JPH02200590A - Rear arm bracket structure for motorcycle body frame - Google Patents

Abstract

PURPOSE:To aim at lightweight and maintain the good outward appearance of a rear arm bracket by forming the upper part of the rear ara bracket sectionally in the shape of a box and the lower part in the shape of a plate, thereby securing large strength at the upper part. CONSTITUTION:The upper part 37 of each rear arm bracket 6 is formed sectionally in the shape of a box and provided with sufficiently large strengh, and the end part of a cross member 7 is fitted into a fitting cylinder body formed integrally at the inner surface of the upper part 37 and welded rigidly. On the other hand, the lower part 38 of the rear arm bracket 6 is formed in the shape of a plate continued integrally from the lower end of the upper part 37, longitudinal ribs 38a, 38b are formed integrally at the longitudinal edges of the inner surface of the lower part 38, an intermediate rib 38c is formed integrally at the longitudinal intermediate part, and thus the specified strength is secured at the lower part 38. In addition, the end part of a lower cross member 7' is fitted into a fitting cylinder body formed integrally at the lower inner surface of the lower part 38 and welded rigidly. The connected outer surface of the upper and lower parts 37, 38 is formed into a smooth continued surface so as to maintain the sense of integration in outside appearance.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a rear arm bracket structure for a motorcycle body frame.

(Prior art) For example, Japanese patent application 1986-
Some of these are shown in the specification and drawings of No. 74497. According to this, the vehicle body frame has a head pipe at the front thereof, and the main frame extends downward from the head pipe. Further, a rear arm bracket projects downward from the rear end of the main frame, and the rear arm bracket is integrally molded as a whole.

A front fork that supports the front wheel is supported on the head pipe so as to be freely steerable, while a rear arm is pivotably supported vertically by a pivot shaft at the vertical midway point of the rear arm bracket. The lower end side supports other vehicle body components.

In the above configuration, when the motorcycle is running, shock from the road surface is transmitted to the vehicle body frame via the front and rear wheels. In this case, in particular, the portion of the vehicle body frame that extends from the head vibrator supported between the front and rear wheels to the pivot shaft, that is, the head vibe, the main frame, and the rear arm bracket above the pivot shaft. (hereinafter, this is simply referred to as the upper part of the rear arm bracket, and the part below this is referred to as the lower part of the rear arm bracket). Further, the portion from the head pipe to the pivot shaft is given a large twist about the imaginary line connecting the head vibrator and the pivot shaft when viewed from the side. For this reason, the head vibe mentioned above.

The main frame and the upper part of the rear arm bracket are formed to have sufficient strength.

(Problems to be Solved by the Invention) The entire rear arm bracket is integrally molded, and its upper and lower parts have the same structure. Therefore, if the strength of the upper part of the rear arm bracket is sufficiently increased as described above, the lower part of the rear arm bracket will also have a correspondingly large strength, but this is because the lower part of the rear arm bracket only supports the engine etc. There is a risk that it will become too strong for the rear arm bracket, and in this case, there will be an inconvenience that the rear arm bracket becomes unnecessarily heavy.

(Object of the Invention) The present invention has been made in view of the above-mentioned circumstances, and is designed to ensure sufficient strength in the upper part of the rear arm bracket, and to improve the strength of the rear arm bracket. The purpose is to prevent the rear arm bracket from becoming heavy as a whole, and to prevent the appearance of the rear arm bracket from deteriorating even in this case.

(Structure of the Invention) The feature of this invention for achieving the above object is that the upper part of the rear arm bracket is formed into a box shape, while the lower part of the rear arm bracket is formed into a plate shape. It is in.

(Function) The function of the above structure is as follows.6 Body frame 2
In this case, the portion from the head vibrator 3 supported between the front and rear wheels 12 and 16 to the pivot shaft 14, that is, the head vibrator 3, the main frame 4, and the upper part 37 of the rear arm bracket 6 has great strength. This is required. Therefore, in the rear arm bracket 6, the upper part 37 is formed to have a box-like cross section, so that the upper part 37 of the rear arm bracket 6 has a sufficiently large strength.

On the other hand, since the load from the rear arm 15 is not directly applied to the lower part 38 of the rear arm bracket 6, the strength of this part is smaller than that of the soil part 37. Therefore, in order to prevent the strength of the lower part 38 of the rear arm bracket 6 from becoming excessive, the lower part 38 is formed into a plate shape.For this reason, the lower part of the rear arm bracket 6 is also made box-shaped in cross section. The weight of this lower part 38 can be made lighter than that of the lower part 38. Also, since it is plate-shaped, this part can be easily molded.

Historically, as mentioned above, the upper part 37 of the rear arm bracket 6 has a box-like cross section, while the lower part 38 has a plate shape, so the outer surfaces of the upper and lower parts 37 and 38 of the rear arm bracket 6 have a substantially flat appearance. It can be done.

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

In FIGS. 2 to 3, 1 is a motorcycle and 2 is its body frame. The vehicle body frame 2 has a head vibrator 3 at the front thereof, and a pair of left and right main frames 4.4 extend rearward and downward from the head vibrator 3, and extend downward from the rear end of each main frame 4. The rear arm bracket 6 extends. The left and right rear arm brackets 6.6 have rectangular cross sections and are firmly connected to each other by vibrator-shaped upper and lower cross members 7.7'.

Further, a pair of left and right seat rails 8.8 extend rearward and upward from the rear end of the main frame 4, and the left and right seat rails 8.8 are firmly connected to each other. A backstay 9 is provided to reinforce the. Then, the seat I where the seat rails 8 are lined up front and rear
O and tandem seat lOa are supported.

A front fork 11 is supported on the above-mentioned Radvibe 3 so as to be freely steerable. A front wheel 12 is supported at the lower end of this front fork 11, and a handle 13 is attached to the upper end of the front fork 11. On the other hand, a rear arm 15 is pivotably supported by a pivot shaft 4 on the left and right rear arm brackets 6.6 so as to be vertically swingable, and a rear wheel 16 is supported at the swinging end of this rear arm 15.

The upper bracket 1 is located midway between the left and right sides of the upper cross member 7.
8 is provided protrudingly, and the front end of the backstay 9 described above is screwed to this with a bolt 19. On the other hand, a link mechanism 21 is installed by a pivot shaft 22 between the front and back midway portions of the rear arm 15 and the one door bracket 20 protruding from the left and right midway portions of the lower cross member 7'. A shock absorber 24 is provided between the upper bracket 18 and the upper bracket 18.
is constructed by a pivot shaft 25.

27 is a 2 cycle parallel 2 for driving the rear wheel I6
This engine 27 is a cylinder engine, and this engine 27 is connected to the main frame 4.
The bolts 29 are screwed to brackets 28 projecting from the upper and lower cross members 7 and 7', respectively. Further, 30 is a carburetor, 31 is a fuel tank 31 for feeding fuel into the carburetor 30, 32 is an intake pipe, 33 is an air cleaner, 34 is an exhaust pipe, and 35 is a radiator.

When the power from the engine 27 is transmitted to the rear wheel I6, the motorcycle becomes able to run, and during this running, the shock absorber 24 expands and contracts, passing from the running surface through the rear wheel I6 and rear arm 15 to the body frame 2 side. It buffers the impact that is about to be transmitted. Also, during this running, when the rear arm 15 rotates upward due to the rear wheel 16 being hit by an uneven running surface (f+), the rear wheel J6 is forced to follow this uneven running surface. As such, the link mechanism 21 non-linearly increases the amount of contraction of the buffer 24.

1 and 3 to 5, the rear arm bracket 6.6 will be explained in more detail. Each rear arm bracket 6 is integrally molded in an aluminum casting tank, and its upper end is firmly welded to the rear end of the main frame 4.

A pivot hole 36 for pivotally supporting each corresponding end of the pivot shaft 14 is provided at the vertical midway point of each rear arm bracket 6.
is formed.

The upper part 37 of each of the rear arm brackets 6 has a box-like cross section, which gives the upper part 37 sufficient strength. Further, a fitting cylinder 37a is integrally formed on the inner surface of this upper part 37, and the end of the upper cross member 7 is fitted into this fitting cylinder 37a and firmly welded.

On the other hand, the lower portion 38 of the rear arm bracket 6 is shaped like a plate and integrally extends to the lower end of the recording portion 37.

Front and rear ribs 38a are provided on the front and rear edges of the inner surface of this lower part 38,
38b is integrally molded, and an intermediate rib 38c is integrally molded at the front and back midway portions of the inner surface, thereby ensuring a predetermined strength in the lower portion 38. Further, a fitting cylinder 38d is integrally formed on the lower inner surface of the lower part 38, and the lower cross member 7 is attached to the fitting cylinder 38d.
’ end is fitted and firmly welded.

In the above case, the outer surfaces of the upper part 37 and the lower part 38 of the rear arm bracket 6 form a smooth continuous surface by intersecting each other at a gentle intersecting angle. Even if the lower part 38 is made into a plate shape and the structures of the two parts are different from each other, the rear arm bracket 6 maintains a sense of unity in appearance, that is, a good appearance is maintained.

(Effects of the invention) According to this invention, there are the following effects. That is, the body frame is required to have high strength from the head pipe supported between the front and rear wheels to the pivot shaft, that is, the head pipe, the main frame, and the upper part of the rear arm bracket.

Therefore, regarding the rear arm bracket mentioned above.

The upper part of the rear arm bracket is formed to have a box-like cross section, and therefore, sufficient strength is ensured in the upper part of the rear arm bracket.

On the other hand, since the load from the rear arm is not directly applied to the lower part of the rear arm bracket, the strength of this part needs to be less than that of the upper part. Therefore, in order to prevent the lower part of the rear arm bracket from becoming too strong, the lower part was formed into a plate shape. The weight of this lower part can be reduced. Also, since it is plate-shaped, this part can be easily molded.

Historically, as described above, the upper part of the rear arm bracket is box-shaped in cross section, while the lower part is plate-shaped, so that both the upper and lower outer surfaces of the rear arm bracket can have a substantially flat appearance.

Therefore, by doing this, the appearance of the rear arm bracket as a whole does not lose its sense of unity (as a result, the rear arm bracket maintains a good appearance).

[Brief explanation of the drawing]

The figures show an embodiment of the invention, and Figure 1 is 1-1 in Figure 3.
A partial cross-sectional view taken along the line, and Figure 2 is an overall side view of the motorcycle.
Figure 3 is a partially enlarged view of Figure 2, Figure 4 is IV of Figure 3.
5 is a sectional view taken along the line V-V of FIG. 3 of the same. 1. Motorcycle, 2. Body frame, 3. Head vibration, 4. Main frame, 6.-Rear arm bracket, 11.. Front fork, 14. Pivot shaft,
15... Rear arm, 16. Rear wheel, 37... Upper part, 38
··beneath. Figure 1

Claims (1)

[Claims] 1. A main frame is extended downward from the head pipe that supports the front fork, and a rear arm bracket is installed downward from the rear end of the main frame, and a pivot point is installed at the upper and lower midpoints of this rear arm bracket. In a body frame for a motorcycle in which a rear arm is vertically swingably supported by a support shaft, a portion of the rear arm bracket above the pivot shaft is formed into a box-like cross section;
A rear arm bracket structure for a motorcycle body frame in which a portion below the pivot shaft is formed into a plate shape.