Patent Publication Number: US-11384679-B2

Title: Exhaust device and straddle-type vehicle

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The disclosure of Japanese Patent Application No. 2019-099496 filed on May 28, 2019, including specification, drawings and claims is incorporated herein by reference in its entirety. 
     BACKGROUND 
     The present invention relates to an exhaust device and a straddle-type vehicle. 
     As an exhaust device for a straddle-type vehicle, there has been known an exhaust device in which an end cap is attached to a rear portion of a muffler via a heat shield cap (see, for example, Patent Literature 1). In the exhaust device described in Patent Literature 1, the heat shield cap is screwed to the rear portion of the muffler with a bolt, and the end cap is screwed to a rear portion of the heat shield cap with a bolt. Since the heat shield cap suppresses heat from the muffler being transferred to the end cap, the end cap can be molded with a resin having high moldability. Therefore, a design property of the end cap at the rear portion of the muffler, which is a heat source, can be improved.
     Patent Literature 1: JP-A-2009-108824   

     SUMMARY 
     According to an aspect of the present invention, there is provided an exhaust device in which a muffler is disposed on a side of a straddle-type vehicle, the exhaust device including: 
     the muffler including a tail pipe configured to discharge exhaust gas and protruding rearward; 
     a tail cover covering a periphery of the tail pipe behind the muffler; and 
     a protector for heat shield interposed between the muffler and the tail cover, wherein 
     inner sides of the tail cover and the protector in a vehicle width direction are configured to be fixed to each other by a fastening member, and 
     an elastic locking portion is formed on an outer side of one of the tail cover and the protector in the vehicle width direction, and a holding portion configured to hold the elastic locking portion is formed on an outer side of another of the tail cover and the protector in the vehicle width direction. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a side view of a motorcycle of an embodiment. 
         FIG. 2  is a rear view of an exhaust device of the embodiment. 
         FIG. 3  is a right side view of the exhaust device of the embodiment. 
         FIG. 4  is a rear view of a muffler of the embodiment. 
         FIG. 5A  is a perspective view of a protector of the embodiment as viewed from the rear. 
         FIG. 5B  is a perspective view of the protector of the embodiment as viewed from the front. 
         FIG. 6A  is a schematic view of a mold of a comparative example. 
         FIG. 6B  is a schematic view of a mold of the embodiment. 
         FIG. 7A  is a perspective view of a tail cover of the embodiment as viewed from the front. 
         FIG. 7B  is a perspective view of the tail cover of the embodiment as viewed from the rear. 
         FIG. 8  is a right side view of a rear portion of an exhaust device of the comparative example. 
         FIG. 9A  is a right side view of a rear portion of the exhaust device of the embodiment. 
         FIG. 9B  is a left side view of the rear portion of the exhaust device of the embodiment. 
         FIG. 10  is a partial sectional view of the exhaust device of the embodiment. 
         FIG. 11  is an explanatory view of an attachment work of the protector to the muffler of the embodiment. 
         FIG. 12  is an explanatory view of an attachment work of the tail cover to the protector of the embodiment. 
     
    
    
     DETAILED DESCRIPTION OF EXEMPLIFIED EMBODIMENT 
     In recent years, as an exhaust device for a straddle-type vehicle, there is a demand for a design in which a fastening member such as a bolt is not seen from the outside, but a head portion of the bolt is exposed from the end cap in the exhaust device described in Patent Literature 1. Although a structure in which a fastening member such as a bolt is hidden in the end cap is also conceivable, it is difficult to fasten the fastening member with a fastening tool or the like, and a fastening work is troublesome. 
     The present invention has been made in view of the above circumstances, and an object thereof is to provide an exhaust device and a straddle-type vehicle that can reduce work burden when the exhaust device is assembled without impairing appearance of the exhaust device. 
     In an exhaust device according to an aspect of the present invention, a tail cover is attached to a muffler, which is disposed on a side of a straddle-type vehicle, via a protector. In this case, inner sides of the tail cover and the protector in a vehicle width direction are fixed by a fastening member, and outer sides of the tail cover and the protector in the vehicle width direction are fixed by elastic locking of an elastic locking portion formed on one of the tail cover and the protector and a holding portion formed on another of the tail cover and the protector. When the straddle-type vehicle is viewed from the side, since the fastening member is positioned in a blind spot on an inner side in the vehicle width direction, appearance of the exhaust device is not impaired by the fastening member. In addition, work burden on a worker is reduced and an assembly property is improved as much as the numbers of fastening portions by the fastening members is reduced. As described above, by combining the fastening of the fastening member and the elastic locking of the elastic locking portion and the holding portion, the work burden when the exhaust device is assembled can be reduced without impairing the appearance of the exhaust device. 
     Hereinafter, an embodiment will be described in detail with reference to the accompanying drawings. Here, an example in which an exhaust device of the present embodiment is applied to a motorcycle as a straddle-type vehicle will be described, but an application object is not limited thereto. For example, the exhaust device may be applied to another straddle-type vehicle such as a buggy type motor tricycle. In addition, in the following drawings, a front side of a vehicle body is indicated by an arrow FR, a rear side of the vehicle body is indicated by an arrow RE, a left side of the vehicle body is indicated by an arrow L, and a right side of the vehicle body is indicated by an arrow R, respectively.  FIG. 1  is a schematic view of a straddle-type vehicle of the present embodiment. 
     As shown in  FIG. 1 , a motorcycle  1  is configured by mounting various components such as an engine  14  and an electrical system on a cradle-type vehicle body frame  10 . The vehicle body frame  10  includes a main tube  12  that extends rearward from a head pipe  11  and then bends downward, and a down tube  13  that extends downward from the head pipe  11  and bends rearward. A rear side of the engine  14  is supported by the main tube  12 , and a front side and a lower side of the engine  14  are supported by the down tube  13 . By supporting the engine  14  on the vehicle body frame  10 , rigidity of the entire vehicle body of the motorcycle  1  is ensured. 
     A pair of left and right front forks  15  are supported on the head pipe  11  via a steering shaft (not shown) so as to be steerable, and a front wheel  16  is rotatably supported on a lower portion of the pair of left and right front forks  15 . A swing arm  17  is swingably supported on a rear side of the main tube  12 , and a rear wheel  18  is rotatably supported on a rear end side of the swing arm  17 . The engine  14  is connected to the rear wheel  18  via a speed reduction mechanism, and power from the engine  14  is transmitted to the rear wheel  18  via the speed reduction mechanism. An exhaust device  21  that discharges exhaust gas from the engine  14  is disposed on a side of the rear wheel  18 . 
     The exhaust device  21  is connected to an exhaust pipe  23  extending rearward from a front surface of the engine  14  via a catalyst case  22 . The exhaust gas from the engine  14  is purified in the catalyst case  22  and discharged to the outside through a muffler  30  of the exhaust device  21 . A tail cover  60  that covers tail pipes  31  (see  FIG. 2 ) of the muffler  30  is provided behind the muffler  30 . Since a design property is required for the tail cover  60 , the tail cover  60  is formed of a resin having high moldability that can be plated, but the resin having such properties has a low heat resistance temperature. Since the muffler  30  reaches a high temperature by the exhaust gas, the tail cover  60  cannot be directly fixed to a rear portion of the muffler  30 . 
     Therefore, a protector  40  having high heat resistance is usually interposed between the muffler  30  and the tail cover  60 . Since the heat transferred from the muffler  30  to the tail cover  60  is suppressed by the protector  40 , the tail cover  60  having the high design property can be provided on a rear side of the high-temperature muffler  30 . However, when the tail cover  60  is fixed to the protector  40  by a fastening member such as a bolt, the fastening member exposed to the rear or a side of the muffler  30  is conspicuous, and appearance of the exhaust device  21  is impaired. In addition, a fastening work of the fastening member is troublesome for a worker, and an assembly property of the protector  40  and the tail cover  60  is deteriorated. 
     Therefore, in the present embodiment, when the muffler  30  is disposed on a side of the motorcycle  1 , focusing on a point that an inner side of the muffler  30  in a vehicle width direction becomes inconspicuous, a fixing method of inner sides of the protector  40  and the tail cover  60  in the vehicle width direction and a fixing method of outer sides of the protector  40  and the tail cover  60  in the vehicle width direction are changed. The inner sides of the protector  40  and the tail cover  60  in the vehicle width direction are fixed by the fastening member, and the outer sides of the  40  and the tail cover  60  in the vehicle width direction are fixed by a snap fit, so that the number of fastening portions of the fastening members is reduced without making the fastening member conspicuous. Accordingly, the assembly property of the protector  40  and the tail cover  60  can be improved without impairing the appearance of the exhaust device  21 . 
     Hereinafter, the exhaust device of the present embodiment will be described with reference to  FIGS. 2 to 7 .  FIG. 2  is a perspective view of an exhaust device of the present embodiment.  FIG. 3  is a right side view of the exhaust device of the present embodiment.  FIG. 4  is a perspective view of a rear portion of the muffler of the present embodiment.  FIG. 5A  is a perspective view of the protector of the present embodiment as viewed from the rear, and  FIG. 5B  is a perspective view of the protector of the present embodiment as viewed from the front.  FIG. 6A  is a schematic view of a mold of a comparative example, and  FIG. 6B  is a schematic view of a mold of the present embodiment.  FIG. 7A  is a perspective view of the tail cover of the present embodiment as viewed from the front, and  FIG. 7B  is a perspective view of the tail cover of the present embodiment as viewed from the rear. 
     As shown in  FIGS. 2 and 3 , in the exhaust device  21  of the present embodiment, the tail cover  60  is attached to the rear portion of the muffler  30  via the protector  40  for heat shield. The pair of upper and lower tail pipes  31  protrude rearward from the rear portion of the muffler  30 , and a periphery of each tail pipe  31  is covered with the tail cover  60  to suppress deterioration of appearance thereof. The muffler  30  has a diameter that increases toward the rear of the vehicle, and is curved so that a center of the rear portion of the muffler  30  swells rearward as viewed from a side. The protector  40  and the tail cover  60  are also curved along a rear shape of the muffler  30 , and the entire device is formed with a design having a sense of unity. 
     As shown in  FIG. 4 , the pair of upper and lower tail pipes  31  that discharge the exhaust gas muffled by the muffler  30  to the atmosphere protrude from a rear surface  32  of the muffler  30 . Three brackets  34  for attaching the protector  40  (see  FIG. 2 ) are provided on the rear surface  32  of the muffler  30  so as to surround the pair of upper and lower tail pipes  31 . Each bracket  34  is formed in a hat shape as viewed in a cross section, and the protector  40  is attached to the bracket  34 , so that the protector  40  is separated from the rear surface  32  of the muffler  30 . An outer edge portion  33  of the muffler  30  extends rearward of the vehicle from the rear surface  32  of the muffler  30 , and an extension amount of the outer edge portion  33  is smaller than a protrusion amount of the bracket  34 . 
     As shown in  FIGS. 5A and 5B , the protector  40  is formed of a resin material having a high heat resistance temperature. As the resin material, for example, a nylon resin may be used, or a fiber reinforced resin using the nylon resin as a base resin may be used. As the fiber reinforced resin, a glass fiber reinforced resin (PA 6 -GF 30 ) in which 30% glass fiber is blended with the polyamide 6 may be used. Incidentally, the resin material of the protector  40  is not particularly limited as long as it is a resin material that can suppress the heat transferred from the muffler  30  (see  FIG. 2 ) to the tail cover  60  (see  FIG. 2 ) via the protector  40  to the heat resistant temperature of the tail cover  60  or lower. 
     The protector  40  has a plate-like portion  41  slightly curved along the rear portion of the muffler  30 . The plate-like portion  41  is formed to have substantially the same outer shape as the rear surface  32  (see  FIG. 4 ) of the muffler  30  as viewed from a rear. Portions in the plate-like portion  41  corresponding to the pair of upper and lower tail pipes  31  bulge rearward, and openings  45  through which the tail pipes  31  are inserted are formed at centers of bulging portions  44 , respectively. The periphery of the tail pipe  31  is covered by the bulging portion  44  of the protector  40 , and only a rear end portion of the tail pipe  31  protrudes rearward from the bulging portion  44  (see  FIG. 2 ). In addition, three through holes  46  are formed at portions in the plate-like portion  41  corresponding to the three brackets  34  (see  FIG. 4 ). 
     In the protector  40 , a left side of a straight line L 1  passing through the uppermost portion  47  and the lowermost portion  48  is a blind spot area that cannot be seen from the side (right side) of the vehicle, and a right side of the straight line L 1  is an exposed area that can be seen from the side of the vehicle. That is, the inner side of the protector  40  in the vehicle width direction is the blind spot area, and the outer side of the protector  40  in the vehicle width direction is the exposed area. A pair of boss portions  49  to which the tail cover  60  is screwed are formed on the inner side of the protector  40  in the vehicle width direction, and four claw portions  51  to which the tail cover  60  is fixed by the snap fits are formed on the outer side of the protector  40  in the vehicle width direction. 
     The pair of boss portions  49  are formed to bulge rearward from a rear surface  42  of the plate-like portion  41 , and extend from a vicinity of an outer edge portion of the plate-like portion  41  on the inner side in the vehicle width direction toward the bulging portions  44 . Each of the boss portions  49  is formed with a screw hole capable of screwing the tail cover  60  from the inner side in the vehicle width direction. The four claw portions  51  are respectively formed on tip end sides of elastic arms  54  erected on the rear surface  42  of the plate-like portion  41 . Each of the claw portions  51  protrudes in a triangular shape as viewed in the cross section toward the outside of the plate-like portion  41 , and is a hook that is held by a holding portion  71  (see  FIG. 10 ) having an inverted triangular shape in a cross section of the tail cover  60 , which will be described later. Incidentally, the detailed shape of the claw portion  51  will be described later. 
     In the plate-like portion  41 , a through hole  55  (see  FIG. 10 ) is formed on a projection surface obtained by projecting the claw portion  51  onto the rear surface  42  of the plate-like portion  41 . This prevents the claw portion  51  from being undercut when the protector  40  is released from a mold. That is, in a case where the through hole  55  is not formed on the protector  40 , as shown in  FIG. 6A , a slide mold  83  is required in addition to an upper mold  81  and a lower mold  82  in order to form the claw portion  51  on the protector  40 . On the other hand, in a case where the through hole  55  is formed on the protector  40 , as shown in  FIG. 6B , the slide mold  83  is not required to form the claw portion  51  on the protector  40 . Incidentally, the through hole  55  also functions as a heat discharge hole. 
     Returning to  FIGS. 5A and 5B , a rear peripheral wall portion  56  protrudes rearward from the outer edge portion of the plate-like portion  41  on the rear surface  42  of the plate-like portion  41 . The rear peripheral wall portion  56  is formed so as to be able to abut an outer edge portion  68  of the tail cover  60  (see  FIG. 7A ) over substantially the entire circumference. Recessed portions  57  are formed on the rear peripheral wall  56  at positions facing the elastic arms  54 , respectively. When the outer edge portion  68  of the tail cover  60  abuts against the rear peripheral wall portion  56 , a through hole is formed in mating surfaces of the protector  40  and the tail cover  60  (see  FIG. 10 ). The through hole functions as a working hole for inserting a tip end of a tool such as a flathead screwdriver in order to release the fixing of the protector  40  and the tail cover  60 . The through hole also functions as the heat discharge hole. 
     On the front surface  43  of the plate-like portion  41 , a front peripheral wall portion  58  protrudes forward from the vicinity of the outer edge portion of the plate-like portion  41 . The front peripheral wall portion  58  is formed along an inner peripheral surface of the outer edge portion  33  (see  FIG. 4 ) of the muffler  30 . As will be described in detail later, since a tip end side of the front peripheral wall portion  58  is accommodated inside the outer edge portion  33  of the muffler  30 , the front peripheral wall portion  58  functions as a hiding member for improving the design property by covering a gap C 2  between the protector  40  and the muffler  30  (see  FIG. 9A ). In addition, the front peripheral wall portion  58  is formed along the inner peripheral surface of the outer edge portion  33  of the muffler  30  excluding an inconspicuous portion in the inner side in the vehicle width direction. As a result, a heat discharge property can be improved without impairing the appearance of the muffler  30 . 
     As shown in  FIGS. 7A and 7B , the tail cover  60  is formed of a resin material that has the high moldability and can be plated. Acrylonitrile butadiene styrene (ABS) may be used as the resin material, for example. Since the protector  40  (see  FIGS. 5A and 5B ) having the high heat resistance temperature is interposed between the tail cover  60  and the muffler  30  (see  FIG. 4 ), the tail cover  60  can be formed of the ABS resin having a low heat resistance temperature. Since the tail cover  60  is formed of the ABS resin, a surface of the tail cover  60  can be given a metallic luster by metal plating while ensuring a degree of freedom in design. 
     The tail cover  60  has a pair of annular bulging portions  61  bulging rearward so as to surround the pair of upper and lower tail pipes  31 . An inner edge portion  62  of each annular bulging portion  61  is folded forward, and an inner side of the inner edge portion  62  is an opening  63  through which the rear end portion of the tail pipe  31  passes. Since each of the annular bulging portions  61  is bulged rearward from the rear end portion of the corresponding tail pipe  31 , the periphery of the tail pipe  31  is entirely covered by the annular bulging portion  61 . In addition, the inner edge portion  62  of the tail cover  60  extends to a vicinity of the bulging portion  44  (see  FIG. 5A ) of the protector  40 . A V-shaped depression  64  that divides the tail cover  60  into upper and lower portions is formed between the pair of annular bulging portions  61 . 
     The tail cover  60  is formed to have substantially the same outer shape as the protector  40  as viewed from the rear. Therefore, in the tail cover  60 , an inner side in the vehicle width direction on a left side of a straight line L 1  passing through the uppermost portion  65  and the lowermost portion  66  is a blind spot area that cannot been seen from the side (right side) of the vehicle, and an outer side in the vehicle width direction on a right side of the straight line L 1  is an exposed area that can be seen from the side of the vehicle. A pair of fastening holes  67  for screwing the tail cover  60  with respect to the protector  40  are formed on the inner side of the tail cover  60  in the vehicle width direction, and the four holding portions  71  fixed to the protector  40  by the snap fits are formed on the outer side of the tail cover  60  in the vehicle width direction. 
     The pair of fastening holes  67  are formed at positions of the tail cover  60  corresponding to the boss portions  49  of the protector  40 . The four holding portions  71  are formed at positions corresponding to the claw portions  51  (see  FIG. 5A ) of the protector  40 . Each of the holding portions  71  protrudes toward the inside of the tail cover  60  in the inverted triangular shape as viewed in the cross section, and is formed so as to hold the claw portion  51  of the protector  40  that has the triangular shape (see  FIG. 10 ) in a cross section and prevent it from coming off. Incidentally, the detailed shape of the holding portion  71  will be described later. The outer edge portion  68  of the tail cover  60  is only in contact with the rear peripheral wall portion  56  of the protector  40 , thereby preventing the tail cover  60  from coming into contact with the muffler  30 . 
     Next, an attachment state of the tail cover to the muffler will be described with reference to  FIGS. 8 to 10 .  FIG. 8  is a right side view of a rear portion of an exhaust device of the comparative example.  FIG. 9A  is a right side view of a rear portion of the exhaust device of the present embodiment, and  FIG. 9B  is a left side view of the rear portion of the exhaust device of the present embodiment.  FIG. 10  is a partial sectional view of the exhaust device of the present embodiment. 
     As shown in  FIG. 8 , the exhaust device of the comparative example is different from the exhaust device of the present embodiment in that a front peripheral wall portion is not formed on a protector  85 . As described above, the protector  85  is fixed to the bracket (not shown) of a muffler  86 . The protector  85  is separated from an outer edge portion  87  of the muffler  86  by the bracket so that heat of the muffler  86  is discharged to the outside. For this reason, a gap C 1  is formed between the protector  85  and the muffler  86 , and appearance of the exhaust device is impaired due to the conspicuous gap C 1 . In this way, in order to discharge the heat of the muffler  86 , the gap C 1  is formed so as to be conspicuous from the outside. 
     On the other hand, as shown in  FIG. 9A , in the exhaust device  21  of the present embodiment, the front peripheral wall portion  58  that fills the gap C 2  between the muffler  30  and the protector  40  is formed on the protector  40 . Since the outer edge portion  33  of the muffler  30  and the front peripheral wall portion  58  of the protector  40  overlap with each other as viewed from the side of the vehicle, the gap C 2  between the muffler  30  and the protector  40  is hidden by the front peripheral wall portion  58 . Although there is the gap C 2  between the muffler  30  and the protector  40 , the front peripheral wall portion  58  makes the gap C 2  between the muffler  30  and the protector  40  inconspicuous from the outside. Therefore, the appearance of the exhaust device  21  is not impaired by the gap C 2  between the muffler  30  and the protector  40 . 
     The front peripheral wall portion  58  is formed excluding the inner side of the protector  40  in the vehicle width direction, and as shown in  FIG. 9B , the gap C 2  between the muffler  30  and the protector  40  is not hidden by the front peripheral wall portion  58  on the inner side in the vehicle width direction. Since the gap C 2  on the inner side in the vehicle width direction, which is the blind spot area, is inconspicuous, even if the gap C 2  is not hidden by the front peripheral wall portion  58 , the appearance of the exhaust device  21  is not impaired. In addition, an increase in weight and cost of the protector  40  is suppressed by an amount that the front peripheral wall portion  58  is not formed on the inner side of the protector  40  in the vehicle width direction. Further, hot air from the muffler  30  can be released to the outside through the gap C 2  on the inner side in the vehicle width direction. 
     As described above, the inner sides of the protector  40  and the tail cover  60  in the vehicle width direction are fixed by the bolts  79 , and the outer sides of the protector  40  and the tail cover  60  in the vehicle width direction are fixed by the snap fits. Therefore, the bolt  79  on the inner side in the vehicle width direction that is the blind spot area is inconspicuous, and the bolt  79  is not used on the outer side in the vehicle width direction that is the exposed area, so that the appearance of the exhaust device  21  is not impaired. In addition, the cost can be reduced by reducing the number of bolts  79  used, and further burden on the worker can be reduced and the assembly property can be improved by reducing the number of fastening portions of the bolts  79 . 
     As shown in  FIG. 10 , on the outer sides of the protector  40  and the tail cover  60  in the vehicle width direction, the claw portion  51  formed on the protector  40  is held by the holding portion  71  formed on the tail cover  60 . The claw portion  51  of the protector  40  is formed in the triangular shape as viewed in the cross section by a flat surface  52  parallel to the rear surface  42  of the plate-like portion  41  and an inclined surface  53  going outward of the plate-like portion  41  as it approaches the rear surface  42  of the plate-like portion  41 . The holding portion  71  of the tail cover  60  is formed in the inverted triangular shape in the cross section by a flat surface  72  parallel to the rear surface  42  of the plate-like portion  41  and a reverse inclined surface  73  going inward of the tail cover  60  as it moves away from the rear surface  42  of the plate-like portion  41 . 
     Therefore, by pressing the tail cover  60  against the protector  40 , the claw portion  51  of the protector  40  is held by the holding portion  71  of the tail cover  60  using elastic deformation of the elastic arm  54  on a base end side of the claw portion  51 . That is, when the inclined surface  53  of the claw portion  51  and the reverse inclined surface  73  of the holding portion  71  abut against each other, the elastic arm  54  is bent and the claw portion  51  is pushed inward by the holding portion  71 . Further, when the outer edge portion  68  of the tail cover  60  abuts against the rear peripheral wall portion  56  of the protector  40 , the pushing of the claw portion  51  by the holding portion  71  is released and the elastic arm  54  returns. Accordingly, the flat surface  52  of the claw portion  51  is locked to the flat surface  72  of the holding portion  71 . 
     The recessed portion  57  is formed on the rear peripheral wall  56  of the protector  40  at the position facing the elastic arm  54 . The through hole is formed on the mating surface of the rear peripheral wall portion  56  of the protector  40  and the outer edge portion  68  of the tail cover  60  by the recessed portion  57 . By inserting the tip end of the tool such as a flathead screwdriver into the through hole and pushing the elastic arm  54  with the tip end of the tool, a locking state of the claw portion  51  and the holding portion  71  is released. The through hole on the mating surface of the protector  40  and the tail cover  60  functions not only as a working hole when the tail cover  60  is removed from the protector  40  but also as the heat discharge hole for releasing the hot air from the muffler  30  to the outside. 
     The through hole  55  is formed in the plate-like portion  41  of the protector  40  at a position facing the flat surface  52  of the claw portion  51 . The through hole  55  is formed in order to prevent the claw portion  51  from being undercut as described above, but the through hole  55  also functions as the heat discharge hole for releasing the hot air from the muffler  30  to the outside. The outer edge portion  33  of the muffler  30  and the front peripheral wall portion  58  of the protector  40  face each other with an gap therebetween. Therefore, the outer edge portion  33  of the muffler  30  does not come into contact with the front peripheral wall portion  58  of the protector  40 , and the heat transferred from the muffler  30  to the protector  40  can be reduced. That is, the protector  40  is not in direct contact with the muffler  30 . 
     There is the gap C 2  between the protector  40  and the muffler  30 , and the hot air from the muffler  30  can be released to the outside through the gap C 2 . Further, there is a gap C 3  between the inner edge portion  62  of the tail cover  60  and the bulging portion  44  of the protector  40 , and the hot air in the tail cover  60  can be released to the outside through the gap C 3 . As described above, contact between the muffler  30 , the protector  40 , and the tail cover  60  is minimized, and the hot air from the muffler  30  is released to the outside through various through-holes or gaps. Therefore, heat damage to the tail cover  60  is effectively suppressed, and the resin material having the low heat resistance temperature can be used for the tail cover  60 . 
     Next, an attachment work of the tail cover to the muffler will be described with reference to  FIGS. 11 and 12 .  FIG. 11  is an explanatory view of an attachment work of the protector to the muffler of the present embodiment.  FIG. 12  is an explanatory view of an attachment work of the tail cover to the protector of the present embodiment. 
     As shown in  FIG. 11 , cushion members  75  are respectively mounted to the openings  45  (see  FIG. 5A ) of the protector  40 . The cushion member  75  is aligned with the bracket  34  on the rear surface  32  of the muffler  30 . The cushion member  75  is so-called H-rubber, and has an opening at a center thereof. The cushion member  75  of the protector  40  is pressed against the bracket  34  of the muffler  30  by passing the tail pipe  31  of the muffler  30  through the opening  45  of the bulging portion  44  of the protector  40 . In this state, the bolt  77  is inserted into the cushion member  75  via a washer (not shown), and the bolt  77  is screwed to the bracket  34 , so that the protector  40  is fixed to the muffler  30 . 
     At this time, only the rear end portion of the tail pipe  31  protrudes from the bulging portion  44  of the protector  40 . In addition, the front peripheral wall portion  58  (see  FIG. 10 ) of the protector  40  is accommodated inside the outer edge portion  33  of the muffler  30 , and the gap C 2  (see  FIG. 10 ) between the muffler  30  and the protector  40  is hidden from a side by the front peripheral wall portion  58 . Since the protector  40  is fixed to the bracket  34  via the cushion member  75 , the bolt  77  is prevented from loosening due to the vibration of the muffler  30 . In addition, since the protector  40  is fixed to the bracket  34  through the cushion member  75  made of the rubber, the heat transferred from the muffler  30  to the protector  40  is suppressed. 
     As shown in  FIG. 12 , when the protector  40  is fixed to the muffler  30 , the tail cover  60  is aligned with the protector  40 . The tail pipe  31  of the muffler  30  is passed through the opening  63  of the tail cover  60 , and the tail cover  60  is pressed against the protector  40 . As a result, the four claw portions  51  of the protector  40  are held by the four holding portions  71  of the tail cover  60  (see  FIG. 10 ), and the outer sides of the protector  40  and the tail cover  60  in the vehicle width direction are fixed. In addition, the pair of fastening holes  67  (see  FIG. 7A ) of the tail cover  60  are aligned with the pair of boss portions  49  of the protector  40 , and the bolts  79  (see  FIG. 9B ) are screwed to the screw holes of the boss portions  49  through the fastening holes  67 , so that the inner sides of the protector  40  and the tail cover  60  in the vehicle width direction are fixed. 
     As described above, exposed sides of the protector  40  and the tail cover  60  are fixed by the snap fits, and blind spot sides of the protector  40  and the tail cover  60  are fixed by the bolts  79 . Therefore, the bolt  79  is not conspicuous, and the appearance of the exhaust device  21  is prevented from being impaired. In addition, since the tail cover  60  is fixed to the muffler  30  via the protector  40 , the heat transferred from the muffler  30  to the tail cover  60  is reduced. Therefore, although the tail cover  60  is formed of the resin material having the low heat resistant temperature, the resin material has the high moldability and can be plated, so that the design property of the tail cover  60  can be improved. 
     As described above, according to the present embodiment, the inner sides of the tail cover  60  and the protector  40  in the vehicle width direction are fixed by the bolt  79 , and the outer sides of the tail cover  60  and the protector  40  in the vehicle width direction are fixed by elastic locking of the claw portion  51  and the holding portion  71 . Since the bolt  79  on the inner side in the vehicle width direction is inconspicuous and the bolt  79  is not used on the outer side in the vehicle width direction, the appearance of the exhaust device  21  is prevented from being impaired. In addition, by reducing the number of the fastening portions of the bolts  79 , the burden on the worker can be reduced, and the assembly property can be improved. 
     In the present embodiment, the holding portion  71  is formed on the outer side of the tail cover  60  in the vehicle width direction, and the claw portion  51  is formed on the outer side of the protector  40  in the vehicle width direction, but the present invention is not limited thereto. The claw portion  51  may be formed on the outer side of one of the protector  40  and the tail cover  60  in the vehicle width direction, and the holding portion  71  may be formed on the outer side of another of the protector  40  and the tail cover  60  in the vehicle width direction. For example, a claw portion may be formed on the outer side of the tail cover  60  in the vehicle width direction, and a holding portion may be formed on the outer side of the protector  40  in the vehicle width direction. 
     In the present embodiment, an elastic locking portion is formed by the elastic arm  54  and the claw portion  51 , but the present invention is not limited thereto. The elastic locking portion may be any configured as long as the protector  40  and the tail cover  60  can be elastically locked. 
     In the present embodiment, a configuration is limited in which the protector  40  and the tail cover  60  are formed of the resin material, but the present invention is not limited thereto. The protector  40  may be formed of any material as long as the material has a higher heat resistance temperature and lower thermal conductivity than the tail cover  60 . 
     In the present embodiment, the front peripheral wall portion  58  of the protector  40  is formed along the inner peripheral surface of the outer edge portion  33  of the muffler  30  excluding the inner side in the vehicle width direction, but the present invention is not limited thereto. The front peripheral wall portion  58  of the protector  40  may be formed along the entire circumference of the inner peripheral surface of the outer edge portion  33  of the muffler  30 . 
     In the present embodiment, the protector  40  is fastened to the tail cover  60  by the bolt  79  as the fastening member, but the present invention is not limited thereto. The fastening member may be any member as long as the member can fasten the tail cover  60  to the protector  40 , and may be a rivet, for example. 
     In the present embodiment, the through hole  55  is formed in the protector  40  in order to prevent the claw portion  51  from being undercut when the protector  40  is formed by the mold, but the present invention is not limited thereto. When the protector  40  is formed by the mold, the through hole  55  may not be formed in the protector  40  using the slide mold  83  or the like. 
     In the present embodiment, the recessed portion  57  is formed on the rear peripheral wall portion  56  of the protector  40 , but the present invention is not limited thereto. The recessed portion  57  may be formed on at least one of the protector  40  and the outer edge portion  68  of the tail cover  60  as long as it is formed on the mating surfaces of the protector  40  and the outer edge portion  68  of the tail cover  60 . For example, the recessed portion may be formed on the outer edge portion  68  of the tail cover  60 , or the recessed portion may be formed in both the rear peripheral wall portion  56  of the protector  40  and the outer edge portion  68  of the tail cover  60 . In the present embodiment, the pair of upper and lower tail pipes  31  protrude from the muffler  30 , but the present invention is not limited thereto. A single tail pipe  31  may protrude from the muffler  30 . In this case, the tail cover  60  may be formed in any manner as long as it covers a periphery of the single tail pipe  31 . 
     The exhaust device  21  of the present embodiment can be appropriately applied to other vehicles on which the muffler  30  is disposed. 
     According to the present embodiment as described above, an exhaust device ( 21 ) in which a muffler is disposed on a side of a straddle-type vehicle (motorcycle  1 ), the exhaust device including: the muffler ( 30 ) including a tail pipe ( 31 ) configured to discharge exhaust gas and protruding rearward; a tail cover ( 60 ) covering a periphery of the tail pipe behind the muffler; and a protector ( 40 ) for heat shield interposed between the muffler and the tail cover, wherein inner sides of the tail cover and the protector in a vehicle width direction are configured to be fixed to each other by a fastening member (bolt  79 ), and wherein an elastic locking portion (claw portion  51 ) is formed on an outer side of one of the tail cover and the protector in the vehicle width direction, and a holding portion ( 71 ) holding the elastic locking portion is formed on an outer side of another of the tail cover and the protector in the vehicle width direction. According to this configuration, the inner sides of the tail cover and the protector in the vehicle width direction are fixed by the fastening member, and the outer sides of the tail cover and the protector in the vehicle width direction are fixed by elastic locking of the elastic locking portion and the holding portion. Since the fastening member on the inner side in the vehicle width direction is inconspicuous, and the fastening member is not used on the outer side in the vehicle width direction, appearance of the exhaust device is prevented from being impaired. In addition, by reducing the number of fastening positions of the fastening members, burden on a worker can be reduced, and an assembly property can be improved. 
     The exhaust device according to the present embodiment, wherein an outer edge portion ( 33 ) of the muffler extends rearward of the vehicle from a rear surface ( 32 ) of the muffler, and a peripheral wall portion (front peripheral wall portion  58 ) protrudes from a front surface ( 43 ) of the protector along an inner peripheral surface of the outer edge portion of the muffler, and wherein the outer edge portion of the muffler and the peripheral wall portion of the protector overlap as viewed from a side of the vehicle. According to this configuration, since the outer edge portion of the muffler overlaps with the peripheral wall portion of the protector, a gap (C 2 ) between the muffler and the protector is hidden by the peripheral wall portion. The appearance of the exhaust device is not impaired by the gap between the muffler and the protector. 
     The exhaust device according to the present embodiment, wherein the outer edge portion of the muffler and the peripheral wall portion of the protector face each other with a gap therebetween. According to this configuration, since there is the gap between the outer edge portion of the muffler and the peripheral wall portion of the protector, heat transferred from the muffler to the tail cover can be reduced via the protector, and heat damage to the tail cover can be suppressed. 
     The exhaust device according to the present embodiment, wherein the peripheral wall portion of the protector is formed along the outer edge portion of the muffler excluding an inner side of the muffler in the vehicle width direction. According to this configuration, since the gap between the muffler and the protector on the inner side in the vehicle width direction is inconspicuous, the appearance of the exhaust device is not impaired even if the gap is not hidden by the peripheral wall portion. In addition, an increase in weight and cost of the protector is suppressed by an amount that the front peripheral wall portion is not formed on the inner side of the protector in the vehicle width direction. Further, hot air from the muffler can be released to the outside through the gap on the inner side in the vehicle width direction. 
     The exhaust device according to the present embodiment, wherein the elastic locking portion is formed on the protector, and the holding portion is formed on the tail cover. According to this configuration, the tail cover can be fixed to the protector by holding the elastic locking portion of the protector on the holding portion of the tail cover. 
     The exhaust device according to the present embodiment, wherein the elastic locking portion includes an elastic arm ( 54 ) erected on a rear surface of the protector and a claw portion ( 51 ) formed at a tip end of the elastic arm. According to this configuration, the tail cover can be fixed to the protector by a snap fit between the claw portion at the tip end of the elastic arm and the holding portion. 
     The exhaust device according to the present embodiment, wherein the protector is formed with a through hole ( 55 ) on a projection surface obtained by projecting the claw portion onto the rear surface ( 42 ) of the protector. According to this configuration, the claw portion is prevented from being undercut when the protector is released from a mold. Therefore, a structure of the mold can be simplified, and the cost can be reduced. In addition, the hot air from the muffler can be released to the outside through the through hole. 
     The exhaust device according to the present embodiment, wherein at least one of mating surfaces of the protector and an outer edge portion of the tail cover is formed with a recessed portion ( 57 ) at a position facing the elastic arm. According to this configuration, a through hole into which a tool can be inserted is formed in the mating surfaces of the protector and the tail cover by the recessed portion on the mating surfaces of the protector and the tail cover. By inserting the tool into the through hole and pushing the elastic arm, the elastic locking of the claw portion and the holding portion can be released. In addition, the hot air from the muffler can be released to the outside through the recessed portion. 
     The exhaust device according to the present embodiment, wherein the tail cover is formed of an acrylonitrile butadiene styrene (ABS) resin, and the protector is formed of a nylon resin. According to this configuration, by forming the protector with the nylon resin having high heat resistance, the tail cover can be formed with the ABS resin having low heat resistance. Since the ABS resin has high moldability and can be plated, a design property of the exhaust device can be improved. 
     A straddle-type vehicle according to the present embodiment including: the exhaust device described above. According to this configuration, it is possible to reduce work burden when the exhaust device is assembled and improve the design property of the straddle-type vehicle. 
     Although the present embodiment has been described, as another embodiment, a power source of the motorcycle is an engine, but an electric motor may be used as the power source. In addition, the above embodiments and modifications may be combined in whole or in part. 
     The technique of the present invention is not limited to the above embodiments, and various changes, substitutions, and modifications may be made without departing from the spirit of the technical idea. Further, the present invention may be implemented by using other methods as long as the technical idea of the present invention can be realized by the methods through progress of the technique or other derivative technology. Accordingly, claims cover all embodiments that may be included within the scope of the technical ideas. 
     According to the exhaust device of the aspect of the present invention, the inner sides of the tail cover and the protector in the vehicle width direction are fixed by the fastening member, and the outer sides of the tail cover and the protector in the vehicle width direction are fixed by elastic locking of the elastic locking portion and the holding portion. Since the fastening member on the inner side in the vehicle width direction is inconspicuous, and the fastening member is not used on the outer side in the vehicle width direction, appearance of the exhaust device is prevented from being impaired. In addition, by reducing the number of fastening positions of the fastening members, burden on a worker can be reduced, and an assembly property can be improved.