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 22 mounted on the second ring 14 of the bearing and provided with a bushing 24 and an insulating lining 26 interposed radially between the second ring 14 and the bushing 24 and made of electrically insulating material. The bushing comprises an annular outer surface 24a and an annular inner surface 24b. The insulating lining 26 is overmolded onto the second ring 14 of the bearing and at least onto one of the outer and inner surfaces of the bushing 24. Said inner or outer surface of the bushing 24 oriented radially towards the second ring is of non-cylindrical annular shape. 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 socket comprises an annular outer surface and an annular inner surface opposite the outer surface.

[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, said inner or outer surface of the sleeve oriented radially in the direction of the second ring is of non-cylindrical annular shape.

[0016] 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.

[0017] Furthermore, the provision of the non-cylindrical annular shape on the inner or outer surface of the sleeve makes it possible to obtain good attachment to the insulating lining since a complementary non-cylindrical annular shape is obtained on the lining during overmolding. The risk of relative displacements between the insulating lining and the sleeve in the circumferential direction is particularly limited, in particular during temperature variations.

[0018] 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.

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

[0020] By "annular-shaped surface" is meant a surface which forms, when viewed in section, a convex plane curve that closes on itself.

[0021] The other outer or inner surface of the sleeve oriented radially on the side opposite the second ring is of cylindrical annular shape.

[0022] Said inner or outer surface of the sleeve may have, when viewed in section, two orthogonal axes of symmetry.

[0023] According to a first design, said inner or outer surface of the socket has, when seen in section, an oblong shape.

[0024] In this case, said inner or outer surface of the sleeve may be provided with two diametrically opposed cylinder portions with different axes, and two rectilinear portions connecting the cylinder portions together. Advantageously, the cylinder portions may be two semi-cylindrical portions.

[0025] According to a second design, said inner or outer surface of the socket has, when viewed in section, an oval shape.

[0026] In this case, said inner or outer surface of the sleeve may be provided with two first diametrically opposed cylinder portions with different axes, and two second cylinder portions connecting the first cylinder portions and different axes together.

[0027] The sleeve may be provided with two front faces delimiting its axial length. Said protuberance may radially extend one of said front faces.

[0028] In a particular embodiment, the sleeve is made of metallic material. The sleeve can thus be easily machined to a predetermined radial tolerance.

[0029] 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.

[0030] 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.

[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 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.

[0033] 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

[0034] The present invention will be better understood upon studying the detailed description of embodiments, taken as non-limiting examples and illustrated by the appended drawings in which:

[0035] [Fig-1] is a half-view in axial section of a bearing device according to an exemplary embodiment of the invention,

[0036] [Fig.2] is a sectional view of a bushing of the bearing device of [Fig.l],

[0037] [Fig.3] is a sectional view along axis III-III of [Fig.2],

[0038] [Fig.4] is a perspective view of the socket of Figures 2 and 3,

[0039] [Fig.5] is a sectional view of the bushing of a bearing device according to another example of embodiment of the invention,

[0040] [Fig.6] is a sectional view along the VLVI axis of [Fig.5], and

[0041] [Fig.7] is a perspective view of the socket of Figures 5 and 6. Detailed description of the invention

[0042] The bearing device illustrated in [Fig. 1] 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.

[0043] The bearing device is designed so as not to be a conductor of electrical currents. The bearing device has integrated electrical insulation.

[0044] 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.

[0045] 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 rollers 16. The bearing 10 may also be equipped with seals or sealing flanges.

[0046] 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.

[0047] 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.

[0048] 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 and the outer surface. The outer surface 14a and the bore 14b delimit the radial thickness of the outer ring 14.

[0049] 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.

[0050] The bearing device also comprises an electrical insulating sleeve 22 mounted on the outer ring 14. The insulating sleeve 22 is mounted on the outer surface 14a of the outer ring 14. The insulating sleeve 22 is integral with the outer ring 14.

[0051] The insulating sleeve 22 comprises a bushing 24 and an insulating lining 26 interposed radially between the outer ring 14 and the bushing 24. The lining insulation 26 is overmolded onto the outer ring 14 and onto the sleeve 24.

[0052] The sleeve 24 is annular in shape. The sleeve 24 extends axially. The sleeve 24 is made here in a single piece. Alternatively, the sleeve 24 could be made in several pieces bearing against each other, for example two identical pieces. The sleeve 24 comprises a cylindrical annular axial outer surface 24a whose axis 25 is coaxial with the axis X-X', and an annular bore 24b radially opposite the outer surface 24a. The bore 24b forms the inner surface of the sleeve 24. The bore 24b is oriented radially inwards, i.e. on the side of the outer ring 14.

[0053] The sleeve 24 also comprises two opposite radial end faces 24c, 24d axially delimiting the bore and the outer surface. The end faces 24c, 24d delimit the axial length of the sleeve. The outer surface 24a and the bore 24b delimit the radial thickness of the sleeve 24. The outer surface 24a of the sleeve delimits the outer surface of the bearing device 10. In other words, the outer surface 24a defines the outer diameter of the bearing device 10.

[0054] The bore 24b of the sleeve is of non-cylindrical shape. As can be seen in Figures 3 and 4, in the illustrated embodiment, the bore 24b is provided with two semi-cylindrical portions 28, 30 with different axes 28a, 30a, and two rectilinear portions 32, 34 connecting the semi-cylindrical portions together. The semi-cylindrical portions 28, 30 are diametrically opposed. The rectilinear portions 32, 34 are diametrically opposed. The axes 28a, 30a are located in the median axial plane of the sleeve. The axes 28a, 30a are located on either side of the axis 25 of the outer surface of the sleeve. The radii R28 and R30 of the semi-cylindrical portions 28, 30 are equal. Alternatively, the radii R28 and R30 of the semi-cylindrical portions 28, 30 could be different.

[0055] The rectilinear portion 32 connects a first end of the semi-cylindrical portion 28 to a first end of the semi-cylindrical portion 32, and the rectilinear portion 34 connects a second end of the semi-cylindrical portion 28 to a second end of the semi-cylindrical portion 32. The first and second ends of each semi-cylindrical portion 28, 30 delimit said semi-cylindrical portion in the circumferential direction. Each rectilinear portion 32, 34 is connected circumferentially on one side to the semi-cylindrical portion 28 and circumferentially on the other side to the semi-cylindrical portion 30. Each rectilinear portion 32, 34 extends in the extension of the semi-cylindrical portions 28, 30 without breaking the slope. The rectilinear portions 32, 34 have a plane shape.

[0056] Viewed in section, the bore 24b of the sleeve has two orthogonal axes Xb X2 of symmetry. The bore 24b has, seen in section, an oblong shape.

[0057] As can be seen in Figures 1, 2 and 4, in the illustrated embodiment, the bore 24b of the sleeve comprises a first protrusion 27 which projects inwardly, i.e. projects in the direction of the outer ring 14. The protrusion 27 projects in relation to the bore 24b. The protrusion 27 extends radially. The protrusion 27 is located at an axial end of the bore 24b of the sleeve. The protrusion 27 extends radially inwardly the front face 24c of the sleeve. The outer face of the protrusion 27 is coplanar with the front face 24c.

[0058] The bore 24b of the sleeve comprises, at its other axial end, a second protrusion 36 which projects inwardly, i.e. projects in the direction of the outer ring 14. The protrusion 36 projects in relation to the bore 24b. The protrusion 36 extends radially. The protrusion 36 extends radially inwardly the front face 24d of the sleeve. The outer face of the protrusion 36 is coplanar with the front face 24d.

[0059] In the illustrated embodiment, the protuberance 36 has a radial dimension equal to that of the protuberance 27. Alternatively, the protuberance 36 could have a radial dimension smaller or larger than that of the protuberance 27. Alternatively, it could be possible not to provide a protuberance 36 and / or a protuberance 27.

[0060] In the illustrated embodiment, the non-cylindrical bore 24b extends over the entire width between the protrusions 27, 36. Alternatively, the non-cylindrical bore 24b could be present over a reduced width and then extend by a cylindrical portion.

[0061] The sleeve 24 is advantageously made of metallic material. Thus, the outer surface 24a of the sleeve can be easily machined if necessary to a predetermined tolerance. Preferably, the sleeve 24 is made of steel. The sleeve 24 can be obtained from a sheet metal blank by cutting, stamping and rolling. Alternatively, the sleeve 24 can be obtained from a tube or from forged and / rolled blanks, or from sintering and stamping.

[0062] The insulating lining 26 is made of electrically insulating material. The insulating lining 26 may for example be made of synthetic material, such as PEEK or PA46, or may be made of elastomeric material, for example rubber.

[0063] The insulating lining 26 is interposed radially between the outer surface 14a of the outer ring and the bore 24b of the sleeve. The insulating lining 26 covers the outer surface 14a of the outer ring. The insulating lining 26 here completely covers the outer surface 14a considering the axial and circumferential directions. The insulating lining 26 also covers the bore 24b of the sleeve. The insulating lining 26 here also completely covers the bore 24b considering the axial and circumferential directions. The insulating lining 26 also covers protrusions 27 and 36.

[0064] As indicated previously, the insulating lining 26 is overmolded onto the outer ring 14 of the bearing and onto the sleeve 24. The insulating lining 26 is overmolded onto the outer surface 14a of the outer ring 14, onto the bore 24b and onto the protrusions 27, 36 of the sleeve 24.

[0065] The insulating lining 26 is annular in shape. The insulating lining 26 extends axially. The insulating lining 26 comprises an axial outer surface 26a, a cylindrical bore 26b radially opposite the outer surface 26a, and two opposite radial end faces 26c, 26d axially delimiting the bore and the outer surface. The end faces 26c, 26d axially delimit the insulating lining 26. The outer surface 26a and the bore 26b delimit the radial thickness of the insulating lining 26. The outer surface 26a is in radial contact with the bore 24b of the sleeve and with the protrusions 27, 36. The bore 26b is in radial contact with the outer surface 14a of the outer ring.

[0066] The outer surface 26a of the insulating lining is of a shape complementary to the bore 24b of the sleeve and to the protrusions 27, 36, and thus has a stepped shape. In the region of the bore 24b, the outer surface 26a is thus provided with two semi-cylindrical portions complementary to the semi-cylindrical portions 28, 30, and two rectilinear portions complementary to the rectilinear portions 32, 34.

[0067] In the illustrated embodiment, the faces 14c, 26c, 24c and 14d, 26d, 24d of the outer ring, the insulating lining and the sleeve are respectively coplanar.

[0068] Alternatively, it is possible to provide other arrangements. For example, the insulating lining 26 could have a reduced axial dimension and remain axially set back from the faces 14c, 14d of the outer ring. Alternatively, the insulating lining 26 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 26 may at least partially cover these faces 14c, 14d. Alternatively, the insulating lining 26 could at least partially cover the faces 24c, 24d of the sleeve.

[0069] In another alternative or combination, the sleeve 24 could extend axially projecting from the insulation lining 26 relative to the faces 26c and 26d, or remain axially set back from these faces.

[0070] To manufacture the bearing device, the procedure is as follows.

[0071] In a first step, the bearing 10 and the sleeve 24 are mounted inside a mold which is provided for overmolding the insulation lining 26. In this position mounted inside the mold, the sleeve 24 is radially spaced from the outer ring 14 of the bearing.

[0072] 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 24.

[0073] Finally, the bearing device, which is in the form of a unitary assembly, is extracted from the mold.

[0074] In the embodiment illustrated in Figures 5 to 7, in which identical elements bear the same references, the bore 24b of the sleeve is also of non-cylindrical shape, but is here provided with first cylinder portions 40, 42 of different axes 40a, 42a, and two second cylinder portions 44, 46 connecting together the first cylinder portions of different axes 44a, 46a. The first cylinder portions 40, 42 are diametrically opposed. The second cylinder portions 44, 46 are diametrically opposed.

[0075] The axes 40a, 42a are located in the median radial plane of the sleeve. The axes 40a, 42a are located on either side of the axis 25 of the outer surface 24a of the sleeve. The radii R40 and R42 of the cylinder portions 40, 42 are equal. The axes 44a, 46a are different from the axes 40a, 42a. The axes 44a, 46a are located in the median axial plane of the sleeve. The 44a, 46a are located on either side of the axis 25. The radii R44 and R46 of the cylinder portions 44, 46 are equal to and less than the radii R40 and R42.

[0076] The second cylinder portion 44 connects a first end of the first cylinder portion 40 to a first end of the first cylinder portion 42, and the second cylinder portion 46 connects a second end of the first cylinder portion 40 to a second end of the first cylinder portion 42. The first and second ends of each cylinder portion 40, 42 delimit said cylinder portion in the circumferential direction.

[0077] Each second cylinder portion 44, 46 is connected circumferentially on one side to the first cylinder portion 40 and circumferentially on the other side to the first cylinder portion 42. Each second cylinder portion 44, 46 extends in the extension of the first cylinder portions 40, 42 without breaking the slope.

[0078] Viewed in section, the bore 24b of the sleeve has two orthogonal axes Xb X2 of symmetry. The bore 24b has, seen in section, an oval shape.

[0079] 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 26 is overmolded is the outer ring.

[0080] Alternatively, it is possible to provide an inverted arrangement in which the second ring 14 on which the insulating lining 26 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. outer surface of the sleeve is annular non-cylindrical. The bore of the sleeve delimits the bore of the bearing device.

[0081] 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 (22) mounted on the second ring (14) of the bearing and provided with a bushing (24) and an insulating lining (26) interposed radially between the second ring (14) and the bushing (24) and made of electrically insulating material, the bushing comprising an annular outer surface (24a) and an annular inner surface (24b) opposite the outer surface, the insulating lining (26) being overmolded onto the second ring (14) of the bearing and at least onto one of the outer and inner surfaces of the bushing (24), characterized in that said inner or outer surface of the bushing (24) oriented radially towards the second ring is of non-cylindrical annular shape.

2. Device according to claim 1, wherein said inner or outer surface of the socket has, seen in section, two orthogonal axes (Xb X2) of symmetry.

3. Device according to claim 1 or 2, wherein said inner or outer surface of the socket has, when viewed in section, an oblong shape.

4. Device according to claim 3, wherein said inner or outer surface of the sleeve is provided with two diametrically opposed cylinder portions (28, 30) with different axes, and two rectilinear portions (32, 34) connecting the cylinder portions together.

5. Device according to claim 4, in which the cylinder portions (28, 30) are two semi-cylindrical portions.

6. Device according to claim 1 or 2, wherein said inner or outer surface of the socket has, when viewed in section, an oval shape.

7. Device according to claim 6, wherein said inner or outer surface of the sleeve is provided with two first cylinder portions (40, 42) diametrically opposed and with different axes, and two second cylinder portions (44, 46) connecting the first cylinder portions and with different axes.

8. Device according to any one of the preceding claims, in which the insulating lining (26) is made of synthetic material or elastomeric material.

9. A device according to any preceding claim, wherein the socket (24) 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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