Patent ID: 7121103

Claim:
A vehicle air conditioning system comprising: an air duct for blowing conditioned air into a passenger compartment; a refrigeration cycle having: a cooling heat exchanger disposed within said air duct to serve as a heat absorber in a dehumidifying mode; a heating heat exchanger disposed downstream of said cooling heat exchanger, in a direction of airflow within said air duct, to serve as a heat radiator in the dehumidifying mode; an external heat exchanger disposed external to said air duct to serve as a heat absorber or a heat radiator in the dehumidifying mode; a first variable throttle valve connected between said heating heat exchanger and said external heat exchanger, wherein said first variable throttle valve is capable of decompressing a refrigerant introduced from said heating heat exchanger as well as changing the degree of valve opening thereof; a second variable throttle valve connected between said external heat exchanger and said cooling heat exchanger, wherein said second variable throttle valve is capable of decompressing the refrigerant introduced from said external heat exchanger as well as changing the degree of valve opening thereof; and a dehumidifying mode circulation path for circulating refrigerant discharged from a refrigerant compressor along a path from said heating heat exchanger through said first variable throttle valve, said external heat exchanger, said second variable throttle valve, and said cooling heat exchanger to said refrigerant compressor; cycle efficiency sensing means for sensing a current cycle efficiency; cycle efficiency determination means for calculating a target cycle efficiency; first throttle valve control means for controlling the degree of opening of said first variable throttle valve in the dehumidifying mode in accordance with a deviation between said target cycle efficiency set by said cycle efficiency determination means and said current cycle efficiency sensed by said cycle efficiency sensing means; and second throttle valve control means for controlling the degree of opening of said second variable throttle valve in the dehumidifying mode in accordance with one of a dehumidifying capacity of said cooling heat exchanger and a heating capacity of said heating heat exchanger.