Abstract: An oil-free scroll compressor prevents wraps from being broken and provides improved reliability. The oil-free scroll compressor includes an orbiting scroll member and fixed scroll members, and has compression channels into which water is injected each formed between the intake port and exhaust port provided in the fixed scroll member. The oil-free scroll compressor includes temperature sensors each of which detects temperature in the compression channel, regulating valves each of which controls ratio of the amount of the water to be injected into the respective compression channels to the total amount of the water to be injected into the compression channels, and controller which controls the opening degrees of the regulating valves such that a difference between the detected temperatures from the compression channels is small.

Abstract: A screw-type rotary fluid machine such as a compressor or a vacuum pump has male and female rotors which rotate within a casing, with or without mutual contact. At least one of the male and female rotors being surface-treated to have a treated surface structure. The treated surface structure is a multi-layered structures composed of a plurality of layers including a non-electrolytic Ni plating layer and at least one covering layer of organic resin. The organic resin may be one or more kinds selected from a group of engineering plastics, so as to improve mechanical strength.