Abstract:
A vehicle lighting control system provides tailored implementation of daytime running light operation. Daytime running light operation is triggered in response to selected vehicle conditions, typically including, ignition key position, release of the park brake and selection of the off state for the vehicle headlamps. The occurrence of additional conditions results in cancellation or suspension of operation. Suspension follows from setting of the parking brake, typically without activation of school bus warning lights.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Technical Field  
         [0002]     The invention relates to vehicle lighting control and more particularly to a system allowing selective, and automatic, operation of a vehicle&#39;s exterior lamps in daytime running mode.  
         [0003]     2. Description of the Problem  
         [0004]     Selected exterior vehicle lights, particularly headlamps, can be operated in the daytime to increase the visibility of the vehicle to others. Such operation is referred to as daytime running light (DRL) operation. DRL operation of vehicle lamps may involve illumination of the headlamps at reduced power to reduce the load on the vehicle electrical system and extend the life of the headlamp bulbs as compared with full power operation. However, whether the lights are operated at reduced power settings or not, DRL operation of the lamps represents a non-negligible electrical load which increases fuel usage and reduces lamp service life. It would be desirable to limit DRL operation to periods when actually required.  
         [0005]     A simplistic approach to the issue might conclude that DRL operation can be limited to when the vehicle is in motion. However, state and provincial law may control DRL operation for school busses, particularly when embarking and disembarking pupils. Such requirements may differ depending upon key ignition status, parking brake status and whether pupil warning lights are activated or not. For example, it is clear that a vehicle should not be in motion when the parking brake is set, however, state requirements may stipulate that the daytime running light operation is required at any time that the pupil warning lights are operating and may require parking brakes be set when children are present.  
       SUMMARY OF THE INVENTION  
       [0006]     The invention provides a lighting control system implementing daytime running light operation, tailored to meet jurisdictional requirements. Daytime running light operation is triggered in response to selected vehicle conditions, typically including at a minimum, ignition key position, release of the park brake, engine operational status and status of pupil warning lights. In a school bus the headlamps are operated in a daytime running light mode unless such operation is canceled or suspended. Cancellation occurs in response to selected conditions being met or no longer holding true.  
         [0007]     Additional effects, features and advantages will be apparent in the written description that follows. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]     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:  
         [0009]      FIG. 1  is a perspective view of a school bus with which the system for control of daytime running lights is advantageously used.  
         [0010]      FIG. 2  is a mixed circuit schematic and block diagram of a electrical control system for a vehicle including lighting control.  
         [0011]      FIG. 3  is a truth table implemented through programming of an electrical system controller or body computer for the vehicle of  FIG. 1 . 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0012]     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 headlamps  14 . Conventionally, daytime running light operation of vehicle exterior lamps includes illuminating the vehicle headlamps  14 , sometimes at a reduced level, to limit the load on the vehicle electrical system and extend lamp service life.  
         [0013]     Referring now to  FIG. 2 , a mixed circuit block diagram schematic illustrates selected vehicle systems, including vehicle exterior lights. The illustrated vehicle controllers include an engine controller  18 , an electrical gauge controller  40  and an electrical system controller (ESC)  30 . Engine controller  18 , electrical gauge controller (EGC)  40  and ESC  30  exchange data over an SAE J1939 datalink  60 , which is a controller area network (CAN) implemented by CAN interfaces  143 ,  43  and  243 , associated with ESC  30 , EGC  40  and the engine controller  18 , respectively. The controllers implement control functions over selected vehicle systems. Engine controller  18  controls the operation of engine  20 , determining the amount of fuel to inject for example, and monitoring and reporting operating variables. A microprocessor  22  is installed in the controller to implement its operational and communication requirements. Electrical gauge controller  40  is generally used to control display gauges and to monitor operator switches, including headlight microswitches  45 . Electrical gauge controller  40  microprocessor  41  is connected to receive and interpret inputs for broadcast over datalink  60 . ESC  30  has more general responsibilities, including controlling the operation of all vehicle exterior lamps, which control is implemented by suitable programming of microprocessor  31 . The ignition input  138  is conventionally directly connected to the ESC  30 .  
         [0014]     DRL operation is implemented by electrical system controller  30  depending upon the status of various vehicle systems and switches. DRL operation here is taken to mean operation of the lowbeams of vehicle headlamps  61 ,  48 , potentially at reduced output levels, by control of the switching state of lowbeam FET  53 . Low Beam FET  53  is one of a plurality of power field effect power (FET) switching transistors  51 ,  52 ,  53 ,  54 ,  55 ,  56 ,  57  and  58 , most of which are employed to turn vehicle exterior lights on and off. In particular FET  51  is connected to drive a warning arm positioning motor coil  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  and FET  57  is connected to drive the brake lamps  45  and FET  58  is connected to illuminate the pupil boarding warning lamps  16 .  
         [0015]     Microprocessor  31  is conventionally programmed as a microcontroller. 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 , DRL operation can be closely tied to operating conditions indicated by the inputs. The particular inputs of interest here are an engine running message generated by the engine controller  20 , the status of a warning light switch determined by the ESC  30  from switches  38  or steering wheel switches  24 , ignition status from ignition  138 , and park brake  140  status. The status of park brake  140  and ignition  138  are applied directly to the ESC  30 .  
         [0016]     As an initial matter, DRL operation is not called for if headlamps are turned on in response to closure of headlight microswitches  45 . Otherwise, DRL operation begins with meeting selected conditions. The conditions to be monitored are: (1) ignition ( 26  or  138 ) status; (2) warning light active status; (3) engine running status; and (4) park brake status.  
         [0017]     The present invention, in a preferred embodiment, allows modifying DRL operation, such as to disable DRL operation of the headlamps when the vehicle is not in motion, unless the vehicle is used as a school bus and is embarking or disembarking pupils. During passenger loading and unloading a school bus operator will engage warning lights  16  and extend a signal arm. Accordingly, microprocessor  31  may be programmed to discontinue DRL operation in response to setting the parking brake unless warning lights have been turned on. Warning lights may be turned on using a switch in a switch pack  38  connected to the microprocessor by an SAE J1708 datalink (or equivalent), or, by use of steering wheel switches  24  where such switches have been modified to implement warning functions.  
         [0018]     Referring now to  FIG. 3 , a truth table  300  illustrates operation of the programming of electrical system controller  30 . The table is applied assuming that the headlamps  61 ,  48  have not been turned on. If the warning lights are on, DRL status is high, regardless of the status of the ignition, engine running variable and park brake position. If the engine is off and the warning lights are off then DRL status is low regardless of the status of the ignition or park brake. If the engine is running, ignition input is true and the park brake applied then the DRL status is low. Finally, if the park brake is released but the engine remains running, the ignition input remains true and the warning lights or off then DRL status is high.  
         [0019]     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.