JPH03100361A - Exhaust gas circular controller of diesel engine - Google Patents

Abstract

PURPOSE:To control the discharge of CO, HC, smoke and the like for a large operation range by controlling an adjusting means which adjusts a circular quantity in the exhaust gas in response to an engine operation based on an output signal from an O2 sensor. CONSTITUTION:In an ECU 13, opening of an intake throttle valve 5 is controlled via a negative pressure control valve 8 and an actuator 6 based on signals of an engine speed sensor 15 and an acceleration opening sensor 16 provided at a fuel injection pump 14. EGR quantity inside an engine 1 is detected by the ECU 13 from exhaust concentration detected by a linear O2 sensor 9 provided at an exhaust passage 4. A variable valve timing system 10 is hydraulically driven via an electromagnetic solenoid valve 12 in response to an operation condition of the engine 1 so as to control the inner EGR quantity by varying an overlapping quantity of an intake/exhaust valve. The inner EGR control of high accuracy based on the operation condition of the engine 1 is performed, and the quantity of CO, CH, smoke and NOx are decreased for a large operation range.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to exhaust gas recirculation (EGR) of diesel engines.
Regarding a control device.

(Conventional technology) EGR as the No. 1 reduction system for diesel engines
There is a system. This EGR system generally includes an exhaust gas recirculation flow control valve (EGR valve) in the exhaust gas recirculation passage (EGR passage) that communicates the exhaust passage and intake passage of the engine, and adjusts the lift amount of the EGR valve based on the engine operating condition. The amount of EGR is changed by controlling according to the amount of fuel, thereby reducing NO8 (external EGR method).

In such an external EGR control system, an oxygen sensor (linear 0 sensor) whose output value changes linearly is generally installed in the exhaust passage, and a target is set according to the engine operating state determined by the engine speed and accelerator opening. A map for determining oxygen concentration is prepared, and the EGR valve is controlled by determining the lift amount of the EGR valve based on a comparison between the target oxygen concentration read from this map and the actual oxygen concentration determined from the output of the oxygen sensor. (See Japanese Unexamined Patent Publication No. 63-201356).

By the way, the above external EGI? Since it is a so-called cold EGR with a low EGR gas temperature, it has the disadvantage of worsening ignition performance and generating white smoke in low rotation and low load areas, and cannot increase EGRli in low rotation and low load areas. Therefore, it was not possible to sufficiently reduce No.

On the other hand, there is an internal EGR method in which part of the exhaust gas after combustion remains in the combustion chamber. This method is based on the overlap of the opening periods of the intake and exhaust valves from the end of the exhaust stroke to the beginning of the intake stroke, and the exhaust gas that has previously exited to the exhaust passage is pulled back into the combustion chamber or intake passage by the intake negative pressure, and the remaining gas is That is. This internal EGR method is also called hot EGR, and because the temperature of the residual gas is relatively high, ignition performance in low rotation and low load ranges is improved.
In the low-speed, high-load region, the NO8 reduction rate decreases, and highly accurate EGRI control according to the operating state of the engine is impossible.

(Objective of the Invention) Therefore, the present invention provides an internal EG control system according to the operating state of the engine.
An object of the present invention is to provide an EGR control device for a diesel engine that can reduce emissions by controlling Ril with high precision.

(Structure of the Invention) The EGR control device according to the present invention includes an oxygen sensor that detects the oxygen concentration in the exhaust system, an adjustment means that adjusts the internal EGR amount, and an output signal from the oxygen sensor.
The present invention is characterized by comprising a control means for controlling the EGR amount adjusting means according to the operating state of the engine.

(Effects of the Invention) According to the present invention, since the internal EGRfJ can be detected indirectly by the output of the oxygen sensor, it is possible to perform highly accurate internal ECR control in accordance with the operating state of the engine. It is possible to reduce the amount of NOx emissions while suppressing emissions of CO, HC, smoke, etc. throughout the region.

(Embodiments) Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a schematic configuration diagram showing one embodiment of the present invention. An engine 1 includes an intake passage 3 that supplies intake air that has passed through an air cleaner 2 to a combustion chamber of each cylinder, and an intake passage 3 that supplies exhaust gas produced by combustion. An exhaust passage 4 for discharging the air to the outside is provided.

The intake passage 3 is provided with an intake throttle valve 5 for performing internal EGR by restricting intake air.
A negative pressure diaphragm type actuator 6 is provided to open and close the throttle valve 10, and a duty control type negative pressure is provided in a negative pressure introduction passage 7 between a negative pressure pump (not shown) and the actuator 6. A control valve 8 is provided,
The opening degree of the intake throttle valve 5 is controlled by controlling the negative pressure within the actuator 6 according to the open/close state and the open/close time ratio (duty ratio) of the control valve 8.

Further, a near-02 sensor 9 whose output value changes linearly is disposed in the exhaust passage 4.

Claims (1)

[Scope of Claims] An oxygen sensor that detects the oxygen concentration in the exhaust system, an adjustment device that adjusts the amount of internal recirculation of exhaust gas, and an adjustment device that adjusts the amount of internal recirculation of the exhaust gas based on the output signal from the oxygen sensor. 1. An exhaust gas recirculation control device for a diesel engine, comprising: control means for controlling according to the operating state of the diesel engine.