JPH03100363A - Exhaust gas reflux controller of diesel engine - Google Patents

Abstract

PURPOSE:To prevent generation of accidental fire and smoke by controlling an EGR valve corresponding to an operation condition based on an output signal of an O2 sensor at the time of normal operation, and based on signal of a lift quantity sensor of the EGR valve at the time of an idle operation. CONSTITUTION:In an ECU 10, signals of an engine speed sensor 12 provided at a fuel injection pump 11, an acceleration opening sensor 13, water temperature sensor 15 and an outer temperature sensor 16 are inputted. An EGR valve 6 is controlled via a negative control valve 7 in response to an operation condition of an engine 1 based on an output signal of an O2 sensor 14 at a normal operation time. At an idle operation time detected by an idle sensor 18, a target EGR lift quantity in response to engine speed and acceleration opening is set so as to control an EGR valve 6 based on signals of an EGR valve lift quantity sensor 17. Generation of rotation variation at the idle operation time, accidental fire and smoke are prevented.

Description

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

(Prior art) In an exhaust gas recirculation control device for a diesel engine, an exhaust gas recirculation control valve (EGR valve) is provided in an exhaust gas recirculation passage that communicates an exhaust passage and an intake passage of the engine, and the EGR valve
By controlling the R valve lift amount according to the operating state of the engine, the EGR amount is changed, thereby reducing noise and smoke. In that case, an oxygen sensor whose output value changes linearly (linear Ot sensor) will be installed in the exhaust passage, and a map will be prepared to determine the target oxygen concentration according to the engine operating condition determined by the engine speed and engine load. However, it is known that the lift amount of the EGR valve is determined 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, and EGRN is feedback-controlled. Based on the output of such an oxygen sensor, feedback control of the EGR amount is effective in obtaining a constant NOx reduction rate without being affected by changes in the engine over time. It is a means.

Incidentally, in a diesel engine, the idle speed may decrease due to factors such as deterioration of the fuel injection nozzle, deterioration of the fuel injection pump, and differences in fuel properties. However, based on the output of the oxygen sensor <EG
In the RI feedback control system, even if the idle speed decreases due to the above-mentioned factors, the oxygen concentration in the exhaust gas, No.

Because the concentration hardly changes, the same amount of EGR as normal
This has the disadvantage of causing white smoke and misfires. In addition, when the idle speed fluctuates due to the above factors, in the feedback control system of <EGR amount based on the output of the oxygen sensor, the difference between the in-cylinder gas component and the exhaust gas component at the location of the oxygen sensor, or the EGR valve Due to the delay in response, etc., it is not possible to supply appropriate EGRM, resulting in increased rotational fluctuations, white smoke, and misfires.

(Objective of the Invention) Therefore, an object of the present invention is to provide an exhaust gas recirculation control device for a diesel engine that can prevent an increase in rotational fluctuations, a misfire, and the generation of white smoke during idling operation.

(Structure of the Invention) In the present invention, during normal operation, the EGR valve is controlled according to the operating state of the engine based on the output signal of an oxygen sensor installed in the exhaust system or the intake system, and during idling operation,
The present invention is characterized in that the EGR valve is controlled according to the operating state of the engine based on the output signal of the EGR valve lift amount sensor.

(Effects of the Invention) According to the present invention, since the EGR valve is feedback-controlled by detecting the lift amount of the EGR valve during idling operation, the EGR amount is set in advance to decrease when the idling speed decreases. By doing so, it becomes possible to supply an appropriate amount of EGR when the idle speed decreases or fluctuates, and it is possible to prevent rotational fluctuations, misfires, and generation of white smoke.

(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, where l is the engine body of a diesel engine, 2 is an intake passage, and 3 is a schematic diagram showing an embodiment of the present invention.
4 is an air cleaner provided upstream of the intake passage 2, and 4 is an exhaust passage. 5 is an exhaust gas recirculation passage that communicates the exhaust passage 4 and the intake passage 2, and this passage 5 has an exhaust gas recirculation amount (
A diaphragm type exhaust gas recirculation amount control valve (EGR valve) 6.6 is provided to control the amount of EGR.

Negative pressure from a vacuum pump 8 controlled by a negative pressure control valve 7.7, which is an electromagnetic solenoid valve, is applied to the negative pressure chamber (not shown) of the EGR valve 6.6 through an i-pressure path 9.9. This controls the lift amount of the EGR valve 6.6. l.

is a controller that connects the exhaust passage 4 to detect the output of the rotation speed sensor 12 of the fuel injection pump 11, the accelerator opening sensor 13 (a potentiometer that detects the lever opening of the injection pump 11), and the oxygen concentration in the exhaust gas. The output of the oxygen sensor 14 provided at the engine, the output of the engine water temperature sensor 15, and the output of the outside air temperature sensor 16 are input.

Further, each EGR valve 6.6 is provided with an EGR valve lift amount sensor 17 consisting of a potentiometer that detects the lift amount thereof, and the outputs of these sensors 17.17 are also input to the controller 10. Further, the fuel injection pump 11 is provided with an idle switch 18 as an idle sensor that detects the idle operating state from the engine speed and the accelerator opening, and the output of the idle switch 18 is also input to the controller IO. The controller 10 performs duty control on the negative pressure control valve 7.7 based on these input signals, thereby controlling the EGR valve 6.7.
6 lift amount is feedback controlled.

FIG. 2 is a diagram showing a flowchart of a program stored in the memory of the controller 10, and the operation of the EGR control device according to the present invention will be explained with reference to this flowchart.

This flow is the engine ignition switch O
The engine rotation speed NE is first detected from the output of the rotation speed sensor 12 of the fuel injection pump 11 in step 31, and then the engine water temperature W/T is detected from the output of the engine water temperature sensor 15 in step S2. In the next step S3, it is determined from the engine rotation speed NE and the engine water temperature W/T whether or not it is in the region where EGR is to be performed. The accelerator opening degree ACC is detected from the output of the sensor 13, and the output VO of the oxygen sensor 14 is further detected in step S5.

In the next step S6, it is determined from the output of the idle switch 18 whether or not the idle operation is being performed, and this determination result indicates that rNO
If it is J, the process advances to step S7.

The memory of the controller 10 stores the target oxygen concentration ■0□ (M) according to the engine speed NB and the accelerator opening ACC.
A first map is stored, and step S
In step 7, the target oxygen concentration ■0□ (M) is read from the above map. Further, in step S8, the actual oxygen concentration vo, (R) is detected from the output of the oxygen sensor 14, and in the next step S9, vO□(M) and vO□(R) are compared. As long as VO, (M)≠V Ot (R) in this judgment, step S
Proceeding to IO, the duty ratio of the control pulse signal for the negative pressure control valve 6.6 is changed to correct the actual EGR valve lift amount, and the process returns to step S8, where the determination in step S9 is Vow (
S8→S9→510-3 until M)-Vow(R)
Repeat step 8. And vow(M)”VOg(R
), the process returns to step S1.

On the other hand, if it is determined in step S6 that the vehicle is in idle operation, the process advances to step Sll.

The memory of the controller 10 stores a target EGR valve lift IIV according to the engine speed NE and accelerator opening ACC.
A second map for determining L(M) is also stored, and this second map is set so that the target EGR valve lift (ILV L(M)) decreases when the idle speed decreases. There is. Then, in step Sll, the target EGR valve lift ilVL(M) is read from the map, and in step S12, the actual EGR valve lift ilVL(R) is detected from the output of the EGR valve lift amount sensor 17, and the next step S 13, VL(M) and VL(R) are compared. As long as VL(M)≠VL(R) in this determination, the process proceeds to step 314, where the duty ratio of the control pulse signal for the negative pressure control valve 6.6 is changed to correct the actual EGR valve lift amount, and step S12 512-513 until the determination in step S13 becomes VL(M)=VL(R).
→514→Repeat the process of S12. And VL(M)
=VL(R), the process returns to step Sl.

As described above, in this embodiment, when idling is detected, the target oxygen concentration VO,(M) corresponding to the operating state read from the first map and the output of the oxygen sensor 14 are determined. Actual oxygen concentration v o z
Based on the comparison with (R) < Target E according to the idle speed read from the second map
GR valve lift) IVL (M) and EGR valve lift amount sensor 1
Actual EGR valve lift IVL (R) determined from the output of 7
Since the switch is made to EGR control based on a comparison with < EGR control, it is possible to perform accurate EGR control while preventing increases in rotational fluctuations, misfires, white smoke, etc. during idling operation.

Note that in the above embodiment, the oxygen sensor 14 is connected to the exhaust passage 4.
However, an oxygen sensor may be provided downstream of the opening of the exhaust gas recirculation passage 5 in the intake passage 2.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment of the present invention, and FIG. 2 is a flowchart showing its operation. - Engine body 2 - Intake passage 4 - Exhaust passage Exhaust gas recirculation passage 6 Negative pressure control valve Vacuum pump 10 1 - Fuel injection pump 12 3 - Accelerator opening sensor 4 - Oxygen sensor 7 - EGR valve lift amount sensor 8-・Idle switch EGR valve controller rotation speed sensor

Claims (1)

[Scope of Claims] In a diesel engine equipped with an exhaust gas recirculation device that recirculates a portion of exhaust gas to the intake system, an exhaust gas recirculation amount control valve provided in an exhaust gas recirculation passage; an oxygen sensor that detects the concentration; a valve lift amount sensor that detects the lift amount of the exhaust gas recirculation amount control valve; an idle sensor that detects the idle operating state of the engine; ,
a first control means for controlling the exhaust gas recirculation amount control valve in accordance with the operating state; and when the idle sensor detects that the idle operation is being performed, based on the output signal of the valve lift amount sensor; An exhaust gas recirculation control device for a diesel engine, comprising: second control means for controlling the exhaust gas recirculation control valve in accordance with operating conditions.