Low-eddy current permanent magnet, and preparation method therefor and use thereof

Abstract

Disclosed in the present invention are a low-eddy current permanent magnet, and a preparation method therefor and a use thereof. According to the present invention, separation slots are formed on the permanent magnet according to specific size requirements, and by means of a specific slot distribution mode (e.g., the length L2 of each separation slot in a second extension direction is 30% or more, preferably 50% or less, of the length of the permanent magnet in the second extension direction), the ratio relationship between the total length L2 in the second extension direction and the perimeter C of a first surface or a second surface of the magnet is controlled, thereby effectively alleviating the problem of reduction of output torque and efficiency of a permanent magnet motor caused by the temperature rise of a magnet, while maintaining the strength of the magnet and avoiding increased costs of the permanent magnet and / or negative impacts on the magnetic flux of the magnet.

Description

Low eddy current permanent magnet and preparation method and application thereof

[0001] The present application claims the priority of two applications: one application with the patent application number 2024104354719 and the invention name "a low eddy current permanent magnet and preparation method and application thereof" filed on April 11, 2024 to the State Intellectual Property Office of China, and the other application with the patent application number 2024104354494 and the invention name "a permanent magnet with an insulation layer and preparation method and application thereof" filed on April 11, 2024 to the State Intellectual Property Office of China. The entire contents of the prior applications are incorporated herein by reference. TECHNICAL FIELD

[0002] The present application belongs to the technical field of rare earth permanent magnet preparation, and relates to a permanent magnet with low eddy current and a preparation method and application thereof, in particular to a rare earth permanent magnet with low eddy current, high strength and excellent corrosion resistance and a preparation method and application thereof. BACKGROUND

[0003] Neodymium-iron-boron permanent magnets are widely used in new energy vehicles, wind power generation, energy-saving elevators, energy-saving home appliances and other energy-saving and new energy fields due to their excellent performance. With the development of motor miniaturization, lightweight and high speed, it is an important issue in the industry to reduce the eddy current loss of the rotor permanent magnet while ensuring the mechanical properties and corrosion resistance of the permanent magnet.

[0004] Currently, there are two main methods to reduce the eddy current loss of the permanent magnet: one is to bond the magnets, i.e. to set a bonding layer between the magnets to form a magnetic assembly. This method has high cost, long processing flow, high requirements for the shape and position of the magnets before bonding, and high requirements for the bonding process such as the method and uniformity of glue coating. The other method is to set a separation groove to improve the resistivity of the permanent magnet itself, such as the prior art CN110890798A, which discloses a permanent magnet provided with one or more separation grooves, which can effectively reduce the magnetic loss. However, it cannot guarantee the insulation between the magnets on both sides of the separation groove, and also reduces the mechanical strength of the permanent magnet. SUMMARY

[0005] To improve the above technical problems, the present application provides a permanent magnet provided with a separation groove. Preferably, the permanent magnet provided with a separation groove has a temperature rise of less than 50℃ after being treated in a medium frequency heating furnace at a frequency of 3KHZ and a current of 2A for 10 minutes.

[0006] According to the embodiments of the present application, the permanent magnet can be a conventional permanent magnet in the art, such as a neodymium-iron-boron magnet.

[0007] According to embodiments of the present application, the separation groove can or can not extend through the permanent magnet in a first extension direction of the separation groove, and the separation groove does not extend through the permanent magnet in a second extension direction of the separation groove, wherein the first extension direction of the separation groove is parallel to the magnetization direction of the permanent magnet, or the first extension direction of the separation groove forms an angle with the magnetization direction of the permanent magnet. The second extension direction of the separation groove is parallel to the width direction or length direction of the permanent magnet, or the second extension direction of the separation groove forms an angle with the width direction or length direction of the permanent magnet. For example, the angle is 0-90°, for example 10°, 20°, 30°, 40°, 50°, 60°, 70°, 80°.

[0008] According to embodiments of the present application, the number of separation grooves can be one, two or more, denoted as N grooves; wherein the length in the first extension direction is denoted as L 1- 1、L 1-2 、L 1-3 、L 1-4 ……L 1-n The sum of the lengths of the separation grooves in the first extension direction is denoted as L1 (mm), then L1 = L 1-1 +L 1-2 +L 1-3 +L 1-4 +……+L 1-n L1 is more than 50%, preferably more than 60%, of the length of the permanent magnet in the first extension direction, for example 50%, 60%, 70%, 80%, 100%.

[0009] According to embodiments of the present application, the length of the separation groove in the second extension direction is denoted as L 2-1 、L 2-2 、L 2-3 、L 2-4 ……L 2-n The sum of the lengths of the separation grooves in the second extension direction is denoted as L2 (mm), then L2 = L 2-1 +L 2-2 +L 2-3 +L 2-4 +……+L 2-n L2 is more than 30% and less than 50% of the length of the permanent magnet in the second extension direction. Preferably, the length L2 of the separation groove in the second extension direction is 30-50% of the length of the permanent magnet in the second extension direction, for example 40%, 50%.

[0010] According to an embodiment of the present application, when the second extension direction of the separation groove has an angle with the width direction or the length direction of the permanent magnet, the projection length of the separation groove with the angle in the second extension direction is more than 30% of the length of the permanent magnet in the second extension direction, and preferably less than 50%; preferably, the projection length of the separation groove with the angle in the second extension direction is 30-50% of the length of the permanent magnet in the second extension direction, and exemplarily 40% or 50%.

[0011] According to an embodiment of the present application, the width of the separation groove is denoted as W (mm), and W is 0.1-0.5 mm, and preferably 0.12-0.25 mm, wherein the width refers to the distance between two side walls in the separation groove.

[0012] According to an embodiment of the present application, when there are multiple separation grooves, the spacing between two adjacent separation grooves is 1-10 mm, and preferably 1-5 mm, and exemplarily 1 mm, 2 mm, 5 mm, 8 mm or 10 mm.

[0013] According to an embodiment of the present application, the distribution of the separation grooves on the permanent magnet is single-side slotting (which is defined as arranging at least one separation groove on one surface of the permanent magnet) or staggered slotting (which is defined as arranging at least one separation groove on each of two opposite surfaces of the permanent magnet), and preferably staggered slotting.

[0014] According to an embodiment of the present application, the surface of the separation groove in the first extension direction is denoted as a first side surface, a second side surface, a third side surface or a fourth side surface; the surface of the separation groove in the second extension direction is denoted as a first surface or a second surface; wherein the circumference of the first surface or the second surface is denoted as C; then 0.2≤L2 / C≤1; more preferably, 0.35≤L2 / C≤0.85.

[0015] When the ratio of the total length L2 in the second extension direction to C is small, the slotting length is too low to significantly cut the magnetic lines of the magnet, and thus the eddy current loss cannot be reduced, and the temperature rise of the magnet is still large. When the ratio of the total length L2 in the second extension direction to C is large, the excessive slotting ratio can cause the strength of the magnet to be reduced or uneven, and the magnet is easy to be damaged.

[0016] According to an embodiment of the present application, the number of the separation grooves on the first side surface, the second side surface, the third side surface or the fourth side surface is denoted as N1, and the number of the separation grooves on the first surface or the second surface is denoted as N2.

[0017] The inventor has unexpectedly found that the length and mode of the slotting in the second extension direction have a great influence on the final performance of the product.

[0018] According to an embodiment of the present invention, the groove of the separation slot is filled with an insulating layer. For example, the insulating layer can be an insulating material such as a glue layer, an expansion coating, or an injection molding agent; preferably, the insulating layer is a glue layer.

[0019] In one embodiment of the present invention, the glue used in the glue layer is selected from one or more combinations of epoxy resin glue, acrylic resin glue, phenolic resin glue and unsaturated polyester resin glue, preferably epoxy resin glue.

[0020] According to an embodiment of the present invention, the viscosity of the glue is 1-5000 mPa·s, preferably 1-2000 mPa·s. The inventors have found that when the viscosity of the glue is too high, its fluidity is poor, making it difficult to penetrate the gaps in the separation grooves, and its wettability is poor, which is not conducive to the adhesion and bonding of the glue. When the viscosity of the glue is too low, the fluidity is good, but it makes it difficult for the glue to be retained and positioned in the gaps in the separation grooves, resulting in a low fill rate and, in turn, low mechanical strength of the permanent magnet.

[0021] In the present invention, the filling ratio P of the insulating layer in any cross section of the separation groove (which is defined as the area of ​​the insulating layer filling material / the cross-sectional area of ​​the separation groove) is recorded as P1 for the first separation groove, P2 for the second separation groove, and so on. The filling ratio of the Nth separation groove is recorded as P n ; Let P = (P1 + P2 + ... + P n ) / N, that is, P is the filling ratio of the entire insulating layer in each separation groove, specifically: the average filling ratio of each separation layer.

[0022] According to an embodiment of the present invention, the filling ratio P of the insulating layer in any separation groove is n ≥50%, preferably 80%-100%, for example, 50%, 60%, 70%, 80%, 90%, 100%; and the filling ratio of the permanent magnet as a whole satisfies: P≥80%, preferably 90-100%, for example, 90%, 95%, 100%.

[0023] According to an embodiment of the present invention, after filling the insulating layer, the flatness of all surfaces of the permanent magnet is ≤0.05 mm. Preferably, the flatness is ≤0.03 mm, for example, 0.15 mm, 0.20 mm, 0.25 mm, or 0.30 mm.

[0024] In this application, flatness refers to the variation of the measured permanent magnet's actual surface relative to its ideal plane (also known as flatness error). Flatness error is calculated by comparing the measured surface with the ideal plane, using the linear distance between the two as the flatness error. Alternatively, the flatness error can be calculated by measuring the relative height differences of several points on the actual surface and converting the linear distance into a flatness error.

[0025] According to an embodiment of the present application, the neutral salt spray of the magnet is > 240h after filling the insulation layer, and examples include 240h, 260h, 270h, 280h, 288h, 300h, 312h, and 320h.

[0026] According to an embodiment of the present application, the shape of the permanent magnet can be a square (e.g., rectangular), a tile (C-shaped), a cylinder, a strip, a bread-shaped, a special-shaped, or the like.

[0027] According to an embodiment of the present application, the permanent magnet can be a conventional permanent magnet in the art, such as a neodymium iron boron magnet.

[0028] The present application also provides a preparation method of the permanent magnet, which comprises preparing a separation groove on the permanent magnet.

[0029] According to an embodiment of the present application, the preparation method further comprises pretreating the permanent magnet with the separation groove.

[0030] According to an embodiment of the present application, the preparation method further comprises filling an insulation layer in the groove of the pretreated permanent magnet.

[0031] According to an embodiment of the present application, the preparation method further comprises curing the permanent magnet after filling the insulation layer.

[0032] According to an embodiment of the present application, the preparation method of the permanent magnet comprises preparing a separation groove on the permanent magnet, pretreating, then filling an insulation layer in the groove of the permanent magnet, and curing the permanent magnet after filling the insulation layer, thereby obtaining the permanent magnet.

[0033] According to an embodiment of the present application, the preparation method of the permanent magnet comprises the following steps:

[0034] (1) Magnet preparation: preparing a permanent magnet with a separation groove, and then pretreating;

[0035] (2) Glue filling: applying glue on the gap of the separation groove, placing it in a container that can be tightly closed and vacuumized, and vacuumizing to fill the glue into the separation groove;

[0036] (3) Curing treatment: curing the permanent magnet with the glue filled in the separation groove, thereby obtaining the permanent magnet.

[0037] According to an embodiment of the present application, the preparation method can further comprise step (4): surface treating the permanent magnet obtained above.

[0038] According to an embodiment of the present application, in step (1), the permanent magnet with the separation groove can be prepared by a method known in the art.

[0039] According to the embodiment of the present application, in step (1), the pre-treatment comprises cleaning, degreasing, and drying treatment of the permanent magnet with the partition groove. Optionally, at least one of phosphating, passivation, vitrification, silanization, chelation, and blackening is included.

[0040] According to the embodiment of the present application, in step (2), the glue filling method can be at least one of dispensing, manual coating, spraying, or dipping. Preferably, the dispensing method is used.

[0041] Preferably, the dispensing speed is 1-50 mm / s, for example, 1 mm / s, 5 mm / s, 10 mm / s, 20 mm / s, 30 mm / s, 40 mm / s, 50 mm / s, or 50 mm / s. The gun head diameter of the dispensing machine used is 0.16-0.26 mm, for example, 0.16 mm, 0.18 mm, 0.20 mm, 0.22 mm, 0.24 mm, or 0.26 mm. When the dispensing speed is too slow, the work efficiency is low. When the dispensing speed is too fast, it is difficult to arrange the glue in the gap, and the glue is easy to overflow.

[0042] According to the embodiment of the present application, in step (2), during the process of applying glue on the gap of the partition groove, at least the glue is applied to part of the area of the partition groove in its second extension direction; preferably, one of the two opposite gaps of the partition groove in its second extension direction is coated; preferably, the coating length L (mm) of the glue is not less than half of the extension length L2 (mm) of the partition groove in its second extension direction, i.e. L≥(1 / 2)L2, preferably the coating length L (mm) of the glue is 70%-90% of the extension length L2 (mm) of the partition groove in its second extension direction, for example, 70%, 80%, or 90%.

[0043] According to the embodiment of the present application, in step (2), the filling ratio P of the glue is ≥50%, preferably 80%-100%, for example, 50%, 60%, 70%, 80%, 90%, or 100%. Wherein, the filling ratio P of the insulation layer in any cross section of the partition groove (which is defined as the insulation layer filler area / the cross section area of the partition groove), the filling ratio of the first partition groove is denoted as P1, the filling ratio of the second partition groove is denoted as P2, and so on, the filling ratio of the Nth partition groove is denoted as PN. n The average filling ratio of the insulation layer is denoted as P=(P1+P2+…+PN) / N. n

[0044] ​According to the embodiment of the present application, in step (2), the vacuumizing can be performed by using a vacuumizing device known in the art. For example, the vacuum pressure is -1.0 bar to 1 mbar, and the vacuum pressure is maintained for more than 1 second. If the vacuum pressure is less than -1.0 bar or greater than 1 mbar, the filling effect is not good.

[0045] According to the exemplary embodiment of the present application, in step (2), the vacuum pressure is -0.8 bar to 0.5 mbar, and the vacuum pressure is maintained for more than 3 seconds.

[0046] According to the embodiment of the present application, in step (2), before the vacuumizing, a film is coated on the surface of the magnet coated with the glue, and the film is used to apply a downward pressure on the glue layer during the pressing process, so that the glue quickly enters the separation groove. The film is used to reduce the vacuum degree in the separation groove, to ensure the sufficient filling of the glue, and to improve the filling ratio of the insulation layer in the separation groove. Preferably, the film is made of semi-rigid plastic, and the material is not limited, and the film can be fully or partially attached to the surface of the magnet after being stressed. Preferably, the thickness of the film is between 0.01 mm and 0.5 mm. Exemplarily, the film can be made of polyethylene, polyvinyl chloride, polypropylene, polyester or nylon material. In the present application, when the film is too thick, it will cause resource waste; and when the film is too thin, the film is easy to be torn by the edges and corners of the magnet during the vacuumizing, so that the sealing effect cannot be achieved, and the film is easy to be sucked into the gap, thereby reducing the flatness of the slotted magnet containing the insulation layer.

[0047] Preferably, the coverage area of the film is not less than the coating area of the glue on one of the two opposite gaps of the separation groove in the second extension direction thereof, and / or the coverage area of the film is not less than the area of the first surface or the second surface of the permanent magnet.

[0048] According to the embodiment of the present application, in step (2), the device capable of vacuumizing is provided with a supporting member for placing the permanent magnet coated with the glue.

[0049] Preferably, the number of the contact points between the supporting member and the permanent magnet is at least two, for example, two, three or more.

[0050] Preferably, the supporting member does not contact the gap of any separation groove. The structure of the supporting member is not particularly limited in the present application, as long as it can stably support the permanent magnet and does not contact the inner wall of the container.

[0051] The inventor surprisingly finds that by applying a top-down pressure on the insulation layer filled in the partition groove through the single-sided film during the pressing process, the glue can quickly enter the partition groove. The suspended support part makes one side of the permanent magnet not contact the inner wall of the container, so that the glue can be more fully filled into the partition groove of the permanent magnet to improve the filling rate and thus improve the bending strength of the permanent magnet.

[0052] According to the embodiment of the application, the glue filling can be one-time filling or multiple-time filling.

[0053] According to the embodiment of the application, in step (3), the temperature of the curing treatment is 20-200℃, preferably 50-150℃, and exemplary values are 20℃, 50℃, 80℃, 100℃, 150℃ and 200℃; and the curing time is 0.5-8h, preferably 1-3h, and exemplary values are 0.5h, 1h, 2h, 3h, 5h and 8h.

[0054] According to the embodiment of the application, in step (4), the post-treatment includes at least one of phosphating and spraying. Through the post-treatment, not only the corrosion resistance of the surface of the permanent magnet is further improved, but also the post-treatment serves as the final protective layer of the permanent magnet without affecting the magnetic performance of the magnet.

[0055] The application also provides an application of the above permanent magnet in the field of electric machines.

[0056] The application also provides an electric machine having a rotor comprising the above permanent magnet.

[0057] Compared with the prior art, the application has the following advantages:

[0058] 1. The permanent magnet of the application has partition grooves, and by limiting the slotting position and size of the partition grooves, the eddy current loss can be significantly reduced, and at the same time, the bending strength is high.

[0059] 2. The application realizes the following effects by opening the partition grooves with specific size requirements on the permanent magnet, and by using a specific slotting distribution mode (such as making the total length L2 of the partition grooves in the second extension direction be more than 30% and less than 50% of the length of the permanent magnet in the second extension direction), and by controlling the ratio relationship between the total length L2 in the second extension direction and the circumference C of the first surface or the second surface of the magnet: in the case of maintaining the strength of the magnet, the problem of the reduction of the output torque and the efficiency of the permanent magnet electric machine caused by the heating of the magnet can be effectively improved without significantly increasing the cost of the permanent magnet or affecting the magnetic flux of the magnet.

[0060] 3. By further filling an insulation layer in the partition grooves of the permanent magnet, the bending strength of the permanent magnet can be improved, the eddy current effect of the permanent magnet can be reduced, and thus the performance of the electric machine after installation is better.

[0061] 4. The application can be applied to permanent magnets with different shape, width and depth of the separation groove by filling the insulating layer in the separation groove of the permanent magnet by vacuum pressing process, the filling rate of the insulating layer (such as glue) in the separation groove of the permanent magnet of the application is high, thereby ensuring the mechanical properties of the permanent magnet; meanwhile, the flatness of the insulating layer after filling the separation groove and the surface of the permanent magnet can be improved after vacuum treatment, thereby improving the overall corrosion resistance of the product.

[0062] 5. The application can accurately obtain permanent magnets with different strength according to target requirements by reasonable regulation and control of the three-dimensional size and filling rate of the separation groove, so as to be suitable for different application scenarios and save cost. BRIEF DESCRIPTION OF DRAWINGS

[0063] Fig. 1(a) is a schematic diagram of the first surface and / or the second surface of the cutting mode of the separation groove in Example 1; Fig. 1(b) is a schematic diagram of the first side surface and / or the second side surface of the cutting mode of the separation groove in Example 1; Fig. 1(c) is a schematic diagram of the third side surface of the cutting mode of the separation groove in Example 1.

[0064] Fig. 2(a) is a schematic diagram of the first surface and / or the second surface of the cutting mode of the separation groove in Example 2; Fig. 2(b) is a schematic diagram of the first side surface and / or the second side surface of the cutting mode of the separation groove in Example 2; Fig. 2(c) is a schematic diagram of the third side surface of the cutting mode of the separation groove in Example 2.

[0065] Fig. 3(a) is a schematic diagram of the first surface and / or the second surface of the cutting mode of the separation groove in Example 3; Fig. 3(b) is a schematic diagram of the first side surface and / or the second side surface of the cutting mode of the separation groove in Example 3; Fig. 3(c) is a schematic diagram of the third side surface of the cutting mode of the separation groove in Example 3.

[0066] Fig. 4(a) is a schematic diagram of the first surface and / or the second surface of the cutting mode of the separation groove in Example 4; Fig. 4(b) is a schematic diagram of the first side surface and / or the second side surface of the cutting mode of the separation groove in Example 4; Fig. 4(c) is a schematic diagram of the third side surface of the cutting mode of the separation groove in Example 4.

[0067] Fig. 5(a) is a schematic diagram of the first surface and / or the second surface of the cutting mode of the separation groove in Example 5; Fig. 5(b) is a schematic diagram of the first side surface and / or the second side surface of the cutting mode of the separation groove in Example 5; Fig. 5(c) is a schematic diagram of the third side surface of the cutting mode of the separation groove in Example 5.

[0068] Fig. 6(a) is a schematic view of the first surface and / or the second surface of the cutting method of the separation slot in Example 6; Fig. 6(b) is a schematic view of the first side surface and / or the second side surface of the cutting method of the separation slot in Example 6; Fig. 6(c) is a schematic view of the third side surface of the cutting method of the separation slot in Example 6.

[0069] Fig. 7(a) is a schematic view of the first surface and / or the second surface of the cutting method of the separation slot in Example 7; Fig. 7(b) is a schematic view of the first side surface and / or the second side surface of the cutting method of the separation slot in Example 7; Fig. 7(c) is a schematic view of the third side surface of the cutting method of the separation slot in Example 7.

[0070] Fig. 8(a) is a schematic view of the first surface and / or the second surface of the cutting method of the separation slot in Example 8; Fig. 8(b1, b2) is a schematic view of the first side surface and / or the second side surface of the cutting method of the separation slot in Example 8; Fig. 8(c) is a schematic view of the third side surface of the cutting method of the separation slot in Example 8.

[0071] Fig. 9(a) is a schematic view of the first surface and / or the second surface of the cutting method of the separation slot in Example 9; Fig. 9(b) is a schematic view of the first side surface and / or the second side surface of the cutting method of the separation slot in Example 9; Fig. 9(c) is a schematic view of the third side surface of the cutting method of the separation slot in Example 9.

[0072] Fig. 10 is a schematic view of the cutting method of the separation slot in Comparative Example 1.

[0073] Fig. 11 is a schematic view of the cutting method of the separation slot in Comparative Example 2.

[0074] Fig. 12 is a schematic view of the cutting method of the separation slot in Comparative Example 3.

[0075] Fig. 13 is a schematic view of the cutting method of the separation slot in Comparative Example 4.

[0076] Fig. 14 is a schematic view of the cutting method of the separation slot in Comparative Example 5.

[0077] Fig. 15 is a schematic view of the cutting method of the separation slot in Comparative Example 6.

[0078] Fig. 16 is a schematic view of the cutting method of the separation slot in Comparative Example 7.

[0079] Fig. 17 is a schematic view of the cutting method of the separation slot in the present application.

[0080] Fig. 18 is a schematic view of the cutting method of the separation slot in the present application with an angle.

[0081] Fig. 19 is a schematic view of the structure of the separation slot in the permanent magnet used in Example 13.

[0082] Figure 20 is a front view of the back surface of the separation groove filled in Example 1.

[0083] Figure 21 is a physical diagram of the separation groove filled in Example 1, which is cut off from the glue. DETAILED DESCRIPTION

[0084] The technical solutions of the present application will be further described in detail below in combination with specific examples. It should be understood that the following examples are only illustratively described and explained, and should not be interpreted as limiting the scope of protection of the present application. Any technology implemented based on the above description of the present application is covered within the scope of protection intended by the present application.

[0085] The experimental methods used in the following examples are conventional methods unless otherwise specified; the reagents, materials, etc. used in the following examples can be obtained from commercial channels unless otherwise specified.

[0086] Test method:

[0087] The permanent magnets prepared in the following examples and comparative examples of the present application were tested for bending strength, neutral salt spray performance, and glue filling rate, and the methods were as follows:

[0088] 1) Bending strength: an electronic universal testing machine was used, and three-point bending test was performed according to the standard YB / T5349-2014, and the measurement was performed three times.

[0089] 2) M agnet temperature detection: Shanghai Hanggong Electrical Appliance, 1500W high-frequency induction heater.

[0090] 3) Glue filling ratio P: the permanent magnet was cut on the first surface of the magnet perpendicular to the second division direction of the separation groove to obtain the cross section of the separation groove, and the cutting method was as shown in Figure 8. The cutting surface was observed under a scanning electron microscope, and a field emission electron probe microanalyzer (FE-EPMA) (JEOL, 8530F) was used for detection, and the area ratio was analyzed by Image-Pro Plus software.

[0091] 4) Neutral salt spray performance (SST experiment): tested according to GB / T 10125-2012.

[0092] 5) Flatness: tested using a dial indicator.

[0093] Examples 1-9 and Comparative Examples 1-8

[0094] A preparation method of a permanent magnet, comprising the following steps:

[0095] Permanent magnets with a size of 40 mm x 12 mm x 4 mm were prepared by using methods known in the art. The permanent magnets in Examples 1-9 and Comparative Examples 1-8 were selected from the grade 45UH.

[0096] The permanent magnets of Examples 1-9 were processed by using a multi-wire cutting method to form the separation grooves. The width of the separation grooves of Examples 1-5 was 0.12 mm, and the width of the separation grooves of Examples 6-9 was 0.2 mm. The length and the number of the separation grooves of Examples 1-9 in the first and second extension directions are shown in Table 1, and the length and the number of the separation grooves of Comparative Examples 1-7 in the first and second extension directions are shown in Table 2. The separation groove processing methods of the permanent magnets of Examples 1-9 and Comparative Examples 1-7 are shown in Figures 1-16, respectively.

[0097] Table 1

[0098] Table 2

[0099] The permanent magnets of Comparative Example 8 were not processed by cutting.

[0100] The permanent magnets of Examples 1-9 and Comparative Examples 1-7 after the processing of the separation grooves were cleaned, degreased, and dried.

[0101] The permanent magnets of Examples 1-9 and Comparative Examples 1-7 after the above processing were subjected to a magnet temperature test at room temperature, and the average value of three measurements was recorded as MIN (℃).

[0102] The permanent magnets of Examples 1-9 and Comparative Examples 1-7 were placed in the same position of a medium-frequency heating furnace, and the same frequency of 3 KHZ and the same current of 2 A were set. The permanent magnets were wrapped with thermal insulation cotton, heated for 10 minutes, and the temperature of the permanent magnets after heating was measured again. The average value of three measurements was recorded as MAX (℃). The permanent magnets of Examples 1-9 and Comparative Examples 1-7 were subjected to a bending resistance test, and the results were recorded as bending strength 1, as shown in Tables 3 and 4.

[0103] In the examples of the present application, the temperature rise values (MIN (℃), MAX (℃)) and the bending strength 1 were measured without filling the insulation layer.

[0104] The permanent magnets of Examples 1-9 and Comparative Examples 1-7 were filled with an insulation layer by the following method: epoxy glue (F-44 type phenolic epoxy resin, CAS number: 9003-36-5) was arranged on the gap of each separation groove on the first surface and the second surface of the permanent magnets obtained in the above step. The glue was arranged by using a dispensing method, in which the dispensing speed was 35 mm / s, and the gun head diameter of the dispensing machine was 0.20 mm.

[0105] Cover the first surface which has been coated with the glue with a polyethylene film, put it into a sealed container, and perform vacuumizing treatment, the vacuum pressure being -0.5 bar, and the maintaining time being 90 seconds.

[0106] The permanent magnets of Examples 1-9 and Comparative Examples 1-7 were filled with glue in the separation groove, and cured at 150℃ for 3h, and then cooled to room temperature, and then phosphorized using a zinc-based phosphorizing liquid (the composition of the zinc-based phosphorizing liquid is: zinc dihydrogen phosphate 100g / L, phosphoric acid 200g / L, tannic acid 15g / L, calcium nitrate 10g / L, ammonium molybdate 20g / L, phytic acid 50g / L, auxiliary film forming agent 30g / L, and the rest is water) mixed with pure water in a volume ratio of 3:1, and the phosphorizing temperature was 50℃, and the phosphorizing time was 2 minutes. The permanent magnets filled with the insulating layer in the separation groove were obtained.

[0107] The permanent magnet samples of Examples 1-9 and Comparative Examples 1-7 filled with the insulating layer were respectively subjected to bending resistance test, and recorded as bending strength 2, and the specific experimental results are shown in Tables 3 and 4.

[0108] Table 3

[0109] Table 4

[0110] Note: Comparative Example 8 is a non-slotted magnet, which is not filled with an insulating layer, and the magnet is not detected for bending strength 2 (equivalent to bending strength 1).

[0111] From the results in Tables 3 and 4, it can be seen that:

[0112] (1) By slitting the permanent magnet, the magnetic lines can be cut, thereby reducing the temperature rise difference of the permanent magnet;

[0113] (2) The sum L1 of the lengths of the separation grooves of Comparative Example 1 in the first extension direction is less than 50% of the length of the permanent magnet in the first extension direction, the sum L2 of the lengths of the separation grooves of Comparative Example 2 in the second extension direction is greater than 50% of the length of the permanent magnet in the second extension direction, and the separation grooves of Comparative Examples 1 and 2 penetrate the permanent magnet in the second extension direction, thereby making the permanent magnet of Comparative Examples 1 and 2 not only increase the eddy current loss, but also increase the temperature rise of the permanent magnet, and the brittleness of the magnet is also significantly increased, and the bending strength is also reduced. Therefore, it is difficult to reduce the temperature rise difference of the permanent magnet by slitting the magnet in the first extension direction and slitting the magnet in the second extension direction. Therefore, the present application preferably slits the magnet in the second extension direction to reduce the temperature rise difference of the permanent magnet.

[0114] (3) The sum L2 of the lengths of the separation slots of Comparative Examples 4-6 in the second extension direction is higher than 50% of the length of the permanent magnet in the second extension direction, and the number of slots of Comparative Example 5 is large (L2 / C is 1.08, which exceeds the upper limit of 0.2≤L2 / C≤1), and the excessive slot ratio significantly reduces the bending strength of the magnet and the uneven strength, so the magnet is easily damaged. Therefore, by controlling the length of the slots in the second extension direction of the permanent magnet, when the ratio of the total length L2 of the slots in the second extension direction to the circumference C of the first surface is between 0.35-0.85, the temperature rise effect of the magnet can be significantly improved.

[0115] (4) Compared with the permanent magnet without slot processing, the present application helps to improve the temperature rise effect of the permanent magnet by providing separation slots in the second extension direction of the permanent magnet, even if the length L2 of the separation slots in the second extension direction is less than 30% of the length in the second extension direction. However, it is difficult to reduce the eddy current loss of the magnetic steel, improve the efficiency of the motor, and improve the effect of rotor temperature rise.

[0116] (5) The results of Examples 7 and 8 show that when the sum L1 of the lengths of the separation slots in the first extension direction is the same as the sum L2 of the lengths of the separation slots in the second extension direction, the present application can significantly reduce the eddy current loss and temperature rise performance of the permanent magnet by providing bidirectional slots to the permanent magnet compared with unidirectional slots.

[0117] (6) The comparison of the results of Example 6 and Example 4 shows that the permanent magnet with a higher slot width can better improve the eddy current loss and temperature rise resistance of the permanent magnet; but too large slot width will also continue to affect the bending strength of the magnet. By filling the gap of the slotted magnet with glue, expanding coating and other insulating layers, the bending strength of the magnet can be significantly improved.

[0118] (7) It is found by comparing Example 6 and Example 7 that when the ratio of the total length L2 of the slots in the second extension direction of the permanent magnet to the circumference C of the first surface is increased, it also helps to improve the eddy current loss and temperature rise performance of the permanent magnet.

[0119] (8) as shown in Fig. 18, the second extending direction of the separation groove is extending from the first side wall to the second side wall in a direction inclined to the first side wall (i.e. not perpendicular to the first side wall, the included angle between the second extending direction of the first separation groove and the length direction of the permanent magnet is greater than 0° and less than 90°), and the length of the first separation groove in the extending direction is less than the distance between the first side wall and the second side wall in the extending direction, i.e. the cutting mode does not penetrate the second side wall, when the second extending direction of the separation groove has an included angle with the width direction or the length direction of the permanent magnet, the projection length of the separation groove with the included angle in the second extending direction is more than 30% and preferably less than 50%, so that the permanent magnet filled with the insulating layer such as glue has better eddy current loss resistance and temperature rise resistance.

[0120] In summary, the present application can make the permanent magnet filled with the insulating layer such as glue have better eddy current loss resistance and temperature rise resistance by opening the separation groove with specific size requirements on the permanent magnet and through specific groove opening distribution mode (such as L2 is more than 30% and preferably less than 50% of the length of the permanent magnet in the second extending direction), and controlling the ratio relationship between the total length L2 in the second extending direction and the circumference C of the first surface or the second surface of the magnet.

[0121] The permanent magnet samples of Examples 1-9 were respectively filled with an insulating layer, and the method was as follows:

[0122] An epoxy glue (F-44 type phenolic epoxy resin) was coated on the gap of each separation groove on the first surface of the permanent magnet obtained in the above step by using a dispensing machine, and the coating length of the glue was equal to the length of the separation groove in the second extending direction, i.e. L=L2; the dispensing speed was 35 mm / s, and the gun head diameter of the dispensing machine was 0.20 mm.

[0123] The grooved permanent magnet with glue filling was placed on a support part, the grooved permanent magnet had contact points with the support part, and then was placed into a polyethylene film sealing bag (size 80 mm*40 mm) with a thickness of 0.03 mm, and was placed into a sealed container for vacuumizing treatment.

[0124] The specific glue length, support point number, vacuumizing pressure time and glue filling number are shown in Table 5.

[0125] Table 5

[0126] (3) Curing treatment:

[0127] For the permanent magnet filled with glue in the separation groove, the curing condition is curing treatment at 150℃ for 3h, and then cooling to room temperature.

[0128] (4) Surface treatment:

[0129] The permanent magnet with insulation layer is put into the BW-231 zinc phosphating solution of Ersim (100g / L of zinc dihydrogen phosphate, 200g / L of phosphoric acid, 15g / L of tannic acid, 10g / L of calcium nitrate, 20g / L of ammonium molybdate, 50g / L of phytic acid, 30g / L of auxiliary film forming agent, and the rest is water. The phosphating solution is mixed with pure water in a volume ratio of 3:1). The phosphating temperature is 50℃, and the phosphating time is 2min. Then, a layer of epoxy resin coating with a thickness of 20μm is sprayed on the permanent magnet to obtain the permanent magnet with insulation layer.

[0130] Example 10

[0131] A method for preparing a permanent magnet, compared with example 1, the difference is that step (2) glue filling: using a dispensing machine, dispensing speed 45mm / s, the gun head diameter of the dispensing machine is 0.26mm. The slotted permanent magnet containing glue filling is put into a polyethylene film sealed bag (size 90mm*40mm) with a thickness of 0.1mm, put into a closed container, vacuum treatment, the vacuum pressure is 0.5bar, the maintenance time is 5s.

[0132] Example 11

[0133] A method for preparing a permanent magnet, compared with example 2, the difference is that step (2) glue filling: using a dispensing machine, dispensing speed 20mm / s, the gun head diameter of the dispensing machine is 0.16mm. The slotted magnet containing glue filling is placed on the supporting part, the contact points of the slotted magnet and the supporting part are 1, put into a polyethylene film sealed bag (size 50mm*30mm) with a thickness of 0.2mm, put into a closed container, vacuum treatment, the vacuum pressure is 0.2bar, the maintenance time is 10s.

[0134] Example 12

[0135] A method for preparing a permanent magnet, compared with example 2, the difference is that step (2) glue filling: using a dispensing machine, dispensing speed 15mm / s, the gun head diameter of the dispensing machine is 0.22mm. The slotted magnet containing glue filling is placed on the supporting part, the contact points of the slotted magnet and the supporting part are 2, a polyethylene film with a thickness of 0.1mm is covered on the first surface of the slotted magnet, which can cover the first surface completely, and the covering area is 300% of the area of the first surface (size 120mm*36mm), put into a closed container, vacuum treatment, the vacuum pressure is 0.5bar, the maintenance time is 2s.

[0136] Example 13

[0137] A method for preparing a permanent magnet, compared with Example 1, the difference is that in step (1) magnet preparation: the permanent magnet is processed with a multi-wire cutting method, and a separation groove is processed, wherein the width of the separation groove is 0.18 mm. And the second extension direction forms an angle of 30° with the extension direction of the side wall, see Figure 10.

[0138] The bending strength of the permanent magnet prepared in Examples 1-13 was detected, and the glue filling ratio P of the smallest separation groove in all separation grooves n , the average filling ratio P of all separation grooves, the flatness, and the neutral salt spray performance, and the results are shown in Table 6.

[0139] Table 6

[0140] Comparative Example 9

[0141] A method for preparing a permanent magnet, compared with Example 2, the difference is that in step (2) the glue filling length is 5 mm.

[0142] Comparative Example 10

[0143] A method for preparing a permanent magnet, compared with Example 2, the difference is that in step (2) the glue filling length is 4 mm.

[0144] Comparative Example 11

[0145] A method for preparing a permanent magnet, compared with Example 2, the difference is that in step (2) the glue filling is: the slotted permanent magnet containing the glue filling is placed on the supporting part, the slotted permanent magnet has a contact point with the supporting part, and then is placed in a polyethylene film sealing bag (size 60mm*40mm) with a thickness of 0.03mm, and is placed in a closed container for natural placement for 10 minutes.

[0146] Comparative Example 12

[0147] A method for preparing a permanent magnet, compared with Example 2, the difference is that in step (2) the glue filling is: the slotted permanent magnet containing the glue filling is placed in a polyethylene film sealing bag (size 60mm*40mm) with a thickness of 0.03mm, and is placed in a closed container for vacuum treatment.

[0148] Comparative Example 13

[0149] A method for preparing a permanent magnet, wherein the difference from Example 1 is that in step (2) glue filling, the slotted permanent magnet with glue filling is placed on a support component, the contact points of the slotted permanent magnet and the support component are two, and the slotted permanent magnet is placed in a closed container for vacuum treatment.

[0150] Comparative Example 14

[0151] A method for preparing a permanent magnet, wherein the difference from Example 1 is that in step (2) glue filling, the slotted permanent magnet with glue filling is placed on a support component, the contact points of the slotted permanent magnet and the support component are two, and the slotted permanent magnet is placed in a closed container for vacuum treatment.

[0152] Comparative Example 15

[0153] A method for preparing a permanent magnet, wherein the difference from Example 1 is that in step (2) glue filling, the slotted permanent magnet with glue filling is placed on a support component, the contact points of the slotted permanent magnet and the support component are two, and the slotted permanent magnet is placed in a closed container for vacuum treatment.

[0154] The bending strength, glue filling ratio, flatness, and neutral salt spray performance of the permanent magnets prepared in Comparative Examples 9-15 are detected, and the results are shown in Table 4.

[0155] Table 4

[0156] As can be seen from the comparison of the results of Examples 1-13 and Comparative Examples 9-15, the bending strength and neutral salt spray time of the permanent magnets prepared in Examples 1-13 are significantly improved by using different cutting methods to separate and groove the permanent magnets and then filling the insulating layer. Since the coating length L (mm) of the glue and the extension length L2 (mm) of the separation groove in the second extension direction do not satisfy L≥50%*L2 in Comparative Example 9 and Comparative Example 10, the average filling ratio of the separation groove is low, and thus the bending strength and neutral salt spray time performance of the obtained permanent magnet are poor. Although the filling ratio of the permanent magnet is increased in Comparative Example 11, Comparative Example 14, and Comparative Example 15, the flatness of the permanent magnet is poor, and the bending strength and neutral salt spray (corrosion resistance) performance of the magnet are also reduced. In Comparative Example 15, an excessively large vacuum treatment is used, and since the vacuum pressure is too large, the vacuum condition is achieved instantaneously before the glue is uniformly distributed under pressure, which is not conducive to the uniform distribution of the glue, and thus the flatness and bending strength of the permanent magnet are reduced.

[0157] The above describes the embodiments of the present application. However, the present application is not limited to the above-described embodiments. Any modification, equivalent replacement, improvement, and the like made within the spirit and principle of the present application should be included in the scope of protection of the present application.

Claims

1. A permanent magnet, characterized in that: The permanent magnet is provided with a separation groove. Preferably, the permanent magnet provided with the separation groove is treated in a medium frequency heating furnace with a frequency of 3 kHz and a current of 2 A for 10 minutes, and the temperature rise is less than 50°C.

2. The permanent magnet according to claim 1, wherein The separating groove passes through or does not pass through the permanent magnet in a first extension direction of the separating groove, and does not pass through the permanent magnet in a second extension direction of the separating groove, wherein the first extension direction of the separating groove is parallel to the magnetization direction of the permanent magnet, or the first extension direction of the separating groove has an angle with the magnetization direction of the permanent magnet; the second extension direction of the separating groove is parallel to the width direction or length direction of the permanent magnet, or the second extension direction of the separating groove has an angle with the width direction or length direction of the permanent magnet. Preferably, the angle is 0-90°.

3. The permanent magnet according to claim 2, wherein The total length of the separation grooves in the first extension direction is denoted as L1 (mm), and L1 is greater than 50% of the length of the permanent magnet in the first extension direction, and preferably greater than 60%. Preferably, the total length of the separation grooves in the second extension direction is denoted as L2 (mm), and L2 is greater than 30% of the length of the permanent magnet in the second extension direction, and preferably less than 50%. Preferably, when the second extension direction of the separating groove has an angle with the width direction or length direction of the permanent magnet, the projected length of the separating groove with the angle in the second extension direction is more than 30% of the length of the permanent magnet in the second extension direction, preferably less than 50%; and / or, the length L2 of the separating groove in its second extension direction is 30 to 50% of the length of the permanent magnet in the second extension direction. Preferably, the projected length of the angled separating groove in the second extension direction is 30-50% of the length of the permanent magnet in the second extension direction; and / or, the width of the separating groove is W (mm), W is 0.1-0.5 mm, preferably 0.12-0.25 mm; and / or, when there are multiple separating grooves, the spacing between two adjacent separating grooves is 1-10 mm, preferably 1-5 mm; Preferably, the separation grooves are distributed on the permanent magnet in a single-side groove or staggered groove manner. Preferably, the surface of the separation groove in the second extension direction is recorded as the first surface or the second surface, and the perimeter of the first surface or the second surface is recorded as C; then 0.2≤L2 / C≤1; more preferably, 0.35≤L2 / C≤0.

85.

4. The permanent magnet according to any one of claims 1 to 3, characterized in that The groove of the separation groove is filled with an insulating layer. For example, the insulating layer may be an insulating material such as a glue layer, an expansion coating, or an injection molding agent; Preferably, the glue used in the glue layer is selected from one or more combinations of epoxy resin glue, acrylic resin glue, phenolic resin glue and unsaturated polyester resin glue.

5. The permanent magnet according to claim 4, characterized in that The filling ratio of the insulation layer in any separation groove satisfies: P n ≥50%, preferably 80%-100%; Preferably, after filling the insulating layer, the flatness of all surfaces of the permanent magnet is ≤0.05mm. Preferably, the flatness is ≤0.03mm; Preferably, after filling the insulating layer, the neutral salt spray of the magnet is greater than 240 hours.

6. The method for preparing a permanent magnet according to any one of claims 1 to 5, characterized in that: The preparation method includes preparing separation grooves on a permanent magnet.

7. The method for preparing a permanent magnet according to claim 6, wherein: The following steps are involved: (1) Magnet preparation: Prepare a permanent magnet with a separation groove and then perform pretreatment; (2) Glue filling: Apply glue to the gap of the separation groove, then vacuum and fill the glue into the separation groove; (3) Curing treatment: curing the permanent magnet filled with glue in the separation groove to obtain the permanent magnet.

8. The method for preparing a permanent magnet according to claim 7, wherein: In step (2), the method for applying glue to the gap of the dividing groove is as follows: applying glue to at least a portion of the dividing groove in its second extension direction; preferably, applying glue to one of the two opposing gaps of the dividing groove in its second extension direction; preferably, the glue application length L (mm) is not less than half of the extension length L2 (mm) of the dividing groove in its second extension direction, that is, L ≥ 50% * L2, and preferably, the glue application length L (mm) is 70%-90% of the extension length L2 (mm) of the dividing groove in its second extension direction; and / or, in step (2), the filling ratio P of the glue is ≥ 50%, preferably 80%-100%; And / or, in step (2), the vacuum pressure is -1.0 bar to 1 mbar, and the vacuum pressure is maintained for ≥ 1 s; And / or, in step (2), before the vacuuming, a thin film may be applied to the surface of the permanent magnet coated with the glue. Preferably, the thickness of the thin film is 0.01-0.5 mm; And / or, in step (2), a support component for placing a permanent magnet for coating glue is placed in the sealed vacuum device; and / or, the number of contact points between the support component and the permanent magnet is at least two; And / or, in step (3), the temperature of the curing treatment is 20-200° C., preferably 50-150° C.; the curing time is 0.5-8 h, preferably 1-3 h.

9. Use of the permanent magnet according to any one of claims 1 to 5 and / or the permanent magnet prepared by the preparation method according to any one of claims 6 to 8 in the field of motors.

10. A motor comprising a rotor, wherein the rotor comprises the permanent magnet according to any one of claims 1 to 5 and / or the permanent magnet prepared by the preparation method according to any one of claims 6 to 8.

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