Axial-flow blood pump with magnetically suspended, radially and axially stabilized impeller

• US 7,070,398 B2
• Filed: 09/24/2004
• Issued: 07/04/2006
• Est. Priority Date: 09/25/2003
• Status: Expired due to Fees

• Current Assignee: Medforte Research Foundation, University of Virginia Patent Foundation (University of Virginia)
• Original Assignee: Medforte Research Foundation
• Inventors: Li, Guoxin, Kipp, Ronald, Wood, Houston G., Lin, Zongli, Jiang, Wei, Allaire, Paul E., Olsen, Don B.
• Primary Examiner(s): FREAY, CHARLES GRANT
• Application Number:
  US10/949,884
• Publication Number:
  US 20050135948A1
• Time in Patent Office: 648 Days
• Field of Search: 417/352, 417/353, 417/365, 417/423.12, 417/355, 417/356, 623/3.13, 623/31.4
• US Class Current: 417/353
• CPC Class Codes: A61M 60/178 drawing blood from a ventricle and returning the blood to the arterial system via a cannula external to the ventricle, e.g. left or right ventricular assist devices
• CPC Class Codes: A61M 60/237 the blood flow through the rotating member having mainly axial components, e.g. axial flow pumps
• CPC Class Codes: A61M 60/422 the force acting on the blood contacting member being electromagnetic, e.g. using canned motor pumps
• CPC Class Codes: A61M 60/82 Magnetic bearings
• CPC Class Codes: F16C 2316/18 Pumps for pumping blood
• CPC Class Codes: F16C 32/0448 by using the electromagnet itself as sensor, e.g. sensorless magnetic bearings
• CPC Class Codes: F16C 32/0461 of stationary parts of the magnetic circuit

Abstract

A blood pump has an impeller rotatably disposed and magnetically suspended within a cavity of a stator by a plurality of magnetic bearings including an axial bearing to support the impeller axially in the cavity. The axial bearing includes adjacent impeller magnets and adjacent stator magnets with axially aligned polarities and reverse polarities with respect to adjacent magnets. A motor includes impeller magnets on the impeller and coils and poles associated with the stator. Radial permanent magnet and electromagnetic bearings are also included. The magnetic bearings and the motor have stator magnets or coils and poles disposed radially across the fluid passage from corresponding impeller magnets to define an annular gap positioned radially between the impeller and the stator, and positioned radially between all of the plurality of magnetic bearings, creating a straight through blood path without secondary flow paths.

Claims

1. A blood pump, comprising:

a stator having a cavity extending therethrough;

an impeller, rotatably disposed and magnetically suspended within the cavity of the stator, the impeller defining an axis of rotation, and the stator and impeller defining a fluid passage therebetween;

a plurality of magnetic bearings, including passive permanent and active electromagnetic magnets, suspending the impeller within the cavity of the stator, including an axial bearing to support the impeller axially in the cavity;

the axial bearing including an array of adjacent bearing sets arrayed axially with respect to the axis of rotation, each bearing set including an impeller magnet on the impeller and a stator magnet on the stator, the impeller and stator magnets being radially aligned across the fluid passage from one another;

adjacent impeller magnets and adjacent stator magnets having axially aligned polarities and reverse polarities with respect to adjacent magnets; and

a motor including impeller magnets on the impeller and coils/magnetic poles associated with the stator.

2. A blood pump in accordance with claim 1, wherein the impeller and stator magnets of each bearing set have reversed polarity with respect to one another.

3. A blood pump in accordance with claim 1, wherein all of the magnetic bearings and the motor have stator magnets or coils/magnetic poles disposed radially across the fluid passage from corresponding impeller magnets to define an annular gap positioned radially between the impeller and the stator, and positioned radially between all of the plurality of magnetic bearings.

4. A blood pump in accordance with claim 1, wherein the plurality of magnetic bearings includes permanent magnet and electromagnetic bearings, with a single, substantially unobstructed fluid passage extending through the stator and around the impeller, between the permanent magnet and electromagnetic bearings, to define a single, substantially unobstructed blood path.

5. A blood pump in accordance with claim 1, wherein the impeller is magnetically suspended within the cavity of the stator without structure spanning the cavity of the stator to define a single, substantially unobstructed blood path through the cavity of the stator and around the impeller.

6. A blood pump in accordance with claim 1, wherein all of the passive permanent magnetic bearings include passive permanent impeller magnets disposed in the impeller, and passive permanent stator magnets disposed on the stator and around the cavity of the stator, without any passive permanent stator magnet disposed in the cavity of the stator.

7. A blood pump in accordance with claim 1, further comprising:

an infuser with at least one inductor blade, disposed on the stator at an inlet of the cavity, and aligned substantially axially with respect to the axis of rotation; and

a diffuser with at least one diffuser blade, disposed on the stator at an outlet of the cavity, and oriented substantially helically with respect to the axis of rotation.

8. A blood pump in accordance with claim 1, wherein the plurality of magnetic bearings further includes a radial permanent magnet bearing, including:

at least a pair of adjacent bearing sets positioned axially with respect to the axis of rotation, each bearing set including an impeller magnet on the impeller and a stator magnet on the stator, the impeller and stator magnets being radially aligned across the fluid passage from one another;

adjacent impeller magnets and adjacent stator magnets having axially aligned polarities and reverse polarities with respect to one another.

9. A blood pump in accordance with claim 8, wherein the impeller and stator magnets of each bearing set of the radial permanent magnet bearing have the same polarity with respect to one another.

10. A blood pump in accordance with claim 8, further comprising:

at least two Hall effect sensors, associated with the stator, one of the Hall effect sensors being positioned to sense a magnetic field produced by the impeller magnets of the axial permanent magnet bearing, and another Hall effect sensor positioned at a different axial location to sense a different magnetic field produced by the impeller magnets of the radial permanent magnet bearing.

11. A blood pump in accordance with claim 8, wherein the plurality of magnetic bearings further includes a radial electromagnetic bearing, including:

impeller magnets, disposed in the impeller; and

coils/magnetic poles, associated with the stator;

the impeller magnets and the coils/magnetic poles positioned radially across the fluid passage from one another.

12. A blood pump in accordance with claim 11, further comprising:

inductor blades, disposed on the stator at an inlet of the cavity;

the poles of the radial electromagnet bearing being disposed within the inductor blades.

13. A blood pump in accordance with claim 11, wherein:

the radial electromagnet bearing is disposed at an inlet to the fluid passage;

the radial permanent magnet bearing is disposed nearer an outlet to the fluid passage; and

the axial permanent magnet bearing is disposed intermediate the radial electromagnet bearing and the radial permanent magnet bearing.

14. A blood pump in accordance with claim 11, further comprising:

a can, radially surrounding the cavity of the stator, and separating the coils/magnetic poles of the stator from the fluid passage.

15. A blood pump in accordance with claim 11, further comprising:

at least two controllers with different biasing current, each operatively coupled to the radial electromagnetic bearing, configured to switch from one to another with one of the controllers starting before another stops.

16. A blood pump in accordance with claim 1, wherein the impeller further includes:

an elongated body; and

at least one helical vane extending from the tubular body and into the fluid passage.

17. A blood pump in accordance with claim 1, wherein the impeller and stator magnets of the adjacent bearing sets include an annular impeller magnet and an annular stator magnet radially surrounding and coaxial with the annular impeller magnet.

18. A blood pump in accordance with claim 1, further comprising:

at least one Hall effect sensor, associated with the stator, and positioned to sense a magnet disposed in the impeller; and

a can, disposed between the at least one Hall effect sensor and the magnet disposed in the impeller.

19. A blood pump in accordance with claim 1, wherein the motor has a direction of rotation that is forced to be unidirectional.

20. A blood pump in accordance with claim 19, wherein the motor further includes:

off-set stator poles which taper to create a magnetic gap between a leading pole edge in a desired direction of rotation smaller than another magnetic gap between a trailing pole edge in an opposite direction of rotation.

21. A blood pump, comprising:

a stator having a cavity extending therethrough;

an impeller, rotatably disposed and magnetically suspended within the cavity of the stator, the impeller defining an axis of rotation, and the stator and impeller defining a fluid passage therebetween;

a plurality of magnetic bearings, including permanent and electromagnet bearings, suspending the impeller within the cavity of the stator, including an axial bearing to support the impeller axially in the cavity;

the axial bearing including an array of adjacent bearing sets arrayed axially with respect to the axis of rotation, each bearing set including an impeller magnet on the impeller and a stator magnet on the stator, the impeller and stator magnets being radially aligned across the fluid passage from one another;

adjacent impeller magnets and adjacent stator magnets having axially aligned polarities and reverse polarities with respect to adjacent magnets;

a motor including impeller magnets on the impeller and coils/magnetic poles associated with the stator; and

all of the magnetic bearings and the motor having stator magnets or coils/magnetic poles disposed radially across the fluid passage from corresponding impeller magnets to define an annular gap positioned radially between the impeller and the stator, and positioned radially between all of the plurality of magnetic bearings.

22. A blood pump, comprising:

a stator with a cavity extending therethrough;

an impeller, rotatably disposed and magnetically suspended within the cavity of the stator, and defining an axis of rotation;

a fluid passage, defined between the stator and the impeller, configured to receive a flow of blood; and

a plurality of magnetic bearings, including permanent and electromagnetic bearings, suspending the impeller within the cavity of the stator, including an axial magnetic bearing to support the impeller axially in the cavity, the axial magnetic bearing including;

a plurality of adjacent impeller magnets disposed axially on the impeller; and

a plurality of adjacent stator magnets disposed axially on the stator; and

the impeller magnets and the plurality of stator magnets being radially aligned across the fluid passage from one another;

the plurality of impeller magnets and the plurality of stator magnets having axially aligned poles with respect to the axis of rotation;

each of the plurality of impeller magnets having sequentially alternating polarity with respect to adjacent impeller magnets with adjacent impeller magnets having opposite axially aligned polarity, each of the plurality of stator magnets having sequentially alternating polarity with respect to adjacent stator magnets with adjacent stator magnets having opposite axially aligned polarity; and

a motor including impeller magnets on the impeller and coils/magnetic poles associated with the stator.

23. A blood pump, comprising:

a) a stator having a cavity extending therethrough;

b) an impeller, rotatably disposed and magnetically suspended within the cavity of the stator, the impeller defining an axis of rotation, and the stator and impeller defining a fluid passage therebetween;

c) a radial, active, electromagnet bearing, disposed nearer an inlet to the fluid passage, to radially support the impeller in the cavity, including;

i) an impeller magnet, disposed nearer a leading end on the impeller; and

ii) a plurality of poles and coils, disposed on the stator radially across the fluid passage from the impeller magnet;

d) an axial, passive, permanent magnet bearing, disposed intermediate along the fluid passage, to axially support the impeller in the cavity, including;

i) a plurality of impeller magnets, disposed intermediate along the impeller, the impeller magnets having axially oriented polarities with sequentially altering polarity; and

ii) a plurality of stator magnets, disposed on the stator radially across the fluid passage from the impeller magnets, the stator magnets having axially oriented polarity with sequentially alternating polarity; and

iii) the impeller and stator magnets being radially aligned across the fluid passage from one another with the polarity of the impeller and stator magnets oppositely aligned with opposite polarities radially aligned across the fluid passage;

e) a radial, passive, permanent magnet bearing, disposed nearer an outlet of the fluid passage, to radially support the impeller in the cavity, including;

i) a plurality of impeller magnets, disposed near a trailing end of the impeller, the impeller magnets having axially oriented polarities with sequentially alternating polarity; and

ii) a plurality of stator magnets, disposed on the stator radially across the fluid passage from the impeller magnets, the stator magnets having axially oriented polarities with sequentially alternating polarity; and

iii) the impeller and stator magnets being radially aligned across the fluid passage from one another with the polarities of the impeller and stator magnets commonly aligned with common polarities radially aligned across the fluid passage; and

f) a motor including impeller magnets on the impeller and coils/magnetic poles associated with the stator.

24. A blood pump in accordance with claim 23, wherein the impeller and stator magnets of the axial, passive, permanent magnet bearing have reversed polarity with respect to one another.

25. A blood pump in accordance with claim 23, wherein the impeller and stator magnets of the radial, passive, permanent magnet bearing have the same polarity with respect to one another.

26. A blood pump in accordance with claim 23, wherein all of the magnetic bearings and the motor have stator magnets or coils/magnetic poles disposed radially across the fluid passage from corresponding impeller magnets to define an annular gap positioned radially between the impeller and the stator, and positioned radially between all of the plurality of magnetic bearings.

27. A blood pump in accordance with claim 23, further comprising:

at least two Hall effect sensors, associated with the stator, one of the Hall effect sensors being positioned to sense a magnetic field produced by the impeller magnets of the axial, passive, permanent magnet bearing, and another Hall effect sensor positioned at a different axial location to sense a different magnetic field produced by the impeller magnets of the radial, passive, permanent magnet bearing.

28. A blood pump in accordance with claim 23, further comprising:

inductor blades, disposed on the stator at an inlet of the cavity;

the poles of the radial, active, electromagnet bearing being disposed within the inductor blades.

29. A blood pump in accordance with claim 23, further comprising:

at least two controllers with different biasing current, each operatively coupled to the radial, active, electromagnet bearing, configured to switch from one to another with one of the controllers starting before another stops.

30. A blood pump in accordance with claim 23, wherein the motor further includes:

off-set stator poles which taper to create a magnetic gap between a leading pole edge in a desired direction of rotation smaller than another magnetic gap between a trailing pole edge in an opposite direction of rotation.