Air spring bellows with supporting fabric and method for manufacturing one

Abstract

An air spring (1) with an air spring bellows (2) made of elastomeric material clamped between an air spring piston (5) and an air spring cover (3), wherein the air spring bellows (2), when filled with compressed air, forms a substantially cylindrical working chamber (7) with a rolled fold (8) that rolls along the air spring piston (2) during compression and rebound, is provided with reinforcing elements (22, 23) embedded in the elastomeric material, and has a protective layer of a textile structure (13) on its outer surface, which extends at least partially over its radially outer surfaces (9), characterized in that the textile structure is designed as a woven fabric (13) of stretchable warp and weft threads (14, 15) running substantially perpendicular to each other, wherein the weft thread(s) (15) has a greater extensibility than the warp thread(s) (14), and the warp threads (14) are arranged longitudinally (20) of the air spring rolling bellows (2), i.e.essentially in the direction of the roll fold (8) and the weft threads (15) are essentially aligned in the circumferential direction (21) of the air spring bellows (2), wherein the reinforcing elements (22, 23) embedded in the elastomeric material are formed in a diamond-shaped cross pattern and the warp threads (14) of the fabric (13) run essentially centrally through the thread diamonds of the crossed fabric layers.

Description

[0001] The invention relates to an air spring with an air spring rolling bellows made of elastomeric material clamped between an air spring piston and an air spring cover, wherein the air spring rolling bellows, when filled with compressed air, forms a substantially cylindrical working chamber with a rolling fold that rolls along the air spring piston during compression and extension, is provided with reinforcements embedded in the elastomeric material and has on its outer side a protective layer made of a textile structure that extends at least partially over its radially outer surface.

[0002] Such air springs are well-known and frequently used in passenger cars, trucks, and railway wagons. They are also known for applications in machine or foundation mountings.

[0003] An air spring bellows for such an air spring in a passenger car is usually made of elastomer materials with reinforcing elements. An air spring bellows is initially manufactured as a cylindrical body from several layers of rubber and layers of - partly rubberized - strength members, i.e. assembled to form a tube with possibly several layers of strength members embedded in the rubber. The strength members are aligned in their layers at an angle of approximately 53°, namely at the so-called thread angle, to the axial normal of the cylindrical body. Furthermore, the strength members in adjacent layers are often arranged crossed to one another, i.e., aligned at an angle to one side and the other with respect to the axis, thus forming a so-called thread diamond. In a developed view of the strength member layers of the cylinder, this would result in a crossed arrangement of the strength members, which in the case of e.g.with only two reinforcement layers it would resemble a hunter's fence.

[0004] As already indicated, the thread angle can be defined differently with respect to the axis, but here it is understood as the angle between the vertical, i.e., the normal to the bellows axis, and the reinforcements. A large angle could then reach 90° in extreme cases, meaning that the reinforcements in such a layer would run parallel to the bellows axis, while a small angle could reach a maximum of 0°, meaning that the reinforcements in such a layer would cross the bellows axis perpendicularly.

[0005] After assembly, the rolled bellows is conically expanded and vulcanized. During this manufacturing step, the different diameters are created and fixed by the heat-curing process.

[0006] Due to the high quality of the materials used, especially the reinforcements, the service life of an air spring bellows of this type is often determined not by the fracture of a reinforcement, but by wear of the bellows wall. The bellows wall is subjected to considerable stress due to the rolling movement and the simultaneous absorption of transverse forces.

[0007] It is therefore known to coat the bellows wall with various substances that improve the sliding properties of the surface

[0008] DE 10 2004 007 332 A1 discloses an air spring in which the air spring bellows are coated with a lubricant intended to reduce the adhesion of dirt to the bellows' outer wall. The lubricant can be applied during vulcanization or after the bellows are finished.

[0009] However, this coating cannot be expected to have a lasting wear-reducing effect, since although it reduces friction, it does not provide any further mechanical protection for the bellows wall.

[0010] EP 1 843 060 A1 discloses a generic air spring in which the air spring bellows has a protective layer extending over at least one of its radial outer surfaces, made of a textile structure formed as a warp-knitted fabric. However, the production of such a warp-knitted fabric, with its complex intermeshing, is not easy and is relatively expensive.

[0011] The invention is based on the object of creating an air spring of the type described at the outset, in which protection against mechanical wear is achieved by measures that are as simple and cost-effective as possible, production is simplified and an improved service life is achieved compared to the prior art under the same load collectives.

[0012] This problem is solved by the features of patent claims 1 and 5. Advantageous further developments are contained in the subclaims.

[0013] The textile structure is designed as a fabric made of stretchable warp and weft threads running essentially at right angles to one another, wherein the weft thread has a greater stretchability than the warp thread and wherein the warp threads are aligned in the longitudinal direction of the air spring bellows, i.e. essentially in the rolling direction of the roll fold and the weft threads are aligned essentially in the circumferential direction of the air spring bellows.

[0014] Such a textile structure has the advantage that the entire elastomeric surface is very well protected against external influences, especially in the rolling areas. Such simple structures, consisting of warp and weft threads, are relatively easy to manufacture and apply and can be securely and permanently bonded to the elastomeric bellows wall, preferably through a vulcanization process.

[0015] The outer fabric structure supports the air spring bellows' structure longitudinally. At the same time, it facilitates the rolling of the bellows on the air spring piston. Both of these factors result in bellows with the inventive outer fabric structure lasting significantly longer.

[0016] An advantageous further development is that the warp thread of the fabric has an extensibility of 15 to 18% of its original length and the weft thread has an extensibility of 40 to 150% of its original length.

[0017] Such a fabric with different elastic directions is surprisingly well suited for the coating of air spring bellows, since the resulting different extensibility of warp and weft leads to particularly good deformability when forming a roll fold and thus does not restrict the mobility of the air spring bellows when rolling on the air spring piston.

[0018] The construction of two threads with different stretch capacities, one of which is more stretchable than the other, also ensures that the fabric is easy to manufacture.

[0019] Another advantageous design, which is particularly easy to manufacture, is the increased stretchability of the weft thread, which is achieved by texturing the outside of the weft thread, unlike the warp thread, such as structuring, ribbing, or embossing. This design can also be used to further increase the difference in stretchability in materials that otherwise have different stretch properties.

[0020] A further advantageous design is that the strength members embedded in the elastomer material are crossed in a diamond shape, and the warp threads of the fabric run essentially centrally through the thread diamonds of the crossed fabric layers. In one test, a cylindrical tubular rolling bellows was provided with the textile structure formed in this way and, surprisingly, completed more than twice as many load cycles in a test bench test as the best standard bellows of the same type tested to date. This surprisingly good result in the durability test can be explained by the fact that, on the one hand, the threads of the two crosswise arranged fabric layers, which form the so-called thread diamonds, absorb the tensile forces within the bellows wall, and that the outer warp threads can absorb some of the internal stresses in the elastomer that surrounds the thread diamonds.This relief, especially under dynamic loads, significantly increases the service life of the air spring bellows. This is, of course, further enhanced by another advantageous design, namely the vulcanized fabric on the outside of the air spring bellows.

[0021] A particularly suitable method for producing an air spring according to the invention involves applying the textile structure as a three-dimensional, cylindrical or conical fabric body to the outer surface of the air spring bellows prior to vulcanization. This type of prefabrication simplifies production simply because the usual manufacturing process does not need to be altered, but only supplemented by a "side line."

[0022] An advantageous development of the process is that the average diameter of the three-dimensionally shaped fabric body is smaller than the outer diameter of the air spring bellows and is pulled onto the air spring bellows under tension, similar to a support stocking. This improves the adaptation of the textile structure / fabric to the air spring bellows. Before vulcanization, the textile structure can be pulled over the air spring bellows like an elastic stocking. This stocking is aligned so that the threads with low stretch run in the direction of the rolling movement of the bellows (longitudinal direction) and the threads with high stretch run perpendicular to this (circumferential direction). Since the diameter of the stocking is smaller than the outer diameter of the air spring bellows, the threads are slightly pre-tensioned in the circumferential direction and securely integrated into the elastomer matrix during vulcanization.

[0023] In terms of simple prefabrication, a further advantageous embodiment of the method consists in the fact that the spatially shaped fabric body is produced from a flat cut of the fabric, preferably from a rectangular, rhombus-shaped, or trapezoidal cut, before being applied to the air spring bellows, by joining two opposite edges of the cut, e.g., by ultrasonic welding, gluing, sewing, etc.

[0024] A further advantageous embodiment of the process involves treating the three-dimensionally shaped fabric body with an adhesive solution, preferably a solution of isocyanate and toluene, before being applied to the air spring bellows (). This is done to ensure the adhesion of the textile structure to the outer rubber of the air spring bellows. Further processing only takes place once the fabric is dry.

[0025] The invention will be explained in more detail using an exemplary embodiment. Fig. 1 an air spring according to the invention in section Fig. 2 on the outside of the air spring according to Fig. 1 applied protective layer made of a textile structure Fig. 3 sketches the production of the textile structure according to Fig. 2 Fig. 4 an air spring bellows of an air spring according to the invention in the not yet installed state directly after production Fig. 5 as a principle sketch the relative position of warp threads and weft threads and diamond-shaped crossed embedded reinforcements on the body of an air spring bellows of an air spring according to Fig. 1 Fig. 6 as a principle sketch the relative position of warp threads and weft threads and diamond-shaped crossed embedded reinforcements in the roll fold of an air spring bellows of an air spring according to Fig. 1

[0026] In the Fig. 1 shows an air spring 1 with an air spring rolling bellows 2. The air spring rolling bellows 2 is made of elastomeric material and is attached gas-tight at its first axial end to an air spring cover 3 by means of a clamping ring 4 and at its second axial end to an air spring piston or rolling piston 5, also by means of a clamping ring 6. The rolling piston 5 is arranged such that its end assigned to the second end of the air spring bellows 2 projects into the interior 7 of the air spring bellows 2 and the air spring rolling bellows 2 forms a rolling fold 8 in a known manner, which rolls along the main axis of the air spring 1 on the outer surface 9 of the rolling piston 5 during relative movements between the air spring cover 3 and the rolling piston 5.

[0027] The air spring cover 3 is attached to a body 10 (not shown in detail) and the rolling piston 5 is attached to a chassis part 11 (not shown in detail) of a vehicle not shown.

[0028] The air spring bellows 2 has a textile structure in the form of a fabric 13 on its outer radial surface 12, which extends over the entire surface 12. The fabric 13 is firmly bonded to the elastomeric material of the air spring bellows 2 by vulcanization. The different extensibility of the warp and weft threads of the textile structure 13, according to the invention, enables good deformation of the protective layer even in the roll fold 8.

[0029] Fig. 2 shows the textile structure 13 as a fabric made of stretchable warp and weft threads 14 and 15 that run essentially at right angles to one another. The weft threads 15 have a greater extensibility / extensibility than the warp threads 14. The warp threads 14 are aligned in the longitudinal direction of the pneumatic spring bellows 2, i.e., essentially in the rolling direction of the roll fold 8, and the weft threads are aligned essentially in the circumferential direction of the pneumatic spring bellows 2. The warp threads 14 of the fabric 13 shown here have an extensibility of 18% of their original length, and the weft threads 15 have an extensibility of 120% of their original length.

[0030] Fig. 3 shows a sketch of the production of the textile structure or fabric 13 as a spatially shaped, cylindrical fabric body 16, which is created from a rectangular blank 17 in this case, by two opposite edges 18 and 19 of the blank 16 being connected to one another by gluing.

[0031] Fig. Figure 4 once again shows an air spring bellows 2 in the not yet installed state, directly after production. Here, the directions in which the warp and weft threads 14 and 15 are arranged relative to the air spring bellows 2 are shown, namely, the warp threads 14 in the longitudinal direction 20 of the air spring bellows 2, i.e., essentially in the rolling direction of the rolled fold 8, and the weft threads 15 essentially in the circumferential direction 21 of the air spring bellows 2.

[0032] Fig. 5 and Fig. 6 shows schematic diagrams of the relative positions of warp threads 14 and weft threads 15 and the diamond-shaped, crossed reinforcements 22 and 23. The warp threads 14 of the fabric run essentially centrally through the thread diamonds of the crossed fabric layers of reinforcements 22 and 23.

[0033] Fig. 5 shows the state of the air spring bellows 2 only loaded by internal pressure, while Fig.6 shows the additionally stretched state in the rolled fold. List of reference symbols 1 air spring 2 air spring bellows 3 air spring covers 4 clamping ring 5 rolling pistons / air spring pistons 6 clamping ring 7 Interior of the air spring bellows, working chamber 8 roll fold 9 Piston surface 5 10 Body 11 Chassis part 12 outer radial surface of the air spring bellows 13 textile structure or fabric 14 warp threads 15 weft threads 16 cylindrical tissue bodies 17 rectangular cut 18 edge 19 edge 20 Longitudinal direction of the air spring bellows 21 Circumferential direction of the air spring bellows 22 strength members 23 Strength members

Claims

[1] Air spring (1) with an air spring rolling bellows (2) made of elastomeric material clamped between an air spring piston (5) and an air spring cover (3), wherein the air spring rolling bellows (2) forms a substantially cylindrical working chamber (7) with a rolling fold (8) that rolls along the air spring piston (2) when filled with compressed air, is provided with strength members (22, 23) embedded in the elastomeric material and has on its outer side a protective layer made of a textile structure (13) that extends at least partially over its radially outer lateral surfaces (9), characterized byin that the textile structure is designed as a woven fabric (13) made of stretchable warp and weft threads (14, 15) which run essentially at right angles to one another, the weft thread(s) (15) having a greater stretchability than the warp thread(s) (14) and in which the warp threads (14) are aligned in the longitudinal direction (20) of the pneumatic spring bellows (2), ie essentially in the rolling direction of the roll fold (8), and the weft threads (15) are aligned essentially in the circumferential direction (21) of the pneumatic spring bellows (2), the strength members (22, 23) embedded in the elastomeric material being crossed in a diamond shape and the warp threads (14) of the woven fabric (13) running essentially centrally through the thread diamonds of the crossed fabric layers. [2] Air spring according to claim 1, wherein the warp thread (14) of the fabric (13) has an extensibility of 15 to 18% of its original length and the weft thread (15) has an extensibility of 40 to 150% of its original length. [3] Air spring according to claim 1 or 2, wherein the increased extensibility of the weft thread (15) is produced by a texturing provided on the outside of the weft thread, in contrast to the warp thread (14). [4] Air spring according to one of claims 1 to 3, wherein the fabric (13) is vulcanized onto the outside of the air spring bellows (2). [5] Method for producing an air spring according to one of claims 1 to 4, in which the textile structure is applied as a three-dimensionally shaped cylindrical or conical fabric body (16) to the outer surface of the air spring bellows (2) before vulcanization. [6] Method according to claim 5, wherein the mean diameter of the three-dimensionally shaped fabric body (16) is smaller than the outer diameter of the air spring rolling bellows (2) and is pulled onto the air spring rolling bellows under tension. [7] Method according to claim 5 or 6, wherein the spatially shaped fabric body (16) is produced from a flat blank (17) of the fabric (13), preferably from a rectangular, rhombus-shaped or trapezoidal blank, before being applied to the air spring bellows (2), by joining two opposite edges (18, 19) of the blank together. [8] Method according to one of claims 5 to 7, wherein the spatially shaped fabric body (16) is treated with an adhesive solution, preferably with a solution of isocyanate and toluene, before being applied to the air spring bellows (2).

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