Patent ID: 7128538

Claim:
A centrifugal fluid pump apparatus comprising a pump body in which an impeller rotates without contacting a housing; and a control mechanism for said pump body, said pump body including: said housing having a blood inlet port and a blood outlet port; a centrifugal pump section including an impeller having a first magnetic material and a second magnetic material and rotating in said housing to feed a fluid by a centrifugal force generated during its rotation; an impeller rotational torque generation section including a rotor having a magnet for attracting said first magnetic material of said impeller and a motor for rotating said rotor; an impeller position control section having an electromagnet for attracting said second magnetic material of said impeller; a position sensor for detecting a position of said impeller; and hydrodynamic bearing means provided on an inner surface of said housing at a side of said rotor or on a surface of said impeller at a side of said rotor, said control mechanism comprising: a position sensor output monitoring function or an electromagnet current monitoring function; a motor current monitoring function; a failure detection function for determining a failure of the sensor by using said position sensor output monitoring function or a failure of the electromagnet by using said electromagnet current monitoring function; and an emergency impeller rotation function operating when said failure detection function detects the failure of the sensor or the failure of the electromagnet to rotate said impeller by utilizing said hydrodynamic bearing means without substantial contact between said impeller and said housing, wherein said emergency impeller rotation function has: rotation termination function of terminating power to the motor and the electromagnet when the failure detection function detects a failure to thereby terminate rotation of the rotor and the impeller; impeller magnetic counterforce application function to apply a current to the electromagnet sufficient to overcome the magnetic coupling force of the rotor to the impeller caused by the magnet; hydrodynamic levitation control detection function of detecting hydraulic bearing coupling and thereby magnetic rotational coupling of the impeller and the rotor under hydraulic bearing conditions by using a motor current monitored by the motor current monitoring function; motor speed control function for increasing the motor speed and hence the impeller rotation speed up to a predetermined value after the hydrodynamic levitation control detection function detects that the hydraulic bearing coupling between the impeller and the rotor has been made; and impeller magnetic counterforce termination function to terminate current to the electromagnet once the predetermined impeller rotation speed is reached.