Refrigeration cycle apparatus

Abstract

A refrigeration cycle apparatus ( 100 A) includes a first compressor ( 101 ) that is an expander-compressor unit, a second compressor ( 102 ), and a controller ( 300 ). The controller ( 300 ) shifts, when an oil level 51 of a first oil pool ( 13 ) becomes equal to or lower than a specified level L, to an oil-equalizing operation in which a rotation speed of a first motor ( 12 ) is decreased only by a specified decrement and a rotation speed of a second motor ( 12 ) is increased by a specified increment, and an opening of a bypass valve ( 70 ) is increased so that a pressure or a temperature of a discharged refrigerant guided to a radiator ( 4 ) through a first pipe ( 3 a ) is kept approximately constant, and returns the rotation speeds of the first motor ( 11 ) and the second motor ( 12 ) as well as the opening of the bypass valve ( 70 ) to conditions before start of the oil-equalizing operation when a specified period of time has elapsed since the start of the oil-equalizing operation.

1 . A refrigeration cycle apparatus comprising:
 a first compressor including a first compression mechanism for compressing a refrigerant, an expansion mechanism for recovering mechanical power from the refrigerant expanding, a first motor coupled to the first compression mechanism and the expansion mechanism by a first shaft, and a first closed casing that accommodates the first compression mechanism, the expansion mechanism, and the first motor and has, in a bottom portion thereof, a first oil pool;   a second compressor including a second compression mechanism for compressing the refrigerant, the second compression mechanism being connected in parallel with the first compression mechanism in a refrigerant circuit, a second motor coupled to the second compression mechanism by a second shaft, a second closed casing that accommodates the second compression mechanism and the second motor and has, in a bottom portion thereof, a second oil pool;   a radiator for radiating heat from the refrigerant discharged from the first compression mechanism and the second compression mechanism;   an evaporator for evaporating the refrigerant discharged from the expansion mechanism;   a first pipe for guiding the refrigerant from the first compression mechanism and the second compression mechanism to the radiator;   a second pipe for guiding the refrigerant from the radiator to the expansion mechanism;   a third pipe for guiding the refrigerant from the expansion mechanism to the evaporator;   a bypass passage extending from the second pipe to the third pipe while bypassing the expansion mechanism;   an opening-adjustable bypass valve provided in the bypass passage; and   a controller that shifts, when an oil level of the first oil pool becomes equal to or lower than a specified level, to an oil-equalizing operation in which a rotation speed of the first motor is decreased and a rotation speed of the second motor is increased, and, in a state in which the first motor and the second motor are being driven, an opening of the bypass valve is increased so that a pressure or a temperature of the discharged refrigerant guided to the radiator through the first pipe is kept approximately constant, and returns the rotation speeds of the first motor and the second motor as well as the opening of the bypass valve to conditions before start of the oil-equalizing operation when a specified period of time has elapsed since the start of the oil-equalizing operation.   
     
     
         2 . A refrigeration cycle apparatus comprising:
 a first compressor including a first compression mechanism for compressing a refrigerant, an expansion mechanism for recovering mechanical power from the refrigerant expanding, a first motor coupled to the first compression mechanism and the expansion mechanism by a first shaft, and a first closed casing that accommodates the first compression mechanism, the expansion mechanism, and the first motor and has, in a bottom portion thereof, a first oil pool;   a second compressor including a second compression mechanism for compressing the refrigerant connected in parallel with the first compression mechanism in a refrigerant circuit, a second motor coupled to the second compression mechanism by a second shaft, a second closed casing that accommodates the second compression mechanism and the second motor and has, in a bottom portion thereof, a second oil pool;   a radiator for radiating heat from the refrigerant discharged from the first compression mechanism and the second compression mechanism;   a first pipe for guiding the refrigerant from the first compression mechanism and the second compression mechanism to the radiator;   a second pipe for guiding the refrigerant from the radiator to the expansion mechanism;   an injection passage, branched from the second pipe, for supplying additionally the refrigerant to the expansion mechanism in an expansion process;   an opening-adjustable injection valve provided in the injection passage; and   a controller that shifts, when an oil level of the first oil pool becomes equal to or lower than a specified level, to an oil-equalizing operation in which a rotation speed of the first motor is decreased and a rotation speed of the second motor is increased, and, in a state in which the first motor and the second motor are being driven, an opening of the injection valve is increased so that a pressure or a temperature of the discharged refrigerant guided to the radiator through the first pipe is kept approximately constant, and returns the rotation speeds of the first motor and the second motor as well as the opening of the injection valve to conditions before start of the oil-equalizing operation when a specified period of time has elapsed since the start of the oil-equalizing operation.   
     
     
         3 . The refrigeration cycle apparatus according to  claim 1  or  2 , further comprising an oil level sensor for detecting that the oil level of the first oil pool becomes equal to or lower than the specified level,
 wherein the controller shifts to the oil-equalizing operation when the oil level sensor detects that the oil level of the first oil pool becomes equal to or lower than the specified level. 
 
     
     
         4 . The refrigeration cycle apparatus according to  claim 1 , wherein the controller determines, at a predetermined interval, that the oil level of the first oil pool becomes equal to or lower than the specified level and shifts to the oil-equalizing operation. 
     
     
         5 . The refrigeration cycle apparatus according to  claim 1 , further comprising an oil-equalizing pipe that couples the first closed casing to the second closed casing so as to bring the first oil pool into communication with the second oil pool. 
     
     
         6 . The refrigeration cycle apparatus according to  claim 1 , wherein the expansion mechanism is immersed in the first oil pool, and the first compression mechanism is located above the expansion mechanism. 
     
     
         7 . The refrigeration cycle apparatus according to  claim 3 , wherein the first compressor further includes an oil pump that is disposed between the expansion mechanism and the first compression mechanism, draws an oil of the first oil pool through an oil suction port, and supplies the oil to the first compression mechanism through an oil supply passage provided in the first shaft, and
 the specified level is set to be higher than the oil suction port.   
     
     
         8 . The refrigeration cycle apparatus according to  claim 7 , wherein the first motor is disposed between the first compression mechanism and the oil pump. 
     
     
         9 . The refrigeration cycle apparatus according to  claim 8 , wherein the first closed casing is configured such that an internal space above the first oil pool is filled with the refrigerant discharged from the first compression mechanism,
 a flow suppressing member for suppressing the oil of the first oil pool from flowing with a flow of the refrigerant in the first closed casing is disposed between the first motor and the oil pump so as to partition a space inside the first closed casing horizontally, and   the oil level sensor is disposed below the flow suppressing member.   
     
     
         10 . The refrigeration cycle apparatus according to  claim 4 , wherein the first compressor further includes an oil pump that is disposed between the expansion mechanism and the first compression mechanism, draws an oil of the first oil pool through an oil suction port, and supplies the oil to the first compression mechanism through an oil supply passage provided in the first shaft, and
 the specified level is set to be higher than the oil suction port.   
     
     
         11 . The refrigeration cycle apparatus according to  claim 10 , wherein the first motor is disposed between the first compression mechanism and the oil pump. 
     
     
         12 . The refrigeration cycle apparatus according to  claim 1 , wherein the controller stores an increment and a decrement that are predetermined in accordance with a difference between the rotation speed of the first motor and that of the second motor, and
 the controller decreases the rotation speed of the first motor and increases the rotation speed of the second motor by the decrement and the increment, respectively, in the oil-equalizing operation.   
     
     
         13 . The refrigeration cycle apparatus according to  claim 4 , wherein the interval is composed of a first set time and a second set time longer than the first set time, and
 the controller ends the oil-equalizing operation when the second set time has elapsed since the start of the oil-equalizing operation and starts the oil-equalizing operation when the first set time has elapsed since the end of the oil-equalizing operation.   
     
     
         14 . The refrigeration cycle apparatus according to  claim 2 , further comprising an oil level sensor for detecting that the oil level of the first oil pool becomes equal to or lower than the specified level,
 wherein the controller shifts to the oil-equalizing operation when the oil level sensor detects that the oil level of the first oil pool becomes equal to or lower than the specified level.   
     
     
         15 . The refrigeration cycle apparatus according to  claim 2 , wherein the controller determines, at a predetermined interval, that the oil level of the first oil pool becomes equal to or lower than the specified level and shifts to the oil-equalizing operation. 
     
     
         16 . The refrigeration cycle apparatus according to  claim 2 , further comprising an oil-equalizing pipe that couples the first closed casing to the second closed casing so as to bring the first oil pool into communication with the second oil pool. 
     
     
         17 . The refrigeration cycle apparatus according to  claim 2 , wherein the expansion mechanism is immersed in the first oil pool, and the first compression mechanism is located above the expansion mechanism. 
     
     
         18 . The refrigeration cycle apparatus according to  claim 14 , wherein the first compressor further includes an oil pump that is disposed between the expansion mechanism and the first compression mechanism, draws an oil of the first oil pool through an oil suction port, and supplies the oil to the first compression mechanism through an oil supply passage provided in the first shaft, and
 the specified level is set to be higher than the oil suction port.   
     
     
         19 . The refrigeration cycle apparatus according to  claim 18 , wherein the first motor is disposed between the first compression mechanism and the oil pump. 
     
     
         20 . The refrigeration cycle apparatus according to  claim 19 , wherein the first closed casing is configured such that an internal space above the first oil pool is filled with the refrigerant discharged from the first compression mechanism,
 a flow suppressing member for suppressing the oil of the first oil pool from flowing with a flow of the refrigerant in the first closed casing is disposed between the first motor and the oil pump so as to partition a space inside the first closed casing horizontally, and   the oil level sensor is disposed below the flow suppressing member.   
     
     
         21 . The refrigeration cycle apparatus according to  claim 15 , wherein the first compressor further includes an oil pump that is disposed between the expansion mechanism and the first compression mechanism, draws an oil of the first oil pool through an oil suction port, and supplies the oil to the first compression mechanism through an oil supply passage provided in the first shaft, and
 the specified level is set to be higher than the oil suction port.   
     
     
         22 . The refrigeration cycle apparatus according to  claim 21 , wherein the first motor is disposed between the first compression mechanism and the oil pump. 
     
     
         23 . The refrigeration cycle apparatus according to  claim 2 , wherein the controller stores an increment and a decrement that are predetermined in accordance with a difference between the rotation speed of the first motor and that of the second motor, and
 the controller decreases the rotation speed of the first motor and increases the rotation speed of the second motor by the decrement and the increment, respectively, in the oil-equalizing operation.   
     
     
         24 . The refrigeration cycle apparatus according to  claim 15 , wherein the interval is composed of a first set time and a second set time longer than the first set time, and
 the controller ends the oil-equalizing operation when the second set time has elapsed since the start of the oil-equalizing operation and starts the oil-equalizing operation when the first set time has elapsed since the end of the oil-equalizing operation.