JPH02283848A - Exhaust gas recirculation control device for engine - Google Patents

Abstract

PURPOSE:To improve reliability by a method wherein the combustion state of each cylinder is monitored by an oxygen sensor, optimum EGR control responding to unevenness in the combustion state of each cylinder is practicable, and during failure in operation of one oxygen sensor, EGR control is practicable based on an output from other sensor. CONSTITUTION:First and second suction manifold passages 5a and 5b, through which two cylinders wherein a suction stroke and an exhaust stroke are not adjoined to each other are connected to each other, and first and second exhaust manifold passages 8a and 8b are interconnected through EGR passages 10a and 10b in which EGR valves 11 (11a and 11b) are located. Each EGR valve 11 controls a lift amount by applying the negative pressure of a vacuum pump 13, controlled by negative pressure control valves 12a and 12b, on the negative pressure chamber of the EGR valve. In this case, oxygen sensors 15 (15a, 15b) are located in the exhaust manifold passages 8a and 8b, respectively, and each EGR valve 11 is controlled according to outputs from the oxygen sensors. When the one oxygen sensor 15 is failed in operation, each EGR valve 11 is controlled based on an output from the other normal oxygen sensor 15.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to exhaust gas recirculation (E
GR) relates to a device for controlling quantity.

(Prior art) In a 2m exhaust gas recirculation control device for a diesel engine,
An exhaust gas recirculation flow control valve (EGR valve) is provided in the exhaust gas recirculation passage that communicates the engine exhaust passage and intake passage, and the EGR valve lift amount is controlled according to the engine operating condition to change the EGRI. , thereby reducing NOl and smoke. In that case, an oxygen sensor whose output value changes linearly (linear 0. sensor) is installed in the exhaust passage, and a map is installed to determine the target oxygen concentration according to the engine operating condition determined by the engine speed and engine load. There is a known method that controls the EGR amount 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.
JP-A-63-94061, JP-A-63-201356
(see publication).

By the way, the EG of a conventional multi-cylinder diesel engine
In R1lllJ control, the oxygen concentration in the exhaust gas of one cylinder is measured using the oxygen sensor, and the E of all cylinders is measured.
Since the amount of GR is controlled, variations in the characteristics of the fuel injection nozzle and fuel injection pump, variations in the degree of deterioration of the fuel injection nozzle for each cylinder, variations in the swirl strength in the combustion chamber, variations in the amount of intake air, etc. Due to these factors, combustion conditions vary between cylinders, and the required EGR amount differs depending on the cylinder. Therefore, when EGRlllJJ is performed based on the output of one oxygen sensor as in the past, there are problems in that drivability is reduced and noise and vibration are increased.

(Object of the invention) Therefore, the present invention aims to optimize the EG according to the combustion state of each cylinder.
It is an object of the present invention to provide an exhaust gas recirculation control device that is capable of performing RiIillm and is equipped with a fuel safety mechanism in case an oxygen sensor fails.

(Structure of the Invention) In the exhaust gas recirculation control device for an engine according to the present invention, an oxygen sensor is disposed in each of a plurality of collective exhaust passages formed by connecting exhaust passages of cylinders whose exhaust strokes are not adjacent to each other. For example, in the case of an in-line four-cylinder engine with an explosion order of 1-3-4-2, the first and fourth cylinders, which have non-adjacent exhaust strokes, form the first group by connecting their exhaust passages. An oxygen sensor is disposed in each of the first collective exhaust passage and the second collective exhaust passage formed by connecting the second and third cylinders, which are not adjacent to each other in their exhaust strokes, as a second group; In addition, EGR passages are led out from the plurality of collective exhaust passages, and EGR valves are placed in each of these EGR passages to perform EGR control 2Tj for each group, and if one oxygen sensor fails, other normal The present invention is characterized in that the operation of a plurality of EGR valves is controlled based on the output of the oxygen sensor.

(Effects of the Invention) According to the present invention, it is possible to monitor the combustion state of each cylinder using an oxygen sensor, and to perform optimal EGR control according to variations in the combustion state of each cylinder using a minimum number of oxygen sensors. Since this can be done using the same engine, noise and vibration of the engine are reduced.

Furthermore, if one oxygen sensor fails, a plurality of EGR valves are controlled based on the outputs of other normal oxygen sensors, so engine reliability can be improved.

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

FIG. 1 shows a schematic configuration of an EGR control device according to the present invention. 3a to 3d are the main bodies of an in-line four-cylinder diesel engine that includes the first to fourth cylinders 2a to 2d and has an exhaust stroke order (explosion order) of 1-3-4-2;
Intake passages 4a to 4d are independently provided for each cylinder d, and exhaust passages 4a to 4d are independently provided to each cylinder 2a to 2d.

Then, the intake passages 3a and 3d of the first cylinder 2a and the fourth cylinder 2d whose exhaust strokes are not adjacent to each other are connected to each other on their upstream sides to form a first collective intake passage 5a. , Similarly, the intake passages 3b of the second cylinder 2b and the third cylinder 2C whose exhaust strokes are not adjacent to each other,
3C are connected to each other on their upstream sides to form a second collective intake passage 5b, and further these two collective intake passages 5a and 5b are connected to each other on their upstream sides,
A common intake passage 7 including an air cleaner 6 is formed.

On the other hand, the exhaust passages 4a and 4d of the first cylinder *2a and the fourth cylinder 2d, which are not adjacent to each other in the exhaust stroke, are also connected to each other on their downstream sides to form a first collective exhaust passage 8a, and similarly The exhaust passages 4b and 4C of the second cylinder 2b and third cylinder 2C which are not adjacent to each other are also connected to each other on their downstream sides to form a second collective exhaust passage 8b, and these two collective exhaust passages 8a and 8b are also connected to each other on their downstream sides to form a second collective exhaust passage 8b. are connected to each other on their downstream sides to form a common exhaust passage 9.

The first collective exhaust passage 8a and the first collective intake passage 5a are communicated through an exhaust gas recirculation passage (EGRijl path>102), and a diaphragm type EGR valve 11a for controlling exhaust gas recirculation 1 (EGRI) is disposed in this passage 10a. Similarly, the second collective exhaust passage 8b and the second collective intake passage 5b are communicated through an EGR passage 10b, and a diaphragm type EGR valve 11b is disposed in this passage lOb.

In the negative pressure chambers (not shown) of the EGR valves 11a and llb,
Negative pressure control valves 12a, 12 consisting of tiff solenoid valves
The negative pressure of the vacuum pump 13 controlled by the EGR valves 11a and 14b is applied through the negative pressure passages 14a and 14b, respectively, thereby controlling the lift amount of the EGR valves 11a and 11b. Further, in the collective exhaust passages 8a and 8b, an oxygen sensor 15a for detecting the oxygen concentration in the exhaust gas,
15b are provided respectively. 16 is a controller, and a rotation speed sensor 18 with which the fuel injection pump 17 is provided.
, the output of the accelerator opening sensor 19 (a potentiometer that detects the lever opening of the injection pump 17), the outputs of the oxygen sensors 15a and 15b, and others are input. Also E
The GR valves 11a and llb are equipped with an EGR valve lift amount sensor 20 consisting of a potentiometer that detects their lift amounts.
a, 20b are provided respectively, and these sensors 2
The outputs of Qa and 20b are also input to the controller 16.

The controller 16 duty-controls the negative pressure control valve 12a based on the output of the oxygen sensor 15a, and controls the EGR valve 1.
The lift amount of cylinder 1a is controlled, thereby performing EGR control for first cylinder 2a and fourth cylinder 2d. Further, the controller 16 performs duty control on the negative pressure control valve 12b based on the output of the oxygen sensor 15b to control the lift amount of the EGR valve 11b, thereby controlling EGRj# for the second cylinder 2b and the third cylinder 2C. I am doing it.

In the memory of the controller 16, as shown in FIG.
Target oxygen concentration VO according to engine speed NB and accelerator opening ACC! (M) is stored, and EGR control is performed based on a comparison between this map value and the actual oxygen concentration vO, (R) detected by the outputs of the oxygen sensors 15a and 15b. It has become.

In this way, in this embodiment, four cylinders 4a to 4d
are divided into two groups and EGR control is performed for each group. In this case, if we look at the intake period and exhaust period of two cylinders whose exhaust strokes are not adjacent, for example, the first cylinder M2a and the fourth cylinder 2d, As shown in FIG. 3, there occurs a period in which the intake stroke of one cylinder and the exhaust stroke of the other cylinder overlap. Therefore, by setting the delay amount of the EGR valve lift signal according to the engine speed in advance, the combustion status of each cylinder can be independently monitored by each oxygen sensor 15a or 15b.
It becomes possible to control GRI.

On the other hand, oxygen sensor (linear 0. sensor) 15a, 15
,b have variations in initial quality and also have individual differences in the degree of deterioration, so the two oxygen sensors 15a, 1
It is necessary to correct the output of 5b.

Further, in this embodiment, there is a possibility that one or both of the oxygen sensors 15a and 15b may fail.Even in such a case, EcR1ll? In order to enable i, a control 411 as shown in the flowchart of FIG. 4 is executed.

That is, first, it is determined whether or not it is the time of fuel cut (during deceleration) (step S1), and when the fuel is cut, (1) the outputs of the oxygen sensors 15a and 15b are both within the setting range shown in FIG. If it is within (step S2), the outputs of the oxygen sensors 15a and tsb are corrected to the set values (step S3), and normal control is performed (step S4).

(2) If the output of one of the oxygen sensors 15aS and 15b is within the set range but the output of the other is outside the set range, the output of the oxygen sensor whose output is within the set range is corrected to the set value. The two systems of EGRt are controlled using the corrected output of the oxygen sensor (steps S5 to S7).

(3) If the outputs of both oxygen sensors 15a and 15b are out of the set range, the target EGR valve lift device L (M ), and performs EGR control based on a comparison between this map value and the actual EGR valve lift amount V L (R) determined by the output of the lift amount sensors 20a and 20b (step S8). .

(4) Normal system except during fuel cut? B is performed (step S9).

Note that in a diesel engine, fuel is stratified in the combustion chamber, so the oxygen sensor 15 is not activated while the exhaust valve is open.
The outputs of a and 15b change. However, as a requirement on the engine side, it is only necessary that EGRI during one stroke can be controlled correctly, and EGR@-t
- does not need to be controlled, therefore the EGR valve 11a,
In order to prevent variations in Ilb, the EGR valve opening degree for the next 360° may be set based on the average value of the oxygen sensor output for 360°.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment of the present invention, FIG. 2 is a target oxygen concentration map, FIG. 3 is a timing chart showing the intake period and exhaust period of the first and fourth cylinders, and FIG. 4
The figure is a control flowchart, Figure 5 is a graph showing the relationship between the oxygen sensor output and the oxygen concentration, and Figure 6 is the target E.
This is a GR valve lift amount map. l--Engine body 2a, 2d-Cylinder 3a-3
d...-Intake passage 4a to 4d-Exhaust passage 5a, 5b.
- Collective intake passage 8a, Bb - Collective exhaust passage 10 a, 10 b - EGR passage 11 a, I l b... EGR valve 12 a, 12 b
--- Negative pressure control valve 13 --- Vacuum pump 16 --- Controller 17 --- Fuel injection pump

Claims (1)

[Claims] In a multi-cylinder engine that performs exhaust gas recirculation control based on the output of an oxygen sensor installed in an exhaust passage, the exhaust passages of cylinders in which exhaust strokes of the multi-cylinder engine are not adjacent are connected to each other. an oxygen sensor disposed in each of the formed plurality of collective exhaust passages, an exhaust gas recirculation passage led out from each of the plurality of collective exhaust passages, and an exhaust gas recirculation amount control valve disposed in each of these exhaust gas recirculation passages. and a control means for operating the plurality of exhaust gas recirculation amount control valves based on the output of other normal oxygen sensors when one oxygen sensor fails. Device.