Refrigerant cycle system for vehicle air conditioner

An air conditioner for a vehicle having a passenger compartment, comprising:

• a front air-conditioning case for defining a first air passage through which air is blown toward a front seat side of the passenger compartment;
• a rear air-conditioning case for defining a second air passage through which air is blown toward a rear seat side of the passenger compartment;
• a compressor for compressing and discharging refrigerant;
• a condenser for cooling and condensing gas refrigerant discharged from said compressor;
• a first pressure-reducing unit for decompressing and expanding liquid refrigerant from said condenser;
• a first evaporator for evaporating refrigerant from said first pressure-reducing unit, said first evaporator being disposed in said front air-conditioning case to cool air passing therethrough;
• a first blower for blowing air toward said first evaporator;
• a second pressure-reducing unit for decompressing and expanding liquid refrigerant from said condenser, said second pressure-reducing unit being disposed parallel to said first pressure-reducing unit relative to a refrigerant flow direction;
• a second evaporator for evaporating refrigerant from said second pressure-reducing unit, said second evaporator being disposed in said rear air-conditioning case to cool air passing therethrough, parallel to said first evaporator relative to the refrigerant flow direction;
• a second blower for blowing air toward said second evaporator;
• and
• a control unit that controls operation of said compressor to change a refrigerant pressure at a suction side of said compressor when a continuous operation time of said compressor passes a predetermined time after said compressor operates,
• wherein said second pressure-reducing unit is a thermal expansion valve which adjusts a super-heating degree of refrigerant at an outlet of said second evaporator.