Title of Invention

FRAME STRUCTURE IN MOTORCYCLE

Abstract

A pivot plate is to be reduced in size and improved in rigidity by improving a frame structure in a motorcycle. In a motorcycle including a main frame 12 extending backward and obliquely downward from a head pipe, rear frames 21, 22 connected to a rear portion of the main frame 12 and extending backward and obliquely upward, and an engine unit 18 supported by a lower portion of the main frame 12, wherein a pivot pipe 114 is provided on a rear face 13a of a pivot plate 13 which is secured to a rear lower portion of the main frame 12, and a rear fork 47 is supported swingably by the pivot pipe 114.

Full Text

[Name of Document] Specification [Title of the Invention] Frame Structure in Motorcycle [Technical Field] [0001] The present invention relates to an improvement of a frame structure in a motorcycle. [Background Art] [0002] As a conventional frame structure in a motorcycle there is known a frame structure wherein a pivot plate is attached to a rear portion of a main frame and a pivot shaft is attached to the pivot plate (see, for example, Patent Document 1) . [Patent Document 1] Japanese Patent Laid-Open No. 3548173 [0003] In Figs. 2 and 5 of Patent Document 1 it is shown that a pivot plate 17 is attached to a rear portion of a main frame 13 which constitutes a body frame, a pivot shaft 20 is attached to the pivot plate 17, and a rear fork 21 which supports a rear wheel is attached to the pivot shaft 20 vertically swingably. [0004] The pivot plate 17 includes right and left flat plate portions 18 and a connecting plate portion 19 for connecting the flat plate portions 18 with each other. The pivot shaft 2 0 is mounted through the right and left flat plate portions 18. [Disclosure of the Invention] [Problems to be Solved by the Invention] [0005] The right and left flat plate portions 18 of the pivot plate 17 are required to be wide enough to let the pivot shaft 2 0 pass therethrough and the longitudinal size thereof becomes large, thus resulting in an increase in size of the pivot plate 17. The pivot plate 17 undergoes a large load because it supports a rear wheel through a rear fork 21 and is therefore required to be further improved in rigidity. [0006] It is an object of the present invention to improve the frame structure in a motorcycle and thereby reduce the size and improve the rigidity of a pivot plate. [Means for Solving the Problems] [0007] In a motorcycle including a main frame extending backward and obliquely downward from a head pipe, a rear frame connected to a rear portion of the main frame and extending backward and obliquely upward, and an engine unit supported by a lower portion of the mainframe, the invention defined in claim 1 is characterized in that a pivot pipe is mounted on a rear face of a pivot plate provided at a rear lower portion of the main frame and a rear fork is supported swingably by the pivot pipe. [0008] Since the pivot pipe is mounted on the rear face of the pivot plate, the width in the longitudinal direction of the pivot plate becomes shorter than in the conventional construction wherein a pivot pipe is extended through right and left pivot plates. Besides, the pivot pipe can be supported by the whole of the rear face of the pivot plate, so that not only the pivot pipe can be supported firmly but also the rigidity of the pivot plate itself is improved. [0009] The invention defined in claim 2 is characterized in that the pivot plate includes a pair of opposed flat plate portions and a connecting plate for connecting rear ends of the flat plate portions with each other and has a generally U-shaped cross-sectional shape having an open front portion, a cutout portion is formed in a rear face of the connecting plate, and the pivot pipe is fitted in the cutout portion. [0010] By fitting the pivot pipe in the cutout portion formed in the rear face of the connecting plate, the longitudinal size of the pivot plate with the pivot pipe attached thereto can be made smaller. Moreover, since the pivot pipe is fitted in the cutout portion, not only the connection between the pivot plate and the pivot pipe becomes strong, but also the rigidity of the pivot plate is improved. [0011] The invention defined in claim 3 is characterized in that a pair of connecting members for connecting the rear frame and the pivot plate with each other are disposed on both sides of the main frame, intermediate portions of the connecting members are connected to the main frame, and front ends of the connecting members are connected to at least the pivot pipe mounted on the rear face of the pivot plate. [0012] Since the pivot pipe is supported not only by the main frame but also by the connecting members connected to the main frame, the rigidity of the pivot portion including the pivot plate and the pivot pipe is further improved. [0013] The invention defined in claim 4 is characterized in that a muffler is supported by a lower rear face of the pivot plate. Since the lower rear face of the pivot plate lies at a position close to the center of the vehicle body and close to the muffler, the size of a muffler supporting stay becomes smaller. [0014] The invention defined in claim 5 is characterized in that pillion step brackets to support pillion steps for a passenger to rest his or her feet thereon are supported by both pivot pipe and rear frame. The pillion step brackets can be supported more firmly because they are supported by both pivot pipe and rear frame. [Effect of the Invention] [0015] According to the invention defined in claim 1, since the pivot pipe is mounted on the rear face of the pivot plate and the rear fork is supported swingably by the pivot pipe, the width in the longitudinal direction of the pivot plate can be shortened and the pivot plate can be made smaller in size. Moreover, since the pivot pipe can be supported by the whole of the rear face of the pivot plate, not only the pivot pipe can be supported firmly but also the rigidity of the pivot plate itself can be improved. [0016] According to the invention defined in claim 2, the pivot plate includes a pair of opposed flat plate portions and a connecting plate for connecting rear ends of the flat plate portions with each other and has a generally U-shaped cross-sectional shape having an open front portions, a cutout portion is formed in a rear face of the connecting plate, and the pivot pipe is fitted in the cutout portion. Consequently, the longitudinal size of the pivot plate with the pivot pipe attached thereto can be reduced and it is possible to reduce the size of the pivot portion including the pivot plate and the pivot pipe. [0017] Further, by the fitting of the pivot pipe into the cutout portion, the connection between the pivot plate and the pivot pipe becomes stronger and the rigidity of the pivot plate can be improved. [0018] According to the invention defined in claim 3, a pair of connecting members for connecting the rear frame and the pivot plate with each other are disposed on both sides of the main frame, intermediate portions of the connecting members are connected to the main frame, and front ends of the connecting members are connected to at least the pivot pipe mounted on the rear face of the pivot plate. Thus, the pivot pipe is supported not only by the main frame but also by the connecting members connected to the main frame, whereby the rigidity of the pivot portion including the pivot plate and the pivot pipe can be further improved. [0019] According to the invention defined in claim 4, since a muffler is supported by a lower rear face of the pivot plate, the lower rear face of the pivot plate and the muffler come close to each other and hence the size of the muffler supporting stay can be reduced. [0020] According to the invention defined in claim 5, since pillion step brackets are supported by both pivot pipe and rear frame, the pillion step can be supported more positively. [Best Mode for Carrying out the Invention] [0021] The best mode for carrying out the present invention will be described hereinunder with reference to the accompanying drawings. The drawings should be seen in the directions of reference numerals. Fig. 1 is a side view of a motorcycle provided with a frame structure according to an embodiment of the present invention. In the motorcycle indicated at 10, an engine unit 18 including an engine 16 and a transmission 17 is supported by both a single main frame 12 extending backward and obliquely downward from a head pipe 11 and a pivot plate 13 attached to a rear end portion of the main frame 12 so as to extend downward. Further, a fuel tank 23 is mounted to a pair of left and right rear frames 21, 2 2 (only this-side numeral 21 is shown) extending backward and obliquely upward from a rear portion of the main frame 12. A baggage box 24 is mounted to the fuel tank 2 3 and the rear frames 21, 22, and a tandem seat 26 is secured to the baggage box 24 so that it can be opened and closed. [0022] A front fork 31 which supports a front wheel 2 8 at a lower end thereof is attached to the head pipe 11 steerably and a bar handle 32 is supported by an upper portion of the front fork 31. A pair of left and right sub-frames 34, 34 (only this-side numeral 34 is shown) are connected bridgewise to the pivot plate 13 and the rear frames 21, 22, and a pair of left and right step supporting frames 41, 42 which respectively support a pair of left and right pillion steps 36, 37 (only the reference numeral 36 on this side is shown) for a passenger are attached to the sub-frames 34, 34. [0023] The head pipe 11, main frame 12, pivot plate 13, rear frames 21, 22 and sub-frames 34, 34 are constituent members of a body frame 45. A rear fork 4 7 which supports a rear wheel 4 6 at a rear end thereof is connected to the pivot plate 13 swingably through a pivot pipe to be described later. [0024] The engine 16 is provided on its front side with a nearly horizontal cylinder portion 50, and an intake system 52 and an exhaust system 53 are connected to a cylinder head 51 provided in the cylinder portion 50. The intake system 52 includes an air cleaner 55 mounted to a front portion of the main frame 12 and a throttle body 57 combined with an injector, the throttle body 57 being connected at one end thereof to the air cleaner 55 and at an opposite end thereof to the cylinder head 51 through an intake pipe 56. [0025] The exhaust system 53 is made up of an exhaust pipe 61 connected at one end thereof to the cylinder head 51, a catalytic converter 62 mounted at a predetermined intermediate position of the exhaust pipe 61, and a muffler 63 connected to a rear end portion of the exhaust pipe 51, the muffler 63 being positioned behind the engine unit 18. The catalytic converter 62 is disposed in a space 64 which is formed under the cylinder portion 5 0 and in front of a crank case 65 to be described later, thereby making its height from the ground larger. [0026] The engine unit 18 includes a crank case 65, and main steps 66, 66 (only this-side numeral 66 is shown) for a rider, which main steps 66, 66 extend respectively to both sides, are secured to a lower portion of the crank case 65. Further, a brake pedal 67 for the rear wheel and a main stand 6 8 are supported swingably by a lower rear end portion of the crank case 65. [0027] The numeral 71 denotes a handle cover, numeral 72 denotes a front cover, numeral 73 denotes a battery-disposed in front of the head pipe 11, numeral 73a denotes a battery supporting bracket secured to a front portion of the head pipe 11 to support the battery 73, numeral 74 denotes a front fender which covers upper and rear portions of the front wheel 28, numeral 76 denotes a leg shield, numeral 77 denotes an oil feed lid equipped with a locking device, the oil feed lid 77 being provided in the leg shield 76 so as to be opened and closed when oil is fed from an oil feed port 23e (see Fig. 3, the numeral 78 denotes a cap for closing the oil feed port) formed in the fuel tank 23, a pair of numerals 81, 81 (only this-side numeral 81 is shown) denote a pair of left and right engine hangers secured to the main frame 12, numeral 82 denotes a drum brake unit secured to a rear wheel axle 83, numeral 84 denotes a torque rod connected bridgewise to both a brake panel (not shown) of the drum brake unit 82 and the rear fork 47 to prevent rotation of the drum brake unit 82, numeral 86 denotes a rear cushion unit connected bridgewise to both a rear cushion bracket 4 7a provided on the rear fork 4 7 and one rear frame 21, numeral 87 denotes a mudguard attached to a rear lower portion of the baggage box 24, numeral 88 denotes a rear fender which covers the upper portion of the rear wheel 46, numeral 91 denotes a grab rail, and numeral 92 denotes a tail lamp. [0028] Fig. 2 is a plan view of principal portions of the motorcycle related to the present invention (the arrow FRONT in the figure represents the front side of the vehicle and this is also true in the other drawings). As shown in the same figure, the exhaust pipe 61 is extended downward and backward from the cylinder head 51 of the engine 16 along a lower surface of the engine unit 18. Near a lower end of the crank case 65 in the engine unit 18 the muffler 63 is connected to the rear end of the exhaust pipe 61 and a pair of left and right stand supporting bosses 65S, 65S are integrally provided at the rear end portion of the crank case 65. Shaft supporting holes 65a and 65b are formed respectively in the stand supporting bosses 65S, 65S and a pivot shaft 101 is passed through the shaft supporting holes 65a and 65b. The brake pedal 67 and the main stand 68 are supported swingably by the pivot shaft 101. [0029] The exhaust pipe 61 extends below the engine unit 18 substantially rectilinearly in the longitudinal direction of the vehicle. The catalytic converter 62 extends in the longitudinal direction of the vehicle, substantially overlaps the cylinder portion 50 of the engine 16 in plan, and is positioned on the front side of the vehicle with respect to a left expanded portion 65c and a right expanded portion 65d of the crank case 65. [0030] The muffler 63 is in an L shape including a wide front portion 63a which is long in the transverse direction of the vehicle and positioned between the engine unit 18 and the rear wheel 46 and a long rear portion 63b which is long in the longitudinal direction of the vehicle and extended backward from the wide portion 63a along the right side face of the rear wheel 46 . Numeral 69 denotes a tail pipe provided at a rear end of the long rear portion 63b. [0031] The muffler 63 is disposed below the rear fork 47 and the tail pipe 69 of the muffler 63 is disposed inside the rear fork 47, more particularly, inside the left and right pillion steps 36, 37 at a position below a right-hand arm portion 104 of the rear fork 47. Therefore, the muffler 63 can be made difficult to be exposed to the exterior. [0032] The wide front portion 63a is provided with a left mounting portion 63c for mounting to a rear face of the pivot plate 13 (see Fig. 1), while the long rear portion 63b is provided with a right mounting portion 63d for mounting to one step supporting frame 42. A front end of the torque rod 84 is secured to a cross member 105 which provides a connection between left and right arm portions 103, 104 of the rear fork 47. [0033] Numeral 111 denotes a mounting bracket for mounting the leg shield 76 to the cylinder portion 50, numeral 112 denotes a change pedal provided in the transmission 17, numeral 113 denotes a side stand, numeral 114 denotes a pivot pipe secured to the pivot plate 13 (see Fig. 1) for supporting the rear fork 47, numeral 116 denotes a kick pedal for starting the engine, numeral 117 denotes a step bar secured to the crank case 6 5 side for connecting the left and right main steps 66, 66 with each other. The pivot pipe 114 not only supports the rear fork 4 7 but also supports the left and right step supporting frames 41, 42. [0034] Fig. 3 is a side view of principal portions of the motorcycle related to the present invention. A flange portion 23a of the fuel tank 23 is secured to tank mounting brackets 121 and 122 with bolts 123 and. nuts 124 (the nuts 124 are fixed to lower surfaces of the tank mounting brackets 121 and 122), the tank mounting brackets 121 and 122 being secured to the left and right rear frames 21, 22 (only this-side reference numeral 21 is shown) respectively. Numeral 125 denotes a fuel pump disposed within the fuel tank 23 and attached to an upper wall of the fuel tank 23. [0035] The tank mounting brackets 121 and 122 are secured respectively to front and rear positions of bent portions 21b and 22b of the rear frames 21 and 22 and the fuel tank 23 is fixed to front and rear positions of the bent portions 21b and 22b. Therefore, the fuel tank 23 can play the role of a reinforcing member for the rear frames 21 and 22, whereby the rigidity of both rear frames 21, 22 can be improved. Further, since the fuel tank 23 is mounted bridgewise to both left and right rear frames 21, 22, it also serves as a cross member in the body frame 45 and thus can contribute remarkably to the improvement of the entire rigidity of the body frame 45. [0036] A rear end portion 12a of the main frame 12 is crushed vertically to make a height H2 smaller than a front-side height HI, whereby the position of a bottom 23f of the fuel tank 23 is lowered to increase the capacity of the fuel tank 23. [0037] The baggage box 24 is provided at the bottom thereof with a pair of left and right downward projecting front portions 24a, 24a (only this-side reference numeral 24a is shown) and a pair of left and right downward projecting rear portions 24b, 24b (only this-side reference numeral 24b is shown). The downward projecting front portions 24a, 24a are secured to a pair of left and right box mounting brackets 126, 126 (only this-side reference numeral 126 is shown) with bolts 128 and nut members 131, the box mounting brackets 126, 126 being secured to an upper surface of the fuel tank 23. The downward projecting rear portions 24b, 24b are secured to box mounting brackets 127 with bolts 128 and nut numbers 131, the box mounting brackets 127 being secured to the rear frames 21 and 22 respectively. [0038] The nut members 131 are each a tubular member having a female screw on internal surface and provided at one end thereof with a flange. The nut members 131 are passed from below to above through insertion holes formed in the box mounting brackets 126 and 127 and are fixed by welding to the box mounting brackets 126 and 127. [0039] Through holes are formed in the downward projecting front portions 24a, 24a and the downward projecting rear portions 24b, 24b of the baggage box 24. The baggage box 24 is mounted to the box mounting brackets 126 and 127 by fitting and positioning the through holes onto projecting portions of the nut members 131 projecting upward from the box mounting brackets 126 and 127 and by subsequently bringing the bolts 128 into threaded engagement with the female screw of the nut members 131. [0040] The muffler 63 is formed by aligning a lower muffler half 135 connected to the exhaust pipe 61 and an upper muffler half 136 vertically with each other into a vessel shape. The bottom of the lower muffler half 135 is provided with a downward expanded portion 13 5a which is expanded downward up to a position where it overlaps the main stand 68 in a sprung-up state in side view. [0041] The left mounting portion 63c of the muffler 63 for mounting to the pivot plate 13 is made up of a mounting bracket 137 secured to the upper muffler half 136 and a nut (not shown) secured to a side face of the mounting bracket 137. A bolt 138 is passed through a stay 139 attached to a rear face of the pivot plate 13 and is threaded into the nut (not shown) provided on the mounting bracket 13 7 side, whereby the left mounting portion 63c is secured to the pivot plate 13 . [0042] The right mounting portion 63d of the muffler 63 for mounting to the step supporting frame 42 is made up of a mounting bracket 141 secured to the upper muffler half 13 6 and a tubular member 142 secured to an upper portion of the mounting bracket 141. The tubular member 142 is mounted with a bolt 146 and a nut 147 to a bracket 144 provided on one step supporting frame 42, whereby the right mounting portion 63d is secured to the step supporting frame 42. [0043] Lower portions of the step supporting frames 41 and 42 are secured with bolts 151 to the pivot pipe 114 coaxially with the rear fork 47, the pivot pipe 114 being attached to the pivot plate 13, while upper portions of the step mounting frames 41 and 42 are secured with bolts 153 to brackets 152, 152 (only this-side reference numeral 152 is shown) which are mounted to the rear frames 21 and 22. [0044] Fig. 4 is a side view of principal portions of the body frame related to the present invention. In the same figure, the rear frames 21 and 22 are welded to the left and right rear portions of the main frame 12, the pivot plate 13 is welded to the lower rear end portion of the main frame 12, the pivot pipe 114 is fitted and welded to a cutout portion 13b formed in a rear face 13a of the pivot plate 13, and one ends of the sub-frames 34, 34 (only this-side reference numeral 34 is shown) are welded to the rear face 13a of the pivot plate 13 and also to an outer periphery surface 114a of the pivot pipe 114. Numeral 13 9 denotes a stay mounted to the lower portion of the rear face 13a of the pivot plate 13. [0045] Intermediate portions of the sub-frames 34, 34 are welded to both side faces 12c, 12c (only this-side reference numeral 12c is shown) of the main frame 12. Numeral 161 denotes a reinforcing pipe which is bridgewise connected for reinforcement to the left and right sub-frames 34, 34. [0046] Figs. 5(a) and (b) are explanatory diagrams showing a pivot portion related to the present invention. (a) is a perspective view of principal portions of the body frame. In the same figure, the pivot plate 13 is an integrally molded product including a pair of left and right flat plate portions 13D, 13E (only one reference numeral 13D is shown) and a connecting plate 13F which connects rear ends of the flat plate portions 13D and 13E with each other. The pivot plate 13 has a generally U- shaped cross-sectional shape having an open front side. [0047] The pivot pipe 114 is fitted in the cutout portion 13b (see Fig. 4) formed on the connecting plate 13F side and the stay 13 9 is secured to the rear face 13a of the connecting plate 13F. The stay 139, which is an L-shaped plate, has a bolt insertion hole 139a formed therein and with a nut 163 attached thereto. [0048] (b) is a perspective view of the pivot plate 13. The cutout portion 13b of the pivot plate 13 is made up of a window portion 13h formed in an intermediate portion of the connecting plate 13F and arcuate rear cutout portions 13j and 13k formed in rear portions of the left and right flat plate portions 13D, 13E. Numerals 13m and 13n denote upper and lower sides, respectively, of the window portion 13h. [0049] For fitting the pivot pipe 114 (see (a) of Fig. 5) into the cutout portion 13b, one end of the pivot pipe 114 is, for example, inserted into one rear cutout portion 13j, then is moved along the upper side 13m and lower side 13n of the window portion 13h, and is projected from the other rear cutout portion 13k. Alternatively, the outer periphery surface of the intermediate portion of the pivot pipe 114 is inserted into the window potion 13h and is moved to inner positions of the rear cutout portions 13j and 13k. Thereafter, the pivot pipe 114 is fixed to the pivot plate 13 by welding. [0050] Since the welding between the pivot plate 13 and the pivot pipe 114 is performed through the upper and lower sides 13m, 13n of the window portion 13h, the rear cutout portions 13j, 13k and the outer periphery surface 114a (see (a) of Fig. 5) of the pivot pipe 114, the welding length can be made large and the connection between the pivot plate 13 and the pivot pipe 114 can be made strong. Thus, a strong connection can be ensured. [0051] Turning back to Fig. 4, according to the pivot plate supporting structure for supporting the pivot plate 13, the pivot plate 13 is secured to the lower rear end portion of the main frame 12, the pivot pipe 114 is secured to the rear face 13a of the pivot plate 13, one ends of the sub-frames 34, 34 are secured to the pivot plate 13 and the pivot pipe 114, the opposite ends of the sub-frames 34, 34 are secured to the rear frames 21 and 22, and intermediate portions of the sub-frames 34, 34 are secured to the rear end portion of the main frame 12. In side view, the main frame 12, pivot plate 13 and sub-frame 34 form a triangular shape, and likewise the main frame 12, rear frame 21, 22 (only this-side reference numeral 21 is shown) and sub-frame 34 form a generally-triangular shape. Thus, a truss structure is adopted. Consequently, the rigidity of a pivot portion 165 including the pivot plate 13 and the pivot pipe 114 can be further improved. [0052] Fig. 6 is a view as seen in the direction of arrow 6 in Fig. 3. As shown in the same figure, intermediate portions of the sub-frames 34, 34 extending from the rear frames 21 and 22 side are secured to both side faces 12c, 12c of the main frame 12, and end portions of the sub-frames 34, 34 are secured to the rear face 13a of the pivot plate 13 and also to the outer periphery surface 114a of the pivot pipe 114. [0053] Thus, the pivot plate 13 attached to the main frame 12 and the pivot pipe 114 attached to the pivot plate 13 are supported also by the sub-frames 34, 34 attached to the main frame 12, so that it is possible to strongly support the pivot plate 13 and the pivot pipe 114 on which a large load is imposed from the rear fork 4 7 side (see Fig. 1). [0054] Fig. 7 is a sectional view taken on line 7-7 in Fig. 4. Fig. 7 shows that a pipe rectangular in section is used as the main frame 12 and that side cover stays 16 7 and 168 for mounting side covers (not shown) are secured to the engine hangers 81, 81 mounted respectively to both side faces 12c, 12c of the main frame 12. Numerals 167a and 168a denote bolt insertion holes for insertion therethrough of engine mounting bolts. [0055] Fig. 8 is a side view of principal portions, showing a modification of the pivot plate related to the present invention. As to the same constructional portions as in Fig. 4, they are identified by the same reference numerals as in Fig. 4, and detailed explanations thereof will be omitted. A pivot plate 171 secured to the rear lower portion of the main frame 12 is an integrally molded member of a pair of left and right flat plate portions 172, 172 (only this-side reference numeral 172 is shown) and a connecting plate 173 for connecting rear ends of the flat plate portions 172, 172 with each other. [0056] Each flat plate portion 172 is made up of an engine hanger portion 175 as a front portion, a pivot plate portion 176 as a rear portion, and a connecting portion 177 which provides a connection between the engine hanger portion 175 and the pivot plate portion 176. [0057] A cutout portion 181 is formed in the rear portion of the pivot plate 171 and the pivot pipe 114 is fitted and welded into the cutout portion 181. Further, end portions of the sub-frames 34, 34 (only this-side one is shown) are welded to the rear face 13a of the connecting plate 173 and also to the outer periphery surface 114a of the pivot pipe 114. [0058] As shown in Figs. 1 and 4, in the motorcycle 10 including the main frame 12 extending backward and obliquely downward from the head pipe 11, the rear frames 21 and 22 connected to the rear portion of the main frame 12 and extending backward and obliquely upward, and the engine unit 18 supported by the lower portion of the main frame 12, the present invention is firstly characterized in that the pivot pipe 114 is provided on the rear face 13a of the pivot plate 13 which is secured to the rear lower portion of the main frame 12 and that the rear fork 47 is supported swingably by the pivot pipe 114. [0059] According to this construction, the width in the longitudinal direction of the pivot plate 13 can be shortened and the size of the pivot plate 13 can be reduced, whereby it is possible to attain the reduction of both weight and cost. Moreover, the pivot pipe 114 can be supported by the whole of the rear face 13a of the pivot plate 13, so that not only the pivot pipe 114 can be supported firmly but also the rigidity of the pivot plate 13 can be improved. [0060] As shown in Figs. 5 and 6, the present invention is secondly characterized in that the pivot plate 13 includes a pair of opposed flat plate portions 13D and 13F and the connecting plate 13F which connects the rear ends of the flat plate portions 13D and 13E with each other, the pivot plate 13 has a generally U-shaped cross-sectional shape, the cutout portion 13b is formed in the rear face 13a of the connecting plate 13F, and the pivot pipe 114 is fitted in the cutout portion 13b. [0061] According to this construction, the longitudinal size of the pivot plate 13 with the pivot pipe 114 attached thereto can be reduced and it is possible to reduce the size of the pivot portion 165 including the pivot plate 13 and the pivot pipe 114. [0062] Moreover, by fitting of the pivot pipe 114 into the cutout portion 13b, not only the connection between the pivot plate 13 and the pivot pipe 114 becomes strong, but also the rigidity of the pivot plate 13 can be improved. [0063] As shown in Figs. 4 and 6, the present invention is thirdly characterized in that intermediate portions of the sub-frames 34, 34 as a pair of connecting members disposed on both sides of the main frame 12 to connect the rear frames 21, 22 and the pivot plate 13 with each other are connected to the main frame 12 and the front ends of the sub-frames 34, 34 are connected to at least the pivot pipe 114 provided on the rear face 13a of the pivot plate 13. [0064] Since the pivot pipe 114 is supported not only by the main frame 12 but also by the sub-frames 34, 34 connected to the main frame 12, the rigidity of the pivot portion 165 including the pivot plate 13 and the pivot pipe 114 can be further improved. [0065] As shown in Fig. 3, the present invention is fourthly characterized in that the muffler 63 is supported by the rear face 13a of the lower portion of the pivot plate 13 through the stay 139. Since the muffler 63 is supported by the rear face 13a of the lower portion of the pivot plate 13, the rear face 13a and the muffler 63, more particularly, the upper muffler half 136, come close to each other, whereby the size of the stay 139 which supports the muffler 63 can be reduced and it is possible to attain the reduction of weight. [0066] As shown in Figs. 2 and 3, the present invention is fifthly characterized in that the step supporting frames 41 and 42 as pillion step brackets for supporting the pillion steps 36 and 37 for a passenger to rest his or her feet thereon are supported by the pivot pipe 114 and the rear frames 21, 22. Since the step supporting frames 41 and 42 are supported by the pivot pipe 114 and the rear frames 21, 22, it is possible to support the pillion steps 36 and 37 in a more positive manner. [0067] Although in this embodiment end portions of the sub-frames 34, 34 are connected to the rear face 13a of the pivot plate 13 and also to the outer periphery surface 114a of the pivot pipe 114, as shown in Fig. 4, no limitation is made thereto. End portions of the sub-frames 34, 34 may be connected to only the outer periphery surface 114a of the pivot pipe 114. [Industrial Applicability] [0068] The frame structure of the present invention is suitable for a motorcycle. [Brief Description of the Drawings] [0069] [Fig. 1] Fig. 1 is a side view of a motorcycle having a frame structure according to the present invention. [Fig. 2] Fig. 2 is a plan view of principal portions of the motorcycle according to the present invention. [Fig. 3] Fig. 3 is a side view of principal portions of the motorcycle according to the present invention. [Fig. 4] Fig. 4 is a side view of principal portions of a body frame according to the present invention. [Fig. 5] Fig. 5 is a perspective view of a body frame according to the present invention. [Fig. 6] Fig. 6 is a view as seen in the direction of arrow 6 in Fig. 3. [Fig. 7] Fig. 7 is a sectional view taken on line 7-7 in Fig. 4. [Fig. 8] Fig. 8 is a side view of principal portions, showing a modification of a pivot plate according to the present invention. [Description of Reference Symbols] [0070] 10 ... motorcycle, 11 ... head pipe, 12 ... main frame, 13 ... pivot plate, 13a ... rear face, 13b ... cutout portion, 13D, 13E . . . flat plate portion, 13F . . . connecting plate, 18 ... engine unit, 21, 22 ... rear frame, 34 ... connecting member (sub-frame), 36, 37 ... pillion step, 41, 42 ... pillion step bracket (step supporting frame), 47 ... rear fork, 63 ... muffler, 114 . . . pivot pipe, 165 . . . pivot portion. [Name of Document] Claims [Claim 1] A frame structure in a motorcycle comprising a main frame extending backward and obliquely downward from a head pipe, a rear frame connected to a rear portion of said main frame and extending backward and obliquely upward, and an engine unit supported by a lower portion of said main frame, wherein a pivot pipe is mounted on a rear face of a pivot plate provided at a rear lower portion of said main frame and a rear fork is supported swingably by said pivot pipe. [Claim 2] The frame structure in the motorcycle according to claim 1, wherein said pivot plate comprises a pair of opposed flat plate portions and a connecting plate for connecting rear ends of said flat plate portions with each other and has a generally U-shaped cross-sectional shape having an open front portion, a cutout portion is formed in a rear face of the connecting plate, and said pivot pipe is fitted in said cutout portion. [Claim 3] The frame structure in the motorcycle according to claim 1 or claim 2, wherein a pair of connecting members for connecting said rear frame and said pivot plate with each other are disposed on both sides of said main frame, intermediate portions of said connecting members are connected to said main frame, and front ends of said connecting members are connected to at least said pivot pipe mounted on the rear face of said pivot plate. [Claim 4] The frame structure in the motorcycle according to claim 2 or claim 3, wherein a muffler is supported by a lower rear face of said pivot plate. [Claim 5] The frame structure in the motorcycle according to any of claims 1 to 4, wherein pillion step brackets to support pillion steps for a passenger to rest his or her feet on are supported by both said pivot pipe and said rear frame. Dated this 27 day of July 2006

Documents:

1318-CHE-2006 ABSTRACT.pdf

1318-CHE-2006 CORRESPONDENCE OTHERS.pdf

1318-CHE-2006 CORRESPONDENCE PO.pdf

1318-CHE-2006 POWER OF ATTORNEY.pdf

1318-che-2006 abstract granted.pdf

1318-che-2006 claims granted.pdf

1318-che-2006 description (complete) granted.pdf

1318-che-2006 drawings granted.pdf

1318-che-2006-abstract.pdf

1318-che-2006-claims.pdf

1318-che-2006-correspondnece-others.pdf

1318-che-2006-description(complete).pdf

1318-che-2006-drawings.pdf

1318-che-2006-form 1.pdf

1318-che-2006-form 18.pdf

1318-che-2006-form 26.pdf

1318-che-2006-form 3.pdf

1318-che-2006-form 5.pdf

1318-che-2006-priority document.pdf