EP1554501A1

EP1554501A1 - Multi-layer bellows

Info

Publication number: EP1554501A1
Application number: EP03773566A
Authority: EP
Inventors: Frank Budde; Georg Wolf
Original assignee: ZF Lemfoerder GmbH
Current assignee: ZF Lemfoerder GmbH
Priority date: 2002-10-21
Filing date: 2003-10-21
Publication date: 2005-07-20
Also published as: DE10249073B4; WO2004038237A1; DE10249073A1

Abstract

The invention relates to a sealing bellows for balljoints, driveshaft connections and similar, characterized in that the wall of the sealing bellows comprises at least two layers of elastomer or polymer (5, 6) with differing material properties. According to the invention, the multi-layer construction of a core and main layer permits materials not previously applicable to the production of sealing bellows to be used for the above purpose. Furthermore, the differing quality-determining factors of, for example, elasticity and surface properties of sealing bellows can be essentially independently optimised. Sealing bellows with optimal quality properties can thus be produced at low cost.

Description

Mehrschichtbalg

description

The invention relates to a sealing bellows for ball joints, drive shafts and the like according to the preamble of patent claim 1.

Sealing bellows of the type mentioned at the outset are used where it is important to protect joints, such as ball joints, or shaft connections, such as universal joints or ball constant velocity joints, from environmental influences, such as dirt and moisture. In particular, generic bellows are used

Sealing ball joints, for example in motor vehicle wheel suspensions. For this purpose, sealing bellows comprise an elastic bellows, which has a pin-side and a joint-side opening. The sealing bellows closes the joint housing to the outside and is penetrated by the joint pin of the ball joint. Another task of such bellows is to prevent the joint from running dry due to the loss of the lubricant. For this purpose, the sealing bellows forms a chamber for receiving the lubricant due to the shape between its inner wall and the joint.

Generic sealing bellows, such as are known for example from DE 198 50 378, are mostly produced from elastomer mixtures such as rubber or chloroprene rubber or from thermoplastic elastomers, and have to meet a multitude of different requirements with regard to design requirements and material properties. These include in particular the required sealing effect between the bellows and the joint, a sufficient one

Temperature resistance at high temperatures as well as sufficient cold flexibility low temperatures; resistance to environmental media, fuels, solvents, lubricants and the like.

In the case of the sealing bellows for ball joints, there is also the fact that, in addition to a good sealing effect, the bellows edge must also slide on one of the parts of the ball joint, usually on the ball neck, in order to enable the ball to rotate in the ball socket in addition to pivoting mobility, without that the bellows is twisted. In order to nevertheless achieve a good sealing effect between the bellows edge and the ball shaft with simultaneous relative mobility, the lowest possible coefficient of friction between the surface of the bellows edge and the

Ball shaft desirable; likewise for reasons of a good sealing effect, however, the highest possible coefficient of friction is desired on the tight fit of the bellows on the joint housing.

These diverse, sometimes diametrically contradicting requirements for the material of a sealing bellows cannot be met optimally with practically none of the common bellows materials in a homogeneous sealing bellows.

Against this background, it is the object of the present invention to create a sealing bellows which does not have the disadvantages mentioned and which, in particular with regard to coefficients of friction, wear resistance, temperature resistance,

Cold flexibility, media resistance and diffusion resistance is superior to the sealing bellows from the prior art, while at the same time being inexpensive to produce.

This object is achieved by a sealing bellows with the features of patent claim 1.

Preferred embodiments are the subject of the subclaims.

The sealing bellows according to the present invention is used in a manner known per se for protection and sealing, in particular, but in no way exclusively, of ball joints, or for example also of shaft connections. According to the invention However, the sealing bellows is characterized in that the wall of the sealing bellows is composed of at least two layers of elastomer or polymer material.

This makes it possible to use different materials that can be optimized in each case, for example for the inside or outside of a sealing bellows. For example, in the case of a sealing bellows having a wall made of two different materials, a material can be used in the inner region of the wall of the sealing bellows that is optimized in particular for elasticity and resistance to the lubricant used, whereas a material can be used on the outside of the sealing bellows. which is particularly resistant to environmental influences such as UV light, aggressive media or moisture.

According to a preferred embodiment of the invention, one of the material layers of the wall of the sealing bellows is designed as a core or carrier layer and a layer arranged on the surface of the wall as a skin layer. The core or carrier layer particularly preferably has a greater wall thickness than the skin layer.

In other words, this means that the sealing bellows has a core or carrier layer which can be optimized essentially with regard to the volume properties of the material, such as elasticity, flexibility, resistance to cold as well as tensile stress and elongation at break, while an outer skin layer of the sealing bellows, for example, essentially the surface properties of the material, such as chemical resistance, wear resistance, coefficient of friction, sealing effect or diffusion resistance can be optimized.

According to a further embodiment of the present invention, the core or carrier layer consists of a foamed material. A whole range of advantages can be achieved by using a foamed material as a carrier layer. In this way it is possible to still produce a sealing bellows with a relatively large wall thickness using only a small amount of material. On the one hand, this saves valuable material, and on the other hand a sealing bellows with a relatively low mass is obtained, which is particularly important when used in the area of the sprung masses on the wheel suspension of a motor vehicle.

Furthermore, in this way materials can also be used for the production of sealing bellows, which would not be suitable for the production of sealing bellows due to their mechanical properties, for example due to their low elasticity. The range of materials that can be used is thus expanded, which on the one hand increases the freedom of choice for the designer, but on the other hand also makes it possible to use particularly inexpensive materials for the production of sealing bellows. However, these advantages are only made possible by the multi-layer structure of the sealing bellows according to the invention, because in this way the sealing bellows can have a mechanically and chemically sensitive foamed core layer, which is, however, provided with protective and / or stabilizing skin layers. This also practically eliminates the lifespan of plasticizers from the sealing bellows, which leads to harmful embrittlement and subsequent failure of the sealing bellows. A foamed sealing bellows is in no way inferior in quality properties to a sealing bellows made of solid material.

Another preferred embodiment of the invention provides that the skin layer has a wall thickness in the range of only 0.01 to 1 mm. This is advantageous, since in this way a particularly high-quality material can be used for the inner and / or outer surface of the sealing bellows, without the

Material costs for the entire bellows would be significantly increased. Thus, the sealing bellows can obtain particularly advantageous chemical or mechanical properties in a largely cost-neutral manner.

According to a further embodiment of the invention, the wall of the

Seal bellows have a skin layer on both surfaces. The two skin layers can, as is provided by a further embodiment of the invention have different material properties or wall thicknesses. For example, it is possible to make the outer skin layer from a material that is particularly resistant to environmental influences, exposure to light and aggressive media and at the same time is particularly resistant to abrasion and abrasion, while the inner skin layer is resistant to the lubricant used and in Regarding the desired friction values between the sealing bellows and its seat on the joint can be optimized.

The mechanical and / or chemical stress on a sealing bellows is often different in different areas of the sealing bellows. For example, the fastening areas at the two axial ends of the sealing bellows are subjected to particularly high mechanical stresses due to the clamping of the sealing bellows arranged there on the joint and due to the friction occurring there between the sealing bellows and the joint. On the other hand, in certain others

A particularly high degree of flexibility is often desirable in areas of the sealing bellows. Against this background, it is provided according to a further embodiment of the invention that the wall of the sealing bellows or one or more of the layers of the wall of the sealing bellows has a wall thickness that varies over the length of the bellows. This can be achieved, for example, by the fact that the semifinished product used to manufacture the bellows already has a wall thickness of one or more layers which varies accordingly over its length. In this way, certain areas of the sealing bellows can be provided with a larger wall thickness and a correspondingly higher load capacity, while those with less load can have a correspondingly reduced wall thickness of one or more layers.

In the case of sealing bellows for ball joints, it is often necessary for the bellows to be defined and firmly seated against the joint housing, while the bellows bearing against the ball shaft of the joint must allow a rotational movement between the bellows and ball shaft due to the necessary rotational mobility of the joint. This means that in the area where the bellows rest on the joint housing, the highest possible coefficient of friction between the bellows material and the joint housing, in the area where the bellows rest on the ball shaft however, the lowest possible coefficient of friction is desired. These conflicting requirements are practically impossible to achieve with conventional sealing bellows. With this background, it is provided according to a further embodiment of the invention that at least one layer or layer of the sealing bellows, in particular a skin layer, particularly preferably the inner skin layer of the sealing bellows, extends only to partial regions of the length of the sealing bellows.

For example, in those areas in which a protective effect, for example of an inner skin layer against the effects of the lubricant located in the interior of the sealing bellows, or a low coefficient of friction between the sealing bellows and the ball neck, is desired, the sealing bellows can be provided with a skin layer which Requirements met optimally. On the other hand, that part of the sealing bellows which is in contact with the joint housing can be kept free of the inner skin layer, which results in optimal coefficients of friction and an optimal sealing effect.

In order to be able to meet further design requirements with the sealing bellows, it is provided according to a further embodiment of the invention that the wall of the sealing bellows comprises at least one further layer of a material that fulfills special functional requirements. This can be, for example, but by no means exclusively, a special barrier layer with which the diffusion of, for example, lubricants or solvents or moisture through the wall of the sealing bellows can be reduced. Another example of an additional functional intermediate layer is the possibility of including a reinforcing layer, for example an intermediate or intermediate layer in the form of a resistant textile fabric.

If materials with very different chemical and / or physical properties are used for the different layers of the wall of a sealing bellows, it can happen that these different material layers do not adhere to one another to the extent desirable for a robust sealing bellows. With this background it is according to a further embodiment of the According to the invention, adhesives or means for improving the compatibility of the layer materials are arranged between different layers or directly in at least one material component of the sealing bellows. The use of adhesives between different layers of the wall of the sealing bellows means that even very different materials, such as, for example, only a core made of rubber and a skin layer made of a polyolefin, adhere well to one another or are intimately connected to one another.

The invention further relates to a method for producing a sealing bellows for ball joints, shaft connections and the like, in which in a first

Method step an essentially prismatic hollow body is generated, which has a wall made of at least two polymer layers. In a further process step, the hollow body is introduced into a mold cavity. The hollow body is then shaped in a further process by applying internal pressure and then vulcanizing, solidifying or solidifying the hollow body in the mold cavity. Finally, in a further process step, the bellows now formed is removed from the mold cavity or removed from the mold.

The way in which the wall of the hollow body receives several layers of material is not important for the invention as long as an intimate connection of the layers to one another or a good adhesion of the layers to one another is ensured. According to a preferred embodiment of the invention, however, a multi-layer hollow body is produced by coating a single or multi-layer hollow body on its inside and / or outside. The coating of the hollow body is particularly preferably carried out by fluidized bed sintering or rotary sintering. That too is

Coating of the hollow body on the inside and / or outside with a film is possible.

According to a further preferred embodiment of the invention, the multilayer hollow body is produced by extrusion of an essentially endless tube with subsequent cutting to the desired length. By using a coextrusion process, it is possible to have one wall with several , """""

WO 2004/038237

to produce different layers of different materials hose or a hollow body. Such a hollow body produced by coextrusion with a multilayer wall can then be placed directly in a blow mold and shaped into a sealing bellows with a multilayer wall.

According to a preferred embodiment of the method according to the invention, at least one layer or layer of the wall of the hollow body is produced only on partial areas of the axial length of the hollow body. This can be done, for example, but by no means exclusively, by switching the nozzle areas of the extruder head on and off (sequential extrusion) or by correspondingly controlling the nozzle widths of the extruder during extrusion.

In other words, such a selective generation of certain layers of the wall of the hollow body enables the production of a sealing bellows, in which certain layers of the wall, for example the inner skin layer, are only present in certain areas of the sealing bellows, while in other areas, for example in fastening areas of the Bellows are missing. On the other hand, it is also possible to provide an (inner and / or outer) skin layer only in one or both fastening regions in order to optimize the sealing effect, the coefficients of friction and the wear resistance in the fastening regions.

As a result, sealing bellows can be produced in this way, which are optimally tailored to the respective requirements, and which in particular meet the requirement for particularly high resistance to the influence of media and the requirement for particularly tight and secure attachment to the ball neck or joint housing ,

Likewise, as is provided according to a further embodiment of the invention, for example by correspondingly controlling the extruder head, one or more layers of the wall of the hollow body can have a thickness that is variable over the axial length of the hollow body during the manufacture of the hollow body. In this way, hollow bodies can be produced which can be further processed directly into sealing bellows with variable wall or layer thicknesses.

The invention is explained in more detail below with reference to drawings showing exemplary embodiments. Show it:

Fig. 1: in a schematic longitudinal sectional view of a core layer and outer

Sealing layer comprising skin layer; Fig. 2: in a sectional view corresponding to Fig. 1 with a sealing bellows

Core layer and inner and outer skin layer; and FIGS. 3, 4: in a representation corresponding to FIGS. 1 and 2, two variants of one

Hollow body for the production of a sealing bellows.

1 and 2 each show half longitudinal sections through the wall of a sealing bellows, which is provided for sealing a ball joint. A first fastening region 1 can be seen in each case, with which the sealing bellows can be arranged and fastened on the joint housing (not shown) of a ball joint. To securely fasten the sealing bellows to the ball joint, the sealing bellows has a circumferential annular groove 2 in the region of its first fastening region 1, into which a ring-like circumferential clamping element, for example a clamping ring, can be inserted after the sealing bellows has been fitted onto the joint housing of the ball joint Fastening area exerts a radially inward clamping force on the sealing bellows. In a similar manner, the sealing bellows is fastened in the region of its second fastening region 3 with the aid of an annular groove 4 arranged there in the outer region and a further clamping ring which can be inserted therein on the ball neck of the joint ball of the ball joint.

In Fig. 1 it can be seen that the sealing bellows shown there has a two-layer wall consisting of core or carrier layer 5 and skin layer 6. Thanks to this two-layer structure, it is possible to choose an elastomer material for the core or carrier layer 5 that optimally meets the requirements regarding elasticity and flexibility at high and low temperatures, sealing effect, and costs, while for the skin layer 6 a if necessary, particularly high quality material can be selected that can be optimized in particular with regard to the resistance to environmental influences such as UV light, salt water or aggressive media.

Another aspect of choosing the optimal skin material is that when using a skin material with a low coefficient of friction, the assembly of the clamping rings in the grooves 2 or 4 is made considerably easier by the fact that the clamping rings move into the grooves 2 and 4 by themselves slide in, whereby the repressing of the clamping rings into the ring grooves, which is often required in the prior art, can be dispensed with without replacement after insertion.

A further embodiment of a sealing bellows is also shown in schematic longitudinal section in FIG. It can be seen that the sealing bellows according to FIG. 2 has a wall made up of three layers. The wall of the sealing bellows according to FIG. 2 has an inner skin layer 1, a core layer 8 and an outer skin layer 9. With such a three-layer wall of a sealing bellows, further structural freedom can be made possible. For example, a particularly inexpensive elastomer material, for example also a recycled material, can be used for the core layer 8, which does indeed meet the mechanical requirements for a sealing bellows, but not the chemical or

Resistance requirements with regard to the surface of the sealing bellows are met, since these requirements are met by the materials that can then be specifically selected for the inner skin layer 7 and the outer skin layer 9. Examples of materials for the core layer are thermoplastic elastomers or rubber mixtures.

With the three-layer structure according to FIG. 2, it is even possible to use a foamed material for the core layer 8, which in particular leads to further material, cost and weight savings. In this way, however, materials that do not have sufficient elasticity in solid form for use as a sealing bellows, such as, for example, only materials from the group of polyolefins, can be used in foamed form as core layer 8 for a sealing bellows. 3 and 4, two variants of a hollow body are shown in a schematic longitudinal sectional view, as it can be used as a starting product for the production of a sealing bellows. 3 shows one half of a longitudinal section through an essentially cylindrical hollow body which has a double-layered wall consisting of core layer 5 and skin layer 6. Such a hollow body with a multilayer wall can be produced, for example, by coextrusion of two different polymer or elastomer materials and subsequent cutting to length. The hollow body can then be inserted into a negative mold having the shape of the sealing bellows and the shape of the sealing bellows can be obtained by blow molding or internal pressure.

Fig. 4 also shows a substantially cylindrical hollow body in a semi-schematic longitudinal section. The hollow body according to FIG. 4, however, has a three-layer wall structure over most of its axial length. An inner skin layer 1, a core layer 8 and an outer skin layer 9 can be seen. After the blow molding, the three wall layers 7, 8, 9 form the corresponding layers of the wall of the sealing bellows. In the case of the hollow body according to FIG. 4, however, the inner skin layer 7 extends only over part of the length of the hollow body or the sealing bellows produced therefrom. The area designated by reference number 10 in FIG. 4 and not having an inner skin layer 7 on the finished sealing bellows corresponds, for example, to the area which comes into contact with the joint housing of a ball and socket joint (see reference number 1 in FIGS. 1 and 2).

Since a firm and tight connection of the sealing bellows and the joint housing is desired in the area of the sealing bellows and joint housing of a ball and socket joint, and since there should be no relative movement between the sealing bellows and the joint housing in this area, a high coefficient of friction between the sealing bellows and the joint housing is desired in this area. This is taken into account in the present case in that, due to the lack of an inner skin layer 7 present in the region 10, the core material 8, which usually has a high coefficient of friction, comes into direct contact with the joint housing of the ball joint. On the other hand, in the area designated by reference number 11, which corresponds to the area designated by reference number 3 in FIGS. 1 and 2, a relatively low coefficient of friction between the sealing bellows and the ball neck of the ball-and-socket joint lying there is desired in order to ensure that despite a certain contact pressure between the

Sealing bellows and the ball neck at 11 still allow a sliding relative movement between the surfaces of the ball neck and sealing bellows. This is the only way to ensure the rotational mobility of the ball in the joint housing, which is necessary for the ball joint to move freely, without the sealing bellows being twisted about its longitudinal axis.

Finally, FIG. 4 also shows that the hollow body shown there already has a wall thickness which can be varied over its axial length. This variable wall thickness on the sealing bellows produced from the hollow body according to FIG. 4 also leads to a wall thickness that varies over the axial length of the sealing bellows, or compensates for the reduction in wall thickness that occurs during blow molding due to radial expansion in such a way that the finished sealing bellows at every point with exactly that constructively provided wall thickness can be provided.

The result clearly shows that thanks to the invention, the structural freedom in the design of sealing bellows, as they are used in particular, but by no means exclusively, to protect and seal ball joints, can be decisively improved by a thanks to the multilayer structure of the sealing bellows A wide range of materials that could not previously be used for this purpose can be used. In addition, thanks to the multilayer according to the invention

Wall structure optimize the numerous quality-determining factors for sealing bellows largely independently of one another. This means that bellows with optimal quality properties can be produced at low costs. LIST OF REFERENCE NUMBERS

First attachment area

ring groove

Second attachment area

ring groove

backing

skin layer

core layer

skin layer

10. Skin-free section

11. Area

Claims

MehrschichtbalgPatentansprüche

1. sealing bellows for ball joints, drive shafts and the like, characterized in that the wall of the sealing bellows comprises at least two layers of elastomer or polymer with mutually different material properties.

2. Bellows according to claim 1, characterized in that at least one layer is formed as a core or carrier layer (5, 8).

3. Bellows according to claim 1 or 2, characterized in that at least one layer arranged on a surface of a wall is designed as a skin layer (6, 1, 9).

4. Sealing bellows according to claim 2 or 3, characterized in that the core or carrier layer (5, 8) is optimized essentially with regard to volume properties and the skin layer (6, 7, 9) essentially with regard to surface properties.

5. sealing bellows according to one of claims 2 to 4, characterized in that the core or carrier layer (5, 8) has a greater wall thickness than the skin layer (6, 7, 9).

6. sealing bellows according to one of claims 2 to 5, characterized in that the core or carrier layer (5, 8) consists of foamed material.

7. sealing bellows according to one of claims 3 to 6, characterized in that the skin layer (6, 1, 9) has a wall thickness in the range of 0.01 to 1 mm.

8. sealing bellows according to one of claims 3 to 7, characterized in that the wall of the sealing bellows has a skin layer (7, 9) on both surfaces.

9. sealing bellows according to claim 8, characterized in that the two skin layers (7, 9) have mutually different material properties and / or material thicknesses.

10. sealing bellows according to one of claims 1 to 9, characterized by variable over the length of the bellows wall thicknesses of core and / or skin layers.

11. Bellows according to one of claims 2 to 10, characterized in that at least one core or skin layer extends only to partial areas of the axial length of the bellows.

12. sealing bellows according to one of claims 1 to 11, characterized in that the wall of the sealing bellows comprises at least one further layer.

13. Bellows according to spoke 12, characterized in that the further layer is designed as a barrier layer to reduce the diffusion of the substance.

14. sealing bellows according spoke 11 or 12, characterized in that the further layer is designed as a fabric layer to increase the strength of the sealing bellows.

15. Sealing bellows according to one of claims 1 to 14, characterized in that adhesives or means for improving the compatibility of the layer materials are arranged between different layers of the sealing bellows or are introduced into at least one material component of the sealing bellows.

16. A method for producing a sealing bellows for ball joints, drive shafts and the like, with the method steps:

Generating an essentially prismatic hollow body having a wall of at least two polymer layers with different material properties;

- Introducing the hollow body into a mold cavity;

- Forming by applying internal pressure and subsequent vulcanization, solidification or solidification of the hollow body in the mold cavity; and

- De-molding of the bellows from the mold cavity.

17. The method according to claim 16, characterized in that in the first method step the multilayer hollow body is produced by coating a single or multilayer hollow body on the inside and / or outside of the wall.

18. The method according to claim 17, characterized in that the coating of the hollow body is carried out by spine sine or rotary sinter.

19. The method according to claim 16, characterized in that in the first process step, the multilayer hollow body is produced by extrusion and subsequent cutting to length.

20. The method according to any one of claims 16 to 19, characterized in that at least one layer of the hollow body (7) is generated only on partial areas of the axial length of the hollow body.

1. Verfaliren according to one of claims 16 to 20, characterized in that the thickness of at least one layer of the hollow body varies over the axial length of the hollow body.