JPH03284496A - Rear swing arm - Google Patents

Abstract

PURPOSE:To lighten the above arm by installing each grade of more than the angle of draft in both the upper and lower half parts of the outer side situated in at least the body outer side of a cast body being attached to a car body, and forming the outer side of an arm pipe being inserted into the inner part, into an incline congruous to the said grade. CONSTITUTION:In a rear swing arm 1 which is installed toward the rear of a car body 2 almost in the horizontal direction, supporting the axle of a rear wheel 3 on the rear end, and it is mae so as to be rocked in the vertical direction from a road surface at time of running with a shaft 4 at the front end as the center at time of impact, such a grade as having a larger angle theta2 than a draft at time of casting is set to both the upper and lower half parts 11a, 11b of an outer side 11 at the outside to a cast body 10, and an inner side part 12 at the inside to the car body should be set to the draft with an ordinary angle theta1. On the other hand, an arm pipe 13 being combinedly installed in this body 10 by means of welding or the like is made to serve as inclines 14, 14 where the longitudinal center is projected outward so as to make it congruent with the tilt angle theta2 of an inner surface of the outer side 11, whereby a ridgeline part 15 is made so as to be formed at the apex part.

Description

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

(Prior Art) As shown in FIG. 4, a rear swing arm 1 of a motorcycle is provided in a substantially horizontal direction toward the rear of a vehicle body 2, and supports an axle of a rear wheel 3 at its rear end. When a shock is received from the road surface while driving, a cushion unit (not shown) swings vertically around a shaft 4 at the front end to absorb the shock.

The conventional swing arm 1 has a planar shape shown in FIG.
As shown in the side view of FIG. 6, arm vibros 6 are integrated by welding or the like at the rear left and right parts of the body 5, which has a bifurcated shape for pivoting to the vehicle body 2, and extend approximately horizontally. , an axle bracket 7.7 for supporting the shaft of the rear wheel 3 is provided at the rear end. In this figure, 8 is a pivot for attaching the cushion unit.

The body 5 is made by casting, and therefore FIGS. 5A-A
As shown in an enlarged view in FIG. 7, the cross section of the line part has a structure in which the outside is cast and the inside has a rectangular arm vibro inserted therein.

By the way, this body 5 is a cast product, and since the upper half 5a and the lower half 5b are cast in separate molds, draft angles of angles θl and θ1 are given to the sides thereof. Since the inner surface is cast using a core, there is no need for a draft angle, and therefore the left and right sides are parallel planes.Therefore, the arm vibro inserted here is also a square tube with a rectangular cross section.

(Problem to be Solved by the Invention) However, in the above-mentioned conventional technology, since the upper half 5a and the lower half 5b of the outer side of the body 5 have draft angles,
The wall thickness t at the center in the vertical direction increases, which causes an increase in weight and causes the weight of the rear swing arm 1 as a whole to increase.

In view of the above points, this invention eliminates the excess wall thickness of the cast body, significantly reduces the total weight of the rear swing arm, and increases the horizontal bending strength of the arm pipe.
Furthermore, the present invention provides a rear swing arm that can have a novel form in terms of design.

[Structure of the invention]

(Means for Solving the Problems) As a means for solving the problems of the prior art described above, the present invention provides at least an upper half and a lower half of an outer part of a cast body attached to a car body, which is located on the outside of the car body. Provide a slope with an angle greater than the required draft angle during casting,
The outer part of the arm pipe to be inserted into the arm pipe is formed into an inclined surface matching the above-mentioned slope, and a ridgeline part is formed at the longitudinal center of the outer length of the arm pipe.

(Function) Since the upper and lower inner and outer surfaces of the outer part of the body part are provided with slopes having angles greater than the required draft angle during casting, the thickness of the cast part becomes approximately equal, and the weight of the body is significantly reduced. In addition, a ridge line is formed at the center of the outer length of the arm pipe in the longitudinal direction, increasing the rigidity of the arm pipe and increasing its strength against horizontal bending force. The ridgeline becomes a highlight line, creating a novel form in terms of design.

(Example) Examples of the present invention will be described below with reference to FIGS. 1 to 3.

The upper and lower half portions 11a and 11b of the cast body 10 are sloped at an angle θ2 larger than the draft angle during casting, and the inner portion 12 inside the car body is sloped with an angle θ2 larger than the draft angle during casting. It is considered to be a draft angle having an angle θ1,
Its inner surface is a flat surface.

The arm pipe 13 connected to the body 10 by welding or the like has an inclined surface 14.14 whose longitudinal center protrudes outward so as to match the inclination angle θ2 of the inner surface of the outer portion 11.
The apex portion forms a ridgeline portion 15 (see FIG. 3).

This arm pipe 13 can be an extruded pipe having a constant cross-sectional shape, a press molded product, or a tapered pipe made by swaging and bulge forming.

Fig. 2 shows an example in which the inner surface of the inner part 12 of the body 10 on the inside with respect to the vehicle body is also sloped to match the draft angle, and the upper and lower halves of the inner part 12 have equal thickness. .

In either embodiment, the weight of the body 10 is significantly reduced because the thick portion of the cast body 10 is reduced or eliminated. In addition, since the arm pipe 13 connected to the body 10 has a linearly protruding ridge portion 15 formed in the longitudinal center of the outer side, the arm pipe 13 has increased rigidity and bending strength. , resulting in a durable swing arm. The light hitting this ridgeline portion 15 creates shadows, emphasizing the three-dimensional effect and expressing novelty in design.

〔Effect of the invention〕

As described above, according to the present invention, there is no extra thickness in the cast body, so the weight of the body can be significantly reduced.
Not only can the weight of the entire swing arm be significantly reduced, but the outer part of the arm pipe has a mid-height shape in the longitudinal direction, increasing rigidity and strength against bending, resulting in a durable swing arm. Furthermore, the ridgeline on the outside of the arm pipe becomes a highlight line, which improves the appearance and provides an excellent design effect.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a rear swing arm according to the present invention.
Fig. 2 is a sectional view of the modified example, Fig. 3 is a perspective view of the arm pipe, Fig. 4 is a side view of a motorcycle embodying the present invention, and Fig. 5 is a plan view of a conventional swing arm. Figure, 6th
The figure is the same side view, and FIG. 7 is an enlarged sectional view taken along line A-A in FIG. 5. 1...Rear swing arm, 2...Vehicle body, 5,10
...body, 11...outer part, 12...inner part,
13... Arm pipe, 14... Inclined surface, 15...
・Ridge line.

Claims (1)

[Claims] In a rear swing arm that supports the rear wheel of a two-wheeled motor vehicle, at least the upper and lower halves of the outer part of the cast body attached to the vehicle body located on the outside of the vehicle body have an angle greater than the required draft angle during casting. A slope is provided, and the outer part of the arm pipe to be inserted into the slope is formed into an inclined surface that matches the slope, so that a ridge line part is formed at the longitudinal center of the outer length of the arm pipe. rear swing arm.