Magnetically suspended pump

Abstract

An axial now blood pump includes a pump housing and first and second stator permanent magnets fixed to the pump housing. A rotor assembly is disposed within the pump housing and includes first and second rotor permanent magnets. The first fixed permanent magnet may be axially offset from the first rotor permanent magnet and the second fixed permanent magnet may be axially offset from the second rotor permanent magnet. The permanent magnets act as passive radial bearings with maintain the rotor coaxial with the housing, and also exert axial forces on the first and second rotor permanent magnets to urge the rotor towards an equilibrium axial position relative to the housing. The rotor may be suspended and positioned within the housing solely by operation of the permanent magnets.

1 . A blood pump comprising:
 a housing having an axis;   first and second stator permanent magnets fixed relative to the housing at axially-spaced locations;   a rotor having an axis disposed within the pump housing including a first rotor permanent magnet associated with and magnetically interacting with the first stator permanent magnet and a second rotor permanent magnet associated with and magnetically interacting with the second stator permanent magnet, so that the interacting magnets urge the rotor into an alignment coaxial with the housing,   wherein the first stator permanent magnet exerts a first axial force on the first rotor permanent magnet in a first axial direction and the second stator permanent magnet exerts a second axial force on the second rotor permanent magnet in a second axial direction opposite to the first axial direction.   
     
     
         2 . A blood pump as claimed in  claim 1 , wherein, over an operating range of axial positions of the rotor relative to housing, the first axial force decreases and the second axial force increases upon movement of the rotor relative to the housing in the first axial direction, whereas the first axial force increases and the second axial force decreases with movement of the rotor relative to the housing in the second axial direction, whereby the first and second axial forces urge the rotor towards an equilibrium position within the operating range. 
     
     
         3 . A blood pump as claimed in  claim 2 , wherein, in operation, the rotor is suspended and positioned within the housing without contact between the rotor and the housing. 
     
     
         4 . A blood pump as claimed in  claim 3 , wherein, in operation, the rotor is suspended and positioned within the housing without feedback control of the axial position of the rotor. 
     
     
         5 . A blood pump as claimed in  claim 3 , wherein, in operation, the rotor is suspended and positioned within the housing solely by the permanent magnets. 
     
     
         6 . A blood pump as claimed In  claim 2 , wherein each stator permanent magnet is generally tubular and symmetrical about the axis of the housing and defines a plurality of opposite magnetic poles axially spaced from one another. 
     
     
         7 . A blood pump as claimed in  claim 6 , wherein each rotor permanent magnet is symmetrical about the axis of the rotor and defines a plurality of opposite magnetic poles axially spaced from one another, and wherein the first rotor permanent magnet is at least partially disposed within the first stator permanent magnet, the second rotor permanent magnet being at least partially disposed within the second stator permanent magnet. 
     
     
         8 . A blood pump as claimed in  claim 7 , wherein the first stator permanent magnet has poles disposed at first axial locations and the first rotor permanent magnet has identical poles disposed at the same first axial locations, plus a first offset distance in the first axial direction, and wherein the second stator permanent magnet has poles disposed at second axial locations and the second rotor permanent magnet has identical poles disposed at the same second axial locations, plus an second offset distance in the second axial direction. 
     
     
         9 . A blood pump as claimed in  claim 8 , wherein the first offset distance is less than an axial spacing distance between any two opposite poles of the first stator permanent magnet and the second offset distance is less than an axial spacing distance between any two opposite poles of the second stator permanent magnet. 
     
     
         10 . A blood pump as claimed in  claim 2 , wherein each stator permanent magnet includes at least one magnetic ring element coaxial with the axis of the housing and each rotor permanent magnet includes at least one magnetic disc or ring element coaxial with the axis of the rotor. 
     
     
         11 . A blood pump as claimed in  claim 10 , wherein each stator permanent magnet includes a plurality of magnetic ring elements having like magnetic poles facing axially toward one another and each rotor permanent magnet includes a plurality of magnetic ring or disc elements having like magnetic poles facing axially toward one another. 
     
     
         12 . The blood pump of  claim 1 , wherein the pump housing has an inflow end and an outflow end, the axis of the housing extends between the inflow and outflow ends, and the rotor includes impeller surfaces arranged to impel blood toward the outflow end upon rotation of the rotor about the axis of the rotor. 
     
     
         13 . The blood pump of  claim 12 , wherein the first rotor permanent magnet is positioned closer to the inflow end than the first stator permanent magnet and the second rotor permanent magnet is positioned closer to the outflow end than second stator permanent magnet, the first stator permanent magnet exerts an axial force on the first rotor permanent magnet toward the inflow end, and the second stator permanent magnet exerts an axial force on the second rotor permanent magnet toward the outflow end. 
     
     
         14 . The blood pump of  claim 12 , wherein the first rotor permanent magnet is positioned further from the inflow end than the first stator permanent magnet, the second rotor permanent magnet is positioned further from the outflow end than the second stator permanent magnet, the first stator permanent magnet exerts a force on the first rotor permanent magnet toward the outflow end, and the second stator permanent magnet exerts a force on the second rotor permanent magnet toward the inflow end.