Composite magnet, method for manufacturing the same, and electric machine

Abstract

The application relates to a composite magnet, a preparation method thereof and a motor. The preparation method of the composite magnet comprises the following steps: according to a critical magnetic flux value B of an Hcb curve of a maximum working temperature of a first magnet and a demagnetization magnetic flux distribution of the first magnet, the first magnet is divided into a first magnetic part and a second magnetic part, the first magnet is located in the first magnetic part, and the demagnetization magnetic flux value of the second magnetic part is greater than or equal to the value B; a second magnet is used to replace the first magnetic part, and the second magnet is connected with the second magnetic part to prepare a composite magnet; wherein the critical magnetic flux value of the Hcb curve of the maximum working temperature of the second magnet is less than the minimum value of the demagnetization magnetic flux of the first magnetic part. Thus, the composite magnet with high demagnetization resistance is obtained, the machining path is optimized, the machining amount is greatly reduced, and the problem of magnet demagnetization in the permanent magnet motor is avoided.

Description

TECHNICAL FIELD

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

[0002] Since the neodymium-iron-boron permanent magnet material, as the third generation of rare earth permanent magnet material, was first commercialized by Sumitomo Metal of Japan and GM Corporation of the United States in 1983, it has been widely used in the fields of power electronics, communication, information, transportation office automation, medical devices and military due to its characteristics of high remanence, high coercivity and high magnetic energy product.

[0003] According to different application fields of the neodymium-iron-boron permanent magnet, its performance and composition also have obvious differences. Generally, the magnet made of rare earth Pr and Nd only has low coercivity and poor anti-demagnetization and high-temperature resistance, and can only be used in the environment with low temperature and low reverse magnetic field. In order to improve the coercivity of the magnet and the anti-demagnetization, so that the permanent magnet motor does not lose magnetism, heavy rare earth elements such as Dy and Tb are generally added, and the high-temperature resistance and anti-demagnetization of the magnet are improved with the increase of the content of Dy and Tb. Since Dy and Tb are rare and expensive resources, the cost of the magnet is also multiplied.

[0004] The analysis of the demagnetization of the permanent magnet motor shows that the demagnetization of the permanent magnet in the motor is uneven. For the magnet adhered to the rotor, the demagnetization always occurs on the side of the magnet close to the air gap, while the part of the magnet close to the middle is basically not demagnetized. The reason for this phenomenon is that when the motor is short-circuited, the stator coil generates high temperature and a very strong reverse magnetic field due to the existence of large current, and the part of the magnet close to the air gap is closest to the stator, so it is most affected by the high temperature and the reverse magnetic field. The existence of high temperature will reduce the magnetic performance of the magnet, especially the Hcb curve (intrinsic demagnetization curve) will be curved with the increase of temperature, and the B (magnetic density) value of the inflection point will increase with the increase of temperature. At the same time, due to the existence of the reverse magnetic field, the working point of the motor decreases along the Hcb line, and when the working point is below the inflection point, the motor is irreversibly demagnetized. However, in order to improve the anti-demagnetization of the magnet and avoid demagnetization of the magnet when the motor is short-circuited, a magnet with higher coercivity is needed, which will lead to a sharp increase in the cost of the motor.

[0005] Therefore, the conventional technology still needs to be further improved. SUMMARY

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

[0007] The technical solution of the present 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 B value of the Hcb curve at the maximum working temperature of the working condition of the first magnet and the demagnetization flux distribution of the first magnet, the first magnet is divided into a first magnetic part and a second magnetic part, the area of the first magnet with a demagnetization flux value less than B is located entirely in the first magnetic part, and the demagnetization flux value in the second magnetic part is greater than or equal to B.

[0010] A second magnet is used to replace the first magnetic part, and the second magnet is connected with the second magnetic part to prepare a composite magnet, wherein the critical magnetic flux value of the Hcb curve at the maximum working temperature of the second magnet is less than the minimum demagnetization flux value of the first magnetic part.

[0011] The method for preparing the composite magnet divides the first magnet into a first magnetic part and a second magnetic part according to the critical magnetic flux B value of the Hcb curve at the maximum working temperature of the working condition of the first magnet and the demagnetization flux distribution of the first magnet, the area of the first magnet with a demagnetization flux value less than B is located entirely in the first magnetic part, and the demagnetization flux value in the second magnetic part is greater than or equal to B. A second magnet is used to replace the first magnetic part, and the second magnet is connected with the second magnetic part to prepare a composite magnet, wherein the critical magnetic flux value of the Hcb curve at the maximum working temperature of the second magnet is less than the minimum demagnetization flux value of the first magnetic part. The magnet with a lower critical magnetic flux value is distributed in the part with a lower magnetic flux value when the permanent magnet motor is short-circuited, that is, the position prone to demagnetization is designed to have a high performance and strong anti-demagnetization capability, and the position not prone to demagnetization is designed to have a low performance and a more advantageous cost, thereby obtaining a composite magnet with high anti-demagnetization capability, optimizing the processing path, greatly reducing the processing amount, and avoiding the problem of demagnetization of the magnet in the permanent magnet motor.

[0012] In some embodiments, the first magnet comprises two first magnetic parts and one second magnetic part, the two first magnetic parts are located on opposite sides of the second magnetic part respectively, 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, the two surfaces of the two first magnetic parts and the second magnetic part perpendicular to the thickness direction are flush with each other respectively.

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

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

[0016] In some embodiments, the first magnetic portion and the second magnetic portion are connected by adhesion.

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

[0018] The second aspect of the present application further provides a composite magnet prepared by the above-mentioned method for preparing a composite magnet, or the composite magnet comprises a first magnet and a second magnet, the first magnet comprises a first magnetic portion and a second magnetic portion, the region in the first magnet with a demagnetization magnetic flux density value less than B value is located entirely within the first magnetic portion, and the demagnetization magnetic flux density value in the second magnetic portion is greater than or equal to B value; the first magnetic portion is replaced by the second magnet, and the critical magnetic flux density value of the Hcb curve of the second magnet at the maximum working temperature is less than the minimum demagnetization magnetic flux density value of the first magnetic portion.

[0019] In some embodiments, the squareness difference between the first magnet and the second magnet is 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] The third aspect of the present application further provides an electric machine comprising the above-mentioned composite magnet. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 FIG. 6 is a magnetic flux density distribution diagram of the side of the first magnet away from the air gap when simulating short circuit of a permanent magnet motor at 120°C in an embodiment;

[0024] Figure 2 FIG. 7 is a magnetic flux density distribution diagram of the side of the first magnet close to the air gap when simulating short circuit of a permanent magnet motor at 120°C in an embodiment;

[0025] Figure 3 FIG. 8 is an example diagram of the first magnetic portion and the second magnetic portion in the first magnet in embodiment 1;

[0026] Figure 4 FIG. 9 is an example diagram of the first magnetic portion and the second magnetic portion in the first magnet in embodiment 2;

[0027] Figure 5FIG. 1 is a diagram showing an example of the first magnetic portion and the second magnetic portion in the first magnet in Example 3.

[0028] BRIEF DESCRIPTION OF DRAWINGS

[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 with specific reference to the embodiments. The present application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and fully convey the scope of the present application to those skilled in the art.

[0031] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in the description of the application herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items.

[0032] As used herein, the terms "and / or", "or / and", "and / or" in the alternative include any one of two or more of the associated listed items, and also include any and all combinations of the associated listed items. It should be noted that when at least two conjunctions selected from "and / or", "or / and", "and / or" are combined to connect at least three items, it should be understood that in the present application, the technical solution undoubtedly includes the technical solution connected by "logical and", and also undoubtedly includes the technical solution connected by "logical or". For example, "A and / or B" includes three parallel solutions of A, B and A+B. For another example, the technical solution of "A, and / or, B, and / or, C, and / or, D" includes any one of A, B, C and D (i.e. the technical solution connected by "logical or"), and also includes any and all combinations of A, B, C and D, i.e. includes the combination of any two or any three of A, B, C and D, and also includes the four-item combination of A, B, C and D (i.e. the technical solution connected by "logical and").

[0033] In the present application, "multiple", "various", "multiple times", "multiple", etc. are used without specific limitation, which means more than two or equal to two in quantity. For example, "one or more" means one or more than two.

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

[0035] As used herein, "suitable", "suitable", "any suitable manner", and the like are subject to the ability to implement the technical solutions of the present application, solve the technical problems of the present application, and achieve the intended technical effects of the present application.

[0036] As used herein, "preferably", "better", "better", "preferably" only describe the better effect of the implementation or embodiment, and it should be understood that it does not constitute a limitation on the protection scope of the present application.

[0037] In the present application, "further", "further", "in particular" and the like are used to describe the purpose, indicating the difference in content, but should not be understood as a limitation on the protection scope of the present application.

[0038] In the present application, "optionally", "optional", "optional" means optional, that is, selected from "yes" or "no" two parallel schemes. If there are multiple "optional" in a technical solution, unless otherwise specified, and there is no contradictory or mutual restrictive relationship, each "optional" is independent.

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

[0040] In the present application, the temperature parameters, unless otherwise specified, allow constant temperature treatment and allow fluctuations within a certain temperature range. It should be understood that the constant temperature treatment allows fluctuations within the accuracy range controlled by the instrument. It is allowed to fluctuate within the range of, for example, ± 5℃, ± 4℃, ± 3℃, ± 2℃, ± 1℃.

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

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

[0043] Permanent magnet synchronous motor generally consists of: stator, rotor, shaft and end cover and other components. Among them, the stator includes a stator core and a stator winding, the stator winding is wrapped around the stator core, and a rotating magnetic field is generated after being powered on. By controlling the frequency of the input current of the stator winding, the magnetic field rotation frequency can be controlled, and in turn the speed can be controlled; the rotor has a permanent magnet on it, usually made of rare earth materials such as neodymium iron boron, used to generate a constant magnetic field; the shaft is used to support and connect the rotor, and to transmit mechanical energy from the motor to the external load.

[0044] As shown in the background, in the conventional technology, in order to improve the demagnetization resistance of the magnet, a magnet with high coercive force needs to be used, which will cause the cost of the motor to increase sharply. In order to improve this problem, some methods currently propose a gradient coercivity magnet, which at least includes two layers of neodymium iron boron magnet layers with different coercivity, one of which has high coercivity. This method can ensure that the magnet has a certain demagnetization resistance 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, the preparation method of the magnet has a big problem. The magnet is made by loading different performance powders into a cavity with a partition during molding, then removing the partition and pressing into a whole, and then sintering. During the pressing field orientation, the powder will rotate and move towards the two pole head directions. In this process, the two kinds of powders will inevitably mix with each other, affecting each other's performance. After orientation, the upper and lower pressing heads will be squeezed towards the middle, and the mutual mixing of the powders will also inevitably occur in this process. Because during pressing, the powder will flow in all directions, not just along the pressing direction. Different performance powders have different sintering aging processes. In this method, the green body composed of two or more powders with different properties needs to be treated under the same sintering aging process, which is obviously inappropriate. It is difficult to ensure that different parts of the same magnet will achieve the magnetic properties it should achieve, and it is difficult to prepare a magnet composed of two or more thin magnet layers with different coercivity.

[0045] Based on this, an embodiment of the present application provides a preparation method of a composite magnet, comprising steps S100-S200.

[0046] Step S100: According to the critical magnetic flux density value B of the Hcb curve at the maximum working temperature of the first magnet under the working condition and the demagnetization flux distribution of the first magnet, the first magnet is divided into a first magnetic part and a second magnetic part. The area of the first magnet with a demagnetization flux value less than B is located entirely within the first magnetic part, and the demagnetization flux value in the second magnetic part is greater than or equal to B.

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

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

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

[0050] In some embodiments, the first magnetic part includes two first magnetic parts and a second magnetic part, the two first magnetic parts are 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 demagnetization zones are located in the two first magnetic parts, respectively.

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

[0052] In some embodiments, the first magnetic part and the second magnetic part are perpendicular to the thickness direction.

[0053] In a specific example, the thickness of the first magnetic part and the second magnetic part is the same.

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

[0055] In a specific example, the thickness of the first magnetic part and the second magnetic part is the same, and only one surface is flush.

[0056] In some embodiments, the first magnetic part 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 of the second magnetic part.

[0057] In some embodiments, the first magnetic part and the second magnetic part are connected by 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 the micro cross or gradual change area at the bonding position of the magnets with different magnetic properties, the processing path is optimized, the processing amount is greatly reduced, and the production efficiency is improved.

[0060] Specifically, the step S200 replaces the first magnetic part with the second magnet and connects the second magnet with the second magnetic part to prepare the composite magnet, which includes steps S210-S220.

[0061] The step S210 replaces the first magnetic part of the first magnet with the second magnet, and processes the first magnet and the second magnet respectively to prepare the first magnet rough and the second magnet rough.

[0062] The step S220 bonds the first magnet rough and the second magnet rough with the adhesive, and corresponds to the first magnet and the second magnet after curing to prepare the composite magnet.

[0063] In some embodiments, after the curing step and before the step of preparing the composite magnet, the cured composite magnet is processed and then electroplated to prepare the composite magnet.

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

[0065] In some embodiments, the size and shape of the different magnetic parts are not limited, and the processing equipment can process the size and shape.

[0066] The preparation method of the composite magnet divides the first magnet into a first magnetic part and a second magnetic part according to the critical magnetic density B value of the Hcb curve at the maximum working temperature of the first magnet and the demagnetization magnetic density distribution of the first magnet, the area of the first magnet with a demagnetization magnetic density value less than B is located in the first magnetic part, and the demagnetization magnetic density value in the second magnetic part is greater than or equal to B; the first magnetic part is replaced by the second magnet, and the second magnet is connected with the second magnetic part to prepare the composite magnet; wherein the critical magnetic density value of the Hcb curve of the second magnet at the maximum working temperature is less than the minimum value of the demagnetization magnetic density of the first magnetic part, the magnet with a lower critical magnetic density value is distributed in the position with a lower magnetic density value when the permanent magnet motor is short-circuited, that is, the position prone to demagnetization is designed to have high performance and strong anti-demagnetization capability, and the position not prone to demagnetization is designed to have low performance and cost advantage, thereby obtaining a composite magnet with high anti-demagnetization capability, optimizing the processing path, greatly reducing the processing amount, and avoiding the demagnetization problem of the magnet in the permanent magnet motor.

[0067] An embodiment of the present application provides a composite magnet prepared by the above method, or the composite magnet comprises a first magnet and a second magnet, the first magnet comprises a first magnetic part and a second magnetic part, the region with a demagnetization magnetic flux density value less than B in the first magnet is located in the first magnetic part, and the demagnetization magnetic flux density value in the second magnetic part is greater than or equal to B; the first magnetic part is replaced by the second magnet, and the critical magnetic flux density value of the Hcb curve of the second magnet at the maximum working temperature is less than the minimum demagnetization magnetic flux density value of the first magnetic part.

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

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

[0070] In some embodiments, the remanences of the first magnetic part and the second magnetic part can be the same, similar or different.

[0071] In some embodiments, the first magnetic part and the second magnetic part are each independently selected from one of sintered neodymium-iron-boron and sintered samarium-cobalt.

[0072] In a specific example, the first magnetic part and the second magnetic part are both sintered neodymium-iron-boron magnets.

[0073] Further, the sintered neodymium-iron-boron magnet can be a magnet produced by a conventional method or a magnet treated by grain boundary diffusion. It can be understood that the composite magnet can be used in a motor, and the maximum working temperature of the motor is the maximum working temperature of the motor.

[0074] In some embodiments, when the maximum working temperature of the motor is 80℃, the first magnet is an N-grade coercivity magnet, and 12kOe≤N-grade coercivity magnet≤14kOe.

[0075] In some embodiments, when the maximum working temperature of the motor is 100℃, the first magnet is an M-grade coercivity magnet, and 14kOe

[0076] In some embodiments, when the maximum working temperature of the motor is 120℃, the first magnet is an H-grade coercivity magnet, and 17kOe

[0077] In some embodiments, when the maximum working temperature of the motor is 150℃, the first magnet is an SH-grade coercivity magnet, and 20kOe

[0078] In some embodiments, when the maximum operating temperature of the motor is 180℃, the first magnet is a UH-grade coercivity magnet, wherein 25kOe

[0079] In some embodiments, when the maximum operating temperature of the motor is 200℃, the first magnet is an EH-grade coercivity magnet, wherein 30kOe

[0080] In some embodiments, when the maximum operating temperature of the motor is 230℃, the first magnet is a TH-grade coercivity magnet, wherein 35kOe

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

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

[0083] The composite magnet of the present application has the magnet with lower critical magnetic density value distributed in the part with lower magnetic density value when the permanent magnet motor is short-circuited, has high demagnetization resistance, and avoids the problem of magnet demagnetization in the permanent magnet motor.

[0084] Another embodiment of the present application further provides a motor comprising the composite magnet prepared by the preparation method of the composite magnet and / or the composite magnet.

[0085] In the motor of the present application, the composite magnet is distributed in two regions with different magnetic properties, has high magnetic properties or special magnetic properties, avoids the problem of magnet demagnetization in the permanent magnet motor, and maximizes the reduction of the cost of rare earth permanent magnet materials while having a simple preparation method.

[0086] The present application will be described in detail below with reference to specific embodiments, but the present application is not limited to the following embodiments, and it should be understood that the appended claims generalize the scope of the present application, and those skilled in the art should realize that certain changes to the embodiments of the present application will be covered by the spirit and scope of the claims of the present application.

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

[0088] Embodiment 1

[0089] First, according to the performance of the first magnet, the distribution of the magnetic 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 2the magnetic flux density distribution of the first magnet at 120℃ when the permanent magnet motor is short-circuited, Figure 1 the magnetic flux density distribution of the first magnet at 120℃ when the permanent magnet motor is short-circuited, Figure 2 the magnetic flux density distribution of the first magnet at 120℃ when the permanent magnet motor is short-circuited,

[0090] In combination with Figure 1 and Figure 2 It can be seen that the area of the first magnet in which the magnetic flux density value is less than the B value is located on the surface of the magnet away from the air gap, and on the opposite sides of the surface.

[0091] Therefore, according to the simulation results, referring to Figure 3 , the first magnetic part 11 and the second magnetic part 12 are divided, and the magnet part of the first magnetic part 11 is replaced with the second magnet. The minimum magnetic flux density in the first magnetic part is 0.05T. Accordingly, the performance of the second magnet is Br=13.4±0.1kGs, and the inflection point B value of the Hcb curve at 120℃ is less than 0.05T.

[0092] According to the above Figure 3 example, the preparation of the composite magnet is as follows: the mother material magnet for preparing the 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 mother material magnet for preparing 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, then solidified, and then the solidified composite magnet assembly rough blank is processed into the shape and size (47*82*22mm) of the first magnet, and then electroplated according to needs, at this time, the final composite magnet is formed, the simulation short-circuit magnetic flux density distribution of the composite magnet is consistent with Figure 2 , the structure is similar to Figure 3 , and the only difference is that the second magnet replaces the first magnetic part in Figure 3 .

[0093] Implementation column 2

[0094] First, according to the performance of the first magnet, the distribution of the 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 the magnetic flux density distribution of the first magnet at 120℃ when the permanent magnet motor is short-circuited, wherein,Figure 1 the magnetic flux density distribution of the first magnet on the side of the magnet far from the air gap when the permanent magnet motor is short-circuited at 120°C, Figure 2 the magnetic flux density distribution of the first magnet on the side of the magnet close to the air gap when the permanent magnet motor is short-circuited at 120°C, are the magnetic flux density distributions of the two magnets 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 the Hcb curve of the magnet at 120°C is 0.32T.

[0095] In combination with Figure 1 and Figure 2 it can be seen that the region of the first magnet in which the magnetic flux density value is less than the B value is entirely located on the surface of the magnet far from the air gap, and is located on the opposite sides of the surface.

[0096] Therefore, according to the simulation results, referring to Figure 4 , the first magnetic part 11 and the second magnetic part 12 are divided, so that the magnet part of the first magnetic part 11 is replaced with the second magnet. The minimum magnetic flux density in the first magnetic part is 0.05T. Accordingly, the performance of the second magnet used is Br=13.4±0.1kGs, and the inflection point B value of the Hcb curve of the magnet at 120°C is less than 0.05T.

[0097] According to the above Figure 4 example, the preparation of the composite magnet is as follows: the mother magnet used to prepare the 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 flush with each other respectively; the mother 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 solidified, and then the solidified composite magnet assembly rough blank is processed into the shape and size (47*82*22mm) of the first magnet, and then electroplated as needed, at which time the final composite magnet is formed, and the structure is similar to Figure 4 , the only difference being that the second magnet replaces the first magnetic part in Figure 4 .

[0098] Implementation column 3

[0099] First, according to the performance of the first magnet, the distribution of the 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 are the magnetic flux density distributions of the magnet of a certain permanent magnet motor simulated when the motor is short-circuited at the maximum working temperature of 120°C, wherein, Figure 1 the magnetic flux density distribution of the first magnet on the side of the magnet far from the air gap when the permanent magnet motor is short-circuited at 120°C,Figure 2 The magnetic flux density distribution of the first magnet near the air gap side of the permanent magnet motor during short circuit is simulated at 120 DEG C, and 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 the 120 DEG C Hcb curve is 0.32T.

[0100] In combination Figure 1 And Figure 2 It can be seen that the magnetic flux density value of the first magnet in the demagnetization region is less than the B value, and the relative two sides of the surface of the magnet far away from the air gap.

[0101] Therefore, according to the simulation results, referring to Figure 5 , the first magnetic part 11 and the second magnetic part 12 are divided, so that the magnet part of the first magnetic part 11 is replaced by the second magnet. The minimum magnetic flux density in the first magnetic part is 0.05T. Accordingly, the performance of the second magnet is Br=13.4±0.1kGs, and the inflection point B value of the 120 DEG C Hcb curve is less than 0.05T.

[0102] According to the above Figure 5 The preparation of the composite magnet is carried out according to the example, and the specific steps are as follows: the mother material magnet for preparing the first magnet is processed into a first magnet rough blank with 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 mother material magnet for preparing the second magnet is processed into a second magnet rough blank with 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 solidified, and then the solidified composite magnet assembly rough blank is processed into the shape and size (47*82*22mm) of the first magnet, and then electroplated according to the needs, at this time, the final composite magnet is formed, and the structure is similar to Figure 5 The difference is that the second magnet replaces the first magnetic part in Figure 5 .

[0103] Therefore, the technical solution of the application can easily design the demagnetization position to be made of a material with high performance and strong anti-demagnetization ability, and the position not easy to demagnetize is made of a material with low performance and more advantageous cost, so as to obtain a composite magnet with high anti-demagnetization ability and avoid the problem of magnet demagnetization in the permanent magnet motor.

[0104] The technical features of the above-described embodiments can be combined in any way. In order to make the description simple, all possible combinations of the technical features in the above-described embodiments are not described, but as long as the combinations of the technical features do not exist, they should be considered as the scope of the description.

[0105] The above embodiments only express several implementation ways of the present application, and the description is relatively specific and detailed, but it should not be understood as a limitation to the patent scope of the application. It should be pointed out that for ordinary skilled persons in the art, several modifications and improvements can be made without departing from the concept of the present application, which all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application should be subject to the appended claims.

Claims

1. A method for preparing a composite magnet, characterized in that: The steps include: The first magnet is divided into a first magnetic portion and a second magnetic portion based on the critical magnetic flux density B value of the Hcb curve under the maximum operating temperature of the first magnet's operating condition and the demagnetization magnetic flux density distribution of the first magnet, wherein all regions of the first magnet having demagnetization magnetic flux density values ​​less than the B value are located within the first magnetic portion, and the demagnetization magnetic flux density value within the second magnetic portion is greater than or equal to the B value; A second magnet is used to replace the first magnetic part and the second magnet is connected to the second magnetic part to prepare a composite magnet; 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, wherein: 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. 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, wherein: Two surfaces of the first magnetic portion and the second magnetic portion perpendicular to the thickness direction are flush with each other.

4. The method for preparing a composite magnet according to claim 2, wherein: 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.

5. The method for preparing a composite magnet according to claim 1, wherein: 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.

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, wherein: 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 using 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 portion and a second magnetic portion, the areas in the first magnet where the demagnetization flux density is less than the B value are all located in the first magnetic portion, and the demagnetization flux density in the second magnetic portion is ≥ the B value; the first magnetic portion is replaced by the second magnet, and the critical flux density value of the Hcb curve of the second magnet at the maximum operating temperature is less than the lowest demagnetization flux density value of the first magnetic portion.

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 and a tile shape.

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

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