Abstract:
A vehicle having left and right lower rear brake lights and a Center High-Mounted Stop Light (CHMSL) flashes the CHMSL when the brakes are initially applied. The lower brake lights do not automatically flash. After a predetermined duration, the CHMSL remains continuously illuminated until the brakes are removed. In an effort to improve on the design referenced by U.S. Pat. No. 5,345,218, a micro-controller circuit is configured to be activated when brakes are applied. Once activated, internal embedded micro code produce a predetermined number cycles of an oscillating output signal that is responsible for causing the CHMSL to flash. After the numbers of cycles have been completed, the embedded micro code forces the output signal to remain in a state that causes the CHMSL to stay illuminated until the brakes have been removed.

Description:
REFERENCES 
     U.S. Patent Documents 
       [0001]      
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                 5,345,218 
                 Sep. 6, 1994 
                 Daniel S. Woods 
               
               
                   
                   
               
             
          
         
       
     
       TECHNICAL FIELD OF THE INVENTION 
       [0002]    The present improved invention relates generally to the operation of vehicle brake lights. More specifically, the present improved invention relates to operating vehicle brake lights so that the brake lights are automatically flashed when activated. 
       BACKGROUND OF THE INVENTION 
       [0003]    Brake lights represent one of the many important safety features included on a vehicle. Brake lights indicate when a vehicle&#39;s brakes are being applied to signal the driver of the following vehicle of the need to slow down to avoid a rear-end collision. However, in spite of the use of brake lights, the incidence of rear-end collisions remain high. To some degree, the high incidence of rear-end collisions is due to a tendency to follow too closely in traffic. But, the high number of collisions is also due to inattention by the following driver. 
         [0004]    Accordingly, brake light systems are designed to grab a following driver&#39;s attention. To this end, brake lights tend to exhibit the color red and to be relatively bright when compared to other lights located at the rear of the vehicle. In recent years, the size of these lights has increased, and a center high-mounted stop light (CHMSL), also called the upper or third brake light, has been added to the rear of the vehicle for improved visibility from behind and an improved attention-getting effect. While such enhancements are widely believed to have improved safety, rear-end collisions still occur far too often. In recent years over 2.5 million rear-end collisions a year have occurred, causing more than 2,149 deaths in one year. 
         [0005]    Alternative brake light operating systems that possess still greater attention-grabbing characteristics are known. From the NHSTA “an extra second of warning time could prevent 90% of all rear collisions, averting 2.25 million rear end crashes”. Such systems often cause brake lights to flash. However, such alternative brake light operating systems suffer from numerous drawbacks and have not gained public acceptance. 
         [0006]    For example, many flashing brake light systems cause brake lights to flash excessively. As a result, the flashing lights become a distraction. After being exposed to such excessive flashing for some time, drivers become immune to the attention grabbing effect of a flashing light and its benefits are lost. 
         [0007]    In addition, many flashing brake light systems, whether the flash excessively or not, possess other features that compromise rather than improve safety. For example, many of such systems incorporate notoriously unreliable devices, such as relays and flashers having physical contacts, motors, cams, levers, and other mechanical devices. Such devices often have failure modes that prevent the brake lights from working at all. Consequently, vehicles having such conventional flashing brake light systems can be expected to experience a total failure of brake lights at least once during the useful life of the vehicle. While some incremental safety improvement may be achieved, the improvement is countered by an extremely dangerous total brake light failure. 
         [0008]    Furthermore, conventional flashing brake light systems tend to be complex devices. Complex devices are highly disadvantageous for several reasons. They tend to weigh more, be less reliable, and be more expensive than more simple devices. Often times, they are difficult to adapt to a vehicle and are impractical to install in vehicles having normal, non-flashing brake light systems, except at great expense. 
       SUMMARY OF THE INVENTION 
       [0009]    Accordingly, it is an advantage of the present invention that an improved flashing brake light system is provided. 
         [0010]    Another advantage of the present invention is that brake lights are flashed in a subtle manner to retain a high attention-grabbing effect and to refrain from significantly decreasing the attention-grabbing effects of non-flashing brake light systems. 
         [0011]    Another advantage of the present invention is that an inexpensive system is provided that is easily installed in existing vehicles having non-flashing brake light systems. 
         [0012]    The above and other advantages of the present invention are carried out in one form by an apparatus for indicating the braking status of a vehicle upon the activation of an input signal. The apparatus consists of three major components. The first component is a semiconductor voltage regulator circuit that provides the appropriate voltage to the micro controller upon activation of the input signal. The second component is an 8-bit Flash Micro controller that utilizes embedded micro code to determine how many times to toggle (cycle) the controller output. This output controls the On &amp; OFF states of a high side digital switch, which is third main component of the apparatus. 
         [0013]    In Short, upon activation of the brakes (the input signal), the voltage regulator powers up the micro controller which in turn toggles its output to turn the digital switch On &amp; Off for a predetermined number of cycles before holding the switch in the ON state until the activation of the brakes has been removed. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]    A more complete understanding of the present invention may be derived by referring to the detailed description and claims when considered in connection with the FIGURES, wherein like reference numbers refer to similar items throughout the FIGURES, and: 
           [0015]      FIG. 1  shows a rear view of a vehicle having a flashing brake light system constructed in accordance with the present invention; 
           [0016]      FIG. 2  shows a timing diagram which describes the operation of the present invention; 
           [0017]      FIG. 3  shows a schematic block diagram of components used in accordance with the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0018]      FIG. 1  shows a rear view of a vehicle  10  configured in accordance with the present invention. In particular, vehicle  10  includes a Center High-Mounted Stop Light (CHMSL)  12  along with left and right lower brake lights  14  and  16 , respectively. Lights  12 - 16  serve as indicators that announce when vehicle brakes are being applied. CHMSL  12  is located above lower lights  14 - 16 . In addition, CHMSL  12  is positioned in the center of vehicle  10  while lower brake lights  14 - 16  are positioned at left and right sides, respectively, of vehicle  10 . Lower lights  14 - 16  may also be associated physically and/or electrically in a conventional manner with turn indicators and with other filaments that serve as running lights. 
         [0019]      FIG. 2  shows a timing diagram that describes the operation of lights  12 - 16 . In particular, trace  18  describes an exemplary sequence associated with the application of brakes within vehicle  10 . As shown in trace  18 , vehicle brakes are applied at a time T 1  and remain applied until removed at a time T 5 . Of course, those skilled in the art will appreciate that the driver of vehicle  10  in response to driving conditions controls the application and removal of brakes. Thus, the sequence shown in trace  18  depicts only one of numerous possible braking scenarios. In addition, trace  18  indicates the application and removal of brakes from the driver&#39;s perspective. Those skilled in the art will appreciate that the actual application of braking forces to vehicle  10  may be pulsed or otherwise varied in accordance with automatic braking systems while brakes are applied as indicated in trace  18 . 
         [0020]    As shown in trace  20 , lower brake lights  14 - 16  are continuously activated in accordance with the application of vehicle brakes. Specifically, both of the lower lights  14 - 16  are activated at time T 1  and remain continuously activated until time T 8 . At time T 8  lights  14 - 16  are deactivated. Thus, whenever vehicle brakes are applied, lower lights  14 - 16  are activated. Whenever vehicle brakes are not applied, lower lights  14 - 16  are not activated turn indicators notwithstanding. 
         [0021]    Traces  22  illustrate the operation of CHMSL  12 . CHMSL  12  operates in a different manner than lower lights  14 - 16 . Whenever vehicle brakes are not applied, CHMSL  12  is deactivated in an identical manner to the lower brake lights  14 - 16 . However, when vehicle brakes are initially applied, as shown at time T 1 , CHMSL  12  begins operation in a flashing mode. In particular, CHMSL  12  is activated from time T 1  to a time T 2 , deactivated from time T 2  to a time T 3 , and so on for a predetermined duration, which trace  22  (a or b) indicates as expiring at a time T 4 . In the preferred embodiment of the present invention, this predetermined duration is in the range of 1.5-4 seconds, and more preferably in the range of 2-3 seconds. The rate of flashing is preferably in the range of three to four flashes per second. After time T 6 , CHMSL  12  remains continuously activated until vehicle brakes are removed at time T 5 . 
         [0022]    The duration of the flashing mode of operation (between times T 1  and T 4 ) accomplishes two goals. First, this duration is preferably relatively short when compared to an average application of brakes. By keeping this duration to less than four seconds, the quantity flashing rear lights experienced by drivers in traffic is held to a low level and excessive flashing is avoided. Consequently, drivers tend not to become immune to attention-grabbing effect of a flashing light, and no significant reduction occurs in the attention-grabbing effect of non-flashing brake lights used by other vehicles. In accordance with a second goal, this duration is preferably long enough so that a significant attention-grabbing effect will result than is achieved from non-flashing light. Hence, improved safety and a reduced likelihood of rear-end collisions may be expected from operating CHMSL  12  in its flashing mode. 
         [0023]    The rate of flashing is established so that a distinctive flashing signature results. Typical vehicle flashers cause turn signals and emergency lights to flash at a rate of around 0.75-3.0 times per second, with most flashing at a rate of around 1-2 times per second. Preferable, CHMSL  12  flashes at a rate faster than most turn signals and emergency lights to give a distinctive appearance and a heightened attention-grabbing effect. A heightened attention-grabbing effect results because the faster flashing rate achieves more flashes within the duration of the flashing mode of operation. 
         [0024]    While CHMSL  12  operates in its flashing mode, lower lights  14 - 16  are continuously activated. This feature of the present invention achieves two goals. First, it allows the flashing light operation of the present invention to have a more subtle effect than would result if all of lights  12 - 14  were flashing. The flashing of CHMSL  12  is balanced by the constancy of lower lights  14 - 16 . Thus, the flashing of CHMSL  12  enhances attention-grabbing effect, but the overall effect when combined with lower lights  14 - 16  avoids excessive flashing and excessive distraction of others. 
         [0025]    The second goal achieved by operating CHMSL  12  in a flashing mode while constantly activating lower lights  14 - 16  concerns failure modes. The present invention employs a circuit, discussed below in connection with  FIG. 3 , to cause CHMSL  12  to behave as indicated in trace  22   a  of  FIG. 2 . No circuit beyond those employed in normal, non-flashing brake light systems is used in connection with lower lights  14 - 16 . Accordingly, a failure in the flashing circuit, which is highly unlikely, will not affect operation of lower lights  14 - 16 . As a result, a total brake light failure is virtually impossible from operating the flashing circuit, and failure modes of the present invention do not negatively impact safety in a significant way. 
         [0026]    Of course, those skilled in the art will appreciate that brakes may be applied many times in a short period of time in situations of heavy traffic. On these occasions, the present invention employs a portion of the circuit that causes the CHMSL  12  to behave as indicated in trace  22   b  of  FIG. 2  when the length of time between T 5  and T 6  is less than a predetermined duration. In the preferred embodiment of the present invention, this predetermined duration is preferably in the range of 7-9 seconds. In this situation, trace  22   b  of  FIG. 2  indicates that subsequent application of the brakes causes the CHMSL  12  to activate in the same manner as lower lights  14 - 16 . 
         [0027]    The elimination of the flashing mode period between successive applications of brakes is desirable because it prevents a driver in heavy traffic situations from continuously flashing CHMSL  12 . The prevention of continuous flashing is desirable because it reduces the likelihood of excessive flashing. In the preferred embodiment of the present invention, the flashing mode period is eliminated if the time between T 5  and T 6  is less than 7-9 seconds. In other words, if the brakes are applied within 7-9 seconds of their removal, the flashing mode period is eliminated and CHMSL  12  activates and remains solid in the same manner as lower lights  14 - 16 . 
         [0028]      FIG. 3  shows a schematic block diagram of a circuit  24  that causes CHMSL  12  to operate as indicated in trace  22  (a or b) of  FIG. 2 . Circuit  24  is preferably inserted in series with conductors that drive CHMSL  12  in accordance with a normal non-flashing brake light system. 
         [0029]    As is conventional, in vehicle  10  (see  FIG. 1 ) a voltage source  26  applies a supply voltage to the first node of a brake switch  28 . Brake switch  28  is operated by brake pedal  30  of vehicle  10 . A second node of switch  28  couples to a supply node  32  of circuit  24  and to first nodes of left and right combining circuits  34  and  36 , respectively. Combining circuits  34  and  36  combine the brake signal with turn signal circuits (not shown) in some vehicles so that the left and right lower lights  14 - 16  can indicate both turning and braking for vehicle  10 . Second nodes of circuits  34  and  36  couple to the first nodes of left and right lower rear lights  14  and  16 , respectively. A ground terminal  38 , which is adapted to receive a common potential, couples to a ground node  40  of circuit  24  and to second nodes of lights  14 - 16 . 
         [0030]    With reference to circuit  24 , ground node  40  couples to a ground terminal  42  of circuit  24 . Supply node  32  couples to the V in  power terminal of a voltage regulator  44  through diode  43 , and to the V cc  power source terminal of High Side driver  66 . The ground terminals of voltage regulator  44  and High Side driver  66  couple to ground terminal  42 . The V cc  output of voltage regulator  44  connects to the V cc  power terminal of 8-bit Flash Micro controller  46 . Accordingly, devices  44  and  46  are energized when brakes are applied through the operation of brake pedal  30  and are de-energized when brakes are removed. Diode  43  prevents failure of devices  44  and  46  when circuit  24  is installed incorrectly by reversing the connections to terminals  32  and  40  causing a reverse voltage situation. 
         [0031]    One output (Out1) of the 8-bit Flash Micro controller  46  connects to the digital input terminal of the High Side driver  66  through input protection resistor  64  to control the activation of the High Side driver  66 . The output terminal of the High Side driver  66  couples to the output supply node  50  of circuit  24 . 
         [0032]    Another output (Out2) of the 8-bit Flash Micro controller  46  connects to the anode terminal of diode  70  through resistor  52 . The cathode terminal of diode  70  then connects to both the positive node of capacitor  54  and one node of resistor  48 . The negative node of capacitor  54  then couples to the ground terminal  42  of circuit  24 . The other node of resistor  48  couples to an input (In) of the 8-bit Flash Micro controller  46 . 
         [0033]    Output supply node  50  of circuit  24  couples to a first node of CHMSL  12 . Accordingly, circuit  24  includes an input node and output node that is designed to couple in series with the signal that drives a conventional non-flashing CHMSL  12 . 
         [0034]    The connection of supply node  32  and diode  43  cause regulator  44  to be energized to produce a digital voltage (V cc ) that provides power to Micro Controller  46 . In other words, when regulator  44  is energized through application of brakes, regulator  44  provides power to Micro Controller  46 . 
         [0035]    When power is applied to Micro Controller  46 , it activates and begins to run its predetermined micro code otherwise known as the internal program. The operation of this internal program is what determines the functionality of Out 1 and Out 2 of Micro Controller  46 . 
         [0036]    In the preferred embodiment of the present invention, the internal program first reads A/D In (analog input) to determine the voltage level of the positive node of capacitor  54 . If it is below a predetermined value, Micro Controller  46  begins to oscillate Out 1 for a predetermined number of cycles, which causes CHMSL  12  to flash. This is indicated by trace  22   a  in  FIG. 2 . If the voltage level read by Micro Controller  46  is NOT below the predetermined value, Micro Controller  46  activates Out 1 and keeps it constant until the power has been removed indicating that the application of the brakes have also been removed. This is indicated by trace  22   b  in  FIG. 2  from time T 6  on. 
         [0037]    The frequency and pulse width of the oscillating Out 1 as well as its duration is controlled through the internal program of Micro Controller  46 . In the preferred embodiment of the present invention, the duration of the oscillation is in the range of 1.5 to 4 seconds and more preferably in the range of 2 to 3 seconds. The duration of the oscillation is depicted in trace  22   a  of  FIG. 2  between times T 1  and T 4 . 
         [0038]    With the brakes still being applied through the duration of the predetermined number of oscillating cycles (T 4 ), Micro Controller  46  stops oscillating Out 1 and keeps it active causing CHMSL  12  to stop flashing and remain solid. This is indicated by trace  22   a . Following the completion of the oscillating cycle on Out 1, time T 4 , Micro Controller  46  activates Out 2. 
         [0039]    Upon activation of Out 2, the current through resistor  52  and diode  70  charges up capacitor  54  causing the voltage level on the positive node of capacitor  70  to increase. This voltage is fed back into the analog input of micro controller  46  through resistor  48  and is used to determine whether or not to initiate the oscillating cycle of Out 2 when 46 becomes active. 
         [0040]    When the application of the brakes has been removed and Micro Controller  44  de-activates, capacitor  54  begins discharging slowly through resistor  48  and the analog input of Micro Controller  46 . The rate at which capacitor  54  discharges is predetermined by the values of capacitor  54  and resistor  48 . Based on the discharge rate of capacitor  54  and the predetermined voltage level threshold seen on the analog input of Micro Controller  46 , a minimum time between the removal of the application of the brakes and the subsequent application of the brakes can be used to reduce excessive flashing of CHMSL  12 . In the preferred embodiment of the present invention, the predetermined minimum duration is in the range of 7 to 9 seconds. 
         [0041]    The prevention of a re-initialized flashing mode upon the quick reapplication of brakes is advantageous because it prevents excessive flashing in situations where brakes are being pumped, as occasionally occurs when vehicles are stopped in traffic. 
         [0042]    The reliability of circuit  24  is extremely high. The high reliability results from its simplicity and the use of semiconductor parts rather than mechanical devices. The only active component of circuit  24  that conducts large current is switch  66 . However, in the unlikely event that switch  66  fails, its most common failure mode is a short between the source and drain. Consequently, in all likelihood, should a failure occur in connection with circuit  24 , the failure will cause light  12  to operate as a conventional non-flashing brake light. The simplicity of circuit  24  also allows it to be manufactured and sold inexpensively. It can be easily installed in vehicles having non-flashing brake lights because its simplicity allows it to occupy an extremely small space and because it requires only the signals that a non-flashing brake light system provides to a CHMSL. 
         [0043]    In summary, the present invention provides an improved flashing brake light system. A vehicle&#39;s brake lights are flashed in a subtle manner. In particular, only the upper brake light is flashed. It is flashed only for a short period of time, after which it is constantly activated. The lower brake lights do not flash, and if brakes are quickly reapplied after being removed, no automatic flashing occurs. The flashing of brake lights produces an improved attention-grabbing effect. The subtle manner in which the present invention flashes brake lights reduces drivers&#39; immunity to the flashing effect and drivers&#39; immunity to non-flashing brake light systems. The present invention employs a circuit that is highly reliable due to its reliance upon semiconductor components rather than mechanical devices. Moreover, the present invention is configured so that in the unlikely event that a failure occurs, the failure will not produce a dangerous condition since, at a minimum, lower brake lights remain operational, and most probably even the CHMSL remains operational in a non-flashing mode. Further, the present invention relies upon an inexpensive circuit that is easily installed in existing vehicles having non-flashing brake light systems. 
         [0044]    The present invention has been described above with reference to a preferred embodiment. However, those skilled in the art will recognize that changes and modifications may be made in this preferred embodiment without departing from the scope of the present invention. For example, those skilled in the art may adapt components other than those mentioned herein to achieve the functions discussed herein. These and other changes and modifications that are obvious to those skilled in the art are intended to be included within the scope of the present invention.