# Patent

## Title
Fuel tank for straddle vehicle

## Abstract

A straddle vehicle includes a main frame obliquely extending downward and rearward from a head pipe. Right and left sub-frames obliquely extend downward and rearward from the main frame, and seat rails obliquely extend upward and rearward from the sub-frames. A cross member extends between the seat rails. A rear cushion unit is supported by the cross member and an upper portion of the rear arm and slants forward. A lower portion of a fuel tank projects downward to a space defined between the rear cushion unit and a rear wheel.

## Background
BACKGROUND OF THE INVENTION 
1. Field of the Invention
This invention relates to a straddle type vehicle such as a motorcycle, for example.
2. Description of Related Art
Conventionally, in straddle type vehicles such as motorcycles etc., some vehicles are known to include a structure that has a single rear cushion unit, i.e., the so-called mono suspension structure as a rear cushion unit (for example, see following Patent Document 1).
The motorcycle disclosed in following Patent Document 1 includes a main frame obliquely extending downward rearward from a head pipe, and a pair of a right and a left seat rail obliquely extending upward rearward from a rear portion of the main frame. A fuel tank is mounted on the seat rails to be positioned under a seat. A rear wheel is supported by a rear end of a rear arm extending in a fore to aft direction. A front end of the rear arm is supported by a pivot shaft for swinging. A cross pipe extends between the right and left seat rails. This cross pipe has a cushion bracket. A top end of the rear cushion is coupled with the cushion bracket, while a bottom end of the rear cushion is coupled with a lower portion of a middle section of the rear arm in the fore to aft direction via a bracket. The rear cushion is entirely positioned below the fuel tank.
[Patent Document 1] JP-A-2002-37169, laid-open application publication
However, in the motorcycle described above, if the rear cushion extends along a locus of the pivotal movement of the rear arm about an axis of the pivot shaft so as to improve the suspension performance, a slant angle of the rear cushion needs to be small, and the rear cushion needs to extend generally vertically to be attached. Thus, a space defined under the seat is inevitably small to restrict layout under the seat.
Also, in the motorcycle described above, the depth of the fuel tank cannot be designed to be larger because it is needed to ensure below the fuel tank a mount space for the rear cushion. Therefore, in order to ensure a necessary capacity of the fuel tank, the fuel tank needs to be elongated in the fore to aft direction or in a transverse direction. Thus, the layout under the seat is restricted by the large area size of the fuel tank in a top plan view.
SUMMARY OF THE INVENTION 
This invention is made under the circumstances, and an object thereof is to improve the degree of freedom for the layout under the seat in a straddle type vehicle employing the mono suspension structure.
A straddle type vehicle according to the present invention is directed to a straddle type vehicle comprising a vehicle body including a vehicle body frame having a head pipe, a front frame connected to the head pipe and obliquely extending downward rearward, and a rear frame connected to the front frame and obliquely extending upward rearward, and an engine supported by the vehicle body frame. The vehicle includes a seat supported by the rear frame, a fuel tank disposed below the seat, a rear arm supported by the vehicle body for swinging about an axis of a pivot shaft and extending rearward, a rear wheel supported by the rear arm for rotation, and a single rear cushion unit having a top support end supported by the rear frame, and a bottom support end supported by an upper portion of the rear arm that is positioned higher than a center thereof in a vertical direction, the single rear cushion unit slanting forward so that the top support end is positioned ahead of the bottom support end, wherein a lower portion of the fuel tank projects toward a space defined by the rear cushion unit and the rear wheel.
The rear cushion unit of the straddle type vehicle slants relatively steeply so that the top support end is positioned forwarder. That is, an upper portion of the rear cushion unit is placed ahead of a location right under the fuel tank. A surplus space is therefore ensured under the fuel tank, specifically, between the rear cushion unit and the rear wheel. The lower portion of the fuel tank of the straddle type vehicle projects toward the surplus space. Accordingly, the degree of freedom for the layout under the seat increases, for example, the fuel tank becomes deeper to make it easy to ensure a sufficient capacity of the tank.
Also, according to the straddle type vehicle described above, the bottom support end of the rear cushion unit is supported by the upper portion of the rear arm. Thus, the rear cushion unit can extend along the locus of the pivotal movement of the rear arm about the axis of the pivot shaft so as to improve the suspension performance. The slant angle of the rear cushion unit can be large, accordingly. A space defined behind the rear cushion can be therefore enlarged to improve the degree of freedom for the layout under the seat.
Preferably, a bottom end of the fuel tank is positioned lower than the top support end of the rear cushion.
Thus, the fuel tank can be much deeper, and the degree of freedom for the layout under the seat can increase, for example, it can be easier to ensure the tank capacity.
The top support end of the rear cushion unit may be positioned ahead of a bottom end of the fuel tank.
Thus, the fuel tank can be made deeper without being disturbed by the top support end of the rear cushion unit.
The straddle type vehicle may include an air cleaner disposed under a front end of the seat, or below and ahead of the front end of the seat, and ahead of the rear cushion unit.
Thus, the rear cushion unit can be disposed in a space defined between the air cleaner and the fuel tank.
Preferably, the air cleaner has a box shape such that a length thereof in the vertical direction is longer than any one of a length thereof in a fore to aft direction and a length thereof in a transverse direction, and the air cleaner extends generally parallel to the rear cushion unit.
Thus, the rear cushion unit is disposed along the air cleaner that is taller than is broad. Thus, the rear cushion and the air cleaner are disposed efficiently in a limited space.
The straddle type vehicle may include a battery disposed under the seat, ahead of the fuel tank, and above the rear cushion.
Thus, the fuel tank, the rear cushion unit, and the battery are disposed efficiently under the seat.
Preferably, a front portion of the fuel tank has a front slant surface slanting rearward while extending downward, and a rear portion of the fuel tank has a rear slant surface slanting forward while extending downward.
The front portion of the fuel tank and the rear cushion unit are prevented from interfering with each other because the fuel tank has the forward slant surface. Also, because the fuel tank has the rear slant surface, the rear portion of the fuel tank and the rear wheel are prevented from interfering with each other. The rear portion of the fuel tank thus can be efficiently disposed in a space defined between the rear cushion unit and the rear wheel
The straddle type vehicle may include a fuel pump disposed within the fuel tank.
Because the lower portion of the fuel tank projects downward, the depth of the fuel tank can be made larger without placing the seat at a higher position. Thus, even though a fuel pump is positioned in the fuel tank, rider's feet can still easily touch the ground in a straddle position because the seat does not need to be raised higher.
The straddle type vehicle may include a seat front cover that is positioned below and ahead of the seat and has a top open concave, in a side elevational view, to define a top open space in front of the seat.
Some of the straddle type vehicles which includes an under bone type frame structure have a concave greatly recessed downward in an area existing in front of the seat to define a relatively large space in the front area of the seat. In order to define such a space, particularly, the under bone type vehicles require to efficiently arrange vehicle components under the seat. The effects described above thus can be remarkable with the under bone type vehicles.
As thus described, in accordance with the present invention, the large space can be ensured behind the rear cushion unit under the seat. The space can increase the degree of freedom for the layout under the seat, for example, it can be easier to ensure the tank capacity.



BRIEF DESCRIPTION OF THE DRAWINGS 
FIG. 1 is a side elevational view of a motorcycle according to an embodiment.
FIG. 2 is a side elevational view, showing an internal structure of the motorcycle.
FIG. 3 is a partial cross sectional view of an air cleaner under a mounted condition thereof.
FIG. 4 is a cross sectional view, taken along the line IV-IV of FIG. 3.
FIG. 5 is a top plan view of the air cleaner under the mounted condition.
FIG. 6 is a perspective view of the air cleaner under the mounted condition.
FIG. 7 is a cross sectional view of a labyrinth structure.
FIG. 8 is a side elevational view, showing an internal structure of a motorcycle according to another embodiment.



DETAILED DESCRIPTION OF THE INVENTION 
Hereunder, an embodiment of the present invention is described in detail, referring to the accompanying drawings.
As shown in FIG. 1, a straddle type vehicle according to an embodiment is a motorcycle 10 having an under bone type frame structure. A detachable seat front cover 12 is attached below and ahead of a seat 11. The seat front cover 12 curves or bends to be a generally concave shape as seen in a side elevational view. The seat front cover 12 defines a space 13 that is recessed downward in front of the seat 11.
As shown in FIG. 2, the motorcycle 10 has a vehicle body frame 14, and an engine 15 supported by the vehicle body frame 14 under a suspended condition. The vehicle body frame 14 and the engine 15 together form a vehicle body 15A. The engine 15 includes a crankcase 24 and a cylinder block 25 obliquely extending upward forward from the crankcase 24. The vehicle body frame 14 includes a head pipe 16, a single main frame 17, a pair of a right and a left sub-frame 18, a pair of a right and a left seat rail 19 and a pair of a right and a left backstay 20.
A steering shaft, which is not shown, passes through the head pipe 16. A lower portion of the steering shaft has a front fork 22a (see FIG. 1). A lower end of the front fork 22a supports a front wheel 21 for rotation.
The main frame 17 is connected to a rear surface of the head pipe 16 and obliquely extends downward rearward. The main frame 17 is rectangular and hollow in cross section. However, the main frame 17 may have any other shapes. A gusset 22 is affixed to a front half area of a bottom surface of the main frame 17. The gusset 22 extends between the bottom surface of the main frame 17 and the rear surface of the head pipe 16.
The sub-frame 18 are affixed to respective right and left side surfaces of the main frame 17. Each sub-frame 18 has a diameter smaller than that of the main frame 17. A cross sectional area of each sub-frame 18 is smaller than that of the main frame 17. The major part of each sub-frame 18 has a circular pipe shape in cross section. However, a flat plate shape replaces the circular shape of a front end of each sub-frame 18 toward the front end. The flat plate shaped portion of the front end of each sub-frame 18 is joined with the respective side surface of the main frame 17 by welding or the like under a condition that a surface of the flat plate shaped portion abuts on the side surface of the main frame 17. Thus, the pair of the right and left sub-frame 18 are connected to the respective side surfaces of the main frame 17.
Each sub-frame 18 bends in such a manner that its center portion in its longitudinal direction extends convexly downward. A front portion (a portion ahead of the bending portion) of each sub-frame 18 extends generally parallel to an axial direction of the cylinder block 25 of the engine 15. A rear portion of each sub-frame 18 has a slope that is gentler than that of the front portion. As discussed, the sub-frame 18 are shaped and disposed along the engine 15.
Each seat rail 19 is joined with the vicinity of the bending portion of the respective sub-frame 18 by welding or the like. Thereby, each seat rail 19 obliquely extends upward rearward from the vicinity of the bending portion of each sub-frame 18. Each seat rail 19 bends in such a manner that its center portion in its longitudinal direction extends convexly upward. Each seat rail 19 is made from a circular pipe.
Each backstay 20 is joined with a rear end of the respective sub-frame 18 by welding or the like. Therefore, each backstay 20 obliquely extends upward rearward from the rear end of the sub-frame 18. A rear end of each backstay 20 is joined with a rear end of the respective seat rail 19 by welding or the like. Similarly to the seat rail 19, each backstay 20 is made from a circular pipe.
The main frame 17 and the sub-frame 18 together form a front frame. The seat rails 19 form a rear frame. Additionally, the sub-frame 18, the seat rails 19 and the backstays 20 may have any shapes other than the circular pipe shape. The vehicle body frame 14 may be made of iron, aluminum or other materials.
A bracket 23 is affixed to the bottom surface of a rear end of the main frame 17. The cylinder block 25 of the engine 15 is attached to the bracket 23 via bolts and nuts. Brackets 26 are affixed to the vicinity of the bending portions of the respective sub-frame 18. The crankcase 24 of the engine 15 is attached to the brackets 26 via bolts and nuts. Another bracket 27 is affixed to respective rear ends of the sub-frame 18. The bracket 27 supports both the crankcase 24 of the engine 15 and rear arms 28. As discussed, the engine 15 is supported by the main frame 17 and the sub-frame 18 under the suspended condition.
A front end of each rear arm 28 is supported by the bracket 27 for swinging about an axis of a pivot shaft 31. A rear end of each rear arm 28 supports a rear wheel 32 for rotation. Additionally, in this embodiment, the vehicle body frame 14 supports the rear arms 28 via the bracket 27. However, a portion of the engine 15 may supports the rear arms 28.
A radiator 30 is disposed ahead of and above the cylinder block 25 of the engine 15 and below the main frame 17. A bracket 29 is affixed to the gusset 22 that is affixed to the bottom surface of the main frame 17. The bracket 29 supports the radiator 30.
A carburetor 33 is disposed above the crankcase 24 of the engine 15 and in the rear and the vicinity of the cylinder block 25. An air cleaner 34 is disposed behind the carburetor 33. The air cleaner 34 is interposed between right and left separated portions of the vehicle body frame 14. That is, the air cleaner 34 is placed between the sub-frame 18 and the seat rail 19 on the right hand side and the sub-frame 18 and the seat rail 19 on the left hand side.
The air cleaner 34 is positioned under the seat front cover 12. Specifically, the air cleaner 34 is positioned under a rear portion of the seat front cover 12 (a portion that descends forward; hereunder, called forward descending portion). Thus, the seat front cover 12 covers a top of the air cleaner 34.
The air cleaner 34 includes a cleaner case 35 and a lid 36. The cleaner case 35 has a box shape such that a length thereof in a vertical direction is longer than either a length thereof in a fore to aft direction or a length thereof in a transverse direction. A top of the cleaner case 35 has an opening, and the lid 36 covers and uncovers the opening. As shown in FIG. 6, the lid 36 and the cleaner case 35 are coupled together by bolts 54 positioned at four corners of the lid 36. Thus, the lid 36 can be easily attached to or detached from the cleaner case 35 by fastening or removing the bolts 54. Also, the air cleaner 34 slants forward so that a top surface of the air cleaner 34 inclines to descend forward. Thus, the concave shape of the seat front cover can be easily realized. A rider can easily get on and off the vehicle, accordingly, as described above.
As shown in FIG. 2, the air cleaner 34 is supported in a forward slanting position so that a top end is positioned ahead of a bottom end. As shown in FIG. 3, respective meeting surfaces of the lid 36 and the cleaner case 35 extend generally parallel to the seat rails 19 and slant to descend forward. Therefore, when the seat front cover 12 is removed and the lid 36 is detached obliquely upward forward, the lid 36 can be taken out from the cleaner case 35. To the contrary, when the lid 36 is putted onto the cleaner case 35 obliquely downward rearward under the condition that the seat front cover 12 is removed, the lid 36 can be attached to the cleaner case 35.
As shown in FIG. 4, a cross pipe 40 extends between the right and left brackets 27. A lower portion of the cleaner case 35 is tapered downward and has a plurality of steps, including a step 39 (see FIG. 3). The step 39 of the cleaner case 35 is supported on the cross pipe 40 via a cushion rubber 41. Additionally, the cushion rubber 41 has a plurality of pins 41a extending downward. Those pins 41a are inserted into the cross pipe 40.
A bracket 42 having an aperture 45 is affixed to a top of each seat rail 19. Each upper portion of the respective right and left side surfaces of the cleaner case 35 has a sheet-like attachment 43 formed with a concave slit 46 (see FIG. 3) therein. Each bracket 42 and the respective attachment 43 are coupled together by a bolt 44 passing through the aperture 45 and the slit 46.
As discussed above, the cleaner case 35 is supported by the cross pipe 40 attached to the respective brackets 27 of the backstays 20 and by the respective brackets 42 of the right and left seat rails 19.
As shown in FIG. 4, a filter element 38 is enclosed in an upper space of the cleaner case 35. A holder 49 having a lying-T-shaped engaging portion 49a surrounds the girth of the filter element 38. A top end periphery of the cleaner case 35 has a groove 50 for receiving the engaging portion 49a of the holder 49. The engaging portion 49a engages with the groove 50 so that the cleaner case 35 detachably supports the holder 49. Additionally, a bottom end periphery of the lid 36 also has a groove 50 for receiving the engaging portion 49a of the holder 49.
The cleaner case 35 protrudes upward above the seat rails 19. Also, as described above, the cleaner case 35 is tapered downward. A width (breadth) of an air cleaner upper portion 51 positioned higher than the seat rails 19 is narrower than a width of an air cleaner lower portion 52 positioned lower than the seat rails 19. Further, the width of the air cleaner upper portion 51 is shorter than a length between a right end of the right hand side seat rail 19 and a left end of the left hand side seat rail 19. That is, the air cleaner 34 is formed not to extend beyond the right and left seat rails 19. The filter element 38 is placed in the air cleaner upper portion 51. The filter element 38 is therefore positioned higher than the seat rails 19.
As shown in FIG. 3, an intake pipe 47 extending obliquely upward rearward is inserted into a rear portion of the lid 36. The intake pipe 47 defines an air intake section of the air cleaner 34. One end of the intake pipe 47 has an air inlet port 47a (see FIG. 5) that opens obliquely upward rearward. Another end of the intake pipe 47 extends into the lid 36 and opens above the filter element 38. An air supply pipe 48 is inserted into the cleaner case 35 through a forward surface thereof to be connected to the carburetor 33 (not shown in FIG. 3, see FIG. 2). One end of the air supply pipe 48 opens at a location below the filter element 38 in the cleaner case 35. Additionally, the air supply pipe 48 opens obliquely downward at a generally center position in the vertical direction. Air taken through the intake pipe 47 passes through the filter element 38 and is supplied to the carburetor 33 through the air supply pipe 48.
As shown in FIG. 2, the intake pipe 47 of the air cleaner 34 is disposed within a space surrounded by the seat 11 and the forward descending portion of the seat front cover 12. The space above and behind the intake pipe 47 is partitioned from the external space by a wall surface 75.
As shown in FIG. 5, the intake pipe 47 is flat so as to be slender in the transverse direction. Therefore, a length of the intake pipe 47 in the fore to aft direction is short. The intake pipe 47 is directed to simply take the air existing behind a center portion of the air cleaner 34 in the fore to aft direction. On the other hand, the intake pipe 47 has a sufficient opening area, even though the length in the fore to aft direction is short, because the length of the intake pipe 47 in the transverse direction is long. The intake pipe 47 has a flange 55 extending outward and circumferentially around an opening end.
As shown in FIG. 2, a hinge mechanism 53 is provided at a lower portion of a front end of the seat 11. The seat 11 pivots about the front end as a fulcrum via the hinge mechanism 53 to open and close.
As shown in FIG. 6, the intake pipe 47 is positioned below the hinge mechanism 53. Below the hinge mechanism 53, a block 57 projects forward, and a flange 56 projects forward and sideward on both sides below the block 57. As a result, a recess 58 concaving rearward is defined between the block 57 and the flange 56. Both right and left side portions of the flange 56 slant obliquely downward rearward to form slant surfaces 56a. 
As shown in FIG. 7, the seat front cover 12 has a projection 59 extending rearward. The projection 59 opposes to the recess 58 under a condition that the projection 59 is interposed between the block 57 and the flange 56. As the result, a zigzag gap is made among the block 57, the projection 59 and the flange 56. The block 57, the projection 59 and the flange 56 overlap with each other in the vertical direction, as discussed, to form a labyrinth structure 60. The labyrinth structure 60 is positioned above (strictly speaking, obliquely forward upward) the intake pipe 47.
Additionally, as described above, the opening end of the intake pipe 47 has the flange 55. Accordingly, not only the block 57, the projection 59 and the flange 56 but also the entire combination of the block 57, the projection 59, the flange 56 and the flange 55 function as one labyrinth structure.
As shown in FIG. 2, a rear cushion unit 63 is disposed behind the air cleaner 34. A cross member 64 extends between the right and left seat rails 19. An upper cushion bracket 67 is affixed to the cross member 64. The upper cushion bracket 67 protrudes downward to a location below the seat rails 19. The top end of the rear cushion unit 63 is supported by the upper cushion bracket 67.
Another cross member 65 extends between the right and left rear arms 28. A lower cushion bracket 68 is affixed to the cross member 65. The lower cushion bracket 68 supports a bottom end of the rear cushion unit 63. The lower cushion bracket 68 protrudes upward to a location above the rear arms 28. Thus, the bottom end of the rear cushion unit 63 is supported by an upper portion of the associated rear arm 28 that is positioned higher than a center position thereof (center line M of the rear arm 28) in the vertical direction.
As discussed, the rear cushion unit 63 extends between the upper cushion bracket 67 and the lower cushion bracket 68. The rear cushion unit 63 slants forward so that an upper supported end 69 is positioned ahead of a lower supported end 70, and extends generally parallel to the air cleaner 34.
As shown in FIG. 2, a battery 61 is disposed behind and above the air cleaner 34, and ahead of and above the rear cushion unit 63. A fuel tank 62 is disposed behind the battery 61. The battery 61 and the fuel tank 62 are positioned under the seat 11. The fuel tank 62 is interposed between the right and left seat rails 19 to be supported by the seat rails 19.
A portion of the fuel tank 62 is positioned lower than the seat rails 19. A lower portion of the fuel tank 62 projects downward to a space 73 defined between the rear cushion unit 63 and the rear wheel 32. A front portion of the fuel tank 62 has a front slant surface 71 slanting rearward while extending downward. A rear portion of the fuel tank 62 has a rear slant surface 72 slanting forward while extending downward.
The upper supported end 69 of the rear cushion unit 63 is positioned ahead of the fuel tank 62. A bottom end of the fuel tank 62 is positioned lower than the upper supported end 69 of the rear cushion unit 63. That is, the top support end of the rear cushion unit 63 is off forward from the bottom end of the fuel tank 62, and the fuel tank 62 and the rear cushion unit 63 partially overlap with each other in a front elevational view.
A storage box 74 for storing small articles etc. is disposed under the seat 11 and behind the fuel tank 62. A top of the storage box 74 has an opening. When the seat 11 is moved to the open position, the opening is externally exposed. Thus, the articles can be putted into or out from the storage box 74 by moving the seat 11 between the open and closed positions.
As has been described, according to the motorcycle 10, the rear cushion unit 63 slants relatively steeply so that the upper supported end 69 is positioned ahead of the fuel tank 62 (see FIG. 2). The lower portion of the fuel tank 62 projects to the space 73 defined between the rear cushion unit 63 and the rear wheel 32. Accordingly, the depth of the fuel tank 62 can be made larger without interfering with the fuel tank 62 and the rear cushion unit 63. Particularly, according to the motorcycle 10, the bottom end of the fuel tank 62 is positioned lower than the upper supported end 69 of the rear cushion unit 63, and thus the fuel tank 62 becomes extremely deep.
Thus, according to the motorcycle 10, the length of the fuel tank 62 in the transverse direction or the width thereof can be smaller. Therefore, the area of the fuel tank 62 in the top plan view can be smaller, and the degree of freedom for the layout of vehicle components under the seat 11 can increase. Additionally, in the motorcycle 10, because the length of the fuel tank 62 in the fore to aft direction becomes shorter, the storage box 74 having a sufficient space for storage is provided behind the fuel tank 62.
The lower supported end 70 of the rear cushion unit 63 is supported by an upper portion of the rear arm 28. Thus, the rear cushion unit 63 can extend along the locus of the pivotal movement of the rear arm 28 about the axis of the pivot shaft 31. The suspension performance of the rear cushion unit 63 can be improved, accordingly.
The rear cushion unit 63 extends generally parallel to the air cleaner 34. Therefore, sufficient use of the space behind the air cleaner 34 can be made. As a result, the rear cushion unit 63 and the air cleaner 34 can be efficiently positioned in the limited space.
Also, according to the motorcycle 10, the battery 61 is placed in the space defined in front of the fuel tank 62 and above the rear cushion unit 63. Thus, the space under the seat 11 is effectively used, and the fuel tank 62, the rear cushion unit 63 and the battery 61 can be efficiently arranged.
The front portion of the fuel tank 62 has the front slant surface 71 that slants rearward. Thus, because the front portion of the fuel tank 62 can extend along the rear cushion unit 63, any possible interference between the fuel tank 62 and the rear cushion unit 63 can be avoided, even though the fuel tank 62 is deep enough. Also, the rear portion of the fuel tank 62 has the rear slant surface 72 that slants forward. Thus, because the rear portion of the fuel tank 62 can extend along the rear wheel 32, any possible interference between the fuel tank 62 and the rear cushion unit 63 can be avoided, even though the fuel tank 62 is deep enough.
Further, according to the motorcycle 10, cleaning of the filter element 38 or replacement thereof with new one can be easily made by removing the seat front cover 12 and taking out the lid 36 of the air cleaner 34 obliquely upward forward. That is, maintenance work of the air cleaner 34 can be made by an approach from an upper location or an obliquely front and upper location. The user thus can replace the filter element 38 with new one or can make other work without stooping or squatting down, i.e., can make the maintenance work for the air cleaner 34 in a comfortable posture of the user.
Particularly, in the motorcycle 10, because the respective meeting surfaces 37 of the lid 36 and the cleaner case 35 incline to descend forward, and the lid 36 is putted on or taken out obliquely upward forward, the seat 11 or the seat rails 19 do not disturb the attaching or detaching work of the lid 36. Thus, the attaching or detaching work of the lid 36 is easy, and the maintenance work of the air cleaner 34 can be easily made.
Because the air cleaner 34 has the box shape that is taller than is broad, the capacity of the air cleaner 34 can be made large without increasing the length of the vehicle in the fore to aft direction or the width thereof. Additionally, the maintenance work of the air cleaner 34 can be made by the approach from the upper location or the obliquely front and upper location. Thus, unlike the maintenance work made by an approach from a lateral side location, the maintenance work is not difficult even though the air cleaner 34 has the shape that is taller than is broad.
Because the air cleaner 34 is supported in the forward slanting position, the length of the air cleaner 34 in the vertical direction (apparent length in the vertical direction) when it is set is shorter than the length of the air cleaner 34 itself in the vertical direction. Thus, the seat 11 positioned above the air cleaner 34 can be placed at a relatively low position. Also, the air cleaner 34 can be efficiently positioned in the narrow space under the seat front cover 12 by making the air cleaner 34 slant forward.
According to the motorcycle 10, the air cleaner 34 is interposed between the right and left sub-frame 18 and seat rails 19, and the upper portion of the air cleaner 34 protrudes upward above the seat rails 19 (see FIG. 4). As discussed, because the seat rails 19 can be placed at a relatively low position, the vehicle can be made slimmer than ever.
Particularly, in the motorcycle 10, the width of the air cleaner 34 is shorter than the distance between the right end of the seat rail 19 on the right hand side and the left end of the seat rail 19 on the left hand side. The air cleaner 34 thus does not extend out beyond the right and left seat rails 19. The vehicle is slimmer, accordingly, even though the air cleaner 34 is positioned between the right and left seat rails 19.
Also, according to the motorcycle 10, the width of the air cleaner upper portion 51 is larger than the width of the air cleaner lower portion 52. Thus, the handling of the air cleaner upper portion 51 is easier for the user. Therefore, the maintenance work of the air cleaner 34 that is made by approaching downward or obliquely downward can be more easily made.
The filter element 38 of the air cleaner 34 is positioned in the upper space of the cleaner case 35. Thus, the filter element 38 can be easily cleaned or replaced with new one by removing the lid 36, without being disturbed by the seat rails 19 etc. Also, because the filter element 38 and the seat rail 19 do not overlap with each other in the transverse direction, the distance between the right and left seat rails 19 does not need to be enlarged even though a width of the filter element 38 becomes larger. The vehicle can be made slimmer than ever, accordingly.
Further, according to the motorcycle 10, the intake pipe 47 of the air cleaner 34 is positioned in a space surrounded by the seat 11 and the forward descending portion of the seat front cover 12 (see FIG. 2). Therefore, the intake pipe 47 is sufficiently spaced apart from the front wheel 21 and the rear wheel 32. Thus, even if mud or the like is raised up by the front wheel 21 or the rear wheel 32, the mud etc. is hardly drawn into the air cleaner 34 through the intake pipe 47.
Also, the intake pipe 47 is not only positioned higher than the front wheel 21 and the rear wheel 32 but also opens obliquely upward forward. In this point of view, again drawing mud or the like through the intake pipe 47 hardly occurs.
Conventionally, the space surrounded by the seat 11 and the forward descending portion of the seat front cover 12 is the so-called dead space that is not effectively used. Particularly, the space below the hinge mechanism 53 at the front end of the seat 11 is the dead space that is not effectively used. According to the motorcycle 10, however, the dead space can be effectively used as a housing space for the intake pipe 47. Also, according to the motorcycle 10, because the seat front cover 12 is not required to be larger upward to house the intake pipe 47 therein, the space 13 in front of the seat 11 is not spoiled. Thus, drawing mud or the like into the air cleaner 34 can be effectively prevented while enjoying advantages of the frame structure of the under bone type.
The air cleaner 34 is disposed behind the engine 15, and the intake pipe 47 is positioned at the rear side of the air cleaner 34. Thus, the air cleaner 34 is interposed between the engine 15 and the intake pipe 47, and the air cleaner 34 insulates the heat from the engine 15. Hot air is inhibited from being drawn into the intake pipe 47, accordingly. Therefore, the temperature of the air supplied to the engine 15 falls, and the density of the drawn air becomes higher. The efficiency of the engine 15 increases.
Additionally, because the intake pipe 47 is directly coupled with the lid 36 of the air cleaner 34, the distance between the intake pipe 47 and the air cleaner 34 is short. Thus, the resistance of the intake air on the inlet port side in the air cleaner 34 is small.
According to the motorcycle 10, the labyrinth structure 60 is located above the intake pipe 47 (see FIG. 7). Therefore, even if drops of water fall from the seat 11 when it rains or on other occasions, the labyrinth structure 60 prevents the downward movement of the drops of water. The drops of water thus hardly enter the intake pipe 47, even though the intake pipe 47 opens obliquely upward. That is, water hardly enters the air cleaner 34 through the intake pipe 47.
As shown in FIG. 2, the space above and behind the intake pipe 47 is generally partitioned from the external space by the wall surface 75. Thus, any mud or the like can be effectively prevented from entering the intake pipe 47 from a location in the rear thereof. Additionally, the wall surface 75 may be defined by an exclusively prepared partition. Alternatively, a portion of a vehicle component may define the wall surface 75. For example, a vehicle component such as a battery, a fuel tank, a storage box or the like may be positioned behind the intake pipe 47 to define the wall surface 75 with the use of a portion of the vehicle component.
In the embodiment, the engine 15 is a carburetor type engine. However, the engine 15, of the motorcycle 10 may be a fuel injection type engine. Next, as another embodiment of the straddle type vehicle according to the present invention, a motorcycle 10 having a fuel injection type engine 15 is described. Incidentally, the same portions as those in the embodiment described above are assigned with the same references as those assigned, and descriptions about them are not repeated.
As shown in FIG. 8, in the motorcycle 10 according to this embodiment, a fuel injection device 82 is disposed in an intake passage 83 extending between the air cleaner 34 and the cylinder block 25 of the engine 15. A fuel pump 80 is disposed within the fuel tank 62. The fuel pump 80 and the fuel injection device 82 are connected to each other through a fuel supply tube 81.
In this embodiment, similarly to the former embodiment described above, the fuel tank 62 is deep. Thus, the fuel pump 80 can be housed in the fuel tank 62 even though the top end of the fuel tank 62 is not raised higher.
Therefore, according to this embodiment, the seat 11 does not need to be raised higher even though the fuel pump 80 is positioned within the fuel tank 62. Thus, rider's feet can still easily touch the ground in the straddle position. The rider can easily get on and off the vehicle, accordingly.
As has been described, the present invention is useful for straddle type vehicles, including motorcycles or the like.

## Claims

1. A straddle vehicle comprising:
a vehicle body including a vehicle body frame having a head pipe, a front frame connected to the head pipe and obliquely extending downward rearward, and a rear frame connected to the front frame and obliquely extending upward rearward, and an engine supported by the vehicle body frame;
a seat supported by the rear frame;
a fuel tank disposed below the seat;
a rear arm supported by the vehicle body for swinging about an axis of a pivot shaft and extending rearward;
a rear wheel supported by the rear arm for rotation; and
a single rear cushion unit having a top support end supported by the rear frame, and a bottom support end supported by an upper portion of the rear arm that is positioned higher than a center thereof in a vertical direction, the single rear cushion unit slanting forward so that the top support end is positioned ahead of the bottom support end, wherein a lower portion of the fuel tank projects toward a space defined by the rear cushion unit and the rear wheel,
wherein the top support end of the rear cushion unit is positioned ahead of a bottom end of the fuel tank.

2. A straddle vehicle comprising:
a vehicle body including a vehicle body frame having a head pipe, a front frame connected to the head pipe and obliquely extending downward rearward, and a rear frame connected to the front frame and obliquely extending upward rearward, and an engine supported by the vehicle body frame;
a seat supported by the rear frame;
a fuel tank disposed below the seat;
a rear arm supported by the vehicle body for swinging about an axis of a pivot shaft and extending rearward;
a rear wheel supported by the rear arm for rotation;
a single rear cushion unit having a top support end supported by the rear frame, and a bottom support end supported by an upper portion of the rear arm that is positioned higher than a center thereof in a vertical direction, the single rear cushion unit slanting forward so that the top support end is positioned ahead of the bottom support end, wherein a lower portion of the fuel tank projects toward a space defined by the rear cushion unit and the rear wheel; and
an air cleaner disposed under a front end of the seat, or below and ahead of the front end of the seat, and ahead of the rear cushion unit.

3. The straddle vehicle according to claim 2, wherein the air cleaner has a box shape such that a length thereof in the vertical direction is longer than any one of a length thereof in a fore to aft direction and a length thereof in a transverse direction, and the air cleaner extends generally parallel to the rear cushion unit.

4. A straddle vehicle comprising:
a vehicle body including a vehicle body frame having a head pipe, a front frame connected to the head pipe and obliquely extending downward rearward, and a rear frame connected to the front frame and obliquely extending upward rearward, and an engine supported by the vehicle body frame;
a seat supported by the rear frame;
a fuel tank disposed below the seat;
a rear arm supported by the vehicle body for swinging about an axis of a pivot shaft and extending rearward;
a rear wheel supported by the rear arm for rotation;
a single rear cushion unit having a top support end supported by the rear frame, and a bottom support end supported by an upper portion of the rear arm that is positioned higher than a center thereof in a vertical direction, the single rear cushion unit slanting forward so that the top support end is positioned ahead of the bottom support end, wherein a lower portion of the fuel tank projects toward a space defined by the rear cushion unit and the rear wheel; and
a battery disposed under the seat, ahead of the fuel tank, and above the rear cushion.

5. A straddle vehicle comprising:
a vehicle body including a vehicle body frame having a head pipe, a front frame connected to the head pipe and obliquely extending downward rearward, and a rear frame connected to the front frame and obliquely extending upward rearward, and an engine supported by the vehicle body frame;
a seat supported by the rear frame;
a fuel tank disposed below the seat;
a rear arm supported by the vehicle body for swinging about an axis of a pivot shaft and extending rearward;
a rear wheel supported by the rear arm for rotation; and
a single rear cushion unit having a top support end supported by the rear frame, and a bottom support end supported by an upper portion of the rear arm that is positioned higher than a center thereof in a vertical direction, the single rear cushion unit slanting forward so that the top support end is positioned ahead of the bottom support end, wherein a lower portion of the fuel tank projects toward a space defined by the rear cushion unit and the rear wheel,
wherein a front portion of the fuel tank has a front surface slanting rearward while extending downward; and
a rear portion of the fuel tank has a rear surface slanting forward while extending downward.

6. A straddle vehicle comprising:
a vehicle body including a vehicle body frame having a head pipe, a front frame connected to the head pipe and obliquely extending downward rearward, and a rear frame connected to the front frame and obliquely extending upward rearward, and an engine supported by the vehicle body frame;
a seat supported by the rear frame;
a fuel tank disposed below the seat;
a rear arm supported by the vehicle body for swinging about an axis of a pivot shaft and extending rearward;
a rear wheel supported by the rear arm for rotation;
a single rear cushion unit having a top support end supported by the rear frame, and a bottom support end supported by an upper portion of the rear arm that is positioned higher than a center thereof in a vertical direction, the single rear cushion unit slanting forward so that the top support end is positioned ahead of the bottom support end, wherein a lower portion of the fuel tank projects toward a space defined by the rear cushion unit and the rear wheel; and
a seat front cover that is positioned below and ahead of the seat and has a top open concave, in a side elevational view, to define a top open space in front of the seat.

7. The straddle vehicle according to any of claims 1-5 and 6, wherein a bottom end of the fuel tank is positioned lower than the top support end of the rear cushion unit.

8. The straddle vehicle according to any of claims 1-5 and 6, further comprising a fuel pump disposed within the fuel tank.