Two-stage rotary expander, expander-integrated compressor, and refrigeration cycle apparatus

A two-stage rotary expander comprising:

• a first cylinder;
• a first piston disposed rotatably in the first cylinder;
• a second cylinder disposed concentrically with the first cylinder;
• a second piston disposed rotatably in the second cylinder;
• a shaft on which the first piston and the second piston are mounted;
• a first vane, disposed slidably in a first vane groove formed in the first cylinder, for partitioning a space between the first cylinder and the first piston into a first suction space and a first discharge space;
• a second vane, disposed slidably in a second vane groove formed in the second cylinder, for partitioning a space between the second cylinder and the second piston into a second suction space and a second discharge space;
• an intermediate plate for separating the first cylinder from the second cylinder, the intermediate plate having a through-hole that communicates the first discharge space with the second suction space so as to form one expansion chamber;
• and
• a variable vane mechanism configured to control movement of the first vane so that a ratio of a period P2 to a period P1 (P2/P1) can be adjusted, where P1 denotes the period during which the first vane is in contact with the first piston in the course of one rotation of the shaft, and P2, denotes the period during which the first vane is spaced from the first piston in the course of one rotation of the shaft, and
• an oil reservoir for storing oil for lubrication,
• wherein the variable vane mechanism controls the movement of the first vane so that a confined volume of the expansion chamber can be adjusted by changing the ratio (P2/P1), when a point in time when the first piston reaches a top dead center is a starting point of the period P2, and
• the variable vane mechanism includes:
• an oil chamber that communicates with the first vane groove so that the oil can be supplied to the first vane groove and the oil can be received from the first vane groove;
• an oil passage, for supplying the oil in the oil reservoir to the oil chamber, and for discharging the oil in the oil chamber to the oil reservoir;
• and
• an opening-adjustable valve provided in the oil passage so that a flow resistance of the oil passage can be increased or decreased.