JPS61116136A - Hydraulic shock absorber - Google Patents

Abstract

PURPOSE:To make a feeling of driving comfortableness yet improvable, by making up an outer circumferential from into a drum type, while preventing the occurrence of sticking in time of piston's sliding motion and thereby improving its slidability so better. CONSTITUTION:With an increase of pressure in an A chamber in time of stretching processes, a skirt 26a receives oil pressure and is deformed to the side of a cylinder 1, and in time of contracting processes, with an increase of pressure in a B chamber 5, a skirt 26b is deformed to the side of the cylinder 1 and sticks fast to it, preventing a leak from occurring. And, since an outer circumference of a plastic band 26 is formed into a drum type, even if a piston 2 is tilted so some extent as it receives lateral force, such a case that an end face of the piston 2 bits into the cylinder 1 and causes a stick penomenon is in no case produced there, thus sliding motion in the piston 2 becomes smoothed, and a feeling of comfortable car driving is yet more improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a hydraulic WI breaker in which a piston is fitted with a resin band having a skirt for preventing oil leakage between the piston and the cylinder.

[Background Art] A hydraulic shock absorber (usually a hydraulic shock absorber) is used in the suspension structure of an automobile. A hydraulic shock absorber consists of a device that includes a piston that is slidable within a cylinder, and that produces a damping effect by utilizing the resistance when oil sealed in the cylinder passes through a boat provided in the piston.

In order for a hydraulic shock absorber to perform its intended function, measures must be taken to prevent oil leakage between the piston and cylinder. Conventional measures against oil leakage between the piston and cylinder are ■
Either provide a ring on the piston side as shown in Figures 8 and 9, ■ Provide a band on the piston side as shown in Figures 10 and 11, or ■ Provide a band on the piston side as shown in Figure 12. Either a ring and a band are provided, or a resin sheet is attached to the outer peripheral surface of the piston as shown in FIG. 13.

Problems to be Solved by the Invention However, each of the above methods has the following problems.

Method (2) is often used for products that do not receive much lateral load, but as shown in FIG. During a transition period when the piston 42 reverses its axial movement, the ring 42 separates from the ring groove of the piston 41, causing a transitional oil leak as shown by the arrow in FIG. In addition, the ring 42 is inserted into the slit 4 as shown in FIG.
2a, leakage also occurs from the slit 42a. When subjected to a rough lateral load, the piston 41 and cylinder 4
It comes into contact with 3 and tends to cause galling.

Method (2) is often used for products that receive large lateral loads, and even when lateral loads are applied, the cylinder 43 and piston 41 do not come into direct contact, and the surface layer 45N of the band 44! Low friction is achieved by contacting with lubricant). However, due to dimensions, there is a gap between the band 44 and the band groove of the piston 41 in the axial direction.
Since a gap is created in the radial direction, a transient oil leak occurs as shown by the arrow in FIG. 10. Furthermore, since the band 44 has a slit 44a as shown in FIG.
Leak also occurs from the slit 44a.

The piston 41 in method (2) has both a ring 42 and a band 44 as shown in FIG.
There are disadvantages of increased cost and friction.

As shown in FIG. 13, the method (2) forcibly covers the outer periphery of the piston 41 with a resin band 46 to obtain good initial contact and seal, and is disclosed in U.S. Patent Nos. 3 and 2.
An example is disclosed in the No. 12,411 specification and drawings. However, conventional pistons usually do not have a resin band skirt as referred to in the present invention, and there was a problem in that the sealing performance was not always good.

Conventionally, the friction between the piston and cylinder was counteracted by installing a sintered layer on the iron plate of low-μ sliding material on the piston side, and using a resin-impregnated bushing as the piston band on the sintered layer. was. In some cases, a low-μ resin or the like is applied to the outer circumferential surface of the piston.

When the piston rod bends and expands and contracts due to lateral loads while the car is running, the piston rod and piston are inclined to the cylinder and come into contact with each other by mV, which reduces the contact area between them and increases the lateral load. In addition, the local surface pressure increases rapidly, which often exceeds the boundary surface pressure and causes stick-slip, which adversely affects ride comfort.

Such a phenomenon occurs to a great extent in strut-type shock absorbers for front-wheel drive automobiles in which the cylinder and piston rod do not have a sufficient length of engagement, because the lateral load on the rod guide and piston portion becomes extremely large.

In order to solve the problem, the sliding gaps between the piston rod and the front guide, and between the piston and the cylinder, should be minimized as much as possible, but in order to ensure smooth operation of the sliding parts, it is necessary to minimize the sliding clearances between the piston rod and the front guide, and between the piston and the cylinder. A gap of In order to solve this problem, Utility Model Publication No. 57-39954 makes the piston outer peripheral surface drum-shaped and the rod guide shaped like a drum to prevent a local increase in surface pressure, but this does not include the concept of a resin band.

The present invention aims to reduce oil leakage between the piston and cylinder by improving the structure of the resin band in a hydraulic shock absorber having a piston equipped with a resin band on the outer circumferential surface. The purpose of this invention is to improve the elasticity between a structured resin band and a cylinder to ensure smooth expansion and contraction of a hydraulic shock absorber.

Means for Solving Problems] The hydraulic shock absorber of the present invention that meets this objective is characterized in that the piston of the hydraulic shock absorber has a piston inserted into the cylinder so as to be freely polished, and the piston is attached to the piston body with a resin band. are fitted and formed, and the stretched side 1. of the resin band is formed. Both ends of the resin band on the binding side extend in the direction along the piston axis from the contact portion with the piston body to form a skirt of the piston, and the outer peripheral surface of the resin band is formed into a drum shape. Become.

In the hydraulic shock absorber, squeeze wrinkles may be formed on the expansion side of the skirt.

Further, the drum-shaped shape of the outer periphery of the resin band may be formed by increasing the thickness of the resin band itself at the center in the axial direction of the piston, or by forming the outer periphery of the piston body into a drum-shaped shape. Good too.

Roughly, unevenness may be formed on the outer circumferential surface of the resin band attachment portion of the piston body.

[Operation] In the hydraulic shock absorber configured as described above, when the piston moves in the cylinder to the extension side, the skirt on the extension side of the resin band is slidably attached to the cylinder by hydraulic pressure, and the screw is closed. In addition, when the piston moves in the cylinder to the contraction side, the skirt of the resin band shrinks and closes to the cylinder so that it can be opened freely by hydraulic pressure, improving the sealing performance between the piston and the cylinder. Improve. By providing the skirt portion in this manner, good sealing performance can be obtained both on the expansion side and on the contraction measurement.

When the expansion side skirt is provided with constriction wrinkles, the expansion side skirt can easily expand in the circumferential direction due to hydraulic pressure, and the sealing performance becomes even better. Since damping force is generally higher on the expansion side than on the contraction side, it is desirable to suppress leakage on the expansion side, and the drawing wrinkles of the present invention satisfy this demand. .

In addition, by making the outer peripheral surface of the resin band into a drum shape, when the piston is tilted under load, the end surface of the piston does not seize against the cylinder.
IQ becomes smoother and riding comfort improves.

Pretext Flow Side] Preferred embodiments of the hydraulic shock absorber of the present invention will be described below with reference to the drawings.

FIG. 1 shows the entirety of a hydraulic shock absorber according to an embodiment of the present invention. In the figure, 1 is a cylinder, into which a piston]/2 is slidably inserted. A piston rod 3 is attached to the piston 2 and extends through one end of the cylinder 1 to protrude outside the cylinder 1.

The side on which the piston rod 3 extends becomes the expansion side of the hydraulic shock absorber, and the opposite side becomes the contraction side. Inside the cylinder 1, the piston 2 creates a chamber A (chamber on the expansion side from the piston 2) 4.8
It is divided into W (on the contraction side from the piston 2) 5, and A chamber 4.
, B=5, a liquid such as oil 6 (hereinafter referred to as oil) is sealed.

The contraction side end of the cylinder 2 (= is provided with a valve case 7. The valve case 7 has an oil sealing space between B and 5.
(Divided into 48 sections.

The cylinder 2 is surrounded by an outer shell 9, and between the outer circumferential surface of the cylinder 2 and the inner circumferential surface of the outer shell 9, a space D to D10 filled with oil and air is formed. D to 10 is connected to C to 8. , DjlO is used to absorb the volume of the piston rod 3 inserted during the contraction side process.

As shown in FIG. 2, an orifice 11 with several circumferences is provided on the upper surface of the piston 2, and a non-return valve 1
2, a seat 13 and a non-return valve spring 14 are installed, and the upper surface of the piston 2 and the lower surface of the non-return valve 12 are installed. The non-return valve 12 is also provided with several holes 15, and the piston 2 is provided with several boats 16 that pass through the piston 2 in the vertical direction. Leaf valve 17, spring seat 18, compression spring 19 on the underside of piston 2
is provided.

As shown in FIG. 3, a conical spring 20 with a weak spring force is attached to the upper surface of the valve case 7. A non-return valve 21 and an orifice 22 are provided. A boat 23 passing through the valve case 7 in the vertical direction is provided, and a leaf valve 24 is provided on the lower surface of the valve case 7.

As shown in FIG. 4, the piston 2 has a piston body 25.
and a resin band 26 fitted around the outer periphery of the piston body 25.
It consists of The resin band 26 does not have a slit in the circumferential direction. Both end portions of the resin band 26 on the expansion side and the contraction side extend in the direction along the piston axis from the contact portion of the resin band with the piston body 25, and are provided with skirts 26a, 26.
b is formed. The skirts 26a and 26b are portions that are not in contact with the outer periphery of the piston body 25.

As shown in FIG. 5, the skirt 26a on the extension side of the skirt is formed with aperture wrinkles that are uneven in the diametrical direction along the circumferential direction.

The outer circumferential surface of the resin band 26 is formed into a drum shape, with the axially central portion bulging in the radial direction and the axially opposite ends contracting in diameter.

This drum-shaped outer peripheral surface may be formed by making the thickness of the resin band 26 itself thicker at the center in the axial direction of the piston and thinner toward both ends, as shown in FIG.
As shown in FIG. 6, the thickness of the resin band 26 may be the same, and the outer peripheral surface of the piston body 25 itself may be formed into a drum shape.

On the outer circumferential surface of the resin band 26 mounting portion of the piston body 25, unevenness 27 that is uneven in the diametrical direction along the vertical direction is formed.

The piston 2 is manufactured as follows.

First, in the piston 2 as shown in FIG. 4, an annular plate-shaped resin sheet in which one of the upper and lower surfaces is raised at the center of the inner and outer peripheries and becomes thicker is attached to the outer periphery of the piston body 25. Press fit and mold. Alternatively, an annular plate-shaped resin sheet having a uniform thickness is press-fitted onto the outer periphery of the piston body 25, and then the outer periphery of the resin band is molded into a drum shape using a jig whose inner periphery is drum-shaped. When press-fitting the resin sheet onto the outer periphery of the piston body 25, use a cylindrical jig with a taper on the inner periphery of the tip, press-fit the resin sheet from the contraction side of the piston body toward the expansion side, and press the inner periphery of the resin sheet. This is done by extending the resin sheet to the contraction side of the piston body 25 and extending the outer periphery of the resin sheet to the expansion side of the piston body. By such press-fitting, the skirts 26a126b can be formed at both ends of the resin band 26, and wrinkles can be naturally formed in the expansion side skirt 26a.

In addition, in the piston 2 as shown in FIG. 6, the outer circumferential surface of the piston body 25 is formed in advance into a drum shape.
This is done by press-fitting an annular resin band of uniform thickness into this.

Note that the resin band 2 is not limited to pasting by press-fitting, and may be formed by injection molding. In this case, by giving the injection mold a drum-shaped shape, the resin band 2
6 can be easily formed into a drum-shaped outer circumference.

Next, the operation of the hydraulic seaming device of the above embodiment will be explained.

First, to explain the damping force generation mechanism during the middle process, in the slow speed region (orifice region), the oil in chamber A 4 passes through several orifices 11 provided on the top surface of the piston 2 to generate damping force. generated and flows to the B chamber 5.

If the speed is a little higher (valve region), it will not be possible to cut by just passing through the orifice 11. By pushing down the leaf valve 17, spring seat 18, and one compression spring, a damping force is generated and flows into Bv5.

In the region where the speed is higher (boat region 1ii), the valve 17 is kept open and oil flows in an amount equal to the area of the boat 16, generating a damping force.

C to 8, D'? to prevent Bi2 from becoming negative pressure. The non-return valve 21 pushes up and opens the conical spring 20, which has a weak spring force, and the oil No. 10 flows into the B air 5.

To explain the damping force generation mechanism during the contraction side process, the pressure of Bi5 increases due to the entry of the piston rod 3, and in the slow speed area (orifice area), the oil of B'[5 is provided on the upper surface of the valve case 7. C! through several orifices 22! i! 8, a damping force is generated.

When the speed is a little higher (valve region), it is not possible to cut the material just by passing through the orifice 22.
A damping force is generated by passing through a notch provided in the non-return valve 21, passing through several boats 23 provided in the valve case 7, and pushing the leaf valve 24 downward, which causes the damping force to flow to the valve 48.

When the speed is higher (boat area), the opening of the leaf valve 24 becomes constant, oil flows in an amount corresponding to the area of the bow 1-23, and a damping force is generated. A sky 4
The oil from B to 5 pushes up the non-return valve spring 14 and the non-return valve 12, which have weak spring force, to open them and flow to Aff4 so that the pressure does not become negative. FIG. 7 shows the relationship between piston speed and damping force.

The damping force is adjusted as follows. First, in the orifice area, the damping force is changed depending on the size of the orifice 11.22.

Further, in the valve region, the damping force is changed by the mounting load and spring constant of the compression spring 19 in the expansion side process, and the damping force is changed by the plate thickness and number of leaf valves 24 in both the contraction processes.

Further, in the boat area, the damping force is changed depending on the size of the area of the boat 16.23.

In the above, the resin band 26 increases the sealing effect and reduces friction when subjected to lateral force. That is, the resin band 26 is 1+, J2 from the end surface of the piston body.
Scars 1-26a and 26b are provided at a distance of z. As shown in FIG. 7, generally the damping force is higher on the expansion side than on the compression side, so in order to suppress leakage on the expansion side more, squeeze wrinkles are provided on the skirt 26a on the expansion side. It is being The drawing wrinkles of the skirt 26a elastically come into close contact with the cylinder 1 in the assembled state, and the AW during the stretching process
As the pressure increases, the skirt 26a deforms toward the cylinder 1 due to the oil pressure, and comes into closer contact with the cylinder 1 to prevent leakage. During the shrinking process, the skirt 26b deforms toward the cylinder side 1 as the pressure in chamber B 5 increases! to prevent leaks.

In addition, since the outer periphery of the resin band 26 is drum-shaped, even if the piston 2 is tilted due to lateral force, the end surface of the piston 2 will not bite the cylinder 1 and stick, and the sliding of the piston 2 will be prevented. becomes smoother, improving the ride comfort of the vehicle.

Also, in the above example! ! ! In the construction, the resin sheet 28
When the resin band 26 is molded from the resin band 26, the cost can be reduced by improving the yield, and the wrinkles on the skirt 26a on the extension side are automatically formed because the molding is performed using a jig 30 having a D-1 taper.

Effects of the Invention As explained above, when using the vacuum shock absorber of the present invention, since piston skirts are formed at both ends of the resin band,
In both the extension process and the contraction process, the skirt comes into close contact with the cylinder, increasing the sealing effect between the piston and the cylinder, and improving the performance of the hydraulic pressure device.

Further, if the expansion side skirt portion is provided with squeeze wrinkles, the sealing effect between the piston and the cylinder can be further enhanced in the expansion side process which requires both forces.

In addition, since the outer peripheral shape of the resin band is thick and shaped, stickiness does not occur and sliding properties are improved, improving the ride comfort of the vehicle.

Further, if the resin band mounting portion of the piston body is provided with unevenness, the resin band can be completely prevented from coming off from the piston body.

[Brief explanation of the drawing]

Fig. 1 is an overall sectional view of a hydraulic shock absorber according to an embodiment of the present invention, Fig. 2 is an enlarged sectional view of the vicinity of the piston in Fig. 1, and Fig. 3 is an enlarged sectional view of the vicinity of the valve case in Fig. 1. FIG. 4 is an enlarged sectional view of the piston in FIG. 1, FIG. 5 is a plan view of the piston in FIG. 4, and FIG. 6 is an enlarged sectional view of the piston in a different form from FIG. 4. , Figure 7 shows the I! of the hydraulic evaporator shown in Figure 1. Temporary force characteristic diagram FIG. 8 is a partial sectional view of a piston with a conventional ring, FIG. 9 is a perspective view of the ring of FIG. 8, FIG. 10 is a partial sectional view of a piston with a conventional band, and FIG. The figures are a perspective view of the band shown in Fig. 10, Fig. 12 is a partial sectional view of a conventional piston having both a ring and a band, and Fig. 13 is a partial sectional view of a conventional piston with a resin sheet attached. . 1...Cylinder 2...Piston 3...Piston body 4...A chamber 5...B to 6...・Oil a... Valve case 8... C chamber 9... Outer shell 10... D seedling 11.22... Orifice 12.21. ...Non-return valve 13...
...Seat 14...Non-return valve spring 15.
...hole 16.23 ... boat 17.24 ... leaf valve 18 ... one spring seat ... compression spring 20 ...
... Conical spring 25 ... - Piston body 26 ... Resin band 26a ... Skirt (expansion side) 26b ... Skirt (contraction side) 27.・・・・・・
・Uneven ridges! ? Figure 5 Figure 7 Figure 8 Figure 9

Claims (5)

[Claims] (1) The piston of the hydraulic shock absorber has a piston slidably inserted into the cylinder, and a resin band is fitted to the piston body, and both ends of the resin band on the expansion side and the contraction side are A hydraulic shock absorber characterized in that the resin band extends in a direction along the piston axis from the contact portion with the piston body to form a skirt of the piston, and the outer peripheral surface of the resin band is formed into a drum shape. . (2) The hydraulic shock absorber according to claim 1, wherein squeeze wrinkles are formed on the expansion side of the skirt. (3) The drum-shaped shape of the outer peripheral surface of the resin band is formed by making the thickness of the resin band itself thicker at the center in the axial direction of the piston and thinner toward both ends in the axial direction of the piston. hydraulic shock absorber. (4) The hydraulic pressure according to claim 1, wherein the drum-shaped outer circumferential surface of the resin band is formed by making the outer circumferential surface of the piston body drum-shaped and making the thickness of the resin band uniform. buffer. (5) The hydraulic shock absorber according to claim 1, wherein an uneven surface is formed on the outer circumferential surface of the resin band mounting portion of the piston body.