Patent ID: 7713040

Claim:
A rotor shaft sealing structure of an oil-free rotary compressor having a pair of male and female rotors accommodated in a compression chamber formed by a rotor casing, each rotor having a rotor shaft extending from both end faces of the rotor to penetrate both side walls of the rotor casing to be supported by the rotor casing via oil lubricated bearings by both the side walls of the rotor casing, the rotor shaft sealing structure comprising: a rotor shaft sealing part comprising two shaft seals provided at each of rotor shaft bearing parts between the bearing and the compression chamber such that an annular airspace is formed between the shaft seals; and a pressurized air supplier that supplies pressurized air to each of the annular airspaces formed between the shaft seals provided at each of the rotor shaft bearing parts; wherein at least one communicating hole for communicating each annular airspace to the outside of the rotor casing is provided such that the communicating hole opens at a bottom part of the annular airspace to communicate the annular airspace to the outside of the rotor casing, and each of the annular airspaces of the male rotor shaft sealing parts and each of those of the female rotor shaft sealing parts are connected by a between-rotor shaft communication passage respectively so that pressurized air supplied to each annular airspace of one of the rotor shaft sealing parts is supplied to each annular airspace of the other rotor shaft sealing part; and wherein pressurized air passages are formed in the rotor casing that respectively connect to said between-rotor shaft communication passages and the pressurized air supplier supplies air to each of the annular airspaces through the pressurized air passages.