Abstract:
A vehicle lighting control system for a school bus allows automatic activation of hazard mode operation of the vehicle&#39;s signaling lights in response to activation of other warning lights. Deactivation follows upon the vehicle exceeding a predetermined maximum speed.

Description:
BACKGROUND OF THE INVENTION 
   1. Technical Field 
   The invention relates to vehicle lighting control and more particularly to a lighting control system providing automatic activation and cancellation of hazard light operation. 
   2. Description of the Problem 
   Motorists are alerted to the embarkation and disembarkation of pupils from school busses by the use of dedicated warning lights. The activation of the hazard avoidance feature of the vehicle&#39;s turn signal lights can be used to supplement the pupil warning lights. Separate switches have been provided for the warning lights and for hazard operation of the turn signal lights. This arrangement necessitates action by the driver to engage hazard mode operation of the lights and a separate action to cancel hazard mode operation after boarding is completed. 
   SUMMARY OF THE INVENTION 
   The invention provides a lighting control system implementing automatic hazard operation of the turn signal lights in conjunction with operation of the pupil warning lights on a school bus. Hazard operation of the turn signal lights is triggered by activation of the pupil warning lights. Hazard operation is canceled by subsequent movement of the bus. 
   Additional effects, features and advantages will be apparent in the written description that follows. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     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: 
       FIG. 1  is a perspective view of a school bus with which the system for control of hazard and pupil warning lights is advantageously used. 
       FIG. 2  is a mixed circuit schematic and block diagram of a electrical control system for a vehicle including lighting control. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Referring now to the figures and in particular to  FIG. 1 , a vehicle  10  is illustrated. Vehicle  10  includes a school bus body  12  installed on a chassis. School bus body  12  is equipped with conventional exterior lamps including at least pupil boarding warning lights  16  and turn signal lights  43  and  64  (front signals only shown). 
   Referring now to  FIG. 2 , a mixed circuit, block diagram schematic illustrates selected features of a vehicle electrical control system, including controllers  18 ,  40  for the engine and gauge cluster, as well as a more general electrical system controller (ESC)  30 , a type of body computer. Each controller includes a programmed microprocessor, including microprocessor  22  for engine controller  18 , microprocessor  41  for electrical gauge controller (EGC)  40  and microprocessor  31  for ESC  30 . The engine controller  18  provides control over the operation of an engine  20 , monitors engine operating variables and may be used to monitor drive shaft speed using a drive shaft tachometer  26  coupled to the drive shaft (not shown) at the transmission (not shown). The drive shaft tachometer  26  signal is used by the engine controller  18  to determine vehicle speed. Alternatively, vehicle speed may be determined by the ESC  30  where the drive shaft tachometer signal is passed by the engine controller  18  to the ESC. Other controllers may supply the vehicle speed signal as well. An example is an antilock brake controller (not shown) which can be used to determine vehicle speed from the average wheel rotational speeds. Electrical system controller  30  provides a number of general services, but in common vehicle control architectures, is charged with lighting system control. 
   The controllers communicate among one another over a bus or controller area network (CAN) conforming to the SEA J1939 standard. Each controller is provided with a controller area network (CAN) interface, including CAN interface  243  for the engine controller  18 , CAN interface  43  for the electrical gauge controller (EGC)  40  and CAN interface  143  for the ESC  30 . The microprocessors  22 ,  41 ,  31  are connected to the CAN interfaces  243 ,  43 ,  143 , respectively, to implement communication over datalink  60 . While much data is exchanged over the CAN datalink  60 , such as head light microswitch  45  status for EGC  40 , the particular data of interest here include a vehicle speed signal. The usual source for the vehicle speed signal is microprocessor  22  in the engine controller  18 . 
   Datalink  60  is not the sole source of data received by ESC  30 . ESC  30  is also connected to receive several switch inputs. One source of switch inputs is a switch pack  38 , which is connected to ESC  30  over an SAE J1708 serial link through a J1708 interface  39 . ESC  30  microprocessor  31  may also be connected to receive directly other switch inputs, such as those from an array of momentary steering wheel switches  24 , a park brake position switch  140  and an ignition switch  138 . The input activating pupil warning lights  16  may come from either switch pack  38  or from the steering wheel switch array  24 . 
   ESC  30  microprocessor  31  controls a plurality of power switching field effect transistors (FETs)  51 ,  52 ,  53 ,  54 ,  55 ,  56 ,  57  and  58 . Among these FETs are a low beam FET  53  which is employed to turn the low beam of the headlamps  48 ,  61  on and off. FET  51  is connected to drive a warning arm positioning motor  36 , park light FET  52  is connected to drive assorted marker, park and tail lights  37 ,  38 , FET  55  is connected to drive the right turn signal lamps  43 , FET  56  is connected to drive left turn signal lamps  64 , FET  57  is connected to drive the brake lamps  45  and FET  58  is connected to illuminate the pupil boarding warning lamps  16 . The hazard lights comprise the left and right turn signal lights  43 ,  64 , operated synchronously, by concurrent switching of FETs  53 ,  56 . Hazard mode may be implemented using different sets of lights than the turn signals, for example, the rear brake lights may be used instead. 
   Microprocessor  31  is conventionally programmed as a microcontroller and the programming directs responses to various status indications and switch inputs, whether directly received, or decoded from messages broadcast over the controller area network, or received over other datalinks, such as a SAE J1708 serial datalink through datalink interface  39 . Because of the availability of status inputs from various sources to microprocessor  31 , hazard operation of the turn signals can be closely tied to operating conditions inferred from the inputs. The particular inputs of interest here are vehicle speed and the status of the switch used to control pupil boarding warning lights  16 . The invention, in its preferred embodiment, provides programming the microprocessor  31  to activate operation of the turn signal lights  43 ,  64  in hazard mode in response to activation of the pupil warning lights  16 . Operation of the turn signal lights  43 ,  64  in hazard mode is cancelled in response to vehicle speed later exceeding a programmed maximum. This maximum speed is user selectable. Alternatively, the hazard mode could be activated in response to other conditions being met, such as setting the park brake  140  concurrently with or following activation of the pupil warning lights  16 . Operation of the turn signal lights  43 ,  64  in hazard mode is also discontinued in response to deactivation of warning lights  16 , detected by the microprocessor  31 . 
   The present invention, in a preferred embodiment, simplifies school bus operation by automating activation and deactivation of the hazard feature for operation of the vehicle&#39;s exterior lights. 
   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.