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

Abstract

[Bearing device with integrated electrical insulation, in particular for an electric motor or machine] The bearing device comprises a bearing 10 provided with a first ring 12 and a second ring 14 capable of rotating relative to each other. The device comprises at least one insulating sleeve 22 mounted on the second ring 14 of the bearing and provided with a bushing 24 and an insulating lining 26 interposed radially between the second ring 14 and the bushing 24 and made of electrically insulating material. The bushing comprises an outer surface 24a and an inner surface 24b which delimit its radial thickness. The insulating lining 26 is overmolded onto the second ring 14 of the bearing and at least onto one of the outer and inner surfaces of the sleeve 24. Said surface of the sleeve comprises at least one protuberance 27 which projects towards the second ring and which is provided with a flattened surface oriented radially towards the second ring.Reference: Figure 1.

Description

Title of the invention: Bearing device with integrated electrical insulation, in particular for an electric motor or machine Technical field of the invention

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

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

[0003] In operation when the shaft is rotating, an electrical potential difference may appear between it and the casing of the motor or the electric machine, which generates an electric current between the inner ring of the rolling bearing which is integral with the shaft, and the outer ring integral with the casing.

[0004] Electric current passing through rolling bearing components can damage these components, including rolling elements and raceways on the inner and outer rings. Electrical discharges can also generate vibrations.

[0005] To overcome these drawbacks, it is known to replace the rolling elements of the bearing made from the same steel as that of the inner and outer rings with rolling elements made from ceramic. This is generally referred to as a hybrid rolling bearing.

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

[0007] To overcome the aforementioned drawbacks, it is also known to equip the outer ring of the rolling bearing with an insulating sleeve provided with a bushing and an insulating lining made of electrically insulating material and interposed radially between the outer ring and the bushing.

[0008] In order to achieve the fixing of the insulating lining on the outer ring and on the sleeve without additional element or particular machining on the outer ring, it is possible to overmould the insulating lining.

[0009] However, with such a solution, a relative separation of the insulation lining and the sleeve may occur during operation.

[0010] The present invention therefore aims to remedy the aforementioned drawbacks by proposing a bearing device of 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 capable of rotating relative to each other.

[0012] The device further comprises at least one insulating sleeve mounted on the second ring of the bearing. The insulating sleeve is provided with a bushing and an insulating lining interposed radially between the second ring of the bearing and the bushing. The insulating lining is made of electrically insulating material.

[0013] The sleeve comprises an outer surface and an inner surface opposite the outer surface and which delimit the radial thickness of said sleeve.

[0014] The insulating gasket is overmolded onto the second ring of the bearing and at least onto one of the outer and inner surfaces of the sleeve.

[0015] According to a general characteristic, said surface of the sleeve comprises at least one protuberance which projects in the direction of the second ring and which is provided with a flattened surface oriented radially in the direction of the second ring.

[0016] Thus, a bearing device with integrated electrical insulation is provided which is economical compared to conventional hybrid rolling bearings. In addition, the device is easy to manufacture and assemble in the associated motor or electrical machine.

[0017] Furthermore, the provision of said protuberance with said flat on the sleeve makes it possible to obtain good attachment to the insulation lining insofar as a flat of complementary shape is formed on the lining during overmolding. The risk of relative displacements between the insulation lining and the sleeve in the circumferential direction is particularly limited, in particular during temperature variations. In addition, the protuberance forms an axial stop surface making it possible to limit the relative displacements between the insulation lining and the sleeve in the axial direction.

[0018] By "axial direction" is meant the direction parallel to the axis of the bearing device.

[0019] By "circumferential direction" is meant the direction which is perpendicular to the times to the axial direction and to a radius of the bearing device, in other words, tangent to a circle whose center is on the axis of the bearing device.

[0020] The sleeve may be provided with two front faces delimiting its axial length. Said protuberance may radially extend one of said front faces.

[0021] In one embodiment, said flat comprises a first circumferential edge which circumferentially connects to an end zone of a cylinder portion of said protuberance. Said flat may comprise a second opposite circumferential edge which circumferentially connects to another end zone of said cylinder portion of said protuberance, or to an end zone of another cylinder portion of said protuberance.

[0022] According to one design, said protrusion is provided with a single cylinder portion and said flat which connects circumferentially to the cylinder portion.

[0023] According to another design, said protrusion is provided with a plurality of flats spaced apart from each other in the circumferential direction, and a plurality of cylinder portions which each extend between two successive flats.

[0024] According to yet another design, said protuberance is provided with a plurality of flats, at least a portion of the flats or all of the flats connecting circumferentially to each other.

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

[0026] In one embodiment, said insulating lining covers the entire surface of said sleeve. In this case, said insulating lining completely covers said surface of the sleeve in the axial direction and in the circumferential direction.

[0027] According to a first design, the sleeve delimits the outer surface of said device. In this case, the second ring is the outer ring of the bearing.

[0028] According to a second alternative design, the sleeve delimits the inner surface of said device. In this case, the second ring is the inner ring of the bearing.

[0029] If the insulation lining is made of synthetic material or elastomeric material, it makes the device less sensitive to temperature variations.

[0030] In a particular 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 metallic material.

[0031] The invention also relates to an electric motor comprising a casing, a shaft and at least one bearing device as defined previously and mounted radially between the casing and the shaft. Brief description of the figures

[0032] The present invention will be better understood upon studying the detailed description of an embodiment, taken as a non-limiting example and illustrated by the appended drawings in which:

[0033] [Fig-1] is a half-view in axial section of a bearing device according to an exemplary embodiment of the invention,

[0034] [Fig.2] is a perspective view of a bushing of the bearing device of [Fig.l],

[0035] [Fig.3] is a side view of the socket of [Fig.2], and

[0036] [Fig.4] is a sectional view along axis IV-IV of [Fig.3]. Detailed description of the invention

[0037] The bearing device illustrated in [Fig.l] comprises a bearing 10 provided with a first ring 12 and a second ring 14 which are capable of rotating relative to each other around the axis X-X' 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.

[0038] As will be described in more detail later, the bearing device is designed so as not to be a conductor of electrical currents. The bearing device has integrated electrical insulation.

[0039] The inner 12 and outer 14 rings of the bearing are concentric and extend axially along the axis X-X' of the bearing. The inner 12 and outer 14 rings are made of steel. The rings are of the solid type.

[0040] In the illustrated embodiment, the bearing 10 also comprises a row of rolling elements 16, here balls, interposed radially between the inner 12 and outer 14 rings. The rolling elements 16 are made of steel. The bearing 10 also comprises a cage 17 for maintaining the regular circumferential spacing of the rollers 16. The bearing 10 may also be equipped with seals or sealing flanges.

[0041] The inner ring 12 comprises a cylindrical bore 12a, a cylindrical axial outer surface 12b radially opposite the bore, and two opposite radial end faces (not referenced) axially delimiting the bore and the outer surface. The bore 12a and the outer surface 12b delimit the radial thickness of the inner ring 12. The bore 12a forms the inner surface of the inner ring.

[0042] The inner ring 12 further comprises an inner raceway 18 for the rolling elements 16 which is formed on the outer surface 12b. The raceway 18 is directed radially outwards.

[0043] The outer ring 14 comprises a cylindrical axial outer surface 14a, a cylindrical bore 14b radially opposite the outer surface 14a, and two opposite radial end faces 14c, 14d axially delimiting the bore and the outer surface. The outer surface 14a and the bore 14b delimit the radial thickness of the outer ring 14.

[0044] The outer ring 14 further comprises an outer raceway 20 for the rolling elements 16 which is formed on the bore 14b. The raceway 20 is directed radially inwards.

[0045] The bearing device also comprises an electrical 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 integral with the outer ring 14.

[0046] The insulating sleeve 22 comprises a bushing 24 and an insulating lining 26 interposed radially between the outer ring 14 and the bushing 24. The lining insulation 26 is overmolded onto the outer ring 14 and onto the sleeve 24.

[0047] The sleeve 24 is annular in shape. The sleeve 24 extends axially. The sleeve 24 is made here in a single piece. The sleeve 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 axis X-X'. The bore 24b forms the inner surface of the sleeve 24.

[0048] The sleeve 24 also comprises two opposite radial end faces 24c, 24d axially delimiting the bore and the outer surface. The end faces 24c, 24d delimit the axial length of the sleeve. The outer surface 24a and the bore 24b delimit the radial thickness of the sleeve 24. The outer surface 24a of the sleeve delimits the outer surface of the bearing device 10. In other words, the outer surface 24a defines the outer diameter of the bearing device 10.

[0049] As can be seen in Figures 2 to 4, the bore 24b of the sleeve comprises a first protrusion 27 which projects inwardly, i.e. projects in the direction of the outer ring 14. The protrusion 27 projects in relation to the bore 24b. The protrusion 27 extends radially.

[0050] The protrusion 27 is located at an axial end of the bore 24b of the sleeve. The protrusion 27 extends the front face 24c of the sleeve radially inward. The outer face of the protrusion 27 is coplanar with the front face 24c.

[0051] The bore of the protuberance 27 is provided with a cylinder portion 28 of axis 25, and a flat 30 which is connected circumferentially to the cylinder portion 28. The flat 30 is oriented radially in the direction of the outer ring 14, i.e. oriented radially inwards. In other words, the flat 30 is located radially on the side of the outer ring 14. The flat 30 projects in relation to the cylinder portion 28. The flat 30 has a plane shape.

[0052] The flat 30 comprises a first circumferential edge 30a which is connected circumferentially to an end zone of the cylinder portion 28, and a second circumferential edge 30b opposite in the circumferential direction which is connected circumferentially to an opposite end zone of the cylinder portion 28. The flat 30 forms a break in slope relative to the cylinder portion 28 in its connection zones with said cylinder portion. The flat 30 here extends over the entire axial length of the protuberance 27.

[0053] In the illustrated embodiment, the flat 30 extends in the axial direction. Alternatively, the flat 30 could be inclined relative to the axial direction so as to also fulfill a function of axially retaining the insulation lining. Alternatively, the flat 30 could be inclined at two angles of convex shape of the diamond type or of shape whose slopes are alternating or not.

[0054] In the illustrated embodiment, the bore 24b of the sleeve comprises, at its other axial end, a second protrusion 31 which extends inwardly projecting, i.e. projecting towards the outer ring 14. The protrusion 31 projects in relation to the bore 24b. The protrusion 31 extends radially. The protrusion 31 extends radially inwardly the front face 24d of the sleeve. The outer face of the protrusion 31 is coplanar with the front face 24d.

[0055] In the illustrated embodiment, the protrusion 31 has a reduced radial dimension compared to that of the protrusion 27. Alternatively, the protrusion 31 could have a radial dimension equal to or greater than that of the protrusion 27. Alternatively, it could be possible not to provide a protrusion 31. In the illustrated embodiment, the protrusion 31 has a cylindrical bore. Alternatively, similarly to the protrusion 27, the protrusion 31 could have at least one flat.

[0056] The sleeve 24 is advantageously made of a metallic material. Thus, the outer surface 24a of the sleeve can be easily machined if necessary to a predetermined tolerance. Preferably, the sleeve 24 is made of steel. The sleeve 24 can be obtained from a sheet metal blank by cutting, stamping and rolling. Alternatively, the sleeve 24 can be obtained from a tube or from forged and / rolled blanks, or from sintering and stamping.

[0057] The insulating lining 26 is made of electrically insulating material. The insulating lining 26 may for example be made of synthetic material, such as PEEK or PA46, or may be made of elastomeric material, for example rubber.

[0058] The insulating lining 26 is interposed radially between the outer surface 14a of the outer ring and the bore 24b of the sleeve. The insulating lining 26 covers the outer surface 14a of the outer ring. The insulating lining 26 here completely covers the outer surface 14a considering the axial and circumferential directions. The insulating lining 26 also covers the bore 24b of the sleeve. The insulating lining 26 here also completely covers the bore 24b considering the axial and circumferential directions. The insulating lining 26 covers the cylinder portion 28 and the flat 30 of the bore of the protuberance 27. The insulating lining 26 also covers the bore of the protuberance 31.

[0059] As indicated previously, the insulating lining 26 is overmolded onto the outer ring 14 of the bearing and onto the sleeve 24. The insulating lining 26 is overmolded onto the outer surface 14a of the outer ring 14 and onto the bore 24b and the protrusions 27, 31 of the sleeve 24.

[0060] The insulating gasket 26 is annular in shape. The insulating gasket 26 extends axially. The insulating gasket 26 comprises an axial outer surface 26a, a cylindrical bore 26b radially opposite the outer surface 26a, and two faces opposite radial front faces 26c, 26d axially delimiting the bore and the outer surface. The front faces 26c, 26d axially delimit the insulating lining 26. The outer surface 26a and the bore 26b delimit the radial thickness of the insulating lining 26. The outer surface 26a is in radial contact with the bore 24b of the sleeve and the protrusions 27, 31. The bore 26b is in radial contact with the outer surface 14a of the outer ring.

[0061] The outer surface 26a of the insulating lining is of a shape complementary to the bore 24b of the sleeve and to the protrusions 27, 31, and thus has a stepped shape. In the region of the protrusion 31, the outer surface 26a is thus provided with a cylindrical portion of a shape complementary to the cylindrical portion 28 of the sleeve, and with a flat of a shape complementary to the flat 30.

[0062] In the illustrated embodiment, the faces 14c, 26c, 24c and 14d, 26d, 24d of the outer ring, the insulating lining and the sleeve are respectively coplanar.

[0063] Alternatively, it is possible to provide other arrangements. For example, the insulating lining 26 could have a reduced axial dimension and remain axially set back from the faces 14c, 14d of the outer ring. Alternatively, the insulating lining 26 could have an increased axial dimension and extend axially projecting from the faces 14c, 14d of the outer ring. In this case, the insulating lining 26 may at least partially cover these faces 14c, 14d. Alternatively, the insulating lining 26 could at least partially cover the faces 24c, 24d of the sleeve.

[0064] In another alternative or combination, the sleeve 24 could extend axially projecting from the insulation lining 26 relative to the faces 26c and 26d, or remain axially set back from these faces.

[0065] To manufacture the bearing device, the procedure is as follows.

[0066] In a first step, the bearing 10 and the sleeve 24 equipped with the protrusions 27, 31 are mounted inside a mold which is provided for the overmolding of the insulating lining 26. In this position mounted inside the mold, the sleeve 24 is radially at a distance from the outer ring 14 of the bearing.

[0067] Then, during a second successive step, the insulating lining 26 is overmolded both on the outer ring 14 of the bearing and on the sleeve 24.

[0068] Finally, the bearing device, which is in the form of a unitary assembly, is extracted from the mold.

[0069] As indicated previously, in this exemplary embodiment, the protuberance 27 of the bore of the sleeve comprises a single flat 30. Alternatively, the protuberance 27 could be provided with a plurality of flats 30 spaced apart from each other in the circumferential direction, two successive flats being separated by a portion of a cylinder.

[0070] In another variant, when the protuberance 27 of the bore 24b of the sleeve comprises a plurality of flats 30, it is possible to provide that several successive flats connect circumferentially to each other, or that all of the flats connect circumferentially to each other. In the latter case, the protuberance 27 is devoid of a cylinder portion.

[0071] When the protuberance 27 of the socket comprises a plurality of flats 30, the flats may be identical to each other, or on the contrary have different lengths and / or circumferential dimensions, and / or different inclinations.

[0072] In the illustrated embodiment, the first ring 12 of the bearing is the inner ring and the second ring 14 on which the insulating lining 26 is overmolded is the outer ring.

[0073] Alternatively, it is possible to provide an inverted arrangement in which the second ring 14 on which the insulating lining 26 is overmolded is the inner ring. In this case, the insulating sleeve is located in the bore 12a of the inner ring. The insulating lining is then interposed radially between the bore 12a of the inner ring and the outer surface of the sleeve. The insulating lining is overmolded on the inner ring and at least on the outer surface of the sleeve. The outer surface of the sleeve is provided with the flattened protrusion(s). The bore of the sleeve delimits the bore of the bearing device.

[0074] In the described embodiments, the bearing of the device is provided with a single row of rolling elements. The bearing may alternatively be provided with several rows of rolling elements. Furthermore, the rolling bearing may comprise other types of rolling elements than balls, for example rollers. In another variant, the bearing may be a sliding bearing without rolling elements.

Claims

Claims

1. Bearing device comprising a bearing (10) provided with a first ring (12) and a second ring (14) capable of rotating relative to each other, and an insulating sleeve (22) mounted on the second ring (14) of the bearing and provided with a bushing (24) and an insulating lining (26) interposed radially between the second ring (14) and the bushing (24) and made of electrically insulating material, the bushing comprising an outer surface (24a) and an inner surface (24b) opposite the outer surface and which delimit the radial thickness of said bushing, the insulating lining (26) being overmolded on the second ring (14) of the bearing and at least on one of the outer and inner surfaces of the bushing (24),characterized in that said surface of the sleeve (24) comprises at least one protrusion (27) which projects towards the second ring and which is provided with a flat (30) oriented radially towards the second ring.,

2. Device according to claim 1, in which the sleeve (24) comprises two front faces (24c, 24d) delimiting the axial length of said sleeve, said protuberance (27) radially extending one of said front faces.

3. A device according to claim 1 or 2, wherein said flat (30) comprises a first circumferential edge (30a) which connects circumferentially to an end zone of a cylinder portion of said protuberance.

4. A device according to claim 3, wherein said flat (30) comprises a second opposite circumferential edge (30b) which connects circumferentially to another end zone of said cylinder portion of said protuberance, or to an end zone of another cylinder portion of said protuberance.

5. A device according to any preceding claim, wherein said protrusion (27) is provided with a single cylinder portion (28) and said flat (30) which connects to the cylinder portion.

6. Device according to any one of claims 1 to 4, wherein said protuberance (27) is provided with a plurality of flats (30) spaced apart from each other in the circumferential direction, and a plurality of cylinder portions (28) which each extend between two successive flats (30).

7. A device according to claim 1 or 2, wherein said protrusion (27) is provided with a plurality of flats (30), at least some of the flats or all of the flats connecting circumferentially to each other.

8. Device according to any one of the preceding claims, in which the insulating lining (26) is made of synthetic material or elastomeric material.

9. A device according to any preceding claim, wherein the socket (24) is made of metallic material.

10. An electric motor comprising a housing, a shaft and at least one bearing device according to any one of the preceding claims mounted radially between the housing and the shaft.

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