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 26 mounted on the second ring of the bearing and having a one-piece bushing 28 and an insulating lining 30 made of electrically insulating material. The insulating lining 30 is overmolded onto the second ring 14 of the bearing and onto at least one of the outer and inner surfaces of the bushing. The bushing 28 includes an axial portion 32a delimiting said surface of the bushing onto which the insulating lining 30 is overmolded, and first and second flanges 32b, 32c extending the axial portion radially on the side of the second ring 14, the radial dimension of the second flange 32c being greater than that of the first flange 32b. 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. 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 bearing ring. The insulating sleeve is provided with a one-piece 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] By "one-piece socket," it is understood that the socket is made in one piece. The socket can be made in one piece, or alternatively in several separate pieces fixed to one or more of each other.

[0014] In other words, the socket forms a single unitary assembly.

[0015] The sleeve comprises an outer surface and an inner surface opposite to the outer surface and which delimit the radial thickness of said sleeve.

[0016] 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.

[0017] According to a general characteristic, the sleeve comprises an axial portion delimiting said surface of the sleeve on which the insulating lining is overmolded, and first and second collars extending the axial portion radially on the side of the second ring.

[0018] According to another general feature, the insulation lining is further overmolded onto an inner face of each of the first and second collars.

[0019] According to another general characteristic, the radial dimension of the second collar is greater than the radial dimension of the first collar of the socket.

[0020] The sleeve's flanged design ensures a secure connection with the insulation. This prevents relative movement between the insulation and the sleeve in the axial direction, particularly during temperature variations.

[0021] By “axial direction”, we mean the direction parallel to the axis of the bearing device.

[0022] Furthermore, the provision of collars having radial dimensions different allows for a bushing with good mechanical resistance on the side of the large flange while easily allowing, on the side of the small flange, the axial mounting of the second ring, or of the bearing as a whole, radially inside the bushing or radially outside of it.

[0023] Thus, we have an electrically insulated bearing device that is economical compared to conventional hybrid rolling bearings and easy to manufacture.

[0024] Preferably, the second collar of the sleeve extends radially beyond an outer or inner surface of the second ring on which the insulation lining is overmolded.

[0025] With such an arrangement, the portion of the insulating seal located axially between the second ring and this second flange of the sleeve is not subjected to shear stresses when significant axial loads are applied to the device mounted inside the housing of the motor or electrical machine associated with this second flange bearing against a shoulder of the housing. In this case, compressive stresses are applied to this portion of the insulating seal. This increases the reliability of the device.

[0026] Preferably, the first flange of the sleeve remains radially recessed from said outer or inner surface of the second ring. Thus, the axial mounting of the second ring, or of the bearing as a whole, relative to the sleeve can be achieved by simple axial thrust.

[0027] A first groove can be formed on a first front face of the second ring and a second groove can be formed on a second front face of the second ring, said first and second grooves axially delimiting the outer or inner surface of the second ring.

[0028] The first collar of the socket can remain radially away from the first groove and the second collar can extend partly from the second groove.

[0029] The insulation lining can be provided with two front faces delimiting its axial length.

[0030] According to a first design, at least one of the first and second collars of the socket is axially flush with one of said front surfaces of the insulation lining.

[0031] According to a second design, each of the first and second collars of the socket is axially flush with one of said front surfaces of the insulation lining.

[0032] Alternatively, one or both of the collars of the socket can be axially offset inwards or outwards relative to the associated front surface of the insulation lining.

[0033] According to a particular design, said surface of the socket is provided with at least one groove extending in the circumferential direction and within which extends a rib for attaching the insulation lining of complementary shape.

[0034] Thus, the axial grip of the insulating lining on the bushing is further increased.

[0035] By "circumferential direction" is meant the direction which is perpendicular to both 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.

[0036] If the insulation lining is made of synthetic material or elastomer material, it makes the device less sensitive to temperature variations.

[0037] In a particular embodiment, the bushing is made of metallic material. The bushing can thus be easily machined to a predetermined radial tolerance. Advantageously, the bushing is obtained from a sheet metal blank by cutting, stamping, and rolling.

[0038] 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 the axial direction and in the circumferential direction.

[0039] 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.

[0040] 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.

[0041] 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.

[0042] 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

[0043] The present invention will be better understood upon study of the detailed description of embodiments, taken by way of non-limiting examples and illustrated by the accompanying drawings, in which:

[0044] [Fig-1] is a half axial cross-sectional view of a bearing device according to an embodiment of the invention,

[0045] [Fig.2] is a partial exploded perspective view of the bearing device of [Fig. 1] on which an insulating lining of said device has not been shown, and

[0046] [Fig.3] is a half axial cross-sectional view of a bearing device according to another example of an implementation of the invention. Detailed description of the invention

[0047] 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.

[0048] The bearing device is designed so as not to conduct electric currents. The bearing device has integrated electrical insulation.

[0049] 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.

[0050] 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 rolling elements 16. The bearing 10 can further be equipped with seals or sealing flanges.

[0051] 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.

[0052] 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.

[0053] 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 defining the bore. The outer surface 14a and the bore 14b define the radial thickness of the outer ring 14.

[0054] In the illustrated embodiment, the outer surface 14a of the ring has two distinct diameters. Alternatively, the outer surface 14a could have a single diameter.

[0055] 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.

[0056] In the illustrated embodiment, a first groove 22 is formed on the front face 14c of the outer ring. The groove 22 is oriented axially outwards from the outer ring. The groove 22 has a bottom that is offset axially inwards from the front face 14c. The bottom of the groove 22 forms a shoulder. The bottom of the groove 22 extends radially here for manufacturing simplicity. The groove 22 is annular.

[0057] Similarly, a second groove 24 is formed on the front face 14d of the outer ring. The groove 24 is oriented axially outwards from the outer ring. The groove 24 has a bottom which is offset axially inwards from the The ring is positioned relative to the front face 14d. The bottom of the groove 24 forms a shoulder. The bottom of the groove 24 extends radially here. The groove 24 is annular here. The grooves 22 and 24 are symmetrical with respect to a median radial plane of the outer ring. The grooves 22 and 24 axially delimit the outer surface 14a.

[0058] The bearing device also includes an electrical insulation sleeve 26 mounted on the outer ring 14. The insulation sleeve 26 is mounted on the outer surface 14a of the outer ring 14. The insulation sleeve 26 is integral with the outer ring 14.

[0059] The insulation sleeve 26 includes a sleeve 28 and an insulation packing 30 interposed radially between the outer ring 14 and the sleeve 28. The insulation packing 30 is overmolded on the outer ring 14 and on the sleeve 28.

[0060] The bushing 28 is annular in shape. The bushing 28 is made from a single piece. The bushing 28 is here made in one piece. Preferably, the bushing 28 is made of steel. The bushing 28 can advantageously be obtained from a sheet blank by cutting, stamping, and rolling. Alternatively, the bushing 28 can be obtained from a tube or from a forged and / or rolled blank, or even from sintering and stamping.

[0061] The sleeve 32 comprises an axial portion 32a, and first and second radial annular flanges 32b, 32c, each extending radially inward from the axial portion. Each flange 32b, 32c extends radially. Each flange 32b, 32c extends from an axial end of the axial portion 32a. In the illustrated embodiment, the flanges 32b, 32c are annular. Alternatively, at least one of the flanges 32b, 32c could be in the form of sectors spaced from each other in the circumferential direction.

[0062] The sleeve 28 comprises a cylindrical axial outer surface 28a and a cylindrical bore 28b radially opposed to the outer surface 28a and whose axis 25 is coaxial with the axis X-X'. The bore 28b forms the inner surface of the sleeve 28. The axial portion 32a of the sleeve delimits the outer surface 28a and the bore 28b. The outer surface 28a and the bore 28b define the radial thickness of the sleeve 28. The outer surface 28a of the sleeve forms the outer surface of the bearing device 10. In other words, the outer surface 28a defines the outer diameter of the bearing device 10.

[0063] The sleeve 28 also includes two opposing radial front faces 28c, 28d axially delimiting the outer surface 28a. The front faces 28c, 28d delimit the axial length of the sleeve. The front face 28c is delimited by the collar 32b, and the front face 28d is delimited by the collar 32c. More precisely, the face frontal 28c is delimited by the outer face of collar 32b, and frontal 28d is delimited by the outer face of collar 32c.

[0064] In the illustrated embodiment, the front faces 28c, 28d of the sleeve are respectively coplanar with the front faces 14c, 14d of the outer ring. Alternatively, other arrangements could be provided. For example, the sleeve 28 could have a smaller or larger axial dimension, remaining axially recessed from the faces 14c, 14d of the outer ring, or projecting from said faces.

[0065] The radial dimension of the collar 32c of the sleeve is greater than the radial dimension of the collar 32b. The collars 32b, 32c of the sleeve are asymmetrical with respect to a median radial plane of the device.

[0066] In the illustrated embodiment, the collar 32b remains radially recessed relative to the outer surface 14a of the outer ring. In other words, the free end of the collar 32b is radially offset outwards relative to the outer surface 14a. The collar 32b remains radially recessed from the groove 22 of the outer ring.

[0067] In the illustrated embodiment, the flange 32c of the sleeve extends radially beyond the outer surface 14a of the outer ring, i.e., radially projecting inwards relative to the outer surface 14a. In other words, the free end of the flange 32c is offset radially inwards relative to the outer surface 14a of the outer ring. The flange 32c extends partially into the groove 24 of the outer ring. The flanges 32b and 32c remain at a distance from the outer ring 14.

[0068] The insulating gasket 30 is made of electrically insulating material. The insulating gasket 30 can, for example, be made of a synthetic material, such as PEEK or PA46, or be made of an elastomeric material, for example rubber.

[0069] The insulating gasket 30 is radially interposed between the outer surface 14a of the outer ring and the bore 28b of the sleeve. The insulating gasket 30 covers the outer surface 14a of the outer ring. The insulating gasket 30 completely covers the outer surface 14a in both the axial and circumferential directions. The insulating gasket 30 also covers the grooves 22, 24 of the outer ring.

[0070] The insulating gasket 30 still covers the bore 28b of the sleeve. The insulating gasket 30 also completely covers the bore 28b here, considering both the axial and circumferential directions. The insulating gasket 30 covers the bore of the axial portion 32a of the sleeve.

[0071] The insulating gasket 30 also covers the inner face of each collar 32b, 32c of the socket. The inner face and the outer face axially opposite the inner face The axial thickness of each collar 32b and 32c is defined. For each collar 32b and 32c, the inner face is oriented axially towards the inside of the device, and the outer face is oriented axially towards the outside of the device. The insulating gasket 30 also covers the free end of each collar 32b, 32c of the socket.

[0072] The insulating gasket 30 is annular in shape. The insulating gasket 30 extends axially. The insulating gasket 30 comprises a cylindrical axial outer surface 30a, a cylindrical bore 30b radially opposed to the outer surface 30a, and two opposing radial front faces 30c, 30d axially delimiting the bore and the outer surface. The radial front faces 30c, 30d axially delimit the insulating gasket 30. The outer surface 30a and the bore 30b define the radial thickness of the insulating gasket 30. The outer surface 30a is in radial contact with the bore 28b of the sleeve. The outer surface 30a is also in radial contact with the free end of each flange 32b, 32c of the sleeve. The outer surface 30a has a stepped shape. The bore 30b is in radial contact with the outer surface 14a of the outer ring and with the grooves 22, 24. The bore 30b has a stepped shape.

[0073] In the illustrated embodiment, the faces 14c, 30c, 28c and 14d, 30d, 28d of the outer ring, the insulating lining and the sleeve are respectively coplanar.

[0074] Alternatively, other arrangements are possible. For example, the insulating gasket 30 could have a reduced axial dimension and remain axially recessed from the faces 14c, 14d of the outer ring. Alternatively, the insulating gasket 30 could have an increased axial dimension and extend axially beyond the faces 14c, 14d of the outer ring. In this case, the insulating gasket 30 can at least partially cover these faces 14c, 14d. As a variant, the insulating gasket 30 could at least partially cover the faces 28c, 28d of the sleeve.

[0075] In another alternative or in combination, the sleeve 28 could extend axially in projection from the insulation lining 30 relative to the faces 30c and 30d, or remain axially recessed from these faces.

[0076] To manufacture the bearing device, the following procedure is used.

[0077] In a first step, the bearing 10 and the bushing 28 are mounted inside a mold designed for overmolding the insulating gasket 30. In this position mounted inside the mold, the bushing 28 is radially distant from the outer ring 14 of the bearing. The bearing 10 has been previously inserted axially into the bushing 28 on the side of the small flange 32b.

[0078] Then, in a second successive step, the insulation lining 30 is overmolded both onto the outer ring 14 of the bearing and onto the bushing 28.

[0079] Finally, the bearing device, which is in the form of a unit assembly, is extracted from the mold.

[0080] The embodiment illustrated in [Fig. 3], in which the identical elements bear the same reference numerals, differs from the previous example in that the bore of the axial portion 32a of the sleeve is provided with two axially spaced grooves 36, 38 that extend circumferentially around the axis 25 of the sleeve bore. Each groove 36, 38 is oriented radially towards the outer ring 14, i.e., radially inwards.

[0081] In the illustrated embodiment, each groove 36, 38 is annular. Alternatively, at least one of the two grooves 36, 38 could not extend over 360°, or could be formed by a succession of turns extending circumferentially and spaced from each other in the circumferential direction.

[0082] Each groove 36, 38 is delimited in the axial direction by two opposing lateral flanks which have a straight profile in axial section and are connected to each other by an axial bottom. Alternatively, other shapes are possible, for example, grooves which, in this case, have an inwardly oriented arc in cross-section. In another embodiment, the sleeve 28 may also be without the grooves 36, 38.

[0083] The insulation lining 30 also includes two ribs 40, 42 extending radially outwards from the outer surface 30a and each housed within one of the grooves 36, 38 of the sleeve. The rib 40, 42 is complementary in shape to the associated groove 36, 38. Each rib 40, 42 projects beyond the outer surface 30a of the insulation lining. Each rib 40, 42 is formed on the outer surface 30a during the overmolding of the insulation lining 30.

[0084] In the illustrated embodiments, the first ring 12 of the bearing is the inner ring and the second ring 14 on which the insulation packing 30 is overmolded is the outer ring.

[0085] Alternatively, an inverted arrangement may be provided in which the second ring 14, onto which the insulating sleeve 30 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 bore of the bushing defines the bore of the bearing device.

[0086] 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. A 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 (26) mounted on the second ring (14) of the bearing and having a one-piece bushing (28) and an insulating lining (30) interposed radially between the second ring (14) and the bushing (28) and made of electrically insulating material, the bushing comprising an outer surface (28a) and an inner surface (28b) opposite the outer surface and defining the radial thickness of said bushing, the insulating lining (30) being overmolded onto the second ring (14) of the bearing and onto at least one of the outer and inner surfaces of the bushing (28), characterized in that the bushing (28) comprises an axial portion (32a) defining said surface of the bushing (28) onto which the lining is overmolded insulation (30), and the first and second collars (32b,32c) extending the axial portion radially on the side of the second ring (14), the insulating lining (30) being further overmolded onto an inner face of each of the first and second flanges (32b, 34b), the radial dimension of the second flange (32c) being greater than the radial dimension of the first flange (32b).

2. Device according to claim 1, wherein the second collar (32c) of the sleeve extends radially beyond an outer (14a) or inner surface of the second ring on which the insulating lining (30) is overmolded.

3. Device according to claim 2, wherein the first collar (32b) of the sleeve remains radially recessed from said outer surface (14a) or inner surface of the second ring.

4. Device according to claim 3, wherein a first groove (22) is formed on a first front face of the second ring (14) and a second groove (24) is formed on a second front face of the second ring (14), said first and second grooves (22, 24) axially delimiting the outer (14a) or inner surface of the second ring, the first collar (32b) of the sleeve remaining radially at a distance from the first groove (22) and the second collar (32c) extending partly from the second groove (24).

5. Device according to any one of the preceding claims, wherein the insulation lining (30) comprises two front faces (30c, 30d) delimiting the axial length of said lining, at least one of the first and second flanges (32b, 32c) of the sleeve being axially flush with one of said front surfaces (30c, 30d) of the insulation lining.

6. Device according to any one of the preceding claims, wherein said surface of the socket (28) is provided with at least one groove (36) extending in the circumferential direction and within which extends a hooking rib (40) of the complementaryly shaped insulation lining.

7. Device according to any one of the preceding claims, wherein the socket (28) is made of metallic material.

8. Device according to claim 7, wherein the bushing (28) is obtained from a sheet metal blank by cutting, stamping and rolling.

9. A device according to any one of the preceding claims, wherein the insulating lining (30) is made of synthetic material or elastomeric material.

10. Electric motor comprising a housing, a shaft and at least one bearing device according to any one of claims 1 to 9 mounted radially between the housing and the shaft.

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