JP3248423B2 - Exhaust manifold of internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an exhaust manifold for an internal combustion engine.

[0002]

2. Description of the Related Art Conventionally, there is known an exhaust manifold of an internal combustion engine in which each branch pipe is formed of a double pipe having an inner pipe and an outer pipe, and an annular heat insulating layer is formed between the inner pipe and the outer pipe. ing. In this exhaust manifold, the amount of heat radiation of the exhaust gas from the exhaust manifold is made as small as possible so that the catalyst provided downstream of the exhaust manifold is quickly heated by the exhaust gas.

However, when each branch pipe is formed of a double pipe in this way, a large temperature difference occurs between the inner pipe and the outer pipe, and therefore a large difference in the amount of thermal expansion in the axial direction occurs between the inner pipe and the outer pipe.
Therefore, each inner pipe was fixed to the corresponding outer pipe at a fixed support portion provided at the upstream end, and supported slidably in the axial direction by the outer pipe at the slide support portion provided at the downstream end. Exhaust manifolds are known (JP-A-7-224).
649).

[0004]

By the way, when the inner pipe is supported by the outer pipe so as to be slidable in the axial direction,
When the internal stress of the inner tube, which tends to extend in the axial direction due to thermal expansion, becomes larger than the frictional force between the outer peripheral surface of the inner tube and the inner peripheral surface of the outer tube, the inner tube starts to move relative to the outer tube. In other words, unless the internal stress of the inner tube overcomes the frictional force, the inner tube does not move relatively. However, as described above, since the temperature of the inner pipe is relatively high, the stiffness of the inner pipe may be reduced and the internal stress of the inner pipe may not be larger than the frictional force. As a result, the inner pipe may be plastically deformed or the inner pipe may be deformed. Cracks may occur. When the branch pipes with a longer distance between the fixed support and the sliding support have a lower rigidity and a larger amount of thermal expansion in the axial direction, so the frictional force between the inner pipe and the outer pipe of each branch pipe is almost the same. It is said that the longer the distance between the support parts between the fixed support part and the slide support part is, the more difficult it is for the internal stress of the inner pipe to overcome the frictional force, and as a result, plastic deformation or cracks are more likely to occur. There is a problem.

[0005]

According to a first aspect of the present invention, each branch pipe is formed of a double pipe having an inner pipe and an outer pipe, and each inner pipe is fixedly supported. In the exhaust manifold of the internal combustion engine, which is fixed to the corresponding outer tube and slidably supported by the outer tube in the axial direction at the sliding support portion, the distance between the supporting portions between the fixed supporting portion and the sliding supporting portion. The longer the branch pipe, the higher the rigidity of the inner pipe of the branch pipe. That is, in the first aspect, even in a branch pipe having a long distance between support portions, it is easy for the internal stress of the inner pipe to overcome the frictional force, and therefore, the durability and reliability of the branch pipe are ensured.

According to a second aspect of the present invention, in order to solve the above-mentioned problem, each branch pipe is formed of a double pipe having an inner pipe and an outer pipe, and each inner pipe corresponds to an outer pipe at a fixed support portion. In the exhaust manifold of an internal combustion engine fixed to the sliding support portion and slidably supported in the axial direction by the outer tube at the sliding support portion, the branch pipe having a longer distance between the support portion between the fixed support portion and the sliding support portion has a larger length. The frictional force between the inner pipe and the outer pipe in the sliding support portion of the branch pipe is reduced. That is, even in the second invention,
Even in a branch pipe having a long distance between the support portions, the internal stress of the inner pipe makes it easy to overcome the frictional force, and thus the durability and reliability of the branch pipe are ensured.

According to a third aspect of the present invention, in order to solve the above-mentioned problems, in the second aspect, the sliding support portion is formed at one end of each branch pipe, and is located at the sliding support portion of at least one branch pipe. A notch is provided in the inner pipe or the outer pipe. As described above, the temperature of the inner tube is higher than the temperature of the outer tube, so that the amount of thermal expansion in the radial direction of the inner tube is larger than the amount of thermal expansion in the radial direction of the outer tube. For this reason, when the temperature of the inner tube and the outer tube thermally expands, the frictional force between the inner tube and the outer tube in the sliding support portion may increase. Therefore, in the third invention, a notch is provided in the inner pipe or the outer pipe located at the sliding support portion of the branch pipe so that the amount of thermal expansion in the radial direction of the inner pipe is larger than the amount of thermal expansion in the radial direction of the outer pipe. When this occurs, the inner tube can be deformed radially inward or the outer tube can be deformed radially outward, so that the frictional force at the sliding support of the branch tube does not increase. Therefore, the durability and reliability of the branch pipe are ensured.

According to a fourth aspect of the present invention, in order to solve the above-mentioned problem, each branch pipe is formed of a double pipe having an inner pipe and an outer pipe, and each inner pipe corresponds to an outer pipe corresponding to a fixed support portion. And an inner pipe of at least one branch pipe is formed of a plurality of pipe members connected in series to each other in an exhaust manifold of an internal combustion engine fixed to the inner pipe and slidably supported by the outer pipe in the sliding support portion in the axial direction. Each of the tube members is fixed to the outer tube at each fixed support portion, and is slidably supported in the axial direction by the outer tube at each slide support portion. That is, in the fourth invention, the distance between the support portions of the branch pipes is prevented from becoming relatively long, so that the internal stress of the inner pipe is increased as compared with the case where the inner pipe is formed of a single pipe member.

According to a fifth aspect of the present invention, in order to solve the above problems, a long pipe and a short branch pipe are provided, and each branch pipe is formed of a double pipe having an inner pipe and an outer pipe. In an exhaust manifold of an internal combustion engine, each inner pipe is fixed to a corresponding outer pipe at a fixed support portion and slidably supported by the outer pipe at a sliding support portion, a fixed support is provided at a long branch pipe. A part is formed at one end of the branch pipe, and a sliding support part is formed at an intermediate portion between both ends of the branch pipe ,
Forming a fixed support at one end of the short branch pipe;
And a sliding support portion is formed at the other end of the branch pipe . That is, in the fifth invention, the distance between the support portions in the long branch pipe is
Since it is shorter than the distance between the support parts in a short branch pipe ,
In a long branch pipe, the internal stress of the inner pipe is increased as compared with the case where the fixed support part and the sliding support part are provided at both ends of the branch pipe.

[0010]

FIG. 1 shows a case where the present invention is applied to an internal combustion engine having three cylinders. However, the present invention can also be applied to an internal combustion engine having two or more cylinders. Referring to FIG. 1, the exhaust manifold 1 includes three branch pipes 2a, 2b, and 2c connected to corresponding cylinders of an internal combustion engine, respectively. These branch pipes 2
a, 2b, 2c are connected to an engine body (not shown) through a common flange 3. In addition, these branch pipes 2a,
2b and 2c are connected to a common collecting pipe 4, and the collecting pipe 4 is connected via a flange 5 to a catalytic converter (not shown) containing a catalyst.

As shown in FIG. 1, each branch pipe 2a, 2
b and 2c are composed of double tubes. That is, the branch pipe 2a
Has an inner tube 6a and an outer tube 7a, the branch tube 2b has an inner tube 6b and an outer tube 7b, and the branch tube 2c has an inner tube 6c and an outer tube 7c. Each of the branch pipes 2a, 2b, 2c has an outer pipe 7a, 7
The b and 7c are fixed to the flange 3 at the upstream end and to the collecting pipe 4 at the downstream end , for example, by welding, to the flange 3 and the collecting pipe 4, respectively.

Each of the inner tubes 6a, 6b, 6c has a corresponding outer tube 7 at the annular fixed support portions 8a, 8b, 8c.
a, 7b and 7c are fixed, for example, by welding. Also,
Each of the inner tubes 6a, 6b, 6c has an annular sliding support 9a, 9
Outer tubes 7a, 7b, 7 respectively corresponding to b, 9c
By c, it is slidably supported in the axial direction. Therefore, the inner tubes 6a, 6b, 6c move undesirably,
Alternatively, it is prevented from vibrating.

The inner tubes 6a, 6b, 6c are provided at the fixed support portions 8a, 8b, 8c and the slide support portions 9a, 9b, 9c.
c is directly supported by the outer tubes 7a, 7b, 7c,
That is, the inner tubes 6a, 6b, 6c and the outer tubes 7a, 7b, 7c
Inner pipes 6a, 6b, 6c without intermediate members
Are supported by the outer tubes 7a, 7b, 7c. In the example shown in FIG. 1, each of the fixed support portions 8a, 8b, 8c is an inner tube 6a,
Sliding supports 9a, 9b, 9c are provided at the upstream ends of 6b, 6c and outer tubes 7a, 7b, 7c, respectively, at the downstream ends of inner tubes 6a, 6b, 6c and outer tubes 7a, 7b, 7c. In each of the branch pipes 2a, 2b, 2c, the temperature at the upstream end adjacent to the engine body is lower than that at the downstream end. Therefore, as in the present embodiment, the fixed support portions 8a and 8
By providing b, 8c at the upstream end of each branch pipe 2a, 2b, 2c, the weld is prevented from being significantly deteriorated.

As described above, the fixed support portions 8a, 8b, 8c are provided at the upstream ends of the respective branch pipes 2a, 2b, 2c.
When a, 9b, 9c is provided at the downstream end of each branch pipe 2a, 2b, 2c, the axial length between the fixed support portions 8a, 8b, 8c and the slide support portions 9a, 9b, 9c, that is, the support The distance between the parts corresponds to the axial length of the corresponding inner tubes 6a, 6b, 6c. As shown in FIG.
b and the distance Lc between the support parts of the branch pipe 2c.
The distance La between the support parts of the branch pipe 2a is substantially equal to the distance Lb, Lc between the support parts of the branch pipes 2b and 2c.
It is set longer than this.

The thickness of each of the outer tubes 7a, 7b, 7c is set substantially equal to each other. On the other hand, the thicknesses of the inner tubes 6b and 6c are set substantially equal to each other, however, the thickness of the inner tube 6a is set larger than the thicknesses of the inner tubes 6b and 6c. Further, the thickness of the inner tubes 6a, 6b, 6c is set smaller than the thickness of the outer tubes 7a, 7b, 7c.

Still referring to FIG. 1, each inner tube 6a, 6
b, 6c and the corresponding outer tubes 7a, 7b, 7c are disposed apart from each other, and these inner tubes 6a, 6c
b, 6c and the outer heat insulating layer 10 between the outer pipes 7a, 7b, 7c.
a, 10b, and 10c are provided, respectively. In the present embodiment, the heat insulating layer is formed from an air layer, but the inner pipe 6a,
A gap between the outer tubes 6a, 6b and the outer tubes 7a, 7b, 7c may be filled with another fluid or a granular material to form a heat insulating layer.

A branch pipe having a relatively long axial length, such as the branch pipe 2a, is usually provided with a curved portion 11. However, when such a curved portion 11 is provided, the bending rigidity of the branch pipe 2a in the curved portion 11 decreases. Therefore, as shown in FIG. 2, the cross section of the branch pipe 2a in the bending portion 11 is made elliptical, thereby preventing the bending rigidity of the branch pipe 2a in the bending portion 11 from being reduced.

When the engine is started, particularly when the engine is started in a cold state, the catalyst downstream of the exhaust manifold 1 may not be at its activation temperature. In this state, even if the exhaust gas is guided to the catalyst, the exhaust gas is satisfactorily purified. May not be able to do so. Therefore, in the exhaust manifold shown in FIG.
b, 6c and the heat insulating layers 10a, 1 between the outer tubes 7a, 7b, 7c.
0b and 10c are provided so that the amount of heat of the exhaust gas radiated through the exhaust manifold 1 is reduced. Also, the thickness of the inner tubes 6a, 6b, 6c is made relatively small so that the heat capacity of the inner tubes 6a, 6b, 6c is increased, and the thickness of the outer tubes 7a, 7b, 7c is made relatively large. The heat capacity of these outer tubes 7a, 7b, 7c is reduced so that the exhaust manifold 1
The temperature of the exhaust gas flowing through the inside is made small. As a result, the temperature of the catalyst can be quickly raised to the activation temperature, so that good purification of exhaust gas can be ensured.

When the amount of heat radiation from the exhaust manifold 1 is reduced in this way, the temperature of the inner tubes 6a, 6b, 6c becomes significantly higher than the temperature of the outer tubes 7a, 7b, 7c, and as a result, The amount of thermal expansion in the axial direction of 6a, 6b, 6c is significantly larger than the amount of thermal expansion in the axial direction of outer tubes 7a, 7b, 7c. Therefore, for example, the inner tubes 6a, 6b, 6
When both ends of c are welded and fixed to the outer tubes 7a, 7b, 7c, the difference in the amount of thermal expansion in the axial direction between the inner tubes 6a, 6b, 6c and the outer tubes 7a, 7b, 7c causes the inner tubes 6a, 6b, 6c to For example, stress concentrates on a welded portion, a curved portion, or the like, and thus the inner tubes 6a, 6b, and 6c are plastically deformed or the inner tubes 6a, 6b, and 6c are deformed.
Cracks may occur in a, 6b and 6c.

Therefore, sliding supports 9a, 9b, 9c are provided at the downstream ends of the branch pipes 2a, 2b, 2c, and the inner pipes 6a, 6b, 6c are axially moved in these sliding supports 9a, 9b, 9c. And the outer tubes 7a, 7b, 7c. That is, when the temperature of the branch pipes 2a, 2b, 2c rises and the amount of thermal expansion of the inner pipes 6a, 6b, 6c in the axial direction becomes larger than that of the outer pipes 7a, 7b, 7c, the inner pipes 6a,
While being supported by the outer tubes 7a, 7b, 7c, the outer tubes 6b, 6c slide in the sliding support portions 9a, 9b, 9c in the axial direction. As a result, the inner pipes 6a, 6b, 6c are connected to the outer pipes 7a, 7b, 7c as shown by broken lines in FIG.
Relative to the inner tubes 6a, 6b, 6c
This prevents the occurrence of stress concentration sites.

By the way, as described at the beginning, the inner tube 6
When a, 6b, and 6c are supported by the outer tubes 7a, 7b, and 7c so as to be slidable in the axial direction, the internal stress of the inner tubes 6a, 6b, and 6c that tends to extend in the axial direction due to thermal expansion is:
Inner pipes 6a, 6b, in sliding support portions 9a, 9b, 9c,
Only when the frictional force between the outer peripheral surface of the outer tube 6c and the inner peripheral surfaces of the outer tubes 7a, 7b, 7c becomes larger does the inner tubes 6a, 6b, 6c begin to move relative to the outer tubes 7a, 7b, 7c. However, as described above, since the temperatures of the inner tubes 6a, 6b, 6c are relatively high, the rigidity of the inner tubes 6a, 6b, 6c is reduced, and as a result, the internal stress of the inner tubes 6a, 6b, 6c is reduced by the frictional force. There are some cases that cannot be overcome. In this case, the inner tubes 6a, 6
There is a possibility that a stress concentration portion is generated in b, 6c and plastic deformation occurs, or a crack is generated in the inner tubes 6a, 6b, 6c.

A branch pipe having a longer distance between support portions has lower rigidity.
Moreover, since the amount of thermal expansion in the axial direction is large, when the frictional force between the inner pipe and the outer pipe is almost the same, it becomes more difficult for the branch pipe with a longer distance between the support parts to overcome the frictional force due to the internal stress of the inner pipe. In addition, plastic deformation or cracks easily occur in the inner pipe. That is,
In the example of FIG. 1, the inner tube 6a is liable to be plastically deformed or cracked.

Therefore, in this embodiment, the rigidity of the inner pipe is made higher as the distance between the support portions is longer, so that the internal stress of the inner pipe which tends to extend in the axial direction by thermal expansion is increased. I have to. That is, in the example of FIG. 1, the rigidity of the inner tube 6a is increased by making the thickness of the inner tube 6a larger than the thickness of the inner tubes 6b and 6c, thereby increasing the internal stress of the inner tube 6a. As a result, the internal stress of the inner tube 6a can easily overcome the frictional force between the inner tube 6a and the outer tube 7a, and therefore, it is possible to prevent the inner tube 6a from being plastically deformed or cracked. Thus, the durability and reliability of the exhaust manifold 1 can be improved.

In order to increase the rigidity of the inner tube 6a, ribs may be provided on the inner tube 6a, or the cross section of the inner tube 6a may be made elliptical as a whole. FIG. 4 shows another embodiment. In FIG. 4, components similar to those in the embodiment of FIG. 1 are indicated by the same reference numerals. Incidentally, as described above, if the internal stress of the inner tubes 6a, 6b, 6c becomes larger than the frictional force, the inner tubes 6a, 6b, 6c become the outer tubes 7a, 7b, 7
Start to move relative to c. Therefore, the inner tubes 6a, 6
If the frictional force between the outer tubes b, 6c and the outer tubes 7a, 7b, 7c is reduced, the relative movement of the inner tubes 6a, 6b, 6c becomes easier. Therefore, in this embodiment, the frictional force between the inner tube and the outer tube in the sliding support portion is reduced as the distance between the support portions increases.

This frictional force is determined by the coefficient of friction between the outer surfaces of the inner tubes 6a, 6b, 6c and the inner surfaces of the outer tubes 7a, 7b, 7c,
The contact area between the inner pipes 6a, 6b, 6c and the outer pipes 7a, 7b, 7c, the inner pipes 6a, 6b, 6c and the outer pipes 7a, 7b, 7c
It is obtained as the product of the surface pressure between them. Therefore, the frictional force can be reduced by reducing at least one of these friction coefficient, contact area, and surface pressure. Therefore,
In the present invention, at least one of the friction coefficient, the contact area, and the surface pressure is set to be smaller as the distance between the support portions is longer.

That is, in the example shown in FIG. 4, the surface roughness of the outer surface of the inner tube 6a is smaller than the surface roughness of the outer surface of the inner tubes 6b and 6c, and the surface roughness of the inner surface of the outer tube 7a. Is smaller than the surface roughness of the inner surfaces of the outer tubes 7b and 7c, so that the coefficient of friction at the sliding supports 9a is smaller than the coefficient of friction at the sliding supports 9b and 9c. The friction coefficient of one of the inner pipe 6a and the outer pipe 7a is determined by the inner pipe 6b, 6c and the outer pipe 7b, 7
You may make it smaller than the friction coefficient of c.

Further, as can be seen from FIG.
a, the axial length Wa of the contact portion between the inner pipe 6a and the outer pipe 7a is determined by the axial length Wb of the sliding support portion 9b and the axial length Wc of the sliding support portion 9c. Shorter than it is. The pipe diameters of the branch pipes 2a, 2b, 2c are substantially equal to each other, so that the contact area between the inner pipe 6a and the outer pipe 7a in the sliding support 9a is equal to the sliding support 9b, 9c.
It is made smaller than in. as a result,
The frictional force at the sliding support portion 9a can be further reduced, so that the durability and reliability of the inner tube 6a having a long distance between the support portions can be secured. The axial length Wb of the sliding support 9b and the axial length Wc of the sliding support 9c are set substantially equal.

In the embodiment shown in FIG. 4, the sliding support 9a
, The surface roughness of the inner tube 6a and the outer tube 7a is made smaller than that of the sliding support portions 9b and 9c, and the axial length of the sliding support portion 9a is made shorter than that of the sliding support portions 9b and 9c. ing. However, one of these may be applied to the exhaust manifold 1. 5 and 6 show another embodiment. 5 and 6
In the figure, the same components as those in the embodiment of FIG. 1 are denoted by the same reference numerals.

As described with reference to FIG. 1, the branch pipe 2a
Is the distance Lb between the support parts of the branch pipes 2b and 2c.
The branch pipe group longer than Lc, and thus, is referred to as a first branch pipe group 1a, and the branch pipe group including the branch pipes 2b and 2c is referred to as a second branch pipe group 1b. First
The distance between the support portions of the respective branch pipes of the branch pipe group 1a is the second branch pipe group 1
b is longer than the distance between the support portions of the branch pipes. Each branch pipe group is composed of at least one branch pipe.

As described above, if the surface pressure in the sliding support portion is reduced, the inner tubes 6a, 6b, 6c and the outer tubes 7a, 7
The frictional force between b and 7c can be reduced. Therefore,
In the present embodiment, the surface pressure at the sliding support portion is set to be smaller as the distance between the support portions is longer, so that the frictional force is reduced as the distance between the support portions is longer.

By the way, as described above, the inner tubes 6a, 6
The temperatures of b and 6c are higher than the temperatures of the outer tubes 7a, 7b and 7c, so that the radial thermal expansion of the inner tubes 6a, 6b and 6c is the radial thermal expansion of the outer tubes 7a, 7b and 7c. Larger than. Therefore, when the temperature of the branch pipes 2a, 2b, 2c increases, the surface pressure at the sliding support portion increases.

On the other hand, the inner tubes 6a, 6b, 6c or the outer tubes 7a, 7b, 7c located on the sliding support portions 9a, 9b, 9c.
In other words, in this embodiment, when a notch is provided at the downstream end of the inner tubes 6a, 6b, 6c or the outer tubes 7a, 7b, 7c, the surface pressure between the inner tubes 6a, 6b, 6c and the outer tubes 7a, 7b, 7c is increased. Is increased, the inner tubes 6a, 6b, 6c can be deformed radially inward or the outer tubes 7a, 7b, 7c can be deformed radially outward. When the inner pipes 6a, 6b, 6c are deformed radially inward or the outer pipes 7a, 7b, 7c are deformed radially outward, the surface pressure at the sliding support portions 9a, 9b, 9c is prevented from increasing. be able to.

Therefore, in the example shown in FIGS.
Inner tube 6a and outer tube 7a of branch tube 1a of only branch tube group 1a
In the sliding support portion 9a, for example, four notches 12,
13 are provided so as to prevent the surface pressure in the sliding support portion 9a from increasing even when the amount of thermal expansion of the inner tube 6a in the radial direction is larger than the amount of thermal expansion of the outer tube 7a. Also, providing such a notch also reduces the contact area between the inner tube 6a and the outer tube 7a. As a result, the frictional force in the sliding support portion 9a can be reduced, so that the durability and reliability of the branch pipe 2a of the first branch pipe group 1a can be secured.

In this embodiment, as shown in FIG. 6, the notch 12 provided on the inner tube 6a and the notch 13 provided on the outer tube 7a are circumferentially aligned with each other. By doing so, the notches 12, 13 can be formed after the formation of the sliding support portion 9a, so that the notches 12, 13 can be easily formed. In this embodiment, notches 1 are formed in both the inner pipe 6a and the outer pipe 7a.
Although notches 2 and 13 are formed, a notch may be formed in one of the inner tube 6a and the outer tube 7a.

Further, a notch may be formed in the sliding support portion of each branch pipe of the second branch pipe group 1b. FIG. 7 shows yet another embodiment. 7, the same components as those in the embodiment of FIG. 1 are indicated by the same reference numerals. Referring to FIG. 7, the branch pipes 2a constituting the first branch pipe group 1a are a pair of double pipes connected in series to each other, that is, the upstream double pipe 2
aa and the downstream double tube 2ab. The upstream double tube 2aa includes an inner tube 6aa, an outer tube 7aa, and a heat insulating layer 10aa therebetween. The outer pipe 7aa is connected to the flange 3 at the upstream end, and connected to the downstream double pipe 2ab at the downstream end. The inner tube 6aa is fixed to the outer tube 7aa at a fixed support portion 8aa provided at the upstream end, and is slidably supported in the axial direction by the outer tube 7aa at a slide support portion 9aa provided at the downstream end. On the other hand, the downstream double pipe 2ab includes an inner pipe 6ab, an outer pipe 7ab, and a heat insulating layer 10ab therebetween. The outer pipe 7ab is connected at an upstream end to the upstream double pipe 2aa, and at a downstream end to the collecting pipe 4. The inner tube 6ab is fixed to the outer tube 7ab at a fixed support portion 8ab provided at the upstream end, and is slidably supported in the axial direction by the outer tube 7ab at a slide support portion 9ab provided at the downstream end.

When the temperature of the branch pipe 2a rises and thermally expands, the inner pipe 6aa slides on the sliding support 9aa to move relative to the outer pipe 7aa, and the inner pipe 6ab moves to the sliding support 9ab. To move relative to the outer tube 7ab. Therefore, undesirable stress concentration on the inner tubes 6aa and 6ab is prevented. When the branch pipe 2a is composed of a plurality of double pipes 2aa and 2ab in this manner, each double pipe 2a
The distances Laa, Lab between the support portions at a, 2ab can be shorter than in the embodiment described with reference to FIGS. 1 to 6. That is, the inner tubes 6aa, 6
The rigidity of ab can be increased. Therefore, the durability and reliability of the branch pipe 2a of the first branch pipe group 1a can be secured. In the present embodiment, the double tubes 2aa, 2aa
The distances Laa, Lab between the support parts in ab are almost the same as the distances Lb, Lc between the support parts of the branch pipes 2b, 2c of the second branch pipe group 1b or shorter than the distances Lb, Lc between the support parts. .

In the embodiment shown in FIG. 7, the inner pipe of the branch pipe 2a is composed of a plurality of pipe members, and the outer pipe is also composed of a plurality of pipe members. However, it is also possible to configure only the inner pipe of the branch pipe 2a from a plurality of pipe members, and to configure the outer pipe from a single pipe. In addition, each of the inner pipes of the branch pipes of the second branch pipe group may be configured in a plurality. FIG. 8 shows still another embodiment. 8, the same components as those in the embodiment of FIG. 1 are indicated by the same reference numerals.

Referring to FIG. 8, the fixed support portion 8a of the branch pipe 2a of the first branch pipe group 1a is provided at the upstream end of the branch pipe 2a as in the embodiments described above. However, the sliding support portion 9a is provided at an intermediate portion between the upstream end and the downstream end of the branch pipe 2a. Therefore, the distance LLa between the support portions of the branch pipe 2a is made shorter than in the embodiment described with reference to FIGS.

As described above, when the distance between the support portions is reduced, the rigidity of the inner tube 6a is prevented from being reduced, so that the durability and reliability of the inner tube 6a can be ensured.
As the distance between the support portions becomes shorter, the rigidity of the inner tube 6a can be increased. However, as the distance between the support parts becomes shorter, that is, as the axial distance D from the downstream end of the branch pipe 2a to the sliding support part becomes larger, the inner pipe 6a cannot be favorably supported. Therefore, the axial distance D
Cannot be too large.

In the embodiments described above, the fixed support portions 8a, 8b, 8c of the branch pipes 2a, 2b, 2c are formed at the upstream ends of the corresponding branch pipes 2a, 2b, 2c. However, these fixed support portions 8a, 8b, 8
c may be formed at an intermediate portion between the corresponding branch pipes 2a, 2b, 2c. Alternatively, the fixed support portions are connected to the branch pipes 2a, 2a.
Sliding supports 9a, 9b, 9c may be formed at the upstream end at the downstream end of b, 2c.

In the embodiments described above, one fixed support and one slide support are provided for each branch pipe. However, a plurality of fixed supports and a plurality of sliding supports may be provided for each branch pipe.

[0042]

As described above, the durability and reliability of the branch pipe can be ensured.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing the entire exhaust manifold.

FIG. 2 is a cross-sectional view of the branch pipe taken along line II-II in FIG.

FIG. 3 is a partially enlarged view of a sliding support portion showing a case where thermal expansion has occurred.

FIG. 4 is an overall view of an exhaust manifold according to another embodiment.

FIG. 5 is an overall view of an exhaust manifold according to yet another embodiment.

FIG. 6 is a partially enlarged view of the exhaust manifold shown in FIG.

FIG. 7 is an overall view of an exhaust manifold according to yet another embodiment.

FIG. 8 is an overall view of an exhaust manifold according to yet another embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Exhaust manifold 1a ... First branch pipe group 1b ... Second branch pipe group 2a, 2b, 2c ... Branch pipe 2aa ... Upstream double pipe 2ab ... Downstream double pipe 4 ... Collecting pipe 6a, 6b, 6c: inner pipes 7a, 7b, 7c: outer pipes 8a, 8b, 8c: fixed support parts 9a, 9b, 9c: sliding support parts 10a, 10b, 10c: heat insulating layers La, Lb, Lc: distance between support parts

Claims (5)

(57) [Claims] 1. Each branch pipe is formed of a double pipe having an inner pipe and an outer pipe, each inner pipe is fixed to a corresponding outer pipe at a fixed support portion, and the outer pipe is formed at a sliding support portion. An exhaust manifold for an internal combustion engine, which is supported so as to be slidable in the axial direction by increasing the rigidity of an inner pipe of the branch pipe as the distance between the support parts between the fixed support part and the slide support part is longer. 2. Each of the branch pipes is formed of a double pipe having an inner pipe and an outer pipe, each inner pipe is fixed to a corresponding outer pipe at a fixed support, and the outer pipe is fixed at a slide support. In the exhaust manifold of the internal combustion engine supported slidably in the axial direction by the inner pipe and the outer pipe in the sliding support section of the branch pipe, the longer the distance between the support sections between the fixed support section and the sliding support section, the longer the distance between the support sections. Exhaust manifold with reduced friction between them. 3. The sliding support section according to claim 2, wherein the sliding support section is formed at one end of each branch pipe, and the inner pipe or the outer pipe located at the sliding support section of at least one branch pipe is provided with a notch. Exhaust manifold. 4. Each branch pipe is formed of a double pipe having an inner pipe and an outer pipe, each inner pipe is fixed to a corresponding outer pipe at a fixed support portion, and said outer pipe is formed at a sliding support portion. In the exhaust manifold of the internal combustion engine supported slidably in the axial direction, the inner pipe of at least one branch pipe is formed from a plurality of pipe members connected in series with each other, and each pipe member is externally connected to each fixed support portion. An exhaust manifold fixed to a pipe and slidably supported in an axial direction by the outer pipe at each sliding support portion. 5. A branch pipe having a long branch pipe and a short branch pipe, each branch pipe being formed of a double pipe having an inner pipe and an outer pipe, each inner pipe being a corresponding outer pipe at a fixed support. In an exhaust manifold of an internal combustion engine fixed to a pipe and slidably supported in an axial direction by the outer pipe at a sliding support portion,
Forming a fixed support at one end of the long branch tube;
And a sliding support portion is formed at an intermediate portion between both ends of the branch pipe.
Along with the short branch pipe, a fixed support is attached to one end of the branch pipe.
An exhaust manifold formed and having a sliding support portion formed at the other end of the branch pipe .