GB2090948A

GB2090948A - Vibration damper valve

Info

Publication number: GB2090948A
Application number: GB8200283A
Authority: GB
Original assignee: Fichtel and Sachs AG
Current assignee: ZF Friedrichshafen AG
Priority date: 1981-01-14
Filing date: 1982-01-06
Publication date: 1982-07-21
Also published as: IT1145747B; BR8200164A; IT8168727A0; GB2090948B; FR2497894B1; IT8153948V0; DE3100910C2; DE3100910A1; FR2497894A1

Abstract

A damping valve for a hydraulic, pneumatic or hydropneumatic vibration damper which comprises a damping piston (6) which is connected to a piston rod (3) and which subdivides the internal chamber of a cylinder into two working chambers (Fig. 1, not shown), comprises damping channels (16), and a rigid valve body (12) which is subjected to the action of a spring (13) and is axially movable on a cylindrical component (11) to close channels (16) and which, on its inside diameter, has a clearance (21) from the cylindrical component to allow alignment of the valve mating surfaces without high tolerance machining of components 11 and 12, the clearance passage sealed by a sealing ring (17). <IMAGE>

Description

SPECIFICATION Vibration damper valve The invention relates to a damping valve for a hydraulic, pneumatic or hydro-pneumatic vibration damper which comprises a damping piston which is connected to a piston rod and which subdivides the internal chamber of a cylinder into two working chambers, there being provided for damping the piston rod movement damping valves which consist of valve plates or valve bodies and damping channels, and at least one of these damping valves comprising a rigid valve body which is subjected to the action of a spring and is axially movable on a cylindrical component and which, on its inside diameter, forms a section of passage with the cylindrical component.

Such damping valves provided with rigid valve bodies and intended for vibration dampers are very expensive in their production since th'ese require a satisfactory guidance on the cylindrical component, on the one hand, and have to cover the valve ports satisfactorily, on the other hand. In order to obtain a faultless function of the damping valve, the piston valve seats and the contact surface of the valve body therefore must be produced so as to be very exactly perpendicular to the piston rod axis. Even slight variations suffice to bring about a considerable damping force deviation due to leakage. Since the section of passage between the cylindrical component and the inside diameter of the valve body mostly serves as the lead section of the damping valve, very close tolerances have to be observed here, too.For the clear formation of the section of lead, there furthermore becomes necessary between the valve body and the cylindrical component an additional guide, for example by way of radial cams. The above statements show the problems which arise when such rigid valve bodies are used in order to ensure that the damping valve has the required damping force behaviour. Even slight tolerance variations result in a very considerable spread of the damping force characteristic.

Even with a very closely toleranced inside diameter of the valve body and a corresponding tolerancing of the outside diameter of the cylindrical body, a satisfactory resting thereof on the valve ports is not ensured without very severe tolerance requirements having to be imposed on the other shock absorber components which are in communication with the valve.

From DE OS 2 548 049 it is known that the valve body co-operates with a control ring, this control ring forming the section of lead.

Depending on the centric position of this control ring relative to the guide pin, one obtains a varying damping action through this section of lead so that, here too, an exactly defined lead damping is not attained.

It is the object of the present invention to provide a clearly defined fixing of the section of lead, while imposing minimal tolerance requirements on a damping valve designed with a rigid valve body and simultaneously attaining a satsifactory valve function.

This problem is solved in that there is provided, in the zone of the section of passage, a sealing ring which shuts this section. Thus the passage of section between the rigid valve body and the cylindrical component is shut in a simple manner, while the tolerance requirements of these components are very low. Minimal inclinations of the plane surfaces also allow the valve body to cover the valve ports satisfactorily, no jamming occurring in this connection between the valve body and the cylindrical component. This construction furthermore allows a clearly defined fixing of the sections of lead since these are formed, for example, by lead discs between the valve body and the valve seat.Due to the low manufacturing tolerance requirements of such a damping valve provided with a rigid valve body, this valve can be produced very inexpensively and there occurs a clearly defined association and dimensioning of the respective valve function. In relation to the saving in manufacturing costs, the low expenditure for the sealing ring and for a lead disc or a section of lead worked into the valve seat is very small.

As the invention shows, the sealing ring may be provided in a circumferential groove of the cylindrical body or, according to another advantageous constructional form, may be axially movable relative to the cylindrical component and connected to the valve body.

As another feature of the invention shows, the valve body has, for the reception of the sealing ring, a recess which is provided in the zone of its inside diameter and is L-shaped in a longitudinal section, while a disc is provided for the axial fixing of the sealing ring. In this way, there is provided a very easy assembly and fixing of the sealing ring in the valve body. The disc may have a double function, in that it fixes the sealing ring, on the one hand, and is provided with the section of lead of the damping valve, on the other hand.

According to another feature of the invention, a pressure-dependent pressing of the sealing ring against the cylindrical component is brought about in a simple manner in that the recess forms with the sealing ring an annulus which extends in the radial direction and in that the disc has at least one section of passage opening into this annulus.

As the invention shows, the annulus is bounded by a surface extending in the valve body obliquely to the axial direction. Such an inclined plane is very easy to produce and causes an exact position of the sealing ring and simultaneously the possibility of exerting, on the outside diameter of the sealing ring, a radially inwardly directed force on the sealing ring by the internal pressure.

According to another constructional form of the invention, the sealing ring is fixedly connected to the valve body on the inside diameter thereof. The connection may be established, for example, by vulcanising or gluing. Likewise, according to a feature of the invention, the sealing ring is arranged on the inside diameter of a thrust washer, which covers the valve body face, for the sealing of the section of passage between the rigid valve body and the cylindrical component.

Hereinafter, the invention will be explained in more detail with the aid of exemplified embodiments illustrated in the drawings, in which: FIGURE 1 shows a two-tube vibration damper in a longitudinal section; FIGURE 2 shows the piston of the vibration damper shown in Fig. 1, which piston is provided with damping valves, in an enlarged representation; FIGURE 3 shows the piston of a vibration damper, the section of passage between the rigid valve body and the cylindrical component being shut by a sealing ring provided in a groove in the cylindrical component; FIGURE 4 shows a piston with a valve body, to the inside diameter of which a sealing ring is secured; FIGURE 5 shows the arrangement of the sealing ring on the inside diameter of a thrust washer located between the valve seat and the valve body; and FIGURE 6 shows a disc-shaped valve body.

The two-tube vibration damper shown in Fig. 1 consists of the cylinder 1 which is surrounded by the container 2, the compensation chamber 9 being located between the cylinder 1 and the container 2. The piston rod 3 is guided in the piston rod guide 4 secured in the container 2 and is sealed by the piston rod seal 5. For centring the cylinder 1 in the container 2, there serves the piston rod guide 4, on the one hand, and the bottom valve 10, on the other hand. The piston 6 is fixedly connected to the piston rod 3 and divides the internal chamber of the cylinder 1 into the working chamber 7 above the piston and the working chamber 8 beneath the piston. The compensating chamber 9 is in communication with the working chamber 8 beneath the piston 6 through the bottom valve 10.

As the enlarged piston representation according to Fig. 2 shows in particular, the piston 6 is arranged on a lug of the piston rod 3 and is secured by the cylindrical component 1 which is provided with an internal thread, by screwing the same on the external thread of the lug. The pulltype valve, which is operative during the extension of the piston rod from the cylinder, consists of the rigid valve body 12 which, on its inside diameter, is guided on the cylindrical component 11 and, with this component, forms the section of passage 21. The valve spring 13 is supported on the valve body 12, on the one hand, and on the abutment 22, which has been screwed on the thread of the lug for setting the spring pre-loading, on the other hand. Associated with the pull valve are the bores 16 in the piston 6 which end in annular grooves on both sides.The disc 1 4 is clamped between the valve seat and the face of the valve body 12, this disc being provided with the section of lead 1 5.

For sealing the section of passage 21, the sealing ring 1 7 is provided in a recess 1 8 in the valve body 12. This recess 1 8 is approximately L-shaped in design and has a surface 1 9 which extends obliquely to the axial direction and which, together with the outside diameter of the sealing ring 17, bounds an annulus 20.

The valve associated with the pressure lift consists of the elastic valve disc 23 which is clamped in the zone of the inside diameter and on which a pressing spring acts. This valve disc 23 co-operates with the axial bores 24, which are associated with the pressure stage, and has channels which allow the damping medium to flow to the axial bores 1 6 which are associated with the pull stage.

The working chambers 7 and 8 in the interior of the cylinder 1 are filled with damping fluid, while the compensation chamber 9 is filled partly with damping fluid and partly with gas. During the pull lift, that is to say when the piston rod 3 extends, damping fluid flows from the working chamber 7 through the appropriate openings in the elastic valve piate 23 into the axial bores 1 6 in the piston 6. As long as the piston speeds are low, the damping fluid flows through the section of lead 15, which is formed by the disc 14, into the working chamber 8 beneath the piston. The flow resistance through the section of lead 1 5 thus determines the damping force of the piston 6 at low piston speeds.As a result of the sealing ring 17, the section of passage formed between the inside diameter of the valve body 12 and the outside diameter of the cylindrical component 11 is shut so that only the section of lead 1 5 formed by the disc 14 is operative in this phase. At higher extension speeds of the piston rod 3, the pressure difference between the working chambers 7 and 8 also increases. If the force acting on the rigid valve body 12 as a result of this pressure difference is greater than that exerted by the valve spring 13, then the valve body 12 lifts from its seat and opens a section which corresponds to the pressure difference.

The relatively large clearance between the valve body 12 and the cylindrical component 11, which is shown as the section of passage 21, makes it possible, even if there are misalignments between the components associated with the pull valve, that the valve body 12 rests uniformly with its face on the ring-shaped valve seat and thus does not leave clear any uncontrolled section whatsoever. The sealing ring 1 7 centres the valve body 12 and ensures that only the section of lead 1 5 formed by the disc 14 can be operative.

The constructional form shown in Fig. 3 differs from that shown in Figs. 1 and 2 in that the sealing ring 1 7 is provided in a circumferential groove 25 in the cylindrical component 11. During the opening and closing movements of the valve body 12, this latter is thus displaced relative to the sealing ring 1 7. The mode of operation of this valve unit corresponds to that shown in Figs. 1 and 2.

As shown in the constructional form of Fig. 4, the valve body 12 carries on its inside diameter a sealing ring 26 and thereby closes the section of passage 21 formed by the cylindrical component.

The fastening of this sealing ring is preferably effected by vulcanising.

Another exemplified embodiment for the sealing of the section of passage 21 is shown in Fig. 5. Herein, there is provided between the face of the rigid valve body and the disc 14 forming the lead 1 5 a thrust washer 27 which carries the sealing ring 28 on its inside diameter. A similar construction is shown in Fig. 6 which differs from that shown in Fig. 5 in that, in a further simplification of the valve construction, there is provided a valve body 29 in the shape of a circular ring disc. Here, too, the sealing ring 28 connected to the thrust washer 27 closes the section of passage 21 formed between the circular-ringdisc-shaped valve body 29 and the cylindrical component 11.

The damping valve shown and described above with reference to piston pull valves can also be readily used on bottom valves of vibration dampers and/or on piston pressure valves.

The sealing rings 17, 26, 28 are resilient to such an extent that they do not hinder the adaptation of the valve bodies 12, 29 to misalignments.

Claims

CLAiMS

1. A damping valve for a hydraulic, pneumatic or hydro-pneumatic vibration damper which comprises a damping piston which is connected to a piston rod and which subdivides the internal chamber of a cylinder into two working chambers, there being provided for damping the piston rod movement damping valves which consist of valve plates or valve bodies and damping channels, and at least one of these damping valves comprising a rigid valve body which is subjected to the action of a spring and is axially movable on a cylindrical component and which, on its inside diameter, forms a section of passage with the cylindrical component, characterised in that in the zone of the section of passage (21) there is provided a sealing ring (1 7, 26, 28) which shuts this section.

2. A damping valve as claimed in Claim 1, characterised in that the sealing ring (17) is provided in a circumferential groove (25) in the cylindrical component (11).

3. A damping valve as claimed in Claim 1, characterised in that the sealing ring (17, 26,28) is arranged so as to be axially movable relative to the cylindrical component (11) and is connected to the valve body (12, 29).

4. A damping valve as claimed in Claims 1 and 3, characterised in that the valve body (12) has a recess (18), which is provided in the zone of its inside diameter and is L-shaped in a longitudinal section, for the reception of the sealing ring (1 7), and in that a disc (14) is provided for the axial guidance of the sealing ring (17).

5. A damping valve as claimed in Claims 1, 3 and 4, characterised in that the recess (1 8) forms, with the sealing ring (17), an annulus (20) which extends in the radial direction, and in that the disc (14) has at least one section of passage which opens into this annulus (20).

6. A damping valve as claimed in Claims 1,3 to 5, characterised in that the annulus (20) is bounded by a surface (19) which extends in the valve body (12) obliquely to the axial direction.

7. A damping valve as claimed in Claims 1 and 3 to 6, characterised in that the disc (14) has the section of lead (15) of the damping valve.

8. A damping valve as claimed in Claims 1 and 3, characterised in that the sealing ring (26) on the inside diameter of the valve body (12) is fixedly connected to this body.

9. A damping valve as claimed in Claims 1 and 3, characterised in that the sealing ring (28) is provided on the inside diameter of a thrust washer (27) which covers the valve body face.

10. A damping valve for a hydraulic, pneumatic or hydro-pneumatic vibration damper substantially as described herein with reference to the accompanying drawings.