Refrigeration cycle apparatus

Abstract

A refrigeration cycle apparatus ( 100 A) is provided with: a first compressor ( 1 ) including a first compression mechanism ( 11 ), an expansion mechanism ( 13 ), and a first motor ( 12 ); a second compressor ( 2 ) including a second compression mechanism ( 21 ), and a second motor ( 22 ); and a control device ( 6 ). The control device ( 6 ) reduces a rotation frequency of the second motor ( 22 ) at a reduction speed greater than a rotation frequency of the first motor ( 12 ) in a stop operation for stopping the first motor ( 12 ) and the second motor ( 22 ) while reducing the rotation frequencies of the first motor ( 12 ) and the second motor ( 12 ).

1 . A refrigeration cycle apparatus comprising:
 a first compressor including a first compression mechanism for compressing a refrigerant, an expansion mechanism for recovering power from the refrigerant that is expanding, and a first motor coupled to the first compression mechanism and the expansion mechanism by a shaft;   a second compressor including a second compression mechanism for compressing the refrigerant, the second compression mechanism being connected in parallel to the first compression mechanism in a refrigerant circuit, and a second motor coupled to the second compression mechanism by a shaft;   a radiator for radiating heat of the refrigerant discharged from the first compression mechanism and the second compression mechanism;   an evaporator for evaporating the refrigerant discharged from the expansion mechanism; and   a control device for reducing a rotation frequency of the second motor at a reduction speed greater than a rotation frequency of the first motor in a stop operation for stopping the first motor and the second motor while reducing the rotation frequencies of the first motor and the second motor.   
     
     
         2 . The refrigeration cycle apparatus according to  claim 1 , wherein
 the control device determines, upon receiving a stop signal, a reduction speed for the first motor and a reduction speed for the second motor, and reduces the rotation frequency of the first motor and the rotation frequency of the second motor at the determined reduction speeds.   
     
     
         3 . The refrigeration cycle apparatus according to  claim 2 , further comprising:
 a first pipe for introducing the refrigerant from the first compression mechanism and the second compression mechanism to the radiator;   a second pipe for introducing the refrigerant from the radiator to the expansion mechanism;   a third pipe for introducing the refrigerant from the expansion mechanism to the evaporator; and   a fourth pipe for introducing the refrigerant from the evaporator to the first compression mechanism and the second compression mechanism.   
     
     
         4 . The refrigeration cycle apparatus according to  claim 3 , further comprising:
 a pre-expansion temperature sensor for detecting a temperature of the refrigerant flowing in the second pipe;   a high pressure side pressure sensor for detecting a pressure of the refrigerant flowing in the second pipe or the first pipe;   a pre-compression temperature sensor for detecting a temperature of the refrigerant flowing in the fourth pipe; and   a low pressure side pressure sensor for detecting a pressure of the refrigerant flowing in the fourth pipe or the third pipe, wherein   the control device calculates, upon receiving a stop signal, a density ratio between the refrigerant flowing in the second pipe and the refrigerant flowing in the fourth pipe, from the temperature and the pressure detected by the pre-expansion temperature sensor and the high pressure side pressure sensor, and the pre-compression temperature sensor and the low pressure side pressure sensor, so as to determine a reduction speed for the first motor and a reduction speed for the second motor from the calculated density ratio.   
     
     
         5 . The refrigeration cycle apparatus according to any  claim 1 , wherein
 the control device completely stops the first motor and the second motor on the basis of a braking time that has been set in advance.   
     
     
         6 . The refrigeration cycle apparatus according to  claim 1 , further comprising:
 an evaporation temperature sensor for detecting an evaporation temperature of the refrigerant in the evaporator, wherein   the control device completely stops the first motor and the second motor on the basis of the evaporation temperature detected by the evaporation temperature sensor.   
     
     
         7 . The refrigeration cycle apparatus according to  claim 3 , further comprising:
 a high pressure side pressure sensor for detecting a pressure of the refrigerant flowing in the first pipe or the second pipe, wherein   the control device completely stops the first motor and the second motor on the basis of the pressure detected by the high pressure side pressure sensor.   
     
     
         8 . The refrigeration cycle apparatus according to  claim 4 , wherein
 the control device completely stops the first motor and the second motor on the basis of the pressure detected by the high pressure side pressure sensor.   
     
     
         9 . The refrigeration cycle apparatus according to  claim 3 , further comprising:
 a pre-compression temperature sensor for detecting a temperature of the refrigerant flowing in the fourth pipe; and   an evaporation temperature sensor for detecting an evaporation temperature of the refrigerant in the evaporator, wherein   the control device completely stops the first motor and the second motor on the basis of a temperature difference between the temperature detected by the pre-compression temperature sensor and the temperature detected by the evaporation temperature sensor.   
     
     
         10 . The refrigeration cycle apparatus according to  claim 4 , further comprising:
 an evaporation temperature sensor for detecting an evaporation temperature of the refrigerant in the evaporator, wherein   the control device completely stops the first motor and the second motor on the basis of a temperature difference between the temperature detected by the pre-compression temperature sensor and the temperature detected by the evaporation temperature sensor.   
     
     
         11 . The refrigeration cycle apparatus according to  claim 5 , wherein
 the control device completely stops the first motor and the second motor simultaneously.   
     
     
         12 . The refrigeration cycle apparatus according to  claim 5 , wherein
 the control device completely stops the second motor prior to the first motor.