Magnetically levitated pump apparatus

DETAILED DESCRIPTION Therefore a main object of the present invention is to provide a maglev pump capable of preventing an impeller from impinging against an inner wall of a pump chamber when a command is issued to provide magnetic levitation.
The present invention provides a maglev pump including: a pump unit outputting a fluid through revolution of a rotative member in a casing; a drive unit magnetically coupled with the rotative member without contacting the rotative member, to rotate the rotative member; a position detection unit detecting a position of the rotative member as the rotative member levitates; and a controlled magnetic bearing unit operative in response to an output of the position detection unit to support the rotative member without contacting the rotative member, and it is characterized in that it is provided with a control means controlling a command signal of the controlled magnetic bearing unit to allow the rotative member to have a position closer to the drive unit when the rotative member starts magnetic levitation.
Thus in the present invention the rotative member can be prevented from impinging against an internal wall of the housing when a command is issued to provide magnetic levitation.
Thus the internal wall of the housing can be protected from damage.
Preferably in magnetic levitation the control means shifts the signal output of the position detection unit gradually to a normal value.
More preferably the control means gradually shifts the signal output from the position detection unit in a direction opposite to a normal value to terminate magnetic levitation.
More preferably the maglev pump configures a blood pump.
More preferably the drive unit is switchable between a mode controlling a revolution rate to be constant and a mode controlling a current to be constant and the control circuit controls a revolution rate to be substantially constant when one of the modes is switched to the other of the modes.
Furthermore the control circuit controls a revolution rate within a tolerance of approximately