Abstract:
An apparatus for protecting a vehicle includes a fob in the possession of a person who whishes to use the vehicle. The fob includes a fob code. A proximity sensor mounted on the vehicle is used to actuate circuitry for interrogating the fob so as to retrieve the fob code. The fob code is then matched to a vehicle code to determine whether the person possessing the fob is authorized to use the vehicle. The proximity sensor may include a capacitive sensor, and inductive sensor, or both.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims the benefit of domestic priority of U.S. provisional application 61/237,996, filed Aug. 28, 2009. The disclosure of this provisional application is incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    The present application is directed to an apparatus for preventing unauthorized use of a vehicle. 
         [0003]    Traditionally, keys have been used to deter unauthorized use of vehicles such as cars. An authorized user of a car is issued a key that is configured to mate with a mechanical lock provided in the car and then to permit the car to be started or stopped by twisting the key. Without access to the proper key, an unauthorized user is unable to easily start the car. 
         [0004]    Recently, security has been increased by the use of so-called transponder keys or “chip” keys. When an attempt is made to start a car with such a key, an interrogation signal is transmitted to the key by circuitry in the car. An integrated circuit that is disposed in a fob associated with the key responds to the interrogation signal by sending a coded signal back to the circuitry in the car. Only if the coded signal received by the circuitry matches a stored code can the car be started. 
         [0005]    While the enhanced security afforded by transponder keys is desirable, they are still keys and thus share inconvenient characteristics that are common to keys. For example, it can sometimes be a nuisance to orient a key properly for insertion into the lock, particularly at night. Furthermore, if a key and an electronic component such as a digital camera or a cell phone are carried in the same pocket or purse, the metal of the key may scratch the electronic component. This can inflict serious damage if a scratch occurs, for example, on the LCD screen of a digital camera. 
       SUMMARY OF THE INVENTION 
       [0006]    An object of the invention is to avoid the inconvenience of needing a key to operate a vehicle, without compromising security. 
         [0007]    Another object is to permit an authorized person to operate a vehicle merely by carrying a fob and touching an activation region on a panel that is located, for example, on a dashboard. A proximity detector adjacent the activation region detects the touch. 
         [0008]    Another object of the invention is to provide a solenoid assembly that permits magnetic coupling with a solenoid in a fob regardless of the orientation of the fob. To this end, the solenoid assembly preferably includes three orthogonally disposed solenoids. 
         [0009]    Another object of the invention is to provide a way to reliably detect intentional actuation of a proximity switch. 
         [0010]    These and other objects that will become apparent from the ensuing detailed description can be attained by providing an apparatus that includes a proximity sensor which is mounted on a vehicle and a fob which is detached from the vehicle, the fob having means for transmitting and receiving signals. The proximity sensor includes a capacitive sensor and/or an inductive sensor. The apparatus also includes means for transmitting an interrogation signal to the fob in response to manual activation of the proximity sensor, for receiving from the fob a signal that includes a fob code, and for determining whether the fob code matches a code assigned to the vehicle. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]      FIG. 1  is a block diagram of a first embodiment of an apparatus according to the present invention; 
           [0012]      FIG. 2  is a schematic diagram of a solenoid assembly that is shown in  FIG. 1 ; 
           [0013]      FIG. 3  is a schematic diagram of a fob that is shown in  FIG. 1 ; 
           [0014]      FIG. 4  illustrates the dashboard of a car in which the embodiment of  FIG. 1  is installed; 
           [0015]      FIG. 5  is a sectional view taken along line  5 - 5  of  FIG. 4 ; 
           [0016]      FIG. 6  is a flowchart illustrating operation of the first embodiment; and 
           [0017]      FIG. 7  is a block diagram of a second embodiment. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0018]      FIG. 1  illustrates a block diagram of a first embodiment of an apparatus for preventing unauthorized use of vehicle such as a car. The apparatus includes a microcontroller  20 , a base station  22 , a solenoid assembly  24 , a proximity sensor such as capacitive sensor  26 , and part of a display section  28 . The elements  20 - 28  are mounted on the car. The apparatus also includes a fob  30  that is carried by a person who is authorized to use the car. The microcontroller  20  of the apparatus communicates with electrical systems for monitoring the car and for controlling the car in accordance with input by the driver. These electrical systems are identified in  FIG. 1  simply as vehicular electronics  32 . 
         [0019]    An example of operation of the apparatus shown in  FIG. 1  will now be described. A person who wants to start the car and who carries fob  30  touches a predetermined activation region and this touch is detected by capacitive sensor  26 . The capacitive sensor  26  signals the microcontroller  20 , which signals base station  22  to energize solenoid assembly  24 . The solenoid assembly  24  then emits an alternating magnetic field that induces an alternating current in a solenoid (not shown in  FIG. 1 ) in the fob  30 . This alternating current provides power for circuitry in the fob  30 . The alternating magnetic field emitted by solenoid assembly  24  also serves as an interrogation signal to the fob  30 , which responds by emitting an encrypted code followed by an instruction (in this example, an instruction to start the car). The encrypted code in the instruction is received by base station  22  by way of solenoid assembly  24 , and then sent to microcontroller  20 . The microcontroller  20  decrypts the code and, if the decrypted code matches a code that has been assigned by the manufacture to the car, the microcontroller  20  forwards the instruction to vehicular electronics  32 . Vehicular electronics  32  then starts the car. The car is stopped by touching the activation region again. 
         [0020]    The alternating magnetic field emitted by solenoid  24  may have a frequency of 125 kHz. 
         [0021]      FIG. 2  shows the solenoid assembly  24 , which includes a solenoid  34  that is oriented in the X direction, the solenoid  36  that is oriented in the Y direction, and a solenoid  38  that is oriented in the Z direction. The reason why three solenoids that are oriented in orthogonal directions are desirable is that fob  30  has a solenoid (not shown in  FIG. 1 ) with an arbitrary orientation, since the orientation of fob  30  itself depends upon how it is carried. The three orthogonal solenoids in assembly  24  ensure that, regardless of the orientation of fob  30 , the inductive coupling between the fob  30  and the solenoid assembly  24  will be adequate for transmission of power to the fob  30  and transmission of the encrypted code and the instruction from fob  30  to the solenoid assembly  24 , if the fob  30  is located within a few feet of the solenoid assembly  24 . 
         [0022]    The construction of the fob  30  is illustrated in  FIG. 3 . The fob  30  includes a solenoid  40  that is inductively coupled to the solenoid assembly  24  when the fob  30  is located fairly close to the assembly  24 . The alternating current induced in solenoid  40  is received by a power supply  42 , which rectifies and filters the power and stores it on a capacitor (not illustrated). A controller  44  receives electricity from the power supply  42 . The fob  30  in this embodiment includes three manually actuated, normally-open switches  46 ,  48 , and  50 . The person carrying the fob  30  closes switch  46  if the person wishes to start the car. Switches  48  and  50  provide an accessory mode and a run mode. In the accessory mode, some of the electrical equipment in the car (such as a radio) become operable. In the run mode, more of the electrical equipment becomes operable. 
         [0023]    The dashboard of the car in the first embodiment is shown in  FIG. 4 , which illustrates such conventional features as a steering wheel (un-numbered) at the left of the drawing and a glove compartment (likewise un-numbered) at the right. The display section  28  ( FIG. 1 ) includes display units  28   a ,  28   b ,  28   c , and  28   d  that are controlled by the vehicular electronics  32 . These display units may include, for example, a fuel display, a mileage display, a tachometer, and various warning indicators. The dashboard may also include a translucent panel  52  having a dimple  54  in it. 
         [0024]    Turning now to  FIG. 5 , the assembly of the present embodiment (except for fob  30 ) is mounted on a printed circuit board  56  that is disposed beneath the panel  52 . The capacitive sensor  26  is mounted on the platform member  58  and is closely spaced from the dimple  54 , which serves as an activation region for the sensor  26 . Pressure from an activating member such as a finger in the dimple  54  slightly deforms the panel  52  and changes the voltage that is supplied to a capacitor via a resistor (neither of which is shown) in the capacitive sensor  56 . It is this change of voltage, if it is greater in magnitude than a predetermined threshold value V t  and if it persists longer than a predetermined threshold value T t , that is interpreted by the microcontroller  20  as an activation signal. 
         [0025]    With the continuing reference to  FIG. 5 , the display section  28  ( FIG. 1 ) includes a display unit  28   e  that is mounted of spacers  58 . Although not shown, the display unit  28   e  includes LEDs that are selectively activated to signal the start, accessory, and run modes. 
         [0026]      FIG. 6  is a flowchart illustrating the overall operation of the first embodiment. In step  60 , the voltage across the capacitor (not illustrated) in capacitive sensor  26  is measured, and if this voltage changes, then the change ΔV is determined. In step  62 , whether the voltage change ΔV is greater than the threshold V t  is determined. If not, the procedure returns to step  60  to continue measuring the voltage across the capacitor. However, if ΔV is greater than the threshold V t , whether ΔV has stayed above V t  for longer than the threshold T t  is determined. If not, the procedure returns to step  60 . However, if both thresholds are exceeded (“Y” at step  64 ), a valid triggering event (that is, pressure intentionally applied to the dimple  54  of  FIG. 5 ) has been detected. Steps  62  and  64  are included in the procedure in order to exclude unintentional activities (such as cleaning the dashboard or accidentally bumping against it) from being interpreted as triggering events. 
         [0027]    With continuing reference to  FIG. 6 , a timer in the microcontroller  20  is set in step  66 . Whether a response has been received from the fob  30  is determined in step  68 . If not, a check is made at step  70  to determine whether the timer has timed out. If not, the procedure returns to step  68  to await the response from fob  30 . If the response has been received, the microcontroller  20  decrypts the ID code in the response in step  72  and determines, in step  74 , whether the decrypted ID code corresponds to the ID code that was assigned to the car by its manufacturer. If the code is not OK, a message is displayed at step  76  (in this embodiment, by blinking all of the LEDs in the display unit  28   e  of  FIG. 5 ) and the procedure returns to step  60 . If the ID code is valid, the desired activity (that is, whether to start the car or to enter the accessory or run modes, depending upon which of switches  46 - 50  in  FIG. 3  has been closed) is determined at step  78 . A command to execute the desired activity is then sent to vehicular electronics  32  ( FIG. 1 ) at step  80 . 
         [0028]      FIG. 7  is a block diagram of a second embodiment to the present invention. It is the same as the first embodiment except that an inductive sensor  26 ′ is used instead of the capacitive sensor  26  in the first embodiment, and also the communication with the fob is RF communication rather than communication based on magnetic interaction. For this reason, the second embodiment employs a radio base station  22 ′ instead of the base station  22  of the first embodiment and an antenna  24 ′ instead of the solenoid assembly  24 . The fob  30 ′ that is used in the second embodiment includes an RF transceiver and lacks the solenoid  40  of the first embodiment. 
         [0029]    It will be apparent to those skilled in the art that many changes and modification could be made in the embodiments that have been described above. Some of them will now be specifically mentioned. 
         [0030]    Instead of the capacitive sensor  26  or the inductive sensor  26 ′, a proximity sensor that includes a capacitor and an inductive sensor could be used. In such a modification the capacitor of the capacitive sensor could be placed inside the coil of the inductive sensor. For example, the coil could be washer-shaped and the capacitor could be located in the center of the coil. 
         [0031]    Another possible modification would be to use a panel  52  ( FIG. 4 ) having three dimples instead of a single dimple  54 . A proximity sensor would be placed behind each of the dimples. In this way, the driver could press different dimples to start the vehicle or enter the accessory or run modes, so that the switches of fob  30  that are shown in  FIG. 3  could be eliminated. That is, the desired activity would be indicated by actuation of the appropriate proximity sensor rather than by closure of a switch on the fob. 
         [0032]    The proximity sensor may be combined with a heptic device (such as piezoelectric vibrator) to provide tactile feedback for the user when the proximity sensor is actuated. 
         [0033]    Instead of a capacitive and/or inductive sensor, a touch panel could be used. A driver could touch different locations on the touch panel to indicate the desired activity. Alternatively, a driver could use a finger to trace different paths over the touch panel (possibly paths such as “S” for start, “A” for the accessory mode, and “R” for the run mode) to identify the desired operation. 
         [0034]    While  FIGS. 4 and 5  show a dimple  54  in the panel  52 , this is preferred but not necessary. The surface of the panel  52  may be uniform, or a blister may replace the dimple. 
         [0035]    The fob can be configured to provide additional functions, particularly if it includes a battery instead of relying on power transmitted from the base station. For example, the switch could be included for locking or unlocking the doors, opening the trunk, and so forth. 
         [0036]    The communication with the fob may be by way of magnetic coupling, such as the 3D 125 kHz bi-directional communication discussed above with respect to the first embodiment. The communication can also be by radio, such as a vehicle passive and/or remote command using 13.56 mHz NFC (Near Field Communications), or by coded infrared signals. 
         [0037]    It will be understood that the above description of the present invention is susceptible to various other modifications, changes, and adaptations, and the same or intended to be comprehended within the meaning and a range of equivalents of the appended claims.