Composite magnet, preparation method thereof and motor

Abstract

The invention relates to a composite magnet, a preparation method thereof and a motor. The preparation method of the composite magnet comprises the following steps: dividing a first magnet into a first magnetic part and a second magnetic part according to a critical flux density value B of an Hcb curve under the maximum working temperature of a use working condition of the first magnet and field loss flux density distribution of the first magnet, all areas with the field loss flux density value smaller than the B value in the first magnet are located in the first magnetic part, and the field loss flux density value in the second magnetic part is larger than or equal to the B value; replacing the first magnetic part with a second magnet, and connecting the second magnet with the second magnetic part to prepare a composite magnet; wherein the critical flux density value of an Hcb curve at the maximum working temperature of the second magnet is smaller than the minimum value of field loss flux density of the first magnetic part. Therefore, the composite magnet with high demagnetization resistance is obtained, the processing path is optimized, the processing amount is greatly reduced, and meanwhile, the problem of magnet loss of excitation in the permanent magnet motor is avoided.

Description

Technical Field

[0001] The present application relates to the technical field of permanent magnetic materials, and in particular to a composite magnet and a preparation method thereof, and a motor. Background Art

[0002] As the third generation of rare earth permanent magnet materials, NdFeB permanent magnet materials have been widely used in power electronics, communications, information, transportation, office automation, medical equipment and military fields since they were first commercialized by Japan's Sumitomo Metal and the United States' GM in 1983. Due to their high remanence, high coercive force and high magnetic energy product, they have been widely used in power electronics, communications, information, transportation, office automation, medical equipment and military fields.

[0003] According to the different fields of use of NdFeB permanent magnets, their performance and composition also have obvious differences. Under normal circumstances, magnets made only of rare earths Pr and Nd have low coercivity, poor anti-demagnetization ability and high temperature resistance, and can only be used in environments with low temperatures and low reverse magnetic fields. In order to improve the coercivity of the magnet, improve the anti-demagnetization ability, and prevent the permanent magnet motor from losing magnetism, heavy rare earth elements such as Dy and Tb are generally added. The high temperature resistance and anti-demagnetization ability of the magnet increase with the increase of Dy and Tb content. Since Dy and Tb are expensive and scarce resources, the cost of magnets has also increased exponentially.

[0004] Analysis of the demagnetization phenomenon of permanent magnet motors shows that the demagnetization of permanent magnets in motors is uneven. For magnets bonded to the rotor, the demagnetization part always occurs on the side of the magnet close to the air gap, while the part close to the middle of the magnet basically does not lose magnetism. The reason for this phenomenon is that when the motor is short-circuited, the stator coil generates high temperature due to the presence of large current, and at the same time generates a very strong reverse magnetic field. The magnet part close to the air gap is closest to the stator, so it is most affected by high temperature and reverse magnetic field. The presence of high temperature will reduce the magnetic properties of the magnet, especially the Hcb curve (intrinsic demagnetization curve) will bend with the increase of temperature, and the B (magnetic flux density) value of the inflection point of the bend will increase with the increase of temperature. At the same time, due to the presence of the reverse magnetic field, the working point of the motor decreases along the Hcb line. When the working point drops below the inflection point, the motor has irreversible demagnetization. However, in order to improve the anti-demagnetization ability of the magnet and avoid demagnetization of the magnet when the motor is short-circuited, it is necessary to use magnets with higher coercive force, which will lead to a sharp increase in the cost of the motor.

[0005] Therefore, the traditional technology still needs to be further improved. Summary of the invention

[0006] Based on this, the present application provides a composite magnet with high anti-demagnetization ability, a preparation method thereof, and a motor.

[0007] The technical solution of this application to solve the above technical problems is as follows:

[0008] In a first aspect of the present application, a method for preparing a composite magnet is provided, comprising the following steps:

[0009] According to the critical magnetic flux density B value of the Hcb curve at the maximum operating temperature of the first magnet use condition and the demagnetization magnetic flux density distribution of the first magnet, the first magnet is divided into a first magnetic part and a second magnetic part, the areas in the first magnet where the demagnetization magnetic flux density value is less than the B value are all located in the first magnetic part, and the demagnetization magnetic flux density value in the second magnetic part is ≥ the B value;

[0010] A composite magnet is prepared by replacing the first magnetic part with a second magnet and connecting the second magnet to the second magnetic part; wherein the critical magnetic density value of the Hcb curve at the maximum operating temperature of the second magnet is less than the minimum demagnetization magnetic density value of the first magnetic part.

[0011] The preparation method of the above-mentioned composite magnet is as follows: according to the critical magnetic flux density B value of the Hcb curve at the maximum operating temperature of the first magnet use condition and the demagnetization magnetic flux density distribution of the first magnet, the first magnet is divided into a first magnetic part and a second magnetic part, the areas in the first magnet where the demagnetization magnetic flux density value is less than the B value are all located in the first magnetic part, and the demagnetization magnetic flux density value in the second magnetic part is ≥ the B value; the first magnetic part is replaced by a second magnet and the second magnet is connected to the second magnetic part to prepare a composite magnet; wherein the critical magnetic flux density value of the Hcb curve at the maximum operating temperature of the second magnet is less than the lowest demagnetization magnetic flux density value of the first magnetic part, and the magnets with lower critical magnetic flux density values ​​are distributed in the parts with lower magnetic flux density values ​​when the permanent magnet motor is short-circuited, that is, the positions that are easy to demagnetize are designed to be materials with high performance and strong anti-demagnetization ability, and the positions that are not easy to demagnetize are set to materials with low performance and more cost advantages, so as to obtain a composite magnet with high anti-demagnetization ability, optimize the processing path, greatly reduce the processing amount, and avoid the problem of magnet demagnetization in the permanent magnet motor.

[0012] In some embodiments, the first magnet includes two first magnetic parts and one second magnetic part, the two first magnetic parts are respectively located on opposite sides of the second magnetic part, and the arrangement direction of the two first magnetic parts is perpendicular to the thickness direction of the second magnetic part.

[0013] In some embodiments, two surfaces of the first magnetic portion and the second magnetic portion perpendicular to the thickness direction are flush with each other.

[0014] In some embodiments, the second magnetic portion is provided with recesses on two opposite sides of the same surface, and the two first magnetic portions are respectively located in the two recesses on the two sides.

[0015] In some embodiments, the first magnet includes a first magnetic portion and a second magnetic portion, and the first magnetic portion and the second magnetic portion are stacked along a thickness direction of the second magnetic portion.

[0016] In some embodiments, the first magnetic part and the second magnetic part are connected by bonding with an adhesive.

[0017] In some embodiments, the adhesive includes at least one of epoxy resin, phenolic resin, and polyurethane.

[0018] In a second aspect of the present application, a composite magnet is provided, which is prepared by the method for preparing a composite magnet as described above; or, the composite magnet includes a first magnet and a second magnet, the first magnet includes a first magnetic part and a second magnetic part, all regions of the first magnet whose demagnetization magnetic flux density is less than the B value are located in the first magnetic part, and the demagnetization magnetic flux density in the second magnetic part is ≥ the B value; the first magnetic part is replaced by the second magnet, and the critical magnetic flux density value of the Hcb curve at the maximum operating temperature of the second magnet is less than the minimum demagnetization magnetic flux density of the first magnetic part.

[0019] In some embodiments, the squareness of the first magnet and the second magnet differ by a value less than 4.

[0020] And / or, the first magnet and the second magnet are each independently selected from one of sintered neodymium iron boron and sintered samarium cobalt.

[0021] And / or, the shape of the composite magnet is selected from one of a square shape and a tile shape.

[0022] According to a third aspect of the present application, a motor is provided, comprising the composite magnet described above. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 : is a magnetic flux density distribution diagram of the first magnet in an embodiment at 120° C. when a permanent magnet motor is short-circuited;

[0024] Figure 2 : is a magnetic flux density distribution diagram of the first magnet in an embodiment at 120° C. when a permanent magnet motor is short-circuited;

[0025] Figure 3 An example diagram of the first magnetic portion and the second magnetic portion of the first magnet in Example 1;

[0026] Figure 4 An example diagram of the first magnetic portion and the second magnetic portion of the first magnet in Example 2;

[0027] Figure 5This is an example diagram of the first magnetic portion and the second magnetic portion in the first magnet in Example 3.

[0028] Description of reference numerals:

[0029] 11. First magnetic portion; 12. Second magnetic portion; Direction X: thickness direction. DETAILED DESCRIPTION

[0030] The method of the present application is further described in detail below in conjunction with specific embodiments. The present application can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the understanding of the disclosure of the present application more thorough and comprehensive.

[0031] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used herein in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0032] The terms "and / or", "or / and", and "and / or" used in this article include any one of two or more related listed items, and also include any and all combinations of related listed items, and the arbitrary and all combinations include any two related listed items, any more related listed items, or a combination of all related listed items. It should be noted that when at least three items are connected by at least two conjunctions selected from "and / or", "or / and", and "and / or", it should be understood that in this application, the technical solution undoubtedly includes technical solutions that are all connected by "logical and", and undoubtedly includes technical solutions that are all connected by "logical or". For example, "A and / or B" includes three parallel solutions of A, B and A+B. For example, the technical solution of "A, and / or, B, and / or, C, and / or, D" includes any one of A, B, C, and D (that is, the technical solution that is all connected by "logical OR"), and also includes any and all combinations of A, B, C, and D, that is, the combination of any two or any three of A, B, C, and D, and also includes the combination of four of A, B, C, and D (that is, the technical solution that is all connected by "logical AND").

[0033] In the present application, "plurality", "multiple", "multiple times", "multiples", etc., unless otherwise specified, refer to a number greater than 2 or equal to 2. For example, "one or more" means one or greater than or equal to two.

[0034] As used herein, "combination thereof", "any combination thereof", "any combination thereof" etc. include all suitable combinations of any two or more of the listed items.

[0035] Herein, the “suitable” mentioned in “suitable combination”, “suitable method”, “any suitable method”, etc., shall be based on the ability to implement the technical solution of this application, solve the technical problems of this application, and achieve the expected technical effects of this application.

[0036] Herein, “preferred”, “better”, “more preferred” and “suitable” are merely used to describe implementation methods or examples with better effects, and it should be understood that they do not constitute limitations on the scope of protection of this application.

[0037] In the present application, "further", "further", "particularly" and the like are used for descriptive purposes to indicate differences in content, but should not be construed as limiting the scope of protection of the present application.

[0038] In this application, "optionally", "optional", and "optional" mean optional or dispensable, that is, any one of the two parallel schemes of "yes" or "no". If multiple "options" appear in a technical solution, unless otherwise specified and there is no contradiction or mutual restriction, each "optional" is independent.

[0039] In the present application, the technical features described in an open manner include closed technical solutions composed of the listed features, and also include open technical solutions containing the listed features.

[0040] The temperature parameters in this application, unless otherwise specified, are allowed to be either constant temperature treatment or to vary within a certain temperature range. It should be understood that the constant temperature treatment allows the temperature to fluctuate within the accuracy range controlled by the instrument. Fluctuations within the range of ±5°C, ±4°C, ±3°C, ±2°C, and ±1°C are allowed.

[0041] In this application, the terms "first", "second", etc. in "first magnetic part", "second magnetic part", "first magnet", "second magnet", etc. are only used for distinguishing descriptive purposes and cannot be understood as indicating or implying relative importance or quantity, nor can they be understood as implicitly indicating the importance or quantity of the indicated technical features. Moreover, "first", "second", etc. only serve the purpose of non-exhaustive enumeration description, and it should be understood that they do not constitute a closed limitation on quantity.

[0042] It should be noted that when a numerical range is disclosed herein, the above range is deemed to be continuous and includes the minimum value and maximum value of the range, and each value or the range determined by any two values ​​between the minimum value and the maximum value.

[0043] Permanent magnet synchronous motors are generally composed of stators, rotors, shafts, and end caps. The stator includes a stator core and a stator winding. The stator winding surrounds the stator core and generates a rotating magnetic field when powered on. By controlling the frequency of the input current of the stator winding, the magnetic field rotation frequency can be controlled, and then the speed can be controlled; permanent magnets are placed on the rotor, usually made of rare earth materials such as neodymium iron boron, to generate a constant magnetic field; the shaft is used to support and connect the rotor to transfer the mechanical energy of the motor to the external load.

[0044] As shown in the background technology, in the traditional technology, in order to improve the anti-demagnetization ability of the magnet, a magnet with high coercive force needs to be used, which will lead to a sharp increase in the cost of the motor. In order to improve this problem, some methods currently propose a magnet with gradient coercive force, the magnet includes at least two layers of NdFeB magnet layers with different coercive forces, one of which has a high coercive force. This method can ensure that the magnet has a certain anti-demagnetization ability to a certain extent, while reducing the cost. However, this method does not really solve the demagnetization problem of the magnet in the permanent magnet motor, but only alleviates it to a certain extent. Secondly, there are major problems in the preparation method of the magnet. The magnet is to put powders with different properties into a cavity with a partition during molding, and then take out the partition and press it into a whole, and then sinter it; when pressing the magnetic field orientation, the powder will rotate and move in the direction of the two pole heads. In this process, the two powders will inevitably mix with each other, thereby affecting each other's performance; after the orientation is completed, the upper and lower pressure heads will squeeze toward the middle, and in this process, the powders will inevitably mix with each other, because during pressing, the powders will flow in all directions, not just along the pressing direction. The sintering and aging processes for powders with different properties are different. This method requires that the green body composed of two or more powders with different properties be treated under the same sintering and aging process, which is obviously inappropriate. It is difficult to ensure that different parts of the same magnet will obtain the magnetic properties they should have, and it is difficult to prepare a magnet composed of two or more very thin magnetic layers with different coercive forces.

[0045] Based on this, an embodiment of the present application provides a method for preparing a composite magnet, including steps S100 to S200.

[0046] Step S100: According to the critical magnetic density value B of the Hcb curve at the maximum operating temperature of the first magnet's operating condition and the demagnetization magnetic density distribution of the first magnet, the first magnet is divided into a first magnetic part and a second magnetic part, and all the areas in the first magnet where the demagnetization magnetic density value is less than the B value are located in the first magnetic part, and the demagnetization magnetic density value in the second magnetic part is ≥ the B value.

[0047] In some of the embodiments, the demagnetization flux density distribution of the first magnet is the demagnetization flux density distribution at the maximum operating temperature of the operating condition.

[0048] Step S200: replacing the first magnetic part with a second magnet and connecting the second magnet to the second magnetic part to prepare a composite magnet; wherein the critical magnetic flux density value of the Hcb curve at the maximum operating temperature of the second magnet is less than the minimum value of the demagnetization magnetic flux density distribution of the first magnetic part.

[0049] In some embodiments, the first magnet has two easily volatile magnetic regions, which are located close to the stator, close to a side of the reverse magnetic field and on opposite sides of the side. The easily volatile magnetic region refers to a region in the first magnet where the demagnetization magnetic flux density value is less than the B value.

[0050] In some embodiments, the first magnet includes two first magnetic parts and one second magnetic part, the two first magnetic parts are respectively located on opposite sides of the second magnetic part, and the arrangement direction of the two first magnetic parts is perpendicular to the thickness direction of the second magnetic part. In other words, the two volatile magnetic regions are respectively located within the two first magnetic parts.

[0051] In some embodiments, two surfaces of the two first magnetic portions and the second magnetic portion perpendicular to the thickness direction are flush with each other.

[0052] In some embodiments, the planes where the surfaces of the first magnetic portion and the second magnetic portion are located are perpendicular to the thickness direction.

[0053] In a specific example, the first magnetic portion and the second magnetic portion have the same thickness.

[0054] In some embodiments, the second magnetic portion is provided with recesses on two opposite sides of the same surface, and the two first magnetic portions are respectively located in the two recesses on the two sides.

[0055] In a specific example, the first magnetic portion and the second magnetic portion have the same thickness, and only one surface is flush with each other.

[0056] In some embodiments, the first magnet includes a first magnetic portion and a second magnetic portion, and the first magnetic portion and the second magnetic portion are stacked along a thickness direction of the second magnetic portion.

[0057] In some embodiments, the first magnetic portion and the second magnetic portion are connected by bonding with an adhesive.

[0058] In some embodiments, the adhesive includes at least one of epoxy resin, phenolic resin, and polyurethane.

[0059] It can be understood that by avoiding microscopic intersections or gradient zones at the bonding points of magnets with different magnetic properties, the processing path is optimized, the processing volume is greatly reduced, and production efficiency is improved.

[0060] Specifically, in step S200, the second magnet is used to replace the first magnetic part and the second magnet is connected to the second magnetic part. The steps of preparing the composite magnet include steps S210 to S220.

[0061] Step S210: replacing the first magnetic portion of the first magnet with the second magnet, and processing the first magnet and the second magnet respectively to prepare a first magnet rough blank and a second magnet rough blank.

[0062] Step S220: bonding the first magnet rough blank and the second magnet rough blank with an adhesive so that they correspond to the first magnet and the second magnet, and after curing, preparing a composite magnet.

[0063] In some of the embodiments, after the above-mentioned solidification step and before the step of preparing the composite magnet, the step further includes processing the solidified composite magnet and then performing electroplating to prepare the composite magnet.

[0064] In some of the embodiments, the first magnet and the second magnet are respectively formed by bonding one or more layers of magnets.

[0065] In some of the embodiments, the sizes and shapes of the different magnetic parts are not limited, and any sizes and shapes that can be processed by processing equipment can be realized.

[0066] The preparation method of the composite magnet is as follows: the first magnet is divided into a first magnetic part and a second magnetic part according to the critical magnetic flux density B value of the Hcb curve at the maximum working temperature of the first magnet use condition and the demagnetization magnetic flux density distribution of the first magnet, the regions in the first magnet where the demagnetization magnetic flux density value is less than the B value are all located in the first magnetic part, and the demagnetization magnetic flux density value in the second magnetic part is ≥ the B value; the first magnetic part is replaced by a second magnet and the second magnet is connected to the second magnetic part to prepare the composite magnet; wherein the critical magnetic flux density value of the Hcb curve at the maximum working temperature of the second magnet is less than the lowest demagnetization magnetic flux density of the first magnetic part, the magnets with lower critical magnetic flux density values ​​are distributed in the parts with lower magnetic flux density values ​​when the permanent magnet motor is short-circuited, that is, the positions that are easy to demagnetize are designed to be materials with high performance and strong anti-demagnetization ability, while the positions that are not easy to demagnetize are set to materials with low performance and more cost advantages, so as to obtain a composite magnet with high anti-demagnetization ability, optimize the processing path, greatly reduce the processing amount, and avoid the problem of magnet demagnetization in the permanent magnet motor.

[0067] One embodiment of the present application provides a composite magnet, which is prepared by the above-mentioned composite magnet preparation method, or the above-mentioned composite magnet includes a first magnet and a second magnet, the above-mentioned first magnet includes a first magnetic part and a second magnetic part, the areas in the above-mentioned first magnet where the demagnetization magnetic flux density value is less than the B value are all located in the above-mentioned first magnetic part, and the demagnetization magnetic flux density value in the above-mentioned second magnetic part is ≥ B value; the above-mentioned first magnetic part is replaced by the above-mentioned second magnet, and the critical magnetic flux density value of the Hcb curve at the maximum operating temperature of the above-mentioned second magnet is less than the minimum demagnetization magnetic flux density value of the above-mentioned first magnetic part.

[0068] In some embodiments, the squareness difference between the first magnetic portion and the second magnetic portion is less than 4.

[0069] In some embodiments, the squareness difference between the first magnetic portion and the second magnetic portion is -0.1 to 0.1.

[0070] In some of the embodiments, the remanence of the first magnetic portion and the remanence of the second magnetic portion may be the same, similar, or different.

[0071] In some embodiments, the first magnetic portion and the second magnetic portion are each independently selected from one of sintered NdFeB and sintered SmCo.

[0072] In a specific example, the first magnetic part and the second magnetic part are both sintered NdFeB magnets.

[0073] Furthermore, the sintered NdFeB magnets can be conventionally produced or processed by grain boundary diffusion. It is understood that the composite magnets can be used in motors, and the maximum operating temperature of the operating conditions is the maximum operating temperature of the motor.

[0074] In some embodiments, when the maximum operating temperature of the motor is 80° C., the first magnet is an N-level coercive force magnet, wherein 12kOe≤N-level coercive force magnet≤14kOe.

[0075] In some embodiments, when the maximum operating temperature of the motor is 100° C., the first magnet adopts an M-level coercive force magnet, wherein 14kOe<N-level coercive force magnet≤17kOe.

[0076] In some embodiments, when the maximum operating temperature of the motor is 120° C., the first magnet is an H-grade coercive force magnet, wherein 17kOe<N-grade coercive force magnet≤20kOe.

[0077] In some embodiments, when the maximum operating temperature of the motor is 150° C., the first magnet is a SH-grade coercive force magnet, wherein 20kOe<N-grade coercive force magnet≤25kOe.

[0078] In some embodiments, when the maximum operating temperature of the motor is 180° C., the first magnet is a UH-grade coercive force magnet, wherein 25kOe<N-grade coercive force magnet≤30kOe.

[0079] In some embodiments, when the maximum operating temperature of the motor is 200° C., the first magnet is an EH-grade coercive force magnet, wherein 30kOe<N-grade coercive force magnet≤35kOe.

[0080] In some embodiments, when the maximum operating temperature of the motor is 230° C., the first magnet is a TH-level coercive force magnet, wherein 35kOe<N-level coercive force magnet.

[0081] In some embodiments, the thickness of the first magnetic portion and the second magnetic portion is greater than 0.5 mm.

[0082] In some embodiments, the shape of the composite magnet is selected from one of a square shape and a tile shape.

[0083] The magnets with lower critical magnetic flux density in the composite magnet of the present application are distributed in the parts with lower magnetic flux density when the permanent magnet motor is short-circuited, and have high anti-demagnetization ability, thus avoiding the problem of magnet demagnetization in the permanent magnet motor.

[0084] Another embodiment of the present application further provides a motor, including a composite magnet prepared by the above-mentioned method for preparing a composite magnet and / or the above-mentioned composite magnet.

[0085] In the above-mentioned motor of the present application, the composite magnet is composed of two magnets with different magnetic properties distributed in a regional manner, having high magnetic properties or special magnetic properties, avoiding the problem of magnet demagnetization in permanent magnet motors, and maximizing the cost reduction of rare earth permanent magnet materials, while having a simple preparation method.

[0086] The present application will be described below in conjunction with specific embodiments, but the present application is not limited to the following embodiments. It should be understood that the attached claims summarize the scope of the present application. Under the guidance of the concept of the present application, technical personnel in the field should realize that certain changes made to the various embodiments of the present application will be covered by the spirit and scope of the claims of the present application.

[0087] The present application is further described below in conjunction with embodiments, but the protection content of the present application is not limited to the scope described in the embodiments.

[0088] Implementation 1

[0089] Firstly, according to the performance of the first magnet, the distribution of magnetic flux density in the magnet when the motor is short-circuited is simulated, so as to determine the size of the first magnetic part. Figure 1 and Figure 2This is the magnetic flux density distribution of a simulated permanent magnet motor at the maximum operating temperature of 120°C when short-circuited. Figure 1 The magnetic flux density distribution of the first magnet away from the air gap when the permanent magnet motor is short-circuited at 120°C is simulated. Figure 2 The magnetic flux density distribution of the first magnet near the air gap when the permanent magnet motor is short-circuited at 120°C is simulated. The magnetic flux density distribution of the two magnets is simulated. The finished size of the first magnet in the figure is 47*82*22mm, the performance of the magnet is 45H, Br=13.4±0.1kGs, Hcj≥19.5kOe, and the inflection point B value of its Hcb curve at 120°C is 0.32T.

[0090] Combination Figure 1 and Figure 2 It can be known that the regions in the first magnet where the demagnetization magnetic flux density value is less than the B value are all located on the surface of the magnet away from the air gap and on two opposite sides of the surface.

[0091] Therefore, according to the simulation results, see Figure 3 , dividing the first magnetic part 11 and the second magnetic part 12, thereby replacing the magnet part of the first magnetic part 11 with the second magnet. The minimum magnetic density in the first magnetic part is 0.05 T. Based on this, the performance of the second magnet is Br=13.4±0.1 kGs, and the inflection point B value of its Hcb curve at 120°C is less than 0.05 T.

[0092] According to the above Figure 3 The composite magnet is prepared according to an example, and the specific steps are as follows: the base material magnet used to prepare the above-mentioned first magnet is processed into a first magnet rough blank of a certain thickness, wherein the first magnet rough blank is provided with recesses on opposite sides of the same surface, and the arrangement direction of the two recesses is perpendicular to the thickness direction X of the first magnet rough blank; the base material magnet used to prepare the second magnet is processed into a second magnet rough blank of a certain thickness; the second magnet rough blank and the first magnet rough blank are bonded with glue and then cured, and then the cured composite magnet assembly rough blank is processed into the shape and size of the first magnet (47*82*22mm), and then electroplated according to needs, at this time, the final composite magnet is formed, and the simulated short-circuit magnetic flux distribution of the composite magnet is Figure 2 Consistent, structured and Figure 3 Similar, except that a second magnet is used instead of Figure 3 The first magnetic portion in.

[0093] Implementation 2

[0094] Firstly, according to the performance of the first magnet, the distribution of magnetic flux density in the magnet when the motor is short-circuited is simulated, so as to determine the size of the first magnetic part. Figure 1 and Figure 2 This is the magnetic flux density distribution of a simulated permanent magnet motor at the maximum operating temperature of 120°C when short-circuited. Figure 1 The magnetic flux density distribution of the first magnet away from the air gap when the permanent magnet motor is short-circuited at 120°C is simulated. Figure 2 The magnetic flux density distribution of the first magnet near the air gap when the permanent magnet motor is short-circuited at 120°C is simulated. The magnetic flux density distribution of the two magnets is simulated. The finished size of the first magnet in the figure is 47*82*22mm, the performance of the magnet is 45H, Br=13.4±0.1kGs, Hcj≥19.5kOe, and the inflection point B value of its Hcb curve at 120°C is 0.32T.

[0095] Combination Figure 1 and Figure 2 It can be known that the regions in the first magnet where the demagnetization magnetic flux density value is less than the B value are all located on the surface of the magnet away from the air gap and on two opposite sides of the surface.

[0096] Therefore, according to the simulation results, see Figure 4 , dividing the first magnetic part 11 and the second magnetic part 12, thereby replacing the magnet part of the first magnetic part 11 with the second magnet. The minimum magnetic density in the first magnetic part is 0.05 T. Based on this, the performance of the second magnet is Br=13.4±0.1 kGs, and the inflection point B value of its Hcb curve at 120°C is less than 0.05 T.

[0097] According to the above Figure 4 The composite magnet is prepared according to an example, and the specific steps are as follows: the base material magnet used to prepare the above-mentioned first magnet is processed into a first magnet rough blank of a certain thickness, wherein the arrangement direction of the two first magnetic parts is perpendicular to the thickness direction X of the second magnetic part, and the two surfaces of the two first magnetic parts and the second magnetic part perpendicular to the thickness direction X are respectively flush; the base material magnet used to prepare the second magnet is processed into a second magnet rough blank of a certain thickness; the second magnet rough blank and the second magnetic part of the first magnet rough blank are bonded with glue, and then cured, and then the cured composite magnet assembly rough blank is processed into the shape and size of the first magnet (47*82*22mm), and then electroplated according to needs, at this time, the final composite magnet is formed, and the structure is the same as Figure 4 Similar, except that a second magnet is used instead of Figure 4 The first magnetic portion in.

[0098] Implementation 3

[0099] Firstly, according to the performance of the first magnet, the distribution of magnetic flux density in the magnet when the motor is short-circuited is simulated, so as to determine the size of the first magnetic part. Figure 1 and Figure 2 This is the magnetic flux density distribution of a simulated permanent magnet motor at the maximum operating temperature of 120°C when short-circuited. Figure 1 The magnetic flux density distribution of the first magnet away from the air gap when the permanent magnet motor is short-circuited at 120°C is simulated. Figure 2 The magnetic flux density distribution of the first magnet near the air gap when the permanent magnet motor is short-circuited at 120°C is simulated. The magnetic flux density distribution of the two magnets is simulated. The finished size of the first magnet in the figure is 47*82*22mm, the performance of the magnet is 45H, Br=13.4±0.1kGs, Hcj≥19.5kOe, and the inflection point B value of its Hcb curve at 120°C is 0.32T.

[0100] Combination Figure 1 and Figure 2 It can be known that the regions in the first magnet where the demagnetization magnetic flux density value is less than the B value are all located on the surface of the magnet away from the air gap and on two opposite sides of the surface.

[0101] Therefore, according to the simulation results, see Figure 5 , dividing the first magnetic part 11 and the second magnetic part 12, thereby replacing the magnet part of the first magnetic part 11 with the second magnet. The minimum magnetic density in the first magnetic part is 0.05 T. Based on this, the performance of the second magnet is Br=13.4±0.1 kGs, and the inflection point B value of its Hcb curve at 120°C is less than 0.05 T.

[0102] According to the above Figure 5 The composite magnet is prepared according to an example, and the specific steps are as follows: the base material magnet used to prepare the above-mentioned first magnet is processed into a first magnet rough blank of a certain thickness, wherein the first magnet rough blank includes a first magnetic part and a second magnetic part, and the first magnetic part and the second magnetic part are stacked along the thickness direction X of the second magnetic part; the base material magnet used to prepare the second magnet is processed into a second magnet rough blank of a certain thickness; the second magnet rough blank and the second magnetic part of the first magnet rough blank are bonded with glue, and then cured, and then the cured composite magnet assembly rough blank is processed into the shape and size of the first magnet (47*82*22mm), and then electroplated according to needs, at this time, the final composite magnet is formed, and the structure is the same as Figure 5 Similar, except that a second magnet is used instead of Figure 5 The first magnetic portion in.

[0103] It can be seen from this that by adopting the technical solution of the present application, the positions that are prone to demagnetization are designed to be made of materials with high performance and strong anti-demagnetization ability, while the positions that are not prone to demagnetization are set to materials with low performance and more cost advantages, thereby obtaining a composite magnet with high anti-demagnetization ability and avoiding the problem of magnet demagnetization in permanent magnet motors.

[0104] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0105] The above-described embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be construed as limiting the scope of the patent application. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent application shall be subject to the attached claims.

Claims

1. A method for preparing a composite magnet, characterized in that: The steps include: According to the critical magnetic flux density B value of the Hcb curve at the maximum operating temperature of the first magnet use condition and the demagnetization magnetic flux density distribution of the first magnet, the first magnet is divided into a first magnetic part and a second magnetic part, the areas in the first magnet where the demagnetization magnetic flux density value is less than the B value are all located in the first magnetic part, and the demagnetization magnetic flux density value in the second magnetic part is ≥ the B value; A composite magnet is prepared by replacing the first magnetic part with a second magnet and connecting the second magnet to the second magnetic part; wherein the critical magnetic density value of the Hcb curve at the maximum operating temperature of the second magnet is less than the minimum demagnetization magnetic density value of the first magnetic part.

2. The method for preparing a composite magnet according to claim 1, characterized in that: The first magnet includes two first magnetic parts and one second magnetic part, the two first magnetic parts are respectively located on opposite sides of the second magnetic part, and the arrangement direction of the two first magnetic parts is perpendicular to the thickness direction of the second magnetic part.

3. The method for preparing a composite magnet according to claim 2, characterized in that: Two surfaces of the first magnetic parts and the second magnetic parts perpendicular to the thickness direction are flush with each other.

4. The method for preparing a composite magnet according to claim 2, characterized in that: The second magnetic part is provided with recesses on two opposite sides of the same surface, and the two first magnetic parts are respectively located in the two recesses on the two sides.

5. The method for preparing a composite magnet according to claim 1, characterized in that: The first magnet includes a first magnetic portion and a second magnetic portion, and the first magnetic portion and the second magnetic portion are stacked in a thickness direction of the second magnetic portion.

6. The method for preparing a composite magnet according to any one of claims 1 to 5, characterized in that: The first magnetic part and the second magnetic part are connected by bonding with an adhesive.

7. The method for preparing a composite magnet according to claim 6, characterized in that: The adhesive includes at least one of epoxy resin, phenolic resin and polyurethane.

8. A composite magnet, characterized in that: The composite magnet is prepared by the preparation method of the composite magnet according to any one of claims 1 to 7; or, the composite magnet includes a first magnet and a second magnet, the first magnet includes a first magnetic part and a second magnetic part, the areas in the first magnet where the demagnetization magnetic flux density is less than the B value are all located in the first magnetic part, and the demagnetization magnetic flux density in the second magnetic part is ≥ the B value; the first magnetic part is replaced by the second magnet, and the critical magnetic flux density value of the Hcb curve at the maximum operating temperature of the second magnet is less than the minimum demagnetization magnetic flux density of the first magnetic part.

9. The composite magnet according to claim 8, characterized in that: The squareness difference between the first magnet and the second magnet is less than 4; And / or, the first magnet and the second magnet are each independently selected from one of sintered neodymium iron boron and sintered samarium cobalt; And / or, the shape of the composite magnet is selected from one of a square shape and a tile shape.

10. A motor, characterized in that: Comprising the composite magnet as described in any one of claims 8 to 9.

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