Title of Invention

INNER/OUTER DOUBLE PIPE TYPE EXHAUST PIPE

Abstract

An inner/outer double pipe type exhaust pipe (1) having an inner/outer double pipe structure, wherein a plurality of separate projection (15) spaced from each other at specific intervals in a circumferential direction, are provided on one of an outer pipe (10) and an inner pipe (11) in such a manner as to project therefrom to the other of said outer pipe (10) and said inner pipe (11) and come in contact therewith, whereby said inner pipe is held on an inner side of said outer pipe (10) by said separate projections (15) arranged at said specific intervals, and the other of said outer pipe (10) and said inner pipe (11), which are in contact with said separate projections (15), are slidably supported by contact portions of said separate projections (15), said exhaust pipe (1) being characterized in that a pressing member (18) for bringing said inner pipe (11) into tight-contact with said separate projections (15) is press-fitted in a gap (17) formed between said outer pipe (10) and said inner pipe (11).

Full Text

FORM 2 THE PATENTS ACT 1970 [39 OF 1970] COMPLETE SPECIFICATION [See Section 10] "INNER/OUTER DOUBLE PIPE TYPE EXHAUST PIPE" HONDA GIKEN KOGYO KABUSHIKI KAISHA, a corporation of Japan, 1-1, Minamiaoyama 2-chome, Minato-ku, Tokyo, Japan The following specification particularly describes the nature of the invention and the manner in which it is to be performed :- [Detailed Description of the Invention] [0001] [Technical Field to Which the Invention Pertains] The present invention relates to an inner/outer double pipe type exhaust pipe used for a motorcycle or the like, and particularly to an inner/outer double pipe type exhaust pipe improved to prevent occurrence of chatter even after a long-term use thereof. [0002] [Related Art] An exhaust pipe of an inner/outer double pipe structure for connecting an engine to a muffler has been known, for example, from Japanese"Patent Laid-open No. Hei 11-303632, wherein separate projections are formed ^.t a rear end portion of the exhaust pipe in such a manner as to project radially, inwardly from an outer pipe and come in contact with an inner pipe, whereby the inner pipe is held with a specific gap kept between the inner pipe and the outer pipe and also the inner pipe is slidably supported in contact so as to allow a movement 2 of the inner pipe relative to the outer pipe caused by an elongation due to thermal expansion (hereinafter, referred to as "thermal elongation"). [0003] [Problem to be Solved by the Invention] By the way, even in the above-described structure, a fine wear gap may occur between the separate projections and the inner pipe due to wear after long-term use, whereby the inner pipe may cause chatter by self-induced vibration thereof due to the wear gap. In view of the foregoing, an object of the present invention is to provide an inner/outer double pipe type exhaust pipe capable of effectively preventing occurrence of chatter even after long-term use thereof. [0004] [Means for Solving the Problem] To solve the above-described problem, according to the present invention, there is provided an inner/outer double pipe type exhaust pipe having an inner/outer double pipe structure, wherein a plurality of separate projections, spaced from each other at specific intervals in a circumferential direction, are provided on one of an outer pipe and an inner pipe in such a manner as to project therefrom to the other of the outer pipe and the inner pipe and come in contact therewith, whereby the inner pipe is held on an inner side of the outer pipe by the separate projections arranged at the specific intervals, and the other of the outer pipe and the inner pipe, which are in contact with the separate projections, are slidably supported by contact portions of the separate projections. The exhaust pipe is characterized in that a pressing member for bringing the inner pipe into tight-contact with the separate projections is press-fitted in a gap formed between the outer pipe and the inner pipe. [0005] In this exhaust pipe, the separate projections may be provided on the outer pipe in such a manner as to project therefrom to the inner pipe, and the pressing member be fixed to the outer pipe by welding. [0006] [Effect of the Invention] The pressing member press-fitted in a gap between the outer pipe and the inner pipe acts to forcibly press the inner pipe to the separate projections. After long-term use of the exhaust pipe in such a state, even if wear occurs between the separate projections and the inner pipe, then the inner pipe is kept as being in tight-contact with the separate projections by the pressing of the pressing member. With a result that it is possible to prevent occurrence of self-induced vibration of the inner pipe, and hence to prevent occurrence of chatter thereof. [0007] In the case of adopting the configuration that the pressing member is welded to the outer pipe, it is possible to certainly position the pressing member, and to simplify press-fit of the pressing member, and further since any welding trace does not remain on a sliding surface of the pressing member, it is possible to eliminate the need of any special finishing work for the sliding surface of the pressing member for ensuring a sliding motion of the inner pipe. [Brief Description of the^Drawings] [FIG. 1] FIG. 1 is a side view of a motorcycle to which an inner/outer double pipe type exhaust pipe of the present invention is applied. [FIG. 2] FIG. 2 is a side view of the inner/outer double pipe type exhaust pipe. [FIG. 3] FIG. 3 is a sectional view taken on line 3-3 of FIG. 2. [FIG. 4] FIG. 4 is a sectional view taken on line 4-4 of FIG. 3. [FIG. 5] FIG. 5 is a view showing a welded portion of a pressing member. [FIGS. 6A and 6B] FIGS. 6A and 6B are enlarged views each showing a welding structure of the pressing member. [FIG. 7] FIG. 7 is a view showing a second embodiment. [FIG. 8] FIG. 8 is a view showing a third embodiment. [FIG. 9] FIG. 9 is a view showing a fourth embodiment. Referring to FIG. 1, there is shown an exhaust pipe 1. An end portion on the upstream side in the flow direction of an exhaust gas (hereinafter, referred to as "front end") of the exhaust pipe 1 is connected to an exhaust port of an engine 2. The exhaust pipe 1 extends downwardly from the exhaust port of the engine 2 while passing a front side of the engine 2, and then extends rearwardly of a vehicular body. An end portion on the downstream side in the flow direction of an exhaust gas (hereinafter, referred to as "rear end") of the exhaust pipe 1 is connected to a muffler 3. Such an exhaust pipe 1 introduces an exhaust gas from the engine 2 to the muffler 3, and discharges the exhaust gas from the muffler 3 to a space spread on the rear side of the vehicular body. [0010] In FIG. 1, reference numeral 4 designates a head pipe, 5 is a body frame, 6 is a pivot, 7 is a rear swing arm having a front end portion swingably supported by the vehicular body via the pivot 6 and also having a rear end portion for supporting a rear wheel (not shown), and 8 is a rear cushion unit provided between the body frame 5 and the rear swing arm 7. [0011] Referring to FIG. 2, there is shown the exhaust pipe 1 having an inner/outer double pipe structure including an outer pipe 10 and an inner pipe 11. A flange 12 is provided at the front end of the exhaust pipe 1. The exhaust pipe 1 is mounted to the exhaust port of the engine 2 by means of the flange 12. The rear end of the exhaust pipe 1 is fitted to a joint pipe 13. [0012] The joint pipe 13 extends in the muffler 3 toward the downstream side in the flow direction of an exhaust gas, to introduce an exhaust gas into a main body of the muffler 3. A connecting portion between the exhaust pipe 1 and the joint pipe 13 is covered with a small-diameter portion 14 formed on a front end portion side of the muffler 3. The small-diameter portion 14 is welded to both the joint pipe 13 and an outer surface of the outer pipe 10. [0013] Referring to FIGS. 3 and 4, each of the outer pipe 10 and the inner pipe 11 is configured as a round pipe made from a suitable metal such as a steel. The inner pipe 11 is disposed in the outer pipe 10 in such a manner as to be nearly concentric therewith with a specific gap D kept therebetween. To dispose the inner pipe 11 concentrically with the outer pipe 10, separate projections 15 are formed at the rear end portion of the exhaust pipe 1 in such a manner as to project from the outer pipe 10 to the inner pipe 11. [0014] The separate projections 15 are formed by subjecting a rear end portion of the outer pipe 10 to press-working in such a manner that some portions, spaced from each other in a circumferential direction, of the rear end portion of the outer pipe 10 integrally project radially, inwardly to come in contact with an outer periphery of the inner pipe 11. According to this embodiment, four pieces of the separate projections 15, spaced from each other at equal intervals in the circumferential direction, are integrally formed on the outer pipe 10. A height of each of the separate projections 15 is set to about the gap D between the outer pipe 10 and the inner pipe 11. Contact portions of the separate projections 15 with the inner pipe 11 are slidable for allowing elongation/contraction of the inner pipe 11 due to thermal elongation. [0015] As is apparent from FIG. 4, at the rear end portion of the exhaust pipe 1, the inner pipe 11 is integrated with the outer pipe 10 by means of the separate projections 15, but at a portion, in front of the rear end portion, of the exhaust pipe 1, the inner pipe 11 is disposed in the outer pipe 10 in such a manner as to be concentric with the outer pipe 10 with the specific gap D kept therebetween. [0016] As is apparent from FIG. 3, a portion between the adjacent separate projections 15 is taken as an outward projection 16 which projects radially, outwardly from the inner pipe 11 side, and a gap 17 is formed inside each outward projection 16. It is to be noted that when the outer pipe 10 is viewed from the inner pipe 11 side, the outward projections 16 are formed in such a manner as to project outwardly from the inner pipe 11; however, the outward projections 16 are portions remaining as non-pressed portions when the separate projections 15 are formed at the rear end portion of the outer pipe 10 by press-working. Accordingly, an outer peripheral portion of each of the outward projections 16 is identical to an outer peripheral portion of the outer pipe 10, and therefore, a distance of the gap 17 in the radial direction becomes the specific gap D. [0017] A pressing member 18 is press-fitted in one of the gaps 17 and is plug-welded to the corresponding outward projection 16 via a plug 19. The pressing member 18 is made from a suitable metal material such as a steel. A wall thickness T of the pressing member 18 is set to a value slightly larger than the distance of the gap 17 in the radial direction, that is, the specific gap D between the outer pipe 10 and the inner pipe 11. Accordingly, the pressing member 18 can be press-fitted in the gap 17 by a relatively light force, for example, given by hammering. [0018] As is apparent from FIGS. 4 and 6, a leading end of the pressing member 18 to be press-fitted is rounded or tapered, or thinned for easy press-fit thereof. Also, as shown in FIG. 5, a length of the pressing member 18 is set to be slightly shorter than a length of the separate projection 15, and further, as shown in FIG. 3, the pressing member 18 is curved in a circular-arc shape so as to be in slide-contact with the outer periphery of the inner pipe 11. [0019] FIG. 5 is a view showing the separate projections 15 provided on the outer pipe 10 and the pressing member 18, as seen in the direction shown by an arrow Y of FIG. 4. The pressing member 18 is plug-welded to the outer pipe 10 via the plug 19 inserted in a through-hole 20 formed in the outward projection 16 provided at the rear end portion of the outer pipe 10. FIG. 6A is a sectional view taken on line 6-6 of FIG. 5, schematically showing the welding structure. [0020] It is to be noted that the fixture of the pressing member 18 is not limited to plug welding but may be any other welding manner. For example, as shown in FIG. 6B, ends portions of the pressing member 18 and the outer pipe 10 are subjected to fillet welding. Such fillet welding can fix the pressing member 18 to the outer pipe 10 in a state that the inner pipe 11 is slidable on the pressing member 18 without occurrence of no problem insofar as a welding bead does not reach the inner pipe 11. [0021] A function of the embodiment will be described below. As shown in FIG. 3, since the pressing member 18 is inserted in one of the gaps 17, the inner pipe 11 is pressed to the separate projection 15 located opposite to the pressing member 18 while being slightly, elastically deformed. When the inner pipe 11 is elongated relative to the outer pipe 10 by thermal elongation in such a state, the inner pipe 11 is slid on the separate projections 15 and the pressing member 18. Meanwhile, when the inner pipe 11 is cooled and thereby contracted relative to the outer pipe 10 in such a state, the inner pipe 11 is also slid on the separate projections 15 and the pressing member 18. [0022] Accordingly, even if the contact portions of the inner pipe 11 with the separate projections 15 and the pressing member 18 are worn after long-term use of the exhaust pipe 1, the inner pipe 11 is left as pressed to the separate projections 15, that is, kept as being in contact therewith by the pressing member 18 which is previously press-fitted in the gap 17 and presses the inner pipe 11. As a result, it is possible to prevent occurrence of a wear gap between the inner pipe 11 and . the separate projections 15, that is, to prevent occurrence of self-induced vibration of the inner pipe 11, and hence to prevent occurrence of chatter which has been conventionally caused after long-term use of the exhaust pipe 1. [0023] Another advantage of this embodiment is to simply form the separate projections 15 by forming the separate projections 15 integrally with the outer pipe 10, and to prevent occurrence of chatter with a simple structure that one pressing member 18 is press-fitted in one of the gaps 17 formed by formation of the separate projections 15. [0024] A further advantage of this embodiment is as follows: namely, since the pressing member 18 is fixed to the outer pipe 10 by plug-welding, it is sufficient for the pressing member 18 to be lightly press-fitted in the gap 17, to facilitate assembling works; and further, since the pressing member 18 is plug-welded to the outer pipe 10 side, the pressing member 18 can be certainly positioned, and the outer pipe 10 can be fitted in the joint pipe 13 without any special post-work, and since any welding trace does not remain on the sliding surface of the pressing member 18 on which the inner pipe 11 is to be slid, it is possible to eliminate the need of any-special finish work for the sliding surface of the pressing member 18 for ensuring a sliding motion of the inner pipe 11 thereon. [0025] FIG. 7 is a view, similar to FIG. 3, showing a second embodiment. In this embodiment, three separate projections 15 are disposed in such a manner as to be spaced from each other at equal intervals in a circumferential direction. Like the previous embodiment, a pressing member 18 is press-fitted in one of three gaps 17. A structure of the pressing member 18 and a fixing configuration thereof are the same as those described in the previous embodiment (the welded portion is not shown in FIG. 7). It is to be noted that in the second and later embodiments, parts corresponding to those described in the previous embodiment are designated by the same reference numerals. [0026] FIG. 8 is a view showing a third embodiment. This embodiment has the same configuration of an outer pipe 10 and an inner pipe 11 as that described in the first embodiment shown in FIG. 3, except that two pressing members 18 are press-fitted in adjacent two gaps 17 in this embodiment. This embodiment is advantageous in that the inner pipe 11 can be more forcibly pressed to two separate projections 15 which are disposed opposite to the pressing members 18 with a center of the inner pipe 11 put therebetween. [0027] FIG. 9 is a view showing a fourth embodiment, in which two separate projections 15 are formed at positions spaced at intervals of 180 and opposed to each other with a center of an outer pipe 10 put therebetween. The separate projection 15 is curved in such a manner as to project radially, inwardly from an inner radius Rll of an inner pipe 11 and the corresponding portion (curved portion) 21 of the inner pipe 11 is similarly curved in such a manner as to project radially, inwardly from the inner radius Rll, and the separate projection 15 is in tight-contact with the curved portion 21. [0028] A pair of outward projections 16 and a pair of gaps 17 are disposed at positions which are offset from the separate projections 15 by 90° and which are spaced from each other at intervals of 180° . Two pressing members 18 are press-fitted in the gaps 17. In the figure, character R10 designates an outer radius of the outer pipe 10. Like the previous embodiments, at a portion, in front of the rear end portion at which the separate projections 15 are formed, of the exhaust pipe 1, the inner pipe 11 is disposed in the outer pipe 10 in such a manner as to be concentric therewith with a specific gap put therebetween. [0029] With this configuration, the contact between the outer pipe 10 and the inner pipe 11 can be tightened by the contact of the separate projections 15 with the curved portions 21, and further, even after long-term use, the tight-contact between the separate projections 15 and the curved portions 21 disposed opposite to each other can be kept by the pressing members 18 disposed opposite to each other, with a result that it is possible to prevent occurrence of chatter, like the previous embodiment. [0030] The present invention is not limited to the above-described embodiments but may be variously changed and applied without departing from the scope of the present invention. For example, the present invention is applicable not only to the exhaust pipe for an engine of a motorcycle but also to an exhaust pipe for an engine of an automobile or the like. With respect to the pressing members 18, one or more pressing members 18 may be provided. As described in the embodiments, the pressing members 18 can be press - fitted in all or part of the gaps 17. The material of the pressing member 18 is not limited to a metal but may fce a material having relatively high hardness, durability and heat-resistance. The degree of press-fit of the pressing member 18 includes a low degree of press-fit by a hand, a medium degree of press-fit by a manual tool such as a hammer, and a large degree of press-fit by a power apparatus. The pressing member 18 may be fixed to the inner pipe 11, and the fixture of the pressing member 18 is not limited to welding. [0031] The separate projections 15 are not necessarily formed on the outer pipe 10 side but may be formed on the inner pipe 11 side. The separate projections 15 may be formed separately from the outer pipe 10 and the inner pipe 11. In this case, the separate projections 15 are preferably fixed to either the outer pipe 10 side or the inner pipe 11 side. [Explanation of Reference Numerals] 1: exhaust pipe, 2: engine, 3: muffler, 10: outer pipe, 11: inner pipe, 15: separate projection, 16: outward projection, 17: gap, 18: pressing" member WE CLAIM: 1. An inner/outer double pipe type exhaust pipe (1) having an inner/outer double pipe structure, wherein a plurality of separate projection (15) spaced from each other at specific intervals in a circumferential direction, are provided on one of an outer pipe (10) and an inner pipe (11) in such a manner as to project therefrom to the other of said outer pipe (10) and said inner pipe (11) and come in contact therewith, whereby said inner pipe is held on an inner side of said outer pipe (10) by said separate projections (15) arranged at said specific intervals, and the other of said outer pipe (10) and said inner pipe (11), which are in contact with said separate projections (15), are slidably supported by contact portions of said separate projections (15), said exhaust pipe (1) being characterized in that a pressing member (18) for bringing said inner pipe (11) into tight-contact with said separate projections (15) is press-fitted in a gap (17) formed between said outer pipe (10) and said inner pipe (11). 2. An inner/outer double pipe type exhaust pipe (1) as claimed in claim 1, wherein said separate projections are provided on said outer pipe (10) in such a manner as to project therefrom to said inner pipe (11), and said pressing member (15) is fixed to said outer pipe (10) by welding. 3. An inner/outer double pipe type exhaust pipe (1) substantially as hereinbefore described with reference to the accompanying drawings. Dated this 18th day of March, 2002

Documents:

261-mum-2002-abstract(1-8-2007).doc

261-mum-2002-abstract(1-8-2007).pdf

261-mum-2002-cancelled pages(1-8-2007).pdf

261-mum-2002-claims(granted)-(1-8-2007).doc

261-mum-2002-claims(granted)-(1-8-2007).pdf

261-mum-2002-correspondence(01-08-2007).pdf

261-mum-2002-correspondence(ipo)-(20-07-2007).pdf

261-mum-2002-drawing(20-4-2007).pdf

261-mum-2002-form 1(1-8-2007).pdf

261-mum-2002-form 13(6-8-2007).pdf

261-mum-2002-form 18(10-2-2006).pdf

261-mum-2002-form 2(granted)-(1-8-2007).doc

261-mum-2002-form 2(granted)-(1-8-2007).pdf

261-mum-2002-form 3(18-3-2002).pdf

261-mum-2002-form 3(2-4-2004).pdf

261-mum-2002-form 3(20-4-2007).pdf

261-mum-2002-form 5(18-3-2002).pdf

261-mum-2002-petition under rule 138(20-4-2007).pdf

261-mum-2002-power of authority-(11-4-2004).pdf

261-mum-2002-power of authority-(20-4-2007).pdf

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