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), the electrically conductive fibers (20) being housed inside the support, a mounting plate (18) fixed to the support (22) and provided with a radially extending body (32), a retaining tongue (34) for axially and radially retaining said support (22), and an axially extending centering portion (36), the mounting plate (18) comprising at least one bearing portion (40), the bearing portion bears radially against the brush support (22) and provides a bearing surface for a tool for inserting the assembly (10) into the seat (4).

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 grounding brush assembly is force-fitted into the hole of the seat, making it difficult to remove.

[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 radially outwardly extending radially relative to the support member; a plurality of centering tongues projecting axially relative to the radially extending portion, each tongue partially radially surrounding and radially contacting the support member of the brush, the support member being held by the tongues to axially bear against the radially extending portion of the mounting plate; and a centering portion extending axially at least from the body, extending axially on the same side as the tongues, radially offset relative to the support member and the tongues, 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 the general features of the invention, the mounting plate further includes at least one bearing portion projecting radially toward the inside of the assembly. The bearing portion is formed by a first curved portion and a second curved portion, the first curved portion extending axially from the body and abutting radially against the upper axial surface of the brush support, the second curved portion extending radially between the first curved portion and the centering portion, the second curved portion defining an axial bearing surface for a tool used to position the assembly.

[0014] Both the centering portion and the first curved portion of the support portion extend from the body in the same axial direction. The diameter of the centering portion is larger than the diameter of the first curved portion, defining a radial offset between the centering portion and the first curved portion.

[0015] 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.

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

[0017] In one embodiment, the tongue and the support portion are alternately distributed in the circumferential direction.

[0018] In an advantageous embodiment, the second curved portion is continued by the axial portion of the centering portion.

[0019] 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

[0020] 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:

[0021] Figure 1 This is an axial cross-sectional view of a grounding brush assembly, at least partially mounted radially between the rotating shaft and the seat of an electric motor, according to an exemplary embodiment of the present invention.

[0022] Figure 2 yes Figure 1 A 3D view of the grounding brush assembly in the image;

[0023] Figure 3 yes Figure 1 Front view of the grounding brush component in the middle;

[0024] Figure 4 yes Figure 3 The component in the diagram is shown in a cross-sectional view along line II.

[0025] Figure 5 yes Figure 3 The component in the cross-sectional view along line II-II; and

[0026] Figure 6 yes Figure 3 The component in the diagram is shown in the cross-sectional view along line III-III. Detailed Implementation

[0027] 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.

[0028] 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.

[0029] 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.

[0030] 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.

[0031] 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.

[0032] 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.

[0033] Mounting plate 18 is fixed to support member 22. Mounting plate 18 includes a body 32, a plurality of tongues 34 and an axial centering portion 36. The body 32 is formed by a radial portion that axially abuts against a first edge 28 of the support member. The plurality of tongues 34 are used to hold brush 16 in the axial and radial directions.

[0034] 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 5 In 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 in the circumferential direction.

[0035] The centering portion 36 is provided with an outer surface 38 that defines the outer diameter of the mounting plate 18 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.

[0036] The tongues 34 extend from the body 32 of the mounting plate 18 and are spaced apart from each other in the circumferential direction. The tongues 34 protrude from the body 32 in the axial direction away from the bearing 8.

[0037] Each retaining tongue 34 extends from the body 32 of the mounting plate 18 such that the retaining tongue 34 partially surrounds the support 22 of the brush 16 radially, while simultaneously contacting the support 22 radially. The support 22 is held axially by the tongue 34. Furthermore, each tongue 34 has a bent edge on the support 22 to create axial contact. The support 22 is held by the tongue 34 to axially bear against the radial portion 32 of the mounting plate 18. Thus, the support 22 is held both axially and radially by the retaining tongue 34.

[0038] In the example shown, the mounting plate 18 includes four retaining tongues 34 that are regularly spaced apart in the circumferential direction. As a variation, the mounting plate includes a different number of retaining tongues 34. If the mounting plate 18 includes multiple centering portions, the positions of the tongues 34 may alternate with the centering portions in the circumferential direction.

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

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

[0041] 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.

[0042] 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.

[0043] In the exemplary embodiment shown, the mounting plate 18 and the support member 22 are two separate pieces. As a variation, the mounting plate 18 and the support member 22 can be manufactured as a single piece, for example, by cutting and pressing. In this case, the body 32 of the mounting plate 18 extends from the first side toward the small-diameter boundary of the edge 28.

[0044] Mounting plate 18 and grounding brush 16 comprise conductive materials such as aluminum, stainless steel, bronze, copper, or another material.

[0045] According to the invention, the mounting plate also includes a plurality of support portions 40 to hold the brush support 22 in the axial direction and to serve as a support for a tool for inserting the assembly 10 into the seat 4.

[0046] Each support portion 40 is formed by a first curved portion 42 and a second curved portion 44. The first curved portion 42 extends axially from the body 32. Both the centering portion 36 and the first curved portion 42 of the support portion 40 extend from the body 32 in the same axial direction. The diameter of the centering portion 36 is larger than the diameter of the first curved portion 42, defining a radial offset between the centering portion and the first curved portion.

[0047] The second curved portion 44 extends radially between the first curved portion 42 and the centering portion 36. The second curved portion 44 forms a radial connection between the two axial portions 42 and 36. Therefore, each support portion 40 forms a radial protrusion toward the inside of the assembly 10.

[0048] The second curved portion 44 is continued in the axial direction by the axial portion 37 of the centering portion 36.

[0049] Advantageously, each support portion 40 is formed by cutting a centering portion 36. More specifically, two cuts 46a, 46b are formed along a defined length and at a defined circumferential interval through the thickness of the centering portion 36. The portion between the two cuts 46a, 46b is then deformed by bending to form two radially inwardly projecting portions 42 and 44. Alternatively, the support portion 40 can be made by notching without removing material.

[0050] According to the invention, each first curved portion 42 extending in the axial direction abuts radially against the upper axial surface of the cylindrical portion 26 of the brush support 22.

[0051] Therefore, the support 22 is held in place radially by a plurality of bearing points 40 and a tongue 34 that are in direct contact with the outer surface of the cylindrical portion 26 of the support 22. This radial holding of the support 22, combined with the axial holding of the support between the tongue 34 and the body 32, ensures that the support 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 22 are positioned relative to the bearing 8, the seat 4, and the rotating shaft 6 to ensure the function of current flow.

[0052] In the example shown, the mounting plate 18 includes four support portions 40 that are regularly spaced apart in the circumferential direction. As a variation, the mounting plate includes a different number of support portions 40.

[0053] 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.

[0054] Furthermore, each second curved portion 44 defines an axial support surface for a tool (not shown) used to position the assembly 10. With this invention, the grounding brush assembly 10 can be easily mounted in the seat 4 and on the rotating shaft 6 without the risk of deformation.

[0055] In practice, according to existing technology (e.g., US-A1-2021 / 0021180), the grounding brush assembly is press-fitted into the hole of the seat by an installation tool that axially abuts against the edge of the tongue and applies force in the axial direction of insertion. This installation method requires proper design of the grounding brush assembly, in particular, the tongue and support 22 need to have sufficient radial dimensions to withstand the applied force.

[0056] Using this invention, the grounding brush assembly 10 is press-fitted into the hole 12 of the seat by an installation tool (not shown) that axially abuts against the lateral face of the second curved portion 44 and applies force in the axial direction of insertion. Therefore, the tongue no longer functions as a support tool and can be appropriately dimensioned solely for its function of holding the support member 22. The tongue 34 and the support member 22 can be dimensioned in a reduced manner relative to prior art assemblies, allowing the assembly 10 to achieve radial compactness.

[0057] Therefore, the tongue 34 and the support 22 are no longer subjected to direct forces applied by the installation tool, thereby eliminating the risk of deformation of the components during the insertion of the assembly 10 into the seat 4.

[0058] The support portion 40 allows for increased rigidity of the centering portion 36, which is forcibly mounted in the seat 4. The risk of deformation of the portion 36 during assembly or removal of component 10 is ultimately reduced.

[0059] 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 extending radially outward relative to the support member (22). - A plurality of centering tongues (34) projecting axially relative to the body (32), each tongue (34) partially radially surrounding and in radial contact with a support (22) of the brush (16), the support (22) being held by the tongues (34) to axially support the body (32) abutting against the mounting plate (18), and - The centering portion (36), extending axially from at least the body (32), extending axially on the same side as the tongue (34), radially offset outward relative to the support (22) and the tongue (34), 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 (18) is characterized in that it further includes at least one support portion (40) projecting radially toward the inner side of the assembly (10), the support portion (40) being formed by: - A first curved portion (42) extends axially from the body (32) and radially abuts against the upper axial surface (26) of the brush support (22), and - A second curved portion (44) extends radially between the first curved portion (42) and the centering portion (46), the second curved portion (44) defining an axial support surface for a tool used to position the component (10).

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 mounting plate (18) includes a plurality of support portions (40) spaced apart from each other in the circumferential direction.

5. The component (10) according to claim 4, characterized in that, The tongue (34) and the support portion (40) are alternately distributed in the circumferential direction.

6. The component (10) according to any one of the preceding claims, characterized in that, The second curved portion (44) is continued by the axial portion (37) of the centering portion (36).

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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