Patent Publication Number: US-6218929-B1

Title: Door entry control by wireless communication

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application relates to and incorporates herein by reference Japanese Patent Application No. 09-171009, filed on Jun. 12, 1997. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a door entry control by wireless communication that can be used for vehicles or the like having an automatic door locking and unlocking mechanism. 
     2. Description of Related Art 
     There are proposed recently various automatic door entry control systems such as vehicle door control systems that unlock vehicle doors without use of a door key. Those systems are disclosed in JP-A-62-86278 or JP-U-63-129643. In one system, a signal transmitter held by a vehicle driver (user) transmits a specific code signal upon a driver&#39;s manual switch operation and a signal receiver mounted in a vehicle receives this code signal, so that the vehicle door may be locked and unlocked when the received code signal coincides with a certifying code. In another system, a signal transmitter/receiver mounted in a vehicle transmits a signal upon a driver&#39;s manual operation of a switch mounted in a vehicle door knob or the like, and a signal transmitter held by the driver transmits in return a code signal to the transmitter/receiver. Those systems require drivers to operate a switch manually, causing inconvenience when the driver has to carry many baggage or the like. 
     It is therefore proposed in JP-A-5-44367 to eliminate a driver&#39;s manual switch operation at the time of unlocking a vehicle door. In this system, a signal transmitter held by a driver continues to transmit a code signal for a certain time period after the turn-on of its door unlocking switch so that the door may be unlocked when the driver approaches to a signal receiver mounted in a vehicle after manually operating the door unlocking switch. Thus, this system also requires the driver to operate the door unlocking switch before approaching to the vehicle, shortening life of a battery in the transmitter. 
     It is also proposed in JP-A-5-156851 that a signal receiver mounted in a vehicle transmits a radio signal for searching an associated signal transmitter and the signal transmitter held by a driver transmits in return a coded radio signal to the receiver upon receiving the searching radio signal from the receiver. This system enables a vehicle door to be unlocked automatically without drive&#39;s manual switch operation for door unlocking. In this system, the vehicle door is locked and unlocked automatically whether the receiver is inside or outside of the radio signal receiving area. As a result, the vehicle door is locked if the driver leaves to an outside of a radio signal receiving area, even if the vehicle door is locked manually by the driver. Although it is possible to disable the transmitter to transmit the radio signal if the vehicle door has been locked manually, this requires the driver to change the mode of the transmitter from a door unlocking-disabling mode to a door unlocking mode without fail before the next use of the vehicle. 
     SUMMARY OF THE INVENTION 
     It is therefore an object of the present invention to improve the conventional door entry control for vehicles or the like by a wireless communication. 
     It is a further object of the present invention to provide a door entry control which enables manual door locking without requiring a user&#39;s additional manual operation for an automatic door unlocking. 
     According to the present invention, a signal transmitter held by a user modulates, in accordance with a code signal assigned specifically to each user, a signal received from a signal transmitter/receiver to transmit the modulated signal in return. When the user holding the transmitter enters from the outside of a signal demodulating area into the inside of the signal demodulating area, a door is switched automatically from the locked condition to the unlocked condition. After a manual door locking, the signal transmitter/receiver disables an automatic door unlocking as long as the modulated code signal is demodulated properly. Thus, the automatic door unlocking is enabled and disabled as long as the user is in the outside of the signal demodulating area and in the inside of the signal demodulating area, respectively. This requires no additional manual operation on the part of the user for switching between the automatic mode and the manual mode. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Other objects, features and advantages of the present invention will become more apparent from the following detailed description made with reference to the accompanying drawings. In the accompanying drawings: 
     FIG. 1 is a block diagram showing a door entry control system according to an embodiment of the present invention; 
     FIGS. 2A and 2B are time charts showing operation of the embodiment shown in FIG. 1; 
     FIG. 3 is a schematic view showing installation of antennas in the embodiment shown in FIG. 1; 
     FIG. 4 is a flow chart showing a control process in the embodiment shown in FIG. 1; and 
     FIG. 5 is a schematic view showing installation of antennas in a modification of the embodiment shown in FIG.  1 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     A door entry control system according to an embodiment is applied to a vehicle. The control system generally comprises a smart card  1  such as a semiconductor integrated circuit type card held by a vehicle driver (user), and a door locking/unlocking control unit  2  mounted in a vehicle. The card  1  and the control unit  3  are constructed to perform a wireless communication. 
     The card  1  is a portable unit that includes therein a modulator circuit (MOD)  101  having a carrier frequency of 2.45 GHz, an antenna  102 , a transmitter circuit (TR)  103  having a transmission frequency of 400 MHz, antenna  104  and a microcomputer (MC)  105 . Those electronic circuits are supplied with electric power from a storage battery  108 . The card  1  has thereon a door locking switch  106  and a door unlocking switch  107 . Those switches  106 ,  107  are operable manually by the driver for instructing an automatic vehicle door locking and unlocking. 
     Specifically, the modulator circuit  101  modulates a radio signal of 2.45 GHz from the control unit  2  by a code signal produced from the microcomputer  105  and the antenna  102  transmits the modulated radio signal. The code signal is assigned to be specific to each card (vehicle user)  1  so that ID (identification) of each card may be certified by the code signal. This code signal is preferably encrypted when produced by the microcomputer  105 . 
     The microcomputer  105  produces a door locking signal in response to manual activation of the locking switch  106  so that the transmitter circuit  103  modulates a radio signal of 400 MHz by the locking signal and the antenna  104  transmits the modulated radio signal. Similarly, the microcomputer  105  produces a door unlocking signal in response to manual activation of the unlocking switch  107  so that the transmitter circuit  103  modulates the radio signal of 400 MHz by the unlocking signal and the antenna  104  transmits the modulated radio signal. 
     The locking/unlocking control unit  2  includes a pair of transmitter/receiver circuits  201 ,  203  of 2.45 GHz and antennas  202 ,  204 . It further includes a receiver circuit of 400 MHz, an antenna  206 , a microcomputer  207  and an output circuit  208  for switching the locking and unlocking of vehicle doors. Those electronic circuits are supplied with electric power from a storage battery  213 . 
     The transmitter/receiver circuits  201 ,  203  are constructed similarly to transmit radio signals of 2.45 GHz from associated antennas  202 ,  204  and to receive the radio signal transmitted in return from the card  1 . The transmitter/receiver circuits  201 ,  203  demodulate the received radio signal to produce the code signals to the microcomputer  207 . The microcomputer  207  is programmed to check whether the code signals produced from the transmitter/receiver circuits  201 ,  203  with a code assigned specifically to each vehicle and stored. 
     The microcomputer  207  turns on and off of the transmitting circuit sections of the transmitter/receiver circuits  201 ,  203  to operate the transmitter/receiver circuits  201 ,  203  as a signal transmitter and a signal receiver alternately as shown in FIGS. 2A and 2B. Each time period for signal transmission and signal reception has  200 ms thereby to save electric power consumption. 
     The antenna  202  connected with the transmitter/receiver circuit  201  is mounted on the vehicle exterior, as shown in FIG. 3, for searching the card  1  held by the driver outside of the vehicle. Specifically, the antenna  202  is a patch type antenna having a high directivity and is attached to the exterior of a swing type window  402  or a pillar  403  near a door knob  401  at the side of a driver&#39;s seat. Thus, the transmitter/receiver circuit  201  limits its demodulating area, i.e., a wireless communication area in which the received signal can be demodulated accurately, to a certain distance from the door knob  401 . The demodulating area may be about 1.5 m from the knob  401 . 
     The antenna  204  connected with the transmitter/receiver circuit  203  is attached to a card holding case in the vehicle interior for searching the card  1  held by the driver inside of the vehicle. The card holding case  3  may be provided on an instrument panel near a steering wheel so that the driver may put the card  1  thereon after entering the passenger compartment. 
     The receiver circuit  205  demodulates the radio signal of 400 MHz received by the antenna  206  to produce a locking signal or an unlocking signal to the microcomputer  207 . It is desired that the demodulating area of the received signal is not too limited to enable manual locking and unlocking by the driver. Therefore, the antenna  206  is a non-directional type and may be installed anywhere. It may be attached at the same position as the exterior antenna  202  for 2.45 GHz. 
     The microcomputer  207  is connected to various detector devices such as an engine switch  209  for detecting engine stop and engine rotation, a courtesy switch  210  for detecting opening and closing of the door, and a door locking switch  211  for detecting locking and unlocking of the door. The card holding case  3  has a card detecting switch  212  for detecting existence and absence of the card  1  thereon. 
     The microcomputer  207  is programmed to produce a door locking signal and a door unlocking signal to a door locking actuator (not shown) through an output circuit  208  in response to various received signals. The microcomputer  207  is further programmed to turn on and off the signal transmitting section of the transmitter/receiver circuit  201  in response to a door locking command and a door unlocking command so that the corresponding radio signal may be transmitted and not transmitted from the antenna  202 , respectively. 
     The operation of the above embodiment is described in more detail with reference to a control routine programmed in the microcomputer  207  as shown in FIG.  4 . 
     The microcomputer  207  starts control routine at step S 1  when the battery  213  is connected to supply an electric power in the control unit  3 . The microcomputer determines at step S 2  whether the engine is at a stop, then advancing to step S 3  in response to only the YES determination (engine stop). The microcomputer  207  further determines at step S 3  whether the vehicle door is closed. With the YES determination (closed door), the microcomputer  207  determines at step S 4  whether the card  1  is on the card holding case  3 . With the NO determination (no card), the microcomputer  207  determines at step S 8  whether the door is locked. The YES determination (locked door) together with the foregoing determinations indicate that the driver is outside the vehicle such as before entering the vehicle. 
     The microcomputer  207  instructs at step S 9  the transmission of the radio signal of 2.45 GHz from the antenna  202  on the vehicle exterior for searching the card  1 . If the card  1  is within the signal demodulating area, that is, the driver is near the vehicle, the card  1  receives the radio signal at the antenna  102 , modulates the received signal by the modulator circuit  101  in accordance with the code signal produced by the microcomputer  105 , and transmits the modulated signal in return from the antenna  102 . 
     The modulated signal is received by the antenna  202  and applied to the microcomputer  207  through the transmitter/receiver circuit  202  that demodulates the received modulated signal for identifying the ID of the card  1  from the code signal included in the modulated signal. The microcomputer  207  then determines at step S 10  whether the ID of the card  1  coincides with the code that is specifically assigned to each vehicle and stored in the microcomputer  207 . If the driver is away from the vehicle (that is, outside the wireless communication area) the electric field strength of the modulated signal received by the antenna  202  will be too low to be demodulated correctly for the ID certification at step S 10 . If the driver is close to the vehicle (that is, inside the wireless communication area), on the other hand, the electric field strength of the modulated signal received by the antenna  202  will be high enough to be demodulated correctly for the ID certification at step S 10 . 
     The microcomputer  207  further determines at step S 11  whether the driver has instructed a door unlocking by the unlocking switch  107  on the card  1 . This determination may be made based on another radio signal of 400 MHz modulated by the transmitter circuit  103  in response to the operation of the switches  106 ,  107  and transmitted from the antenna  104 . This modulated signal is received by the antenna  206  and demodulated by the receiver circuit  205 . With the YES determination (certified ID) at step S 10  or the YES determination (unlocking signal) at step S 11 , the microcomputer  207  produces the door unlocking command signal to the output circuit  208  at step S 12  thereby to effect the door unlocking automatically. The microcomputer  207  then stops a signal transmission operation of the transmitter/receiver circuit  201  and the antenna  202  at step S 13 . 
     With the No determinations (uncertified ID and no unlocking signal) at steps S 10  and S 11 , the microcomputer  207  repeats steps S 9  through S 11  assuming that the driver is far away from the vehicle and the door unlocking is not instructed. 
     The microcomputer  207  determines at step S 14  whether a predetermined time period, for instance  30  seconds, has elapsed after the automatic door unlocking operation. With the NO determination (less that 30 seconds), the microcomputer  207  determines at step S 15  whether the door is open. With the NO determination (closed door), the microcomputer  207  returns to step S 14  to continue the checking unless the door opens actually. With the YES determination (more than 30 seconds) at step S 14 , the microcomputer  207  assumes that the driver has no intention to enter the vehicle and produces at step S 16  a door locking command to the output circuit  208  thereby to effect automatically the locking of the door once unlocked in step S 12 . After steps S 15 , S 16 , the microcomputer returns to step S 2  to transmit the radio signal from the antenna  202  again as described above. 
     The microcomputer  207  assumes in response to the YES determination (open door) that the driver has entered the vehicle. In this instance, as long as the driver sets the card  1  in the holding case  3  in the vehicle compartment, the card  1  activates the card switch  212  so that the processing of the microcomputer  207  moves from step S 4  to step S 5  to cause the transmitter/receiver circuit  203  to transmit another radio signal of 2.45 GHz from the interior antenna S 5 . The card  1  transmits in return the radio signal modulated in the same manner as described above. This modulated signal is received by the antenna  204  and demodulated by the transmitter/receiver circuit  203  so that the code signal is applied to the microcomputer  207 . The microcomputer  207  then certifies the ID code at step S 6  in the same manner as in step S 10 . With the YES determination (certified ID) at step S 6 , the microcomputer  207  stops the transmission of the radio signal from the antenna  204  and returns to step S 2 . As long as the engine runs (NO determination at step S 2 ) for a vehicle drive, the microcomputer  207  repeats only step S 2 . 
     When the engine stops after the vehicle drive, the control moves from step S 2  to step S 3 . The driver will take up the card  1  from the holding case  3  and leave the vehicle after closing the door. In this instance, the control moves from step S 3  to step S 8  through step S 4 . The control will further move to step S 17  because the door will not be locked (NO determination at step S 8 ) immediately after the door closing. 
     The microcomputer  207  determines at step S 17  whether a door locking instruction from card  1  is received by the antenna  206 . This locking instruction may be issued by the driver&#39;s manual operation on the locking switch  106  and included in the radio signal modulated by the transmitter circuit  103  in the same manner as the radio signal is modulated by the door unlocking switch  107 . The microcomputer  207  repeats steps S 2 -S 4 , S 8 , S 17  unless the door locking instruction is issued from the driver. Upon reception of the door locking signal (YES determination at step S 17 ), the microcomputer  207  produces at step S 18  the door lock command to the output circuit  208  to effect door locking. 
     The microcomputer  207  then causes at step S 19  the transmitter/receiver circuit  201  and the exterior antenna  202  to transmit the radio signal. As the driver will still be near the vehicle immediately after closing the door for leaving, the electric field strength of the radio signal received in return from the card  1  after the modulation by the code signal in the card  1  will be high enough to be demodulated by the transmitter/receiver circuit  201 . The microcomputer  207  certifies at step S 20  the ID of the card  1  in the same manner as in steps S 6 , S 10 . The microcomputer  207  repeats steps S 19 , S 20  with the YES determination (certified ID). Thus, the door will be kept locked and the automatic unlocking is disabled, as long as long as the driver holding the card  1  is within the demodulating area from the vehicle. With NO determination at step S 20  indicating that the driver has left far away from the vehicle, transmission of the radio signal from the transmitter/receiver circuit  201  and antenna  202  may be stopped. With NO determination (no manual locking instruction) at step S 17 , the control of the microcomputer  207  returns to step S 2 . In this instance, it is preferred to perform the radio signal transmission and the ID certification as in steps, S 18 , S 19 , and to lock the door automatically as in step S 18  if the ID certification becomes impossible. 
     The electric field strength of the radio signal transmitted from the card  1  will become too low to demodulate in the control unit  2  as the driver leaves far away from the vehicle. Thus, the microcomputer  207  repeats steps S 9 -S 11  after steps S 2 -S 4 , S 8  as in the case of driver&#39;s approaching to the vehicle. If the driver approaches closely enough to the vehicle again even immediately after the locking of the door, the door will be unlocked automatically through steps S 10  and S 12  without manual activation of the door unlocking switch  107  by the driver. 
     It is to be noted in the above embodiment that the electric power consumption can be minimized, because the microcomputer  207  disables at step S 13  the radio signal transmission from the transmitter/receiver circuit  201  and the antenna  202  in response to the door unlocking signal from the card  1  and enables at step S 19  the radio signal transmission in response to the door locking signal from the card  1 . It is also possible to minimize the power consumption by other control or to eliminate the minimization of power consumption. 
     In the control returning from step S 15  to step S 14 , a door locking signal checking step that is the same as step S 17  may be executed so that the control moves to step S 18  with the reception of the locking instruction from the card  1 . This enables the door locking even before the elapse of 30 seconds. 
     It is also possible to eliminate steps S 14 -S 16  that automatically locks the door when the door is not opened for the predetermined time period. In this instance, after the door is unlocked at step S 12  the control moves to step S 17  from steps S 2 -S 4 , S 8 . Therefore, the door locking is effected only by the activation of the locking switch  106  on the card  1 . 
     Although the door locking may be effected only by the activation of the door locking switch  106 , the door is preferably locked automatically when the driver leaves away out of the demodulating area of the control unit  2 . This automatic locking may be performed as disclosed in JP-A-5-156851. That is, after the door locking (steps S 17 , S 18 ) by the activation of the door locking switch  106 , the door unlocking may be prohibited as long as the card  1  is in the demodulating area from the vehicle so that the automatic unlocking and the locking by the manual switch operation may not collide. Thus, when the driver approaches to the vehicle next time to enter the vehicle, the door will be unlocked automatically without any manual switching operation on the part of the driver. As this system is capable of locking the door automatically, this modification will be advantageous particularly in vehicles such as a package delivery vehicle from which packages are loaded into and unloaded from the vehicle frequently. In this instance, the exterior antenna  202  is mounted preferably on both of the vehicle door at the driver&#39;s seat side and the rear package loading/unloading door  404 . 
     Still further, the frequency of the radio signals may be other than 2.45 GHz and 400 MHz, and the infrared signal may be used for a wireless communication between the card  1  and the control unit  2  instead of the radio signal. 
     The manual locking of the door may be performed not only by the manual switch operation on the card  1  but also by a conventional ignition or door key as long as the door is operable by a wireless locking/unlocking mechanism and by a mechanical key locking/unlocking mechanism. 
     Still further, the present invention is not limited to doors in a vehicle as disclosed in the above embodiment and its modifications. The present invention may also be applied to other doors as in buildings or the like.