grounding brush arrangement

Abstract

This grounding brush arrangement (10) comprises a grounding brush (16) and a mounting plate (18) for the brush (16), wherein the brush (16) is provided with several conductive fibers (20) and with a carrier (22) in which the conductive fibers (20) are housed, wherein the mounting plate (18) is attached to the carrier (22) and is provided with a radially extending main body (32), with retaining tongues (34) for axially and radially retaining the carrier (22), and with an axially extending centering section (36), wherein the mounting plate (18) comprises at least one flange (40) that extends the distal end of the axial section (36) radially inwards.

Description

Technical field of the invention

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

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

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

[0004] The electric 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 rings. 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 containing 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] Due to the conductivity of the fibers, the brush is held at the same electrical potential as the housing of the electric motor. The inner and outer races of the roller bearing are also at the same electrical potential, which reduces or even eliminates problematic electrical discharges through the roller bearing.

[0007] Document US-A1-2021 / 0021180 discloses a grounding brush assembly comprising a grounding brush provided with a carrier and with several conductive fibers attached to that carrier, and an annular mounting plate provided with several tongues for radially and axially retaining the grounding brush carrier and with an annular outer flange radially surrounding the brush and the tongues. The tongues are formed by plastic deformation of the mounting plate.

[0008] Such a grounding brush assembly is pressed into the bore of the housing, making the grounding brush assembly difficult to remove.

[0009] The present invention aims to eliminate this disadvantage. Summary of the invention

[0010] The invention relates to an earthing brush arrangement for an electric motor which is provided with a rotating shaft, a stationary housing and a bearing.

[0011] The assembly comprises a grounding brush equipped with multiple conductive fibers and a carrier in which the conductive fibers are attached. The assembly also includes a brush mounting plate attached to the brush carrier.

[0012] The mounting plate comprises: a main body formed by a radial section extending radially outward with respect to the support; several centering tongues projecting axially with respect to the radial section, each tongue locally radially surrounding the brush support and in radial contact with the support, the support being held axially against the radial section of the mounting plate by the tongues; and a centering section extending the main body at least axially, extending axially on the same side as the tongues, offset radially outward with respect to the support and the tongues, and provided with an outer surface defining the outer diameter of the mounting plate to center the mounting plate after it has been fastened in a bore of the housing of an associated electric motor.

[0013] According to a general feature of the invention, the centering section comprises at least one flange that extends the distal end of the axial section radially inwards.

[0014] In one embodiment, the centering section can be ring-shaped. Alternatively, the centering section can comprise several axial sections that are spaced apart from each other in the circumferential direction.

[0015] In one embodiment, the flange is annular. Alternatively, the mounting plate comprises several flanges spaced apart from one another in the circumferential direction, each flange extending the distal end of an axial section of the centering section radially inwards.

[0016] The invention also relates to an electric machine or electric motor comprising a housing, a shaft and an earthing brush arrangement as defined above, which is at least partially radially fixed between the housing and the shaft, wherein the conductive fibers of the arrangement are in contact with the shaft.

[0017] According to a preferred embodiment of the invention, the flange of the mounting plate of the arrangement is radially located in the bore of the housing. The centering section extends axially within the bore, but does not extend beyond its end. Brief character description

[0018] The present invention will be better understood by studying the detailed description of embodiments given as non-limiting examples and illustrated by the accompanying drawings, in which: [ Fig. 1] an axial sectional view of a grounding brush arrangement which is at least partially radially mounted between a rotating shaft and a housing of an electric motor according to an exemplary embodiment of the invention; [ Fig. 2] a perspective view of the grounding brush arrangement in Fig. 1 is; [ Fig. 3] a front view of the grounding brush arrangement in Fig. 1 is; [ Fig. 4] a sectional view of the arrangement in Fig. 3 along line II; and [ Fig. 5] a sectional view of the arrangement in Fig. 3 along line II-II. Detailed description of the invention

[0019] Fig. Figure 1 shows, in axial section, a part of an electric motor or electric machine 2, comprising a stationary housing 4, a rotating shaft 6 of axis XX, which is radially supported by a bearing 8. The bearing 8 is, for example, a ball bearing. As an alternative, other rolling elements, such as rollers, can be used. Alternatively, a plain bearing can be used.

[0020] The motor 2 comprises a grounding brush assembly 10, which is at least partially radially mounted between the bore 12 of the housing and the cylindrical outer surface 14 of the shaft. The assembly 10 is, for example, pressed into the bore 12 of the housing.

[0021] In the remainder of the description, the adjectives "axial" and "radial" and the adverbs "axial" and "radial" are defined in relation to the central axis X. An axial section or part is thus parallel to the axis X, while a radial section is perpendicular to and surrounds this axis. Additionally, a radial section has an "inner" surface oriented towards the axis X and an "outer" surface oriented away from this axis.

[0022] As in the Fig. As shown more clearly in Figures 2 to 5, the grounding brush assembly 10 generally has a ring-shaped form. The assembly 10 comprises a grounding brush 16 and a mounting plate 18 for the brush 16.

[0023] The grounding brush 16 comprises several conductive fibers 20 and a carrier 22, the conductive fibers being housed within the carrier 22 of the brush 16. The conductive fibers 20 can be made, for example, of carbon, stainless steel, conductive plastics such as acrylic fibers, or nylon fibers. The multiple conductive fibers 20 are in the form of an open ring. In the illustrated example, the conductive fibers 20 are bent around a connecting wire 24. The distal free end of the conductive fibers 20 is designed to come into radial contact with the outer surface 14 of the shaft 6.

[0024] To ensure the attachment and retention of the conductive fibers 20, the support 22 comprises a cylindrical section 26, a first lateral edge 28 extending the cylindrical section 26 for one part, and a second lateral edge 30 extending the cylindrical section 26 for the other part. The first edge 28 is positioned axially towards the outside of the assembly, while the second edge 30 is positioned axially towards the bearing 8, with the edges 28 and 30 being axially opposite to the cylindrical section 26 and the fibers 20, respectively.

[0025] The mounting plate 18 is attached to the carrier 22. The mounting plate 18 comprises a main body 32, formed by a radial section that is in axial contact with the first edge 28 of the carrier, several tongues 34 for axially and radially holding the brush 16, and an axial centering section 36.

[0026] The centering section 36 of the mounting plate 18 extends axially from the main body 32 in a direction away from the bearing 8. According to the Fig. In the embodiment shown in Figures 1 to 5, the centering section 36 consists of an annular cylindrical section. As an alternative, it would be possible to provide that the centering section comprises several axial sections that are spaced apart from each other in the circumferential direction.

[0027] The centering section 36 is provided with an outer surface 38 that defines the outer diameter of the mounting plate 18 in order to center the mounting plate after it has been fastened in the bore 12 of the housing 4 of the associated electric motor 2. The centering section 36 is preferably pressed into the bore 12 of the housing 4 to create a diametrical interference to ensure the mechanical retention of the mounting plate 18 in the housing 4.

[0028] The retaining tongues 34 extend from the main body 32 of the mounting plate 18 and are spaced apart from each other in the circumferential direction. The tongues 34 project axially from the main body 32 in a direction away from the bearing 8.

[0029] Each retaining tongue 34 extends from the main body 32 of the mounting plate 18, such that the retaining tongue 34 locally radially surrounds the brush carrier 22 while maintaining radial contact with the carrier 22. The carrier 22 is held axially by the tongues 34. Furthermore, each tongue 34 has a curved edge on the carrier 22 to create axial contact. The carrier 22 is held axially against the radial section 32 of the mounting plate 18 by the tongues 34. The carrier 22 is thus held axially and radially by the retaining tongues 34.

[0030] In the example shown, the mounting plate 18 comprises eight retaining tongues 34 spaced evenly around its circumference. As a variant, the mounting plate comprises a different number of retaining tongues 34. If the mounting plate 18 includes several centering sections, the positions of the tongues 34 can alternate circumferentially with the centering sections.

[0031] The centering section 36 extends the main body 32 axially, extends axially on the same side as the support 22 and the tongues 34, and is radially offset outwards with respect to the support 22 and the tongues 34.

[0032] The cylindrical section 26 of the support 22 is in radial contact with the retaining tongues 34, and the second side edge 30 is in axial contact with the tongues. The cylindrical section 26 extends the large-diameter edge of the first side edge 28. The cylindrical section 26 extends axially here.

[0033] The second side edge 30 of the carrier 22 extends the cylindrical section 26 radially inwards. The second side edge 30 extends the cylindrical section 26 on the side opposite the first side edge 28. The cylindrical section 26 and the first and second side edges 28, 30 are annular in shape and define a channel that is radially open on the inside and in which one end of the conductive fibers 20 is positioned. The first and second side edges 28, 30 axially clamp the conductive fibers 20. The conductive fibers 20 are axially aligned with the first and second side edges 28, 30 on each side.

[0034] In the illustrated exemplary embodiment, the conductive fibers 20 are arranged radially against the cylindrical section 26, with the first and second side edges 28, 30 extending obliquely inwards from the cylindrical section 26. Alternatively, the first and second side edges 28, 30 could extend radially.

[0035] In the illustrated exemplary embodiment, the mounting plate 18 and the support 22 are two separate parts. Alternatively, the mounting plate 18 could be manufactured as a single part with the support 22, for example by cutting or pressing. In this case, the main body 32 of the mounting plate 18 extends the small-diameter edge of the first side edge 28.

[0036] The mounting plate 18 and the grounding brush 16 comprise an electrically conductive material, such as aluminium, stainless steel, bronze, copper or another material.

[0037] According to the invention, the mounting plate 18 also includes an annular flange 40 which extends the distal end of the axial and annular centering section 36 of the mounting plate 18 radially inwards.

[0038] In the example shown, the flange 40 has a connecting section for joining with the curved centering section 36 and a radially extending section that extends this connecting section. Alternatively, the flange 40 could extend purely radially.

[0039] Again with reference to Fig.In the first section, the arrangement 10 is partially radially fixed between the bore 12 of the housing and the cylindrical outer surface 14 of the shaft, such that the radial section 32 of the mounting plate rests axially against a shoulder of the housing 4. The centering section 36 of the mounting plate rests radially against the bore 12 of the housing.

[0040] According to the invention, the grounding brush arrangement 10 can be easily attached in a housing 4 and on a rotating shaft 6 without risk of deformation.

[0041] In fact, according to the prior art, for example US-A1-2021 / 0021180, a grounding brush assembly is pressed into the bore of the housing by a fastening tool in axial contact with the edges of the tongues, and by applying a force in the axial direction of insertion. Such a fastening method requires a suitable design of the grounding brush assembly, in particular a sufficient radial dimension of the tongues and the carrier 22 to withstand the applied force.

[0042] With the present invention, the grounding brush assembly 10 is pressed into the bore 12 of the housing by a fastening tool (not shown) in axial contact with the lateral surface of the flange 40, and by applying a force in the axial direction of insertion. Consequently, the tongues no longer have the function of supporting the tool and can only be appropriately dimensioned for their function of holding the support 22. The tongues 34 and the support 22 can be dimensioned in a reduced manner compared to a prior art arrangement, allowing the assembly 10 to gain radial compactness. The flange, for its part, is appropriately dimensioned for the supporting function of the fastening tool without affecting the radial compactness of the assembly 10.

[0043] Consequently, the tongues 34 and the support 22 are no longer subjected to direct force exerted by the fastening tool, thus eliminating the risk of deformation of the parts during insertion of the arrangement 10 into a housing 4.

[0044] According to the illustrated embodiment, the annular flange 40 of the mounting plate 18 of the arrangement 10 is radially located in the bore 12 of the housing 4. The centering section 36 extends axially within the bore 12 but does not extend beyond its end. The arrangement 10 thus maintains optimized axial compactness. According to a variant, not shown, and depending on the specific requirements, the centering section 36 could extend beyond the bore 12, in which case the flange 40 would be located outside the bore 12.

[0045] The flange 40 extends radially inwards, thus enabling the use of a removal tool (not shown) to remove the assembly 10 from the housing 4. Such a tool can be designed to enter the space defined between the radial section 32 of the plate and the flange 40, in order to come into axial contact with the lateral inner surface of the flange. The removal tool can then exert an axial force in a direction opposite to the direction of insertion, on the side opposite the housing 4. The assembly 4 can thus be secured and then easily removed. Maintenance work can be easily carried out to replace an assembly 10 according to the invention.

[0046] Finally, the flange allows for increased rigidity of the centering section 36, which is forcibly fastened in the housing 4. The risks of deformation of the section 36 during fastening or removal of the assembly 10 are thus reduced.

[0047] Furthermore, all or only some of the technical features of the various designs can be combined. This allows the grounding brush arrangement to be adapted in terms of cost, performance, and user-friendliness. QUOTES INCLUDED IN THE DESCRIPTION

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

[0000] US-A1-2021 / 0021180 [0007, 0041]

Claims

[1] Grounding brush assembly (10) for an electric motor (2) having a shaft (6) rotating about an axis (X), a stationary housing (4) and a bearing (8), comprising a grounding brush (16) having several conductive fibers (20) and a carrier (22) in which the conductive fibers (20) are fixed, and a brush mounting plate (18) attached to the carrier (22) of the brush, wherein the mounting plate (18) - a main body (32) formed by a radial section extending radially outwards with respect to the support (22), - several centering tongues (34) which project axially in relation to the main body (32), each tongue (34) locally radially surrounding the carrier (22) of the brush (16) and being in radial contact with the carrier (22), the carrier (22) being held axially against the main body (32) of the mounting plate (18) by the tongues (34), and - a centering section (36) which extends the main body (32) at least partially axially, extends axially on the same side as the tongues (34), is offset radially outwards with respect to the support (22) and the tongues (34), and is provided with an outer surface (38) which defines the outer diameter of the mounting plate (18) in order to center the mounting plate (18) after it has been fastened in a bore (12) of the housing (4) of an associated electric motor (2), characterized bythat the mounting plate (18) includes at least one flange (40) which extends the distal end of the centering section (36) radially inwards. [2] Arrangement (10) according to claim 1, wherein the centering section (36) is ring-shaped. [3] Arrangement (10) according to claim 1, wherein the centering section (36) comprises several axial sections spaced apart from each other in the circumferential direction. [4] Arrangement (10) according to one of the preceding claims, wherein the flange (40) is annular. [5] Arrangement (10) according to one of claims 1 to 4, wherein the mounting plate (18) comprises several flanges (40) spaced apart from each other in the circumferential direction. [6] Electric motor (2) comprising a housing (4), a shaft (6) and an earthing brush arrangement (10) according to one of the preceding claims, which is at least partially radially fixed between the housing (4) and the shaft (6), wherein the conductive fibers (20) of the arrangement are in contact with the shaft (6). [7] Motor (2) according to claim 6, wherein the flange (40) of the mounting plate (18) of the arrangement (10) is radially accommodated in the bore (12) of the housing (4).

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