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 an axially extending centering section (36), with retaining tongues (34) for axially holding the carrier (22), wherein the arrangement also comprises support sections (40) consisting of radial deformations of the centering section (36) to axially hold the carrier (22).

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 arrangement has a relatively large radial dimension. It would not be possible to install this arrangement in electric motor applications with low radial compactness.

[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, wherein the brush carrier is in axial contact with the main body; and a centering section extending the main body at least axially, extending axially on the same side as the brush carrier, offset radially outwards with respect to the carrier and provided with an outer surface defining the outer diameter of the mounting plate in order to center the mounting plate after it has been fitted into a bore in the housing of an associated electric motor.

[0013] According to a general feature of the invention, the mounting plate comprises several retaining tongues for the carrier and several support sections for the carrier.

[0014] According to the invention, the retaining tongues extend radially from the centering section towards the inside of the assembly. Each retaining tongue comes into axial contact with the brush carrier on the side axially opposite the main body, whereby the carrier is thus held axially on one side by the main body and on the other side by the retaining tongues.

[0015] The support sections consist of radial deformations extending radially from the centering section towards the inside of the assembly. The support sections are in radial contact with an upper axial surface of the brush holder.

[0016] 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.

[0017] In one embodiment, the retaining tongues and the support sections are alternately distributed in the circumferential direction.

[0018] According to one embodiment, the support sections consist of local radial deformations, each formed over an angular range of less than or equal to 5°, preferably less than or equal to 1°.

[0019] According to an alternative embodiment, the support sections consist of radial deformations that extend in the circumferential direction and are each formed over an angular range between 5° and 40°, preferably between 15° and 30°.

[0020] 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. Brief character description

[0021] 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 radially partially fixed between a rotating shaft and a housing of an electric motor according to a first 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 is; [ Fig. 5] a sectional view of the arrangement in Fig. 3 along line II-II is; [ Fig. 6] a sectional view of the arrangement in Fig. 3 along line III-III is; and [ Fig. 7] an axial sectional view of a grounding brush arrangement according to a second exemplary embodiment of the invention, which is radially partially mounted between a rotating shaft and a housing of an electric motor. Detailed description of the invention

[0022] 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, and axis XX, which is radially supported by a bearing 8. The bearing 8 is, for example, a ball bearing. Alternatively, other rolling elements, such as rollers, can be used. Another alternative is a plain bearing.

[0023] 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.

[0024] 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.

[0025] As in the Fig. As shown more clearly in Figures 2 to 6, 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.

[0026] 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. 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.

[0027] To ensure the attachment and retention of the conductive fibers 20, the support 22 comprises a cylindrical section 26, which forms an upper axial surface of the support 22, 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 arrangement, 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.

[0028] The mounting plate 18 is attached to the support 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 support, and an axial centering section 36.

[0029] 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 6, 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.

[0030] 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.

[0031] According to the invention, the mounting plate comprises several retaining tongues 34 for axially holding the brush 16.

[0032] The retaining tongues 34 extend radially from the centering section 36 of the mounting plate 18 towards the inside of the arrangement 10. Each tongue 34 consists of a substantially radial section that is bent inwards from the axial section 36. The tongues 34 are spaced apart from each other in the circumferential direction.

[0033] Each retaining tongue 34 extends from the centering section 36 of the mounting plate 18 such that the retaining tongue 34 establishes axial contact with the lateral edge 30 of the carrier 22. On the axially opposite side, the other lateral edge 28 of 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 by the retaining tongues 34.

[0034] In the example shown, the mounting plate 18 comprises four retaining tongues 34 spaced evenly apart in the circumferential direction. As a variant, the mounting plate comprises a different number of retaining tongues 34.

[0035] The centering section 36 extends the main body 32 axially, extends axially on the same side as the support 22 held by the tongues 34 and is radially offset outwards with respect to the support 22.

[0036] The cylindrical section 26 of the support 22 is radially spaced from the centering section 36, 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.

[0037] 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.

[0038] 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.

[0039] The mounting plate 18 and the grounding brush 16 comprise an electrically conductive material, such as aluminium, stainless steel, bronze, copper or another material.

[0040] According to another aspect of the invention, the mounting plate 18 also includes several support sections 40 for axially holding the brush carrier 22.

[0041] According to the first embodiment of the invention, which is described in the Fig. As shown in Figures 2 to 6, the support sections 40 consist of locally limited radial deformations extending radially from the centering section 36 towards the inside of the arrangement 10.

[0042] The support sections 40 are each formed over an angular range of less than or equal to 5°, preferably less than or equal to 1°.

[0043] In the illustrated example, the deformations are of a substantially conical shape, with an inner wall 42 inclined towards the inside of the arrangement 10. According to other variations not shown, the support sections can also have other shapes, such as spheres, cylinders, parallelepipeds, etc., without this deviating from the scope of the present invention. In practice, the deformations 40 can be produced, for example, by pressing. The material of the centering section 36 is deformed radially inwards by a punch that exerts a radial force from the upper surface 38 of the centering section 36.

[0044] Each of the support sections 40 comes into radial contact with an upper axial surface of the cylindrical section 26 of the brush carrier 22. More precisely, the inclined inner wall 42 of each support section 40 comes into direct radial contact with the cylindrical surface 26 via a support surface 44.

[0045] The support 22 is thus held radially in position by the multiple support points 44 in direct contact with the outer surface of the cylindrical section 26 of the support 22. This radial holding of the support 22, in combination with its axial holding between the tongues 34 and the main body 32, ensures that the support 22 is held in position with the mounting plate 18. Since the mounting plate 18 is itself mounted in a bore 12 of the housing 4, the fibers 20 fixed in the support 22 are positioned with respect to the bearing 8, the housing 4, and the rotating shaft 6 to ensure the passage of electrical current.

[0046] In the example shown, the mounting plate 18 comprises four support sections 40 spaced evenly spaced in the circumferential direction. As a variant, the mounting plate comprises a different number of support sections 40.

[0047] In the example shown, the retaining tongues 34 and the support sections 40 are alternately distributed around the circumference. As a variation, the tongues and support sections can be positioned according to other distributions, for example, two or more support sections between two consecutive tongues, or two or more tongues between two consecutive support sections.

[0048] According to the invention, the grounding brush arrangement 10 can be designed to have reduced radial compactness compared to a prior art arrangement, for example in US-A1-2021 / 0021180.

[0049] Furthermore, the support sections 40 improve the rigidity of the mounting plate 18. The centering section 36 is pressed into a housing 4, and the risk of deformation of the centering section 36, the main body 32, or the connecting section between them is high. The deformations of the support sections 40 provide inclined walls 42, which help to stiffen the assembly.

[0050] A second embodiment of the invention is described in Fig. Figure 7 shows a different embodiment than the previous one in terms of the dimensions of the support sections.

[0051] The mounting plate 18 comprises several support sections 50 for axially holding the brush carrier 22. The support sections 50 consist of extensive radial deformations that extend radially from the centering section 36 towards the inside of the arrangement 10.

[0052] The support sections 50 are each formed over an angular range, which in the example shown is equal to 20°. This angular range could be smaller or larger, between 5° and 40°.

[0053] The deformations of the support sections 50 each have inner walls 52 that are inclined towards the inside of the arrangement 10. Each of the support sections 50 comes into radial contact with an upper axial surface of the cylindrical section 26 of the brush carrier 22. More precisely, the inclined inner walls 52 come into direct radial contact with the cylindrical surface 26 via a support surface 54.

[0054] 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, 0048]

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, wherein the brush carrier (22) is in axial contact with the main body (32), - a centering section (36) which extends the main body (32) at least axially, extends axially on the same side as the brush carrier (22), is offset radially outwards with respect to the carrier (22), and is provided with an outer surface 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 by , that the mounting plate also includes: - several retaining tongues (34) for the carrier, wherein the tongues (34) extend radially from the centering section (36) towards the inside of the arrangement, each tongue coming into axial contact with the brush carrier (22) on the axially opposite side of the main body (32), wherein the carrier (22) is thus held axially by the main body (32) on one side and by the retaining tongues (34) on the other side, and - several support sections (40; 50) for the carrier (22), wherein the support sections (40; 50) consist of radial deformations extending radially from the centering section (36) towards the inside of the arrangement (10), wherein the support sections (40; 50) come into radial contact with an upper axial surface (26) of the brush carrier (22). [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 retaining tongues (34) and the support sections (40; 50) are alternately distributed in the circumferential direction. [5] Arrangement (10) according to one of the preceding claims, wherein the support sections (40) consist of local radial deformations, each of which is formed over an angular range of less than or equal to 5°, and preferably less than or equal to 1°. [6] Arrangement (10) according to any one of claims 1 to 4, wherein the support sections (50) consist of radial deformations extending in the circumferential direction, each of which is formed over an angular range between 5° and 40°, and preferably between 15° and 30°. [7] 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).

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