US-20260128637-A1 - GROUNDING BRUSH ASSEMBLY

US20260128637A1US 20260128637 A1US20260128637 A1US 20260128637A1US-20260128637-A1

Abstract

A grounding brush assembly includes a grounding brush and a mounting plate for the brush, the brush being provided with a plurality of conductive fibers and with a support inside of which the conductive fibers are housed. The mounting plate is secured to the support and is provided with a radially extending main body, with retaining tongues for axially and radially holding the support, and with an axially extending centering portion. The mounting plate includes at least one bearing portion in radial abutment against the brush support and providing a bearing surface for a tool for inserting the assembly within a housing.

Inventors

Thomas Perrotin
Emmanuel BENEVISE
Kevin Wattieaux
Bruno Constant
Jean-Marie Gerard
Benoit Arnault

Assignees

AKTIEBOLAGET SKF

Dates

Publication Date: 20260507
Application Date: 20251028
Priority Date: 20241107

Claims (7)

1 . A grounding brush assembly for an electric motor, the electric motor including a shaft rotatable about an axis, a fixed housing and a bearing coupling the shaft with the housing, the grounding brush comprising: a grounding brush including a support and a plurality of conductive fibers disposed at least partially within the support; and a brush mounting plate secured to the support of the brush and including a main body formed by a radial portion extending radially outwardly with respect to the support, a plurality of centering tongues protruding axially with respect to the main body, each centering tongue locally radially surrounding and in radial contact with the support of the brush such that the support is held axially bearing against the main body of the mounting plate by the tongues, a centering portion extending at least axially from the main body on a same axial side of the main body as the tongues and being offset radially outwardly with respect to the support and the tongues, the centering portion having an outer surface defining the outer diameter of the mounting plate and being configured to center the mounting plate within the bore of the housing of the electric motor, and at least one bearing portion including a first bent portion extending axially from the main body and radially abutting an upper axial surface of the brush support and a second bent portion extending radially between the first bent portion and the centering portion, the second bent portion having an axial bearing surface engageable by a tool for positioning the grounding brush assembly.
2 . The assembly according to claim 1 , wherein the centering portion is annular.
3 . The assembly according to claim 1 , wherein the centering portion includes a plurality of axial portions spaced circumferentially apart from each other.
4 . The assembly according to claim 1 , wherein the mounting plate includes a plurality of the bearing portions spaced circumferentially apart from each other.
5 . The assembly according to claim 4 , wherein the retaining tongues and the bearing portions are arranged alternating in the circumferential direction.
6 . The assembly according to claim 1 , wherein an axial portion of the centering portion extends from an outer radial end of the second bent portion.
7 . The electric motor comprising: a housing; a shaft; and a grounding brush assembly according to claim 1 mounted at least partially radially between the housing and the shaft, the conductive fibers of the assembly being in contact with the shaft.

Description

CROSS-REFERENCE This application claims priority to French patent application no. 2412170 filed on Nov. 7, 2024, the contents of which are fully incorporated herein by reference. BACKGROUND OF THE INVENTION The present invention relates to grounding devices for controlling the shaft current generated in electric motors or machines, and more particularly to grounding brush assemblies. In an electric motor or machine, at least one rolling bearing is mounted between the housing of the electric motor or machine and the rotary shaft in order to support this shaft. In operation, when the shaft is rotating, a difference in electrical potential may arise between the shaft and the housing of the electric motor or machine, which may generate an electric current between the inner race of the rolling bearing, which is secured to the shaft, and the outer race secured to the housing. Such an electric current passing through the components of the rolling bearing may damage these components, in particular the rolling elements and the raceways formed on the inner and outer races. Electrical discharges can also generate vibrations. In order to remedy these drawbacks, it is a known practice to earth or ground the rotary shaft by using a grounding brush comprising conductive fibers. The grounding brush is generally mounted in the bore of the housing of the electric motor in such a way that the free ends of the fibers are in radial contact with the outer surface of the rotary shaft. Due to the conductivity of the fibers, the brush is kept at the same electrical potential as the housing of the electric motor. The inner and outer races of the rolling bearing are also at the same electrical potential, which reduces or even eliminates problematic electrical discharges through the rolling bearing. US Patent Publication No. 2021/0021180 A1 discloses a grounding brush assembly comprising a grounding brush provided with a support and with a plurality of conductive fibers mounted in this support, and an annular mounting plate provided with a plurality of tongues for radially and axially retaining the grounding brush support and with an annular outer flange radially surrounding the brush and the tongues. The tongues are formed by plastic deformation of the mounting plate. Such a grounding brush assembly is force-fit into the bore of the housing, the grounding brush assembly therefore being difficult to remove. SUMMARY OF THE INVENTION The present invention aims to remedy the drawback described above. The invention relates to a grounding brush assembly for an electric motor provided with a rotating shaft, with a fixed housing and with a bearing. The assembly comprises a grounding brush provided with a plurality of conductive fibers and with a support inside which the conductive fibers are mounted. The assembly also comprises a brush mounting plate which is secured to the support of the brush. The mounting plate includes: a main body formed by a radial portion extending radially outwards with respect to the support; a plurality of centering tongues protruding axially with respect to the radial portion, each tongue locally radially surrounding the support of the brush and being in radial contact with the support, the support being held axially bearing against the radial portion of the mounting plate by the tongues; and a centering portion at least axially extending the main body, extending axially on the same side as the tongues, offset radially outwards with respect to the support and the tongues, and provided with an outer surface defining the outer diameter of the mounting plate in order to center the mounting plate after mounting in a bore of the housing of an associated electric motor. According to a general feature of the invention, the mounting plate also includes at least one bearing portion protruding radially toward the inside of the assembly. The bearing portion is formed by a first bent portion extending axially from the main body and coming into radial abutment on an upper axial surface of the brush support, and by a second bent portion extending radially between the first bent portion and the centering portion, the second bent portion defining an axial bearing surface for a tool for positioning the assembly. The centering portion and the first bent portion of the bearing portion both extend in the same axial direction from the main body. The centering portion is larger in diameter than the first bent portion, a radial offset being defined between these portions. In one embodiment, the centering portion may be annular. Alternatively, the centering portion may comprise a plurality of axial portions spaced apart from one another in the circumferential direction. In one embodiment, the mounting plate comprises a plurality of bearing portions spaced apart from one another in the circumferential direction. In one embodiment, the retaining tongues and the bearing portions are distributed alternately in the circumferential direction.