Fuel tank system of a motor bicycle

Abstract: A fuel tank system (5) of a motor bicycle according to the present invention comprises: a tank main body (26) made of a synthetic resin, which is formed into a reverse U-letter shape in its longitudinal section (27) in a manner of riding on a front head portion of a vehicle-body frame (2); a fuel supply port (50) which is provided on an upper portion of the tank main body (26); a receiving pan portion (51) which is provided in the fuel supply port; a relay joint (80) which is arranged in a vicinity of a bottom portion of the tank main body and whose attaching direction is the substantially same as an attaching direction of the receiving pan portion; and a drain pipe (85) which comprises a soft hose, passes through an interior of the tank main body, and connects between the receiving pan portion and the relay joint. Further, a fixing member for fixing the tank main body to the vehicle-body frame is formed out of a rigid material independently from the tank main body, a fixing portion on the tank main body side of the fixing member has a shape formed so as to surround a fixture plate of the relay joint, and the fixing member has a shape in its side view such that at least part of the fixing member is situated on a position lower than the relay joint when the fixing member is fixed to the tank main body.

Description: BACKGROUND OF THE INVENTION The present invention relates to a motor bicycle fuel tank system according to the preamble of claim 1 wherein its tank main body is integrally molded out of a synthetic resin so as to freely form a shape of the tank, increase a capacity of the tank, and to facilitate a manufacture of the tank. Such a motor bicycle fuel tank system is shown by JP 60092928. For example, in the case where a fuel supply port of the aforesaid tank main body made of a synthetic resin is provided with a flat surface recessed type tank cap which is so-called as an aircraft type, there has been employed a structure in which the fuel supply port of the tank main body is provided with a metallic receiving pan portion, and a tank cap is fixed onto the receiving pan portion by means of a bolt. By the way, water or fuel is easy to be gathered on the receiving pan portion in rainy weather driving or in refueling; for this reason, there is a need of a drain pipe for discharging water or fuel from the receiving pan portion. Conventionally, a metallic pipe has been used as the drain pipe, and the metallic pipe is provided passing through an interior of the tank main body in a manner of connecting the receiving pan portion with a relay joint provided in the tank main body. The relay joint is attached to an inconspicuous place such as an inside of a portion where the tank main body rides on a vehicle-body frame, and is connected so that a hose extends to the outside therefrom. However, the tank main body made of a synthetic resin has the following tendency. Specifically, the tank main body swells due to contact with a fuel, and then, is slightly deformed (mainly enlarged) in its whole dimensional shape. JP 60092928 discloses a U-shaped fuel tank for a tricycle or motorbike made of a synthetic resine to be mounted on a longitudinally extending tube of the tricycle frame and preventing dimensional deformations by a plurality of convex stripes formed in a direction crossing the longitudinal direction of the fuel tank: Due to the deformation of the tank, there is a possibility that a dimension between the receiving pan portion of the fuel supply port and the relay joint varies. In such a case, a metallic drain pipe having no expandability is not adaptable to a dimensional deformation between the receiving pan portion and the relay joint, and then, an unreasonable force is applied to a connective section of the drain pipe, there is a possibility of causing a deterioration in a seal performance. Further, the metallic drain pipe is not formed into a complicate curved shape; for this reason, a drain discharge direction can not be freely selected. Moreover, if the tank main body is made of metal, in its assembling (welding process), the drain pipe is simultaneously assembled into the interior of the tank main body. US 4,807,472 discloses a fuel level gauge for a metal tank of a motorbike with a receiving pan welded on. The assembly comprises a rigid metal drain pipe connected on one side to the receiving pan and extending into the inner of the tank towards a relay joint, to be connected therewith on the other side, while the receiving pan and the relay joint are pointing directly towards each other. If the tank main body is made of a synthetic resin, however, the following process is required; specifically, after the tank main body is molded, a worker inserts hid hand from the fuel supply port into the interior of the tank main body to assemble the relay joint and the drain pipe therein, and finally, the receiving pan portion is attached to the fuel supply port. For this reason, there has occurred a case where assembling workability of the tank main body becomes very worse depending upon a position where the relay joint is provided. Also, as described above, the tank main body swells due to contact with a fuel; for this reason, a fixed portion of the tank main body must be attached so as to be relatively movable with respect to the vehicle-body frame. Further, the fixed portion must be floatingly fixed to the vehicle-body frame so that vibration-proof for the tank main body can be achieved. To give an example of a conventionally general fuel tank system, a front portion of the tank main body made of a synthetic resin has been provided with right and left two front portion fixing members while a rear portion thereof being provided with one rear portion fixing member. The front portion fixing member is formed like a plate parallel with a central surface of the vehicle body (in a longitudinal direction), and the front portion fixing member is fastened to the vehicle-body frame by means of a fixed bolt penetrating in a vehicle width direction. On the other hand, the rear portion fixing member is formed like a substantially horizontal plate, and the rear portion fixing member is fastened to the vehicle-body frame by means of a fixed bolt penetrating in a vertical (up and down) direction. For example, a fixed bolt insertion hole of the rear portion fixing member is formed like a slot. Even if a dimension of the tank main body varies due to swelling, the rear portion fixing member is relatively slidable with respect to the fixed bolt so that a dimensional deformation of the tank main body can be absorbed. Further, a cushion rubber or the like is interposed between respective front and rear three fixing members and the fixed bolt, and thereby, a vibration of the vehicle body has been prevented from being transmitted directly to the tank main body. As described above, the front portion fixing member supporting the front portion of the tank main body has been formed like a plate parallel with the central surface of the vehicle body. For this reason, if the tank main body becomes a large scale, high load acts on a direction of shearing the cushion rubber. Moreover, in bad road driving or the like, a great push-up reactive force from a front fork is applied to the tank main body via the front portion fixing member. Therefore, the cushion rubber is crushed; as a result, there has arisen a problem that a sufficient vertically vibration-proof effect is hard to be obtained. In addition, if the tank main body becomes a large scale, a dimensional deformation becomes large when the tank main body swells while being caused in various directions. For this reason, even if only one of fixing members is fixed so as to be relatively movable with respect to the vehicle frame, it is impossible to absorb a dimensional deformation of the whole tank main body. For this reason, there is high possibility that an unreasonable deformation stress is applied to the tank main body. Further, there is a motor bicycle in which the tank main body made of a synthetic resin is covered with a frame cover made of a synthetic resin in order to protect the tank main body and to freely make a design of appearance. In this type of motor bicycle, if a structure is employed such that the frame cover is fixed directly to the tank main body, an unreasonable force is applied to the frame cover due to a dimensional deformation by swelling of the tank main body; for this reason, the frame cover is warped or broken down. In view of the above circumstances, conventionally, the following fixing structure has been employed. Specifically, the frame cover is fixed to other members (vehicle-body frame or the like) positioning at the vicinity of the tank main body without fixing it directly to the tank main body. Or, only one portion of the frame cover is fixed to the tank main body, and other portions of the frame cover are fixed to the tank main body with use of a surface fastener or the like so that a positioning correction can be easily made. In the case where a relatively small tank main body is covered by a one-piece type frame cover, there is no problem even if the aforesaid fixing structure is employed. However, if the tank main body is a large scale, it is difficult to perform integral molding of the frame cover, and the frame cover must be constructed in a manner of being divided into a plurality cover members and joining these cover members together. For this reason, with the aforesaid fixing structure, a shift, unevenness or the like is caused between the plurality of cover members or between these cover members and the tank main body; as a result, there is a problem that a visible appearance around the fuel tank system is remarkably deteriorated. In a general fuel tank system of a motor bicycle, the tank main body has a shape of a reverse U-letter longitudinal section (substantially a shape of a horseshoe), and is located in a manner of riding on the front head portion of the vehicle-body frame. Two or three fixing brackets provided on the front and rear portions of the tank main body are fixed and supported to the vehicle-body frame. In particular, if the tank main body has a large capacity, a pair of right and left cushion members provided on the side of the vehicle-body frame are abutted against inner right and left longitudinal wall surfaces of a reverse U-letter sectional portion of the tank main body, and thereby, a great motion of the tank main body to a vehicle width direction is limited. In this manner, when a great force is applied from the side to the tank main body by fall-down or collision of a motor bicycle, a stress to the fixing bracket is prevented from being concentrated and from being broken down. The attachment structure as described above is effective in a tank main body made of metal. However, in the tank main body is integrally molded out of a synthetic resin, the tank main body is swelled (expanded) by contact with a fuel; for this reason, elastic cushion members provided on the vehicle-body side is abutted against the inner longitudinal wall surfaces. And then, when the tank main body swells and deforms, the inner longitudinal wall surfaces is pressed against elastic cushion members over the necessity ; as a result, there is the possibility that a deformation is generated in the tank main body or a stress concentrated to respective fixing brackets is generated. Further, regardless of a material quality of the tank main body, in order to interpose the elastic cushion member between the vehicle-body frame and the inner longitudinal wall surface of the tank main body, a space between the vehicle-body frame and the tank main body must be made wide. For this reason, there is a problem that a capacity of the tank main body need to be reduced. By the way, in order to provide another independent component such as a tank cap or the like on the tank main body, the following method is employed. Specifically, when the tank main body is integrally molded out of a synthetic resin, a metallic insert nut is embedded, and the another independent component is fastened to the insert nut by means of a bolt. In the case of attaching the tank cap, a ring-like gasket (made of rubber) is interposed between the tank main body and the tank cap so that a fuel leakage can be prevented. However, the insert nut embedded when the tank main body is integrally molded out of a synthetic resin has a tendency such that the distal end surface is projected about 0.5 to 1.0 mm from the surface of the tank main body by hardening and shrinkage of the synthetic resin material after the tank main body is molded out of a synthetic resin. For this reason, for instance, in the case where the gasket is interposed between the tank main body and the tank cap to attach the tank cap as described above, the gasket bits into the projected distal end surface of the insert nut. Thus, seal performance remarkably deteriorates, and there is the possibility that the gasket is broken down if the worst comes to the worst. Further, without being limited to the tank cap, in the case where other components made of a synthetic resin are fastened to the insert nut, there is the possibility that soft other components are damaged by contact with the insert nut. Furthermore, the projection of various insert nuts is uneven; for this reason; it is difficult to stably fasten other components to all of insert nuts. SUMMARY OF THE INVENTION In order to solve the aforesaid problems, a motor bicycle fuel tank system has been invented according to the present invention as defined in claim 1. Preferred embodiments are defined in the dependent claims. A first object of the present invention is to provide a fuel tank system having a tank main body made of a synthetic resin which is provided with an embedded (recessed) type tan cap, wherein a seal performance in a drain pipe connective portion of a tank cap is prevented from being deteriorated by a dimensional deformation due to swelling of the tank main body, a drain discharge direction or the like is freely selected, and an assembling workability of the tank main body relative to a drain pipe arrangement is improved. Further, a second object of the present invention is to prevent a seal performance between the tank main body a relay joint of the drain pipe from being deteriorated by swelling of the tank main body, and to protect the relay joint from being broken down by an external force. Further, a third object of the present invention is to exhibit a sufficient vibration-proof effect while supporting a heavy weight of the tank main body even if the tank main body made of a synthetic resin is a large scale. Further, a fourth object of the present invention is to reasonably absorb a dimensional deformation when the tank main body swells. Further, a fifth object of the present invention is to prevent a recess surface for a knee grip provided on right and left sides of the tank main body made of a synthetic resin from being deformed by swelling of the tank main body without making complicate a mold for molding the tank main body. Further, a sixth object of the present invention is to, in the case where the tank main body of a synthetic resin is covered by the frame cover, prevent a unreasonable force from being applied to a frame cover when the tank main body swells, and to preferably maintain a visible appearance. Further, a seventh object of the present invention is to, in the case where the frame cover is attached to the tank main body made of a synthetic resin by means of an independent cover bracket, simplify a structure of a fixed portion on the tank main body side of the cover bracket, and to protect the tank main body by preventing a stress from being concentrated to the tank main body when a great external force is applied from the side to the cover bracket. Further, a eighth object of the present invention is to prevent various fixing brackets from being broken down by a stress concentration when a great external force is applied from the side to the tank main body, to prevent an unreasonable force from being applied to the tank main body when the tank main body swells and deforms even if the tank main body is made of a synthetic resin, and to secure a large capacity of the tank main body while improving an assembling performance to the vehicle-body frame. Further, a nineth object of the present invention is to, in the case where other components are fastened to an insert nut embedded in the tank main body made of a synthetic resin, prevent other components from being broken down by the insert nut, and to stably fasten other components thereto. To achieve the above first object, the present invention provides a fuel tank system of a motor bicycle comprising: a tank main body made of a synthetic resin, which is formed into a reverse U-letter shape in its longitudinal section in a manner of riding on a front head portion of a vehicle-body frame; a fuel supply port which is provided on an upper portion of the tank main body; a receiving pan portion which is provided in the fuel supply port; a relay joint which is arranged in a vicinity of a bottom portion of the tank main body and whose attaching direction is the substantially same as an attaching direction of the receiving pan portion; and a drain pipe which comprises a soft hose, passes through an interior of the tank main body, and connects between the receiving pan portion and the relay joint. With the above construction, even if the tank main body swells and a dimensional deformation is generated between the receiving pan portion and the relay joint, since the drain pipe comprising a soft hose is adaptable to the dimensional deformation of the tank main body, the seal performance of the connective portion of the drain pipe is not deteriorated when an unreasonable force is applied thereto. Moreover, a curved shape of the drain pipe is freely set, so that the drain discharge direction or the like can be freely selected. Further, since the attachment direction of the relay joint arranged in the vicinity of the bottom portion of the tank main body is the substantially same as that of the receiving pan portion, positioning or the like is readily performed when assembling the relay joint or connecting the drain pipe in a state that a worker inserts his hand from the fuel supply port into the interior of the tank main body; therefore, an assembling workability of the tank main body can be improved. Further, to achieve the above second object, the present invention provides the fuel tank system of a motor bicycle, wherein a fixing member for fixing the tank main body to the vehicle-body frame is formed out of a rigid material independently from the tank main body, a fixing portion on the tank main body side of the fixing member has a shape formed so as to surround a fixture plate of the relay joint, and the fixing member has a shape in its side view such that at least part of the fixing member is situated on a position lower than the relay joint when the fixing member is fixed to the tank main body. With the above construction, even if the tank main body swells and the fixture plate of the relay joint is dimensionally deformed, the fixing member is foxed so as to surround the fixture plate, so that the fixture plate can be prevented from being dimensionally deformed by rigidity of the fixing member. Therefore, the seal performance between the tank main body and the relay joint can be prevented from being deteriorated. Moreover, since the relay joint is surrounded by the fixing member when the fixing member is fixed to the tank main body, in the case where the tank main body is removed from the vehicle-body frame of the motor bicycle, and then, is put on the floor or the like, at least part of the tank fixing member contacts with the floor prior to the relay joint. Therefore, the relay joint does not contact directly with the floor or the like, so that the relay joint can be protected from being broken down by an external force from side or below. Further, to achieve the above third object, the present invention provides the fuel tank system of a motor bicycle, wherein a front portion fixing member is provided above and forward a reverse U-letter sectional portion of the tank main body, a side view angle of a load acting surface thereof is set within an angular range from the horizontal to an angle orthogonal to a longitudinal direction of a front fork, the load acting surface is floatingly fixed to the vehicle-body frame. With the above construction, a shearing load is not applied to a floating member (cushion rubber, etc.) of the front portion fixing member by a weight of the tank main body or a push-up reactive force from the front fork, so that a sufficient vibration-proof effect can be exhibited with respect to the vertical (up and down) direction in the front portion of the tank main body. Further, to achieve the above fourth object, the present invention provides the fuel tank system of a motor bicycle, wherein side portion fixing members are provided forward the tank main body and on both sides at a lower portion of the reverse U-letter sectional portion, an angle of respective load acting surfaces thereof is set so as to become substantially parallel with a vehicle body central surface, the respective load acting surfaces are fixed so as to be floatingly and relatively movable with respect to the vehicle-body frame, a relatively movement direction of the respective load acting surfaces is parallel with a dimensional enlargement direction when the tank main body swells. And also, to achieve the above fourth object, the present invention provides the fuel tank system of a motor bicycle, wherein a rear portion fixing member of the tank main body is provided on the rearmost portion of the tank main body, a load acting surface thereof is fixed so as to be floatingly and relatively movable with respect to the vehicle-body frame, a relatively movement direction of the load acting surface is parallel with a dimensional enlargement direction when the tank main body swells. With the above construction, a load by rolling in a lateral (right and left) direction of the tank main body is released to the vehicle-body frame via the side portion fixing members which are floatingly fixed to the vehicle-body frame, and the rearmost portion of the tank main body is also floatingly fixed to the vehicle-body frame via the rear portion fixing members, so that the whole of tank main body can be supported with respect to the vehicle-body frame so as to effect the vibration-proof. Since the side portion fixing members and the rear portion fixing member are relatively movable in the swelling direction of the tank main body with respect to the vehicle-body frame, even if the tank main body swells and dimensionally deforms, the dimensional deformation can be absorbed by relative movement of respective fixing members and the vehicle-body frame. According to such constructions mentioned above, even if the tank main body is a large scale, vibration-proof effect can be sufficiently exhibited with respect to vertical (up and down) and lateral (right and left) directions while supporting a high load, and further, a dimensional deformation when the tank main body swells can be reasonably absorbed. Further, to achieve the above fifth object, the present invention provides the fuel tank system of a motor bicycle, wherein respective right and left side surfaces of the tank main body are formed with a recessed surface for knee grip, a plurality of grip grooves is formed so that the recess surface has a section like a wave, a longitudinal direction of respective grip grooves is parallel with a divisional direction of a mold for molding the tank main body, the grip grooves are provided with a draft by enlarging a width dimension of an upper end of the grip groove than a width dimension of a lower end thereof, further, the upper end of the grip groove is formed like an open shape, and the lower end of the grip groove is formed like a closed shape. With the above construction, a rigidity of the recessed surface for knee grip is improved, so that the recessed surface can be prevented from being deformed by swelling of the tank main body. The longitudinal direction of the plurality of grooves is parallel with the divisional direction of the mold for molding the tank main body, and is provided with a draft. Further, the upper end of each groove is formed like an open shape; on the other hand, the lower end thereof is formed like a closed shape. Therefore, no undercut is caused when the tank main body is molded, so that a complication of the mold can be avoided. Further, to achieve the above sixth object, the present invention provides the fuel tank system of a motor bicycle, wherein a fixing reference portion of a frame cover covering the tank main body is fitted into a fuel supply portion positioned at the top of the tank main body, tank fastening parts of the frame cover are floating fixed to the tank main body with use of both fastening members and cushion members, and fastening member insertion holes of the tank fastening parts are formed into a slot extending to a radial direction from the fixing reference portion. With the above construction, the fixing reference portion of the frame cover is fitted into the fuel supply portion of the fuel tank, and thereby, the whole of frame cover can be accurately positioned with respect to the fuel tank. Further, the tank fastening member of the frame cover is floatingly fixed to the fuel tank, and thereby, a rotation or motion to the vertical (up and down) direction of the frame cover can be restricted with respect to the fuel tank. When the fuel tank swells, the fuel tank entirely becomes large in its shape; for this reason, a shift is caused between the fuel tank and the frame cover. Since the fixing reference portion of the frame cover is fixed to the fuel supply portion on the top portion of the fuel tank, the tank fastening part relatively separating from the fixing reference portion is movable on the upper surface of the fuel tank along the direction radially extending from the fuel supply portion. At this time, the fastening member fixing the tank fastening part is relatively movable along the longitudinally axial direction of the fastening member insertion hole of the fastening part, so that each tank fastening part can be moved on the surface of the fuel tank without an unreasonable force being applied to the whole of frame cover. As described above, even if the fuel tank swells, an unreasonable force is not applied to the frame cover, and the whole of frame cover is fixed directly to the fuel tank. This serves to obtain the following effect. Specifically, even if the frame cover is divided into a plurality of cover members and these cover member are joined together, a shift, unevenness or the like is hard to be caused between respective cover members or between these cover members and the fuel tank; therefore, a visible appearance can be preferably maintained. Further, to achieve the above seventh object, the present invention provides the fuel tank system of a motor bicycle, wherein a structure is provided such that one end of an independent cover bracket is fixed to a side of the tank main body and the frame cover is fixed to the other end of the cover bracket, the side of the tank main body is provided with a recess portion having a shape resembling to the cover bracket, one end of the cover bracket is fixed into the recess portion, and the cover bracket is provided with rigidity lowering means for lowering a side bending rigidity of the cover bracket at a position overlapping with a side profile of the tank main body. With the above construction, since 'motion to a rotating direction of the cover bracket is restricted by the recessed portion formed in the fuel tank, only one fastening member is sufficient for fixing the cover bracket to the fuel tank; therefore, a structure of the fixing portion on the fuel tank side can be simplified. Further, in the case where a great external force is applied from side to the cover bracket when the motor bicycle falls down, the cover bracket is bent into the fuel tank side from the portion of rigidity lowering means thereof. Since the rigidity lowering means is provided at a position such that the cover bracket overlaps with the fuel tank in its side profile, a stress to the fuel tank by the bending of cover bracket is prevented from being concentrated, so that the fuel tank can be protected. Further, to achieve the above eighth object, the present invention provides the fuel tank system of a motor bicycle, wherein the whole of tank main body is floatingly fixed to the vehicle-body frame, inner longitudinal wall surfaces of the reverse U-letter sectional portion of the tank main body are provided with recess portions, the recess portions are formed in its side view so as to be open in a direction separating from each other substantially at the right angle to the upper portion of the reverse U-letter section portion, elastic cushion members are individually interposed between one of the recess portions and the side surface of the vehicle-body frame and between the other of the recess portions and the same, and elastic cushion members are fixed to the vehicle-body frame side so that a clearance is defined between one of the elastic cushion members and one of the recess portions and between the other of the elastic cushion members and the other of recess portions thereof. With the above construction, even if the fuel tank made of a synthetic resin swells and deforms, the inner longitudinal wall surface (recess portion) of the fuel tank is not unreasonably pressed against the elastic cushion member. Further, if a great force is applied from side to the fuel tank, since the inner longitudinal wall surface (recess portion) of the fuel tank is abutted against the elastic cushion member, a stress is prevented from being concentrated to the fixing bracket supporting the fuel tank; therefore, a breakdown can be avoided. Further, since the elastic cushion member is provided in the recess portion on the inner longitudinal wall surface of the fuel tank in a manner of being embedded in the fuel tank, there is no need of making wide a space between the vehicle-body frame and the fuel tank. Therefore, the elastic cushion member can be provided without reducing a capacity of the fuel tank. Furthermore, the recess portion is formed in its side view so as to be open in a direction separating from each other substantially at the right angle to the upper portion of the reverse U-letter section portion, in the case where the fuel tank is attached from above to the vehicle-body frame, the elastic cushion member is hard to interfere with the fuel tank. Therefore, an assembling performance of the fuel tank to the vehicle-body frame can be improved. Further, to achieve the above nineth object, the present invention provides the fuel tank system of a motor bicycle, wherein an insert nut embedded in the tank main body is constructed so that other components are fastened thereto, and the insert nut is embedded so that an external exposure surface thereof becomes lower than an insert nut embedded surface of the tank main body. With the above construction, the insert nut does not bite into other components fastened to the tank main body made of a synthetic resin, and therefore, other components can be prevented from being broken down by the insert nut. Further, other components are fully closely fitted into the insert nut embedded surface of the tank main body, so that other components can be stably fastened to the tank main body. BRIEF DESCRIPTION OF THE DRAWINGS In the accompanying drawings: Fig. 1 is a left side view showing one example of a motor bicycle to which the present invention is applicable; Fig. 2 is an enlarged left side view showing the vicinity of a front portion of the motor bicycle shown in Fig. 1; Fig. 3 is a left side view of a fuel tank system which is mounted onto the motor bicycle shown in Fig. 1 and 2; Fig. 4 is a plan view of the fuel tank system; Fig. 5 is a front view of the fuel tank system; Fig. 6 is a cross-sectional view cut along the line VI-VIof Fig. 3: Fig. 7 is a cross-sectional view cut along the line VII-VIIof Fig. 3; Fig. 8 is a cross-sectional view cut along the line VIII-VIIIof Fig. 3; Fig. 9 is a view from a direction indicated by an arrow IX of Fig. 3; Fig. 10 is a longitudinally cross-sectional view cut along the line X-X of Fig. 4; Fig. 11 is an enlarged view of a portionX of Fig. 2; Fig. 12 is a view from a direction indicated by an arrow X of Fig. 2; Fig. 13 is a left side view showing a state in which a tank side cover and a tank upper cover covering a tank main body of the fuel tank system are combined; Fig. 14 is a plan view of the tank upper cover; Fig. 15 is an exploded perspective view showing the tank side cover and the tank upper cover; Fig. 16 is a longitudinally cross-sectional view cut along the line XVI-XVIshown in Fig. 4 and Figs. 13 and 14; Fig. 17 is a longitudinally cross-sectional view cut along the line XVII-XVIIof Fig. 3; Fig. 18 is a side view of a cover bracket for fixing the tank side cover to the tank main body; Fig. 19 is a longitudinally cross-sectional view cut along the lineX X-X X of Fig. 18; and Fig. 20 is a longitudinally cross-sectional view showing a state in which the cover bracket is fastened onto a recess portion of the tank main body. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the accompanying drawings. Fig. 1 is a left side view showing one example of a motor bicycle to which the present invention is applicable, and Fig. 2 is an enlarged left side view showing the vicinity of a front portion of the motor bicycle shown in Fig. 1; A motor bicycle 1 is equipped with, for example, a semi-double cradle type vehicle-body frame 2 (see Fig. 2). The front portion of the vehicle-body frame 2 is mounted with power apparatuses such as an engine 3, a carburetor 4 or the like. An upper portion of the engine 3 is provided with a fuel tank system 5, and a seat 6 is provided following a rear portion of the fuel tank system 5. On the other hand, a front fork 7 is pivotally supported to a head pipe 2a situated on a front head portion of the vehicle-body frame 2 so as to be rotatably right and left. A front wheel 8 is supported to a distal end of the front fork 7, and an upper portion of the front fork 7 is provided with a handlebar 9. Further, a swing arm 12 is supported to a pivot shaft 11 stretched to a central lower portion of the vehicle-body frame 2 so as to be swingably up and down, and a rear wheel 13 is supported to a rear portion of the swing arm 12. A power of the engine 3 is transmitted to the rear wheel 13 via a chain 14. A frame cover 16 made of a synthetic resin, which covers respective portions of the vehicle body, is mounted. The frame cover 16 is constructed by joining together a plurality of divided cover members, that is, a front cowl 18, a tank side cover 19, a tank upper cover 20, an engine side cover 21, a seat side cover 22, and a tail cover 23. The front cowl 18 is situated on a forward portion of the handlebar 9, and a head light 17 or the like is attached thereto. The tank side cover 19 extends backward while connecting with a lower portion of the front cowl 18 so as to covers a side face of the fuel tank system 5 (i.e., a tank main body 26 which will be described later). The tank upper cover 20 covers an upper portion of the fuel tank system 5. The engine side cover 21 connects with a lower portion of the tank side cover 19 so as to cover upper right and left side faces of the engine. The seat side cover 22 covers right and left lower portions of the seat 6. Further, the tail cover 23 is provided so as to connect with a rear portion of the seat 6. Fig. 3, Fig. 4 and 5 are a left side view, a plan view and a front view of the fuel tank system 5, respectively. Also, Fig. 6 and 7 are cross-sectional view cut along the lines VI-VI and VII-VII of Fig. 3, Fig. 8 is a cross-sectional view cut along the line VIII-VIII of Fig. 3, Fig. 9 is a view from a direction indicated by an arrow IX of Fig. 3, and Fig. 10 is a longitudinally cross-sectional view cut along the line X-X of Fig. 4. The fuel tank system 5 includes a tank main body 26 which is integrally molded out of a synthetic resin material such as PE or the like. The tank main body has a substantially reverse U-letter section shape as riding from above on a main pipe 2b positioned on the front head portion of the vehicle-body frame 2. Further, the tank main body 26 is fixed to the vehicle-body frame 2 via a front portion fixing member 27, side portion fixing members 28L and 28R and a rear portion fixing member 29, which are formed by subjecting rigid materials such as plate and sheet to press molding. As shown in Fig. 2 to Fig. 5, the front portion fixing member 27 is arranged above a reverse U-letter sectional portion 26a on the front side of the tank main body 26. Further, the front portion fixing member 27 has a fastening surface 27a and a load acting surface 27b, and is formed into a substantially L-letter shape in its side. The fastening surface 27a is fastened onto an insert nut 32 embedded in the front side of the tank main body 26 by means of two bolts 31. A side view angle of the load acting surface 27b, when the front portion fixing member 27 is fixed to the tank main body 26 as described above, is set so as to orthogonal to a longitudinal direction of the front fork 7 in this embodiment. In this case, the angle of the load acting surface 27b may be set within an angular range from this angle to the horizontal. The load acting surface 27b is formed with a circular hole 27c, and cushion rubbers 34 and 35 and a spacer 36 of a metallic pipe are fitted into the circular hole 27c. A bolt 37 inserted into the spacer 36 from above is fastened to a fixing bracket 2c (see Fig. 2) just after the head pipe 2a of the vehicle-body frame 2. Thus, the load acting surface 27b is floatingly (vibration proof) fixed with respect to the vehicle-body frame 2 by an elasticity of these cushion rubbers 34 and 35. On the other hand, side portion fixing members 28L and 28R are arranged on both sides at the lower portion of the reverse U-letter sectional portion 26a on the front side of the tank main body 26. These side portion fixing members 28L and 28R have a fastening surface 28La;28Ra and a load acting surface 28Lb;28Rb, and are formed into a substantially L-letter shape, respectively. Respective fastening surfaces 28La;28Ra are fastened onto an insert nut 39 embedded in the lower portion on the front side of the tank main body 26 by means of two bolts 38. An angle of respective fastening surfaces 28La;28Ra, when these side portion fixing members 28L and 28R are fixed to the tank main body 26, is set so as to be substantially parallel with a vehicle-body central surface C (see Fig. 5 and 6). Respective load acting surfaces 28Lb and 28Rb are formed with a slot 28c (see Fig. 3), and a cushion rubber 41 and a spacer 42 shown in Fig. 5 are respectively fitted into the slot 28c. A bolt 43 inserted through the spacer 42 from the outside is fastened to a fixing bracket 2d (see Fig. 29) which is located at right and left sides on the front portion of the vehicle-body frame 2. Thus, these load acting surfaces 28La and 28Ra are fixed to the vehicle-body frame 2 so as to be floatingly and relatively movable in a longitudinal axial direction of the slot 28c by an elasticity of the cushion rubber 41. The longitudinal axial direction of the slot 28c is parallel with a dimensional enlargement direction A (see Fig. 3) when the tank main body swells. Further, the rear portion fixing member 29 is formed having a fastening surface 29a and a load acting surface 29b. The fastening surface 29a is fastened to an insert nut 45 (see Fig. 4) embedded in the lower face on the rear portion of the tank main body 26 by means of four bolts 44 (see Fig. 9). An angle of the load acting surface 29b when the rear portion fixing member 29 is fixed to the tank main body is set so as to become substantially horizontal. The load acting surface is formed with a pair of right and left slots 29c;29c at its rear portion. A cushion rubber 47 and a spacer 48 shown in Fig. 3 are fitted into each of slots 29c;29c. A bolt 49 inserted through the spacer 48 from above is fastened to a fixing bracket 2e (see Fig. 2) which is located above an intermediate portion of the vehicle-body frame 2. Thus, the load acting surface 29b is fixed to the vehicle-body frame 2 so as to be floatingly and relatively movable in a longitudinally axial direction of the slot 28c by an elasticity of the cushion rubber 47. The longitudinally axial direction of the respective slots 29c;29c is parallel with a dimensional enlargement direction B (see Fig. 3) when the tank main body swells. As described above, the side view angle of the load acting surface 27b of the front portion fixing member 27 is set within an angular range from the horizontal to an angle orthogonal to the longitudinal direction of the front fork 7. For this reason, a weight of the tank main body 26 and a push-up reactive force from the front fork 7 do not apply a shearing load to the cushion rubbers 34 and 35 of the front portion fixing member 27. Therefore, These cushion rubbers 34 and 35 carry only load in a vertical direction, so that these cushion rubbers 34 and 35 can sufficiently exhibit a vibration proof effect in the vertical direction on the front portion of the tank main body 26. Further, a load due to rolling in a lateral (right and left) direction of the tank main body 26 is released to the vehicle-body frame 2 via side portion fixing members 28L and 28R and the cushion rubber 41, and a load the rear portion of the tank main body 26 is applied to the vehicle-body frame 2 via the rear portion fixing member 29 and the cushion rubber 47. As described above, respective portions of the tank main body 26 are floatingly supported as a whole, and a load from one direction is only applied to these cushion rubbers 34, 35, 41 and 47; therefore, no shearing load is applied. Thus, even if the tank main body 26 is a large-scale tank, vibration proof effect can be sufficiently exhibited in the vertical direction and the right and left direction while carrying a high load of the tank. Further, the longitudinally axial direction of the slots 28c of the side portion fixing member 28L and 28R and the longitudinally axial direction of the slots 29c of the rear portion fixing member 29 and 28R, are parallel with the dimensional enlargement directions A and B when the tank main body 26 swells, respectively. Therefore, even if the tank main body 26 swells due to contact with a fuel and is dimensionally deformed (e.g., enlarged), the side portion fixing members 28L and 28R and the rear portion fixing member 29 are relatively movable with respect to the vehicle-body frame 2 along the above dimensional enlargement direction A and B, so that a dimensional deformation of the tank main body 26 can be reasonably absorbed. As shown in Fig. 2 to Fig. 4, Fig. 10 and 11, the upper portion of the tank main body 26 is provided with a fuel supply port 50. The fuel supply port 50 has a circular receiving pan fixing surface 51 which is lower one step than the upper surface of the tank main body 26, and is formed with an opening 52 at its central portion. The receiving pan fixing surface 51 is formed with an annular shallow gasket groove 53 which surrounds the opening 52. Several insert nuts 54 are embedded along the gasket groove 53. An annular and strip-like gasket 55 formed of a chemical proof rubber or the like is fitted into the gasket groove 53, and then, a metallic receiving pan portion 56 is placed thereon, and further is fastened to the insert nuts 54 by means of some bolts 57. The receiving pan portion 56 has a pan member 59 which is pressed and molded into a dish shape, a cylindrical member 60 fixed to a hole formed at the center of the pan member 59, and a union member 61 which extends downward vertically from one side of the pan member 59 to the interior of the tank main body 26. The gasket 55 is closely attached to the lower surface of the pan member 59. As shown in Fig. 10, a recessed type (so-called aircraft type) tank cap 62 is fixed to the pan member 56 by means of several bolts 63. The tank cap 62 has a construction in which a cap assembly 65 is attached to a cap base 64 so as to freely opened and closed. When the cap assembly 65 is closed, a lock lever 66 of the cap assembly 65 is latched on a lower portion of the cylindrical member 60 of the pan member 56, and then, the cap assembly 65 is locked. The cap assembly 65 is equipped with a key cylinder 67. The latch of the lock lever is released by inserting a specified key into the key cylinder 67 and twisting it, and then, the cap assembly 65 is opened. A reference numeral 68 denotes a lid of the key cylinder 65. Meanwhile, a bottom portion on the left side of the tank main body 26 is provided with two kinds of fixture plates 70 and 71 at its front and rear. As shown in Fig. 3, a remained fuel gauge 72 is attached toward inside to the fixture plate 70 on the front side; on the other hand, a fuel cock 73 is attached from the outside to the fixture plate 71 on the rear side. The remained fuel gauge 72 is fastened to some insert nuts 74 embedded in the fixture plate 70 by means of a bolt 75. Also, the fuel cock 73 is connected with a fuel hose 76 and a vacuum hose 77, and the other ends of these hoses 76 and 77 are connected to the carburetor 4. Further, as shown in Fig. 9, the bottom portion on the left side of the tank main body 26 is provided with a fixture plate 79, and a relay joint 80 is fixed to the fixture plate from the outside by means of two vises 81. The attachment direction of the relay joint is the substantially identical direction as that of the receiving pan portion 56. Thus, this serves to facilitate a assembling work of the relay joint 80 when a worker inserts hid hand into the interior of the tank main body 26 from the fuel supply port, and a positioning work when making a connection of a drain pipe 85 which will be described later. Therefore, assembling workability of the tank main body 26 can be improved. The relay joint 80 is an integral molding product of for example, a synthetic resin, and includes an outer union 82 extending outside the tank main body 26, and an inner union 83 extending inside the tank main body 26. An external hose 84 (see Fig. 2) connected to the outer union 82 is extended downward, and its free end is open outside. One end of the drain pipe 85 is connected to the inner union 83; the other end the drain pipe 85 is connected to the union member 61 of the receiving pan portion 56. In such a manner, the drain pipe 85 extends from the receiving pan portion 56 of the fuel supply port 50, and passes through the interior of the tank main body 26, and then, is connected to the relay joint 80. The drain pipe 85 is a hose made of a soft material such as rubber or the like, and is molded so that a immediately rear portion of the drain pipe 85 extending from the inner union 83 is bent at a right angle (90 dgree) and is directed toward the receiving pan portion 56. For example, in rainy weather running or in supplying a fuel, water or fuel flowing into the receiving pan portion 56 is discharged from the external hose 84 to the outside via the drain pipe 85 and the relay joint 80. Even if when the tank main body swells due to contact with a fuel, a dimensional deformation is slightly caused between the receiving pan portion 56 and the relay joint slightly varies, the drain pipe 85 is adaptable to the dimensional deformation because it is a soft hose. Therefore, even if an unreasonable force is applied to the connective portion of the drain pipe 85, no deterioration is caused in seal performance. Further, it is possible to freely set a bent shape of the drain pipe 85; therefore, the drain discharge direction (a locating place of the relay joint 80) can be freely selected. Meanwhile, as shown in Fig. 4 and 9, the rear portion fixing member 29 for fixing the rear portion of the tank main body 26 to the vehicle body frame 2 is formed into a substantially U-letter shape such that a fixing portion on the tank main body 26 side surrounds the fixture plate 79 of the relay joint 80. Even if the tank main body 26 swells and a dimensional deformation is caused in the fixture plate 79, the dimensional deformation can be prevented by rigidity of the rear portion fixing member 29. Therefore, a warp is hard to be caused in the fixture plate 79, and also, it is possible to prevent deterioration in seal performance between the tank main body 26 and the relay joint 80. As shown in Fig. 3, when the fastening surface 29a of the rear portion fixing member 29 is fixed to the lower surface on the rear portion of the tank main body 26, the rear portion fixing member 29 has a side sectional shape such that at least part of the rear portion fixing member 29 is situated on a position lower than the relay joint 80. In the present embodiment, the rear portion fixing member 29 is slightly bent in its side view at a portion between the fastening surface 29a and the load acting surface 29b; therefore, the load acting surface 29b is formed so as to become lower than the relay joint 80. Thus, in the case of removing the tank main body 26 from the vehicle-body frame 2 and putting it on a floor or the like, the relay joint 80 does not directly contact with the floor or the like because the rear portion fixing member 29 contacts with the floor or the like prior to the relay joint 80. Therefore, the relay joint 80 can be effectively protected from a breakdown by an external force acting from the side or lower direction. Meanwhile, as shown in Fig. 2 to Fig. 4 and 7, right and left sides of the tank main body 26 are formed with a recessed surface 87 which is slightly recessed inwardly. The recessed surface 87 serves to make stable a riding posture in a state in which a rider who rides on the motor bicycle 1 grips the tank main body 26 at his knee. The recessed surface 87 is formed with a plurality of grip grooves 88 which extends in a substantially longitudinal direction. The recess surface 87 is formed like a wave in its section by these grip grooves 88. As shown in Fig. 3, a longitudinal direction of the respective grip grooves 88 is parallel with a divisional direction D of a mold for molding the tank main body 26. The divisional direction D is orthogonal to an upper side 26b of the reverse U-letter sectional portion 26a, for example. Further, a width dimension 88a of the upper end of the grip grooves 88 is larger than a width dimension 88b of the lower end thereof, and thereby, the grip groove 88 is provided with a draft. The upper end of the grip groove 88 is formed like an open shape; on the other hand, the lower end thereof is formed like a closed shape. The aforesaid plurality of grip grooves 88 is provided on the recessed surface 87, and thereby, rigidity of the recessed surface 87 is remarkably improved; for this reason, the recessed surface 87 is hard to be deformed (hard to be swelled) when the tank main body 26 swells. These grip groove 88 are parallel with the divisional direction D of the mold, and are provided with a draft, and further, their upper and lower ends are formed into an open-like shape and a closed-like shape, respectively; for this reason, there is no generation of undercut when molding the tank main body 26. Therefore, complicate (multiple divided) molds do not need, so that the cost spent for these molds can be restricted more cheaply. As shown in Fig. 12, the front side of the tank main body 26 is formed with a pair of right and left thick relief grooves 89 which extend in a longitudinal direction. These relief grooves 89 serves to prevent the front fork 7 from contacting with the tank main body 26 when the handlebar 9 of the motor bicycle 1 is cut to the right and left. Also, the tank main body 26 has a front surface formed into a substantially flat surface except the aforesaid two relief grooves 89, and an inclination angle on the front side of tank main body 26 is set so as to meet a caster angle of the front fork 7. Further, as shown in Fig. 4, the tank main body 26 is formed so that the forefront portion thereof has the maximum width, and the front portion of the tank main body 26 is constructed so as not to be overhung ahead the front fork 7. The front portion of the tank main body 26 is formed into the shape as described above, and thereby, a capacity of the tank main body 26 is increased to the maximum limit while sufficiently securing the rigidity of the front portion of the tank main body 26. In this manner, it is possible to restrict a deformation by swelling of the tank main body 26, or to facilitate an absorption of the deformation by swelling. On the other hand, as shown in Fig. 3 and 8, inner longitudinal wall surface 26c and 26c on the reverse U-letter sectional portion 26a of the tank main body 26 is provided with recess portions 26d and 26d. These recess portions 26d and 26d are formed so as to be open in a direction separating from each other substantially at the right angle to the upper portion 26b of the reverse U-letter section portion 26a in its side view (see Fig. 3), and to have an opened shape as being widened toward the end. Meanwhile, one metallic pipe 91 extending in a vehicle width direction is stretched across the front portion of the vehicle-body frame 2 at a position corresponding to recess portions 26d and 26d of the tank main body 26. The metallic pipe 91 is provided so as to be slidably in the vehicle width direction in a manner of penetrating through reinforcement plates 2f and 2f stack to the front portion of the vehicle-body frame 2. And then, elastic cushion members 92 and 92 formed of elastic materials such as rubber or the like are attached to right and left both ends of the metallic pipe 91. Thus, the elastic cushion members 92 and 92 are fixed on the vehicle-body frame 2 side, and interposed between recess portions of the tank main body 26 and the side (reinforcement plates 2f and 2f) of the vehicle-body frame 2. Metallic plates 93 and 93 are embedded in the elastic cushion members 92 and 92. The elastic cushion members 92 and 92 is inserted into the metallic pipe 91 until the metallic plates 93 and 93 abut against the right and left both ends of the metallic pipe 91. Also, as shown in Fig. 8, a clearance 94 is defined between the right elastic cushion member 92 and the recess portion 26d of the tank main body 26 and between,the left elastic cushion member 92 and the recess portion 26d thereof. A width of the clearance is set to about several millimeters. As described above, clearances 94 and 94 are defined between the right and left elastic cushion members 92 and the tank main body 26 (recess portion 26d and 26d). Thus, even if the tank main body 26 made of a synthetic resin swells and is deformed due to contact with a fuel, the inner longitudinal wall surfaces 26c and 26c (recess portion 26d and 26d) are not forcedly pressed against the elastic cushion members 92 and 92. Therefore, it is possible to effectively avoid a deformation of the tank main body 26 or breakdown of respective fixing members 27, 28L, 29R and 29 by stress concentration. In the case where a great force acts on the tank main body 26 from the side when the motor bicycle 1 is slipped and fall down and has a collision, although the tank main body 26 floatingly fixed to the vehicle-body frame 2 is slightly moved toward the side, either of right and left inner longitudinal wall surfaces 26c and 26c (recess portions 26d and 26d) of the tank main body 26 is directly abutted against the elastic cushion members 92 and 92. For this reason, the tank main body is not moved toward the side any more. This serves to prevent the breakdown of the tank main body 26 and the breakdown of respective fixing members 27, 28L, 29R and 29 by stress concentration. Moreover, these elastic cushion members 92 and 92 are provided so as to be received in the recess portions 26d and 26d of the tank main body 26. For this reason, unlike the prior art, there is no need of widen an interval (distance) between the vehicle-body frame 2 and the tank main body 26 in order to provide elastic cushion members 92 and 92, so that a basic interval E (see Fig. 8) between the vehicle-body frame 2 and the tank main body 26 can be set so as to be narrower. Therefore, this make it possible to locate these elastic cushion members 92 and 92 without decreasing the capacity of the tank main body 26. Also, the formation of recess portions 26d and 26d serve to greatly improve the rigidity of the inner longitudinal wall surface 26c and 26c. As described above, these recess portions 26d and 26d are formed so as to be open in a direction separating from each other substantially at the right angle to the upper portion 26b of the reverse U-letter section portion 26a in its side view, and to have a opened shape as being widened toward the end. For this reason, in the case where the tank main body 26 is attached to the vehicle-body frame 2 (main pipe 2b) from top, the elastic cushion members 92 and 92 is hard to interfere with the tank main body 26, so that the tank main body 26 can be smooth assembled into the vehicle-body frame 2. By the way, Fig. 13 is a left side view showing a state in which a tank side cover 19 and a tank upper cover 20 constituting the frame cover 16 are combined, and Fig. 14 is a plan view showing the tank upper cover 20. Also, Fig. 15 is an exploded perspective view showing the tank side cover 19 and the tank upper cover 20. Further, Fig. 16 is a longitudinally cross-sectional view cut along the line XVI-XVI shown in Fig. 4 and Figs. 13 and 14, and 17 is a longitudinally cross-sectional view cut along the line XVII-XVII of Fig. 3. As described before, right and left side portions of the tank main body 26 is covered by the tank side cover 19; on the other hand, the upper portion thereof is covered by the tank upper cover 20. The tank upper cover 20 is formed with a circular opening 97 as a fixing reference portion on the center thereof. An inner diameter of the opening 97 is set so as to be closely fitted into an outer diameter of the fuel supply portion of the tank main body 26, for example, the receiving pan portion 56 (pan member 59) provided on the fuel supply port 50. Further, the tank upper cover 20 is provided with totaled three tank fastening members 98, 98 and 99 at the right and left portions thereof and at the rear portion thereof. Each of these fastening parts 98, 98 and 99 is formed with a fastening member insertion hole 100. Each fastening member insertion hole 100 is formed into a short slot extending along a radial direction F (see Fig. 14 and Fig.15) from the opening 97. Further, the tank upper cover 20 is provided with cover fastening parts 101, 101, 102 and 102 at each of four corners thereof. A nut plate 103 is fixed to the cover fastening parts 101 and 101 on the front side from below by means of two rivets 104 or the like; on the other hand, a clip nut is inserted into the cover fastening parts 102 and 102 on the rear side. On the other hand, each of right and left tank side covers 19 is provided with front and rear two tank fastening parts 107 and 108 at the lower side portion thereof. These tank fastening parts 107 and 108 are formed with a fastening member insertion hole 109 and 110, respectively. The fastening member insertion hole 109 of the front tank fastening part 107 is formed into a short slot extending from the opening 97 of the tank upper cover 20 to a radial direction F (see Fig. 13 and Fig. 15) when the tank side cover 19 is connected and fixed to the tank upper cover 20. Also, the fastening member insertion hole 110 of the rear tank fastening part 108 is formed into a slot extending substantially along to a longitudinal direction G (see Fig. 15) from the opening 97 of the tank upper cover 20. Further, the tank side cover 19 is provided with totaled five cover fastening parts 111 to 115 at the upper side portion thereof. Cover attaching holes 116 and 117 is provided on front and rear sides of respective tank fastening parts 107 and 108. A clip nut 118 is inserted into each three cover fastening parts 111 to 113 on the front side. A rubber push 119 having a small hole is fitted into each of the cover attaching holes 116 and 117. Meanwhile, as shown in Fig. 4 and 16, both shoulder portions of the tank main body 26 is formed with an inclined flat cover fastening surface 121 in which an insert nut 122 is embedded. Also, the rear portion of the fuel supply port 50 of the tank main body 26 is formed with a cover fastening surface 123 in which an insert nut 124 is embedded (see Fig. 4). As shown in Figs. 2, 3, 5 and 6, a recess portion 126 is formed at each of right and left sides on the front lower portion of the tank main body 26, and an insert nut 127 is embedded therein. As shown in Figs. 2, 3 and 17, on right and left sides of the rear lower portion of the tank main body 26, there is formed a convex portion 128 which is situated on the backward of the recess portion 126, and an insert nut 129 is embedded therein. As shown in Fig. 18 to Fig. 20, an upper end of a cover bracket 131 which is formed by subjecting plate and sheet to press molding is fastened to the insert nut 127 of the recess portion 126. The cover bracket 131 is formed into a substantially elliptic shape, and a nut 133 is fixed and attached from inside to the lower end of cover bracket 131. The opening 97 of the tank upper cover 20 is engaged with (fitted into) the receiving pan portion 56 of the tank main body 26 while three tank fastening parts 98, 98 and 99 thereof being floatingly fixed to the tank main body 26. As shown in Fig. 15 and 16, a cushion member 135 such as rubber bush or the like and a metallic pipe spacer 136 are fitted into each of these three tank fastening parts 98, 98 and 99, and a vise (screw) 137 is inserted into each spacer 136 from outside. These vises 137 are individually fastened to the insert nuts 122 and 124 of the cover fastening surfaces 121 and 123 of the tank main body 26. Since a claming force of respective fastening members (vises) 137 is released to the tank main body 26 via the spacer 136, the cushion member 135 is not crushed. Thus, respective tank fastening parts 98, 98 and 99 are floating fixed to the tank main body 26 by the elasticity of cushion member 135. The tank side cover 19 is connected and fixed to the tank upper cover 20 by its cover fastening parts 114 and 115 being respectively fastened and fixed onto the cover fastening part 101 (nut plate 103) and the cover fastening part 102 (clip nut 105) of the tank upper cover 20 by means of the vises 139. Also, the cover fastening parts 114 and 115 and the vises 139 are not exposed on the exterior surface because they are covered from top by the front cowl 18 and the seat 6. Further, the cushion member 141 such as rubber push or the like and the metallic pipe spacer 142 are fitted into each of two fastening parts 107 and 108 of respective tank side covers 19, and then, the vise 143 is inserted from outside into each spacer 142. Subsequently, these vises 143 are fastened to the nut 133 of the cover bracket 131 fixed on the tank main body 26 and the insert nut 129 of the convex portion 128 of the tank main body 26. Here, a claming force of respective fastening members (vises) 143 is also released to the cover bracket 131 and the tank main body 26 via the spacer 142. Thus, respective tank fastening parts 107 and 108 are floating fixed to the cover bracket 131 and the tank main body 26 by the elasticity of cushion member 135. As seen from the above description, the tank upper cover 20 and the tank side covers 19 are connected and fixed to each other while being floating fixed to the tank main body 26. Also, the front cowl 18 is fastened and fixed to the clip nut 118 inserted into the cover fastening parts 111, 112 and 113 of the tank side cover 19 by means of a vise (not shown). Further, a protrusion (not shown) formed on the inner surface of the engine side cover 21 is fitted into the rubber bush 119 of the cover fastening hole 116 and 117 of the tank side cover 19. The opening 97 of the tank upper cover 20 is fitted into the receiving pan portion 56 of the tank main body 26, and thereby, the tank upper cover 20 is accurately positioned with respect to the tank main body 26 (vehicle body). Also, the tank side covers 19 connected to the tank upper cover 20 (in addition, the whole of frame cover 16) is accurately positioned with respect to the tank main body 26 (vehicle body). Further, respective tank fastening parts 98, 99, 107 and 108 of the tank upper cover 20 and the tank side cover 19 are floatingly fixed to the tank main body 26, and thereby, a rotation and a vertical (up and down) motion of the tank upper cover 20 and the tank side covers 19 with respect to the tank main body 26 can be restricted. Now, in the case where the tank main body swells due to contact with a fuel, the whole of tank main body becomes large in its shape; for this reason, a dimensional deformation is generated between the tank main body 26, the tank side covers 19 and the tank upper cover 20. However, the opening 97 which is a fixing reference portion of the tank upper cover 20 is fixed to (fitted into) the receiving pan portion 56 of the tank main body 26, so that the tank fastening parts 98, 99 107 relatively separating from the opening 97 can be moved on the upper surface of the tank main body 26 along the direction F radially extending from the receiving pan portion 56. At that time, fastening members 137 and 143 fixing these tank fastening parts 98, 99 and 107 are relatively moved along the longitudinal direction (F) of the fastening member insertion hole of respective tank fastening parts 98, 99 107 together with cushion members 135 and 141 and spacers 136 and 142, so that no unreasonable force is applied to the tank upper cover 20 and the tank side covers 19 due to a dimensional deformation by swelling of the tank main body 26. Moreover, since the tank upper cover 20 and the tank side covers 19 are directly fixed to the tank main body 26, a shift, unevenness or the like is hard to be caused between two cover members 19 and 20 and between these cover members 19 and 20 and the tank main body 26. Therefore, a visible appearance around the fuel tank system 5 can be preferably maintained. In the present embodiment, only fastening member insertion hole 110 of the rear tank fastening parts 108 of the tank side cover 19 is exceptionally formed into a slot extending along the longitudinal direction G of the tank side cover 19. This is because of absorbing a dimensional deformation in front and rear direction when the tank side cover 19 having a shape extending long front and rear swells or shrinks. By the way, as described before, the cover bracket 131 for fixing the tank side cover 19 is fixed to the tank main body 26. The cover bracket 131 is fastened and fixed to the insert nut 127 embedded in the recess portion 126 formed on right and left sides of the front lower portion of the tank main body 26 by means of the bolt 132. The recess portion 126 is formed into a similar figure which is slightly larger than the cover bracket 131. Therefore, the cover bracket 131 fixed in the recess portion 126 is restricted from being rotated, and further, the cover bracket 131 is fixed to the tank main body by means of only one bolt 132 without being rotated. This contributes to simplification of a fixing portion structure on the tank main body 26 side of the cover bracket 131. Further, the cover bracket 131 is molded by subjecting plate and sheet to press molding. As shown in Fig. 18 to Fig. 20, the cover bracket 131 is formed with a short longitudinal wall-like flange 145 over the entire circumference thereof. A linear portion of the flange 145 is formed with a pair of notches 146. The notch 146 functions as rigidity lowering means for lowering a side bending rigidity of the cover bracket 131. Further, the position of notch 146 is set at a position such that the cover bracket 131 overlaps with a side profile of the tank main body 26 in its side view. For this reason, in the case where a great force is applied from side to the cover bracket 131 when the motor bicycle 1 is slipped and fall down, the cover bracket 131 is bent from the notch portion 146 into the tank main body 26 side, as a cover bracket 131a shown in Fig. 20. Since the notch 146 is provided at the position such that the cover bracket 131 overlaps with a side profile of the tank main body 26, a stress to the tank main body 26 due to bending of the cover bracket 131 is prevented from being concentrated, so that the tank main body 26 can be effectively protected. Meanwhile, as being enlarged in Fig. 11, the insert nut 54 embedded in the fuel supply port 50 (gasket groove 53) is embedded so that an external exposure surface 54a thereof becomes about 0.5 to 1.0 mm lower than the insert embedded surface of the tank main body 26, that is, a bottom surface 53a of the gasket groove 53. By doing so, the insert nut 54 is prevented from biting into the gasket 55 of the receiving pan portion 56 fastened to the inserted nut 54, and the gasket 55 is also prevented from being damaged by the insert nut 54. Moreover, the gasket 55 is fully closely fitted into the gasket groove 53 over the entire circumference of the bottom surface 53a of the gasket groove 53, so that seal performance of the gasket 55 can be greatly improved. Even in the case where the receiving pan portion 56 is fastened directly onto the receiving pan fixing surface 51 without interposing the gasket 55 between the receiving pan portion 56 and the tank main body 26, if the external exposure surface 54a of the insert nut 54 is set so as to become lower than the receiving pan fixing surface 51, the receiving pan portion 56 is fully closely abutted against the receiving pan fixing surface 51, so that the receiving pan portion 56 can be stably fastened thereto. Further, without being limited to the insert nut 54 for fastening the receiving pan portion 56, the embedded structure as described above may be applied to other insert nuts embedded in the tank main body 26, for example, insert nuts 32, 39 and 45 for fastening respective fixing members 27, 28L, 28R and 29, the insert nut 74 for fastening the remained fuel gauge 72, insert nuts 122, 124, 127 and 129 for fastening the tank side covers 19 and the tank upper cover 20, etc.

Claims: A motor bicycle fuel tank system (5) comprising a tank main body (26) made of a synthetic resin material and configured into a reverse U-shaped sectional portion (26a) with respect to a longitudinal axis of the tank main body (26) so as to straddle a front head portion of a motor bicycle body frame (2) when the motor bicycle fuel tank system (5) is arranged on the motor bicycle (1) while in an assembled state, and a fuel supply port (50) provided on an upper portion of the tank main body (26), characterised in that it further comprises a receiving pan portion (56) detachably fastened in the fuel supply port (50) and configured to extend along an attachment direction when attached to the fuel supply port (50); a circular receiving pan fixing surface (51) in the fuel supply port (50), which is lower than an upper surface of the tank main body (26) and is formed with an opening (52) at its central portion; a relay joint (80) arranged in a vicinity of a bottom portion of the tank main body (26) and configured to be attached to the bottom portion of the tank main body (26) along a direction that is substantially the same as the attachment direction of the receiving pan portion (56); and a drain pipe (85) comprising a soft hose passing through an interior of the tank main body (26) and connected to the receiving pan portion (56) and the relay joint (80) when the receiving pan portion (56) is detachably fastened to the fuel supply port (50) and when relay joint (80) is attached to the bottom portion of the tank main body (26). The motor bicycle fuel tank system (5) according to claim 1 comprising: a fixing member (29) formed out of a rigid material independent from the tank main body (26) and configured to fix the tank main body (26) to the motor bicyde frame (2) when the motor bicycle fuel tank system (5) is in the assembled state, said fixing member (29) having a fixing portion on the tank main body (26) side and configured to surround a fixture plate (79) of the relay joint (80), and wherein the fixing member (29) has a shape in its side view such that at least part of the fixing member (29) is situated on a position lower than the relay joint (80) when the fixing member (29) is fixed to the tank main body (26). The motor bicycle fuel tank system (5) according to claim 1, further comprising: a front portion fixing member (27) provided at a top front location of the reverse U-shaped sectional portion (26a) of the tank main body (26) and having a load acting surface (27b) extending from the top front location along a direction substantially parallel to the longitudinal axis of the tank main body (26) so as to define a side view angle between a horizontal direction and an angle substantially orthogonal to a longitudinal direction of a front fork (7) of the motor bicycle (1) so that the load acting surface (27b) of the front portion fixing member is floatingly fixed to the motor bicycle body frame (26) when the fuel tank system (5) is arranged on the motor bicycle (1) while in the assembled state. The motor bicycle fuel tank system (5) according to claims 1 or 3, further comprising: a plurality of side portion fixing members (28L, 28R) each provided at a forward location of the tank main body (26) and on both sides of a lower portion of the reverse U-shaped sectional portion (26a) and each having a load acting surface (28Lb, 28Rb) extending from the forward location along a direction substantially perpendicular to a dimensional enlargement direction of the tank main body (26) and defining an angle substantially parallel to a central surface of the motor bicycle body frame (2) so that the respective load acting surfaces are floatingly fixed and relatively movable with respect to the motor bicycle body frame (2) when the motor bicycle fuel tank system (5) is arranged on the motor bicycle (1) while in the assembled state, and such that a relative movement direction of each of the respective load acting surfaces of the side portion fixing members (28L, 28R) is parallel to the dimensional enlargement direction when the tank main body (26) swells. The motor bicycle fuel tank system (5) according to any of claims 1, 2, or 3, further comprising: a rear portion fixing member (29) provided on a rearmost portion of the tank main body (26) and having a load acting surface (29b) extending from the rearmost portion along a direction substantially perpendicular to a dimensional enlargement direction of the tank main body (26) so as to be floatingly fixed and relatively movable with respect to the motor bicycle body frame (2) when the motor bicycle fuel tank system (5) is arranged on the motor bicyde (1) while in the assembled state, and such that a relative movement direction of the load acting surface (29b) is parallel to the dimensional enlargement direction when the tank main body (26) swells. The motor bicycle fuel tank system (5) according to claim 1, further comprising: at least one recessed knee grip surface formed on a side surface of the tank main body (26); and a plurality of grip grooves (88) formed on opposite sides of the at least one recessed knee grip surface so that the side surface of the tank main body (26) defines a wave shape, and configured such that a longitudinal direction of each respective grip groove (88) is parallel to a divisional direction of a mold for molding the tank main body (26), said plurality of grip grooves (88) each having a draft configured such that a width dimension of an upper end of the grip groove (88) is greater than a width dimension of a lower end thereof, and the upper end of the grip groove (88) defines an open shape and the lower end of the grip groove (88) defines a closed shape. The motor bicycle fuel tank system (5) according to claim 1, further comprising: a frame cover (16) configured to cover the tank main body (26), said frame cover (16) having a fixing reference portion fitted into a fuel supply portion (50) positioned at a top location of the tank main body (26), and a plurality of tank fastening parts (98, 99) each configured to cooperate with a respective fastening member and a respective cushion member so as to floatingly fix the frame cover (16) to the tank main body when the motor bicycle fuel tank system (5) is in the assembled state, said tank fastening parts (98, 99) each having fastening member insertion holes (100) formed into a slot extending along a radial direction from the fixing reference portion. The motor bicycle fuel tank system (5) according to claim 1, further comprising: a recess portion (126) provided on a side of the tank main body (26); and an independent cover bracket (131) having a first end fixed into the recess portion (126) provided on the side of the tank main body (26), a second end fixed to the frame cover (16) when the motor bicycle fuel tank system (5) is in the assembled state, and a rigid lowering structure configured for allowing a side of the cover bracket (131) to be lowered in an bending fashion about a position adjacent to a side profile of the tank main body (26) in response to a force applied to a side of the cover bracket (131). The motor bicycle fuel tank system (5) according to claim 1, further comprising: recess portions (26d) provided on inner longitudinal wall surfaces of the reverse U-shaped sectional portion (26c) of the tank main body (26), each of the recess portions (26d) configured relative to a side view so as to be open in a direction separating from each other substantially at the right angle with respect to the upper portion of the reverse U-shaped sectional portion (26c), and elastic cushion members (92) each individually interposed between one of the recess portions (26d) and a respective side surface of the motor bicycle body frame (2), said elastic cushion members (92) configured to be fixed to the motor bicycle body frame (2) side surface so that a clearance (94) is defined between each of the elastic cushion members (92) and each of the recess portions (26d) when the fuel tank system (5) is placed on the motor bicycle (1) such that the tank main body (26) straddles the front head portion of the motor bicycle body frame (2). The motor bicycle fuel tank system (5) according to any of claims 1, 2, 3, 7, 8 or 9, further comprising: an insert nut (54) embedded in the tank main body (26), so as to define and external exposure and an insert nut embedded surface of the tank main body (26), said insert nut (54) being configured so that other components are fastened thereto, and such that the external exposure (54a) surface thereof becomes lower than the insert nut embedded surface of the tank main body (26) when embedded in the tank main body (26).

Inventors: NATSUME TETSUJI, TOKUNAGA KATSUHIKO, NATSUME, TETSUJI, TOKUNAGA, KATSUHIKO
Applicants: SUZUKI CO LTD, SUZUKI KABUSHIKI KAISHA
Application year: 1997
Main classification: B62J35
IPC codes: B62J35