JPH0544507A - Exhaust reflux device of diesel engine - Google Patents

Abstract

PURPOSE:To prevent shortage of an intake new air quantity at the time of rapid acceleration, in an exhaust reflux device of a diesel engine which controls opening of an intake throttle valve via a stepping motor or the like. CONSTITUTION:There are provided an exhaust reflux quantity control means 24 which adjusts opening of an intake throttle valve 10 in response to an operational condition, a bypass valve 17 which opens and closes a bypass passage 16 which communicates the upstream side with the downstream side by the intake throttle valve 10 of an intake passage 3, a means 25 which discriminates the time of rapid acceleration of an engine, and an intake new air quantity control means 26 which opens the bypass valve 17 at the time of the rapid acceleration.

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 for a diesel engine.

[0002]

2. Description of the Related Art For diesel engines for automobiles, N
In order to reduce the amount of Ox emission, an exhaust gas recirculation device that recirculates a part of the exhaust gas to the engine through an exhaust gas recirculation passage that connects the intake passage and the exhaust passage is provided.

In order to accurately control this exhaust gas recirculation amount,
The applicant has proposed that the opening of the intake throttle valve is controlled via a stepping motor according to the engine operating state, and the pressure in the intake passage to which the exhaust gas recirculation passage is connected is adjusted. 63-198458, gazette).

[0004]

However, in such a conventional device, since the opening degree of the intake throttle valve is adjusted through the stepping motor, the intake fresh air amount of the engine is responsive to the stepping motor. Limited by For example, at the time of sudden acceleration in which the fuel injection amount sharply increases as shown in FIG. 3, the opening degree change of the intake throttle valve is delayed as shown in FIG. For this reason, as shown in FIG. 9, the amount of fresh air inhaled was insufficient and the particulate matter deteriorated.

Although the responsiveness of the stepping motor is improved to some extent by increasing its size, new problems arise in terms of weight increase and vehicle mountability.

In view of the above points, the present invention provides an exhaust gas recirculation device for a diesel engine in which the opening of an intake throttle valve is driven via a stepping motor or the like, and the intake fresh air amount is supplied without shortage during sudden acceleration. The object is to provide a device that can.

[0007]

According to the present invention, an intake throttle valve 10 is provided upstream of a confluence portion of an intake passage 3 with an exhaust gas recirculation passage, and drive means for adjusting the opening degree of the intake throttle valve 10. In the exhaust gas recirculation system for a diesel engine, the exhaust gas recirculation device includes an exhaust gas recirculation device 21, a device 23 for detecting an engine operating condition, and an exhaust gas recirculation amount control device 24 for adjusting the opening of the intake throttle valve 10 according to the operating condition. A bypass passage 16 that connects the upstream side and the downstream side of the throttle valve 10, a bypass valve 17 that opens and closes the bypass passage 16, a means 22 that drives the bypass valve 17 to open and close, and a means 25 that determines when the engine is in rapid acceleration. The intake fresh air amount control means 26 for opening the bypass valve 17 at the time of sudden acceleration is provided.

[0008]

In normal operation other than during rapid acceleration of the engine, the exhaust gas recirculation amount control means 24 adjusts the opening degree of the intake throttle valve 10 in accordance with the exhaust gas recirculation rate set according to the engine operating condition, to reduce NOx, etc. Suppress the occurrence.

When the fuel injection amount suddenly increases, the intake throttle valve 10
The exhaust gas recirculation amount control means 24 opens the intake passage 3 via the intake throttle valve 10 and the intake fresh air amount control means 26 at the time of sudden acceleration of the engine in which the opening operation of the valve cannot follow this.
By temporarily opening the bypass passage 16 via the bypass valve 17, the pressure in the intake passage 3 downstream of the intake throttle valve 10 is promptly recovered. Therefore, the fresh air amount can be increased without delaying the increase in the fuel injection amount, and the generation of particulates and the like can be suppressed.

[0010]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

In FIG. 2, 4 is an exhaust gas recirculation passage that connects the exhaust passage 2 and the intake passage 3 of the engine 1, and 5 is an exhaust gas recirculation control valve that is interposed in the middle thereof. Is provided with a valve body 5c which is interlocked with a diaphragm 5b which is displaced according to the negative pressure introduced into the negative pressure chamber 5a. 6
Is a pressure adjusting valve that detects the pressure in the exhaust gas recirculation passage 4 downstream of the exhaust gas recirculation control valve 5 and controls the opening of the exhaust gas recirculation control valve 5 so as to maintain this pressure at a predetermined value. Is a pressure chamber 6a for introducing the pressure of the exhaust gas recirculation passage 4, an atmosphere chamber 6c defined by the diaphragm 6b to communicate with the atmosphere, a vacuum pump 7 and an exhaust gas recirculation control valve 5
The negative pressure passage 8 connecting the negative pressure chamber 5a of the above is provided with a nozzle portion 6e capable of communicating through a valve body 6b, and a spring 6f for setting the predetermined pressure, and the pressure introduced into the pressure chamber 6a is provided. Accordingly, the valve body 6d operates via the diaphragm 6b to adjust the amount of atmospheric dilution into the negative pressure passage 8 to control the opening degree of the exhaust gas recirculation control valve 5. Reference numeral 9 is an exhaust gas recirculation orifice provided in the vicinity of the confluence portion of the exhaust gas recirculation passage 4 with the intake air passage 3.

On the other hand, an intake throttle valve 10 whose passage opening area is variable according to engine operating conditions is provided upstream of the confluence portion of the intake passage 3 with the exhaust gas recirculation passage 4. A stepping motor 15 is provided as a drive means for the intake throttle valve 10.

As a result, the internal pressure of the exhaust gas recirculation passage 4 is feedback-controlled to a constant value by the pressure adjusting valve 6 via the exhaust gas recirculation control valve 5, and the intake pressure is adjusted by the intake throttle valve 10 so that the exhaust gas return The flow rate can be controlled accurately.

Further, in the present invention, the bypass passage 16 connecting the upstream side and the downstream side of the intake throttle valve 10 of the intake passage 3 is provided, and the bypass valve 17 for opening and closing the bypass passage 16 is provided in the middle of the bypass passage 16. As a drive means of the bypass valve 17, a rotary solenoid 18 for opening and closing the bypass valve 17 is provided.

A control unit 14 for controlling the opening / closing of the intake throttle valve 10 and the bypass valve 17 is provided. The control unit 14 is a signal representative of the operating state, and includes a load signal from the opening sensor 12 of the control lever sensor 12 of the fuel injection pump, a rotation speed signal from the engine rotation sensor 13, and a cooling water temperature sensor 1.
Input the water temperature signal from 1 respectively. The control unit 14 performs exhaust gas recirculation control via the intake throttle valve 10 on the basis of these detected values, as will be described later, while the control unit 14 controls the increase in the fuel injection amount as shown in FIG.
As shown in (1), a control is performed in which the intake valve is opened and the bypass valve 17 is opened to increase the intake fresh air amount.

The means for discriminating the sudden acceleration calculates the rate of increase of the fuel injection amount based on the signal from the lever opening sensor 12, compares the rate of increase with a set value, and opens the intake throttle valve 10. It is for determining whether or not the operation follows. The set value for comparing the rate of increase of the fuel injection amount is not a constant value, but is set to a smaller value as the engine operating condition before acceleration is low rotation and low load.

The control means for opening the bypass valve 17 at the time of sudden acceleration when it is determined that the intake throttle valve 10 does not follow the opening operation, the control means applies the pulse voltage shown in FIG. 5 to the rotary solenoid 18 in accordance with the acceleration state. It is something to send. The energization time of the pulse voltage is not a constant value, and is set longer as the engine operating state before acceleration is low rotation and low load, and is set longer as the increase rate of the fuel injection amount is larger.

The bypass valve 17 is opened by the pulse voltage sent from the control unit 14 via the rotary solenoid 18 as shown in FIG. 6, and the characteristic is matched with the opening degree of the intake throttle valve 10 shown in FIG. As shown in FIG. 7, the value increases significantly with the increase of fuel, and as shown in FIG. 8, it is possible to approach the opening characteristic of the intake throttle valve required at the time of acceleration.

From the above, it can be prevented that the pressure on the downstream side of the intake throttle valve 10 in the intake passage 3 is promptly recovered even during sudden acceleration, and the fresh air amount is insufficient with respect to the increase in the fuel injection amount.
It is possible to appropriately maintain the excess air ratio and suppress the generation of particulates.

[0020]

As described above, according to the present invention, in the exhaust gas recirculation device for a diesel engine, which controls the opening of the intake throttle valve via a stepping motor or the like, the opening of the intake throttle valve is adjusted according to the operating state. Exhaust gas recirculation amount control means, a bypass valve that opens and closes a bypass passage that connects upstream and downstream sides of the intake throttle valve of the intake passage, a means that determines when the engine is in rapid acceleration, and a bypass valve that is opened during rapid acceleration Since the intake fresh air amount control means and the like are provided, the exhaust gas recirculation amount is appropriately adjusted through the intake throttle valve during normal operation, and NOx can be effectively reduced, while the bypass valve during rapid acceleration when the fuel is suddenly increased. It is possible to prevent a shortage of fresh air intake amount through the, and to obtain the effect of reducing particulates.

[Brief description of drawings]

FIG. 1 is a configuration diagram of the present invention.

FIG. 2 is a schematic configuration diagram showing an embodiment of the present invention.

FIG. 3 is a characteristic diagram of fuel injection quantity.

FIG. 4 is a characteristic diagram of an intake throttle valve opening degree.

FIG. 5 is a characteristic diagram of a pulse voltage similarly.

FIG. 6 is a characteristic diagram of a bypass valve of the same.

FIG. 7 is a characteristic diagram in which the opening degrees of the intake throttle valve and the bypass valve are also combined.

FIG. 8 is a characteristic diagram of a required intake throttle valve opening.

FIG. 9 is a characteristic diagram of an intake fresh air amount of a conventional device.

[Explanation of symbols]

 3 intake passage 10 intake throttle valve 16 intake bypass passage 21 drive means 22 drive means 23 engine operating state detection means 24 exhaust gas recirculation amount control means 25 sudden acceleration time determination means 26 bypass valve control means

Claims (1)

[Claims] 1. An intake throttle valve provided upstream of a confluence portion of an intake passage with an exhaust gas recirculation passage, a drive means for adjusting an opening degree of the intake throttle valve, and a means for detecting an engine operating state. In an exhaust gas recirculation system for a diesel engine, comprising an exhaust gas recirculation amount control means for adjusting the opening degree of an intake throttle valve according to an operating state, a bypass passage communicating upstream and downstream of an intake throttle valve in an intake passage, and a bypass. A bypass valve that opens and closes the passage, a means that drives the bypass valve to open and close, a means that determines when the engine is in rapid acceleration, and an intake fresh air amount control means that opens the bypass valve during rapid acceleration are provided. Exhaust gas recirculation system for diesel engines.