JP2717442B2 - Engine exhaust gas recirculation control device - Google Patents

Description

The present invention relates to a diesel engine exhaust gas recirculation (EGR).
It relates to a device for controlling the quantity.

(Prior Art) In an exhaust gas recirculation control device for a diesel engine, an exhaust gas recirculation amount control valve (EGR valve) is provided in an exhaust gas recirculation passage connecting an exhaust passage of the engine and an intake passage.
By controlling in accordance with the lift amount to the operating condition of the engine, changing the EGR amount, thereby working to reduce of the NO _X and smoke.

By the way, when the air cleaner, the EGR valve, the fuel injection nozzle, or the like is deteriorated due to aging, the actual EGR amount is different from the required EGR amount. Therefore, an oxygen sensor (linear O ₂ sensor) whose output value changes linearly is provided in the exhaust passage, and a map is prepared that represents a target oxygen concentration according to the operating state of the engine determined by the engine speed and the engine load. There is known a method in which a lift amount of an EGR valve is determined based on a comparison between a target oxygen concentration read from this map and an actual oxygen concentration obtained from the output of the oxygen sensor, and the EGR amount is controlled (Japanese Patent Application Laid-Open No. H10-163,878). 63-9
4061, JP-A-63-201356).

However, with the conventional EGR control method using the target oxygen concentration map as described above, it is possible to perform almost ideal EGR control during steady operation, but especially during transient operation, due to a sudden change in the fuel injection amount, It is not possible to set an appropriate EGR amount due to a difference between the exhaust gas component in the exhaust passage portion where the oxygen sensor is provided and the in-cylinder gas component, or due to a response delay of the oxygen sensor and the EGR valve. As a result, there has been a problem that the EGR valve causes hunting to deteriorate drivability and emission characteristics.

(Object of the Invention) It is an object of the present invention to provide a control device capable of performing optimal EGR control even when an air cleaner, an EGR valve, a fuel injection nozzle, or the like is deteriorated.

(Structure of the Invention) In the present invention, a map representing the target lift amount of the EGR valve in accordance with the operating state of the engine is prepared, EGR control is performed based on this map value, and actual operation is performed by the oxygen sensor only during steady operation. Detects the oxygen concentration, compares the actual oxygen concentration with a map value representing the target oxygen concentration, detects the difference between the two, and learns and corrects the target lift read from the target lift map of the EGR valve based on this difference. It is characterized by doing.

(Effect of the Invention) According to the present invention, the map value of the target EGR amount map, which is the basis of the EGR control, is learned and corrected based on the difference between the actual oxygen concentration during steady operation and the map value of the target oxygen concentration map. Therefore, optimum EGR control can be performed without being affected by deterioration of the air cleaner, the EGR valve, the combustion injection nozzle, and the like.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a schematic diagram showing one embodiment of the present invention.
Is the engine body of the diesel engine, 2 is the intake passage,
Reference numeral 3 denotes an air cleaner provided upstream of the intake passage 2, and reference numeral 4 denotes an exhaust passage. Reference numeral 5 denotes an exhaust gas recirculation passage connecting the exhaust passage 4 and the intake passage 2, and a diaphragm type exhaust gas recirculation amount control valve (EGR valve) 6 for controlling an exhaust gas recirculation amount control valve (EGR amount) in the passage 5. 6 are provided.

Negative pressure chambers (not shown) of the EGR valves 6, 6 are supplied with negative pressure of a vacuum pump 8 controlled by negative pressure control valves 7, 7, which are electromagnetic solenoid valves, through negative pressure passages 9, 9, respectively. Thus, the lift amount of the EGR valves 6, 6 is controlled. Reference numeral 10 denotes a controller, which is a rotation speed sensor 12 of a fuel injection pump 11 and an acrylic opening sensor 13 (injection pump 11
The output of a potentiometer for detecting the lever opening of the exhaust gas and the exhaust passage 4 for detecting the oxygen concentration in the exhaust gas.
The outputs of the oxygen sensor 14, the engine water temperature sensor 15, and the outside air temperature sensor 16 are input. Also
Each of the EGR valves 6 and 6 is provided with an EGR valve lift amount sensor 17 composed of a potentiometer for detecting the lift amount.
Is input to The controller 10 performs duty control of the negative pressure control valves 7, 7 based on these input signals, thereby performing feedback control of the lift amounts of the EGR valves 6, 6.

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

This flow is based on the ignition switch of the engine.
Starting with ON, the engine speed NE is detected from the output of the engine speed sensor 12 of the fuel injection pump 11 in step S1, and 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 whether or not it is a region where EGR is performed based on the engine speed NE and the engine water temperature W / T, and this determination is “YES”.
If so, the process proceeds to step S4, and the accelerator opening ACC is detected from the output of the accelerator opening sensor 13 of the pump 11. In the memory of the controller 10, a map representing a target EGR valve lift amount VL _O (M) according to the engine speed NE and the accelerator opening ACC is stored. In step S5, this map value is read. Then, the actual EGR valve lift amount VL (R) is detected from the output of the EGR valve lift amount sensor 17.
Then, in the next step S7, it is determined whether or not all of the engine speed NE, the accelerator opening ACC, and the actual EGR valve lift amount VL (R) are constant for a certain period of time. If it is changing in step S8
Proceed to. In step S8, it is determined whether the actual EGR valve correction amount ΔVL (R) has been calculated. In this case, since the determination result is “NO”, the value VL read from the target EGR valve lift amount map in step S9 is determined. _O (M) is used as map value VL
(M). Next, in step S10, it is determined whether or not VL (M)> 0. If VL (M)> 0, the process proceeds to step S11, and the actual EGR valve lift amount VL (R) detected in step S6.
And the map value VL (M). VL (M)
While ≠ VL (R), the process proceeds to step S12 to correct the actual EGR valve lift amount VL (R) by changing the duty ratio of the control pulse signal for the negative pressure control valves 6,6. Step S
If the judgment of 10 is "NO", VL (M) = 0 in step S13.
And

On the other hand, when it is determined in step S7 that the engine speed NE, the accelerator opening ACC, and the actual EGR valve lift amount VL (R) are all constant for a certain period of time, the process proceeds to step S14. The engine speed NE is stored in the memory of the controller 10.
Also, a map representing the target oxygen concentration O ₂ (M) corresponding to the accelerator opening is also stored. In step S14, the target oxygen concentration O ₂ (M) is read from this map. Also step
In S15, the actual oxygen concentration O ₂ (R) is detected from the output of the oxygen sensor 14, and in the next step S16, O ₂ (M) and O ₂ (R) are compared. If O ₂ (M) = O ₂ (R), the process returns to step S1, but if O ₂ (M) ≠ O ₂ (R), the difference ΔO ₂ between the _{two is obtained.}
= O ₂ (R) −O ₂ (M) is calculated, and the EGR valve lift amount VL (ΔO ₂ ) corresponding to the oxygen concentration difference ΔO ₂ is calculated in step S17.
Calculate as GR valve lift correction value ΔVL (R)
Return to S8. In this case, since the determination in step S8 is “YES”, the process proceeds to step S18, where the map value VL (M) of the target EGR valve lift amount is corrected by ΔVL (R), and VL (M) = VL
_O (M) + ΔVL (R). In step S11, the corrected map value VL (M) is used as the actual EGR valve lift amount VL.
Compared with (R), if VL (R) ≠ VL (M), the actual EGR valve lift amount VL (R) is corrected in step S12, and step S1
Return to

As is clear from the above description, according to the present invention, EGR
Since the map value of the target EGR valve lift amount map, which is the basis of control, is learned and corrected based on the difference between the actual oxygen concentration and the map value of the target oxygen concentration map during steady operation,
Optimal EGR control can be performed without being affected by deterioration of the air cleaner, the EGR valve, the fuel injection nozzle, and the like.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing one embodiment of the present invention, and FIG. 2 is a flowchart showing the operation thereof. DESCRIPTION OF SYMBOLS 1 ... Engine main body 2 ... Intake passage 4 ... Exhaust passage 5 ... Exhaust gas recirculation passage 6 ... EGR valve, 7 ... Negative pressure control valve 8 ... Vacuum pump, 10 ... Controller 11 ... Fuel injection pump, 12 Rotation speed sensor 13 Accelerator opening sensor 14 Oxygen sensor 17 EGR valve lift sensor

 ────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Katsuhiro Yokomizo 3-1 Shinchi, Fuchu-cho, Aki-gun, Hiroshima Prefecture Inside Mazda Co., Ltd. (56) References JP-A-1-178760 (JP, A) JP-A-1 −182566 (JP, A)

Claims (1)

(57) [Claims] An engine having an exhaust gas recirculation amount control valve in an exhaust gas recirculation passage for recirculating a part of the exhaust gas to an intake system, and an oxygen sensor for detecting the oxygen concentration of the exhaust gas in the exhaust passage. And a second map representing a target lift amount of the recirculation amount control valve according to the operating state of the engine and a second map representing a target oxygen concentration in the exhaust passage according to the operating state of the engine. Means including a memory; means for controlling the recirculation amount control valve based on a comparison between the actual lift amount of the recirculation amount control valve and a target lift amount read from the first map; Means for comparing the actual oxygen concentration detected by the oxygen sensor with the target oxygen concentration read from the second map to detect a difference between the actual oxygen concentration and the target oxygen concentration; The target lift amount read from the first map, the detected exhaust gas recirculation control system for an engine, characterized in that based on the difference and a means for correcting.