JPH0436917B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a rear wheel suspension system for a motorcycle in which spring characteristics gradually become stiffer as the amount of upward movement of the rear wheel increases.

In motorcycles, the spring is softer when the stroke (amount of upward movement) of the rear wheel is small, and stiffer when the stroke is large, creating a so-called progressive (quadratic curve) spring characteristic.
It is desirable to have it on the rear wheel suspension. In this case, it is possible to soften the riding comfort when the rear wheel stroke is small, and to prevent the cushion unit from bottoming out when the stroke is large.

In order to obtain such progressive spring characteristics, a link mechanism is provided near the pivot shaft that pivotally supports the front end of the rear arm on the vehicle body frame, and the cushion unit is pivotally supported via this link mechanism. Proposed. However, all of the conventional mechanisms have a four-bar link mechanism including a pivot shaft, and one link that is pivotally attached to the rear arm is provided behind the pivot shaft. For this reason, the reaction force of the cushion unit is concentrated on this link and one pivot point of the rear arm, resulting in a large stress concentration, and it has become necessary to increase the rigidity of the entire rear arm. As a result, there was a problem in that the rear arm weight increased, and furthermore, the unsprung weight increased, which worsened the ground contact of the rear wheels.

In addition, motorcycles usually use a cylindrical cushion unit, but it is preferable for the amount of oscillation of this cushion unit to be small when the rear wheel stroke changes, from the standpoint of accommodating the cushion unit, and the weight of the cushion unit is considerable. Since it is large, it is desirable to install it low and lower the center of gravity in order to increase stability.

The present invention was developed in view of the above circumstances, and it is possible to reduce the stress concentration of the rear arm, reduce the weight of the rear arm, and further reduce the unsprung weight, and further reduce the swing angle of the cushion unit. It is an object of the present invention to provide a suspension system for a motorcycle that can reduce the weight and lower the center of gravity.

In a motorcycle in which the front end of a rear arm that holds a rear wheel at the rear end is pivotally supported on a body frame by a pivot shaft so as to be able to swing vertically, a part of the rear arm is used as one side below the rear arm, and a part of the rear arm is placed on the side of the body frame. A four-bar link mechanism that does not include a pivot point is formed, and the lower end of the front side of the four-bar link mechanism is connected to the vehicle body frame below the pivot shaft by an auxiliary link, and a cylindrical type is formed near the rear end of the lower side of the four-bar link mechanism. This is achieved by a rear wheel suspension system for a motorcycle characterized in that the lower end of the cushion unit is pivotally supported. The present invention will be explained in detail below based on the illustrated embodiments.

FIG. 1 is a side view of essential parts showing one embodiment of the present invention;
FIG. 2 is a side view showing the same operation. In these figures, the reference numeral 10 is a known double cradle type vehicle body frame, and its down tube 1
2, the seat pillar tube 14, and the backstay 16. There are a pair of left and right brackets 18 with a predetermined gap between them, but they are not shown in the drawings.

Reference numeral 20 denotes a rear arm, the rear part of which is formed into a forked shape, and a rear wheel 22 is disposed between the forked rear parts. 24 is the rear wheel axle and rear arm 2
It is held at the rear end of 0. The front end of the rear arm 20 is pivotally supported by the bracket 18 by a pivot shaft 26, and as a result, the rear arm 20 can swing up and down about the pivot shaft 26.

Two links 28 and 30 are sequentially connected to the rear arm 20 behind the pivot shaft 26, and the lower ends of these links 28 and 30 are connected by a link 32. This results in these links 28,3
0, 32, and a part of the rear arm 20, the vehicle body frame 10 has a part of the rear arm 20 as one side.
A four-bar link mechanism is formed that does not include a side pivot point. Link 28, which is the front side of this four-bar link mechanism
An auxiliary link 34 is connected to the lower end of the pivot shaft 26, and the other end of the auxiliary link 34 is connected to the vehicle body frame 10 below the pivot shaft 26.

A cylindrical cushion unit 36 is composed of a known cylindrical hydraulic shock absorber 38 and a coil spring 40. This cushion unit 36 is disposed almost vertically between the pivot shaft 26 and the rear wheel 22 so as to vertically pass through the rear arm 20, and its lower end forms a link 32 that forms the lower side of the four-bar link mechanism.
It is pivotally supported near the rear end, while its upper end is pivotally supported by the vehicle body frame 10. In FIG. 2, A and B are the center lines of the cushion unit 36, A indicates when the rear wheel 22 is fully rebound, that is, when the rear wheel 22 is the lowest, and B indicates when the rear wheel 22 is at full bump, that is, when the rear wheel 22 is the lowest. Indicates when it has risen.

When the rear arm 20 now rotates upward from the full rebound position shown by the solid line in FIG. 2, the links 28, 30, 32 are pulled upward accordingly.
The cushion unit 36 is being compressed. At this time, the auxiliary link 34 rotates counterclockwise and pulls the lower link 32 of the four-bar link mechanism forward. Therefore, the displacement of the rear end of the link 32 in the left-right direction is extremely small, and the cushion unit 36
The amount of oscillation, that is, the amount of change in straight lines A and B is small.
Also, the length of each link 28, 30, 32, 34 is
The amount of change in length of the cushion unit 36 is determined to gradually increase in response to an increase in the amount of upward movement of the rear wheel 22, thereby obtaining the progressive spring characteristic. In addition, in Fig. 2, 20a, 2
8a to 34a indicate the positions of the rear arm 20 and links 28 to 34 at the time of full bump.

On the other hand, the reaction force of the cushion unit 36 is
Since the reaction force of the cushion unit 36 is transmitted to the rear arm 20 via the links 8 and 30, the reaction force of the cushion unit 36 is distributed to two locations, that is, to the upper end shaft fulcrums of the links 28 and 30. Therefore, the stress concentration of the reaction force on the cushion unit 36 is alleviated.

As described above, the present invention forms a four-bar link mechanism that does not include a pivot shaft on the vehicle body frame side such as a pivot shaft below the rear arm, and connects the lower end of the front side of the four-bar link mechanism below the pivot shaft by an auxiliary link. The cylindrical cushion unit is connected to the vehicle body frame, and the lower end of the cylindrical cushion unit is pivotally supported near the rear end of the lower side of the four-bar link mechanism, so the reaction force of the cushion unit is transferred to the front side of the four-bar link mechanism. It is distributed over two pivot points: the rear side and the rear arm. As a result, the stress concentration of this reaction force is alleviated, making it possible to design the rear arm with lower rigidity, which reduces the weight of the rear arm and further reduces the unsprung load, which improves the road surface grip of the rear wheels. becomes possible. In other words, since the amount of rocking of the cushion unit can be reduced, the space for accommodating it can be reduced. Furthermore, since the cushion unit is pivotally supported near the rear end of the lower side of the four-bar linkage mechanism, the position of the cushion unit is lowered, lowering the center of gravity of the entire vehicle and improving running stability. becomes possible.

[Brief explanation of drawings]

Figure 1 is a side view of essential parts of an embodiment of the present invention, Figure 2 is a side view of essential parts of an embodiment of the present invention;
The figure is a side view showing the operation. 10...Vehicle frame, 20...Rear arm,
22...Rear wheel, 26...Pivot axis, 28...Link as front side, 32...Link as lower side, 34...Auxiliary link, 36...Cushion unit.

Claims (1)

[Claims] 1. In a motorcycle in which the front end of a rear arm that holds a rear wheel at the rear end is pivotally supported on a body frame by a pivot shaft so as to be able to swing vertically, a part of the rear arm is placed below the rear arm on one side and is on the side of the body frame. A four-bar link mechanism is formed that does not include a pivot point, and the lower end of the front side of the four-bar link mechanism is connected to the vehicle body frame below the pivot shaft by an auxiliary link, and a cylinder is provided near the rear end of the lower side of the four-bar link mechanism. A rear wheel suspension system for a motorcycle, characterized in that the lower end of a type cushion unit is pivotally supported.