Bearing device with integrated electrical insulation, in particular for an electric motor or machine

Abstract

The bearing device comprises a bearing 10 provided with a first ring 12 and a second ring 14 which can rotate relative to each other. The device comprises at least one insulating sleeve 22 which is fixed to the second ring 14 of the bearing and is provided with a bushing 24 and an insulating insert 26 which is inserted radially between the second ring 14 and the bushing 24 and is made of electrically insulating material. The bushing includes an outer surface 24a and an inner surface 24b that define its radial thickness. The insulating insert 26 is molded onto the second ring 14 of the bearing and onto at least one of the outer and inner surfaces of the bushing 24. The surface of the bushing comprises at least one projection 27 which projects towards the second ring and is provided with a flattening which is oriented radially towards the second ring.

Description

Technical field of the invention

[0001] The present invention relates to the field of bearings used in particular in electric motors, electrical machines and related devices. State of the art

[0002] In an electric motor or an electrical machine, at least one rolling bearing is mounted between the housing of the electric motor or electrical machine and the rotating shaft in order to support this shaft.

[0003] During operation, when the shaft rotates, an electrical potential difference may occur between the shaft and the housing of the motor or electric machine, generating an electric current between the inner ring of the rolling bearing, which is rigidly connected to the shaft, and the outer ring, which is rigidly connected to the housing.

[0004] The electrical current flowing through the components of the rolling bearing can damage these components, especially the rolling elements and raceways on the inner and outer rings. Electrical discharges can also generate vibrations.

[0005] To overcome these disadvantages, a well-known solution is to replace the bearing's rolling elements, which are made of the same steel as the inner and outer rings, with ceramic rolling elements. This is commonly referred to as a hybrid bearing.

[0006] However, such a hybrid rolling bearing is relatively expensive.

[0007] To overcome the above-mentioned disadvantages, another known solution consists in equipping the outer ring of the rolling bearing with an insulating sleeve provided with a bushing and an insulating insert made of electrically insulating material, which is inserted radially between the outer ring and the bushing.

[0008] In order to attach the insulating insert to the outer ring and the bushing without additional elements or special machining on the outer ring, the insulating insert can be formed.

[0009] However, such a solution may result in a relative decoupling of the insulating insert and the socket during operation.

[0010] Therefore, the object of the present invention is to overcome the above-mentioned disadvantages by providing a bearing device with a simple and economical design. Summary of the invention

[0011] The invention relates to a bearing device comprising a bearing provided with a first ring and a second ring that can rotate relative to each other.

[0012] The device further comprises at least one insulating sleeve attached to the second ring of the bearing. The insulating sleeve is provided with a bushing and an insulating insert radially inserted between the second ring of the bearing and the bushing. The insulating insert is made of an electrically insulating material.

[0013] The bushing comprises an outer surface and an inner surface opposite the outer surface, which limit the radial thickness of the sleeve.

[0014] The insulating insert is molded onto the second ring of the bearing and onto at least one of the outer and inner surfaces of the bushing.

[0015] According to a general feature, the surface of the bushing comprises at least one projection projecting towards the second ring and provided with a flattening oriented radially towards the second ring.

[0016] This provides a bearing device with integrated electrical insulation that is economical compared to conventional hybrid rolling bearings. Furthermore, the device is easy to manufacture and integrate into the associated electric motor or machine.

[0017] Furthermore, the provision of the projection with the flat on the bushing allows for a good connection with the insulating insert, as a flat with a matching shape is formed on the insert during molding. The risk of relative movement between the insulating insert and the bushing in the circumferential direction is limited, especially during temperature fluctuations. Furthermore, the projection forms an axial stop surface, which allows for limiting relative movement between the insulating insert and the bushing in the axial direction.

[0018] The “axial direction” means the direction parallel to the axis of the bearing device.

[0019] The term “circumferential direction” means the direction that is perpendicular to both the axial direction and a radius of the bearing device, in other words, the tangent of a circle whose center lies on the axis of the bearing device.

[0020] The bushing may be provided with two end faces that limit its axial length. The projection may extend radially along one of the end faces.

[0021] In one embodiment, the flattening comprises a first circumferential edge that is circumferentially connected to an end region of a cylindrical portion of the projection. The flattening may comprise a second opposite circumferential edge that is circumferentially connected to another end region of the cylindrical portion of the projection or to an end region of another cylindrical portion of the projection.

[0022] According to one embodiment, the projection is provided with a single cylinder portion and the flattening which is circumferentially connected to the cylinder portion.

[0023] According to a further embodiment, the projection is provided with a plurality of flats spaced apart from one another in the circumferential direction and a plurality of cylinder sections each extending between two successive flats.

[0024] According to yet another embodiment, the projection is provided with a plurality of flattened portions, wherein at least some or all of the flattened portions are circumferentially connected to one another.

[0025] In a particular embodiment, the bushing is made of a metal material. The bushing can thus be easily machined to a predetermined radial tolerance.

[0026] In one embodiment, the insulating insert covers the entire surface of the bushing. In this case, the insulating insert completely covers the surface of the bushing in both the axial and circumferential directions.

[0027] According to a first embodiment, the bushing defines the outer surface of the device. In this case, the second ring is the outer ring of the bearing.

[0028] According to a second alternative embodiment, the bushing defines the inner surface of the device. In this case, the second ring is the inner ring of the bearing.

[0029] If the insulating insert is made of synthetic or elastomeric material, it makes the device insensitive to temperature fluctuations.

[0030] In a specific embodiment, the bearing comprises at least one row of rolling elements arranged between raceways of the first and second rings. The rolling elements may be made of metal.

[0031] The invention also relates to an electric motor comprising a housing, a shaft and at least one bearing device as defined above, which is mounted radially between the housing and the shaft. Short description of the characters

[0032] The present invention will be better understood by reference to the detailed description of an embodiment provided as a non-limiting example and illustrated by the accompanying drawings in which: [ Fig. 1] is a half view of an axial section of a bearing device according to an embodiment of the invention; [ Fig. 2] a perspective view of a bushing of the bearing device of Fig. 1 is; [ Fig. 3] a side view of the socket of Fig. 2 is; and [ Fig. 4] a sectional view along the IV-IV axis of Fig. 3 is. Detailed description of the invention

[0033] The Fig. The bearing device illustrated in Figure 1 comprises a bearing 10 provided with a first ring 12 and a second ring 14 that can rotate relative to each other about the X-X' axis of the bearing. In the illustrated embodiment, the first ring 12 is the inner ring of the bearing, and the second ring 14 is the outer ring.

[0034] As described in more detail below, the bearing device is designed not to conduct electrical currents. The bearing device has integrated electrical insulation.

[0035] The inner ring 12 and outer ring 14 of the bearing are concentric and extend axially along the X-X' axis of the bearing. The inner ring 12 and outer ring 14 are made of steel. The rings are solid rings.

[0036] In the illustrated embodiment, the bearing 10 also includes a series of rolling elements 16, in this case balls, radially inserted between the inner ring 12 and the outer ring 14. The rolling elements 16 are made of steel. The bearing 10 also includes a cage 17 to maintain uniform circumferential spacing of the rollers 16. The bearing 10 can also be equipped with seals or flanges.

[0037] The inner ring 12 comprises a cylindrical bore 12a, a cylindrical axial outer surface 12b radially opposite the bore, and two opposing radial end surfaces (without reference numerals) that axially define the bore and the outer surface. The bore 12a and the outer surface 12b define the radial thickness of the inner ring 12. The bore 12a forms the inner surface of the inner ring.

[0038] The inner ring 12 also includes an inner raceway 18 for the rolling elements 16, formed on the outer surface 12b. The raceway 18 is directed radially outward.

[0039] The outer ring 14 comprises a cylindrical axial outer surface 14a, a cylindrical bore 14b radially opposite the outer surface 14a, and two opposing radial end surfaces 14c, 14d axially defining the bore and the outer surface. The outer surface 14a and the bore 14b define the radial thickness of the outer ring 14.

[0040] The outer ring 14 also includes an outer raceway 20 for the rolling elements 16, formed on the bore 14b. The raceway 20 is directed radially inward.

[0041] The bearing device also includes an electrically insulating sleeve 22 mounted on the outer ring 14. The insulating sleeve 22 is mounted on the outer surface 14a of the outer ring 14. The insulating sleeve 22 is rigidly connected to the outer ring 14.

[0042] The insulating sleeve 22 comprises a bushing 24 and an insulating insert 26 radially inserted between the outer ring 14 and the bushing 24. The insulating insert 26 is molded onto the outer ring 14 and the bushing 24.

[0043] The bushing 24 takes on an annular shape. The bushing 24 extends axially. In this case, the bushing 24 is manufactured as a single piece. The bushing 24 comprises a cylindrical axial outer surface 24a and a cylindrical bore 24b radially opposite the outer surface 24a and whose axis 25 is coaxial with the X-X' axis. The bore 24b forms the inner surface of the bushing 24.

[0044] The bushing 24 also includes two opposing radial end surfaces 24c, 24d that axially define the bore and the outer surface. The end surfaces 24c, 24d define the axial length of the bushing. The outer surface 24a and the bore 24b define the radial thickness of the bushing 24. The outer surface 24a of the bushing defines the outer surface of the bearing device 10. In other words, the outer surface 24a defines the outer diameter of the bearing device 10.

[0045] As in the Fig. As can be seen in Figures 2 to 4, the bore 24b of the bushing includes a first projection 27 that projects inward, i.e., toward the outer ring 14. The projection 27 projects from the bore 24b. The projection 27 extends radially.

[0046] The projection 27 is located at one axial end of the bushing bore 24b. The projection 27 extends the bushing end face 24c radially inward. The outer side of the projection 27 is coplanar with the end face 24c.

[0047] The bore of the projection 27 is provided with a cylindrical portion 28 with an axis 25 and a flattened portion 30 that is circumferentially connected to the cylindrical portion 28. The flattened portion 30 is aligned radially toward the outer ring 14, i.e., oriented radially inward. In other words, the flattened portion 30 is located radially on the side of the outer ring 14. The flattened portion 30 protrudes from the cylindrical portion 28. The flattened portion 30 assumes a flat shape.

[0048] The flattening 30 comprises a first circumferential edge 30a, which is circumferentially connected to an end region of the cylindrical portion 28, and a second opposite circumferential edge 30b in the circumferential direction, which is circumferentially connected to an opposite end region of the cylindrical portion 28. The flattening 30 forms an interruption of the inclination relative to the cylindrical portion 28 in its connection zones with the cylindrical portion. In this case, the flattening 30 extends over the entire axial length of the projection 27.

[0049] In the illustrated embodiment, the flat 30 extends in the axial direction. Alternatively, the flat 30 could be inclined relative to the axial direction to also fulfill the function of axially retaining the insulating insert. Alternatively, the flat 30 could be inclined at two angles, assuming a convex diamond-type shape or a shape whose slopes may or may not be alternating.

[0050] In the illustrated embodiment, the bore 24b of the bushing includes, at its other axial end, a second projection 31 that projects inward, i.e., toward the outer ring 14. The projection 31 projects from the bore 24b. The projection 31 extends radially. The projection 31 extends the end face 24d of the bushing radially inward. The outer side of the projection 31 is coplanar with the end face 24d.

[0051] In the illustrated embodiment, the projection 31 has a limited radial dimension compared to that of the projection 27. Alternatively, the projection 31 could have a radial dimension equal to or greater than that of the projection 27. Alternatively, a projection 31 may not be provided. In the illustrated embodiment, the projection 31 has a cylindrical bore. Alternatively, the projection 31 could have at least one flat, similar to the projection 27.

[0052] The bushing 24 is advantageously made of metal. Thus, the outer surface 24a of the bushing can be easily machined to a specified tolerance if necessary. Preferably, the bushing 24 is made of steel. The bushing 24 can be obtained by cutting, punching, and rolling from a sheet metal plate. Alternatively, the bushing 24 can be obtained from a tube or from forged / rolled blanks, or even by sintering and punching.

[0053] The insulating insert 26 is made of electrically insulating material. The insulating insert 26 can be made, for example, of a synthetic material such as PEEK or PA46, or even of an elastomer material such as rubber.

[0054] The insulating insert 26 is inserted radially between the outer surface 14a of the outer ring and the bore 24b of the bushing. The insulating insert 26 covers the outer surface 14a of the outer ring. In this case, the insulating insert 26 completely covers the outer surface 14a in the axial and circumferential directions. The insulating insert 26 also covers the bore 24b of the bushing. In this case, the insulating insert 26 also completely covers the bore 24b in the axial and circumferential directions. The insulating insert 26 covers the cylindrical section 28 and the flattened portion 30 of the bore of the projection 27. The insulating insert 26 also covers the bore of the projection 31.

[0055] As already mentioned, the insulating insert 26 is molded onto the outer ring 14 of the bearing and onto the bushing 24. The insulating insert 26 is molded onto the outer surface 14a of the outer ring 14 and onto the bore 24b and the projections 27, 31 of the bushing 24.

[0056] The insulating insert 26 takes on an annular shape. The insulating insert 26 extends axially. The insulating insert 26 includes an axial outer surface 26a, a cylindrical bore 26b radially opposite the outer surface 26a, and two opposing radial end surfaces 26c, 26d axially delimiting the bore and the outer surface. The end surfaces 26c, 26d axially delimit the insulating insert 26. The outer surface 26a and the bore 26b limit the radial thickness of the insulating insert 26. The outer surface 26a is in radial contact with the bore 24b of the bushing and the projections 27, 31. The bore 26b is in radial contact with the outer surface 14a of the outer ring.

[0057] The outer surface 26a of the insulating insert corresponds to the shape of the bore 24b of the bushing and the projections 27, 31, thus assuming a stepped shape. In the area of ​​the projection 31, the outer surface 26a is thus provided with a cylindrical section whose shape corresponds to the cylindrical section 28 of the bushing, and with a flattened portion whose shape corresponds to the flattened portion 30.

[0058] In the illustrated embodiment, the surfaces 14c, 26c, 24c and 14d, 26d, 24d of the outer ring, the insulating insert and the bushing are each coplanar.

[0059] Alternatively, other arrangements may be provided. For example, the insulating insert 26 could have a limited axial dimension and remain axially recessed from the surfaces 14c, 14d of the outer ring. Alternatively, the insulating insert 26 could have a larger axial dimension and project axially from the surfaces 14c, 14d of the outer ring. In this case, the insulating insert 26 can at least partially cover these surfaces 14c, 14d. In one variant, the insulating insert 26 could at least partially cover the surfaces 24c, 24d of the bushing.

[0060] As a further alternative or in combination, the bushing 24 could project axially from the insulating insert 26 relative to the surfaces 26c and 26d or could remain axially recessed relative to these surfaces.

[0061] The bearing device is manufactured as follows.

[0062] In a first step, the bearing 10 and the bushing 24, which is equipped with the projections 27, 31, are mounted in a mold provided for molding the insulating insert 26. In this position, in which it is mounted in the mold, the bushing 24 is radially spaced from the outer ring 14 of the bearing.

[0063] Then, in a second subsequent step, the insulating insert 26 is formed onto both the outer ring 14 of the bearing and the bushing 24.

[0064] Finally, the bearing device, which forms a uniform arrangement, is removed from the mold.

[0065] As already mentioned, in this embodiment, the projection 27 of the bore of the bushing comprises a single flat 30. Alternatively, the projection 27 could be provided with a plurality of flats 30 spaced from one another in the circumferential direction, with two consecutive flats being separated by a cylindrical section.

[0066] In another variant, if the projection 27 of the bushing bore 24b comprises a plurality of flats 30, it can be ensured that several consecutive flats are circumferentially connected to one another, or even that all flats are circumferentially connected to one another. In the latter case, the projection 27 does not have a cylindrical section.

[0067] When the projection 27 of the bushing comprises a plurality of flats 30, the flats may be identical to one another or, on the contrary, may have different lengths and / or circumferential dimensions and / or different inclinations.

[0068] In the illustrated embodiment, the first ring 12 of the bearing is the inner ring and the second ring 14, on which the insulating insert 26 is formed, is the outer ring.

[0069] Alternatively, a reverse arrangement may be provided, in which the second ring 14, on which the insulating insert 26 is molded, is the inner ring. In this case, the insulating sleeve is located in the bore 12a of the inner ring. The insulating insert is then radially inserted between the bore 12a of the inner ring and the outer surface of the bushing. The insulating insert is molded onto the inner ring and at least onto the outer surface of the bushing. The outer surface of the bushing is provided with one or more flat projections. The bore of the bushing defines the bore of the bearing device.

[0070] In the described embodiments, the bearing of the device is provided with a single row of rolling elements. In one variant, the bearing can be provided with multiple rows of rolling elements. Additionally, the rolling bearing can comprise other types of rolling elements than balls, for example, rollers. In another variant, the bearing can be a plain bearing without rolling elements.

Claims

[1] A bearing device comprising a bearing (10) provided with a first ring (12) and a second ring (14) which are rotatable relative to each other, and an insulating sleeve (22) fixed to the second ring (14) of the bearing and provided with a bushing (24) and an insulating insert (26) which is radially inserted between the second ring (14) and the bushing (24) and is made of electrically insulating material, the bushing comprising an outer surface (24a) and an inner surface (24b) opposite the outer surface, which delimit the radial thickness of the bushing, the insulating insert (26) being molded onto the second ring (14) of the bearing and onto at least one of the outer and inner surfaces of the bushing (24), characterized by that the surface of the bushing (24) comprises at least one projection (27) which projects towards the second ring and is provided with a flattening (30) which is oriented radially towards the second ring. [2] Device according to claim 1, wherein the bushing (24) comprises two end faces (24c, 24d) which limit the axial length of the bushing, the projection (27) extending radially one of the end faces. [3] Device according to claim 1 or 2, wherein the flattening (30) comprises a first circumferential edge (30a) which is circumferentially connected to an end region of a cylindrical portion of the projection. [4] Device according to claim 3, wherein the flattening (30) comprises a second opposite peripheral edge (30b) which is peripherally connected to another end region of the cylindrical portion of the projection or to an end region of another cylindrical portion of the projection. [5] Device according to one of the preceding claims, wherein the projection (27) is provided with a single cylinder portion (28) and the flat (30) connected to the cylinder portion. [6] Device according to one of claims 1 to 4, wherein the projection (27) is provided with a plurality of flats (30) spaced from each other in the circumferential direction and a plurality of cylinder sections (28) each extending between two successive flats (30). [7] Device according to claim 1 or 2, wherein the projection (27) is provided with a plurality of flats (30), at least some or all of the flats being circumferentially connected to one another. [8] Device according to one of the preceding claims, wherein the insulating insert (26) is made of synthetic material or elastomeric material. [9] Device according to one of the preceding claims, wherein the bushing (24) is made of a metal material. [10] Electric motor comprising a housing, a shaft and at least one bearing device according to one of the preceding claims, which is mounted radially between the housing and the shaft.

Images