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 mounting plate (40) comprises a plurality of centering tabs (44) for centering a support (32) of the brush and a plurality of securing members (50) for rigidly securing the centering tabs to the support (32), the securing members (50) being different from the support (22) and the centering tabs (44).

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] The tabs (for axially and radially retaining the support) are formed by cutting and bending ( / curving) the radial portion of the mounting plate that bears on the support in the axial direction.

[0009] In order to be able to create these retaining tabs, it is necessary to make large cutouts in the radial portion of the mounting plate. This compromises the mechanical strength of the mounting plate relative to the forces applied (vis-à-vis) when it is mounted in a hole in the housing of the associated electric motor.

[0010] Furthermore, stresses may be concentrated during the bending of such a tab on the support of the brush, taking into account the bending length of the retaining tab.

[0011] The present invention aims to overcome these disadvantages. Summary of the invention

[0012] 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.

[0013] According to a general feature, the mounting plate comprises a plurality of centring tabs for centring the support of the brush.

[0014] According to another general characteristic, the assembly also comprises a plurality of securing means for rigidly securing said centering tab to the support. Said securing means are distinct from the support and the centering tab.

[0015] Utilize this design, because lug only performs radial centering function and not axial retention function, so the bending length of lug can be small, and this limits the stress concentration on mounting plate.In addition, the size of the cutout made on mounting plate for forming lug is also small.

[0016] Preferably, the fixing member may be made of a conductive material, which further promotes the dissipation of electric charges.

[0017] The fixing means may include glue and / or adhesive and / or weld and / or braze.

[0018] According to a first design, each fixing part at least partially covers the free end of the associated centering tab and the adjacent region of the support.

[0019] According to a second alternative design, each fixing part is radially interposed between the associated centering tab and the support.

[0020] According to a third design, each fixing part covers the free end of the associated centering tab and the adjacent region of the support and is radially interposed between the associated centering tab and the support.

[0021] In one embodiment, the support of the brush comprises a mounting portion and two lateral flanks extending from the mounting portion and clamping the conductive fibers in the axial direction. One of the lateral flanks of the support may bear against the mounting plate in the axial direction.

[0022] Preferably, the centering tabs of the mounting plate are set axially to the wings back from the other side of the support. This further facilitates obtaining a short tab length.

[0023] The mounting plate may comprise an annular radial portion against which the grounding brush bears axially. In the present case, said lateral wings of the brush support may bear axially against the radial portion of the mounting plate.

[0024] In a specific embodiment, the centering tab extends from a radial portion of the mounting plate. As another option, the centering tab can extend from another portion of the mounting plate.

[0025] In one embodiment, the mounting plate comprises at least one centering portion extending at least axially from the radial portion, the at least one centering portion being offset radially outwardly relative to the support and having an outer surface defining an outer diameter of the mounting plate.

[0026] Preferably, the mounting plate is made in one piece.

[0027] 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

[0028] 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:

[0029] [ Figure 1 ] is an axial cross-sectional view of a grounding brush assembly installed in a radial direction between a rotating shaft and a housing of an electric motor;

[0030] [ Figure 2 ] is a perspective view of a grounding brush assembly according to a first exemplary embodiment of the present invention;

[0031] [ Figure 3 ]yes Figure 2 An end view of a grounding brush assembly;

[0032] [ Figure 4 ] is along Figure 3 A cross-sectional view along the axis IV-IV;

[0033] [ Figure 5 ] is a cross-sectional view of a grounding brush assembly according to a second exemplary embodiment of the present invention; and

[0034] [ Figure 6 ]yes Figure 5 Perspective view of the grounding brush assembly. DETAILED DESCRIPTION

[0035] 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.

[0036] 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 .

[0037] The grounding brush assembly 20 makes it possible to continuously dissipate charge accumulated on the shaft 14 of the motor during operation of the motor by transferring the charge to the housing 12 .

[0038] Reference Figures 2 to 4 , a grounding brush assembly 20 according to a first example will now be described.

[0039] 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 center the brush 30 in a radial direction.

[0040] As will be described in more detail below, the brush mounting plate 40 is rigidly secured to the brush 30 by added means.

[0041] 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.

[0042] 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.

[0043] As in Figure 4 As can be seen more clearly in FIG. 3 , the support 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. The conductive fiber 31 bears against the inner surfaces of the lateral flanks 36, 38 on both sides in the axial direction.

[0044] 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.

[0045] 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.

[0046] 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.

[0047] As explained above, especially in Figure 2 and Figure 3As can be seen in the figure, the brush 30 takes the form of an open ring. This allows the brush to be adapted to different motor shaft diameters. Typically, the ends of the brush are not attached to each other. In a variant, these ends of the brush 30 can be attached to each other.

[0048] The mounting plate 40 is produced by cutting and forming. 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.

[0049] Reference Figure 2 and Figure 4 The brush mounting plate 40 includes an annular radial portion 42 and a plurality of centring tabs 44 extending from the radial portion 42 .

[0050] 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.

[0051] The tabs 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 tabs 44. As another option, a greater or indeed lesser number of tabs 44 can be provided. Two tabs 44 or at least four tabs can be provided. Preferably, the number of tabs 44 is at least equal to two.

[0052] Each lug 44 projects axially relative to the radial portion 42. Each lug 44 partially radially surrounds the support 32 of the brush 30 and is in radial contact with the mounting portion 34 of said support. In the present case, the lugs 44 are identical to one another.

[0053] As in Figure 4 As can be seen more clearly in FIG. 4 , each tab 44 consists of an axial portion extending axially from the radial portion 42, partially radially surrounding the support 32 and in radial contact with the support 32. Each tab 44 has no curved portion at the free end of the axial portion. In the exemplary embodiment shown, each tab 44 is set axially backward relative to the lateral wings 38 of the support.

[0054] The brush mounting plate 40 also includes a plurality of centering 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 (notch / cutout) is formed on the radial portion 42. Figure 2 ). The lug 46 is formed by cutting and bending the radial portion 42.

[0055] 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 from the same side as the tab 44. Alternatively, the lug 46 may extend axially from the opposite side.

[0056] 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.

[0057] like Figure 2 and Figure 3 As shown, the lugs 46 are spaced apart from each other in the circumferential direction, in the present case, regularly ( / equally) 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.

[0058] As set forth above, the brush mounting plate 40 is rigidly fixed to the brush 30 .

[0059] To this end, the assembly 20 includes a securing means 50 ( Figures 2 to 4 ), each fixing member 50 is associated with one of the lugs 44 of the mounting plate and is associated with the support 32. Therefore, the number of fixing members 50 is equal to the number of lugs 44.

[0060] The fixing member 50 is an element different from the tab 44 and the support member 32 , and is added to the tab 44 and the support member 32 .

[0061] In the exemplary embodiment shown, each fixing member 50 is disposed between the free end of the associated tab 44 of the mounting plate and the adjacent area of ​​the support 32. More specifically, each fixing member 50 is disposed between the free end of the associated tab 44 and the adjacent area of ​​the outer surface of the mounting portion 34 of the support. Each fixing member 50 covers the free end of the associated tab 44 and partially covers the outer surface of the mounting portion 34 of the support. In the present case, each fixing member 50 comprises a weld. Each tab 44 of the mounting plate is in direct radial contact with the mounting portion 34 of the support by being welded to the mounting portion 34 of the support. As another option, the fixing member 50 may include at least one of the following: glue, adhesive or braze.

[0062] The support 32 (which bears axially against the radial portion 42 of the mounting plate) is held in place by the fixing means 50. The tabs 44 allow only radial centering of the brush 30.

[0063] Advantageously, each fixing part 50 is made of a conductive material to facilitate the dissipation of electric charges. Thus, the electric charges accumulated on the shaft 6 during operation of the electric machine 2 are dissipated toward the housing 4 through the conductive fibers 31, the support 32 of the brush 30, the fixing parts 50 and the mounting plate 40. However, it is possible to provide fixing parts 50 made of non-conductive material.

[0064] Figure 5 and Figure 6 The exemplary embodiment shown in FIG. 2 (wherein like elements have like reference numerals) differs from the first example shown mainly in that the assembly 20 comprises a fixing member 52 radially interposed between each lug 44 of the mounting plate and the support 32. Each fixing member 52 is radially interposed between the inner surface of the associated lug 44 and the outer surface of the mounting portion 34 of the support. Each lug 44 is in indirect radial contact with the mounting portion 34 of said support, with the associated fixing member 52 radially interposed between them.

[0065] In this exemplary embodiment, the lugs 44 of the mounting plate have an increased axial dimension. The lugs 44 extend until near the lateral wings 38 of the support member and are set axially backward relative to the lateral wings 38 of the support member. Each fixing member 52 can include glue and / or adhesive. Preferably, each fixing member 52 is made of a conductive material to promote the dissipation of electric charges. As another option, the fixing member 52 can be made of a non-conductive material.

[0066] In the embodiment shown, the tabs 44 of the mounting plate are set axially rearward relative to the lateral wings 38 of the brush support. As another alternative, the tabs 44 may protrude axially relative to the lateral wings 38 of the support. In this case, a fixing member associated with each tab may be provided so that the fixing member is arranged between the inner surface of the tab and the outer surface of the mounting portion 34 of the support and / or the outer surface of the lateral wings 38.

[0067] In the described embodiment, the tabs 44 of the mounting plate are attached to the support 32 only by means of the fixing means 50 or 52. As another alternative, a radial interference of the tabs 44 of the mounting plate against the support 32 may be provided in combination with the fixing means, so that in the region of each retaining tab 44 the outer diameter of the mounting portion 34 of the support in the assembled state is strictly smaller than its outer diameter in the free (i.e., unassembled) state.

[0068] 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), characterized in that: The mounting plate (40) includes a plurality of centering tabs (44) for centering a support (32) of the brush, and the grounding brush assembly includes a plurality of fixing members (50, 52) for rigidly fixing the centering tabs to the support (32), the fixing members (50, 52) being different from the support (32) and the centering tabs (44).

2. The grounding brush assembly according to claim 1, characterized in that: The fixing components (50, 52) are made of conductive material.

3. The grounding brush assembly according to claim 1 or 2, characterized in that: The fixing means (50, 52) include glue and / or adhesive and / or welding and / or soldering.

4. A grounding brush assembly according to any one of the preceding claims, characterized in that Each fixing part (50) at least partially covers the free end of the associated centering tab (44) and an adjacent region of the support (32).

5. The grounding brush assembly according to any one of claims 1 to 3, characterized in that: Each fixing member (52) is radially interposed between the associated centering tab (44) and the support (32).

6. A grounding brush assembly according to any one of the preceding claims, characterized in that The brush support (32) comprises a mounting portion (34) and two lateral wings (36, 38) extending from the mounting portion and axially clamping the conductive fibers (31), one of the lateral wings (36, 38) of the support axially abutting against the mounting plate.

7. The grounding brush assembly according to claim 6, characterized in that: The centering tab (44) of the mounting plate is set axially rearward from the other lateral wing (38) of the support member.

8. 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.

9. The grounding brush assembly according to claim 8, characterized in that: The centering tab (44) extends from a 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) 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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