A small-diameter brushless DC motor

Abstract

This application provides a small-diameter brushless DC motor, belonging to the technical field of motor structures for servo motors. Specifically, it includes a housing, a stator assembly, a stator key, and a rotor assembly. The stator assembly is sleeved around the outer periphery of the rotor assembly and fixed inside the housing. The stator assembly includes a stator core and stator windings. A straight slot corresponding to the stator core and extending along the axial direction of the stator assembly is provided on the inner wall of the housing. The stator key is fixed in the straight slot. A positioning groove cooperating with the stator key is provided on the outer wall of the stator core. An annular groove is provided on the inner wall of the housing, corresponding to the portion of the stator winding extending beyond the end face of the stator core. Adhesive is filled in the annular groove and between the portion of the stator winding extending beyond the end face of the stator core and the inner wall of the housing. Through the solution of this application, the reliability of the motor is improved while ensuring that the small-diameter motor achieves the required load performance.

Description

Technical Field

[0001] This application relates to the field of motor structures for servo motors, and more particularly to a small-diameter brushless DC motor. Background Technology

[0002] Brushless DC motors are used in the mechanical self-locking mechanism of the missile's front section. This mechanism is the self-locking system of the servo motors in various missile systems, and its reliability directly determines the missile's accuracy. With the rapid development of the ground weaponry industry, electric missile servo motors have gradually replaced pneumatic and hydraulic servo motors. To meet the requirements of longer range and higher accuracy, the requirements for the diameter and reliability of motors are becoming increasingly stringent. In existing technology, for 24VDC brushless DC motors with a diameter of 22mm, the stator outer diameter and housing inner diameter are increased to achieve the required load performance. This results in an excessively thin housing and a shallow stator key embedding depth, which easily leads to stator misalignment during motor operation. Summary of the Invention

[0003] In view of this, this application provides a small-diameter brushless DC motor, which solves the problems in the prior art and improves the reliability of the motor while ensuring that the small-diameter motor achieves the required load performance.

[0004] The small-diameter brushless DC motor provided in this application adopts the following technical solution:

[0005] A small-diameter brushless DC motor includes a housing, a stator assembly, a stator key, and a rotor assembly. The stator assembly is sleeved on the outer periphery of the rotor assembly and fixed inside the housing. The stator assembly includes a stator core and a stator winding. A straight slot corresponding to the stator core and extending along the axial direction of the stator assembly is provided on the inner wall of the housing. The stator key is fixed in the straight slot. A positioning groove that mates with the stator key is provided on the outer wall of the stator core. An annular groove is provided on the inner wall of the housing, corresponding to the portion of the stator winding extending out of the end face of the stator core. Adhesive is filled in the annular groove and between the portion of the stator winding extending out of the end face of the stator core and the inner wall of the housing.

[0006] Optionally, the rotor assembly includes a rotating shaft, a bushing, a front dynamic balancing ring, a rear dynamic balancing ring, a plurality of N-pole magnets and a plurality of S-pole magnets. The bushing is fitted onto the rotating shaft, the front dynamic balancing ring is fitted onto the rotating shaft at one end of the bushing, and the rear dynamic balancing ring is fitted onto the rotating shaft at the other end of the bushing. The N-pole magnets and S-pole magnets are alternately distributed around the bushing in the circumferential direction, and the N-pole magnets and S-pole magnets are fixed on the bushing.

[0007] Optionally, the outer sidewall of the bushing has a polygonal cross-section perpendicular to the axial direction, and the N-pole magnet and the S-pole magnet are bonded to the plane of the bushing sidewall.

[0008] Optionally, the inner sides of the opposite end faces of the front and rear dynamic balancing rings are provided with annular grooves, and both ends of the N-pole magnet and the S-pole magnet are provided with bosses that extend into the annular grooves.

[0009] Optionally, the housing has openings at both ends, one end of the housing is fixedly connected to the front cover, and the other end is fixedly connected to the rear cover. The front cover and the rear cover have positioning holes at their mounting points. The front cover and the rear cover are made of stainless steel, and the front cover and the rear cover have bearing chambers inside.

[0010] Optionally, the outer side of the inner wall of the housing is chamfered.

[0011] Optionally, the front end of the rotor assembly's shaft is connected to the bearing chamber of the front cover via a first bearing, and the rear end of the rotor assembly's shaft is connected to the bearing chamber of the rear cover via a second bearing. The bearing chamber of the front cover is equipped with a ball bearing disc spring, which is positioned at the end of the first bearing opposite to the second bearing. The ball bearing disc spring applies axial preload to the circumferential sidewall of the first bearing. The bearing chamber of the rear cover is equipped with a perforated elastic retaining ring, which abuts against the end face of the second bearing opposite to the first bearing.

[0012] Optionally, it also includes a circuit assembly, which includes a circuit board, a Hall sensor, and a multilayer ceramic capacitor. The circuit board is an epoxy double-sided glass cloth board, and a high-temperature insulating varnish layer is coated on the circuit board. The Hall sensor and the multilayer ceramic capacitor are fixed on the circuit board.

[0013] Optionally, it also includes a sensor rotor, which includes a sensor magnetic ring, an upper sensor pad, and a lower sensor pad arranged coaxially. The upper sensor pad and the lower sensor pad are respectively fixed on the two end faces of the sensor magnetic ring. The inner ring of the sensor magnetic ring is provided with a flat bottom platform, which is fixed on a flat shaft at the end of the rotating shaft away from the front cover. The N and S pole positions of the sensor magnetic ring correspond to the N and S pole positions of the rotor assembly.

[0014] In summary, this application includes the following beneficial technical effects:

[0015] To ensure motor reliability, stator keys are installed and welded into the straight slots to prevent circumferential rotation of the stator assembly during motor operation. High-temperature resistant organic adhesive is then applied to the annular grooves to prevent axial displacement of the stator assembly during operation, thus resolving the problem of stator misalignment during motor operation. Attached Figure Description

[0016] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a schematic diagram of the overall structure of the small-diameter brushless DC motor of this application;

[0018] Figure 2 This is a schematic diagram of the structure of the housing and stator assembly of this application;

[0019] Figure 3 This is a schematic diagram of the shell structure of this application;

[0020] Figure 4 This is a structural diagram of the stator assembly of this application;

[0021] Figure 5 This is a schematic diagram of the rotor assembly of this application;

[0022] Figure 6 This is a cross-sectional view of the rotor assembly of this application;

[0023] Figure 7 This is a schematic diagram of the circuit components of this application;

[0024] Figure 8 This is a structural diagram of the sensor rotor in this application.

[0025] Explanation of reference numerals in the attached drawings: 1. Protective cover; 3. Hexagonal thin nut; 4. Sensor rotor; 41. Lower sensor gasket; 42. Sensor magnetic ring; 43. Upper sensor gasket; 6. Circuit assembly; 61. Circuit board; 62. Hall sensor; 63. Multilayer ceramic capacitor; 7. Hole retaining ring; 8. Second bearing; 9. Bearing gasket; 10. Housing; 101. Front cover; 102. Stator assembly; 1021. Stator... Sub-winding; 1022, Stator core; 104, Stator key; 105, Rear cover; 106, Annular groove; 107, Straight groove; 108, Positioning hole; 11, Rotor assembly; 111, Front dynamic balance ring; 112, Shaft; 113, Rear dynamic balance ring; 114, N pole magnet; 115, S pole magnet; 116, Boss; 117, Bushing; 118, Groove; 12, First bearing; 13, Ball bearing disc spring. Detailed Implementation

[0026] The embodiments of this application will now be described in detail with reference to the accompanying drawings.

[0027] The following specific examples illustrate the implementation of this application. Those skilled in the art can easily understand other advantages and effects of this application from the content disclosed in this specification. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. This application can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of this application. It should be noted that, in the absence of conflict, the following embodiments and features in the embodiments can be combined with each other. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0028] It should be noted that various aspects of embodiments within the scope of the appended claims are described below. It will be apparent that the aspects described herein can be embodied in a wide variety of forms, and any particular structure and / or function described herein is merely illustrative. Based on this application, those skilled in the art will understand that one aspect described herein can be implemented independently of any other aspect, and two or more of these aspects can be combined in various ways. For example, any number of aspects set forth herein can be used to implement the device and / or practice the method. Additionally, this device and / or method can be implemented using structures and / or functionalities other than one or more of the aspects set forth herein.

[0029] It should also be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of this application. The drawings only show the components related to this application and are not drawn according to the actual number, shape and size of the components in the actual implementation. In the actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0030] Furthermore, specific details are provided in the following description to facilitate a thorough understanding of the examples. However, those skilled in the art will understand that the described aspects can be practiced without these specific details.

[0031] This application provides a small-diameter brushless DC motor.

[0032] like Figures 1-3As shown, a small-diameter brushless DC motor includes a housing 10, a stator assembly 102, a stator key 104, and a rotor assembly 11. The stator assembly 102 is sleeved on the outer periphery of the rotor assembly 11 and fixed inside the housing 10. The stator assembly 102 includes a stator core 1022 and a stator winding 1021. The inner wall of the housing 10 is provided with straight slots corresponding to the stator core 1022 and extending along the axial direction of the stator assembly 102. 107, the stator key 104 is fixed in the straight slot 107, the outer wall of the stator core 1022 is provided with a positioning groove that cooperates with the stator key 104, the inner wall of the housing 10 is provided with an annular groove 106, the annular groove 106 corresponds to the part of the stator winding 1021 that extends out of the end face of the stator core 1022, and adhesive is filled in the annular groove 106 and between the part of the stator winding 1021 that extends out of the end face of the stator core 1022 and the inner wall of the housing 10.

[0033] To improve motor load performance while ensuring structural strength, the stator outer diameter is increased to reduce iron losses. Increasing the stator outer diameter increases the radial length of the stator slots and the slot area, allowing for thicker wire diameters and reducing copper losses, thereby improving motor efficiency and stall torque, and reducing temperature rise. The housing 10 is made of stainless steel. The increased stator outer diameter results in a thinner housing 10 wall, with a minimum wall thickness of 0.35mm. To ensure motor reliability, stator keys 104 are installed and welded into the straight slots 107 to prevent circumferential rotation of the stator assembly 102 during operation. High-temperature resistant organic adhesive is used to seal the annular grooves 106 to prevent axial displacement of the stator assembly 102 during operation, thus resolving the issue of stator misalignment during motor operation.

[0034] like Figure 4 As shown, the stator core 1022 assembly is composed of multiple stator laminations stacked together, using the inner hole of the stator laminations as a reference, and then stator end plates are glued to both ends with adhesive. After the laminations are stacked, the outer and inner diameters of the stator core 1022 assembly need to be machined to ensure the fit dimensions between the core assembly and the inner wall of the housing 10, and to prevent the rotor from rubbing against the stator core 1022 during motor operation. The stator end plates are made of epoxy glass cloth laminate to ensure the insulation characteristics of the stator. The stator laminations are stamped from soft magnetic aluminum alloy strips and have 18 evenly distributed stator slots. The slots are sloping shoulder flat bottom slots and have a stator key 104 slot to facilitate the positioning of the laminations during the stacking process and ensure product consistency. The stator winding 1021 is made of polyesterimide enameled round copper wire, and is wound with two enameled wires of different diameters to form a double wire. Each phase winding has one winding lead.

[0035] like Figure 5 and Figure 6The rotor assembly 11 includes a rotating shaft 112, a bushing 117, a front dynamic balancing ring 111, a rear dynamic balancing ring 113, a plurality of N-pole magnets 114, and a plurality of S-pole magnets 115. The bushing 117 is fitted onto the rotating shaft 112. The front dynamic balancing ring 111 is fitted onto the rotating shaft 112 at one end of the bushing 117, and the rear dynamic balancing ring 113 is fitted onto the rotating shaft 112 at the other end of the bushing 117. The N-pole magnets 114 and S-pole magnets 115 are alternately distributed around the bushing 117 in the circumferential direction and are fixed to the bushing 117. The bushing 117 and the shaft are coated with an anaerobic adhesive layer, and laser welding is performed after assembly to ensure the tightness of the assembly connection.

[0036] The outer wall of the bushing 117 has a polygonal cross-section perpendicular to the axial direction, and the N-pole magnet 114 and S-pole magnet 115 are bonded to the plane of the side wall of the bushing 117. In one embodiment, the outer wall of the bushing 117 is hexagonal with six planes.

[0037] The inner sides of the opposite end faces of the front dynamic balancing ring 111 and the rear dynamic balancing ring 113 are provided with annular grooves 118. Both ends of the N-pole magnet 114 and the S-pole magnet 115 are provided with bosses 116 extending into the annular grooves 118. This prevents them from falling off during motor operation and improves motor reliability. The front and rear dynamic balancing rings 113 are bonded to the shaft with adhesive and fixed with laser welding to ensure the rotor's structural strength. After assembly, the outer diameter of the magnets is machined to ensure the rotor's outer diameter and roundness, preventing friction between the motor and stator during operation and ensuring the distribution of the rotor's circumferential magnetic field. After machining, weight reduction is used at the front and rear dynamic balancing rings 113 to adjust the dynamic balance, ensuring smooth rotor operation.

[0038] The housing 10 has openings at both ends. One end of the housing 10 is fixedly connected to the front cover 101, and the other end is fixedly connected to the rear cover 105. Positioning holes 108 are provided at the assembly points of the front cover 101 and the rear cover 105 to ensure product consistency during assembly. After assembly, the housing 10 and the front and rear covers 105 are laser-welded to ensure the structural strength of the motor. The front cover 101 and the rear cover 105 are made of stainless steel and contain bearing chambers. When selecting materials, materials with a small difference in thermal expansion coefficient compared to the bearing, or materials of the same type, are chosen to avoid compression or loosening of the bearing outer wall under high or low temperature conditions, thereby improving the reliability of the motor and reducing abnormal noise during operation. The specific difference in the thermal expansion coefficients of the materials can be selected based on actual conditions, such as a difference of less than 2 micrometers / degree Celsius. The rear cover 105 of the housing 10 has lead wire holes and is chamfered to prevent the insulation layer of the winding leads from being scratched, ensuring the insulation performance of the motor.

[0039] The outer side of the inner wall of the housing 10 is chamfered. This prevents sharp edges from damaging the insulating varnish layer of the stator winding 1021 during the press-fitting of the stator assembly 102, thus ensuring the insulation withstand voltage characteristics of the motor.

[0040] The front end of the rotor assembly 11's shaft 112 is connected to the bearing chamber of the front cover 101 via a first bearing 12, and the rear end of the rotor assembly 11's shaft 112 is connected to the bearing chamber of the rear cover 105 via a second bearing 8. A ball bearing disc spring 13 is provided in the bearing chamber of the front cover 101. The ball bearing disc spring 13 is positioned at the end of the first bearing 12 opposite to the second bearing 8. The ball bearing disc spring 13 applies axial preload to the circumferential sidewall of the first bearing 12. The outer diameter of the ball bearing disc spring 13 is larger than the outer diameter of the first bearing 12, and the outer ring of the ball bearing disc spring 13 abuts against the circumferential sidewall of the first bearing 12, applying radial preload to the circumferential sidewall of the first bearing 12. This ensures a gapless connection between the rotor, bearing, and housing 10, reducing vibration and extending the motor's service life. The bearing chamber of the rear cover 105 is provided with a perforated elastic retaining ring 7, which abuts against the end face of the second bearing 8 facing away from the first bearing 12. The end face of the second bearing 8 facing the first bearing 12 is provided with a bearing gasket 9 that abuts against the inner wall of the bearing chamber of the rear cover 105.

[0041] like Figure 7 As shown, the small-diameter brushless DC motor also includes a circuit assembly 6, which comprises a circuit board 61, a Hall sensor 62, and a multilayer ceramic capacitor 63. The circuit board 61 is an epoxy double-sided glass cloth board coated with a high-temperature insulating varnish layer. The Hall sensor 62 and the multilayer ceramic capacitor 63 are fixed to the circuit board 61. The circuit board 61 has two circular holes for binding and fixing the lead wires of the circuit board 61 with cotton thread, and then coating it with high-temperature insulating varnish to ensure insulation properties. The circuit board 61 also has two semi-circular slots for changing the circumferential position of the circuit board 61 assembly during motor debugging. After the electronic components are soldered onto the circuit board 61, it is potted and fixed with adhesive to ensure the mechanical strength of the circuit board 61 assembly. Both sides of the circuit board 61 are coated with a three-proof protective agent to isolate oxygen and prevent mold growth in humid environments.

[0042] like Figure 1 and Figure 8As shown, the small-diameter brushless DC motor also includes a sensor rotor 4. The end of the sensor rotor 4 away from the inner side of the housing 10 is provided with a hexagonal thin nut 3 threadedly connected to the rotating shaft 112 to fix the sensor rotor 4 on the rotating shaft 112. The sensor rotor 4 includes a sensor magnetic ring 42, an upper sensor gasket 43, and a lower sensor gasket 41 arranged coaxially. The upper sensor gasket 43 and the lower sensor gasket 41 are respectively fixed on the two end faces of the sensor magnetic ring 42. The inner ring of the sensor magnetic ring 42 is provided with a flat bottom platform, which is fixed on the flat shaft of the rotating shaft 112 away from the front cover 101. The N and S pole positions of the sensor magnetic ring 42 correspond to the N and S pole positions of the rotor assembly 112. Specifically, with the flat bottom direction as the reference, the magnetic ring is symmetrically saturated with six poles in the radial direction, so that the N and S pole positions of the sensor magnetic ring 42 correspond to the N and S pole positions of the rotor assembly 11, ensuring that the Hall element accurately positions the motor operation. The rear cover 105 is provided with a protective cover 1 that covers the sensor rotor 4. The protective cover 1 is made of stainless steel and is fixed to the rear cover 105 of the housing 10 by slotted countersunk screws, which serves to protect the circuit board 61 assembly, the rotor assembly 11 and the sensor rotor 4.

[0043] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A small-diameter brushless DC motor, characterized in that, The device includes a housing, a stator assembly, a stator key, and a rotor assembly. The stator assembly is sleeved on the outer periphery of the rotor assembly and fixed inside the housing. The stator assembly includes a stator core and a stator winding. The inner wall of the housing has a straight groove corresponding to the stator core and extending along the axial direction of the stator assembly. The stator key is fixed in the straight groove. The outer wall of the stator core has a positioning groove that mates with the stator key. The inner wall of the housing has an annular groove corresponding to the portion of the stator winding that extends out of the end face of the stator core. Adhesive is filled in the annular groove and between the portion of the stator winding that extends out of the end face of the stator core and the inner wall of the housing. The rotor assembly includes a rotating shaft, a bushing, a front dynamic balancing ring, a rear dynamic balancing ring, a plurality of N-pole magnets and a plurality of S-pole magnets. The bushing is fitted onto the rotating shaft. The front dynamic balancing ring is fitted onto the rotating shaft at one end of the bushing, and the rear dynamic balancing ring is fitted onto the rotating shaft at the other end of the bushing. The N-pole magnets and S-pole magnets are alternately distributed around the bushing in the circumferential direction, and the N-pole magnets and S-pole magnets are fixed on the bushing. The outer sidewall of the bushing has a polygonal cross-section perpendicular to the axial direction, and the N-pole magnet and the S-pole magnet are bonded to the plane of the sidewall of the bushing. The inner sides of the opposite end faces of the front and rear dynamic balancing rings are provided with annular grooves, and both ends of the N-pole magnet and the S-pole magnet are provided with bosses that extend into the annular grooves. The housing has openings at both ends. One end of the housing is fixedly connected to the front cover, and the other end is fixedly connected to the rear cover. The front cover and the rear cover have positioning holes at their connection points. The front cover and the rear cover are made of stainless steel, and the front cover and the rear cover have bearing chambers inside.

2. The small-diameter brushless DC motor according to claim 1, characterized in that, The outer side of the inner wall of the shell is chamfered.

3. The small-diameter brushless DC motor according to claim 1, characterized in that, The front end of the rotor assembly's shaft is connected to the bearing chamber of the front cover via a first bearing, and the rear end of the rotor assembly's shaft is connected to the bearing chamber of the rear cover via a second bearing. The bearing chamber of the front cover is equipped with a ball bearing disc spring, which is located at the end of the first bearing opposite to the second bearing. The ball bearing disc spring is used to apply axial preload to the circumferential sidewall of the first bearing. The bearing chamber of the rear cover is equipped with a perforated elastic retaining ring, which abuts against the end face of the second bearing opposite to the first bearing.

4. The small-diameter brushless DC motor according to claim 1, characterized in that, It also includes circuit components, which include a circuit board, a Hall sensor, and a multilayer ceramic capacitor. The circuit board is an epoxy double-sided glass cloth board, and a high-temperature insulating varnish layer is coated on the circuit board. The Hall sensor and the multilayer ceramic capacitor are fixed on the circuit board.

5. The small-diameter brushless DC motor according to claim 1, characterized in that, It also includes a sensor rotor, which includes a sensor magnetic ring, an upper sensor pad, and a lower sensor pad arranged coaxially. The upper and lower sensor pads are respectively fixed on the two end faces of the sensor magnetic ring. The inner ring of the sensor magnetic ring is provided with a flat bottom platform, which is fixed on a flat shaft at the end of the rotating shaft away from the front cover. The N and S pole positions of the sensor magnetic ring correspond to the N and S pole positions of the rotor assembly.

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