Vehicle air conditioner with refrigerant flow-amount control of compressor

An air conditioner for a vehicle having an engine for powering the vehicle, the air conditioner comprising:

• a refrigerant cycle having a variable-displacement compressor rotated by power from the engine, a rotational speed and capacity of the compressor being directly related to a rotational speed of the engine, the compressor being disposed to suck and compress refrigerant so that the refrigerant discharged from the compressor has a pressure equal to or higher than critical pressure of the refrigerant;
• a fixed throttle disposed at a refrigerant discharge side of the compressor;
• and
• a control unit which changes a theoretical flow amount of the refrigerant discharged from the compressor based on a pressure difference between upstream and downstream sides of the fixed throttle in a refrigerant flow direction;
• wherein:
• the control unit is set in such a manner that the flow amount of the refrigerant discharged from the compressor has an upper limit as the rotational speed of the compressor is increased due to an increase in the rotational speed of the engine.

A refrigerant cycle comprising:

• a rotary compressor disposed to suck and compress the refrigerant so that refrigerant discharged from the compressor has a pressure equal to or higher than critical pressure of refrigerant;
• a high-pressure side heat exchanger which is disposed to cool the refrigerant discharged from the compressor;
• a decompression unit disposed to decompress the refrigerant flowing from the high-pressure side heat exchanger;
• a low-pressure side heat exchanger disposed to evaporate the refrigerant flowing from the decompression unit;
• and
• a control unit which is mechanically connected to the compressor and is disposed to prevent a flow amount of the refrigerant discharged from the compressor from becoming larger than a predetermined value as a rotational speed of the compressor is increased.