JP2007295360A - Coil antenna - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a coil antenna which is compact and thin and has a high impact resistance. <P>SOLUTION: The coil antenna includes a magnetic core 1 and two conductors 2 and 3 wound around the magnetic core 1, and the magnetic core 1 is a magnetic member made of a mixture of soft magnetic powder and an organic binder and has flexibility. The conductors 2 and 3 are wound in parallel so as to have the same winding axis. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a coil antenna used for transmission / reception of a plurality of frequencies, and particularly for a keyless system for an automobile, a transmission antenna for an immobilizer, a reception antenna, a transmission antenna for a house door key, a reception antenna, and an IC card reader / writer The present invention relates to a coil antenna suitable for a transmission / reception antenna, a broadcast reception antenna such as a radio, and a reception antenna for a radio clock.

  In recent years, communication terminals have become smaller and more versatile, and terminals using radio wave communication are often seen. As a transmission / reception coil antenna, a coil using a magnetic core of a magnetic material such as ferrite and a transmission / reception coil antenna using an air-core coil are widely used.

  Of the transmission / reception coil antennas, the transmission coil antenna is usually tuned to the operating frequency by connecting an inductor and a capacitor in series. By applying a voltage (current) of a frequency used for this LC series circuit, it is possible to generate an AC magnetic field and send information in a non-contact manner. It is mainly used in keyless systems and immobilizers for automobiles.

  The receiving coil antenna is usually tuned to the operating frequency by connecting to a parallel circuit of an inductor and a capacitor. It is mainly used in keyless systems, immobilizers, radio receivers, radio clocks, etc. for automobiles (for example, disclosed in Patent Documents 1 and 2).

  The transmitting / receiving antenna is tuned by being connected in parallel or in series with a capacitor according to the frequency used or the purpose of use. It is used for IC card reader / writer devices, mobile phone fee payment, train fee payment, etc. (for example, disclosed in Patent Document 3).

  As described above, the transmission / reception coil antenna is used in various places, but it is required to be used in a narrow space such as an automobile handle or a mobile phone, or to be used in a plurality of frequencies. It has become to.

JP 2006-28956 A JP 2006-54588 A Japanese Patent Laid-Open No. 2006-40028

  The problem of the present invention is that, when transmission / reception at a plurality of frequencies is possible, an antenna having a plurality of specifications is inevitably required, and the use of the antenna in a narrow space becomes difficult.

  In addition, coil antennas using ferrite material magnetic cores (sintered ferrite) are available from the market in terms of impact resistance (preventing defects such as magnetic core cracks) and diversification of shapes (unusual shapes, light thinness, small size, and large size). Although required, there are problems such as impact resistance and poor manufacturability. In particular, recent remote keys for automobiles are convenient because the keys can be opened and closed with the keys in the pockets, but they are always required to be thinner and lighter due to the characteristics of mobile phones (pockets etc.). Core damage due to impact is a fatal failure and impact resistance is required.

  In order to satisfy these demands, ceramic cores such as ferrite cause magnetic core cracks when they are thin, and impact resistance cannot be ensured, and lamination of metal magnetic cores such as amorphous magnetic cores has been attempted. However, there is a problem that the cost is high due to the high cost and manufacturability, because the hardness is high and the processing is difficult. For this reason, plastic ferrite combined with resin has been studied, but impact and manufacturability are improved to some extent, but pursuing characteristics as an antenna, it is necessary to increase the filling rate of ferrite, Eventually, the plastic ferrite material satisfying the antenna characteristics has a problem that the impact resistance becomes weak like the sintered ferrite.

  In addition, when the sintered ferrite magnetic core becomes a long shape or a thin plate shape, warping occurs, and flatness is required after pressing / sintering, so that a machining press finish is required and a large press machine proportional to the size is required. .

  An object of the present invention is to solve the above-described problems and provide a coil antenna that is small, thin, and has high impact resistance.

  According to the present invention, the magnetic core is provided with one magnetic core and a plurality of conductive wires wound around the magnetic core, and the magnetic core is a magnetic body made of a mixture of soft magnetic powder and an organic binder. A coil antenna characterized by having flexibility is obtained.

  In addition, according to the present invention, it is possible to obtain the coil antenna described above, wherein the conductive wires are wound in a parallel positional relationship (so that the winding axes are the same).

  Further, according to the present invention, there is obtained the coil antenna as described above, wherein the conducting wires are wound in a vertical positional relationship (so that the winding axes are perpendicular to each other).

  In addition, according to the present invention, it is possible to obtain the above-described coil antenna characterized in that the inductance values of the coils made of the conducting wires are all different.

  In addition, according to the present invention, it is possible to obtain the coil antenna as described above, wherein each coil made of the conducting wire is tuned to a different frequency.

  Further, according to the present invention, the soft magnetic powder is made of iron aluminum silicon alloy (Sendust), iron nickel alloy (permalloy), iron cobalt alloy, iron cobalt silicon alloy, iron silicon, vanadium alloy having a high frequency magnetic permeability. , Iron-cobalt boron alloy, cobalt-based amorphous alloy, iron-based amorphous alloy, oxide magnetic powder (ferrite), carbonyl iron, molybdenum permalloy, pure iron dust soft magnetic material, or a combination thereof, and the organic The binder is a polyester resin, polyvinyl chloride resin, polyvinyl butyral resin, polyurethane resin, cellulose resin, nitrile-butadiene rubber, styrene-butadiene rubber or other thermoplastic resin or copolymer thereof, epoxy resin, Phenolic resin, amide resin, imide resin Thermosetting resins butter, and the like, or a halide of an organic flame retardant, a coil antenna of the above description can be obtained, which is a one or a magnetic material consisting of a combination of these brominated polymers.

  In addition, according to the present invention, it is possible to obtain the coil antenna, wherein the soft magnetic powder is a flat and / or needle-shaped powder.

  In addition, according to the present invention, there is obtained the above coil antenna, wherein the soft magnetic powder is an oxide film, a powder that is insulation-coated with an organic binder, or a conductive powder.

  According to the present invention, there is obtained the above coil antenna, wherein the magnetic core has a flat plate shape.

  That is, according to the present invention, by winding a plurality of conductive wires around the same magnetic core, the antenna can be formed small and thin while enabling transmission and reception at a plurality of frequencies.

  In addition, the use of a magnetic body made of a mixture of soft magnetic powder and an organic binder, which is flexible and can be freely bent, provides high impact resistance and requires a large press. First, with ferrite, it becomes possible to make an antenna of an unrealizable size.

  The transmission / reception coil antenna of the present invention is small, thin, and has high impact resistance while enabling transmission / reception of a plurality of frequencies.

  Hereinafter, embodiments of the present invention will be described.

  FIG. 1 is a diagram showing an appearance of a coil antenna (parallel winding) in an embodiment of the present invention. In FIG. 1, the higher the number of turns and the higher the inductance value corresponds to the low frequency (for example, 125 kHz). The smaller the number of turns and the lower the inductance value corresponds to a high frequency (for example, 13.56 MHz). FIG. 2 is a diagram showing the appearance of the coil antenna (vertical winding) in the embodiment of the present invention. In FIG. 2, a higher inductance value corresponds to a low frequency, and a smaller inductance value corresponds to a high frequency.

  FIG. 3 is a circuit diagram showing the connection between the 125 kHz and 13.56 MHz composite antenna in the embodiment of the present invention, and FIG. 3A is a diagram showing a state in which the coil antenna of the present invention is connected to the 125 kHz transmission system. FIG. 3B is a diagram showing a state in which the coil antenna of the present invention is connected to the 13.56 MHz card reader / writer system. FIG. 4 is a circuit diagram showing the connection between the AM and the FM radio antenna according to the embodiment of the present invention. In FIG. 4, since a synth-tuned radio receiver is used, a tuning capacitor is not connected.

  As shown in FIG. 1, in the coil antenna of the present invention, a first coil antenna 5 (FIG. 3) is formed by winding a 0.22 mm, 50T conductor 2 around a 3 × 12 × 50 mm square plate-like magnetic core 1. And As the conducting wire, a copper wire coated with a polyurethane insulating film was used. Further, a lead wire 3 having a diameter of 0.26 mm and 3T is wound around the same magnetic core 1 in parallel with the lead wire 2 to form a second coil antenna 6 (FIG. 3).

  At this time, as shown in FIG. 3, the inductance of the first coil antenna 5 was 100 μH (measured at 125 kHz) and the inductance of the second coil antenna 6 was 0.5 μH (measured at 13.56 MHz).

  The first coil antenna 5 was tuned to 125 kHz by connecting it in series with a 16000 pF capacitor 7, and the second coil antenna 6 was tuned to 13.56 MHz by connecting it in parallel with a 275 pF capacitor 8.

  When each coil antenna (including a capacitor) was connected to the 125 kHz transmission system 9 and the 13.56 MHz card reader / writer system 10 and the respective communication states were confirmed, both were able to communicate simultaneously.

  It was also confirmed that simultaneous communication was possible even when the conductor 4 was wound perpendicularly to the conductor 2 instead of the conductor 3.

  Similarly, a 3 × 3 × 40 mm square-plate-shaped magnetic core 1 is wound with φ0.15 mm, 100T, φ0.15 mm, and 2T conductors to form a two-frequency composite antenna. As shown in FIG. When connected to the machine 13, it was also confirmed that AM broadcasting (MF band) and FM broadcasting (HF band) can be received.

  As the magnetic core 1, a flexible material made of a soft magnetic material powder and an organic binder was used. The soft magnetic powder in the present embodiment is an iron silicon aluminum alloy powder. The soft magnetic powder may be another powder. For example, the soft magnetic powder may be carbonyl iron, ferrite powder, or pure iron powder. The soft magnetic powder may be a powder made of iron-nickel-cobalt alloy, cobalt-based amorphous alloy, iron-based amorphous alloy, or molybdenum permalloy. Further, the soft magnetic powder may be a combination of the above powders.

  The soft magnetic powder in the present embodiment is a flat powder. Each powder has an aspect ratio of 5 or more and a particle size of 35 μm.

  The insulator layer formed on each surface of the soft magnetic powder is made of a nonmagnetic material. Specifically, the insulator layer is an oxide film and is formed by annealing soft magnetic powder. The insulator layer may be formed of an organic binder. When the insulator layer is formed of an organic binder, the organic binder may be the same as or different from the organic binder in the hybrid.

  The organic binder (included in the hybrid) in the present embodiment is chlorinated polyethylene, and in the present embodiment, a titanate coupling agent is added thereto. Instead of this, a silane coupling agent or an aluminate coupling agent may be used, or a coupling agent may not be used.

  In the present embodiment, the blending ratio of the soft magnetic powder in the hybrid is 80% by weight, and the total blending ratio of the organic binder and the coupling agent is 20% by weight. In order to obtain antenna characteristics suitable for practical use and to make the magnetic core flexible, the blending ratio of the soft magnetic powder in the hybrid is preferably 60% by weight to 95% by weight. The blending ratio of the organic binder is preferably 5% by weight or more and 40% by weight or less.

  When a coupling agent is used, the blending ratio of the coupling agent in the mixture is 5% by weight or less.

  The magnetic core according to the present embodiment was measured using a type A durometer in accordance with JISK6253. As a result, the magnetic core according to the present embodiment had a rubber hardness of 60 or more. Moreover, the tensile strength measured according to JISK6263 was 3.8 MPa.

  In this embodiment, a two-frequency composite antenna has been described. However, it is possible to cope with multiple frequencies by increasing the number of coils to three or four.

The figure which shows the external appearance of the coil antenna (parallel winding) in embodiment of this invention. The figure which shows the external appearance of the coil antenna (vertical winding) in embodiment of this invention. The circuit diagram which shows the connection of 125 kHz and 13.56 MHz composite antenna in embodiment of this invention. Fig.3 (a) is a figure which shows the state which connected the coil antenna of this invention to the 125kHz transmission system. FIG.3 (b) is a figure which shows the state which connected the coil antenna of this invention to the 13.56MHz card reader-writer system. The circuit diagram which shows the connection of AM of embodiment of this invention, and FM radio antenna.

Explanation of symbols

1 Magnetic core 2 Conductor 3 (of the first coil antenna) Conductor 4 (of the second coil antenna in the case of parallel winding) Conductor 5 (of the second coil antenna in the case of vertical winding) 5 First coil Antenna 6 Second coil antenna 7 Capacitor 8 Capacitor 9 125 kHz transmission system 10 13.56 MHz card reader / writer system 11 Coil for AM radio antenna 12 Coil for FM radio antenna 13 Radio receiver

Claims (9)

  One magnetic core and a plurality of conductive wires wound around the magnetic core, and the magnetic core is a magnetic body made of a mixture of soft magnetic powder and an organic binder and has flexibility. A coil antenna characterized by that.   The coil antenna according to claim 1, wherein the conductive wire is wound so that a winding axis is the same.   The coil antenna according to claim 1, wherein the conducting wires are wound so that winding axes are perpendicular to each other.   The coil antenna according to claim 1, wherein inductance values of the coils made of the conducting wires are all different.   2. The coil antenna according to claim 1, wherein each coil made of the conducting wire is tuned to a different frequency.   The soft magnetic powder is iron aluminum silicon alloy, iron nickel alloy, iron cobalt alloy, iron cobalt silicon alloy, iron silicon, vanadium alloy, iron cobalt boron alloy, cobalt amorphous alloy, iron amorphous alloy, oxide magnetic powder , Composed of one or more kinds of soft magnetic materials such as carbonyl iron, molybdenum permalloy, and pure iron dust, and the organic binder is polyester resin, polyvinyl chloride resin, polyvinyl butyral resin, polyurethane resin, cellulose resin , Nitrile-butadiene rubber, styrene-butadiene rubber and other thermoplastic resins or copolymers thereof, epoxy resins, phenol resins, amide resins, imide resins and other thermosetting resins, or organic flame retardants. It consists of one or more of a certain halide or brominated polymer. Coil antenna according to any one of claims 2-5, which is a magnetic body.   7. The coil antenna according to claim 6, wherein the soft magnetic powder is flat and / or needle-shaped powder.   8. The coil antenna according to claim 6, wherein the soft magnetic powder is an oxide film, a powder that is insulation-coated with an organic binder, or a conductive powder.   The coil antenna according to any one of claims 6 to 8, wherein the magnetic core has a flat plate shape.

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