Bearing devices with integrated electrical insulation, particularly for electric motors or machines, and associated manufacturing processes

Abstract

[Bearing device with integrated electrical insulation, particularly for electric motors or machines, and associated manufacturing methods] The bearing device comprises a bearing 10 having a first ring 12 and a second ring 14. The device includes at least one insulating sleeve 26 mounted on the second ring 14 and having 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 insulating lining is overmolded onto the second ring 14 and at least onto one of the outer and inner surfaces of the bushing 28 that define its radial thickness. At least one first groove 32, 34 is formed on at least one of the bushing 28 and the second ring 14 and delimited in the circumferential direction by two lateral flanks, the insulating lining being further overmolded inside said first groove and covering the lateral flanks.Reference: Figure 1.

Description

Title of the invention: Electrically insulated bearing device, particularly for electric motors or machines, and associated manufacturing processes. 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 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 bushing comprises an outer surface and an inner surface opposite the outer surface, which define the radial thickness of said bushing. The insulating lining is overmolded onto the second bearing ring and at least onto one of the outer and inner surfaces of the bushing.

[0014] According to a general feature, at least one first groove is formed on at least one of the sleeve and the second ring. Said first groove is delimited in the circumferential direction by two lateral flanks.

[0015] According to another general feature, the insulation lining is further overmolded inside said first groove and covers the lateral sides thereof.

[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 provision of said first groove on at least one of the bushing and the second bearing ring allows the bushing and / or the second ring to be secured to the insulating seal in the circumferential direction. Indeed, the overmolded insulating seal covers the lateral sides of said groove.

[0018] The risk of relative displacements between the insulation lining and the sleeve and / or the second ring in the circumferential direction is limited, particularly during temperature variations.

[0019] 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.

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

[0021] According to a first conception, at least one first groove is provided only on the socket.

[0022] According to a second design, at least a first groove is provided only on the second ring of the bearing.

[0023] According to a third particularly advantageous design, each of the second bearing ring and bushing comprises at least one first groove delimited in the circumferential direction by two lateral flanks, the insulating lining being overmolded inside each first groove and covering the lateral flanks of each first groove. In this case, the first groove of the The second bearing ring can be located in the radial extension of the first groove in the bushing. Alternatively, the first groove of the second ring can be offset circumferentially relative to the first groove in the bushing.

[0024] The sleeve may also include two opposing radial front faces that define the axial length of said sleeve. Preferably, said first groove opens onto one of the front faces of the sleeve or of the second ring of the bearing.

[0025] In one embodiment, at least one first and one second groove are formed on at least one of the sleeve and the second ring, each delimited in the circumferential direction by two lateral flanks. In this case, the insulating lining is further overmolded inside said first and second grooves and covers the lateral flanks of each of said first and second grooves. The first and second grooves may be diametrically opposed.

[0026] If the insulation lining is made of synthetic material or elastomeric material, it makes the device less sensitive to temperature variations.

[0027] In a particular embodiment, the bushing is made of metallic material. The bushing can thus be easily machined to a predetermined radial tolerance.

[0028] 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.

[0029] 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.

[0030] 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.

[0031] 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.

[0032] 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.

[0033] The invention also relates to a method for manufacturing a bearing device as defined above, comprising the following successive steps:

[0034] - a machining step of at least the first groove,

[0035] - a step of mounting the bushing and at least the second bearing ring the inside of a manufacturing mold, and

[0036] - an overmolding step of the insulating lining onto the second ring, at less on said surface of the socket and inside said first groove. Brief description of the figures

[0037] 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:

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

[0039] [Fig.2] is a half axial cross-sectional view of the bearing device of [Fig.1] according to a another cross-section,

[0040] [Fig.3] is a side view of the bearing device of Figures 1 and 2,

[0041] [Fig.4] is a perspective view of the bearing device of Figures 1 to 3,

[0042] [Fig.5] is a partial exploded perspective view of the bearing device of the figures 1 to 4, and

[0043] [Fig.6] is a flowchart illustrating the manufacturing process of the device level of figures 1 to 5. Detailed description of the invention

[0044] The bearing assembly illustrated in Figures 1 and 2 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.

[0045] The bearing device is designed so as not to conduct electric currents. The bearing device has integrated electrical insulation.

[0046] 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.

[0047] 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.

[0048] 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.

[0049] 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.

[0050] 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. The outer surface 14a and the bore 14b define the radial thickness of the outer ring 14.

[0051] The outer ring 14 further includes an outer raceway 20 for the rolling elements 16 which is formed on the bore 14b. The raceway 20 is directed radially inwards.

[0052] In the illustrated embodiment, a groove 22 is formed on the front face 14c of the outer ring. The groove 22 is oriented and axially open towards the outside of the outer ring. The groove 22 has a bottom that 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 extends radially here for manufacturing simplicity. The groove 22 is annular.

[0053] Similarly, a groove 24 is formed on the front face 14d of the outer ring. The groove 24 is oriented and axially open towards the outside of the outer ring. The groove 24 has a bottom that is axially offset 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 with respect to a median radial plane of the outer ring. The grooves 22, 24 axially delimit the outer surface 14a. Alternatively, it might be possible to omit the grooves 22, 24.

[0054] 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.

[0055] The insulation sleeve 26 comprises 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.

[0056] As can be seen in particular in [Fig. 5], first and second grooves 32 and first and second grooves 34 are formed respectively on the outer ring 14 and on the sleeve 28 to make the insulating lining rotationally fixed to said sleeve and to said outer ring

[0057] In the embodiment shown, the grooves 32 are identical and diametrically opposed. Alternatively, the outer ring 14 could comprise a single groove 32, or at least three grooves 32.

[0058] Each groove 32 is formed on the outer surface 14a of the outer ring and opens onto the front face 14d. Each groove 32 is axially open outwards. Each groove 32 is oriented and radially open outwards.

[0059] Each groove 32 is delimited in the circumferential direction by two lateral sides 32a, 32b which are connected to each other by a radial base 32c. The lateral sides 32a, 32b are opposite each other in the circumferential direction. Alternatively, if the circumferential dimension of each groove 32 is larger, the lateral sides 32a, 32b may not be opposite each other.

[0060] In the illustrated embodiment, each groove 32 also includes an axial bottom 32d which connect to the flanks 32a, 32b and the radial bottom 32c. Alternatively, each groove 32 could be without an axial bottom 32d and open radially into the bore 14b of the outer ring.

[0061] The sides 32a, 32b of each groove are straight and extend radially for ease of manufacturing. Alternatively, the sides 32a, 32b of each groove could have other shapes, for example, not be parallel, be dovetail-type, have a stepped profile, etc. The radial bottom 32c also extends radially and is oriented axially outwards. Alternatively, each groove 32 could be without a bottom, the sides 32a, 32b then joining directly.

[0062] The sleeve 28 is annular in shape. The sleeve 28 extends axially. The sleeve 28 is made here in one piece. Alternatively, the sleeve 28 could be made in several pieces supported against each other, for example, two identical pieces. The sleeve 28 comprises an axial cylindrical annular outer surface 28a, and an annular bore 28b radially opposed to the outer surface 28a. The bore 28b forms the inner surface of the sleeve 28.

[0063] Referring again to Figures 1 and 2, the bore 28b of the bushing is oriented radially inwards, i.e., towards the outer ring 14 and the insulating gasket. The bushing 28 also includes two opposing radial front faces 28c, 28d axially delimiting the bore and the outer surface. The front faces 28c, 28d define the axial length of the bushing. The outer surface 28a and the bore 28b define the radial thickness of the bushing 28. The outer surface 28a of the bushing defines the outer surface of the bearing device 10. In other words, the outer surface 28a defines the outer diameter of the bearing device 10.

[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 and remain axially recessed from faces 14c, 14d of the outer ring, or projecting from said faces.

[0065] Referring again to [Fig. 5], each groove 34 is formed on the bore 28b of the sleeve and opens onto the front face 28d. Each groove 34 is oriented and axially open outwards. Each groove 34 opens radially into the bore 28b of the sleeve. In the illustrated embodiment, each groove 34 also opens radially onto the outer surface 28a of the sleeve. Alternatively, each groove 34 might not open onto the outer surface 28a.

[0066] Each groove 34 is delimited in the circumferential direction by two lateral sides 34a, 34b which are connected to each other by a radial base 34c. The lateral sides 34a, 34b are opposite each other in the circumferential direction. Alternatively, if the circumferential dimension of each groove 34 is larger, the sides 34a, 34b may not be opposite each other.

[0067] The sides 34a, 34b of each groove are straight and extend radially for ease of manufacturing. Alternatively, the sides 34a, 34b of each groove could have other shapes, for example, not be parallel, be dovetail-type, have a stepped profile, etc. The radial bottom 34c also extends radially and is oriented axially outwards. Alternatively, each groove 34 could be without a bottom, the sides 34a, 34b then joining directly.

[0068] In the embodiment shown, the grooves 34 are identical and diametrically opposed. Alternatively, the sleeve 28 could comprise a single groove 34, or at least three grooves 34.

[0069] 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.

[0070] Referring to Figures 1 to 4, the insulating gasket 30 is interposed radially 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. The insulating gasket 30 also covers the grooves 32 of the outer ring. The insulating gasket 30 covers the flanks, the axial bottom, and the radial bottom of each of the grooves 32.

[0071] The insulating gasket 30 still covers the bore 28b of the bushing. The insulating gasket 30 also completely covers the bore 28b here, considering both the axial and circumferential directions. The insulating gasket 30 also covers the grooves 34 of the socket. The insulation lining 30 covers the sides and bottom of each of the grooves 34.

[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 delimit the axial length of the insulating gasket 30.

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

[0074] 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.

[0075] The outer surface 30a of the insulating gasket is in radial contact with the bore 28b of the sleeve. The bore 30b is in radial contact with the outer surface 14a of the outer ring and with the grooves 22, 24.

[0076] The portions of the insulating lining 30 that cover the grooves 32 of the outer ring of the bearing form two protrusions 36 that extend radially inwards. The protrusions 36 extend radially inwards from the bore 30b.

[0077] Each protrusion 36 is located inside one of the grooves 32. Each protrusion 36 is form-fitting with its associated groove 32. Each protrusion 36 bears circumferentially against the flanks 32a, 32b of its associated groove. Each protrusion 36 bears axially against the radial bottom 32c and radially against the axial bottom 32d of its associated groove.

[0078] The portions of the insulating lining 30 that cover the grooves 34 of the socket form two protrusions 38 that extend radially outwards. The protrusions 38 extend radially outwards from the outer surface 30a.

[0079] Each protrusion 38 is located inside one of the grooves 34. Each protrusion 38 is form-fitting with its associated groove 34. Each protrusion 38 bears circumferentially against the flanks 34a, 34b of its associated groove. Each protrusion 38 bears axially against the radial bottom 32c of its associated groove. Each protrusion 38 is radially flush with the outer surface 30a of the sleeve.

[0080] In the illustrated embodiment, the protrusions 36 are flush with the front face 14d of the outer ring and the protrusions 38 are flush with the front face 28d of the sleeve. Alternatively, the protrusions 36, 38 could remain recessed relative to the front faces 14d, 28d of the outer ring and the sleeve, or extend axially in projection relative to these faces.

[0081] To manufacture the bearing device, the following procedure is used.

[0082] In a first step 50 schematically illustrated in [Fig.5], the grooves 32 and 34 of the outer ring 14 of the bearing and of the bushing 28 are machined.

[0083] In a second successive step 52, the bearing 10, or the outer ring 14 alone, and the bushing 28 are mounted inside a mold which is intended for overmolding the insulating lining 30. In this position mounted inside the mold, the bushing 28 is radially distant from the outer ring 14 of the bearing.

[0084] In a third successive step 54, the insulating seal 30 is overmolded onto both the outer ring 14 of the bearing and the bushing 28. The projections 36, 38 are formed during this step. The seal 30 and the projections 36, 38 form a single unit.

[0085] Then, in a fourth and final step 56, the unit assembly formed by the bearing 10, or the single outer ring 14, the bushing 28 and the insulating lining 30 is extracted out of the mold.

[0086] 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.

[0087] 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.

[0088] In the described embodiments, the device bearing 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 besides balls, for example rollers. In another variant, the bearing can 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 (26) mounted on the second ring (14) of the bearing and having 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 define the radial thickness of said bushing, the insulating lining (30) being overmolded onto the second ring (14) of the bearing and at least onto one of the outer and inner surfaces of the bushing (28), characterized in that at least a first groove (32, 34) is provided on at least one of the bushing (28) and the second ring (14) of the landing and delimited in the circumferential direction by two lateral sides (32a, 32b, 34a,34b), the insulating lining being further overmolded inside said first groove and covering the side sides.

2. Device according to claim 1, wherein lateral flanks (32a, 32b, 34a, 34b) of said first groove (32, 34) are opposite each other in the circumferential direction.

3. Device according to claim 1 or 2, wherein said first groove (32, 34) opens onto one of the front faces (28d, 14d) of the bushing or of the second ring of the bearing.

4. Device according to any one of the preceding claims, wherein at least a first and a second groove (32, 34) are provided on at least one of the bushing (28) and the second ring (14) of the bearing and each delimited in the circumferential direction by two lateral flanks (32a, 32b, 34a, 34b), the insulating lining being further overmolded inside said first and second grooves and covering the lateral flanks of each of said first and second grooves.

5. Device according to claim 4, wherein the first and second grooves (32, 34) are diametrically opposed.

6. A device according to any one of the preceding claims, wherein each of the second bearing ring and the bushing comprises at least one first groove (32, 34) delimited in the circumferential direction by two lateral flanks (32a, 32b, 34a, 34b), the insulation lining being surmounted inside each first groove and covering the lateral flanks of each first groove.

7. Device according to claim 6, wherein the first groove (32) of the second bearing ring is located in the radial extension of the first groove (34) of the bushing.

8. A method for manufacturing a bearing device according to any one of claims 1 to 7 comprising the following successive steps: - a machining step of at least the first groove (32, 34), - a mounting step of the bushing (28) and at least the second ring (14) of the bearing inside a manufacturing mold, and - an overmolding step of the insulating lining (30) onto the second ring (14), at least on said surface of the bushing (28) and inside said first groove (32, 34).

9. Electric motor comprising a housing, a shaft and at least one bearing device according to any one of claims 1 to 7 mounted radially between the housing and the shaft.

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