Patent Publication Number: US-8978819-B2

Title: Spark arrestor, muffler, and straddle type vehicle

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a spark arrestor, a muffler, and a straddle type vehicle. 
     2. Description of the Related Art 
     In a straddle type vehicle, such as an ATV (All-Terrain Vehicle) or the like, a spark arrestor that prevents spark discharges to the outside may be provided in a muffler connected to an exhaust pipe of an engine. 
     Japanese Patent Laid-Open Publication 2003-184541 discloses a technique for performing expansion and contraction of exhaust in a spark arrestor that is mounted to straddle a plurality of expansion chambers provided in a muffler. This technique, however, may lead to a spark arrestor and a muffler that are undesirably large in size in the axial direction thereof. 
     SUMMARY OF THE INVENTION 
     In view of the problems described above, preferred embodiments of the present invention provide a spark arrestor, a muffler, and a straddle type vehicle that are small in size while improving the exhaust sound reduction capability and the spark prevention capability. 
     A spark arrestor according to a preferred embodiment of the present invention is mounted to a muffler connected to an exhaust pipe of an engine and includes a cylindrical portion including an opening therein that extends therethrough from an outside to an inside thereof, two caps that respectively close first and second ends of the cylindrical portion, a mesh portion that covers the opening, and a tail pipe extending from the inside to the outside of the cylindrical portion, wherein the exhaust flows outside the cylindrical portion in a first direction along an axis of the cylindrical portion, and the exhaust flows in a channel of the cylindrical portion in a second direction opposite to the first direction. 
     A further preferred embodiment of the present invention provides a muffler including the above-described spark arrestor. 
     An additional preferred embodiment of the present invention provides a straddle type vehicle including the above-described muffler. 
     According to a preferred embodiment of the present invention, a channel where exhaust flows in the opposite direction is provided inside the cylindrical portion making it possible to ensure a longer length for the entire exhaust channel from the opening of the cylindrical portion to the outlet of the tail pipe, and also to reduce the flow speed of the exhaust in an area where the exhaust flow is bent. As a result, it is possible to reduce the size of the spark arrestor and the muffler while improving the exhaust sound reduction capability and the spark prevention capability. 
     The above and other elements, features, steps, characteristics and advantages of the present invention will become more apparent from the following detailed description of the preferred embodiments with reference to the attached drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side view of a straddle type vehicle according to a preferred embodiment of the present invention. 
         FIG. 2  is a cross-sectional view of a muffler according to a preferred embodiment of the present invention. 
         FIG. 3  is a cross-sectional view of a muffler according to another preferred embodiment of the present invention. 
         FIG. 4  is a perspective view of a spark arrestor according to a preferred embodiment of the present invention. 
         FIG. 5  is a cross-sectional view of a spark arrestor according to a preferred embodiment of the present invention. 
         FIG. 6  is a cross-sectional view of a spark arrestor according to another preferred embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Preferred embodiments of the present invention will be described with reference to the drawings. 
       FIG. 1  is a side view of a straddle type vehicle  1  according to a preferred embodiment of the present invention. The arrow F in the diagram indicates the forward direction. The straddle type vehicle  1  in the present preferred embodiment is, for example, an ATV (All Terrain Vehicle), which is preferred for running on uneven ground. However, not being limited to the above, the straddle type vehicle  1  may be a motorcycle or the like, for example. 
     A pair of front wheels  2  spaced apart from each other in the left-right direction are mounted to a lower front portion of the straddle type vehicle  1 , while a pair of rear wheels  3  spaced apart from each other in the left-right direction are mounted to a lower rear portion of the straddle type vehicle  1 . A handle bar  4  for a driver to operate is mounted in an upper front portion of the straddle type vehicle  1 . A seat  5  for a driver to straddle is mounted on an upper rear portion of the straddle type vehicle  1 . 
     A muffler  6  according to a preferred embodiment of the present invention is mounted to a rear lateral portion of the straddle type vehicle  1 . The muffler  6  is connected to the rear end portion of an exhaust pipe  59  extending rearward from an engine (not shown). In the present preferred embodiment, the muffler  6  preferably is positioned on the left side of the straddle type vehicle  1 , for example. 
       FIG. 2  is a cross-sectional view of the muffler  6  according to a preferred embodiment of the present invention.  FIG. 2  shows a cross-sectional structure of the muffler  6  sectioned along the up-down direction passing through the central axis of the muffler  6 . The arrow A in  FIG. 2  indicates the directions along the center axis of the muffler  6  and the spark arrestor  7 . 
     The muffler  6  includes an outer cylindrical member  61 , an inner cylindrical member  62 , and glass wool  63 , in which the inner cylindrical member  62  has a diameter slightly smaller than that of the outer cylindrical member  61  and is mounted on the inner side of the outer cylindrical member  61 , and the glass wool  63  is sandwiched between the outer cylindrical member  61  and the inner cylindrical member  62 . The outer cylindrical member  61  and the inner cylindrical member  62  are fixed to each other by an annular fastening member  64 . Numerous small holes are provided in the inner cylindrical member  62  so that the exhaust inside the muffler  6  is exposed to the glass wool  63 . 
     The front ends of the outer cylindrical member  61  and the inner cylindrical member  62  are covered by a cap member  65 . The exhaust pipe  59  extends through the cap member  65  to the inside of the muffler  6 . The rear ends of the outer cylindrical member  61  and the inner cylindrical member  62  are covered by a cap member  66 . A spark arrestor  7  according to a preferred embodiment of the present invention is removably mounted to the cap member  66 . A specific structure of the spark arrestor  7  will be described below. 
     A plurality of partition members  67 ,  68  spaced apart from each other in the front-back direction are fixed to the inner circumferential surface of the inner cylindrical member  62 . The space inside the muffler  6  is sectioned into a plurality of expansion chambers  6 A to  6 C by these partition members  67 ,  68 . In the present preferred embodiment, three expansion chambers  6 A to  6 C are defined by the two partition members  67 ,  68 . These include a first expansion chamber  6 A, a second expansion chamber  6 B, and a third expansion chamber  6 C, in order, from the front. 
     The rear end portion of the exhaust pipe  59  is arranged inside the first expansion chamber  6 A so that exhaust is discharged from the exhaust pipe  59  into the first expansion chamber  6 A. 
     A catalyst pipe  60  that holds a catalyst is mounted in the partition member  67  between the first expansion chamber  6 A and the second expansion chamber  6 B. The exhaust in the first expansion chamber  6 A passes to the second expansion chamber  6 B through the catalyst pipe  60 . Thus, the exhaust is purified by the catalyst held in the catalyst pipe  60 . 
     Communicating holes (not shown) are provided in the partition member  68  between the second expansion chamber  6 B and the third expansion chamber  6 C. The exhaust in the second expansion chamber  6 B passes to the third expansion chamber  6 C through these communicating holes. 
     The spark arrestor  7  is mounted inside the third expansion chamber  6 C. The exhaust in the third expansion chamber  6 C passes inside the spark arrestor  7  to be discharged to the outside from the tail pipe  76 . 
     The exhaust discharged from the exhaust pipe  59  to the inside of the muffler  6  flows mainly in a direction toward the rear cap member  66 , among the two directions indicated by the arrow A, along the central axis of the muffler  6 . 
     In  FIG. 2 , the main direction in which the exhaust flows inside the third expansion chamber  6 C is indicated by the arrow having an alternate long and short dashed line. The exhaust in the third expansion chamber  6 C flows mainly toward the opening  7   a  along the outer surface of the cylindrical member  71  of the spark arrestor  7 . 
     Note that the muffler  6  is not limited to the above mentioned preferred embodiment.  FIG. 3  is a cross-sectional view of a muffler  6  according to another preferred embodiment of the present invention. The structure that is similar to that described above is given the same reference numerals, and detailed description thereof is partly omitted. 
     In the present preferred embodiment, the catalyst pipe  60  is mounted in the rear end portion of the exhaust pipe  59 . The exhaust from the exhaust pipe  59  passes through and is purified in the catalyst pipe  60 , and is discharged into the first expansion chamber  6 A. 
     In the present preferred embodiment, two expansion chambers  6 A,  6 B are defined by one partition member  67 . The exhaust in the first expansion chamber  6 A passes through the communication cylinder  69  mounted in the partition member  67  to the second expansion chamber  6 B where the spark arrestor  7  is mounted. 
     The mufflers  6  shown in  FIGS. 2 and 3  each include the spark arrestor  7  according to a preferred embodiment of the present invention. The spark arrestor  7  is superior in the exhaust sound reduction capability, as described below. Therefore, in the muffler  6  including the spark arrestor  7 , it is possible to simplify and reduce the size of the structure upstream of the spark arrestor  7 . 
       FIGS. 4 and 5  are a perspective view and a cross-sectional view, respectively, of the spark arrestor  7  according to a preferred embodiment of the present invention.  FIG. 5  shows a cross-sectional structure of the spark arrestor  7  sectioned in the up-down direction passing through the central axis. That is,  FIG. 5  is an enlarged diagram of the spark arrestor  7  shown in  FIG. 2 . The arrow A in  FIG. 5  indicates the directions along the central axis of the muffler  6  and the spark arrestor  7 , similar to the arrow A in  FIG. 2 . 
     The spark arrestor  7  includes a cylindrical member  71  and two cap members  73 ,  74  that respectively cover both ends of the cylindrical member  71 . Below, of the two directions along the central axis of the spark arrestor  7  indicated by the arrow A, the direction toward the cap member  74  relative to the cylindrical member  71  is referred to as a “first direction”, while the direction toward the cap member  73  relative to the cylindrical member  71  is referred to as “a second direction”. 
     A plurality of rectangular or substantially rectangular openings  7   a  provided in the cylindrical member  71  are arranged along the circumferential direction thereof. In the present preferred embodiment, three openings  7   a , for example, are arranged in the circumferential direction preferably having an equidistant interval. The length of the opening  7   a  along the central axis of the spark arrestor  7  is half or substantially half of the length of the cylindrical member  71 , for example. In the present preferred embodiment, the opening  7   a  is located at a position closer to the end of the cylindrical member  71  in the second direction than the end in the first direction. 
     The spark arrestor  7  further includes a cylindrical mesh member  72  covering each opening  7   a  in the cylindrical member  71 . The cylindrical mesh member  72  is wound around the outer surface of the cylindrical member  71  and covers all of the openings  7   a . The cylindrical mesh member  72  is made of, for example, a metal mesh or the like made by crossing metal wires so as to provide sufficiently small mesh relative to the opening  7   a . Note that the mesh is not shown in  FIGS. 4 and 5 . 
     The spark arrestor  7  further includes a tail pipe  76  extending from the inside to the outside of the cylindrical member  71  through the cap member  74 . The inlet  76   a  of the tail pipe  76 , located inside the cylindrical member  71 , is positioned closer to the cap member  73  in the second direction. Specifically, the inlet  76   a  of the tailpipe  76  is positioned farther in the second direction than the opening  7   a  of the cylindrical member  71 . Further, the tail pipe  76  is preferably bent downward outside of the cylindrical member  71  with the outlet  76   b  thereof directed downward. 
     The cap member  74  includes a flange portion  741  having a diameter larger than that of the cylindrical member  71 , and an inner circumferential portion  743  positioned on an inner circumferential side of the flange portion  741  and bent toward the second direction in a stepwise manner and inserted into the cylindrical member  71 . The flange portion  741  is fixed to the cap member  66  of the muffler  6  (see  FIG. 2 ), and the inner circumferential portion  743  is fixed to the tail pipe  76 . Further, an annular supporting member  75  is fixed in the space between the inner circumferential portion  743  and the tail pipe  76 . 
     The spark arrestor  7  further includes a guide member  77  mounted inside the cylindrical member  71 . The guide member  77  includes a large diameter portion  772  having a diameter that is equal or substantially equal to that of the cylindrical member  71 , and a small diameter portion  774  having a diameter smaller than that of the cylindrical member  71  but larger than that of the tail pipe  76 . The large diameter portion  772  is fixed to the inner circumferential surface of the cylindrical member  71  at a position farther in the second direction than the opening  7   a . The small diameter portion  774  extends from the large diameter portion  772  in the first direction and extends across the shortest path between the opening  7   a  and the inlet  76   a  of the tail pipe  76 . Specifically, the tip end  77   a  of the small diameter portion  774  is positioned farther in the first direction than the opening  7   a.    
     In  FIG. 5 , a main direction in which the exhaust flows outside and inside the spark arrestor  7  is indicated by the alternate long and short dashed line. Since the guide member  77  is mounted inside the cylindrical member  71 , the exhaust flowing from the opening  7   a  through the mesh member  72  to the inside of the cylindrical member  71  moves along the guide member  77  in the first direction, namely a direction away from the inlet  76   a  of the tail pipe  76 . 
     Then, the exhaust having reached the tip end  77   a  of the guide member  77  reverses the flow direction to move between the guide member  77  and the tail pipe  76  in the second direction, namely a direction approaching the inlet  76   a  of the tail pipe  76 . Note that the direction of the exhaust flow is here switched 180 degrees from the first direction to the second direction. In this manner, a channel where the exhaust flows in the second direction is provided inside the cylindrical member  71 . The channel is defined by the inner circumferential surface of the guide member  77  and the outer circumferential surface of the tail pipe  76 . 
     Thereafter, the exhaust having reached the inlet  76   a  of the tail pipe  76  reverses the flow direction thereof, flows into the inside of the tail pipe  76  to move again in the first direction, and then is discharged from the outlet  76   b . Again, the direction of the exhaust flow is here switched 180 degrees from the second direction to the first direction. 
     According to the present preferred embodiment, since a channel where the exhaust flows in the second direction, namely the direction opposite to the first direction, is provided inside the cylindrical member  71 , it is possible to ensure a longer length for the entire channel from the opening  7   a  of the cylindrical member  71  to the outlet  76   b  of the tail pipe  76 , and also to reduce the speed of the exhaust flow where the exhaust flow is bent. With the above arrangement, it is possible to improve the exhaust sound reduction capability and the spark prevention capability, and also to reduce the size of the spark arrestor  7  and the muffler  6 . 
     According to the present preferred embodiment, since the outer wall of the tail pipe  76  is used as a portion of the channel where the exhaust flows in the second direction, it is possible to reduce the diameter of the spark arrestor  7 . 
     According to the present preferred embodiment, since the guide member  77  is mounted so as to extend across the space between the opening  7   a  of the cylindrical member  71  and the inlet  76   a  of the tail pipe  76 , and the exhaust flow is thus bent, it is possible to ensure a longer length for the entire exhaust channel, and also to reduce the speed of the exhaust flow. 
     According to the present preferred embodiment, since the guide member  77  guides the exhaust flowing from the opening  7   a  to the inside of the cylindrical member  71  so as to flow in the first direction, namely a direction away from the inlet  76   a  of the tail pipe  76 , and the exhaust flow is thus bent, it is possible to ensure a longer length for the entire exhaust channel, and also to reduce the speed of the exhaust flow. 
     According to the present preferred embodiment, since the opening  7   a  of the cylindrical member  71  is positioned farther in the first direction than the inlet  76   a  of the tail pipe  76 , it is possible to ensure a longer length for the entire exhaust channel. 
     According to the present preferred embodiment, since the tip end  77   a  of the guide member  77  is positioned farther in the first direction than the opening  7   a  of the cylindrical member  71 , it is possible to ensure a longer length for the entire exhaust channel. 
     Note that the spark arrestor  7  is not limited to the above mentioned preferred embodiments.  FIG. 6  is a cross-sectional view of a spark arrestor  7  according to another preferred embodiment of the present invention. The structure that is similar to that in the above preferred embodiments is given the same reference numerals, and a detailed description thereof is partly omitted. 
     In the present preferred embodiment, the opening  7   a  of the cylindrical member  71  is located at a position closer to the end of the cylindrical member  71  in the first direction than that in the second direction. Accordingly, the distance from the opening  7   a  to the inlet  76   a  of the tail pipe  76  is longer than that in the above described preferred embodiments. 
     In the present preferred embodiment, the spark arrestor  7  includes a plurality of annular guide members  78 ,  79  mounted between the opening  7   a  of the cylindrical member  71  and the inlet  76   a  of the tail pipe  76 . These guide members  78 ,  79  are mounted to extend across the shortest path between the opening  7   a  and the inlet  76   a  of the tail pipe  76 . 
     The guide member  78  is fixed to the inner circumferential surface of the cylindrical member  71  such that a small space is provided between the guide member  78  and the outer circumferential surface of the tail pipe  76 . Meanwhile, the other guide member  79  is fixed to the outer circumferential surface of the tail pipe  76  such that a small space is provided between the guide member  79  and the inner circumferential surface of the cylindrical member  71 . 
     The guide member  78  fixed to the inner circumferential surface of the cylindrical member  71  and the guide member  79  fixed to the outer circumferential surface of the tail pipe  76  are alternately arranged along the central axis of the spark arrestor  7 . Further, the guide member  79  fixed to the outer circumferential surface of the tail pipe  76  has a flange shape at the inlet  76   a  of the tail pipe  76 . 
     In  FIG. 6 , the main direction in which the exhaust flows outside and inside the spark arrestor  7  is indicated by the arrows having an alternate long and short dashed line. Note that the respective directions of the flows of exhaust inside the spark arrestor  7  in the vicinity of the inner circumferential surface of the cylindrical member  71 , the outer circumferential surface of the tailpipe  76 , and the surfaces of the guide members  78 ,  79  are indicated by the arrows having an alternate long and short dashed line. 
     Since the opening  7   a  of the cylindrical member  71  is positioned farther in the first direction than the inlet  76   a  of the tail pipe  76 , the exhaust moving outside the cylindrical member  71  in the first direction reverses the flow direction thereof when flowing into the cylindrical member  71  from the opening  7   a  through the mesh member  72  to move mainly in the second direction, namely a direction approaching the inlet  76   a  of the tailpipe  76 . Note that the direction of the exhaust flow here is changed or reversed 180 degrees from the first direction to the second direction. In this manner, a channel where the exhaust flows in the second direction is provided inside the cylindrical member  71 . The channel is defined by the inner circumferential surface of the cylindrical member  71  and the outer circumferential surface of the tail pipe  76 . 
     Since the guide members  78 ,  79  are mounted between the opening  7   a  and the inlet  76   a  of the tail pipe  76 , the exhaust moving mainly in the second direction between the cylindrical member  71  and the tail pipe  76  also moves in the radial direction of the cylindrical member  71 , which is orthogonal or substantially orthogonal to the second direction. In detail, the exhaust moving in the second direction between the opening  7   a  and the guide member  78  moves inward in the radial direction near the surface of the guide member  78 . Further, the exhaust having passed through the space between the guide member  78  and the tail pipe  76  moves outward in the radial direction near the surface of the guide member  78 . Further, the exhaust moving in the second direction between the guide member  78  and the guide member  79  moves outward in the radial direction near the surface of the guide member  79 . Further, the exhaust having passed through the space between the guide member  79  and the cylindrical member  71  moves inward in the radial direction near the surface of the guide member  79 . 
     Thereafter, the exhaust having reached the inlet  76   a  of the tail pipe  76  changes the flow direction thereof 90 degrees to flow into the tail pipe  76 , and then moves inside the tail pipe  76  in the first direction to be ultimately discharged from the outlet  76   b.    
     According to the present preferred embodiment, since a channel where the exhaust flows in the second direction, namely the direction opposite to the first direction, is provided inside the cylindrical member  71 , it is possible to ensure a longer length for the entire exhaust channel from the opening  7   a  of the cylindrical member  71  to the outlet  76   b  of the tail pipe  76 , and also to reduce the speed of the exhaust flow where the exhaust flow is bent. With the above arrangement, it is possible to improve the exhaust sound reduction capability and the spark prevention capability, and to reduce the size of the spark arrestor  7  and the muffler  6 . 
     According to the present preferred embodiment, since the outer wall of the tail pipe  76  is used as a portion of the channel where the exhaust flows in the second direction, it is possible to reduce the diameter of the spark arrestor  7 . 
     According to the present preferred embodiment, since the opening  7   a  of the cylindrical member  71  is positioned farther in the first direction than the inlet  76   a  of the tail pipe  76 , it is possible to ensure a longer length for the entire exhaust channel. 
     According to the present preferred embodiment, since the guide members  78 ,  79  are mounted so as to extend across the space between the opening  7   a  of the cylindrical member  71  and the inlet  76   a  of the tail pipe  76 , and the exhaust flow is thus bent, it is possible to ensure a longer length for the entire exhaust channel and also to reduce the flow speed of the exhaust flow. 
     According to the present preferred embodiment, since the guide members  78 ,  79  guide the exhaust flowing into the cylindrical member  71  from the opening  7   a  and then toward the inlet  76   a  of the tailpipe  76  so as to flow in the radial direction of the cylindrical member  71 , which is orthogonal or substantially orthogonal to the second direction, and the exhaust flow is thus bent, it is possible to ensure a longer length for the entire exhaust channel, and also to reduce the flow speed of the exhaust flow. 
     Although preferred embodiments of the present invention have been described in the above, the present invention is not limited to the above described preferred embodiments, and various modified preferred embodiments are possible for a person skilled in the art. 
     For example, the cylindrical member  71 , the mesh member  72 , the cap member  73 , the cap member  74 , and the inner circumferential portion  743  or the like, which are positioned inside the cylindrical member  71 , may be integral and unitary with each other. Further, the opening  7   a  in the cylindrical member  71  may be formed by attaching the cap member  73  to a notch on an end portion of the cylindrical member  71 . Further, the tail pipe  76  may extend to the outside through the notch on the end portion of the cylindrical member  71 . 
     While preferred embodiments of the present invention have been described above, it is to be understood that variations and modifications will be apparent to those skilled in the art without departing from the scope and spirit of the present invention. The scope of the present invention, therefore, is to be determined solely by the following claims.