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 36 mounted on the second ring 14 of the bearing and provided with a bushing 40 and an insulating lining 38 interposed radially between the second ring 14 and the bushing 28 and made of electrically insulating material. The second ring 14 comprises an outer surface 14a and an inner surface 14b opposite the outer surface and which delimit the radial thickness of said second outer ring. The insulating lining 38 is overmolded on the bushing 40 and at least on one of the outer and inner surfaces of the second ring 14. At least first grooves are formed on said outer or inner surface of the second ring.The grooves are spaced apart from each other in the circumferential direction and within each of which extends a complementary shaped insulation lining attachment rib. 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 second ring comprises an outer surface and an inner surface opposite the outer surface and which delimit the radial thickness of said second outer ring.

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

[0015] According to a general characteristic, said outer or inner surface of the second ring has a stepped shape with a cylindrical main part and at least one first cylindrical lateral part arranged axially on one side of the main part and offset radially on the side of the other inner or outer surface of the second ring relative to the main part.

[0016] According to another general characteristic, said outer or inner surface of the second ring is further provided with a first connecting face extending between the first cylindrical lateral part and the cylindrical main part.

[0017] According to yet another general characteristic, at least the first connection face is provided with a plurality of first grooves spaced apart from each other in the circumferential direction and inside each of which extends a rib for attaching the insulation lining of complementary shape.

[0018] 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.

[0019] Furthermore, the provision of grooves on said outer or inner surface of the second ring of the bearing makes it possible to obtain good attachment to the insulating lining insofar as said attachment ribs are formed inside them during overmolding. The risk of relative displacements between the insulating lining and the second ring in the axial and circumferential directions is particularly limited, in particular during temperature variations.

[0020] By "axial direction" is meant the direction parallel to the axis of the bearing device.

[0021] 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.

[0022] Furthermore, the provision of grooves on the first connecting face of said outer or inner surface of the second ring of the bearing makes it possible to limit the variation in material thickness around the area provided with grooves, compared to a arrangement of the grooves at the level of the main part in the area adjacent to the first connection face. This limits the phenomenon of stress concentrations in the areas of reduced thickness of the second ring.

[0023] Preferably, the first connecting face of said outer or inner surface of the second ring extends at least partly radially from the cylindrical main part.

[0024] According to a first design, the first connecting face extends at least partly obliquely from the cylindrical main part, i.e. both radially and axially.

[0025] According to a second design, the first connecting face extends at least partly purely radially from the cylindrical main part.

[0026] Each of the first grooves of the first connecting face of said outer or inner surface of the second ring may be delimited in the circumferential direction by two facing lateral flanks.

[0027] In one embodiment, said outer or inner surface of the second ring is provided only with the cylindrical main part and the first cylindrical side part.

[0028] In another embodiment, said outer or inner surface of the second ring is provided with a second cylindrical lateral portion and radially offset on the side of the other inner or outer surface of the second ring relative to the main portion, the first and second cylindrical lateral portions being arranged axially on either side of the cylindrical main portion. The first and second lateral portions may have equal or different diameters.

[0029] In this case, said outer or inner surface of the second ring is provided with a second connecting face extending between the second cylindrical lateral part and the central part. Preferably, the second connecting face is provided with a plurality of second grooves spaced apart from each other in the circumferential direction and inside each of which extends a rib for attaching the insulating lining of complementary shape.

[0030] According to a particular design, the cylindrical main part of said outer or inner surface of the second ring may be provided with a plurality of grooves spaced apart from each other in the circumferential direction and inside each of which extends a rib for attaching the insulating lining of complementary shape.

[0031] If the insulation lining is made of synthetic material or elastomeric material, it makes the device less sensitive to temperature variations.

[0032] In a particular embodiment, the sleeve is made of metallic material. The sleeve can thus be easily machined to a predetermined radial tolerance.

[0033] 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.

[0034] 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.

[0035] 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.

[0036] 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

[0037] 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:

[0038] [Fig-1] is a half axial sectional view of a bearing device according to an example of carrying out the invention,

[0039] [Fig.2] is a perspective view of the outer ring of the bearing device of the [Fig.l],

[0040] [Fig.3] is a detail view of [Fig.2],

[0041] [Fig.4] is a perspective view of the outer ring of a bearing device according to another exemplary embodiment of the invention,

[0042] [Fig.5] is a detail view of [Fig.4],

[0043] [Fig.6] is a half axial sectional view of a bearing device according to another example of embodiment of the invention,

[0044] [Fig.7] is a perspective view of the outer ring of the bearing device of the [Fig.6],

[0045] [Fig.8] is a detail view of [Fig.7]. Detailed description of the invention

[0046] 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.

[0047] The bearing device is designed so as not to be a current conductor. electrical. The bearing device has integrated electrical insulation.

[0048] 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.

[0049] 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 rolling elements 16. The bearing 10 may also be equipped with seals or sealing flanges.

[0050] 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.

[0051] 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.

[0052] 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 outer surface and the bore. The outer surface 14a and the bore 14b delimit the radial thickness of the outer ring 14.

[0053] The outer surface 14a has a stepped shape. The outer surface 14a is provided with a large-diameter annular cylindrical central portion 20, and first and second small-diameter annular cylindrical lateral portions 22, 24 arranged axially on either side of the central portion. The lateral portions 22, 24 are offset radially inward relative to the central portion 20, i.e. offset radially on the side of the bore 14b relative to the central portion 20.

[0054] The outer surface 14a is also provided with a first annular connecting face 26 extending between the first lateral part 22 and the central part 20. The first connecting face 26 has a frustoconical part extending from the central part 20 obliquely inwards in the radial direction and outwards in the axial direction, and a radial part extending a small diameter edge of the frustoconical part and connecting to the first lateral part 22.

[0055] The outer surface 14a is also provided with a second annular connecting face 28 extending between the second lateral part 24 and the part central part 20. The second connecting face 38 has a frustoconical part extending from the central part 20 obliquely inwards in the radial direction and outwards in the axial direction, and a radial part extending a small diameter edge of the frustoconical part and connecting to the second lateral part 24. The outer ring 14 is symmetrical with respect to a median radial plane passing through the center of the rolling elements 16.

[0056] Referring to Figures 2 and 3, the outer ring 14 is provided with first grooves 30 provided on the first connecting face 26. The first grooves 30 are provided on the frustoconical portion of the first connecting face 26. The first grooves 30 extend radially inward from the first connecting face 26. The first grooves 30 are immediately adjacent to each other in the circumferential direction. Each first groove 30 is delimited in the circumferential direction by two facing lateral flanks which have a rectilinear profile in axial section and which are connected to each other.

[0057] The first grooves 30 are here arranged over the entire circumference of the first connecting face 26. Alternatively, the first grooves 30 could extend over an angular sector of less than 360°, or even be arranged in the form of groups of grooves spaced apart from each other in the circumferential direction. The first grooves 30 may be formed on the first connecting face 26 by knurling.

[0058] The outer ring 14 is also provided with second grooves 32 formed on the second connecting face 38. The grooves 32 are formed on the frustoconical portion of the first connecting face 28. The second grooves 32 extend radially inward from the second connecting face 38. The second grooves 32 are immediately adjacent to each other in the circumferential direction. Each second groove 32 is delimited in the circumferential direction by two facing lateral flanks which have a rectilinear profile in axial section and which are connected to each other.

[0059] The second grooves 32 are here arranged over the entire circumference of the first connecting face 26. Alternatively, the second grooves 32 could extend over an angular sector of less than 360°, or even be arranged in the form of groups of grooves spaced apart from each other in the circumferential direction. The second grooves 32 can be formed on the second connecting face 38 by knurling.

[0060] Referring again to [Fig. 1], the outer ring 14 further comprises an outer raceway 34 for the rolling elements 16 which is formed on the bore 14b. The raceway 20 is directed radially inward.

[0061] The bearing device also comprises an electrical insulating sleeve 36 mounted on the outer ring 14. The insulating sleeve 36 is mounted on the outer surface 14a of the outer ring 14. The insulating sleeve 36 is integral with the outer ring 14.

[0062] The insulating sleeve 36 comprises a bushing 40 and an insulating lining 38 interposed radially between the outer ring 14 and the bushing 40. The insulating lining 38 is overmolded onto the outer ring 14 and onto the bushing 40.

[0063] The sleeve 40 is annular in shape. The sleeve 40 extends axially. The sleeve 40 is made here in a single piece. Alternatively, the sleeve 40 could be made in several pieces bearing against each other, for example two identical pieces. The sleeve 40 comprises an axial portion 42, a first radial collar 44 extending radially inward one end of the axial portion 42, and a second radial collar 46 extending radially inward the opposite end of the axial portion 42. In the illustrated embodiment, the radial collars 44, 46 are annular. The radial collars 44, 46 remain at a distance from the outer ring 14.

[0064] The sleeve 40 comprises a cylindrical axial outer surface 40a, and a cylindrical bore 40b radially opposite the outer surface 40a. The bore 40b forms the inner surface of the sleeve 40. The axial portion 42 of the sleeve delimits the outer surface 40a and the bore 40b. The outer surface 40a and the bore 40b delimit the radial thickness of the sleeve 40. The outer surface 40a of the sleeve forms the outer surface of the bearing device 10. In other words, the outer surface 40a defines the outer diameter of the bearing device 10.

[0065] The sleeve 40 also comprises two opposite radial end faces 40c, 40d axially delimiting the outer surface 40a. The end faces 40c, 40d delimit the axial length of the sleeve. The end face 40c is delimited by the radial collar 44, and the end face 40d is delimited by the radial collar 46. More precisely, the end face 40c is delimited by the outer face of the radial collar 44, and the end face 40d is delimited by the outer face of the radial collar 46.

[0066] In the illustrated embodiment, the front faces 40c, 40d of the sleeve are respectively coplanar with the front faces 14c, 14d of the outer ring. Alternatively, it could be possible to provide other arrangements. For example, the sleeve 40 could have a smaller, or larger, axial dimension and remain axially set back from the faces 14c, 14d of the outer ring, or project from said faces.

[0067] The insulating lining 38 is made of electrically insulating material. The insulating lining 38 may for example be made of synthetic material, such as PEEK or PA46, or may be made of elastomeric material, for example rubber.

[0068] The insulating lining 38 is interposed radially between the outer surface 14a of the outer ring and the bore 40b of the sleeve. The insulating lining 38 covers the outer surface 14a of the outer ring. The insulating lining 38 here completely covers the outer surface 14a considering the axial and circumferential directions.

[0069] The insulating lining 38 further covers the bore 40b of the sleeve. The insulating lining 38 also here completely covers the bore 40b considering the axial and circumferential directions. The insulating lining 38 also covers the internal face of the radial collar 44, 46 of the sleeve. The insulating lining 38 also covers the free end of the radial collar 44, 46 of the sleeve.

[0070] The insulating lining 38 is annular in shape. The insulating lining 38 extends axially. The insulating lining 38 comprises a cylindrical axial outer surface 38a, a cylindrical bore 38b radially opposite the outer surface 38a, and two opposite radial end faces 38c, 38d axially delimiting the bore and the outer surface. The radial end faces 38c, 38d axially delimit the insulating lining 38. The outer surface 38a and the bore 38b delimit the radial thickness of the insulating lining. The outer surface 38a is in radial contact with the bore 40b of the sleeve. The outer surface 38a is also in radial contact with the free end of each radial collar 44, 46 of the sleeve. The outer surface 38a has a stepped shape. The bore 38b is in radial contact with the outer surface 14a of the outer ring. The bore 38b has a stepped shape.

[0071] In the illustrated embodiment, the faces 14c, 38c, 38c and 14d, 38d, 38d of the outer ring, the insulating lining and the sleeve are respectively coplanar.

[0072] Alternatively, it is possible to provide other arrangements. For example, the insulating lining 38 could have a reduced axial dimension and remain axially set back from the faces 14c, 14d of the outer ring. Alternatively, the insulating lining 38 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 38 may at least partially cover these faces 14c, 14d. Alternatively, the insulating lining 38 could at least partially cover the faces 38c, 38d of the sleeve.

[0073] In another alternative or combination, the sleeve 40 could extend axially projecting from the insulation lining 38 relative to the faces 38c and 38d, or remain axially set back from these faces.

[0074] The insulating gasket 38 also includes a plurality of first ribs extending inwardly from the bore 38b and each housed within one of the grooves 30 of the outer ring. Each first rib is of complementary shape to the associated groove 30. Each first rib projects beyond the bore 38b of the insulating gasket. Each first rib is formed on bore 38b when overmolding the insulation gasket 38.

[0075] The insulating gasket 38 also comprises a plurality of second ribs extending inwardly from the bore 38b and each housed within one of the grooves 32 of the outer ring. Each second rib is of complementary shape to the associated groove 32. Each second rib projects beyond the bore 38b of the insulating gasket. Each second rib is formed on the bore 38b during overmolding of the insulating gasket 38.

[0076] To manufacture the bearing device, the procedure is as follows.

[0077] In a first step, the bearing 10 and the sleeve 40 are mounted inside a mold which is provided for overmolding the insulation lining 26. In this position mounted inside the mold, the sleeve 40 is radially spaced from the outer ring 14 of the bearing.

[0078] 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 40. The first and second ribs of the insulating lining are formed during this step.

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

[0080] The embodiment illustrated in Figures 4 and 5, in which identical elements bear the same references, differs from the previous example in that the outer surface of the outer ring 14 is provided with third grooves 50 arranged on the central part 20. The grooves 50 remain at a distance from the grooves 30, 32. The grooves 50 extend radially inwards from the central part 20. The grooves 50 are immediately adjacent to each other in the circumferential direction. Each groove 50 is delimited in the circumferential direction by two facing lateral flanks which have a rectilinear profile in axial section and which are connected to each other.

[0081] The grooves 50 are here provided around the entire circumference of the first connecting face 26. Alternatively, the grooves 50 could extend over an angular sector of less than 360°, or even be arranged in the form of groups of grooves spaced apart from each other in the circumferential direction. The grooves 50 may be formed on the central portion 20 by knurling. In a similar manner to the first and second grooves, third ribs extending inwardly from the bore 38b and each housed inside one of the grooves 50 of the outer ring, are formed during the overmolding of the insulation lining.

[0082] The embodiment illustrated in Figures 6 to 8, in which identical elements bear the same references, differs from the first example in that the outer surface 14a is provided with a first connecting face 52 extending between the first lateral portion 22 and the central portion 20 and having a radial portion extending from the central portion 20 radially inwards, and a concave clearance extending a small diameter edge of the radial portion and connecting to the first lateral portion 22. The grooves 30 are formed on the connecting face 52. The grooves 30 are formed on the radial portion of the connecting face 52.

[0083] The outer surface 14a is also provided with a second connecting face 54 extending between the second lateral portion 24 and the central portion 20 and having a radial portion extending from the central portion 20 radially inward, and a concave recess extending a small diameter edge of the radial portion and connecting to the second lateral portion 24. The ridges 32 are formed on the connecting face 54. The ridges 32 are formed on the radial portion of the connecting face 54.

[0084] In an alternative embodiment, it could also be possible to provide third grooves on the central portion 20 of the outer surface of the outer ring as described previously.

[0085] In the illustrated embodiments, the first ring 12 of the bearing is the inner ring and the second ring 14 on which the insulating lining 38 is overmolded is the outer ring.

[0086] Alternatively, it is possible to provide an inverted arrangement in which the second ring 14 on which the insulating lining 38 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 outer surface of the sleeve, and on the bore of the inner ring provided with grooves which forms the inner surface of the inner ring. The bore of the sleeve delimits the bore of the bearing device.

[0087] 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 (36) mounted on the second ring (14) of the bearing and provided with a bushing (40) and an insulating lining (38) interposed radially between the second ring (14) and the bushing (40) and made of electrically insulating material, the second ring (14) comprises an outer surface (14a) and an inner surface (14b) opposite the outer surface and which delimit the radial thickness of said second outer ring, the insulating lining (38) being overmolded on the bushing (40) and at least on one of the outer and inner surfaces of the second ring (14),characterized in that: - said outer or inner surface of the second ring has a stepped shape with a cylindrical main part (20) and at least one first cylindrical lateral part (22) arranged axially on one side of the main part (20) and offset radially on the side of the other inner or outer surface of the second ring relative to the main part (20), - said outer or inner surface of the second ring is further provided with a first connecting face (26; 52) extending between the first cylindrical lateral part (22) and the cylindrical main part (20), - at least the first connecting face (26; 52) is provided with a plurality of first grooves (30) spaced apart from each other in the circumferential direction and inside each of which extends a rib for attaching the insulating lining of complementary shape.,

2. Device according to claim 1, in which the first connecting face (26; 52) of said outer or inner surface of the second ring extends at least partly radially from the main cylindrical part (20).

3. Device according to claim 2, in which the first connecting face (26) of said outer or inner surface of the second ring extends at least partly obliquely from the cylindrical main part (20).

4. Device according to claim 2, in which the first rac- cord (52) of said outer or inner surface of the second ring extends at least partly purely radially from the cylindrical main part (20).

5. Device according to any one of the preceding claims, in which each of the first grooves (30) of the first connecting face (26; 52) of said outer or inner surface of the second ring is delimited in the circumferential direction by two facing lateral flanks.

6. Device according to any one of the preceding claims, wherein said outer or inner surface of the second ring is provided with a second cylindrical lateral portion (24) radially offset on the side of the other inner or outer surface of the second ring relative to the main portion (20), the first and second cylindrical lateral portions (22, 24) being arranged axially on either side of the cylindrical main portion (20), and with a second connecting face (28; 54) extending between the second cylindrical lateral portion (24) and the central portion (20), the second connecting face (28; 54) being provided with a plurality of second grooves (32) spaced apart from each other in the circumferential direction and inside each of which extends a rib for attaching the insulating lining of complementary shape.

7. Device according to any one of the preceding claims, in which the main cylindrical part (20) of said outer or inner surface of the second ring is provided with a plurality of grooves (50) spaced from each other in the circumferential direction and inside each of which extends a rib for hooking the insulating lining of complementary shape.

8. A device according to any preceding claim, wherein the second ring (14) is the outer ring of the bearing.

9. A device according to any preceding claim, wherein the socket (40) 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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