Bearing device with integrated electrical insulation, in particular for an electric motor or an electrical machine

Abstract

The bearing device comprises a bearing 10 provided with a first ring 12 and a second ring 14 which are rotatable relative to each other. The device comprises at least one insulating sleeve 22 which is fixed to the second ring 14 of the bearing and is provided with a bushing 24 and an insulating insert 26 which is inserted radially between the second ring 14 and the bushing 24 and is made of an electrically insulating material. The bushing includes an outer surface 24a and an inner surface 24b that define its radial thickness. The insulating insert 26 is molded onto the second ring 14 of the bearing and onto at least one of the outer or inner surfaces of the bushing 24. The surface of the bushing 24 is provided with at least one helical groove 28, in which a fastening rib 30 of the insulating insert of complementary shape extends.

Description

Technical field of the invention

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

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

[0003] During operation, as the shaft rotates, a different electrical potential may occur between the shaft and the housing of the electric motor or electric machine, generating an electric current between the inner ring of the rolling bearing, which is rigidly connected to the shaft, and the outer ring, which is rigidly connected to the housing.

[0004] The electrical current flowing through the components of the rolling bearing can damage these components, especially the rolling elements and raceways on the inner and outer rings. The electrical discharges can also cause vibrations.

[0005] To overcome 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 rolling elements made of ceramic. This is commonly referred to as a hybrid rolling bearing.

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

[0007] In order to overcome the above-mentioned disadvantages, it is also known to equip the outer ring of the rolling bearing with an insulating sleeve 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] In order to fix the insulating insert to the outer ring and to the bushing without an additional element or specific machining on the outer ring, it is possible to form the insulating insert.

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

[0010] The present invention therefore aims to overcome the above-mentioned disadvantages by proposing a bearing device which has 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 further comprises 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 inserted radially between the second ring of the bearing and the bushing. The insulating insert is made of an electrically insulating material.

[0013] The bushing includes an outer surface and an inner surface opposite to the outer surface that defines the radial thickness of the bushing.

[0014] The insulating insert is molded onto the second ring of the bearing and onto at least one of the outer or inner surfaces of the bushing.

[0015] According to a general feature, the surface of the bushing is provided with at least one helical groove, in which extends a fixing rib of the insulating insert with a complementary shape to the helical groove.

[0016] According to another general feature, the helical groove extends circumferentially over at least one complete revolution around the axis of the surface of the bushing. In other words, the helical groove extends over at least 360° in the circumferential direction.

[0017] This provides a bearing device with integral electrical insulation that is economical compared to conventional hybrid rolling bearings. Furthermore, the device is easy to manufacture and install in the associated electric motor or machine.

[0018] Furthermore, the provision of the helical groove on the bushing allows for effective attachment to the insulating insert, to the extent that the mounting rib is formed in the insulating insert during molding. The risk of relative displacement between the insulating insert and the bushing in the axial and circumferential directions is particularly limited, especially in the case of temperature fluctuations.

[0019] This is made possible by the provision of the helical groove on the bushing, which extends over at least one complete revolution when the axis of the helix is ​​taken into account.

[0020] The “axial direction” means the direction parallel to the axis of the bearing device.

[0021] The term “circumferential direction” means the direction perpendicular to both the axial direction and a radius of the bearing device, in other words the tangent to a circle, the center of which is on the axis of the bearing device.

[0022] The helical groove of the bushing may advantageously extend over at least two complete revolutions around the axis of rotation of the surface of the bushing, ie over at least 720°, to form at least two turns spaced apart from one another in the axial direction.

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

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

[0025] This makes it possible to further improve the attachment of the insulating insert to the socket.

[0026] According to a first embodiment, the helical groove of the bushing is delimited in the radial direction by a base, with the flanks extending therefrom to project toward the outside. In other words, each lateral flank forms an inclination kink relative to the base in its connection area with the base.

[0027] The term “radial direction” means the direction along a radius of the bearing device, i.e. any direction that intersects an axis of the bearing device and is perpendicular to that axis.

[0028] The lateral flanks extend to protrude relative to the base at least radially toward the outside. The lateral flanks may extend to protrude relative to the base in a purely radial direction. This further improves the attachment of the insulating insert to the bushing. As a variant, however, it is possible to provide for the lateral flanks to protrude obliquely relative to the base, i.e., both in the radial and axial directions.

[0029] According to a second embodiment, the helical groove of the bushing may have no base. In this case, the lateral flanks of the groove are connected to each other and extend obliquely.

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

[0031] The bushing may be provided with two end faces that limit its axial length.

[0032] According to a first embodiment, the helical groove extends from one of the end faces toward the other end face. The helical groove can open into the other end face or remain at an axial distance from it.

[0033] According to a second embodiment, the helical groove can remain at a distance from the two end faces of the bushing. In other words, in this case, the helical groove does not open into the end faces of the bushing.

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

[0035] Preferably, the helical groove extends in the radial thickness of the bushing by being blind.

[0036] In a particular embodiment, the surface of the bushing is provided with at least one additional helical groove, wherein a fastening rib of the insulating insert with a complementary shape extends therein, and wherein the additional helical groove extends in the axial direction opposite to the direction of the helical groove.

[0037] This also allows for improved attachment relative to the insulating insert and the bushing. The additional helical groove can extend circumferentially for at least one complete revolution around the axis of the bushing surface, or, as a variant, for at least one complete revolution.

[0038] If the insulating insert is made of a synthetic material or an elastomer, it allows the device to be insensitive to temperature fluctuations.

[0039] In one specific embodiment, the bushing is made of metal. The bushing can therefore be easily machined to a specified 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 a second alternative 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 specific embodiment, the bearing comprises at least one row of rolling elements arranged between the raceways of the first and second rings. The rolling elements can be made of metal.

[0044] The invention further relates to an electric motor comprising a housing, a shaft and at least one bearing device as defined above, which is mounted radially between the housing and the shaft. Short description of the characters

[0045] The present invention will be more clearly understood when considering the detailed description of embodiments given as non-limiting examples and illustrated by the accompanying drawings in which: [ Fig. 1] is a partial view, in axial section, of a bearing device according to an exemplary embodiment of the invention, [ Fig. 2] a perspective view of a bushing of the bearing device of Fig. 1 is, [ Fig. 3] a sectional view of the socket Fig. 2 is, [ Fig. 4] is a perspective view of the bushing of a bearing device according to another exemplary embodiment of the invention, [ Fig. 5] a sectional view of a bushing from Fig. 4 is, [ Fig. 6] is a sectional view of the bushing of a bearing device according to another exemplary embodiment of the invention, and [ Fig. 7] is a sectional view of a bushing of a bearing device according to another exemplary embodiment of the invention. Detailed description of the invention

[0046] The storage device, which is Fig. 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 X-X' 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] As described in more detail below, the bearing device is designed not to conduct electrical currents. The bearing device has integrated electrical insulation.

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

[0049] In the exemplary embodiment shown, the bearing 10 also includes a series of rolling elements 16, in this case balls, radially inserted 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 ensure uniform circumferential spacing of the rollers 16. The bearing 10 can also be provided with sealing rings or sealing flanges.

[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 define 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 oriented radially toward the outer side.

[0052] 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 defining the bore and the outer surface. The outer surface 14a and the bore 14b define the radial thickness of the outer ring 14.

[0053] 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 oriented radially toward the inner side.

[0054] The bearing assembly also includes an electrically insulating sleeve 22 secured to the outer ring 14. The insulating sleeve 22 is secured to the outer surface 14a of the outer ring 14. The insulating sleeve 22 is secured to the outer ring 14.

[0055] The insulating sleeve 22 comprises a bushing 24 and an insulating insert 26, which is inserted radially between the outer ring 14 and the bushing 24. The insulating insert 26 is molded onto the outer ring 14 and the bushing 24.

[0056] The bushing 24 is annular. The bushing 24 extends axially. In this case, the bushing 24 is made from a single piece. The bushing 24 comprises a cylindrical, axial outer surface 24a and a cylindrical bore 24b radially opposite the outer surface 24a, whose axis 25 is coaxial with the axis X-X'. The bore 24b forms the inner surface of the bushing 24.

[0057] The bushing 24 also includes two radially opposite end faces 24c, 24d that radially define the bore and the outer surface. The end faces 24c, 24d define the axial length of the bushing. The outer surface 24a and the bore 24b define the radial thickness of the bushing 24. The outer surface 24a of the bushing defines the outer surface of the bearing device 10. In other words, the outer surface 24a defines the outer diameter of the bearing device 10.

[0058] As in the Fig. As shown in Figures 1 to 3, the bore 24b of the bushing is provided with a helical groove 28 extending along the bore. The groove 28 extends around and along the axis 25 of the bore of the bushing. The helical groove 28, in this case, extends from the end face 24c and opens into the end face 24d. The groove 28 forms a sequence of turns that are spaced apart from one another in the axial direction. The turns of the groove 28 are not adjacent. In other words, two consecutive turns of the groove 28 are separated from one another by the bore 24b of the bushing.

[0059] In this case, the helical groove 28 extends circumferentially over four complete revolutions around the axis 25 of the bushing bore. Alternatively, it is possible to provide a different number of revolutions, while still maintaining at least one complete revolution.

[0060] In this case, the helical groove 28 has a circular arc shape in cross-section, oriented toward the inside. Alternatively, other shapes can be provided by a groove that is delimited in the axial direction by two opposite lateral flanks that have a straight profile in axial section.

[0061] As a variant, it might 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 bush.

[0062] The bushing 24 is advantageously made of metal. The outer surface 24a of the bushing can then be easily machined to a predetermined tolerance if necessary. The bushing 24 is preferably made of steel. The bushing 24 can be obtained from a sheet metal blank by cutting, pressing, and rolling. Alternatively, the bushing 24 can be obtained from a tube or from forged and rolled blanks, or even by sintering and stamping. The helical groove 28 can be formed, for example, by removing material, for example by machining, or even by stamping material.

[0063] The insulating insert 26 is made of an electrically insulating material. The insulating insert 26 can, for example, be made of a synthetic material, such as PEEK or PA46, or of an elastomer, such as rubber.

[0064] The insulating insert 26 is inserted radially between the outer surface 14a of the outer ring and the bore 24b of the bushing. The insulating insert 26 covers the outer surface 14a of the outer ring. In this case, the insulating insert 26 completely covers the outer surface 14a when viewed in the axial and circumferential directions. The insulating insert 26 also covers the bore 24b of the bushing. In this case, the insulating insert 26 also completely covers the bore 24b when viewed in the axial and circumferential directions.

[0065] As mentioned above, the insulating insert 26 is molded onto the outer ring 14 of the bearing and onto the bushing 24. The insulating insert 26 is molded onto the outer surface 14a of the outer ring 14 and onto the bore 24b of the bushing 24.

[0066] The insulating insert 26 has an annular shape. The insulating insert 26 extends axially. The insulating insert comprises a cylindrical axial outer surface 26a, a cylindrical bore 26b radially opposite the outer surface 26a, and two radially opposite end faces 26c, 26d axially delimiting the bore and the outer surface. The end faces 26c, 26d axially delimit the insulating insert 26. The outer surface 26a and the bore 26b delimit the radial thickness of the insulating insert 26. The outer surface 26a is in radial contact with the bore 24b. The bore 26b is in radial contact with the outer surface 14a of the outer ring.

[0067] In the exemplary embodiment shown, the sides 14c, 26c, 24c and 14d, 26d, 24d of the outer ring, the insulating insert and the bushing are each coplanar.

[0068] Alternatively, other arrangements are also possible. For example, the insulating insert 26 could have a reduced axial dimension and be axially recessed from the surfaces 14c, 14d of the outer ring. Alternatively, the insulating insert 26 could have a larger axial dimension and extend to project axially from the sides 14c, 14d of the outer ring. In this case, the insulating insert 26 can at least partially cover these sides 14c, 14d. As a variant, the insulating insert 26 could at least partially cover the sides 24c, 24d of the bushing.

[0069] In a further alternative or in combination, the bushing 24 could extend to project axially from the insulating insert 26 relative to the sides 26c and 26d, or be axially recessed from the sides.

[0070] The insulating insert 26 also includes a rib 30 extending from the outer surface 26a toward the outside and housed within the groove 28 of the bushing. The rib 30 has a complementary shape to the groove 28. The rib 30 then has a helical shape along the outer surface 26a of the insulating insert. The rib 30 extends around and along the axis of the outer surface 26a of the insulating insert, which is coaxial with the axis X-X'. The rib 30 extends to project relative to the outer surface 26a of the insulating insert. The rib 30 is formed on the outer surface 26a during the molding of the insulating insert 26.

[0071] To produce the bearing device, the invention is as follows.

[0072] In a first step, the bearing 10 and the bushing 24, which is provided with the helical groove, are mounted in a mold intended for forming the insulating insert 26. In this position, mounted in the mold, the bushing 24 is radially spaced from the outer ring 14 of the bearing.

[0073] Then, during a second subsequent step, the insulating insert 26 is molded onto both the outer ring 14 of the bearing and the bushing 24. As stated above, the rib 30 of the insulating insert is formed in this step, which promotes attachment to the bushing 24.

[0074] Finally, the bearing device, which has the form of a single assembly, is removed from the mold.

[0075] As indicated above, the helical groove 28 of the bushing in this exemplary embodiment extends from the end face 24c and terminates in the end face 24d. Alternatively, it is possible to provide other arrangements. For example, as shown in the Fig. 4 and Fig. 5, the groove 28 can maintain a distance from the end faces 24c, 24d of the bushing by being centered in the bore or alternatively by being decentered.

[0076] In the exemplary, in Fig. In the embodiment shown in Figure 6, the bore 24b of the bushing is also provided with a second helical groove 32 extending along the bore in the axial direction opposite to that of the first helical groove 28. Starting from the radial center plane of the bushing, the helical groove 32 extends in the direction of the end face 24c, and the groove 28 extends in the direction of the end face 24d.

[0077] In this exemplary embodiment, the proximal ends of the grooves 28 and 32, i.e., the ends located axially on the side of the radial center plane of the bushing 24, are axially spaced from each other and are axially disposed on each side of the plane. Alternatively, the proximal ends of the grooves 28, 32 could be disposed on the same side of the plane.

[0078] In the exemplary, in Fig. In the embodiments illustrated in Figure 7, the proximal ends of the helical grooves 28, 32 are adjacent and are arranged in the radial center plane of the sleeve 24. Alternatively, the proximal ends of the grooves 28, 32 could be arranged on the same side of the plane.

[0079] In the exemplary, in the Fig. 7 and Fig.8, the grooves 28, 32 are symmetrical relative to the radial center plane of the bushing 24. Alternatively, the groove 32 could be different from the groove 28 and have a different pitch and / or lead angle and / or length.

[0080] In the illustrated embodiments, the first ring 12 of the bearing is the inner ring and the second ring 14 is the outer ring onto which the insulating insert 26 is molded.

[0081] Alternatively, it is possible to provide a reverse arrangement, in which the second ring 14, onto which the insulating insert 26 is molded, is the inner ring. In this case, the insulating sleeve is arranged in the bore 12a of the inner ring. The insulating insert is thus radially inserted between the bore 12a of the inner ring and the outer surface of the bushing. The insulating insert is molded onto the inner ring and at least onto the outer surface of the bushing. The outer surface of the bushing is provided with the helical groove. The bore of the bushing defines the bore of the bearing device.

[0082] In the described exemplary embodiments, the bearing of the device is provided with a single row of rolling elements. As a variant, the bearing can be provided with multiple rows of rolling elements. Additionally, the rolling bearing can include other types of rolling elements besides balls, for example, rollers. In a further variant, the bearing can be a plain bearing that is not provided with rolling elements.

Claims

[1] A bearing device comprising a bearing (10) provided with a first ring (12) and a second ring (14) which are rotatable relative to each other, and an insulating sleeve (22) which is fixed to the second ring (14) and is provided with a bushing (24) and an insulating insert (26) which is radially inserted between the second ring (14) and the bushing (24) and is made of an electrically insulating material, wherein the bushing comprises an outer surface (24a) and an inner surface (24b) which is opposite to the outer surface and which limits the radial thickness of the bushing, and wherein the insulating insert (26) is formed on the second ring (14) of the bearing and on at least one of the outer or inner surfaces of the bushing (24), characterized byin that the surface of the bushing (24) is provided with at least one helical groove (28), wherein a fastening rib (30) of the insulating insert with a complementary shape extends therein, and wherein the helical groove (28) extends circumferentially over at least one complete revolution around the axis (25) of the surface of the bushing. [2] The device of claim 1, wherein the helical groove (28) of the bushing extends circumferentially over at least two complete revolutions about the axis of rotation of the surface of the bushing and forms at least two turns spaced apart in the axial direction. [3] Device according to claim 1 or 2, wherein the helical groove (28) of the bushing is limited in the axial direction by two opposite side flanks having a rectangular profile in axial section. [4] Device according to one of the preceding claims, wherein the bushing (24) comprises two end faces (24c, 24d) which limit the axial length of the bushing, the helical groove (28) extending from one of the end faces to the other end face. [5] Device according to one of claims 1 to 3, wherein the bushing (24) comprises two end faces (24c, 24d) which limit the axial length of the bushing, the helical groove (28) remaining at a distance from the end faces. [6] Device according to one of the preceding claims, wherein the pitch of the helical groove (28) of the bushing is constant. [7] Device according to one of claims 1 to 5, wherein the pitch of the helical groove (28) of the bushing is variable. [8] Device according to one of the preceding claims, wherein the surface of the bushing (24) is provided with at least one additional helical groove (32) extending therein with a fastening rib of the insulating insert of complementary shape, the additional helical groove (32) extending in an axial direction opposite to the direction of the helical groove (28). [9] Device according to one of the preceding claims, wherein the bushing (24) is made of metal. [10] Electric motor comprising a housing, a shaft and at least one bearing device according to one of the preceding claims, which is mounted radially between the housing and the shaft.

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