JP2015223981A - Vehicular authentication system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a vehicular authentication system capable of appropriately determining whether a portable machine exists nearby a vehicle when a distance is measured using sound waves.SOLUTION: A vehicular authentication system, for use in performing electronic authentication on the basis of communication between a portable machine 40 and a vehicular authentication apparatus 20 incorporated in a vehicle 10, includes: a first transmission-reception part 26, disposed in the vehicular authentication apparatus 20, for externally outputting a sound wave signal; a first transmission-reception part 41 of the portable machine 40, the part for receiving the sound wave signal; and a control part 22 for calculating a relative distance between the vehicular authentication apparatus 20 and the portable machine 40 on the basis of time from output of the sound wave signal to the reception thereof. The control part 22 further performs: determining a portable machine 40 exists nearby the vehicular authentication apparatus 20 if the relative distance is within a predetermined determination distance; and setting the determination distance in a case where a distance immeasurable sound wave signal is received before a distance measurable sound wave signal is received.

Description

  The present invention relates to a vehicle authentication system including a portable device carried by a user and a vehicle authentication device that performs electronic authentication of the portable device.

As a system for performing wireless communication between a portable device owned by a user and an in-vehicle communication device, a system for locking and unlocking a door of a vehicle without using a mechanical key is already known.
For example, Patent Document 1 proposes a system that calculates the distance between an in-vehicle device and a portable device using sound waves. This system radiates radio waves from the in-vehicle device and radiates sound waves after a predetermined time after radio wave transmission. A portable device measures the time from reception of radio waves to reception of sound waves. The portable device transmits the measured time to the vehicle-mounted device, and the vehicle-mounted device calculates the distance to the portable device based on the time measured by the portable device, the speed of sound waves, and the like.

JP2013-104247A

  However, as shown in FIG. 8, in the system that uses sound waves for ranging, there is a shield such as the user 100 between the in-vehicle device 111 and the portable device 112, and the wall 101 is in the vicinity of the portable device 112. When there is a reflection object such as, the direct wave D received by the portable device 112 without being reflected is received in a state attenuated by the shielding object. In addition, the reflected wave R reflected by the reflector is also received by the portable device 112. In such a case, when ranging is performed based on the reflected wave R instead of the attenuated direct wave D, the relative distance between the in-vehicle device 111 and the portable device 112 is calculated to be longer than the actual distance. For this reason, for example, even when the portable device 112 exists in the vicinity of the vehicle, it may be determined that the portable device 112 does not exist in the vicinity of the vehicle 10.

  The present invention has been made in view of such a situation, and an object of the present invention is to appropriately determine whether or not the portable device exists in the vicinity of the vehicle when performing distance measurement using sound waves. The object is to provide a vehicle authentication system.

Hereinafter, means for solving the above-described problems and the effects thereof will be described.
A vehicle authentication system that solves the above problem is a vehicle authentication system that performs electronic authentication based on communication between a vehicle authentication device mounted on a vehicle and a portable device, and a signal output unit that outputs a sound wave signal A signal receiving unit that receives the sound wave signal, and a distance measuring unit that calculates a relative distance between the vehicle authentication device and the portable device based on a time from when the sound wave signal is output until it is received; A determination unit that determines that the portable device is present in the vicinity of the vehicular authentication device if the relative distance is within a predetermined determination distance, and the determination unit can measure the distance by the signal reception unit. If a sound wave signal that cannot be measured is received before receiving a sound wave signal, the determination distance is set to be large.

  According to the above configuration, when a sound wave signal that cannot be measured is received before the signal receiving unit receives a sound wave signal that can be measured, the sound wave signal that cannot be measured is And the sound wave signal that can be measured is estimated to be a signal reflected by a reflector. In addition, when performing distance measurement based on a sound wave signal that can be measured, a sound wave that can be measured by the signal receiving unit is used as a determination distance for determining whether the portable device is present in the vicinity of the vehicle authentication device. Since it is set larger than the case where only the signal is received, it is suppressed that the portable device is not present in the vicinity even though the portable device is actually present in the vicinity.

  In the vehicular authentication system, when the signal receiving unit receives a sound wave signal that cannot be measured before the signal receiving unit receives a sound wave signal that can be measured, the determination unit receives the sound wave signal that cannot be measured. When the mobile device is determined to move in relation to the vehicle based on a shift in time difference between the reception time of the sound wave signal and the reception time of the sound wave signal that can be measured, and the mobile device is determined to be approaching the vehicle Preferably, the determination distance is set large.

  When the portable device approaches the vehicle, the time difference between the reception time of the sound wave signal that cannot be measured and the reception time of the sound wave signal that can be measured increases, and the sound wave that cannot be measured when the portable device moves away from the vehicle. The time difference between the reception time of the signal and the reception time of the sound wave signal that can be measured is gradually reduced. According to the above configuration, since the moving direction of the portable device is determined based on the time difference and the determination distance is increased only when it is determined that the portable device is approaching the vehicle, is the portable device present in the vicinity of the vehicle? It can be judged appropriately whether or not.

  In the vehicular authentication system, when the signal receiving unit receives a sound wave signal that cannot be measured before the signal receiving unit receives a sound wave signal that can be measured, the determination unit receives the sound wave signal that cannot be measured. The movement direction of the portable device relative to the vehicle based on the deviation of the arrival time from when the sound is output until it is received or the deviation of the arrival time from when the sound wave signal that can be measured is output to when it is received It is preferable to set the determination distance large when it is determined that the portable device is approaching the vehicle.

  When the portable device approaches the vehicle, the arrival time from when a sound wave signal that cannot be measured is output until it is received gradually increases. Also, when the portable device approaches the vehicle, the arrival time from when a sound wave signal that can be measured is output until it is received gradually decreases. According to the above configuration, since the moving direction of the portable device is determined based on the arrival time and the determination distance is increased only when the portable device is determined to be approaching the vehicle, the portable device exists in the vicinity of the vehicle. It is possible to appropriately determine whether or not.

  About the said vehicle authentication system, after the said determination part sets the said determination distance larger than an initial value, it judges the moving direction of the said portable device with respect to the said vehicle, and the said portable device is approaching the said vehicle It is preferable to determine that the portable device is in the vicinity of the vehicular authentication device.

  According to the above configuration, it is possible to suppress erroneous determination when the relative distance calculated based on the sound wave signal that can be measured exceeds the determination distance even though the portable device exists in the vicinity of the vehicle.

  About the said vehicle authentication system, the said signal receiving part judges the correlation with the received sound wave signal and the reference signal which has the waveform which the said signal output part outputs, The said received sound wave signal and the said reference signal When a peak position with high correlation exists, it is determined whether or not the intensity of the signal at the peak position is greater than or equal to a threshold value, and a sound wave capable of measuring a sound wave signal whose intensity at the peak position is equal to or greater than the threshold value Preferably it is a signal.

  According to the above configuration, after the correlation between the received sound wave signal and the reference signal is determined, it is determined whether or not the received sound wave signal can be measured. It is possible to appropriately determine whether or not the portable device exists in the vicinity of the vehicle.

The block diagram which shows the schematic structure about one Embodiment of the authentication system for vehicles. The figure which illustrates the reception state of the sound wave of a portable machine when a portable machine approaches a vehicle over (a)-(c). (A)-(c) is a figure which shows the example of the waveform of the sound wave which a portable machine receives corresponding to the receiving state of the sound wave illustrated to FIG. 2 (a)-(c), respectively. The figure which shows the example of the reception state of the sound wave of a portable device. The sequence diagram which shows the transmission procedure of the ultrasonic signal and radio wave signal of the embodiment. The flowchart explaining operation | movement of the portable device in the embodiment. The flowchart explaining operation | movement of the authentication apparatus for vehicles in the same embodiment. The figure explaining the reception aspect of the sound wave to a portable machine.

  Hereinafter, an embodiment embodying a vehicle authentication system will be described with reference to FIGS. The vehicle authentication system according to the present embodiment includes a portable device possessed by a user and a vehicle authentication device that performs electronic authentication of the portable device.

  The configuration of the vehicular authentication device will be described with reference to FIG. The vehicle authentication device 20 provided in the vehicle 10 includes a control unit 22 as a distance measurement unit and a determination unit, a first transmission / reception unit 26 as a signal output unit, and a second transmission / reception unit 27. The control unit 22 is equipped with a function for performing computation for electronic authentication, a function for performing distance measurement with respect to the portable device 40, and a function for determining whether or not the portable device 40 exists in the vicinity of the vehicle authentication device 20. ing. The control unit 22 includes, for example, a central processing unit (CPU) and a memory, and realizes these arithmetic functions by executing a program stored in the memory. However, the hardware is not limited to software processing by the CPU, and may be dedicated hardware such as an ASIC that performs calculations for electronic authentication.

  The first transmission / reception unit 26 is hardware having a function of transmitting an ultrasonic signal and a function of receiving, and includes, for example, a microphone and a speaker. Here, the ultrasonic signal is a sound wave signal having a frequency higher than the audible frequency band. The first transmitter / receiver 26 is provided so as to be able to transmit and receive an ultrasonic signal to / from a transmitter / receiver outside the vehicle. For example, when the 1st transmission / reception part 26 is provided in the door of a vehicle, it is preferable to provide in the door of the left side part of the vehicle 10, and the door of a right side part.

  The control unit 22 controls communication using the ultrasonic signal with the portable device 40 via the first transmission / reception unit 26. The control unit 22 generates an ultrasonic signal composed of a pulse signal, and transmits the ultrasonic signal from the first transmission / reception unit 26. The portable device 40 stores information held by a legitimate user, and when receiving an ultrasonic signal from the vehicular authentication device 20, transmits the ultrasonic signal including this information to the vehicular authentication device 20. When it is determined that the received identification signal is valid, the control unit 22 authenticates that the user who owns the portable device 40 is a valid user of the vehicle 10.

The second transmitter / receiver 27 has a function of receiving radio waves in a predetermined frequency range transmitted outside the vehicle and a function of transmitting radio waves in the frequency range to the outside of the vehicle.
The control unit 22 controls communication using the radio signal with the portable device 40 via the second transmission / reception unit 27. The radio wave signal transmitted from the portable device 40 includes information related to the reception time of the ultrasonic signal transmitted from the vehicle authentication device 20. The control unit 22 calculates the relative distance between the first transmission / reception unit 26 and the first transmission / reception unit 41 of the portable device 40 based on the time from the transmission time of the ultrasonic signal to the reception time.

  The vehicle authentication device 20 is connected to the door lock system 32 of the vehicle 10 so as to be communicable. The door lock system 32 performs automatic control of locking and releasing of the door of the vehicle 10. The vehicular authentication device 20 determines that the portable device 40 is within the effective range when the relative distance calculated by the distance measurement is equal to or less than a determination distance for determining that the portable device 40 is present in the vicinity of the vehicle. The door is unlocked under a predetermined condition. The effective range is, for example, a circular range having a determination distance as a radius.

  Next, the configuration of the portable device 40 will be described. The portable device 40 may be a dedicated device for authentication or a device having other uses. In the present embodiment, the portable device 40 includes a device having a telephone function, such as a smartphone, and includes a telephone line communication unit 44. The portable device 40 includes a central processing unit (CPU) 46, a nonvolatile memory 48, and a RAM 50, which are connected to each other via an input / output port 52.

  The portable device 40 includes a first transmission / reception unit 41 as a signal reception unit. The first transmission / reception unit 41 has a function of transmitting and receiving an ultrasonic signal. Specifically, the first transmission / reception unit 41 may include a speaker as a device that transmits an ultrasonic signal and a microphone as a device that receives the ultrasonic signal as separate members. . Furthermore, the portable device 40 includes a second transmission / reception unit 42 that transmits and receives radio signals.

  The CPU 46 is hardware having a function of executing various programs stored in the nonvolatile memory 48. The nonvolatile memory 48 is a rewritable memory that holds data regardless of whether power is supplied. In particular, in the present embodiment, an authentication program 48 a is stored in the nonvolatile memory 48. The authentication program 48 a is an application program that defines processing executed on the portable device 40 side when electronic authentication or the like is performed by communication between the portable device 40 and the vehicle authentication device 20.

  In addition, when the first transmission / reception unit 41 receives the ultrasonic signal, the CPU 46 of the portable device 40 digitizes and records the received ultrasonic signal. Also, a reference signal for performing correlation processing on the digitized ultrasonic signal is registered in the nonvolatile memory 48 of the portable device 40. The reference signal has the same waveform as the request signal transmitted from the vehicular authentication device 20. In the correlation processing, the correlation between the waveform of the received ultrasonic signal and the reference signal is determined. And the place where the correlation with the reference signal is the highest among the received ultrasonic signals is the peak position.

  When the first transmission / reception unit 41 receives an ultrasonic signal highly correlated with the reference signal, the CPU 46 of the portable device 40 receives the ultrasonic wave transmitted from the first transmission / reception unit 41 from the vehicle authentication device 20. A response signal for responding to the signal is transmitted. At this time, the CPU 46 acquires the transmission time TS2 at which the response signal is transmitted.

  Further, when the waveform intensity at the peak position is equal to or higher than a preset threshold, the CPU 46 of the portable device 40 regards this ultrasonic signal as a signal that can be measured, and detects the time at the peak position as the reception time TR2. To do. Here, “intensity” is a parameter that can determine the degree of attenuation of the ultrasonic signal, and includes, for example, amplitude, sound pressure, energy density, and the like. When the intensity of the waveform at the peak position is less than a preset threshold, the ultrasonic signal is regarded as a signal that cannot be measured, but the time of the peak position or the like is estimated in order to estimate the moving direction of the portable device 40. Is detected as the reception time TR3.

  Next, with reference to FIG. 2, an example of an ultrasonic signal reception mode by the portable device 40 will be described. For example, when there is no shielding object between the portable device 40 and the first transmission / reception unit 26 of the vehicle authentication device 20 and the portable device 40 is present in the vicinity of the vehicle 10, the portable device 40 is A direct wave having an intensity equal to or greater than a threshold value is received from the authentication device 20. At this time, the CPU 46 regards the direct wave as a signal capable of ranging and calculates the reception time TR2.

  However, as shown in FIG. 2A, if there is a shielding object such as the user 100 between the portable device 40 and the first transmission / reception unit 26, even if the portable device 40 exists in the vicinity of the vehicle 10, The direct wave D is received by the portable device 40 while being blocked by the shielding object and attenuated by diffraction, absorption, or the like. Further, when there is a reflecting object made of a fixed object such as the wall 101 in the vicinity of the portable device 40, the reflected wave R transmitted from the first transmitting / receiving unit 26 and reflected by the reflecting object is attenuated compared to the direct wave D. Not received, that is, received by the portable device 40 with high intensity. 2 schematically illustrates the path of the reflected wave R received by the portable device 40.

  Further, as shown in FIGS. 2B and 2C, when the user 100 holding the portable device 40 approaches the vehicle 10, the direct wave D is transmitted and then received by the portable device 40. The time until is gradually shortened. On the other hand, since the user 100 moves away from the reflecting object such as the wall 101, the time from when the reflected wave R is transmitted to when it is received by the portable device 40 becomes gradually longer.

  The waveforms shown in FIGS. 3A to 3C are directions in which the user 100 as a shield approaches the vehicle 10 and moves away from the reflector such as the wall 101 as shown in FIGS. 6 illustrates the waveforms of the direct wave D and the reflected wave R received by the first transmission / reception unit 41 of the portable device 40 when moving to. 3A to 3C start from transmission times TSa, TSb, and TSc of ultrasonic signals from the vehicular authentication device 20.

  As shown in FIG. 3A, the portable device 40 first receives the attenuated direct wave D, and then receives the reflected wave R having a higher intensity than the direct wave D. Even in such a case, if the intensity of the direct wave D is equal to or greater than the threshold value, the direct wave D is regarded as a signal that can be measured, and the reflected wave R is excluded from the object of distance measurement. Is less than the threshold value, the direct wave D is regarded as a signal that cannot be measured, and the reflected wave R is regarded as a signal that can be measured.

  As shown in FIGS. 3B and 3C, the direct wave arrival time from the transmission time of the direct wave D to the reception time as the user 100 approaches the vehicle 10 and moves away from the reflecting object such as the wall 101. TD is shortened. Further, the reflected wave arrival time TR from the transmission time to the reception time of the reflected wave R becomes longer. Furthermore, the reception time difference ΔT between the reception time TR2 of the direct wave D and the reception time TR3 of the reflected wave R becomes longer.

  That is, when the direct wave D and the reflected wave R are detected, if at least one of the direct wave arrival time TD is shortened, the reflected wave arrival time TR is long, and the reception time difference ΔT is long is satisfied. There is a high possibility that the user 100 is moving in a direction approaching the vehicle 10. Conversely, when the direct wave D and the reflected wave R are detected, at least one of the direct wave arrival time TD, the reflected wave arrival time TR being shortened, and the reception time difference ΔT being shortened is satisfied. For example, there is a high possibility that the user 100 is moving away from the vehicle 10. In this embodiment, when it is determined that the reception time difference ΔT between the reception time TR2 of the direct wave D and the reception time TR3 of the reflected wave R is longer due to the vehicle authentication device 20 communicating with the portable device 40. It is assumed that the user 100 is moving in a direction approaching the vehicle 10. Note that the moving direction of the user 100 may be estimated using a plurality of the above-described conditions.

  In this embodiment, it is recognized by the vehicular authentication device 20 that the portable device 40 has received an ultrasonic signal that cannot be measured and an ultrasonic signal that can be measured, and the user 100 can recognize the vehicle 10. When it is determined that the mobile device 40 is moving in the direction approaching the vehicle, the determination distance for determining that the portable device 40 is in the vicinity of the vehicle is set large. Normally, this determination distance is, for example, the radius of a circular effective range centered on the vehicle 10 (for example, 2 m). Then, in order to perform distance measurement using the reflected wave R having a long path length, the determination distance is set larger than the initial value.

  As shown in FIG. 4, the reflected wave R <b> 1 that is reflected by the portable device 40 and then attenuated by being shielded by the user 100 or the like and the reflected wave that is repeatedly reflected between the wall 101 and the vehicle 10. It is also assumed that R2 is received. In such a case, the first transmission / reception unit 41 receives, for example, a direct wave D that cannot be measured, a reflected wave R1 that cannot be measured, and a reflected wave R2 that can be measured. Even in such a case, in the vehicular authentication device 20, the portable device 40 receives the direct wave D and the reflected wave R attenuated by the shield based on the radio wave signal transmitted from the portable device 40. Estimate that it is, and set a large determination distance.

Next, with reference to FIG. 5, the procedure of ranging by the vehicle authentication device 20 and the portable device 40 will be described.
In ranging, the control unit 22 of the vehicular authentication device 20 outputs a request signal requesting output of an ultrasonic signal from the portable device 40 via the first transmission / reception unit 41 (step S11). This request signal is an ultrasonic signal and includes, for example, a synchronization code, an ID code, a challenge code, and a distance measurement code. The synchronization code is a preamble, and the ID code is for specifying the vehicle 10. The challenge code is a signal that requests the portable device 40 to transmit identification information for identifying the portable device 40, and is used to generate an identification signal that includes the identification information. The distance measurement code is a code used for measuring the distance between the first transmission / reception unit 26 and the portable device 40.

  When receiving the ultrasonic signal transmitted by the vehicular authentication device 20, the portable device 40 generates and transmits an ultrasonic signal including a distance measurement code and a response code as a response signal to the ultrasonic signal (step S12). . Here, the distance measurement code is a code obtained by logically inverting each bit of the distance measurement code transmitted from the first transmission / reception unit 26 of the vehicular authentication device 20. The response code is generated by logically synthesizing a code (encryption key) having identification information for identifying the portable device 40 with the challenge code. This response code includes information for identifying the portable device 40, and serves as an input signal when the vehicular authentication apparatus 20 performs authentication to the effect that the portable device 40 is valid.

When determining that the response signal is received from the portable device 40 through correlation processing or the like, the vehicular authentication device 20 determines whether or not the response code included in the response signal is valid.
In addition, the CPU 46 of the portable device 40 performs the above-described correlation processing, and calculates a reception time TR2 that is the time of the peak position for a signal that can be measured. Further, the time difference Ti2 required from the reception time TR2 to the transmission time TS2 at which the response signal is transmitted is calculated. The timing for performing the correlation process may be before the transmission of the ultrasonic signal, and is not particularly limited.

  Further, as a result of the correlation processing, the CPU 46 of the portable device 40 calculates a reception time TR3 when a waveform that is highly correlated but cannot be measured, that is, a waveform whose intensity is less than the above threshold is detected.

  After outputting the ultrasonic signal, the CPU 46 of the portable device 40 transmits a radio wave signal including the time difference Ti2 (step S13). At this time, when the reception time TR3 is calculated, the difference between the reception time TR2 of the direct wave D and the reception time TR3 of the reflected wave R is calculated as the reception time difference ΔT, and this reception time difference ΔT is included in the radio signal.

When receiving the radio signal, the control unit 22 of the vehicular authentication device 20 uses the time difference Ti2 included in the radio signal to use the first transmission / reception unit 26 of the vehicular authentication device 20 and the first of the portable device 40. The relative distance from the transmitter / receiver 41 is calculated. At this time, the relative distance L between the first transmission / reception unit 26 of the vehicle 10 and the first transmission / reception unit 41 of the portable device 40 is calculated based on the following mathematical formula. Ti1 is the time difference between the transmission time TS1 at which the request signal is transmitted from the first transmission / reception unit 26 of the vehicular authentication device 20 and the reception time TR1 at which the response signal is received from the portable device 40, and is “C”. Is the speed of sound. Note that the speed of sound may be variable depending on the temperature.

L = {(Ti1-Ti2) / 2} .C

Next, with reference to FIG. 6, the operation from when the portable device 40 receives a request signal until it transmits a radio wave signal will be described in detail.

  The CPU 46 of the portable device 40 waits for reception of the ultrasonic signal that is the request signal (step S21), and determines that the ultrasonic signal has been received (step S21: YES), the received ultrasonic signal and the reference signal are obtained. Correlation processing is performed to confirm the correlation while shifting on the time axis (step S22).

  Then, the CPU 46 of the portable device 40 determines whether or not the ultrasonic signal is an ultrasonic signal transmitted from the vehicular authentication device 20 based on the result of the correlation process (step S23). If it is determined that the ultrasonic signal is not transmitted from the vehicular authentication device 20 (step S23: NO), the process returns to step S21.

  When it is determined that the ultrasonic signal is an ultrasonic signal transmitted from the vehicular authentication device 20 (step S23: YES), the portable device 40 transmits a response signal (step S24). Then, the CPU 46 of the portable device 40 determines whether or not the received ultrasonic signal is a signal capable of ranging based on the intensity of the waveform at the peak position detected by the correlation process (step S25). Here, as described above, it is determined whether or not the intensity of the waveform at the peak position is greater than or equal to the threshold value.

  When it is determined that the received ultrasonic signal is not a signal that can be measured, such as when the direct wave D shielded by the user 100 is received (step S25: NO), the CPU 46 of the portable device 40 determines the time of the peak position. Is set as the reception time TR3 (step S30), the reception time TR3 is stored in the RAM 50 or the like, and the process returns to step S21. In this embodiment, steps S21 to S25 and step S30 are repeated until an ultrasonic signal that can be measured is detected. Therefore, when a plurality of waveforms that are highly correlated and cannot be measured are detected, a plurality of waveforms are detected. The reception time TR3 is stored in the RAM 50 or the like.

  On the other hand, when it is determined that the received ultrasonic signal is a signal that can be measured, such as when the direct wave D or the reflected wave R that is not attenuated by the shield is received (step S25: YES), the CPU 46 of the portable device 40 The time at the peak position is set as a reception time TR2 used for distance measurement (step S26).

  Then, the CPU 46 of the portable device 40 calculates a time difference Ti2 between the reception time TR2 and the transmission time TS2 at which the response signal is transmitted (step S27), and transmits a radio wave signal including the time difference Ti2 (step S28). . The time difference Ti2 is a time lag between the timepiece built in the vehicular authentication device 20 and the timepiece built in the portable device 40, and until the CPU 46 detects it after the transmission / reception unit 42 of the portable device 40 actually receives the ultrasonic signal. The delay time is included. At this time, when the reception time TR3 is detected in addition to the reception time TR2, the reception time difference ΔT between the reception time TR2 and the reception time TR3 is also included in the radio signal and transmitted. When the radio wave signal is transmitted, the process returns to step S21 to wait for reception of the ultrasonic signal.

Next, with reference to FIG. 7, the operation after the vehicular authentication device 20 receives the radio signal will be described in detail.
The control unit 22 of the vehicular authentication device 20 waits for reception of a radio signal (step S40), and when receiving the radio signal (step S40: YES), stores the information included in the radio signal in its storage unit. Further, the control unit 22 calculates the relative distance L by the above-described procedure (see FIG. 5) based on the time difference Ti2 included in the radio signal (step S41).

  Further, the control unit 22 determines whether or not the reception time difference ΔT is included in the radio wave signal, so that the portable device 40 receives the signal that can be measured after receiving the signal that cannot be measured. It is determined whether or not there is (step S42).

  For example, when only the direct wave D that is not attenuated by the shield is received, the control unit 22 does not receive both the signal that the portable device 40 cannot measure and the signal that can be measured in that order. (Step S42: NO), the control unit 22 sets the determination distance to an initial value (for example, 2 m) (step S50). Then, it is determined whether or not the relative distance calculated in step S41 is equal to or less than the determination distance (step S51). If the relative distance is equal to or smaller than the determination distance (step S51: YES), it is determined that the portable device 40 is within an effective range having the radius of the initial determination distance (step S52), and the relative distance is greater than the determination distance. If it is larger (step S51: NO), it is determined that the portable device 40 is outside the effective range (step S53).

  If the control unit 22 determines that the portable device 40 has received a signal that can be measured after receiving the signal that cannot be measured (step S42: YES), the portable device 40 is based on a plurality of reception times TR3. It is determined whether or not the vehicle 10 is approaching (step S43). At this time, the control unit 22 reads the reception time difference ΔT stored in its own storage unit, and when a predetermined number of reception time differences ΔT that are two or more are stored, the reception time difference ΔT tends to increase. Judge whether there is. If the reception time difference ΔT tends to increase, it is determined that the portable device 40 is approaching. When the number of stored reception time differences ΔT is less than a predetermined number, when the reception time difference ΔT is decreased, or when the reception time difference ΔT does not change, the portable device 40 is at least in the direction of approaching the vehicle 10. Judge that it has not moved.

  If it is determined that the portable device 40 is approaching the vehicle 10 (step S43: YES), the control unit 22 reads the determination distance from its own storage unit and determines whether the determination distance is an initial value (step). S44). When the determination distance is the initial value (step S44: YES), the control unit 22 sets the determination distance larger than the initial value, for example, 5 m (step S45).

  After setting the determination distance to be large, the control unit 22 determines whether or not the relative distance L calculated in step S41 is within the determination distance (step S46). If it is determined that the distance is within the determination distance (step S46: YES), it is determined that the portable device 40, that is, the user 100 is within the effective range (step S47). If it is determined that the distance is greater than the determination distance (step S46: NO), it is determined that the portable device 40, that is, the user 100 exists outside the effective range (step S49). Also, when it is determined in step S43 that the portable device 40 is not approaching the vehicle 10 (step S43: NO), it is determined that the portable device 40, that is, the user 100 exists outside the effective range (step S49).

  As described above, when it is determined whether or not the portable device 40 is within the effective range, the control unit 22 determines whether or not the distance measurement is completed (step S48). The distance measurement end condition is that the door is unlocked, the engine is started, or a predetermined operation on the portable device 40 is performed. If the distance measurement is not finished (step S48: NO), the process returns to step S40. If the control unit 22 determines that the distance measurement is to be ended (step S48: YES), the process ends.

  As described above, when the user 100 approaches the vehicle 10 after the determination distance is set to be larger than the initial value and the portable device 40 is determined to be within the effective range, the path of the reflected wave R becomes long. The relative distance L calculated based on the reflected wave R may exceed the determination distance. For this reason, if the user 100 continues to approach the vehicle 10 after the determination distance is set to be large, it is determined that the portable device 40 is within the effective range. Specifically, when it is determined in step S44 that the determination distance is not the initial value (step S44: NO), the control unit 22 determines that the portable device 40 is within the effective range (step S47). For this reason, although the portable device 40 actually exists in the vicinity of the vehicle 10, it is suppressed that the portable device 40 is outside the effective range.

As described above, according to the present embodiment, the following effects can be obtained.
(1) According to the above configuration, if the portable device 40 receives an ultrasonic signal that cannot be measured before receiving an ultrasonic signal that can be measured, the portable device 40 cannot perform the distance measurement. It is estimated that the ultrasonic signal is the direct wave D attenuated by the shielding object, and the ultrasonic signal that can be measured is the reflected wave R. In addition, when performing distance measurement based on a sound wave signal that can be measured, a determination distance for determining whether the portable device 40 is present in the vicinity of the vehicular authentication device is set larger than the initial value. Although the portable device 40 actually exists within the effective range, it is suppressed that the portable device 40 is determined to be outside the effective range. Therefore, for example, when the user 100 exists in the vicinity of the door of the vehicle 10, a situation in which the door lock is not released can be suppressed.

  (2) When the vehicular authentication device 20 receives an ultrasonic signal that cannot be measured before receiving an ultrasonic signal that can be measured, the vehicle authentication device 20 measures the reception time of the ultrasonic signal that cannot be measured and the measurement time. The moving direction of the portable device 40 is determined based on the deviation of the time difference from the reception time of the ultrasonic signal capable of being separated. Then, the vehicular authentication device 20 sets the determination distance to be large only when it is determined that the portable device 40 is approaching the vehicle 10, and is determined when the portable device 40 is determined to be away from the vehicle 10. Set a smaller distance. For this reason, it can be judged appropriately whether a portable machine exists in the vicinity of vehicles.

  (3) If the vehicle authentication device 20 determines that the portable device 40 continues to approach the vehicle 10 after setting the determination distance to be larger than the initial value, the portable device 40 determines that the portable device 40 continues to approach the vehicle 10. It is judged that it exists in the vicinity. For this reason, although the portable device 40 exists in the vicinity of the vehicle 10, it is possible to suppress erroneous determination when the relative distance calculated based on the sound wave signal that can be measured exceeds the determination distance.

  (4) The portable device 40 performs a correlation process for determining the correlation between the received ultrasonic signal and the reference signal, and when there is a peak position where the correlation between the received ultrasonic signal and the reference signal is high. Then, it is determined whether or not the intensity of the signal at the peak position is greater than or equal to a threshold value. Then, an ultrasonic signal whose peak position intensity is equal to or greater than a threshold is set as an ultrasonic signal that can be measured. Accordingly, the correlation between the received ultrasonic signal and the reference signal is determined, and it is then determined whether or not the received ultrasonic signal can be measured. Whether or not 40 exists in the vicinity of the vehicle 10 can be appropriately determined.

(Other embodiments)
In addition, each said embodiment can also be implemented with the following forms.
In the above embodiment, the vehicle authentication device 20 determines whether or not the user 100 is approaching the vehicle 10 based on the reception time difference ΔT received from the portable device 40. However, the portable device 40 transmits the transmission time TS1. The determination may be made based on the reception times TR2, TR3 and the like. At this time, information indicating whether or not the user 100 is approaching the vehicle 10 is transmitted from the portable device 40 to the vehicle authentication device 20.

  In the above embodiment, whether or not the user 100 is approaching the vehicle 10 is determined based on the reception time difference ΔT received from the portable device 40. Other than this, the deviation of the arrival time from the output of the ultrasonic signal that cannot be measured until it is received, or the deviation of the arrival time from the output of the ultrasonic signal that can be measured to the reception thereof. Based on the shift, it may be determined whether or not the portable device 40 is approaching the vehicle 10.

  In the above embodiment, the distance is measured by transmitting the ultrasonic wave from both directions (the vehicle authentication device 20 and the portable device 40). However, even if the distance is measured by transmitting the ultrasonic wave from one direction. Good. In this case, an ultrasonic signal is transmitted from the vehicular authentication device 20, and the portable device 40 detects a reception time that is a time when the ultrasonic signal is received, and transmits the reception time by including the reception time in the radio signal. The vehicular authentication device 20 basically calculates the distance by multiplying the difference between the reception time and the transmission time of the ultrasonic signal by the speed of sound C.

  In the above embodiment, the portable device 40 transmits a response signal and a radio signal only when receiving a signal capable of ranging. In addition to this, at least one of the response signal and the radio signal may be transmitted every time an ultrasonic signal with high correlation is received regardless of whether or not the waveform can be measured. In this case, the radio signal includes the reception time and intensity of the signal. Then, the vehicle authentication device 20 determines the reception status of the portable device 40 based on the radio wave signal, the portable device 40 receives the attenuated direct wave D and the reflected wave R, and the portable device 40 authenticates the vehicle. When it is determined that the device 20 is approaching, the determination distance is set larger than the initial value.

  In the above embodiment, whether or not the ultrasonic signal can be measured is determined by comparing the intensity of the ultrasonic signal received by the first transmission / reception unit 41 with a threshold value. It may be determined based on the parameters.

In the above embodiment, authentication and distance measurement of the portable device 40 are performed using an ultrasonic signal. However, authentication of the portable device 40 may be performed using a radio wave signal and distance measurement may be performed using an ultrasonic signal.
In the above embodiment, the vehicular authentication device 20 performs authentication, distance measurement, and change of the effective range, but the portable device 40 performs at least one of authentication, distance measurement, and determination distance change. May be.

  The vehicular authentication device 20 may transmit an ultrasonic signal other than a signal including a synchronization code, an ID code, a challenge code, and a distance measurement code. The portable device 40 may transmit an ultrasonic signal other than a signal including a distance measurement code and a response code.

  In the above embodiment, the vehicular authentication device 20 is provided with the second transmission / reception unit 27 for transmitting / receiving radio wave signals, and the portable device 40 is provided with the second transmission / reception unit 42 for transmitting / receiving radio wave signals. This may be omitted in the case where transmission is performed by ultrasonic waves.

The vehicle authentication device 20 may be connected to an engine control unit or the like in addition to the door lock system 32.
In the above embodiment, an ultrasonic signal having a frequency higher than that of the audible frequency band (20 Hz or more and less than 20 kHz) is used as the sound wave signal.

  The vehicle authentication device 20 only needs to include at least a control unit 22 that performs distance measurement, and the first transmission / reception unit 26 and the second transmission / reception unit 27 use a common device provided in the vehicle 10. May be.

  -When measuring the relative distance between the vehicle authentication device 20 and the portable device 40, the vehicle authentication device 20 outputs an ultrasonic signal in response to the ultrasonic signal transmitted by the portable device 40, The relative distance may be calculated on the portable device 40 side. Alternatively, the transmission time of the ultrasonic signal from the portable device 40 and the reception time of the ultrasonic signal from the vehicular authentication device 20 may be transmitted to the vehicular authentication device 20 by a radio wave signal or the like.

  When the vehicular authentication device 20 determines that the portable device 40 has received both a sound wave signal that cannot be measured and a sound wave signal that can be measured in that order, the portable device 40 receives the signal from the vehicle 10. The determination distance may be made larger than the initial value without determining whether or not the vehicle is approaching.

  DESCRIPTION OF SYMBOLS 10 ... Vehicle, 20 ... Vehicle authentication apparatus, 22 ... Control part, 26 ... 1st transmission / reception part, 27 ... 2nd transmission / reception part, 32 ... Door lock system, 40 ... Portable machine, 41 ... 1st transmission / reception part 42 ... second transmission / reception unit, 44 ... telephone line communication unit, 46 ... CPU, 48 ... nonvolatile memory, 48a ... authentication program, 50 ... RAM, 52 ... input / output port, 100 ... user, 101 ... wall, D: Direct wave, R, R1, R2: Reflected wave.

Claims (5)

In a vehicle authentication system that performs electronic authentication based on communication between a vehicle authentication device mounted on a vehicle and a portable device,
A signal output unit for outputting a sound wave signal;
A signal receiving unit for receiving the sound wave signal;
A distance measuring unit that calculates a relative distance between the vehicle authentication device and the portable device based on a time from when the sound wave signal is output until it is received;
A determination unit that determines that the portable device is present in the vicinity of the vehicular authentication device if the relative distance is within a predetermined determination distance;
The determination unit is configured to set the determination distance large when the signal reception unit receives a sound wave signal that cannot be measured before receiving a sound wave signal that can be measured. Vehicle authentication system.   When the signal receiving unit receives a sound wave signal that cannot be measured before receiving a sound wave signal that can be measured, the determination unit receives the time when the sound wave signal that cannot be measured and the distance measurement The moving direction of the portable device with respect to the vehicle is determined based on a deviation of a time difference from the reception time of a possible sound wave signal, and the determination distance is set large when it is determined that the portable device is approaching the vehicle. The vehicle authentication system according to claim 1.   When the signal receiving unit receives a sound wave signal that cannot be measured before receiving a sound wave signal that can be measured, the determination unit receives the sound wave signal that cannot be measured after the sound wave signal is output. Determining the direction of movement of the portable device relative to the vehicle based on a deviation in arrival time until the vehicle is received, or a deviation in arrival time from when the sound wave signal capable of ranging is output to reception, and the portable device The vehicle authentication system according to claim 1, wherein the determination distance is set to be large when it is determined that the vehicle is approaching the vehicle.   The determination unit determines the moving direction of the portable device relative to the vehicle after setting the determination distance larger than an initial value, and the portable device is in the vehicle while the portable device is approaching the vehicle. The vehicle authentication system according to claim 1, wherein the vehicle authentication system is determined to be present in the vicinity of the vehicle authentication device.   The signal receiving unit determines a correlation between the received sound wave signal and a reference signal having a waveform output from the signal output unit, and has a peak position where the correlation between the received sound wave signal and the reference signal is high. If present, it is determined whether or not the intensity of the signal at the peak position is greater than or equal to a threshold value, and an acoustic wave signal having the intensity of the peak position is greater than or equal to the threshold value is set as a sound wave signal capable of ranging. 5. The vehicle authentication system according to any one of 4 above.

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