Active magnetic bearing system for blood pump

DETAILED DESCRIPTION In accordance with the present invention, a rotary blood pump is provided.
The pump comprises a pump housing and a rotor mounted for rotation within the housing.
The rotor has a shaft portion and an impeller carried by the shaft portion.
A rotor motor is provided.
The motor includes a plurality of permanent magnets carried by the impeller and a motor stator including electrically conductive coils and pole pieces located within the housing.
The motor is operable to transmit torque and also to provide an axial magnetic force that acts as an axial bearing.
In the illustrative embodiment, the rotary blood pump includes passive radial magnetic bearings carried by the shaft portion and radial magnetic bearings carried by the housing.
A sensor is provided for detecting axial deflection of the impeller and a circuit is provided for energizing the stator in response to the detector.
In the illustrative embodiment, there is a first motor stator positioned on one side of the impeller and a second motor stator positioned on an opposite side of the impeller.
The motor stators each include electrically conductive coils and pole pieces located within the housing.
A detector senses the axial position of the impeller.
If the axial position is neutral, then current to the stators is not varied.
However, if the axial position is other than neutral the relative currents to the first and second stators are varied to provide an axial force to return the impeller to neutral.
A more detailed explanation of the invention is provided in the following description and claims, and is illustrated in the accompanying drawings.