US Patent 7100923 Magnetic fluid seal device

A magnetic fluid seal device that increases a permissible value of eccentricity for two members to improve sealability and decreases a variation of quality by injecting a magnetic fluid before assembling of parts, that saves structural members to achieve thinning, and that is easy to produce. An annular magnet 3 is buoyantly supported by the magnetic fluid 4 and 5 retained, and the space between a housing 1 and a shaft 2 is sealed by the annular magnet 3 and magnetic fluid 4 and 5.