Bearing system including a grounding brush assembly

Abstract

[Bearing system comprising a grounding brush assembly] The bearing system comprises a bearing 10 and a grounding brush assembly 14 fixed to the outer ring 14 of the bearing and comprising a brush 30 offset axially outward from the inner ring 16 of the bearing and provided with a plurality of conductive fibers 31 and a support 32 for the conductive fibers. The conductive fibers 31 comprise a first group of fibers 31a whose free ends define the inner diameter of the brush 30 and a second group of fibers with a reduced radial protrusion length and whose free ends are offset radially outward from the bore of the inner ring 16 of the bearing. Reference: Figure 3

Description

Title of the invention: Bearing system comprising a grounding brush assembly Technical field of the invention

[0001] The present invention relates to the general field of grounding devices for controlling shaft current generated in electric motors or machines, and in particular to grounding brush assemblies. 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 ground or earth the rotating shaft using a grounding brush or broom having conductive fibers. The grounding brush is generally mounted in the bore of the electric motor housing such that the free ends of the fibers are in radial contact with the outer surface of the rotating shaft.

[0006] Thanks to the conductivity of the fibers, the brush is maintained at the same electrical potential as the electric motor housing. The inner and outer rings of the bearing are also at the same electrical potential, which reduces, or even eliminates, problematic electrical discharges through the bearing.

[0007] A set of setting brushes is known from document US-A1-2021 / 0021180 to grounding comprising a grounding brush provided with a plurality of conductive fibers, a support within which the conductive fibers are mounted, and an annular mounting plate comprising a plurality of radial and axial retaining tabs for the support and an outer annular flange radially surrounding said brush and the tabs.

[0008] It is also possible to equip the bearing with the grounding brush assembly.

[0009] However, with such a solution, mounting this assembly between the housing and the rotating shaft of the electric motor may be difficult to achieve.

[0010] The present invention aims to remedy this drawback. Summary of the invention

[0011] The invention relates to a bearing system comprising a bearing provided with a first ring and a second ring capable of rotating relative to each other.

[0012] The system also includes a grounding brush assembly fixed to the outer ring of the bearing and comprising a brush offset axially outwards relative to the inner ring of the bearing and provided with a plurality of conductive fibers and a support within which the conductive fibers are mounted. The conductive fibers extend radially inwards relative to the support.

[0013] According to a general characteristic, the conductive fibers of the brush of the grounding brush assembly comprise a first group of fibers whose free ends define the inner diameter of the brush.

[0014] According to a general characteristic, the conductive fibers of the brush comprise a second group of fibers whose radial protruding length is reduced compared to the radial protruding length of the first group of fibers and whose free ends are radially offset outwards relative to the bore of the inner ring of the bearing.

[0015] With such a design of the brush of the grounding brush assembly, the bearing system can easily be mounted inside the housing of the associated electric motor by simple axial push on the inner ring of the bearing by passing axially through the area or areas of reduced radial dimension of the conductive fibers of the brush which are radially delimited by the second group of fibers.

[0016] The free ends of the second group of fibers of the conducting fibers can be located in the area radially between the immediate vicinity of the bore of the inner ring of the bearing, for example at the top of an entry chamfer of the bore, and between the outer surface of the inner ring.

[0017] The free ends of the first group of conductive fibers may be radially offset inward relative to the bore of the inner ring of the bearing, or alternatively flush with the bore. Alternatively, the free ends of the conductive fibers could be radially recessed by relation to the bore in the particular design in which the bearing system further includes a sleeve mounted in bore 16a of the inner ring.

[0018] In one embodiment, the bore of the brush of the grounding brush assembly has a crenellated shape, each opening of the crenellated shape being delimited radially by conductive fibers of the second group of fibers and circumferentially by conductive fibers of the first group of fibers.

[0019] In one embodiment, the grounding brush assembly is fixed directly to the outer ring of the bearing without the interposition of an intermediate element. Alternatively, it remains possible to provide for the grounding brush assembly to be fixed with an intermediate element, but this increases the overall cost of the system.

[0020] Preferably, the grounding brush assembly is fixed inside a groove formed in the bore of the outer ring of the bearing. Alternatively, the grounding brush assembly can be fixed to another area of ​​the outer ring of the bearing, for example on a front face or on its outer surface, with or without the interposition of an intermediate element.

[0021] The grounding brush assembly may further include a brush mounting plate which is integral with the brush support and which is fixed to the outer ring of the bearing.

[0022] In a particular embodiment, the bearing of the system comprises at least one row of rolling elements arranged between raceways of the first and second rings. Alternatively, the bearing could be of the plain bearing type.

[0023] The invention also relates to a kit comprising a bearing system as defined above and an assembly tool comprising at least one finger having a radial dimension less than the radial distance between the bore of the inner ring of the bearing and the free ends of the second group of fibers of the conductive fibers of the brush of the grounding brush assembly.

[0024] The invention also relates to an electric motor comprising a housing, a shaft and at least one bearing system as defined above and mounted radially between the housing and the shaft, the first group of fibers of the conductive fibers of the brush of the grounding brush assembly being in contact with the shaft.

[0025] The invention further relates to a method of mounting a bearing system as defined above between a housing and a shaft of an electric motor in which the bearing system is pushed along said shaft using a mounting tool arranged radially between the shaft and the free ends of the second group of fibers of the conductive fibers of the brush of the grounding brush assembly, and coming axially to bear against the inner ring of the bearing. Brief description of the figures

[0026] The present invention will be better understood upon study of the detailed description of an embodiment, taken by way of non-limiting example and illustrated by the accompanying drawings, in which:

[0027] [Fig-1] is a perspective view of a bearing system according to an exemplary embodiment of the invention,

[0028] [Fig.2] is a front view of the bearing system of [Fig.1],

[0029] [Fig.3] is a half-sectional view along axis III-III of [Fig.2],

[0030] [Fig.4] is a half-sectional view along axis IV-IV of [Fig.2],

[0031] [Fig.5]

[0032] [Fig.6] are perspective views of an assembly of grounding brushes of the bearing system of [Fig.1], and

[0033] [Fig.7] is a half-sectional view schematically illustrating the mounting of the bearing system of [Fig.1] inside an electrical machine housing. Detailed description of the invention

[0034] The bearing system illustrated in figures 1 to 4 and referenced 10 as a whole is intended to be mounted radially between a housing and a rotating shaft of an electric motor or machine.

[0035] The bearing system 10 includes a bearing 12 and an assembly 14 of grounding brushes mounted on the bearing.

[0036] The bearing 12 is provided with an inner ring 16 and a second outer ring 18 which are able to rotate relative to each other about the axis (not shown) of the bearing. The inner ring 16 and outer ring 18 of the bearing are concentric and extend axially along the axis of the bearing. The inner ring 16 and outer ring 18 are made of steel. The rings are of the solid type.

[0037] In the illustrated embodiment, the bearing 12 also includes a row of rolling elements 20, here balls, interposed radially between the inner ring 16 and outer ring 18. The bearing 10 also includes a cage 22 for maintaining the regular circumferential spacing of the rolling elements 20.

[0038] The inner ring 16 comprises a cylindrical bore 16a, an axial cylindrical outer surface 16b radially opposed to the bore, and first and second radially opposed front faces 16c, 16d axially delimiting the bore and the outer surface. The bore 16a and the outer surface 16b define the radial thickness of the inner ring 16. The front faces 16c, 16d define the axial length of the inner ring 16.

[0039] The outer ring 18 comprises a cylindrical axial outer surface 18a, a cylindrical bore 18b radially opposed to the outer surface 18a, and first and second opposing radial front faces 18c, 18d axially delimiting the bore 18b and the outer surface 18a. The outer surface 18a and the bore 18b delimit the radial thickness of the outer ring 18. The faces 18c, 18d delimit the axial length of the outer ring 18.

[0040] The outer ring 18 further comprises first and second annular grooves 24, 26 formed on the bore 18b and extending radially outwards. Each groove 24, 26 is oriented radially towards the side of the inner ring 16.

[0041] The grooves 24, 26 are arranged axially on either side of the row of rolling elements 20. The groove 24 is located axially near the front face 18c of the outer ring, and the groove 26 is located axially near the front face 18d. The grooves 24, 26 are symmetrical to each other with respect to the radial median plane of the bearing system. Alternatively, the outer ring 18 could comprise only the groove 24.

[0042] The grounding brush assembly 14 is fixed in the groove 24 of the outer ring of the bearing. The assembly 14 has a generally annular shape. The assembly 14 comprises a grounding brush 30 and a brush mounting plate 40 configured to radially center said brush 30. The mounting plate 40 is fixed in the groove 24 of the outer ring of the bearing.

[0043] The brush 30 is axially offset outwards relative to the inner ring 16 of the bearing. In other words, the brush 30 is axially spaced from the inner ring 16 of the bearing. The brush 30 is positioned outside the bearing 12.

[0044] The brush 30 comprises a plurality of individual conductive fibers 31 intended to surround the rotating shaft of the motor. The conductive fibers 31 may be made of carbon, stainless steel, conductive plastics such as acrylic fibers, or nylon. In Figures 1, 2, 5, and 6, the conductive fibers 31 are shown schematically.

[0045] The brush 30 further includes a retaining member or support 32 inside which the conductive fibers 31 are mounted. The conductive fibers 31 extend radially inwardly relative to the support 32.

[0046] As will be described in more detail later, the conductive fibers 31 comprise a first group of fibers 31a and a second group of fibers 31b having different radial lengths projecting from the support 32.

[0047] In the illustrated embodiment, the support 32 is in the form of an open ring. The support 32 is made of a rigid material. The support 32 can be produced by cutting and stamping. The support 32 is made of an electrically conductive material, such as, for example, aluminum, stainless steel, bronze, copper, or other material. Alternatively, the support 32 can be made made of electrically non-conductive material with a conductive coating or conductive paint.

[0048] The brush 30 also preferably includes a ring 33 around which the conductive fibers 31 are arranged inside the support 32. The ring 33 serves as a support for the conductive fibers 31. The ring 33 is mounted inside the support 32.

[0049] The brush support 32 comprises an axial mounting portion 34 and two opposing lateral flanks 36, 38 extending inwards from the mounting portion 34 and axially enclosing the conductive fibers 31. The conductive fibers 31 are axially supported on both sides against the lateral flanks 36, 38. The conductive fibers 31 are radially supported against the mounting portion 34. The conductive fibers 31 extend radially inwards relative to the lateral flanks 36, 38 of the support.

[0050] The mounting portion 34 and the two lateral sides 36, 38 define a channel open radially on the inner side and within which the conducting fibers 31 are partly located.

[0051] The side flange 36 extends from one end of the mounting portion 34, and the side flange 38 extends from the opposite end. The side flanges 36 and 38 extend obliquely inward from the mounting portion 34. The side flanges 36 and 38 are symmetrical with respect to a median radial plane of the support 32. Alternatively, only one of the side flanges 36 and 38 could extend obliquely inward. In another embodiment, both side flanges 36 and 38 could extend radially. The mounting portion 34 extends axially in this case. Alternatively, the mounting portion 34 could extend obliquely.

[0052] The brush 30 is in the form of an open ring. This allows the brush to adapt to different diameters of the motor shaft. Generally, the ends of the brush are not fixed to each other. Alternatively, it is possible to fix these ends of the brush 30 to each other.

[0053] As previously stated, the conducting fibers 31 comprise a first group of fibers 31a and a second group of fibers 31b of different radial lengths.

[0054] The conductive fibers 31a of the first group have distal free ends that are intended to come into radial contact with the outer surface of the rotating shaft of the motor. The free ends of the conductive fibers 31a of the first group define the inner diameter of the conductive fibers 31, and more generally the inner diameter of the brush 30.

[0055] In the illustrated embodiment, the free ends of the conductive fibers 31a are radially offset inwards relative to the bore 16a of the ring inside the bearing. In other words, the free ends of the conductive fibers 31a project radially from the bore 16a of the inner ring. Alternatively, the free ends of the conductive fibers 31a could be radially flush with the bore 16a. In another alternative, the free ends of the conductive fibers 31a could be radially recessed from the bore 16a if the bearing system further includes a sleeve mounted in the bore 16a of the inner ring.

[0056] The conductive fibers 31b of the second group have distal free ends that are designed to remain radially away from the outer surface of the rotating shaft of the motor. The radial length of the fibers 31b of the second group protruding from the support 32 is less than the radial length of the fibers 31a of the first group protruding from said support 32.

[0057] The free ends of the conductive fibers 31b are radially offset outwards relative to the bore 16a of the inner ring of the bearing. In other words, the free ends of the conductive fibers 31b are radially recessed relative to the bore 16a of the inner ring.

[0058] Preferably, the free ends of the conductive fibers 31b are located at a radial distance from the bore 16a which is between 25% and 50% of the radial thickness of the inner ring 16.

[0059] As will be described in more detail later, the conductive fibers 31b of the second group of reduced radial dimension are provided for mounting the bearing system 10 inside the associated electric motor.

[0060] The bore of the conductive fibers 31, and more generally the bore of the brush 30, has a crenellated shape. Each opening 39 or cutout of the crenellated shape is delimited radially by conductive fibers 31b of the second group of fibers and circumferentially by conductive fibers 31a of the first group of fibers.

[0061] Thus, in the illustrated embodiment, there is, in the circumferential direction, a succession of conducting fibers 31a from the first group and conducting fibers 31b from the second group. The conducting fibers 31a of the first group are arranged in subgroups spaced circumferentially from one another, and the conducting fibers 31b of the second group are arranged in subgroups spaced circumferentially from one another, with a subgroup of conducting fibers 31b interposed circumferentially between two successive subgroups of conducting fibers 31a. The conducting fibers 31a form a ring of fibers that continues circumferentially between these two ends.

[0062] The circumferential dimension of the subgroups of the conducting fibers 31a of the first group is greater than the circumferential dimension of the subgroups of the conducting fibers 31b of the second group.

[0063] The openings 39 of the conducting fibers 31 are spaced circumferentially, here at regular intervals. Alternatively, irregular circumferential spacing may be provided. There are four openings 39. Alternatively, a greater or lesser number of openings 39 may be provided. A single opening may also be provided.

[0064] The mounting plate 40 of the grounding brush assembly includes an annular radial portion 42 and a plurality of axial and radial retaining tabs 44 for the brush 30 extending from the radial portion 42.

[0065] The mounting plate 40 also includes a fixing portion 46 fixed in the groove 24 of the outer ring 18 of the bearing, and a connecting portion 48 linking the fixing portion 46 to the radial portion 42.

[0066] The radial portion 42 of the mounting plate bears axially against the support 32 of the brush 30. More precisely, the radial portion 42 bears axially against the lateral side 36 of the support. The radial portion 42 is axially offset outwards relative to the inner ring 16 of the bearing. The radial portion 42 remains axially clear of the front face 16c of the inner ring. The brush support 32 is axially supported against the radial portion 42 axially on the side opposite the inner ring 16. Alternatively, depending on the design of the mounting plate, the brush support 32 can be axially supported against the radial portion 42 axially on the side of the inner ring 16. In this case, the support 32 is arranged axially between the radial portion 42 of the mounting plate and the face 16c of the inner ring, remaining axially spaced from this face 16c.

[0067] The tabs 44 are spaced circumferentially from one another, here at regular intervals. Alternatively, irregular circumferential spacing may be provided. In the illustrated embodiment, there are eight tabs 44. Alternatively, a greater or lesser number of tabs 44 may be provided. Two tabs 44 may be provided, or at least four. Preferably, the number of tabs 44 is at least two.

[0068] Each tab 44 extends axially in projection relative to the radial portion 42. Each tab 44 locally surrounds the support 32 of the brush 30 radially and is in radial contact with the mounting portion 34 of said support. The support 32 is held axially against the radial portion 42 of the mounting plate by the tabs 44. The tabs 44 allow for axial and radial retention The grounding brush 30. The lateral side 36 of the support rests against the radial portion 42 of the mounting plate and the lateral side 38 rests against the tabs 44. The tabs 44 are identical here.

[0069] Each tab 44 is provided with an axial portion extending axially from the radial portion 42, locally surrounding the support 32 radially and in radial contact with it, and with a portion folded radially inwards which is provided at the free end of the axial portion. The folded portion of each tab allows the support 32 to be axially retained from the grounding brush 30. The folded portion of each tab is in axial contact against the lateral side 38 of the support.

[0070] The mounting portion 46 of the mounting plate is press-fitted into the groove 24 of the outer ring 18 of the bearing. In the illustrated embodiment, the mounting portion 46 is formed in the form of sectors folded back on themselves to conform to the shape of the groove 24. The sectors are spaced circumferentially from one another. Alternatively, the mounting portion 46 could be annular. The mounting portion 46 defines the outer diameter of the mounting plate 40.

[0071] The fixing portion 46 is offset radially outwards relative to the tabs 44 and axially offset inwards towards the bearing 12 relative to the tabs 44.

[0072] The connecting portion 48 of the mounting plate is annular and has a stepped shape. The connecting portion 48 extends between the large diameter edge of the radial portion 42 and the small diameter edge of the fixing portion 46.

[0073] A plurality of through-holes 50 are formed in the thickness of the radial portion 42 and the connecting portion 48 of the mounting plate. The openings 50 are formed during the partial cutting of the mounting plate 40 to form the tabs 44. The tabs 44 are formed by cutting, folding, and crimping the mounting plate 40. The openings 50 are spaced circumferentially from one another. Each tab 44 is circumferentially aligned with its associated opening 50. The number of openings 50 corresponds to the number of tabs 44. As can be seen in [Fig. 6], the root of each tab 44 extends from an inner edge of the associated opening 50, which is located on the radial portion 42.

[0074] The mounting plate 40 is made by cutting and stamping. The mounting plate 40 is made of a conductive material, such as, for example, aluminum, stainless steel, bronze, copper, or other materials. Alternatively, the mounting plate 40 can be made of an electrically non-conductive material with a conductive coating or conductive paint. The mounting plate is made here in one piece.

[0075] As previously stated, the conductive fibers 31b of the second group of reduced radial dimension are provided for mounting the bearing system 10 inside the associated electric motor.

[0076] As illustrated in [Fig.7], to mount the brush system 10 inside the bore 52 of the housing of the associated electric motor and on the rotating shaft 54 ​​of the motor, a mounting tool 56, partially represented by dotted lines, is used.

[0077] The tool 56 is brought axially to bear against the front face 16c of the inner ring of the bearing so that it can axially push the system 10 until it comes to bear against a stop surface of the housing of the associated electric motor which is provided for this purpose.

[0078] The tool 56 extends axially through the cutouts 39 in the conductive fibers 31 of the brush, remaining at a distance from the fibers. The tool 56 has a plurality of fingers, each extending axially through one of the cutouts 39 in the conductive fibers 31. The fingers of the tool 56 are arranged radially between the shaft 54 ​​of the electric motor and the free ends of the second group of fibers 31b and bear axially against the inner ring 16 of the bearing. Each finger of the tool has a radial dimension smaller than the radial distance between the bore 16a of the inner ring of the bearing and the free ends of the second group of fibers 31b of the brush. Each finger of the tool also has a circumferential dimension smaller than the circumferential dimension of the cutouts 39 in the conductive fibers 31 of the brush.

[0079] During the operation of the electric motor, the electrical charges which accumulate on the shaft 54 ​​are dissipated towards the housing 52 through the conductive fibers 31, the support 32 of the brush, and the mounting plate 40 of the assembly.

Claims

Demands

1. Bearing system (10) comprising a bearing (12) having an inner ring (16) and an outer ring (18) capable of rotating relative to each other, and a grounding brush assembly (14) fixed to the outer ring (14) of the bearing and comprising a brush (30) offset axially outwards relative to the inner ring (16) of the bearing and having a plurality of conductive fibers (31) and a support (32) within which the conductive fibers are mounted, the conductive fibers (31) extending radially inwardly relative to the support (32) characterized in that the conductive fibers (31) of the brush of the grounding brush assembly (20) comprise at least a first group of fibers (31a) whose free ends define the inner diameter of the brush (30),and a second group of fibers (31b) whose radial protruding length is reduced compared to the radial protruding length of the first group of fibers (31a) and whose free ends are radially offset outwards relative to the bore (16a) of the inner ring of the bearing.

2. System according to claim 1, wherein the free ends of the first group of fibers (31a) of the conducting fibers are radially offset inwards relative to the bore (16a) of the inner ring of the bearing or are flush with the bore.

3. System according to claim 1 or 2, wherein the bore of the brush (30) of the grounding brush assembly has a crenellated shape, each opening (39) of the crenellated shape being delimited radially by conductive fibers of the second group of fibers (31b) and circumferentially by conductive fibers of the first group of fibers (31a).

4. System according to any one of the preceding claims, wherein the grounding brush assembly is fixed directly to the outer ring (16) of the bearing without interposition of an intermediate element.

5. System according to any one of the preceding claims, in the grounding brush assembly is fixed inside a groove (24) formed in the bore of the outer ring of the bearing.

6. System according to any one of the preceding claims, wherein the grounding brush assembly (14) further comprises a brush mounting plate (40) which is integral with the brush support (32) and which is fixed to the outer ring (14) of the bearing.

7. Kit comprising a bearing system (10) according to any one of claims 1 to 6 and an assembly tool (56) comprising at least one finger having a radial dimension less than the radial distance between the bore (16a) of the inner ring of the bearing and the free ends of the second group of fibers (31b) of the conductive fibers of the brush of the grounding brush assembly.

8. Electric motor comprising a housing (52), a shaft (54) and at least one bearing system (10) according to any one of claims 1 to 6 mounted radially between the housing and the shaft, the first group of fibers (31a) of the conductive fibers of the brush of the grounding brush assembly being in contact with the shaft.

9. A method of mounting a bearing system according to any one of claims 1 to 6 between a housing and a shaft of an electric motor in which the bearing system is pushed along said shaft by means of a mounting tool arranged radially between the shaft and the free ends of the second group of fibers (31b) of the conductive fibers of the brush of the grounding brush assembly, and coming axially to bear against the inner ring (16) of the bearing.

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