초록 ▼

A frame structure for a motorcycle includes a front fork which journals a front wheel and that is capable of being steered and supported by a head pipe. Front end portions of a pair of right and left pipe members are connected contiguously to the head pipe and extend downwardly and rearwardly from t

A frame structure for a motorcycle includes a front fork which journals a front wheel and that is capable of being steered and supported by a head pipe. Front end portions of a pair of right and left pipe members are connected contiguously to the head pipe and extend downwardly and rearwardly from the head pipe. The pair of right and left pipe members each have a substantially prismatic cross sectional shape and are each bent at their longitudinally intermediate portions so as to be outwardly convex with respect to the sides of the motorcycle frame. An engine is disposed between lower portions of both pipe members in an engine mounting space. The present invention narrows the distance between the upper portions of the right and left pipe members and effectively increases the space between the lower portions of the pair of right and left pipe members.

대표청구항 ▼

What is claimed is: 1. A motorcycle frame comprising: a head pipe; a front fork for supporting a front wheel through a shaft, wherein said front fork is rotatable with respect to and supported by said head pipe; and a pair of right and left pipe members connected contiguously at front end portions

What is claimed is: 1. A motorcycle frame comprising: a head pipe; a front fork for supporting a front wheel through a shaft, wherein said front fork is rotatable with respect to and supported by said head pipe; and a pair of right and left pipe members connected contiguously at front end portions thereof to said head pipe, the pipe members being curved in an outwardly convex shape with respect to a longitudinal centerline of said motorcycle frame at a longitudinally intermediate position of each pipe member when viewed from a top view, wherein a distance between lower portions at the longitudinally intermediate position of each pipe member is greater than a distance between upper portions at the longitudinally intermediate position of each pipe member, each of the pipe members including an inner wall and an outer wall; the inner wall being formed with a substantially continuous inwardly and downwardly facing concave surface throughout an overall length of each pipe member and with respect to a vertical direction of each pipe member, and the outer wall being formed with a substantially continuous outwardly and upwardly facing convex surface and being substantially parallel with the inner wall, and wherein the inner wall and the outer wall of each of the pipe members join each other at an upper-most edge, the upper-most edge of each of the pipe members being curved in an upward direction when viewed from a side view, and having an outwardly facing convex shape when viewed from a top view. 2. The motorcycle frame according to claim 1, further comprising an engine mounting space being disposed between lower portions of said right and left pipe members. 3. The motorcycle frame according to claim 1, further comprising a pair of engine hangers secured to the front end portions of the right and left pipe members. 4. The motorcycle frame according to claim 3, wherein the respective engine hanger is welded to a lower portion of the respective pipe member. 5. The motorcycle frame according to claim 1, further comprising: a pair of right and left pivot plates extending downward from rear end portions of the right and left pipe members; and a first cross pipe extending across a span between the front end portions of the right and left pipe members. 6. The motorcycle frame according to claim 5, further comprising: a second cross pipe extending across a span between upper portions of the pivot plates; and a third cross pipe extending across a span between lower portions of the pivot plates. 7. The motorcycle frame according to claim 5, further comprising a pair of seat rails extending rearwardly and upwardly with respect to and being connected with the rear end portions of both right and left pipe members. 8. The motorcycle frame according to claim 7, wherein the head pipe includes a cylindrical portion for rotatably supporting the front fork, and a pair of right and left gussets extending rearward and downward from the cylindrical portion of the head pipe. 9. The motorcycle frame according to claim 8, further comprising a right and a left main frame, wherein each of said right and left main frames include a respective gusset, one of said pipe members welded at the front end portion thereof to the gussets, and pipe portions integral with the pivot plates and welded to rear ends of the pipe members. 10. The motorcycle frame according to claim 9, wherein each of said pipe members includes a respective rib that partitions an interior of the pipe member. 11. The motorcycle frame according to claim 1, wherein the head pipe includes a cylindrical portion for rotatably supporting the front fork, and a pair of right and left gussets extending rearward and downward from the cylindrical portion of the head pipe. 12. The motorcycle frame according to claim 1, further comprising: a pair of right and left pivot plates extending downward from rear end portions of the right and left pipe members; and a first cross pipe extending across a span between the front end portions of the right and left pipe members. 13. The motorcycle frame according to claim 12, further comprising: a second cross pipe extending across a span between upper portions of the pivot plates; and a third cross pipe extending across a span between lower portions of the pivot plates. 14. The motorcycle frame according to claim 1, wherein each of said pipe members includes a respective rib that vertically partitions an interior of the pipe member, said rib being provided between vertically intermediate inner wall portions of each pipe member. 15. A motorcycle comprising: an engine; a front wheel and a rear wheel; a head pipe; a front fork for supporting the front wheel through a shaft, wherein said front fork is rotatable with respect to and supported by said head pipe; and a pair of right and left pipe members connected contiguously at front end portions thereof to said head pipe, the pipe members being curved in an outwardly convex shape with respect to a longitudinal centerline of said motorcycle at a longitudinally intermediate position of each pipe member when viewed from a top view, wherein a distance between lower portions at the longitudinally intermediate position of each pipe member is greater than a distance between upper portions at the longitudinally intermediate position of each pipe member, each of the pipe members including an inner wall and an outer wall; the inner wall being formed with a substantially continuous inwardly and downwardly facing concave surface throughout an overall length of each pipe member and with respect to a vertical direction of each pipe member, and the outer wall being formed with a substantially continuous outwardly and upwardly facing convex surface and being substantially parallel with the inner wall, wherein the inner wall and the outer wall of each of the pipe members join each other at an upper-most edge, the upper-most edge of each of the pipe members being curved in an upward direction when viewed from a side view, and having an outwardly facing convex shape when viewed from a top view, and wherein the engine is disposed between lower portions of said right and left pipe members. 16. The motorcycle according to claim 15, further comprising: a pair of engine hangers secured to the front end portions of both right and left pipe members. 17. The motorcycle according to claim 16, further comprising: a pair of right and left pivot plates extending downward from rear end portions of the right and left pipe members; and a first cross pipe extending across a span between the front end portions of the right and left pipe members. 18. The motorcycle according to claim 17, further comprising: a second cross pipe extending across a span between upper portions of the pivot plates; and a third cross pipe extending across a span between lower portions of the pivot plates. 19. The motorcycle according to claim 18, further comprising: a pair of seat rails extending rearwardly and upwardly with respect to and being connected with the rear end portions of the right and left pipe members; and wherein the head pipe includes a cylindrical portion for rotatably supporting the front fork, and a pair of right and left gussets extending rearward and downward from the cylindrical portion of the head pipe. 20. A motorcycle frame comprising: a head pipe; a front fork for supporting a front wheel through a shaft, wherein said front fork is rotatable with respect to and supported by said head pipe; a pair of right and left pipe members each having a substantially prismatic shape, wherein each of said right and left pipe members is bent in an outwardly convex shape with respect to a longitudinal centerline of said motorcycle frame at a longitudinally intermediate position of each pipe member, the pipe members extending upwardly toward and being connected contiguously to the head pipe; and a pair of right and left pivot plates extending downward from rear end portions of the right and left pipe members; a first cross pipe extending across a span between front end portions of the right and left pipe members; a second cross pipe extending across a span between upper portions of the pivot plates; and a third cross pipe extending across a span between lower portions of the pivot plates, each of the pipe members further including an inner wall which is formed as a substantially continuous concave curve throughout an overall length of the pipe members and with respect to a vertical direction of the pipe member, and an outer wall which extends substantially parallel with the inner wall, wherein upper portions of the inner walls of the pipe members are closer to each other than are lower portions of the inner walls of the pipe members, wherein the inner wall and the outer wall of each of the pipe members join each other at an upper-most edge, the upper-most edge of each of the pipe members being curved in an upward direction when viewed from a side view, and having an outwardly facing convex shape when viewed from a top view.