JP2015220512A - Three-axis antenna - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a small and thin three-axis antenna that can be assembled easily, while ensuring high reception sensibility, and can be manufactured inexpensively.SOLUTION: A three-axis antenna includes a first antenna coil and a second antenna coil each combining a trunk, a single flange magnetic core located on one end side in the thickness direction and having a flange integrated with the trunk, and a base member of thin plate arranged on the other end side of the trunk and including a plurality of terminals held in a resin portion, and abutting against one end side of the trunk and the base member, and held therebetween, and a third antenna coil including the trunk. Each antenna coil has a different winding axis direction, and is connected with the terminal.

Description

  The present invention relates to an antenna used for an electronic key for a keyless system, and more particularly to a triaxial antenna used for an electronic key such as a door key for a vehicle, an engine start key, or a door key for a house.

2. Description of the Related Art A keyless system (also called an electronic key system) is known that controls locking and unlocking of a house or vehicle door according to a specific electronic key when opening and closing a door of an automobile or a house and starting an engine.
For example, in the case of an electronic key for doors, an authentication electronic key carried by a person receives a low-frequency request signal from the door key device by bidirectional wireless communication between the electronic key side and the key device side. Then, a response signal is transmitted. The key device of the door that has received the response signal authenticates the identification, and after the authentication is successful, detects the opening operation of the door knob and releases the door lock.

  An antenna of a key device or an electronic key has an antenna coil configured by laying a winding by appropriately performing insulation treatment on a magnetic core mainly made of a soft magnetic material such as soft ferrite or amorphous, and the antenna coil And a capacitor are configured to resonate at a predetermined frequency.

  In bidirectional communication between the key device and the electronic key, the communication direction is extremely short or the communication direction cannot be communicated in the positional relationship between the axial direction of one antenna coil and the direction of the magnetic field generated from the other antenna coil. There is a problem that there is. Therefore, in order to be able to detect all electromagnetic waves in the three-dimensional direction efficiently and to obtain good communication, the authentication electronic key has an omnidirectional 3 combining an X-axis antenna, a Y-axis antenna, and a Z-axis antenna. An axial antenna is used. Since the authentication electronic key itself is small, the three-axis antenna used for it is also strongly required to be small. However, since the three-axis antenna is configured to use a plurality of antennas, the three-axis antenna is likely to be larger than a single-axis antenna including a single antenna. Therefore, a triaxial antenna having a configuration in which three antenna coils of the X axis, the Y axis, and the Z axis are arranged in one magnetic core has come to be used.

  The configuration of such a three-axis antenna will be described with reference to the drawings. For example, Patent Document 1 shows a basic configuration example of a three-axis antenna. FIG. 22 is a perspective view for explaining an embodiment of the antenna. FIG. 23 is a perspective view showing an appearance of a magnetic core on which an antenna coil is laid, and FIG. 24 is a perspective view for explaining another embodiment of the antenna.

  The triaxial antenna 300 includes a magnetic core 320 formed of a flat ferrite core having a plurality of grooves and antenna coils 310 to 312. The magnetic core 320 includes a body portion 301 having a recessed side surface of the ferrite core and a pair of flange portions 302 located on both ends thereof, and a plurality of groove portions 305 are provided so as to divide the flange portion 302 into four. ing. Hereinafter, a magnetic core having a flange on both ends of the body is referred to as a double magnetic core.

  Three antenna coils are wound around the trunk portion 301 between the groove portion 305 and the flange portion of the magnetic core 320 so that the winding axis directions thereof are orthogonal to each other, so that an X-axis antenna coil, a Y-axis antenna coil, and a Z-axis antenna coil are A three-axis antenna provided with antenna coils 310, 311, and 312. Further, the triaxial antenna shown in FIG. 24 is housed in a case 330 in which an external connection terminal 340 is formed, and can be surface-mounted on a circuit board or the like.

  Another aspect of the triaxial antenna disclosed in Patent Document 2 will be described. The structure is shown in FIGS. FIG. 25 is a perspective view showing the appearance of the triaxial antenna. FIG. 26 is an exploded perspective view of an assembly used for the triaxial antenna. The triaxial antenna 401 uses a double magnetic core in which members 420 and 450 made of two ferrite cores are combined, and a base member 430 provided with an external connection terminal 431 for mounting is placed between the flanges of the two magnetic cores. Use the assembled assembly. The first member 420 constituting both the magnetic cores is a single magnetic core having a body portion and a flange portion at one end thereof, and the second member 450 is a plate-shaped magnetic core forming the other flange portion. Combining the first member 420 and the second member 450 results in substantially the same form as the two magnetic cores of Patent Document 1. In the assembly, antenna coils 410, 411, and 412 to be an X-axis antenna coil, a Y-axis antenna coil, and a Z-axis antenna coil are wound. Further, although not shown, resin molding is performed while leaving the external connection terminal 431. Configured.

JP 2003-92509 A International Publication No. 201/129347

  Since the triaxial antenna of Patent Document 1 has a complicated shape having a plurality of grooves in both the magnetic cores, it is difficult to manufacture the magnetic cores by general compression molding. Therefore, it is necessary to process or use a near net shape molding method such as injection molding. The use of cutting and injection molding increases the manufacturing cost and makes it difficult to provide a triaxial antenna at low cost. In addition, the antenna coils are laid sequentially in the grooves of both the magnetic cores. However, since the winding axis is different, when the antenna coil is wound and then another antenna coil is wound, the end of the already formed antenna coil is Is temporarily fixed to prevent the coil from loosening and prevent it from being caught, which is complicated and increases the number of steps.

  In order to enable surface mounting, it has been proposed to accommodate a triaxial antenna in a case 330 in which an external connection terminal 340 is formed. For connection between each antenna coil 310, 311, 312 and the external connection terminal 340, each antenna coil 310 is connected to a plate-like terminal (not shown) which is a terminal connection portion provided inside the case and connected to the external connection terminal 340. 311 and 312 need to be entangled. Since the plate-like terminal is located inside the case 330, the smaller the antenna is, the smaller the space for connection work becomes and the work becomes difficult, and the connection reliability between the antenna coil and the terminal is difficult to obtain. Requires man-hours and skill. In consideration of connection workability, the case 330 may be enlarged to secure a space for connection work. However, there is a problem that the size of the three-axis antenna is increased.

  In Patent Literature 2, a flat base member 430 is used instead of the case as in Patent Literature 1. According to such a configuration, there is no wall portion that hinders the connection work, and the connection workability between the end of the antenna coil and the external connection terminal is improved. Further, by forming the two magnetic cores with the two members 420 and 450, it is easy to obtain by compression molding. Moreover, the obtained triaxial antenna becomes excellent in weather resistance by the resin mold.

  However, using a plurality of members simply increases the number of manufacturing steps and causes an increase in cost. In addition, the second member 450 having a plate-like magnetic core formed thinner than the first member 420 is formed with a groove for accommodating the antenna coil 410, and therefore has a certain thickness to ensure strength and prevent deformation. There is a limit to reducing the thickness of the triaxial antenna by further reducing the thickness of both the magnetic cores formed by the first member 420 and the second member 450. If the second member 450 is warped, an air gap may be formed between the second member 450 and the reception sensitivity may be deteriorated. In addition, since the base member 430 is provided between the first member 420 and the second member 450 constituting both the magnetic cores, the winding width for providing the antenna coil 412 is reduced by that thickness, making winding difficult.

  Therefore, an object of the present invention is to provide a three-axis antenna that can be easily assembled and can be manufactured at low cost while maintaining small size and thinness.

  The present invention includes a body portion, a single-sided magnetic core having an integral flange portion on one end side in the thickness direction, and a plurality of terminals held on the resin portion disposed on the other end side of the body portion. A first antenna coil and a second antenna coil that are in contact with and sandwich one end side of the body portion and the base member, and a third antenna coil that includes the body portion. Each antenna coil is a three-axis antenna characterized by having a different winding direction and being connected to the terminal.

  In the three-axis antenna of the present invention, the flange portion and the base member of the one-sided magnetic core are projected on the outer periphery of the body portion of the one-sided magnetic core when viewed in the thickness direction, and the flange portion of the one-sided magnetic core of the base member It is preferable that the terminal is provided in a portion protruding to the outer periphery.

  Further, the one-sided magnetic core has four first groove portions extending from the flange portion to the base member in the thickness direction of the body portion, and a second groove portion continuous to two of the first groove portions on the flange portion side. The base member has a third groove portion facing the second groove portion of the one-sided magnetic core, and the first antenna coil includes the first groove portion, the second groove portion, and the third groove portion. The second antenna coil is wound around the second winding part including the remaining first groove part of the assembly so as to intersect at both ends of the first antenna coil and the one-sided magnetic core, It is preferable that the third antenna coil is wound around a third winding portion including the body portion of the one-sided magnetic core.

  In the present invention, it is preferable that the first antenna coil, the second antenna coil, and the third antenna coil are arranged without contacting each other.

  In the present invention, it is preferable that the one-sided magnetic core has a convex portion on the other end side of the trunk portion, and the base member has an opening for receiving the convex portion.

  In the triaxial antenna of the present invention, the first antenna coil, the second antenna coil, the third antenna coil, and the base member are sealed with an insulating resin except for the terminal of the assembly. preferable.

  In the triaxial antenna of the present invention, it is preferable that the third antenna coil has a self-inductance greater than that of the first antenna coil and the second antenna coil.

1 is an external perspective view showing a triaxial antenna according to an embodiment of the present invention. It is a front view of the 3 axis | shaft antenna which concerns on one Example of this invention. It is a top view of the triaxial antenna which concerns on one Example of this invention. It is a bottom view of the triaxial antenna which concerns on one Example of this invention. 1 is a side view of a three-axis antenna according to an embodiment of the present invention. It is sectional drawing of the a-a 'cross section of the triaxial antenna which concerns on one Example of this invention. It is an external appearance perspective view of the single core magnetic core used for the triaxial antenna which concerns on one Example of this invention. It is a front view of the single-sided magnetic core used for the triaxial antenna which concerns on one Example of this invention. It is a top view of the single core magnetic core used for the triaxial antenna which concerns on one Example of this invention. It is a bottom view of the single core magnetic core used for the triaxial antenna which concerns on one Example of this invention. It is a side view of the single core magnetic core used for the triaxial antenna which concerns on one Example of this invention. It is an external appearance perspective view of the one side magnetic core of the other aspect used for the triaxial antenna which concerns on one Example of this invention. It is a top view of the other aspect single core magnetic core used for the triaxial antenna which concerns on one Example of this invention. It is a bottom view of the single-sided magnetic core of the other aspect used for the triaxial antenna which concerns on one Example of this invention. It is an external appearance perspective view of the base member used for the triaxial antenna which concerns on one Example of this invention. It is a front view of the base member used for the triaxial antenna which concerns on one Example of this invention. It is a top view of the base member used for the triaxial antenna which concerns on one Example of this invention. It is a bottom view of the base member used for the triaxial antenna which concerns on one Example of this invention. It is a side view of the base member used for the triaxial antenna which concerns on one Example of this invention. It is an external appearance perspective view which shows the state which is the triaxial antenna which concerns on one Example of this invention, and was resin-sealed. It is a circuit block diagram for demonstrating the evaluation method of the sensitivity characteristic of a triaxial antenna. It is an external appearance perspective view which shows one embodiment of the conventional triaxial antenna. It is an external appearance perspective view which shows one embodiment of the double magnetic core used for the conventional triaxial antenna. It is an external appearance perspective view which shows the other embodiment of the conventional triaxial antenna. It is an external appearance perspective view which shows the other embodiment of the conventional triaxial antenna. It is a disassembled perspective view which shows the structure of the assembly which comprises the conventional triaxial antenna shown in FIG.

  The triaxial antenna of the present invention will be described with reference to FIGS. 1 is an external perspective view showing an embodiment of a triaxial antenna, FIG. 2 is a front view of the triaxial antenna shown in FIG. 1, FIG. 3 is a top view thereof, and FIG. 4 is a bottom view thereof. 5 is a side view, and FIG. 6 is a cross-sectional view of the three-axis antenna taken along the line aa ′.

  The triaxial antenna 1 has a basic configuration in which a body, a single core 20 formed of a ferrite core having a flange on one end thereof, and a base in which a plurality of external connection terminals 31 are integrated with an insulating resin. The antenna 30 includes three antenna coils 11a, 11b, and 11c wound around the member 30, the one-sided magnetic core 20 and the base member 30, and in the illustrated embodiment, each antenna coil 11a, 11b, and 11c and one piece The magnetic core 20 and the base member 30 are sealed with an insulating resin 200. The resin-molded triaxial antenna 1 has a terminal 31 exposed on the surface for connection with other components, and can be mounted on a circuit board or the like. In each figure, the resin portion is indicated by a dotted line so as to easily confirm the internal configuration, and the internal portion is shown through the interior or omitted.

  The external connection terminal 31 is connected to fixed portions sx, ex, sy, ey, sz, and ez that are wound around the end of the antenna coil. The end of the antenna coil 11a is entangled with the fixed portions sx and ex, the end of the antenna coil 11b is entangled with the fixed portions sy and ey, and the end of the antenna coil 11c is entangled with the fixed portions sz and ez. . The end of each antenna coil is connected to each fixed part by connecting means such as soldering or welding.

  One embodiment of the single-sided magnetic core 20 used for the triaxial antenna 1 is shown in FIGS. FIG. 7 is an external perspective view of a single core, FIG. 8 is a front view of the single core, FIG. 9 is a top view, FIG. 10 is a bottom view, and FIG. 11 is a side view.

The single-sided magnetic core 20 has a body portion 21 and a flange portion 22 connected to one end thereof. The flange portion 22 and the body portion 21 are provided with four groove portions 23 and 24 having a bottom portion inward from the outer peripheral edge of the body portion 21 toward the inside from the outer peripheral edge thereof. The two opposing groove portions 23 and the other two groove portions 24 are preferably arranged so that the line segments connecting the respective groove portions are orthogonal to each other.
Further, the flange portion 22 is provided with a groove portion 25 that crosses the XY plane and connects the groove portions 23. The other end of the body portion 21 has a convex portion 26 inside the outer peripheral edge. The convex portion 26 is used for positioning a base member to be described later. The flange portion 22 and the body portion 21 are configured to have four fan-shaped portions by the groove portions 23 and 24. 12 to 14 show other embodiments of the single core 20. In this one-sided magnetic core 20, the flange portion 22 and the trunk portion 21 have four rectangular portions by the groove portions 23 and 24, and the area thereof is formed large in a cross section perpendicular to the thickness direction of the trunk portion 21. it can. Moreover, if the area of the convex part 26 is made large when viewed in the thickness direction of the body part 21, the volume of the body part 21 can be further increased. According to such a form, the inductance of each antenna coil increases, and the receiving sensitivity can be improved.

  One embodiment of the base member used for the triaxial antenna is shown in FIGS. 15 is an external perspective view of the base member, FIG. 16 is a front view of the base member, FIG. 17 is a top view of the base member, FIG. 18 is a bottom view, and FIG. 19 is a side view.

The base member 30 includes a plurality of terminals 31 held in a resin portion made of a heat resistant resin, and is formed in a thin plate shape. An opening 34 for receiving the convex portion 26 of the one-sided magnetic core is provided at the center of the resin portion, and four rectangular projecting portions 35 are provided at the corners. When viewed in the thickness direction of the base member 30, the opening portion 34 is formed with substantially the same shape and area as the convex portion 26, thereby functioning as a positioning with the single core.
A metal member constituting the terminal 31 is inserted into each protrusion 35. On the periphery of the protruding portion 35, a fixing portion 32 and a terminal 31 for connecting the antenna coil appear. Furthermore, the groove part 33 which goes inward from the outer periphery to the resin part is provided in four places. One surface side 30a of the base member 30 is formed to be substantially flat, and abuts against the end portion of the body portion 21 of the one-sided magnetic core 20. On the other hand, a groove portion 37 that connects the two groove portions 33 facing each other is provided on the facing one surface 30b side. The resin portion 36 around the opening 34 has a different thickness on the one surface 30b side, and the first portion 36a of the groove portion 37 is thinner than the second portion 36b. The resin portion is preferably formed of a resin having insulating properties, heat resistance, and moldability. Specifically, polyphenylene sulfide, liquid crystal polymer, polyethylene terephthalate, polybutylene terephthalate, and the like are preferable. An injection molding method can be used for these moldings.

The single core 20 and the base member 30 are combined to form an assembly. In order to make an assembly, the convex portion 26 formed on the body portion 21 of the one-sided magnetic core 20 is fitted into the opening 34 formed on the base member 30 and fixed with an adhesive. The convex portion 26 is combined with the base member 30 and has a size that does not protrude from the first portion 36 a on the one surface 30 b side of the base member 30. At the time of combination, the extending direction of the groove portion 25 provided in the single core 20 and the extending direction of the groove portion 37 formed in the base member 30 are set to be the same direction.
The assembly thus formed includes four groove portions in which the groove portions 23 and 24 of the single-core magnetic core 20 and the groove portion 33 of the base member 30 extend in the thickness direction of the body portion, and the groove portions of the single-core magnetic core 20 that are arranged to face each other. 23 has a groove portion 25 on the flange portion 22 side, and a groove portion 37 on the base member 30 side facing the groove portion 25.

  The first antenna coil 11a includes two groove portions extending in the thickness direction of the body portion of the one-sided magnetic core and a groove portion 25 on the side of the flange portion 22 connecting the groove portions 23 of the one-sided magnetic core 20 arranged opposite to each other; The first winding portion including the groove portion 25 and the groove portion 37 on the base member 30 side facing the groove portion 25 is wound, and the end portion is connected to the fixing portion 32 of the base member 30. Next, the second antenna coil 11b is wound around the second winding portion including the remaining two groove portions of the assembly so as to intersect the first antenna coil 11a, and the end portion is similarly fixed to the base member 30. Connected to the unit 32. Next, the third antenna coil 11 c includes the body portion 21 of the one-sided magnetic core 20, and the first antenna coil 11 a and the second antenna are placed on the third winding part between the one-sided magnetic core 20 and the base member 30. It is wound around the antenna coil 11b. The end portion is connected to the fixing portion 32 of the base member 30.

  In order to reduce interference among the first antenna coil 11a, the second antenna coil 11b, and the third antenna coil 11c, it is desirable to make the winding axes orthogonal.

  Further, each time the antenna coil is wound, it is possible to prevent the coil from loosening and the terminal from being caught by sequentially fixing the terminal conductors.

The reception sensitivity may be impaired by the parasitic capacitance generated between the antenna coils. The formation depths of the first groove and the second groove are not in contact with each other after the antenna coils are wound, and the antenna coils are spaced from each other. The depth is configurable. The first antenna coil 11a is wound in contact with the first portion 36a of the base member 30, and the second antenna coil 11b is wound in contact with the second portion 36b of the base member 30. With this configuration, the base member 30 is held integrally with the one-sided magnetic core 20 and does not fall off. In addition, the number of parts can be reduced by configuring the magnetic core only by the single-sided magnetic core 20.
Further, if the single-core magnetic core is used, the height of the body portion 21 around which the third antenna coil 11c of the third winding portion is wound can be made larger than that of the double-magnetic core without increasing the height of the three-axis antenna. By increasing the number of turns of the third antenna coil 11c, the self-inductance can be increased without reducing the quality factor Q of the antenna coil. Therefore, it is possible to form a triaxial antenna with little difference in reception sensitivity in all directions. Further, as shown in FIG. 20, the portion other than the terminal 31 is resin-molded and sealed with a heat-resistant resin, whereby a three-axis antenna having excellent weather resistance is obtained.

  Hereinafter, embodiments of the three-axis antenna of the present invention will be described in detail, but the basic configuration is the same as that described above with reference to FIGS.

  In Example 1, the single-sided magnetic core shown in FIG. 7 was used. In this one-sided magnetic core 20, the flange portion 22 and the trunk portion 21 are formed in a circular shape in plan view excluding the groove portion, and the outer shape of the flange portion 22 is φ12.28 mm, the thickness is 0.6 mm, and the outer shape of the trunk portion 21. Is φ10.2 mm and the height is 1.36 mm. A first antenna coil 11a, a second antenna coil 11b, and a third antenna coil 11c are sequentially laid on an assembly of a single core 20 and a base member 30 in which a terminal 31 made of phosphor bronze is insert-molded using a liquid crystal polymer. The end was connected to the terminal 31.

  In Example 2, the single core shown in FIG. 12 was used. In this one-sided magnetic core 20, the shape of the flange portion 22 and the trunk portion 21 is rectangular in plan view. The outer shape of the flange portion 22 is 11.12 mm on one side and the thickness is 0.6 mm, and the outer shape of the trunk portion 21 is 9.2 mm on one side and 1.41 mm in height. The first antenna coil 11 a, the second antenna coil 11 b, and the third antenna coil 11 c were sequentially laid on the assembly of the single-sided magnetic core 20 and the base member 30, and the end portion was connected to the terminal 31.

  Furthermore, resin sealing was performed using polyphenylene sulfide to obtain a triaxial antenna having a size of 12.8 mm × 13.6 mm × 3.6 mm and 12.2 mm × 13 mm × 3.6 mm, respectively. In addition, NiZn ferrite having an initial permeability of 500 was used for the single-sided magnetic core 20 in each example.

  For Examples 1 and 2, the self-inductance, quality factor Q, and induced electromotive force of each antenna coil were evaluated. The results and the number of turns of each antenna coil are shown in Table 1. The self-inductance and the quality factor Q are evaluated using an impedance analyzer, and the received electromotive force is evaluated with an oscilloscope as an index corresponding to the reception sensitivity.

  FIG. 21 shows a method for evaluating an induced electromotive force generated as a response to a magnetic field. The oscillator 501 oscillates an AC signal having a measurement frequency of 125 kHz, and a Helmholtz coil 502 generates a uniform parallel magnetic field. The antenna coil in the direction to be measured was inserted vertically into the parallel magnetic field, and the induced voltage was amplified with the probe amplifier 503 and then observed with the oscilloscope 504.

  According to the triaxial antenna of the present invention, the number of components is small, the assembly is easy, and a large induced electromotive force is obtained in each antenna coil while being compact without greatly changing the shape and size.

DESCRIPTION OF SYMBOLS 1 3 axis antenna 11a, 11b, 11c Antenna coil 20 Single-sided magnetic core 21 trunk | drum 22 collar 30 base member 31

Claims (7)

  A body portion, a one-sided magnetic core having a flange portion integrated with the body portion on one end side in the thickness direction, and a plurality of terminals held on the resin portion disposed on the other end side of the body portion. A first antenna coil and a second antenna coil that are in contact with and sandwiched between the one end side of the body and the base member, and a third antenna coil that encloses the body. Each antenna coil has a different winding axis direction and is connected to the terminal. The triaxial antenna according to claim 1, wherein
The flange portion of the one-sided magnetic core and the base member are projected on the outer periphery of the trunk portion of the one-sided magnetic core when viewed in the thickness direction, and the portion of the base member that protrudes on the outer periphery than the flange portion of the one-sided magnetic core A triaxial antenna characterized by comprising a terminal. The triaxial antenna according to claim 2, wherein
The one-sided magnetic core has four first groove portions that reach the flange portion and the base member in the thickness direction of the body portion, and a second groove portion that continues to two of the first groove portions on the flange portion side,
The base member has a third groove portion facing the second groove portion of the one-sided magnetic core,
A first antenna coil is wound around a first winding part including the first groove part, the second groove part, and the third groove part,
The second antenna coil is wound around the second winding part including the remaining first groove part of the assembly so as to intersect the first antenna coil and the both end sides of the one-sided magnetic core,
A three-axis antenna, wherein a third antenna coil is wound around a third winding portion including a body portion of the one-sided magnetic core. The triaxial antenna according to claim 2 or 3,
The three-axis antenna, wherein the first antenna coil, the second antenna coil, and the third antenna coil are arranged without contacting each other. The triaxial antenna according to any one of claims 1 to 4,
The one-sided magnetic core has a convex portion on the other end side of the trunk portion,
The three-axis antenna, wherein the base member has an opening for receiving the convex portion. A triaxial antenna according to any one of claims 1 to 5,
The three-axis antenna, wherein the first antenna coil, the second antenna coil, the third antenna coil, and the base member are sealed with an insulating resin except for the terminals of the assembly. The triaxial antenna according to any one of claims 1 to 6,
The three-axis antenna, wherein a self-inductance of the third antenna coil is larger than that of the first antenna coil and the second antenna coil.

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