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 26 mounted on the second ring 14 of the bearing and provided with a 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 comprises an outer surface 28a and an inner surface 28b which delimit its radial thickness. The insulating lining 30 is overmolded onto the second ring 14 of the bearing and at least onto one of the outer and inner surfaces of the sleeve 28. The sleeve 28 is made in at least two parts 32, 34, each part comprising an axial portion 32a, 34a and a radial collar 32b, 34b extending the axial portion radially inwards.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, the sleeve is made in at least two distinct parts, each part comprising an axial portion and a radial collar extending the axial portion at least radially inwards.

[0016] According to another general characteristic, the axial portions of said two parts jointly delimit at least in part said surface of the sleeve on which the insulating lining is overmolded.

[0017] According to yet another general characteristic, the insulating lining is also overmolded on an internal face of the radial collar of each of said two parts of the sleeve.

[0018] The production of said two parts of the sleeve with radial collars makes it possible to obtain good connection with the insulation lining. The risk of relative displacements between the insulation lining and the sleeve in the axial direction is avoided, in particular during temperature variations.

[0019] By "axial direction" is meant the direction parallel to the axis of the bearing device.

[0020] Furthermore, compared to a single-piece embodiment of the socket equipped with a collar lerettes, the production of this in at least two separate parts facilitates the installation of the second ring inside the mold intended for the overmolding of the insulation gasket.

[0021] Thus, a bearing device with integrated electrical insulation is provided which is economical compared to conventional hybrid rolling bearings and easy to manufacture.

[0022] Preferably, the radial collar of at least one of said two parts of the sleeve extends radially beyond an outer or inner surface of the second ring on which the insulating lining is overmolded.

[0023] With such an arrangement, the part of the insulating lining which is located axially between the second ring and this radial collar of the sleeve is not subjected to shear stresses when the significant axial loads are applied to the device mounted inside the casing of the motor or the associated electrical machine with this collar bearing against a shoulder of the casing. Indeed, in this case, compressive stresses are applied to this part of the insulation gasket. This increases the reliability of the device.

[0024] Advantageously, the radial collar of each of said two parts of the sleeve extends radially beyond said outer or inner surface of the second ring on which the insulating lining is overmolded.

[0025] Alternatively, it remains possible to provide that at least one of the two radial collars or that both collars are flush with said outer or inner surface of the second ring or remain radially recessed.

[0026] In one embodiment, said two parts of the sleeve are symmetrical with respect to a median radial plane of said device. This makes it possible to reduce the manufacturing cost of the device.

[0027] According to a particular design, the axial portions of said two parts of the sleeve are axially in contact with each other and jointly delimit the entirety of said surface of the sleeve on which the insulating lining is overmolded.

[0028] According to another design, the axial portions of said two parts of the sleeve are axially spaced from each other. In this case, the sleeve may further comprise an additional ring interposed axially between the axial portions of said two parts and jointly delimiting, with the axial portions of said two parts of the sleeve, said surface of the sleeve on which the insulation lining is overmolded.

[0029] According to a particular design, said surface of the sleeve is provided with at least one groove extending in the circumferential direction and inside which extends a rib for attaching the insulation lining of complementary shape.

[0030] This further increases the axial attachment of the insulation lining to the sleeve.

[0031] By "circumferential direction" is meant the direction which is perpendicular to both the axial direction and a radius of the bearing device, in other words, tangent to a circle whose center is on the axis of the bearing device.

[0032] Each axial portion of said two parts of the sleeve may be provided with at least one groove extending in the circumferential direction and inside which extends a rib for attaching the insulating lining of complementary shape.

[0033] The socket may be provided with two front faces delimiting its axial length.

[0034] According to a first design, the radial collar of at least one of said two parts are axially flush with one of said front surfaces of the sleeve.

[0035] According to a second design, the radial collar of each of said two parts of the sleeve is axially flush with one of said front surfaces of the sleeve.

[0036] Alternatively, one or each of the radial flanges may be axially offset inwardly or outwardly relative to the associated end surface of the bushing.

[0037] If the insulation lining is made of synthetic material or elastomeric material, it makes the device less sensitive to temperature variations.

[0038] In a particular embodiment, the sleeve is made of metallic material. The sleeve can thus be easily machined to a predetermined radial tolerance.

[0039] 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.

[0040] 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.

[0041] 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.

[0042] 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.

[0043] 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.

[0044] The invention also relates to a method of manufacturing a bearing device as defined above comprising:

[0045] - a step of mounting one of said parts of the socket at the bottom of a mold of fa brication,

[0046] - a step of placing the second ring inside the mold of fa brication,

[0047] - a step of mounting the other of said parts of the sleeve inside the mold manufacturing,

[0048] - a step of overmolding the insulation gasket on the second ring and at less on said surface of the socket, and

[0049] - an assembly step with the first ring of the bearing of the assembly formed by the second ring, said parts of the sleeve and the insulating gasket. Brief description of the figures

[0050] 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:

[0051] [Fig-1] is a half-view in axial section of a bearing device according to an exemplary embodiment of the invention,

[0052] [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,

[0053] [Fig.3] is a half-view in axial section of one of the parts of a socket of the device of the bearing of [Fig.l], and

[0054] [Fig.4] is a flowchart illustrating the manufacturing process of the device of landing of [Fig.l]. Detailed description of the invention

[0055] 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.

[0056] 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.

[0057] 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.

[0058] 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.

[0059] 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.

[0060] 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.

[0061] 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. The outer surface 14a and the bore 14b delimit the radial thickness of the outer ring 14.

[0062] 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.

[0063] 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.

[0064] In the illustrated embodiment, a groove 22 is provided on the front face 14c of the outer ring. The groove 22 is oriented axially towards the outside of the outer ring. The groove 22 has a bottom which is offset axially towards the inside of the ring relative to the front face 14c. The bottom of the groove 22 forms a shoulder. The bottom of the groove 22 here extends radially for reasons of simplicity of manufacture. The groove 22 is here annular.

[0065] Similarly, a groove 24 is provided on the front face 14d of the outer ring. The groove 24 is oriented axially towards the outside of the outer ring. The groove 24 has a bottom which is offset axially towards the inside of the ring 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, 24 are symmetrical to each other relative to a median radial plane of the outer ring. The grooves 22, 24 axially delimit the outer surface 14a.

[0066] The bearing device also comprises an electrical insulating sleeve 26 mounted on the outer ring 14. The insulating sleeve 26 is mounted on the outer surface 14a of the outer ring 14. The insulating sleeve 26 is integral with the outer ring 14.

[0067] The insulating sleeve 26 comprises a bushing 28 and an insulating lining 30 interposed radially between the outer ring 14 and the bushing 28. The insulating lining 30 is overmolded onto the outer ring 14 and onto the bushing 28.

[0068] The sleeve 28 is annular in shape. The sleeve 28 is made up of two separate parts 32, 34. These two separate parts 32, 34 form half-flaps which here bear axially against each other. In the illustrated embodiment, the parts 32, 34 of the sleeve are identical and symmetrical with respect to a median radial plane of the device in order to reduce manufacturing costs. Alternatively, it is of course possible to provide non-symmetrical parts 32, 34. In another variant, it could be possible to provide for the sleeve 28 to be made up of more than two parts. Preferably, the parts 32, 34 of the sleeve 28 are made of steel. The parts 32, 34 can advantageously be obtained from a sheet metal flank by cutting, stamping and rolling. Alternatively, parts 32, 34 may be obtained from a tube or from forged and / or rolled blanks, or from sintering and stamping.

[0069] Each part 32, 34 of the sleeve comprises an annular axial portion 32a, 34a, and an annular radial collar 32b, 34b extending the axial portion radially inward. The axial portions 32a, 34a are axially in abutment against each other. The radial collar 32b, 34b extends the end of the axial portion 32a, 34a located axially on the outer side of the device. In the illustrated embodiment, the radial collars 32b, 34b are annular. Alternatively, at least one of the radial collars 32b, 34b could be in the form of sectors spaced apart from each other in the circumferential direction.

[0070] The sleeve 28 comprises a cylindrical axial outer surface 28a, and a cylindrical bore 28b radially opposite 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 portions 32a, 34a of the parts of the sleeve jointly delimit the outer surface 28a. Similarly, the axial portions 32a, 34a of the parts jointly delimit the bore 28b. The outer surface 28a and the bore 28b delimit 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.

[0071] The sleeve 28 also comprises two opposite radial end faces 28c, 28d axially delimiting the outer surface 28a. The end faces 28c, 28d delimit the axial length of the sleeve. The end face 28c is delimited by the radial collar 32b, and the end face 28d is delimited by the radial collar 34b. More precisely, the end face 28c is delimited by the outer face of the radial collar 32b, and the end face 28d is delimited by the outer face of the radial collar 34b.

[0072] 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, it could be possible to provide other arrangements. For example, the sleeve 28 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.

[0073] In the illustrated embodiment, the radial flanges 32b, 34b of the parts of the sleeve extend radially beyond the outer surface 14a of the outer ring, i.e. radially projecting inwardly relative to the outer surface 14a. In other words, the free ends of the radial flanges 32b, 34b are offset radially inwardly relative to the outer surface 14a of the outer ring. The radial flanges 32b, 34b extend partly into the grooves 22, 24 of the outer ring. The radial flanges 32b, 34b remain at a distance from the inner ring 12.

[0074] The bore of the axial portion 32a, 34a of each part 32, 34 of the sleeve is provided with a groove 36, 38 which extends circumferentially around the axis 25 of the bore of the sleeve. Each groove 36, 38 is oriented radially on the side of the outer ring 14, i.e. radially inwards.

[0075] 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 apart from each other in the circumferential direction.

[0076] Each groove 36, 38 is delimited in the axial direction by two facing lateral flanks which have a rectilinear profile in axial section and which are connected to each other by an axial bottom. Alternatively, it is possible to provide other shapes, for example grooves here having in cross section a shape of an arc of a circle oriented inwards. In another variant, the sleeve 28 may also be devoid of grooves 36, 38.

[0077] The insulating lining 30 is made of electrically insulating material. The insulating lining 30 may for example be made of synthetic material, such as PEEK or PA46, or may be made of elastomeric material, for example rubber.

[0078] The insulating lining 30 is interposed radially between the outer surface 14a of the outer ring and the bore 28b of the sleeve. The insulating lining 30 covers the outer surface 14a of the outer ring. The insulating lining 30 here completely covers the outer surface 14a considering the axial and circumferential directions. The insulating lining 30 also covers the grooves 22, 24 of the outer ring.

[0079] The insulating lining 30 further covers the bore 28b of the sleeve. The insulating lining 30 here also completely covers the bore 28b considering the axial and circumferential directions. The insulating lining 30 covers the bore of the axial portion 32a, 34a of each part 32, 34 of the sleeve.

[0080] The insulating lining 30 also covers the inner face of the radial collar 32b, 34b of each part 32, 34 of the sleeve. The inner face and the outer face axially opposite the inner face of each radial collar 32b and 34b delimit the axial thickness of said collar. For each radial collar 32b and 34b, 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 lining 30 also covers the free end of the radial collar 32b, 34b of each part 32, 34 of the sleeve.

[0081] 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 opposite the outer surface 30a, and two opposite radial end faces 30c, 30d axially delimiting the bore and the outer surface. The radial end faces 30c, 30d axially delimit the insulating lining 30. The outer surface 30a and the bore 30b delimit the radial thickness of the insulating lining 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 the radial collar 32b, 34b of each part 32, 34 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.

[0082] 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.

[0083] Alternatively, it is possible to provide other arrangements. For example, the insulating lining 30 could have a reduced axial dimension and remain axially set back from the faces 14c, 14d of the outer ring. Alternatively, the insulating lining 30 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 30 may at least partially cover these faces 14c, 14d. Alternatively, the insulating lining 30 could at least partially cover the faces 28c, 28d of the sleeve.

[0084] In another alternative or combination, the sleeve 28 could extend axially projecting from the insulation lining 30 relative to the faces 30c and 30d, or remain axially set back from these faces.

[0085] The insulating lining 30 also comprises two ribs 40, 42 extending radially outward from the outer surface 30a and each housed inside one of the grooves 36, 38 of the sleeve. The rib 40, 42 is of complementary shape to the associated groove 36, 38. Each rib 40, 42 projects beyond the outer surface 30a of the insulating lining. Each rib 40, 42 is formed on the outer surface 30a during the overmolding of the insulating lining 30.

[0086] To manufacture the bearing device, the procedure is as follows.

[0087] In a first step 50, the first part 32 of the sleeve is mounted inside a mold which is provided for overmolding the insulation lining 30.

[0088] In a second successive step 52, the outer ring 14 equipped with the grooves 22, 24 is placed inside the mold.

[0089] Then, in a third step 54, the second part 34 of the sleeve is mounted inside the mold axially in abutment against the first part 32. In this position mounted inside the mold, the first part 32 and the second part 34 of the sleeve are radially at a distance from the outer ring 14.

[0090] Then, in a fourth successive step 56, the insulating lining 30 is overmolded both on the outer ring 14 and on the first and second parts 32, 34 of the sleeve 28. The ribs 40, 42 of the insulating lining are formed during this step.

[0091] In a fifth successive step 58, the unitary assembly formed by the outer ring 14, by the first and second parts 32, 34, the sleeve 28 and by the insulating lining 30 is extracted from the mold.

[0092] Then, in a sixth successive step 60, the front faces 14c, 14d and the faces 28c, 28d of the sleeve are ground. Given the presence of the collars 32b and 34b of the sleeve, the grinding operation is carried out mainly on the latter and the outer ring, and not on the insulating lining 30. During this step, the outer surface 28a of the sleeve and the raceway 20 of the outer ring can also be ground.

[0093] Then, in a seventh step 62, the unitary assembly formed by the outer ring 14, the first and second parts 32, 34, the sleeve 28 and the insulating lining 30 is assembled with the row of rolling elements 16, the cage 17 and the inner ring 12.

[0094] 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 30 is overmolded is the outer ring.

[0095] Alternatively, it is possible to provide an inverted arrangement in which the second ring 14 on which the insulating lining 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 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 bore of the sleeve delimits the bore of the bearing device.

[0096] 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 (26) mounted on the second ring (14) of the bearing and provided with a 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 which delimit the radial thickness of said bushing, the insulating lining (30) being overmolded on the second ring (14) of the bearing and at least on one of the outer and inner surfaces of the bushing (28), characterized in that the bushing (28) is made in at least two separate parts (32, 34), each part comprising an axial portion (32a, 34a) and a radial collar (32b,34b) extending radially inwards the axial portion, the axial portions (32a, 34a) of said two parts jointly delimiting at least in part said surface of the sleeve (28) on which the insulating lining (30) is overmolded, the insulating lining (30) being further overmolded on an internal face of the radial collar (32b, 34b) of each of said two parts of the sleeve.,

2. Device according to claim 1, in which the radial collar (32b, 34b) of at least one of said two parts 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, in which the radial collar (32b, 34b) of each of said two parts of the sleeve extends radially beyond said outer (14a) or inner surface of the second ring on which the insulating lining (30) is overmolded.

4. Device according to any one of the preceding claims, wherein said two parts (32, 34) of the socket are symmetrical with respect to a median radial plane of said device.

5. Device according to any one of the preceding claims, in which the axial portions (32a, 34a) of said two parts of the sleeve are axially in contact with each other and jointly delimit the entirety of said surface of the sleeve (28) on which the insulating lining (30) is overmolded.

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

7. Device according to claim 6, wherein each axial portion (32a, 34a) of said two parts of the sleeve (28) is provided with at least one groove (36, 38) extending in the circumferential direction and inside which extends a rib (40, 42) for hooking the insulating lining of complementary shape.

8. Device according to any one of the preceding claims, in which the sleeve (28) comprises two front faces (28c, 28d) delimiting the axial length of said sleeve, the radial collar (32b, 34b) of at least one of said two parts (32, 34) being axially flush with one of said front surfaces (28c, 28d) of the sleeve.

9. A method of manufacturing a bearing device according to any one of claims 1 to 8 comprising: - a step of mounting one of said parts (32, 34) of the sleeve at the bottom of a manufacturing mold, - a step of placing the second ring (14) inside the manufacturing mold, - a step of mounting the other of said parts (32, 34) of the sleeve inside the manufacturing mold, - a step of overmolding the insulating lining (36) on the second ring (14) and at least on said surface of the sleeve (28), and - a step of assembling with the first ring (12) of the bearing the assembly formed by the second ring (14), said parts (32, 34) of the sleeve and the insulating lining (36).

10. An electric motor comprising a housing, a shaft and at least one bearing device according to any one of claims 1 to 8 mounted radially between the housing and the shaft.

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