Grounding brush assembly
By configuring an electrically insulating spacer washer between the mounting plate of the ground brush assembly and the bearing or seat, the problem of damage caused by contact between the conductive fiber and the bearing is solved, and safer charge dissipation and bearing protection are achieved.
Patent Information
- Application Number
- CN202411196847.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Priority Date
- 2023-08-30
- Filing Date
- 2024-08-29
- Publication Date
- 2025-02-28
AI Technical Summary
The existing ground brush assembly is prone to contact with the bearing during installation, resulting in bearing damage.
A ground brush assembly is designed to limit the risk of contact between the conductive fiber and the bearing by configuring a spacer gasket between the mounting plate and the bearing or seat. The spacer washer is made of an electrically insulating material, further preventing the charge from dissipating to the bearing.
It effectively limits the risk of contact between conductive fibers and bearings, avoids bearing damage, and prevents charge from dissipating to the bearings.
Smart Images
Figure CN119542860A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the field of grounding devices for controlling shaft currents generated in electric motors or machines, and more particularly to grounding brush assemblies. Background Art
[0002] In an electric motor or an electric machine, at least one rolling bearing is installed between a housing of the electric motor or the electric machine and a rotating shaft to support the shaft.
[0003] In operation, as the shaft rotates, a potential difference develops between the shaft and the seat of the electric motor or electrical machine, which generates a current between the inner race (fixed to the shaft) and the outer race (fixed to the seat) of the rolling bearing.
[0004] The current flowing through the components of the rolling bearing may damage these components, especially the rolling elements and the raceways formed on the inner race and the outer race. The discharge may also generate vibration.
[0005] To compensate for these drawbacks, it is known to earth or ground the rotating shaft by using an earthing brush comprising conductive fibers. The earthing brush is usually mounted in a hole in the seat of the electric motor so that the free end of the fibers is in radial contact with the outer surface of the rotating shaft.
[0006] By virtue of the conductivity of the fibers, the brushes are kept at the same electrical potential as the seat 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 discharges through the rolling bearing.
[0007] For further details on 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 support, the conductive fibers being mounted inside the support; and an annular mounting plate comprising a plurality of tongues for radially and axially retaining the support.
[0008] Depending on the relative axial position of the grounding brush assembly and the bearing, during operation of the electric machine there may be contact between the conductive fibers of the assembly and the rolling elements on the one hand and / or the inner race of the bearing on the other hand.
[0009] This may damage the bearings.
[0010] The present invention aims to remedy this disadvantage. Summary of the invention
[0011] The present invention relates to a grounding brush assembly, comprising a grounding brush, the grounding brush being provided with a plurality of conductive fibers and a support, the conductive fibers being mounted inside the support, and a brush mounting plate being fixed to the support of the brush.
[0012] According to one general feature, the assembly further comprises a spacer washer supported by the mounting plate and arranged axially on a side of the mounting plate opposite to the brush.
[0013] By this design, the risk of contact between the conductive fibers of the assembly and the bearing is limited. In particular, the spacer washer makes it possible to maintain an axial space between the mounting plate of the assembly and the bearing or housing.
[0014] Advantageously, the spacer washer protrudes axially relative to the mounting plate. Thus, the risk of contact between the conductive fibers of the assembly and the bearing is further limited.
[0015] Preferably, the spacer washer is made of an electrically insulating (in other words, non-conductive) material. This makes it possible to prevent electrical charges from dissipating towards the bearing in the event of contact between the bearing and the component.
[0016] According to one particular design, the spacer washer is annular. Alternatively, the spacer washer may be open at a point on its circumference.
[0017] The mounting plate may include a radial portion against which the brushes and the spacer washers are mounted, pressing against the radial portion axially on each side.
[0018] The mounting plate may include at least one mounting portion extending from the radial portion at least in the axial direction, and the spacer washer is mounted on the at least one mounting portion. The mounting portion may extend from a small diameter edge of the radial portion of the mounting plate.
[0019] In a particular embodiment, said mounting plate comprises a plurality of tongues for retaining said supports of said brush extending from said radial portions.
[0020] In one embodiment, the mounting plate comprises at least one centring portion extending at least axially from the radial portion, the at least one centring portion being radially outwardly offset relative to the support and having an outer surface defining an outer diameter of the mounting plate.
[0021] The mounting plate may be made in one piece.
[0022] Preferably, the spacer washer is flush with or radially set back from the outer surface of the centering portion. This makes it possible to facilitate mounting of the assembly inside the associated seat.
[0023] The invention also relates to an electric motor comprising a housing, a shaft and at least one grounding brush assembly as defined above and mounted radially between the housing and the shaft, the conductive fibers of the brush of the assembly being in contact with the shaft. BRIEF DESCRIPTION OF THE DRAWINGS
[0024] The invention will be better understood by studying the detailed description of embodiments given by way of non-limiting examples and illustrated by the accompanying drawings, in which:
[0025] Figure 1 It is an axial cross-sectional view of a grounding brush assembly installed radially between the rotating shaft and the seat of the electric motor.
[0026] Figure 2 and Figure 3 is a perspective view of a grounding brush assembly according to an exemplary embodiment of the present invention,
[0027] Figure 4 yes Figure 2 and Figure 3 Front view of the grounding brush assembly,
[0028] Figure 5 It is along Figure 4 A cross-sectional view of line VV in FIG. 1 , and
[0029] Figure 6 It is along Figure 4 Cross-sectional view along line VI-VI in FIG. DETAILED DESCRIPTION
[0030] Figure 1A portion of an electric motor 10 or electric machine is shown in axial section, comprising a fixed housing 12, a rotating shaft 14 having an axis XX, which is radially supported by rolling bearings 16. The bearings 16 are mounted radially between the housing 12 and the rotating shaft 14. In this example, the bearings are of the ball bearing type. As another option, other rolling elements or plain journal bearings may be provided.
[0031] The motor 10 further includes a grounding brush assembly 20 which is installed radially between the hole 12 a of the seat 12 and the outer cylindrical surface 14 a of the rotating shaft 14 .
[0032] The grounding brush assembly 20 is used to continuously dissipate the charge accumulated on the shaft 14 of the motor during operation of the motor by transferring the charge to the seat 12 .
[0033] Now refer to Figures 2 to 6 A grounding brush assembly 20 according to an exemplary embodiment of the present invention is described.
[0034] The grounding brush assembly 20 has an annular overall shape. The assembly 20 includes a grounding brush 30 and a brush mounting plate 40 configured to radially center the brush 30.
[0035] As will be described in greater detail below, the assembly 20 also includes a spacer washer 50 supported by the mounting plate 40 .
[0036] The brush 30 comprises a plurality of electrically conductive individual fibers 31 intended to surround the rotating shaft of the motor. The electrically conductive fibers 31 may be made of carbon, stainless steel, electrically conductive plastic, such as fibers made of acrylic or nylon.
[0037] The brush 30 also includes a holding or support member 32, and the conductive fibers 31 are mounted inside the holding or support member 32. In the exemplary embodiment shown, the support 32 is in the form of an open ring. The support 32 can be manufactured by cutting and pressing. The support 32 is made of a conductive material such as aluminum, stainless steel, bronze, copper or other materials. As another option, the support 32 can be made of a non-conductive material with a conductive coating or conductive paint.
[0038] like Figure 5 and Figure 6As more clearly shown in FIG. 1 , the support member 32 includes an axial mounting portion 34 and two opposite lateral flanks 36, 38 extending inwardly from the mounting portion 34 and axially gripping the conductive fiber 31. The conductive fiber 31 is pressed against the lateral flanks 36, 38 axially on each side. The conductive fiber 31 is pressed against the inner faces of the lateral flanks 36, 38 on both sides axially.
[0039] The mounting portion 34 and the two lateral wings 36 , 38 delimit a radially internally open channel, inside which the conductive fibers 31 are partially located.
[0040] In the example shown, the conductive fiber 31 is bent around the connection line 39 of the support 32. The free distal end of the conductive fiber 31 is intended to be in radial contact with the outer surface of the rotating shaft of the motor. The proximal end of the conductive fiber 31 is in radial contact with the mounting portion 34 of the support.
[0041] A lateral wing 36 extends from one end of the mounting portion 34 and a lateral wing 38 extends from the opposite end of the portion. The lateral wings 36, 38 extend obliquely inwardly from the mounting portion 34. The lateral wings 36, 38 are symmetrical to each other about a radial midplane of the support 32. The mounting portion 34 here extends in the axial direction. As another option, the mounting portion 34 can extend obliquely.
[0042] As mentioned above, the brush 30 is in the form of an open ring, in particular as in Figure 2 and Figure 3 This allows the brush to adapt to motor shafts of different diameters. Generally, the ends of the brush are not joined together. As a variant, the ends of the brush 30 can be joined together.
[0043] Reference Figure 2 , Figure 5 and Figure 6 The mounting plate 40 includes an annular radial portion 42 and a plurality of centring tongues 44 extending from the radial portion 42 .
[0044] The radial portion 42 of the mounting plate bears axially against the support 32 of the brush 30. More specifically, the radial portion 42 bears axially against the lateral wings 36 of the support.
[0045] The tongues 44 are spaced apart from each other in the circumferential direction, in the present example, the tongues 44 are spaced apart from each other uniformly in the circumferential direction. As another option, irregular circumferential spacing can be provided. In the exemplary embodiment shown, there are eight tongues 44. As another option, a greater or lesser number of tongues 44 can be provided. Two tongues 44 or at least four tongues can be provided. Preferably, the number of tongues 44 is at least equal to two.
[0046] Each tongue 44 projects axially relative to the radial portion 42. Each tongue 44 partially radially surrounds the support 32 of the brush 30 and is in radial contact with the mounting portion 34 of said support. The support 32 is held axially against the radial portion 42 of the mounting plate by means of the tongues 44. The tongues 44 serve to hold the grounding brush 30 axially and radially. The lateral wings 36 of the support bear against the radial portion 42 of the mounting plate and the lateral wings 38 bear against the tongues 44. In the present case, the tongues 44 are identical to one another.
[0047] As in Figure 5 As more clearly shown in FIG. 1 , each tongue 44 is provided with an axial portion and a bent-over portion at the free end of the axial portion, the axial portion extending axially from the radial portion 42, partially radially surrounding the support 32 and in radial contact with the support 32. The bent-over portion 44b of each tongue is used to axially hold the support 32 of the grounding brush 30. The bent-over portion 44b of each tongue is in axial contact against the lateral wing 38 of the support.
[0048] The brush mounting plate 40 also includes a plurality of centring tabs 46 extending from the radial portion 42 and spaced apart from each other in the circumferential direction. Figure 2 ) is formed between each pair of immediately consecutive tabs 46 on the radial portion 42. The tabs 46 are formed by cutting and bending the radial portion 42.
[0049] Each lug 46 extends in the axial direction from the radial portion 42. The lug 46 extends obliquely from the large diameter edge of the radial portion 42. The lug 46 extends in the axial direction from the same side as the tongue 44.
[0050] Each lug 46 partially radially surrounds the support 32 of the brush 30 while remaining separated from the support 32. The lugs 46 are partially offset radially outward relative to the tongue 44. In the present case, the lugs 46 are identical to each other. The lugs 46 define the outer diameter of the mounting plate 40. Each lug 46 extends obliquely here. As another option, the lugs 46 can extend in the axial direction. Each lug 46 is in the form of a portion of a cylinder. The hole in each lug 46 is radially spaced apart from the support 32 by a non-zero radial distance. The outer surface of the lug 46 defines the outer diameter of the mounting plate 40. Once the mounting plate has been mounted in the hole of the seat of the associated electric motor, the lugs 46 provide centering (centring) of the mounting plate.
[0051] As in Figure 2 and Figure 4 As shown in , the lugs 46 are spaced apart from each other in the circumferential direction, and in this example, the lugs 46 are evenly spaced apart from each other in the circumferential direction. As another option, irregular circumferential spacing can be provided. Each lug 46 is located between two immediately consecutive tongues 44 in the circumferential direction. Each lug 46 is spaced apart from two immediately adjacent tongues 44 in the circumferential direction. In this example, the circumferential dimension of each lug 46 is greater than the circumferential dimension of the tongue 44.
[0052] Refer again Figure 5 and Figure 6 The mounting plate 40 further includes a mounting portion 52, which extends axially from the radial portion 42 on the side opposite to the tongue 44 and the lug 46 in the axial direction. In this example, the mounting portion 52 extends axially and has an annular shape. The mounting portion 52 extends from the small diameter edge of the radial portion 42.
[0053] 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 other materials. As another option, the mounting plate 40 can be made of a non-conductive material with a conductive coating or conductive paint. In this example, the mounting plate 40 is made as a single piece.
[0054] As described above, the assembly 20 includes a spacer washer 50 supported by the mounting plate 40. The washer 50 is a distinct portion from the mounting plate 40. The washer 50 is axially disposed on the side opposite the brush 30 with respect to the radial portion 42 of the mounting plate.
[0055] The washer 50 is mounted on the mounting portion 52 of the mounting plate. The washer 50 is centered on the mounting portion 52. The washer 50 is mounted to be pressed against the radial portion 42 of the mounting plate in the axial direction on the side opposite to the brush 30 in the axial direction. The brush 30 and the washer 50 are mounted to be pressed on each side of the radial portion 42 in the axial direction. The washer 50 partially protrudes toward the outside in the axial direction relative to the mounting portion 52 of the mounting plate. In the exemplary embodiment shown, the washer 50 has an annular shape. As another option, the washer 50 can be opened at a point on its circumference.
[0056] The washer 50 comprises a cylindrical axial outer surface 50a, a cylindrical hole 50b radially opposite to the outer surface 50a, and two radially opposite front faces 50c, 50d axially delimiting the hole and the outer surface. The front face 50c of the washer is mounted to press axially against the radial portion 42 of the mounting plate. The front face 50d is offset axially toward the outside relative to the free end of the mounting portion 52 of the mounting plate. The hole 50b of the washer is mounted to press radially against the outer surface of the radial portion 42 of the mounting plate. The outer surface 50a is offset radially toward the inside relative to the free large diameter edge of the tabs 46 of the plate.
[0057] The gasket 50 is advantageously made of an electrically insulating material. The gasket 50 can be made of, for example, a synthetic material, a plastic, in particular PEEK, PBT, PPS, PAI.
[0058] When the electric machine is in operation, the charge accumulated on the shaft is dissipated to the seat 4 through the conductive fibers 20, the support 22 of the brush and the mounting plate 40 of the assembly.
[0059] By means of the washer 50 , contact between the conductive fibers 20 of the brush and the bearing is prevented.
[0060] In the exemplary embodiment shown, the mounting plate 40 of the grounding brush assembly includes a plurality of centering tabs 46. As another alternative, the tabs may be replaced by an annular flange forming an annular centering portion.
Claims
1. A grounding brush assembly (20), comprising a grounding brush (30) and a brush mounting plate (40), wherein the grounding brush (30) is provided with a plurality of conductive fibers (31) and a support member (32), wherein the conductive fibers are mounted inside the support member (32), and the brush mounting plate (40) is fixed to the support member (32) of the brush, characterized in that: The assembly further includes a spacer washer (50) supported by the mounting plate (40) and arranged axially on a side of the mounting plate opposite to the brush (30).
2. The grounding brush assembly according to claim 1, characterized in that: The spacer washer (50) protrudes in the axial direction relative to the mounting plate (40).
3. The grounding brush assembly according to claim 1 or 2, characterized in that: The spacer gasket (50) is made of an electrically insulating material.
4. A grounding brush assembly according to any one of the preceding claims, characterized in that The spacer gasket (50) is annular.
5. A grounding brush assembly according to any one of the preceding claims, characterized in that The mounting plate (40) includes a radial portion (42) against which the brush (30) and the spacer washer (50) are mounted, pressing on the radial portion (42) on both sides in the axial direction.
6. The grounding brush assembly according to claim 5, characterized in that: The mounting plate includes at least one mounting portion (52) extending from the radial portion (42) at least in the axial direction, and the spacer washer (50) is mounted on the at least one mounting portion (52).
7. The grounding brush assembly according to claim 5 or 6, characterized in that: The mounting plate includes a plurality of tongues (44) for retaining the support member (32) of the brush extending from the radial portion (42).
8. The grounding brush assembly according to any one of claims 5 to 7, characterized in that: The mounting plate includes at least one centering portion (46) extending at least axially from the radial portion (42), the at least one centering portion (46) being radially outwardly offset relative to the support member (32) and having an outer surface defining an outer diameter of the mounting plate (40).
9. The grounding brush assembly according to claim 8, characterized in that: The outer surface of the spacer washer (50) is flush with the outer surface of the centering portion (46) or is set back in the radial direction from the outer surface of the centering portion (46).
10. An electric motor comprising a seat (12), a shaft (14) and at least one grounding brush assembly (20) according to any one of the preceding claims mounted radially between the seat (12) and the shaft (14), the conductive fibers of the brush of the assembly being in contact with the shaft.