JPS63208658A - Control method and device for exhaust gas recirculation in internal combustion engine - Google Patents

Abstract

PURPOSE:To preform suitable exhaust gas recirculation (EGR) in proper quantities by determining an engine load in starting EGR action according to the number of engine revolutions, and controlling an EGR device so that EGR may be performed when the engine load is above the above-mentioned engine load. CONSTITUTION:During the operation of an internal combustion engine 1, a decision is given on whether the number of engine revolutions detected by an engine speed sensor 51 is below its first fixed value or not, and when it is below the first fixed value, a throttle opening in starting EGR is set to the minimum value. On the other hand, when it is not below the first fixed value, a decision is given on whether a difference between the detected number of engine revolutions and the first fixed number of engine revolutions is below the second fixed value (> the first fixed value) or not, and when the above-mentioned difference is not below the second fixed value, the throttle opening in starting EGR is set to the maximum value. When the actual throttle opening obtained by a throttle opening sensor 52 is wider than the throttle opening in starting EGR set as mentioned above, a negative pressure control valve 45 is turned on, and the negative pressure is therefore introduced into the diaphragm chamber 27 of an EGR valve 20 to open it for starting EGR action.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an exhaust gas recirculation control method for an internal combustion engine used in a vehicle such as an automobile, and an exhaust gas recirculation method used to implement the exhaust gas recirculation control method. Related to equipment.

2. Description of the Related Art It has been well known that exhaust gas recirculation is performed in internal combustion engines used in vehicles such as automobiles in order to reduce NOx in the exhaust gas discharged from the internal combustion engine.

Exhaust gas recirculation of an internal combustion engine is not carried out when the load of the internal combustion engine is below a predetermined value, but is carried out when the load of the internal combustion engine is above a predetermined value, in order to achieve both reduction of NOx and operability of the internal combustion engine. Therefore, conventionally, exhaust gas recirculation is performed when the throttle opening is above a predetermined value or when the intake pipe pressure is above a predetermined value. The device is disclosed in, for example, Utility Model Application No. 53-22920, Utility Model Publication No. 58-23975,
It is shown in the official gazette.

Problems to be Solved by the Invention In an exhaust gas recirculation device that is configured to perform exhaust gas recirculation when the throttle opening is above a predetermined value, exhaust gas recirculation starts quickly at the time of starting. If the opening pressure of the negative pressure-operated exhaust gas recirculation control valve is set low as shown in FIG.
When the engine speed is high, the intake pipe pressure becomes low, which causes unnecessary exhaust gas recirculation in the high speed and low throttle opening range, which deteriorates the operability of the internal combustion engine. There is a risk that unburned components in the exhaust gas will increase.

On the other hand, in an exhaust gas recirculation device configured to perform exhaust gas recirculation when the intake pipe pressure is above a predetermined value, the exhaust gas recirculation device is configured to perform exhaust gas recirculation during idle operation. Once the recirculation start intake pipe pressure is set, the required exhaust gas recirculation will not occur in the high rotation range where the intake pipe pressure decreases even during non-idling driving when the accelerator pedal is depressed. There is a risk.

SUMMARY OF THE INVENTION An object of the present invention is to provide an improved exhaust gas recirculation control method that solves the above-mentioned problems, and an exhaust gas recirculation device used to implement the control method.

Means for Solving the Problems According to the present invention, the above-mentioned object is to detect the rotational speed of an internal combustion engine, determine the engine load for starting exhaust gas recirculation according to the rotational speed, and An exhaust gas recirculation control method for an internal combustion engine, which performs exhaust gas recirculation when the load is equal to or higher than the exhaust gas recirculation start engine load, and an exhaust gas recirculation device used to implement this control method. , an exhaust gas recirculation control valve that is provided in the middle of the exhaust gas recirculation passage and increases its opening amount in accordance with an increase in the negative pressure introduced into the diaphragm chamber, and a negative pressure passage means for guiding the negative pressure to the diaphragm chamber. an orifice element provided upstream of the exhaust gas recirculation control valve in the exhaust gas recirculation passage and defining a pressure chamber between the exhaust gas recirculation control valve and the exhaust gas recirculation control valve; and an orifice element in the middle of the negative pressure passage means. a negative pressure regulating valve provided in the pressure chamber to adjust the negative pressure supplied to the diaphragm chamber in response to exhaust gas pressure in the pressure chamber; and a negative pressure regulating valve provided in the middle of the negative pressure passage means to communicate with the negative pressure passage means. a negative pressure control valve that is switched between a first switching position and a second switching position that opens the negative pressure passage means to the atmosphere; and a control device for switching the negative pressure switching valve to the first switching position.

Effects and Effects of the Invention According to the exhaust gas recirculation control method and exhaust gas recirculation device according to the present invention, the exhaust gas recirculation area changes depending on the rotation speed of the internal combustion engine, thereby preventing the start of exhaust gas recirculation. Exhaust gas recirculation can be carried out in an appropriate state with no excess or deficiency even if it is carried out depending on the throttle opening or intake pipe pressure.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will now be described in detail by way of embodiments with reference to the accompanying drawings.

FIG. 1 shows one embodiment of an exhaust gas recirculation device according to the invention. In the figure, 1 indicates an internal combustion engine, which sucks a mixture into a combustion chamber through a throttle valve 2, a surge tank 4, and an intake manifold 5, and exhausts burned gas, that is, exhaust gas. It is designed to be discharged to manifold 6.

The exhaust manifold 6 is provided with an exhaust gas intake boat 7 for exhaust gas recirculation, and the surge tank 4 is provided with an exhaust gas injection boat 8. are connected to each other by a conduit 9 for exhaust gas recirculation, an exhaust gas recirculation control valve 20 and a conduit 10.

The exhaust gas recirculation control valve 20 has an inlet port 21 and an outlet port 22, the inlet boat 21 being connected in communication with the exhaust gas intake port 7 by a conduit 9, and the outlet boat 2
2 is connected in communication with the exhaust gas injection port 8 by a conduit 10. Exhaust gas recirculation control valve 20 is connected to valve port 23
and a valve element 24, and the valve port 23 has a valve element 24.
4, and the degree of opening is controlled to control the exhaust gas recirculation flow rate. The valve element 24 is connected to a diaphragm 26 of a diaphragm device 25, and when a negative pressure greater than a predetermined value is not introduced into the diaphragm chamber 27, it is pushed down by the spring force of a compression coil spring 28 to close the valve port 23 and open the diaphragm chamber 27. When a negative pressure greater than a predetermined value is introduced into the valve boat 27, the valve boat 23 rises in response to the negative pressure against the spring force of the compression coil spring 28 to open the valve boat 23.

The diaphragm chamber 27 of the exhaust gas recirculation control valve 20 is connected to an intake pipe negative pressure outlet port 32 provided in the surge tank through two conduits, a negative pressure regulating valve 30 for controlling back pressure, and a conduit 31. There is. As shown in the figure, the intake pipe negative pressure take-out port 32 is provided downstream of the throttle valve 2 and is always subjected to intake pipe negative pressure.

The negative pressure regulating valve 30 has a valve element 36 that opens and closes the valve boat 35 and a diaphragm 37 supporting the valve element. A chamber 38 and a diaphragm chamber 39 are defined on the lower side, and the diaphragm closes the valve by the action of a compression coil spring 40 when pressure (positive pressure) higher than a predetermined value is not introduced into the diaphragm chamber 39. Element 3
6 is separated from the valve port 35 to open the valve port, and when pressure above a predetermined value is introduced into the diaphragm chamber 39, the valve moves upward in the figure against the action of the compression coil spring 40. Displace the valve element 36 from the valve boat 35
The valve boat is located in a position where the valve boat is brought into contact with the valve boat and the valve boat is closed.

The diaphragm chamber 39 of the negative pressure regulating valve 30 is connected by a conduit 41 to a pressure chamber 4 between the valve port 23 of the exhaust gas recirculation control valve 20 and an orifice 42 provided on the downstream side thereof.
3, and the exhaust gas pressure in the pressure chamber is introduced.

The structure consisting of the negative pressure regulating valve 30 and the orifice 42 as described above is a well-known back pressure control mechanism, and the diaphragm of the exhaust gas recirculation control valve 20 keeps the exhaust gas pressure in the pressure chamber 43 almost constant at all times. The negative pressure supplied to the chamber 20 is adjusted, in other words, the opening degree of the valve port 23 is adjusted, thereby maintaining the ratio of the exhaust gas recirculation flow rate to the intake air flow rate, that is, the EGR rate, almost constant at all times. It looks like this.

The atmosphere opening chamber 38 of the negative pressure regulating valve 30 is connected to an intake pipe negative pressure outlet port 46 through a conduit 47 . The intake pipe negative pressure take-out port 46 is located upstream of the throttle valve 2 when the opening is below a predetermined opening, and is located downstream of the throttle valve 2 when the opening is more than the predetermined opening to release the intake pipe negative pressure. It is now being influenced by

In this embodiment, the intake pipe negative pressure appearing at the intake pipe negative pressure take-out port 46 according to the opening degree of the throttle valve 2 is supplied to the atmosphere opening chamber 38 of the negative pressure regulating valve 30, thereby achieving medium load operation. At times, the EGR rate will increase.

A negative pressure control valve 45 is provided in the middle of the conduit 29 .

The negative pressure control valve 45 is configured as an electromagnetically actuated three-way switching valve, and includes a port a connected to the diaphragm chamber 27, a port b connected to the negative pressure regulating valve 34, and a port C open to the atmosphere. When energized, that is, in the on state, port a is disconnected from port C and connected to port b, while when not energized, that is, in the off state, port a is disconnected from port b and connected to port C. It is designed to be connected to the The supply of electricity to the negative pressure control valve 45 is controlled by a control device 50 such as a microcomputer.

The control device 50 is provided with information regarding the rotation speed of the internal combustion engine 1 from the rotation speed sensor 51 and information regarding the opening amount of the throttle valve 2 from the throttle opening sensor 52, and based on these information, the control device 50 operates as shown in FIG. The power supply to the negative pressure control valve 45 is controlled according to the flowchart shown in FIG.

Next, one embodiment of the energization control of the negative pressure control valve 45 will be described with reference to the flowchart shown in FIG.

First, in step 10, the rotation speed sensor 51 detects
The engine rotation speed No. is a predetermined first predetermined value N.
A determination is made as to whether or not it is equal to or less than e5etl. Ne≦
If N5eset +, proceed to step 12; otherwise, proceed to step 14.

In step 12, the EGR starting throttle opening e
set to the minimum value θff1in.

In step 14, the engine speed difference ΔNe is calculated by subtracting the first predetermined value Nθ5etl from the engine speed Ne detected by the speed sensor 51.

After step 14, the process advances to step 16.

In step 16, the rotational speed difference ΔNe is set to a second predetermined value N that is larger than a predetermined first predetermined value Ne5et+.
0ΔN for which it is determined whether it is smaller than eset2
If e≦N eset2, the process proceeds to step 20; otherwise, the process proceeds to step 18.

In step 18, the EGR starting throttle opening θs
et is set to the maximum value θWaX.

In step 20, the EGR starting throttle opening e set is calculated according to the following formula.

eset -emin + (emax -emln
) (ΔNe/N eset2) As mentioned above, in steps 12.18 and 20, EG
The R starting throttle opening degree θset is set according to the engine speed Ne, as shown in FIG.

Steps 12.18 and 20 are followed by step 22.

In step 22, it is determined whether the throttle opening θ detected by the throttle opening sensor 52 is smaller than the EGR starting throttle opening e set. e
If ≦e set, the process proceeds to step 24; otherwise, the process proceeds to step 26.

In step 24, the negative pressure control valve 45 is de-energized to turn it off. When the negative pressure control valve 45 is in the OFF state, boat A is in the OFF state.
Since the diaphragm chamber 27 is opened to the atmosphere, exhaust gas recirculation is not performed.

In step 26, the negative pressure control valve 45 is energized to turn it on. At this time, boat a is connected to boat b, negative pressure is introduced into the diaphragm chamber 27, and exhaust gas recirculation is performed.

By controlling the energization to the negative pressure control valve 45 as described above, exhaust gas recirculation is performed when the throttle opening e is equal to or greater than the EGR starting throttle opening eset, as shown in FIG. This EGR starting throttle opening increases as the engine speed Ne increases, and correspondingly, when the engine speed Ne is high, the exhaust gas recirculation range in the low throttle opening range decreases.

FIG. 4 shows another embodiment of the energization control of the negative pressure control valve 45 in the exhaust gas recirculation device according to the present invention.

In the embodiment shown in FIG. 4, the control device 52 is provided with information regarding the intake pipe pressure from an intake pressure sensor 53 instead of the throttle opening sensor 52, and a water temperature sensor 54.
Information regarding the cooling water temperature of the internal combustion engine 1 can be provided.

In the flowchart shown in FIG. 4, in the first step 30, the cooling water temperature Tv detected by the water temperature sensor 54 is set to a predetermined value Twsets.
For example, it is determined whether the temperature is 30° C. or higher. Tw
>Tvset, the process proceeds to step 32; otherwise, the process proceeds to step 48 so that exhaust gas recirculation is not performed.

In step 32, the engine rotation speed Ne detected by the rotation speed sensor 51 is set to a predetermined first predetermined value Ne.
A determination is made as to whether or not it is less than or equal to 5 etl. Ne≦N
If e5et+, the process proceeds to step 34; otherwise, the process proceeds to step 36.

In step 34, EGR start intake pipe pressure P 1s
Setting et to a maximum value P Imax is performed.

In step 36, the engine speed difference ΔNe1 is calculated by subtracting the first predetermined value Ne5etl from the engine speed Ne. Step 36 is followed by step 38
Proceed to.

In step 38, it is determined whether the rotational speed difference ΔNel is equal to or less than a second predetermined value N eset2, which is larger than the first predetermined value N esetl . If ΔNel≦N eset2, the process proceeds to step 42; otherwise, the process proceeds to step 40.

In step 40, EGR starting intake pipe pressure P l5
Setting et to a minimum value P 1 mIn is performed.

In step 42, the rotation speed difference ΔNe1 is subtracted from the second predetermined value N eset2 to obtain another rotation speed difference ΔN.
Calculating e2 is performed. After step 42, the process proceeds to step 44.

In step 44, the EGR start intake pipe pressure P1set is determined according to the following formula.

P 1set −P 1m1n+ (P ia+ax
-P twin) (ΔNe2/ N eset2
) As mentioned above, in steps 34, 40 and 44, E is determined as shown in FIG.
Determining the GR starting intake pipe pressure P 1set is performed.

Steps 34, 40 and 44 are followed by step 46, and in step 46, the intake pipe pressure P1 detected by the intake pressure sensor 53 is equal to the EGR start intake pipe pressure Pl5.
A determination is made as to whether or not it is smaller than et. pt≦P l
If it is 5et, proceed to step 48; otherwise, proceed to step 50.

In step 48, the negative pressure control valve 45 is de-energized to turn it off. Therefore, no exhaust gas recirculation takes place at this time.

In step 50, the negative pressure control valve 45 is energized to turn it on. Exhaust gas recirculation therefore takes place at this time.

As described above, by controlling the energization to the negative pressure control valve 45, the exhaust gas recirculation area changes depending on the engine speed, and when the engine speed is high, the exhaust gas recirculation area changes in the low intake pipe pressure area. The recirculation area will now be expanded.

FIG. 6 shows another embodiment of the energization control of the negative pressure control valve of the exhaust gas recirculation device according to the present invention. In this embodiment, the exhaust gas recirculation area is determined according to the engine speed using values from a data map as shown in Table 1 and interpolation calculations.

Table 1 Mo 1000 M2 1500 M3 33.5 M4 2000 Mnmax-15000 Mnmax 20 In the flowchart shown in FIG. 6, in the first step 100, the address number n of the data map can be set to 0. It will be done.

After step 100, the process proceeds to step 102, in which a first predetermined value Ne5et of the engine speed is set.
l is the engine speed stored in address 0 M (1) of the data map, in this example, the lowest value is 1000.
rpa+ is performed. Further, in step 102, a second predetermined value Neset2 of the engine speed is set to the engine speed stored at address na+ax-1 and Mnmax-1 of the data map, which is the highest value in this embodiment, 5000. The setting to rpm is performed.

After step 102, the process proceeds to step 104, in which it is determined whether the engine rotation speed Ne detected by the rotation speed sensor 51 is greater than or equal to the first predetermined value Ne5et1. When Ne>Ne5etl, the process proceeds to step 108; otherwise, the process proceeds to step 106.

In step 106, the intake pipe pressure stored at address 1 M of the data map, in this example, 35
kpa is set to the EGR start intake pipe pressure P1set.

In step 108, it is determined whether the engine speed Ne is less than or equal to a second predetermined value Neset2.

When N e < N eset2, step 11
If not, proceed to step 110.

In step 110, the data map nlllax
The intake pipe pressure stored at the address Mnmax, for example 20 kpa, is set as the EGR start intake pipe pressure Pl5et.

In step 112, a second predetermined value N of the engine speed is determined.
The engine speed stored at address n+2 of the data map is set as eset2. Step 112
Next, the process advances to step 114.

In step 114, the engine speed Ne is set to step 1.
The second predetermined value N eset2 rewritten in 12
A determination is made as to whether or not it is less than or equal to the following. Ne < Ne
If it is set 2, the process advances to step 118; otherwise, the process advances to step 116.

In step 116, the address number n is rewritten to a value two larger, and after step 116, the process returns to step 112.

As a result, the second predetermined value N eset2 is maintained until a YES determination is made in determining N e < N eset2.
begins to increase.

In step 118, the first intake pipe pressure PII is determined from the intake pipe pressure stored at address n+1 of the data map, and the second intake pipe pressure Pi2 is determined from the intake pipe pressure stored at address n+3 of the data map. A determination is made from the pipe pressure. Further, the third predetermined value N eset3 is set to n
Determination is performed based on the engine speed stored in the address.

After step 118, the process proceeds to step 120, where the first intake pipe pressure P11 is subtracted from the second intake pipe pressure Pi2 to calculate the intake pipe pressure difference ΔP1. Step 128 includes Step 122
Proceed to.

In step 122, a second predetermined value N eset2
Subtract the third predetermined value Neset3 to obtain the rotational speed difference Δ
A calculation of N eset is performed. Step 12
After step 2, the process proceeds to step 124.

In step 124, a third predetermined value Neset3 is subtracted from the engine rotation speed Ne to calculate the rotation speed difference ΔNe. Step 124 is followed by step 12
Proceed to step 6.

In step 126, the EGR start intake pipe pressure P1set is calculated according to the following formula.

Plset-Pi H+ (ΔNe/ΔNese
t) ΔPl As mentioned above, in steps 106, 110 and 126, E is set according to the engine speed Ne.
The GR starting intake pipe pressure P 1set is determined, and in this example, the EGR starting intake pipe pressure P 1set is determined.
5et changes in accordance with the engine speed Ne in a manner having a singular point as shown in FIG.

Step 106. Next to 110 and 126 is step 12
Proceed to step 8.

In step 128, it is determined whether the intake pipe pressure P1 of the internal combustion engine 1 detected by the intake pressure sensor 53 is equal to or lower than the EGR start intake pipe pressure P1set.

When Pi<Plset, the process proceeds to step 130; otherwise, the process proceeds to step 132.

In step 130, the negative pressure control valve 45 is de-energized to turn it off.

In step 132, the negative pressure control valve 45 is energized to turn it on.

In this embodiment, the exhaust gas recirculation area is set according to the characteristics shown in FIG.

Although the present invention has been described in detail above with reference to specific embodiments, it is understood that the present invention is not limited thereto and that various embodiments are possible within the scope of the present invention. This will be obvious to businesses.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram showing one embodiment of the exhaust gas recirculation device according to the present invention, FIG. FIG. 3 is a graph showing the exhaust gas recirculation area by the exhaust gas recirculation control according to the flowchart shown in FIG. 2, and FIG. A flowchart showing an example,
FIG. 5 is a graph showing the exhaust gas recirculation area in the exhaust gas recirculation control according to the flowchart shown in FIG.
FIG. 6 is a flowchart showing another embodiment of energization control of the negative pressure control valve of the exhaust gas recirculation device according to the present invention;
FIG. 7 is a graph showing the exhaust gas recirculation area in the exhaust gas recirculation control according to the flowchart shown in FIG.

Claims (2)

[Claims] (1) Detect the rotation speed of the internal combustion engine, determine the exhaust gas recirculation start engine load according to the rotation speed, and when the load of the internal combustion engine is equal to or higher than the exhaust gas recirculation start engine load, exhaust gas recirculation is started. A method for controlling exhaust gas recirculation for an internal combustion engine, characterized by performing circulation. (2) An exhaust gas recirculation control valve that is provided in the middle of the exhaust gas recirculation passage and increases its opening amount in accordance with an increase in the negative pressure introduced into the diaphragm chamber, and a negative pressure that guides the negative pressure to the diaphragm chamber. an orifice element defining a pressure chamber between the passage means and the exhaust gas recirculation control valve, the orifice element being disposed upstream of the exhaust gas recirculation control valve in the exhaust gas recirculation passage; and the negative pressure passage means. A negative pressure regulating valve provided in the middle of the pressure chamber and regulating the negative pressure supplied to the diaphragm chamber in response to exhaust gas pressure in the pressure chamber communicates with the negative pressure passage means provided in the middle of the negative pressure passage means. a negative pressure control valve that is switched between a first switching position in which the negative pressure passage means is opened to the atmosphere and a second switching position in which the negative pressure passage means is opened to the atmosphere; an exhaust gas recirculation device for an internal combustion engine, comprising: a control device that switches the negative pressure switching valve to the first switching position when the negative pressure switching valve is greater than or equal to the negative pressure switching position;