JP2002129954A - Exhaust tube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an exhaust tube capable of reducing an emission noise level without increasing its thickness. SOLUTION: A lot of protrusions 4 are formed in the inner wall 2 of the exhaust tube 1 introducing exhaust gas discharged from an engine to a muffler. Hemispherical protrusions 4 which are arranged in the inner wall 2 at a predetermined pitch, cause the exhaust gas flowing along the inner wall 2 to flow in the center. Thus, most of the exhaust gas flow is made to move away from the inner wall to flow in the center of the tube so that pulsating exhaust gas is prevented from directly hitting the inner wall to cause the exhaust tube to vibrate then to produce emission noise.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust pipe for guiding exhaust gas discharged from an engine of an automobile or the like to a muffler.

[0002]

2. Description of the Related Art Conventionally, an exhaust pipe has been manufactured using a pipe as a material. From the perspective of car weight reduction,
It is preferable that the thickness of the pipe used as the material is thin, but if the thickness is small, noise of exhaust gas passing through the exhaust pipe is easily radiated to the outside of the exhaust pipe. Therefore, the thickness of the pipe used as the material of the exhaust pipe has been determined from the viewpoint of weight reduction and noise reduction.

[0003]

However, in such a conventional device, in order to reduce the sound radiated from the exhaust pipe, the thickness of the pipe used as the material of the exhaust pipe must be increased, and the weight is reduced. There is a problem that the cost increases as the number increases.

An object of the present invention is to provide an exhaust pipe capable of reducing radiated sound without increasing the thickness.

[0005]

In order to achieve the above object, the present invention takes the following means to solve the problem. That is, in an exhaust pipe for guiding exhaust gas discharged from an engine to a muffler, the exhaust pipe is characterized in that a number of projections are formed on an inner wall.

[0006] It is preferable that the projection is a projection that causes a flow of the exhaust gas along the inner wall toward the center. Further, the protrusion may be hemispherical, or the protrusion may be wedge-shaped. The protrusion may be shaped to reduce radiated sound.

[0007]

Embodiments of the present invention will be described below in detail with reference to the drawings. As shown in FIG. 1, reference numeral 1 denotes an exhaust pipe. The upstream side of the exhaust pipe 1 communicates with an exhaust port of an engine (not shown), and the downstream side communicates with a muffler (not shown). In the present embodiment, a pipe is used as a material of the exhaust pipe 1, and a large number of protrusions 4 are formed on the inner wall 2 of the exhaust pipe 1.
Are formed.

In the present embodiment, the projection 4 is formed in a hemispherical shape, and when the flow of the exhaust gas along the inner wall 2 hits the projection 4, a flow toward the center is generated.
The height of the projection 4 is determined so that the exhaust gas can be prevented from directly hitting the inner wall 4.

[0009] The height of the projections 4 is sufficient if an exhaust gas flow toward the center is generated, and need not be large enough to restrict the exhaust gas flow. The height of the projection 4 may be determined by experiments or the like. Since the effective cross-sectional area of the exhaust pipe 1 with respect to the exhaust gas flow is reduced by the height of the projection 4, the diameter of the exhaust pipe 1 may be increased.

In this embodiment, a large number of projections 4 are provided.
Exhaust gas collides with each projection 4, and the exhaust gas flows toward the center at each projection 4. By arranging a large number of projections 4, the exhaust gas is prevented from directly hitting the inner wall 4. It is arranged at a pitch that can be used. The arrangement pitch may be determined by experiments or the like.

Next, the operation of the exhaust pipe of the above-described embodiment will be described. First, exhaust gas flows in the exhaust pipe 1 from the upstream side on the engine side to the downstream side on the muffler side. Further, the exhaust gas discharged from the engine is pulsating.
When the exhaust gas flowing along the inner wall 2 of the exhaust pipe 1 collides with the projection 4, a flow is generated toward the center of the exhaust pipe 1.

Since a large number of projections 4 are provided, a flow of exhaust gas toward the center side occurs at each projection 4. Most of the flow of the exhaust gas is separated from the inner wall 2 of the exhaust pipe 1 by the flow toward the center of each projection 4. This allows
Most of the exhaust gas flows away from the inner wall 2 and flows on the center side of the exhaust pipe 1. Therefore, it is possible to prevent the pulsating exhaust gas from directly hitting the inner wall 2 and vibrating the exhaust pipe 1 to generate radiated sound. In addition, the provision of the projections 4 improves the rigidity of the exhaust pipe 1 itself. Thereby, the vibration can be suppressed, and the radiated sound can be reduced.

Next, an exhaust pipe according to a second embodiment different from the above-described embodiment will be described with reference to FIG. In this exhaust pipe 11, the shape of the projection 14 formed on the inner wall 12 is different from that of the above-described embodiment. The protrusion 14 is formed in a wedge shape, and is formed to be inclined so as to protrude from the inner wall 2 side toward the center side from the upstream side to the downstream side. The height and pitch of the projections 14 may be determined in the same manner as described above, and may be determined by experiments or the like.

Similarly, when the exhaust gas strikes the projection 14, a flow toward the center of the exhaust pipe 11 occurs. Due to the flow toward the center at each of the large number of projections 14, most of the flow of the exhaust gas is changed to the inner wall 12 of the exhaust pipe 11.
Separated from As a result, most of the exhaust gas flows away from the inner wall 12 and flows on the center side of the exhaust pipe 11. Therefore, it is possible to prevent the pulsating exhaust gas from directly hitting the inner wall 12 and vibrating the exhaust pipe 1 to generate radiated sound. By forming the projections 14, the surface rigidity of the exhaust pipe 11 is improved, and radiation noise can be reduced.

As described above, the present invention is not limited to such an embodiment at all, and can be implemented in various modes without departing from the gist of the present invention.

[0016]

As described in detail above, the exhaust pipe of the present invention
When the exhaust gas hits the projection, a flow toward the center of the exhaust pipe occurs, the flow of the exhaust gas is separated from the inner wall, and most of the flow of the exhaust gas is separated from the inner wall and flows on the center side of the exhaust pipe. Therefore, it is possible to prevent the pulsating exhaust gas from directly hitting the inner wall, causing the exhaust pipe to vibrate and generating radiated sound. Further, by forming the projection, the surface rigidity of the exhaust pipe is improved. Therefore, there is an effect that the radiation sound level can be reduced without increasing the thickness of the exhaust pipe.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of an exhaust pipe as one embodiment of the present invention.

FIG. 2 is a cross-sectional view of an exhaust pipe according to a second embodiment.

[Explanation of symbols]

 1,11 ... exhaust pipe 2,12 ... inner wall 4,14 ... projection

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Mitsuo Suzuki 1 Ochaya, Hashime-cho, Okazaki City, Aichi Prefecture Inside Futaba Sangyo Co., Ltd. (72) Inventor Koji Toshima 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Motor Stock In-company (72) Inventor Jun Kobayashi F-term (reference) 3G004 BA02 DA01 3H025 CA01 CB11 1 Toyota Town, Toyota City, Aichi Prefecture

Claims (5)

[Claims] 1. An exhaust pipe for guiding exhaust gas discharged from an engine to a muffler, wherein a number of projections are formed on an inner wall of the exhaust pipe. 2. The exhaust pipe according to claim 1, wherein the projection is a projection that generates a flow of the exhaust gas along the inner wall toward a center side. 3. The exhaust pipe according to claim 1, wherein the projection has a hemispherical shape. 4. The exhaust pipe according to claim 1, wherein the projection has a wedge shape. 5. The exhaust pipe according to claim 1, wherein the projection is shaped to reduce radiated sound.