JPH09119314A - Dual structure exhaust manifold - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve temperature rising characteristics of exhaust gas at the time of starting an engine and absorb a difference in thermal expansion between an outer cylinder and an inner pipe reliably. SOLUTION: A core for forming a clearance between an inner pipe 302 and an outer cylinder 301 can be drawn out from a communication part with a clearance 331 between the inner pipe 302 and the outer cylinder 301, therefore, forming a sand removing hole for removing core sand is not required. It is also possible to decrease the wall thickness of the inner tube. By covering the clearance 331 between the inner pipe 302 and the outer cylinder 3O1 with a gasket 311, it is possible to prevent exhaust gas from flowing into the clearance between the inner pipe 302 and the outer cylinder 301, and suppress exhaust gas temperature from dropping.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a seal structure for an engine-side clearance of an exhaust manifold, which is connected to an engine and a catalyst for purifying exhaust gas of the engine, has an inner pipe cast into a double pipe structure.

[0002]

2. Description of the Related Art In automobiles, a catalyst is arranged downstream of an exhaust pipe to purify exhaust gas.
In this case, in terms of purification efficiency, there is a problem when the engine is started. When the engine is started, both the catalyst and the exhaust gas have a low temperature. Therefore, since the catalyst temperature does not reach the activation temperature, a chemical change does not occur, and a situation occurs in which the unburned components in the exhaust gas cannot fully react.

In order to deal with this, a double-piped exhaust manifold for keeping heat of exhaust gas has been proposed. The double-pipe exhaust manifold has an inner pipe concentrically arranged with a gap inside the outer pipe, and a hollow heat insulating layer is secured between the outer pipe and the inner pipe.

In the double-pipe exhaust manifold, the outer pipe ensures structural strength, and the inner pipe forming the exhaust gas passage is made as thin as possible to reduce the heat capacity of the portion in contact with the exhaust gas. be able to. Further, since the hollow heat insulating layer is provided between the inner pipe and the outer pipe, it is possible to reduce heat escape through the outer pipe. Therefore,
When the engine is started, the temperature of the inner wall of the exhaust manifold can be quickly raised, and the heat retention effect of exhaust gas can be enhanced.

However, in a structure in which a thin-walled inner tube is covered with an outer tube obtained by pressing a plate material such as stainless steel,
It is necessary to use an expensive material so that the plate material of the outer tube is not corroded by salt damage or the like. Further, since the exhaust gas may leak from the mating surfaces of the two plate members being welded to the outside air, a leak test using compressed air and a rework are required, which makes the product expensive. Therefore, a prior art of a double pipe structure in which the inner pipe is cast with cast iron is disclosed in Japanese Patent Laid-Open No. 63-215803.

Further, in the dual structure exhaust manifold, if exhaust gas leaks into the gap between the inner pipe and the outer cylinder, the temperature of the exhaust gas lowers, so it is necessary to seal the gap between the inner pipe and the outer cylinder. Since a large temperature difference occurs between the inner pipe and the outer cylinder, it is necessary to adopt a structure in which the outer pipe holds the inner pipe while absorbing the thermal expansion of both.

Conventionally, as an example of such a structure, FIG.
The one shown in 11 is known.

In FIG. 9, the tip portion 921 of the inner pipe 902 is attached to the outer cylinder 9
The double pipe exhaust manifold is formed by bending the inner pipe 902 to the 01 side and casting the inner pipe 902 with cast iron or the like.

FIG. 10 shows a support 1022 for the inner tube 1002.
And the support 1022 is cast with cast iron or the like.

FIG. 11 shows an inner tube 1 which is not bent to the outer cylinder side.
The structure is such that 102 is cast with cast iron or the like.

[0011]

By the way, in the inner pipe casting dual structure exhaust manifold shown in FIG.
The stainless steel material, which does not easily deteriorate at high temperature even when exposed to high temperature exhaust gas, is provided on the outer cylinder 901 side to expand the bending diameter.
It is necessary to increase the wall thickness of the inner pipe 902. Further, a sand-type sand removing hole 920 for casting the inner pipe 902 is provided, and after the sand removing process is completed, the sand is removed so that exhaust gas does not leak to the outside air from the gap 931 between the inner pipe 902 and the outer cylinder 901. Hole 920 needs to be sealed. In addition, since it is difficult for sand-shaped sand to escape from the bent portion of the inner pipe 920 and the portion of the outer cylinder 901, it is necessary to add a sand removing process such as air blow.

In the inner pipe casting double structure exhaust manifold shown in FIG. 10, the inner pipe 1002 is supported 10
Since it is held at 22, it is not necessary to expand the diameter of the inner pipe 1002, and the inner pipe 1002 can be made thin. However, the sand removal hole 1 of the sand mold when the inner pipe 1002 is cast
020 is provided, and after the sand removal processing is completed, the inner pipe 1002
It is necessary to seal the sand removing hole 1020 so that the exhaust gas does not leak to the outside through the gap 1031 of the outer cylinder 1001. It is the same as in FIG. 9 that the sand of the sand between the support 1022 and the outer cylinder 1001 is hard to come off.

In the inner pipe casting double structure exhaust manifold shown in FIG. 11, since the tip of the inner pipe 1102 is cast while the inner pipe 1102 is in a cylindrical state, a support component is unnecessary, and as shown in FIG. Similarly, since it is not necessary to expand the diameter of the inner pipe 1102, the inner pipe 1102 can be made thin. However, the sand type sand removing hole 1120
After the sand removal process is completed, it is necessary to seal the sand removal hole 1120 so that the exhaust gas does not leak to the outside air through the gap 1131 between the inner pipe 1102 and the outer cylinder 1101. As in the case of FIG. 9, it is difficult for sand-type sand in the gap between the inner pipe 1102 and the outer cylinder 1101 to come off at the portion where the inner pipe 1102 is cast.

In consideration of the above circumstances, the present invention aims to improve the temperature rise characteristic of exhaust gas at the time of engine startup in a dual structure exhaust manifold which is manufactured at low cost by encasing the inner pipe with cast iron. It is an object of the present invention to provide a dual structure exhaust manifold for an engine that is capable of reliably absorbing the difference in thermal expansion between the outer pipe and the inner pipe.

[0015]

According to a first aspect of the present invention, there is provided a dual structure exhaust manifold for an engine, wherein an inner pipe formed of stainless steel and having a thin wall is cast with cast iron, and the inner pipe serves as an exhaust gas passage. At the engine side flange portion of the inner pipe, one end of the strip-shaped plate material is welded and fixed to the outer cylinder side of the inner pipe, the other end extends from the inner pipe in the R shape toward the outer cylinder, and the tip is cast into the outer cylinder. A plurality of fixed inner pipe holding members and a tip of the inner pipe on the engine side are expanded in diameter toward the outer cylinder side, and the expanded portion of the inner pipe is an end face of the flange portion of the exhaust port of the engine. The diameter of the inner pipe is expanded from the inner diameter, and the tip of the inner pipe and the engine side flange of the exhaust manifold are machined on the same surface. The inner pipe holder welded and fixed to the pipe On the downstream side of the member, the thermal expansion absorption structure of the inner pipe in which a part of the inner pipe bulges in an R-shaped convex shape toward the outer cylinder side, and the exhaust gas between the engine head and the exhaust manifold And a gasket having a hole smaller than the inner diameter of the diameter expansion portion of the inner pipe.

A second aspect of the present invention is the dual structure exhaust manifold according to the first aspect, wherein the engine-side tip end portion of the inner pipe is located inside the engine-side flange surface of the exhaust manifold without expanding the inner diameter. The inner pipe located and the gasket are made of metal such as stainless steel, and have a cylindrical portion inside the gasket, which is bent toward the exhaust manifold side, and the cylindrical portion is mounted between the exhaust manifold and the engine. And having a gasket attached to the outer circumference of the inner pipe.

According to a third aspect of the present invention, there is provided the dual structure exhaust manifold according to the first aspect, wherein a diameter of the inner pipe at the engine-side end portion is expanded toward the engine side, and the inner pipe has a tip end. The inner pipe located inside the engine-side flange surface and the gasket are made of metal such as stainless steel, and have a cylindrical portion in which the inside of the gasket is bent toward the exhaust manifold side, and the cylindrical portion is inside the exhaust manifold. The diameter of the inner pipe is reduced, and the gasket is mounted inside the diameter expansion portion of the inner pipe in a state of being mounted between the exhaust manifold and the engine.

According to a fourth aspect of the present invention, there is provided the dual structure exhaust manifold according to the first aspect, wherein the engine-side flange surface of the exhaust manifold is provided on the engine side without expanding the inner diameter at the engine-side end portion of the inner pipe. A first gasket, which seals the exhaust gas that adheres to the outer circumference of the inner pipe and the flange of the exhaust manifold, between the inner pipe located at the position, the flange of the exhaust manifold, and the engine; and a first gasket that is larger than the inner diameter of the exhaust port of the engine. The second which has a hole and sticks closely to the engine
And a hole larger than the outer diameter of the inner pipe between the first gasket and the second gasket,
The distal end of the inner tube has a support having a thickness located in the hole of the support.

According to a fifth aspect of the present invention, in the dual structure exhaust manifold according to the fourth aspect, the support member has a hole smaller than the inner pipe, and a U-shaped groove is entirely formed on the exhaust manifold side. It is characterized in that it is formed over the circumference, and the engine-side tip portion of the inner pipe is inserted into the U-shaped groove.

A sixth aspect of the present invention is the dual structure exhaust manifold according to the first aspect, characterized in that the gasket is made of metal such as stainless steel.

The invention of claim 7 is the dual structure exhaust manifold according to claim 1, wherein the inner pipe is provided downstream of the inner pipe holding member fixed to the inner pipe by welding.
It is characterized in that it has a plurality of thermal expansion absorbing structures for the inner tube, which bulges a part of the inner tube into an R-shaped convex shape toward the outer cylinder side.

An eighth aspect of the present invention is the dual structure exhaust manifold according to the first aspect, wherein the inner pipe holding member is fixed to the outer periphery of the inner pipe by spot welding.

A ninth aspect of the present invention is the dual structure exhaust manifold according to the second aspect, wherein the engine side flange portion of the exhaust manifold is formed in a cylindrical shape with a metal material such as stainless steel, and the outer periphery is exhausted. When the manifold is cast, the inner surface is narrowed from the flange surface toward the inside of the exhaust manifold, and the inner diameter is larger than the inner pipe of the dual structure exhaust manifold at the smallest diameter, and the engine side tip of the inner pipe. Has a length to the inside of the part, the inner surface is processed to be smooth, and the engine side surface is processed to be the same surface as the flange surface of the exhaust manifold, or is cast inside the exhaust manifold. Ring support and the smallest inner diameter of the ring support, The ring gasket is made of a metal ring gasket having an outer diameter of a core larger than the gap between the outer diameter of the inner pipe and the exhaust manifold attached to the engine. It is characterized in that it is tightly mounted between the inner surface and the flange surface of the engine.

A tenth aspect of the present invention is the dual structure exhaust manifold according to the second aspect, wherein one of the inner pipes is formed at a tip end portion of the inner pipe on the engine side and faces the outer cylinder side. In the thermal expansion absorbing structure of the inner pipe that bulges in a R-shaped convex shape, and in the engine-side flange portion of the exhaust manifold, a flat surface such that the inner diameter decreases from the engine-side smooth surface of the flange toward the inside of the exhaust manifold. With the processed lunge smooth cut part,
Consisting of a metal ring gasket having a core outer diameter larger than the gap between the smallest inner diameter of the flange smooth cut portion and the outer diameter of the inner pipe, the ring gasket being in a state in which the exhaust manifold is attached to an engine. , The outer periphery of the engine side tip portion of the inner pipe, or the outer periphery of the convex portion of the thermal expansion absorption structure of the inner pipe, the flange smooth cut portion, and the flange surface of the engine to be tightly mounted Is characterized by.

According to an eleventh aspect of the present invention, in the dual structure exhaust manifold according to the tenth aspect, a thermal expansion absorption structure is provided in the inner pipe on the engine side of the inner pipe holding member welded and fixed to the inner pipe. An inner pipe located inside the exhaust manifold from the engine-side flange surface of the exhaust manifold without provision, and the ring gasket in a state in which the exhaust manifold is attached to the engine, the outer periphery of the engine-side tip portion of the inner pipe, and It is characterized in that it is tightly mounted between the flange smooth cut portion and the flange surface of the engine.

According to a twelfth aspect of the present invention, there is provided the dual structure exhaust manifold according to the ninth aspect, wherein the inner pipe has a tip end portion on the engine side, in which the diameter of the inner pipe is reduced toward the engine side. The tip end of the engine-side diameter reduction and a ring support whose inner surface is narrowed from the flange surface toward the inside of the exhaust manifold, and in a state where the exhaust manifold is attached to the engine, the ring gasket is the inner pipe. It is characterized in that it is tightly mounted between the outer periphery of the diameter-reduced tip portion, the inner surface of the ring support, and the flange surface of the engine.

According to a thirteenth aspect of the present invention, in the dual structure exhaust manifold according to the tenth aspect, the engine-side tip portion of the inner pipe that is not fixed to the outer cylinder, and the front tube side of the exhaust manifold, From the front tube side flange surface of the exhaust manifold, the front tube side tip of the inner tube located on the front tube side, and the front tube side flange portion of the exhaust manifold, from the front tube side smooth surface of the flange to the inside of the exhaust manifold. Toward the front, the flange smooth cut portion that is machined to have a smaller inner diameter, the front tube having an inner diameter larger than the outer diameter of the inner pipe, the smallest inner diameter of the flange smooth cut portion and the outer portion of the inner pipe. Outside the core larger than the gap with the diameter A ring gasket made of metal having the front tube attached to the exhaust manifold, the ring gasket is tightly attached to the outer circumference of the inner tube, the flange smooth cut portion, and the flange surface of the front tube. It is characterized by being done.

According to a fourteenth aspect of the present invention, there is provided the dual structure exhaust manifold according to the thirteenth aspect, wherein the engine-side flange surface of the exhaust manifold is provided on the engine side without expanding the inner diameter at the engine-side tip portion of the inner pipe. Between the inner pipe located at, and the gasket that has a hole larger than the inner diameter of the exhaust port of the engine and adheres closely to the engine, and between the gasket on the engine side flange surface of the exhaust manifold and the gasket that has a hole larger than the outer diameter of the inner pipe. In a state where the tip end portion of the inner pipe is formed of a support having a thickness located in the hole of the support and the exhaust manifold is attached to the engine,
The ring gasket is densely mounted on the outer circumference of the inner pipe, the flange smooth cut portion, and the side surface of the exhaust manifold of the support.

[0029]

According to the first aspect of the present invention, the core for forming a gap between the inner pipe and the outer cylinder, which is used when the inner pipe and the inner pipe holding member are cast, is provided between the inner pipe and the outer cylinder. Since it can be extracted from the part that communicates with the gap, it is not necessary to provide a sand removal hole for extracting core sand, which improves workability and prevents the core from remaining between the inner tube and the outer cylinder. It can be prevented.

Furthermore, since the wall thickness of the inner tube can be made thin, the heat capacity of the inner tube is small and the wall temperature of the inner tube rises early. Therefore, the amount of heat transferred from the exhaust gas to the inner pipe is suppressed to a low level, the temperature drop of the exhaust gas is suppressed, and as a result, the inlet gas temperature of the catalyst installed behind the exhaust manifold can be increased.

Further, the gap between the inner pipe and the outer cylinder is closed by the gasket, so that the exhaust gas can be prevented from flowing into the gap between the inner pipe and the outer cylinder, and the temperature of the exhaust gas can be prevented from lowering.

When the temperature is high, the position of the inner pipe on the engine side is fixed by the inner pipe holding member, and the diameter of the inner pipe is expanded to the outer cylinder side. By absorbing the expansion in the radial direction, it is possible to prevent damage to the tip, and the thermal expansion absorption structure provided on the downstream side of the inner pipe holding member prevents expansion due to thermal expansion of the inner pipe downstream from the inner pipe holding member. Absorb and prevent damage to the inner tube.

According to the second aspect of the present invention, since the cylindrical portion of the metal gasket is mounted on the outer circumference of the inner pipe, the exhaust gas can be prevented from flowing into the gap between the inner pipe and the outer cylinder, and the temperature of the exhaust gas can be lowered. Can be suppressed.

Further, at high temperature, the expansion due to thermal expansion of the inner pipe on the engine side of the inner pipe holding member welded and fixed to the inner pipe is absorbed by the cylindrical portion of the metal gasket.
It is possible to prevent damage to the inner pipe.

In the third aspect of the invention, since the cylindrical portion of the metal gasket is mounted inside the inner pipe, the exhaust gas can be prevented from flowing into the gap between the inner pipe and the outer cylinder, and the temperature of the exhaust gas can be lowered. Can be suppressed.

Further, at high temperature, the expansion due to the thermal expansion of the inner pipe on the engine side of the inner pipe holding member welded and fixed to the inner pipe is absorbed by the radially expanded portion of the inner pipe and the cylindrical portion of the metal gasket. Therefore, damage to the inner pipe can be prevented.

According to the invention of claim 4, the first gasket prevents the exhaust gas from leaking into the gap between the inner pipe and the outer cylinder without expanding the engine side end of the inner pipe or bending the gasket. , Suppressing a decrease in exhaust gas temperature. Further, the support member can absorb the elongation of the inner pipe at high temperature and prevent the inner pipe from being damaged.

According to the fifth aspect of the invention, the first gasket for preventing the exhaust gas from leaking into the gap between the inner pipe and the outer cylinder can suppress the deterioration of the gasket due to the contact of the exhaust gas for a long time, and the high temperature resistance. It does not have to be a material resistant to oxidation.

According to the sixth aspect of the present invention, the extension of the tip of the inner pipe is suppressed by the metal gasket, and it is possible to suppress the occurrence of scratches on the engine side due to the inner pipe.

According to the invention of claim 7, it is possible to prevent the deterioration of the inner pipe holding member due to the expansion of the thermal expansion of the inner pipe at a high temperature.

According to the invention of claim 8, the inner pipe holding member can be easily fixed by welding, and the heat capacity of the member directly contacting the inner pipe is reduced, so that the temperature of the exhaust gas can be raised quickly. .

According to the ninth aspect of the present invention, the gap between the outer cylinder and the inner tube of the exhaust manifold and the flange surface of the outer cylinder and the engine are sealed by the ring gasket, so that the exhaust gas is dispersed to the outside of the exhaust manifold. It is possible to prevent the inner pipe from flowing into the gap between the outer pipe and the inner pipe, which is easily positioned when the exhaust manifold is attached to the engine.

Further, the diameter of the ring gasket can be reduced by using the ring support which is separate from the exhaust manifold main body. Further, since the inner diameter of the ring support is sufficiently larger than the outer diameter of the inner pipe, sand removal after casting is easy.

According to the tenth aspect of the invention, since the R portion of the thermal expansion absorbing structure of the inner pipe and the smooth cut portion of the flange of the exhaust manifold are sealed with the ring gasket, a separate ring support is not required.

In the eleventh aspect of the present invention, since the tip end of the cylindrical inner pipe and the smooth cut portion of the flange of the exhaust manifold are sealed with a ring gasket having a large diameter,
No separate ring support or thermal expansion absorption structure at the tip of the inner tube is required.

According to the twelfth aspect of the invention, the diameter of the tip portion of the inner pipe is reduced toward the engine side, and the ring support separate from the exhaust manifold reduces the inner diameter toward the inside of the exhaust manifold. Since the size is reduced, the ring gasket can be easily attached.

According to the thirteenth aspect of the present invention, since the ring gasket seals the gap between the inner tube and the outer tube and the outer tube and the front tube on the front tube side of the exhaust manifold, the inner tube can be positioned and held. Easy,
The inner pipe holding member is not required at the engine side flange portion.

In the fourteenth aspect of the present invention, the ring gasket prevents the exhaust gas from leaking into the gap between the inner pipe and the outer cylinder without expanding or contracting the end of the inner pipe on the engine side.
Suppress the decrease in exhaust gas temperature. Further, the support member can absorb the elongation of the inner pipe at high temperature and prevent the inner pipe from being damaged.

[0049]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is an external view of an exhaust manifold according to the present invention. FIG. 2 is a cross-sectional view of the engine-side flange portion of the exhaust manifold according to the present invention before the flange surface processing, the sectional view on the right side of FIG. 2 is an I-I cross section, and FIG. It is a figure.

[Embodiment 1] The inner pipe 302 is exposed to high-temperature exhaust gas during high-speed traveling and the like, and is made of stainless steel so as to have a thin wall (for example, 0.5 mm) in order to prevent deterioration due to oxidation and corrosion. ) Is molded. Also, the inner pipe 302
By pressing or bending the pipe,
It is molded into the shape of an exhaust manifold. The diameter of the engine-side tip portion 305 of the inner pipe is expanded toward the outer cylinder 301 side, and the diameter of the tip portion 305 of the inner pipe is larger than the diameter of the exhaust port of the engine on the surface of the flange 303. There is. In the vicinity of the flange 303 of the inner pipe 302, a plurality of inner pipe holding members 304 formed of strip-shaped plate members are welded and fixed to the outer peripheral portion of the inner pipe 302. The inner pipe holding member 304 is formed in an R shape from the inner pipe 302 toward the outer cylinder 301, and the tip thereof is the outer cylinder 301.
It is cast around.

On the downstream side of the portion of the inner pipe 302 where the inner pipe holding member 304 is welded, there is formed a thermal expansion absorbing portion 310 which bulges in a convex shape toward the outer cylinder 301 side. The size of the hole of the gasket 311 that seals the exhaust gas and the engine so that the exhaust gas does not leak outside is larger than the inner diameter of the engine side tip portion 305 of the inner pipe 302. In the downstream part of the inner pipe 302,
A thermal expansion absorber 310 that bulges in a convex shape toward the outer cylinder side is appropriately formed.

The rigidity and strength of the entire exhaust pipe and the structure for preventing exhaust gas containing harmful components from leaking to the outside air are as follows.
The inner tube 302 is formed of an outer cylinder 301 that surrounds the inner tube. Therefore, the outer cylinder 301 itself has a function of an exhaust manifold that is conventionally mounted on an automobile engine.
Furthermore, the inner pipe 302 and the outer cylinder 301 have an appropriate gap (for example, about 3 mm to 5 mm), and the inner pipe 302 is not directly fixed to the outer cylinder 301. The outer cylinder 301 is formed integrally with the engine side flange 303 and a front tube side flange (not shown).

When the distal end of the inner pipe 302 and the inner pipe holding member 304 welded and fixed to the inner pipe 302 is to be cast into a double pipe shape, a core is inserted into the gap between the inner pipe 302 and the outer cylinder 301, and the casting is performed. It will be round. After the casting is completed, the core sand is removed, but when the core sand is left in the gap between the inner pipe 302 and the outer cylinder 301, the core sand is placed behind the exhaust pipe (not shown). As a result, the performance of the catalyst may be deteriorated, the purification efficiency of exhaust gas may be deteriorated, and harmful exhaust gas may be emitted to the outside air. In the double-pipe structure exhaust manifold according to the present embodiment, the outer cylinder 30
Since the core sand for forming the gap 331 can be extracted from the gap 331 between the inner pipe 302 and the inner pipe 302, it is not necessary to provide a new sand removal hole, and further sand removal is performed at the end of the core. Since it is performed, it becomes easy to remove the core sand from the gap 331, and the core sand does not remain in the gap. In addition, since the inner tube holding member 304 has a small width, it does not close the gap 331 as shown in FIG.
It will not remain at 31.

The tip portion 305 of the inner pipe 302 projects outward from the surface of the engine side flange 303, and
2 and the inner pipe holding member 304 are integrally cast, and when the engine side flange 303 surface is flattened, the inner pipe 302
Processing is performed so that the tip of the and the surface of the flange 303 are the same. As a result, since the tip of the inner pipe 302 contacts the gasket 311, it is possible to suppress the exhaust gas in the inner pipe 302 from flowing into the gap 331.

Next, the operation of the dual structure exhaust manifold of the above embodiment will be described.

First, the temperature rise of the exhaust gas temperature when the engine is started will be described.

Except immediately after the engine is stopped, the temperature of the outer cylinder 301 and the inner pipe 302 of the dual structure exhaust manifold at the time of starting the engine is the same as the outside air temperature. After the engine is started, inside the dual structure exhaust manifold, the exhaust gas flowing in the inner pipe 302 causes the inner pipe 302
Is warmed. As a result, the wall temperature of the inner pipe 302 rises, but the temperature of the exhaust gas falls by the amount of heat given to the inner pipe 302.

In the dual structure exhaust manifold of the present embodiment, since the inner tube 302 is made thin, the heat capacity of the inner tube 302 is small and the wall temperature of the inner tube 302 rises early. Therefore, the amount of heat transferred from the exhaust gas to the inner pipe 302 is suppressed to a low level, and the temperature decrease of the exhaust gas is suppressed. As a result, the inlet gas temperature of the catalyst installed behind the dual structure exhaust manifold of the present embodiment. Can be raised early.

At this time, if the exhaust gas leaks into the gap between the inner pipe 302 and the outer cylinder 301, as shown in FIG. 8, the exhaust gas flows into the catalyst installed behind the exhaust pipe, especially immediately after the engine is started. This greatly reduces the temperature and deteriorates the exhaust gas purification efficiency. In the double pipe structure exhaust manifold according to the present embodiment, the tip of the inner pipe 302 is the same as the surface of the flange 303. Since the hole of the gasket 311 attached to the flange 303 is smaller than the inner diameter of the tip portion of the inner pipe 302, the tip of the inner pipe 302 is in contact with the gasket 311, and the gap between the inner pipe 302 and the gap 331.
Is sealed by a gasket 311 and the exhaust gas has a gap 33.
It is possible to prevent the gas from leaking out to No. 1 and improve the purification efficiency of the catalyst.

Next, in a state where exhaust gas and exhaust manifold are sufficiently warmed when driving in urban areas, the inner pipe 30
2 and the outer cylinder 301, the difference in the temperature of the tube wall and the difference in the material forming the tube cause a difference in thermal expansion between the inner tube 302 and the outer cylinder 301.

That is, since the outer cylinder 301 is not directly exposed to the exhaust gas and is cooled by the running wind, the surface temperature is low and the thermal expansion is less than that of the inner pipe 302.
On the other hand, the inner pipe 302, which is directly exposed to high-temperature exhaust gas and is thermally insulated by the air layer in the gap 331 between the inner pipe 302 and the outer cylinder 301, has a high temperature and a large thermal expansion occurs.

Most of the thermal expansion of the inner pipe 302 is absorbed by the thermal expansion absorbing portion 310 which is formed in the middle of the inner pipe 302 and is formed in a convex shape toward the outer cylinder side. At the engine side flange 303, the expansion due to the thermal expansion of the inner pipe 302 is absorbed by the thermal expansion absorbing portion 310 near the inner pipe holding member 304, so that the stress on the inner pipe holding member 304 is relieved and the inner pipe holding member 304 is relaxed. The deformation and damage of 304 can be prevented.

Since the inner pipe holding member 304 fixes the position where the inner pipe holding member 304 of the inner pipe 302 is fixed by welding, the expansion of the inner pipe 302 from the inner pipe holding member 304 on the engine side due to thermal expansion does not occur. Only a small amount. This slight extension is absorbed by the expansion of the diameter of the inner pipe 302 toward the outer cylinder 301 at the engine side tip portion 305 and the R portion of the inner pipe holding member 304. Therefore, the expansion of the inner pipe 302 is suppressed by the gasket 311 and the engine, and the tip portion 30 of the inner pipe 302 is suppressed.
It is possible to prevent 5 from being damaged.

The flange structure on the front tube side of the dual structure exhaust manifold has the same structure as the engine side flange 303 structure, so that core sand can be efficiently extracted without providing a sand removal hole. Further, it is possible to suppress a decrease in gas temperature due to the exhaust gas leaking into the gap 331, and it is possible to prevent damage to the inner pipe 302 due to thermal expansion and contraction.

[Embodiment 2] FIG. 4 is a sectional view of an engine side flange portion of Embodiment 2 of the present invention. An inner pipe holding member 404 is welded and fixed to the inner pipe 402, and a thermal expansion absorber 410 that bulges in a convex shape toward the outer cylinder 401 side is formed downstream of the inner pipe holding member 404. Inner tube 4
The engine-side tip portion 406 of No. 02 extends to the engine side without changing the size of the diameter, and the tip portion 406 is located inside the engine-side flange 403 surface. The gasket 411 that seals the exhaust manifold and the engine is made of metal such as stainless steel, and the inside is bent toward the exhaust manifold side to form a cylindrical portion 412. The inner diameter of the cylindrical portion 412 is formed slightly larger than the outer diameter of the inner pipe 402.

With the gasket 411 mounted between the engine and the flange 403 of the exhaust manifold, the outer circumference of the inner pipe 402 of the exhaust manifold is
It is inserted into the cylindrical portion 412 of the gasket. At this time,
Since the gap between the inner tube 402 and the cylindrical portion 412 of the gasket is small, they are in a fitted state. The structures and functions of the inner pipe holding member 404 and the thermal expansion absorber 410 are the same as in the first embodiment.

In the dual structure exhaust manifold according to the present embodiment, the inner pipe 402 is the cylindrical portion 412 of the gasket.
The exhaust gas flowing in the inner pipe 402 can be largely prevented from flowing into the gap 431 between the inner pipe 402 and the outer cylinder 401 because it is tightly inserted in the inner pipe 402. Further, at a high temperature, due to thermal expansion on the engine side of the welded fixing portion of the inner pipe 402 to the inner pipe holding member 404, the inner pipe 402 and the cylindrical portion 412 of the gasket are not fixed. It is absorbed by moving in the cylindrical portion 412 of the gasket.

[Third Embodiment] FIG. 5 is a sectional view of an engine side flange portion according to a third embodiment of the present invention. An inner pipe holding member 504 is welded and fixed to the inner pipe 502, and a thermal expansion absorbing portion 510 that bulges in a convex shape toward the outer cylinder 501 side is formed downstream of the inner pipe holding member 504. The diameter of the engine-side tip portion 505 of the inner pipe is expanded toward the outer cylinder 501 side, and the diameter of the tip portion 505 of the inner pipe is larger at the tip portion than the diameter of the exhaust port of the engine. The engine side tip portion 505 of the inner pipe 502 is located inside the engine side flange 503 of the exhaust manifold. The gasket 511 that seals the exhaust manifold and the engine is formed of a metal such as stainless steel having oxidation resistance and high temperature resistance, and the inside is bent toward the exhaust manifold side to form the cylindrical portion 5
12 are formed. The cylindrical portion 512 is a gasket 5
The diameter is slightly reduced from the disk-shaped surface of 11 toward the tip, and the outer diameter of the cylindrical portion 512 is the tip portion 5 of the inner pipe 502.
It is formed to be slightly smaller than the inner diameter of 05.

With the gasket 511 mounted between the engine and the flange 503 of the exhaust manifold, the cylindrical portion 512 of the gasket 511 is inserted into the inner pipe 502 of the exhaust manifold. At this time,
The tip portion 505 of the inner pipe 502 has a diameter that increases toward the tip, while the tip portion of the cylindrical portion 512 of the gasket 511 has a reduced diameter, and thus is in a fitted state. The structure and operation of the inner pipe holding member 504 and the thermal expansion absorber 510 are the same as those of the first embodiment. In the dual structure exhaust manifold according to the present embodiment, the cylindrical portion 512 of the gasket is closely inserted into the inner pipe 502. Therefore, the exhaust gas flowing in the inner pipe 502 is not separated from the inner pipe 502 by the gap 5 between the outer pipe 501.
The flow into 31 can be further suppressed as compared with the above-mentioned embodiment. Further, at a high temperature, the internal pipe 502 and the cylindrical portion 512 of the gasket 511 are not fixed to the inner pipe 502 due to thermal expansion on the engine side of the weld-fixed portion of the inner pipe 502 and the inner pipe holding member 504. Are absorbed by moving around the outer circumference of the cylindrical portion 512 of the gasket.

[Fourth Embodiment] FIG. 6 is a sectional view of an engine side flange portion according to a fourth embodiment of the present invention. An inner pipe holding member 604 is welded and fixed to the inner pipe 602, and a thermal expansion absorber 610 that bulges in a convex shape toward the outer cylinder 601 side is formed downstream of the inner pipe holding member 604. Inner tube 6
The No. 02 engine-side tip portion 606 extends to the engine side without changing the size of the diameter, and the tip portion 606 is located outside the engine-side flange 603 surface.

A first gasket 611, a support member 614 and a second gasket 613 for sealing exhaust gas are mounted between the engine and the exhaust manifold. The first gasket is formed such that the diameter of the hole is slightly larger than the outer diameter of the inner pipe 602, and is in close contact with the engine side flange 603 of the exhaust manifold so as to hold the inner pipe 602. In addition, the first gasket 611
Is partially exposed to high-temperature exhaust gas, and is therefore formed of a material having high temperature resistance and oxidation resistance. The second gasket is larger than the inner diameter of the inner pipe 602 and the exhaust port of the engine and is in close contact with the engine side. The support member 614 has a hole larger than the outer diameter of the inner pipe 602, and has a first gasket 611 and a second gasket 613.
And the tip 606 of the inner tube 602 is positioned within the support member 614. The inner pipe holding member 60
4 and the structure and operation of the thermal expansion absorber 610 are the same as in the first embodiment.

In the dual structure exhaust manifold according to the present embodiment, since the inner pipe 602 is closely inserted into the first gasket 611, the exhaust gas flowing through the inner pipe 602 is divided into the inner pipe 602 and the outer cylinder 601. It is possible to suppress the flow into the gap 631. Further, the flange 603 of the inner pipe 602 for holding the inner pipe 602 with the first gasket 611.
Inner pipe 602 at the part protruding from the surface and at high temperature
The expansion due to thermal expansion on the engine side of the welded fixed portion of the inner pipe holding member 604 is absorbed in the support member 614 having a hole diameter larger than the outer diameter of the inner pipe 602. At this time, the elongation of the entire inner pipe 602 is the same as in the first embodiment.
The expansion of the inner pipe 602 within the support member 614 is small because it is absorbed by the thermal expansion absorbing portion 610 formed in the middle of the, so that the tip 606 of the inner pipe 602 may hit the engine and be damaged. Absent.

[Fifth Embodiment] FIG. 7 is a sectional view of an engine side flange portion according to a fifth embodiment of the present invention. The structure other than the support 714 inserted between the first gasket 711 and the second gasket 713 and the inner pipe 702 is the same as that of the fourth embodiment.
Is the same as The inner tube 702 has an inner diameter larger than the inner diameter of the exhaust port of the engine on the engine side of the thermal expansion absorber 710. The other structure is the same as that of the fourth embodiment. The support member 714 is formed such that the inner diameter of the hole is equal to that of the exhaust port of the engine and smaller than the inner diameter of the tip portion 706 of the inner pipe 702 of the exhaust manifold. On the exhaust manifold side of the support member 714, a U-shaped groove 715 is formed over the entire circumference. With the exhaust manifold attached to the engine, the tip portion 706 of the inner pipe 702 is inserted into the U-shaped groove 715 of the support member 714.

In the dual structure exhaust manifold according to the present embodiment, it is possible to prevent the exhaust gas from directly hitting the first gasket 711 and prevent the deterioration of the first gasket 711. Therefore, the first gasket 711 is resistant to oxidation. No need to use high temperature resistant material. Other effects are the same as those in the fourth embodiment.

The effect of changing the inner diameter of the inner tube 702 other than the thermal expansion absorber 710 is the same.
Further, even if the diameter of the tip portion 706 of the inner pipe 702 expands toward the outer cylinder 701, the same effect is obtained.

[Sixth Embodiment] In the first embodiment, the gasket 311 for sealing the exhaust gas is made of a metal such as stainless steel having oxidation resistance and high temperature resistance.

In this embodiment, the extension of the tip 305 of the inner pipe 302 is suppressed by the metal gasket 311.
It is possible to suppress the occurrence of scratches on the engine side due to the inner pipe 302.

[Seventh Embodiment] In the first embodiment, the inner pipe 30 is used.
A plurality of second thermal expansion absorbers 310 are installed on the downstream side of the portion where the inner pipe holding member 304 is welded.

In this embodiment, the stress applied to the inner pipe holding member 304 can be reduced, and the inner pipe holding member 304 can be made to have low adaptability.

[Embodiment 8] In Embodiment 1, the welding of the inner pipe holding member 304 to the inner pipe 302 is spot welding.

In this embodiment, the inner pipe holding member 304 is easily welded to the inner pipe 302, and the contact portion with the inner pipe 302 is reduced, so that the amount of heat escaping from the inner pipe 302 to the outer cylinder 301 is reduced. And suppresses a decrease in the wall temperature of the inner tube 302,
This leads to an early rise in exhaust gas temperature.

[Ninth Embodiment] FIG. 12 shows a ninth embodiment of the present invention.
FIG. 13 is a cross-sectional view of the engine-side flange portion of FIG. 13, showing a state before being attached to the engine, and FIG.

The inner pipe 1202 has an inner pipe holding member 1204.
Are fixed by welding, and a thermal expansion absorber 1210 that bulges in a convex shape toward the outer cylinder 1201 side is formed downstream of the inner pipe holding member 1204. The tip end of the inner pipe 1202 on the engine side extends to the engine side without changing the size of the diameter, and the tip end of the inner pipe 1202 is located inside the surface of the engine side flange 1203. A ring support 1232 made of a metal material such as stainless steel is cast into the engine side flange portion 1203 of the exhaust manifold. The flange 1203 side of the exhaust manifold of the ring support 1232 is the flange 12
No. 03 is machined on the same plane or located inside the flange 1203, and has a length such that the engine-side tip of the inner pipe 1202 is located near the center in the length direction of the ring support 1232. In addition, the inner surface of the ring support 1232 is smoothed so that the diameter decreases from the flange surface 1203 of the exhaust manifold toward the inside. The outer diameter of the core of the ring gasket 1233 is the inner tube 12
02 is larger than the gap between the outer diameter of the cylindrical portion of the engine-side tip and the inner diameter of the ring support 1232 having the smallest diameter.

The exhaust manifold 1 is attached to the engine.
With the 201 attached, the ring gasket 12
The inner pipe 33 is in close contact with the outer periphery of the cylindrical portion of the inner pipe 1202 at the tip on the engine side, the smoothed inner surface of the ring support 1232, and the flange surface of the engine.
A gap 1231 between the outer tube 1201 and the outer tube 202 and the inner tube 1202
The inside is sealed on the engine side of the exhaust manifold. The structures and functions of the inner pipe holding member 1204 and the thermal expansion absorber 1210 are the same as in the first embodiment.

In the dual structure exhaust manifold according to this embodiment, the ring support 1232 and the inner pipe 1202 are provided.
Since a large gap is formed between and, it is easy to remove the core sand after casting, and the core sand does not remain in the gap.

On the engine side of the exhaust manifold, the front end of the inner pipe 1202 and the outer cylinder 1201 are sealed by the ring gasket 1233 via the ring support 1232, so that the exhaust gas flowing in the inner pipe 1202 has a gap. It is possible to prevent leakage to the 1231 and improve the purification efficiency of the catalyst. Further, the flange 1203 of the exhaust manifold and the flange portion of the engine are similarly sealed by the ring gasket 1233 via the ring support 1232, so that the exhaust gas does not leak to the outside air. Further, at high temperature, the inner pipe 1202 and the ring gasket 1233 are not fixed to each other due to the expansion due to the thermal expansion on the engine side of the welded fixing portion of the inner pipe 1202 to the inner pipe holding member 1204.
202 is absorbed as it moves in the ring gasket 1233.

It should be noted that the same effect can be obtained even if a plate-shaped gasket is mounted on the flange 1203 of the exhaust manifold and the flange surface of the engine.

[Embodiment 10] FIG. 14 is a sectional view of an engine side flange portion of Embodiment 10 of the present invention. Inner tube 14
The engine-side tip portion of 02 extends to the engine side without changing the diameter, and the thermal expansion absorption portion 1410 that bulges in a convex shape toward the outer cylinder 1401 side is formed at the tip portion of the inner tube 1402. And its tip is positioned inside the surface of the engine side flange 1403.

Exhaust manifold flange 14
On the inner pipe 1402 side of 03 part, a flange smooth cut portion 1434 is flat-machined so that the inner diameter becomes smaller from the engine-side smooth surface toward the inside of the exhaust manifold. The outer diameter of the core of the ring gasket 1433 is larger than the gap between the outer diameter of the cylindrical portion of the inner pipe 1402 at the engine side tip and the inner diameter of the flange smooth cut portion 1434 having the smallest diameter.

The engine is equipped with an exhaust manifold 1
With 401 attached, ring gasket 14
33 is the outer circumference of the cylindrical portion of the engine-side tip of the inner pipe 1402, the R-shaped convex portion of the thermal expansion absorber 1410 formed at the engine-side tip of the inner pipe 1402, and the flat surface of the flange smooth cut portion 1434 of the exhaust manifold. Since it comes into close contact with the flange surface of the engine, the gap 1431 between the inner tube 1402 and the outer cylinder 1401 and the inside of the inner tube 1402 are
Sealed on the engine side of the exhaust manifold.

In the dual structure exhaust manifold according to the present embodiment, the space between the outer cylinder 1401 and the inner pipe 1402 is narrowed, but since a gap is formed, it is not difficult to remove the core sand after casting. Also, there is no core sand left in the gap.

On the engine side of the exhaust manifold, the end portion of the inner pipe 1402, and the thermal expansion absorbing portion 1410 and the outer cylinder 1401 near the end portion are the ring gasket 1
Since it is sealed by 433, it is possible to prevent the exhaust gas flowing in the inner pipe 1402 from leaking into the gap 1431 and improve the purification efficiency of the catalyst. Prevention of exhaust gas leakage from the exhaust manifold 1401 and the flange surface of the engine is the same as in the ninth embodiment. Also,
The thermal expansion of the inner pipe 1402 at high temperature is absorbed by the thermal expansion absorbing portion 1410 formed at the engine side tip of the inner pipe 1402.

[Embodiment 11] FIG. 15 is a sectional view of an engine side flange portion of an embodiment 11 of the invention. Inner tube 15
The engine-side tip portion of 02 extends to the engine side without changing the size of the diameter, and the tip thereof is located inside the engine-side flange 1503 surface. With the exhaust manifold attached to the engine, a plate-shaped gasket 1511 is mounted between the flange 1503 surface of the exhaust manifold and the flange surface of the engine. The structure other than the tip of the inner pipe 1502 and the plate-shaped gasket is the same as that of the tenth embodiment.

In the dual structure exhaust manifold according to this embodiment, since the outer diameter of the core of the ring gasket 1533 is large, the pressure of the exhaust gas becomes high at high temperature, and the exhaust gas may escape from the ring gasket 1533 to the outside air. However, it can be prevented by the plate-shaped gasket 1511. There is no problem even if the exhaust gas leaks into the gap 1531 between the inner pipe 1502 and the outer cylinder 1501 at high temperature.

[Embodiment 12] FIG. 16 is a sectional view of an engine side flange portion of Embodiment 12 of the present invention. Inner tube 16
The leading end of 02 is composed of a diameter reducing portion 1635 that reduces the diameter toward the engine side. Diameter reduction part 16 of inner tube 1602
The structure other than 35 is the same as that of the ninth embodiment.

In the dual structure exhaust manifold according to the present embodiment, since the diameter reducing portion 1635 is formed at the engine side tip portion of the inner pipe 1602, the ring gasket 1
The attachment of 633 becomes easy.

[Embodiment 13] FIGS. 17 and 18 are a sectional view of a flange portion on an engine side and a sectional view of a front tube side according to Embodiment 13 of the present invention. The present embodiment has a structure in which the inner pipe holding member for fixing the inner pipe 1702 to the outer cylinder 1701 in the tenth embodiment is eliminated on the engine side of the exhaust manifold. On the front tube 1843 side of the exhaust manifold, the inner tube 1802
The front tube 1843 side end portion of the front tube 184 from the front tube side flange 1844 surface of the exhaust manifold without changing the diameter.
It is located on the 3rd side. Exhaust manifold 180
In the front tube side flange 1844 portion of No. 1, the flange smooth cut portion 1834 is planarly processed so that the inner diameter becomes smaller from the front tube side smooth surface of the flange 1844 toward the inside of the exhaust manifold. The front tube 1843 has an inner diameter larger than the outer diameter of the inner pipe 1802 of the exhaust manifold. The metal ring gasket 1832 has a core outer diameter larger than the gap between the smallest inner diameter of the flange smooth cut portion 1834 and the outer diameter of the inner pipe 1802 of the exhaust manifold. Exhaust manifold 1801
When the front tube 1843 is attached to the ring gasket 1833, the ring gasket 1833 is attached to the outer circumference of the inner pipe 1802 of the exhaust manifold and the flange smooth cut portion 1834.
Then, the front tube 1843 is densely mounted on the surface of the flange 1842.

In the dual structure exhaust manifold according to this embodiment, the inner pipe 170 of the exhaust manifold is
2, 1802 are ring gaskets 1733, 1833
Inner tube 170 for being positioned and held by
No inner tube holding member for positioning and holding 2,1802 is required.

[Fourteenth Embodiment] FIG. 19 is a sectional view of an engine side flange portion according to a fourteenth embodiment of the present invention. Inner tube 19
The engine-side tip portion 1906 of No. 02 extends toward the engine side without changing the size of the diameter.
Are located outside the surface of the engine side flange 1903.

A support member 1914 and a plate-shaped gasket 1913 are provided between the engine and the exhaust manifold.
Is installed. The support member 1914 is the inner tube 19
02, which has a hole larger than the outer diameter of 02, is inserted between the flange 1903 of the exhaust manifold and the plate-shaped gasket 1913, and the distal end portion 1906 of the inner pipe 1902 is located in the support member 1914. On the inner pipe 1902 side of the flange portion 1903 of the exhaust manifold, the flange smooth cut portion 1 is formed so that the inner diameter becomes smaller from the engine side smooth surface toward the inside of the exhaust manifold.
934 is flat-machined. Ring gasket 193
The outer diameter of the core of No. 3 is larger than the gap between the outer diameter of the cylindrical portion of the inner tube 1902 at the tip on the engine side and the inner diameter of the flange smooth cut portion 1934 having the smallest diameter.

The engine is equipped with an exhaust manifold 1
Although the tip portion 1906 of the inner pipe of the exhaust manifold is not in close contact with the support member 1914 with the 901 attached, the ring gasket 1933 is provided on the outer periphery of the cylindrical portion of the inner pipe 1902 on the engine side tip and the flange of the exhaust manifold. Since the flat surface of the smooth cut portion 1934 and the flat surface of the support member on the exhaust manifold side are in close contact with each other, the gap 1931 between the inner pipe 1902 and the outer cylinder 1901 and the inside of the inner pipe 1902 are sealed on the engine side of the exhaust manifold. .

In the dual structure exhaust manifold according to the present embodiment, the expansion due to the thermal expansion of the inner pipe 1902 on the engine side from the welded fixing portion of the inner pipe 1902 to the inner pipe holding member 1904 at a high temperature is larger than the outer diameter of the inner pipe 1902. It is absorbed in the support member 1914 having a diameter.

[0104]

As described above, according to the first aspect of the invention, the core for forming the gap between the inner pipe and the outer cylinder used when the inner pipe and the inner pipe holding member are casted. Since it can be extracted from the communication part between the inner tube and the gap between the outer cylinder, there is no need to provide a sand removal hole for removing core sand,
It is possible to improve workability and prevent the core from remaining between the inner tube and the outer cylinder.

Furthermore, since the wall thickness of the inner tube can be made thin, the heat capacity of the inner tube is small and the wall temperature of the inner tube rises early. Therefore, the amount of heat transferred from the exhaust gas to the inner pipe is suppressed to a low level, the temperature drop of the exhaust gas is suppressed, and as a result, the inlet gas temperature of the catalyst installed behind the exhaust manifold can be increased.

Further, the gap between the inner pipe and the outer cylinder is closed by the gasket, so that the exhaust gas can be prevented from flowing into the gap between the inner pipe and the outer cylinder, and the exhaust gas temperature can be prevented from lowering.

When the temperature is high, the position of the inner pipe on the engine side is fixed by the inner pipe holding member, and the diameter of the inner pipe is expanded toward the outer cylinder. By absorbing the expansion in the radial direction, it is possible to prevent damage to the tip, and the thermal expansion absorption structure provided on the downstream side of the inner pipe holding member prevents expansion due to thermal expansion of the inner pipe downstream from the inner pipe holding member. Absorb and prevent damage to the inner tube.

According to the second aspect of the invention, since the cylindrical portion of the metal gasket is mounted on the outer circumference of the inner pipe, the exhaust gas can be prevented from flowing into the gap between the inner pipe and the outer cylinder, and the exhaust gas can be prevented. The temperature drop can be suppressed.

Further, at the time of high temperature, the expansion due to the thermal expansion of the inner pipe on the engine side of the inner pipe holding member welded and fixed to the inner pipe is absorbed by the cylindrical portion of the metal gasket.
It is possible to prevent damage to the inner pipe.

According to the third aspect of the invention, since the cylindrical portion of the metal gasket is mounted inside the inner pipe, it is possible to prevent the exhaust gas from flowing into the gap between the inner pipe and the outer cylinder, and The temperature drop can be suppressed.

Further, at high temperature, the expansion due to the thermal expansion of the inner pipe on the engine side of the inner pipe holding member welded and fixed to the inner pipe is absorbed by the radially expanded portion of the inner pipe and the cylindrical portion of the metal gasket. Therefore, damage to the inner pipe can be prevented.

According to the invention of claim 4, the first gasket prevents the exhaust gas from leaking into the gap between the inner pipe and the outer cylinder without expanding the engine-side tip of the inner pipe and bending the gasket. To prevent the exhaust gas temperature from decreasing. Further, the support member can absorb the elongation of the inner pipe at high temperature and prevent the inner pipe from being damaged.

According to the fifth aspect of the present invention, it is possible to suppress the deterioration of the gasket due to the contact of the exhaust gas for a long time with the first gasket which prevents the exhaust gas from leaking into the gap between the inner pipe and the outer cylinder.

According to the sixth aspect of the present invention, the extension of the tip of the inner pipe is suppressed by the metal gasket, and it is possible to suppress the occurrence of scratches on the engine side due to the inner pipe.

According to the invention of claim 7, it is possible to prevent the deterioration of the inner pipe holding member due to the expansion of the thermal expansion of the inner pipe at a high temperature.

According to the invention of claim 8, the inner pipe holding member can be easily fixed by welding, and the heat capacity of the member directly in contact with the inner pipe can be reduced, so that the temperature of the exhaust gas can be raised quickly. You can

According to the ninth aspect of the invention, since the gap between the outer cylinder and the inner tube of the exhaust manifold and the flange surface of the outer cylinder and the engine are sealed with the ring gasket,
Dissipation of exhaust gas to the outside of the exhaust manifold,
It is possible to prevent the flow into the gap between the inner tube and the outer tube,
Further, when the exhaust manifold is attached to the engine, positioning of the inner pipe becomes easy.

Also, by using a ring support which is separate from the exhaust manifold main body, the diameter of the ring gasket can be reduced. Further, since the inner diameter of the ring support is sufficiently larger than the outer diameter of the inner pipe, sand removal after casting is easy.

According to the tenth aspect of the invention, since the R portion of the thermal expansion absorbing structure of the inner pipe and the smooth cut portion of the flange of the exhaust manifold are sealed with the ring gasket, a separate ring support is not required.

According to the eleventh aspect of the present invention, since the distal end portion of the cylindrical inner pipe and the smooth cut portion of the flange of the exhaust manifold are sealed with a ring gasket having a large diameter, a separate ring support or inner pipe is used. No thermal expansion absorption structure at the tip is required.

According to the twelfth aspect of the present invention, the diameter of the tip portion of the inner pipe is reduced toward the engine side, and the ring support, which is separate from the exhaust manifold, is provided.
Since the inner diameter is reduced toward the inside of the exhaust manifold, the ring gasket can be easily attached.

According to the thirteenth aspect of the present invention, since the ring gasket seals the gap between the inner tube and the outer tube and the outer tube and the front tube on the front tube side of the exhaust manifold, the inner tube is positioned. The holding is facilitated, and the holding member for the inner pipe is not required at the engine side flange portion.

According to the fourteenth aspect of the present invention, the ring gasket prevents the exhaust gas from leaking into the gap between the inner pipe and the outer cylinder without expanding or contracting the tip of the inner pipe on the engine side, and the exhaust gas is exhausted. Suppress the decrease in gas temperature. Further, the support member can absorb the elongation of the inner pipe at high temperature and prevent the inner pipe from being damaged.

[Brief description of the drawings]

FIG. 1 is a schematic structural diagram of an automobile exhaust manifold to which the present invention is applied.

FIG. 2 is a cross-sectional view showing an exhaust manifold showing an embodiment of the present invention before flange surface processing.

FIG. 3 is a diagram showing a state in which the engine according to the embodiment of the present invention is mounted.

FIG. 4 is a diagram showing a state in which the engine is mounted on an engine according to a second embodiment of the present invention.

FIG. 5 is a diagram showing a state in which the engine is mounted on an engine according to a third embodiment of the present invention.

[Fig. 6] Fig. 6 is a view showing a state where the engine is mounted on an engine showing Embodiment 4 of the present invention.

FIG. 7 is a diagram showing a state in which the engine is mounted on an engine according to a fifth embodiment of the present invention.

FIG. 8 is a diagram showing changes in the temperature of exhaust gas flowing into a catalyst according to the present invention.

FIG. 9 is a longitudinal sectional view of a conventional example.

FIG. 10 is a vertical sectional view of a conventional example.

FIG. 11 is a vertical sectional view of a conventional example.

[Fig. 12] Fig. 12 is a diagram showing a state before being mounted on an engine showing a ninth embodiment of the present invention.

FIG. 13 is a diagram showing a state in which the engine is mounted on an engine showing Example 9 of the present invention.

[Fig. 14] Fig. 14 is a view showing a state where the engine is mounted according to the tenth embodiment of the present invention.

FIG. 15 is a diagram showing a state in which the engine is mounted on an engine according to an eleventh embodiment of the present invention.

FIG. 16 is a diagram showing a state in which the engine is mounted on an engine showing Example 12 of the present invention.

FIG. 17 is a diagram showing a state in which the engine is mounted on an engine according to a thirteenth embodiment of the present invention.

[Fig. 18] Fig. 18 is a view showing a state of being attached to the front tube showing the thirteenth embodiment of the present invention.

FIG. 19 is a diagram showing a state in which the engine is mounted on the engine according to Example 14 of the present invention.

[Explanation of symbols]

301, 401, 501, 601, 701, 1201
Outer cylinders 302, 402, 502, 602, 702, 1202
Inner tube 303, 403, 503, 603, 703, 1203
Flange 304, 404, 504, 604, 704, 1204
Inner pipe holding member 310,410,510,610,710,1210
Thermal expansion absorption structure 311, 411, 511 Gasket 613, 713 Second gasket 614, 714, 1914 Support 331, 431, 531, 631, 731, 1231
Gap between inner pipe and outer cylinder 1232 Ring support 1233, 1833 Ring gasket 1434, 1834 Flange smooth cut portion 1635 Inner pipe diameter reduction portion 1843 Front tube

Claims (14)

[Claims] 1. A dual structure exhaust manifold for an engine, wherein an inner pipe formed of a thin material of stainless steel is cast with cast iron, and the inside of the inner pipe serves as an exhaust gas passage, wherein an engine-side flange portion of the inner pipe comprises: A plurality of strip-shaped plate members are welded and fixed to the outer cylinder side of the inner pipe, the other end of the plate member extends from the inner pipe toward the outer cylinder in an R shape, and the tip of the plate member is fixed by casting into the outer cylinder. The inner pipe holding member and the engine-side tip of the inner pipe are expanded in diameter toward the outer cylinder side, and the expanded portion of the inner pipe has a diameter larger than the inner diameter of the exhaust port of the engine at the end face of the flange portion. The tip of the inner pipe and the engine-side flange of the exhaust manifold are welded to the inner pipe of the inner pipe and the tip of the engine-side diameter expansion of the inner pipe that is machined on the same surface. Downstream of the inner pipe holding member In the above, the exhaust gas is sealed between the engine expansion head and the exhaust manifold, and the thermal expansion absorbing structure of the inner tube in which a part of the inner tube bulges in an R-shaped convex shape toward the outer cylinder side. A dual structure exhaust manifold having a gasket having a hole smaller than the inner diameter of the diameter expansion portion of the inner pipe. 2. The dual structure exhaust manifold according to claim 1, wherein an inner pipe located at an engine-side tip end portion of the inner pipe without expanding an inner diameter thereof is located inside an engine-side flange surface of the exhaust manifold. , The gasket is made of metal such as stainless steel, and has a cylindrical portion bent toward the exhaust manifold side inside the gasket, and the cylindrical portion is mounted between the exhaust manifold and the engine, and the inner pipe is A dual structure exhaust manifold that has a gasket attached to the outer periphery of the. 3. The dual structure exhaust manifold according to claim 1, wherein a diameter of an inner pipe at an engine-side tip portion thereof is expanded toward an engine side, and a tip of the inner pipe has an engine-side flange surface. The inner pipe located on the inner side and the gasket are made of metal such as stainless steel, and have a cylindrical portion in which the inside of the gasket is bent toward the exhaust manifold side, and the diameter of the cylindrical portion decreases toward the inside of the exhaust manifold. A dual structure exhaust manifold having a gasket mounted inside the diameter expansion portion of the inner pipe in a state of being mounted between the exhaust manifold and an engine. 4. The dual structure exhaust manifold according to claim 1, wherein the engine-side tip end portion of the inner pipe is located on the engine side from the engine-side flange surface of the exhaust manifold without expanding the inner diameter. When,
Between the flange of the exhaust manifold and the engine, there is a first gasket that seals the exhaust gas that adheres to the outer periphery of the inner pipe and the flange of the exhaust manifold, and a hole that is larger than the inner diameter of the exhaust port of the engine and adheres to the engine. Between the second gasket and the first and second gaskets, there is a hole larger than the outer diameter of the inner pipe, and the tip of the inner pipe is located in the hole of the support. A dual structure exhaust manifold characterized by having a thick support. 5. The dual structure exhaust manifold according to claim 4, wherein the support member has a hole smaller than the inner pipe, and a U-shaped groove is formed on the exhaust manifold side over the entire circumference. A dual structure exhaust manifold, wherein the engine-side tip portion of the inner pipe is inserted into the U-shaped groove. 6. The dual structure exhaust manifold according to claim 1, wherein the gasket is made of metal such as stainless steel. 7. The dual structure exhaust manifold according to claim 1, wherein the inner pipe is downstream of the inner pipe holding member welded and fixed to the inner pipe, and the outer pipe is provided. A dual structure exhaust manifold having a plurality of thermal expansion absorbing structures of an inner tube that bulges a part of the inner tube into an R-shaped convex shape. 8. The dual structure exhaust manifold according to claim 1, wherein the inner pipe holding member is fixed to the outer periphery of the inner pipe by spot welding. 9. The dual structure exhaust manifold according to claim 2, wherein the engine-side flange portion of the exhaust manifold is formed into a cylindrical shape with a metal material such as stainless steel, and the outer periphery is cast during casting of the exhaust manifold. , The inner surface is narrowed from the flange surface toward the inside of the exhaust manifold, and at the smallest diameter, larger than the inner pipe of the double structure exhaust manifold and to the inner side from the engine side tip portion of the inner pipe. It has a length and the inner surface is processed smoothly,
The surface on the engine side is machined on the same surface as the flange surface of the exhaust manifold, or is cast inside the exhaust manifold, the smallest inner diameter of the ring support, and the inner pipe. The ring gasket is made of a metal ring gasket having a core outer diameter larger than the gap between the outer diameter and the exhaust manifold attached to the engine, the ring gasket, the outer circumference of the inner pipe and the inner surface of the ring support, A dual structure exhaust manifold that is closely mounted between the engine and the flange surface. 10. The dual structure exhaust manifold according to claim 2, wherein a part of the inner pipe is formed into a round shape toward the outer cylinder side, which is formed at a front end portion of the inner pipe on the engine side. In the thermal expansion absorption structure of the inner tube that bulges in a convex shape, and in the engine-side flange portion of the exhaust manifold, a flange smoothed surface is machined so that the inner diameter decreases from the engine-side smooth surface of the flange toward the inside of the exhaust manifold. A cut portion, which is made of a metal ring gasket having a core outer diameter larger than the gap between the smallest inner diameter of the flange smooth cut portion and the outer diameter of the inner pipe, with the exhaust manifold attached to the engine, The ring gasket is the outer periphery of the engine side tip portion of the inner pipe, or the convex portion of the thermal expansion absorption structure of the inner pipe. Periphery and said flange smoothing and cutting unit, dual structure exhaust manifold, characterized in that it is tightly fitted between the flange surface of the engine. 11. The dual structure exhaust manifold according to claim 10, wherein the inner pipe on the engine side of the inner pipe holding member welded and fixed to the inner pipe is provided with no thermal expansion absorbing structure. The inner pipe located inside the exhaust manifold from the engine-side flange surface of the, and the ring gasket, in the state where the exhaust manifold is attached to the engine, the outer periphery of the engine-side tip portion of the inner pipe, and the flange smooth cut portion. A dual structure exhaust manifold, which is closely mounted between the engine and the flange surface. 12. The dual structure exhaust manifold according to claim 9, wherein a diameter of the inner pipe is reduced at an engine-side tip portion of the inner pipe toward the engine side. A tip portion and a ring support, the inner surface of which has an inner diameter narrowed from the flange surface toward the inside of the exhaust manifold, and in a state in which the exhaust manifold is attached to an engine, the ring gasket reduces the diameter of the inner pipe. A dual structure exhaust manifold, wherein the exhaust manifold is closely mounted between the outer periphery of the engine, the inner surface of the ring support, and the flange surface of the engine. 13. The dual structure exhaust manifold according to claim 10, wherein the engine-side tip portion of the inner pipe that is not fixed to the outer cylinder and the front tube side of the exhaust manifold have a front surface of the exhaust manifold. At the front tube side tip of the inner pipe located on the front tube side from the tube side flange surface and the front tube side flange portion of the exhaust manifold, the inner diameter from the front tube side smooth surface of the flange toward the inside of the exhaust manifold. The flange smooth cut portion that is machined so as to be smaller, the front tube having an inner diameter larger than the outer diameter of the inner pipe, and the gap between the smallest inner diameter of the flange smooth cut portion and the outer diameter of the inner pipe. A metal core with a large core outer diameter In the state in which the front tube is attached to the exhaust manifold, the ring gasket is densely attached to the outer circumference of the inner tube, the flange smooth cut portion, and the flange surface of the front tube. Dual structure exhaust manifold with. 14. The dual structure exhaust manifold according to claim 13, wherein the engine-side tip of the inner pipe is located closer to the engine than the engine-side flange surface of the exhaust manifold without expanding the inner diameter. When,
A gasket that has a hole larger than the inner diameter of the exhaust port of the engine and adheres closely to the engine, and a hole that is larger than the outer diameter of the inner pipe between the engine-side flange surface of the exhaust manifold and the gasket, and has a tip portion of the inner pipe. Consists of a support having a thickness positioned in the hole of the support, and in a state in which the exhaust manifold is attached to the engine, the ring gasket has an outer periphery of the inner pipe, a smooth cut portion of the flange, and the support. A dual structure exhaust manifold that is densely mounted on the side of the exhaust manifold.