JP2013185344A - Electronic key with charging function - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electronic key with a charging function capable of securing user-friendliness by delaying such a situation that a battery runs out.SOLUTION: A battery voltage determination part 15 monitors a voltage Vk of a primary battery 6 as a main power supply for an electronic key 1. When a voltage Vx is equal to or less than a threshold value Vk, a restricting operation part 16 changes over the operation mode of an RFID tag 9 into an operation restricting mode to restrict the power consumption increasing operation of the RFID tag 9 during short-distance radio communication. A charge execution part 17 supplies part of power obtained by the operation restriction, out of radio waves received as a power supply from an external reader writer 8, to a power storage device 13 to charge the power storage device 13. Thus, the power storage device 13 can be used as an alternative power supply when the primary battery 6 runs out.

Description

  The present invention relates to an electronic key with a charging function that can be charged by radio waves received by short-range wireless communication.

  As is well known in the art, many current vehicles are equipped with an electronic key system that performs ID verification wirelessly using an electronic key. In this type of electronic key system, there is a key operation-free system in which the vehicle and the electronic key perform ID verification (smart verification) by narrow-band wireless communication (LF-UHF bidirectional communication) (see Patent Document 1 and the like). The electronic key for the key operation free system performs communication operation using the primary battery in the key as a power source.

JP 2005-262915 A

  By the way, when the battery of the electronic key runs out, the electronic key cannot perform the communication operation. At this time, the vehicle is operated by, for example, performing mechanical ID verification using a mechanical key housed in an electronic key, or performing ID verification using a transponder with a built-in key. However, for a user who does not know how to deal with this situation, if the battery of the electronic key runs out of battery, it may be confused if the vehicle cannot be moved. Therefore, there has been a need for technology development that enables the user to use the electronic key for as long as possible.

  The objective of this invention is providing the electronic key with a charge function which can ensure a user's convenience by postponing the condition where a battery runs out.

  In order to solve the above problems, in the present invention, a key main power supply, a short-range wireless verification unit that operates with radio waves received from a communication partner, and performs authentication by short-range wireless communication with the communication partner, In the electronic key with a charging function, comprising: power storage means that is an auxiliary power supply of the key main power supply; voltage monitoring means that monitors the voltage of the key main power supply; and when the voltage of the key main power supply is equal to or lower than a threshold value, The gist of the invention is that the short-range wireless verification unit includes a limiting unit that limits an operation that consumes a large amount of power, and a charging execution unit that charges the power storage unit with a part of the power obtained by the limitation.

  According to the configuration of the present invention, the voltage of the key main power supply is monitored, and when the voltage of the key main power supply becomes equal to or lower than the threshold, the operation with high power consumption is limited in the short-range wireless verification unit, and the power obtained by the limitation The power storage means is charged by a part of the power supply means, so that the power storage means can be used as an alternative power source when the battery of the key main power source is exhausted. For this reason, even if the key main power source runs out of battery, the electronic key can be operated by the electric power of the power storage means, so that the usage period of the electronic key can be extended. Therefore, it is possible to reduce the frequency of battery life of the electronic key to a low level, and the effect of securing user convenience is enhanced.

  In the present invention, the key main power source is used as a power source, and a narrow-range wireless verification unit that performs authentication with the communication partner and the communication partner with the communication partner is provided. By substituting for the key main power supply, the gist of the invention is to enable the narrow band wireless verification unit to operate even when the key main power supply runs out of batteries. According to this configuration, since the power storage means is used as an alternative power source for the narrow-range wireless verification unit, it is possible to continue supplying power to the narrow-range wireless verification unit even if the key main power source runs out of battery. For this reason, even if the key main power source runs out of battery, it is possible to continue the collation by the narrow band wireless communication using the electronic key.

  The gist of the present invention is that the part of the power is surplus power obtained from the difference between the power of the radio wave received as a power source and the power required by the short-range wireless verification unit after the restriction. . According to this configuration, since the power storage unit is charged with the surplus power obtained when the operation with high power consumption of the short-range wireless matching unit is restricted, it is possible to charge the power storage unit with relatively large power. . For this reason, it becomes possible to charge an electrical storage means efficiently in a short time.

  The gist of the present invention is that the power storage means is capable of storing electric power that allows the narrow area wireless verification unit to perform the narrow area wireless communication at least once. According to this configuration, since a small-scale member may be prepared as the power storage means, even if the power storage means is provided in the electronic key, it contributes to downsizing of the electronic key.

  In the present invention, the restriction is released on condition that at least one of the voltage of the key main power source is equal to or higher than a threshold value and that the power storage unit stores a certain amount of power is satisfied. The gist of the invention is that it includes a restriction releasing means. According to this configuration, it is possible to return the electronic key to the original state when the restriction release conditions are aligned.

  ADVANTAGE OF THE INVENTION According to this invention, a user's convenience can be ensured by postponing the condition where a battery runs out.

The schematic block diagram of the electronic key of one Embodiment. The timing chart which shows the communication sequence of near field communication. A graph showing power consumption required for each operation of the RFID tag. Explanatory drawing which shows the concept of the surplus electric power for charge. Operation | movement explanatory drawing when an external reader / writer is a smart phone. Operation | movement explanatory drawing when an external reader / writer is an immobilizer communication apparatus.

An embodiment of an electronic key with a charging function embodying the present invention will be described below with reference to FIGS.
As shown in FIG. 1, the electronic key 1 is a vehicle key for performing ID collation with the vehicle 2 through wireless communication using an electronic key system. The electronic key system is a kind of key system in which the electronic key 1 and the vehicle 2 perform ID collation by narrow-band radio (communication distance: several meters) in response to communication from the vehicle 2. The electronic key 1 corresponds to an electronic key with a charging function, and the vehicle 2 corresponds to a communication partner.

  The electronic key 1 transmits a central processing unit (CPU) 3 that mainly controls the electronic key 1, a receiving unit 4 that receives radio waves in the LF (Low Frequency) band, and radio waves in the UHF (Ultra High Frequency) band. A transmission unit 5 is provided. The electronic key 1 is provided with a primary battery 6 as a power source for the electronic key 1. A diode 7 is connected between the CPU 3 and the primary battery 6 to prevent reverse current flow of the primary battery 6. The CPU 3 executes smart communication according to the electronic key system in the electronic key 1. The electronic key 1 performs smart communication with the vehicle 2 using the primary battery 6 as a power source. Note that the CPU 3 corresponds to a narrow-area wireless verification unit, and the primary battery 6 corresponds to a key main power source.

  The vehicle 2 periodically transmits a request signal Srq by LF radio waves and monitors the presence of the electronic key 1. When receiving the request signal Srq, the electronic key 1 transmits the electronic key ID signal Sid registered in the electronic key 1 to the vehicle 2 in a UHF manner in response to the request signal Srq. The vehicle 2 performs smart matching based on the electronic key ID signal Sid received from the electronic key 1. At this time, if the vehicle outside smart collation is established with the electronic key 1 outside the vehicle, the door locking / unlocking operation is permitted / executed. If the vehicle internal smart collation is established with the electronic key 1 inside the vehicle, one Engine start operation by a push-type engine switch is permitted.

  The electronic key 1 is also a key capable of wireless communication with the external reader / writer 8 by the short-range wireless communication system. Short-range wireless communication is established only in the immediate vicinity (communication distance: about 10 cm). For short-range wireless communication, load modulation communication is used. For example, immobilizer communication or NFC (Near Field Communication) communication is employed. The load modulation communication is a communication in which a signal is put on a non-modulated wave by turning on / off the load on the electronic key 1 side. The external reader / writer 8 constitutes a communication partner.

  The electronic key 1 is provided with an RFID (Radio Frequency IDentification) tag 9 as an IC (Integrated Circuit) for short-range wireless communication. The RFID tag 9 is provided with a tag control unit 10 for controlling the operation of the RFID tag 9, an antenna 11 capable of transmitting and receiving LF radio waves, and a memory 12 in which various data handled by short-range radio are written and stored. . The RFID tag 9 performs near field communication (load modulation communication) with the external reader / writer 8. The RFID tag 9 can exchange signals with the CPU 3 by serial communication, and can acquire, for example, remaining battery data of the primary battery 6. The RFID tag 9 corresponds to a short-range wireless verification unit.

  The external reader / writer 8 periodically performs near field communication (load modulation communication) with the RFID tag 9. The external reader / writer 8 is a mobile phone such as a smartphone when the near field communication is NFC, for example. The external reader / writer 8 is an immobilizer communicator disposed in the vicinity of the engine switch when the short-range wireless communication is immobilizer communication.

  As shown in FIG. 2, the external reader / writer 8 regularly transmits a wake signal Swk by a polling operation to monitor whether the RFID tag 9 is held over itself. The external reader / writer 8 starts communication with the RFID tag 9 when receiving the ack signal Sack with respect to the wake signal Swk. Thereafter, the external reader / writer 8 continuously transmits an unmodulated carrier wave Svc serving as a power source for the RFID tag 9 to execute load modulation communication. At this time, the external reader / writer 8 transmits a transmission signal to the RFID tag 9 by placing the transmission data Ddt on the carrier wave Svc. When responding to the transmission signal, the RFID tag 9 superimposes the response signal (load modulation signal) Src on the carrier wave Svc by switching on / off of the internal load. The external reader / writer 8 receives the response from the RFID tag 9 by reading the response signal Src on the carrier wave Svc.

  The external reader / writer 8 first performs authentication communication with the RFID tag 9 after establishing the communication that has received the ACK signal Sack from the RFID tag 9. When the validity of the RFID tag 9 can be confirmed, the external reader / writer 8 shifts to communication data exchange. The authentication of the RFID tag 9 is authentication for confirming the communication standard, the ID of the RFID tag 9 and the like, for example.

  The operations performed by the RFID tag 9 during load modulation communication include, for example, encryption processing, data writing to the memory 12 (memory write), data reading from the memory 12 (memory read), data transmission, data reception, and standby. Of course, the RFID tag 9 also performs other operations.

  As shown in FIG. 1, the electronic key 1 is provided with a charging function capable of charging the key power supply by the carrier wave Svc received from the external reader / writer 8. In the charging function of this example, when the voltage Vx of the primary battery 6 is equal to or less than the threshold value Vk, a part of the carrier wave Svc received from the external reader / writer 8 during short-range wireless communication is charged to the power storage device 13 in the electronic key 1. It is a function to do. Thereby, even if the primary battery 6 runs out of battery, for example, several smart communications can be performed by the power of the power storage device 13. The power storage device 13 corresponds to power storage means (auxiliary power source).

  The power storage device 13 includes a power storage device such as an electric double layer capacitor. The power storage device 13 is connected to the CPU 3 via a diode 14 for preventing a backflow of current. The power storage device 13 can store enough power for the electronic key 1 to perform smart communication several times.

  FIG. 3 shows the relationship of the power consumption Px of each operation in the RFID tag 9. As shown in the figure, the power consumption Px required for each operation of the RFID tag 9 is in the order of high power, for example, encryption processing → memory writing → data reception → memory reading → data transmission → waiting, There are different current conditions depending on the processing content. In the case of this example, for example, operations of cryptographic processing and memory writing are operations with relatively large power consumption Px.

  The external reader / writer 8 transmits the carrier wave Svc with a constant transmission power Pr and supplies power to the RFID tag 9. The transmission power Pr of the carrier wave Svc is set to a value that can secure at least the power required for the encryption process so that the encryption process, which is the operation with the largest power consumption Px in the RFID tag 9, can be executed.

  In the case of this type of electronic key 1 shown in FIG. 1, the primary battery 6 is consumed every time smart communication is performed. Therefore, if the number of times of use increases, the voltage Vx of the primary battery 6 is near “0”. The battery will eventually run out. When electronic key 1 runs out of battery, smart communication verification cannot be performed. A user who is not present is confused when he cannot move the vehicle 2.

  Therefore, as shown in FIG. 4, the charging function of this example monitors the voltage Vx of the primary battery 6 of the electronic key 1, and when the voltage Vx of the primary battery 6 is equal to or lower than the threshold value Vk, the operation mode of the RFID tag 9 Is switched to the operation restriction mode (energy saving mode) to restrict the operation with large power consumption Px. Thus, if the operation of the RFID tag 9 is restricted, the power used in the RFID tag 9 is floated by this restriction. Therefore, the power storage device 13 is charged with the surplus power Prs that is the floated power, and the power storage device 13 is replaced with the primary battery. 6 ready to be used as an alternative power source. FIG. 4 illustrates memory writing as an example.

  As shown in FIG. 1, the tag control unit 10 has a battery voltage determination unit 15 that monitors the voltage Vx of the primary battery 6, a restriction operation unit 16 that restricts the operation of the RFID tag 9, and is obtained by this operation restriction. And a charge execution unit 17 that charges the power storage device 13 with a part of the power that can be generated. The battery voltage determination unit 15 corresponds to a voltage monitoring unit, the limiting operation unit 16 corresponds to a limiting unit, and the charging execution unit 17 corresponds to a charging execution unit.

  The battery voltage determination unit 15 is electrically connected to the primary battery 6 through electric wiring. The battery voltage determination unit 15 sequentially monitors the voltage Vx of the primary battery 6 and outputs the detected voltage data to the limiting operation unit 16.

  The restriction operation unit 16 compares the voltage Vx of the primary battery 6 with the threshold value Vk, and switches the operation mode of the RFID tag 9 to the operation restriction mode when the voltage Vx is equal to or less than the threshold value Vk. As described above, the restriction operation unit 16 restricts processing with large power consumption Px in the RFID tag 9 by setting the RFID tag 9 in the operation restriction mode. That is, when the RFID tag 9 performs short-range wireless communication with the external reader / writer 8, if the voltage Vx of the primary battery 6 is equal to or lower than the threshold value Vk, communication is performed while restricting the operation with large power consumption Px.

  When the RFID tag 9 is in the operation restriction mode, the charging execution unit 17 sends a part of the carrier wave Svc received as power to the power storage device 13 to charge the power storage device 13. The charging execution unit 17 of this example efficiently charges the power storage device 13 with the surplus power Prs generated by switching to the operation restriction mode. As shown in FIG. 4, the surplus power Prs is power corresponding to the difference between the power Pr received as a power source from the external reader / writer 8 and the power Pmin that is minimum required by the RFID tag 9 after restriction.

  As shown in FIG. 1, the tag control unit 10 is provided with a restriction release unit 18 that releases the operation restriction mode of the RFID tag 9. For example, when the electric charge stored in the power storage device 13 becomes equal to or greater than a certain value, the restriction release unit 18 returns the operation mode of the RFID tag 9 to the original normal mode. In addition, when the voltage Vx returns to the maximum value (including its neighborhood value), for example, when the primary battery 6 is replaced, the restriction release unit 18 returns the operation mode of the RFID tag 9 to the original normal mode. . The restriction release unit 18 corresponds to restriction release means.

Next, the operation of the electronic key 1 having the charging function of this example will be described with reference to FIGS. 1 and 4 to 6.
As shown in FIG. 1, it is assumed that the electronic key 1 is held over an external reader / writer 8 and short-range wireless communication is performed between them. At this time, the RFID tag 9 performs short-range wireless communication by performing an operation corresponding to each request received from the external reader / writer 8. That is, the RFID tag 9 performs various processes such as encryption processing, memory writing, memory reading, data reception, data transmission, and standby in response to a request from the external reader / writer 8.

  The battery voltage determination unit 15 sequentially monitors the voltage Vx of the primary battery 6 and outputs the voltage data to the limiting operation unit 16. The restriction operation unit 16 compares the voltage Vx and the threshold value Vk, and when the voltage Vx becomes equal to or less than the threshold value Vk, the operation mode of the RFID tag 9 is switched to the operation restriction mode as shown in FIG. Therefore, the RFID tag 9 is short-range wireless under the operation restriction mode, and communicates with the external reader / writer 8 while restricting processing with large power consumption Px. At this time, a restriction is imposed on the operation with large power consumption Px, and accordingly, excessive surplus power Prs as shown in FIG. 4 is generated. The charge execution unit 17 supplies the surplus power Prs to the power storage device 13 to efficiently charge the power storage device 13.

  As shown in FIG. 5, when the external reader / writer 8 is a smartphone, for example, when the electronic key 1 is held over the external reader / writer 8, the RFID tag 9 transmits the remaining battery level data of the primary battery 6 to the external reader / writer 8. . The external reader / writer 8 grasps the remaining battery level of the electronic key 1 based on the received remaining battery level data. If the remaining battery level is equal to or lower than the threshold value, the external reader / writer 8 displays, A message such as “It is out of charge. Please recharge” is displayed. At this time, the charging execution unit 17 charges the power storage device 13 with a part of the carrier wave Svc received from the external reader / writer 8 (surplus power Prs).

  Further, as shown in FIG. 6, when the external reader / writer 8 is an immobilizer communication device, for example, when the electronic key 1 is held over the external reader / writer 8, the immobilizer is connected between the RFID tag 9 in the electronic key 1 and the external reader / writer 8. Communication is performed. Also at this time, the charging execution unit 17 charges the power storage device 13 with a part of the carrier wave Svc (surplus power Prs) received from the external reader / writer 8 during immobilizer communication.

  The “restriction” in this example is a process that does not perform (cancel) the operation in the RFID tag 9. In this case, short-range wireless communication is not established, but if the external reader / writer 8 is notified that communication is not established, the user can be notified that the remaining amount of the primary battery 6 is low. The “restriction” may be a minimum power level at which communication can be established. In this case, it is possible to establish near field communication.

  The power storage device 13 is a power storage device such as an electric double layer, and can store power capable of performing smart communication several times. Therefore, even if the primary battery 6 runs out of battery, smart communication can be executed several times with the electronic key 1 using the power of the power storage device 13 as a power source. Therefore, as a result, the battery life of the electronic key 1 can be extended, and the frequency at which the electronic key 1 falls out of battery can be reduced. Therefore, it is also a care for a user who does not know how to deal with the battery of the electronic key 1 when the battery runs out.

According to the configuration of the present embodiment, the following effects can be obtained.
(1) During short-range wireless communication, the voltage Vx of the primary battery 6 is monitored, and when the voltage Vx falls below the threshold value Vk, the RFID tag 9 restricts the operation with large power consumption Px, and surplus power obtained by the restriction The power storage device 13 is charged by Prs, and the power storage device 13 can be used as an alternative power source when the primary battery 6 is dead. For this reason, even if the primary battery 6 runs out of battery, it is possible to continue supplying power to the electronic key 1 by the power storage device 13, so that the usage period of the electronic key 1 can be extended. Therefore, since the frequency of battery exhaustion of the electronic key 1 can be suppressed to a low level, the effect of securing user convenience is enhanced.

  (2) Since the voltage Vx of the primary battery 6 is monitored, it can be accurately determined whether or not the primary battery 6 is nearly exhausted. Thus, charging of the power storage device 13 can be performed at an optimal timing.

  (3) The power storage device 13 is used as an alternative power source for the primary battery 6, and the primary battery 6 is charged with the carrier wave Svc of the external reader / writer 8 for short-range wireless communication. For this reason, both the power used in the RFID tag 9 and the power used in the smart communication of the electronic key 1 are transferred from the external reader / writer 8 to the electronic key 1 without changing the configuration (radio wave output) of the external reader / writer 8. Can be supplied.

  (4) Since the power storage device 13 is used as an alternative power source for the CPU 3, it is possible to continue supplying power to the CPU 3 even when the primary battery 6 runs out of battery. For this reason, even if the primary battery 6 runs out of battery, smart communication can be continued with the electronic key 1.

  (5) Of the carrier wave Svc transmitted from the external reader / writer 8, the power storage device 13 is charged with the power (surplus power Prs) obtained by restricting the operation of the RFID tag 9, so that the carrier wave Svc is used effectively. The power storage device 13 can be charged. Therefore, the power storage device 13 can be efficiently charged without transmitting a new radio wave for charging the power storage device 13 from the external reader / writer 8. In addition, since the power storage device 13 can be charged with relatively large electric power, the power storage device 13 can be efficiently charged in a short time.

  (6) The power storage device 13 is an electric double layer capacitor, and the capacitor is charged with electric power necessary for performing smart communication several times. For this reason, it is possible to use a small-scale component as the power storage device 13, so that even if the power storage device 13 is provided in the electronic key 1, the effect of reducing the size and cost of the key is enhanced.

(7) Since the restriction release unit 18 is provided in the tag control unit 10, the RFID tag 9 can be returned to the original normal mode.
Note that the embodiment is not limited to the configuration described so far, and may be modified as follows.

  The threshold value Vk is not limited to a fixed value, and may be a variable value, for example. In this case, the threshold value Vk can be optimized, for example, by switching the threshold value Vk according to the ambient environmental temperature.

The release of the operation restriction mode is not limited to the replacement of the primary battery 6 or the full charge of the power storage device 13, and can be changed to other modes, for example, returning to the original normal mode when a predetermined time elapses.
-The communication sequence of near field communication is not limited to the example shown in FIG. 2, If the communication distance is a short distance, it can be changed into another aspect.

The operation of the RFID tag 9 is not limited to encryption processing, memory writing, memory reading, data reception, data transmission, standby, etc., and includes other operations.
The amount of power that can be charged by the power storage device 13 is not limited to the amount that allows smart communication to be performed several times, and can be changed to other values such as the amount that can perform smart communication several tens of times.

The power storage device 13 is not limited to an electric double layer capacitor, and can be changed to other types.
-An electrical storage means is not limited to the electrical storage apparatus 13, For example, it is good also as a secondary battery.
The key main power source is not limited to the primary battery 6 that is the power source of the CPU 3, that is, the power source for smart communication of the electronic key 1, and may be any power source for the electronic key 1.

The RFID tag 9 is not limited to being a separate member with respect to the CPU 3, and may be incorporated in the CPU 3, for example.
-A short-distance radio | wireless collation part is not limited to RFID tag 9, What is necessary is just a member which implements short-distance radio | wireless.

The key operation free system may be appropriately changed to another configuration as long as it performs ID collation with the electronic key 1 by narrow-band radio triggered by communication from the vehicle 2.
The short-range wireless communication system is not limited to the immobilizer system or the NFC system, and may be changed as appropriate to other systems.

The charging of the power storage device 13 is not limited to being performed with the surplus power Prs obtained by restricting the operation of the RFID tag 9, and may be a part of the surplus.
The battery voltage determination unit 15, the restriction operation unit 16, the charge execution unit 17, and the restriction release unit 18 are not limited to being provided in the RFID tag 9, and may be provided outside.

-The electronic key 1 is not limited to the key of the vehicle 2, and can be changed into another apparatus and apparatus.
Next, technical ideas that can be grasped from the above-described embodiment and other examples will be described below together with their effects.

  (A) In any one of claims 1 to 5, the short-range wireless verification unit that is in the mode for carrying out the restriction is provided with restriction release means for returning to the original mode. According to this configuration, it is possible to return the short-range wireless verification unit to the original mode.

  DESCRIPTION OF SYMBOLS 1 ... Electronic key with a charge function, 2 ... Vehicle which comprises a communicating party, 3 ... CPU as a narrow area | region radio | wireless collation part, 6 ... Primary battery as a key main power supply, 8 ... External reader / writer which comprises a communicating party, 9 ... RFID tag as short-range wireless verification unit, 13... Power storage device as power storage means (auxiliary power supply), 15... Battery voltage determination unit as voltage monitoring means, 16. Charging execution unit as means, 18... Restriction release unit as restriction release means, Vx... Voltage, Vk... Threshold, Svc .. carrier wave as radio wave for power supply, Px ... power consumption, Pr ... transmission power as power supply, Pmin ... restricted power as a part of radio waves for power supply, Prs ... power required by the wireless communication unit at the time of restriction.

Claims (5)

In an electronic key with a charging function that includes a key main power supply and a short-range wireless verification unit that operates with the communication partner and performs authentication by short-range wireless communication by operating radio waves received from the communication partner.
Power storage means which is an auxiliary power source of the key main power source;
Voltage monitoring means for monitoring the voltage of the key main power supply;
When the voltage of the key main power source is equal to or lower than a threshold value, limiting means for limiting an operation with large power consumption in the short-range wireless verification unit;
An electronic key with a charging function, comprising: charging execution means for charging the power storage means with a part of the electric power obtained by the restriction. The key main power source is a power source, and includes a narrow-band wireless verification unit that performs authentication with the communication partner and the communication partner with the communication partner,
The charging execution means charges the power storage means to substitute for the key main power supply, so that the narrow band wireless verification unit can be operated even when the key main power supply runs out of batteries. The electronic key with a charging function according to claim 1. The part of the electric power is surplus electric power obtained from a difference between electric power of a radio wave received as a power source and electric power required by the short-range wireless matching unit after the restriction. 2. An electronic key with a charging function according to 2. 4. The electronic key with a charging function according to claim 2, wherein the power storage unit is capable of storing electric power at which the narrow area wireless verification unit can perform the narrow area wireless communication at least once. 5. Restriction release means for releasing the restriction on condition that at least one of the voltage of the key main power source is equal to or higher than a threshold and that the electric power storage means stores a certain amount of electric power. The electronic key with a charging function according to claim 1, wherein the electronic key has a charging function.