Refrigerant cycle system

Abstract

In a refrigerant cycle system, a compression mechanism of an electric compressor sucks and compresses refrigerant, and an electric motor that drives the compression mechanism is cooled by the refrigerant. A variable throttle mechanism decompresses the refrigerant discharged from the electric compressor. A motor temperature detector detects a temperature of the electric motor. A motor protection determiner determines whether the temperature of the electric motor detected by the motor temperature detector is equal to or higher than a criterion value. A motor protection controller controls the variable throttle mechanism so that an opening degree of the variable throttle mechanism does not decrease when the motor protection determiner determines that the temperature of the electric motor is equal to or higher than the criterion value.

1 . A refrigerant cycle system comprising:
 an electric compressor that includes a compression mechanism, which sucks and compresses refrigerant, and an electric motor, which drives the compression mechanism and is cooled by the refrigerant at a suction side of the compression mechanism;   a variable throttle mechanism that decompresses the refrigerant discharged from the electric compressor;   a motor temperature detector that detects a temperature of the electric motor;   a motor protection determiner that determines whether the temperature of the electric motor detected by the motor temperature detector is equal to or higher than a criterion value; and   a motor protection controller that controls the variable throttle mechanism so that opening degree of the variable throttle mechanism does not decrease when the motor protection determiner determines that the temperature of the electric motor is equal to or higher than the criterion value.   
   
   
       2 . The refrigerant cycle system according to  claim 1 , further comprising a drive circuit that controls operation of the electric motor, wherein:
 the drive circuit detects a motor current, which is an electric current outputted to the electric motor, and a rotational speed of the electric motor; and   the motor temperature detector detects the temperature of the electric motor by calculating the temperature of the electric motor from the rotational speed and the motor current of the electric motor, which are detected by the drive circuit, with reference to a control characteristic data map, which is prepared in advance and indicates a relationship of the temperature of the electric motor with respect to the rotational speed and the motor current of the electric motor.   
   
   
       3 . The refrigerant cycle system according to  claim 2 , wherein:
 the criterion value is specified in the control characteristic data map to corresponds to the rotational speed and the motor current of the electric motor; and   the motor protection determiner determines whether the temperature of the electric motor calculated by the motor temperature detector is equal to or higher than the criterion value specified in the control characteristic data map.   
   
   
       4 . The refrigerant cycle system according to  claim 3 , wherein:
 the criterion value specified in the control characteristic data map is a first criterion value;   a second criterion value that is higher than the first criterion value is specified in the control characteristic data map;   the motor protection determiner determines whether the temperature of the electric motor calculated by the motor temperature detector is equal to or higher than the first criterion value;   the motor protection determiner further determines whether the temperature of the electric motor calculated by the motor temperature detector is equal to or higher than the second criterion value when the motor protection determiner determines that the temperature of the electric motor calculated by the motor temperature detector is equal to or higher than the first criterion value;   the motor protection controller controls the variable throttle mechanism so that the opening degree of the variable throttle mechanism does not decrease when the motor protection determiner determines that the temperature of the electric motor calculated by the motor temperature detector is equal to or higher than the first criterion value and is lower than the second criterion value; and   the motor protection controller controls the variable throttle mechanism so that the opening degree of the variable throttle mechanism increases when the motor protection determiner determines that the temperature of the electric motor calculated by the motor temperature detector is equal to or higher than the second criterion value.   
   
   
       5 . The refrigerant cycle system according to  claim 3 , further comprising:
 a suction refrigerant superheating degree detector that detects a degree of superheat of the refrigerant at the suction side of the electric compressor; and   a control characteristic selector that selects one control characteristic data map from among a plurality of control characteristic data maps, each of which is prepared in advance and indicates a relationship of the temperature of the electric motor with respect to the rotational speed and the motor current of the electric motor, on a basis of the degree of superheat of the refrigerant detected by the suction refrigerant superheating degree detector, wherein   the motor protection determiner determines whether the temperature of the electric motor calculated by the motor temperature detector is equal to or higher than the criterion value specified in the one control characteristic data map.   
   
   
       6 . The refrigerant cycle system according to  claim 3 , wherein the refrigerant cycle system is a heat pump system that operates in a cooling operation mode in which the refrigerant cools heat-exchange target fluid and in a heating operation mode in which the refrigerant heats the heat-exchange target fluid, the refrigerant cycle system further comprising
 a control characteristic selector that selects a first control characteristic data map in the cooling operation mode from among a plurality of control characteristic data maps, each of which is prepared in advance and indicates a relationship of the temperature of the electric motor with respect to the rotational speed and the motor current of the electric motor, and selects a second control characteristic data map in the heating operation mode from among the plurality of control characteristic data maps so that the criterion value specified in the first control characteristic data map is lower than the criterion value specified in the second control characteristic data map, wherein   the motor protection determiner determines whether the temperature of the electric motor calculated by the motor temperature detector is equal to or higher than the criterion value specified in the first control characteristic data map or the second control characteristic data map that is selected by the control characteristic selector.   
   
   
       7 . The refrigerant cycle system according to  claim 1 , further comprising a heat-radiating heat exchanger that cools the refrigerant at a discharge side of the electric compressor, wherein:
 the variable throttle mechanism decompresses the refrigerant at an outlet side of the heat-radiating heat exchanger so that a pressure of the refrigerant at the discharge side of the electric compressor becomes closer to a target high pressure that is determined on a basis of a temperature of the refrigerant at the outlet side of the heat-radiating heat exchanger; and   the motor protection controller lowers the target high pressure when the temperature of the electric motor detected by the motor temperature detector is equal to or higher than the criterion value.   
   
   
       8 . The refrigerant cycle system according to  claim 7 , further comprising:
 a first electric blower that blows exterior air to the heat-radiating heat exchanger; and   a first electric blower controller that controls a rotational speed of the first electric blower, wherein   the first electric blower controller raises the rotational speed of the first electric blower when the motor protection determiner determines that the temperature of the electric motor detected by the motor temperature detector is equal to or higher than the criterion value.   
   
   
       9 . The refrigerant cycle system according to  claim 6 , further comprising:
 an evaporator that vaporizes the refrigerant decompressed by the variable throttle mechanism;   a second electric blower that blows heat-exchange target fluid to the evaporator; and   a second electric blower controller that controls a rotational speed of the second electric blower, wherein   the second electric blower controller lowers the rotational speed of the second electric blower when the motor protection determiner determines that the temperature of the electric motor detected by the motor temperature detector is equal to or higher than the criterion value.   
   
   
       10 . The refrigerant cycle system according to  claim 6 , further comprising:
 an evaporator that vaporizes the refrigerant that is decompressed by the variable throttle mechanism; and   an interior/exterior air switcher that switches an air introducing mechanism between an interior air mode, in which air blown to the evaporator is introduced from an interior, and an exterior air mode, in which the air blown to the evaporator is introduced from an exterior, wherein   the interior/exterior air switcher switches the air introducing mechanism to the interior air mode when the motor protection determiner determines that the temperature of the electric motor detected by the motor temperature detector is equal to or higher than the criterion value.   
   
   
       11 . The refrigerant cycle system according to  claim 1 , wherein
 the motor temperature detector includes a motor temperature detection sensor for detecting the temperature of the electric motor.