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 radial portion 42 of the mounting plate comprises at least one protrusion 50 extending axially outward from 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 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 and an outer annular flange radially surrounding said brush and the tabs.

[0008] Depending on the relative axial positioning of the grounding brush assembly and of the bearing, contacts may occur during the operation of the electrical machine 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 characteristic, the radial portion of the mounting plate includes at least one protrusion extending axially outward from 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 aforementioned protrusion on the radial portion of the mounting plate makes it possible to maintain axial spacing between the brush and the bearing or housing.

[0015] According to a particular design, said protrusion can be made as a single piece with the radial portion of the mounting plate. In this case, said protrusion can be formed by local deformation of the material of the radial portion.

[0016] According to another design, said protrusion may be a separate part of the radial portion of the mounting plate and fixed thereto by any suitable means, for example by gluing.

[0017] With such a design, it may be possible to make said protrusion from a material different from that of the radial portion of the mounting plate. Said protrusion 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 protrusion. Said protrusion may, for example, be made of a synthetic material, a plastic material in particular PEEK, PBT, PPS, PAL

[0018] In one embodiment, the mounting plate comprises a plurality of centering portions spaced in the circumferential direction.

[0019] In this case, it is possible to foresee that said protuberance of the radial portion of the mounting plate has a reduced circumferential dimension compared to that of the centering portions.

[0020] In another embodiment, the mounting plate may include an annular centering portion.

[0021] According to a particular design, the radial portion of the mounting plate comprises a plurality of protrusions spaced in the circumferential direction.

[0022] The mounting plate may include a plurality of brush holder retaining tabs extending from the radial portion. The centering portion may be radially offset outwards relative to the retaining tabs.

[0023] In one embodiment, the mounting plate includes a plurality of retaining tabs for the brush support extending from the radial portion.

[0024] If the radial portion of the mounting plate is provided with a plurality of protrusions, each protrusion can be located in the circumferential direction between two successive retaining tabs.

[0025] 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.

[0026] The mounting plate can be made in one piece.

[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 an embodiment, taken by way of non-limiting example 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] is a perspective view of an assembly of grounding brushes according to an exemplary embodiment of the invention,

[0031] [Fig.3] is a front view of the grounding brush assembly of [Fig.2],

[0032] [Fig.4] is a cross-sectional view along axis IV-IV of [Fig.3], and

[0033] [Fig.5] is a cross-sectional view along the VV axis of [Fig.3]. Detailed description of the invention

[0034] Figure 1 shows, in axial section, a portion of a motor 10 or electrical machine comprising a fixed housing 12, a rotating shaft 14, of axis XX, radially supported by a roller bearing 16. The bearing 16 is mounted radially between the The housing 12 and the rotating shaft 14. The bearing here is of the ball type. Alternatively, other rolling elements, or even a plain bearing, can be used.

[0035] 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.

[0036] 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.

[0037] 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.

[0038] 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.

[0039] 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.

[0040] 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.

[0041] 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 conductive paint.

[0042] As more clearly illustrated in Figures 4 and 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 conductive fibers 31 are axially supported on both sides against the lateral sides 36, 38. The conductive fibers 31 are axially supported on both sides against the inner faces of the lateral sides 36, 38.

[0043] 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.

[0044] In the illustrated example, the conductive fibers 31 are bent around a wire of connection 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.

[0045] 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.

[0046] 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.

[0047] With reference to figures 2, 4 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.

[0048] 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.

[0049] 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.

[0050] Each tab 44 extends axially beyond the radial portion 42. Each tab 44 locally surrounds the support 32 of the brush 30 radially and is in radial contact with the mounting portion 34 of said support. The support 32 is held axially against the radial portion 42 of the mounting plate by the tabs 44. The tabs 44 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.

[0051] As more clearly illustrated in [Fig. 4], each tab 44 is provided with an axial portion extending axially from the radial portion 42, surrounding the The support 32 is radially held in place by 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.

[0052] 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.

[0053] 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. The legs 46 extend axially in projection relative to the tabs 44.

[0054] Each leg 46 locally surrounds the support 32 of the brush 30 radially while remaining at a distance from it. The legs 46 are partially offset radially outwards relative to the tabs 44. The legs 46 are identical to each other. The legs 46 define the outer diameter of the mounting plate 40. Each leg 46 extends obliquely. Alternatively, the legs 46 could extend axially. Each leg 46 is in the form of a portion of a cylinder. The bore of each leg 46 is radially spaced from the support 32 by a non-zero radial distance. The outer surfaces of the legs 46 define the outer diameter of the mounting plate 40. The legs 46 allow the mounting plate to be centered after installation in the bore of the housing of the associated electric motor.

[0055] As illustrated in Figures 2 and 3, 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.

[0056] As previously stated, the mounting plate 40 is also configured to maintain axial spacing between the brush 30 and the bearing or housing.

[0057] For this purpose, the mounting plate 40 comprises a plurality of protrusions 50 formed on the radial portion 42 and extending axially outward on the side opposite the support 32. Each protrusion 50 extends axially outwards.

[0058] In the illustrated embodiment, each protrusion 50 is formed by local deformation of material in the radial portion 42. Each protrusion 50 is formed by local displacement of material. Each protuberance 50 extends axially in projection relative to the rest of the undeformed radial portion 42.

[0059] 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. As previously stated, the protrusions 50 are formed here by local deformation of the material of the radial portion 42. Each protrusion 50 thus extends axially beyond the rest of the undeformed outer face.

[0060] Each protrusion 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. Each protrusion 50 is located circumferentially along the extension of one of the tabs 46. Each protrusion 50 is located circumferentially between two immediately successive tabs 44. Each protrusion 50 has a smaller circumferential dimension compared to that of the tabs 46.

[0061] The protrusions 50 are spaced circumferentially, here at regular intervals. Alternatively, irregular circumferential spacing may be provided. In the illustrated embodiment, there are four protrusions 50. Alternatively, a greater or lesser number of protrusions 50 may be provided. It is possible to provide one protrusion 50, and preferably at least two.

[0062] The protrusions 50 are identical here. Each protrusion 50 has a convex shape when viewed from the side. Alternatively, it could be possible to provide other shapes, for example, flat, pointed, wavy, etc. Each protrusion 50 has a circular shape when viewed from the front. Alternatively, it could be possible to provide other shapes, for example, polygonal such as square, rectangular, hexagonal, etc., or even a wavy shape.

[0063] 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.

[0064] During the operation of the electric machine, the electrical charges which accumulate on the shaft are dissipated towards the housing 12 through the conductive fibers 31, the support 32 of the brush, and the mounting plate 40 of the assembly.

[0065] Thanks to the protrusions 50 of the mounting plate, contact between the conductive fibers 31 of the brush and the bearing is avoided.

[0066] In the illustrated embodiment, 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 radial portion (42) of the mounting plate comprises at least one protrusion (50) extending axially projecting from the side opposite the support (32).

2. Assembly according to claim 1, in which said protuberance (50) is made in one piece with the radial portion (42) of the mounting plate, in particular by local deformation of material of the radial portion (42).

3. An assembly according to claim 1, wherein said protrusion (50) is a separate part from the radial portion (42) of the mounting plate and fixed to the radial portion (42).

4. An assembly according to claim 3, wherein said protrusion (50) is made of electrically insulating material.

5. An assembly according to any preceding claim, wherein the mounting plate (40) comprises a plurality of circumferentially spaced centering portions (46), said protrusion (50) of the radial portion of the mounting plate having a reduced circumferential dimension relative to that of the centering portions (46).

6. An assembly according to any preceding claim, wherein the radial portion (42) of the mounting plate comprises a plurality of circumferentially spaced protrusions (50).

7. 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).

8. An assembly according to claim 7 dependent on claim 6, wherein each protrusion (50) of the radial portion of the plate mounting is located in the circumferential direction between two successive retaining tabs (44).

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

10. An electric motor comprising a housing (12), a shaft (14), and at least one grounding brush assembly (20) of 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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