Air conditioning systems for vehicles

Abstract

An air conditioning system for vehicles includes a refrigeration cycle having a variable displacement compressor with a displacement control valve, for controlling a discharge amount of the compressor, so that a pressure difference (Pd-Ps) between a discharged refrigerant pressure (Pd) and a drawn-refrigerant pressure (Ps) equals a set value, an acceleration state detecting device, and an engine rotational speed detecting device. The system further includes a device for determining a condition in which the acceleration state is detected or a condition in which the engine rotational speed equals or is greater than a set value as an elevated compressor load condition, and during the elevated compressor load condition, controlling the discharge amount of the compressor, so that the pressure difference (Pd-Ps) equals or is less than a pressure difference (Pd-Ps) immediately before elevated the compressor load condition. Both superior acceleration performance of a vehicle and driver comfort due to air conditioning may be achieved.

1 . An air conditioning system for vehicles comprising a refrigeration cycle comprising a variable displacement compressor with a displacement control valve for controlling a discharge amount of said compressor, so that a pressure difference (Pd-Ps) between a discharged refrigerant pressure Pd and a drawn-refrigerant pressure Ps of said compressor equals a set value, means for detecting an acceleration state of a vehicle, and means for detecting an engine rotational speed of said vehicle, said air conditioning system comprising: 
 means for determining a condition in which said acceleration state is detected or a condition in which said engine rotational speed is greater than or equal to a set value as an elevated compressor load condition, and during said elevated compressor load condition, controlling said discharge amount of said compressor by said displacement control valve, so that said pressure difference (Pd-Ps) after discharge is less than or equal to a pressure difference (Pd-Ps) immediately before discharge in said elevated compressor load condition.    
   
   
       2 . The air conditioning system of  claim 1 , wherein said air conditioning system further comprises a means for estimating a present value of said pressure difference (Pd-Ps), and for estimating said pressure difference (Pd-PS) during said elevated compressor load condition, said compressor is driven by setting an estimated value of said pressure difference (Pd-Ps) immediately before said elevated compressor load condition as a target control value of said displacement control valve.  
   
   
       3 . The air conditioning system of  claim 2 , wherein said air conditioning system further comprises means for estimating a torque of said compressor, and said means for estimating the pressure difference (Pd-Ps) estimates said pressure difference (Pd-Ps) from an estimated torque of said compressor or an outside air temperature or a physical value having a correlation with an amount of air flowing into a heat exchanger provided outside of a vehicle interior per a unit time or an engine rotational speed or a vehicle running speed or combinations thereof.  
   
   
       4 . The air conditioning system of  claim 1 , wherein said pressure difference (Pd-Ps) during said elevated compressor load condition is controlled at or less than said pressure difference (Pd-Ps) immediately before said elevated compressor load condition, by controlling said discharge amount of said compressor, so that a power for driving said compressor is equal to or less than a set value.  
   
   
       5 . The air conditioning system of  claim 4 , wherein said set value of said power for driving said compressor is determined with reference to a physical value having a correlation with an accelerator actuating amount and a vehicle running speed.  
   
   
       6 . The air conditioning system of  claim 4 , wherein a sufficient cooling ability is determined from a vehicle interior air temperature or an evaporator exit air temperature or an outside air temperature, or combinations thereof, and said set value of said power for driving said compressor is determined in accordance with said determined sufficient cooling ability.  
   
   
       7 . The air conditioning system of  claim 1 , wherein said means for detecting the acceleration state detects said acceleration state of said vehicle with reference to at least a physical value correlated with an accelerator actuating amount and a vehicle running speed.  
   
   
       8 . The air conditioning system of  claim 1 , wherein said air conditioning system is configured as a heat pump cycle.  
   
   
       9 . A method for controlling the displacement of a compressor in a vehicle air conditioning system during vehicle acceleration, said method comprising the steps of: 
 detecting a value of an evaporator exit air temperature at air conditioning system start up and assigning said value as a target value;    measuring a discharged refrigerant pressure and a drawn-refrigerant pressure;    estimating a pressure difference between said discharged refrigerant pressure and said drawn-refrigerant pressure;    determining a displacement control signal during vehicle acceleration as a function of said estimated pressure difference; and    controlling said compressor during acceleration by said displacement control signal, so that a detected value of said evaporator exit air temperature sensor during acceleration equals said target value.    
   
   
       10 . The method of  claim 9 , wherein said air conditioning system further comprises a condenser and a condenser fan, and further comprising the steps of estimating a compressor torque value; and measuring a vehicle speed, an outside ambient air temperature, a condenser fan voltage, and a compressor rotational speed and wherein said pressure difference is a function of said estimated compressor torque, said vehicle speed, said outside ambient air temperature, said condenser fan voltage, and said compressor rotational speed.  
   
   
       11 . The method of  claim 10 , wherein said estimated compressor torque is a function of said discharged refrigerant pressure and said compressor rotational speed.  
   
   
       12 . A method for controlling the displacement of a compressor in a vehicle air conditioning system during vehicle acceleration, wherein said air conditioning system further comprises a condenser and a condenser fan, said method comprising the steps of: 
 detecting a value of an evaporator exit air temperature at air conditioning system start up and assigning said value as a target value;    measuring a vehicle speed, an outside ambient air temperature, a condenser fan voltage, and a compressor rotational speed;    determining a target compressor torque;    determining a displacement control signal during vehicle acceleration as a function of said target compressor torque, said vehicle speed, said outside ambient air temperature, said condenser fan voltage, and said compressor rotational speed; and    controlling said compressor during acceleration by said displacement control signal, so that a detected value of said evaporator exit air temperature sensor during acceleration equals said target value.    
   
   
       13 . The method of  claim 12 , further comprising the steps of determining a target power consumption for said compressor and determining said target compressor torque as a function of said target power consumption for said compressor and said compressor rotational speed.