Grounding brush assembly
By designing a brush mounting plate in the ground brush assembly to maintain the axial space between the conductive fibers and the bearing, the problem that existing ground brush assembly may cause bearing damage is solved, achieving the effect of protecting the bearing.
Patent Information
- Application Number
- CN202411196839.7
- 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
Existing ground brush assembly can cause bearing damage in electric motors or electric machines because of the contact between the conductive fibers and the bearing.
A ground brush assembly is designed, which includes conductive fibers, support members and brush mounting plates. The brush mounting plate passes through its connecting part and centering part to ensure that the axial space is maintained between the conductive fibers and the bearings, reducing the risk of contact.
Through this design, the risk of contact between the conductive fiber and the bearing is limited, and the bearing is effectively protected and damage and vibration caused by discharge is avoided.
Smart Images
Figure CN119542858A_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 on the inside of which the conductive fibers are mounted; and an annular mounting plate comprising a plurality of tongues for radially and axially retaining the support and an annular outer flange ( / flange) radially surrounding the brush and the tongues.
[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] The mounting plate includes a radial portion and at least one centring portion extending at least axially from the radial portion, the at least one centring portion being radially offset outwardly relative to the support and having an outer surface defining an outer diameter of the mounting plate.
[0013] According to one general feature, the mounting plate further comprises at least one connecting portion connecting the radial portion to the centering portion and provided with at least one oblique part extending obliquely outwardly from the radial portion and on the opposite side to the support.
[0014] By this design, the risk of contact between the conductive fibers of the assembly and the bearing is limited. In particular, said connection portion of the mounting plate makes it possible to maintain an axial space between the brush and the bearing or seat.
[0015] In one embodiment, the connecting portion of the mounting plate extends from the large diameter edge of the radial portion. In this case, the inclined portion of the connecting portion may extend from the large diameter edge of the radial portion.
[0016] As another option, the connecting portion of the mounting plate may extend from another portion of the radial portion.
[0017] According to a particular design, the connecting portion of the mounting plate is provided with a bent portion extending from the inclined portion and connected to the centering portion.
[0018] According to another design, the connecting portion of the mounting plate may be provided with a portion having a different shape, such as a radial portion, extending from the inclined portion and connected to the centering portion.
[0019] According to yet another design, the inclined portion of the connecting portion of the mounting plate may be directly connected to the centering portion.
[0020] The mounting plate may include a plurality of tongues extending from the radial portion for retaining the brush support, the centering portion being radially outwardly offset relative to the retaining tongues.
[0021] According to one design, the mounting plate may include a plurality of centering portions spaced apart in the circumferential direction, and a plurality of connecting portions each connecting one of the centering portions to the radial portion.
[0022] According to an alternative design, the mounting plate may include an annular centering portion. In this case, the mounting plate may include a single connecting portion, or a plurality of connecting portions spaced apart from each other in the circumferential direction.
[0023] The brush may be mounted axially against a radial portion of the mounting plate. Alternatively, the brush may be mounted axially against another radial portion of the mounting plate.
[0024] The mounting plate may be made in one piece.
[0025] The invention also relates to an electric motor comprising a housing, a shaft, at least one bearing mounted radially between the housing and the shaft, and at least one grounding brush assembly as defined above 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
[0026] 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:
[0027] 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.
[0028] Figure 2 is a perspective view of a grounding brush assembly according to an exemplary embodiment of the present invention,
[0029] Figure 3 yes Figure 2 Front view of the grounding brush assembly,
[0030] Figure 4 It is along Figure 3 A cross-sectional view along line IV-IV in FIG. 1 , and
[0031] Figure 5 It is along Figure 3 Cross-sectional view along line VV in FIG. DETAILED DESCRIPTION
[0032] 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.
[0033] 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 .
[0034] 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 housing 12 .
[0035] Now refer to Figures 2 to 5 A grounding brush assembly 20 according to an exemplary embodiment of the present invention is described.
[0036] 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.
[0037] As will be described in greater detail below, the mounting plate 40 is also configured to maintain an axial space between the brush 30 and the bearing or seat.
[0038] 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.
[0039] 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 member ( / support portion) 32 is in the form of an open ring. The support member 32 can be manufactured by cutting and pressing. The support member 32 is made of a conductive material (such as aluminum, stainless steel, bronze, copper or other materials). As another option, the support member 32 can be made of a non-conductive material with a conductive coating or conductive paint.
[0040] like Figure 4 and Figure 5As 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.
[0041] 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.
[0042] 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.
[0043] 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.
[0044] 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.
[0045] Reference Figure 2 , Figure 4 and Figure 5 The mounting plate 40 includes an annular radial portion 42 and a plurality of centering tongues 44 extending from the radial portion 42 .
[0046] 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.
[0047] 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.
[0048] 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.
[0049] As in Figure 4 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.
[0050] The brush mounting plate 40 also includes a plurality of centring tabs 46 and a plurality of connecting portions 50 each connecting one of the tabs 46 to the radial portion 42 .
[0051] Tabs 46 are spaced apart from each other in the circumferential direction. Cutouts 48 ( Figure 2 ) is formed between each pair of immediately consecutive lugs 46 on the radial portion 42. The lugs 46 are formed by cutting and bending the radial portion 42.
[0052] Each lug 46 extends in the axial direction from the associated connecting portion 50. The lug 46 extends obliquely from the large diameter edge of the associated connecting portion 50. The lug 46 extends in the axial direction from the same side as the tongue 44. The lug 46 protrudes in the axial direction relative to the tongue 44.
[0053] 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 this 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 installed in the hole of the seat of the associated electric motor, the lug 46 provides centering of the mounting plate.
[0054] As in Figure 2 and Figure 3 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.
[0055] As described above, the mounting plate 40 is also configured to maintain an axial space between the brush 30 and the bearing or seat. To this end, a connecting portion 50 connecting the lug 46 to the radial portion 42 is formed.
[0056] Each connecting portion 50 is provided with an oblique portion 50a extending obliquely outward from the radial portion 42 on the side opposite to the support member 32 and the tongue 44. The oblique portion 50a of each connecting portion is offset in the axial direction relative to the support member 32 and the tongue 44 on the side opposite to the radial portion 42 of the mounting plate. The oblique portion 50a of each connecting portion extends from the large diameter edge of the radial portion 42.
[0057] The radial portion 42 of the mounting plate has an inner face against which the support 32 is mounted, pressed axially against the inner face, and an outer face axially facing away from the inner face. The inner face and the outer face define the axial thickness of the radial portion 42. The inclined portion 50a of each connecting portion protrudes relative to the outer face of the radial portion 42.
[0058] Each connecting portion 50 is also provided with a curved part 50b extending from the inclined part 50a and connected to the associated lug 46. The curved part 50b has a rounded convex shape oriented outward in the axial direction (i.e., on the side opposite to the support member 32). The curved part 50b forms a bend. The small diameter edge of the curved part 50b is connected to the large diameter edge of the associated inclined part 50a, and the large diameter edge of the curved part 50b is connected to the associated lug 46.
[0059] In the present case, the connecting portions 50 are identical to one another. The circumferential dimension of each connecting portion 50 is equal to the circumferential dimension of the associated tab 46. As another alternative, the connecting portions 50 may be provided with a reduced circumferential dimension compared to the circumferential dimension of the tab 46.
[0060] 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 is made as a single piece.
[0061] 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.
[0062] By virtue of the connecting portion 50 of the mounting plate, contact between the conductive fibers 20 of the brush and the bearing is prevented.
[0063] 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.
[0064] With this design, the mounting plate 40 may include a single annular connecting portion, a single connecting portion extending over an angular sector less than 360°, or a plurality of connecting portions spaced apart from one another in the circumferential direction.
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), wherein the brush mounting plate (40) is fixed to the support member (32) of the brush, wherein the mounting plate (40) comprises a radial portion (42) and at least one centering portion (46) extending from the radial portion (42) at least in the axial direction, wherein the at least one centering portion (46) is radially outwardly offset relative to the support member (32) and has an outer surface defining an outer diameter of the mounting plate (40), wherein: The mounting plate (40) further comprises at least one connecting portion (50) connecting the radial portion (42) to the centering portion (46) and provided with at least one inclined portion (50a) extending obliquely outward from the radial portion and on a side opposite to the support member (32).
2. The grounding brush assembly according to claim 1, characterized in that: The connecting portion (50) of the mounting plate extends from a large diameter edge of the radial portion (42).
3. The grounding brush assembly according to claim 2, characterized in that: The inclined portion (50a) of the connecting portion of the mounting plate extends from a large diameter edge of the radial portion (42).
4. A grounding brush assembly according to any one of the preceding claims, characterized in that The connection portion (50) of the mounting plate is provided with a bent portion (50b) extending from the inclined portion (50a) and connected to the centering portion (46).
5. A grounding brush assembly according to any one of the preceding claims, characterized in that The mounting plate includes a plurality of tongues (44) extending from the radial portion (42) for retaining the brush support (32), the centering portion (46) being radially outwardly offset relative to the retaining tongues (44).
6. A grounding brush assembly according to any one of the preceding claims, characterized in that The mounting plate (40) is made as a single piece.
7. A grounding brush assembly according to any one of the preceding claims, characterized in that The mounting plate (40) includes a plurality of centering portions (46) spaced apart in the circumferential direction and a plurality of connecting portions (50) each connecting one of the centering portions (46) to the radial portion (42).
8. The grounding brush assembly according to any one of claims 1 to 6, characterized in that: The mounting plate (40) includes an annular centering portion.
9. A grounding brush assembly according to any one of the preceding claims, characterized in that The brush (30) is mounted axially against a radial portion (42) of the mounting plate.
10. An electric motor comprising a seat (12), a shaft (14), at least one bearing (16) mounted radially between the seat and the shaft, 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.