Patent ID: 8136365
Filing Date: 2012-03-20
Classification: F25B,Y02B

Abstract:
1. A refrigerator comprising: a heat-insulated box having a storage compartment for housing an object to be cooled; a refrigeration cycle including a compressor configured to be driven by an electric motor having a controllable rotating speed, a condenser cooling refrigerant configured to be discharged from the compressor, a throttle valve configured to enable the refrigerant discharged from the condenser to pass therethrough and an evaporator configured to perform a cooling operation by the refrigerant having passed through the throttle valve; an inner fan configured to circulate cold air produced by a cooling action of the evaporator into the storage compartment; a first physical quantity detector configured to detect a physical quantity representing a temperature of an object to be cooled by the cooling operation of the evaporator; a temperature control device configured to control a rotating speed of the motor based on the physical quantity detected by the first physical quantity detector so that the object is cooled approximately to a target temperature; a second physical quantity detector configured to detect a physical quantity corresponding to a performance margin of the refrigeration cycle; and a rotating speed control device configured to determine an upper limit of the rotating speed of the motor and control the rotating speed of the motor at or below the upper limit, the determination of the upper limit being based on a physical quantity detected by the second physical quantity detector; wherein the second physical quantity detector comprises a temperature sensor configured to detect a room temperature in the area surrounding but not within the refrigerator, wherein the rotating speed control device is configured to determine the upper limit such that the upper limit increases as the room temperature in the area surrounding but not within the refrigerator decreases; wherein the temperature control device is configured to control the rotating speed of the motor in a range from a lower limit to the upper limit determined by the rotating speed control device, so as to maintain the temperature of the object to be cooled at approximately the target temperature; wherein the rotating speed control device is configured to determine the lower limit; wherein the temperature control device is configured to compare a measured temperature gradient of the object to be cooled with a stored target temperature gradient, and to control the rotating speed of the motor such that the rotating speed is set higher if the measured temperature gradient of the object to be cooled is less than the stored target temperature gradient and the rotating speed is set lower if the measured temperature gradient of the object to be cooled is greater than the stored target temperature gradient; and wherein the rotating speed control device is configured to determine the upper limit further based on the physical quantity detected by the first physical quantity detector, such that the upper limit increases as the physical quantity detected by the first physical quantity detector decreases.