Bearing system including a ground brush assembly
By designing a grounding brush assembly with conductive fibers offset axially, the problem of difficult installation in electric motors was solved, the installation process was simplified, and the risk of damage to rolling bearings and vibration was reduced.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- AB SKF SKF PATENT DEPARTMENT
- Filing Date
- 2025-11-24
- Publication Date
- 2026-06-05
Smart Images
Figure CN122148667A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the general field of grounding devices for controlling shaft currents generated in electric motors or machines, and particularly to grounding brush assemblies. Background Technology
[0002] In an electric motor or electric machine, at least one rolling bearing is installed between the housing (casing) of the electric motor or electric machine and the rotating shaft to support the shaft.
[0003] During operation, when the shaft rotates, a potential difference may occur between the shaft and the housing of an electric motor or electric machine, thereby generating a current between the inner ring (connected to the shaft) and the outer ring (connected to the housing) of the rolling bearing.
[0004] Current flowing through the components of a rolling bearing can damage these components, especially the rolling elements and the raceways on the inner and outer rings. Discharge can also cause vibration.
[0005] To remedy these drawbacks, a known practice is to ground the rotating shaft using a grounding brush that includes conductive fibers. The grounding brush is typically installed in a hole in the motor mount, such that the free end of the fiber makes radial contact with the outer surface of the rotating shaft.
[0006] Thanks to the conductivity of the fibers, the brush and the motor mount are kept at the same potential. The inner and outer rings of the rolling bearing are also at the same potential, which reduces or even eliminates problematic discharges through the rolling bearing.
[0007] Document US-A1-2021 / 0021180 discloses a grounding brush assembly, which includes a grounding brush, a plurality of conductive fibers disposed therein, a support member in which the conductive fibers are mounted, and an annular mounting plate. The annular mounting plate includes a plurality of retaining tongues for retaining the support member radially and axially, and an annular outer flange (flange) radially surrounding the brush and the tongues.
[0008] Grounding brush assemblies can also be equipped for rolling bearings.
[0009] However, using this solution, the installation of the component between the electric motor's mount and the rotating shaft can be difficult to perform.
[0010] The present invention aims to remedy this drawback. Summary of the Invention
[0011] The present invention relates to a bearing system comprising a bearing having an inner ring and an outer ring rotatable relative to each other.
[0012] The system also includes a grounding brush assembly fixed to the outer ring of the bearing and comprising a brush offset axially outward relative to the inner ring of the bearing and provided with multiple conductive fibers and a support. The conductive fibers are mounted in the support. The conductive fibers protrude radially inward relative to the support.
[0013] According to a general feature, the conductive fibers of the grounding brush assembly include a first set of fibers, the free ends of which define the inner diameter of the brush.
[0014] According to a general characteristic, the conductive fibers of the brush include a second set of fibers, the radial length of which is reduced relative to the radial length of which is reduced relative to the radial length of which is reduced relative to the first set of fibers, and the free ends of the second set of fibers are radially offset relative to the bore of the inner ring of the bearing.
[0015] With this design of the brush in the grounding brush assembly, the bearing system can be easily installed inside the housing of the associated electric motor by pushing the bearing system axially onto the inner ring of the bearing while simultaneously passing the bearing system axially through one or more radially reduced zones defined radially by a second set of fibers of the brush's conductive fibers.
[0016] The free ends of the second set of conductive fibers can be located in the region between the radially adjacent area of the bore in the inner ring of the bearing (e.g., at the top of the bore entrance chamfer) and the outer surface of the inner ring.
[0017] The free ends of the first set of conductive fibers can be radially offset inward relative to the bore of the inner ring of the bearing, or alternatively, flush with the bore. In another alternative, in a particular design where the bearing system also includes a sleeve mounted in the bore 16a of the inner ring, the free ends of the conductive fibers can be radially set back relative to the bore.
[0018] In one embodiment, the brush holes of the grounding brush assembly have a crenellated shape, each opening of the crenellated shape being defined radially by the conductive fibers of the second set of fibers and circumferentially by the conductive fibers of the first set of fibers.
[0019] In one embodiment, the grounding brush assembly is directly fixed to the outer ring of the bearing without interposition. Alternatively, it is still possible to use an interposition element to fix the grounding brush assembly, but this increases the overall cost of the system.
[0020] Preferably, the grounding brush assembly is fixed in a groove formed in a hole in the outer ring of the bearing. Alternatively, the grounding brush assembly can be fixed to another zone of the outer ring of the bearing, such as to an end face or the outer surface of the outer ring, with or without the insertion of intermediate elements.
[0021] The grounding brush assembly may further include a brush mounting plate, which is integral with the brush support and fixed to the outer ring of the bearing.
[0022] In one particular embodiment, the system's bearing includes at least one row of rolling elements arranged between the raceways of the first and second rings. Alternatively, the bearing may be a sliding bearing type.
[0023] The present invention also relates to a kit comprising a bearing system as defined above and an installation tool, the installation tool comprising at least one finger whose radial dimension is smaller than the radial distance between the bore of the inner ring of the bearing and the free end of a second set of conductive fibers of the brush of the grounding brush assembly.
[0024] The present invention also relates to an electric motor comprising a casing, a shaft, and at least one bearing system as defined above, the at least one bearing system being radially mounted between the casing and the shaft, wherein a first set of conductive fibers of the brush of the grounding brush assembly is in contact with the shaft.
[0025] The present invention also relates to a method for mounting a bearing system as defined above between a seat and a shaft of an electric motor, wherein the bearing system is pushed along the shaft by means of an mounting tool arranged radially between the shaft and the free ends of a second set of conductive fibers of the brush of the grounding brush assembly, and axially supporting an abutment against the inner ring of the bearing. Attached Figure Description
[0026] The invention will now be better understood by studying the detailed description of the embodiments, which are given by way of completely non-limiting example and illustrated in the accompanying drawings, in which:
[0027] Figure 1This is a perspective view of a bearing system according to an exemplary embodiment of the present invention.
[0028] Figure 2 yes Figure 1 Front view of the bearing system in the image.
[0029] Figure 3 It is along Figure 2 Half-section view of line III-III in the middle.
[0030] Figure 4 It is along Figure 2 Half-section view of line IV-IV in the middle.
[0031] Figure 5 and Figure 6 yes Figure 1 A perspective view of the grounding brush assembly of the bearing system in the image; and
[0032] Figure 7 It is shown schematically. Figure 1 A half-section view of the bearing system installed in the motor housing. Detailed Implementation
[0033] Figures 1 to 4 The bearing system shown and generally indicated by 10 is designed to be mounted radially between the housing and the rotating shaft of an electric motor or electric machine.
[0034] The bearing system 10 includes a bearing 12 and a grounding brush assembly 14 mounted on the bearing.
[0035] Bearing 12 is provided with an inner ring 16 and a second outer ring 18 that are rotatable relative to each other about the bearing axis (not shown). The inner ring 16 and the outer ring 18 are concentric and extend axially along the bearing axis. The inner ring 16 and the outer ring 18 are made of steel. The rings are solid.
[0036] In the exemplary embodiment shown, the bearing 12 further includes a row of rolling elements 20, in this case balls, radially positioned between the inner ring 16 and the outer ring 18. The bearing 12 also includes a cage 22 for maintaining a regular circumferential spacing of the rolling elements 20.
[0037] The inner ring 16 includes a cylindrical bore 16a, a cylindrical axial outer surface 16b radially opposite the bore, and opposing first radial end faces 16c and second radial end faces 16d axially defining the bore and the outer surface. The bore 16a and the outer surface 16b define the radial thickness of the inner ring 16. The end faces 16c and 16d define the axial length of the inner ring 16.
[0038] The outer ring 18 includes a cylindrical axial outer surface 18a, a cylindrical hole 18b radially opposite to the outer surface 18a, and a first radial end face 18c and a second radial end face 18d axially defining the hole 18b and the outer surface 18a. The outer surface 18a and the hole 18b define the radial thickness of the outer ring 18. The surfaces 18c and 18d define the axial length of the outer ring 18.
[0039] The outer ring 18 also includes a first annular groove 24 and a second annular groove 26 formed in the hole 18b and extending radially outward. Each groove 24, 26 is radially oriented toward the inner ring 16.
[0040] Grooves 24 and 26 are arranged axially on either side of the row of rolling elements 20. Groove 24 is axially positioned close to the end face 18c of the outer ring, and groove 26 is axially positioned close to the end face 18d. Grooves 24 and 26 are symmetrical with respect to the radial midplane of the bearing system. Alternatively, the outer ring 18 may consist only of groove 24.
[0041] The grounding brush assembly 14 is fixed in a groove 24 in the outer ring of the bearing. The assembly 14 has a generally annular shape. The assembly 14 includes a grounding brush 30 and a brush mounting plate 40, which is configured to center the brush 30 radially. The mounting plate 40 is fixed in the groove 24 of the outer ring of the bearing.
[0042] The brush 30 is axially offset outward relative to the inner ring 16 of the bearing. In other words, the brush 30 is axially spaced from the inner ring 16 of the bearing. The brush 30 is arranged on the outer side of the bearing 12.
[0043] The brush 30 includes multiple individual conductive fibers 31 designed to rotate around the motor's axis of rotation. The conductive fibers 31 can be made of carbon, stainless steel, or conductive plastics, such as fibers made of acrylic or nylon. Figure 1 , Figure 2 , Figure 5 and Figure 6 The conductive fiber 31 is schematically shown in the diagram.
[0044] The brush 30 also includes a retaining or supporting member 32, inside which conductive fibers 31 are mounted. The conductive fibers 31 protrude radially inward relative to the support member 32.
[0045] As will be described in more detail below, the conductive fiber 31 includes a first group of fibers 31a and a second group of fibers 31b, the first group of fibers 31a and the second group of fibers 31b having different radial lengths protruding relative to the support member 32.
[0046] In the exemplary embodiment shown, the support 32 is in the form of an open ring. The support 32 is made of a rigid material. The support 32 can be produced by cutting and pressing. The support 32 is made of a conductive material (such as aluminum, stainless steel, bronze, copper, or another material). Alternatively, the support 32 can be made of a non-conductive material with a conductive coating or conductive paint.
[0047] The brush 30 preferably also includes a ring 33, around which conductive fibers 31 are disposed on the inner side of the support 32. The ring 33 serves as a support for the conductive fibers 31. The ring 33 is mounted on the inner side of the support 32.
[0048] The brush support 32 includes an axial mounting portion 34 and two opposing lateral flanks 36, 38 extending inward from the mounting portion 34 and axially gripping the conductive fiber 31. The conductive fiber 31 presses against the lateral flanks 36, 38 on each side axially. The conductive fiber 31 presses against the mounting portion 34 radially. The conductive fiber 31 protrudes radially inward relative to the lateral flanks 36, 38 of the support.
[0049] Mounting portion 34 and two lateral sides 36, 38 define a radially inwardly opening channel, within which conductive fiber 31 is partially positioned.
[0050] Lateral flank 36 extends from one end of mounting portion 34, and lateral flank 38 extends from the opposite end of said portion. Lateral flanks 36 and 38 extend obliquely inward from mounting portion 34. Lateral flanks 36 and 38 are symmetrical about each other with respect to the radial midplane of support member 32. Alternatively, only one of lateral flanks 36 and 38 may extend obliquely inward. In another variation, both lateral flanks 36 and 38 may extend radially. Mounting portion 34 extends axially here. Alternatively, mounting portion 34 may extend obliquely.
[0051] Brush 30 is in the form of an open ring. This allows the brush to adapt to different diameters of the motor shaft. Generally, the ends of the brush are not joined together. As a variation, these ends of brush 30 can still be joined together.
[0052] As indicated above, the conductive fiber 31 includes a first group of fibers 31a and a second group of fibers 31b having different radial lengths.
[0053] The first set of conductive fibers 31a has a distal free end intended to make radial contact with the outer surface of the rotating shaft of the motor. The free end of the first set of conductive fibers 31a defines the inner diameter of the conductive fiber 31, and more generally defines the inner diameter of the brush 30.
[0054] In the exemplary embodiment shown, the free end of the conductive fiber 31a is radially offset inward relative to the bore 16a of the inner ring of the bearing. In other words, the free end of the conductive fiber 31a protrudes radially relative to the bore 16a of the inner ring. Alternatively, the free end of the conductive fiber 31a may be radially flush with the bore 16a. In another alternative, if the bearing system also includes a sleeve mounted in the bore 16a of the inner ring, the free end of the conductive fiber 31a may be radially set back relative to the bore 16a.
[0055] The second group of conductive fibers 31b has a distal free end designed to maintain a certain distance in the radial direction from the outer surface of the rotating shaft of the motor. The radial length of the second group of fibers 31b protruding relative to the support 32 is less than the radial length of the first group of fibers 31a protruding relative to the support 32.
[0056] The free end of the conductive fiber 31b is offset radially outward relative to the bore 16a of the inner ring of the bearing. In other words, the free end of the conductive fiber 31b is retracted radially relative to the bore 16a of the inner ring.
[0057] Preferably, the radial distance between the free end of the conductive fiber 31b and the hole 16a is between 25% and 50% of the radial thickness of the inner ring 16.
[0058] As will be described in more detail below, a second set of conductive fibers 31b with reduced radial dimensions is provided to mount the bearing system 10 inside the associated electric motor.
[0059] The holes of the conductive fiber 31 (and more generally, the holes of the brush 30) have a serrated shape. Each opening 39 or cutout of the serrated shape is defined radially by the conductive fiber 31b of the second group of fibers and circumferentially by the conductive fiber 31a of the first group of fibers.
[0060] Therefore, in the exemplary embodiment shown, there are conductive fibers 31a of a first group of fibers and conductive fibers 31b of fibers that are continuous in the circumferential direction. Thus, the conductive fibers 31a of the first group are configured as subgroups spaced apart from each other in the circumferential direction, and the conductive fibers 31b of the second group are configured as subgroups spaced apart from each other in the circumferential direction, with the subgroups of conductive fibers 31b located circumferentially between two continuous subgroups of conductive fibers 31a. The conductive fibers 31 are formed as a continuous fiber loop in the circumferential direction between these two ends.
[0061] The circumferential dimension of the subgroup of conductive fiber 31a in the first group is larger than the circumferential dimension of the subgroup of conductive fiber 31b in the second group.
[0062] The openings 39 in the conductive fiber 31 are spaced apart from each other in the circumferential direction. In this case, the openings 39 in the conductive fiber 31 are uniformly spaced apart from each other in the circumferential direction. Alternatively, irregular circumferential spacing can be provided. There are four openings 39. Alternatively, more or fewer openings 39 can be provided. A single opening can be provided.
[0063] The mounting plate 40 of the grounding brush assembly includes an annular radial portion 42 and a plurality of retaining tongues 44 for retaining the brush 30 in the axial and radial directions and extending from the radial portion 42.
[0064] Mounting plate 40 also includes a fixing portion 46 fixed in a groove 24 of the outer ring 18 of the bearing and a connecting portion 48 connecting the fixing portion 46 to the radial portion 42.
[0065] The radial portion 42 of the mounting plate axially supports the support member 32 of the brush 30. More specifically, the radial portion 42 axially supports the lateral flank 36 of the support member. The radial portion 42 is axially offset outward relative to the inner ring 16 of the bearing. The radial portion 42 remains at a distance axially from the end face 16c of the inner ring. The brush support member 32 axially supports the radial portion 42 on the side opposite the inner ring 15. Alternatively, depending on the design of the mounting plate, the brush support member 32 may axially support the radial portion 42 on one side of the inner ring 16. In this case, the support member 32 is axially positioned between the radial portion 42 of the mounting plate and the inner ring face 16c, remaining axially spaced from the face 16c.
[0066] The tongues 44 are spaced apart from each other in the circumferential direction; in this case, the tongues 44 are evenly spaced apart in the circumferential direction. Alternatively, irregular circumferential spacing can be provided. In the exemplary embodiment shown, there are eight tongues 44. Alternatively, more or fewer 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 two.
[0067] Each tongue 44 protrudes axially relative to the radial portion 42. Each tongue 44 partially surrounds the support 32 of the brush 30 radially and is in radial contact with the mounting portion 34 of the support. The support 32 is held axially against the radial portion 42 of the mounting plate by the tongues 44. The tongues 44 are used to hold the ground brush 30 axially and radially. Lateral side 36 of the support supports the radial portion 42 of the mounting plate, and lateral side 38 supports the tongues 44. In this case, the tongues 44 are identical to each other.
[0068] Each tongue 44 has an axial portion and a radially inwardly bent-over portion located at the free end of the axial portion. The axial portion extends axially from the radial portion 42, partially surrounds the support 32 radially, and radially contacts the support. The bent portion of each tongue serves to axially hold the support 32 of the grounding brush 30. The bent portion of each tongue axially contacts the lateral side 38 of the support.
[0069] The retaining portion 46 of the mounting plate is force-fitted into a groove 24 in the outer ring 18 of the bearing. In the exemplary embodiment shown, the retaining portion 46 is made in the form of sectors that fold back onto themselves to match the shape of the groove 24. The sectors are spaced apart from each other in the circumferential direction. Alternatively, the retaining portion 46 may be annular. The retaining portion 46 defines the outer diameter of the mounting plate 40.
[0070] The fixed portion 46 is offset radially outward relative to the tongue 44 and axially toward the inside of the bearing 12 relative to the tongue 44.
[0071] The connecting portion 48 of the mounting plate is annular and has a stepped shape. The connecting portion 48 extends between the large-diameter edge of the radial portion 42 and the small-diameter edge of the fixing portion 46.
[0072] Multiple through holes 50 are formed in the thickness of the radial portion 42 and the connecting portion 48 of the mounting plate. Openings 50 are formed during partial cutting of the mounting plate 40 to form tongues 44. Tongues 44 are formed by cutting, bending, and crimping ( / flanging / folding) the mounting plate 40. Openings 50 are spaced apart from each other in the circumferential direction. Each tongue 44 is aligned circumferentially with its associated opening 50. The number of openings 50 corresponds to the number of tongues 44. (As in...) Figure 6 As can be seen, the root of each tongue 44 extends from the inner edge of the associated opening 50 located on the radial portion 42.
[0073] Mounting plate 40 is manufactured by cutting and pressing. 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. In this case, the mounting plate is manufactured as a single piece.
[0074] As indicated above, a second set of conductive fibers 31b with reduced radial dimensions is provided to mount the bearing system 10 inside the associated electric motor.
[0075] like Figure 7 As shown, in order to mount the brush system 10 inside the hole 52 of the associated electric motor seat and onto the rotating shaft 54 of the electric motor, an installation tool 56 (partially shown by dashed lines) is used.
[0076] Tool 56 is axially supported against the end face 16c of the inner ring of the bearing so as to be able to push the system 10 axially until the system support abuts against the stop surface provided for this purpose by the seat of the associated electric motor.
[0077] The tool 56 extends axially through a notch 39 in the conductive fiber 31 of the brush, maintaining a certain distance from the fiber. The tool 56 has multiple fingers, each extending axially through one of the notches 39 in the conductive fiber 31. The fingers of the tool 56 are arranged radially between the shaft 54 of the electric motor and the free end of the second set of fibers 31b, and are axially supported against the inner ring 16 of the bearing. Each finger of the tool has a radial dimension smaller than the radial distance between the hole 16a in the inner ring of the bearing and the free end of the second set of fibers 31b of the brush. Each finger of the tool also has a circumferential dimension smaller than the circumferential dimension of the notch 39 in the conductive fiber 31 of the brush.
[0078] When the electric motor is in operation, the charge accumulated on the shaft 54 is dissipated to the seat 52 through the conductive fibers 31 of the brush, the support 32 and the mounting plate 40 of the assembly.
Claims
1. A bearing system (10) comprising a bearing (12) and a grounding brush assembly (14), the bearing (12) having an inner ring (16) and an outer ring (18) rotatable relative to each other, the grounding brush assembly (14) being fixed to the outer ring (18) of the bearing and comprising a brush (30) axially outwardly offset relative to the inner ring (16) of the bearing and having a plurality of conductive fibers (31) and a support (32), the conductive fibers being mounted in the support (32), the conductive fibers (31) protruding radially inwardly relative to the support (32), characterized in that, The conductive fibers (31) of the brush of the grounding brush assembly (14) include at least a first set of fibers (31a) and a second set of fibers (31b), the free end of the first set of fibers (31a) defining the inner diameter of the brush (30), the protruding radial length of the second set of fibers (31b) decreasing relative to the protruding radial length of the first set of fibers (31a), and the free end of the second set of fibers (31b) being radially outward relative to the hole (16a) of the inner ring of the bearing.
2. The system according to claim 1, characterized in that, The free end of the first group of fibers (31a) of the conductive fiber is radially offset inward relative to or flush with the hole (16a) of the inner ring of the bearing.
3. The system according to claim 1 or 2, characterized in that, The holes of the brush (30) of the grounding brush assembly have a serrated shape, each opening (39) of the serrated shape being defined radially by the conductive fibers of the second set of fibers (31b) and circumferentially by the conductive fibers of the first set of fibers (31a).
4. The system according to any one of the preceding claims, characterized in that, The grounding brush assembly is directly fixed to the outer ring (16) of the bearing without the need for an intermediate component.
5. The system according to any one of the preceding claims, characterized in that, The grounding brush assembly is fixed in a groove (24) formed in a hole in the outer ring of the bearing.
6. The system according to any one of the preceding claims, characterized in that, The grounding brush assembly (14) also includes a brush mounting plate (40), which is integral with the brush support (32) and fixed to the outer ring (18) of the bearing.
7. A kit comprising a bearing system (10) according to any one of claims 1 to 6 and an installation tool (56), the installation tool (56) comprising at least one finger, the radial dimension of the at least one finger being smaller than the radial distance between the bore (16a) of the inner ring of the bearing and the free end of a second set of fibers (31b) of the conductive fibers of the brush of the grounding brush assembly.
8. An electric motor comprising a housing (52), a shaft (54), and at least one bearing system (10) according to any one of claims 1 to 6, the at least one bearing system (10) being radially mounted between the housing and the shaft, wherein a first set of conductive fibers (31a) of the brush of the grounding brush assembly is in contact with the shaft.
9. A method for mounting a bearing system according to any one of claims 1 to 6 between a housing and a shaft of an electric motor, wherein, The bearing system is pushed along the shaft by means of an installation tool, which is arranged radially between the shaft and the free end of the second set of conductive fibers (31b) of the brush of the grounding brush assembly, and axially supported against the inner ring (16) of the bearing.