JP2877988B2 - Engine failure diagnosis device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an engine failure diagnosis apparatus for diagnosing whether an exhaust gas recirculation apparatus has failed.

[0002]

2. Description of the Related Art NO _X contained in engine exhaust gas
An engine equipped with an exhaust gas recirculation device that recirculates exhaust gas to an intake system in order to reduce the exhaust gas is generally known. This exhaust gas recirculation device is a diaphragm type exhaust gas recirculation control valve (EGR control valve) provided in an exhaust gas recirculation passage (EGR passage) connecting an exhaust system and an intake system.
And a back pressure adjusting valve such as an electromagnetic valve that adjusts the back pressure of the EGR control valve. The EGR control valve is controlled by controlling the back pressure adjusting valve according to the operating state of the engine. Is opened and closed to control the amount of recirculated exhaust gas.

[0003] In the above-mentioned engine, if a failure occurs in a component constituting the exhaust gas recirculation device such as an EGR control valve, there are various inconveniences. Therefore, an apparatus for diagnosing the failure is provided. Various proposals have been made. Japanese Patent Application Laid-Open No. 63-90653 is an example of such a device, and the device disclosed in Japanese Patent Application Publication No.
A temperature sensor for detecting the temperature of the passage is provided, and when the temperature detected by the temperature sensor when the exhaust gas is introduced into the EGR passage is equal to or lower than a predetermined value, it is determined that the exhaust gas recirculation device is malfunctioning. It is configured as follows. Also, paying attention to the characteristic that when the exhaust gas is recirculated to the intake system, the combustion speed is reduced and the engine speed is reduced, and by detecting the degree of decrease in the engine speed when the exhaust gas recirculation device is operated, the exhaust gas is detected. It has been proposed to determine whether a recirculation device has failed.

[0004]

However, in the method for determining the failure of the exhaust gas recirculation system by detecting the temperature of the EGR passage as described above, since the response of the temperature sensor is still poor, the diagnosis of the failure is difficult. It may not be performed properly.

[0005] On the other hand, a method of diagnosing a failure by detecting the degree of a drop in the engine speed at the time of exhaust gas recirculation can solve the above problem, but when the engine speed drops in this way, If it is determined that the exhaust gas recirculation device is operating normally, the engine speed will always drop if the exhaust gas recirculation device is normal at the time of failure diagnosis, and as a result, combustion stability will be further reduced. There is a problem in that the vibration is worsened, giving the driver a sense of incongruity or discomfort, and furthermore, depending on the degree of deterioration of the engine, the engine may be stuck.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has been made in consideration of the above circumstances, and has been described in view of the above description. The purpose is to obtain a diagnostic device.

[0007]

According to the present invention, when the exhaust gas recirculation device is normal, the engine speed does not change.
Further, the above problem is solved by setting the engine speed to change in the rising direction when a failure occurs, and the configuration is as shown in FIG. That is, the engine failure diagnosis device according to the present invention is an engine failure diagnosis device provided with an exhaust gas recirculation device that recirculates exhaust gas of the engine to the intake system, wherein the engine is in a predetermined operating state. A recirculation device forcibly operating the exhaust gas recirculation device forcibly operating the exhaust gas to recirculate the exhaust gas, and an intake of the engine when the recirculation device forcible operation device is operated and the exhaust gas is recirculated. Intake air amount increasing correction means for increasing the air amount by a predetermined amount; and a rotation increasing state determining means for determining an increasing state of the engine speed when the recirculation device forcibly operating means and the intake air amount increasing correcting means are both operated. The failure determination means which receives the output of the rotation increase state determination means and determines that the exhaust gas recirculation device has failed when the degree of increase in the engine speed is equal to or greater than a predetermined value. And it said that there were pictures.

[0008] It is preferable that the recirculation device forcibly operating means is operated when the gear position of the transmission is in a neutral position to execute exhaust gas recirculation for failure determination.

Further, the above-mentioned rotation increasing state determining means may directly determine the degree of increase in the engine speed.

Further, the intake air amount increase correction means performs feedback correction of the engine speed during idling by adjusting the amount of air bypassing the throttle valve of the engine intake system. The failure of the exhaust gas recirculation device may be determined based on the degree of decrease in the feedback correction amount by the increase correction means.

[0011]

When a failure is diagnosed, the exhaust gas recirculation device is operated by the exhaust gas recirculation control means, and the amount of intake air supplied to the intake system controls, for example, the amount of air bypassing the throttle valve. Is increased by a predetermined amount. At this time, the degree of increase in the engine speed is determined to be a predetermined value or more by directly looking at the degree of increase in the engine speed or by determining the degree of decrease in the feedback correction amount of the bypass air amount. In such a case, it is determined that the exhaust gas recirculation device is out of order.

[0012] When the gear position is in the neutral position, it is easy to determine the fluctuation of the rotation of the engine, so that the failure determination is more reliable.

[0013]

Embodiments will be described below with reference to the drawings.

FIG. 2 is an overall system diagram of an embodiment of the present invention.

In this embodiment, an intake passage 2 of an engine 1 is connected to an air cleaner 3, and the air cleaner 3
A throttle valve 4 is provided downstream of the throttle valve. A surge tank 5 is formed downstream of the throttle valve 4 in the intake passage 2, and a fuel supply injector 7 is provided at a downstream end of an independent intake passage 6 for each cylinder branched from the surge tank 5. I have. In the intake passage 2,
A bypass passage 7 communicating the upstream and downstream of the throttle valve 4 is formed, and an ISC (idle speed control) valve 8 is provided in the bypass passage 7.

An exhaust gas take-out port 10 for exhaust gas recirculation is provided in an exhaust passage 9 of the engine 1, and an exhaust gas introduction port for introducing recirculated exhaust gas is provided at a position downstream of the throttle valve 4 in the intake passage 2. 11 are provided respectively. The exhaust gas extraction port 10 and the exhaust gas introduction port 11 are connected to an exhaust gas recirculation passage (EGR).
In the middle of the EGR passage 12, a diaphragm type exhaust gas recirculation control valve (E) is connected.
A GR valve 13 is interposed. The EGR valve 13 includes a diaphragm device 14 and the diaphragm device 1.
The valve member 15 connected to the diaphragm 4 and the valve member 1
It has a valve port 16 which is opened and closed by 5. Further, one working chamber of the diaphragm device 14 is selectively communicated with the surge tank 5 directly downstream of the air cleaner 3 via a duty-controlled three-way solenoid valve 17. The EGR valve 13 is configured such that the working chamber of the diaphragm device 14 is a three-way solenoid valve 17.
When the operation chamber is connected to the surge tank 5 when the working chamber is connected to the surge tank 5, the valve port 16 is closed according to the magnitude of the negative pressure. Controlled to open.

A three-way solenoid valve 17 and an ISC valve 8 for controlling the operating pressure of the EGR valve 13 are controlled by a control unit 18. The control unit 18 also outputs a control signal to a warning lamp 19 for notifying when the exhaust gas recirculation device including the EGR valve 13 has failed. As information for these controls, a control unit 18 includes an output signal of a throttle position sensor 20 attached to the throttle valve 4, an engine speed signal from a rotation sensor 21, a neutral signal, and a pressure in the working chamber of the diaphragm device 14. An output signal from the pressure sensor 22 for detecting the pressure is input.

In this embodiment, at the time of the first idle warm-up increasing operation by the open control at the time of the cold start, the EGR valve 13 is forcibly opened to diagnose the failure of the exhaust gas recirculation device. The ISC valve 8 is opened to cancel the decrease in the engine speed due to the introduction of. Then, at this time, the degree of increase in the engine speed is detected, and when this is equal to or higher than a predetermined value, it is determined that the exhaust gas recirculation device is malfunctioning, and the warning lamp 19 is turned on.

That is, as shown in FIG. 3, when the EGR valve 13 is opened and operated in the FI region until the first idle (FI) speed reaches the normal idle speed (dashed line), the valve 13 operates normally. In this case, the FI rotation speed is reduced by the amount indicated by X in the figure due to the introduction of exhaust gas, but the intake air amount is increased so as to cancel the reduced amount, and is indicated by Y in the figure. Since the rotation speed is increased by the amount, the variation of the FI rotation speed due to the introduction of the exhaust gas is deducted to 0, while
When the exhaust gas recirculation device is out of order and the EGR valve 1 is not operating normally, the decrease (X) in the rotational speed is small and the increase (Y) is at the same level as above, so that Y
> X, and as a result, the FI rotation speed changes to the rising side due to the introduction of the exhaust gas.

Next, the above-described fault diagnosis control of this embodiment will be described with reference to a flowchart shown in FIG. Note that S
101 to S110 indicate each step.

In this flow, when starting, first, in S101, it is determined whether the gear position is neutral or not.
In step S103, it is sequentially determined whether or not the engine speed is 1000 rpm or more. In step S104, it is determined whether or not the throttle valve opening (TVO) is in an idling state. Only the process proceeds to S105, and if any of the conditions is NO, the condition for failure diagnosis is not satisfied, and this flow ends.

In step S105, a start signal for forcibly operating the EGR valve 13 is transmitted. And S106
After a predetermined delay time (A), the EGR valve 1
By applying a negative pressure to the sensing negative pressure port 3, the valve port 16 is opened to introduce exhaust gas into the intake passage 2, and at the same time, an opening signal for increasing air is output to the ISC valve 8 in S 107.

Next, in S108, it is determined whether or not the degree of increase in the engine speed is equal to or more than a predetermined value.
If YES, it is determined that a failure has occurred in S109, and if NO, it is determined that it is normal in S110, and this flow ends.

In the above embodiment, the case where the control of the ISC valve 8 is performed by the open control has been described. However, in the case of performing the closed control with the rotation feedback to the target rotation speed, the following embodiment is also possible. . FIG.
FIGS. 6A and 6B show control characteristic diagrams of another embodiment of the present invention in which the SC valve is closed-controlled, wherein FIG. 7A shows a normal state and FIG.

In this embodiment, when the exhaust gas recirculation device is operating normally, as shown in FIG. 7A, even if the recirculated exhaust gas is introduced at the time of failure diagnosis, the FI rotational speed and the ISC rotational feedback The control amount (G _FB ) does not change from the normal state, but when the exhaust gas recirculation device is out of order, as shown in (b), the FI rotation speed is changed to the EGR valve 1
3, the ISC rotation feedback control amount (G _FB ) fluctuates to the lower side by an amount corresponding to the reduction amount of the recirculated exhaust gas. Therefore, it is possible to determine the failure of the exhaust gas recirculation device by detecting that the amount of decrease of the _GFB has become equal to or more than the predetermined value.

Next, the failure diagnosis control in this embodiment will be described with reference to the flowchart shown in FIG. Note that S
Reference numerals 201 to S211 indicate steps.

In this flow, S201 to S207
Steps S101 to S101 of the previous embodiment are performed, respectively.
Since there is no difference from each step of 107, detailed description is omitted.

In this flow, after the opening signal for increasing the amount of air is output to the ISC valve 8 in S207, the flow proceeds to S208.
The SC rotation feedback control amount (G _FB ) is read, and then, in S209, it is determined whether the degree of decrease of G _FB is equal to or greater than a predetermined value.

In the case of YES, it is determined that a failure has occurred in S210, and in the case of NO, it is determined that it is normal in S211 and this flow is terminated.

[0030]

As described above, the present invention is constructed as described above, so that the failure diagnosis of the exhaust gas recirculation device can be reliably performed without causing engine stall or giving the driver an uncomfortable feeling. Further, by performing this failure diagnosis when the gear position is in the neutral position, the determination can be made more reliably.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of the present invention.

FIG. 2 is an overall system diagram of an embodiment of the present invention.

FIG. 3 is an explanatory diagram of control characteristics of the embodiment.

FIG. 4 is a flowchart for executing control of the embodiment.

FIG. 5 is a control characteristic diagram according to another embodiment of the present invention.

FIG. 6 is a flowchart for executing control of the embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Engine 2 Intake passage 4 Throttle valve 7 Bypass passage 8 ISC valve 12 EGR passage 13 EGR valve 17 Three-way solenoid valve 18 Control unit 19 Warning lamp 21 Rotation sensor

Continuation of the front page (58) Fields surveyed (Int. Cl. ⁶ , DB name) F02M 25/07 550 F02D 41/22 315 F02D 45/00 370 F02M 69/32

Claims (4)

(57) [Claims] 1. An engine failure diagnosis device comprising an exhaust gas recirculation device for recirculating exhaust gas from an engine to an intake system, wherein the exhaust gas recirculation device is provided when the engine is in a predetermined operating state. Forcibly operating the recirculation device for forcibly operating the exhaust gas to recirculate the exhaust gas; and increasing the intake air amount of the engine by a predetermined amount when the recirculation device forcible operation device is operated and the exhaust gas is recirculated. Means for increasing the amount of intake air to be increased, means for increasing the number of revolutions of the engine when the recirculation device forcibly operating means and the means for increasing the amount of intake air are both operated, Failure judgment means for judging that the exhaust gas recirculation device is malfunctioning when the degree of increase in the engine speed is equal to or greater than a predetermined value, receiving the output of the means. Engine failure diagnosis device. 2. The recirculation device forcibly operating means operates when the gear position of the transmission is in a neutral position to execute exhaust gas recirculation for failure determination.
An engine failure diagnostic apparatus according to the above. 3. The failure diagnosis device for an engine according to claim 1, wherein the rotation increase state determination means directly determines the degree of increase in the engine speed. 4. An intake air amount increase correction means for feedback-correcting the engine speed during idling by adjusting an air amount bypassing a throttle valve of an engine intake system, and the rotation increase state determination means includes: 3. The failure diagnosis device for an engine according to claim 1, wherein a failure of the exhaust gas recirculation device is determined based on a degree of reduction of the feedback correction amount by the air amount increase correction unit.