JPS59215953A - Exhaust gas recirculation controlling method in diesel engine - Google Patents

Abstract

PURPOSE:To check the discharge of white or black smoke in time of running at highland, by determining a fundamental exhaust recirculation flow rate according to engine load, while compensating this recirculation flow rate for reduction in proportion to a drop in suction pressure, and controlling the exhaust circulation. CONSTITUTION:In time of engine operation, at a control unit 25, first a fundamental duty ratio D is determined on the basis of an engine speed Ne detected at an engine speed sensor 26 and a fuel injection quantity Fq detected at a fuel injection quantity sensor 29. Then, a compensation coefficient K is determined on the basis of the engine speed Ne and suction pressure Pm detected at a suction pressure sensor 30. In succession, operation that adds the compensation coefficent K to the fundamental duty ratio ratio D takes place whereby an output duty ratio Do is found, giving a pulse signal by this output duty ratio Do to a suction pressure control valve 43. And, the suction pressure controlled by the said valve 43 is led into a diaphragm chamber 41, thus the opening of an EGR control valve 34 is controlled.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an exhaust gas recirculation control method for a diesel engine used in a vehicle such as an automobile.

Exhaust gas recirculation of diesel engines used in vehicles such as automobiles is carried out at a flow rate depending on the engine load in order to replace a portion of the excess intake air drawn into the engine combustion chamber with exhaust gas. ing.

Even when the amount of intake air relative to the engine load decreases due to intake throttling or high-altitude driving, etc., if exhaust gas is recirculated at the same flow W as when it is not, oxygen deficiency will occur, resulting in white smoke or black smoke. Emissions will increase.

The present invention performs exhaust gas recirculation by correcting the flow rate so that the amount of white smoke or black smoke does not increase even if the amount of intake air that affects the engine load is reduced due to intake throttling or high-altitude driving, etc. Provides exhaust gas recirculation control method [
It is considered to be one target.

According to the present invention, this purpose is to detect the load and intake pressure of the diesel engine, determine the basic exhaust gas recirculation flow rate according to the load of the diesel engine, and adjust the basic exhaust gas recirculation flow rate to the intake pressure. This is achieved by a method of controlling exhaust gas recirculation for a D-Hill engine, in which a reduction is corrected in accordance with the reduction in flow rate, and exhaust gas is recirculated at the corrected flow rate.

Intake pressure decreases as atmospheric pressure decreases due to intake throttling or high-altitude driving, so the basic exhaust gas recirculation flow rate determined according to the load of the diesel engine is reduced in accordance with the decrease in intake pressure. Even if the intake air flow decreases due to intake throttling or high-altitude driving, exhaust gas recirculation will not be performed at an excessive flow rate, and the generation of white smoke or black smoke will be avoided. .

The invention will now be described in detail by way of example embodiments with reference to the accompanying drawings.

FIG. 1 shows an embodiment of a diesel engine equipped with an exhaust gas recirculation device implementing the exhaust gas recirculation control method according to the present invention. In the figure, 1 indicates a diesel engine, which has a cylinder bore 2, in which a piston 3 is slidably received;
A combustion chamber 4 is defined above the piston 3. The diesel engine 1 includes a swirl chamber 6 communicating with a combustion chamber 4 through a nozzle 5.
The vortex chamber has a combustion chamber. Liquid fuel for the Reso Easel engine is injected and supplied from the F+1 injection nozzle 7. The diesel engine 1 sucks air into the combustion chamber 4 via an intake throttle device 8 and an intake manifold 9 via an intake boat (not shown), and from the combustion chamber 4 to an exhaust port 10.
Exhaust gas is discharged to the exhaust manifold 11 through. The intake boat and the exhaust port 10 are each opened and closed by poppet valves, and in the figure, only the poppet valve for 111 air is indicated by reference numeral 12.

The intake throttle device 8 includes a main intake throttle valve 14 that opens and closes the main intake passage 13, and a sub-intake throttle valve 16 that opens and closes a sub-intake passage 15 provided by bypassing the intake passage 13. . The main intake throttle valve 1/I is drivingly connected to the accelerator pedal 17, and when the accelerator pedal 17 is released, it is in the fully open position as shown in the figure. The valve is opened in accordance with the increase in depression of the pedal 17. The sub-intake throttle valve 1G is drivingly connected to the double diaphragm device 1B, and the diaphragm chamber 1
When atmospheric pressure is introduced to both 9 and 20, all questions 4C as shown! When located in the field and atmospheric pressure is introduced into one diaphragm chamber and negative pressure is introduced into diaphragm chamber 20, it is located in the half-open position, and negative pressure is introduced into both diaphragm chambers 19 and 20. Sometimes it is in the fully open position.

The diaphragm chambers 19 and 20 each have a negative pressure control valve 21.2.
2. J: Negative pressure and atmospheric pressure are selectively introduced. The negative pressure control valves 21 and 22 are both electromagnetic negative pressure control valves, and when energized, the negative pressure of the negative pressure tank 23 is introduced into the diaphragm chamber 19 or 20, and when not energized, atmospheric pressure is introduced into the diaphragm chamber 19 or 20. It is set to be introduced. The negative pressure control valves 21 and 22 are energized and controlled by a control device 25, which will be described later.

The exhaust manifold 11 includes an exhaust gas intake boat 31.
Each intake manifold 9 is provided with an exhaust gas injection boat 32, and the exhaust gas intake boat 31 is connected to a dedicated pipe 33.
, an exhaust gas recirculation control valve 34 and a conduit 35 to the exhaust gas injection port 32 .

The exhaust gas recirculation control valve 34 includes a valve element 37 for opening and closing the valve port 36, which is connected by a valve rod 38 to a diaphragm device 39 and in a diaphragm chamber 41 provided on one side of the diaphragm 40. When negative pressure is not introduced, the pressure is pushed down by the spring force of the compression spring 42 to close the valve port 36, whereas when negative pressure is introduced into the diaphragm chamber/11, the compression spring 42 is pressed down. The valve port 36 is opened in accordance with the magnitude of the negative pressure.

Negative pressure and atmospheric pressure are selectively introduced into the diaphragm chamber 41 by a negative pressure control valve 43. The negative pressure control valve 43 is an electromagnetic zero-pressure control valve, which introduces the negative pressure of the negative pressure tank 23 into the diaphragm chamber 41 when energized, and introduces atmospheric pressure into the diaphragm chamber 41 when not energized. By repeating a energized state and a non-energized state by being given a pulse signal of a predetermined frequency, negative pressure is supplied to the diaphragm chamber 41, which increases in accordance with an increase in the decoupage ratio of the pulse signal.

The control device 25 controls the energization of the negative pressure control valve 43 .

The control device 25 is an electric type such as a microcomputer, and receives information regarding the engine rotation speed from a rotation speed sensor 26, information regarding opening/closing from an engine switch (ignition switch) 27, and information regarding opening/closing from an engine switch (ignition switch) 27. 2
8, the information regarding the engine cooling water temperature is
The intake throttle device 8J receives information regarding the fuel injection interval from the 1-hung sensor 29, and information regarding the intake pressure in the intake passage on the downstream side of the intake throttle device 8J based on the intake flow from the intake pressure sensor 30. The control valves 21, 22 and 43 are designed to control energization. The fuel injection peak sensor 29 may be of a type that detects the spill ring position of the fuel injection pump and detects the fuel injection interval from this. Further, the time between fuel injections may be detected based on the amount of depression of the accelerator pedal.

The control device 25 energizes both the Ω sweat control valves 21 and 22 when the engine switch 27 is closed and the engine cooling water temperature detected by the water temperature sensor 28 is below a predetermined value, for example 60°C. When the 1n11 cooling water temperature is higher than a predetermined value, only the negative pressure control valve 22 is energized, and when the engine switch 27 is opened to stop the engine, a predetermined period of time has elapsed since the engine switch 27 was opened. The program is designed to energize both negative pressure control valves 21 and 22 until the time is reached.

As described above, by controlling the energization to the zero pressure control valves 21 and 22, the sub intake throttle valve 16 is brought to the fully open position when the engine is warmed up, and is brought to the half open position after the engine is warmed up. When stopped, it is brought to the fully open position. During idling, the accelerator pedal 17 is released and the main intake throttle valve 14 is in the fully open position, and at this time, intake throttle is performed by intake air through the auxiliary intake passage 15 only with the lever. This idle intake throttle becomes larger after warm-up is completed than during warm-up because the opening position of the auxiliary intake throttle 16 is controlled as described above.

The control device 25 adjusts a predetermined basic duty ratio between the engine rotation speed Ne detected by the rotation speed sensor 26 and the engine rotation speed Ne detected by the rotation speed sensor 26, for example, as shown in FIG. It is determined by calculation or read from the data memory according to the FQ detected by the fuel injection m sensor 29, and is determined in advance according to the intake pressure and engine speed, as shown in FIG. 3, for example. correction coefficient K
is calculated or read from the data memory and determined according to the engine rotation @Ne and the intake pressure pm detected by the intake pressure sensor 30, the correction coefficient 1 is multiplied by the basic duty ratio, and this product is output. The duty ratio is set to DO.

Next, an example of the implementation procedure of the exhaust gas recirculation control method according to the present invention will be explained with reference to the flowchart shown in FIG.

The routine of the flowchart shown in FIG. 4 is executed by time interrupt or engine crank angle interrupt, and in the first step 1, information from each sensor is input.

Next, in step 2, the engine speed Ne detected by the engine speed sensor 26 and the fuel injection [1 sen + fuel injection ff1Fq detected at J29 as shown in FIG. The basic duty ratio is determined according to such characteristics. This basic duty ratio is the fuel injection IJ
It decreases as 1i increases and the engine speed increases. Note that, in a diesel engine using an electronically controlled fuel supply system, the basic duty ratio -0- may be determined according to the fuel injection interval determined electronically.

Next, in step 3, the engine speed is determined as shown in FIG. A correction coefficient is determined according to the characteristics.

Correction coefficient 1 (intake pressure is standard atmospheric pressure 760 ml1)
-1g or less, it is 1.0, and when the pressure is below standard atmospheric pressure, it decreases to 1.0 or less as the intake pressure decreases.

Next, in step 4, an operation n is performed in which the correction coefficient K stored in step 3 is multiplied by the basic duty ratio determined in step 2, and this product is the output duty ratio I). o, and a pulse signal based on this output duty ratio Do is given to the negative pressure control valve 43. At this time, the exhaust gas recirculation flow rate is reduced and corrected in accordance with the decrease in intake pressure, and even if the intake pressure is decreased due to intake throttling or high-altitude driving, an appropriate flow rate is maintained according to the intake air amount at that time.
- Exhaust gas recirculation is carried out, so there is no oxygen shortage and no white or black smoke is generated.

The basic duty ratio, in other words, the basic exhaust gas recirculation flow rate reduction correction coefficient may be the product of a correction coefficient according to the intake pressure and a correction coefficient according to the engine speed.

FIG. 5 is a flowchart showing the procedure for controlling the basic exhaust gas recirculation flow rate using a correction coefficient based on intake pressure and a correction coefficient based on engine speed. The routine of the flowchart shown in FIG. 5 is executed by time interrupt or time crank angle interrupt, and in the first step 1, input from each sensor is performed.

Next, in step 2, it is determined whether the diesel engine 1 is being operated at idle.

Idling operation can be determined by fuel 11'! l injection ffl sensor 2
This is done based on the fuel injection amount detected by 9. Incidentally, if an accelerator depression amount detection sensor for detecting the amount of depression of the accelerator pedal is provided, h (the detection may be performed based on the amount of depression of the accelerator pedal detected by this sensor).

If the vehicle is not idling, the process proceeds to step 5, but if the vehicle is idling, the process proceeds to step 3.

In step 3, a correction coefficient 1<1 is determined based on the intake pressure Pm detected by the intake pressure sensor 30 at this time. + in the correction coefficient for the intake pressure Pm is the 6th
As shown in the figure, the intake pressure is standard human pressure 760.
mm1-10 J: 1. When the value is above a slightly lower predetermined value.
0, and when it is less than the predetermined value, it decreases to 1.0 or less as the intake pressure decreases.

In step 4, + is recorded in the correction coefficient determined in step 3.

In step 5, a correction coefficient 1<2 is determined in accordance with the engine speed N+3 detected by the engine speed sensor 26. The correction coefficient for engine speed NO is 2.
As shown in FIG. 7, when the engine speed is below a predetermined value, it is 1.0, and when it is above the predetermined value, it decreases to 1.0 or less as the engine speed increases.

Next, in step 6, the engine speed Ne detected by the engine speed sensor 26 and the fuel injection! ) 1 sensor 29
The basic duty ratio is determined according to the characteristics shown in FIG. 2 in accordance with the fuel injection ff1FQ detected by the fuel injection ff1FQ.

Next, in step 7, the correction coefficient stored in step 4 is multiplied by 1 and the correction coefficient determined in step 5 is multiplied by 2, based on the basic duty ratio determined in step 5. The calculation is performed, and this product is the output duty ratio 1'
)0, and a pulse signal based on the output duty ratio is given to the negative pressure control valve 43.

Therefore, in this embodiment as well, the exhaust gas recirculation flow rate is reduced and corrected according to the decrease in intake pressure, and even if the intake pressure decreases due to intake throttling or when driving at high altitudes, the exhaust gas recirculation flow rate is reduced according to the intake air amount at that time. Exhaust gas recirculation takes place at appropriate flow rates.

Although the present invention has been described in detail with respect to specific embodiments above, the present invention is not limited thereto, and various embodiments are possible within the scope of the present invention. This should be obvious to those skilled in the art.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram showing one embodiment of a diesel engine equipped with an exhaust gas recirculation device that implements the exhaust gas recirculation control method according to the present invention, and FIG. Figure 3 is a graph showing the correction coefficient characteristics.
FIG. 4 is a flowchart showing one implementation procedure of the exhaust gas recirculation control method according to the present invention, FIG. 5 is a flowchart showing another implementation procedure of the exhaust gas recirculation control method according to the invention, and FIG. FIG. 7 is a graph showing the correction coefficient characteristic depending on the intake pressure, and FIG. 7 is a graph showing the correction coefficient characteristic depending on the engine speed. 1...Diesel engine, 2...Cylinder bore, 3.
... Piston, 4... Combustion chamber, 5... Nozzle, 6...
- Vortex chamber. 7... Combustion injection nozzle, 8... Intake throttle device, 9...
...Intake manifold, 10...Exhaust boat, 11.
...Exhaust manifold, 12...Popets 1~valve, 13
...Main intake -1/I- passage, 1/I...Main intake throttle valve, 15...Sub-intake passage. 16... Sub-intake throttle valve, 17... Accelerator pedal,
18...Double diere flam device, 19.20...
Diaphragm chamber, 21.22...Negative pressure control valve, 23.
...0 pressure tank, 25...control device, 26...rotation speed sensor. 27... Engine switch, 28... Water wetness sensor, 29
...Fuel injection ■sensor, 30...Intake pressure sensor,
31... Exhaust gas intake boat, 32... Exhaust gas injection boat, 33... Conduit, 34... Exhaust gas recirculation control valve. 35... Conduit, 36... Valve port, 37... Valve element, 38... Valve rod, 39... Diaphragm device, 40... Diaphragm, /11... Diaphragm chamber, 42... ...Compression coil spring, 43...Negative pressure control valve patent applicant: Toyota Motor Corporation representative
Attorney Patent Attorney Akashi 8 Takeshi 15- Fig. 1 Fig. 2 Engine speed Ne Fig. 3 Engine rotation speed Ne Fig. 4 Fig. 5 Fig. 6 760 mmHg Intake pressure Pm - Fig. 7 Engine speed Ne

Claims (1)

[Claims] The load and intake pressure of the diesel engine are detected, the basic exhaust gas recirculation flow rate is determined according to the load of the diesel engine, the basic exhaust gas recirculation flow rate is corrected to be reduced according to the decrease in the intake pressure, and this reduction is A method for controlling exhaust gas recirculation for a diesel engine, characterized by performing exhaust gas recirculation at a corrected flow rate.