Bearing devices with integrated electrical insulation, particularly for electric motors or machines, and associated manufacturing processes

Abstract

[Bearing device with integrated electrical insulation, particularly for electric motors or machines, and associated manufacturing processes] The bearing device comprises a bearing 10 having a first ring 12 and a second ring 14. The device includes at least one insulating sleeve 26 mounted on the second ring 14 and having a bushing 28 and an insulating lining 30 made of electrically insulating material. The insulating lining is overmolded onto the second ring 14 and at least onto one of the outer and inner surfaces of the bushing 28. Said bushing surface has at least one first groove 36 within which extends a first rib 40 for attaching the insulating lining, which has a complementary shape. Said first groove 36 extends circumferentially around a first axis that is radially offset with respect to the axis 29 of said bushing surface. Reference: Figure 1

Description

Title of the invention: Electrically insulated bearing device, particularly for electric motors or machines, and associated manufacturing processes. Technical field of the invention

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

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

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

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

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

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

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

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

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

[0010] The present invention therefore aims to remedy the aforementioned drawbacks by proposing a bearing device of simple and economical design. 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 bearing ring. The insulating sleeve is provided with a bushing and an insulating gasket interposed radially between the second bearing ring and the bushing. The insulating gasket is made of electrically insulating material.

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

[0014] According to a general characteristic, said surface of the socket is provided with at least one first groove inside which extends a first rib for attaching the insulation lining of complementary shape.

[0015] According to another general feature, said first groove extends circumferentially around a first axis which is offset radially with respect to the axis of said surface of the socket.

[0016] Thus, an economical integrated electrically insulated bearing device is available compared to conventional hybrid rolling bearings. Furthermore, the device is easy to manufacture and assemble in the associated motor or electrical machine.

[0017] Furthermore, the provision of said groove on said surface of the socket allows for good bonding with the insulation lining insofar as said gripping rib is formed inside it during overmolding.

[0018] The risk of relative displacements between the insulation lining and the sleeve in the axial and circumferential directions is particularly limited, especially during temperature variations, given the off-centering of the groove axis relative to the axis of said sleeve surface.

[0019] By “axial direction”, we mean the direction parallel to the axis of the bearing device.

[0020] By “circumferential direction”, we mean the direction that is perpendicular to both 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.

[0021] In one embodiment, said first groove of said socket surface is annular. Alternatively, said first groove could extend circumferentially around said first axis over an angular sector of less than 360°.

[0022] Preferably, the first groove of said socket surface is located in the median axial plane, or alternatively in the median radial plane of said socket.

[0023] The sleeve may comprise two opposing radial front faces that define the axial length of said sleeve. Said first groove of said surface of the sleeve may remain at a distance from said front faces. Alternatively, said first groove may open axially onto one of the front faces.

[0024] In a particular embodiment, said socket surface is provided with at least a second groove inside which extends a second rib for attaching the insulation lining of complementary shape.

[0025] According to a first design, said second groove extends circumferentially around a second axis which is offset radially with respect to the axis of said surface of the socket.

[0026] The second axis of the second groove may be radially offset on the same side as the first axis of the first groove relative to the axis of said socket surface. Alternatively, the second axis of the second groove may be radially offset on the opposite side to the first axis of the first groove relative to the axis of said socket surface.

[0027] According to a second design, said second groove extends circumferentially around the second axis which is coaxial with the axis of said surface of the socket.

[0028] Said second groove may be axially spaced from said first groove. Alternatively, said first and second grooves may be contiguous.

[0029] In one embodiment, said second groove of said sleeve surface is annular. Alternatively, said second groove could extend circumferentially around said second axis over an angular sector of less than 360°. Said second groove may remain at a distance from the front faces of the sleeve. Alternatively, said second groove may open axially onto one of the front faces.

[0030] In one embodiment, said first groove and / or said second groove may have in cross-section a circular arc shape.

[0031] In another embodiment, said first groove and / or said second groove may be delimited in the axial direction by two opposing lateral flanks which have a straight profile in axial section.

[0032] This further increases the grip of the insulation lining on the socket.

[0033] According to a first design, said first groove and / or said second groove is delimited in the radial direction by a base from which the sides project outwards. In other words, each lateral side forms a break in slope with respect to the base in its area of ​​connection with said base.

[0034] 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.

[0035] The side wings extend beyond the base at least in the radial direction. The side wings can extend beyond the base in a purely radial direction. This further improves the grip of the insulation lining on the socket. Alternatively, however, it is possible to have the side wings extend obliquely beyond the base, that is, both in the radial direction and also in the axial direction.

[0036] According to a second design, said first groove and / or said second groove may not have a bottom. In this case, the lateral sides of said first groove and / or said second groove connect with each other and may, for example, extend obliquely.

[0037] Regardless of the design of said first groove and / or said second groove with or without bottom, when the lateral flanks extend obliquely, these flanks, seen in axial section, can be symmetrical considering a radial plane or asymmetrical.

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

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

[0040] In one embodiment, said insulating lining covers the entire surface of said socket. In this case, said insulating lining completely covers said surface of the socket in the axial direction and in the circumferential direction.

[0041] According to a first conception, the sleeve delimits the outer surface of said device. In this case, the second ring is the outer ring of the bearing.

[0042] According to a second alternative design, the sleeve defines the inner surface of said device. In this case, the second ring is the inner ring of the bearing.

[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 above and mounted radially between the casing and the shaft. Brief description of the figures

[0045] The present invention will be better understood upon study of the detailed description of embodiments, taken by way of non-limiting examples and illustrated by the accompanying drawings in which:

[0046] [Fig-1] is a half axial cross-sectional view of a bearing device according to an example of the realization of the invention,

[0047] [Fig.2] is a cross-sectional view of a bushing of the bearing device of [Fig.1],

[0048] [Fig.3] is a cross-sectional view along axis III-III of [Fig.2],

[0049] [Fig.4] is a cross-sectional view along axis IV-IV of [Fig.3],

[0050] [Fig. 5] is a cross-sectional view of a bushing of a bearing device according to another example of an implementation of the invention,

[0051] [Fig.6] is a cross-sectional view along axis VI-VI of [Fig.5],

[0052] [Fig.7] is a cross-sectional view along axis VII-VII of [Fig.5], and

[0053] [Fig.8] is a cross-sectional view along axis VIII-VIII of [Fig.6]. Detailed description of the invention

[0054] The bearing device illustrated in [Fig. 1] comprises a bearing 10 provided with a first ring 12 and a second ring 14 which are able to rotate relative to each other about the axis X-X' of the bearing. In the illustrated embodiment, the first ring 12 is the inner ring of the bearing and the second ring 14 is the outer ring.

[0055] The bearing device is designed so as not to conduct electric currents. The bearing device has integrated electrical insulation.

[0056] The inner ring 12 and outer ring 14 of the bearing are concentric and extend axially along the X-X' axis of the bearing. The inner ring 12 and outer ring 14 are made of steel. The rings are of the solid type.

[0057] In the illustrated embodiment, the bearing 10 also includes a row of rolling elements 16, here balls, interposed radially between the inner ring 12 and the outer ring 14. The rolling elements 16 are made of steel. The bearing 10 also includes a cage 17 for maintaining the regular circumferential spacing of the rolling elements 16. The bearing 10 can further be equipped with seals or sealing flanges.

[0058] The inner ring 12 comprises a cylindrical bore 12a, an axial cylindrical outer surface 12b radially opposed to the bore, and two opposing radial front faces (not referenced) axially delimiting the bore and the outer surface. The bore 12a and the outer surface 12b define the radial thickness of the inner ring 12. The bore 12a forms the inner surface of the inner ring.

[0059] The inner ring 12 further includes an inner raceway 18 for the rolling elements 16 which is formed on the outer surface 12b. The raceway 18 is directed radially outwards.

[0060] The outer ring 14 comprises a cylindrical axial outer surface 14a, a cylindrical bore 14b radially opposed to the outer surface 14a, and two Opposing radial front faces 14c, 14d axially define 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.

[0061] In the illustrated embodiment, the outer surface 14a of the ring has two distinct diameters. Alternatively, the outer surface 14a could have a single diameter.

[0062] The outer ring 14 further includes an external raceway 20 for the rolling elements 16 which is formed on the bore 14b. The raceway 20 is directed radially inwards.

[0063] In the illustrated embodiment, a groove 22 is formed on the front face 14c of the outer ring. The groove 22 is oriented and axially open towards the outside of the outer ring. The groove 22 has a bottom that is axially offset towards the inside of the ring relative to the front face 14c. The bottom of the groove 22 forms a shoulder. The bottom of the groove 22 extends radially here for manufacturing simplicity. The groove 22 is annular.

[0064] Similarly, a groove 24 is formed on the front face 14d of the outer ring. The groove 24 is oriented and axially open towards the outside of the outer ring. The groove 24 has a bottom that is axially offset towards the inside of the ring relative to the front face 14d. The bottom of the groove 24 forms a shoulder. The bottom of the groove 24 extends radially here. The groove 24 is annular here. The grooves 22, 24 are symmetrical to each other with respect to a median radial plane of the outer ring. The grooves 22, 24 axially delimit the outer surface 14a. Alternatively, it might be possible to omit the grooves 22, 24.

[0065] The bearing device also includes an electrical insulation sleeve 26 mounted on the outer ring 14. The insulation sleeve 26 is mounted on the outer surface 14a of the outer ring 14. The insulation sleeve 26 is integral with the outer ring 14.

[0066] The insulation sleeve 26 includes a sleeve 28 and an insulation packing 30 interposed radially between the outer ring 14 and the sleeve 28. The insulation packing 30 is overmolded on the outer ring 14 and on the sleeve 28.

[0067] The sleeve 28 is annular in shape. The sleeve 28, with axis X-X', extends axially. The sleeve 28 is made here in one piece. Alternatively, the sleeve 28 could be made in several pieces supported against each other, for example, two identical pieces. The sleeve 28 comprises an axial annular cylindrical outer surface 28a, and an axial annular cylindrical bore 28b radially opposed to the outer surface 28a. The bore 28b forms the inner surface of the sleeve 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'.

[0068] The sleeve 28 also includes two opposing radial front faces 28c, 28d that axially define the bore and the outer surface. The front faces 28c, 28d define the axial length of the sleeve. The outer surface 28a and the bore 28b define the radial thickness of the sleeve 28. The outer surface 28a of the sleeve 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.

[0069] In the illustrated embodiment, the front faces 28c, 28d of the sleeve are respectively coplanar with the front faces 14c, 14d of the outer ring. Alternatively, other arrangements could be provided. For example, the sleeve 28 could have a smaller or larger axial dimension and remain axially recessed from the faces 14c, 14d of the outer ring, or protrude from said faces.

[0070] As can be seen in Figures 1, 2 and 4, the bore 28b of the bushing is provided with first and second grooves 36, 38 spaced axially and extending circumferentially. Each groove 36, 38 is oriented radially towards the side of the insulating lining 30 and the outer ring 14 of the bearing, i.e. radially inwards.

[0071] In the illustrated embodiment, each groove 36, 38 is annular. Alternatively, at least one of the two grooves 36, 38 might not extend over 360°.

[0072] Each groove 36, 38 is delimited in the axial direction by two opposing lateral flanks which have a straight profile in axial section and are connected to each other by an axial bottom. Alternatively, other shapes may be provided, for example, grooves having an inwardly oriented arc in cross-section. The bottom of each groove 36, 38 is radially offset outwards relative to the bore 28b of the sleeve. The grooves 36, 38 extend into the radial thickness of the sleeve 28, being blind.

[0073] The groove 36 extends circumferentially around a first axis 36a which is radially offset with respect to the axis 29 of the bore of the sleeve. In the illustrated embodiment, the axis 36a of the groove is located in the median axial plane Pa of the sleeve 28. Alternatively, the axis 36a could be located in the median radial plane Pr of the sleeve 28.

[0074] Similarly, the groove 38 extends circumferentially around a second axis 38a which is radially offset from the axis 29 of the sleeve bore. 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 sleeve bore 28b.

[0075] In the illustrated embodiment, the grooves 36, 38 of the bore 28b of the sleeve are identical to each other. Alternatively, the grooves 36, 38 could, for example, have different diameters and / or different widths.

[0076] Alternatively, it might also be possible to provide on the outer surface 14a of the outer ring at least one groove of the same type as those provided on the bore 28b of the sleeve.

[0077] The bushing 28 is advantageously made of metallic material. Thus, the outer surface 28a of the bushing can be easily machined, if necessary, to a predetermined tolerance. Preferably, the bushing 28 is made of steel. The bushing 28 can be obtained from a sheet metal blank by cutting, stamping, and rolling. Alternatively, the bushing 28 can be obtained from a tube or from forged and / or rolled blanks, or even from sintering and stamping. The grooves 36, 38 can, for example, be formed by material removal, for example by machining, or by material spinning.

[0078] The insulating gasket 30 is made of electrically insulating material. The insulating gasket 30 can, for example, be made of a synthetic material, such as PEEK or PA46, or be made of an elastomeric material, for example rubber.

[0079] The insulating gasket 30 is radially interposed between the outer surface 14a of the outer ring and the bore 28b of the sleeve. The insulating gasket 30 covers the outer surface 14a of the outer ring. The insulating gasket 30 completely covers the outer surface 14a in both the axial and circumferential directions. The insulating gasket 30 also covers the grooves 22, 24 of the inner ring. The insulating gasket 30 also covers the bore 28b of the sleeve. The insulating gasket 30 completely covers the bore 28b in both the axial and circumferential directions.

[0080] As previously stated, the insulating packing 26 is overmolded onto the outer ring 14 of the bearing and onto the bushing 28. The insulating packing 26 is overmolded onto the outer surface 14a of the outer ring 14 and onto the bore 28b of the bushing 28.

[0081] The insulating sleeve 30 is annular in shape. The insulating sleeve 30 extends axially. The insulating sleeve 30 comprises a cylindrical axial outer surface 30a, a cylindrical bore 30b radially opposed to the outer surface 30a, and two opposing radial front faces 30c, 30d axially delimiting the bore and the outer surface. The radial front faces 30c, 30d define the axial length of the insulating sleeve 30. The outer surface 30a and the bore 30b define the radial thickness of the insulating sleeve 30. The outer surface 30a is in radial contact with the bore 28b of the sleeve. The bore 30b is in radial contact with the outer surface 14a of the outer ring, and with the grooves 22, 24. The bore 30b has a stepped shape.

[0082] In the illustrated embodiment, the faces 14c, 30c, 28c and 14d, 30d, 28d of the outer ring, the insulating lining and the sleeve are respectively coplanar.

[0083] Alternatively, other arrangements are possible. For example, the insulating gasket 30 could have a reduced axial dimension and remain axially recessed from the faces 14c, 14d of the outer ring. Alternatively, the insulating gasket 30 could have an increased axial dimension and extend axially beyond the faces 14c, 14d of the outer ring. In this case, the insulating gasket 30 can at least partially cover these faces 14c, 14d. As a variant, the insulating gasket 30 could at least partially cover the faces 28c, 28d of the sleeve.

[0084] In another alternative or in combination, the sleeve 28 could extend axially in projection from the insulation lining 30 relative to the faces 30c and 30d, or remain axially recessed from these faces.

[0085] The insulating sleeve 30 also includes first and second ribs 40, 42 extending radially outwards from the outer surface 30a and each housed respectively inside the first and second grooves 36, 38 of the sleeve. Each rib 40, 42 projects outwards from the outer surface 30a of the insulating sleeve. Each rib 40, 42 has a shape complementary to its associated groove 36, 38. Each rib 40, 42 therefore has a radial dimension projecting outwards from the outer surface 30a that varies when moving in the circumferential direction. Each rib 40, 42 is formed on the outer surface 30a during the overmolding of the insulating sleeve 30.

[0086] To manufacture the bearing device, the following procedure is used.

[0087] In a first step, the bearing 10 and the bushing 28 equipped with the first and second grooves 36, 38 are mounted inside a mold which is intended for overmolding the insulation lining 30. In this position mounted inside the mold, the bushing 28 is radially distant from the outer ring 14 of the bearing.

[0088] Then, in a second successive step, the insulating packing 30 is overmolded both onto the outer ring 14 of the bearing and onto the bushing 28. As previously stated, the ribs 40, 42 of the insulating packing are formed during this step.

[0089] Finally, the bearing device, which is in the form of a unit assembly, is extracted from the mold.

[0090] The embodiment illustrated in Figures 5 to 8, in which the identical elements bear the same reference numerals, differs from the first example in that the axis 38a of the groove 38 of the sleeve bore is radially offset on the opposite side to the axis 36a of the groove 36 relative to the axis 29 of the bore. The axes 36a, 38a are located on either side of the axis 29 of the sleeve bore 28b.

[0091] Axes 36a, 38a are located here in the median axial plane Pa of the sleeve. Alternatively, axes 36a, 38a could be located in the median radial plane Pr of the sleeve 28.

[0092] In the illustrated embodiments, the bore of the sleeve is provided with the two grooves 36, 38. Alternatively, it might be possible to provide on the bore of the sleeve a single groove or at least three grooves.

[0093] In the illustrated embodiments, the first ring 12 of the bearing is the inner ring and the second ring 14 on which the insulation packing 30 is overmolded is the outer ring.

[0094] Alternatively, an inverted arrangement may be provided in which the second ring 14, onto which the insulating sleeve 30 is overmolded, is the inner ring. In this case, the insulating sleeve is located in the bore 12a of the inner ring. The insulating sleeve is then interposed radially between the bore 12a of the inner ring and the outer surface of the bushing. The insulating sleeve is overmolded onto the inner ring and at least onto the outer surface of the bushing. The outer surface of the bushing is provided with groove(s) whose axis or axes are radially offset from the axis of the cylindrical outer surface. The bore of the bushing defines the bore of the bearing device.

[0095] In the described embodiments, the bearing of the device is provided with a single row of rolling elements. Alternatively, the bearing may be provided with several rows of rolling elements. Furthermore, the rolling bearing may include other types of rolling elements than balls, for example, rollers. In another embodiment, the bearing may be a sliding bearing without rolling elements.

Claims

Demands

1. Bearing device comprising a bearing (10) having a first ring (12) and a second ring (14) capable of rotating relative to each other, and an insulating sleeve (26) mounted on the second ring (14) of the bearing and having a bushing (28) and an insulating lining (30) interposed radially between the second ring (14) and the bushing (28) and made of electrically insulating material, the bushing comprising a cylindrical outer surface (28a) and a cylindrical inner surface (28b) opposite the outer surface and which define the radial thickness of said bushing, the insulating lining (30) being overmolded onto the second ring (14) of the bearing and at least onto one of the outer and inner surfaces of the bushing (28),characterized in that said surface of the socket (28) is provided with at least one first groove (36) within which extends a first rib (40) for attaching the insulating lining of complementary shape, said first groove (36) extending circumferentially around a first axis (36a) which is radially offset with respect to the axis (29) of said surface of the socket.

2. Device according to claim 1, wherein said first groove (36) of said surface of the socket is annular.

3. Device according to claim 1 or 2, wherein said first groove (36) of said surface of the sleeve is located in the median axial plane (Pa) or in the median radial plane (Pr) of said sleeve (28).

4. Device according to any one of the preceding claims, wherein the sleeve (28) comprises two front faces (28c, 28d) delimiting the axial length of said sleeve, said first groove (36) of said surface of the sleeve remaining at a distance from said front faces.

5. Device according to any one of the preceding claims, wherein said socket surface (28) is provided with at least one second groove (38) within which extends a second rib (42) for attaching the insulating lining of complementary shape, said second groove (38) extending circumferentially around a second axis (38a) which is offset radially with respect to the axis (29) of said socket surface.

6.

7.

8.

9. Device according to claim 5, wherein the second axis (38a) of said second groove is radially offset on the same side as the first axis (36a) of the first groove relative to the axis (29) of said surface of the sleeve. Device according to claim 5, wherein the second axis (38a) of said second groove is radially offset on the opposite side to the first axis (36a) of the first groove relative to the axis (29) of said surface of the socket. Device according to any one of the preceding claims, wherein the socket (28) is made of metallic material. Electric motor comprising a housing, a shaft and at least one bearing device according to any one of claims 1 to 8 mounted radially between the housing and the shaft.

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