JP3810514B2 - Double pipe for vehicle exhaust system - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a vehicle exhaust system double pipe that is used in an exhaust system of a vehicle such as an automobile.
[0002]
[Prior art]
In an exhaust system of a vehicle such as an automobile, a double pipe in which an inner pipe is inserted into an outer pipe is used in order to suppress a decrease in exhaust temperature. For example, an exhaust manifold into which exhaust gas from an engine flows is connected to the exhaust pipe. As an example in which a double pipe is used, the one shown in Japanese Patent Application Laid-Open No. 7-317540 is known. As an example in which the double pipe is used for a front pipe that leads exhaust gas from an exhaust manifold to a catalytic converter or the like, What is shown in Japanese Patent Publication No. 8-2415 is known.
[0003]
[Problems to be solved by the invention]
However, in the conventional double pipe, a gap is formed between the outer pipe and the inner pipe, and both the pipe surfaces are formed of a smooth surface. The outer tube has a problem that the membrane vibrates and generates exhaust noise.
Therefore, the present invention has been made to solve the above problems, and an object of the present invention is to provide a vehicle exhaust system double pipe that generates less noise.
[0004]
[Means for Solving the Problems]
The present invention relates to a vehicle exhaust system double pipe in which an inner pipe is inserted into an outer pipe and a gap is formed between the outer pipe and the inner pipe.
The outer tube is formed with irregularities by repeating pyramidal convex portions continuously in the circumferential direction and the axial direction of the outer tube, and all the irregularities are not parallel to the outer peripheral surface of the inner tube. Only the surface is formed .
[0005]
When forming irregularities by protrusions pyramid the outer tube is repeated continuously in the circumferential direction and the axial direction of the outer tube, the outer peripheral surface of the inner Rutotomoni rigidity of the outer tube is high and all the irregularities tube and since only non-parallel faces are formed, even if the inner tube vibrates film by pulsation of the exhaust gas can be suppressed membrane vibration of the outer tube.
[0006]
DETAILED DESCRIPTION OF THE INVENTION
The unevenness may be formed only at a predetermined portion of the outer tube, or may be formed on the entire surface of the outer tube portion having a predetermined distance from the inner tube.
Concave-convex shape, to repeat the unevenness of the fixed shape.
Irregularities are you form only the outer peripheral surface and a non-parallel surfaces of the inner tube in order to suppress membrane vibration of the outer tube.
[0007]
【Example】
Hereinafter, embodiments of the present invention will be described with reference to FIGS.
1-3, a first embodiment of a vehicle exhaust system for the double tube of the present invention is shown, this embodiment than it was also applied to the double pipe to the branch pipes 2 of the exhaust manifold 1 of the present invention .
[0008]
As shown in FIG. 1, the inflow side flange 3 fixed to the exhaust side port (not shown) of the engine has one end of four branch pipes 2 into which exhaust gas from the engine (not shown) flows. The other end of the four branch pipes 2 are connected together and connected to one end of the cylindrical collecting pipe 4. The other end of the collecting pipe 4 is connected to the outflow side flange 5. .
[0009]
As shown in FIG. 2, the branch pipe 2 is formed of a double pipe in which an inner pipe 7 is inserted into the outer pipe 6, and both end portions of the outer pipe 6 (only the outer pipe end portion 6 a on the inflow side flange 3 side are shown). ) Is reduced in diameter, both ends of the inner pipe 7 (only the inner pipe end 7a on the inflow side flange 3 side) and both ends of the outer pipe 6 (only the outer pipe end 6a on the inflow side flange 3 side) are shown. And a gap 12 is formed between the outer tube main body 6b and the inner tube 7 disposed between both ends of the outer tube 6 (only the outer tube end 6a on the inflow flange 3 side is shown). Yes.
[0010]
The upstream outer pipe end portion 6a and the inner pipe end portion 7a are spot-welded 8 at the joint portion, and the outer pipe end portion 6a is welded to the inflow side flange 3 all around.
The downstream outer pipe end (not shown) and the inner pipe end (not shown) are slidably formed without welding, and the outer pipe end (not shown) and the collecting pipe 4 are welded. (Not shown).
[0011]
As shown in FIGS. 2-3, the pyramid-shaped convex part 10 is repeated continuously in the circumferential direction and axial direction of the outer pipe | tube main body 6b, and the unevenness | corrugation 11 is formed in the outer pipe | tube main body 6b. Only the surface that is not parallel to the outer peripheral surface of the inner tube 7 is formed on all the irregularities 11.
[0012]
When exhaust gas flows into the branch pipe 2 from the exhaust port (not shown) of the engine, the inner pipe 7 of the branch pipe 2 vibrates with the pulsation of the exhaust gas, and radiated sound is generated. since it is propagated, the outer tube 6 the unevenness 11 is formed, together with high rigidity, only the outer peripheral surface and a non-parallel surfaces of the inner tube 7 to all irregularities 11 are formed, an outer tube main body 6b Therefore, the exhaust noise radiated from the outer tube main body 6b to the outside can be reduced. In this example, the exhaust noise was reduced by 5 db as compared with the case where the irregularities 11 were not formed on the outer tube main body 6b. In addition, since a gap is formed between the outer tube main body 6b and the inner tube 7, exhaust heat is not easily transmitted from the inner tube 7 to the outer tube main body 6b, and the rigidity of the outer tube main body 6b is reduced as the temperature rises. Even if the vehicle travels for a long time, the exhaust noise radiated to the outside from the outer tube main body 6b can be reduced.
[0013]
4 to 5 show a second embodiment of the double pipe for a vehicle exhaust system of the present invention. In this embodiment, the double pipe of the present invention is interposed between an exhaust manifold and a catalytic converter. This is applied to the front pipe 20.
As shown in FIG. 4, the front pipe 20 is formed of a main pipe 21, an upstream flange 22 and a downstream flange 23 connected to both end portions 21 a and 21 b of the main pipe 21.
As shown in FIG. 5, the main pipe 21 is formed of a double pipe in which an inner pipe 25 is inserted into an outer pipe 24.
[0014]
Both ends of the outer pipe 24 (only the outer pipe end 24a on the upstream flange 22 side is reduced), both ends of the inner pipe 25 (only the inner pipe end 25a on the upstream flange 22 side) and the outer pipe are reduced. 24 both ends (only the outer pipe end 24a on the upstream flange 22 side is shown) are joined, and arranged between both ends (only the outer pipe end 24a on the upstream flange 22 side is shown) of the outer pipe 24. A gap 29 is formed between the outer tube main body 24 b and the inner tube 25.
The joint portion of the upstream outer tube end 24a and the inner tube end 25a is spot-welded 26, and the outer tube end 24a is welded 27 to the upstream flange 22 on the entire circumference.
The outer pipe end (not shown) and the inner pipe end (not shown) on the downstream side are formed to be slidable without being welded, and the outer pipe end (not shown) and the downstream flange 23 are formed. All-around welding (not shown) is performed.
[0015]
The outer tube main body 24b of the outer tube 24 has the same unevenness 28 as that of the first embodiment, and the front pipe 20 of this embodiment also has the same function and effect as the exhaust manifold 1 of the first embodiment.
[0016]
【The invention's effect】
According to the present invention, in a vehicle exhaust system double pipe in which an inner pipe is inserted into an outer pipe and a gap is formed between the outer pipe and the inner pipe, the outer pipe has a pyramid-shaped convex portion. since the formation of the irregularities by repeated continuously in the circumferential direction and the axial direction of the outer tube, a high rigidity of the outer tube Rutotomoni, and non-parallel outer peripheral surface of the inner tube in all uneven Since only the surface is formed and the membrane vibration of the outer pipe can be suppressed, the exhaust noise radiated from the outer pipe to the outside is reduced, and the quietness of the vehicle during traveling is improved. Further, since the gap is formed between the outer tube and the inner tube, the exhaust heat is hardly transmitted to the outer tube from the inner tube, the stiffness reduction of the outer tube due to the Atsushi Nobori is suppressed, the vehicle even traveling long it is possible to reduce the exhaust noise emitted to the outside from the outer tube, the quietness of the vehicle is maintained.
[Brief description of the drawings]
FIG. 1 is a diagram in which a vehicle exhaust system double pipe of the present invention is applied to a branch pipe of an exhaust manifold.
FIG. 2 is a partial cross-sectional view of a branch pipe of an exhaust manifold.
FIG. 3 is a partially enlarged view of the surface of the branch pipe of the exhaust manifold.
FIG. 4 is a diagram in which a vehicle exhaust system double pipe of the present invention is applied to a front pipe.
FIG. 5 is a partial cross-sectional view of a front pipe.
[Explanation of symbols]
6 Outer tube 6b Outer tube body 7 Inner tube 11 Unevenness 24 Outer tube 24b Outer tube body 25 Inner tube 28 Unevenness

Claims (1)

In a double pipe for a vehicle exhaust system in which an inner pipe is inserted into an outer pipe and a gap is formed between the outer pipe and the inner pipe,
The outer tube is formed with irregularities by repeating pyramidal convex portions continuously in the circumferential direction and the axial direction of the outer tube, and all the irregularities are not parallel to the outer peripheral surface of the inner tube. A double pipe for a vehicle exhaust system characterized by forming only a surface .

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