CN113903542B

CN113903542B - Magnetizing method and device for linear Halbach array

Info

Publication number: CN113903542B
Application number: CN202111027887.XA
Authority: CN
Inventors: 吕以亮; 吕雷熠; 李亮
Original assignee: Huazhong University of Science and Technology
Current assignee: Huazhong University of Science and Technology
Priority date: 2021-09-02
Filing date: 2021-09-02
Publication date: 2022-05-20
Anticipated expiration: 2041-09-02
Also published as: CN113903542A

Abstract

The invention provides a linear Halbach array magnetizing method and device, and the method comprises the following steps: arranging a plurality of permanent magnets with different to-be-magnetized directions into a linear array according to a preset rule; the main coil is arranged right above or right below the linear array and translates along the linear direction of the linear array so as to magnetize a plurality of permanent magnets step by step, each step of magnetization fully magnetizes one main magnet and magnetizes partial areas of the auxiliary magnets adjacent to the main magnet; when the main coil can cause demagnetization influence on the magnetized permanent magnet, the auxiliary coil is added in the area near the magnetized permanent magnet to change the magnetic field distribution in the area near the magnetized permanent magnet so as to reduce the demagnetization influence; and after all the permanent magnets are magnetized, obtaining the linear Halbach array. The invention can overcome the problem of difficult pre-magnetizing assembly of the Halbach permanent magnet motor, and can also avoid the problem that the magnetizing field can demagnetize the magnetized area when the Halbach array is subjected to conventional integral magnetizing.

Description

Magnetizing method and device for linear Halbach array

Technical Field

The invention belongs to the field of Halbach arrays, and particularly relates to a magnetizing method and device of a linear Halbach array.

Background

For the traditional permanent magnet motor structure, the magnetic field intensity on the other side is greatly improved due to the mutual superposition of the tangential magnetic field and the radial magnetic field after the Halbach array is decomposed, so that the volume of the motor can be effectively reduced, and the power density of the motor is improved; in the traditional permanent magnet motor, because the air gap magnetic field inevitably has harmonic waves, the influence of the harmonic waves is weakened by adopting a chute on a stator and rotor framework, but in the Halbach motor, because the air gap magnetic field has higher sine distribution degree and low harmonic content, the stator and the rotor can be free of the chute; due to the unilateral property of the Halbach array, the rotor can provide a passage for the Halbach array without using a ferromagnetic material, so that a large space is provided for the selection of the motor rotor material; because the Halbach array permanent magnet is magnetized in different directions, the working point of the permanent magnet is higher, and the utilization rate of the permanent magnet is improved; and the motor winding can adopt a centralized winding because the magnetic field sine distribution degree is higher and the harmonic content is low. Due to the excellent characteristics of the Halbach array, the Halbach array is widely applied to a plurality of fields of linear motors, high-speed motors, high-precision servo motors, maglev train systems, magnetic bearings, medicine and the like.

For the Halbach permanent magnet motor, in order to ensure the excellent characteristics of the Halbach permanent magnet motor, the smaller the gap between the permanent magnets is, the better the gap is, and the force bearing direction of each permanent magnet is changed regularly due to the diversity of the magnetization directions of the magnets in the Halbach array. Meanwhile, with the increase of the power and the volume of the motor, the volume of the permanent magnet in the permanent magnet motor is continuously increased, although the Halbach array has higher permanent magnet utilization rate, the size of the permanent magnet in the Halbach permanent magnet motor is slightly smaller than that of the traditional permanent magnet motor when the motor has the same power and the same volume, the permanent magnet is more difficult to assemble and reinforce due to small gap and changeability of the force direction; meanwhile, the magnetization directions of the permanent magnets in the Halbach array are not only along the same axial direction, so that the conventional magnetization mode after assembly is difficult to satisfy the magnetization of all the permanent magnets.

The conventional Halbach linear motor is basically assembled in a pre-magnetizing and reassembling mode, and because the Halbach linear array air gap flux density harmonic content is very sensitive to the distance between permanent magnets, the assembling precision requirement is very high, and the stress direction of each permanent magnet in the array is changeable, the assembly after magnetizing is very difficult, the assembling efficiency is low, and the overall performance can be influenced; the existing magnetization mode after assembly is multi-purpose for a surface-mounted permanent magnet motor, the arrangement mode of magnetic poles of permanent magnets is mostly N poles and S poles which are alternately arranged, a magnetic field at the edge of the axis of a coil is only utilized during integral magnetization, the magnetic field at the lower side of the coil is not utilized, and when the permanent magnets are thick or the gaps between the magnetic poles are small, measures are needed to weaken the magnetic field.

Disclosure of Invention

Aiming at the defects of the prior art, the invention aims to provide a linear Halbach array magnetizing method and device, and aims to solve the problems that the conventional Halbach permanent magnet motor is difficult to assemble after pre-magnetizing, and especially the assembly after pre-magnetizing can influence the overall performance.

In order to achieve the above object, in a first aspect, the present invention provides a method for magnetizing a linear Halbach array, comprising the steps of:

arranging a plurality of permanent magnets with different to-be-magnetized directions into a linear array according to a preset rule; the preset rule is as follows: the to-be-magnetized directions of the adjacent permanent magnets rotate at intervals of a preset angle in a preset hour direction; the different directions to be magnetized comprise vertical directions, the permanent magnets are divided into main magnets and auxiliary magnets, the directions to be magnetized of the main magnets are along the vertical direction, and the directions to be magnetized of the auxiliary magnets are non-vertical directions;

the main magnet is arranged right above or right below the linear array and translates along the linear direction of the linear array so as to magnetize a plurality of permanent magnets step by step, each step of magnetization fully magnetizes one main magnet and magnetizes partial areas of the auxiliary magnets adjacent to the main magnet;

when the main coil can cause demagnetization influence on the magnetized permanent magnet in the current magnetizing step, adding an auxiliary coil in the area near the magnetized permanent magnet to change the magnetic field distribution in the area near the magnetized permanent magnet so as to reduce the demagnetization influence and ensure that the magnetization saturation degree of the preset area of the magnetized permanent magnet is kept above a preset proportion;

and after all the permanent magnets are magnetized, obtaining the linear Halbach array.

The preset hour hand direction can be a clockwise direction or a counterclockwise direction.

Wherein, the preset angle interval may be 30 °, 45 °, 60 °, 90 °, 120 °, and the like.

It can be understood that the included angle of the angle interval preset in engineering application needs to be divided by 360 degrees, and the included angle needs to be smaller than 180 degrees, namely, the number of the auxiliary magnets is ensured to be an integer. In general, the included angle is less than or equal to 90 degrees, and the most common included angle is 90 degrees. The number of the auxiliary magnets between the two main magnets is not necessarily only one, and the width of the auxiliary magnets is not necessarily the same as the width of the main magnets, for example, in the case of 30 °, there are 5 auxiliary magnets between the two main magnets, and the total width of the 5 auxiliary magnets is not necessarily the same as the width of the main magnets, and is generally larger than the width of the main magnets.

Theoretically, for the main magnet and the auxiliary magnet which are magnetized, if the main magnet and the auxiliary magnet are not affected by demagnetization, the magnetization saturation degree of a preset area needs to be kept above a preset proportion; in theory, all permanent magnets should ensure 99% saturation of the region to 99%, which is understood as being unaffected by demagnetization. In practice, the preset region is preferably 99% for the main magnet, and the auxiliary magnet may be slightly lower. In addition, in practical application, the magnetization saturation degree can be widened to 80% -99% according to actual needs, and if the magnetization saturation degree is lower than a preset value in the middle of 80% -99%, the magnetized permanent magnet is considered to be demagnetized.

In an optional example, the method further comprises the steps of:

determining a magnetizing standard and a demagnetizing standard of a permanent magnet to be magnetized, and specifically comprising the following steps of:

determining the flux density value of a minimum external magnetizing field required by the permanent magnet when the permanent magnet is subjected to orientation magnetizing and reaches saturation magnetizing; when the included angle between the direction of the external magnetic field and the to-be-magnetized direction of the permanent magnet is smaller than a preset included angle, the direction of the external magnetic field is considered to be the same as the to-be-magnetized direction, and the external magnetic field is oriented and magnetized;

when an included angle exists between the external magnetic field and the to-be-magnetized direction of the permanent magnet, determining the magnetic flux density value of the minimum external magnetizing magnetic field required by the permanent magnet to reach saturation magnetizing under different included angles;

when the saturated and magnetized permanent magnets are respectively arranged in external demagnetization fields with different included angles with the magnetization direction of the permanent magnets, determining the magnetic flux density value of the minimum external demagnetization field of the permanent magnets reaching the demagnetization standard under different included angles; the demagnetization standard is as follows: and if the magnetization saturation degree of the non-preset area in the permanent magnet is kept above the preset proportion, the saturated and magnetized permanent magnet is considered to be demagnetized.

In an alternative example, the main magnet is translated along the linear direction of the linear array to charge the plurality of permanent magnets in steps, each step of charging fully magnetizing a main magnet and magnetizing a partial region of the auxiliary magnet adjacent to the main magnet, specifically comprising:

when magnetizing in each step, the main coil is arranged right above a main magnet, the direction of a central magnetic field of a magnetic field generated by the main coil is controlled to be the same as the direction to be magnetized of the main magnet right below the main coil, and the central magnetic field of the magnetic field generated by the main coil is enabled to carry out orientation magnetizing on the main magnet right below the main coil by controlling the distance between the main coil and the main magnet and the parameters of the main coil;

determining the magnetic field distribution generated by the main coil when the main coil is arranged right above or right below the main magnet through simulation, wherein the magnetic field distribution comprises the following steps: the size and the direction of the magnetic flux density in the main magnet area, the size of the magnetic flux density in the auxiliary magnet area and the included angle between the magnetic field and the to-be-magnetized direction of the auxiliary magnet;

according to the included angle between the magnetizing magnetic field generated by the main magnet and the direction to be magnetized of the auxiliary magnet, the magnetic flux density value of the minimum external magnetizing magnetic field required by the permanent magnet to reach saturation magnetization under the external magnetic field orientation magnetization and the different included angles magnetization in the predetermined permanent magnet magnetizing standard, the magnetic flux density value of the magnetic field generated by the main magnet, which is required by magnetizing the partial region of the auxiliary magnet adjacent to the main magnet, is determined, and the main magnet is completely magnetized in each step of magnetization.

In an optional example, when the magnetic field of the main coil in the current magnetizing step may cause a demagnetization effect on the magnetized permanent magnet, specifically:

determining an included angle between a magnetic field generated by the main magnet and the magnetization direction of the magnetized permanent magnet when the main magnet coil is arranged right above or right below the main magnet to be magnetized in the current step through simulation;

determining the magnetic flux density of the magnetic field generated by the main coil in the current step in the magnetized permanent magnet area;

and determining whether the magnetic field generated by the main coil can cause demagnetization influence on the magnetized permanent magnet in the current magnetizing step or not based on the included angle between the magnetic field generated by the main coil and the magnetizing direction of the magnetized permanent magnet and the flux density value of the minimum external demagnetization magnetic field of the permanent magnet reaching the demagnetization standard under different included angles in the predetermined demagnetization standard of the permanent magnet.

In an optional example, an auxiliary coil is added to the area near the magnetized permanent magnet, and a magnetic field generated by the auxiliary coil changes the magnetic field distribution in the area near the magnetized permanent magnet to reduce the demagnetization influence, specifically:

and adding an auxiliary coil in the area near the magnetized permanent magnet, determining the overall magnetic field distribution generated by the auxiliary coil and the main coil in a simulation manner, and designing a proper auxiliary coil and a proper main coil by combining the magnetizing standard and the demagnetizing standard of the permanent magnet so that the magnetizing saturation degree of the preset area of the magnetized permanent magnet is kept above a preset proportion during magnetizing.

In a second aspect, the present invention provides a linear Halbach array magnetizing apparatus, comprising: a main coil and an auxiliary coil;

the main coil is arranged right above or right below the linear array and translates along the linear direction of the linear array so as to magnetize the plurality of permanent magnets step by step, and each step of magnetization fully magnetizes one main magnet and magnetizes partial areas of the auxiliary magnets adjacent to the main magnet; the linear array is formed by arranging a plurality of permanent magnets in different directions to be magnetized according to a preset rule; the preset rule is as follows: the to-be-magnetized directions of the adjacent permanent magnets rotate at intervals of a preset angle in a preset hour direction; the different directions to be magnetized comprise vertical directions, the permanent magnets are divided into main magnets and auxiliary magnets, the directions to be magnetized of the main magnets are along the vertical direction, and the directions to be magnetized of the auxiliary magnets are non-vertical directions;

the auxiliary coil is used for placing the auxiliary coil in the area near the magnetized permanent magnet when the main coil can cause demagnetization influence on the magnetized permanent magnet in the current magnetizing step, changing the magnetic field distribution in the area near the magnetized permanent magnet to reduce the demagnetization influence and ensure that the magnetization saturation degree of the preset area of the magnetized permanent magnet is kept above a preset proportion; and after all the permanent magnets are magnetized, obtaining the linear Halbach array.

In an optional example, the apparatus further comprises: the coil auxiliary positioning structure, the coil reinforcing structure and the array positioning structure;

the coil auxiliary positioning structure is used for carrying out auxiliary positioning on the main coil and the auxiliary coil according to the positions of the main coil and the auxiliary coil required by the current magnetizing step;

the coil reinforcing structure is used for reinforcing the main coil and the auxiliary coil;

the array positioning structure is used for sequentially positioning the linear array formed by the permanent magnets from head to tail.

In an optional example, during each step of magnetizing, the main coil is placed right above one main magnet, the direction of a central magnetic field of a magnetic field generated by the main coil is controlled to be the same as the direction to be magnetized of the main magnet right below the main coil, and the central magnetic field of the magnetic field generated by the main coil is enabled to carry out orientation magnetizing on the main magnet right below the main coil by controlling the distance between the main coil and the main magnet and the parameters of the main coil;

when the main coil is arranged right above or right below the main magnet, the magnetic field distribution generated by the main coil is determined through simulation, and the method comprises the following steps: the size and the direction of the magnetic flux density in the main magnet area, the size of the magnetic flux density in the auxiliary magnet area and the included angle between the magnetic field and the to-be-magnetized direction of the auxiliary magnet; according to the included angle between the magnetizing magnetic field generated by the main magnet and the direction to be magnetized of the auxiliary magnet, the magnetic flux density value of the minimum external magnetizing magnetic field required by the permanent magnet to reach saturation magnetization under the external magnetic field orientation magnetization and the different included angles magnetization in the predetermined permanent magnet magnetizing standard, the magnetic flux density value of the magnetic field generated by the main magnet, which is required by magnetizing the partial region of the auxiliary magnet adjacent to the main magnet, is determined, and the main magnet is completely magnetized in each step of magnetization.

In an optional example, when the magnetic field of the main coil may affect demagnetization of the magnetized permanent magnet in the current magnetizing step, an auxiliary coil is added to the area near the magnetized permanent magnet, overall magnetic field distribution generated by the auxiliary coil and the main coil is determined through simulation, and the auxiliary coil and the main coil are designed appropriately in combination with the magnetizing standard and the demagnetizing standard of the permanent magnet so that the magnetizing saturation degree of the preset area of the magnetized permanent magnet is kept above a preset proportion during magnetizing.

In an optional example, the magnetization standard and the demagnetization standard of the permanent magnet to be magnetized specifically include:

when an included angle exists between the external magnetic field and the to-be-magnetized direction of the permanent magnet, determining the magnetic flux density value of the minimum external magnetizing magnetic field required by the permanent magnet to reach saturation magnetization under different included angles;

Generally, compared with the prior art, the above technical solution conceived by the present invention has the following beneficial effects:

the invention provides a linear Halbach array magnetizing method and device, and aims to solve the problems that the conventional Halbach permanent magnet motor is difficult to pre-magnetize and assemble, and particularly the assembly after pre-magnetizing can influence the overall performance. The permanent magnets have no magnetic force under the nonmagnetic condition, and the temporary fixing device does not need to overcome the acting force between the magnetic blocks during assembly, so that the assembly is simpler and safer, and the production efficiency is improved; meanwhile, the positions of the permanent magnets can be completely installed and fixed according to theoretical design, so that the installation precision is higher.

Meanwhile, aiming at the problems that the conventional assembled magnetizing technology can cause demagnetization of a magnetized permanent magnet in the integral magnetizing process of the Halbach array and the permanent magnet is completely saturated due to the fact that partial permanent magnet is difficult to be magnetized once, the invention provides a scheme of step-by-step magnetizing.

Drawings

Fig. 1 is a schematic structural diagram of a Halbach linear array to be magnetized according to embodiment 1 of the present invention;

fig. 2 is a schematic view of a first step of magnetization provided in embodiment 1 of the present invention;

FIG. 3 is a schematic view of a second step of magnetization provided in embodiment 1 of the present invention;

fig. 4 is a schematic view of a third step of magnetization provided in embodiment 1 of the present invention;

fig. 5 is a schematic diagram of a coil assembly provided in embodiment 1 and magnetized in a third step;

fig. 6 is a schematic view of magnetization current and magnetic flux density at the center of a permanent magnet provided in embodiment 1 of the present invention;

fig. 7 is a schematic view of the magnetic flux density distribution of a number 2 permanent magnet provided in embodiment 1 of the present invention;

fig. 8 is a schematic view of the flux density distribution of a permanent magnet No. 3 according to embodiment 1 of the present invention;

fig. 9 is a schematic view of the magnetic flux density distribution of a number 4 permanent magnet provided in embodiment 1 of the present invention;

fig. 10 is a schematic view of the magnetic flux density distribution of a number 5 permanent magnet provided in embodiment 1 of the present invention;

fig. 11 is a schematic view of the magnetic flux density distribution of a number 6 permanent magnet provided in embodiment 1 of the present invention;

FIG. 12 is a graph showing the magnetic flux density contrast of the air gap provided in example 1 of the present invention;

fig. 13 is a schematic structural diagram of a Halbach linear array to be magnetized according to embodiment 2 of the present invention;

fig. 14 is a schematic view of the magnetic flux density distribution of permanent magnet No. 1 according to embodiment 2 of the present invention;

fig. 15 is a schematic view of the magnetic flux density distribution of permanent magnet No. 2 according to embodiment 2 of the present invention;

fig. 16 is a schematic view of the magnetic flux density distribution of a permanent magnet No. 3 according to embodiment 2 of the present invention;

fig. 17 is a schematic view of the magnetic flux density distribution of a number 4 permanent magnet provided in embodiment 2 of the present invention;

fig. 18 is a schematic view of the magnetic flux density distribution of a number 5 permanent magnet provided in embodiment 2 of the present invention;

fig. 19 is a schematic view of the flux density distribution of a permanent magnet No. 6 according to embodiment 2 of the present invention;

fig. 20 is a schematic view of the magnetic flux density distribution of permanent magnet No. 7 according to embodiment 2 of the present invention;

fig. 21 is a flowchart of a method for magnetizing a linear Halbach array according to an embodiment of the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

Example 1:

the integral magnetizing condition when the magnetizing direction changing angle of the Halbach array is 90 degrees:

the permanent magnets with different magnetization directions are arranged according to a certain rule to form the Halbach array. The most common Halbach array is shown in fig. 1, wherein an arrow represents a to-be-magnetized direction of a permanent magnet, the to-be-magnetized direction between adjacent permanent magnets rotates anticlockwise or clockwise, and the rotation angle beta is 90 degrees. The magnets in the array can be mainly divided into two types, the magnets to be magnetized in the vertical direction can be called main magnets, and the other magnets with the magnetization directions are auxiliary magnets. In practical applications, the two types of magnets may not have equal sizes, and the rotation angle β may be various angles, which are commonly 30 °, 45 °, 60 °, 90 °, 120 °, and so on.

The technical scheme provided by the invention is as follows:

step 1, testing the material characteristics of a permanent magnet to be magnetized, and obtaining the magnetization and demagnetization standards of the permanent magnet to be magnetized through the test;

step 1.1, taking a group of permanent magnet samples to be magnetized, enabling 3 parts of magnetic blocks to be supersaturated and magnetized (magnetizing magnetic field is oriented, magnetic flux density is larger than 6[ T ]), respectively placing the magnetic blocks in the same Helmholtz coil, and calibrating saturated magnetic flux by a Czochralski method (taking an average value);

step 1.2, taking another 3 parts of samples, respectively carrying out orientation magnetization for multiple times, measuring the saturation degree of the samples after each magnetization, and measuring the lowest saturation flux density of the orientation magnetization of the batch of permanent magnets; after the external magnetic field exceeds a certain threshold value, the saturation degree of the permanent magnet basically cannot be increased along with the increase of the external magnetic field, and the threshold value is considered to be the saturation flux density of the batch of permanent magnet samples in the orientation direction;

the oriented magnetization refers to the fact that the direction of an external magnetizing magnetic field is consistent with the magnetization direction of the permanent magnet to be magnetized.

Step 1.3, taking a plurality of samples, respectively carrying out angle magnetization for a plurality of times (a certain included angle exists between the direction of an external magnetic field and the direction to be magnetized), respectively taking the included angles as 30 degrees, 50 degrees, 60 degrees, 70 degrees and 80 degrees, and measuring the lowest external magnetic field required by the batch of samples for reaching saturation when the samples are magnetized under different included angles (in the same step, the threshold values of the external magnetic field under different angles are measured, the larger the included angle is, the larger the required magnetic field is, and when the included angle between a possible magnetic field and the orientation direction of a permanent magnet is larger than a certain value, the permanent magnet cannot reach saturation no matter how large the external magnetic field is);

and step 1.4, taking a plurality of samples which are saturated by magnetization, respectively placing the samples in external magnetic fields with the included angles of 90 degrees, 100 degrees, 110 degrees, 120 degrees and 180 degrees with the magnetization direction for demagnetization test, and determining the density of the external magnetic field when the magnetization saturation degree of the samples of the batch reaches 80-99% under the demagnetization fields with different included angles. The following description will be given by taking 90% as an example.

The demagnetization and magnetization of the permanent magnet are different, after the external magnetic field exceeds a certain threshold value, the magnetization saturation degree of the permanent magnet is rapidly reduced along with the increase of the external magnetic field, the threshold value point on the demagnetization curve is an inflection point, and the inflection point is positioned in the interval of 80% -99% of the saturation degree of the permanent magnet, so that the magnetic density of the external magnetic field is the maximum value of the magnetic density of the demagnetization field when the saturation degree of the permanent magnet reaches 90% under different included angles, namely the demagnetization degree of the permanent magnet is higher when the magnetic density of the demagnetization field is larger than the threshold value, and the demagnetization degree of the permanent magnet is lower when the magnetic density of the demagnetization field is smaller than the threshold value.

In embodiment 1, the external magnetic field standard that the magnetization of the permanent magnet reaches saturation in different external magnetization magnetic fields and the external magnetic field standard that the demagnetization degree of the magnetized and saturated permanent magnet exceeds 10% in different demagnetization fields are given.

And 2, determining the topology and ampere-turns of the magnetizing coil (coil group) according to the size and the material characteristics of the permanent magnet to be magnetized. In fig. 2, an included angle between adjacent permanent magnets in the to-be-magnetized direction is 90 degrees.

Specifically, the ampere turn is a unit of magnetomotive force, and is equal to the product of the number of turns of the coil and the current passed by the coil, and the larger the ampere turn is, the stronger the generated magnetic field is.

Step 2.1, as shown in fig. 2, the shaded area in fig. 2 represents the area (the dotted line in fig. 2 is the central axis of the auxiliary magnet) required to be completely magnetized during the first step of magnetization, generally speaking, when the shaded area of the auxiliary magnet on the right side can be ensured to be saturated and magnetized, the main magnet at the center can be completely magnetized, because the magnetization field of the permanent magnet is provided by the coil (coil group), and the magnetization area is positioned at the bottom of the coil (coil group), according to the right-hand spiral rule, the direction of the magnetic field in the lower axial area of the main coil (magnetization coil) (i.e. the main magnet area to be magnetized) is mainly vertical, and the direction of the magnetic field in the outer boundary area of the coil (i.e. the auxiliary magnet area to be magnetized) gradually changes from inclined to horizontal to inclined, in order to make the matching degree of the magnetization magnetic field and the orientation of the permanent magnet as high as possible, the width of the single side of the main coil section is preferably equal to the width of the auxiliary magnet, the distance between the coils is preferably equal to the width of the main magnet, and the topological structure can utilize the magnetic field at the lower side of the coils to the maximum extent, so that the orientation included angle between the magnetizing magnetic field and the permanent magnet is smaller, the needed magnetizing magnetic field is lower, and the ampere-turn number of the coils and the energy needed by magnetizing can be reduced;

step 2.2, as described in 2.1, no magnetized area exists before the first step of magnetization, so that when the influence of the magnetizing magnetic field on other permanent magnets is not considered, the topology and the ampere-turns of the coil can be preliminarily determined according to the size of the permanent magnet sample measured in step 1 and the magnetizing magnetic flux density (magnetic density for short) required by saturation magnetization of the permanent magnet sample and a given reasonable current density (generally less than 500A/mm ^2, when the size of the coil is not changed, the energy required by magnetization of the permanent magnet is smaller when the current density is smaller, namely, the direction of the main magnetizing magnetic field in the area to be magnetized, namely, the included angle between the magnetizing field direction of the No. 1 permanent magnet area and the orientation direction thereof in FIG. 2 is not more than 30 degrees, the included angle between the magnetizing field direction of the No. 2 permanent magnet whole area and the orientation direction thereof is not more than 70 degrees, and the included angle between the magnetizing field direction of the shadow area and the orientation direction thereof is not more than 60 degrees), namely, the topology structure of the required magnetizing coil is determined (the width, the thickness, and the thickness, of the magnetic field of the coil cross-section of the coil are not more than 60 degrees, High and inner diameter), and then obtaining the lowest current density required by the magnetizing coil when the magnetizing magnetic field reaches the lowest value of the saturation magnetization of the permanent magnet according to the magnetization parameters of the permanent magnet sample measured in the step 1, that is, under the current density, the magnetizing magnetic field generated by the magnetizing coil in fig. 2 can satisfy: the lowest magnetic flux density of the No. 1 permanent magnet area in the orientation direction is larger than the lowest saturated magnetic flux density measured in the step 1.2; the distribution of the magnetizing magnetic field size in the shadow area of the No. 2 permanent magnet meets the lowest magnetic density of the saturation magnetization of the permanent magnet under different included angles of the magnetizing magnetic field measured in the step 1.3, so that the lowest ampere-turns of the magnetizing coil are determined;

and 2.3, according to the topology obtained by the step 2.2 and the number of ampere turns of the coil, after the coil is magnetized at the position shown in the figure 2, translating the coil or the permanent magnet array, and simultaneously exchanging the positive and negative electrode wiring of the magnetizing coil, wherein the relative positions of the coil and the permanent magnet array are shown in the figure 3, and the completely filled area in the figure 3 is a magnetized area, and the shadow area is the magnetizing area. For the No. 2 permanent magnet, at least the right half area is completely magnetized in the step of magnetizing 2.2, and the step magnetizes at least the left half area, because the permanent magnet is repeatedly magnetized in the same direction when being magnetized, the demagnetization of the permanent magnet can not be caused, and when the step is magnetized, the included angle between the magnetizing magnetic field in the magnetized area of the No. 2 magnetic steel and the magnetizing direction of the permanent magnet can not be very large, the demagnetization of the magnetized area can not be caused, and the No. 2 permanent magnet can be completely magnetized by two steps of magnetizing; similarly, the permanent magnet number 4 will magnetize at least half of its area when it is magnetized in this step, and then all its areas will be completely magnetized by the next step of magnetizing.

After the magnetizing in steps 2.4 and 2.3 is completed, the permanent magnet or the coil is moved again, the positive and negative electrode wiring lines of the magnetizing coil are exchanged again, the relative position of the main coil and the permanent magnet is shown in fig. 4, the fully filled area in fig. 4 is the magnetized area, the shaded area is the magnetized area, and similarly to the previous step, the magnetizing of this time can magnetize the non-magnetized area of the No. 4 permanent magnet, the integral area of the No. 5 permanent magnet and the partial area of the No. 6 permanent magnet.

Step 2.5, for the magnetizing steps described in 2.3 and 2.4, two cases may occur due to the thickness of the permanent magnet, since there is a magnetized area before the magnetization: firstly, the magnetic leakage field at the edge of the magnetizing coil is low, so that demagnetization in a magnetized area (mainly a No. 1 permanent magnet area for step 2.3 and mainly a No. 2 and No. 3 permanent magnet areas for step 2.4) is avoided or the degree of demagnetization is low, namely, as shown in step 1.4, the distribution of the magnetic leakage field in the magnetized area meets the requirement that the magnetic density of the magnetic leakage field is smaller than the magnetic density value of the inflection point of a demagnetization curve under a corresponding included angle; secondly, the higher leakage magnetic field at the edge of the magnetizing coil causes higher degree demagnetization or even complete demagnetization of partial areas of the magnetized permanent magnet (mainly the area of the No. 1 permanent magnet for the step 2.3, and mainly the area of the No. 2 and the No. 3 permanent magnets for the step 2.4), and at the moment, an auxiliary coil needs to be added in the area adjacent to the magnetized permanent magnet to change the magnetic field shape and weaken the leakage magnetic field, so that the demagnetization influence of the leakage magnetic field on the magnetized area is reduced.

As shown in fig. 5, the shape and position of the auxiliary coil are not fixed, as long as the influence of the leakage magnetic field on the magnetized permanent magnet can be weakened, and the auxiliary coil shown in fig. 5 is only used for reference. The auxiliary coil can be connected with the main coil in series or used by another set of power supply independently, the timing sequence of the auxiliary coil is matched with the power supply of the main coil, and the current waveform also needs to be basically consistent with that of the main coil so as to weaken the leakage magnetic field in the whole pulse time;

step 2.6, in conclusion, the topology and ampere-turns of different coils (coil groups) can be determined according to the shape and material characteristics of different permanent magnets.

Step 3, determining parameters of the magnetizing power supply

1) According to the topology and ampere-turns of the coil (coil group) determined in the step 2, the number of turns of the coil and the peak value of magnetizing current are determined after a lead with a proper section is selected, so that the energy required for magnetizing is determined, and the capacitor voltage range required for saturation magnetizing can be determined when the capacitance value of the pulse power supply is known;

2) if the back iron exists, considering that the back iron generates an eddy current effect under the pulse magnetic field to weaken the magnetizing magnetic field, the discharge voltage can be increased to increase the magnetic field, the capacitance value can be increased to increase the pulse width to weaken the eddy current effect, or the back iron is manufactured by silicon steel laminations or is segmented in the process to weaken the eddy current effect.

Step 4, determining the cooling mode of the coil (coil group)

1) According to the coil (coil group) and the magnetizing power supply selected in the

steps

2 and 3, the heat productivity of the coil (coil group) in one magnetizing process can be obtained, and therefore the heat insulation temperature rise of the coil can be obtained;

2) according to the practical situation, a proper cooling mode is selected, the discharge interval is very long, the coil can be naturally cooled (air cooling), the discharge interval is short, the limitation on the temperature rise of the coil is high, a hollow copper wire can be adopted to wind the coil, and the coil is cooled by introducing constant-temperature pure water (oil) or the coil (coil group) is selectively soaked in liquid nitrogen (helium) for cooling.

Step 5, determining a coil (coil group) reinforcing structure

1) Because the permanent magnet is positioned on the outer side of the coil during magnetization, the coil mostly adopts a runway type, saddle-shaped, rectangular and other special-shaped structures to ensure the uniformity of a magnetic field, and the outer side of the coil is reinforced by fiber winding under the condition of a single coil;

2) aiming at the coil group structure, after the outside of each coil is independently wound with fiber for reinforcement, the whole coil group is required to be reinforced, and a fixing clamp or a whole cladding fiber can be adopted for reinforcement.

Step 6, integral tool and auxiliary structure

1) Under the condition of high field and heavy current, the coil has larger stress and also can generate larger suction force or repulsion force to the outer permanent magnet or back iron, and in this case, a proper tool needs to be set for the whole magnetizing structure, so that the safety of the device and personnel is ensured;

2) because the coil is arranged on one side of the permanent magnet array during magnetization, the specific position of the permanent magnet is difficult to directly observe by naked eyes, and the position of the permanent magnet in the array relative to the magnetizing coil (coil group) is important during magnetization, so that an auxiliary positioning structure needs to be made according to actual conditions.

Step 7, integral step-by-step magnetizing

1) As shown in fig. 2, fig. 3 and fig. 4, under the support of the auxiliary positioning structure, the whole coil (coil assembly) or the whole array is translated according to the actual situation, and the Halbach array is magnetized integrally in steps from one side to the other side, i.e. the magnetizing mode shown in fig. 3 and fig. 4 is repeated.

In a more specific embodiment, the magnetizing method and device provided by the invention comprise the following parts:

1. and (3) testing the sample to obtain the following minimum requirements of the magnetizing magnetic field: the magnetic density in the easy axis direction (orientation direction) is more than 3T, the magnetic density in the hard axis direction (vertical to the orientation direction) is less than 4T, and the magnetizing condition can meet the magnetizing requirement of most common-grade permanent magnets. The demagnetizing field requirement of the magnetized area is as follows: when the included angle between the magnetic field and the magnetized direction is 80 degrees, the included angle is less than 4.2T; when the included angle between the magnetic field and the magnetized direction is 90 degrees, the included angle is less than 2.8T; when the included angle between the magnetic field and the magnetized direction is 100 degrees, the included angle is less than 2.3T; when the included angle between the magnetic field and the magnetized direction is 110 degrees, the included angle is less than 2.1T; when the included angle between the magnetic field and the magnetized direction is 120 degrees, the included angle is less than 1.8T; when the included angle between the magnetic field and the magnetized direction is 180 degrees, the included angle is less than 1.4T.

2. The size of the permanent magnet to be magnetized is 30mm 10mm 50mm (width thickness length). The directions to be magnetized are arranged according to the array shown in figure 1. Considering tooling and reinforcement, a magnetizing gap between a permanent magnet and a coil is selected to be 15mm, a square copper wire with the length of 4mm to 3mm is selected as a wire, the magnetizing is determined by adopting a coil group mode according to the magnetizing requirement and the demagnetization requirement of materials, 96 turns (8 layers, 12 turns in each layer) of a main coil and 22 turns (2 layers, 11 turns in each layer) of an auxiliary coil are adopted, the number of ampere turns of the coil required for magnetizing is about 1050kA during integral magnetizing, and the current of the coil is about 11 kA.

3. The capacitance value of the selected pulse power supply is 3.2mF, the protection inductor is contained in the power supply, the protection inductor is 1mH, and the peak voltage required by magnetizing is about 10 kV. The time-dependent change lines of the magnetizing current and the magnetic density at the center of the No. 5 permanent magnet are shown in FIG. 6.

As shown in fig. 5, the overall magnetic density of the permanent magnet region 1 at the peak time in the third step of magnetizing is lower than 0.6T, so demagnetization cannot be caused;

the flux density distribution of the permanent magnet No. 2 is shown in FIG. 7, wherein (a) in FIG. 7 is a flux density distribution cloud picture of a leakage magnetic field in the permanent magnet No. 2 region, and (b) is a flux density distribution cloud picture of an included angle between the leakage magnetic field in the permanent magnet No. 2 region and the magnetization direction of the permanent magnet, it can be seen that there is no intersection between the flux density region greater than 1.8T and the included angle greater than 100 degrees, and it can be considered that the integral region No. 2 is not demagnetized;

the magnetic density distribution of the No. 3 permanent magnet is as shown in 8, in FIG. 8, (a) is a cloud picture of the magnetic leakage field in the No. 3 permanent magnet region and the included angle between the magnetization directions of the permanent magnets, and (b) is a cloud picture of the magnetic density distribution of the magnetic leakage field in the No. 3 permanent magnet region, it can be seen that the regions with the magnetic densities larger than 4T and the included angle larger than 80 degrees do not intersect, and it can be considered that the No. 3 whole region does not demagnetize;

the flux density distribution of the permanent magnet No. 4 is shown in FIG. 9, (a) is a distribution cloud picture of the region where the flux density hard axis component of the permanent magnet No. 4 is less than 4T, (b) is a distribution cloud picture of the region where the flux density easy axis component of the permanent magnet No. 4 is greater than 3T, and (c) is an intersection of the region where the flux density hard axis component of the permanent magnet No. 4 is less than 4T and the region where the flux density easy axis component is greater than 3T, that is, the region where the permanent magnet No. 4 can ensure complete magnetization in the magnetization in this step;

the magnetic density distribution of the No. 5 permanent magnet is shown in FIG. 10, wherein (a) in FIG. 10 is a cloud picture of magnetic density easy axis component distribution of the No. 5 permanent magnet region, and (b) is a cloud picture of magnetic density hard axis component distribution of the No. 5 permanent magnet region, the easy axis component of the No. 5 permanent magnet region is larger than 3T, and the hard axis component is smaller than 4T, so that the No. 5 permanent magnet can be completely magnetized;

the magnetic density distribution of the permanent magnet No. 6 is shown in FIG. 11, (a) is a distribution cloud picture of the region where the magnetic density hard axis component of the permanent magnet No. 6 is less than 4T, (b) is a distribution cloud picture of the region where the magnetic density easy axis component of the permanent magnet No. 6 is greater than 3T, and (c) is an intersection of the region where the magnetic density hard axis component of the permanent magnet No. 6 is less than 4T and the region where the magnetic density easy axis component is greater than 3T, that is, the region where the permanent magnet No. 6 can ensure complete magnetization in the magnetization in this step. The magnetizing requirements of No. 4, 5 and 6 permanent magnets are met, and meanwhile, the areas of No. 1, 2 and 3 permanent magnets cannot be demagnetized.

4. The example is only for experiments, and the discharge frequency is not frequent, so the heat dissipation adopts natural heat dissipation, namely, the external heat dissipation mode is not considered.

5. In the embodiment, the coil group is adopted for magnetizing, so that two coils need to be reinforced respectively and then are integrally reinforced.

6. The coil group is fixed during integral magnetization, and the array is sequentially magnetized after being positioned through the positioning holes from head to tail.

7. The overall magnetizing and the pre-magnetizing and re-assembling air gap magnetic densities in an ideal state are in a distribution pair on the axis of 1mm on the upper surface of the permanent magnet as shown in fig. 12, and it can be seen that the air gap magnetic densities of the overall magnetized area are almost the same as the distribution of the pre-magnetizing and re-assembling air gap magnetic densities in the ideal state.

Example 2:

the Halbach array has the integral magnetizing condition when the magnetizing direction change angle is 45 degrees:

similar to example 1, the array also required multiple steps of magnetization, one of which was selected for bulk analysis, as shown in fig. 13. The arrow on the permanent magnet in fig. 13 indicates the direction of magnetization, the fully filled area in fig. 13 is the magnetized area, and the shaded area is the area to be magnetized in this step.

Fig. 14 shows the magnetic density distribution (fig. 14 (a)) of the (magnetized) region of the permanent magnet No. 1 and the angle distribution (fig. 14 (b)) between the magnetic field direction and the magnetized direction thereof during the magnetizing in this step, and it can be seen that the magnetic density of the whole region of the permanent magnet No. 1 is low (less than 1.4T), and the whole region is not demagnetized;

fig. 15 shows the magnetic density distribution (fig. 15 (a)) of the (magnetized) region of the No. 2 permanent magnet and the angle distribution (fig. 15 (b)) between the magnetic field direction and the magnetized direction during the magnetization in this step, and it can be seen that the magnetic density of the whole region of the No. 2 permanent magnet is low (less than 1.8T) and the angle between the magnetic field direction and the magnetized direction is small (less than 120 °), and the whole region does not demagnetize;

fig. 16 shows the distribution of the magnetic density of the (magnetized) region of the permanent magnet No. 3 (fig. 16 (a)) and the distribution of the included angle between the magnetic field direction and the magnetized direction thereof (fig. 16 (b)) during the magnetizing in this step, and it can be seen that the included angle between the magnetic field direction and the magnetized direction of the whole region of the permanent magnet No. 3 is small (less than 80 °), and the whole region is not demagnetized;

fig. 17 shows the distribution of the magnetic density of the (magnetized) region of the No. 4 permanent magnet (fig. 17 (a)) and the distribution of the included angle between the magnetic field direction and the magnetized direction thereof (fig. 17 (b)) during the magnetization in this step, and it can be seen that the included angle between the magnetic field direction and the magnetized direction of the entire region of the No. 4 permanent magnet is small (only 45 ° at the highest), the entire region does not demagnetize, and a certain complementary magnetization effect is also obtained;

fig. 18 shows that, during the magnetizing in this step, the magnetic density easy axis component of the (partially magnetized) area of the permanent magnet No. 5 is greater than the distribution of the area 3T (fig. 18 (a)) and the magnetic density hard axis component is less than the distribution of the area 4T (fig. 18 (b)), it can be seen that the magnetic density hard axis component in the entire area of the permanent magnet No. 5 is less than 4T, and the area with the easy axis component greater than 3T meets the requirement of the area to be magnetized in fig. 14, it can be considered that the magnetizing in this step can fully magnetize the permanent magnet No. 5 without demagnetizing the magnetized area;

fig. 19 shows the distribution of the region with magnetic density easy axis component greater than 3T (fig. 19 (a)) and the distribution of the region with magnetic density hard axis component less than 4T (fig. 19 (b)) of the No. 6 permanent magnet (unmagnetized) region during the magnetization of this step, and it can be seen that the magnetic density easy axis component is greater than 3T and the hard axis component is less than 4T in the entire region of the No. 6 permanent magnet, so it can be considered that the magnetization of this step can completely magnetize all regions of the No. 6 permanent magnet;

fig. 20 shows the distribution of the region with magnetic density easy axis component greater than 3T (fig. 20 (a)) and the distribution of the region with magnetic density hard axis component less than 4T (fig. 20 (b)) of the No. 7 permanent magnet (unmagnetized) region during the magnetization in this step, and it can be seen that the magnetic density easy axis component is greater than 3T and the hard axis component is less than 4T in the entire region of the No. 7 permanent magnet, so it can be considered that the magnetization in this step can completely magnetize all the regions of the No. 7 permanent magnet;

according to the symmetry of the magnetic field, the No. 8 permanent magnet is consistent with the No. 6 permanent magnet, and the No. 9 permanent magnet is consistent with the No. 5 permanent magnet, so that the complete magnetization of the region to be magnetized, which is shown in FIG. 13, can be ensured by the magnetization in the step.

It can be understood that, referring to the embodiment 1 and the embodiment 2, when the change angle of the magnetization direction of the Halbach array is other angles, the magnetization can be realized by the magnetization device and the method provided by the invention, and the embodiment of the invention will not be described again.

In the invention, a method for integrally magnetizing the Halbach array is also provided. The method comprises the steps that for non-magnetized permanent magnets which are arranged according to a Halbach array in an oriented mode, the array is wholly magnetized in a single coil or coil group mode, the magnetizing coil or coil group is translated and magnetized step by step according to a certain sequence from the first permanent magnet of the Halbach array, and each step can completely magnetize one main magnet and magnetize partial areas of one or more auxiliary magnets.

Fig. 21 is a flowchart of a magnetizing method for a linear Halbach array according to an embodiment of the present invention, and as shown in fig. 21, the magnetizing method includes the following steps:

s101, arranging a plurality of permanent magnets with different to-be-magnetized directions into a linear array according to a preset rule; the preset rule is as follows: the to-be-magnetized directions of the adjacent permanent magnets rotate at intervals of a preset angle in a preset hour direction; the different directions to be magnetized comprise vertical directions, the permanent magnets are divided into main magnets and auxiliary magnets, the directions to be magnetized of the main magnets are along the vertical direction, and the directions to be magnetized of the auxiliary magnets are non-vertical directions;

s102, placing the main magnet directly above or below the linear array, and translating along the linear direction of the linear array to magnetize a plurality of permanent magnets step by step, wherein each step of magnetization completely magnetizes one main magnet and magnetizes partial regions of the auxiliary magnets adjacent to the main magnet;

s103, when the main coil can cause demagnetization influence on the magnetized permanent magnet in the current magnetizing step, adding an auxiliary coil in the area near the magnetized permanent magnet to change the magnetic field distribution in the area near the magnetized permanent magnet so as to reduce the demagnetization influence and ensure that the magnetization saturation degree of the preset area of the magnetized permanent magnet is kept above a preset proportion;

and S104, after all the permanent magnets are magnetized, obtaining the linear Halbach array.

In an optional example, the method further comprises the steps of:

when the saturated and magnetized permanent magnets are respectively arranged in external demagnetization fields with different included angles with the magnetization direction of the permanent magnets, determining the size of the minimum external demagnetization field of the permanent magnets reaching the demagnetization standard under different included angles; the demagnetization standard is as follows: and if the magnetization saturation degree of the non-preset area in the permanent magnet is kept above the preset proportion, the saturated and magnetized permanent magnet is considered to be demagnetized.

according to the included angle between the magnetizing magnetic field generated by the main magnet and the direction to be magnetized of the auxiliary magnet, the minimum external magnetizing magnetic field flux density value required by saturated magnetization of the permanent magnet under the external magnetic field orientation magnetization and the different included angle magnetization in the predetermined permanent magnet magnetizing standard, the fact that one main magnet is completely magnetized by each step of magnetization is determined, and the size and the distribution of the flux density of the magnetic field generated by the main magnet and required by the part of the auxiliary magnet adjacent to the main magnet are magnetized.

It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.

Claims

1. A linear Halbach array magnetizing method is characterized by comprising the following steps:

the main magnet is arranged right above or right below the linear array and is translated along the linear direction of the linear array so as to magnetize a plurality of permanent magnets step by step, and each step of magnetization fully magnetizes one main magnet and magnetizes partial areas of the auxiliary magnets adjacent to the main magnet;

2. The method of magnetizing a linear Halbach array according to claim 1, further comprising the steps of:

3. A method of magnetizing a linear Halbach array according to claim 1 or 2, wherein the main coil is translated along the linear direction of the linear array to magnetize the plurality of permanent magnets in steps, each step of magnetizing completely magnetizing a main magnet and magnetizing a partial region of the auxiliary magnet adjacent to the main magnet, in particular comprising:

4. The method according to claim 3, wherein said primary coil magnetic field, in the current magnetizing step, will cause a demagnetization effect on the magnetized permanent magnet, specifically:

5. The method according to claim 1 or 2, wherein an auxiliary coil is added to the area near the magnetized permanent magnet, and the auxiliary coil generates a magnetic field to change the magnetic field distribution in the area near the magnetized permanent magnet, so as to reduce the demagnetization effect, specifically:

6. A linear Halbach array magnetizing apparatus, comprising: a main coil and an auxiliary coil;

7. The linear Halbach array magnetizing apparatus of claim 6, further comprising: the coil auxiliary positioning structure, the coil reinforcing structure and the array positioning structure;

8. The charging device of a linear Halbach array as claimed in claim 6, wherein, in each step of charging, the main coil is disposed directly above one main magnet, the direction of the central magnetic field of the magnetic field generated by the main coil is controlled to be the same as the direction to be charged of the main magnet directly below the main coil, and the central magnetic field of the magnetic field generated by the main coil is oriented to charge the main magnet directly below the main coil by controlling the distance between the main coil and the main magnet and the parameters of the main coil;

9. The magnetizing device of the linear Halbach array according to claim 8, wherein when the field of the primary coil will cause demagnetization to the magnetized permanent magnet in the current magnetizing step, an auxiliary coil is added to the area near the magnetized permanent magnet, the overall magnetic field distribution generated by the auxiliary coil and the primary coil is determined by simulation, and the appropriate auxiliary coil and primary coil are designed in combination with the magnetizing standard and the demagnetizing standard of the permanent magnet so that the magnetization saturation degree of the preset area of the magnetized permanent magnet is kept above the preset proportion during magnetizing.

10. The magnetizing device of the linear Halbach array according to claim 8 or 9, wherein the magnetizing standard and the demagnetizing standard of the permanent magnet to be magnetized specifically include: