JP2007043588A - Coil antenna - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a coil antenna wherein the shock resistance of a magnetic body core is enhanced, a magnetic field output is easily improved, and a resonance frequency can be set over a wide adjustment width. <P>SOLUTION: The coil antenna 11 is formed by winding coils 13A, 13B on the magnetic body cores 12A, 12B, respectively. The magnetic body cores 12A, 12B are arranged so that their center axes are almost coincident with each other and linked by a joint part of a frame 14A. Small-sized columnar cores 15A to 15C are arranged to the joint part so as to be nearly perpendicularly directed and arranged to the core axes, respectively. An LC series resonance circuit is configured by connecting the coils 13A, 13B in parallel and a capacitor 19 is connected in series with the LC series resonance circuit. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a coil antenna used in a short-range communication system in the LF band (long wave 30 kHz to 300 kHz).

  FIG. 1 shows a configuration example of a coil antenna 1 disclosed in Patent Document 1. The coil antenna 1 includes a magnetic core 2 and a base 4 joined to the magnetic core 2. For the magnetic core 2, for example, Mn—Zn-based ferrite exhibiting ferromagnetism, other amorphous magnetic materials, and compression-molded magnetic fine powder are used. A conductive wire is wound around the magnetic core 2 to form a coil 3. Further, the base 4 is parallel to the core axis (the axis parallel to the interlinkage magnetic flux generated in the coil and passing through the center of the cross section of the magnetic core perpendicular to the interlinkage magnetic flux). A female screw hole is provided. A small core 5 made of a magnetic material threaded on a cylindrical side surface is screwed into the female screw hole of the base 4.

  A capacitor is connected in series to the coil of the coil antenna 1 to form an LC series resonance circuit. This LC series resonance circuit is connected to an AC power source (oscillating at a resonance frequency), so that a large coil current can flow through the coil 3 even at a low voltage, and a large magnetic field output can be obtained. Such a coil antenna 1 is suitable as a transmission coil antenna for an LF band (long wave 30 kHz to 300 kHz) short-range communication system or the like.

In such a configuration, the gap dimension between the magnetic core 2 and the small core 5 can be adjusted by the screwing amount of the small core 5, and the effective dimension in the axial direction of the core (hereinafter referred to as the core length) can be changed. Thereby, the inductance value of the coil and the resonance frequency of the circuit using the coil antenna 1 can be finely adjusted.
International Publication No. 2005/036761 Pamphlet

  By the way, magnetic materials such as the above-mentioned ferrite used for the magnetic core have extremely low toughness and are susceptible to brittle fracture. Therefore, in the conventional coil antenna, the magnetic core may be damaged only by applying a small impact load or a small bending load. Moreover, it is known that a large magnetic core output can be obtained in a coil antenna when a long magnetic core is used. However, when a long magnetic core is used, brittle fracture is more likely to occur. It has been difficult to increase the magnetic field output of the coil antenna using a long magnetic core.

  Also, in the conventional configuration in which the resonance frequency is adjusted by adjusting the small core, in order to adjust the resonance frequency to a desired value, the fluctuation range of the coil inductance value is too small to obtain the desired resonance frequency. was there.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a coil antenna that can easily increase the magnetic field output while improving the shock resistance of a magnetic core and can set a resonance frequency with a wide adjustment range.

  Then, a coil antenna suitable as a transmission coil antenna used in an LF band short-range communication system or the like is provided.

  The coil antenna according to the present invention includes a plurality of magnetic cores, a plurality of coils wound around the plurality of magnetic cores, and a joint that joins the magnetic cores, and the linkage of the plurality of coils. The plurality of magnetic cores are arranged via the joints so that the directions of magnetic fluxes substantially coincide.

  Thus, since a coil antenna is comprised with a some magnetic body core, the core length of each magnetic body core can be shortened. Thereby, when an impact load is applied or a bending load is applied, the load relating to each of the magnetic cores is suppressed, and damage to the magnetic cores can be prevented. In addition, by arranging the magnetic cores so that the directions of the interlinkage magnetic flux of the coils substantially coincide with each other, the magnetic cores can be magnetically coupled to increase the effective core length, resulting in a large magnetic field output. A coil antenna can be realized. Further, the magnetic cores are not brought into contact with each other by the joint, and damage due to contact can be prevented.

  Therefore, even if the effective core length is increased by a plurality of magnetic cores to realize a coil antenna having a large magnetic field output, the impact resistance performance of each magnetic core can be ensured. As a result, a coil antenna suitable as a transmission coil antenna used in an LF band short-range communication system or the like can be realized.

  In the coil antenna of the present invention, a small magnetic core is accommodated between the magnetic cores of the joint.

  With such a configuration, the small core can be magnetically coupled to the magnetic cores on both sides of the joint. This makes it possible to adjust the inductance value using a small core. In addition, since magnetic field coupling acts on the coils on both sides of the small core, the inductance value of both coils can be changed by a single adjustment, and the fluctuation range of the inductance value can be made larger than in the past.

  In the coil antenna according to the present invention, the small core is accommodated in a freely rotating state, has a shape with different vertical and horizontal dimensions on the rotating surface, and the direction of the rotation axis is substantially perpendicular to the direction of the interlinkage magnetic flux. It is.

  With such a configuration, the resonance frequency can be adjusted simply by rotating the small core. Since the vertical and horizontal dimensions of the rotating surface of the small core are different, the clearance dimension between the small core and the magnetic core can be adjusted by rotation. Then, the resonance frequency can be adjusted while suppressing the amount of rotation of the small core.

  In the coil antenna of the present invention, a plurality of the small cores are arranged so as to be arranged substantially perpendicular to the direction of the interlinkage magnetic flux.

  With such a configuration, more magnetic cores can be provided in the joint while the interval between the small core and the magnetic core is narrowed. Thereby, the coupling between the magnetic cores on both sides of the joint can be increased, and the magnetic field output of the coil antenna can be increased. Further, the resonance frequency can be finely adjusted by a plurality of small coils.

  The coil antenna according to the present invention includes a plurality of coils connected in parallel to form a parallel circuit, and a capacitor element connected in series to the parallel circuit.

  As a result, the actual resistance of the coil can be reduced as much as the coils are connected in parallel. In addition, by forming an LC series resonance circuit by connecting capacitors in series, a large coil current can be obtained even when used at a low voltage. As a result, a coil antenna having a large magnetic field output, which is more suitable as a transmission coil antenna used in an LF band short-range communication system or the like, can be realized.

  According to the present invention, it is possible to provide a coil antenna in which the magnetic core has high impact resistance and the inductance value can be adjusted with a wide fluctuation range.

  In addition, it is possible to provide a coil antenna having a large magnetic field output suitable as a transmission coil antenna used in an LF band short-range communication system or the like.

Next, the configuration of the coil antenna according to the first embodiment will be described with reference to FIGS.
FIG. 2A is a top view of the coil antenna 11. In this figure, for the convenience of illustration, a part of the outer case 16 is shown as being transparent. FIG. 2B is a cross-sectional view of the coil antenna 11 taken along line XX ′ shown in FIG. FIG. 2C is a cross-sectional view of the coil antenna 11 taken along the YY ′ portion shown in FIG. FIG. 2D illustrates a circuit in which the coil antenna 11 is connected to the AC power supply 100.
The coil antenna 11 includes two magnetic cores 12A and 12B made of Mn—Zn ferrite, which is a ferromagnetic material. As the magnetic cores 12A and 12B, it is also preferable to use an amorphous magnetic material other than a ferromagnetic ferrite or a magnetic powder finely bonded thereto.

  The magnetic core 12A is accommodated in the frame 14A, and the magnetic core 12B is accommodated in the frame 14B. Each of the frame body 14A and the frame body 14B is formed by plastic molding of PBT (polybutylene terephthalate). The frame body 14A and the frame body 14B protect the magnetic cores 12A and 12B so that the magnetic core is not damaged by a bending load or an impact load applied during the manufacturing process or product use.

  Each of the magnetic core 12A and the magnetic core 12B has a bar shape (a flat rectangular parallelepiped) and has a cross-sectional shape perpendicular to the core axis in a rectangular shape with four corners chamfered. The tip of the magnetic core 12B is protruded from the frame 14B, and the protruding portion is joined to the frame 14A. As a result, the magnetic core 12A and the magnetic core 12B are joined via the frame 14A, and the magnetic core 12A and the magnetic core 12B are arranged substantially coaxially with the core axes in a straight line. In addition, this causes the magnetic core 12A and the magnetic core 12B to face each other through a frame body 14A that is a joint in a cross section perpendicular to the interlinkage magnetic flux of coils 13A and 13B described later.

  As described above, since the magnetic core 12A and the magnetic core 12B are joined by the frame body 14A, even if an impact load or a bending load is applied to the coil antenna 11, the load is applied to the magnetic body. Dispersed in the cores 12A and 12B, the magnitude of the load associated with each can be suppressed, and the magnetic cores 12A and 12B can be prevented from being damaged. In addition, by fixing by loose joining (such as loose fitting) that is deformed when an impact is applied, the impact is absorbed by deformation at that portion to prevent breakage of the magnetic core, and the impact resistance of the coil antenna 11 Performance can be increased. Also, the magnetic cores 12A and 12B can be magnetically coupled to increase the effective core length, thereby realizing a large magnetic field output.

  Further, coils 13A and 13B are wound around the magnetic cores 12A and 12B, respectively. The coils 13A and 13B are each formed by winding a film-insulated wire (conductive wire) made of copper (Cu) around frame bodies 14A and 14B containing magnetic cores 12A and 12B. By arranging the core axes of the coils 13A and 13B to substantially coincide with each other, the directions of the interlinkage magnetic fluxes of the coils 13A and 13B substantially coincide with each other, and the coils 13A and 13B are magnetically coupled. Thereby, the coil antenna 11 with a large magnetic field output is realizable. Note that the coils 13A and 13B may be formed of different wire rods or may be formed of a single continuous wire rod. When configured with different wire rods, a coil can be wound for each frame even when the frame 14A and the frame 14B are not joined. Moreover, when it comprises with a single continuous wire, the number of winding processes and winding process time can be suppressed.

  Further, as shown in FIG. 2D, the coils 13A and 13B are configured to be connected in parallel. And the capacitor | condenser 19 is connected in series with respect to the parallel connection, and LC series resonance circuit is comprised. As a result, the actual resistance of the coil is reduced, and a large coil current is obtained even when the coil is used at a low voltage. And a big magnetic field output is implement | achieved and the coil antenna 11 is made suitable as a transmission coil antenna.

  The coil antenna 11 includes an outer case 16 and an outer cap 17. The outer case 16 has a bottomed cylindrical shape. The exterior case 16 accommodates the aforementioned frame bodies 14A and 14B therein, and further, an exterior cap 17 is fitted into the opening portion of the bottomed cylinder. As a result, the coil antenna is built in the outer case 16 and the outer cap 17. Further, the outer cap 17 is provided with a through-hole passing through the two external connection lines 18, and this through-hole is configured to be sealed with a sealing material (not shown). Thereby, the environmental resistance of the coil antenna 11 is improved.

  Next, the frame bodies 14A and 14B will be described in detail with reference to FIG. 3A is a top view showing the configuration of the frame body 14A, and FIG. 3B is a top view showing the configuration of the frame body 14B.

  First, the frame body 14A will be described in detail. The frame body 14A is formed by integrally molding the joint portion 21, the tip portion 22, and the leg portions 23A and 23B. The joint portion 21 and the tip portion 22 are configured to be connected by leg portions 23A and 23B parallel to the core axis.

  The joint portion 21 and the distal end portion 22 have rectangular shapes in which the outer shapes of the surfaces perpendicular to the core axis (both left and right in the figure) are chamfered at the four corners.

  One surface (right surface in the figure) perpendicular to the core axis of the joint portion 21 is joined to the magnetic core 12A. A groove (not shown) for fitting the magnetic core 12A is provided on the surface (right side in the figure) to be joined to the magnetic core 12A. In order to press-fit and fix the magnetic core 12A, the groove has a cross-sectional shape substantially equal to the cross-sectional shape of the magnetic core 12A. Further, leg portions 23A and 23B are provided from this surface (the right surface in the figure) so as to extend in the core axial direction.

  Further, a groove (not shown) is also provided on the face (left face in the drawing) of the joint portion 21 facing the surface to be joined to the magnetic core 12A. A portion protruding from the frame body 14B of the magnetic core 12B is fitted into this groove and fixed (press-fit). The cross-sectional shape of the groove is substantially equal to the cross-sectional shape perpendicular to the core axis of the magnetic core 12B.

  Also, one surface (front side in the figure) of the joint portion 21 parallel to the core axis is provided with bottomed holes 24A, 24B, 24C for accommodating the small cores 15A, 15B, 15C. The bottomed holes 24A, 24B, and 24C are appropriately designed to accommodate a small core. The small holes 15A, 15B, and 15C are accommodated in the bottomed holes 24A, 24B, and 24C. Each small core has an elliptic cylinder shape and is made of a magnetic material. In addition, the small core does not necessarily have an elliptical column shape, and may have any shape having different cross-sectional dimensions. In particular, cross-sectional shapes such as an ellipse, an ellipse, a semicircle, and a rectangle are suitable.

  Since the small cores 15A, 15B, and 15C are disposed in the bottomed holes 24A, 24B, and 24C between the magnetic core 12A and the magnetic core 12B, each core is magnetically coupled. In addition, since the small cores 15A, 15B, and 15C have an elliptical cylindrical shape, when the small cores 15A, 15B, and 15C are rotated, the small cores 15A, 15B, and 15C and the magnetic cores 12A and 12B are interposed. The gap changes, and the coupling amount between each magnetic core and each small core changes. Therefore, the inductance value of the coil can be adjusted by rotating the small cores 15A, 15B, and 15C. That is, the resonance frequency of the circuit shown in FIG. 2D can be adjusted. In addition, each small core after adjustment is fixed with an adhesive.

  Moreover, the front-end | tip part 22 of 14 A of frame bodies is a cylindrical shape which the surface (both surfaces on the right and left of a figure) perpendicular to a core axis penetrates, and press-fixes the magnetic body core 12A to the through-hole. Further, the leg portions 23A and 23B are connected to one surface of the tip portion 22 perpendicular to the core axis.

  Further, the leg portions 23A and 23B of the frame body 14A are provided with a protruding portion 26 that protrudes outwardly perpendicular to the core axis. The protrusions 26 are used for locking the wire when the coil is wound, and the positions and the numbers are appropriately designed according to the number of turns of the coil. The projection 26 is provided at a position that is the end of the coil 13 </ b> A, and is partitioned through the projection 26. By providing the projection 26, workability when winding the coil 13A is enhanced.

  In addition, the magnetic core 12A is exposed from the portion of the opening 25 surrounded by the joint portion 21, the tip portion 22, the leg portion 23A, and the leg portion 23B, and thus the coil antenna 11 can be thinned. As a result, the effective winding diameter of the coil 13A is reduced, and the actual resistance of the coil 13A is reduced.

  Next, the frame body 14B will be described in detail. The frame 14B is formed by integrally molding the tip 32, the base 31, and the legs 33A, 33B. And the front-end | tip part 32 and the base part 31 are comprised so that it may connect with the leg parts 33A and 33B parallel to a core axis | shaft.

  The base part 31 and the tip part 32 have a rectangular shape in which the outer shapes of the surfaces perpendicular to the core axis (both left and right in the figure) are chamfered at the four corners.

  One surface (right surface in the figure) perpendicular to the core axis of the base portion 31 is joined to the magnetic core 12B. A groove (not shown) for fitting the magnetic core 12B is provided on the surface (right side in the figure) to be joined to the magnetic core 12B. In order to press-fit and fix the magnetic core 12B, the groove has a cross-sectional shape substantially equal to that of the magnetic core 12B. Further, from this surface (the right surface in the figure), leg portions 33A and 33B are provided so as to extend in the core axial direction.

  In addition, an opening 39 penetrating through the opposite surface is provided on one surface (the front surface in the drawing) of the surfaces of the base portion 31 parallel to the core axis. The opening 39 is provided with a wiring terminal therein, and the capacitor 19 is connected to the wiring terminal. The configuration provided with such an opening 39 contributes to the suppression of the component area of the coil antenna 11. Further, since the opening 39 is provided, the coil antenna 11 is light in weight as a whole, and has high impact resistance against an impact load such as a drop impact.

  In addition, input / output terminals 38A and 38B are provided on the opposite surface (the left surface in the drawing) of the base portion 31 in contact with the magnetic core 12B. Connecting. Further, projecting coil connection terminals 37A and 37B are provided on a surface perpendicular to the core axis, and the coils 13A and 13B are connected to the coil connection terminals 37A and 37B. The input / output terminals 38A and 38B and the coil connection terminals 37A and 37B are connected to each other through a terminal provided in the opening 39 of the base portion or an element such as the capacitor 19.

  Moreover, the front-end | tip part 32 of the frame 14B is a cylinder shape which the surface (both surfaces on the right and left in the figure) perpendicular to the core axis penetrates, and the magnetic core 12B is press-fitted and fixed in the through hole. Further, the distal end portion 32 is configured to be connected to the leg portions 33A and 33B.

  Further, the leg portions 33A and 33B of the frame body 14B are provided with projecting portions 36 that project outward and perpendicular to the core axis. The protrusion 36 is for locking the wire when the coil is wound, and the position and the number are appropriately designed according to the number of turns of the coil. The projection 36 is provided at a position that is the end of the coil 13B, and is partitioned through the projection 36. By providing the projection 36, workability when winding the coil 13B is enhanced.

  Further, the magnetic core 12B is exposed from the portion of the opening 35 surrounded by the base portion 31, the tip portion 32, the leg portion 33A, and the leg portion 33B. Can be thinned. As a result, the effective winding diameter of the coil 13B is reduced, and the actual resistance of the coil 13B is reduced.

  Using the frame bodies 14A and 14B as described above, the coil antenna 11 is configured, and a plurality of magnetic cores 12A and 12B having a short core length are combined, so that the effective core length is kept long, It has high impact resistance, can adjust the inductance value with a wide fluctuation range, and can obtain a high magnetic field output suitable for a coil antenna for transmission used in an LF band short-range communication system.

  The shapes of the magnetic cores 12A and 12B and the shapes of the frame bodies 14A and 14B are not limited to the configuration shown in the present embodiment, and may be anything. For example, the coil may be wound directly around the magnetic core without providing the leg portions 23A, 23B, 33A, 33B and the like. Further, the tip portions 22 and 32 may be eliminated, or the tip portions 22 and 32 may be separated.

  Further, the coil connection terminals 37A and 37B provided on the frame body 14B do not need to be arranged on both sides as shown in the present embodiment, and each may be provided on one side. Further, the opening 39 provided in the frame body 14B is not necessarily required, and the capacitor 19 may not be integrally formed.

  The coils 13A and 13B do not necessarily have a circuit configuration connected in parallel, and may have a circuit configuration connected in series.

  Also, the number of magnetic cores and coils is not necessarily two, more magnetic cores may be used, and more coils may be used.

  Further, when the exterior case 16 is filled with a potting material, a coil antenna with further improved impact resistance can be provided. As the potting material, silicon rubber or urethane rubber may be used.

It is a figure which shows the structure of the conventional coil antenna. It is a figure explaining the coil antenna which concerns on 1st Embodiment. It is a figure which shows the structure of the frame of the coil antenna which concerns on 1st Embodiment.

Explanation of symbols

1, 11-coil antenna 2, 12A, 12B-magnetic core 3, 13A, 13B-coil 4-base 5, 15A, 15B, 15C-small core 14A, 14B-frame 16-exterior case 17-exterior cap 18 -External connection line 19-Capacitor 21-Joint part 22, 32-Tip part 23A, 23B, 33A, 33B-Leg part 24A, 24B, 24C-Bottomed hole 25, 29, 35, 39-Opening 26, 36-Projection Part 31-base part 37A, 37B-coil connection terminal 38A, 38B-input / output terminal 100-AC power supply

Claims (5)

  A plurality of magnetic cores, a plurality of coils wound around the plurality of magnetic cores, and a joint for joining the magnetic cores, and the directions of the interlinkage magnetic fluxes of the plurality of coils substantially coincide with each other. A coil antenna in which the plurality of magnetic cores are arranged via the joints.   The coil antenna according to claim 1, wherein a small magnetic core is accommodated between the magnetic cores of the joint.   3. The coil antenna according to claim 2, wherein the small core is housed in a freely rotating state, has a shape with different vertical and horizontal dimensions on a rotating surface, and a direction of a rotation axis is substantially perpendicular to a direction of the interlinkage magnetic flux. .   The coil antenna according to claim 2 or 3, wherein the plurality of small cores are arranged so as to be arranged substantially perpendicular to the direction of the interlinkage magnetic flux.   A coil antenna in which a plurality of coils according to any one of claims 1 to 4 are connected in parallel to form a parallel circuit, and a capacitor element is connected in series to the parallel circuit.

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