JP2007118951A - Cast motorcycle rear arm - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a cast rear arm of a two-wheeled vehicle that is lightweight, has high rigidity and high productivity.
SOLUTION: A front block (30) and a pair of side arms (21, 22) extending rearward from both sides of the block (30) are individually formed by casting, and the block (30) A head pipe for connecting the vehicle body and an escape portion for passing the suspension are formed, and a rear wall (30c) standing up and down is formed at the rear portion, and each side arm (21, 22) supports the rear wheel. The support holes (23) are formed, and flanges (21c, 22c) projecting in the thickness direction on the outer peripheral part and the inner peripheral part, lattice-shaped reinforcing ribs (21f, 22f), and connecting ribs (21e, 22e) are provided. It is formed continuously, and the front part of each side arm (21, 22) is brought into contact with the block (30), and the connecting rib (21e, 22e) is brought into contact with both sides of the rear wall (30c) of the block. Let each The contact portion is welded to integrally connect the block (30) and the side arms (21, 22).
[Selection] Figure 1

Description

  The present invention relates to a rear arm that supports a rear wheel of a motorcycle, and more particularly to a cast rear arm formed by die casting or the like.

  The conventional rear arm is configured as shown in FIGS. 7 to 9, reference numeral 1 denotes a rear arm of a motorcycle, which is formed of an aluminum alloy square pipe material, a round pipe material, a plate material, or the like. That is, the rear bracket 3 (3a, 3b) that supports the rear wheel shaft is welded and fixed to the rear end (right end in FIG. 1) of the side arms 2 (2a, 2b) made of a pair of left and right square pipes. A head pipe 4 made of a round pipe is welded to the front end of each side arm 2 and a cross pipe 5 made of a square pipe is welded to the middle part in the front-rear direction to hold each side arm 2 at a predetermined interval. The lower bracket 6 is fixed to the center of the lower surface of the cross pipe 5 by welding.

  A reinforcing plate 7 formed by bending the plate in a triangular shape in side view is welded and fixed to the upper portion on the front side of the side arm 2, and the suspension 11 (FIG. 9) passes through the center of the upper surface of the reinforcing plate 7. A relief hole 8 is formed. Also, a beam member 9 bent into a U-shape with a plan view is formed by a square pipe material, the intermediate portion 9a of the beam member 9 is formed at the top of the reinforcing plate 7, and the rear end of the right side 9c is formed at the right portion. The rear end of the left side 9b is welded and fixed to the upper surface of the left rear bracket 3a on the rear upper surface of the side arm 2b. The left side 9b of the beam member 9 projects outward from the left side arm 2a, and a through hole 10 (FIG. 8) through which a rear wheel drive chain (not shown) passes is formed in this portion.

  As shown in FIG. 9, the rear arm 1 formed as described above is connected to the vehicle body 12 via the head pipe 4 so as to be swingable in the vertical direction, and the triangular link 13 can be rotated to the lower bracket 6. The link 13 is pivotably connected to the lower end of the suspension 11 suspended from the vehicle body 12, and the lower portion of the link 13 is pivotable to a link arm 14 extending rearward from the vehicle body. Link. Then, the rear wheel shaft 15 is supported on the rear portion of the rear arm 1 via the rear bracket 3, and the rear portion of the vehicle body is supported via the suspension 11 and the rear arm 1.

  Since the conventional rear arm 1 is formed by welding and fixing a square pipe material, a round pipe material, a plate material, and the like, a large number of parts and man-hours are required, and the productivity is lowered and the welding point is reduced. The quality was difficult to stabilize due to the increase.

  An object of the present invention is to obtain a cast rear arm of a motorcycle that is lightweight, has high rigidity, and high productivity.

  The present invention is configured as follows to achieve the above object. That is, in the invention according to claim 1, the front block and the pair of side arms extending rearward from both sides of the block are individually formed by casting, and the block is connected to the front end portion of the vehicle body. The head pipe is formed by integrally forming a clearance passage for suspension passage at the front left and right middle part, and a planar rear wall standing up and down at the rear part. A support hole for supporting the rear wheel is formed in the part, and a flange and a grid-like reinforcing rib projecting in the thickness direction continuously from each other on the outer peripheral part and the inner peripheral part, and both sides of the rear wall of the block on the front part The connecting ribs that are continuous with the flange and the reinforcing rib are integrally formed so as to face each other in the thickness direction, the respective side arms face each other, and the front portion abuts against the block As well as The coupling rib is abutted on either side of the rear wall of the block is obtained by the arrangement of integrally connected with said block and each side arm by welding the respective contact portions.

  In the invention according to claim 1 of the present application, when the front block is formed by casting, the head pipe for connecting the vehicle body and the escape portion for passing the suspension are formed at the same time, and each side arm is cast. Since the support holes for supporting the rear wheels are formed at the same time, it is not necessary to attach them in a later process or by machining, etc., and the number of parts and man-hours can be reduced. become. In addition, a rear wall standing up and down is formed at the rear part of the block, and a flange projecting in the thickness direction, a grid-like reinforcing rib, and a connecting rib are formed on the side arm continuously with each other. Each side arm is lightweight and highly rigid. Then, the front part of each side arm is brought into contact with the block, and the connecting rib of each side arm is brought into contact with both sides of the rear wall of the block so that both are welded and fixed. The side arms are firmly connected to each side arm, and the finished rear arm is lighter in weight and has higher lateral and torsional rigidity and strength.

  Embodiments of the present invention will be described below with reference to the drawings. 1 is a partially sectional plan view showing a first embodiment of the present invention, FIG. 2 is a sectional view taken along II-II in FIG. 1, FIG. 3 is a sectional view taken along III-III in FIG. 2, and FIG. FIG. 5 is a partially sectional plan view showing a second embodiment of the present invention, and FIG. 6 is a VI-VI sectional view of FIG.

  1 to 4, reference numeral 1 denotes an aluminum alloy rear arm formed by die casting, and includes a pair of left and right side arms 21 and 22 extending in the front-rear direction (left and right in FIG. 1), and the side arms 21 and 22. The blocks 30 interposed in the front part are individually formed by die casting, and these are integrally connected by welding.

  As shown in FIGS. 1 and 4, each of the side arms 21 and 22 has a gradual mountain shape in a side view gradually increasing from the front and rear ends toward the center in the front and rear direction, and the rear portions 21b and 22b are front portions. It is assumed that it is a lightning bolt in plan view that is biased to the outside via gentle curved portions 21c and 22c with respect to 21a and 22a. Each of the side arms 21 and 22 is integrally formed with endless flanges 21d and 22d projecting in the opposing direction (thickness direction) over substantially the entire outer periphery thereof, and the curved portions 21c and 22c are Connecting ribs 21e and 22e projecting in opposite directions are integrally formed on the entire upper and lower portions of the connecting portions of the front portions 21a and 22a and the rear portions 21b and 22b, and the wall surfaces surrounded by the flanges 21d and 22d are substantially formed. Lattice-like reinforcing ribs 21f and 22f projecting in the opposite direction are formed integrally on the entire area, and the side arms 21 and 22 are formed by the flanges 21d and 22d, the connecting ribs 21e and 22e, and the reinforcing ribs 21f and 22f. Stiffness and strength are increased.

  In addition, support holes 23 and 23 for supporting the rear wheel are formed in the rear end portions of the side arms 21 and 22, and the end portion of the head pipe 31 described later is fitted in the front end portions of the side arms 21 and 22. As shown in FIG. 4, the rear wheel drive chain (not shown) passes through the upper and lower intermediate portions of the curved portion 21c projecting from the left side arm 21 and the arc portion 24 to be joined. A through hole 25 is formed.

  The block 30 described above is formed in a cylindrical shape having a triangular shape in side view substantially corresponding to the outer shape of the front portion of the side arms 21 and 22. That is, the left and right end surfaces of the upper and lower walls 30a and 30b are shaped so as to follow the end surfaces of the front flanges 21d and 22d of the side arms 21 and 22, and the rear wall 30d rises up and down and follows the end surfaces of the connecting ribs 21e and 22e. A head pipe 31 for connecting the vehicle body is formed at the front end portion, a bracket 32 for connecting the link arm is formed on the lower surface, and a cylindrical portion (relief portion) 33 penetrating in the vertical direction is formed on the front portion. Suspensions (not shown) that are integrally formed and supported by hanging from the vehicle body are inserted into the cylindrical portion 33. Further, an annular reinforcing rib 34 protruding in the center direction is integrally formed on the inner peripheral portion of the block 30, and the rigidity and strength of the block 30 are enhanced.

 Then, as shown in FIG. 4, the side arms 21 and 22 are faced to each other, and the block 30 is disposed between the front portions of the side arms 21 and 22, and the upper and lower walls 30 a and 30 b of the block 30 are arranged. The left and right end surfaces and the left and right end surfaces of the rear wall 30d are brought into contact with the end surfaces of the front flanges 21d and 22d of the side arms 21 and 22 and the end surfaces of the connecting ribs 21e and 22e, respectively. Further, the left and right end portions of the head pipe 31 are fitted to arc portions 24 and 24 formed at the front end portions of the side arms 21 and 22, respectively, and the two are integrally welded to fix the rear arm 20 as shown in FIG. Form.

  5 and 6 show a second embodiment. In this, a head pipe 26 for connecting the vehicle body is formed coaxially at the front end of each side arm 21, 22, and the front wall 30 c of the block 30 stands up behind the head pipe 26, An arcuate recess (escape portion) 35 for escaping the suspension is formed in the left and right central portion of the front wall 30c. In addition, predetermined reinforcing ribs 21f ′ and 22f ′ formed on the side arms 21 and 22 are formed facing each other at portions corresponding to the left and right end surfaces of the front wall 30c, and the upper and lower walls 30a and 30b of the block 30 are formed. The left and right end surfaces are in contact with the end surfaces of the front flanges 21d and 22d of the side arms 21 and 22, the end surfaces of the connecting ribs 21e and 22e, and the reinforcing ribs 21f 'and 22f', respectively. Has been. The other structure is substantially the same as that of the first embodiment.

It is a partial cross section top view which shows 1st Example of this invention. It is II-II sectional drawing of FIG. FIG. 3 is a sectional view taken along line III-III in FIG. 2. It is a perspective view which shows the combination state before the assembly | attachment by 1st Example of this invention. It is a partial cross section top view which shows 2nd Example of this invention. It is VI-VI sectional drawing of FIG. It is a top perspective view which shows a prior art example. It is a bottom perspective view showing a conventional example. It is a partial cross section side view which shows the attachment state to the vehicle body of the conventional rear arm.

Explanation of symbols

20 Rear arm 21 Left side arm 21a Front part 21b Rear part 21c Curved part 21d Flange 21e Connection rib 21f Reinforcement rib 22 Right side arm 22a Front part 22b Rear part 22c Curved part 22d Flange 22e Connection rib 22f Reinforcement rib 23 Support Hole 24 Arc part 25 Through hole 30 Block 30a, 30b Upper and lower walls 30c Front wall 30d Rear wall 31 (26) Head pipe 32 Bracket 33 Cylindrical part (relief part)
34 Reinforcement rib 35 Recess

Claims (1)

  A block on the front side and a pair of side arms extending rearward from both sides of the block are individually formed by casting, and the block has a head pipe for connecting the vehicle body at the front end and a left and right middle of the front. Each of the side arms has a support hole for supporting the rear wheel at the rear end. A flange and a lattice-shaped reinforcing rib that are formed on the outer peripheral portion and the inner peripheral portion and continuously project in the thickness direction are formed on the front portion and project in the thickness direction so as to face both sides of the rear wall of the block. In addition, connecting ribs that are continuous with the flanges and the reinforcing ribs are integrally formed, the side arms face each other and their front portions abut against the block, and the connecting ribs are connected to the block. Is brought into contact with both sides of the rear wall, cast rear arm of the two-wheeled vehicle, characterized in that said connecting respective contact portions welded to the integrally with said block and each side arm.

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