Magnet and method of manufacturing the same, rotor, and electric machine

Abstract

The application provides a magnet and a manufacturing method thereof, a rotor and a motor. The magnet comprises a main body having opposite first and second surfaces, and a notch formed in at least one of the first and second surfaces of the main body, the notch having an arc shape or a ring shape, and the notch is non-through in the depth direction of the notch. By adopting the technical scheme of the application, the stress of the magnet can be dispersed, the physical performance of the magnet can be improved while reducing the magnetic loss and the eddy current loss of the magnet. Meanwhile, for the non-through arc and ring notch in the application, a new slotting method is provided, which can minimize the damage to the phase structure of the magnet surface during processing, reduce the range of the damaged layer, the remelted layer and the heat affected layer, and thus minimize the reduction of the magnetic flux caused by the processing of the magnet.

Description

Technical Field

[0001] This invention relates to magnets and their manufacturing methods, rotors, and motors. Background Technology

[0002] Magnets, due to their high energy product and high coercivity, are now widely used in various high-efficiency and energy-saving motors.

[0003] Because magnets are good conductors of electricity and are usually large when used in motors, they are prone to generating strong eddy currents in high-frequency alternating magnetic fields. This causes the magnets to heat up, and the temperature rises, which can easily cause reversible or irreversible magnetic losses in the magnets, as well as increase the energy consumption and reduce the efficiency of the motor.

[0004] To reduce eddy current losses in magnets, small magnets are usually glued together to form a larger magnet using insulating adhesive, or straight grooves are cut into the magnet. However, both of these methods degrade the physical properties of the magnet, especially its bending strength. Summary of the Invention

[0005] To overcome at least one aspect of the aforementioned defects and problems in the prior art, the present invention provides a magnet with improved physical properties.

[0006] According to a specific embodiment of the present invention, a magnet is provided, comprising: a body having opposing first and second surfaces; and a slot formed in at least one of the first and second surfaces of the body, the slot having an arcuate or annular shape, the slot being non-penetrating in the depth direction of the slot.

[0007] In a preferred embodiment, the groove is filled with a substance whose resistivity is greater than that of the material of the body.

[0008] In a preferred embodiment, the first and second surfaces of the body are parallel to each other.

[0009] In a preferred embodiment, the magnet is cubic in shape.

[0010] In a preferred embodiment, the depth direction of the slot is perpendicular to at least one of the first surface and the second surface.

[0011] In a preferred embodiment, the slot is elliptical.

[0012] In a preferred embodiment, the slot includes a first slot formed in a first surface of the body and a second slot formed in a second surface of the body, the first slot and the second slot having an annular shape.

[0013] In a preferred embodiment, when viewed in a direction perpendicular to the first surface or the second surface, the first slot surrounds the second slot and is spaced apart from the second slot.

[0014] In a preferred embodiment, the groove further includes a third groove formed in a first surface of the body, the third groove having an annular shape.

[0015] In a preferred embodiment, when viewed in a direction perpendicular to the first or second surface, the first slot surrounds and is spaced apart from the second slot, and the second slot surrounds and is spaced apart from the third slot.

[0016] In a preferred embodiment, the slot further includes a third slot formed in a first surface of the body and a fourth slot formed in a second surface of the body, the third slot and the fourth slot having an annular shape.

[0017] In a preferred embodiment, when viewed in a direction perpendicular to the first or second surface, the first slot, the second slot, the third slot, and the fourth slot are arranged sequentially from the outside to the inside and are spaced apart from each other.

[0018] According to another specific embodiment of the present invention, a method for manufacturing a magnet is provided, comprising the steps of: providing a magnet, the magnet comprising: a body having opposing first and second surfaces; and forming a slot in the first surface of the body, the slot having an arcuate shape or an annular shape, the slot being non-penetrating in the depth direction of the slot.

[0019] In a preferred embodiment, forming a groove in the first surface of the body includes: forming the groove by multiple cuts using a laser beam, wherein the depth of each cut is a portion of the total depth of the groove.

[0020] In a preferred embodiment, forming a groove using a laser beam through multiple cuts includes:

[0021] First cut: A laser beam is focused on the first surface of the body or at a position between the first and second surfaces of the body to form a first portion of the groove in the depth direction of the groove. During the first cut, the focal point of the laser beam is at a first predetermined distance from the first surface of the body.

[0022] Second cut: The laser beam is focused on the position between the first and second surfaces of the main body to form a second part of the groove in the depth direction of the groove. In the second cut, the focal point of the laser beam is a second predetermined distance away from the first surface of the main body. The second predetermined distance is greater than the first predetermined distance.

[0023] In a preferred embodiment, the depth of the second cut is 90%-110% of the depth of the first cut.

[0024] In a preferred embodiment, the power of the laser beam is adjusted during the process of forming a groove by multiple cuts using a laser beam.

[0025] In a preferred embodiment, the slot is in the shape of "└┘" or U.

[0026] In a preferred embodiment, forming a groove in the first surface of the body includes: forming the groove by laser beam cutting, and cooling the cutting position while performing laser cutting, with the cooling position moving synchronously with the trajectory of laser cutting.

[0027] In a preferred embodiment, the laser beam is cooled within 1 second as it passes through the location.

[0028] In a preferred embodiment, when the main material is a neodymium iron boron phase, the temperature at the cooling position is below 1100 degrees Celsius; when the main material is a rare earth-rich phase, the temperature at the cooling position is below 430 degrees Celsius.

[0029] In a preferred embodiment, air is drawn in at the location where the laser beam passes.

[0030] According to another specific embodiment of the present invention, a rotor for an electric motor is provided, comprising the above-described magnet.

[0031] According to another specific embodiment of the present invention, an electric motor is provided, comprising the rotor described above.

[0032] In summary, by employing the technical solution of this invention, the stress of the magnet can be dispersed, thereby improving the physical properties of the magnet while reducing magnetic loss and eddy current loss. Furthermore, for the non-penetrating arc and annular grooves in this invention, a new grooving method is provided. During processing, this method minimizes damage to the phase structure of the magnet surface, reducing the extent of the damaged layer, remelted layer, and heat-affected layer, thus minimizing the reduction in magnetic flux caused by processing. The grooving method of this invention also results in a smooth magnet surface after processing, with a "└┘" shaped cut, preventing stress concentration at a single point and reducing the impact of laser cutting on bending strength. Attached Figure Description

[0033] Appendix Figure 1 This is a schematic diagram of the structure of magnet one;

[0034] Appendix Figure 2 This is a cross-sectional view of magnet one;

[0035] Appendix Figure 3 This is a schematic diagram of the structure of magnet two;

[0036] Appendix Figure 4 This is a cross-sectional view of magnet two;

[0037] Appendix Figure 5 For the appendix Figure 3 Top view;

[0038] Appendix Figure 6 For the appendix Figure 3 A bottom view;

[0039] Appendix Figure 7 This is a schematic diagram of the structure of magnet three;

[0040] Appendix Figure 8 This is a cross-sectional view of magnet three;

[0041] Appendix Figure 9 For the appendix Figure 7 Top view;

[0042] Appendix Figure 10 For the appendix Figure 7 A bottom view;

[0043] Appendix Figure 11 This is a schematic diagram of the structure of magnet four;

[0044] Appendix Figure 12 This is a cross-sectional view of magnet four;

[0045] Appendix Figure 13 For the appendix Figure 11 Top view;

[0046] Appendix Figure 14 For the appendix Figure 11 A bottom view;

[0047] Appendix Figure 15 This is a schematic diagram of the magnet structure in Comparative Example 1;

[0048] Appendix Figure 16 This is a schematic diagram of the magnet structure in Comparative Example 2;

[0049] Appendix Figure 17 This is a schematic diagram illustrating the effect of laser processing on magnets.

[0050] Appendix Figure 18 This is a schematic diagram comparing single-stage laser processing and double-stage laser processing. Detailed Implementation

[0051] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only 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.

[0052] Example 1, refer to Appendix Figure 1 ~Attached Figure 14 .

[0053] As shown in the attached figures, this embodiment provides a magnet, which includes a body 99. The body 99 has two opposing surfaces, namely a first surface 19 and a second surface 18. At least one of the two surfaces has at least one slot 10. The slot 10 has an arc-shaped or annular shape and is non-penetrating, meaning that the slot 10 is not penetrating in its depth direction. The arc-shaped or annular slot 10 can disperse the stress of the magnet, thereby improving the physical properties of the magnet (compared to conventional slotted magnets). This technical solution can improve the physical properties of the magnet while reducing magnetic loss and eddy current loss.

[0054] Preferably, the groove 10 is filled with a substance whose resistivity is greater than that of the main body material 99, which is used to increase the resistivity of the magnet and compensate for the low bending resistance and other physical properties caused by the groove. Further, this substance is a high-resistivity adhesive.

[0055] Preferably, the magnet is cubic in shape and includes two oriented surfaces and four non-oriented surfaces. The two oriented surfaces are a first surface 19 and a second surface 18, respectively, and the first surface 19 and the second surface 18 are parallel to each other.

[0056] Preferably, the depth direction of the slot 10 is perpendicular to at least one of the first surface 19 and the second surface 18.

[0057] Based on the technical solution of Embodiment 1, several specific magnets are provided below:

[0058] Magnet 1, see attached document Figure 1 ~Attached Figure 2 .

[0059] The magnet is square, with specific dimensions of 33.5 × 22.0 × 5.5 mm. It includes two oriented surfaces and four non-oriented surfaces. The two oriented surfaces are a first surface 19 and a second surface 18, which are parallel to each other. One of the two surfaces has a groove 10, which is annular. Further, the groove 10 is elliptical.

[0060] Preferably, the major axis of the groove 10 is 17mm and the minor axis is 11mm. The groove width is 0.2mm and the groove depth is 3.25mm.

[0061] Magnet 2, see attached document Figure 3 ~Attached Figure 6 .

[0062] The magnet is square, with specific dimensions of 33.5 × 22.0 × 5.5 mm. It includes two oriented surfaces and four non-oriented surfaces. The two oriented surfaces are a first surface 19 and a second surface 18, which are parallel to each other. Both the first surface 19 and the second surface 18 have annular slots 10. Specifically, the first surface 19 has a first slot 11, and the second surface 18 has a second slot 13, with the first slot 11 and the second slot 13 forming annular shapes.

[0063] Preferably, the first groove 11 and the second groove 13 are elliptical.

[0064] Preferably, the slots 10 on the two surfaces are not connected to avoid further reduction in bending strength.

[0065] Preferably, when viewed in a direction perpendicular to the first surface 19 or the second surface 18, the first slot 11 surrounds the second slot 13 and is spaced apart from the second slot 13. It should be noted that the phrase "when viewed in...direction" in this invention refers to a reference point defining the feature and is not related to whether it can be directly seen. Although not all slots may be directly visible in a certain direction, their spatial relationship objectively exists, and the same applies below.

[0066] Preferably, the major axis of the first groove 11 is 22 mm and the minor axis is 16 mm; the major axis of the second groove 13 is 11 mm and the minor axis is 8 mm. The groove width is 0.2 mm and the groove depth is 3.25 mm.

[0067] Magnet 3, see attached document Figure 7 ~Attached Figure 10 .

[0068] The magnet is square, specifically measuring 33.5 × 22.0 × 5.5 mm. It includes two oriented surfaces and four non-oriented surfaces. The two oriented surfaces are a first surface 19 and a second surface 18, which are parallel to each other. The first surface 19 has two slots 10, and the second surface 18 has one slot 10, which is annular. Specifically, the first surface 19 has a first slot 11 and a third slot 12, with the third slot 12 located inside the first slot 11. The second surface 18 has a second slot 13. The first slot 11, second slot 13, and third slot 12 are annular. When viewed perpendicular to the first surface 19 or the second surface 18, the first slot 11 surrounds and is spaced apart from the second slot 13, and the second slot 13 surrounds and is spaced apart from the third slot 12. That is, when the first surface 19 is the projection surface of the above three annular slots, the second slot 13 is located between the first slot 11 and the third slot 12.

[0069] Preferably, the first groove 11, the third groove 12, and the second groove 13 are elliptical.

[0070] Preferably, all the slots 10 on the two surfaces are not connected to each other to avoid further reduction in bending strength.

[0071] Preferably, the orthographic projections of the slots 10 on the two surfaces do not coincide on either surface.

[0072] Preferably, the major axis of the first groove 11 is 25.5 mm and the minor axis is 18 mm; the major axis of the third groove 12 is 8.5 mm and the minor axis is 6 mm; and the major axis of the second groove 13 is 17 mm and the minor axis is 12 mm. The groove width is 0.2 mm and the groove depth is 3.25 mm.

[0073] Magnet 4, see attached document Figure 11 ~Attached Figure 14 .

[0074] The magnet is square, with dimensions of 33.5 × 22.0 × 5.5 mm. It includes two oriented surfaces and four non-oriented surfaces. The two oriented surfaces are a first surface 19 and a second surface 18, which are parallel to each other. The first surface 19 has two slots 10, and the second surface 18 has two slots 10, which are annular. Specifically, the first surface 19 has a first slot 11 and a third slot 12, with the third slot 12 located inside the first slot 11. The second surface 18 has a second slot 13 and a fourth slot 14, with the fourth slot 14 located inside the second slot 13. The first slot 11, second slot 13, third slot 12, and fourth slot 14 are annular. When viewed perpendicular to the first surface 19 or the second surface 18, the first slot 11, second slot 13, third slot 12, and fourth slot 14 are arranged sequentially from the outside to the inside and are spaced apart from each other. That is, when the first surface 19 is the projection surface of the above four annular slots, they are the fourth slot 14, the third slot 12, the second slot 13, and the first slot 11 from the inside to the outside.

[0075] Preferably, the first groove 11, the third groove 12, the second groove 13, and the fourth groove 14 are elliptical.

[0076] Preferably, all the slots 10 on the two surfaces are not connected to each other to avoid further reduction in bending strength.

[0077] Preferably, the orthographic projections of the slots 10 on the two surfaces do not coincide on either surface.

[0078] Preferably, the major axis of the first groove 11 is 28 mm and the minor axis is 20 mm; the major axis of the third groove 12 is 14 mm and the minor axis is 10 mm; the major axis of the second groove 13 is 21 mm and the minor axis is 15 mm; and the major axis of the fourth groove 14 is 7 mm and the minor axis is 5 mm. The groove width is 0.2 mm and the groove depth is 3.25 mm.

[0079] Comparative Example 1, see Appendix Figure 15 .

[0080] Comparative Example 1 provides a standard magnet, which is square in shape and has a length, width and height of 33.5×22.0×5.5mm, and does not have an annular groove.

[0081] Comparative Example 2, see Appendix Figure 16 .

[0082] Comparative Example 2 provides a conventional slotted magnet. The magnet is square, with specific dimensions of 33.5×22.0×5.5mm. Four slots with a length of 16.5mm, a depth of 5.5mm, and a width of 0.2mm are evenly opened along the elongation direction. The slots are opened perpendicular to the long side of the magnet, and one end of the slot is aligned with the long side.

[0083] Example 2, refer to Appendix Figure 17 ~Attached Figure 18 .

[0084] This embodiment provides a method for manufacturing a magnet, which can be processed based on a common magnet to obtain a slotted magnet as shown in Embodiment 1. The method includes: providing a magnet, the magnet including a body 99, the body 99 having opposing first surfaces 19 and second surfaces 18; and forming a slot 10 in the first surface 19 of the body 99, the slot 10 having an arc shape or an annular shape, and the slot 10 being non-penetrating in its depth direction.

[0085] In the field of magnetic materials, common processing methods for magnets include multi-wire cutting, internal circular cutting, and electrical discharge machining (EDM). The processing principle of multi-wire cutting involves the high-speed movement of diamond-coated metal wires to cut the magnet, producing straight grooves, as shown in the attached image. Figure 16As shown. The working principle of electrical discharge machining (EDM) relies on electro-erosion to remove excess metal when there is a discharge between the machine tool and the workpiece (positive and negative electrodes), thereby achieving the processing of the workpiece's size, shape, and surface quality. This cutting method can cut any shape, but all are through grooves, and it requires cutting from one surface to the inside. The working principle of internal circular cutting is that a diamond-coated blade rotates at high speed, continuously grinding the magnet to complete the cutting. This cutting method can cut non-through grooves, but the groove cross-section is an arc, and it can only cut straight grooves. None of the above commonly used methods can cut the arc or annular grooves in Embodiment 1 of this invention. The grooving method in this embodiment mainly uses laser cutting. It should be noted that laser cutting is not a conventional method because the high temperature of laser cutting will destroy the phase structure of the magnet surface (melting the main phase of the cutting area), see Appendix. Figure 17 In the diagram, the inverted triangle represents the laser. The high temperature from laser cutting propagates from the contact point. Based on the distribution of different temperature ranges, it can be divided into three layers: the destructive layer A, the remelted layer B, and the heat-affected layer C. The destructive layer A and the remelted layer B affect the main phase, causing a reduction in the magnetic flux of the magnet. Therefore, the industry is currently mainly experimenting with this method. The grooving method in this embodiment is an improvement on traditional laser technology, enabling its application in the field of magnet processing. Furthermore, the grooving method of this invention can reduce the size of these two regions.

[0086] Preferably, forming a groove in the first surface of the body 99 includes:

[0087] The groove is formed by laser beam cutting. While the laser cutting is being performed, the cutting position is cooled. The cooling position moves synchronously with the laser cutting trajectory.

[0088] The specific method for slotting this magnet is as follows:

[0089] S1. Place the magnet to be processed on the worktable and position it. Set the laser processing parameters in the control center.

[0090] S2. Turn on the laser, airflow device, and cooling nozzle. The laser generates a laser beam, and at the same time, the airflow device blows or sucks air onto the laser-cut area to blow or suck away the molten material generated by the laser processing from the cut. During processing, the laser and airflow device move synchronously. The cooling nozzle is behind the laser and airflow device. The cooling nozzle can spray out gaseous or liquid cooling substances, and its spray position moves along the laser cutting trajectory.

[0091] S3. After completing the predetermined cutting, the laser, airflow device, and cooling nozzle are shut off.

[0092] Preferably, when the grooves are provided on two or more surfaces, the method further includes:

[0093] S4. Flip the magnet to the surface to be processed, and then repeat S1 to S3.

[0094] Preferably, the cooling nozzle ensures that the processed area is cooled within 2 seconds after the laser passes. Further, the cooling nozzle ensures that the processed area is cooled within 1 second after the laser passes.

[0095] Preferably, the cooling substance sprayed from the cooling nozzle is liquid nitrogen.

[0096] Preferably, when the magnet material is NdFeB main phase, the cooling nozzle needs to ensure that the temperature at the spray position is below 1100 degrees Celsius; when the magnet material is rare earth rich main phase, the cooling nozzle needs to ensure that the temperature at the spray position is below 430 degrees Celsius.

[0097] Preferably, the airflow device can draw air from the laser-cut area and remove the molten slag produced by laser cutting. If the airflow device blows air, although most of the molten slag can be blown away, a small portion of the molten slag will fall onto the magnet surface. Under the action of the subsequent cooling nozzle, this molten slag will solidify rapidly and affect the flatness of the magnet surface.

[0098] Preferably, when the depth of the groove is relatively deep, in step S1, when setting the laser processing parameters, the single laser cut is changed to multiple laser cuts. The groove is formed by multiple cuts using the laser beam, and the depth of the groove formed by each cut is a part of the total groove depth. This is because when processing some grooves with relatively deep grooves, refer to the attached... Figure 18 If you choose to process the product in one step, you will need to select a higher power laser. See the appendix. Figure 18 The diagram at the top shows that due to the deep processing depth, a higher-power laser is required. This leads to higher temperatures, a larger area of ​​the damaged layer A, remelted layer B, and heat-affected layer C, a greater influence of magnetic flux, and a rough surface in the damaged area. The cut is V-shaped, and stress is concentrated at the tip, affecting bending strength. Therefore, this invention also improves the laser cutting method by changing the single laser cutting process to two or more laser processing steps. See attached diagram. Figure 18 The two images at the bottom show how the focal point gradually shifts downwards with each cut. This results in a shallow cut depth, low laser power, and low temperature, consequently reducing the areas of the damaged layer A, remelted layer B, and heat-affected layer C. The damaged area has a smoother surface, and the cut is shaped like a "└┘" or U, preventing stress concentration at a single point and minimizing the impact of laser cutting on bending strength. Furthermore, from the perspective of slag production, two or more laser processes reduce the amount of slag generated, keeping the magnet surface smooth. When using multiple laser cuts, the depth of each cut can be evenly distributed according to the depth of the groove.

[0099] Preferred options are shown in the appendix. Figure 18 The method of forming a groove 10 by multiple cuts using a laser beam includes:

[0100] First cut: A laser beam is focused on the first surface 19 of the body 99 or at a position between the first surface 19 and the second surface 18 of the body 99 to form a first portion 98 of the groove 10 in its depth direction. In the first cut, the focal point of the laser beam is a first predetermined distance A from the first surface of the body 99.

[0101] Second cut: The laser beam is focused on the body 99 at the position between the first surface 19 and the second surface 18 to form the second part 97 of the groove in the depth direction of the groove. In the second cut, the focal point of the laser beam is a second predetermined distance B from the first surface of the body 99. The second predetermined distance B is greater than the first predetermined distance A.

[0102] Preferably, the depth of the second cut is 90%-110% of the depth of the first cut.

[0103] Example 3.

[0104] This embodiment provides a rotor, which includes the magnet in Embodiment 1 or a magnet formed by the method of Embodiment 2.

[0105] Other implementation methods in this embodiment are the same as in Embodiment 1 or Embodiment 2.

[0106] Example 4.

[0107] This embodiment provides an electric motor, which includes the rotor of Embodiment 3.

[0108] The other implementation methods in this embodiment are the same as in Embodiment 3.

[0109] The technicians of this invention conducted the following tests on the magnets obtained by the different grooving methods described above, and the testing methods of this invention are described below:

[0110] 1. Method for testing magnetic flux: At room temperature (20℃), the magnet is measured using a fluxmeter in reverse order.

[0111] 2. Magnetic loss test method: Place the magnet in an oven and bake it at 90℃ for 1.5 hours. Then remove it and let it cool to room temperature. Measure its magnetic flux and compare it with the magnetic flux before baking. The magnetic loss is calculated as: (Magnetic flux before baking - Magnetic flux after baking) / Magnetic flux before baking.

[0112] 3. Test method for eddy current loss ratio: The eddy current loss ratio of the magnet is simulated using MAXWELL software.

[0113] 4. Test method for bending strength: Use a universal electronic testing machine to test the magnet using the 3-point bending test method.

[0114] Using the above testing methods, we tested magnets one through four in Example 1 using the magnet grooving method provided in Example 2. Each magnet was processed in three different ways: normal cooling after one cut, normal cooling after two cuts (each cut is half the depth of the groove), and liquid nitrogen cooling after two cuts.

[0115] The test results (related performance) are summarized below:

[0116]

[0117]

[0118]

[0119] The test data in the table above shows that:

[0120] 1. Magnet four has the same number of slots as Comparative Example 2, but it can achieve a nearly 3-fold increase in the bending strength of the magnet, while the magnetic loss remains basically unchanged and the eddy current loss is reduced. Magnet one, magnet two, and magnet one three also perform better than Comparative Example 1 and Comparative Example 2. Therefore, by setting arc or annular slots on the surface of the magnet, it is possible to improve the physical properties of the magnet while reducing the magnetic loss and eddy current loss of the magnet, and thus achieve better performance.

[0121] 2. Magnets formed by "one-time cutting" have lower magnetic flux than magnets formed by "two-time cutting." Magnetic flux is a parameter determined by the magnet's structure and material; however, by using multiple cutting processes to reduce the extent of the damaging layer A, remelted layer B, and heat-affected layer C, the magnetic flux of the magnet can indeed be increased. In Embodiment 1 of this invention, the slot width of the magnet is only 0.2 mm. If a multi-cutting processing scheme is applied to magnets with larger slot widths, the increase in magnetic flux will be even greater.

[0122] 3. Magnets processed using liquid nitrogen cooling exhibit greater magnetic flux than those processed using normal cooling. Magnetic flux is a parameter determined by the magnet's structure and material; however, rapid liquid nitrogen cooling reduces the impact of high temperatures generated during laser cutting on the main phase, thereby increasing the magnet's flux. In Embodiment 1 of this invention, the magnet's slot width is only 0.2 mm. Applying rapid cooling to magnets with wider slots would result in an even greater increase in magnetic flux.

[0123] 4. Magnets processed using the "single-cut, normal cooling" method exhibit a 2% to 4% increase in magnetic flux compared to magnets processed using the "double-cut, liquid nitrogen cooling" method. Furthermore, the greater the number of slots, the greater the increase in magnetic flux. While magnetic flux is a parameter determined by the magnet's structure and material, the processing method in Example 2 can still enhance it. The slot width in Example 1 is only 0.2 mm; applying the processing scheme of Example 2 to magnets with wider slots would result in an even greater increase in magnetic flux.

[0124] The above are all preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Therefore, all equivalent changes made in accordance with the structure, shape and principle of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A magnet, comprising: The body has opposing first and second surfaces; as well as A groove is formed in at least one of the first and second surfaces of the body, the groove being annular in shape and non-penetrating in the depth direction of the groove; The slot includes a first slot formed in a first surface of the body and a second slot formed in a second surface of the body, the first slot and the second slot having an annular shape; When viewed in a direction perpendicular to the first or second surface, the first slot surrounds the second slot and is spaced apart from the second slot.

2. The magnet according to claim 1, characterized in that: The groove is filled with a substance whose resistivity is greater than that of the main body material.

3. The magnet according to claim 1, characterized in that: The first and second surfaces of the main body are parallel to each other.

4. The magnet according to claim 1, characterized in that: The magnet is cubic in shape.

5. The magnet according to claim 1, characterized in that: The depth direction of the slot is perpendicular to at least one of the first surface and the second surface.

6. The magnet according to claim 1, characterized in that: The slot is elliptical in shape.

7. The magnet according to claim 1, characterized in that: The groove also includes a third groove formed in the first surface of the body, the third groove having an annular shape.

8. The magnet according to claim 7, characterized in that: When viewed in a direction perpendicular to the first or second surface, the first slot surrounds and is spaced apart from the second slot, and the second slot surrounds and is spaced apart from the third slot.

9. The magnet according to claim 1, characterized in that: The groove also includes a third groove formed in the first surface of the body and a fourth groove formed in the second surface of the body, the third groove and the fourth groove having annular shapes.

10. The magnet according to claim 9, characterized in that: When viewed in a direction perpendicular to the first or second surface, the first slot, the second slot, the third slot, and the fourth slot are arranged sequentially from the outside to the inside and are spaced apart from each other.

11. A method for manufacturing a magnet, comprising the steps of: A magnet is provided, the magnet comprising: The body has opposing first and second surfaces; as well as Grooves are formed in the first and second surfaces of the main body. The grooves are annular in shape and are not through-holes in the depth direction of the grooves. When viewed in a direction perpendicular to the first surface or the second surface, the first slot surrounds the second slot and is spaced apart from the second slot.

12. The method according to claim 11, characterized in that: Forming a groove in the first surface of the body includes: A groove is formed by multiple cuts using a laser beam, with the depth of each cut being a portion of the total groove depth.

13. The method according to claim 12, characterized in that: Creating grooves using a laser beam through multiple cuts includes: First cut: A laser beam is focused on the first surface of the body or at a position between the first and second surfaces of the body to form a first portion of the groove in the depth direction of the groove. During the first cut, the focal point of the laser beam is at a first predetermined distance from the first surface of the body. Second cut: The laser beam is focused on the position between the first and second surfaces of the main body to form a second part of the groove in the depth direction of the groove. In the second cut, the focal point of the laser beam is a second predetermined distance away from the first surface of the main body. The second predetermined distance is greater than the first predetermined distance.

14. The method according to claim 13, characterized in that: The depth of the second cut is 90%-110% of the depth of the first cut.

15. The method according to claim 12, characterized in that: The power of the laser beam is adjusted during the process of forming a groove by multiple cuts using a laser beam.

16. The method according to claim 15, characterized in that: The groove is shaped like a "└┘" or a U.

17. The method according to claim 11, characterized in that: Forming a groove in the first surface of the body includes: The groove is formed by laser beam cutting. While the laser cutting is being performed, the cutting position is cooled. The cooling position moves synchronously with the laser cutting trajectory.

18. The method according to claim 17, characterized in that: The laser beam is cooled within 1 second as it passes through the location.

19. The method according to claim 17, characterized in that: When the main material is NdFeB, the temperature at the cooling location is below 1100 degrees Celsius; when the main material is rare earth-rich, the temperature at the cooling location is below 430 degrees Celsius.

20. The method according to claim 17, characterized in that: Air is drawn in at the location where the laser beam passes.

21. A rotor for an electric motor, comprising: The magnet according to any one of claims 1 to 10.

22. An electric motor, comprising: The rotor according to claim 21.

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