Bearing device with integrated electrical insulation, particularly for electric motors or machines, and associated manufacturing process

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 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 and at least onto 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.Each first and second flange 32b, 32c of the sleeve extends radially beyond an outer surface of the second ring on which the insulating lining 30 is overmolded. Reference: Figure 1.

Description

Title of the invention: Bearing device with integrated electrical insulation, particularly for electric motors or machines, and associated manufacturing method. Technical field of the invention

[0001] The present invention relates to the field of bearings used in particular in electric motors, electrical machines and associated equipment. Prior art

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

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

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

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

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

[0007] To remedy the aforementioned disadvantages, it is also known to equip the outer ring of the bearing with an insulating sleeve provided with a bushing and an insulating lining made of electrically insulating material and interposed radially between the outer ring and the bushing.

[0008] In order to achieve the fixing of the insulation lining on the outer ring and on the sleeve without additional element or special machining on the outer ring, it is possible to overmold the insulation lining.

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

[0010] The present invention therefore aims to remedy the aforementioned drawbacks by proposing a bearing device of simple and economical design.

[0011] The invention relates to a bearing device comprising a bearing provided with a first ring and a second ring capable of rotating relative to each other.

[0012] The device further comprises at least one insulating sleeve mounted on the second bearing ring. The insulating sleeve is provided with a 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 meant that the socket is made in one piece. The socket is made in one piece.

[0014] The sleeve comprises an outer surface and an inner surface opposite to the outer surface and which delimit the radial thickness of said sleeve.

[0015] 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.

[0016] According to a general characteristic, the sleeve includes an axial portion delimiting said surface of the sleeve on which the insulation lining is overmolded, and first and second collars extending the axial portion radially on the side of the second ring.

[0017] According to another general feature, the insulation lining is further overmolded onto an inner face of each of the first and second collars.

[0018] According to another general feature, each of the first and second collars of the sleeve extends radially beyond an outer or inner surface of the second ring on which the insulating lining is overmolded.

[0019] 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.

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

[0021] Furthermore, the fact of having first and second collars of the socket which extend radially beyond the outer or inner surface of the second ring onto which the insulation lining is overmolded, resulting in a socket with good mechanical resistance.

[0022] Indeed, with such an arrangement, each portion of the insulating seal located axially between the second ring and one of the sleeve flanges is not subjected to shear stresses when significant axial loads are applied to the device mounted inside the housing of the motor or associated electrical machine, with one of these flanges 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.

[0023] The second ring has first and second front faces defining its axial length. In a particular embodiment, the first flange of the sleeve is axially offset outwards relative to the first front face of the second ring. Alternatively, or in combination, the second flange of the sleeve may be axially offset outwards relative to the second front face of the second ring.

[0024] The insulation lining is provided with two front faces delimiting its axial length of said lining.

[0025] According to a first design, at least one of the first and second flanges of the socket can be axially flush with one of said front faces of the insulation lining.

[0026] According to a second design, each of the first and second collars of the socket is axially flush with one of said front faces of the insulation lining.

[0027] Alternatively, one or both of the collars of the socket can be axially offset inwards or outwards relative to the associated front face of the insulation lining.

[0028] 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.

[0029] Thus, the axial attachment of the insulation lining to the socket is further increased.

[0030] 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.

[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 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.

[0033] 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.

[0034] 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.

[0035] 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.

[0036] 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.

[0037] 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.

[0038] The invention further relates to a method for manufacturing a bearing device as defined above, comprising at least the following successive steps:

[0039] - a radial positioning step of the second bearing ring relative to said surface of the socket, the socket having in cross-section at this stage an L-shaped form formed by the first collar and by the axial portion,

[0040] - a step of partially folding the axial portion to form the second collar from the socket,

[0041] - an overmolding step of the insulating lining onto the second ring and onto said surface of the socket and the inner face of each of the first and second collars, and

[0042] - an assembly step with the first bearing ring of the assembly formed by the second ring, the socket and the insulation lining.

[0043] Advantageously, the process further comprises, after the partial bending step and before the overmolding step, a heat treatment step of the bushing and the second bearing ring positioned one inside the other. Brief description of the figures

[0044] 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:

[0045] [Fig-1] is a half axial cross-sectional view of a bearing device according to an embodiment of the invention,

[0046] [Fig.2] is a flowchart illustrating the manufacturing process of the bearing device of [Fig.1],

[0047] [Fig.3]

[0048] [Fig.4]

[0049] [Fig.5]

[0050] [Fig.6] are half-sectional views illustrating steps in the manufacturing process of the bearing device of [Fig.1], and

[0051] [Fig.7] is a half axial cross-sectional view of a bearing device according to another embodiment of the invention. Detailed description of the invention

[0052] 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.

[0053] The bearing device is designed so as not to conduct electric currents. The bearing device has integrated electrical insulation.

[0054] 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.

[0055] 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.

[0056] The inner ring 12 comprises a cylindrical bore 12a, an axial cylindrical outer surface 12b radially opposed to the bore, and opposing radial first and second 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. The first and second faces define the axial length of the inner ring 12.

[0057] 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.

[0058] The outer ring 14 comprises a cylindrical axial outer surface 14a, a cylindrical bore 14b radially opposed to the outer surface 14a, and opposing radial first and second faces 14c, 14d axially delimiting the bore 14b and the outer surface 14a. The outer surface 14a and the bore 14b define the radial thickness of the outer ring 14. The first and second faces 14c, 14d define the axial length of the outer ring 14.

[0059] 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.

[0060] The bearing device also includes an electrical insulation sleeve 26 mounted on the outer ring 14. The insulation sleeve 26 is mounted on the surface outer 14a of the outer ring 14. The insulation sleeve 26 is integral with the outer ring 14.

[0061] 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.

[0062] 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.

[0063] The sleeve 28 comprises an axial portion 32a, and first and second annular radial flanges 32b, 32c, each extending radially inward from the axial portion. Each flange 32b, 32c extends radially. Each flange 32b, 32c extends 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.

[0064] 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.

[0065] The sleeve 28 also includes two opposing radial front faces 28c, 28d axially defining the axial length of said sleeve. The front face 28c is defined by the flange 32b, and the front face 28d is defined by the flange 32c. More precisely, the front face 28c is defined by the outer face of the flange 32b, and the front face 28d is defined by the outer face of the flange 32c.

[0066] In the illustrated embodiment, the front faces 28c, 28d of the sleeve are offset outwards relative to the front faces 14c, 14d of the outer ring. Alternatively, other arrangements could be provided. For example, the outer ring 14 could have a larger axial dimension, and the front faces 28c, 28d of the sleeve could be coplanar with the front faces 14c, 14d of the outer ring.

[0067] Each of the flanges 32b, 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 each flange 32b, 32c is offset radially inwards relative to the outer surface 14a of the outer ring. The flanges 32b, 32c remain axially distant from the outer ring 14.

[0068] In the illustrated embodiment, the radial dimensions of the flanges 32b, 32c of the sleeve are equal. The flanges 32b, 32c of the sleeve are symmetrical with respect to a median radial plane of the device. Alternatively, the radial dimension of the flange 32c of the sleeve could be different from the radial dimension of the flange 32b.

[0069] In the illustrated embodiment, the sleeve 28 further includes an annular groove 34 provided in the connection area between the axial portion 32a and the flange 32c on the bore side 28b. As will be described in more detail later, this facilitates the formation of the flange 32c of the sleeve.

[0070] 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.

[0071] 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 of the outer ring in both the axial and circumferential directions. The insulating gasket 30 also covers the front faces 14c, 14d of the outer ring.

[0072] 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.

[0073] The insulating gasket 30 also covers the inner face of each flange 32b, 32c of the socket. The inner face and the outer face axially opposite the inner face of each flange 32b and 32c define the axial thickness of said flange. For each flange 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 flange 32b, 32c of the socket.

[0074] The insulating gasket 30 is annular in shape. The insulating gasket 30 extends axially. The insulating gasket 30 comprises an axial cylindrical outer surface 30a and a cylindrical bore 30b radially opposed to the outer surface. 30a, and two opposing radial front faces 30c, 30d axially delimit 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 and with the front faces 14c, 14d of the outer ring. The bore 30b has a stepped shape.

[0075] In the illustrated embodiment, the faces 30c, 28c and 30d, 28d of the insulating gasket and the socket are respectively coplanar. Alternatively, other arrangements are possible. For example, the socket 28 could extend axially outward from the insulating gasket 30 relative to the faces 30c and 30d, or remain axially recessed from these faces.

[0076] We will now describe, with reference to figures 2 to 6, an example of the manufacturing process of the bearing device.

[0077] In a first step 50, the sleeve 28 is formed to have an L-shaped cross-section as illustrated in [Fig. 3]. At this stage, the sleeve 28 comprises the flange 32b and the axial portion 32a. The axial portion 32a has an axial dimension greater than its final dimension because the flange 32c is not yet formed and is therefore in the form of an axial extension extending from the groove 34. The sleeve 28 is formed, for example, by cutting and stamping.

[0078] In a second successive step 52, as illustrated in [Fig.4], the outer ring 14 of the bearing is positioned radially inside the sleeve 28 which at this stage still has an L-shaped cross-section.

[0079] Next, in a third step 54, the axial portion 32a of the sleeve is partially bent to form the collar 32c of the sleeve, thus obtaining the final shape of the sleeve, which in cross-section has a general U-shape as illustrated in [Fig. 5]. The collar 32c is formed, for example, by rolling. The collar 32c of the sleeve is bent until it rests against the front face 14d of the outer ring. The groove 34 facilitates the bending of the collar 32c of the sleeve. Alternatively, it is possible to provide other means for creating a bending initiation point; for example, the thickness of the collar 32c could be reduced relative to the rest of the sleeve. In another embodiment, it is possible not to provide such means for creating a bending initiation point.

[0080] In a fourth successive step 56, the sleeve 28 and the outer ring 14 undergo a heat treatment step together. The sleeve 28 and the outer ring 14 are thus heated together to the same temperature. The sleeve 28 and the outer ring 14 remain positioned one inside the other during this step, in the position illustrated in [Fig.5].

[0081] Then, in a fifth step 58, the bushing 28 and the outer ring 14 of the bearing are mounted inside a mold which is intended for overmolding the insulation lining 30.

[0082] Next, in the sixth step 60, the insulation lining 30 is overmolded both onto the outer ring 14 and onto the sleeve 28 as illustrated in [Fig.6].

[0083] In a seventh successive step 62, the unit assembly formed by the outer ring 14, the sleeve 28 and the insulating lining 30 is extracted from the mold.

[0084] Then, in an eighth step 64, the front faces 28c, 28d of the bushing are ground. During this step, the outer surface 28a of the bushing and the raceway 20 of the outer ring can also be ground.

[0085] Finally, in a ninth step 66, the unit assembly formed by the outer ring 14, the bushing 28 and the insulation lining 30 is assembled with the row of rolling elements 16, the cage 17 and the inner ring 12.

[0086] The embodiment illustrated in [Fig. 7], 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 70, 72 extending circumferentially around the axis 25 of the sleeve bore. Each groove 70, 72 is oriented radially towards the outer ring 14, i.e., radially inwards.

[0087] In the illustrated embodiment, each groove 70, 72 is annular. Alternatively, at least one of the two grooves 70, 72 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.

[0088] Each groove 70, 72 is delimited in the axial direction by two opposing lateral sides which have a straight profile in axial section and are connected to each other by an axial bottom. Alternatively, it is possible to provide other shapes, for example grooves having here in cross-section a shape of an arc of a circle oriented inwards.

[0089] The insulating sleeve 30 also includes two ribs 74, 76 extending radially outwards from the outer surface 30a and each housed within one of the grooves 70, 72 of the sleeve. The rib 74, 76 is complementary in shape to the associated groove 70, 72. Each rib 74, 76 projects beyond the outer surface 30a of the insulating sleeve. Each rib 74, 76 is formed on the outer surface 30a during the overmolding of the insulation lining 30.

[0090] 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.

[0091] 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 interposed radially 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. The flanges of the bushing extend radially beyond the inner surface of the inner ring, i.e., the bore of the inner ring, i.e., they project radially outward from the inner surface of the inner ring.

[0092] 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) radially interposed 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, 32c) of the sleeve, each of the first and second flanges (32b, 32c) extending radially beyond an outer (14a) or inner surface of the second ring onto which the insulating lining (30) is overmolded.

2. Device according to claim 1, wherein the second ring (14) is provided with first and second front faces (14c, 14d) delimiting the axial length of said second ring, the first collar (32b) of the sleeve being axially offset outwards relative to the first front face (14c) of the second ring and the second collar (32c) of the sleeve being axially offset outwards relative to the second front face (14d) of the second ring.

3. Device according to claim 1 or 2, 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 faces (30c, 30d) of the insulation lining.

4. Device according to claim 3, wherein each of the first and second collars (32b, 32c) of the sleeve is axially flush with one of said front faces (30c, 30d) of the insulation lining.

5. Device according to any one of the preceding claims, wherein said surface of the socket (28) is provided with at least one groove (70) extending in the circumferential direction and within which extends a hooking rib (74) of the complementaryly shaped insulation lining.

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

7. Device according to claim 6, wherein the bushing (28) is obtained from a sheet metal blank by cutting, stamping and rolling.

8. A method for manufacturing a bearing device according to any one of the preceding claims comprising at least the following successive steps: - a step of radially positioning the second ring (14) of the bearing relative to said surface of the bushing (28), the bushing having in cross-section at this step an L-shaped form formed by the first flange (32b) and by the axial portion (32a), - a step of partially folding the axial portion (32a) to form the second flange (32c) of the bushing, - a step of overmolding the insulating lining (30) onto the second ring (14) and onto said surface of the bushing (28) and the inner face of each of the first and second flanges (32b, 32c), and - a step of assembling with the first ring (12) of the bearing the assembly formed by the second ring (14), the bushing (28) and the insulating lining (30).

9. A method according to claim 8, further comprising, after the partial bending step and before the overmolding step, a heat treatment step of the bushing (28) and the second ring (14) of the bearing positioned one inside the other.

10. 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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