US-20260128636-A1 - GROUNDING BRUSH ASSEMBLY

US20260128636A1US 20260128636 A1US20260128636 A1US 20260128636A1US-20260128636-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, retaining tongues for axially and radially holding the support, and with an axially extending centering portion. The mounting plate further includes at least one flange extending radially inwardly from a distal end of the axial portion.

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 motor including a shaft rotating about an axis, a fixed housing with a bore, and a bearing coupling the shaft with the bore, the grounding brush assembly including: 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 of the grounding brush, a plurality of centering tongues protruding axially from one side of the main body, each tongue locally radially surrounding and in radial contact with the support of the brush so as to hold the support axially against the main body of the mounting plate, a centering portion extending at least axially from the one side of the main body, having a distal end spaced axially from the main body and being offset radially outwardly with respect to the support of the brush and the centering tongues, the centering portion having an outer surface defining an 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 flange extending radially inwardly from the distal end of the centering portion.
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 flange is annular.
5 . The assembly according to claim 1 , wherein the at least one flange includes a plurality of flange sections spaced circumferentially apart from each other.
6 . An 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.
7 . The motor according to claim 6 , wherein the flange of the mounting plate of the grounding brush assembly is housed radially within the bore of the housing.

Description

CROSS-REFERENCE This application claims priority to French patent application no. 2412168 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 typically mounted between a housing of the electric motor or machine and a rotary shaft in order to rotatably support the shaft and couple the shaft with the housing. During operation of the motor or machine, as the shaft rotates, a difference in electrical potential between the shaft and the housing of the electric motor or machine can be present, which may generate an electric current between an inner race of the rolling bearing, which is secured to the shaft, and an outer race of the bearing that is secured to the housing. Any 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. Such electrical discharges can also generate vibration. 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 within 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. 2021/0021180A1 discloses a grounding brush assembly comprising a grounding brush provided with a support and with a plurality of conductive fibers mounted within the 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 mounted in an electrical machine by force-fitting the assembly into the bore of the housing, which typically makes the grounding brush assembly difficult to remove. The present invention aims to remedy this drawback. SUMMARY OF THE INVENTION The present 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 comprises: 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 present invention, the centering portion includes at least one flange extending radially inwardly from a distal end of the axial portion. 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 flange is annular. Alternatively, the mounting plate may include a plurality of flanges spaced apart from one another in the circumferential direction, each flange extending radially inwardly from the distal end of an axial portion of the centering portion. The present invention also relates to an electric machine or motor comprising a housing, a shaft, and a grounding brush assembly as defined above mounted at least partially radially between the housing and the shaft, the conductive fibers of the assembly being in contact with the shaft. According to a preferred embodiment of the invention, the flange of the mounting plate of the assembly is housed radially within the bore of the housing. The centering