GB2045892A

GB2045892A - Fluid separation valves in hydropneumatic shock absorbers

Info

Publication number: GB2045892A
Application number: GB8006054A
Authority: GB
Original assignee: Tokico Ltd
Current assignee: Tokico Ltd
Priority date: 1979-02-23
Filing date: 1980-02-22
Publication date: 1980-11-05
Also published as: BR8001068A; DE3006174C2; GB2045892B; FR2449827B1; FR2449827A1; DE3006174A1

Abstract

A hydraulic damper comprises a dual-tube type housing consisting of inner and outer tubes 2, 6, a piston working in the inner tube and dividing the interior thereof into two oil chambers, a piston rod 10 secured to the piston and extending through one of the oil chambers and to the outside of the housing, a reservoir chamber C defined between the inner and outer tubes and containing therein oil and gas, a seal member 17 sealing the housing from the outside and receiving slidably therethrough the piston rod, a resilient valve member 20 having an annular lip portion 20b acting as a one-way valve for allowing fluid flow only from the one oil chamber to the gas containing portion of the reservoir chamber C. The lip portion of the valve member extends in the direction generally parallel to the axis of the damper and the base portion 20c of the lip portion is retained to prevent deformation thereof in the radially inward direction with respect to the axis of the damper. The base portion 20c is retained either by part of the seal as shown or by a rigid member disposed between the seal and the valve member. <IMAGE>

Description

SPECIFICATION Hydraulic damper This invention relates to hydraulic dampers for use in such as vehicle suspension systems.

One of prior art hydraulic dampers includes a dual tube type housing consisting of inner and outer tubes, a piston working in the inner tube and dividing the interior thereof into two oil chambers, a piston rod secured to the piston and extending through one of the oil chambers and to the outside of the housing, and a reservoir chamber defined between the inner and outer tubes and containing therein oil and gas. In response to the movement of the piston the oil in the inner tube communicates with the oil in the reservoir chamber to compensate the volumetric change of the inner tube which is caused of the piston rod moving into or out of the inner tube.In operating the damper small amount of gas will sometimes be contained in the inner tube according to aeration phenomenon or the like and it is neces sary to return the gas in the inner tube to reservoir chamber for maintaining the normal damping characteristics of the damper. Further, it is required to prevent the gas in the reservoir chamber from entering into the inner tube particularly when the pressure in the one oil chamber decreases in the contraction stroke of the damper.

Therefore, the one chamber in the inner tube through which the piston rod extends has usually been connected with gas containing portion of the reservoir through passage means having a check valve. The check valve allows the fluid flow from the one oil chambertothe reservoir and blocks the fluid flow in the opposite direction. The check valve usually comprises a resilient valve member having a lip portion movable to open or close the valve. The valve member shall have sufficient flexibility so as to displace quickly in opening the valve and, also, shall have sufficient stiffness so as to maintain the closed condition of the valve against the gas pressure in the reservoir chamber. However, it is difficult to satisfy these contrary requirements and various proposals have been made with respect to the material, hardness, thickness or the like.For example, when the base portion of the lip portion is made of soft material or formed to have a thin thickness to satisfy the former requirement, then the valve member cannot withstand the gas pressure. When the stiffness of the base portion of the lip portion is increased, the valve opening characteristics will be impaired.

The present invention solves the problems aforementioned and, according to the invention, there is provided a hydraulic damper comprising a dual-tube type housing consisting of inner and outer tubes, a piston working in the inner tube and dividing the interior thereof into two oil chambers, a piston rod secured to the piston and extending through one of the oil chambers and to the outside of the housing, a reservoir chamber defined between the inner and outer tubes and containing therein oil and gas, passage means connecting the one oil chamber with gas containing portion of the reservoir chamber, a seal member sealing the housing from the outside and receiving slidablytherethroughthe piston rod, a resilient valve member having a lip portion acting as a one-way valve for allowing fluid flow only from the one oil chamber to the gas containing portion of the reservoir chamber through the passage means, the lip portion extending from the base portion generally in the direction of the axis of the damper, and means for retaining the base portion of the valve member to receive at least a part of a force of gas pressure acting on the base portion in the radially inward direction with respect to the axis of the damper.

Preferably, a rod guide is secured to the inner tube to close said one oil chamber and to guide the sliding movement of the piston rod, a cover is secured to the outer tube to close one end of the housing and retaining the seal member, passage means includes the clearance between the rod guide and the piston rod, and the lip portion of the valve member coacts with the rod guide.

For a better understanding of the invention, reference will now be made to the accompanying drawings, in which: Fig. 1 is a longitudinal sectional view of a hydraulic damper according to the invention; Fig. 2 is an enlarged view of the essential portion of Fig. 1; and Fig. 3 is a view similar to Fig. 2 but showing a modified form.

The hydraulic damper illustrated in Figs. 1 and 2 comprises a dual-tube type housing 1 consisting of an inner tube 2 and an outer tube 6. The inner tube 2 is formed of a tubular body 3, a rod guide 4 closing the upper end of the tubular body 3 and a bottom flange 5 closing the lower end of the tubular body 3.

The outer tube 6 is formed of a tubular body 7 with the upper and lower ends of which being closed respectively by an end cover 8 and the end flange 5.

The rod guide 4 acts to locate the innertube 2 coaxially with respect to the outer tube 6. A piston 9 works in the inner tube 2 and divides the interior thereof into two oil chambers A and B. A piston rod 10 secured to the piston 9 extends through the oil chamber B, which is referred as one oil chamber, the rod guide 4, a seal member 17 retained by the end cover 8, and the end cover 8, to the outside of the housing 1. Mounting rings 11 are secured respectively to the outer end of the piston rod 10 and to the end flange 5 for mounting the hydraulic damper on such as a vehicle.

The chambers A and B are filled with oil 12, and a reservoir chamber C defined in an annular space between the inner and outer tubes 2 and 6 contains oil 12 in the lower portion thereof and pressurized gas 13 in the upper portion thereof. The lower portion of the reservoir chamber C is connected to the oil chamber A through an opening 14 which is formed in the lower portion of the inner tube 2 and the passage area of which is determined to have a throttling effect. A damping force generating mechanism known perse is provided on the piston 9. In the embodiment, the mechanism includes a plurality of passages 15 formed through the piston 9 to connect the chambers A and B, and a resilient valve disc 16 for opening or closing the passages 15.

As shown clearly in Fig. 2, the seal member 17 slidably engages with the outer circumference of the piston rod 10 and is fitted in the inner periphery of the end cover 8 thereby sealing the interior of the housing 1 from the outside. An annular valve chamber D is defined in the space between the seal member 17 and the rod guide 4. The valve chamber D communicates with the oil chamber B through a small clearance 18 between the piston rod 10 and the rod guide 4 and is connected with gas receiving portion of the reservoir chamber C through acut-out portion or passage 19 in the rod guide 4. Thus, the chambers B and C are connected by passage means including passages 18 and 19 and the chamber D.

Disposed in the valve chamber D is a valve member 20 formed of a resilient material such as rubber or the like. The valve member 20 has an annulay form with a flange portion 20a extending in generally radial direction with respect to the axis of the damper and an annular lip portion 20b extending in generally vertically downward direction. The flange portion 20a is urged againstthe lower surface of the seal member 17 by a spring 22 acting between the rod guide 4 and a retainer 21.

An annular recess 4a is formed in the upper surface of the rod guide 4, and a valve seat 4b cooperating with the lip portion 20b of the valve member 20 is defined on the inside wall of the recess 4a. When the lip portion 20b engages with the valve seat 4b, the valve member divides the valve chamber D into an inner chamber D, communicating with the passage 18 and an outer chamber D2 communicating with the passage 19 and isolates the communication there between thus isolating the reservoir chamber C from the oil chamber B. When the lip portion 20b sepa rates from the valve seat 4b the chambers B and C are connected.

The displacement of the lip portion 20b with respect to the valve seat 4b in engaging therewith or separating therefrom is effected by the rocking movement of the lip portion 20b in the direction of the radius of the piston rod 10 and around a base portion 20c of the lip portion 20b. The base portion 20c is defined by the portion connecting the lip portion 20b and the flange portion 20a. The base portion 20c has a thickness larger than that of the tip end portion of the lip portion 20c and is supported by an annular projection 17a of the seal member 17 projecting from the lower surface of the seal member 17. The projection 17a receives slidablythe piston rod 10 therethrough and has a sufficient thickness in the radial direction to support the base portion 20c thereby preventing the lip portion 20b from excessive radially inward deformation.Further, the flange portion 20a of the valve member 20 and the lower surface of the seal member 17 to which the flange portion 20a abuts are inclined upwards in the radially outward direction whereby the valve member 20 can reliably be aligned with respect to the seal member 17. The valve member 20 may integrally be secured to the seal member 17 by bond ing agents or the like.

The valve member 20 has another lip portion 20d on the outer circumference of the flange portion 20a for engaging with the inner surface of the end cover 8 thereby enhansing the sealingness of the housing 1. The lip portion 20d can act as a check valve in filling pressurized gas into the reservoir chamber C.

For performing easily the gas filling operation there is formed at least one-cut portion 1 7b in the outer circumference of the seal member 17. In filling gas into the reservoir chamber C the seal member 17 is displaced downward to communicate the cut-out portion 17b with the outside, and pressurized gas is supplied from the outside. The lip portion 20d deflects radially inwardly and separates from the end cover 8. Thus, pressurized gas is supplied to the reservoir chamber C. Thereafter, the pressing force applied on the seal member 17 is released, then, according to the resilient force of the lip portion 20d and to the spring force of the spring 22, the lip portion 20d engages with the inner surface of the end cover 8 to isolate the reservoir chamber C from the outside.

In operation, when the piston rod 10 is pressed inwardly or downwards in the drawing oil 12 in the oil chamber A is compressed by the piston 9 which is secured to the piston rod 10. The outer peripheral portion of the valve disc 16 is deflected in the upward direction, and the oil in the chamber A flows into the chamber B with a damping force being generated. The oil in the chamber A also flows into the reservoir chamber C through the opening 14. The volume of the gas 13 in the reservoir chamber C decreases by an amount corresponding to the ingress of the piston rod 10 into the inner tube 2.The pressure of the gas in the reservoir chamber C acts on the outer circumference of the lip portion 20b to maintain it in the closed condition, but excessive deformation of the lip portion 20b in the radially inward direction is prevented by the base portion 20c abutting with the projecting portion 17a of the seal member 17.

When the piston rod 10 moves in the extending direction or upwards in the drawing, the oil 12 in the oil chamber B is compressed. The inner peripheral portion of the valve disc 16 is deflected downwardly, and the oil in the chamber B flows into the chamber A generating a damping force. Any gas which would be contained in the chamber B due to the aeration phenomenon or the like will pass through the clearance 18 and flow into the inner chamber D1 and, in the extending stroke of the piston, deflects outwardly the lip portion 20b of the valve member 20 and flows into the outer chamber D2. The projecting portion 17a of the seal member 17 does not impede the movement of the lip portion 20b in the radially outward direction, thus the gas in the chamber B will reliably be returned to the reservoir chamber C.

In the embodiment, the damping force generatin'g mechanism mounted on the piston 9 acts in the extension and contraction strokes of the damper, however, a damping force generating mechamism effective in the contraction stroke may be mounted on the bottom end of the chamber A, with the damping force generating mechanism mounted on the piston 9 being effective only in the extension stroke of the damper.

Fig. 3 shows another embodiment of the present invention, wherein an annular retainer 23 having a radially extending flange portion 23a and a vertically extending tubular portion 23b formed of a rigid mat erial such as metals, a hard synthetic resin material or the like is disposed between the seal member 17 and the valve member 20. The tubular portion 23b engages snugly with the radially inner surface of the base portion 20c of the lip portion 20b of the valve member 20 and prevents the base portion 20c from the displacement or deformation thereof in the radially inward direction. The valve member 20 may integrally be secured to the retainer 23 by baking or by bonding agents or the like.

The operation of the embodiment illustrated in Fig. 3 is similar two that of the first embodiment.

As described heretofore, the deformation or dis placement of the lip portion of the valve member in the valve closed condition due to the pressure of the gas in the reservoir chmaber can reliably be prevented and, the valve member can be formed to operate satisfactorily such that the one way valve can open quickly and easily as desired and maintain reliably the closed condition when any gas is not contained in the oil chamber B, thus the operating characteristics of the damper can be improved.

Claims

1. A hydraulic damper comprising a dual-tube type housing consisting of inner and outer tubes, a piston working in the inner tube and dividing the interior thereof into two oil chambers, a piston rod secured to the piston and extending through one of the oil chambers and to the outside of the housing, a reservoir chamber defined between the inner and outer tubes and containing therein oil and gas, passage means connecting said one oil chamber with gas containing portion of said reservoir chamber, a seal member sealing the housing from the outside and receiving slidablytherethrough the piston rod, a resilient valve member having a lip portion acting as a one-way valve for allowing fluid flow only from said one oil chamber to the gas containing portion of the reservoirchamberthrough said passage means, said lip portion extending from a base portion generally in the direction of the axis of the damper, and means for retaining the base portion of the valve member to receive at least a part of a force of gas pressure acting on the base portion in the radially inward direction with respect to the axis of the damper.

2. A hydraulic damper as set forth in Claim 1, further comprising a rod guide secured to the inner tube to close said one oil chamber and guiding the sliding movement of the piston rod, and a cover secured to the outer tube to close one end of the housing and retaining said seal member, said passage means includes the clearance between the rod guide and the piston rod, and said lip portion of the valve member coacts with the rod guide.

3. A hydraulic damper as set forth in Claim 1 wherein said retaining means is an annular projection formed integrally to the seal member and extending in the direction of the axis of the damper, the inner circumference of the projection slidably engaging with the piston rod and the outer circumference thereof snugly engaging with the inner circumference of the base portion of the valve member.

4. A hydraulic damper as set forth in Claim 1 wherein the base portion of the valve member is secured to the inner circumference of an annular retainer which is formed of a rigid material, said retainer being urged against the axially inner surface of the seal member.

5. A hydraulic damper as set forth in Claim 2 wherein said valve member is urged against the axially inner surface of the seal member by a spring acting between the rod guide and the valve member.

6. A hydraulic damper as set forth in Claim 5, wherein the valve member has a second lip portion sealingly engaging with the inner surface of the cover.

7. A hydraulic damper substantially as hereinbefore described with reference to Figures 1 and 2 or Figure 3 of the accompanying drawings.