Abstract:
A method and apparatus for easily and safely releasing a brake interlock function of a vehicle audio/video system. The vehicle audio/video system is designed to enable both a driver and a passenger to watch a video with a display unit. For safety reasons, a brake interlock function is incorporated to disable the display unit when the vehicle is in motion. The brake interlock function is released if the display unit is installed for passengers in the rear seats. Various release devices including a mechanical and an electrical switch are disclosed for releasing the brake interlock function for the display unit in the vehicle audio/video system. The release device is established within a display compartment mounted on a front or middle seat when the display unit is installed in the display compartment.

Description:
FIELD OF THE INVENTION 
   This invention relates to a vehicle audio/video system with a display unit having a brake interlock function, and more particularly, to a method and apparatus which safely and easily release a brake interlock function of the audio/video system, thereby enabling a display unit in a vehicle to display video images. 
   BACKGROUND OF THE INVENTION 
   Vehicles have been normally equipped with a radio, a cassette player or a CD (Compact Disk) player and speakers. Recently, more and more people want to equip with not only such audio equipment but also video equipment since they tend to enjoy movies or TV shows in their vehicles just like in their homes. Such a vehicle audio/video system typically includes a TV tuner, a VCR or a DVD (Digital Versatile Disc or Digital Video Disc) player and monitor screen for displaying video images. In a more sophisticated audio/video system, a navigation system is incorporated to provide both audio sound and video images as well as a route guidance function to guide a user to his/her destination. 
     FIG. 1  shows a typical example of audio/video system when it is installed in a dashboard  12  of a vehicle (the front passenger side is not shown). The audio/video system includes a display unit  11  which is normally placed about the center of the dashboard  12  and a DVD player  13  which may also include a TV tuner. If a navigation system is installed in the vehicle, the display unit  11  also functions as a monitor screen for the navigation system, and a driver is always allowed to watch the navigation status on the display unit. 
   However, because of the safety reason, while the vehicle is moving, the driver is not allowed by law to watch a movie, a TV program, a video game or any other moving images (hereafter “video”) which may distract the driver except for the navigation message or vehicle information. Namely, current traffic regulations for safe driving prohibit the display unit  11  from playing the video within the driver&#39;s view when the vehicle is in motion. To comply with this rule, a typical audio/video system includes an interlock function to disable a display unit under predetermined conditions. Such an interlock function checks the status of a footbrake and a handbrake (parking brake) to disable any video display unit. This feature is sometimes called a “brake interlock function”, the details of which will be described later. 
     FIG. 2A  shows an example of the display unit  11  installed in the rear of a headrest  21  of a front seat or a middle seat. An interface cable  22  connects the display unit  11  and the DVD player  13  (or AV interface unit  47  shown in  FIG. 4A ).  FIG. 2B  shows another example of the display unit  11  which is installed in the rear of a seat  23  (front or a middle seat). Passengers in the rear seats or middle seats are always allowed to watch a video, since it will not directly affect the safe driving. Therefore, the brake interlock function for a display unit for rear seat passengers is not required but is required only for a display unit for a driver. 
   There are several types of audio/video system. The first type is an audio/video system only for a driver. As mentioned before, the brake interlock system is required for this type of system. The second type is an audio-video system only for passengers in the rear seats. This type needs not be controlled like the first one because passengers in middle seats or rear seats are always allowed to watch the video. Thus, the brake interlock function for the display unit is not required. 
   The third one is an audio/video system for both a driver and passengers, to which the present invention is advantageously applied. For this type, the brake interlock system is only required when a display unit is installed in the dashboard for a driver. On the other hand, the display unit should not be disabled when the display unit is installed for passengers in the rear seat or middle seat. This type of the audio/video system is preferable in terms of design and production cost because the same components such as display units can be used for a driver (front seat) and passengers (rear seat) except for the feature of the brake interlock function. 
   However, if a display unit can be used commonly for a driver&#39;s seat and rear passenger&#39;s seat, a vehicle must have a brake interlock function to disable the display unit for the driver when the vehicle is in motion. In contrast, when the display unit is installed for passengers in the rear or middle seats, such a brake interlock function should be released. In other words, the common display unit with the brake interlock function can be used for both a driver and a passenger if the audio/video system has a feature to release the brake interlock function when the display unit is installed for rear passengers. 
     FIG. 3  shows an example of the display unit  11  which can be used for both a driver and a passenger. Typically, the display unit  11  has a color LCD (Liquid Crystal Display) panel (screen)  11   a . The display unit  11  has various buttons such as a power switch  11   b , a volume up button  11   c  and a volume down button  11   d , a select button  11   e , and a display key  11   f . For example, the volume up button  11   c  and down button  11   d  are used to adjust the sound volume or to adjust an image such as brightness, and the select button  11   e  is used to select an input source or a function for the display unit  11 . The display button  11   f  is used to select a display mode such as “wide” or “normal” of the screen  11   a . The display unit  11  is used either as a video screen or navigation screen. Namely, the select button  11   e  is used to choose an input source, a video from audio/video source such as a DVD or navigation data from the navigation system. 
   A wire  47   a  for releasing the brake interlock function comes with the display unit  11  when an end user purchases the display unit  11 . The wire  47   a  is used only when the display unit  11  is installed at locations other than the front seat. In the case where the display unit is installed for rear seat passengers, the wire  47   a  is connected by a technician of a dealer to release the brake interlock function. Such a releasing procedure is done in accordance with instructions provided by a manufacturer of the audio/video display system. In other words, the user has to go to the dealer to activate the display unit for rear seat passengers. 
     FIG. 4A  is an example of conventional audio/video system with the brake interlock function which can be used for both a driver (front seat) and a passenger (rear seat). In this example, the audio/video system is comprised of a display unit  11 , a footbrake  44 , a handbrake  45 , an AV interface unit  47 , a video source unit such as a DVD player  46 , and a navigation system  48 . Depending on the design of the system, the AV interface unit  47  may be formed within the housing of the display unit  11 . The video source unit can be a TV tuner or a video game player instead of the DVD player  46 . It is assumed that when two or more display units  11  are used, two or more AV interface units  47  will be provided corresponding to the display units so that each pair of display unit and AV interface unit can operate independently from one another. 
   In this example, both audio and video signals are sent from the DVD player  46  to the display unit  11  through the AV interface unit  47 . The navigation data is also sent to the display unit  11  from the navigation system  48  through the AV interface unit  47 . The display unit  11  has the select button  11   e  ( FIG. 3 ) to select either a video screen or a navigation screen. 
   The AV interface unit  47  controls the brake interlock function in the audio/video system. The AV interface unit  47  monitors ON/OFF status of the footbrake  44  and the handbrake  45 , and controls the display unit  11  to prohibit a driver from operating the DVD player or watching a video when the vehicle is running. Typically, the display unit  11  is designed to be used for both a passenger and a driver. If the display unit  11  is installed for a rear seat passenger, the brake interlock function must be released as noted above. 
   Also noted above, the wire  47   a  is used for releasing the brake interlock function. For example, the wire end is connected to the ground to release the brake interlock function. As a result, the AV interface unit  47  stops interlocking the DVD player  46  or display unit  11 , allowing the passengers to watch the video when the vehicle is in motion. 
   Timing chart of  FIG. 4B  shows an example of brake interlock function as to how the display unit  11  is disabled or enabled in accordance with ON/OFF states of the foot brake and hand brake. In  FIG. 4B , “Foot Brake ON” indicates that the footbrake is pressed, and “Foot Brake OFF” indicates that the footbrake is released. Further, “Hand Brake ON” indicates that the parking brake (handbrake) is used, and “Hand Brake OFF” indicates that the parking brake is released. “Display” indicates that the display unit  11  is either allowed or inhibited. 
   Suppose the vehicle is in motion, the display unit  11  is disabled (status  43   a ). The display unit  11  can be activated only when the vehicle is stationary. To show that the vehicle is in the stationary state, a driver must do the following steps. First, the driver presses the footbrake (status  41   a ) until the vehicle stops. Second, in the condition of pressing the footbrake, the driver activates the handbrake (status  42   a ) after the vehicle stops completely. Third, still in the condition of pressing the footbrake, the driver releases the handbrake (status  42   b ) and activates the handbrake again (status  42   c ). Fourth, the driver releases the footbrake (status  41   b ). 
   After all the above procedures of the footbrake and the handbrake, the brake interlock function is released (status  43   b ), thereby enabling the display unit  11 . During this procedure, if the handbrake is released (status  42   d ), the display unit is disabled again (status  43   c ). The display unit is disabled without regard to whether the footbrake is activated or not (status  41   c ). If the handbrake is activated again, the display unit  11  is activated (status  43   d ). 
   Such a brake interlock function described above must be released when the display unit is used in the rear seat. To do this in the conventional technology, a user has to drive a car to a dealer to release this function. This is burdensome and time consuming to the user. Further, even if the law prohibits, a user may illegally use the wire to release the brake interlock function when the display unit is installed in the front seat. Therefore, it is necessary to establish a new method which can solve the above noted problems. 
   SUMMARY OF THE INVENTION 
   It is, therefore, an object of the present invention to provide a method and apparatus for a vehicle audio/video system which is able to easily and securely release a brake interlock function when the display unit is installed only for middle or rear seat passengers. 
   It is another object of the present invention to provide a method and apparatus for a vehicle audio/video system for releasing the brake interlock function easily by a user without violating the traffic laws. 
   It is a further object of the present invention to provide a method and apparatus for a vehicle audio/video system which enables a user to easily install the display unit while easily releasing the brake interlock function for the display unit. 
   In this invention, the vehicle audio/video system is designed to enable both a driver and a passenger to watch a video using the same car audio video system. Thus, the brake interlock function is incorporated in the vehicle in accordance with the traffic regulation if a display unit has to be installed in the dashboard of the vehicle. On the other hand, the brake interlock function should be released if a display unit is installed, for example, in the rear of the seat for rear seat passengers. Various methods and structures for releasing the brake interlock function are described in the present invention. 
   One aspect of the present invention is an apparatus for releasing a brake interlock function of a vehicle audio/video system. The apparatus includes a display unit for the vehicle audio/video system for displaying images, a display compartment for receiving the display unit therein, and a release device attached to the display unit and the display compartment for producing a release signal when the display unit is installed in the display compartment. The brake interlock function disables the display unit (except for the navigation function) when the display unit is mounted on a dashboard of the vehicle and when the vehicle is in motion, while the brake interlock function is released by the release signal when the display compartment having the display unit is mounted on a rear of a front or middle seat, thereby enabling the display unit. 
   The rear of the front or middle seat is a rear of a headrest of the front or middle seat of the vehicle wherein the display compartment is so configured to be fit solely with a recess formed on the rear of the headrest. Alternatively, the rear of the front or middle seat is a rear of a seat back of the front or middle seat of the vehicle wherein the display compartment is so configured to be fit solely with a recess formed on the seat back of the front or middle seat. 
   An example of the release device is a mechanical switch which is pressed by an inner wall of the display compartment when the display unit is installed in the display compartment, thereby generating the release signal. Another example of the release device is a mechanical switch which works as a connector where a pin of the connector is inserted in a receptacle of the connector when the display unit is installed in the display compartment, thereby generating the release signal. A further example of the release device is a mechanical switch comprised of two electrical terminals and a rod for electrically shorting the two terminals when the display unit is installed in the display compartment, thereby generating the release signal, where the two terminals are provided on the display unit, and the rod is placed on an inner wall of the display compartment, or vice versa. 
   A further example of the release device is comprised of a magnetic sensor and a permanent magnet, and the magnetic sensor detects a magnetic field produced by the permanent magnet when the display unit is installed in the display compartment, thereby generating the release signal, where the magnetic sensor is provided on the display unit and the permanent magnet is provided on an inner wall of the display compartment, or vice versa. A further example of the release device is comprised of an optical sensor and an optical source, and the optical sensor detects light energy produced by the optical source when the display unit is installed in the display compartment, thereby generating the release signal, where the optical sensor is provided on the display unit and the optical source is provided on an inner wall of the display compartment, or vice versa. 
   Another aspect of the present invention is a method for releasing a brake interlock function of a vehicle audio/video system. The method includes the steps of providing a display unit for the vehicle audio/video system for displaying images, receiving the display unit in a display compartment, producing a release signal by a release device attached to the display unit and the display compartment when the display unit is received in the display compartment, and mounting the display compartment having the display unit on a rear of a front seat or middle seat of the vehicle. The brake interlock function disables the display unit when the display unit is mounted on a dashboard of the vehicle and when the vehicle is in motion while the brake interlock function is released by the release signal when the display compartment having the display unit is mounted on the rear of the seat, thereby enabling the display unit. 
   According to the present invention, in any embodiments for releasing the brake interlock function, the conventional accessary cable is not used. Moreover, a user can easily install the display unit in the rear of the front seat for passengers in the rear seat and the brake interlock function is automatically released by the installation of the display unit. Since the display compartment for receiving the display unit therein is designed only for the attachment to the rear of the front seat, the user can release the brake interlock function without violating the traffic regulations. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a schematic diagram showing an example of audio/video system having a display unit and a DVD player which is mounted on a dashboard of a vehicle. 
       FIG. 2A  is a schematic diagram showing an example of a display unit installed in a headrest, and  FIG. 2B  is a schematic diagram showing an example of a display unit installed in a rear of the seat back. 
       FIG. 3  is a schematic diagram showing an example of display unit for a vehicle audio/video system. 
       FIG. 4A  is a schematic diagram showing a typical car audio/video system in the conventional technology, and  FIG. 4B  is a timing diagram showing an example of operation of the brake interlock function. 
       FIGS. 5A-5B  are schematic diagrams showing a first embodiment of the present invention where a mechanical switch is installed to release the brake interlock function. 
       FIGS. 6A-6B  are schematic diagrams showing a second embodiment of the present invention where a mechanical switch is installed to release the brake interlock function. 
       FIGS. 7A-7B  are schematic diagrams showing a third embodiment of the present invention where a mechanical switch is installed to release the brake interlock function. 
       FIGS. 8A-8B  are schematic diagrams showing a fourth embodiment of the present invention where a magnetic sensor is installed to release the brake interlock function. 
       FIGS. 9A-9B  are schematic diagrams showing a fifth embodiment of the present invention where an optical sensor is installed to release the brake interlock function. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   The method and apparatus for releasing the brake interlock function in the present invention is described with reference to  FIGS. 5A-9B . Throughout the embodiments shown in  FIGS. 5A-9B , a display unit  11  is installed on a rear of a headrest  21 , although the present invention is not limited to such specific examples. The display unit  11  can be installed in other locations such as on a rear of a seat back such as shown in  FIG. 2B . 
   The first embodiment is shown in  FIGS. 5   a  and  5 B which utilizes a mechanical switch to release the drive interlock function.  FIG. 5A  shows an example of location of the mechanical switches in this embodiment.  FIG. 5B  shows how the mechanical switch works when a display unit  11  is installed in a display compartment  67  which is sometimes called a “headrest cup” when it is installed in a headrest. The display compartment  67  is so designed that it cannot be installed with the display unit  11  in a dashboard of the vehicle. Namely, the display compartment  67  itself is a part of the apparatus of the present invention for releasing the brake interlock function. 
   Referring back to  FIG. 5A , in the first embodiment, mechanical switches  61  are provided on the side panel on the right of the display unit  11 . To install the display unit  11  in the headrest  21 , the display compartment (headrest cup)  67 , which is a part of installation kit, is used. Before installing the display unit  11  in the headrest  21 , a recess (hollow) is formed on the headrest  21  to create the display compartment  67  to receive the display unit  11  therein. 
   In the example of  FIG. 5B , each mechanical switch  61  is formed of a switch base  61   a , a switch head  61   b  and a switch wire  61   c . Typically, the switch head  61   b  is biased outwardly with a spring. An inner conductive terminal in the switch base  61   a  is electrically shorted (ON) when the switch head  61   b  is pressed inwardly. The inner conductive terminal is electrically open (OFF) unless the switch head  61  is pressed inwardly. Such ON/OFF state is transmitted through the switch wire  61   c.    
     FIG. 5B  shows front views of the switch  61  and the display compartment  67 .  FIG. 5B  also includes a perspective view of the display compartment  67 . When the display unit  11  is installed in the display compartment  67 , the switch head  61   b  is pushed inwardly by the side panel  67   a , which turns the switch  61  to the ON state. Thus, a signal indicating the ON state is sent to the display unit  11  through the switch wire  61   c . As a result, the display unit  11  generates a release signal which is sent to the AV interface unit  47  ( FIG. 4A ) in order to release the brake interlock function. A cable  22  is to transmit the audio/video signal to the display unit  11  as well as to send the release signal to the AV interface unit  47 . Since this method does not use any accessary such as the wire  47   a  and wire end  47   b  in the conventional method as shown in  FIG. 4A , no illegal installation is possible. 
     FIGS. 6A-6B  show the second embodiment of the present invention where mechanical switches are attached to the back panel of the display unit  11 . The structure of mechanical switches are different from the mechanical switches  61  in  FIGS. 5A-5B . The mechanical switch in this case is a connector which is formed of a pin  66  and a receptacle  65 . The receptacles  65  are attached to an inner back wall of the display compartment  67  and the pin  66  is attached to the back panel of the display unit  11  as shown in  FIGS. 6A-6B . 
     FIG. 6B  further shows a cross sectional side view of the display unit  11  and the display compartment  67 . The receptacle  65  is both horizontally and vertically aligned such that the receptacle  65  contacts the pin  66  when the display unit  11  is installed in the display compartment  67 . Namely, as shown in the bottom of  FIG. 6B , when the display unit  11  is installed in the display compartment  67 , a pair of pins  66  contact each other as the pins  66  are pressed in the receptacle  65 . The switch is electrically closed (ON) when the pins mechanically contact each other, and the display unit  11  generates a release signal. The display unit  11  sends the release signal to the AV interface  47  ( FIG. 4   a ) through the cable  22 . Thus, the brake interlock function is released for the display unit  11 . 
     FIGS. 7A-7B  show the third embodiment of the present invention where mechanical switches are attached to the back panel of the display unit  11 . As shown in  FIG. 7A , two terminals  68  and a rod  69  made of conductive material form a mechanical switch. Each terminal  68  is attached on the back panel  11   g  of the display unit  11  as shown in the FIG.  7 A. On the other hand, the rod  69  is attached to the inner back wall of the display compartment  67 . The terminals  68  are horizontally and vertically aligned such that the terminals  68  are electrically shorted by the rod  69  when the display unit  11  is installed in the display compartment  67 . The terminals  68  have wires  68   a  to transmit a signal to the display unit  11  which sends a release signal to the AV interface unit  47  through the cable  22 . As a result, the drive interlock function is released for the display unit  11 . 
     FIGS. 8A-8B  show the fourth embodiment of the present invention where a magnetic sensor  70  is attached to the back panel of the display unit  11 . The magnetic sensor  70  is placed on the back panel  11   g  of the display unit  11  while a permanent magnet  71  is attached on an inner back wall of the display compartment  67 . The magnetic sensor  70  is wired to the display unit  11  to transmit a sensor signal. The magnet  71  is typically covered with plastic film or other coating for mechanical protection. 
   The position of the magnetic sensor  70  and the permanent magnet  71  is adjusted such that the magnetic sensor  70  detects the magnetic field of the permanent magnet  71  when the display unit  11  is inserted into the display compartment  67 . In this embodiment, the magnetic sensor  70  does not need to mechanically contact the magnet  71  because the magnetic sensor  70  only needs to detect the magnetic field produced by the permanent magnet  71 . When the magnetic sensor  70  detects the magnetic field, a detection signal is sent to the display unit  11  via wire  70   a , then a release signal is generated in the display unit  11  and is sent to the AV interface unit. In this embodiment, it is apparent that the positions of the magnetic sensor  70  and the permanent magnet  71  can be reversed: 
     FIGS. 9A-9B  show the fifth embodiment of the present invention where an optical sensor  72  is attached to the back panel of the display unit  11 . As shown in  FIG. 9A , on the back panel  11   g  of the display unit  11 , a photo diode (photo transistor)  72  is provided as an optical sensor. An optical source such as an LED (Light Emitting Diode)  73  is placed on the inner back wall of the display compartment  67 . The wire  73   a  provides power for the LED  73  through the wire  22 . 
   The positions of the optical sensor  72  and the optical source  73  are adjusted such that the photo sensor  72  can detect the light energy from the optical source  73  effectively. Thus, when the display unit  11  is inserted into the display compartment  67 , the distance between the photo transistor and the LED becomes short enough for the optical sensor  72  to receive the light energy. As a result, the optical sensor  72  sends a detection signal via wire  72   a  to the display unit  11  which sends a release signal to the AV interface unit. As a result, the drive interlock function is released for the display unit  11 . 
   As one of variations of the fifth embodiment, an optical sensor may be placed on the inner back wall of the display compartment  67  and an optical source may be attached to the back panel of the display unit  11 . In such an arrangement, the release signal is produced by the photo transistor on the inner back wall of the display compartment  67  and is directly sent to the AV interface unit to release the brake interlock function. 
   In the foregoing example, the release signal is sent to the AV interface unit to release the brake interlock function, however, there are many other ways to enable the display unit. For example, instead of sending the release signal to the AV interface unit, the release signal can be directly used by the display unit as an activation signal for the display unit. As noted above, depending on the actual design, the AV interface unit can be formed within the housing of the display unit. 
   The foregoing descriptions concerning  FIGS. 6-9  only show the case where the releasing apparatuses (such as switches) are placed on the back panel of the display unit and on the inner back wall of the display compartment. However, as in the example such as shown in  FIGS. 5A-5B , the releasing apparatus in  FIGS. 6-9  can be installed on the side of the display unit or the inner side wall of the display compartment. The releasing apparatus in  FIGS. 6-9  can also be formed within the display unit or the display compartment so as not to be easily broken or shown to the user. Further, it is apparent that the positions of the components forming the mechanical switches in the embodiments of  FIGS. 5A-5B ,  6 A- 6 B and  7 A- 7 B can be reversed. 
   As has been described above, according to the present invention, in any embodiments for releasing the brake interlock function, the conventional accessary cable is not used. Moreover, a user can easily install the display unit in the rear of the front seat for passengers in the rear seat and the brake interlock function is automatically released by the installation of the display unit. Since the display compartment for receiving the display unit therein is designed only for the attachment to the rear of the front seat, the user can release the brake interlock function without violating the traffic regulations. 
   Although the invention is described herein with reference to the preferred embodiments, one skilled in the art will readily appreciate that various modifications and variations may be made without departing from the spirit and the scope of the present invention. Such modifications and variations are considered to be within the purview and scope of the appended claims and their equivalents.