JPH03164390A - Swing arm for motorcycle - Google Patents

Abstract

PURPOSE:To obtain a light and low-cost swing arm having a good appearance by applying the forward end parts of bulged forks to a shaft cylinder and welding them with it, and welding and connecting the front parts of the forks with each other by a bridge equipped with suspension bosses. CONSTITUTION:A pipe material cut in a predetermined length is set in an outer die, it is pressurized on both end sides while an oil pressure is given to the inner side to be bulged, so right and left forks 1 having thick forward parts 5 and thin forward and rear parts and rectangular sections are formed, the front ends of them are applied to a shaft cylinder 6 to be welded, and the forward parts 5 of the right and left forks 1 are welded and connected with each other by a bridge 8 equipped with suspension bosses 7. In this constitution, the right and left forks 1 has a uniform thickness while the forward parts 5 where the largest load is applied when the bridge 8 is connected with them are formed to have thick sections, with the end parts being thin and light- weighting corresponding to the load to be applied. The welded parts are only between the right and left forks 1 and the shaft cylinder 6, and between the forks 1 and the bridge 8, so the welding length can be short to make the cost low, and the weld marks can be small.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a swing arm for a motorcycle.

(Prior art) In a motorcycle, the front end of a swing arm is pivotally attached to a frame, a suspension is connected between the front part of the swing arm and the upper part of the frame, and the rear wheel is attached to the rear end of the swing arm. It is designed to fasten a rotatably supported axle. Generally, a swing arm is manufactured by selecting a vibrator material with a desired strength and welding the materials together. In addition, the left and right hawk parts are made by cutting the plate material into two and press forming them.
Some products are manufactured by welding this to match the middle shape. Furthermore, there is also a model in which the front part, which receives a large load, is integrally formed by casting, and pipe material hawks are welded to the left and right rear ends. For example, Utsukai Showa 81-111
See Publication No. 892.

(Problems to be Solved by the Invention) In the swing arm, the portion that connects the front suspension receives the largest load, and the load decreases from there toward the front or rear. For this reason, it is necessary to make the suspension connecting portion near the front of the swing arm the strongest.

A vibrator made by welding vibrator materials has the disadvantage that the front and rear parts, which receive less load, have excessive strength and become heavy.

By splitting the left and right forks into two, press-forming them from plate material, and then welding them together, the cross section can be changed depending on the required strength, and the weight can be reduced. However, the welding length is long, the welding cost is high, and the welding marks are unsightly. Furthermore, if the front part of the swing arm is integrally formed by casting, each cross section can be changed depending on the desired strength, but since the material of a cast product is rougher than pipe material,
It is necessary to increase the wall thickness accordingly to maintain strength, and there is an inconvenience that the weight cannot be reduced.

In view of the above, an object of the present invention is to obtain a swing arm for a motorcycle that can be made lightweight by changing the cross section to the required strength using a pipe material, and can be finished at a low welding cost and with good appearance.

(Means for Solving the Problems) In order to achieve the above object, the swing arm of a motorcycle of the present invention is produced by setting a pipe material cut to a predetermined length in an outer mold, and applying pressure from both ends to the inside of the swing arm. The left and right hawks with a long rectangular cross section are thickened at the front and thinner at the front and back by applying hydraulic pressure to form a bulge. The front part is welded and connected with a bridge equipped with a suspension boss.

(Function) The left and right hawks are made by pressurizing the pipe material from both sides and applying hydraulic pressure to the inside to form a bulge, thereby making the wall thickness uniform and making it the largest bridge that connects the bridge with the suspension boss. The front part that receives the load can be made thicker, and the front and rear parts can be thinner and lighter to accommodate the load. The welding points are only between the left and right forks and the shaft cylinder, and between the left and right forks and the bridge, and the welding length is short, the welding cost is low, and the welding traces are small and inconspicuous.

(Example) Embodiments of the present invention will be described below with reference to the drawings.

As shown in Fig. 3, the left and right hawks 1 are made by cutting an extruded pipe material 2 made of light alloy or the like to a desired length as shown in (a), and cutting it into two pieces as shown in (b). Set it in the outer mold. Then, while applying pressure from both ends with the pressing die 4, hydraulic pressure is applied to the inside to form a bulge, and as shown in (c), the front part 5 is The hawk 1 is formed into a long rectangular cross section with the longest length and narrower at the front and back, as shown in (2), and cut at the front and back to form the hawk 1. The front ends of the pair of left and right hawks 1 thus formed are brought into contact with the shaft cylinder 6 and welded,
Inside the thick part 6 of the front part 5 of the left and right hawks 1 =,
A tubular bridge 8 provided with a suspension boss 7 is welded and connected. An axle hole 9 is bored in the rear ends of the left and right forks 1. The shaft cylinder 6 is pivotally attached to the frame, a suspension is connected to the suspension boss 7 so that a swinging bush 5 can be mounted, and the axle of the rear wheel is fastened to the axle hole 9.

(Effects of the Invention) As explained above, since the present invention is configured as described above, the left and right forks are bulged using pipe material, and the cross section is made to have the required strength while making the wall thickness uniform. It can be changed to make it lighter. In addition, there are fewer welding locations, which reduces welding costs, resulting in lower costs, and fewer welding marks, resulting in a beautiful finish.

[Brief explanation of the drawing]

The drawings show one embodiment of the present invention; FIG. 1 is a plan view, FIG. 2 is a side view, and FIG. 3 is a forming explanatory view showing the forming of the hawk in the order of (a) to (ii). 1...Hawk, 2...Pipe material, 3...Outer mold, 5
...Front part, 6...Axle tube, 7...Suspension boss, 8...Bridge.

Claims (1)

[Claims] Pipe material cut to a predetermined length is set in an outer mold, and while pressure is applied from both ends, hydraulic pressure is applied to the inside to create a bulge, creating left and right hawks with a rectangular cross section that is thicker at the front and narrower at the front and back. A swing arm for a motorcycle, characterized in that the front ends of the left and right forks abut against and weld to the shaft cylinder, and the front parts of the left and right forks are welded and connected by a bridge provided with a suspension boss. .