Grounding brush assembly

Abstract

[Grounding Brush Assembly] This grounding brush assembly (10) comprises a grounding brush (16) and a brush (16) mounting plate (18), said brush (16) being provided with a plurality of conductive fibers (20) and a support (22) within which the conductive fibers (20) are housed, the mounting plate (18) being integral with the support (22) and provided with a radially extending main body (32), retaining tabs (34) for axially and radially retaining said support (22), and an axially extending centering portion (36), the mounting plate (18) comprising at least a bearing portion (40) bearing radially against the brush support (22) and providing a bearing surface for an insertion tool of the assembly (10) into a housing (4). Figure for the abridged version: Fig 1.

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] Such an assembly of grounding brushes is press-fitted into the bore of the housing, the assembly of grounding brushes is therefore difficult to disassemble.

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

[0010] The invention relates to an assembly of grounding brushes for an electric motor equipped with a rotating shaft, a fixed housing, and a bearing.

[0011] The assembly includes a grounding brush provided with a plurality of conductive fibers and a support within which the conductive fibers are mounted. The assembly also includes a brush mounting plate which is integral with the brush support.

[0012] The mounting plate comprises: a main body formed by a radial portion extending radially outwards relative to the support; a plurality of centering tabs extending axially in projection relative to the radial portion, each tab locally surrounding radially the brush support and being in radial contact with the support, said support being held axially in contact against the radial portion of the mounting plate by the tabs; and a centering portion extending at least axially from the main body, extending axially on the same side as the tabs, offset radially outwards relative to the support and the tabs, and provided with an outer surface defining the outer diameter of the mounting plate in order to allow centering of the mounting plate after mounting in a bore of the housing of an associated electric motor.

[0013] According to a general feature of the invention, the mounting plate also includes at least one support portion projecting radially towards the inside of the assembly. The support portion is formed by a first folded portion extending axially from the main body and bearing radially on an upper axial surface of the brush support, and by a second folded portion extending radially between said first folded portion and the centering portion, said second folded portion defining an axial support surface for a tool for positioning the assembly.

[0014] The centering portion and the first bent portion of the support portion both extend along the same axial direction from the main body. The centering portion has a larger diameter than the first bent portion, with a radial offset defined between the two.

[0015] In one embodiment, the centering portion may be annular. Alternatively, the centering portion may comprise a plurality of axial portions spaced from each other in the circumferential direction.

[0016] In one embodiment, the mounting plate comprises a plurality of support portions spaced from each other in the circumferential direction.

[0017] In one embodiment, the retaining tabs and the support portions are distributed alternately in the circumferential direction.

[0018] According to an advantageous embodiment, the second folded portion is continued by an axial portion of the centering portion.

[0019] The invention also relates to an electric machine or motor comprising a housing, a shaft, an assembly of grounding brushes as defined above mounted radially at least in part between the housing and the shaft, the conductive fibers of said assembly being in contact with the shaft. Brief description of the figures

[0020] 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:

[0021] [Fig-1] is an axial cross-sectional view of an assembly of grounding brushes mounted radially partly between a rotating shaft and an electric motor housing according to an embodiment of the invention;

[0022] [Fig.2] is a perspective view of the grounding brush assembly of [Fig.1];

[0023] [Fig.3] is a front view of the grounding brush assembly of [Fig.1];

[0024] [Fig.4] is a cross-sectional view of the whole of [Fig.3] along axis II;

[0025] [Fig.5] is a cross-sectional view of the entire [Fig.3] along axis II-II; and

[0026] [Fig.6] is a cross-sectional view of the whole of [Fig.3] along axis III-III. Detailed description of the invention

[0027] Figure 1 shows, in axial section, a portion of an electric motor or machine 2 comprising a fixed housing 4, a rotating shaft 6, with axis XX, radially supported by a bearing 8. The bearing 8 is, for example, a ball bearing. Alternatively, other rolling elements, such as rollers, may be provided. In another embodiment, a plain bearing may also be provided.

[0028] The motor 2 includes a grounding brush assembly 10 mounted radially in part between the bore 12 of the housing and the external cylindrical surface 14 of the shaft. The assembly 10 is, for example, press-fitted into the bore 12 of the housing.

[0029] In the following description, the adjectives "axial" and "radial" and the adverbs "axially" and "radially" are defined with respect to the central axis X. Thus, an axial portion or part is parallel to the axis X, while a radial portion or part is perpendicular to this axis and surrounds it. Furthermore, a radial portion is provided with a an "interior" surface oriented towards the X axis, and an "exterior" surface oriented in the opposite direction to this axis.

[0030] As more clearly illustrated in Figures 2 to 6, the grounding brush assembly 10 has a generally annular shape. The assembly 10 comprises a grounding brush 16 and a mounting plate 18 for the brush 16.

[0031] The grounding brush 16 comprises a plurality of conductive fibers 20 and a support 22, the conductive fibers being housed inside the support 22 of the brush 16. The conductive fibers 20 are, for example, made of carbon, stainless steel, conductive plastics such as acrylic fibers, or nylon. The plurality of conductive fibers 20 are in the form of an open ring. In the illustrated example, the conductive fibers 20 are bent around a connecting wire 24. The free distal end of the conductive fibers 20 is intended to come into radial contact with the external surface 14 of the shaft 6.

[0032] To ensure the mounting and retention of the conductive fibers 20, the support 22 comprises a cylindrical portion 26 defining an upper axial surface for the support 22, a first lateral rim 28 extending from the cylindrical portion 26 on one side, and a second lateral rim 30 extending from the cylindrical portion 26 on the other. The first rim 28 is located axially towards the outside of the assembly, while the second rim 30 is located axially towards the bearing 8, said rims 28 and 30 being axially opposed with respect to the cylindrical portion 26 and the fibers 20.

[0033] The mounting plate 18 is integral with the support 22. The mounting plate 18 comprises a main body 32 formed by a radial portion which is axially supported against the first rim 28 of the support, a plurality of axial and radial retaining tabs 34 for the brush 16, and an axial centering portion 36.

[0034] The centering portion 36 of the mounting plate 18 extends axially from the main body 32, in a direction opposite to the bearing 8. According to the embodiment illustrated in Figures 1 to 5, the centering portion 36 consists of an annular cylindrical portion. Alternatively, it could be provided that the centering portion comprises a plurality of axial portions spaced from each other in the circumferential direction.

[0035] The centering portion 36 is provided with an outer surface 38 defining the outer diameter of the mounting plate 18 in order to allow the centering of said mounting plate after mounting in the bore 12 of the housing 4 of the associated electric motor 2. The centering portion 36 is preferably press-fitted into the bore 12 of the housing 4 in order to create a diametrical interference to ensure mechanical retention of the mounting plate 18 in said housing 4.

[0036] The retaining tabs 34 extend from the main body 32 of the mounting plate 18 and are spaced apart from each other in the direction circumferential. The tabs 34 extend axially from the main body 32 in a direction opposite to the bearing 8.

[0037] Each retaining tab 34 extends from the main body 32 of the mounting plate 18 such that the retaining tab 34 locally and radially surrounds the support 22 of the brush 16, being in radial contact with the support 22. The support 22 is axially held by the tabs 34. In addition, each tab 34 is provided with a folded edge on the support 22 to create axial contact. The support 22 is axially held against the radial portion 32 of the mounting plate 18 by the tabs 34. The support 22 is thus held axially and radially by the retaining tabs 34.

[0038] In the example shown, the mounting plate 18 comprises four retaining tabs 34 spaced regularly in the circumferential direction. Alternatively, the mounting plate comprises a different number of retaining tabs 34. In the case where the mounting plate 18 comprises a plurality of centering portions, the positions of the tabs 34 may alternate circumferentially with said centering portions.

[0039] The centering portion 36 extends axially from the main body 32, extends axially on the same side as the support 22 and the tabs 34, and is radially offset outwards relative to the support 22 and the tabs 34.

[0040] The cylindrical portion 26 of the support 22 is in radial contact with the retaining tabs 34, and the second lateral rim 30 is in axial contact with said tabs. The cylindrical portion 26 extends from the large-diameter edge of the first lateral rim 28. The cylindrical portion 26 extends axially here.

[0041] The second lateral rim 30 of the support 22 extends radially inwards from the cylindrical portion 26. The second lateral rim 30 extends the cylindrical portion 26 on the side opposite the first lateral rim 28. The cylindrical portion 26 and the first and second lateral rims 28, 30 are annular in shape and define a channel open radially on the inner side, inside which one end of the conductive fibers 20 is located. The first and second lateral rims 28, 30 axially enclose the conductive fibers 20. The conductive fibers 20 are axially supported on both sides against the first and second lateral rims 28, 30.

[0042] In the illustrated embodiment, the conductive fibers 20 come radially to rest against the cylindrical portion 26, the first and second lateral edges 28, 30 extending obliquely inwards from the cylindrical portion 26. Alternatively, the first and second lateral edges 28, 30 could extend radially.

[0043] In the illustrated embodiment, the mounting plate 18 and the support 22 are two separate parts. Alternatively, the mounting plate 18 could be made of a single piece with the support 22, for example made by cutting and stamping. In this case, the main body 32 of the mounting plate 18 extends the small diameter edge of the first lateral rim 28.

[0044] The mounting plate 18 and the grounding brush 16 comprise an electrically conductive material, such as, for example, aluminium, stainless steel, bronze, copper or other material.

[0045] According to the invention, the mounting plate also includes a plurality of support portions 40 to axially maintain the brush support 22, and to serve as a support for an insertion tool of the assembly 10 in a housing 4.

[0046] Each support portion 40 is formed by a first bent portion 42 and a second bent portion 44. The first bent portion 42 extends axially from the main body 32. The centering portion 36 and the first bent portion 42 of the support portion 40 both extend in the same axial direction from the main body 32. The centering portion 36 has a larger diameter than the first bent portion 42, a radial offset being defined between the two.

[0047] The second folded portion 44 extends radially between the first folded portion 42 and the centering portion 36. The second folded portion 44 forms a radial connection between the two axial portions 42 and 36. Each support portion 40 thus forms a radial projection towards the inside of the assembly 10.

[0048] The second folded portion 44 is continued along an axial direction by an axial portion 37 of the centering portion 36.

[0049] Advantageously, each support portion 40 is formed by cutting out the centering portion 36. More precisely, two cutouts 46a, 46b are made with a defined circumferential length and spacing across the thickness of the centering portion 36. The portion between the two cutouts 46a, 46b is then deformed by folding to form the two portions 42 and 44, which project radially inward. Alternatively, the support portions 40 can be formed by notching without material removal.

[0050] According to the invention, each first folded portion 42, which extends along an axial direction, comes into radial contact on an upper axial surface of the cylindrical portion 26 of the brush support 22.

[0051] The support 22 is thus held radially in position by the plurality of bearing points 40 and tabs 34 in direct contact with the outer surface of the cylindrical portion 26 of said support 22. This radial holding of the support 22, in combination with its axial holding between the tabs 34 and the main body 32, ensures that said support 22 is held in position with the mounting plate 18. The mounting plate 18 being itself fitted into a bore 12 of the housing 4, the fibers 20 mounted in the support 22 are thus positioned relative to the bearing 8, to the casing 4, and to the rotating shaft 6 in order to ensure a function of passing electric current.

[0052] In the example shown, the mounting plate 18 comprises four bearing portions 40 spaced regularly in the circumferential direction. Alternatively, the mounting plate comprises a different number of bearing portions 40.

[0053] In the example shown, the retaining tabs 34 and the support portions 40 are distributed alternately in the circumferential direction. Alternatively, the tabs and the support portions can be positioned according to other distributions, for example two or more support portions between two successive tabs circumferentially, or two or more tabs between two successive support portions.

[0054] Furthermore, each second folded portion 44 defines an axial support surface for a tool (not illustrated) for positioning the assembly 10. Thanks to the invention, the grounding brush assembly 10 can be mounted simply and without risk of deformation in a housing 4 and on a rotating shaft 6.

[0055] Indeed, a grounding brush assembly according to the prior art, for example US-A1-2021 / 0021180, is press-fitted into the housing bore by an assembly tool bearing axially against the edges of the tabs and exerting a force in the axial direction of insertion. Such an assembly method implies a suitable design of the grounding brush assembly, in particular a sufficient radial dimension of the tabs and the support 22 to withstand the applied force.

[0056] With the present invention, the grounding brush assembly 10 is press-fitted into the bore 12 of the housing by an assembly tool (not shown) bearing axially against the lateral face of the second folded portion 44 and exerting a force along the axial direction of insertion. Consequently, the tabs no longer serve as support for the tool and can be dimensioned appropriately solely for their function of retaining the support 22. The tabs 34 and the support 22 can be dimensioned in a smaller size compared to a prior art assembly, thus allowing the assembly 10 to be more radially compact.

[0057] Consequently, the tabs 34 and the support 22 no longer undergo direct force exerted by the assembly tool, thus eliminating the risk of deformation of these parts when inserting the assembly 10 into a housing 4.

[0058] The support portions 40 allow increased rigidity of the centering portion 36, which is press-fitted into the housing 4. The risks of deformation of said portion 36 during the fitting or removal of the assembly 10 are thereby reduced.

[0059] Furthermore, the technical characteristics of the different embodiments can be combined with each other, in whole and only for some of them. Thus, the grounding brush assembly can be adapted in terms of cost, performance and ease of implementation.

Claims

Demands

1. A grounding brush assembly (10) for an electric motor (2) having a shaft (6) rotating about an axis (X), a fixed housing (4) and a bearing (8), and comprising a grounding brush (16) having a plurality of conductive fibers (20) and a support (22) in which the conductive fibers are mounted, and a brush mounting plate (18) integral with the brush support (22), the mounting plate (18) comprising: - a main body (32) formed by a radial portion extending radially outward from the support (22), - a plurality of centering tabs (34) extending axially projecting from the main body (32), each tab (34) locally surrounding the brush support (22) radially and being in radial contact with the support (22),said support (22) being axially supported against the main body (32) of the mounting plate (18) by the tabs (34), and - a centering portion (36) extending at least axially from the main body (32), extending axially on the same side as the tabs (34), offset radially outwards relative to the support (22) and the tabs (34), and provided with an outer surface (38) defining the outer diameter of the mounting plate (18) in order to allow centering of the mounting plate (18) after mounting in a bore (12) of the housing (4) of an associated electric motor (2), characterized in that the mounting plate (18) also includes at least one support portion (40) projecting radially inwards from the assembly (10),said support portion (40) being formed by: - ​​a first folded portion (42) extending axially from the main body (32) and bearing radially on an upper axial surface (26) of the brush support (22), and - a second folded portion (44) extending radially between said first folded portion (42) and the centering portion (46), said second folded portion (44) defining an axial support surface for a tool for positioning the assembly (10).

2. Assembly (10) according to claim 1, wherein the centering portion (18) is annular.

3. Assembly (10) according to claim 1, wherein the centering portion (18) comprises a plurality of axial portions spaced from each other in the circumferential direction.

4. Assembly (10) according to any one of the preceding claims, wherein the mounting plate (18) comprises a plurality of support portions (40) spaced from each other in the circumferential direction.

5. Assembly (10) according to claim 4, wherein the retaining tabs (34) and the support portions (40) are distributed alternately in the circumferential direction.

6. Assembly (10) according to any one of the preceding claims, wherein said second folded portion (44) is continued by an axial portion (37) of the centering portion (36).

7. Electric motor (2) comprising a housing (4), a shaft (6), an assembly (10) of grounding brush according to any one of the preceding claims mounted radially at least in part between the housing (4) and the shaft (6), the conductive fibers (20) of said assembly being in contact with the shaft (6).

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