Title of Invention

A FRAME STRUCTURE IN MOTORCYCLE

Abstract

In a motorcycle which includes a vehicle body frame having a main frame extending downwardly rearwards from a head pipe, and a left-right pair of rear frames connected to a rear portion of the main frame and extending upwardly rearwards, and an engine unit disposed on the lower side of the main frame and hung from the vehicle body frame, to simplify the shapes of component parts while reducing the number of component parts of the vehicle body frame. For this purpose, flat portions (14d) opposed to side surfaces of the main frame (13) formed of an angular pipe with a tetragonal cross section are provided at front ends of the rear frames (14), respectively, and the flat portions (14d) of the rear frames (14), a pivot plate (17) having at least flat plate portions (18) opposed to side surfaces of the main frame (13) and supporting a rear fork (21), and hanger plates (16) formed in a flat plate shape at least at portions opposed to the side surfaces of the main frame (13) and supporting the engine unit are fitted directly to the side surfaces of the main frame (13).

Full Text

DESCRIPTION FRAME STRUCTURE IN MOTORCYCLE FIELD OF THE INVENTION The present invention relates to a motorcycle which comprises a vehicle body frame comprising a main frame extending downwardly rearwards from a head pipe, and a left-right pair of rear frames connected to a rear portion of the main frame and extending upwardly rearwards, and an engine unit disposed on the lower side of the main frame and hung from the vehicle body frame, and particularly to an improvement in the frame structure. BACKGROUND ART Hitherto, such a motorcycle as above has been known, for example, as disclosed in Japanese Patent Application Laid-open No. 10-16859, in which front end portions of seat rails and rear frames formed of angular pipes with a tetragonal cross section are fitted to opposite side surfaces of a main frame formed of a pipe with a circular cross section. However, in the above-mentioned conventional structure, in order to fit the front end portions of the seat rails and the rear frames formed of an angular pipe to the main frame formed of a round pipe, brackets or the like fitted to the main frame are provided with flat surfaces, and non-worked front end portions of the rear frames and seat rails are fitted to the flat surfaces. Therefore, the component constitution of the brackets or the like is complicated, and shape accuracy of the component parts must be enhanced. The present invention has been made in consideration of the above situations, and it is an object of the invention to provide a frame structure in a motorcycle which can simplify the shapes of component parts while reducing the number of component parts of the vehicle body frame of a motorcycle. DISCLOSURE OF THE INVENTION In order to attain the above object, the present invention is characterized firstly in that, in a motorcycle which comprises a vehicle body frame comprising a main frame extending downwardly rearwards from a head pipe, and a left -right pair of rear frames connected to a rear portion of the main frame and extending upwardly rearwards, and an engine unit disposed on the lower side of the main frame and hung from the vehicle body frame, flat portions opposed to side surfaces of the main frame formed of an angular pipe with a tetragonal cross section are provided at front ends of the rear frames, respectively, and the flat portions of the rear frames, a pivot plate having at least flat plate portions opposed to side surfaces of the main frame and supporting a rear fork, and hanger plates formed in a flat plate shape at least at portions opposed to side surfaces of the main frame and supporting the engine unit are fitted directly to the side surfaces of the main frame. According to the constitution of the first characteristic feature, it is unnecessary to fit brackets or the like to the main frame, and the flat portions at the front ends of the rear frames, and the portions opposed to the main frame of the pivot plate and the hanger plates can be fitted directly to the main frame. Since the brackets are needless, the number of component parts can be reduced that much. Besides, since opposite side surfaces of the main frame are flat surfaces, the shape of the front end portions of the rear frames may be simple flat portions, and the pivot plate and the hanger plates need not be worked specially for fitting to the main frame. Thus, the shapes of the component parts of the vehicle body frame can be simplified. In addition to the constitution of the first characteristic feature, the present invention is characterized secondly in that a cross member connecting between front portions of the rear frames is fitted to an upper surface of a rear portion of the main frame. According to this constitution, the rear portion of the main frame can be utilized as a reinforcing member for the left-right pair of rear frames. Further, in addition to the constitution of the first characteristic feature, the present invention is characterized thirdly in that the pivot plate is formed to have a roughly U-shaped cross sectional shape opened to the front side while comprising a pair of the flat plate portions parallel to each other and a connecting plate portion connecting rear ends of the flat plate portions to each other, and intermediate portions of a pair of connecting pipes disposed on opposite sides of the main frame and connecting between front portions of the rear frames and the connecting plate portion are fitted respectively to opposite side surfaces of the rear portion-pf the main frame. According to the constitution of the third characteristic feature, it is possible to preliminarily assemble a front-side frame assembly including the main frame and the pivot plate and a rear-side frame assembly including the left-right pair of rear frames, then to couple the front- side and rear-side frame assemblies to each other and to connect the front-side and rear-side frame assemblies to each other through the connecting pipes, thereby constituting the vehicle body frame of a motorcycle. Therefore, efficiency of mounting work can be enhanced. Accordingly the present invention provides a frame structure in a motorcycle which comprises a vehicle body frame (F) comprising a main frame extending downwardly rearwards from a head pipe and a left-right pair of rear frames connected to a rear portion of said main frame and extending upwardly rearwards, and an engine unit (E) disposed on the lower side of said main frame and hung from said vehicle body frame (F), characterized in that flat portions opposed to side surfaces of said main frame formed of an angular pipe with a tetragonal cross section are provided at front ends of said rear frames, respectively, and said flat portions of said rear frames, a pivot plate having at least flat plate portions opposed to side surfaces of said main frame and supporting a rear fork, and hanger plates formed in a flat plate shape at least at portions opposed to side surfaces of said main frame and supporting said engine unit (E) are fitted directly to said side surfaces of said main frame. BRIEF DESCRIPTION OF THE DRAWINGS With reference to accompanying drawings in which: Figs. 1 to 8 show a first embodiment of the present invention, in which Fig. 1 is a side view of a motorcycle; Fig. 2 is a side view of a vehicle body frame; Fig. 3 is a plan view taken in the direction of an arrow 3 of Fig. 2; Fig. 4 is a rear view taken in the direction of an arrow 4 of Fig. 2; Fig. 5 is a perspective view of the vehicle body frame; Fig. 6 is a partly cutout vertical sectional side view of a rear portion of the motorcycle; Fig. 7 is a sectional view taken along a line 7-7 of Fig. 6; and Fig. 8 is a perspective view, corresponding to Fig. 5, at the time of assembly of the vehicle body frame; and Fig. 9 is a plan view, corresponding to Fig. 3, of a second embodiment. BEST MODE FOR CARRYING OUT THE INVENTION The first embodiment of the present invention will be described referring to Figs. 1 to 8. First, in Fig. 1, a vehicle body frame F constituting a skeleton of this motorcycle comprises a head pipe 12 steerably supporting a front fork 11, a single main frame 13 extending downwardly rearwards from the head pipe 12, and a left-right pair of rear frames 14 connected to a rear portion of the main frame 13 and extending upwardly rearwards. A front wheel WF is rotatably shaft - supported at a lower end of the front fork 11, and a steering handle 15 is connected to an upper end of the front fork 11. Referring to Figs. 2 to 5 also, the main frame 13 is formed of an angular pipe with a tetragonal cross section having a left-right pair of side surfaces extending vertically in parallel to each other. Hanger plates 16, 16 are directly fitted by welding respectively to opposite side surfaces of an intermediate portion of the main frame 13, and a pivot plate 17 is directly fitted by welding to opposite side surfaces of a rear portion of the main frame 13. The hanger plates 16, 16 are formed in a flat plate shape at least at portions opposed to the side surfaces of the main frame 13, and the portions opposed to the main frame 13 of the hanger plates 16, 16 are directly fitted to the side surfaces of the main frame 13. The pivot plate 17 is formed to have a roughly U-shaped cross sectional shape opened to the front side while comprising a pair of flat plate portions 18, 18 parallel to each other opposed to the side surfaces of the main frame 13, and a connecting plate portion 19 connecting the rear ends of the flat plate portions 18, 18 to each other, and upper portions of the flat plate portions 18, 18 are directly fitted to the side surfaces of the rear portion of the main frame 13. An engine unit E is disposed on the lower side of the main frame 13, and the engine unit E is hung from the vehicle body frame F so as to be supported by the hanger plates 16, 16 and the pivot plate 17. A cylindrical support shaft 20 having opposite ends projected to the outside of the flat plate portions 18, 18 of the pivot plate 17 is provided between the flat plate portions 18, 18, and front end portions of a left-right pair of rear forks 21 are vertically oscillatably supported on opposite end portions of the support shaft 20, and a rear wheel WR is shaft-supported between the rear ends of the rear forks 21. The rear frame 14 is formed by bending a round pipe with a circular cross section, and integrally has a first frame portion 14a which is formed to extend upwardly rearwards from a side surface of a rear portion of the main frame 13 and to part more away from the main frame 13 in the width direction of the vehicle body frame F as it goes rearwards, a second frame portion 14b extending upwardly rearwards from the rear end of the first frame portion 14a at an inclination angle larger than that of the first frame portion 14a, and a third frame portion 14c extending upwardly rearwards from the rear end of the second frame portion 14b at an inclination angle smaller than that of the second frame portion 14b. The rear ends of the rear frames 14, 14, namely, the rear ends of the third frame portions 14c, 14c are connected by a tail frame 22. At the front ends of the rear frames 14, 14, namely, at the front ends of the first frame portions 14a, 14a, flat portions 14d, 14d opposed to side surfaces of the main frame 13 are formed by, for example, skewly cutting the round pipe, and the flat portions 14d, 14d are directly fitted by welding to the side surfaces of the main frame 13, respect ively. A first cross member 23 formed of a round pipe is provided between the rear ends of the second frame members 14b, 14b of the rear frames 14, 14, and a second cross member 24 formed of a round pipe is provided between the rear ends of the first frame members 14a, 14a of the rear frames 14, 14. An intermediate portion of the second cross member 24 is fitted by welding to an upper surface of a rear portion of the main frame 13. In addition, a support plate 25 is provided between the rear frames 14, 14 on the front side of the second cross member 24. Further, a pair of connecting pipes 26, 26 are disposed on the opposite sides of a rear portion of the main frame 13. One end of each of the connecting pipes 26, 26 is fitted by welding to a bent portion between the first and second frame portions 14a, 14b in the rear frames 14, 14, and the other end of each of the connecting pipes 26, 26 is fitted in common by welding to a rear surface of the connecting plate 19 in the pivot plate 17. Namely, each of front portions of the rear frames 14, 14 and the connecting plate 19 are connected to each other by the pair of connecting pipes 26, 26 disposed on the opposite sides of the main frame 13, and intermediate portions of the connecting pipes 26, 26 are fitted by welding to the side surfaces of a rear portion of the main frame 13, respectively. Referring to Figs. 6 and 7 also, the upper side of the rear wheel WR is covered by a rear fender 27 fitted to the rear frames 14, 14. On the upper side of the rear fender 27, a fuel tank 29 is disposed which is supported by support blocks 28, 28 attached to the bent portions between the second and third frame portions 14b, 14c; 14b, 14c in the rear frame 14, 14 and by rear portions of the third frame portions 14c, 14c. Pairs of bracket plates 30, 31 are attached to the bent portions between the second and third frame portions 14b, 14c; 14b, 14c in the rear frames 14, 14 so as to be disposed on the lower side of the support blocks 28, 28, and rear cushion units 32 are respectively provided between the bracket plates 30, 31 and rear portions of the rear forks 21. A weld nut 33 is attached to an inside surface of the inner bracket plate 31 of the pair of bracket plates 30, 31, and a bolt 34 piercing through the bracket plates 30, 31 and an upper end portion of the rear cushion unit 32 sandwiched therebetween from the side of the bracket plate 30 is mated with the weld nut 33, whereby the upper end portion of the rear cushion unit 32 is connected to the rear frame 14 through the bracket plates 30, 31. Incidentally, the fuel tank 29 is disposed on the inner side of the bracket plates 30, 31, and it is desirable to dispose the tip end of the bolt 34 as close as to the fuel tank 29 for minimizing the width of the motorcycle. However, if the tip end of the bolt 34 is directly opposed to a side surface of the fuel tank 29, the tip end of the bolt 34 may make contact with the side surface of the fuel tank 29 due to vibration or the like when the motorcycle is running. In consideration of this, the rear fender 27 is integrally provided with a partition wall plate 27a to be intermediately disposed between the bracket plate 31 and the fuel tank 29. Therefore, even though the tip end of the bolt 34 is disposed as close as to the fuel tank 29, the presence of the partition wall plate 27a prevents the tip end of the bolt 34 from making contact with the fuel tank 29. A luggage box 35 for containing a helmet or the like not shown is disposed on the front side of the fuel tank 29. The luggage box 35 is fixedly supported by the support plate 25 provided between front portions of the rear frames 14, 14 and the support blocks 28, 28 fitted respectively to the rear frames 14, 14. The vehicle body frame F is fitted with a synthetic resin made cover 38 covering the vehicle body frame F. The cover 38 comprises front side covers 39 disposed on both left and right sides of the main frame 13, leg shields 40 connected to front portions of the front side covers 39 so as to cover leg portions of a rider from the front side, a front top cover 41 connected to the leg shields 40 so as to cover the head pipe 12 from the front side, a main frame top cover 42 connected to the front top cover 41 so as to cover the head pipe 12 from the rear side and cover the main frame 13 from the upper side, under covers 43 connected to lower portions of the front side covers 39, and rear side covers 44 for covering the rear frames 14 f 14, the fuel tank 29 and the luggage box 35 from opposite sides. A tandem seat 45 covering the luggage box 35 and the fuel tank 29 from the upper side is disposed between upper portions of the rear side covers 44, openably so that luggage can be put into and out of the luggage box 35. Next, the operation of the first embodiment will be described. Front end portions of the rear frames 14, 14 are provided respectively with the flat portions 14d, 14d opposed to the side surfaces of the main frame 13 reduced in weight and enhanced in stiffness by being formed of an angular pipe with a tetragonal cross section, the pivot plate 17 is provided with the flat plate portions 18, 18 opposed to the side surfaces of the main frame 13, and the hanger plates 16, 16 are formed to have a flat plate shape at least at portions opposed to the side surfaces of the main frame 13. Therefore, in fitting the front end portions of the rear frames 14, 14, the pivot plate 17 and the hanger plates 16, 16 to the main frame 13, it is unnecessary to fit brackets or the like to the main frame 13, and the flat portions 14d, 14d at the front ends of the rear frames 14, 14 and the portions opposed to the main frame 13 of the pivot plate 17 and the hanger plates 16, 16 can be directly fitted to the side surfaces of the main frame 13. Because the brackets are needless, the number of component parts can be reduced that much. Moreover, because the side surfaces of the main frame 13 are flat surfaces, the front end portions of the rear frames 14, 14 may well be in the shape of the flat portions 14d, 14d, and the pivot plate 17 and the hanger plates 16, 16 need not be worked specially for fitting to the main frame 13. Thus, the shapes of component parts constituting the vehicle body frame F can be simplified. In addition, since the second cross member 24 connecting between the front portions of the rear frames 14, 14 is fitted to the upper surface of the rear portion of the main frame 13, the rear portion of the main frame 13 can be utilized as a reinforcing member for the left-right pair of rear frames 14, Further, the pivot plate 17 is formed to have a roughly U-shaped cross sectional shape opened to the front side while comprising the pair of flat plate portions 18, 18 parallel to each other and the connecting plate portions 19 connecting the rear ends of the flat plate portions 18 to each other, and intermediate portions of the pair of connecting pipes 16, 16 disposed on the opposite sides of the main frame 13 and connecting between the front portions of the rear frames 14, 14 and the connecting plate portion 19 are fitted respectively to the side surfaces of the rear portion of the main frame 13. Therefore, as shown in Fig. 8, it is possible to preliminarily assemble a front-side frame assembly UF including the head pipe 12, the main frame 13, the hanger plates 16, 16 and the pivot plate 17 and a rear-side frame assembly UR including a left-right pair of the rear frames 14, 14, the tail frame 22, the first and second cross members 23, 2 4 and the support plate 25, to couple the front - side and rear-side frame assemblies UF, UR with each other and to connect the front-side and rear-side frame assemblies UF, UR to each other by the connecting pipes 26, 26, thereby constituting the vehicle body frame F of the motorcycle. Therefore, efficiency of mounting work can be enhanced. Fig. 9 shows a second embodiment of the present invention, in which front end portions of the rear frames 14, 14 may be collapsed to form flat portions 14d', 14df, and the flat portions 14d', 14d' may be directly fitted to opposite side surfaces of a rear portion of the main frame 13. While embodiments of the present invention have been described above, the invention is not limited to or by the above embodiments, and various design modifications can be made without departure from the invention as set forth in claims. WE CLAIM 1. A frame structure in a motorcycle which comprises a vehicle body frame (F) comprising a main frame (13) extending downwardly rearwards from a head pipe (12), and a left-right pair of rear frames (14) connected to a rear portion of said main frame (13) and extending upwardly rearwards, and an engine unit (E) disposed on the lower side of said main frame (13) and hung from said vehicle body frame (F), characterized in that flat portions (14d, 14df) opposed to side surfaces of said main frame (13) formed of an angular pipe with a tetragonal cross section are provided at front ends of said rear frames (14), respectively, and said flat portions (14d, 14d?) of said rear frames (14), a pivot plate (17) having at least flat plate portions (18) opposed to side surfaces of said main frame (13) and supporting a rear fork (21), and hanger plates (16) formed in a flat plate shape at least at portions opposed to side surfaces of said main frame (13) and supporting said engine unit (E) are fitted directly to said side surfaces of said main frame (13). 2. The frame structure in a motorcycle as claimed in claim 1, wherein a cross member (24) connecting between front portions of said rear frames (14) is fitted to an upper surface of a rear portion of said main frame (13). 3. The frame structure in a motorcycle as claimed in claim 1, wherein said pivot plate (17) is formed to have a roughly U- shaped cross sectional shape opened to the front side while comprising a pair of said flat plate portions (18) parallel to each other and a connecting plate portion (19) connecting rear ends of said flat plate portions (18) to each other, and intermediate portions of a pair of connecting pipes (26) disposed on opposite sides of said main frame (13) and connecting between front portions of said rear frames (14) and said connecting plate portion (19) are fitted respectively to opposite side surfaces of the rear portion of said main frame (13). 4. A frame structure in a motorcycle substantially as herein above described with reference to the accompanying drawings.

Documents:

0131-chenp-2004 abstract-granded.pdf

0131-chenp-2004 claims-granded.pdf

0131-chenp-2004 description (complete)-granded.pdf

0131-chenp-2004 drawings-granded.pdf

131-chenp-2004-abstract.pdf

131-chenp-2004-claims.pdf

131-chenp-2004-correspondnece-others.pdf

131-chenp-2004-correspondnece-po.pdf

131-chenp-2004-description(complete).pdf

131-chenp-2004-drawings.pdf

131-chenp-2004-form 1.pdf

131-chenp-2004-form 26.pdf

131-chenp-2004-form 3.pdf

131-chenp-2004-form 5.pdf

131-chenp-2004-others.pdf

131-chenp-2004-pct.pdf