JP2005198255A - Antenna and electric wave time-piece using the same, keyless entry system, and rfid system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an antenna capable of demonstrating high characteristics even in a cabinet which restricts the direction of an electromagnetic wave incident from the outside of the cabinet. <P>SOLUTION: A magnetic sensor type antenna comprises a main magnetic path member in which a coil is wound around the coil made of a magnetic material, and receives the magnetic field component of the electromagnetic wave by the main magnetic path member. The antenna is equipped with the main magnetic path member and a cabinet formed of a material of relative permeability of 2 or higher and smaller than that of the main magnetic path member. The cabinet can be formed by injection molding or potting etc. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a timepiece that receives a magnetic field component in an electromagnetic wave including time information and adjusts the time, a radio timepiece, or a smart keyless entry system that detects the approach of an owner by electromagnetic waves and opens and closes a car or a house key ( Hereinafter, it is referred to as a keyless entry system), or a magnetic sensor type electromagnetic wave receiving antenna suitable for use in an RFID tag system or the like (hereinafter referred to as an RFID system) that transmits and receives information by a modulation signal placed on an electromagnetic wave. is there.

Here, the background art will be described using an antenna for a radio timepiece as an example.
A radio clock is a clock that receives time information transmitted by a carrier wave of a predetermined frequency and corrects its own time based on the time information, and is currently put into practical use in various forms such as a table clock, a wall clock, and a wrist watch.
A radio wave used in a radio clock or the like uses a long wave band of 40 kHz to 200 kHz or less, and one wavelength of the radio wave has a length of several kilometers. In order to efficiently receive this radio wave as an electric field, an antenna length exceeding several hundred meters is required, and it is practically difficult to use it for wristwatches, keyless entry systems, RFID systems, etc. that require miniaturization. It is necessary to receive a magnetic field component using a magnetic core.
Specifically, the carrier wave uses two types of radio waves of 40 kHz and 60 kHz in Japan. Even overseas, time information is mainly provided using frequencies below 100 kHz, so in order to receive radio waves of these frequencies, a magnetic material is used as a magnetic core to efficiently converge the magnetic field component of the electromagnetic wave. A magnetic sensor type antenna in which a coil is wound is mainly used.

Conventionally, as an antenna for a radio timepiece, for example, Patent Document 1 discloses a small antenna mainly used for a wristwatch in which a coil is wound around a magnetic core made of an amorphous metal laminate.
Patent Document 2 discloses a small antenna formed by winding a coil around a magnetic core made of ferrite.
Patent Document 3 discloses an antenna in which a conductive sealing member is provided between a metal case and the antenna.
Further, Patent Document 4 includes a main magnetic path member in which a coil is wound around a magnetic core and a sub magnetic path member in which the coil is not wound around a magnetic core, and a closed loop magnetic path along the magnetic core. An antenna is disclosed in which an air gap is provided in a part of the antenna so that the magnetic flux generated inside does not easily leak to the outside during resonance.

JP 2003-110341 A JP-A-8-271659 JP 2002-168978 A Japanese Patent No. 3512782

A wristwatch is mainly composed of a housing (case), a movement (driving unit module) and its peripheral components (a dial, a motor, a battery, etc.), a non-metallic (glass) lid, and a metal back lid. In the case of incorporating an antenna in this, conventionally, it is often provided outside the casing. However, recently, it has been required to be provided inside the housing due to the trend of miniaturization and weight reduction. As shown in FIG. 10, the periphery of the movement 22 and the back cover 24, mainly the battery, the motor for moving the clock hand, etc. It arrange | positions in the clearance gap between the components 26. FIG. The antenna 1 in the front view of FIG. 10 is indicated by a solid line to show the structure, but is actually housed in a space closed by the casing 25, the movement 22, the peripheral component 26, and the back cover 24.
The antennas of Patent Documents 1 and 2 described above are formed by a coil in which the magnetic field component of electromagnetic waves is converged by using an amorphous foil or ferrite having a high relative permeability as a magnetic core, and the converged magnetic flux is wound around the outside of the magnetic core. It is an antenna that detects a component whose magnetic flux changes with time as a voltage. Therefore, in this respect, it is desirable that the casing is made of a resin material that does not inhibit the magnetic field component of electromagnetic waves. However, if a part of it is made of resin, there are restrictions in terms of design and design. In general, the design of a wristwatch is a selling point. For example, a metal casing is preferred in terms of luxury and aesthetics. In view of this, cases such as middle and high-end watches and automobiles are often made of metal cases. In this case, depending on the conventional antenna structure and arrangement, a metal case or the like acts as a shield against electromagnetic waves, and there is a problem that reception sensitivity is greatly reduced.

  In addition, as an antenna, a voltage is induced in the coil as a result of magnetic flux due to electromagnetic waves entering from the outside passing through the magnetic core. As shown in the equivalent circuit diagram of FIG. 9, this voltage resonates at a desired frequency by a capacitor C connected in parallel with the coil 8, and a Q-fold voltage is applied to the coil 8 by resonating. The resonance current flows through the coil 8. Due to this resonance current, a magnetic field is generated around the coil 8, and the magnetic flux mainly enters and exits from both ends of the magnetic core. Here, when a metal approaches the antenna, the magnetic flux generated by the resonance current penetrates the metal and generates an eddy current. That is, if there is a metal with low electrical resistance near the antenna, the magnetic field energy at the time of resonance is lost as eddy current loss and appears as loss of the antenna coil. As a result, the Q value is lowered and the antenna sensitivity is effectively reduced. This leads to a decrease in. Therefore, in Patent Document 3, the Q value is maintained by arranging the antenna outside the metal case and through a shield member. However, enlargement and design restrictions were inevitable. In this regard, according to the antenna disclosed in Patent Document 4, the magnetic flux flowing toward the outside at the time of resonance is selectively guided to the sub magnetic path member side provided with the air gap, and the magnetic flux is directed to the outside. It is said that it is difficult to leak, and thus the reduction of the Q value due to eddy current loss can be suppressed.

  A similar problem exists in a keyless entry system or an RFID system in which a magnetic sensor type antenna is accommodated in a metal casing or close to a metal part. A keyless entry system is, for example, a remote control of a vehicle key such as a passenger car, which consists of a transmission / reception unit equipped with an antenna that opens and closes by a specific electromagnetic wave. The remote operation can be done without contact. In addition, an RFID (Radio Frequency Identification) system transfers information stored in a tag by an antenna that operates by a specific electromagnetic wave. For example, an RFID tag to which destination information such as a bus is input is used as a bus. If the RFID tag to which the timetable information is attached and embedded is embedded in the display board of the hall, the user can recognize various traffic information without contact. In these systems, it is required to increase the sensitivity of the antenna as well as to reduce the size of the housing and the antenna.

  In consideration of these problems, the inventors of the present application provide a small and easily adjustable antenna capable of solving the problem of eddy current loss without increasing the installation area and volume and obtaining a highly sensitive output. For this purpose, as a magnetic sensor type antenna that receives the magnetic field component of the electromagnetic wave by the main magnetic path member, the main magnetic path member and other sub-magnets made of a material having a relative permeability smaller than that of the main magnetic path member are used. Applications for antennas with several configurations provided with magnetic path members have been filed separately.

  However, when actually manufactured, it is unexpectedly difficult to provide a sub magnetic path member in addition to the main magnetic path member in an antenna which is a small component. The positioning of the two magnetic core members and the fragile magnetic core of the main magnetic path member are difficult. There was room for further study to assemble without destroying. In view of the above, the present invention provides a main magnet for providing a small and easy-to-adjust sensitivity antenna which can solve the problem of eddy current loss without increasing the installation area and volume and can obtain a highly sensitive output. It is an object of the present invention to provide an antenna comprising a path member and a sub magnetic path member, and having a structure that takes into consideration both assembling property and antenna characteristics. In particular, the present invention provides a radio timepiece, particularly a radio timepiece, a keyless entry system, an antenna suitable for an RFID system, and the system using the same, which can exhibit high antenna characteristics in a limited small space.

  The antenna of the present invention has a main magnetic path member in which a coil is wound around a magnetic core made of a magnetic material, and the main magnetic path member is an antenna of a magnetic sensor type that receives a magnetic field component of electromagnetic waves by the main magnetic path member. And a case made of a material having a relative permeability of 2 or more and smaller than that of the main magnetic path member as a secondary magnetic path member. By using a material having a relative permeability smaller than that of the main magnetic path member as the sub magnetic path member, the above object can be solved. It is preferable that the case has a relative magnetic permeability of about 2 to 1000, more preferably about 3 to 500, and more preferably about 5 to 100.

Further, the present invention is characterized in that the case is injection molded. That is, the present invention includes a main magnetic path member in which a coil is wound around a magnetic core made of a magnetic material, and a magnetic sensor type antenna that receives a magnetic field component of electromagnetic waves by the main magnetic path member. A case in which at least a part of the outer peripheral portion of the main magnetic path member is injection molded with a material having a relative magnetic permeability of 2 or more and smaller than the main magnetic path member. is there.
By using the case itself as a sub magnetic path member in this way, the assembly of the main magnetic path member and the sub magnetic path member can be facilitated, the number of parts can be reduced, and further, the case can be accommodated without preparing a separate case. Can be installed.

  The soft magnetic material constituting the magnetic core is preferably a high relative magnetic permeability material of over 100 to about 300,000, such as silicon steel, permalloy, amorphous metal, nanocrystalline metal, and ferrite. This is preferably a high relative permeability material of about 500 to 100,000. In addition, the case needs to have a relative permeability higher than that of air and smaller than that of the main magnetic path member. By using the case of the low relative permeability material as the secondary magnetic path in this way, a part of the incident magnetic flux enters the magnetic core by returning around the main magnetic circuit through the case of the low relative permeability. The amount of magnetic flux passing through the coil is effectively increased, resulting in a highly sensitive antenna. In addition, the case that plays the role of the secondary magnetic path is not assembled to the main magnetic path member as in the prior art, and it is sufficient to put the main magnetic path member inside as a case. It also serves to protect the magnetic core. The case preferably has a shape capable of positioning and storing the main magnetic path member in order to improve assemblability. The magnetic core may be a single body or a laminated body of thin ribbons, or may be a plate-like ferrite.

  Here, Q is defined as ωL / R, where ω is the angular frequency of the radio wave, R is the resistance of the resonance circuit composed of the antenna and the capacitor, and L is the self-inductance of the coil section. R described here is the sum of the DC resistance and AC resistance of the coil. In particular, the AC resistance of an antenna placed in a metal case increases. The reason for this is that resonance occurs between a coil around which a magnetic core that collects magnetic flux is wound and a capacitor added outside, resulting in a Q-fold resonance voltage. A high voltage is generated at both ends of the coil due to this resonance current. This is because magnetic flux is generated near both ends. This is eddy current loss that occurs when magnetic flux due to the resonance phenomenon penetrates the metal. Here, by providing a case with low relative permeability, the magnetic flux flowing into the magnetic core not only flows through the coil and flows out from the other end of the magnetic core, but also part of it returns to the case with low relative permeability and again from the outside. It merges with the inflowing magnetic flux and passes through the inside of the coil to generate more voltage. In addition, since the magnetic flux generated by the resonance current flows back through the case with low relative permeability, the total amount of magnetic flux that exits from both ends of the antenna can be reduced, and the magnetic flux penetrating through adjacent metal cases is reduced. Equivalent increase in AC resistance can be suppressed. Therefore, the increase in the resistance component R described above is minimized, and as a result, the Q value is increased and the loss due to eddy currents is reduced.

As shown in FIG. 3C, the case may be formed so that the trunk portion of the main magnetic path member is accommodated and the end portion is exposed outside the case. By adopting such a case shape, it is easy to take in external magnetic flux, and the antenna characteristics can be improved even if it is installed in a metal casing.
As another antenna configuration, as shown in FIG. 3 (b), the case has a relative permeability of 2 or more for housing the trunk of the main magnetic path member and a relative permeability smaller than that of the main magnetic path member. A soft magnetic case portion made of a material and an end portion of the main magnetic path member that accommodates the end portion of the main magnetic path member and has a lower relative permeability than the soft magnetic case portion may be formed. . The case end may be made of a nonmagnetic material. In this way, by reducing the relative permeability of the end of the case covering the end of the main magnetic path member, the magnetic field component of the electromagnetic wave passes through the main magnetic path member without being blocked by the case as in the case of the above antenna, and the antenna There is no loss of properties.
As another antenna configuration, as shown in FIG. 4 (f), the case has a relative magnetic permeability of 2 or more and continuously covers the main magnetic path member from one end to the other end. A soft magnetic material case portion made of a material having a relative permeability smaller than that of the path member, and a nonmagnetic material case portion made of a nonmagnetic material that continuously covers from one end portion to the other end portion of the main magnetic path member. You may do it. By using a part of the case as a non-magnetic material, the magnetic field component of the electromagnetic wave passes through the main magnetic path member without being blocked by the case as in the case of the antenna, and the antenna characteristics are not impaired. Although non-magnetic is preferable, application is possible even with a material having a relative permeability lower than that of the soft magnetic case portion.

An antenna that suppresses the generation of eddy currents can be achieved by using a magnetic core of the main magnetic path member as a single body or a laminated body of thin ribbons. When the magnetic core of the main magnetic path member is composed of a laminate in which soft magnetic ferrite or soft magnetic metal ribbon is laminated, the magnetic flux flowing between the main magnetic path member and the case substantially passes through the laminated section of the metal ribbon. Is preferable. That is, the case is installed so as to be adjacent to the laminated cross section, not in the plane direction of the metal ribbon of the main magnetic path member on which the thin film magnetic metal is laminated. As a result, eddy currents from individual ribbons are reduced with respect to eddy currents generated in the case of stacking, the loss can be suppressed, and the antenna characteristics can be further improved.
For example, when a magnetic flux flows in the direction passing through the plate surface of the metal ribbon 4 on which the main magnetic path members are laminated as shown in FIG. 7, a large eddy current 9 is generated inside the metal ribbon 4 and the loss is large. And Q value decreases. When the eddy current 9 is generated, the antenna characteristics that have been lowered due to the installation inside the metal casing are further deteriorated, resulting in a decrease in antenna efficiency. On the other hand, as shown in FIG. 6, it is possible to minimize the eddy current generated inside the magnetic core by installing the case so that the magnetic flux 8 passes from the end laminated section of the metal ribbon 4 and the loss can be reduced. The number of antennas can be reduced.

  The case is a composite material composed of soft magnetic ferrite powder, soft magnetic metal powder, or soft magnetic metal flake and a plastic polymer material such as resin or rubber. The magnetic flux incident from the outside is received by the main magnetic path member, but the magnetic flux radiated from the inside can be adjusted so that the balance of the closed magnetic path of the present invention is adjusted by the case of the secondary magnetic path so that it is difficult to leak to the outside. The case is smaller than the relative permeability of the main magnetic path member, but if the relative permeability is too large, it is difficult to receive the magnetic flux concentrated on the main magnetic path member. Moreover, even if it is too small, the effect as a secondary magnetic path will become low. The case preferably has a relative magnetic permeability of 2 to 1000, more preferably 3 to 500, even more preferably 5 to 100, and even more preferably 10 to 60. Therefore, a composite material having flexibility is preferable because an appropriate relative magnetic permeability can be adjusted by adjusting the mixing ratio of the soft magnetic powder and the resin material, and the thickness can be easily adjusted. In addition, since it has flexibility, the air gap can be easily filled and the degree of processing is high, so it is easy to handle. However, flexibility is not essential.

  Further, according to the present invention, the case is formed by putting a curable slurry containing soft magnetic material powder in a mold and immersing the main magnetic path member and then curing the case. A case formed of a material having a relative permeability smaller than that of the member may be used. As the slurry to be cured, for example, a thermosetting or volatile curing type slurry containing a soft magnetic material powder, a thermosetting resin, an organic solvent, or the like can be applied. The slurry is poured into a container-shaped mold, and the main magnetic path member is immersed in the slurry and cured. By using a technique generally called potting, an antenna provided with a case serving as a secondary magnetic path of the present invention can be easily obtained.

For soft magnetic metal flakes, ferrite powder, amorphous alloy powder or the like can be used. An average particle size of 0.1-50μm and an average thickness of 3μm produced by grinding a granular powder produced from a nanocrystalline magnetic alloy such as Fe-Cu-Nb-Si-B by water atomization with an attritor Flat shape powders such as carbonyl iron alloy, amorphous alloy, Fe-Si alloy, molybdenum permalloy, supermalloy, etc. can be used as the flat shape powders of metal. These are dispersed in a flexible polymer material and formed into a case shape by injection molding, or injection molded around the magnetic core to form a secondary magnetic path member.
The flexible polymer material is an organic material that is flexible and has a specific gravity of 1.5 or less, preferably a weather resistant resin, such as chloroprene rubber, butyl rubber, urethane rubber, silicone resin, vinyl chloride resin, phenol resin. Etc.

  By using such a composite material, the magnetic flux can be fed back into the closed magnetic circuit without providing an air gap that is troublesome to adjust. In addition, since it is not necessary to provide an air gap, it is advantageous in that it is easy to manufacture without requiring fine accuracy and can maintain stable performance. When an open type case is used, after the main magnetic path member is accommodated in the case, a non-magnetic resin may be poured into the case instead of the lid.

  In the antenna of the present invention, when the casing is a metal casing or a metal member is provided inside the casing, the metal casing or the metal member (such as a metal printed wiring on a circuit board) It is preferable that the end of the magnetic core be bent away from the installation position. For example, in a radio-controlled wristwatch, it is preferable to bend in the direction of the glass lid. The bending angle is vertical or oblique, and an arbitrary angle can be set depending on the situation inside the casing. By bending the end portion of the magnetic core for converging the magnetic field component so as to be directed in the magnetic flux inflow direction, the tip portion converges a large amount of magnetic flux incident on the inside of the housing, and a highly sensitive antenna is obtained. In addition, this shape is based on the property that the magnetic flux generated by the resonance current from the capacitor connected in parallel with the voltage induced in the coil wound around the magnetic core mainly enters and exits from both ends of the magnetic core. As a result, the eddy current generated in the metal casing can be reduced and the electrical Q value can be kept high, leading to higher sensitivity as an antenna. The tip of the magnetic core end may be further bent in a different direction. As a result, the incident magnetic flux can be captured more widely from four directions, and an antenna with higher sensitivity can be obtained.

The present invention also relates to a radio-controlled timepiece in which a magnetic sensor-type antenna is incorporated in a wristwatch having a metal casing, a movement (including peripheral parts), a non-metal lid, and a metal back lid. A radio timepiece using any one of the antennas described above, wherein the main magnetic path member is disposed on the inner side of the metal casing and the sub magnetic path member is disposed on the peripheral edge side of the metal casing. Usually, the frequency of occurrence of eddy currents can be reduced by moving the sub magnetic path member away from the metal casing. However, in general, there are many space restrictions on the inner side of the housing, and the sub magnetic path member cannot always be arranged. In this respect, if the secondary magnetic path member is formed of a composite material as a case and is provided along the peripheral side, the space can be effectively used, and the thickness and area of the case can be easily adjusted and the assembly is excellent. As a result, adverse effects due to eddy currents can be offset, and further effects can be expected. However, this does not prevent the main magnetic path member from being disposed on the peripheral edge side of the metal casing and the case from being disposed on the inner side of the metal casing. In this case, the magnetic field entering from the outside easily converges to the magnetic core of the main magnetic path member close to the metal casing, while the case is far from the metal casing, so that the magnetic field leaking from the inside faces toward the casing. It is difficult to generate an eddy current, and the effect can be expected. Therefore, it can be said that it is desirable to select these configurations according to individual circumstances and desired effects.
As described above, the antenna of the present invention is suitable for use in a small radio wristwatch that receives a radio wave including time information and adjusts the time. Further, it is suitable for use in a keyless entry system that remotely controls the opening and closing of a key of a passenger car or a residence. Furthermore, the present invention is suitable for use in an RFID system that transmits and receives information using a tag storing information.

According to the antenna of the present invention, the magnetic flux incident from the outside is received by the main magnetic path member, and the radiated magnetic flux at the time of resonance is guided from the main magnetic path member to the case serving as the secondary magnetic path so that the inside of the magnetic circuit can be efficiently performed. I can return. As a result, a high output voltage can be obtained and the Q value can be kept high. Further, by using a sub magnetic path member having no air gap, particularly a composite material having a low relative permeability, the feedback of magnetic flux can be adjusted, and a high Q value and sensitivity can be obtained. Further, by directly connecting the case and the main magnetic path member magnetically without an air gap, the fringing magnetic flux is small and the eddy current can be further reduced. Further, by using the sub magnetic path member as a case, even a fragile magnetic core can be protected from an external impact by the case, and the safety is high. Furthermore, by forming the case so that the main magnetic path member can be fitted, it is easy to assemble without requiring position adjustment, and the structure is excellent in workability.
In addition, an antenna with even less loss can be obtained by using a case that does not magnetically block the magnetic flux so that the magnetic flux is guided to the end of the main magnetic path member.
Further, the main magnetic path member constituted by the laminated metal strips is used so that the magnetic flux flowing between the main magnetic path member and the case substantially passes through the end of the metal strip of the main magnetic path member. By doing so, the eddy current loss which generate | occur | produces in the strip | belt surface of a main magnetic path member can be decreased, and an antenna with little loss can be obtained.

Also, by bending the end of the magnetic core away from the installation position of the metal casing or metal member (including metal printed wiring on the circuit board, etc.), the tip of the casing is the casing. A high sensitivity antenna is obtained by converging many magnetic fluxes incident on the inside. In addition, this shape is based on the property that the magnetic flux generated by the resonance current from the capacitor connected in parallel with the voltage induced in the coil wound around the magnetic core mainly enters and exits from both ends of the magnetic core. As a result, the eddy current generated in the metal casing can be reduced and the electrical Q value can be kept high, leading to higher sensitivity as an antenna. If the tip of the magnetic core end is further bent in a different direction, the incident magnetic flux can be captured more widely from four directions, and an antenna with higher sensitivity can be obtained.
As described above, the sensitivity and the Q value equivalent to the case where the metal watch is disposed away from the metal part are obtained while the installation area in the radio timepiece is the same. In addition, the effective sensitivity can be increased by suppressing the outflow of magnetic flux due to the resonance current. And workability and assemblability are good. Due to the above synergistic effect, a highly sensitive antenna with a small installation area but a high degree of freedom in arrangement and relatively small design constraints.
Such an antenna can be suitably used in a small high-performance radio timepiece, radio wristwatch, keyless entry system, RFID system, and the like.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 shows an embodiment of the main magnetic path member. The main magnetic path member 10a of FIG. 1A is formed by winding a coil 8 around a magnetic core 14a made of rod-shaped ferrite, and a case (not shown) is provided around the main magnetic path member. The main magnetic path member 10b in FIG. 1 (b) has end portions 11b where both ends of a rod-like ferrite material rise vertically and bend. It has a main magnetic circuit formed by winding the coil 8 at the center, and is formed by winding the coil 8, thereby constituting the main magnetic circuit. The main magnetic path member 10c in FIG. 1 (c) is substantially the same as the main magnetic path member 10b, but has a quadrilateral ferrite core. In the case of a square, it is desirable in terms of ease of assembly when it is installed in a casing such as a metal case. The main magnetic path member 10d shown in FIG. 1 (d) is a ribbon obtained by integrally punching from a band of amorphous metal foil (thickness of 20 μm or less) into a U-shape with a bent end 11d as shown in the figure. A plurality of the ribbons are laminated and the coil 8 is wound around the center. The main magnetic path member 10e shown in FIG. 1 (e) is formed by laminating ribbons punched from an amorphous metal foil. In this example, the lamination directions are different, and the end portion 11e of the ribbon is formed by separately bending both ends of the ribbon punched out into a rectangular shape. In addition, in the laminated type and the thin line type in which a plurality of fine wires are bundled as shown in FIG. 1 (h), it is desirable that an insulating film is coated between the thin ribbons or individual fine wires and laminated or bundled through the insulating layer. A main magnetic path member 10f in FIG. 1 (f) is obtained by winding a coil 8 around a plate-like magnetic core 14f made of ferrite having a recess 16f to form a main magnetic circuit. The main magnetic path member 10g in FIG. 1 (g) is a laminate of thin ribbons punched from amorphous metal foil. The end portion 11g of the ribbon is formed by bending both ends of the ribbon striped into a rectangular shape obliquely upward. The main magnetic path member 10h shown in FIG. 1 (h) is obtained by bundling a plurality of thin wires into a magnetic core 14h, bending both ends, and providing a coil at the center.

  FIG. 2 shows another embodiment of the main magnetic path member according to the present invention. The main magnetic path member 30a shown in FIG. 2 (a) has a rod-shaped ferrite material that has both ends 31a that rise vertically and bend, and the tip 32a is bent in a direction parallel to the magnetic core 34a. It is. A coil 8 is wound around the center, and a case (not shown) serving as a secondary magnetic path member is provided around the coil 8. The main magnetic path member 30b in FIG. 2 (b) is a thin strip obtained by integrally punching the end portions 31b and 32b as shown in the figure from a strip of metal foil in the same manner as the main magnetic path member 10d in FIG. 1 (d). A plurality of layers are laminated, and a coil 8 is wound around the center thereof. The main magnetic path member 30c in FIG. 2 (c) is the same as that in FIG. 1 (e), but has a tip portion 32c formed by further bending the end portion 31c. The main magnetic path member 30d in FIG. 2 (d) is obtained by bending the end portion in FIG. 2 (c) obliquely upward. Further, the tip portion may be bent in two directions, or may be shaped so that the tip portion of the laminated magnetic core becomes a fan shape.

  According to the above embodiment, the incident magnetic flux not only passes through the main magnetic circuit of the magnetic core wound with the coil, but also partly feeds back through the gap sub magnetic path member and circulates in the main magnetic circuit. Thus, the introduced magnetic flux is efficiently rotated by a closed magnetic circuit different from the main magnetic circuit, and as a result, a high output voltage is obtained.

Hereinafter, for evaluation, the antenna output voltage and the like were measured and compared along the test device imitating the radio wave wristwatch shown in FIG. 8 and the equivalent circuit shown in FIG.
In FIG. 9, L is a coil composed of the antenna magnetic core 1 and the winding 8. R is the sum of the DC resistance and AC resistance of the coil. A voltage V due to the time variation of the magnetic flux is detected in this coil. Here, a capacitor C is connected in parallel with the antenna, the capacitor C and the coil L described above electrically resonate, and a Q-fold voltage is generated at both ends of the capacitor to operate as an antenna. In the comparative test, an evaluation antenna was placed in a 1 mm-thick metal (stainless steel SUS403) housing 70 imitating the radio wave wristwatch shown in FIG. 8, and the voltage V by the equivalent circuit was measured.

(Example 1)
As Example 1, antennas 1a to 1d shown in FIGS. The magnetic core 4 shown in FIGS. 3A to 3C has a barbell shape having a length of 23 mm made of ferrite, abdominal width of 2 mm, and an end width of 2.5 mm. The magnetic core 4 in FIG. 3D is a soft magnetic metal foil strip such as an amorphous alloy having a length of 30 mm and a width of 2 mm, a nanocrystalline magnetic alloy such as Fe-Cu-Nb-Si-B, or an Fe-Si magnetic alloy ( 20 to 30 layers) is laminated, and the end is bent obliquely upward as shown in FIG. 2D, and the tip is parallel to the center. The winding 8 was formed by winding 1200 turns of enamel-coated copper wire having a wire diameter of 0.07 mm around the magnetic core 4 in a range of 12 mm in length. The main magnetic path member thus created was mounted so as to be in contact with the cases 7a to 7d serving as sub magnetic paths. The material of the case is formed by injection molding of a composite material mainly composed of soft magnetic metal flakes obtained by pulverizing a ribbon made of a nanocrystalline magnetic alloy such as Fe—Cu—Nb—Si—B and a resin. The case 7a is integrally formed in a box shape. The case 7b is obtained by injection molding of a soft magnetic case part having a shape obtained by removing both ends from the case 7a and a nonmagnetic material case part made of a resin component not including soft magnetic metal flakes in two colors. The case 7c is formed so as to match the length of the main magnetic path member and to expose the end of the main magnetic path member. In addition, the case 7c has a convex shape on the inner abdomen along with the irregularities on the abdomen of the magnetic core 4, and a shape on which the main magnetic path member can be fitted. In the case 7d, the end of the magnetic core 4 with the thin ribbons is placed in a recess provided in the end of the case and positioned. Alternatively, after the main magnetic path member is placed in the case, a nonmagnetic resin may be poured to fill the main magnetic path member in the case.
By using these cases, this case serves as a secondary magnetic path, as demonstrated in the reference example described later, and a part of the incident magnetic flux has this low relative permeability. The main magnetic circuit is fed back through the case, and the amount of magnetic flux that has entered the magnetic core is effectively increased compared to the case where the main magnetic path member is used alone, resulting in a highly sensitive antenna. Further, in order to protect the brittle magnetic core, it is possible to provide a highly safe product that is not damaged even if it is incorporated in a portable article such as a wristwatch.
Furthermore, compared to a reference example described later, the attachment of the sub magnetic path is simple, the productivity is improved, and variations in the characteristics of each manufactured product can be suppressed as much as possible, which is very advantageous in production. Further, when the nonmagnetic case portion and the soft magnetic case portion are combined as in the case 7b, the flow of the magnetic flux from the outside entering the main magnetic path member is not hindered, and the antenna performance equal to or better than the above reference example is achieved. Can be maintained. Further, by forming the main magnetic path end portion to be exposed as in the case 7c, the antenna performance equivalent to or higher than that of the reference example can be maintained, and the cost can be reduced. Further, it is preferable to provide an unevenness for fixing the main magnetic path member as in the case 7c because the assemblability becomes very good.

(Example 2)
As Example 2, antennas 1e to 1i shown in FIGS. 4 (e) to (i) were manufactured. The main magnetic path member was the same as that used in Example 1. Around this main magnetic path member, injection molding was performed using a material mixed with soft magnetic metal flakes obtained by pulverizing a ribbon made of a nanocrystalline magnetic alloy such as Fe-Cu-Nb-Si-B and a resin, A case serving as a magnetic path was formed.
The case 7e is integrally cast around the entire periphery. The case 7f is formed so as to match the length of the main magnetic path member and to expose the end of the main magnetic path member. The case 7g is formed by injection molding half of the main magnetic path member from the center portion of the main magnetic path member with the above-described mixed material of soft magnetic metal flakes and resin to form a soft magnetic case portion, and the other is made of a resin component not containing soft magnetic metal flakes A non-magnetic material case is formed by injection molding in two colors. Case 7h is formed by injection molding a mixed material made of soft magnetic metal flakes and resin only on the abdomen of the main magnetic path member. The case 7i is formed by casting the entire main magnetic path member in the same manner as the case 7e, but the main magnetic path member has a magnetic core having the shape shown in FIG. 2 (d).
By forming these secondary magnetic paths by injection molding into cases, this case serves as the secondary magnetic path, and the incident magnetic flux, as demonstrated in the reference example described later. Part of the magnetic flux is fed back through the main magnetic circuit through the case of this low relative permeability, and the amount of magnetic flux that has entered the magnetic core is effectively increased compared to the case where the main magnetic path member is used alone. And it becomes a highly sensitive antenna. Further, in order to protect the brittle magnetic core, it is possible to provide a highly safe product that is not damaged even if it is incorporated in a portable article such as a wristwatch.
Furthermore, since the soft magnetic part is molded without gaps around the main magnetic path member by injection molding, the case of the sub magnetic path and the main magnetic path member are not misaligned after assembly, resulting in variations in characteristics. It is possible to provide an antenna that is eliminated and that has a very high strength and less damage. In addition, the soft magnetic case part and the non-magnetic case can be simultaneously injection molded in two colors by injection molding, and the case shape as shown in FIG. The degree of freedom is very high.

(Example 3)
As Example 3, an antenna was manufactured using the potting technique shown in FIG. First, a predetermined amount of 7 L of a material obtained by mixing a soft magnetic metal flake obtained by pulverizing a ribbon made of a nanocrystalline magnetic alloy such as a Fe—Cu—Nb—Si—B system and a resin was poured into a vessel-shaped mold. Then, the main magnetic path member was immersed in the slurry of this formwork. The main magnetic path member was held at a predetermined position by suspending using the coil winding end and gradually immersing it. The magnetic core 4 has a barbell shape having a length of 23 mm, an abdominal width of 2 mm, and an end width of 2.5 mm made of the ferrite used in FIGS. The blending ratio of the soft magnetic metal flakes and the resin was determined so that the slurry had a relative magnetic permeability of 5 to 100 when cured. As in the case of FIG. 3A, the final shape of the antenna is such that the periphery of the main magnetic path member is integrally covered with a case that becomes a sub magnetic path.
By forming these secondary magnetic paths by potting into a case, the effect of improving the antenna characteristics by the secondary magnetic path can be obtained as described above. Further, since the stress applied to the magnetic core is smaller than the injection during the molding of the case, a brittle material can be manufactured without breaking even as a magnetic core.

(Reference Examples 1 and 2)
In order to see the effect of the presence or absence of the secondary magnetic path, the antenna 3c of FIG. Mn-Zn ferrite (Hitachi Metals Ferrite MT80D), 1.5 mm square, 16 mm long, 7.5 mm bent part height is used as the magnetic core, and winding 8 is a wire that insulates the surface of the ferrite core 1200 turns of enamel-coated copper wire having a diameter of 0.07 mm was wound in a range of 12 mm in length. Next, the secondary magnetic path member 15c is made of the same ferrite as above with a plate thickness of 0.5 mm and a width of 1.5 mm, and an interposition member made of plastic (PET) is placed and both ends have a gap G = 0.2 mm. A sub magnetic path member was formed. The installation area of this antenna is the same as a width of 1.5 mm and a length of 16 mm.
As Comparative Example 1, an antenna in which a winding was wound around a linear magnetic core (without a secondary magnetic path member) was used. Using the same ferrite as the magnetic core of Reference Example 1, the width is 1.5 mm, the length is 16 mm, the height is 2.5 mm including the rise as a winding stopper, and the winding 8 has the same thin wire as in Example 1 under the same conditions. It is the one wound by.
Further, as Reference Example 2, an antenna 3d shown in FIG. As a magnetic core, a cobalt-based amorphous (Hitachi Metals ACO-5SF) metal foil (thickness 15 μm) is punched into a ribbon with a width of 1 mm, a length of 16 mm, and a bent portion height of 7.5 mm. Lamination was performed to obtain a laminate having a thickness of 0.45 mm as a magnetic core. Then, the winding 8 was wound with 1200 turns of enamel-coated copper wire having a wire diameter of 0.07 mm within a range of 12 mm after insulating the surface of the laminated core. For the sub magnetic path member with gap, a single member 15d having a width of 1.5 mm is prepared using the same amorphous metal foil as described above, and a gap G = 0.2 mm at both ends by an intermediate member made of plastic (PET). Formed.
The above antenna was installed in a metal case 70 shown in FIG. 8, and an output voltage was measured by applying a magnetic field having a frequency of 40 kHz and a magnetic field strength of 14 pT as an effective value of an alternating magnetic field corresponding to the magnetic field component of the electromagnetic wave from the outside. The results are shown in Table 1. It was found that the antenna characteristics changed dramatically depending on the presence or absence of the secondary magnetic path.

(Reference Examples 3 and 4)
Next, the effect of antenna characteristics due to the gap between the main magnetic path member and the sub magnetic path was compared in a situation where the antenna was not housed in the metal case.
As Reference Example 3, an antenna 10g shown in FIG. A magnetic core 14g having the same structure as that of the conventional example shown in FIG. 11 was used, and the same ferrite member 15g having a plate thickness of 0.5 mm and a width of 1.5 mm was installed thereon. The central gap G was adjusted and changed with a plastic (PET) member.
Reference example 4 is the antenna 10h of FIG. A magnetic core 14h having the same structure as the conventional example shown in FIG. 11 was used, and the same ferrite member 15h having a plate thickness of 0.5 mm, a width of 1.5 mm, and a length of 16 mm was provided. The gap G on both sides was adjusted and changed with a plastic (PET) member.
Further, as Comparative Example 2, the same antenna structure as in FIG. 12H was used, but the sub magnetic path member was not a magnetic material but a copper plate that was an electrical good conductor. The copper plate had a thickness of 0.25 mm, a width of 10 mm, and a length of 20 mm, and the gap G on both sides was adjusted and changed with a plastic (PET) member.
In the conventional example, the antenna shown in FIG. 11 is used.
The output voltage was measured by applying a magnetic field having a frequency of 40 kHz and a magnetic field strength of 14 pT as an effective value of an alternating magnetic field corresponding to the magnetic field component of the electromagnetic wave from the outside. The Q value was measured using an impedance meter at a drive voltage of 0.05V. The results are shown in Table 2. When assembling the main magnetic path member and the sub magnetic path member, the antenna characteristics cannot be obtained stably when assembling the main magnetic path member and sub magnetic path member due to the presence or absence of a gap. It turns out how to improve becomes an important problem.

Example 4
Next, FIG. 10 shows a front view and a side view of the radio-controlled wristwatch incorporating the antenna of the first embodiment. In the front view, the antenna is shown by a solid line for easy understanding of the arrangement. The radio-controlled wristwatch includes a metal (for example, stainless steel) case 25, a movement 22, peripheral components, a glass lid, and a metal (for example, stainless steel) back cover 24. It arrange | positions between the back covers 24. When the case 1 is composed of a soft magnetic case portion and a nonmagnetic case portion as shown in FIG. 4 (f), the soft magnetic case portion serving as the secondary magnetic path is installed toward the side closer to the metal casing such as the back cover. The The nonmagnetic case part is on the glass lid side. Further, in the antenna 1, when the end of the magnetic core is bent as shown in FIGS. 1B and 1C, the tip is bent and arranged in the direction of the glass lid so as to rise from the bottom. Therefore, although the center part of the magnetic core is adjacent to the back cover side, the end part 11 and the front end part 32 of the magnetic core serving as the entrance and exit of the magnetic flux have a structure facing the incident direction of the electromagnetic wave. Such an arrangement has a relatively high degree of freedom and is excellent in sensitivity adjustment and assembly.
A watch is a movement that consolidates driving functions and occupies most of the volume, and a display surface (clockface) for humans is also essential. For this reason, the antenna must be arranged near the back cover. In this case, the antenna is surrounded by metal parts, but according to this embodiment, the end of the magnetic core where the magnetic flux due to the resonance current of the antenna flows out most is separated from the metal around the bottom part of the magnetically shielded casing. In this way, it is erected by bending toward the non-metal part (glass lid or the like). Thereby, the amount of magnetic flux flowing from the outside is large, more magnetic flux near the glass surface far from the housing bottom metal can be captured, and the influence of the metal approaching of the housing bottom can be minimized.
In the radio-controlled wristwatch, the end of the magnetic core that stands up may appear on the surface as part of the design of the clock face. For example, the end of the magnetic core penetrates the dial and appears on the display surface, which is used as a design. At this time, the end of the magnetic core protrudes to the display portion, so that the sensitivity becomes higher. On the contrary, the end portion does not need to be erected vertically. It is only necessary to have a direction and an angle at which magnetic flux can be easily received depending on the surrounding conditions.

  In keyless entry systems and RFID systems that use transceivers and tags, the antenna of the present invention is effective because the antenna is required to be housed in a narrow space surrounded by metal in the housing, similar to a radio clock. The effect can also be obtained in the same manner as in the above embodiment.

  The antenna of the present invention can be used for radio wave receiving antennas used in radio timepieces, keyless entry systems such as automobiles and houses, and RFID tag systems. In particular, it is suitable for radio wristwatches because of its great freedom of shape.

It is a schematic structure figure of the magnetic core used for the present invention. It is a schematic structure figure of another magnetic core used for the present invention. 1 is a schematic structural diagram of an antenna showing an embodiment of the present invention. It is a schematic structural drawing of the antenna which shows another Example of this invention. It is a figure which shows an example of the construction state of this invention. It is a schematic structure figure of the present invention showing relation between magnetic flux and eddy current. It is a schematic structure diagram for reference showing the relationship between magnetic flux and eddy current. 1 is a schematic diagram of an apparatus in which an embodiment of the present invention was tested. It is a figure which shows the equivalent circuit of the antenna of this invention. It is the front view and side view which show the example which has arrange | positioned the antenna of an Example in a wristwatch. It is a schematic structure figure of the conventional antenna. This is an antenna provided with a reference secondary magnetic path member for verifying the effect of the secondary magnetic path.

Explanation of symbols

1, 3: Antenna 4, 14, 34: Magnetic core 7: (Case) Sub magnetic path member 8: Coil, winding 9: Eddy current 10, 30, Magnetic core 22: Movement 24: Back cover 25: Metal casing 26: Peripheral parts

Claims (14)

In a magnetic sensor type antenna having a main magnetic path member in which a coil is wound around a magnetic core made of a magnetic material and receiving a magnetic field component of an electromagnetic wave by the main magnetic path member, the main magnetic path member and a relative permeability are And a case made of a material having a relative magnetic permeability smaller than that of the main magnetic path member. The antenna according to claim 1, wherein the case is formed so as to accommodate a body portion of the main magnetic path member and an end portion thereof is exposed outside the case. The case includes a soft magnetic case portion formed of a material having a relative permeability of 2 or more and a smaller relative permeability than the main magnetic path member for housing the body portion of the main magnetic path member, and the main magnetic path member. The antenna according to claim 1, comprising an end portion and a case end portion made of a material having a relative permeability smaller than that of the soft magnetic case portion. The case includes a soft magnetic case portion formed of a material having a relative permeability of 2 or more and smaller than the main magnetic path member, which continuously covers from one end portion to the other end portion of the main magnetic path member. The antenna according to claim 1, comprising a nonmagnetic case portion made of a nonmagnetic material that continuously covers from one end portion to the other end portion of the main magnetic path member. The antenna according to claim 1, wherein the case has a shape capable of positioning and storing the main magnetic path member. A magnetic sensor type antenna having a main magnetic path member in which a coil is wound around a magnetic core made of a magnetic material and receiving a magnetic field component of an electromagnetic wave by the main magnetic path member, wherein the main magnetic path member and the main magnetic path An antenna comprising: a case formed by injection molding with a material having a relative permeability of 2 or more and smaller than that of the main magnetic path member on at least a part of an outer peripheral portion of the member. The antenna according to claim 6, wherein the case is formed so as to accommodate a body portion of the main magnetic path member and an end portion is exposed outside the case. The case includes a soft magnetic case portion formed of a material having a relative permeability of 2 or more and a smaller relative permeability than the main magnetic path member for housing the body portion of the main magnetic path member, and the main magnetic path member. The antenna according to claim 6, comprising an end portion and a case end portion made of a material having a lower relative permeability than the soft magnetic case portion. The case includes a soft magnetic case portion formed of a material having a relative permeability of 2 or more and smaller than the main magnetic path member, which continuously covers from one end portion to the other end portion of the main magnetic path member. The antenna according to claim 6, further comprising a nonmagnetic case portion made of a nonmagnetic material that continuously covers from one end portion to the other end portion of the main magnetic path member. The antenna according to claim 1, wherein the case is a composite material in which soft magnetic ferrite powder, soft magnetic metal powder, or soft magnetic metal flake is mixed with resin or rubber. In a magnetic sensor type antenna having a main magnetic path member in which a coil is wound around a magnetic core made of a magnetic material and receiving a magnetic field component of an electromagnetic wave by the main magnetic path member, the main magnetic path member and a mold are softened. A case made of a material having a relative magnetic permeability of 2 or more and smaller than that of the main magnetic path member, which is formed by putting a curable slurry containing magnetic material powder, immersing the main magnetic path member and then curing it. An antenna comprising the antenna. In a radio-controlled timepiece in which a magnetic sensor type antenna is incorporated in a wristwatch having a metal casing, a movement (including peripheral parts), a non-metallic lid, and a metallic back lid, the magnetic sensor type antenna includes: A radio timepiece using the antenna according to any one of the above, wherein the case is disposed on a peripheral edge side of a metal casing. A keyless entry system, wherein the antenna according to any one of claims 1 to 11 is used in any one of a transmitter / receiver incorporating the antenna. 12. An RFID system using the antenna according to claim 1 incorporated in an RFID tag.

Images