DE102013105326B4 - Hydraulic bush - Google Patents

Abstract

Hydraulic bush having an outer bushing (12), a bearing core (14) and an elastomeric body (42) disposed between the outer bushing (12) and the bearing core (14) and defining at least two fluid-filled chambers (44, 46) wherein the chambers (44, 46) are interconnected via a passage (48, 50) to which is associated a valve (52, 54), the elastomeric body (42) having a decoupling membrane (56) between the passageway (48). 48, 50) and a cavity (58) introduced into the elastomeric body (42), and wherein a cage (20) is vulcanised into the elastomeric body (42), which has a membrane window (32) on which a decoupling membrane (56 ) is arranged.

Description

The invention relates to a hydraulic bush having an outer bushing, a bearing core and an elastomeric body which is arranged between the outer bushing and the bearing core and delimits at least two chambers filled with a fluid, wherein the chambers are connected to one another via a passage to which a valve is assigned ,

Such hydraulic bushes are used in particular in the chassis area for damping vibrations as a result of unbalance excitations on the front axle in the direction of travel of passenger cars. Here, the vibrations introduced lead to a relative movement of the core and outer sleeve, whereby the volume of a chamber increases and at the same time the volume of the other chamber is reduced. Thereby, the fluid experiences a differential pressure so that the fluid flows from the chamber of reduced volume to the chamber of increased volume via the damping passage. Due to the small diameter of the damping channel and associated friction by the viscosity of the fluid or by Tilgereffekte the fluid in the channel, the induced vibrations are damped.

Particularly in the acoustically relevant area, that is to say in the case of high-frequency oscillations of small amplitudes, conventional hydraulic bushings increase the dynamic rigidity. Due to inertial effects, the liquid can no longer flow through the damping channel following the exciting vibrations. Vibration-induced volume changes cause the diaphragms of the elastomeric body to stretch, the internal pressure in the chambers increases. Since the static stiffness now has to be added to the membrane stiffness, the resulting stiffness compared to the initial stiffness is significantly increased. In addition, there is the effect of dynamic hardening of rubber compounds at low amplitudes, which is also known under the name Payne effect. Both effects lead to a high dynamic rigidity of the bearing, which leads to poor acoustic properties, that is, to a low isolation through the bearing. This is acoustically perceptible to the vehicle occupant.

If the fluid chambers are limited by thick lateral membranes, they are naturally more robust than thin lateral membranes. Local stress strains may decrease, age-related surface cracks take longer to progress through the membranes and lead to leakage. Also, thicker membranes can make a significant contribution to the static stiffness of the bearing. However, thick membranes result in higher dynamic stiffness of the bearing when the sum of the swelling stiffnesses of all the membranes surrounding the chamber is high. High dynamic stiffnesses at high frequencies in turn lead to poor acoustic properties of the jacks and are therefore undesirable.

By contrast, thin membranes lead to low dynamic stiffnesses and are acoustically advantageous. However, they scarcely contribute to the static rigidity of the bearing, show high strains very quickly and, in individual cases, can even chafe through to leakage.

From the DE 10 2008 058 239 A1 a hydraulically damping bush of the aforementioned type is known, which has a core, an outer sleeve and an elastomer body arranged between the core and the outer sleeve. By the elastomeric body, the interior of the socket is divided into two working chambers, which are connected to each other via a channel. Furthermore, a valve designed as a ramp valve is provided.

From the DE 101 46 154 B4 For example, a hydraulic damping bushing is known which has a working chamber and a compensation chamber which are connected to one another via a channel. The working chamber is associated with a decoupling membrane, which decouples the damping in vibrations with high frequencies and small amplitudes. As a result, a dynamic hardening of the socket is avoided.

In the known hydraulic bushings, the decoupling membranes are loaded at each deflection of the bearing, even if this deflection is quasi-static, that is, carried out so slowly that a pressure equalization between the fluid chambers can be established via the channels. As a result, the membranes are loaded by both the hydraulic pressures, as well as by the static deflection. A shorter life compared to membranes that are not burdened by the relative movement of core and outer tube is the result.

DE 41 37 692 C1 discloses a hydraulically damped bearing in which the closing force of a valve is substantially independently and reproducibly fixed. DE 199 18 350 A1 discloses a hydraulic bearing that can be used for example on rear axles of vehicles. The task was to optimize the opening behavior of a valve member.

The object of the invention is to propose a hydraulic damping socket, in which the effectiveness of the decoupling in all Operating conditions is ensured and at the same time has a long service life of the membranes.

This object is achieved by the hydraulic bush according to claim 1. Advantageous embodiments of the invention are the subject of the dependent claims.

The bush according to the invention is characterized in that the elastomeric body has an additional decoupling membrane which is arranged between the passage and a cavity introduced into the elastomeric body. In the elastomeric body, a cage is vulcanized, which has a membrane window on which the decoupling membrane is arranged. The inventive arrangement of the decoupling membrane is achieved that it lies outside the load path and is not stressed by static deflections. This ensures effective decoupling in all operating conditions. In particular, the decoupling membrane is not stressed by static deflections of the socket.

Advantageously, the chambers are interconnected by two passages, which are each associated with a valve and a decoupling membrane. The valves are designed so that they release the passage only in a flow direction.

In order to simplify the production, the decoupling membrane is advantageously formed integrally with the elastomer body, wherein on the fluid side facing away from the decoupling membrane, a cavity is housed, which may be connected to the ambient air.

In an advantageous embodiment, a cage is vulcanized into the elastomer body, which has a membrane window on which the decoupling membrane is arranged.

The decoupling membrane can extend over the entire membrane window or only over parts of the membrane window. The desired decoupling effect can be adjusted by selecting the size of the decoupling membrane, that is to say the extent in the membrane window.

Advantageously, the cage has spaced webs extending in the axial direction of the cage and defining the membrane window.

Advantageously, the web has two axially spaced annular end pieces, which are interconnected via the circumferentially spaced webs.

The valve is advantageously a ramp valve, wherein the ramp valve is preferably made of an elastomer and more preferably vulcanized to the elastomeric body.

In an advantageous embodiment, the valve is arranged in the region of the decoupling membrane. These pressure relief valves placed near the decoupled decoupling membrane protect the very dull decoupling membrane from excessive loads due to pressure peaks, such as strong braking maneuvers.

In an advantageous embodiment, a valve is arranged in each passage, wherein the valve releases the associated passage only in a fixed flow direction.

A cooperating with the bearing core stop is advantageously provided to prevent damage to the socket due to high forces and moments.

In an advantageous embodiment of the stop is designed as a separate stop member, which is inserted in a recess of the cage.

Advantageously, a first stop is arranged opposite a second stop, wherein the core is arranged between the first stop and the second stop.

In a further advantageous development of the passage connecting the chambers channel is connected in parallel.

The invention will be explained in more detail with reference to embodiments shown schematically in the drawing. Herein show:

1 a vertical section through the socket according to the invention;

2 a longitudinal section through the inventive socket according to 1 ;

3 a longitudinal section through a second embodiment of a socket according to the invention; and

4 a perspective view of the cage of the hydraulic sleeve according to 1 ,

In the 1 illustrated hydraulic jack 10 includes an outer sleeve 12 and a bearing core arranged coaxially therewith 14 that is about an elastomeric body 42 on the outer socket 12 supported. The outer bush 12 has an interior 18 on, in which the storage core 14 is arranged.

In the elastomeric body 42 is a cage 20 vulcanised, which consists of plastic. 4 shows a perspective view of the cage 20 , The cage 20 has two annular end pieces 22 . 24 which are spaced apart in the axial direction. The tails 22 . 24 are over jetties 28 . 30 interconnected, which are circumferentially spaced. Through the two spaced webs 28 . 30 becomes a window 32 limited.

How out 1 shows, divided the elastomer body 42 an interior 18 the hydraulic jack 10 in a first chamber 44 and a second chamber 46 , The first chamber 44 is about a first pass 48 with the second chamber 46 connected. In the first round 48 is a first valve 52 provided on the outer circumference of the cage 20 is vulcanized.

The second chamber 46 is about a passage 50 with the first chamber 44 connected. In the passage 50 is a second valve 54 intended.

The valves 52 . 54 are each designed as a ramp valve, so that the flow of the fluid can only take place in a circumferential direction.

At the passages 48 . 50 is in each case a thin decoupling membrane 56 provided at the window 32 of the cage 20 is vulcanized. Each decoupling membrane 56 is one in the elastomeric body 42 introduced hollow chamber 58 assigned. Thus, the decoupling membrane 56 between the passage 48 . 50 and the air-filled hollow chamber 58 positioned. The decoupling membranes 56 are designed soft and yielding, so that at low exciter amplitudes, the damping is decoupled. The decoupling membranes 56 extend over the entire width of the passages 48 . 50 ,

The valves 52 . 54 are designed as a ramp valve and in each case in the region of the decoupling membrane 56 arranged. As a result, a fast response of the valves is achieved at high pressures, causing damage to the decoupling membrane 56 be avoided.

2 shows a first embodiment of the socket 10 in which the side walls 16 . 17 of the elastomeric body 42 have a relatively large thickness. In contrast, in the in 3 illustrated socket 10 the side walls 16 . 17 much thinner running. In the 3 embodiment shown is mainly used in hydraulic bushings in which no decoupling membrane 56 is used.

Furthermore, the socket 10 attacks 36 . 38 on top of that with the storage core 14 interact and limit its deflection. This will damage the socket 10 avoided by overuse. The attacks 36 . 38 are each formed as a separate stop member, which in a recess in the cage 20 is used.

Below is the operation of the hydraulic jack 10 explained.

Will the storage core 14 in 1 deflected upward, so is the volume of the first chamber 44 decreases, whereby fluid is displaced. When a limit pressure is exceeded, this opens in the passage 48 arranged valve 42 , whereby fluid from the first chamber 44 in the second chamber 46 can flow. In principle, the same way leads the deflection of the bearing core 14 in 1 down to a compression of the second chamber 46 , which creates fluid in the passageway 50 is displaced.

This occurs especially with static loads and vibrations with high amplitude. By the overflow of the fluid and in the passage 48 oscillating liquid column is achieved damping of vibrations occurring.

For high-frequency oscillations with small amplitude, the thin decoupling membranes carry 56 for decoupling. Thus, the high-frequency vibrations are decoupled from the damping, whereby the acoustic properties are improved. Damage to the decoupling membrane 56 is caused by the in the area of the decoupling membrane 56 arranged valve 52 . 54 prevented.

Because in the passages 48 . 50 arranged decoupling membranes 56 Beyond the load path, these are not caused by static deflections of the bearing core 14 claimed. Thus, their operation is guaranteed in all operating conditions.

LIST OF REFERENCE NUMBERS

10

Hydraulic bush

12

outer bush

14

bearing core

16

Side wall

17

Side wall

18

inner space

20

Cage

22

tail

24

tail

28

web

30

web

32

window

36

attack

38

attack

42

elastomer body

44

First chamber

46

Second Chamber

48

First try

50

Second round

52

First valve

54

Second valve

56

decoupling membrane

58

cavity

Claims (11)

Hydraulic bush with an external bushing ( 12 ), a storage core ( 14 ) and an elastomeric body ( 42 ) between the outer bush ( 12 ) and the storage core ( 14 ) is arranged and at least two filled with a fluid chambers ( 44 . 46 ), the chambers ( 44 . 46 ) over a passage ( 48 . 50 ), to which a valve ( 52 . 54 ), wherein the elastomeric body ( 42 ) a decoupling membrane ( 56 ), which between the passage ( 48 . 50 ) and one in the elastomeric body ( 42 ) introduced cavity ( 58 ), and wherein in the elastomeric body ( 42 ) a cage ( 20 ) is vulcanised, which is a membrane window ( 32 ), on which a decoupling membrane ( 56 ) is arranged. Bush according to claim 1, characterized in that the chambers ( 44 . 46 ) through two passes ( 48 . 50 ), each having a valve ( 52 . 54 ) and a decoupling membrane ( 56 ) assigned. Bushing according to claim 1 or 2, characterized in that the decoupling membrane ( 56 ) integral with the elastomeric body ( 42 ), wherein the cavity ( 58 ) of the elastomeric body ( 42 ) and the decoupling membrane ( 56 ) is limited. Bush according to one of the preceding claims, characterized in that the cage ( 20 ) spaced webs ( 28 . 30 ), which in the axial direction of the cage ( 20 ) and the membrane window ( 32 ) limit. Bush according to claim 4, characterized in that the cage ( 20 ) two axially spaced annular end pieces ( 22 . 24 ), which over the circumferentially spaced webs ( 28 . 30 ) are interconnected. Bush according to one of the preceding claims, characterized in that the valve ( 52 . 54 ) is a ramp valve, which is preferably made of an elastomer and more preferably on the elastomeric body ( 42 ) is vulcanized. Bush according to one of the preceding claims, characterized in that the valve ( 52 . 54 ) in the region of the decoupling membrane ( 56 ) is arranged. Bush according to one of the preceding claims, characterized in that in each passage ( 48 . 50 ) a valve ( 52 . 54 ) is arranged, wherein the valve ( 52 . 54 ) the assigned passage ( 48 . 50 ) releases only in one direction of flow. Bush according to one of the preceding claims, characterized in that one with the bearing core ( 14 ) co-operative stop ( 36 . 38 ) is provided. Bush according to claim 9, characterized in that the stop ( 36 . 38 ) is formed as a separate stop member which is inserted in a recess of the cage. Bush according to one of claims 9 or 10, characterized in that a first stop ( 36 ) a second stop ( 38 ) is arranged opposite one another, wherein the core ( 14 ) between the first stop ( 36 ) and the second stop ( 38 ) is arranged.

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