Patent ID: 7207379

Claim:
An automotive air conditioning system comprising: an air conditioning duct for sending air into a passenger compartment of an automobile; a main heating unit for heating air passing through said air conditioning duct using cooling water of an engine; a refrigeration cycle device comprising: a cooling refrigerant circulating circuit which includes a refrigerant compressor for introducing hot refrigerant into a refrigerant condenser, a first pressure reducing device and a refrigerant evaporator in that order, the refrigerant evaporator being connected to the refrigerant compressor to return said refrigerant to said refrigerant compressor, a heating refrigerant circulating circuit which causes hot refrigerant discharged from said refrigerant compressor to bypass said refrigerant condenser so as to be introduced to a second pressure reducing device and said refrigerant evaporator in that order, a heater mounted along a oath of said heating refrigerant circulating circuit, an outside air temperature sensor for detecting a temperature of air outside the passenger compartment, and an air conditioning control unit (ECU) for controlling the refrigeration cycle device, wherein the air conditioning control unit includes: means for controlling the refrigerant compressor in a manner that when said automotive air conditioning system is operated using the heating refrigerant circulating circuit, said refrigerant compressor is switched on after a first predetermined time has elapsed after said engine is activated when the outside air temperature is egual to or lower than a predetermined value, and said refrigerant compressor is switched on without a delay of the first predetermined time when the outside air temperature is higher than the predetermined value, means for controlling the heater in a manner that the heater is switched on in the event that the outside air temperature is equal to or lower than the predetermined value after the engine has been started, and is kept switched on until a second predetermined time longer than the first predetermined time has elapsed, thereby the heater has been switched on for the first predetermined time before the heating refrigerant circulating circuit is operated by switching the compressor on, and means for determining the first predetermined time that represents a time to increase a temperature of said refrigerant in said heating refrigerant circulating circuit to prevent generation of negative pressure immediately after an activation of said refrigerant compressor under a condition where the outside air temperature is extremely low.