Abstract:
A remote control apparatus comprises a vehicle-mounted unit including a transmitter ( 26, 28, 23 ) for transmitting an ID request, a receiver ( 32, 33 ) for receiving a reply ID transmitted in response to the ID request, controller ( 31 ) for controlling the operation state of equipment ( 40, 60 ) depending on whether the receiver ( 32, 33 ) receives the ID, as well as a portable unit ( 10 ) for transmitting a reply ID in response to the ID request. When a hand sensor ( 1 ) provided in a door handle of a vehicle senses no hand and the receiver ( 32, 33 ) receives an ID, the controller ( 31 ) decreases the transmission power of the ID request. The hand sensor ( 1 ) comprises a slot antenna having an outside door handle, the surface of which is formed of a conductive material, a slit formed in the conductive material, and feeding points. The antenna is used for transmission of the ID request.

Description:
FIELD OF THE INVENTION 
     The present invention relates to a remote control apparatus which effects changeover between different operation states of equipment, such as locked and unlocked states of a vehicle door, when a user carrying a portable unit approaches to or moves away from the door. 
     BACKGROUND OF THE INVENTION 
     A remote control apparatus of the above-described type suitable for locking and unlocking a vehicle door is called a keyless entry system or a smart entry system. For example, Japanese Patent Application Laid-Open No. 5-106376 discloses a system comprising a portable radio unit and a vehicle-mounted radio unit. The portable radio unit includes first transmission means which transmits a reply signal or response signal when first reception means receives a transmission request signal or call signal. The vehicle-mounted radio unit includes second transmission means for transmitting the call signal at predetermined intervals, and control means which outputs a signal for unlocking doors of a vehicle when second reception means receives the response signal and outputs a signal for locking doors of a vehicle after passage of a predetermined period of time during which the response signal is not received. When a driver carrying the portable radio unit approaches to the vehicle in order to enter the vehicle, the driver-side door is automatically unlocked, and when the driver exits and moves away from the vehicle, the door is automatically locked. 
     When the driver is outside the vehicle, the second transmission means transmits the call signal. That is, the call signal is transmitted when the engine of the vehicle is stopped. Accordingly, the transmission of the call signal imposes a load on a power source (battery) onboard the vehicle, so that battery electrical power is consumed. If the transmission interval of the call signal is increased in order to reduce power consumption and the communicable distance is relatively short, there arises a problem that the driver carrying the portable radio unit reaches the driver-side door from an incommunicable position during a period between transmission of a call signal and transmission of a next call signal, with the result that the door is not opened even though the driver attempts to open the door. This problem can be mitigated if the transmission power of the call signal is increased in order to increase the communicable distance. In this case, since the amount of consumed power per transmission of the call signal increases, this method is not suitable for reduction of battery power consumption. Accordingly, the transmission interval of the call signal cannot be simply increased. 
     SUMMARY OF THE INVENTION 
     A first object of the present invention is to provide a remote control apparatus which can reduce power consumption resulting from repeated transmission of a transmission request signal. 
     In accordance with the invention, a controller outputs a transmission request signal to a portable unit via an object sensor. The object sensor outputs to the controller a signal indicting whether or not an object, such as a human hand, is present. The controller reduces the transmission power of the transmission request signal when the object sensor senses no object and a receiver receives a reply signal which is transmitted by the portable unit in response to the transmission request signal. The controller unlocks a door after reception of a predetermined ID code from the portable unit and when the object sensor detects the presence of the object. Since the transmission power of the transmission request signal is reduced when the receiver receives a reply signal, electrical power required for transmission can be reduced. The door is unlocked when the portable unit that transmits a reply signal representing the predetermined identification code approaches the receiver, and the sensor senses the human hand. Thus, a person carrying the portable unit can open the door. 
     Preferably, the controller transmits the transmission request signal with high transmission power at predetermined interval t 1  when the receiver receives no reply signal, stops transmission of the transmission request signal when the receiver receives a reply signal, subsequently waits up to a predetermined period t 2  until the object sensor detects an object, and transmits the transmission request signal with low transmission power at predetermined intervals t 4  when a predetermined period t 2  has elapsed during which the object sensor senses no object. Therefore, electrical power required for transmission can be conserved. When the object sensor does not sense an object even after the predetermined period t 2  has elapsed, the controller resumes transmission of the transmission request signal. However, since the transmission power is low, the power consumption is low. Although the transmission power is low, communications between the controller, the portable unit, and the receiver can be performed properly, because the portable unit is located in the vicinity of the receiver. 
     Preferably, the apparatus of the invention further comprises an open/close sensor for generating a signal indicating an open/close state of the door. The controller opens a door window when, after unlocking the door, the object sensor continuously detects an object and the open/close sensor continuously outputs a door close signal for a predetermined period t 6 . 
     By virtue of the above-described structure, after the door is unlocked, the window of the door is opened when the predetermined period t 6  has elapsed without the door being opened even though the object sensor detects an object. That is, the window of the door is opened when a person carrying the portable unit remains within a sensing area of the object sensor for the period t 6  or longer. 
     Preferably, the controller locks the door when, after the door is unlocked, the object sensor does not detect an object and the open/close sensor continuously outputs a door close signal for a predetermined period t 5 . 
     By virtue of the above-described structure, the door is automatically brought back to the locked state when the door is not opened after the door is unlocked, and the object sensor comes into an object-undetected state. Therefore, automatic locking can be performed with improved reliability when a person carrying the portable unit does not open the door. 
     Preferably, the object sensor comprises a slot antenna having an outside door handle, at least the surface of which is formed of a conductive material, a slit formed in the conductive material, and feeding points provided on the conductive material; and the transmitter supplies the feeding points with a radio wave transmission voltage. 
     In this case, since the outside door handle itself is used as a conductive plate of the slot antenna, only the slit and the feeding points are required to be added to obtain an antenna function. Therefore, the number of parts required for radiation of radio waves is small. Since the outside door handle has a finite size and does not have a completely flat surface, the slot antenna is considerably different from an ideal slot antenna, so that the performance of the slot antenna is considerably low as compared with an ideal performance. However, effective radio waves are radiated within a small area in the vicinity of the door. The number of parts and the number of steps of assembly for providing an antenna are small, and the antenna can be disposed (or formed) in the outside door handle even though the interior or the surface of the outside door handle is metal (conductive material). In addition, since the antenna is inconspicuous, other persons cannot find the antenna. 
     Preferably, the object sensor comprises changeover switch for changing the transmission output between a high-power output (i.e., high gain) and a low-power output (i.e., low gain). The changeover switch increases and decreases the transmission power of the transmission request signal. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Other objects and features of the present invention will be readily appreciated as the same becomes better understood by reference to the following detailed description of the preferred embodiments when considered in connection with the accompanying drawings, in which: 
     FIG. 1 a  is a block diagram showing the structure of an on-vehicle unit; 
     FIG. 1 b  is a block diagram showing the structure of a portable unit used for unlocking a door of a vehicle on which the unit of FIG. 1 a  is mounted; 
     FIG. 2 a  is a block diagram showing the structure of an object sensor shown in FIG. 1 a;    
     FIG. 2 b  is a block diagram showing the structure of a sensing circuit shown in FIG. 2 a;    
     FIG. 3 is an electrical circuit diagram showing the structure of a detection circuit shown in FIG. 2 b;    
     FIG. 4 a  is a front view of a door handle equipped with an antenna shown in FIG. 1 a;    
     FIG. 4 b  is a cross-sectional view taken along line IVB—IVB in FIG. 4 a;    
     FIG. 5 is an electrical circuit diagram showing the structure of the portable unit shown in FIG. 1; 
     FIGS. 6 a  and  6   b  are flowcharts showing an “entry process” ENP 1  that is performed by a controller shown in FIG. 1 in order to unlock the driver-side door or open the window in response to approach of a driver carrying the portable unit; 
     FIGS. 7 a  and  7   b  are flowcharts showing an “entry process” ENP 2  that is performed by a controller according to another embodiment of the present invention; and 
     FIG. 8 is a plan view showing a communicable area A 1  of the antenna shown in FIG. 1 at the time of high output power, and a communicable area As of the antenna at the time of low output power. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 a  shows the structure of a first embodiment of the present invention. A control apparatus  30  for locking and unlocking a driver-side door of a vehicle and for opening the window of the driver-side door comprises a controller  31 , which includes a CPU and an input/output interface (input/output electric circuit). Electricity is supplied to the controller  31  from a battery  54  of the vehicle. The controller  31  receives a signal IG from an ignition switch  51 , a signal DSW from a door courtesy switch  52  for detecting an open state of the door, and a signal KSW from a key-unlock warning switch  53  for detecting whether an engine key is inserted in a key cylinder. 
     The controller  31  outputs a transmission request signal to a portable unit  10  via an object sensor  1 . That is, when the controller  31  supplies a transmission command RFR to a transmission circuit  26 , the transmission circuit  26  transmits a request signal from an antenna  23  via a feeder balun  28 . In the object sensor  1 , the output of the transmission circuit  26  is also supplied to a sensing circuit  2 . The sensing circuit  2  outputs to the controller  31  a signal SEN indicating whether or not an object, such as a human hand, is present. Further, a binary signal representing an ID code that has been received by an antenna  32  and demodulated by a receiver  33  is input to the controller  31 . 
     A driver-side door lock/unlock apparatus  40  includes a lock/unlock drive motor  42  and a relay circuit  41  for supplying electricity to the motor  42  in a forward or reverse direction for a lock or unlock operation. A door control switch  43  for instructing the lock or unlock operation is connected to the relay circuit  41  and outputs a lock or unlock command signal to the relay circuit  41  via command signal lines. The controller  31  also outputs a lock or unlock command signal to the command signal lines. 
     A driver-side window drive apparatus  60  includes a window open/close drive motor  62  and a relay circuit  61  for supplying electricity to the motor  62  in a forward or reverse direction for an opening or closing operation. A window open/close switch  63  for instructing opening or closing of the window is connected to the relay circuit  61  and outputs a window open or close command signal to the relay circuit  61  via command signal lines. The controller  31  also outputs a window open or close command signal to the command signal lines. 
     The controller  31  detects receipt of a signal from the portable unit  10  shown in FIG. 1 b  and brings the lock/unlock apparatus  40  into a locked state or an unlocked state, based on whether a received ID code is a predetermined code registered in the controller  31  and whether the output signal SEN of the sensing circuit  2  of the objector sensor  1  represents presence of an object. The controller  31  outputs a window open command signal to the window drive apparatus  60  when predetermined conditions are satisfied. 
     FIG. 2 a  shows the structure of the transmission circuit  26  of the object sensor  1 . The transmission circuit  26  comprises an oscillation circuit  26   a  that oscillates at a constant frequency, a variable gain amplifier  26   b  for amplifying an output signal from the oscillation circuit  26   a  at a high or low gain as designated, an analog electronic switch  26   c  for effecting changeover between two biases for designating different gains, and a modulator  26   d  composed of an electronic switching circuit for turning the output of the amplifier  26   b  ON and OFF. The controller  31  outputs to the analog electronic switch  26   c  a two-level signal Gc for designating a gain. When the two-level signal Gc is high, a low gain is designated, and when the two-level signal Gc is low, a high gain is designated. The controller  31  outputs to the modulator  26   d  request data RFR (bit series) for requesting transmission of an ID code. That is, in the present embodiment, the high-frequency signal generated by the oscillation circuit  26   a  is subjected to on/off modulation (ASK (Amplitude Shift Keying) modulation) to thereby transmit the request data RFR. The high frequency signal that has been ASK-modulated in accordance with the request data RFR and has been sent to the feed line is output to the antenna  23  via the balun  28 , which establishes optimal impedance matching with the antenna  23  (50Ω in this case). The sensing circuit  2  is connected to the feed line. 
     FIG. 2 b  shows the structure of the sensing circuit  2  of the object sensor  1 , and FIG. 3 shows the structure of a detection circuit  2   a  of the sensing circuit  2 . As shown in FIGS. 2 b  and  3 , the sensing circuit  2  comprises the detection circuit  2   a,  an AC amplifying circuit  2   b,  a comparator circuit  2   c,  a DC amplifying circuit  2   d,  a comparator circuit  2   e,  and an OR gate  2   f.  The AC amplifying circuit  2   b  amplifies an AC component of a detection voltage. The comparator circuit  2   c  outputs a relative change signal that attains a high level H when the output of the AC amplifying circuit  2   b  deviates from a predetermined voltage range (predetermined voltage V 1  to V 2 , which is higher than V 1 ). The DC amplifying circuit  2   d  amplifies a DC component of the detection voltage. The comparator circuit  2   e  outputs an absolute change signal which attains a high level H when the output of the DC amplifying circuit  2   d  exceeds the predetermined voltage V 2 . The OR gate  2   f  outputs a sensor signal SEN that attains a high level H when either the relative change signal output from the comparator  2   c  or the absolute change signal output from the comparator  2   e  attains a high level H. Attainment of the high level H by the sensor signal SEN of the OR gate  2   f  indicates that an object such as a human hand  9  is in contact with or in proximity to the antenna  23 . 
     The oscillation circuit  26   a  shown in FIG. 2 a  oscillates at a constant frequency (in the present embodiment, at 2.45 GHz). When the variable gain amplifier  26   b  is set to a low gain, and the modulator  26   d  is in an ON state, the oscillating signal is fed to the antenna  23  such that the impedance is adjusted to 50Ω for matching with the antenna  23 . When a dielectric object  9  such as a hand of a person is present in the vicinity of the antenna  23 , the input impedance of the antenna  23  changes, with the result that the above-described matched state is cancelled and an unmatched state is created. Consequently, when the object  9  approaches to the antenna  23 , the voltage standing wave in the feed line changes, so that the voltage in the feed line increases by a certain amount. 
     That is, when the object  9  is in proximity to the antenna  23 , a radio wave radiated from the antenna  23  reflects on the object  9  and is received by the antenna  23 , so that interference arises in the feed line between the transmitted signal and the received signal. While the object  9  is moving the degree of the interference changes in accordance with the speed of approach. An interference wave is detected by the detection circuit  2   a,  and an. AC component of the detection voltage is amplified in order to produce a relative change signal that corresponds to the relative speed of the object  9  with respect to the antenna  23 . Further, a DC component of the detection voltage is amplified in order to produce an absolute change signal that corresponds to a position of the object  9  in relation to the antenna  23 . That is, the AC component of the detection voltage represents a relative change that corresponds to a speed of approach of the object  9  to the antenna  23 ; i.e., variation in voltage due to the Doppler effect, and the DC component of the detection voltage represents the distance between the object  9  and the antenna  23 . Sensing of the object  9  based on the AC component of the detection voltage becomes possible earlier than does sensing of the object  9  based on the DC component of the detection voltage. 
     The structure of the antenna  23  will now be described with reference to FIGS. 4 a  and  4   b.  An outside handle (hereinafter referred to as a “door handle”)  20  is provided on a driver-side door of the vehicle. The door handle  20  is formed of die cast zinc and its surface is coated with chromium plating. The door handle  20  is equipped with a key cylinder  27  and includes a base plate member  21  and a doorknob  22 . A depression is formed on the outer side of the base plate member  21  in order to allow a driver to insert his/her hand into the door handle  20 . The doorknob  22  can be turned relative to the base plate member  21  in a clockwise direction as viewed in FIG. 4 b.  A straight slit for the antenna  23  is cut in the bottom wall  21 a of the base plate member  21 . The slit is filled with a synthetic resin, such that the opening of the slit is closed by the synthetic resin. In the present embodiment, the slit assumes the form of a straight line; however, the shape of the slit is not limited thereto. 
     Two seating bases  23  are provided on the bottom wall  21   a,  and threaded holes are formed in the seating bases  23 . Screws  24  and  25  are screwed into the threaded holes, and an output-side terminal of the balun  28  is integrally connected to the screws  24  and  25 . One end of a coaxial cable (feed line) is connected to the input-side terminal of the balun  28 . The other end of the coaxial cable is connected to the transmission circuit  26 . The slit provided in the door handle  20  serves as the antenna  23  that transmits a request signal to the portable unit  10 . That is, the object sensor  1  functions as a transmitter for transmitting the request signal. The doorknob is not limited to a pull-up type door handle (a door handle that swings in the vertical direction) as shown in FIG. 4 b,  and may assume the form of a grip-type door handle (a door handle that swings in the widthwise direction of the vehicle). 
     The circuit configuration of the portable unit  10  will now be described with reference to FIG. 5. A signal received by an antenna  18  is detected and amplified by a receiver  17  serving as a detector and is then input to the controller  11 . The output of an amplifier  17 a of the receiver  17  attains a high level H when a reception signal is detected, and attains a low level L when no reception signal is detected. A lock switch  14  and an unlock switch  13  are normal-open switches. When a driver depresses the lock switch  14  or the unlock switch  13 , the lock switch  14  or the unlock switch  13  supplies to the controller  11  a high level signal from a DC power supply  12 . 
     When the controller  11  receives a high-level trigger signal from the amplifier  17   a,  the lock switch  14 , or the unlock switch  13 , the controller  11  serially reads out an ID code stored in an internal register and serially outputs the ID code to the transmitter  15  while adding bits K 0 -K 2  thereto. 
     The controller  11  sets bit K 0  to 1 (H) when a high level trigger is output from the amplifier  17   a,  sets bit K 2  to 1 when a high level trigger is output from the lock switch  14 , and sets bit K 1  to 1 when a high level trigger is output from the unlock switch  13 . 
     The ID code is data that identifies the portable unit  10 , and the same ID code is stored in the controller  31  of the control apparatus  30 . 
     The output of the controller  11  is supplied to a resonator element  15   a  and a variable capacitance diode  15   b,  and is applied to the base of a transistor  15   c  via the resonator element  15   a.  Therefore, the capacitance of the variable capacitance diode  15   b  changes depending on whether each bit of the ID code assumes the value 1 (H) or 0 (L). The emitter of the transistor  15   c  is grounded via a capacitor  15   e  and a resistor  15   f.  The collector of the transistor  15   c  is connected to one end of a communications antenna  16 . A capacitor  15   d  is connected between the base and the emitter of the transistor  15   c.    
     The transistor  15   c  is in an ON state regardless of whether each bit of the ID code is 1 (H) or 0 (L). The load capacitance of the resonator element  15   a  changes depending on the level of each bit of the ID code, and the oscillation frequency of the transmitter  15  changes in accordance with the change in the load capacitance. Thus, a wave that has been frequency-modulated in accordance with the ID code is transmitted from the antenna  16 . 
     FIGS. 6 a  and  6   b  show the details of an “entry processing” ENP 1  performed by the controller  31  of the control apparatus  30 . The entry processing ENP 1  is performed when the driver-side door is locked while the vehicle is in a parked state. 
     Referring to FIG. 6 a,  in step S 100 , the controller  31  outputs a high-power transmission command to the transmission circuit  26  to thereby transmit request data (a transmission request signal). Subsequently, the controller  31  waits until the receiver  33  receives a reply signal. Upon receipt of the reply signal, the controller  31  checks whether an ID code represented by the received reply signal coincides with an ID code stored in the controller  31 . When no signal is received within a predetermined period, or when the received ID code does not coincide with the stored ID code, the controller  31  transmits request data again after awaiting passage of a time period t 1  (steps S 101  and S 102 ). In the present embodiment, t 1 =600 msec. 
     When the ID code represented by the received reply signal coincides with the ID code stored in the controller  31 , the controller  31  enters a human sensor mode or an object-approach monitor mode, in which the controller  31  waits, while measuring a wait time t, until the output signal SEN of the sensing circuit  2  becomes H to indicate detection of, for example, a hand present in front of the slit  23  of the door handle (S 103  and S 104 ). 
     When the output signal SEN of the sensing circuit  2  becomes H (when the sensing circuit  2  has sensed an object), in step S 105 , the controller  31  brings to an L level the unlock signal line of the door lock control switch  43 . That is, the controller  31  unlocks the door. 
     After unlocking the door, in step S 106 , the controller  31  starts timers which measure passage of time td and passage of time ts, and waits until the door is opened (step S 107 ). When the door is opened, the entry processing ENP 1  is ended, and the controller  31  returns to an unillustrated main routine. subsequently, the controller  31  waits until the door is closed (until the driver enters the vehicle and closes the door). Subsequently, the controller  31  further waits until the ignition switch  51  is opened (the engine is stopped), the door is opened (the driver exits the vehicle), and the door is then closed (the door is closed by the driver who has exited the vehicle). After the wait operation, the controller  31  starts an “exit processing” for closing the window and locking the door. In the exit processing, when the window of the driver-side door is in an opened state, the controller  31  closes the window, and outputs a low-power transmission command to the transmission circuit  26  at predetermined intervals to thereby transmit request data (transmission request signal). During a period in which a response (ID code) corresponding the request data is received, the controller  31  repeats the transmission of the low-power transmission command, and locks the door when the transmission is performed a predetermined number of times after receipt of the response becomes impossible. Subsequently, the controller  31  returns to the main routine. Since the vehicle is in a parked state and the door is in a locked state, the controller  31  starts the entry processing ENP 1 . 
     When it is determined in step S 107  of the entry processing ENP 1  that the door is not opened, the controller  31  judges in step S 108  whether the output signal SEN of the sensing circuit  2  is H (whether an object is sensed or a hand is present between the door knob  22  and the base plate member  21 ). If no hand is present (SEN=L) and the clocked time td exceeds t 5  (30 sect, the controller  31  judges that the driver has no intention to open the door, and locks the door (steps S 108 -S 110 ). Subsequently, the controller  31  returns to step S 100 . When a hand is detected before the clocked time td reaches t 5  (30 sec), the controller  31  judges the clocked time ts to be greater than t 6  (1 sec). If the clocked time ts is equal to or less than t 6  (1 sec), it is highly probable that the driver wishes to open the door, and the controller  31  waits until the door is opened. However, when the clocked time ts exceeds t 6 , the controller  31  starts a drive for opening the window, and continues the drive for opening the window until the window is fully opened (steps S 111 -S 114 ). This operation enables the window to be opened when the driver touches the door handle for the predetermined period t 6  after detection of coincidence between the received ID code and the stored ID code. Thus, a special switch or the like becomes unnecessary. 
     As shown in FIG. 6 b,  during a predetermined period t 2  after detection of ID code coincidence, the controller  31  checks (in step S 115 ) whether the output signal SEN of the sensing circuit  2  is H (whether a hand is sensed). When no hand is detected within the period t 2 , the controller  31  outputs a low-power transmission command to the transmission circuit  26  in order to transmit request data (transmission request signal). Subsequently, the controller  31  waits until the receiver  33  receives a reply signal. Upon receipt of the reply signal, the controller  31  checks whether an ID code represented by the received reply signal coincides with the ID code stored in the controller  31 . When no signal is received within a predetermined period, or when the received ID code does not coincide with the stored ID code, the controller  31  transmits request data again after awaiting passage of time t 4  (100 msec) (steps S 117 -S 120 ). When no ID code is received even after the transmission of the low-power transmission command is repeated for t 3  (5 sec), the controller  31  returns to step S 100 . 
     FIG. 8 shows an area within which the above-described request data (transmission request signal) are transmitted. When a high-power transmission command (request data) is transmitted, the portable unit  10  can receive the request data (transmission request signal) if the portable unit  10  is located within a wider area Ai. By contrast, when a low-power transmission command is transmitted, the portable unit  10  can receive the request data only when the portable unit  10  is located within a narrower area As. 
     Transmission in a wide area mode or transmission of the high-power transmission command is performed at intervals t 1  (600 msec). Transmission in a narrow area mode or transmission of the low-power transmission command is performed at intervals t 4  (100 msec). Therefore, the interval t 4  is one-sixth of the interval t 1 . 
     When no hand is sensed within the predetermined period t 2  (5 sec) after detection of coincidence between the stored ID code and a response ID code transmitted in response to the high-power transmission command, the transmission power is reduced, and coincidence of the ID codes is checked again. Therefore, the consumed power is reduced. 
     FIGS. 7 a  and  7   b  shows the details of “entry processing” ENP 2  performed by the controller  31  according to another embodiment of the present invention. In the present embodiment, after locking the door in step S 110 , the controller  31  proceeds to a narrow area mode in step S 117 . When the time period t 5  has elapsed without the door being opened and a hand becomes undetectable after initial detection of ID code coincidence and presence of the hand, the controller proceeds to step S 117  and transmits a low-power transmission command. Thus, consumed power is decreased as in the above-described case. 
     While preferred embodiments of the invention have been shown and described above, a number of changes and modifications are possible. Accordingly, the invention is not intended to be limited to the specific constitution or arrangement disclosed herein, but the right is reserved to all changes and modifications coming within the scope of invention defined by the appended claims.