Wheel bearing units

Abstract

The invention relates to a wheel bearing unit, which has at least one outer ring (4) and at least two inner rings (3), between which rolling elements guided in a cage are arranged, two adjacent inner rings bear against each other via their mutually facing axial end faces (6), and a sealing device (8) is arranged to seal the interface between the two inner rings, the sealing device is formed by an annular retaining element (10), and at least one sealing element (11) is arranged on the retaining element, the sealing element is in the form of a sealing ring (12), which has at least two contact points with the retaining element and at least one contact point with one inner ring in each case, at least one of the contact points being designed so that the at least one contact point has a flat surface.

Description

Technical Field

[0001] The invention relates to a wheel bearing unit, in particular a wheel bearing unit for a motor vehicle. Background Art

[0002] Wheel bearing units with preassembled press-fit roller bearing units are used, for example, for commercial vehicles when a wheel bearing which usually consists of at least two wheel bearing units cannot be mounted correctly in a vehicle workshop.

[0003] When it comes to the installation of wheel bearings, a clean working environment and numerous precautions are essential for correct installation. Unfortunately, these measures cannot be followed under certain conditions. In general, contamination of the rolling space often leads to a loss of service life for wheel bearings. The same problem also occurs with other types of bearings, especially in the automotive sector.

[0004] It is conceivable to use a replaceable wheel bearing unit, the rolling space of which does not need to be opened during installation and therefore there is no risk of contaminating the rolling space. However, in this case, the cost of the material is relatively high, making the wheel bearing expensive.

[0005] For this purpose, so-called insert wheel bearing units, in particular insert tapered roller bearing units, have been developed in the past, which can be delivered and transported in a pre-assembled state without unnecessarily revealing the rolling space during installation or otherwise. In the pre-assembled state, the insert wheel bearing unit is pressed laterally into the wheel carrier or into or onto the wheel hub.

[0006] Such a tapered roller bearing has axially acting and radially acting sealing means, wherein the radially acting sealing means seals the gap between the two inner rings in end-face contact. In several exemplary embodiments, the sealing ring is always arranged on the radial inside of the two inner rings in a common annular groove, which is formed by depressions in the region of the mutually facing end faces of the two inner rings. The common annular groove formed by these depressions for receiving the sealing ring has in each case a rectangular cross-sectional geometry.

[0007] In order to achieve the desired sealing performance and also to allow pressure equalization between the inner space of the bearing and the environment or to allow ventilation thereof, the sealing rings designed in different ways in the variants each comprise a metal clamping element which exerts a radial contact pressure on the sealing ring in the direction of the inner ring forming the annular groove and secures the sealing ring in the annular groove and allows pressure equalization. In this respect, the known sealing rings are all relatively expensive rubber-metal parts which, due to their design, do not allow a gas-tight sealing of the inner space of the roller bearing.

[0008] A double-row tapered roller bearing mounted as a wheel bearing in a wheel hub of a vehicle is also known from WO 97 / 42425 A1. The two-piece inner ring of this tapered roller bearing is protected from the ingress of undesirable substances, such as oil from the axle region, by means of a sealing system which covers the adjacent end faces of the two inner rings and is arranged in the inner space of the bearing. This sealing system consists of two O-rings, one of which is formed in an associated annular groove on the outer circumference of each of the inner rings. The two O-rings are also radially surrounded by a metal ring which presses the two O-rings against the associated inner ring in a sealing manner. The four-row roller bearing known from DE 39 15 624 A1 presents a similar design, but does not use O-rings, but a sealing device designed in a different way, which is inserted into a common annular groove with a rectangular cross section on the inner ring and is retained by a sheet metal ring.

[0009] Finally, a double-row roller bearing with a multi-part inner and outer ring is known from DE 36 21 381 A1. In the case of this roller bearing, the outer rings are axially spaced apart from one another by means of spacing rings, while the inner ring is connected by means of a mounting ring with a U-shaped cross section, the legs of which engage in correspondingly assigned circumferential grooves in the inner ring.

[0010] In this roller bearing, the outer rings are axially spaced from each other by means of a spacing ring, while the inner ring is connected by means of a mounting ring with a U-shaped cross section, the legs of which engage in a correspondingly allocated circumferential groove in the inner ring. In both cases, a deterioration in performance and a shortening of the bearing life of the roller bearing can be expected. In some embodiments there are criticisms, for example, that the axial support of the two inner rings against each other is not sufficient, so that foreign bodies can overcome the seal in the area of ​​the dividing line between the end faces of the inner rings. In the case of other embodiments, the seal can be pressed against the inner ring by means of a separate sheet metal ring or by a sheet metal ring incorporated in a rubber material of the seal having an effect sufficient for the sealing purpose, which sealing rings are judged to be relatively expensive to manufacture. . Summary of the invention

[0011] The invention is based on the object of providing a wheel bearing unit which can be sealed reliably against external influences.

[0012] According to the present invention, this object is achieved by a wheel bearing unit, which has at least one outer ring and at least two inner rings, rolling elements guided in a retaining frame are arranged between the at least one outer ring and the at least two inner rings, two adjacent inner rings bear against each other through their mutually facing axial end faces, and a sealing device is provided to seal the interface of the two inner rings, the sealing device is formed by an annular retaining element, and at least one sealing element is arranged on the retaining element, the sealing element is in the form of a sealing ring, the sealing ring has at least two contact points with the retaining element and at least one contact point with one inner ring in each case, at least one of the contact points is designed so that the at least one contact point has a flat surface.

[0013] The invention is based on the knowledge that the center seals known from the prior art are axially tensioned and therefore seal axially. However, insufficient axial tensioning of the wheel bearing unit results in insufficient axial tensioning of the center seal and thus inability to seal correctly.

[0014] According to the invention, a sealing element is provided in the retaining element of the sealing device, the sealing element being designed such that the sealing element has at least two radial contact points with the retaining element and at least one radial contact point with one inner ring in each case, and at least one of the contact points is designed such that the at least one contact point has a flat surface. The flat surface increases the adhesion forces generated in the region of the sealing device, which can improve the sealing performance. In the case of pointed surfaces known from the prior art, an additional medium is always required to exert the required pressure on the seal. Another advantage of the embodiment according to the invention is that the contact points and their contact areas remain unchanged throughout the service life. In addition, the flat surface prevents the sealing element from folding during the service life. Therefore, according to the invention, an airtight sealing and self-locking sealing device is provided, which reliably and effortlessly prevents the ingress of foreign bodies and / or prevents the migration of lubricants via the abutting end face of the inner ring into or out of the space of the wheel bearing unit in which the rolling elements are arranged.

[0015] According to an embodiment of the invention, the sealing element has at least one lead-in chamfer, wherein the lead-in chamfer is formed by a first angle and a second angle. The size of the angle generally depends on the lead-in chamfer of the surrounding components. Advantageously, the first angle is at least 15°. The second angle is designed to be slightly steeper and is at least 20°. The lead-in chamfer allows the sealing element to be simply pushed onto the inner ring.

[0016] Preferably, the sealing element has a minimum profile thickness which depends on the hardness of the material. In order to ensure that the sealing effect is not reduced, the minimum profile thickness must be selected in such a way that, in combination with the selected material hardness, the sealing lip exerts a sufficiently large contact force on the surrounding components to ensure an adequate sealing effect. The minimum profile thickness is also selected in such a way that, in the presence of media and possible chemical surface stresses as well as temperature stresses on the sealing element material, the basic sealing function continues to be provided by a sufficiently intact core material. For example, the ratio of the minimum profile thickness to the minimum height of the sealing element can be 85 Shore A:minimum 6:1 or 70 Shore A:minimum 8:1.

[0017] According to an embodiment of the invention, the sealing device is arranged in a common annular groove of the inner ring, which is formed by a depression in the region of the mutually facing end faces of the inner ring. By providing this sealing device, sufficient radial tensioning of the sealing element can be achieved. In addition, the depression forms edges on the respective inner ring, which edges are simultaneously used for aligning, centering and positioning the sealing device.

[0018] According to an alternative embodiment of the invention, the retaining element is designed in a U-shape and has two side rings connected by means of a circumferential web. This ensures that the sealing element is fixedly held in the retaining element during assembly and operation of the wheel bearing unit. In addition, this can prevent axial displacement of the sealing element.

[0019] Preferably, at least one of the side rings forms a positioning aid which is centered and positioned on the edge of the annular groove.

[0020] Preferably, at least one of the side rings has at least one interruption. Advantageously, several interruptions are arranged evenly distributed around the circumference on both side rings. This enables cost-effective demoulding during the manufacture of the retaining element. In addition, such a design of the retaining element facilitates the assembly of the sealing element and the final assembly on the wheel bearing unit.

[0021] According to an embodiment of the invention, the sealing ring is made of a rubber-elastic material. This makes it possible to achieve particularly good nesting of the sealing element in the retaining element.

[0022] Preferably, the retaining element is made of plastic.

[0023] Preferably, the rolling elements are designed as tapered rollers. However, the rolling elements can also be needle rollers, cylindrical rollers, barrel rollers or spherical rollers suitable for heavy commercial vehicles or for high-load transmissions. Alternatively, spherical rolling elements are also conceivable. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Two exemplary embodiments of the present invention are shown below with reference to three drawings. In the drawings:

[0025] Figure 1 shows a longitudinal section of a wheel bearing unit according to the invention,

[0026] Figure 2 shows a longitudinal section of a sealing device of a wheel bearing unit according to the invention,

[0027] Figure 3 shows a longitudinal section of a sealing device of a wheel bearing unit according to the invention,

[0028] Figure 4 Shows Figure 3 An enlarged view of the sealing device shown in

[0029] Figure 5 shows a longitudinal section of a sealing device of a wheel bearing unit according to the invention,

[0030] Figure 6a A diagram showing a change in position of a sealing device of a wheel bearing unit according to the invention,

[0031] Figure 6b A diagram showing a change in position of a sealing device of a wheel bearing unit known from the prior art,

[0032] Figure 7 A perspective view of a sealing device of a wheel bearing unit according to the present invention is shown. DETAILED DESCRIPTION

[0033] Figure 1 A longitudinal section through a wheel bearing unit 1 according to the invention is shown. The wheel bearing unit is designed as a double-row tapered roller bearing 2. The tapered roller bearing 2 has an inner ring 3 and an outer ring 4. A tapered roller 5 is arranged between the running surfaces formed by the inner ring 3 and the outer ring 4, on which the tapered roller rolls.

[0034] One end face 6 of each of the two inner rings 3 bears against each other and thus forms an interface 7. A sealing device 8 is provided to seal the interface 7. Figure 1 It can be seen in FIG. 1 that the two inner rings 3 form an annular groove 9. This is formed by corresponding depressions in the two inner rings 3.

[0035] The sealing device 8 is formed by an annular retaining element 10, on which at least one sealing element 11 is arranged. The sealing element is designed as a sealing ring 12. The sealing ring 12 is made of a rubber elastic material. Figure 2 , Figure 3 and Figure 4The sealing element 11 is described in more detail. The sealing ring 12 has two contact points 13, 14 with the retaining element 10 and contact points 15, 16 with the respective inner ring 3. By means of this special design, the sealing ring 12 is radially pressed against the inner ring 3 during installation and is correspondingly radially tensioned. This provides the advantage that the radial sealing or radial tensioning of the sealing element 11 is still not affected even if the inner ring 3 is axially displaced.

[0036] At least one of the contact points 13, 14, 15, 16 is designed such that it has a flat surface X. This flat surface increases the adhesive forces generated in the area of ​​the sealing device 8, which can improve the sealing performance. In the case of pointed surfaces of the sealing element 11 known from the prior art, an additional medium is always required to exert the required pressure on the seal. Another advantage of the embodiment according to the invention is that the contact points 13, 14, 15, 16 and their contact areas remain unchanged throughout the service life. In addition, the flat surface prevents the sealing element 11 from folding during its service life.

[0037] The sealing element 11 has at least one lead-in chamfer, and wherein the lead-in chamfer is formed by a first angle a and a second angle b. The size of the angles a, b usually depends on the lead-in chamfers of the surrounding components. Advantageously, the first angle is at least 15°. The second angle is designed to be slightly steeper and is at least 20°. The lead-in chamfer allows the sealing element 11 to be simply pushed onto the inner ring 3.

[0038] As from Figure 5 It can also be seen that the sealing element 11 has a minimum profile thickness y. The minimum profile thickness depends on the hardness of the material. In order to ensure that the sealing effect is not reduced, the minimum profile thickness must be selected in such a way that, in combination with the selected material hardness, the sealing element 11 exerts a sufficiently large contact force on the surrounding components to ensure an adequate sealing effect. The minimum profile thickness is also selected in such a way that, in the presence of media and possible chemical surface stresses as well as temperature stresses on the sealing element material, the basic sealing function continues to be provided by the sufficiently intact core material.

[0039] Figure 6a and Figure 6b The variation in position of a seal of a wheel bearing unit according to the invention and the variation in position of a seal of a wheel bearing unit known from the prior art are shown. Figure 6a An embodiment according to the present invention is shown, and Figure 6b A sealing element 22 from the prior art is used. Figure 6aIt can be seen that the sealing effect of the sealing element 11 is independent of the change in position of the sealing element 11 during the axial movement L of the seal itself or of the inner ring 3. The contact points 13, 14, 15, 16 are always designed as flat surfaces X and remain unchanged during any movement. Figure 6b It is shown that the contact point 23 is affected by the axial movement L of the sealing element 22. The pointed contact point 23 is folded during the axial movement L and is therefore minimized after the change of position.

[0040] Figure 7 The design of the sealing device 8 is shown. The retaining element 10 is designed in a U-shape and has two side rings 17 , 18 which are connected by means of a circumferential web 19 . This ensures that the sealing element 11 is fixedly held in the retaining element 8 .

[0041] As can also be seen, the side rings are designed such that they have several interruptions 20 , 21 distributed around the circumference. The side rings 17 , 18 simultaneously form positioning aids which are centered and positioned on the edge of the annular groove 9 .

[0042] Description of Reference Numerals

[0043] 1 Wheel bearing unit 2 Tapered roller bearing 3 Inner ring 4 Outer ring 5 Tapered roller 6 End face 7 Interface 8 Seal 9 Annular groove 10 Retaining element 11 Sealing element 12 Sealing ring 13 Contact point 14 Contact point 15 Contact point 16 Contact point 17 Side ring 18 Side ring 19 Web 20 Interruption 21 Interruption 22 Sealing element from prior art 23 Contact point X Flat surface a First angle b Second angle y Minimum profile thickness L Axial movement.

Claims

1. A wheel bearing unit, the wheel bearing unit having at least one outer ring (4) and at least two inner rings (3), rolling elements guided in a cage being arranged between the at least one outer ring and the at least two inner rings, two adjacent inner rings (3) bearing against each other via their mutually facing axial end faces (6), and a sealing device (8) being provided to seal the interface between the two inner rings (3), the sealing device (8) being formed by an annular retaining element (10), and at least one sealing element (11) being provided on the retaining element (10), the sealing element (11) being in the form of a sealing ring (12), the sealing ring having at least two contact points with the retaining element (10) and at least one contact point with one inner ring (3) in each case, at least one of the contact points being designed so that the at least one contact point has a flat surface (X), characterized in that The retaining element (10) is designed in a U-shape and has two side rings (17, 18) connected by means of a circumferential web (19), at least one of the side rings (17, 18) having at least one interruption (20, 21), and the retaining element (10) is made of plastic; The sealing device (8) is arranged in a common annular groove (9) of the inner ring (3), which is formed by a depression in the region of the mutually facing end faces (6) of the inner ring (3).

2. The wheel bearing unit according to claim 1, wherein: The sealing element (11) has at least one lead-in chamfer, and wherein the lead-in chamfer is formed by a first angle (a) and a second angle (b).

3. Wheel bearing unit according to any one of the preceding claims, wherein: The sealing element (11) has a minimum profile thickness (y) which depends on the hardness of the material.

4. The wheel bearing unit according to claim 1, wherein: At least one of the side rings (17, 18) forms a positioning aid which is centered and positioned on the edge of the annular groove (9).

5. The wheel bearing unit according to claim 1 or 2, wherein: The sealing element (11) is made of rubber elastic material.

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