阅读说明：本技术 车载设备、车辆用通信系统及到来方向推定方法 (In-vehicle device, communication system for vehicle, and arrival direction estimation method ) 是由 松冈健二 于 2018-05-29 设计创作，主要内容包括：提供一种车载设备、车辆用通信系统及到来方向推定方法。车载设备从分隔配置于车辆的多个发送天线发送信号,根据来自接收到信号的便携设备的响应信号而进行处理,其中,所述车载设备具备：接收部,通过分隔配置于车辆的多个接收天线的每一个来接收响应信号；及推定部,基于通过多个接收天线的每一个接收到的响应信号的相位差,来推定响应信号的到来方向。(Provided are an in-vehicle device, a communication system for a vehicle, and an arrival direction estimation method. An in-vehicle device that transmits a signal from a plurality of transmitting antennas separately disposed in a vehicle and performs processing based on a response signal from a portable device that receives the signal, the in-vehicle device comprising: a receiving unit configured to receive a response signal by each of a plurality of receiving antennas separately disposed in a vehicle; and an estimating unit that estimates the arrival direction of the response signal based on the phase difference of the response signal received by each of the plurality of receiving antennas.)

1. An in-vehicle device that transmits a signal from a plurality of transmission antennas separately disposed in a vehicle and performs processing based on a response signal from a portable device that receives the signal, the in-vehicle device comprising:

a receiving unit configured to receive the response signal by each of a plurality of receiving antennas separately disposed on the vehicle; and

and an estimating unit configured to estimate an arrival direction of the response signal based on a phase difference of the response signal received by each of the plurality of receiving antennas.

2. The in-vehicle apparatus according to claim 1,

the vehicle-mounted device includes a transmission control unit that changes a combination of the plurality of transmission antennas that transmit signals, when the response signal from the portable device is not received for the signals transmitted from the plurality of transmission antennas.

3. The in-vehicle apparatus according to claim 1 or 2,

transmitting the signals of an LF (Low frequency) band from the plurality of transmission antennas.

4. The vehicle-mounted apparatus according to any one of claims 1 to 3,

at least two of the plurality of transmitting antennas are arranged to be spaced apart in the front-rear direction or in the left-right direction in the traveling direction of the vehicle,

the signals are simultaneously transmitted from the two transmission antennas disposed at a front-back or left-right separation.

5. The in-vehicle apparatus according to claim 4,

the on-vehicle device includes a phase control unit that controls phases of signals simultaneously transmitted from the two transmission antennas.

6. The vehicle-mounted apparatus according to any one of claims 1 to 5,

transmitting a signal for activating the portable device through the plurality of transmission antennas.

7. The vehicle-mounted device according to any one of claims 1 to 6, comprising:

the plurality of transmitting antennas are respectively arranged at tire positions where a plurality of tires are arranged on the vehicle,

the transmission antenna disposed at each tire position transmits a signal to a plurality of detection devices, which are provided in the plurality of tires, and wirelessly transmit an air pressure signal obtained by detecting the air pressure of the tire.

8. A communication system for a vehicle is provided with:

the vehicle-mounted device of any one of claims 1 to 7;

a plurality of transmitting antennas separately disposed in a vehicle;

a portable device that receives the signal transmitted from the in-vehicle device and transmits a response signal according to the received signal; and

and a plurality of receiving antennas which are separately arranged on the vehicle and respectively receive the response signals from the portable equipment.

9. An arrival direction estimating method for transmitting a signal from a plurality of transmitting antennas spaced apart from a vehicle and estimating an arrival direction of a response signal from a portable device receiving the signal, wherein,

receiving the response signal by separating each of a plurality of receiving antennas provided to the vehicle,

estimating an arrival direction of the response signal based on a phase difference of the response signal received through each of the plurality of receiving antennas.

Technical Field

The invention relates to an in-vehicle device, a communication system for a vehicle, and an arrival direction estimation method.

The present application claims priority based on japanese application No. 2017-119775 filed on 19/6/2017, and incorporates the entire contents of the description of said japanese application.

Background

A vehicle communication system that locks and unlocks a vehicle door without using a mechanical key is in practical use. Specifically, a keyless entry system that locks or unlocks a vehicle door by wireless remote operation using a portable device held by a user, a smart entry (registered trademark) system that unlocks a vehicle door only by a user holding a portable device approaching a vehicle or grasping a door handle, and the like are in practical use.

In addition, a vehicle communication system that starts the engine of a vehicle without using a mechanical key is also put to practical use. Specifically, a push start system is also put into practical use in which a user holding a portable device starts an engine by simply pushing an engine start button.

Further, a system of a light for a passenger car that lights an interior lamp or an exterior lamp when a user holding a portable device approaches a vehicle is put to practical use.

In the vehicle communication system, the in-vehicle device and the portable device perform wireless communication. The wireless communication is performed as follows: various signals are transmitted from a transmission antenna of the in-vehicle device to the mobile device using an LF (Low Frequency) band radio wave, and the mobile device that has received the signals transmits a response signal using an UHF (Ultra High Frequency) band radio wave. The in-vehicle device performs control such as unlocking, locking, engine starting, and lighting of a visitor light after authentication and position confirmation of the portable device.

However, the signal transmitted from the vehicle-mounted device is in the LF band, and the transmission range of the signal is limited to a predetermined range around the vehicle. In order to detect the position of the portable device with high accuracy or to detect the portable device approaching the vehicle in advance, the reception sensitivity of the portable device to the signal may be set to high sensitivity, but the life of a battery driving the portable device is shortened.

Patent document 1 discloses the following technique: the reception sensitivity of the portable device is set to high sensitivity when it is determined that the portable device is present in the vehicle interior or within a predetermined distance from the vehicle, and the reception sensitivity of the portable device is set to low sensitivity when it is determined that the portable device is not present in the vehicle interior or within the predetermined distance from the vehicle.

Prior art documents

Patent document

Patent document 1: japanese patent laid-open publication No. 2015-113644

Disclosure of Invention

Problems to be solved by the invention

However, in patent document 1, the reception sensitivity of the portable device remains low until the portable device approaches the vehicle, and therefore the portable device approaching the vehicle cannot be detected in advance. In addition, if it is erroneously determined that the mobile device is not within the predetermined distance from the vehicle, the reception sensitivity of the mobile device is in a low-sensitivity state, and therefore, there is a problem that it is difficult to detect the position of the mobile device.

An object of the present invention is to provide an in-vehicle device, a vehicle communication system, and an arrival direction estimation method that can expand a transmission range of a signal transmitted from a transmission antenna of the in-vehicle device and can estimate an arrival direction of a response signal transmitted from a portable device.

Means for solving the problems

An in-vehicle device according to an aspect of the present invention is an in-vehicle device that transmits a signal from a plurality of transmission antennas separately disposed in a vehicle and performs processing based on a response signal from a portable device that receives the signal, the in-vehicle device including: a receiving unit configured to receive the response signal by each of a plurality of receiving antennas separately disposed on the vehicle; and an estimating unit configured to estimate an arrival direction of the response signal based on a phase difference of the response signal received by each of the plurality of receiving antennas.

A vehicle communication system according to an aspect of the present invention includes: the aforementioned in-vehicle device; a plurality of transmitting antennas separately disposed in a vehicle; a portable device that receives the signal transmitted from the in-vehicle device and transmits a response signal according to the received signal; and a plurality of reception antennas that are separately disposed in the vehicle and that individually receive the response signals from the portable device.

An arrival direction estimating method according to an aspect of the present invention is a method for transmitting a signal from a plurality of transmitting antennas spaced apart from a vehicle, and estimating an arrival direction of the response signal based on a response signal from a portable device that receives the signal, wherein the response signal is received by each of a plurality of receiving antennas spaced apart from the vehicle, and the arrival direction of the response signal is estimated based on a phase difference of the response signal received by each of the plurality of receiving antennas.

The present application can be realized not only as an in-vehicle device including such a characteristic processing unit or a transmission unit, but also as a signal transmission method in which the characteristic processing is performed as a step, or as a program for causing a computer to execute the step. Further, the present invention may be implemented as a semiconductor integrated circuit that implements part or all of the in-vehicle device, or as another system including the in-vehicle device.

Effects of the invention

According to the above, the transmission range of the signal transmitted from the transmission antenna of the in-vehicle device can be expanded, and the arrival direction of the response signal transmitted from the portable device can be estimated.

Drawings

Fig. 1 is a schematic diagram illustrating a configuration example of a vehicle communication system according to embodiment 1.

Fig. 2 is a block diagram showing a configuration example of the in-vehicle apparatus 1.

Fig. 3A is an explanatory diagram for explaining a transmission range when signals are transmitted from LF transmission antennas individually.

Fig. 3B is an explanatory diagram for explaining a transmission range when signals are transmitted from LF transmission antennas individually.

Fig. 4A is an explanatory diagram for explaining transmission ranges when signals are simultaneously transmitted from 2 LF transmission antennas.

Fig. 4B is an explanatory diagram for explaining a transmission range when signals are simultaneously transmitted from 2 LF transmission antennas.

Fig. 5 is a block diagram showing a configuration example of the detection device.

Fig. 6 is a block diagram showing a configuration example of the mobile device.

Fig. 7 is a flowchart showing a processing procedure of the in-vehicle device and the portable device.

Fig. 8 is a block diagram illustrating a configuration example of the in-vehicle transmission unit according to embodiment 2.

Fig. 9 is a distribution diagram showing an example of the magnetic field distribution of the signal wave transmitted from the LF transmission antenna.

Detailed Description

The present invention will be described with reference to embodiments. At least some of the embodiments described below may be arbitrarily combined.

An in-vehicle device according to an aspect of the present invention transmits a signal from a plurality of transmission antennas separately disposed in a vehicle, and performs processing based on a response signal from a portable device that receives the signal, and includes: a receiving unit configured to receive the response signal by each of a plurality of receiving antennas separately disposed on the vehicle; and an estimating unit configured to estimate an arrival direction of the response signal based on a phase difference of the response signal received by each of the plurality of receiving antennas.

In this aspect, the response signal from the mobile device is received by each of the plurality of receiving antennas, and the arrival direction of the response signal is estimated based on the phase difference between the received response signals. Further, using the estimation result, the position and the moving direction of the mobile device that is the transmission source of the response signal can be detected.

The in-vehicle device according to an aspect of the present invention transmits the signal in the LF band from the plurality of transmission antennas.

In this embodiment, since the signals simultaneously transmitted from the respective transmission antennas are signals in the LF band, the amplitudes of the signals are the same in the vehicle periphery. As a result, in a region where the directions of the magnetic fields of the signal waves emitted from the respective transmitting antennas are the same, the signals are attenuated without interfering with each other, and the signal strength is increased by simple overlapping of the signals.

In the in-vehicle device according to the aspect of the present invention, at least two transmission antennas among the plurality of transmission antennas are disposed to be spaced apart in the front-rear direction or the left-right direction in the traveling direction of the vehicle, and the signals are simultaneously transmitted from the two transmission antennas disposed to be spaced apart in the front-rear direction or the left-right direction.

In this aspect, when signals are simultaneously transmitted from two transmission antennas arranged at a distance from each other in the front-rear direction of the vehicle in the traveling direction, the transmission range of the signals is expanded, for example, in the left-right direction of the vehicle. Similarly, when signals are simultaneously transmitted from two transmission antennas that are disposed at a distance from each other in the traveling direction of the vehicle, the transmission range of the signals is expanded, for example, in the front-rear direction of the vehicle. In the case where signals are simultaneously transmitted from a plurality of transmission antennas arranged in the front-rear and left-right directions in the traveling direction of the vehicle, the transmission range of the signals is expanded in the front-rear and left-right directions of the vehicle.

An in-vehicle device according to an aspect of the present invention includes a phase control unit that controls phases of signals simultaneously transmitted from the two transmission antennas.

In this aspect, by controlling the phases of the signals to be simultaneously transmitted, the direction in which the transmission range of the signals is expanded can be controlled.

An in-vehicle device according to an aspect of the present invention transmits a signal for activating the portable device via the plurality of transmission antennas.

In this aspect, the transmission range of the signal for activating the mobile device can be expanded. Therefore, the portable device located further away from the vehicle can be started.

In the vehicle-mounted device according to an aspect of the present invention, the plurality of transmitting antennas are disposed at tire positions of the vehicle where the plurality of tires are disposed, respectively, and signals are transmitted from the transmitting antennas disposed at the respective tire positions to the plurality of detecting devices that are disposed at the plurality of tires, respectively, and that wirelessly transmit air pressure signals obtained by detecting air pressures of the tires.

In this aspect, the in-vehicle device can communicate with the detection device that detects the air pressure of the tire using the plurality of transmission antennas, and can communicate with the portable device using the transmission antennas.

A vehicle communication system according to an aspect of the present invention includes: the aforementioned in-vehicle device; a plurality of transmitting antennas separately disposed in a vehicle; a portable device that receives the signal transmitted from the in-vehicle device and transmits a response signal according to the received signal; and a plurality of reception antennas that are separately disposed in the vehicle and that individually receive the response signals from the portable device.

In this aspect, the transmission range of the signal transmitted from the transmission antenna of the in-vehicle device can be expanded. Therefore, the in-vehicle device can perform wireless communication with the remote portable device, and can execute processing corresponding to the result of the wireless communication.

An arrival direction estimating method according to an aspect of the present invention is a method for estimating an arrival direction of a response signal transmitted from a plurality of transmitting antennas spaced apart from a vehicle, the arrival direction of the response signal being estimated based on a response signal from a portable device that receives the signal, wherein the response signal is received by each of a plurality of receiving antennas spaced apart from the vehicle, and the arrival direction of the response signal is estimated based on a phase difference of the response signal received by each of the plurality of receiving antennas.

In this aspect, the response signal from the mobile device is received by each of the plurality of receiving antennas, and the arrival direction of the response signal is estimated based on the phase difference of the received response signals. Further, using the estimation result, the position and the moving direction of the mobile device that is the transmission source of the response signal can be detected.

The present invention will be specifically described below with reference to the drawings showing embodiments of the present invention.

(embodiment mode 1)

Fig. 1 is a schematic diagram illustrating a configuration example of a vehicle communication system according to embodiment 1. The vehicle communication system of the present embodiment includes an in-vehicle device 1 installed at an appropriate position of a vehicle body, a plurality of detection devices 2 installed on each of wheels of a plurality of tires 3 installed on a vehicle C, a notification device 4, a mobile device 5, and a vehicle exterior illumination unit 6, and constitutes a tire air pressure monitoring system and a passenger light system.

The in-vehicle device 1 is connected with a first LF transmission antenna 14a, a second LF transmission antenna 14b, a third LF transmission antenna 14c, and a fourth LF transmission antenna 14 d. The first to fourth LF transmission antennas 14a, 14b, 14C, and 14d are disposed at respective positions spaced apart from each other at the tire positions on the front right, rear right, front left, and rear left of the vehicle C on which the 4 tires 3 are mounted, for example. The tire position is a position of the tire housing and the periphery thereof, and is a position at which the detection device 2 provided in each tire 3 can individually receive the signals transmitted from the first to fourth LF transmission antennas 14a, 14b, 14c, and 14 d.

In the following description, when it is not necessary to distinguish the first to fourth LF transmission antennas 14a, 14b, 14c, and 14d from each other, the first to fourth LF transmission antennas 14a, 14b, 14c, and 14d will be referred to as LF transmission antennas.

In a vehicle communication system functioning as a tire air pressure monitoring system, an in-vehicle device 1 transmits an air pressure information request signal requesting air pressure information of a tire 3 from first to fourth LF transmission antennas 14a, 14b, 14c, and 14d to each detection device 2 individually by using radio waves in an LF band. The detection device 2 detects the air pressure of the tire 3 based on the air pressure information request signal, and wirelessly transmits an air pressure signal including the detected air pressure information and its own sensor identifier to the in-vehicle device 1 by using radio waves of the UHF band. The in-vehicle device 1 includes RF receiving antennas 13a and 13b arranged separately, receives the air pressure signal transmitted from each detection device 2 by the RF receiving antennas 13a and 13b, and acquires the air pressure information of each tire 3 from the air pressure signal. The in-vehicle device 1 is connected to the notification device 4 via a communication line, and the in-vehicle device 1 transmits the acquired air pressure information to the notification device 4. The notification device 4 receives the air pressure information transmitted from the in-vehicle apparatus 1 and notifies the air pressure information of each tire 3. The notification device 4 issues a warning when the air pressure of the tire 3 is less than a predetermined threshold value.

On the other hand, in the vehicle communication system functioning as a passenger lighting system, the in-vehicle device 1 transmits a signal (position detection signal) for detecting the portable device 5 located in the periphery of the vehicle C from the first to fourth LF transmission antennas 14a, 14b, 14C, and 14d to the portable device 5 by using the radio wave in the LF band. The portable device 5 receives the signals transmitted from the first to fourth LF transmission antennas 14a, 14b, 14c, and 14d, and transmits a response signal corresponding to the received signal to the in-vehicle device 1 using a radio wave in the UHF band. The in-vehicle device 1 receives the response signal transmitted from the portable device 5 by the RF receiving antennas 13a and 13 b. The in-vehicle device 1 turns on the exterior illumination unit 6 when the authentication of the mobile device 5 is successful by wireless communication with the mobile device 5. By lighting the vehicle exterior lighting unit 6, the surroundings of the vehicle C are illuminated to meet the user.

The LF band and the UHF band used in the vehicle communication system of the present embodiment are examples of a radio band region used for wireless communication, and are not necessarily limited thereto.

Fig. 2 is a block diagram showing a configuration example of the in-vehicle apparatus 1. The in-vehicle device 1 includes a control unit 11 that controls operations of the respective components of the in-vehicle device 1. The storage unit 12, the in-vehicle receiving unit 13, the in-vehicle transmitting unit 14, and the in-vehicle communication unit 15 are connected to the control unit 11.

The control unit 11 includes, for example, a cpu (central Processing unit), a rom (read Only memory), a ram (random Access memory), and an input/output interface. The CPU of the control unit 11 is connected to the storage unit 12, the in-vehicle receiving unit 13, the in-vehicle transmitting unit 14, and the in-vehicle communication unit 15 via the input/output interface. The control unit 11 controls the operations of the respective components by executing the control program stored in the storage unit 12, and executes processing relating to a function of detecting the position of the mobile device 5, a passenger light function, and a tire air pressure monitoring function.

The control unit 11 is not limited to the above configuration, and may be one or more processing circuits including a single-core CPU, a multi-core CPU, a microcomputer, a volatile or nonvolatile memory, and the like. The control unit 11 may also have functions of a clock for measuring time, a timer for measuring an elapsed time from when the measurement start instruction is given to when the measurement end instruction is given, a counter for counting the number of times, and the like.

The storage unit 12 is a nonvolatile memory such as an EEPROM (Electrically Erasable Programmable ROM) or a flash memory. The storage unit 12 stores a control program for realizing the passenger light function and the tire air pressure monitoring function by the control unit 11 controlling the operations of the respective components of the in-vehicle device 1.

The in-vehicle receiving unit 13 is connected to a plurality of RF receiving antennas 13a and 13b that are separately disposed in the vehicle C. The in-vehicle receiving unit 13 receives a signal transmitted from the portable device 5 or the detection device 2 using radio waves in the RF band by the RF receiving antennas 13a and 13 b. The in-vehicle receiving unit 13 is a circuit that demodulates the received signal and outputs the demodulated signal to the control unit 11. The carrier wave is a UHF band of 300MHz to 3GHz, but is not limited to this band. In the present embodiment, a mode in which 2 RF receiving antennas 13a and 13b are connected is described, but 3 or more RF receiving antennas may be mounted.

The first to fourth LF transmission antennas 14a, 14b, 14c, and 14d are connected to the in-vehicle transmission unit 14. The first to fourth LF transmission antennas 14a, 14b, 14c, and 14d include a bar-shaped magnetic core made of ferrite and a coil wound around the outer periphery of the magnetic core. A capacitor is connected to the coil to form a resonance circuit. The resonance circuit is connected to the in-vehicle transmission unit 14. The in-vehicle transmission unit 14 is a circuit that modulates a signal output from the control unit 11 into a signal in the LF band, and transmits the modulated signal from the first to fourth LF transmission antennas 14a, 14b, 14c, and 14d to the portable device 5 or the detection apparatus 2 simultaneously or individually. The in-vehicle transmission unit 14 causes a current to flow to the coil so that the transmission range of the signal transmitted from the first to fourth LF transmission antennas 14a, 14b, 14c, 14d is within a fixed range around the vehicle, and transmits the signal. The transmission range is a range in which the portable device 5 can receive the signal. Note that, although the LF band of 30kHz to 300kHz is used as the carrier wave, the carrier wave is not limited to this band.

Fig. 3A and 3B are explanatory diagrams illustrating transmission ranges when signals are transmitted from the LF transmission antennas 14a, 14B, 14c, and 14d, respectively. Fig. 3A conceptually shows the transmission ranges 7a, 7b, 7c, and 7d when signals are transmitted from the first to fourth LF transmission antennas 14a, 14b, 14c, and 14d, respectively. Fig. 3B is a time chart of signals transmitted from the first to fourth LF transmission antennas 14a, 14B, 14c, 14 d. The horizontal axis represents time, and "signal" surrounded by a rectangle represents the transmission time of the signal.

The transmission range 7a of the signal transmitted from the first LF transmission antenna 14a alone stays within a predetermined range centered on the first LF transmission antenna 14 a. Similarly, the transmission range 7b of the signal transmitted from the second LF transmission antenna 14b alone stays within a predetermined range centered on the second LF transmission antenna 14 b. Therefore, the strength of the signal at the center portion in the front-rear direction of the vehicle C is weak, and the mobile device 5 at the position shown in fig. 3A cannot receive the signals transmitted from the first and second LF transmission antennas 14a and 14 b.

Similarly, the transmission ranges 7c and 7d of the signals transmitted from the third and fourth LF transmission antennas 14c and 14d stay within predetermined ranges centered on the third and fourth LF transmission antennas 14c and 14d, respectively.

Fig. 4A and 4B are explanatory diagrams illustrating transmission ranges when signals are simultaneously transmitted from 2 LF transmission antennas 14A and 14B (14c and 14 d). Fig. 4A conceptually shows a transmission range 7ab when signals are simultaneously transmitted from the first and second LF transmission antennas 14A and 14b, and a transmission range 7cd when signals are simultaneously transmitted from the third and fourth LF transmission antennas 14c and 14 d. Fig. 4B is a time chart of signals transmitted from the first to fourth LF transmission antennas 14a, 14B, 14c, 14 d. The horizontal axis represents time, and "signal" surrounded by a rectangle represents the transmission time of the signal.

As shown in fig. 4A, the transmission range 7ab of the signals transmitted simultaneously from the first and second LF transmission antennas 14A, 14b is wider than the transmission range 7a (7b) of the signals transmitted from the first LF transmission antenna 14A (or the second LF transmission antenna 14b) alone. Since the signals transmitted from the first and second LF transmission antennas 14a and 14b are in the LF band, the amplitude of the signals is the same around the vehicle C, and the signals transmitted from the first and second LF transmission antennas 14a and 14b overlap each other without being cancelled by interference, and the amplitude increases. Therefore, for example, the mobile device 5 at the position shown in fig. 4A can receive signals transmitted simultaneously from the first and second LF transmission antennas 14A and 14 b.

Similarly, the transmission range 7cd of the signals transmitted simultaneously from the third and fourth LF transmission antennas 14c, 14d is wider than the transmission range 7c (7d) of the signal transmitted from the single third LF transmission antenna 14c (or fourth LF transmission antenna 14 d). Since the signals transmitted from the third and fourth LF transmission antennas 14C and 14d are in the LF band, the amplitude of the signals is the same around the vehicle C, and the signals transmitted from the third and fourth LF transmission antennas 14C and 14d overlap each other without being cancelled by interference, and the amplitude increases.

In this way, when signals are transmitted simultaneously from a plurality of LF transmission antennas, the transmission range can be expanded. On the other hand, since the signals are transmitted simultaneously, it is not possible to determine from which LF transmission antenna the response signal is obtained when the signal is transmitted, and the position and the moving direction of the mobile device 5 cannot be specified. In the present embodiment, in order to enlarge the transmission range of the signal transmitted from the in-vehicle device 1 and to specify the position and the moving direction of the mobile device 5, the in-vehicle device 1 estimates the arrival direction of the signal based on the phase difference of the signals received by the RF receiving antennas 13a and 13b, respectively. The method of estimating the direction of arrival will be described in detail later.

On the other hand, when transmitting the wake-up signal for activating the detection device 2 of each tire 3 or when transmitting the air pressure information request signal to each detection device 2, the in-vehicle transmission unit 14 transmits the wake-up signal or the air pressure information request signal from each of the first to fourth LF transmission antennas 14a, 14b, 14c, and 14 d.

In the present embodiment, although the case where the signals transmitted simultaneously from the 2 or more first to fourth LF transmission antennas 14a, 14b, 14c, and 14d are the same will be mainly described, this is an example and the signals need not be completely the same. Further, the signals simultaneously transmitted from the 2 or more first to fourth LF transmission antennas 14a, 14b, 14c, and 14d may overlap to increase the amplitude, and the phases of the signals may be shifted. The signals transmitted from the 2 or more first to fourth LF transmission antennas 14a, 14b, 14c, and 14d need not be transmitted at exactly the same time, and the signals may overlap and have increased amplitudes, or the transmission times of the signals may be shifted.

The in-vehicle communication unit 15 is a communication circuit that performs communication according to a communication protocol such as can (controller Area network) or lin (local interconnection network), and is connected to the notification device 4 and the outside-vehicle illumination unit 6. The in-vehicle communication unit 15 transmits the air pressure information of the tire 3 to the notification device 4 according to the control of the control unit 11. When detecting the mobile device 5 located in the periphery of the vehicle C, the in-vehicle communication unit 15 transmits a lighting control signal to the exterior lighting unit 6 under the control of the control unit 11.

The notification device 4 is, for example, a display unit that notifies the air pressure information of the tire 3 transmitted from the in-vehicle communication unit 15 by an image or sound, an audio device provided with a speaker, a display unit provided in a meter of an instrument panel, or the like. The display unit is a liquid crystal display, an organic EL display, a head-up display, or the like. For example, the notification device 4 displays air pressure information of each tire 3 provided in the vehicle C.

The exterior lighting unit 6 includes, for example, a mirror or a light source provided in a door of the vehicle C, a drive circuit for supplying power to the light source to turn on the light source, a receiving circuit for receiving a lighting control signal transmitted from the vehicle interior communication unit 15, and the like. The vehicle exterior illumination unit 6 turns on the light source when receiving the lighting control signal transmitted from the vehicle interior communication unit 15. When the vehicle exterior illumination unit 6 is turned on, the surroundings of the vehicle C are illuminated.

In the present embodiment, the exterior lighting unit 6 for illuminating the exterior of the vehicle is exemplified as the lighting for realizing the passenger lighting function, but the interior of the vehicle may be illuminated.

Fig. 5 is a block diagram showing a configuration example of the detection device 2. The detection device 2 includes a sensor control unit 21 that controls operations of the respective components of the detection device 2. The sensor control unit 21 is connected to a sensor storage unit 22, a sensor transmission unit 23, a sensor reception unit 24, and an air pressure detection unit 25.

The sensor control unit 21 includes, for example, a CPU, a ROM, a RAM, an input/output interface, and the like. The CPU of the sensor control unit 21 is connected to the sensor storage unit 22, the sensor transmission unit 23, the sensor reception unit 24, and the air pressure detection unit 25 via the input/output interface. The sensor control unit 21 reads out a control program stored in the sensor storage unit 22, and controls each unit. The detection device 2 includes a battery, not shown, and operates by electric power from the battery.

The sensor control unit 21 is not limited to the above configuration, and may be any one or more processing circuits including a single-core CPU, a multi-core CPU, a microcomputer, a volatile or nonvolatile memory, and the like. The sensor control unit 21 may also have functions of a clock for measuring time, a timer for measuring the elapsed time from the time when the measurement start instruction is given to the time when the measurement end instruction is given, a counter for counting the number of times, and the like.

The sensor storage unit 22 is a nonvolatile memory. The sensor storage unit 22 stores a control program for the sensor control unit 21 to perform processing related to the detection of the air pressure of the tire 3 and the transmission of the air pressure signal. A sensor identifier unique to the detection device 2 for distinguishing itself from the other detection devices is stored.

The air pressure detecting unit 25 includes, for example, a diaphragm, and detects the air pressure of the tire 3 based on the amount of deformation of the diaphragm that changes according to the magnitude of the pressure. The signal indicating the air pressure of tire 3 detected by air pressure detecting unit 25 is output to sensor control unit 21. The sensor control unit 21 acquires the air pressure of the tire 3 from the air pressure detection unit 25 by executing a control program, generates an air pressure signal including air pressure information and a sensor identifier unique to the detection device 2, and outputs the air pressure signal to the sensor transmission unit 23.

A temperature detection unit (not shown) may be provided to detect the temperature of the tire 3 and output a signal indicating the detected temperature to the sensor control unit 21. In this case, the sensor control unit 21 generates an air pressure signal including air pressure information, temperature information, a sensor identifier, and the like, and outputs the air pressure signal to the sensor transmission unit 23.

An RF transmission antenna 23a is connected to the sensor transmission unit 23. The sensor transmission unit 23 modulates the barometric pressure signal generated by the sensor control unit 21 into a signal in the UHF band, and transmits the modulated barometric pressure signal using the RF transmission antenna 23 a.

An LF reception antenna 24a is connected to the sensor receiver 24. The sensor receiving unit 24 receives the air pressure information request signal transmitted from the in-vehicle device 1 using the radio wave in the LF band by the LF receiving antenna 24a, and outputs the received air pressure information request signal to the sensor control unit 21.

Fig. 6 is a block diagram showing a configuration example of the mobile device 5. The mobile device 5 includes a mobile control unit 51 that controls operations of the respective components of the mobile device 5. The portable control unit 51 is a microcomputer having one or more CPUs, multi-core CPUs, and the like, for example. The portable control unit 51 is provided with a portable device storage unit 52, a portable transmission unit 53, and a portable reception unit 54. The mobile device 5 includes a battery, not shown, and operates by electric power from the battery.

The portable control unit 51 reads a control program, which will be described later, stored in the portable device storage unit 52, and controls the operations of the respective components. The portable control unit 51 has a rest state in which power consumption is small and an activation state in which power consumption is large. In the inactive state, when the mobile device 5 receives a signal (e.g., a wake-up signal) transmitted from the in-vehicle device 1, the mobile control unit 51 shifts from the inactive state to the active state and starts operating. In the activated state, after the required processing is finished, when a predetermined time has elapsed without the portable device 5 receiving the signal from the in-vehicle device 1, the state transitions to the deactivated state again.

The portable device storage unit 52 is a nonvolatile memory similar to the storage unit 12. The portable device storage unit 52 stores a control program for executing a process for confirming that the correct portable device 5 is present around the vehicle C by the portable control unit 51 controlling the operations of the respective components of the portable device 5.

The portable transmission unit 53 is connected to the RF transmission antenna 53a, and transmits a response signal corresponding to the signal transmitted from the in-vehicle device 1 under the control of the portable control unit 51. The portable transmitting unit 53 transmits the response signal using the radio wave of the UHF band. The UHF band is an example of a radio frequency band for transmitting signals, and is not necessarily limited thereto.

The portable receiving unit 54 is connected to the LF reception antenna 54a via the reception signal strength detecting unit 55, receives various signals transmitted from the in-vehicle device 1 using radio waves in the LF band, and outputs the signals to the portable control unit 51. The LF reception antenna 54a is, for example, a 3-axis antenna, and can obtain a certain reception signal strength regardless of the orientation or posture of the mobile device 5 with respect to the vehicle C.

The reception signal strength detection unit 55 is a circuit that detects the reception signal strength of a signal received by the LF reception antenna 54a, particularly the reception signal strength of a detection signal for detecting the position of the mobile device 5, and outputs the detected reception signal strength to the mobile control unit 51. The received signal strength may also be used when detecting the position of the portable device 5 relative to the vehicle C.

The method of detecting the mobile device 5 by the in-vehicle device 1 of the present embodiment will be described below.

Fig. 7 is a flowchart showing a processing procedure of the in-vehicle device 1 and the mobile device 5. The control unit 11 of the in-vehicle apparatus 1 executes the following processing at an appropriate time after the ignition switch of the vehicle C is turned off and the doors are locked, for example. The control unit 11 selects 2 LF transmission antennas from among the first to fourth LF transmission antennas 14a, 14b, 14C, and 14d mounted on the vehicle C (step S101), and controls the in-vehicle transmission unit 14 to simultaneously transmit the position detection signal from the selected 2 LF transmission antennas (step S102). For example, the control unit 11 selects the first and second LF transmission antennas 14a and 14b as the first combination, and simultaneously transmits the position detection signal from the selected first and second LF transmission antennas 14a and 14 b.

The mobile device 5 monitors a signal transmitted from the outside even in a sleep state, and receives the position detection signal by the mobile receiving unit 54 when the position detection signal is transmitted from the in-vehicle device 1 (step S151). The portable control unit 51 of the portable device 5 that has received the position detection signal shifts from the inactive state to the active state (step S152), and transmits a response signal including its own identifier to the in-vehicle device 1 by the portable transmission unit 53 (step S153).

The control unit 11 of the in-vehicle device 1 that transmitted the position detection signal by the processing of step S102 determines whether or not the response signal transmitted from the mobile device 5 is received by the 2 RF receiving antennas 13a and 13b within a predetermined waiting time (step S103).

When determining that the response signal has been received (yes in S103), the control unit 11 estimates the arrival direction of the response signal based on the phase difference between the response signals received by the 2 RF receiving antennas 13a and 13b (step S104). As a method of estimating the arrival direction of the response Signal, known methods such as a beam forming method, a Capon method, a line shape prediction method, a minimum norm method, a MUSIC method (Multiple Signal Classification), an ESPRIT method (Estimation of Signal Parameters via a rotation invariant technique), and the like can be used.

As an example, the estimation direction of the arrival direction by the MUSIC method will be described. First, K is an integer of 2 or more, and an array antenna of K elements is considered. Let λ be the wavelength of the incoming wave, L be the number of incoming waves, and θ be the angle of arrival of the ith incoming wave_i(i 1, …, L), the array response vector a (θ) for the ith incoming wave_i) Is given by the following formula.

a(θ_i)＝[exp{jΨ₁(θ_i)},…,exp{jΨ_K(θ_i)}]^T

Here, Ψ_n(θ_i)＝-(2π/λ)d_nsin(θ_i) And indicates the reception phase of the i-th wave in the n-th array element. In addition, d is_nThe distance from the reference point to each element is shown.

At this time, the autocorrelation matrix R is given by the following equation.

R＝E[x(t)x^H(t)]

Here, x (t) is a K-dimensional received signal vector having the received signal of the nth element (1. ltoreq. n. ltoreq.K) as an element, and R is a K × K matrix. E [ …]Means set average, x^H(t) denotes the complex conjugate transpose of x (t).

The autocorrelation matrix R is subjected to eigen expansion to obtain an eigen vector e corresponding to a very small eigen value_i(i is more than or equal to 1 and less than or equal to L). L is a dimension of a noise partial space, and can be estimated by using a dimension estimation method such as AIC (Akaike Information criterion: Chichi Information criterion).

If the array response vector of the arrival angle theta is set as a (theta), when theta is consistent with the arrival angle of the incident wave, a (theta) is orthogonal to the noise part space, so that e is satisfied_i ^Ha (θ) ═ 0 (1. ltoreq. i. ltoreq.L). According to this equation, the MUSIC spectrum P can be defined as follows_MU(θ)。

P_MU(θ)＝a^H(θ)a(θ)/(Σ|e_i ^Ha(θ)|²)

At angle theta to the incoming angle theta of the incident wave_i(i is more than or equal to 1 and less than or equal to L) are consistent, the MUSIC frequency spectrum P_MU(θ) has L sharp peaks. In the present embodiment, the reception signal received by each of the 2 RF receiving antennas 13a and 13b is input from the in-vehicle receiving unit 13 to the control unit 11. For example, if the phase of one of the 2 received signals inputted from the in-vehicle receiving unit 13 is fixed, the control unit 11 uses the MUSIC spectrum P_MU(θ) the phase of the other received signal is searched so as to have a peak value, and the arrival angle θ of the received response signal can be estimated_i(i＝1,…,L)。

In the present embodiment, the order of estimating the arrival angle (arrival direction) of the response signal by the MUSIC method has been described as an example, but the arrival direction of the response signal may be estimated by any method such as the beam forming method, Capon method, line shape prediction method, minimum norm method, ESPRIT method, and the like.

The control unit 11 of the in-vehicle device 1 detects the position and the moving direction of the mobile device 5 based on the arrival direction of the response signal estimated in step S104 (step S105). In the present embodiment, it is not necessary to detect a strict position of the mobile device 5, and a configuration may be adopted in which positions of the front, side, rear, and the like of the vehicle C are detected separately.

When the position and the moving direction of the mobile device 5 are detected, the control unit 11 of the in-vehicle device 1 executes a process corresponding to the detection result (step S106). For example, the control unit 11 may perform a process of turning on the vehicle exterior illumination unit 6 provided at a position corresponding to the detected position by transmitting the lighting control signal to the vehicle exterior illumination unit 6. The control unit 11 sends a control signal to a drive control unit (not shown) that pushes up the door knob, thereby performing a process of pushing up the door knob provided at a position corresponding to the detected position.

If the response signal from the mobile device 5 is not received within the predetermined waiting time in step S103 (no in S103), the control unit 11 selects another combination of LF transmission antennas (for example, the third and fourth LF transmission antennas 14b and 14c) that transmit the position detection signal (step S107), returns the process to step S102, and continues the position detection process of the mobile device 5.

According to the in-vehicle device 1 and the vehicle communication system configured as described above, the transmission range of signals can be expanded by simultaneously transmitting signals from the 2 LF transmission antennas. Further, the in-vehicle device 1 can estimate the arrival direction of the response signal in the transmission range and can estimate the position and the moving direction of the mobile device 5 based on the phase difference of the response signals received by using the 2 RF receiving antennas 13a and 13 b.

In the present embodiment, the configuration in which the passenger lighting function is realized using the first to fourth LF transmission antennas 14a, 14b, 14c, and 14d constituting the tire air pressure monitoring system has been described, but it is needless to say that the passenger lighting function may be realized using an LF transmission antenna constituting an intelligent entry (registered trademark) or any other system.

In addition, although the present embodiment describes an example in which the same signal is simultaneously transmitted from a combination of 2 LF transmission antennas, it is needless to say that the same signal may be simultaneously transmitted from a combination of 3 or more LF transmission antennas.

In the present embodiment, the LF transmission antenna is disposed at each tire position, but the arrangement of the LF transmission antenna is not limited to each tire position. For example, the LF transmission antenna may be disposed in the rear portion of the vehicle in addition to the tire positions, or the LF transmission antenna may be disposed in the right side surface, left side surface, rear portion, or the like of the vehicle.

The present invention is applicable not only to a system that realizes the function of a visitor light but also to a walk-away turn-off function, a smart entry (registered trademark) function, and any other system that needs to communicate with the portable device 5.

In the present embodiment, although the in-vehicle device 1 transmits signals using radio waves in the LF band, the signals transmitted from the 2 LF transmission antennas may be cancelled without interfering with each other in a range where communication with the mobile device 5 is necessary, and the frequency of the signals is not particularly limited.

(embodiment mode 2)

In embodiment 2, a configuration for controlling the phase of signals simultaneously transmitted from 2 LF transmission antennas will be described.

Fig. 8 is a block diagram illustrating an example of the configuration of the in-vehicle transmission unit 14 according to embodiment 2. The in-vehicle transmission unit 14 includes first to fourth transmission units 140a, 140b, 140c, and 140d that generate LF-band signals transmitted from the first to fourth LF transmission antennas 14a, 14b, 14c, and 14d, respectively. In embodiment 2, the first to fourth LF transmission antennas 14a, 14b, 14c, and 14d include rod-shaped magnetic cores made of ferrite and coils wound around the magnetic cores, and the winding directions of the coils wound around the magnetic cores are the same.

The first transmitter 140a includes a signal generator 141a and a phase shifter 142 a. The signal generation circuit 141a superimposes a signal wave of a signal (for example, a position detection signal) input from the control unit 11 on a carrier (carrier) and modulates the signal wave into a signal in an LF band. The carrier wave is generated by an RC oscillation circuit, a crystal oscillation circuit, or the like, which is not shown in the figure. The phase shift circuit 142a receives the signal wave (modulated wave) modulated by the signal generation circuit 141 a. The phase shift circuit 142a controls the phase of the input signal wave (modulated wave) based on, for example, a phase shift control signal input from the control unit 11. The first transmitting unit 140a transmits the signal wave whose phase is controlled by the phase shift circuit 142a to the outside via the first LF transmission antenna 14 a.

The second to fourth transmitters 140b, 140c, and 140d have the same configuration as the first transmitter 140 a. That is, the second transmission unit 140b includes a signal generation circuit 141b and a phase shift circuit 142b, the third transmission unit 140c includes a signal generation circuit 141c and a phase shift circuit 142c, and the fourth transmission unit 140d includes a signal generation circuit 141d and a phase shift circuit 142 d. The second to fourth transmission units 140b, 140c, and 140d modulate a signal wave of a signal (for example, a position detection signal) input from the control unit 11 onto a carrier wave to modulate the signal wave into a signal in the LF band, control the phase based on the phase shift control signal input from the control unit 11, and transmit the signal wave with the controlled phase to the outside from the second to fourth LF transmission antennas 14b, 14c, and 14 d.

Fig. 9 is a distribution diagram showing an example of the magnetic field distribution of the signal wave transmitted from the LF transmission antenna. In the example of fig. 9, the directions of the magnetic fields generated when the signals of opposite phases are simultaneously transmitted from the first and second LF transmission antennas 14a and 14b are shown. In the map shown in fig. 9, the X axis is a direction that coincides with the left-right direction of the vehicle C, and the Y axis is a direction that coincides with the front-rear direction of the vehicle C. Both the first and second LF transmission antennas 14a and 14b are disposed on the Y axis and are provided at positions equidistant from the X axis (for example, positions 1.2m from the X axis). The magnetic cores of the first and second LF transmission antennas 14a and 14b are parallel to the Y axis in the axial direction, and the winding directions of the coils wound around the magnetic cores are the same.

When the signal waves having opposite phases are transmitted from the first and second LF transmission antennas 14a and 14b, the directions of the magnetic fields of the respective transmitted signal waves are opposite in the vicinity of the Y axis. As a result, it is found that the signal strength in the vicinity of the Y axis (particularly, in the region between the first and second LF transmission antennas 14a and 14b) is smaller than that in the case where one LF transmission antenna is driven alone.

On the other hand, in the region separated from the Y axis, the magnetic fields of the signal waves transmitted from the first and second LF transmission antennas 14a and 14b have components in the X axis direction, respectively. When signal waves having opposite phases are transmitted from the first and second LF transmission antennas 14a and 14b, the directions of the magnetic fields of the respective transmitted signals are substantially the same in the vicinity of the X axis. As a result, it is found that the signal intensity of the region in the vicinity of the X axis (for example, in the vicinity of the position of the mobile device 5 shown in fig. 4A) separated from the Y axis is greater than that in the case where one LF transmission antenna is driven alone.

In addition, when the outputs of the first and second LF transmission antennas 14a and 14b are not strong, the magnetic field strength at the position separated from the respective LF transmission antennas decreases, and therefore the influence of one magnetic field on the other magnetic field decreases. Therefore, the magnetic field strength at the front side of the first LF transmission antenna 14a and the magnetic field strength at the rear side of the second LF transmission antenna 14b show the same values as the magnetic field strength when the LF transmission antennas are driven individually.

As described in embodiment 1, the transmission range 7a of the signal when the first LF transmission antenna 14a is used alone stays within a predetermined range centered on the first LF transmission antenna 14 a. Similarly, the transmission range 7b when the second LF transmission antenna 14b is used alone stays within a predetermined range centered on the second LF transmission antenna 14 b.

On the other hand, when the inverted signal waves are simultaneously transmitted from the first LF transmission antenna 14a and the second LF transmission antenna 14b, the respective transmitted signal waves overlap in the vicinity of the X axis separated from the Y axis, and the transmission range 7ab specified by the combined magnetic field extends in the left-right direction in the vicinity of the center in the front-rear direction of the vehicle C.

Although not shown, similarly, when inverted signal waves are simultaneously transmitted from the third and fourth LF transmission antennas 14C and 14d, the transmission range of the signal waves can be expanded in the left-right direction in the vicinity of the center in the front-rear direction of the vehicle C.

As described above, in embodiment 2, the transmission range of the signal wave can be expanded in the left-right direction in the vicinity of the center in the front-rear direction of the vehicle C. With this configuration, for example, by enlarging the transmission range of the position detection signal for detecting the mobile device 5, the mobile device 5 can be detected earlier by approaching the vehicle C from the lateral direction.

In embodiment 2, the winding directions of the coils constituting the first to fourth LF transmission antennas 14a, 14b, 14c, and 14d are the same, and therefore, the transmission range is expanded by transmitting the signal waves in opposite phases, but for example, when the winding directions of the coils constituting the first and second LF transmission antennas 14a and 14b are opposite, the transmission range may be expanded by transmitting the signal waves in the same phase from the first and second LF transmission antennas 14a and 14 b.

In embodiment 2, the configuration of controlling the phases of the first and second LF transmission antennas 14a and 14b (the third and fourth LF transmission antennas 14c and 14d) arranged in the front-rear direction has been described, but the configuration of controlling the phases of the first and third LF transmission antennas 14a and 14c (the second and fourth LF transmission antennas 14b and 14d) arranged in the left-right direction may be adopted.

It should be noted that the embodiments disclosed herein are merely illustrative and not restrictive in all respects. The scope of the present invention is disclosed not by the above-described meaning but by the claims, and is intended to include all modifications equivalent in meaning and scope to the claims.

Description of the reference symbols

1 vehicle-mounted device

2 detection device

3 tyre

4 informing device

5 Portable device

6 exterior lighting part

7a, 7b, 7c, 7d transmission range

7ab, 7cd transmission range

11 control part (estimating part)

12 storage part

13 vehicle-mounted receiving part (receiving part)

13a, 13b RF receiving antenna

14 vehicle-mounted transmitting part

14a first LF transmitting antenna (transmitting antenna)

14b second LF transmitting antenna (transmitting antenna)

14c third LF transmitting antenna (transmitting antenna)

14d fourth LF transmitting antenna (transmitting antenna)

15 in-vehicle communication unit

21 sensor control part

22 storage unit for sensor

23 sensor transmitting part

23a RF transmitting antenna

24 sensor receiving part

24a LF receiving antenna

25 air pressure detecting part

51 Portable control part

52 storage unit for mobile device

53 Portable transmitting part

53a RF transmitting antenna

54 portable receiving part

54a LF receiving antenna

55 received signal strength detecting part

140a first transmitting part

140b second transmitting part

140c third transmitting part

140d fourth transmitting part

141a, 141b, 141c, 141d signal generating circuit

142a, 142b, 142c, 142d phase shift circuits (phase control units)

And C, vehicles.