Hollow cup brushless motor and stator assembly thereof

Abstract

The invention discloses a coreless brushless motor and a stator assembly thereof, and relates to the technical field of motors. The stator assembly comprises a shell, a stator iron core and an armature coil which are sequentially arranged in a sleeving mode from outside to inside, a containing cavity is formed in the middle of the armature coil, and the containing cavity is used for containing a rotor assembly of the coreless brushless motor; the adapter plate is fixedly arranged at the end part of the stator core through a first bracket; the adapter plate is used for connecting the wire outlet end of the armature coil with a first outgoing line, and the first outgoing line is connected with external equipment; the Hall plate is fixedly arranged on the adapter plate through a second bracket; the Hall plate is used for obtaining rotation angle information of the rotor assembly, and the Hall plate is connected with an external device through a second outgoing line. According to the technical scheme provided by the invention, the production efficiency of the coreless brushless motor can be improved.

Description

Technical Field

[0001] This invention relates to the field of motor technology, and in particular to a hollow cup brushless motor and its stator assembly. Background Technology

[0002] Coreless brushless motors belong to the category of DC permanent magnet servo micro motors. The main difference between them and ordinary brushless DC motors is that the armature core has no slots, and the motor windings are manufactured into a cup shape using a special winding process. Compared to traditional slotted motors, they have the following advantages: 1. High efficiency: Coreless motors generally have an efficiency of over 70%, with some products even approaching 90%, while traditional slotted motors of the same size and weight have efficiencies below 70%; 2. Small size, light weight, and high power and torque density: Due to improved efficiency and reduced losses, the power density of coreless motors is significantly increased, and their size and weight can be reduced by about 30% compared to traditional slotted motors; 3. Good control performance: The absence of cogging effect results in less torque fluctuation and smoother motor operation; the low electromechanical time constant and good dynamic response are also advantages. The motor's inductance is very low, with a conventional electrical time constant within 0.1ms and an electromechanical time constant around 2ms. This results in rapid motor response and precise control, making them suitable for high-precision drive systems, such as those in communications, robotics, security, aerospace, and steering systems.

[0003] A coreless brushless motor typically consists of a stator assembly, a rotor assembly, and front and rear end covers. Under high load and high power output conditions, a large current flows through the armature coil of the coreless brushless motor. The conventional approach is to weld the armature coil leads to the leads, then bind the leads to the end of the stator assembly before leading them out. This method requires manual binding, which is time-consuming and labor-intensive, resulting in low production efficiency for coreless brushless motors.

[0004] It should be noted that the above content is only used to help understand the technical solution of the present invention, and does not represent an admission that the above content is prior art. Summary of the Invention

[0005] The main objective of this invention is to propose a hollow cup brushless motor and its stator assembly, aiming to improve the production efficiency of the hollow cup brushless motor.

[0006] To achieve the above objectives, the present invention proposes a stator assembly for a hollow cup brushless motor; Specifically, the stator assembly includes: The device consists of a housing, a stator core, and an armature coil, arranged sequentially from the outside to the inside. The armature coil has a receiving cavity in the middle, which is used to accommodate the rotor assembly of the hollow cup brushless motor. An adapter plate is fixedly mounted on the end of the stator core via a first bracket; the adapter plate is used to connect the output end of the armature coil to a first lead wire, wherein the first lead wire is connected to an external device. A Hall plate is fixedly mounted on the adapter plate via a second bracket, and the Hall plate is located on the side of the adapter plate closer to the rotor assembly; the Hall plate is used to acquire the rotation angle information of the rotor assembly, and the Hall plate is connected to an external device via a second lead wire.

[0007] In one embodiment, the first bracket has a cylindrical structure, one end of the first bracket along its axial direction is fixedly connected to the stator core, and the other end of the first bracket along its axial direction is provided with an annular recess, and the adapter plate is fitted and connected to the recess.

[0008] In one embodiment, the adapter plate has a plurality of wire-passing grooves along its outer periphery, and each wire-passing groove corresponds to a lead-out end of the armature coil; the lead-out end of the armature coil is connected to the wire-passing groove.

[0009] In one embodiment, the thickness of the adapter plate is greater than the thickness of the Hall plate; and / or, the adapter plate is provided with series and parallel conductive lines, and the output terminal of the armature coil is connected in series and parallel with the first lead through the conductive lines.

[0010] In one embodiment, the second bracket includes an annular member with a through hole in the middle for the shaft of the rotor assembly to pass through; at least two connecting posts are provided on the side of the annular member facing the adapter plate, and the annular member is fixedly connected to the adapter plate through the connecting posts; the annular member has a protrusion protruding towards the adapter plate, and the Hall plate is mounted on the free end of the protrusion.

[0011] In one embodiment, the second bracket includes two connecting posts, which are symmetrically arranged about the axis of the annular member.

[0012] In one embodiment, the housing, the stator core, the armature coil, the adapter plate, and the Hall plate are potted to form an integral stator structure.

[0013] To achieve the above objectives, the present invention proposes a hollow cup brushless motor, the hollow cup brushless motor comprising a rotor assembly and a stator assembly as described in any of the preceding claims.

[0014] In one embodiment, the rotor assembly includes a shaft and a magnet sleeved around the shaft, the magnet being located within the receiving cavity; and the magnet is surrounded by a metal sheath.

[0015] In one embodiment, the hollow cup brushless motor includes a front cover and a rear cover, the front cover and the rear cover being respectively disposed at both axial ends of the housing; and a first bearing component is installed inside the front cover, and a second bearing component is installed inside the rear cover; the two ends of the rotating shaft are respectively sleeved on the first bearing component and the second bearing component.

[0016] The technical solution of this invention uses two independent PCB boards: an adapter board and a Hall effect sensor board. The adapter board connects the armature coil's output terminal to the first lead wire to supply power to the armature coil. The Hall effect sensor board acquires the rotation angle information of the rotor assembly and connects this data to an external device via a second lead wire to control the coreless brushless motor. The adapter board and the Hall effect sensor board are connected to each other via a second bracket and then fixedly connected to the stator core end via a first bracket, thus forming an integrated stator assembly structure that simultaneously realizes the adapter and Hall effect sensing functions. Furthermore, since the armature coil's output terminal is directly electrically connected to the connecting board and then uniformly led out by the adapter board, the traditional "wire bonding + manual binding" steps are completely eliminated, significantly reducing assembly time and labor costs, thereby improving the production efficiency of the coreless brushless motor. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 A schematic diagram of the overall structure of an embodiment of the hollow cup brushless motor provided by the present invention; Figure 2 An exploded view of the overall structure of an embodiment of the hollow cup brushless motor provided by the present invention; Figure 3 A schematic diagram of the internal structure of an embodiment of the hollow cup brushless motor provided by the present invention; Figure 4 This is a schematic diagram of the internal structure of an embodiment of the stator assembly provided by the present invention; Figure 5 This is an exploded view of the structure of an embodiment of the stator assembly provided by the present invention; Figure 6 This is a schematic diagram of the structure of the second bracket in one embodiment of the stator assembly provided by the present invention; Figure 7 A wiring diagram of the adapter plate in one embodiment of the stator assembly provided by the present invention; Explanation of reference numerals in the attached figures: 10. Housing; 20. Stator core; 30. Armature coil; 31. Receiving cavity; 32. Outgoing terminal; 40. Adapter plate; 41. Wire groove; 50. First bracket; 51. Recessed part; 60. Hall plate; 70. Second bracket; 71. Ring part; 72. Through hole; 73. Connecting column; 74. Protrusion; 80. Rotor assembly; 81. Shaft; 82. Magnet; 83. Metal sheath; 91. Front end cover; 911. First bearing component; 92. Rear end cover; 921. Second bearing component; The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0019] The technical solutions of this invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only a portion of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0020] It should be noted that if the embodiments of the present invention involve directional indicators (such as up, down, left, right, front, back, etc.), the directional indicators are only used to explain the relative positional relationship and movement of the components in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indicators will also change accordingly.

[0021] Furthermore, it should be noted that the descriptions involving "first," "second," etc., in this invention are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of that feature. Additionally, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or impossible to implement, such a combination of technical solutions should be considered non-existent and not within the scope of protection claimed by this invention.

[0022] A coreless brushless motor typically consists of a stator assembly, a rotor assembly, and front and rear end covers. Under high load and high power output conditions, a large current flows through the armature coil of the coreless brushless motor. The conventional approach is to weld the armature coil leads to the leads, then bind the leads to the end of the stator assembly before leading them out. This method requires manual binding, which is time-consuming and labor-intensive, resulting in low production efficiency for coreless brushless motors.

[0023] To address the aforementioned technical problems, this invention proposes a stator assembly for a hollow cup brushless motor.

[0024] Please see Figures 1 to 5 In one embodiment of the present invention, the stator assembly includes: The outer shell 10, stator core 20 and armature coil 30 are sequentially arranged from the outside to the inside. The armature coil 30 has a receiving cavity 31 in the middle, which is used to receive the rotor assembly 80 of the hollow cup brushless motor. The adapter plate 40 is fixedly mounted on the end of the stator core 20 via the first bracket 50. The adapter plate 40 is used to connect the output terminal 32 of the armature coil 30 to the first lead (not shown in the figure), wherein the first lead is connected to an external device (not shown in the figure). Hall plate 60 is fixedly mounted on adapter plate 40 via second bracket 70, and Hall plate 60 is located on the side of adapter plate 40 closer to rotor assembly 80; Hall plate 60 is used to obtain rotation angle information of rotor assembly 80, and Hall plate 60 is connected to external device (not shown in the figure) via second lead wire (not shown in the figure).

[0025] The technical solution of this invention uses two independent PCB boards: an adapter board 40 and a Hall effect sensor board 60. The adapter board 40 connects the output terminal 32 of the armature coil 30 to the first lead wire to supply power to the armature coil 30. The Hall effect sensor board 60 acquires the rotation angle information of the rotor assembly 80 and connects the data to an external device via a second lead wire to control the coreless brushless motor. The adapter board 40 and the Hall effect sensor board 60 are connected to each other via a second bracket 70 and then fixedly connected to the end of the stator core 20 via a first bracket 50, thus forming an integrated stator assembly structure that can simultaneously realize the adapter and Hall effect sensing functions. Furthermore, since the output terminal 32 of the armature coil 30 is directly electrically connected to the connecting board and then uniformly led out by the adapter board 40, the traditional "wire bonding + manual binding" steps are completely eliminated, significantly reducing assembly time and labor costs, thereby improving the production efficiency of the coreless brushless motor.

[0026] Since the Hall plate 60 is existing technology, its structure and principle will not be described in detail here. In general, the Hall plate 60 integrates a Hall chip (not shown in the attached diagram). When the magnet 82 of the rotor assembly 80 rotates, the N and S poles alternately pass over the receiving end of the Hall chip. The Hall chip outputs a high-low level (or sinusoidal voltage) sequence, forming an electrical signal that corresponds one-to-one with the position of the magnetic poles of the magnet 82 of the rotor assembly 80. These electrical signals are the raw data of the "rotation angle information," which are directly wired to the pads of the Hall plate 60 and then sent to external devices via the second lead. After receiving the signal, the external device immediately knows which magnet 82 is at which angle, and calculates the order and duty cycle of the three phases of the stator to be energized, generating a new PWM drive command. The power stage MOSFETs switch according to the command, the stator magnetic field "takes a step" forward, and the rotor is attracted to rotate forward by another angle. The Hall plate 60 continues to sample, creating a closed-loop cycle, thus enabling the coreless brushless motor to rotate smoothly and continuously.

[0027] It should be noted that the number of the first and second leads is not limited. Those skilled in the art can select multiple first and second leads according to actual conditions to meet the operating requirements of the hollow cup brushless motor.

[0028] As a preferred embodiment of the above, the first bracket 50 has a cylindrical structure. One end of the first bracket 50 along its axial direction is fixedly connected to the stator core 20, and the other end of the first bracket 50 along its axial direction has an annular recess 51. The adapter plate 40 is fitted into the recess 51. This configuration, since the stator core 20 is typically cylindrical, correspondingly sets the first bracket 50 to a cylindrical structure to maximize the contact area between the first bracket 50 and the stator core 20 along its axial direction. This effectively improves the firmness between the first bracket 50 and the stator core 20 when subsequently bonded and fixed with adhesive. Then, the edge of the annular adapter plate 40 is embedded into the recess 51 of the first bracket 50 to provide 360-degree support and positioning for the adapter plate 40, ensuring resistance to floating and warping during subsequent potting.

[0029] As a preferred embodiment of the above, the adapter plate 40 has a plurality of wire-passing grooves 41 along its outer periphery, and the wire-passing grooves 41 correspond one-to-one with the output terminals 32 of the armature coil 30; the output terminals 32 of the armature coil 30 are connected in the wire-passing grooves 41. With this arrangement, since the wire-passing grooves 41 correspond one-to-one with the output terminals 32 of the armature coil 30, the wiring status of the output terminals 32 of the armature coil 30 can be observed through the wire-passing grooves 41, thereby ensuring that the wiring method of the armature coil 30 meets the preset requirements.

[0030] As a preferred embodiment of the above, the thickness of the adapter plate 40 is greater than the thickness of the Hall plate 60. This arrangement ensures that the adapter plate 40, whose function is to supply current, can withstand high currents without burning out, since the Hall plate 60 does not need to handle excessive current. In this embodiment, the thickness of the adapter plate 40 is at least 2mm to ensure it can handle a maximum current of 20A; the thickness of the Hall plate 60 is 0.8mm.

[0031] As a preferred embodiment of the above, the adapter plate 40 is provided with series and parallel conductive lines, and the output terminal 32 of the armature coil 30 is connected in series and parallel with the first lead through the conductive lines. With this configuration, as can be seen from the parallel current division, the current in the parallel branch is half of the original current when the voltage is the same; therefore, the series-parallel connection method adopted in this embodiment can effectively reduce the branch current, enabling the hollow cup brushless motor to withstand a larger current.

[0032] Specifically, see the attached document. Figure 7The adapter plate 40 is provided with an A-phase connection terminal, a B-phase connection terminal, a C-phase connection terminal, and a common connection terminal. In this embodiment, the adapter plate 40 is provided with 24 wire slots 41. The output terminals 32 of the armature coil 30 corresponding to each wire slot 41 are defined as 1, 2, 3...24 respectively. The output terminals 32 of the armature coil 30 connected to the A-phase connection terminal are defined as the A-phase winding. The A-phase winding consists of two windings LA1 and LA2. The LA1 winding includes 1, 2, 8, and 7 connected in series in sequence. The LA2 winding includes 13, 14, 20, and 19 connected in series in sequence. The beginning ends of the LA1 winding and the LA2 winding are connected to the A-phase connection terminal, and the end ends of the LA1 winding and the LA2 winding are connected to the common connection terminal, so that the LA1 winding and the LA2 winding form a closed parallel circuit in the A-phase winding, with equal voltage current division, so that the current in the windings at both ends of LA1 and LA2 is only 1 / 2 of the total current of the A-phase. The output terminal 32 of the armature coil 30 connected to the B-phase connection terminal is defined as the B-phase winding. The B-phase winding consists of two windings LB1 and LB2. The LB1 winding includes windings 5, 6, 12, and 11 connected in series in sequence. The LB2 winding includes windings 17, 18, 24, and 23 connected in series in sequence. The beginning ends of the LB1 and LB2 windings are connected to the B-phase connection terminal, and the end ends of the LB1 and LB2 windings are connected to the common connection terminal, so that the LB1 and LB2 windings form a closed parallel circuit in the B-phase winding, with equal voltage current division, so that the current in the windings at both ends of LB1 and LB2 is only 1 / 2 of the total B-phase current. The output terminal 32 of the armature coil 30 connected to the C-phase connection terminal is defined as the C-phase winding. The C-phase winding consists of two windings, LC1 and LC2. The LC1 winding includes windings 9, 10, 16, and 15 connected in series, and the LC2 winding includes windings 21, 22, 4, and 3 connected in series. The beginning ends of the LC1 and LC2 windings are connected to the C-phase connection terminal, and the end ends of the LC1 and LC2 windings are connected to the common connection terminal. This allows the LC1 and LC2 windings to form a closed parallel circuit in the C-phase winding, achieving equal voltage current division, so that the current in the windings at both ends of LC1 and LC2 is only 1 / 2 of the total C-phase current. Through the above connection method, a star connection structure is formed between the armature coil 30 and the adapter plate 40.

[0033] As a preferred embodiment of the above embodiments, refer to Figure 6The second support 70 includes an annular member 71, with a through hole 72 in the middle for the shaft 81 of the rotor assembly 80 to pass through. At least two connecting posts 73 are provided on the side of the annular member 71 facing the adapter plate 40, and the annular member 71 is fixedly connected to the adapter plate 40 via the connecting posts 73. The annular member 71 has a protrusion 74 protruding towards the adapter plate 40, and the Hall plate 60 is mounted on the free end of the protrusion 74. This arrangement serves two purposes: firstly, the protrusion 74 of the annular member 71 supports and fixes the Hall plate 60; secondly, the annular member 71 is positioned between the Hall plate 60 and the rotor assembly 80 to prevent direct impact on the Hall plate 60 during installation into the receiving cavity 31, which could damage the Hall chip in the Hall plate 60. Simultaneously, after the Hall plate 60 is installed, the sensing distance between the Hall chip and the magnet 82 of the rotor assembly 80 must be at most 5mm to ensure that the Hall chip can accurately measure the position of the magnet 82 to obtain the rotation angle information of the rotor assembly 80.

[0034] Furthermore, the second support 70 includes two connecting posts 73, which are symmetrically arranged around the axis of the annular member 71. This arrangement ensures the lateral force balance of the annular member 71 through the symmetrically arranged connecting posts 73, which helps to improve the stability of the annular member 71.

[0035] As a preferred embodiment, the housing 10, stator core 20, armature coil 30, adapter plate 40, and Hall plate 60 are potted to form an integral stator structure. This design eliminates the risk of the armature coil 30 detaching after prolonged operation of the coreless brushless motor, improves the electrical insulation performance of the coreless brushless motor, optimizes heat dissipation efficiency, enhances resistance to external impacts, and extends the service life of the coreless brushless motor. Furthermore, after potting the stator assembly, the gap between the inner hole of the potting compound and the outer circle of the rotor assembly 80 must be at least 0.2 mm to prevent friction between the stator and rotor.

[0036] To achieve the above objectives, the present invention proposes a coreless brushless motor, which includes a rotor assembly 80 and a stator assembly as described in any of the above embodiments. The specific structure of the stator assembly can be referred to the above embodiments. Since this coreless brushless motor adopts all the technical solutions of all the above embodiments, it possesses at least all the beneficial effects brought about by the technical solutions of the above embodiments, which will not be elaborated further here.

[0037] Specifically, refer to Figures 1 to 3The rotor assembly 80 includes a shaft 81 and magnets 82 sleeved around the shaft 81, with the magnets 82 located within the receiving cavity 31. Specifically, the magnets 82 employ a segmented magnet design. Unlike the integral magnets 82 in existing technologies, the segmented magnets 82 divide the rotor magnetic circuit into several independent segments. Each segment of magnet 82 can be magnetized according to an ideal orientation, resulting in a more concentrated and regular magnetic field distribution and a significant improvement in the overall air gap magnetic flux density. Simultaneously, the naturally formed inter-pole gaps between the magnets 82 act as magnetic shielding, effectively suppressing inter-pole leakage and sudden changes in local magnetic fields, resulting in a smoother electromagnetic torque output and further reducing pulsation and noise during low-speed operation.

[0038] Furthermore, a metal sheath 83 is fitted around the magnet 82. This arrangement, with the metal sheath 83 surrounding the magnet 82, effectively provides the rotor assembly 80 with a continuous clamping ring, firmly pressing the segmented magnets 82 radially against the shaft 81, completely eliminating the risk of the magnets 82 flying off during high-speed rotation. The high tensile strength of the sheath replaces the centrifugal tension borne by the magnets 82 themselves, preventing overstress cracking or demagnetization. The metal sheath 83 also forms part of a closed magnetic circuit, reducing inter-pole leakage flux, increasing the effective component of the air gap magnetic flux density, and resulting in a more abundant electromagnetic torque output.

[0039] Specifically, refer to Figures 1 to 3 The hollow cup brushless motor includes a front cover 91 and a rear cover 92, which are respectively disposed at both axial ends of the housing 10. A first bearing 911 is installed inside the front cover 91, and a second bearing 921 is installed inside the rear cover 92. Both ends of the rotating shaft 81 are respectively fitted with the first bearing 911 and the second bearing 921. This arrangement ensures the stability of the rotor assembly 80 relative to the stator assembly when rotating.

[0040] It should be noted that other aspects of the hollow cup brushless motor and its stator assembly disclosed in this invention are prior art and will not be repeated here.

[0041] The above are merely optional embodiments of the present invention and do not limit the patent scope of the present invention. Any application of the present invention directly or indirectly in other related technical fields is included within the patent protection scope of the present invention.

Claims

1. A stator assembly for a hollow cup brushless motor, characterized in that, The stator assembly includes: The device consists of a housing, a stator core, and an armature coil, arranged sequentially from the outside to the inside. The armature coil has a receiving cavity in the middle, which is used to accommodate the rotor assembly of the hollow cup brushless motor. An adapter plate is fixedly mounted on the end of the stator core via a first bracket; the adapter plate is used to connect the output end of the armature coil to a first lead wire, wherein the first lead wire is connected to an external device. A Hall plate is fixedly mounted on the adapter plate via a second bracket, and the Hall plate is located on the side of the adapter plate closer to the rotor assembly; the Hall plate is used to acquire the rotation angle information of the rotor assembly, and the Hall plate is connected to an external device via a second lead wire.

2. The stator assembly as claimed in claim 1, characterized in that: The first bracket has a cylindrical structure. One end of the first bracket along its axial direction is fixedly connected to the stator core. The other end of the first bracket along its axial direction is provided with an annular recess. The adapter plate is fitted and connected to the recess.

3. The stator assembly as claimed in claim 1, characterized in that: The adapter plate has several wire-passing grooves along its outer periphery, and each wire-passing groove corresponds to a lead-out end of the armature coil; the lead-out end of the armature coil is connected to the wire-passing groove.

4. The stator assembly as claimed in claim 1, characterized in that: The thickness of the adapter plate is greater than the thickness of the Hall plate; and / or, the adapter plate is provided with series and parallel conductive lines, and the output terminal of the armature coil is connected in series and parallel with the first lead through the conductive lines.

5. The stator assembly as claimed in claim 1, characterized in that: The second bracket includes an annular component, the middle of which has a through hole for the shaft of the rotor assembly to pass through; at least two connecting posts are provided on the side of the annular component facing the adapter plate, and the annular component is fixedly connected to the adapter plate through the connecting posts; the annular component has a protrusion protruding towards the adapter plate, and the Hall plate is mounted on the free end of the protrusion.

6. The stator assembly as claimed in claim 5, characterized in that: The second bracket includes two connecting columns, which are symmetrically arranged about the axis of the annular member.

7. The stator assembly as claimed in any one of claims 1 to 6, characterized in that: The housing, the stator core, the armature coil, the adapter plate, and the Hall plate are potted to form an integral stator structure.

8. A hollow cup brushless motor, characterized in that: The hollow cup brushless motor includes a rotor assembly and a stator assembly as described in any one of claims 1 to 7.

9. The hollow cup brushless motor as described in claim 8, characterized in that: The rotor assembly includes a rotating shaft and a magnet sleeved around the rotating shaft, the magnet being located within the receiving cavity; and the magnet is surrounded by a metal sheath.

10. The hollow cup brushless motor as described in claim 9, characterized in that: The hollow cup brushless motor includes a front cover and a rear cover, which are respectively disposed at both ends of the housing along the axial direction. Furthermore, a first bearing component is installed inside the front end cover, and a second bearing component is installed inside the rear end cover; the two ends of the rotating shaft are respectively sleeved on the first bearing component and the second bearing component.

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