Bearing device with integrated electrical insulation, particularly for electric motors or machines

Abstract

[Bearing device with integrated electrical insulation, particularly for electric motors or machines] The bearing device comprises a bearing 10 having a first ring 12 and a second ring 14 capable of rotating relative to each other. The device includes at least one insulating sleeve 22 mounted on the second ring 14 of the bearing and having a bushing 24 and an insulating gasket 26 interposed radially between the second ring 14 and the bushing 24 and made of electrically insulating material. The bushing has an outer surface 24a and an inner surface 24b that define its radial thickness. The insulating packing 26 is overmolded onto the second ring 14 of the bearing and at least onto one of the outer and inner surfaces of the bushing 24. Said surface of the bushing includes at least one protrusion 27 which extends in projection towards the second ring and which is provided with a flat oriented radially towards the second ring.Reference: Figure 1.

Description

Title of the invention: Bearing device with integrated electrical insulation, particularly for electric motors or machines. 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. Prior art

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

[0003] During operation when the shaft is rotating, an electrical potential difference may appear between it and the housing of the motor or electrical machine, which generates an electric current between the inner ring of the bearing which is attached to the shaft, and the outer ring attached to the housing.

[0004] The electric current passing through the components of the rolling bearing can damage these components, in particular the rolling elements and the raceways formed on the inner and outer rings. Electrical discharges can also generate vibrations.

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

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

[0007] To remedy the aforementioned disadvantages, it is also known to equip the outer ring of the 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 insulation lining on the outer ring and on the sleeve without additional element or special machining on the outer ring, it is possible to overmold the insulation lining.

[0009] However, with such a solution, a relative separation of the insulation lining and the socket 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.

[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 bearing ring. The insulating sleeve is provided with a bushing and an insulating gasket interposed radially between the second bearing ring and the bushing. The insulating gasket is made of electrically insulating material.

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

[0014] The insulation lining is overmolded onto the second ring of the bearing and at least onto one of the outer and inner surfaces of the bushing.

[0015] According to a general characteristic, said surface of the sleeve includes at least one protrusion which extends in projection towards the second ring and which is provided with a flat oriented radially towards the second ring.

[0016] Thus, an economical integrated electrically insulated bearing device is available compared to conventional hybrid rolling bearings. Furthermore, the device is easy to manufacture and assemble in the associated motor or electrical machine.

[0017] Furthermore, the inclusion of said protrusion with said flat on the sleeve ensures a secure bond with the insulation lining, as a complementary flat is formed on the lining during overmolding. The risk of relative movement between the insulation lining and the sleeve in the circumferential direction is particularly limited, especially during temperature variations. In addition, the protrusion forms an axial stop surface, thus limiting relative movement between the insulation lining and the sleeve in the axial direction.

[0018] By “axial direction”, we mean the direction parallel to the axis of the bearing device.

[0019] By “circumferential direction”, we mean the direction that is perpendicular to both 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 socket may be provided with two front faces defining its axial length. Said protrusion may radially extend one of said front faces.

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

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

[0023] According to another conception, said protuberance is provided with a plurality of flats spaced from one another in the circumferential direction, and with a plurality of cylindrical portions which each extend between two successive flats.

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

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

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

[0027] According to a first conception, 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 defines 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 above and mounted radially between the casing and the shaft. Brief description of the figures

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

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

[0034] [Fig.2] is a perspective view of a bushing of the bearing device of [Fig.1],

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

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

[0037] The bearing device illustrated in [Fig. 1] comprises a bearing 10 provided with a first ring 12 and a second ring 14 which are able to rotate relative to each other about 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 conduct electric currents. The bearing device has integrated electrical insulation.

[0039] 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 of the solid type.

[0040] In the illustrated embodiment, the bearing 10 also includes a row of rolling elements 16, here balls, interposed radially 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 for maintaining the regular circumferential spacing of the rollers 16. The bearing 10 can further be equipped with seals or sealing flanges.

[0041] The inner ring 12 comprises a cylindrical bore 12a, an axial cylindrical outer surface 12b radially opposed to the bore, and two opposing radial front faces (not referenced) axially delimiting 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.

[0042] The inner ring 12 further includes 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 opposed to the outer surface 14a, and two opposing radial front faces 14c, 14d axially delimiting the bore and the outer surface. The outer surface 14a and the bore 14b define the radial thickness of the outer ring 14.

[0044] The outer ring 14 further includes an external 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 includes an electrical insulation sleeve 22 mounted on the outer ring 14. The insulation sleeve 22 is mounted on the outer surface 14a of the outer ring 14. The insulation sleeve 22 is integral with the outer ring 14.

[0046] The insulation sleeve 22 includes a sleeve 24 and an insulation lining 26 interposed radially between the outer ring 14 and the sleeve 24. The insulation lining 26 is overmolded on the outer ring 14 and on the sleeve 24.

[0047] The sleeve 24 is annular in shape. The sleeve 24 extends axially. The sleeve 24 is made here in one piece. The sleeve 24 comprises a cylindrical axial outer surface 24a, and a cylindrical bore 24b radially opposed to 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 includes two opposing radial front faces 24c, 24d that axially define the bore and the outer surface. The front faces 24c, 24d define the axial length of the sleeve. The outer surface 24a and the bore 24b define the radial thickness of the sleeve 24. The outer surface 24a of the sleeve 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.

[0049] As can be seen in figures 2 to 4, the bore 24b of the sleeve includes a first protrusion 27 which extends inwards, i.e. in the direction of the outer ring 14. The protrusion 27 extends in projection relative to the bore 24b. The protrusion 27 extends radially.

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

[0051] The bore of the protrusion 27 is provided with a cylindrical portion 28 with axis 25, and a flat 30 which connects circumferentially to the cylindrical portion 28. The flat 30 is oriented radially towards the outer ring 14, i.e., radially inwards. In other words, the flat 30 is located radially on the side of the outer ring 14. The flat 30 projects beyond the cylindrical portion 28. The flat 30 has a planar shape.

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

[0053] In the illustrated embodiment, the flat 30 extends along the axial direction. Alternatively, the flat 30 could be inclined with respect to the axial direction so as to also perform an axial retention function for 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 inward, i.e., in the direction of the outer ring 14. The protrusion 31 extends inward relative to the bore 24b. The protrusion 31 extends radially. The protrusion 31 extends radially inward from 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 smaller 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 might be possible to omit the 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 bushing 24 is advantageously made of metallic material. Thus, the outer surface 24a of the bushing can be easily machined, if necessary, to a predetermined tolerance. Preferably, the bushing 24 is made of steel. The bushing 24 can be obtained from a sheet blank by cutting, stamping, and rolling. Alternatively, the bushing 24 can be obtained from a tube or from forged and / or rolled blanks, or even from sintering and stamping.

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

[0058] The insulating gasket 26 is radially interposed between the outer surface 14a of the outer ring and the bore 24b of the sleeve. The insulating gasket 26 covers the outer surface 14a of the outer ring. The insulating gasket 26 completely covers the outer surface 14a in both the axial and circumferential directions. The insulating gasket 26 also covers the bore 24b of the sleeve. The insulating gasket 26 also completely covers the bore 24b in both the axial and circumferential directions. The insulating gasket 26 covers the cylindrical portion 28 and the flat 30 of the bore of the protrusion 27. The insulating gasket 26 also covers the bore of the protrusion 31.

[0059] As previously stated, the insulating packing 26 is overmolded onto the outer ring 14 of the bearing and onto the bushing 24. The insulating packing 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 bushing 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 opposed to the outer surface 26a, and two opposing radial front faces 26c, 26d axially delimiting the bore and the outer surface. The front faces 26c, 26d axially delimit the insulating gasket 26. The outer surface 26a and the bore 26b define the radial thickness of the insulating gasket 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 gasket is complementary in shape to the bore 24b of the sleeve and to the protrusions 27, 31, and thus has a stepped shape. In the area of ​​the protrusion 31, the outer surface 26a is provided with a cylindrical portion complementary in shape to the cylindrical portion 28 of the sleeve, and a flat area complementary in shape to the flat area 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, other arrangements are possible. For example, the insulating gasket 26 could have a reduced axial dimension and remain axially recessed from the faces 14c, 14d of the outer ring. Alternatively, the insulating gasket 26 could have an increased axial dimension and extend axially beyond the faces 14c, 14d of the outer ring. In this case, the insulating gasket 26 can at least partially cover these faces 14c, 14d. As a variant, the insulating gasket 26 could at least partially cover the faces 24c, 24d of the sleeve.

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

[0065] To manufacture the bearing device, the following procedure is used.

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

[0067] Then, in a second successive step, the insulation lining 26 is overmolded both onto the outer ring 14 of the bearing and onto the bushing 24.

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

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

[0070] In another embodiment, when the protrusion 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 even that all the flats connect circumferentially to each other. In the latter case, the protrusion 27 is devoid of a cylindrical portion.

[0071] When the protrusion 27 of the socket includes 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 insulation packing 26 is overmolded is the outer ring.

[0073] Alternatively, an inverted arrangement may be provided in which the second ring 14, onto which the insulating sleeve 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 sleeve is then radially interposed between the bore 12a of the inner ring and the outer surface of the bushing. The insulating sleeve is overmolded onto the inner ring and at least onto the outer surface of the bushing. The outer surface of the bushing is provided with the flat protrusion(s). The bore of the bushing defines 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. Alternatively, the bearing may be provided with several rows of rolling elements. Furthermore, the rolling bearing may include other types of rolling elements than balls, for example, rollers. In another embodiment, the bearing may be a sliding bearing without rolling elements.

Claims

Demands

1. Bearing device comprising a bearing (10) having 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 having 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 define the radial thickness of said bushing, the insulating lining (26) being overmolded onto the second ring (14) of the bearing and at least onto one of the outer and inner surfaces of the bushing (24),characterized in that said surface of the socket (24) comprises at least one protrusion (27) which projects outwards towards the second ring and which is provided with a flat (30) oriented radially towards the second ring, said flat (30) comprising a first circumferential edge (30a) which connects circumferentially to an end area of ​​a cylindrical portion of said protrusion.

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

3. Device according to claim 1 or 2, wherein said flat (30) comprises a second opposite circumferential edge (30b) which connects circumferentially to another end zone of said cylinder portion of said protrusion, or to an end zone of another cylinder portion of said protrusion.

4. Device according to any one of the preceding claims, wherein said protrusion (27) is provided with a single portion of cylinder (28) and said flat (30) which connects to the portion of cylinder.

5. Device according to any one of claims 1 to 3, wherein said protrusion (27) is provided with a plurality of flats (30) spaced from each other in the circumferential direction, and with a plurality of cylindrical portions (28) which each extend between two successive flats (30).

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

7. Device according to any one of the preceding claims, wherein the insulation lining (26) is made of synthetic material or elastomeric material.

8. Device according to any one of the preceding claims, wherein the socket (24) is made of metallic material.

9. 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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