Abstract: It is an object of the present invention to reduce the constraint that the density ratio is constant as small as possible, and to obtain high power recovering effect in a wide operation range by using an expander which is operated in accordance with a flowing direction of refrigerant.

Abstract: It is an object of the present invention to reduce the constraint that the density ratio is constant as small as possible, and to obtain high power recovering effect in a wide operation range. A refrigeration cycle apparatus uses carbon dioxide as refrigerant and has a compressor, an outdoor heat exchanger, an expander and an indoor heat exchanger. An injection circuit for introducing high pressure refrigerant is provided in a halfway of an expansion process of said expander.

Abstract: It is an object of the present invention to reduce the constraint that the density ratio is constant as small as possible, and to obtain high power recovering effect in a wide operation range by using an expander which is operated in accordance with a flowing direction of refrigerant. An expander used in a refrigeration cycle uses carbon dioxide as refrigerant and has a compressor, an outdoor heat exchanger and an indoor heat exchanger. The expander comprises a cylindrical cylinder, a rotor which rotates in the cylinder, a vane which divides an expansion space formed between an inner peripheral surface of the cylinder and an outer peripheral surface of the rotor into a plurality of spaces, and a vane groove provided in the rotor for accommodating the vane therein. The vane groove is provided with a back pressure chamber which pushes the vane against the inner peripheral surface of the cylinder, and the refrigerant in the supercritical state is introduced into the back pressure chamber.

Abstract: It is an object of the present invention to reduce the constraint that the density ratio is constant as small as possible, and to obtain high power recovering effect in a wide operation range. A refrigeration cycle apparatus uses carbon dioxide as refrigerant and has a compressor, an outdoor heat exchanger, an expander, an indoor heat exchanger and an auxiliary compressor. The auxiliary compressor is driven by power recover by the expander. When refrigerant flows using the indoor heat exchanger as an evaporator, a discharge side of the auxiliary compressor becomes a suction side of the compressor, and when refrigerant flows using the indoor heat exchanger as a gas cooler, a discharge side of the compressor becomes a suction side of the auxiliary compressor.

Abstract: A scroll compressor, whose back pressure is easily controlled and compression efficiency is high, is provided. The scroll compressor includes a plurality of compression chambers formed by engaging a fixed-scroll wrap and a orbiting-scroll wrap, and a back pressure chamber formed at an opposite side of the orbiting-scroll wrap of a orbiting-scroll. The scroll compressor additionally includes a high pressure chamber and a middle pressure chamber, which are formed by dividing the back pressure chamber using a seal. Moreover, the scroll compressor includes a first path for supplying lube oil from the high pressure chamber to the middle pressure chamber, and a second path for supplying the lube oil from the middle pressure chamber to an suction chamber of the compression chambers. The first path is intermittently opened by orbit of the orbiting-scroll.

Abstract: According to a scroll compressor of the present invention, lubricant is supplied to a compression chamber in the proportions of 2% by weight or more and less than 20% by weight of the lubricant to the sucked refrigerant amount. With this, it is possible to provide an efficient scroll compressor even when carbon dioxide is used as the refrigerant.