JPH04252850A - Exhaust gas recirculation system for internal combustion engine - Google Patents

Abstract

PURPOSE:To reduce the extent of heat load in an actuator as well as to make improvements in durability and reliability. CONSTITUTION:A temperature rise at the side of an actuator A is checked by a synergetic effect between radiation by means of a mounting seat (heat slinger) 12 extending sideward installed in the upper end of a body 8 and a radiation shielding action of radiant heat from the body 8, and in addition, since a clearance 18 is formed in a joint between the body 8 and the actuator A by means of a projection 14 on top of the body 18, a contact area with each other becomes lessened, and thus any possible heat conduction to the side of the actuator A from the body 8 is suppressed.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas recirculation device installed in an exhaust system of an internal combustion engine, and more particularly to a device designed to reduce the thermal load on an actuator section.

0002

[Prior Art] A typical exhaust gas recirculation device of this type recirculates a part of the exhaust gas to the intake system to lower the combustion temperature in the cylinder, and removes harmful exhaust gases, especially N.
EGR valves designed to reduce emissions of NOx (nitrogen oxides) consisting of O, NO2, etc.
43451)).

[0003] Such an EGR valve is generally installed on the upstream side of the exhaust pipe, that is, in a position close to the exhaust manifold in the engine. Engines are constantly exposed to high temperatures due to heat conduction and radiant heat from the pipes, and the temperature rise is particularly severe in large diesel engines with a large amount of exhaust gas recirculation.

Generally, an EGR valve consists of a body that houses a port for exhaust gas recirculation and a valve body that opens and closes the port, and an actuator unit that is integrally attached to the body and drives the valve body to open and close. Therefore, if the actuator section is exposed to high temperatures, the wear resistance of the piston sliding surface in a piston type actuator and the durability of the diaphragm, seal member, etc. in a diaphragm type actuator are impaired.

[0005] For this reason, in the past, for example, expensive materials with excellent heat resistance and abrasion resistance were used, or the actuator part was separated from the exhaust gas introduction part and the body in which the valve body was housed. The amount of heat input to the actuator section is reduced to reduce the heat load.

[0006] However, the use of the above-mentioned expensive materials is disadvantageous in terms of cost and inevitably results in an increase in manufacturing costs. Furthermore, if the actuator section is separated from the base body by a large distance, it becomes large and heavy, which not only requires a large installation space and limits the mounting position, but also goes against the trend of reducing the size and weight of engines, and reduces reliability against vibration. is also low.

[0007]

[Problems to be Solved by the Invention] The present invention has been made to solve the above problems, and its purpose is to suppress the amount of heat input to the actuator section, and
An object of the present invention is to provide a compact exhaust gas recirculation device for an internal combustion engine that improves cooling performance, reduces heat load, and has excellent durability and reliability.

[0008]

[Means for Solving the Problems] The above object is to provide a body having a port for exhaust gas circulation and housing a valve body for opening and closing the port, and a body having a valve body provided at an upper end of the body. In an exhaust gas recirculation device for an internal combustion engine, the body and the actuator are fixed together such that a required gap communicating with outside air is formed between opposing surfaces of the body and the actuator.
This can be achieved by providing heat sinks extending laterally of the body at the joints. Preferably, an air hole is provided on the bottom surface of the actuator to communicate the air vent chamber in the actuator with the gap.

[0009]

[Function] Due to the synergistic effect of the heat dissipation effect of the laterally extending heat sink provided at the upper end of the body and the heat shielding effect of the radiant heat from the body, the temperature rise on the actuator side is suppressed, and the Since the protrusion forms a gap at the joint between the body and the actuator, the contact area between them becomes small, and heat conduction from the body to the actuator side is suppressed.

[0010] When an air hole is provided on the bottom of the actuator, when the outside air enters and exits the air opening chamber of the actuator through the air hole, the high temperature air stagnant in the gap is stirred and released to the outside air. Therefore, the cooling performance of the heat sink increases.

[0011]

Embodiments Hereinafter, embodiments of the present invention will be explained based on the drawings. FIG. 1 shows a first embodiment of an EGR valve (1) used in a large diesel engine, and is used by being attached to an engine as shown in FIG. 3, for example.

That is, the exhaust manifolds (2) (2) installed on both sides of the multi-cylinder diesel engine (E), which is generally V-shaped when viewed from the front, are equipped with exhaust pipes (3) at the rear ends thereof.
(3) are connected to each other, and on the inner surface of the proximal end of both exhaust pipes (3), there is a flange part (4a) (see Fig. 1) that is perpendicular to the exhaust pipe (3) and opens upward in the middle part. A bypass pipe (4) is connected thereto.

[0013] The EGR valve (1) has the above-mentioned flange portion (
4a) is mounted vertically on top and its port outlet end is connected via an inlet pipe (5) to a communication pipe (7) which brings both intake pipes (6) (6) into communication with each other.

Next, the details of the EGR valve (1) are shown in FIG.
Explain with reference to. (8) is a cast body having an elbow-shaped recirculation port (9) with the exhaust gas inlet opening facing downward and the exit side opening laterally (forward in Figure 3). The end has flanges (10) (1
0) is integrally formed. (11) is the body (
8) is a heat dissipation fin formed around.

At the upper end of the body (8), there is a relatively large circular mounting seat (12) that extends horizontally laterally from the body (8) and acts as a heat shield and a heat sink. The mounting seat (12) is integrally molded with a required distance from the middle part of the body (8), and the mounting seat (12) has a plurality of thin plate-like ribs (13) extending downward from the lower surface thereof toward the middle part of the body (8). reinforced by.

A plurality of projections (14) with smooth upper surfaces are integrally molded on the upper surface of the mounting seat (12), and a through hole (15a) of a required size is provided at the center of each projection (14). , a spring receiver (15) having approximately the same diameter as the mounting seat (12), and a capped cylindrical cylinder (16) of the actuator (A) on the upper surface of the spring receiver (15). Insert the bolt (1
7) is integrally fixed by screwing it in.

As a result, a slight gap (18) communicating with the outside air is formed between the upper surface of the mounting seat (12) and the lower surface of the spring receiver (15).

[0018] (19) is a sealing member with low thermal conductivity that is interposed between the spring receiver (15) and the cylinder (16).

Inside the cylinder (16) is a cylindrical piston (20) whose top surface is closed and which is in close contact with a thick walled part (16a) formed at the middle part of the inner circumferential surface of the cylinder (16), and is slidable up and down. It is inserted as a.

The upper surface of the cylinder (16) receives air from a compressed air source (not shown) such as a compressor.
16) is connected with a pipe (21) for supplying the inside.

[0021] The lower surface of the cylinder (16) and the piston (20
) is a high pressure chamber (operating pressure chamber) (22a).
Furthermore, the empty chamber surrounded by the piston (20) is a low pressure chamber (atmosphere open chamber) (22b).

[0022] (23) is a compression coil spring that is contracted in the high pressure chamber (22a) and constantly presses the piston (20) downward.

A valve guide (24) is press-fitted into the center of the body (8), and its upper end is connected to the spring receiver (1).
The piston (2) passes through the central through hole (15a) of the piston (2).
It is located at the bottom of 0).

[0024] The above-mentioned through hole (15a) and the valve guide (24
) and the outer circumferential surface of the air hole (
25).

The shaft (26a) of a mushroom-shaped valve body (26) is slidably inserted into the valve guide (24), and the shaft end located within the piston (20) has a The retainer (27) has a tapered hole (2
7a), a pair of cotters (28) (28) fitted externally into an annular groove (26b) formed on the outer circumferential surface of the shaft portion are internally fitted to be fixedly attached.

[0026] The lower surface of the retainer (27) and the spring receiver (15)
) A return spring (compression coil spring) (29) is compressed between the upper surface of the spring and the upper surface of the spring.

As a result, the valve body (26) is always urged upward, and under normal conditions, the valve seat (30) with the umbrella portion (26c) fitted into the lower end opening of the reflux port (9)
By coming into close contact with the reflux port (9), the reflux port (9) is closed.

[0028] Also, under normal conditions, the piston (20)
The inner bottom surface of is in contact with the shaft end surface of the valve body (26) due to the biasing force of the compression coil spring (23) contracted in the high pressure chamber (22a), and when the valve body (26) is closed. ,piston(
A required gap is formed between the lower end of spring receiver (20) and spring receiver (15). This gap becomes the maximum lift amount of the valve body (26), that is, the opening/closing stroke.

Next, the operation of the above embodiment will be explained. When the engine (E) is in a high speed and high load operating range and compressed air is forced into the high pressure chamber (22a) by the operation of a control device (not shown), the piston (20) and the valve body (26) The piston (20) is pressed down integrally against the spring (29), and the lower end of the piston (20) is attached to the spring receiver (15).
It stops when it comes into contact with.

As a result, the valve body (26) is opened, and the exhaust gas flowing into the bypass pipe (4) is directed to the recirculation port (9).
It passes through the introduction pipe (5) and is fed into each cylinder (not shown) of the engine from the communication pipe (7). the result,
The combustion state becomes slow, the combustion temperature is kept low, and the N
Ox emissions are reduced.

When the engine (E) enters the operating range of medium-low speed and low load, the control device operates again to stop the supply of compressed air, thereby reducing the valve body (26) and piston (20).
) is returned by the return spring (29), and the reflux port (9) is automatically closed.

When the valve body (26) is closed, high-temperature and relatively high-pressure exhaust gas passes through the recirculation port (9), so the entire body (8) becomes quite hot, and its radiant heat increases. Therefore, it is expected that the actuator (A) will also reach a high temperature.

However, the EGR valve of this first embodiment (
In 1), a mounting seat (12) with a large area is integrally molded on the upper end of the body (8) to enhance its own heat dissipation effect.
In addition, the radiant heat from the body (8) is shielded from dissipating toward the actuator (A) above, and a plurality of protrusions (14) are provided on the upper surface of the mounting seat (12) to prevent the spring receiver (15) from dissipating. ) is made small to suppress heat conduction from the body side, so the actuator (A) is not exposed to high temperatures.

Furthermore, due to the vertical movement of the piston (20), outside air passes through the gap (18) between the mounting seat (12) and the spring receiver (15) and the air hole (25),
0), the high temperature air stagnant in the gap (18) is agitated and released to the atmosphere, improving the cooling performance of the mounting seat (12).

Furthermore, the cross-sectional area of the connecting portion between the mounting seat (12) and the lower part of the body (8) is made relatively small, and a plurality of thin plate-shaped ribs (13) are connected between them. Mounting seat (12)
Heat conduction to the sides can be suppressed, and at the same time, the strength and rigidity of the mounting seat (12) can be increased.

Since the air hole (25) is formed closer to the center where the valve guide (24) passes through, which is farther from the outside air,
Dust, water droplets, etc. are prevented from entering the piston (20).

As explained above, E of the first embodiment
In the GR valve (1), the thermal influence from the body (8) is reduced, so the actuator (A) can be installed relatively close to the body (8), making the device smaller and lighter. Not only can the actuator (
Since the thermal load on each component of A) is reduced, durability and
Reliability is improved, and it is not necessary to use expensive materials that require heat resistance, so costs can be reduced.

Next, a second embodiment of the present invention will be explained based on FIG. 2. The body (8) is almost the same as that of the first embodiment, so common members are given the same reference numerals, and only different points will be explained.

The case body (31) of the diaphragm actuator (A) is mounted on the upper surface of the mounting seat (12b), which has a large circular shape with a smooth upper surface and is connected to the upper end of the body (8).
At the bottom thereof, a flange (31b) and a mounting seat (12b) are connected to the bottom wall (31a) of the case body (31) at a slight distance.
) are fixed by bolts with a packing (32) having low thermal conductivity interposed therebetween.

[0040] The valve body (26) located inside the case body (31)
) has a rubber diaphragm (33), a retaining plate (34), and a cylindrical spring retainer (35) attached to the male thread (26d) at the upper end of the diaphragm (33).
The nut (36
) is attached.

The outer peripheral end of the diaphragm (33) is held between the case body (31) and the cover body (37) attached to the upper part thereof, and is fastened with a plurality of bolts (38).
It is fixed in such a way that airtightness is maintained.

A return spring (29) is compressed between the inner bottom surface of the case body (31) and the upper and lower end surfaces of the spring retainer (35), and the valve body (26) is connected to the constant return port (9). is biased in the valve closing direction (upward).

The upper side partitioned by the diaphragm (33) is a high pressure chamber (39), and the lower side is a low pressure chamber (40).
Compressed air is supplied into the high pressure chamber (39) through a pipe (21) fixed to the upper surface of the cover body (37).

A plurality of air holes are provided in the center of the bottom wall (31a) of the case body (31), that is, near the insertion part of the valve guide (24), for communicating the low pressure chamber (40) with the outside air. (41) is drilled.

Also in the EGR valve (1) of this second embodiment, the body (
8) The radiant heat, etc. from 8) is not directly transmitted to the actuator (A) side. In addition, the gap (42) between the case body (31) and the flange (31b) forms an air insulating layer, and the pumping action of the diaphragm (33) accompanying the opening and closing of the valve body (26) Since the outside air passes through the gap (42) between the case body (31) and the flange (31b) and flows through the air hole (41), high-temperature air does not stagnate in the gap (42). Therefore, the temperature rise of the actuator (A) is suppressed, and deterioration of the diaphragm (33) etc. can be prevented.

[0046] In this second embodiment, the mounting seat (
12b) or the lower surface of the flange (31b).
A protrusion similar to the embodiment may be provided to reduce the contact area with the flange (31b). In this way, heat conduction from the body (8) is suppressed and the actuator (A
) can further reduce the heat load.

[0047] The present invention is not limited to the above embodiments, but can take various forms. For example, in the first and second embodiments, the mounting seat (1
2) (12b) is integrally molded with the body (8), but a separately molded heat sink may be fixed to the joint between the body (8) and the actuator (A).

In the first embodiment, the projection (14) provided on the top surface of the mounting seat (12) may be provided protruding from the bottom surface of the spring receiver (15) on the actuator (A) side, or both may be provided on the bottom surface of the spring receiver (15) on the actuator (A) side. They may be provided alternately.

[0049] In place of the protrusion (14), a plurality of separately molded spacers with low thermal conductivity may be used.

In the second embodiment, the actuator (A
) may be replaced with a negative pressure chamber and an actuator that utilizes negative pressure may be used.

In this case, the pipe (21) is connected to a negative pressure source, and the return spring (29) is connected to the high pressure chamber (
39) side, and the shape of the port (9) of the part where the lower end of the valve body (26) and it abuts is set opposite to the example, when the valve body (26) moves upward. Port (9)
The structure may be such that it is open.

The present invention can be applied not only to the EGR valve described above but also to waste gate valves for turbochargers and the like.

[0053]

According to the present invention, since the thermal load on the actuator is reduced, its durability and reliability can be greatly improved. In addition, as the heat load is reduced, there is no need to use expensive materials with high heat resistance and high wear resistance for the actuator components, and the actuator and body can be placed close to each other. , it is possible to provide an inexpensive and compact device.

[Brief explanation of the drawing]

FIG. 1 is a central longitudinal sectional front view showing an EGR valve according to a first embodiment of the present invention.

FIG. 2 is a central longitudinal sectional front view showing the EGR valve of the second embodiment.

FIG. 3 is a plan view schematically showing an example of mounting the EGR valve of the present invention on a large diesel engine.

[Explanation of symbols]

(1) EGR valve
(2) Exhaust manifold (3) Exhaust pipe
(4) Bypass pipe (4a) flange
(5) Introduction pipe (6)
intake pipe
(7) Communication pipe (8) Body
(9) Reflux port (10) Flange (1
1) Heat sink (12) (12b) mounting seat (heat sink)
(12a) Boss part (13) Rib
(1
4) Protrusion (15) Spring receiver
(15a) Through hole (16) Cylinder
(16a) Thick wall part (18) Gap
(19) Seal member (20) Piston (21)
Pipe (22a) High pressure chamber (working pressure chamber)
(22b) Low pressure chamber (atmosphere open chamber) (23) Compression coil spring
(24) Valve guide (25) Air hole
(26) Valve body (26
a) Shaft part
(26b) Annular groove (26c) Umbrella part
(26d) Male thread (27) Retainer
(27a) Tapered hole (28) Cotter
(29) Return spring (30) Valve seat
(31) Case body (31a) bottom wall (bottom surface)
(31b) Flange (3
2) Packing
(33) Diaphragm (34) Holding plate
(35) Spring retainer (36) Nut
(37) Cover body (38) Bolt
(39) High pressure chamber (operating pressure chamber) (40) Low pressure chamber (atmosphere open chamber)
(41) Air hole (42) Gap

Claims (5)

[Claims] 1. A body having a port for exhaust gas circulation and accommodating a valve body for opening and closing the port, and an actuator provided at the upper end of the body for driving the valve body to open and close. In the exhaust gas recirculation device for an internal combustion engine, the body and the actuator are fixed to each other such that a required gap communicating with the outside air is formed between their opposing surfaces, and the side of the body is attached to the joint portion of each other. 1. An exhaust gas recirculation device for an internal combustion engine, characterized in that it is provided with a heat sink that extends in both directions. [Claim 2] The actuator is operated by a pressure difference between the operating pressure chamber and the atmosphere release chamber, and is characterized in that an air hole is provided in the bottom surface of the actuator to communicate the atmosphere release chamber and the gap. The exhaust gas recirculation device for an internal combustion engine according to claim 1. 3. The exhaust gas recirculation device for an internal combustion engine according to claim 1, wherein the heat sink is provided integrally with the body or the actuator. 4. The gap is formed by a plurality of protrusions provided on at least one of the upper end surface of the body and the lower end surface of the actuator and brought into contact with the other end surface. 3. The exhaust gas recirculation device for an internal combustion engine according to any one of 3. 5. The internal combustion engine according to claim 1, wherein the gap is formed by a spacer with low thermal conductivity interposed between the upper end surface of the body and the lower end surface of the actuator. Exhaust gas recirculation device.