VIBRATION DAMPER WITH A TRACTION STOP

Abstract

A vibration damper for a vehicle chassis may comprise a damper tube, a piston rod that is movable in an oscillating manner in an axial direction in the damper tube, a working piston disposed on the piston rod, and a closure package that closes the damper tube and through which the piston rod is guided. A spring element that is disposed in a region between the working piston and the closure package may comprise an annular basic body that surrounds the piston rod to form an annular chamber, an upper side facing the closure package, and a lower side facing the working piston. To reduce vibrations and noise from reaching a vehicle body, the spring element may include a lip element on the upper and/or lower side, and a spring rigidity of the lip element may be lower than a rigidity of the annular basic body.

Claims

1.-12. (canceled)

13. A vibration damper for a chassis of a motor vehicle, the vibration damper comprising: a damper tube; a piston rod that is movable in an oscillating manner in an axial direction in the damper tube; a working piston that is disposed on the piston rod; a closure package that closes the damper tube, wherein the piston rod is guided through the closure package; and a spring element that is disposed in a region between the working piston and the closure package, wherein the spring element comprises an annular basic body that surrounds the piston rod and forms an annular chamber between the annular basic body and the piston rod, an upper side that faces the closure package, a lower side that faces the working piston, and a lip element disposed on the upper side or the lower side, wherein a spring rigidity of the lip element is lower than a spring rigidity of the annular basic body.

14. The vibration damper of claim 13 wherein the lip element is a first lip element, the spring element further comprising a second lip element disposed on the lower side.

15. The vibration damper of claim 14 wherein the first and second lip elements are integral with the annular basic body.

16. The vibration damper of claim 13 wherein the spring element comprises pressure equalizing openings through which a damping medium can flow out of or into the annular chamber during elastic deformation of the spring element.

17. The vibration damper of claim 16 wherein the lip element is a first lip element, the spring element further comprising a second lip element disposed on the lower side of the spring element, wherein the pressure equalizing openings are configured as pressure equalizing bores that are disposed in the first and second lip elements and in the annular basic body.

18. The vibration damper of claim 13 further comprising a rebound buffer spring disposed between the working piston and the closure package, wherein the spring element is disposed between the rebound buffer spring and the closure package.

19. A spring element that is positionable in a vibration damper for a motor vehicle, between a working piston and a closure package that closes a damper tube of the vibration damper, wherein the spring element comprises: an annular basic body that is positionable to surround a piston rod of the vibration damper to form an annular chamber between the annular basic body and the piston rod; an upper side that faces the closure package; a lower side that faces the working piston; a lip element disposed on the upper side or on the lower side, wherein a spring rigidity of the lip element is lower than a spring rigidity of the annular basic body.

20. The spring element of claim 19 wherein the lip element is a first lip element that is disposed on the upper side, the spring element further comprising a second lip element disposed on the lower side.

21. The spring element of claim 20 wherein the first and second lip elements are integral with the annular basic body.

22. The spring element of claim 19 comprising pressure equalizing openings through which a damping medium can flow out of or into the annular chamber during elastic deformation of the spring element.

23. The spring element of claim 22 wherein the lip element is a first lip element that is disposed on the upper side, the spring element further comprising a second lip element disposed on the lower side, wherein the pressure equalizing openings are configured as pressure equalizing bores that are disposed in the first and second lip elements and in the annular basic body.

24. The spring element of claim 19 wherein the spring rigidity of the lip element is lower than a spring rigidity of a rebound buffer spring disposed between the working piston and the closure package in the vibration damper.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0018] FIG. 1 shows a half section of a vibration damper according to the invention;

[0019] FIG. 2 shows the assembly consisting of the rebound buffer spring and the spring element according to the invention in a lateral view without a damper tube;

[0020] FIGS. 3a, 3b show the spring element according to the invention in a top view (FIG. 3a) and in a half section (FIG. 3b) along the intersecting line A-A from FIG. 3a;

[0021] FIG. 4 shows a force/distance diagram, in which the force/distance behavior of the spring element according to the invention is compared to that of an elastomeric body which is known from the prior art (e.g. DE 10 2006 005 621 A1) without lip elements.

EMBODIMENTS OF THE INVENTION

[0022] In the various figures, identical parts are always provided with the same reference signs and are therefore generally also only referred to or mentioned once in each case.

[0023] FIG. 1 illustrates a vibration damper according to the invention. Arranged in a damper tube 1 is a piston rod 2 which is movable to and fro in an oscillating manner in the direction of the longitudinal axis of the damper tube (i.e. in the axial direction), to which a working piston 3 is fastened. The damper tube is filled with damping medium (e.g. hydraulic oil) and, in the driving mode, flows through the working piston, generating damping forces, when the piston rod moves out of the damper tube (what is referred to as the rebound stage movement of the piston rod) or moves into the damper tube (what is referred to as the compression stage movement or else compression movement of the piston rod). The working piston 3 divides the interior space of the damper tube 1 into a piston-rod-side working chamber and a piston-rod-remote working chamber. The closure package 4 sits firmly in the damper tube and closes the latter tightly in relation to the surroundings. The closure package 4 is penetrated by the piston rod 2. The movements of the piston rod are guided through the closure package 4. The closure package is therefore also frequently referred to as a sealing and guiding package.

[0024] FIG. 2 shows the vibration damper according to the invention as per FIG. 1 in order to improve the clarity in a somewhat enlarged illustration and without the damper tube 1 and also without further components of the vibration damper. In the piston-rod-side working chamber, a rebound buffer spring 5 which, in the exemplary embodiment illustrated, is designed as a mechanical helical spring is arranged between the working piston 3 and the closure package 4. At its end facing the working piston, the rebound buffer spring 5 is supported on a spring plate 21 which, for its part, is supported on the piston rod 2 in the axial direction. At its end facing the closure package 4, the rebound buffer spring 5 is supported on a spring plate 22 which, for its part, is supported on the piston rod 2 in the axial direction. The spring element 6 according to the invention is arranged between the rebound buffer spring 5 and the closure package 4. The spring element 6 has a basic body 7, on the upper side of which facing the closure package 4 and on the lower side of which facing the working piston 3 respective lip elements 10 are arranged. The spring rigidity of the lip elements 10 is lower than that of the basic body 7 and that of the rebound buffer spring 5. From a predetermined amplitude, the spring element 6 is placed with its upper-side lip element against the closure package 4 during a rebound movement of the piston rod 2 (rebound stage movement). During a persisting rebound movement of the piston rod 2, the lip elements 10 are then first of all compressed. As a result, vibrations and impacts are damped and the vibration and impact energy is converted into deformation energy and thus absorbed. With its lip elements 10, the spring element 6 according to the invention therefore prevents vibrations and impacts from being undesirably transmitted via the rebound buffer spring 5 into the piston rod 2 and by the latter into the vehicle body and therefore into the passenger cell.

[0025] Even if, from a position in contact with the closure package 4, the spring element 6 disengages again from the closure package because of a compression stage movement of the piston rod 2 (piston rod 2 moves into the damper tube 1), vibrations and/or impacts are introduced into the piston rod and transmitted into the vehicle body. This likewise leads to an undesirable development of noise in the passenger compartment. Even these vibrations and impacts are effectively damped and absorbed by the lip elements 10 of the spring element 6 according to the invention. The production of undesirable noises as the spring element 6 disengages from the closure package 4 is thereby significantly reduced or minimized.

[0026] The spring element 6 has pressure equalizing bores 11 which are arranged firstly in the basic body 7 and secondly in the lip elements 10. Damping medium can flow out of the annular chamber between the piston rod 2 and the spring element 6 through said pressure equalizing bores 11 when the spring element 6 is compressed over the course of a rebound stage movement of the piston rod 2. Similarly, damping medium can flow out of the piston-rod-side working chamber of the vibration damper into the annular chamber between the piston rod 2 and the spring element 6 when the spring element 6 relaxes again from a compressed state over the course of a compression stage movement of the piston rod 2. The pressure equalization resulting therefrom ensures that the spring element 6 does not attach or adhere to the closure package 4 and no longer disengages from the closure package 4.

[0027] FIG. 3a shows the spring element 6 according to the invention in top view. The upper side 8 of the spring element 6, which upper side faces the closure package in the installed state, and the lip element 10 which is arranged on the upper side 8 and comprises the pressure equalizing bores 11 which are arranged therein can be seen. FIG. 3b shows the spring element 6 according to FIG. 3a in an axial half section along the intersecting line A-A from FIG. 3a. The spring element 6 comprises a basic body 7 which is of bellows-shaped design and arches radially outward. Pressure equalizing bores 11, of which one can be seen in FIG. 3b, are provided in the basic body 7. Lip elements 10 are arranged on both sides on the basic body 7. The lip elements 10 are formed integrally with the basic body 7. Pressure equalizing bores 11 are arranged in the lip elements 10. The spring element 6 is designed as an injection molded part. The lip elements 10 comprise a substantially lower spring rigidity in relation to the basic body 7. Said lower spring rigidity is firstly achieved by the significantly smaller wall thickness of the lip elements 10 in comparison to the basic body 7. In addition, after the injection molding, other aftertreatment measures (e.g. tempering) can also be carried out in order to set the desired spring rigidity of the lip elements 10.

[0028] FIG. 4 shows a force/distance diagram for an assembly consisting of a rebound buffer spring and the spring element 6 according to the invention. The force/distance characteristic 30 (solid line) of a spring element 6 according to the invention and the force/distance characteristic 31 (dashed line) of an elastomeric basic body without lip elements according to the prior art are plotted in comparison to each other in the diagram. It can very clearly be seen that, in the case of the elastomeric body from the prior art, there is a rapid rise in force with a large gradient even after short deformation distances. The force profile runs steeply and approximately linearly upward even at relatively short deformation distances. In the case of such a characteristic profile, a relatively undamped introduction of vibrations into the vehicle body takes place. The hysteresis of the force/distance characteristic of the spring element according to the prior art is relatively small. The dissipation of force during relaxation of the spring element according to the prior art runs substantially in parallel and therefore equally steeply to the rise in force during compression.

[0029] By contrast, in the case of the spring element 6 according to the invention, the build up of force starts only at significantly greater deformation distances. In other words, in the case of the spring element 6 according to the invention, a much smaller force builds up over the same deformation distance in comparison to the spring element according to the prior art. In the case of the spring element 6 according to the invention, only a very small force builds up over a relatively large deformation distance (range A). This is the range in which the lip elements 10 are deformed. After the lip elements 10 have completely deformed, the deformation of the basic body 7 begins (range B). Within this range, the force/distance characteristic profile is determined by the spring rigidity of the basic body 7. The adjoining range C constitutes the range in which the rebound buffer spring runs up against a block. The force/distance characteristic for the spring element 6 according to the invention comprises significantly greater hysteresis in comparison to the characteristic for the spring element according to the prior art, said hysteresis indicating a greater damping extent and therefore a greater energy absorption capacity of the assembly consisting of rebound buffer spring 5 and spring element 6 than in the prior art.

LIST OF REFERENCE SIGNS

[0030] 1 Spring element [0031] 2 Piston rod [0032] 3 Working piston [0033] 4 Closure package [0034] 5 Rebound buffer spring [0035] 6 Spring element [0036] 7 Basic body [0037] 8 Upper side [0038] 9 Lower side [0039] 10 Lip element [0040] 11 Pressure equalizing openings; pressure equalizing bores [0041] 21 Spring plate [0042] 22 Spring plate [0043] 30 Force/distance characteristic [0044] 31 Force/distance characteristic [0045] A Range [0046] B Range [0047] C Range