Bearing unit provided with sealing device
By designing staggered shaped surfaces and tortuous paths in the sealing device within the bearing unit, the problems of lubricant leakage and friction loss when the sealing device resists external contaminants are solved, achieving high-efficiency sealing performance and low friction loss.
Patent Information
- Application Number
- CN202510623430.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Priority Date
- 2024-05-20
- Filing Date
- 2025-05-15
- Publication Date
- 2025-11-21
AI Technical Summary
Existing bearing unit sealing devices, while resisting external contaminants, are prone to lubricant leakage and increased friction loss, affecting service life and energy consumption.
The optimized sealing device design includes first and second shielding elements and an elastomeric sealing element. It forms a tortuous path through staggered shaped surfaces to reduce contact friction and achieves non-contact sealing through narrow sections and multiple directional changes to prevent contaminants from entering.
It effectively prevents contaminants from entering the bearing unit, while reducing friction loss, maintaining lubricant seal, and improving the service life and energy efficiency of the bearing unit.
Smart Images
Figure CN120990995A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present invention relates to a bearing unit provided with sealing means, preferably but not exclusively for all industrial applications which can involve rather high stresses. BACKGROUND
[0002] The known bearing units comprise an outer ring and an inner ring which can rotate with respect to each other by means of the interposition of a row of rolling bodies and also have respective sealing means interposed between the two rings to protect the bearing unit against the intrusion of external contaminants.
[0003] According to the prior art, the sealing means comprise:
[0004] - a first metal shield anchored by means of interference in a housing groove integrally formed to the outer ring,
[0005] - a first elastomeric sealing element rigidly fixed to the shield in one piece by means of a vulcanization process. The sealing element has at least one radially internal contact lip for frictional contact with the inner ring of the bearing unit,
[0006] - a second metal shield axially external with respect to the first shield, rigidly fixed to the inner ring by means of interference, thus being rotatable with respect to the first shield,
[0007] - a second elastomeric sealing element rigidly fixed to the second shield in one piece by means of a vulcanization process and provided with at least one axially internal contact lip for frictional contact with the first shield.
[0008] Therefore, the known sealing means ensure sealing against external contaminants, but must also prevent the lubricant from leaking out of the bearing unit. The retention of the lubricating grease is a very important characteristic for bearing units for industrial applications: it must be ensured that there is sufficient lubrication, including in environments which involve extreme contamination.
[0009] If the known sealing means are provided with several contact lips, these sealing means can ensure good performance. However, this type of solution leads to an increase in friction losses and therefore to higher temperatures and dissipated power.
[0010] From the above, the technical problems to be solved are:
[0011] - a seal against external contaminants, which does not reduce the service life of the bearing unit and seals the lubricant inside the bearing unit,
[0012] - friction losses due to the contact lips. SUMMARY
[0013] To substantially solve the technical problems set out above, the present application defines a bearing unit provided with a sealing device which offers high performance and is optimized in terms of shape and geometry.
[0014] The present application therefore provides a bearing unit provided with a sealing device and having the characteristics set out in the independent claim.
[0015] Preferred and / or particularly advantageous further embodiments of the present application are described in terms of the characteristics set out in the attached dependent claims. BRIEF DESCRIPTION OF DRAWINGS
[0016] The present application will now be described with reference to the attached drawings, which show non-limiting embodiments of the present application, in which:
[0017] - Figure 1 is a cross-sectional view of a bearing unit provided with a sealing device according to a preferred embodiment of the present application,
[0018] - Figure 2 shows, on a larger scale, Figure 1 the sealing device of
[0019] - Figure 3 shows, on an even larger scale, Figure 1 a detail of the anchoring portion of the sealing device of DETAILED DESCRIPTION
[0020] With reference to Figure 1 , the reference 30 generally indicates a bearing unit having an axis of rotation X, which is housed inside a housing 20 and comprises:
[0021] - a radial outer ring 31 provided internally and towards the axis X with at least one annular and shaped anchoring groove 31a,
[0022] - a radial inner ring 34,
[0023] - a plurality of rolling elements 32, in this example balls, interposed between the outer ring 31 and the inner ring 34,
[0024] - a cage 38 for holding and retaining the rolling bodies 32.
[0025] According to the preferred embodiment of the application described herein, the outer ring 31 is a stationary ring, while the inner ring 34 is a ring that is rotatable about the axis X.
[0026] Throughout the present description and claims, the terms and expressions indicating position and orientation, such as "radial" and "axial", will be understood with reference to the central rotation axis X of the bearing unit 30.
[0027] On the other hand, expressions such as "axially external" and "axially internal" refer to the sealing device when installed in the bearing unit, and in the present case preferably mean, respectively, the side via which the sealing device is inserted into the housing groove of the radially external ring and the side opposite the insertion side.
[0028] The outer ring 31 and the inner ring 34 define between them a cavity 35, which, if not shielded, would allow the entry of contaminants and impurities inside the bearing unit 30.
[0029] The bearing unit 30 also comprises a sealing device 40, positioned inside the cavity 35, to shield and protect said bearing unit 30 from the intrusion of contaminants and impurities.
[0030] Reference is also made to Figure 2 , the sealing device 40 comprises:
[0031] - a first shield 50, annular and shaped, preferably made of sheet metal, with a standard thickness of about 0.5 mm, so as to be sufficiently rigid and anchored in the housing groove 31a, internally formed to the outer ring 31, by means of interference. The shield 50 is therefore stationary,
[0032] - a first elastomeric sealing element 60, rigidly fixed to the shield 50 in a single piece with said shield by means of a vulcanization process. The sealing element is provided with at least one radially internal contact lip 60a for frictional contact with the inner ring 34 of the bearing unit 30. In the embodiment shown in the figures, there are three lips 60a, axially adjacent and with a substantially radial direction,
[0033] - a second shield 70, also annular and shaped, and preferably made of sheet metal, with a standard thickness of about 0.5 mm so as to be sufficiently rigid. The shield 70 is axially external with respect to the first shield 50 and is rigidly fixed to the radially external surface 34a of the inner ring 34 by interference. The shield 70 is therefore rotatable,
[0034] - a second elastomeric sealing element 80 rigidly fixed to the second shield 70 in one piece by means of a vulcanization process and provided with at least one axially internal contact lip 80a for frictional contact with the first shield 50. In the embodiment shown in the figures, there are two lips 80a, which are radially adjacent and extend obliquely in the direction away from the rotation axis X.
[0035] According to the application and also with reference to Figure 3 , the first sealing element 60 is provided with an annular portion 61 radially internal and axially external, having a shaped surface 69 axially external. The second sealing element 80 is also provided with an annular portion 81 radially internal and axially internal, having a shaped surface 89 axially internal. The two portions 61 and 81 are axially opposed.
[0036] In particular, the shaped surface 69 of the first portion 61 defines a plurality of annular ridges 62 or protrusions and a plurality of annular valleys 63 or grooves, radially alternating axially external. Both ridges and valleys are obtained by 360° rotation of a geometry corresponding to an isosceles trapezium. Each valley 63 is delimited by a pair of inclined surfaces 64, 66 and a bottom surface 65. Each ridge 62 is delimited by a pair of inclined surfaces 66, 68 and a top surface 67. Adjacent ridges and valleys share the inclined surface 66 of the pair of inclined surfaces.
[0037] Likewise, the shaped surface 89 of the second annular portion 81 defines a plurality of annular ridges 82 and a plurality of annular valleys 83, radially alternating axially internal. Both ridges and valleys are obtained by 360° rotation of a geometry corresponding to an isosceles trapezium. Each valley 83 is delimited by a pair of inclined surfaces 84, 86 and a bottom surface 85. Each ridge 82 is delimited by a pair of inclined surfaces 86, 88 and a top surface 87. Adjacent ridges and valleys share the inclined surface 86 of the pair of inclined surfaces.
[0038] According to the application, the first shaped surface 69 of the first portion 61 and the second shaped surface 89 of the second portion 81 are axially opposite and radially staggered, so that each ridge 62 of the first shaped surface 69 corresponds to a valley 83 of the second shaped surface 89, and vice versa, each ridge 82 of the second shaped surface 89 corresponds to a valley 63 of the first shaped surface 69.
[0039] The mutual position of the shaped surfaces 69 and 89 of the sealing elements 60, 80 defines a non-contact seal or a winding path P that is difficult for contaminants to cross.
[0040] The axial play of the bearing unit can further enhance this effect, especially under certain favorable conditions. In particular, the distance d between the top surface 67 of a general ridge 62 of the first shaped surface 69 and the bottom surface 85 of the corresponding valley 83 of the second shaped surface 89 (or, vice versa, the distance d between the top surface 87 of a general ridge 82 of the second shaped surface 89 and the bottom surface 65 of the corresponding valley 63 of the first shaped surface 69) can be no greater than 0.4 mm in the presence of the maximum axial play and as little as 0 mm in the presence of the minimum axial play. The distance d between the top surface 67 of a ridge 62 and the bottom surface 85 of a valley 83 (or, vice versa, the distance d between the top surface 87 of a ridge 82 and the bottom surface 65 of a corresponding valley 63) is approximately 0.2 mm. As mentioned above, the axial play of the bearing unit can vary this average distance, which depends on the dimensions and tolerances of the constituent parts of the bearing unit. However, given the standard applications of the bearing unit, the variability of the average distance resulting from the axial play will be within ± 0.1 mm / 0.2 mm.
[0041] The barrier effect of the winding path P is further enhanced by the fact that this path has a plurality of narrow sections S for the passage of contaminants. The narrow sections S have a minimum distance d m , the minimum distance d m corresponds to the distance between the two edges P 62 and P 82 of the top surfaces 67, 87 of the respective ridges 62, 82 that are axially opposite and radially staggered belonging to the corresponding first and second shaped surfaces 69, 89. Based on simple geometric considerations, the minimum distance d m will be between 50% and 75% of the distance d between the bottom of the valley and the top of the corresponding ridge.
[0042] Finally, the length of the tortuous path P, due to the number of changes of direction induced by the shaped surfaces 69, 89, is about 2 to 3 times the length of a pure radial path (pure radial path being defined if the facing surfaces 69, 89 are not shaped but pure annular).
[0043] The successive changes of direction in the narrow sections S and in the tortuous path P defined above create a real "bottleneck" for the contaminants. In particular, they have a "barrier" effect against the solid contaminants, which are trapped upstream of the narrow sections, and, like the effect induced by the converging channel, the speed of the liquid contaminants is slowed down, the path of the liquid contaminants being further blocked by the barrier of solid contaminants trapped upstream of the narrow sections.
[0044] This solution, as well as the preferred embodiment applied in the figures shown, can be used in all applications of sealing devices in which there are a fixed shield and a rotatable shield facing each other, both bearing elastomeric sealing elements.
[0045] During the assembly process, grease should be inserted between these ridges and valleys. It is sufficient to add the grease between the ridges of the first sealing element or, alternatively, between the ridges of the second sealing element before assembling them in the bearing unit. The addition of the grease has two advantages:
[0046] - it further improves the barrier effect of the tortuous path against external contaminants,
[0047] - in the event of frictional contact between the shaped surfaces 69, 89 due to the axial play, the presence of the grease will mitigate any friction generated between the contact surfaces.
[0048] The ridges and valleys can have alternative shapes without thereby departing from the scope of the proposed invention. For example, the top surface 67, 87 of a generic ridge can have zero length in the radial direction. In this case, the figure generating the ridge will be a triangle, for example an isosceles triangle. The same configuration can be applied to a valley with the bottom surface 65, 85 having zero length in the radial direction and with the isosceles triangle as the generating figure. This alternative configuration can be implemented:
[0049] - only on the first sealing element 60,
[0050] - only on the second sealing element 80,
[0051] - on both sealing elements.
[0052] A hybrid profile can also be defined: all the ridges of the second sealing element 80 can have a triangular generating figure and all the valleys a trapezoidal generating figure, and vice versa, for the first sealing element 60, with trapezoidal ridges and triangular valleys. Naturally, this hybrid profile can also be produced in the opposite configuration: all the ridges of the first sealing element can have a triangular generating figure and all the valleys a trapezoidal generating figure, and vice versa, for the second sealing element 80, with trapezoidal ridges and triangular valleys.
[0053] All these alternative configurations, comprising at least one element (ridge or valley) generated by a triangle instead of a trapezoid, will have the advantage of further reducing the minimum distance d m characterizing the narrow section S.
[0054] In summary, the bearing unit provided with a sealing device according to the present application ensures better sealing performance, thanks to the non-contact seal defining a tortuous path for the contaminants with multiple changes of direction and a plurality of narrow sections, thus creating a real barrier effect against the contaminants, without increasing the friction losses.
[0055] In addition to the embodiments of the application described above, it should be understood that there are many other variations. It should also be understood that the described embodiments are merely examples and do not limit the scope of the application, its application or its possible configurations. On the contrary, although the above description makes it possible for a person skilled in the art to apply the application according to at least one example of an embodiment, it should be understood that many variations of the described components are possible without thereby deviating from the scope of the application as defined in the attached claims, interpreted literally and / or according to their legal equivalents.
Claims
1. A bearing unit (30) having a central rotation axis (X) and comprising: - Fixed radial outer ring (31), - A rotatable radial inner ring (34), which, together with the radial outer ring (31), defines a cavity (35), and - A sealing device (40), housed in the cavity (35) and further comprising: - The first shielding element (50), integral with the radial outer ring (31) and supporting the first sealing element (60), - The second shielding element (70), integral with the radial inner ring (34) and supporting the second sealing element (80), The bearing unit (30) is characterized in that the first sealing element (60) and the second sealing element (80) are provided with corresponding first forming surface (69) and second forming surface (89). - The first forming surface (69) and the second forming surface (89) are axially opposite each other but do not contact each other. - The first forming surface (69) and the second forming surface (89) define a plurality of ridges (62, 82) and valleys (63, 83), wherein, on each forming surface (69, 89), each ridge (62, 82) alternates with a valley (63, 83) radially, and - The first forming surface (69) and the second forming surface (89) are radially staggered such that each ridge (62) of the first forming surface (69) corresponds to a valley (83) of the second forming surface (89), and each ridge (82) of the second forming surface (89) corresponds to a valley (63) of the first forming surface (69).
2. The bearing unit according to claim 1, characterized in that, Each ridge (62, 82) is defined by a pair of inclined surfaces (66, 68) and (86, 88) and a top surface (67, 87).
3. The bearing unit according to claim 1 or 2, characterized in that, Each valley (63, 83) is defined by a pair of inclined surfaces (64, 66) and (84, 86) and a bottom surface (65, 85).
4. The bearing unit according to any one of the preceding claims, characterized in that, The two edges (P) of the top surfaces (67, 87) of the corresponding ridges (62, 82) of the first forming surface (69) and the second forming surface (89) that are axially opposite and radially staggered are the top surfaces of ... corresponding ridges (62, 82) of the corresponding first forming surface (69) and the second forming surface (89). 62 P 82 The distance between (d) m The distance (d) between the top surface (67, 87) of the ridge (62, 82) and the bottom surface (85, 65) of the corresponding valley (83, 63) is between 50% and 75%.
5. The bearing unit according to any one of the preceding claims, characterized in that, Both the ridges (62, 82) and the valleys (63, 83) are obtained by rotating the geometry corresponding to an isosceles trapezoid by 360°.
6. The bearing unit according to any one of claims 1 to 4, characterized in that, Both the ridges (62, 82) and the valleys (63, 83) are obtained by rotating the geometry corresponding to an isosceles triangle by 360°.
7. The bearing unit according to any one of claims 1 to 4, characterized in that, The ridge (62) and valley (63) of the first shaped surface (69) are both obtained by rotating 360° of a geometric shape corresponding to an isosceles trapezoid, while the ridge (82) and valley (83) of the second shaped surface (89) are both obtained by rotating 360° of a geometric shape corresponding to an isosceles triangle.
8. The bearing unit according to any one of claims 1 to 4, characterized in that, The ridge (82) and valley (83) of the second forming surface (89) are both obtained by rotating 360° around a geometric shape corresponding to an isosceles trapezoid, while the ridge (62) and valley (63) of the first forming surface (69) are both obtained by rotating 360° around a geometric shape corresponding to an isosceles triangle.
9. The bearing unit according to any one of claims 1 to 4, characterized in that, The ridge (62) of the first shaped surface (69) is obtained by rotating 360° around a geometric shape corresponding to an isosceles trapezoid, while the valley (63) of the first shaped surface (69) is obtained by rotating 360° around a geometric shape corresponding to an isosceles triangle.
10. The bearing unit according to claim 9, characterized in that, The valley (83) of the second shaped surface (89) is obtained by rotating 360° around a geometric shape corresponding to an isosceles trapezoid, while the ridge (82) of the second shaped surface (89) is obtained by rotating 360° around a geometric shape corresponding to an isosceles triangle.