Patent ID: 7870758

Claim:
An ejector cycle using a refrigerant, the ejector cycle comprising: a compressor for drawing the refrigerant and compressing the refrigerant; a high-pressure heat exchanger in communication with a discharge outlet of the compressor for cooling the refrigerant discharged from the compressor; a low-pressure heat exchanger for evaporating the refrigerant after the refrigerant has been decompressed; a variable throttle device disposed at a refrigerant outlet side of the high-pressure heat exchanger, the variable throttle device having a throttle open degree that is changed in accordance with a super-heating degree on a refrigerant outlet side of the low-pressure heat exchanger; an ejector disposed in a refrigerant path through which the refrigerant flows from the high pressure heat exchanger to the compressor, the ejector including a nozzle for decompressing and expanding the refrigerant flowing in the refrigerant path from the variable throttle device by converting pressure energy of the refrigerant to speed energy of the refrigerant, and a pressure-increasing portion that is disposed to increase a pressure of the refrigerant by converting the speed energy of the refrigerant to the pressure energy of the refrigerant while mixing the refrigerant jetted from the nozzle and the refrigerant sucked from the low-pressure heat exchanger; a gas-liquid separator disposed between the ejector and the compressor, the gas-liquid separator in communication with an outlet of the ejector, a suction inlet of the compressor and an inlet of the low-pressure heat exchanger for separating the refrigerant from the ejector into gas refrigerant and liquid refrigerant, the gas-liquid separator having a gas refrigerant outlet coupled to the suction inlet of the compressor, and a liquid refrigerant outlet coupled to the inlet of the low-pressure heat exchanger; a bypass passage through which at least a part of the refrigerant flowing out of the high-pressure heat exchanger is introduced to the nozzle while bypassing the variable throttle device; a valve device which opens and closes the bypass passage; and a control unit which controls switching operation of the valve device so that a flow speed of the refrigerant flowing in the low-pressure heat exchanger remains in a predetermined flow speed range, the predetermined flow speed range being set to a flow speed range without an oil stay within the low-pressure heat exchanger; wherein the refrigerant flows in the ejector cycle in this order of the compressor, the high pressure heat exchanger, the ejector and the gas-liquid separator; the gas refrigerant separated in the gas-liquid separator returning to the compressor without passing through the ejector; and the liquid refrigerant separated in the gas-liquid separator flows in this order of the low-pressure heat exchanger and the ejector.