Patent ID: 7467930

Claim:
A magnetically levitated pump, comprising: a pump unit including a disk-shaped impeller for feeding liquid; a magnetic bearing unit provided opposite to one of end faces along an axial direction of said impeller; and a casing unit provided opposite to the other of said end faces; wherein said magnetic bearing unit includes: rotary driving means for transmitting a rotational driving force to said impeller, and an electro-magnet for a magnetic bearing; said pump unit includes: a soft magnetic member opposite to the electro-magnet provided on said one of said end faces of said impeller and provided opposite to said electro-magnet for magnetic bearing, and an impeller-side ferromagnetic body provided on said other of said end faces of said impeller; said casing unit includes a casing-side ferromagnetic body provided opposite to said impeller-side ferromagnetic body and attracting said impeller toward said casing unit; said electro-magnet for the magnetic bearing has a magnetizing current flowing therethrough controlled to balance an attractive force between said electro-magnet for the magnetic bearing and said soft magnetic member opposite to the electro-magnet, an attractive force between said impeller-side ferromagnetic body and said casing-side ferromagnetic body, a force acting on said impeller generated by said rotary driving means, and other disturbance influencing said impeller; and opposite surfaces of said impeller-side ferromagnetic body and said casing-side ferromagnetic body are adapted to have mutually different shapes from each other, so that a maximum required attractive force is suppressed between said electro-magnet for the magnetic bearing and said soft magnetic member opposite to the electro-magnet.