Miniature rotary transformer and coreless motor

Abstract

The invention belongs to the technical field of displacement sensors, and particularly relates to a micro rotary transformer suitable for a coreless motor and the coreless motor. The miniature rotary transformer comprises a stator, a rotor, excitation coils and output coils, and is characterized in that the stator is an annular steel sheet with the outer diameter of 13mm, a plurality of coil units are arranged on the surface of the stator, each coil unit comprises an output coil and an excitation coil which are stacked, the excitation coils are fixed on the surface of the stator, and the output coils and the excitation coils are fixed on the surface of the stator. 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, the rotary transformer is assembled in the hollow cup motor, the requirements of the hollow cup motor for precision and complex control are met, the rotary transformer structure is more compact, and the rotary transformer is more compact in structure and more compact in structure under the condition that the requirement of a use scene for the size is met. And more turns of the output coil can be arranged, so that a reasonable output amplitude is obtained, and the detection precision is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of displacement sensors, and in particular relates to a micro rotary transformer suitable for a coreless motor and the coreless motor. Background Art

[0002] Against the backdrop of the vigorous development of modern robotics technology, coreless motors have been widely used in the field of robot joint drives due to their unique advantages.

[0003] In existing technology, coreless motors typically use Hall sensors to obtain angular position and angular velocity information. However, Hall sensors have certain limitations, including limited measurement accuracy, which results in insufficient motor control precision. In some applications requiring high motor control accuracy, such as precision instruments and humanoid robot knuckles, existing Hall sensor measurement solutions fail to meet actual needs. Furthermore, there is a severe shortage of high-precision angle sensors specifically designed for coreless motors on the market.

[0004] Eddy current rotary transformers in the prior art generally use PCB boards to process the excitation coil and output coil. Due to the size of the hollow cup motor, PCB boards are also used to process the rotary transformer of the hollow cup motor. On the one hand, the size of the PCB board is too small, which increases the difficulty of processing and sharply increases the cost. On the other hand, as the size of the PCB board decreases, the volume of the embedded conductor inside it also decreases accordingly, the current it can withstand decreases, and the output voltage signal is weak, which is not conducive to capture by the decoding chip. Summary of the Invention

[0005] In view of the deficiencies in the prior art, the present invention designs a micro rotary transformer suitable for a coreless motor, and a coreless motor having the micro rotary transformer.

[0006] The technical solutions of the present invention are as follows:

[0007] A micro-rotating transformer includes a stator, a rotor, an excitation coil and an output coil. The stator is an annular steel sheet with an outer diameter of 13 mm and a thickness of 0.1 mm. The surface of the stator is provided with multiple coil units, and the coil units include stacked output coils and excitation coils. 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 between the output coil and the excitation coil is 3:1. The present invention limits the outer diameter of the stator to ensure that the processed micro-rotating transformer can be assembled in a hollow cup motor to meet the requirements of the use scenario. Secondly, the structure of the coil unit is limited, and the excitation coil and the 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 the excitation coil is limited. The thickness of the output coil and the excitation coil depends on the number of turns of the coil. While ensuring that the volume requirements of the use scenario are met, it is beneficial to arrange a larger number of turns of the output coil to obtain a reasonable output amplitude.

[0008] Furthermore, the stator surface is provided with 16 coil units, and the coil units are runway-shaped windings. The width of the coil units is 1.5 mm and the length is 2.8 mm, so that the winding area is as large as possible. Moreover, 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 thicknesses of the excitation coil and the output coil are limited here, thereby ensuring that the micro rotary transformer can be applied to the hollow cup motor.

[0010] Furthermore, the output coil and the excitation coil are wound with enameled wire with a wire diameter of 0.1 mm. Compared with the wiring of the PCB board, the use of enameled wire increases the wire diameter, allowing a larger current to pass through, thereby increasing the output voltage amplitude of the output coil and making the signal easier to be captured by the decoding chip.

[0011] Furthermore, the number of turns of the single-layer coils of the excitation coil and the output coil is less than or equal to 7. Due to the previous limitations on wire diameter and thickness, the number of turns of the single-layer coils of the excitation coil and the output coil must be less than or equal to 7, thereby ensuring the thickness of the excitation coil and the output coil, and meeting the volume requirements of the hollow cup motor.

[0012] Furthermore, the number of turns of the excitation coil is 5, and the winding directions of adjacent excitation coils are opposite. The specific number of turns of the excitation coil is given here. By using the excitation coil with the above number of turns, a reasonable output amplitude can be obtained, which better ensures the reliability of the resolver signal.

[0013] Furthermore, the number of turns of the output coil is 14, and the output coils of the 16 coil units are divided into two groups, one group is a SIN winding, and the other group is a COS winding, and the SIN winding and the COS winding are arranged at intervals. 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, and 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 is in the shape of pole lobes, and the number of rotor pole pairs is 4.

[0015] Furthermore, the coil unit is fixed to the stator by gluing.

[0016] The hollow cup motor is characterized by comprising the above-mentioned micro rotary transformer, wherein the rotor is connected to the motor shaft, and the stator and the coil unit are fixed to the end cover of the hollow cup motor.

[0017] In summary, the present invention has the following beneficial effects:

[0018] 1. The present invention designs a miniature rotary transformer, which is assembled inside a hollow cup motor to meet the hollow cup motor's requirements for precision and complex control. Furthermore, the coils of the present invention are arranged in a stacked manner, making the rotary transformer structure more compact and further limiting the thickness of the excitation coil and the output coil.

[0019] While ensuring that the volume requirements of the usage scenario are met, it is beneficial to arrange a larger number of turns in the output coil, thereby obtaining a reasonable output amplitude, thereby improving the detection accuracy of the micro-rotary transformer.

[0020] 2. The present invention uses windings made of enameled wire, which increases the wire diameter of the winding and allows a larger current to pass through, thereby increasing the output voltage amplitude of the output coil and making it easier for the signal to be captured by the decoding chip. On the other hand, the enameled wire is used to wind the output coil and the excitation coil, which can be processed within the factory without outsourcing, thereby reducing the raw material cost and production cost, and effectively controlling the cost of the rotary transformer, which is also beneficial to the cost control of the improved hollow cup motor and is more conducive to the promotion and application of the product. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 is a three-dimensional schematic diagram of a micro rotary transformer of the present invention;

[0022] Figure 2 A schematic diagram of the coil winding of the present invention;

[0023] Figure 31 is a side view schematic diagram of the micro rotary transformer of the present invention;

[0024] Figure 4 Schematic diagram of the stator (including coil unit) of the present invention;

[0025] Figure 5 Schematic cross-sectional view of a coreless motor according to an embodiment of the present invention;

[0026] In the figure, 1 is the stator, 2 is the rotor, 3 is the excitation coil, 4 is the output coil, and 5 is 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 DESCRIPTION

[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 the present invention and implement it. However, the embodiments are not intended to limit the present invention.

[0029] It should be noted that when an element is referred to as being "disposed on" or "fixed on" another element, it may be directly on the other element or there may be a central element. When an element is referred to as being "fixed on" another element, or "fixedly connected" to another element, they may be fixed in a detachable manner or in a non-detachable manner. When an element is considered to be "connected" or "rotatably connected" to another element, it may be directly connected to the other element or there may be a central element at the same time. The terms "vertical", "horizontal", "left", "right", "upper", "lower" and similar expressions used are for illustrative purposes only and do not represent the only implementation method.

[0030] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this invention pertains. The terms used herein in the specification of the present invention are for the purpose of describing specific embodiments only and are not intended to constrain the present invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0031] The terms "first", "second", "third" and the like in the present invention do not represent specific quantities and orders, but are only used to distinguish names.

[0032] With the development of hollow cup motors, the existing Hall sensor detection method cannot meet the needs of the development of hollow cup motors. Therefore, a high-precision angle sensor suitable for hollow cup motors is developed to help solve the problem of information collection of robot joints. The rotary transformer has the advantages of higher precision, accurate speed feedback and meeting complex control requirements. However, due to the small size of the hollow cup motor, the installation space left for the rotary transformer in the hollow cup motor is small, so there is a problem in miniaturizing the rotary transformer.

[0033] Figure 1 The present invention is a three-dimensional schematic diagram of a miniature rotary transformer, in which 1 is a stator, 2 is a rotor, 3 is an excitation coil, and 4 is an output coil. In order to meet the needs 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. The surface of the stator 1 is provided with a plurality of coil units 5, and the coil units 5 include a stacked output coil 4 and an excitation coil 3. The excitation coil 3 is fixed on 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 the figure, the thickness of the output coil is represented by H1, and the thickness of the excitation coil is represented by H2. The present invention limits the outer diameter of the stator to ensure that the processed micro-rotary transformer can be assembled in the hollow cup motor to meet the needs of the use scenario. Secondly, the structure of the coil unit is limited, and the excitation coil and the output coil are arranged in a stacked manner, so that the rotary transformer structure is more compact and smaller in size. Furthermore, the thickness of the output coil and the excitation coil is limited. On the one hand, the overall thickness of the coil unit is ensured to be controllable, thereby ensuring that the overall thickness of the micro-rotary transformer can meet the installation requirements of the hollow cup motor. On the other hand, the thickness of the output coil and the excitation coil depends on the number of turns of the coil. While ensuring that the volume requirements of the use scenario are met, it is beneficial to arrange a larger number of turns of the output coil, thereby obtaining a reasonable output amplitude, and thus improving the detection accuracy of the micro-rotary transformer.

[0034] See also 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 are limited here, thereby ensuring that the micro rotary transformer can be installed inside the hollow cup motor.

[0035] See also Figure 1As shown, 16 coil units 5 are provided on the surface of the stator 1, and the coil units are in a runway-shaped winding. The width of the coil units is 1.5 mm and the length is 2.8 mm. This embodiment limits the number of coil units on the stator surface, thereby further limiting 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 use of a runway-shaped winding increases the area of ​​the winding, realizes that the winding area is as large as possible, and the winding arrangement is as dense as possible. Furthermore, the runway-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 wire diameter of 0.1mm. Compared with the wiring of the PCB board, the output coil and the excitation coil are wound with enameled wire. On the one hand, since the volume of the rotary transformer of this embodiment is relatively small, if the winding is made of PCB material, the size of the conductive strip of the PCB board is relatively small, and the current it can carry is prioritized. The winding made of enameled wire in this embodiment increases the wire diameter of the winding, allowing a larger current to pass through, so that the output voltage amplitude of the output coil is increased, and the signal is more easily captured by the decoding chip. On the other hand, the output coil and the excitation coil are wound with enameled wire, which can be processed within the factory without outsourcing, thereby reducing the raw material cost and production cost, and effectively controlling the cost of the rotary transformer, which is also beneficial to the cost control of the improved hollow cup motor and is more conducive to the promotion and application of the product.

[0037] Furthermore, the number of turns of the single-layer coils of the excitation coil and the output coil is less than or equal to 7. Due to the previous limitations on wire diameter and thickness, as well as the size of the stator and the number of coil units, each coil unit only occupies 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 of the single-layer coils of the excitation coil and the output coil must be less than or equal to 7, thereby ensuring the thickness and width dimensions of the excitation coil and the output coil, and meeting the volume requirements of the hollow cup motor.

[0038] Furthermore, the number of turns of the excitation coil is 5, and the winding directions of adjacent excitation coils are opposite. The specific number of turns of the excitation coil is given here. Considering the tolerance requirements of actual production, the preferred number of turns of the excitation coil in this embodiment is 5, which is convenient for winding the coil and reduces the processing difficulty. The excitation coil is referenced in a plane. Figure 2The winding is carried out according to the winding diagram, and the winding directions of adjacent excitation coils are opposite. When adjacent coils are fed with AC excitation currents of the same phase, they generate magnetic fields with opposite polarities in each adjacent excitation coil, thereby forming alternating N poles and S poles on the circumference of the stator, establishing a magnetic field that periodically changes in space, which is conducive to ensuring a more uniform and symmetrical distribution of the magnetic field in the circumferential direction and improving the consistency of the output signal of the resolver.

[0039] Furthermore, the number of turns of the output coil 4 is 20, 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, and the SIN winding and the COS winding are arranged at intervals. 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, and the winding directions of the coils of adjacent SIN windings are opposite. In this embodiment, the number of turns of the output coil is limited. First, the thickness requirements of the output coil and the excitation coil are met. On the one hand, the extreme number of turns is not adopted, 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 cooperates with the number of turns of the excitation coil to meet the requirements of the transformation ratio, thereby ensuring the measurement accuracy. Specifically, the output coil in this embodiment is stacked and wound in three layers, the number of turns of the first layer coil is 7, the number of turns of the second layer coil is 7, and the number of turns of the third layer coil is 6.

[0040] join Figure 1 As shown, the rotor 2 is in the shape of pole lobes, and the number of rotor pole pairs is 4. First, the rotor is made of steel. Second, the maximum outer diameter of the rotor is 13 mm, which is compatible with the outer diameter of the rear 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 glue. 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 the mold, and then the output coil is stacked and epoxy-cured, thereby ensuring the position accuracy between the excitation coil and the output coil. Furthermore, the coil unit is glued to the stator by glue, which not only ensures the firmness 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. The magnetic field acts on the rotor through the stator and the air gap, and then generates 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 to cause friction and collision 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 reaction 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 micro-rotary transformer 6 , the rotor 2 connected to the motor shaft 70 , and the stator 1 and the coil unit fixed to the end cover 71 of the coreless motor 7 .

[0044] The resolution of a resolver can reach thousands or even tens of thousands of lines / turn, and it can provide accurate position and speed information to meet the needs of high-precision control. For example, in situations where extremely high precision is required, such as servo systems and robots, resolvers can accurately measure the linear displacement or rotation angle of an object and determine its specific position in space. Hall sensors have lower precision and usually only provide rough position information, such as 60 degrees or 120 degrees of electrical angle resolution. They are generally only suitable for situations where precision requirements are not high, such as household appliances or low-cost motor control. High-precision closed-loop control of motors (such as hollow cup motors) usually requires precise position loop, speed loop and torque loop control. Resolvers can provide real-time position, speed and direction information of the motor shaft, helping the controller to detect and adjust the motor's motion state in real time to achieve precise closed-loop control.

[0045] In summary, the present invention has the following beneficial effects:

[0046] 1. The present invention designs a miniature rotary transformer, which is assembled inside a hollow cup motor to meet the hollow cup motor's requirements for precision and complex control. Furthermore, the coils of the present invention are arranged in a stacked manner, making the rotary transformer structure more compact and further limiting the thickness of the excitation coil and the output coil.

[0047] While ensuring that the volume requirements of the usage scenario are met, it is beneficial to arrange a larger number of turns in the output coil, thereby obtaining a reasonable output amplitude, thereby improving the detection accuracy of the micro-rotary transformer.

[0048] 2. The present invention uses windings made of enameled wire, which increases the wire diameter of the winding and allows a larger current to pass through, thereby increasing the output voltage amplitude of the output coil and making it easier for the signal to be captured by the decoding chip. On the other hand, the enameled wire is used to wind the output coil and the excitation coil, which can be processed within the factory without outsourcing, thereby reducing the raw material cost and production cost, and effectively controlling the cost of the rotary transformer, which is also beneficial to the cost control of the improved hollow cup motor and is more conducive to the promotion and application of the product.

[0049] Based on the described embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work shall fall within the scope of protection of the present invention.

Claims

1. A micro 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 13 mm. A plurality of coil units are provided on the surface of the stator. The coil units include a stacked output coil and an excitation coil. The excitation coil is fixed on 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 micro-rotary transformer according to claim 1, wherein: The stator surface is provided with 16 coil units, each of which is in a racetrack-shaped winding. The width of each coil unit is 1.5 mm and the length is 2.8 mm.

3. The micro-rotating transformer according to claim 2, wherein: The thickness of the excitation coil is 0.1 mm, and the thickness of the output coil is 0.3 mm.

4. The micro-rotary transformer according to any one of claims 1 to 3, characterized in that: The output coil and the excitation coil are wound with enameled wire with a wire diameter of 0.1 mm.

5. The micro-rotary transformer according to claim 1, wherein: The number of turns of the single-layer coils of the excitation coil and the output coil is less than or equal to 7.

6. The micro-rotary transformer according to claim 4, characterized in that: The number of turns of the excitation coil is 5, and the winding directions of adjacent excitation coils are opposite.

7. The micro-rotary transformer according to claim 4, characterized in that: The number of turns of the output coil is 14, and the output coils of the 16 coil units are divided into two groups, one group is a SIN winding and the other group is a COS winding, and the SIN winding and the COS winding are arranged at intervals. 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, and 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 micro-rotary transformer according to claim 1, wherein: The rotor is in the shape of pole lobes, and the number of pole pairs of the rotor is 4.

9. The micro-rotary transformer according to claim 1, wherein: The coil unit is fixed on the stator by gluing.

10. Hollow cup motor, characterized by: The micro- The rotary transformer has a rotor connected to the motor shaft, and a stator and a coil unit fixed to the end cover of the hollow cup motor.

Images