Grounding brush assembly

Abstract

The ground brush assembly (20) comprises a ground brush (30) and a mounting plate (40) of the brush, the ground brush (30) being provided with a plurality of electrically conductive fibers (31) and a support (32), the electrically conductive fibers being mounted within the support (32), the mounting plate (40) being rigidly fixed to the support (32) of the brush. The ground brush (30) takes the form of a split ring and is provided with a first end (30a) and a second end (30b) spaced apart from each other in the circumferential direction and facing each other. The mounting plate includes at least one anti-rotation lug (50) disposed in a circumferential space separating a first end (30a) and a second end (30b) of the ground brush.

Description

Technical Field

[0001] The present invention relates to the field of grounding devices for controlling shaft voltage generated in electric motors or machines, and in particular to grounding brush assemblies. Background Art

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

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

[0004] The current flowing through the components of the rolling bearing may damage the components, particularly the rolling elements and the raceways formed on the inner and outer rings. The discharge may also generate vibrations.

[0005] To overcome these drawbacks, it is known practice to use a grounding brush comprising conductive fibers to ground or connect the rotating shaft to ground or earth. The grounding brush is usually mounted in a hole in the housing of the electric motor so that the free end of the fibers is in radial contact with the outer surface of the rotating shaft.

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

[0007] US-A1-2021 / 0021180 discloses a grounding brush assembly, which includes: a grounding brush provided with a plurality of conductive fibers; a support member ( / support) in which the plurality of conductive fibers are installed; and an annular mounting plate including a plurality of tabs ( / tabs) and an annular outer flange, wherein the plurality of tabs are used to radially and axially retain the support member, and the annular outer flange radially surrounds the brush and the tabs.

[0008] With such grounding brush assemblies, during operation when the shaft of the associated electric machine rotates, contact may be lost between the mounting plate and the support, which limits the flow of current through the assembly.

[0009] The present invention aims to overcome this disadvantage. Summary of the invention

[0010] The invention relates to a grounding brush assembly, which comprises a grounding brush, wherein the grounding brush is provided with a plurality of conductive fibers and a support, wherein the conductive fibers are mounted in the support, and the assembly further comprises a brush mounting plate, wherein the brush mounting plate is rigidly fixed to the brush support.

[0011] The grounding brush takes the form of an open ring and is provided with a first end and a second end spaced apart from the first end, the first end and the second end facing each other in a circumferential direction.

[0012] The first end and the second end define a circumferential length of the brush.

[0013] According to a general feature, the mounting plate includes at least one anti-rotation lug disposed in a circumferential space separating the first end and the second end of the grounding brush.

[0014] The lug of the mounting plate forms a means for blocking the rotation of the brush in the event of a circumferential movement of the brush relative to the mounting plate. The lug makes it possible to block the rotation of the brush by contacting one of the ends of the brush in the circumferential direction.

[0015] This prevents the risk of friction wear and heating between the mounting plate and the support of the conductive fibers. This makes it possible to prevent heating and electroerosion, which could lead to a loss of contact between the mounting plate and the support. Thus, the flow of current through the assembly is reliably ensured during operation.

[0016] No additional components are provided on the mounting plate and / or the brushes to perform this anti-rotation function by axial interference.

[0017] The mounting plate may include a plurality of retaining tabs for retaining a support for the brush. Preferably, the anti-rotation lugs of the mounting plate are distinct from the retaining tabs.

[0018] The mounting plate may comprise an annular radial portion against which the grounding brush bears axially. In this case, the support of the brush may bear axially against the radial portion of the mounting plate.

[0019] In a specific embodiment, the retaining tab of the mounting plate extends from a radial portion of the mounting plate. As another option, the retaining tab of the mounting plate can extend from another portion of the mounting plate.

[0020] In one embodiment, the mounting plate includes at least one centring portion extending axially from the radial portion, the at least one centring portion being radially outwardly offset relative to the support and having an outer surface defining an outer diameter of the mounting plate.

[0021] According to one design, the anti-rotation lug extends from a radial portion of the mounting plate.

[0022] Alternatively, the anti-rotation tab may extend from another portion of the mounting plate, such as a retaining tab or a centering portion.

[0023] Preferably, the mounting plate is made in one piece.

[0024] Advantageously, the anti-rotation lug of the mounting plate is formed at least by plastic deformation of the mounting plate. The anti-rotation lug may be formed by cutting and plastic deformation of the mounting plate.

[0025] Alternatively, the mounting plate can be obtained by other manufacturing methods, for example by additive manufacturing, in other words, by any manufacturing method based on building up the mounting plate layer by layer by adding material. In the present case, one or more anti-rotation lugs are obtained during the manufacturing of the mounting plate.

[0026] The invention also relates to an electric motor comprising a casing, a shaft and at least one grounding brush assembly as defined above and mounted radially between the casing and the shaft, the conductive fibers of the brush of the grounding brush assembly being in contact with the shaft. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The invention will be more clearly understood on reading the detailed description of embodiments provided by way of non-limiting example and illustrated by the accompanying drawings, in which:

[0028] [ Figure 1 ] is an axial cross-sectional view of a grounding brush assembly radially mounted between a rotating shaft and a housing of an electric motor;

[0029] [ Figure 2 ]and[ Figure 3 ] is a perspective view of a grounding brush assembly according to a first exemplary embodiment of the present invention;

[0030] [ Figure 4 ]yes Figure 2 and Figure 3 An end view of a grounding brush assembly;

[0031] [ Figure 5 ] is along Figure 4 A cross-sectional view of the axis VV;

[0032] [ Figure 6 ] is a perspective view of a grounding brush assembly according to a second exemplary embodiment of the present invention;

[0033] [ Figure 7 ]yes Figure 6 An end view of a grounding brush assembly;

[0034] [ Figure 8 ] is a perspective view of a grounding brush assembly according to a third exemplary embodiment of the present invention;

[0035] [ Fig. 9 ]yes Figure 8 An end view of a grounding brush assembly;

[0036] [ Fig.10 ]and[ Fig.11 ] is a perspective view of a grounding brush assembly according to a third exemplary embodiment of the present invention;

[0037] [ Fig.12 ]yes Fig.10 and Fig.11 End view of the grounding brush assembly. DETAILED DESCRIPTION

[0038] Figure 1 A portion of an electric motor or machine 10 is shown in axial section, comprising a fixed casing 12, a rotating shaft 14 with an axis XX supported radially by rolling bearings 16. In the present case, the bearings are ball bearings. Alternatively, other rolling elements or sliding bearings may be envisaged.

[0039] The motor 10 further includes a grounding brush assembly 20 installed radially between the hole 12 a of the housing 12 and the cylindrical outer surface 14 a of the rotating shaft 14 .

[0040] The grounding brush assembly 20 makes it possible to continuously dissipate charges accumulated on the shaft 14 of the motor during operation of the motor by transferring the charges to the housing 12 .

[0041] Reference Figures 2 to 5 , a grounding brush assembly 20 according to a first example will now be described.

[0042] The grounding brush assembly 20 has a generally annular shape. The assembly 20 includes a grounding brush 30 and a brush mounting plate 40 configured to hold the brush 30 axially and radially.

[0043] As will be described in greater detail below, the brush mounting plate 40 is also configured to block rotation of the brush 30 .

[0044] The brush 30 includes a plurality of individual conductive fibers 31 for positioning around the rotation axis of the motor. The conductive fibers 31 may be made of carbon, stainless steel, conductive plastic such as acrylic or nylon fibers.

[0045] The brush 30 also includes a holding member or support 32, in which the conductive fibers 31 are mounted. In the exemplary embodiment shown, the support 32 is in the form of an open ring. The support 32 can be produced by cutting and shaping. The support 32 is made of a conductive material (e.g., aluminum, stainless steel, bronze, copper ( / red copper) or another material). As another option, the support 32 can be made of a non-conductive material with a conductive coating or conductive paint.

[0046] As in Figure 5 As can be seen more clearly in FIG. 1 , the support member 32 comprises an axial mounting portion 34 and two opposite lateral flanks 36, 38 extending inwardly from the mounting portion 34 and axially clamping the conductive fiber 31. The conductive fiber 31 bears against the lateral flanks 36, 38 on both sides in the axial direction.

[0047] The mounting portion 34 and the two lateral wings 36 , 38 delimit a channel which is open radially inwards and in which the conductive fiber 31 is partially located.

[0048] In the example shown, the conductive fiber 31 is bent around a connecting wire 39 of the support 32. The free distal end of the conductive fiber 31 is used to radially contact the outer surface of the rotating shaft of the motor. The proximal end of the conductive fiber 31 is in radial contact with the mounting portion 34 of the support.

[0049] The lateral wings 36 extend from one end of the mounting portion 34, and the lateral wings 38 extend from the opposite end of the mounting portion 34. The lateral wings 36, 38 extend obliquely inwardly from the mounting portion 34. The lateral wings 36, 38 are symmetrical to each other about the middle radial plane of the support 32. In the present case, the mounting portion 34 extends in the axial direction. As another option, the mounting portion 34 can extend obliquely. As another option, the lateral wings 36, 38 can be asymmetrical.

[0050] As explained above, the brush 30 takes the form of an open ring and as particularly Figure 3 and Figure 4 As can be seen in the figure, the brush 30 is provided with a first end 30a and an opposite second end 30b, the second end 30b being circumferentially spaced from the first end. The first end 30a and the second end 30b are circumferentially spaced from each other. This circumferential spacing between the two ends of the brush 30 allows the brush to be adapted to different motor shaft diameters.

[0051] Typically, the first end 30a and the second end 30b of the brush are not attached to each other. In a variant, the first end and the second end of the brush 30 may be attached to each other.

[0052] In the exemplary embodiment shown, each of the first end 30a and the second end 30b is formed by both the conductive fiber 31 and the support 32. In a variation, if the conductive fiber 31 protrudes in the circumferential direction relative to the support 32, each of the first end 30a and the second end 30b may be formed by only the conductive fiber 31 or only the support 32, and vice versa.

[0053] The brush mounting plate 40 includes an annular radial portion 42 and a plurality of tabs 44 extending from the radial portion 42 for axially and radially retaining the brush 30 .

[0054] The mounting plate 40 is produced by cutting and shaping. The mounting plate 40 is made of a conductive material (e.g., aluminum, stainless steel, bronze, copper, or another material). As another option, the mounting plate 40 can be made of a non-conductive material with a conductive coating or a conductive paint.

[0055] The radial portion 42 of the mounting plate bears axially against the support 32 of the brush 30. More specifically, the radial portion 42 bears axially against the lateral wings 36 of the support.

[0056] The lugs 44 are spaced apart from each other in the circumferential direction, in the present case regularly (regularly) spaced apart from each other. As another option, irregular circumferential spacing can be provided. In the exemplary embodiment shown, there are eight lugs 44. As another option, a greater or indeed lesser number of lugs 44 can be provided. Two lugs 44 or at least four lugs can be provided. Preferably, the number of lugs 44 is at least equal to two.

[0057] Each tab 44 projects axially relative to the radial portion 42. Each tab 44 partially radially surrounds the support 32 of the brush 30 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 means of the tabs 44. The tabs 44 make it possible to hold the grounding brush 30 axially and radially. The lateral wings 36 of the support bear against the radial portion 42 of the mounting plate, and the lateral wings 38 bear against the tabs 44. In the present case, the tabs 44 are identical to one another.

[0058] As in Figure 5 As can be seen more clearly in FIG. 1 , each lug 44 includes: an axial portion 44a extending axially from the radial portion 42, partially radially surrounding the support 32, and in radial contact with the support 32; and a radially inwardly curved portion ( / a portion curved radially inwardly) 44b, provided at the free end of the axial portion. The curved portion 44b of each lug makes it possible to axially hold the support 32 of the grounding brush 30. The curved portion 44b of each lug is in axial contact with the lateral wing 38 of the support.

[0059] The brush mounting plate 40 also includes a plurality of centring lugs 46 extending from the radial portion 42 and spaced apart from each other in the circumferential direction. Between each pair of consecutive lugs 46, a notch 48 is formed on the radial portion 42. The lugs 46 are formed by cutting and bending the radial portion 42.

[0060] Each lug 46 extends axially from the radial portion 42. The lug 46 extends obliquely from the large diameter edge of the radial portion 42. In the present case, the lug 46 extends axially on the same side as the tab 44. Alternatively, the lug 46 may extend axially on the opposite side.

[0061] Each lug 46 partially radially surrounds the support 32 of the brush 30 while being at a distance from the support 32 of the brush 30. The lugs 46 are partially radially offset outwards relative to the lugs 44. In the present case, the lugs 46 are identical to one another. The lugs 46 define the outer diameter of the mounting plate 40. In the present case, each lug 46 extends obliquely. As another option, the lugs 46 can extend in the axial direction. Each lug 46 takes the form of a cylindrical portion. The hole of each lug 46 is radially spaced apart from the support 32 by a non-zero radial distance. The outer surface of the lug 46 defines the outer diameter of the mounting plate 40. The lugs 46 make it possible to center the mounting plate after it is installed in the hole of the housing of the associated electric motor.

[0062] like Figures 2 to 4 As shown, the lugs 46 are spaced apart from each other in the circumferential direction, in the present case, regularly spaced apart from each other. As another option, irregular circumferential spacing can be provided. Each lug 46 is located between two consecutive lugs 44 in the circumferential direction. Each lug 46 is spaced apart from two adjacent lugs 44 in the circumferential direction. In the present case, the circumferential dimension of each lug 46 is greater than the circumferential dimension of the lug 44.

[0063] As explained above, the brush mounting plate 40 is also configured to block rotation of the brush 30 .

[0064] To this end, the mounting plate 40 includes an anti-rotation lug 50 extending in a circumferential space separating the first end 30a and the second end 30b of the brush. The lug 50 extends from the radial portion 42. The lug 50 protrudes in the axial direction relative to the radial portion 42. The lug 50 extends circumferentially in a space separating the first end 30a and the second end 30b of the brush.

[0065] The lug 50 faces the first end 30a and the second end 30b of the brush in the circumferential direction. A circumferential gap is provided between the lug 50 and the first end 30a of the brush on the one hand, and a circumferential gap is provided between the lug 50 and the second end 30b of the brush on the other hand. This allows the brush 30 to still be adapted to shafts of different diameters of the motor.

[0066] The lug 50 is different from the tab 44. The lug 50 is located between two consecutive tabs 44 in the circumferential direction.

[0067] The lug 50 is formed by cutting and bending the radial portion 42. During this cutting, a window 52 is formed on the radial portion 42 to create the lug 50. In the present case, the window 52 is a through window. The window 52 passes axially through the thickness of the radial portion 42. The window 52 opens radially inwardly.

[0068] In the exemplary embodiment shown, the lug 50 includes a radially inwardly curved portion 50a extending from the radial portion 42 and an axial portion 50b extending from the curved portion 50a and disposed in a circumferential space separating the first and second ends 30a, 30b of the brush.

[0069] In the exemplary embodiment shown, one of the lugs 46 partially radially surrounds the lug 50. In the exemplary embodiment shown, the root of the lug 50 is radially located on the periphery of the radial portion 42 of the mounting plate. In other words, the root of the lug 50 is radially located on the same side as the large diameter edge of the window 52. As another alternative, the lug 50 may be formed on the radial portion 42 so that its root is radially located inside the radial portion 42. In this case, the root of the lug 50 will extend from the small diameter edge of the window 52, ​​and the window will not open radially inward.

[0070] If the brush 30 moves in the circumferential direction relative to the mounting plate 40 , the lug 50 of the mounting plate 40 makes it possible to block the rotation of the brush by contacting the first end 30 a or the second end 30 b of the brush in the circumferential direction.

[0071] Figure 6 and Figure 7 The exemplary embodiment shown in FIG. 4 (wherein identical elements have identical reference numerals) differs from the first example shown in that the mounting plate 40 comprises an anti-rotation lug 60 extending from one of the two lateral edges of the window 52. Thus, in the present case, the root of the lug 60 extends from said lateral edge of the window 52.

[0072] The lug 60 protrudes in the axial direction relative to the radial portion 42. The lug 60 is placed in the circumferential space separating the first end 30a and the second end 30b of the brush. The lug 60 includes: a bent portion ( / a portion bent in the axial direction) 60a extending from the lateral edge of the window 52; and an axial portion 60b extending from the bent portion 60a and placed in the circumferential space separating the first end 30a and the second end 30b of the brush.

[0073] The lug 60 faces the first end 30a and the second end 30b of the brush in the circumferential direction. A circumferential gap is also provided between the lug 60 and the first end 30a of the brush on the one hand, and between the lug 60 and the second end 30b of the brush on the other hand, in this case, the values ​​of the gaps are different. Alternatively, the values ​​of the gaps can be equal.

[0074] Figure 8 and Fig. 9The exemplary embodiment shown in FIG. 4 (where like elements have like reference numerals) differs from the previously described exemplary embodiments in that the mounting plate 40 includes an additional anti-rotation lug 62 extending from a lateral edge of the window 52 opposite the edge from which the lug 60 extends. The lug 62 is also disposed in the circumferential space separating the first end 30a and the second end 30b of the brush.

[0075] The lug 62 protrudes axially relative to the radial portion 42. The lug 62 includes: an axially bent portion 62a extending from a lateral edge of the window 52 opposite to the lug 60; and an axial portion 62b extending from the bent portion 62a and disposed in a circumferential space separating the first end 30a and the second end 30b of the brush.

[0076] The lug 60 circumferentially faces the first end 30 a of the brush, and the lug 62 circumferentially faces the second end 30 b of the brush while being at a distance from the second end 30 b of the brush.

[0077] Figures 10 to 12 The exemplary embodiment shown in (wherein like elements have like reference numerals) differs from the first example shown in that the mounting plate 40 includes an anti-rotation lug 70 which extends from the radial portion 42 and is bent on itself and on the radial portion 42 to locally form a double thickness of material.

[0078] The lug 70 is placed in the circumferential space separating the first end 30a and the second end 30b of the brush. The lug 70 protrudes in the axial direction relative to the radial portion 42. The lug 70 is placed in the circumferential space separating the first end 30a and the second end 30b of the brush in the circumferential direction. The lug 70 includes: a radial portion 70a extending radially outward from the radial portion 42; and a bent portion 70b extending from the radial portion 70a and bending axially against the radial portion. As another option, the radial portion 70a of the lug may extend radially inward.

[0079] The bent portion 70b of the lug is placed in the circumferential space separating the first end 30a and the second end 30b of the brush. The lug 70 faces the first end 30a and the second end 30b of the brush in the circumferential direction. A circumferential gap is provided between the lug 70 and the first end 30a of the brush on the one hand, and a circumferential gap is provided between the lug 70 and the second end 30b of the brush on the other hand. In this exemplary embodiment, the lug 70 is located between two consecutive lugs 46 in the circumferential direction.

[0080] In the embodiment shown, the one or more anti-rotation lugs of the mounting plate are circumferentially spaced a certain distance from the first end 30a and the second end 30b of the grounding brush. Alternatively, the one or more anti-rotation lugs of the mounting plate may be arranged to contact one of the ends 30a, 30b of the grounding brush, or to contact both ends 30a, 30b.

[0081] In the embodiment shown, each lug of the mounting plate 40 projects axially relative to the lateral wing 36 of the support, but is set axially rearward relative to the lateral wing 38. Alternatively, the lug could also project axially relative to the lateral wing 38 of the support.

[0082] In the illustrated embodiment, the mounting plate 40 of the grounding brush assembly includes a plurality of centering lugs 46. As another alternative, the lugs may be replaced by an annular flange forming an annular centering portion.

Claims

1. A grounding brush assembly (20), comprising a grounding brush (30) and a brush mounting plate (40), wherein the grounding brush (30) is provided with a plurality of conductive fibers (31) and a support member (32), wherein the conductive fibers are mounted in the support member (32), and the mounting plate (40) is rigidly fixed to the brush support member (32), wherein the grounding brush (30) is in the form of an open ring and is provided with a first end (30a) and a second end (30b) which are spaced apart from each other in the circumferential direction and face each other, wherein: The mounting plate (40) includes at least one anti-rotation lug (50, 60, 60, 62, 70) disposed in a circumferential space separating a first end (30a) and a second end (30b) of the grounding brush.

2. The grounding brush assembly according to claim 1, characterized in that: The mounting plate (40) includes a plurality of retaining tabs (44) for retaining the brush support (32).

3. The grounding brush assembly according to claim 2, characterized in that: The anti-rotation tabs (50, 60, 60, 62, 70) of the mounting plate are distinct from the retaining tabs (44).

4. A grounding brush assembly according to any one of the preceding claims, characterized in that The mounting plate (40) includes an annular radial portion (42) against which the grounding brush (30) is supported in the axial direction.

5. The grounding brush assembly according to claim 4, characterized in that: The anti-rotation tabs (50, 60, 60, 62, 70) extend from a radial portion (42) of the mounting plate.

6. A grounding brush assembly according to claim 4 or 5 as dependent on claim 2, characterized in that The mounting plate retaining tab (44) extends from the radial portion (42) of the mounting plate.

7. The grounding brush assembly according to any one of claims 4 to 6, characterized in that: The brush support (32) bears axially against a radial portion (42) of the mounting plate.

8. The grounding brush assembly according to any one of claims 4 to 7, wherein: The mounting plate (40) includes at least one centering portion (32) extending at least axially from the radial portion (42), the at least one centering portion (32) being radially outwardly offset relative to the support member (22) and having an outer surface defining an outer diameter of the mounting plate (18).

9. A grounding brush assembly according to any one of the preceding claims, characterized in that The anti-rotation lugs (50, 60, 60, 62, 70) are formed at least by plastic deformation of the mounting plate.

10. An electric motor comprising a housing (12), a shaft (14) and at least one grounding brush assembly (20) according to any one of the preceding claims, the grounding brush assembly (20) being mounted radially between the housing (12) and the shaft (14), the conductive fibers of the brush of the grounding brush assembly being in contact with the shaft.

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