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 outer surface 24a and an inner surface 24b which delimit its radial thickness. 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 sleeve 24. Said surface of the sleeve 24 is provided with at least one helical groove 28 inside which extends a rib 30 for attaching the insulating lining of complementary 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 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, said surface of the sleeve is provided with at least one helical groove inside which extends a rib for attaching the insulation lining of a shape complementary to the helical groove.

[0016] According to another general characteristic, said helical groove extends circumferentially over at least one complete turn around the axis of said surface of the sleeve. In other words, said helical groove extends circumferentially over at least 360°.

[0017] 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.

[0018] Furthermore, the provision of said helical groove on the sleeve makes it possible to obtain good attachment to the insulation lining insofar as said attachment rib is formed inside the latter during overmolding. The risk of relative displacements between the insulation lining and the sleeve in the axial and circumferential directions is particularly limited, in particular during temperature variations.

[0019] This is made possible by providing said helical groove on the bushing which extends over at least one complete turn considering the axis of the helix.

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

[0021] By "circumferential direction" is meant the direction which is perpendicular to the times to the axial direction and to a radius of the bearing device, in other words, tangent to a circle whose center is on the axis of the bearing device.

[0022] Advantageously, said helical groove of the sleeve may extend circumferentially over at least two complete turns around the axis of revolution of said surface of the sleeve, i.e. over at least 720°, and to form at least two turns spaced apart in the axial direction.

[0023] In one embodiment, the helical groove may have a circular arc shape in cross section.

[0024] In another embodiment, the helical groove may be delimited in the axial direction by two facing lateral flanks which have a rectilinear profile in axial section.

[0025] This makes it possible to further increase the grip of the insulation lining on the socket.

[0026] According to a first design, the helical groove of the sleeve is delimited in the radial direction by a bottom from which the flanks project outwards. In other words, each lateral flank forms a break in slope relative to the bottom in its connection zone with said bottom.

[0027] By radial direction is meant the direction along a radius of the bearing device, that is to say any direction intersecting the axis of the bearing device and perpendicular to this axis.

[0028] The lateral flanks project outwards relative to the base at least in the radial direction. The lateral flanks may project relative to the base in a purely radial direction. This further improves the attachment of the insulating lining to the sleeve. Alternatively, however, it is possible to provide that the lateral flanks project obliquely relative to the base, i.e. both in the radial direction and also in the axial direction.

[0029] According to a second design, the helical groove of the sleeve may not have a bottom. In this case, the lateral flanks of the groove connect to each other and extend obliquely.

[0030] Regardless of the design of the helical groove with or without a bottom, when the lateral flanks extend obliquely, these flanks, seen in axial section, can be symmetrical considering a radial plane or asymmetrical.

[0031] The socket may be provided with two front faces delimiting its axial length.

[0032] According to a first design, said helical groove extends from a of said front faces towards the other front face. Said helical groove may open onto the other front face or remain axially at a distance from it.

[0033] According to a second design, said helical groove can remain at a distance from the two front faces of the socket. In other words, said helical groove does not open in this case onto the front faces of the socket.

[0034] In one embodiment, the pitch of said helical groove is constant. Alternatively, the pitch of said helical groove may be variable.

[0035] Preferably, said helical groove extends in the radial thickness of the sleeve while being blind.

[0036] In a particular embodiment, said surface of the sleeve is provided with at least one additional helical groove inside which extends a rib for attaching the insulating lining of complementary shape, said additional helical groove extending in an axial direction opposite to the direction of said helical groove.

[0037] This further increases the relative connection of the insulating lining and the sleeve. Said additional helical groove may extend circumferentially over at least one complete turn around the axis of said surface of the sleeve, or alternatively over less than one complete turn.

[0038] If the insulation lining is made of synthetic material or elastomeric material, it makes the device less sensitive to temperature variations.

[0039] In a particular embodiment, the sleeve is made of metallic material. The sleeve can thus be easily machined to a predetermined radial tolerance.

[0040] 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.

[0041] 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.

[0042] 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.

[0043] 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.

[0044] 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

[0045] 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:

[0046] [Fig-1] is a half-view in axial section of a bearing device according to an exemplary embodiment of the invention,

[0047] [Fig.2] is a perspective view of a bushing of the bearing device of [Fig.l],

[0048] [Fig.3] is a sectional view of the socket of [Fig.2],

[0049] [Fig.4] is a perspective view of a bushing of a bearing device according to a another example of embodiment of the invention,

[0050] [Fig.5] is a sectional view of the socket of [Fig.4],

[0051] [Fig.6] is a sectional view of a bushing of a bearing device according to another exemplary embodiment of the invention, and

[0052] [Fig.7] is a sectional view of a bushing of a bearing device according to yet another exemplary embodiment of the invention. Detailed description of the invention

[0053] 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.

[0054] 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.

[0055] 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.

[0056] 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.

[0057] 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.

[0058] 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.

[0059] 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.

[0060] 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.

[0061] The bearing device also comprises an electrical insulation 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.

[0062] 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 insulating lining 26 is overmolded onto the outer ring 14 and onto the bushing 24.

[0063] The sleeve 24 is annular in shape. The sleeve 24 extends axially. The sleeve 24 is made here in a single piece. The sleeve 24 comprises a cylindrical axial outer surface 24a, and a cylindrical bore 24b radially opposite the outer surface 24a and whose axis 25 is coaxial with the axis X-X'. The bore 24b forms the inner surface of the sleeve 24.

[0064] 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.

[0065] As can be seen in Figures 1 to 3, the bore 24b of the sleeve is provided with a helical groove 28 which extends along said bore. The groove 28 extends around and along the axis 25 of the bore of the sleeve. The helical groove 28 extends here from the front face 24c and opens onto the front face 24d. The groove 28 forms a succession of turns spaced apart from each other in the axial direction. The turns of the groove 28 are not contiguous. In other words, two successive turns of the groove 28 are separated from each other by the bore 24b of the sleeve.

[0066] The helical groove 28 extends circumferentially here over four complete turns around the axis 25 of the bore of the sleeve. Alternatively, it is possible to provide a different number of turns while retaining at least one complete turn.

[0067] The helical groove 28 here has in cross section a shape of an arc of a circle oriented inwards. Alternatively, it is possible to provide other shapes, by a groove delimited in the axial direction by two lateral flanks facing each other which have in axial section a rectilinear profile.

[0068] Alternatively, it could also be possible to provide on the outer surface 14a of the outer ring a helical groove of the same type as that provided on the bore 24b of the sleeve.

[0069] The sleeve 24 is advantageously made of a 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. The helical groove 28 can for example be formed by removing material, for example by machining, or by spinning material.

[0070] 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.

[0071] 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.

[0072] 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 and onto the bore 24b of the sleeve 24.

[0073] The insulating lining 26 is annular in shape. The insulating lining 26 extends axially. The insulating lining 26 comprises a cylindrical 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. The bore 26b is in radial contact with the outer surface 14a of the outer ring.

[0074] 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.

[0075] 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 socket.

[0076] 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.

[0077] The insulating lining 26 also comprises a rib 30 extending radially outward from the outer surface 26a and housed inside the groove 28 of the sleeve. The rib 30 is of a shape complementary to the groove 28. The rib 30 therefore has a helical shape along the outer surface 26a of the insulating lining. The rib 30 extends around and along the axis of the outer surface 26a of the insulating lining which is coaxial with the axis X-X'. The rib 30 projects relative to the outer surface 26a of the insulating lining. The rib 30 is formed on the outer surface 26a during the overmolding of the insulating lining 26.

[0078] To manufacture the bearing device, the procedure is as follows.

[0079] In a first step, the bearing 10 and the sleeve 24 equipped with the helical groove 28 are mounted inside a mold which is provided for the overmolding of the insulating lining 26. In this position mounted inside the mold, the sleeve 24 is radially at a distance from the outer ring 14 of the bearing.

[0080] 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. As indicated previously, the rib 30 of the insulating lining promotes the attachment to the sleeve 24 and is formed during this step.

[0081] Finally, the bearing device, which is in the form of a unitary assembly, is extracted from the mold.

[0082] As indicated previously, in this exemplary embodiment, the helical groove 28 of the sleeve extends from the front face 24c and opens onto the front face 24d. Alternatively, it is possible to provide other arrangements. For example, as illustrated in FIGS. 4 and 5, the groove 28 can remain at a distance from the front faces 24c, 24d of the sleeve by being centered in the bore or alternatively by being off-center.

[0083] In the embodiment illustrated in [Fig.6], the bore 24b of the sleeve is further provided with a second helical groove 32 which extends along said bore in an axial direction opposite to that of the first helical groove 28. Starting from the median radial plane of the sleeve 24, the helical groove 32 extends in the direction of the front face 24c and the groove 28 extends in the direction of the front face 24d.

[0084] In this embodiment, the proximal ends of the grooves 28 and 32, i.e. the ends which are located axially on the side of the median radial plane of the sleeve 24, are axially spaced from each other and located axially on either side of said plane. Alternatively, these proximal ends of the grooves 28, 32 could be located on the same side of said plane.

[0085] In the embodiment illustrated in [Fig.7], the proximal ends of the grooves 28, 32 are contiguous and located in the median radial plane of the sleeve 24. Alternatively, the proximal ends of the grooves 28, 32 could also be located on the same side of said plane.

[0086] In the embodiments illustrated in Figures 7 and 8, the grooves 28, 32 are symmetrical with respect to the median radial plane of the sleeve 24. Alternatively, the groove 32 could be different from the groove 28 and have a different pitch and / or helix angle and / or length.

[0087] 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.

[0088] 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. The outer surface of the sleeve is provided with the helical groove. The bore of the sleeve delimits the bore of the bearing device.

[0089] 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 outer surface (24a) and an inner surface (24b) opposite the outer surface and which delimit the radial thickness of said bushing, the insulating lining (26) being overmolded on the second ring (14) of the bearing and at least on one of the outer and inner surfaces of the bushing (24), characterized in that said surface of the bushing (24) is provided with at least one helical groove (28) inside which extends a rib (30) for attaching the complementary shaped insulation trim,said helical groove (28) extending circumferentially over at least one complete turn around the axis (25) of said surface of the sleeve.,

2. A device according to claim 1, wherein said helical groove (28) of the sleeve extends circumferentially over at least two complete turns around the axis of revolution of said surface of the sleeve and forms at least two turns spaced apart in the axial direction.

3. Device according to claim 1 or 2, in which the helical groove (28) of the sleeve is delimited in the axial direction by two facing lateral flanks which have a rectilinear profile in axial section.

4. Device according to any one of the preceding claims, wherein the sleeve (24) comprises two front faces (24c, 24d) delimiting the axial length of said sleeve, said helical groove (28) extending from one of said front faces towards the other front face.

5. Device according to any one of claims 1 to 3, in which the sleeve (24) comprises two front faces (24c, 24d) delimiting the axial length of said sleeve, said helical groove (28) remaining at a distance from said front faces.

6. Device according to any one of the preceding claims, in which the pitch of said helical groove (28) of the sleeve is constant.

7. Device according to any one of claims 1 to 5, in which the pitch of said helical groove (28) of the sleeve is variable.

8. Device according to any one of the preceding claims, wherein said surface of the sleeve (24) is provided with at least one additional helical groove (32) inside which extends a rib for attaching the insulation lining of complementary shape, said additional helical groove (32) extending in an axial direction opposite to the direction of said helical groove (28).

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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