JPH1089159A - Exhaust reflux device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the thermal damage of a synthetic resin intake manifold at a connection part to be connected with an exhaust reflux tube. SOLUTION: A point part of an exhaust reflux tube 12 to be connected with an exhaust reflux tube insertion hole 11 of a synthetic resin intake manifold 1, has a double tube structure formed by an outer tube 13, and an adiabatic air layer 14 is formed on an intermediate part. A microgap 18 is kept between the outer tube 13 and an inner peripheral face of the insertion hole 11. A notch part 20 expanded in the shape of taper, is formed on an opening edge of the insertion hole 11, corresponding to the point small diameter part 13c of the outer tube 13, and a recessed part 21 is formed between the notch part 20 and the small diameter part 13c. By forming the notch part 20, the concentration of heat at an edge of the opening edge can be prevented. The turbulent flow is generated in the recessed part 21 by the flow of the intake air, thereby the point of the exhaust reflux tube 12 and the neighborhood of the taper face of the notch part are cooled.

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 for recirculating a part of exhaust gas from an exhaust system of an internal combustion engine to an intake system, and more particularly to a connecting portion for connecting an exhaust gas recirculation pipe to a synthetic resin intake manifold. Regarding improvement.

[0002]

2. Description of the Related Art In an exhaust gas recirculation system for an internal combustion engine, recirculated exhaust gas (EGR gas) is introduced from an exhaust system to an intake system, for example, an intake manifold via a metal exhaust gas recirculation pipe. When the intake manifold is made of synthetic resin for weight reduction, since the EGR gas introduced through the exhaust gas recirculation pipe is extremely high temperature, the end of the exhaust gas recirculation pipe and the intake manifold made of synthetic resin must be connected to each other. At the connection, some measures must be taken to ensure that the intake manifold is not thermally damaged.

[0003] For example, in Japanese Utility Model Laid-Open Publication No. 1-146565, the tip of an exhaust gas recirculation pipe is slightly projected into an intake manifold made of synthetic resin, and an EG is formed on a wall made of synthetic resin.
In addition to preventing direct contact of the R gas, a slight gap is secured between the inner peripheral surface of the hole formed in the intake manifold wall and the outer peripheral surface of the exhaust gas recirculation pipe, and There is disclosed a configuration for preventing a specific heat transfer.

[0004]

However, even in such a conventional configuration in which the inner peripheral surface of the hole and the outer peripheral surface of the exhaust gas recirculation tube are not in contact with each other, the radiant heat transmitted from the exhaust gas recirculation tube to the inner peripheral surface of the hole is not sufficient. From the EGR gas that has flowed into the intake manifold from the tip of the exhaust gas recirculation pipe, the edge of the opening edge of the hole is likely to be locally high in temperature, and the exhaust gas recirculation amount has exceeded the design value for some reason. Occasionally, there is a risk of thermal damage centering on this edge portion.

[0005]

SUMMARY OF THE INVENTION Accordingly, the present invention is directed to a synthetic resin intake manifold, in which an exhaust gas recirculation pipe insertion hole is formed through a side surface near an intake port, and the exhaust gas recirculation pipe is connected to an outer peripheral surface thereof. In an exhaust gas recirculation device for an internal combustion engine, which is inserted with a small gap kept between itself and the inner peripheral surface of the insertion hole, and the tip of the exhaust gas recirculation pipe is opened in the intake manifold, the intake air of the exhaust gas recirculation pipe insertion hole is provided. It is characterized in that a cutout portion that expands in a tapered shape is provided at the edge of the opening into the manifold.

[0006] By providing such a notch, there is no edge in which a heat load tends to be locally concentrated. Further, when the intake air passes through the front surface of the opening of the exhaust gas recirculation pipe insertion hole, a turbulent flow occurs in the notch, and the cooling of the exhaust gas recirculation pipe tip and the notch itself facing the tip is promoted. .

According to the second aspect of the present invention, the opening of the end of the exhaust gas recirculation pipe is located at a position protruding from the inner wall surface of the intake manifold.

Accordingly, the tip of the exhaust gas recirculation pipe is actively cooled by the intake air, and the EGR gas discharged from the exhaust gas recirculation pipe immediately mixes with the intake air to give to the inner wall surface near the exhaust gas recirculation pipe insertion hole. The effect of heat is reduced.

In the invention of claim 3, an outer tube surrounding the outer periphery of the exhaust gas recirculation pipe is provided at the tip of the exhaust gas recirculation pipe, and a small diameter portion of the outer tube is joined to the tip of the exhaust gas recirculation pipe. A heat insulating air layer is formed between the outer tube and the exhaust gas recirculation pipe, the heat insulating air layer being open to the outside at one end toward the outside of the intake manifold, and the outer peripheral surface of the outer tube and the inner peripheral surface of the exhaust gas recirculation tube insertion hole. Is provided with a minute gap.

In other words, the exhaust gas recirculation pipe has a double-pipe structure in which the end of the recirculation pipe is surrounded by an outer tube, and has an adiabatic air layer in between. Therefore, the outer tube is maintained at a relatively low temperature, and the heat transmitted from the outer tube to the exhaust gas recirculation tube insertion hole is further reduced.

Further, in the invention according to claim 4, the outer tube has a stepped portion between the general portion and the small-diameter portion at the tip,
An axial depth of the notch is set, and a concave portion is defined by the tapered surface of the notch, the step, and the small-diameter portion at the tip.

As described above, a turbulent flow is generated in the concave portion, and the tip of the exhaust gas recirculation pipe and the vicinity of the notch opposed to the tip are cooled.

According to a fifth aspect of the present invention, the exhaust gas recirculation pipe insertion hole is opened on a side surface of a passage portion extending from the intake port to the intake manifold, and is provided adjacent to an upstream side of the intake port. The exhaust gas recirculation pipe insertion hole is arranged so as to be deviated from the center of rotation of the valve toward the side where the throttle valve moves to the upstream side of the intake air during the opening operation.

When the butterfly valve is opened, one end moves to the upstream side of the flow of intake air and the other end moves to the downstream side. When the throttle valve is at the intermediate opening degree, the intake air flows to the downstream side of the throttle valve through two crescent-shaped gaps, but the throttle valve end is located at the upstream side compared to the side where the throttle valve end moves downstream. On the side that moves to the side, the flow rate of intake air is relatively large. Therefore, the EGR gas is introduced into a portion of the passage section where the intake air flow rate is large,
The EGR gas discharged from the exhaust gas recirculation pipe tip is positively mixed with the intake air.

[0015]

According to the exhaust gas recirculation apparatus for an internal combustion engine according to the present invention, local heat load can be prevented from being concentrated on the edge at the opening edge of the exhaust gas recirculation pipe insertion hole opened in the synthetic resin intake manifold. Thus, thermal damage to the edge portion can be prevented. Further, the intake air flowing from the intake inlet of the intake manifold passes through the front surface of the opening of the exhaust gas recirculation pipe insertion hole, thereby generating a turbulent flow in the notch, and the exhaust gas recirculation pipe tip and the tip face each other. The end of the exhaust gas recirculation pipe insertion hole can be effectively cooled.

Further, according to the present invention, the exhaust gas recirculation pipe tip is actively cooled by the intake air, and the heat transmitted from the EGR gas discharged from the exhaust gas recirculation pipe to the inner wall surface near the insertion hole is reduced.

According to the third aspect of the present invention, the exhaust gas recirculation pipe tip has a double pipe structure surrounded by an outer tube, and a heat insulating air layer is formed in the middle thereof, so that heat transmitted to the exhaust gas recirculation pipe insertion hole is formed. Is further reduced. In addition, when the outer tube and the exhaust gas recirculation tube are joined to each other in such a double-pipe structure, the temperature is relatively high because the air layer does not have a heat insulating effect. Since the notch is formed so as to be away from the tip, local thermal damage can be reliably avoided.

According to the fourth aspect of the present invention, turbulence is generated in the concave portion defined by the tapered surface of the notch and the outer tube, so that the vicinity of the end of the exhaust gas recirculation pipe where the heat load is high is further ensured. Can be cooled.

According to the fifth aspect of the present invention, since the EGR gas is introduced into a portion of the passage cross section having a large intake flow rate, the EGR gas discharged from the exhaust gas recirculation pipe tip is positively mixed with the intake air. , While improving the distribution characteristics to each cylinder,
The effect that the EGR gas goes straight and heats the opposing wall surface is weakened.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 shows an intake manifold 1 made of synthetic resin to which the present invention is applied. This intake manifold 1
Is for an in-line six-cylinder internal combustion engine as an example,
A collector part 2 having an elongated box shape along the cylinder row direction,
Six branch portions 3 extending from the side surface of the collector portion 2
An intake inlet 4 connected to one end of the collector portion 2; an intake inlet flange 7 which is located at one end of the intake inlet 4 and has an intake inlet 5 opened and a throttle chamber 6 (see FIG. 3) attached thereto. , And each part is molded integrally with an appropriate synthetic resin. Further, a cylinder head mounting flange 8 connected to each cylinder connected to a side surface of a cylinder head (not shown) is integrally formed at the tip of the branch portion 3.

A passage section 9 extending from the intake port 5 to the inside of the collector section 2 is formed in the intake section 4 with a substantially constant passage sectional area. The passage portion 9 has a true circular shape corresponding to the inlet 5 on the intake inlet 5 side, and is gradually flattened toward the collector portion 2. And the intake introduction part 4
An exhaust gas recirculation pipe insertion hole 11 is formed through the exhaust gas recirculation pipe mounting seat 10 on the side surface and into the passage portion 9. The exhaust gas recirculation pipe insertion hole 11 is formed along a direction orthogonal to the flow of intake air in the passage portion 9 and has a circular cross section.

The distal end of a metal exhaust gas recirculation pipe 12 for guiding EGR gas from the exhaust system is connected to the exhaust gas recirculation pipe insertion hole 11. FIG. 2 shows the configuration of the connecting portion. A metal outer tube 13 is attached to the end of the exhaust gas recirculation pipe 12 so as to surround the outer circumference of the exhaust gas recirculation pipe 12. The outer tube 13 has a general portion 13a having an outer diameter slightly smaller than the inner diameter of the exhaust gas recirculation pipe insertion hole 11, and a small-diameter portion 13c formed at a distal end of the outer tube 13 via a step 13b. This tip small diameter portion 13
c has an inner diameter that fits relatively closely to the outer peripheral surface of the exhaust gas recirculation pipe 12 having a simple cylindrical shape, and is fitted to the tip of the exhaust gas recirculation pipe 12 and then welded together. The distal end face of the distal small-diameter portion 13c of the outer tube 13 and the distal end face of the exhaust gas recirculation pipe 12 coincide with each other. In addition, a flange portion 13d is formed at a base end portion of the outer tube 13 so as to expand toward the outer peripheral side. Between the outer tube 13 and the exhaust gas recirculation pipe 12, a heat insulating air layer 14 having an open end on the outside of the intake manifold 1 is formed in a cylindrical shape.

The distal end of the exhaust gas recirculation pipe 12 having the outer tube 13 is fixedly supported on the intake manifold 1 by the fixing plate 15 welded to the flange 13d. The fixing plate 15 has an opening 15a sufficiently larger than the outer diameter of the exhaust gas recirculation pipe 12, and has a pair of bolt through holes. As shown in FIG. 10, the flange 13 d of the outer tube 13 is fixed to the exhaust gas recirculation pipe mounting seat 1 by a pair of bolts 16.
It is sandwiched between the zero bearing surface. When the outer tube 13 is thus fixed, the distal end opening 12a of the exhaust gas recirculation pipe 12 is located at a position slightly protruding from the inner wall surface 17 of the intake manifold 1, and the outer tube 13 and the exhaust gas recirculation Between the pipe insertion hole 11 and the inner peripheral surface,
A minute gap 18 is held over the entire circumference. further,
An annular seal member 19 disposed on the seat surface of the exhaust gas recirculation pipe mounting seat portion 10 abuts on the fixed plate 15 to seal the minute gap 18.

As shown in FIG. 2, a notched portion 20 extending in a tapered shape is formed over the entire circumference at the opening edge of the exhaust gas recirculation pipe insertion hole 11 into the intake manifold 1.
The axial depth of the notch 20 corresponds to the position of the step 13b of the outer tube 13 inserted here.
In other words, the notch 20 is formed so as to surround the outer periphery of the small-diameter portion 13c at the distal end of the outer tube 13. Therefore, the annular space formed by the notch 20 and the annular space formed by the small-diameter portion 13c of the outer tube 13 are substantially integrated with each other. 21 are constituted.
That is, the annular concave portion 21 is defined by the tapered surface of the cutout portion 20, the step portion 13b, and the small diameter portion 13c.

FIG. 3 shows the exhaust gas recirculation pipe insertion hole 11.
3 shows a positional relationship between the throttle valve 25 and the throttle valve 25. As shown in FIG. 3, the throttle valve 25 composed of a butterfly valve has a lower end 25a centered on the throttle shaft and an upper end 25b positioned downstream of the throttle shaft during the opening operation. To try to move each. The exhaust gas recirculation pipe insertion hole 11 is
Are arranged in a lower part of the passage portion 9 on the side moving to the upstream side. In particular, when the passage portion 9 is divided into upper and lower portions around the throttle shaft, the entire area below the exhaust gas recirculation tube insertion hole 11 is included in a region below the passage portion 9.

In the structure of the above embodiment, the exhaust gas recirculation pipe 12 becomes extremely hot due to the EGR gas flowing inside, but the space between the exhaust gas recirculation pipe 12 and the outer tube 13 is insulated by the heat insulating air layer 14. In addition, since the space between the outer tube 13 and the exhaust gas recirculation pipe insertion hole 11 is insulated by the minute gap 18, the heat received on the inner peripheral surface of the exhaust gas recirculation pipe insertion hole 11 is extremely small. Further, since the end of the exhaust gas recirculation pipe 12 is joined to the outer tube 13, the temperature becomes higher than that of the portion having the heat insulating air layer 14. Since it is retracted to the outer peripheral side by the part 20,
The effect of radiant heat is reduced. In particular, the provision of the cutout portion 20 eliminates the edge of the opening edge where heat tends to concentrate locally, thereby avoiding heat concentration. Moreover, when the intake air flows from the intake inlet 5 of the intake manifold 1 along the inner wall surface 17 as shown by an arrow A in FIG. The tapered surface of the portion 20 and the small diameter portion 13c of the outer tube 13
To cool. This cooling prevents thermal damage near the tapered surface.

Since the end opening 12a of the exhaust gas recirculation pipe 12 projects beyond the inner wall surface 17, the opening 12a
The EGR gas flowing out of the air immediately mixes with the intake air flow, and the surrounding inner wall surface 17 is not heated. Moreover, as described above, since the exhaust gas recirculation pipe insertion hole 11 is provided on the side where the throttle valve 25 opens to the upstream side,
In the cross section of the passage portion 9, the flow rate of the intake air passing through the front surface of the exhaust gas recirculation pipe insertion hole 11 increases, and the cooling effect due to the turbulent flow in the concave portion 21 can be more reliably secured, and the mixing of the EGR gas and the intake air is promoted. Is done.

FIGS. 4 and 5 show the method and results of an experiment conducted to confirm the cooling effect of the above-described cutout portion 20. FIG. That is, the exhaust gas recirculation pipe 12 ′ having a simplified shape is inserted into the exhaust gas recirculation pipe insertion hole 11 in a non-contact state, and the notch 20 is formed in the lower half of the opening edge of the exhaust gas recirculation pipe insertion hole 11. The upper half was formed in a straight line without providing the notch 20. Then, EGR gas is introduced in a state where the intake air is allowed to flow through the passage portion 9, and a
The temperature was measured at three points, point b, and point c. According to this experiment, as shown in FIG. 5, when the notch 20 was not provided, the inner wall temperature of the exhaust gas recirculation pipe insertion hole 11 near the outer wall of the intake manifold 1, that is, the temperature at the point c,
Although the temperature at the point b near the opening of the exhaust gas recirculation pipe 12 'becomes high, when the notch 20 is provided, the temperature at the point a becomes c.
The result was that the temperature was lower than the temperature at the point.
That is, by providing the cutout portion 20, the turbulent flow is positively generated as described above, and receives the cooling action.

[Brief description of the drawings]

FIG. 1 is a partially cutaway plan view of a synthetic resin intake manifold provided with an exhaust gas recirculation device of the present invention.

FIG. 2 is a sectional view of an exhaust gas recirculation pipe connection portion.

FIG. 3 is an explanatory diagram showing a positional relationship between a throttle valve and an exhaust gas recirculation pipe insertion hole.

FIG. 4 is an explanatory diagram of a temperature measurement experiment.

FIG. 5 is a characteristic diagram showing measured temperatures of respective parts.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Intake manifold 9 ... Passage part 11 ... Exhaust gas recirculation pipe insertion hole 13 ... Outer tube 14 ... Insulated air layer 18 ... Micro gap 20 ... Notch part 21 ... Concave part

Claims (5)

[Claims] An exhaust gas recirculation pipe insertion hole is formed through a side surface of an intake manifold made of a synthetic resin in the vicinity of an intake port, and an exhaust gas recirculation pipe is minutely disposed between an outer peripheral surface thereof and the inner peripheral surface of the insertion hole. In the exhaust gas recirculation device for an internal combustion engine, which is inserted while maintaining a gap, and the tip of the exhaust gas recirculation pipe is opened in the intake manifold, the opening edge of the exhaust gas recirculation pipe insertion hole into the intake manifold is tapered. An exhaust gas recirculation device for an internal combustion engine, comprising a cutout portion extending in a shape. 2. The exhaust gas recirculation device for an internal combustion engine according to claim 1, wherein an end opening of the exhaust gas recirculation pipe is located at a position protruding from an inner wall surface of the intake manifold. 3. An outer tube surrounding an outer periphery of the exhaust gas recirculation pipe is provided at a tip of the exhaust gas recirculation pipe, and a small-diameter portion of the outer tube is joined to a tip of the exhaust gas recirculation pipe. Between the tube and the exhaust gas recirculation pipe, an adiabatic air layer opened to the outside at one end toward the outside of the intake manifold is formed, and a minute gap is formed between the outer peripheral surface of the outer tube and the inner peripheral surface of the exhaust gas recirculation tube insertion hole. The exhaust gas recirculation device for an internal combustion engine according to claim 1 or 2, further comprising: 4. An axial depth of the notch is set corresponding to a step between a general portion of the outer tube and a small-diameter portion at the tip, and a tapered surface of the notch and the step are formed. The exhaust gas recirculation device for an internal combustion engine according to claim 3, wherein a concave portion is defined by the portion and the small-diameter portion at the front end. 5. The exhaust gas recirculation pipe insertion hole is opened on a side surface of a passage portion extending from an intake port to a collector, and is provided at a rotation center of a throttle valve provided adjacent to an upstream side of the intake port. 5. The internal combustion engine according to claim 1, wherein the exhaust gas recirculation pipe insertion hole is arranged so as to be biased toward a side in which the throttle valve moves to the intake upstream side during the opening operation. 6. Exhaust gas recirculation device.