JPH054611Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a structure of a piston portion of a hydraulic shock absorber.

For example, in a front fork that supports the front wheel of a two-wheeled vehicle, an inner cylinder and an outer cylinder fit together slidably,
The structure is such that the upper end piston of the seat pipe installed at the bottom of the outer cylinder slides against the inner periphery of the inner cylinder, and the front fork itself is attached to the vehicle body at an angle.

Therefore, when the inner cylinder moves up and down, both the inner and outer circumferences of the inner cylinder become sliding surfaces, and the sliding resistance is inevitably large. Moreover, as described above, since the front fork itself is attached to the vehicle body at an angle, the support point of the inner cylinder changes from moment to moment, and at the same time, the direction of the load applied to the piston portion also changes.

Incidentally, conventionally, a bush coated with a soft resin has been used as the ring member fitted around the outer periphery of the piston portion in order to minimize the sliding resistance.

However, in the case of a front fork of a two-wheeled vehicle, etc., which is repeatedly subjected to severe impacts, the above-mentioned measures are not sufficient, and not only the sliding resistance is still large, but in the worst case, galling may even occur.

The present invention was developed to solve this problem, and its purpose is to change the ring posture of the piston in response to the direction of the load that changes in a complex manner.
To provide a piston part structure of a hydraulic shock absorber that can suppress sliding resistance of the piston part as low as possible.

In order to achieve such an object, the present invention provides a hydraulic shock absorber in which a band-shaped ring member is fitted around the outer circumference of a piston that slides in a pipe, in which the inner circumferential surface of the ring member and the outer circumferential surface of the piston are made circular. The gist is that they are fitted in an arc-shaped engagement relationship.

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

Fig. 1 is a longitudinal cross-sectional side view of a hydraulic shock absorber having a piston structure according to the present invention, and Fig. 2 is Fig. 1A.
FIG.

In the hydraulic shock absorber shown in FIG. 1, 1 is an outer cylinder, and an inner cylinder 2 is fitted into the outer cylinder 1 from above so as to be vertically slidable. An oil seal 3 that slides on the outer periphery of the inner tube 2 is fitted on the upper inner periphery of the outer tube 1, and a dust seal 4 that also slides on the outer periphery of the inner tube 2 is fitted at the upper end opening of the outer tube 1. It is blocked by.

Also, a seat pipe 5 is installed at the bottom of the outer cylinder 1 with an oil lock piece 6 and bolts 7.
The tip of the seat pipe 5 constitutes a piston portion 5a, and the piston portion 5a is in sliding contact with the inner periphery of the inner cylinder 2 via a band-shaped ring member 8 as shown.

By the way, as shown in detail in FIG. 2, the ring member 8 is fitted into a recess 5b formed on the outer periphery of the piston portion 5a of the seat pipe 5, and a recess 8a having an arcuate cross section is formed on the inner peripheral surface of the recess 5b. A protrusion 5c having a semicircular cross section that protrudes from the outer periphery of the piston portion 5a is engaged with the groove 8a. Due to this engagement relationship, the ring member 8 can be tilted around the groove 8a provided on the inner circumferential surface of the ring member 8.

On the other hand, a free valve 9 that slides on the outer periphery of the seat pipe 5 is fitted on the inner periphery of the lower part of the inner cylinder 2, and a fork bolt 1 is fitted on the upper end of the inner cylinder 2.
0 is screwed on, and a coil spring 11 is stretched between the fork bolt 10 and the seat pipe 5 in the inner cylinder 2 as shown in the figure.

Thus, hydraulic oil is sealed in the hydraulic shock absorber, and in particular, air at a predetermined pressure is sealed in the upper part of the inner cylinder 2.

When the above hydraulic shock absorber is used, for example, as a front fork of a two-wheeled vehicle, the upper end of the inner cylinder 2 is connected to the vehicle body side, the lower end of the outer cylinder 1 is connected to the axle side,
The entire shock absorber is installed inclined at a predetermined angle depending on the caster angle.

When the inner and outer cylinders 2 and 1 relatively expand and contract, the hydraulic oil sealed inside flows, and due to the flow loss that occurs when this hydraulic oil passes through the free valve 9 etc., the required amount is A damping force is generated, and the impact applied from the outside is effectively absorbed and alleviated by this damping force.

By the way, when the outer cylinders 2 and 1 move relative to each other, the inner periphery of the inner cylinder 2 and the piston portion 5a of the seat pipe 5 come into sliding contact via the ring member 8, and there is no sliding contact between these sliding surfaces. Dynamic resistance occurs.

However, as described above, since the cylinder member 8 is tiltable around the engagement portion with the outer periphery of the piston portion 5a of the seat pipe 5, the ring member 8 is tilted in the direction where the sliding resistance is minimized. That is, the ring member 8 and the inner cylinder 2 are inclined in a direction in which they come into uniform sliding contact, and as a result, the pressure distribution on the sliding surfaces of both 2 and 8 becomes uniform, and the sliding resistance is suppressed to a minimum. Furthermore, since the ring member 8 and the inner cylinder 2 come into uniform sliding contact in this way, local contact can be avoided and disadvantageous situations such as so-called galling phenomenon do not occur. Particularly when the hydraulic shock absorber is used as a front fork of a two-wheeled vehicle as described above, the direction of the load applied to the piston portion 5a changes moment by moment, but the ring member 8 follows this change and tilts to minimize sliding resistance. Keep it to.

FIG. 3 is a view similar to FIG. 2 showing a modified embodiment of the present invention, and this is a view in which a concave groove 105c is formed on the outer periphery of the piston portion 105a, and a groove 105c is formed on the inner periphery of the ring member 108, contrary to the one shown in FIG. However, in this modified embodiment, the same effects as described in the first embodiment can be obtained.

As is clear from the above description, according to the present invention, in a hydraulic shock absorber comprising a band-shaped ring member fitted around the outer circumference of a piston sliding in a pipe, the inner circumferential surface of the ring member and the outer circumferential surface of the piston Because the ring member is fitted while maintaining an arc-shaped engagement relationship, the ring member changes its posture in accordance with the direction of the load that changes in a complicated manner, thereby minimizing the sliding resistance of the piston part. be able to.

[Brief explanation of drawings]

The drawings show an embodiment of the present invention.
The figure is a vertical side view of the hydraulic shock absorber, and Figure 2 is Figure 1A.
FIG. 3 is an enlarged detail view of a portion similar to FIG. 2 of a modified embodiment of the present invention. In the drawings, 1 is an outer cylinder, 2 is an inner cylinder, 5 is a seat pipe, 5a is a piston portion, 8 is a ring member, 9 is a free valve, and 11 is a coil spring.

Claims (1)

[Scope of utility model registration request] In the piston part of a hydraulic shock absorber, which is formed by fitting a band-shaped ring member into a recess formed on the outer periphery of a piston that slides in a pipe, an arc-shaped projection is provided at the axial center of the bottom surface corresponding to the outer peripheral surface of the recess. , or a concave groove, and one of the protrusion, an arc-shaped concave groove, or a protrusion that engages with the protrusion or the concave groove is formed in the axial center of the inner peripheral surface of the band-shaped ring member. Piston structure of hydraulic shock absorber.