Metal working – Method of mechanical manufacture – Structural member making
Reexamination Certificate
1998-12-18
2001-04-24
Rosenbar, I Cuda (Department: 3726)
Metal working
Method of mechanical manufacture
Structural member making
C029S897300, C029S897000, C280S284000, C280S281100
Reexamination Certificate
active
06219919
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a rear swing arm for a motor-bike using a tapered rectangular pipe member and a method for manufacturing this tapered rectangular pipe member.
BACKGROUND OF THE PRIOR ART
As the rear swing arm for a motor-bike, a tapered pipe having a longitudinal rectangular sectional surface has been used. As one example of this manufacturing method, there are methods disclosed in Japanese Patent Laid-open Nos. Hei 2-286488 and 2-286489.
These methods are operated such that at first a round raw pipe is formed. The raw pipe is then formed into a tapered pipe in a rotary swagging step where some dies are rotated around the raw pipe to crush it and then lastly form the pipe into a rectangular sectional shape by a bulging step or a compression forming step.
In view of the foregoing, the aforesaid prior art examples require a total number of two steps in the rotary swagging step and the subsequent bulging step or compression forming step in order to obtain the rectangular pipe from the round raw pipe. Accordingly, the number of steps is increased.
In addition, due to application of the rotary swagging step, a degree of freedom of the shape is reduced by the facts that the taper has an axial symmetrical formation and an arcuate (an angle R) shape at the corner part of the rectangular pipe which results in certain restrictions.
In addition to this fact, although each of the wall parts within a longitudinal sectional surface shows a certain variation in wall thickness, each of the walls within the cross-sectional surface, i.e. a sectional surface crossing at a right angle with a longitudinal direction has a uniform wall thickness. Accordingly, it is not possible to optionally set a wall thickness at each of the wall parts within the cross-sectional surface and to efficiently assure a section modulus.
In addition, since an application of load in the rear swing arm of a motor-bike is different in each of the upper, lower, rightward or leftward directions, respectively, it is desirable to form the swing arm with irregular wall thicknessed in which each of the upper, lower, rightward or leftward directions in the cross-sectional surface of the pipe member has a different wall thickness, respectively. However, such an irregular thickness wall formation is impossible in the aforesaid prior art forming method. In addition, it is desired to have a large ground clearance or a long suspension stroke with the rear swing arm.
SUMMARY OF THE INVENTION
It is an object of the present invention to realize the above-noted requirements. In discussing the present invention, the upper, lower, right and left sides of the pipe member will be defined such that a longitudinal direction of the cross-sectional surface is in a vertical direction and a direction crossing at a right angle with the longitudinal direction is expressed as a lateral direction. In addition, a front side is defined as an advancing direction of a vehicle body when it is used as a rear swing arm of the motor-bike.
In order to solve the aforesaid problems, the rear swing arm for a motor-bike of the present invention is constructed of a rectangular pipe which is pivotally supported at its front end to a vehicle body. The rear end of the rectangular pipe supports a rear wheel at a rear wheel supporting part. The rear end of the rectangular pipe is tapered at least partially in a longitudinal direction. The tapered rectangular pipe has sectional surfaces taken perpendicular to a longitudinal direction and has a longitudinal rectangular shape. At least a partial wall surface of at least one of an upper, lower, left-side and right-side walls of the rectangular pipe being thicker than the other walls. One of the longitudinal end parts is made thinner than that of the other end part.
At this time, a lower end of the tapered rectangular pipe can be made straight and an upper end part can be made as a tapered one. In addition, the upper end rear side of the tapered rectangular pipe is made thin to form the rear wheel supporting part and concurrently a brake caliper can be installed above this thin part.
In addition, it is also possible to arrange the tapered part to be narrowed toward a front end of the rectangular pipe and to fix a bearing member connected to the vehicle body to the extremity end of the tapered part.
In addition, in the case that some burrs are found at the surface of the tapered rectangular pipe and concurrently a separate component part is fixed to the surface, it is also possible to form a releasing concave part at a part overlapping the burrs of the separate component part.
As a method for manufacturing a tapered rectangular pipe for a vehicle which is preferable for a rear swing arm of a motor-bike, two steps can be involved. A first step involves extruding a rectangular raw pipe having a rectangular sectional surface and a second step involves forming at least a partial wall surface of the rectangular raw pipe into a tapered shape in a longitudinal direction.
A taper formation in this method can be carried out by a non-rotating swagging step. The non-rotating swagging process is a forming process for swagging without rotating the dies.
In addition, in the first step, the rectangular raw pipe can be formed under an optional irregular wall thickness condition in which at least a partial wall surface is made thicker than that of the other wall in each of the upper, lower, right and left walls in the longitudinal rectangular section.
In this case, it is possible that the upper and lower walls are made thicker than those of the right and left walls or their thick walls are of an integral rib extending in a longitudinal direction at either the inner wall or the outer wall.
In the first step, it is also possible that an inner space of the rectangular raw pipe is divided into a plurality of segments by an integral partition wall extending in a longitudinal direction.
At this time, in the second step, a side wall of a chamber having no wall surface formed into a tapered shape of each of the chambers defined into a plurality of segments by a partition wall is made thinner than a side wall of a chamber having a taper formed wall surface.
A rear swing arm for a motor-bike constructed by a tapered rectangular pipe member of the present invention is characterized in that said tapered rectangular pipe has a longitudinal rectangular sectional shape and at least a partial wall surface of each of upper, lower, left-side and right-side walls is set to have a thicker irregular thickness than that of other walls and either one of the longitudinal end parts is made thinner than that of the other end.
In this way, it is possible to manufacture a light weight and less-expensive rear swing arm of a motor-bike constructed by the tapered rectangular pipe having the most-suitable load distribution.
At this time, when the lower end of the tapered rectangular pipe is made substantially straight and its upper end is tapered, a position of the suspension link can be set at a higher level than the ground, resulting in an increased ground clearance.
In addition, when the upper end rear part of the tapered rectangular pipe is made thin to form a rear wheel supporting part and a brake caliper is installed above the fine part, arrangement of the brake caliper can be set low and a stroke of the rear suspension can be increased only at that portion, making it possible to eliminate an undesirable decrease in capacity of the muffler thereabove.
If the tapered part is arranged at the front end of the rectangular pipe and is made to be narrow toward a front side and a bearing connected to the vehicle body is fixed to the extremity end of the tapered part, the fixing of the bearing member may be facilitated under utilization of the tapered part.
In addition, in the case that the surface of the tapered rectangular pipe has some burrs and a separate component element is fixed to the surface, forming of the releasing recess at a part overlapping on the burrs of the separate component element enables this separate component element to b
Gogo Kazuhiko
Oka Tomoo
Birch & Stewart Kolasch & Birch, LLP
Honda Giken Kogyo Kabushiki Kaisha
Nguyen Trinh
Rosenbar I Cuda
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