JPH05321770A - Exhaust gas circulating control valve device for internal combustion engine - Google Patents

Abstract

PURPOSE:To reduce the exhaust volume of the harmful exhaust gas of NOx or the like by controlling the exhaust gas circulating quantity so as to be proportional to the lift quantity of a valve element to open/close the circulating port. CONSTITUTION:The internal shape of a body 4 surrounding the region where a valve element 20 moves is enlarged to the tapered or similar shape so as to gradually increase the sectional area toward the opening position from the closing position of the valve element 20. This arrangement allows the clearance between the valve element 20 and the body 4 to be increased approximately in proportion to the lift quantity of the valve element 20, and the circulating quantity of the exhaust gas to be controlled approximately in proportion to the lift quantity of the valve element 20.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control valve device for controlling the exhaust gas recirculation flow rate in an exhaust gas recirculation device mounted in an exhaust system of an internal combustion engine.

[0002]

2. Description of the Related Art As a typical exhaust gas recirculation system for an internal combustion engine, a part of exhaust gas is recirculated to an intake system,
An EGR valve that lowers the combustion temperature in the cylinder and reduces the amount of harmful exhaust gas, particularly NOx (nitrogen oxide) composed of NO, NO _2, etc. (see, for example, Japanese Utility Model Publication No. 2-43451). There is.

The present applicant has filed a patent application (Japanese Patent Application No. 3-23707) for the exhaust gas recirculation system shown in FIG. 2 for the purpose of solving the problems in the EGR valve. In order to understand the present invention, the apparatus of FIG. 2 will be described below.

The EGR valve (1) is mounted vertically on a flange portion (2a) opened at an upper end of a bypass pipe (2) connected to an exhaust pipe of a multi-cylinder diesel engine, and its port outlet end is provided. Is connected to the intake pipe of the engine via the introduction pipe (3).

The cast body (4) has an elbow-shaped recirculation port (5) having an exhaust gas inlet side facing downward and an outlet side laterally opening, and at each opening end. The flanges 6 and 6 are integrally formed.

At the upper end of the body (4), a relatively large circular mounting seat (7) acting as a heat shield plate and a heat radiating plate by extending horizontally to the side of the body (4) is provided. The mounting seat (7) is formed integrally with the intermediate part of (4) with a required distance.
Is reinforced by a plurality of thin plate-shaped ribs (8) extending downward from the lower surface thereof toward the middle part of the body (4).

A plurality of protrusions (9) having a smooth upper surface are integrally formed on the upper surface of the mounting seat (7), and a plurality of through holes (10a) are provided near the center of each protrusion (9). , A spring bearing (10) having approximately the same diameter as the mounting seat (7), and further on the upper surface of the spring bearing (10),
The cylinder (11) with a top of the actuator (A) is integrally formed by screwing the bolts (12) toward the plurality of bosses (7a) on the upper surface of the outer peripheral portion of the mounting seat (7). Is stuck to.

As a result, the upper surface of the mounting seat (7) and the spring bearing are
A small gap (13) communicating with the outside air is formed between the lower surface of (10) and the lower surface.

Reference numeral (14) is a seal member having a small thermal conductivity, which is interposed between the spring bearing (10) and the cylinder (11).

Inside the cylinder (11), a cylindrical viston (15) with an upper surface closed, which is in close contact with a thick portion (11a) formed in the intermediate portion of its inner peripheral surface, is vertically slidable. It has been inserted.

A pipe (16) for supplying air from a compressed air source (not shown) such as a compressor into the cylinder (11) is connected to the upper surface of the cylinder (11).

The space between the lower surface of the cylinder (11) and the upper surface of the piston (15) is a high pressure chamber (operating pressure chamber) (17a), and the space surrounded by the piston (15) is a low pressure chamber. It is a room (open to the atmosphere) (17b).

Numeral (18) is a compression coil spring compressed in the high pressure chamber (17a), and constantly pushes the piston (15) downward.

At the center of the body (4), the valve guide (1
9) is press-fitted, and its upper end penetrates the center of the spring bearing (10) and is located in the lower part inside the piston (15).

A shaft portion (20a) of a mushroom-shaped valve body (20) is slidably fitted and inserted into the valve guide (19), and a shaft end portion located inside the piston (15) is A pair of cotters (22) (22) in which the retainer (21) is externally fitted in the annular groove (20b) formed on the outer peripheral surface of the shaft portion in the tapered hole (21a) formed in the center thereof.
It is fixed by fitting the inside.

A return spring (compression coil spring) (23) is provided between the lower surface of the retainer (21) and the upper surface of the spring bearing (10).
Has been reduced.

As a result, the valve body (20) is always urged upward, and the umbrella portion (20c) is in close contact with the valve seat (24) fitted in the lower end opening of the return port (5) during normal operation. As a result, the return port (5) is closed.

In a normal state, the inner bottom surface of the piston (15) has a compression coil spring (18) compressed inside the high pressure chamber (17a).
The urging force of the valve element (20) makes contact with the shaft end surface of the valve element (20),
When the valve is closed, the lower end of the piston (15) and the spring bearing (1
The required gap is formed between 0). This gap becomes the maximum lift amount of the valve body (20), that is, the opening / closing stroke.

The operation of the EGR valve (1) shown in FIG. 2 is as follows. When the engine enters a low-medium speed and low-load operating range, and compressed air is pumped into the high-pressure chamber (17a) by the operation of a control device (not shown), the piston (15) and the valve disc (20) are connected to the return spring. It is pushed down integrally against (23) and stops when the lower end of the piston (15) comes into contact with the spring bearing (10).

As a result, the valve body (20) is opened, and the exhaust gas flowing into the bypass pipe (2) passes through the recirculation port (5) and the introduction pipe (3) and is connected to the inside of each cylinder of the engine through the communication pipe. Sent to. As a result, the combustion state becomes slower, the combustion temperature is kept low, and the NOx emission amount is reduced.

When the engine enters the high speed and high load operation region, the control device works again to stop the supply of the compressed air, whereby the valve body (20) and the piston (15) are returned by the return spring (23). , The return port (5) is automatically closed.

[0022]

In the exhaust gas recirculation device as described above, the recirculation amount of the exhaust gas sent into the cylinder of the engine is stepwise or stepless in accordance with the engine speed and the magnitude of the load. It is desirable to control it dynamically.

However, in the apparatus of FIG. 2, the valve body (20) moves in proportion to the compressed air pressure injected into the high pressure chamber (17a), but the amount of exhaust gas passing through the recirculation port (5) is Disc (2
It is not proportional to the lift amount of 0). The reason is that the shape of the inner surface of the body (4) between the closing portion by the valve body (20) and the connecting portion for the bypass pipe (2) is a right cylindrical shape.

That is, as shown in FIG. 4, the body (4)
When the inner surface (125) of the above portion is formed into a cylindrical shape having a constant diameter, the gap (d) between the outer edge of the umbrella portion (20c) of the valve body (20) and the inner surface (125) is It is constant regardless of the position of (20).
Therefore, the cross-sectional area of the exhaust gas passage formed when the valve body (20) opens reaches the maximum value immediately after the umbrella portion (20c) of the valve body (20) separates from the valve seat (24). The cross-sectional area of the exhaust gas passage does not change even if the valve body (20) is opened further.

Therefore, as shown by the dotted line in FIG. 5, the amount of exhaust gas passing through the recirculation port (5) reaches the maximum flow rate rapidly in the early stage of opening the valve body (20), and thereafter changes little. Instead, it becomes almost constant.

That is, in the exhaust gas recirculation device of FIG.
Even if the valve body (20) is opened stepwise or steplessly according to the engine speed and load, the amount of exhaust gas sent to the cylinder should be proportional to the lift amount of the valve body (20). Therefore, there is a problem that the NOx emission amount cannot be effectively reduced according to the engine speed. Further, since the cross-sectional area is sharply narrowed at the inlet to the recirculation port (5) which is the closed portion of the valve body (20), the flow resistance becomes large and the maximum flow rate of exhaust gas is limited.

An object of the present invention is to provide an exhaust gas recirculation system for an internal combustion engine which solves this problem.

[0028]

In order to achieve the above object, the present invention is configured as follows.

Exhaust gas recirculation control for an internal combustion engine, comprising an exhaust gas circulation port and a body accommodating a valve body for opening and closing the port, and an actuator attached to the body for opening and closing the valve body. In the valve device, an inner surface shape of the body surrounding a region where the valve body moves is expanded so that a cross-sectional area gradually increases from a closed position to an open position of the valve body. Exhaust gas recirculation control valve device.

It is desirable that the inner surface of the body surrounding the region where the valve body moves be tapered.

[0031]

If the inner surface of the body is expanded so that the cross-sectional area gradually increases from the closed position to the open position of the valve body, the distance between the outer edge of the umbrella portion of the valve body and the inner surface wall of the body is increased. It changes according to the moving amount of the valve body, and the recirculation amount of the exhaust gas increases according to the lift amount of the valve body.

By expanding the inner surface of the body in a tapered shape, the amount of exhaust gas recirculation can be increased almost in proportion to the amount of lift of the valve body.

[0033]

FIG. 1 is a sectional view showing an exhaust gas recirculation control valve device according to an embodiment of the present invention. This control valve device has almost the same configuration as that shown in FIG. 2, and the same members are designated by the same reference numerals and detailed description thereof will be omitted.

The EGR valve (1), the bypass pipe (2) having the flange (2a), the introduction pipe (3) and the actuator (A) are
It is the same as that of FIG.

The body (4) is similar to FIG. 2 except that the shape of the inner surface (25) of the connecting portion to the bypass pipe (2) is different, and the return port (5), the flanges (6) (6), Mounting seat (7), boss (7
It has a), ribs (8) and protrusions (9).

The spring receiver (10) is the same as that of FIG. 2 including the through hole (10a).

The actuator (A) has the same structure as that shown in FIG. 2, and includes a cylinder (11), a bolt (12), a gap (13), a seal member (14), a piston (15), a pipe (16), A high pressure chamber (operating pressure chamber) (17a), a low pressure chamber (atmospheric pressure chamber) (17b), a compression coil spring (18), a retainer (21), a cotter (22), and a return spring (23) are provided.

Similarly to the one shown in FIG. 2, the shaft portion of the valve body (20) is attached to the valve guide (19) press-fitted into the center of the body (4).
(20a) is inserted and retained by engaging the retainer (21) at the shaft end and the pair of cotters (22) and (22) in the annular groove (20b) formed at the shaft end. There is.

The umbrella portion (20c) formed at the lower end of the valve body (20) is
At normal times, the return spring (23) is in close contact with the valve seat (24) by the urging force to close the return port (5), and at the time of operation, the compressed air pressure sent from the pipe (16) causes the piston (15) 2), the valve body (20) is moved to open the return port (5) in the same manner as in FIG.

In the device of the present invention shown in FIG. 1, the shape of the inner surface of the body (4) surrounding the region where the valve body (20) moves between the position where the return port (5) is closed and the position where it is opened is changed from the closed position. As shown in FIG. 2, the cross-sectional area is gradually expanded toward the open position.
Is different from the one.

In the conventional apparatus shown in FIG. 2, this area (125) is formed in a right cylindrical shape, but in the embodiment shown in FIG.
5) is formed in a taper shape that widens from the closed portion where the peripheral edge of the umbrella portion (20c) of the valve body (20) is in close contact with the connection portion to the bypass pipe (2).

By forming the region (25) in a tapered shape, the dimension between the peripheral edge of the umbrella portion (20c) of the valve body (20) and the inner surface of the region (25) is the lift amount of the valve body (20). It is possible to change the flow rate of the exhaust gas passing through this gap according to the lift amount of the valve body (20).

FIG. 3 is a diagram showing a state in which the gap (d) changes according to the lift amount of the valve body (20). When the valve body (20) moves downward from the closed position indicated by the alternate long and short dash line, the umbrella portion
The gap (d) between the periphery of (20c) and the inner surface of region (25) is
It increases almost directly in proportion to the lift amount (L) of 0).

The area of the exhaust gas passage formed in the gap between the inner surface of the region (25) and the umbrella portion (20c) is the lift amount (from the closed position where the valve body (20) abuts the valve seat (24) ( L), so that the recirculation amount of the exhaust gas passing through the recirculation port (5) increases according to the area of the passage. That is, as shown by the solid line in FIG. 5, the recirculation amount of the exhaust gas increases almost directly in proportion to the lift amount of the valve body (20) from the closed position.

Therefore, the lift amount of the valve body (20) is appropriately adjusted by the air pressure supplied to the cylinder (11) through the pipe (16) or an appropriate actuator (not shown) according to the rotation speed of the engine and the magnitude of the load. The exhaust gas amount that recirculates to the intake system of the engine through the recirculation port (5) is finely controlled by lowering the combustion temperature in the cylinder of the engine to reduce the harmful exhaust gas amount. Can be reduced. Also, as in the past, the return port
Since the cross-sectional area of the entrance to (5) is not sharply reduced,
Exhaust gas flows smoothly and the maximum flow rate increases.

[0046]

The present invention has the following effects. (a) Since the recirculation amount of the exhaust gas that recirculates into the engine cylinder can be increased or decreased according to the opening degree of the valve body that opens or closes the exhaust gas recirculation port, the valve can be adjusted according to the engine speed or load. By controlling the opening of the body, it is possible to effectively reduce the emission amount of harmful exhaust gas such as NOx.

(B) Since the inner surface of the body surrounding the moving region of the valve body is tapered, the exhaust gas recirculation amount can be controlled substantially in proportion to the valve lift amount. it can.

[Brief description of drawings]

FIG. 1 is a central longitudinal front view showing an embodiment of an exhaust gas recirculation control valve device of the present invention.

FIG. 2 is a central longitudinal front view showing a conventional exhaust gas recirculation control valve device.

FIG. 3 is an explanatory view showing a valve open state of the valve body of the present invention.

FIG. 4 is an explanatory diagram showing a valve opening state of a valve body in a conventional device.

FIG. 5 is an explanatory diagram showing a relationship between a valve body lift amount and an exhaust gas recirculation amount in the present invention and a conventional device.

[Explanation of symbols]

(1) EGR valve (2) Bypass pipe (3) Inlet pipe (4) Body (5) Reflux port (7) Mounting seat (10) Spring bearing (11) Cylinder (15) Piston (16) Pipe (17a) High pressure Chamber (operating pressure chamber) (17b) Low pressure chamber
(Atmospheric pressure chamber) (18) Compression coil spring (19) Valve guide (20) Valve body (20a) Shaft part (20b) Annular groove (20c) Umbrella part (21) Retainer (22) Cotter (23) Return spring ( 24) Valve seat (25) (125) Body inner surface (d) Gap (L) Lift amount

Claims (2)

[Claims] 1. An exhaust gas for an internal combustion engine, comprising: a body having a port for circulating exhaust gas and accommodating a valve body for opening and closing the port; and an actuator attached to the body for driving to open and close the valve body. In the recirculation control valve device, the internal surface shape of the body surrounding the region where the valve body moves is expanded so that the cross-sectional area gradually increases from the closed position to the open position of the valve body. Exhaust gas recirculation control valve device for engines. 2. The exhaust gas recirculation control valve device for an internal combustion engine according to claim 1, wherein an inner surface of a body surrounding a region where the valve body moves is formed in a tapered shape.