Abstract: A refrigerant circulating system that uses a highly polar refrigerant, as typified by a hydrofluorocarbon-based one, and a refrigerating oil that has slight solubility with a liquid refrigerant on the condensation side. Also, a refrigerant circulating cycle that uses a highly polar refrigerant, as typified by a hydrofluorocarbon-based one, and a refrigerating oil that has a slight solubility with a liquid refrigerant and which has a greater specific gravity than the liquid refrigerant. Thereby, it provides a high electrical insulation and moisture resistance, good oil return to the compressor, and high reliability.

Abstract: A multicylinder rotary compressor has a plurality of cylinders housing rolling pistons which are rotated inside the cylinders by a common crankshaft. Each cylinder has a separate suction pipe. At least one of the suction pipes has a check valve which may be closed to unload the cylinder to which the suction pipe is connected. The check valve has a housing and a slider which can slide inside the housing between an open position and a closed position. The check valve may be closed by introduction of high-pressure refrigerant gas into the space beneath the slider to push it to the closed position when a cylinder is to be unloaded. In another form of the invention, the check valve is closed by a spring made of a shape-memory alloy and a heater for heating the spring above a prescribed temperature at which the allow changes shape. When a cylinder is to be unloaded, the heater is turned on, and the shape-memory alloy deforms into a shape such as to force the slide to the closed position.

Abstract: A belt-pulley drive mechanism comprising a pulley having a plurality of circumferentially extending grooves of V-shaped cross-sectional configuration, a belt adapted to be passed around the pulley and stretched under tension so that the belt is engaged with the pulley in torque transmitting relationship, the belt being formed with a plurality of longitudinally extending ridges of V-shaped cross-sectional configuration which are adapted to be engaged with the grooves in the pulley when the tension is applied to the belt. The grooves or the ridges or both are formed in a cross-section along a concave line so that a clearance is formed between the pulley and the belt when the tension is removed from the belt, the clearance being larger at a transversely central portion than at side edge portions.