KR20080078387A - Shock absorber with free piston having good linear movement capabilty - Google Patents

Abstract

A shock absorber having a free piston with excellent linear mobility is provided to prevent abrasion or scratch on the inner periphery of a tube by using a contact member of teflon material. A shock absorber having a free piston with excellent linear mobility comprises a tube(10) wherein a piston valve(20) is placed, and a free piston(30). The free piston, vertically moved by the reciprocal movement of the piston valve, divides the inside of the tube into an oil chamber(12) and a gas chamber(14). The free piston also has a body(32), and a contact member(34) surface-contacted with the inner periphery of the tube. The contact member is a ring type member inserted into an assembling groove formed along the outer periphery of the body.

Description

Shock absorber with pre-piston with good linear mobility {SHOCK ABSORBER WITH FREE PISTON HAVING GOOD LINEAR MOVEMENT CAPABILTY}

1 is a cross-sectional view showing a shock absorber according to an embodiment of the present invention.

Figure 2 is a view showing a comparison between the present invention and the prior art.

Figure 3 is a view for explaining a shock absorber according to another embodiment of the present invention.

<Code Description of Main Parts of Drawing>

10: tube 12: oil chamber

12a: height chamber 12b: compression chamber

14: gas chamber 20: piston valve

22: piston rod 30: pre-piston

32: body 34: contact member

36: O-ring

The present invention relates to a shock absorber having a pre-piston, and more particularly, to a single tube shock absorber having a pre-piston having good linear mobility.

In general, the shock absorber is installed between the axle and the vehicle body to absorb vibrations or shocks received from the road surface while driving the vehicle to improve ride comfort, and is filled with a fluid such as oil to generate a damping force therein.

Shock absorbers are largely classified into double tube shock absorbers and single tube shock absorbers according to their structure. The double tubular shock absorber is provided with a piston valve in an oil filled inner tube and a gas for use in compensating for pressure changes in the inner tube in an outer tube that is in selective communication with the inner tube.

In particular, the single tubular shock absorber is configured to be provided with an oil chamber and a gas chamber together in a single tube to compensate for the pressure change of the oil chamber through the volume change of the gas chamber. In order to separate the gas chamber and the oil chamber, the pre-piston is installed to move up and down inside the tube.

The conventional pre-piston includes a body having an O-ring insertion groove formed on an outer circumferential surface thereof, and an O-ring having a substantially circular cross section in line contact with the inner circumferential surface of the tube while being fitted in the O-ring insertion groove. The body of the prepiston is designed to have a constant clearance with respect to the inner circumferential surface of the tube and to avoid friction with the tube.

However, in the conventional pre-piston, only a portion of the O-ring is in line with the inner circumferential surface of the tube, so that the left and right eccentricity of the body portion occurs during the movement thereof. Causes partial friction. Such abrasion or partial friction causes wear or scratch on the inner circumferential surface of the tube, and the wear or scratched portion prevents proper separation between the oil chamber and the gas chamber. In addition, the O-ring is thermally cured while in constant contact with the inner circumferential surface of the tube, which is one of the causes of wear on the inner circumferential surface of the tube.

Therefore, the conventional shock absorber using the pre-piston is not strict separation of the gas chamber and the oil chamber is generated a damping lag (damping lag), accordingly, the lack of attenuation in the compression stroke and the reduction of gas reaction force and There is a problem that causes noise and deterioration of the ride caused.

In the conventional shock absorber, the problems caused when the prepiston is operated eccentrically are summarized as follows.

-An abnormal gap occurs between the tube and the prepiston, and oil from the oil chamber may flow into the gas chamber.

-Gas in the gas chamber can be introduced into the oil chamber through the above gap, and some of the gas is dissolved in the oil, but some remain in the top of the oil in the form of bubbles, which is the main cause of the damping force lag phenomenon. May be.

Increasing the amount of oil in the gas chamber interferes with normal compression stroke, and the reaction force rises as much as the volume of the gas chamber is reduced, so that the impact is transmitted to the vehicle, thereby reducing the riding comfort.

In contrast, a technique has been proposed in which the outer peripheral surface of the prepiston body is anodized so that the anodizing surface contacts the inner surface of the tube. However, the anodizing process is expensive, and there is a problem in that it is very difficult to control the thickness of the anodizing layer for processing such that the inner surface of the tube and the anodizing surface are in contact with each other.

SUMMARY OF THE INVENTION The present invention has been made to solve the problems of the prior art, and means for suppressing abrasion or scratch on the inner circumferential surface of a tube and improving the linear mobility of the prepiston, on a small cost and in a simple manner, on the outer circumferential surface of the prepiston. There is a technical problem in providing the shock absorber.

The present invention provides a shock absorber including a tube in which a piston valve is reciprocally received, and a pre-piston which is vertically moved by a reciprocating motion of the piston valve and partitions the inside of the tube into an oil chamber and a gas chamber. The pre-piston includes a body and a contact member made of Teflon material provided on the outer circumferential surface of the body and in surface contact with the inner circumferential surface of the tube.

The contact member may be a ring-shaped member fitted into an assembly groove formed along the outer circumferential surface of the body, or may be molded on the outer circumferential surface of the body.

In addition, the pre-piston is preferably provided on the body so as to be spaced apart from the contact member in the longitudinal direction, and preferably further comprises an O-ring in line contact with the inner peripheral surface of the tube.

Hereinafter, exemplary embodiments of the present invention will be described with reference to the accompanying drawings.

Example

1 is a longitudinal sectional view showing a shock absorber according to an embodiment of the present invention.

Referring to FIG. 1, the shock absorber 1 according to the present embodiment includes a cylindrical tube 10, a piston valve 20 accommodated in the tube 10, and one end of the piston valve 20. Piston rod 22 is connected to the other end and the other end extending to the outside of the tube 10, and the pre-piston 30 for partitioning the tube 10 into the oil chamber 12 and the gas chamber 14 It includes.

The piston valve 20 is located in the oil chamber 12 and reciprocates in the tube 10 according to the relative movement between the piston rod 22 and the tube 10. The oil chamber 12 is divided into an expansion chamber 12a immediately above the piston valve 20 and a compression chamber 12b directly above the prepiston 30 by the piston valve 20. When the piston valve 20 rises by the rebound stroke, the pressure in the compression chamber 12b is lowered. When the piston valve 20 drops by the compression stroke, the pressure in the compression chamber 12b is decreased. Increases. As such, as the pressure in the compression chamber 12b decreases, the pre-piston 30 also repeatedly rises and falls.

The pre-piston 30 is provided to compensate for the pressure change in the oil chamber 12 according to the reciprocating motion of the piston valve 20, the enlarged view of Figure 1 is a preferred structure of the pre-piston 30 well Is shown.

Referring to the enlarged view of FIG. 1, the prepiston 30 includes a body 32, a contact member 34, and an o-ring 36. For example, the body 32 may be made of a metal material, such as aluminum, which is lightweight and has good corrosion resistance, or may be made of a resin material such as an engineering plastic that well withstands high temperature and high pressure conditions. In addition, an O-ring insertion groove 322 is formed on an outer circumferential surface of the body 32, and an O-ring 36 having an approximately circular or oval cross section is fitted into the O-ring insertion groove 322.

At this time, the O-ring 36 is inserted into the O-ring inserting groove 322 to protrude slightly from the outer circumferential surface of the body 32, so that the inner circumferential surface and the approximately line of the tube 10 by the cross-sectional shape of a substantially circular or elliptical shape Can be contacted. The o-ring 36 may be slightly pressed against the inner circumferential surface of the tube 10 to some extent contact, but the most ideal contact form is a line contact in a circular or elliptical cross-sectional state, so in this specification, the o-ring 36 is a tube ( 10) is considered to be in line contact.

The contact member 34 is installed on the outer circumferential surface of the body 32 to be spaced apart from the O-ring 36 in the longitudinal direction and in surface contact with the inner circumferential surface of the tube 10. According to a preferred embodiment of the present invention, the contact member 34 is formed by molding a TEFLON resin on the outer circumferential surface of the body 32. The Teflon resin forms a very stable compound due to the strong chemical bonding of fluorine and carbon, and thus has almost perfect chemical low friction coefficient, chemical inertness and heat resistance, and non-tackiness. At this time, since the contact member 34 made of Teflon resin having a low friction coefficient is in surface contact with the inner circumferential surface of the tube 10, the pre-piston 30 performs linear movement without any eccentric behavior from side to side within the tube 10. You can do it. At this time, the contact member 34 of the pre-piston 30 is preferably the same as the Teflon material employed between the piston valve 20 and the tube 10.

2 is a view for comparing the behavior in the tube 10 of the pre-piston 30 and the behavior in the tube 10 'of the conventional pre-piston 30 according to the above embodiment.

Referring to Figure 2 (a), the pre-piston 30 of the present embodiment, since the contact member 34 made of Teflon resin is in surface contact with the inner peripheral surface of the tube 10 without play, the pre-piston 30 in any situation ) Can do linear movement without eccentricity from side to side. On the other hand, referring to Figure 2 (b), the conventional pre-piston (30 ') is between the tube 10 and the outer peripheral surface of the body 32 with the O-ring 36' in line contact with the inner circumferential surface of the tube (10) Since there is play in the pre-piston 30 ', the pre-piston 30' may be eccentric left and right, which means that the corner portion of the pre-piston body 32 'is abnormally rubbed on the inner circumferential surface of the tube 10', so that the tube 10 ' ), Furthermore, causing wear or scratch on the body 32 '. In addition, such abrasion or scratches may cause gas in the gas chamber 14 to flow into the oil chamber 12, thereby causing a lack of attenuation and a reduction in gas reaction force in the compression stroke due to the damping lag. In addition, such a lack of attenuation and gas reaction force degradation may cause noise and deterioration of ride comfort.

3 is a view for explaining the structure of the pre-piston 30 according to another embodiment of the present invention, referring to FIG. 3, the pre-piston 30 of the present embodiment, unlike the pre-piston of the previous embodiment, Teflon A ring-shaped contact member 34 preformed with resin is inserted into the assembly groove 324 formed along the outer circumferential surface of the body 32. The contact member 34 according to the present embodiment is also in surface contact with the inner circumferential surface of the tube 10. In this embodiment, since the contact member 34 is formed in a simple manner of fitting into the assembly groove 324, it is easier to produce the pre-piston 30 having a structure in which the Teflon resin is in surface contact with the tube 10. Makes it possible.

In the description of the above embodiment, only the pre-piston 30 is installed with the contact member 34 and the O-ring 36, but the pressure in the tube 10 is small, the oil chamber 12 only by the contact member 34 The o-ring 36 may be omitted in the shock absorber having a specification capable of the gas chamber 14.

While the invention has been described above with reference to specific embodiments, various modifications, changes or modifications may be made in the art within the spirit and scope of the appended claims, and thus, the foregoing description and drawings It should be construed as illustrating the present invention rather than limiting the technical spirit of the present invention.

According to the present invention, for example, in a single tubular shock absorber including a pre-piston, by using a Teflon-based contact member that can be installed on the outer circumferential surface of the pre-piston in a low cost and simple manner, the conventional pre-piston It can easily suppress abrasion or scratches on the inner circumferential surface of the tube caused by abnormal conditions and behavior of the tube.

Claims (5)

A tube in which the piston valve is reciprocally received; It includes a pre-piston is moved up and down by the reciprocating motion of the piston valve, partitioning the tube into an oil chamber and a gas chamber; The pre piston has a body and a contact member provided on an outer circumferential surface of the body and in surface contact with an inner circumferential surface of the tube; Shock absorber comprising a. The shock absorber according to claim 1, wherein the contact member is a ring-shaped member which is fitted into an assembly groove formed along an outer circumferential surface of the body. The shock absorber according to claim 1, wherein the contact member is molded on the outer circumferential surface of the body. The shock absorber according to any one of claims 1 to 3, wherein the prepiston further includes an O-ring installed in the body so as to be spaced apart from the contact member in the longitudinal direction, and contacting the inner circumferential surface of the tube. . The shock absorber according to any one of claims 1 to 3, wherein the contact member is made of Teflon material.

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