PURPOSE: To improve lubricity by providing an oil extracting port on a lower bearing between a permanent magnet fixed to the lower bearing having an oil groove communicated to the oil sump section of a piston section and a rotor inside it.
CONSTITUTION: A fixed shaft 6 is constituted integrally with a shaft 1 and a piston section 2, and a permanent magnet 16 is fixed to a lower bearing 14. An oil extracting port 20 is provided in a gap 21 between the permanent magnet 16 fixed to the lower bearing 14 and a rotor inside it to penetrate the lower bearing 14. The oil lubricating an upper bearing 12 is scattered to the inner wall of a housing 18 then drops to the lower section of the housing 18 through the oil extracting port 20, thus the oil quantity required for lubrication can be invariably secured.
WATANABE TAKEJI
NOGUCHI MASAO
