Motor rotor core, motor cogging torque reduction method and device

Abstract

The present application relates to the field of servo motors, and discloses a motor rotor core, a method and a device for reducing motor cogging torque. The present application is a motor rotor core with a semi-spherical structure, which is composed of a core buckle point structure and a permanent magnet ring, and its bottom outer contour is a quasi-circular shape formed by connecting a plurality of three-segment geometric lines, and has a unique three-segment rotor core outer circle structure. This structure can reduce the cogging torque and improve the sinusoidality of the motor back electromotive force waveform, and optimize the pole arc coefficient by changing the size of the circumscribed angle between the straight line segment and the arc segment, and the size of the eccentricity between the center of the arc segment and the center of the rotor core, and achieve the design goal by using finite element simulation analysis, and finally achieve the effect of reducing the motor cogging torque, improving the sinusoidality of the back electromotive force waveform, and ensuring the positioning and control accuracy of the motor.

Description

Technical Field

[0001] The present application relates to the field of servo motors, and more specifically, to a motor rotor core, a motor cogging torque reduction method and a device. Background Art

[0002] The cogging torque of a permanent magnet motor is its inherent property, which together with the ripple torque causes the torque fluctuation of the permanent magnet motor. The cogging torque is caused by the tangential component of the interaction force between the stator core slots and the permanent magnets, while the ripple torque is caused by the deviation of the current and back-EMF waveforms, and its main influencing factor is the harmonic distortion rate of the motor back-EMF. Torque fluctuations can cause motor operation jitter, affect the positioning and speed control accuracy of the motor, and further affect the indicator status of the control system.

[0003] The existing technology mainly reduces the cogging torque by optimizing the motor structure such as complex stator core closed slots, adding auxiliary slots, stator and rotor skewed pole slots, etc. However, although the existing technology can reduce the cogging torque to a certain extent, it fails to fundamentally solve the contradiction between the torque increase and cogging torque reduction brought about by the built-in permanent magnet rotor core structure. When optimizing the motor structure, the existing technology mostly only optimizes the cogging torque in a single dimension, and does not fully consider the impact of the motor operation mode, drive control strategy, etc. on the torque fluctuation, resulting in limited optimization effect, and the motor structure design is relatively complex and the cost is high.

[0004] Based on this, the present application provides a motor rotor core, which effectively makes up for the deficiencies of the prior art. Summary of the invention

[0005] In view of this, the present application provides a motor rotor core, a motor cogging torque reduction method and a device, which can reduce the motor cogging torque, improve the sinusoidal nature of the back electromotive force waveform, and ensure the positioning and control accuracy of the motor.

[0006] A motor rotor core, which is composed of a core buckle point structure and a permanent magnet ring, and presents a hemispherical structure;

[0007] The bottom outer contour of the hemispherical body is a quasi-circular shape formed by connecting a plurality of three-segment geometric lines;

[0008] Each of the three-segment geometric lines includes a first straight line segment, a circular arc segment, and a second straight line segment that are sequentially connected, and the first straight line segment and the second straight line segment are symmetrical about the circular arc segment.

[0009] Optionally, the permanent magnet ring is a ring-like structure consisting of a glue storage tank and a plurality of permanent magnets, wherein the built-in plurality of permanent magnets are connected in sequence, and the gaps at both ends of each permanent magnet are set as the glue storage tank;

[0010] The bottom outer contour of the hemispherical body is a quasi-circular shape formed by connecting the three-segment geometric lines corresponding to the permanent magnets.

[0011] Optionally, the circumscribed angle between the first straight line segment and the tangent line of the outer circle of the arc segment, and the eccentricity distance between the corresponding center of the arc segment and the center of the motor rotor core are determined by finite element simulation based on the width of the permanent magnet ring.

[0012] A method for reducing the cogging torque of a motor, using a motor rotor core as described in any one of the above, the method comprising:

[0013] Get the width of the permanent magnet applied to the target motor;

[0014] Performing finite element method simulation based on the permanent magnet width, and determining a target circumscribed angle and a target eccentricity distance corresponding to an optimal simulation result;

[0015] Determine a three-segment geometric line according to the target circumscribed angle and the target eccentricity distance, and form the bottom outer contour of the motor rotor core;

[0016] A motor rotor core is designed and constructed based on the bottom outer contour and applied to the target motor.

[0017] A motor cogging torque reduction device, applied to a motor rotor core as described above, comprising:

[0018] A width acquisition unit, used for acquiring a width of a permanent magnet applied to a target motor;

[0019] A simulation test unit, used for performing finite element method simulation based on the width of the permanent magnet, and determining a target circumscribed angle and a target eccentricity distance corresponding to an optimal simulation result;

[0020] A contour design unit, used for determining a three-segment geometric line according to the target circumscribed angle and the target eccentricity distance, and forming a bottom outer contour of the motor rotor core;

[0021] The core construction unit is used to design and construct a motor rotor core based on the bottom outer contour, and apply the core to the target motor.

[0022] It can be seen from the above technical solutions that the embodiments of the present application provide a motor rotor core, a method and a device for reducing the motor cogging torque. The present application is a motor rotor core with a hemispherical structure, which is composed of a core buckle point structure and a permanent magnet ring. The outer contour of its bottom is a quasi-circular shape formed by connecting multiple three-segment geometric lines, and has a unique three-segment rotor core outer circle structure. This structure can reduce the cogging torque and improve the sinusoidal nature of the motor back electromotive force waveform. The pole arc coefficient is optimized by changing the size of the circumscribed angle between the straight line segment and the arc segment, and the size of the eccentricity between the center of the arc segment and the center of the rotor core. The design goal is achieved by using finite element simulation analysis, and finally the effect of reducing the motor cogging torque, improving the sinusoidal nature of the back electromotive force waveform, and ensuring the positioning and control accuracy of the motor is achieved.

[0023] In terms of performance improvement, the three-section rotor core outer circle structure of the present application can reduce the cogging torque, improve the sinusoidality of the motor back electromotive force waveform, and ensure the positioning and control accuracy of the motor. In terms of cost control, the built-in magnetic steel rotor core structure adopted by the present application can achieve the corresponding magnetic field effect with less magnetic steel compared to the surface-mounted type, thereby reducing the amount of magnetic steel used and reducing costs. In addition, this structure is beneficial to the magnetic field distribution of the motor at high speed, ensuring high-speed operation performance. From the perspective of structural optimization, the present application only needs to optimize the outer circle structure of the rotor core, abandoning the complex designs such as the closed slots of the stator core, the addition of auxiliary slots, and the stator and rotor skewed pole slots required to reduce the cogging torque of the motor in the past, avoiding the design and manufacturing difficulties and possible increased costs caused by the complex structure, making the optimization process more operational and efficient. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying any creative work.

[0025] Figure 1 A schematic diagram of the structure of a motor rotor core disclosed in an embodiment of the present application;

[0026] Figure 2 A schematic diagram of the outer circle structure of a motor rotor core disclosed in an embodiment of the present application;

[0027] Figure 3 A flow chart of a method for reducing motor cogging torque disclosed in an embodiment of the present application;

[0028] Figure 4 A schematic diagram of a cogging torque simulation curve disclosed in an embodiment of the present application;

[0029] Figure 5 A schematic diagram of a back electromotive force waveform curve before and after optimization of a motor disclosed in an embodiment of the present application;

[0030] Figure 6 This is a schematic diagram of a motor cogging torque reduction device disclosed in an embodiment of the present application. DETAILED DESCRIPTION

[0031] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0032] First, the implementation principle of this application is introduced, as follows:

[0033] At present, when the servo motors in mass production on the market adopt the built-in permanent magnet rotor core structure and the slot-pole matching mode to improve the power density and the maximum speed of operation, there is a contradiction between the motor output torque improvement of the built-in magnetic steel magnetic circuit and the reduction of the cogging torque. The present invention aims to solve this problem. Starting from the selection and optimization of the motor rotor core structure, a three-section rotor outer circle structure is innovatively proposed. From the analysis of the cogging torque expression, it is understood that the pole arc coefficient is the key factor affecting the cogging torque. It is theoretically deduced that for the motor with fixed slot pole matching, there is a fixed pole arc coefficient relationship that makes the cogging torque zero or approximately zero. Then, the pole arc coefficient is optimized by changing the angle between the straight line segment and the circular arc segment, and the eccentricity between the center of the circular arc segment and the center of the rotor core. The selected parameters are verified by using finite element simulation software to find the optimal angle between the straight line segment and the circular arc segment, and the eccentricity between the center of the circular arc segment and the center of the rotor core, and finally the target requirements of reducing the motor cogging torque and improving the sinusoidality of the back electromotive force waveform are achieved, thereby effectively solving the contradictions existing in the prior art.

[0034] Assuming that the magnetic permeability of the silicon steel sheets used in the motor stator and rotor core is infinite (compared to the air permeability of the air gap), according to the definition of cogging torque and the energy law theory, it can be obtained:

[0035]

[0036] In the formula, represents the cogging torque; w represents the magnetic field energy; represents the relative position angle between the stator and the rotor; Z represents the number of stator slots; p represents the number of pole pairs; L represents the length of the rotor core; represents the inner radius of the stator; represents the outer radius of the rotor; μ is the magnetic permeability.

[0037] From theoretical analysis, we know that the remanence of permanent magnets It has a great influence on the cogging torque, but not all The Fourier coefficients of all have an effect on the cogging torque, only The order Fourier coefficient has an impact on the cogging torque. In the case of a motor with 12 slots and 10 poles, the cogging torque is only related to It is related to the 5n (n is a positive integer)th Fourier coefficient.

[0038] The Fourier decomposition coefficients are:

[0039]

[0040] From the above formula, we can see that the polar arc coefficient It is the key factor affecting remanence. Value makes the residual magnetism The cogging torque produced is zero or approximately zero.

[0041] Therefore, when the width of the magnetic steel is fixed, the key factor affecting the pole arc coefficient is the geometric shape of the outer circle of the rotor core. Based on this, the present application optimizes the pole arc coefficient by changing the size of the circumscribed angle between the straight line segment and the arc segment, and the size of the eccentricity between the center of the arc segment and the center of the rotor core, and uses finite element simulation analysis to achieve the design goals, ultimately achieving the effect of reducing the motor cogging torque, improving the sinusoidality of the back electromotive force waveform, and ensuring the positioning and control accuracy of the motor.

[0042] Next, the present application scheme is introduced. The present application proposes the following technical scheme, please see below for details.

[0043] Figure 1 This is a schematic diagram of the structure of a motor rotor core disclosed in an embodiment of the present application.

[0044] Figure 2 This is a schematic diagram of the outer circle structure of a motor rotor core disclosed in an embodiment of the present application.

[0045] Among them, 1 is the iron core buckle point structure, 2 is the first straight line segment, 3 is the arc segment, 4 is the second straight line segment, 5 is the glue storage tank, and 6 is the permanent magnet (magnetic steel).

[0046] like Figure 1 and Figure 2 As shown, the motor rotor core is composed of an iron core buckle structure and a permanent magnet ring, presenting a hemispherical structure;

[0047] The bottom outer contour of the hemispherical body is a quasi-circular shape formed by connecting a plurality of three-segment geometric lines;

[0048] Each of the three-segment geometric lines includes a first straight line segment, a circular arc segment, and a second straight line segment that are sequentially connected, and the first straight line segment and the second straight line segment are symmetrical about the circular arc segment.

[0049] Specifically, the motor rotor core adopts a semi-spherical structure. This unconventional shape design has unique advantages in space utilization and magnetic field coupling. Inside the motor, the shape of the rotor affects the distribution path and strength of the magnetic field. The semi-spherical structure can make the magnetic field more evenly distributed around the rotor, reducing the situation where the local magnetic field is too strong or too weak.

[0050] The core buckle structure plays a key supporting and connecting role in the hemispherical body. It not only connects the cores of various parts tightly together, but also participates in the conduction and distribution of the magnetic field. A properly designed core buckle structure can enhance the mechanical strength of the rotor as a whole and prevent deformation or damage during high-speed rotation.

[0051] Furthermore, the permanent magnet ring is a ring-like structure consisting of a glue storage tank and a plurality of permanent magnets, wherein the built-in plurality of permanent magnets are connected in sequence, and the gaps at both ends of each permanent magnet are set as the glue storage tank;

[0052] The bottom outer contour of the hemispherical body is a quasi-circular shape formed by connecting the three-segment geometric lines corresponding to the permanent magnets.

[0053] Specifically, the permanent magnet ring is an important component for generating a magnetic field. The ingenious design of the ring-like structure composed of multiple permanent magnets and a glue storage tank lies in the arrangement and connection of the permanent magnets. The existence of the glue storage tank not only facilitates the installation and fixation of the permanent magnets, but also can buffer the stress of the permanent magnets during operation to a certain extent.

[0054] One of the core innovations of this design is that the three-segment geometric lines of the bottom outer contour are connected to form a quasi-circular shape. The combination of the first straight line segment, the arc segment, and the second straight line segment, and the symmetry of the first straight line segment and the second straight line segment about the arc segment, helps to form a balanced distribution of magnetic lines of force during the magnetic field generation process. The design of the straight line segment and the arc segment can accurately control the edge effect of the magnetic field. In a traditional circular outer contour rotor, the magnetic field may suddenly change at the edge, resulting in adverse effects such as cogging torque, while this design can make the magnetic field smoother in the transition area through the three-segment geometric lines.

[0055] In addition, the circumscribed angle between the first straight line segment and the tangent line of the outer circle of the arc segment, and the eccentricity distance between the center of the arc segment and the center of the motor rotor core are both determined by finite element method simulation based on the width of the permanent magnet ring.

[0056] Specifically, through finite element simulation, the circumscribed angle between the first straight line segment and the tangent line of the arc segment and the eccentric distance between the center of the arc segment and the center of the rotor core are determined according to the width of the permanent magnet ring. Finite element simulation can take into account the physical properties of the material such as magnetic permeability and electrical conductivity, as well as the boundary conditions when the motor is running, so as to accurately find the optimal geometric parameters. These parameters directly affect the pole arc coefficient, which in turn has an important impact on the cogging torque and back electromotive force waveform.

[0057] Cogging torque is caused by the interaction between the stator and rotor of the motor. The three-segment rotor core outer circle structure of the present application can effectively reduce the torque fluctuation caused by this interaction by optimizing the geometric parameters. When the circumscribed angle and the eccentricity of the straight segment and the circular arc segment are adjusted to the optimal value, the magnetic field is more evenly distributed between the teeth, thereby reducing the cogging torque. Theoretically, the cogging torque is closely related to the pole arc coefficient of the motor. By changing the parameters of the three-segment geometric line to optimize the pole arc coefficient, the cogging torque can be reduced to a minimum during the operation of the motor, which is crucial to improving the running stability and efficiency of the motor.

[0058] The sinusoidality of the back-EMF waveform directly affects the control accuracy and operating performance of the motor. The three-segment geometry design can make the magnetic field generated by the rotor closer to the ideal sinusoidal distribution. When the motor is running, the back-EMF waveform generated by the stator winding cutting the magnetic lines of force is smoother and closer to a sine wave, which helps to reduce the harmonic loss of the motor and improve the power factor and efficiency of the motor. Good back-EMF waveform sinusoidality can also reduce the complexity of the motor in the control system. In high-precision motor control applications, such as servo motors, this feature can make it easier for the motor to achieve precise speed and position control.

[0059] The use of a built-in magnetic steel rotor core structure can reduce the amount of magnetic steel used compared to a surface-mounted permanent magnet motor. This is because the built-in structure can more efficiently utilize the magnetic field generated by the magnetic steel while ensuring the performance of the motor through a reasonable magnetic field design. Reducing the amount of magnetic steel used not only directly reduces the material cost, but may also reduce the processing costs related to the magnetic steel during the production process, such as the cost of cutting and assembling the magnetic steel. The present application can achieve the purpose of reducing the cogging torque and improving the sinusoidal nature of the back electromotive force waveform only by optimizing the outer circle structure of the rotor core. This optimization method avoids the design and manufacturing difficulties brought about by the above-mentioned complex structure, making the production process of the motor simpler and more efficient. For example, during the manufacturing process, there is no need to perform complex notch processing and assembly operations of the oblique pole and oblique slot, which reduces the complexity of the production process and production costs and improves production efficiency.

[0060] When the motor is running at high speed, the stability and uniformity of the magnetic field are crucial to the performance of the motor. The built-in magnetic steel rotor core structure can better maintain the distribution of the magnetic field when rotating at high speed, reducing the magnetic field distortion caused by centrifugal force and other factors. This structure is conducive to maintaining stable output torque and efficiency of the motor when running at high speed, and improving the reliability and service life of the motor.

[0061] Figure 3 This is a flow chart of a method for reducing motor cogging torque disclosed in an embodiment of the present application.

[0062] like Figure 3 As shown, the method applies the above motor rotor core, and the method may include:

[0063] Step S1, obtaining the width of the permanent magnet applied to the target motor.

[0064] Specifically, the width of the permanent magnet directly affects the strength and distribution of the magnetic field generated by the motor rotor. In different motor application scenarios, the width of the permanent magnet may vary depending on factors such as the motor's power, size, and performance requirements. Accurately obtaining the width of the permanent magnet of the target motor is the basis for subsequent simulation and design.

[0065] Step S2: performing finite element simulation based on the permanent magnet width, and determining a target circumscribed angle and a target eccentricity distance corresponding to an optimal simulation result.

[0066] Specifically, the finite element method is a powerful numerical analysis method that is widely used in motor design. It discretizes the physical structure of the motor into many small units and simulates the operating characteristics of the motor by solving the electromagnetic field equations of these units. In this method, a finite element model of the motor is constructed based on the given permanent magnet width. In the finite element model, various physical properties of the motor can be considered, such as the magnetic permeability, electrical conductivity of the material, and the residual magnetism of the permanent magnet. By setting different circumscribed angles and eccentricity distances as variables, multiple simulation calculations are performed.

[0067] During the simulation, the cogging torque is evaluated under different parameter combinations. Cogging torque is an important indicator of motor performance. Smaller cogging torque means smoother motor operation and higher efficiency. By comparing different simulation results, the target circumscribed angle and target eccentricity distance that minimize the cogging torque are found.

[0068] In this application, the finite element method simulation is used to compare and iterate the optimization calculation of different parameters, namely the external included angle and the eccentricity, and the obtained polar arc coefficients are also quite different. When the eccentricity e=3.4mm is used as the rotor core outer circle structure, the peak-to-valley value of the motor's cogging torque is significantly reduced from 134.21mN.M before optimization to only 10.06mN.M. At this time, the cogging torque only accounts for a percentage of the motor's rated torque. , the cogging torque simulation curves before and after motor optimization are as follows Figure 4 shown.

[0069] Figure 5 The back electromotive force waveform curve before and after motor optimization. Figure 5 It is obvious that the back EMF waveform of the motor whose rotor core outer contour is composed of two straight lines and one eccentric arc line segment is more sinusoidal than that of the traditional motor whose outer contour is not optimized. The sinusoidalization of the motor back EMF waveform is beneficial to reducing the cogging torque and the harmonic distortion rate of the air gap magnetic field, thereby improving the motor control positioning accuracy, etc.

[0070] Step S3, determining a three-segment geometric line according to the target circumscribed angle and the target eccentricity distance, and forming the bottom outer contour of the motor rotor core.

[0071] Specifically, once the target circumscribed angle and the target eccentricity distance are determined, the shape of the three-segment geometry line can be accurately determined. The three-segment geometry line (including the first straight line segment, the arc segment, and the second straight line segment) is designed according to these parameters, and they are connected to form the bottom outer contour of the motor rotor core. This outer contour design is based on the previous simulation optimization results, and aims to control the magnetic field distribution through optimized geometry, thereby reducing the cogging torque.

[0072] Step S4: designing and constructing a motor rotor core based on the bottom outer contour, and applying it to the target motor.

[0073] Specifically, according to the determined bottom outer contour, the structure of the entire motor rotor core is further designed. This includes the design of the core buckle structure, the integration of the permanent magnet ring and the rotor core, etc. After the design is completed, the motor rotor core is manufactured according to the design requirements and applied to the target motor. In this way, the effect of reducing the cogging torque can be achieved in the target motor, and the overall performance of the motor can be improved.

[0074] The present application optimizes the pole arc coefficient by changing the angle between the straight line segment and the arc segment, and the eccentricity between the center of the arc segment and the center of the rotor core, and verifies the selected parameters using finite element simulation software to find the optimal angle between the straight line segment and the arc segment, and the eccentricity between the center of the arc segment and the center of the rotor core, so as to reduce the cogging torque of the motor and achieve the design target requirements.

[0075] It can be seen from the above technical solutions that the embodiments of the present application provide a motor rotor core, a method and a device for reducing the motor cogging torque. The present application is a motor rotor core with a hemispherical structure, which is composed of a core buckle point structure and a permanent magnet ring. The outer contour of its bottom is a quasi-circular shape formed by connecting multiple three-segment geometric lines, and has a unique three-segment rotor core outer circle structure. This structure can reduce the cogging torque and improve the sinusoidal nature of the motor back electromotive force waveform. The pole arc coefficient is optimized by changing the size of the circumscribed angle between the straight line segment and the arc segment, and the size of the eccentricity between the center of the arc segment and the center of the rotor core. The design goal is achieved by using finite element simulation analysis, and finally the effect of reducing the motor cogging torque, improving the sinusoidal nature of the back electromotive force waveform, and ensuring the positioning and control accuracy of the motor is achieved.

[0076] In terms of performance improvement, the three-section rotor core outer circle structure of the present application can reduce the cogging torque, improve the sinusoidality of the motor back electromotive force waveform, and ensure the positioning and control accuracy of the motor. In terms of cost control, the built-in magnetic steel rotor core structure adopted by the present application can achieve the corresponding magnetic field effect with less magnetic steel compared to the surface-mounted type, thereby reducing the amount of magnetic steel used and reducing costs. In addition, this structure is beneficial to the magnetic field distribution of the motor at high speed, ensuring high-speed operation performance. From the perspective of structural optimization, the present application only needs to optimize the outer circle structure of the rotor core, abandoning the complex designs such as the closed slots of the stator core, the addition of auxiliary slots, and the stator and rotor skewed pole slots required to reduce the cogging torque of the motor in the past, avoiding the design and manufacturing difficulties and possible increased costs caused by the complex structure, making the optimization process more operational and efficient.

[0077] A motor cogging torque reduction device provided in an embodiment of the present application is described below. The motor cogging torque reduction device described below and the motor cogging torque reduction method described above can refer to each other and apply the above-mentioned motor rotor core.

[0078] See also Figure 6 , Figure 6 This is a schematic diagram of a motor cogging torque reduction device disclosed in an embodiment of the present application.

[0079] like Figure 6 As shown, the motor cogging torque reduction device may include:

[0080] A width acquisition unit 110, used to acquire a width of a permanent magnet applied to a target motor;

[0081] A simulation test unit 120, configured to perform a finite element method simulation based on the permanent magnet width, and determine a target circumscribed angle and a target eccentricity distance corresponding to an optimal simulation result;

[0082] A contour design unit 130, configured to determine a three-segment geometric line according to the target circumscribed angle and the target eccentricity distance, and form a bottom outer contour of the motor rotor core;

[0083] The core construction unit 140 is used to design and construct a motor rotor core based on the bottom outer contour, and apply it to the target motor.

[0084] It can be seen from the above technical solutions that the embodiments of the present application provide a motor rotor core, a method and a device for reducing the motor cogging torque. The present application is a motor rotor core with a hemispherical structure, which is composed of a core buckle point structure and a permanent magnet ring. The outer contour of its bottom is a quasi-circular shape formed by connecting multiple three-segment geometric lines, and has a unique three-segment rotor core outer circle structure. This structure can reduce the cogging torque and improve the sinusoidal nature of the motor back electromotive force waveform. The pole arc coefficient is optimized by changing the size of the circumscribed angle between the straight line segment and the arc segment, and the size of the eccentricity between the center of the arc segment and the center of the rotor core. The design goal is achieved by using finite element simulation analysis, and finally the effect of reducing the motor cogging torque, improving the sinusoidal nature of the back electromotive force waveform, and ensuring the positioning and control accuracy of the motor is achieved.

[0085] In terms of performance improvement, the three-section rotor core outer circle structure of the present application can reduce the cogging torque, improve the sinusoidality of the motor back electromotive force waveform, and ensure the positioning and control accuracy of the motor. In terms of cost control, the built-in magnetic steel rotor core structure adopted by the present application can achieve the corresponding magnetic field effect with less magnetic steel compared to the surface-mounted type, thereby reducing the amount of magnetic steel used and reducing costs. In addition, this structure is beneficial to the magnetic field distribution of the motor at high speed, ensuring high-speed operation performance. From the perspective of structural optimization, the present application only needs to optimize the outer circle structure of the rotor core, abandoning the complex designs such as the closed slots of the stator core, the addition of auxiliary slots, and the stator and rotor skewed pole slots required to reduce the cogging torque of the motor in the past, avoiding the design and manufacturing difficulties and possible increased costs caused by the complex structure, making the optimization process more operational and efficient.

[0086] Finally, it should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the presence of other identical elements in the process, method, article or device including the elements.

[0087] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0088] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A motor rotor core, characterized in that: It is composed of an iron core buckle point structure and a permanent magnet ring, presenting a hemispherical structure; The bottom outer contour of the hemispherical body is a quasi-circular shape formed by connecting a plurality of three-segment geometric lines; Each of the three-segment geometric lines includes a first straight line segment, a circular arc segment, and a second straight line segment that are sequentially connected, and the first straight line segment and the second straight line segment are symmetrical about the circular arc segment they sandwich; The permanent magnet ring is a ring-like structure consisting of a glue storage tank and a plurality of permanent magnets, wherein the built-in plurality of permanent magnets are connected in sequence, and the gaps at both ends of each permanent magnet are set as the glue storage tank; The bottom outer contour of the hemispherical body is a quasi-circular shape formed by connecting the three-segment geometric lines corresponding to the permanent magnets.

2. The motor rotor core according to claim 1, characterized in that: The circumscribed angle between the first straight line segment and the tangent line of the outer circle of the arc segment, and the eccentricity distance between the center of the arc segment and the center of the motor rotor core are both determined by finite element method simulation based on the width of the permanent magnet ring.

3. A method for reducing motor cogging torque, characterized in that: The application includes the motor rotor core as claimed in claim 2, and the method includes: Get the permanent magnet width applied to the target motor; Performing finite element method simulation based on the permanent magnet width, and determining a target circumscribed angle and a target eccentricity distance corresponding to an optimal simulation result; Determine a three-segment geometric line according to the target circumscribed angle and the target eccentricity distance, and form the bottom outer contour of the motor rotor core; A motor rotor core is designed and constructed based on the bottom outer contour and applied to the target motor.

4. A motor cogging torque reduction device, characterized in that: The application includes the motor rotor core as claimed in claim 2, and the device includes: A width acquisition unit, used for acquiring a width of a permanent magnet applied to a target motor; A simulation test unit, used for performing finite element method simulation based on the width of the permanent magnet, and determining a target circumscribed angle and a target eccentricity distance corresponding to an optimal simulation result; A contour design unit, used for determining a three-segment geometric line according to the target circumscribed angle and the target eccentricity distance, and forming a bottom outer contour of the motor rotor core; The core construction unit is used to design and construct a motor rotor core based on the bottom outer contour, and apply the core to the target motor.

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