Seal unit having a synthetic resin silicone coating

Abstract

The present invention relates to a seal unit (1) having a seal carrier (2), a sealing lip unit (3), which has at least one sealing lip (3.1) and is held by the seal carrier (2), and having a sealing disc (4), which is in contact with the at least one sealing lip (3.1). The at least one sealing lip (3.1) is coated with a synthetic resin silicone (5.1). The present invention also relates to a wheel bearing unit (RL) having such a seal unit (1).

Description

[0001] P240948

[0002] - 1 -

[0003] Sealing unit with a synthetic resin silicone coating

[0004] The present disclosure relates to a sealing unit, in particular for sealing a wheel bearing unit, comprising a sealing carrier, a sealing lip unit having at least one sealing lip and being held by the sealing carrier, and a sealing disc which is in contact with the at least one sealing lip.

[0005] A wheel bearing unit serves to support a vehicle wheel and is typically located between the vehicle's transmission and the wheel. Such a wheel bearing unit is usually designed using a rolling bearing system. It is typically sealed to prevent water from entering the unit.

[0006] Against this background, for example the printed text reveals

[0007] DE10 2017 100765 A1 describes a rolling bearing or wheel bearing unit in which a seal carrier is pressed onto an outer ring of the wheel bearing unit and a so-called flinger, i.e., a sealing washer, is attached to an inner ring of the wheel bearing unit. This combination of seal carrier and sealing washer forms a sealing unit for sealing the wheel bearing unit. However, a disadvantage is that water can enter the bearing at the points between the outer ring and the seal carrier, as well as between the sealing washer and the inner ring. This, in turn, leads to corrosion and thus significantly impairs or reduces the service life of the wheel bearing unit.

[0008] To address this problem, a further development of a seal or sealing unit for a wheel bearing unit in the prior art provided a sealing lip unit between the seal carrier and the sealing disc. This sealing lip unit has at least one sealing lip that is in contact with these two components. With such a seal, the at least one sealing lip contacts the sealing disc, resulting in frictional forces in practice. P240948

[0009] -2 - These frictional forces within the sealing unit lead to increased wear of at least one sealing lip or the entire sealing unit and thus reduce the safety of such a sealing unit.

[0010] In the prior art, to reduce friction, the sealing units, or in particular at least one sealing lip, were coated with various materials, mostly PTFE-containing materials. However, the coatings do not adhere to the surface of the sealing unit, which is often made of an elastomer, or they detach and have a stiffening effect on the sealing unit. With the materials used in the prior art, this results in a significantly higher contact force of the sealing lip against the contact surface of the sealing disc, which in turn leads to an increase in friction and frictional forces.

[0011] Against this background, the present disclosure aims to provide a sealing unit in which the frictional forces that occur can be (significantly) reduced.

[0012] This problem is solved by the subject matter with the features of the independent claim and by the subject matter with the features of the dependent claim. Advantageous embodiments are the subject of the dependent claims.

[0013] The sealing unit according to independent claim 1, which is used in particular for sealing a wheel bearing unit, preferably for a vehicle, comprises a sealing carrier, a sealing lip unit having at least one sealing lip and held by the sealing carrier, and a sealing disc that is in contact with the at least one sealing lip. According to the disclosure / invention, the at least one sealing lip is coated with a synthetic silicone resin. In other words, the at least one sealing lip has a synthetic silicone resin coating, in particular a PTFE-free coating.

[0014] Such an optimized sealing unit, at least one of whose sealing lip is coated with the synthetic resin silicone, can reduce friction or a generated frictional torque P240948

[0015] - 3 - significantly, more precisely by 18%, compared to uncoated sealing units.

[0016] The synthetic resin silicone coating protects the underlying material of at least one sealing lip or the sealing unit (often an elastomer) from abrasion and wear. Accordingly, the sealing unit according to the invention has a higher wear resistance than conventional sealing units. Thus, the service life of the sealing unit according to the invention is also increased compared to conventional sealing units.

[0017] Advantageously, the silicone resin used is PTFE (polytetrafluoroethylene)-free and contains no components belonging to the PFAS group. PTFE belongs to the PFAS group, which stands for "per- and polyfluoroalkyl substances." Materials containing PFAS are harmful to health and should therefore not be used. In contrast, the PTFE-free silicone resin is safe from a health perspective.

[0018] Furthermore, synthetic silicone resin is highly thermally resistant. This means that synthetic silicone resins can withstand high temperatures without altering their physical properties. Coating the sealing unit, or at least one sealing lip, with synthetic silicone resin allows for a temperature range of -40°C to 180°C for the sealing unit.

[0019] Furthermore, the coating of at least one sealing lip or the sealing unit with synthetic resin silicone ensures less adhesion of dirt or dirt deposits to the sealing unit compared to conventional sealing units. This also increases the wear resistance of the sealing unit according to the invention.

[0020] Furthermore, the synthetic silicone resin used for the sealing unit has a self-lubricating property, which helps in the event of insufficient lubrication of the sealing unit. The synthetic silicone resin coating also has the advantage that lubricants are absorbed more effectively and retained better in the position of the grease cord. This P240948

[0021] -4 -advantageously leads to a uniform distribution of the lubricating medium (grease) over the contact surface.

[0022] Preferably, the synthetic resin silicone may comprise the following components: a binder, which is a synthetic resin and / or a silicone resin, a filler or additive, and a solvent.

[0023] The binder is the main component of the silicone resin and determines the mechanical and chemical properties of the coating. The synthetic resin (epoxy resin, polyester resin, acrylic resin, polyurethane resin, etc.) usually serves as the load-bearing matrix, while the silicone resin is primarily responsible for its heat resistance, flexibility, and low surface energy, resulting in good sliding properties.

[0024] Solid lubricants such as molybdenum disulfide or graphite are used. The fillers mentioned serve to further improve the lubricity of the synthetic resin silicone coating and thus of the sealing unit, to reduce friction, and to minimize wear. Additives, such as hardeners, thickeners, or stabilizers, are used to promote curing or to adjust the viscosity of the coating.

[0025] The solvent serves to thin the synthetic silicone resin so that the coating can be applied to the sealing lips or the sealing unit in the desired consistency and evaporates during the drying process. Xylene, toluene, or acetone can be used as solvents. Alternatively, there are also water-based solvents such as alcohol solutions, glycol ethers, ethyl acetate, polyethylene glycol, etc.

[0026] In other words, a synthetic silicone resin is preferably selected, comprising as a synthetic resin one from the group consisting of epoxy resin, polyester resin, acrylic resin, or polyurethane resin and / or a silicone resin, as a binder molybdenum disulfide or graphite, or as an additive hardener, thickener, or stabilizer, and as a solvent xylene, toluene, acetone, alcohol solutions, glycol ether, ethyl acetate, or polyethylene glycol. P240948

[0027] - 5 -

[0028] In particular, it is intended that the entire sealing unit, especially the whole unit, is coated with the synthetic resin silicone. Coating the entire sealing unit with the synthetic resin silicone is technically easy to achieve. Furthermore, this reduces friction at every point of the sealing unit with the surrounding components (sections of the sealing unit itself or the surrounding wheel bearing unit).

[0029] Furthermore, it is conceivable that the sealing unit itself has an elastomer surface. The synthetic resin silicone coating adheres particularly well to the elastomer surface of the sealing unit.

[0030] It is even more advantageous if the synthetic resin silicone is transparent. This makes the synthetic resin silicone coating barely or not at all visually apparent. Furthermore, the underlying surface of the sealing unit can then be seen despite the coating.

[0031] Furthermore, the thickness of the synthetic resin silicone coating can be between 3 pm and 12 pm. Due to this very thin layer thickness, the surface of the sealing unit remains optically transparent and shows no visible changes.

[0032] Furthermore, it can be provided that at least one sealing lip has an axial sealing lip section extending axially from the sealing carrier and a transverse sealing lip section directly adjoining the axial sealing lip section, extending obliquely from the axial sealing lip section towards the sealing disc, with only the transverse sealing lip section being coated with the synthetic resin silicone. The transverse sealing lip section is the part of the sealing unit that is subject to the greatest friction. The use of the synthetic resin silicone coating is particularly relevant at this point on the sealing unit or sealing lip. At the same time, this local application of the synthetic resin silicone coating to the sealing unit saves the amount of synthetic resin silicone used, compared to coating the entire sealing lip or even the entire sealing unit. P240948

[0033] -6 -

[0034] Furthermore, it is possible that the sealing washer has a (first and) second axial sealing washer section and a radial sealing washer section, and that at least one sealing lip is positioned above the second axial sealing washer section, with only the portion of the sealing lip's transverse section facing the second axial sealing washer section coated with the synthetic resin silicone. In other words, only the underside of the sealing lip's transverse section has the synthetic resin silicone coating. At this point in the sealing unit, the friction (within the sealing unit) is greatest, and therefore the application of the synthetic resin silicone coating is most relevant. Compared to the previously described application of the synthetic resin silicone coating to the entire transverse sealing lip section, the amount of synthetic resin silicone used can be further reduced here.

[0035] Furthermore, it may be provided that the sealing lip unit has two sealing lips, the cross-section of which is coated with the synthetic resin silicone.

[0036] If the sealing lip unit has two sealing lips, each coated with synthetic resin silicone, such a sealing unit seals particularly well and can also reduce friction particularly effectively at the relevant point.

[0037] Furthermore, the problem underlying the present disclosure is solved by a wheel bearing unit, in particular for a vehicle, according to the dependent claim, which comprises an outer ring, an inner ring, a rolling bearing unit, and the sealing unit according to the invention described above, which is arranged between the outer ring and the inner ring. The wheel bearing unit comprising the sealing unit according to the invention thus exhibits the advantages associated with the sealing unit according to the invention (and described above).

[0038] The revelation is explained below with the help of drawings. They show:

[0039] Fig. 1 shows a cross-sectional view of a wheel bearing unit comprising a sealing unit according to the invention; and P240948

[0040] - 7 - Fig.2 a line diagram showing the frictional torque of an uncoated sealing unit, a PTFE-coated sealing unit and a synthetic resin silicone-coated sealing unit.

[0041] The figures are purely schematic and serve only to illustrate the invention. The same elements are identified by the same reference symbols.

[0042] Fig. 1 is a cross-sectional view of a wheel bearing unit RL, which has a sealing unit 1 according to the invention. The sealing unit 1 has a sealing carrier 2, a sealing lip unit 3, which has (here several) sealing lips 3.1 to 3.3 and is held by the sealing carrier 2, and a sealing disc 4, which is in contact with the sealing lips 3.1 to 3.3.

[0043] The sealing lip unit 3 more precisely comprises a first sealing lip 3.1, a second sealing lip 3.2, and a third sealing lip 3.3. The first sealing lip 3.1 and the second sealing lip 3.2 extend between the sealing carrier 2 and the sealing disc 4, extending essentially in the axial direction A. The third sealing lip 3.3 extends between the sealing carrier 2 and the sealing disc 4 essentially in the radial direction R. The first and second sealing lips 3.1, 3.2 are identical in design and shape. The first sealing lip 3.1 is located above the second sealing lip 3.2 in the radial direction R. The first and second sealing lips 3.1, 3.2 are arranged parallel to each other. The first and second sealing lips 3.1, 3.2 are spaced apart from each other in the radial direction R. The third sealing lip 3.3 is smaller, in particular shorter and narrower, than the first and second sealing lips 3.1, 3.2.

[0044] The sealing carrier 2 is essentially L-shaped. It has an axial section 2.1 extending in the axial direction A. It also has a radial section 2.2 extending in the radial direction R. The axial sections 2.1 and 2.2 form a 90° angle with each other. The axial section 2.2 is not completely straight but has a bend. P240948

[0045] - 8 - The sealing washer 4 is essentially C-shaped. The sealing washer 4 has a first and a second axial sealing washer section 4.1, 4.2, each extending in the axial direction A. The sealing washer 4 has a radial sealing washer section 4.3, which extends in the radial direction R. The radial sealing washer section 4.3 is located between the first and the second axial sealing washer sections 4.1, 4.2.

[0046] The first sealing washer axial section 4.1 is located (completely) below the sealing carrier axial section 2.1 when viewed in the radial direction R. The second sealing washer axial section 4.2 is located below the sealing carrier radial section 2.2 when viewed in the radial direction R.

[0047] The sealing lip unit 3 extends completely along the surface of the sealing carrier 2 facing the sealing disc 4. The sealing lip unit 3 encases the outermost sections of the sealing carrier axial section 2.1 and the sealing carrier radial section 2.2. From the sealing carrier axial section 2.2, the first and second sealing lips 3.1, 3.2 extend towards the sealing disc radial section 4.3. The third sealing lip 3.3 extends from the outermost end of the sealing carrier radial section 2.2 to the second sealing disc axial section 4.2.

[0048] The first and second sealing lips 3.1, 3.2 each have an axial sealing lip section 3.1a, 3.2a extending in the axial direction A. The first and second sealing lips 3.1, 3.2 each have a transverse sealing lip section 3.1b, 3.2b extending obliquely to the axial direction A (approximately at an angle of 45° to the axial direction A). The transverse sealing lip section 3.1b, 3.2b extends obliquely upwards from the axial sealing lip section 3.1a, 3.2a. The outer end of the transverse sealing lip section 3.1b, 3.2b contacts the radial sealing disc section 4.3.

[0049] A synthetic resin silicone coating 5.1, 5.2 is applied or provided on the underside of each of the sealing lip transverse sections 3.1b, 3.2b. The underside of the sealing lip transverse sections 3.1b, 3.2b faces the second sealing disc axial section 4.2. P240948

[0050] - 9 - The wheel bearing unit RL has an outer ring 6 and an inner ring 7. A rolling element unit 8 is located between the inner ring 6 and the outer ring 7. To prevent the ingress of water and / or dirt into the wheel bearing unit RL, the sealing unit 1 is provided. The sealing unit 1 is arranged between the outer ring 6 and the inner ring 7.

[0051] Fig. 2 shows a line graph illustrating, by way of example, the frictional torque or sealing friction DR of an uncoated sealing unit (see line OB), a PTFE-coated sealing unit (see line PTFE-B), and a synthetic resin silicone-coated sealing unit (see line KHS-B). The sealing friction DR is shown in the diagram on the Y-axis in units of Nm. The rotational speed (DZ) of the wheel bearing unit is shown on the X-axis in rpm. In other words, Fig. 2 shows a comparative example of the frictional torque of the sealing unit according to the invention (KHS-B) with two conventional sealing units (OB, PTFE-B).

[0052] As can be clearly seen in Fig. 2, the curves for the uncoated sealing unit (line OB, line with circles) and the sealing unit with the PTFE coating (line PTFE-B, line with triangles) increasingly lie above the curve for the sealing unit with the synthetic resin silicone coating (line KHS-B, line with squares) as the rotational speed DZ increases. This means that while the sealing friction DR increases for each sealing unit, regardless of the coating, the (absolute) values ​​of the sealing friction DR for the uncoated sealing unit (OB) and the sealing unit with the PTFE coating (PTFE-B) (always at the same investigated rotational speed) are significantly higher than for the sealing unit with the synthetic resin silicone coating (KHS-B). In other words, the frictional torque is higher.The sealing friction (DR) of the sealing unit with the synthetic resin silicone coating KHS-B is significantly lower than that of the other two (conventional) comparison sealing units.

[0053] To give specific values, in this example the frictional torque at a speed of 1500 rpm is 0.22 Nm for the sealing unit without coating OB and for the sealing unit with PTFE coating PTFE-B, and for the sealing unit P240948

[0054] - 10 - sealing unit with the KHS-B synthetic resin silicone coating only 0.18 Nm. Furthermore, the specific values ​​for this comparison example for all three sealing units can be found in the line diagram in Fig. 2. It should be noted that the sealing unit without coating and the sealing unit with PTFE coating have identical values ​​for sealing friction at speeds of 900, 1300 and 1500 rpm (namely 0.2, 0.21 and 0.22 Nm, respectively). At a speed of 100 rpm, the sealing unit with PTFE coating and the sealing unit with the synthetic resin silicone coating each have the same sealing friction value of 0.13 Nm.

[0055] Accordingly, Fig. 2 demonstrates the technical benefit or effect (and superiority) of the sealing unit according to the invention with the synthetic resin silicone coating compared to conventional sealing units from the prior art. P240948

[0056] - 11 - List of reference symbols

[0057] 1 sealing unit

[0058] 2 sealing carriers

[0059] 2.1 Seal carrier axial section

[0060] 2.2 Seal carrier radial section

[0061] 3 sealing lip unit

[0062] 3.1 First sealing lip

[0063] 3.2 second sealing lip

[0064] 3.3 Third sealing lip

[0065] 3.1a, 3.2a Sealing lip axial section

[0066] 3.1b, 3.2b Sealing lip cross section

[0067] 4 sealing washer

[0068] 4.1 First sealing disc axial section

[0069] 4.2 Second sealing disc axial section

[0070] 4.3 Sealing disc radial section

[0071] 5.1, 5.2 Synthetic resin silicone coating

[0072] 6 outer ring

[0073] 7 inner ring

[0074] 8 rolling bearing unit

[0075] A Axial direction

[0076] DR sealing friction

[0077] DZ speed

[0078] KHS-B sealing unit with synthetic resin silicone coating OB sealing unit without coating

[0079] PTFE-B sealing unit with PTFE coating

[0080] R Radial direction

[0081] RL wheel bearing unit

Claims

P240948 - 12 - Patent claims 1. Sealing unit (1 ) comprising a sealing carrier (2), a sealing lip unit (3) which has at least one sealing lip (3.1) and is held by the sealing carrier (2), and a sealing disc (4) which is in contact with the at least one sealing lip (3.1), characterized in that the at least one sealing lip (3.1) is coated with a synthetic resin silicone (5.1).

2. Sealing unit (1 ) according to claim 1 , wherein the entire sealing unit (1 ) is coated with the synthetic resin silicone (5.1, 5.2).

3. Sealing unit (1 ) according to claim 1 or 2, wherein the sealing unit (1 ) itself has an elastomer surface.

4. Sealing unit (1) according to one of claims 1 to 3, wherein the synthetic resin silicone (5.1, 5.2) is transparent.

5. Sealing unit (1) according to any one of claims 1 to 4, wherein the thickness of the synthetic resin silicone coating (5.1, 5.2) is between 3 pm and 12 pm.

6. Sealing unit (1) according to any one of claims 1 to 5, wherein the synthetic resin silicone comprises the following components: a binder which is a synthetic resin and / or a silicone resin, a filler or an additive and a solvent.

7. Sealing unit (1) according to one of claims 1 to 6, wherein the at least one sealing lip (3.1) has a sealing lip axial section (3.1a) extending from the sealing carrier (2) in the axial direction (A), and has a sealing lip transverse section (3.1b) directly adjoining the sealing lip axial section (3.1a), which extends obliquely from the sealing lip axial section (3.1a) in the axial direction (A) towards the sealing disc (4), and only the sealing lip cross section (3.1b) is coated with the synthetic resin silicone (5.1, 5.2). P240948 - 13 - 8. Sealing unit (1) according to claim 7, wherein the sealing disc (4) has a sealing disc axial section (4.2) and a sealing disc radial section (4.3) and the at least one sealing lip (3.1) is arranged above the sealing disc axial section (4.2) and only the section of the sealing lip transverse section (3.1b) is coated with the synthetic resin silicone (5.1, 5.2) which faces the sealing disc axial section (4.2).

9. Sealing unit (1 ) according to claim 7, wherein the sealing lip unit (3) has two sealing lips (3.1, 3.2) whose sealing lip transverse section (3.1b, 3.2b) is each coated with the synthetic resin silicone (5.1, 5.2).

10. Wheel bearing unit (RL) comprising an outer ring (6), an inner ring (7), a rolling bearing unit (8) and the sealing unit (1) according to one of the previous claims, which is arranged between the outer ring (6) and the inner ring (7).

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