GB2269437A

GB2269437A - Shock absorbers

Info

Publication number: GB2269437A
Application number: GB9316436A
Authority: GB
Inventors: Juergen Breitenbacher; Dieter Wiltsch; Martin Scheffel; Andreas Berner; Hans Haecker; Dieter Kawa; Martin Kirschner; Steffen Schneider; Ewald Spiess
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1992-08-08
Filing date: 1993-08-06
Publication date: 1994-02-09
Also published as: KR940004232A; FR2694613A1; DE4320446A1; JPH06185563A; GB9316436D0

Abstract

In a shock absorber, in which an adjustable control valve device (36) for influencing the damping for both compression and extension is disposed inside the piston (14), a connection (50), including a non-return valve (43), leads from a second working chamber (22) or a storage chamber (30) into a first working chamber (21). The connection (50) prevents foaming of the pressure medium in the first chamber (21). <IMAGE>

Description

2269437

DESCRIPTION SHOCK ABSORBERS

The invention relates to shock absorbers for motor vehicles for influencing a relative movement between two masses which are movable relative to one another. One of the two masses is a vehicle body and the other mass is a wheel carrier carrying a rotatable vehicle wheel.

In a known shock absorber, a piston rod, penetrates a cylinder. and has a pistonf which is supported in an axially displaceable manner in the cylinder and divides an interior of the cylinder into a top working chamber and a bottom working chamber. There is also a storage chamber which is partially filled with a gas. An extension-damping valve and a non-return valve are situated in the piston. The storage chamber is connected via a further non-return valve and via a compression-damping valve to the second working chamber remote from the piston rod. During the outward or extension stroke, the non-return valve in the piston is closed and the volume displaced from the first working chamber flows via the extension-damping throttle into the second working chamber and, at the same time, pressure medium may flow from the storage chamber via the second nonreturn valve into the second working chamber. During -2an inward or compression stroke, the second non-return valve. between the second working chamber and the storage chamber is closed and the volume displaced by the piston rod flows via the compression-damping valve into the storage chamber. At the same timei pressure medium may pass, via the first non-return valve in the piston, from the second working chamber into the first working chamber. During the outward stroke, the extension-damping throttle in the piston determines the damping of the shock absorber and, during an inward stroker the compression-damping valve connected to the cylinder determines the damping of the shock absorber. A known shock absorber of said type is generally referred to as a double-tube shock absorber. Such a shock absorber is illustrated, for example, in the book by Reimpell: 11Fahrwerktechnik: Stopd&mpfer" (Chassis technology: shock absorbers)y lst edition 1983, Vogel-Buchverlag WUrzburgi on page 22.

Such a shock absorber is used preferably as passive, i.e. noncontrollable shock absorbers. If the damping of said shock absorber is to be controllable, it is a drawback that the extensiondamping valve responsible for the outward stroke is disposed in the piston and the compression-damping valve responsible for the inward stroke is disposed on the cylinder. This namely has the drawback of - 3requiring electric leadwires to be laid to both valves. Since-the piston or the piston rod moves relative to the cylinder, a suitable and simple laying of the electric leadwires is not possible and an early breakdown of controllability has to be expected. due to defective electric leadwires.

An attempt to avoid the problem outlined above involved placing the valve responsible for the inward stroke and the valve responsible for the outward stroke in the piston. Such a shock absorber is illustrated in DEA-32 46 697. The field of application for this shock absorber is however very limited because, a problem-free meaningful variation in the damping force is not possible. With this shock absorber, in the event of excessive damping during an inward stroke, too much pressure medium is pressed out of the diminishing bottom working chamber via a bore into the storage chamber and there is an insufficient afterflow of pressure medium into the top annular working chamber, with the result that the pressure in the t op working chamber drops too much and the pressure medium situated there foams up. ioe. gas bubbles may escape from the pressure medium. This is very unpleasant, especially as, at the start of an outward stroke, the space arising as a result of gas evolution completely flattens out first before damping -4may set in again. With the shock absorber. the maximum adjustable damping for the inward stroke is very limited.

There is also a shock absorber in which an attempt is made to avoid gas evolution or foaming of the pressure medium during the inward stroke in the rod-side working chamber. Such a shock absorber is disclosed in DE-A33 03 293 or in the patent belonging to the same family, US 45 61 524. This shock absorber however demands a high constructional outlay and is therefore very expensive. in addition, at the bottom end the shock absorber requires an additional slide valve which has to be fitted in very precisely and which. at the slightest manufacturing defect and/or dirt in the pressure medium, may have a tendency to jam. The additional slide valve is situated between the working chamber at the bottom end and the storage chamber. in said shock absorber, during an inward stroke pressure medium should be able to pass from the storage chamber into the top working chamber surrounding the piston rod. During an outward stroke. however, the reverse path has to be blocked. For appropriate control of the process, the additional slide valve disposed in the bottom region of the cylinder is required.

In accordance with the present invention there is provided a shock absorber for influencing a relative movement between two masses which are movable relative to one another, having a cylinder containing a pressure medium, a piston rod and a piston which divides an interior of the cylinder into a first working chamber and a second working chamber, the cylinder being adapted to be coupled to one of the two masses and the piston being supported in an axially displaceable manner in the interior of the cylinder and being adapted to be coupled to the other of the two masses via the piston rod penetrating the first working chamber, the shock absorber further having a storage chamber, the storage chamber being connected via a valve device to the second working chamber, an adjustable control valve device via which the two working chambers are connectable to one another, and a connection monitored by a non-return valve, via which pressure medium may be supplied from the second working chamber via the valve device into the first working chamber and/or from the storage chamber into the first working chamber.

This has the advantage that foaming of the pressure medium or evolution of gas dissolved in the pressure medium is avoided by simple, operationally reliable measures.

Preferably the control valve device is disposed in the piston, which is effective both during the inward stroke and during the outward stroke, without said measure giving rise to the risk of foaming of the pressure medium.

From the second working chamber, the pressure medium may pass via the valve device into the connection leading into the first working chamber. During an inward stroke, the volume displaced by the piston rod passes into the storage chamber.

The provision of throttle device, through which the pressure medium flowing from the valve device into the storage chamber has to flow, ensures an increase of the pressure in the connection. which offers the advantage that the pressure medium passes via the connection with a slightly increased pressure into the first working chamber so that. even in the case of a connection with a narrow cross section, foaming of the pressure medium is avoided.

If the pressure medium flowing through the throttle device is branched off not at the start of the connection but part-way along said connection, this leads, with little effort and a slight throttling of the pressure medium, and to a reliable increase in the pressure of the pressure medium flowing via the connection into the first working chamber.

Preferably, there are two tubes one inserted into the other. The inner tube accommodates the two working chambers and the connection is conveyed through the gap formed between said two tubes. This offers the advantage of ease of manufacture and the connection advantageously increases the overall volume of the shock absorber only very marginally.

If the clearance between the two tubes, viewed in cross section, is arranged with a differing radial clearance relative to one another. then, given the same free cross-sectional area between the two tubes, the resistance for the pressure medium flowing through the connection is advantageously particularly low.

By way of example only specific embodiments of the present invention will now be described with reference to the accompanying drawings, in which:Figures 1 to 6 each show a sectional view through one embodiment of a shock absorber constructed in accordance with the invention.

The shock absorber according to the invention may be used in all cases where the intention is to enable influencing of the relative movement between two masses which are movable relative to one another and where said influencing is to be controllable. The shock absorber may be used particularly in motor vehicles to influence the relative movement between a -8vehicle body and a wheel carrier carrying a vehicle wheel, Figures 1 to 4 show the essential features of the invention. In order to be able to show the essential features as large as possible while taking up a reasonable amount of room, various gaps inside the shock absorber are shown in a truncated form. In particular, the stroke of the shock absorber relative to the diameter of the shock absorber may be much greater than is suggested by Figures 1 to 4. And, s ilarly to allow the essential features of the invention to be shown as large as possible. Figures 1 to 4 and 6 in each case show only the left half of the shock absorber. It is a simple matter for the person skilled in the art to complete the shock absorber by adding on the other half.

Figure 1 shows a cylinder 2 of a shock absorber. The cylinder 2 comprises an inner tube 4, a middle tube 6, an outer tube 8, a rod-side end 10 and a bottom end 12. Inside the inner tube 4 of the cylinder 2, an inner chamber is formed between the two ends 10, 12. In the inner chamber, a piston 14 is supported in an axially displaceable manner on the inner tube 4. The piston 14 is connected to a piston rod 16. The piston rod 16 penetrates the rod-side end 10 and leads out of the inner chamber of the cylinder -g2. In the region of the end remote from the piston 14, the piston rod 16 is connected to a first mass 18. The cylinder 2 is coupled or connected to a second mass 19. The first mass 18 is, for example, a vehicle body and the second mass 19 is, for example, a wheel carrier such as, for example, a vehicle axle on which a vehicle wheel (not shown) is supported.

The piston 14 divides the inner chamber of the cylinder 2 into a first working chamber 21 and a second working chamber 22. The first working chamber 21 is situated between the rod-side end 10 and the piston 14 and is penetrated by the piston rod 16. The second working chamber 22 is situated between the piston 14 and the bottom end 12. A seal 24 provided between the rod-side end 10 and the piston rod 16 seals off the first working chamber 21 from the outside. A guide element 26 disposed on the outer periphery of the piston 14 provides a seal between the piston 14 and the cylinder 2 and hence ensures that. should a gap arise between the piston 14 and the tube 4 of the cylinder 2, no pressure medium may flow back and forth between the two working chambers 21 and 22.

The tubes 4, 6, 8 take the form of circular, cylindrical tube pieces. Each of said tube 4. 6, 8 extends between the two ends 10. 12 and is fastened in a pressure-tight manner in the region of the two ends -1010, 12. The three tubes are inserted one inside the other and the internal diameters and external diameters of the three tubes 4, 6, 8 are so dimensioned that a gap 28 is left free between the inner tube 4 and the middle tube 6 and a storage chamber 30 is left free between the middle tube 6 and the outer tube 8.

The working chambers 21 and 22 contain a pressure medium, preferably an oil. The storage chamber 30 is filled partly with the pressure medium and partly with a gas. A liquid surface 31 forms between the pressure medium and the gas. In a departure from the illustrated embodiments, it is alternatively possible to provide a diaphragm which separates the gas from the pressure medium or, for example, a separating piston.

The gas in the storage chamber 30 is preferably preloaded by a preloading pressure.

A control device 32 is disposed in the region of the first mass 18. A control line 34 leads through the piston rod 16 to a control valve device 36 disposed in the region of the piston 14. A control passage 38 leads through the piston 14 and opens out at one end into the first working chamber 21 and at the other end into the second working chamber 22. The control valve device 36 is situated part-way along the control passage 38.

The control device 32 is, for example, an electronic circuit and the control line 34 is, for example, an electric line. In dependence upon sensors (not shown) or in dependence upon preselected setpoint values or an entered programr the control device 32 may communicate control signals via the control line 34 to the control valve device 36. With said control signals the control valve device 36 may be adjusted. In dependence upon said adjustment, the pressure medium flowing out of the first working chamber 21 through the.control passage 38 into the second working chamber 22 is throttled to a greater or lesser extent. The pressure medium flowing out of the second working chamber 22 into the first working chamber 21 is also throttled with the aid of the control valve device 36 to a greater or lesser extent in dependence upon the control signals. The control valve device 36 may be so constructed that the pressure medium flowing through the control passage 38 is throttled to the same extent in both directions and an adjustment of the throttling for one direction means an adjustment of the throttling to a corresponding extent for the other direction. The control valve device 36 may, however, alternatively be so constructed that the flow of pressure medium through the control passage 38 in -12both directions may be throttled independently of one another and adjusted independently of one another.

A valve device 40 is disposed in the region of the bottom end 12 of the cylinder 2. The valve device 40 comprises, for example, a non-return valve 41 and a valve 42. A non-return valve 43 is disposed in the region of the rod-side end 10 of the cylinder 2. In the presently proposed shock absorber, there is a connection 50. A passage 46 or 46a, 46b connects the valve device 40 to the second working chamber 22. Since the passage in the illustrated embodiment comprises two parallel channels, the passage is designated 46a and 46b in the drawing. A further passage 47 leads from the valve device 40 into the gap 28, and a further passage 48 connects the valve device 40 to the storage chamber 30. In the illustrated embodiment, the passages 47. 48 are laid in such a way that a section of each of them extends inside a common channel. A passage 49 leads from the gap 28 into the first working chamber 21. Disposed part-way along said passage 49 is the non-return valve 43.

Starting from the second working chamber 22, the connection 50 leads through the valve device 40. through the passage 47, through the gap 28. through the passage 49 and through the non-return valve 43 into the first working chamber 21. The non-return -13valve 43 part-way along the connection 50 is disposed in such a way that the pressure medium, as it flows into the first working chamber 21, is substantially unthrottled by the non-return valve 43 yet the nonreturn valve 43 substantially prevents any escape of pressure medium out of the first working chamber 21 through the connection 50. As slight leakages in blocking direction through the non-return valve 43 are of no importance as far as operation of the shock absorber is concerned, it is possible to use a very simple non-return valve 43. The valve device 40 is fashioned in such a way that the pressure medium, as it flows from the direction of the second working chamber 22, is throttled or preloaded in the predetermined manner by the valve device 40 yet the valve device 40 allows a substantially unthrottled flow of pressure medium from the direction of the storage chamber 30 into the second working chamber 22.

In the embodiment illustrated in Figure 1, the valve device 40 comprises the non-return valve 41 and the valve 42. Said arrangement is by way of example only and was chosen for the particular reason of making the drawing as clear as possible. The nonreturn valve 41 and the valve 42 could equally well be realized by a single element. For instance, said purpose could be served by a plate valve which in one -14direction allows the pressure medium to flow substantially unthrottled and in the other flow direction throttles the pressure medium to a predeterminable extent. Since such valves are known to the person skilled in the art, there is no need for a detailed description of the individual components of the valve.

During an inward stroke, occasionally also referred to as a compression stage, the two masses 18, 19 move towards one another. During an outward stroke, occasionally also referred to as a tension stage, the two masses 18, 19 pull apart from one another.

When the shock absorber is in the course of an inward stroke, the piston rod 16 dips to an increasing extent into the cylinder 2. whereupon the volume of the first working chamber 21 increases and the volume of the second working chamber 22 decreases. Since, during the inward stroke, the piston rod 16 dips into the interior of the cylinder 2, the volume of the first working chamber 21 does not increase to the extent that the volume of the second working chamber 22 decreases. Thus, during the inward stroke, some of the pressure medium has to escape into the storage chamber 30. During'an outward stroke, the piston rod 16 emerges from the interior of the cylinder 2, - is- whereupon the volume of the second working chamber 22 increases to a greater extent than the volume of the first working chamber 21 decreases. Thus. during the outward stroke, some of the pressure medium has to be able to flow from the storage chamber 30 into the working chamber 22. in the embodiment illustrated in Figure 1r this occurs through the passage 48 via the valve device 40 and, in the specially illustrated embodiment, the pressure medium may flow out of the storage chamber 30 virtually unthrottled through the non-return valve 41 of the valve device 40 into the second working chamber 22. During an inward stroke, the pressure medium flowing out of the second working chamber 22 into the storage chamber 30 is throttled and, in the illustrated special embodiment, throttling of the pressure medium is effected by the preloaded valve 42 of the valve device 40.

During an inward stroke, pressure medium flows out of the second working chamber 22 through the control valve device 36 into the first working chamber 21, during which process it is throttled by the control valve device 36 with the aid of the control device 32 in a predeterminable, variable manner. During an outward stroke, pressure medium flows out of the first working chamber 21 through the control valve device 36. During said process, the pressure medium -16is throttled in accordance with the control signals preselected by the control device 32 and flows into the second working chamber 22.

During an inward stroke a pressure difference. which is caused by and may be influenced by the control valve device 36, arises in the pressure medium flowing through the control passage 38 from the second working chamber 22 into the first working chamber 21. And a pressure difference also arises inside the valve device 40 as a result of the pressure medium flowing out of the second working chamber 22 towards the storage chamber 30. When the pressure difference in the region of the control valve device 36 is smaller than the pressure difference in the region of the valve device 40, then nothing flows through the connection 50 into the first working chamber 21. The control valve device 36 may be varied, for example, between 0 bar pressure difference and a pressure difference which is virtually as great as the pressure difference in the region of the valve device 40. Within said range, problem-free adjustment of the control valve device 36 is possible.

When, during an inward stroke, the pressure medium is throttled by the control valve device 36 to a greater extent than in the region of the valve device 40, then, were it not for the connection 50, the pressure -17in the first working chamber 21 would drop to such an extent that the pressure medium situated in the first working chamber 21 would foam up or there would be a risk of dissolved gas escaping from the pressure medium situated inside the first working chamber 21. Said risk does not arise with the shock absorber presently proposed because, owing to the connection 50 leading into the working chamber 21, pressure medium coming from the storage chamber 30 or coming from the second working chamber 22 may flow into the first working chamber 21. Since the non-return valve 43 in the connection 50 throttles the pressure medium at most to an insubstantial extent, at least the preloading pressure prevailing in the storage chamber 30 in any case prevails in the first working chamber 21. A further measure counteracting gas evolution or foaming in the working chamber 21 is to provide the gas in the storage chamber 30 with an increased preloading pressure. For several reasons, said measure may however be used only to a very limited extent because the increased preloading pressure increases the friction between the seal 24 and the piston rod 16 and because the increased preloading pressure drives the piston 14 in the direction of the outward stroke.

During an outward stroke, the non-return valve 43 -18inside the connection 50 is closed and the shock absorber operates in the same manner as a previously known shock absorber so that there is no need for a detailed explanation of the mode of operation of the shock absorber in said direction of movement.

Figure 2 shows a further embodiment of the shock absorber.

In all of the drawings, identical parts or parts of identical function are provided with the sam reference numerals. The following embodiments are largely identical in construction to the first embodiment according to Figure 1. apart from the variations indicated below. Details of the various embodiments may be combined with one another.

In the embodiment illustrated in Figure 2, the non-return valve 43 situated part-way along the connection 50 is disposed not in the rod-side end 10 but in the region of the bottom end 12, and indeed is disposed in the passage 47 between the valve device 40 and the gap 28.

Furthermore. the control valve device 36 comprises two electrically adjustable control valve devices 36a and 36b of which, for example, the control valve device 36a is responsible for the inward stroke and the control valve device 36b is responsible for the outward stroke. Two control passages 38a and 38b -19connect the two working chambers 21, 22. The control valve device 36a is situated part-way along the control passage 38a. In a corresponding manner, the control passage 38b leads through the control valve device 36b.

Furthermore, in a departure from Figure 1, in Figure 2 the non-return valve 41 and the valve 42 of the valve device 40 are combined into a single unit, with the valve device 40 in Figure 2, for improved understanding of its mode of operation, symbolically exhibiting a nonpreloaded non-return valve and a springpreloaded non-return valve. The passage 46 connects the second working chamber 22 to the valve device 40.

Figure 3 shows a further embodiment.

Compared to Figures 1 and 2, the embodiment shown in Figure 3 additionally comprises a throttle device 55. The throttle device is situated in the region of the bottom end 12 and is constructed and disposed in such a way that during an inward stroke, when the pressure medium is displaced out of the second working chamber 22 through the valve 42 of the valve device 40, the pressure medium displaced into the storage chamber 30 has additionally to flow through the throttle device 55,'where it is additionally throttled in accordance with the style of construction of the -20throttle device 55. The throttle device 55 is constructed and disposed in such a way that the pressure medium flowing from the valve device 40 through the connection 50 into the first working chamber 21 is not throttled by the throttle device 55.

The throttle device 55 is preferably constructed and disposed in such a way that, during an outward stroke, the pressure medium flowing from the storage chamber 30 through the valve device 40 into the second working chamber 22 is not influenced.

The throttle device 55 is disposed part-way along a channel 57. The channel 57 opens out into the connection 50 at the point where the passage 47 leads into the gap 28. At its other end, the channel 57 leads into the storage chamber 30 below the liquid surface 31.

The throttle device 55 may, for example, have a simple fixed decrease in cross-sectional area. However, it is alternatively possible to use, for example, a spring-loaded valve element which is pressed against a valve seat and has any preselected throttle characteristic and a flow direction from the valve device 40 towards the storage chamber 30.

Figure 4 shows a further embodiment of the shock absorber.

Compared to Figure 3, the channel 57 is missing -21in Figure 4. Instead, in Figure 4 there is a passage 60. The passage 60, emanates from the gap 28 of the connection 50 and leads below the liquid surface 31 into the storage chamber 30.

As already explained above, it is possible, depending on the operating state. for pressure medium to flow during an inward stroke out of the second working chamber 22 through the connection 50 into the first working chamber 21. Since it is technically not possible for the free cross section part-way along the connection 50 to be indefinitely large, there is, part-way along the connection 50, an unavoidable pressure drop. Because the external diam ter of the shock absorber may not be too large, the free cross section of the gap 28 should also be as small as possible. Given a small free cross section of the connection 50, the pressure drop arising part-way along the connection 50 is no longer negligible. At the end of the connection 50, to prevent the oil from foaming, the pressure of the pressure medium may not fall below a specific value. In order, despite not too excessive throttling of the pressure medium by the throttling device 55. to obtain an adequate pressure at the end of the connection 50, it is advantageous if the channel, which leads through the throttle device 55 into the storage chamber 30, branches off - not at -22the start of the connection 50 - but only at a point where the pressure medium has already flowed some way through the connection 50. It is particularly advantageous if the length of the connection 50 between the branching-off point into the passage 60 and the opening into the first working chamber 21 is as short as possible. Out of consideration for the length of the passage 60 it is, on the other hand, also not necessary for the passage 60 to branch off directly at the end of the connection 50.

So that as little gas as possible dissolves in the pressure medium, up to a specific oblique position of the shock absorber the passage 60 should open out into the storage chamber 30 below the liquid surface 31.

In Figure 4, the non-return valve 41 and the nonreturn valve 43 take the form of plate valves or socalled flutter valves. Such valves are frequently used at various points in shock absorbers. This type of valve is very low-mass so that these valves may react quickly to a reversal of the flow direction. In the permitted flow direction, these valves allow virtually unthrottled flow of the pressure medium. In the reverse flow direction. they block quickly and reliably.

Figure 5 shows a further embodiment of the shock absorber.

One essential difference between the shock absorber according to Figure 5and the vibration dampers and/or shock absorbers described with reference to Figures 1 to 4 is that the piston 14. at its face remote from the piston rod 16, is provided with a compensating rod 17 which dips into a compensating chamber and/or a storage chamber 301 filled with the liquid pressure medium, e.g. pressure oil. Unlike the embodiments according to Figures 1 to 4, the storage chamber 301 is to a certain extent enclosed by an extension of the outer tube 8 which reaches as far as the bottom end 12 of the cylinder 2. The bottom end of the second working chamber 22 which in the other embodiments is formed by the bottom end 12 of the cylinder 2 - in the embodiment according to Figure 5 is formed by a transversely extending wall 12a in which is disposed. as with the other embodiments, the valve device 40. The present embodiment does not have the middle tube 6, which in the other embodiments was used to delimit the gap 28,. and the connection 50 comprises a connecting tube 64 which extends from the top end of the first working chamber 21 to the wall 12a and in the region of the wall 12a is connected via a non-return valve 431 -24corresponding to the non-return valve 43 to the compensating chamber 301.

In the embodiment according to Figure 5. the connecting tube 64 lies in a gap 30a between the inner tube 4 and the outer tube 8. The gap 30a being connected via at least one opening 66 in the wall 12a to the compensating and/or storage chamber 301. The upper part of the gap 30a may once again, as in the previously described embodiments, be filled with gas as is indicated in the drawing of Figure 5 by the liquid surface 31.

A major advantage of the shock absorber according to Figure 5 is that the use of the compensating rod 17 makes it possible to achieve a greater spread during an inward stroke, with 11 spread" being taken to mean the bandwidth over which the damping force dependent upon the piston speed may be adjusted so as to produce hard damping, soft damping or a mean value of damping. Whereas, namely, in the previously described shock absorbers the spread theoretically possible during the inward stroke is determined by the, structurally. frequently extremely limited selection of the ratio of piston area to piston rod area, in the shock absorber according to Figure 5 as a result of the relatively free selection of the diameter of the compensating rod 17 it is possible within a wide range to adjust the -25desired damping characteristic. 'Unward stroke" means thatIthe shock absorber is compressed and so this is frequently referred to as a compression stage. A wide spread means a large difference between minimum and ximum damping.

As Figure 5 reveals, use of the compensating rod 17 also opens up the advantageous possibility of installing a displacement sensor 68 which projects into the. in the embodiment, hollow compensating rod 17 and may be connected by incoming lines 71 in the bottom end of the cylinder 2. The sensor 68 may cooperate. for example. with associated magnetic devices on the inside of the compensating rod 17 which may be of a conventional design and are therefore not specifically shown in the drawing.

Figure 6 shows a further embodiment of the shock absorber.

The shock absorber according to Figure 6 differs from the shock absorbers according to Figures 1 to 4 in that there is no middle tube 6 and the gas volume, which in the embodiments according to Figures 1 to 4 is enclosed at the top end of the storage chamber 30 between the middle tube 6 and the outer tube 8, is enclosed in a gas chamber 70 delimited on the one hand by the outer tube 8 and on the other hand by a movable separating element 72 which may be, for example, a -26movable wall and in the embodiment according to Figure 6 is formed by a diaphragm, although a displaceable separating piston could, for example, be used in its place. The gas in the gas chamber 70 is preloaded. and the movable separating element 72 is acted upon by the pressure of the liquid pressure medium in the compensating and/or storage chamber 30, which is connected on the one hand by the valve device 40 to the second working chamber 22 and in the region of the rod-side end 10 of the cylinder 2 is connected by the non-return valve 43 to the first working chamber 21. In the embodiment according to Figure 6, the connection 50 existing in the embodiments according to Figures 1 to 4 and delimited by the middle tube 6 therefore also comprises the storage chamber 30, which is connected on the one hand to the valve device 40 and on the other hand to the non-return valve 43 via corresponding channels of the rod-side end 10 and the bottom end 12 of the cylinder 2. The channel in the rod-side end 10 and leading to the non-return valve 43 is extended up to an annular groove 74. which surrounds the piston rod 16 and is sealed off from the first working chamber 21 by means of a separate guide ring 76 which may be slotted in a radial direction, this markedly improving its mounting arrangements and similarly the frictional force and guide quality. In -27the embodiment, the annular groove 74 is sealed off in an upward and outward direction by means of a slot ring 78 or other suitable seal, and it is additionally possible to provide, on the outside of the slot ring 78, a scraper 80 which during the inward stroke protects the slot ring 78 or the like from damage by dirt particles.

As is usual in shock absorbers, in the present shock absorber too, the inner tube 4 may have a circular. annular cross section. The middle tube 6 too may have a circular. annular cross section. The two tubes 4. 6 may be arranged concentrically relative to one another. Preferably, however, the two tubes 4, 6 may alternatively be arranged eccentrically relative to one another. with the two centre lines being displaced far enough for the two tubes 4, 6 to touch one another at one side. The free cross section at the opposite side is therefore correspondingly increased without altering the outer periphery of the shock absorber. By virtue of the eccentric arrangement of the two tubes 4. 6. the flow resistance through the gap 28 is less than with a concentric arrangement of the two tubes 4, 6, this being particularly evident in the case of a relatively viscous pressure medium. Depending on the pressure medium used and depending on the dimension of the gap -2828, the flow resistance through the gap may. given the most-extreme possible eccentric arrangement of the two tubes 4. 6, be smaller by a factor 2.5 than with concentric arrangement of the two tubes 4, 6.

In the description of the embodiments. there is always only one nonreturn valve 43 described. It goes without saying that it is also possible to provide a plurality of nonreturn valves 43 acting parallel to one another. Given the same overall flow, it is thereby possible for each one of the non-return valves 43 to be correspondingly reduced in size. The same also applies to other components of the shock absorber but in particular to the storage chamber 30, the devices 36, 40, 55, the valves 41, 42. the connection 50 and the passages 46, 471 48r 49r 57, 60.

Claims

-29CLAIMS -1. A shock absorber for influencing a relative movement between

two masses which are movable relative to one another. having a cylinder containing a pressure medium, a piston rod and a piston which divides an interior of the cylinder into a first working chamber and a second working chamber, the cylinder being adapted to be coupled to one of the two masses and the piston being supported in an axially displaceable manner in the interior of the cylinder and being adapted to be coupled to the other of the two masses via the piston rod penetrating the first working chamber, the shock absorber further having a storage chamber, the storage chamber being connected via a valve device to the second working chamber, an adjustable control valve device via which the two working chambers are connectable to one another, and a connection monitored by a non-return valve, via which pressure medium may be supplied from the second working chamber via the valve device into the first working chamber and/or from the storage chamber into the first working chamber.
2. A shock absorber according to claim 1, wherein the control valve device is disposed in the region of the piston.
3. A shock absorber according to claim 1 or 2, wherein the cylinder has a bottom end remote from the piston rod and that the valve device is disposed in the region of said bottom end.
4. A shock absorber according to any one of claims 1 to 3, wherein the valve device is designed such that a substantially unthrottled flow from the direction of the storage chamber towards the second working chamber is possible yet the pressure medium when flowing from the second working chamber towards the storage chamber is throttled in the region of the valve device.
5. A shock absorber according to any one of the preceding claims, wherein a throttle device is constructed and disposed in such a manner that the pressure medium when flowing from the valve device towards the storage chamber is throttled.
6. A shock absorber according to claim 5, wherein a passage leads from part-way along the connection via the throttle device into the storage chamber.
7. A shock absorber according to any one of the preceding claimst wherein the connection extends between two cylindrical tubes which are inserted one into the other.
8. A shock absorber according to any one of -31claims 1 to 7. wherein the connection is conveyed through a connecting tube.
9. A shock absorber according to claim 7, wherein the two tubes are disposed with a differing radial clearance one from the other.
10. A shock absorber according to any one of the preceding claims, wherein the connection is a gap surrounding the working chambers.
11. A shock absorber according to any one of the preceding claims, wherein the storage chamber takes the form of an annular chamber surrounding the working chambers.
12. A shock absorber according to claim 1, wherein the piston at its face remote from the piston rod is provided with a compensating rod.
13. A shock absorber according to claim 12, wherein the storage chamber is disposed in an axial extension of the second working chamber and is separated from the latter by a wall of the cylinder, said wall containing the valve device.
14. A shock absorber according to claim 13, wherein the non-return valve is in the wall.
15. A shock absorber according to claim 14, wherein the connection comprises a connecting tube between the non-return valve and the first working chamber.
16. A shock absorber according to one any of claims 1 to 3, wherein the storage chamber is separated by means of a movable separating element from a gas chamber containing a gas and the connection monitored by the non-return valve is formed at least partially by the storage chamber itself.
17. A shock absorber constructed and adapted to operate substantially as hereinbefore described with reference to, and as illustrated in, the accompanying drawings.

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