EP2069656A1

EP2069656A1 - Geräuschoptimierter schwingungsdämpfer

Info

Publication number: EP2069656A1
Application number: EP07818191A
Authority: EP
Inventors: Alexander Kruse; Rudolf Starobinski
Original assignee: ZF Friedrichshafen AG
Current assignee: ZF Friedrichshafen AG
Priority date: 2006-09-26
Filing date: 2007-09-18
Publication date: 2009-06-17
Also published as: DE102006045236A1; WO2008037372A1

Abstract

The invention relates to a vibration damper (1), comprising a damping-medium-filled cylinder (3) in which a piston rod (5) with a piston (7) is guided in an axially movable fashion, wherein the piston (7) divides the cylinder (3) into two working spaces (9;11) and the volume which is displaced in the event of a piston rod movement flows through at least one damping valve (15;17;19;21) and is compensated by a compensating space (23) which is connected to at least one of the working spaces, wherein in addition to the compensating space (23), a functional element (27) is connected to at least one working space, wherein the functional element (27) elastically absorbs high-frequency vibrations within the damping medium.

Description

Noise-optimized vibration damper

(Description)

Technical area

The invention relates to a noise-optimized vibration damper according to the preamble of patent claim 1.

In a vibration damper damping medium is displaced by a damping valve at each stroke of a piston rod. Starting from a rest position of the piston rod, the damping medium is compressed. The compressed in a working space of the vibration damper damping medium acts on all the working space limiting components and exerts a force that can be heard as a noise. This effect also occurs when the compressive preload has dissipated through the damping valve. It can, for. B. be that the cylinder of the shock absorber expands in a barely detectable extent under pressure and at a discharge again assumes its initial shape.

State of the art

With adjustable vibration dampers then the switching behavior of the damping valve has been changed so that z. B. is switched only up to a certain pressure level. For example, reference is made to DE 41 13 305 A1. A disadvantage of this solution is that the dynamics of the adjustable damping valve suffers.

An alternative solution has hitherto been to change the damping valves in the direction of a softer opening and closing behavior. Furthermore, one can bypass the effect in limits by using an amplitude-selective damping valve, such. B. in DE 10 2004 015 065 A1 discloses. High-frequency suggestions with small stroke movement of the piston rod cause virtually no pressure increase in the working space of the vibration, so that no noise. The serious one Disadvantage of this solution, however, is that it engages clearly in the Dämpfkraftkennlinie the vibration and thus u. U. in a decidedly sporty vehicle would have to accept a too soft Dämpfkrafseinstellung.

Presentation of the invention

The object of the present invention is to remedy the noise problems that occur in particular in the case of high-frequency excitation of the vibration damper.

According to the invention the object is achieved in that in addition to the compensation space, a functional element is connected to at least one working space, wherein the functional element elastically absorbs high-frequency vibrations within the damping medium.

With the functional element of the vibration damper is acoustically tuned. On a classic damping force-speed characteristic curve, one will not notice any influence of the functional unit and thus also accept disadvantages not known from the prior art.

The functional element has at least one housing with at least two chambers which are sealed off from one another by a partition element, damping medium being present in one of the chambers. Structurally, the functional element may be prefabricated like a cartridge.

The functional unit comprises a throttle point, which generates a pressure gradient, wherein the damping medium displaced by the throttle point is supported by an elastically mounted separating element.

Preferably, the separating element is formed by a membrane. The membrane can be clamped at the edge. In addition, the membrane can be pillowed executed, for. B. to achieve an acoustic damping to two excitation frequencies.

Furthermore, the membrane is limited on the side facing away from the damping medium by a support means in its deformation in order to achieve a good fatigue strength.

Alternatively, there is the possibility that the separating element is formed by an axially movable plate sealed to the housing.

For sealing the separating element to the housing, there are different solutions. For example, the plate-shaped separating element can be sealed by a flexible element, for. B. according to an advantageous subclaim of a membrane.

However, you can also use a bellows. An essential decision criterion for a particular embodiment lies in the size of the functional unit and the frequencies to be damped.

In a further advantageous embodiment, the separating element is biased by a gas pressure in the space remote from the damping medium of the housing. This makes it possible to achieve a suspension-dependent vapor deposition of the disturbing noises.

Alternatively or additionally, the separating element can be prestressed by a mechanical spring in the space of the housing facing away from the damping medium. There is z. B. the possibility that the separating element performs a first working path against a gas pressure and in the further working path additionally against a mechanical spring. This method can be used to steam several frequencies. Furthermore, at least one of the spaces of the functional unit can at least partially be filled with a sound-absorbing material.

There is also the possibility that the throttle point is adjustable in its throttle action.

According to an advantageous subclaim, the functional unit is arranged within a pressure connection connection between the two working spaces. It should only be the pressure in the workspace transferred to the functional unit. A significant volume flow in the functional unit is not provided.

In a first variant, the pressure connection connection is executed within the assembly piston rod piston. The advantage is that it can be acoustically damped with a functional unit at work spaces and thus both directions of movement of the piston rod.

Alternatively, there is the possibility that the pressure connection connection is designed in a bypass to at least one piston valve.

However, you can also arrange the functional element outside of the vibration damper, if z. B. the space in the vibration damper for an internal solution is not available.

You can connect the functional unit to a pressure-biased expansion chamber to achieve a support of the separating element.

A further variant is characterized in that both working spaces are designed with a functional unit, wherein both functional units are arranged in a common housing and there is a separate separating element for each working space, wherein the two separating elements bound a biasing space. There is the possibility that the preload space is adjustable via a pressure medium connection in its pressure level.

In addition, the two separating elements can perform a different elastic working movement.

Another way to place the functional element in the vibration damper is to place it on the piston rod.

The functional element has an annular design and thus encloses the piston rod.

Within the annular functional element at least one gas-filled cushion is arranged.

If one executes at least one lateral surface of the functional element with at least one throttle opening, one can use the top surfaces for the axial fixing of the functional element to the piston rod.

Brief description of the drawings

The invention will be explained in more detail with reference to the following description of the figures. It shows:

Fig. 1; 3 - 5 Vibration damper with functional unit in various embodiments

Fig. 2 Exemplary embodiment of the functional unit

Ways to carry out the invention

Fig. 1 shows the schematic diagram of a vibration damper 1 in two-pipe design. In a cylinder 3 is a piston rod 5 with a piston. 7 guided axially movable. The piston 7 divides the cylinder 3 in a piston rod side and a piston rod remote working space 9; 11, wherein both working spaces are completely filled with a hydraulic damping medium. In the piston 7 and in a bottom 13 are generally known damping valves 15; 17; 19; 21 executed, the damping medium exchange between the two working spaces 9; 11 or the piston rod remote working space 11 and a compensation chamber 23 throttle. The compensation chamber 23 compensates for the damping medium volume of the piston rod 5 extending and retracting into the cylinder 3

For each excitation, which is transmitted via the cylinder 3 and a cylinder enveloping the container tube 25 to the piston rod 5 of the vibration damper 1, the damping medium in a working space 9; 11 compressed. The pressure acts on all surfaces of the affected working space and opens one of the damping valves 15-21 in the piston and / or in the bottom. During the opening movement of the valve pending pressure gradients can cause a noise that is clearly audible in a vehicle. In the present vibration damper 1, in addition to the compensation chamber 23 at least one working space 9; 11 connected to a functional unit 27 which receives high-frequency vibrations within the damping medium elastic.

The functional unit 27 can be embodied at different positions on or in the vibration damper and comprises at least one housing 45 with at least two chambers 35 sealed from one another by a partition element 37; 41, wherein a gap 35 to one of the working spaces 9; 11 of the vibration damper 1 is connected. For example, between the two working spaces 9; 11, a pressure port connection 29; 31 exist within which the functional unit 27 is arranged. In the left half of the drawing, the pressure connection connection is located as a bypass line to at least one piston valve 15; 17 outside of the vibration damper 1 before. Alternatively, the functional unit can also be positioned in a wall of the cylinder 3 or a piston rod guide 46. Furthermore, as shown in FIG. 2, the functional unit 27 comprises at least one throttle point 33, which has a pressure difference between one of the working spaces 9; 11 and the gap 35 within the functional unit causes. The throttle body 33 may be adjustable manually or by means of an actuator, not shown. The space is separated by a separator 37, z. B. a membrane and can perform an operating movement, eg an elastic deformation movement. The displaced by the throttle body 33 and supported by the partition volume is very low and on a damping force-speed diagram not recognizable as part of the Dämpfkraftkennlinie.

The membrane 37 is clamped edge and can be designed as a closed disc or pillow-shaped. On the side facing away from the damping medium, the operating movement of the separating element or the membrane is limited by a support means 43. In the left half of the drawing, a plate-shaped separating element is used, which is biased by a biasing spring 39. In the right-hand version, there is a downstream pressure chamber 41 with a gas bias. In addition, if necessary at least one support grid 43 is used. But you can also combine a gas bias and the mechanical biasing spring to dampen several noise frequencies. For sealing the plate-shaped separating element to the housing, several options are available. You can z. B. an annular membrane, but also use a bellows 46. The membrane does not have to have inherent elasticity but can also be formed by a fabric or a film.

In the intermediate space 35, a sound-absorbing substance 48 may additionally be included, as he z. B. is known for packaging sensitive goods.

In a piston rod movement, the damping medium column is supported in a working space at the throttle point 33, wherein in the working space of the pressure p1 is present. The throttle point 33 causes a pressure gradient, so that in the intermediate space 35, a smaller compared to the pressure p1 pressure p2 prevails, which causes an adjustment or deformation movement of the separating element 37. In the case of low-frequency (<50 Hz) quasi-static damper oscillations, these movements and the resulting changes in the volumes in the functional unit 27 are negligibly small in comparison with damper working spaces, so that the functional unit 27 has no influence on damper oscillations.

During an opening or closing movement of the damping valve in the piston or in the bottom valve, a high-frequency (> 100 Hz) excitation of the damper structure takes place. This excitation is also in the form of pressure pulses on the

Functional unit 27 transmitted in the functional unit 27 adjustment or

Excite deformation movement of the separating element 37. The vibration energy in a certain frequency range is thus eliminated from the damper structure. The high frequency vibrations (sounds) are from the

Function unit 27 damped.

The vibration damping can be explained as follows in the exemplary embodiment of the functional unit 27 in the upper damper working space 9.

For impulsive (with acceleration) displacement of the oil through the throttle, the necessary force is equal to the force needed to accelerate the mass of the oil in it:

dp_9 ^* FFF -dp_A ^* FFF = M ^* W (1)

With

FFF - cross section of the throttle 33 (m ² ) dp_9 ^* FFF - the damper side force (working space 9) (N) dp_A ^* FFF - the force in the functional element (gap 35) (N)

W - acceleration of the mass M (m / sec ² ) M - the mass of oil in the throttle 33 (kg)

M = PP ^* FFF ^* LL (2) with PP (kg / m ³ ) - the density of the oil

It is known that for the sinusoidal vibrations of mass M, the inertial force (F_in) is the same

F_in = M ^* W = - (M ^* Ω ² ) ^* dx (3) with dx - the vibration amplitude of the oil in the throttle 33 (m) Ω = 2π * Freq - angular frequency, (R / s)

One can also write for the pressure drop (dp_9 - dp_A):

(dp_9 - dp_A) = dp_in = - PP ^* LL ^* (M ^* Ω ² ) ^* dx (4)

Volume flowing into the gap 35 through the throttle 33 is the same

dQ = FFF ^* dx (5)

with replacing dx from 5 in 4 follows

(dp_9 - dp_A) = dp_in = - IND ^* (M ^* Ω ² ) ^* dQ (6)

The inductance (Ind) is calculated as follows

Ind = PP ^* UFFF (kg / m ⁴ ) (7)

The additional volume that enters the intermediate space 35 increases the pressure in the intermediate space 35, acts on the air volume 41 and / or the mechanical spring 39 via the separating element 37 dp_A = K_A ^* dQ (8) with

K_A - is the volumetric stiffness of the system "air membrane" (PsJm ³ )

After replacing (6) in (8), the following equation is given: dp_9 = (K_a - Ind ^* Ω ² ) ^* dQ = Kdyn'dQ (9)

In this way, the full dynamic stiffness of the functional element 27 is of positive (elastic) rigidity, which is not dependent on the frequency and negative (inertial) stiffness, which is dependent on Ω ² . At certain (resonant) frequencies, the stiffness Kdyn can be minimized by tuning K_a and Ind (close to zero). As a result, the masses displaced in the intermediate space 35 by pressure oscillations dp_9 become very large. The changes of the oil volume in the intermediate space 35 are thus comparable to those in the working chamber 9 of the damper, which determines the effect of the functional element on this frequency. By tuning K_a and Ind, this effect is made frequency-selective.

The vibration damper 1 in conjunction with the functional unit 27 is comparable to an organ pipe, which is tunable by adjusting the action of the throttle body 33, the size and the force support of the separator 37 such that at an external excitation no noise is heard.

In the embodiment of FIG. 3, the functional unit 27 is shown in a vibration damper 1 according to the monotube principle. The filling pressure of the gas in the compensation chamber 23 serves as a support of the separating element 37 in the functional unit, in which between the compensation chamber 23 and the housing 45 of the functional unit, the pressure connection connection 29; 31 is present. In a monotube vibration damper, damping valves 15; 17 executed for both directions of movement, so that the damping medium in each case by the Pressure connection connection 29 is coupled in the piston rod-side working space 9 to the functional unit 27.

4 shows an embodiment of the vibration damper 1, in which both working spaces 9; 11 with a functional unit 27a; 27b in a common

Housing are arranged. Both functional units 27a; 27b have a separate partition 37a; 37b, which delimit a biasing space 47. Of the

Vorspannraum 47 can via a pressure medium connection 49 in his

Pressure level can be adjusted. Furthermore, there is the possibility that the two separating elements 37a; 37bb due to divergent geometric

Dimensions and / or inherent elasticity can perform a different work movement.

The Fig. 5 is limited in the representation of a section of the piston rod 5 with the piston 7. Between the piston 7 and an axial

Fastening means on the piston rod 5, the functional element 27 in annular

Construction arranged. In the annular housing 45 throttle openings 33 are executed. You can also use a grid structure. In the annular space between the housing and the piston rod, which functionally corresponds to the intermediate space 35 according to FIG. 2, at least one gas-filled cushion 41 is arranged to float. With regard to the function, reference is also made to FIG. Of course, such a functional unit for both

Workrooms 9; 11 respectively above and below the piston 7 at the

Be fixed piston rod 5 and / or the piston 7, wherein the functional unit would not have to be attached for their own effectiveness. A simple floating storage would be just as possible, but then could mechanical

Impact noises occur, which one would have to remedy.

Claims

claims

1. Vibration damper comprising a filled with damping medium cylinder in which a piston rod is guided axially movable with a piston, wherein the piston divides the cylinder into two working spaces and at a

Piston rod displacement displaced volume flows through at least one damping valve and is compensated by a compensation chamber which is connected to at least one of the working spaces, characterized in that in addition to the compensation chamber (23) a functional element (27) with at least one working space (9; is, wherein the functional element (27) elastically absorbs high-frequency vibrations within the damping medium.

2. Vibration damper according to claim 1, characterized in that the functional element (27) at least one housing (45) with at least two by a separating element (37) from each other sealed spaces (35; 41), wherein in one of the spaces (35) damping medium is present ,

3. Vibration damper according to claim 1, characterized in that the functional unit (27) comprises a throttle point (33) which generates a pressure gradient, wherein the by the throttle point (33) displaced damping medium is supported by an elastically mounted separating element (37).

4. Vibration damper according to claim 2, characterized in that the separating element (37) is formed by a membrane.

5. Vibration damper according to claim 2, characterized in that the separating element (37) is formed by a housing (45) sealed, axially movable plate.

6. Vibration damper according to claim 5, characterized in that the plate-shaped separating element (37) is sealed by a flexible element.

7. Vibration damper according to claim 6, characterized in that the plate-shaped separating element (37) is sealed by a membrane.

8. Vibration damper according to claim 6, characterized in that the plate-shaped separating element (37) by a bellows (46) is sealed to the housing.

9. Vibration damper according to claim 2, characterized in that the separating element (37) is biased by a gas pressure in the space remote from the damping medium (35) of the housing (45).

10. Vibration damper according to claim 2, characterized in that the separating element (37) by a mechanical spring (39) is biased in the space remote from the damping medium space (35) of the housing (45).

11. Vibration damper according to claim 2, characterized in that at least one of the spaces (35) of the functional unit (27) is at least partially filled with a sound-absorbing material (48).

12. Vibration damper according to claim 4, characterized in that the membrane (37) is designed cushion-shaped.

13. Vibration damper according to claim 4, characterized in that the membrane (37) is clamped at the edge.

14. Vibration damper according to claim 4, characterized in that the membrane (37) on the side facing away from the damping medium by a support means (43) is limited in its deformation.

15. Vibration damper according to claim 3, characterized in that the throttle point (37) is adjustable in its throttle effect.

16. Vibration damper according to claim 1, characterized in that the functional unit (27) within a pressure connection connection (29;

31) between the two working spaces (9; 11) is arranged.

17. Vibration damper according to claim 16, characterized in that the pressure connection connection (29; 31) within the assembly

Piston rod piston (5; 7) is executed.

18. Vibration damper according to claim 16, characterized in that the pressure connection connection (29; 31) in a bypass to at least one piston valve (15; 17) is executed.

19. Vibration damper according to claim 16, characterized in that the functional element (27) outside of the vibration damper (1) is arranged.

20. Vibration damper according to claim 1, characterized in that the functional unit (37) is connected to a pressure-biased expansion chamber (23).

21. Vibration damper according to one of claims 1 to 20, characterized in that both working spaces (9; 11) are designed with a functional unit (27a; 27b), wherein both functional units (27a; 27b) are arranged in a housing (45) and for each one working space (9; 11) there is a separate separating element (37a; 37b), wherein the two separating elements (37a; 37b) delimit a preloading space (47).

22. Vibration damper according to claim 21, characterized in that the biasing space (47) via a pressure medium connection (49) is adjustable in its pressure level.

23. Vibration damper according to claim 21, characterized in that the two separating elements (37a, 37b) perform a different elastic working movement.

24. Vibration damper according to claim 1, characterized in that the functional element (27) on the piston rod (5) is arranged.

25. Vibration damper according to claim 24, characterized in that the functional element (27) has an annular design.

26. Vibration damper according to claim 24, characterized in that in the annular functional element (27) at least one gas-filled cushion (41) is arranged.

27. Vibration damper according to claim 25, characterized in that a lateral surface of the functional element (27) is designed with at least one throttle opening (33)