Abstract:
An ambiance lighting system for a vehicular passenger compartment has a variable color light output which is automatically responsive to temperature changes. First and second light sources of different colors (e.g., blue and red) are positioned immediately behind the air discharge vents and are selectively energized by a control circuit so that the first light source radiates light through the vent when the temperature falls below a predetermined value and the second light sources energizes the second color of light when the air temperature rises above a predetermined value. Sensors are used to detect the temperature of air, preferably in the ducting plenum. Various control strategies can be deployed to achieve aesthetically interesting light presentations which enhance ambiance within the passenger compartment.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to an ambiance lighting system for a vehicular passenger compartment, and more particularly toward a lighting system having a variable color light output responsive to temperature changes within the passenger compartment. 
     2. Related Art 
     In vehicular applications, and particularly those pertaining to passenger automobiles, every effort is made to enhance the comfort, convenience and ambiance within the passenger compartment. New vehicles are more likely to attract buyer attention with enhanced features and a pleasing ambiance. One technique used to affect ambiance within the passenger compartment involves techniques which affect lighting. A well-executed lighting system can have a positive aesthetic impact on people within the passenger compartment. 
     Accordingly, any device or technique which is aesthetically pleasing and affects the lighting ambiance within a passenger compartment will be readily accepted within the industry. 
     SUMMARY OF THE INVENTION AND ADVANTAGES 
     The subject invention comprises an ambiance lighting system for a vehicular passenger compartment having a variable color light output responsive to temperature changes within the passenger compartment. The system comprises an air discharge vent within the passenger compartment. A detector senses the temperature of air delivered to the vent. A lighting device projects light within the passenger compartment. And a control circuit, which is responsive to the detector, energizes the lighting device to project a first color of light when the air temperature is below a predetermined value and to project a second color of light when the air is above a predetermined value. The first and second colors of projected light are different and the ambiance within the passenger compartment is enhanced by the selective changing of colors in response to the sensed temperature of air delivered to the vent. 
     According to another aspect of the invention, an ambiance lighting system for a vehicular passenger compartment has a variable color light output responsive to temperature changes within the passenger compartment. The system comprises a plenum for conducting air, an air discharge vent operatively connected to the plenum for directing air from the plenum into the passenger compartment, a detector for sensing the temperature of air in the plenum, a lighting device disposed within the plenum adjacent the vent for projecting light through the vent into the passenger compartment, and a control circuit responsive to the detector for energizing the lighting device to project a first color of light when the air temperature is below a predetermined value and for energizing the lighting device to project a second color of light when the air is above a predetermined value. Again, the first and second colors are different and the ambiance within the passenger compartment is enhanced by the automatic changing of colors in response to the sensed temperature of air delivered to the vent. 
     According to yet another aspect of the invention, a method for ambiance lighting a passenger compartment in a motor vehicle in response to temperature changes within the passenger compartment is provided. The method comprises the steps of discharging air through a vent within the passenger compartment, sensing the temperature of the air, and projecting a first color of light within the passenger compartment when the sensed air temperature is below a predetermined value and projecting a second color of light within the passenger compartment when the sensed air temperature rises above a predetermined value. As before, the first and second colors are different and the ambiance within the passenger compartment is enhanced by the automatic changing of colors in response to the sensed temperature of air within the passenger compartment. 
     Among these various aspects of the invention, a unique and aesthetically pleasing presentation of light within the passenger compartment is manifested. The first and second colors of projected light can be selected amongst any in the visible spectrum. For example, the second color may be in the red color family and the first color may be in the blue color family. In this manner, an occupant would see the color red when the temperature of the air is high, and see the color blue when the air temperature is low. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Other advantages of the present invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein: 
         FIG. 1  is an exemplary view of an interior passenger compartment in a motor vehicle in which numerous air vents are provided; 
         FIG. 2  is a schematic illustrating an exemplary heating, ventilation, and air conditioning system within a motor vehicle through which air traveling a plenum network are delivered to various discharge vents within a passenger compartment; and 
         FIG. 3  is a simplified circuit diagram illustrating an exemplary embodiment of the subject control circuit. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to the Figures, wherein like numerals indicate like or corresponding parts throughout several views, the passenger compartment in all exemplary motor vehicle is generally shown at  10 . The passenger compartment  10  includes a dashboard, generally indicated at  12 , into which a typical climate control system, generally indicated at  14 , may be mounted. Although the climate control system  14  will vary from one vehicle make and model to the next, there is generally provided a mode selector  16  from which the type of air treatment and discharge location can be controlled, a fan speed control selector  18 , and one or more temperature control selectors  20 . In the example illustrated in  FIG. 1 , a second temperature control selector  22  may be provided for independently controlling the temperature of air discharged from the right, or passenger, side of the vehicle; whereas the temperature control selector  20  would be used to control air discharged from the driver&#39;s side of the vehicle. 
     As is typical with most motor vehicles, the heating ventilation and air conditioning (HVAC) system includes multiple air discharge vents within the passenger compartment. In the example of  FIG. 1 , the air discharge vents include a front defroster vent  24 , an array of dashboard mounted vents  26 , and a floor vent  28 . In  FIG. 2 , these various vents are shown schematically together with a rear vent  30  which discharges toward the rear of the passenger compartment  10 . These various vents communicate with a common plenum, generally indicated at  32 , which is part of the overall HVAC air handling system. Other components in the HVAC system may include a blower  34 , an evaporator  36 , a heater core  38 , a fresh air inlet  40 , a re-circulated air valve  42  and an A/C bypass valve  44 . Of course, these various components can be found in other arrangements and configurations, and are presented in  FIG. 2  merely for illustrative purposes. 
     A detector, shown here in the form of independent first  46  and second  48  sensors, is provided for sensing the temperature of air delivered to each of the vents  24 - 30 . The first sensor  46  is configured to determine when the air temperature falls below a predetermined value, and therefore it may be optimally located near the evaporator  36 . Conversely, the second sensor is configured to sense when the temperature of air rises above a predetermined value, such that its location may be optimally positioned on the down stream side of the heater core  38 . While the sensors  46 ,  48  are shown and described as being located within the plenum  32 , they can alternatively be located outside of the air handling system in any other convenient or advantageous location. 
     A lighting device projects light within the passenger compartment in such a manner so as to change the color of emitted light in response to the sensed temperature of air. The lighting device can be located anywhere within the passenger compartment  10 , or even outside the passenger compartment  10  provided its light is visible to occupants within the passenger compartment  10 . The lighting device may comprise a single light source capable of emitting two or more colors of light. Such lighting devices can be of any type of light producing device, including incandescent, fluorescent, light emitting diode, or otherwise. Those of the LED type are sometimes referred to bi-color or tri-color LED&#39;s. In the preferred embodiment, however, the lighting device includes a first mono-color light source  50  and a separate, second mono-color light source  52 . A control circuit, generally shown at  54  in  FIG. 3 , is responsive to the first  46  and second  48  sensors for automatically energizing the light sources  50 ,  52  to project a first color of light from the first light source  50  when the air temperature is below a predetermined value and for energizing the second light source  52  to project a second color of light when the air temperature is above a predetermined value. The first and second colors of light are different from one another and have the affect of enhancing the ambiance and visual aesthetics within the passenger compartment. The first light source  50  can be any color at all, however, since it is visible only when the air temperature falls below a predetermine value, its color might be selected from those from within the families of “cool” colors having lower wave lengths. For example, the first light color may have a predominant wave length below 5,500 angstroms. The second color may have a predominant wave length above 5,500 angstroms and be within the family of colors perceived as “warm.” Although the first  50  and second  52  light sources can be of any type of light producing device, including incandescent, fluorescent, or otherwise, these devices may comprise light emitting diodes (LEDs) with the first light source  50  having a predominantly blue color and the second light source  52  having a predominantly red color. Again, these color choices are subjective and can be varied to achieve any desired lighting effect. 
     Referring again to  FIG. 2 , the first  50  and second  52  light sources are shown disposed within the plenum  32  immediately up stream of each of the vents  24 ,  26 ,  28 , and  30 . In this configuration, occupants within the passenger compartment are shielded from a direct view of the light sources  50 ,  52 , however, their projected light fills the plenum and radiates from each of the vents  24 - 30  to create a particularly interesting so-called “back light,” effect. Instead of individual LEDs for each of the light sources, a single light source can be used for each of the first and second colors, with optical wave guides routed to pipe the light to the various locations. Again, this indirect back lighting technique, while a preferred application of the invention, is by no means the only implementation option. Alternatives include effects to illuminate the vents per se and/or their escutcheon features. The selector knobs  16 - 22  and/or features associated with the selectors can be illuminated by the control circuit  54 . Or, illuminated features within the passenger compartment  10  wholly segregated from the HVAC and climate control system are within the scope of the invention. 
     In  FIG. 3 , the control circuit  54  is shown with the first and second light sources  50 ,  52  comprising light emitting diodes and the first  46  and second  48  sensors comprising thermistors. The sensors  46 ,  48  may be of a functional type other than a thermistor. A power source  56  draws voltage from the vehicular electrical system. In most vehicles in current use, the power source  56  comprises  12  volts, however, other system voltages and polarities may be used with only minimal modifications required. 
     Electricity from the power source  56  is directed to the first  46  and second  48  sensors, respectively, which, being of the thermistor type, have a high negative temperature co-efficient of resistance so that their resistance decreases as the temperature increases. Adjustable resistors  58 ,  60  are useful to tune the respective sensors  46 ,  48  so that an appropriate voltage and/or current is supplied to the respective positive legs of differential amplifiers  62 ,  64 . The negative legs of the first  62  and second  64  differential amplifiers are connected to line  65  which extends between electrical ground  66  and the power source  56  through resistors  68 . 
     When the difference between the voltages applied between the two input legs to the second differential amplifier  64  are sufficient, the second light source  52  is energized and projects light (e.g., red) within the passenger compartment  10 . This happens automatically when the temperature rises above a predetermined value, thus lowering the resistivity within the second sensor  48  and allowing a high enough voltage to enter the positive leg of the second differential amplifier  64 . 
     The wiring configuration for the first light source  50  is similar to that of the second light source  52 . However, in order to reverse its functionality a PNP transistor  70  is wired between the first differential amplifier  62  and the first light source  50 , with a lead to the power source  56 . A reverse logic is achieved. In other words, the transistor  70  functions as a “digital not” and accomplishes the reversal of the methodology exhibited in the circuitry leading to the second light source  52 . Thus, as the temperature rises above the predetermined value and the first sensor  46  allows increase voltage and current to enter the first differential amplifier  62 , the transistor  70  operates as an “open” switch. However, when the temperature falls below the predetermined value so that the first sensor  46  curtails the flow of current to the first differential amplifier  62 , the transistor  70  acts as a “closed” switch allowing the electricity from the power source  56  to energize the first light source  50 . 
     Depending upon how each of the sensors  46 ,  48  are tuned by the respective adjustable resistors  58 ,  60 , the predetermined temperature value can be different for each of the first  50  and second  52  light sources. If the predetermined temperature values are exactly the same, the first light source  50  will be de-energized the moment the second light source  52  is energized. However, if different temperature values are used to tune the sensors  46 ,  48 , various scenarios can result, with a mid-temperature range over which both light sources  50 ,  52  are energized or else neither light source  50 ,  52  is energized. Additionally, the control circuit  54  can be wired into the climate control system  14  so that the power source  56  is only active when both the fan control selector  18  and the mode selector  16  are in conditions calling for active operation of the HVAC system. In this latter scenario, the first  50  and second  52  light sources would be incapable of operating if either the mode selector  16  is in an inoperative position or if the fan control selector  18  is in the off position. 
     In a variation of the embodiments described, a separate control circuit  54  can be used for the passenger side of the vehicle if separate temperature controls  20 ,  22  are provided for the driver and passenger sides of the vehicle. In this condition, the passenger may choose a relatively hot setting in which case all of the vents associated with the right side of the passenger compartment  10  will be illuminated by the second light source  52 , and the driver may choose a relatively low temperature setting in which case all of the vents associated with the left side of the passenger compartment  10  are illuminated by the first light source  50 . Thus, an entire secondary lighting device is independently operatively controlled by the control circuit  54 , or by a parallel control circuit. According to another variation of the invention, the respective vents,  24 - 30  can be selectively and independently illuminated by their associated light sources  50 ,  52  based upon the condition of the mode selector  16 . Thus, if mode selector  16  is set to floor vent condition only, then light sources  50 ,  52  associated directly with the floor vent  28  will be energized yet all other light sources associated with the defroster  24  and dash  26  vents will be dormant, and so forth. 
     The invention has been described in an illustrative manner, and it is to be understood that the terminology which has been used is intended to be in the nature of words of description rather than of limitation. Obviously, many modifications and variations of the present invention are possible in light of the above teachings. It is, therefore, to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described. The invention is defined by the claims.