Motor

Abstract

The present invention relates to a motor, comprising a stator and a rotor arranged in the stator, wherein the rotor comprises a rotor core and a plurality of permanent magnets, the rotor core comprises a plurality of magnetic pole units uniformly distributed around the center of the rotor core, the magnetic pole unit comprises a first slot distributed in a V-shape, a permanent magnet is arranged in the first slot, and the first slot is symmetrical about the direct axis; the magnetic pole unit comprises a groove radially recessed inward from the outer peripheral surface of the rotor core, the groove comprises two opposite first surfaces and a bottom surface connecting the two first surfaces, the first slot is located between the center and the bottom surface of the rotor core in the radial direction of the rotor core, the planes where the two first surfaces are located intersect outside the rotor core, and the angle θ of the two first surfaces satisfies 40°≤θ≤55°. The motor of the present invention has excellent performance in heat dissipation performance, torque improvement, cost control, inductance characteristics, magnetic line transmission and weak magnetic speed expansion capability, and is suitable for a wide range of fields such as electric tools, air conditioning compressors, and electric vehicles.

Description

Technical Field

[0001] The present invention relates to the technical field of motors, and in particular to a permanent magnet synchronous reluctance motor. Background Art

[0002] In the field of motor technology, permanent magnet synchronous motors have been shining in industrial production with their significant advantages such as compact size, light weight, excellent energy efficiency and high power factor. However, with the continuous soaring prices of high-performance rare earth permanent magnet materials, the cost problem of rare earth permanent magnet synchronous motors has become increasingly prominent, becoming a bottleneck restricting their further development. In order to solve this problem, the permanent magnet synchronous reluctance motor (PMSynRM) was proposed as an innovative built-in permanent magnet synchronous motor concept and quickly became a hot topic in the field of motor research.

[0003] Specifically, the birth of PM SynRM is the result of the fusion of Permanent Magnetic Synchronous Machine (PMSM) and Synchronous Reluctance Machine (SynRM) technologies. PMSM is known for its simple structural design, efficient energy conversion capability, excellent power factor and high torque density, and supports direct drive, and its control strategy is also becoming more mature; however, in the face of extreme working conditions, the risk of irreversible demagnetization of permanent magnets cannot be ignored, coupled with the price fluctuations of rare earth materials and the instability of the supply chain, the application of PMSM faces challenges. At the same time, in view of the scarcity of rare earth resources and environmental pressure, a global upsurge in the research and development of rare earth-free permanent magnet material motor systems has been set off, and SynRM came into being; although SynRM avoids rare earth dependence, significantly reduces costs, and has strong instantaneous overload capacity, its shortcomings in torque density, structural strength and torque stability limit its wide application.

[0004] It is in this context that the permanent magnet synchronous reluctance motor was born by ingeniously integrating an appropriate amount of permanent magnets into the magnetic circuit design of SynRM, which not only enhanced the salient pole effect of the magnetic circuit, but also significantly improved the power factor and torque density of the motor. PMSynRM not only inherits the respective advantages of PMSM and SynRM, achieving a perfect combination of high torque, high power density and wide speed regulation range, but also further reduces costs by reducing the use of rare earths, thereby enhancing market competitiveness.

[0005] Conventional surface-mounted permanent magnet brushless motors do not generate reluctance torque because the quadrature-axis inductance and direct-axis inductance of the motor are equal. The motor torque is generated by the permanent magnet torque. The quadrature-axis inductance and direct-axis inductance of the built-in permanent magnet brushless motor are not equal. In addition to the permanent magnet torque generated by the permanent magnet, it can also generate reluctance torque. The combined force of the two torques provides the output torque of the motor. From the definition and basic principles, the reluctance torque comes from the reluctance difference between the motor magnetic field and the rotor magnetic field. Specifically, this is caused by the difference between the direct-axis and quadrature-axis magnetic permeability of the motor; when the reluctance between the two axes changes, a force that tries to minimize the reluctance is generated, namely the reluctance torque. Furthermore, the magnitude of the reluctance torque is affected by many factors. The difference between the direct-axis and quadrature-axis magnetic permeability in the magnetic circuit design, the magnetic permeability and magnetic saturation characteristics of the permanent magnet material, and the control strategy of the stator current will directly or indirectly affect the generation and magnitude of the reluctance torque.

[0006] At present, permanent magnet synchronous reluctance motors are the preferred drive system in the electric vehicle industry due to their excellent performance, enhancing power and endurance; in the field of wind power generation, they are the core of direct-drive generators, improving overall efficiency and stability; in industrial automation, they are high-precision drive devices, ensuring reliability and precise control. However, most existing motor structures only consider the use of reluctance torque, and do not take into account the optimization and integration of the motor's natural heat dissipation channel.

[0007] In view of this, it is indeed necessary to provide an improved motor to overcome the defects of the prior art. Summary of the invention

[0008] In view of the shortcomings of the prior art, the present invention aims to provide a motor with low cost, good performance and strong heat dissipation capacity. In particular, it relates to an internal permanent magnet synchronous motor with a high salient pole ratio, which can not only improve the reluctance torque by utilizing the high salient pole effect, indirectly reduce the amount of permanent magnet material, but also effectively improve the heat dissipation capacity of the motor.

[0009] The technical solution adopted by the present invention to solve the problems of the prior art is: a motor, comprising a stator and a rotor arranged in the stator, the rotor being rotatably arranged relative to the stator, the rotor comprising a rotor core and a plurality of permanent magnets embedded in the rotor core, the rotor core comprising a plurality of magnetic pole units uniformly distributed around the center of the rotor core, the magnetic pole unit comprising a first groove distributed in a V shape, the permanent magnet being arranged in the first groove, the first groove being symmetrical about the direct axis, and characterized in that: the magnetic pole unit comprises a groove radially recessed inwardly from the outer peripheral surface of the rotor core, the groove comprising two opposite first surfaces and a bottom surface connecting the two first surfaces, the first groove being located between the center of the rotor core and the bottom surface in the radial direction of the rotor core, the planes where the two first surfaces are located intersect outside the rotor core, and the angle θ between the two first surfaces satisfies the following relationship: 40°≤θ≤55°.

[0010] A further improved solution is: the first slot includes an empty slot arranged on a side close to the straight axis and an installation slot arranged on a side away from the straight axis, the empty slot and the installation slot are connected to each other, the permanent magnet is arranged in the installation slot, and a first magnetic bridge is formed between the bottom surface and the radial outer side surface of the empty slot.

[0011] A further improvement is that the bottom surface, the radial outer side surface of the empty slot and the radial inner side surface of the empty slot are arc surfaces with the same central axis, and the dimension h1 of the first magnetic bridge on the straight axis and the dimension h2 of the first slot on the straight axis satisfy the following relationship: 0.8≤h1 / h2≤1.

[0012] A further improved solution is: the magnetic pole unit includes a second slot opened on the first slot near the center of the rotor core, and a second magnetic bridge is formed between the radial inner side surface of the empty slot and the radial outer side surface of the second slot.

[0013] A further improvement is that the radial inner side surface of the empty slot, the radial outer side surface of the second slot and the radial inner side surface of the second slot are arc surfaces with the same central axis, and the dimension h3 of the second magnetic bridge on the direct axis and the dimension h4 of the second slot on the direct axis satisfy the following relationship: 0.8≤h3 / h4≤1.

[0014] A further improvement scheme is: the farthest point on the first surface from the center of the rotor core is the first point, the closest point on the bottom surface to the center of the rotor core is the second point, the closest point on the inner surface of the second slot to the center of the rotor core is the third point, and the distance hs between the first point and the second point on the direct axis and the distance hb between the second point and the third point on the direct axis satisfy the following relationship: 0.8≤hs / hb≤1.

[0015] A further improvement scheme is: the rotor core is composed of four magnetic pole units, each of the magnetic pole units is symmetrically arranged about the corresponding direct axis, the center of the two permanent magnets of each magnetic pole unit is arranged at an obtuse angle to the center of the rotor core, and the permanent magnet is arranged outside the angle area of ​​the two first surfaces of the magnetic pole unit.

[0016] A further improved solution is: the shortest distance Rib between two of the first grooves of two adjacent magnetic pole units satisfies the following relationship: 4 mm≤Rib≤5.5 mm.

[0017] A further improvement is as follows: a chamfer is provided at a connection position between the first surface and the outer surface of the rotor core, and a distance between the two first surfaces of the groove is not less than 5 mm.

[0018] A further improvement is as follows: a shaft mounting hole is provided at the center of the rotor core, and a distance between the shaft mounting hole and the second slot is not less than 1.5 mm.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] 1. Efficient heat dissipation: A unique groove is provided on the rotor core. The groove includes two opposite first surfaces and a bottom surface connecting the two first surfaces. The planes where the two first surfaces are located intersect outside the rotor core. The angle θ between the two first surfaces satisfies the following relationship: 40°≤θ≤55°. The groove not only optimizes air flow and realizes air cooling, but also reduces dependence on external fans, reduces no-load current and loss, and improves overall performance.

[0021] 2. Improved reluctance torque and reduced use of permanent magnets: Through the multi-layer magnetic barrier design, that is, opening the first slot and the second slot on the magnetic pole unit, and adjusting the size ratio of the first magnetic bridge and the second magnetic bridge, the proportion of reluctance torque to total torque is significantly improved, which is about 16% higher than that of traditional motors. At the same time, the use of permanent magnets is reduced by about 21%, effectively controlling costs;

[0022] 3. Large inductance difference and significantly increased salient pole rate: The groove is opened in the direct axis direction of the permanent magnet, which increases the difference between the direct axis and the quadrature axis inductance, enhances the magnetic resistance torque effect, improves the motor efficiency, and enhances the motor's pull-in synchronization capability and overload capacity;

[0023] 4. Optimize the transmission of magnetic lines of force: Improve the structure of the magnetic pole unit to make the no-load magnetic lines of force more densely distributed and the magnetic circuit transmission efficiency higher, ensuring smooth and efficient energy conversion;

[0024] 5. Strong weak magnetic speed expansion capability: The no-load back-EMF fundamental wave amplitude is small, which is helpful for the trapezoidal wave control and weak magnetic speed expansion of the motor, making the motor perform better at high speed operation;

[0025] 6. High structural strength and flexibility: The rotor core is formed by precisely stacking silicon steel sheets, and the distance between multiple structures of the magnetic pole unit is reasonably controlled, ensuring mechanical strength and meeting the requirements of high-speed rotation; at the same time, the layout of grooves and permanent magnets is flexible and can be adjusted according to different application requirements, which improves the versatility and adaptability of the design.

[0026] In summary, the motor of the present invention performs well in terms of heat dissipation performance, torque improvement, cost control, inductance characteristics, magnetic field line transmission and weak magnetic field speed expansion capability, and is suitable for a wide range of fields such as power tools, air-conditioning compressors, and electric vehicles. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The specific embodiments of the present invention are further described in detail below in conjunction with the accompanying drawings:

[0028] Figure 1 It is a structural schematic diagram of the motor of the present invention;

[0029] Figure 2 yes Figure 1 A schematic diagram of the structure of the rotor of the motor shown;

[0030] Figure 3 yes Figure 1 A schematic diagram of the structure of the rotor core of the motor shown;

[0031] Figure 4 yes Figure 1 A schematic diagram of the dimensions of the rotor core of the motor shown;

[0032] Figure 5a A schematic diagram of the structure of a motor in the prior art is shown;

[0033] Figure 5b The structural schematic diagram of the motor of the present invention is shown;

[0034] Figure 6a It is a schematic diagram of the no-load magnetic field line distribution of the motor in the prior art;

[0035] Figure 6b Schematic diagram of no-load magnetic field line distribution of the motor of the present invention;

[0036] Figure 7a It is the no-load back-EMF waveform diagram of the prior art motor;

[0037] Figure 7b is a no-load back-EMF waveform diagram of the motor of the present invention;

[0038] Figure 8aIt is the inductance waveform diagram of the direct axis and quadrature axis of the motor in the prior art;

[0039] Figure 8b It is the inductance waveform diagram of the direct axis and quadrature axis of the motor of the present invention.

[0040] Meaning of the reference numerals in the figures:

[0041] 1. rotor; 10. rotor core; 100. magnetic pole unit; O. center; 11. permanent magnet; 2. stator; 21. stator core; 210. stator teeth; 211. stator yoke; 22. stator winding; 3. groove; 3a. first surface; 3b. bottom surface; 30. first slot; 300. empty slot; 301. mounting slot; 31. first magnetic bridge; 40. second slot; 41. second magnetic bridge; 500. motor; 6. shaft mounting hole; 7. bridging part. DETAILED DESCRIPTION

[0042] The terms used in the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. In the description of the embodiments of the present invention, the technical terms "first", "second", etc. are only used to distinguish different objects, and cannot be understood as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features. The reference to "embodiment" in this article means that the specific features, structures or characteristics described in conjunction with the embodiment may be included in at least one embodiment of the present invention. The appearance of this phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0043] In the description of the embodiments of the present invention, the term "and / or" is only a description of the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B may represent: A exists, A and B exist at the same time, and B exists. In addition, the character " / " in this document generally indicates that the associated objects before and after are in an "or" relationship.

[0044] In the description of the embodiments of the present invention, the orientation or positional relationship indicated by the technical terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the embodiments of the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the embodiments of the present invention. For example, if the device or element in the figure is inverted, then the element described as being "below" or "below" or "below" or "bottom" of other elements or features will be oriented "above" or "top" of the other elements or features. Therefore, the term "below" can cover both the above and below orientations depending on the context in which the term is used, which will be obvious to a person skilled in the art. The material can be oriented in other ways (e.g., rotated 90 degrees, inverted, flipped), and the spatially relative descriptors used herein can be interpreted accordingly.

[0045] The embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0046] See also Figure 1 As shown, a motor 500 involved in the present invention is shown; the motor 500 is an inner rotor brushless motor; the motor 500 can also be a permanent magnet synchronous reluctance motor, which is mainly used in power tools, air-conditioning compressors, electric vehicles and fan systems.

[0047] The motor 500 includes a stator 2 and a rotor 1 disposed in the stator 2, and the rotor 1 is rotatably disposed relative to the stator 2; the rotor 1 includes a rotor core 10 and a plurality of permanent magnets 11 embedded in the rotor core 10; the stator 2 includes a stator core 21 and a stator winding 22 wound on the stator core 21, and the stator core 21 is composed of a stator yoke 211 disposed in an annular shape and a plurality of stator teeth 210 extending inward from the stator yoke 211, and a slot is formed between two adjacent stator teeth 210, and a group of coils is wound on each slot. The stator 2 in the figure has 18 slots, and the specific number of slots is not limited, as long as the total number of slots of the stator 2 can be divided by the number of phases (the number of phases is usually 3); the more slots the stator 2 has, the better the magnetic resistance torque acquisition effect, and the specific number of slots can be: 9, 12, 15, 18, 24, etc. The outer diameter D1 of the stator 2 is 80-120 mm. When the ratio of the inner diameter D2 of the stator to the outer diameter D1 of the stator is 0.59, the output torque of the motor 500 is the highest. To facilitate the control of machining errors, the inner and outer diameters of the stator 2 are rounded as much as possible.

[0048] Please combine Figure 2 and Figure 3As shown, the rotor 1 is shown in the form of a front view. The rotor core 10 of the rotor 1 is usually formed by stacking silicon steel sheets; by accurately stacking and fixing multiple silicon steel sheets to form the structure of the rotor core 10, it can not only effectively reduce eddy current losses and improve motor efficiency, but also ensure mechanical strength to meet the requirements of high-speed rotation and various forces of the motor 500. The rotor core 10 has a center O, and the rotor core 10 includes a plurality of magnetic pole units 100 evenly distributed around the center O. The magnetic pole unit 100 includes a first slot 30 distributed in a V shape, and the first slot 30 is arranged axially through the rotor core 10. A permanent magnet 11 is arranged in the first slot 30, and the first slot 30 is symmetrical about the direct axis Od. Specifically, the rotor 1 has 4 poles, and each pole is composed of two permanent magnets 11. Two permanent magnets arranged in a V shape are embedded in each magnetic pole unit 100, and the two permanent magnets 11 are symmetrically arranged about the direct axis Od. The magnetic flux generated by the permanent magnet 11 of the rotor 1 is the main magnetic flux, and its path is the direct axis Od (direct-axis), while the magnetic flux path generated by the current of the stator winding 22 is the quadrature axis Oq (quadrature-axis); in a synchronous motor, the electrical angle between the direct axis Od and the quadrature axis Oq is 90°.

[0049] Please combine Figure 4 As shown, each magnetic pole unit 100 includes a groove 3 that is radially recessed inward from the outer peripheral surface of the rotor core 10. Specifically, the groove 3 is a dovetail-shaped groove that axially passes through the rotor core 10, which is narrow on the outside and wide on the inside. The groove 3 includes two opposite first surfaces 3a and a bottom surface 3b connecting the two first surfaces 3a. The first groove 30 is located between the center O and the bottom surface 3b of the groove 3 in the radial direction of the rotor core 10. The planes where the two first surfaces 3a are located intersect outside the rotor core 10. The intersection of the two planes is shown as point A in the figure; the angle θ (i.e. ∠EAF) between the two first surfaces 3a satisfies the following relationship: 40°≤θ≤55°. During the rotation of the rotor 1, the groove 3 can effectively drive the air around it to cool the motor 500; in some cases, the fan can be omitted and only the groove 3 can be used for heat dissipation; or the groove 3 can be combined with the fan for double heat dissipation.

[0050] In another embodiment of the present invention, the groove 3 may be a spiral groove provided on the outer circumference of the rotor core 10. The silicon steel sheet provided with the groove 3 may be manufactured and formed by rotating the silicon steel sheet regularly at a certain angle during assembly, thereby obtaining a better cooling effect. In another embodiment of the present invention, the groove 3 may be a semicircular arc groove provided on the outer circumference of the rotor core 10. In another embodiment of the present invention, the planes where the two first surfaces 3a of the groove 3 are located intersect inside the rotor core 10, that is, the groove 3 is a groove that is wide outside and narrow inside.

[0051] Please combine Figure 3 and Figure 4As shown. The first slot 30 includes an empty slot 300 arranged on the side close to the direct axis Od and a mounting slot 301 arranged on the side away from the direct axis Od. The empty slot 300 and the mounting slot 301 are connected to each other. The permanent magnet 11 is arranged in the mounting slot 301. A first magnetic bridge 31 is formed between the bottom surface 3b of the groove 3 and the radial outer side surface of the empty slot 300. In this embodiment, two first slots 30 are respectively arranged on both sides of the direct axis Od. The inner ends of the two first slots 30 on the magnetic pole unit 100 are spaced and opposite to each other to form a bridge 7 therebetween. The bridge 7 is used to ensure the structural strength of the rotor core 10. In another embodiment of the present invention, the empty slot 300 may not be provided. In another embodiment of the present invention, the bridge 7 may not be provided. The first slot 30 is provided on both sides of the direct axis Od, that is, the empty slots on both sides of the direct axis Od are connected; when the bridge 7 is not provided, the magnetic circuit conduction is faster, and the rate is increased by about 10%.

[0052] Preferably, the bottom surface 3b of the groove 3, the radial outer side surface of the empty slot 300 and the radial inner side surface of the empty slot 300 are arc surfaces with the same central axis, or the three surfaces have the same curvature. The dimension h1 of the first magnetic bridge 31 on the direct axis Od and the dimension h2 of the first slot 30 on the direct axis Od satisfy the following relationship: 0.8≤h1 / h2≤1.

[0053] The magnetic pole unit 100 includes a second slot 40 opened on the first slot 30 near the center O of the rotor core 10. The second slot 40 plays a role in reducing weight. The second slot 40 is preferably an arc-shaped slot symmetrical with respect to the direct axis Od. A second magnetic bridge 41 is formed between the radial inner side surface of the empty slot 300 and the radial outer side surface of the second slot 40.

[0054] Preferably, the radial inner side surface of the empty slot 300, the radial outer side surface of the second slot 40 and the radial inner side surface of the second slot 40 are arc surfaces having the same central axis, or the three surfaces have the same curvature. The dimension h3 of the second magnetic bridge 41 on the direct axis Od and the dimension h4 of the second slot 40 on the direct axis Od satisfy the following relationship: 0.8≤h3 / h4≤1.

[0055] The farthest point on the first surface 3a from the center O of the rotor core 10 is the first point A1, the closest point on the bottom surface 3b to the center O of the rotor core 10 is the second point A2, the closest point on the inner surface of the second slot 40 to the center O of the rotor core 10 is the third point A3, and the distance hs between the first point A1 and the second point A2 on the direct axis Od and the distance hb between the second point A2 and the third point A3 on the direct axis Od satisfy the following relationship: 0.8≤hs / hb≤1.

[0056] In this embodiment, the rotor core 10 is composed of four magnetic pole units 100, the angle between two adjacent cross axes Oq is 90°, each magnetic pole unit 100 is symmetrically arranged about the corresponding direct axis Od, and the center of the two permanent magnets 11 of each magnetic pole unit 100 is arranged at an obtuse angle to the center O of the rotor core 10; in addition, the permanent magnet 11 is arranged outside the angle area of ​​the two first surfaces 3a of the magnetic pole unit 100, and the mounting groove 301 for mounting the permanent magnet 11 is shown in the figure as being arranged outside the angle area of ​​the straight line AE and the straight line AF. Such an arrangement can reduce the use of the permanent magnet 11 and ensure a higher reluctance torque.

[0057] The length of the permanent magnet 11 is defined by ΔAEF, point A is the orthographic projection of the intersection of the two first surfaces 3a, point E and point F are the intersections of the two first surfaces 3a and the two intersection axes Oq located on both sides of the direct axis Od, respectively, the permanent magnet 11 is preferably arranged outside the region where ΔAEF is located, and the length and thickness of the permanent magnet 11 are not specifically limited in the present invention. In this embodiment, the thickness of the permanent magnet 11 is 3.2 mm, and the length of the permanent magnet 11 is 6.6 mm.

[0058] In another embodiment of the present invention, the rotor core 10 is composed of six or more even-numbered magnetic pole units 100, and each magnetic pole unit 100 is embedded with a group of two permanent magnets 11 distributed in a "V-shape". In another embodiment of the present invention, each magnetic pole unit 100 is embedded with only one permanent magnet 11 symmetrical about the direct axis Od, and the permanent magnet 11 can be "U-shaped" or "single-shaped", etc. In another embodiment of the present invention, each magnetic pole unit 100 is embedded with permanent magnets 11 arranged in a "double V-shape" or other multi-layer forms.

[0059] Please combine Figure 2 As shown, in order to ensure smooth transmission of the magnetic circuit and obtain a larger reluctance torque, the shortest distance Rib between the two first slots 30 of two adjacent magnetic pole units 100 satisfies the following relationship: 4 mm≤Rib≤5.5 mm.

[0060] Please combine Figure 4 As shown, a shaft mounting hole 6 is provided at the center O of the rotor core 10. To ensure the structural strength of the rotor core 10, the distance between the shaft mounting hole 6 and the second slot 40 is not less than 1.5 mm, that is, h5 ≥ 1.5 mm.

[0061] In addition, a chamfer is provided at the connection position between the first surface 3a of the groove 3 and the outer surface of the rotor core 10; the distance between the two first surfaces 3a of the groove 3 is not less than 5 mm, that is, Figure 4 W1 ≥ 5 mm is shown.

[0062] Preferably, each magnetic pole unit 100 is symmetrically arranged about its corresponding direct axis Od; in other embodiments, the magnetic pole units 100 may not be arranged in this symmetrical manner.

[0063] Next, the advantages of the motor 500 proposed by the present invention will be introduced in detail.

[0064] The motor 500 proposed in the present invention not only takes into account the improvement effect of multi-layer magnetic barriers on the magnetic resistance torque, but also the groove 3 of the rotor 1 greatly improves the heat dissipation performance of the motor 500, providing a possibility for a fanless motor rotor structure. The fanless structure can also reduce the problems of excessive no-load current and no-load loss caused by an external fan, thereby greatly improving the motor performance.

[0065] In addition, the magnitude of the reluctance torque of the built-in permanent magnet motor is closely related to the control angle of the stator current, but the traditional Id=0 control strategy does not utilize the reluctance torque. The motor 500 proposed in the present invention can appropriately change the motor torque by changing the current angle; and the experiment shows that when the current angle is -30°, that is, when the current leads the voltage by 30° electrical angle, the total torque of the motor 500 is the largest. Due to the additive effect of the reluctance torque, the total torque of the motor 500 is higher than the torque when the current angle is 0°, which is increased by about 20%. This part of the torque is increased "for free" because there is no increase in the amount of permanent magnets, current or winding turns, so it is very meaningful for reducing costs and increasing efficiency of products.

[0066] See also Figure 5a and Figure 5b The figures show the structures of the motor in the prior art and the motor of the present invention respectively. Figure 5a The prior art motor shown is a V-shaped internal 18-slot 4-pole motor structure, with no grooves on the straight axis of its rotor core, and its heat dissipation effect is average. Specific parameter comparisons are shown in Table 1 below:

[0067] Existing structure The present invention proposes a structure No-load magnetic field line distribution See Figure 6a See Figure 6b No-load back EMF waveform See Figure 7a See Figure 7b Dq axis inductance waveform See Figure 8a See Figure 8b Back EMF fundamental amplitude (V) 118.1 51.2 Permanent magnet dosage (Kg) 0.99 0.78 Total torque(Nm) 7 5.5 Permanent magnet torque(Nm) 5.6 3.5 Reluctance torque(Nm) 1.4 2.0 Direct axis inductance(mH) 17.8 15.2 Quadrature axis inductance(mH) 23.6 27.5 <![CDATA[Salient pole ratio L q / L d > 1.32 1.81

[0068] Table 1

[0069] It can be seen from Table 1 that the motor 500 of the present invention has the following advantages compared with the motors in the prior art:

[0070] First, the proportion of reluctance torque in the total torque is significantly improved. The reluctance torque of the prior art motor is 1.4 Nm, the total torque is 7 Nm, and the reluctance torque of the prior art motor accounts for 20% of the total torque; while the reluctance torque of the motor 500 of the present invention is 2.0 Nm, the total torque is 5.5 Nm, and the reluctance torque of the motor 500 of the present invention accounts for about 36% of the total torque, and the proportion of reluctance torque in the total torque is significantly improved.

[0071] Second, the reluctance torque becomes larger, and the amount of permanent magnets used is significantly reduced. The larger the reluctance torque of the motor, the more permanent magnets the motor can save, that is, the reluctance torque is generated by the asymmetry of the magnetic circuit to compensate for the total electromagnetic torque. The prior art motor consumes 0.99 kg of permanent magnets; while the motor 500 of the present invention consumes only 0.78 kg of permanent magnets, saving 0.21 kg of permanent magnets, and the amount of permanent magnets can be reduced by about 21%, effectively controlling the material cost.

[0072] Third, the difference between the inductance of the direct axis Od and the quadrature axis Oq increases significantly. Figure 8a and Figure 8b As shown, the prior art motor has a direct-axis inductance of 17.8 mH, a quadrature-axis inductance of 23.6 mH, and a difference of 5.8 Mh between the direct-axis inductance and the quadrature-axis inductance; while the motor 500 of the present invention has a direct-axis inductance of 15.2 mH, a quadrature-axis inductance of 27.5 mH, and a difference of 12.3 Mh between the direct-axis inductance and the quadrature-axis inductance. The greater the difference between the direct-axis inductance and the quadrature-axis inductance, the greater the magnetic resistance torque and the higher the motor efficiency.

[0073] Fourth, the salient pole ratio is significantly increased. The salient pole ratio is also called the magnetic pole prominence ratio or salient pole ratio, which is defined as the ratio of the inductance of the cross and direct axes, thus reflecting the strength of the salient pole effect of the motor; the factors affecting the salient pole ratio of the permanent magnet synchronous motor include: the number of motor phases, the number of winding turns, the slot-pole matching, the winding factor, and the effective armature length. The salient pole ratio of the prior art motor is 1.32; while the salient pole ratio of the motor 500 of the present invention is 1.81, and the salient pole ratio is significantly increased, which can make full use of the magnetic resistance torque generated by the larger salient pole ratio, and the larger salient pole ratio can improve the pull-in synchronization capability of the motor 500 and the overload multiple of the motor.

[0074] Please combine Figure 6a and Figure 6b As shown, Figure 6a Schematic diagram of the no-load magnetic field line distribution of the prior art motor. Figure 6b Schematic diagram of no-load magnetic force lines distribution of the motor 500 of the present invention. As can be seen from the figure: the no-load magnetic force lines of the motor 500 of the present invention are more concentrated, the magnetic circuit and the thermal circuit are in a highly efficient isolation state, and the magnetic field energy transfer efficiency is high.

[0075] Please combine Figure 7a and Figure 7b As shown, Figure 7a It is the no-load back electromotive force waveform of the prior art motor. Figure 7bThe figure is a no-load back-EMF waveform diagram of the motor 500 of the present invention. The back-EMF fundamental amplitude of the prior art motor is 118.1V; while the back-EMF fundamental amplitude of the motor 500 of the present invention is 51.2V, which is significantly smaller, and is beneficial to reducing the power supply capacity and realizing the lightweight design of the electric tool product. For a brushless DC motor, the flatter the no-load back-EMF waveform is, the more beneficial it is to the trapezoidal wave control of the motor; and the smaller the no-load back-EMF fundamental amplitude is, the more beneficial it is to the weak magnetic field speed expansion of the motor. The no-load back-EMF amplitude of the motor is proportional to its rotational speed. Therefore, when the motor DC bus voltage Udc is constant, since the motor 500 of the present invention has a smaller back-EMF fundamental amplitude, its weak magnetic field speed expansion capability is significantly increased.

[0076] The motor 500 proposed in the present invention, as an inner rotor brushless permanent magnet synchronous reluctance motor, has significant advantages: 1. Efficient heat dissipation: a unique groove 3 is provided on the rotor core 10, the groove 3 includes two opposite first surfaces 3a and a bottom surface 3b connecting the two first surfaces 3a, the planes where the two first surfaces 3a are located intersect outside the rotor core 10, and the angle θ between the two first surfaces 3a satisfies the following relationship: 40°≤θ≤55°; the groove 3 not only optimizes the air flow and realizes air cooling and heat dissipation, but also reduces the dependence on the external fan, reduces the no-load current and loss, and improves the overall performance; 2. The reluctance torque is improved and the amount of permanent magnets is reduced: through the multi-layer magnetic barrier design, that is, the first groove 30 and the second groove 40 are provided on the magnetic pole unit 100, and the size ratio of the first magnetic bridge 31 and the second magnetic bridge 41 is adjusted at the same time, so that the proportion of the reluctance torque to the total torque is significantly improved, which is about 16% higher than that of the traditional motor, and the amount of permanent magnets is reduced by about 21%, which effectively controls the cost; 3. Large inductance difference and significantly increased salient pole ratio: The groove 3 is opened in the direction of the direct axis Od of the permanent magnet 11, so that the inductance difference between the direct axis Od and the quadrature axis Oq is increased, the magnetic resistance torque effect is enhanced, the motor efficiency is improved, and the pull-in synchronization capability and overload capacity of the motor 500 are enhanced; 4. Optimization of magnetic line transmission: The structure of the magnetic pole unit 100 is improved, so that the no-load magnetic line distribution is denser and the magnetic circuit transmission efficiency is higher, ensuring smooth and efficient energy conversion; 5. Strong weak magnetic speed expansion capability: The no-load back electromotive force fundamental wave amplitude is small, which is conducive to the trapezoidal wave control and weak magnetic speed expansion of the motor 500, making the motor 500 have better performance under high-speed operation; 6. High structural strength and flexibility: The rotor core 10 is formed by precisely stacking silicon steel sheets, and the distance between multiple structures of the magnetic pole unit 100 is reasonably controlled, ensuring mechanical strength and meeting the requirements of high-speed rotation; at the same time, the layout of the groove 3 and the permanent magnet 11 is flexible and can be adjusted according to different application requirements, improving the versatility and adaptability of the design.

[0077] In summary, the motor 500 of the present invention performs well in terms of heat dissipation performance, torque improvement, cost control, inductance characteristics, magnetic field line transmission and weak magnetic field speed expansion capability, and is suitable for a wide range of fields such as power tools, air-conditioning compressors, and electric vehicles.

[0078] The present invention is not limited to the above specific embodiments. A person skilled in the art can easily understand that there are many alternatives to the motor of the present invention without departing from the principle and scope of the present invention. The protection scope of the present invention shall be subject to the content of the claims.

Claims

1. A motor, comprising a stator and a rotor arranged in the stator, wherein the rotor is rotatably arranged relative to the stator, the rotor comprising a rotor core and a plurality of permanent magnets embedded in the rotor core, the rotor core comprising a plurality of magnetic pole units uniformly distributed around the center of the rotor core, the magnetic pole unit comprising a first slot distributed in a V-shape, the permanent magnet being arranged in the first slot, the first slot being symmetrical about a direct axis, characterized in that: The magnetic pole unit includes a groove that is radially recessed inward from the outer circumferential surface of the rotor core, and the groove includes two opposite first surfaces and a bottom surface connecting the two first surfaces. The first groove is located between the center of the rotor core and the bottom surface in the radial direction of the rotor core, and the planes where the two first surfaces are located intersect outside the rotor core. The angle θ between the two first surfaces satisfies the following relationship: 40°≤θ≤55°; the first groove includes an empty groove arranged on a side close to the direct axis and an installation groove arranged on a side away from the direct axis, the empty groove and the installation groove are connected to each other, the permanent magnet is arranged in the installation groove, and a first magnetic bridge is formed between the bottom surface and the radial outer side surface of the empty groove, and the dimension h1 of the first magnetic bridge on the direct axis and the dimension h2 of the first groove on the direct axis satisfy the following relationship: 0.8≤h1 / h2≤1.

2. The motor according to claim 1, characterized in that: The bottom surface, the radial outer side surface of the hollow groove and the radial inner side surface of the hollow groove are arc surfaces having the same central axis.

3. The motor according to claim 1, characterized in that: The magnetic pole unit includes a second slot opened on a side of the first slot close to the center of the rotor core, and a second magnetic bridge is formed between a radial inner side surface of the empty slot and a radial outer side surface of the second slot.

4. The motor according to claim 3, characterized in that: A dimension h3 of the second magnetic bridge on the direct axis and a dimension h4 of the second slot on the direct axis satisfy the following relationship: 0.8≤h3 / h4≤1.

5. The motor according to claim 4, characterized in that: The radial inner side surface of the empty groove, the radial outer side surface of the second groove, and the radial inner side surface of the second groove are arc surfaces having the same central axis.

6. The motor according to claim 3, characterized in that: The farthest point on the first surface from the center of the rotor core is the first point, the closest point on the bottom surface to the center of the rotor core is the second point, the closest point on the inner surface of the second slot to the center of the rotor core is the third point, and the distance hs between the first point and the second point on the direct axis and the distance hb between the second point and the third point on the direct axis satisfy the following relationship: 0.8≤hs / hb≤1.

7. The motor according to claim 1, characterized in that: The rotor core is composed of four magnetic pole units, each of which is symmetrically arranged about the corresponding direct axis, the center of the two permanent magnets of each magnetic pole unit is arranged at an obtuse angle to the center of the rotor core, and the permanent magnet is arranged outside the angle area of ​​the two first surfaces of the magnetic pole unit.

8. The motor according to claim 1, characterized in that: The shortest distance Rib between two of the first grooves of two adjacent magnetic pole units satisfies the following relationship: 4 mm≤Rib≤5.5 mm.

9. The motor according to claim 1, characterized in that: A chamfer is provided at a connection position between the first surface and the outer surface of the rotor core, and a distance between the two first surfaces of the groove is not less than 5 mm.

10. The motor according to claim 3, characterized in that: A shaft mounting hole is provided at the center of the rotor core, and a distance between the shaft mounting hole and the second slot is not less than 1.5 mm.

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