A ring core with uniform magnetic density and a preparation method thereof

Abstract

The embodiment of the present specification relates to the technical field of soft magnetic material, and provides a toroidal core with uniform magnetic density and a preparation method thereof, the toroidal core comprises a plurality of nested nanocrystalline ring bands, and the magnetic permeability of the plurality of nested nanocrystalline ring bands increases gradually along the radial direction from the inner layer to the outer layer, so that the magnetic flux density distribution of the toroidal core tends to be balanced.The toroidal core of the embodiment of the present specification solves the problem of uneven magnetic density distribution inside and outside the single magnetic permeability core, thereby reducing the temperature difference inside and outside the toroidal core, improving the thermal stability of the toroidal core, and maximizing the utilization rate of the internal material.

Description

Technical Field

[0001] The embodiments in this specification relate to the field of soft magnetic materials technology, and in particular to a toroidal magnetic core with uniform magnetic density and its preparation method. Background Technology

[0002] Toroidal magnetic cores are commonly used magnetic components in electronic devices, typically made of magnetic materials such as ferrite or iron powder cores, and have wide applications in electronic circuits and other fields. Toroidal magnetic cores operate primarily based on the principle of electromagnetic induction. When a current flows through a coil wound around a toroidal core, a magnetic field is generated inside the core. The magnitude and direction of this magnetic field are related to the magnitude and direction of the current. According to Ampere's circuital law, in the closed structure of a toroidal core, the magnetic field is mainly concentrated inside the core, forming a closed magnetic field loop. When the current changes, the magnetic field also changes accordingly, thus inducing an electromotive force (EMF) in the core. This electromagnetic induction phenomenon enables toroidal magnetic cores to perform various functions, such as energy storage, voltage transformation, and filtering.

[0003] However, existing toroidal magnetic cores suffer from uneven magnetic flux density distribution on both the inner and outer sides. Specifically, because the magnetic flux path is larger on the outer side of the core than on the inner side, while the permeability is the same on both sides, the magnetic flux tends to concentrate inside the toroidal core. When the magnetic density inside the core becomes too high and reaches magnetic saturation, the permeability drops sharply, and the change in magnetic flux is no longer proportional to the magnetic field strength. This leads to increased hysteresis losses, generating more heat and significantly raising the temperature in the magnetic saturation region. This further exacerbates the uneven temperature distribution inside the core, increasing the temperature difference between the inside and outside, thus affecting the thermal stability of the core and reducing the utilization rate of internal materials. Therefore, it is urgent to design a toroidal magnetic core to solve the problem of uneven magnetic flux density distribution inside existing toroidal magnetic cores. Summary of the Invention

[0004] In view of the above-mentioned problems in the prior art, the purpose of the embodiments of this specification is to provide a toroidal magnetic core with uniform magnetic flux density and a method for preparing the same, so as to solve the problem of uneven magnetic flux density distribution inside the toroidal magnetic core in the prior art.

[0005] To solve the above-mentioned technical problems, the specific technical solutions of the embodiments in this specification are as follows:

[0006] On one hand, embodiments of this specification provide a toroidal magnetic core with uniform magnetic flux density. The toroidal magnetic core includes multiple nested nanocrystalline rings, the permeability of which increases radially from the inner layer to the outer layer, so that the magnetic flux density distribution of the toroidal magnetic core tends to be uniform.

[0007] Furthermore, the thickness of the plurality of nested nanocrystalline rings is the same.

[0008] Furthermore, the number of layers, thickness, and permeability of the nanocrystalline rings are determined using the following method:

[0009] Based on the target radial thickness of the toroidal core, multiple toroidal core simulation models are divided into multiple sub-layers along the radial direction on an average basis, resulting in multiple toroidal core simulation models with different numbers of sub-layers.

[0010] The permeability of each sublayer in the simulation model of each toroidal core is calculated based on the preset magnetic reluctance distribution.

[0011] The number of layers, permeability and thickness of each sub-layer of the simulation model of each toroidal magnetic core are input into the finite element analysis model for simulation, and the magnetic flux density distribution curve of each toroidal magnetic core simulation model is obtained accordingly.

[0012] Calculate the degree of fluctuation in the magnetic flux density distribution curve of each toroidal core simulation model;

[0013] The number of layers, the permeability of each sublayer, and the thickness of the toroidal core simulation model corresponding to the magnetic flux density distribution curve with the smallest fluctuation are selected as the target number of layers, target thickness, and target permeability of the nanocrystalline toroidal band.

[0014] Further, the calculation of the permeability of each sublayer in each toroidal core simulation model based on the preset reluctance distribution includes:

[0015] The thickness of each sub-layer is determined based on the target radial thickness of the toroidal core and the number of layers in the simulation model of each toroidal core.

[0016] The magnetic flux path length of each sublayer is determined based on the thickness of each sublayer.

[0017] The magnetoresistance of each sublayer is determined according to the preset magnetoresistance distribution;

[0018] The permeability of each sublayer is calculated based on the flux path length and magnetic reluctance of each sublayer.

[0019] Further, determining the magnetic flux path length of each sublayer based on the thickness of each sublayer includes:

[0020] The flux path length of each sublayer is determined using the following formula:

[0021] l e (n)=2π(r in +dr);

[0022] Among them, l e (n) represents the flux path length of the nth sublayer, r in dr represents the inner diameter of the nth sublayer, and dr represents the thickness of the nth sublayer.

[0023] Furthermore, the magnetoresistance distribution is represented by the following formula:

[0024]

[0025] Where N represents the number of coil turns, i represents the coil current, and r in r represents the inner diameter of the nth sublayer. on Let φ(n) represent the outer diameter of the nth sublayer, and let φ(n) represent the magnetic flux of the nth sublayer. This represents the magnetoresistance of the nth sublayer.

[0026] Further, the calculation of the permeability of each sublayer based on the magnetic flux path length and magnetic reluctance of each sublayer includes:

[0027] The permeability of each sublayer is calculated using the following formula:

[0028]

[0029] Where, μ r (n) represents the permeability of the nth sublayer, l e (n) represents the magnetic flux path length of the nth sublayer. Let μn represent the magnetoresistance of the nth sublayer, μ0 represent the free permeability, and An represent the magnetic reluctance of the nth sublayer. c (n) represents the cross-sectional area of ​​the nth sublayer.

[0030] On the other hand, embodiments of this specification provide a method for preparing a toroidal magnetic core with uniform magnetic flux density, the method comprising:

[0031] Determine the target number of nanocrystalline ribbon layers, the target thickness of each nanocrystalline ribbon layer, and the target permeability of the toroidal magnetic core to be prepared.

[0032] Obtain several nanocrystalline ribbons with target thickness and target magnetic permeability;

[0033] The target layer consists of several nanocrystalline ribbons whose magnetic permeability increases radially from the inner to the outer layer to form a ring-shaped magnetic core.

[0034] Furthermore, the method for preparing the nanocrystalline ribbon with the target magnetic permeability includes:

[0035] The degree of fragmentation is determined based on the target magnetic permeability of each layer of nanocrystalline ribbon.

[0036] Each layer of nanocrystalline ribbon is crushed using a crushing device;

[0037] The degree of breakage of each layer of nanocrystalline ribbon after the breakage process is detected using a breakage degree sensor;

[0038] The magnetic permeability of each layer of nanocrystalline ribbon after crushing is determined based on the detection signal fed back by the crushing degree sensor.

[0039] If not, the crushing pressure of the crushing device is adjusted according to the detection signal, and the nanocrystalline ribbon is crushed again according to the adjusted crushing pressure until the magnetic permeability of the nanocrystalline thin sheet after crushing reaches the target magnetic permeability.

[0040] Furthermore, determining the corresponding degree of fragmentation based on the target magnetic permeability of each layer of nanocrystalline ribbon includes:

[0041] The degree of fragmentation for each layer of nanocrystalline ribbon is determined using the following formula:

[0042]

[0043] Where D(n) represents the degree of fragmentation of the nth layer of nanocrystalline ribbon, μ r (n) represents the target magnetic permeability of the nth nanocrystalline ribbon, μ initial (n) represents the initial magnetic permeability of the nth layer of nanocrystalline ribbon.

[0044] Furthermore, the combination of several nanocrystalline ribbons in the target layer according to a radial gradient increase in magnetic permeability from the inner to the outer layer includes:

[0045] Using a rolling mill, several nanocrystalline ribbons of the target layer are wound layer by layer according to the radial gradient of magnetic permeability from the inner layer to the outer layer to form a ring-shaped magnetic core.

[0046] Furthermore, one side of the nanocrystalline ribbon is covered with pressure-sensitive adhesive, which is used to bond adjacent layers during the winding of the nanocrystalline ribbon;

[0047] The pressure-sensitive adhesive is covered with a release film, which is used to prevent interlayer adhesion of the nanocrystalline ribbon before winding.

[0048] Furthermore, the roller pressing equipment includes a first drive roller, a second drive roller, a release film recovery roller, a first support roller, and a second support roller;

[0049] The method of using a rolling mill to wind several nanocrystalline ribbons of the target layer layer by layer according to the radial gradient of magnetic permeability from the inner layer to the outer layer to form a ring-shaped magnetic core includes:

[0050] The nanocrystalline ribbon with the lowest magnetic permeability is fixed to the first drive roller. The first drive roller drives the nanocrystalline ribbon to rotate and is transmitted to the second drive roller through the first support roller and the second support roller.

[0051] The second drive roller peels off the release film covering the nanocrystalline ribbon and transfers the release film to the release film recycling roller, and the second drive roller winds the nanocrystalline ribbon after peeling off the release film into the inner layer of the nanocrystalline ribbon core.

[0052] The release film recovery roller receives the release film and winds it around for collection;

[0053] By sequentially replacing nanocrystalline ribbons with increasing magnetic permeability, the above steps are repeated. Each layer of nanocrystalline ribbon is bonded together with pressure-sensitive adhesive to form a toroidal magnetic core.

[0054] Some embodiments of this specification provide one or more technical solutions, which have at least the following technical effects:

[0055] The toroidal magnetic core provided in this specification comprises multiple nested nanocrystalline bands, with the permeability of these bands increasing radially from the inner to the outer layer. This achieves uniform magnetoresistance across the inner and outer layers of the toroidal core, resulting in a more balanced magnetic flux density distribution and resolving the problem of uneven magnetic flux density distribution within a single permeability core. Furthermore, the uniform magnetic flux density distribution within the toroidal core reduces the temperature difference between its inner and outer layers, improving its thermal stability and maximizing the utilization of internal materials.

[0056] The above description is merely an overview of some embodiments of the technical solutions in this specification. In order to better understand the technical means of some embodiments of this specification and to implement them in accordance with the content of the specification, and to make the above and other objects, features and advantages of the embodiments of this specification more apparent and understandable, preferred embodiments are described below in detail with reference to the accompanying drawings. Attached Figure Description

[0057] To more clearly illustrate the technical solutions in the embodiments or prior art of this specification, the drawings used in the description of the embodiments or prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this specification. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0058] Figure 1 A schematic diagram and unfolded view of the toroidal magnetic core are shown.

[0059] Figure 2 The toroidal inductor and its equivalent magnetoresistance model are shown;

[0060] Figure 3 Conceptual diagrams of toroidal magnetic cores with uniform magnetic flux density and their equivalent reluctance models are shown in some embodiments of this specification;

[0061] Figure 4 The flowchart illustrating the process of determining the number of layers, thickness, and permeability of nanocrystalline bands in some embodiments of this specification is shown.

[0062] Figure 5(a) shows the magnetic flux density distribution curves of a single permeability toroidal core in some embodiments of this specification;

[0063] Figure 5(b) shows the magnetic flux density distribution curves of a set of gradient permeability toroidal cores in some embodiments of this specification;

[0064] Figure 5(c) shows the magnetic flux density distribution curves of another set of gradient permeability toroidal cores in some embodiments of this specification;

[0065] Figure 5(d) shows the magnetic flux density distribution curves of another set of gradient permeability toroidal cores in some embodiments of this specification;

[0066] Figure 6 A schematic flowchart of a method for preparing a toroidal magnetic core with uniform magnetic flux density is shown in some embodiments of this specification;

[0067] Figure 7 A schematic flowchart illustrating the preparation method of nanocrystalline ribbons with target magnetic permeability in some embodiments of this specification is shown;

[0068] Figure 8 A process flow diagram for preparing a toroidal magnetic core with a target permeability is shown in some embodiments of this specification;

[0069] Figure 9(a) shows a thermal image of a single permeability toroidal core;

[0070] Figure 9(b) shows a thermal image of a set of toroidal magnetic cores with gradient permeability.

[0071] Explanation of symbols in the attached drawings:

[0072] A1, First drive roller;

[0073] A2, Second drive roller;

[0074] B1, First support roller;

[0075] B2, Second support roller;

[0076] B3. Release film recovery roller. Detailed Implementation

[0077] The technical solutions in the embodiments of this specification will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this specification, and not all embodiments. Based on the embodiments in this specification, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this specification.

[0078] It should be noted that the terms "first," "second," etc., used in this specification, claims, and the foregoing drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, apparatus, product, or device that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or devices. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0079] In the description of this specification, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this specification.

[0080] In the description of this specification, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection between two components. Those skilled in the art can understand the specific meaning of the above terms in this specification based on the specific circumstances.

[0081] The existing toroidal magnetic cores suffer from uneven magnetic flux density distribution on both the inner and outer sides. Specifically, a schematic diagram and extended view of an existing toroidal magnetic core are shown below. Figure 1 As shown, the top view of the toroidal magnetic core is trapezoidal, with the top path l nThe core is relatively long, while the bottom path l1 is relatively short. If the toroidal core is divided into n layers, n magnetic flux paths l will be generated. The cross-sectional area of ​​the toroidal core can be divided into several small areas, each of which can be represented as:

[0082] A c (n)=hdr (1)

[0083] Among them, A c (n) represents the area of ​​the nth sublayer, h is the height of the toroidal core, and dr is the thickness of each sublayer. The toroidal inductor and its reluctance model based on the toroidal core are as follows: Figure 2 As shown, r i and r o The inner and outer radii of the toroidal core are represented by , i represents the excitation current, N is the number of coil turns, and R1, R2...R n The magnetic reluctance represents the path of the shunt magnetic flux along the radial direction. Similar to the resistance in a circuit, the concept of magnetic reluctance can be used to qualitatively describe the distribution of magnetic flux within a magnetic core. The magnetic reluctance R can be calculated as follows:

[0084]

[0085] Where R represents the reluctance of the toroidal core, l e μ represents the flux path length of a toroidal core. r The relative permeability of the toroidal core is represented by μ0, where μ0 represents the permeability of free space, and A is the relative permeability of the toroidal core. c This represents the cross-sectional area of ​​the toroidal core, where the magnetic flux path le is simplified to: l e =(r i +r o Therefore, since the permeability is the same on both the inner and outer sides, the magnetic reluctance on both sides of the toroidal core can be considered constant. However, from... Figure 1 As can be seen, the length of the magnetic flux path along the radius is not the same. The magnetic flux path on the outside of the core is larger than that on the inside. When the permeability of the inside and outside is the same, the magnetic reluctance along the radius is not equal. Therefore, the magnetic flux is often concentrated inside the toroidal core. When the magnetic density inside the core is too high and reaches the magnetic saturation state, the permeability will drop sharply. The change in magnetic flux is no longer proportional to the magnetic field strength. This will lead to an increase in additional hysteresis loss, generate more heat, and cause the temperature in the magnetic saturation region to rise significantly. This further aggravates the uneven temperature distribution inside the core, increases the temperature difference between the inside and outside, and thus affects the thermal stability of the core and reduces the utilization rate of the internal materials.

[0086] To address the aforementioned problems, embodiments of this specification provide a toroidal magnetic core with uniform magnetic flux density. Figure 3 This is a schematic diagram of a toroidal magnetic core with uniform magnetic flux density provided in the embodiments of this specification, specifically as follows: Figure 3As shown, the toroidal magnetic core includes multiple nested nanocrystalline rings, the permeability of which increases radially from the inner to the outer layer, so that the magnetic flux density distribution of the toroidal magnetic core tends to be uniform.

[0087] The above analysis shows that there are differences between the inner and outer structures of the toroidal core. The traditional simplification of the inner and outer magnetic flux paths is (r... i +r o ) / 2 is unreasonable. Therefore, considering the differences in the internal and external structures of the toroidal core, the magnetic flux path in the embodiments of this specification should be given by the following formula:

[0088] l e (n)=2π(r in +dr) (3)

[0089] Among them, l e (n) represents the flux path length of the nth sublayer of the toroidal core, r in dr represents the inner diameter of the nth sublayer, and dr represents the thickness of the nth sublayer.

[0090] Therefore, the magnetic reluctance along the radial direction can be expressed as:

[0091]

[0092] Where, μ r (n) represents the permeability of the nth sublayer, l e (n) represents the magnetic flux path length of the nth sublayer. Let μn represent the magnetoresistance of the nth sublayer, μ0 represent the free permeability, and An represent the magnetic reluctance of the nth sublayer. c (n) represents the cross-sectional area of ​​the nth sublayer.

[0093] Then, the following expression can be derived to describe Figure 2 Reluctance distribution in:

[0094]

[0095] Where N represents the number of coil turns, i represents the coil current, and r in r represents the inner diameter of the nth sublayer. on Let φ(n) represent the outer diameter of the nth sublayer, and let φ(n) represent the magnetic flux of the nth sublayer. A represents the magnetoresistance of the nth sublayer. c Let N(n) represent the cross-sectional area of ​​the nth sublayer, and B(n) represent the magnetic flux density of the nth sublayer. For a given inductor, N, μ0, and A... c(n) is fixed, and under the same current excitation, Ni (magnetomotive force) remains constant. For each sublayer, R(n) is different, meaning the reluctance increases radially from the inside to the outside. This explains the non-uniform magnetic flux density distribution in the core. Therefore, the key to obtaining the same reluctance along the radius is to maintain l... e (n) / μ r (n) should be as similar as possible, due to l e (n) increases radially from the inside to the outside, therefore μ r The value of (n) needs to change with l e The permeability increases with the increase of (n). A conceptual diagram of a toroidal core with gradient permeability is shown below. Figure 3 As shown, by adjusting the permeability of each sublayer and setting the inner layer to a relatively low permeability, the magnetic reluctance difference within the core is reduced, thereby ensuring that the magnetic flux density of each sublayer is as similar as possible.

[0096] In some embodiments of this specification, multiple nested nanocrystalline rings have the same thickness. As the above analysis shows, from a magnetic circuit design perspective, the gradient increase in permeability between the inner and outer layers is to match changes in magnetic field strength. This is because the inner layer typically has a higher magnetic field strength than the outer layer, thus requiring lower permeability in the inner layer and higher permeability in the outer layer to maintain a balanced magnetic flux density. When the thickness dr of each nanocrystalline ring is the same, the cross-sectional area A of each nanocrystalline ring is... c (n) = hdr is the same, the magnetic flux path length l e (n) increases linearly along the radius from the inner layer to the outer layer, when the permeability μ r (n) When the gradient increases along the radius from the inner layer to the outer layer, the magnetoresistance of each layer can be made equal, thus ensuring a uniform distribution of magnetic flux density. However, if the thickness dr of each nanocrystalline ring layer is different, such as the inner layer being thicker and the outer layer being thinner (i.e., dr(inner) > dr(outer), the cross-sectional area of ​​the inner layer is larger. Even if the permeability is low, the magnetoresistance may be lower, causing the magnetic flux to concentrate in the inner layer and become unbalanced. In addition, when the thickness of each layer is different, a complex gradient of permeability needs to be designed based on the nonlinear changes in the magnetic flux path and cross-sectional area, resulting in high fabrication costs and difficulty in controlling precision.

[0097] It is understood that the number of layers, permeability, and thickness of a toroidal magnetic core are crucial to the uniform distribution of magnetic flux density within the toroidal core. In some embodiments of this specification, reference is made to... Figure 4 As shown, the number of nanocrystalline ring layers, thickness, and permeability were determined using the following method:

[0098] S401: Based on the target radial thickness of the toroidal core, multiple toroidal core simulation models are divided into multiple sub-layers along the radial direction to obtain multiple toroidal core simulation models with different numbers of sub-layers.

[0099] S402: Calculate the permeability of each sublayer in the simulation model of each toroidal core based on the preset magnetic reluctance distribution;

[0100] S403: Input the number of layers, permeability and thickness of each sub-layer of the simulation model of each toroidal magnetic core into the finite element analysis model for simulation, and obtain the magnetic flux density distribution curve of each toroidal magnetic core simulation model accordingly.

[0101] S404: Calculate the degree of fluctuation in the magnetic flux density distribution curve of each toroidal core simulation model;

[0102] S405: Select the number of layers, permeability and thickness of each sub-layer of the simulation model of the toroidal core corresponding to the magnetic flux density distribution curve with the smallest fluctuation as the target number of layers, target thickness and target permeability of the nanocrystalline toroidal band.

[0103] In this embodiment of the specification, the target radial thickness is set to 10 mm, and the desired magnetic reluctance distribution is set according to equation (5). Figures 5(a)-5(d) The simulated magnetic flux density distribution and corresponding magnetic flux density distribution curves within four sets of magnetic cores are shown. Figure 5(a) shows the magnetic flux density distribution curve for a single permeability, where μ = 1500. From Figure 5(a), it can be seen that when the permeability of each nanocrystalline ring layer is the same, the magnetic flux density distribution is non-uniform, with the inner layer having a higher magnetic flux density than the outer layer, which is consistent with the theoretical analysis above. When the permeability of the ring core increases in a gradient, such as... Figures 5(b)-5(d)The magnetic flux density curve along the radius is sawtooth-shaped, and the number of sawtooths is consistent with the number of sublayers. The toroidal core in Figure 5(b) consists of four nanocrystalline rings with permeability ranging from 1500-2000-2500-3000 from the inside to the outside, with a gradient of 500. The permeability is calculated according to equation (4), and each layer has the same thickness of 2.5 mm. As can be seen from Figure 5(b), in each sublayer, the magnetic flux density value along the radial direction tends to decrease from the inside to the outside. However, the trend of magnetic flux density change is opposite along the entire radius. Due to the lower permeability, the magnetic flux density value of the inner layer is lower than that of the outer layer. The same situation exists in Figure 5(d). The toroidal core in Figure 5(d) consists of eight nanocrystalline rings with a thickness of 1.25 mm. The permeability ranges from 1400-2800 from the inside to the outside, with a gradient of 200. The toroidal core in Figure 5(c) consists of four nanocrystalline rings, each 2.5 mm thick, with permeabilities of 1600, 1800, 2000, and 2200 from the inside out. Figure 5(c) shows that within each sublayer, the magnetic flux density along the radial direction tends to decrease from the inside out. However, across the entire radius, the magnetic flux density fluctuation in Figure 5(c) is smaller compared to Figures 5(b) and 5(d). This indicates that when the number of layers is fixed, reducing the permeability gradient helps to balance the magnetic flux distribution. Comparing Figure 5(c) and 5(d), it can be shown that when the permeability gradient is the same, increasing the number of layers does not make the magnetic flux distribution more uniform. This is because increasing the number of layers further increases the permeability difference between the outer and inner layers, leading to a higher difference in magnetic flux density, thus failing to alleviate the problem of uneven magnetic flux distribution.

[0104] Through the magnetic flux density simulation of the four sets of toroidal cores, under the same magnetoresistance distribution, the magnetic flux density distribution curve in Figure 5(c) exhibits the least fluctuation. Compared to Figures 5(a), 5(b), and 5(d), its magnetic flux density distribution is the most uniform. Therefore, the number of layers, the permeability of each sublayer, and the thickness corresponding to Figure 5(c) can be used as the target number of layers, target thickness, and target permeability of the nanocrystalline toroidal core. Fabricating toroidal cores based on these target number of layers, target thickness, and target permeability can make the magnetic flux density distribution inside the toroidal core tend to be uniform.

[0105] Based on the above-described toroidal magnetic core, this specification provides a method for preparing a toroidal magnetic core with uniform magnetic flux density, such as... Figure 6 As shown in the diagram. This specification provides the operational steps of the methods described in the embodiments or flowcharts, but based on conventional or non-inventive labor, more or fewer operational steps may be included. The order of steps listed in the embodiments is merely one possible execution order among many steps and does not represent the only execution order. In actual system or device products, the methods shown in the embodiments or drawings can be executed sequentially or in parallel. Specifically, as shown in the diagram... Figure 6As shown, the method may include:

[0106] S601: Determine the target number of nanocrystalline ribbon layers, the target thickness of each nanocrystalline ribbon layer, and the target permeability of the toroidal magnetic core to be prepared;

[0107] S602: Obtain several nanocrystalline ribbons with target thickness and target permeability;

[0108] S603: Combine several nanocrystalline ribbons of the target layer according to the radial gradient of magnetic permeability from the inner layer to the outer layer to form a ring-shaped magnetic core.

[0109] It is understandable that the target number of nanocrystalline ribbon layers, the target thickness of each nanocrystalline ribbon layer, and the target permeability of the toroidal magnetic core to be fabricated are determined by... Figure 4 The method is determined in this specification. In some embodiments, multiple nanocrystalline ribbons are wound layer by layer according to a radial gradient increase in magnetic permeability from the inner layer to the outer layer to form a toroidal magnetic core. In other embodiments, multiple nanocrystalline ribbons can also be formed into a toroidal magnetic core through processes such as nesting, stacking, or bonding.

[0110] In some embodiments of this specification, such as Figure 7 and Figure 8 As shown, the method for preparing nanocrystalline ribbons with the target magnetic permeability includes:

[0111] S701: Determine the corresponding degree of fragmentation based on the target magnetic permeability of each layer of nanocrystalline ribbon;

[0112] S702: Each layer of nanocrystalline ribbon is crushed using a crushing device;

[0113] S703: The degree of breakage of each layer of nanocrystalline ribbon is detected by a breakage degree sensor after the breakage is completed;

[0114] S704: Based on the detection signal fed back by the crushing degree sensor, determine whether the magnetic permeability of each layer of nanocrystalline ribbon after crushing reaches the corresponding target magnetic permeability;

[0115] S705: If so, the nanocrystalline ribbon after the crushing is completed will be used as the ribbon for preparing the toroidal magnetic core.

[0116] S706: If not, adjust the crushing pressure of the crushing device according to the detection signal, and re-crush the nanocrystalline ribbon according to the adjusted crushing pressure until the magnetic permeability of the nanocrystalline thin sheet after crushing reaches the target magnetic permeability.

[0117] It is understandable that if the target radial thickness of the toroidal magnetic core to be prepared is 10 mm, Figure 5(c) shows that the target number of nanocrystalline ribbon layers for the toroidal magnetic core to be prepared is 4, the target thickness of each nanocrystalline ribbon layer is 2.5 mm, and the target permeability of each layer is 1600-1800-2000-2200. The corresponding degree of fragmentation D can be determined based on the target permeability of each nanocrystalline ribbon layer. The degree of fragmentation D can be used to describe the crushing process of the nanocrystalline ribbon. In some embodiments of this specification, the degree of fragmentation corresponding to each nanocrystalline ribbon layer is determined using the following formula:

[0118]

[0119] Where D(n) represents the degree of fragmentation of the nth layer of nanocrystalline ribbon, μ r (n) represents the target magnetic permeability of the nth nanocrystalline ribbon, μ initial (n) represents the initial magnetic permeability of the nth layer of nanocrystalline ribbon. In the embodiments of this specification, the initial magnetic permeability of the nanocrystals is 10000. Therefore, according to equation (6), the target degree of fragmentation of each layer can be calculated, as shown in Table 1.

[0120] Table 1

[0121]

[0122] After determining the degree of fragmentation of each layer of nanocrystalline ribbon, a crushing device is needed to crush the nanocrystalline ribbon. In some embodiments of this specification, the crushing device includes a crushing roller, a fragmentation degree sensor, and a controller, such as... Figure 8As shown, a downward pressure F is applied vertically to the surface of the nanocrystalline ribbon by a crushing roller to bring the magnetic permeability of the nanocrystalline ribbon closer to the target magnetic permeability. After the crushing roller completes the crushing process of the nanocrystalline ribbon, it is necessary to accurately know the actual degree of crushing achieved in this process to determine whether the target magnetic permeability has been reached. Therefore, a crushing degree sensor can be used for detection. The crushing degree sensor can measure the current degree of crushing of the nanocrystalline ribbon and convert it into a processable detection signal, which is transmitted to the controller. Since there is a correlation between the degree of crushing and the magnetic permeability, the detection signal fed back by the crushing degree sensor can be used in conjunction with the correspondence in Table 1 to determine whether the current magnetic permeability of the nanocrystalline ribbon has reached the preset target magnetic permeability. If the determination shows that the magnetic permeability of the nanocrystalline ribbon has reached the target magnetic permeability, then the crushing process is successful, and this layer of nanocrystalline ribbon can be used for the subsequent preparation of toroidal magnetic cores, serving as qualified raw material for the next preparation stage. If the determination shows that the magnetic permeability of the nanocrystalline ribbon has not reached the target magnetic permeability, the crushing process needs to be adjusted. Based on the detection signal fed back by the crushing degree sensor, the controller can calculate the difference between the current crushing degree and the target crushing degree, and then adjust the crushing pressure of the crushing roller. After adjusting the crushing pressure, the crushing device is used again to crush the nanocrystalline ribbon, and the above detection and judgment steps are repeated until the magnetic permeability of the nanocrystalline ribbon reaches the target magnetic permeability.

[0123] In this embodiment, one side of the nanocrystalline ribbon is covered with pressure-sensitive adhesive. The pressure-sensitive adhesive is used to bond adjacent layers during the winding process of the nanocrystalline ribbon. Optionally, the thickness of the pressure-sensitive adhesive is 3 μm. A release film is covered on the pressure-sensitive adhesive. The release film is used to prevent interlayer adhesion of the nanocrystalline ribbon before winding. Optionally, the thickness of the release film is 75 μm.

[0124] In the embodiments described in this specification, such as Figure 8As shown, a rolling mill is used to wind several nanocrystalline ribbons of the target layer layer by layer according to a radial gradient of magnetic permeability from the inner layer to the outer layer, forming a ring-shaped magnetic core. The rolling mill includes a first drive roller A1, a second drive roller A2, a release film recovery roller B3, a first support roller B1, and a second support roller B2. The first drive roller A1 is used to fix the starting end of the nanocrystalline ribbon with the lowest magnetic permeability, serving as the inner layer reference for winding, and provides unwinding power through constant speed rotation, controlling the ribbon transport speed. The second drive roller A2 is used to separate the release film from the ribbon through roller surface friction, exposing the pressure-sensitive adhesive, and winding the stripped release film into the inner layer of the nanocrystalline ribbon core, providing winding power. The release film recovery roller B3 is used to simultaneously collect the release film peeled off by the second drive roller A2, preventing film accumulation. The first support roller B1 and the second support roller B2 constitute a two-point support structure for ribbon transport, preventing ribbon sagging or serpentine deviation and ensuring the stability of the winding process. The first drive roller A1, the second drive roller A2, the release film recovery roller B3, and the second support roller B2 rotate clockwise, while the first support roller B1 rotates counterclockwise.

[0125] In some embodiments of this specification, such as Figure 8 As shown, the method of using a rolling mill to wind several nanocrystalline ribbons of the target layer layer by layer according to the radial gradient of magnetic permeability from the inner layer to the outer layer to form a ring-shaped magnetic core includes:

[0126] The nanocrystalline ribbon with the lowest magnetic permeability is fixed to the first drive roller A1. The first drive roller A1 drives the nanocrystalline ribbon to rotate and is transmitted to the second drive roller A2 through the first support roller B1 and the second support roller B2.

[0127] The second drive roller A2 peels off the release film covering the nanocrystalline ribbon and transfers the release film to the release film recycling roller B3, and the second drive roller A2 winds the nanocrystalline ribbon after peeling off the release film into the inner layer of the nanocrystalline ribbon core.

[0128] The release film recovery roller B3 receives the release film and winds it around for collection;

[0129] By sequentially replacing nanocrystalline ribbons with increasing magnetic permeability, the above steps are repeated. Each layer of nanocrystalline ribbon is bonded together with pressure-sensitive adhesive to form a toroidal magnetic core.

[0130] In some embodiments of this specification, to verify the uniform magnetic flux density distribution performance of the prepared toroidal magnetic core, the internal thermal distribution of a toroidal magnetic core with four nanocrystalline bands, each 2.5 mm thick, and permeabilities of 1600, 1800, 2000, and 2200 from the inside out, was compared with that of a toroidal magnetic core with a single permeability (μ = 1500). Verifying the uniform magnetic flux density distribution performance of the toroidal magnetic core through thermal distribution is primarily because measuring the magnetic flux density distribution within the toroidal magnetic core would require disrupting its physical structure (e.g., drilling), which could affect the accuracy of the verification results. Since the internal losses of the magnetic core ultimately translate into thermal rise, the internal thermal distribution of the magnetic core can effectively reflect the magnetic flux density distribution. In the thermal rise verification, the magnetic induction was excited by a sinusoidal signal with a frequency of 30 kHz, and the excitation voltage could be modulated to control the peak magnetic induction intensity Bm in each group. Temperature data were recorded over 15 minutes when Bm was 0.45 T, as shown in Table 2.

[0131] Table 2

[0132]

[0133] TP1, TP2, and TP3 are thermal sensors arranged in the toroidal core with a 2.5mm gap along the radial direction, used to measure the temperature of the toroidal core. Schematic diagrams of the temperature rise of the two sets of toroidal cores are shown in Figures 9(a) and 9(b). It can be observed that at μ = 1500, the heat distribution is very uneven, with the temperature on the inner side of the core being higher than on the outer side, reaching a maximum of 92.2℃ and a minimum of 82.86℃, a temperature difference of 9.34℃. In contrast, the toroidal core with a gradient increase in permeability from the inner to the outer layer exhibits a more uniform heat distribution, with a maximum temperature of 88.72℃ and a minimum of 86.21℃, a temperature difference of only 2.51℃. Therefore, by setting a gradient increase in permeability from the inside to the outside of the toroidal core, the magnetic flux density distribution of the toroidal core can be made more uniform, thereby reducing the temperature difference between the inside and outside of the toroidal core and improving the thermal stability and utilization rate of the internal materials.

[0134] In summary, the toroidal magnetic core with uniform magnetic flux density and its fabrication method provided in this specification achieve a more uniform magnetic flux density distribution by setting a gradient increase in permeability from the inside to the outside of the toroidal magnetic core. This reduces the temperature difference between the inside and outside of the toroidal magnetic core, improves its thermal stability, and maximizes the utilization rate of internal materials. Furthermore, compared to other methods for manufacturing constant flux inductors, the toroidal magnetic core fabrication method provided in this specification uses automated machinery, resulting in a simple fabrication process that eliminates the need for complex windings, material configurations, and stringent sintering processes, thus improving production efficiency.

[0135] It should be understood that in the various embodiments of this specification, the sequence number of each process does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this specification.

[0136] It should also be understood that, in the embodiments of this specification, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this specification generally indicates that the preceding and following related objects have an "or" relationship.

[0137] The various embodiments in this invention are described in a progressive manner. For the same or similar parts between the various embodiments, please refer to each other. Each embodiment focuses on describing the differences from other embodiments.

[0138] In the description of this invention, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the present invention. In this invention, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this invention, as well as the features of different embodiments or examples.

[0139] The above description is merely an embodiment of this application and is not intended to limit the scope of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of the claims of this application.

Claims

1. A toroidal magnetic core with uniform magnetic flux density, characterized in that, The toroidal magnetic core comprises multiple nested nanocrystalline rings, the permeability of which increases radially from the inner to the outer layer, so as to make the magnetic flux density distribution of the toroidal magnetic core tend to be uniform.

2. The toroidal magnetic core according to claim 1, characterized in that, The multiple nested nanocrystalline rings have the same thickness.

3. The toroidal magnetic core according to claim 2, characterized in that, The number of layers, thickness, and permeability of the nanocrystalline rings were determined using the following method: Based on the target radial thickness of the toroidal core, multiple toroidal core simulation models are divided into multiple sub-layers along the radial direction on an average basis, resulting in multiple toroidal core simulation models with different numbers of sub-layers. The permeability of each sublayer in the simulation model of each toroidal core is calculated based on the preset magnetic reluctance distribution. The number of layers, permeability and thickness of each sub-layer of the simulation model of each toroidal magnetic core are input into the finite element analysis model for simulation, and the magnetic flux density distribution curve of each toroidal magnetic core simulation model is obtained accordingly. Calculate the degree of fluctuation in the magnetic flux density distribution curve of each toroidal core simulation model; The number of layers, the permeability of each sublayer, and the thickness of the toroidal core simulation model corresponding to the magnetic flux density distribution curve with the smallest fluctuation are selected as the target number of layers, target thickness, and target permeability of the nanocrystalline toroidal band.

4. The toroidal magnetic core according to claim 3, characterized in that, The calculation of the permeability of each sublayer in each toroidal core simulation model based on the preset reluctance distribution includes: The thickness of each sub-layer is determined based on the target radial thickness of the toroidal core and the number of layers in the simulation model of each toroidal core. The magnetic flux path length of each sublayer is determined based on the thickness of each sublayer. The magnetoresistance of each sublayer is determined according to the preset magnetoresistance distribution; The permeability of each sublayer is calculated based on the flux path length and magnetic reluctance of each sublayer.

5. The toroidal magnetic core according to claim 4, characterized in that, The step of determining the magnetic flux path length of each sublayer based on the thickness of each sublayer includes: The flux path length of each sublayer is determined using the following formula: l e (n)=2π(r in +dr); Among them, l e (n) represents the flux path length of the nth sublayer, r in dr represents the inner diameter of the nth sublayer, and dr represents the thickness of the nth sublayer.

6. The toroidal magnetic core according to claim 4, characterized in that, The magnetic reluctance distribution is represented by the following formula: Where N represents the number of coil turns, i represents the coil current, and r in r represents the inner diameter of the nth sublayer. on Let φ(n) represent the outer diameter of the nth sublayer, and let φ(n) represent the magnetic flux of the nth sublayer. This represents the magnetoresistance of the nth sublayer.

7. The toroidal magnetic core according to claim 4, characterized in that, The calculation of the permeability of each sublayer based on the magnetic flux path length and magnetic reluctance of each sublayer includes: The permeability of each sublayer is calculated using the following formula: Where, μ r (n) represents the permeability of the nth sublayer, l e (n) represents the magnetic flux path length of the nth sublayer. Let μn represent the magnetoresistance of the nth sublayer, μ0 represent the free permeability, and An represent the magnetic reluctance of the nth sublayer. c (n) represents the cross-sectional area of ​​the nth sublayer.

8. A method for preparing a toroidal magnetic core with uniform magnetic flux density, characterized in that, The method includes: Determine the target number of nanocrystalline ribbon layers, the target thickness of each nanocrystalline ribbon layer, and the target permeability of the toroidal magnetic core to be prepared. Obtain several nanocrystalline ribbons with target thickness and target magnetic permeability; The target layer consists of several nanocrystalline ribbons whose magnetic permeability increases radially from the inner to the outer layer to form a ring-shaped magnetic core.

9. The method according to claim 8, characterized in that, Methods for preparing nanocrystalline ribbons with target magnetic permeability include: The degree of fragmentation is determined based on the target magnetic permeability of each layer of nanocrystalline ribbon. Each layer of nanocrystalline ribbon is crushed using a crushing device; The degree of breakage of each layer of nanocrystalline ribbon after the breakage process is detected using a breakage degree sensor; The magnetic permeability of each layer of nanocrystalline ribbon after crushing is determined based on the detection signal fed back by the crushing degree sensor. If not, the crushing pressure of the crushing device is adjusted according to the detection signal, and the nanocrystalline ribbon is crushed again according to the adjusted crushing pressure until the magnetic permeability of the nanocrystalline thin sheet after crushing reaches the target magnetic permeability.

10. The method according to claim 9, characterized in that, The determination of the corresponding degree of fragmentation based on the target magnetic permeability of each layer of nanocrystalline ribbon includes: The degree of fragmentation for each layer of nanocrystalline ribbon is determined using the following formula: Where D(n) represents the degree of fragmentation of the nth layer of nanocrystalline ribbon, μ r (n) represents the target magnetic permeability of the nth nanocrystalline ribbon, μ initial (n) represents the initial magnetic permeability of the nth layer of nanocrystalline ribbon.

11. The method according to claim 8, characterized in that, The step of combining several nanocrystalline ribbons of the target layer according to a radial gradient increase in magnetic permeability from the inner to the outer layer includes: Using a rolling mill, several nanocrystalline ribbons of the target layer are wound layer by layer according to the radial gradient of magnetic permeability from the inner layer to the outer layer to form a ring-shaped magnetic core.

12. The method according to claim 8, characterized in that, One side of the nanocrystalline ribbon is covered with pressure-sensitive adhesive, which is used to bond adjacent layers during the winding of the nanocrystalline ribbon. The pressure-sensitive adhesive is covered with a release film, which is used to prevent interlayer adhesion of the nanocrystalline ribbon before winding.

13. The method according to claim 11, characterized in that, The roller pressing equipment includes a first drive roller, a second drive roller, a release film recovery roller, a first support roller, and a second support roller; The method of using a rolling mill to wind several nanocrystalline ribbons of the target layer layer by layer according to the radial gradient of magnetic permeability from the inner layer to the outer layer to form a ring-shaped magnetic core includes: The nanocrystalline ribbon with the lowest magnetic permeability is fixed to the first drive roller. The first drive roller drives the nanocrystalline ribbon to rotate and is transmitted to the second drive roller through the first support roller and the second support roller. The second drive roller peels off the release film covering the nanocrystalline ribbon and transfers the release film to the release film recycling roller, and the second drive roller winds the nanocrystalline ribbon after peeling off the release film into the inner layer of the nanocrystalline ribbon core. The release film recovery roller receives the release film and winds it around for collection; By sequentially replacing nanocrystalline ribbons with increasing magnetic permeability, the above steps are repeated. Each layer of nanocrystalline ribbon is bonded together with pressure-sensitive adhesive to form a toroidal magnetic core.

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