CN213879575U

CN213879575U - Electric machine

Info

Publication number: CN213879575U
Application number: CN202023184505.8U
Authority: CN
Inventors: 杨宇盟; 吴建刚
Original assignee: Emerson Climate Technologies Suzhou Co Ltd
Current assignee: Copeland Suzhou Co Ltd
Priority date: 2020-12-17
Filing date: 2020-12-25
Publication date: 2021-08-03
Anticipated expiration: 2030-12-25
Also published as: CN114649910A

Abstract

The utility model relates to a motor, include: a shaft; a rotor assembly comprising a rotor disk and a bushing, the bushing being disposed between the shaft and the rotor disk, the rotor assembly being secured to the shaft by the bushing; and a commutator adapted to deliver electrical power to the coil, the total number N of segments of the commutator satisfying the formula: u/[ (N-p)/2 ]. p <30, and (N +1)/p is an integer or (N-1)/p is an integer; u is the rated voltage of the motor, and p is the pole pair number of the motor. The plurality of commutator segments are arranged at regular intervals along a circumference centered on an axis of the motor, the plurality of brushes of the motor are arranged in pairs, two brushes of each pair of brushes are arranged symmetrically with respect to the axis and are configured such that a circumferential width of each brush satisfies a formula: wb < Ws/2+ Wi 3/2, Wb is a circumferential width of each brush, Ws is a circumferential width of each segment, and Wi is a circumferential width of a gap between every two adjacent segments. The utility model provides a can reduce the commutator electric spark in order to be applied to the motor of high voltage.

Description

Electric machine

Technical Field

The present invention relates to electric machines, and more particularly to an improved coreless disk-type electric machine.

Background

In the field of motors, a direct current disc type motor is a driving motor which adopts an axial magnetic field and adopts a coreless structure as a rotor. The coreless disk type direct current motor has the advantages of no cogging torque, low noise, low rotational inertia, sensitive work response, small axial size, high efficiency, simple structure and the like, and is widely applied to the industries of household appliances, automobiles, electric bicycles and the like.

The armature of the coreless disk motor has two structures: printed circuit boards and coil disks. The printed circuit board type armature is printed on a copper clad laminate by using a corrosion method, an electrochemical deposition method and the like, and has the advantages of simple structure, small volume, light weight and high manufacturing cost. Coil disks are typically molded from a molded coil using a thermoset material (e.g., epoxy), which is less expensive to manufacture than printed circuit boards and is more versatile.

However, the disc type coreless dc motor is generally supplied by a storage battery, and has a low rated voltage, generally 12V to 48V, so that the motor cannot be directly applied to a place with a high voltage (for example, 120V or 220V).

The patent CN 201805335U discloses a coreless disk-type motor, which includes a rotor end cover, a rotor, a coil winding, and an electromagnetic disk, which are sleeved on the same motor shaft, are in a flat disk shape, and are coaxially arranged in sequence, wherein the rotor end cover, the rotor, and the electromagnetic disk are nested with the motor shaft through a bearing embedded in the center, a center hole of the coil winding as a stator is directly fastened and nested outside the motor shaft, the rotor end cover and the rotor are fixed into a whole, and gaps are left among the rotor, the coil winding, and the electromagnetic disk; and a plurality of pieces of magnetic steel which are uniformly distributed are fixedly arranged on one surface of the rotor, which faces the coil winding. The motor reduces the weight and volume of the motor in an open structure. The motor is a brushless motor and has no commutator structure, and corresponding drive is required to be equipped in use.

Patent CN 203617869U discloses a totally closed aluminum alloy disk motor, this motor makes up into hollow casing by aluminum alloy frame and cap, the pivot supports on the bearing in the casing and the one end of pivot stretches out outside the casing, be fixed with the rotor that no iron core plastic envelope dish type rotor dish formed in the pivot in the casing, be fixed with the stator of the motor that magnet formed on the contralateral shell cover of rotor dish, still be fixed with the brush combination on the shell cover, the brush combination is for rotor coil power transmission with the commutator cooperation on the rotor dish, install the skeleton oil blanket between frame and the pivot. The magnetic yoke iron piece is installed on the aluminum alloy base in an embedding or die-casting mode. The motor adopts a fully-closed structure, can effectively meet the requirements of water resistance, oil resistance and dust resistance, and has the advantages of no maintenance and long service life.

Patent CN 204465265U discloses a constant temperature disk type dc motor, a base fixedly connected in sequence, a housing, a rotating shaft with one end extending out of the base is supported by a bearing on the axis of a housing, a rotor cavity formed between the base and the housing is provided with a rotor disk fixed on the rotating shaft and electrically connected with a commutator and provided with a rotor winding, the outer cylindrical surface of the rotor disk in the rotor cavity is uniformly provided with radiating blades, the outer side of the radiating blade is uniformly provided with a circle of radiating holes which are radially communicated with each other relative to the housing, the commutator is fixed on the rotating shaft, an electric brush fixed on the housing is in contact with the commutator to conduct electricity, the inner wall surfaces of the base and the housing are uniformly adhered with a circle of magnets with even number of magnetic poles, and a rotor cavity formed by combining the base and the housing forms a closed magnetic circuit space. The base and the shell are respectively an integrated iron piece formed by stamping or an aluminum alloy part formed by die casting by taking an iron sheet as a magnet yoke insert. When the motor works, the radiating fin blades rotate along with the rotor disc to discharge heat generated by the rotor disc through air convection, and the faster the motor rotates, the faster the radiating fan blades rotate, the more heat is discharged, and vice versa. Therefore, the motor generates heat balance, the temperature rise is in a reasonable range, and the motor can stably work for a long time.

In the design of the motor commutator in the prior art, the number of commutator segments needs to ensure that the voltage between the commutator segments cannot be overlarge, generally does not exceed 30V, and overlarge easily causes large commutation spark. For a typical disc motor, the number of commutator segments and coils is typically small due to limited internal space, but typically does not cause large sparks due to low voltage ratings. However, when the rated voltage is high, the number of segments needs to be increased to prevent the commutator from generating larger sparks.

Regarding the commutator design of the motor in the prior art, the inventor of the present application noted that, for the winding of the disc motor, a single-wave winding method is generally adopted, and the number of branches of the winding method is always 2, regardless of the number of brushes and the number of poles. The inventors of the present application also noted that: the larger number of brushes results in an increased number of shorted coils in the armature winding and a reduced number of practically useful coils as compared to the two-brush solution, resulting in an increased voltage between the segments and an increased commutator spark. Meanwhile, the width of the brush cannot be too wide, and too wide causes the number of commutator segments in contact with the brush to be increased, the number of short-circuit coils to be increased, and the voltage between the commutator segments to be increased.

Secondly, for a coreless disk motor rotor, the rotor is conventionally manufactured by molding a thermosetting material and then interference-fitting the thermosetting material to a shaft of the motor. When the motor is operated in a loaded state, the torque is directly transmitted to the shaft through the rotor coil disc. Because macromolecular material is unstable under high temperature for the connection between rotor coil dish and the axle is weak, can't bear great torque, especially is changeing under the condition of frequent start-stop and high temperature and leads to the connection failure.

Furthermore, for the casing of the disc motor, a certain magnetic permeability is required to form the magnetic circuit. The material cost can be saved by adopting the aluminum alloy and the embedded magnet yoke iron piece, but the process is complex and the reliability is not high; a simpler way is to directly use an iron housing. The iron shell can be manufactured by adopting a stamping or machining method, but if the stamping method is adopted, the thickness of the shell cannot be too thick due to the limitation of a stamping process, otherwise, the iron shell cannot be manufactured, but the thinner the thickness of the shell is, the larger the magnetic resistance is, and the lower the motor efficiency is. Therefore, in order to improve the efficiency of the motor, it is necessary to ensure a certain thickness of the casing.

In summary, the armature structure of the coreless disk motor in the prior art has the following defects: the printed circuit board type armature has high cost; the coil disc type voltage is low, so that the coil disc type voltage cannot be directly used for high voltage and is easy to generate electric sparks; rotor attachment is not secure; the component reluctance on the flux path is high and the cost is high.

It should be noted here that the technical content provided in this section is intended to assist the understanding of the present invention by those skilled in the art, and does not necessarily constitute prior art.

SUMMERY OF THE UTILITY MODEL

It is an object of the present invention to reduce the possibility of commutator sparks being applied to high voltage electrical machines by an improved brush and commutator construction.

An object of the utility model is to provide with low costs, part attach intensity is high, the performance is high, compact structure's motor.

The utility model provides a motor, include: a shaft; a rotor assembly comprising a rotor disc and a bushing, the bushing being arranged between the shaft and the rotor disc, the rotor assembly being fixed to the shaft by the bushing, the rotor disc having coils disposed therein; and a commutator adapted to convey electric power to the coil, the commutator including a plurality of commutator segments, a total number N of the commutator segments satisfying the following formula: u/[ (N-p)/2 ]. p <30, and (N +1)/p is an integer or (N-1)/p is an integer; wherein, U is the rated voltage of the motor, and p is the pole pair number of the motor.

And the plurality of commutator segments are arranged at regular intervals along a circumference centered on an axis of the motor, the motor further including a plurality of brushes adapted to contact the commutator segments to transmit electric power, the plurality of brushes being arranged in pairs, the two brushes of each pair being arranged symmetrically with respect to the axis, the two brushes of each pair being configured such that a circumferential width of each brush satisfies the following formula: wb < Ws/2+ Wi 3/2, where Wb is a circumferential width of each brush, Ws is a circumferential width of each segment, and Wi is a circumferential width of a gap between every two adjacent segments.

Advantageously, the radially outer side of the bushing is provided with a lobe embedded in the rotor disc.

Advantageously, the bushing is a copper sleeve with an interference fit with the shaft and/or the bushing is integrally moulded with the rotor disc using a thermosetting material.

Advantageously, the rotor disc has a radially outer area and a radially central area, the electric machine further comprising a first end cover arranged on a first side of the rotor disc and facing the radially outer area, and a second end cover arranged on a second side of the rotor disc opposite to the first side and facing the radially outer area, such that the rotor disc is located within a space defined by the first end cover and the second end cover.

Advantageously, the first end cap and the second end cap are made of magnetically permeable material.

Advantageously, the electric machine further comprises a permanent magnet disposed on an inner surface of the first end cap facing the radially outer region, and wherein: the permanent magnet is a circular permanent magnet and the coil is a diamond-shaped coil, or the permanent magnet is a fan-shaped permanent magnet and the coil is a fan-shaped coil

Advantageously, the commutator in the form of a disc is arranged on the second side of the rotor disc and is attached to the radially central region, and the commutator protrudes through a hole of the second end cover.

Advantageously, the electric machine further comprises: the motor comprises a cylindrical shell, a first bearing cover and a second bearing cover, wherein the first bearing cover, the first end cover, the cylindrical shell, the second end cover and the second bearing cover are sequentially connected along the axis of the motor, the first bearing cover and the second bearing cover face the radial central area, and the cylindrical shell, the first bearing cover and the second bearing cover are made of non-magnetic materials.

Advantageously, a brush holder of a brush assembly of the electric machine is fixed to the second bearing cap, to which brush holder a brush of the brush assembly of the electric machine is attached in a telescopic motion and can be kept in contact with the commutator.

Advantageously, the motor is a motor with a rated voltage of 120V or more and implemented with a single-wave winding using the coil.

The utility model also provides a motor, include: a rotor assembly comprising a rotor disk having coils disposed therein; a commutator adapted to deliver power to the coil, the commutator including a plurality of commutator segments evenly spaced along a circumference centered on an axis of the motor; and two brushes adapted to be in contact with the commutator segments to transmit electric power, the two brushes being symmetrically arranged about the axis, the two brushes being configured such that a circumferential width of each brush satisfies the following formula to reduce a voltage between the commutator segments: wb < Ws/2+ Wi 3/2, where Wb is a circumferential width of each brush, Ws is a circumferential width of each segment, and Wi is a circumferential width of a gap between every two adjacent segments.

Compared with the existing motor design, the beneficial effects of the utility model reside in that: 1. the motor commutator is suitable for higher voltage, the number of commutator segments is related to the rated voltage of the motor, and the higher the voltage is, the more the number of commutator segments is, so that the voltage between the commutator segments is reduced, and the spark is reduced; 2. limiting the width of the electric brush to reduce commutation spark; 3. a copper sleeve with teeth is embedded in the rotor component to transmit larger torque; 4. the parts of the magnetic flux path are made of magnetic conductive materials, so that the performance is improved, and the parts of the non-magnetic flux path are made of non-magnetic conductive materials, so that the material cost and the processing cost are reduced; 5. the motor has compact structure and small axial size.

Drawings

The features and advantages of the present invention will be more readily understood from the following detailed description of the specific embodiments that is provided with reference to the accompanying drawings. In the drawings, wherein like features or components are designated with like reference numerals throughout the several views and are not necessarily drawn to scale, and wherein:

fig. 1 is a schematic cross-sectional view of an electric machine with an improved armature structure according to the present invention.

Fig. 2A and 2B are schematic longitudinal and axial cross-sectional views, respectively, of a rotor assembly of the electric machine of fig. 1, including a commutator, a rotor disc, and a bushing.

Fig. 3A is a schematic axial cross-sectional view of the brush assembly of fig. 1 in mating contact with a commutator segment.

Fig. 3B is a schematic sectional view developed along a circumferential broken line of fig. 3A.

Detailed Description

Exemplary embodiments of the present invention will be described in detail below with reference to the accompanying drawings. The description of the exemplary embodiments is for purposes of illustration only and is not intended to limit the invention, its application, or uses.

The utility model of this application thinks about and lies in: the total number of commutator segments is designed by relating the number of segments to the rated voltage of the power supply and the number of pole pairs of the motor so that the higher the voltage, the more the number of segments, thereby reducing the voltage between the segments and reducing the generation of sparks. The utility model discloses the design still lies in, based on the motor operation with the commutator segment's of brush contact figure, designs commutator segment and brush's structure such as width to reduce the voltage between the commutator segment, reduce the production of spark.

Next, the motor of the present invention will be described with reference to fig. 1 to 3B. The motor of the utility model uses the coreless disk permanent magnet direct current motor as an example, and can be applied to other motors.

Referring to fig. 1 to 2B, the motor of the present invention includes: a shaft 5; a rotor assembly 7, the rotor assembly 7 being fixed to the shaft 5 and comprising a rotor disc 71 in which the coils are arranged; and a commutator 73 adapted to deliver power to the coil, the commutator comprising a plurality of commutator segments 73A, the commutator 73 being configured according to the rated voltage and pole pair number of the motor such that the total number N of commutator segments 73A satisfies the following formula to reduce the voltage between the commutator segments: u/[ (N-p)/2 ]. p < 30; and (N +1)/p is an integer, or (N-1)/p is an integer, wherein U is a rated voltage and p is a pole pair number. The utility model discloses a motor with above-mentioned characteristic is applicable to higher voltage, and commutator segment number is relevant with the rated voltage of motor, and voltage is higher, and commutator segment number is more to reduce commutator segment voltage, reduce the spark.

In one aspect according to this embodiment, the rated voltage of the motor may be 150V, the number of pole pairs P is 3, and it can be found from the above formula that the total number of commutator segments N > 33, N may be, for example, an odd number, and the total number of commutator segments may be set to 35 as necessary, or may be set to different values as necessary (for example, a configuration and a cost factor, etc.). In another aspect of the embodiment, the number of pole pairs P may be different numbers of pole pairs, such as 4 pairs (8 poles), 5 pairs (10 poles), and 6 pairs (12 poles).

And in conjunction with fig. 3A and 3B, a plurality of commutator segments 73A are arranged at regular intervals along a circumference centered on the axis of the motor, and the size of each commutator segment is uniform. The motor further includes two brushes 10A adapted to contact the commutator segments 73A to transmit electric power, the two brushes being arranged symmetrically (180 ° apart) with respect to an axis of the motor, the two brushes being configured such that a circumferential width of each brush 10A satisfies the following formula: wb < Ws/2+ Wi 3/2, where Wb is a circumferential width of each brush, Ws is a circumferential width of each segment, and Wi is a circumferential width of a gap between every two adjacent segments.

Specifically, in one aspect according to the embodiment, the motor may be a motor having a rated voltage of 120V or more and implemented with a coil in a single-wave winding, the brush may be a carbon brush, and 35 (numbered 1 to 35) commutator segments are arranged at regular intervals along the circumference. Assuming that one brush 10A is located at the center of commutator segment 73A numbered 1 in the initial state, since two brushes are symmetrically arranged at 180 degrees, the other brush 10A is located at the center of commutator segment 73A numbered 18 and 19. Since the number of commutator segments in contact with the brush is increased, the number of short-circuit coils is increased, and the voltage between the commutator segments is increased, so that sparks are more likely to occur. The brushes and segments are designed according to the above formula Wb < Ws/2+ Wi 3/2 to ensure that the number of segments in contact with the brushes during rotation does not exceed 3 at all times, that is, to ensure that when the above-mentioned one brush 10A is in contact with segment 2, the other brush 10A has already been disengaged from segment 18, that is, to ensure that D1 is greater than D2, thereby reducing the voltage between the segments and reducing or eliminating the generation of electric sparks, which is particularly suitable when the rated voltage of the motor is high.

Although the circumferential width Wb of the brush shown in fig. 3B is smaller than the circumferential width Ws of the commutator segments, those skilled in the art will appreciate that the above formula is equally applicable to the case when the circumferential width Wb of the brush is larger than the circumferential width Ws of the commutator segments.

Furthermore, the number of brushes shown in the figures is a pair of brushes arranged symmetrically, while those skilled in the art will appreciate that brushes may be arranged in pairs of pairs, with two brushes in each pair being arranged symmetrically and ensuring that the number of segments of the commutator in simultaneous contact with the two brushes is always no more than 3. For example, when a plurality of brushes are arranged in two pairs, the number of segments of commutator with which the two brushes of each pair simultaneously contact always does not exceed 3, and the total number of segments of commutator with which the brushes simultaneously contact always does not exceed 6.

And rotor assembly 70 may further include a bushing 72, bushing 72 being disposed between shaft 5 and rotor disc 71, and a radially outer side of the bushing being provided with a tooth 72A embedded in rotor disc 71 to improve mechanical strength between the rotor disc and the bushing, thereby transmitting a greater torque. As shown in fig. 2A and 2B, the bushing 72 is a copper bushing that is interference fit with the shaft 5, and/or the bushing 72 and the rotor disc 71 are integrally molded using a thermosetting material, which may be epoxy resin or phenolic resin, so as to achieve a reliable fixed connection of the rotor assembly and the shaft.

In another advantageous aspect according to an embodiment of the invention, the rotor disc 71 has a radially outer area and a radially central area, the electric machine further comprises a first end cap 2 and a second end cap 11, the first end cap 2 being arranged on a first side of the rotor disc 71 and facing the radially outer area, the second end cap 11 being arranged on a second side of the rotor disc 71 opposite to the first side and facing the radially outer area, such that the rotor disc 71 is located within a space defined by the first end cap 2 and the second end cap 11. The motor further comprises permanent magnets 3 arranged on the inner surface of the first end cap 2 facing the radially outer area. In one example, 6 pieces of cylindrical permanent magnets 3 are bonded to the inner surface of the first end cap 2 and uniformly distributed along the circumference while being arranged with the N and S poles crossed.

With the above arrangement, a closed magnetic path is formed from the permanent magnet 3, the first end cover 2, the second end cover 11, the rotor disc 71 and back to the permanent magnet 3 when the electric machine is operated with current, wherein the rotor disc 71 is arranged in the gap between the second end cover 11 and the permanent magnet 3. The first end cap 2 and the second end cap 11, which are located on the closed magnetic flux path, are made of a magnetically conductive material, which may be, for example, 10 gauge steel, to reduce the reluctance and improve the motor performance.

Advantageously, the permanent magnet 3 is a circular permanent magnet and the coil is a diamond-shaped coil, or the permanent magnet 3 is a fan-shaped permanent magnet and the coil is a fan-shaped coil, so that the effective length in the magnetic field cutting range is increased and the coil utilization rate is improved.

Turning again to fig. 1, the motor further comprises: the motor comprises a cylindrical shell 1 and a first bearing cover 4 and a second bearing cover 9, wherein the first bearing cover 4, the first end cover 2, the cylindrical shell 1, the second end cover 11 and the second bearing cover 9 are sequentially connected along the axis of the motor, and a shaft 5 is supported by a first bearing 6 and a second bearing 8 which are respectively arranged in the first bearing cover 4 and the second bearing cover 9. Also, the first bearing cap 4 and the second bearing cap 9 face the radial central region, and the cylindrical casing 1, the first bearing cap 4 and the second bearing cap 9 are made of a non-magnetic conductive material, which may be an aluminum alloy, to reduce costs. Advantageously, a commutator 73 in the form of a disc is arranged on the second side of the rotor disc 71 and attached to the radially central region, and the commutator 73 protrudes through a hole of the second end cover 11 to come into contact with the brush 10A of the brush assembly 10. By means of the arrangement, the motor can be compact in structure and small in axial size.

In an advantageous aspect of the embodiment, the brush holder of the brush assembly 10 of the electric machine is fixed to the second bearing cap 9, the brush 10A of the brush assembly 10 of the electric machine being attached to the brush holder in a telescopic motion and being able to maintain contact with the commutator for reliable power transmission.

In still another embodiment according to the present invention, a motor includes: a rotor assembly 7 comprising a rotor disc 71 in which coils are arranged; a commutator 73 adapted to transmit electric power to the coil, the commutator including a plurality of commutator segments 73A, the plurality of commutator segments 73A being uniformly spaced along a circumference centered on an axis of the motor; and two brushes 10A, the two brushes 10A being adapted to be in contact with the commutator segments 73A to transmit electric power, the two brushes being symmetrically arranged about the axis, the two brushes being configured such that a circumferential width of each brush satisfies the following formula to reduce a voltage between the commutator segments: wb < Ws/2+ Wi 3/2, where Wb is a circumferential width of each brush, Ws is a circumferential width of each segment, and Wi is a circumferential width of a gap between every two adjacent segments, thereby reducing a voltage between the segments and reducing or eliminating generation of an electric spark.

Although preferred embodiments of the present invention have been described in detail herein, it is to be understood that the invention is not limited to the precise construction herein described and illustrated, and that other modifications and variations may be effected by one skilled in the art without departing from the spirit and scope of the invention. All such modifications and variations are intended to fall within the scope of the claims appended hereto.

Claims

1. An electric machine, characterized by comprising:

a shaft;

a rotor assembly comprising a rotor disc and a bushing, the bushing being arranged between the shaft and the rotor disc, the rotor assembly being fixed to the shaft by the bushing, the rotor disc having coils disposed therein; and

a commutator adapted to deliver electrical power to the coil, the commutator comprising a plurality of commutator segments,

the total number N of commutator segments satisfies the following formula: u/[ (N-p)/2] p <30, and

(N +1)/p is an integer or (N-1)/p is an integer,

wherein U is the rated voltage of the motor, and p is the pole pair number of the motor;

and the plurality of commutator segments are arranged at regular intervals along a circumference centered on an axis of the motor,

the motor further includes a plurality of brushes adapted to contact the commutator segments to transmit electric power, the plurality of brushes being arranged in pairs, two brushes of each pair being symmetrically arranged about the axis,

the two brushes of each pair are configured such that a circumferential width of each brush satisfies the following formula:

Wb<Ws/2+Wi*3/2，

where Wb is a circumferential width of each brush, Ws is a circumferential width of each commutator segment, and Wi is a circumferential width of a gap between every two adjacent commutator segments.

2. An electric machine as claimed in claim 1, characterized in that the radially outer side of the bushing is provided with a tooth embedded in the rotor disc.

3. The electric machine of claim 2, wherein the bushing is a copper sleeve that is an interference fit with the shaft, and/or wherein the bushing is integrally molded with the rotor disk using a thermoset material.

4. The electric machine according to any of claims 1 to 3, characterized in that:

the rotor disk has a radially outer region and a radially central region,

the electric machine also includes a first end cover disposed on a first side of the rotor disk and facing the radially outer area, and a second end cover disposed on a second side of the rotor disk opposite the first side and facing the radially outer area such that the rotor disk is located within a space defined by the first end cover and the second end cover.

5. The electric machine of claim 4, wherein the first end cap and the second end cap are made of magnetically permeable material.

6. The electric machine of claim 4, further comprising a permanent magnet disposed on an inner surface of the first end cap facing the radially outer region, and wherein: the permanent magnet is a circular permanent magnet and the coil is a diamond-shaped coil, or the permanent magnet is a fan-shaped permanent magnet and the coil is a fan-shaped coil.

7. An electric machine according to claim 4, characterized in that the commutator in the shape of a disc is arranged on the second side of the rotor disc and attached to the radially central area, and the commutator protrudes through a hole of the second end cover.

8. The electric machine of claim 4, further comprising:

cylindrical casing, and

a first bearing cover and a second bearing cover,

wherein the first bearing cap, the first end cap, the cylindrical case, the second end cap, and the second bearing cap are sequentially connected along an axis of the motor, and the first bearing cap and the second bearing cap face the radial central region, and the cylindrical case, the first bearing cap, and the second bearing cap are made of a non-magnetic conductive material.

9. The electric machine of claim 8, wherein a brush carrier of a brush assembly of the electric machine is secured to the second bearing cap, a brush of the brush assembly of the electric machine being telescopically movably attached to the brush carrier and being capable of maintaining contact with the commutator.

10. The electric machine according to any of claims 1 to 3, characterized in that the electric machine is a machine rated for a voltage of 120V or more and implemented with the coil in a single-wave winding.