JPH026670B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a frame structure suitable for a motorcycle for competition that runs at high speeds on the road. The purpose is to obtain.

Conventionally, a so-called cradle-shaped frame having a main column extending rearward from a steering shaft tube and a pair of left and right descending tubes is known as a frame for a motorcycle (for example, Japanese Utility Model Publication No. 13379/1983). However, in this type of frame, the engine is loaded and unloaded from the side of the vehicle body, so a large opening is required on the side of the frame, which inevitably reduces the rigidity of the vehicle body.

The purpose of this invention is to eliminate such problems by connecting the front lower part of the descending pipe and the central part of the main column with a reinforcing frame, and also connecting the left and right descending pipes near the front end of the horizontal part. It is characterized by connecting and reinforcing the descending pipes and suspending the engine between them.

Hereinafter, the present invention will be explained with reference to illustrated embodiments. Reference numeral 1 designates a frame of a motorcycle, which includes a main pillar 3 extending rearward and diagonally downward from a steering shaft tube 2;
It has a pair of left and right descending pipes 4 that once extend downward and then bend backward. The main column 3 and the descending tube 4 have a cylindrical shape with a square cross section, and are made of pultruded aluminum alloy.The rear ends are connected to each other by a bracket 5 made of an aluminum plate with a thickness of about 10 mm. connected. 6 is a reinforcing stay that supports the main pillar, 7 is a support frame for the passenger seat 8, and 9 is its support.

Note that 11 is a front fork rotatably supported by the steering shaft tube 2, and 12 is a front wheel supported at its lower end. Further, 13 is a front cover of the vehicle body frame, and 14 is a fuel tank.

The rear arm 1 is connected to the bracket 5 by a shaft 15.
6 is supported so as to be vertically swingable. 17 is a rear wheel. The rear arm 16 integrally has a chevron-shaped reinforcing member 18 at its upper portion, and the reinforcing member 18 is connected via a rod 19 and a link 21 to a shock absorber 22 with a coil spring mounted on the vehicle body in the left-right direction. The above structure is not particularly different from conventionally known frames for motorcycles.

The characteristic structure of the present invention is that a first reinforcing frame 23 is provided between the bending part 4a of the descending pipe 4 and the main pillar 3, and a second reinforcing frame 23 is provided between the right and left of the descending pipe 4 immediately above the bending part 4a. 24, and a power unit 25 consisting of an engine and a transmission is mounted between them. Power unit 25 includes a V-engine having an upper cylinder 26 and a lower cylinder 27. 28 and 29 are their exhaust pipes, and 31 is a carburetor.

As shown in FIG. 2, the first reinforcing frame 23 is
and the descending pipe 4 by welding and constructing the outer plate 23.
a and an inner plate 23b, both plates 23a,
23b has the front and rear edges bent and abutting W.
The parts are welded and formed into a box shape. A cylindrical boss 32 is bridged and welded between the outer plate 23a and the inner plate 23b, and supports the power unit 25 with a bolt 34 via a rubber damper 33. Therefore, by removing the bolt 34, the power unit can be lowered below the frame.

The second reinforcing frame 24 is made of a drawn aluminum alloy tube with a square cylindrical cross section, and as shown in FIG. 3, the center part is set back. Thus, when the front wheel 12 moves upward as indicated by the imaginary line F due to the cushioning action of the front fork 11, the second reinforcing frame 24
Never come into contact with. That is, the descending pipe 4 is placed as far forward as possible and the power unit 25 is mounted forward to increase the load acting on the front wheels, thereby increasing the running stability of a competition motorcycle where the front wheel load tends to be small. be able to.

As described above, the present invention includes a main column extending diagonally downward from the steering shaft tube toward the rear, and a pair of left and right descending tubes having a bent portion extending downward from the steering shaft tube and bending backward from there. , in which the main column and the descending pipe are connected by a bracket, since the vicinity of the bending part and the main column are connected by the first reinforcing frame, the side opening of the frame is reduced,
The weight of the power unit borne by the descending pipe can be distributed to the main column, increasing the rigidity of the frame. Also,
The descending pipes are connected to each other by a second reinforcing frame,
Since the power unit is suspended between the horizontal portions of the descending pipe, the power unit can be easily loaded and unloaded.

[Brief explanation of drawings]

The drawings show one embodiment of the invention,
FIG. 1 is a side view showing the frame structure of a motorcycle, FIG. 2 is a sectional view thereof, and FIG. 3 is a sectional view thereof. FIG. 4 is a perspective view of the frame. DESCRIPTION OF SYMBOLS 1... Frame, 2... Steering axis tube, 3... Main column, 4... Descending tube, 23... First reinforcing frame, 24...
...Second reinforcement frame.

Claims (1)

[Scope of Claims] 1. A main pillar extending diagonally downward from the steering shaft tube toward the rear, and a pair of left and right descending pipes having a bending portion that extends downward from the steering shaft tube and bends backward from there. wherein the main pillar and the rear end of the descending pipe are connected by a bracket, in which the vicinity of the bending part of the descending pipe and the main pillar are connected by a first reinforcing frame, and the descending pipes are connected to each other at the bending part. A motorcycle frame in which a power unit is suspended between left and right descending pipes and connected by a second reinforcing frame in the vicinity. 2. The frame for a motorcycle according to item 1, wherein the second reinforcing frame is formed with an intermediate portion retracted rearward in the traveling direction of the vehicle.