JP2985488B2 - Failure diagnosis device for exhaust gas recirculation device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a failure diagnosis apparatus for judging an excessive recirculation exhaust gas amount failure of an exhaust gas recirculation apparatus.

[0002]

Some of the prior art exhaust gas is recirculated into the fuel chamber from the exhaust system, lowering the combustion temperature by the heat capacity possessed by the inert gas is a main component of the exhaust gas, the exhaust gas to reduce the generation amount of the NO _x Recirculation devices are known.

[0003] In such an exhaust gas recirculation device,
The amount of exhaust gas to be recirculated is controlled by the operating state of the internal combustion engine. However, if an exhaust gas excess is excessively supplied to the combustion chamber for some reason, a misfire occurs. Therefore, the amount of generated HC increases.

In recent years, exhaust gas regulations have become stricter in each country, and such a failure in the exhaust gas recirculation system must be repaired at an early stage, and therefore, it is necessary to inform the user of the failure accurately. is there.

Japanese Utility Model Laid-Open No. 2-1454 discloses a failure diagnosis in which a misfire is detected from fluctuations in the rotation of an internal combustion engine, and if a misfire is detected during recirculation of exhaust gas, it is determined that the above-described failure has occurred. An apparatus is described.

[0006]

However, misfires are also caused by, for example, failures of the ignition system, the fuel injection system, etc. According to the above-described failure diagnosis apparatus, no excessive exhaust gas failure has occurred. Nevertheless, if a failure of the ignition system or the like occurs during the exhaust gas recirculation, it is determined that the exhaust gas amount is excessive.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a failure diagnosis device for an exhaust gas recirculation device capable of accurately determining an excessive exhaust gas failure.

[0008]

In order to achieve the above-mentioned object, a failure diagnosis apparatus for an exhaust gas recirculation system according to the present invention comprises an exhaust gas recirculation system for controlling an amount of recirculated exhaust gas in accordance with an engine operating state. In the device failure diagnosis device, detecting means for detecting misfire of the engine, and reducing means for reducing the amount of recirculated exhaust gas when misfire is detected by the detecting means,
A determination unit configured to determine that an excessive exhaust gas amount failure has occurred if a misfire is not detected by the detection unit in accordance with the reduction in the amount of recirculated exhaust gas by the reduction unit.

[0009]

The exhaust gas recirculation device failure diagnosis device described above is:
When the misfire is detected by the detecting means, the reducing means reduces the recirculated exhaust gas amount. At this time, if the cause of the misfire is other than the excessive exhaust gas failure, the misfire should occur even if the amount of the recirculated exhaust gas is reduced. It is determined that an excessive quantity failure has occurred.

[0010]

FIG. 1 is a schematic diagram of an exhaust gas recirculation device 2 of an internal combustion engine to which a failure diagnostic device 1 according to the present invention is mounted. 3, reference numeral 3 denotes an internal combustion engine, 4 denotes an intake passage provided with a throttle valve 5, and 6 denotes an exhaust passage.

The exhaust gas recirculation device 2 includes a passage 7 for exhaust gas recirculation communicating the exhaust passage 6 with the downstream side of the throttle valve 5 in the intake passage 4, and a valve element provided in the passage 7. 8a and diaphragm device 8b for opening and closing it
And a negative pressure supply passage 9 for supplying a negative pressure to the diaphragm device 8b.

The negative pressure supply passage 9 communicates the diaphragm device 8b with the upstream side of the throttle valve 5 of the intake passage 4 through a temperature sensing valve 10 which senses the temperature of the cooling water. On the side of the passage 4, the control chamber 11 a of the negative pressure control device 11 is opened via a control valve 11 b.

Atmospheric pressure is constantly supplied to the control chamber 11a, and the magnitude of the negative pressure in the negative pressure supply passage 9 is controlled by opening and closing the control valve 11b. Control valve 11b
Is connected to the exhaust passage 6 side of the passage 7 from the valve body 8a.

Since the exhaust gas recirculation device 2 is configured as described above, the temperature sensing valve 10 is opened when the exhaust gas recirculation is performed when the cooling water temperature is equal to or higher than a predetermined value, and the intake passage is opened. The negative pressure in the exhaust gas 4 is supplied to the diaphragm device 8b of the exhaust gas recirculation control device 8, the valve body 8a is opened, and the exhaust gas is recirculated to the intake passage 4 through the passage 7.

At this time, the exhaust passage 6 is
The exhaust gas pressure on the negative side is controlled by the negative pressure control device 11 depending on the pressure.
Controls the magnitude of the negative pressure supplied to the diaphragm device 8b, and the valve body 8a is controlled to open and close by the negative pressure.
The feedback control is performed so as to be constant, so that the amount of exhaust gas recirculated is recirculated at a constant ratio to the amount of intake air.

The failure diagnosing device 1 attached to the exhaust gas recirculation device 2 includes a closing valve 12 provided on the intake passage 4 side from the valve body 8a of the passage 7 for exhaust gas recirculation.
And a diaphragm actuator 13 for opening and closing the closing valve 12, and a control device 15 for switching the diaphragm actuator 13 and controlling the same via an electromagnetic valve 14.

The diaphragm chamber 13a of the diaphragm actuator 13 is communicated by the communication passage 16 with the intake passage 4 on the downstream side of the throttle valve 5, and the switching electromagnetic valve 1 is connected.
4 supplies a negative pressure or atmospheric pressure in the intake passage 4. Atmospheric pressure is constantly supplied to the pressure chamber 13b on the drive shaft 17 side of the diaphragm actuator 13. Normally, atmospheric pressure is supplied to the diaphragm chamber 13a, and the diaphragm 13d is urged to the illustrated position by the spring 13c provided therein, and the drive shaft 17 opens the closing valve 12, but the negative pressure is supplied. Then, the diaphragm 13d is pulled leftward from the position shown in the figure opposite to the spring 13c, and the drive shaft 17 closes the closing valve 12 as shown by a dotted line.

The control device 15 is connected to sensors for determining the operating state of the engine, such as a rotation angle sensor and a throttle valve opening sensor (not shown). The control device 15 controls opening and closing of the closing valve 12 via a switching solenoid valve 14. The ignition timing and fuel injection amount are controlled.

The control device 15 in the failure diagnosis device 1
Will be described with reference to FIG. First, in step 101, it is determined based on a signal from a throttle valve opening sensor or the like whether or not the engine operation state is a steady state. If steady state, step 10
In step 2, a change in the number of rotations per unit time is calculated based on the signal from the rotation angle sensor. If the change is equal to or greater than a predetermined value, it is determined that a misfire has occurred, and the routine proceeds to step 103.
In step 103, since the closing valve 12 is initially open, a negative pressure is supplied to the diaphragm chamber 13a via the switching solenoid valve 14 in step 104, and the closing valve 1 is closed.
2 is closed, and in steps 105 and 106, the ignition timing and the fuel injection amount are set to optimal values when exhaust gas recirculation is not performed.

If it is determined in step 101 that the engine operating state is not the steady state, the flowchart is terminated. This is because the misfire detection in step 102 is performed based on the rotation speed fluctuation, and therefore, the operation state in which the rotation fluctuation is equal to or more than a predetermined value even when no misfire has occurred, such as at start-up, sudden acceleration, or at the time of forecut. This is because accurate misfire detection cannot be performed.

If no misfire is detected in step 102, the process proceeds to step 107, where the first closing valve 1
Since 2 is in the open state, the process ends.

This flow chart is repeated. If a misfire is detected again in step 102 after the misfire is detected, the flow proceeds to step 109 because the closing valve 12 is already closed in step 103, and the driver is instructed. A misfire warning is issued, and the closing valve 12 is
Is opened, and then in steps 111 and 112, the ignition timing and the fuel injection amount are set to the optimum values for performing the exhaust gas recirculation.

Step 102 after the misfire is detected.
If no misfire is detected in step 107, the flow proceeds to step 108 because the shut-off valve 12 has already been closed in step 107, and a warning is issued to the driver for an excessive recirculation exhaust gas amount failure.

The failure diagnosis device 1 for an exhaust gas recirculation device according to the present invention forcibly stops the exhaust gas recirculation when a misfire is detected. If the cause of the misfire is determined to be an excessive exhaust gas failure of the exhaust gas recirculation system and a misfire nevertheless occurs, the cause of the misfire is other than the excessive exhaust gas failure, such as an ignition system or a fuel supply system. And so on. As a result, the driver can be accurately warned of the excessive exhaust gas failure, and the failure can be repaired at an early stage. Until this malfunction is repaired, exhaust gas recirculation will be stopped and misfires will not occur.
It is possible to prevent a large amount of HC generated due to misfire from being released to the atmosphere.

The exhaust gas recirculation device to which the failure diagnosis device of the present embodiment can be applied is not limited to a device using a negative pressure for the drive mechanism of the valve element of the exhaust gas recirculation control device. Obviously, it is also applicable to those that do.

Further, the failure diagnosis apparatus 1 of this embodiment has a closing valve 12 which can close the passage 7 for exhaust gas recirculation separately from the valve element 8a of the exhaust gas recirculation control device 8.
However, even if the exhaust gas recirculation control device 8 is provided with means for forcibly opening and closing the valve element 8a and the closing valve 12 is omitted, the exhaust gas due to the excessive opening of the valve element 8a, which usually occurs, is likely to occur. It is clear that overload faults can be accurately determined.

By separately providing the closing valve 12 as in the present embodiment, it is possible to eliminate the above-mentioned normal exhaust gas excess failure.
Excessive exhaust gas failure due to the valve body 8a being open and not closed can also be accurately determined.

The actuator of the closing valve 12 is not limited to the one utilizing the negative pressure in the intake passage, but may be an actuator having another structure such as a step motor.

In the failure diagnosis flowchart shown in FIG. 2, after the misfire is detected, the closing valve 12 is closed in step 104 to stop the exhaust gas recirculation.
If at least the amount of exhaust gas to be recirculated is reduced, it is possible to similarly determine an excessive exhaust gas failure based on whether or not a misfire has occurred thereafter.

Further, in this flowchart, the determination as to whether or not exhaust gas recirculation is being performed before and after the detection of misfire is omitted. Since no misfire warning is issued in step 109 after passing through steps 104, 105, and 106, no problem occurs.

[0031]

As described above, the failure diagnosis apparatus for an exhaust gas recirculation apparatus according to the present invention is different from the conventional failure diagnosis apparatus which determines that an excessive amount of exhaust gas has failed if a misfire occurs during exhaust gas recirculation. After the occurrence of a misfire, the amount of exhaust gas to be recirculated is reduced. The driver can be distinguished and notified accurately, and the trouble of fixing the faulty part at the time of repair can be omitted, and the repair period can be shortened.

[Brief description of the drawings]

FIG. 1 is a schematic view of an exhaust gas recirculation device of an internal combustion engine to which a failure diagnosis device according to the present invention is attached.

FIG. 2 is a failure diagnosis flowchart of the failure diagnosis device according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Failure diagnosis device 2 ... Exhaust gas recirculation device 3 ... Internal combustion engine 4 ... Intake passage 6 ... Exhaust passage 8 ... Exhaust gas recirculation control device 12 ... Closing valve 13 ... Diaphragm actuator 14 ... Switching electromagnetic valve 15 ... Control device

Claims (1)

(57) [Claims] 1. A failure diagnosis device for an exhaust gas recirculation device for controlling an amount of recirculated exhaust gas in accordance with an operating state of an engine, comprising: detection means for detecting a misfire of the engine; Reducing means for reducing the amount of recirculated exhaust gas, and judging means for judging that an excessive exhaust gas amount failure has occurred unless a misfire is detected by the detecting means in accordance with the decrease in the amount of recirculated exhaust gas by the reducing means. ,
A failure diagnosis device for an exhaust gas recirculation device, comprising: