GB2085556A

GB2085556A - Valve construction

Info

Publication number: GB2085556A
Application number: GB8130103A
Authority: GB
Original assignee: Deutsche ITT Industries GmbH; ITT Industries Inc
Current assignee: TDK Micronas GmbH; ITT Inc
Priority date: 1980-10-08
Filing date: 1981-10-06
Publication date: 1982-04-28
Also published as: GB2085556B; DE3138826C2; SE8105848L; SE453528B; FR2491583A1; NL175456C; NL175456B; DE3138826A1; NL8005547A

Abstract

A shock absorber has a piston (1) in a cylinder (2) attached to a piston rod (3) by means of a bolt (8). Trapped between the piston (1) and an annular valve (13) are two damping members (5, 6) loaded by a spring (14). Each of these damping members is provided with a different number of calibrated damping passages (11) so that they can be assembled in such a way as to provide different damping characteristics. <IMAGE>

Description

SPECIFICATION Valve construction The invention relates to a valve construction, in particular for use in a hydraulic shock absorber, of the kind provided with a piston having liquid passages debouching on a seat face and a valve by which the liquid passages can be closed.

A valve construction of this kind is known from Dutch patent specification 97.561.

The damping characteristic curve of a shock absorber provided with this known valve construction can be adjusted over a certain range by greater or less tensioning of the valve spring.

However, the adjustment range of a damping characteristic curve, obtained in this manner, is insufficient and is extended by selection out of a number of pistons of which the number and the cross section of the liquid passages to the seat face of the valve differ with respect to each other.

In this way the damping characteristic curve can be varied over a wide range by selection of the proper piston combined with a certain adjustment of the valve spring tension.

A drawback of this adjustment method is that a great number of different kinds of pistons, each with its own number and cross section of liquid passages must be separately manufactured and stored. Another drawback is that the pistons in finished condition are very susceptible to damage.

An object of the valve construction according to the invention is to obviate this drawback. This is attained by giving no damping function to the liquid passages in the pistons, by which all pistons can be provided with an equal number of passages with a fixed, relative large cross section. Thus all pistons are equal. The damping function is taken over by an annular damping member between the piston and the valve. By selection, during assembling of the shock absorber, of one damping member out of a number of kinds of damping members with mutual different numbers and cross sections of damping passages, one can meet the requirement of a very wide adjustment range and yet with the application of only one kind of piston.

According to the invention in its broadest aspect, a valve construction, in particular for use in a hydraulic shock absorber, of the kind referred to, is characterised in that at least one annular damping member is arranged between the piston and the valve, this damping member being provided with a number of damping passages extending parallel to the axis of the valve construction.

A further advantage of the valve construction according to the invention is that the application of several stacked damping members between the piston and the valve considerably decreases the required number of different kinds of damping members. It can easily be seen that with the application of, for example, three different kinds of damping members, of which at most two are applied, nine different adjustments can be selected. It is also possible to provide the damping members with slots, whereby two damping members at a time are superimposed and a greater or lesser part of the slots is overlapped by relative rotation of both damping members, by which is created the possibility of continuous or stepwise adjustment.

The damping members are preferably manufactured from sintered material. In this manner damping passages in the damping members are obtained with a very uniform size whereby subsequent calibration is not necessary.

Moreover, this material has a high wear resistance so that wearing of the damping members due to moving contact with the valve is very small.

With the application of the valve construction according to the invention to a piston with a deepened seat face, such as shown for example in Dutch patent specification 97.561, a further advantage can be obtained. Very high demands are made upon a seat face of a valve with regard to the flatness and finishing in connection with leakage which otherwise will appear. However, it is difficult to obtain a deepened seat face for such a finishing. With the application of intermediate damping members according to the invention the demands made upon a deepened face are decreased and this face no longer co-operates with the valve. The face that now co-operates with the valve forms part of the damping member which has, of course, already been machined by grinding before mounting thereof.

Embodiments of the invention will now be described by way of example with reference to the accompanying drawings, of which: Fig. 1 shows a longitudinal section of a part of a hydraulic shock absorber wherein a valve construction according to the invention is applied; and Fig. 2 shows in perspective a set of damping members according to a modified embodiment.

Fig. 1 shows a piston indicated by the reference number 1, which piston can move in a cylinder shown schematically at 2. The piston rod 3 and the piston 1 are fixed together in that the latter is enclosed between the valve housing 4 on the one side and the annular damping members 5 and 6 and the sleeve 7 on the other side, the whole being kept together by means of a bolt 8 threaded in the piston rod 3. Piston 1 is provided with a number of liquid passages 9 equally spaced from the axis, the passages on one side being in communication through the valve housing 4 with the space 10 and on the other side debouching on the damping member 5. Each of the damping members 5 and 6 is provided with a number of calibrated damping passages 11 regularly spaced over a pitch circle, these damping passages debouching on a circular groove 12.The damping passages of the damping members 6 debouch against the annular valve 13 provided with a number of radial cams, which valve is pressed against the damping member 6 by means of a spring 14. The thrust of this spring can be adjusted by rotating the adjustment nut 15.

The shock absorber functions with an outward stroke as follows. At the initiation of this movement a pressure will be built up in the space 10, which pressure is transmitted through the medium within the valve housing 4, the liquid passages 9, the groove 12, and the damping passages of the damping member 6 up to the valve 13. At the moment that the pressure is increased to such an extent that the valve is lifted in opposition to the thrust of the spring 14, the medium will flow from the space 10 to the space at the other side of the piston.

During this movement, a desired piston velocity/damping-force characteristic must be obtained. The desired characteristic can be obtained by a combination of an adjustment of spring 14 by means of the adjustment nut 1 5 and a selection of the number and kind of the damping members 5 and 6. If one can select the damping members out of four kinds, each kind comprising a different number of damping passages or another diameter of damping passages, it can easily be seen that fifteen combinations of damping members are possible when two damping members at a time are placed in the valve. Of course, it is also possible to apply one damping member for each valve construction, in which case for each different damping member adjustment another kind of damping member is required.

The valve construction according to the invention can also be provided with damping member within another embodiment. This embodiment is shown in Fig. 2, in which the two damping members 16 and 1 7 are of identical pattern but are only placed in different relative positions. Both damping members are placed together from the drawn position and applied in the valve construction instead of the damping members 5 and 6. The damping action of both damping members together is determined by their relative position; by relative rotation the overlapping portion of the slot-shaped channels 1 8 becomes smaller or larger and therewith the damping action is increased or decreased.In order to assure that a position once selected does not alter, each damping member is provided with an axial projection 19, engaging one of a series of recesses 20 at the periphery of the other damping member when both damping members are engaged with each other in a certain position. The two members are thus locked together. The recesses are numbered so that, during mounting, an adjustment can be selected in a simple way.

Naturally the projection 1 9 of damping member 1 6 is located at its bottom side and cannot be seen in the drawings.

The different damping members can be manufactured at low cost according to sintering techniques with such close tolerances that no finishing or calibration is required. Moreover, the material has a very high wear resistance which is advantageous because the movable valve 1 3 is resting against it.

The damping during the inward stroke of the shock absorber is assured by a more outwardly located valve construction forming no part of the invention. The function thereof is obvious so that no further description thereof is needed.

Claims

1. A valve construction, in particular for use in a hydraulic shock absorber, of the kind provided with a piston having liquid passages debouching on a seat face and a valve by which the liquid passages can be closed, characterised in that at least one annular damping member is arranged between the piston and the valve, this damping member being provided with a number of damping passages extending parallel to the axis of the valve construction.

2. A valve construction according to claim 1, characterised in that one flat side of a damping member is provided with a round extending groove on which the damping passages debouch, and the position of the groove is selected so that this corresponds with that of the liquid passages in the piston.

3. A valve construction according to claim 2, characterised in that the damping characteristic thereof is also determined by the application of one, or the piling up of several, damping members selected out of a limited number of different kinds of damping members.

4. A valve construction according to claim 1, characterised in that two damping members are applied, that the damping passages in the damping members are slot-shaped, the slots extending over a part of a concentric circle, so that the adjustment of the damping characteristic can be made by relative rotation of both damping members.

5. A valve construction according to claim 4, characterised in that both damping members are equal and each is provided with an axial projection engageable in a recess of the other damping member.

6. A valve construction according to any one of the preceding claims, characterised in that the damping members consist of sintered material.

7. A valve construction, in particular for use in a hydraulic shock absorber, substantially as described with reference to the accompanying drawings.