Abstract: In a lysholm compressor having intermeshing male and female rotors rotated in a casing to compress an axially flowing gas, discharge-side shafts of the rotors are borne by discharge-side bearings to fix the discharge-side shafts in thrust direction while suction-side shafts of the rotors are borne by suction-side bearings to allow the suction-side shafts to move in the thrust direction. Clearances of the rotors to the casing are properly set or selected.

Abstract: Oil feed and discharge lines (34) and (35) are respectively connected between an engine (15) and an external oil feed type engine-driven supercharger (I) so as to circulate a lubricating oil (0) between them. The lubricating oil (0) used in the engine (15) is fed through the oil feed line (34) to the supercharger (I) while the lubricating oil (0) used in the supercharger (I) is returned through the oil discharge line (34) to the engine (15). As a result, the lubricating oil and associated parts exclusively for the supercharger can be eliminated.

Abstract: The center of gravity of a retaining pin which is struck into a retaining-pin receiving hole to join a rotor barrel with a rotor shaft is eccentrically positioned toward the leading end of the pin beyond the axis of the shaft so that upon rotation of the rotor, the pin is forced to thrust toward the bottom of the hole by the centrifugal force, thereby preventing the pin from pulling out of the hole.