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

Abstract

The invention relates to a bearing arrangement with integrated electrical insulation, in particular for an electric motor or an electric machine. The bearing arrangement comprises a bearing (10) provided with a first ring (12) and a second ring (14) rotatable relative to each other. The device comprises at least one insulating sleeve (22) mounted on the second ring of the bearing and provided with a bushing (24) and an insulating insert (26) positioned radially between the second ring and the bushing (24) and made of an electrically insulating material. The bushing has a cylindrical annular outer surface (24a) and a cylindrical annular inner surface (24b). An insulating insert (26) is overmolded onto the second ring of the bearing and at least onto one of the outer and inner surfaces of the bushing (24). The surface of the bushing comprises at least one projection (27) extending towards the second ring and provided with a non-cylindrical annular surface radially facing the second ring.

Description

Technical Field

[0001] The present invention relates to the field of bearings, in particular to the field of bearings for electric motors, electric machines and associated equipment. Background Art

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

[0003] During operation, when the shaft rotates, a potential difference may occur between the housing of the electric motor or electric machine and the shaft, resulting in a current flow between the inner ring (rigidly connected to the shaft) and the outer ring (rigidly connected to the housing) of the rolling bearing.

[0004] The current flowing through the components of the rolling bearing can damage these components, in particular the rolling elements and the raceways provided on the inner and outer rings. The discharge can also generate vibrations.

[0005] In order to overcome these drawbacks, it is known to replace the rolling elements of the bearing made of the same steel as the inner and outer rings with rolling elements made of ceramic. The expression "hybrid rolling bearing" is then often used.

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

[0007] In order 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 insert made of an electrically insulating material and positioned radially between the outer ring and the bushing.

[0008] In order to attach the insulating insert to the outer ring and the bushing without any additional elements or specific machining of the outer ring, the insulating insert may be over-molded.

[0009] However, with this solution, relative uncoupling of the insulating insert and the bushing may occur during operation.

[0010] It is therefore an object of the present invention to overcome the aforementioned disadvantages by providing a bearing arrangement having a simple and economical design. Summary of the Invention

[0011] The present invention relates to a bearing arrangement 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 mounted on the second ring of the bearing. The insulating sleeve is provided with a bushing and an insulating insert, the insulating insert being radially positioned between the second ring of the bearing and the bushing. The insulating insert is made of an electrically insulating material.

[0013] The bushing has a cylindrical annular outer surface and a cylindrical annular inner surface opposite to the outer surface.

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

[0015] According to general characteristics, the surface of the bushing comprises at least one projection extending towards the second ring and provided with a non-cylindrical annular surface radially facing the second ring.

[0016] This provides a bearing arrangement with integrated electrical insulation which is economical compared to conventional hybrid rolling bearings. Furthermore, the arrangement is easy to manufacture and assemble into an associated electric motor or electric machine.

[0017] Furthermore, providing the bushing with the aforementioned protrusion having a non-cylindrical annular shape makes it possible to achieve a very rigid connection with the insulating insert, provided that a complementary non-cylindrical annular shape is achieved on the insert during overmolding. The risk of any relative movement between the insulating insert and the bushing in the circumferential direction is particularly limited, particularly in the event of temperature fluctuations. Furthermore, the protrusion forms an axial abutment surface for limiting relative movement between the insulating insert and the bushing in the axial direction.

[0018] "Axial direction" is understood to mean a direction parallel to the axis of the bearing arrangement.

[0019] "Circumferential direction" is understood to mean a direction perpendicular to the axial direction and perpendicular to a radius of the bearing arrangement, in other words tangent to a circle centred on the axis of the bearing arrangement.

[0020] An "annular surface" is understood to mean a surface which, in cross-section, forms a convex flat curve which is closed on itself.

[0021] The surface of the protrusion of the bushing may have two orthogonal axes of symmetry in a cross-sectional view.

[0022] According to a first design, the surface of the protrusion of the bushing has an oblong shape in a cross-sectional view.

[0023] In this case, the surface of the protrusion of the bushing may be provided with two diametrically opposed cylindrical portions having different axes and two rectilinear portions connecting the cylindrical portions to each other. Advantageously, the body portion may be two semi-cylindrical portions.

[0024] According to a second design, the surface of the protrusion of the bushing has an oval shape in a cross-sectional view.

[0025] In this case, the surface of the projection of the bush may be provided with two diametrically opposed first cylindrical portions having different axes and two second cylindrical portions connecting the first cylindrical portions to each other and having different axes.

[0026] The bushing may be provided with two front faces defining its axial extent.The protrusion may be continued radially from one of the front faces.

[0027] In a specific embodiment, the bushing is made of a metal material. Therefore, the bushing can be easily machined to a predetermined radial tolerance.

[0028] According to a first design, the bushing defines the outer surface of the device. In this case, the second ring is the outer ring of the bearing.

[0029] According to an alternative second design, the bushing defines the inner surface of the device. In this case, the second ring is the inner ring of the bearing.

[0030] If the insulating insert is made of a synthetic or elastomeric material, this makes the device relatively insensitive to temperature changes.

[0031] In a particular embodiment, the bearing comprises at least one row of rolling elements arranged between the raceway of the first ring and the raceway of the second ring.The rolling elements may be made of a metallic material.

[0032] The invention also relates to an electric motor comprising a housing, a shaft and at least one bearing device as defined above, mounted radially between the housing and the shaft. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The invention will be better understood by studying the detailed description of embodiments thereof given by way of non-limiting examples and illustrated by the accompanying drawings, in which:

[0034] Figure 1 is a semi-axial cross-sectional view of a bearing device according to an exemplary embodiment of the present invention,

[0035] Figure 2 yes Figure 1 Cross-sectional view of the bushing of the bearing assembly,

[0036] Figure 3 It is along Figure 2 A cross-sectional view along axis III-III,

[0037] Figure 4 yes Figure 2 and Figure 3 A three-dimensional view of the bushing in

[0038] Figure 5 is a cross-sectional view of a bushing of a bearing device according to another exemplary embodiment of the present invention,

[0039] Figure 6 It is along Figure 5 A cross-sectional view along axis VI-VI in FIG. 1 , and

[0040] Figure 7 yes Figure 5 and Figure 6 A three-dimensional view of the bushing in FIG. DETAILED DESCRIPTION

[0041] Figure 1 The bearing arrangement shown in comprises a bearing 10 provided with a first ring 12 and a second ring 14 rotatable relative to each other about an axis XX' of the bearing. In the embodiment shown, the first ring 12 is the inner ring of the bearing and the second ring 14 is the outer ring.

[0042] The bearing arrangement is designed such that the bearing arrangement does not conduct electrical current. The bearing arrangement has integrated electrical insulation.

[0043] 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 of solid type.

[0044] In the illustrated embodiment, bearing 10 also includes an array of rolling elements 16 (in this case, balls) positioned radially between inner ring 12 and outer ring 14. Rolling elements 16 are constructed of steel. Bearing 10 also includes a cage 17 for maintaining even circumferential spacing of rollers 16. Bearing 10 may also be equipped with seals or sealing flanges.

[0045] Inner ring 12 includes a cylindrical bore 12a, a cylindrical axial outer surface 12b radially opposite the bore, and two opposing radial front faces (not shown) axially delimiting the bore and the outer surface. Bore 12a and outer surface 12b define the radial thickness of inner ring 12. Bore 12a forms the inner surface of the inner ring.

[0046] The inner ring 12 further comprises an inner raceway 18 formed on the outer surface 12b for the rolling elements 16. The raceway 18 points radially outward.

[0047] The outer ring 14 includes a cylindrical axial outer surface 14a, a cylindrical hole 14b radially opposite the outer surface 14a, and two opposite radial front faces 14c, 14d axially delimiting the hole and the outer surface. The outer surface 14a and the hole 14b define the radial thickness of the outer ring 14.

[0048] The outer ring 14 further includes an outer raceway 20 formed on the bore 14b for the rolling elements 16. The raceway 20 points radially inward.

[0049] The bearing arrangement further comprises an electrically insulating sleeve 22 mounted on the outer ring 14. The insulating sleeve 22 is mounted on the outer surface 14a of the outer ring 14. The insulating sleeve 22 is rigidly connected to the outer ring 14.

[0050] The insulating sleeve 22 includes a bushing 24 and an insulating insert 26 positioned radially between the outer ring 14 and the bushing 24. The insulating insert 26 is overmolded onto the outer ring 14 and the bushing 24.

[0051] The bushing 24 is annular. The bushing 24 extends in the axial direction. In the present case, the bushing 24 is made as a single piece. Alternatively, the bushing 24 can be made of multiple parts (e.g., two identical parts) that abut against each other. The bushing 24 has a cylindrical annular axial outer surface 24a and a cylindrical annular hole 24b that is radially opposite to the outer surface 24a, and the axis 25 of the cylindrical annular hole 24b is coaxial with the axis XX'. The hole 24b forms the inner surface of the bushing 24.

[0052] Bushing 24 also includes two opposing radial front faces 24 c and 24 d that axially define the bore and the outer surface. Front faces 24 c and 24 d define the axial length of the bushing. Outer surface 24 a and bore 24 b define the radial thickness of bushing 24. Bushing outer surface 24 a defines the outer surface of bearing assembly 10. In other words, outer surface 24 a defines the outer diameter of bearing assembly 10.

[0053] like Figure 1 、 Figure 2 and Figure 4 As shown, the bore 24b of the bushing comprises a first protrusion 27 extending inwardly (ie towards the outer ring 14). The protrusion 27 extends relative to the bore 24b. The protrusion 27 extends in the radial direction.

[0054] The projection 27 is located at the axial end of the hole 24b of the bushing. The projection 27 continues radially inwardly from the front face 24c of the bushing. The outer surface of the projection 27 is coplanar with the front face 24c.

[0055] The projection 27 comprises an annular hole 27a oriented radially inwards, ie towards the outer ring 14. The hole 27a is non-cylindrical.

[0056] like Figure 3 and Figure 4 As shown, in the exemplary embodiment shown, the hole 27a is provided with two semi-cylindrical portions 28, 30 having different axes 28a, 30a, and two straight portions 32, 34 connecting the semi-cylindrical portions to each other. The semi-cylindrical portions 28, 30 are diametrically opposite. The straight portions 32, 34 are diametrically opposite. The axes 28a, 30a are located in the axial midplane of the bushing. The axes 28a, 30a are located on either side of the axis 25 of the hole 24b of the bushing. The radius R of the semi-cylindrical portions 28, 30 is 28 、R 30 As another option, the radius R of the semi-cylindrical parts 28, 30 28 and R 30 It can be different.

[0057] The straight portion 32 connects the first end of the semi-cylindrical portion 28 to the first end of the semi-cylindrical portion 30, and the straight portion 34 connects the second end of the semi-cylindrical portion 28 to the second end of the semi-cylindrical portion 30. The first and second ends of each semi-cylindrical portion 28, 30 circumferentially define the semi-cylindrical portion. Each straight portion 32, 34 is connected to the semi-cylindrical portion 28 on one side in the circumferential direction and to the semi-cylindrical portion 30 on the other side in the circumferential direction. Each straight portion 32, 34 extends in the continuation of the semi-cylindrical portion 28, 30 without a drop-off. The straight portions 32, 34 have a flat shape.

[0058] The hole 27a of the projection has two orthogonal axes of symmetry X1, X2 in cross-section or side view.The hole 27a has an oblong shape in cross-section or side view.

[0059] In the exemplary embodiment shown, the bushing's bore 24b includes a second protrusion 36 at its other axial end, extending inward (i.e., toward the outer ring 14). Protrusion 36 extends relative to bore 24b. Protrusion 36 extends radially. Protrusion 36 continues radially inwardly toward the bushing's front face 24d. The outer face of protrusion 36 is coplanar with front face 24d.

[0060] In the exemplary embodiment shown, the radial dimension of protrusion 36 is equal to the radial dimension of protrusion 27. Alternatively, the radial dimension of protrusion 36 may be smaller or larger than the radial dimension of protrusion 27. Alternatively, protrusion 36 may not be provided. In the exemplary embodiment shown, protrusion 36 has a non-cylindrical annular hole that is the same as hole 27a of protrusion 27. Alternatively, protrusion 36 may be angularly offset relative to protrusion 27. According to another alternative, the hole of protrusion 36 may be a cylindrical annular hole.

[0061] The bushing 24 is advantageously made of a metal material. This allows the outer surface 24a of the bushing to be easily machined to a predetermined tolerance when necessary. Preferably, the bushing 24 is made of steel. The bushing 24 can be obtained from a sheet metal blank by cutting, stamping, and rolling. Alternatively, the bushing 24 can be obtained from a tube or a rolled-forged blank, or by sintering and stamping.

[0062] The insulating insert 26 is made of an electrically insulating material. The insulating insert 26 may, for example, be made of a synthetic material such as PEEK or PA46, or the insulating insert 30 may be made of an elastomeric material such as rubber.

[0063] Insulating insert 26 is positioned radially between outer ring outer surface 14a and bushing bore 24b. Insulating insert 26 covers outer ring outer surface 14a. In this case, insulating insert 26 completely covers outer surface 14a in the axial and circumferential directions. Insulating insert 26 also covers bushing bore 24b. Insulating insert 26 also covers protrusion bore 27a and the bore of protrusion 36. In this case, insulating insert 26 also completely covers these bores in the axial and circumferential directions.

[0064] As described above, the insulating insert 26 is overmolded onto the outer race 14 of the bearing and onto the bushing 24. The insulating insert 26 is overmolded onto the outer surface 14a of the outer race 14, the bore 24b of the bushing 24, and the projections 27,36.

[0065] Insulating insert 26 is annular and extends axially. It includes an axially outer surface 26a, a cylindrical bore 26b radially opposite outer surface 26a, and two opposing radial front faces 26c and 26d axially delimiting the bore and outer surface. Front faces 26c and 26d axially delimit insulating insert 26. Outer surface 26a and bore 26b define the radial thickness of insulating insert 26. Outer surface 26a radially contacts bore 24b and protrusions 27 and 36 of the bushing. Bore 26b radially contacts outer surface 14a of the outer ring.

[0066] The outer surface 26a of the insulating insert has a shape complementary to the bore 24b of the bushing and to the projections 27, 36 and therefore has a stepped shape. Thus, in the region of each projection 27, 36, the outer surface 26a is provided with two semi-cylindrical portions complementary to the semi-cylindrical portions 28, 30 and with two straight portions complementary to the straight portions 32, 34.

[0067] In the embodiment shown, the faces 14c, 26c, 24c and 14d, 26d, 24d of the outer race, insulating insert and bushing, respectively, are coplanar.

[0068] Alternatively, other configurations may be provided. For example, the insulating insert 26 may have a reduced axial dimension and remain axially set back from the outer ring faces 14c, 14d. Alternatively, the insulating insert 26 may have a larger axial dimension and protrude axially from the outer ring faces 14c, 14d. In this case, the insulating insert 26 may at least partially cover these faces 14c, 14d. As a variant, the insulating insert 26 may at least partially cover the bushing faces 24c, 24d.

[0069] In another alternative or combination, the bushing 24 may protrude axially from the insulating insert 26 relative to the faces 26 c and 26 d , or may remain axially set back from these faces.

[0070] The bearing device is manufactured as follows.

[0071] In a first step, the bearing 10 and the bushing 24 equipped with the protrusions 27, 36 are mounted inside a mould provided for overmoulding the insulating insert 26. In this position mounted inside the mould, the bushing 24 is radially spaced from the outer ring 14 of the bearing.

[0072] Then, in a second, successive step, an insulating insert 26 is overmoulded onto the outer ring 14 of the bearing and onto the bushing 24 .

[0073] Finally, the bearing device is removed from the mold in the form of an integral assembly.

[0074] exist Figures 5 to 7 In the exemplary embodiment shown in FIG, in which like elements bear like reference numerals, the hole 27 a of the projection 27 is also non-cylindrical, but in this case, the hole 27 a of the projection 27 is provided with first cylindrical portions 40, 42 having different axes 40 a, 42 a, and two second cylindrical portions 44, 46 connecting the first cylindrical portions to each other and having different axes 44 a, 46 a. The first cylindrical portions 40, 42 are diametrically opposed. The second cylindrical portions 44, 46 are diametrically opposed.

[0075] The axes 40a, 42a lie in the radial mid-plane of the bushing. The axes 40a, 42a lie on either side of the axis 25 of the bore 24b of the bushing. The radius R of the cylindrical portion 40, 42 is 40 、R 42 Equal. Axes 44a, 46a are different from axes 40a, 42a. Axes 44a, 46a are located in the axial midplane of the bushing. Axes 44a, 46a are located on both sides of the axis 25 of the bore 24b of the bushing. The radius R of the cylindrical portion 44, 46 44 、R 46 are equal to and smaller than the radius R 40 、R 42 .

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

[0077] Each second cylindrical portion 44, 46 is circumferentially connected on one side to the first cylindrical portion 40 and on the other side to the first cylindrical portion 42. Each second cylindrical portion 44, 46 extends in continuation of the first cylindrical portion 40, 42 without interruption.

[0078] The hole 27a of the projection has two orthogonal axes of symmetry X1 , X2 in cross-section or side view.The hole 27a has an elliptical shape in cross-section or side view.

[0079] In the exemplary embodiment shown, the bushing's protrusion 36 has a non-cylindrical annular hole that is identical to the hole 27a of the protrusion 27. Alternatively, the protrusion 36 may be angularly offset relative to the protrusion 27. According to another alternative, the hole of the protrusion 36 may be a cylindrical annular hole. In another alternative, the bushing may lack the protrusion 36.

[0080] In the embodiment shown, the first ring 12 of the bearing is the inner ring and the second ring 14 onto which the insulating insert 26 is overmolded is the outer ring.

[0081] Alternatively, a reverse configuration can be provided, in which the second ring 14 onto which the insulating insert 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 insert is then positioned radially between the bore 12a of 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 one or more protrusions having a non-cylindrical outer surface. The bore of the bushing defines the bore of the bearing arrangement.

[0082] In the described embodiment, the bearing of the device is provided with a single row of rolling elements. In one variation, the bearing may be provided with multiple rows of rolling elements. Furthermore, the rolling bearing may include other types of rolling elements besides balls, such as rollers. In another variation, the bearing may be a plain bearing without rolling elements.

Claims

1. A bearing device comprising a bearing (10) and an insulating sleeve (22), the bearing (10) being provided with a first ring (12) and a second ring (14) which are rotatable relative to each other, the insulating sleeve (22) being mounted on the second ring (14) of the bearing and being provided with a bushing (24) and an insulating insert (26), the insulating insert (26) being positioned radially between the second ring (14) and the bushing (24) and being made of an electrically insulating material, the bushing having a cylindrical annular outer surface (24a) and a cylindrical annular inner surface (24b) opposite the outer surface, the insulating insert (26) being overmolded onto the second ring (14) of the bearing and overmolded onto at least one of the outer surface and the inner surface of the bushing (24), characterized in that The surface of the bushing (24) comprises at least one protrusion (27) extending towards the second ring and provided with a non-cylindrical annular surface (27a) facing the second ring in a radial direction.

2. The device according to claim 1, characterized in that The surface (27a) of the protrusion of the bushing has two orthogonal axes of symmetry (X1, X2) in a cross-sectional view.

3. The device according to claim 1 or 2, characterized in that The surface (27a) of the protrusion of the bushing has an oblong shape in a cross-sectional view.

4. The device according to claim 3, characterized in that The surface (27a) of the projection of the bushing is provided with two diametrically opposed cylindrical portions (28, 30) having different axes and two straight portions (32, 34) connecting the cylindrical portions to each other.

5. The device according to claim 4, characterized in that The cylindrical parts (28, 30) are two semi-cylindrical parts.

6. The device according to claim 1 or 2, characterized in that The surface (27a) of the protrusion of the bushing has an elliptical shape in a cross-sectional view.

7. The device according to claim 6, characterized in that The surface (27a) of the projection of the bushing is provided with two diametrically opposed first cylindrical portions (40, 42) having different axes and two second cylindrical portions (44, 46) connecting the first cylindrical portions to each other and having different axes.

8. The device according to any one of the preceding claims, characterized in that The insulating lining (26) is made of synthetic material or elastomeric material.

9. The device according to any one of the preceding claims, characterized in that The bushing (24) is made of metal material.

10. An electric motor comprising a housing, a shaft and at least one bearing arrangement according to any one of the preceding claims, the bearing arrangement being mounted radially between the housing and the shaft.

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