JP2002225775A - Cast rear arm of two-wheeler - Google Patents

Abstract

PROBLEM TO BE SOLVED: To cast a rear arm having predetermined rigidity and strength. SOLUTION: A pair of right and left side arms (21, 25) are casted, the side arms (21, 25) are gradually raised from front and rear ends to a center part in the longitudinal direction, and rear parts (21b, 25b) are deviated outwardly with respect to front parts (21a, 25a) via curved parts (21c, 25c). Connection ribs (23, 27) protruded in the facing direction are provided in upper and lower areas of a connection part of the front parts (21a, 25a) to the rear parts (21b, 25b), and flanges (22, 26) protruded in the facing direction and reinforcement ribs (24, 28) intersecting with each other in the longitudinal and transverse directions are provided on outer circumferential parts of the side arms (21, 25) and the inner circumferential part of a wall surface, and release parts (30) of a suspension separate from each other are provided on facing parts on the front end side of the front parts (21a, 25a), respectively. Flanges (22a, 26a) facing each other of the front parts (21a, 25a) except the release parts (30) and the connection ribs (23, 27) are integrally connected to each other, and a suspension fitting member (36) is integrally provided on a lower surface except the release parts (30) of the front parts (21a, 25a).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rear arm for supporting a rear wheel of a motorcycle, and more particularly, to a cast rear arm formed by die casting or the like.

[0002]

2. Description of the Related Art A conventional rear arm is shown in FIGS. 7 to 9, reference numeral 1 denotes a rear arm of the motorcycle, which is formed of a square pipe, a round pipe, a plate, and the like made of an aluminum alloy. That is, a pair of left and right side arms 2 (2a, 2a) made of square pipes.
b) A rear bracket 3 (3a, 3b) for supporting the rear wheel shaft is fixed to the rear end (right end in FIG. 1) by welding. A head pipe 4 made of a round pipe is provided at the front end of each side arm 2.
In addition, a cross pipe 5 made of a square pipe is welded and fixed to an intermediate portion in the front-rear direction to hold each side arm 2 at a predetermined interval, and a lower bracket 6 is welded and fixed to the lower surface center of the cross pipe 5. .

A reinforcing plate 7 formed by bending a plate into a triangular shape in a side view is welded and fixed to an upper portion on the front side of the side arm 2, and a suspension 11 is attached to the center of the upper surface of the reinforcing plate 7.
An escape hole 8 through which (FIG. 9) passes is formed. Further, a beam member 9 bent in a U-shape having a different shape in plan view is formed by a square pipe material, and an intermediate portion 9a of the beam member 9 is provided on the top of the reinforcing plate 7, and a rear end of the right side 9c is provided on a right portion. On the rear upper surface of the side arm 2b, attach the rear end of the left side 9b to the left rear bracket 3.
are fixed by welding to the upper surface of each of them. The left side 9b of the beam member 9 projects outward beyond the left side arm 2a to form a through hole 10 (FIG. 8) through which a rear wheel drive chain (not shown) passes.

[0004] The rear arm 1 formed as described above,
As shown in FIG. 9, a head pipe 4 is connected to a vehicle body 12 so as to be vertically swingable, a lower bracket 6 is connected to a triangular link 13 so as to be rotatable, and a front portion of the link 13 is connected to the lower bracket 6. The lower end of the link 13 is rotatably connected to a link arm 14 extending rearward from the vehicle body. Then, a rear wheel axle 15 is supported at a rear portion of the rear arm 1 via a rear bracket 3, and a rear portion of the vehicle body is supported via the suspension 11 and the rear arm 1.

[0005]

The above-mentioned conventional rear arm 1 is formed by welding and fixing a square pipe material, a round pipe material, a plate material and the like, so that many parts and man-hours are required. It was difficult to stabilize the quality due to a decrease in productivity and an increase in welding locations. An object of the present invention is to obtain a cast rear arm of a two-wheeled vehicle that is lightweight, has high productivity, and is stable in quality by being dividedly formed by casting.

[0006]

Means for Solving the Problems The present invention is configured as follows to achieve the above object. That is, in the invention according to claim 1, a pair of left and right side arms extending in the front-rear direction is formed by casting, and each of the side arms is gradually raised from the front-rear end to the center in the front-rear direction, and the rear part is formed. Connecting ribs which are deflected outward with respect to the front part via the curved part and project in the facing direction over the entire vertical direction of the connecting part between the front part and the rear part are provided on the outer peripheral part of each side arm and the inner peripheral part of the wall surface. A flange protruding in the facing direction and a reinforcing rib intersecting vertically and horizontally, and a relief portion of the suspension which is separated from each other at the facing portion on the front end side of each of the front portions, and the opposite flanges of the front portion except the relief portion are provided. And the connecting ribs facing each other are integrally connected to each other, and a mounting member for the suspension is integrally provided on the lower surface of each front portion except for the relief portion. The invention according to claim 2 is a lower flange (22a-1, 26a-1) formed on the front part (21a, 25a) excluding the relief part (30) of each side arm (21, 25). Further, the head pipe is integrally formed at the front ends of the pair of left and right side arms.

[0007]

Embodiments of the present invention will be described below with reference to the drawings. In the drawings, FIG. 1 is a partial cross-sectional plan view showing a first embodiment of the present invention, FIG. 2 is a cross-sectional view taken along the line II-II of FIG. 1, FIG. FIG. 2 is a sectional view corresponding to FIG. 2, showing another assembled state of the mounting member.
FIG. 5 is a perspective view showing a combined state before assembling showing a second embodiment of the present invention, and FIG. 6 is a partially sectional plan view showing a third embodiment of the present invention.

1 to 3, reference numeral 1 denotes an aluminum alloy rear arm formed by die casting. A pair of left and right side arms 21 and 25 extending in the front-rear direction (left and right in FIG. 1) are individually formed by die casting. They are formed and fixed integrally by welding, and the fixing plate 35 and the mounting member 36 are integrally fixed to the fixed side arms 21 and 25.

As shown in FIGS. 1 and 3, each of the side arms 21 and 25 has a gentle mountain shape in a side view which gradually increases from the front and rear ends toward the center in the front and rear direction.
The rear portions 21b and 25b are biased outward (in the opposite surface direction) from the rear ends of the front portions 21a and 25a via the gentle curved portions 21c and 25c. Endless flanges 22 and 26 projecting in the facing direction (thickness direction) are formed integrally over substantially the entire outer peripheral portion of each side arm 21 and 25, and the front portion 2 is formed.
Front flanges 22a, 26a formed on 1a, 25a
Is a rear flange 20 formed on the rear portions 21b and 25b.
b, 26b, and project in the facing direction.

The rear ends of the front flanges 22a, 26a are extended to the curved portions 21c, 25c.
The connecting ribs 23 and 27 projecting in the facing direction with a projecting amount substantially equal to those of the flanges 22 and 26 are integrally formed. 24, 28 are the flanges 22,
The protrusions are formed in the facing direction with a protrusion amount substantially equal to 26, and the rigidity and strength of each side arm 21, 25 are enhanced by the flanges 22, 26, the connecting ribs 23, 27, and the reinforcing ribs 24, 28. The connecting ribs 23, 2
7. The front flanges 22a and 26a and the front-side reinforcing ribs 24a and 28a are each formed to be symmetrical with respect to the plane, and can contact each other.

As shown in FIG. 3, each of the side arms 21 and 25 has a support hole 29 at a rear end thereof for supporting a rear wheel.
An arc-shaped relief portion 30 that is recessed in the direction away from each other is provided on the front facing side of the front portions 21a and 25a at the upper and lower middle portions of the curved portion 21c that protrudes outward from the left side arm 21. A through-hole 31 through which a wheel drive chain (not shown) passes is formed.
A head pipe 32 connected to the vehicle body side is integrally formed at the front end of the head 5.

As shown in FIG. 3, the side arms 21 and 25 face each other such that the flanges 22 and 26 face each other, and the opposite flanges 22a and 26a of the front portions 21a and 25a excluding the escape portion 30. To form a main part of the rear arm by welding and fixing them together.
An abutment plate 35 made of an aluminum alloy pipe material is fitted and fixed to the escape portion 30 by welding, and an aluminum alloy made of aluminum alloy is attached to the rear lower surface of the front portions 21a and 25a of the side arms 21 and 25 fixed by welding. Is fixed by welding, thereby forming the rear arm 20 as shown in FIG.
The mounting member 36 is provided at the rear lower surface of each of the front portions 21a and 25a, ie, the lower flange 22a-1 and the lower flange 26a.
Rectangular base 36a having an area substantially corresponding to -1
And a bracket 36b protruded and fixed to the lower surface thereof, and the base 36a is attached to the lower flange 22a-
1, 26a-1, and fixed by welding.
6b is connected to the lower part of the suspension attached to the vehicle body.

FIG. 4 shows the mounting member 36 connected to each of the front portions 21.
Another example of welding and fixing to the rear lower surface of a, 25a is shown. In this example, the protrusions of the flanges 22a-1 and 26a-1 at the portion corresponding to the base 36a of the mounting member 36 are reduced to form a rectangular recess (a) at this portion, and FIG.
As shown in FIG. 7, the base 36a is fitted into the recess (a), and the periphery thereof is surrounded by the lower flanges 22a-1 and 22a-1.
You may make it weld-fixed to the inner periphery of the flange 22a-1. The recesses (A) are provided on the side arms 21 and
5 is formed at the time of casting.

FIG. 5 shows a second embodiment. In this device, an arc portion 40 extending in the left-right (width) direction is formed at the front end of each side arm 21, 25, and a separate aluminum alloy head pipe 41 is fitted into the arc portion 40 and welded. To secure them together. The other structure is substantially the same as that of the first embodiment.

FIG. 6 shows a third embodiment. In this embodiment, a U-shaped relief portion 30-1 having a front end opening when the two arms are joined to each other is formed on a facing portion on the front end side of each of the side arms 21 and 25. The head pipe 32 formed at the front end of each of the side arms 21 and 25 is divided into right and left parts by welding and fixing a backing plate 35-1 curved in a U shape in a plan view around the circumference. The other structure is substantially the same as that of the first embodiment.

In the case of a model that does not require much strength of the rear arm 20, the above-mentioned backing plates 35, 35-
1 may be omitted. In addition, the above-described mounting member 36 may be divided into two parts at the time of casting each side arm 21 and 25, and may be formed at the same time.

[0017]

As is apparent from the above description, according to the first aspect of the present invention, the left and right side arms are separately formed by casting, and these are integrally connected to form the main portion of the rear arm. Is formed, the number of parts and man-hours are reduced, productivity is increased, and the number of welds is reduced, welding heat distortion is reduced, and a rear arm with stable quality can be obtained. Further, since the number of welds is reduced, it is possible to prevent the appearance from being deteriorated due to welding beats. Each of the side arms is gradually raised from the front and rear ends toward the center in the front and rear direction, and the rear portion is biased outward with respect to the front portion via a curved portion, so that the connecting portion between the front portion and the rear portion is formed. The connecting ribs protruding in the facing direction are provided in the entire upper and lower areas of the front and rear ends, and the endless flanges protruding in the facing direction and the reinforcing ribs intersecting vertically and horizontally are provided on the outer peripheral portion and the inner peripheral portion of the wall surface. Since the flanges of the parts are brought into contact with each other to connect them integrally, rigidity in the lateral and torsion directions and strength are increased while being lightweight. Also,
In the invention according to claim 2, the mounting member of the suspension is fitted to the lower flange portion formed at the front portion of each side arm and integrally connected, so that the mounting member can be easily fixed by welding. Become. The invention according to claim 3 is
Since the head pipe was formed at the front end of each side arm,
There is no need to form the head pipe separately, so that the number of parts and welds are further reduced, and productivity, quality and appearance are further improved.

[Brief description of the drawings]

FIG. 1 is a partial sectional plan view showing a first embodiment of the present invention.

FIG. 2 is a sectional view taken along line II-II of FIG.

FIG. 3 is a perspective view showing a combined state before assembling according to the first embodiment of the present invention.

FIG. 4 is a sectional view corresponding to FIG. 2, showing another mounting state of the mounting member.

FIG. 5 is a perspective view showing a combined state before assembling according to a second embodiment of the present invention.

FIG. 6 is a partial sectional plan view showing a third embodiment of the present invention.

FIG. 7 is a top perspective view showing a conventional example.

FIG. 8 is a bottom perspective view showing a conventional example.

FIG. 9 is a partial cross-sectional side view showing a state where a conventional rear arm is attached to a vehicle body.

[Explanation of symbols]

 Reference Signs List 20 rear arm 21 left side arm 21a front part 21b rear part 21c curved part 22 flange 22a (22a-1) front flange 22b rear flange 23 connecting rib 24 reinforcing rib 24a front reinforcing rib 25 right side arm 25a front part 25b rear part 25c curved part 26 flange 26a (26a-1) front flange 26 rear flange 27 connecting rib 28 reinforcing rib 28a front reinforcing rib 29 support hole 30 relief part 31 through hole 32 head pipe 35 backing plate 36 Mounting member 36a Base 36b Bracket 40 Arc part 41 Head pipe (A) Depression

Claims (3)

[Claims] 1. A pair of left and right side arms (21, 25) extending in the front-rear direction are formed by casting, and each of the side arms (21, 25) is gradually raised from the front-rear end toward the center part in the front-rear direction. In addition, the rear portions (21b, 25b) are connected to the front portions (21a, 25c) via the curved portions (21c, 25c).
a), the front portions (21a, 25)
a) connecting ribs (23, 27) protruding in the facing direction over the entire vertical region of the connecting portion between the rear portion (21b, 25b) and the outer peripheral portion of each side arm (21, 25) and the inner peripheral portion of the wall surface; Flanges (22, 26) protruding in the facing direction and reinforcing ribs (24, 28) intersecting vertically and horizontally are attached to the front portions (21a,
The relief portions (30) of the suspension which are separated from each other are provided on the facing portion on the front end side of 25a), and the relief portions (3) are provided.
0), the opposite flanges (22a, 26a) of the front portions (21a, 25a) and the opposite connecting ribs (2).
3, 27) are integrally connected to each other, and the escape portion (30)
A casting rear arm for a motorcycle, wherein a suspension mounting member (36) is integrally provided on the lower surface of each of the front portions (21a, 25a) except for (1). 2. A relief portion (3) for each side arm (21, 25).
The suspension mounting member (36) is fitted and integrally connected to the lower flanges (22a-1, 26a-1) formed on the front parts (21a, 25a) except for the part (0). Two-wheeled cast rear arm. 3. The cast rear arm of a motorcycle according to claim 1, wherein a head pipe (32) is integrally formed at a front end of the pair of left and right side arms (21, 25).