Title of Invention

"A FRAME STRUCTURE OF A MOTORCYCLE"

Abstract

[Object] To provide a frame structure of a motorcycle, in which a high accurate body frame can be obtained at a low cost using a main pipe and sub-pipes not required to have high dimensional accuracies and also not required to be subjected to a special machining step. [Solving Means] A frame structure of a motorcycle has a body frame 2 including one main pipe 4 from which an internal combustion engine is suspended downward, and a pair of right and left sub-pipes 6, 8 connected to a rear portion of the main pipes 4. Each of the sub-pipes 6, 8 is formed in a square shape in cross-section. Plates 5, 7 having flat surfaces are welded to side surfaces of the rear portion of the main pipe 4, and front portions of the sub-pipes 6, 8 are welded to the flat surfaces of the plates 5, 7, to form the body frame 2. [Selected Drawing]

Full Text

[Technical Field of the Invention] The present invention relates to a frame structure of a motorcycle. [Related Art] Various types of frame structures of motorcycles have been known. One of them is of a type having a body frame including a main pipe extending rearward from a head pipe, wherein sub-pipes such as seat rails extend rearward from the main pipe with its front portions joined to a rear portion of the main pipe. In the above frame structure, the sub-pipes have been generally joined to the main pipe by butting and welding the sub-frames to the main pipe. On the other hand, Japanese Utility Model Publication No. Sho 60-39350.,Foreign references should bereplaed by Indian eguivalentshas proposed a method of joining a main pipe composed of a square pipe to sub-frames composed of cylindrical pipes. In this method, a front end Df each of the cylindrical sub- frames is flattened to have a flat surface, and the flat surface is brought in contact with and welded to each side surface of the main pipe. [Problem to be Solved by the Invention] In the former method of butting the main pipe to the sub-pipes, it is required to ensure high dimensional accuracies of the main pipe and the sub- frames for keeping the assembling accuracy at a high level, resulting in the increased cost. In the latter method of bringing the flattened front end of sub-frame in contact with each side surface of the main pipe, it is not required to ensure high dimensional" accuracies of the main pipe and the sub-frames because the dimensional adjustment therebetween can be performed during assembling; however, the step of flattening the front end of each sub-frame is added to the manufacturing process, resulting in the increased cost. In view of the foregoing, the present invention has been made, and an object of the present invention is to provide a frame structure of a motorcycle, in which a high accurate body frame can be obtained at a low cost using a main pipe and sub-pipes not required to have high dimensional accuracies and also not required to be subjected to a special machining step. [Means for Solving the Problem, Function, and Effect] To achieve the above object, according to an invention described in claim 1, there is provided a frame structure of a motorcycle having a body frame including one main pipe from which an internal combustion engine suspended downward and a pair of right and left sub-pipes connected to a rear portion of the main pipe, characterized in that each of the sub-pipes is formed in a square shape in cross-section; and plates having flat surfaces are welded on both side surface of the rear portion of the main pipe, and front portions of the sub-pipes are welded on the flat surfaces of the plates. In the invention having the above configuration, since the front portion of each of the sub-pipes composed of square pipes is welded on the flat surface of the plate welded on each side surface of the rear portion of the main pipe, it is possible to compensate for an error occurring when the main pipe is joined to the sub-pipes, and hence to eliminate the necessity of a step of machining the pipes as well as the necessity of giving high dimensional accuracies to the main pipe and the sub-pipes. This is effective to simplify the manufacturing process and .to reduce the cost. According to an invention described in claim 2, in addition to the configuration of the invention described in claim 1, the above plate is a hanger plate for supporting an internal combustion engine, with this configuration, it is possible to eliminate the necessity of provision of plates specialized for joining the main pipe to the sub-pipes and hence to simplify the structure and reduce the cost. According to an invention described in claim 3, in addition to the configuration of the invention described claim 1 or 2, the main pipe is formed in a cylindrical shape. With this configuration, the invention can be applied to a frame structure using a cylindrical main pipe. According to an invention described in claim 4, in addition to the configuration of the invention described in claim I, a mounting stay integrally having upper and lower fastening portions is provided on a head pipe formed at a front end of the main pipe in such a manner as to project forward from the head pipe, and a front cover and a front basket are sequentially superimposed on the mounting stay, and are co-fastened to the mounting stay by the upper and lower fastening portions. With this configuration, it is possible to optionally mount the front basket in a simple manner with its mounting accuracy not affected by the frame accuracy so much, and to reduce the number of parts. According to an invention described in claim 5, in addition to the configuration of the invention described in claim 1, a tool box integrated with a battery case is provided under a fuel tank supported by the sub-pipes With this configuration, it is possible to contain a tool in a tool box different from a small-article container and ensure a capacity of the small-article container, to collect large-weight matters such as a battery and a tool and make lower the center of gravity of the body, and to reduce the number of parts. According to an invention described in claim\6, in addition to the configuration of the invention described in claim 5, a cover detaching driver different from a tool contained in the tool box is disposed under a seat, with this configuration, it is possible to ensure a capacity of the small-article container, and to detach a cover of the tool box using the cover detaching driver disposed under the seat and hence to keep a preferable maintenance performance. According to the present invention there is provided a frame structure of a motorcycle having a body frame including one main pipe from which an internal combustion engine is suspended downward through an engine hanger, a pair of right and left seat rails being connected to an intermediate portion of said main pipe, and a pair of right and left back stays being connected to a rear portion of said main pipe, characterised in that said main pipe is constructed by a round pipe formed in a cylindrical shape, said seat rails and said back stays are formed in a square shape in cross section, front portions of said seat rails are welded on side surfaces of right and left front engine hanger plates which are provided on an intermediate portion of said cylindrical main pipe. each of said front engine hanger plates comprises a curve portion to be fitted to said cylindrical main pipe and a hanger portion offsetting outward and extending downward from a rear part of said curve portion. right and left rear engine hanger plates provided on the rear portion of said cylindrical main pipe, each of said rear engine hanger plates comprising a curve portion to be fitted to said cylindrical main pipe, a hanger portion offsetting outward and extending downward from said curve portion, a rear fork pivot provided on said hanger portion, and a flat surface extending along a vertical plan, and inside surfaces of the forwardly extending front portions of said back stays are welded on said flat surfaces of said rear engine hanger plates above said rear fork pivot thereof. [Brief Description of the ACCOMPANYING Drawings] [Fig. 1] A side view of the entire configuration of a motorcycle as one embodiment of the present invention. [Fig. 2] A side view of a body frame of the motorcycle shown in Fig. 1. [Fig. 3] A plan view of Fig. 2. [Fig. 4] A rear view of Fig. 2. [Fig. 5] A exploded view in perspective of the body frame shown in Fig. 2. [Fig. 6] An exploded side view showing one step of assembling of the body frame shown in Fig. 2. [Fig. 7] An upper view, seen along an arrow VII of Fig. 6, showing a front side engine hanger plate. [Fig. 8] A front view, seen along an arrow VIII of Fig. 6, showing the front side engine hanger plate. [Fig. 9] An upper view, seen along an arrow IX of Fig. 6, showing a rear side engine hanger plate. [Fig. 10] A rear view, seen along an arrow X of Fig. 6, showing the rear side engine hanger plate. [Fig. 11] A partial side view of an essential portion showing a mounting structure of a front basket, with parts partially cutaway. [Fig. 12] A front view of a front top cover. [Fig. 13] A side view of Fig. 12, with parts partially cutaway. [Fig. 14] A right side view of a box member. [Fig. 15] An upper view of Fig. 14 [Fig. 16] A right side view of a lid member. [Fig. 17] An upper view of Fig. 16. [Fig. 18] A partial side view of an essential portion showing a modification of the mounting structure of the front basket, with parts partially cutaway. [Preferred Embodiments of the Invention] One embodiment of the present invention will be described with reference to Figs. 1 to 17. Fig. 1 is a side view of the entire configuration of a motorcycle 1 in this embodiment, and Fig. 2 is a side view of a body frame 2 of the motorcycle 1 . The body frame 2 includes a cylindrical main pipe 4 extending rearward, obliquely, downward from a head pipe 3 provided at a front portion of the body. A pair of right and left front side engine hanger plates 5, 5 are welded on the main pipe 4 at a position offset slightly rearward from the center of the main pipe 4 in the longitudinal direction, and front ends of right and left seat rails 6, 6 are welded to the front side engine hanger plates 5, 5 in such a manner that the right and left seat rails 6, 6 extend rearward, obliquely, upward therefrom. [0016] Back stays 8, 8 are interposed between a pair of right and left rear side engine hanger plates 7, 7 welded on a rear end of the main pipe 4 and portions of the seat rails 6, 6 offset slightly forward from the rear ends of the seat rails 6, 6. Each of the seat rail 6 and the back stay 8 is formed in a square shape in cross-section. The head pipe 3 is connected to the main pipe 4 by a reinforcing gusset 9. A first cross-plate 10, a second cross-bar 11, and a third cross-plate 12 are sequentially provided in this order from the front side in the longitudinal direction between the right and left seat rails 6, 6 to reinforce the seat rails 6, 6. An internal combustion engine 15 is suspended from the front side engine hanger plates 5, 5 and the rear side engine hanger plates 7, 7 provided on the lower portion of the main pipe 4 of the body frame 2. A handlebar 17 extending right and left is provided at an upper portion of a steering shaft rotatably supported on the head pipe 3 provided at the front portion of the body frame 2, and a front wheel 19 is rotatably supported on lower ends of a front fork 18 connected to a lower portion of the steering shaft and extending downward therefrom. The rear side engine hanger plates 7 for suspending the internal combustion engine 15 also serves to pivotably support a front end of a rear fork 20 via a pivot 21. A rear wheel 22 is rotatably supported on rear ends of the rearward extending rear fork 20 in such a manner as to be vertically rockable, and right and left rear cushions 23, 23 are interposed between the rear ends of the rear fork 20 and the seat rails 6, 6. The internal combustion engine 15 is suspended in such a manner that a crank case 15a is suspended from the front side engine hanger plates 5, 5 and the rear side engine hanger plates 7 , 7 via supporting pins 16a, 16b with a cylinder 15b projecting forward from the crank case 15a in a state being inclined forward nearly in the horizontal direction. A carburetor 26 is disposed over the cylinder 15b via an intake pipe 25, and an air cleaner 27 is positioned over the carburetor 26 in a state being supported by the main pipe 4 . An exhaust pipe 28 extends rearward from a lower portion of the cylinder 15b along a lower surface of the crank case 15a, being offset rightward, and is connected to a muffler 29 provided on the right side of the rear wheel 22. On the seat rails 6, 6, a fuel tank 30 is positioned on its front half portions in a state being supported by the first cross-plate 10 and a small-article container 31 is disposed behind the fuel tank 30. The fuel tank 30 and the small-article container 31 are covered with a seat 32 which is rockably opened/closed with its front end pivotably supported. A space in a triangular shape in a side view is formed under the fuel tank 30 by the main pipe 4, the seat rails 6,6 and the back stays 8, 8, and a box member 33 integrally having a battery box 34 and a tool box 35 is fitted in and supported by the space. A battery 36 and a tool 37 are contained in the battery box 34 and the tool box 35, respectively. In the motorcycle 1, a front portion of the head pipe 3 is covered with a front top cover 40; a portion extending rearward from a rear side of the head pipe 3 to an upper side of the main pipe 4 is covered with a main pipe cover 41; and a pair of right and left front side covers 42, 42 and a pair of right and left leg seals 43, 43 are provided between the front top cover 40 and the main pipe cover 41. The front side covers 42, 42 cover right and left sides of an upper portion of the cylinder 15b of the internal combustion engine 15 and right and left sides of an intake system including the carburetor 26 and the air cleaner 27, and the leg seals 43, 43 extending right and left cover front portions of driver's legs. Side covers 44, 44 are provided to cover right and left sides of the box member 33, and a rear cover 45 is provided under the seat 32 to cover surroundings of the fuel tank 30 and the small-article container 31. A front fender 46 is provided to cover an upper side of the front wheel 19, and a rear fender 47 is provided to cover a portion extending from an upper side to a rear side of the rear wheel 22. In addition, a front basket 48 is mounted in front of the front top cover 40. Hereinafter, the joining structure of the body frame 2 of the motorcycle 1 having the above-described configuration will be described. Referring to Figs. 5 to 8, each of the front side engine hanger plates 5 welded to the main pipe 4 is composed of a fitting curve portion 5a to be fitted to the cylindrical main pipe 4, and a hanger portion 5b offset outward from a rear portion of the fitting curve portion 5a and extending downward therefrom. A lower portion of the hanger portion 5b has a mounting hole 5c for hanging a mount portion of the internal combustion engine 15 with the aid of the supporting pin 16a. A central portion of the fitting curve portion 5a is slightly recessed outward, to form a vertical flat surface 5d. When the fitting curve portion 5a of the front side engine hanger plate 5 is fitted sidewise to the cylindrical main pipe 4 and welded thereto, the flat surface 5d which is the outer surface of the fitting curve portion 5a is directed vertically and the hanger portion 5b is offset outward from the flat surface 5d and is directed vertically (see Fig. 8) . In addition, the front side engine hanger plates 5, 5 are provided symmetrically on the right and left sides of the main pipe 4 . Ref erring to Figs. 5, 6, 9 and 10, each of the rear side engine hanger plates 7, 7 includes a fitting curve portion 7a to be fitted to the cylindrical main pipe 4, 4 horizontal stepped portion 7b provided at a lower end of the fitting curve portion 7a, and a hanger portion 7c offset outward from the horizontal stepped portion 7b and extending downward therefrom. In the hanger portion 7c, a vertical flat portion 7d is formed on an upper portion; a mounting hole 7e for supporting a rear mount portion of the internal combustion engine 15 with the aid of a supporting pin 16b is formed at a position near a central portion of a front edge of the hanger portion 7c; a pivot hole 7f allowing the pivot 21 pivotably supporting the rear fork 20 to pass therethrough for supporting it is formed at a lower portion of the flat surface 7d; and a pivotably supporting hole 7g for pivotably supporting a main stand 39 is formed at a position lower than the pivot hole 7f in the vertical direction (see Fig. 6). When the fitting curve portion 7a of the rear side engine hanger plate 7 is fitted sidewise to a rear portion of the cylindrical main pipe 4 and welded thereto, the flat surface 7d of the hanger portion 7c is offset outward from the fitting curve portion 7a and extends downward therefrom in the vertical direction, and the remaining portion of the hanger portion 7c having the mounting hole 7e, pivot 7f and pivotably supporting hole 7g further extends downward in the vertical direction. In addition, the rear side engine hanger plates 7, 7 are provided symmetrically on the right and left sides of the main pipe 4. The front side engine hanger plates 5, 5 and the rear side engine hanger plates 7, 7 are thus welded to the main pipe 4. Further, in the front half portion of the body frame 2, a mounting piece 51 is provided on a front surface of the lower portion of the head pipe 3 in such a manner as to project forward therefrom; cover brackets 52, 52 are projectingly provided on right and left sides of the gusset 9; and cover brackets 53, 53 are projectingly provided on right and left sides of the front side engine hanger plates 5, 5. On the other hand, in the rear half portion of the body frame 2, the right and left seat rails 6 are welded to the right and left back stays 8, and the right and left seat rails 6, 6 are connected to each other by the first cross-plate 10, second cross-bar 11 and third cross-plate 12 which are sequentially provided in this order from the front side in the longitudinal direction. The second cross-bar 11 is hung between right and left triangular columns lla, lla which are welded to the right and left seat rails 6, 6. Supporting shafts l1b, l1b are provided on the supporting columns lla, lla in such a manner as to project outward therefrom, and upper ends of the rear cushions 23, 23 are pivotably supported on the supporting shafts l1b, l1b. After the front half portion and the rear half portion of the body frame 2 is thus separately assembled, the main pipe 4 constituting the front half portion of the body frame 2 is connected to the seat rails 6, 6 and the back stays 8, 8 constituting the rear half portion of the body frame 2 via the front side engine hanger plates 5, 5 and the rear side engine hanger plates 7, 7. Specifically, a front end portion of each seat rail 6 is brought in contact, from the outside, with the outer flat surface 5d of each front side engine hanger plate 5 fixed on the main pipe 4 ( see Figs .2,7 and 8 ) , and at the same time a front end portion of each back stay 8 is brought in contact, from the outside, with the outer flat surface 7d of each rear side engine hanger plate 7 fixed on the rear portion of the main pipe 4 (see Figs. 2, 9 and 10). At this time, it is possible to adjust the mounting position and hence to compensate for dimensional errors of the front half portion and rear half portion of the body frame 2. After the front half portion and the rear half portion of the body frame 2 are thus assembled in a suitable positional relationship, the front end portions of the seat rails 6, 6 are welded to the front side engine hanger plates 5, 5 and the front end portions of the back stays 8, 8 are welded to the rear side engine hanger plates 7, 7, to thereby integrally join the front half portion and the rear half portion of the body frame 2 to each other. According to this embodiment, since it is possible to compensate for dimensional errors of the front half portion and the rear half portion of the body frame 2 upon joining thereof, the main pipe 4, seat rails 6, 6 and back stays 8, 8 can be easily manufactured without being required not to have high dimensional accuracies, and also the seat rails 6, 6 and the back stays 8, 8 are not required to be subjected to special machining. This is effective to simplify the manufacturing process and to reduce the cost. Further, in this embodiment, the front side engine hanger plates 5, 5 and the rear side engine hanger plates 7, 7 interposed between the main pipe 4 constituting the front half portion of the body frame 2 and the seat rails 6, 6 and back stays 8, 8 constituting the rear half portion of the body frame 2 function as plates suspending the internal combustion engine 5, and also the rear side engine hanger plates 7, 7 serve as a pivot bearing for pivotably supporting the rear fork 20, so that it is possible to reduce the number of parts and simplify the structure, and hence to further reduce the cost. The mounting piece 51 projects from the head pipe 3 provided at the front end of the body frame 2 thus assembled, and a mounting stay 55 is fixed to the mounting piece 51. As shown in Fig. 11, the mounting stay 55 includes a main plate 55a having its front surface directed forward, obliquely, upward, and a connecting piece 55b projecting from a rear surface of ttie main plate 55a. The mounting piece 51 is fixed to the connecting piece 55b by two fore and aft bolts. The main plate 55a of the mounting stay 55 has a threaded fastening hole 55c positioned at the center of the upper portion, and threaded fastening holes 55d, 55d positioned at right and left points of the lower portion. The front top cover 40 is superimposed on the front surface of the main plate 55a of the mounting stay 55, and the front basket 48 is mounted thereto via collars 56. As show in Figs. 12, 13, the front top cover 40 is composed of plates which are symmetric on right and left sides and slightly curved for covering the front portion of the head pipe 3. The front top cover 40 has a mounting hole 40a formed at the center, and right and left mounting holes 40b, 40b formed in slightly recessed portions lower than the mounting hole 40a. The three mounting holes 40a, 40b, 40b correspond to the three threaded fastening holes 55c, 55d, 55d of the mounting stay 55, respectively. A rear wall 48a of the front basket 48 has three mounting fixtures 49, 49, 49 formed at positions corresponding to those of the three threaded fastening holes 55c, 55d, 55d of the mounting stay 55. The front basket 48 is mounted by a manner of superimposing the front top cover 40 on the front surface of the main plate 55a of the mounting stay 55 with the threaded holes 55c, 55d, 55d aligned with the mounting holes 40a, 40b, 40b; interposing the cylindrical collars 56, 56, 56 in recessed portions of the mounting holes 40a, 40b, 40b; superimposing the front basket 48 on the front top cover 40 with the mounting fixtures 49, 49, 49 of the rear wall 48a of the front basket 48 brought in contact with the collars 56; inserting three screws 57, 57, 57 into the mounting fixtures 49, 49, collars 56, 56, 56, and mounting holes 40a, 40b, 40b from the inside of the front basket 48; and screwing the three screws 57, 57, 57 in the threaded holes 55c, 55d, 55d of the mounting stay 55, thereby co-fastening the front basket 48 to the mounting stay 55 with the front .top cover 40 (see Fig. 11). In this embodiment, with respect to the mounting stay 55 to which the front basket 48 is co-fastened with the front top cover 40, the upper threaded fastening hole 55c and the lower threaded fastening holes 55d, 55d are integrally formed, so that the mounting position and the mounting posture of the front basket 48 is not affectedvby the frame accuracy. Consequently, the frame is not required to have a high accuracy. Since the front basket 48 is co-fastened to the mounting stay 55 together with the front top cover 40, it is possible to reduce the number of parts. In the case where the front basket 48 is not mounted, only the front top cover 40 may be fastened to the mounting stay 55 with the screws 57. In other words, the front basket 48 can be optionally provided. In this embodiment, the mounting stay 55to which the front basket 48 is to be mounted is bolt-fixed the mounting piece 51 projecting from the head pipe 3,which is separated from the mounting stay 55; however, with respect to this configuration, the embodiment can be modified as shown in Fig. 18, in which a mounting piece 60a projecting from a rear surface of a main plate 60a of a mounting stay 60 is directly welded to the head pipe 3. In the modification shown in Fig. 18, parts (for example, front basket 48, front top cover 40 and the like) corresponding to those shown in the previous embodiment are indicated by the same characters. '[0043] The box member 33, which is fitted in and supported by the space formed in the triangular shape in a side view by the main pipe 4, seat rails 6, 6, and back stays 8, 8 at a substantially center portion of the body frame 2, integrally having the battery box 34 and the tool box 35 as described above. As shown in Fig. 14 (which is a right side view of the box member 33) and Fig. 15, a right side wall 33a in a substantially triangular shape is recessed leftward to the central portion into a vertically elongated rectangular shape to form the battery box 34, and is further recessed leftward on the front side of the battery box 34 into a substantially square shape to form the tool box 35. Accordingly, each of the battery box 34 and the tool box 35 is opened on the right side, and four mounting holes 33b formed in the peripheral edge of the right side wall 33a are screwed with mounting brackets provided on the body frame 2, to thereby fix the box member 33 to the body frame 2. A lid member 38 is provided on the right side wall 33a to block both openings of the battery box 34 and the tool box 35. In the right side wall 33a of the box member 33, a threaded hole 33c for mounting the lid member 38 is provided in an upper portion; a vertically elongated locking hole 33d is provided in a front portion; and a pivotably holding piece 33e is formed on a lower portion. As shown in Figs. 16, 17, the lid member 38 is formed in such a shape as to block the vertically elongated rectangular opening of the battery 34 and the square opening of the tool box 35, and has a mounting hole 38a corresponding to the threaded hole 33c of the right side wall 33a of the box member 33; a projecting locking piece 38b corresponding to the locking hole 33d; and a pivotably supporting shaft 38c corresponding to the pivotably holding piece 33e. A locking claw is formed at the leading end of the locking piece 38b. The pivotably supporting shaft 38c of the lid member 38 is previously fitted with the pivotably holding piece 33e of the lower portion of the box member 33 such that the lid member 38 is supported rockably around the lower pivotably supporting shaft 38c. The lid member 38 is rocked and brought in contact with a right side surface of the box member 33; the locking piece 38b is inserted in the locking hole 33d of the front portion of the right side wall 33a to cover the battery box 34 and the tool box 35 by the lid member 38; and a screw is screwed in the mounting hole 38a aligned with the upper threaded hole 33c. The lid member can be opened in accordance with the operation reversed as described above. Thus, the opening/ closing of the lid member 38 can be easily performed. Differently from the tool 37 contained in the tool box 35, only a driver 58 is held in a holder 59 formed on a bottom plate 32a of the seat 32 (see Fig. 1). Accordingly, the driver 58 is taken off by opening the seat 32 upward upon maintenance, which is used to loosen the mounting screw of the right side cover 44 for removing the side cover and also to loosen the screwing of the lid member 38 to open the lid member. The tool 37 can be thus taken off from the tool box 35. In this way, the frame structure of the present invention is excellent in maintenance performance. Further, since the tool box 35 is provided separately from the small-article container 31, it is possible to sufficiently ensure the capacity of the small-article container 31 positioned under the seat. Since the tool box 35 and the battery box 34 are integrally formed, it is possible to collect the heavy matters, that is, the battery 36 and the tool 37; and since the box member 33 is disposed under the fuel tank 30, it is possible to dispose the heavy matters, that is, the battery 36 and the tool 37 at a relatively low position of the body, and hence to make lower the center of gravity of the body. Additionally, since the tool box 35 and the battery box 34 are integrally formed into the box member 33, it is posible to reduce the number of parts. [Reference Numeral] 1: motorcycle, 2: body frame, 3: head pipe, 4: main pipe, 5: front side engine hanger plate, 6: seat rail, 7: rear side engine hanger plate, 8: back stay, 9: gusset, 10: first cross-plate, 11: second cross-bar, 12: third cross-plate, 15: internal combustion engine, 17: handlebar, 18: front fork, 19: front wheel, 20: rear fork, 21: pivot, 22: rear wheel, 23: rear cushion, 25: intake pipe, 26: carburetor, 27: air cleaner, 28: exhaust pipe, 29: muffler, 30: fuel tank, 31: small-article container, 32: seat, 33: box .member, 34: battery box, 35: tool box, 36: battery, 37: tool, 38: lid member, 39: main stand, 40: front top cover, 41: main pipe cover, 42: front side cover, 43: leg shield, 44: side cover, 45: rear cover, 46: front fender, 47: rear fender, 48: front basket, 49: mounting fixture, 51: mounting piece, 52, 53: cover bracket, 55: mounting stay, 56: collar, 57: screw, 58: driver, 59: holder, 60: mounting stay We Claim: 1. A frame structure of a motorcycle having a body frame including one main pipe (4) from which an internal combustion engine is suspended downward through an engine hanger, a pair of right and left seat rails (6) being connected to an intermediate portion of said main pipe (4), and a pair of right and left back stays (8) being connected to a rear portion of said main pipe (4), characterised in that said main pipe (4) is constructed by a round pipe formed in a cylindrical shape, said seat rails (6) and said back stays (8) are formed in a square shape in cross section, front portions of said seat rails (6) are welded on side surfaces of right and left front engine hanger plates (5) which are provided on an intermediate portion of said cylindrical main pipe (4). each of said front engine hanger plates (5) comprises a curve portion (5a) to be fitted to said cylindrical main pipe (4) and a hanger portion (5b) offsetting outward and extending downward from a rear part of said curve portion (5a). right and left rear engine hanger plates (7) provided on the rear portion of said cylindrical main pipe (4), each of said rear engine hanger plates (7) comprising a curve portion (7a) to be fitted to said cylindrical main pipe (4), a hanger portion (7c) offsetting outward and extending downward from said curve portion (7a), a rear fork pivot (7f) provided on said hanger portion (7c), and a flat surface (7d) extending along a vertical plan, and inside surfaces of the forwardly extending front portions of said back stays (8) are welded on said flat surfaces (7d) of said rear engine hanger plates (7) above said rear fork pivot (7f) thereof. A frame structure of a motorcycle as claimed in claim 1, wherein said curve portions (5a) of said front engine hanger plates (5) are formed with flat surfaces on which front inside surfaces of said seat rails (6) are welded. A frame structure of a motorcycle substantially as herein described with reference to the accompanying drawings.

Documents:

1485-del-1997-abstract.pdf

1485-del-1997-claims.pdf

1485-del-1997-correspondence-others.pdf

1485-del-1997-correspondence-po.pdf

1485-del-1997-description (complete).pdf

1485-del-1997-drawings.pdf

1485-del-1997-form-1.pdf

1485-del-1997-form-13.pdf

1485-del-1997-form-19.pdf

1485-del-1997-form-2.pdf

1485-del-1997-form-3.pdf

1485-del-1997-form-4.pdf

1485-del-1997-form-6.pdf

1485-del-1997-gpa.pdf

1485-del-1997-petition-137.pdf

1485-del-1997-petition-138.pdf

abstract.jpg