Abstract:
An engine compartment fire suppression system for an HVAC system of a vehicle monitors conditions including, but not limited to, a collision sensor, an air conditioning system pressure sensor, engine coolant temperature, exhaust gas temperature, or an engine load calculation. The fire suppression system discharges a fire suppression composition when a controller receives a specified combination of the monitored conditions.

Description:
TECHNICAL FIELD 
       [0001]    This disclosure relates to a system that discharges a fire suppression material in the engine compartment of a vehicle in a collision. 
       BACKGROUND 
       [0002]    Vehicle air conditioning systems circulate a refrigerant through air conditioning lines, a compressor, an evaporator and other components of the air conditioning system. Prior art systems circulated Freon®, non-flamable refrigerants, R134a, CO 2 , or other types of refrigerants. 
         [0003]    Global warming potential (GWP) refrigerants are proposed for use in vehicle HVAC systems that are flammable if exposed to an ignition source with the concentration of the refrigerant within the flammability limits of the GWP refrigerant. The pressure within the HVAC system can expel refrigerant in the engine compartment if the system is compromised in a collision. 
         [0004]    This disclosure is directed to the above problems and other problems as summarized below. 
       SUMMARY 
       [0005]    According to one aspect of this disclosure, a fire suppression system is provided for an HVAC system for a vehicle. The fire suppression system comprises a refrigerant circulation loop that circulates a flammable refrigerant. A pressure sensor is operatively connected to the circulation loop to sense a reduction in pressure within the loop. A collision sensor is operatively connected to the vehicle to sense the occurrence of a collision. A controller receives a pressure signal from the pressure sensor and a collision signal from the collision sensor. The controller actuates the fire suppression composition distribution system to dispense the fire suppression composition in response to the pressure signal and the collision signal. 
         [0006]    According to other aspects of the fire suppression system an optional temperature sensor on the vehicle provides a temperature signal to the controller in addition to the pressure signal and the collision signal before actuating the fire suppression system. The temperature sensor may be an engine coolant temperature sensor or an exhaust gas temperature sensor. 
         [0007]    Alternatively, the fire suppression system may include an optional engine load calculating system that receives operating data from the vehicle and calculates a load value representing engine load. The controller receives the engine load value in addition to the pressure signal and the collision signal before actuating the fire suppression system. 
         [0008]    The pressure sensor may be an air conditioning pressure switch signal that detects a reduction in the pressure in the circulation loop and sends the pressure signal to the controller. The collision sensor may be a restraints control module that detects a collision and sends the pressure signal to the controller. The collision sensor may be an accelerometer in the restraints control module. 
         [0009]    The fire suppression system may include a distribution system that contains the fire suppression composition under pressure, and includes at least one nozzle for dispensing the fire suppression composition in an engine compartment of the vehicle. The fire suppression composition may be a fire retardant chemical, nitrogen gas (N 2 ), or an inert gas. 
         [0010]    According to another aspect of this disclosure a method is disclosed for suppressing an engine compartment fire in a vehicle having an HVAC system circulating a flammable refrigerant. The method includes the steps of sensing a pressure value in the HVAC system and providing a pressure signal, sensing a vehicle collision and providing a collision signal. The pressure signal and collision signal are received at a controller and a fire suppressant is discharged into the engine compartment when the rate of change of the pressure signal is below a predetermined rate of change of the pressure value. The rate of change is monitored to avoid discharge of the fire suppression composition if there is only a slow leak. 
         [0011]    According to other aspects of the method, a temperature sensor on the vehicle provides a temperature signal in addition to the pressure signal and the collision signal before discharging the fire suppressant. The temperature sensor may be an engine coolant temperature sensor or an exhaust gas temperature sensor. 
         [0012]    The method may include the step of calculating an engine load value based upon operating data received from the vehicle. The controller receives the engine load value and compares the engine load value to a predetermined engine load value before discharging the fire suppressant. 
         [0013]    The discharging step may further comprise dispensing the fire suppressant through at least one nozzle in an engine compartment of the vehicle. The fire suppressant is a fire retardant chemical or an inert gas. 
         [0014]    The aspects of this disclosure as summarized above and other aspects will be described below in greater detail with reference to the attached drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]      FIG. 1  is a top plan view of a vehicle in phantom lines that illustrates one example of the disclosed fire suppression system. 
           [0016]      FIG. 2  is a flowchart of one embodiment of an algorithm for the fire suppressant system. 
           [0017]      FIG. 3  is a flowchart of another embodiment of an algorithm for the fire suppressant system. 
       
    
    
     DETAILED DESCRIPTION 
       [0018]    A detailed description of the illustrated embodiments of the present invention is provided below. The disclosed embodiments are examples of the invention that may be embodied in various and alternative forms. The figures are not necessarily to scale. Some features may be exaggerated or minimized to show details of particular components. The specific structural and functional details disclosed in this application are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art how to practice the invention. 
         [0019]    Referring to  FIG. 1 , a fire suppression system  10  is shown installed on a vehicle  12 . The fire suppression system  10  is disposed in the engine compartment  14  of the vehicle  12 . A refrigeration circulation loop  16  is part of a heating ventilation and air conditioning (HVAC) system  18 . The HVAC system  18  circulates a refrigerant through the refrigerant circulation loop  16 . The HVAC system  18  condenses and evaporates and contains the refrigerant as is well known in the art. A controller  20  may be a stand-alone controller  20  or incorporated in the engine control module or other controller on the vehicle  12 . The controller  20  receives signals from a restraints module  22 . 
         [0020]    Referring to  FIGS. 1 and 2 , the HVAC system  18  includes an air conditioning (A/C) pressure sensor  24 . The A/C pressure sensor  24  may be a pressure sensor that is used to detect high pressure conditions in the HVAC system  18 . The A/C pressure sensor  24  may be used to also provide a signal to the controller  20  indicating that the refrigeration circulation loop  16  is ruptured or compromised resulting in a rapid loss of pressure. A restraints control module  22  may provide a collision signal to the controller  20 . The A/C pressure sensor  24  may provide a pressure signal to the controller  20 . The collision signal is evaluated at  28 . If a collision signal is received from the restraints control module  22 , the controller then looks at  30  to determine whether a pressure signal indicating a rapid reduction in pressure is received from the A/C pressure sensor  24 . If no collision signal is received from the restraints control module  22 , the controller, at  32 , directs the fire suppression system  10  and does not activate the suppression system. 
         [0021]    If the collision signal is indicated to be received at  28 , the controller  20  looks to the pressure signal at  30  and if the pressure signal is received at  30  indicating a rapid loss of pressure from the A/C pressure sensor  24 , the controller  20  activates the suppression system at  34 . If no pressure signal is received at  30 , the controller does not activate the suppression system at  36 . 
         [0022]    Referring to  FIG. 3 , an alternative embodiment is disclosed in the form of a fire suppression system algorithm  40 . The fire suppression system algorithm  40  may receive an A/C pressure switch signal at  42 . A crash sensor signal is provided at  44  to a controller indicated by the box  46 . The controller evaluates the A/C pressure switch signal  42  and the collision sensor signal  44  as illustrated by the flowchart within the controller  46 . Other signals may also be incorporated and evaluated by the system. In particular, a temperature signal may be measured at  48  by measuring the engine coolant temperature. Alternatively, a temperature may be inferred from an exhaust gas temperature at  50 . Based upon the engine coolant exhaust gas temperature, the controller  46  may determine whether the temperature within the engine compartment  14  is sufficient to ignite the flammable refrigerant circulating through the refrigerant circulation loop  16  (shown in  FIG. 1 ). 
         [0023]    Alternatively, an engine load calculation  52  may be developed based upon data provided from the engine control module or other source of data representative of the engine load. From the engine load calculation  52 , the controller  46  can infer temperature of the engine compartment  14 . 
         [0024]    The controller  46  evaluates the under-hood temperature at  54  to determine whether the under-hood temperature is greater than a predetermined temperature T D . If the temperature is not greater than T D , the controller  46  continues to monitor the system. If the under-hood temperatures are greater than T D , the controller then evaluates at  56  whether the rapid reduction in pressure in the air conditioning system indicates that the system is breached. If the air conditioning system is breached, refrigerant may be released from the refrigerant recirculation loop  16  (shown in  FIG. 1 ). The controller then determines at  58  whether a collision signal was detected as indicated by receiving a signal from the crash sensor signals. If so, the controller  46  actuates the fire suppression system at  60 . Depending upon the type of fire suppression system, a gas, such as nitrogen (N 2 ) or an inert gas may be dispensed within the engine compartment  14 . If the fire suppression system dispenses a fire retardant, the fire retardant may be sprayed through nozzle  62  (shown in  FIG. 1 ). As used herein, the term fire suppression composition should be understood and interpreted to refer to either a gas purge or fire retardant dispensing fire suppression system. 
         [0025]    While exemplary embodiments are described above, it is not intended that these embodiments describe all possible forms of the invention. Rather, the words used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the invention. Additionally, the features of various implementing embodiments may be combined to form further embodiments of the invention.