Title of Invention	FRAME STRUCTURE OF SCOOTER-TYPE VEHICLE
Abstract	Each of side frames 13 has a lower frame section 13b extending below a floor 26, and a rising frame section 13c connected to a rear end of the lower frame section 13b and upwardly rising behind the floor 26. Rear sub-frames 18 attached to the side frames 13 are disposed such that at least parts of which are disposed behind the rising frame sections 13c. Pivot plates 36 are respectively provided between side frames 13 and the rear sub-frames. A body-frame-side pivot shaft 45 of a link 1 mechanism 42 provided between a power unit P and a body frame F is supported between the pivot plates 36.

Title of Invention

FRAME STRUCTURE OF SCOOTER-TYPE VEHICLE

Abstract

Each of side frames 13 has a lower frame section 13b extending below a floor 26, and a rising frame section 13c connected to a rear end of the lower frame section 13b and upwardly rising behind the floor 26. Rear sub-frames 18 attached to the side frames 13 are disposed such that at least parts of which are disposed behind the rising frame sections 13c. Pivot plates 36 are respectively provided between side frames 13 and the rear sub-frames. A body-frame-side pivot shaft 45 of a link 1 mechanism 42 provided between a power unit P and a body frame F is supported between the pivot plates 36.

Full Text	FORM 2 THE PATENTS ACT, 1970 (39 of 1970) COMPLETE SPECIFICATION (See Section 10; rule 13) TITLE FRAME STRUCTURE OF SCOOTER-TYPE VEHICLE APPLICANT HONDA MOTOR CO., LTD. 1-1 Minamiaoyama 2-chome Minato-ku Tokyo Japan Nationality: Japan The following specification particularly describes the nature of this invention and the manner in which it is to be performed FRAME STRUCTURE OF SCOOTER-TYPE VEHICLE The present application claims foreign priority based on Japanese Patent Applications No. P.2005-088501, filed on March 25, 2005 and No. P.2005-351930, filed on December 6, 2005, the contents of them are incorporated herein by reference. BACKGROUND OF THE INVENTION The present invention relates to a frame structure of a scooter-type vehicle in which a pair of right and left side frames is joined to a head pipe that steerably supports a front fork which journals a front wheel. Disclosed in JP-B2-3423487 is a scooter-type vehicle with a pair of right and left side frames, each having a down-frame section suspended downwardly from a head pipe, a lower frame section extending downwardly from a lower end of the down-frame section, and a front end joined to the head pipe, such that the side frames are reinforced by a pair of right and left down-tubes disposed below both the side frames. In the scooter-type vehicle disclosed in JP-B2-3423487, the side frames and rear ends of the down-tubes are connected and fixed to each other by suspension brackets, and a body-frame-side pivot shaft provided between a body frame and a power unit is supported by the suspension brackets. In this - 1 - frame structure, since a large load is applied to portions of the side frames and down-tubes for connection with the suspension brackets, the size of the side frames and down-tubes may be increased. Therefore, there is a need for further increasing the rigidity around the body-frame-side pivot shaft. However, if the size of the side frames and down-tubes increases, the rear space of the floor may be narrowed as well as the weight of the overall scooter-type vehicle may be increased. The invention has been made in consideration of such 10 circumstances. It is therefore a first object of the invention to provide a frame structure of a scooter-type vehicle which makes it possible to sufficiently increase the rigidity around a body-frame-side pivot shaft while avoiding increasing the size of side frames, and to expand the rear space of a floor. Further, in the scooter-type vehicle disclosed in JP-B2-3423487, the side frames are made of pipe so as to integrally have down-frame sections suspended downwardly from the head pipe and lower frame sections extending rearwardly from rear ends of the down-frame sections, and a support pipe which supports a riding seat is adapted to be joined to the side frames. Thus, the number of parts increases and the number of assembling processes of the vehicle frame increases. The invention has been made in consideration of such circumstances. It is therefore a second object of the invention to provide a frame structure of a scooter-type vehicle which makes it possible to reduce the number of parts and the number of assembling processes. - 2 - SUMMARY OF THE INVENTION In accordance with one or more embodiments of the present invention, a frame structure of a scooter-type vehicle in which 5 a pair of right and left side frames is joined to a head pipe which steerably supports a front fork which journals a front wheel is provided with pivot plates respectively provided between the pair of right and left side frames and a pair of right and left rear sub-frames. Each of the side frames has a lower frame section extending below the floor, and a rising frame section connected to a rear end of the lower frame section and upwardly rising behind the floor. At least parts of the pair of right and left rear sub-frames are disposed behind the rising frame sections and attached to both the side frames. A body-frame-side pivot shaft of a link mechanism provided between a power unit and a body frame is supportedby the pivot plates. The body frame is constituted by the head pipe, both the side frames, and the rear sub-frames. Further, in accordance with one or more embodiments of the present invention, intermediate portions of both the rear sub-frames maybe bent so as to approach the rising frame sections of the side frames. In accordance with one or more embodiments of the present invention, in a frame structure of a scooter-type vehicle in which a pair of right and left side frames is joined to a head pipe which steerably supports a front fork which journals a front wheel, each of both the side frames integrally has: a - 3 - down-frame section suspended downwardly from the head pipe; a lower floor section connected to a lower end of the down-frame section and extending rearwardly below the floor; a rising frame section connected to a rear end of the lower frame section 5 and rising upwardly behind the floor, and a seat rail section extending rearwardly from an upper end of the rising frame section to support a riding seat. Bending a single pipe forms each of the side frames. Further, in accordance with one or more embodiments of the present invention, the side frames, and pipe members having a smaller diameter than the side frames and reinforcing the side frames may be disposed such that they are juxtaposed in pairs in front of, below, and behind the floor, in side view. Further, in accordance with one or more embodiments of 15 the present invention, the pipe members may correspond to the center frame 14, 54, the rear sub-frames 18, 61, the U-shaped section 32 and the connecting frames 55. According to one or more embodiments of the invention, a body-frame-side pivot shaft of a link mechanism is supported by the pivot plates provided between side frames and rear sub-frames at least parts of which are disposed behind the rising frame sections provided in the side frames and which is attached to both the side frames. Thus, it is possible to increase the rigidity around the body-frame-side pivot shaft while avoiding increasing the size of the side frames. By avoiding increasing the size of the side frame in this way, the rear space of the floor can be increased. - 4 - Further, according to one or more embodiments of the present invention, the power unit can be disposed on the front side while avoiding interference of the power unit with the rear sub-frames, thereby making the wheelbase shorter. According to one or more embodiments of the present invention, since each side frame integrally has the down-frame section, the lower floor section, the rising frame section, and the seat rail section, and the side frame is formed by bending a single pipe. As a result, the number of parts can be reduced, and the number of assembling processes of the body frame can be reduced. Moreover, according to one or more embodiments of the present invention, the lightweight and high-rigidity body frame can be constructed. Other aspects and advantages of the invention will be apparent from the following description and the appended claims. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a side view of a scooter-type vehicle of a first embodiment. Fig. 2 is a side view of a body frame. Fig. 3 is a plan view as viewed in the direction of arrow 3 in Fig. 2. Fig. 4 is a plan view as viewed in the direction of arrow 4 in Fig. 2. Fig. 5 is a longitudinal sectional side view showing the - 5 - structure of a link mechanism. Fig. 6 is a side view of a scooter-type vehicle of a second embodiment. Fig. 7 is a side view of a body frame. Fig. 8 is a plan view as viewed in the direction of arrow 8 in Fig. 7. Fig. 9 is a plan view as viewed in the direction of arrow 9 in Fig. 7. Fig. 10 is a side view showing the structure of a link mechanism. 11: FRONT FORK 12: HEAD PIPE 15 13, 53: SIDE FRAME 13a, 53a: DOWN-FRAME SECTION 13b, 53b: LOWER FRAME SECTION 13c, 53c: RISING FRAME SECTION 14, 54: CENTER FRAME 20 15: MAIN PIPE 17, 55: CONNECTING FRAME 21: STEERING WHEEL 22: HANDLE GRIP 2 6: FLOOR 31: GUSSET 32: U-SHAPED SECTION 33: SUPPORT SECTION - 6 - 37: RADIATOR 42, 72: LINK MECHANISM 45, 73: BODY-FRAME-SIDE PIVOT SHAFT 49, 77: POWER-UNIT-SIDE PIVOT SHAFT C: IMAGINARY CIRCULAR ARC FA, FB: BODY FRAME P: POWER UNIT WF: FRONT WHEEL DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS Exemplary embodiments of the invention will be described with reference to the accompanying drawings. Figs. 1 to 5 show a first embodiment of the invention, specifically, Fig. 1 is a side view of a scooter-type vehicle, Fig. 2 is a side view of a body frame, Fig. 3 is a plan view as viewed in the direction of arrow 3 in Fig. 2, Fig. 4 is a plan view as viewed in the direction of arrow 4 in Fig. 2, and Fig. 5 is a longitudinal sectional side view showing the structure of a link mechanism. Referring first to Fig. 1, a front fork 11 journaling a front wheel WF is steerably supported by a head pipe 12 at a front end of a body frame FA provided in a scooter-type vehicle having a low-floor-type floor 26. Both ends of a bar-shaped steering handle 21 connected to an upper portion of the front fork 11 are provided with handle grips 22, 22, respectively. Also, a body frame FA so as to be rockable up and down via a link mechanism supports a front portion of a power unit P - 7 - 42 . The power unit Pic comprised of an engine E and a transmission M which changes power from the engine E to transmit it to a rear wheel WR. A rear portion of the power unit P supports the rear wheel W. A rear cushion unit 23 is provided between 5 a rear portion of the body frame FA and a rear portion of the power unit P. The body frame FA includes the head pipe 12, a pair of right and left side frames 13 having their front ends joined to the head pipe 12, a center frame 14 suspended downwardly through vicinities of front portions of the side frames 13 from the head pipe 12 between both the side frames 13, a main pipe 15 suspended from the head pipe 12, a front cross main bar 16 which connects the front portions of both the side frames 13 to each other and allows a lower end of the main pipe 15 to be joined thereto, a connecting frame 17 disposed below the floor 2 6 to reinforce the center frame 14 and both the side frames 13, a pair of right and left rear sub-frames 18 attached to both the side frames 13, and a rear cross main bar 19 which connects rear ends of both the side frames to each other. The body frame FA is covered with a vehicle body cover 24 made of synthetic resin. The vehicle body cover 24 includes a leg shield 25 which covers the front of rider's legs, the floor 26 which is connected to a lower portion of the leg shield 25 to allow the rider's feet to be placed thereon, and a side cover 27 which is connected to the floor 26 to cover the rear portion of the vehicle body from both lateral sides. A tandem -8 - riding seat 30 which covers a storage box 28 and a fuel tank 29 disposed behind the storage box 28 in such a manner to be opened and closed from above is provided on the side cover 27. Referring to Figs. 2 to 4, each side frame 13 integrally has a down-frame section 13a suspended downwardly from the head pipe 12, a lower floor section 13b connected to a lower end of the down-frame section 13a and extending rearwardly below the floor 26, a rising frame section 13c connected to a rear end of the lower frame section 13b and rising upwardly behind the floor 26, and a seat rail section 13dextending rearwardly from an upper end of the rising frame section 13c to support the riding seat 30. Bending and forming a single pipe obtain the side frame. A gusset 31 is provided between the head pipe 12 and the main pipe 15 suspended from the head pipe 12, and an upper end of the down-frame section 13a of the side frame 13 is joined to both the head pipe 12 and the gusset 31. Also, an upper portion of the center frame 14 is connected to the main pipe, and the gusset, as in this embodiment, may be welded or fastened using bolts. The lower frame section 13b is comprised of a horizontal portion 13ba substantially horizontally extending rearwardly from the lower end of the down-frame section 13a and an inclined portion 13bb inclined rearwardly and upwardly from a rear end of the horizontal portion 13ba. The connecting frame 17 is disposed above the lower frame - 9 - sections 13b of both the side frames 13 and below the floor 26. This connecting frame is comprised of a U-shaped section 32 which is formed in a substantially "U" shape in plan view, and has a closed front end and rear ends connected to the inclined 5 portions 13bb in the down-frame sections 13b of both the side frames 13, and a support section 33 which connects the vicinity of a widthwise middle portion of the front end of the U-shaped section 32 to connected portions between the down-frame sections 13a and lower frame sections 13b in both the side frames 13. In this embodiment, the U-shaped section 32 has a smaller diameter than the side frames 13, and is formed by bending a single pipe member, and the support section 33, which is composed of a pair of right and left pipe members 34 and 34, connects two spots in the vicinity of the widthwise middle 15 portion of the front end of the U-shaped section 32 to the connected portions between the down-frame sections 13a and the lower frame sections 13b. In side view, the lower frame section 13b in each side frame 13 and the U-shaped section 32 formed to have a smaller diameter than the side frame 13 and disposed above the lower frame section 13b are disposed such that they are juxtaposed vertically in a pair. The center frame 14, which has a laterally long rectangular cross-sectional shape whose width Wl (see Fig. 4) in the width direction of the vehicle is larger that a width W2 (see Fig. 2) in the forward and backward directions of the vehicle, may be made of an angled cylindrical pipe or may be molded of cast - 10 - iron. A lower end of the center frame 14 whose upper portion is connected to the main pipe 15 is joined to the widthwise middle portion of the front end of the U-shaped section 32 in the connecting frame 17. In side view, the down-frame section 13a of each side frame 13 and the U-shaped section 32 made of a pipe member having a smaller diameter than the down-frame section 13a are disposed in front of the floor 26 such that they are juxtaposed back and forth in a pair. A pair of right and left rear sub-frames 18 at least parts of which are disposed behind the rising frame sections 13c is attached to both the side frames 13. In this embodiment, each rear sub-frame 18 is disposed below the lower frame section 13b of each side frame 13 and behind the rising frame section 13c. A front end of the rear sub-frame 18 is joined to a rear face of a front end of the inclined portion 13bb in the lower frame section 13b in front of a joined portion of the U-shaped section 32 in the connecting frame 17, and a rear end of the rear sub-frame 18 is joined to a bottom face in the vicinity of a front portion of the seat frame section 13d in the side frame 13. Moreover, intermediate portions of both the rear sub-frames 18 are bent so as to approach the rising frame sections 13c of the side frames 13. Pivot plates 36 are provided between both the side frames 13 and both the rear sub-frames 18, respectively, below the bent intermediate portions. Each rear sub-frame 18 is made of a pipe member having a smaller diameter that the side frame 13. In side view, the - 11 - lower frame section 13b and rising frame section 13c in the side frame 13 and the rear sub-frame 18 made of a pipe member having a small diameter are disposed such that they are juxtaposed in a pair below and behind the floor 26. As clearly shown in Fig. 1, a radiator 37 is disposed between the down-frame sections 13a of both the side frames 13 and the center frame 14. A top face of the floor 26 is set to a position lower than a vertical center position CP of the radiator 37. As clearly shown in Fig. 4, a pair of right and left support arms 38 provided in an upper portion of the radiator 37 is elastically supported by a pair of right and left stays 39 provided in the front cross main bar 16, Also, both right and left ends of a guard pipe 40 which covers a lower portion of the radiator 37 from its front side are respectively joined to front faces of lower ends of the down-frame sections 13a in both the side frames 13. A stay 41 directed toward a middle portion of the guard pipe 40 elastically supports a lower middle portion of the radiator 37. Referring to Fig. 5, a support plate 43 is secured to the connected portion between the lower floor section 13b and the rising frame section 13c in each side frame 13 so as to protrude rearwardly. A lower portion of the engine E in the power unit P is provided with a bracket 44. In addition, the link mechanism 42 includes a pair of right and left first link arms 46 which is rotatably supported by the pivot plates 36 via a body-frame-side pivot shaft 45, - 12 - a second link arm 48 whose one end is rotatably connected to the other end of each of the first link arms 46 via a connecting shaft 47, a power-unit-side pivot shaft 49 which is fixed to the other end of the second link arm 48 and rotatably supported 5 by the bracket 44, an upwardly extending regulating arm 51 whose one end is connected to the power-unit-side pivot shaft 49 and whose intermediate portion is rotatably supported by each support plate 43 via a pivot 50, and an elastic member 52 mounted on the other end of the regulating arm 51. The rotation of the regulating arm is regulated between a position where the elastic member 52 comes into a resilient contact with a lower rear face of the rising frame section 13c in each side frame 13 and a position where the elastic member 49 comes into a resilient contact with a regulating plate 43a provided in each support plate 43 from the front side. Moreover, the body-frame-side pivot shaft 45 of the link mechanism 42 is disposed in front of the rear face of the rising frame section 13c in the side frame 13. The power-unit-side pivot shaft 49, as shown in Fig. 1, is disposed within an imaginary circular arc C passing through the center of rotation of the front wheel WF about the hand grip 22, on a projection view drawn by projecting the vehicle onto a plane orthogonal to a rotation axis of the front wheel WF. Next, the operation of the first embodiment will be described. The body frame FA includes the pair of right and left side frames 13, each having the down-frame section 13a suspended downwardly from the head pipe 12 and the lower frame - 13 - section 13b extending rearwardly from the lower end of the down-frame section 13a, the center frame 14 suspended downwardly from the head pipe 12 between both the side frames 13, and the connecting frame 17 which is disposed above the lower floor 5 sections 13b to reinforce the center frame 14 and both the side frames 13, and the connecting frame 17 is disposed below the low-floor-type floor 26. Accordingly, the lower frame sections 13b of both the side frames 13 are set to sufficiently lower positions, and the connecting frame 17 which reinforces 10 both the side frames 13 and the center frame 14 suspended downwardly from the head pipe 12 between both the side frames 13 are disposed above the lower floor sections 13b and below the floor 26. As a result, the flat floor 26 that sufficiently ensures a footrest space is formed, thereby improving usability, 15 and the balance between the longitudinal rigidity and torsional rigidity of the body frame FA can be improved. In addition, such effects can be achieved not only by the connecting frame 17 having the U-shaped section 32 and the support section 33 but also by a connecting frame adapted 20 to linearly connect rear portions of the lower frame sections 13b of the side frames 13 to the down-frame sections 13a in a substantially horizontal plane. Moreover, since the center frame 13 has a laterally long rectangular cross-sectional shape, it is possible to increase the rigidity of the center frame 14 while easily ensuring the backward and rearward installation space for the center frame 14 to be disposed in front of the floor 26. - 14 - Besides, the connecting frame 17 has the U-shaped section 32 which is formed in a substantially "U" shape in plan view, and has a closed front end and rear ends connected to both the side frames 13, and the support section 33 which connects 5 the vicinity of a widthwise middle portion of the front end of the U-shaped section 32 to the side frames 13. Thus, the flat floor 26 that sufficiently ensures a footrest space while ensuring a sufficient rigidity is formed, thereby improving usability, and the torsional rigidity of the body frame FA 1 can be adjusted. In addition, such effects can be achieved even if the center frame 14 is omitted. Further, the gusset 31 is provided between the head pipe 12 and the main pipe 15 suspended from the head pipe 12, and the upper ends of the down-frame sections 13a of both the side frames 13 are joined to both the head pipe 12 and the gusset 31. As a result, the rigidity of joint between both the side frames 13 and the head pipe 12 can be increased. Also, since the upper portion of the center frame 14 is connected to the main pipe 15, the rigidity of the upper portion of the center frame 14 can be increased. Moreover, each side frame 13 integrally has the down-frame section 13a suspended downwardly from the head pipe 12, the lower floor section 13b connected to the lower end of the down-frame section 13a and extending rearwardly below the floor 2 6, the rising frame section 13c connected to the rear end of the lower frame section 13b and rising upwardly behind the - 15 - floor 26, and the seat rail section 13d extending rearwardly from the upper end of the rising frame section 13c. Bending and forming a single pipe obtain the side frame. As a result, the number of parts can be reduced, and the number of assembling processes of the body frame FA can be reduced. Moreover, the side frames 13, the center frame 14 having a smaller diameter than the side frames 13 and reinforcing the side frames 13, the U-shaped section 32 of the connecting frame 17, and the rear-sub frames 18 are disposed such that 10 they are juxtaposed in pairs in front of, below, and behind the floor 2 6, in side view. Thus, the lightweight and high-rigidity body frame FA can be constructed. Further, the radiator 37 is disposed between the down-frame sections 13a of both the side frames 13 and the center frame 14. Accordingly, by increasing the vertical length of the radiator 37 while expanding the space of the flat floor 26, the capacity of the radiator 37 can be increased, thereby improving the cooling performance for the engine E In addition, since the top face of the floor 26 is set to a position below the vertical center position CP of the radiator 37, the position of the floor 26 can be set as near to the bottom as possible, thereby improving the property that a rider gets on/out of the vehicle. Moreover, the pair of right and left rear sub-frames 18 25 at least parts of which are disposed behind the rising frame sections 13c is attached to both the side frames 13, and the body-frame-side pivot shaft 45 of the link mechanism 42 provided - 16 - between the body frame FA and the power unit P is supposed by the pivot plates 36 provided between both the side frames 13 and both the rear sub-frames 18. Thus, it is possible to increase the rigidity around the body-frame-side pivot shaft 5 45 while avoiding increasing the size of the side frames 13. By avoiding increasing the size of the side frame 13 in this way, the rear space of the floor 26 can be increased. Moreover, since the body-frame-side pivot shaft 45 of the link mechanism 42 is disposed in front of the rear face of the rising frame section 13c, the body-frame-side pivot shaft 45 of the link mechanism 42 can be disposed as near to the front as possible, thereby shortening the wheelbase. Further, sine the intermediate portions of both the rear sub-frames 18 are bent so as to approach the rising frame sections 15 13c of the side frames 13, the power unit P can be disposed on the front side while avoiding interference of the power unit P with the rear sub-frames 18, thereby making the wheelbase shorter. Moreover, the power-unit-side pivot shaft 49 of the link mechanism 42 is disposed within the imaginary circular arc C passing through the center of rotation of the front wheel WF about the hand grip 22, on a projection view drawn by projecting the vehicle onto a plane orthogonal to the rotation axis of the front wheel WF. As a result, the power-unit-side pivot 25 shaft 49 of the link mechanism 42 can be disposed as near to the front as possible, thereby further shortening the wheelbase. Figs. 6 to 10 show a second embodiment of the invention, - 17 - specifically, Fig. 6 is a side view of a scooter-type vehicle of the second embodiment, Fig. 7 is a side view of a body frame, Fig. 8 is a plan view as viewed in the direction of arrow 8 in Fig. 7, Fig. 9 is a plan view as viewed in the direction 5 of arrow 9 in Fig. 7, and Fig. 10 is a side view showing the structure of a link mechanism. In addition, in the description of the second embodiment, the parts corresponding to those in the first embodiment are denoted by the same reference numerals, and the detailed description thereof will be substituted by illustration only. Referring first to Fig. 6, a front portion of the power unit P comprised of the engine E and the transmission M is supported by a body frame FB provided in a scooter-type vehicle having the low-floor-type floor 26 so as to be rockable up 15 and down via the link mechanism 42. The rear cushion unit 23 is provided between a rear portion of the body frame FB and a rear portion of the power unit P. Referring to Figs. 7 to 9, the body frame FB includes the head pipe 12, a pair of right and left side frames 53 having their front ends joined to the head pipe 12, a center frame 54 made of a pipe member and suspended downwardly through vicinities of front portions of the side frames 53 from the head pipe 12 between both the side frames 53, connecting frames 55 extending back and forth below the floor 26 provided in the body cover 24 and having their both ends connected to both the side frames 53, a support stay 56 disposed below both the connecting frames 55 to connect both the side frames 53 to - 18 - each other and connected to a lower end of the center frame 54, a front cross main bar 57 which connects the front portions of both the side frames 13 to each other and allows a lower end of the main pipe 15 to be joined thereto, a first intermediate 5 cross main bar 58 which connects intermediate portions of both the side frames 53, a second intermediate cross main bar 59 which connects intermediate portions of both the side frames 53 behind the first cross main bar 58, a rear cross main bar 60 which connects rear ends of both the side frames 53 to each 10 other, and a pair of right and left rear sub-frames 61 attached to both the side frames 13. Each side frame 53 integrally has a down-frame section 53a suspended downwardly from the head pipe 12, a lower floor section 53b connected to a lower end of the down-frame section 53a and extending rearwardly below the floor 26, a rising frame section 53c connected to a rear end of the lower frame section 53b and rising upwardly behind the floor 26, and a seat rail section 53d extending rearwardly from an upper end of the rising frame section 53c to support the riding seat The side frame is obtained by bending and forming a single pipe. The seat rail sections 53d of both the side frames 53 are obliquely formed so as to approach each other as they extend rearward. The front main cross bar 57 connects intermediate portions of the down-frame sections 53a in both the side frames 53 to each other, the first intermediate cross main bar 58 connects upper portions of the rising frame sections 53c in both the side frames 53 to each other, and the second intermediate cross - 19 - main bar 60 connects intermediate portions of the seat rail sections 53d in both the side frames 53 to each other. The upper ends of the down-frame sections 53a in both the side frames 53 are joined to the head pipe 12, and a lower gusset 62 is provided between the head pipe 12 and lower portions of the joined portions of the down-frame sections 53a to the head pipe 12. Also, a lower gusset 63 is provided between the head pipe 12 and upper portions of the joined portions of the down-frame sections 53a to the head pipe 12. An upper end of the center frame 54 is joined to the upper gusset 63. The lower frame section 53b is comprised of a horizontal portion 53ba substantially horizontally extending rearwardly from the lower end of each down-frame section 13a and an inclined portion 53bb inclined rearwardly and upwardly from a rear end 15 of the horizontal portion 53ba. The connecting frame 55 is disposed above the lower frame sections 53b of both the side frames 53 and below the floor 26, and has a front end joined to a lower portion of the down-frame section 53a in each side frame 53 and a rear end joined to 20 the inclined portion 53bb in the lower frame section 53b of the side frame 53. A pair of right and left rear sub-frames 61 at least parts of which are disposed behind the rising frame sections 53c is attached to both the side frames 53. In this embodiment, 25 each rear sub-frame 61 is disposed below the lower frame section 53b of each side frame 53 and behind the rising frame section 53c. A front end of the rear sub-frame 61 is joined to a rear - 20 - face of a front end of the inclined portion 53bb in the lower frame section 53b in front of a joined portion of a rear end of the connecting frame 55, and a rear end of the rear sub-frame 61 is joined to a bottom face in the vicinity of a front portion of the seat frame section 53d in the side frame 53. Moreover, intermediate portions of both the rear sub-frames 61 are bent so as to approach the rising frame sections 53c of the side frames 53. Pivot plates 64 are provided between both the side frames 63 and both the rear sub-frames 61, respectively, below the bent intermediate portions. Each rear sub-frame 61 is made of a pipe member having a smaller diameter that the side frame 53. In side view, the lower frame section 53b and rising frame section 53c in the side frame 53 and the rear sub-frame 61 made of a pipe member having a small diameter are disposed such that they are juxtaposed in a pair below and behind the floor 26. As clearly shown in Fig, 6, a radiator 37 is disposed between the down-frame sections 53a of both the side frames 13 and the center frame 54. A top face of the floor 26 is 20 set to a position lower than a vertical center position CP of the radiator 37. As clearly shown in Fig. 9, a pair of right and left support arms 38 provided in an upper portion of the radiator 37 is elastically supported by a pair of right and left stays 65 25 provided in the front cross main bar 57. Also, both right and left ends of a guard pipe 40 which covers a lower portion of the radiator 37 from its front side are respectively joined - 21 - to front faces of lower ends of the down-frame sections 53a in both the side frames 53. A stay 41 directed toward a middle portion of the guard pipe 40 elastically supports a lower middle portion of the radiator 37. Referring to Fig. 10, a support plate 67 is secured to the connected portion between the lower floor section 53b and the rising frame section 53c in each side frame 13 so as to protrude rearwardly. A lower portion of the engine E in the power unit P is provided with a bracket 44. In addition, the link mechanism 72 includes a pair of right and left first link arms 74 which is rotatably supported by the pivot plates 64 via a body-frame-side pivot shaft 73, a second link arm 7 6 whose one end is rotatably connected to the other end of each of the first link arms 74 via connecting 15 shaft 75, a power-unit-side pivot shaft 77 which is fixed to the other end of the second link arm 7 6 and rotatably supported by the bracket 44, an arm 79 which is located outside one second link arm 76 of both the second link arms 76, which is located on the left side of the motorcycle as seen in its traveling direction, and which has one end connected to an intermediate portion of the second link mechanism 76 via a connecting pipe 78 and the other end connected to an end of the power-unit-side pivot shaft 77, and an upwardly extending regulating arm 81 whose one end is connected to the power-unit-side pivot shaft 25 77 and whose other end is rotatably supported by each support plate 67 via a pivot 80. An intermediate portion of the regulating arm 81 is connected to each support plate 67 via - 22 - a rubber bush 82 and a connecting shaft 83. Moreover, an upwardly protruding regulating protrusion 84 is integrally provided in the regulating arm 81, and a recess 8 5 is provided in the support plate 67 for receiving the regulating protrusion 84. The rotation of the regulating arm 81 around the axis of the pivot 80 is regulated to a range within which the regulating protrusion 84 can move within the recess 85, Moreover, the body-frame-side pivot shaft 73 of the link mechanism 72 is disposed in front of the rear face of the rising 10 frame section 53c in the side frame 53. The power-unit-side pivot shaft 77, as shown in Fig. 6, is disposed within an imaginary circular arc C passing through the center of rotation of the front wheel WF about the hand grip 22, on a projection view drawn by projecting the vehicle onto a plane orthogonal to a rotation axis of the front wheel WF. Next, the operation of the second embodiment will be described. The body frame FB includes the pair of right and left side frames 53, each having the down-frame section 53a suspended downwardly from the head pipe 12 and the lower frame section 53b extending rearwardly from the lower end of the down-frame section 53a, the center frame 54 suspended downwardly from the head pipe 12 between both the side frames 53, the pair of right and left connecting frames 55 having their front ends connected to the down-frame sections 53a above the lower 25 floor sections 53b of both the side frames 53 and having their rear ends connected to the lower frame sections 53b, the support stay 56 which connects the lower frame sections 53b of both - 23 - the side frames 53 to each other, and the center frame 54 suspended downwardly through vicinities of front portions of the side frames 53 from the head pipe 12 between both the side frames 53 and having its lower end connected to the support stay 56, and the connecting frames 55 are disposed below the low-floor-type floor 26. Accordingly, the lower frame sections 53b of both the side frames 53 are set to sufficiently lower positions, and the support stay 56 and the connecting frames 55 which reinforce both the side frames 53 and the center frame 54 suspended downwardly from the head pipe 12 between both the side frames 53 are disposed above the lower floor sections 53b and below the floor 26. As a result, the flat floor 26 that sufficiently ensures a footrest space is formed, thereby improving usability, and the balance between the longitudinal rigidity and torsional rigidity of the body frame FB can be improved. Moreover, each side frame 53 integrally has the down-frame section 53a suspended downwardly from the head pipe 12, the lower floor section 53b connected to the lower end of the down-frame section 53a and extending rearwardly below the floor 26, the rising frame section 53c connected to the rear end of the lower frame section 53b and rising upwardly behind the floor 26, and the seat rail section 53d extending rearwardly from the upper end of the rising frame section 53c. The side frame is obtained by bending and forming a single pipe. As a result, the number of parts can be reduced, and the number of assembling processes of the body frame FB can be reduced. - 24 - Moreover, the side frames 53, the center frame 54 having a smaller diameter than the side frames 53, and the rear-sub frames 61 are disposed such that they are juxtaposed in pairs in front of, below, and behind the floor 26, in side view. 5 Thus, the lightweight and high-rigidity body frame FB can be constructed. Further, the radiator 37 is disposed between the down-frame sections 53a of both the side frames 53 and the center frame 54. Accordingly, by increasing the vertical length of the radiator 37 while expanding the space of the flat floor 26, the capacity of the radiator 37 can be increased, thereby improving the cooling performance for the engine E. In addition, since the top face of the floor 26 is set to a position below the vertical center position CP of the radiator 37, the position of the floor 26 can be set as near to the bottom as possible, thereby improving the property that a rider gets on/out of the vehicle. Moreover, the pair of right and left rear sub-frames 61 at least parts of which are disposed behind the rising frame sections 53c is attached to both the side frames 53, and the body-frame-side pivot shaft 73 of the link mechanism 72 provided between the body frame FB and the power unit P is supposed by the pivot plates 64 provided between both the side frames 53 and both the rear sub-frames 61. Thus, it is possible to increase the rigidity around the body-frame-side pivot shaft 73 while avoiding increasing the size of the side frames 53. By avoiding increasing the size of the side frame 52 in this - 25 - way, the rear space of the floor 26 can be increased. Moreover, since the body-frame-side pivot shaft 7 3 of the link mechanism 72 is disposed in front of the rear face of the rising frame section 53c, the body-frame-side pivot shaft 73 of the link mechanism 72 can be disposed as near to the front as possible, thereby shortening the wheelbase. Further, sine the intermediate portions of both the rear sub-frames 61 are bent so as to approach the rising frame sections 53c of the side frames 53, the power unit P can be disposed on the front side while avoiding interference of the power unit P with the rear sub-frames 61, thereby making the wheelbase shorter. Moreover, the power-unit-side pivot shaft 77 of the link mechanism 42 is disposed within the imaginary circular arc 15 C passing through the center of rotation of the front wheel WF about the hand grip 22, on a project ion view drawn by project ing the vehicle onto a plane orthogonal to the rotation axis of the front wheel WF. As a result, the power-unit-side pivot shaft 77 of the link mechanism 42 can be disposed as near to the front as possible, thereby further shortening the wheelbase. It will be apparent to those skilled in the art that various modifications and variations can be made to the described embodiments of the present invention without departing from the spirit or scope of the invention. Thus, it is intended 25 that the present invention cover all modifications and variations of this invention consistent with the scope of the appended claims and their equivalents. -26-

Full Text

FORM 2
THE PATENTS ACT, 1970 (39 of 1970)
COMPLETE SPECIFICATION
(See Section 10; rule 13)
TITLE
FRAME STRUCTURE OF SCOOTER-TYPE VEHICLE
APPLICANT
HONDA MOTOR CO., LTD.
1-1 Minamiaoyama 2-chome
Minato-ku
Tokyo
Japan
Nationality: Japan
The following specification particularly describes
the nature of this invention and the manner
in which it is to be performed

FRAME STRUCTURE OF SCOOTER-TYPE VEHICLE
The present application claims foreign priority based on Japanese Patent Applications No. P.2005-088501, filed on March 25, 2005 and No. P.2005-351930, filed on December 6, 2005, the contents of them are incorporated herein by reference.
BACKGROUND OF THE INVENTION

The present invention relates to a frame structure of a scooter-type vehicle in which a pair of right and left side frames is joined to a head pipe that steerably supports a front fork which journals a front wheel.

Disclosed in JP-B2-3423487 is a scooter-type vehicle with a pair of right and left side frames, each having a down-frame section suspended downwardly from a head pipe, a lower frame section extending downwardly from a lower end of the down-frame
section, and a front end joined to the head pipe, such that the side frames are reinforced by a pair of right and left down-tubes disposed below both the side frames.
In the scooter-type vehicle disclosed in JP-B2-3423487, the side frames and rear ends of the down-tubes are connected and fixed to each other by suspension brackets, and a body-frame-side pivot shaft provided between a body frame and a power unit is supported by the suspension brackets. In this
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frame structure, since a large load is applied to portions of the side frames and down-tubes for connection with the suspension brackets, the size of the side frames and down-tubes may be increased. Therefore, there is a need for further increasing the rigidity around the body-frame-side pivot shaft. However, if the size of the side frames and down-tubes increases, the rear space of the floor may be narrowed as well as the weight of the overall scooter-type vehicle may be increased. The invention has been made in consideration of such 10 circumstances. It is therefore a first object of the invention to provide a frame structure of a scooter-type vehicle which makes it possible to sufficiently increase the rigidity around a body-frame-side pivot shaft while avoiding increasing the size of side frames, and to expand the rear space of a floor.
Further, in the scooter-type vehicle disclosed in JP-B2-3423487, the side frames are made of pipe so as to integrally have down-frame sections suspended downwardly from the head pipe and lower frame sections extending rearwardly from rear ends of the down-frame sections, and a support pipe which supports a riding seat is adapted to be joined to the side frames. Thus, the number of parts increases and the number of assembling processes of the vehicle frame increases.
The invention has been made in consideration of such circumstances. It is therefore a second object of the invention to provide a frame structure of a scooter-type vehicle which makes it possible to reduce the number of parts and the number of assembling processes.
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SUMMARY OF THE INVENTION
In accordance with one or more embodiments of the present invention, a frame structure of a scooter-type vehicle in which 5 a pair of right and left side frames is joined to a head pipe which steerably supports a front fork which journals a front wheel is provided with pivot plates respectively provided between the pair of right and left side frames and a pair of right and left rear sub-frames. Each of the side frames has a lower frame section extending below the floor, and a rising frame section connected to a rear end of the lower frame section and upwardly rising behind the floor. At least parts of the pair of right and left rear sub-frames are disposed behind the rising frame sections and attached to both the side frames.
A body-frame-side pivot shaft of a link mechanism provided between a power unit and a body frame is supportedby the pivot plates. The body frame is constituted by the head pipe, both the side frames, and the rear sub-frames.
Further, in accordance with one or more embodiments of the present invention, intermediate portions of both the rear sub-frames maybe bent so as to approach the rising frame sections of the side frames.
In accordance with one or more embodiments of the present invention, in a frame structure of a scooter-type vehicle in which a pair of right and left side frames is joined to a head pipe which steerably supports a front fork which journals a front wheel, each of both the side frames integrally has: a
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down-frame section suspended downwardly from the head pipe; a lower floor section connected to a lower end of the down-frame section and extending rearwardly below the floor; a rising frame section connected to a rear end of the lower frame section 5 and rising upwardly behind the floor, and a seat rail section extending rearwardly from an upper end of the rising frame section to support a riding seat. Bending a single pipe forms each of the side frames.
Further, in accordance with one or more embodiments of the present invention, the side frames, and pipe members having a smaller diameter than the side frames and reinforcing the side frames may be disposed such that they are juxtaposed in pairs in front of, below, and behind the floor, in side view.
Further, in accordance with one or more embodiments of 15 the present invention, the pipe members may correspond to the center frame 14, 54, the rear sub-frames 18, 61, the U-shaped section 32 and the connecting frames 55.
According to one or more embodiments of the invention, a body-frame-side pivot shaft of a link mechanism is supported by the pivot plates provided between side frames and rear sub-frames at least parts of which are disposed behind the rising frame sections provided in the side frames and which is attached to both the side frames. Thus, it is possible to increase the rigidity around the body-frame-side pivot shaft while avoiding increasing the size of the side frames. By avoiding increasing the size of the side frame in this way, the rear space of the floor can be increased.
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Further, according to one or more embodiments of the present invention, the power unit can be disposed on the front side while avoiding interference of the power unit with the rear sub-frames, thereby making the wheelbase shorter. According to one or more embodiments of the present invention, since each side frame integrally has the down-frame section, the lower floor section, the rising frame section, and the seat rail section, and the side frame is formed by bending a single pipe. As a result, the number of parts can be reduced, and the number of assembling processes of the body frame can be reduced.
Moreover, according to one or more embodiments of the present invention, the lightweight and high-rigidity body frame can be constructed.
Other aspects and advantages of the invention will be apparent from the following description and the appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a side view of a scooter-type vehicle of a first embodiment.
Fig. 2 is a side view of a body frame.
Fig. 3 is a plan view as viewed in the direction of arrow 3 in Fig. 2.
Fig. 4 is a plan view as viewed in the direction of arrow 4 in Fig. 2.
Fig. 5 is a longitudinal sectional side view showing the

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structure of a link mechanism.
Fig. 6 is a side view of a scooter-type vehicle of a second embodiment.
Fig. 7 is a side view of a body frame. Fig. 8 is a plan view as viewed in the direction of arrow
8 in Fig. 7.
Fig. 9 is a plan view as viewed in the direction of arrow
9 in Fig. 7.
Fig. 10 is a side view showing the structure of a link mechanism.

11: FRONT FORK
12: HEAD
PIPE 15 13, 53: SIDE FRAME
13a, 53a: DOWN-FRAME SECTION
13b, 53b: LOWER FRAME SECTION
13c, 53c: RISING FRAME SECTION
14, 54: CENTER FRAME 20 15: MAIN PIPE
17, 55: CONNECTING FRAME
21: STEERING WHEEL
22: HANDLE GRIP
2 6: FLOOR
31: GUSSET
32: U-SHAPED SECTION
33: SUPPORT SECTION
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37: RADIATOR
42, 72: LINK MECHANISM
45, 73: BODY-FRAME-SIDE PIVOT SHAFT
49, 77: POWER-UNIT-SIDE PIVOT SHAFT
C: IMAGINARY CIRCULAR ARC
FA, FB: BODY FRAME
P: POWER UNIT
WF: FRONT WHEEL
DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS
Exemplary embodiments of the invention will be described with reference to the accompanying drawings.
Figs. 1 to 5 show a first embodiment of the invention, specifically, Fig. 1 is a side view of a scooter-type vehicle,
Fig. 2 is a side view of a body frame, Fig. 3 is a plan view as viewed in the direction of arrow 3 in Fig. 2, Fig. 4 is a plan view as viewed in the direction of arrow 4 in Fig. 2, and Fig. 5 is a longitudinal sectional side view showing the structure of a link mechanism.
Referring first to Fig. 1, a front fork 11 journaling a front wheel WF is steerably supported by a head pipe 12 at a front end of a body frame FA provided in a scooter-type vehicle having a low-floor-type floor 26. Both ends of a bar-shaped steering handle 21 connected to an upper portion of the front fork 11 are provided with handle grips 22, 22, respectively.
Also, a body frame FA so as to be rockable up and down via a link mechanism supports a front portion of a power unit P
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42 . The power unit Pic comprised of an engine E and a transmission M which changes power from the engine E to transmit it to a rear wheel WR. A rear portion of the power unit P supports the rear wheel W. A rear cushion unit 23 is provided between 5 a rear portion of the body frame FA and a rear portion of the power unit P.
The body frame FA includes the head pipe 12, a pair of right and left side frames 13 having their front ends joined to the head pipe 12, a center frame 14 suspended downwardly through vicinities of front portions of the side frames 13 from the head pipe 12 between both the side frames 13, a main pipe 15 suspended from the head pipe 12, a front cross main bar 16 which connects the front portions of both the side frames 13 to each other and allows a lower end of the main pipe 15 to be joined thereto, a connecting frame 17 disposed below the floor 2 6 to reinforce the center frame 14 and both the side frames 13, a pair of right and left rear sub-frames 18 attached to both the side frames 13, and a rear cross main bar 19 which connects rear ends of both the side frames to each other.
The body frame FA is covered with a vehicle body cover 24 made of synthetic resin. The vehicle body cover 24 includes a leg shield 25 which covers the front of rider's legs, the floor 26 which is connected to a lower portion of the leg shield 25 to allow the rider's feet to be placed thereon, and a side cover 27 which is connected to the floor 26 to cover the rear portion of the vehicle body from both lateral sides. A tandem
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riding seat 30 which covers a storage box 28 and a fuel tank 29 disposed behind the storage box 28 in such a manner to be opened and closed from above is provided on the side cover 27.
Referring to Figs. 2 to 4, each side frame 13 integrally has a down-frame section 13a suspended downwardly from the head pipe 12, a lower floor section 13b connected to a lower end of the down-frame section 13a and extending rearwardly below the floor 26, a rising frame section 13c connected to
a rear end of the lower frame section 13b and rising upwardly behind the floor 26, and a seat rail section 13dextending rearwardly from an upper end of the rising frame section 13c to support the riding seat 30. Bending and forming a single pipe obtain the side frame.
A gusset 31 is provided between the head pipe 12 and the main pipe 15 suspended from the head pipe 12, and an upper end of the down-frame section 13a of the side frame 13 is joined to both the head pipe 12 and the gusset 31. Also, an upper portion of the center frame 14 is connected to the main pipe, and the gusset, as in this embodiment, may be welded or fastened using bolts.
The lower frame section 13b is comprised of a horizontal portion 13ba substantially horizontally extending rearwardly from the lower end of the down-frame section 13a and an inclined portion 13bb inclined rearwardly and upwardly from a rear end of the horizontal portion 13ba.
The connecting frame 17 is disposed above the lower frame
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sections 13b of both the side frames 13 and below the floor 26. This connecting frame is comprised of a U-shaped section 32 which is formed in a substantially "U" shape in plan view, and has a closed front end and rear ends connected to the inclined 5 portions 13bb in the down-frame sections 13b of both the side frames 13, and a support section 33 which connects the vicinity of a widthwise middle portion of the front end of the U-shaped section 32 to connected portions between the down-frame sections 13a and lower frame sections 13b in both the side frames 13.
In this embodiment, the U-shaped section 32 has a smaller diameter than the side frames 13, and is formed by bending a single pipe member, and the support section 33, which is composed of a pair of right and left pipe members 34 and 34, connects two spots in the vicinity of the widthwise middle
15 portion of the front end of the U-shaped section 32 to the connected portions between the down-frame sections 13a and the lower frame sections 13b.
In side view, the lower frame section 13b in each side frame 13 and the U-shaped section 32 formed to have a smaller diameter than the side frame 13 and disposed above the lower frame section 13b are disposed such that they are juxtaposed vertically in a pair.
The center frame 14, which has a laterally long rectangular cross-sectional shape whose width Wl (see Fig. 4) in the width direction of the vehicle is larger that a width W2 (see Fig. 2) in the forward and backward directions of the vehicle, may be made of an angled cylindrical pipe or may be molded of cast
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iron. A lower end of the center frame 14 whose upper portion is connected to the main pipe 15 is joined to the widthwise middle portion of the front end of the U-shaped section 32 in the connecting frame 17. In side view, the down-frame section 13a of each side frame 13 and the U-shaped section 32 made of a pipe member having a smaller diameter than the down-frame section 13a are disposed in front of the floor 26 such that they are juxtaposed back and forth in a pair.
A pair of right and left rear sub-frames 18 at least parts of which are disposed behind the rising frame sections 13c is attached to both the side frames 13. In this embodiment, each rear sub-frame 18 is disposed below the lower frame section 13b of each side frame 13 and behind the rising frame section 13c. A front end of the rear sub-frame 18 is joined to a rear face of a front end of the inclined portion 13bb in the lower frame section 13b in front of a joined portion of the U-shaped section 32 in the connecting frame 17, and a rear end of the rear sub-frame 18 is joined to a bottom face in the vicinity of a front portion of the seat frame section 13d in the side frame 13.
Moreover, intermediate portions of both the rear sub-frames 18 are bent so as to approach the rising frame sections 13c of the side frames 13. Pivot plates 36 are provided between both the side frames 13 and both the rear sub-frames 18, respectively, below the bent intermediate portions.
Each rear sub-frame 18 is made of a pipe member having a smaller diameter that the side frame 13. In side view, the

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lower frame section 13b and rising frame section 13c in the side frame 13 and the rear sub-frame 18 made of a pipe member having a small diameter are disposed such that they are juxtaposed in a pair below and behind the floor 26.
As clearly shown in Fig. 1, a radiator 37 is disposed between the down-frame sections 13a of both the side frames 13 and the center frame 14. A top face of the floor 26 is set to a position lower than a vertical center position CP of the radiator 37.
As clearly shown in Fig. 4, a pair of right and left support arms 38 provided in an upper portion of the radiator 37 is elastically supported by a pair of right and left stays 39 provided in the front cross main bar 16, Also, both right and left ends of a guard pipe 40 which covers a lower portion of the radiator 37 from its front side are respectively joined to front faces of lower ends of the down-frame sections 13a in both the side frames 13. A stay 41 directed toward a middle portion of the guard pipe 40 elastically supports a lower middle portion of the radiator 37.
Referring to Fig. 5, a support plate 43 is secured to the connected portion between the lower floor section 13b and the rising frame section 13c in each side frame 13 so as to protrude rearwardly. A lower portion of the engine E in the power unit P is provided with a bracket 44.
In addition, the link mechanism 42 includes a pair of right and left first link arms 46 which is rotatably supported by the pivot plates 36 via a body-frame-side pivot shaft 45,
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a second link arm 48 whose one end is rotatably connected to the other end of each of the first link arms 46 via a connecting shaft 47, a power-unit-side pivot shaft 49 which is fixed to the other end of the second link arm 48 and rotatably supported 5 by the bracket 44, an upwardly extending regulating arm 51 whose one end is connected to the power-unit-side pivot shaft 49 and whose intermediate portion is rotatably supported by each support plate 43 via a pivot 50, and an elastic member 52 mounted on the other end of the regulating arm 51. The rotation of the regulating arm is regulated between a position where the elastic member 52 comes into a resilient contact with a lower rear face of the rising frame section 13c in each side frame 13 and a position where the elastic member 49 comes into a resilient contact with a regulating plate 43a provided in each support plate 43 from the front side.
Moreover, the body-frame-side pivot shaft 45 of the link mechanism 42 is disposed in front of the rear face of the rising frame section 13c in the side frame 13. The power-unit-side pivot shaft 49, as shown in Fig. 1, is disposed within an imaginary circular arc C passing through the center of rotation of the front wheel WF about the hand grip 22, on a projection view drawn by projecting the vehicle onto a plane orthogonal to a rotation axis of the front wheel WF.
Next, the operation of the first embodiment will be described. The body frame FA includes the pair of right and left side frames 13, each having the down-frame section 13a suspended downwardly from the head pipe 12 and the lower frame
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section 13b extending rearwardly from the lower end of the down-frame section 13a, the center frame 14 suspended downwardly from the head pipe 12 between both the side frames 13, and the connecting frame 17 which is disposed above the lower floor 5 sections 13b to reinforce the center frame 14 and both the side frames 13, and the connecting frame 17 is disposed below the low-floor-type floor 26. Accordingly, the lower frame sections 13b of both the side frames 13 are set to sufficiently lower positions, and the connecting frame 17 which reinforces 10 both the side frames 13 and the center frame 14 suspended downwardly from the head pipe 12 between both the side frames 13 are disposed above the lower floor sections 13b and below the floor 26. As a result, the flat floor 26 that sufficiently ensures a footrest space is formed, thereby improving usability, 15 and the balance between the longitudinal rigidity and torsional rigidity of the body frame FA can be improved.
In addition, such effects can be achieved not only by the connecting frame 17 having the U-shaped section 32 and the support section 33 but also by a connecting frame adapted 20 to linearly connect rear portions of the lower frame sections 13b of the side frames 13 to the down-frame sections 13a in a substantially horizontal plane.
Moreover, since the center frame 13 has a laterally long rectangular cross-sectional shape, it is possible to increase the rigidity of the center frame 14 while easily ensuring the backward and rearward installation space for the center frame
14 to be disposed in front of the floor 26.
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Besides, the connecting frame 17 has the U-shaped section 32 which is formed in a substantially "U" shape in plan view, and has a closed front end and rear ends connected to both the side frames 13, and the support section 33 which connects 5 the vicinity of a widthwise middle portion of the front end of the U-shaped section 32 to the side frames 13. Thus, the flat floor 26 that sufficiently ensures a footrest space while ensuring a sufficient rigidity is formed, thereby improving usability, and the torsional rigidity of the body frame FA
1 can be adjusted.
In addition, such effects can be achieved even if the center frame 14 is omitted.
Further, the gusset 31 is provided between the head pipe 12 and the main pipe 15 suspended from the head pipe 12, and the upper ends of the down-frame sections 13a of both the side frames 13 are joined to both the head pipe 12 and the gusset 31. As a result, the rigidity of joint between both the side frames 13 and the head pipe 12 can be increased. Also, since the upper portion of the center frame 14 is connected to the main pipe 15, the rigidity of the upper portion of the center frame 14 can be increased.
Moreover, each side frame 13 integrally has the down-frame section 13a suspended downwardly from the head pipe 12, the lower floor section 13b connected to the lower end of the down-frame section 13a and extending rearwardly below the floor 2 6, the rising frame section 13c connected to the rear end of the lower frame section 13b and rising upwardly behind the
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floor 26, and the seat rail section 13d extending rearwardly from the upper end of the rising frame section 13c. Bending and forming a single pipe obtain the side frame. As a result, the number of parts can be reduced, and the number of assembling processes of the body frame FA can be reduced.
Moreover, the side frames 13, the center frame 14 having a smaller diameter than the side frames 13 and reinforcing the side frames 13, the U-shaped section 32 of the connecting frame 17, and the rear-sub frames 18 are disposed such that 10 they are juxtaposed in pairs in front of, below, and behind the floor 2 6, in side view. Thus, the lightweight and high-rigidity body frame FA can be constructed.
Further, the radiator 37 is disposed between the down-frame sections 13a of both the side frames 13 and the center frame
14. Accordingly, by increasing the vertical length of the radiator 37 while expanding the space of the flat floor 26, the capacity of the radiator 37 can be increased, thereby improving the cooling performance for the engine E In addition, since the top face of the floor 26 is set to a position below the vertical center position CP of the radiator 37, the position of the floor 26 can be set as near to the bottom as possible, thereby improving the property that a rider gets on/out of the vehicle.
Moreover, the pair of right and left rear sub-frames 18 25 at least parts of which are disposed behind the rising frame sections 13c is attached to both the side frames 13, and the body-frame-side pivot shaft 45 of the link mechanism 42 provided
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between the body frame FA and the power unit P is supposed by the pivot plates 36 provided between both the side frames 13 and both the rear sub-frames 18. Thus, it is possible to increase the rigidity around the body-frame-side pivot shaft 5 45 while avoiding increasing the size of the side frames 13. By avoiding increasing the size of the side frame 13 in this way, the rear space of the floor 26 can be increased.
Moreover, since the body-frame-side pivot shaft 45 of the link mechanism 42 is disposed in front of the rear face of the rising frame section 13c, the body-frame-side pivot shaft 45 of the link mechanism 42 can be disposed as near to the front as possible, thereby shortening the wheelbase.
Further, sine the intermediate portions of both the rear sub-frames 18 are bent so as to approach the rising frame sections 15 13c of the side frames 13, the power unit P can be disposed on the front side while avoiding interference of the power unit P with the rear sub-frames 18, thereby making the wheelbase shorter.
Moreover, the power-unit-side pivot shaft 49 of the link mechanism 42 is disposed within the imaginary circular arc C passing through the center of rotation of the front wheel WF about the hand grip 22, on a projection view drawn by projecting the vehicle onto a plane orthogonal to the rotation axis of the front wheel WF. As a result, the power-unit-side pivot 25 shaft 49 of the link mechanism 42 can be disposed as near to the front as possible, thereby further shortening the wheelbase.
Figs. 6 to 10 show a second embodiment of the invention,
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specifically, Fig. 6 is a side view of a scooter-type vehicle of the second embodiment, Fig. 7 is a side view of a body frame, Fig. 8 is a plan view as viewed in the direction of arrow 8 in Fig. 7, Fig. 9 is a plan view as viewed in the direction 5 of arrow 9 in Fig. 7, and Fig. 10 is a side view showing the structure of a link mechanism.
In addition, in the description of the second embodiment, the parts corresponding to those in the first embodiment are denoted by the same reference numerals, and the detailed description thereof will be substituted by illustration only.
Referring first to Fig. 6, a front portion of the power unit P comprised of the engine E and the transmission M is supported by a body frame FB provided in a scooter-type vehicle having the low-floor-type floor 26 so as to be rockable up 15 and down via the link mechanism 42. The rear cushion unit 23 is provided between a rear portion of the body frame FB and a rear portion of the power unit P.
Referring to Figs. 7 to 9, the body frame FB includes the head pipe 12, a pair of right and left side frames 53 having their front ends joined to the head pipe 12, a center frame 54 made of a pipe member and suspended downwardly through vicinities of front portions of the side frames 53 from the head pipe 12 between both the side frames 53, connecting frames 55 extending back and forth below the floor 26 provided in the body cover 24 and having their both ends connected to both the side frames 53, a support stay 56 disposed below both the connecting frames 55 to connect both the side frames 53 to
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each other and connected to a lower end of the center frame 54, a front cross main bar 57 which connects the front portions of both the side frames 13 to each other and allows a lower end of the main pipe 15 to be joined thereto, a first intermediate 5 cross main bar 58 which connects intermediate portions of both the side frames 53, a second intermediate cross main bar 59 which connects intermediate portions of both the side frames 53 behind the first cross main bar 58, a rear cross main bar 60 which connects rear ends of both the side frames 53 to each
10 other, and a pair of right and left rear sub-frames 61 attached to both the side frames 13.
Each side frame 53 integrally has a down-frame section 53a suspended downwardly from the head pipe 12, a lower floor section 53b connected to a lower end of the down-frame section 53a and extending rearwardly below the floor 26, a rising frame section 53c connected to a rear end of the lower frame section 53b and rising upwardly behind the floor 26, and a seat rail section 53d extending rearwardly from an upper end of the rising frame section 53c to support the riding seat The side frame is obtained by bending and forming a single pipe. The seat rail sections 53d of both the side frames 53 are obliquely formed so as to approach each other as they extend rearward.
The front main cross bar 57 connects intermediate portions of the down-frame sections 53a in both the side frames 53 to each other, the first intermediate cross main bar 58 connects upper portions of the rising frame sections 53c in both the side frames 53 to each other, and the second intermediate cross
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main bar 60 connects intermediate portions of the seat rail sections 53d in both the side frames 53 to each other.
The upper ends of the down-frame sections 53a in both the side frames 53 are joined to the head pipe 12, and a lower gusset 62 is provided between the head pipe 12 and lower portions of the joined portions of the down-frame sections 53a to the head pipe 12. Also, a lower gusset 63 is provided between the head pipe 12 and upper portions of the joined portions of the down-frame sections 53a to the head pipe 12. An upper end of the center frame 54 is joined to the upper gusset 63.
The lower frame section 53b is comprised of a horizontal portion 53ba substantially horizontally extending rearwardly from the lower end of each down-frame section 13a and an inclined portion 53bb inclined rearwardly and upwardly from a rear end 15 of the horizontal portion 53ba.
The connecting frame 55 is disposed above the lower frame sections 53b of both the side frames 53 and below the floor 26, and has a front end joined to a lower portion of the down-frame section 53a in each side frame 53 and a rear end joined to 20 the inclined portion 53bb in the lower frame section 53b of the side frame 53.
A pair of right and left rear sub-frames 61 at least parts of which are disposed behind the rising frame sections 53c is attached to both the side frames 53. In this embodiment, 25 each rear sub-frame 61 is disposed below the lower frame section 53b of each side frame 53 and behind the rising frame section 53c. A front end of the rear sub-frame 61 is joined to a rear
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face of a front end of the inclined portion 53bb in the lower frame section 53b in front of a joined portion of a rear end of the connecting frame 55, and a rear end of the rear sub-frame 61 is joined to a bottom face in the vicinity of a front portion of the seat frame section 53d in the side frame 53.
Moreover, intermediate portions of both the rear sub-frames 61 are bent so as to approach the rising frame sections 53c of the side frames 53. Pivot plates 64 are provided between both the side frames 63 and both the rear sub-frames 61, respectively, below the bent intermediate portions.
Each rear sub-frame 61 is made of a pipe member having a smaller diameter that the side frame 53. In side view, the lower frame section 53b and rising frame section 53c in the side frame 53 and the rear sub-frame 61 made of a pipe member having a small diameter are disposed such that they are juxtaposed in a pair below and behind the floor 26.
As clearly shown in Fig, 6, a radiator 37 is disposed between the down-frame sections 53a of both the side frames 13 and the center frame 54. A top face of the floor 26 is 20 set to a position lower than a vertical center position CP of the radiator 37.
As clearly shown in Fig. 9, a pair of right and left support arms 38 provided in an upper portion of the radiator 37 is elastically supported by a pair of right and left stays 65 25 provided in the front cross main bar 57. Also, both right and left ends of a guard pipe 40 which covers a lower portion of the radiator 37 from its front side are respectively joined
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to front faces of lower ends of the down-frame sections 53a in both the side frames 53. A stay 41 directed toward a middle portion of the guard pipe 40 elastically supports a lower middle portion of the radiator 37.
Referring to Fig. 10, a support plate 67 is secured to the connected portion between the lower floor section 53b and the rising frame section 53c in each side frame 13 so as to protrude rearwardly. A lower portion of the engine E in the power unit P is provided with a bracket 44.
In addition, the link mechanism 72 includes a pair of right and left first link arms 74 which is rotatably supported by the pivot plates 64 via a body-frame-side pivot shaft 73, a second link arm 7 6 whose one end is rotatably connected to the other end of each of the first link arms 74 via connecting 15 shaft 75, a power-unit-side pivot shaft 77 which is fixed to the other end of the second link arm 7 6 and rotatably supported by the bracket 44, an arm 79 which is located outside one second link arm 76 of both the second link arms 76, which is located on the left side of the motorcycle as seen in its traveling direction, and which has one end connected to an intermediate portion of the second link mechanism 76 via a connecting pipe 78 and the other end connected to an end of the power-unit-side pivot shaft 77, and an upwardly extending regulating arm 81 whose one end is connected to the power-unit-side pivot shaft
25 77 and whose other end is rotatably supported by each support plate 67 via a pivot 80. An intermediate portion of the regulating arm 81 is connected to each support plate 67 via
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a rubber bush 82 and a connecting shaft 83.
Moreover, an upwardly protruding regulating protrusion 84 is integrally provided in the regulating arm 81, and a recess
8 5 is provided in the support plate 67 for receiving the regulating protrusion 84. The rotation of the regulating arm 81 around
the axis of the pivot 80 is regulated to a range within which the regulating protrusion 84 can move within the recess 85, Moreover, the body-frame-side pivot shaft 73 of the link mechanism 72 is disposed in front of the rear face of the rising
10 frame section 53c in the side frame 53. The power-unit-side pivot shaft 77, as shown in Fig. 6, is disposed within an imaginary circular arc C passing through the center of rotation of the front wheel WF about the hand grip 22, on a projection view drawn by projecting the vehicle onto a plane orthogonal to a rotation axis of the front wheel WF.
Next, the operation of the second embodiment will be described. The body frame FB includes the pair of right and left side frames 53, each having the down-frame section 53a suspended downwardly from the head pipe 12 and the lower frame section 53b extending rearwardly from the lower end of the down-frame section 53a, the center frame 54 suspended downwardly from the head pipe 12 between both the side frames 53, the pair of right and left connecting frames 55 having their front ends connected to the down-frame sections 53a above the lower
25 floor sections 53b of both the side frames 53 and having their rear ends connected to the lower frame sections 53b, the support stay 56 which connects the lower frame sections 53b of both
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the side frames 53 to each other, and the center frame 54 suspended downwardly through vicinities of front portions of the side frames 53 from the head pipe 12 between both the side frames 53 and having its lower end connected to the support stay 56, and the connecting frames 55 are disposed below the low-floor-type floor 26. Accordingly, the lower frame sections 53b of both the side frames 53 are set to sufficiently lower positions, and the support stay 56 and the connecting frames 55 which reinforce both the side frames 53 and the center frame
54 suspended downwardly from the head pipe 12 between both the side frames 53 are disposed above the lower floor sections 53b and below the floor 26. As a result, the flat floor 26 that sufficiently ensures a footrest space is formed, thereby improving usability, and the balance between the longitudinal rigidity and torsional rigidity of the body frame FB can be improved.
Moreover, each side frame 53 integrally has the down-frame section 53a suspended downwardly from the head pipe 12, the lower floor section 53b connected to the lower end of the down-frame section 53a and extending rearwardly below the floor 26, the rising frame section 53c connected to the rear end of the lower frame section 53b and rising upwardly behind the floor 26, and the seat rail section 53d extending rearwardly from the upper end of the rising frame section 53c. The side frame is obtained by bending and forming a single pipe. As a result, the number of parts can be reduced, and the number of assembling processes of the body frame FB can be reduced.
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Moreover, the side frames 53, the center frame 54 having a smaller diameter than the side frames 53, and the rear-sub frames 61 are disposed such that they are juxtaposed in pairs in front of, below, and behind the floor 26, in side view. 5 Thus, the lightweight and high-rigidity body frame FB can be constructed.
Further, the radiator 37 is disposed between the down-frame sections 53a of both the side frames 53 and the center frame 54. Accordingly, by increasing the vertical length of the radiator 37 while expanding the space of the flat floor 26, the capacity of the radiator 37 can be increased, thereby improving the cooling performance for the engine E. In addition, since the top face of the floor 26 is set to a position below the vertical center position CP of the radiator 37, the position of the floor 26 can be set as near to the bottom as possible, thereby improving the property that a rider gets on/out of the vehicle.
Moreover, the pair of right and left rear sub-frames 61 at least parts of which are disposed behind the rising frame sections 53c is attached to both the side frames 53, and the body-frame-side pivot shaft 73 of the link mechanism 72 provided between the body frame FB and the power unit P is supposed by the pivot plates 64 provided between both the side frames 53 and both the rear sub-frames 61. Thus, it is possible to increase the rigidity around the body-frame-side pivot shaft 73 while avoiding increasing the size of the side frames 53. By avoiding increasing the size of the side frame 52 in this
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way, the rear space of the floor 26 can be increased.
Moreover, since the body-frame-side pivot shaft 7 3 of the link mechanism 72 is disposed in front of the rear face of the rising frame section 53c, the body-frame-side pivot shaft 73 of the link mechanism 72 can be disposed as near to the front as possible, thereby shortening the wheelbase.
Further, sine the intermediate portions of both the rear sub-frames 61 are bent so as to approach the rising frame sections 53c of the side frames 53, the power unit P can be disposed on the front side while avoiding interference of the power unit P with the rear sub-frames 61, thereby making the wheelbase shorter. Moreover, the power-unit-side pivot shaft 77 of the link mechanism 42 is disposed within the imaginary circular arc 15 C passing through the center of rotation of the front wheel WF about the hand grip 22, on a project ion view drawn by project ing the vehicle onto a plane orthogonal to the rotation axis of the front wheel WF. As a result, the power-unit-side pivot shaft 77 of the link mechanism 42 can be disposed as near to the front as possible, thereby further shortening the wheelbase.
It will be apparent to those skilled in the art that various modifications and variations can be made to the described embodiments of the present invention without departing from the spirit or scope of the invention. Thus, it is intended 25 that the present invention cover all modifications and variations of this invention consistent with the scope of the appended claims and their equivalents.
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Documents:

539-che-2006-abstract.pdf

539-che-2006-claims.pdf

539-che-2006-correspondance- others.pdf

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

539-che-2006-diagrams.pdf

539-che-2006-form 1.pdf

539-che-2006-form 3.pdf

539-che-2006-form 5.pdf

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Patent Number

229999

Indian Patent Application Number

539/CHE/2006

PG Journal Number

13/2009

Publication Date

27-Mar-2009

Grant Date

24-Feb-2009

Date of Filing

24-Mar-2006

Name of Patentee

HONDA MOTOR CO., LTD.

Applicant Address

1-1 Minamiaoyama 2-chome, Minato-ku, Tokyo,

Inventors:

#	Inventor's Name	Inventor's Address
1	MORIKAWA, Yuichiro	C/o. Honda R&D Co., Ltd., 4-1, Chuo l-chome, Wako-shi, Saitama 351-0193,
2	HOSOYA, YUKIO	C/o. Honda R&D Co., Ltd., 4-1, Chuo l-chome, Wako-shi, Saitama 351-0193,

PCT International Classification Number

B62K11/10

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1	2005-088501	2005-03-25	Japan
2	2005-351930	2005-12-06	Japan