JP2674445B2 - Exhaust gas recirculation system for internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas recirculation system.

[0002]

2. Description of the Related Art Conventionally, an exhaust gas recirculation device (hereinafter referred to as an EGR device) and a swirl control valve (hereinafter referred to as an SC
(Hereinafter referred to as "V") to control the EGR device in cooperation with the operating state of the SCV (for example, JP-A-59-49359 and JP-A-63-96).
No. 69).

For example, a main intake system that supplies intake air to a combustion chamber at a predetermined load and a predetermined number of revolutions or more, and a sub intake system that throttles the main intake system in a region below that and supplies intake air for swirl generation, Independently installed in the same combustion chamber just upstream of the intake valve, the EGR control valve for exhaust gas recirculation to the intake system is operated under the SCV closed condition in addition to the predetermined opening / closing control condition. There was one configured to control.

That is, if the EGR rate is increased, NO
_{Although x} decreases, engine surge increases, so a certain limit is set. When the EGR device is combined with the SCV, the engine surge with respect to the same EGR rate is reduced. Therefore, it was intended to increase the EGR rate and significantly reduce NO _x .

[0005]

However, in such a conventional EGR device for an internal combustion engine, the operating condition in which the SCV is closed is detected by detecting the closed state of the SCV, and the closed state is detected. When detecting the, the EGR control valve was operated.

Therefore, even if the operating condition is SCV closed, SCV is stuck due to SCV sticking, SCV operation control valve failure, etc.
If the engine did not operate, there was a problem in that drivability might be deteriorated due to an engine surge.

The present invention has been made by paying attention to such a conventional problem, and it is possible to ensure drivability at the time of SCV failure and to prevent an increase in NO _x emission amount. It is intended to provide an EGR device for an engine.

[0008]

Therefore, according to the present invention, in an internal combustion engine having an exhaust gas recirculation device and a swirl control valve, a detection means for detecting a closed state of the swirl control valve is provided, and a set closing operation of the swirl control valve is provided. When there is a difference between the state and the actual operating state detected by the detection means, it is determined that the swirl control valve has failed, the exhaust gas recirculation rate is reduced, and the ignition timing is controlled.

[0009]

When the swirl control valve fails and does not close despite the closing command, the exhaust gas recirculation rate is reduced and the ignition timing is controlled. Therefore, it does not enter the surge area.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings. 1 to 4 are views showing an embodiment of the present invention.

First, the configuration will be described with reference to FIG. 1 is an engine, 2 is an air flow meter, 3 is a throttle valve, 4 is an SCV that is installed in the intake manifold 11 and generates swirl in the combustion chamber of the engine 1, and 5 is an SCV
A closed state detecting means that is turned on when fully closed to detect the closed state;
Reference numeral 6 is an SCV actuator that operates by driving the intake pipe negative pressure and drives the SCV 4. Reference numeral 7 is a solenoid valve for introducing the intake pipe negative pressure in accordance with the operating state of the engine 1, that is, in response to a signal from the control unit 15. SCV control valve to control, 8 EGR passage 12
An EGR valve for opening and closing the valve, 9 an EGR control valve for controlling the negative operating pressure of the EGR valve 8 by a solenoid valve, 10 an intake pipe, 13 an exhaust pipe, 14 a catalyst, 1
Reference numeral 5 is a control unit for detecting the engine operating conditions such as engine speed and intake air amount and the SCV fully closed condition detecting device 5
The SCV fully-closed state signal is input and the control signals to the SCV control valve 7 and the EGR control valve 9 are output.

Next, the operation will be described. The SCV closed state detecting means 5 for detecting the operating state of the SCV 4, that is, the fully closed state, determines whether or not the SCV is operating normally in its operating range.

In the normal case, MAP-1 which is a map as set is used to send a signal to the EGR control valve 9 so that the set EGR rate is obtained, and the opening degree of the EGR valve 8 is adjusted, and the ignition timing is set. Set.

In case of abnormality, the control unit 1
MAP-2, which is a map for abnormality preset to 5
Is selected to decrease the EGR rate and advance the ignition timing.

The control operation will be described with reference to the flowchart of FIG.

First, in step S1, the air flow meter 2
The characteristic values indicating the engine operating state, such as the air amount and the engine speed measured in step 2, are read.

In step S2, it is determined based on the characteristic value read in step S1 whether the operating state is in the EGR region. If it is in the EGR region, the process proceeds to step S3. If it is not in the EGR region, the process proceeds to step S9.

In step S3, a signal is output from the control unit 15 to the SCV control valve 7 to close the SCV4.

At step S4, the SCV 4 is closed by the SCV closed state detection switch 5, that is, the switch O
Whether or not N is detected. Here, if the SCV closed state detection switch 5 is in the ON state, the SCV 4 is operating normally as set, and if it is not in the ON state, step S3.
Even though the SCV 4 was closed in step S6, it has not been closed, so some abnormality has occurred.

In step S5, since the SCV 4 is operating normally, the EGR rate corresponding to the operating state when the SCV is closed is stored from the EGR rate map stored in advance.
The GR rate MAP-1 is looked up to set the EGR rate, and the EGR control valve 9 is operated to set the EGR rate.
Control the rate.

Further, in step S6, similarly, from the ignition timing map, the ignition timing MAP-1 in which the ignition timing corresponding to the operating state when the SCV is closed is stored is looked up to set the ignition timing.

In step S7, although the SCV 4 has failed for some reason and the closing operation command is output from the control unit 15, it is in the open state. Therefore, EGR
EGR rate MAP-2 having a lower EGR rate than rate MAP-1
Is looked up and the EGR control valve 9 is operated to control the EGR rate.

In step S8, similarly, the ignition timing MA
The ignition timing is set by the ignition timing MAP-2 set on the advance side of P-1.

In step S9, since it is not in the EGR region, the EGR valve 8 is fully closed to stop the EGR.

In step S10, since it is not in the EGR region, the ignition timing MAP-0 during non-EGR is looked up to control the ignition timing.

After that, the control operation described above is repeated, and the control operation is ended by stopping the engine.

In the control operation described above, if the swirl control valve 4 is controlled as set and normally closed, the control point between the exhaust gas recirculation rate and the ignition timing becomes point A as shown in FIG. You never enter the area.

On the other hand, when the swirl control valve 4 is closed or abnormal, the control point between the exhaust gas recirculation rate and the ignition timing is point A in the surge region, as shown in FIG. According to this, since the state is controlled from the point A to the point B, it is possible to prevent the increase of the NO _x exhaust amount while ensuring the drivability.

FIG. 5 shows another embodiment of the control operation of the present invention. This example is described in B. P. T. Formula or V.I. V.
T. The present invention is applied to a conventional exhaust gas recirculation device.

Hereinafter, only control steps different from the one embodiment will be described, the same reference numerals are given to the control steps having the same contents as the one embodiment, and the description thereof will be omitted.

That is, when it is judged in step S4 that the closing operation of the SCV is abnormal, the EGR cut valve 21 is operated to introduce the atmosphere into the EGR control valve 9 and the exhaust gas recirculation is stopped in step S21.

Here, B. P. T. Type exhaust gas recirculation system and V.I. V. T. The exhaust gas recirculation device will be described.

Referring to FIG. P. T. Expression (Back Pr
An example of the configuration of the exhaust transducing device is shown.

In order to reduce the exhaust amount of NO _x , it is effective to increase the recirculation amount in the normal operation region, but in the control of the recirculation amount by the negative pressure, a large amount is recirculated to the low load operation region. Drivability and fuel efficiency are reduced. B. P. T. According to the system type exhaust gas recirculation device, the exhaust pressure negative pressure can be utilized to recirculate the gas in a wide operating range at a constant recirculation rate to reduce the amount of NO _x emission without impairing drivability and fuel consumption.

B. P. T. Type exhaust gas recirculation device P.
T. It is composed of a valve 16, an EGR control valve 9, and a TV valve 17 incorporating a bimetal 18 that reverses when the temperature rises, and an orifice 20 is incorporated in a negative pressure passage 19 for more precise control.

In the present embodiment, the negative pressure passage 1
9 is provided with an EGR cut valve 21, and when it is determined that the SCV is abnormal, the EGR cut valve 21 is operated to send the atmosphere to the EGR control valve 9, and the exhaust gas recirculation is stopped.

In FIG. V. T. Expression (Venturi
An example of the configuration of an exhaust gas recirculation device is shown. This device utilizes the fact that the Venturi negative pressure is proportional to the intake air amount, and is designed to increase the exhaust gas recirculation amount, focusing on the high load region where the NO _x emission amount is large.
V. V. T. Valve 22, EGR control valve 9
It is composed of

In this embodiment, EG is provided in the negative pressure passage 23.
When the SCV is determined to be abnormal through the R cut valve 21, the EGR cut valve 21 is operated to send the atmosphere to the EGR control valve 9 to stop the exhaust gas recirculation.

Further, when it is determined in step S2 that the EGR operation range is not set, the EGR cut valve 21 is operated to stop the exhaust gas recirculation.

Thus, in this embodiment, the SCV
When the closing operation of 4 is abnormal, the exhaust gas recirculation is stopped to prevent entry into the surge region.

[0041]

As described above, according to the present invention, it is possible to ensure drivability when a swirl control valve fails, and to prevent an increase in NO _x emission amount.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing an outline of a configuration of an embodiment of the present invention.

FIG. 2 is a flowchart showing a control operation of the embodiment.

FIG. 3 is a diagram for explaining a control state when the SCV closing operation of the embodiment is normal.

FIG. 4 is a diagram for explaining a control state when the SCV closing operation of the embodiment is abnormal.

FIG. 5 is a flowchart showing an example of another control operation of the present invention.

FIG. 6B. P. T. The block diagram which shows the example of a structure when this invention is applied to a conventional exhaust gas recirculation device.

FIG. V. T. The block diagram which shows the example of a structure when this invention is applied to a conventional exhaust gas recirculation device.

[Explanation of symbols]

 3 ... Throttle valve 4 ... Swirl control valve 5 ... SCV closed state detection device 7 ... SCV control valve 8 ... EGR valve 9 ... EGR control valve 12 ... EGR passage 13 ... Exhaust pipe 15 ... Control unit 16 ... P. V. T. Valves 19, 23 ... Negative pressure passage 21 ... EGR cut valve 22 ... V.V. V. T. valve

Claims (1)

(57) [Claims] 1. An internal combustion engine having an exhaust gas recirculation device and a swirl control valve, wherein detection means for detecting a closed state of the swirl control valve is provided, and a set closed operation state of the swirl control valve and an actual operation detected by the detection means. An exhaust gas recirculation system for an internal combustion engine, which judges that a swirl control valve has failed when a difference between the states occurs and reduces the exhaust gas recirculation rate and controls the ignition timing.