JPS6117715B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a progressive type rear wheel shock absorber for a motorcycle that is capable of increasing the rate of increase in the shock absorbing force of a shock absorber in response to rocking displacement of a rear wheel support frame that supports the rear wheel.

More specifically, a downwardly extending portion is formed on a bracket member that connects and supports the rear part of the engine to the vehicle body frame, and the rotating portion is pivotally connected to the rear wheel support frame and connects the lower end of the shock absorber. By installing a rod member between the parts and connecting the end of the rod member, which increases the rate of increase in buffering force, to the above-mentioned bracket member of the engine, it is possible to utilize existing parts, improve strength, and change the buffering characteristics. The present invention relates to a rear wheel shock absorbing device for a motorcycle, which facilitates the use of a motorcycle.

In motocross and off-road motorcycles that travel on rough terrain, the amount of vertical swing of a swingable rear wheel support frame such as a rear fork is secured to be greater than in general motorcycles.

In addition, in this type of off-road motorcycle, the buffering characteristics of the rear wheel shock absorber are not proportional to the upward swinging displacement of the rear wheel support frame, and the increase rate of the buffer force of the shock absorber is not proportional to the upward swing displacement of the rear wheel support frame. A progressive type shock absorber is used which allows the amount of vibration to be increased.

In this type of shock absorber, the lower end of the shock absorber, whose upper end is connected to the vehicle body frame, is connected to a rotating member pivotally connected to the rear wheel support frame, and a rod is installed between the fixed member such as the vehicle body frame and this rotating member. The rotating member is rotated by axial loads such as tensile force and compressive force generated on the rod member by the swinging of the rear wheel support frame, thereby increasing the amount of compression of the shock absorber and creating a large spring. A force is generated to obtain the above-mentioned buffering force increase rate that increases along a curved line.
According to this, the shock load transmitted from the road surface to the vehicle body via the rear wheels can be effectively absorbed, and ride comfort is improved.

A progressive type shock absorber having such functions and effects is constructed by adding a rotating member and a rod member as described above, but the amount of contraction of the shock absorber is increased when the rear wheel support frame swings. An extremely large axial load is generated on the rod member corresponding to this amount of reduction, and therefore, the member that connects and supports the rod member is required to have strength capable of resisting this load.

In addition, a configuration in which new parts must be prepared separately to connect and support the rod members is undesirable because it increases the number of parts and changes the design specifications of the motorcycle, so it is preferable to use existing parts. It is desirable to have a configuration in which the rod members can be connected and supported by changing the shape of the rod members, so that existing parts can be used effectively. Furthermore, it is desirable for off-road motorcycles to be able to change the shock absorbing force characteristics of the shock absorber as appropriate depending on road conditions, for example, during racing, and it is important to have a structure that meets such demands. Moreover, it is necessary to have a structure that allows the work of changing the buffering force characteristics to be carried out easily in a short period of time.

The inventors of the present invention have devised the present invention in order to effectively meet the requirements of a progressive type shock absorber as described above.

An object of the present invention is to do this by simply changing the shape of an already prepared part that constitutes a part of a motorcycle, without requiring the provision of a new part for connecting and supporting the rod member. By making it possible to form connecting support parts, we aim to make use of existing parts, and by making it possible to connect and support the rod members with sufficiently high rigidity and strength, we aim to improve the strength, and further improve the buffering force characteristics of the shock absorber. An object of the present invention is to provide a rear wheel shock absorbing device for a motorcycle, which can be changed in a short time by simple work, and is designed to facilitate the change work.

A preferred embodiment of the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 is a side view showing the main parts of an off-road motorcycle to which the device according to the present invention is applied, FIG. 2 is a bottom view of FIG. 1, and FIG. 3 is an exploded view.

1 is an engine, 2 is a body frame, and 3 is a rear wheel. The engine 1 is connected to the bottom 2a of the vehicle body frame 2.
The rear end of the bottom part 2a is bent and raised approximately vertically to form a rising part 2b.
A bracket 4 having a hole 4a as shown in FIG. 3 is welded to b. Reference numeral 5 shown in FIG. 3 is a bracket member conventionally used to connect and support the rear part of the engine 1 to the vehicle body frame 2. It consists of a cylindrical part 5c made of a cylindrical member that connects across the cylindrical part. Holes 6 and 7 are provided at the top and bottom of each of the side plates 5a and 5b, with the cylindrical portion 5c in between. Insert the bracket member 5 into the holes 6, 1a and 7, 1.
The bracket member 5 is attached to the rear part of the engine 1 by inserting and screwing bolts 8 and 9 into b.

Reference numeral 10 denotes a rear wheel support frame, ie, a rear fork, which supports the rear wheel 3 at its rear end. In this embodiment, the rear fork 10 is of a monocot type. A pair of protrusions 1 are provided at the tip of the rear fork 10.
0a and 10b are provided, and while inserting the bracket member 5 into the recess 11 as shown in FIG.
2b, and a pivot shaft 13 is inserted into the hole 4a of the bracket 4 of the upright portion 2b, the hole 12 formed in the protruding portions 10a and 10b of the rear fork 10, and the cylindrical portion 5c of the bracket member 5.
Insert in common. As a result, the rear portion of the engine 1 is connected and supported by the bracket member 5 to the vehicle body frame 2, and the tip of the rear fork 10 is pivoted to the vehicle body frame 2 so as to be able to swing up and down about the pivot shaft 13 as a fulcrum.

Reference numeral 14 denotes a rotating member, and as shown in FIG. 1, the rotating member 14 has a substantially triangular side surface and a dogleg shape with a central portion bent outward. rear 1
4a is bifurcated as shown in Figure 3,
A hole 15 is formed in each branch part, and a hole 15 is formed in a pair of receiving parts 16, 16 protruding from the upper surface of the rear fork 10.
By aligning the bolts 5 and inserting and screwing together the bolts 17, 17, the rotary member 14 is attached to the rear fork 10 at the rear part 14a so as to be rotatable up and down. The lower end of the shock absorber 18 configured as a spring damper is attached to the center of the rotating member 14 with a bolt 1.
The shock absorber 18 is extendable and retractable, and its upper end (not shown) is pivotally connected to the vehicle body frame 2, so that one shock absorber 18 can be connected to the vehicle body frame 2. It is installed between the rotating member 14 attached to the rear fork 10. The front part 14b of the rotating member 14 is made to protrude from the lower surface of the rear fork 10 through a hole 20 formed through the rear fork 10, and the rear end of the rod member 21 is pivotally connected to this protruding end with a bolt 22. The rod member 21 has threaded rod ends 21a at both ends as shown in FIG.
21b, and the length can be finely adjusted by screwing the rod ends 21a and 21b to move them forward and backward.

The side plates 5a and 5b of the bracket member 5, which connects the rear part of the engine to the vehicle body frame 2, are extended downward, and extending portions 23 and 24 are integrally formed below the hole 7 position. Cylindrical portions 23a and 24a facing each other with a gap are provided on the inner surfaces of the lower ends of the extension portions 23 and 24, and the front rod end 21b of the rod member 21 is inserted into the gap to tighten the bolt 25 to the cylindrical portions 23a and 24a. By inserting and screwing together, the front end of the rod member 21 is pivotally connected to the lower end of the bracket member 5.

As described above, the rod member 21 is installed between the bracket member 5 and the rotating member 14, and the bracket member 5, which is originally prepared as a component of the motorcycle, is installed to connect and support the engine 1 to the vehicle body frame 2.
serves as a front end connecting support part of the rod member 21, and downwardly extending portions 2 are provided on the side plates 5a, 5b of the bracket member 5.
The rod members 21 are connected only by changing the shape of integrally forming the rod members 3 and 24, and existing parts are utilized.

Next, we will discuss the effect.

Assume that the motorcycle is running and the rear wheel 3 moves up and down due to the unevenness of the road surface, and the rear fork 10 swings upward from the chain line position to the solid line position in FIG. 1 using the pivot shaft 13 as a fulcrum. As the rear fork 10 swings, the rotating member 14 also rises. The rotating member 14, whose rear part 14a is pivotally attached to the rear fork 10 with bolts 17, has a rod member 21 connected to its front part 14b, and the rod member 21 The pivot member 14 pivots in a clockwise direction when the rear fork 10 pivots because it pivots in an arcuate trajectory centered on the bolt 25.

Therefore, the shock absorber 18 whose lower end is connected to the central portion of the rotating member 14 is reduced and deformed by the amount of rotation of the rotating member 14 added to the amount of rocking of the rear fork 10, and as a result, the spring of the shock absorber 18 is reduced. The buffering force due to the elastic force increases at a larger rate than the swinging displacement of the rear fork 10, and the rate of increase in the buffering force can be increased more than the swinging amount of the rear fork 10.

FIG. 4 is a graph showing an increase in the buffer force F with respect to the swing angle θ of the rear fork 10. As the swing angle θ increases, the buffer force F increases at an increasing rate of a quadratic curve.

In the above, when the rotating member 14 rotates clockwise, an axial load in the compression direction is generated on the rod member 21, and this load causes the rotating member 14 to rotate, and the shock absorber 18 The axial load is extremely large because the spring is contracted against the spring force. However, the bracket member 5, which connects and supports the front end of the rod member 21, is formed into a gate shape consisting of side plates 5a, 5b and a cylindrical portion 5c, and has sufficiently high rigidity and strength, so that the rod member 21 can be connected and supported. It is now possible to effectively support the axial load generated at 21.
An increase in strength is achieved.

The preload spring load and buffering force increase rate of the shock absorber 18 are determined by the length dimension of the rod member 21, and the rod ends 21a, 21b constituting the rod member 21 are determined by the length dimension of the rod member 21.
By moving forward and backward to adjust the length dimension, it is possible to change the rate of increase in buffering force, etc., but FIGS. 5, 6, and 7 show examples for changing the rate of increase in buffering force within a larger range.

As shown in FIGS. 5, 6, and 7, three types of bracket members 5 are prepared, and the extending portions 23 and 24 connecting the rod members 21 are extended forward at an angle 5-
1. Prepare 5-2 which is extended vertically and 5-3 which is tilted backward. By appropriately converting the bracket member 5 into these 5-1, 5-2, and 5-3, the shock absorbing characteristics of the shock absorber 18 can be changed. If this is combined with the length adjustment of the rod member 21, the shock absorbing characteristics of the shock absorber can be finely adjusted over a wide range. Bracket member 5
The conversion can be easily carried out by attaching and detaching the bolts 8, 9, 25 and the pivot shaft 13, and the operation can be completed in a short time.

In the above embodiments, the rear wheel support frame is a rear fork, but a swing arm that cantilever supports the rear wheel may also be used.

As is clear from the above description, according to the present invention, the bracket member for connecting and supporting the rear part of the engine to the vehicle body frame is used as the part connecting the front end of the rod member, so that existing parts can be utilized. By simply changing the shape of a bracket member, which is already prepared as a part of a motorcycle, by forming a downwardly extending part, it can be used as a connecting support part for a rod member, and a new part can be prepared separately. This eliminates the need to do so, and can solve conventional problems such as an increase in the number of parts and changes in design specifications. In addition, the bracket member itself has high rigidity and strength, and is suitable as a connecting support component for the rod member, which generates a large axial load when creating a buffering force in the shock absorber, and can sufficiently resist this axial load, improving strength. Achieve.

Furthermore, if the length of the rod member is freely adjustable as in the embodiment, and a plurality of bracket members are prepared with different directions of extension of the downward extending portion, the buffer characteristics and buffer force increase rate of the shock absorber can be changed arbitrarily. This makes it possible to obtain shock absorbing properties according to the road surface conditions, etc., making it suitable for off-road motorcycles.Moreover, this modification work can be done with simple work such as removing and installing bolts, making workability faster and easier. contribute to

[Brief explanation of the drawing]

FIG. 1 is a side view of main parts of a motorcycle to which the shock absorber according to the present invention is applied, FIG. 2 is a bottom view of FIG. 1,
Fig. 3 is an exploded view of the shock absorber, Fig. 4 is a graph showing the rate of increase in damping force against the swing angle of the rear wheel support frame, and Figs. FIG. 7 is a side view showing a plurality of bracket members prepared with different extension directions of the projecting portions. In the drawing, 1 is the engine, 2 is the vehicle frame,
3 is a rear wheel, 5 is a bracket member, 10 is a rear fork that is a rear wheel support frame, 14 is a rotating member, 18 is a shock absorber, 21 is a rod member, and 23 and 24 are extension parts.

Claims (1)

[Claims] 1. The rear part of the engine is connected and supported to the vehicle body frame by a bracket member, and the front end of the rear wheel support frame, which supports the rear wheels at the rear end, is pivotally connected to the vehicle body frame so as to be able to swing vertically, and the rear wheel support frame can be rotated to the rear wheel support frame. A shock absorber is constructed between the vehicle body frame and the rotating member by attaching the member so as to be vertically movable, and a downwardly extending portion is formed in the bracket member, and the extending portion and the rotating member are connected to each other. A rear wheel shock absorber for a motorcycle, characterized in that a rod member is installed between the rear wheel shock absorber and the rear wheel shock absorber.