JP2005308649A - Coil antenna - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a compact, high-strength, and high-quality antenna for a radio controlled timepiece, while securing sufficient reception level. <P>SOLUTION: A drum type core 1 is constituted by layering a plurality of magnetic films in which an insulating resin is applied to at least one surface. The drum type core is inserted in an insulating bobbin 2. A coil 3 is wound on the insulating bobbin. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a coil antenna, and more particularly to a coil antenna used in a radio timepiece that receives a predetermined radio wave including time information and corrects the time.

  In Japan, radio waves are output from two stations, a frequency of 60 kHz in Fukushima and a frequency of 40 kHz in Saga, and a radio clock (RCC) receives the radio waves and adjusts the time. Of course, quartz is also included in the radio clock, but the radio wave transmitted from the station is aligned with the atomic clock, so it is very accurate and indicates Japan standard time. The signal transmitted from the station encodes not only time but also date information. Therefore, the radio timepiece does not require any time adjustment as long as the battery is inserted.

  As an antenna mounted on a radio timepiece, a bar antenna in which a winding is applied to a bar core formed mainly of ferrite is used.

  Since such a bar antenna has a long length, the radio clock is mainly applied to relatively large clocks such as wall clocks and alarm clocks. However, in recent years, it has been studied to configure a wristwatch as a radio timepiece. In addition, it has been studied to mount a radio clock on home appliances and cars that have a time display function.

  As a result, the space for storing antennas has become smaller, and it has become necessary to reduce the size of antennas built into radio timepieces. Furthermore, recently, even a radio timepiece is required to have a design that is inferior to a conventional timepiece.

  In detail, in the early days of the release of radio timepieces, the radio timepiece requires an antenna, and the antenna length is required to obtain the required sensitivity characteristics of the antenna. It was thought. Similarly, in order to secure the sensitivity of the antenna, it has been recognized that the radio timepiece uses a non-metal, for example, a plastic case with good transparency. However, recently, design is the most important issue even for radio timepieces. That is, not only the small and thin shape but also the full metal case is required to have a high-class design.

  However, in the conventional bar antenna, the induced voltage of the bar antenna decreases as the cross-sectional area and length of the bar core decrease. As a result, the conventional bar antenna has a problem that the sensitivity is lowered under a weak electric field.

  Moreover, in the conventional bar antenna, the space | interval of a coil | winding part (coil part) cannot fully be ensured because core size becomes small. Therefore, it is difficult to increase the inductance to a sufficient level with the conventional bar antenna. Moreover, even if winding is possible in this state, a considerable number of turns is required. For this reason, in the conventional bar antenna, a loss occurs due to an increase in the DC resistance of the winding (coil), and as a result, the value of Q representing the sharpness of resonance of the antenna decreases.

  In addition, the full metal case has problems such as shielding radio waves of necessary time information, and electromagnetic interference between the full metal case and the coil antenna, thereby deteriorating antenna characteristics.

  The present invention has been made to address such problems.

  That is, an object of the present invention is to provide a small radio timepiece antenna while ensuring a sufficient reception level.

  Another object of the present invention is to provide an antenna for a radio timepiece having high strength and high quality.

  According to the first aspect of the present invention, there is provided a coil antenna built in a radio-controlled timepiece, wherein the drum core is formed by laminating a plurality of magnetic films coated with an insulating resin on at least one surface, and the drum mold A coil antenna having an insulating bobbin into which the core is inserted and a coil wound on the insulating bobbin is obtained.

  According to the second aspect of the present invention, there is provided a coil antenna built in a radio-controlled timepiece, wherein a drum-type core formed by laminating a plurality of magnetic films coated with an insulating resin on at least one surface, and the drum-type A coil antenna having an insulating tape wound around a core and a coil wound on the insulating tape is obtained.

  In the coil antenna according to the first or second aspect of the present invention, each of the plurality of magnetic films may be formed by, for example, extracting a soft magnetic metal ribbon into a drum shape. The insulating bobbin preferably has a structure having at least one surface opened.

  According to a third aspect of the present invention, there is provided a radio timepiece incorporating the coil antenna, comprising a soft magnetic sheet disposed close to at least one surface of the coil antenna. To get a radio clock.

  In the radio timepiece according to the third aspect of the present invention, it is preferable that the soft magnetic sheet is made of an insulating soft magnetic layer. The insulating soft magnetic layer may be formed of, for example, soft magnetic powder, dielectric powder, and an organic binder. On at least one surface of the soft magnetic sheet, a metal case may be disposed in proximity, a printed circuit board may be disposed in proximity, or an electronic component may be disposed in proximity. A cable or a flexible printed circuit board may be arranged in close proximity.

  According to the present invention, since a drum-type core formed by alternately stacking a plurality of magnetic films and a plurality of insulating resins is used as the core, a better characteristic than the conventional coil antenna can be obtained. . In addition, it is possible to provide a coil antenna that is thin, small, and less affected by the metal case.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 shows a coil antenna according to a first embodiment of the present invention. The illustrated coil antenna includes a drum core 1, a bobbin 2, a coil 3, and a flexible substrate 4.

  The drum core 1 is manufactured as follows. First, a magnetic film is made by punching or etching a soft magnetic metal ribbon into a drum shape. Here, the soft magnetic metal ribbon is selected from, for example, permalloy ribbon, FeSi ribbon, amorphous ribbon, and nanocrystal ribbon. A large number of magnetic films are formed in a hoop shape. An insulating resin is applied to one or both sides of the magnetic film formed in the hoop shape. The insulating resin is, for example, an epoxy resin. For example, 20 to 50 magnetic films coated with this insulating resin are laminated. Then, the laminated magnetic film is cured at the curing temperature of the resin. Thereby, the drum core 1 is manufactured.

  The drum core 1 has, for example, a total length of 20 mm, a core width of the winding portion of 0.5 mm, and a laminated core thickness of 0.5 mm.

  The drum core 1 is attached to a bobbin 2 that has been subjected to insulation treatment. That is, the bobbin 2 is insulative. Then, a coil antenna is obtained by forming the coil 3 on the bobbin 2 by winding a copper wire having a wire diameter of 0.04 mm, for example, 3000 times. In the present embodiment, for example, a flexible substrate 4 is used as a terminal of the coil antenna.

  The coil antenna of the present invention thus obtained has an antenna gain of about 1 dB or more larger than that of a conventional bar coil antenna having the same shape.

  FIG. 2 is a graph showing the relationship between the Q characteristic of the coil antenna and the antenna gain. In FIG. 2, the horizontal axis indicates the value of Q, and the vertical axis indicates the antenna gain (dB). The antenna gain was measured by the 10 cm method. FIG. 2 shows that the coil antenna according to the present invention is superior to the conventional coil antenna in terms of both Q characteristics and antenna gain.

  FIG. 2 shows a comparison between the characteristics of a coil antenna equipped with the soft magnetic sheet of the present invention and a coil antenna not equipped with the same. It can be seen that by attaching the soft magnetic sheet, the antenna gain of 0.5 dB or more is improved as compared with the case where it is not attached.

  FIG. 3 is a sectional view showing a coil antenna according to the second embodiment of the present invention. The illustrated coil antenna includes a drum core 7, an insulating bobbin 8 having an opening 11, a coil 9, and a terminal 10.

  The coil antenna having such a configuration is manufactured as follows. The drum core 7 is attached to the insulating bobbin 8 having the opening 11 from the opening 11. Next, the coil 9 is wound around the insulating bobbin 8. Then, the terminal 10 is connected to the coil 9. Thereby, a coil antenna is manufactured. The opening 11 may not be covered and the drum core 7 may be left exposed.

  Since the coil antenna having such a configuration has the opening 11, the member can be saved. Moreover, the assembly work for closing the lid can be reduced, which is economical. Further, since the thickness of the lid can be reduced, a thin coil antenna can be provided.

  4 and 5 are views showing a radio timepiece to which the coil antenna according to the present invention is applied. In the illustrated radio timepiece, a soft magnetic material sheet 14 is mounted between a metal case 6 and an antenna coil 13. The effect in that case is that the antenna gain is improved by 0.5 dB or more as shown in FIG.

  In this example, the soft magnetic sheet 14 is mounted between the metal case 6 and the coil antenna 13, but the soft magnetic sheet 14 may be mounted between the printed circuit board and the coil antenna. The magnetic sheet 14 may be mounted between the electronic component and the coil antenna, or the soft magnetic sheet 14 may be mounted between the cable or flexible printed board and the coil antenna.

  The present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention. For example, in the above-described embodiment, the drum core is inserted into the insulating bobbin. Instead, an insulating tape may be wound around the drum core. In this case, a coil is wound on the insulating tape.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows the structure of the coil antenna which concerns on the 1st Embodiment of this invention, (A) is a top view, (B) is a right view, (C) is a bottom view. It is a figure which shows the example of an antenna characteristic which shows the characteristic of the coil antenna shown in FIG. 1 with the characteristic of the conventional coil antenna. It is sectional drawing which shows the structure of the coil antenna which concerns on the 2nd Embodiment of this invention. It is a figure which shows the outline of the radio timepiece to which the coil antenna by this invention is applied. It is a figure which shows the internal structure of the radio timepiece to which the coil antenna by this invention is applied.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Drum type core 2 Bobbin 3 Coil 4 Flexible board 6 Metal case 7 Drum type core 8 Bobbin 9 Coil 10 Terminal 11 Opening part 13 Coil antenna 14 Soft-magnetic-material sheet | seat

Claims (11)

A coil antenna built in a radio clock,
A drum core formed by laminating a plurality of magnetic films coated with an insulating resin on at least one surface; an insulating bobbin into which the drum core is inserted; and a coil wound on the insulating bobbin. Having coil antenna. A coil antenna built in a radio clock,
A drum-type core formed by laminating a plurality of magnetic films coated with an insulating resin on at least one surface; an insulating tape wound around the drum-type core; and a coil wound around the insulating tape. Coil antenna.   The coil antenna according to claim 1 or 2, wherein each of the plurality of magnetic films is formed by extracting a soft magnetic metal ribbon into a drum shape.   The coil antenna according to claim 1, wherein the insulating bobbin has an opening on at least one surface.   A radio timepiece incorporating the coil antenna according to any one of claims 1 to 4, further comprising a soft magnetic sheet disposed close to at least one surface of the coil antenna. Radio clock.   The radio timepiece according to claim 5, wherein the soft magnetic sheet is made of an insulating soft magnetic layer.   The radio timepiece according to claim 6, wherein the insulating soft magnetic layer is formed of soft magnetic powder, dielectric powder, and an organic binder.   The radio timepiece according to any one of claims 5 to 7, wherein a metal case is disposed adjacent to at least one surface of the soft magnetic material sheet.   The radio-controlled timepiece according to any one of claims 5 to 7, wherein a printed circuit board is disposed close to at least one surface of the soft magnetic material sheet.   The radio timepiece according to any one of claims 5 to 7, wherein an electronic component is disposed close to at least one surface of the soft magnetic material sheet. The radio timepiece according to any one of claims 5 to 7, wherein a cable or a flexible printed circuit board is disposed close to at least one surface of the soft magnetic material sheet.

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