Patent ID: 8245528

Claim:
A fluid machine disposed in a refrigerant circuit operating in a refrigeration cycle by circulating refrigerant therethrough, comprising: a compression mechanism for compressing the refrigerant; an expansion mechanism disposed above the compression mechanism for generating power by expansion of the refrigerant; a rotary shaft coupling the compression mechanism to the expansion mechanism; and a container-shaped casing containing the compression mechanism, the expansion mechanism and the rotary shaft, the rotary shaft having an oil feeding channel foamed therein to feed lubricating oil accumulated in part of the casing located towards the compression mechanism to the expansion mechanism, the expansion mechanism being configured to introduce the lubricating oil fed through the oil feeding channel into an expansion chamber for expanding the refrigerant therein and discharge the lubricating oil together with the refrigerant after expansion, the expansion mechanism being constituted by a rotary expander including: a cylinder both ends of which are closed; a piston engaged with the rotary shaft and contained in the cylinder to form the expansion chamber; and a blade for partitioning the expansion chamber into a high-pressure chamber and a low-pressure chamber, a front head, which closes an end surface of the cylinder, and through which the rotary shaft is inserted, being arranged in a lower end of the expansion mechanism, the rotary shaft having a branch channel formed therein to be branched from the oil feeding channel and open at a portion of the outer periphery of the rotary shaft, the portion of the outer periphery sliding with the front head, the expansion mechanism having an oil introduction channel formed to introduce the lubricating oil discharged through the branch channel to the sliding surface of the blade, the cylinder having a through hole foamed therein to pass through the cylinder in a thickness direction of the cylinder and receive the blade, the oil introduction channel having an end opening into the through hole in the cylinder to feed the lubricating oil to the sliding surface of the blade, one end of the oil feeding channel opening at an end surface of the rotary shaft closer to the expansion mechanism, the expansion mechanism having a connection channel formed to communicate the through hole in the cylinder with the one end of the oil feeding channel opening at the end surface of the rotary shaft, the oil introduction channel being formed in the front head, the beginning of the oil introduction channel being open in at a side wall of a center hole formed on the front head so that the rotary shaft is inserted through the center hole, and the lubricating oil flowing in the branch channel being fed to sliding surfaces between the front head and the rotary shaft, and the oil introduction channel.