JP4905844B2 - Antenna, radio clock using the same, keyless entry system, RFID system - Google Patents

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 timepiece or the like uses a long wave band of 40 kHz to 200 kHz or less, and one wavelength of the radio wave is several km long. 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 provided mainly using frequencies of 100 kHz or less, and in order to receive radio waves of these frequencies, a magnetic material is used as a magnetic core in order to efficiently converge the magnetic field component of electromagnetic waves. A magnetic sensor type antenna in which a coil is wound is mainly used.

Conventionally, as an antenna for a radio-controlled 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 to prevent leakage of the magnetic flux generated inside 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, due to the trend toward smaller and lighter weights, it has been required to be provided inside the housing. As shown in FIG. 18, the periphery of the movement 22 and the back cover 24, mainly the battery, the motor for moving the clock hand, etc. Arranged in the gap of the component 26. The antenna 1 in the front view of FIG. 18 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. 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 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. 17, 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. 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 leaks to the outside. Therefore, it is possible to suppress a decrease in Q value due to eddy current loss.

  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.

  From the above, the present invention has a magnetic sensor type antenna arranged in a metal casing, and eliminates the problem of eddy current loss without increasing the installation area and volume, thereby obtaining a highly sensitive output. An object of the present invention is to provide a small antenna that can be easily adjusted in sensitivity. 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. In addition to the main magnetic path member, a sub magnetic path member with a gap is provided in a part of the magnetic core. As a more specific antenna configuration, the antenna of the first aspect 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 receives the magnetic field component of electromagnetic waves by the main magnetic path member. In the magnetic sensor type antenna, apart from the main magnetic path member and the main magnetic path member, a sub magnetic path member with a gap is provided in a part of the magnetic core, and the end of the sub magnetic path member is a main magnetic path member. It is installed in the middle part of the said magnetic core away from the edge part of a road member, It is characterized by the above-mentioned. By connecting the sub magnetic path member from the middle part of the main magnetic path member, the main magnetic path member and the sub magnetic path member are not in a complete loop shape, and the end of the main magnetic path member is projected. By projecting the end of the main magnetic path member in this way, it is easy to take in external magnetic flux, and even if it is installed in a metal housing or the like as will be described later, the end of the main magnetic path member is bent to make the antenna The characteristics can be improved. The antenna of the second aspect of the present invention is 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 electromagnetic waves by the main magnetic path member. In addition to the main magnetic path member and the main magnetic path member, a sub magnetic path member with a gap is provided in a part of the magnetic core, and the magnetic core is a single body or a laminated body in which a thin ribbon is laminated. To do. An antenna that suppresses generation of eddy currents can be obtained by using a magnetic core as a laminate.
The sub magnetic path member is provided with a gap at one end or both ends with the magnetic core, or a gap is provided at the center of the sub magnetic path member, and the gap is set to 0.025 to 3 mm. If the gap is less than 0.025 mm, the resistance of the sub magnetic path member becomes too small to accept the magnetic flux incident from the outside. If it exceeds 3 mm, the resistance of the secondary magnetic path member becomes too large, and the effect is not preferred. The gap is more preferably about 0.1 to 2 mm. Further, when the gap is provided near the center of the sub magnetic path member (see the antennas 10a, 10f, 10g, and 10i in FIG. 1) or at one end (see the antenna 10e in FIG. 1), it is 0. 2 to 2 mm is desirable. On the other hand, when the gap is provided at two locations such as both ends of the sub magnetic path member (see antennas 10b, 10c, 10d, and 10h in FIG. 1), it is desirable that the gap at one location is about 0.1 to 1 mm.

  With this antenna configuration, a part of the incident magnetic flux is fed back through the main magnetic circuit via the gap-added sub magnetic path member, and the amount of magnetic flux incident on the magnetic core is effectively increased, resulting in high sensitivity. Antenna. 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 the gap-attached secondary magnetic path member, 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 gap-added secondary magnetic path member 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 sub-magnetic path member with a gap, the total amount of magnetic flux coming out from both ends of the antenna can be reduced, and the magnetic flux penetrating through the 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.

  A third aspect of the present invention is a magnetic sensor antenna for receiving electromagnetic waves, comprising a main magnetic path member comprising a magnetic core and a coil wound around the magnetic core, and a pair of sub magnetic path members attached to the magnetic core. And the sub magnetic path member is made of a material having a relative permeability smaller than that of the magnetic core. The magnetic flux incident from the outside flows through the main magnetic path member having a small magnetic resistance. With respect to the radiated magnetic flux at the time of resonance, the magnetic flux can be guided from the main magnetic path member to the sub magnetic path member side, and the inside of the magnetic circuit can be efficiently returned. As a result, the magnetic flux penetrating through the adjacent metal cases is reduced, a high output voltage is obtained, and the Q value can be kept high. In the present invention, the relative magnetic permeability of the material constituting the sub magnetic path member is preferably 2 or more. If the relative permeability of the secondary magnetic path member is less than 2, the magnetic flux generated by the resonance current is difficult to return to the secondary magnetic path side, and a part of the magnetic flux penetrates the adjacent metal cases to increase the loss due to eddy current or the like. .

  According to a fourth aspect of the present invention, there is provided 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 antenna is characterized in that a sub magnetic path member having a relative magnetic permeability of 2 or more and smaller than the main magnetic path member constituting a closed magnetic path by connecting the member and the main magnetic path member without an air gap is provided. As a result, most of the magnetic flux generated by the resonance current passes through the main magnetic path member, and as a result, the reduction in the Q of the coil can be minimized and a highly sensitive antenna can be obtained. The relative magnetic permeability is preferably 100 or less. When the relative permeability exceeds 100, the magnetic flux from the outside passes through the sub magnetic path member, and as a result, the coil induced voltage is lowered and the sensitivity may be lowered. If the relative permeability of the secondary magnetic path member is less than 2, the magnetic flux generated by the resonance current is difficult to return to the secondary magnetic path side, and a part of the magnetic flux penetrates the adjacent metal cases to increase the loss due to eddy current or the like. . The ease of flow of the magnetic flux at this time is adjusted by the relative permeability and cross-sectional area of the secondary magnetic path member, and the area facing the main magnetic path member, but this is much easier than adjusting the air gap. Excellent workability.

Furthermore, a fifth aspect of the present invention is 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. A path member, a first sub magnetic path member having a relative permeability equal to or smaller than that of the magnetic core, and the main magnetic path member and the first sub magnetic path member are connected without an air gap. And a second sub magnetic path member having a relative permeability smaller than that of the first sub magnetic path member constituting the closed magnetic path.
As a result, the magnetic flux entering the outside from the inside passes through both ends of the main magnetic path member, and the magnetic flux going from the inside to the outside easily flows to the closed magnetic path side because there is no air gap. Since the relative magnetic permeability of the secondary magnetic path member 1 is set to be relatively high, the magnetic flux can easily pass through the second secondary magnetic path member having a lower relative permeability, and most of them return to the closed magnetic path. To do. Therefore, there is little eddy current loss, and the amount of magnetic flux that has entered the magnetic core is effectively increased through the coil, resulting in a highly sensitive antenna. This example is also excellent in workability because there is no air gap.

  The end of the sub magnetic path member is preferably installed so as to contact the middle part of the magnetic core. The reason is the same as described above. Here, the sub magnetic path member or the second sub magnetic path member is a flexible composite material formed by mixing soft magnetic ferrite powder, soft magnetic metal powder, or soft magnetic metal flake, and resin or rubber. It is desirable. That is, the magnetic flux incident from the outside is received by the main magnetic path member, but the magnetic flux radiated from the inside is adjusted to the balance of the closed magnetic path of the present invention by the second sub magnetic path member so that it does not leak to the outside. I can do it. The sub magnetic path member or the second sub magnetic path member is smaller than the relative magnetic permeability of the main magnetic path member, but if the relative magnetic permeability exceeds 100, it is difficult to receive the magnetic flux concentrated on the main magnetic path member. Become. 100-5 are preferable, More preferably, it is 60-10. 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. Also, if it is difficult to assemble the secondary magnetic path member because the antenna is small, the structure is complicated, etc., simply apply paint that contains soft magnetic powder such as soft magnetic ferrite powder and has viscosity. It can also be used as a secondary magnetic path member.

When the magnetic core of the main magnetic path member is composed of a laminate in which soft magnetic ferrites or soft magnetic metal ribbons are laminated, the magnetic flux flowing between the main magnetic path member and the sub magnetic path member is substantially a laminated section of the metal ribbon. It is preferable to pass through. That is, the sub magnetic path member is installed not adjacent to the plane of the metal ribbon of the main magnetic path member on which the thin film magnetic metal is laminated, but adjacent to the laminated section. 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. 10, a large eddy current 9 is generated inside the metal ribbon 4 and the loss is large. As a result, the Q value decreases. When the eddy current 9 is generated, the antenna characteristics that are deteriorated by being installed inside the case are further deteriorated, resulting in a decrease in antenna efficiency. On the other hand, as shown in FIG. 9, it is possible to minimize the eddy current generated inside the magnetic core by installing the secondary magnetic path member so that the magnetic flux 8 passes from the end laminated section of the metal ribbon 4. , An antenna with less loss can be obtained.
In addition, when the secondary magnetic path member is also composed of a laminated body of soft magnetic metal ribbons or soft magnetic ferrite, the eddy current is reduced and the loss is suppressed by arranging both so that the laminated cross section is opposed. In addition, the antenna characteristics can be further improved. The soft magnetic material constituting the magnetic core is preferably a high relative permeability material of about 5000 to 100,000 such as silicon steel, permalloy, amorphous metal, nanocrystalline metal, ferrite, etc., and the first sub magnetic path member is the main magnetic path member. It is preferably smaller than that, specifically, about 300 to 5000 is preferable.

  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 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. 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, there are generally many space restrictions on the inner side of the casing, and the sub magnetic path member side cannot always be arranged. In the first place, if the sub magnetic path member side for adjusting the sensitivity faces the inside of the timepiece, there is a problem in adjustment workability. In this regard, if the secondary magnetic path member is formed of a flexible composite material and is provided along the peripheral side, the space can be effectively used, and the thickness and area of the secondary magnetic path member can be easily adjusted and assembled. Is excellent. In this way, the adverse effect caused by the eddy current can be offset and a further effect 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 sub magnetic path member 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 sub magnetic path member is far from the metal casing, so the magnetic field leaking from the inside to the outside is in the direction of the casing. Therefore, it can be expected that the eddy current is difficult to be generated. 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 sub magnetic path member side to efficiently return in the magnetic circuit. can do. As a result, a high output voltage can be obtained and the Q value can be kept high. Further, at this time, by using a flexible composite material having a low relative permeability by using a secondary magnetic path member having no air gap, it is possible to adjust the feedback of magnetic flux and obtain a high Q value and sensitivity.
Further, by directly connecting the sub magnetic path member and the main magnetic path member without interposing an air gap, the fringing magnetic flux is reduced and the eddy current can be further reduced. Further, the contact portion of the secondary magnetic path member with the main magnetic path member is made of a low relative permeability material so that the magnetic flux passes between the secondary magnetic path member and the main magnetic path member via the low relative permeability material. With this configuration, the magnetic circuit has characteristics similar to those of a closed magnetic circuit, and can suppress the magnetic flux passing through the surface by fringing, thereby further reducing the eddy current. Furthermore, in this case, compared with the case where an air gap is provided, fine inductance adjustment (magnetic circuit constant adjustment) is possible depending on the cross-sectional area of the low relative permeability material and the area facing the main magnetic path member. It is much easier than adjusting the position of the sub magnetic path members to adjust the inductance by the air gap, and the workability is excellent.
Also, using the main magnetic path member constituted by the laminated metal ribbons, the magnetic flux flowing between the main magnetic path member and the sub magnetic path member is substantially transferred to the end of the metal ribbon of the main magnetic path member. By passing through, an eddy current loss generated on the band surface of the main magnetic path member can be reduced, and an antenna with a small 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.

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 schematic structural drawing of the antenna which shows another Example of this invention. It is a perspective view of the antenna which shows a 5th Example. FIG. 10 is a schematic structural diagram of an antenna showing a sixth embodiment. FIG. 10 is a schematic structural diagram of an antenna showing a seventh embodiment. It is a schematic structural drawing of the antenna which shows an 8th Example. It is a schematic structural drawing of the antenna which shows a 9th Example. 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. 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 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 front view which shows the example which has arrange | positioned another antenna in a wristwatch. It is a figure which shows the example which applied the antenna of this invention to the key main body for keyless entry systems. 1 is a schematic diagram of an apparatus in which an embodiment of the present invention was tested. 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 radio wristwatch which incorporates the conventional antenna. It is a schematic structure figure of the conventional antenna.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 shows an embodiment of an antenna according to the present invention. The antenna 10a shown in FIG. 1A is formed by winding a coil 8 around a magnetic core 14a made of a rod-like ferrite, thereby constituting a main magnetic circuit. Further, a gap G is provided at the center by a sub magnetic path member 15a extending from both ends of the coil 8. The sub magnetic path member 15a may be a magnetic material, but for example, manganese-based ferrite, nickel-based ferrite, and cobalt-based amorphous are preferable. Moreover, although the distance of the gap G is preferably 0.1 to 2 mm, it is practically about 1 mm if it is a single gap as in this example, and about 0.5 mm if it is divided into two gaps. The same applies to the following embodiments.
The antenna 10b in FIG. 1B has an end portion 11b where both ends of a rod-shaped ferrite material rise vertically and bend. It has a main magnetic circuit formed by winding the coil 8 at the center, and a step is provided at the end 11b located at both ends of the coil 8, and a sub-magnetic path member 15b such as ferrite is bridged on both sides thereof. A sub magnetic path member with a gap parallel to the magnetic core 14b through the gap G is used. In this example, since the gap is an example of two locations, the gap G is about 0.5 mm as described above.
An antenna 10c shown in FIG. 1C is substantially the same as the antenna 10b, except that the ferrite serving as a magnetic core is formed into a quadrangular shape. 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 antenna 10d shown in FIG. 1 (d) obtains a thin ribbon obtained by integrally punching a U-shaped member having a bent end 11d as shown in the figure from a band of amorphous metal foil (plate thickness of 20 μm or less). A plurality of thin ribbons are stacked and a coil 8 is wound around the center. And the sub magnetic path member 15d is provided in the both ends via the gap G so that the both ends of the coil 8 may be connected. The sub magnetic path member 15d uses an amorphous foil (made by Hitachi Metals) made of the same material as the magnetic core 14d. The gap can be formed by a method of sandwiching a PET film.
The antenna 10e shown in FIG. 1 (e) is formed by laminating thin 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. The sub magnetic path member with gap uses a part of the laminated ribbon as the sub magnetic path member 15e, and forms the gap G only on one side.
The antenna 10f in FIG. 1 (f) uses an amorphous metal foil common to the antenna 10e, but the gap-attached sub magnetic path member uses the left and right metal foil sub magnetic path members 15f. A gap G is formed at the center. Therefore, this example is configured by magnetic gap coupling at one central location.
As the antennas 10d to 10f, a laminated type having a high strength can be obtained. The laminated type shown in FIG. 1 (d) is desirable because it can be integrally formed by punching and can be bent in difficult directions, and the degree of freedom of the plate shape is increased. In addition, in the laminated type and the thin line type in which a plurality of fine lines shown in FIG. 1 (j) are bundled, it is desirable to coat or bundle the thin films through an insulating layer by coating an insulating film between the thin ribbons or individual fine lines.

In the antenna 10g of FIG. 1 (g), a main magnetic circuit is formed by winding a coil 8 around a plate-like magnetic core 14g made of ferrite having a concave portion 16g, and sub-magnetic path members 15g made of ferrite at both ends of the magnetic core 14g. And a gap G is provided at the center.
The antenna 10h in FIG. 1 (h) uses a magnetic core 14h having the same structure as that of the antenna 10g. A gap G is provided at both ends of the magnetic core 1h with a resin intervening member (not shown) interposed therebetween. A sub magnetic path member with a gap is formed. In this example, the distance of the gap G is adjusted by the resin member.
Since the antennas 10g and 10h use a plate-like magnetic core and have a plate-like sub magnetic path member mounted thereon, the antennas 10g and 10h are easy to manufacture and relatively easy to arrange even in a narrow place. In addition, when the sub magnetic path member is formed of a composite material in which resin or the like and magnetic powder are mixed, the material itself has magnetic characteristics that already possess the gap, so the mechanical gap is 0 mm. Can be regarded magnetically as possessing a gap. It is also possible to form the sub-magnetic path member with such a composite material to constitute the antenna as described above.
The antenna 10i in FIG. 1 (i) is a laminate of thin ribbons punched from amorphous metal foil, as in FIGS. 1 (e) and 1 (f). The end portion 11i of the ribbon is formed by bending both ends of the ribbon striped into a rectangular shape obliquely upward. The sub magnetic path member with gap uses a part of the laminated ribbon as the sub magnetic path member 15i, and forms a gap G in the center.
The antenna 10j in FIG. 1 (j) is formed by bundling a plurality of thin wires into a magnetic core 14j and bending both ends away from the gap-attached sub magnetic path member 15j. The secondary magnetic path member with a gap is made of a ferrite material and is fixed so as to be adjacent to the coil 8, and a gap G corresponding to the thickness of the coil is formed at both ends of the secondary magnetic path member 15 j.
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.

FIG. 2 shows another embodiment of the antenna according to the present invention. The antenna 30a shown in FIG. 2 (a) has a rod-shaped ferrite material that has both ends 31a that vertically rise and bend, and the tip 32a is bent in a direction parallel to the magnetic core 34a. Then, the coil 8 is wound around the central portion, and a secondary magnetic path member 35a that connects both ends of the coil 8 is provided, and the secondary magnetic path member is provided with a gap G at the center.
The antenna 30b shown in FIG. 2B is formed by laminating a plurality of thin strips 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 antenna 10d shown in FIG. 1D. The secondary magnetic path member 35b is provided so as to form the gap G by winding the coil 8 around the center thereof.
The antenna 30c of FIG. 2 (c) is the same as that of FIG. 1 (e), except that a tip portion 32c obtained by further bending the end portion 31c is formed and a gap G is formed at the center portion. This is a magnetic path member.
The antenna 30d in FIG. 2 (d) is the same as the antenna 30b as shown in the figure, but the sub magnetic path member 35d is provided on the side surface of the magnetic core 34d and is provided via the central gap G.
The antenna 30e shown in FIG. 2 (e) has a sub magnetic path member 35e provided on the side surface of the magnetic core 34e, but has a gap G provided between the side surface of the magnetic core 34e.
The antenna 30f in FIG. 2 (f) is obtained by bending the end portion in FIG. 2 (c) obliquely upward. A sub magnetic path member 35f is provided to connect both ends of the magnetic core 34f so as to communicate with each other, and a gap G is interposed in the center.

  FIG. 3 shows still another embodiment of the antenna according to the present invention. FIG. 3A shows an antenna in which a tip 52a is bent in two directions. FIG. 3B shows a stacked type, but the tip 52b is fan-shaped and has a widening. In FIG. 3 (c), the end portions 52c of the laminated ribbons are bent radially to have a spread. FIG. 3 (d) is formed by changing the bending direction of the tip 52d with respect to FIG. 3 (c). Also in these antennas 50a to 50d, the same effect as the above-described embodiment can be obtained.

Examples will be described below. Here, the output voltage and the like of the antenna of the present invention and the conventional antenna were measured and compared along the test apparatus imitating the radio wave wristwatch shown in FIG. 16 and the equivalent circuit shown in FIG.
In FIG. 17, L is a coil composed of the magnetic core 1 and the winding 8 of the antenna. 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) casing 70 imitating the radio wave wristwatch shown in FIG. 16, and the voltage V by the equivalent circuit was measured.

(Examples 1 and 2)
As Example 1, an antenna 10c shown in FIG. Mn-Zn ferrite (Hitachi Metals Ferrite MT80D) as a magnetic core, 1.5 mm square cross section, 16 mm length, 7.5 mm bend height, 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. The shape of the winding coil is not particularly limited, but a circular shape is desirable for manufacturing.
The conventional example is performed using an antenna in which a winding is wound around a straight magnetic core (without a secondary magnetic path member). Using the same ferrite as the magnetic core of the first embodiment, 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 is the same thin wire as in the first embodiment under the same conditions. It is the one wound by.
As Example 2, the antenna 10d shown in FIG. As a magnetic core, a cobalt-based amorphous (Hitachi Metals ACO-5SF) metal foil (plate 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. 16, 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.

(Examples 3 and 4)
Next, in a situation where the antenna is not housed in the metal case, the effect of the antenna provided with the sub magnetic path member with a gap was compared and examined.
As Example 3, the antenna 10g shown in FIG. A magnetic core 14g having the same structure as that of the conventional example shown in FIG. 19 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 therein. The central gap G was adjusted and changed with a plastic (PET) member.
Example 4 is the antenna 10h of FIG. 1 (h). As the magnetic core 14h, the same structure as that of the conventional example shown in FIG. 19 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.
As a comparative example, the same antenna structure as that shown in FIG. 1 (h) was used, but the sub magnetic path member was not a magnetic material but a copper plate that was a good electrical 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.
The conventional example uses the antenna shown in FIG.
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.

In Example 3, the gap G was 1.0 to 4.0 mm, which was higher than the conventional example together with the output voltage and the Q value, and the effect of providing the sub magnetic path member with the gap was confirmed. However, in the case of this antenna structure, when the gap G is 4.0 mm, the output voltage and the Q value tend to be lower than those of 3.0 mm. Also, even if the gap G is less than 1.0 mm, the Q value does not differ greatly, but the output voltage is considered to decrease. However, in any case, characteristics higher than the conventional example were obtained.
In Example 4, the gap G in which both the output voltage and the Q value were high and balanced was 0.5 mm. When the gap becomes smaller, the Q value still tends to be lower than the output voltage. However, a value higher than the conventional example was obtained even at 0.025 mm.
The comparative example is considered to be similar to the structure provided with the conductive shield member of Patent Document 3, but the measurement is not performed because the output voltage is much smaller than that of the above embodiment. When the gap G is 0 mm, the function of capturing the magnetic flux is suppressed, and the output voltage decreases rapidly. Further, when the gap G is 8.0 mm or more, the Q value is increased because the influence of the copper plate is eliminated.
As described above, according to the present invention, by providing a gap-added secondary magnetic path member having a high magnetic resistance in a part of the magnetic core, a part of the magnetic flux flowing into the magnetic core is retained inside, and a high Q value is obtained. A high output voltage can be obtained. Further, the distance of the gap G varies depending on the antenna structure, but it is effective to adjust the distance between 0.025 and 3 mm. In addition, since the magnetic flux flowing out to the outside due to the resonance current is reduced in the antenna using the sub magnetic path member with a gap, an advantageous result can be obtained even when the antennas of Examples 3 and 4 are housed in a metal casing. It was.
Further, as described above, a highly sensitive antenna having a degree of freedom of installation can be achieved while converging a large amount of magnetic flux by bending a part of the magnetic core installed at the bottom of the casing. The magnetic core can be any of the ferrite, amorphous, and microcrystalline material rods, plates, and lines described in the embodiments. It is also possible to cut out the dial and show the coil part and the magnetic core end part to the outside in design. The bending of the end portion of the magnetic core is not limited to both ends, and the bending angle can be arbitrarily set even if only one end is bent. Further, the present invention can also be implemented as a wire type antenna in which a plurality of fine wires are bundled and wound with a coil.

(Example 5)
As Example 5, the antenna 70 of FIG. As the magnetic core 71, a soft magnetic metal foil strip (plate thickness of 20 μm or less) such as an amorphous alloy, a nanocrystalline magnetic alloy such as an Fe—Cu—Nb—Si—B system, or an Fe—Si based magnetic alloy has a length of 23 mm and a width of 2. 20-30 layers were laminated as 5 mm. In addition, a soft magnetic metal foil strip having a length of 40 mm and a width of 2.5 mm was coated on one side of the laminated magnetic core, and then 4 to 10 layers were laminated. 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 71 in a range of 12 mm in length. Thereafter, the end portions of the long soft magnetic metal foil strips laminated later are made to face each other, and the intermediate portion thereof is fixed by an intermediate member 90 made of plastic (PET), thereby forming the sub magnetic path member 7 provided with the gap G. . The secondary magnetic path member 7 makes a return route of the magnetic flux at the time of resonance. However, since the optimum value of the return amount varies depending on the material, shape, and dimensions of the housing metal on which the antenna is placed, The optimum value is determined by appropriately increasing and decreasing the area, the contact area with the main magnetic path member, and the like. Further, when the antenna itself is small or the structure is complicated, the assembly of the sub magnetic path member is substantially difficult and the cost increases. For example, as shown in FIG. 4B, a sub-magnetic path member can be formed by applying a viscous paint containing magnetic powder so as to cover the outer diameter portion of the coil and continue to the magnetic core.

(Example 6)
Next, a specific antenna embodiment of the present invention when a sub magnetic path member is installed without a gap will be described with reference to the drawings.
FIG. 5 is a front view (a) and a side view (b) of an antenna showing a sixth embodiment, and is a schematic diagram for explanation in which a case such as a bobbin is omitted (the same applies to the following embodiments). As shown in the figure, the magnetic core 1a of the antenna is made of an amorphous alloy, a nanocrystalline magnetic alloy such as Fe—Cu—Nb—Si—B, or a soft magnetic metal foil strip (plate thickness of 20 μm or less) such as an Fe—Si based magnetic alloy. It is punched into a barbell shape, and 30 to 40 thin ribbons are laminated and integrated through an insulator. A main magnetic path member 4a is formed by winding a coil 8a of about 800 to 1400 turns around the center of the magnetic core. A secondary magnetic path member 3a having a relative magnetic permeability of 100 or less is connected to the lower end surfaces 5a at both ends of the magnetic core 1a to form a closed magnetic path without providing an air gap. This secondary magnetic path member makes a return route of magnetic flux at resonance, but the optimal value varies depending on the material, shape and dimensions of the housing metal where the antenna is placed, so the relative permeability of the member, The optimum value is determined by appropriately increasing or decreasing the cross-sectional area and the contact area with the main magnetic path member. This is described below.

(Example 7)
FIG. 6 is a schematic diagram of an antenna front view (a) and a side view (b) showing a seventh embodiment. This antenna comprises a magnetic core 1b made of a laminated body of soft magnetic metal ribbons like the magnetic core 1a and a coil 8b wound in the same manner, and constitutes a main magnetic path member 4b, and is equivalent to the magnetic core 1b or Relative permeability so that an air gap does not occur between the first sub magnetic path member 7b having a lower relative permeability, the lower end surfaces 5b of both ends of the main magnetic path member, and the first sub magnetic path member 7b. Is connected via the second sub magnetic path member 3b of 100 or less to form a closed magnetic path. The first sub magnetic path member 7b is made of a soft magnetic metal foil strip (plate thickness) such as soft magnetic ferrite or amorphous alloy, nanocrystalline magnetic alloy such as Fe-Cu-Nb-Si-B, or Fe-Si based magnetic alloy. 20 μm or less), or a laminate or a bulk material similar to the magnetic core 1b. However, the relative permeability is equal to or less than that of the magnetic core 1b. For example, when the relative permeability of the magnetic core 1b is 100,000 to 80,000, that of the first sub magnetic path member 7b is about 100,000 to 300. In addition, a second secondary magnetic path member 3b having a smaller relative permeability is interposed between the two. The relative permeability is set to 100 or less, and the return route of the magnetic flux at resonance is adjusted by adjusting the cross-sectional area orthogonal to each other, the contact area with the main magnetic path member, and the like. Further, in this example, the lamination direction of the main magnetic path member 4b and the first sub magnetic path member 7b is made the same, that is, the eddy current due to the flow of magnetic flux at resonance is made so that the ribbons do not cross each other. It is difficult to occur.

(Example 8)
FIG. 7 is a schematic diagram of a front view (a) and a side view (b) of an antenna according to an eighth embodiment. In this antenna, a main magnetic path member 4c including a magnetic core 1c and a coil 8c has the same configuration as that of the above-described embodiment. Here, the first sub magnetic path member 7c is constituted by a laminated body in which a plurality of ribbons having a relative magnetic permeability equal to or lower than that of the magnetic core 1c are laminated. This is the same as in the second embodiment. Then, a second sub magnetic path member 3c is connected between the first sub magnetic path member 7c and the lower end surface 5c of the main magnetic path member 4c so as not to generate an air gap. A first sub magnetic path member 7c is connected to the other surface of the member 3c to constitute a closed magnetic path. Further, in this example, the main magnetic path member 4c and the first sub magnetic path member 7c cross each other and the eddy current is generated more easily than in the second embodiment. By shifting the axis of the first auxiliary magnetic path member 7c, the magnetic flux flows in parallel as much as possible so as to suppress the eddy current. And the return route of the magnetic flux at the time of resonance can be adjusted similarly to the said Example.
The magnetic core of the main magnetic path member and the first sub magnetic path member may be in the form of a rod, plate, or wire of ferrite, amorphous, nanocrystalline material, etc. in addition to the metal ribbon.

Example 9
FIG. 8 shows a ninth embodiment, and is a schematic diagram of a front view (a) and a side view (b) of an antenna constructed by removing the seventh sub magnetic path member 3b and having an air gap. The secondary magnetic path member 7d is formed of a laminate in which a plurality of ribbons having a relative permeability equal to or less than that of the magnetic core 4c are laminated. The sub magnetic path member is fixed by a bobbin (not shown) so that the magnetic flux passes through the end face 5d of the main magnetic path member and the air gap, thereby forming a closed magnetic path. Further, in this example, the stacking direction of the main magnetic path member and the sub magnetic path member 7d does not intersect with each other, and the eddy current is hardly generated as in the second embodiment.

  The sub magnetic path member or the second sub magnetic path member used in the embodiment is obtained by dispersing metal magnetic powder (ferrite powder, amorphous alloy powder, etc.) in a flexible polymer material (resin material or rubber material). Thus, a flexible composite material having an electromagnetic wave absorbing function can be used. For example, an electromagnetic wave reflection layer in which a conductive fibrous material is dispersed in a flexible polymer material, and a first electromagnetic wave absorption in which a metal magnetic material flat shape powder is dispersed in a flexible polymer material on both front and back surfaces There are layers in which a layer and a second electromagnetic wave absorbing layer in which metal magnetic particle-shaped powder is dispersed in a flexible polymer material are sequentially laminated and thermocompression bonded. The conductive material dispersed in the electromagnetic wave reflection layer is, for example, carbon fiber or metal fiber, which is dispersed in a flexible polymer material and formed into a sheet shape. In addition, the metal magnetic powder used for the electromagnetic wave absorbing layer is produced by grinding with an attritor particle-shaped powder produced from a nanocrystalline magnetic alloy such as an Fe-Cu-Nb-Si-B system by a water atomization method. A flat powder having an average particle diameter of 0.1 to 50 μm and an average thickness of 3 μm, which is dispersed in a flexible polymer material and formed into a sheet shape to form an electromagnetic wave absorbing layer. is there. On the other hand, flat metal powder such as carbonyl iron alloy, amorphous alloy, Fe-Si alloy, molybdenum permalloy, supermalloy, etc. is used as a metal magnetic flat powder and dispersed in a flexible polymer material to form a sheet. To form an electromagnetic wave absorbing layer. In addition, 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, chloride resin, and the like. A vinyl resin, a phenol resin, etc. are mentioned. In addition, for example, a single layer structure in which the first electromagnetic wave absorbing layer and the second electromagnetic wave absorbing layer described above are used independently is also desirable, and a conventionally used flexible composite material having a low relative permeability can be used. . After all, in the present invention, the structure of the composite material is not limited as long as the relative permeability is satisfied.

  By using such a flexible composite material, the part using the composite material has a magnetic characteristic having a gap by itself, and it can be regarded magnetically as if it has a gap. As a result, the magnetic flux can be returned to the closed magnetic path without providing an air gap that is troublesome to adjust. Moreover, since it is not necessary to provide an air gap, it is advantageous in that it is easy to manufacture without requiring subtle accuracy and can maintain stable performance. In addition, the magnetic core and the coil are conventionally housed in a resin case. However, the magnetic core and the coil are made into a resin case that also accommodates the secondary magnetic path member. It is also possible to integrally mold the sub magnetic path member by pouring the raw material of the material into a part of the injection-molded coil bobbin. Further, after the first sub magnetic path member as described above is accommodated in the resin case, the flexible composite material is formed in the gap formed between the main magnetic path member and the first sub magnetic path member. The second sub magnetic path member can be integrally formed by pouring the raw material. If such a means is used, it is further inexpensive and excellent in productivity.

(Example 10)
In Example 10, the first sub magnetic path member and the second sub magnetic path member have the antenna structure shown in FIG. 6, and the magnetic core has Mn—Zn ferrite (Hitachi Metals ferrite MT80D), and the cross section is 1 .5 mm square and 16 mm length were used, and winding 8 was formed by winding 1200 turns of enamel-coated copper wire having a wire diameter of 0.07 mm, which insulated the surface of the ferrite core, in a range of 12 mm in length. Next, the first sub magnetic path member uses a ferrite plate having a plate thickness of 0.5 mm, a width of 1.5 mm, and a relative permeability of 500, and the second sub magnetic path member is a flexible having a relative permeability of about 50. The composite material was closely attached, and the Q value and sensitivity (output voltage) were measured when the cross-sectional area of contact with the magnetic core was constant and the thickness t of the flexible composite material was changed.
This antenna was installed in a metal case 70 shown in FIG. 16, 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 3.

(Example 11)
In Example 11, the sub magnetic path member has the antenna structure shown in FIG. 5 and uses Mn—Zn ferrite (Hitachi Metal Ferrite MT80D) as a magnetic core, a cross-section of 1.5 mm square, and a length of 16 mm. The winding 8 was formed by winding 1200 turns of enamel-coated copper wire having a wire diameter of 0.07 mm, which insulated the surface of the ferrite core, in a range of 12 mm in length. The sub magnetic path member is formed by using a flexible composite material having a plate thickness of 0.5 mm, a width of 1.5 mm, and a relative magnetic permeability of 50, in close contact with the main magnetic path member (magnetic core). At this time, the Q value and sensitivity (output voltage) when the thickness t of the flexible composite material was changed were measured.
This antenna was installed in a metal case 70 shown in FIG. 16, 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 4.

  As described above, it was confirmed that the Q value and the sensitivity were improved by providing the sub magnetic path member from Examples 10 and 11. The Q value and sensitivity change by changing the thickness of the flexible composite material. Thereby, the optimal value which draws out the effect of a submagnetic path member can be adjusted. For example, in this example, the Q value and the sensitivity are both high in the case of Example 1 in the case of t = 0.5 to 1.0 mm, and in the case of Example 2, t = 1.0 to 2.0 mm. It is. Even when the main magnetic path member and the first sub magnetic path member are formed of a laminate or when the material is changed, a high Q value and sensitivity can be easily achieved by changing the thickness of the second sub magnetic path member. Can be put out. The same adjustment is possible by changing the contact area instead of adjusting the thickness, that is, adjusting the cross-sectional area. These are remarkable effects compared with the case where adjustment is performed by providing an air gap because gap adjustment is required on the order of microns.

(Example 12)
Next, FIG. 11 shows a front view and a side view of a radio-controlled wristwatch with a built-in antenna. 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 21, a movement 22, peripheral components, a glass lid 23, and a metal (for example, stainless steel) back cover 24, and the antenna 10 is moved to the movement 22. And the back cover 24. In the antenna 10 shown in FIG. 1, the end portion 11 of the magnetic core is bent in the direction of the glass lid 23 so as to rise from the bottom surface. Therefore, although the central part of the magnetic core is adjacent to the back cover side, the magnetic core end part 11 serving as the entrance and exit of the magnetic flux has a structure facing the incident direction of the electromagnetic wave. Also, as shown in FIG. 12, the tip 32 of the end 31 may be bent in a direction different from the end. Thereby, it can be set as the radio timepiece which can catch a magnetic flux more easily.
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.
Further, the antenna 1e is arranged such that the main magnetic path member 4e side is directed to the inside (center) side in the casing, and the sub magnetic path members 7e and 3e including the first and second sub magnetic path members are the peripheral portions of the casing. Arranged along the side. Such an arrangement has a relatively high degree of freedom and is excellent in sensitivity adjustment and assembly.

(Example 13)
FIG. 13 shows a front view of a radio wave wristwatch incorporating another antenna. Except for the difference in antenna shape, the configuration is the same as that of the radio-controlled wristwatch shown in the twelfth embodiment. The outer shape of the antenna 1 is formed so as to be substantially along the inner peripheral surface of a metal case (for example, stainless steel) case 21 of the radio-controlled wristwatch. The sub magnetic path member 7 was formed between the main magnetic path and an external metal casing. By forming the sub magnetic path member on the side of the metal casing outside the main magnetic path in this way, the magnetic flux flowing in the main magnetic path is larger than that provided on the inner side of the main magnetic path. It becomes difficult to escape to the body, resulting in improved antenna characteristics. Although the shape is appropriately determined by the mechanism of the movement, it is preferable to design the sub magnetic path member so as to be formed on the metal housing side outside the main magnetic path.

(Example 14)
FIG. 14 shows a front view of a key body for a keyless entry system, which is a kind of RFID tag incorporating the antenna of the present invention. In the front view, the antenna is shown by a solid line for easy understanding of the arrangement. The key body is mainly composed of a metal casing case 74, a key opening / closing button 73, a circuit board 71 for receiving / transmitting, and the antenna 1. Further, as shown in the drawing, the outer periphery of both ends is formed in a substantially arc shape so as to match the inner shape of the housing case, so that the space in the key body can be effectively utilized. The sub magnetic path member 7 is provided along the peripheral edge side in order to effectively use the space in the key body.
As another antenna arrangement, as shown in FIG. 15, the sub magnetic path members 3 and 7 are bonded on the printed wiring board 200 side, and the end of the magnetic core is bent away from the printed wiring board. You can also. The magnetic core in FIG. 15 is Mn-Zn ferrite (Hitachi Metals ferrite MT80D), the secondary magnetic path member 3 is a product name: Hitachi K-E050 absolute shield material, and the secondary magnetic path member 7 is a product name: Hitachi Metals. An absolute shield material of K-E025 was used. The size of the entire antenna is 11 mm, the height is 2.9 mm, and the width is 3 mm. The sub magnetic path member 3 was manufactured with a thickness of 0.5 mm and the sub magnetic path member 7 with a thickness of 0.25 mm. Since a wide variety of wiring and circuit components are incorporated in the printed wiring board, in this test, an iron plate 201 is pasted on the back side of the antenna mounting surface of the printed wiring board, and the frequency is measured at 125 kHz sensitivity (output voltage measurement). ) And the magnetic field strength of 45 nT. Table 5 shows the output voltage and the Q value. For comparison, an output voltage and a Q value measured with an antenna without a sub magnetic path member are also shown.

  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.

DESCRIPTION OF SYMBOLS 1a-1d: Magnetic core 3, 7: Sub magnetic path member 4a-4d: Main magnetic path member 8: Coil, winding 9: Eddy current 10, 30, 50, 70: Antenna 21: Metal housing 22: Movement 23 : Glass lid 24: Back lid 25: Resin casing 26: Peripheral parts 70: Metal casing G: Gap, air gap

Claims (12)

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 sub magnetic path member separate from the main magnetic path member are provided, and the sub magnetic path member is arranged so that both ends thereof are adjacent to the main magnetic path member via a gap. The antenna is characterized in that the main magnetic path member and the sub magnetic path member are formed to have at least a part of surfaces adjacent to each other.   The antenna according to claim 1, wherein the magnetic core of the main magnetic path member is a single ribbon or a laminate of thin ribbons.   The antenna according to claim 2, wherein the sub magnetic path member is disposed in a side surface direction on the same surface of the ribbon as to the ribbon of the main magnetic path member.   The secondary magnetic path member is a single ribbon or a laminate of thin ribbons, and the thin ribbon of the magnetic core of the main magnetic path member and the thin ribbon of the secondary magnetic path member are arranged in parallel. 3. The antenna according to 3.   The antenna according to claim 1, wherein the magnetic core is made of plate-like ferrite.   6. The antenna according to claim 1, wherein the gap is 0.025 to 3 mm.   7. The antenna according to claim 1, wherein the sub magnetic path member is made of a material having a relative permeability smaller than that of the main magnetic path member.   The antenna is installed in a metal casing or a casing provided with a metal member therein. When the antenna is installed in the casing, the end of the magnetic core is opposed to the metal casing or the metal member. The antenna according to claim 1, wherein the portion is bent in a direction away from the antenna.   9. The antenna according to claim 8, wherein the tip end portion of the magnetic core end portion is further bent in a different direction.   A radio 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, wherein the magnetic sensor type antenna is defined in claims 1 to 9. 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. Radio clock.   A keyless entry system, wherein the antenna according to any one of claims 1 to 9 is used in any one of a transmitter / receiver incorporating the antenna.   An RFID system comprising the antenna according to claim 1 incorporated in an RFID tag.

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