Assembly of a Vibration Damper Associated with a Wheel of a Vehicle

Abstract

A vibration damper, assigned to a wheel of a vehicle, includes a damper cylinder, a damper piston with a piston rod configured to be guided in the damper cylinder, and a damper chamber, formed in the damper chamber on each side of the damper piston. The vibration damper further includes a pressure accumulator, in the form of a gas pressure cushion, connected to the damper chamber lying opposite the piston rod. The vibration damper is mounted on the vehicle body by a damper mount with a rubber-elastic body that is deformable in a shifting direction of the damper piston. A hydraulic pressure chamber is formed in the damper mount, and is connected via a fluid-conducting connection to the damper chambers whose volumes are respectively reduced when the wheel is deflected in relation to the vehicle body. The damper chambers are connected hydraulically to one another via a hydraulic pump driven by a motor. The damper mount includes a spring element that acts on the rubber-elastic body in the shifting direction of the damper piston, such that a spring force of the spring element, in the case of a stationary damper piston and equality of pressure in the two damper chambers, results in forces acting on the rubber-elastic body in the shifting direction of the damper piston to at least approximately cancel one another out.

Claims

1. A vibration damper assigned to a wheel of a vehicle, comprising: a damper cylinder; a damper piston with a piston rod configured to be guided in the damper cylinder; a damper chamber, formed in the damper chamber on each side of the damper piston; and a pressure accumulator, in the form of a gas pressure cushion, connected to the damper chamber lying opposite the piston rod, wherein the vibration damper is mounted on the vehicle body by a damper mount with a rubber-elastic body that is deformable in a shifting direction of the damper piston, wherein a hydraulic pressure chamber is formed in the damper mount, said pressure chamber being connected via a fluid-conducting connection to the damper chambers whose volumes are respectively reduced when the wheel is deflected in relation to the vehicle body, wherein the damper chambers are connected hydraulically to one another via a hydraulic pump driven by a motor, wherein the damper mount comprises a spring element that acts on the rubber-elastic body in the shifting direction of the damper piston, and wherein a spring force of said spring element, in the case of a stationary damper piston and equality of pressure in the two damper chambers, results in forces acting on the rubber-elastic body in the shifting direction of the damper piston to at least approximately cancel one another out.

2. The vibration damper as claimed in claim 1, wherein the spring element is supported directly or indirectly in relation to the vehicle body.

3. The vibration damper as claimed in claim 1, wherein the hydraulic pressure chamber in the damper mount is a hydraulic cylinder bounded by a pressure equalization piston that is configured to be shifted in the shifting direction of the damper piston and is supported on the rubber-elastic body by said spring element.

4. The vibration damper as claimed in claim 3, wherein, in the case of the stationary damper piston and equality of pressure in the two damper chambers, the shiftable pressure equalization piston is pressed against a stop by the spring element.

5. The vibration damper as claimed claim 1, wherein an end of the piston rod which projects out of the damper cylinder is connected to the elastic body of the damper mount, and the fluid-conducting connection runs through the piston rod.

6. The vibration damper as claimed claim 2, wherein an end of the piston rod which projects out of the damper cylinder is connected to the elastic body of the damper mount, and the fluid-conducting connection runs through the piston rod.

7. The vibration damper as claimed claim 3, wherein an end of the piston rod which projects out of the damper cylinder is connected to the elastic body of the damper mount, and the fluid-conducting connection runs through the piston rod.

8. The vibration damper as claimed claim 4, wherein an end of the piston rod which projects out of the damper cylinder is connected to the elastic body of the damper mount, and the fluid-conducting connection runs through the piston rod.

9. The vibration damper as claimed in claim 1, further comprising a hydraulic damping device in the damper mount, comprising a fluid-filled first working space in the elastic body, a second working space in the damper mount outside the elastic body, and at least one throttle plate between the two working spaces.

10. The vibration damper as claimed in claim 2, further comprising a hydraulic damping device in the damper mount, comprising a fluid-filled first working space in the elastic body, a second working space in the damper mount outside the elastic body, and at least one throttle plate between the two working spaces.

11. The vibration damper as claimed in claim 3, further comprising a hydraulic damping device in the damper mount, comprising a fluid-filled first working space in the elastic body, a second working space in the damper mount outside the elastic body, and at least one throttle plate between the two working spaces.

12. The vibration damper as claimed in claim 4, further comprising a hydraulic damping device in the damper mount, comprising a fluid-filled first working space in the elastic body, a second working space in the damper mount outside the elastic body, and at least one throttle plate between the two working spaces.

13. The vibration damper as claimed in claim 5, further comprising a hydraulic damping device in the damper mount, comprising a fluid-filled first working space in the elastic body, a second working space in the damper mount outside the elastic body, and at least one throttle plate between the two working spaces.

14. The vibration damper as claimed in claim 9, wherein a gas-filled equalization space is formed in the damper mount, and a diaphragm is provided between the equalization space and the second working space.

15. The vibration damper as claimed in claim 10, wherein a gas-filled equalization space is formed in the damper mount, and a diaphragm is provided between the equalization space and the second working space.

16. The vibration damper as claimed in claim 11, wherein a gas-filled equalization space is formed in the damper mount, and a diaphragm is provided between the equalization space and the second working space.

17. The vibration damper as claimed in claim 12, wherein a gas-filled equalization space is formed in the damper mount, and a diaphragm is provided between the equalization space and the second working space.

18. The vibration damper as claimed in claim 13, wherein a gas-filled equalization space is formed in the damper mount, and a diaphragm is provided between the equalization space and the second working space.

19. The vibration damper as claimed in claim 1, wherein a material which damps pressure oscillations is provided at least partially in the pressure chamber.

20. An assembly of a vibration damper assigned to a wheel of a vehicle, comprising: a damper cylinder; a damper piston with a piston rod configured to be guided in the damper cylinder; a damper chamber, formed in the damper chamber on each side of the damper piston; a pressure accumulator, in the form of a gas pressure cushion, connected to the damper chamber lying opposite the piston rod; and a damper mount configured to mount the vibration damper on the vehicle body with a rubber-elastic body that is deformable in a shifting direction of the damper piston, wherein the damper mount comprises a hydraulic pressure chamber connected via a fluid-conducting connection to the damper chambers whose volumes are respectively reduced when the wheel is deflected in relation to the vehicle body, wherein the damper chambers are connected hydraulically to one another via a hydraulic pump driven by a motor, and a spring element that acts on the rubber-elastic body in the shifting direction of the damper piston, wherein a spring force of said spring element, in the case of a stationary damper piston and equality of pressure in the two damper chambers, results in forces acting on the rubber-elastic body in the shifting direction of the damper piston to at least approximately cancel one another out.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0018] FIG. 1 shows a basic illustration of a vibration damper arrangement according to the invention with separate illustration of the relevant areas (for the explanation of the physical relationship), deviating from the real installation position in the horizontal position,

[0019] FIG. 2 shows an isometric illustration of a section through a first exemplary embodiment of a damper mount according to the invention, and

[0020] FIG. 3 shows, in an illustration similar to FIG. 2, a section through a second exemplary embodiment of a damper mount according to the invention.

DETAILED DESCRIPTION OF THE DRAWINGS

[0021] FIG. 1 shows a schematic, highly simplified view of a vibration damper 1 with a damper mount 2. The damper mount 2 is attached by its housing 13 to a bodywork of a vehicle (not illustrated figuratively), i.e. to the vehicle body. The damper mount 2 is also connected to a piston rod 6 of the vibration damper 1, and this piston rod 6 is mounted in the damper mount 2 in a way which is explained in more detail below. The piston rod 6 is connected in a fixed fashion to a damper piston 5. The damper piston 5 is guided in a linearly movable fashion in a damper cylinder 3, filled with hydraulic fluid, essentially in the vertical direction in contrast to the figurative illustration. The damper cylinder 3 is generally also referred to as a damper tube of the vibration damper 1. The damper cylinder 3 is usually, and also here, arranged on the wheel side with a connection 4 and is for this purpose (in contrast to the figurative illustration with its cylinder axis oriented essentially in the vertical direction ) connected, for example, to a wheel carrier or a wheel-conducting control arm of the respective vehicle wheel. The damper piston 5 divides the damper cylinder 3 into a first damper chamber 7, here above the piston 5 (i.e. the damper chamber 7 faces the vehicle body) and a second damper chamber 8, here underneath the piston 5 (i.e. the damper chamber 8 faces the vehicle wheel). In the case of deflection or rebounding of the wheel, the piston 5 moves counter to the damper cylinder 3, wherein the second damper chamber 8 is reduced in size in what is referred to as the compression stage of the vibration damper 1 if the wheel is deflected toward the vehicle body, while the first damper chamber 7 is reduced in size in what is referred to as the rebounding stage of the vibration damper 1 if the vehicle wheel rebounds away from the vehicle body.

[0022] FIG. 1 furthermore shows a hydraulic pump 9 which can be driven by an electric machine 10 and which is hydraulically connected or operatively connected to the two damper chambers 7, 8. It is therefore a case here of an active damper system or an active vibration damper 1, since the damper piston 5 can be adjusted or shifted in relation to the damper cylinder 3 by means of the hydraulic pump 9. By means of such active hydraulic adjustment of the damper piston 5 it is possible, for example, to counteract rolling movements of the vehicle body. In this case, the damper piston 5 and the damper cylinder 3 and therefore the vibration damper 1 act as a force-regulating hydraulic cylinder. Furthermore, FIG. 1 shows a hydraulic pressure accumulator 11 which is connected to the hydraulic circuit of the two damper cylinders 7, 8 and the hydraulic pump 9. In this pressure accumulator 11 it is possible to store, in particular, that quantity of hydraulic fluid which is, as it were, expelled in the compression stage of the vibration damper 1 through the piston rod 6 within the damper cylinder 3 (or in the damper chamber 7 thereof). When the vibration damper is embodied as a single-tube damper, this pressure accumulator 11 (in the form of what is referred to as an equalization space) is usually located on the base of the vibration damper, composed of a gas cushion and a separating piston. When the vibration damper is embodied as a two-tube damper, this pressure accumulator 11 or the function thereof can also be integrated into the wall, then doubled as is customary, of the damper tube 3.

[0023] The unit composed of the hydraulic pump 9 and electric machine 10 can also be used as a generator to generate electrical energy if, as is customary, the damper piston 5 is shifted (vertically) in relation to the damper cylinder 3 in the driving mode of the vehicle during the deflection or rebounding of the wheel by vehicle movement dynamics influences or by influences of the underlying surface on the vehicle body. In this context, the damping of this deflection movement and rebounding movement which oscillate to a limited extent takes place virtually only by means of the generator mode of the electric machine 10 which is then driven by the hydraulic pump 9, for which reason, in contrast to the customary passive vibration dampers, no throttled passage openings for hydraulic fluid are provided in the damper piston 5.

[0024] As shown by FIG. 1, a fluid-conducting connection 12 is formed in the piston rod 6. This fluid-conducting connection 12 opens with its first end into the damper chamber 8 which is located underneath the damper piston 5, and with its second end in the damper mount 2, specifically in a pressure chamber 15 thereof, as is explained below.

[0025] The damper mount 2 has a housing 13, wherein, for example, screw bolts via which this housing 13 and therefore the vibration damper 1 are attached to the body of the vehicle can be attached to the upper side of the housing 13. The piston rod 6 of the vibration damper 1 is mounted within the housing 13 via an elastic body 14 (for example composed of rubber) which is referred to above as a rubber-elastic body 14. This rubber-elastic body 14 is illustrated here in a simplified fashion embodied as a hollow-cylindrical disk into which the free end of the piston rod 6 is inserted or with which the piston rod 6 is fixedly connected in a way which is not illustrated in more detail here. In contrast, with its outer circumference this hollow-cylindrical rubber-elastic body 14 is fixedly connected to the inner wall of the housing 13. As is generally customary, i.e. in particular on suitable vibration dampers in the chassis of motor vehicles, relatively high frequency vibrations of the vehicle wheel which do not bring about visible shifting between the damper cylinder 3 and the damper piston 5, but would be transmitted toward the vehicle body by the piston rod 6, are to be successfully damped by means of this chassis or by means of this rubber-elastic body 14.

[0026] A cavity which is bounded by a section of the inner wall of the housing 13 and by the rubber-elastic body 14 and functions as a hydraulic pressure chamber, and is therefore also referred to as a hydraulic pressure chamber 15, is formed in the damper mount 2. The fluid-conducting connection 12 which runs in the piston rod 6 opens into this hydraulic pressure chamber 15. With the exception of this fluid-conducting connection 12, the pressure chamber 15 is formed in a fluid-tight fashion within the damper mount 2. Furthermore, a spring element 40, which is embodied as a compression spring and acts, at one end, on the side of the rubber-elastic body 14 lying opposite the pressure chamber 15 and is supported, at the other end, i.e. with its other end section, on the housing 13 of the damper mount 2 and therefore ultimately on the body of the vehicle, is provided here within the housing 13. In this context, reference is expressly made to the fact that the arrangement of the spring element 40 should be understood to be non-limiting and that other arrangements are also possible (for example, an arrangement according to FIG. 3) with which the desired effect of the spring element 40 (described below) and the pressure chamber 15, can be achieved.

[0027] The vibration damper 1 is assumed to be located in a stationary state and firstly, for the sake of simplicity, no pressure is generated in either of the chambers 7, 8 of the vibration damper 1 by the hydraulic pump 9 either. The same hydraulic pressure then prevails in the two chambers 7, 8 of the vibration damper 1 as well as in the pressure chamber 15 of the damper mount 2 (via the fluid-conducting connection 12 through the piston rod 6). The hydraulic pressure is determined by the pilot pressure of the pressure accumulator 11 and is usually of the order of magnitude of 30 bar in the case of a single-tube damper.

[0028] When there is equality (assumed initially for the sake of simplicity) between the areas A.sub.1 and A.sub.4, specifically the area A.sub.1 of the piston 5 in the damper chamber 8 and the area A.sub.4 of the rubber-elastic body 14, lying perpendicularly with respect to the piston rod 6 or with respect to the shifting direction of the damper piston 5, in the pressure chamber 15, the forces which result from the pressure in the damper chamber 8 and in the pressure chamber 15 and act on the rubber-elastic body 14 consequently cancel one another out. There is therefore still the force which results from the pressure in the other damper chamber 7 and from this area A.sub.2 of the damper piston 3, which is reduced compared to the area A.sub.1 by the area A.sub.3 of the piston rod 6, and which via the piston rod 6 is transferred to the rubber-elastic body 14 and which is to be compensated so that the rubber-elastic body 14 is, as desired, essentially free of introduced forces or additional forces. A or the spring element 40 is provided for this, which counteracts the force resulting from the hydraulic pressure in the damping chamber 7 and acts on the rubber-elastic body 14. The rubber-elastic body 14 is therefore, at least considered in terms of steady state, free of forces acting in the shifting direction of the damper piston 5 and can consequently, as has been explained expressly above, perform its function, specifically the damping of relatively high frequency vibrations as well as possible. Only for the sake of completeness, reference will be made once more to the fact that the hydraulic pressure prevailing in the steady state in the damper chambers 7, 8 is permanently predefined by the configuration of the vibration damper 1 and is essentially independent of significantly changing peripheral conditions, with the exception of a slight change in pressure as a function of the deflection state (resulting from the change in the gas volume of the pressure accumulator 11 with changed volume expelled by the piston rod 6) and of temperature influences.

[0029] Without the equality of areas introduced here only by way of a remedy, the following relationship or the following (algebraic) equation must then apply so that, considered in the steady state, an equilibrium of forces prevails at the rubber-elastic body 14 in the shifting direction of the damper piston 5:

F=0=pA.sub.1pA.sub.2pA.sub.4+F.sub.40,

[0030] where, [0031] is the algebraic symbol for a sum, [0032] p is the hydraulic pressure prevailing in the steady state in the chambers 7, 8 of the damper cylinder 3 (which is the same for both chambers 7, 8), [0033] represents an algebraic multiplication, [0034] represents an algebraic difference, [0035] + represents an algebraic summation, [0036] A.sub.1 to A.sub.4 are as described above and as illustrated in the figures, and [0037] F.sub.40 is the suitably directed force of the spring element 40 and F is a force.

[0038] If an additional hydraulic pressure is built up by the hydraulic pump 9 in one of the chambers 7 or 8 of the damper cylinder 3 and at the same time hydraulic pressure is built up in the other damper chamber (8 or 7), this results in the shifting of the damper cylinder 3 (with respect to the damper piston 5). However, the equilibrium of forces at the rubber-elastic body 14 remains essentially uninfluenced for this, i.e. there is also no additional force acting on this as a result of a build up of pressure or reduction of pressure in the damper chambers 7, 8 as long as the pressure prevailing in the damper chamber 8 is propagated into the pressure chamber 15 through the fluid-conducting connection 15. In this context, a slight time delay as a consequence of the relatively small cross section of the fluid-conducting connection 12in relation to the effective areas in the damper chambers 7, 8 and in the pressure chamber 15is advantageous in respect of the desired equilibrium of forces even during a relative movement between the damper piston 5 and the damper cylinder 3.

[0039] When this equilibrium of forces is present or when this equation above is at least approximately satisfied, even when the damper piston 5 is shifted by means of the hydraulic pump 9 driven by the electric machine 10 and the vibration damper 1 according to the invention therefore acts as a hydraulic actuator, the rubber-elastic body 14 remains virtually free of significant additional forces which would adversely its actual function, specifically the damping of relatively high frequency vibrations.

[0040] FIG. 2 shows partially in more detail a damper mount 2 according to the invention with the end section of the piston rod 6 facing the latterthen in an actual installation position in the vehicle. In this context, screw bolts (which are not characterized in more detail) and via which the housing 13 and therefore the vibration damper 1 is attached to the body of the vehicle are illustrated here on the upper side of the damper mount housing 13. The rubber-elastic body 14 which is formed in abstracted fashion in the manner of a hollow cylinder is located in the housing 13. The hydraulic pressure chamber 15 in which the fluid-conducting connection 12 which runs in the piston rod 6 opens is provided within this rubber-elastic body 14. In order to attach the piston rod 6 in a central position in the rubber-elastic body 14, an attachment plate 16, which is itself embedded in the rubber-elastic body 14, is located on the piston rod 6. The force which is transmitted by the piston rod 6 and slight movements of the piston rod 6 which vibrate at a relatively high frequency (in particular in the vertical direction, i.e. in the longitudinal direction of the piston rod 6), are transmitted via this attachment plate 16 into the rubber-elastic body 14. From the rubber-elastic body 14, the force which is applied by the piston rod 6 and firstly actually also the movements of the piston rod 6 which vibrate at a relatively high frequency are transmitted into the body of the vehicle via the housing 13 on which the rubber-elastic body 14 is supported. However, the latter, specifically undamped transmission of movements of the piston rod 6 which vibrate at a relatively high frequency into the vehicle body is undesired because such movements should be damped or attenuated as intensively as possible by the rubber-elastic body 14 which therefore should be at least approximately free of additional forces, in particular resulting from a use of this vibration damper 1 as an active hydraulic actuator. Therefore, in view of this not only the pressure chamber 15 which acts on the rubber-elastic body 14 in a manner analogous to FIG. 1 but also a or the spring element 40 which acts on the rubber-elastic body 14 in a manner analogous to FIG. 1 are provided, the spring element 40 being clamped here in between the attachment plate 16 and a suitable shoulder or projection 13 of the housing 13 of the damper mount.

[0041] FIG. 2 also shows an additional hydraulic damping device which can be integrated into the damper mount 2 or, according to this exemplary embodiment (in contrast to the embodiments according to FIGS. 1 and 3) is integrated into the damper mount 2. This hydraulic damping device comprises a first working space 20 which is embodied in the rubber-elastic body 14 itself, specifically on the side of the attachment plate 16 facing away from the hydraulic pressure chamber 15. Furthermore, a throttle plate 22 which is annular here and in which a multiplicity of through-openings for hydraulic fluid are provided is inserted into the rubber-elastic body 14. This throttle plate 22 separates the first working space 20 from a second working space 21. The second working space 21 is located outside or underneath the rubber-elastic body 14, still inside the housing 13. Furthermore, a gas-filled equalization space 23 is provided in the housing 13. The gas-filled equalization space 23 is separated from the second working space 21 by means of a diaphragm 24. As is shown in FIG. 2, the first working space 20, the second working space 21, the throttle plate 22, the equalization space 23 and the diaphragm 24 are arranged as annular elements concentrically about the piston rod 6. If a certain (vibrating) movement is applied into the elastic body 14 in the longitudinal direction of the piston rod 6 via the piston rod 6, hydraulic fluid overflows between the two working spaces 20 and 21 through the passage openings of the throttle plate 22, as a result of which additional damping of such high-frequency movements or vibration excitations takes place.

[0042] In the exemplary embodiment according to FIG. 3, in a way analogous to the preceding variants according to FIGS. 1 and 2 it is ensured that the rubber-elastic body 14 is at least approximately free of additional forces, in particular resulting from a use of this vibration damper 1 as an active hydraulic actuator, wherein in a particularly advantageous way this rubber-elastic body 14 itself does not come into contact with the hydraulic fluid of the vibration damper 1. In a way analogous to FIG. 2, the piston rod 6 is mounted here by means of or via an attachment plate 16 in the rubber-elastic body 14, wherein here the rubber-elastic body 14 is again essentially in a purely hollow-cylindrical shape (in a way analogous to FIG. 1) and is suitably clamped into the housing 13 of the damper mount 2, in that it is inserted into a cutout thereof. In this context, the attachment plate 16 rests on a shoulder 6a of the piston rod 6 and is attached by means of a screw nut 41 for which a thread is formed on an end section 6b of the piston rod, which end section 6b is reduced in cross section. A spring plate 42 rests on this screw nut 41, therefore on the side thereof facing away from the attachment plate 16, and is plugged onto this piston rod end section 6b on which a or the spring element 40, whose function was explained in detail with reference to FIG. 1, rests or is supported. By its other end, the spring element 40 rests on what is referred to as a pressure equalization piston 43, or the pressure equalization piston 43 which can be shifted over a certain distance inside the housing 13 of the damper mount 2 in the direction of the piston rod 6 or in shifting direction of the damper piston 5 (and is suitably guided by the inner wall of the housing 13), is supported on the spring element 40. On the side of the pressure equalization piston 43 which faces away from the spring element 40, the pressure chamber 15, into which the fluid-conducting connection 12 which runs in the piston rod 6 opens, is provided in the housing 13. The hydraulic pressure which prevails in the damper chamber 8 of the vibration damper 1 (cf. in this respect FIG. 1) via the fluid-conducting connection 12 into the pressure chamber 15 and from the latter via the pressure equalization piston 43 counteracts the hydraulic pressure in the damper chamber 8 at the rubber-elastic body 14 after it has been reduced by the force of the spring element 40. Therefore, the rubber-elastic body 14 is, as desired, essentially free of the effect of (additional) forces acting in the shifting direction of the damper piston 5. As is illustrated figuratively, the shiftable pressure equalization piston 43 is pressed, in the case of a stationary damper piston 5 and equality of pressure in the two damper chambers 7, 8, by the spring element 40 against a stop 44 which is formed in the inner wall of the housing 13.

[0043] A development which is possible for all the exemplary embodiments and according to which a material which damps pressure vibrations is provided at least partially in the pressure chamber 15 is not illustrated figuratively. Therefore, relatively high frequency pressure oscillations of the hydraulic fluid, or in the hydraulic fluid, which occur (once more) in the pressure chamber 15 and could be transmitted into the pressure chamber 15 from the damper chamber 8 via the fluid-conducting connection 12 can possibly be damped, with the result that there is no risk of the latter being introduced into the vehicle body via the housing 13 of the damper mount 2. Of course, this material must not fill the pressure chamber 15 to such an extent that it can no longer carry out its function described above of establishing an equilibrium of forces. This material which damps pressure oscillations can be, for example, a suitable foamed material with which, for example, the walls of the pressure chamber 15 are lined, as illustrated in FIG. 2 in the form of the component of the elastic body 14. However, the pressure chamber 15 in, for example, FIG. 3, can alternatively be filled with elastic, i.e. compressible, balls, or other measures which are known to a person skilled in the art for vibration damping are implemented.

[0044] The foregoing disclosure has been set forth merely to illustrate the invention and is not intended to be limiting. Since modifications of the disclosed embodiments incorporating the spirit and substance of the invention may occur to persons skilled in the art, the invention should be construed to include everything within the scope of the appended claims and equivalents thereof.