JPS5819993Y2 - Front fork of a motorcycle - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a front fork for a two-wheeled motor vehicle, and particularly to a telescopic type front fork in which an upper cylinder and a lower cylinder are slidably fitted.

In this type of front fork, the upper tube is attached to the fork bracket, and the lower end of the lower tube is attached to the front wheel.While the motorcycle is running, the attachment part to the fork bracket, especially the lower fork bracket, is attached to the front fork. A large bending load is applied to the front fork at the attachment point.

The purpose of the present invention is to provide a front fork with sufficient strength in order to deal with such problems, and its feature is that the upper cylinder uses a cylinder with a larger diameter than the lower cylinder. , the lower cylinder slides within the upper cylinder, and the upper cylinder has an increased outer diameter at least at the lower part of the attachment to the fork bracket, and has an increased section modulus; The purpose is to gradually reduce the section modulus by gradually decreasing the outer diameter downward while keeping the inner diameter constant.

In particular, in the present invention, the outer cylinder is attached to the upper fork bracket at the upper part and to the lower fork bracket at the lower part, and the outer cylinder has a thick wall at the lower fork bracket attachment part, and the outer cylinder is attached to the upper fork bracket. The wall thickness gradually becomes thinner toward the bottom.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In FIG. 1, a pair of front forks 1 are fixed to an upper fork bracket 3 and a lower fork bracket 4 attached to a handlebar 2, and a front wheel 5 is attached to the lower end. installed.

The shaft 6 between the brackets 3 and 4 fits into a pipe 7 at the front end of the vehicle body frame.

The front fork 1 includes an upper cylinder 12 and a lower cylinder 13, and the lower cylinder 13 is inserted into the upper cylinder 12.

A sleeve bearing 14.15 made of a bearing material such as bronze is attached to the inwardly facing lower part of the upper cylinder 12 by a method such as press fitting, and the outer surface of the lower cylinder 13 is attached to this bearing 14.
, 15 so as to be slidable in the axial direction.

A lubricant such as grease is sealed between the bearings 14 and 15.

A protection tube 16 is provided to protect the outer surface of the lower tube 13, which serves as a sliding tube.

The lower end of the protective tube 16 is attached to the bracket 8 at the lower end of the lower tube 13 with screws 9 or the like.

Further, a dust seal 17 is arranged between the upper cylinder 12 and the lower cylinder 13.

A free piston 18 is arranged at the bottom of the lower cylinder 13,
A chamber 19 below the free piston 18 is filled with pressurized gas.

A piston 20 having a suitable restricting orifice is further disposed within the lower cylinder 13 to allow the upper oil chamber 2 to pass through the lower cylinder 13.
1 and a lower oil chamber 22.

The upper end of the lower cylinder 13 is closed by an end wall 23, and the piston rod 27 fixed to the piston 20 is closed by the end wall 23.
3 and extends in the axial direction inside the upper cylinder 12.

An end plate 2 having ventilation holes 24 and 25 at the upper end of the upper tube 12
6 is fixed by screws or the like, and the upper end of the piston rod 27 is fixed to this end plate 26.

A cap 28 is attached to the end plate 26.

A compression spring 29 is disposed within the upper tube 12 so as to act between the end wall 23 of the lower tube 13 and the end plate 26 of the upper tube 12.

The upper tube 12 has a mounting portion 1 to the lower fork bracket 4.
2a is configured to be thicker than its upper portion, and the wall thickness gradually decreases downward from the lower fork bracket mounting portion 12a.

All of this reduction in wall thickness is provided by a change in the outer diameter of the upper tube 12.

In this way, by increasing the wall thickness of the upper tube 12 at the attachment portion 12a, the section modulus of this portion against bending increases, and the bending strength increases.

Therefore, it is possible to reduce the wall thickness of the upper cylinder 12 as a whole and make it lightweight.

Note that the weight can be further reduced by configuring the outer diameter of the attachment portion 12a to be an ellipse that is long in the running direction.

Further, since the wall thickness of the upper tube 12 gradually decreases upward and downward from the lower fork bracket mounting portion 12a, the bending stress generated in the upper tube against the bending load can be made uniform.

Furthermore, the outer cylinder can maintain the required rigidity while keeping the weight to a minimum.

As explained above, in the present invention, the upper cylinder has a larger diameter than the lower cylinder, and the lower cylinder is slidably inserted into the upper cylinder, so that the large diameter cylinder with strong bending strength can be used to handle large bending loads. Fork bracket mounting can be used for mounting parts, and by increasing the outside diameter, the section modulus of the upper cylinder at the fork bracket mounting part can be increased, making the upper cylinder thinner overall and reducing the weight of the front fork. It becomes possible to measure.

In addition, the section modulus of the upper tube is gradually reduced by gradually decreasing the outer diameter while keeping the inner diameter constant downward from the fork bracket mounting area, so that the section modulus of the upper tube is reduced in response to bending loads. Bending stress can be made uniform.

Furthermore, parts such as springs are placed inside the upper cylinder, so
If the inner diameter is changed vertically to change the wall thickness of the upper cylinder, the inner diameter must be expanded to avoid interference with the parts placed inside the upper cylinder, making the entire upper cylinder larger. However, in the present invention, since the inner diameter of the upper cylinder is constant, it is possible to make the outer cylinder as small as possible.

[Brief explanation of drawings]

The drawing is a partially cutaway front view of a front fork showing an embodiment of the present invention. 3... Upper fork bracket, 4...
・Lower fork bracket, 12... Upper tube,
13...Lower cylinder.

Claims (1)

[Scope of utility model registration request] It consists of an upper cylinder and a lower cylinder that are slidably fitted into each other,
In the front fork of a two-wheeled motor vehicle, the upper tube is attached to the upper fork bracket at the upper part and to the lower fork bracket at the lower part thereof, and the lower tube is attached to the front wheel at the lower end, the upper tube is attached to the front wheel. A lower cylinder having a larger diameter than the lower cylinder is inserted into the upper cylinder, and the cross-sectional shape of the upper cylinder is thickened at the lower fork bracket mounting portion by gradually changing the outer diameter while keeping the inner diameter constant; A front fork for a two-wheeled motor vehicle, characterized in that the front fork is gradually thinner upward and downward from the lower fork bracket attachment part.