Expander-compressor unit and refrigeration cycle apparatus having the same

An expander-compressor unit comprising:

• a closed casing having, in a bottom portion thereof, an oil reservoir for holding an oil;
• a motor provided in the closed casing;
• a compression mechanism for compressing a working fluid drawn from outside of the closed casing and discharging it into the closed casing, the compression mechanism being disposed below the motor in the closed casing;
• an expansion mechanism for allowing the working fluid drawn from outside of the closed casing to expand and discharging it out of the closed casing, the expansion mechanism being disposed below the compression mechanism in the oil reservoir in the closed casing;
• a shaft extending vertically and being coupled to the motor, the compression mechanism, and the expansion mechanism;
• a first oil supply passage for supplying the oil held in the oil reservoir to the compression mechanism;
• and
• a second oil supply passage for supplying the oil held in the oil reservoir to the expansion mechanism,
• wherein the compression mechanism and the expansion mechanism are separated from each other so that a buffer space extending around the shaft is formed between the compression mechanism and the expansion mechanism in the oil reservoir,
• a first oil suction portion for drawing the oil in the oil reservoir toward the first oil supply passage is located above the expansion mechanism and faces the buffer space,
• a second oil suction portion for drawing the oil in the reservoir toward the second oil supply passage is located below the first oil suction portion
• the shaft has a compression mechanism side shaft coupling the motor to the compression mechanism, and an expansion mechanism side shaft connected to the expansion mechanism,
• the expander-compressor unit further comprises a coupling mechanism for coupling the compression mechanism side shaft to the expansion mechanism side shaft at a position between the compression mechanism and the expansion mechanism
• a vertical flow passage extending in an axial direction of the compression mechanism side shaft and opening at least downward is formed in the compression mechanism side shaft;
• a stopper member for closing a lower side of the vertical flow passage is inserted into a lower end portion of the compression mechanism side shaft;
• a suction port opening laterally in the compression mechanism side shaft and leading to the vertical flow passage is formed in a portion of the compression mechanism side shaft, the portion being above the stopper member;
• and
• the vertical flow passage constitutes the first oil supply passage, and the suction port constitutes the first oil suction portion.