Grounding brush assembly

Abstract

[Grounding Brush Assembly] The grounding brush assembly 20 comprises a grounding brush 30 having a plurality of conductive fibers 31 and a support 32 within which the conductive fibers are mounted, and a brush mounting plate 40 which is integral with the brush support 32. The mounting plate comprises a radial portion 42 and at least one centering portion 46 extending at least axially from the radial portion 42, offset radially outward from the support 32 and having an outer surface defining the outer diameter of the mounting plate 18. The mounting plate 40 comprises at least one tab 50 projecting from the radial portion 42 on the side opposite the support 32. Reference: Figure 5

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 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] For more details on the design of such an assembly of grounding brushes, reference may be made, for example, to document US-A1-2021 / 0021180, which describes an assembly comprising a grounding brush provided with a plurality of conductive fibers, a support inside which the conductive fibers are mounted, and an annular mounting plate comprising a plurality of radial and axial retaining tabs for the support.

[0008] Depending on the relative axial positioning of the grounding brush assembly and the bearing, it may occur during the operation of the electrical machine contacts between on the one hand the conductive fibers of the assembly and on the other hand the rolling elements and / or the inner ring of the bearing.

[0009] This can damage the bearing.

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

[0011] The invention relates to a grounding brush assembly comprising 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 includes a radial portion and at least one centering portion extending at least axially from the radial portion, offset radially outwards from the support and provided with an outer surface defining the outer diameter of the mounting plate.

[0013] According to a general feature, the mounting plate includes at least one tab extending in projection from the radial portion on the side opposite the support.

[0014] With this design, the risk of contact between the conductive fibers of the assembly and the bearing is limited. Indeed, the tab on the mounting plate makes it possible to maintain axial spacing between the brush and the bearing or the housing.

[0015] According to one design, said tab of the mounting plate extends axially in projection.

[0016] According to another design, said tongue is folded axially against the radial portion.

[0017] In one embodiment, the mounting plate comprises a plurality of retaining tabs for the brush support extending from the radial portion, said centering portion being radially offset outwards relative to the retaining tabs. Said tab is distinct from the retaining tabs and extends axially on the side opposite said retaining tabs.

[0018] Said tab of the mounting plate can be offset radially inwards with respect to said centering portion.

[0019] According to a particular design, said tongue is made as a single piece with the radial portion of the mounting plate. This simplifies the manufacture of the mounting plate. Said tongue can be formed by local deformation of the material of the radial portion.

[0020] According to another design, said tab may be a separate piece from the radial portion of the mounting plate and fixed thereto by any suitable means, for example by bonding. After fixing, said tab protrudes from the radial portion of the mounting plate.

[0021] With such a design, it may be possible to make said tab from a material different from that of the radial portion of the mounting plate. Said tab may, for example, be made of an electrically insulating, i.e., electrically non-conductive material. This prevents the dissipation of electrical charges to the bearing in the event of contact between the bearing and said tab. Said tab may, for example, be made of a synthetic material, a plastic material, in particular PEEK, PBT, PPS, PAI.

[0022] In one embodiment, the mounting plate includes at least two tabs extending in projection from the radial portion on the side opposite the support and diametrically opposed.

[0023] The brush can be mounted axially against the radial portion of the mounting plate. Alternatively, the brush can be mounted axially against another radial portion of the mounting plate.

[0024] The mounting plate can be made in one piece.

[0025] In one embodiment, the mounting plate comprises a plurality of centering portions spaced in the circumferential direction.

[0026] In another embodiment, the mounting plate may include an annular centering portion.

[0027] The invention also relates to an electric motor comprising a housing, a shaft and at least one grounding brush assembly as defined above and mounted radially between the housing and the shaft, the conductive fibers of the brush of said assembly being in contact with the shaft. Brief description of the figures

[0028] 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:

[0029] [Fig. 1] is an axial cross-sectional view of a radially mounted grounding brush assembly between a rotating shaft and an electric motor housing,

[0030] [Fig.2]

[0031] [Fig.3] are perspective views of an assembly of grounding brushes according to a first embodiment of the invention,

[0032] [Fig.4] is a front view of the grounding brush assembly of Figures 2 and 3,

[0033] [Fig.5] is a cross-sectional view along the VV axis of [Fig.4], and

[0034] [Fig.6]

[0035] [Fig.7]

[0036] [Fig.8] are perspective views of an assembly of grounding brushes res respectively according to the second, third and fourth examples of embodiment of the invention. Detailed description of the invention

[0037] Figure 1 shows, in axial section, a portion of a motor 10 or electrical machine comprising a fixed housing 12, a rotating shaft 14, with axis XX, radially supported by a roller bearing 16. The bearing 16 is mounted radially between the housing 12 and the rotating shaft 14. The bearing is of the ball type. Alternatively, other rolling elements, or even a plain bearing, may be used.

[0038] The motor 10 further includes a radially mounted grounding brush assembly 20 between the bore 12a of the housing 12 and the external cylindrical surface 14a of the rotating shaft 14.

[0039] The grounding brush assembly 20 allows for the continuous dissipation of electrical charges which accumulate on the shaft 14 of the motor during motor operation by transferring them to the housing 12.

[0040] With reference to figures 2 to 5, an assembly 20 of grounding brushes according to an example of an embodiment of the invention will now be described.

[0041] The grounding brush assembly 20 has a generally annular shape. The assembly 20 comprises a grounding brush 30 and a brush mounting plate 40 configured to radially center said brush 30.

[0042] As will be described in more detail later, the mounting plate 40 is also configured to maintain axial spacing between the brush 30 and the bearing or housing.

[0043] The brush 30 comprises a plurality of individual conductive fibers 31 intended to come around 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.

[0044] The brush 30 further comprises a retaining member or support 32 within which the conductive fibers 31 are mounted. In the illustrated embodiment, the support 32 is in the form of an open ring. The support 32 can be made 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 of an electrically non-conductive material with a conductive coating or paint.

[0045] As more visibly illustrated in [Fig. 5], the support 32 comprises an axial mounting portion 34 and two opposing lateral sides 36, 38 extending inwards from the mounting portion 34 and axially enclosing the conductive fibers 31. The conducting fibers 31 are axially supported on both sides against the lateral flanks 36, 38. The conducting fibers 31 are axially supported on both sides against the internal faces of the lateral flanks 36, 38.

[0046] 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.

[0047] In the illustrated example, the conductive fibers 31 are bent around a connecting wire 39 of the support 32. The free distal end of the conductive fibers 31 is intended to come into radial contact with the outer surface of the rotating shaft of the motor. The proximal end of the conductive fibers 31 is in radial contact with the mounting portion 34 of the support.

[0048] 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. The mounting portion 34 extends axially here. Alternatively, the mounting portion 34 could extend obliquely.

[0049] As previously stated, the brush 30 is in the form of an open ring, as can be seen in particular in Figures 2 and 3. 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.

[0050] With reference to figures 2, 3 and 5, the mounting plate 40 comprises an annular radial portion 42, and a plurality of centering tabs 44 extending from the radial portion 42.

[0051] The radial portion 42 of the mounting plate is axially supported against the support 32 of the brush 30. More precisely, the radial portion 42 is axially supported against the lateral side 36 of the support.

[0052] 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.

[0053] 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 The support is axially held against the radial portion 42 of the mounting plate by the tabs 44. The tabs 44 provide axial and radial retention for the grounding brush 30. The lateral side 36 of the support bears against the radial portion 42 of the mounting plate, and the lateral side 38 bears against the tabs 44. The tabs 44 are identical in this case.

[0054] As more clearly illustrated in [Fig. 5], each tab 44 has an axial portion extending axially from the radial portion 42, locally surrounding the support 32 radially and in radial contact with it, and a folded portion at the free end of the axial portion. The folded portion 44b of each tab axially retains the support 32 of the grounding brush 30. The folded portion 44b of each tab is in axial contact against the lateral side 38 of the support.

[0055] The brush mounting plate 40 also includes a plurality of centering lugs 46 extending from the radial portion 42 and spaced circumferentially from one another. A notch 48 ([Fig. 2]) is formed on the radial portion 42 between each pair of immediately successive lugs 46. The lugs 46 are formed by cutting and bending the radial portion 42.

[0056] Each leg 46 extends axially from the radial portion 42. The legs 46 extend obliquely from a large diameter edge of the radial portion 42. The legs 46 extend axially on the same side as the tabs 44.

[0057] Each tab 46 locally surrounds the support 32 of the brush 30 radially while remaining at a distance from it. The tabs 46 are partially offset radially outwards relative to the tabs 44. The tabs 46 are identical to each other. The tabs 46 define the outer diameter of the mounting plate 40. Each tab 46 extends obliquely. Alternatively, the tabs 46 could extend axially. Each tab 46 is in the form of a portion of a cylinder. The bore of each tab 46 is radially spaced from the support 32 by a non-zero radial distance. The outer surfaces of the tabs 46 define the outer diameter of the mounting plate 40. The tabs 46 allow the mounting plate to be centered after installation in the bore of the housing of the associated electric motor.

[0058] As illustrated in Figures 2 and 4, the tabs 46 are spaced circumferentially from one another, here at regular intervals. Alternatively, irregular circumferential spacing could be provided. Each tab 46 is located circumferentially between two immediately successive tabs 44. Each tab 46 is spaced circumferentially from the two immediately adjacent tabs 44. Each tab 46 has a circumferential dimension greater than that of the tabs 44.

[0059] As previously stated, the mounting plate 40 is also configured to maintain axial spacing between the brush 30, and the bearing or the housing.

[0060] To this end, the mounting plate 40 further includes tabs 50 extending axially from the radial portion 42 on the side opposite the tabs 44 and the lugs 46, as can be seen in Figures 2, 3, and 5. The tabs 50 extend axially on the side opposite the support 32. The tabs 50 project outwards from the radial portion 42. The tabs 50 extend axially here. Alternatively, the tabs 50 could extend obliquely, i.e., axially and radially.

[0061] The radial portion 42 of the mounting plate has an inner face against which the support 32 is axially mounted, and an outer face axially opposite the inner face. The inner and outer faces define the axial thickness of the radial portion 42. The tabs 50 extend axially in projection from the outer face of the radial portion 42.

[0062] Each tab 50 is located radially between the smaller diameter edge of the radial portion 42 defining the bore of the mounting plate and the larger diameter edge of said radial portion. The root of each tab 50 is located radially on the side of the larger diameter edge of said radial portion. The root of each tab 50 has a curved shape, and said tab extends axially from this root. Each tab 50 is radially offset inward relative to the tabs 44 and the lugs 46.

[0063] Each tab 50 is located circumferentially along the extension of one of the legs 46. Each tab 50 is located circumferentially between two immediately successive tabs 44. Each tab 50 has a smaller circumferential dimension compared to that of the legs 46. Each tab 50 also has a smaller circumferential dimension compared to that of the tabs 44. Alternatively, the circumferential dimension of the tabs 50 could be equal to or greater than that of the tabs 44.

[0064] In the illustrated embodiment, the principal faces of each tab 50 defining the thickness of said tab are oriented radially. In other words, in this example, one of the principal faces of each tab 50 is oriented radially inwards and the other principal face is oriented radially outwards.

[0065] The tabs 50 are spaced circumferentially, here at regular intervals. Alternatively, irregular circumferential spacing may be used. In the illustrated embodiment, there are four tabs 50. Alternatively, a greater or lesser number of tabs 50 may be used. Preferably, the number of tabs 50 is at least two. The tabs 50 are identical to each other. Alternatively, the tabs could have different shapes and / or dimensions.

[0066] 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.

[0067] During the operation of the electric machine, the electrical charges which accumulate on the shaft are dissipated towards the housing 4 through the conductive fibers 20, the support 22 of the brush, and the mounting plate 40 of the assembly.

[0068] Thanks to the tabs 50 of the mounting plate, contact between the conductive fibers 20 of the brush and the bearing is avoided.

[0069] The embodiment illustrated in [Fig.6], in which the identical elements bear the same references, differs from the previous example only in the orientation of the mounting of the tabs 52 of the mounting plate.

[0070] The tabs 52 are formed here by making cuts 53 on the radial portion 42, and the root of each tab 50 is connected to a lateral edge delimiting the associated opening 53. Thus, one of the main faces of each tab 50 is oriented circumferentially on one side and the other main face is oriented circumferentially on the opposite side.

[0071] The embodiment illustrated in [Fig.7], in which the identical elements bear the same references, differs mainly from the first example by the location of the mounting of the tabs 54 of the mounting plate.

[0072] The socket of each tab 54 is located between two successive legs 46. Each tab 50 is radially offset inwards only with respect to the legs 46, but not with respect to the tabs 44. In this example, there are two tabs 54, diametrically opposed. Alternatively, it is possible to provide a greater or lesser number of tabs 54.

[0073] The embodiment illustrated in [Fig. 8], in which the identical elements bear the same reference numerals, differs from the first embodiment in that the mounting plate 40 comprises tabs 56, each extending from the radial portion 42 and folded axially against the radial portion. Each tab 56 is folded against the outer face of the radial portion 42. Each tab 56 projects beyond the radial portion 42 on the side opposite the support 32. Each tab 56 extends from the smaller diameter edge of the radial portion 42. The root of each tab 56 has a curved shape, and said tab extends radially from this base. Each tongue 56 remains radially recessed relative to the large diameter edge of the radial portion 42.

[0074] Each tab 56 is located circumferentially along the extension of one of the legs 46. Each tab 56 is located circumferentially between two immediately successive tabs 44. Each tab 56 has a smaller circumferential dimension compared to that of the legs 46. Each tab 56 has a circumferential dimension greater than that of the tabs 44. Alternatively, the circumferential dimension of the tabs 56 could be equal to or less than that of the tabs 44.

[0075] The tabs 56 are spaced circumferentially, here at regular intervals. Alternatively, irregular circumferential spacing may be provided. In the illustrated embodiment, there are four tabs 56. Alternatively, a greater or lesser number of tabs 56 may be provided. Preferably, the number of tabs 56 is at least two. The tabs 56 are identical here. Alternatively, the tabs could have different shapes and / or dimensions.

[0076] In the illustrated embodiments, the mounting plate 40 of the grounding brush assembly comprises a plurality of centering lugs 46. Alternatively, the lugs could be replaced by an annular flange forming an annular centering portion.

Claims

Claims

1. A grounding brush assembly (20) comprising a grounding brush (30) provided with a plurality of conductive fibers (31) and a support (32) within which the conductive fibers are mounted, and a brush mounting plate (40) which is integral with the brush support (32), the mounting plate (40) comprising a radial portion (42) and at least one centering portion (46) extending at least axially the radial portion (42), offset radially outwardly relative to the support (32) and provided with an outer surface defining the outer diameter of the mounting plate (18), characterized in that the mounting plate (40) comprises at least one tab (50, 52, 54, 56) extending projecting from the radial portion (42) on the side opposite the support (32).

2. An assembly according to claim 1, wherein said tab (50, 52, 54) of the mounting plate extends axially projecting.

3. An assembly according to claim 1, wherein said tab (56) of the mounting plate is axially folded against the radial portion (42).

4. An assembly according to any preceding claim, wherein the mounting plate comprises a plurality of brush holder (32) retaining tabs (44) extending from the radial portion (42), said centering portion (46) being radially offset outwardly relative to the retaining tabs (44) and said tab (50, 52, 54, 56) being distinct from the retaining tabs (44) and extending axially on the side opposite said retaining tabs.

5. An assembly according to any preceding claim, wherein said tab (50, 52, 54, 56) of the mounting plate is offset radially inwardly relative to said centering portion (46).

6. An assembly according to any one of the preceding claims, wherein said tab (50, 52, 54, 56) is made in one piece with the radial portion (42) of the mounting plate.

7. An assembly according to any preceding claim, wherein the mounting plate (40) comprises at least two tabs (50, 52, 54, 56) extending projecting from the radial portion (42) on the side opposite the support (32) and diametrically opposed.

8. An assembly according to any preceding claim, in wherein the brush (30) is mounted axially against the radial portion (42) of the mounting plate.

9. An assembly according to any preceding claim, wherein the mounting plate (40) is made in one piece.

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

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