Abstract:
A band-like member which is made to wrap on an outer periphery of an exhaust pipe is interposed between the exhaust pipe and a heat insulator covering the exhaust pipe. Both end portions of the band-like member in the length direction and attaching portions formed at a pair of edge portions along the length direction of the heat insulator oppose each other and overlap each other. These members are fastened together by a bolt and nut, which have interposed therebetween a collar to ensure proper separation of ends of the band-like member and heat insulator.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a structure for attaching a heat insulator to an exhaust pipe of a vehicle. 
     2. Background Art 
     It is known to attach a heat insulator to an exhaust pipe. For example, Japanese Patent Publication No. 26045/1990 discloses an exhaust pipe and heat insulator construction in which a stay is welded to the exhaust pipe, a band-like member is welded to an inner side of the heat insulator and the band-like member is fastened to the stay by a screw. Further, it is also known that a nut may be directly welded to an exhaust pipe in place of the stay, and a band-like member is directly fastened thereto by a screw. 
     According to the conventional examples, members to be attached to an exhaust pipe must be welded to both of the exhaust pipe and the heat insulator, or at least any members must be welded on the side of the exhaust pipe. Accordingly, the number of fabrication steps is increased, therefore, resulting in significant manufacturing costs. Further, in the case where the heat insulator is directly fastened to a nut on the exhaust pipe by the screw, an accuracy of a weld position is liable to deteriorate by thermal influence in welding the nut. Therefore, positioning of the heat insulator relative to the exhaust pipe becomes difficult and an assembly operation may be difficult. In addition, to facilitate attachment of the heat insulator, it is conceivable to constitute a screw hole on a side of the heat insulator; however, vibration noise is liable to occur since the exhaust pipe inherently constitutes a vibration source. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a structure of attaching a heat insulator dispensing with welding operation. 
     In order to solve the above-described problem, according to a first aspect of the present invention, there is provided a structure of attaching a heat insulator to an exhaust pipe. The structure includes a band-like member made to wrap on an outer periphery of the exhaust pipe and the heat insulator for covering the exhaust pipe from an outer side thereof. Both end portions in a length direction of the band-like member and a pair of edge portions of the heat insulator along a length direction of the exhaust pipe are simultaneously coupled to thereby attach the heat insulator to the exhaust pipe via the band-like member. 
     According to a second aspect of the present invention, there is provided the structure of attaching a heat insulator according to the first aspect, where attaching portions are integrally provided respectively to the pair of edge portions of the heat insulator along the length direction thereof. The attaching portions on a side of the heat insulator are made to overlap on outer sides of a pair of attaching portions provided at the both end portions in the length direction of the band-like member. The respective attaching portions on the side of the heat insulator and on a side of the band-like member are integrally coupled by a bolt and a nut in a state in which a collar is interposed between the attaching portions on the side of the band-like member. 
     According to the first aspect of the present invention, when the band-like member is firstly made to wrap on the outer periphery of the exhaust pipe, the heat insulator is further made to cover the band-like member from an outer side thereof, and both end portions in the length direction of the band-like member and the pair of edge portions of the heat insulator along the length direction of the exhaust pipe are made to overlap to thereby integrally couple with each other. Moreover, the band-like member is made to wrap and fixed onto a surrounding of the exhaust pipe and the heat insulator is coupled to the band-like member. Therefore, the heat insulator is attached to the exhaust pipe via the band-like member. 
     Therefore, welding attaching members to the heat insulator and the exhaust pipe as in the conventional structure is not required. The band-like member can be made separate from the heat insulator and the exhaust pipe until the attaching operation. Accordingly, the conventional welding process is eliminated, therefore, reducing the number of fabrication steps in assembling the heat insulator and the exhaust pipe. This results in enhanced fabrication performance and enables a reduction in manufacturing costs. 
     Moreover, by eliminating the welding operation, a deterioration in accuracy at the attaching portion caused by welding can be prevented. Moreover, according to the present invention the requirement of providing a screw hole in the heat insulator is eliminated; therefore, vibration as a result of the exhaust pipe does not occur. 
     According to the second aspect of the present invention, when the attaching portions are respectively provided at the both end portions in the length direction of the band-like member and the pair of edge portions of the heat insulator along the length direction of the exhaust pipe, the attaching members are made to overlap each other and fastened together by the bolt and the nut in a state in which the collar is interposed between the attaching portions on the side of the band-like member, thus, the heat insulator can easily be integrated to the exhaust pipe. In this case, by interposing the collar, the attaching portions can easily be attached even when there is deviation in accuracy of a dimension between the respective attaching portions. 
     Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention are given by way of illustration only, since various changes and modifications within the sprit and scope of the invention will become apparent to those skilled in the art from this detailed description. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus are not imitative of the present invention, and wherein: 
     FIG. 1 is a perspective view of a heat insulator according to an embodiment of the present invention; 
     FIG. 2 is a side view of a four wheel vehicle; 
     FIG. 3 is a side view of specific portions of the four wheel vehicle body; 
     FIG. 4 is a perspective view of particular portions of the four wheel body; 
     FIG. 5 is a perspective view of an exhaust pipe having a heat insulator attached thereto according to an embodiment of the present invention; 
     FIG. 6 is a cross-sectional view taken along a line  6 — 6  of FIG. 5; 
     FIG. 7 is a side view illustrating an arrangement of an exhaust pipe and portions of an intake system according to an embodiment of the present invention; and 
     FIG. 8 is a plan view illustrating an arrangement of an exhaust pipe and portions of an intake system according to an embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The present invention will hereinafter be described with reference to an embodiment shown in the drawings. The drawings refer to a four wheel vehicle, however the use of such a vehicle type is for illustrative purposes only, and should not be construed as limiting of the present invention. The present invention may be employed on various vehicle types. 
     FIG. 1 is a perspective view of a heat insulator according to an embodiment of the present invention; FIG. 2 is a side view of a four wheel vehicle; FIG. 3 is a side view of specific portions of the four wheel vehicle body; and FIG. 4 is a perspective view of particular portions of the four wheel body. 
     According to the buggy vehicle, pairs of front wheels  2  and rear wheels  3  comprising low pressure balloon tires are supported respectively on a left and right sides of a front and a rear portion of a vehicle body frame  1 . The body frame  1  is driven by a power unit  4  mounted at a central portion of the vehicle body frame  1 . The body frame  1  also includes a front cushion  5  and a rear cushion  6 . 
     Reference numeral  7  in FIG. 2 designates a front fender,  8  designates a sub fender, and  9  designates a rear fender. Furthermore,  10  designates a front panel,  11  designates a steering shaft,  12  designates a handlebar,  13  designates a fuel tank,  14  designates a saddle riding type seat,  15  designates a rear panel,  16  designates a cooling unit and  17  designates a muffler. Additionally, reference numberal  18  in FIG. 3 designates an air cleaner,  19  designates a snorkel duct and  20  designates a carburetor. 
     Next, an explanation will be given of structure of the vehicle body frame  1 . As shown by FIGS. 3 and.  4 , the vehicle frame  1  is provided with respective left and right pairs of upper pipes  30  extended in a front and rear direction substantially in parallel with each other and in a linear shape. The vehicle frame  1  is also provided with front pipes  31  being extended in an up and down direction from front end portions thereof, lower pipes  32  being extended in a rear direction from lower end portions thereof and center pipes  33  extended in an upper direction from rear end portions thereof and connected to positions shifted rearward from middle portions of the upper pipe  30 . 
     Moreover, the vehicle body frame  1  is provided with respective left and right pairs of reinforcement pipes  34  connected from front end portions of the upper pipes  30  to front half side portions of the lower pipes  32  in an oblique direction. Middle pipes  35  are connected to respective middle portions of the reinforcement pipes  34  and the front pipes  31  in the front and rear direction. The vehicle body frame also includes reinforcement pipes  36  and  37  which are connected to middle portions of the center pipes  33 , and a cross member  40 , cross pipes  41  and  42  and cross members  43 ,  44 ,  45 ,  46  and the like are respectively made to span left and right members of the vehicle body frame  1 . Each of the described members constitute the vehicle body frame  1  and are connected and integrated together to form the vehicle shown in FIGS. 2-4. 
     The cross member  40  is provided between front end portions of the upper pipes  30  and is connected with the cross pipe  41 , which is arranged on a rear side thereof. The cross member  40  and the cross pipe  41  are in parallel and are separated by head portion pipes  47  formed in a shape of a mountain in side view in the front and rear direction. An upper portion of the steering shaft  11  is rotatably supported by a stay  48  provided at top portions of the head portion pipes  47 . A lower end portion of the steering shaft  11  is axially supported by a bearing portion provided at the middle pipes  35 . 
     Furthermore, an upper end portion of the front cushion  5  is supported by both left and right ends of the cross member  40  and a lower end portion of the front cushion  5  is attached to upper arms constituting a front wheel suspension of a double wishbone type (not illustrated). The upper arms are pivotably supported by the middle pipes  35  and lower arms paired therewith are pivotably supported by front end portions of the lower pipes  32 . 
     Pivot plates  50  are provided at corner portions of lower portions of the center pipes  33  and rear ends of the lower pipes  32  and front end portions of rear swing arms  51  are pivotably supported thereby. The rear swing arm  51  contains a drive shaft constituting a rear wheel drive mechanism. The upper pipes  30  are extended further rearward from portions thereof and are connected with the center pipes  33 . An upper end portion of the rear cushion  6  is supported by stays  52 , and the muffler  17  is supported by another stay  53 . 
     An exhaust pipe  21 , a rear end portion of which is connected to the muffler  17 , is extended in the front direction substantially in a linear shape and a front end portion thereof is bent substantially in a U-like shape and is connected to an exhaust port provided at a cylinder head of the power unit  4 . Furthermore, the cooling unit  16  is hung from and supported by the upper pipes  30  on a front side of the power unit  4 . The cooling unit  16  is integrated with an oil cooler  22  and a cooling fan  23 . Reference numeral  24  designates a motor thereof, and reference numerals  25  and  26  designate hoses connected to the power unit  4 . 
     Furthermore, steps  54  extended to outer sides are provided at portions of the left and right lower pipes  32  for mounting the power unit  4 . The steps  54  are protruded from the lower pipes  32  in outer side directions, step frames  55  are bent to connect front ends thereof and the lower pipes  32  and the sub fender  8  are mounted on and attached to these members (the sub fender  8  on the right side of the vehicle body is not illustrated). 
     Next, an explanation will be given of a heat shielding structure of an exhaust pipe according to the present invention. FIG. 1 is a drawing showing an exhaust pipe  21  in a state attached with a heat insulator  60  from inside of a vehicle body, FIG. 5 is a drawing showing the exhaust pipe  21  from an opposite side, that is, from outside of the vehicle body and FIG. 6 is a cross-sectional view taken along a line  6 — 6  of FIG.  5 . 
     As shown by these drawings, the heat insulator  60  is constituted by a metal or the like having heat resistance and heat insulating performance to some degree. The heat insulator  60  covers an outer periphery of the exhaust pipe  21  in a range of about ¾ turn while maintaining a pertinent interval therebetween, and covers the exhaust pipe  21  substantially over an entire length thereof (refer to FIG.  1  and FIG.  6 ). 
     A pair of edge portions  61  of the heat insulator  60  along a length direction thereof, is integrally formed with attaching portions  62  to be opposed to each other at pertinent intervals in the length direction thereof. The attaching portions  62  are formed with through holes  63 . Band-like members  64  are interposed between the heat insulator  60  and the exhaust pipe  21  on inner sides of positions of the heat insulator  60  provided with the attaching portions  62  (see FIG.  6 ). 
     The band-like member  64  is the member comparatively rich in elasticity in a strip-like shape comprising a pertinent material of a leaf spring or the like made of a metal. The band-link member  64  is similarly made to wrap around the outer peripheral portion of the exhaust pipe  21  in the range of about a ¾ turn, and both end portions  65  thereof in the length direction of the band-like member  64  are bent to overlap the attaching portions  62  of the edge portions opposed thereto and formed with through holes  66  coinciding with the through holes  63 . 
     Collars  67  are arranged between the left and right through holes  66  and when the through holes  63 , the through holes  66  and the collars  67  are coaxially arranged, bolts  68  are inserted therethrough from the through holes  63  on one side and fastened with nuts  69  on other side. Therefore, the heat insulator  60  is attached to the exhaust pipe  21  via the band-like members  64 . 
     That is, by fastening the left and right both end portions  65  in the length direction by the bolts  68  and the nuts  69  while interposing the collars  67  therebetween, the band-like members  64  are fixed in a state in which the band-like members  64  are made to overlap the outer periphery of the exhaust pipe  21 . 
     At the same time, the left and right attaching portions  62  are brought into close contact with and integrated to the left and right both end portions  65  in the length direction by the bolts  68  and the nuts  69  and accordingly, the heat insulator  60  is attached to the outer periphery of the exhaust pipe  21  while maintaining a predetermined interval therebetween. 
     Next, an explanation will be given of a structure of arranging exhaust pipe  21  and parts of an intake system. FIG. 7 is a drawing illustrating an arrangement of these parts from a side of the vehicle body and FIG. 8 is a drawing illustrating the arrangement from a plan view. 
     As illustrated by these drawings, the exhaust pipe  21  passes above a crank case  70  constituting the power unit  4  substantially linearly in the front and rear direction and a front end portion thereof is connected to an exhaust port provided at a cylinder head  71  of the power unit  4 . 
     A rear portion of the exhaust pipe  21  partially overlaps a side portion of the air cleaner  18  and thereafter is bent to an outer side and connected to the muffler  17 . On the upper side of the exhaust pipe  21 , a connecting tube  72  is extended in the rear direction from an intake port of the cylinder head  71  via the carburetor  20  and is connected to substantially a central portion of a front face of the air cleaner  18 . 
     A rear end of the snorkel type duct  19  is connected to the front face of the air cleaner  18  side by side with the connecting tube  72  and a connecting portion thereof is deviated to the side of the exhaust pipe  21 . The snorkel type duct  19  is extended to a front side of the cylinder head  71  above the exhaust pipe  21 , and a front end portion thereof is opened in a side direction to overlap a rear face of the fuel tank  13 , which is disposed at a position higher than the muffler  17  and can intake air even when the lower portion of the vehicle body is sunk in water. 
     Moreover, there is arranged a blowby gas returning hose  73  from a vicinity of the connecting portion of the snorkel type duct  19  connected to the front face of the air cleaner  18  in the front and rear direction substantially side by side with the snorkel duct  19  respectively, and a front end portion thereof is connected to a valve  74  on the front side of the cylinder head  71 . A blowby gas flow-in hose  75  is extended from the valve  74  in the rear direction and connected to the cylinder head  71 . 
     The snorkel type duct  19  and the blowby gas returning hose  73  are arranged to substantially overlap the exhaust pipe  21  in a range of from the air cleaner  18  to the cylinder head  71 . Moreover, an opening portion formed between the pair of edge portions  61  along the length direction of the heat insulator  60  is directed to the inner side of the vehicle body in an oblique lower direction. 
     Therefore, although the exhaust pipe  21  is arranged such that radiation heat thereof is liable to effect thermal influence directly on the parts of the intake system such as the air cleaner  18  and the snorkel type duct  19  and the blowby gas returning hose  73  or the like, the concern of the thermal influence can be reduced by the heat insulator  60 . 
     That is, the rear portion of the heat insulator  60  overlaps substantially the side face of the air cleaner  18 , and the front end portion covers substantially the entire length of the exhaust pipe  21  extended to a vicinity of the exhaust port. An opening portion formed between the pair of edge portions  61  of the heat insulator  60  is directed to the inner side of the vehicle body and in the oblique lowered direction; therefore, the radiation heat of the exhaust pipe  21  is prevented from directly influencing various parts of the intake system such as the air cleaner  18 , the snorkel type duct  19  and the like and the blowby gas returning hose  73  or the like by the heat insulator  60 . 
     Next, an explanation will be given of operation of an embodiment according to the present invention. When the band-like members  64  are made to overlap the outer periphery of the exhaust pipe  21 , the heat insulator  60  is made to cover the band-like members  64  from outer sides thereof. The both end portions  65  of the band-like members  64  in the length direction and the pairs of attaching portions  62  provided at the pairs of edge portions  61  of the heat insulator  60  along the length direction of the exhaust pipe  21 , are made to overlap each other, the through holes  66  and  63  respectively formed thereto are made to coincide with each other and the heat insulator  60 , the heat insulator  60  and the band-like members  64  are fastened together by the bolts  68  and the nuts  69 . The collars  67  are interposed between the both end portions  65  of the band-like members  64  in the length direction, thereby, the heat insulator  60  can be integrated to the exhaust pipe  21  easily and firmly. 
     Accordingly, there is no need to weld the attaching members to the heat insulator  60  and the exhaust pipe  21  as in the conventional structure. The band-like members  64  are separate from the heat insulator  60  and the exhaust pipe  21  until the attaching operation and therefore, the conventional welding process is dispensed with. The number of fabrication steps of the heat insulator  60  and the exhaust pipe  21  are respectively reduced to thereby reduce manufacturing steps and increase cost saving during the manufacturing process. Furthermore, by using the interposing collars  67 , the attaching operation can be carried out easily even when there is deviation in the accuracy of dimensions between the attaching portions. 
     The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claim.