Wheel bearing unit

Abstract

Wheel bearing unit comprising two cylindrical components (2, 3) which are rotatable relative to each other via interposed rolling elements, wherein the space (4) between the components (2, 3) is sealed on at least one side by a sealing arrangement (5) in the form of a cassette seal (6), which comprises a first sealing part (7) with a cylindrical outer flange (8) with which it is pressed into a seat (9) of the outer component (2), and a second sealing part (10) with a cylindrical inner flange (11) with which it is pressed onto a seat (12) of the inner component (3), wherein at least one sealing element (13) is provided on the first or on the second sealing part (7, 10) which seals towards the other sealing part (7, 10) or towards a component (2, 3), characterized in that between the seat (9, 12) of the outer and / or the inner component (2, 3) and The respective sealing part (7, 10) has at least one plastic ring (15) which is permeable to air,However, it is designed to be moisture-proof.

Description

[0001] The invention relates to a wheel bearing unit comprising two cylindrical components which are rotatable relative to each other via rolling elements arranged between them, wherein the space between the components is sealed on at least one side by a sealing arrangement in the form of a cassette seal, which comprises a first sealing part with a cylindrical outer flange with which it is pressed into a seat of the outer component, and a second sealing part with a cylindrical inner flange with which it is pressed onto a seat of the inner component, wherein at least one sealing element is provided on the first or on the second sealing part, which seals towards the other sealing part or towards a component.

[0002] In such a wheel bearing unit, the cassette seals are used to seal the inside of the bearing in order to prevent lubricant from escaping from the inside of the bearing and to prevent dirt from entering the inside of the bearing.

[0003] Temperature increases that occur during operation, for example, due to the brake disc heating up during braking, cause the air inside the bearing to heat up. The resulting overpressure is equalized via the cassette seal or the flexible sealing element. During further operation, the temperature inside the bearing returns to normal. This cooling results in a slight negative pressure inside, which then causes the sealing element, usually in the form of one or more sealing lips, to be pressed more firmly against its sliding partner, such as the other component or sealing element. This leads to increased friction, and the sealing element, and thus the cassette seal, can wear out more quickly.

[0004] Ventilation devices for cassette seals are known from the prior art. DE 10 2017 102 061 A1, JP 2005-220 984 A, JP 2009-030 620 A, JP 2007-177 903 A and DE 38 06 928 A1 describe solutions, which, however, are sometimes complex and require individual adaptation.

[0005] The invention is therefore based on the problem of providing an improved wheel bearing unit in comparison.

[0006] To solve this problem, in a wheel bearing unit of the type described above, the invention provides that at least one plastic ring, which is permeable to air but impermeable to moisture, is provided between the seat of the outer and / or the inner component and the respective sealing part.

[0007] In the wheel bearing unit according to the invention, a plastic ring is integrated in the area of ​​the seat of the outer and / or inner component. This ring serves to enable a defined pressure equalization between the bearing interior and the environment, preventing the build-up of overpressure and, in particular, underpressure, which can promote wear, during operation. The plastic ring provided at the seat is permeable to air, allowing air exchange and thus pressure equalization. At the same time, however, it is impermeable to moisture, preventing moisture from penetrating the bearing interior from outside. Normally, even a bearing seat—that is, the area where the sealing element sits firmly on the respective component—is leaky, especially the seat of the sealing element in the outer component, for example, the wheel hub or the outer bearing race. This area is therefore usually rubberized to achieve complete sealing.According to the invention, this rubber coating is now omitted. Instead, this area is used for the integration of the plastic ring, in order to utilize the fact that this area is not completely airtight, while simultaneously ensuring, through the moisture-impermeable property of the plastic ring, that no moisture can penetrate, thus maintaining the seal against moisture and dirt.

[0008] The wheel bearing unit according to the invention therefore has a number of advantages. Firstly, as explained above, no special rubberized seat is required on the corresponding component. The air exchange made possible by the integration of the plastic ring according to the invention allows for pressure equalization, thus preventing the build-up of a vacuum and consequently also preventing excessive stress on the sealing element(s) due to varying pressures. This results in lower friction and therefore also lower heat generation in this area, leading to reduced wear and a shorter service life.

[0009] Depending on the design of the seat and the arrangement of the respective sealing element on the component, various configurations are possible. The plastic ring can be positioned between the seat and the outer or inner flange. This means that the plastic ring is located between the cylindrical seat and the cylindrical flange, thus sealing at that point.

[0010] Alternatively, the plastic ring can also be arranged between the seat and an adjoining section of the respective sealing element that extends obliquely radially inwards or outwards. In this case, the seat can, for example, have a cylindrical radial seating surface and an axial seating surface against which the sealing element also rests, with the corresponding flange sections of the sealing element being connected to each other via an oblique section. The plastic ring can then be arranged in this transition area in this configuration.

[0011] A third alternative involves placing the plastic ring between the seat and the sealing element. In this case, the seal is created between the seat and the actual sealing element, such as the sealing lip.

[0012] The plastic ring itself is preferably made of a PTFE-based material, in particular porous PTFE. PTFE (polytetrafluoroethylene) is a material that can be manufactured to be both air-permeable and moisture-impermeable. For example, PTFE can be produced in sintered form, i.e., as porous PTFE, which is air-permeable due to its porosity but also moisture-impermeable due to its small pore size. Woven PTFE can also be produced with these properties. Creating minute perforations by laser is also conceivable. The pore size should be as small as possible, preferably ≤ 0.9 mm. Furthermore, PTFE also exhibits sufficiently high temperature stability, allowing it to be used in this thermally stressed environment.

[0013] The plastic ring itself preferably has an axial length that corresponds to between one quarter and one half of the axial length of the outer or inner flange, particularly when the plastic ring is positioned between the seat and the cylindrical flange.

[0014] The seat itself can have a groove- or rabbet-like recess into which the plastic ring is inserted. Alternatively, the plastic ring can be placed on the cylindrical seat and engage in a groove- or rabbet-like recess formed on the outer or inner flange. In any case, the design is such that a sufficiently tight, slightly compressed ring seat is achieved, ensuring that the plastic ring rests firmly against both surfaces.

[0015] The plastic ring preferably has a rectangular cross-section, i.e., flat contact surfaces. This is particularly true if the plastic ring is positioned between the seat and the outer or inner flange, i.e., the cylindrical elements involved. If it is positioned elsewhere, for example, in the transition zone between a radial and an axial seat section, its geometry can be selected accordingly.

[0016] In addition to the wheel bearing unit itself, the invention further relates to a sealing arrangement in the form of a cassette seal, suitable for a wheel bearing unit of the type described above, wherein the sealing arrangement comprises a first sealing part with a cylindrical outer flange and a second sealing part with a cylindrical inner flange, wherein at least one sealing element is provided on the first or the second sealing part. The sealing arrangement is characterized in that at least one plastic ring, which is air-permeable but moisture-impermeable, and which bears against the other sealing part or an adjacent component in the assembly position, is provided on the outer flange and / or on the inner flange or on a section adjoining it that extends obliquely radially inwards or outwards, of the respective sealing part.

[0017] In the sealing arrangement according to the invention, the plastic ring is therefore part of the sealing arrangement and is thus fixedly attached to one of the sealing components. It can either be pressed or glued onto it, so that it is consequently installed with the sealing arrangement. Instead of integrating it into the sealing arrangement as a fixed element, it is of course also possible to fix the plastic ring to one of the components before assembling the sealing arrangement and only then to mount the sealing arrangement.

[0018] The plastic ring of the sealing arrangement according to the invention is preferably made of a PTFE-based material, in particular porous, woven, or perforated PTFE. It should have an axial length that corresponds to between one quarter and one half of the axial length of the outer or inner flange when it is arranged on it.

[0019] Regarding the arrangement of the plastic ring, two alternatives are conceivable. According to the first alternative, the outer or inner flange can have a rebate- or groove-like recess into which the plastic ring is inserted. The flange is thus geometrically designed so that the corresponding recess is formed, into which the plastic ring is inserted, for example, glued. This design is readily possible since such a sealing component of the sealing assembly typically has a metal support or is made of metal, usually a suitable metal sheet that is appropriately formed. The corresponding recess can be formed during this forming process.

[0020] Alternatively, the plastic ring can also be placed on the cylindrical outer or inner flange, or on the adjoining section extending obliquely radially inwards or outwards. If it is placed on the flange, a rebate- or groove-like receptacle must be provided on the corresponding opposite component. If it is placed on the oblique section, it engages in the corresponding transition area of ​​the component seat.

[0021] The invention is explained below with reference to exemplary embodiments and the drawings. The drawings are schematic representations and show: Fig. 1 A schematic representation of a wheel bearing unit according to the invention with a sealing arrangement according to the invention in a first embodiment, Fig. 2 a schematic representation of a wheel bearing unit according to the invention with a sealing arrangement according to a second embodiment, Fig. 3 a schematic representation of a wheel bearing unit according to the invention with a sealing arrangement according to the invention in a third embodiment, Fig. 4 a schematic representation of a wheel bearing unit according to the invention with a sealing arrangement according to the invention in a fourth embodiment, Fig. 5 a schematic representation of a wheel bearing unit according to the invention with a sealing arrangement according to the invention in a fifth embodiment.

[0022] Fig. Figure 1 shows a wheel bearing unit 1 according to the invention, comprising a first cylindrical outer component 2, for example a wheel hub or a bearing outer ring, and a second inner cylindrical component 3, for example the inner ring of a bearing. The two components 2, 3 are rotatable relative to each other via rolling elements (not shown in detail), wherein the resulting bearing interior 4 between the components 2, 3 is sealed at least on one side, preferably on both sides, by a sealing arrangement 5 in the form of a cassette seal 6. The cassette seal 6 has a first sealing part 7 with a cylindrical outer flange 8, with which it is pressed into a seat 9 of the outer component 2. The cassette seal 6 further has a second sealing part 10, which is pressed onto a cylindrical seat 12 of the inner component 3 with a cylindrical inner flange 11.In the example shown, a sealing element 13 is arranged on the first sealing part 7. This sealing element, via several sealing lips 14, seals against the second sealing part 10 on one side and against component 3 on the other, once the sealing lips 14 are in contact with it. Since components 2 and 3 rotate relative to each other, a sliding sealing arrangement is therefore formed.

[0023] According to the invention, a plastic ring 15 is provided in the wheel bearing unit 1, which consists of an air-permeable but moisture-impermeable material such as, in particular, PTFE, which has sufficient porosity or a sufficient pore volume that, on the one hand, allows air passage and thus pressure equalization between the bearing interior 4 and the bearing exterior, but, on the other hand, prevents the penetration of moisture or other dirt from the bearing exterior into the bearing interior 4.

[0024] The plastic ring 15, which is essentially rectangular in cross-section and can alternatively be perforated, for example, by laser, is received in a substantially form-compatible, fold-like receptacle 16 formed at the seat 9. It is fixed in this receptacle, for example, by adhesive bonding or by an interference fit to the outer flange 8, which overlaps the plastic ring 15. Consequently, cylindrical contact surfaces are formed on the plastic ring 15, with which it rests flat against the receptacle 16 on one side and against the outer flange 8 on the other.

[0025] This air-permeable plastic or PTFE ring allows for pressure equalization between the bearing interior 4 and the bearing environment, so that no overpressure or, in particular, no underpressure develops in the bearing interior 4, which can promote wear.

[0026] Fig. Figure 2 shows a second embodiment of a wheel bearing unit 1 according to the invention, wherein the same reference numerals are used for identical components.

[0027] Here too, an outer component 2 and an inner component 3 are used; the bearing interior 4 is in turn sealed via a sealing arrangement 5 in the form of a cassette seal 6 with the two sealing parts 7 and 10.

[0028] Again, a receptacle 16 is formed on the outer component 2, into which the plastic ring 15, preferably made of PTFE, is inserted, so that it seals the seat 9 to the outer flange 8, so that neither dirt nor moisture can penetrate, but at the same time air exchange and thus pressure equalization is possible.

[0029] Unlike the design according to Fig. 1 Here, the outer component 2 has a further fold-like recess 17 into which corresponding flange projections 18, 19 of the sealing parts 7, 10 engage and form an additional labyrinth seal in this area, which additionally prevents moisture or water and dirt from accumulating on the plastic ring 15.

[0030] In the design according to Fig. Figure 3 shows a wheel bearing unit 1 with the two components 2, 3 and the sealing arrangement 5 in the form of a cassette seal 6, in which a slightly differently shaped sealing element 13 is arranged on one sealing part 7. This element also has the three sealing lips 14 that seal towards the second sealing part 10 and the inner component 3. However, the sealing element 13 also extends towards the outer component 2 and engages under the cranked outer flange 8, as shown. Fig. Figure 3 clearly shows that an additional seal can be achieved in this seat area via this sealing element, which is drawn section by section between the seat 9 and the outer flange 8.

[0031] The plastic ring 15, again preferably made of PTFE, is positioned between the seat 12 of the second component 3 and the inner flange 11. The inner flange 11 has a rebate-like recess 20 into which the form-fitting plastic ring 15 is inserted, preferably bonded. It again rests flat against the seat 12 of component 3 and against the inner flange 11 in the area of ​​the recess 20, sealing against dirt and moisture in this area, but allowing air to pass through and enabling pressure equalization.

[0032] Fig. Figure 4 shows a wheel bearing unit 1 with an outer component 3, on which the sealing part 7 with the sealing element 13 is arranged, and the inner component 3, which here is again designed as an inner ring, but which has a radial seat section 12a and an axial seat section 12b. The second sealing part 10 is designed as a guide plate, which rests with its inner flange 11 on the radial seat section 12a and with an axial flange 21 abuts the axial seat section 12b. In this embodiment, the plastic ring 15, preferably made of PTFE, is accommodated in the resulting interior space 22, i.e., it is located between the inner ring and the guide plate forming the second sealing part 10. This has the advantage that the sealing element 13 as well as the guide plate, i.e., the second sealing part 10, can remain unchanged; rather, the available space 22 is used for the integration of the PTFE plastic ring 15.

[0033] Fig.Figure 5 shows a wheel bearing unit 1 in which the plastic ring 15 is received in a corresponding receptacle 16 on the outer component 2. The sealing arrangement 5, in the form of the cassette seal 6, again has a first sealing part 7 with the sealing element 13, the sealing part 7 being pressed into the seat 9 of the outer component 2 via the outer flange 8. The second sealing part 10, with an outer flange 11, is also pressed onto the seat 12 of the inner component 3. In this configuration, which serves, for example, as a gearbox-side seal in the wheel hub or in the outer wheel bearing race, the plastic ring 15 seals against the sealing element 13, which has a corresponding radially extending sealing section 23 with which it seals against the plastic ring 15, or rather, rests on this ring. Since both are fixed to the outer component 2, no relative movement takes place between them.Here too, air permeability between the storage interior and the environment is therefore ensured, while at the same time the ingress of moisture and dirt is prevented. Reference symbol list 1 wheel bearing unit 2 first outer cylindrical component 3 second inner cylindrical component 4 Storage area 5 Sealing arrangement 6 cassette seals 7 first sealing part 8 cylindrical outer flange 9 seat 10 second sealing part 11 cylindrical inner flange 12 cylindrical seat 12a radial seat section 12b axial seat section 13 Sealing element 14 sealing lips 15 plastic rings 16 recording 17 fold-like recesses 21 axial flange 22 Interior 23 Sealing section

Claims

[1] Wheel bearing unit comprising two cylindrical components (2, 3) which are rotatable relative to each other via rolling elements arranged between them, wherein the space (4) between the components (2, 3) is sealed on at least one side by a sealing arrangement (5) in the form of a cassette seal (6) which comprises a first sealing part (7) with a cylindrical outer flange (8) with which it is pressed into a seat (9) of the outer component (2), and a second sealing part (10) with a cylindrical inner flange (11) with which it is pressed onto a seat (12) of the inner component (3), wherein at least one sealing element (13) is provided on the first or on the second sealing part (7, 10) which seals towards the other sealing part (7, 10) or towards a component (2, 3), characterized by, that at least one plastic ring (15) which is permeable to air but impermeable to moisture is provided between the seat (9, 12) of the outer and / or inner component (2, 3) and the respective sealing part (7, 10). [2] Wheel bearing unit according to claim 1, characterized by , that the plastic ring (15) is arranged between the seat (9, 12) and the outer or inner flange (8, 11) or a section of the respective sealing part (7, 10) or sealing element (13) extending obliquely radially inwards or outwards thereto. [3] Wheel bearing unit according to claim 1 or 2, characterized by , that the plastic ring (15 (is made of a material based on PTFE, in particular porous or woven or perforated PTFE. [4] Wheel bearing unit according to one of the preceding claims, characterized by, that the plastic ring (15) has an axial length which is between one quarter and one half of the axial length of the outer or inner flange (8, 11). [5] Wheel bearing unit according to one of the preceding claims, characterized by , that the seat (9, 12) has a rebate- or groove-like receptacle (16) into which the plastic ring (15) is inserted, or that the plastic ring (15) is placed on the cylindrical seat (9, 12) and the outer or inner flange (8, 11) has a rebate- or groove-like receptacle (20) for the plastic ring (15). [6] Wheel bearing unit according to one of the preceding claims, characterized by , that the plastic ring (15) has a rectangular cross-section. [7] Sealing arrangement in the form of a cassette seal (6), suitable for a wheel bearing unit (1) according to one of the preceding claims, comprising a first sealing part (7) with a cylindrical outer flange (8) and a second sealing part (10) with a cylindrical inner flange (11), wherein at least one sealing element (13) is provided on the first or on the second sealing part (8, 10), characterized by , that at least one plastic ring (15) which is permeable to air but impermeable to moisture and which, in the assembly position, rests against an adjacent component (2, 3) on the other sealing part (7, 10) is provided on the outer flange (8) and / or on the inner flange (11) or on a section of the respective sealing part (7, 10) extending obliquely radially inwards or outwards. [8] Sealing arrangement according to claim 7, characterized by, that the plastic ring (15) is made of a material based on PTFE, in particular porous or woven or perforated PTFE. [9] Sealing arrangement according to claim 7 or 8, characterized by , that the plastic ring (15) has an axial length which is between one quarter and one half of the axial length of the outer or inner flange (8, 11). [10] Sealing arrangement according to one of claims 7 to 9, characterized by , that the outer or inner flange (8, 11) has a rebate- or groove-like receptacle (20) into which the plastic ring (15) is inserted, or that the plastic ring (15) is placed on the cylindrical outer or inner flange (8, 11) or the adjoining section extending obliquely radially inwards or outwards.

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