Patent ID: 8434316

Claim:
A compressor inlet pressure estimation apparatus for a refrigeration cycle system, the refrigeration cycle system comprising: a compressor for sucking, compressing and discharging a refrigerant; a cooler for cooling the refrigerant discharged from the compressor; a decompressor for reducing the pressure of the refrigerant cooled by the cooler; an evaporator for evaporating the refrigerant, which is reduced in pressure by the decompressor, by absorbing heat from air, the compressor inlet pressure estimation apparatus comprising: a temperature sensor for detecting the surface temperature of the evaporator; a refrigerant temperature estimation means estimating the refrigerant temperature in the evaporator upon lapse of a certain time after starting the compressor based on a function indicating a relationship between an estimated temperature in the evaporator and time; and a pressure estimation means estimating the refrigerant inlet pressure of the compressor based on the refrigerant temperature estimated by the refrigerant temperature estimation means; wherein the function connects, with a downwardly convex curve, the surface temperature of the evaporator detected by the temperature sensor at the time of starting the compressor and an estimated target temperature constituting the refrigerant temperature upon lapse of a predetermined time after starting the compressor, on an X-Y coordinate system with Y axis representing the estimated refrigerant temperature in the evaporator and X axis representing the time, wherein the estimated target temperature is a variable having a value that increases with time after a predetermined time period from the starting of the compressor elapses, and wherein the estimated refrigerant temperature in the evaporator is determined based on the estimated target temperature or the surface temperature of the evaporator detected by the temperature sensor, whichever is lower.