Rotary blood pump with opposing spindle magnets, bore and drive windings
Various “contactless” bearing mechanisms including hydrodynamic and magnetic bearings are provided for a rotary pump as alternatives to mechanical contact bearings. In one embodiment, a pump apparatus includes a pump housing defining a pumping chamber. The housing has a spindle extending into the pumping chamber. A spindle magnet assembly includes first and second magnets disposed within the spindle. The first and second magnets are arranged proximate each other with their respective magnetic vectors opposing each other. The lack of mechanical contact bearings enables longer life pump operation and less damage to working fluids such as blood.
1. A method of suspending a rotor in a centrifugal blood pump during pumping comprising:
disposing the rotor in a housing assembly around a center post;
biasing said rotor axially in a first direction prior to rotation of said rotor;
causing said rotor to rotate and thereby pump blood ;
inducing hydrodynamic forces on said rotor in opposition to said biasing of said rotor;
balancing said biasing and said hydrodynamic forces so as to suspend said rotor in said housing assembly during rotation of said rotor; and,
further comprising adjusting the configuration of a passive axial magnetic bearing between said center post and said rotor so as to modify the biasing of said rotor axially in said first direction.
2. A method according to claim 1 , wherein inducing hydrodynamic forces includes causing a film of blood to form on contoured surfaces between said rotor and said housing assembly during rotation of the rotor.
3. A method according to claim 2 , wherein said contoured surfaces are curved and tapered ramps.
4. A method according to claim 3 , wherein said contoured surfaces are disposed on said rotor.
5. A method according to claim 1 , wherein said adjusting includes axially moving said center post component of said passive axial magnetic bearing relative to rotor component of said passive axial magnetic bearing.
6. A method according to claim 1 , further comprising causing leakage flow of said blood to occur between an annular gap between said center post and said rotor.
7. A method of operating a centrifugal blood pump comprising:
obtaining a centrifugal blood pump having a housing that encloses a spindle as well as a rotor that is positioned to spin around said spindle and wherein said rotor is biased axially in a first direction prior to spinning of said rotor;
causing said rotor to spin and thereby pump blood;
inducing hydrodynamic forces on said rotor in opposition to said biasing of said rotor;
balancing said biasing and said hydrodynamic forces so as to suspend said rotor in said housing during spinning of said rotor, and
wherein said rotor is biased axially by passive magnetic forces between the rotor and the spindle.
8. A method according to claim 7 , wherein inducing hydrodynamic forces includes causing a film of blood to form on contoured surfaces between said rotor and said housing assembly.
9. A method according to claim 8 , wherein said contoured surfaces are curved and tapered ramps.
10. A method according to claim 9 , wherein said contoured surfaces are disposed on said rotor.
11. A method according to claim 7 , further comprising adjusting the configuration of a passive axial magnetic bearing between said spindle and said rotor so as to modify the biasing of said rotor axially in said first direction.
12. A method according to claim 11 , wherein said adjusting includes axially moving a spindle component of said passive axial magnetic bearing relative to a rotor component of said passive axial magnetic bearing.
13. A method according to claim 7 , further comprising causing leakage flow of said blood to occur between an annular gap between said spindle and said rotor.
14. A method of balancing a rotor in a centrifugal blood pump comprising:
obtaining said pump in a state where said rotor is pre-biased in a first direction before rotation of said rotor;
causing said rotor to rotate and thereby pump blood;
inducing hydrodynamic forces on said rotor in opposition to said pre-biasing of said rotor;
balancing said pre-biasing and said hydrodynamic forces so as to suspend said rotor during rotation of said rotor, and
further comprising adjusting the configuration of a passive axial magnetic bearing between a center post and said rotor so as to modify the pre-biasing of said rotor axially in said first direction.
15. A method according to claim 14 , wherein inducing hydrodynamic forces includes causing a film of blood to form on contoured surfaces between said rotor and a housing assembly of said centrifugal blood pump.
16. A method according to claim 15 , wherein said contoured surfaces are curved and tapered ramps.
17. A method according to claim 16 , wherein said contoured surfaces are disposed on said rotor.
18. A method according to claim 15 , wherein said rotor is pre-biased by magnetic forces.
19. A method according to claim 14 , wherein said adjusting includes axially moving said center post component of said passive axial magnetic bearing relative to rotor component of said passive axial magnetic bearing.
20. A method according to claim 14 , further comprising causing leakage flow of said blood to occur between an annular gap between said center post and said rotor.