JPH0652065B2 - Engine exhaust gas recirculation system - Google Patents

Description

The present invention relates to an exhaust gas recirculation (hereinafter referred to as EGR) device for an engine, and more particularly to an EGR EGR device suitable for confirming the functional operation of EGR.

[Conventional technology]

In recent years, as a device of this type, as described in JP-A-52-125979, the EGR amount is calculated and controlled on the basis of engine information such as the intake air amount, the engine speed, etc., and more precise exhaust gas purification is performed. The function is achieved. Of course, E for reducing NOx
It has been known for a long time in various documents that the GR device has a great effect.

However, this type is also established when the EGR device is functioning normally. For example, when the EGR valve fails or when the control means of the EGR valve fails, exhaust gas purification is performed. Performance will be reduced, which in turn will adversely affect air pollution.

The above-mentioned conventional technology does not take into consideration the confirmation of operation functions similar to those of the device system or the monitoring in the mounted state, and in Japan, there is a problem that it can be extracted only in the process due to the vehicle inspection system etc. .

An object of the present invention is to provide an EGR device for an engine that is suitable for monitoring the EGR function without requiring a new device and effectively utilizing the existing function.

[Means for solving problems]

The above object is to provide an exhaust manifold of an engine, an exhaust gas recirculation passage for recirculating exhaust gas passing through the exhaust manifold to an intake manifold of the engine,
A valve disposed in the exhaust gas recirculation passage for controlling exhaust gas passing through the exhaust gas recirculation passage, and a control for controlling the valve according to the engine state and monitoring the operation of the exhaust gas purification function. In an exhaust gas recirculation system for an engine, which includes a device and an air-fuel ratio detection device for detecting an air-fuel ratio of exhaust gas, the control device controls the valve for a predetermined time to monitor the operation of an exhaust gas purification function. A means for opening the valve, a means for obtaining the time during which the air-fuel ratio on the exhaust side in the opened state is on the lean side, a means for comparing the obtained time with the predetermined time, and the result of the comparison. And a means for making a failure judgment.

[Action]

That is, in the predetermined condition of the engine, when the EGR amount is large, since the residual oxygen in the EGR amount is added to the fresh air to be supplied to the engine signal of the O ₂ sensor is changed to the lean side, directly monitoring the change The EGR
You can check whether the device is operating normally.

〔Example〕

 An embodiment of the present invention will be described below with reference to the drawings.

FIG. 2 is a block diagram of an engine control device to which an embodiment of the present invention described later is applied. In the figure, 8 is an intake air amount sensor for detecting an intake air amount, and 7 is an ignition energy supply to each cylinder of the engine. And a built-in rotation angle sensor 12 for detecting the rotation angle of the engine. 10
Is an O ₂ sensor for detecting the exhaust gas concentration and is arranged in the passage of the exhaust manifold 3. 1 is an engine,
An intake manifold 2 provided with a throttle valve 9 having the intake air amount sensor and an opening detector 15 is arranged on the upstream side thereof, and the exhaust manifold and muffler 13 are arranged on the downstream side of the engine. The intake manifold is equipped with a fuel injection valve 6 for supplying fuel. Further, the exhaust manifold 3 has an exhaust gas recirculation passage 14 for recirculating a part of the exhaust gas to the intake manifold 2.
a and 14b are provided, and an EGR valve for controlling the exhaust gas recirculation amount (EGR amount) is arranged in the middle of the exhaust passage. Reference numeral 4 denotes an engine control computer, which inputs signals from the rotation angle sensor 12, the intake air amount sensor 8, the O ₂ sensor 3, the opening degree detector 15, and the other operating state detector 11 such as the engine temperature. Based on this signal, the fuel amount by the fuel injection valve 6 and the EGR valve 5
The exhaust gas recirculation amount and the ignition timing are calculated and controlled. In addition, 16 is an indicator which shows the failure of an engine control device, for example.

FIG. 1 shows an embodiment of the present invention, in which the EG when the engine speed is fixed by the engine control device shown in FIG.
The relationship between the operation of the R valve, the EGR amount, and the signal of the O ₂ sensor is shown.

In this operating state, the EGR valve is kept for a predetermined time T _E
The A / F concentration supplied to the engine is made lean only in the time period of T _E by activating only the ON side to increase the EGR amount from small to large. As a result, during the after the delay time T _R via the steps up to the combustion from the intake, the signal of the O ₂ sensor are reflected in the exhaust gas concentration T _{A (≒} T _E), are migrated to dilute side (lean side) Will be.

FIG. 3 shows a schematic flow chart of the engine control device of FIG. 2 which realizes the function shown in FIG. 1, and the function of one embodiment will be described with this flow chart. When the engine is started, the engine control computer repeatedly performs arithmetic processing at a predetermined cycle according to a predetermined control program, and controls each device (not shown). In this arithmetic operation, the EGR check mode, for example, in the idle state, the process proceeds to the interrupt processing routine of step 100. When the O ₂ sensor is not in the active region, the process moves to step 116 and waits for the next interrupt request. On the other hand, O ₂
When the sensor is in the active region, the process moves from step 100 to step 101, the EGR check counter is incremented, the process proceeds to step 102, the O ₂ F / B control is stopped, and the process proceeds to step 103. In step 103, the air-fuel ratio (A / F) is fixed at a position slightly higher than the three-way point (theoretical air-fuel ratio 14.7). Next, at step 104, the EGR valve is operated for a predetermined time T _E to move it to the side where the EGR amount increases, and then the process proceeds to step 105. Step 1
At 05, it is determined whether or not the counter of step 101 has reached the desired value N times, and when it is less than N times, the routine proceeds to step 108. Then monitoring between the _{O 2} sensor signal time _{T E ~2T} E of step 109 waits for the step 108 delay time _{T R,} the time present in the dilute side (than atmospheric A / F is 3 Mototen) measure. After this, at step 110, O ₂ F / B
Restart and move to step 111, where step 109
It is determined whether or not the time measured in step T is _{equal to} or longer than the desired time T _{E
When E} or less, the EGRNG counter is incremented at step 112. On the other hand, when more than _{T E} is step 116
Wait for the next interrupt request. Then when the value of EGRNG counter proceeds from step 112 to step 113 has reached _{N F} times to determine Taka not decreased to _{N F} times step 11
Go to 4.

On the other hand, if it is less than N _F times, the process moves to step 116 to wait for the next interrupt request. Next, in step 114, the EGRFAIL flag is set, and in step 115, an alarm indicating the EGR function NG is displayed, and then the next interrupt request is awaited. The EGR check counter and EGRNG
When the EGR check counter reaches N times at step 105, the counters at step 106 and step 10
Clear with 7.

Here, as the display at step 115, the display 16 of the engine control device to which the embodiment of FIG. 2 is applied is typified. The display is stored in the memory of the engine control computer, and externally if necessary. It may be one that emits a signal.

As described in the above embodiment, if the exhaust gas concentration changes to the lean side when the EGR amount is increased, it is determined that the EGR function is normal operation, while the exhaust gas concentration changes even if the EGR amount is increased. If there is no EGR function, it is determined that the EGR function is lost, and the point is that the change in the EGR amount is detected by the change in the exhaust gas concentration, and the quality of the EGR function is determined and confirmed.

〔The invention's effect〕

As described above, according to the present invention, it is possible to confirm the EGR function without adding a new device, and it is possible to prevent the cost increase due to the function improvement, and to keep the driver in a steady operation while the engine is mounted. It has the effect of being able to self-check functions.

Further, since the EGR function can be confirmed in the entire engine control system, it is possible to prevent air pollution such as NOx increase due to defective EGR function, which is advantageous in exhaust gas countermeasures.

[Brief description of drawings]

FIG. 1 is an operational relationship diagram of EGR amount and exhaust gas concentration, which is an embodiment of the present invention, FIG. 2 is a configuration diagram of an engine control device to which the embodiment shown in FIG. 1 is applied, and FIG. It is a flow chart of one Example shown in a figure. 4 ... Engine control computer, 5 ... EGR valve, 10 ... O ₂ sensor, 14a, 14b ... Exhaust gas recirculation passage, 16 ... Failure indicator.

Claims (1)

[Claims] 1. An exhaust manifold of an engine, and an exhaust gas recirculation passage for recirculating exhaust gas passing through the exhaust manifold to an intake manifold of the engine.
A control valve disposed in the exhaust gas recirculation passage for controlling exhaust gas passing through the exhaust gas recirculation passage, and controlling the valve according to the engine state and monitoring the operation of the exhaust gas purification function. In an exhaust gas recirculation device for an engine, which includes a control device and an air-fuel ratio detection device for detecting an air-fuel ratio of exhaust gas, the control device controls the valve to a predetermined value for monitoring the operation of an exhaust gas purification function. The means for opening the time, the means for obtaining the time when the air-fuel ratio on the exhaust side in the opened state is on the lean side, the means for comparing the obtained time with the predetermined time, and the comparison An exhaust gas recirculation system for an engine, comprising: means for making a failure determination based on a result.