Method for widening a protective bellows of a motor vehicle air spring

Abstract

Method for widening an elastomeric protective bellows (3) of a vehicle air spring, which is partially connected to a connecting part (4) of the air spring, characterized by the following steps: - Providing an expansion device (1) with a radially extendable mandrel (2), - at least partially sliding the protective bellows (3) onto the pin (2), - radially expanding the mandrel (2) so that the protective bellows (3) is radially expanded beyond its nominal diameter in at least one area, - wherein the protective bellows (3) is removed from the mandrel (2) immediately after expansion and is then partially placed onto the connecting part (4) of the air spring, wherein the connecting part (4) has an outer diameter in the connection area which is larger than the nominal diameter of the protective bellows (3).

Description

[0001] The invention relates to a method for widening a protective bellows of a motor vehicle air spring according to the preamble of claim 1.

[0002] Air springs or air struts, which are clamped between the chassis and body of a motor vehicle and feature a rolling diaphragm that is in turn mounted between a cover and a rolling piston, are known in a variety of designs. During operation, the air spring is under internal overpressure, and the rolling diaphragm rolls along the outer surface of the concentric rolling piston during spring movement, forming a roll fold. To limit expansion, the rolling diaphragm is enclosed by a sleeve-shaped outer guide.

[0003] From DE 10 2009 003 829 A1, a freestanding air spring in an "upside-down" position is known, comprising a rolling piston and a cover. A rolling diaphragm is clamped pressure-tight between the rolling piston and the cover and rolls along both the rolling piston and the cover during spring movements, forming a rolling fold. To protect the rolling diaphragm and its rolling folds from contamination and damage, a bellows is provided, which is attached to the rolling piston on one side and to a lower end of the outer guide on the other. The bellows is attached to the outer guide by a positive-locking connection. For this purpose, an outwardly projecting collar is formed at the lower end of the outer guide, around which a fold of the bellows is folded, the fold being blow-molded into a designated shape.A disadvantage of this positive locking fastening is that the bellows end can detach from the fastening collar during operation of the air spring, leaving the bellows unprotected from contamination.

[0004] To prevent this, clamps or similar devices are generally used, as is known, for example, from DE 10 2004 023 561 A1. A secure connection is created by means of a holder that engages externally in the connection area between the bellows and the air spring cover.

[0005] From US patent 3,438,309 A, an air spring with a protective sleeve is known, wherein the protective sleeve is mounted on an outer edge of a rolling piston and is held without a clamp or the like. Further air springs with protective bellows connected by force, form, or friction are known from documents DE 10 2020 203 171 A1, JP 2004 - 156 663 A, EP 4 027 034 A1, DE 38 15 967 A1 and DE 10 2019 211 605 A1.

[0006] In general, a pneumatically operated assembly tool is known for mounting protective bellows, which includes expanding elements for inflating the bellows. The bellows is pulled over the expanding elements, which are then radially expanded by means of compressed air, thus inflating the bellows. Subsequently, the expanding elements, together with the bellows, are pushed over a component with a larger diameter than the nominal diameter of the bellows. After the inflated bellows has been positioned over the larger component, the expanding elements are released and the bellows can be removed.

[0007] The object of the invention is to simplify the connection of a protective bellows to an associated connecting part of an air spring, which is reliable in operation and also more economical.

[0008] This problem is solved by the features of claim 1. Preferred embodiments of the invention are set out in the dependent claims.

[0009] According to the invention, a method for widening an elastomeric protective bellows of a vehicle air spring is proposed, in which the protective bellows is connected to a connecting part of the air spring in certain areas, wherein the following steps are carried out: - Providing a reaming device with a radially extendable mandrel, - at least partially sliding the protective bellows onto the spike, - radially expanding the mandrel so that the protective bellows is radially expanded beyond its nominal diameter in at least one area, - wherein the protective bellows is removed from the mandrel immediately after expansion and then partially placed onto the connecting part of the air spring, the connecting part having an outer diameter in the connection area which is larger than the nominal diameter of the protective bellows.

[0010] The process for expanding an elastomeric protective bellows, which is subsequently connected to a connecting part of an air spring, is carried out using an expansion device specifically designed to expand the protective bellows radially. After vulcanization, the protective bellows has a specific shape and different nominal diameters in various areas. The nominal diameter refers to the protective bellows in its initial state and after vulcanization. Since the protective bellows has a conical shape, for example, it has different nominal diameters at its ends.

[0011] The expanding device comprises a mandrel made up of segments that can be moved radially outward from a retracted initial position. Preferably, the segments are divided into upper and lower segments, so that the protective bellows is expanded to different diameters in different areas along its length. With the mandrel in its initial position, the protective bellows is pushed or placed onto the mandrel at a defined position, either mechanically or manually. The mandrel, or rather its segments, are then moved uniformly radially outward. The segments are moved by force and displacement controlled by pneumatic or servo-driven actuators.

[0012] In the area where the pin engages the protective bellows, the bellows is stretched outwards. This expansion preferably occurs within its elastic range or below its material-specific elastic limit, but it can also extend beyond this limit into plastic deformation. The crucial factor is that the expansion does not cause the protective bellows to tear.

[0013] Due to the inherent elasticity of the protective bellows material, it contracts at least partially after expansion. This means the expanded diameter decreases after the mandrel is retracted and the protective bellows is removed. However, the elastic expansion of the protective bellows caused by the expansion is temporary, or rather, the return to its original shape is so slow that the protective bellows can be pulled onto the air spring connection part within this timeframe. The air spring connection part has an outer diameter that is larger than the nominal diameter of the protective bellows in the area to be connected. The protective bellows, once fitted in this manner, is then frictionally connected to the connection part. This is because radially inward restoring forces, resulting from the temporary expansion, subsequently act upon it.This creates a frictional force between the protective bellows and the connecting part in the connection area, thus securely holding the protective bellows to the connecting part. The proposed method therefore allows a connection between a protective bellows and an air spring connecting part without the need for additional clamping or tensioning devices.

[0014] Preferably, both the expansion and the retraction of the protective bellows are thermally influenced. For example, the protective bellows is heated before and / or during the expansion process. This can be achieved, for instance, by a heating device that irradiates the protective bellows with infrared light. The heating softens the bellows material, making it easier and safer to stretch, thus better preventing tearing.

[0015] Furthermore, the protective bellows is cooled by a cooling device during and / or after the expansion process. This can be done, for example, with a cold air blower. Cooling makes the bellows material harder, so the retraction is slower, allowing more time to pull the bellows onto the connecting part.

[0016] The described method enables an air spring in which the protective bellows is connected to a connecting part by friction.

[0017] The invention is explained in more detail with reference to the following description of figures. These show: Fig. 1 an exemplary expanding device with a protective bellows, Fig. 2 a first exemplary connection of the protective bellows with a connecting part, Fig. 3 a second exemplary connection of the protective bellows with a connecting part, and Fig. 4 a third exemplary connection of the protective bellows with several connecting parts.

[0018] The Fig. Figure 1 shows a 3D model of an exemplary expanding device 1 with a radially outwardly movable mandrel 2 onto which a protective bellows 3 is pushed. The mandrel 2 has two, three, or four segments 9 and 10, which can be individually moved radially outward from a home position. By uniformly moving apart segments 9 and 10, the protective bellows 3 is expanded beyond its nominal diameter.

[0019] Thus, the mandrel comprises two upper segments 9 and axially located lower segments 10, which can be moved radially independently of each other. This means that the upper segments 9 and the lower segments 10 can be controlled separately. This allows for different radial expansions of the protective bellows 3 in different areas.

[0020] Protective bellows 3 consists of several folds and is therefore also called a bellows. Protective bellows 3 is made of an elastomeric material. Depending on the elastomer chosen for protective bellows 3, it can be expanded elastically or plastically without damage. Protective bellows 3 is conical in the form shown. Protective bellows 3 comprises a first upper end, which is smaller in diameter than a second lower end. The second, lower, and larger end of protective bellows 3 is typically used to connect to an outer air spring guide. In its initial state, i.e., when not installed, protective bellows 3 has a so-called nominal diameter. The nominal diameter varies along the length of protective bellows 3. The nominal diameter is therefore the diameter that protective bellows 3 has after vulcanization.

[0021] When protective bellows 3 is pushed onto mandrel 2, the segments of mandrel 2 are moved radially outwards, thus expanding protective bellows 3. If protective bellows 3 is expanded beyond its nominal diameter, it will retract, at least partially, due to its inherent elasticity. During this time, it is possible to easily pull protective bellows 3 over a connecting part of an air spring, where the connecting part has an outer diameter larger than the nominal diameter of protective bellows 3.

[0022] For example, with mandrel 2 it is possible to widen protective bellows 3 in one or more different areas beyond the nominal diameter and then to connect the differently widened areas with different connecting parts of an air spring.

[0023] This method therefore supports an exemplary connection of protective bellows 3 with a connecting part 4 according to the Fig. 2 and Fig. 3. The Fig. Figure 2 illustrates a friction-fit connection between the protective bellows 3 and the connecting part 4. This connection requires no external clamping or tensioning devices and is held solely by the frictional force between the protective bellows 3 and the connecting part 4. This connection is supported and facilitated by the fact that the protective bellows 3, in its unconnected state, has a nominal diameter that is smaller than the outer diameter of the connecting part 4. Once the protective bellows 3 is connected to the connecting part 4, and the diameter of the protective bellows 3 in the connection area is larger than its nominal diameter, an additional elastic restoring force is exerted (indicated by the arrow). In this way, a reliable connection between the protective bellows 3 and the connecting part 4 is created, requiring no further fasteners.

[0024] The Fig. Figure 3 illustrates a further support for the friction-fit connection in that the connection area of ​​connecting part 4 includes a conically widened area 5, which makes it difficult to remove the protective bellows 3 because the protective bellows would have to expand further against its elastic restoring force, which in turn increases the restoring force. In this way, a self-locking connection is thus realized.

[0025] With the Fig.Figure 4 shows another exemplary connection of protective bellows 3, which is now frictionally connected to connecting parts of an air spring at three connection points. In a first point, protective bellows 3 is exclusively frictionally connected to an air spring cover 6. In a second point, protective bellows 3 is exclusively frictionally connected to an outer guide 8. Finally, in a third point, protective bellows 3 is exclusively frictionally connected to an air spring rolling piston 7.

[0026] The various connection areas have different diameters. These were made possible, for example, by the method described above. This method allows very small diameters in the central area of ​​a protective bellows to be connected to a connecting part for the first time. Reference symbol list 1 Expanding device 2 Dorn 3 Protective bellows 4 Connection part 5 conically widened section 6 air spring covers 7 air spring rolling pistons 8 Exterior guidance 9 upper segments 10 lower segments

Claims

[1] Method for widening an elastomeric protective bellows (3) of a vehicle air spring, which is partially connected to a connecting part (4) of the air spring, characterized by the following steps: - Providing an expansion device (1) with a radially extendable mandrel (2), - at least partially sliding the protective bellows (3) onto the pin (2), - radially expanding the mandrel (2) so that the protective bellows (3) is radially expanded beyond its nominal diameter in at least one area, - wherein the protective bellows (3) is removed from the mandrel (2) immediately after expansion and is then partially placed onto the connecting part (4) of the air spring, wherein the connecting part (4) has an outer diameter in the connection area which is larger than the nominal diameter of the protective bellows (3). [2] Method according to claim 1, characterized by, that the mandrel (2) comprises individual segments (9, 10) which are individually radially movable. [3] Method according to claim 1, characterized by , that the segments are divided into upper segments (9) and lower segments (10), whereby the protective bellows (3) is widened to different diameters in different areas. [4] Method according to any one of claims 1 to 3, characterized by , that the protective bellows (3) is heated before and / or during expansion. [5] Method according to any one of claims 1 to 4, characterized by , that the protective bellows (3) is cooled during and / or after the expansion.

Images