JP5460550B2 - Electronic key system - Google Patents

Description

  The present invention relates to an electronic key system.

  In a conventional electronic key system, when an electronic key carried by a user enters a communication area formed around a vehicle or a house, the door can be locked and unlocked through wireless communication between the electronic key and the vehicle. It is configured.

  For example, in the electronic key system described in Patent Document 1, the communication area is set as follows. That is, the electronic key detects the received electric field strength of the radio signal from the vehicle and transmits the detection result to the vehicle through wireless communication. The vehicle compares the received electric field strength of the radio signal acquired through this radio communication with a preset threshold value. When the vehicle determines that the received electric field strength of the radio signal is greater than or equal to the threshold, the vehicle is permitted to lock and unlock the vehicle door through mutual authentication with the electronic key, assuming that the electronic key exists in the communication area. To do. When the vehicle determines that the received electric field strength of the wireless signal is less than the threshold value, the vehicle does not perform mutual authentication with the electronic key, assuming that the electronic key exists outside the communication area. Thus, the size of the communication area is determined based on the threshold value. Specifically, the communication area is set smaller as the threshold value increases.

JP 2007-118899 A

  By the way, noise may be applied to the wireless signal transmitted from the vehicle to the electronic key depending on the surrounding environment of the vehicle. For example, the reception electric field strength of a radio signal becomes large due to the influence of noise, and even if it is outside the original communication area in an environment where there is no noise, the reception electric field strength exceeds the threshold value, and between the electronic key and the vehicle. There is a risk of mutual authentication. Thus, the communication area may become larger than the original communication area due to the influence of noise. In this case, there is a possibility that the vehicle door can be unlocked through an electronic key carried by the user even though the user is located far away from the vehicle.

  The present invention has been made in view of such circumstances, and an object thereof is to provide an electronic key system in which the size of a communication area is appropriately maintained even in a noisy environment.

Hereinafter, means for achieving the above-described object and its operation and effects will be described.
According to the first aspect of the present invention, control of the control target is executed through wireless communication between the control target and the electronic key, and the reception electric field strength of the radio signal received by the electronic key from the control target is first. In the electronic key system in which the control of the control target is prohibited, assuming that the electronic key exists outside the communication area when less than the threshold value, the wireless signal has an on time and a signal level at which the signal level oscillates. An off time that is fixed to zero is set, provided in the electronic key, and a detection unit that detects the received electric field strength of the radio signal a plurality of times over the on time and the off time, and a detection result of the detection unit The electronic key remains in the communication area even if the reception electric field strength of the wireless signal is equal to or higher than the first threshold when it is determined that noise is applied to the wireless signal. As not obtained confirmation that exist in, and that and a determination unit that prohibits control of the control object as its gist.

  According to this configuration, the on time and the off time are set in the radio signal transmitted from the controlled object to the electronic key. The signal level of the radio signal vibrates during the on time, and the signal level of the radio signal is fixed to zero during the off time. The detection unit detects the received electric field strength of the radio signal a plurality of times over the on time and the off time. The determination unit determines whether noise is applied to the radio signal based on the detection result of the detection unit.

  Here, in a configuration in which the on time and the off time are not set in the radio signal, in a situation where noise is applied to the radio signal, the reception electric field strength of the radio signal is reduced even though the electronic key exists outside the communication area. There is a risk that it is determined that the electronic key exists in the communication area when the threshold value is greater than or equal to the first threshold. In that respect, according to the above configuration, it is possible to determine whether noise is applied to the radio signal based on the received electric field strength at the on time and the off time. This is because, in a situation where there is no noise, the received electric field strength is zero during the off time, but when the noise is applied, the received electric field strength similar to the on time is maintained even during the off time. . When it is determined that noise is applied to the radio signal, it is determined that the electronic key is present in the communication area, and control of the control target is prohibited. Therefore, expansion of the communication area under a noise environment is suppressed, and the size of the communication area is appropriately maintained.

  According to a second aspect of the present invention, in the electronic key system according to the first aspect of the present invention, the electronic key system further includes a calculation unit that calculates an average value of the received electric field strengths in the radio signal detected through the detection unit, The gist is to determine that noise is applied to the radio signal when it is determined that the average value is equal to or greater than a second threshold value that is set to be greater than the first threshold value.

  According to this configuration, when the calculated average value is equal to or greater than the second threshold value, it is determined that noise is applied to the radio signal. In this manner, it is possible to easily determine whether noise is applied to the radio signal through the average value of the received electric field strengths over the on time and the off time in the radio signal.

  According to a third aspect of the present invention, in the electronic key system according to the second aspect, the determination unit is provided in the control target, the arithmetic unit is provided in the electronic key, and the electronic key is the radio signal. Is received, the ACK signal including the average value calculated through the arithmetic unit is transmitted, and the determination unit indicates that the average value included in the ACK signal received by the control target is greater than or equal to the second threshold value. The gist of the determination is that it is determined that noise is applied to the radio signal.

  According to the configuration, the determination unit is provided in the control target. Therefore, the electronic key can be configured more compactly than when the determination unit is provided in the electronic key. Here, since the electronic key is required to be more compact than the control target from the viewpoint of portability, this is particularly beneficial.

  According to a fourth aspect of the present invention, in the electronic key system according to the second aspect, the determination unit and the calculation unit are provided in the electronic key, and the determination unit calculates the average value calculated through the calculation unit. Is determined to be greater than or equal to the first threshold value and less than the second threshold value, an ACK signal is transmitted to the control target, and the average value is determined to be outside the range The transmission of the ACK signal to the control target is restricted, and when the control target receives the ACK signal, the mutual authentication with the electronic key is continued and the control is executed when the mutual authentication is established. The gist is to do.

  According to this configuration, the determination unit and the calculation unit are provided in the electronic key, and an ACK signal is transmitted to the control target when the average value is equal to or greater than the first threshold and less than the second threshold. Further, when the average value is out of the range, the ACK signal is not transmitted to prohibit the control of the control target. Therefore, compared with the case where a determination part is provided in a control object, the power consumption concerning transmission of an ACK signal can be reduced.

  According to the present invention, in the electronic key system, the size of the communication area can be appropriately maintained even in a noisy environment.

The block diagram of the electronic key system in 1st Embodiment. The signal diagram transmitted between the vehicle-mounted apparatus and electronic key in 1st Embodiment. FIG. 3 is a signal diagram of a wake signal and an RSSI measurement signal in the first embodiment. The top view of the vehicle which showed the communication area outside a vehicle in 1st Embodiment. The graph which shows the 1st and 2nd threshold value in 1st Embodiment. The control program which the electronic key control part in a 1st embodiment performs. The control program which the determination part in 1st Embodiment performs.

(First embodiment)
Hereinafter, a first embodiment in which an electronic key system according to the present invention is embodied will be described with reference to FIGS.

  As shown in FIG. 1, the electronic key system 1 includes an electronic key 10 possessed by a driver of the vehicle 2 and an in-vehicle device 20 disposed in the vehicle 2. Mutual communication is performed between the electronic key 10 and the in-vehicle device 20 through a wireless signal.

  First, a radio signal transmitted and received between the in-vehicle device 20 and the electronic key 10 will be briefly described with reference to FIG. The in-vehicle device 20 transmits a wake signal Swk and an RSSI measurement signal Srs around the vehicle 2. When receiving the wake signal Swk and the RSSI measurement signal Srs, the electronic key 10 transmits an ack signal Sac. When receiving the ACK signal Sac, the in-vehicle device 20 transmits a vehicle ID signal Svi. The electronic key 10 transmits the key ID signal Sid after confirming the validity of the received vehicle ID signal Svi. The in-vehicle device 20 permits the locking and unlocking of the vehicle door when the validity of the received key ID signal Sid is confirmed. Hereinafter, specific configurations and operations of the electronic key 10 and the in-vehicle device 20 will be described.

<Electronic key 10>
As shown in FIG. 1, the electronic key 10 includes an electronic key control unit 11 configured by a computer unit including a CPU and the like. The electronic key control unit 11 is electrically connected to an LF receiving unit 12 that receives a radio signal in the LF (Low Frequency) band and a UHF transmission unit 13 that transmits a radio signal in the UHF (Ultra High Frequency) band. Has been.

  When the LF receiver 12 receives the LF band wake signal Swk and the RSSI measurement signal Srs transmitted from the in-vehicle device 20 via the receiving antenna 12a, the LF receiver 12 demodulates these signals into pulse signals, and the demodulated demodulated signals are demodulated. Output to the electronic key control unit 11.

  The electronic key control unit 11 includes a nonvolatile memory 11a, and a key ID code unique to the electronic key 10 and a vehicle ID code unique to the vehicle 2 are stored in the memory 11a. When the electronic key control unit 11 recognizes the wake signal Swk, the electronic key control unit 11 generates an ack signal Sac. The ACK signal Sac is added with RSSI information described later based on the RSSI measurement signal Srs. Then, the electronic key control unit 11 outputs an ACK signal Sac to the UHF transmission unit 13. The UHF transmission unit 13 modulates the ACK signal Sac into a UHF band signal, and transmits the modulated signal to the in-vehicle device 20 as a radio signal via the transmission antenna 13a. In response to the ACK signal Sac, the vehicle-mounted device 20 transmits an LF band vehicle ID signal Svi. When receiving the vehicle ID signal Svi via the receiving antenna 12a, the LF receiving unit 12 demodulates the vehicle ID signal Svi into a pulse signal and outputs the demodulated demodulated signal to the electronic key control unit 11. When the demodulated signal of the vehicle ID signal Svi is input from the LF receiving unit 12, the electronic key control unit 11 recognizes the vehicle ID code included in the vehicle ID signal Svi. Then, the electronic key control unit 11 collates the vehicle ID code included in the vehicle ID signal Svi with the vehicle ID code stored in the memory 11a. When the verification of the vehicle ID code is established, the electronic key control unit 11 generates a key ID signal Sid including the key ID code stored in the memory 11a, and outputs this signal to the UHF transmission unit 13. The UHF transmitter 13 modulates the key ID signal Sid and transmits the key ID signal Sid to the in-vehicle device 20 as a UHF band radio signal via the transmission antenna 13a.

  The LF receiving unit 12 includes an RSSI detection circuit 16. The RSSI detection circuit 16 detects the received signal strength RSSI (Receive Signal Strength Indication) of the RSSI measurement signal Srs at regular intervals. The RSSI detection circuit 16 recognizes the reception period of the RSSI measurement signal Srs based on the reception timing of the wake signal Swk, and detects RSSI in the reception period.

  Specifically, as shown in FIG. 3, RSSI is detected at times t11 to tn in the reception period of the RSSI measurement signal Srs. Here, an on time Ton and an off time Toff are set in the RSSI measurement signal Srs. The on time Ton and the off time Toff are set to the same time, and are set in the order of the on time Ton and the off time Toff. The signal level oscillates with a constant amplitude during the on time Ton, and the signal level is fixed to zero during the off time Toff. The electronic key control unit 11 calculates an average value Vav of RSSI at each time t11 to tn set over the on time Ton and the off time Toff. The electronic key control unit 11 includes the average value Vav as RSSI information in the ACK signal Sac.

  By setting the ON time Ton and the OFF time Toff in the RSSI measurement signal Srs, it is possible to determine whether noise is applied to the RSSI measurement signal Srs based on the average value Vav. Specifically, in a situation where no noise is applied to the RSSI measurement signal Srs, each RSSI detected in the off time Toff is zero, and thus the average value Vav is lowered accordingly. On the other hand, in a situation where noise is applied to the RSSI measurement signal Srs, each RSSI detected in the off time Toff also detects the same value as the on time Ton. Thereby, the average value Vav is raised. Therefore, it is possible to determine whether noise is applied to the RSSI measurement signal Srs based on the average value Vav. In this example, this determination is performed on the vehicle side through a second threshold, which will be described later.

  Here, in order to detect the RSSI of the RSSI measurement signal Srs as described above, the electronic key control unit 11 needs to recognize the wake signal Swk. In other words, if the electronic key control unit 11 does not recognize the wake signal Swk, the reception period of the RSSI measurement signal Srs cannot be recognized, and the RSSI of the RSSI measurement signal Srs is not detected. Therefore, the premise that noise applied to the RSSI measurement signal Srs is a problem is that the noise does not affect the recognition of the wake signal Swk in the electronic key control unit 11.

  Specifically, as shown by the broken line in FIG. 3, noise smaller than the amplitude of the signal level is applied when the wake signal Swk is received. In this case, even if noise is applied to the wake signal Swk, the electronic key control unit 11 can recognize the wake signal Swk through the LF reception unit 12. In the reception period of the RSSI measurement signal Srs, noise larger than the noise amplitude in the reception period of the wake signal Swk is applied. In this case, as described above, the RSSI similar to the on-time Ton is detected also in the off-time Toff. Further, even when application of noise smaller than the signal level of the wake signal Swk is continued until the reception period of the RSSI measurement signal Srs, each RSSI in the off time Toff becomes a value close to each RSSI in the on time Ton. . Therefore, the average value Vav is similarly increased.

<In-vehicle device 20>
The in-vehicle device 20 includes an in-vehicle control unit 21 configured by a computer unit including a CPU and the like. The in-vehicle control unit 21 includes a nonvolatile memory 21a, and the memory 21a stores the same key ID code and vehicle ID code as the code stored in the memory 11a of the electronic key 10. The in-vehicle control unit 21 is electrically connected to an in-vehicle transmission unit 22, an in-vehicle reception unit 24, a door handle sensor 32, a lock switch 33, and a door lock device 34.

  The in-vehicle control unit 21 generates the wake signal Swk and the RSSI measurement signal Srs, and outputs these signals to the in-vehicle transmission unit 22. The in-vehicle transmission unit 22 modulates the wake signal Swk and the RSSI measurement signal Srs from the in-vehicle control unit 21, and transmits these modulated signals as LF band radio signals via the transmission antenna 22a. The wake signal Swk and the RSSI measurement signal Srs are transmitted to the periphery of the vehicle 2 at regular intervals.

  Specifically, as shown enlarged in the circle of FIG. 4, the transmission antenna 22a is built in the outside door handle 4 of each vehicle door 5, and the bottom centered on the transmission antenna 22a is the front and rear of the vehicle. The wake signal Swk and the RSSI measurement signal Srs are transmitted to the semicircular communication area 30 along the direction.

  As shown in FIG. 1, the in-vehicle receiving unit 24 receives the ACK signal Sac transmitted from the electronic key 10 via the receiving antenna 24a, demodulates the ACK signal Sac into a pulse signal, and converts the demodulated signal into the pulse signal. Output to the in-vehicle controller 21.

  Here, the in-vehicle receiving unit 24 includes a determination unit 25. The determination unit 25 includes a non-volatile memory 25a, and a first threshold value Vth1 and a second threshold value Vth2 are stored in the memory 25a. When the determination unit 25 recognizes the RSSI information included in the ACK signal Sac, the determination unit 25 compares the average value Vav that is the RSSI information with the first threshold value Vth1 and the second threshold value Vth2 stored in the memory 25a. As shown in FIG. 5, the position and environment of the electronic key 10 are recognized based on the comparison between the average value Vav and the first threshold value Vth1 and the second threshold value Vth2. Specifically, when the determination unit 25 determines that the average value Vav is greater than or equal to the first threshold value Vth1 and less than the second threshold value Vth2, the electronic key 10 is present in the communication area 30. The communication permission signal is output to the in-vehicle control unit 21.

  When receiving the communication permission signal, the in-vehicle control unit 21 generates a vehicle ID signal Svi including a vehicle ID code stored in its own memory 21 a and transmits the generated vehicle ID signal Svi to the in-vehicle transmission unit 22. To do. The in-vehicle transmission unit 22 modulates the vehicle ID signal Svi from the in-vehicle control unit 21, and transmits the modulated signal as an LF band radio signal via the transmission antenna 22a.

  Here, the first threshold value Vth1 is set based on the desired size of the communication area 30. For example, when it is desired to increase the communication area 30, the first threshold value Vth1 is set smaller. When the communication area 30 is desired to be reduced, the first threshold value Vth1 is set larger. Therefore, when the determination unit 25 determines that the average value Vav is less than the first threshold value Vth1, the determination unit 25 outputs a communication prohibition signal to the in-vehicle control unit 21 assuming that the electronic key 10 exists outside the communication area 30. When receiving the communication prohibition signal, the in-vehicle control unit 21 does not transmit the subsequent vehicle ID signal Svi.

  As described above, when noise is applied to the RSSI measurement signal Srs, the average value Vav increases. The second threshold value Vth2 is set empirically by comparing the average value Vav corresponding to the presence or absence of noise applied to the RSSI measurement signal Srs. Therefore, when the determination unit 25 determines that the average value Vav is equal to or larger than the second threshold value Vth2, the determination unit 25 determines that noise is applied to the RSSI measurement signal Srs, and sends a communication prohibition signal to the in-vehicle control unit 21. Output. When receiving the communication prohibition signal, the in-vehicle control unit 21 does not transmit the subsequent vehicle ID signal Svi. Thus, for example, when the electronic key 10 is present at the position 51 indicated by a cross in FIG. 4, even if the average value Vav is equal to or greater than the first threshold value Vth1 due to the influence of noise, the average value Vav is the same. Since the second threshold Vth2 is also exceeded, the processing after the vehicle ID signal Svi transmission is not performed between the electronic key 10 and the vehicle-mounted device 20 at the position 51. Therefore, the size of the communication area 30 is appropriately maintained.

  As described above, the key ID signal Sid is transmitted when collation of the vehicle ID code is established in the electronic key 10 that has received the vehicle ID signal Svi. When the in-vehicle controller 21 receives the key ID signal Sid through the in-vehicle receiver 24 or the like, the in-vehicle controller 21 collates the key ID code included in the key ID signal Sid with the key ID code stored in the memory 21a. When the verification of the key ID code is established, the in-vehicle control unit 21 enters a locking / unlocking permission state.

  The door handle sensor 32 is provided on the outside door handle 4 as shown enlarged in the circle of FIG. The door handle sensor 32 detects contact of the user with the outside door handle 4 and outputs a signal indicating that to the vehicle-mounted control unit 21. The lock switch 33 is provided on the outside door handle 4 and outputs an operation signal to that effect to the in-vehicle control unit 21 when pushed.

  When the vehicle-mounted control unit 21 recognizes that the user has touched the outside door handle 4 through the door handle sensor 32 in the unlocking and unlocking permitted state, the vehicle-mounted control unit 21 unlocks the vehicle door through the door lock device 34. Moreover, the vehicle-mounted control part 21 will lock a vehicle door, if the lock switch 33 recognizes that the push operation was carried out in the locking / unlocking permission state.

  Next, a control program related to the calculation of the average value Vav executed by the electronic key control unit 11 will be described. The program is executed according to the flowchart of FIG. 6 and started when the wake signal Swk is recognized.

  First, the RSSI at each time t11 to tn in the RSSI measurement signal Srs is recognized through the RSSI detection circuit 16 (S101). Then, an average value Vav is calculated based on these RSSIs (S102). Next, the calculated average value Vav is included in the ACK signal Sac, and the ACK signal Sac is transmitted through the UHF transmitter 13 (S103). This is the end of the program.

  When the determination unit 25 recognizes the ACK signal Sac transmitted in step S103, the determination unit 25 starts a control program for determining the average value Vav. The program is stored in the memory 25a and executed according to the flowchart of FIG.

  When the ACK signal Sac is recognized, it is determined whether or not the average value Vav included in the signal as RSSI information is equal to or greater than the first threshold value Vth1 and less than the second threshold value Vth2 (S201). ). When it is determined that the average value Vav is within the above range (YES in S201), a communication permission signal is output to the in-vehicle control unit 21 (S202). Then, the control program is terminated. Thereby, the vehicle-mounted control unit 21 can transmit the vehicle ID signal Svi.

  On the other hand, when it is determined that the average value Vav is not less than the first threshold value Vth1 and less than the second threshold value Vth2 (NO in S201), the electronic key 10 exists outside the communication area 30, or Assuming that noise is applied to the RSSI measurement signal Srs, a communication prohibition signal is output to the in-vehicle controller 21 (S203). Then, the control program is terminated. Thus, when the electronic key 10 is outside the communication area 30 or when noise is applied to the RSSI measurement signal Srs, the in-vehicle control unit 21 does not transmit the vehicle ID signal Svi, and thus unlocks the vehicle door. Is regulated. Therefore, the size of the communication area 30 is appropriately maintained even in a noisy environment.

As described above, according to the embodiment described above, the following effects can be obtained.
(1) An on time Ton and an off time Toff are set in the RSSI measurement signal Srs transmitted from the in-vehicle device 20 to the electronic key 10. During the on time Ton, the signal level of the RSSI measurement signal Srs vibrates with a constant amplitude, and during the off time Toff, the signal level of the RSSI measurement signal Srs is fixed to zero. The RSSI detection circuit 16 detects the RSSI of the RSSI measurement signal Srs a plurality of times over the on time Ton and the off time Toff. The determination unit 25 determines whether noise is applied to the RSSI measurement signal Srs based on the detection result of the RSSI detection circuit 16.

  Here, a configuration in which the on time Ton and the off time Toff are not set in the RSSI measurement signal Srs will be considered. In this configuration, when noise is applied to the RSSI measurement signal Srs, the RSSI of the RSSI measurement signal Srs is equal to or higher than the first threshold Vth1 even though the electronic key 10 exists outside the communication area 30. The electronic key 10 may be determined to exist in the communication area 30. In that respect, according to the above configuration, it can be determined whether noise is applied to the RSSI measurement signal Srs based on the RSSI in the on time Ton and the off time Toff. This is because, in the absence of noise, the RSSI is zero at the off time Toff, but when the noise is applied, the RSSI similar to the on time Ton is continued at the off time Toff. Therefore, when noise is applied, the average value Vav of each RSSI of the RSSI measurement signal Srs is large, and when no noise is applied, the average value Vav of each RSSI of the RSSI measurement signal Srs is small. Become. The second threshold value Vth2 is set empirically by comparing the average value Vav corresponding to the presence or absence of noise in the RSSI measurement signal Srs. When the calculated average value Vav is equal to or greater than the second threshold value Vth2, it is determined that noise is applied to the RSSI measurement signal Srs. As described above, it is possible to easily determine whether noise is applied to the RSSI measurement signal Srs through the average value Vav of each RSSI over the ON time Ton and the OFF time Toff in the RSSI measurement signal Srs. When it is determined that noise is applied, it is determined that the electronic key 10 is present in the communication area 30 and communication between the in-vehicle device 20 and the electronic key 10 is performed thereafter. I will not. According to the above configuration, expansion of the communication area 30 in a noise environment is suppressed, and an appropriate size of the communication area 30 is maintained.

  (2) The determination unit 25 is provided in the in-vehicle device 20 (more precisely, the in-vehicle reception unit 24). Therefore, the electronic key 10 can be configured more compactly than when the determination unit 25 is provided in the electronic key 10. Here, since the electronic key 10 is required to have a higher compactness than the vehicle-mounted device 20 from the viewpoint of portability, this is particularly beneficial.

(Second Embodiment)
Hereinafter, a second embodiment in which the electronic key system according to the present invention is embodied will be described. The electronic key system of this embodiment is different from the first embodiment in that a determination unit is provided in the electronic key. The electronic key system of this embodiment has substantially the same configuration as the electronic key system of the first embodiment shown in FIG. Hereinafter, a description will be given focusing on differences from the first embodiment.

  As shown in FIG. 1, in the first embodiment, the determination unit 25 provided in the in-vehicle reception unit 24 is omitted. And the determination part 15 is provided in the UHF transmission part 13 as shown with a dashed-dotted line in FIG. The determination unit 15 is configured similarly to the determination unit 25 of the first embodiment. That is, when the determination unit 15 determines that the average value Vav calculated by the electronic key control unit 11 is in the range of the first threshold value Vth1 or more and less than the second threshold value Vth2, the determination unit 15 passes the UHF transmission unit 13 through the UHF transmission unit 13. Then, the communication permission code is included in the ACK signal Sac as RSSI information and transmitted. When the vehicle-mounted control unit 21 recognizes the communication permission code included in the ACK signal Sac received through the vehicle-mounted receiving unit 24 or the like, the vehicle-mounted control unit 21 receives the vehicle ID signal Svi in the same manner as when receiving the communication permission signal in the first embodiment. Send.

  Also, when the determination unit 15 determines that the average value Vav calculated by the electronic key control unit 11 is not less than the first threshold value Vth1 and less than the second threshold value Vth2, it passes through the UHF transmission unit 13. The communication prohibition code is included in the ACK signal Sac as RSSI information and transmitted. When the in-vehicle control unit 21 recognizes the communication prohibition code included in the ACK signal Sac received through the in-vehicle receiving unit 24 or the like, it transmits the vehicle ID signal Svi in the same manner as when the communication prohibition signal is received in the first embodiment. do not do.

As described above, according to the embodiment described above, in addition to the function and effect of (1) of the first embodiment, the following function and effect can be achieved.
(3) The determination unit 15 is provided in the electronic key 10, and an ACK signal is transmitted to the in-vehicle device 20 when the average value Vav is equal to or greater than the first threshold value Vth1 and less than the second threshold value Vth2. Further, when the average value Vav is not within the above range, the ACK signal Sac is not transmitted to prohibit the control of the in-vehicle device 20. Therefore, compared with the case where the determination part 15 is provided in the vehicle equipment 20, the power consumption concerning transmission of the ACK signal Sac can be reduced.

(Third embodiment)
A third embodiment that embodies an electronic key system according to the present invention will be described below. The electronic key system of this embodiment is different from the second embodiment in that a warning is issued for an unauthorized attempt to unlock the vehicle door. The electronic key system of this embodiment has substantially the same configuration as the electronic key system of the second embodiment. Hereinafter, the difference from the second embodiment will be mainly described.

  In the present embodiment, the vehicle-mounted control unit 21 repeatedly transmits the wake signal Swk and the RSSI measurement signal Srs a predetermined number of times when the user's contact with the door handle 4 is recognized through the door handle sensor 32.

  In addition, when it is determined through the determination unit 15 that the average value Vav is equal to or greater than the second threshold value Vth2, an ACK signal Sac that indicates that it is in a noise environment is transmitted to the in-vehicle device 20. When the in-vehicle control unit 21 recognizes that there is a noise environment through the ACK signal Sac received through the in-vehicle receiving unit 24, the in-vehicle control unit 21 warns through an alarm that unauthorized unlocking may be attempted.

  According to the above configuration, when the electronic key 10 exists outside the communication area 30 in a noisy environment, the third person illegally attempts to unlock the vehicle door by taking advantage of the user being away from the vehicle 2. A warning is made. This can intimidate a third party and inform the user that an attempt is being made to unlock the vehicle door illegally.

  In addition, when the in-vehicle control unit 21 recognizes an ACK signal including that it is in a noise environment, the wake signal Swk and RSSI measurement are performed assuming that the vicinity of the vehicle 2 is in the noise environment and communication with the electronic key 10 is difficult. The transmission of the service signal Srs is suspended for a fixed time.

As described above, according to the embodiment described above, in addition to the function and effect of (3) of the second embodiment, the following function and effect can be achieved.
(4) Even when the electronic key 10 exists outside the communication area 30 in a noisy environment and the vehicle door is illegally unlocked (contact with the door handle in this example), A warning can be given to it. Therefore, security can be improved.

  (5) When the vehicle-mounted control unit 21 recognizes an ACK signal indicating that the vehicle is in a noise environment, the in-vehicle control unit 21 pauses transmission of the wake signal Swk and the RSSI measurement signal Srs for a certain period of time. Thereby, it is suppressed that the wake signal Swk and the RSSI measurement signal Srs are transmitted unnecessarily. Therefore, power consumption related to these signal transmissions can be reduced.

In addition, the said embodiment can be implemented with the following forms which changed this suitably.
-In 1st Embodiment, the determination part 25 was provided in the vehicle-mounted receiving part 24. FIG. However, the in-vehicle control unit 21 may also serve as the determination unit 25. Similarly, in the second and third embodiments, the electronic key control unit 11 may also serve as the determination unit 15.

  In the first to third embodiments, the on time Ton and the off time Toff are set in this order. However, conversely, the off time Toff and the on time Ton may be set in this order.

  In the first to third embodiments, the RSSI measurement signal Srs is an independent signal from the wake signal Swk, but the RSSI measurement signal Srs is included in the wake signal Swk and transmitted as the wake signal Swk. Also good.

  In the first to third embodiments, it is determined whether noise is applied to the RSSI measurement signal Srs through a comparison between the RSSI average value Vav and the second threshold value Vth2 at each time t11 to tn. It was. However, it is not limited to the average value Vav, but may be an integrated value of RSSI at each time t11 to tn, for example. In this case, the first threshold value Vth1 and the second threshold value Vth2 are set larger than those in the above embodiments.

  In the first to third embodiments, only the RSSI of the RSSI measurement signal Srs is detected through the RSSI detection circuit 16. However, RSSI of various received signals may always be detected. In this case, the electronic key control unit 11 recognizes the RSSI of the RSSI measurement signal Srs based on the reception timing and the signal length of the RSSI measurement signal Srs stored in advance in the memory 11a, and calculates the average value Vav. To do.

  In the first embodiment, the electronic key control unit 11 calculates the average value Vav based on each RSSI recognized through the RSSI detection circuit 16 as a calculation unit. However, the determination unit 25 may calculate the average value Vav as a calculation unit. In this case, the electronic key control unit 11 transmits the detection result (each RSSI of the RSSI measurement signal Srs) included in the ACK signal Sac through the UHF transmission unit 13. In this configuration, it is possible to reduce the processing load related to the calculation of the average value Vav in the electronic key control unit 11.

  In the first to third embodiments, the on time Ton and the off time Toff are set to the same time. However, the on time Ton and the off time Toff may be set to different times. For example, by setting the off time Toff to be large, it is possible to increase the difference between the average value Vav in a noise environment and the average value Vav in the absence of noise. As a result, the presence or absence of noise can be more reliably determined through the second threshold value Vth2.

Next, the technical idea that can be grasped from the embodiment will be described together with the effects.
(A) In the electronic key system according to claim 2, the determination unit and the calculation unit are provided in the electronic key, and the determination unit determines that the average value calculated through the calculation unit is the first threshold value. When it is determined that the value is less than the second threshold value, the first ACK signal is transmitted to the control target, and when the average value is determined to be equal to or greater than the second threshold value, the radio signal is transmitted. A second ACK signal indicating that noise is applied to the control object, and the control object transmits the radio signal when its own control is attempted, and receives the first ACK signal when the electronic device receives the first ACK signal. An electronic key system that performs control when mutual authentication with a key is continued and the mutual authentication is established, and issues a warning when the second ACK signal is received.

  According to the configuration, even when the control of the control target is illegally attempted by taking advantage of the presence of the electronic key outside the communication area in a noisy environment, a warning can be given to that.

  DESCRIPTION OF SYMBOLS 1 ... Electronic key system, 10 ... Electronic key, 15, 25 ... Determination part, 16 ... RSSI detection circuit (detection part), 30 ... Communication area.

Claims (4)

When the control of the control target is executed through wireless communication between the control target and the electronic key, and the received electric field strength of the radio signal received from the control target by the electronic key is less than a first threshold, the electronic key is In the electronic key system in which the control of the controlled object is prohibited as it exists outside the communication area,
The wireless signal is set to an on time at which the signal level vibrates and an off time at which the signal level is fixed to zero,
A detection unit provided in the electronic key and detecting the received electric field strength of the wireless signal a plurality of times over the on-time and the off-time;
When it is determined that noise is applied to the radio signal based on the detection result of the detection unit,
A determination unit that prohibits control of the control target, assuming that the electronic key is not present in the communication area even if the received electric field strength of the wireless signal is equal to or greater than the first threshold; Electronic key system with The electronic key system according to claim 1.
An arithmetic unit that calculates an average value of each received electric field strength in the radio signal detected through the detection unit;
When the determination unit determines that the average value is equal to or greater than a second threshold value set to be greater than the first threshold value, the electronic key system determines that noise is applied to the wireless signal. The electronic key system according to claim 2.
The determination unit is provided in the control target, and the calculation unit is provided in the electronic key.
When the electronic key receives the wireless signal, the electronic key transmits an ACK signal including an average value calculated through the arithmetic unit,
The electronic key system, wherein when the determination unit determines that the average value included in the ACK signal received by the control target is equal to or greater than the second threshold, it determines that noise is applied to the wireless signal. The electronic key system according to claim 2.
The determination unit and the calculation unit are provided in the electronic key,
The determination unit transmits an ACK signal to the control target when determining that the average value calculated through the calculation unit is equal to or greater than the first threshold and within a range less than the second threshold. , Restricting transmission of the ACK signal to the control target when it is determined that the average value is out of the range,
When the control object receives the ACK signal, it continues mutual authentication with the electronic key, and executes control when the mutual authentication is established.

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