Miniature resolver and air core cup motor
By designing a miniature rotary transformer, using a toroidal steel sheet stator and stacked excitation and output coils, the problems of insufficient measurement accuracy of Hall sensors and weak signals of rotary transformers in coreless motors are solved. This achieves high-precision angle and speed measurement, reduces production costs, and is suitable for high-precision control applications.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- CHANGZHOU HUAXUAN SENSING TECH CO LTD
- Filing Date
- 2025-08-08
- Publication Date
- 2026-07-14
AI Technical Summary
In the existing technology, the Hall sensor of the coreless motor has insufficient measurement accuracy, and there is a lack of existing high-precision angle sensors. The rotary transformer processed by PCB board has weak current carrying capacity and insufficient signal output in small size, making it difficult to meet the requirements of high-precision control.
Design a miniature rotary transformer that uses a toroidal steel sheet stator and stacked excitation and output coils wound with enameled wire. The number of coil turns and thickness are limited. The rotor adopts a pole leaf structure. The coils are fixed with glue to ensure that the rotary transformer structure is compact and has high signal strength.
It achieves high-precision angle and speed measurement, improves signal output strength, reduces production costs, meets the complex control requirements of coreless motors, and is suitable for high-precision control applications.
Smart Images
Figure CN224503130U_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of displacement sensor technology, and specifically relates to a miniature rotary transformer suitable for a hollow cup motor and the hollow cup motor itself. Background Technology
[0002] Against the backdrop of the booming development of modern robotics technology, coreless motors have been widely used in the field of robot joint drive due to their unique advantages.
[0003] In existing technologies, coreless motors typically use Hall effect sensors to acquire angular position and angular velocity information. However, Hall effect sensors have certain limitations, including limited measurement accuracy, which leads to insufficient precision in motor control. In applications requiring high motor control accuracy, such as precision instruments and the finger joints of humanoid robots, existing Hall effect sensor measurement solutions are insufficient to meet practical needs. More importantly, there is a severe shortage of high-precision angle sensors specifically designed for coreless motors on the market.
[0004] In existing technologies, eddy current rotary transformers generally use PCB boards to process the excitation coil and output coil. Due to the limited size of coreless motors, using PCB boards to process rotary transformers for coreless motors has several drawbacks. First, the small size of the PCB board increases the processing difficulty and drastically raises the cost. Second, as the PCB board becomes smaller, the volume of the conductors embedded inside also becomes smaller, which reduces the current it can withstand and results in a weaker output voltage signal, making it difficult for the decoding chip to capture. Summary of the Invention
[0005] To address the shortcomings of existing technologies, this invention designs a miniature rotary transformer suitable for hollow cup motors, and a hollow cup motor having the miniature rotary transformer.
[0006] The technical solution of the present invention is as follows:
[0007] A miniature rotary transformer includes a stator, a rotor, an excitation coil, and an output coil. The stator is a ring-shaped steel sheet with an outer diameter of 13 mm and a thickness of 0.1 mm. Multiple coil units are arranged on the surface of the stator. Each coil unit includes stacked output coils and excitation coils. The excitation coil is fixed to the surface of the stator, and the output coil is stacked on top of the excitation coil. The thickness ratio between the output coil and the excitation coil is 3:1. This invention limits the outer diameter of the stator, ensuring that the miniature rotary transformer can be assembled into a coreless motor to meet the requirements of the application scenario. Secondly, the structure of the coil units is limited; the excitation coil and output coil are arranged in a stacked manner, making the rotary transformer structure more compact and smaller in size. Furthermore, the thickness of the output coil and excitation coil is limited; the thickness depends on the number of turns of the coil. While ensuring that the size requirements of the application scenario are met, it is beneficial to arrange a larger number of turns in the output coil, thereby obtaining a reasonable output amplitude.
[0008] Furthermore, the stator surface is provided with 16 coil units, which are racetrack-shaped windings. The width of each coil unit is 1.5mm and the length is 2.8mm, which maximizes the winding area. In addition, the coil structure is symmetrical, which optimizes the distribution of the magnetic field and is more conducive to the magnetic field coupling of the output coil.
[0009] Furthermore, the thickness of the excitation coil is 0.1 mm, and the thickness of the output coil is 0.3 mm. The thickness of the excitation coil and the output coil are limited here to ensure that the miniature rotary transformer can be used in a coreless motor.
[0010] Furthermore, the output coil and excitation coil are made of enameled wire with a diameter of 0.1mm. Compared with the wiring on the PCB board, the use of enameled wire increases the wire diameter, allowing a larger current to pass through, which increases the output voltage amplitude of the output coil and makes the signal easier for the decoding chip to capture.
[0011] Furthermore, the number of turns in a single layer of the excitation coil and output coil is less than or equal to 7. Due to the limitations on wire diameter and thickness mentioned earlier, the number of turns in a single layer of the excitation coil and output coil must be less than or equal to 7, thereby ensuring the thickness of the excitation coil and output coil and meeting the volume requirements of the coreless motor.
[0012] Furthermore, the excitation coil has 5 turns, and the winding directions of adjacent excitation coils are opposite. The specific number of turns of the excitation coil is given here. Using the excitation coil with the above number of turns can obtain a reasonable output amplitude and better ensure the reliability of the resolver signal.
[0013] Furthermore, the output coil has 14 turns, and the output coils of the 16 coil units are divided into two groups: one group is the SIN winding and the other group is the COS winding. The SIN winding and the COS winding are spaced apart. The coils of the SIN winding are connected in series with each other, and the coils of the COS winding are also connected in series with each other. The winding directions of the coils of adjacent SIN windings are opposite, and the winding directions of the coils of adjacent SIN windings and COS windings are opposite.
[0014] Furthermore, the rotor adopts a pole blade shape, and the rotor has 4 pole pairs.
[0015] Furthermore, the coil unit is fixed to the stator by adhesive.
[0016] A coreless motor, characterized in that it includes the aforementioned miniature rotary transformer, wherein the rotor is connected to the motor shaft, and the stator and coil unit are fixed to the end cover of the coreless motor.
[0017] In summary, the present invention has the following beneficial effects:
[0018] 1. This invention designs a miniature rotary transformer, which is assembled inside a coreless motor to meet the precision and complex control requirements of the coreless motor. Furthermore, the coils of this invention are arranged in a stacked manner, making the rotary transformer structure more compact, and the thickness of the excitation coil and the output coil are further limited.
[0019] While ensuring that the size requirements of the application scenario are met, it is beneficial to arrange more turns of the output coil, thereby obtaining a reasonable output amplitude, which in turn improves the detection accuracy of the miniature rotary transformer.
[0020] 2. This invention uses enameled wire windings, which increases the wire diameter and allows for a larger current to pass through. This results in a larger output voltage amplitude of the output coil, making the signal easier for the decoding chip to capture. On the other hand, using enameled wire for winding the output coil and excitation coil allows for in-house processing, eliminating the need for outsourcing. This reduces raw material and production costs and effectively controls the cost of the rotary transformer. Consequently, it also helps control the cost of the improved coreless motor, making the product more suitable for widespread application. Attached Figure Description
[0021] Figure 1 This is a three-dimensional schematic diagram of the miniature rotary transformer of the present invention;
[0022] Figure 2 This is a schematic diagram of the coil winding process of the present invention;
[0023] Figure 3This is a side view of the miniature rotary transformer of the present invention;
[0024] Figure 4 This is a three-dimensional schematic diagram of the stator (including coil units) of the present invention;
[0025] Figure 5 This is a cross-sectional schematic diagram of a hollow cup motor according to an embodiment of the present invention;
[0026] In the diagram, 1 represents the stator, 2 the rotor, 3 the excitation coil, 4 the output coil, and 5 the coil unit.
[0027] 6 is a rotary transformer, 7 is a coreless motor, 70 is a motor shaft, and 71 is an end cover. Detailed Implementation
[0028] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand and implement the present invention. However, the embodiments described are not intended to limit the present invention.
[0029] It should be noted that when a component is referred to as being "set on" or "fixed to" another component, it can be directly on the other component or there may be an intermediate component. When a component is referred to as being "fixed to" another component, or "fixedly connected" to another component, the fixing method can be detachable or non-detachable. When a component is considered to be "connected" or "rotatably connected" to another component, it can be directly connected to the other component or there may be an intermediate component. The terms "vertical," "horizontal," "left," "right," "upper," "lower," and similar expressions used are for illustrative purposes only and do not represent the only possible implementation.
[0030] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of this invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.
[0031] In this invention, terms such as "first," "second," and "third" are used not to represent specific quantities or orders, but merely to distinguish names.
[0032] With the development of coreless motors, the existing Hall sensor detection methods cannot meet the needs of coreless motor development. Therefore, it is necessary to develop a high-precision angle sensor suitable for coreless motors to help solve the problem of information acquisition in robot joints. Rotary transformers have the advantages of higher precision, accurate speed feedback and meeting complex control requirements. However, due to the small size of coreless motors, the installation space left for rotary transformers inside the coreless motor is small, so there is a problem in miniaturizing rotary transformers.
[0033] Figure 1 This is a three-dimensional schematic diagram of the miniature rotary transformer of the present invention. In the figure, 1 is the stator, 2 is the rotor, 3 is the excitation coil, and 4 is the output coil. To meet the requirements of miniaturization, the size and thickness of the stator are limited. The stator 1 is an annular steel sheet with an outer diameter of 13 mm and a thickness of 1 mm. Multiple coil units 5 are provided on the surface of the stator 1. Each coil unit 5 includes stacked output coils 4 and excitation coils 3. The excitation coil 3 is fixed to the surface of the stator 1, and the output coil 4 is stacked on the upper surface of the excitation coil 3. The thickness ratio between the output coil and the excitation coil is 3:1. Figure 3 In this invention, the thickness of the output coil is represented by H1, and the thickness of the excitation coil is represented by H2. By limiting the outer diameter of the stator, this invention ensures that the fabricated miniature rotary transformer can be assembled inside a coreless motor to meet the requirements of the application scenario. Secondly, the structure of the coil unit is limited, with the excitation coil and output coil arranged in a stacked manner, making the resolver structure more compact and smaller in size. Furthermore, the thickness of the output coil and excitation coil is limited. On the one hand, this ensures that the overall thickness of the coil unit is controllable, thereby ensuring that the overall thickness of the miniature rotary transformer meets the installation requirements of the coreless motor. On the other hand, the thickness of the output coil and excitation coil depends on the number of turns of the coil. While ensuring that the size requirements of the application scenario are met, it is beneficial to arrange more turns of the output coil to obtain a reasonable output amplitude, thereby improving the detection accuracy of the miniature rotary transformer.
[0034] See Figure 1 and Figure 3 As shown, the thickness of the excitation coil 3 is 0.1 mm, and the thickness of the output coil 4 is 0.3 mm. The thickness of the excitation coil and the output coil is limited here to ensure that the miniature rotary transformer can be installed inside the hollow cup motor.
[0035] See Figure 1As shown, the stator 1 has 16 coil units 5 on its surface. The coil units are racetrack-shaped windings. The width of each coil unit is 1.5 mm and the length is 2.8 mm. This embodiment limits the number of coil units on the stator surface, which further limits the size of each coil unit. Specifically, in this embodiment, each coil unit is 1.5 mm wide and 2.8 mm long, and the semicircles at both ends are semicircles with a diameter of 1.5 mm. The racetrack-shaped winding increases the area of the winding, making the winding area as large as possible and the winding arrangement as dense as possible. Furthermore, the racetrack-shaped coil has a symmetrical structure, which optimizes the distribution of the magnetic field and is more conducive to the magnetic field coupling of the output coil.
[0036] Figure 2 This is a schematic diagram of the coil winding of the present invention. The output coil and the excitation coil are wound with enameled wire with a diameter of 0.1mm. Compared with the wiring on the PCB board, using enameled wire to wind the output coil and the excitation coil has two advantages. First, since the rotary transformer in this embodiment is small in size, if the winding is made of PCB material, the conductive strip of the PCB board is small, and the current it can carry is limited. However, the winding made of enameled wire in this embodiment increases the wire diameter of the winding, allowing a larger current to pass through, which increases the output voltage amplitude of the output coil and makes the signal easier for the decoding chip to capture. Second, using enameled wire to wind the output coil and the excitation coil can be processed in-house without outsourcing, thereby reducing the raw material cost and production cost, effectively controlling the cost of the rotary transformer, and thus facilitating the cost control of the improved coreless motor, which is more conducive to the promotion and application of the product.
[0037] Furthermore, the number of turns in a single layer of the excitation coil and output coil is less than or equal to 7. Due to the limitations on wire diameter and thickness, as well as the size of the stator and the number of coil units, each coil unit occupies only a 22.5° sector area on the stator surface. In order to accommodate more winding turns and leave enough space to ensure that the units do not contact each other, the number of turns in a single layer of the excitation coil and output coil must be less than or equal to 7. This ensures that the thickness and width dimensions of the excitation coil and output coil meet the volume requirements of the coreless motor.
[0038] Furthermore, the excitation coil has 5 turns, and adjacent excitation coils are wound in opposite directions. A specific number of turns for the excitation coil is given here. Considering the tolerance requirements of actual production, this embodiment preferably uses 5 turns for the excitation coil. This facilitates coil winding and reduces processing difficulty. The excitation coil is referenced in one plane. Figure 2The winding diagram is used for winding, and the winding directions of adjacent excitation coils are opposite. When an AC excitation current of the same phase is passed through adjacent coils, they generate magnetic fields with opposite polarities in each adjacent excitation coil, thereby forming alternating N poles and S poles on the stator circumference, establishing a periodically changing magnetic field in space. This helps to ensure that the magnetic field is more uniform and symmetrical in the circumferential direction, and improves the consistency of the resolver's output signal.
[0039] Furthermore, the output coil 4 has 20 turns, and the output coils of the 16 coil units 5 are divided into two groups: one group is the SIN winding 40, and the other group is the COS winding 41. The SIN winding and COS winding are spaced apart. The coils of the SIN winding are connected in series, and the coils of the COS winding are also connected in series. The winding directions of adjacent SIN winding coils are opposite. In this embodiment, the number of turns of the output coil is limited. First, it meets the thickness requirements of the output coil and the excitation coil. On the one hand, it does not use the extreme number of turns, which facilitates the winding of the output coil, reduces the processing difficulty, and is more conducive to ensuring the dimensional accuracy of the coil unit. On the other hand, it is coordinated with the number of turns of the excitation coil to meet the transformation ratio requirements, thereby ensuring the measurement accuracy requirements. Specifically, in this embodiment, the output coil is stacked in three layers. The first layer of coil has 7 turns, the second layer of coil has 7 turns, and the third layer of coil has 6 turns.
[0040] join Figure 1 As shown, the rotor 2 adopts a pole blade shape, and the rotor has 4 pole pairs. First, the rotor is made of steel. Second, the maximum outer diameter of the rotor is 13mm, which is compatible with the outer diameter of the back cover of the hollow cup motor. The outer contour of the rotor is determined by calculation using formula ①.
[0041]
[0042] Furthermore, the coil unit 5 is fixed to the stator 1 by adhesive. The coil unit includes an excitation coil and an output coil, both of which are first wound with enameled wire. After processing, the excitation coil is first epoxy cured in a mold, and then the output coil is stacked and epoxy cured again, thus ensuring the positional accuracy between the excitation coil and the output coil. Furthermore, the coil unit is glued to the stator, which not only ensures the firmness of the fixation between the coil unit and the stator, but also ensures the accurate position of the coil unit on the stator, which is beneficial to improving the measurement accuracy. When an alternating current is passed through the excitation coil, an alternating magnetic field is generated around it. This magnetic field acts on the rotor through the stator and the air gap, thereby generating an induced electromotive force in the output coil. In this embodiment, the air gap between the rotor and the surface of the coil unit is 0.2 mm. The appropriate air gap size is crucial to ensuring the performance of the rotary transformer. If the air gap is too small, it is easy for friction and collision to occur between the rotor and the stator, affecting the normal operation of the rotary transformer. If the air gap is too large, the magnetic field transmission efficiency will be reduced, weakening the reactive electromotive force in the output coil, thereby reducing the measurement accuracy.
[0043] Figure 5 This is a cross-sectional view of a coreless motor according to an embodiment of the present invention. The coreless motor includes the aforementioned miniature rotary transformer 6. The rotor 2 is connected to the motor shaft 70, and the stator 1 and the coil unit are fixed to the end cover 71 of the coreless motor 7.
[0044] Resolvers can achieve resolutions of thousands or even tens of thousands of lines per turn, providing precise position and velocity information to meet the demands of high-precision control. For example, in applications requiring extremely high precision, such as servo systems and robots, resolvers can accurately measure the linear displacement or rotation angle of an object to determine its specific position in space. In contrast, Hall effect sensors have lower precision and typically provide only coarse position information, such as an electrical angle resolution of 60 or 120 degrees. They are generally only suitable for applications with lower precision requirements, such as household appliances or low-cost motor control. High-precision closed-loop control of motors (such as coreless motors) usually requires precise position, velocity, and torque loop control. Resolvers can provide real-time position, velocity, and direction information of the motor shaft, helping the controller to detect and adjust the motor's motion state in real time, achieving precise closed-loop control.
[0045] In summary, the present invention has the following beneficial effects:
[0046] 1. This invention designs a miniature rotary transformer, which is assembled inside a coreless motor to meet the precision and complex control requirements of the coreless motor. Furthermore, the coils of this invention are arranged in a stacked manner, making the rotary transformer structure more compact, and the thickness of the excitation coil and the output coil are further limited.
[0047] While ensuring that the size requirements of the application scenario are met, it is beneficial to arrange more turns of the output coil, thereby obtaining a reasonable output amplitude, which in turn improves the detection accuracy of the miniature rotary transformer.
[0048] 2. This invention uses enameled wire windings, which increases the wire diameter and allows for a larger current to pass through. This results in a larger output voltage amplitude of the output coil, making the signal easier for the decoding chip to capture. On the other hand, using enameled wire for winding the output coil and excitation coil allows for in-house processing, eliminating the need for outsourcing. This reduces raw material and production costs and effectively controls the cost of the rotary transformer. Consequently, it also helps control the cost of the improved coreless motor, making the product more suitable for widespread application.
[0049] Based on the described embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
Claims
1. A miniature rotary transformer, comprising a stator, a rotor, an excitation coil, and an output coil, characterized in that: The stator is an annular steel sheet with an outer diameter of 13mm. The surface of the stator is provided with multiple coil units. Each coil unit includes an output coil and an excitation coil stacked together. The excitation coil is fixed to the surface of the stator, and the output coil is stacked on the upper surface of the excitation coil. The thickness ratio of the output coil to the excitation coil is 3:
1.
2. The miniature rotary transformer according to claim 1, characterized in that: The stator surface is provided with 16 coil units, which are racetrack-shaped windings. The width of each coil unit is 1.5 mm and the length is 2.8 mm.
3. The miniature rotary transformer according to claim 2, characterized in that: The thickness of the excitation coil is 0.1 mm, and the thickness of the output coil is 0.3 mm.
4. The miniature rotary transformer according to any one of claims 1-3, characterized in that: The output coil and excitation coil are made of enameled wire with a diameter of 0.1mm.
5. The miniature rotary transformer according to claim 1, characterized in that: The number of turns in a single layer of the excitation coil and the output coil is less than or equal to 7.
6. The miniature rotary transformer according to claim 4, characterized in that: The excitation coil has 5 turns, and the winding directions of adjacent excitation coils are opposite.
7. The miniature rotary transformer according to claim 4, characterized in that: The output coil has 14 turns, and the output coils of the 16 coil units are divided into two groups: one group is the SIN winding and the other group is the COS winding. The SIN winding and the COS winding are spaced apart. The coils of the SIN winding are connected in series with each other, and the coils of the COS winding are also connected in series with each other. The winding directions of the coils of adjacent SIN windings are opposite, and the winding directions of the coils of adjacent SIN windings and COS windings are opposite.
8. The miniature rotary transformer according to claim 1, characterized in that: The rotor is pole-bladed and has 4 pole pairs.
9. The miniature rotary transformer according to claim 1, characterized in that: The coil unit is fixed to the stator by adhesive.
10. A hollow cup motor, characterized in that: The miniature rotary transformer includes any one of claims 1-9, wherein the rotor is connected to the motor shaft, and the stator and coil unit are fixed to the end cover of the hollow cup motor.