Grounding brush assembly
By designing the tongue structure on the brush mounting plate of the ground brush assembly, limiting the contact between the conductive fibers and the bearing, the problem of existing ground brush assembly that may cause bearing damage is solved, achieving more effective charge dissipation and bearing protection.
Patent Information
- Application Number
- CN202411196841.4
- 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 has a radial portion and an axial centering portion, including a tongue structure, to limit the risk of contact between the conductive fiber and the bearing.
Through the tongue structure of the mounting plate, contact between the conductive fibers and the bearing is effectively prevented, the dissipation of charge is reduced, the bearing is protected, and vibration and damage caused by discharge is avoided.
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Figure CN119542859A_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] 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 comprises at least one tongue projecting from the radial portion on the side opposite 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 tongue of the mounting plate makes it possible to maintain an axial space between the brush and the bearing or seat.
[0015] According to one design, the tongue of the mounting plate protrudes in the axial direction.
[0016] According to another design, said tongue is bent over axially against the radial portion.
[0017] In one embodiment, the mounting plate comprises a plurality of tongues extending from the radial portion for holding the brush support, the centering portion being radially offset outwardly relative to the holding tongues. The tongues are different from the holding tongues and extend axially on a side opposite to the holding tongues.
[0018] The tongue of the mounting plate may be offset radially inwardly relative to the centering portion.
[0019] According to a particular design, the tongue is made in one piece with the radial portion of the mounting plate. This simplifies the manufacture of the mounting plate. The tongue can be formed by locally deforming the material of the radial portion.
[0020] According to another design, the tongue can be a portion different from the radial portion of the mounting plate and attached to the radial portion of the mounting plate by any suitable means (e.g., by adhesive bonding). After attachment, the tongue protrudes from the radial portion of the mounting plate.
[0021] By means of this design, the tongue can be made of a material different from the material of the radial portion of the mounting plate. The tongue can be made, for example, of an electrically insulating (in other words, non-conductive) material. This makes it possible to prevent electrical charges from being dissipated toward the bearing in the event of contact between the bearing and the tongue. The tongue can be made, for example, of a synthetic material, a plastic, in particular of PEEK, PBT, PPS, PAI.
[0022] In one embodiment, the mounting plate comprises at least two tongues protruding from the radial portion on a side opposite to the support and diametrally opposite to each other.
[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] In one embodiment, the mounting plate comprises a plurality of centering portions spaced apart in the circumferential direction.
[0026] In another embodiment, the mounting plate may include an annular centering portion.
[0027] The invention also relates to an electric motor comprising a housing, a shaft and at least one grounding brush assembly as defined above mounted radially between said housing and said shaft, the conductive fibers of the brush of said assembly being in contact with said shaft. BRIEF DESCRIPTION OF THE DRAWINGS
[0028] 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:
[0029] 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.
[0030] Figure 2 and Figure 3 is a perspective view of a grounding brush assembly according to a first exemplary embodiment of the present invention,
[0031] Figure 4 yes Figure 2 and Figure 3 Front view of the grounding brush assembly,
[0032] Figure 5 It is along Figure 4A cross-sectional view of line VV in FIG. 1 , and
[0033] Figure 6 , Figure 7 and Figure 8 1 and 2 are perspective views of grounding brush assemblies according to a second exemplary embodiment, a third exemplary embodiment, and a fourth exemplary embodiment, respectively. DETAILED DESCRIPTION
[0034] Figure 1 A 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.
[0035] 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 .
[0036] 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 .
[0037] Now refer to Figures 2 to 5 A grounding brush assembly 20 according to an exemplary embodiment of the present invention is described.
[0038] 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.
[0039] 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.
[0040] 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.
[0041] 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.
[0042] like Figure 5 As 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.
[0043] 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.
[0044] 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.
[0045] 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.
[0046] 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.
[0047] Reference Figure 2 , Figure 3 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 .
[0048] 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.
[0049] 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.
[0050] 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.
[0051] 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.
[0052] 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 ) are 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.
[0053] 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.
[0054] 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 of the mounting plate.
[0055] 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.
[0056] As described above, the mounting plate 40 is also configured to maintain an axial space between the brush 30 and the bearing or seat.
[0057] For this purpose, the mounting plate 40 further includes a tongue 50 extending axially from the radial portion 42 on the side opposite to the tongue 44 and the tab 46 in the axial direction, as shown in Figure 2 , Figure 3 and Figure 5 . The tongue 50 extends axially on the side opposite to the support 32. The tongue 50 projects outwardly relative to the radial portion 42. The tongue 50 extends axially here. As another option, the tongue 50 can extend obliquely, in other words, the tongue 50 can extend axially and radially.
[0058] The radial portion 42 of the mounting plate has an internal face against which the support 32 is mounted, axially pressed against the internal face, and an external face axially facing away from the internal face. The internal face and the external face define the axial thickness of the radial portion 42. The tongue 50 protrudes axially relative to the external face of the radial portion 42.
[0059] Each tongue 50 is located radially between the small diameter edge of the radial portion 42 defining the hole in the mounting plate and the large diameter edge of the radial portion. The root of each tongue 50 is located radially on one side of the large diameter edge of the radial portion. The root of each tongue 50 has a curved shape and the tongue extends axially from the root. Each tongue 50 is offset radially toward the inside relative to the tongue 44 and the lug 46.
[0060] Each tongue 50 is located in the extension of one of the lugs 46 in the circumferential direction. Each tongue 50 is located between two immediately consecutive tongues 44 in the circumferential direction. Each tongue 50 has a reduced circumferential dimension compared to the circumferential dimension of the lug 46. In this example, each tongue 50 also has a reduced circumferential dimension compared to the circumferential dimension of the tongue 44. As another option, the circumferential dimension of the tongue 50 can be greater than or equal to the circumferential dimension of the tongue 44.
[0061] In the example shown, the main faces of each tongue 50 that define the thickness of the tongue are oriented radially. In other words, in this example, one of the main faces of each tongue 50 is oriented radially inwards, while the other main face is oriented radially outwards.
[0062] The tongues 50 are spaced apart from each other in the circumferential direction, in the present example, the tongues 50 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 four tongues 50. As another option, a greater or lesser number of tongues 50 can be provided. Preferably, the number of tongues 50 is at least equal to two. In the present case, the tongues 50 are identical to each other. As a variant, the tongues can have different shapes and / or sizes.
[0063] 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.
[0064] 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.
[0065] By virtue of the tongue 50 of the mounting plate, contact between the conductive fibers 20 of the brush and the bearing is prevented.
[0066] Figure 6The exemplary embodiment shown in , in which identical elements have the same reference numerals, differs from the above-described example only with regard to the orientation of the root of the tongue 52 of the mounting plate.
[0067] In the present example, the tongues 52 are formed by forming cuts 53 on the radial portion 42, and the root of each tongue 50 is connected to the lateral edge delimiting the associated opening 53. Thus, one of the main faces of each tongue 50 is oriented circumferentially on one side, while the other main face is oriented circumferentially on the opposite side.
[0068] Figure 7 The exemplary embodiment shown in , in which identical elements have the same reference numerals, differs from the first example primarily in the position of the root of the tongue 54 of the mounting plate.
[0069] The root of each tongue 54 is located between two consecutive lugs 46. Each tongue 50 is radially offset inwardly only relative to the lugs 46 and not relative to the tongues 44. In this example, there are two diametrically opposed tongues 54. As another option, a greater or lesser number of tongues 54 may be provided.
[0070] Figure 8 The exemplary embodiment shown in (wherein the same elements have the same reference numerals) differs from the first example in the fact that the mounting plate 40 includes tongues 56, each extending from the radial portion 42, bent over axially against the radial portion. Each tongue 56 is bent over the outer face of the radial portion 42. Each tongue 56 protrudes relative to the radial portion 42 on the side opposite to the support 32. Each tongue 56 extends from the small diameter edge of the radial portion 42. The root of each tongue 56 has a curved shape, and the tongue extends radially from the root. Each tongue 56 is set back radially from the large diameter edge of the radial portion 42.
[0071] Each tongue 56 is located in the extension of one of the lugs 46 in the circumferential direction. Each tongue 56 is located between two immediately consecutive tongues 44 in the circumferential direction. Each tongue 56 has a reduced circumferential dimension compared to the circumferential dimension of the lug 46. In this example, the circumferential dimension of each tongue 56 is greater than the circumferential dimension of the tongue 44. As another option, the circumferential dimension of the tongue 56 can be less than or equal to the circumferential dimension of the tongue 44.
[0072] The tongues 56 are spaced apart from each other in the circumferential direction, in the present example, the tongues 56 are spaced apart from each other uniformly in the circumferential direction. As another option, irregular circumferential spacings can be provided. In the exemplary embodiment shown, there are four tongues 56. As another option, a greater or lesser number of tongues 56 can be provided. Preferably, the number of tongues 56 is at least equal to two. In the present case, the tongues 56 are identical to each other. As a variant, the tongues can have different shapes and / or sizes.
[0073] 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), 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) comprises at least one tongue (50, 52, 54, 56) projecting from the radial portion (42) on a side opposite to the support (32).
2. The grounding brush assembly according to claim 1, characterized in that: The tongues (50, 52, 54) of the mounting plate protrude in the axial direction.
3. The grounding brush assembly according to claim 1, characterized in that: The tongue (56) of the mounting plate is bent axially over the radial portion (42).
4. 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 offset outwardly relative to the retaining tongues (44), and the tongues (50, 52, 54, 56) being different from the retaining tongues (44) and extending axially on a side opposite to the retaining tongues.
5. A grounding brush assembly according to any one of the preceding claims, characterized in that The tongues (50, 52, 54, 56) of the mounting plate are radially offset inwardly relative to the centering portion (46).
6. A grounding brush assembly according to any one of the preceding claims, characterized in that The tongues (50, 52, 54, 56) are made in one piece with the radial portion (42) of the mounting plate.
7. A grounding brush assembly according to any one of the preceding claims, characterized in that The mounting plate (40) comprises at least two tongues (50, 52, 54, 56) projecting from the radial portion (42) on a side opposite to the support (32) and diametrically opposite to each other.
8. 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.
9. 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.
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.