Sensorless magnetic bearing type blood pump apparatus

A sensorless magnetic bearing type blood pump apparatus comprising:

• a blood pump;
• and
• a control mechanism for controlling the blood pump;
• the blood pump comprising:
• a housing having a liquid inflow port and a liquid outflow port;
• a rotatable body rotatably positioned in the housing to feed liquid and provided with a first magnetic body;
• a rotating body rotational torque generating unit which attracts the first magnetic body of the rotatable body to rotate the rotatable body;
• a rotating body magnetic bearing unit which magnetically attracts the rotatable body in a direction different from a direction of attraction of the rotatable body by the rotating body rotational torque generating unit to rotate the rotatable body in a non-contact condition in the housing;
• a hydrodynamic bearing section provided in an inside surface of the housing on a side of the rotating body rotational torque generating unit, or in a surface of the rotatable body on a side of the rotating body rotational torque generating unit, to permit the rotatable body to be rotated in a non-contact condition in the housing in a hydrodynamic bearing mode when operation of the rotating body magnetic bearing unit in a magnetic bearing mode is stopped;
• the blood pump apparatus being devoid of any sensor for measuring a position of the rotatable body;
• and
• the rotating body magnetic bearing unit comprising an electromagnet in the rotatable body for attracting the first magnetic body or a second magnetic body provided separately from the first magnetic body;
• the control mechanism comprising:
• a pulse width modulation type electromagnet driving unit for driving the electromagnet;
• a carrier component measuring unit for measuring carrier components of voltage and current in the pulse width modulation type electromagnet driving unit;
• rotating body position data and modulation factor calculating units which respectively calculate rotating body position data and a modulation factor of a pulse width modulated waveform using carrier wave data measured by the carrier component measuring unit;
• rotating body position controlling means for controlling the pulse width modulation type electromagnet driving unit utilizing the rotating body position data calculated by the rotating body position data calculating unit;
• monitoring means for monitoring a current of the rotating body rotational torque generating unit;
• bearing mode changing-over means for effecting change-over from the magnetic bearing mode to the hydrodynamic bearing mode by stopping driving of the pulse width modulation type electromagnet driving unit when the modulation factor calculated by the modulation factor calculating unit is outside a predetermined range and for restarting the driving of the pulse width modulation type electromagnet driving unit to return to the magnetic bearing mode upon confirmation of satisfaction of predetermined conditions after the change-over to the hydrodynamic bearing mode, the bearing mode changing-over means effecting the return to the magnetic bearing mode by judging that the predetermined conditions are satisfied when the monitoring means determines that the rotating body rotational torque generating unit current is within a current range of the rotating body rotational torque generating unit.