Bearing device with integrated electrical insulation, particularly for electric motors or machines

Abstract

[Electrically insulated bearing device, particularly for electric motors or machines] The device comprises a bearing 10 having a first ring 12 and a second ring 14. The device includes an insulating sleeve 26 mounted on the second ring 14 and having a bushing 28 and an insulating gasket 30. The insulating gasket is fixed to the second ring 14 and to at least one of the outer and inner surfaces of the bushing 28. The bushing 28 also includes first and second front faces 28c, 28d defining the axial length of said bushing. A first connecting chamfer 28e links the first front face 28c of the bushing to the outer surface and has a first radius connecting to the first front face by forming a sharp edge and a spherical surface connecting to the outer surface by forming another sharp edge and connecting to the radius. Reference: Figure 1

Description

Title of the invention: Bearing device with integrated electrical insulation, particularly for electric motors or machines. 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] During the mounting of this bearing device inside the engine casing or during its removal, the bore of the casing may be damaged.

[0009] The present invention aims to remedy this drawback. Summary of the invention

[0010] 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.

[0011] The device further comprises at least one insulating sleeve mounted on the second bearing ring. The insulating sleeve is provided with a socket and a An insulating gasket is radially interposed between the second bearing ring and the bushing. The insulating gasket is made of electrically insulating material.

[0012] The sleeve comprises a cylindrical outer surface and a cylindrical inner surface opposite the outer surface, which define the radial thickness of said sleeve. The sleeve also comprises first and second front faces defining the axial length of said sleeve.

[0013] The insulation lining is fixed to the second ring of the bearing and at least to one of the outer and inner surfaces of the bushing.

[0014] According to a general feature, a first connecting chamfer links the first front face of the socket to said other surface of the outer and inner surfaces of the socket.

[0015] The first connecting chamfer is provided with a radius connecting to the first front face by forming a sharp edge, and with a spherical surface connecting to said other surface of the socket by forming another sharp edge and connecting to the radius.

[0016] The value of the radius of the spherical surface increases in the direction of said other surface of the socket.

[0017] Thus, we have an economical integrated electrically insulated bearing device compared to conventional hybrid rolling bearings.

[0018] Moreover, the device is easy to assemble in the motor or associated electrical machine without risk of damage to the bore of the motor or electrical machine due to the presence of the first truncated chamfer for connection.

[0019] Each sharp edge forms a break in slope between the first connecting chamfer and the first front face of the socket, or between the first connecting chamfer and said other surface of the socket.

[0020] The spherical surface of the first connecting chamfer makes it possible to reduce the salient character of the sharp edge between the first connecting chamfer and said other surface of the socket.

[0021] Preferably, the spherical surface of the first connecting chamfer connects to the radius tangentially.

[0022] The value of the radius of the spherical surface of the first connecting chamfer is advantageously greater than the value of the radius of said first chamfer.

[0023] Advantageously, a second connecting chamfer links the second front face of the socket to said other surface of the socket. The second connecting chamfer is provided with a radius connecting to the second front face by forming a sharp edge, and with a spherical surface connecting to said other surface of the socket by forming another sharp edge and connecting to the radius. The value the radius of the spherical surface increases in the direction of said other surface of the socket.

[0024] Preferably, the spherical surface of the second connecting chamfer connects to the radius tangentially.

[0025] The value of the radius of the spherical surface of the second connecting chamfer is advantageously greater than the value of the radius of said second chamfer.

[0026] Advantageously, the sleeve is made of metallic material. The sleeve can, for example, be obtained by stamping or machining.

[0027] Preferably, the insulating packing is overmolded onto the second bearing ring and at least onto said bushing surface. Alternatively, the insulating packing can be fixed by any other suitable means, for example by bonding.

[0028] If the insulation lining is made of synthetic material or elastomeric material, it makes the device less sensitive to temperature variations.

[0029] 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.

[0030] By "axial direction" is meant the direction parallel to the axis of the bearing device.

[0031] By “circumferential direction”, we mean the direction which 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.

[0032] 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.

[0033] 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.

[0034] 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.

[0035] 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.

[0036] The invention further relates to a method for manufacturing a bushing for a bearing device as defined above, comprising the following successive steps:

[0037] - a step in producing a rough socket giving it its geometry of base, said other surface of the socket blank having a spherical shape,

[0038] - a heat treatment step to give the socket blank hardness required

[0039] - a radial grinding step of the first front face of the blank socket and a portion of the radius of the first connecting chamfer that is adjacent to the first front face, and

[0040] - an axial grinding step of said other surface of the bushing blank to give it its cylindrical shape, the spherical surface of the first connecting chamfer remains unrectified. Brief description of the figures

[0041] 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:

[0042] [Fig-1] is a half axial cross-sectional view of a bearing device according to an embodiment of the invention,

[0043] [Fig.2]

[0044] [Fig.3] are detailed views of a socket of the device in [Fig.1],

[0045] [Fig.4]

[0046] [Fig.5] are detailed views of the device socket [Fig.1] before the steps rectification.

[0047] [Fig.6] is a half axial cross-sectional view of a bearing device according to another example of an implementation of the invention,

[0048] [Fig.7] is a half-view in axial section of a bearing device according to yet another example of an implementation of the invention, and

[0049] [Fig.8]

[0050] [Fig.9] are detail views of a socket of the device in [Fig.7]. Detailed description of the invention

[0051] 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.

[0052] The bearing device is designed so as not to conduct electric currents. The bearing device has integrated electrical insulation.

[0053] 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.

[0054] 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 be further equipped with seals or sealing flanges.

[0055] 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.

[0056] 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.

[0057] 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 delimiting the outer surface and the bore. The outer surface 14a and the bore 14b define the radial thickness of the outer ring 14. The outer surface 14a here has a stepped shape. Alternatively, the outer surface 14a could have a single diameter.

[0058] 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.

[0059] 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.

[0060] 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 here overmolded on the outer ring 14 and on the sleeve 28.

[0061] The sleeve 28 is annular in shape. The sleeve 28, with axis X-X', extends axially. The sleeve 28 is made up of two separate parts 32, 34. These two separate parts 32, 34 form half-flanges which are axially supported against each other. In the illustrated embodiment, the parts 32, 34 of the sleeve are identical and symmetrical with respect to a median radial plane of the device in order to reduce manufacturing costs. Alternatively, it is possible to provide for asymmetrical parts 32, 34. In another variant, it could be possible to provide for the sleeve 28 to be made up of more than two parts. Preferably, the parts 32, 34 of the sleeve 28 are made of steel. The parts 32, 34 can advantageously be obtained from a sheet metal blank by cutting or stamping. and rolling. Alternatively, parts 32, 34 can be obtained from a tube or from forged and / or rolled blanks, or from sintering and stamping.

[0062] Each portion 32, 34 of the sleeve comprises an annular axial portion 32a, 34a, and an annular radial flange 32b, 34b extending radially inward from the axial portion. The axial portions 32a, 34a are axially supported against each other. The radial flange 32b, 34b extends from the end of the axial portion 32a, 34a located axially on the outer side of the device. In the illustrated embodiment, the radial flanges 32b, 34b are annular.

[0063] The sleeve 28 comprises a cylindrical axial outer surface 28a and a cylindrical bore 28b radially opposed to the outer surface 28a and whose axis is coaxial with the X-X' axis. 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 and the insulating gasket 30. The axis of the bore 28b is coaxial with the X-X' axis. The axial portions 32a, 34a of the sleeve parts jointly define the outer surface 28a. Similarly, the axial portions 32a, 34a of the parts jointly define the bore 28b. The outer surface 28a and the bore 28b define the radial thickness of the bushing 28. The outer surface 28a of the bushing forms the outer surface of the bearing device 10. In other words, the outer surface 28a defines the outer diameter of the bearing device 10.

[0064] The sleeve 28 also includes opposing first and second radial front faces 28c, 28d that axially delimit the outer surface 28a. The front faces 28c, 28d define the axial length of the sleeve. The front face 28c is delimited by the radial flange 32b, and the front face 28d is delimited by the radial flange 34b. More precisely, the front face 28c is delimited by the outer face of the radial flange 32b, and the front face 28d is delimited by the outer face of the radial flange 34b.

[0065] 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, remaining axially recessed from the faces 14c, 14d of the outer ring, or projecting from said faces.

[0066] The sleeve 28 further includes first and second annular connecting chamfers 28e, 28f respectively connecting the front faces 28c, 28d to the outer surface 28a. The connecting chamfers 28e, 28f are symmetrical with respect to the median radial plane of the device.

[0067] As illustrated in [Fig. 2], the first connecting chamfer 28e is provided with a convex radius 28ei connecting to the front face 28c, and a spherical surface 28e2 connecting to the outer surface 28a and to the radius 28eb

[0068] The radius 28ei connects directly to the front face 28c. The spherical surface 28e2 connects directly to the outer surface 28a. In other words, for the radius 28eb there is no additional surface between this first radius and the front face 28c, and for the spherical surface 28e2, there is no additional surface between this spherical surface and the outer surface 28a.

[0069] The radius 28eise connects to the front face 28c by forming a sharp edge ai, and the spherical surface 28e2se connects to the outer surface 28a by forming another sharp edge a2. The center of the radius 28ei is referenced as C28ei. The sharp edge ai is radially offset outwards, i.e., towards the outer surface 28a, with respect to the center C28eb. The sharp edge a2 is axially offset inwards with respect to the center C28eb.

[0070] The spherical surface 28e2 connects tangentially to the radius 28ei. The axial length of the spherical surface 28e2 is referenced as Li in [Fig. 2]. The spherical surface 28e2 flares outwards towards the outer surface 28a. In other words, the radius of the spherical surface 28e2 increases towards the outer surface 28a. The radius of the spherical surface 28e2 is greater than the radius of 28e. The center (not shown) of the spherical surface 28e2 is, for example, located in the radial median plane of the sleeve, while being located outside the sleeve.

[0071] Identical to the first connecting chamfer 28e and as illustrated in [Fig. 3], the second connecting chamfer 28f is provided with a convex radius 28f i connecting to the front face 28d, and a spherical surface 28f2 connecting to the outer surface 28a and to the radius 28fb

[0072] The radius 28fi connects directly to the front face 28d. The spherical surface 28f2 connects directly to the outer surface 28a. For the radius 28fb there is no additional surface between this first radius and the front face 28d, and for the spherical surface 28f2, there is no additional surface between this spherical surface and the outer surface 28a.

[0073] The radius 28f connects to the front face 28d by forming a sharp edge a3, and the spherical surface 28f2 connects to the outer surface 28a by forming another sharp edge a4. The center of the radius 28f is referenced C28fb. The sharp edge a3 is radially offset outwards, i.e., towards the outer surface 28a, with respect to the center C28fb. The sharp edge a4 is axially offset inwards with respect to the center C28fb.

[0074] The spherical surface 28f2 connects tangentially to the radius 28fi. The axial length of the spherical surface 28f2 is referenced as L2 in [Fig. 3]. The spherical surface 28e2 flares outwards towards the outer surface 28a. In other words, the radius of the spherical surface 28f2 increases towards the outer surface 28a. The radius of the spherical surface 28f2 is greater than the radius 28f2. The center (not shown) of the spherical surface 28f2 is, for example, located in the radial median plane of the sleeve, while being located outside the sleeve.

[0075] To manufacture the socket 28, the following procedure is used.

[0076] In a first step, a draft is made for each part 32, 34 of the socket giving it its basic geometry with the rough shape of the outer surface 28a, the bore 28b, the front face 28c or 28d and the connecting chamfer 28e or 28f as partially illustrated in figures 4 and 5. At this stage, the outer surface 28a of the socket is not yet cylindrical but spherical.

[0077] Next, in a second successive step, the rough parts of the bushing 32, 34 are heat-treated to give them the required hardness.

[0078] Then, in a third successive step, the front face 28c of the sleeve blank and a portion of the radius 28ei of the first chamfer adjacent to this front face 28c are rectified in the radial direction, as well as the front face 28d of the sleeve blank and a portion of the radius 28fi of the second chamfer adjacent to this front face 28d. The sharp edges ai and a3 are formed during this step.

[0079] During this third step, the outer surface 28a of the sleeve blank is also ground along the axial direction to give it its cylindrical shape. The sharp edges a2 and a4 are formed during this step. The spherical surfaces 28e2 and 28f2 are not ground.

[0080] With the rectification steps, the first and second chamfers 28e, 28f of the socket connection are truncated.

[0081] After these rectification steps, the socket 28 has its final shape and dimensions.

[0082] 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.

[0083] 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.

[0084] The insulating gasket 30 also covers the bore 28b of the sleeve. The insulating gasket 30 also completely covers the bore 28b in both the axial and circumferential directions. The insulating gasket 30 also covers the inner face of the radial flange 32b, 34b of each portion 32, 34 of the sleeve. The inner face and the outer face axially opposite the inner face of each radial flange 32b and 34b define the axial thickness of said flange. For each radial flange 32b and 34b, the inner face is oriented axially towards the inside of the device, and the outer face is oriented axially towards the outside of the device. The insulating gasket 30 also covers the free end of the radial flange 32b, 34b of each portion 32, 34 of the sleeve.

[0085] The insulating gasket 30 is annular in shape. The insulating gasket 30 extends axially. The insulating gasket 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 gasket 30. The outer surface 30a and the bore 30b define the radial thickness of the insulating gasket 30. The outer surface 30a is in radial contact with the bore 28b of the sleeve. The outer surface 30a is also in radial contact with the free end of each radial flange 32b, 34b of the sleeve. The outer surface 30a has a stepped shape. The bore 30b is in radial contact with the outer surface 14a of the outer ring. The bore 30b has a stepped shape.

[0086] 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.

[0087] 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.

[0088] 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.

[0089] The embodiment illustrated in [Fig. 6], in which the identical elements bear the same reference numerals, differs from the first example in that the socket 28 is made in one piece. The bushing 28 is made in one piece. The bushing 28 thus comprises a single axial portion 36 in place of the two axial portions 32a, 34a of the first example, and the two radial collars 32b, 34b.

[0090] In this example, the radial dimension of the flange 32b of the sleeve is greater than the radial dimension of the flange 34b. The flanges 32b, 34b of the sleeve are asymmetrical with respect to the median radial plane of the device.

[0091] In the illustrated embodiment, the collar 34b remains radially recessed relative to the larger diameter portion of the outer surface 14a of the outer ring. In other words, the free end of the collar 34b is radially offset outwards relative to this larger diameter portion of the outer surface 14a.

[0092] In the illustrated embodiment, the flange 32b of the sleeve extends radially beyond the larger diameter portion of the outer surface 14a of the outer ring, i.e., radially projecting inwards relative to this larger diameter portion. In other words, the free end of the flange 32b is offset radially inwards relative to the larger diameter portion of the outer surface 14a of the outer ring. The flanges 32b and 34b remain at a distance from the outer ring 14.

[0093] The embodiment illustrated in Figures 7 to 9, in which the identical elements bear the same reference numerals, differs from the second embodiment in that the radial flanges 32b, 34b of the sleeve have a reduced radial dimension. The radial flanges 32b, 34b remain radially recessed relative to the larger diameter portion of the outer surface 14a of the outer ring. The radial flanges 32b, 34b are symmetrical here with respect to the median radial plane of the device.

[0094] In this example, the axial lengths Li and L2 of the spherical surfaces 28e2 and 28f2 of the first and second connecting chamfers are increased compared to the other illustrated examples. The radii of the spherical surfaces 28e2 and 28f2 are smaller than those of the other illustrated examples.

[0095] 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 fixed is the outer ring.

[0096] Alternatively, an inverted arrangement may be provided in which the second ring 14, to which the insulating sleeve 30 is attached, 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 radially interposed between the bore 12a of the inner ring and the outer surface of the sleeve. The insulating sleeve is fixed to the inner ring and at least to the outer surface of the sleeve. The bore of the bushing defines the bore of the bearing device. The connecting chamfer(s) then connect the front faces of the bushing to the bore.

[0097] 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, and first and second front faces (28c, 28d) defining the axial length of said bushing, the insulating lining (30) being fixed on the second ring (14) of the bearing and at least on one of the outer and inner surfaces of the bushing (28),characterized in that a first connecting chamfer (28e) links the first front face (28c) of the socket to said other surface of the outer and inner surfaces of the socket (28), the first connecting chamfer (28e) being provided with a radius (28ei) connecting to the first front face (28c) by forming a sharp edge (aj, and a spherical surface (28e2) connecting to said other surface of the socket (28) by forming another sharp edge (a2) and connecting to the radius, the value of the radius of the spherical surface (28e2) increasing in the direction of said other surface of the socket (28).

2. Device according to claim 1, wherein the spherical surface (28e2) of the first connecting chamfer (28e) connects to the radius (28ei) tangentially.

3. Device according to claim 1 or 2, wherein the value of the radius of the spherical surface (28e2) of the first connecting chamfer (28e) is greater than the value of the radius (28ei) of said first chamfer.

4. A device according to any one of the preceding claims, wherein a second connecting chamfer (28f) connects the second front face (28d) of the socket to said other surface of the socket (28), the second connecting chamfer (28f) having a radius (28fi) connecting to the second front face (28d) by forming a sharp edge (a3), and a spherical surface (28f2) connecting to said other surface of the socket (28) by forming a another sharp edge (a4) and connecting to the radius, the value of the radius of the spherical surface (28f2) increasing in the direction of said other surface of the socket (28).

5. Device according to claim 4, wherein the spherical surface (28f2) of the second connecting chamfer (28f) connects to the radius (28fi) tangentially.

6. Device according to claim 4 or 5, wherein the value of the radius of the spherical surface (28f2) of the second connecting chamfer (28f) is greater than the value of the radius (28fi) of said second chamfer.

7. Device according to any one of the preceding claims, wherein the socket (28) is made of metallic material.

8. Device according to claim 7, wherein the sleeve (28) is obtained by stamping or machining.

9. A method for manufacturing a bushing for a bearing device according to any one of the preceding claims comprising the following successive steps: - a step of producing a bushing blank giving it its basic geometry, said other surface of the bushing blank having a spherical shape, - a heat treatment step to give the bushing blank the required hardness, - a step of radially grinding the first front face (28c) of the bushing blank and a portion of the radius (28ei) of the first connecting chamfer which is adjacent to the first front face, and - a step of axially grinding said other surface of the bushing blank to give it its cylindrical shape, the spherical surface (28e2) of the first connecting chamfer remaining unground.

10. 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.