Grounding brush assembly

Abstract

This grounding brush assembly (10) comprises a grounding brush (22) having a plurality of conductive fibers (26) and a support (24) comprising a mounting portion (32) within which the conductive fibers (26) are housed, and first and second lateral edges (34, 36) extending from the mounting portion (32) and axially enclosing the conductive fibers (26), the assembly (10) comprising a mounting plate (28) integral with the support (24) and having at least one radial portion (38) extending radially outwards from the mounting portion (32) of the support (24), the free end (44) of said radial portion (38) of the mounting plate (28) defining at least part of the outside diameter of said assembly (10). Figure for the abbreviation: Fig 2.

Description

Title of the invention: Grounding brush assembly Technical field of the invention

[0001] The present invention relates to the field of grounding devices for controlling shaft current generated in electric motors or machines, and in particular 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 rotating 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 grounding brush assembly is known from US patent 2021 / 0021180. This assembly comprises a grounding brush with a support and a plurality of conductive fibers mounted in the support, and an annular mounting plate with a plurality of radial and axial retaining tabs for the grounding brush support, and an outer annular flange radially surrounding the brush and the tabs. The tabs are formed by plastic deformation of the mounting plate.

[0008] However, such an assembly of grounding brushes is not suitable when the The bearing is mounted axially free inside the engine casing and preloaded axially by a spring.

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

[0010] The invention relates to an assembly of grounding brushes comprising a grounding brush provided with a plurality of conductive fibers and a support comprising a mounting portion inside which the conductive fibers are housed, and first and second lateral edges extending the mounting portion and axially enclosing the conductive fibers.

[0011] The assembly includes a mounting plate attached to the support and provided with at least one radial portion extending radially outwards relative to the mounting portion of the support.

[0012] According to a general feature of the invention, the free end of said radial portion of the mounting plate defines at least part of the outside diameter of said assembly. In other words, the radial portion of the mounting plate is not extended axially or obliquely from its edge of large diameter.

[0013] Advantageously, said radial portion of the mounting plate extends purely radially.

[0014] In one embodiment, the mounting plate is provided with at least one elastically deformable tab, originating from said radial portion and extending axially in projection relative to said radial portion.

[0015] Preferably, the tab and the mounting plate are made in one piece, in particular by stamping. This facilitates the manufacture of the grounding brush assembly.

[0016] Preferably, the radial portion of the mounting plate, the first and second lateral edges, and the mounting portion each have an annular shape. Alternatively, the radial portion of the mounting plate, the first and second lateral edges, and the mounting portion may extend over an angular sector of less than 360°.

[0017] In a particular embodiment, the mounting plate and the support are made in one piece.

[0018] In another embodiment, the mounting plate comprises a plurality of tabs for axial and radial retention on the support. In this embodiment, the mounting plate and the support are two separate parts.

[0019] The invention also relates to an electric machine or motor comprising a housing, a shaft, a grounding brush assembly as defined above mounted radially between the housing and the shaft, and at least one bearing interposed between the shaft and the bore of the housing, a retaining means attached to the housing, and at least one axial preloading means located axially at least in part between said radial portion of the mounting plate of said assembly and the retaining means, the conductive fibers of said assembly being in contact with the shaft, a radial clearance remaining between the free end of said radial portion of the mounting plate and the bore of the housing.

[0020] Such a grounding brush assembly allows the axially free bearing to be mounted inside the motor housing while maintaining the dissipation properties of the assembly for electrical charges accumulating on the shaft. During motor operation, the electrical charges can be dissipated via the brush assembly, the axial preload means, and the retaining means.

[0021] Advantageously, said radial portion of the mounting plate is mounted in axial support against one of the front faces of the bearing.

[0022] In a particular embodiment, said axial prestressing means and said radial portion of the mounting plate are made in one piece. In this case, said axial prestressing means may be formed by said tab of the mounting plate.

[0023] In another embodiment, said axial preloading means includes a spring interposed axially between said radial portion of the mounting plate and the retaining means.

[0024] Preferably, said axial prestressing means exerts on the retaining means an axial prestressing force greater than the friction torque exerted by the conductive fibers on the shaft. Brief description of the figures

[0025] 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:

[0026] [Fig-1] is an axial cross-sectional view of a mounted grounding brush assembly radially between a rotating shaft and an electric motor housing according to a first embodiment of the invention;

[0027] [Fig.2] is a radial sectional view of the entire [Fig.1];

[0028] [Fig.3] is a front view of an assembly of grounding brushes according to a second example of the realization of the invention;

[0029] [Fig.4] is a cross-sectional view along axis IV-IV of [Fig.3];

[0030] [Fig.5] is a cross-sectional view along the VV axis of [Fig.3];

[0031] [Fig.6] is an axial cross-sectional view of a mounted grounding brush assembly radially between a rotating shaft and an electric motor housing according to a third embodiment of the invention; and

[0032] [Fig.7] is an axial cross-sectional view of the entire [Fig.6] mounted radially between a rotating shaft and an electric motor housing. Detailed description of the invention

[0033] Figure 1 shows, in axial section, a portion of a motor 2 or electrical machine comprising a fixed housing 4, a rotating shaft 6, of axis XX, radially supported by a bearing 8, the bearing 8 being axially free in one direction. The bearing 8 is, for example, a ball bearing. Alternatively, other rolling elements, for example rollers, may be provided. In another embodiment, a plain bearing may also be provided.

[0034] The motor 2 includes a grounding brush assembly 10 mounted radially between the bore 12 of the housing and the external cylindrical surface 14 of the shaft 6.

[0035] The assembly 10 is radially dimensioned so that a radial clearance 15 remains between the assembly 10 and the bore 12 of the housing, the assembly 10 thus being axially free. The assembly 10 is therefore not press-fitted into the bore 12 of the housing.

[0036] The motor 2 includes a retaining means 16 fixed to the housing 4 and projecting radially inwards from the bore 12 of the housing. The retaining means 16 is in the form of a retaining ring or circlip. Alternatively, the retaining means 16 could be formed as a single unit with the housing 4, and for example, formed by a shoulder of the latter.

[0037] The motor 2 includes a spring 18 interposed axially between the assembly 10 and the retaining means 16. The spring 18 is in contact with the retaining means 16 on one side, and with the grounding brush assembly 10 on the other. In the illustrated embodiment, the spring 18 is a helical spring with rectangular cross-section coils. Alternatively, coils with other cross-sections, for example square or circular, may be used. Alternatively, the spring could be formed by a stack of Belleville conical washers.

[0038] During the operation of the motor 2, the grounding brush assembly 10 is in contact with the shaft 6 and comes into contact with a front face 20 of the bearing 8 so that the electrical charges accumulating on the shaft 4 during the operation of the motor 2 are dissipated. The charges are transferred from the shaft 6 to the mounting plate 28 and the support 24 of the grounding brush assembly 10, then from the assembly 10 to the spring 18, then from the spring 18 to the means and retainer 16 and finally from the retainer 16 to the bore 12 of the housing.

[0039] As more clearly illustrated in [Fig. 2], the grounding brush assembly 10 has a generally annular shape. The assembly 10 comprises a grounding brush 22 including a support 24 and conductive fibers 26, as well as a mounting plate 28, support 24 housing conductive fibers 26.

[0040] The brush 22 comprises a plurality of individual conductive fibers 26 intended to be wrapped around the shaft 6 of the motor 2. The conductive fibers 26 are, for example, made of carbon, stainless steel, conductive plastics such as acrylic fibers, or nylon. The plurality of conductive fibers 26 is in the form of an open ring. In the illustrated example, the conductive fibers 26 are bent around a connecting wire 30. The free distal end of the conductive fibers 26 is intended to come into radial contact with the external cylindrical surface 14 of the shaft 6.

[0041] To ensure the mounting and retention of the conductive fibers 26, the support 24 includes a mounting portion 32, a first lateral rim 34 extending the mounting portion 32 on one side and a second lateral rim 36 extending the mounting portion 32 on the other.

[0042] The mounting plate 28 has an annular shape. The mounting plate 28 extends substantially radially. The mounting plate 28 comprises an annular radial portion 38 extending radially outward from the mounting portion 32 of the support 24. The radial portion 38 comprises two opposing front faces 40, 42 defining its axial thickness. The free end 44 of the radial portion 38 defines the outside diameter of the grounding brush assembly 10. The free end 44 of the radial portion 38 is the large-diameter edge of the radial portion 38. The radial clearance 15 ([Fig. 1]) remains between the free end 44 of the radial portion 38 and the bore 12 of the housing.

[0043] In the illustrated embodiment, the mounting plate 28 is formed in one piece with the support 24. The mounting plate 28 is therefore integral with the support 24. The first lateral edge 34 extends from a small-diameter edge of the radial portion 38. The first lateral edge 34 is folded over and bears against the radial portion 38 to form a crease and locally achieve a double thickness of material. The first lateral edge 34 bears against the front face 42 of the radial portion 38.

[0044] The mounting portion 32 extends the first lateral rim 34 axially on the side opposite the radial portion 38. The mounting portion 32 extends a large-diameter edge of the first lateral rim 34. The mounting portion 32 extends axially here. Alternatively, the mounting portion 32 could extend obliquely.

[0045] The second lateral rim 36 extends radially inwards the mounting portion 32. The second lateral rim 36 extends the mounting portion 32 on the opposite side to the first lateral rim 34.

[0046] The mounting portion 32 and the first and second lateral edges 34, 36 are annular in shape and define a channel open radially on the inner side, within which one end of the conducting fibers 26 is located. The first and The second lateral edges 34, 36 axially enclose the conducting fibers 26. The conducting fibers 26 are axially supported on both sides against the first and second lateral edges 34, 36.

[0047] In the illustrated embodiment, the conductive fibers 26 come radially to rest against the mounting portion 32, the first and second lateral edges 34, 36 extending obliquely inwards from the mounting portion 32. Alternatively, the first and second lateral edges 34, 36 could extend radially.

[0048] The radial portion 38, the first lateral rim 34, the mounting portion 32 and the second lateral rim 36 are made in one piece, for example made by cutting and stamping an electrically conductive material, such as for example aluminium, stainless steel, bronze, copper or other material.

[0049] The front face 40 of the radial portion 38 bears axially against the front face 20 of the bearing 8 ([Fig. 1]). The front face 42 bears axially against the spring 18. The spring 18 provides axial preload for the assembly 10 against the bearing 8. Preferably, the spring 18 exerts on the retaining means 16 an axial preload force greater than the frictional torque exerted by the conductive fibers 26 on the shaft 6.

[0050] The embodiment illustrated in figures 3 to 5, on which the identical elements bear the same references, differs from the example illustrated in figures 1 and 2 in that the mounting plate 28 and the support 24 of the brush 22 are two separate parts.

[0051] The mounting plate 28 comprises a main body 46 axially supported against the first lateral edge 34 of the support 24, a plurality of axial and radial retaining tabs 48 of the brush 22 and a plurality of radial portions 38. In the example shown, the mounting plate 28 comprises six radial portions 38 and six retaining tabs 48 regularly spaced in the circumferential direction.

[0052] The retaining tabs 48 extend from the main body 46 and are spaced circumferentially from one another, with the radial portions 38 located circumferentially between two successive retaining tabs 48. Each retaining tab 48 extends from the main body 46 such that it locally and radially surrounds the support 24 of the brush 22, being in radial and axial contact with the support 24. The support 24 is thus held axially and radially by the retaining tabs 48.

[0053] The radial portions 38 extend purely radially from the main body 46. Each radial portion 38 projects radially outwards from the mounting portion 32 of the support 24. The radial portions 38 are spaced from each other circumferentially, here at regular intervals. The The free ends 44 of the radial portions 38 jointly define the outer diameter of the grounding brush assembly 10. In the mounted position inside the housing 4, the radial clearance 15 remains between the free ends 44 of the radial portions 38 and the bore 12 of the housing.

[0054] In the example shown, a circumferential space is provided between each radial portion 38 and each adjacent retaining tab 48. In another embodiment, the number of radial portions 38 and the number of retaining tabs 48 may be different. The circumferential dimensions of the radial portions 38 and the retaining tabs 48 may be different. The radial portions 38 and the retaining tabs 48 may not be evenly distributed in the circumferential direction.

[0055] The embodiment illustrated in Figures 6 and 7, on which the identical elements bear the same references, differs from the example illustrated in Figures 1 and 2 in particular in that the mounting plate 28 is provided with elastically deformable tabs 50 in the axial direction, originating from the radial portion 38 and extending axially in projection relative to the radial portion 38.

[0056] Each deformable tab 50 extends circumferentially from the radial portion 38 over a limited angular sector, for example between 5° and 15°.

[0057] The deformable tabs 50 and the radial portion 38 are, for example, one-piece, for example, formed by stamping the mounting plate 28, the mounting plate 28 being made of an elastically deformable conductive material. In another embodiment, the deformable tabs 50 may be add-on parts fixed to the radial portion 38, for example, welded to the radial portion 38.

[0058] The deformable tabs 50 extend from the radial portion 38 and are spaced regularly from each other in the circumferential direction. In another embodiment, the number of deformable tabs 50 may be different, and the deformable tabs 50 may be distributed non-uniformly in the circumferential direction. Alternatively, it is also possible to provide a single deformable tab 50.

[0059] The deformable tabs 50 bear axially against the retaining means 16. The deformable tabs 50 form an axial prestressing means for the assembly 10 against the bearing 8. Preferably, the deformable tabs 50 exert on the retaining means 16 an axial prestressing force greater than the frictional torque exerted by the conductive fibers 26 on the shaft 6.

[0060] In this embodiment, the radial portion 38 is formed as a single piece with the support 24. Alternatively, it could be provided that the radial portion 38 and the support 24 are two separate parts, identically to the illustrated example. in figures 3 to 5.

Claims

Demands

1. Electric motor (2) comprising: - a housing (4), - a shaft (6), - a grounding brush assembly (10) mounted radially between the housing (4) and the shaft (6), the grounding brush assembly (10) comprising a grounding brush (22) having a plurality of conductive fibers (26) and a support (24) comprising a mounting portion (32) within which the conductive fibers (26) are housed, and first and second lateral flanges (34, 36) extending from the mounting portion (32) and axially enclosing the conductive fibers (26), the assembly (10) comprising a mounting plate (28) integral with the support (24) and having at least one radial portion (38) extending radially outwards relative to the mounting portion (32) of the support (24),the free end (44) which forms the large diameter edge of the radial portion (38) of the mounting plate (28) defining at least partially the outside diameter of said assembly (10), - at least one bearing (8) interposed between the shaft (6) and the bore (12) of the housing, a retaining means (16) integral with the housing (4), and - at least one axial preload means (18, 50) located axially at least partially between said radial portion (38) of the mounting plate (28) of said assembly (10) and the retaining means (16), the conductive fibers (26) of said assembly (10) being in contact with the shaft (6), characterized in that a radial clearance (15) remains between the free end (44) of said radial portion (38) of the mounting plate (28) and the bore (12) of the housing, and in which said radial portion (38) of The mounting plate (28) is mounted axially against one of the front faces (20) of the bearing (8).

2. Motor (2) according to claim 1, wherein said radial portion (38) of the mounting plate (28) extends purely radially.

3. Motor (2) according to claim 1 or 2, wherein said axial preload means (18, 50) and said radial portion (38) of the mounting plate (28) are made in one piece.

4. Motor (2) according to claim 3, wherein the mounting plate (28) is provided with at least one elastically deformable tab (50) originating from said radial portion (38) and extending axially in projection relative to said radial portion (38).

5. Motor (2) according to any one of claims 1 to 4, wherein the mounting plate (28) comprises a plurality of tabs (48) for axial and radial retention on the support (24).

6. Motor (2) according to claim 1 or 2, wherein said axial preload means (18, 50) comprises a spring (18) interposed axially between said radial portion (38) of the mounting plate (28) and the retaining means (16).

7. Motor (2) according to any one of the preceding claims, wherein the mounting plate (28) and the support (24) are made in one piece.

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