Shaft seal device

A shaft seal assembly sealing between a housing and a rotation shaft inserted into an axial hole of the housing, comprising:

• a seal cover formed in a cylindrical shape and provided on an outer periphery of the rotation shaft;
• a flexible member that connects the seal cover to the housing;
• an auxiliary seal portion provided on an interior side of the shaft seal device in an axial direction of the seal cover;
• a magnetic fluid seal portion provided on an exterior side of the shaft seal device from the auxiliary seal portion in the axial direction of the seal cover;
• and
• a bearing unit that supports a load of the magnetic fluid seal portion,
• the shaft seal device sealing an annular clearance formed between the axial hole of the housing and the rotation shaft inserted into the axial hole, wherein
• a pressure buffering chamber in which pressure is maintained to be lower than pressure in an external space of the housing is provided between the auxiliary seal portion and the magnetic fluid seal portion in the seal cover, wherein
• in the seal cover, a communication passage providing communication between the pressure buffering chamber and a vacuum pump is provided at a position between the auxiliary seal portion and the magnetic fluid seal portion in the axial direction of the seal cover,
• the bearing unit includes a pair of bearings between which the magnetic fluid seal portion is sandwiched in the axial direction, and
• the communication passage is positioned between the auxiliary seal portion and one of the pair of bearings positioned on the interior side.