Grounding brush assembly
By using a spiral grounding brush assembly in the motor, the problem of component damage and wear caused by roller bearing current is solved, achieving the effect of reducing wear and friction torque, while maintaining the stability of electrical performance.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-09-17
- Publication Date
- 2026-03-27
AI Technical Summary
In motors or electric machines, current flow in roller bearings can cause component damage and vibration. Existing grounding brush assemblies suffer wear on conductive fibers and increased frictional torque, affecting electrical performance.
A spiral grounding brush assembly, including conductive fibers and retainers, is installed between the rotating shaft and the housing. The spiral shape reduces wear and uses a spiral propeller to expel excess oil, thus maintaining electrical performance.
It reduces shaft wear, limits frictional torque, and maintains the electrical performance of the grounding brush assembly, effectively dissipating charge.
Smart Images
Figure CN121748896A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present invention relates to the field of grounding devices for controlling shaft currents generated in a motor or electric machine, in particular a brush assembly. BACKGROUND
[0002] In a motor or electric machine, at least one roller bearing is mounted between the housing of the motor or electric machine and the rotating shaft to support said shaft.
[0003] During operation, when the shaft rotates, a potential difference can appear between the shaft and the housing of the motor or electric machine, which generates an electric current between the inner ring (rigidly connected to the shaft) and the outer ring (rigidly connected to the housing) of the roller bearing.
[0004] The electric current flowing through the constituent parts of the roller bearing can damage said constituent parts, in particular the rolling elements and the raceways formed on the inner and outer rings. Discharges can also generate vibrations.
[0005] To overcome these drawbacks, it is known practice to ground the rotating shaft using a brush comprising electrically conductive fibers. The brush is generally mounted in an orifice of the housing of the electric motor, so that the free ends of the fibers are in radial contact with the outer surface of the rotating shaft.
[0006] Thanks to the electrical conductivity of the fibers, the brush is maintained at the same potential as the housing of the electric motor. The inner and outer rings of the roller bearing are also at the same potential, which reduces or even eliminates the problematic discharges through the roller bearing.
[0007] During operation of the electric machine, the brushing of the electrically conductive fibers of the brush on the outer surface of the rotating shaft results in wear and an increase in the friction torque.
[0008] One known solution for limiting these effects is to reduce the thickness of the electrically conductive fibers of the brush. However, this is detrimental to the electrical performance of the brush assembly.
[0009] The present invention aims to overcome this drawback. SUMMARY
[0010] To this end, the application proposes a grounding brush assembly comprising a grounding brush provided with a plurality of electrically conductive fibers and a holder, the electrically conductive fibers being mounted inside the holder. The assembly further comprises a brush mounting plate rigidly connected to the holder of the brush.
[0011] The holder and the electrically conductive fibers of the brush each extend helically, the holder being provided with a first end and a second end opposite the first end, the first and second ends defining a circumferential dimension of the holder and being axially offset relative to each other.
[0012] This grounding assembly is intended to be mounted radially between a rotating shaft and a housing of an electric motor, the brush encircling the rotating shaft, with the electrically conductive fibers of the brush being in contact with an outer cylindrical surface of the rotating shaft. The brush is also helical due to the overall shape of the brush imparted by the holder.
[0013] Thus, during operation of the electric machine, the brush will brush the outer cylindrical surface of the shaft in a larger zone in axial direction compared to the case where the same brush would extend entirely in the same plane, i.e. in the case where the brush is straight, while the instantaneous contact surface between the brush and the shaft will be substantially the same as in the case where the brush is straight.
[0014] Thus, the wear of the shaft is reduced while the electrical performance of the brush assembly is maintained. In addition, when the shaft is lubricated with oil, the brush acts like an auger to expel any excess oil, thereby limiting the friction torque that such excess oil can cause. The helical winding direction can be particularly adapted to the direction of rotation of the shaft to expel the oil in a predetermined direction, for example to move the oil away from a roller bearing in the vicinity of which the brush assembly is mounted.
[0015] According to one feature, the mounting plate comprises a radial portion and at least one centring portion, the at least one centring portion at least continuing in axial direction from the radial portion, being radially offset outwardly relative to the holder and being provided with an outer face defining an outer diameter of the mounting plate, and wherein the radial portion of the mounting plate defines a through opening through which the holder of the brush extends.
[0016] Moreover, the radial portion of the mounting plate is annular and extends radially between an inner edge defining the opening and an outer edge from which the centring portion extends, the holder of the brush being at least partially axially bearing against the inner edge.
[0017] In addition, the radial portion of the mounting plate is provided with a first lateral face defining a thickness of the radial portion and a second lateral face on an opposite side of the first lateral face, a first end of the holder of the brush axially bearing against the first lateral face and / or a second end of the holder of the brush axially bearing against the second lateral face.
[0018] Advantageously, the radial portion of the mounting plate is locally provided with a protrusion extending radially on the inside of the opening, the first end and / or the second end axially bearing against a locking protrusion.
[0019] In addition, the length of the protrusion of the radial portion of the mounting plate is greater than the gap between the first end and the second end of the holder of the brush, with respect to the circumferential direction.
[0020] According to another feature, the mounting plate comprises a plurality of members for retaining the holder of the brush.
[0021] Moreover, some of the retaining members are formed on the first lateral face of the radial portion of the mounting plate and some of the retaining members are formed on the second lateral face of the radial portion of the mounting plate.
[0022] For example, the retaining members comprise centring tabs each having an axial arm and a radial arm continuing radially and inwardly from the axial arm, the holder axially bearing against at least some of the radial arms of the centring tabs and radially bearing against at least some of the axial arms of the centring tabs.
[0023] The present 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 described above mounted radially between the housing and the shaft, the electrically conductive fibers of the brush of the assembly being in contact with the shaft. BRIEF DESCRIPTION OF DRAWINGS
[0024] Further objects, advantages and features of the present invention will become apparent from the following description, given by way of example only, making reference to the accompanying drawings in which:
[0025] Figure 1 is an axial sectional view of a grounding brush assembly mounted radially between a rotating shaft and a housing of an 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 is Figure 2 and Figure 3 is a front view of the grounding brush assembly in
[0028] Figure 5 is a sectional view along the line V-V in Figure 4
[0029] Figure 6 is a detailed view of Figure 5 ; and
[0030] Figure 7 is a sectional view along the line VII-VII in Figure 4 DETAILED DESCRIPTION
[0031] Figure 1 An axial section of a motor 10 or electric machine is shown, the motor 10 or electric machine comprising a fixed housing 12 and a rotating shaft 14 having an axis X-X radially supported by a roller bearing 16. The bearing 16 is mounted radially between the housing 12 and the rotating shaft 14. Here, the bearing is a ball bearing. As an alternative, other rolling elements can be envisaged, or a sliding bearing can be envisaged.
[0032] The motor 10 also comprises a grounding brush assembly 20 mounted radially between an orifice 12a of the housing 12 and an outer cylindrical surface 14a of the rotating shaft 14.
[0033] The grounding brush assembly 20 makes it possible to continuously dissipate the electrical charges that accumulate on the shaft 14 of the motor during the operation of the motor by transferring these charges to the housing 12.
[0034] Reference will now be made to Figures 2 to 7 a grounding brush assembly 20 according to an exemplary embodiment of the application.
[0035] The grounding brush assembly 20 has an overall annular shape and thus defines a through-opening 55 that forms a passage for the rotating shaft 14. The assembly 20 comprises a grounding brush 30 and a brush mounting plate 40 that is configured to centre the brush 30 radially.
[0036] As can be seen in particular in Figure 2 and Figure 3 , the brush 30 has a helical shape in the circumferential direction. Here, the brush 30 also extends through the opening 55 and protrudes in the axial direction on both sides of the opening 55. Alternatively, the brush 30 can extend entirely on one or the other side of the opening 55. Alternatively, the brush 30 can extend in the opening 55 and protrude only on one side of the opening 55.
[0037] The brush 30 comprises a plurality of individual electrically conductive fibres 31 that are intended to rotate around the rotating shaft of the motor. The electrically conductive fibres 31 can be made of carbon, stainless steel or electrically conductive plastic, such as acrylic or nylon fibres.
[0038] The brush 30 also comprises a holding member or holder 32 inside which the electrically conductive fibres 31 are mounted. In the embodiment shown, the holder 32 is in the form of an open ring.
[0039] As in Figure 2 and Figure 3As can be seen, the retainer 32 is rigidly connected to the mounting plate 40 such that the retainer 32 extends helically in the circumferential direction between a first end 32a and a second end 32b opposite to the first end 32a. The first end 32a and the second end 32b define the circumferential dimension of the retainer. Therefore, the first end 32a and the second end 32b are offset from each other in the axial direction. Furthermore, here, the retainer 32 extends through the opening 55 such that the ends 32a and 32b are located on either side of the opening 55 in the axial direction. Alternatively, the retainer 32 may extend entirely on one side or the other side of the opening 55. Alternatively, the retainer 32 may extend in the opening 55 and protrude only on one side of the opening 55.
[0040] The retainer 32 can be manufactured by cutting and stamping. The retainer 32 is made of a conductive material (such as aluminum, stainless steel, bronze, copper, or another material). Alternatively, the retainer 32 can be made of a non-conductive material with a conductive coating or conductive paint.
[0041] As in Figure 6 As shown more clearly in the diagram, the retainer 32 includes an axially mounted portion 34 and two opposing lateral walls 36, 38, which extend inwardly from the mounted portion 34 and axially clasp the conductive fiber 31. The conductive fiber 31 is axially supported on either side against the lateral walls 36, 38. The conductive fiber 31 is axially supported on both sides against the inner faces of the lateral walls 36, 38.
[0042] Mounting portion 34 and two side walls 36, 38 define a channel that opens radially inward, and conductive fiber 31 is partially located inside the channel.
[0043] The conductive fiber 31 can be bent around the connecting line (not shown) of the retainer 32. The free distal end of the conductive fiber 31 is intended to make radial contact with the outer surface 14a of the rotating shaft 14 of the motor 10. The proximal end of the conductive fiber 31 makes radial contact with the mounting portion 34 of the retainer.
[0044] Similar to retainer 32, conductive fiber 31 also extends spirally. Lateral wall 36 of retainer 32 continues from one end of mounting portion 34, and lateral wall 38 continues from the opposite end of mounting portion 34. Lateral walls 36 and 38 extend inwardly from mounting portion 34 substantially parallel to each other. Alternatively, lateral walls 36 and 38 may extend inwardly obliquely from mounting portion 34. Lateral walls 36 and 38 are symmetrical to each other with respect to the radial mid-plane of retainer 32. Here, mounting portion 34 extends axially. Alternatively, mounting portion 34 may extend obliquely.
[0045] As indicated above, brush 30 is in the form of an open ring, especially in Figures 2 to 4 This can be seen in the image. This allows the brush to be adapted to different diameters of the motor shaft. The ends of brush 30 are not fastened to each other.
[0046] Mounting plate 40 includes an annular radial portion 42 that extends radially between an inner annular edge 51 or a small-diameter edge and an outer annular edge 52 or a large-diameter edge opposite to the inner annular edge 51.
[0047] The inner annular edge 51 defines the central opening 55.
[0048] The radial portion 42 is axially located on the first lateral surface 53. Figure 3 ) and the second lateral surface 54 on the opposite side of the first lateral surface 53 ( Figure 2 Extending between ), lateral surfaces 53 and 54 define the thickness of the radial portion 42.
[0049] The radial portion 42 has a wider radial portion forming a locking protrusion 56 on its inner side (i.e., on the side where the central opening 55 is located). The locking protrusion 56 extends radially to the free end 57. The locking protrusion 56 extends in the circumferential direction between the first end 56a and the second end 56b opposite to the first end 56a.
[0050] Mounting plate 40 also includes a plurality of retaining members formed on radial portion 42. These retaining members take the form of centering tabs 44 extending from radial portion 42. Alternatively, the retaining members may be solder points between retainer 32 and mounting plate 40.
[0051] Some of the tabs 44 are formed on the first lateral surface 53, and some of the tabs 44 are formed on the second lateral surface 54. More specifically, the plurality of centering tabs 44 include a first centering tab 441 extending from the first lateral surface 53 and a second centering tab 442 extending from the second lateral surface 54. Thus, tabs 441 and 442 extend in opposite axial directions.
[0052] The first protrusion 441 and the second protrusion 442 are also alternately positioned in the circumferential direction, that is, each second protrusion 442 is located between two consecutive first protrusions 441 in the circumferential direction.
[0053] Each centering tab 44 is provided with an axial arm 44a extending axially from the radial portion 42 and a radial arm 44b extending radially inward from the axial arm 44a, such that the centering tab 44 has an L-shaped profile. (As shown in...) Figures 5 to 7 As can be seen in, and more specifically as in Figure 6 As can be seen, the axial arm 44a has an inner face 58 that is radially inwardly oriented and flush with the inner edge 51, that is, the inner face 58 extends axially beyond the inner edge 51. The radial arm 44b extends facing the opening 55.
[0054] Overall, the tabs 44 and the radial portion 42 are configured to retain the brush 30 in the axial and radial directions.
[0055] The brush 30 is positioned on the mounting plate 40 such that the retainer 32 (more specifically, the mounting portion 34 of the retainer 32) is radially supported against the inner edge 51 of the radial portion 42 and against at least some of the inner surfaces 58 of the axial arm 44a.
[0056] Furthermore, the brush 30 is positioned on the mounting plate 40 such that at least one of the ends 32a and 32b of the retainer 32 is axially supported against the locking protrusion 56, while the remainder of the retainer 32 is supported against at least some of the radial arms 44b of the centering tab 44.
[0057] More specifically, when the ends 32a and 32b are located on either side of the radial portion 42 in the axial direction, the first end 32a is supported against the first lateral surface 53 in the axial direction and the second end 32b is supported against the second lateral surface 54 in the axial direction.
[0058] In addition, such as in Figure 6 As can be seen, the lateral wall 36 of the retainer 32 axially supports the radial arm 44b of the first tab 441, while the lateral wall 38 axially supports the radial arm 44b of the second tab 442.
[0059] Furthermore, in the circumferential direction, the length of the axial arm 44a of the first protrusion 441 gradually decreases from one first protrusion 441 to the next, while the length of the axial arm 44a of the second protrusion 442 gradually increases from one second protrusion 442 to the next second protrusion. In other words, in the circumferential direction, the distance between the radial arm 44b and the radial portion 42 of the first protrusion 441 gradually decreases from one first protrusion 441 to the next, while the distance between the radial arm 44b and the radial portion 42 of the second protrusion 442 gradually increases from one second protrusion 442 to the next second protrusion.
[0060] Therefore, the tab 44 and the radial portion 42 define an installation path extending along a helical trajectory between them, in which the retainer 32 is received and guided. More specifically, the path is axially defined on one side by the radial arm 44b of the first tab 441 and on the opposite side by the radial arm 44b of the second tab 442, while the path is radially defined by the inner edge 51 of the tab 44 and the axial arm 44a. By guiding the retainer 32, the path gives the retainer 32 and thus the brushes 30 their helical shape.
[0061] It should be noted that in the first tab 441 and the second tab 442, there is a tab 441a and a tab 442a respectively, on which the length of the axial arm 44a is substantially equal to the thickness of the radial arm 44b extending from the axial arm, such that the inner surface of the radial arm 44b oriented toward the opening 55 is aligned axially with the corresponding lateral surface 53 or 54.
[0062] It should be noted that, in the circumferential direction, the length of the locking protrusion 56 (i.e., the distance between the ends 56a and 56b of the locking protrusion 56) is greater than the gap between the ends 32a and 32b of the retainer 32. If the gap between the ends 32a and 32b increases, for example to accommodate the diameter of the rotating shaft 14, the ends 32a and 32b will therefore slide on the locking protrusion 56 and remain axially supported against the locking protrusion.
[0063] Depending on other features, the tabs 44 are spaced apart from each other in the circumferential direction, here uniformly (or evenly). Alternatively, non-uniform circumferential spacing can be envisioned. The number of first tabs 441 is equal to the number of second tabs 442. In the exemplary embodiment shown, there are six tabs 44: three first tabs 441 and three second tabs 442.
[0064] Alternatively, a larger or smaller number of protrusions 44 can be envisioned. Two protrusions 44, or at least four protrusions, can be envisioned. Preferably, the number of protrusions 44 is at least two.
[0065] Furthermore, here, the tab 44 extends only on one circumferential portion of the radial portion 42. In other words, the radial portion 42 has a circumferential portion without the tab 44, which entirely comprises the locking protrusion 56.
[0066] The brush mounting plate 40 also includes a plurality of centering lugs 46, which extend from the radial portion 42 and are spaced apart from each other in the circumferential direction. Notch 48 Figures 2 to 4 The lugs 46 are formed on the radial portion 42 between each pair of closely spaced lugs 46. The lugs 46 are formed by cutting and bending the radial portion 42.
[0067] Each lug 46 extends axially from the radial portion 42. The lug 46 extends obliquely from the large-diameter edge of the radial portion 42 (i.e., from the outer annular edge 52 of the radial portion 42). The lug 46 is partially offset radially outward relative to the tab 44. Here, the lugs 46 are identical to each other. The lug 46 defines the outer diameter of the mounting plate 40. Here, each lug 46 extends obliquely. Alternatively, the lug 46 may extend axially. Each lug 46 is in the form of a cylindrical portion. The orifice of each lug 46 is radially spaced from the holder 32 by a non-zero radial distance. The outer surface of the lug 46 defines the outer diameter of the mounting plate 40. The lugs 46 allow the mounting plate to be centered after installation in the orifice of the associated electric motor housing.
[0068] As in Figures 2 to 4 As can be clearly seen, the lugs 46 are spaced apart from each other in the circumferential direction, and here they are evenly spaced. Alternatively, a non-uniform circumferential spacing can be conceived. Each tab 44 is located between two consecutive lugs 46 in the circumferential direction. Each tab 44 is spaced apart from two adjacent lugs 46 in the circumferential direction. Here, the circumferential dimension of each lug 46 is larger than the circumferential dimension of the tab 44.
[0069] Mounting plate 40 is manufactured by cutting and stamping. Mounting plate 40 is made of a conductive material (such as aluminum, stainless steel, bronze, copper, or another material). Alternatively, mounting plate 40 can be made of a non-conductive material with a conductive coating or conductive paint. Here, the mounting plate is manufactured as a single piece.
[0070] During the operation of the electric machine, the charge accumulated on the shaft dissipates toward the housing 4 through the conductive fiber 31, the brush holder 32, and the mounting plate 40 of the assembly.
[0071] The helical shape of brush 30 allows it to brush the outer cylindrical surface of rotating shaft 14 over a relatively large area without affecting the instantaneous contact surface between brush 30 (more specifically, conductive fiber 31) and shaft 14. This limits wear on shaft 14 while preserving the electrical properties of brush assembly 20. Additionally, when shaft 14 is lubricated with oil, brush 30 acts like an auger to expel any excess oil, thus limiting the frictional torque that such excess oil might cause. The helical winding direction of retainer 32 and brush 30 can be specifically adapted to the rotational direction of shaft 14 to expel oil in a predetermined direction, for example, away from the movement of roller bearing 16 on which brush assembly 20 is mounted nearby.
[0072] Component 20 is installed such that the centering lug 46 of the mounting plate is axially positioned on the same side as the bearing.
[0073] In the exemplary embodiment shown, the mounting plate 40 of the grounding brush assembly includes a plurality of centering lugs 46. Alternatively, the lugs 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 retainer (32), the conductive fibers being mounted inside the retainer (32), and the brush mounting plate (40) being rigidly connected to the brush retainer (32), characterized in that, The retainer (32) and conductive fiber (31) of the brush extend spirally, the retainer (32) being provided with a first end (32a) defining the circumferential dimension of the retainer (32) and a second end (32b) opposite to the first end (32a), the first end (32a) and the second end (32b) being offset relative to each other in the axial direction.
2. The component according to claim 1, characterized in that, The mounting plate (40) includes a radial portion (42) and at least one centering portion (46), the at least one centering portion (46) extending at least axially from the radial portion (42), offset radially outward relative to the retainer (32) and having an outer surface defining the outer diameter of the mounting plate (18), wherein the radial portion (42) of the mounting plate (40) defines a through opening (55) through which the retainer (32) of the brush (30) extends.
3. The component according to claim 2, characterized in that, The radial portion (42) of the mounting plate (40) is annular and extends radially between the inner edge (51) defining the opening (55) and the centering portion (46) extending from its outer edge (52), and the retainer (32) of the brush (30) is at least partially supported radially against the inner edge (51).
4. The component according to claim 2 or 3, characterized in that, The radial portion (42) of the mounting plate (40) is provided with a first lateral surface (53) defining the thickness of the radial portion (42) and a second lateral surface (54) on the opposite side of the first lateral surface (53), the first end (32a) of the holder (32) of the brush (30) is axially supported against the first lateral surface (53) and / or the second end (32b) of the holder (32) of the brush (30) is axially supported against the second lateral surface (54).
5. The component according to claim 4, characterized in that, The radial portion (42) of the mounting plate (40) partially has a protrusion (56) extending radially inside the opening (55), the first end (32a) and / or the second end (32b) being axially supported against the locking protrusion (56).
6. The component according to claim 5, characterized in that, Relative to the circumferential direction, the length of the protrusion (56) of the radial portion (42) of the mounting plate (40) is greater than the gap between the first end (32a) and the second end (32b) of the retainer (32) of the brush (30).
7. The component according to any one of the preceding claims, characterized in that, The mounting plate (40) includes a plurality of components (44) for holding the brush (30) in place of a retainer (32).
8. The component according to claim 7 when dependent on any one of claims 4 to 6, characterized in that, Some of the retaining members (44) are formed on a first lateral surface (53) of the radial portion (42) of the mounting plate (40), and some of the retaining members (44) are formed on a second lateral surface (54) of the radial portion (42) of the mounting plate (40).
9. The component according to any one of claims 7 and 8, characterized in that, The retaining member includes centering tabs (44), each of the centering tabs (44) having an axial arm (44a) and a radial arm (44b) extending radially and inwardly from the axial arm (44a). The retaining member (32) axially supports at least some of the radial arms (44b) of the centering tab (44) and radially supports at least some of the axial arms (44a) of the centering tab (44).
10. An electric motor comprising a housing (12), a shaft (14), at least one bearing (16) radially mounted between the housing (12) and the shaft (14), and at least one grounding brush assembly (20) according to any one of the preceding claims radially mounted between the housing (12) and the shaft (14), wherein the conductive fibers (31) of the brush (30) of the assembly (20) are in contact with the shaft.