Vehicle air conditioning system

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;
• throttle valve control means for controlling the degree of opening of any one of said first variable throttle valve and said second 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;
• capacity overload sensing means for sensing a capacity overload on said heating heat exchanger, wherein
• said refrigerant compressor is a motor-driven refrigerant compressor rotatably driven by a drive motor that is controllably activated by an inverter serving as a drive power supply,
• said cycle efficiency sensing means is high-pressure sensing means for sensing a high pressure in said refrigeration cycle,
• said cycle efficiency determination means is high-pressure determination means, having refrigerant temperature sensing means for sensing a temperature of the refrigerant at an outlet of said external heat exchanger, for calculating a target high pressure providing a maximum cycle efficiency in accordance with the temperature of the refrigerant sensed by said refrigerant temperature sensing means at the outlet of said external heat exchanger, and
• when a capacity overload on said heating heat exchanger is sensed by said capacity overload sensing means, said throttle valve control means controls the degree of opening of any one of said first variable throttle valve and said second variable throttle valve in accordance with a pressure deviation between a current high pressure sensed by said high-pressure sensing means and the target high pressure set by said high-pressure determination means.

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;
• throttle valve control means for controlling the degree of opening of any one of said first variable throttle valve and said second 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;
• blowing temperature determination means for calculating a target blowing temperature of conditioned air blown into the passenger compartment;
• a dehumidifying or defogging switch for requesting dehumidification of a passenger compartment or defogging of a glass window in an ON state;
• and
• dehumidifying mode selection means for selecting a dehumidifying mode as an operation mode of said refrigeration cycle when the target blowing temperature set by said blowing temperature determination means is within a predetermined range or when said dehumidifying or defogging switch is in an ON state, wherein
• said refrigerant compressor is a motor-driven refrigerant compressor rotatably driven by a drive motor that is controllably activated by an inverter serving as a drive power supply,
• said dehumidifying mode selection means is dehumidifying mode setting means for requesting either a dehumidifying mode of a dehumidifying priority mode or a blowing temperature priority mode, and
• said vehicle air conditioning system further comprises:
• dehumidifying capacity sensing means for sensing a dehumidifying capacity of said cooling heat exchanger,
• dehumidifying capacity determination means for calculating a target dehumidifying capacity of said cooling heat exchanger,
• heating capacity sensing means for sensing a heating capacity of said heating heat exchanger,
• heating capacity determination means for calculating a target heating capacity of said heating heat exchanger, and
• air conditioning control means for controlling a rotational speed of said refrigerant compressor in accordance with a deviation between a dehumidifying capacity sensed by said dehumidifying capacity sensing means and the target dehumidifying capacity set by said dehumidifying capacity determination means when the dehumidifying priority mode is requested by said dehumidifying mode setting means as well as for controlling the degree of opening of any other of said first variable throttle valve and said second variable throttle valve in accordance with a deviation between a heating capacity sensed by said heating capacity sensing means and the target heating capacity set by said heating capacity determination means, or for controlling a rotational speed of said refrigerant compressor in accordance with a deviation between a heating capacity sensed by said heating capacity sensing means and the target heating capacity set by said heating capacity determination means when the blowing temperature priority mode is requested by said dehumidifying mode setting means as well as for controlling the degree of opening of any other of said first variable throttle valve and said second variable throttle valve in accordance with a deviation between a dehumidifying capacity sensed by said dehumidifying capacity sensing means and the target dehumidifying capacity set by said dehumidifying capacity determination means.