JP7311010B2 - ferrite core - Google Patents

Description

TECHNICAL FIELD The present invention relates to a ferrite magnetic core used in various electronic devices and a coil component using the same.

EVs (Electric Vehicles) and PHEVs (Plug-in Hybrid Electric Vehicles), which have rapidly spread in recent years, are one type of electric transportation equipment. , coil parts such as transformers and choke windings that can withstand high voltages and large currents, and electronic parts using them are required for power supply devices used in these devices. Coil components generate heat due to resistance loss in windings and magnetic energy loss in ferrite cores. In particular, the heat generated by the windings is remarkable. Therefore, the coil components are stabilized at a temperature slightly higher than the maximum environmental temperature to which they are exposed, preventing thermal runaway in which the ferrite core loses its magnetism, and preventing thermal damage to the windings themselves and the members that make up the coil components. is required.

As a countermeasure for the heat generated by the coil component, it is common to dissipate the heat to a heat sink functioning as a cooler or a frame having a large heat capacity through a mounting body such as a mounting board or a metal case. Japanese Patent Laid-Open No. 2002-200001 describes that the heat generated by windings or the like is radiated by bringing a heat radiating member (mounted body) into contact with a ferrite core 1 as shown in FIG. 10 . The heat dissipating member is, for example, a metal member with high thermal conductivity such as a copper plate or an aluminum plate. A so-called E-type ferrite core is known as a ferrite core used in such coil components. The E-shaped ferrite core has a pair of outer legs 20a and 20b, a middle leg (not shown) provided therebetween, and a connecting portion 30 connecting them.

JP 2013-131540

In a conventional coil component, while avoiding interference between the winding 200 provided on the middle leg of the ferrite core 1 and the mounting body, the contact area between the ferrite core 1 and the mounting body can be increased. The rear surface of the connecting portion 30 is used. However, since a thermal gap 210 is formed in the heat path between the ferrite cores (indicated by arrows in the figure), which lowers the thermal conductivity of the combined surfaces, the windings and wires far from the mounting body in the y-axis direction are formed. In some cases, the heat dissipation of the ferrite core becomes insufficient. In addition, since there is a connecting portion 30 of the ferrite core 1 between the winding 200 that generates a large amount of heat and the mounting body, it is also difficult to shorten the distance of the heat path between them.

Therefore, the present invention provides a ferrite core that can improve heat dissipation by reducing the gap between the winding and the mounting body while ensuring the contact area between the ferrite core and the mounting body, and a coil component using the ferrite core. intended to provide

A first invention comprises a pair of outer legs projecting in the same direction, a middle leg between the pair of outer legs and projecting in the same direction as the outer legs, the outer leg and the middle leg. a connecting portion for connecting the pair of outer legs to each other, wherein the direction in which each leg protrudes is in the z-axis direction, the direction perpendicular to the z-axis is the x-axis direction, When the direction perpendicular to the x-axis and the z-axis is defined as the y-axis direction and the ferrite core is viewed from the z-axis direction with the connecting portion on the lower side, the middle leg portion has a circular shape with a radius R1, and the pair of The outer leg is linearly symmetrical with respect to a y-axis passing through the center of the middle leg, and is flat on the far side defined by the x-axis with respect to the center of the middle leg. having a second side surface concentric with the middle leg portion and having a radius R2 on the side facing the middle leg portion, and on both sides in the y-axis direction , each having flat third and fourth side surfaces, a distance h1 in the y-axis direction between the fourth side surface farther from the central leg and the center, and a third flat surface closer to the middle leg. The distance h2 between the side surface and the center in the y-axis direction is different, and the relationship of h1>R2>h2>R1 is satisfied. The width WM at the center of the ferrite core, the width WT of the third side surface, and the width WB of the fourth side surface have a relationship of WM<WT<WB.

In the present invention, it is preferable that the connection portion is a side surface recessed toward the middle leg portion on both sides in the y-axis direction.

Further, in the present invention, the pair of outer legs has a portion not connected to the connecting portion on a part of the side surface on the side defined by the axis in the x-axis direction with respect to the center of the middle leg. Preferably, the side surface of said portion is a flat surface substantially parallel to the side surface on the far side defined by the axis in the x-axis direction.

A second invention is provided with a pair of ferrite cores and windings according to the first invention, wherein the mounting surface of the coil component is the fourth side surface of the ferrite core, and the ends of the windings are mounted from the third side surface side. It is a coil component that pulls out the

ADVANTAGE OF THE INVENTION According to the present invention, a ferrite core capable of improving heat dissipation by reducing the distance between a winding and a mounting body while securing a contact area between the ferrite core and the mounting body, and a coil component using the ferrite core. can be provided.

1 is a perspective view showing the structure of a ferrite core according to one embodiment of the present invention; FIG. FIG. 2 is a front view of the ferrite core shown in FIG. 1; FIG. 2 is a right side view of the ferrite core shown in FIG. 1; FIG. 2 is a rear view of the ferrite core shown in FIG. 1; FIG. 2 is a plan view of the ferrite core shown in FIG. 1; FIG. 2 is a bottom view of the ferrite core shown in FIG. 1; FIG. 2 is a perspective view of a coil component using the ferrite core shown in FIG. 1; FIG. 8 is an exploded perspective view for explaining a method of assembling the coil component shown in FIG. 7; 1 is a perspective view of a bobbin used for a coil component according to one embodiment of the present invention; FIG. 1 is a perspective view of a conventional coil component arranged on the surface of a mounted body; FIG.

Hereinafter, a specific description will be given of a ferrite magnetic core according to an embodiment of the present invention and a coil component using the same, but the present invention is not limited to this, and various It is of course possible to make changes. In addition, the drawings used for the explanation mainly show the main parts so that the gist of the invention can be easily understood, and the details are omitted as appropriate. Parts having the same function are given common numbers and symbols throughout the drawings.

1 to 6 show the structure of a ferrite magnetic core according to one embodiment of the present invention. 1 is a perspective view, FIG. 2 is a front view, FIG. 3 is a right side view, FIG. 4 is a rear view, FIG. 5 is a plan view, and FIG. 6 is a bottom view. This ferrite magnetic core 1 has a pair of outer leg portions 20a and 20b and a middle leg portion 10 located between the pair of outer leg portions 20a and 20b and connected via connecting portions 30a and 30b. The pair of outer leg portions 20a and 20b are also referred to as the first outer leg portion 20a and the second leg portion 20b. The first outer leg portion 20a, the second outer leg portion 20b and the middle leg portion 10 are formed to extend in the same direction from the connecting portions 30a and 30b.

The direction in which each leg protrudes is the z-axis direction, which is orthogonal to the z-axis, the direction in which the outer legs are opposed to each other is the y-axis direction, and the direction orthogonal to the y-axis and the z-axis is the x-axis direction. When the ferrite core is viewed from the z-axis direction with the connection portion of the ferrite core on the lower side, the first outer leg portion 20a and the second outer leg portion 20b extend along the y-axis direction passing through the center of the middle leg portion 10 (hereinafter referred to as "the axis in the y-axis direction passing through the center of the middle leg 10" is also referred to as "the axis in the y-axis direction"). FIG. 2 shows the state when the ferrite core is viewed from the z-axis direction with the connecting portion of the ferrite core facing downward.

The middle leg 10 only needs to have a cross-sectional area that does not cause magnetic saturation during use. I don't mind. As will be described later, the position of the middle leg portion 10 is offset in the y-axis direction from the center of the ferrite core 1 in the y-axis direction. As shown in FIG. 2, in the circular shape of the middle leg viewed from the z-axis direction, the radius of the circle is defined as R1.

The first outer leg portion 20a and the second outer leg portion 20b have a flat first side surface SW3 on the far side defined by the axis in the x-axis direction with respect to the center of the middle leg portion 10, An arc concentric with the middle leg 10 and having a radius R2 is arranged on the near side facing the middle leg 10 so as to follow the outer shape of the winding 200 which is substantially entirely arranged on the side surface OW of the middle leg 10. The distance from the center of the middle leg 10 to the side (second side) near the first outer leg 20a and the second outer leg 20b is approximately I'm assuming it's the same. Although the above-mentioned distance is allowed to vary slightly, in consideration of preventing interference with the winding 200 and improving heat dissipation, the distance between the side surface OW and the first outer leg 20a in the radial direction of the middle leg 10 should be The difference between the distance between the second side surface SW3 and the distance between the side surface OW and the second side surface SW3 of the second outer leg portion 20b is preferably 1 mm or less at maximum.

The first outer leg portion 20a and the second outer leg portion 20b have a third side surface SW2 and a fourth side surface SW4 on both sides defined by the axis in the y-axis direction. The fourth side surface SW4 is a flat surface. Further, the distance h1 in the y-axis direction between the flat fourth side SW4 on the far side from the middle leg 10 and the center of the middle leg, and the flat third side SW2 on the side closer to the middle leg and the middle leg The distance h2 in the y-axis direction from the center of the part is different, and the relationship is h1>R2>h2>R1. In the x-axis direction, the outer legs 20a and 20b have a width WM at the center of the middle leg, a width WT of the third side surface SW2, and a width WB of the fourth side surface SW4. , WM<WT<WB.

Further, the area of the end surface of the first outer leg portion 20a and the area of the end surface of the second outer leg portion 20b when viewed from the z-axis direction are substantially the same, and the area of the middle leg portion 10 is the same as that of the first outer leg portion 20a and the second outer leg portion 20a. It is substantially the same as the sum of areas S of the end faces of the leg portions 20b. Since the winding 200 is arranged in the middle leg 10 and it is a portion that tends to cause magnetic saturation, it may be set larger than the sum of areas S of the outer legs. Since the first outer leg portion 20a and the second outer leg portion 20b are likely to cause leakage magnetic flux, the area of the middle leg portion 10 is set to an area that does not cause magnetic saturation, and the area of the middle leg portion 10 is set to the outer leg portion. may be smaller than the sum of areas S of .

The first outer leg portion 20a and the second outer leg portion 20b have a portion of the side surface closer to the middle leg portion 10 that is not connected to the connecting portion, and the side surface of the portion is defined by the axis in the x-axis direction. The flat surface SW5 may be substantially parallel to the side surface on the far side of the substrate.

The side surfaces of the connecting portions 30a and 30b of the ferrite core 1 preferably have constrictions S1 and S2. As shown in FIG. 2, the connection portions 30a and 30b of the ferrite core 1 have bent side surfaces CW1 and CW2 on one side and straight side surfaces CW3 on the other side, and constrictions S1 and S2. Configure. The side surface CW1 of the connecting portion is flush with the third side surface SW2 of the outer leg. The ferrite magnetic core 1 is usually obtained by compressing ferrite granules and sintering the compact. It is possible to reduce the occurrence of deformation and cracks in the middle leg portion 10 during sintering. Further, the constrictions S1 and S2 can also be used for positioning a bobbin that combines the ferrite core 1 with the constrictions S1 and S2.

The back surface 50 side of the ferrite core 1 is a flat surface. In consideration of the separation of the molded product from the mold during molding and the prevention of chipping and breakage at the edge corners, the edges of the back surface 50 are chamfered one-sidedly, and the edge corners of each part are chamfered with curved surfaces. are provided. A coil component is composed of such a ferrite core 1 , windings disposed on the middle leg 10 , and a bobbin combined with the ferrite core 1 .

FIG. 7 is a perspective view of a coil component using a ferrite core. FIG. 8 is an exploded perspective view for explaining assembly of the coil component, and FIG. 9 is a perspective view showing an example of a bobbin used for the coil component. The bobbin 60 partitions between the winding 200 and the ferrite core 1, and the body 70 has a cylindrical shape surrounding the middle leg 10 of the ferrite core 1. It has a collar portion 80 that has been shaped. Positioning portions 90 and 95 are provided at positions opposed to each of the flange portions 80 . The positioning portion 90 is formed to fit in a constriction provided on the side surface CW3 of the connection portions 30a and 30b of the ferrite core 1, and the positioning portion 95 is formed in a constriction provided on the side surface CW2 of the connection portions 30a and 30b of the ferrite core 1. It is formed so as to accommodate and cover the side surfaces CW2 of the connecting portions 30a and 30b of the ferrite core 1 and the side surfaces SW2 of the first outer leg portion 20a and the second outer leg portion 20b. A winding 200 is arranged in a region partitioned by the pair of flanges 80 . The positioning portion 95 is provided with a protrusion 85 that serves as a hook for winding the conductor wire and separates the ends of the winding 200 .

The middle leg portion 10 of the ferrite core 1 is inserted into the body portion 70 of the hollow bobbin 60 around which the winding 200 is wound, and the middle leg portions of the pair of ferrite cores 1, 1 are inserted and combined. A tape (not shown) is attached to the outer periphery of the ferrite cores 1 , 1 , or fixed by adhesion to form a coil component 100 .

The bobbin 60 is a former for winding the winding 200 and ensures insulation from the ferrite core 1 . Therefore, it is preferable to form the bobbin from a resin having excellent insulating properties, heat resistance and moldability. Polyphenylene sulfide, liquid crystal polymer, polyethylene terephthalate, polybutylene terephthalate, etc. are preferred, and those molded by known methods such as injection molding can be used.

A conductor wire used for the winding 200 is a coated wire having an insulating coating on a conductor made of a conductive material such as copper, aluminum, or an alloy thereof. In general, an enameled wire coated with polyamide-imide for insulation is used as a conducting wire, and it is preferable to use a litz wire prepared by twisting a plurality of enameled wires. The number of turns of the winding 200 can be appropriately set based on the required performance, and the wire diameter can also be appropriately selected according to the current to be supplied. When the coil component is a transformer, there is no limitation on the winding method of the primary winding and the secondary winding, and any one of bifilar winding, sandwich winding, split winding, etc. may be appropriately selected.

The coil component 100 is used with the fourth side surfaces SW4 of the first outer leg portions 20a and the second outer leg portions 20b of the ferrite cores 1, 1 in contact with or in close proximity to a metallic mounting body. Non-magnetic metals having excellent thermal conductivity, such as aluminum or its alloys, magnesium or its alloys, copper or its alloys, can be used for the mounting body. In order to improve the adhesion between the mounting body and the ferrite core 1, a highly heat-resistant heat-dissipating grease may be applied.

In the ferrite core 1 of the present invention, the width (the width in the x-axis direction) of the fourth side surface SW4 of the first outer leg portion 20a and the second outer leg portion 20b is increased to increase the area facing the mounting body. ing. Further, by setting the middle leg 10 away from the fourth side surface SW4, which serves as the mounting surface, the outer circumference of the winding wire 200 does not protrude from the fourth side surface SW4, but is close to the mounting body. . Also, the positions of the mating surfaces of the ferrite cores 1, 1 are set so as to avoid the positions where a thermal gap 210 is formed in the middle of the heat path as in the conventional case.

According to such a configuration, the heat generated by the winding 200 can be efficiently released to the mounting body through the ferrite core 1, and the heat generated by the winding 200 and the ferrite core 1 at a portion far from the mounting body in the y-axis direction can also be dissipated. , heat dissipation can be ensured and released to the outside by a heat path that does not pass through a thermal gap or a heat path in the circumferential direction of the winding itself.

The heat dissipation can be further improved by fixing the coil component 100 to a metal mounting body and filling at least the space between the windings 200 and the mounting body with a resin containing a heat conductive filler. The resin is preferably a silicone resin, and the heat-conducting filler is preferably selected from ceramics having excellent heat conductivity, such as Al2O3, ZrO2, SiO2, Si3N4, and MgO. It is desirable to adjust the amount of the ceramic filler mixed with the silicone resin so as to obtain the desired heat dissipation, deformability, and strength. Further, if the entire coil component 100 is embedded in a resin containing a heat-conducting filler, the heat dissipation of the coil component 100 can be further enhanced.

1 ferrite magnetic core 10 middle leg portion 20a first outer leg portion 20b second outer leg portions 30a, 30b connecting portion 60 bobbin 100 coil component 200 winding

Claims (6)

A pair of outer leg portions projecting in the same direction, a middle leg portion between the pair of outer leg portions and projecting in the same direction as the outer leg portions, and a connection connecting the outer leg portion and the middle leg portion. A ferrite magnetic core having a part,
The direction in which each leg protrudes is the z-axis direction, which is orthogonal to the z-axis, the direction in which the pair of outer legs are opposed to each other is the x-axis direction, and the direction orthogonal to the x-axis and the z-axis is the y-axis direction, and the connection When the ferrite core is viewed from the z-axis direction with the part facing downward,
The middle leg has a circular shape with a radius of R1,
The pair of outer legs are linearly symmetrical with respect to an axis in the y-axis direction passing through the center of the middle leg, and are far from the center of the middle leg defined by the axis in the x-axis direction. It has a flat first side surface on the side, and an arc-shaped second side surface concentric with the middle leg portion and having a radius R2 on the near side facing the middle leg portion, and in the y-axis direction. has flat third and fourth side surfaces on both sides thereof, and the distance h1 in the y-axis direction between the fourth side surface farther from the middle leg and the center has a relationship of h1>R2 > R1 located in
A ferrite core , wherein the fourth side surface is a surface for mounting a coil component . The h1 is different from the distance h2 in the y-axis direction between the third side surface closer to the middle leg and the center, and the relationship h1>R2>h2>R1 is satisfied. Item 1. The ferrite core according to item 1. In the width in the x-axis direction, the pair of outer legs has a width WM at the center position of the middle leg, a width WT at the third side surface, and a width WB at the fourth side surface. , WM<WT<WB. 2. The ferrite core according to claim 1, wherein said second side is a side capable of accommodating a winding whose outer circumference radius is smaller than h1. 2. The ferrite core according to claim 1, wherein said connection portion has side surfaces recessed toward said middle leg portion on both sides in the y-axis direction. 2. The ferrite magnetic core according to claim 1, wherein the pair of outer legs are provided with the connecting portion on a part of a side surface near the center of the middle leg defined by an axis in the x-axis direction. A ferrite core having a portion that is not connected, the side surface of the portion being a flat surface substantially parallel to the side surface on the far side defined by the axis in the x-axis direction.

Images