Permanent magnet motor rotor and permanent magnet motor and preparation method

Abstract

The application discloses a permanent magnet motor rotor and a permanent magnet motor and a preparation method, and relates to the field of permanent magnet motors. The permanent magnet motor rotor comprises a rotor core and a permanent magnet, the permanent magnet is embedded in a permanent magnet slot of the rotor core; the rotor core has a gap side and a rotating shaft side which are oppositely arranged along a radial direction; the permanent magnet comprises a first permanent magnet region and a second permanent magnet region; the first permanent magnet region is located at an end of the permanent magnet which faces at least one of the gap side and the rotating shaft side, and the length of each first permanent magnet region along the radial direction accounts for 5% to 7% of the total length of the permanent magnet in the radial direction; and the resistivity of the permanent magnet material of the first permanent magnet region is higher than that of the second permanent magnet region. By using the permanent magnet with the high-resistivity permanent magnet material at the end and the low-resistivity permanent magnet material in the middle region, the resistivity of the permanent magnet region close to the gap side and the rotating shaft side is high, the penetration path of the eddy current on the surface of the permanent magnet is blocked, and meanwhile, the magnetic performance of the permanent magnet is maintained.

Description

Technical Field

[0001] This invention relates to the field of permanent magnet motors, and in particular to a permanent magnet motor rotor, a permanent magnet motor, and a method for manufacturing them. Background Technology

[0002] In heavy-duty, low-speed direct-drive applications such as mining conveyor belts, the drive motor needs to operate in harsh environments with high dust and high impact for extended periods, placing extremely stringent demands on system reliability, efficiency, and ease of maintenance. Traditional asynchronous motors and reducers suffer from reduced reliability, frequent maintenance, high operating noise, complex structure, and poor compactness. Therefore, replacing them with high-torque-density, low-speed direct-drive permanent magnet motors is imperative. Spoke-type permanent magnet motors, due to their unique magnetic focusing effect, can effectively improve the air gap magnetic flux density, and their direct-drive approach eliminates the need for a reduction gear, demonstrating significant advantages in low-speed, high-torque applications.

[0003] In particular, for multi-pole, few-slot permanent magnet motors with a double-slotted structure, the basic conditions for the occurrence of magnetic field modulation effect are met, which can then enhance torque density by leveraging the characteristics of multiple working magnetomotive forces under this effect. However, the abundant stator magnetomotive force spatial harmonic content of this type of motor also directly leads to high eddy current losses in its permanent magnets. At the same frequency, the eddy current losses of this type of motor are 5-10 times higher than those of traditional multi-slot, few-pole permanent magnet motors.

[0004] To suppress eddy current losses in permanent magnets, existing technologies typically employ radial segmentation of the permanent magnet, with the number of segments increasing as the motor's operating frequency rises. This method can reduce eddy current losses to some extent in traditional multi-slot, few-pole permanent magnet motors.

[0005] However, in multi-pole, few-slot Spoke-type permanent magnet motors, the main harmonic component generating eddy current losses is the (zp) pole pair, whose order is always lower than that of the motor's fundamental component, the p pole pair. This results in a larger calculated standard eddy current penetration depth for multi-pole, few-slot motors. Therefore, even using the traditional radial segmentation method, it is usually difficult to completely prevent eddy currents from penetrating the entire permanent magnet region. Eddy currents will still be concentrated on the surface of the magnet closest to the stator slot opening, and the eddy currents induced by the stator magnetomotive force spatial harmonics penetrating deep into the permanent magnet will also concentrate near the side edges of the permanent magnet due to the skin effect. Eddy current losses directly lead to increased permanent magnet temperature, increased risk of demagnetization, and reduced motor operational reliability.

[0006] Therefore, there is an urgent need for a permanent magnet for Spoke-type multi-pole few-slot direct-drive permanent magnet motors, so as to achieve both improved torque density and safe and reliable operation. Summary of the Invention

[0007] The purpose of this invention is to provide a permanent magnet motor rotor, a permanent magnet motor, and a method for manufacturing them, which can suppress eddy current losses in permanent magnets, thereby solving the above-mentioned technical problems.

[0008] To solve the above-mentioned technical problems, the present invention provides a permanent magnet motor rotor, comprising: The rotor core and permanent magnets are provided, with the permanent magnets embedded in the permanent magnet slots of the rotor core; the rotor core has an air gap side and a shaft side arranged opposite to each other in the radial direction. The permanent magnet includes a first permanent magnet region and a second permanent magnet region; The first permanent magnet region is located at the end of the permanent magnet facing at least one of the air gap side and the shaft side, and the length of each first permanent magnet region in the radial direction accounts for 5% to 7% of the total radial length of the permanent magnet; The resistivity of the permanent magnet material in the first permanent magnet region is higher than that in the second permanent magnet region.

[0009] Optionally, the permanent magnet material in the first permanent magnet region is bonded NdFeB, and the permanent magnet material in the second permanent magnet region is sintered NdFeB.

[0010] Optionally, the resistivity of the permanent magnet material in the first permanent magnet region is 50 to 100 times that of the permanent magnet material in the second permanent magnet region.

[0011] Optionally, the first permanent magnet region is located at the ends of the permanent magnet facing the air gap side and the shaft side, and the second permanent magnet region is located at the middle position between the two first permanent magnet regions.

[0012] Optionally, the second permanent magnet region includes at least two second sub-permanent magnet regions, with adjacent second sub-permanent magnet regions bonded together by an adhesive.

[0013] Optionally, the second permanent magnet region includes at least two second sub-permanent magnet regions, and a stepped interlocking structure is provided between two adjacent second sub-permanent magnet regions.

[0014] Optionally, the surface of the permanent magnet is provided with an insulating layer.

[0015] The present invention also provides a method for preparing a permanent magnet motor rotor, used to prepare a permanent magnet motor rotor as described in the above embodiments, comprising: Prepare a first permanent magnet material and a second permanent magnet material, wherein the resistivity of the first permanent magnet material is higher than that of the second permanent magnet material; The first permanent magnet material and the second permanent magnet material are bonded together to form a permanent magnet that includes a first permanent magnet region and a second permanent magnet region in the radial direction, wherein the first permanent magnet region is located at at least one end of the permanent magnet in the axial direction. The permanent magnet is embedded in the permanent magnet slot of the rotor core to form a permanent magnet motor rotor.

[0016] Optionally, bonding the first permanent magnet material to the second permanent magnet material to form a permanent magnet including a first permanent magnet region and a second permanent magnet region in the radial direction further includes: An insulating layer is coated on the surface of the permanent magnet.

[0017] The present invention also provides a permanent magnet motor, comprising: Stator core; The permanent magnet motor rotor as described in the above embodiments is coaxially disposed within the stator core, forming an air gap with the stator core.

[0018] The permanent magnet motor rotor provided by this invention uses a permanent magnet with high resistivity permanent magnet material in the end region and low resistivity permanent magnet material in the middle region. This results in high resistivity in the permanent magnet regions near the air gap and shaft sides, blocking the penetration path of eddy currents on the permanent magnet surface while maintaining the magnetic properties of the permanent magnet. The high resistivity material region near the air gap side suppresses eddy currents induced by cogging harmonics on the permanent magnet surface, and the high resistivity material region near the shaft side surface suppresses eddy currents induced by stator magnetomotive force space harmonics penetrating deep into the permanent magnet; the low resistivity, high remanence material in the middle region ensures the magnetic properties of the permanent magnet.

[0019] This application effectively suppresses eddy current losses in the permanent magnets of multi-pole, few-slot Spoke-type permanent magnet motors, reducing eddy current losses by approximately 27.5%, while torque density decreases by only about 3.1%. This portion of the loss can be completely compensated for by increasing the armature winding current. The reduction in permanent magnet eddy current losses reduces permanent magnet heating, lowers the risk of permanent magnet demagnetization, and improves the reliability of motor operation. Attached Figure Description

[0020] To more clearly illustrate the technical solutions of the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a schematic diagram of the radial segmentation of a permanent magnet motor rotor according to existing technology; Figure 2This is a schematic diagram of radial segmentation of a permanent magnet motor rotor according to an embodiment of the present invention; Figure 3 A model diagram of a permanent magnet motor based on existing technology; Figure 4 According to Figure 3 A 3D simulation diagram of the eddy current distribution in the permanent magnet of a permanent magnet motor; among which... Figure 4 (a) is a diagram showing the distribution of stator magnetomotive force harmonic induced eddy currents. Figure 4 (b) is a diagram showing the distribution of stator cog harmonic induced eddy currents. Figure 5 A model diagram of a permanent magnet motor according to the present invention; Figure 6 According to Figure 5 A 3D simulation diagram of the eddy current distribution in the permanent magnet of a permanent magnet motor; among which... Figure 6 (a) is a diagram showing the distribution of stator magnetomotive force harmonic induced eddy currents. Figure 6 (b) is a diagram showing the distribution of stator cog harmonic induced eddy currents. Figure 7 A comparison diagram of eddy current losses between a permanent magnet motor according to the prior art and a permanent magnet motor according to the present invention; Figure 8 This is a flowchart illustrating the method for preparing a permanent magnet motor rotor according to the present invention.

[0022] In the diagram, 1: rotor core; 2: first permanent magnet section; 3: second permanent magnet section; 4: first magnetic barrier; 5: second magnetic barrier; 6: first permanent magnet region on the air gap side; 7: second permanent magnet region on the air gap side; 8: second permanent magnet region on the shaft side; 9: first permanent magnet region on the shaft side; 10: permanent magnet; 11: stator core; 12: armature winding; 20: first permanent magnet region; 30: second permanent magnet region; 100: permanent magnet motor. Detailed Implementation

[0023] The core of this invention is to provide a permanent magnet motor rotor. In the prior art, the sources of eddy current losses in permanent magnets mainly include two aspects: first, spatial harmonics in the stator winding magnetomotive force; and second, cogging harmonics introduced by stator slotting. Traditional methods for suppressing eddy current losses include... Figure 1 As shown. This method divides the permanent magnet into radial segments (generally, the number of segments increases with the motor's operating frequency, but should not be excessive). For example, the permanent magnet is divided radially into a first permanent magnet segment 2 located on the air gap side and a second permanent magnet segment 3 located on the shaft side. However, in practice, this method is difficult to fully utilize in multi-pole, few-slot permanent magnet motors, especially Spoke-type multi-pole, few-slot permanent magnet motors, for the following reasons: 1) Eddy currents will still be concentrated on the surface of the permanent magnet closest to the stator slot opening; 2) In multi-pole, few-slot permanent magnet motors, the main harmonic component generating eddy current losses is the (zp) pole pair, whose order is always less than that of the motor's fundamental component, p pole pair. The standard penetration depth (δ) of the eddy current is defined as:

[0024] In the formula, The spatial frequency (proportional to the number of pole pairs) is used to generate eddy current loss harmonics. The relative permeability of the permanent magnet; is the electrical conductivity of the permanent magnet.

[0025] Therefore, compared to multi-slot, few-pole permanent magnet motors, multi-pole, few-slot permanent magnet motors will always have a larger calculated standard eddy current penetration depth, even when using... Figure 1 The radial segmentation method shown is usually difficult to prevent eddy currents from completely penetrating the entire permanent magnet region.

[0026] In the technical solution of this application, the proposed permanent magnet motor rotor uses a permanent magnet with high resistivity permanent magnet material in the end region and low resistivity permanent magnet material in the middle region. This results in high resistivity in the permanent magnet region near the air gap and shaft side, blocking the penetration path of eddy currents on the permanent magnet surface while maintaining the magnetic properties of the permanent magnet. The high resistivity material region near the air gap side suppresses eddy currents induced by cogging harmonics on the permanent magnet surface, and the high resistivity material region near the shaft side surface suppresses eddy currents induced by stator magnetomotive force space harmonics penetrating deep into the permanent magnet. The low resistivity and high remanence material in the middle region ensures the magnetic properties of the permanent magnet.

[0027] To enable those skilled in the art to better understand the present invention, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. Obviously, the described embodiments are merely some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0028] In this application, the axial direction refers to the direction parallel to the center line of the permanent magnet motor shaft, that is, the direction through which the motor runs "from beginning to end".

[0029] The radial direction refers to the direction perpendicular to the center line of the rotating shaft and radiating outward from the center of the rotating shaft, that is, the direction from the center of the circle to the air gap (or from the air gap to the center of the circle).

[0030] The circumferential direction refers to the direction along the tangent of the rotor circumference, that is, the tangent direction of the trajectory of each point when the rotor rotates.

[0031] The permanent magnet motor rotor, permanent magnet motor, and manufacturing method provided in the embodiments of the present invention are described below with reference to the accompanying drawings.

[0032] Reference Figure 1 and Figure 2 The permanent magnet motor rotor of the present invention may include: The rotor core 1 and the permanent magnet 10 are provided, with the permanent magnet 10 embedded in the permanent magnet slot of the rotor core 1; the rotor core 1 has an air gap side and a shaft side arranged opposite to each other in the radial direction. The permanent magnet 10 includes a first permanent magnet region 20 and a second permanent magnet region 30; The first permanent magnet region 20 is located at the end of the permanent magnet 10 facing at least one of the air gap side and the shaft side, and the length of each first permanent magnet region 20 in the radial direction accounts for 5% to 7% of the total radial length of the permanent magnet 10; The resistivity of the permanent magnet material in the first permanent magnet region 20 is higher than that of the permanent magnet material in the second permanent magnet region 30.

[0033] In this embodiment, the permanent magnet motor rotor is generally a Spoke-type permanent magnet motor. (Refer to...) Figure 2 A permanent magnet motor rotor typically includes a rotor core 1, which is generally made of stacked silicon steel sheets and is cylindrical in shape. An air gap is formed between its outer circumference and the inner circumference of the stator. In the radial direction, the side of the rotor core closer to the air gap is called the air gap side, and the side closer to the center of the shaft is called the shaft side.

[0034] The rotor core 1 has permanent magnet slots extending radially. These slots typically adopt an "I" shape or a "V" shape, with the slot opening facing the air gap side or the shaft side. The two side walls of the slot are used to constrain the radial and circumferential positions of the permanent magnet. In one feasible embodiment, the width and height of the permanent magnet slots are both greater than the size of the permanent magnet.

[0035] The permanent magnets 10 are embedded in permanent magnet slots for positioning and fixation. The permanent magnets 10 are arranged in a radial pattern along the rotor, with the magnetization direction being radial, and the polarities of adjacent magnetic poles are arranged alternately. Multiple permanent magnets 10 are evenly arranged around the rotor circumference to form a ring of magnetic poles, with the polarities of adjacent magnetic poles alternating (N pole and S pole alternate).

[0036] Regarding the shape of the permanent magnet 10, the permanent magnet 10 is, for example, in the shape of a long strip plate. When viewed from the rotor cross section, a single permanent magnet 10 is arranged in the radial direction, with its length direction consistent with the rotor radius direction, its width direction consistent with the rotor circumferential direction, and its thickness direction consistent with the rotor axial direction.

[0037] In this embodiment, the permanent magnet 10 includes a first permanent magnet region 20 and a second permanent magnet region 30. The first permanent magnet region 20 is located at at least one end of the permanent magnet 10 facing the air gap side and the shaft side, that is, at least one of the uppermost and lowermost ends of the permanent magnet 10 in the radial direction. The second permanent magnet region 30 is located in other regions of the permanent magnet 10 besides the first permanent magnet region 20. The radial length of the first permanent magnet region 20 accounts for 5% to 7% of the total radial length of the permanent magnet 10, which is mainly determined based on the distribution of eddy current density on the surface of the permanent magnet in the three-dimensional finite element simulation results. In a feasible implementation, the radial length of the first permanent magnet region 20 accounts for 5% of the total radial length of the permanent magnet 10.

[0038] The resistivity of the permanent magnet material in the first permanent magnet region 20 (also referred to herein as the first permanent magnet material) is higher than that of the permanent magnet material in the second permanent magnet region 30 (also referred to herein as the second permanent magnet material). In one feasible embodiment, the resistivity of the first permanent magnet material is 50 to 100 times that of the second permanent magnet material. In one feasible embodiment, the first permanent magnet material is bonded NdFeB, and the second permanent magnet material is sintered NdFeB. The resistivity of the bonded NdFeB material is approximately 1.4 × 10⁻⁶. -4 The resistivity of sintered NdFeB material is approximately 1.8 × 10⁻⁶ Ω·m. -6 The resistivity of the former is nearly 100 times that of the latter, with a resistivity of Ω·m. Due to this significant difference in resistivity, bonded NdFeB materials can effectively block the penetration path of eddy currents inside the permanent magnet.

[0039] Regarding magnetic properties, the remanence of sintered NdFeB materials is approximately 1.2 T to 1.3 T, while that of bonded NdFeB materials is approximately 0.6 T. Since the first permanent magnet region 20, such as the bonded NdFeB region, accounts for only a small proportion of the total length of the permanent magnet, its impact on the overall magnetic properties of the permanent magnet 10 is very limited. The main body of the permanent magnet 10 still maintains high remanence and energy product, thereby ensuring that the motor has high air gap magnetic flux density and output torque.

[0040] During motor operation, the harmonic magnetic field generated by the stator windings induces eddy currents in the permanent magnet 10, and the region with the highest concentration of eddy current losses is located at the axial end of the permanent magnet 10. Specifically, the air gap side end of the permanent magnet 10 closest to the stator slot opening is directly exposed to the air gap harmonic magnetic field, and harmonic flux most easily enters the permanent magnet 10 from this position and induces strong eddy currents; at the same time, once eddy currents are generated at the end, they will penetrate radially into the interior of the permanent magnet 10. Therefore, in a feasible embodiment, in order to achieve better eddy current loss suppression, the permanent magnet 10 includes two first permanent magnet regions 20, which are located at the ends of the permanent magnet 10 facing the air gap side and the shaft side, respectively; a second permanent magnet region 30 is located in the middle position between the two first permanent magnet regions 20.

[0041] The first permanent magnet region 20 located on the air gap side (also referred to herein as the air gap side first permanent magnet region 6) serves to suppress eddy currents induced by cogging harmonics on the surface of the permanent magnet. The first permanent magnet region 20 located on the shaft side (also referred to herein as the shaft side first permanent magnet region 9) serves to suppress eddy currents induced by stator magnetomotive force spatial harmonics penetrating deep into the permanent magnet. These eddy currents are concentrated near the side edges of each permanent magnet due to the skin effect. The first permanent magnet region 20 is positioned at both ends rather than in the middle of the permanent magnet to balance torque density. This combined design of the air gap side first permanent magnet region 6 and the shaft side first permanent magnet region 9 can form an effective resistance barrier at the source and penetration path of eddy current loss, confining the eddy current to a smaller end region, significantly reducing the overall eddy current loss and temperature rise of the permanent magnet.

[0042] To improve manufacturing efficiency, the first permanent magnet region 6 on the air gap side and the first permanent magnet region 9 on the shaft side can be slightly different. For example, the radial length of the first permanent magnet region 6 on the air gap side can be slightly greater than the radial length of the first permanent magnet region 9 on the shaft side, but it still needs to block the area where eddy currents are most concentrated. However, for ease of manufacturing, the two can be made the same. The radial lengths of the first permanent magnet region 6 on the air gap side and the first permanent magnet region 9 on the shaft side can be the same, for example, 5% of the total radial length of the permanent magnet.

[0043] In this embodiment, the second permanent magnet region 30 is located in the permanent magnet 10, excluding the first permanent magnet region 20, i.e., the middle region excluding the ends. In a feasible implementation, the second permanent magnet region 30 may include at least two second sub-permanent magnet regions. Adjacent second sub-permanent magnet regions may be bonded together with an adhesive, or a stepped interlocking structure may be provided between adjacent second sub-permanent magnet regions to achieve physical isolation. Generally, the number of second sub-permanent magnet regions is usually two or less. If the number of second sub-permanent magnet regions 30 is more than two, more material boundaries need to be set in the radial direction of the permanent magnet 10. This would significantly increase the rotor assembly process. Each additional material boundary requires an additional positioning, bonding, or pressing process, making it difficult to guarantee the assembly accuracy and consistency of the permanent magnet 10 within the permanent magnet slot. At the same time, an increase in material interfaces introduces more bonding surfaces or gaps. Under the centrifugal force of high-speed rotation, stress concentration is easily generated at the interface, posing a risk of permanent magnet breakage or detachment. Therefore, by limiting the number of second permanent magnet regions 30 to two or less, and setting the first permanent magnet regions 20 only at the head and tail ends of the permanent magnet, it is possible to effectively suppress eddy currents while taking into account the simplicity of the assembly process, the reliability of the mechanical structure, and the maximization of magnetic performance.

[0044] In one feasible implementation, the second permanent magnet region 30 includes an air gap-side second permanent magnet region 7 and a shaft-side second permanent magnet region 8. The air gap-side second permanent magnet region 7 and the shaft-side second permanent magnet region 8 can be bonded together with an adhesive, or a stepped interlocking structure can be provided between them to achieve physical isolation.

[0045] In one feasible implementation, a magnetic isolation bridge is typically provided between the rotor core 1 and the permanent magnet 10. The magnetic isolation bridge is a narrow magnetic circuit channel on the rotor core of the built-in permanent magnet motor, located at the connection between the permanent magnet slot and the solid part of the rotor core, serving both mechanical fixing and magnetic circuit control functions. In this embodiment, the magnetic isolation bridge can be a conventional arrangement, such as... Figure 1 and Figure 2 As shown, you can choose according to your actual needs.

[0046] In one feasible implementation, such as Figure 2 As shown, near the shaft side of the permanent magnet slot, the rotor core 1 is provided with a first magnetic barrier 4 and a second magnetic barrier 5, which are arranged sequentially along the circumference of the rotor core. The extremely narrow channel between the two is the magnetic isolation bridge.

[0047] The first magnetic barrier 4 is located between two adjacent permanent magnet slots, connecting the rotor core portion of two adjacent magnetic poles. The second magnetic barrier 5 is located at the end of the permanent magnet slot near the shaft side, in the same radial direction as the permanent magnet, providing mechanical support and restraint for the permanent magnet 10 embedded in the permanent magnet slot towards the shaft side, preventing the permanent magnet 10 from sliding towards the shaft side under the action of centrifugal force or thermal stress.

[0048] The first magnetic barrier 4 and the second magnetic barrier 5 work together to impede magnetic flux as much as possible, because the flux passing through this area is leakage flux and does not participate in the electromechanical energy conversion of the motor. The first magnetic barrier 4 controls the leakage flux between poles and connects adjacent magnetic poles, while the second magnetic barrier 5 supports the end of the permanent magnet and conducts the magnetic circuit of the yoke, together ensuring the mechanical reliability and electromagnetic performance of the rotor at high speeds. The magnetic isolation bridge is in a magnetically saturated state during motor operation, thereby limiting leakage flux short circuits between adjacent magnetic poles and ensuring that more magnetic flux generated by the permanent magnet passes through the air gap into the stator, increasing the effective magnetic flux linkage of the motor. At the same time, the magnetic isolation bridge provides a mechanical connection for the pole shoe portion of adjacent magnetic poles, enhancing the structural integrity of the rotor outer ring and preventing the pole shoes from deforming or breaking under centrifugal force.

[0049] In addition, an external magnetic bridge (not shown) is usually provided near the air gap side of the permanent magnet slot to prevent the permanent magnet from flying out under the action of centrifugal force, and at the same time suppress the leakage magnetic short circuit between poles.

[0050] In this embodiment, the other structures of the rotor are all conventional structures in the art, and those skilled in the art can design and select them according to actual needs.

[0051] The following is based on Figure 2 The rotor structure of the permanent magnet motor in the example will be described in more detail.

[0052] like Figure 2 As shown, the permanent magnet motor rotor includes a rotor core 1 and permanent magnets. The permanent magnets include a first permanent magnet region 6 on the air gap side and a first permanent magnet region 9 on the shaft side, as well as a second permanent magnet region 7 on the air gap side and a second permanent magnet region 8 on the shaft side located between the two first permanent magnet regions. The first permanent magnet region 6 and the second permanent magnet region 7 on the air gap side constitute a first permanent magnet segment 2; the first permanent magnet region 9 and the second permanent magnet region 8 on the shaft side constitute a second permanent magnet segment 3. The first permanent magnet region 6 on the air gap side and the first permanent magnet region 9 on the shaft side have the same length in the radial direction and account for 5% of the total radial length of the permanent magnets. Both the first permanent magnet region 6 on the air gap side and the first permanent magnet region 9 on the shaft side include bonded NdFeB, and both the second permanent magnet region 8 on the shaft side and the second permanent magnet region 7 on the air gap side include sintered NdFeB. In addition, a first magnetic barrier 4 and a second magnetic barrier 5 are provided to impede magnetic flux as much as possible, thereby reducing magnetic leakage.

[0053] In summary, the permanent magnet motor rotor of the present invention achieves a significant eddy current loss suppression effect by using high resistivity bonded NdFeB material at both ends of the permanent magnet to form eddy current barriers, while retaining low resistivity and high magnetic properties sintered NdFeB material in the main body of the permanent magnet.

[0054] This invention also provides a method for manufacturing a permanent magnet motor rotor. (Refer to...) Figure 8 The methods for manufacturing permanent magnet motor rotors include: S1: Prepare the first permanent magnet material and the second permanent magnet material.

[0055] In this step, the resistivity of the first permanent magnet material is higher than that of the second permanent magnet material. As described above, for example, the first permanent magnet material is bonded NdFeB, and the second permanent magnet material is sintered NdFeB.

[0056] The resistivity of the bonded NdFeB material is approximately 1.4 × 10⁻⁶. -4 The resistivity of sintered NdFeB material is approximately 1.8 × 10⁻⁶ Ω·m. -6 The resistivity of the former is nearly 100 times that of the latter (Ω·m). Sintered NdFeB has high energy product and high coercivity, which are used to provide the main magnetic flux; bonded NdFeB is used to reduce eddy current losses.

[0057] S2: The first permanent magnet material and the second permanent magnet material are bonded together to form a permanent magnet that includes a first permanent magnet region and a second permanent magnet region in the radial direction.

[0058] In this step, two different materials are combined to form a permanent magnet that includes different regions.

[0059] In one feasible implementation, such as Figure 2 As shown, when the first permanent magnet region 20 is located at both ends of the permanent magnet (hereinafter referred to as the air gap side first permanent magnet region 6 and the shaft side first permanent magnet region 9, respectively) and the second permanent magnet region 30 includes two second sub-permanent magnet regions (hereinafter referred to as the air gap side second permanent magnet region 7 and the shaft side second permanent magnet region 8), step S2 specifically includes: bonding the shaft side first permanent magnet region 9 and the shaft side second permanent magnet region 8 with an adhesive to form a second permanent magnet segment 3, and bonding the air gap side first permanent magnet region 6 and the air gap side second permanent magnet region 7 with an adhesive to form a first permanent magnet segment 2.

[0060] There are no particular restrictions on the type of adhesive used. In one feasible implementation, anaerobic adhesive can be used. To ensure that the presence of the adhesive does not affect the performance of the permanent magnet, the thickness of the adhesive layer is generally only about 0.1 mm, for example, in the range of 0.05 to 0.15 mm.

[0061] In this embodiment, after the corresponding permanent magnet regions are bonded together, an insulating layer can be coated on the surface. For the type of insulating layer, an epoxy insulating layer is generally used in this embodiment. Furthermore, there are no particular limitations on the method of forming the insulating layer; for example, the insulating layer can be plated onto the surface of the permanent magnet.

[0062] After step S2, a permanent magnet or a permanent magnet segment is formed. For example, when the first permanent magnet region is located only at one end of the permanent magnet and the second permanent magnet region is integral, a complete permanent magnet is formed after this step.

[0063] S3: The permanent magnet is embedded in the permanent magnet slot of the rotor core to form a permanent magnet motor rotor.

[0064] In this step, the permanent magnet or permanent magnet segment formed in step S2 is embedded into the permanent magnet slot in the radial direction to form a permanent magnet motor rotor.

[0065] In one feasible implementation, when the first permanent magnet region is located only at one end of the permanent magnet and the second permanent magnet region is integral, the permanent magnet obtained in step S2 is embedded in the permanent magnet slot of the rotor core to form a permanent magnet motor rotor.

[0066] In one feasible implementation, when the first permanent magnet region is located at both ends of the permanent magnet and the second permanent magnet region includes two second sub-permanent magnet regions, two permanent magnet segments, namely the first permanent magnet segment 2 and the second permanent magnet segment 3, are formed in step S2. When embedding the permanent magnet, the permanent magnet segment on the shaft side, i.e., the second permanent magnet segment 3, is embedded first, and then the permanent magnet segment on the air gap side, i.e., the first permanent magnet segment 2, is embedded to form a complete permanent magnet. The two permanent magnet segments can be bonded together at their mating surfaces using an adhesive layer during embedding; alternatively, an interlocking structure can be provided at the mating surfaces of the two permanent magnet segments to physically separate them. For example, when using adhesive bonding, adhesive such as glue can be applied to the surface of one of the second sub-permanent magnet regions of one of the two permanent magnet segments, and then the mating surfaces of the two permanent magnet segments are bonded together when embedding into the permanent magnet groove. Furthermore, after all permanent magnets are embedded, all air gaps in the permanent magnet groove can be potted using a specially formulated glue.

[0067] To allow space for the adhesive layer within the permanent magnet slot, as mentioned above, both the width and height of the permanent magnet slot are larger than the permanent magnet dimensions. Typically, the permanent magnet slot width = permanent magnet width + 0.2, and the permanent magnet slot height = permanent magnet height + 0.2.

[0068] The following section describes the manufacturing method of the permanent magnet motor rotor structure shown in the figure in more detail.

[0069] The methods for manufacturing permanent magnet motor rotors include: S1': Prepare bonded NdFeB and sintered NdFeB; S2': Bonded NdFeB and sintered NdFeB are bonded together with adhesive to form two permanent magnet segments, namely the first permanent magnet segment 2 and the second permanent magnet segment 3, and the bonded NdFeB regions of the first permanent magnet segment 2 and the second permanent magnet segment 3 have the same radial length; and an epoxy insulating layer is formed on the surface of the two permanent magnet segments. S3': Apply adhesive to the surface of the sintered NdFeB region of the second permanent magnet segment 3, embed the second permanent magnet segment 3 into the permanent magnet groove, and then embed the first permanent magnet segment 2 into the same permanent magnet groove. The two permanent magnet segments are bonded together with adhesive. Optionally, a specially formulated adhesive can be used to fill all air gaps in the permanent magnet groove to form a permanent magnet rotor.

[0070] The present invention also provides a permanent magnet motor, comprising: Stator core 11; and As described in the above embodiment, the permanent magnet motor rotor is coaxially disposed inside the stator core 11, forming an air gap between it and the stator core.

[0071] In this embodiment, the permanent magnet motor may include the rotor of the present invention, as well as the stator core 11 and armature winding 12. The connection relationship and specific details between the components can be referred to the known content in the prior art, and will not be repeated here.

[0072] The present invention will be explained and described in more detail below through specific embodiments.

[0073] The following section uses a 72-slot, 84-pole Spoke permanent magnet motor as an example to illustrate the implementation of the design method. The known parameters are as follows:

[0074] The model of a permanent magnet motor using traditional radial segmentation is as follows: Figure 3 As shown, a three-dimensional finite element simulation analysis was conducted on it, and the eddy current distribution of the permanent magnet was obtained as follows. Figure 4 As shown, for clarity, only a set of segmented permanent magnets and stator cores are shown in the figure.

[0075] Figure 4 (a) This figure illustrates the eddy current distribution within the permanent magnet when the stator magnetomotive force harmonics dominate in a prior art permanent magnet motor 100. As can be seen from the figure, the maximum eddy current density is concentrated on the side surfaces of the permanent magnets, most notably the surface closest to the slot opening, the surface where the two permanent magnets meet, and the surface furthest from the slot opening. The width of the eddy current center region measured at the surfaces closest to and furthest from the slot opening is approximately 3.50 mm. The maximum eddy current density reaches 1.04 × 10⁻⁴ mm. 6 W / m 3 .

[0076] Figure 4(b) illustrates the eddy current distribution within the permanent magnet when stator slot harmonics dominate. As can be seen from the figure, the maximum eddy current density is concentrated near the side edge of the permanent magnet closest to the slot opening. The width of this central eddy current region is measured to be approximately 3.98 mm. The maximum eddy current density reaches 2.07 × 10⁻⁶ mm. 6 W / m 3 .

[0077] Therefore, considering both the width of the eddy current center region and the torque density under the above two conditions, a thickness of 3.00 mm for the bonded NdFeB region is selected. The permanent magnet motor model of this invention is as follows: Figure 5 As shown. Similarly, the eddy current distribution under the dominance of stator magnetomotive force harmonics and cogging harmonics was obtained through three-dimensional finite element simulation, as follows. Figure 6 As shown. Figure 6 (a) illustrates the eddy current distribution within the permanent magnet when the stator magnetomotive force harmonics dominate in the permanent magnet motor 100 of the present invention. As can be seen from the figure, the width of the central eddy current region is approximately 2.72 mm, and the maximum eddy current density reaches 8.12 × 10⁻⁶ mm. 5 W / m 3 . Figure 6 (b) illustrates the eddy current distribution within the permanent magnet when stator cogging harmonics dominate. The figure shows that the width of the central eddy current region is approximately 2.72 mm, and the maximum eddy current density reaches 8.12 × 10⁻⁶ mm. 5 W / m 3 .and Figure 4 (a) and Figure 4 (b) Compared with the existing permanent magnet motor, the width of the eddy current center region is reduced by approximately 0.78 mm and approximately 1.26 mm, respectively, and the maximum eddy current density is reduced by approximately 2.28 × 10⁻⁶ mm, respectively. 5 W / m 3 and 1.258×10 6 W / m 3 .

[0078] Therefore, the permanent magnet motor rotor structure of the present invention, namely the permanent magnet including bonded NdFeB region 1 and bonded NdFeB region 2, effectively reduces the width of the eddy current region closest to the slot opening and the maximum eddy current density, thereby suppressing the eddy current loss of the permanent magnet.

[0079] Furthermore, a group of permanent magnets with the same relative stator position were selected, and the magnitudes of eddy current losses before and after were compared. The results are as follows: Figure 7As shown in the figure, the average eddy current loss of this group of permanent magnets using the traditional method is 25.3W. After applying the method proposed in this invention, the average loss drops to 18.3W, a decrease of 27.5%, verifying the effectiveness of the proposed method. Simultaneously, the torque density decreases by only about 3.1%, a loss that can be completely mitigated by increasing the armature winding current. Although this increases the stator temperature rise, its insulation level is high, and permanent magnets are prone to demagnetization at high temperatures.

[0080] Therefore, the method proposed in this invention can effectively suppress the eddy current loss of permanent magnets in multi-pole, few-slot Spoke type motors, and can improve the reliability of motor operation and reduce the risk of permanent magnet demagnetization.

[0081] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since it corresponds to the method disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to in the method section.

[0082] Those skilled in the art will further recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of both. To clearly illustrate the interchangeability of hardware and software, the components and steps of the various examples have been generally described in terms of functionality in the foregoing description. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementations should not be considered beyond the scope of this invention.

[0083] The steps of the methods or algorithms described in conjunction with the embodiments disclosed herein can be implemented directly by hardware, a software module executed by a processor, or a combination of both. The software module can be located in random access memory (RAM), main memory, read-only memory (ROM), electrically programmable ROM, electrically erasable programmable ROM, registers, hard disk, removable disk, CD-ROM, or any other form of storage medium known in the art.

[0084] Finally, it should be noted that in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0085] The present invention provides a detailed description of a permanent magnet motor rotor, a permanent magnet motor, and a method for its fabrication. Specific examples have been used to illustrate the principles and implementation methods of the invention. These examples are merely illustrative and are intended to aid in understanding the method and core concepts of the invention. It should be noted that those skilled in the art can make various improvements and modifications to the invention without departing from its principles, and these improvements and modifications also fall within the scope of protection of the claims.

Claims

1. A permanent magnet motor rotor, characterized in that, include: The rotor core and permanent magnets are provided, with the permanent magnets embedded in the permanent magnet slots of the rotor core; the rotor core has an air gap side and a shaft side arranged opposite to each other in the radial direction. The permanent magnet includes a first permanent magnet region and a second permanent magnet region; The first permanent magnet region is located at the end of the permanent magnet facing at least one of the air gap side and the shaft side, and the length of each first permanent magnet region in the radial direction accounts for 5% to 7% of the total radial length of the permanent magnet; The resistivity of the permanent magnet material in the first permanent magnet region is higher than that in the second permanent magnet region.

2. The permanent magnet motor rotor according to claim 1, characterized in that, The permanent magnet material in the first permanent magnet region is bonded NdFeB, and the permanent magnet material in the second permanent magnet region is sintered NdFeB.

3. The permanent magnet motor rotor according to claim 2, characterized in that, The resistivity of the permanent magnet material in the first permanent magnet region is 50 to 100 times that of the permanent magnet material in the second permanent magnet region.

4. The permanent magnet motor rotor according to claim 1, characterized in that, The first permanent magnet region is located at the ends of the permanent magnet facing the air gap side and the shaft side, and the second permanent magnet region is located at the middle position between the two first permanent magnet regions.

5. The permanent magnet motor rotor according to claim 1, characterized in that, The second permanent magnet region includes at least two second sub-permanent magnet regions, and adjacent second sub-permanent magnet regions are bonded together by an adhesive.

6. The permanent magnet motor rotor according to claim 1, characterized in that, The second permanent magnet region includes at least two second sub-permanent magnet regions, and a stepped interlocking structure is provided between two adjacent second sub-permanent magnet regions.

7. The permanent magnet motor rotor according to claim 1, characterized in that, An insulating layer is provided on the surface of the permanent magnet.

8. A method for preparing a permanent magnet motor rotor, used to prepare a permanent magnet motor rotor as described in any one of claims 1 to 7, characterized in that, include: Prepare a first permanent magnet material and a second permanent magnet material, wherein the resistivity of the first permanent magnet material is higher than that of the second permanent magnet material; The first permanent magnet material and the second permanent magnet material are bonded together to form a permanent magnet that includes a first permanent magnet region and a second permanent magnet region in the radial direction, wherein the first permanent magnet region is located at at least one end of the permanent magnet in the axial direction. The permanent magnet is embedded in the permanent magnet slot of the rotor core to form a permanent magnet motor rotor.

9. The preparation method according to claim 8, characterized in that, Bonding the first permanent magnet material to the second permanent magnet material to form a permanent magnet including a first permanent magnet region and a second permanent magnet region along the radial direction further includes: An insulating layer is coated on the surface of the permanent magnet.

10. A permanent magnet motor, characterized in that, include: Stator core; The permanent magnet motor rotor as described in any one of claims 1 to 7, wherein the permanent magnet motor rotor is coaxially disposed within the stator core, forming an air gap with the stator core.

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