JPH04262986A - Frame of motorcycle - Google Patents

Abstract

PURPOSE:To reduce deformation in bending work and make appearance attractive by making a main tube of a pipe material having a vertically long rectangular section, and forming a recess in the center of the outside part and projections longitudinally above and below the recess. CONSTITUTION:Upper left and right main tubes 1 forming a frame of a motorcycle have the front parts bent inside and the front ends butted against a head pipe 2 mounting a front fork and welded thereto. The main tube 1 having a vertically long rectangular section is formed on the central part of the outside surface with a recess 3 and above and below the recess with projections 4 bulging outside to provide a pipe material drawn out longitudinally. When the main tube 1 is worked to bend and set to the head pipe 2, the outside surface of the main tube 1 receives the largest tension. However, since the rigidity is improved by the recess 3 and projections 4 above and below the same, the deformation is prevented. Also, the streaks on the recess 3 and projection 4 provide accents on the appearance.

Description

[Detailed description of the invention]

0001

FIELD OF THE INVENTION This invention relates to motorcycle frames.

0002

2. Description of the Related Art Motorcycle frames are manufactured by selecting steel pipes or light alloy pipes with appropriate strength, cutting them into predetermined lengths, bending them, and welding them together. Pipe materials generally have a circular cross section, but recently, pipe materials with a rectangular or rectangular cross section are also being used to make them look more appealing. For example, JP-A No. 60-33177, JP-A No. 61-24681
See publication.

0003

The main tube, which is disposed at the upper front part of the frame, has its front part bent inward so that it abuts against and is welded to the head pipe at the front end. In this case, if a pipe material with a vertically elongated rectangular cross section is used for the main tube, excessive force will be applied to the pipe material during bending, causing deformation such as dents, especially in the inner and outer parts to be bent. There is an inconvenience. If the deformation is large, it may become unusable due to aesthetic issues.

[0004] In view of the above, an object of the present invention is to provide a motorcycle frame having left and right main tubes that are less deformed during bending and have a good appearance.

[0005]

[Means for Solving the Problems] In order to achieve the above object, the motorcycle frame of the present invention has the front parts of the upper left and right main tubes forming the frame bent inward so as to abut against the head pipe at the front end. The basic shape of the left and right main tubes is a pipe material with a vertically long rectangular cross section, and a concave is formed in the center of the outer part of the main tube, and convex portions that swell outward above and below the concave part are formed. The reason is that the pipe material is formed in the length direction.

The left and right main tubes are cut to a predetermined length, the front parts are bent inward so that the front ends are centered, and the front ends of the left and right main tubes are brought into contact with the head pipe and welded. When bending the main tube, the outer surface, which is most stretched, has a recess and a protrusion above and below the recess, so the recess and the protrusion increase the rigidity and reduce deformation during bending. Also, the concave and convex parts serve as accents, giving it a good appearance.

[0007]

Embodiments Hereinafter, embodiments of the present invention will be explained with reference to FIGS. 1 and 2. The front upper left and right main tubes 1 forming the frame are bent inward at their front ends, and their front ends abut against a head pipe 2 to which a front fork is attached, and are welded and connected.

[0008]The left and right main tubes 1 are made of pipe material having a basic shape of a vertically elongated rectangle in cross section, and a recess 3 is provided in the center on the outer surface of the main tube 1, and bulges are formed outwardly above and below the recess 3. The pipe material is provided with a convex part 4 and pulled out in the length direction. The interval between the upper and lower convex portions 4 with respect to the total height L is preferably set to l/L=0.4 to 0.7.

[0009] In order to fit the front end of the main tube 1 to the head pipe 2, the main tube 1 is cut to a predetermined length, and then the front portion is bent inward. During this bending process, the outer surface of the main tube 1 receives the most tensile force. At this time,
Since the rigidity is increased by the recesses 3 and the upper and lower convex portions 4, deformation of the main tube 1 due to bending can be prevented.

0010

[Effects of the invention] As explained above, the present invention is constructed as described above, so the main tube is made of pipe material with a vertically rectangular cross section, and a recess is provided in the center of the outer part, and convex parts are formed above and below the main tube. Since the main tube is formed with a portion, deformation during bending of the main tube can be prevented by the rigidity of the concave portion and the upper and lower convex portions, thereby preventing the occurrence of defective products. Furthermore, the concavities on the outer surface and the lines created by the convex portions on the top and bottom serve as accents, giving a good appearance.

[Brief explanation of the drawing]

FIG. 1 is an enlarged sectional view taken along the line A-A in FIG. 2;

FIG. 2 is a perspective view of the entire frame showing an embodiment of the present invention.

[Explanation of symbols]

1 Main tube 2 Head pipe 3 Dent 4 Convex part

Claims (1)

[Claims] Claim 1: The front parts of the upper left and right main tubes that form the frame are bent inward and welded against the head pipe at the front end, and the basic shape of the left and right main tubes is a vertically long rectangular pipe in cross section. The frame of the motorcycle is characterized in that the frame is made of a pipe material, and has a recess formed in the center of the outer part of the main tube, and protrusions that bulge outward above and below the main tube in the length direction.