Two-stage pressurising refrigeration cycle device

Abstract

A refrigerant discharge capacity of a high-pressure side compression mechanism and a refrigerant discharge capacity of a low-pressure side compression mechanism can be independently controlled, in a two-stage pressurizing refrigeration cycle device. The refrigerant discharge capacity of the low-pressure side compression mechanism is determined based on an outside air temperature, an air temperature at the evaporator, and a preset temperature. Furthermore, the refrigerant discharge capacity of the high-pressure side compression mechanism is determined based on the determined refrigerant discharge capacity of the low-pressure side compression mechanism such that an effective capacity ratio is not less than 1 nor more than 3. Therefore, in the two-stage pressurizing refrigeration cycle device, COP can be improved with a simple structure and control.

1 - 8 . (canceled) 
     
     
         9 . A two-stage pressurizing refrigeration cycle device comprising:
 a low-pressure side compression mechanism, which compresses a low-pressure refrigerant into a first intermediate-pressure refrigerant, and discharges the first intermediate-pressure refrigerant therefrom;   a high-pressure side compression mechanism, which compresses the first intermediate-pressure refrigerant discharged from the low-pressure side compression mechanism into a high-pressure refrigerant to discharge the high-pressure refrigerant therefrom;   a radiator, which exchanges heat between outdoor air and the high-pressure refrigerant discharged from the high-pressure side compression mechanism, to dissipate heat from the refrigerant;   an intermediate-pressure expansion valve, which decompresses and expands the high-pressure refrigerant flowing from the radiator into a second intermediate-pressure refrigerant to flow the second intermediate-pressure refrigerant into a suction side of the high-pressure side compression mechanism;   a low-pressure expansion valve, which decompresses and expands the high-pressure refrigerant flowing from the radiator into a low-pressure refrigerant;   an evaporator, which evaporates the low-pressure refrigerant decompressed and expanded by the low-pressure expansion valve by exchanging heat with air to be blown into a space for cooling, and is connected to a suction side of the low-pressure side compression mechanism to cause the evaporated refrigerant to flow into the suction side of the low-pressure side compression mechanism;   a first discharge capacity controller configured to determine a refrigerant discharge capacity of at least the low-pressure side compression mechanism, such that the refrigerant discharge capacity is increased in accordance with an increase in at least one of an outside air temperature of the outdoor air for exchanging heat with the high-pressure refrigerant at the radiator and an air temperature of air for exchanging heat with the low-pressure refrigerant at the evaporator; and   a second discharge capacity controller configured to determine a refrigerant discharge capacity of the high-pressure side compression mechanism based on the determined refrigerant discharge capacity of the-low-pressure side compression mechanism,   wherein the second discharge capacity controller determines the refrigerant discharge capacity of the high-pressure side compression mechanism, such that an effective capacity ratio defined as N 2 ×V 2 /N 1 ×V 1  is within a predetermined reference range, when V 1  is a discharge capacity of the high-pressure side compression mechanism, N 1  is the number of revolutions of the high-pressure side compression mechanism, V 2  is a discharge capacity of the low-pressure side compression mechanism, and N 2  is the number of revolutions of the low-pressure side compression mechanism.   
     
     
         10 . The two-stage pressurizing refrigeration cycle device according to  claim 9 , wherein
 the intermediate-pressure expansion valve decompresses and expands one high-pressure refrigerant flow branched at a branching portion in which the high-pressure refrigerant flowing from the radiator is branched, and   the low-pressure expansion valve decompresses and expands an other high-pressure refrigerant flow branched at the branching portion,   said refrigeration cycle device further comprising
 an intermediate heat exchanger in which heat is exchanged between the low-pressure refrigerant decompressed and expanded by the intermediate-pressure expansion valve and the other high-pressure refrigerant branched by the branching portion. 
   
     
     
         11 . The two-stage pressurizing refrigeration cycle device according to  claim 9 , wherein when an absolute value of a difference in temperature between the air temperature at the evaporator and a target cooling temperature of the space for cooling is equal to or less than a predetermined reference temperature difference, the second discharge capacity controller determines the refrigerant discharge capacity of the high-pressure side compression mechanism based on the refrigerant discharge capacity of the low-pressure side compression mechanism. 
     
     
         12 . The two-stage pressurizing refrigeration cycle device according to  claim 11 , wherein when the air temperature at the evaporator is higher than the target cooling temperature, and when the absolute value of the difference in temperature between the air temperature at the evaporator and the target cooling temperature of the space for cooling is equal to or less than the predetermined reference temperature difference, the second discharge capacity controller determines the refrigerant discharge capacity of the high-pressure side compression mechanism based on the refrigerant discharge capacity of the low-pressure side compression mechanism. 
     
     
         13 . The two-stage pressurizing refrigeration cycle device according to  claim 9 , wherein each of the high-pressure side compression mechanism and the low-pressure side compression mechanism is configured by a fixed displacement compression mechanism having a fixed discharge capacity,
 said refrigeration cycle device further comprising:   a high-pressure side electric motor, which rotatably drives the high-pressure side compression mechanism; and   a low-pressure side electric motor, which rotatably drives the low-pressure side compression mechanism,   wherein the number of revolutions of the high-pressure side electric motor and the number of revolutions of the low-pressure side electric motor are independently controllable.   
     
     
         14 . The two-stage pressurizing refrigeration cycle device according to  claim 9 , wherein
 each of the high-pressure side compression mechanism and the low-pressure side compression mechanism is configured by a variable displacement compression mechanism having a variable discharge capacity, and   the discharge capacity of the high-pressure side compression mechanism and the discharge capacity of the low-pressure side compression mechanism are independently controllable.   
     
     
         15 . The two-stage pressurizing refrigeration cycle device according to  claim 9 , wherein the second discharge capacity controller determines the refrigerant discharge capacity of the high-pressure side compression mechanism, such that the effective capacity ratio satisfies the following formula:
   1 ≦N 2× V 2 /N 1× V 1≦3.