JPH0637855B2 - Exhaust gas purification device for diesel engine - Google Patents

Description

Detailed Description of the Invention [Industrial applications]

The present invention relates to an exhaust gas purifying apparatus for a diesel engine, and more particularly to an improvement of an exhaust gas purifying apparatus for a diesel engine equipped with an exhaust gas recirculation device.

[Prior art]

In order to reduce NOx in exhaust gas in a diesel engine, especially a diesel engine for automobiles,
So-called exhaust gas recirculation (hereinafter referred to as EGR) is performed in which a part of the exhaust gas is returned to the engine intake system. As such a thing, for example, JP-A-58-72
664, and those proposed in JP-A-58-72665.

[Problems to be Solved by the Invention]

However, even in the case of the diesel engine equipped with the above EGR, when decelerating, the excess air ratio in the cylinder is large, so that the temperature of gas in the cylinder and the temperature of the inner wall of the cylinder during the compression process are low, and the fuel injection amount is also low. Is large, and the fuel is slightly discharged from the injection pump due to the governor characteristics of the injection pump. Therefore, under such a condition, there is a problem that the inside of the cylinder is temporarily misfired and HC spikes occur as shown by a chain line A in FIG. Further, there is a problem that white smoke and noise increase when the engine is cold as the amount of HC increases.

[Object of the Invention]

The present invention has been made to solve the above-mentioned conventional problems, and reduces the amount of HC discharged during deceleration, prevents white smoke and noise from increasing, and also reduces vibration. An object is to provide an exhaust gas purifying device for an engine.

[Means for solving problems]

The present invention relates to an exhaust gas recirculation passage for guiding a part of exhaust gas to an engine intake system, an exhaust gas recirculation control means for controlling a flow rate of exhaust gas flowing through the exhaust gas recirculation passage, and a fuel injection amount during idling. Idle fuel reduction means for reducing
Exhaust gas recirculation operation means for operating the exhaust gas recirculation control means, and a deceleration control for detecting a deceleration state and operating the idle fuel reduction means and the exhaust gas recirculation operation means by the deceleration detection signal. Means to achieve the above object.

[Action]

In the present invention, during deceleration, the idle fuel injection means is operated to reduce the fuel injection amount at the time of idling, and the EGR is performed to reduce the emission amount of HC, thereby reducing white smoke and noise. It is possible to prevent the increase and reduce the vibration. That is, by reducing the fuel injection amount and the excess air ratio, the intake air temperature is raised to facilitate ignition, and the exhaust gas emission amount is reduced. Moreover, these factors interact with each other. And H
The emission amount of C can be reduced.

【Example】

Embodiments of the present invention will be described in detail below with reference to the drawings. In the EGR device of the diesel engine 10 of the embodiment to which the present invention is applied, as shown in FIG. 1, the EGR passage that communicates the exhaust system 12 and the intake system 14 and guides a part of the exhaust gas to the intake system 14. 16 and an EGR valve 18 that controls the effective passage area of the EGR passage 16 to control the flow rate of exhaust gas flowing through the EGR passage 16.
The R passage 16 and the EGR valve constitute the EGR control means 15. The EGR valve 18 has a diaphragm chamber 18A.
The effective passage area of the EGR passage 16 is controlled according to the negative pressure acting on the. Further, the idle fuel amount reducing means 30 for reducing the fuel injection amount at the time of idling, the EGR operating means 32 for operating the EGR control means 15, and the deceleration state are detected, and the idle fuel amount reducing signal is detected by the deceleration detection signal. Deceleration control means 3 for operating the means 30 and the exhaust gas recirculation operation means 32
And 4 are provided. The idle fuel reducing means 30 includes a fuel injection pump 36.
The idle rotation setting lever 38 is changed from the opening position at the time of normal idling so that the opening becomes smaller to reduce the fuel injection amount at idling.
A lever position changing actuator 40 having a stepped diaphragm chamber 42A, 42B and a rod 46 connected to the diaphragm 44A, 44B of the diaphragm chamber 42A, 42B, and a negative pressure pump for the diaphragm chamber 42A, 42B of the actuator 40. It is composed of negative pressure switching valves 48 and 50 which act on the negative pressure from 20 according to a command from the control means 34 during deceleration described later. The EGR actuating means 32 includes a negative pressure pump 2 in the diaphragm chamber 18A of the EGR valve 18 as the EGR control means 15.
It is composed of a negative pressure switching valve 52 that applies a negative pressure from 0 according to a command from the deceleration control means 34 described later.
By operating the negative pressure switching valve 52, the negative pressure pump 20
The negative pressure is applied to the diaphragm chamber 18A of the EGR valve 18 to perform EGR. The deceleration control means 34 includes a throttle opening sensor 54 for detecting the throttle opening, an engine rotation sensor 56 for detecting the engine speed, an acceleration sensor 58 for detecting the acceleration of the vehicle, and an acceleration sensor 58 for detecting the acceleration of the vehicle. A deceleration state is determined based on the detection signal, and when the deceleration state is determined, the negative pressure switching valves 48 and 50 of the idle fuel reducing means 30 are operated and the negative pressure switching valve 5 of the EGR operating means 32 is operated.
2 and an electronic control unit (hereinafter referred to as ECU) 28 for operating the control unit 2. The ECU 28 detects a deceleration state other than the deceleration state at the time of gear shift, when the throttle opening is in an idle position state, the engine speed is equal to or higher than a set speed, and the acceleration is zero or more for several seconds. When the deceleration state is detected, the negative pressure switching valves 48, 50 and 52 are operated. Next, the operation of this embodiment will be described. The throttle opening sensor 54 and the engine rotation sensor 5
6, E based on the detection signals of the acceleration sensor 58
When the CU 28 detects a deceleration other than the deceleration state during shifting,
The ECU 28 operates the negative pressure switching valves 48 and 50 of the idle fuel reducing means 30 and the negative pressure switching valve 52 of the EGR operating means 32 to operate the idle fuel reducing means 30.
And each of the EGR operating means 32 are operated. That is, by operating the negative pressure switching valves 48 and 50, the negative pressure of the negative pressure pump 20 is applied to the diaphragm chambers 42A and 42B of the actuator 40, and the diaphragm 44
The rod 46 connected to A and 44B is moved rightward in the figure. Along with the movement of the rod 46, the idle rotation setting lever 38, which is elastically pressed against the tip of the rod 46 by a spring or the like, rotates counterclockwise in the drawing to reduce the fuel injection amount during idling. Therefore, a smaller amount of fuel than the normal idle fuel injection amount is injected. The relationship between the opening degree of the idle rotation setting lever 38 and the fuel injection amount with respect to this opening degree is shown in FIG. As is clear from FIG. 2, it can be seen that the fuel injection amount decreases as the opening degree of the idle rotation setting lever 38 decreases. Further, by operating the negative pressure switching valve 52, the negative pressure from the negative pressure pump 20 is applied to the diaphragm chamber 1 of the EGR valve 18.
8A to perform EGR via the EGR valve 18. Therefore, according to the present embodiment, the fuel injection amount is reduced to reduce the exhaust gas discharge amount, and the EGR is performed to reduce the excess air ratio in the cylinder to raise the intake air temperature and ignite. Further, by interacting with each other, the amount of HC emission can be reduced. In the present embodiment, the reason why the set engine speed is equal to or higher than the set value for detecting the deceleration state is to prevent the engine stall. Therefore, when the deceleration control means 34 is not operating, the normal idle rotation is maintained. FIG. 3 is a diagram showing the HC emission characteristics during deceleration. The dashed-dotted line A shows the HC emission characteristics when the idle speed is 800 RPM and EGR is not performed, that is, the solid line B shows the idle rotation speed. When the EGR is performed at the number of 700 RPM, that is, the HC emission characteristic according to the present embodiment is shown. As is clear from FIG. 3, according to this embodiment, HC discharge can be effectively suppressed during deceleration. In the present embodiment, the idle fuel reducing means 30
Actuator 40 is installed in the two-stage diaphragm chamber 4 in series.
As a two-stage operation having 2A and 42B, the fuel injection amount at the time of deceleration is reduced in two steps to more precisely reduce the fuel injection amount, but the present invention is not limited to this. The actuator 40 may be a one-stage operation type, or may be a continuously changing type instead of a stepwise changing type. Further, in this embodiment, in order to detect the deceleration state,
A throttle opening sensor 54, an engine rotation sensor 56,
Although each detection signal of the acceleration sensor 58 is used,
The present invention is not limited to this. For example, instead of the signal of the acceleration sensor 58, the signals of the neutral switch and the clutch switch may be used together. Further, in the present embodiment, the idle fuel amount reducing means 30 is constituted by the actuator 40 that changes the lever position of the idle rotation setting lever 38, but the present invention is not limited to this, and the actuator 40 controls, for example. The lever to be operated is not limited to the idle rotation setting lever such as the speed control lever, and other means capable of changing the idle rotation may be used. Further, the actuator 40 is assumed to be operated by a negative pressure having the diaphragm chambers 42A and 42B, but the present invention is not limited to this, and may be operated by, for example, an electric motor or the like.

【The invention's effect】

As described above, according to the present invention, by reducing the fuel injection amount when the engine is decelerating and using EGR together, it is possible to reduce the HC generated due to misfire, and to prevent the increase in noise accordingly. In addition, white smoke can be reduced, vibrations due to changes in positive and negative torque can be reduced, and further fuel efficiency can be improved as the fuel injection amount is reduced.

[Brief description of drawings]

FIG. 1 shows a configuration of an embodiment of an exhaust gas purifying apparatus for a diesel engine according to the present invention, which is a pipeline diagram including a partial sectional view and a block diagram, and FIG. 2 shows various lever opening states. FIG. 3 is a diagram showing the relationship between the engine speed and the fuel injection amount, and FIG. 3 is a diagram showing the changing state of the HC emission amount during deceleration. 12 ... Exhaust system, 14 ... Intake system, 18 ... Exhaust gas recirculation valve (EGR valve), 20 ... Negative pressure pump, 28 ... Electronic control unit (ECU), 30 ... Idle fuel reduction means, 32 ... EGR actuation means 34 ... deceleration control means 36 ... fuel injection pump

Claims (1)

[Claims] 1. An exhaust gas recirculation passage for guiding a part of exhaust gas to an engine intake system, an exhaust gas recirculation control means for controlling a flow rate of exhaust gas flowing through the exhaust gas recirculation passage, and a fuel injection during idling. The exhaust gas recirculation control means for operating the exhaust gas recirculation control means, and the deceleration detection signal to detect the deceleration detection signal. An exhaust gas purifying apparatus for a diesel engine, comprising: a deceleration-time control means for operating a circulation operation means.