Magnetic fluid shaft sealing device and method and device for driving the same

PURPOSE:To provide a magnetic fluid shaft sealing device which can prevent breakage of magnetic fluid film without controlling pressure of an intermediate chamber with high precision in the magnetic fluid shaft sealing device which utilizes the intermediate chamber for differential air exhaust. CONSTITUTION:It is a magnetic fluid shaft sealing device which has a main pole piece 2 which faces a process chamber 21 and is arranged around a rotary shaft 1, a main magnet 3 which is arranged close to or in contact with the main pole piece 2, an intermediate chamber 31 which is surrounded by magnetic closed circuit which is formed by the main magnet 3, and a pump 18 which exhausts air in the intermediate chamber 31. Difference in pressure between the process chamber 21 and intermediate chamber 31 is maintained by a magnetic fluid film 4 which is formed between the main pole piece 2 and the rotary shaft 1. The main magnet 3 which forms the magnetic fluid film 4 is arranged quite close to the main pole piece 3.