Bearing device with integrated electrical insulation, in particular for an electric machine or motor, and associated manufacturing method

Abstract

The bearing device comprises a bearing 10, which is provided with a first ring 12 and a second ring 14. The device comprises at least one insulating sleeve 26, which is attached to the second ring 14 and is provided with a bushing 28 and with an insulating insert 30 made of an electrically insulating material. The insulating insert is overmolded onto the second ring 14 and onto at least one of the outer and inner surfaces of the bushing 28. The surface of the bushing is provided with at least one first slot 36 in which a first fastening rib 40 of the insulating insert extends with complementary shape, wherein the first slot 36 extends circumferentially about a first axis which is radially offset with respect to the axis 29 of the surface of the bushing.

Description

Technical field of the invention

[0001] The present invention relates to the field of bearings, which are used in particular in electric motors, electrical machines and related devices. State of the art

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

[0003] During operation, when the shaft rotates, a difference in electrical potential can occur between the shaft and the housing of the electric machine or motor, generating an electric current between the inner ring of the rolling bearing connected to the shaft and the outer ring connected to the housing.

[0004] The electric current flowing through the components of the rolling bearing can destroy these components, especially the rolling elements and raceways formed on the inner and outer rings. The electric shocks can also cause vibrations.

[0005] To eliminate these disadvantages, it is known to replace the bearing's rolling elements, which are made of the same steel as the inner and outer rings, with ceramic rolling elements. This type of bearing is commonly referred to as a "hybrid rolling bearing".

[0006] However, such hybrid roller bearings are relatively expensive.

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

[0008] To attach the insulating insert to the outer ring and the bushing without additional components or special machining of the outer ring, it is possible to overmold the insulating insert.

[0009] However, with such a solution, a relative separation of the insulating insert and the bushing can occur during operation.

[0010] The present invention therefore aims to overcome the aforementioned disadvantages by providing a storage device with a 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 which are rotatable relative to each other.

[0012] The device also includes at least one insulating sleeve attached to the second ring of the bearing. The insulating sleeve is provided with a bushing and an insulating insert, which is radially inserted between the second ring of the bearing and the bushing. The insulating insert is made of electrically insulating material.

[0013] The bushing comprises a cylindrical outer surface and a cylindrical inner surface on the opposite side from the outer surface, which define the radial thickness of the bushing. The insulating insert is overmolded onto the second ring of the bearing and onto at least one of the outer and inner surfaces of the bushing.

[0014] According to a general characteristic, the surface of the socket is provided with at least one first slot in which a first fastening rib of the insulating insert of complementary shape extends.

[0015] According to another general characteristic, the first slot extends circumferentially around a first axis that is radially offset with respect to the axis of the socket surface.

[0016] This results in a bearing device with integrated electrical insulation, which is more economical compared to conventional hybrid rolling bearings. Furthermore, the device is easy to manufacture and fits into the associated electric machine or motor.

[0017] Furthermore, the provision of the slot in the surface of the socket enables a firm connection with the insulating insert, insofar as the fastening rib is formed in the latter during overmolding.

[0018] The risk of relative movements between the insulating insert and the bushing in axial and circumferential directions is particularly limited, especially in the case of temperature fluctuations, due to the decentering of the axis of the slot relative to the axis of the aforementioned surface of the bushing.

[0019] The term "axial direction" refers to the direction that is parallel to the axis of the bearing device.

[0020] The term "circumferential direction" means the direction that is perpendicular to both the axial direction and the radius of the bearing device, in other words the tangent to a circle whose center is on the axis of the bearing device.

[0021] In one embodiment, the first slot in the surface of the socket is annular. Alternatively, the first slot could extend circumferentially around the first axis through an angular region of less than 360°.

[0022] Preferably, the first slot in the surface of the bushing is located in the axial median plane or alternatively in the radial median plane of the bushing.

[0023] The bushing can comprise two opposing radial end faces that define its axial length. The first slot in the bushing's surface can be located at a distance from the end faces. Alternatively, the first slot can open axially onto one of the end faces.

[0024] In a particular embodiment, the surface of the socket is provided with at least one second slot in which a second fastening rib of the insulating insert of complementary shape extends.

[0025] According to a first embodiment, the second slot extends circumferentially around a second axis, which is radially offset with respect to the axis of the surface of the bushing.

[0026] The second axis of the second slot can be radially offset on the same side as the first axis of the first slot with respect to the axis of the bushing surface. Alternatively, the second axis of the second slot can be radially offset on the opposite side from the first axis of the first slot with respect to the axis of the bushing surface.

[0027] According to a second embodiment, the second slot extends circumferentially around the second axis, which is coaxial to the axis of the surface of the bushing.

[0028] The second slot can be axially spaced from the first slot. Alternatively, the first and second slots can be contiguous.

[0029] In one embodiment, the second slot in the bushing surface is annular. Alternatively, the second slot could extend circumferentially around the second axis through an angular region of less than 360°. The second slot can be located at a distance from the end faces of the bushing. Alternatively, the second slot can open axially at one of the end faces.

[0030] In one embodiment, the first slot and / or the second slot can have the shape of a circular arc in cross-section.

[0031] In another embodiment, the first slot and / or the second slot can be bounded in the axial direction by two lateral flanks that are opposite each other and have a straight profile in axial section.

[0032] This makes it possible to further improve the attachment of the insulating insert to the socket.

[0033] According to a first embodiment, the first slot and / or the second slot is bounded radially by a base from which the flanks project outwards. In other words, each lateral flank forms a change in inclination with respect to the base in the area where it is attached to the base.

[0034] The term “radial direction” means the direction along a radius of the bearing device, i.e. any direction that intersects the axis of the bearing device and is perpendicular to that axis.

[0035] The lateral flanks project from the base at least along the radial direction. The lateral flanks can project from the base along a purely radial direction. This further improves the attachment of the insulating insert to the socket. In one variant, however, the lateral flanks can project obliquely from the base, i.e., both radially and axially.

[0036] According to a second embodiment, the first slot and / or the second slot may not have a bottom. In this case, the lateral flanks of the first slot and / or the second slot meet and may, for example, extend diagonally.

[0037] Regardless of the design of the first slot and / or the second slot, with or without a bottom, if the lateral flanks extend obliquely, these flanks can be symmetrical or asymmetrical with respect to a radial plane, as seen in the axial section.

[0038] If the insulating insert is made of synthetic or elastomeric material, this makes the device less sensitive to temperature fluctuations.

[0039] In one particular embodiment, the bushing is made of a metal material. The bushing can therefore be easily machined to a predetermined radial tolerance.

[0040] In one embodiment, the insulating insert covers the entire surface of the bushing. In this case, the insulating insert completely covers the surface of the bushing in both the axial and circumferential directions.

[0041] According to a first embodiment, the bushing defines the outer surface of the device. In this case, the second ring is the outer ring of the bearing.

[0042] According to an alternative second embodiment, the bushing defines the inner surface of the 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 series of rolling elements arranged between the raceways of the first and second rings. The rolling elements may be made of a metallic material.

[0044] The invention also relates to an electric motor comprising a housing, a shaft and at least one bearing device as defined above and mounted radially between the housing and the shaft. Brief character description

[0045] The present invention will be better understood by considering the detailed description of embodiments listed as a completely non-limiting example and illustrated by the accompanying drawings, in which: [ Fig. 1] a half view, in axial section, of a bearing device according to an exemplary embodiment of the invention is, [ Fig. 2] a sectional view of a bushing of the bearing device made of Fig. 1 is, [ Fig. 3] a sectional view along line III-III in Fig. 2 is, [ Fig. 4] a sectional view along line IV-IV in Fig. 3 is, [ Fig. 5] a sectional view of a bushing of a bearing device according to another exemplary embodiment of the invention is, [ Fig. 6] a sectional view along line VI-VI in Fig. 5 is, [ Fig. 7] a sectional view along line VII-VII in Fig. 5 is and [ Fig. 8] a sectional view along line VIII-VIII in Fig. 6 is. Detailed description of the invention

[0046] The in Fig. The bearing device shown in Figure 1 comprises a bearing 10 provided with a first ring 12 and a second ring 14, which are rotatable relative to each other about the axis XX' of the bearing. In the exemplary embodiment shown, the first ring 12 is the inner ring of the bearing and the second ring 14 is the outer ring of the bearing.

[0047] The bearing device was designed so that it does not conduct electrical currents. The bearing device has integrated electrical insulation.

[0048] The inner ring 12 and the outer ring 14 of the bearing are concentric and extend axially along the axis XX' of the bearing. The inner ring 12 and the outer ring 14 are made of steel. The rings are solid.

[0049] In the illustrated exemplary embodiment, the bearing 10 also includes a series of rolling elements 16, in this case balls, which are inserted 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 to maintain the uniform circumferential spacing of the rolling elements 16. The bearing 10 may also be equipped with seals or flange rings.

[0050] The inner ring 12 comprises a cylindrical bore 12a, a cylindrical axial outer surface 12b radially opposite the bore, and two opposing radial end faces (without reference numerals) that axially delimit 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.

[0051] The inner ring 12 also includes an inner raceway 18 for the rolling elements 16, which is formed on the outer surface 12b. The raceway 18 is directed radially towards the outside.

[0052] The outer ring 14 comprises a cylindrical, axial outer surface 14a, a cylindrical bore 14b radially opposite the outer surface 14a, and two opposing radial end faces 14c, 14d that axially delimit the bore. The outer surface 14a and the bore 14b define the radial thickness of the outer ring 14. The bore 14b has a stepped shape.

[0053] In the illustrated exemplary embodiment, the outer surface 14a of the ring has two different diameters. Alternatively, the outer surface 14a could have a single diameter.

[0054] The outer ring 14 also includes an outer raceway 20 for the rolling elements 16, which is formed on the bore 14b. The raceway 20 is directed radially inwards.

[0055] In the illustrated exemplary embodiment, a groove 22 is formed on the end face 14c of the outer ring. The groove 22 is axially oriented towards the outside of the outer ring and is open. The groove 22 has a bottom that is axially offset towards the inside of the ring with respect to the end face 14c. The bottom of the groove 22 forms a shoulder. For the sake of simplifying manufacturing, the bottom of the groove 22 extends radially in this case. The groove 22 is annular in this case.

[0056] Similarly, a groove 24 is formed on the end face 14d of the outer ring. The groove 24 is axially oriented towards the outside of the outer ring and is open. The groove 24 has a bottom that is axially offset towards the inside of the ring relative to the end face 14d. The bottom of the groove 24 forms a shoulder. For the sake of simplicity in manufacturing, the bottom of the groove 24 extends radially. In this case, the groove 24 is annular. The grooves 22 and 24 are mutually symmetrical with respect to a radial center plane of the outer ring. The grooves 22 and 24 axially delimit the outer surface 14a. Alternatively, it would be possible to omit the grooves 22 and 24.

[0057] The bearing assembly also includes an electrically insulating sleeve 26, which is attached to the outer ring 14. The insulating sleeve 26 is attached to the outer surface 14a of the outer ring 14. The insulating sleeve 26 is secured to the outer ring 14.

[0058] The insulating sleeve 26 comprises a bushing 28 and an insulating insert 30, which is inserted radially between the outer ring 14 and the bushing 28. The insulating insert 30 is overmolded onto the outer ring 14 and the bushing 28.

[0059] The bushing 28 has an annular shape. The bushing 28 of axis XX' extends axially. In this case, the bushing 28 is formed from a single piece. Alternatively, the bushing 28 could be made from several parts that abut one another, for example, two identical parts. The bushing 28 comprises a cylindrical, annular, axial outer surface 28a, and a cylindrical, annular, axial bore 28b, which is radially located on the side opposite the outer surface 28a. The bore 28b forms the inner surface of the bushing 28. The bore 28b is oriented radially inwards, i.e., towards the outer ring 14. The axis 29 of the bore 28b is coaxial with the axis X-X'.

[0060] The bushing 28 also includes two opposing radial end faces 28c, 28d, which axially define the bore and the outer surface. The end 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.

[0061] In the illustrated exemplary embodiment, the end faces 28c, 28d of the bushing are each coplanar to the end faces 14c, 14d of the outer ring. Alternatively, other arrangements could be provided. For example, the bushing 28 could have a smaller or larger axial dimension and be axially recessed from the end faces 14c, 14d of the outer ring, or project from these faces.

[0062] As in the Fig. 1, Fig. 2 and Fig. As can be seen in Figure 4, the bore 28b in the bushing is provided with first and second slots 36, 38, which are axially spaced and extend circumferentially. Each slot 36, 38 is directed radially towards the insulating insert 30 and the outer ring 14 of the bearing, i.e., radially towards the inside.

[0063] In the illustrated exemplary embodiment, each slot 36, 38 is annular. Alternatively, at least one of the two slots 36, 38 could not extend over 360°.

[0064] Each slot 36, 38 is bounded axially by two opposing lateral flanks, which have a straight profile in axial section and are connected to each other by an axial base. Alternatively, other shapes are possible, for example, slots with a cross-sectional shape resembling an arc pointing inwards. The base of each slot 36, 38 is offset radially outwards with respect to the bore 28b in the bushing. The slots 36, 38 extend into the radial thickness of the bushing 28 and are blind.

[0065] The slot 36 extends circumferentially around a first axis 36a, which is radially offset with respect to the axis 29 of the bore in the bushing. In the illustrated exemplary embodiment, the axis 36a of the slot is located in the axial center plane Pa of the bushing 28. Alternatively, the axis 36a could be located in the radial center plane Pr of the bushing 28.

[0066] Similarly, the slot 38 extends circumferentially around a second axis 38a, which is radially offset with respect to the axis 29 of the bore in the bushing. In this case, the axis 38a is coaxial with the axis 36a. The axes 36a and 38a are located on the same side of the axis 29 of the bore 28b in the bushing.

[0067] In the illustrated exemplary embodiment, the slots 36, 38 in the bore 28b in the bushing are identical to each other. Alternatively, the slots 36, 38 could, for example, have different diameters and / or different widths.

[0068] In one variant, it would also be possible to provide at least one slot of the same type in the outer surface 14a of the outer ring as those provided in the bore 28b of the bushing.

[0069] The bushing 28 is advantageously made of a metal material. The outer surface 28a of the bushing can therefore, if necessary, be easily machined to a predetermined radial tolerance. Preferably, the bushing 28 is made of steel. The bushing 28 can be obtained from a sheet blank by cutting, pressing, and roll forming. Alternatively, the bushing 28 can also be produced from a tube or from a forged and / or rolled blank, or by sintering and stamping. The slots 36, 38 can be obtained, for example, by removing material, such as by machining, or by pressing material back into the blank.

[0070] The insulating insert 30 is made of an electrically insulating material. The insulating insert 30 can be made, for example, of a synthetic material such as PEEK or PA46, or of an elastomeric material such as rubber.

[0071] The insulating insert 30 is inserted radially between the outer surface 14a of the outer ring and the bore 28b in the bushing. The insulating insert 30 covers the outer surface 14a of the outer ring. In this case, the insulating insert 30 completely covers the outer surface 14a in both the axial and circumferential directions. The insulating insert 30 also covers the grooves 22 and 24 in the outer ring. The insulating insert 30 also covers the bore 28b in the bushing. In this case, the insulating insert 30 completely covers the bore 28b in both the axial and circumferential directions.

[0072] As stated above, the insulating insert 30 is overmolded onto the outer ring 14 of the bearing and onto the bushing 28. The insulating insert 30 is overmolded onto the outer surface 14a of the outer ring 14 and onto the bore 28b in the bushing 28.

[0073] The insulating insert 30 has an annular shape. The insulating insert 30 extends axially. The insulating insert 30 comprises a cylindrical axial outer surface 30a, a cylindrical bore 30b radially opposite the outer surface 30a, and two opposing radial end faces 30c, 30d that axially delimit the bore and the outer surface. The radial end faces 30c, 30d delimit the axial length of the insulating insert 30. The outer surface 30a and the bore 30b delimit the radial thickness of the insulating insert 30. The outer surface 30a is in radial contact with the bore 28b in the bushing. The bore 30b is in radial contact with the outer surface 14a of the outer ring and with the grooves 22, 24. The bore 30 has a stepped shape.

[0074] In the exemplary embodiment shown, the surfaces 14c, 30c, 28c and 14d, 30d, 28d of the outer ring, the insulating insert and the bushing are each coplanar.

[0075] Alternatively, other arrangements are possible. For example, the insulating insert 30 could have a smaller axial dimension and be axially recessed from surfaces 14c, 14d of the outer ring. Alternatively, the insulating insert 30 could have a larger axial dimension and project axially from surfaces 14c, 14d of the outer ring. In this case, the insulating insert 30 can at least partially cover these surfaces 14c, 14d. In one variant, the insulating insert 30 could at least partially cover surfaces 28c, 28d of the bushing.

[0076] Alternatively, or in combination, the bushing 28 could project axially from the insulating insert 30 with respect to the surfaces 30c and 30d, or be axially recessed from these surfaces.

[0077] The insulating insert 30 also includes a first and second rib 40, 42, which extend radially from the outer surface 30a towards the outside, and each is accommodated in the first and second slots 36, 38 in the bushing. Each rib 40, 42 projects from the outer surface 30a of the insulating insert. Each rib 40, 42 has a shape that is complementary to that of the associated slot 36, 38. Each rib 40, 42 therefore has a radial dimension projecting from the outer surface 30a that changes along the circumferential direction. Each rib 40, 42 is formed on the outer surface 30a during the overmolding of the insulating insert 30.

[0078] The following procedure is followed to manufacture the storage device.

[0079] In a first step, the bearing 10 and the bushing 28, which is provided with the first and second slots 36, 38, are fixed in a mold designed for overmolding the insulating insert 30. In this position in the mold, the bushing 28 is radially spaced from the outer ring 14 of the bearing.

[0080] Then, during a subsequent second step, the insulating insert 30 is overmolded onto both the outer ring 14 of the bearing and the bushing 28. As indicated above, the ribs 40, 42 of the insulating insert are formed during this step.

[0081] Finally, the storage device, which is in the form of a single, unified whole, is removed from the mold.

[0082] The in the Fig.The exemplary embodiment shown in Figures 5 to 8, in which identical elements bear the same reference numerals, differs from the first example in that the axis 38a of the slot 38 in the bore in the bushing is radially offset from the axis 36a of the slot 36 with respect to the axis 29 of the bore. The axes 36a and 38a are located on both sides of the axis 29 of the bore 28b in the bushing.

[0083] In this case, axes 36a and 38a are located in the axial center plane Pa of the bushing. Alternatively, axes 36a and 38a could be located in the radial center plane Pr of the bushing 28.

[0084] In the illustrated exemplary embodiment, the bore in the bushing is provided with two slots 36, 38. Alternatively, it would be possible to provide a single slot or at least three slots in the bore in the bushing.

[0085] In the exemplary embodiment shown, the first ring 12 of the bearing is the inner ring, and the second ring 14, onto which the insulating insert is formed, is the outer ring.

[0086] Alternatively, a reverse arrangement is possible in which the second ring 14, onto which the insulating insert 30 is formed, is the inner ring. In this case, the insulating sleeve is located in the bore 12a in the inner ring. The insulating insert is then inserted radially between the bore 12a in the inner ring and the outer surface of the bushing. The insulating insert is overmolded onto the inner ring and at least onto the outer surface of the bushing. The outer surface of the bushing is provided with the slot(s) whose axis(es) are radially offset with respect to the axis of the cylindrical outer surface. The bore in the bushing delimits the bearing arrangement.

[0087] In the described exemplary embodiment, the bearing of the device is provided with a single row of rolling elements. In one variant, the bearing can be provided with multiple rows of rolling elements. Furthermore, the rolling bearing can include elements other than balls, such as rollers. In another variant, the bearing can be a plain bearing without rolling elements.

Claims

[1] Bearing device comprising a bearing (10) having a first ring (12) and a second ring (14) rotatable relative to each other, and an insulating sleeve (26) attached to the second ring (14) of the bearing and provided with a bushing (28) and with an insulating insert (30) inserted radially between the second ring (14) and the bushing (28) and made of an electrically insulating material, wherein the bushing comprises a cylindrical outer surface (28a) and a cylindrical inner surface (28b) on the side opposite the outer surface, which define the radial thickness of the bushing, wherein the insulating insert is 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 by, that the surface of the bushing (28) is provided with at least one slot (36) in which a first fastening rib (40) of the insulating insert extends with complementary shape, wherein the first slot (36) extends circumferentially about a first axis (36a) which is radially offset with respect to the axis (29) of the surface of the bushing. [2] Device according to claim 1, wherein the first slot (36) in the surface of the bushing is annular. [3] Device according to claim 1 or 2, wherein the first slot (36) is located in the surface of the bushing in the axial median plane (Pa) or in the radial median plane (Pr) of the bushing (28). [4] Device according to one of the preceding claims, wherein the bushing (28) comprises two end faces (28c, 28d) which limit the axial length of the bushing, wherein the first slot (36) in the surface of the bushing is at a distance from the end faces. [5] Device according to one of the preceding claims, wherein the surface of the bushing (28) is provided with at least one second slot (38) in which a second fastening rib (42) of the insulating insert extends with complementary shape, wherein the second slot (38) extends circumferentially about a second axis (38a) which is radially offset with respect to the axis (29) of the surface of the bushing. [6] Device according to claim 5, wherein the second axis (38a) of the second slot is radially offset on the same side as the first axis (36a) of the first slot with respect to the axis (29) of the surface of the bushing. [7] Device according to claim 5, wherein the second axis (38a) of the second slot is radially offset on the opposite side from the first axis (36a) of the first slot with respect to the axis (29) of the surface of the bushing. [8] Device according to one of the preceding claims, wherein the bushing (28) is made of a metal material. [9] Electric motor comprising a housing, a shaft and at least one bearing device according to any one of claims 1 to 8, which is mounted radially between the housing and the shaft.

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