JPH1150918A - Exhaust reflux system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce an amount of black smoke by expediting the closure of an exhaust reflux valve and making better the sharpness of exhaust reflux at the time of making an exhaust reflux system into being inoperative from a state of doing the reflux operations. SOLUTION: When a first solenoid valve 1, installed in a passage supplying controlling air pressure to a pneumatic control type exhaust reflux valve 3 installed in a passage making a part of exhaust of an internal combustion engine 10 flow back to the intake air side, has made the electromagnetic coil into a state of being energized, the controlling air pressure is interconnected to the atmosphere as well as when this controlling air pressure has come to the atmospheric pressure, a passage making a part of exhaust of the internal combustion engine 1 flow back to the intake air side is made into a cutoff state by the exhaust reflux valve 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is applied to an internal combustion engine. The present invention relates to a technique (EGR, Exhost) for recirculating a part of exhaust gas discharged from an internal combustion engine to an intake side of the internal combustion engine.
Gas Recirculation).

[0002]

2. Description of the Related Art Since the exhaust gas of an internal combustion engine has a high temperature, it is not appropriate to use an exhaust gas recirculation valve itself for recirculating exhaust gas to intake air as a solenoid valve. Therefore, the exhaust gas recirculation valve that recirculates exhaust gas to the intake pipe is an air pressure control type valve, and the control air pressure supplied to the air pressure control type exhaust gas recirculation valve is controlled by another solenoid valve. It is configured in two stages by an electric circuit and a pneumatic circuit so as to be controlled by: The program control circuit receives an accelerator sensor output, an output of a rotation sensor of the internal combustion engine, an output of a temperature sensor of the internal combustion engine, and other inputs, and operates in conjunction with a main control circuit that controls a fuel supply control valve (rack) of the internal combustion engine. Alternatively, it is provided integrally with a main control circuit for controlling the internal combustion engine, and is configured to perform optimal control in relation to fuel supply and air supply of the internal combustion engine.

[0003]

DISCLOSURE OF THE INVENTION The inventors of the present application have conducted test improvements on a diesel engine mounted on a large-sized automobile to reduce harmful components of exhaust gas. When the accelerator pedal was released and the step margin was zero and the accelerator pedal was suddenly and strongly depressed to accelerate the vehicle, a phenomenon was noticed immediately after which black smoke was generated in the exhaust gas. The analysis revealed that the exhaust gas recirculation system installed in the diesel engine had a delay in operation, and this was one of the causes of the generation of black smoke during rapid acceleration. In other words, it was found that if the amount of fuel supplied to the internal combustion engine was increased while a part of the exhaust gas was being recirculated to the intake air, oxygen contained in the intake air became insufficient, resulting in incomplete combustion in the cylinder. Was.

Further analysis of this phenomenon shows that this operation delay is not due to the mechanical operation delay of the exhaust gas recirculation valve itself, but to the operation delay of the solenoid valve for sending control air pressure to the exhaust gas recirculation valve. Was. That is, as described above, the exhaust gas recirculation valve of the exhaust gas recirculation device is controlled by air pressure, and the air pressure is controlled by the electromagnetic valve. Then, as shown in FIG. 2, a diode 5 is connected to the solenoid valve in parallel with its winding. this is,
This is for absorbing a surge voltage generated in the electromagnetic winding. That is, in FIG. 2, when the switch S is switched from the conductive state to the cut-off state, the winding current I1 which has been continuously flowing up to that time generates an electromotive force for causing the winding current to continue by the inductor of the winding. . This electromotive force has a considerably high voltage between both terminals of the winding immediately after the relay contact (switch S in FIG. 2) for controlling the winding current is opened.
Since the high voltage may break the insulation of the electromagnetic winding and the surrounding electric circuit, the diode 5 is fixedly connected between both terminals of the electromagnetic winding in a direction to absorb the electromotive force. Things. The connection direction of the diode 5 is just opposite to the voltage applied to the electromagnetic winding for opening and closing the solenoid valve (the direction for blocking the current). Immediately after the voltage supplied to the electromagnetic winding of the solenoid valve via the switch S disappears, a current I2 flows through the diode 5. This allows the diode 5
Until the electric energy accumulated in the inductance of the winding via the winding is consumed by the resistance of the winding, the current I2 continues to flow while gradually weakening in the direction of holding the on-off valve in the winding. The above-mentioned operation delay is caused by the current I2 flowing through the diode 5 so as to be weakened with time.
It was found that this occurred because the solenoid valve did not recover until the value fell below the holding current of the solenoid valve.

[0005] This diode 5 cannot be removed. If the diode 5 is removed, the voltage between the winding terminals immediately after the disappearance of the winding current becomes abnormally high, and it is conceivable that the insulation of the winding and its peripheral circuits is destroyed. In order to quickly eliminate the current circulating through the diode 5, it is conceivable to reduce the winding resistance, reduce the conduction resistance of the diode 5, and the like. It is not easy.

The present invention has been made in view of such a background, and the present invention is to stop the recirculation operation from the state in which the exhaust gas recirculation device is performing the recirculation operation and increase the fuel supply amount to the internal combustion engine. Immediately after it is performed, an object is to reduce black smoke generated in exhaust gas due to incomplete combustion. An object of the present invention is to reduce the operation delay of the exhaust gas recirculation valve. SUMMARY OF THE INVENTION It is an object of the present invention to provide a device for eliminating an operation delay of an exhaust gas recirculation valve from a recirculation state to a shut-off state irrespective of an operation delay of an electromagnetic valve supplying air pressure to the exhaust gas recirculation valve. According to the present invention, even when it may take time for the electric energy stored in the inductor of the winding to disappear immediately after the winding current of the solenoid valve is cut off, what is the timing at which it suddenly accelerates the internal combustion engine? The aim is to provide a device that can be independent. Further, the present invention is applicable to a case where a failure occurs in an electromagnetic valve that supplies air pressure to an exhaust gas recirculation valve.
It is an object of the present invention to provide a device that can eliminate the inconvenience that the exhaust gas recirculation continues without being released.

[0007]

SUMMARY OF THE INVENTION The present invention improves the responsiveness of an exhaust gas recirculation valve that recirculates a part of exhaust gas discharged from an internal combustion engine to an intake side in accordance with an operation state to reduce the generation of black smoke. It is characterized by doing.

That is, according to the present invention, an air pressure control type exhaust gas recirculation valve (3) provided in a passage for recirculating a part of exhaust gas of an internal combustion engine to an intake side thereof, and a control air pressure is supplied to the exhaust gas recirculation valve. First solenoid valve (1) provided in the passage
A control circuit (4) for supplying a current to the electromagnetic winding of the first solenoid valve, and a direction in which the current is not conducted in parallel to the electromagnetic winding and to a voltage for supplying a current to the electromagnetic winding. The first solenoid valve (1) communicates the control air pressure with the atmosphere when the electromagnetic winding is energized, and controls the control air pressure. When the pressure is at atmospheric pressure, the exhaust gas recirculation valve (3) shuts off the recirculating passage.

A second solenoid valve (2) is inserted into the air circuit on the air pressure input side of the first solenoid valve (1), and the control circuit (4) controls the solenoid of the first solenoid valve (1). It is desirable to include means for controlling the second solenoid valve (2) so as to shut off the air circuit on the air pressure input side when a predetermined current does not flow even when a voltage is applied to the winding.

The exhaust gas recirculation valve (3) is of a four-stage control type (one stage closed and three stages open), and is provided with two first solenoid valves, each of which is a respective one. The control air pressure can be cut off when the electromagnetic winding is energized, and one second electromagnetic common to the air circuit on the air pressure input side of the individually provided first electromagnetic valve is provided. When the valve (2) is inserted and the control circuit (4) applies a voltage to the electromagnetic winding of the separately provided first solenoid valve and a predetermined current does not flow through either of them, the air pressure input is performed. Means for controlling the second solenoid valve (2) to shut off the side air circuit.

The control circuit (4) cuts off the supply of current to the electromagnetic winding of the first solenoid valve (1) when the exhaust gas recirculation valve (3) recirculates part of the exhaust gas to the intake side. The line (21) is opened (conducted in the conventional example) and the control air pressure is supplied to the exhaust gas recirculation valve (3). The exhaust gas recirculation valve (3) is opened by the supply of the control air pressure, and recirculates a part of the exhaust gas of the internal combustion engine to the intake side.

When the exhaust gas recirculation is stopped, the control circuit (4) supplies a current to the electromagnetic winding of the first solenoid valve (1) (in a conventional case, cuts off) to block the pipe (21). Then, the supply of control air pressure to the exhaust gas recirculation valve (3) is stopped. By stopping the supply of the control air pressure, the exhaust gas recirculation valve (3) closes a passage for supplying a part of the exhaust gas to the intake side so that the exhaust gas is not recirculated.

A feature of the present invention is that when such a state of the exhaust gas recirculation is shifted to a state in which the exhaust gas recirculation is stopped, a current is supplied to the electromagnetic winding of the first solenoid valve (1). When a current is supplied from a state where the current is not supplied, the first solenoid valve (1) communicates control air pressure to the atmosphere with the current being supplied to the electromagnetic winding, and the exhaust gas recirculation valve (3) When the control air pressure is the atmospheric pressure, a passage for recirculating exhaust gas from the internal combustion engine to the intake side is to be closed.

Thus, when the winding current is supplied from the state where there is no winding current from the control circuit (4) to the first solenoid valve (1), and when the exhaust gas recirculation is stopped from the state of exhaust gas recirculation. Can be reduced, and the generation of black smoke caused by the operation delay of the first solenoid valve (1) can be reduced. When a current is supplied to the winding of the first solenoid valve (1), there is a time delay for storing energy in the winding inductance. However, this current is supplied from a vehicle battery. Since the internal resistance is smaller than the resistance in the conduction direction of the diode 5, the time delay from interruption to conduction is smaller than the time delay from conduction to interruption.

Since the second solenoid valve (2) is provided in the air circuit on the air pressure input side of the first solenoid valve (1), any abnormality occurs in the first solenoid valve (1) and the electromagnetic winding is performed. Even if a predetermined current does not flow when current is supplied to the wire, the second solenoid valve (2) is operated to shut off the air circuit on the air pressure input side, and the exhaust recirculation valve (3) is operated. Can not be. In this case, the operation of exhaust gas recirculation is stopped, but there is no problem in running.

When the opening degree of the exhaust gas recirculation valve (3) is controlled in four steps, the first solenoid valves (1A) and (1B) operate according to the control output of the control circuit (4). The exhaust recirculation valve (3) shuts off the air circuit on the air pressure input side by connecting the control air pressure to the atmosphere while the respective electromagnetic windings of the first solenoid valves (1A) and (1B) are energized.

Also in this case, the air circuit on the air pressure input side of the first solenoid valves (1A) and (1B) which are individually provided is provided with one second solenoid valve (2) in common. When the control circuit (4) applies a voltage to the electromagnetic windings of the first solenoid valves (1A) and (1B), if a predetermined current does not flow through one of them, the second Solenoid valve (2)
To shut off the air circuit on the air pressure input side so that the exhaust gas recirculation valve (3) does not operate.

With this configuration of the present invention, the operation delay of the exhaust gas recirculation valve from the recirculation state to the shut-off state is reduced irrespective of the operation delay of the solenoid valve for supplying air pressure to the exhaust gas recirculation valve, Immediately after the winding current of the solenoid valve is cut off, it may take time for the electric energy stored in the winding inductance to disappear, regardless of the timing at which the internal combustion engine is suddenly accelerated. It is possible to reduce the black smoke generated in the exhaust gas due to incomplete combustion immediately after the recirculation operation is stopped and the fuel supply amount to the internal combustion engine is increased from the state in which the exhaust gas recirculation device is performing the recirculation operation. Can be.

Further, even when a failure occurs in the solenoid valve that supplies air pressure to the exhaust gas recirculation valve, it is possible to eliminate the inconvenience that the exhaust gas recirculation continues without being released.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION

[0021]

Next, an embodiment of the present invention will be described with reference to the drawings.

(First Embodiment) FIG. 1 is a block diagram showing a configuration of a main part of an apparatus according to a first embodiment of the present invention.

In the first embodiment of the present invention, the exhaust gas recirculation valve 3 comprises an air pressure control type three-way valve provided in a passage for recirculating a part of the exhaust gas of the internal combustion engine 10 to the intake side thereof.
A first solenoid valve 1 provided in a passage for supplying control air pressure to the exhaust gas recirculation valve 3, a control circuit 4 for supplying a current to an electromagnetic winding of the first solenoid valve 1, An exhaust gas recirculation device comprising: a diode 5 connected in parallel with the winding and in a direction in which the diode 5 is nonconductive to a voltage for supplying a current to the electromagnetic winding.

Here, the feature of the present invention is that the first solenoid valve 1 communicates the control air pressure with the atmosphere when the electromagnetic winding is energized, and the control air pressure is atmospheric pressure. At this time, the exhaust gas recirculation valve 3 is set so as to shut off a passage for recirculating the engine exhaust gas to the engine intake air.

That is, the exhaust gas recirculation valve 3 is a mechanical valve,
When the control air pressure supplied to the pipe 18 is high,
When the exhaust air is recirculating to the intake air and the control air pressure supplied to the pipeline 18 becomes atmospheric pressure, the communication between the exhaust air and the intake air is established by the action of a return spring provided on the on-off valve. It is configured to shut off.

In the present invention, a state in which the control air pressure supplied to the pipe 18 is high is a state in which no current flows through the electromagnetic winding of the first solenoid valve 1, and a state in which the pipe 18 is set to the atmospheric pressure. Is set so that the state is such that the electromagnetic winding of the first electromagnetic valve 1 is energized, that is, a state in which current flows through the electromagnetic winding of the first electromagnetic valve 1. This is a configuration not disclosed in any of the conventionally known configurations.

Further, the second solenoid valve 2 is inserted in the air circuit on the air pressure input side of the first solenoid valve 1, and the control circuit 4 applies a voltage to the electromagnetic winding of the first solenoid valve 1. Means for controlling the second solenoid valve 2 so as to shut off the air circuit on the air pressure input side when a predetermined current does not flow is included.

The double line in FIG. 1 shows the pneumatic circuit, and the single line shows the connection of the electric circuit. The supply of air pressure to the first electromagnetic valve 1 is performed from the air tank 6 via the pressure reducing valve 7 and further via the second electromagnetic valve 2. The second solenoid valve 2 has the same structure as the conventional one. When current is supplied from the control circuit 4 to the electromagnetic winding, air pressure is supplied from the air tank 6 to the exhaust gas recirculation valve 3, and supply of air pressure is stopped when supply of current is interrupted.

In this case, the timing of shifting from the problematic exhaust gas recirculation state to the state in which the exhaust gas recirculation is stopped is determined by the state in which the winding current of the first solenoid valve 1 is not supplied and the winding current is supplied. It is time to shift to. FIG.
FIG. 4 is an electric circuit diagram for explaining the operation principle of the first solenoid valve according to the first embodiment of the present invention. Referring to FIG. 2, the timing at which the switch S is turned on is set not as the timing at which the switch S is turned off, but as the timing at which the exhaust gas recirculation is stopped. When the switch S in FIG. 2 is turned off, the current continues afterwards due to the inductance of the electromagnetic winding. However, when the switch S is turned on, the battery B having a strong internal resistance of the vehicle is low.
, The operation of the solenoid valve is rapid and the operation delay is extremely small. Conversely, the timing when the switch S in FIG. 2 is turned off is the timing when the exhaust gas recirculation valve 3 causes the exhaust gas to communicate with the intake air.

Further, if a failure occurs in the control circuit 4 or in the wiring of the electric circuit from the control circuit 4 to the solenoid valve 1, the exhaust gas recirculation valve 3 will be in a state of communicating the exhaust gas with the intake air. Regarding this point, the second electromagnetic valve 2 is provided in the air supply circuit of the first electromagnetic valve 1, and when there is any abnormality in the first electromagnetic valve 1, the second electromagnetic valve 2 is closed. The exhaust gas recirculation valve 3 is set so as not to operate.

That is, a second feature of the present invention is that the second solenoid valve 2 is provided in the air circuit on the air pressure input side of the first solenoid valve 1.
And the control circuit 4 shuts off the air circuit on the air pressure input side when a predetermined current does not flow even when a voltage is applied to the electromagnetic winding of the first electromagnetic valve 1. 2 that includes means for controlling. Therefore, if there is an abnormality in either the first solenoid valve 1 or the second solenoid valve 2, the exhaust gas recirculation valve 3 does not operate and the exhaust gas is not recirculated.

FIG. 3 is a sectional view showing the structure of a first solenoid valve used in the first embodiment of the present invention.

The first solenoid valve 1 has a core 12 having an electromagnetic winding 11 wound on the outer periphery thereof, and a plunger slidably inserted into a cylindrical hole formed in a part of the axis of the core 12. 13
And a spring 14 for biasing the plunger 13,
A connecting portion 15 that contains the plunger 13 and connects the exhaust gas recirculation valve 3 and the atmospheric pressure by a pipe, a yoke 16 that houses the electromagnetic winding 11 and the core 12, an air tank 6 that is fixed to one end face of the core 12, And a connecting portion 17 that connects the two by a conduit.

An air pressure passage 12a communicating with the air pressure supply port 17a of the connection portion 17 is formed inside the core 12, and the air pressure passage 1 which communicates with or shuts off the air pressure passage 12a depending on the position where the air pressure passage 12a is also moved inside the plunger 13.
3a is formed.

FIG. 4 is a sectional view showing the structure of the exhaust gas recirculation valve used in the first embodiment of the present invention.

Exhaust gas recirculation valve 3 used in the first embodiment
Is a main body 24 having a piston 22, a cylinder 23 into which the piston 22 is slidably inserted, and a spring 2 provided in the main body 24 to bias the piston 22.
5 and a cover 27 for closing the opening of the cylinder 23 in the main body 24.

The main body 24 has an air pressure supply port 26a for connecting the conduit 18 from the first solenoid valve 1, an exhaust recirculation inlet 26c for recirculating exhaust gas to the intake side, and an exhaust recirculation outlet 26d for the intake manifold 21. It is formed. An umbrella-like opening / closing valve 29 is connected to the piston 22, and the opening / closing valve 29 opens and closes the exhaust gas recirculation inlet 26 c as the piston 22 moves.

Next, the operation of the first solenoid valve 1 of the first embodiment of the present invention will be described.

When no current is supplied from the control circuit 4 to the electromagnetic winding 11, the first solenoid valve 1 does not generate a magnetic field due to the electromagnetic winding 11, so that the plunger 13 biases the spring 14. As shown by the broken line in FIG.
The discharge port 15a is closed in a state in which the discharge port 15a is in contact with the inner end surface of the discharge port 15a. At this time, the air pressure passage 13a of the plunger 13 and the air pressure passage 12a in the core 12 are in a communicating state.

As a result, the control air pressure from the air tank 6 is increased by the air pressure supply port 17 as indicated by the dashed arrow.
a, Pneumatic passage 12a in core 12 and plunger 1
The air is supplied to the exhaust gas recirculation valve 3 through an air pressure passage 13 a in the air passage 3. The supply of the control air pressure pressurizes the piston chamber 28 of the exhaust gas recirculation valve 3 and pushes the piston 22 to the position of the distance L in the direction of arrow A shown in FIG. This piston 22
The opening / closing valve 29 also moves to the position L indicated by the two-dot chain line to open the exhaust gas recirculation inlet 26c, and a part of the exhaust gas of the internal combustion engine 1 from the exhaust manifold 20 shown in FIG. Reflux to the manifold 21.

When the exhaust gas recirculation is stopped from the state of the exhaust gas recirculation, the control circuit 4 supplies a current to the electromagnetic winding of the first electromagnetic valve 1. When a current is supplied to the electromagnetic winding, the plunger 13 compresses the spring 14 and is attracted to the core 12 as shown by the solid line in FIG.

By the movement of the plunger 13, the air pressure inlet of the air pressure passage 13a formed therein is disengaged from the outlet of the air pressure passage 12a formed in the core 12, and the communication between the air pressure passage 13a and the air pressure passage 12a is established. The supply of the control air pressure from the air tank 6 to the exhaust gas recirculation valve 3 is stopped.

At the same time, the contact state between the inner end face of the discharge port 15a of the connecting portion 15 and the end face of the plunger 13 is released, and the discharge port 15a and the exhaust gas recirculation port 15b communicating with the exhaust gas recirculation valve 3 communicate with each other. The control air pressure supplied into the valve 3 is released from the discharge port 15a to the atmosphere.

Thus, the electromagnetic winding 1 of the first solenoid valve 1
When power is supplied to the first solenoid valve, the control air, which has caused the exhaust gas recirculation valve 3 to be in the exhaust gas recirculation state at the same time as the current is supplied, shuts off the passage for recirculating the exhaust gas to the intake side and shuts off the first electromagnetic wave. The generation of black smoke caused by the operation delay of the valve 1 is avoided.

FIG. 5 is a diagram for explaining the result of a test on the improvement of the operation delay by the first solenoid valve used in the first embodiment of the present invention. This is because when the accelerator pedal is released and the stepping allowance is zero and the accelerator pedal is suddenly and strongly depressed beyond the accelerator opening threshold to accelerate the vehicle, the exhaust gas recirculation valve 3 is turned on. The operation of the on-off valve when the state is changed from the off state to the off state is recorded.

According to the results of this experiment, the time indicated by the broken line conventionally required the time from when the exhaust gas recirculation valve 3 was turned off from the on state to when the passage for recirculating exhaust gas to the intake side was completely shut off. According to the present invention, it can be seen that the time is shortened by the time t as shown by the solid line. As a result, the exhaust gas is not recirculated for the reduced time, and the generation of black smoke can be suppressed.

(Second Embodiment) FIG. 6 is a block diagram showing a configuration of a main part of a device according to a second embodiment of the present invention.

In the second embodiment of the present invention, a four-stage control type is used for the exhaust gas recirculation valve 30 including a state in which the opening thereof is closed.
Solenoid valves 1A and 1B for setting the stage are separately provided, and both are connected so as to shut off the control air pressure when the electromagnetic winding is energized. In addition, one second solenoid valve 2 is inserted in common into the air circuits on the air pressure input side of the first solenoid valves 1A and 1B provided separately, and the first solenoid valve 1A and the Means for controlling the second electromagnetic valve 2 so as to shut off the air circuit on the air pressure input side when a predetermined current does not flow through one of the electromagnetic windings 1B even when a voltage is applied to the electromagnetic winding 1B. Other configurations are the same as those of the first embodiment.

FIG. 7 is a sectional view showing the structure of the exhaust gas recirculation valve used in the second embodiment of the present invention.

Exhaust gas recirculation valve 3 used in the second embodiment device
0 is a first piston 31, a second piston 32,
A cylinder 33 in which a first piston 31 is slidably inserted and a second piston 32 is fixed to one end thereof;
A body 34 having a cylindrical interior and a cylinder 33 slidably inserted therein, a spring 35 provided in the body 34 to bias the first piston 31, the second piston 32 and the cylinder 33; Second piston 3 of body 34
A cover 37 fixed to the second side and formed with an air pressure supply port 36b for connecting the air pressure line from the first solenoid valve 1B.
And are provided.

In the main body 34, an air pressure supply port 36a for connecting a conduit from the first solenoid valve 1A, an exhaust gas recirculation inlet 36c for recirculating exhaust gas to the intake side, and an exhaust gas recirculation outlet 36d to the intake manifold 21 are formed. Is done. An umbrella-shaped opening / closing valve 39 is connected to the first piston 31, and the opening / closing valve 39 opens and closes the exhaust gas recirculation inlet 36 c with the movement of the first piston 31.

The first solenoid valves 1A and 1B are constructed and operate in the same manner as in the first embodiment shown in FIG.

Next, the operation of the thus configured second embodiment apparatus will be described.

The first solenoid valves 1A and 1B are connected to the control circuit 4
When no current is supplied from the controller, the control air pressure from the air tank 6 is supplied to the exhaust gas recirculation valve 30 to perform exhaust gas recirculation. When current is supplied from the control circuit 4 to stop the exhaust gas recirculation from the state of the exhaust gas recirculation, the supply of control air pressure from the air tank 6 to the exhaust gas recirculation valve 30 is stopped, and the exhaust gas recirculation valve is stopped. The control air pressure in 30 is released to the atmospheric pressure, and the exhaust gas recirculation valve 30 is closed to stop the exhaust gas recirculation.

When the control air pressure is not supplied from the first solenoid valves 1A and 1B, the exhaust gas recirculation valve 30 has the first piston 31 and the second piston 32 at the positions shown in FIG. 39 closes the exhaust gas recirculation inlet 36c, and the exhaust gas recirculation is stopped.

In this state, when the control air pressure is supplied to the air pressure supply port 36b from the first solenoid valve 1B, the control air pressure is applied to the second piston 32. Since the second piston 32 and the cylinder 33 are fixed, the cylinder 33 moves by a distance L1 in the direction of the arrow B and stops by this air pressure. At this time, the on-off valve 3
Reference numeral 9 moves to the position of L1 (the position of the opening degree of the second stage) indicated by the two-dot chain line.

When the first piston 31 and the second piston 32 are at the positions shown in FIG.
When the control air pressure is supplied to a from the first solenoid valve 1A, the air pressure causes the first piston 31 to move a distance L2 in the direction of arrow B and stop. At this time, the on-off valve 39
Is the position of L2 indicated by the two-dot chain line (the position of the opening in the third stage)
To increase the amount of exhaust gas recirculation from the second stage.

When the first piston 31 and the second piston 32 are at the positions shown in FIG.
A supplies control air pressure to the air pressure supply port 36a from the air pressure supply port 36a, and simultaneously supplies air pressure supply port 3 from the first solenoid valve 1B.
When the control air pressure is supplied to 6b, the cylinder 33
The first piston 31 moves the distance L2 while moving the distance L1 in the direction of the arrow. At this time, the on-off valve 39 moves to the position of L1 + L2 (position of the fourth stage opening degree) indicated by the two-dot chain line, and further increases the amount of exhaust gas recirculation as compared with the third stage.

When the opening / closing valve 39 is at the position (L1 + L2) of the fourth degree of opening, the first electromagnetic valve 1A supplies the first electromagnetic pressure to the air pressure supply port 36a. When a current is supplied to the electromagnetic winding 11 of the valve 1B and the control air pressure is released to the atmosphere, the supply of the control air pressure to the air pressure supply port 36b of the exhaust gas recirculation valve 30 is stopped. Due to the stop of the air pressure supply, the cylinder 33 is returned by the distance L1 under the bias of the spring 35, and the on-off valve 39 is moved to the position L2 of the third opening degree shown by the two-dot chain line to reduce the amount of exhaust gas recirculation. .

Similarly, when the opening / closing valve 39 is at the fourth-stage opening position (L1 + L2), the first solenoid valve 1B supplies the air pressure for control to the air pressure supply port 36b. When a current is supplied to the electromagnetic winding 11 of the solenoid valve 1A to release the control air pressure to the atmosphere and the supply of the control air pressure to the air pressure supply port 36a of the exhaust gas recirculation valve 3 is stopped, the spring 35 is biased. The first piston 31
Is returned by the distance L2, and the on-off valve 39 moves to the position L1 of the opening degree of the second stage indicated by the two-dot chain line to further reduce the amount of exhaust gas recirculation.

In order for the control circuit 4 to stop the exhaust gas recirculation,
When the supply of control air pressure from the first solenoid valves 1A and 1B to the exhaust gas recirculation valve 30 is simultaneously stopped, the first solenoid valve 1
In order for A and 1B to be in communication with the atmospheric pressure, the control air pressure supplied to the piston chamber 38 is urged by the spring 35 to reach the atmospheric pressure via the first solenoid valves 1A and 1B. The air pressure released to the second piston 32 is also released to the atmosphere at the same time. As a result, the on-off valve 39 closes the exhaust gas recirculation inlet 36c, and the exhaust gas recirculation is stopped.

In the second embodiment, the first solenoid valve 1
A and 1B use the same electromagnetic valves as in the first embodiment, so that the control air pressure is shut off when the respective electromagnetic windings are energized, and at the same time as the shutoff, the control air pressure is released into the atmosphere. , The generation of black smoke due to the operation delay can be reduced.

Further, since the second solenoid valve 2 is provided as in the first embodiment, when a predetermined current does not flow through either the first solenoid valve 1A or 1B. In accordance with the control of the control circuit 4, the second solenoid valve 2 shuts off the air circuit on the air pressure input side and the exhaust gas recirculation is stopped.

[0064]

As described above, according to the present invention, the operation delay of the exhaust gas recirculation valve from the recirculation state to the shut-off state can be reduced irrespective of the operation delay of the solenoid valve for supplying air pressure to the exhaust gas recirculation valve. Even if it may take time for the electric energy stored in the inductance of the winding to disappear immediately after the winding current of the solenoid valve is cut off, regardless of the timing at which it suddenly accelerates the internal combustion engine, Is possible,
Immediately after the recirculation operation is stopped and the fuel supply amount to the internal combustion engine is increased from the state where the exhaust gas recirculation device is performing the recirculation operation, it is possible to reduce black smoke generated in the exhaust gas due to incomplete combustion.

Further, even when a malfunction occurs in the solenoid valve that supplies air pressure to the exhaust gas recirculation valve, it is possible to eliminate the inconvenience that the exhaust gas recirculation continues without being released.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a main part of an apparatus according to a first embodiment of the present invention.

FIG. 2 is a view for explaining the operation principle of a first solenoid valve according to the first embodiment of the present invention.

FIG. 3 is a sectional view showing the structure of a first solenoid valve used in the first embodiment of the present invention.

FIG. 4 is a sectional view showing a structure of an exhaust gas recirculation valve used in the first embodiment of the present invention.

FIG. 5 is a diagram for explaining an improvement in operation delay caused by a first solenoid valve used in the first embodiment of the present invention.

FIG. 6 is a block diagram showing a configuration of a main part of a second embodiment of the present invention.

FIG. 7 is a sectional view showing the structure of an exhaust gas recirculation valve used in the second embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1, 1A, 1B 1st electromagnetic valve 2 2nd electromagnetic valve 3, 30 Exhaust recirculation valve 4 Control circuit 5, 5 'diode 6 Air tank 7 Pressure reducing valve 10 Internal combustion engine 11 Electromagnetic winding 12 Core 12a, 13a Air pressure passage 13 Plunger 14, 25, 35 Spring 15, 17 Connection 15a Discharge port 15b Exhaust recirculation port 16 Yoke 17a, 26a, 36a, 36b Air pressure supply port 18 Pipeline 20 Exhaust manifold 21 Intake manifold 22 Piston 23, 33 Cylinder 24, 34 Body 26c, 36c Exhaust gas recirculation inlet 26d, 36d Exhaust gas recirculation outlet 27, 37 Cover 28, 38 Piston chamber 29, 39 On-off valve 31 First piston 32 Second piston 33 Cylinder

Claims (4)

[Claims] 1. An air pressure control type exhaust gas recirculation valve (3) provided in a passage for recirculating a part of exhaust gas of an internal combustion engine to an intake side thereof, and a gas pressure control valve provided in a passage for supplying control air pressure to the exhaust gas recirculation valve. A first electromagnetic valve (1), a control circuit (4) for supplying current to the electromagnetic winding of the first electromagnetic valve, and a current supply to the electromagnetic winding in parallel with the electromagnetic winding. And a diode (5) connected in a direction in which the control air pressure is non-conductive with respect to a voltage to be applied. The exhaust gas recirculation device is characterized in that the exhaust gas recirculation valve (3) is set to shut off the recirculating passage when the control air pressure is atmospheric pressure. 2. A second solenoid valve (2) is inserted into an air circuit on an air pressure input side of the first solenoid valve (1), and the control circuit (4) controls the first solenoid valve (1). 2. The exhaust system according to claim 1, further comprising means for controlling said second electromagnetic valve (2) so as to shut off an air circuit on the air pressure input side when a predetermined current does not flow even when a voltage is applied to said electromagnetic winding. Reflux device. 3. The exhaust gas recirculation valve (3) has a four-stage control opening degree, and is provided with two first electromagnetic valves, each of which is provided with its respective electromagnetic winding energized. The exhaust gas recirculation device according to claim 1, wherein the exhaust gas recirculation device is connected so as to cut off control air pressure. 4. A single second solenoid valve (2) is commonly inserted into an air circuit on the air pressure input side of the individually provided first solenoid valve, and the control circuit (4) Even if a voltage is applied to the electromagnetic windings of one of the electromagnetic valves (1A, 1B), when a predetermined current does not flow through one of the electromagnetic valves, the second electromagnetic valve (2) shuts off the air circuit on the air pressure input side. 4. The exhaust gas recirculation apparatus according to claim 3, further comprising means for controlling the exhaust gas recirculation.