Patent ID: 7824160

Claim:
A scroll compressor comprising a compression mechanism composed of a fixed scroll, an orbiting scroll and a drive unit that drives the compression mechanism, the compression mechanism and the drive unit being accommodated in a closed vessel, one of the scrolls being provided on a back surface thereof with a back pressure chamber filled with gas refrigerant, the one of the scrolls being pressed against the other of the scrolls by pressure of the gas refrigerant in the back pressure chamber, the scroll compressor being used in a refrigerating cycle, which includes a condenser and an evaporator, wherein the back pressure chamber is composed of a space of suction pressure and a space of discharge pressure, the summation of the suction pressure and the discharge pressure pressing the one of the scrolls against the other of the scrolls, a compression chamber defined by the fixed scroll and the orbiting scroll is constructed to enable injection of both of gas refrigerant and liquid refrigerant there into from downstream of the condenser of the refrigerating cycle, and the scroll compressor further comprising a controller that controls injection of gas refrigerant into the compression chamber such that injection of gas refrigerant into the compression chamber is performed when a ratio (Pd/Ps) of the suction pressure Ps of the refrigerant sucked into the compressor and the discharge pressure Pd of the refrigerant discharged from the compressor is larger than a set volume ratio of the compressor and smaller than a predetermined value, the predetermined value being larger than the set volume ratio, and injection of liquid refrigerant into the compression chamber is performed when the ratio (Pd/Ps) is larger than the predetermined value, the set volume ratio being a ratio of a volume of the compression chamber when the orbiting scroll is at a position just after the scroll compressor starts confinement therein and a volume of the compression chamber when the orbiting scroll is at a position just before communication is made to a discharge space.