Grounding brush assembly

Abstract

A ground brush assembly. The ground brush assembly (10) comprises a ground brush (16) and a mounting plate (18) for the brush (16), the brush (16) being provided with a plurality of electrically conductive fibers (20) and a support (22) inside which the electrically conductive fibers (20) are housed, the mounting plate (18) being fixed to the support (22) and being provided with a radially extending body (32), an axially extending centering portion (36), a retaining tongue (34) for axially retaining the support (22), the assembly further comprises a bearing portion (40) consisting of a radially deformed portion of the centering portion (36) to axially retain the support (22).

Description

Technical Field

[0001] This invention relates to the field of grounding devices for controlling shaft current generated in electric motors or machines, and particularly to grounding brush assemblies. Background Technology

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

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

[0004] Current flowing through the components of a rolling bearing can damage these components, particularly the rolling elements and the raceways formed on the inner and outer rings. Discharge can also generate vibration.

[0005] To overcome these drawbacks, a known practice is to ground the rotating shaft using a grounding brush that includes conductive fibers. The grounding brush is typically installed in a hole in the motor mount, such that the free end of the fiber makes radial contact with the outer surface of the rotating shaft.

[0006] Thanks to the conductivity of the fibers, the brush maintains the same potential as the motor housing. The inner and outer rings of the rolling bearing also operate at the same potential, which reduces or even eliminates problematic discharges through the rolling bearing.

[0007] Document US-A1-2021 / 0021180 discloses a grounding brush assembly including a grounding brush and an annular mounting plate. The grounding brush is provided with a support and multiple conductive fibers mounted in the support. The annular mounting plate is provided with multiple tongues for holding the grounding brush support in the radial and axial directions, and an annular outer flange surrounding the brush and tongues in the radial direction. The tongues are formed by plastic deformation of the mounting plate.

[0008] This type of grounding brush assembly has a relatively large radial dimension. For electric motor applications where radial compactness is reduced, this assembly cannot be installed.

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

[0010] The present invention relates to a grounding brush assembly for an electric motor, the electric motor having a rotating shaft, a fixed housing, and bearings.

[0011] The component includes a grounding brush with multiple conductive fibers and a support, the conductive fibers being mounted inside the support. The component also includes a brush mounting plate fixed to the brush support.

[0012] The mounting plate includes: a body formed of a radial portion, against which the brush support axially abuts; and a centering portion extending axially from at least the body on the same side as the brush support, radially offset relative to the support, and having an outer surface defining the outer diameter of the mounting plate to center the mounting plate after it is installed in a hole in the seat of an associated electric motor.

[0013] According to a general feature of the invention, the mounting plate includes a plurality of retaining tongues for the support and a plurality of bearing portions for the support.

[0014] According to the invention, the retaining tongues extend radially toward the inside of the assembly from the centering portion. Each retaining tongue axially abuts against the brush support on the axially opposite side of the body, the support being thus axially held on one side by the body and on the other side by the retaining tongues.

[0015] The support portion is composed of radial deformations extending radially inward from the centering portion toward the inside of the assembly. The support portion abuts radially against the upper axial surface of the brush support.

[0016] In one embodiment, the centering portion may be annular. Alternatively, the centering portion may include a plurality of axial portions spaced apart from each other in the circumferential direction.

[0017] In one embodiment, the retaining tongue and the supporting portion are alternately distributed on the circumferential portion.

[0018] According to one embodiment, the support portion is composed of local radial deformation portions, each local radial deformation portion being formed on an angular sector of less than or equal to 5°, preferably, each local radial deformation portion being formed on an angular sector of less than or equal to 1°.

[0019] According to an alternative embodiment, the support portion is composed of radially deformable portions extending in the circumferential direction, each radially deformable portion being formed in an angular sector between 5° and 40°, preferably, each radially deformable portion being formed in an angular sector between 15° and 30°.

[0020] The present invention also relates to an electric machine or motor, comprising a base, a shaft, and a grounding brush assembly as defined above, the grounding brush assembly being at least partially radially mounted between the base and the shaft, the conductive fibers of the assembly being in contact with the shaft. Attached Figure Description

[0021] The invention will be better understood by studying the detailed description of the embodiments given by way of non-limiting example and illustrated in the accompanying drawings, in which:

[0022] Figure 1 This is an axial cross-sectional view of a grounding brush assembly partially mounted radially between the rotating shaft and the seat of an electric motor according to a first exemplary embodiment of the present invention.

[0023] Figure 2 yes Figure 1 A 3D view of the grounding brush assembly in the image;

[0024] Figure 3 yes Figure 1 Front view of the grounding brush component in the middle;

[0025] Figure 4 yes Figure 3 The component in the diagram is shown in a cross-sectional view along line II.

[0026] Figure 5 yes Figure 3 The component in the diagram is shown in a cross-sectional view along line II-II;

[0027] Figure 6 yes Figure 3 The components in the diagram are shown in cross-sectional view along line III-III; and

[0028] Figure 7 This is an axial cross-sectional view of a grounding brush assembly partially mounted radially between the rotating shaft and the seat of an electric motor according to a second exemplary embodiment of the present invention. Detailed Implementation

[0029] Figure 1 A portion of an electric motor or machine 2 is shown in axial section. The electric motor or machine 2 includes a fixed base 4 and a rotating shaft 6 having an axis XX, which is radially supported by a bearing 8. The bearing 8 is, for example, a spherical rolling bearing. As a variation, other rolling elements, such as rollers, can be envisioned. In another variation, a sliding bearing can be envisioned.

[0030] Motor 2 includes a grounding brush assembly 10, which is at least partially mounted radially between a bore 12 in the housing and an outer cylindrical surface 14 of the shaft. The assembly 10 is, for example, force-fitted into the bore 12 in the housing.

[0031] In the remainder of the specification, the adjectives "axial" and "radial," and the adverbs "in the axial direction" and "in the radial direction," are defined relative to the central axis X. Therefore, the axial portion or component is parallel to the axis X, while the radial portion or component is perpendicular to and surrounds the axis. Furthermore, the radial portion is provided with an "inner" surface oriented toward the axis X and an "outer" surface oriented away from the axis X.

[0032] like Figures 2 to 6 As can be seen more clearly, the grounding brush assembly 10 has a generally annular shape. The assembly 10 includes a grounding brush 16 and a mounting plate 18 for the brush 16.

[0033] The grounding brush 16 includes multiple conductive fibers 20 and a support 22, with the conductive fibers housed within the support 22. The conductive fibers 20 can be made of, for example, carbon, stainless steel, or conductive plastics (such as acrylic fibers or fibers made of nylon). The multiple conductive fibers 20 are in the form of open rings. In the example shown, the conductive fibers 20 are bent around a connecting wire 24. The distal free ends of the conductive fibers 20 are intended to make radial contact with the outer surface 14 of the shaft 6.

[0034] To ensure the mounting and retention of the conductive fiber 20, the support 22 includes a cylindrical portion 26 defining an upper axial surface for the support 22, a first lateral edge 28 extending from a portion of the cylindrical portion 26, and a second lateral edge 30 extending from another portion of the cylindrical portion 26. The first edge 28 is axially positioned outward of the assembly, while the second edge 30 is axially positioned towards the bearing 8, and the edges 28 and 30 are axially opposite to the cylindrical portion 26 and the fiber 20.

[0035] Mounting plate 18 is fixed to support member 22. Mounting plate 18 includes a body 32 and an axially centered portion 36. The body 32 is formed by a radial portion that axially abuts against a first edge 28 of the support member.

[0036] The centering portion 36 of the mounting plate 18 extends axially from the body 32 in a direction away from the bearing 8. Figures 1 to 6In the embodiment shown, the centering portion 36 is composed of an annular cylindrical portion. As a variation, it is conceivable that the centering portion includes a plurality of axial portions spaced apart from each other on the circumferential portion.

[0037] The centering portion 36 is provided with an outer surface 38 that defines the outer diameter of the mounting plate 18, so as to center the mounting plate after it is installed in the hole 12 of the associated electric motor 2 seat 4. The centering portion 36 is preferably press-fitted into the hole 12 of the seat 4 to create diametrical interference, thereby ensuring the mechanical retention of the mounting plate 18 in the seat 4.

[0038] According to the invention, the mounting plate includes a plurality of retaining tongues 34 for retaining the brush 16 in the axial direction.

[0039] The tongue 34 extends radially toward the inside of the assembly 10 from the centering portion 36 of the mounting plate 18. Each tongue 34 is formed by a basic radial portion that curves inward from the axial portion 36. The tongues 34 are spaced apart from each other in the circumferential direction.

[0040] Each retaining tongue 34 extends from the centering portion 36 of the mounting plate 18 such that the retaining tongue 34 forms axial contact with the lateral boundary 30 of the support member 22. On the axially opposite side, the other lateral boundary 28 of the support member 22 is held by the tongue 34 to axially bear against the radial portion 32 of the mounting plate 18. Thus, the support member 22 is held axially by the retaining tongue 34.

[0041] In the example shown, the mounting plate 18 includes four retaining tongues 34 that are regularly spaced apart on the circumferential portion. As a variation, the mounting plate includes a different number of retaining tongues 34.

[0042] The centering portion 36 extends axially from the body 32, extends axially on the same side as the support 22 held by the tongue 34, and is radially offset outward relative to the support 22.

[0043] The cylindrical portion 26 of the support member 22 is radially spaced from the centering portion 36, and the second lateral edge 30 abuts against the tongue in axial contact. The cylindrical portion 26 extends from the large-diameter boundary of the first lateral edge 28. The cylindrical portion 26 extends axially here.

[0044] The second lateral edge 30 of the support 22 extends radially inward from the cylindrical portion 26. The second lateral edge 30 extends from the cylindrical portion 26 on the side opposite to the first lateral edge 28. The cylindrical portion 26, the first lateral edge 28, and the second lateral edge 30 are annular in shape and define a radially inwardly open channel in which one end of the conductive fiber 20 is positioned. The first lateral edge 28 and the second lateral edge 30 axially clamp the conductive fiber 20. The conductive fiber 20 axially abuts against the first lateral edge 28 and the second lateral edge 30 on each side.

[0045] In the exemplary embodiment shown, the conductive fiber 20 radially abuts against the cylindrical portion 26, and the first lateral edge 28 and the second lateral edge 30 extend inwardly at an angle from the cylindrical portion 26. As a variation, the first lateral edge 28 and the second lateral edge 30 may extend radially.

[0046] Mounting plate 18 and grounding brush 16 comprise conductive materials such as aluminum, stainless steel, bronze, copper, or another material.

[0047] According to another aspect of the invention, the mounting plate 18 further includes a plurality of support portions 40 to hold the brush support 22 in the axial direction.

[0048] according to Figures 2 to 6 In the first embodiment of the present invention shown, the support portion 40 is composed of a partially radially deformable portion extending radially from the centering portion 36 toward the inside of the assembly 10.

[0049] Each of the support portions 40 is formed in an angular sector of less than or equal to 5°, preferably in an angular sector of less than or equal to 1°.

[0050] In the example shown, the deformable portion is basically conical, having an inner wall 42 that slopes inward toward the inside of assembly 10. According to other variations not shown, the support portion can have other shapes, such as spheres, cylinders, parallelepipeds, etc., without departing from the scope of the invention. In practice, the deformable portion 40 can be produced, for example, by pressing. The material of the centering portion 36 is radially deformed inward by a punch that applies a radial force from the upper surface 38 of the centering portion 36.

[0051] Each of the support portions 40 radially abuts against the upper axial surface of the cylindrical portion 26 of the brush support 22. More specifically, the inclined inner wall 42 of each support portion 40 is in direct radial contact with the cylindrical surface 26 via the support surface 44.

[0052] Therefore, the support member 22 is held in place radially by a plurality of support points 44 that directly contact the outer surface of the cylindrical portion 26 of the support member 22. This radial holding of the support member 22, combined with the axial holding of the support member between the tongue 34 and the body 32, ensures that the support member 22 is held in place by means of the mounting plate 18. Since the mounting plate 18 itself is fitted into the hole 12 of the seat 4, the fibers 20 installed in the support member 22 are positioned relative to the bearing 8, the seat 4, and the rotating shaft 6 to ensure the function of current flow.

[0053] In the example shown, the mounting plate 18 includes four support portions 40 that are regularly spaced apart in a circumferential manner. As a variation, the mounting plate includes a different number of support portions 40.

[0054] In the example shown, the tongue 34 and the support portion 40 are alternately distributed in the circumferential direction. As a variation, the tongue and support portion can be positioned according to other distribution patterns, such as two or more support portions between two consecutive tongues in the circumferential direction, or two or more tongues between two consecutive support portions.

[0055] Compared to components of the prior art, such as those in US-A1-2021 / 0021180, the grounding brush assembly 10 can be configured to have reduced radial compactness by means of the present invention.

[0056] Additionally, the support portion 40 can increase the rigidity of the mounting plate 18. The centering portion 36 is press-fitted into the seat 4, and the centering portion 36, the main body 32, or the connection between the centering portion and the main body are at higher risk of deformation. The deformable portion of the support portion 40 provides an inclined arm 42, which helps to strengthen the assembly.

[0057] Figure 7 The second embodiment of the invention is shown, which differs from the previous embodiment in terms of the size of the support portion.

[0058] Mounting plate 18 includes a plurality of support portions 50 for axially holding brush support 22. The support portions 50 are formed by an extended radially deformable portion extending radially from centering portion 36 toward the inside of assembly 10.

[0059] In the example shown, each support portion 50 is formed in an angular sector equal to 20°. This angular sector can be small or large, between 5° and 40°.

[0060] Each deformable portion of the support portion 50 has an inner wall 52 that slopes inward toward the assembly 10. Each support portion of the support portion 50 radially abuts against the upper axial surface of the cylindrical portion 26 of the brush support 22. More specifically, the sloped inner wall 52 is in direct radial contact with the cylindrical surface 26 via the support surface 54.

[0061] Furthermore, all or some of the technical features of the various embodiments can be combined with each other. Therefore, the grounding brush assembly can be adapted in terms of cost, performance, and ease of use.

Claims

1. A grounding brush assembly (10) for an electric motor (2), the electric motor (2) having a shaft (6) rotatable about an axis (X), a fixed seat (4), and a bearing (8), and the grounding brush assembly (10) including a grounding brush (16) and a brush mounting plate (18), the grounding brush (16) having a plurality of conductive fibers (20) and a support member (22), the conductive fibers being installed inside the support member (22), the brush mounting plate (18) being fixed to the support member (22) of the brush, the mounting plate (18) comprising: - The main body (32) is formed by a radial portion, and the brush support (22) abuts axially against the main body (32). - The centering portion (36), extending axially from at least the body (32), extending axially on the same side as the brush support (22), radially offset outward relative to the support (22), and provided with an outer surface (38) defining the outer diameter of the mounting plate (18) to center the mounting plate (18) after it is installed in the hole (12) of the seat (4) of the associated electric motor (2). The mounting plate is characterized in that it further includes: - A plurality of retaining tongues (34) for the support member, the tongues (34) extending radially toward the inside of the assembly (10) from the centering portion (36), each tongue (34) axially abutting against the brush support member (22) on an axially opposite side of the body (32), the support member (22) being held axially on one side by the body (32) and on the other side by the retaining tongues (34), and - A plurality of support portions (40; 50) for the support member (22), the support portions (40; 50) being composed of radially deformed portions extending radially toward the inside of the assembly (10) from the centering portion (36), the support portions (40; 50) abutting radially against the upper axial surface (26) of the brush support member (22).

2. The component (10) according to claim 1, characterized in that, The centering portion (36) is annular.

3. The component (10) according to claim 1, characterized in that, The centering portion (36) includes a plurality of axial portions spaced apart from each other in the circumferential direction.

4. The component (10) according to any one of the preceding claims, characterized in that, The retaining tongue (34) and the supporting portion (40; 50) are alternately distributed in the circumferential direction.

5. The component (10) according to any one of the preceding claims, characterized in that, The support portion (40) is composed of local radial deformation portions, each of which is formed on an angular sector of less than or equal to 5°, preferably each of which is formed on an angular sector of less than or equal to 1°.

6. The component (10) according to any one of claims 1 to 4, characterized in that, The support portion (50) is composed of radially deformable portions extending in the circumferential direction, each radially deformable portion being formed in an angular sector between 5° and 40°, preferably each radially deformable portion being formed in an angular sector between 15° and 30°.

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

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