Heat pump type air conditioning system for automotive vehicle

Abstract

A heat pump type air conditioning system (A) for air-conditioning a passenger compartment of an automotive vehicle. The air conditioning system comprises first and second units (10, 20). The first unit includes a heater core (12) and a first evaporator (13) while the second unit includes a second condenser (22) and a second evaporator (23). A compressor (2) and a first condenser (3) are disposed outside the first and second units which constitute a refrigeration cycle including the first evaporator (13). A circuit change-over valve (4) is provided to cause flow of the refrigerant discharged from the compressor (2) to be changed over between a refrigeration operation refrigerant circuit including the first condenser and a heating operation refrigerant circuit including a bypass passage for allowing the refrigerant to flow bypassing the first condenser. A third evaporator (30) is disposed outside the first and second units (10, 20). A flow control valve (31) is provided to control a flow amount of the engine coolant circulating through the third evaporator (30) in accordance with a thermal load condition of the vehicle under control of an opening degree of the flow control valve, during the heating operation of the air conditioning system. The flow control valve (31) is set to take its fully closed state to prevent the engine coolant from circulating through the third evaporator (30) when a discharge pressure of the compressor (2) rises to a level not lower a first set value which is lower than a standard value to stop an operation of the compressor, and to take its fully opened state to allow the engine coolant to circulate through the third evaporator (30) when the discharge pressure of the compressor (2) lowers to a level not higher than a second set value which is lower than the first set value.