JP2012239020A - Antenna device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an antenna device the frame of which can be made compact while reducing the component cost, even if a resonance frequency adjustment mechanism is provided.SOLUTION: The out-vehicle transmitter (in-vehicle transmitter) of a vehicle comprises an antenna unit 14 for transmitting LF waves, for example. The antenna unit 14 includes a coil unit 16 where a coil 19 is wound multiple number of turns around a bobbin 18, and a core 17 having a high permeability. The antenna unit 14 includes a first resonance frequency adjustment mechanism 23 which adjusts the resonance frequency of the antenna by shifting the position of the core 17 for the coil 19. Inductance of the antenna, i.e., the resonance frequency, can thereby be adjusted by moving the core 17 in the axial direction of the coil for the coil unit 16 and aligning the core 17 and the coil unit 16.

Description

  The present invention relates to an antenna device for wireless communication.

  Conventionally, there is a need for miniaturization / high output in an antenna device, and it is generally known that a Q (Quality factor) value is increased to satisfy this need. The Q value is obtained by Q = ωL / R (L: inductance, R: resistance). If the Q value is set high, L takes a high value. If L is large, a high output can be obtained even if the current is small. Therefore, setting the Q value to a high value satisfies the miniaturization / high output of the antenna device.

  FIG. 10 shows the Q-value waveform characteristics. In addition, the vertical axis | shaft of the same figure is an impedance, and a horizontal axis is a frequency. As shown in the figure, if the Q value is low, the fluctuation variation in impedance (resonance frequency) is small, but if the Q value is high, the fluctuation variation in impedance (resonance frequency) becomes large. Therefore, if the Q value is increased with the aim of downsizing / higher output of the antenna device, there is a concern that the variation in electric field strength due to fluctuations in the resonance frequency will increase.

  Therefore, for example, the techniques disclosed in Patent Documents 1 to 3 are well known in order to suppress the resonance frequency fluctuation within a narrow range. These documents 1 to 3 are techniques for adjusting the resonance frequency by changing the position and orientation of the sub-core with respect to the main antenna in which the antenna wire is wound around the core. Patent Document 1 is a technique for moving a screw core back and forth with respect to an antenna. Patent Document 2 is a technique for rotating a half-moon-shaped core with respect to an antenna. Patent Document 3 is a technique for moving a plate-like core back and forth.

Japanese Patent No. 3735104 Japanese Patent No. 4186818 Japanese Patent No. 4254859

  However, since Patent Documents 1 to 3 are technologies that require a sub-core in addition to the main antenna, there is a problem that the total length of the device size is increased by the amount corresponding to the sub-core, or the component cost is increased.

  An object of the present invention is to provide an antenna device that can reduce the size of the device and keep the component cost low even if a resonance frequency adjusting mechanism is provided.

  In order to solve the above problems, in the present invention, in an antenna device in which an antenna wire is wound around a high permeability core and the annular antenna wire becomes a coil of a resonance circuit, at least for the coil unit including the coil, The gist is that a resonance frequency adjusting mechanism for adjusting a resonance frequency by adjusting the position by moving the core itself is provided.

  According to the configuration of the present invention, the resonance frequency is adjusted by moving the core itself with respect to the coil unit, so that no other components are required to adjust the resonance frequency. Therefore, even if the antenna device is provided with a function for adjusting the resonance frequency, the device size can be kept small, and the component cost can be kept low.

  In the present invention, the resonance frequency adjusting mechanism includes a protrusion provided on one of the core and the coil unit, and a plurality of grooves provided on the other of the two, and one of the plurality of grooves. In summary, the core is positioned with respect to the coil unit by locking the protrusion, and the resonance frequency is determined at the position. According to this configuration, since the position of the core with respect to the coil unit is determined by the locking between the protrusion and the groove, it is easy to align the core. In addition, since the structure is such that the protrusion and the groove are caught at the time of positioning, it is possible to prevent the core from being displaced.

  In the present invention, a second resonance frequency adjusting mechanism is provided that adjusts the resonance frequency by adjusting the interval between the main winding and the auxiliary winding by dividing the coil into a main winding and an auxiliary winding. This is the summary. According to this configuration, since the resonance frequency can be adjusted also by the interval (gap) between the main winding and the auxiliary winding, the resonance frequency can be easily matched with a desired value.

  In the present invention, when the coil unit into which the core is inserted is attached to the case, the position of the protrusion and the groove is maintained by pressing the spring-like protrusion with the wall surface of the case. The gist is that a holding mechanism is provided. According to this configuration, since the protrusion is firmly fixed to the groove by the position holding mechanism, the effect of preventing the misalignment of the core is enhanced.

  According to the present invention, even if a resonance frequency adjusting mechanism is provided, the size of the apparatus can be reduced, and the component cost can be kept low.

The block diagram of the key operation free system of one Embodiment. The perspective view of a transmitter. The disassembled perspective view when a transmitter is seen from one side. The exploded perspective view when a transmitter is seen from the other side. The exploded perspective view of an antenna unit. Sectional drawing which shows the structure of a 1st resonance frequency adjustment mechanism. (A) is a graph which shows the relationship between a core position and an inductance change rate, (b) is a schematic diagram of each antenna which changed the coil gap. The graph which shows the relationship between a coil gap and an inductance change rate. (A) is a graph which shows the relationship between a coil turns ratio and an inductance change rate, (b) is a schematic diagram of each antenna which changed coil turn ratio. The graph which shows the frequency characteristic of the conventional Q value.

Hereinafter, an embodiment of an antenna device embodying the present invention will be described with reference to FIGS.
As shown in FIG. 1, the vehicle 1 is provided with a key operation free system 3 that performs ID collation wirelessly with an electronic key 2 using communication from the vehicle 1 as a trigger. In this case, the vehicle 1 includes a key verification device 4 that performs ID verification with the electronic key 2, a door lock device 5 that manages the locking and unlocking operation of the vehicle door, and an engine starter 6 that manages the operation of the engine. These are provided and connected via a bus 7 in the vehicle.

  The key verification device 4 is provided with a verification ECU (Electronic Control Unit) 8 that controls the key verification device 4 in an integrated manner. The ID code of the electronic key 2 is registered in the verification ECU 8. The verification ECU 8 includes an in-vehicle transmitter 9 that transmits radio waves in the LF (Low Frequency) band outside the vehicle, an in-vehicle transmitter 10 that transmits LF radio waves in the car, and a vehicle that receives the radio waves in the UHF (Ultra High Frequency) band. A receiver 11 is connected. The vehicle-side transmitter 9 and the vehicle-side transmitter 10 constitute an antenna device.

  When the vehicle 1 is in a parked state, the verification ECU 8 intermittently transmits a request signal Srq from the outside-vehicle transmitter 9 to execute smart communication (outside-vehicle smart communication). When the electronic key 2 enters the outside communication area of the request signal Srq and the electronic key 2 receives the request signal Srq, the electronic key 2 is activated and transmits the ID signal Sid by UHF radio waves. The ID signal Sid includes an ID code registered in the electronic key 2. When the verification ECU 8 receives the ID signal Sid after transmitting the request signal Srq, it performs smart verification (external vehicle smart verification) as ID verification, and if this verification is established, permits or executes door lock locking / unlocking.

  When the user gets in the vehicle, the in-vehicle transmitter 10 starts transmission of the request signal Srq instead of the previous out-of-vehicle transmitter 9 and executes smart communication (in-vehicle smart communication). Smart collation (in-car smart collation) similar to that outside the vehicle is performed inside the vehicle, and if this collation is established, operation of power supply transition and engine start by the push momentary engine switch 12 installed in the vehicle is permitted.

  2 to 6 show the structure of the outside transmitter 9. Since the in-vehicle transmitter 10 has the same structure as the out-of-vehicle transmitter 9, only the out-of-vehicle transmitter 9 will be described here. The out-of-vehicle transmitter 9 is provided with a resin case 13 that houses various components of the out-of-vehicle transmitter 9. The case 13 has a long and thin hollow box shape and is made of resin. The out-of-vehicle transmitter 9 is assembled to a vehicle body body (iron plate such as a metal) such as a door with screws or the like.

  As shown in FIGS. 3 and 4, the antenna unit 14 of the vehicle-mounted transmitter 9 is housed inside the case 13. In the case 13, an opening 15 is formed on the side in the longitudinal direction (the side on the right side of FIG. 2 and FIG. 3), and the antenna unit 14 is accommodated inside the case 13 from the opening 15.

  As shown in FIG. 5, the antenna unit 14 is provided with a coil unit 16 in which a plurality of antenna wires (electric wires) are wound, and a rod-shaped core 17 made of a material with high magnetic permeability (for example, ferrite). . The coil unit 16 is provided with a resin bobbin 18 for winding the antenna wire, and a coil 19 formed of a group of annular antenna wires wound around the bobbin 18. In the bobbin 18, an opening 20 is provided on the side in the longitudinal direction (the left side in FIG. 5), and the core 17 is accommodated in the bobbin 18 from the opening 20. The antenna unit 14 includes a series circuit in which the coil 19 is L (inductance) and a capacitor mounted on a substrate (not shown) of the antenna unit 14 is C (capacitance). The coil 19 is in an attached state in which the coil unit 19 is wound around the core 17 when the antenna unit 14 is attached to the bobbin 18.

  At the base of the bobbin 18, a pair of locking protrusions 21 and 21 (only one is shown in FIGS. 3 to 5) for fixing the antenna unit 14 to the case 13 are provided. Therefore, when the antenna unit 14 is attached to the case 13, the locking protrusions 21, 21 are locked in the locking holes 22, 22 of the case 13, so that the antenna unit 14 is prevented from coming off from the case 13.

  As shown in FIGS. 3 to 5, the antenna unit 14 is provided with a first resonance frequency adjusting mechanism 23 that adjusts the resonance frequency fc of the antenna by moving the position of the core 17 with respect to the coil 19. By the way, it is known that the resonance frequency fc is obtained by the following equation, where L is the inductance of the series resonance circuit and C is the capacitance.

ここで、コイル１９に対してコア１７をコイル１９の軸心方向（コイル軸心方向：図３及び図５のＸ軸方向）に動かすと、コイル１９のインダクタンスが変化する現状がある。よって、コア１７をコイル１９に対して動かしてインダクタンスを調整すれば、結果として、共振周波数ｆｃを所望の値に切り換えることが可能である。従って、本例の共振周波数調整機構２３は、この原理を用いて、共振周波数ｆｃを調整する。

Here, when the core 17 is moved with respect to the coil 19 in the axial direction of the coil 19 (coil axial direction: X-axis direction in FIGS. 3 and 5), the inductance of the coil 19 changes. Therefore, if the inductance is adjusted by moving the core 17 with respect to the coil 19, as a result, the resonance frequency fc can be switched to a desired value. Therefore, the resonance frequency adjusting mechanism 23 of this example adjusts the resonance frequency fc using this principle.

  In this case, the core 17 can be linearly reciprocated in the coil axis direction with respect to the coil unit 16 (bobbin 18). Then, the core 17 is moved with respect to the bobbin 18 so as to be positioned at a predetermined position, thereby matching the desired resonance frequency fc.

  As shown in FIG. 6, the first resonance frequency adjusting mechanism 23 of this example is provided with a position setting unit 24 that sets the position of the core 17 in the coil axis direction stepwise. In this case, the bobbin 18 is provided with a spring-like bobbin protrusion 25 that can be locked to the core 17. The bobbin protrusion 25 moves in the height direction (Z-axis direction in FIG. 6) with the root as a fulcrum. On the other hand, on the upper surface of the core 17, a plurality of recesses 26 to which the bobbin protrusion 25 is locked are provided at the end in the insertion direction. The plurality of recesses 26 are arranged at equal intervals along the longitudinal direction of the core 17. The bobbin protrusion 25 corresponds to a protrusion, and the recess 26 corresponds to a groove.

  The resonance frequency adjusting mechanism 23 is provided with a position holding mechanism 27 that firmly holds the position determined by the position setting unit 24. In this case, on the upper surface of the bobbin projection 25, a restraining projection 28 that functions when the positioning state of the bobbin projection 25 is maintained is partially provided. When the antenna unit 14 is housed in the case 13, the bobbin protrusion 25 is pressed against the bobbin protrusion 25 by the inner surface (wall surface) 13 a of the case 13, whereby the bobbin protrusion 25 is strongly fixed to the recess 26.

  Furthermore, the antenna unit 14 of this example is provided with a second resonance frequency adjusting mechanism 29 that adjusts the resonance frequency fc by dividing the coil 19 into divided windings. In the case of this example, the front side of the core 17 in the insertion direction is the first divided coil 19a, and the back side of the core 17 in the insertion direction is the second divided coil 19b. Then, an interval between the first divided coil 19a and the second divided coil 19b (hereinafter referred to as a coil gap T) and the number of turns (the number of coil turns N) of the first divided coil 19a and the second divided coil 19b are adjusted. Thus, the inductance (resonance frequency fc) is adjusted. The divided coils 19a and 19b constitute a main winding and an auxiliary winding.

Next, the effect | action of the antenna of this example is demonstrated using FIGS.
When the outside transmitter 9 (in-vehicle transmitter 10) is assembled, as shown in FIG. 5, the core 17 is inserted into the prepared coil unit 16, and the bobbin protrusion 25 is set to a predetermined one of the plurality of recesses 26. Lock. At this time, the bobbin protrusion 25 is engaged with the recess 26 that is a core position capable of outputting a desired resonance frequency fc among the plurality of recesses 26, and the core 17 is attached to the coil unit 16. By assembling the components, the coil unit 16 and the core 17 become one antenna unit 14, and the resonance frequency fc of the antenna matches a desired value.

  Then, the antenna unit 14 is inserted into the case 13 through the opening 15, and the antenna unit 14 is assembled to the case 13. At this time, as shown in FIG. 6, the bobbin protrusion 25 is pushed from above by the inner surface 13 a of the case 13, and the bobbin protrusion 25 is firmly fixed to the recess 26. As a result, the core 17 is firmly fixed to the coil unit 16 (bobbin 18), and it is difficult for a situation where the core 17 is displaced with respect to the coil unit 16.

  FIG. 7A shows the relationship between the position of the core 17 and the variation rate of the inductance. In this case, as shown in FIG. 7B, four patterns having a coil gap T of 5 mm, 10 mm, 15 mm, and 20 mm are illustrated. As can be seen from the figure, if the core 17 is moved with respect to the bobbin 18, the rate of change in inductance changes, and as a result, the inductance (resonance frequency fc) can be adjusted. Therefore, the core 17 is slid relative to the bobbin 18, and the core 17 is disposed at a position where a desired resonance frequency fc can be transmitted.

  Next, FIG. 8 shows the relationship between the coil gap T and the rate of change in inductance per 1 mm of core movement. As can be seen from the figure, as the coil gap T increases, the rate of change in inductance per 1 mm of core movement increases. Accordingly, when it is desired to switch the resonance frequency fc with a small value, the coil gap T is set to be small, while when it is desired to switch the resonance frequency fc to be large, the coil gap T is set to be large.

  FIG. 9A shows the relationship between the turn ratio of the first split coil 19a and the second split coil 19b and the rate of change in inductance per 1 mm of core movement, and FIG. 9B shows the turn ratio. The appearance of the antenna is shown. As can be seen from the figure, when the turn ratio increases, the rate of change in inductance per 1 mm of core movement increases. Therefore, when it is desired to switch the resonance frequency fc with a small value, the turn ratio is set to be small. On the other hand, when it is desired to switch the resonance frequency fc to be large, the turn ratio is set to be large.

  As described above, in this example, since the first resonance frequency adjusting mechanism 23 capable of adjusting the resonance frequency fc by moving the core 17 itself with respect to the coil unit 16 is provided, the resonance can be achieved without using other separate components. The frequency fc can be adjusted to a desired value. Therefore, even if this type of resonance frequency adjusting mechanism is provided in the antenna unit 14, it is possible to adjust the resonance frequency fc of the antenna unit 14 while keeping the device size small and keeping the component cost low. Become.

According to the configuration of the present embodiment, the following effects can be obtained.
(1) The first resonance frequency adjusting mechanism 23 that adjusts the resonance frequency fc of the antenna unit 14 by moving the core 17 along the coil axis direction with respect to the coil unit 16 is provided. Therefore, the resonance frequency fc can be adjusted without using other separate components. Therefore, even if this type of resonance frequency adjustment mechanism is provided in the antenna unit 14, the coil unit in the direction of the coil axis of the antenna unit 14 can be adjusted. The device size can be kept small.

  (2) Since the first resonance frequency adjusting mechanism 23 has a structure that does not require other components such as a sub-core, the cost of components of the antenna unit 14 and thus the vehicle transmitter 9 and the vehicle transmitter 10 can be kept low.

  (3) The first resonance frequency adjusting mechanism 23 locks the bobbin protrusion 25 provided on the bobbin 18 with a specific one of the plurality of recesses 26 provided on the core 17, that is, the position of the core 17. A structure for determining the resonance frequency fc is adopted. Therefore, since the position of the core 17 with respect to the coil unit 16 can be determined by the operation of simply hooking the protrusion into the groove, there is an advantage that the core 17 can be easily aligned. Further, at the time of positioning, the bobbin protruding portion 25 is caught by the recessed portion 26, so that the position shift of the core 17 can be hardly caused.

  (4) By switching the gap T between the first divided coil 19a and the second divided coil 19b and the winding ratio (number of turns N) of the first divided coil 19a and the second divided coil 19b, the resonance frequency A second resonance frequency adjusting mechanism 29 capable of adjusting fc is provided. Therefore, the resonance frequency fc can be adjusted to a desired value by adjusting the coil gap T and the winding ratio.

  (5) A position holding mechanism 27 for holding the position of the core 17 set by the first resonance frequency adjusting mechanism 23 (bobbin protrusion 25 and recess 26) is provided. Therefore, since the bobbin protrusion 25 is firmly fixed to the recess 26 by the position holding mechanism 27, the effect of preventing the displacement of the core 17 is enhanced.

Note that the embodiment is not limited to the configuration described so far, and may be modified as follows.
-After locking the bobbin projection part 25 to the recessed part 26, you may fix these with an adhesive agent, for example.

The coil gap T and the coil turn number N can be changed as appropriate according to the required electric field strength.
The resonance circuit is not limited to a series resonance circuit, and may be a parallel resonance circuit.

The antenna device installation location is not limited to the vehicle body, and can be appropriately changed to another location.
The antenna device is not limited to a bar antenna, and other antenna types can be used.

  -The 1st resonance frequency adjustment mechanism 23 is not limited to having the position setting part 24 which consists of a protrusion and a some groove | channel. For example, the core 17 may be simply attached to the bobbin 18 by press fitting, and the inductance (resonance frequency fc) may be adjusted by the insertion amount of the core 17.

-The coil unit 16 is not limited to the unit component which consists of the bobbin 18 and the coil 19, and may be comprised only from the coil 19, for example.
In the case where the bobbin 18 and the core 17 are provided with positioning protrusions and grooves, the bobbin 18 may be provided with a plurality of positioning grooves and the core 17 may be provided with protrusions.

-The shape of the bobbin protrusion part 25 or the recessed part 26 is not limited to what was described in embodiment, and can be changed suitably.
The position holding mechanism 27 is not limited to a structure in which the bobbin protrusion 25 is held by the inner surface 13a of the case 13, and for example, a new protrusion may be provided on the case 13, and the bobbin protrusion 25 may be pressed by this protrusion. .

-When making the coil 19 into a division type, it is not limited to dividing into two, and it is good also as three or more.
When moving the core 17 relative to the coil unit 16, the reference position for starting movement may be any position.

-A protrusion is not limited to the spring-shaped bobbin protrusion part 25, For example, a simple mountain-shaped protrusion may be sufficient.
-The shape and depth of the hole / hole of the groove can be changed as appropriate.
The antenna device is not limited to being applied to both the in-vehicle transmitter 9 and the in-vehicle transmitter 10, and may be applied to only one of them.

-An antenna apparatus is not limited to a vehicle antenna, You may apply to another apparatus and apparatus.
Next, technical ideas that can be grasped from the above-described embodiment and other examples will be described below together with their effects.

  (A) In any one of claims 1 to 4, a position fixing mechanism for holding a position when the core is moved with respect to the coil unit is provided. According to this configuration, the core and the coil unit can be held in the positioning state by the position fixing mechanism.

  (B) In any one of claims 1 to 4 and the technical idea (A), the coil unit includes the coil and a bobbin around which the coil is wound. According to this configuration, the antenna wire can be wound around the bobbin and used as a coil unit.

  DESCRIPTION OF SYMBOLS 9 ... Outside transmitter which comprises antenna apparatus, 10 ... In-vehicle transmitter which comprises antenna apparatus, 13 ... Case, 13a ... Inner surface as wall surface, 16 ... Coil unit, 17 ... Core, 19 ... Coil, 19a ... Main winding A first divided coil constituting a wire or an auxiliary winding, 19b ... a second divided coil constituting a main winding or an auxiliary winding, 23 ... a first resonance frequency adjusting mechanism as a resonance frequency adjusting mechanism, 25 ... as a protrusion Bobbin projections, 26... Recesses as grooves, 27... Position holding mechanism, 29... Second resonance frequency adjusting mechanism, fc... Resonance frequency, T.

Claims (4)

In an antenna device in which an antenna wire is wound around a core with high permeability and the annular antenna wire becomes a coil of a resonance circuit,
An antenna apparatus comprising: a resonance frequency adjusting mechanism that adjusts a resonance frequency by moving and adjusting the position of a core unit including at least the coil. The resonance frequency adjusting mechanism includes a protrusion provided on one of the core and the coil unit, and a plurality of grooves provided on the other of the two members, and the protrusion is provided on one of the plurality of grooves. The antenna device according to claim 1, wherein the core is positioned with respect to the coil unit by locking a portion, and a resonance frequency is determined at the position. A second resonance frequency adjusting mechanism that adjusts a resonance frequency by adjusting the interval between the main winding and the auxiliary winding as a split winding of the main winding and the auxiliary winding is provided. The antenna device according to claim 1 or 2. When the coil unit into which the core is inserted is attached to the case, a position holding mechanism is provided to hold the position of the protrusion and the groove by pressing the spring-like protrusion on the wall surface of the case. The antenna device according to claim 2 or 3, wherein

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