grounding brush arrangement

Abstract

The grounding brush assembly 20 comprises a grounding brush 30, which is provided with several conductive fibers 31 and with a carrier 32 in which the conductive fibers are attached, and a brush mounting plate 40, which is attached to the carrier 32 of the brush. The arrangement further includes a spacer disc 50, which is supported by the mounting plate 40 and is arranged axially on the side opposite the brush 30 with respect to the mounting plate.

Description

Technical field of the invention

[0001] The present invention relates to the field of grounding devices for controlling the shaft current generated in electric motors or machines, in particular to grounding brush assemblies. State of the art

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

[0003] During operation, as the shaft rotates, an electrical potential difference may occur between the shaft and the housing of the electric motor or electrical machine, generating an electric current between the inner race of the rolling bearing, which is attached to the shaft, and the outer race, which is attached to the housing.

[0004] The electrical current flowing through the components of the rolling bearing can damage these components, especially the rolling elements and the raceways formed on the inner and outer races. Electrical discharges can also generate vibrations.

[0005] To overcome these disadvantages, it is common practice to ground or connect the rotating shaft to earth using a grounding brush comprising conductive fibers. The grounding brush is typically mounted in the bore of the electric motor housing so that the free ends of the fibers are in radial contact with the outer surface of the rotating shaft.

[0006] Due to the conductivity of the fibers, the brush is maintained at the same electrical potential as the electric motor housing. The inner and outer races of the rolling bearing also have the same electrical potential, which reduces or even eliminates problematic electrical discharges through the rolling bearing.

[0007] For further details regarding the design of such a grounding brush assembly, 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 holder in which the conductive fibers are fixed, and an annular mounting plate comprising a plurality of tongues for the radial and axial support of the carrier.

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

[0009] This can damage the bearing.

[0010] The present invention aims to remedy this disadvantage. 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 carrier in which the conductive fibers are mounted. The assembly also comprises a brush mounting plate attached to the brush carrier.

[0012] According to a general feature, the assembly further comprises a spacer washer carried by the mounting plate and arranged axially on the side opposite the brush with respect to the mounting plate.

[0013] This design limits the risk of contact between the conductive fibers of the assembly and the bearing. More specifically, the spacer allows for axial clearance to be maintained between the assembly's mounting plate and the bearing or housing.

[0014] Advantageously, the spacer disc projects axially from the mounting plate. This further limits the risk of contact between the conductive fibers of the assembly and the bearing.

[0015] Preferably, the spacer is made of a material that is electrically insulating, in other words, electrically non-conductive. This prevents the dissipation of electrical charge to the bearing in the event of contact between it and the assembly.

[0016] According to a specific embodiment, the spacer disc is annular. Alternatively, the spacer disc can be open at one point along its circumference.

[0017] The mounting plate may comprise a radial portion against which the brush and the spacer disk are mounted, pressing axially on each side.

[0018] The mounting plate may include at least one attachment portion extending at least axially from the radial portion and to which the spacer washer is attached. The attachment portion may extend over a small-diameter edge of the radial portion of the mounting plate.

[0019] In a particular embodiment, the mounting plate comprises a plurality of tongues for holding the brush carrier, which tongues extend from the radial portion.

[0020] In one embodiment, the mounting plate comprises at least one centering portion extending at least axially along the radial portion which is offset radially outwardly with respect to the carrier and has an outer surface defining the outer diameter of the mounting plate.

[0021] The mounting plate can be designed as one piece.

[0022] Preferably, the spacer is flush with or radially recessed from the outer surface of the centering section. This simplifies the assembly of the device in the associated housing.

[0023] The invention further relates to an electric motor comprising a housing, a shaft and at least one grounding brush assembly as defined above, mounted radially between the housing and the shaft, the conductive fibers of the brush of the assembly being in contact with the shaft. Short description of the characters

[0024] The present invention will be better understood from the detailed description of an embodiment given as a non-limiting example and illustrated by the accompanying drawings in which: [ Fig. 1] is an axial section view of a grounding brush assembly mounted radially between a rotating shaft and a housing of an electric motor, [ Fig. 2] [ Fig. 3] are perspective views of a grounding brush assembly according to an exemplary embodiment of the invention, [ Fig. 4] a view of the grounding brush arrangement of the Fig. 2 and Fig. 3 from the front, [ Fig. 5] a sectional view along the line VV in Fig. 4 is, and [ Fig. 6] a view in section along the line VI-VI in Fig. 4 is. Detailed description of the invention

[0025] Fig. Figure 1 shows, in axial section, a portion of an electric motor 10 or an electric machine, comprising a stationary housing 12, a rotating shaft 14 with axis XX, which is radially supported by a rolling bearing 16. The bearing 16 is mounted radially between the housing 12 and the rotating shaft 14. In this case, the bearing is a ball bearing. Alternatively, it is also possible to provide other rolling elements or a plain bearing.

[0026] The motor 10 further includes a ground brush assembly 20 mounted radially between the bore 12a of the housing 12 and the outer cylindrical surface 14a of the rotating shaft 14.

[0027] The grounding brush assembly 20 serves to continuously dissipate the electrical charge that builds up on the shaft 14 of the motor when the motor is in operation by transferring this charge to the housing 12.

[0028] A grounding brush assembly 20 according to an exemplary embodiment of the invention will now be described with reference to Fig. 2 to 6.

[0029] The grounding brush assembly 20 has an overall annular shape. The assembly 20 includes a grounding brush 30 and a brush mounting plate 40 configured to radially center the brush 30.

[0030] As will be described in more detail below, the assembly 20 further includes a spacer 50 carried by the mounting plate 40.

[0031] The brush 30 comprises a plurality of individual conductive fibers 31 designed to extend around the rotating shaft of the motor. The conductive fibers 31 can be made of carbon, stainless steel, or conductive plastic, such as acrylic or nylon fibers.

[0032] The brush 30 further comprises a holding or support element 32, inside which the conductive fibers 31 are secured. In the illustrated exemplary embodiment, the support 32 is in the shape of an open ring. The support 32 can be manufactured by cutting and pressing. The support 32 is made of an electrically conductive material such as aluminum, stainless steel, bronze, copper, or another material. Alternatively, the support 32 can be made of an electrically non-conductive material with a conductive coating or a conductive paint.

[0033] As in the Fig. 5 and Fig. 6, the carrier 32 comprises an axial mounting portion 34 and two opposing lateral flanks 36, 38 extending inwardly from the mounting portion 34 and axially engaging the conductive fibers 31. The conductive fibers 31 press axially on each side against the lateral flanks 36, 38. The conductive fibers 31 press axially on each side against the inner surfaces of the lateral flanks 36, 38.

[0034] The fastening section 34 and the two lateral flanks 36, 38 define a channel which is open radially on the inside and in the interior of which the conductive fibers 31 are partially positioned.

[0035] In the example shown, the conductive fibers 31 are bent around a connecting wire 39 of the carrier 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 carrier.

[0036] The lateral flank 36 extends one end of the fastening section 34, and the lateral flank 38 extends the opposite end of the section. The lateral flanks 36, 38 extend obliquely inward from the fastening section 34. The lateral flanks 36, 38 are symmetrical to one another about a radial center plane of the carrier 32. The fastening section 34 extends axially here. Alternatively, the fastening section 34 could also extend obliquely.

[0037] As mentioned above, the brush 30 is in the form of an open ring, as particularly shown in the Fig. 2 and Fig. 3. This allows the brush to adapt to different motor shaft diameters. Generally, the ends of the brush are not connected to each other. In one variant, it is possible to connect these ends of the brush 30.

[0038] With reference to the Fig. 2, Fig. 5 and Fig. 6, the mounting plate 40 includes an annular radial portion 42 and a plurality of centering tabs 44 extending from the radial portion 42.

[0039] The radial portion 42 of the mounting plate axially abuts the carrier 32 of the brush 30. More precisely, the radial portion 42 axially abuts the side flank 36 of the carrier.

[0040] The tongues 44 are circumferentially spaced from one another, in this case evenly. Alternatively, it might be possible to provide an irregular circumferential spacing. In the exemplary embodiment shown, there are eight tongues 44. Alternatively, it is possible to provide a larger or smaller number of tongues 44. It is possible to provide two tongues 44 or at least four tongues. Preferably, the number of tongues 44 is at least two.

[0041] Each tongue 44 projects axially relative to the radial portion 42. Each tongue 44 locally radially surrounds the support 32 of the brush 30 and is in radial contact with the support's mounting portion 34. The support 32 is held axially against the radial portion 42 of the mounting plate by the tongues 44. The tongues 44 serve to hold the grounding brush 30 axially and radially. The side flank 36 of the support bears against the radial portion 42 of the mounting plate, and the side flank 38 bears against the tongues 44. The tongues 44 are identical to one another in this case.

[0042] As in Fig. As shown more clearly in Figure 5, each tongue 44 is provided with an axial portion extending axially from the radial portion 42, locally radially surrounding the carrier 32, and in radial contact therewith, and with a bent portion at the free end of the axial portion. The bent portion 44b of each tongue serves to axially retain the carrier 32 of the grounding brush 30. The bent portion 44b of each tongue is in axial contact with the side flank 38 of the carrier.

[0043] The brush mounting plate 40 also includes a plurality of centering tabs 46 extending from the radial portion 42 and spaced circumferentially from each other. A cutout 48 ( Fig. 2) is formed on the radial portion 42 between each pair of immediately adjacent tabs 46. The tabs 46 are formed by cutting and bending the radial portion 42.

[0044] Each tab 46 extends axially from the radial section 42. The tabs 46 extend obliquely from an edge of the large-diameter radial section 42. The tabs 46 extend axially from the same side as the tongues 44.

[0045] Each tab 46 locally radially surrounds the carrier 32 of the brush 30, but remains separate from it. The tabs 46 are partially offset radially outward with respect to the tongues 44. The tabs 46 are identical to one another in this case. The tabs 46 define the outer diameter of the mounting plate 40. Each tab 46 extends obliquely here. Alternatively, the tabs 46 could extend axially. Each tab 46 is in the shape of a section of a cylinder. The bore in each tab 46 is radially spaced from the carrier 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 provide centering for the mounting plate once it has been mounted in the bore of the housing of the associated electric motor.

[0046] As in the Fig. 2 and Fig. 4, the tabs 46 are circumferentially spaced from each other, in this case evenly. Alternatively, it might be possible to provide an irregular circumferential spacing. Each tab 46 is positioned circumferentially between two immediately adjacent tongues 44. Each tab 46 is spaced circumferentially from the two immediately adjacent tongues 44. In this case, each tab 46 has a circumferential dimension that is larger than that of the tongues 44.

[0047] With reference again to the Fig. 5 and Fig. 6, the mounting plate 40 further comprises a fastening portion 52 that extends the radial portion 42 axially on the side opposite the tongues 44 and the tabs 46. The fastening portion 52, in this case, extends axially and is annular. The fastening portion 52 extends a small-diameter edge of the radial portion 42.

[0048] The mounting plate 40 is manufactured by cutting and pressing. The mounting plate 40 is made of a conductive material such as aluminum, stainless steel, bronze, copper, or another material. Alternatively, the mounting plate 40 can be made of an electrically non-conductive material with a conductive coating or conductive paint. In this case, the mounting plate 40 is made of a single piece.

[0049] As mentioned above, the assembly 20 includes the spacer disc 50, which is carried by the mounting plate 40. The disc 50 is a separate part from the mounting plate 40. The disc 50 is arranged axially on the side opposite the brush 30 with respect to the radial portion 42 of the mounting plate.

[0050] The disc 50 is mounted on the mounting portion 52 of the mounting plate. The disc 50 is centered on the mounting portion 52. The disc 50 is mounted to axially press against the radial portion 42 of the mounting plate on the side opposite the brush 30. The brush 30 and the disc 50 are mounted to axially press on each side of the radial portion 42. The disc 50 projects partially outward axially relative to the mounting portion 52 of the mounting plate. In the exemplary embodiment shown, the disc 50 is annular. Alternatively, the disc 50 could be open at one point along its circumference.

[0051] The disc 50 comprises a cylindrical axial outer surface 50a, a cylindrical bore 50b radially opposite the outer surface 50a, and two radially opposite end surfaces 50c, 50d axially delimiting the bore and the outer surface. The end surface 50c of the disc is mounted to axially press against the radial portion 42 of the mounting plate. The end surface 50d is offset axially outward with respect to the free end of the fastening portion 52 of the mounting plate. The bore 50b of the disc is mounted to radially press against the outer surface of the radial portion 42 of the mounting plate. The outer surface 50a is offset radially inward with respect to the free large-diameter edges of the plate tabs 46.

[0052] The disc 50 is advantageously made of an electrically insulating material. The disc 50 can be made, for example, of a synthetic material, of plastic, in particular of PEEK, PBT, PPS, or PAI.

[0053] While the electric machine is in operation, the electrical charge that builds up on the shaft is discharged to the housing 4 via the conductive fibers 20, the carrier 22 of the brush and the mounting plate 40 of the assembly.

[0054] The disc 50 prevents contact between the conductive fibers 20 of the brush and the bearing.

[0055] In the illustrated exemplary embodiment, the mounting plate 40 of the grounding brush assembly includes a plurality of centering tabs 46. Alternatively, the tabs could be replaced by an annular flange forming an annular centering portion. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] US-A1-2021 / 0021180

[0007]

Claims

[1] Grounding brush assembly (20) comprising a grounding brush (30) provided with a plurality of conductive fibers (31) and with a carrier (32) in which the conductive fibers are fixed, and a brush mounting plate (40) fixed to the carrier (32) of the brush, characterized by that the assembly further comprises a spacer disc (50) carried by the mounting plate (40) and arranged axially on the side opposite the brush (30) with respect to the mounting plate. [2] Arrangement according to claim 1, wherein the spacer disc (50) projects axially with respect to the mounting plate (40). [3] An arrangement according to claim 1 or 2, wherein the spacer disc (50) is made of a material that is electrically insulating. [4] Arrangement according to one of the preceding claims, wherein the spacer disc (50) is annular. [5] An assembly according to any preceding claim, wherein the mounting plate (40) comprises a radial portion (42) to which the brush (30) and the spacer disc (50) are mounted, pressing axially on each side. [6] An assembly according to claim 5, wherein the mounting plate comprises at least one fastening portion (52) extending at least axially from the radial portion (42) and to which the spacer disc (50) is fastened. [7] An assembly according to claim 5 or 6, wherein the mounting plate comprises a plurality of tongues (44) for holding the carrier (32) of the brush, said tongues extending from the radial portion (42). [8] Arrangement according to one of claims 5 to 7, wherein the mounting plate comprises at least one centering portion (46) extending at least axially from the radial portion (42) which is offset radially outwardly with respect to the carrier (32) and has an outer surface defining the outer diameter of the mounting plate (18). [9] Arrangement according to claim 8, wherein the outer surface of the spacer disc (50) is flush with the outer surface of the centering section (46) or is radially recessed therefrom. [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 mounted radially between the housing (12) and the shaft (14), the conductive fibers of the brush of the assembly being in contact with the shaft.

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