Method for expanding a protective bellows of a motor vehicle air spring and air spring with a protective bellows

Abstract

Method for expanding an elastomeric protective bellows (3) of a vehicle air spring, which is connected to a connecting part (4) of the air spring in some areas, characterized by the following steps: - Providing an expanding device (1) with a radially extendable mandrel (2), - at least partially pushing the protective bellows (3) onto the mandrel (2), - radially extending the mandrel (2) so that the protective bellows (3) is radially expanded in at least one region beyond its nominal diameter, wherein the expansion takes place within an elasticity range of the protective bellows material, and air spring for a motor vehicle, comprising an elastomeric rolling bellows which is fastened in a pressure-tight manner between two attachments (6, 7) of the air spring, whereby a volume-elastic pressure chamber filled with compressed air is delimited and the rolling bellows rolls on one of the attachments to form a rolling fold, wherein the rolling bellows is protected from contamination by an elastomeric protective bellows (3), wherein the protective bellows (3) is connected in regions to a connecting part (4), wherein the protective bellows (3) is frictionally connected to the connecting part (4).

Description

[0001] The invention relates to a method for expanding a protective bellows of a motor vehicle air spring according to the preamble of the independent method claim and an air spring for a motor vehicle with a protective bellows according to the preamble of the independent device claim

[0002] Air springs or air struts, which are clamped between the chassis and the body of a motor vehicle and feature a rolling bellows, which in turn is secured between a cover and a rolling piston, are known in a wide variety of designs. During operation, the air spring is subjected to internal overpressure, and the rolling bellows rolls during spring movements, forming a rolling fold on the outer surface of the concentric rolling piston. To limit expansion, the rolling bellows is enclosed by a sleeve-shaped outer guide.

[0003] DE 10 2009 003 829 A1 discloses a free-standing air spring in the "overhead position" which comprises a rolling piston and a cover, wherein a rolling bellows is clamped pressure-tight between the rolling piston and the cover and rolls on the rolling piston and on the cover during spring movements, forming a rolling fold. To protect the rolling bellows or its rolling folds from contamination and damage, a bellows is provided which is fastened on the one hand to the rolling piston and on the other hand to a lower end of the outer guide. The bellows is fastened to the outer guide by a positive connection. For this purpose, an outwardly projecting collar is formed at the lower end of the outer guide, around which collar a fold of the bellows is slipped, wherein the fold is blow-molded into a shape provided for this purpose.The disadvantage of this form-fitting fastening is that the end of the bellows can become detached from the fastening collar during operation of the air spring, meaning that the rolling bellows is no longer protected from contamination.

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

[0005] 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 and also cheaper.

[0006] This problem is solved by the features of the independent method claim and the features of the independent device claim. Preferred embodiments of the invention are set forth in the respective subclaims.

[0007] Thus, according to the invention, a method for expanding 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 an expanding device with a radially extendable mandrel, - at least partially pushing the protective bellows onto the mandrel, - radially extending the mandrel so that the protective bellows is radially expanded beyond its nominal diameter in at least one area.

[0008] The process for expanding an elastomeric protective bellows, which is then partially connected to a connecting part of an air spring, is carried out using an expansion device specially designed to expand the protective bellows radially. After vulcanization, the protective bellows has a specific shape and different nominal diameters in different areas. The nominal diameter therefore refers to the protective bellows in its initial state or after vulcanization. Since the protective bellows has a conical shape, for example, it has different nominal diameters at its end areas.

[0009] The expanding device comprises a mandrel constructed from sub-segments that can be moved radially outward from a retracted home position. The segments are preferably divided into upper and lower segments, so that the protective bellows is expanded to different diameters in different areas, viewed longitudinally. When the mandrel is in its home position, the protective bellows is mechanically or manually pushed or placed onto the mandrel in a defined position. The mandrel or its segments are then moved uniformly radially outward. The segments are moved force- and displacement-controlled, using pneumatic or servo-controlled drives.

[0010] In the area where the mandrel engages the protective bellows, the bellows expands outward. The expansion or widening of the protective bellows preferably occurs within its elastic range or below its material-specific elastic limit, but it can also occur beyond this range, resulting in plastic deformation. It is crucial that the expansion does not cause the protective bellows to tear.

[0011] Due to the inherent elasticity of the protective bellows material, it contracts at least partially again after expansion. This means that the expanded diameter decreases after the mandrel is retracted and the protective bellows is removed from the mandrel. However, the elastic expansion of the protective bellows caused by the expansion only lasts for a short time and the recovery is so slow that the protective bellows can be pulled onto the air spring connecting part within this time window. The air spring connecting part has an outer diameter which is larger than the nominal diameter of the protective bellows in the area to be connected. The protective bellows pulled on in this way is then frictionally connected to the connecting part. This is because radially inward-directed restoring forces result from the temporary expansion.This creates a frictional force between the protective bellows and the connecting part in the connection area, which securely holds the protective bellows to the connecting part. The proposed method thus makes it possible to connect a protective bellows to an air spring connecting part without the need for additional clamping or tensioning devices.

[0012] Preferably, the expansion and recovery 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 example, by a heating device that irradiates the protective bellows with infrared light. The heating softens the protective bellows material, making it easier and more secure to expand, thus better preventing tearing apart.

[0013] In addition, the protective bellows is cooled or cooled down with a cooling device, for example, during and / or after the expansion process. This can be done using a cold air blower, for example. Cooling hardens the protective bellows material, slowing its recovery and allowing more time for the protective bellows to be pulled onto the connecting part.

[0014] The invention also includes an air spring for a motor vehicle, comprising an elastomeric rolling bellows which is fastened in a pressure-tight manner between two attachments of the air spring, whereby a volume-elastic pressure chamber filled with compressed air is delimited and the rolling bellows rolls on one of the attachments, forming a rolling fold, wherein the rolling bellows is protected from contamination by an elastomeric protective bellows, wherein the protective bellows is connected in regions to a connecting part, wherein the protective bellows is frictionally connected to the connecting part.

[0015] The described method enables an air spring in which the protective bellows is connected to a connecting part by frictional engagement. Additional means for securing the protective bellows to the connecting part are no longer required. The frictional connection is particularly effective because the outer diameter of the connecting part is larger than the nominal diameter of the protective bellows in its normal state. If the protective bellows is elastically expanded beyond its nominal diameter, a restoring force acts, holding it to the connecting part.

[0016] This reliable connection between the protective bellows and the connecting part is further enhanced by a conically widened section of the connecting part. The connecting part's diameter is tapered outward in the connection area. This means that the protective bellows must expand in diameter if it is removed from the connecting part. This expansion creates a greater restoring force, so the removal force must first increase to successfully remove the protective bellows from the connecting part. This design feature creates a self-locking effect.

[0017] Preferably, the connecting part has an increased surface roughness in the connection area with the protective bellows. The surface roughness of the connecting part is rougher in the connection area than in the remaining (unconnected) area of ​​the connecting part. The increased surface roughness promotes or reinforces the frictional connection. The increased surface roughness is achieved by ridges, grooves, ridges, or roughening.

[0018] Preferably, the connecting part is an air spring outer guide that surrounds the rolling bellows. However, the connecting part is also preferably an air spring cover or an air spring rolling piston. Particularly preferably, the protective bellows is frictionally connected to each of these connecting parts at various areas.

[0019] It is understood that the protective bellows and the connecting parts are rotationally symmetrical bodies.

[0020] The invention is explained in more detail with reference to the following description of the figures. Fig. 1 an exemplary expansion 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.

[0021] The Fig. Figure 1 shows a 3D model of an exemplary expansion device 1 with a mandrel 2 that can be moved radially outward, onto which a protective bellows 3 is pushed. Mandrel 2 has two, three, or four-part segments 9 and 10, which can be individually moved radially outward from a basic position. By evenly moving segments 9 and 10 apart, the protective bellows 3 is expanded beyond its nominal diameter.

[0022] Thus, mandrel 2 comprises upper segments 9 and lower segments 10 located axially below them, which can be moved radially independently of one another. This means that upper segments 9 and lower segments 10 can be controlled separately. This allows different radial expansions of the protective bellows 3 to occur in different areas.

[0023] Protective bellows 3 consists of several folds and is therefore also called a conical bellows. Protective bellows 3 is made of an elastomer material. Depending on the elastomer selected for protective bellows 3, it can be expanded elastically or plastically without damage. Protective bellows 3 is conical in the shape shown. Protective bellows 3 comprises a first upper end which is smaller in diameter than a second lower end. As a rule, the second lower and larger end of protective bellows 3 is used to connect to an air spring outer guide. In its initial state or in an uninstalled state, 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.

[0024] Thus, when protective bellows 3 is pushed onto mandrel 2, the segments of mandrel 2 are moved radially outward, expanding the protective bellows 3. If the protective bellows 3 is expanded beyond its nominal diameter, it will at least partially retract after expansion due to its inherent elasticity. Within this time, it is possible to easily pull the protective bellows 3 over a connecting part of an air spring, whereby the connecting part has an outer diameter larger than the nominal diameter of the protective bellows 3.

[0025] For example, using mandrel 2 it is possible to expand protective bellows 3 in one or more different areas beyond the nominal diameter and then to connect the various expanded areas to different connecting parts of an air spring.

[0026] 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 frictional connection between protective bellows 3 and connecting part 4. This connection does not require any external clamping or tensioning devices and is held solely by the frictional force between protective bellows 3 and connecting part 4. This connection is supported or promoted by the fact that protective bellows 3, in the unconnected state, has a nominal diameter that is smaller than the outer diameter of the connecting part 4. This is because, after 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 (illustrated by the arrow) acts. In this way, a reliable connection between protective bellows 3 and connecting part 4 is created that does not require any additional connecting devices.

[0027] The Fig. Finally, Figure 3 illustrates a further enhancement of the frictional 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 realized.

[0028] 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 areas. Thus, in a first area, protective bellows 3 is exclusively frictionally connected to an air spring cover 6. Furthermore, in a second area, protective bellows 3 is exclusively frictionally connected to an outer guide 8. Furthermore, in a third area, protective bellows 3 is exclusively frictionally connected to an air spring roll piston 7.

[0029] The various connection areas have different diameters. This was made possible, for example, by the process described above. This process makes it possible to connect very small diameters in the center area of ​​a protective bellows with a connecting part for the first time. List of reference symbols 1 expanding device 2 thorn 3 protective bellows 4 connecting part 5 conically widened section 6 air spring covers 7 air spring rolling pistons 8 External guide 9 upper segments 10 lower segments QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] DE 10 2009 003 829 A1

[0003] DE 10 2004 023 561 A1

[0004]

Claims

[1] Method for expanding an elastomeric protective bellows (3) of a vehicle air spring, which is connected to a connecting part (4) of the air spring in some areas, characterized by the following steps: - Providing an expanding device (1) with a radially extendable mandrel (2), - at least partially pushing the protective bellows (3) onto the mandrel (2), - radially expanding the mandrel (2) so that the protective bellows (3) is radially expanded beyond its nominal diameter in at least one area. [2] Method according to claim 1, characterized by that the mandrel (2) comprises individual segments (9, 10) which can be moved radially individually. [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 expanded to different diameters in different areas. [4] Method according to one of claims 1 to 3, characterized by that the protective bellows (3) is placed in sections on the connecting part (4) of the air spring immediately after the expansion, 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). [5] Method according to one of claims 1 to 4, characterized by that the protective bellows (3) is heated before and / or during expansion. [6] Method according to one of claims 1 to 5, characterized by that the protective bellows (3) is cooled during and / or after expansion. [7] Air spring for a motor vehicle, comprising an elastomeric bellows which is fastened in a pressure-tight manner between two attachments of the air spring, whereby a volume-elastic pressure chamber filled with compressed air is defined and the bellows rolls on one of the attachments, forming a rolling fold, wherein the bellows is protected from contamination by an elastomeric protective bellows (3), wherein the protective bellows (3) is partially connected to a connecting part (4), characterized by that the protective bellows (3) is frictionally connected to the connecting part (4). [8] Air spring according to claim 7, characterized by that the protective bellows (3) is connected to the connecting part (4) without the use of an external clamping or tensioning device. [9] Air spring according to claim 7 or 8, characterized by that the protective bellows (3) in the unconnected state has a nominal diameter which is smaller than the outer diameter of the connecting part (4). [10] Air spring according to one of claims 7 to 9, characterized by that the connecting part (4) comprises a conically widened section (5) in the connection area. [11] Air spring according to one of claims 7 to 10, characterized by that the connecting part (4) has a higher surface roughness in the connection area than in the area not connected to the protective bellows (3). [12] Air spring according to one of claims 7 to 11, characterized by that the connecting part is an external guide (8) which surrounds the rolling bellows in some areas. [13] Air spring according to one of claims 7 to 12, characterized by that the connecting part is an air spring cover (6) or an air spring rolling piston.

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