JP3502806B2 - Exhaust pipe manufacturing method for motorcycles - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing an exhaust pipe of a motorcycle, and more particularly to a method of manufacturing an exhaust pipe bent into a three-dimensional curve. FIG. 5 shows an exhaust system of a four-cylinder engine for a motorcycle. Four exhaust branch pipes 2 connected to respective exhaust ports of an engine 1 are connected via a collecting pipe 3. Collective exhaust pipe 3
0, and the exhaust muffler 6 is connected to the rear end of the collective exhaust pipe 30. The shape of the collective exhaust pipe 30 is curved as viewed from the side as shown in FIG. 5 and also curved as viewed from above as shown in FIG. 6, and is generally curved three-dimensionally. Formed in a tube. In such a collective exhaust pipe 30, in order to reduce transmitted sound and improve exhaust sound quality, a double wall structure is adopted, and a cushioning material such as SUS wool is inserted between the double walls. It is effective to do. Conventionally, a double wall structure as described above has been adopted,
In addition, when a cushioning material such as SUS (stainless steel wool) is mounted inside, a so-called “Monaka structure” shown in FIG. 7 is employed. That is, in FIG. 7, a pair of half-cylindrical inner plates 31a and 31b integrally having lugs 36 at both ends in the radial direction, and a pair of half-cylindrical cylinders integrally having lugs 35 at both radial ends. The outer plates 32a and 32b form a double wall structure, and a buffer material 40a such as SUS wool is inserted into a half-shaped chamber Sa between one inner plate 31a and the outer plate 32a, and the other inner plate 31b A buffer material 40b such as SUS wool is also inserted into the half-shaped chamber Sb between the outer plate 32b and the outer plate 32b, the lugs 35 and 36 overlap each other, and are joined by welding W from the outside. As a prior art document, there is JP-A-10-159549. [0006] In the case of manufacturing an exhaust pipe with a double-walled "monaka structure" as shown in FIG. 7, the number of parts increases and the cost of press molding increases. (It becomes large), the number of processing steps such as welding increases, and the cost also increases.
Further, since the ear portions 35 and 36 and the welding beat W are visible from the outside, the appearance is not good. Further, when the exhaust pipe itself is three-dimensionally curved as described above, the ears 35,
It is difficult to arrange the 36 and the welding beat W into a beautiful line as seen from the outside as shown in FIG. Further, each of the pipes 31a, 31b, 32a,
When titanium or a titanium alloy is used as 32b, oxidation of the beat portion must be prevented by employing a welding method of shielding with an inert gas, for example, inert gas arc welding or TIG welding, as shown in FIG. In order to weld a long distance along the line by the inert gas arc welding or the like, the welding operation is troublesome. Further, the back shield gas may need to be gas-shielded on the back side. SUMMARY OF THE INVENTION An object of the present invention is to provide a method for manufacturing an exhaust pipe of a motorcycle which has a low mold cost, reduces the number of processing steps, and has a good external appearance. [0009] In order to achieve the above object, the present invention provides a straight pipe inner pipe made of titanium or a titanium alloy and having no seams in the circumferential direction.
At the same time as being inserted into a cylindrical outer pipe made of titanium or a titanium alloy and having no seams in the circumferential direction, an annular chamber formed between the two pipes is filled with a water-resistant cushioning material. One end portion in the length direction of the cylinder, which is formed by forming a constricted portion on the outer pipe or an enlarged portion on the inner pipe, is connected by gas shield welding using inert gas, and then water is introduced into the inner pipe and the annular chamber. Into the shape of a three-dimensionally bent by bending, then the other end of the two pipes in the length direction of the cylinder, formed a constricted portion on the outer pipe or an enlarged diameter portion on the inner pipe A method of manufacturing an exhaust pipe for a motorcycle, comprising joining parts by gas shield welding using inert gas. As a result, the number of parts is reduced, the mold cost is reduced, and the length of the pipe is reduced in comparison with the case of manufacturing an exhaust pipe having a “monaka structure” using a half-cylindrical member as shown in FIG. By eliminating the need for welding along the line, the number of processing steps is reduced and the appearance is improved. Further, by filling the cushioning material between the two pipes, the transmitted sound can be reduced and the exhaust sound quality can be improved. Further, since the inner pipe and the outer pipe are made of titanium or a titanium alloy, and the pipes are connected by gas shield welding, not only can light weight be achieved, but also labor-intensive welding is almost unnecessary. Thereby, processing efficiency is improved. FIG. 1 shows an exhaust system of a four-cylinder engine for a motorcycle to which the present invention is applied. As shown in FIG. Exhaust branch pipes 2 connected to each other, and a collecting pipe 3 for gathering these four exhaust branch pipes 2
A collecting exhaust pipe 5 connected to a rear end of the collecting pipe 3;
It comprises an exhaust muffler 6 and the like connected to the rear end of the collective exhaust pipe 5. The collective exhaust pipe 5 is curved midway and extends rearward and upward as viewed from the side as shown in FIG.
As shown in FIG. 2 which is a plan view of FIG. 2, it is curved at two places even when viewed from above, and is a three-dimensionally curved pipe as a whole. FIG. 3 is an enlarged longitudinal sectional view (III-III sectional enlarged view of FIG. 2) of the collective exhaust pipe 5 of FIG.
Has a double-walled structure composed of an inner pipe 11 and an outer pipe 12. An annular chamber S is formed between the two pipes 11 and 12 so as to extend over substantially the entire length of the collective exhaust pipe 5. A buffer material 13 such as SUS wool or water-resistant glass wool is packed therein. The enlarged diameter portions 11 a and 11 b are integrally formed at both ends in the length direction of the inner pipe 11, and the enlarged diameter portions 11 a and 11 b abut on the inner surface of the outer pipe 12.
It is fixed by welding. The inner pipe 11
It is also possible to press the outer pipe 12 so as to reduce the diameter after packing the SUS wool or the like with the same diameter. FIG. 4 is an enlarged cross-sectional view taken along the line IV-IV of FIG. 1, wherein the inner pipe 11 is formed of a metal pipe member having no seam in the circumferential direction, and the outer pipe 12 is also made of metal having no seam in the circumferential direction. The pipes 11 and 12 are formed of a pipe member, and titanium or a titanium alloy is used as a material of the pipes 11 and 12. (1) In FIG. 4, first, a straight cylindrical inner pipe 11 before bending and a straight cylindrical outer pipe 12 before bending are prepared, and the inner pipe 11 is placed in the outer pipe 12. At the same time, a buffer material 13 such as SUS wool (or water-resistant glass wool) is packed in the annular chamber S between the pipes 11 and 12, and the front end enlarged diameter portion 11 a of the inner pipe 11 of FIG. It is connected to the inner peripheral surface of the front end by welding. When the pipes 11 and 12 are made of titanium or a titanium alloy, the welding is performed by a welding method of shielding with inert gas, for example, gas shield arc welding or TIG welding. (2) One end A side of FIG. 3 where the above welding is performed is closed with a cap, water is filled in the inner pipe 11 and the SUS wool 13 (the annular chamber S), and the other end B side is also capped. Close with Then, by freezing the water inside, the entire exhaust pipe is brought into a linear solid pillar state. (3) The entire exhaust pipe 5 in the form of a solid column, which is formed in a straight line, is formed into a three-dimensionally bent shape as shown in FIGS. 1 and 2 by bending. (4) After bending, both caps are removed, and the ice inside is melted and discharged. Then, the rear end enlarged portion 11b of the inner pipe 11 of FIG.
Bonding is performed by welding in the same manner as 1a. Alternatively, the outer pipe 12 is welded with a reduced diameter. Other Embodiments (1) The present invention can be applied to the exhaust branch pipe 2 shown in FIG. (2) As the inner pipe 11, a pipe having a punched hole can be used. As described above, according to the present invention, (1) a straight cylindrical inner pipe made of titanium or a titanium alloy and having no joint in the circumferential direction is manufactured of titanium or a titanium alloy. At the same time, it is inserted into a cylindrical outer pipe with no seams in the circumferential direction, and at the same time, an annular chamber formed between the two pipes is filled with a water-resistant cushioning material. Then, the portion of the outer pipe where the constricted portion or the enlarged diameter portion is formed on the inner pipe is joined by gas shield welding with inert gas, then water is poured into the inner pipe and the annular chamber to freeze and bend. The three pipes have a three-dimensionally bent shape. The two parts are joined together by gas shield welding using inert gas, so that the two-part cylindrical members shown in FIG. Compared with the method of manufacturing the wall exhaust pipe, the number of parts can be reduced and the cost of the mold can be reduced. (2) Long ears along the length of the exhaust pipe become unnecessary and welding is no longer necessary.
The appearance can be kept clean, and the occurrence of distortion such as welding distortion can be eliminated. Also, since there are no protrusions such as ears on the surface of the exhaust pipe, buffing work becomes easy. (3) Since it is not necessary to perform long welding along the length of the exhaust pipe, the number of welding steps is reduced, and the efficiency of manufacturing operation is improved. (4) By packing the cushioning material 13 in the annular chamber S between the inner pipe 11 and the outer pipe 12, it is possible to reduce the amount of transmission of exhaust sound and improve the quality of exhaust sound. Further, at the time of bending, the cushioning material 13 acts as a practical material in the annular chamber S. Therefore, even if the annular chamber S is not filled with water (ice) at the time of bending, the inner pipe 11 and the outer pipe are not required. 12 can be maintained. (5) When the inner pipe 11 and the outer pipe 12 are made of titanium or a titanium alloy, not only can the weight be reduced, but also the welding process by the gas shield can be reduced, thereby reducing work efficiency. The effect becomes remarkable.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side view of an exhaust device of a four-cylinder engine for a motorcycle having an exhaust pipe manufactured according to the present invention. FIG. 2 is a plan view of FIG. FIG. 3 is a vertical cross-sectional view (an enlarged cross-sectional view taken along the line III-III in FIG. 2) of the collective exhaust pipe. FIG. 4 is an enlarged cross-sectional view taken along the line IV-IV in FIG. 3; FIG. 5 is a side view of a conventional example. FIG. 6 is an enlarged cross-sectional view taken along line VI-VI of FIG. 5; FIG. 7 is an enlarged cross-sectional view taken along the line VII-VII of FIG. 5; [Description of Signs] 2 Exhaust branch pipe 3 Collecting pipe 5 Collecting exhaust pipe 6 Exhaust muffler 13 Buffer material S Annular chamber

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Takao Kusuura 1-1, Kawasaki-cho, Akashi-shi, Hyogo Kawasaki Heavy Industries, Ltd. Inside the Akashi Factory (56) References JP-A-60-11795 (JP, A) -13058 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) F01N 7/08

Claims (1)

(57) [Claims] [Claim 1] When made of titanium or titanium alloy,
In the circumferential seamless in the direction straight cylindrical inner pipe, Ji
At the same time as being inserted in the outer pipe of a straight cylindrical shape made of tongue or titanium alloy and having no seams in the circumferential direction ,
Packed cushioning material having water resistance to the annular chamber formed between the two pipes, there then a cylindrical longitudinal end portion comrades the pipes, the outer
-Form a constricted part on the pipe or an enlarged part on the inner pipe
Parts joined by gas shield welding with inert gas
And then the allowed to freezing Pour water in the inner pipe and the annular chamber, bent by the curved shape three-dimensionally, there then a tube length direction end portion comrades the pipes, the outer
-Form a constricted part on the pipe or an enlarged part on the inner pipe
Parts joined by gas shield welding with inert gas
A method for manufacturing an exhaust pipe of a motorcycle.