JPH0921357A - Exhaust gas recirculation system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realiz a low cost, and to reduce a black smoke when an accelerator pedal is converted from OFF to ON, by adopting an EGR control valve, for passenger car. SOLUTION: A cutoff valve 18 driven by an air cylinder and to cut off an EGR gas in the accelerator pedal OFF condition, by the switching signal from a control unit 20, is provided in an EGR passage 15 between an exhaust gas maniford 12 and an EGR control valve 16.

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 (hereinafter referred to as EGR) device for an automobile engine.

[0002]

2. Description of the Related Art A diesel engine for a truck is also equipped with an EGR device for returning a part of exhaust gas to the intake system and returning it to the engine in order to suppress NOx generation during combustion and improve emission. It

By the way, since the truck employs the exhaust brake system, a high exhaust pressure acts on the EGR control valve of the EGR device when the exhaust brake is operated.

Therefore, the EGR control valve is required to have a high pressure resistance, and a large force is required to open the valve (because the opening direction is restricted). Therefore, as shown in FIG. Compared with the valve body 1A of the EGR control valve ((a) of FIG. 3), the valve body 1B of the EGR control valve for trucks ((b) of FIG. 3)
Used to be sturdy and heavy.

[0005]

However, the above-mentioned E
The GR device requires a sturdy and heavy valve element, which causes a problem of increased cost.

Further, since there is no shutoff mechanism between the exhaust manifold and the EGR control valve, there is a possibility that EGR gas will flow even when the accelerator pedal is turned off, where the EGR device is not desired to operate (such as when decelerating in a high engine speed state). There was also a problem that this is a factor that causes black smoke when the accelerator pedal is turned on.

Incidentally, in Japanese Utility Model Laid-Open No. 4-1657, EG
There is disclosed a technique in which an RV passage is provided with a shutoff valve that shuts off the flow of EGR gas when the exhaust pressure exceeds a predetermined level, separately from the EGR control valve. There is a possibility that the EGR gas will flow when the pedal is turned off, and this will cause the generation of black smoke when the accelerator pedal is turned on.

Therefore, an object of the present invention is to provide an exhaust gas recirculation system capable of reducing the cost by adopting a control valve and reducing black smoke when the accelerator pedal is switched from OFF to ON.

[0009]

In the exhaust gas recirculation system according to the present invention, a shutoff valve for shutting off EGR gas when the accelerator pedal is turned off is provided between the exhaust manifold and the EGR control valve.
It is characterized by being provided in the R passage.

If the shutoff valve is gradually opened when the accelerator pedal is switched from OFF to ON, excessive EGR during transient will occur.
This is preferable because the rate can be avoided.

When the shutoff valve is opened and closed by using air, the valve is opened due to the response delay of the air itself, which is preferable in terms of simplification of the device.

If the shut-off valve is opened after a predetermined time when the accelerator pedal is turned on, the E
The GR rate is reduced and an ON-OFF valve can be used,
It is suitable.

According to the above construction, the accelerator pedal is turned off.
At times, by blocking the EGR passage between the exhaust manifold and the EGR control valve, it is possible to prevent the exhaust pressure from acting on the EGR control valve when the exhaust brake is activated.

When the accelerator pedal is off, EGR
Even if the control valve opens, the shutoff valve is closed.
Gas does not flow back to the intake system, so the accelerator pedal is turned on.
It is avoided that the air is returned to the intake system at a high EGR rate when it is switched to.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of an exhaust gas recirculation system according to the present invention will be described below in detail with reference to the accompanying drawings. FIG.
2 is a schematic configuration diagram of an exhaust gas recirculation device, and FIG. 2 is a structural explanatory diagram of a shutoff valve.

In FIG. 1, 10 is a diesel engine main body,
An intake manifold 11 is led out from one side of the diesel engine body 10, and an exhaust manifold 12 is led out from the other side.

An intake pipe 13 is connected to the intake manifold 11, and an exhaust pipe 14 is connected to the exhaust manifold 12, and the intake pipe 13 and the exhaust manifold 12 are communicated with each other through an EGR passage 15, and the EGR passage 15 is connected. An EGR control valve 16 is provided in the passage 15.

An exhaust brake valve 17 is provided in the exhaust pipe 14 and an EGR upstream of the EGR control valve 16 is provided.
A cutoff valve 18 is provided in the passage 15.

The EGR control valve 16 is connected to an opening / closing drive control device 19, and the opening / closing drive control device 19 is operated by a drive signal from a control unit 20.

The shutoff valve 18 is connected to the air tank 22 via a switching valve 21, and the switching valve 21
Is operated by an opening / closing signal from the control unit 20.

The control unit 20 includes an accelerator switch 2 for detecting ON-OFF of the accelerator pedal.
When the signal from 3 is input and the accelerator pedal OFF signal is input, the switching valve 21 is switched to supply the air from the air tank 22 to the shutoff valve 18.

Various control signals are input to the control unit 20, and the EGR control valve 16 is controlled to be opened / closed according to the operating state of the engine through the opening / closing drive control device 19 based on these input signals. Is as before.

The shut-off valve 18 is, as shown in FIG.
The plate-shaped valve body 30 that shuts off the GR passage 15 has a piston rod 31.
The piston rod 31 is always urged upward (in the valve opening direction) by the spring 33 in the cylinder 32.

Air is supplied from the air tank 22 to the piston upper chamber 34 in the cylinder 32 by the switching valve 21, so that the piston rod 31 descends against the urging force of the spring 33, and the plate-shaped valve body 30 Shuts off the EGR passage 15.

With this configuration, the driver releases his / her foot from the accelerator pedal at the time of deceleration including idling or exhaust brake operation, and the accelerator switch 2
When 3 is turned off, the control unit 20 switches the switching valve 21 to close the shutoff valve 18.

That is, the air from the air tank 22 is supplied to the piston upper chamber 34 of the shutoff valve 18, and the plate-shaped valve body 30
Shuts off the EGR passage 15.

As a result, the EGR control valve 16 downstream of the shutoff valve 18 is not subjected to high exhaust pressure when the exhaust brake is actuated, and therefore the valve body of the EGR control valve 16 is a simple valve body for passenger vehicles (see FIG. 3 (a)) can be used.

During the above operation, the EGR control valve 16
Even if the valve is opened, the shutoff valve 18 is closed so that the exhaust gas does not flow back to the intake system. Therefore, when the accelerator pedal is switched on, the exhaust gas is prevented from flowing back to the intake system at a high EGR rate.

As a result, it is possible to suppress the generation of black smoke when the accelerator pedal is switched from OFF to ON.

Further, in this embodiment, since the shutoff valve 18 is driven to open and close by the air cylinder, the responsiveness of the valve opening when the accelerator pedal is switched from OFF to ON becomes insensitive, which causes a transient time. The generation of black smoke can be reduced by suppressing the EGR amount.

The delay in the valve opening response of the shutoff valve 18 can be achieved by an electric opening / closing means without using an air cylinder. Further, it goes without saying that the amount of EGR during transition can be suppressed and the generation of black smoke can be reduced by opening the shut-off valve 18 after waiting for a predetermined time instead of gradually opening it.

[0032]

As described above, according to the present invention, since the shutoff valve for shutting off the EGR gas when the accelerator pedal is turned off is provided in the EGR passage between the exhaust manifold and the EGR control valve, the EGR valve is turned off when the accelerator pedal is turned off. By blocking the passage, the exhaust pressure at the time of operating the exhaust brake is prevented from acting on the EGR control valve, so that the valve body of the EGR control valve can be a simple valve body for passenger cars, which reduces the cost and mass. Can be reduced.

Even if the EGR control valve is opened when the accelerator pedal is OFF, the EGR gas does not flow back to the intake system because the shut-off valve is closed, so that when the accelerator pedal is switched ON, a high EGR gas is produced. It is possible to prevent the smoke from being returned to the intake system at a high rate, and suppress the generation of black smoke.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment of an exhaust gas recirculation device according to the present invention.

FIG. 2 is also a structural explanatory view of a shutoff valve.

FIG. 3 is a comparative explanatory view of EGR control valves.

[Explanation of symbols]

 10 Diesel Engine Main Body 11 Intake Manifold 12 Exhaust Manifold 13 Intake Pipe 14 Exhaust Pipe 15 EGR Passage 16 EGR Control Valve 17 Exhaust Brake Valve 18 Shutoff Valve 18 19 Open / Close Drive Control Device 20 Control Unit 21 Switching Valve 22 Air Tank 23 Accelerator Switch

Claims (4)

[Claims] 1. An exhaust gas recirculation device, characterized in that a shutoff valve for shutting off EGR gas when the accelerator pedal is turned off is provided in an EGR passage between an exhaust manifold and an EGR control valve. 2. The exhaust gas recirculation system according to claim 1, wherein the shutoff valve is gradually opened when the accelerator pedal is turned from OFF to ON. 3. The exhaust gas recirculation device according to claim 2, wherein the shutoff valve is opened and closed by using air. 4. The exhaust gas recirculation device according to claim 1, wherein the shutoff valve is opened after a predetermined time when the accelerator pedal is turned from OFF to ON.