Patent ID: 7350366

Claim:
A heat pump comprising: a compressor; a radiator; a first throttling device having a variable opening; an expander; a second throttling device having a variable opening; an evaporator; piping that connects the compressor, the radiator, the first throttling device, the expander, the second throttling device, and the evaporator so that refrigerant circulates in that order; and a control device for controlling the opening of the first throttling device and the opening of the second throttling device, wherein the control device performs control (a) of decreasing the opening of the first throttling device and increasing the opening of the second throttling device, and control (b) of increasing the opening of the first throttling device and decreasing the opening of the second throttling device, wherein the control device executes, in the following order: step A of calculating an optimum pressure P IT of the refrigerant flowing into the expander, or an optimum value R IT of a predetermined pressure or temperature that is related to the pressure of that refrigerant; and step B of determining which of the two of the optimum pressure P IT and an actual pressure P I of said refrigerant is the greater either from the optimum pressure P IT and the actual pressure P I or from the optimum value R IT and an actual value R I of said predetermined pressure or temperature corresponding to the optimum value R IT , and executing the control (a) if the actual pressure P I is greater than the optimum pressure P IT and executing the control (b) if the optimum pressure P IT is greater than the actual pressure P I .