges that the exhaust gas recirculation system is operating normally when the detected temperature is a predetermined value or higher. The diagnosis device is provided with at least information on the intake air amount per engine stroke and atmospheric pressure obtained from the cooling water temperature of the internal combustion engine, the intake air flow rate of the internal combustion engine, and the rotational speed, and based on these information The diagnosis of the exhaust gas recirculation device is characterized in that the diagnosis of the exhaust gas recirculation device is not performed until a predetermined time elapses from the moment when the operating state of the internal combustion engine is judged to have entered the exhaust gas recirculation region. apparatus.