Exhaust silencer

Abstract: The invention provides an exhaust silencer in which relative elongation of an inner cylinder to an outer cylinder is permitted, and assembling workability is enhanced. An exhaust silencer (30) has a structure in which relative elongation of an inner cylinder (31) to an outer cylinder (41) is permitted by blocking a rear end portion (43) of the outer cylinder (41) with a stepped disc (50), by slidably mounting a rear end portion (33) of the inner cylinder (31) on a step portion (51) of the stepped disc (50). A fuse portion (70) is provided at the rear end portion (43) of the inner cylinder (31), and is welded to the step portion (51) of the stepped disc(50) to track temporarily the stepped disc (50)to the inner cylinder (31) at a temporary assembly stage. The fuse portion (70) is constituted to be fractured by thermal expansion of the inner cylinder when exhaust gas flows.

Description: The present invention relates to an exhaust silencer constituted to permit relative elongation of an inner cylinder to an outer cylinder. For example, in an exhaust silencer disclosed in JP-A No. H7-77041 "muffler for motorcycle", respective front end portions of an outer cylinder and an inner cylinder are integrated with each other, and respective rear end portions of them are constituted to be blocked by a tail plate (hereinafter, referred to as "stepped disc"). The stepped disc is provided with a small diameter portion (hereinafter, referred to as "step portion") loosely fitted in the rear end portion of the inner cylinder, and a large diameter portion (hereinafter, referred to as "enlarged diameter portion") tightly fitted in the rear end portion of the outer cylinder. The rear end portions of the outer cylinder and the inner cylinder can be blocked by the stepped disc, by loosely fitting the small diameter portion in the rear end portion of the inner cylinder and also tightly fitting the large diameter portion in the rear end portion of the outer cylinder. Additionally, when the inner cylinder is thermally expanded by heat of exhaust gas, the rear end portion of the inner cylinder can be slid relative to the step portion, since the step portion in the rear end portion of the inner cylinder is loosely fitted. Thus, the relative elongation of the inner cylinder to the outer cylinder is permitted. Meanwhile, when the stepped disc is assembled to the inner cylinder and the outer cylinder, firstly the step portion of the stepped disc is loosely fitted in the rear end portion of the inner cylinder, and next, the rear end portion of the outer cylinder is tightly fitted on the enlarged diameter portion of the stepped disc. Thus, when the rear end portion of the outer cylinder is fitted on the enlarged diameter portion of the stepped disc, the stepped disc is liable to be deviate from a regular location. When the stepped disc is deviated from the regular location, the assembly work to fit the enlarged diameter portion in an opening of the rear end portion of the outer cylinder is difficult, and workability cannot be enhanced. In order to eliminate the deviation of the stepped disc from the regular location, the stepped disc may be fixed by a fixing jig. However, for utilizing the fixing jig, it takes a lot of time to mount or demount the fixing jig on or from the stepped disc. The workability cannot be enhanced. Thus, an object of the present invention is to provide an exhaust silencer permitting a relative elongation of an inner cylinder to an outer cylinder, and enhancing assembling workability. To achieve the above object, in an exhaust silencer according to claim 1, one end portion of an outer cylinder sandwiching glass wool between the outer cylinder and an inner cylinder, is coupled to one end portion of the inner cylinder having a plurality of expansion chambers inside thereof. The relative elongation of the inner cylinder to the outer cylinder is permitted by blocking the other end portion of the outer cylinder with a stepped disc, and by slidably mounting the other end portion of the inner cylinder on a step portion of the stepped disc. The structure for exhaust silencer is characterized in that a fuse portion which is fractured when prescribed force is operated, is provided at the other end portion of the inner cylinder. The structure for exhaust silencer is further characterized in that the fuse portion is welded to the step portion of the stepped disc or to a wall surface constituting the step portion to tack temporarily the stepped disc to the inner cylinder at a temporary assembly stage, and the inner cylinder is separated from the stepped disc by the fracture of the fuse portion caused by thermal expansion of the inner cylinder when exhaust gas flows. The fuse portion has a constitution capable of tacking temporarily the stepped disc to the inner cylinder by welding the fuse portion to the step portion of the stepped disc or to the wall surface constituting the step portion. Therefore, when performing assembly work of following processes such as welding of the rear end portion of the outer cylinder to the stepped disc, the deviation of the stepped disc from a regular location is prevented. Further, the fuse portion is fractured to separate the inner cylinder from the stepped disc, when thermal expansion of the inner cylinder is occurred. Thus, the rear end portion of the inner cylinder is slid relative to the step portion of the stepped disc and the relative elongation of the inner cylinder to the outer cylinder is permitted. An embodiment of the present invention will be described with reference to the attached drawings. Fig. 1 shows a side elevational view illustrating a motorcycle provided with an exhaust silencer according to the present invention, Fig. 2 shows a sectional view illustrating an exhaust silencer according to the present invention, Fig. 3 shows an exploded perspective view illustrating an essential portion of an exhaust silencer according to the present invention, Fig. 4 shows a plan view illustrating an essential portion of an exhaust silencer according to the present invention, Fig. 5 shows a first explanatory view illustrating an assembly procedure of an exhaust silencer according to the present invention, Fig. 6 shows a second explanatory view illustrating an assembly procedure of an exhaust silencer according to the present invention, Fig. 7 shows an explanatory view illustrating an operation of an exhaust silencer according to the present invention, Fig. 8 shows a first explanatory view illustrating the other assembly procedure of an exhaust silencer according to the present invention, and Fig. 9 shows a second explanatory view illustrating the other assembly procedure of an exhaust silencer according to the present invention. Here, "front", or, "rear" is a direction viewed from a driver. Meanwhile, drawings are seen in directions of numerals. Fig. 1 shows a side elevational view illustrating a motorcycle provided with an exhaust silencer according to the present invention. A motorcycle 10 is a scooter type motorcycle constituted of a body frame 11, a front fork 13 mounted on a head pipe 12 of the body frame 11, a front wheel 14 mounted on the front fork 13, a handlebar 15 connected to the front fork 13, an engine 16 mounted on a rear portion of the body frame 11, a power transmission mechanism 17 vertically swingably mounted on the engine 16, a rear wheel 18 mounted on the power transmission mechanism 17, a rear cushion 19 suspended with the rear end portion of the power transmission mechanism 17 from the body frame 11, a storage box 21 mounted on a rear upside of the body frame 11, a seat 22 arranged above the storage box 21 and openably /closably mounted thereon, an exhaust pipe 29 extended to a rearward from the engine 16, and an exhaust silencer 30 mounted on the rear portion of the exhaust pipe 29. Numeral 23 denotes a floor step, numeral 24 denotes a fuel tank, and numeral 25 denotes an air cleaner. Fig. 2 shows a sectional view illustrating an exhaust silencer according to the present invention. The exhaust silencer 30 is provided with a first, a second, and a third expansion chambers 37, 38, and 39 in order from a rear end side disposed inside an inner cylinder 31. One end portion (front end portion) 32 of the inner cylinder 31 is welded and coupled to a front lid 35, one end portion (front end portion) 42 of an outer cylinder 41 is welded and coupled to the front lid 35, and glass wool 45 is sandwiched between the outer cylinder 41 and the inner cylinder 31. The other end portion (rear end portion) 43 of the outer cylinder 41 is blocked with a stepped disc 50 and the other end portion (rear end portion) 33 of the inner cylinder 31 is slidably fitted on a step portion 51 of this stepped disc 50. The outer cylinder 41 is a cylindrical body formed in an elliptic shape. The inner cylinder 31 is formed in the elliptic shape to have a constant clearance between the inner cylinder 31 and the outer cylinder 41, and is a cylindrical body formed with recesses 34 ···(··· indicates plural number) for reinforcement at prescribed intervals. The stepped disc 50 is constituted of an enlarged diameter portion 54 of the elliptic shape fittably formed in the rear end portion 43 of the outer cylinder 41, the step portion 51 of the elliptic shape slidably and fittably formed in the rear end portion 33 of the inner cylinder 31, and glass wool 46 stored in a portion 52 inside the step portion 51. As mentioned above, since the stepped disc 50 is divided into the step portion 51 and the enlarged diameter portion 54, the glass wool 46 can be stored in the stepped disc 50. Accordingly, a noise damping effect of the exhaust silencer 30 is improved. Numeral 60 denotes a first bulkhead, and numeral 61 denotes a second bulkhead. In this exhaust silencer 30, the exhaust gas from the engine 16 (illustrated in Fig. 1) is introduced from an exhaust pipe 29 into an inlet pipe 62, as shown by an arrow mark 1 ○. Exhaust gas flowing into the inlet pipe 62 is introduced into the first expansion chamber 37 through catalysts 63a and 63b as shown by an arrow mark 2 ○, and the exhaust gas is introduced into the second expansion chamber 38 through a first communicating tube 64 as shown by an arrow mark 3 ○. The exhaust gas flowing into the second expansion chamber 38 is introduced into the third expansion chamber 39 through a second communicating tube 65 as shown by an arrow mark 4 ○, and the exhaust gas of the third expansion chamber 39 is discharged to the outside of the exhaust silencer 30 through tail pipes 66 and 67 as shown by an arrow mark 5 ○. Fig. 3 shows an exploded perspective view illustrating an essential portion of an exhaust silencer according to the present invention and illustrates the rear end portion 33 of the inner cylinder 31 and the stepped disc 50. The inner cylinder 31 is formed into the cylindrical body of an elliptic shape and is provided with a pair of fuse portions 70, 70 on an longitudinal axis of the rear end portion 33 and the pair of fuse portions 70, 70 are welded to the step portion (outer periphery 51a of step portion 51) in a state where the rear end portion 33 of the inner cylinder is slidably fitted on the step portion 51 of the stepped disc 50. Thus, the step portion 51 constituting the stepped disc 50 can be tacked temporarily to the inner cylinder 31 in a temporary assembly stage. Fig. 4 shows a plan view illustrating an essential portion of an exhaust silencer according to the present invention, and illustrates the rear end portion 33 of the inner cylinder 31 and the stepped disc 50. In the fuse portion 70, a protruding piece 71 is formed at the rear end portion 33 of the inner cylinder 31. A substantially rectangular opening 73 is formed forward the protruding piece 71, and a tip portion 72 of the protruding piece 71 is welded to the outer periphery 51a of the step portion 51 constituting the stepped disc 50. Fracture portions 78, 79 are formed by stretching out both ends 74, 75 of the opening 73 by respectively distances L and L to both sides of the protruding piece 71. By protruding the protruding piece 71 from the rear end portion 33 of the inner cylinder 31, corner portions 76, 77 are formed between the protruding piece 71 and the rear end portion 33. Thus, stress is likely to concentrate on the corner portions 76, 77 and the fracture portions 78, 79 can be surely fractured. Next, an assembly procedure of the exhaust silencer 30 will be explained. Fig. 5 (a) and Fig. 5 (b) are first explanatory views illustrating an assembly procedure of an exhaust silencer according to the present invention. In Fig. 5 (a), a step portion 51 is fitted in the rear end portion 33 of the inner cylinder 31 as shown by an arrow mark 6 ○. Simultaneously, a fitting hole 53 of the step portion 51 is fitted on the tail pipe 66. In Fig. 5 (b), the tip portion 72 of the protruding piece 71 constituting the fuse portion 70 is welded to the outer periphery 51a of the step portion 51. In the temporary assembly stage, the step portion 51 can be tacked temporarily to the inner cylinder 31. Accordingly, assembly work of following processes is simplified to save the trouble. Next, the glass wool 46 is stored in the step portion 51 as shown by an arrow mark 7 ○. Next, a fitting portion 55 of the enlarged diameter portion 54 is fitted in the step portion 51 as shown by an arrow mark 8 ○. Simultaneously, a fitting hole 54a of the enlarged diameter portion 54 is fitted on the tail pipe 66. Fig. 6 (a) and Fig. 6 (b) are second explanatory views illustrating an assembly procedure of an exhaust silencer according to the present invention. In Fig. 6 (a), a rear end portion 51b of the step portion 51 is welded and fixed to a fitting portion 55 of the enlarged diameter portion 54. The two welding positions are preferable at 180° intervals, however, the welding place is not limited to this, for example circumferential welding may be applied. In this case, as illustrated in Fig. 5 (b), the step portion 51 is tacked temporarily to the inner cylinder 31 in the temporary assembly stage. Therefore, when the enlarged diameter portion 54 is welded to the step portion 51, the step portion 51 is not deviated from a regular location at all. Thus, the enlarged diameter portion 54 can simply be welded with little trouble to the step portion 51. In Fig. 6 (b), the glass wool 45 is mounted on the outer periphery 31a of the inner cylinder 31, and this glass wool 45 is sandwiched between the inner cylinder 31 and the outer cylinder 41 by covering the glass wool 45 with the outer cylinder 41. Simultaneously, the enlarged diameter portion 54 is fitted in the rear end portion 43 of the outer cylinder 41, and the rear end portion 43 of the outer cylinder 41 is circumferentially welded to the outer periphery 56 of the enlarged diameter portion 54. Thus, the outer cylinder 41 is fixed to the enlarged diameter portion 54. In this case, since the stepped disc 50 is tacked temporarily to the inner cylinder 31, the stepped disc 50 is prevented from deviating from the regular location. Thus, the rear end portion 43 of the outer cylinder 41 can simply be welded with little effort to the outer periphery 56 of the enlarged diameter portion 54. Next, an operation of an exhaust silencer will be explained. Fig. 7 (a), and Fig. 7 (b) are explanatory views illustrating an operation of an exhaust silencer according to the present invention. In Fig. 7 (a), by flowing exhaust gas into the exhaust silencer 30 as shown by an arrow mark, the inner cylinder 31 and the outer cylinder 41 are thermally expanded. In this case, since the outer cylinder 41 is brought into contact with atmospheric air, temperature thereof can be lowered compared with that of the inner cylinder 31. Therefore, the elongation of the inner cylinder 31 is larger than the elongation of the outer cylinder 41. Here, the front end portion 32 of the inner cylinder 31 is welded (illustrated in Fig. 2) to the front lid 35 and the rear end portion 33 of the inner cylinder 31 is welded to the step portion 51 of the stepped disc 50. Therefore, when the inner cylinder 31 is thermally expanded, stress is concentrated on the corner portions 76, 77 of the fuse portion 70 and cracks 80 and 81 are generated at the fracture portions 78, 79. In Fig. 7 (b), the fracture portions 78, 79 of the fuse portion 70 are fractured and the rear end portion 33 of the inner cylinder 31 is separated from the stepped disc 50. Thus, the rear end portion 33 of the inner cylinder 31 is slid as shown by a white arrow mark relative to the step portion 51 of the stepped disc 50. The relative elongation of the inner cylinder 31 to the outer cylinder 41 is permitted by sliding the rear end portion 33 of the inner cylinder 31. Next, the other assembly procedure of the exhaust silencer 30 will be explained. Fig. 8 (a) and Fig. 8 (b) are first explanatory views illustrating the other assembly procedure of an exhaust silencer according to the present invention. In Fig. 8 (a), after the glass wool 46 is stored in the step portion 51 of the stepped disc 50, the enlarged diameter portion 54 is fitted in the step portion 51. In Fig. 8 (b), the stepped disc 50 is integrally assembled with each other by welding the rear end portion 51b of the step portion 51 to the fitting portion 55 of the enlarged diameter portion 54. Next, the step portion 51 of the stepped disc 50 is fitted in the rear end portion 33 of the inner cylinder 31. Fig. 9 is a second explanatory view illustrating the other assembly procedure of an exhaust silencer according to the present invention. A tip portion 72 of the protruding piece 71 constituting the fuse portion 70 is bumped against a wall surface 54a (that is, wall surface constituting step portion) of the enlarged diameter portion 54. Next, the tip portion 72 of the protruding piece 71 is welded to the wall surface 54a of the enlarged diameter portion 54. Thus, in the temporary assembly stage, the stepped disc 50 can be tacked temporarily to the inner cylinder 31. Meanwhile, the tip portion 72 of the protruding piece 71 can be welded to the outer periphery 51a of the step portion 51 in place of being welded to the wall surface 54a of the enlarged diameter portion 54. Returning to Fig. 6 (b), the glass wool 45 and the outer cylinder 41 are mounted on the outside of the inner cylinder 31. In this case, since the stepped disc 50 is tacked temporarily to the inner cylinder 31, when welding the outer cylinder 41 to the outer periphery 56 of the enlarged diameter portion 54, the stepped disc can be prevented from deviating from the regular location. Therefore, the rear end portion 43 of the outer cylinder 41 can simply be welded with little trouble to the outer periphery 56 of the enlarged diameter portion 54. Meanwhile, in the above, there is explained an example of adopting the exhaust silencer 30 of the present invention for the motorcycle 10. However, the exhaust silencer 30 can be adopted, for example, for a three-wheeled vehicle, or an automobile. Further, there is described an example of providing the fuse portion 70 at the rear end portion 33 of the inner cylinder 31. However, even if the fuse portion 70 is provided at the front end portion of the inner cylinder, the same effect as that of the example can be obtained. In the fuse portion 70, a notch may be formed at the corner portion. By forming the notch, the fracture portion can further surely be fractured. Further, the opening 73 of the fuse portion 70 is formed substantially in a shape of rectangular, however, the shape of the opening 73 can optionally be selected. There is described an example of providing a pair of the fuse portions 70, 70 at the rear end portion 33 of the inner cylinder 31. However, the number of the fuse portion 70 can optionally be selected such as one piece or three pieces of them. Additionally, regarding the fuse portion 70, there is described an example of welding the tip portion 72 of the protruding piece 71 to the step portion (outer periphery 51a of step portion 51 or wall surface 54a of enlarged diameter portion 54) of the stepped disc 50. However, both side edges of the tip portion 72 may be welded to the outer periphery 51a of the step portion 51. The present invention exhibits following effects according to the constitution described above. In claim 1, a fuse portion is constituted to tack temporarily a stepped disc to an inner cylinder by welding the fuse portion to a step portion of the stepped disc or to a wall surface constituting the step portion. When performing assembly work of a following process, such as a case where the stepped disc is welded to a rear end portion of an outer cylinder, the stepped disc is prevented from deviating from a regular location. Accordingly, assembly work of an exhaust silencer is simplified to save the trouble. Further, when thermal expansion is generated to the inner cylinder, the fuse portion is constituted to separate the inner cylinder from the stepped disc by the fracture of the fuse portion. Therefore, a rear end portion of the inner cylinder is slid relative to the step portion of the stepped disc, and relative elongation of the inner cylinder to the outer cylinder is permitted. In summary it is an object toprovide an exhaust silencer in which relative elongation of an inner cylinder to an outer cylinder is permitted, and assembling workability is enhanced. To achieve this, an exhaust silencer 30 has a structure in which relative elongation of an inner cylinder 31 to an outer cylinder 41 is permitted by blocking a rear end portion 43 of the outer cylinder 41 with a stepped disc 50, by slidably mounting a rear end portion 33 of the inner cylinder 31 on a step portion 51 of the stepped disc 50. A fuse portion 70 is provided at the rear end portion 33 of the inner cylinder 31, and is welded to the step portion 51 of the stepped disc 50 to tack temporarily the stepped disc 50 to the inner cylinder 31 at a temporary assembly stage. The fuse portion 70 is constituted to be fractured by thermal expansion of the inner cylinder when exhaust gas flows. Explanation of Reference Numerals 10···Motorcycle, 30···Exhaust Silencer, 31···Inner Cylinder, 32···One End Portion (Front End Portion) of Inner Cylinder, 33···Other End Portion (Rear End Portion) of Inner Cylinder, 37···Expansion Chamber (First Expansion Chamber) 38···Expansion Chamber (Second Expansion Chamber) 39···Expansion Chamber (Third Expansion Chamber)41···Outer Cylinder, 42···One End Portion (Front End Portion) of Outer Cylinder, 43···Other End Portion (Rear End Portion) of Outer Cylinder, 45, 46···Glass Wool, 50···Stepped Disc, 51···Step portion, 51a··· Step portion (Outer Periphery of Step portion), 54···Enlarged Diameter Portion, 54···Wall surface constituting Step portion (Wall Surface 54a of Enlarged Diameter Portion 54), 70···Fuse Portion, 71··· Protruding Piece, 72···Tip Portion of Protruding Piece, 73··· Opening, 76, 77···Corner Portion, 78, 79···Fracture portion.

Claims: A structure for an exhaust silencer (30), in which one end portion (42) of an outer cylinder (41) sandwiching glass wool (45) between the outer cylinder (41) and an inner cylinder (31) is coupled to one end portion (32) of the inner cylinder (31) having a plurality of expansion chambers (37) inside thereof, and relative elongation of the inner cylinder (31) to the outer cylinder (41) is permitted by blocking the other end portion (43) of the outer cylinder (41) with a stepped disc (50), and by slidably mounting with the other end portion (33) of the inner cylinder (31) on a step portion (51) of the stepped disc (50), characterized in that : a fuse portion (70) which is fractured when prescribed force is operated, is provided at the other end portion (33) of the inner cylinder (31); the fuse portion (70) is welded to the step portion (51) of the stepped disc (50) or to a wall surface (54) constituting the step portion (51) to tack temporarily the stepped disc (50) to the inner cylinder (31) at a temporary assembly stage, and the inner cylinder (31) can be separated from the stepped disc (50) by the fracture of the fuse portion (70) caused by thermal expansion of the inner cylinder (31), when exhaust gas flows.

Inventors: MINAMI KAZUTAKA, NOJIRI SATORU, MINAMI, KAZUTAKA, NOJIRI, SATORU
Applicants: HONDA MOTOR CO LTD, HONDA GIKEN KOGYO KABUSHIKI KAISHA
Application year: 2001
Main classification: F01N1
IPC codes: F01N1, F01N13