JP2009004670A - Drum-type inductor and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a drum-type and small inductor which satisfies a high inductance and a low resistance at the same time and to provide its manufacturing method. <P>SOLUTION: The inductor is formed by applying a magnetic resin 2 which is a homogeneous mixture of a magnetic powder 5 and a resin 6 at a constant compounding ratio for covering the periphery 1a of a coil 3 and lateral flange peripheries 1b and the flange surface 1c of a drum core 1 when needed. Also, the magnetic resin 2 is dried and hardened while permanent magnets 4 are arranged on one or both flange surfaces 1c of the drum core 1. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a drum type inductor used in a small electronic device such as a portable device.

  The drum-type inductor has two flange portions, and a coil is wound directly on the winding portion of a drum-type magnetic core (hereinafter referred to as “drum core”) having a concave winding portion sandwiched between the flanges. This is an important electronic component used for so-called smoothing that suppresses the peak value of the voltage and current flowing in the device and reduces the electrical stress on the peripheral components by an open magnetic circuit type inductor constituted by wires.

  In addition, the drum-type inductor is configured by winding a coil directly on a magnetic core, so it is easy to downsize and can be manufactured at low cost. Has a market.

  In recent years, electronic devices have become low voltage and large current, and accordingly, the requirement for handling inductors in the devices has become strict. In an inductor, it is particularly important to cope with a large current. Since the peak value of the current increases as the current increases, a high inductance is required to suppress and smooth the peak value. At the same time, a reduction in resistance is also required in order to suppress loss and heat generation due to the winding resistance component of the coil and a decrease in power supply efficiency.

  FIG. 3 is a diagram for explaining a conventional drum-type inductor. FIG. 3A is a top view, FIG. 3B is a cross-sectional view, and FIG. 3C is an enlarged cross-sectional view of the magnetic resin coating portion. In the conventional drum type inductor, in order to improve the inductance characteristics, as shown in FIGS. 3B and 3C, the magnetic powder 5 is uniformly mixed with the resin 6 at a blending ratio of about 30 vol%. The magnetic resin 2 is applied and filled so as to cover both inner edges of the drum core 1 around which the coil 3 is wound, thereby forming the magnetic resin application portion 8 to form a closed magnetic circuit type structure. At this time, the distribution state of the magnetic powder 5 of the magnetic resin 2 is distributed in a state where the distance A between the magnetic powders is uniformly separated. Such a drum-type inductor is disclosed in, for example, Patent Document 1.

JP 2007-67081 A

  The conventional drum type inductor described above has a structure in which a closed magnetic circuit is formed by applying and filling a magnetic resin so as to cover the outer periphery of the coil wound around the winding portion sandwiched between both ends of the drum core. By increasing the blending ratio of the magnetic powder in the magnetic resin, it is possible to increase the effective magnetic permeability by narrowing the distance between the magnetic powders in the magnetic resin and obtain a high inductance. When the viscosity of the magnetic resin increases, the work efficiency at the time of applying the magnetic resin deteriorates, the magnetic resin filling property to the coil details wound around the drum core deteriorates, and the fixing strength of the magnetic resin portion after curing becomes brittle and peels off. In addition, there was a drawback that breakage easily occurs. For these reasons, there is a limit to the blending ratio of the magnetic powder amount, and the upper limit is about 40 vol%. Therefore, there is a limit to increasing the inductance by the above method.

  In order to obtain a higher inductance, the only way to increase the number of turns of the coil wound around the drum core is to increase the DC resistance of the winding coil or to suppress the increase in DC resistance. Therefore, the wire diameter of the winding coil has to be increased, and there has been a problem that the outer dimensions of the product increase. Therefore, it has been impossible to realize a high inductance with a small shape and with suppressed increase in DC resistance.

  Accordingly, an object of the present invention is to provide a drum-type inductor that satisfies both a compact shape, a high inductance, and a low resistance, and a manufacturing method thereof.

  In order to solve the above-mentioned problems, the present invention applies a magnetic resin so as to cover the entire outer periphery of a coil wound around a concave winding portion sandwiched between both drum cores of a drum-type inductor, thereby providing a closed magnetic circuit type. When an inductor is formed and the magnetic resin is hardened, a permanent magnet is arranged on the surface of the collar portion on the surface perpendicular to the winding center axis direction of the coil of the drum core, so that the magnetism in the magnetic resin is increased. The powder is attracted to the magnetized drum core side, and hardens in a distribution state in which the inner part, which is a part close to the coil of the magnetic resin, is the densest and the outer part, which is a part away from the coil, is the most sparse.

  As a result, the magnetic flux is densely packed, the distance between the magnetic powders is narrow, and the magnetic flux passes through the vicinity of the coil, which has a narrow gap structure, and the average magnetic path length is shortened. As a result, even higher inductance characteristics can be obtained without increasing the number of turns of the coil, and at the same time, an increase in the DC resistance of the coil and an increase in the size of the product can be suppressed.

  Further, by adjusting the magnetic force of the permanent magnet disposed on the surface of the collar portion or the upper surface thereof that is perpendicular to the winding central axis direction of the coil of the drum core, not only the distribution density of the magnetic powder but also the magnetic orientation It is possible to control the inductance characteristics.

  Furthermore, since the magnetic powder density in the magnetic resin is low and the resin density is high in the vicinity of the flange side periphery of the drum core, the fixing strength between the magnetic resin and the drum core can be increased.

  According to the present invention, there is provided an inductor formed by forming a coil in the winding portion of a drum-type magnetic core having two winding portions and a winding portion sandwiched between the flange portions, and at least of the coil A magnetic resin mixed with magnetic powder and resin is disposed so as to cover the outer peripheral portion, and the magnetic resin has a magnetic powder density in a portion near the coil in the outer peripheral portion and a magnetic powder in a portion away from the coil. A drum type inductor characterized by being higher than the density is obtained.

  According to the present invention, a coil is formed in the winding portion of a drum-type magnetic core having two flange portions and a winding portion sandwiched between the flange portions so as to cover at least the outer peripheral portion of the coil. A magnetic resin mixed with magnetic powder and a resin is disposed, and the magnetic resin is cured in a state where a permanent magnet is disposed on a surface orthogonal to the winding central axis direction of the coil of the flange portion. A method for manufacturing a drum-type inductor is obtained.

  According to the present invention, the inductance characteristic is adjusted by combining at least two elements selected from the characteristics of the magnetic powder, the mixing ratio of the magnetic powder and the resin, and the magnetic characteristics of the permanent magnet. A method for manufacturing a drum-type inductor is obtained.

  As described above, according to the present invention, an inductor that forms a closed magnetic circuit by applying a magnetic resin so as to cover the outer periphery of the coil of the drum-type inductor and, if necessary, the flange-side periphery and the flange surface of the drum core. In this case, the magnetic powder in the magnetic resin is attracted to the magnetized drum core side by curing the magnetic resin in a state where a permanent magnet is installed on one or both surfaces of the flange part of the drum core when the magnetic resin is cured. Since the gap between them is narrowed and the effective magnetic permeability of the inductor is increased, a high inductance can be obtained without increasing the number of coil turns, and an increase in DC resistance and an increase in product shape can be suppressed. Furthermore, the fixing strength of the magnetic resin portion can also be improved.

  Further, as a method of adjusting the inductance, in addition to the conventional method of changing the magnetic characteristics and the blending ratio of the magnetic powder, a method of changing the magnetic characteristics of the permanent magnet is also possible. Therefore, the inductance characteristics can be adjusted with high precision and efficiency by combining at least two elements selected from the magnetic characteristics of the magnetic powder, the mixing ratio of the magnetic powder and the resin, and the magnetic characteristics of the permanent magnet. Is possible.

  Embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a diagram for explaining a drum type inductor according to the present invention and a manufacturing method thereof. 1A is a top view, FIG. 1B is a cross-sectional view, and FIG. 1C is an enlarged cross-sectional view of a magnetic resin coating portion.

  As shown in FIG. 1A and FIG. 1B, after the coil 3 is formed in the winding portion sandwiched between the flange portions of the drum core 1, the outer peripheral portion 1a of the coil 3 and the flange portion of the drum core 1 are formed. A magnetic resin coating portion 8 is formed by applying magnetic resin 2 in which magnetic powder 5 and resin 6 are mixed at an arbitrary blending ratio so as to cover side peripheral portion 1 b, and further perpendicular to the winding central axis direction of drum core 1. The permanent magnet 4 is dried and hardened in a state where the permanent magnet 4 is disposed on the collar surface 1c that is a surface to be worked.

  As a result, as shown in FIG. 1C, the magnetic powder 5 of the magnetic resin 2 is attracted to the flange side peripheral portion 1b of the drum core 1 magnetized by the permanent magnet 4 and the outer peripheral portion 1a of the coil 3. It is distributed in a state where the distance B between the magnetic powders is narrow and close. Therefore, a narrow gap structure is formed, the effective permeability of the inductor is increased, and a high inductance can be obtained.

  FIG. 2 is a diagram for explaining the average magnetic path length of the drum-type inductor according to the present invention. The average magnetic path length is a magnetic constant attributed to the shape of the inductor and greatly affects the inductance characteristics. When the length is long, the inductance is small, and when the length is short, the inductance is large.

  FIG. 2A is a diagram showing an average magnetic path length when the permanent magnet 4 is not disposed when the magnetic resin 2 is cured. Since the magnetic powder 5 of the magnetic resin 2 is uniformly distributed, the magnetic flux is magnetic. It can be seen that the average magnetic path length 7 becomes longer because the resin 2 passes almost the center of the coating thickness.

  On the other hand, FIG. 2B is a diagram showing the average magnetic path length when the permanent magnet 4 is arranged on the flange surface 1c of the drum core 1 when the magnetic resin 2 is cured, and the magnetic powder 5 of the magnetic resin 2 is a coil. 3 is concentrated in the outer peripheral portion 1a, so that the magnetic flux passes through the portion, and the average magnetic path length 7 is shortened.

  The material of the drum core 1 is a Ni—Zn ferrite material, but may be a Mn—Zn ferrite material or any magnetic material such as a dust core.

  The shape of the middle leg portion and the collar portion of the drum core 1 described above is a disc shape with a circular cross section. However, any shape may be used as long as it is a square shape, a polygonal shape, or a plate shape having a cross section such as an ellipse or an oval shape. The shape may be acceptable. However, since the structure is wound directly on the drum core, in order to avoid mechanical damage to the insulating film of the winding material, it is desirable to make the middle leg part a cylindrical shape with a circular cross section without corners. .

  In the magnetic resin 2 described above, the blending ratio of the magnetic powder 5 and the resin 6 is 40 vol%. However, since the balance with the initial viscosity of the resin 6 itself is also affected, the blending ratio is appropriately adjusted depending on the resin to be selected. desirable. When the blending ratio of the magnetic powder 5 is increased in order to increase the inductance, the viscosity is lowered, and the coating workability and the adhesion between the drum core and the coil are lowered and become brittle. Therefore, the blending ratio of the magnetic powder is preferably in the range of about 20 to 80%, but about 40 to 70% is preferable. It is even better to use a low viscosity resin. Moreover, about the application | coating position, the outer peripheral part 1a of a coil should just be covered, and the collar part side peripheral part 1b and collar part surface 1c of a drum core may be covered, or may be exposed.

  Although the above-mentioned coil 3 uses the insulation coating copper wire of a general circular cross section, you may use the rectangular copper wire etc. which have a square or an oval cross section.

  The permanent magnet 4 described above may be a general-purpose product such as a sintered magnet made of ferrite, metal, rare earth, or a bonded magnet mixed with resin, and the material, shape, and dimensions are appropriately selected so that the magnetic force can be adjusted. desirable. Regarding the shape, a rod-shaped rectangular parallelepiped or an ellipsoidal shape is suitable in consideration of workability, handling workability, and the like. The dimension should just have a magnitude | size sufficient to cover the whole surface of the collar part surface 1c of the drum core 1. FIG. Further, it is desirable that the magnetizing method is a direction perpendicular to the flange surface 1c. Furthermore, although the arrangement method here is in direct contact with the collar surface 1c of the drum core, a jig or the like is interposed between the drum core and the permanent magnet in consideration of mass productivity and workability of attaching and detaching the permanent magnet. It may be arranged in a state slightly separated from the flange surface 1c.

  The magnetic powder 5 includes Ni-Zn and Mn-Zn ferrite powders, metal powders such as iron, cobalt, and nickel, and alloys such as amorphous, permalloy, and sendust that are mixed by appropriately adjusting their blending ratio. Any of powder may be sufficient.

  The resin 6 described above is preferably an epoxy-based viscous resin such as thermosetting or ultraviolet curable, and it is desirable to select the material and viscosity appropriately in consideration of applicability and workability.

  The drum core 1 uses a Ni-Zn ferrite core having a magnetic permeability of 400, a flange outer diameter of 3.8 mm, a flange thickness of 0.5 mm, a middle leg diameter of 1.8 mm, and a height of 1.5 mm. A polyurethane-coated copper wire with a wire diameter of 0.16 mm was used as the wire, and the number of windings was 10 turns. Magnetic resin 2 is an epoxy thermosetting resin (product name: S70, Resin Kasei Co., Ltd.) in which magnetic powder 5 is mixed with iron-based amorphous powder at a blending ratio of 40 vol%, and outer periphery 1a of coil 3 and flange portion of drum core 1 are mixed. It applied with a dispenser so that side peripheral part 1b might be covered. The permanent magnet 4 is a disk having a size of φ5 × 3 mm, a neodymium-based rare earth magnet magnetized in the thickness direction and having a magnetic force of 5 Tesla, and is brought into direct contact with the surface 1c of one of the drum cores 1 The drum type inductor of the present invention shown in FIG. 1 was obtained by putting in a bath and drying and curing.

  Table 1 shows the results of measuring the electromagnetic characteristics and the peel strength of the magnetic resin for the structure according to the present invention shown in FIG. 1 and the conventional drum type inductor shown in FIG. Show. The peel strength of the magnetic resin was measured by pulling the lead at the beginning of winding of the winding coil in the coil outer peripheral direction.

  As shown in Table 1, in the structure of the drum type inductor according to the present invention, the direct current resistance is almost the same as that of the conventional structure, but the inductance is about 30% or more, and the peel strength of the magnetic resin is about 1.7 times. It turns out that it is improving.

  Further, in order to confirm the influence of the inductance due to the magnetic force of the permanent magnet, the permanent magnet 4 having different magnetic force of 5 Tesla and 10 Tesla is prepared, and the drum type inductor of the present invention shown in FIG. Table 2 shows the results of measuring and comparing the respective inductances.

  As shown in Table 2, in the structure of the drum-type inductor according to the present invention, it can be seen that the higher the magnetic force of the permanent magnet arranged, the higher the inductance, and that the inductance can be adjusted by the strength of the permanent magnet. It was.

  The embodiments of the present invention have been described above using the embodiments. However, the present invention is not limited to these embodiments, and the present invention is not limited to the scope of the present invention. Included in the invention. That is, various changes and modifications that can be naturally made by those skilled in the art are also included in the present invention.

  The drum-type inductor of the present invention can contribute to the construction of a small, low-cost, high-performance smoothing inductor market that can cope with low voltage and large current of small electronic devices such as mobile phones.

FIG. 1A is a top view, FIG. 1B is a cross-sectional view, and FIG. 1C is an enlarged cross-sectional view of a magnetic resin portion. FIG. 2A is a diagram illustrating the average magnetic path length of the drum-type inductor of the present invention, FIG. 2A is a diagram illustrating the average magnetic path length when no permanent magnet is disposed, and FIG. 2B is a case where a permanent magnet is disposed. The figure explaining the average magnetic path length. FIG. 3A is a top view, FIG. 3B is a cross-sectional view, and FIG. 3C is an enlarged cross-sectional view of a magnetic resin portion.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Drum core 1a Peripheral part 1b Saddle side peripheral part 1c Saddle part surface 2 Magnetic resin 3 Coil 4 Permanent magnet 5 Magnetic powder 6 Resin 7 Average magnetic path length 8 Magnetic resin application part A, B Distance between magnetic powders

Claims (3)

  An inductor formed by forming a coil in the winding portion of a drum-type magnetic core having two winding portions and a winding portion sandwiched between the flange portions so as to cover at least the outer peripheral portion of the coil A magnetic resin mixed with magnetic powder and resin is arranged, and the magnetic resin has a magnetic powder density in a portion near the coil in the outer peripheral portion higher than a magnetic powder density in a portion away from the coil. Drum-type inductor that features.   A drum-type magnetic core having two winding parts and a winding part sandwiched between the hook parts, a coil is formed on the winding part, and magnetic powder and resin are mixed so as to cover at least the outer peripheral part of the coil A method of manufacturing a drum-type inductor, characterized in that the magnetic resin is cured in a state in which the magnetic resin is disposed and a permanent magnet is disposed on a surface of the flange portion perpendicular to the winding central axis direction of the coil. .   3. The inductance characteristic is adjusted by combining at least two elements selected from characteristics of the magnetic powder, a mixing ratio of the magnetic powder and the resin, and magnetic characteristics of the permanent magnet. The manufacturing method of the drum type inductor as described.

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