Abstract:
Vehicle high intensity discharge lamps are available with three wire ballasts which emit a signal indicating proximate shutdown of the ballast and thus failure of the bulb energized by the ballast. The signal provides indication to a vehicle electrical controller which can be relayed to a remote facility which schedules replacement of the bulb.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Technical Field 
         [0002]    The present invention relates generally to commercial motor vehicles and more particularly to an automated system for indicating imminent failure of a high intensity discharge lamp. 
         [0003]    2. Description of the Problem 
         [0004]    Metal halide high intensity discharge (HID) lamps have made great inroads in automobile applications in recent years, but have not proven quite so popular in truck and heavy duty commercial vehicle applications. Traditionally no provision has been made for predicting lamp failure in vehicles because of the wide statistical variance in occurrences of failure. However, three wire HID ballasts generate a signal on one line which varies with ballast age and relative immanence of ballast shutdown. 
       SUMMARY OF THE INVENTION 
       [0005]    According to the invention there is provided a high intensity discharge lamp system for a vehicle incorporating ballasts with three wires. One of the wires carries a signal indicating proximate shutdown of the ballast and thus failure of the bulb energized by the ballast. The signal provides indication to a vehicle electrical controller which can be relayed to a remote facility which schedules replacement of the bulb. 
         [0006]    Additional effects, features and advantages will be apparent in the written description that follows. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]    The novel features believed characteristic of the invention are set forth in the appended claims. The invention itself however, as well as a preferred mode of use, further objects and advantages thereof, will best be understood by reference to the following detailed description of an illustrative embodiment when read in conjunction with the accompanying drawings, wherein: 
           [0008]      FIG. 1  is a perspective view of a commercial vehicle equipped with lighting systems with which the present invention is advantageously employed. 
           [0009]      FIG. 2  is a circuit schematic for a motor vehicle lighting system and related controls. 
           [0010]      FIG. 3  is a flow chart of a program executed on the electrical system controller for implementing the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0011]    Referring to the drawings and in particular referring to  FIG. 1  a motor vehicle internal electrical communication backbone  112 , typically an SAE J1939 bus, is electrically engaged to provide a communication path between various electronic devices and controllers as part of a vehicle on-board electrical system VOS  101 . The vehicle  111  has an engine  113  engaged to a transmission  114 . The transmission is engaged to a drive train  118  for driving the wheels  126 . The engine  113  is controlled and monitored by an engine electronic control module (ECM)  140  that is electrically engaged to the communication backbone  112 . The engine ECM  140  may receive and communicate status of the engine and auxiliary equipment including but not limited to engine performance, engine coolant parameters, engine oil system variables, air intake quality, and other monitored variables. The transmission  114 , if automatic or semi-automatic, may be controlled and monitored by a transmission electronic control module  150  that is electrically engaged to the communication backbone  112 . The vehicle  111  has an onboard computer (OBC)  30  which is connected to the communications backbone  112  and which acts as the lead message arbitrator or lead controller for the vehicle  111 . 
         [0012]    The OBC  30  collects input data and sends requests from and to a communication system for relay to a remote facility  190  which collects and analyses fleet data for scheduling of maintenance and other functions, generally termed in the art “telematics”. The communication system may take a number of forms, such as a satellite access antenna  115  that may be included in a sun visor  128  or a cellular phone antenna  116  with a phone transceiver  160 . The communication system may additionally be any vehicle to land method and equipment. 
         [0013]    On-board computer system  30  receives data inputs from a number of sources, while some vehicle systems may be under its direct control. In the example vehicle of the illustration the wheels  126  include anti-lock (ABS) brakes. The anti-lock brakes may be controlled by an anti-lock brake electronic control module (ABS ECM)  117 . The ABS ECM  117  is electrically engaged to the communication backbone  112  and like the other ECMs provides status of the system to the OBC  30 . A tire pressure sensor  170  is mounted on each wheel. The tire pressure sensor  170  measures each tires pressure and sends a radio signal to a receiver  171  that is electrically engaged to the communication backbone  112 . Tire pressure is an indicator of tire wear, the need for a pressure adjustment, or vehicle loading depending on the pressure distribution across the tires and a specific vehicle history maintained by either the OBC  130  or the remote facility  190 . An electronic odometer may also be tied to the communication backbone  112  to provide input of miles traveled to the OBC  30 . A navigation system such as those based on GPS and Dead Reckoning may be installed and engaged to the communication backbone  112  with an appropriate antenna  136  and transceiver  137  for providing input of the vehicle  111 &#39;s geographic position. The above mentioned ECMs and sensors are just examples of specific vehicle inputs providing a specific vehicle status. 
         [0014]    Other sensors on the vehicle  111  provide the VOS  101  with indications of external conditions that may be valuable to other vehicles communicating with remote facility  190 . Some examples include a road ice sensor  123 . The road ice sensor  123  can be a simple as an infrared transceiver directed downwards to a road surface  133 . Road surfaces  133  with ice, snow, black ice, or water, or dry will give different infrared reflective signals back to the road ice transceiver  123 . The road ice transceiver  123  is also electrically engaged to the communication backbone  112 . 
         [0015]    The lead message arbitrator or lead electronic controller may be programmed for communication with the off board communication network through the communication means engaged to the internal communication backbone  112 . The lead electronic controller is also programmed for transmitting an indication of an abnormal condition in one of the monitored vehicle components to the off board communication network  100  through the vehicle internal communication backbone  112  and the communication means. The lead electronic controller may be programmed for receiving instructions for action to address the abnormal condition from the off board network  100  through the communication means. The lead electronic controller may also be programmed for notifying a driver of the vehicle  111  of driver actions of the received instructions from the off board network  100 . 
         [0016]    Of present interest are the vehicle&#39;s headlamps  70 , which are under the direct control of the OBC  30  through ballasts  71 . Vehicle headlamps  70  are metal halide type high intensity discharge (HID) lamps, which are energized by the ballasts  71 . The ballasts  71  respond to control signals applied by the OBC  30 . A representative example of such a ballast is described in U.S. Pat. No. 6,975,077. Metal halide lamps are a type of arc discharge lamp with two or three ionizing media. In a typical motor vehicle application the lamp will contain trace amounts of xenon, mercury, and the metal halides of choice, for example, sodium iodide. When the lamp is cold a high voltage discharge is used which ionizes the xenon, thereby increasing the temperature of the lamp enough to vaporize the mercury, which in turn is ionized raising the temperature still further until the metal halide is vaporized and the lamp reaches a steady operating state. Lamp  70  output is controlled in various ways. In the &#39;077 patent the frequency of the signal used to control the operating frequency of a DC to AC inverter is varied to provide the desired output signals to the lamp. In order to do this ballast control is responsive to a number of signals, most particularly current drawn by the lamp  70 . In steady state operation this should be a constant for a particular beam setting. Over time however, with progressive degradation of the lamp, the current drawn will began to fall. The rate of decline, or a specific trigger level, may be used as an indicator of impending failure. The trigger level (or rate of change) may be tailored to a chosen mean time to failure level. Ballasts are typically designed to shut down when current levels reach a certain point and thus the current level is indicative of the number of hours until such occurrence. 
         [0017]      FIG. 2  illustrates lighting pin connections for a OBC  30 , which here is illustrated as an electrical system controller. OBC  30  in conventional designs directly energizes most vehicle exterior lamps (and the horn  36 ) by use of a series of Field Effect Transistor (FET) switches  51 ,  52 ,  53 ,  54 ,  55 ,  56 ,  57 ,  58 . For the sake of simplicity only parking marker lights  37  are shown. Fewer than the number of FETs required are illustrated because the specific circuit element is simply repeated up to the number of lamp circuits for which support is required. Switches  53  and  54  have been taken over to provide off/on control signals to ballast unit  71 , which in turn includes a ballast controller  72  and the ballast proper  73 . ESC  30  is in turn connected to an electrical gauge controller (EGC)  40  over the communications backbone  112  (which is illustrated as a twisted pair cable  60  connecting controller area network (CAN) controllers  43 ,  143 ). EGC  40  is connected in turn to a set of micro-switches  45  by which a vehicle operator turns lights on and off, as detected by micro-controller  41 . OBC  30  is a programmable body systems computer used to control many vehicle electrical system functions, most of which are not shown. In the past, many of these functions were controlled by switches, relays and other independently wired and powered devices. OBC  30  is based on a microprocessor  31  which executes programs and which controls switching of the plurality of power FETs  52 ,  55 ,  56 ,  57  and  58  used to actuate most vehicle exterior lights. The telematics link  200  is implemented over the communication system under the control of OBC  30  as already described. 
         [0018]    To implement the present invention ballast control  72 , which provides a variable frequency control signal to ballast electronics  73  and which monitors output frequency, current and voltage, supplies the current measurement to microprocessor  31  which is programmed to determine likely time to failure based on the current level. The diagram shows both the low beam and high beam control signals being applied to ballast controller  72 , which implies two steady state levels of current may be reported. The particulars of implementing high and low beams however is not considered pertinent to the invention and in fact differing headlamps may be used, though doing so would be unusual. 
         [0019]      FIG. 3  is a high level flow chart of the comparison tests which may be implemented on microprocessor  31  and remote telematics facility  190 . Upon a request for illumination from the headlamps  70 , the program begins measuring current (step  300 ) and comparing the measurements until the current value settles to a steady state value (step  304 ). A wait step  302  may be part of this operation. Once a steady state is achieved the current may again be measured (step  306 ) or the last measurement taken from the steady state test may be used to determine if the measured current (step  308 ) is less than a trigger level indicating approaching failure of the lamp. Until the trigger level is reached the test cycles. Once the trigger level is reached the remote facility  190  is signaled (step  310 ) along with a report of the vehicle&#39;s position. The remote facility  312  checks position and itinerary and selects a repair facility along the vehicle&#39;s scheduled route for the repair (step  312 ). In this way availability of the proper lamp may be assured and downtime minimized. The operator is advised (step  314 ) and the operation is illustrated and concluding. 
         [0020]    The invention provides for indicating approaching failure of an HID vehicle headlamp and for providing scheduling of repair before failure occurs. 
         [0021]    While the invention is shown in only one of its forms, it is not thus limited but is susceptible to various changes and modifications without departing from the spirit and scope of the invention.