Patent Publication Number: US-2007115095-A1

Title: Occupant approach detection apparatus, occupant approach detection system, and occupant approach detection method

Description:
BACKGROUND OF THE INVENTION  
      1. Field of Invention  
      The present invention relates to an occupant approach detection apparatus, an occupant approach detection system and an occupant approach detection method which detect a vehicle occupant approaching the vehicle.  
      2. Description of Related Art  
      There is a technology for detecting a vehicle occupant, who carries a portable unit, approaching the vehicle by performing radio communication between an on-vehicle unit mounted on the vehicle and the portable unit carried by the occupant. Such a technology is used as an element technology, for example, in a so-called smart entry system, which automatically locks/unlocks doors of the vehicle according to the occupant&#39;s approach or departure. In the smart entry system, it is desirable that only the door approached by the occupant be locked or unlocked. In order to achieve this, proposed is a technology for detecting, from a plurality of doors of the vehicle, a door approached by the occupant carrying the portable unit.  
      The Japanese Patent Application Laid-open Publication No. H10 (1998)-317754 discloses a technology in which transmission request signals are sequentially transmitted, in a time-division manner, from a plurality of transmitting antennas respectively provided to the plurality of doors of the vehicle in a corresponding manner. It is then determined at which timing a response signal is received from the portable unit carried by the vehicle occupant, the response signal responding to the sent transmission request signal. Accordingly, detection is made for a door which is one of the plurality of doors, and which is approached by the vehicle occupant.  
     SUMMARY OF THE INVENTION  
      However, with the aforementioned technology, the transmission request signals are sequentially transmitted, in the time-division manner, from the plurality of transmitting antennas in order to determine a door which is one of the plurality of doors, and which is approached by the vehicle occupant. Accordingly, it is necessary to set a period of operation time long enough for a controller which drives and controls the transmitting antennas, and to set a period of standby time long enough for a receiver which receives the response signal from the portable unit. For this reason, there is a problem that power consumption of the controller and of the receiver increases.  
      The present invention has been made to solve the aforementioned problem, and an object of the invention is to provide an occupant approach detection apparatus, an occupant approach detection system, and an occupant approach detection method with which it is made possible to determine a door, which is one of a plurality of doors, and which is approached by a vehicle occupant carrying a portable unit, without increasing the power consumption.  
      An aspect of the present invention is an occupant approach detection apparatus, comprising: a transmitting device which individually transmit transmission request signals from a plurality of transmitting antennas provided to a plurality of doors of a vehicle in a corresponding manner; a receiving device which receives a response signal returned, as a response to one of the transmission request signals, from a portable unit having received the relevant transmission request signal; and control device which controls operations of the transmitting device and the receiving device, and which detects an approach of a vehicle occupant carrying the portable unit based on the response signal received by the receiving device, wherein each of the transmission request signals transmitted from the plurality of transmitting antennas includes identification information for identifying a corresponding one of the transmitting antennas or a corresponding one of the doors provided with the corresponding one of the transmitting antennas, and the response signal includes identification information corresponding to the identification information included in the transmission request signal received by the portable unit, and the control device determines which of the plurality of doors is approached by the vehicle occupant carrying the portable unit on the basis of the identification information included in the response signal received from the portable unit by the receiving device. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The invention will now be described with reference to the accompanying drawings wherein:  
       FIG. 1  is a system configuration diagram for schematically showing an entire configuration of a vehicle door lighting system to which the present invention is applied.  
       FIG. 2  is a schematic view for showing an example of placement positions of first to third transmitting antennas and detection areas formed by driving the respective transmitting antennas.  
       FIG. 3  is a diagram for showing an example of a format of transmission request signals transmitted from the first to third transmitting antennas.  
       FIG. 4  is a diagram for showing an example of a format of response signals returned from a portable unit as a response to one of the transmission request signals.  
       FIG. 5  is a flowchart for showing a flow of a process periodically executed by a control circuit of a control unit of an on-vehicle unit in the vehicle door lighting system to which the present invention is applied.  
       FIG. 6  is a flowchart for showing a flow of a process executed by the portable unit in the vehicle door lighting system to which the present invention is applied.  
       FIG. 7  is a time chart for explaining that the control unit needs a longer period of time for start-up in a case where a plurality of transmitting antennas are sequentially driven in a time-division manner.  
       FIG. 8  is a time chart for explaining that power consumption is reduced by shortening the start-up time for the control unit in the vehicle door lighting system to which the present invention is applied.  
       FIG. 9  is a system configuration diagram for schematically showing an entire configuration of a smart entry system to which the present invention is applied. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
      Embodiments of the present invention will be explained below with reference to the drawings, wherein like members are designated by like reference characters.  
     First Embodiment  
      First, as a first embodiment of the present invention, descriptions are provided for an example of a vehicle door lighting system to which the present invention is applied. In the example, lights illuminating around a plurality of doors of a vehicle are provided to the respective doors in a corresponding manner. When a vehicle occupant approaches any one of the doors, a light, which is provided to the approached door in a corresponding manner, is turned on to provide hospitality.  
       FIG. 1  is a system configuration diagram for schematically showing an entire configuration of the vehicle door lighting system according to the first embodiment of the present invention. As shown in  FIG. 1 , the vehicle door lighting system of the first embodiment includes an on-vehicle unit  1 , which is mounted on the vehicle, and a portable unit  2 , which is carried by the vehicle occupant, and performs radio communication between the on-vehicle unit  1  and the portable unit  2  to implement the aforementioned lighting control of the lights.  
      In the vehicle door lighting system of the first embodiment, the on-vehicle unit  1  mounted on the vehicle includes a control unit  10  as a main constituent. This control unit  10  is connected to first to third three transmitting antennas  11 ,  12  and  13  and to a receiving antenna  14 . Moreover, the control unit  10  is also connected to a driver side door light  15 , which illuminates around a door at a side of a driver&#39;s seat of the vehicle, a front passenger side door light  16 , which illuminates around a door at a side of a front passenger&#39;s seat of the vehicle, and a back door light  17 , which illuminates around a back door of the vehicle. Turning on and off of these lights  15 ,  16  and  17  are controlled by the control unit  10 .  
      Among the three transmitting antennas  11 ,  12  and  13  provided to the on-vehicle unit  1 , the first transmitting antenna  11  is placed, for example, as shown in  FIG. 2 , in a door  101  at the side of the driver&#39;s seat of a vehicle  100 , on which the on-vehicle unit  1  is mounted. When driven, the first transmitting antenna  11  forms a detection area A 1  in the vicinity of the door  101  at the side of the driver&#39;s seat. The second transmitting antenna  12  is placed in a door  102  at the side of the front passenger&#39;s seat of the vehicle  100 . When driven, the second transmitting antenna  12  forms a detection area A 2  in the vicinity of the door  102  at the side of the front passenger&#39;s seat. The third transmitting antenna  13  is placed in a back door  103  of the vehicle  100 . When driven, the third transmitting antenna  13  forms a detection area A 3  in the vicinity of the back door  103 . These detection areas A 1 , A 2  and A 3  are respectively ranges where the transmission request signals reach, the transmission request signals being transmitted, as radio waves, from the respective first to third transmitting antennas  11  to  13 . In other words, these ranges are areas where radio communication is possible between the on-vehicle unit  1  and the portable unit  2 . When the vehicle occupant carrying the portable unit  2  enters one of the detection areas A 1 , A 2  and A 3 , the on-vehicle unit  1  receives a response signal from the portable unit  2 .  
      The driver side door light  15 , the front passenger side door light  16  and the back door light  17  are placed on door handles, under door mirrors, or the like, of the doors  101 ,  102  and  103  so as to illuminate around the doors  101 ,  102  and  103 , respectively.  
      As shown in  FIG. 10 , transmitting circuits  21 ,  22  and  23  are provided as first to third transmitting devices/transmission means, which respectively correspond to the first to third transmitting antennas  11 ,  12  and  13 , in the control unit  10 . Moreover, a receiving circuit  24  and a control circuit  25  are provided in the control unit  10 . The receiving circuit  24 , as a receiving device/reception means, corresponds to the receiving antenna  14 . The control circuit  25 , as a control device/control means, controls over an entire operation of the on-vehicle unit  1 . The control circuit  25  is configured as a microcomputer including a CPU, a ROM, a RAM and the like. The control circuit  25  executes a process based on a predetermined operation control program to control operations of the first to third transmitting circuits  21 ,  22  and  23  as well as the receiving circuit  24 , and to control turning on and off of the driver side door light  15 , the front passenger side door light  16  and the back door light  17 .  
      The control circuit  25  of the control unit  10  is supplied with power from a battery at a predetermined frequency, and repeatedly starts and stops on a periodic basis while the vehicle  100 , on which the on-vehicle unit  1  is mounted, is parked with an ignition switch of the vehicle  100  being off. While being activated, the control circuit  25  operates the first to third transmitting circuits  21  to  23  at a predetermined cycle, and causes the first to third transmitting circuits  21  to  23  to respectively transmit transmission request signals from the first to third transmitting antennas  11  to  13 , the transmission request signals corresponding to the transmitting circuits  21  to  23 . As shown in  FIG. 2 , the detection areas A 1  to A 3  are thus formed in the vicinities of the driver side door  101 , front passenger side door  102  and the back door  103 , respectively. Accordingly, radio communication between the on-vehicle unit  1  and the portable unit  2  is made possible.  
      The transmission request signals, which the first to third transmitting circuits  21  to  23  respectively transmit from the first to third transmitting antennas  11  to  13  under the control of the control circuit  25 , are request signals to request a response from the portable unit  2 . In this event, especially in the vehicle door lighting system of the first embodiment, the transmission request signals, which are respectively transmitted from these first to third antennas  11  to  13 , are configured to include individual antenna IDs as information for identifying the respective transmitting antennas  11  to  13 . Specifically, each of the transmission request signals, which are transmitted from the transmitting antennas  11  to  13 , has a format shown in  FIG. 3 , for example. In the format, in addition to an instruction for requesting the response signal from the portable unit  2 , an antenna ID as identification information of the transmitting antenna, from which the transmission request signal is transmitted, is written in a data area between a header and an EOM (End of Message). In the transmission request signal transmitted from the first transmitting antenna  11  by the first transmitting circuit  21 , the antenna ID of the first transmitting antenna  11  is written in the data area. In the transmission request signal transmitted from the second transmitting antenna  12  by the second transmitting circuit  22 , the antenna ID of the second transmitting antenna  12  is written in the data area. In the transmission request signal transmitted from the third transmitting antenna  13  by the third transmitting circuit  23 , the antenna ID of the third transmitting antenna  13  is written in the data area.  
      While being activated, the control circuit  25  of the control unit  10  causes the transmission request signals to be transmitted from the first to third transmitting antennas  11  to  13 . Thereafter, the control circuit  25  sets the receiving circuit  24  in a state of standby for a predetermined time, and causes the receiving circuit  24  to receive the response signal, which is returned from the portable unit  2 , as a response to one of the transmission request signals. While being activated at the predetermined cycle, the control unit  10  repeats the above control of transmitting the transmission request signals and of waiting for the response signal until the response signal from the portable unit  2  is received.  
      When the transmission request signal, which is transmitted from one of the first to third transmitting antennas  11  to  13 , is received, the portable unit  2 , which is carried by the vehicle occupant, returns the response signal as a response to the received transmission request signal. Specifically, when the portable unit  2  in the detection area A 1  in the vicinity of the driver side door  101  of the vehicle  100  receives the transmission request signal from the first transmitting antenna  11 , the portable unit  2  returns the response signal as a response to the transmission request signal from the first transmitting antenna  11 . When the portable unit  2  in the detection area A 2  in the vicinity of the front passenger side door  102  of the vehicle  100  receives the transmission request signal from the second transmitting antenna  12 , the portable unit  2  returns the response signal as a response to the transmission request signal from the second transmitting antenna  12 . When the portable unit  2  in the detection area A 3  in the vicinity of the back door  103  of the vehicle  100  receives the transmission request signal from the third transmitting antenna  13 , the portable unit  2  returns the response signal as a response to the transmission request signal from the third transmitting antenna  13 .  
      In this event, especially in the vehicle door lighting system of the first embodiment, the response signal, which is returned from the portable unit  2  as the response to the transmission request signals, is configured to include the antenna ID (or identification information corresponding to the antenna ID) identical to that included in the received transmission request signal. Specifically, the response signal returned from the portable unit  2  has a format shown in  FIG. 4 , for example. In addition to a portable unit ID as identification information of the portable unit  2 , the antenna ID, which is identical to that included in the received transmission request signal, is written in a data area between a header and an EOM (End of Message). Specifically, in the response signal returned from the portable unit  2  within the detection area A 1  in the vicinity of the driver side door  101  of the vehicle  100 , the antenna ID, which indicates the first transmitting antenna  11 , is written. In the response signal returned from the portable unit  2  within the detection area A 2  in the vicinity of the front passenger side door  102  of the vehicle  100 , the antenna ID, which indicates the second transmitting antenna  12 , is written. In the response signal returned from the portable unit  2  within the detection area A 3  in the vicinity of the back door  103  of the vehicle  100 , the antenna ID, which indicates the third transmitting antenna  13 , is written.  
      When the response signal is received from the portable unit  2  by means of the receiving circuit  24 , the control circuit  25  of the control unit  10  verifies the portable unit ID included in the response signal with a portable unit ID previously registered to perform user authentication according to whether the portable unit ID included in the response signal from the portable unit  2  matches the portable unit ID previously registered. In a case where the portable unit ID included in the response signal from the portable unit  2  matches the portable unit ID previously registered, the control circuit  25  determines that a legitimate user (the vehicle occupant who owns the portable unit  2 ) exists in the detection area.  
      When it is determined that the vehicle occupant, who is the legitimate user, exists in the detection area, the control circuit  25  of the control unit  10  reads the antenna ID included in the response signal from the portable unit  2 , and determines to which of the transmission request signals respectively transmitted from the first to third transmitting antennas  11  to  13  the response signal from the portable unit  2  is a response, i.e., in which of the detection areas A 1  to A 3  the vehicle occupant carrying the portable unit  2  exists. According to a determination result, the control circuit  25  performs control of turning on only a light, which is one of the driver side door light  15 , front passenger side door light  16 , and back door light  17 , and which corresponds to the door approached by the vehicle occupant carrying the portable unit  2 .  
      Specifically, in a state where the transmission request signals are respectively transmitted from the first to third transmitting antennas  11  to  13 , it is supposed that the vehicle occupant carrying the portable unit  2  enters the detection area A 1  formed in the vicinity of the driver side door  101  of the vehicle  100 . The transmission request signal transmitted from the first transmitting antenna  11  is received by the portable unit  2 , and the response signal, which is returned from the portable unit  2  as a response to the transmission request signal, includes the antenna ID indicating the first transmitting antenna  11 . When the antenna ID, which is included in the response signal from the portable unit  2 , indicates the first transmitting antenna  11 , the control circuit  25  determines that the vehicle occupant carrying the portable unit  2  has entered the detection area A 1 , and that the occupant is approaching the driver side door  101  of the vehicle  100 . The control circuit  25  then turns on the driver side door light  15 . In a state where the transmission request signals are respectively transmitted from the first to third transmitting antennas  11  to  13 , when the vehicle occupant carrying the portable unit  2  enters the detection area A 2  formed in the vicinity of the front passenger side door  102  of the vehicle  100 , the transmission request signal transmitted from the second transmitting antenna  12  is received by the portable unit  2 , and the response signal, which is returned from the portable unit  2  as a response to the transmission request signal, includes the antenna ID indicating the second transmitting antenna  12 . When the antenna ID included in the response signal from the portable unit  2  indicates the second transmitting antenna  12 , the control circuit  25  determines that the vehicle occupant carrying the portable unit  2  has entered the detection area A 2 , and that the occupant is approaching the front passenger side door  102  of the vehicle  100 . The control circuit  25  then turns on the front passenger side door light  16 . In a state where the transmission request signals are respectively transmitted from the first to third transmitting antennas  11  to  13 , when the vehicle occupant carrying the portable unit  2  enters the detection area A 3  formed in the vicinity of the back door  103  of the vehicle  100 , the transmission request signal transmitted from the third transmitting antenna  13  is received by the portable unit  2 , and the response signal, which is returned from the portable unit  2  as a response to the transmission request signal, includes the antenna ID indicating the third transmitting antenna  13 . When the antenna ID included in the response signal from the portable unit  2  indicates the third transmitting antenna  13 , the control circuit  25  determines that the vehicle occupant carrying the portable unit  2  has entered the detection area A 3 , and that the occupant is approaching the back door  103  of the vehicle  100 . The control circuit  25  then turns on the back door light  17 .  
      As described above, in the vehicle door lighting system of the first embodiment, it is determined which door is approached by the vehicle occupant by confirming the antenna ID included in the response signal, which is returned from the portable unit  2  carried by the vehicle occupant, as a response to one of the transmission request signals respectively transmitted from the first to third transmitting antennas  11  to  13  of the on-vehicle unit  1 . When the vehicle occupant approaches one of the doors, a light, which is one of the driver side door light  15 , the front passenger side door light  16  and the back door light  17 , and which is provided to the door approached by the vehicle occupant in a corresponding manner, is turned on, thus providing hospitality.  
      Moreover, after the light, which is provided to the door approached by the vehicle occupant in a corresponding manner, is turned on, the vehicle door lighting system of the first embodiment may be configured to perform control of unlocking a door lock unit provided to the relevant door. In this case, since the door approached by the vehicle occupant is already known, the door lock unit provided to the door may be automatically unlocked. Alternatively, the door lock unit provided to the door may be unlocked after user authentication is again performed by communication between the on-vehicle unit  1  and the portable unit  2 , the user authentication being triggered by a switch provided in the vicinity of a door handle of the door being operated. Such repeated user authentication by the communication between the on-vehicle unit  1  and the portable unit  2  makes it possible to unlock the relevant door at the timing at which the vehicle occupant, who is the legitimate user, is clearly approaching the door illuminated by turning on the light. Hence, it is highly effective in improving security.  
      Moreover, any one of a plurality of door lock units can be freely set to be unlocked. For example, in a case where it is determined that the vehicle occupant, who is the legitimate user, approaches the driver side door, all of the door lock units, which are respectively provided to the doors of the vehicle, may be unlocked. In a case where it is determined that the occupant approaches the front passenger side door or the back door, only the door lock unit of the relevant door may be unlocked.  
      Descriptions will be provided for a series of operations in the vehicle door lighting system of the first embodiment with reference to flowcharts of  FIGS. 5 and 6 .  FIG. 5  is a flowchart for showing a flow of a process periodically executed by the control circuit  25  in the control unit  10  of the on-vehicle unit  1 , and  FIG. 6  is a flowchart for showing a flow of a process executed by the portable unit  2 .  
      In the vehicle door lighting system of the first embodiment, as shown in the flowchart of  FIG. 5 , when the control circuit  25  in the control unit  10  of the on-vehicle unit  1  is supplied with power from the on-vehicle battery to be activated while the vehicle is parked, in step S 101 , the control circuit  25  first operates and causes the first to third transmitting circuits  21  to  23  to respectively transmit, from the first to third transmitting antennas  11  to  13 , the transmission request signals including the individual antenna IDs as identification information of the respective antennas. Next, in step S 102 , the control circuit  25  operates the receiving circuit  24 , and determines whether the response signal from the portable unit  2  is received by the receiving circuit  24 . The determination in this step S 102  is repeated until it is determined, in step S 103 , that a predetermined period of time (standby time) has elapsed. When the response signal from the portable unit  2  is received by the receiving circuit  24  within the predetermined period of time, the process proceeds to step S 104 . When the predetermined period of time elapses before the response signal from the portable unit  2  is received by the receiving circuit  24 , the control circuit  25  is made to be in a sleep state (a state where the power supply is stopped) until the next activation cycle.  
      Meanwhile, as shown in the flowchart of  FIG. 6 , the portable unit  2  carried by the vehicle occupant constantly determines whether the portable unit  2  receives the transmission request signal from the on-vehicle unit  1  (step S 201 ). In step S 202 , when the transmission request signal is received from the on-vehicle unit  1 , the portable unit  2  reads the antenna ID from the received transmission request signal. In step S 203 , The portable unit  2  forms a response signal, in which the antenna ID read from the received transmission request signal and the portable unit ID are incorporated, as identification information of the portable unit  2 . In step S 204 , the portable unit  2  returns the response signal, which is formed in the step S 203 , as a response to the received transmission request signal from the on-vehicle unit  1 .  
      Subsequently, in step S 104 , when the response signal is received from the portable unit  2  by the receiving circuit  24 , the control circuit  25  in the control unit  10  of the on-vehicle unit  1  reads the portable unit ID included in the response signal received from the portable unit  2 . Thereafter, in step S 105 , the control circuit  25  determines whether the portable unit ID, which is included in the response signal, matches the portable unit ID previously registered as the portable unit ID of the legitimate user. In a case where the portable unit ID, which is included in the response signal from the portable unit  2 , does not match the portable unit ID previously registered, the control circuit  25  directly terminates the process. In a case where the portable unit ID, which is included in the response signal from the portable unit  2 , matches the portable unit ID previously registered, the control circuit  25  reads, in step S 106 , the antenna ID included in the response signal from the portable unit  2 . In step S 107 , based on the antenna ID read in the step S 106 , the control circuit  25  specifies the door, which is one of the driver side door, the front passenger side door, and the back door of the vehicle, and which is approached by the vehicle occupant carrying the portable unit  2 . In next step S 108 , the control circuit  25  performs control of turning on a light which is one of the driver side door light  15 , front passenger side door light  16  and back door light  17 , and which corresponds to the door specified, in the step S 106 , to be one approached by the vehicle occupant.  
      As described above, in the vehicle door lighting system of the first embodiment, the transmission request signals transmitted to the portable unit  2  respectively from the first to third transmitting antennas  11  to  13 , which are provided to the driver side door, the front passenger side door, and the back door in a corresponding manner, are configured to include the individual antenna IDs as identification information on the respective transmitting antennas  11  to  13 . Moreover, the response signal returned from the portable unit  2 , by which one of the transmission request signals is received as a response to the transmission request signal, is configured to include the antenna ID (or identification information corresponding to the antenna ID) identical to the antenna ID included in the received transmission request signal. Based on the antenna ID included in the response signal which is returned from the portable unit  2 , and which is received by the receiving circuit  24 , the control circuit  25  in the control unit  10  of the on-vehicle unit  1  determines which of the driver side door, the front passenger side door and the back door of the vehicle is approached by the vehicle occupant, and turns on the light corresponding to the door which is determined to be the door approached by the vehicle occupant.  
      According to the vehicle door lighting system of the first embodiment, even when the transmission request signals are simultaneously transmitted from the first to third transmitting antennas  11  to  13 , it is apparent, from the antenna ID included in the response signal from the portable unit  2 , which of the transmitting antennas transmits the transmission request signal received by the portable unit  2 . Accordingly, it is made possible to reliably determine which door is approached by the vehicle occupant carrying the portable unit  2 , and to properly perform control of turning on the light corresponding to the door approached by the vehicle occupant without increasing power consumption.  
      Specifically, as a method of determining which of the plurality of doors is approached by the vehicle occupant, another method can be considered as described below. Transmission request signals are sequentially transmitted respectively from a plurality of transmitting antennas, which are provided, in a corresponding manner, to the plurality of doors in a time division manner (at timings of t 0 _s 1 , t 0 _s 2 , and t 0 _s 3  in  FIG. 7 ). Thereafter, it is determined which timing the transmission request signal is transmitted and the response signal corresponding to the transmission request signal is received from the portable unit carried by the vehicle occupant. As shown in  FIG. 7 , however, with such a method, receivers need to be individually operated at several timings (t 0 _r 1 , t 0 _r 2 , and t 0 _r 3  in  FIG. 7 ) according to the respective timings at which the transmitting antennas are driven. Moreover, the receivers need to be in a state of waiting for a response signal from the portable unit. It is therefore demanded that an activation time T 0  of the control unit be longer between each of the cycle, the activation time T 0  being the period of time when the control unit is periodically activated while the vehicle is parked. Accordingly, the power consumption is increased.  
      On the other hand, in the vehicle door lighting system of the first embodiment, the transmission request signals are simultaneously (at a timing of time t 1 _s in  FIG. 8 ) transmitted from the first to third transmitting antennas  11  to  13 . Accordingly, a period of time t 1 _r for the receiving circuit  24  to wait for the response signal from the portable unit  2  may be short, and activation time T 1  of the control unit  10  can be set shorter. Hence, according to the vehicle door light system, it is made possible to reliably determine which door is approached by the vehicle occupant carrying the portable unit  2 , and to properly perform control of turning on the light which corresponds to the door approached by the vehicle occupant while reducing power consumption. In particular, the vehicle door lighting system of the first embodiment operates with power supplied from the on-vehicle battery in a state where the vehicle is parked, and thus where the on-vehicle battery is not further charged. Accordingly, such reduction in power consumption has great significance from the viewpoint of prevention of problems such as running out of the on-vehicle battery.  
     Second Embodiment  
      Next, descriptions are provided for an example of a smart entry system to which the present invention is applied as a second embodiment of the present invention. With this smart entry system, when a vehicle occupant approaches one of the doors, a door lock unit, which is provided to the relevant door in a corresponding manner, is automatically unlocked.  
       FIG. 9  is a system configuration diagram for schematically showing an entire configuration of the smart entry system as the second embodiment of the present invention. As shown in  FIG. 9 , the smart entry system of the second embodiment has a configuration substantially similar to the aforementioned vehicle door lighting system (see  FIG. 1 ) of the first embodiment. In the second embodiment, the electric equipment, which is controlled by the on-vehicle unit  1 , is different from that of the first embodiment. Specifically, in the vehicle door lighting system of the first embodiment, the driver side door light  15 , the front passenger side door light  16  and the back door light  17  are controlled by the on-vehicle unit  1 . On the other hand, in the smart entry system of the second embodiment, a first door lock unit  31 , which is provided to the driver side door, a second door lock unit  32 , which is provided to the front passenger side door, and a third door lock unit  33 , which is provided to the back door, are controlled by the on-vehicle unit  1 .  
      Other constituents in the smart entry system of the second embodiment are identical to those of the vehicle door lighting system of the first embodiment. Hereinafter, the identical constituents as those of the vehicle door lighting system of the first embodiment are denoted by the identical reference numerals, and the detailed descriptions thereof are omitted.  
      In the smart entry system of the second embodiment, as in the case of the vehicle door lighting system of the aforementioned first embodiment, under control of the control circuit  25  in the control unit  10  of the on-vehicle unit  1 , the first to third transmitting circuits  21  to  23  are operated to simultaneously transmit transmission request signals from the first to third transmitting antennas  11  to  13 . In this event, the transmission request signals, which are respectively transmitted from the first to third transmitting antennas  11  to  13 , include the individual antenna IDs for identifying the transmitting antennas.  
      When one of the transmission request signals, which are simultaneously transmitted from the first to third transmitting antennas  11  to  13  of the on-vehicle unit  1 , is received, the portable unit  2 , which is carried by the vehicle occupant, forms a response signal in which an antenna ID (or identification information corresponding to the antenna ID) identical to the antenna ID included in the received transmission request signal and the portable unit ID, as identification information of the portable unit  2 , are incorporated. Thereafter, the portable unit  2  returns the formed response signal as a response to the received transmission request signal.  
      After the transmission request signals are respectively transmitted from the first to third transmitting antennas  11  to  13 , the control unit  25  in the control unit  10  of the on-vehicle unit  1  operates and causes the receiving circuit  24  to be in a state of waiting for the response signal from the portable unit  2 . When the response signal is received from the portable unit  2  by the receiving circuit  24 , the control unit  25  reads the portable unit ID included in the response signal, and verifies the read portable unit ID with the portable unit ID previously registered. Accordingly, user authentication is performed according to whether the portable unit ID included in the response signal from the portable unit  2  matches the portable unit ID previously registered.  
      In a case where the portable unit ID included in the response signal from the portable unit  2  matches the portable unit ID previously registered, the control circuit  25  reads the antenna ID included in the response signal from the portable unit  2 , and determines which of the first to third transmitting antennas  11  to  13  has transmitted the transmission request signal, to which the response from the portable unit  2  corresponds. That is, the control circuit  25  determines which of the driver side door, the front passenger side door and the back door is approached by the vehicle occupant carrying the portable unit. According to a determination result, the control circuit  25  performs control of unlocking only the door lock unit which corresponds to the door approached by the vehicle occupant carrying the portable unit  2 , the door lock unit being one of the first door lock unit  31 , which is provide to the driver side door, the second door lock unit  32 , which is provided to the front passenger side door, and the third door lock unit  33 , which is provided to the back door.  
      As described above, in the smart entry system of the second embodiment, the transmission request signals transmitted to the portable unit  2  from the first to third transmitting antennas  11  to  13 , which are respectively provided to the driver side door, the front passenger side door and the back door of the vehicle in a corresponding manner, are configured to include the individual antenna IDs as identification information on the respective transmitting antennas  11  to  13 . Moreover, the response signal, which is returned, as a response to the transmission request signal, by the portable unit  2 , which has received one of the transmission request signals, is configured to include the antenna ID (or identification information corresponding to the antenna ID) identical to the antenna ID included in the received transmission request signal. Based on the antenna ID, which is included in the response signal returned from the portable unit  2 , and which is received by the receiving circuit  24 , the control circuit  25  in the control unit  10  of the on-vehicle unit  1  determines which of the driver side door, the front passenger side door and the back door of the vehicle is approached by the vehicle occupant, and unlocks the door lock unit corresponding to the door which is determined to be the door approached by the vehicle occupant.  
      According to the smart entry system of the second embodiment, among the transmission request signals simultaneously transmitted from the first to third transmitting antennas  11  to  13 , the transmitting antenna, from which the transmission request signal received by the portable unit  2  is transmitted, is known from the antenna ID included in the response signal from the portable unit  2 . Accordingly, as in the case of the aforementioned vehicle door lighting system of the first embodiment, it is made possible to reliably determine which door is approached by the vehicle occupant carrying the portable unit  2 , and properly perform control of unlocking only the door lock unit corresponding to the door which is approached by the vehicle occupant without increasing the power consumption.  
      The above described vehicle door lighting system of the first embodiment and the smart entry system of the second embodiment are merely application examples of the present invention. It is obvious that the technical scope of the present invention is not limited by the contents disclosed in the above descriptions of the embodiments, and that the technical scope of the present inventions includes various alternative techniques which can be easily derived from these disclosures. For example, in the descriptions of the aforementioned embodiments, the transmission request signals respectively transmitted from the first to third transmitting antennas  11  to  13  are configured to include the individual antenna IDs as identification information on the respective transmitting antennas. However, instead of the antenna IDs, the transmission request signals may include identification information on the transmitting circuits corresponding to the respective transmitting antennas, or may include identification information on the doors of the vehicle corresponding to the respective transmitting antennas. In the descriptions of the aforementioned embodiments, the on-vehicle unit  1  transmits the transmission request signals respectively from three antennas, which are the first to third transmitting antennas  11  to  13 , the transmission request signals being respectively corresponding to the three doors including the driver side door, the front passenger side door and the back door. However, the on-vehicle door  1  may transmit, for example, the transmission request signals from two transmitting antennas, the transmission request signals being respectively corresponding to two doors including the driver side door and the front passenger side door, or may transmit the transmission request signals from four or more transmitting antennas, the transmission request signals respectively corresponding to four or more doors. Furthermore, the descriptions of the aforementioned embodiments are provided for the lighting units and the door lock units, which are respectively provided to the individual doors in a corresponding manner, as examples of the electric equipment controlled by the control unit  10 . However, the electric equipment is not limited to these, and the present invention can be applied to any one of electric equipment provided to the respective doors of the vehicle in a corresponding manner.  
      The present disclosure relates to subject matters contained in Japanese Patent Application No. 2005-335321, filed on Nov. 21, 2005, the disclosures of which is expressly incorporated herein by reference in its entirety.