JP2014086993A - Communication area formation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a communication area formation device capable of forming a desired communication area regardless of an antenna mounting direction.SOLUTION: A first transmission antenna 24 has two bar antennas 41 and 42 which are orthogonal to each other and are driven simultaneously. Individually setting values of drive currents Ix and Iy supplied to both bar antennas 41 and 42 makes it possible to arbitrarily control magnetic distribution, which is a direction and magnitude of directivity of a synthetic magnetic field Hxy synthesized from a magnetic field Hx by one bar antenna 41 and a magnetic field Hy by the other bar antenna 42, in a communication area 51. Thereby, a desired communication area 51 can be formed regardless of a mounting direction of the first transmission antenna 24. Second and third transmission antennas 25 and 26 are similar to the first transmission antenna 24.

Description

  The present invention relates to a communication area forming apparatus.

  2. Description of the Related Art Conventionally, an electronic key system that controls a vehicle through wireless communication between a portable device held by a user and the vehicle is well known. In this system, when a portable device enters a communication area set around or in the vehicle, mutual wireless communication is automatically performed between the vehicle and the portable device. When the vehicle determines that the communication target is an authorized portable device through the wireless communication, the vehicle permits the unlocking of the vehicle door or the start of the engine.

JP 2006-022606 A

  For example, in the electronic key system disclosed in Patent Document 1, a uniaxial coil antenna is provided in a vehicle as an antenna for transmitting a radio signal to the communication area described above. In the uniaxial coil antenna, the directivity of the magnetic field distribution is determined in a specific uniaxial direction. Therefore, the direction of the directivity of the magnetic field distribution is determined by the mounting direction of the coil antenna with respect to the vehicle. That is, it is possible to adjust the direction of the magnetic field by changing the mounting direction of the coil antenna with respect to the vehicle, thereby forming a desired communication area.

  However, when there are some mounting restrictions on the vehicle, the mounting direction of the coil antenna may inevitably be determined by the mounting restrictions. In this case, since a coil antenna cannot be provided in the mounting direction in which a desired communication area can be formed, it may be difficult to form a desired communication area.

  The present invention has been made to solve the above problems, and an object of the present invention is to provide a communication area forming apparatus capable of forming a desired communication area regardless of the mounting direction of the antenna.

  A communication area forming apparatus that solves the above problems forms a communication area with a communication terminal by transmitting radio waves through control by a control circuit, and is integrally provided so that the axes cross each other and are simultaneously driven. And at least two antenna coils, and an adjustment circuit for individually adjusting the amount of current supplied to the antenna coils.

  According to this configuration, the magnetic field distribution in the communication area is a magnetic field distribution obtained by combining the magnetic field generated by one antenna coil and the magnetic field generated by the other antenna coil. By individually adjusting the amount of current supplied to at least two antenna coils through the adjustment circuit, the direction of the directivity of the combined magnetic field, that is, the magnetic field distribution in the communication area can be arbitrarily adjusted. For this reason, a desired communication area can be formed regardless of the mounting direction of the antenna coil.

  The communication area forming apparatus may be configured as follows. That is, the communication terminal receives the radio wave and transmits a radio signal, and the control circuit is set based on the received signal strength of the radio signal from the communication terminal located at the boundary of a normal communication area. When the received signal strength of the wireless signal is out of the threshold value, the amount of current supplied to the at least two antenna coils through the adjustment circuit is adjusted individually to match the received signal strength with the threshold value. Adjust.

  There is a correlation between the received signal strength and the communication distance. For this reason, when the received signal strength approximates to the threshold value, it can be said that a communication terminal exists near the boundary of the normal communication area and a radio signal is transmitted from the communication terminal. Therefore, by individually setting the amount of current to be supplied to at least two antenna coils according to the comparison result between the received signal strength of the wireless signal transmitted from the communication terminal and the threshold value, the received signal strength is adjusted to the threshold value, That is, a normal communication area can be formed.

  The communication area forming apparatus may be configured as follows. That is, the communication terminal receives the radio wave and transmits a radio signal, and the control circuit is in a situation where the communication terminal exists in the communication area if the communication area is normal. However, when the wireless signal is not received, the current amounts for the at least two antenna coils are individually adjusted through the adjustment circuit in order to expand the current communication area.

  When the communication area is normal, when the radio signal for the radio wave is not received even though the communication terminal exists in the communication area, the current communication area is narrower than the normal communication area. However, it is thought that it is only formed. For this reason, it is possible to approximate the normal communication area by expanding the current communication area.

  The communication area forming apparatus may be configured as follows. That is, the communication area includes a first communication area and a second communication area, and the control circuit supplies the at least two antenna coils with an amount of current (first output) when forming the first communication area. Set value) and the amount of current (second set value) supplied to each of the at least two antenna coils when forming the second communication area, and storing the at least two antennas through the adjustment circuit. The first and second communication areas are switched and formed by individually adjusting the amount of current supplied to the coil.

  According to this configuration, two communication areas can be switched and formed by a single communication area forming apparatus.

  According to the present invention, a desired communication area can be formed regardless of the antenna mounting direction.

The block diagram of an electronic key system. The top view of a transmitting antenna similarly. (A) is a schematic diagram which shows the normal magnetic field direction of a transmission antenna, (b) is a top view of the vehicle which similarly shows the communication area by normal magnetic field distribution. (A) is a schematic diagram showing the direction of a magnetic field when the magnetic field of one bar antenna is smaller than that of a normal state and the magnetic field of another bar antenna is larger than that of a normal state. FIG. 3 is a plan view of a vehicle showing a communication area when a magnetic field of one of the two bar antennas is smaller than that in a normal state and a magnetic field of another antenna is larger than that in a normal state. (A) is a schematic diagram showing a magnetic field direction when the magnetic field of one bar antenna is larger than that of a normal state and the magnetic field of another bar antenna is smaller than that of a normal state. FIG. 3 is a plan view of a vehicle showing a communication area when a magnetic field of one bar antenna is larger than that of a normal one of two bar antennas and a magnetic field of another bar antenna is smaller than that of a normal state. The top view of the vehicle which shows the communication area in 4th Embodiment. (A) is a plan view of a vehicle showing an optimal vehicle exterior area when the transmission antenna is configured by a single bar antenna as a comparative example, and (b) is a mounting of a single bar antenna in which the optimal vehicle exterior area is formed. Schematic diagram showing the direction, (c) is a plan view of the vehicle showing an optimal in-vehicle area when the transmission antenna is constituted by a single bar antenna as a comparative example, and (d) is an optimal in-vehicle area. The schematic diagram which shows the mounting direction of one bar antenna. (A) is a plan view of the vehicle showing the total communication area in the fourth embodiment, (b) is a schematic diagram showing the direction of the magnetic field that is optimal for the communication area outside the vehicle, and (c) is the same. The schematic diagram which shows the magnetic field direction which becomes the optimal for a communication area outside a vehicle. The front view which shows the structure of the biaxial transmission antenna in other embodiment.

<First Embodiment>
Hereinafter, a first embodiment in which the communication area forming apparatus is embodied in an electronic key system of a vehicle will be described.

<System overview>
As shown in FIG. 1, a door lock device 12 and an engine starter 13 are connected to an ECU (electronic control unit) 11 of the vehicle 10. The door lock device 12 performs locking and unlocking of the door, respectively. The engine starting device 13 controls starting and stopping of the engine, respectively.

  The ECU 11 is connected to first to third transmission antennas 24, 25, and 26 via first to third transmission circuits 21, 22, and 23, respectively. In addition, a reception antenna 28 is connected to the ECU 11 via a reception circuit 27. The first transmission antenna 24 is provided on the right door of the vehicle 10, and the second transmission antenna 25 is provided on the left door of the vehicle 10. The third transmitting antenna 26, the receiving circuit 27, and the receiving antenna 28 are each provided in the vehicle.

  The first and second transmission circuits 21 and 22 each send a response request signal Srq, which is a radio signal in the LF (Low Frequency) band, toward the periphery of the vehicle 10 based on a command from the ECU 11. The third transmission circuit 23 transmits a response request signal Srq toward the inside of the vehicle based on a command from the ECU 11. The response request signal Srq is a command signal for requesting a response to the portable device 29 possessed by the user. By transmitting the response request signal Srq, a reception area for the response request signal Srq, that is, a communication area between the vehicle 10 and the portable device 29 is formed around the left and right doors and in the vehicle. The communication area is an area where a response from the portable device 29 is expected, and the working distance of the portable device 29 (the portable device 29 is transmitted from the vehicle 10) required according to the product specifications of the electronic key system. It is set based on the distance to the vehicle 10 that can receive the radio signal.

  The first to third transmission circuits 21 to 23 have first to third current adjustment circuits 31, 32, and 33, respectively. The first to third current adjustment circuits 31 to 33 individually adjust the amount of current supplied to the first to third transmission antennas 24 to 26 based on commands from the ECU 11, respectively. Through adjustment of the amount of current, it is possible to control the output intensity (transmission output) of the first to third transmission antennas 24 to 26. The communication area outside the vehicle changes according to the output strength of the first and second transmission antennas 24 and 25, and the communication area inside the vehicle changes according to the output strength of the third transmission antenna 26, respectively. These communication areas will be described in detail later.

  The receiving circuit 27 receives a UHF (Ultra High Frequency) band radio signal via the receiving antenna 28. Here, the radio signal in the UHF band refers to a response signal Srp transmitted from the portable device 29 in response to the response request signal Srq from the vehicle 10. The response signal Srp includes identification information unique to the portable device 29.

  In the storage device 11a of the ECU 11, identification information of the regular portable device 29 corresponding to the host vehicle is stored. The ECU 11 acquires the identification information of the portable device 29 included in the response signal Srp through the receiving circuit 27. The ECU 11 determines the legitimacy of the portable device 29 by comparing the identification information of the portable device 29 with the identification information stored in the storage device 11a.

Further, the ECU 11 transmits the response request signal Srq through the first to third transmission antennas 24 to 26 at a period determined for each. The ECU 11 is based on whether the received response signal Srp is a response to the response request signal Srq transmitted from which transmission antenna, the position of the portable device 29 with respect to the vehicle 10, that is, whether the portable device 29 exists outside the vehicle, or exists in the vehicle. It is determined whether. When the ECU 11 determines that the portable device 29 exists outside the vehicle, the ECU 11 executes or permits the locking / unlocking of the vehicle door through the door lock device 12. Further, the ECU 11 permits the engine to be started through the engine starting device 13 when it is determined that the portable device 29 is present in the vehicle.

  The storage device 11a stores setting values that define the amounts of current supplied to the first to third transmission antennas 24 to 26, respectively. The set value is set based on the viewpoint of forming communication areas required in accordance with the product specifications described above in the vicinity of the left and right doors and in the vehicle. The ECU 11 supplies currents corresponding to the set values to the first to third transmission antennas 24 to 26 through the first to third current adjustment circuits 31 to 33, respectively.

<Transmitting antenna>
As shown in FIG. 2, the first to third transmission antennas 24 to 26 each have a substrate 40 and two bar antennas 41 and 42. The bar antenna is obtained by winding an electric wire (antenna coil) around a core made of a magnetic material such as ferrite. The two bar antennas 41 and 42 are provided on the same plane of the substrate 40. The coil axes Lx and Ly of the two bar antennas 41 and 42 are orthogonal to each other. A total of three sets of the bar antennas 41 and 42 of the first to third transmission antennas 24 to 26 have a driving current Ix that is a current amount corresponding to a set value from the first to third current adjustment circuits 31 to 33, respectively. , Iy are supplied.

  As shown in FIG. 3A, when the drive currents Ix and Iy are supplied to the two bar antennas 41 and 42, respectively, the coil axes Lx of the two bar antennas 41 and 42 according to the drive currents Ix and Iy. , Ly generate magnetic fields Hx and Hy, respectively. When the two bar antennas 41 and 42 are driven simultaneously, a combined magnetic field Hxy is generated by combining the two magnetic fields Hx and Hy generated from the bar antennas 41 and 42.

  That is, the directivity direction of the composite magnetic field Hxy is determined by the output intensity ratio (electric field intensity ratio) of the two bar antennas 41 and 42 orthogonal to each other. There is a correlation between the output intensity of the two bar antennas 41 and 42 and the drive currents Ix and Iy supplied to the two bar antennas 41 and 42. Therefore, the direction of the combined magnetic field Hxy can be controlled by individually setting the drive currents Ix and Iy.

  Incidentally, the relationship between the directivity direction of the combined magnetic field Hxy and the output intensity ratio of the two bar antennas 41 and 42, and hence the drive currents Ix and Iy, is expressed by the following equation (A). Note that the directivity direction of the composite magnetic field Hxy can be represented by an angle θ of the directivity direction of the composite magnetic field Hxy with respect to the magnetic field Hx direction of the bar antenna 41.

θ = arctan (Vy / Vx) = arctan (Iy / Ix) (A)
However, Vx is the output intensity of the bar antenna 41, and Vy is the output intensity of the bar antenna 42.

<Communication area>
Next, the communication area will be described. Here, a communication area formed by the first transmission antenna 24 provided on the right door among the first to third transmission antennas 24 to 26 will be described as an example.

  The first transmission antenna 24 is provided, for example, such that the coil axis Lx is along the vehicle front-rear direction and the coil axis Ly is along the vehicle width direction. When the direction and magnitude of the directivity of the composite magnetic field Hxy are the direction and magnitude indicated by the arrows in FIG. 3A, the vicinity of the right door of the vehicle 10 is shown in FIG. A normal communication area 51 is formed. As shown in the figure, when the vehicle 10 is viewed from above, a radio signal transmitted from the first transmission antenna 24 propagates around the right door of the vehicle 10 so that the longitudinal direction of the vehicle is the long axis. A semi-elliptical communication area 51 is formed.

  Here, as described above, the mounting direction of the first transmission antenna 24 may be determined due to some mounting restrictions in the vehicle 10. In this respect, according to the present example, by setting the drive currents Ix and Iy supplied to the two bar antennas 41 and 42 individually, the direction of the directivity of the combined magnetic field Hxy by the two bar antennas 41 and 42 can be arbitrarily set. Can be adjusted to. Therefore, it is possible to form the normal communication area 51 shown in FIG. 3B regardless of the mounting direction of the first transmission antenna 24 with respect to the vehicle 10.

  For example, as shown in FIG. 4A, when the magnitude of the magnetic field Hx of the bar antenna 41 is smaller than normal and the magnitude of the magnetic field Hy of the bar antenna 42 is larger than normal, the combined magnetic field Hxy The angle θ1 of the combined magnetic field Hxy with respect to the direction, that is, the direction of the magnetic field Hx of the bar antenna 41 is larger than the normal angle θ shown in FIG. At this time, a communication area 52 shown in FIG. 4B is formed around the right door. The communication area 52 is shifted to the front of the vehicle 10 as compared with the normal communication area 51 shown in FIG. 3B, and the range in the vehicle width direction is extremely narrow.

  In this case, the magnitude of the magnetic field Hx of the bar antenna 41 and the magnitude of Hy of the bar antenna 42 may be reduced by setting the drive currents Ix and Iy supplied to the two bar antennas 41 and 42. As a result, the magnitudes of the magnetic fields Hx and Hy of the two bar antennas 41 and 42 can be brought close to the normal magnitudes shown in FIG. In other words, the abnormal communication area 52 can be brought close to the normal communication area 51 shown in FIG. At the time of factory shipment or the like, the values of the drive currents Ix and Iy supplied to both the bar antennas 41 and 42 when the normal communication area 51 is formed are stored in the storage device 11a as current regulation values, respectively. .

  Further, as shown in FIG. 5A, when the magnitude of the magnetic field Hx of the bar antenna 41 is larger than normal and the magnitude of the magnetic field Hy of the bar antenna 42 is slightly smaller than normal, the combined magnetic field Hxy. The angle θ2 of the combined magnetic field Hxy with respect to the direction of the bar antenna 41, that is, the direction of the magnetic field Hx of the bar antenna 41 is smaller than the normal angle θ shown in FIG. At this time, a communication area 53 shown in FIG. 5B is formed around the right door. The communication area 53 is shifted rearward of the vehicle 10 as compared with the normal communication area 51 shown in FIG. 3B, and the range in the vehicle width direction is also narrow.

  In this case, the magnitude of the magnetic field Hx of the bar antenna 41 and the magnitude of the magnetic field Hy of the bar antenna 42 may be slightly increased through the setting of the drive currents Ix and Iy supplied to the two bar antennas 41 and 42. . As a result, the magnitude of the combined magnetic field Hxy by the two bar antennas 41 and 42 can be brought close to the normal magnitude shown in FIG. In other words, the abnormal communication area 53 can be brought closer to the normal communication area 51 shown in FIG. When the normal communication area 51 is formed at the time of factory shipment, the values of the drive currents Ix and Iy supplied to the two bar antennas 41 and 42 are stored in the storage device 11a as current regulation values, respectively. The

  Thus, by individually setting the values of the drive currents Ix and Iy supplied to the two bar antennas 41 and 42, the output intensity ratio of the two bar antennas 41 and 42 can be adjusted. As a result, the direction and magnitude of the combined magnetic field Hxy by the two bar antennas 41 and 42 can be set to a direction and magnitude suitable for forming the normal communication area 51 shown in FIG. it can.

  The second and third transmission antennas 25 and 26 are the same as the first transmission antenna 24. That is, by setting the values of the drive currents Ix and Iy supplied to the two bar antennas 41 and 42 individually, the left door is independent of the mounting direction of the second and third transmission antennas 25 and 26 with respect to the vehicle 10. It is possible to form a desired communication area around the vehicle and in the vehicle.

<Effect of Embodiment>
Therefore, according to the present embodiment, the following effects can be obtained.
(1) The first transmission antenna 24 includes two bar antennas 41 and 42 that are orthogonal to each other. Both bar antennas 41 and 42 are driven simultaneously. By individually setting the amount of current (drive currents Ix, Iy) to be supplied to both bar antennas 41, 42, the output intensity ratio of both bar antennas 41, 42 can be adjusted, and consequently combined by both bar antennas 41, 42. It is possible to control the direction of directivity of the magnetic field Hxy. By appropriately adjusting the directivity direction of the combined magnetic field Hxy, the first transmitting antenna 24 can form a magnetic field distribution in a desired direction without being restricted by the mounting direction. That is, the desired communication area 51 can be formed without changing the mounting direction. Since the first transmission antenna 24 can be mounted on the vehicle 10 regardless of the directivity direction of the composite magnetic field Hxy to be formed, the degree of freedom of mounting the first transmission antenna 24 on the vehicle 10 is improved. The same applies to the second and third transmission antennas 25 and 26.

  (2) When the values of the drive currents Ix and Iy supplied to the two bar antennas 41 and 42 are constant values (Ix = Iy), the intensity of the magnetic field generated from the two bar antennas 41 and 42 is It is strongly influenced by variations in impedance and inductance depending on the number of turns. For this reason, due to variations in the magnetic field strength between the two bar antennas 41 and 42, the magnetic field direction of the first transmission antenna 24 does not become the intended direction, and there is a possibility that the normal communication area 51 cannot be formed. In this respect, in this example, the drive currents Ix and Iy supplied to the two bar antennas 41 and 42 are individually set, so that the first transmission antenna 24 is mounted on the vehicle 10 regardless of the mounting direction of FIG. It is possible to form a normal communication area 51 shown in FIG. The same applies to the second and third transmission antennas 25 and 26. That is, by correcting the variations in the magnetic field strength of the second and third transmission antennas 25 and 26 through adjustment of the drive currents Ix and Iy supplied to both the bar antennas 41 and 42, normality around the left door and in the vehicle Communication area 51 is formed.

<Second Embodiment>
Next, a second embodiment of the communication area forming apparatus will be described. This example shows an example of a method for adjusting a communication area when the vehicle 10 is shipped from a factory, for example, and is basically the same as the first embodiment shown in FIGS. It has a configuration. For this reason, the same code | symbol is attached | subjected to the member structure same as 1st Embodiment, and the detailed description is abbreviate | omitted. Also, in this example, the first transmitting antenna 24 will be described as an example, and the communication area 53 shown in FIG. 5B is assumed to be an initial state before adjustment work.

  As indicated by a two-dot chain line in FIG. 1, the ECU 11 has a detection circuit 61 that detects the received signal strength (RSSI) of the received radio signal. The storage device 11a stores a threshold value (more precisely, a threshold range) that serves as a reference when determining whether or not the received signal strength is normal. The threshold is set based on the received signal strength when a wireless signal (response signal Srp) is received from the portable device 29 located near the boundary of the normal communication area 51.

The ECU 11 determines the signal strength of the received radio signal through a comparison between the threshold value and the received signal strength acquired through the detection circuit 61 and the threshold value.
When it is determined that the signal strength of the received radio signal is stronger than the threshold, the ECU 11 recognizes that the current communication area 53 is narrower than the normal communication area 51 in the vehicle width direction. This is because the signal strength of the radio signal from the portable device 29 received by the receiving antenna 28 becomes stronger as the distance between the receiving antenna 28 and the portable device 29 is shorter. That is, when the portable device 29 wirelessly transmits the response signal Srp to the response request signal Srq from the vehicle 10, the stronger the received signal strength detected by the detection circuit 61, the closer the portable device 29 is to the reception antenna 28. This means that the response request signal Srq has been received. In other words, the portable device 29 has received the response request signal Srq on the inner side (vehicle 10 side) than the boundary of the normal communication area 51.

  When it is determined that the received signal strength is stronger than the threshold, the ECU 11 sets the amount of current supplied to both the bar antennas 41 and 42, that is, the values of the drive currents Ix and Iy, so that the received signal strength matches the threshold. . The ECU 11 sets the values of the drive currents Ix and Iy to be supplied to both the bar antennas 41 and 42 according to the degree of difference between the current received signal strength and the threshold, for example. As described above, in the example of FIG. 5A, the magnitude of the magnetic field Hx of the bar antenna 41 is larger than normal, and the magnitude of the magnetic field Hy of the bar antenna 42 is slightly smaller than normal. For this reason, when the value of the drive current Ix supplied to the bar antenna 41 is small and the value of the drive current Iy supplied to the bar antenna 42 is slightly increased, the direction of the directivity of the combined magnetic field Hxy by both the bar antennas 41 and 42 And the size approach the normal direction and size shown in FIG. That is, the current communication area 53 is approximate to the normal communication area 51.

  The ECU 11 repeats the above-described detection of the received signal strength and setting of the values of the drive currents Ix and Iy several times, and the drive currents Ix and Iy supplied to both the bar antennas 41 and 42 when the received signal strength matches the threshold value. Are stored in the storage device 11a as current regulation values. After the current regulation value is set, the ECU 11 supplies drive currents Ix and Iy corresponding to the newly set current regulation value to both the bar antennas 41 and 42, respectively.

  Incidentally, even when it is determined that the received signal strength is weaker than the threshold value, the values of the drive currents Ix and Iy supplied to both the bar antennas 41 and 42 are adjusted in order to match the received signal strength to the threshold value as described above. To do. Thereby, a normal communication area 51 is formed.

  The second and third transmission antennas 25 and 26 are the same as the first transmission antenna 24. ECU11 sets the electric current regulation value which prescribes | regulates the drive currents Ix and Iy supplied to both the bar antennas 41 and 42 through the comparison with a received signal strength and a threshold value, respectively. Note that the threshold for adjusting the communication area around the left door by the second transmission antenna 25 is set according to the normal communication area formed by the second transmission antenna 25. Further, the threshold value relating to the adjustment of the communication area in the vehicle by the third transmission antenna 26 is set according to the normal communication area formed by the third transmission antenna 26.

Therefore, according to the present embodiment, in addition to the effects (1) and (2) of the first embodiment, the following effects can be obtained.
(3) The ECU 11 receives the radio signal from the portable device 29 located near the boundary of the normal communication area 51 formed by the first transmission antenna 24 and the strength of the signal received via the reception antenna 28. The threshold value set based on the received signal strength is compared. When the ECU 11 determines that the received signal strength deviates from the threshold value, the ECU 11 determines the values of the drive currents Ix and Iy to be supplied to the both bar antennas 41 and 42 through the first current adjustment circuit 31 in order to adjust the received signal strength to the threshold value. Adjust each of them. As a result, a normal communication area 51 is formed. The communication area formed by the second and third transmission antennas 25 and 26 is similarly adjusted. Thus, a desired communication area can be formed by adjusting the values of the drive currents Ix and Iy supplied to both the bar antennas 41 and 42 based on the received signal strength.

<Third Embodiment>
Next, a third embodiment of the communication area forming apparatus will be described. This example shows an example of a communication area adjustment method that is automatically performed during normal use of the vehicle 10, and basically corresponds to the first embodiment shown in FIG. 1 and FIG. It has the same configuration.

  As indicated by a two-dot chain line in FIG. 1, the ECU 11 is connected with the same number of touch sensors 62 as a plurality of door handles (not shown). The touch sensor 62 is provided on each door handle and detects whether or not the user's hand has touched the door handle.

  When the ECU 11 detects that the user's hand has touched the door handle through the touch sensor 62, the ECU 11 generates a response request signal Srq and outputs it to the left and right doors via the first and second transmission antennas 24 and 25. Send to the surroundings. Further, when the opening / closing of the door is detected after the authentication of the portable device 29 is established through wireless communication outside the vehicle, or when the operation of an engine switch (not shown) in the vehicle is detected, the ECU 11 A response request signal Srq is transmitted through the vehicle 26 to the vehicle interior.

  The storage device 11a stores the standard values (TYP values) of the drive currents Ix and Iy supplied to the three sets of bar antennas 41 and 42, each of which is a set of two, and the correction values of the drive currents Ix and Iy. ing. The correction value is set in consideration of variations in the radiated magnetic field strength of both bar antennas 41 and 42 resulting from variations in impedance and inductance depending on the number of turns of the coil. For example, when the standard value of current is supplied to both the bar antennas 41 and 42, the correction value becomes the normal communication area when the communication area becomes the narrowest due to the aforementioned variation. It is set to the amount of current required to expand. The correction value is obtained by experiments or the like.

Next, a method for adjusting the communication area will be described. Here, the communication area 51 formed by the first transmission antenna 24 will be described as an example.
The ECU 11 supplies standard currents to both the bar antennas 41 and 42 during the initial communication. At this time, it is assumed that, for example, the communication area 52 shown in FIG. 4B is formed around the right door due to the above-described variation. As described above, the communication area 52 has a significantly narrower range in the vehicle width direction than the normal communication area 51 shown in FIG. For this reason, although the user is approaching the vehicle 10 to such an extent that the user can operate the door handle, it is assumed that the portable device 29 is located outside the communication area 52. In this situation, since the portable device 29 is located outside the communication area 52, the response request signal Srq from the vehicle 10 is not received and the response signal Srp is not transmitted.

  When the response signal Srp from the portable device 29 is not received even though the ECU 11 detects that the user's hand has touched the door handle through the touch sensor 62, the current communication area 52 is the normal communication area 51. Judge that it is narrower than. Then, the ECU 11 switches the values of the drive currents Ix and Iy supplied to the two bar antennas 41 and 42 of the first transmission antenna 24 through the first current adjustment circuit 31 from the standard value to the correction value.

  Here, when the communication area 52 shown in FIG. 4B is formed, the magnetic fields Hx and Hy of the bar antennas 41 and 42 are respectively in the state shown in FIG. 4A. That is, the magnitude of the magnetic field Hx of one bar antenna 41 is smaller than normal, and the magnitude of the magnetic field Hy of the other bar antenna 42 is slightly larger than normal. For this reason, when the value of the drive current Ix supplied to the bar antenna 41 is increased and the value of the drive current Iy supplied to the bar antenna 42 is slightly reduced, the direction of the directivity of the combined magnetic field Hxy by both the bar antennas 41 and 42 And the size approach the normal direction and size shown in FIG.

  Accordingly, the correction value for one bar antenna 41 is set larger than the standard value and the correction value for the other bar antenna 42 is set smaller than the standard value, whereby the direction of the combined magnetic field Hxy by both bar antennas 41 and 42 is set. The direction and size of sex approach the normal direction and size shown in FIG. As a result, the direction and magnitude of the directivity of the combined magnetic field Hxy by both the bar antennas 41 and 42 are changed, so that the current communication area 52 is expanded to the extent that it approximates the normal communication area 51.

  Then, the ECU 11 supplies the drive currents Ix and Iy defined by the correction values to the bar antennas 41 and 42, respectively, and tries communication with the portable device 29 again. At this time, if the normal communication area 51 shown in FIG. 3B is formed, the portable device 29 is located in the communication area 51 (more precisely, the communication area approximate to the communication area 51). In response to response request signal Srq from vehicle 10, response signal Srp is transmitted.

  As for the second and third transmission antennas 25 and 26, similarly to the first transmission antenna 24, when there is no response from the portable device 29 at the time of the initial communication, the two antennas 41 and 42 are respectively connected. A desired communication area can be formed around the left door and in the vehicle by individually changing the values of the drive currents Ix and Iy to be supplied.

  Incidentally, when considering the above-mentioned variation, only the values of the drive currents Ix and Iy required for forming the largest communication area may be set as the correction value, or the maximum communication area is formed. Multi-step correction values may be set between the drive currents Ix and Iy and the standard value.

<Effect of Embodiment>
Therefore, according to the present embodiment, in addition to the effects (1) and (2) of the first embodiment, the following effects can be obtained.

  (4) When a response signal Srp from the portable device 29 is not received despite the user's operation on the vehicle 10 being detected such as touching the door handle, a communication area narrower than the normal communication area is formed. The probability is high. In this case, the ECU 11 switches the values of the drive currents Ix and Iy supplied to both the bar antennas 41 and 42 of the first transmission antenna 24 from the standard value to the correction value, for example, so that the communication by the first transmission antenna 24 is performed. Enlarge the area. For this reason, the portable device 29 is easily located in the communication area 51 and can perform wireless communication with the vehicle 10. The communication area formed by the second and third transmission antennas 25 and 26 is similarly adjusted.

  (5) Since the adjustment of the communication area inside and outside the vehicle is automatically performed during normal vehicle use, the first to third transmission antennas 24 to 26 need not be adjusted in the production process of the vehicle 10. Also good. Therefore, the production man-hours of the vehicle 10 can be reduced.

<Fourth embodiment>
Next, a fourth embodiment of the communication area forming apparatus will be described. This example also basically has the same configuration as that of the first embodiment.

  As shown in FIG. 6, a first transmission antenna 24 is provided on the right door of the vehicle 10, and a second transmission antenna 25 is provided on the left door. In the first embodiment, both the third transmission circuit 23 and the third transmission antenna 26 provided in the vehicle are omitted. As shown in the figure, the radio signal transmitted from the first transmitting antenna 24 propagates around the right door of the vehicle and inside the vehicle. When the vehicle is viewed from above, the radio signal transmitted from the first transmission antenna 24 forms a circular or elliptical communication area 71. Further, the radio signal transmitted from the second transmission antenna 25 propagates around the left door of the vehicle 10 and in the vehicle. When the vehicle 10 is viewed from above, the radio signal transmitted from the second transmission antenna 25 forms a circular or elliptical communication area 72. Moreover, these communication areas 71 and 72 overlap in the vehicle.

Next, a method for determining the position (presence detection) of the portable device 29 by the ECU 11 will be described.
The ECU 11 determines the position of the portable device 29 relative to the vehicle 10 based on whether the received response signal Srp is a response to the response request signal Srq transmitted from either the first transmission antenna 24 or the second transmission antenna 25. The ECU 11 alternately forms communication areas 71 and 72 by alternately transmitting response request signals Srq from the first and second transmission antennas 24 and 25. Therefore, the ECU 11 can determine which transmission antenna the response signal Srp is a response to the response request signal Srq transmitted from, based on the timing of receiving the response signal Srp.

  When the portable device 29 returns the response signal Srp only in response to the response request signal Srq from the first transmitting antenna 24, the ECU 11 places the portable device in the communication area 71, more precisely in the communication area 71 outside the vehicle. It is determined that 29 is located.

  When the portable device 29 returns the response signal Srp only to the response request signal Srq from the second transmission antenna 25, the ECU 11 places the portable device in the communication area 72, more precisely in the communication area 72 outside the vehicle. It is determined that 29 is located.

  When the response signal Srp is returned to both of the response request signals Srq from the first and second transmission antennas 24 and 25, the ECU 11 is in a region where the two communication areas 71 and 72 overlap, that is, in the vehicle. It is determined that the portable device 29 is located.

  Here, as shown in FIGS. 7A and 7C, a case where the first and second transmission antennas 24 and 25 are each constituted by a single bar antenna 73 will be considered. In this case, depending on the mounting angle of the bar antenna 73 with respect to the vehicle 10, the communication areas 71 and 72 (only the communication area 71 is shown in FIG. 7) when the radio signal is transmitted are changed. For this reason, it is necessary to determine the mounting angle of the bar antenna 73 so that the optimal communication areas 71 and 72 are formed, respectively. As shown in FIGS. 7B and 7D, the mounting angle here refers to the angle of the coil axis La of the bar antenna 73 with respect to the traveling direction of the vehicle 10 when the vehicle 10 is viewed from above.

  However, since the required communication areas 71 and 72 are different between the case where the portable device 29 is present outdoors and the case where the portable device 29 is present indoors, the mounting angle at which the optimum communication areas 71 and 72 can be formed for one situation. However, there is a possibility that the communication areas 71 and 72 that are satisfactory for the other situation cannot be formed.

  As shown in FIGS. 7A and 7C, for example, the communication area 71 includes a vehicle exterior area 71a formed outside the vehicle and a vehicle interior area 71b formed inside the vehicle. In this example, as shown in FIG. 7B, when the bar antenna 73 is tilted to the opposite side of the traveling direction by “angle θa” with respect to the traveling direction of the vehicle 10, it is shown in FIG. An optimal outside area 71a is formed. On the other hand, as shown in FIG. 7D, when the bar antenna 73 is tilted to the opposite side of the traveling direction by “angle θb” with respect to the traveling direction of the vehicle 10, it is shown in FIG. An optimal in-vehicle area 71b is formed. The magnitude relationship between the two angles θa and θb is as shown in the following equation (B).

θa> θb (B)
As shown in FIGS. 7A and 7B, the optimal outside area 71a is formed by setting the mounting angle of the bar antenna 73 to the angle θa, but the range in which the inside area 71b is formed is insufficient. It is. In the example shown in FIG. 7A, the in-vehicle area 71b is formed only to the vicinity of the center of the vehicle 10 in the vehicle width direction. On the other hand, as shown in FIGS. 7C and 7D, although the optimal interior area 71b is formed by setting the mounting angle of the bar antenna 73 to the angle θb, the exterior area 71a is formed. The range is insufficient. In the example shown in FIG. 7B, the range of the in-vehicle area 71b in the vehicle width direction of the vehicle 10 is narrower than the optimum outside area 71a shown in FIG. The communication area 72 has the same problem as the communication area 71.

  In this regard, the first transmission antenna 24 includes two bar antennas 41 and 42 that are orthogonal to each other. The ECU 11 then drives the drive currents Ix and Iy supplied to the two bar antennas 41 and 42 according to whether the authentication of the portable device 29 through wireless communication is highly likely to be performed outdoors or according to whether the probability is to be performed indoors. Adjust the value of. As a result, the direction and magnitude of the directivity of the combined magnetic field Hxy by the two bar antennas 41 and 42, and thus the state of the magnetic field distribution in the communication area 71 change.

  In the storage device 11a, the first set value that defines the values of the drive currents Ix and Iy that form the optimum outside area 71a, and the values of the drive currents Ix and Iy that form the optimum inside area 71b are stored. Is stored. The first and second set values are obtained by experiments using vehicle models, respectively.

  For example, when the door is locked with the engine stopped, the ECU 11 determines that the probability that the authentication of the portable device 29 is performed outside the vehicle is high. The ECU 11 determines that the authentication of the portable device 29 is highly likely to be performed in the vehicle when the opening / closing of the door is detected after the door is unlocked through wireless communication with the portable device 29 in the outside area 71a, for example. . Then, the ECU 11 determines the values of the drive currents Ix and Iy supplied to the two bar antennas 41 and 42 according to whether the probability that the authentication of the portable device 29 is performed outdoors is high or the probability that the authentication is performed indoors is high. Switch between the set value and the second set value.

  Specifically, the ECU 11 determines the values of the drive currents Ix and Iy supplied to the two bar antennas 41 and 42 as the first set value when it is determined that the probability that the authentication of the portable device 29 is performed outdoors is high. Switch to. That is, as shown in FIG. 8 (b), the ECU 11 sends the two bar antennas 41 and 42 so that the directivity direction of the combined magnetic field Hxy with respect to the coil axis Lx along the traveling direction of the vehicle 10 forms an angle θa. The supplied drive currents Ix and Iy are adjusted. As a result, the optimal outside area 71a shown in FIG. 7A is formed.

  In addition, when it is determined that there is a high probability that authentication of the portable device 29 is performed indoors, the ECU 11 determines the values of the drive currents Ix and Iy supplied to the two bar antennas 41 and 42 from the first set value to the second value. Switch to the set value. That is, the ECU 11 determines the values of the drive currents Ix and Iy supplied to the two bar antennas 41 and 42 so that the direction of the directivity of the combined magnetic field Hxy with respect to the coil axis Lx along the traveling direction of the vehicle 10 forms an angle θb. Adjust each one. As a result, the optimum in-vehicle area 71b shown in FIG. 7B is formed.

  As shown in FIG. 8A, as a whole, the optimum outside area 71a and the optimum inside area 71b are respectively switched by switching the values of the drive currents Ix and Iy supplied to the two bar antennas 41 and 42. It can be said that the communication area 71 is expanded to the extent that it is included.

  Note that the second transmitting antenna 25 can be formed by switching between the optimal outside area 71a and the optimal in-vehicle area 71b in the same manner as the first transmitting antenna 24.

Therefore, according to the present embodiment, in addition to the effects (1) and (2) of the first embodiment, the following effects can be obtained.
(6) The values of the drive currents Ix and Iy supplied to the two bar antennas 41 and 42 are set according to whether the probability that the authentication of the portable device 29 is performed outdoors is high or the probability that the authentication is performed indoors is high. Switch between the set value and the second set value. When the values of the drive currents Ix and Iy are set to the first set value, the optimum outside area 71a is formed, and when the value is set to the second set value, the optimum inside area 71b is formed. Thereby, when authenticating the portable device 29 outside the vehicle and when authenticating the portable device 29 inside the vehicle, the communication areas 71 and 72 suitable for each situation can be formed. By optimizing the communication areas 71 and 72 according to the situation, wireless communication between the vehicle 10 and the portable device 29 is suitably performed.

<Other embodiments>
Each of the above embodiments may be modified as follows.
In the second embodiment, the detection circuit 61 is provided in the ECU 11, but may be provided as an IC chip independent of the ECU 11 or may be provided in the reception circuit 27.

  In the first and second embodiments, the values of the drive currents Ix and Iy supplied to the two bar antennas 41 and 42 are individually set based on a command from the ECU 11, but as follows Also good. That is, the values of the drive currents Ix and Iy are individually changed by directly acting on the first to third transmission circuits 21 to 23, more precisely, the first to third current adjustment circuits 31 to 33, without going through the ECU 11. To do. For example, a tool is connected to the ECU 11 or the first to third current adjustment circuits 31 to 33, and the values of the drive currents Ix and Iy are individually set.

In the first to fourth embodiments, the cores of the bar antennas 41 and 42 may be omitted.
In the first to third embodiments, all the first to third transmission antennas 24 to 26 have the two bar antennas 41 and 42. However, the first to form a communication area outside the vehicle. Further, only the second transmission antennas 24 and 25 may have the two bar antennas 41 and 42. Even in this case, at least the first and second transmission antennas 24 and 25 can form a desired communication area without changing the mounting direction with respect to the vehicle 10.

  In the first to third embodiments, two bar antennas 41 are provided for the first to third transmission antennas 24 to 26, and in the fourth embodiment, the first and second transmission antennas 24 and 25 are provided. , 42, but may be as follows. That is, as shown in FIG. 9, the transmission antenna 81 has a core 82, a first antenna coil 83, and a second antenna coil 84. The core 82 is formed of a magnetic material such as ferrite, for example, in a rectangular parallelepiped shape. The first and second antenna coils 83 and 84 are wound around the core 82 so that the conducting wires intersect with each other (in this example, orthogonal). That is, the transmission antenna 81 is a so-called biaxial antenna that radiates a magnetic field in two directions along the axes of the first and second antenna coils 83 and 84 orthogonal to each other. Even in this case, the magnetic field Hx in the axial direction of the first antenna coil 83 and the second antenna coil 84 are controlled by individually controlling the amount of current supplied to the first and second antenna coils 83 and 84. The direction of the directivity of the combined magnetic field Hxy with the magnetic field Hy in the axial direction (here, the angle θ of the combined magnetic field Hxy with respect to the magnetic field Hx) can be controlled. Further, since the size of the transmission antenna 81 can be made smaller than when the first and second antenna coils 83 and 84 are arranged on the same plane, the mountability to the vehicle 10 is improved. The core 82 may be omitted.

  In the first to fourth embodiments, the two bar antennas 41 and 42 are provided so as to be orthogonal to each other, but are not necessarily orthogonal. The two bar antennas 41 and 42 may be provided so as to cross each other.

  Although the first to third transmission antennas 24 to 26 are configured as biaxial antennas having two bar antennas 41 and 42 that are orthogonal to each other, the first to third transmission antennas 24 to 26 are respectively connected to each other. It is good also as a 3-axis antenna which consists of three orthogonal bar antennas. By individually setting the amount of current supplied to the three bar antennas, the direction of the directivity of the combined magnetic field can be arbitrarily changed.

The electronic key system in the first to fourth embodiments may be applied to a so-called hybrid vehicle or electric vehicle.
In the first to fourth embodiments, the communication area forming apparatus is applied to an electronic key system for a vehicle, but may be applied to an electronic key system for a house. The number of transmitting antennas is adjusted as appropriate. The number of transmission antennas may be singular or plural.

  -In 1st Embodiment, although the communication area formation apparatus was applied to the electronic key system of a vehicle, you may apply to TMPS (tire pressure monitoring system) mounted in a vehicle. The TPMS is a system that monitors the tire air pressure and warns when a decrease in the air pressure is detected. The so-called direct TPMS has an initiator provided near each tire of the vehicle and a sensor unit provided inside each tire or each wheel. Each initiator transmits a trigger signal toward a tire sensor unit corresponding to the initiator at a predetermined timing. Each sensor unit detects the tire air pressure and the like, and triggers reception of the trigger signal to wirelessly transmit an answer signal including a detection result of the air pressure to the receiver on the vehicle body side. The transmission antenna of the first embodiment may be used as the transmission antenna provided in this initiator. It can also be used as a transmission antenna of the sensor unit.

<Other technical ideas>
Next, the technical idea that can be grasped from the above embodiment will be added below.
(A) The adjustment circuit individually sets the amount of current to be supplied to the two antenna coils based on a command from the control circuit.

(B) The communication terminal is owned by the user.
(C) The communication area forming device is mounted on a vehicle and forms a communication area for performing mutual wireless communication between the portable device as the communication terminal and the vehicle at least around the vehicle.

  (D) The control circuit recognizes that the operation of the communication area forming apparatus to be mounted is detected and the communication terminal exists in the communication area if the communication area is normal.

  DESCRIPTION OF SYMBOLS 11 ... Electronic control apparatus (control circuit), 29 ... Portable machine (communication terminal), 31-33 ... Current adjustment circuit, 41, 42 ... Bar antenna (antenna coil), 51, 71 ... Communication area.

Claims (4)

In a communication area forming apparatus that forms a communication area with a communication terminal by transmitting radio waves through control by a control circuit,
A communication area forming apparatus comprising: at least two antenna coils that are integrally provided so that their axes cross each other and are simultaneously driven; and an adjustment circuit that individually adjusts the amount of current supplied to these antenna coils. In the communication area formation apparatus of Claim 1,
The communication terminal receives the radio wave and transmits a radio signal,
The control circuit stores a threshold value set based on a received signal strength of a radio signal from a communication terminal located at a boundary of a normal communication area, and the received signal strength of the radio signal is out of the threshold value. And a communication area forming device for individually adjusting the amount of current supplied to the at least two antenna coils through the adjustment circuit to adjust the received signal strength to a threshold value. In the communication area formation device according to claim 1,
The communication terminal receives the radio wave and transmits a radio signal,
If the wireless communication signal is not received even though the communication terminal is present in the communication area if the communication area is normal, the control circuit is configured to expand the current communication area. A communication area forming apparatus that individually adjusts an amount of current for the at least two antenna coils through a circuit. In the communication area formation device according to claim 1,
The communication area includes first and second communication areas,
The control circuit supplies current to each of the at least two antenna coils when forming the first communication area, and supplies each of the at least two antenna coils when forming the second communication area. A communication area forming device that stores the amount of current to be switched and individually forms the amount of current supplied to the at least two antenna coils through the adjustment circuit, thereby switching between the first and second communication areas. .