JP3623720B2 - Thin inductor - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to a thin inductor used for a power inductor of a DC / DC converter.
[0002]
[Prior art]
As electronic devices are miniaturized, power inductors used in these power supply circuits are also required to be small, light, and thin. In addition, the power supply voltage tends to be lowered, and a power inductor capable of flowing a large current at a low voltage is required. As such an inductor, for example, an inductor as shown in FIG. 11 is conventionally used. This is a coil 1 made of a rectangular wire coated with insulation and wound edgewise on a middle leg 2a of an E-shaped core 2, and 3 is a flat core that is abutted against the upper surface of the E-shaped core 2.
[0003]
[Problems to be solved by the invention]
The power inductor is required to have a large maximum allowable current Io. If the number of turns of the inductor is N, a maximum magnetomotive force of Io × N is generated in the core when the maximum allowable current Io flows through the inductor, so a core having a large magnetomotive force is required. Assuming that the magnetic resistance of the core is Rm, the maximum saturation magnetic flux density which is the material characteristic of the core is Bs, and the effective sectional area of the core is S, the maximum magnetomotive force Fm allowed for the core is Fm = Rm · Bs · S.
It becomes. Therefore, in order to increase the magnetomotive force F in the inductor having the same maximum saturation magnetic flux density Bs, it is only necessary to increase the effective sectional area S of the core or to increase the magnetic resistance Rm by providing an air gap.
[0004]
In order to increase the effective sectional area S, it is necessary to increase the thickness of the outer leg 2b, the connecting portion 2c, and the core 3 as well as the sectional area of the middle leg 2a of the core 2 in FIG. For this reason, there is a problem that it is difficult to reduce the thickness of the inductor. On the other hand, if the magnetoresistance Rm is increased to increase the magnetomotive force F, the number of turns for obtaining a predetermined inductance increases. As a result, since the occupied volume of the coil 1 is increased, it is difficult to reduce the thickness. Wide rectangular wires are troublesome to manufacture and also have problems that edgewise winding is difficult.
[0005]
[Means for Solving the Problems]
A thin inductor according to the present invention includes a pair of cores that form a closed magnetic path facing each other and a single wire made of a meandering flat metal conductor plate, and meanders formed on an opposing surface of at least one of the cores. In the thin inductor in which the wire is fitted into the groove and both ends of the wire are led out of the groove and used as electrodes, the core formed with the groove is provided with a first crank-shaped groove. The first structural unit and the second structural unit provided with a second crank-shaped groove that is in a line-symmetric relationship with the first crank-shaped groove are alternately arranged so that the groove is connected to one. It is characterized by connecting and integrating any number .
[0006]
【Example】
1 and 2 show an embodiment of the inductor of the present invention. Reference numerals 10 and 40 denote a pair of cores made of an insulating magnetic material such as Ni-Zn ferrite. The pair of cores 10 and 40 are fixed in a state of being laminated with an epoxy resin adhesive or the like through the sheet 30. The pair of cores 10 and 40 form a closed magnetic circuit, and the magnetic resistance is adjusted by the gap formed by the sheet 30. The upper core 40 has a flat plate shape, and a meandering groove 12 is formed on the upper surface of the lower core 10. Both ends of the groove 12 communicate with two opposing side surfaces of the core 10.
[0007]
A wire 20 made of a metal conductor plate such as copper is punched in accordance with the shape of the groove 12. After the wire rod 20 is fitted into the groove 12 of the core 10 as shown in FIG. 3, both end portions 21 and 22 are led out to the opposite side surfaces of the core 10. As is apparent from FIG. 2, both end portions 21 and 22 are bent along the surface of the core 10 and extend to the bottom surface of the core 10, and both end portions 21 and 22 themselves form electrodes.
[0008]
Attachment of the wire 20 to the core 10 at this time can be performed as follows. First, in the case of an elastic flexible wire rod 20, both end portions 21 and 22 that are bent in advance are fitted into the groove 12 while being fitted into the side surface of the core 10. On the other hand, in the case of the soft wire 20 that is easily deformed, both ends 21 and 22 are bent after the wire 20 is fitted into the groove 12 of the core 10.
[0009]
In the case of the wire 20 made of a hard and hard-to-bend metal conductor plate, both end portions 21 and 22 may be bent toward the flat core 40 as shown in FIG. That is, it is possible to easily assemble by inserting the flat core 40 from the lateral direction after fitting the wire 20 having both end portions 21 and 22 bent upward in advance into the groove 12 of the core 10.
[0010]
These inductors have a chip-type configuration in which meandering metal conductor plate wires 20 are fitted in meandering grooves 12 of cores 10 and 40 and electrodes are provided at both ends. FIG. 5 shows the relationship between current and magnetic flux when current is passed through the wire 20 of the inductor. A broken line arrow on the wire 20 indicates the direction of current, and a solid line arrow indicates the direction of magnetic flux. Even if the direction of the current is changed, the interlinkage magnetic flux is positively coupled without canceling each other, so that the inductance is formed without weakening.
[0011]
In this inductor structure in which a wire 20 made of a metal conductor plate is fitted in the meandering groove 12 of the core 10, the cores 10 and 40 are effectively cut without increasing the thickness compared to the conventional EE type or EI type core. The area can be increased. For this reason, according to the inductor structure of the present invention, a larger inductance and magnetomotive force can be obtained.
[0012]
The shape of the core 10 in which the inductor groove 12 is formed as described above is such that the first structural unit 10A provided with the first crank-shaped groove 12A shown in FIG. 6 and the first crank-shaped groove 12A are line symmetric. It can be considered that the second structural unit 10B provided with the second crank-shaped groove 12B having the above relationship is combined. Here, the crank shape means a shape in which both ends of a straight line are bent at right angles in opposite directions.
[0013]
The shape of the core 10 in FIG. 3 is such that the second structural unit 10B is sandwiched between two first structural units 10A as shown in FIG. In other words, the first structural unit 10A and the second structural unit 10B are alternately connected in a line, and the first structural unit 10A is arranged at both ends of the line. Each of the crank-shaped grooves 12A and 12B is a serpentine groove connected to one.
[0014]
FIG. 8 shows another configuration example of the core 10 in which the groove 12 is formed. This core has a shape in which the number of alternately connected first structural unit 10A and second structural unit 10B is two. Also in this case, the crank-shaped grooves 12A and 12B are connected to form one meandering groove.
[0015]
As described above, by increasing the number of the first structural unit 10A and the second structural unit 10B that are alternately arranged, it is possible to obtain a core shape in which a larger inductance can be obtained without increasing the thickness of the core. .
[0016]
FIG. 9 shows another embodiment of the inductor according to the present invention, which is an example in which a conductive magnetic material such as Mn—Zn ferrite is used for the cores 10 and 40. This inductor is obtained by adding an insulating base 50 to an inductor that is substantially the same as that shown in FIGS. As shown in FIG. 10, a recess 52 is formed on the upper surface of the base 50. The lower portion of the core 10 is fitted and fixed in the recess 52, and both end portions 21 and 22 of the wire 20 are bent and pulled out to the bottom surface of the base 50. In this case, the wire 20 used is an insulating coating, and the insulating coatings on both end portions 21 and 22 are peeled off to form electrodes.
[0017]
【The invention's effect】
The present invention has an advantage that an inductor having a large current capacity can be configured in a very low profile. In addition, since the structure is simple without any complicated winding, assembly is easy and the manufacturing cost can be reduced.
[Brief description of the drawings]
FIG. 1 is an exploded perspective view showing a first embodiment of the inductor of the present invention. FIG. 2 is a front view of the inductor. FIG. 3 is a plan view of a part of the inductor. FIG. 5 is an explanatory view showing the relationship between current and magnetic flux in the inductor. FIG. 6 is a plan view showing first and second structural units of the grooved core. FIG. 8 is a plan view showing another combination example of the first and second structural units. FIG. 9 is a front view showing a third embodiment of the inductor of the present invention. 10 is an exploded perspective view of a part of the inductor. FIG. 11 is an exploded perspective view of a conventional inductor.
10 core 10A first structural unit 10B second structural unit 12 groove 20 wire 40 core 50 base

Claims (2)

A pair of cores that face each other to form a closed magnetic path and a single wire made of a meandering flat metal conductor plate, and the wire is placed in a meandering groove formed on the facing surface of at least one of the cores. In a thin inductor that is inserted into the electrode and led to both ends of the wire rod outside the groove ,
The shape of the core in which the groove is formed is such that the first structural unit provided with the first crank-shaped groove and the second crank-shaped groove having a line-symmetric relationship with the first crank-shaped groove. A thin inductor characterized in that an arbitrary number of second structural units are alternately connected and integrated so that grooves are connected to one . A base insulating forming a recess on an upper surface, a portion of the core is fixed is fitted to the recess, according to claim 1, wherein by bending both end portions of the wire and the electrode is pulled out to the bottom surface of the base Thin inductor.

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