JP6256255B2 - Muffler structure of motorcycle - Google Patents

Description

  The present invention relates to a muffler structure that exhausts exhaust gas discharged from an engine of a motorcycle through a first muffler and a second muffler.

  2. Description of the Related Art Conventionally, in a motorcycle, an exhaust structure that exhausts engine exhaust gas through an exhaust pipe connected to the engine and a muffler connected to the downstream end side of the exhaust pipe has been adopted. As this exhaust structure, for example, as disclosed in Patent Document 1, a first muffler (exhaust chamber) and a second muffler (silencer) connected to the first muffler via a connecting pipe are provided. There is a configuration.

  As described in Patent Document 1, the configuration including the first muffler and the second muffler can reduce the size of the second muffler while reducing the exhaust noise, and thus the overall length of the exhaust structure. It can be shortened.

  In Patent Document 1, the first muffler includes an outer wall portion having a structure that can be divided into upper and lower portions, and a catalyst and an inner exhaust pipe disposed inside the outer wall portion. The inner exhaust pipe is connected to the downstream end side of the catalyst and is formed in a curved shape so as to reverse the exhaust gas flowing backward. A reflux pipe is provided at a position protruding forward of the first muffler, and the downstream end side of the inner exhaust pipe is connected to the reflux pipe. The recirculation pipe is formed in a curved shape so as to reverse the exhaust gas flowing forward through the inner exhaust pipe. In Patent Document 1, by providing a reflux pipe in the first muffler, an increase in the size of the vehicle is suppressed while ensuring a reduction in exhaust noise and an improvement in engine output.

JP 2009-162094 A

  However, in Patent Document 1, since the exhaust pipe length is earned by the reflux pipe outside the outer wall portion, there is a problem that the space required for installing the first muffler and the reflux pipe is increased in the front-rear direction. Moreover, in Patent Document 1, three pipes are arranged in the vehicle width direction (left-right direction) by the exhaust pipe connecting the engine and the first muffler and the curved reflux pipe, and there is a space required for installing them. There is also a problem of increasing in the left-right direction.

  The present invention has been made in view of the above points, and a muffler for a motorcycle capable of reducing the space in the front-rear direction and the left-right direction of the vehicle body for installing the first muffler while ensuring the required performance. The purpose is to provide a structure.

  A muffler structure for a motorcycle according to the present invention includes an automatic muffler having a first muffler mounted on a downstream end side of an exhaust pipe through which exhaust gas from an engine flows, and a second muffler through which exhaust gas passes through the first muffler. A muffler structure of a motorcycle, wherein the first muffler includes an outer wall portion that forms an expansion chamber in which the exhaust gas expands, and a catalyst that is disposed on the inlet side of the first muffler and inside the outer wall portion. An open end forming portion provided on the downstream side of the inner exhaust pipe and an inner exhaust pipe disposed on the inner side of the outer wall portion, and having an upstream end connected to the catalyst. Exhaust gas that has flowed through the inner exhaust pipe via is exhausted into the outer wall portion, the inner exhaust pipe is formed in a spiral shape, and the open end forming portion is disposed above the catalyst. Features.

  According to this configuration, since the inner exhaust pipe is formed in a spiral shape, it is possible to suppress the front-rear and left-right widths while securing the pipe length, and thus to reduce the installation space in the front-rear direction and the left-right direction of the first muffler. it can. In addition, since the open end forming portion is located above the catalyst, the limited space behind the engine can be effectively utilized in the height direction, and the muffler volume necessary for noise reduction is ensured, and it is necessary for engine output. The exhaust pipe length can be secured.

  In the muffler structure of the motorcycle, the open end forming portion may be disposed inside the inner exhaust pipe in a plan view. In this configuration, the exhaust gas discharged from the open end forming portion easily hits the inner exhaust pipe and diffuses, thereby enhancing the silencing effect. Further, it is possible to suppress the exhaust gas discharged from the open end forming portion from directly striking the outer wall portion and to suppress noise such as chatter noise.

  In the muffler structure of the motorcycle, a part of the inner exhaust pipe is disposed between the open end forming portion and the outlet of the first muffler, and the open end forming portion and the outlet of the first muffler are arranged. Should be shifted in the height direction. In this configuration, the exhaust gas discharged from the open end forming portion can be diffused or attenuated by hitting the inner exhaust pipe before being discharged from the outlet of the first muffler. Therefore, the silencing effect of the first muffler can be enhanced also by this.

  In the muffler structure of the motorcycle, the open end forming portion may be disposed substantially directly below the uppermost forming portion of the outer wall portion. In this configuration, the open end forming portion can be disposed in a portion of the outer wall portion where the volume is maximized in the height direction, and the exhaust gas released from the open end forming portion is easily diffused, so that the silencing effect can be enhanced.

  In the muffler structure of the motorcycle, an interference hole is formed in a vehicle width direction of the inner exhaust pipe, the inner exhaust pipe is disposed between the interference hole and an outlet of the first muffler, and the interference hole and the The outlet of the first muffler may be shifted in the height direction. In this configuration, before the exhaust gas discharged from the interference hole is discharged from the outlet of the first muffler, it can be diffused or attenuated by hitting the inner exhaust pipe, so that the silencing effect can be further enhanced. .

  According to the present invention, it is possible to reduce the space in the front-rear direction and the left-right direction of the vehicle body for installing the first muffler while ensuring the required performance.

FIG. 2 is a right side view of the entire motorcycle according to the present embodiment. It is the figure which looked at the partial structure of the said motorcycle from the vehicle body front. FIG. 3 is a right side view of a partial configuration of the motorcycle. It is the figure which looked at the left side of the body of a part of the motorcycle. It is the figure which looked at the bottom of the body of a part of the motorcycle. It is a schematic perspective view of the muffler structure of the motorcycle. It is a schematic perspective view of a partial configuration of the first muffler having the muffler structure. FIG. 3 is a left side view of a partial configuration of the first muffler. It is the figure which planarly viewed the partial structure of the said 1st muffler. FIG. 3 is a right side view of a partial configuration of the first muffler.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following, an example in which the muffler structure according to the present invention is applied to a naked type motorcycle will be described, but the application target is not limited to this and can be changed. For example, the muffler structure according to the present invention may be applied to other types of motorcycles. Regarding the direction, the front of the vehicle is indicated by an arrow FR, the rear of the vehicle is indicated by an arrow RE, the left side of the vehicle is indicated by an arrow L, and the right side of the vehicle is indicated by an arrow R. In the following drawings, some components may be omitted for convenience of explanation.

  First, referring to FIG. 1, a schematic configuration of the entire motorcycle according to the present embodiment will be described. FIG. 1 is a right side view of the entire motorcycle according to the present embodiment.

  As shown in FIG. 1, a motorcycle 1 includes a body frame 2 made of steel or aluminum alloy on which a power unit and electrical components are mounted. The main tube 3 of the vehicle body frame 2 extends rearward from the head pipe 4 located at the front end. The down tube 5 of the vehicle body frame 2 is provided so as to extend rearward and obliquely downward from the head pipe 4. A fuel tank 7 in which fuel is accommodated is disposed behind the head pipe 4. A seat 8 on which a driver is seated is mounted behind the fuel tank 7.

  A single cylinder engine 14 is suspended on the main tube 3 and the down tube 5 in the vehicle body frame 2. The engine 14 includes an engine case 16 supported by the down tube 5, and a cylinder 17 and a cylinder head 18 provided above the engine case 16. In the present embodiment, the cylinder 17 is connected to the upper side of the engine case 16 in a forwardly inclined state. A clutch side cover 19 is mounted on the right side of the vehicle body of the engine case 16 (front side in FIG. 1), and a magnet side cover (not shown) is provided on the left side of the vehicle body of the engine case 16 (back side in FIG. 1). It is installed. A center stand 20 for allowing the vehicle to stand by itself with the rear wheel 34 floating is provided below the rear side of the engine 14 so as to be rotatable. The detailed configuration of the center stand 20 will be described later.

  An upper end (upstream end) side of an exhaust pipe (exhaust pipe) 21 is connected to the cylinder 17. A first muffler 23 is attached to the lower end (downstream end) side of the exhaust pipe 21, and exhaust gas discharged from a combustion chamber (not shown) of the cylinder 17 flows through the exhaust pipe 21 and flows into the first muffler 23. The exhaust gas that has passed through the first muffler 23 flows into the second muffler 24 and is discharged to the outside from the exhaust port 25 at the rear end. In this exhaust gas discharge, the exhaust noise is reduced by each of the first muffler 23 and the second muffler 24. The second muffler 24 is disposed behind the first muffler 23 and on the right side of the vehicle body of the rear wheel 34 (the front side in FIG. 1). Further, the second muffler 24 is set to a longitudinal length in which the rear end portion is positioned forward of the rotational center position of the rear wheel 34. The muffler structure of the motorcycle 1 according to the present embodiment includes an exhaust pipe 21, a first muffler 23, and a second muffler 24. The detailed configuration of the first muffler 23 and its peripheral part will be described later.

  A front fork 27 is rotatably supported at a front end portion of the main tube 3 via a steering shaft (not shown) provided in the head pipe 4. A handlebar 28 is provided at the upper end of the steering shaft, and grips 29 are attached to both ends of the handlebar 28. A front wheel 31 is rotatably supported on the lower portion of the front fork 27. An upper portion of the front wheel 31 is covered with a front fender 32.

  A rear wheel 34 is rotatably supported behind the engine 14 via a swing arm 33. Between the swing arm 33 and the vehicle body frame 2, a suspension 35 is arranged to reduce the impact from the road surface. A rear fender 36 is disposed above the rear wheel 34 and behind the seat 8. Various body exteriors such as a cover are attached to the body frame 2.

  Next, the detailed configuration of the center stand 20 will be described with reference to FIGS. 2 to 5. 2 is a diagram of a partial configuration of the motorcycle as viewed from the front of the vehicle body, FIG. 3 is a diagram of a partial configuration of the motorcycle as viewed from the right side of the vehicle body, and FIG. FIG. 5 is a diagram of a partial configuration of the motorcycle as viewed from the bottom of the vehicle body.

  As shown in FIG. 2, the center stand 20 includes a right leg portion 40, a left leg portion 41, and a connecting portion 42 that connects the distal end side from the center in the extending direction and extends in the left-right direction. The base end sides of the right leg portion 40 and the left leg portion 41 are pivotally supported via a support bracket 44 so as to swing. Accordingly, the center stand 20 can swing between the standing position shown in FIG. 2 and the storage position shown in FIGS. 3 to 5, and becomes the storage position when the vehicle is running.

  Grounding plates 45 each having a curved shape are provided on the distal end sides of the right leg portion 40 and the left leg portion 41. The right leg 40 is provided with a spring member 46 that urges the center stand 20 to the storage position. Further, the left leg 41 is provided with a foot bar 47, and the center stand 20 can be swung from the stowed position to the standing position by stepping on the foot bar 47 with a foot.

  Next, the detailed configuration of the first muffler 23 and its peripheral part will be described with reference to FIGS. 6 to 10 in addition to FIGS. FIG. 6 is a schematic perspective view of the muffler structure according to the present embodiment.

  As shown in FIG. 6, the first muffler 23 includes an outer wall portion 51 that forms an expansion chamber in which exhaust gas expands. The outer wall portion 51 has a left and right case 53 and a right case 54 and has a structure that can be divided into left and right portions, and a substantially intermediate position in the left and right direction of the outer wall portion 51 is a dividing position. The downstream end side of the exhaust pipe 21 is connected to a position straddling the left case 53 and the right case 54 at the front end portion of the outer wall portion 51, and this connection portion serves as the inlet 23 a of the first muffler 23.

  FIG. 7 is a schematic perspective view of a partial configuration of the first muffler, and FIG. 8 is a left side view of the partial configuration of the first muffler. As shown in FIGS. 6 to 8, the outer wall 51 has a central region 51 a in the front-rear direction raised upward, and a top surface of the outer wall 51 forms an uppermost formation portion 51 b positioned at the uppermost position in the outer wall 51. . The front area 51c of the outer wall 51 is set to a size that is slightly larger than the thickness of the exhaust pipe 21, and is formed in a size that can accommodate a catalyst device 60 described later. The rear region 51d of the outer wall portion 51 is set to a size that is higher than the front region 51c and lower than the uppermost formation portion 51b, and is sized to accommodate an inner exhaust pipe 70 described later.

  An opening 54a is formed on the right side surface of the right case 54, and an expansion member 55 is provided so as to close the opening 54a (not shown in FIG. 7). The expansion member 55 is a separate component from the right case 54 and is fixed to the right case 54 by means such as welding. The expansion member 55 is formed so as to partially bulge from the right side surface of the right case 54 to the right side. Accordingly, a part of the expansion chamber formed by the outer wall portion 51 is formed and expanded by the internal space of the expansion member 55.

  An outlet 23b of the first muffler 23 is formed on the right side surface of the expansion member 55, and a connecting pipe 57 is attached to the outlet 23b. Here, the outlet 23b of the first muffler 23, which is the attachment position of the connecting pipe 57, is the attached portion of the connecting pipe 57 in the outer wall portion 51. The attached portions include the left side surface of the left case 53 and the right case 54. Of the right side of the right case 54, that is, the right side of the right case 54. The downstream end (rear end) side of the connecting pipe 57 is connected to the inlet 24 a of the second muffler 24. As a result, the outlet 23b of the first muffler 23 and the inlet 24a of the second muffler 24 are communicated with each other via the connecting pipe 57, and the exhaust gas discharged from the first muffler 23 passes through the connecting pipe 57 and passes through the second muffler. 24.

  As shown in FIGS. 3 to 5, the outer wall portion 51 is disposed behind the engine 14, and the front region 51 c is disposed at a position overlapping the rear end side of the engine 14 in the vertical direction. The outer wall portion 51 is disposed at a position that fits between the right leg portion 40 and the left leg portion 41 of the center stand 20 in the storage position in the left-right direction. Further, the outer wall portion 51 is disposed in front of the connecting portion 42 in the center stand 20 at the storage position. Accordingly, the rear region 51d of the outer wall portion 51 is disposed in a space surrounded by the right leg portion 40, the left leg portion 41, and the connecting portion 42 in the center stand 20 at the storage position.

  The outer wall portion 51 is arranged so that the uppermost formation portion 51 b is positioned between the front ends of the swing arm 33 that is divided into two forks. Therefore, as shown by the dotted lines in FIGS. 3 and 4, the uppermost formation portion 51 b that is the upper surface of the first muffler 23 is disposed so as to overlap the swing arm 33 in a side view of the vehicle body.

  As shown in FIGS. 7 and 8, the first muffler 23 includes a catalyst device 60 disposed on the inlet 23 a side and inside the front region 51 c in the outer wall portion 51. The catalyst device 60 has a cylindrical shape extending in the front-rear direction, and the front end (upstream end) side communicates with the rear end (downstream end) side of the exhaust pipe 21. The catalyst device 60 includes a catalyst (not shown) for purifying the exhaust gas, and is provided so as to purify the exhaust gas introduced from the front through the exhaust pipe 21 and discharge it to the rear.

  The first muffler 23 further includes an inner exhaust pipe 70 disposed inside the central region 51a and the rear region 51d in the outer wall portion 51. The upstream end side of the inner exhaust pipe 70 is connected to the downstream end (rear end) side of the catalyst device 60. The inner exhaust pipe 70 includes a first bending pipe 71, a second bending pipe 72, and a third bending pipe 73 in order in the direction in which the exhaust gas flows, and is raised while rotating from the catalyst device 60 by these bending pipes 71 to 73. It is formed in a spiral shape.

  The first muffler 23 is supported on the inner peripheral surface of the outer wall portion 51 via an upper bracket 75 and a lower bracket 76 (not shown in FIG. 7). The upper bracket 75 is welded and fixed to the upper surface side of the third bending pipe 73 and the upper inner surface in the rear region 51 d of the outer wall portion 51. The lower bracket 76 is welded and fixed to the second bending tube 72 and the inner surface of the right case 54 on the side.

  An open end forming portion 78 is provided on the downstream end side of the third bending pipe 73 that is the downstream end side of the inner exhaust pipe 70, and the open end forming portion 78 is also disposed inside the outer wall portion 51. The open end forming portion 78 is configured by forming a number of exhaust holes 78a in the outer peripheral portion of the cylindrical member. A cap 78b (not shown in FIG. 8) is provided on the distal end side of the open end forming portion 78. A piece-like bracket 79 (not shown in FIG. 8) extending forward is fixed to the cap 78b. The exhaust gas flowing from the inner exhaust pipe 70 to the open end forming portion 78 is discharged through the exhaust hole 78 a and expands inside the outer wall portion 51.

  9 is a plan view of a partial configuration of the first muffler, and FIG. 10 is a right side view of the partial configuration of the first muffler. As shown in FIG. 9, the first to third bending tubes 71 to 73 are curved and formed in a semicircular arc shape or a U shape in a plan view of the vehicle body, and the first and third bending tubes 71 and 73 are curved. Both ends in the extending direction are directed forward, and the second bending tube 72 has both curved ends in the extending direction directed rearward. Further, as shown in FIG. 10, the first and third bending pipes 71 and 73 are formed such that the downstream end is positioned higher than the upstream end. Therefore, the 1st muffler 23 makes the exhaust gas which flows through the inner side exhaust pipe 70 1 and a half by a vehicle body planar view by connecting in order of the 1st-3rd bending pipes 71-73.

  As shown in FIGS. 8 and 10, interference holes 80 are formed in the vehicle width direction on the upstream end side of the first bending pipe 71, that is, on the left side and the right side. The interference hole 80 is formed through the first bending tube 71, and exhaust gas is discharged from the interference hole 80 in addition to the open end forming portion 78. The interference hole 80 and the outlet 23b of the first muffler 23 are disposed at positions shifted in the height direction. In the present embodiment, the interference hole 80 is disposed below the outlet 23b of the first muffler 23. . A first bending tube 71 is disposed between the interference hole 80 and the outlet 23 b of the first muffler 23.

  Next, the layout of each component inside the outer wall portion 51 will be described below with reference to FIGS.

  Since the inner exhaust pipe 70 extends in a spirally rising direction from the catalyst device 60, the open end forming portion 78 is disposed above the catalyst device 60. The open end forming portion 78 is located on the right side of the catalyst device 60 in a plan view shown in FIG. Accordingly, the open end forming portion 78 is disposed near the right side surface of the right case 54 provided with the expansion member 55 among the left side surface of the left case 53 and the right side surface of the right case 54. Thereby, the distance from the catalyst apparatus 60 to the open end formation part 78 can be lengthened, and the pipe | tube length of the inner side exhaust pipe 70 can be earned by extension.

  The open end forming portion 78 is disposed inside the inner exhaust pipe 70 having an annular shape in plan view. Specifically, the open end forming portion 78 is arranged inside the second bending tube 72 in a plan view, and the lower half region overlaps the second bending tube 72 in a side view as shown in FIG. Has been placed.

  Further, between the open end forming portion 78 and the outlet 23 b of the first muffler 23, the downstream end side of the second bending pipe 72 and the upstream end side of the third bending pipe 73 that are part of the inner exhaust pipe 70 are arranged. Is done. The open end forming portion 78 and the outlet 23b of the first muffler 23 are disposed at positions shifted in the height direction. In the present embodiment, the open end forming portion 78 is disposed above the outlet 23b of the first muffler 23. It is installed.

  The open end forming portion 78 is disposed substantially directly below (or directly below) the uppermost forming portion 51 b of the outer wall portion 51. In other words, the uppermost formation portion 51b of the outer wall portion 51 is disposed substantially directly above (or directly above or near the open end formation portion 78).

  As described above, in the present embodiment, since the rear region of the outer wall portion 51 fits between the right leg portion 40 and the left leg portion 41 of the center stand 20, the left and right widths of the first muffler 23 can be reduced, and the bank Earn horns. Moreover, since the outer wall part 51 is located ahead of the connection part 42 of the center stand 20, the front-rear width of the first muffler 23 can also be reduced. On the other hand, the components behind the motorcycle 1 are not crowded at the rear of the engine 14 and there is a relatively large space, and the height of the first muffler 23 is set as described above using this space. The necessary muffler volume can be secured.

  Further, since the inner exhaust pipe 70 is formed in a spiral shape and the open end forming portion 78 extends so as to be positioned above the catalyst device 60, the left and right widths and the front and rear widths of the inner exhaust pipe 70 are suppressed. can do. Thereby, the space which has the allowance mentioned above can be utilized, making the installation space of the front-back direction and the left-right direction of the 1st muffler 23 small. As a result, the pipe length of the inner exhaust pipe 70 can be earned, and the length of the muffler structure including the second muffler 24 can be shortened while securing the output of the engine 14.

  Further, since the inner exhaust pipe 70 is accommodated in the outer wall portion 51, the appearance can be improved. In addition, the inner exhaust pipe 70 can be prevented from being contaminated by mud or the like, and the inner exhaust pipe 70 can be prevented from being rusted.

  Furthermore, since the uppermost formation part 51b of the outer wall part 51 is located above the open end formation part 78, in other words, the open end formation part 78 is located below the uppermost formation part 51b of the outer wall part 51. The open end forming portion 78 is disposed in a portion where the volume is the largest in the height direction of 51. Thereby, the exhaust gas discharged from the open end forming portion 78 is easily diffused inside the outer wall portion 51, and the exhaust sound can be better silenced.

  Further, since the outlet 23b of the first muffler 23 is provided on the right case 54 side, the distance between the outlet 23b and the interference hole 80 can be increased. In addition, since a part of the inner exhaust pipe 70 is disposed between the interference hole 80 and the outlet 23b of the first muffler 23, the exhaust gas discharged from the interference hole 80 is discharged from the outlet 23b of the first muffler 23. Before being discharged, the inner exhaust pipe 70 and the inner surface of the outer wall 51 can be applied. Thereby, exhaust gas can be diffused or attenuated, and the noise reduction effect can be further enhanced.

  In addition, since the outer wall portion 51 can be divided into the left and right cases 53 and 54 in the left and right directions, it is possible to secure a wide surface on which the divided portions are not located on both the left and right sides of the outer wall portion 51, compared to the structure that is divided vertically. it can. Thereby, the attachment position of the expansion member 55, the formation position of the outlet 23 b of the first muffler 23, and the attachment position of the connecting pipe 57 in the first muffler 23 can be given flexibility.

  Further, since the expansion member 55 as a separate part is provided on the outer wall portion 51, the volume of the outer wall portion 51 can be easily increased at a low cost without changing the mold for molding the entire outer wall portion 51.

  Further, by arranging the open end forming portion 78 in the above-described layout, the exhaust gas discharged from the open end forming portion 78 is made to hit the inner exhaust pipe 70 before being discharged from the outlet 23b of the first muffler 23. Can do. Thereby, exhaust gas can be diffused or attenuated, and the noise reduction effect can be further enhanced. Further, the exhaust gas discharged from the open end forming portion 78 can be prevented from striking the outer wall portion 51 directly, and noise such as chatter noise in the outer wall portion 51 can be suppressed.

  In addition, this invention is not limited to the said embodiment, It can change and implement variously. In the above-described embodiment, the size, shape, direction, and the like illustrated in the accompanying drawings are not limited to this, and can be appropriately changed within a range in which the effect of the present invention is exhibited. In addition, various modifications can be made without departing from the scope of the object of the present invention.

  For example, the open end forming portion 78 is not limited to the illustrated configuration example, and may be formed using a mesh member as long as the exhaust gas flowing from the inner exhaust pipe 70 can be diffused and discharged.

  In the above embodiment, the outlet 23b of the first muffler 23 is formed on the expansion member 55. However, the expansion member 55 is omitted, and the outlet 23b of the first muffler 23 is formed on the side surface of the outer wall portion 51. 57 may be connected.

  Further, the inner exhaust pipe 70 may be formed in a spiral shape that rotates and rises one and a half times in a plan view.

  As described above, the present invention has an effect that the installation space in the front-rear direction and the left-right direction of the first muffler can be reduced, and is useful for a motorcycle having the first muffler disposed behind the engine. It is.

1 Motorcycle 14 Engine 21 Exhaust pipe (exhaust pipe)
23 First Muffler 24 Second Muffler 33 Swing Arm 51 Outer Wall 51b Topmost Forming Part 55 Expansion Member 57 Connecting Pipe 60 Catalytic Device 70 Inner Exhaust Pipe 78 Open End Forming Part 80 Interference Hole

Claims (5)

A muffler structure for a motorcycle including a first muffler attached to a downstream end of an exhaust pipe through which exhaust gas from an engine flows, and a second muffler through which exhaust gas passes through the first muffler,
The first muffler includes an outer wall portion that forms an expansion chamber in which the exhaust gas expands, a catalyst that is disposed on the inlet side of the first muffler and inside the outer wall portion, and an upstream end connected to the catalyst. And an inner exhaust pipe disposed inside the outer wall portion, and an open end forming portion provided on the downstream side of the inner exhaust pipe, and the inner exhaust pipe is disposed through the open end forming portion. The exhaust gas that has flowed is discharged into the outer wall,
The muffler structure for a motorcycle, wherein the inner exhaust pipe is formed in a spiral shape, and the open end forming portion is disposed above the catalyst.   The muffler structure for a motorcycle according to claim 1, wherein the open end forming portion is disposed inside the inner exhaust pipe in a plan view.   A part of the inner exhaust pipe is disposed between the open end forming portion and the outlet of the first muffler, and the open end forming portion and the outlet of the first muffler are shifted in the height direction. The muffler structure for a motorcycle according to claim 1 or 2, wherein the muffler structure is a motorcycle.   The muffler structure for a motorcycle according to any one of claims 1 to 3, wherein the open end forming portion is disposed substantially directly below an uppermost forming portion of the outer wall portion. An interference hole is formed in the vehicle width direction of the inner exhaust pipe,
The inner exhaust pipe is disposed between the interference hole and the outlet of the first muffler, and the interference hole and the outlet of the first muffler are shifted in the height direction. Item 5. A muffler structure for a motorcycle according to any one of Items 4 to 6.

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