JP2019065624A - Electronic key system - Google Patents

Abstract

To provide an electronic key system capable of more appropriately suppressing power consumption of a portable unit.SOLUTION: When an Ack signal, which is a response from a portable unit in response to a start signal, is continuously received, and a response signal, which is the response from the portable unit in response to a challenge signal, is not received, an ECU increases transmission output for transmitting the challenge signal. Then, when the response signal is received, the ECU determines a position of the portable unit based on a RSSI value contained in the response signal. The ECU stops periodic transmission of the start signal when the portable unit is determined to be positioned outside a specified communication area. Moreover, when the Ack signal is continuously received, and the response signal is received but is not correct, the ECU decreases the transmission output for transmitting the start signal more than usual. Then, the ECU stops the periodical transmission of the start signal when there is no response from the portable unit in response to the start signal.SELECTED DRAWING: Figure 4

Description

  The present invention relates to an electronic key system.

  Conventionally, as described in, for example, Patent Document 1, an electronic key system is known which performs control of a vehicle through wireless communication between a portable device carried by a user and the vehicle. In the system, the control device of the vehicle forms a communication area around each door by transmitting a response request through a transmitting antenna provided on each door of the vehicle. When the control device receives a response from the portable device to the response request, the control device permits locking and unlocking of the door when the ID information included in the response is authenticated.

  When the portable device continues to be present in the communication area, the control device reduces the communication area until the response from the portable device is lost by reducing the transmission output of the transmitting antenna. Since the portable device is located outside the reduced communication area, it does not receive a response request from the vehicle and does not respond to the response request. As described above, when the user who holds the portable device does not intend to get in the vehicle, when the portable device continues to be present in the communication area, the power consumption of the portable device can be reduced by the amount that the portable device does not respond.

  After reducing the communication area, the control device periodically checks whether the portable device exists in the communication area before the reduction. The control device maintains the communication area in a contracted state when the portable device is present in the communication area before the contraction. As a result, the useless response of the portable device is continuously suppressed. On the other hand, when there is no portable device in the communication area before reduction, the control device restores the communication area to the communication area before reduction. This is because it is no longer necessary to reduce the communication area, and it is preferable to return to the communication area before the reduction from the viewpoint of securing user convenience.

JP, 2015-42810, A

  However, in the electronic key system of Patent Document 1, the following is concerned. That is, as described above, after the communication area is reduced, it is periodically checked whether the portable device exists in the communication area before the reduction. Therefore, when the portable device continues to exist in the communication area before reduction, the portable device responds every time presence confirmation is performed. The portable device consumes power for responding to the presence confirmation. The amount of power consumed by the portable device depends on the frequency at which the portable device presence check is performed.

  An object of the present invention is to provide an electronic key system capable of suppressing power consumption of a portable device more appropriately.

  An electronic key system that can achieve the above object includes an on-vehicle device that wirelessly transmits a response request to a communication area set around the vehicle, and a portable device that wirelessly transmits a response to the response request. The in-vehicle device authenticates the portable device upon receipt of a first response to a first response request periodically transmitted to detect an approach of the portable device to a vehicle. And the second response to the second response request is received, and when it is determined that the portable device is located in the communication area, the door lock operation of the vehicle is performed. To give permission. Further, when the first response is continuously received, the in-vehicle device increases or decreases the transmission output of the in-vehicle device according to the reception status of the second response, and the in-vehicle device subsequently receives the second response. The transmission of the first response request is stopped based on the response status of the aircraft.

  Due to the distance between the vehicle and the portable device, the reception status of the portable device changes. For example, even if the first response request is properly received by the portable device, the portable device responds to the first response request periodically transmitted from the on-vehicle device depending on the reception status of the second response request. It is possible that the machine continues to send the first response in vain. Incidentally, since the first response to the first response request is received by the in-vehicle device, it is assumed that the portable device exists at a position where it can receive at least the first response request from the vehicle. Ru.

  According to the above configuration, when the first response is continuously received, the transmission output of the in-vehicle device is increased or decreased according to the reception status of the second response. Then, based on the subsequent response status of the portable device, the transmission of the first response request is stopped. Since the portable device does not continue to send back the first response, wasteful power consumption of the portable device can be suppressed.

  In the above electronic key system, the in-vehicle device requests at least the second response when the second response is not received as the reception status of the second response when the first response is continuously received. When the second response is received as a response status of the portable device after that, the portable device is determined to be located within the communication area, while increasing the transmission output when transmitting If not, it is preferable to stop the transmission of the first response request.

  For example, due to the distance between the vehicle and the portable device, the first response request may be received by the portable device, but the second response signal may not be received by the portable device. When the portable device continues to exist under such circumstances, the portable device continues to uselessly reply the first response to the periodically transmitted first response request.

  According to the above configuration, when the second response is not received under the situation where the first response is continuously received, the transmission power at the time of transmitting at least the second response request is increased more than usual. The portable device can easily receive the second response request. Thereafter, when the second response to the second response request is received by the in-vehicle device, the transmission of the first response request is stopped when it is not determined that the portable device is located within the prescribed communication area. . Since the portable device does not continue to send back the first response, wasteful power consumption of the portable device can be suppressed.

  In the above electronic key system, the in-vehicle device receives the second response as the reception status of the second response when the first response is continuously received, but the second response is correct. If the first response is not received, the transmission power when transmitting the first response request is reduced than usual, and the first response is not received as the subsequent response status of the portable device. It is preferable to stop sending the request.

  For example, due to the distance between the vehicle and the portable device, it is considered that the second response to the second response request is received by the on-vehicle device but the received second response is not correct. Be When the portable device continues to exist under such circumstances, the portable device continues to uselessly reply the first response to the periodically transmitted first response request.

  According to the above configuration, under the situation where the first response is continuously received, the second response is received by the in-vehicle device, but the received second response is not correct. The transmission power when transmitting the response request is reduced than usual. For this reason, it is suppressed that a portable machine receives a 1st response request and by extension, a portable machine responds to a 1st response request. Since the portable device does not continue to send back the first response, wasteful power consumption of the portable device can be suppressed.

  In the above electronic key system, the in-vehicle device performs a predetermined number of times when the second response to the second response request is not received or when the second response received is not correct. Preferably, the second response request is re-sent.

  According to this configuration, it is possible to suppress that the communication between the in-vehicle device and the portable device is disturbed by the influence of temporary environmental noise or the like. For example, even if the portable device does not respond to the first response request, the portable device may obtain a correct response to the second response request. For this reason, the reliability of communication between the in-vehicle device and the portable device can be secured.

  In the above electronic key system, when the number of times of reception of the first response in a predetermined period exceeds a threshold number of times, the on-vehicle device determines that the first response is continuously received. May be

  According to the electronic key system of the present invention, the power consumption of the portable device can be suppressed more appropriately.

FIG. 2 is a block diagram illustrating an embodiment of an electronic key system. The top view of the vehicle which shows arrangement | positioning of a transmitting antenna, and communication area when the vehicle equipped with the electronic key system of one Embodiment is seen from the top. (A) is a block diagram showing an arrangement of a start signal and a challenge signal which is an example of the response request signal, (b) is a block diagram showing the arrangement of an Ack signal and a response signal which is an example of the response signal. (A) is a timing chart showing transmission and reception of a wireless signal when wireless communication between the electronic control unit and the portable unit is normally performed, (b) is normal wireless communication between the electronic control unit and the portable unit The timing chart which shows the 1st condition which is not performed to (c) is a timing chart which shows the 2nd condition where the wireless communication between an electronic control unit and a portable machine is not performed normally. FIG. 1 is a plan view of a vehicle showing a prescribed communication area and a non-prescribed communication area. FIG. 3 is a front view showing an example of the positional relationship between a vehicle parked at the user's home and a portable device placed at home. (A) is a plan view showing a situation where the portable device is located in a communication area (receivable area) outside the specification, and (b) shows a situation where the portable device is located in the enlarged communication area Plan view. (A) is a plan view showing a situation where the portable device is located in a communication area (receivable area) out of specification, and (b) shows a situation where the portable device is located outside the reduced communication area Plan view. The flowchart which shows the procedure of the determination processing which concerns on adjustment of a communication area performed by an electronic control unit. The flowchart which shows the procedure of the process performed after determining that the electronic control unit expands a communication area. The timing chart which shows exchange of the radio signal between an electronic control unit and a portable machine, after determining that an electronic control unit expands a communication area. The flowchart which shows the procedure of the process performed after determining that the electronic control unit shrinks | contracts a communication area. The timing chart which shows exchange of the radio signal between an electronic control unit and a portable machine, after determining that an electronic control unit reduces communication area.

Hereinafter, an embodiment in which the electronic key system is embodied will be described.
As shown in FIG. 1, the electronic key system 10 includes an on-vehicle device 12 mounted on a vehicle 11 and a portable device 13 held by a user. Wireless communication is performed between the on-vehicle device 12 and the portable device 13. The in-vehicle device 12 authenticates the portable device 13 through the exchange of wireless signals with the portable device 13.

<Configuration of in-vehicle device>
As shown in FIG. 1, the on-vehicle device 12 includes an ECU (Electronic Control Unit) 21, transmission circuits 22 and 23, and a reception circuit 24.

  The touch sensor 31, the lock switch 32, and the door lock device 33 are connected to the ECU 21. The touch sensor 31 and the lock switch 32 are respectively provided on a door handle (not shown). The touch sensor 31 detects a touch on the door handle by the user. The touch sensor 31 is normally maintained in a stopped state. The lock switch 32 is pressed to lock the door when getting off. The door lock device 33 performs locking and unlocking of the door, respectively.

  Further, transmission antennas 22 a and 23 a are connected to the ECU 21 via transmission circuits 22 and 23. For example, the transmitting antenna 22 a is provided at the right door of the vehicle 11, and the transmitting antenna 23 a is provided at the left door of the vehicle 11. Further, a reception antenna 24 a is connected to the ECU 21 via the reception circuit 24. The receiving circuit 24 and the receiving antenna 24a are provided in the car.

  Each of the transmission circuits 22 and 23 transmits a response request signal Srq, which is a radio signal of a low frequency (LF) band, toward the periphery of the vehicle 11 through the transmission antennas 22a and 23a based on an instruction from the ECU 21. The response request signal Srq is a command signal for requesting a response from the portable device 13 held by the user. By transmitting the response request signal Srq to the outside of the vehicle at a predetermined control cycle, a communication area with the portable device 13 is formed outside the vehicle (around the left and right doors).

  As the transmission circuits 22 and 23, for example, a PWM (pulse width modulation) method is adopted. The transmission circuits 22 and 23 have PWM circuits 22 b and 23 b. The PWM circuits 22b and 23b adjust the pulse width of the voltage supplied to the transmitting antennas 22a and 23a through the setting of the duty ratio based on the command from the ECU 21. Control of the output voltage to the transmitting antennas 22a and 23a is possible through the adjustment of the pulse width. That is, the PWM circuits 22 b and 23 b function as adjusting means for adjusting the transmission output of the transmission circuits 22 and 23.

  As the duty command value that is a command from the ECU 21 increases, the pulse width of the voltage supplied to the transmitting antennas 22a and 23a, that is, the transmission output of the transmitting circuits 22 and 23 increases. The communication area expands as the transmission power increases, while the communication area shrinks as the transmission power decreases. In this example, the PWM circuits 22b and 23b switch the transmission output level of the transmission circuits 22 and 23 from the initial value (reference value) to the first transmission output or the second transmission output, based on an instruction from the ECU 21. The first transmission output is set to a value larger than the initial value. The second transmission output is set to a value smaller than the initial value.

  The receiving circuit 24 receives a radio signal in a UHF (Ultra-High Frequency) band via the receiving antenna 24a. Here, the response signal Srp transmitted from the portable device 13 to the response request signal Srq from the vehicle 11 is assumed as the wireless signal in the UHF band. The response signal Srp includes identification information unique to the portable device 13.

  When the vehicle 11 is in a parked state (vehicle power off, all doors closed, door locked), the ECU 21 transmits a response request signal Srq at predetermined intervals through the transmission antennas 22a and 23a. For example, the ECU 21 transmits the response request signal Srq alternately from the transmission antennas 22a and 23a.

  When the ECU 21 receives the response signal Srp from the portable device 13 via the receiving circuit 24, the identification information of the portable device 13 included in the response signal Srp and the identification information stored in its own storage device 21a are Match. The ECU 21 activates the touch sensor 31 when the collation of the identification information is established. When the touch on the door handle is detected through the touch sensor 31, the ECU 21 unlocks all the doors through the door lock device 33.

  Further, the ECU 21 transmits the response request signal Srq through the transmitting antennas 22a and 23a also when it is detected that the lock switch 32 is operated in the parking state (vehicle power off, all doors closed, door unlocking). . When the ECU 21 receives the response signal Srp from the portable device 13 through the receiving circuit 24, the ECU 21 collates the identification information of the portable device 13 included in the response signal Srp with the identification information stored in its own storage device 21a. . The ECU 21 locks all the doors through the door lock device 33 when the collation of the identification information is established.

<Configuration of portable device>
As shown in FIG. 1, the portable device 13 has a control circuit 41, a receiving circuit 42 and a transmitting circuit 43. A receiving antenna 42 a is connected to the control circuit 41 via the receiving circuit 42. Further, a transmitting antenna 43 a is connected to the control circuit 41 via the transmitting circuit 43.

  The receiving circuit 42 receives a radio signal of the LF band, here, a response request signal Srq from the vehicle 11 through the receiving antenna 42a. The receiving circuit 42 also has a detection circuit 44 that detects the signal strength (RSSI: Received Signal Strength Indicator) of the received wireless signal.

The transmission circuit 43 transmits a radio signal in the UHF band, here, a response signal Srp in this case through the transmission antenna 43a based on a command from the control circuit 41.
When receiving the response request signal Srq through the receiving circuit 42, the control circuit 41 generates a response signal Srp, and transmits the generated response signal Srp through the transmission antenna 43a.

  Here, when the battery serving as the operation power supply of the portable device is exhausted, there is a possibility that wireless communication can not be performed between the on-vehicle device 12 and the portable device 13. That is, in this case, even if the user carrying the portable device 13 enters the communication areas A1 and A2 formed around the door of the vehicle 11, the unlocking of the door is not permitted. Therefore, from the viewpoint of suppressing battery consumption in the portable device 13, the portable device 13 usually maintains a so-called sleep state (power saving state). The portable device 13 is activated upon receiving the response request signal Srq transmitted from the vehicle 11 after entering the communication areas A1 and A2, and transmits a response signal Srp.

<Communication area>
As shown in FIG. 2, by transmitting response request signals Srq alternately from transmission antennas 22a and 23a, communication areas A1 between vehicle 11 and portable device 13 are respectively provided around the left and right doors of vehicle 11. , A2 are alternately formed. These communication areas A1 and A2 are areas where a response from the portable device 13 is expected, and the working distance of the portable device 13 required according to the product specification of the electronic key system etc. It sets based on distance with the vehicle 11 which can receive the transmitted radio signal.

<Configuration of wireless signal>
As shown in FIG. 3A, as the response request signal Srq, a start signal Swk and a challenge signal Sch are present. The wakeup signal Swk is a signal for requesting the mobile device 13 in the so-called sleep state to wake up, and includes a Wake code. The challenge signal Sch is a signal for authenticating the portable device 13. The challenge signal Sch includes a vehicle code, a challenge code, and a key code. The vehicle code is a unique code for identifying each vehicle and is stored in the storage device 21a. The challenge code is a code for authenticating the portable device 13 and includes, for example, a random number sequence. The challenge code is generated differently each time the challenge signal Sch is transmitted. The key code is a code unique to the portable device 13 registered in the vehicle 11, and is stored in the storage device 21a.

  As shown in FIG. 3B, an acknowledgment (acknowledgement) signal Sac and a response signal Sres are present as the response signal Srp. The Ack signal Sac is a signal indicating that the operation request (such as the activation request) from the ECU 21 has been correctly received or that the requested operation has been completed. The response signal Sres is a response to the challenge signal Sch. The response signal Sres includes the RSSI value, the encryption result and the identification information (ID). The RSSI value is information indicating the signal strength of the received challenge signal Sch. The encryption result is information indicating the result of encrypting the challenge code included in the received challenge signal Sch using an encryption key. The identification information is a unique code for identifying each portable device, and is stored in the storage device 41a.

<Aspect of wireless signal transmission / reception>
Next, one aspect of transmission and reception of wireless signals between the vehicle 11 and the portable device 13 will be described in detail. The vehicle 11 is in a parked state, and each door is locked.

  As shown in FIG. 4A, the ECU 21 of the vehicle 11 transmits the start signal Swk to the outside of the vehicle through the transmitting antennas 22a and 23a. As a result, communication areas A1 and A2 as detection areas of the portable device 13 are formed around the door of the vehicle 11. In this state, when the portable device 13 possessed by the user enters the communication areas A1 and A2 and receives the activation signal Swk, the portable device 13 determines the validity of the Wake code included in the activation signal Swk.

When it is determined that the Wake code is valid, the portable device 13 is activated and sends back an Ack signal Sac to the vehicle side.
The ECU 21 receives the Ack signal Sac, determines that the portable device 13 is present in the communication areas A1 and A2, and transmits a challenge signal Sch.

  When the challenge signal Sch is received, the portable device 13 collates the vehicle code included in the received challenge signal Sch with the vehicle code registered in itself. When the collation of these vehicle codes is established, the portable device 13 determines that the vehicle code registered in itself is a code registered in the vehicle 11 which is the transmission source of the challenge signal Sch. Further, the portable device 13 collates the key code included in the challenge signal Sch with the key code registered in itself. When the collation of the key code is established, the portable device 13 determines that the key code of its own is a code registered in the vehicle 11 which is a transmission source of the challenge signal Sch. Then, the portable device 13 transmits the response signal Sres when the collation of the vehicle code and the collation of the key code are both established.

  Specifically, the control circuit 41 of the portable device 13 obtains an RSSI value indicating the signal strength of the received challenge signal Sch through the detection circuit 44. In addition, the control circuit 41 obtains a cryptographic result by encrypting the challenge code included in the challenge signal Sch with a cryptographic key of its own. The control circuit 41 also takes in the identification information stored in the storage device 41a. Then, the control circuit 41 generates a response signal Sres including the RSSI value, the encryption result, and the identification information, and transmits the generated response signal Sres.

  When the response signal Sres is received, the ECU 21 collates the identification information included in the response signal Sres with the identification information registered in itself. Further, the ECU 21 collates the encryption result obtained by encrypting the challenge code generated by itself with the encryption key (the encryption key the same as that of the portable device 13) with the encryption result included in the response signal Sres. When the collation of the identification information and the collation of the encryption result are both established, the ECU 21 determines that the communication partner is the portable device 13 registered in the vehicle 11, and permits the unlocking of the door.

<Receivable area>
Here, depending on the communication environment or the reception sensitivity of the portable device 13, the portable device 13 may receive a wireless signal from the vehicle 11 even if it is located outside the prescribed communication areas A1 and A2. However, since the signal strength of the wireless signal from the vehicle becomes weak and unstable as it gets away from the vehicle, when the portable device 13 is located outside the prescribed communication areas A1 and A2, the wireless signal from the vehicle can not be received normally. There is a fear.

  For example, when the frame length of the challenge signal Sch is longer than the frame length of the activation signal Swk, the portable device 13 can normally receive the activation signal Swk but can not normally receive the challenge signal Sch. . This is because in a situation where the signal strength of the radio signal from the vehicle 11 is weak and unstable, as the frame length is longer, a bit error may occur during transmission of the radio signal, or the radio signal may be transmitted due to attenuation of the radio signal. This is because the probability of not completing is higher. Further, in a situation where the signal strength of the radio signal from the vehicle 11 is weak and unstable, being susceptible to environmental noise is also a factor that hinders normal radio communication.

  For this reason, the area where the portable device 13 can receive the wireless signal from the vehicle 11 (hereinafter referred to as "receivable area") can be divided into a plurality of areas including the prescribed communication areas A1 and A2. An example is as follows.

  As shown in FIG. 5, for example, the receivable area Ap formed around the right door of the vehicle 11 is divided into three regions by the first threshold line L1, the second threshold line L2 and the third threshold line L3. Be done. The innermost first area divided by the first threshold line L1 is a prescribed communication area A1 based on product specifications and the like. In the prescribed communication area A1, transmission and reception of radio signals between the vehicle 11 and the portable device 13 are appropriately performed. Although the second region partitioned by the first threshold line L1 and the second threshold line L2 outside the first threshold line L1 is outside the prescribed communication area A1, depending on the communication environment or the reception sensitivity of the portable device 13, the vehicle This is an area in which transmission and reception of wireless signals between the portable device 13 and the portable device 13 are appropriately performed. The outermost third region defined by the second threshold line L2 and the third threshold line L3 outside the second threshold line L2 is outside the prescribed communication area A1, and is between the vehicle 11 and the portable device 13. This is an area in which transmission and reception of wireless signals are not properly performed. For example, in the third region, it is assumed that the portable device 13 can normally receive the start signal Swk from the vehicle 11, but can not receive the challenge signal Sch. In this case, the portable device 13 located in the third area sends back only the Ack signal Sac in response to the activation signal Swk.

  Here, even when the portable device 13 is located outside the prescribed communication areas A1 and A2 such as when the portable device 13 is located in the second area in the receivable area Ap, the door is unlocked. May be permitted. For this reason, in this example, as the unlocking permission condition of the door, in addition to the verification of the identification information of the portable device 13 being established and the verification of the encryption result of the challenge code being established The condition is that they exist in the areas A1 and A2.

  The ECU 21 determines the position of the portable device 13 with respect to the vehicle 11 based on the RSSI value included in the response signal Sres in order to determine whether the portable device 13 exists in the specified communication areas A1 and A2. The radio signal transmitted from the vehicle 11 (the transmitting antennas 22 a and 23 a which are radiation points) attenuates as the distance from the vehicle 11 increases. That is, there is an interphase relationship between the distance between the vehicle 11 and the portable device 13 and the signal strength (RSSI value) of the wireless signal received by the portable device 13. For this reason, based on the RSSI value, it is possible to determine the distance between the vehicle 11 and the portable device 13, and in turn, whether the portable device 13 is located within the prescribed communication areas A1 and A2.

  As one example, the ECU 21 determines whether the RSSI value is a value within a predetermined threshold range. The threshold range is set based on the signal strength when the portable device 13 located in the prescribed communication areas A1 and A2 receives a radio signal from the vehicle 11. When the RSSI value included in the response signal Sres is a value within the threshold range, the ECU 21 determines that the portable device 13 is located within the prescribed communication areas A1 and A2. When the RSSI value included in the response signal Sres is a value outside the threshold range, the ECU 21 determines that the portable device 13 is located outside the prescribed communication areas A1 and A2.

  Based on the RSSI value included in the response signal Sres, the ECU 21 is requested according to the product specification of the electronic key system 10, etc. by determining whether the portable device 13 exists in the specified communication areas A1 and A2. The door can be unlocked at an appropriate working distance.

<A situation where the portable device continues to exist in the receivable area>
However, as the use condition of the vehicle 11, it is assumed that the portable device 13 continues to be present in the receivable area Ap.

  As shown in FIG. 6, for example, when the user parks the vehicle 11 in the vicinity of the home 51, when the user who got off the vehicle 11 places the portable device 13 in a shoe box 52 or the like provided at the entrance of the home 51 The portable device 13 may continue to be present in the coverage area Ap. In particular, when the portable device 13 is present in the outermost third area in the receivable area Ap, two situations can be considered for the transmission and reception of radio signals between the vehicle 11 and the portable device 13.

  As shown in FIG. 7A, as a first situation, it is assumed that although the portable device 13 can receive the activation signal Swk transmitted from the vehicle 11, it can not receive the subsequent challenge signal Sch. This may be attributed, for example, to the fact that the distance between the vehicle 11 and the portable device 13 is long and the wireless signal transmitted from the vehicle 11 is attenuated in the process of reaching the portable device 13 or is affected by environmental noise. . In this first situation, the mode of transmission and reception of wireless signals between the vehicle 11 and the portable device 13 is as follows. The vehicle 11 is in a parked state, and each door is locked.

  As shown in FIG. 4 (b), the ECU 21 of the vehicle 11 periodically transmits the activation signal Swk to the outside of the vehicle. When the portable device 13 receives the activation signal Swk, when it is determined that the Wake code included in the activation signal Swk is appropriate, the portable device 13 is activated and sends back an Ack signal Sac to the vehicle side. The ECU 21 transmits a challenge signal Sch upon receiving the Ack signal Sac. Here, since the portable device 13 can not receive the challenge signal Sch, it does not return the response signal Sres. If the response signal Sres is not received even after a predetermined standby time has elapsed since the challenge signal Sch was transmitted, the ECU 21 again transmits the challenge signal Sch (first retry). Incidentally, the waiting time is set based on the time when the response signal Sres is expected to be returned after the challenge signal Sch is transmitted. When the response signal Sres to the challenge signal Sch is not received again, the ECU 21 finally transmits the challenge signal Sch once again (second retry). When there is no response from the portable device 13 to the last challenge signal Sch, the ECU 21 again transmits a start signal to start execution detection of the portable device 13. Thereafter, the portable device 13 continues to send back the Ack signal Sac in response to the activation signal Swk repeatedly transmitted from the vehicle 11.

  As shown in FIG. 8A, as the second situation, it is assumed that although the ECU 21 receives the response signal Sres to the challenge signal Sch, the response signal Sres is not correct. This is because, for example, the distance between the vehicle 11 and the portable device 13 is long, and a wireless signal transmitted from the vehicle 11 is attenuated in the process of reaching the portable device 13 or is affected by environmental noise. The occurrence of bit errors in the signal Sch can be considered as a factor. In this second situation, the mode of transmission and reception of wireless signals between the vehicle 11 and the portable device 13 is as follows. The vehicle 11 is in a parked state, and each door is locked.

  As shown in FIG. 4C, the ECU 21 of the vehicle 11 transmits a challenge signal Sch when an Ack signal Sac, which is a response from the portable device 13 to the start signal Swk, is received. Here, for example, a bit error occurs in the challenge signal Sch during transmission of the challenge signal Sch (process leading to the portable device 13). In particular, when a bit error occurs in the challenge code, the portable device 13 generates an incorrect response code based on the wrong challenge code. Therefore, in response to the challenge signal Sch, the portable device 13 sends back a response signal Sres (NG) including an incorrect response code. The ECU 21 receives the response signal Sres and attempts to check the encryption result included in the received response signal Sres, but this check is not established. After that, the ECU 21 transmits the start signal Swk again when the correct response signal Sres is not received even if the transmission of the challenge signal Sch is retried only twice at the same time as the first situation described above. Then, the execution detection of the portable device 13 is started. Thereafter, the portable device 13 continues to send back the Ack signal Sac in response to the activation signal Swk repeatedly transmitted from the vehicle 11.

  As described above, it is assumed that the portable device 13 continues to respond to the response request from the vehicle 11 (transmission of the Ack signal Sac or the erroneous response signal Sres) even though the user has no intention of getting into the vehicle. Be done. Even though the user has no intention of getting in, it is useless to exchange wireless signals between the vehicle 11 and the portable device 13. In addition, the portable device 13 operates by consuming the power of the built-in battery, and continues to waste power by continuing to respond to the response request from the vehicle 11.

  Therefore, in the present embodiment, when the portable device 13 continues to be present in the outermost third area in the receivable area Ap in order to suppress unnecessary power consumption of the portable device 13, it is useless through adjustment of the receivable area Ap. The ECU 21 has a function of suppressing wireless communication.

<Determination processing procedure concerning adjustment of receivable area>
Next, the procedure of the determination process related to the adjustment of the receivable area Ap executed by the ECU 21 will be described according to the flowchart of FIG.

  As shown in FIG. 9, the ECU 21 determines whether the Ack signal Sac is continuously received (step S101). The ECU 21 determines that the Ack signal Sac is being received continuously, for example, when the number of receptions of the Ack signal Sac in a predetermined period exceeds the threshold number of times. The determination process of step S101 is a process for confirming whether the communication state between the vehicle 11 and the portable device 13 is the communication state shown in FIG. 4 (b) or FIG. 4 (c). It is.

  When it is determined that the Ack signal Sac is continuously received (YES in step S101), the ECU 21 determines whether retry communication (two re-transmissions of the challenge signal Sch) fails (step S102). . Also in the determination process of step S102, a process for checking whether the communication state between the vehicle 11 and the portable device 13 is the communication state shown in FIG. 4 (b) or FIG. 4 (c). It is.

  When it is determined that the retry communication has failed (YES in step S102), the ECU 21 determines that the portable device 13 is present in a communication area other than the specification (step S103). Here, the out-of-spec communication area refers to the outermost third area in the receivable area Ap, that is, the area to which the Ack signal Sac, which is a response to the activation signal Swk, is continuously returned. Further, as shown in FIG. 4 (b), when the portable device 13 does not respond to two re-transmissions of the challenge signal Sch at all, or as shown in FIG. 4 (c), 2 of the challenge signal Sch. When an incorrect response signal Sres (NG) is sent back from the portable device 13 in response to this re-transmission, the ECU 21 determines that the retry communication has failed.

  Next, the ECU 21 determines whether the response signal Sres has not been received at the time of retry communication (step S104). In the determination process of step S104, the communication state between the vehicle 11 and the portable device 13 is either one of the state shown in FIG. 4 (b) and the state shown in FIG. 4 (c). It is a process for determining whether there is any.

  When it is determined that the response signal Sres is not received during retry communication (YES in step S104), the ECU 21 transmits the transmission output of the transmission circuits 22 and 23 when transmitting the wireless signal (here, the challenge signal Sch). It is determined that the situation should be increased (step S105), and the process ends. When the response signal Sres is not received at the time of retry communication, the portable device 13 is positioned in the third area in the receivable area Ap shown in FIG. 7A and the vehicle 11 and the portable device 13 The communication state between them is assumed to be the first situation shown in FIG. 4 (b).

  When it is determined that the response signal Sres is received during retry communication (NO in step S104), the ECU 21 transmits the transmission output of the transmission circuits 22 and 23 when transmitting the wireless signal (here, the activation signal Swk). It is determined that the situation should be decreased (step S105), and the process ends. When the response signal Sres (NG) is received in the retry communication, the portable device 13 is located in the third area in the receivable area Ap shown in FIG. 8A, and the vehicle 11 and the portable device are also received. It is assumed that the communication state between 13 and 13 is the second state shown in FIG. 4 (c).

  When it is determined that the Ack signal Sac is not continuously received in the previous step S101 (NO in step S101), and when it is determined in the previous step S102 that the retry communication is not a failure. (NO in step S102), the transmission outputs of the transmission circuits 22 and 23 are set to initial values (step S107), and the process is ended.

<Processing after Determination of Transmission Output Increase>
Next, the process executed by the ECU 21 after it is determined that the transmission output of the transmission circuits 22 and 23 should be increased in step S105 in the flowchart of FIG. 9 will be described. The portable device 13 continues to exist in the outermost third area in the coverage area Ap.

  As shown in the flowchart of FIG. 10, the ECU 21 transmits a start signal Swk (step S201). When the Ack signal Sac from the portable device 13 is received (step S202), the ECU 21 transmits a challenge signal Sch (step S203). When transmitting the challenge signal Sch in step S203, the ECU 21 increases the transmission output of the transmission circuits 22 and 23. That is, the ECU 21 switches the transmission output of the transmission circuits 22 and 23 from the initial value to the first transmission output (> initial value).

  As shown in FIG. 11, the signal level (signal strength) of the challenge signal Sch transmitted in the previous step S203 is higher than the signal level of the activation signal Swk which is the reference level. The reference level refers to the signal level of a radio signal transmitted with the transmission output of the transmission circuits 22 and 23 set to the initial value. Further, as shown in FIG. 7B, when the challenge signal Sch is transmitted, the transmission output of the transmission circuits 22 and 23 is increased, so that the wireless signal is exchanged between the vehicle 11 and the portable device 13. The properly performed area is expanded, for example, from a first area and a second area hatched in FIG. 7A to a third area hatched in FIG. 7B. Thus, the challenge signal Sch is properly received by the portable device 13 even when the portable device 13 is located in the third area. Therefore, the portable device 13 transmits the correct response signal Sres.

  When the response signal Sres from the portable device 13 is received (step S204), the ECU 21 determines the position of the portable device 13 based on the RSSI value included in the received response signal Sres (step S205). This determines whether the portable device 13 is located within the prescribed communication areas A1 and A2 in order to unlock the door with an appropriate working distance required according to the product specification of the electronic key system and the like. Because it is necessary.

Here, the ECU 21 determines that the portable device 13 is located outside the specified communication areas A1 and A2 (step S206).
When it is determined that the portable device 13 is located outside the specified communication areas A1 and A2, the ECU 21 stops the transmission of the wireless signal (the activation signal Swk) (step S207), and ends the process. As a result, it is suppressed that the portable device 13 continues to respond to the activation signal Swk periodically transmitted from the vehicle 11, and that the portable device 13 consumes power unnecessarily.

<Processing after judgment of decrease of transmission output>
Next, the process executed by the ECU 21 will be described after it is determined that the transmission output of the transmission circuits 22 and 23 should be decreased in step S106 in the flowchart of FIG. 9 described above. The portable device 13 continues to exist in the outermost third area in the coverage area Ap.

  As shown in the flowchart of FIG. 12, the ECU 21 transmits the activation signal Swk (step S301). The ECU 21 reduces the transmission output of the transmission circuits 22 and 23 when transmitting the activation signal Swk. That is, the ECU 21 switches the transmission output of the transmission circuits 22 and 23 from the initial value to the second transmission output (<initial value).

  As shown in FIG. 13, the signal level of the activation signal Swk transmitted in the previous step S201 is lower than the reference level. Further, as shown in FIG. 8B, when the activation signal Swk is transmitted, the transmission output of the transmission circuits 22 and 23 is reduced, so that transmission and reception of wireless signals between the vehicle 11 and the portable device 13 are performed The appropriately performed area is reduced, for example, from the first area and the second area hatched in FIG. 8A to the first area hatched in FIG. 8B. Thus, the activation signal Swk is suppressed from being received by the portable device 13 located in the third area. Since the portable device 13 does not receive the activation signal Swk, it does not return an Ack signal Sac, which is a response to the activation signal Swk.

  When the Ack signal Sac from the portable device 13 is not received (step S302), the ECU 21 stops the transmission of the wireless signal (start signal Swk) (step S303), and ends the process. As a result, it is suppressed that the portable device 13 continues to respond to the activation signal Swk periodically transmitted from the vehicle 11, and that the portable device 13 consumes power unnecessarily.

<Resume transmission of wireless signal>
Next, the processing of the ECU 21 when the transmission of the start signal Swk is resumed after the transmission of the start signal Swk is stopped in the previous step S207 or step S303 will be described. Here, the vehicle 11 is in a parked state, and each door is locked.

  After stopping the transmission of the activation signal Swk, the ECU 21 activates the touch sensor 31 of the door handle. When the touch on the door handle is detected through the touch sensor 31, the ECU 21 resumes the transmission of the activation signal Swk through the transmission antennas 22a and 23a. At this time, the transmission outputs of the transmission circuits 22 and 23 are set to initial values. Thereafter, as shown in FIG. 4A, the unlocking of the door 11 is permitted through the wireless communication between the vehicle 11 and the portable device 13.

<Effect of the embodiment>
Therefore, according to the present embodiment, the following effects can be obtained.
(1) The ECU 21 does not receive the response signal Sres (NG), which is a response from the portable device 13 to the challenge signal Sch, when the Ack signal, which is a response from the portable device 13 to the activation signal Swk, is continuously received. At the same time, the transmission output of the transmission circuits 22 and 23 is increased. When the correct response signal Sres is received after the transmission output is increased, the ECU 21 determines the position of the portable device 13 based on the RSSI value included in the received response signal Sres. The ECU 21 stops the periodic transmission of the activation signal Swk when it is determined that the portable device 13 is located outside the prescribed communication areas A1 and A2. For this reason, the portable device 13 does not continue to respond to the start signal Swk. Therefore, wasteful consumption of power in the portable device 13 is suppressed. The life of the battery serving as the operation power supply of the portable device 13 can be further extended.

  (2) When the Ack signal, which is a response from the portable device 13 to the start signal Swk, is continuously received, the ECU 21 receives a response signal Sres (NG), which is a response from the portable device 13 to the challenge signal Sch. At the same time, the transmission output of the transmission circuits 22 and 23 is decreased. When the ECU 21 transmits the activation signal Swk after reducing the transmission output, the periodic transmission of the activation signal Swk is stopped when the Ack signal Sac from the portable device 13 is not received. For this reason, the portable device 13 does not continue to respond to the start signal Swk. Therefore, wasteful consumption of power in the portable device 13 is suppressed.

  (3) It is also conceivable that wireless communication between the vehicle 11 and the portable device 13 is disturbed by the influence of environmental noise around the vehicle. Therefore, when the response signal Sres, which is a response from the portable device 13 to the challenge signal Sch, is not received normally, the ECU 21 repeats so-called retry communication of sending the challenge signal Sch a set number of times (two in this example). Run. For example, if environmental noise is temporarily occurring, even if the first challenge response authentication fails, there is a high probability that the second or third time will be successful. Therefore, the influence of temporary environmental noise on the wireless communication between the vehicle 11 and the portable device 13 can be suppressed. Therefore, the noise resistant performance required as the electronic key system 10 can be secured. Moreover, the reliability of the wireless communication between the vehicle 11 and the portable device 13 can be secured.

  Incidentally, when the response signal Sres is not received even if the ECU 21 executes the retry communication, a situation in which a larger environmental noise is generated to the extent that the reception of the challenge signal Sch by the portable device 13 is inhibited is also assumed. Also, when the ECU 21 executes the retry communication, although the response signal Sres is received, when this is not correct, a smaller environmental noise is generated that does not prevent the portable device 13 from receiving the challenge signal Sch. Situations are also envisioned. Therefore, the ECU 21 can also determine the communication environment (the degree of the environmental noise) based on the presence or absence of the response signal Sres when the retry communication is performed. The application of the determination result of the communication environment does not matter.

  (4) The ECU 21 individually adjusts the transmission output at the time of transmitting the challenge signal Sch or the activation signal Swk next time, based on the reception presence or absence of the response signal Sres when the retry communication is performed. According to the communication condition between the vehicle 11 and the portable device 13, the unnecessary output of the portable device 13 can be suppressed by changing the transmission output only when transmitting the required specific wireless signal. it can.

<Other Embodiments>
The present embodiment may be modified as follows.
In the present embodiment, the response request signal Srq transmitted from the vehicle 11 is a radio signal in the LF band, but it may be changed as long as it is a frequency band used in so-called short distance wireless communication. For example, it may be UHF band, SHF (Super High Frequency), 2.4 GHz band or 5 GHz band.

  -In this example, although ECU21 determined whether the portable device 13 was located in prescription | regulation communication area A1, A2 based on the RSSI value contained in the response signal Sres, you may employ | adopt different determination methods. For example, the ECU 21 determines the position of the portable device 13 with respect to the vehicle 11 based on the time from the transmission of the response request (Swk, Sch) to the reception of the response (Sac, Sres) from the portable device 13 Is also possible. Alternatively, a method of determining the position of the portable device 13 with respect to the vehicle 11 through the exchange of sound waves between the vehicle 11 and the portable device 13 may be employed.

  The ECU 21 transmits the transmission circuit 22 only when transmitting a specific wireless signal (challenge signal Sch, activation signal Swk) based on the determination result whether or not the response signal Sres is received during retry communication (step S104 in FIG. 9). Although the transmission output of 23 is changed, the transmission output may be changed for all radio signals. That is, the ECU 21 does not have to change the transmission output of the transmission circuits 22 and 23 in accordance with the transmission timing of a specific wireless signal, and may merely change the transmission output of the transmission circuits 22 and 23.

  The processes of steps S102 and S103 in the flowchart of FIG. 9 may be omitted. In this case, when it is determined that the Ack signal Sac is continuously received in step S101 (YES in step S101), the ECU 21 shifts the process to step S104.

  The process of step S106 in the flowchart of FIG. 9 may be omitted. In this case, when it is determined in step S104 that the response signal Sres is not received in the retry communication (NO in step S104), the ECU 21 ends the process. Even in this case, wasteful power consumption of the portable device 13 can be suppressed at least in the first situation where the communication state between the vehicle 11 and the portable device 13 is shown in FIG. 4B.

  Although the ECU 21 switches the transmission output of the transmission circuits 22 and 23 from the initial value to the first transmission output (> initial value) in step S203 in the flowchart of FIG. 10, the response signal Sres may not be received. Conceivable. In this case, the ECU 21 may increase the transmission output of the transmission circuits 22 and 23 stepwise or continuously until the response signal Sres is received.

  -Even though the ECU 21 switches the transmission output of the transmission circuits 22 and 23 from the initial value to the second transmission output (<initial value) in step S301 in the flowchart of FIG. 12, the Ack signal Sac is received. Is also conceivable. In this case, the ECU 21 may decrease the transmission output of the transmission circuits 22 and 23 stepwise or continuously until the Ack signal Sac is not received.

  In the process of step S303 in the flowchart of FIG. 12, instead of stopping the transmission of the wireless signal (the activation signal Swk), the transmission of the activation signal Swk is continued with the transmission output of the transmission circuits 22 and 23 reduced. You may By keeping the receivable area Ap in a reduced state, the portable device 13 receives the activation signal Swk, and the portable device 13 responds to the activation signal Swk periodically transmitted from the vehicle 11. It can be suppressed to continue.

  DESCRIPTION OF SYMBOLS 10 ... Electronic key system, 11 ... Vehicle, 12 ... Vehicle-mounted device, 13 ... Portable device, 33 ... Door lock device (door lock), A1, A2 ... Communication area, Swk ... Activation signal (1st response request), Sch ... challenge signal (second response request), Sac ... Ack signal (first response), Sres ... response signal (second response).

Claims (5)

The in-vehicle device wirelessly transmits a response request to a communication area set around the vehicle, and the portable device wirelessly transmits a response to the response request.
The in-vehicle device authenticates the portable device upon receipt of a first response to a first response request periodically transmitted to detect an approach of the portable device to a vehicle. And the second response to the second response request is received, and when it is determined that the portable device is located in the communication area, the door lock operation of the vehicle is performed. In the permitted electronic key system,
When the first response is continuously received, the in-vehicle device increases or decreases the transmission output of the in-vehicle device according to the reception status of the second response, and based on the subsequent response status of the portable device. An electronic key system for stopping transmission of the first response request. In the electronic key system according to claim 1,
The in-vehicle device transmits at least the second response request when the second response is not received as the reception status of the second response when the first response is continuously received. If the second response is received as the subsequent response status of the portable device, the first response is not determined that the portable device is located within the communication area. Electronic key system to stop sending response requests. In the electronic key system according to claim 1 or 2,
When the second response is received as the reception status of the second response in the case where the first response is continuously received, the in-vehicle device receives the second response, but the second response is not correct. An electronic device for reducing the transmission power when transmitting the response request of 1, and stopping the transmission of the first response request when the first response is not received as a subsequent response status of the portable device Key system. The electronic key system according to any one of claims 1 to 3.
When the second response to the second response request is not received, or the second response received is not correct, the on-vehicle device performs the second response request a predetermined number of times. Electronic key system to retransmit. The electronic key system according to any one of claims 1 to 4.
The electronic key system determines that the in-vehicle device continues to receive the first response when the number of receptions of the first response in a predetermined period exceeds a threshold number of times.