JP2017183835A - Vehicle communication system and on-vehicle apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a vehicle communication system capable of adjusting a resonant frequency of a transmission antenna for transmitting a signal for detecting a position of a portable apparatus in a timely and automatic manner.SOLUTION: A vehicle communication system detects a position of a portable apparatus 2 by transmitting signals from a plurality of LF transmission antennas 3 provided on a vehicle C to the portable apparatus 2 and receiving a response signal from the portable apparatus 2. A LF transmission antenna 3 comprises a resonant circuit including a coil and a variable capacitor having capacitance capable of being changed. An on-vehicle apparatus 1 makes the LF transmission antenna 3 transmit a signal a plurality of times while varying the capacitance of the variable capacitor in a timely manner. The on-vehicle apparatus 1, on the basis of reception signal intensity of each signal, determines capacitance of the variable capacitor at the time of the LF transmission antenna 3 resonating and stores the capacitance.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a vehicle communication system and a vehicle-mounted device that detect the position of a portable device.

A vehicle communication system that locks and unlocks a vehicle door without using a mechanical key has been put into practical use. Specifically, a keyless entry system that locks or unlocks a vehicle door by wireless remote control using a portable device possessed by the user, a user who possesses the portable device only approaches the vehicle or holds the door handle Smart entry (registered trademark) system for unlocking vehicle doors has been put into practical use.
Further, a vehicle communication system that starts a vehicle engine without using a mechanical key has been put into practical use. Specifically, a smart start (registered trademark) system that starts an engine simply by a user holding a portable device pressing an engine start switch has been put into practical use.
In the above communication system, the in-vehicle device performs authentication by wireless communication with the portable device, and performs control such as unlocking, locking, and engine starting after confirming that the portable device exists at a predetermined position. For example, when the request switch is operated, the in-vehicle device confirms that the portable device is outside the vehicle and locks and unlocks the vehicle door. When the engine start button is operated, the in-vehicle device confirms that the portable device is in the vehicle and starts the engine.

  As a method for confirming the position of a portable device, a method using received signal strength in the portable device is known. Specifically, when detecting the position of the portable device, the in-vehicle device transmits position detection signals from a plurality of transmission antennas provided in the vehicle using radio waves in the LF (Low Frequency) band. The portable device measures the received signal strength of signals transmitted from a plurality of transmitting antennas, and transmits a response signal including the measured received signal strength to the in-vehicle device. The in-vehicle device receives the response signal transmitted from the portable device, and determines whether or not the portable device is in the vehicle based on the received signal strength included in the received response signal. Since the received signal strength corresponds to the distance between each transmitting antenna provided in the vehicle and the portable device, the in-vehicle device can specify the position of the portable device with respect to the vehicle using the received signal strength. .

  If the position detection accuracy of the portable device is low, there is a problem that the portable device is locked by mistake and the portable device is trapped inside the vehicle, or the vehicle is unlocked from outside the vehicle by a suspicious person who does not have the portable device. For this reason, accuracy is required for detecting the position of the portable device.

  The transmission antenna has a resonance circuit composed of a coil and a capacitor, and in order to efficiently transmit a signal, the resonance frequency of the resonance circuit is designed to substantially match the frequency of the signal to be transmitted. However, when the transmission antenna is actually attached to the vehicle, if there is a metal part of the vehicle body in the vicinity of the transmission antenna, the resonance frequency shifts and the intensity of the signal transmitted from the transmission antenna changes. If the intensity of the signal transmitted from the transmission antenna changes, the position of the portable device may be erroneously determined. For this reason, conventionally, the resonance frequency of the resonance circuit is shifted in advance in consideration of the amount of change in the resonance frequency when attached to the vehicle, and when the transmission antenna is mounted on the vehicle, the resonance frequency becomes the transmission frequency. To be matched.

JP 2006-121278 A

  However, in order to adjust the resonance frequency as described above, there is a problem that the number of development man-hours increases because it is necessary to make a prototype of the transmission antenna again and again.

  An object of the present invention is to provide a vehicle communication system and an in-vehicle device capable of automatically adjusting the resonance frequency of a transmission antenna that transmits a signal for position detection of a portable device in a timely manner.

  The vehicle communication system according to this aspect includes an in-vehicle device that transmits signals from a plurality of transmission antennas provided in the vehicle, a response that receives a signal transmitted from the in-vehicle device, and includes a received signal strength of the received signal A portable device that transmits a signal, the in-vehicle device receives the response signal transmitted from the portable device, and detects the position of the portable device based on a received signal strength included in the received response signal In the vehicle communication system, the one transmission antenna includes a resonance circuit having a variable capacitor and a coil whose capacity can be changed, and the in-vehicle device receives a signal from the one transmission antenna a plurality of times. A transmission unit for transmission, a change unit for changing the capacity of the variable capacitor each time a signal is transmitted by the transmission unit, and the portable device according to each signal transmitted a plurality of times by the transmission unit A receiving unit that receives the received response signal; a determining unit that determines a capacity of the variable capacitor based on a plurality of received signal strengths included in the response signal received by the receiving unit; A storage unit that stores the capacitance of the variable capacitor determined by the unit.

  The in-vehicle device according to this aspect transmits a signal from a plurality of transmission antennas provided in the vehicle to the portable device, receives a response signal including the received signal strength of the signal received by the portable device, and receives the received response A vehicle-mounted device that detects the position of the portable device based on a received signal strength included in a signal, wherein the one transmission antenna includes a resonance circuit having a variable capacitor and a coil whose capacitance can be changed. Furthermore, a transmission unit that transmits a signal from the one transmission antenna a plurality of times, a change unit that changes the capacitance of the variable capacitor each time a signal is transmitted by the transmission unit, and a transmission unit that transmits the signal a plurality of times A reception unit that receives the response signal transmitted from the portable device according to each received signal, and the variable capacitor based on a plurality of received signal strengths included in the response signal received by the reception unit. Comprising a determining unit for determining a volume, and a storage unit that stores the capacity of the variable capacitor determined by the determination unit.

  Note that the present application can be realized not only as a vehicle communication system and an in-vehicle device including such a characteristic processing unit, but also as a resonance frequency adjustment method using such characteristic processing as a step. It can be realized as a program for causing a computer to execute the steps. Moreover, it can implement | achieve as a semiconductor integrated circuit which implement | achieves a part or all of a vehicle communication system and vehicle equipment, or can implement | achieve as another system containing a vehicle communication system and vehicle equipment.

  According to the above, it is possible to provide a vehicle communication system and an in-vehicle device that can automatically adjust the resonance frequency of a transmission antenna that transmits a signal for position detection of a portable device in a timely manner.

It is a schematic diagram which shows one structural example of the communication system for vehicles which concerns on Embodiment 1 of this invention. It is a block diagram which shows the example of 1 structure of the vehicle equipment which concerns on Embodiment 1 of this invention. It is a schematic diagram which shows one structural example of LF transmission antenna. It is a graph which shows the capacity | capacitance value of a variable capacitor, the relationship of received signal strength, etc. It is a block diagram which shows the example of 1 structure of the portable device which concerns on Embodiment 1 of this invention. It is a flowchart which shows the procedure of the resonance frequency adjustment process which concerns on Embodiment 1 of this invention. It is a conceptual diagram which shows the resonance frequency adjustment method. It is a flowchart which shows the procedure of the resonance frequency adjustment process which concerns on Embodiment 2 of this invention.

[Description of Embodiment of the Present Invention]
First, embodiments of the present invention will be listed and described. Moreover, you may combine arbitrarily at least one part of embodiment described below.

(1) A vehicle communication system according to this aspect includes an in-vehicle device that transmits signals from a plurality of transmission antennas provided in the vehicle, a signal transmitted from the in-vehicle device, and a received signal strength of the received signal. A portable device that transmits a response signal including: the vehicle-mounted device receives the response signal transmitted from the portable device, and based on the received signal strength included in the received response signal, A vehicle communication system for detecting a position, wherein one transmission antenna includes a resonance circuit having a variable capacitor and a coil whose capacity can be changed, and the vehicle-mounted device receives a signal from the one transmission antenna. According to each signal transmitted a plurality of times by the transmitting unit, a changing unit for changing the capacitance of the variable capacitor each time a signal is transmitted by the transmitting unit, A receiving unit that receives the response signal transmitted from the receiver, a determination unit that determines a capacity of the variable capacitor based on a plurality of received signal strengths included in the response signal received by the receiving unit, And a storage unit that stores the capacity of the variable capacitor determined by the determination unit.

According to this aspect, at least one transmission antenna has a variable capacitor and a coil constituting a resonance circuit, and the resonance frequency of the transmission antenna can be changed by changing the capacitance of the variable capacitor.
When adjusting the resonance frequency of one transmission antenna, the vehicle-mounted device transmits a signal multiple times while changing the capacity of the variable capacitor.
The portable device receives each signal transmitted a plurality of times from the in-vehicle device, and transmits a response signal including the received signal strength of each signal to the in-vehicle device. The portable device may be configured to transmit a response signal including the received signal strength every time a signal transmitted from the in-vehicle device is received, or the received signal strength of a plurality of signals transmitted from the in-vehicle device. May be transmitted, or a response signal including a plurality of received signal strengths may be transmitted in a plurality of times.
The in-vehicle device receives the response signal transmitted from the portable device, and determines the capacity of the variable capacitor based on the received signal strength included in the received response signal. As the coincidence between the resonant frequency of the transmitting antenna and the frequency of the signal to be transmitted increases, the received signal strength tends to increase (see FIG. 4). The in-vehicle device uses a variable capacitor capacity when the resonance frequency of the transmitting antenna and the frequency of the signal to be transmitted are high from the capacity of the variable capacitor when each signal is transmitted and the received signal strength of the signal. Can be determined. Then, the in-vehicle device stores the determined capacitance of the variable capacitor. Therefore, the vehicle-mounted device can automatically adjust the resonance frequency of the transmission antenna to match the frequency of the signal transmitted when detecting the position of the portable device.

(2) The capacity of the variable capacitor when each of the plurality of signals is transmitted by the transmission unit is associated with the received signal strength of the plurality of signals included in the response signal, and the determination unit is A configuration for determining the capacitance of the variable capacitor when the received signal intensity is maximum is preferable.

  In this aspect, the determination unit sets the capacity when the received signal strength is maximum, that is, the capacity when the resonance frequency of the transmission antenna substantially matches the frequency of the signal to be transmitted, to the variable capacitor. Determine as capacity.

(3) The in-vehicle device includes a determination unit that determines whether or not the received signal strength included in the response signal is less than a threshold value, and the determination unit has the received signal strength equal to or greater than the threshold value in the determination unit. When it is determined that the capacitance of the variable capacitor is determined, it is preferable to determine the capacitance of the variable capacitor.

  In this aspect, when the received signal strength included in the response signal is greater than or equal to the threshold value, that is, when the portable device is within the predetermined range of one transmission antenna, the process of adjusting the resonance frequency of the transmission antenna Execute. Therefore, the resonance frequency of the transmission antenna can be adjusted under the condition that the portable device is within the predetermined range and the resonance frequency can be adjusted accurately.

(4) The in-vehicle device according to this aspect transmits a signal from a plurality of transmission antennas provided in the vehicle to the portable device, receives a response signal including the received signal strength of the signal received by the portable device, and receives the response signal. A vehicle-mounted device that detects the position of the portable device based on the received signal strength included in the response signal, wherein one transmitting antenna has a variable capacitor and a coil whose capacitance can be changed. A transmission unit that transmits a signal a plurality of times from the one transmission antenna, a change unit that changes the capacity of the variable capacitor each time a signal is transmitted by the transmission unit, and the transmission unit A receiving unit that receives the response signal transmitted from the portable device according to each signal transmitted a plurality of times, and a plurality of received signal strengths included in the response signal received by the receiving unit, Variable Comprising a determining unit for determining the capacity of the capacitor, and a storage unit that stores the capacity of the variable capacitor determined by the determination unit.

  In this aspect, as in aspect (1), the in-vehicle device automatically adjusts the resonance frequency of the transmission antenna appropriately and automatically to match the frequency of the signal transmitted when detecting the position of the portable device. be able to.

[Details of the embodiment of the present invention]
A specific example of a vehicle communication system according to an embodiment of the present invention will be described below with reference to the drawings. In addition, this invention is not limited to these illustrations, is shown by the claim, and intends that all the changes within the meaning and range equivalent to the claim are included.

(Embodiment 1)
FIG. 1 is a schematic diagram illustrating a configuration example of a vehicle communication system according to Embodiment 1 of the present invention. The vehicle communication system according to the first embodiment includes an in-vehicle device 1 that transmits and receives various signals using a plurality of LF transmitting antennas 3 and RF receiving antennas 10 provided in the vehicle C, and the in-vehicle device 1. And a portable device 2 for transmitting and receiving signals.

  The plurality of LF transmission antennas 3 are disposed, for example, at the driver side pillar, the passenger side pillar, and the front and rear parts of the vehicle C. The LF transmitting antenna 3 provided in the driver side pillar and the passenger side pillar is an antenna outside the vehicle that mainly transmits signals to the outside of the vehicle, and hereinafter, each transmitting antenna is appropriately connected to the first LF transmitting antenna 3 and the first LF transmitting antenna 3. 2 LF transmitting antennas 3. The LF transmission antennas 3 provided at the front and rear of the vehicle C are in-vehicle antennas that mainly transmit signals to the interior of the vehicle. Hereinafter, each of the transmission antennas is appropriately set to the third LF transmission antenna 3 and the fourth LF transmission antenna 3. The LF transmitting antenna 3 is called. Each LF transmitting antenna 3 transmits a signal using LF band radio waves. The LF band is an example of a radio wave band used when performing wireless communication, and is not necessarily limited thereto.

  The in-vehicle device 1 according to the first embodiment sequentially transmits a signal for determining whether or not the portable device 2 is in the vehicle from the plurality of LF transmission antennas 3 using radio signals. The portable device 2 receives the signal transmitted from each LF transmission antenna 3 and measures the received signal strength of each received signal. The portable device 2 transmits a response signal including the measured received signal strength to the in-vehicle device 1 using a radio wave in the UHF (Ultra High Frequency) band. The in-vehicle device 1 receives the response signal transmitted from the portable device 2, and determines whether the portable device 2 is inside or outside the vehicle based on the received signal strength included in the received response signal. And execute a predetermined process according to the determination result. For example, the in-vehicle device 1 executes processing such as locking or unlocking of a vehicle door, starting of an engine, warning of forgetting to lock the vehicle door, and the like.

  FIG. 2 is a block diagram illustrating a configuration example of the vehicle-mounted device 1 according to the first embodiment of the present invention. The in-vehicle device 1 includes an in-vehicle control unit 11 that controls the operation of each component of the in-vehicle device 1. The in-vehicle controller 11 is provided with an in-vehicle receiver 12, an in-vehicle transmitter 13, and a storage unit 14.

  The in-vehicle control unit 11 is a microcomputer having, for example, one or a plurality of CPUs (Central Processing Units), a multi-core CPU, a ROM (Read Only Memory), a RAM (Random Access Memory), an input / output interface, a timer, and the like. The CPU of the in-vehicle controller 11 is connected to the in-vehicle receiver 12, the in-vehicle transmitter 13, and the storage unit 14 through an input / output interface. The in-vehicle control unit 11 controls the operation of each constituent unit by executing a computer program to be described later stored in the storage unit 14, and executes predetermined processing according to the in-vehicle determination / in-vehicle determination of the portable device 2. To do. Moreover, the vehicle-mounted control part 11 performs the process which adjusts automatically the resonant frequency of each LF transmission antenna 3 at the appropriate time.

  The storage unit 14 is a nonvolatile memory such as an EEPROM (Electrically Erasable Programmable ROM) or a flash memory. The storage unit 14 is a computer for executing processing related to determination of the inside / outside of the portable device 2 and adjustment of the resonance frequency of the LF transmitting antenna 3 by the vehicle-mounted control unit 11 controlling the operation of each component of the vehicle-mounted device 1. I remember the program. The storage unit 14 stores a capacity table. The capacity table stores an antenna identifier for identifying a plurality of LF transmission antennas 3 and information related to a capacity value to be described later for setting the resonance frequency of the antenna in association with each other (see the lower diagram of FIG. 7). ).

  An RF receiving antenna 10 is connected to the in-vehicle receiving unit 12. The in-vehicle receiving unit 12 receives a response signal transmitted from the portable device 2 by radio through the RF receiving antenna 10. The in-vehicle receiving unit 12 is a circuit that removes a carrier wave component from the received response signal or the like, extracts the received signal, and outputs the extracted received signal to the in-vehicle control unit 11. As a carrier wave, a radio wave in the UHF band of 300 MHz to 3 GHz is used, but the carrier wave is not limited to this frequency band.

  The in-vehicle transmission unit 13 is a circuit that modulates a signal output from the in-vehicle control unit 11 into a radio signal using a carrier wave and transmits the signal to each portable device 2 from each LF transmission antenna 3. The in-vehicle transmission unit 13 includes a switch that switches the LF transmission antenna 3 that transmits a signal, and the in-vehicle transmission unit 13 can transmit a signal from one LF transmission antenna 3 that is switched by the switch. As a carrier wave, an LF band of 30 kHz to 300 kHz is used, but it is not limited to this frequency band.

  A request switch 4 and a door locking device 5 are connected to the in-vehicle device 1. A request signal corresponding to the operation state of the request switch 4 is input to the in-vehicle control unit 11, and the in-vehicle control unit 11 can recognize the operation state of the request switch 4 based on the input request signal. The request switch 4 is, for example, a switch for locking or unlocking a vehicle door on the driver's seat side or on the passenger seat side, and is provided on a door handle outside the driver seat or outside the passenger seat. In place of the push button, a contact sensor for detecting the contact of the user's hand with the door handle may be provided. Moreover, the vehicle-mounted control part 11 may acquire directly the request signal corresponding to operation of the request switch 4, and may acquire via door ECU (Electronic Control Unit), other ECUs, etc.

  The door locking device 5 includes a locking mechanism that locks and unlocks each vehicle door, and an actuator that drives the locking mechanism. When the request switch 4 is operated, the vehicle-mounted control unit 11 detects the position of the portable device 2 by performing wireless communication with the portable device 2, and the regular portable device 2 is located in the vicinity of the request switch 4 outside the vehicle. If it is, the locking drive signal or the unlocking drive signal is output to the actuator of each vehicle door. The door locking device 5 locks or unlocks each vehicle door according to a locking drive signal or an unlocking drive signal.

Furthermore, a notification unit 6 is connected to the in-vehicle device 1. The notification unit 6 is for notifying the operator of the position where the portable device 2 is to be arranged when adjusting the resonance frequency of the LF transmission antenna 3. Specifically, the notification unit 6 includes a display unit, a lighting device, and a communication interface. Etc. The resonance frequency of the LF transmission antenna 3 needs to be adjusted by placing the portable device 2 in the vicinity of the LF transmission antenna 3. The in-vehicle control unit 11 informs the arrangement of the portable device 2 by the notification unit 6. Show.
The display unit is a liquid crystal display, an organic EL display, or the like, and displays the arrangement of the portable device 2 under the control of the in-vehicle control unit 11. Moreover, the vehicle-mounted control part 11 may alert | report the arrangement | positioning of the portable device 2 by lighting the lighting device provided in the vicinity of the LF transmission antenna 3 to be adjusted. Furthermore, the vehicle-mounted control part 11 may transmit the information which concerns on arrangement | positioning of the portable device 2 to an external computer terminal via a communication interface. The operator can recognize the arrangement of the LF transmission antenna 3 and the portable device 2 to be adjusted using a computer terminal.

FIG. 3 is a schematic diagram illustrating a configuration example of the LF transmission antenna 3. The LF transmission antenna 3 includes a resonance circuit 31 housed in a resin housing 30. The resonance circuit 31 is configured by connecting in series a coil 31b of a conductive wire wound around the outer periphery of a core 31a made of a rod-shaped magnetic material and a variable capacitor 31c whose capacity can be changed. The resonance circuit 31 is connected to the in-vehicle transmission unit 13, and when the resonance circuit 31 resonates in accordance with the electric signal output from the in-vehicle transmission unit 13 and a current flows through the coil 31 b, the resonance circuit 31 is wirelessly transmitted from the LF transmission antenna 3. A signal is transmitted. The variable capacitor 31c is connected to the in-vehicle control unit 11 via a communication line, and changes the capacity according to a signal output from the in-vehicle control unit 11. The configuration of the variable capacitor 31c is not particularly limited. For example, the variable capacitor 31c includes a thin film dielectric layer whose relative dielectric constant changes depending on the voltage of an input signal. The in-vehicle controller 11 can change the capacitance of the variable capacitor by changing the voltage of the signal output to the variable capacitor 31c.
FIG. 4 is a graph showing the relationship between the capacitance value of the variable capacitor 31c and the received signal strength. The graph shown in the upper diagram shows the relationship between the frequency of the electrical signal applied to the LF transmission antenna 3 and the impedance of the resonance circuit 31. A plurality of drawn solid graphs indicate the relationship between frequency and impedance when the capacitance of the variable capacitor 31c is set to a different value. As the capacity of the variable capacitor 31c increases, the resonance frequency of the resonance circuit 31 decreases as indicated by the white arrow.
The middle diagram shows the relationship between the capacitance value of the variable capacitor 31 c and the impedance of the resonance circuit 31 when an electric signal of 125 kHz is applied to the LF transmission antenna 3. As shown in the graph, when the capacitance value of the variable capacitor 31c reaches a specific value, the resonance circuit 31 enters a resonance state, and the impedance of the resonance circuit 31 is minimized.
The lower diagram shows the relationship between the capacitance value of the variable capacitor 31c and the received signal strength of the signal in the portable device 2 when a signal is transmitted by applying an electrical signal of 125 kHz to the LF transmitting antenna 3. As can be seen from the graph, when the capacitance value of the variable capacitor 31c reaches a specific value, the resonance circuit 31 enters a resonance state and the signal strength increases. As a result, the received signal measured by the portable device 2 Strength is maximized.
Thus, it turns out that when the resonance frequency of the LF transmission antenna 3 and the frequency of the signal to be transmitted are in a resonance state, the received signal strength measured in the portable device 2 is maximized. The frequency of the signal to be transmitted is, for example, 125 kHz.

  FIG. 5 is a block diagram illustrating a configuration example of the portable device 2 according to the first embodiment of the present invention. The portable device 2 includes a portable control unit 21 that controls the operation of each component of the portable device 2. The portable control unit 21 is a microcomputer having, for example, one or a plurality of CPUs, a multi-core CPU, and the like. The portable control unit 21 is provided with a portable reception unit 22, a portable transmission unit 23, a portable storage unit 24, and a received signal strength measurement unit 25.

  The portable control unit 21 reads out a control program described later stored in the portable storage unit 24 and controls the operation of each component by controlling the operation of each component. A process of transmitting information necessary for position detection to the in-vehicle device 1 is executed.

  The portable storage unit 24 is a nonvolatile memory similar to the storage unit 14. The portable storage unit 24 is a process of transmitting a response signal including information for detecting the position of the portable device 2 to the in-vehicle device 1 by the portable control unit 21 controlling the operation of each component of the portable device 2. The control program for executing is stored.

  The portable receiving unit 22 is connected to the LF receiving antenna 22 a and receives various signals such as a position detection signal transmitted from the vehicle-mounted device 1 using radio waves in the LF band and outputs the signals to the portable control unit 21. The LF receiving antenna 22a is, for example, a triaxial antenna, and a constant received signal strength can be obtained regardless of the orientation or posture of the portable device 2 with respect to the vehicle C.

  The reception signal strength measurement unit 25 is a circuit that detects the reception signal strength of the signal transmitted from the plurality of LF transmission antennas 3 and received by the LF reception antenna 22 a and outputs the detected reception signal strength to the portable control unit 21. .

The portable transmission unit 23 is connected to the RF transmission antenna 23 a and transmits a signal corresponding to the signal transmitted from the portable device 2 according to the control of the portable control unit 21. When the portable device 2 receives a signal for position detection, the portable transmission unit 23 uses the received signal strength measurement unit 25 as information for detecting the position of the portable device 2 relative to the in-vehicle device 1 according to the control of the portable control unit 21. Transmits a response signal including the measured received signal strength. The portable transmitter 23 transmits a response signal using UHF radio waves.
Although the operation when detecting the position of the portable device 2 has been described here, the signal transmitted from the in-vehicle device 1 when adjusting the resonance frequency of the LF transmission antenna 3 is the same signal. Similarly, 2 transmits a response signal including the received signal strength of the signal to the vehicle-mounted device 1.
The UHF band is an example of a radio wave band for transmitting signals, and is not necessarily limited to this.

FIG. 6 is a flowchart showing a procedure of resonance frequency adjustment processing according to the first embodiment of the present invention, and FIG. 7 is a conceptual diagram showing a resonance frequency adjustment method. The in-vehicle control unit 11 executes the following process at an arbitrary timing at which the resonance frequency of the LF transmission antenna 3 needs to be adjusted. For example, in the assembly process of the vehicle C, the operator inputs a signal for starting the resonance frequency adjustment process to the in-vehicle device 1 to execute the following process.
First, the in-vehicle control unit 11 substitutes 1 for a variable n indicating one LF transmission antenna 3 whose resonance frequency is to be adjusted (step S11), and corresponds to the capacitance value set for the one LF transmission antenna 3. 1 is substituted into the variable m to be executed (step S12).

  Next, the in-vehicle controller 11 determines whether or not the variable n is equal to or less than the number N of antennas of the LF transmission antenna 3 mounted on the vehicle C (step S13). In the case of the first embodiment, the number N of antennas is four. When it is determined that the variable n is equal to or less than the number N of antennas (step S13: YES), the in-vehicle control unit 11 selects the nth LF transmission antenna 3 as a resonance frequency adjustment target (step S14). For example, when n = 1, the first LF transmission antenna 3, that is, the LF transmission antenna 3 provided on the driver side pillar is selected.

  And the vehicle-mounted control part 11 alert | reports the position of the nth LF transmission antenna 3 which should arrange | position the portable device 2 in the alerting | reporting part 6 (step S15). Next, the in-vehicle control unit 11 sets the capacitance value of the variable capacitor 31c to the capacitance value related to the variable m by outputting a signal corresponding to the variable m to the variable capacitor 31c configuring the nth LF transmission antenna 3. (Step S16). Hereinafter, the capacitance value set in the nth LF transmitting antenna 3 by the variable m is appropriately expressed as “C_n_m”. And the vehicle-mounted control part 11 switches to the said nth LF transmission antenna 3 as a transmission antenna used for signal transmission, and transmits a signal only from the said LF transmission antenna 3 (step S17). An unmodulated carrier wave may be used as the signal.

  The portable device 2 receives the signal transmitted from the nth LF transmission antenna 3 and measures the received signal strength of the received signal. Then, the portable device 2 transmits a response signal including the measured received signal strength to the in-vehicle device 1.

  The vehicle-mounted control unit 11 that has transmitted the signal in step S17 monitors the response signal transmitted from the portable device 2, and receives the response signal transmitted from the portable device 2 by the vehicle-mounted receiving unit 12 (step S18). ). Then, as shown in the upper diagram of FIG. 7, the in-vehicle controller 11 stores the received signal strength included in the received response signal in association with the nth LF transmitting antenna 3 and the variable m (step S19). . Hereinafter, the received signal strength obtained when a signal is transmitted from the nth LF transmitting antenna 3 in which the capacitance value related to the variable m is set is appropriately expressed as “RSSI_n_m”.

  Next, the vehicle-mounted control unit 11 determines whether or not the variable m is less than the upper limit value M corresponding to the settable capacity value (step S20). If it is determined that the variable m is not less than the upper limit value M (step S20: NO), the vehicle-mounted control unit 11 adds 1 to the variable n (step S22), returns the process to step S12, and the other LF transmitting antenna 3 The same processing is executed for.

  When it determines with the variable m being less than the upper limit M (step S20: YES), the vehicle-mounted control part 11 adds 1 to the variable m (step S21), and returns a process to step S16.

  If it is determined in step S13 that the variable n is not less than or equal to the number N of antennas (step S13: NO), the in-vehicle controller 11 determines the capacity value when the received signal strength is maximum for each of the plurality of LF transmission antennas 3. That is, the variable XX related to the capacitance value is specified (step S23). Next, as shown in the lower diagram of FIG. 7, the in-vehicle control unit 11 stores the identified capacity value, that is, the variable XX for setting the capacity value and the antenna identifier indicating each LF transmission antenna 3 in association with each other. It memorize | stores in the part 14 (step S24), and complete | finishes a process. Specifically, the vehicle-mounted control unit 11 stores the antenna identifier and the variable XX in association with each other in the capacity table.

  Thereafter, when transmitting a signal from the LF transmission antenna 3, the in-vehicle control unit 11 outputs a signal corresponding to the variable XX stored in the capacity table to the variable capacitor 31c constituting each LF transmission antenna 3. The capacitance value related to the variable XX is set and a signal is transmitted.

  According to the vehicle communication system and the vehicle-mounted device 1 configured as described above, the resonance frequency of the LF transmission antenna 3 can be adjusted to the signal frequency by executing the processing shown in FIG. 6 at an arbitrary timing. .

(Embodiment 2)
The vehicular communication system according to the second embodiment has the same configuration as that of the first embodiment, and only the processing procedure for adjusting the resonance frequency of the LF transmission antenna 3 is different. In the following, the above differences will be mainly described, and the corresponding parts will be denoted by the same reference numerals, and detailed description thereof will be omitted.

  FIG. 8 is a flowchart showing a procedure of resonance frequency adjustment processing according to the second embodiment of the present invention. The vehicle-mounted control part 11 performs the process similar to step S11-step S13, and when it was determined that the variable n is not below the antenna number N (step S13: NO), it transmitted using each LF transmitting antenna 3. It is determined whether the maximum value of the received signal strength of the plurality of signals is less than a predetermined threshold (step S223). The threshold value is a lower limit value of the received signal strength necessary for accurately adjusting the resonance frequency of the LF transmitting antenna 3. When it determines with the maximum value of received signal strength being less than a threshold value (step S223: YES), the vehicle-mounted control part 11 notifies the error information to the effect that adjustment of the resonance frequency has failed (step S224), and finishes the process. . The notification method of the error information is not particularly limited. For example, the notification unit 6 may perform notification in the same manner as the arrangement of the portable device 2. For example, an error may be displayed on the display unit, a lamp may blink, or error information may be transmitted to an external computer terminal.

  When it is determined that the maximum value of the received signal strength is greater than or equal to the threshold (step S223: NO), the in-vehicle control unit 11 performs the same processing as step S23 and step S24 in step S225 and step S226. The variable XX when the LF transmission antenna 3 resonates and the antenna identifier are stored in the storage unit 14 in association with each other.

  According to the vehicle communication system and the in-vehicle device 1 according to the second embodiment, it is possible to adjust the resonance frequency after confirming that the resonance frequency of the LF transmission antenna 3 can be accurately adjusted.

  In the above embodiment, the example of adjusting the resonance frequency of the LF transmitting antenna 2 for locking and unlocking the vehicle door has been mainly described. However, the system for starting the engine of the vehicle by wireless communication with the portable device, the vehicle The present invention can be applied to any system such as a system for monitoring tire air pressure by wireless communication with an air pressure sensor provided in each tire.

  In addition, the example of adjusting the resonance frequency of the LF transmitting antenna 2 in the factory has been mainly described. However, the adjustment timing is not particularly limited, and the user can adjust the resonance frequency after the vehicle C is shipped. It may be configured.

DESCRIPTION OF SYMBOLS 1 In-vehicle device 2 Portable device 3 LF transmission antenna 4 Request switch 5 Door locking device 6 Notification unit 10 RF reception antenna 11 In-vehicle control unit 12 In-vehicle reception unit 13 In-vehicle transmission unit 14 Storage unit 21 Portable control unit 22 Portable reception unit 22a LF reception Antenna 23 Portable Transmitter 23a RF Transmit Antenna 24 Portable Storage Unit 25 Received Signal Strength Measuring Unit 30 Housing 31 Resonant Circuit 31a Core 31b Coil 31c Variable Capacitor C Vehicle

Claims (4)

A vehicle-mounted device that transmits signals from a plurality of transmission antennas provided in the vehicle; and a portable device that receives a signal transmitted from the vehicle-mounted device and transmits a response signal including the received signal strength of the received signal. The in-vehicle device is a vehicle communication system that receives the response signal transmitted from the portable device and detects the position of the portable device based on a received signal strength included in the received response signal,
One of the transmission antennas is
A resonance circuit having a variable capacitor and a coil whose capacitance can be changed,
The in-vehicle device is
A transmitter that transmits a signal multiple times from the one transmission antenna;
A change unit that changes the capacity of the variable capacitor each time a signal is transmitted by the transmission unit;
A receiver that receives the response signal transmitted from the portable device in response to each signal transmitted a plurality of times by the transmitter;
A determining unit that determines a capacity of the variable capacitor based on a plurality of received signal strengths included in the response signal received by the receiving unit;
A vehicle communication system comprising: a storage unit that stores a capacity of the variable capacitor determined by the determination unit. The capacity of the variable capacitor when each of the plurality of signals is transmitted by the transmission unit and the received signal strength of the plurality of signals included in the response signal are associated with each other,
The determination unit
The vehicular communication system according to claim 1, wherein a capacity of the variable capacitor is determined when the received signal strength becomes maximum. The in-vehicle device is
A determination unit that determines whether or not the received signal strength included in the response signal is less than a threshold;
The determination unit
The vehicle communication system according to claim 1 or 2, wherein when the determination unit determines that the received signal strength is equal to or greater than a threshold value, a capacity of the variable capacitor is determined. A signal is transmitted from a plurality of transmission antennas provided in the vehicle to the portable device, a response signal including the received signal strength of the signal received by the portable device is received, and the received signal strength included in the received response signal is Based on the on-vehicle device that detects the position of the portable device,
One of the transmission antennas includes a resonance circuit having a variable capacitor and a coil whose capacitance can be changed,
And a transmitter that transmits the signal multiple times from the one transmission antenna;
A change unit that changes the capacity of the variable capacitor each time a signal is transmitted by the transmission unit;
A receiver that receives the response signal transmitted from the portable device in response to each signal transmitted a plurality of times by the transmitter;
A determining unit that determines a capacity of the variable capacitor based on a plurality of received signal strengths included in the response signal received by the receiving unit;
An in-vehicle device comprising: a storage unit that stores a capacity of the variable capacitor determined by the determination unit.

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