Ferrite magnetic core preparation method

Abstract

The invention discloses a ferrite magnetic core preparation method, which comprises the following steps: determining the material types of an air gap filling medium and a magnetic core main body magnetic material, the air gap filling medium can perform magnetic conduction, and the magnetic conductivity of the air gap filling medium is far less than the magnetic conductivity of the magnetic core main body magnetic material; preparing particles of the air gap filling medium and the magnetic core main body magnetic material; the air gap filling medium and the magnetic core main body magnetic material are integrally prepared and formed, and a final formed blank is obtained; sintering the finally formed blank to obtain a ferrite core main body with the air gap filling medium; and then preparing another ferrite magnetic core main body with the same shape, and assembling the two ferrite magnetic core main bodies and the electrified coil to form a magnetic circuit closed loop. The air gap filling medium is added into the ferrite magnetic core body, magnetic lines in a magnetic circuit can be restrained to penetrate through the medium, large magnetic resistance can be formed when the magnetic lines pass through the air gap, and the magnetic leakage phenomenon is effectively reduced while the energy of the magnetic core body is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of magnetic core preparation, and in particular relates to a method for preparing a ferrite magnetic core. Background Art

[0002] Since the magnetic permeability of soft ferrite, power ferrite and other types of magnetic cores is generally very high, magnetic saturation is easily generated with a slight excitation electric field. Therefore, in the actual application of magnetic components such as transformers and inductors, it is usually adopted to increase the air gap in the magnetic circuit to reduce the effective magnetic permeability, so that the magnetic components can store more magnetic energy.

[0003] However, the introduction of the air gap is bound to enhance the leakage magnetic field distribution of the inductor. The leakage magnetic field of the magnetic component can be divided into external leakage magnetic field and internal leakage magnetic field. When the internal leakage magnetic field passes through the coil, eddy currents will be generated in the coil. The appearance of eddy currents will dissipate energy and cause magnetic energy loss in the magnetic component; when the external leakage magnetic field passes through the coil, current will be induced in the coil. If the intensity of the external leakage magnetic field is large enough, a large induced electromotive force and current will be generated in the coil, causing noise, interference and other impacts on the lines and equipment.

[0004] In order to solve the above problems, the Chinese invention patent with application number 201520957617.2 provides a segmented air gap magnetic core structure, which inserts multiple manganese-zinc ferrite materials of the same material with the same size as the middle column of the magnetic material into the single-segment air gap of the existing magnetic core, and uses non-ferromagnetic media to isolate these materials to form multiple smaller air gaps to form segmented air gaps, thereby greatly reducing the leakage magnetic phenomenon of the magnetic element. However, in the above-mentioned magnetic element, the magnetic circuit between the segmented air gap magnetic material and the magnetic core body located at the top is disconnected at the non-ferromagnetic medium, and leakage magnetic phenomena will still occur at these two places when the magnetic core is working, so the magnetic core structure still cannot effectively solve the leakage magnetic problem.

[0005] Based on the above, a method for preparing a ferrite core is urgently needed to solve the technical problems existing in the prior art. Summary of the invention

[0006] The object of the present invention is to provide a method for preparing a ferrite core, which can further reduce the problem of magnetic leakage when magnetic lines of force pass through the core and effectively increase the total magnetic energy reserve of the core.

[0007] To achieve this object, the present invention adopts the following technical solutions:

[0008] A method for preparing a ferrite core, comprising:

[0009] S1. Determine the material types of the air gap filling medium and the magnetic material of the magnetic core body, the air gap filling medium can be magnetically conductive, and the magnetic permeability of the air gap filling medium is much smaller than the magnetic permeability of the magnetic material of the magnetic core body, and determine the length of the air gap and the filling amount of the air gap filling medium;

[0010] S2, preparing the granular material of the air gap filling medium and the granular material of the magnetic core main body magnetic material;

[0011] S3, integrally preparing and molding the air gap filling medium and the magnetic core main body magnetic material to obtain a final molded blank;

[0012] S4, sintering the final formed blank to obtain a ferrite core body with the air gap filling medium;

[0013] S5. Prepare another ferrite core body, wherein the two ferrite core bodies have the same shape, and assemble the two ferrite core bodies with the energized coil to form a closed magnetic circuit.

[0014] Optionally, the final molded blank is prepared by a powder multi-station molding process.

[0015] Optionally, S3 specifically includes the following steps:

[0016] S31, performing a first pressing and forming of part of the granular material of the magnetic core main body magnetic material through a mold to obtain a primary formed blank;

[0017] S32, opening the mold, and filling a set amount of granular material of the air gap filling medium into a designated position in the mold;

[0018] S33, filling the entire mold with the remaining particulate material of the magnetic core main body magnetic material and then performing a second compression molding to obtain the final molded blank.

[0019] Optionally, the density of the initially formed blank is 90% to 95% of the density of the finally formed blank.

[0020] Optionally, the final formed blank is an "E"-shaped structure.

[0021] Optionally, the final formed blank comprises side columns and a center column, at least one of the side columns and the center column being provided with the air gap filling medium.

[0022] Optionally, the air gap filling medium is nickel-manganese ferrite powder, and the main magnetic material of the magnetic core is manganese-zinc ferrite.

[0023] Optionally, the granular material of the air gap filling medium and the granular material of the core main body magnetic material are both prepared by a wet process.

[0024] Optionally, the method further comprises the steps of:

[0025] S6. Grinding the mating surfaces of the two sintered ferrite core bodies.

[0026] Beneficial effects: The present invention assembles two ferrite core bodies of the same shape with an energized coil to form a closed magnetic circuit, which can eliminate the air gap with air as the medium on the magnetic flux path, greatly reducing the possibility of magnetic leakage between the two ferrite core bodies; in addition, by setting an air gap in the ferrite core body and filling the air gap with a medium that can conduct magnetic conductivity and has a magnetic permeability less than that of the magnetic material of the core body, since the medium has a certain magnetic permeability, it can constrain the magnetic lines of force to penetrate the medium, and can form a large magnetic resistance when the magnetic lines of force pass through the air gap, thereby improving the magnetic energy storage capacity of the core body while effectively reducing the magnetic leakage phenomenon. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a schematic flow chart of the method for preparing the ferrite core provided by the invention;

[0028] Figure 2 It is a specific flow chart of step S3 in the method for preparing a ferrite core provided by the present invention;

[0029] Figure 3 It is a schematic diagram of the forming of the primary forming blank formed at the first station in the present invention;

[0030] Figure 4 It is a schematic diagram of forming after adding air gap filling medium to the primary forming blank in the present invention;

[0031] Figure 5 It is a schematic diagram of the final formed blank formed at the second station in the present invention;

[0032] Figure 6 is a front view of the ferrite core provided by the present invention;

[0033] Figure 7 It is a schematic diagram of the structure formed by abutting the end faces of the paths through which the magnetic lines of force of two ferrite core bodies pass.

[0034] In the figure:

[0035] 1. Initially formed blank; 2. Final formed blank; 21. Center column; 22. Side column; 23. Matching surface;

[0036] 30. Pressing column; 31. First upper die; 32. Concave die; 321. Pressing groove; 33. Lower die; 34. Second upper die;

[0037] 4. Air gap filling medium. DETAILED DESCRIPTION

[0038] In the description of the present invention, it should be noted that the terms "center", "up", "down", "left", "right", "vertical", "horizontal", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance. Among them, the terms "first position" and "second position" are two different positions.

[0039] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection or a detachable connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, and it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0040] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0041] Combine the following Figures 1 to 7 The ferrite core preparation method provided by the present invention is introduced with specific embodiments. For the convenience of description, the preparation method of the ferrite core with an "E" type structure is used as an example to meet the application fields requiring efficient current transmission such as inductors. Of course, in some other embodiments, those skilled in the art can also design the cross-sectional shape of the ferrite core into other shapes such as "U" shape and "P" shape according to the actual working conditions. As long as it can be ensured that the two ferrite cores produced later can form a closed magnetic circuit after being assembled with the energized coil, it is within the protection scope of the present invention.

[0042] Specifically, Figure 1 As shown, the ferrite core preparation method includes the following steps:

[0043] S1. Determine the material types of the air gap filling medium 4 and the main magnetic material of the magnetic core. The air gap filling medium 4 can conduct magnetic conductivity, and the magnetic permeability of the air gap filling medium 4 is much smaller than the magnetic permeability of the main magnetic material of the magnetic core. Determine the length of the air gap and the filling amount of the air gap filling medium 4.

[0044] That is to say, first, it is determined that an air gap is to be set in the ferrite core. Setting the air gap can reduce the effective magnetic permeability of the ferrite core, and can make the ferrite core store more energy under the same magnetic field strength. Secondly, illustratively, this embodiment selects nickel-manganese ferrite powder as the air gap filling medium 4, and selects manganese-zinc ferrite (i.e., adding a set content of manganese dioxide, etc. to manganese-zinc ferrite) as the main magnetic material of the magnetic core. On the one hand, this makes the magnetic permeability of the main body of the magnetic core larger, ensuring that the related magnetic components have good performance; on the other hand, since a set content of non-magnetic elements (such as copper, calcium, etc.) is usually added to nickel-manganese ferrite, the magnetic permeability of the air gap can be made smaller, which is conducive to reducing the magnetic permeability of the magnetic core to a certain extent. Finally, according to the specific requirements for the inductance (ability to store and release magnetic energy) of the ferrite core under actual working conditions, the set air gap length and the filling amount of the air gap filling medium 4 are calculated in combination with the empirical formula.

[0045] S2. Prepare granular material of the air gap filling medium 4 and granular material of the magnetic core main body magnetic material.

[0046] Optionally, in this embodiment, the air gap filling medium 4 and the magnetic material of the magnetic core body are prepared by a wet process. For example, the preparation of the granular material of the air gap filling medium 4 is used as an example for explanation: first, the air gap filling medium 4 is prepared according to the proportion of the components; then the air gap filling medium 4 is added to the grinder, and sufficient water or other grinding media are added and then the grinder is turned on for grinding. By adjusting the speed and time of the grinder, the air gap filling medium 4 material can be gradually ground and crushed to reach the required particle size. After the grinding is completed, the granular material and the grinding medium in the grinder are separated by centrifugation or filtration; then, the granular material is prepared into a suitable suspension, and after heating, it is sprayed into a drying chamber through a sprayer, and the sprayed suspension is heated and dried by high-temperature air in the drying chamber, so that the air gap filling medium 4 quickly loses moisture and forms particles, and the particles are collected after drying; finally, the particles are added to the rotary kiln for pre-burning, so that the material of the air gap filling medium 4 has a higher chemical purity and magnetic properties, thereby meeting the specific requirements for the magnetic permeability of the air gap filling medium 4 under actual working conditions.

[0047] It should be noted that the preparation process of the granular material of the core main body magnetic material is the same as the process of preparing the granular material of the air gap filling medium 4, and the present invention will not be repeated here.

[0048] S3, integrally preparing and molding the air gap filling medium 4 and the core main body magnetic material to obtain a final molded blank 2.

[0049] For example, in this embodiment, the air gap filling medium 4 and the magnetic core main body magnetic material are integrally prepared by a powder multi-station molding process. The final molded blank 2 is formed through multiple processing steps, which can effectively improve the controllability and stability of the molding process and help extend the service life of the molded part.

[0050] Specifically, refer to Figure 2 As shown, the specific steps of integrally preparing the air gap filling medium 4 and the magnetic core main body magnetic material include:

[0051] S31, performing a first pressing and forming of part of the granular material of the magnetic core main body magnetic material through a mold to obtain a primary formed blank 1.

[0052] In this step, the primary molded blank 1 is pressed and molded at the first station. Figure 3 As shown, firstly, some granular materials of the magnetic core main body magnetic material are filled into the mold for pressing. The density of the initial molded blank 1 obtained by pressing is required to reach 90% to 95% of the density of the final product. This can ensure that the initial molded blank 1 formed by pressing has a certain stability and strength, thereby laying a foundation for subsequent processing and sintering, and can also reduce the unevenness and deformation during subsequent processing and sintering.

[0053] Specifically, Figure 3 As shown, the mold includes a first upper mold 31, a die 32 and a lower mold 33. In the first workstation, the cross-sectional shapes of the first upper mold 31 and the lower mold 33 are the same, and both include three parallel and spaced pressing columns 30. Correspondingly, the die 32 is provided with three pressing grooves 321 corresponding to the pressing columns 30. The three pressing columns 30 of the lower mold 33 are inserted into the three pressing grooves 321 one by one with limited positions, and then part of the granular material of the magnetic material of the magnetic core body is added into the pressing grooves 321 of the die 32, and then the three pressing columns 30 of the first upper mold 31 are inserted into the pressing grooves 321 of the die 32 one by one with corresponding positions, and part of the granular material of the magnetic material of the magnetic core body is pressed, so that a part of the middle column 21 and a part of each side column 22 can be pressed to form the above-mentioned primary molded blank 1.

[0054] S32, opening the mold, and filling a set amount of granular material of the air gap filling medium 4 into a designated position in the mold.

[0055] In this step, refer to Figure 4 As shown, the mold is opened and a set amount of granular material of the air gap filling medium 4 is added into the concave mold 32. Figure 5As shown, the final formed blank 2 obtained after the air gap filling medium 4 and the magnetic core main body magnetic material are integrally prepared is an "E"-shaped structure, which includes a middle column 21 and two side columns 22, and the energized coil (not shown in the figure) is wound at the position of the middle column 21. In this embodiment, a set amount of granular material of the air gap filling medium 4 is added at the position of the middle column 21. This is because the width of the middle column 21 is usually greater than the width of the side column 22, so that the magnetic path and magnetic flux density at the middle column 21 are greater than the magnetic path at the side column 22. By setting an air gap at the position of the middle column 21, the magnetic flux density can be reduced at this point, thereby increasing the inductance value to enhance the performance of equipment such as inductors.

[0056] Of course, in some other parallel embodiments, air gaps may be provided at both the middle column 21 and the side column 22, which can not only enhance the performance of devices such as inductors; but also, when the current increases and causes the magnetic flux to saturate the magnetic core, providing an air gap at the side column 22 can cause a magnetic potential difference to appear in the air gap, thereby compensating for the saturation effect and ensuring the linear characteristics of the inductor.

[0057] In some other parallel embodiments, an air gap may be provided only at the side column 22. Since the side column is usually located at the periphery of the ferrite core, it is easier to be ventilated and cooled, which helps to alleviate the problem of excessive temperature of the ferrite core and improves heat dissipation.

[0058] S33, after the remaining particulate material of the magnetic core main body magnetic material fills the entire mold, a second pressing molding is performed to obtain a final molded blank 2.

[0059] In this step, refer to Figure 6 As shown, the final molded blank 2 is press-formed at the second station; in the second station, the cross-sectional shapes of the second upper die 34 and the lower die 33 are different, and only the lower die 33 includes three parallel and spaced pressure columns 30, and the width of the pressure column 30 of the upper die is equal to the width between the two outer pressure columns 30 in the lower die 33, and the depth of the pressure groove 321 of the die 32 is less than the depth of the entire inner cavity of the die 32; the three pressure columns 30 of the lower die 33 are still in the state of being inserted in the pressure groove 321, at this time, the remaining part of the granular material of the magnetic core main body magnetic material is added to fill the entire pressure groove 321 of the die 32, and then the pressure column 30 of the upper die is inserted into the remaining part of the inner cavity of the die 32 for pressing, so that the other part of the middle column 21, the other part of each side column 22 and the "beam" part of the final molded blank 2 can be pressed integrally with the primary molded blank 1, thereby obtaining the final molded blank 2.

[0060] S4. Sintering the final formed blank 2 to obtain a ferrite core body with an air gap filling medium.

[0061] Specifically in this embodiment, the above-mentioned final molded blank 2 is placed in a nitrogen kiln, and by controlling the sintering temperature, insulation time and oxygen content, the nickel-manganese ferrite material and the manganese-zinc ferrite material used in this embodiment are co-fired to complete the ferritization process of the final molded blank 2, thereby obtaining a ferrite core body with an air gap that has the electromagnetic properties and mechanical strength required under actual working conditions.

[0062] It should be noted that, in this embodiment, the air gap filling medium 4 and the magnetic core main body magnetic material are required to be co-fired, that is, the shrinkage rate of the final formed blank during sintering in a nitrogen kiln should be kept basically the same to prevent cracking; in addition, the air gap filling medium 4 and the magnetic core main body magnetic material are required to have a small permeability to each other, so as to reduce the magnetic resistance between the air gap and the magnetic core main body, thereby improving the performance of equipment such as inductors. Therefore, the present invention does not limit the type of material used for the air gap filling medium 4, as long as it can satisfy the requirements of having a certain magnetic permeability, and can be co-fired with the magnetic core main body magnetic material, and the permeability between the magnetic core main body magnetic material is small, it is within the protection scope of the present invention.

[0063] S5. Prepare another ferrite core body, and the two ferrite core bodies have the same shape, and assemble the two ferrite core bodies with the energized coil to form a closed magnetic circuit.

[0064] That is to say, the air gap may not be set in the other ferrite core body prepared, and the other ferrite core body is prepared by an integral die-casting method, and the cross-section of the other ferrite core body is also in an "E" shape, so that the middle column 21 and the side column 22 of the two ferrite core bodies can respectively abut against each other to prevent the magnetic lines from passing through the path ( Figure 7 The dotted line shown in the figure represents the movement path of the magnetic lines of force, and the dotted arrows represent the movement direction of the magnetic lines of force) an air gap with air as the medium appears; when the magnetic core is working, a segmented air gap distribution is also formed on the magnetic circuit.

[0065] Further, in this embodiment, referring to Figure 7 As shown, another ferrite core body is also prepared by step S3 (i.e., step S31 to step S33) so that both ferrite core bodies form segmented air-gap cores. Through the above arrangement, the magnetic design can be further optimized, and the efficiency and thermal performance of devices such as inductors can be further improved; in addition, by setting an air gap in each ferrite core body, the magnetic field can be effectively prevented from radiating into the environment, reducing the power loss of devices such as inductors.

[0066] Through the above-mentioned arrangement, the two ferrite core bodies of the same shape are produced and assembled with the energized coil to form a closed magnetic circuit loop, which can eliminate the air gap with air as the medium on the magnetic flux path, and greatly reduce the possibility of magnetic leakage between the two ferrite core bodies; in addition, by setting an air gap in one of the ferrite core bodies and filling the air gap with a medium that can conduct magnetic conductivity and has a magnetic permeability less than that of the magnetic material of the core body, since the medium has a certain magnetic permeability, it can constrain the magnetic lines of force to penetrate the medium, and can form a large magnetic resistance when the magnetic lines of force pass through the air gap, thereby improving the magnetic energy storage capacity of the core body while effectively reducing the magnetic leakage phenomenon.

[0067] Optionally, in this embodiment, the following steps are also included:

[0068] S6. Grinding the mating surfaces 23 of the two sintered ferrite core bodies.

[0069] That is, the mating surfaces 23 of the two ferrite core bodies formed after sintering in the nitrogen kiln are ground so that the mating surfaces 23 of the two ferrite core bodies can be closely fitted, thereby effectively reducing the magnetic leakage phenomenon of the two ferrite core bodies.

[0070] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the embodiments here. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. A method for preparing a ferrite core, characterized in that: include: S1. Determine the material types of the air gap filling medium (4) and the main magnetic material of the magnetic core, the air gap filling medium (4) can be magnetically conductive, and the magnetic permeability of the air gap filling medium (4) is much smaller than the magnetic permeability of the main magnetic material of the magnetic core, and determine the length of the air gap and the filling amount of the air gap filling medium (4); S2, preparing the granular material of the air gap filling medium (4) and the granular material of the magnetic core main body magnetic material; S3, integrally preparing and molding the air gap filling medium (4) and the magnetic core main body magnetic material to obtain a final molded blank (2); S4, sintering the final formed blank (2) to obtain a ferrite core body with the air gap filling medium (4); S5. Prepare another ferrite core body, wherein the two ferrite core bodies have the same shape, and assemble the two ferrite core bodies with the energized coil to form a closed magnetic circuit.

2. The method for preparing a ferrite core according to claim 1, characterized in that: The final formed blank (2) is prepared by adopting a powder multi-station forming process.

3. The method for preparing a ferrite core according to claim 2, characterized in that: S3 specifically includes the following steps: S31, performing a first pressing and forming of part of the granular material of the magnetic core main body magnetic material by a mold to obtain a primary formed blank (1); S32, opening the mold, and filling a set amount of granular material of the air gap filling medium (4) into a designated position in the mold; S33, filling the entire mold with the remaining particulate material of the magnetic core main body, and then performing a second compression molding to obtain the final molded blank (2).

4. The method for preparing a ferrite core according to claim 3, characterized in that: The density of the primary formed blank (1) is 90% to 95% of the density of the final formed blank (2).

5. The method for preparing a ferrite core according to claim 1, characterized in that: The final formed blank (2) is an "E"-shaped structure.

6. The method for preparing a ferrite core according to claim 5, characterized in that: The final formed blank (2) comprises a side column (22) and a middle column (21), and at least one of the side column (22) and the middle column (21) is provided with the air gap filling medium (4).

7. The method for preparing a ferrite core according to claim 1, characterized in that: The air gap filling medium (4) is made of nickel-manganese ferrite powder, and the main magnetic material of the magnetic core is made of manganese-zinc ferrite.

8. The method for preparing a ferrite core according to claim 1, characterized in that: The granular material of the air gap filling medium (4) and the granular material of the magnetic core main body magnetic material are both prepared by a wet process.

9. The method for preparing a ferrite core according to claim 1, characterized in that: Also includes the steps: S6. Grinding the mating surfaces (23) of the two sintered ferrite core bodies.

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