阅读说明：本技术 中心杆磁体 (Center rod magnet ) 是由 C·R·山姆巴弗 M·E·塔斯金 S·P·麦克 J·A·拉罗斯 于 2018-05-18 设计创作，主要内容包括：一种泵转子,该泵转子包括限定主纵向轴线的毂。磁体沿着主纵向轴线设置在毂内。多个转子叶片从毂远离纵向轴线向外突出并且沿围绕纵向轴线的周向方向彼此间隔开。多个转子叶片中的每一个在其远离毂的外端处限定流体动力支承部。多个转子叶片限定多个流动通道。多个转子叶片中的每一个均构造成在转子绕轴线旋转时驱动流体通过流动通道。(A pump rotor includes a hub defining a main longitudinal axis. The magnet is disposed within the hub along the major longitudinal axis. A plurality of rotor blades project outwardly from the hub away from the longitudinal axis and are spaced apart from one another in a circumferential direction about the longitudinal axis. Each of the plurality of rotor blades defines a hydrodynamic bearing at its outer end remote from the hub. The plurality of rotor blades define a plurality of flow channels. Each of the plurality of rotor blades is configured to drive a fluid through the flow channel as the rotor rotates about the axis.)

1. A pump rotor, comprising:

a hub defining a main longitudinal axis;

a magnet disposed within the hub along the major longitudinal axis; and

a plurality of rotor blades projecting outwardly from the hub away from the longitudinal axis and spaced apart from one another in a circumferential direction about the longitudinal axis, each of the plurality of rotor blades defining a hydrodynamic bearing at an outer end thereof remote from the hub, the plurality of rotor blades defining a plurality of flow channels, each of the plurality of rotor blades being configured to drive fluid through the flow channels as the rotor rotates about the axis.

2. The rotor of claim 1 wherein the plurality of rotor blades are non-ferromagnetic.

3. The rotor of claim 1 or 2, wherein the plurality of rotor blades define an aggregate area at an outer periphery of the rotor distal from the hub, and wherein the flow channels define an aggregate area at the outer periphery, and wherein the aggregate area defined by the plurality of rotor blades at the outer periphery is greater than the aggregate area defined by the flow channels at the outer periphery.

4. The rotor of any one of claims 1-3 wherein the magnets are solid one-piece and coaxial with the hub, the magnets being radially magnetized and defining a plurality of radial poles.

5. The rotor of claim 4 wherein said magnets are cylindrical.

6. The rotor of any one of claims 1-5, wherein the hub comprises tapered end portions and an intermediate portion disposed between the end portions, the intermediate portion housing the magnets, and the rotor blades extending from the intermediate portion.

7. The rotor of any one of claims 1-6, wherein the magnets comprise neodymium.

8. The rotor of any one of claims 1-7, wherein the plurality of rotor blades and the hub are non-ferromagnetic.

9. The rotor of any one of claims 1-8, wherein the plurality of rotor blades and the hub are made of a polymeric material.

10. The rotor of any one of claims 1-9, wherein the plurality of rotor blades and the hub are made of a biocompatible material, and the magnet comprises a non-biocompatible material.

11. The rotor of any one of claims 1-10 wherein the magnets are enclosed within the rotor.

12. The rotor of claim 11 wherein said magnets are sealed within said rotor.

13. The rotor of any one of claims 1-12, wherein the hub is sized to be received within a human patient.

14. A rotor according to any of claims 1-13, wherein the rotor is dimensioned to be received within an implantable blood pump.

Technical Field

The invention relates to a rotor for a blood pump and to a blood pump having such a rotor.

Background

In certain disease states, the heart lacks sufficient pumping capacity to maintain adequate blood flow to the organs and tissues of the body. For example, diseases such as ischemic heart disease and hypertension may render the heart ineffective for filling and pumping. This disease, also known as congestive heart failure, can lead to serious health complications including respiratory distress, cardiac asthma, and even death. Indeed, congestive heart failure is one of the leading causes of death in the western world.

This deficiency of the heart can be alleviated by providing a mechanical blood pump, also known as a ventricular assist device ("VAD"), to supplement the pumping action of the heart. VADs can be used to assist the right ventricle, left ventricle, or both. For example, the VAD may assist the left ventricle by mechanically pumping oxygenated blood from the left ventricle into the aorta.

One form of VAD includes an axial flow pump. In an axial flow pump, blood is delivered through a chamber from an inlet to an outlet in a path substantially parallel to the axis of rotation of a rotor disposed in the chamber. The rotor has blades that work on the fluid to cause the fluid to flow toward the outlet. As shown, for example, in us patent No. 7,959,551, an axial flow rotor may be supported within a chamber by a support (bearing) separate from the rotor itself and driven by stator coils mounted to the pump and arrayed around the rotor. The stator coils generate a rotating magnetic field that interacts with the rotor to rotate the rotor about its axis. Another axial blood pump shown in U.S. patent No. 7,934,909 uses a system of magnetic and hydrodynamic bearings to support and position the rotor within the chamber. These systems require elements in the flow path other than the rotor hub and blades. These additional elements may impede blood flow through the pump and may cause thrombus to form within the pump.

Another type of blood pump described in U.S. patent No. 7,699,586 ("the' 586 patent"), the disclosure of which is incorporated herein by reference, uses a rotor having wide blades with hydrodynamic bearing surfaces on the tip surfaces of the blades. As the rotor rotates, hydrodynamic interaction between bearing surfaces on the tips of the blades and the chamber walls suspends the rotor in the chamber and maintains the axis of the rotor coaxial with the chamber. Certain embodiments of the rotor shown in the' 586 patent have permanent magnets embedded in the rotor blades. These permanent magnets interact with the rotating magnetic field generated by the stator, causing the rotor to rotate about its axis. The magnetic interaction between the magnets and the ferromagnetic elements incorporated into the stator holds the rotor in a desired position along the axis. However, such an arrangement requires assembly of multiple parts, precise positioning of each magnet, and identical magnetization of the individual magnets to prevent unbalanced forces acting on the rotor, which can be challenging. To avoid these challenges, some wide bladed axial flow rotors have been made as a one-piece body formed of ferromagnetic material with permanent magnetization transverse to the rotor axis. However, the ferromagnetic material from which such rotors are made must not only be ferromagnetic, but must also be biocompatible and wear resistant. Materials such as platinum alloys that can meet both requirements are expensive and difficult to manufacture. Furthermore, magnetic wide bladed rotors are typically made with an even number of blades, most commonly four blades, to ensure balanced operation.

SUMMARY

The present invention advantageously provides a pump rotor including a hub defining a major longitudinal axis. The magnet is disposed within the hub along the major longitudinal axis. A plurality of rotor blades project outwardly from the hub away from the longitudinal axis and are spaced apart from one another in a circumferential direction about the longitudinal axis. Each of the plurality of rotor blades defines a hydrodynamic bearing at its outer end (outer extent) remote from the hub. The plurality of rotor blades define a plurality of flow channels. Each of the plurality of rotor blades is configured to drive a fluid through the flow channel as the rotor rotates about the axis.

In another aspect of this embodiment, the plurality of rotor blades are non-ferromagnetic.

In another aspect of this embodiment, the plurality of rotor blades define an aggregate area (collective area) at an outer periphery of the rotor distal from the hub, and wherein the flow channels define the aggregate area at the outer periphery, and wherein the aggregate area defined by the plurality of rotor blades at the outer periphery is greater than the aggregate area defined by the flow channels at the outer periphery.

In another aspect of this embodiment, the magnet is a one-piece solid body and is coaxial with the hub, the magnet being radially magnetized and defining a plurality of radial poles.

In another aspect of this embodiment, the magnet is cylindrical.

In another aspect of this embodiment, the hub includes tapered end portions and an intermediate portion disposed between the end portions, the intermediate portion housing the magnets, and the rotor blades extending from the intermediate portion.

In another aspect of this embodiment, the magnet comprises neodymium.

In another aspect of this embodiment, the plurality of rotor blades and the hub are non-ferromagnetic.

In another aspect of this embodiment, the plurality of rotor blades and the hub are made of a polymeric material.

In another aspect of this embodiment, the plurality of rotor blades and the hub are made of a biocompatible material and the magnet comprises a non-biocompatible material.

In another embodiment, a blood pump includes a flow chamber defining an axis. A motor stator having stator coils is disposed about the flow chamber. The rotor includes a hub defining a main longitudinal axis. The magnet is disposed within the hub along the major longitudinal axis. A plurality of rotor blades project outwardly from the hub away from the longitudinal axis and are spaced apart from one another in a circumferential direction about the longitudinal axis. Each of the plurality of rotor blades defines a hydrodynamic bearing at its outer end remote from the hub. The plurality of rotor blades define a plurality of flow channels. Each of the plurality of rotor blades is configured to drive a fluid through the flow channel as the rotor rotates about the axis. The stator coil is configured to generate a magnetic field within the flow chamber that rotates about an axis of the flow chamber. The rotating magnetic field interacts with the magnets of the rotor to drive the rotor about its axis.

In another aspect of this embodiment, the motor stator includes back-iron (back-iron), and wherein the magnet and the back-iron passively attract each other during operation and cooperate to limit axial displacement of the rotor within the flow chamber.

In another aspect of this embodiment, the magnet is enclosed within the rotor.

In another aspect of this embodiment, the magnets are sealed within the rotor.

In another aspect of this embodiment, the plurality of rotor blades are non-ferromagnetic.

In another aspect of this embodiment, the plurality of rotor blades define an aggregate area at an outer periphery of the rotor distal from the hub, and wherein the flow channel defines an aggregate area at the outer periphery, and wherein the aggregate area defined by the plurality of rotor blades at the outer periphery is greater than the aggregate area defined by the flow channel at the outer periphery.

In another aspect of this embodiment, the magnet is a one-piece solid body and is coaxial with the hub, the magnet being radially magnetized and defining a plurality of radial poles.

In another aspect of this embodiment, the plurality of rotor blades and the hub are made of a polymeric material.

In another aspect of this embodiment, the plurality of rotor blades and the hub are made of a biocompatible material and the magnet comprises a non-biocompatible material.

In yet another embodiment, a method of operating a blood pump includes generating a rotating magnetic field configured to rotate a rotor of the blood pump. The rotor includes a hub and a magnet disposed within the hub.

Brief description of the drawings

A more complete understanding of the present invention, and the attendant advantages and features thereof, will be more readily understood by reference to the following detailed description when considered in conjunction with the accompanying drawings wherein:

FIG. 1 is a perspective view of a rotor according to an embodiment of the present disclosure;

FIG. 2 is an elevational view of the rotor shown in FIG. 1;

FIG. 3A is a front view of the rotor shown in FIG. 1;

FIG. 3B is a cross-sectional view taken along line B-B shown in FIG. 3A;

FIG. 3C is a cross-sectional view taken along line C-C of FIG. 2;

FIG. 4 is an exploded view of the rotor shown in FIG. 1;

FIG. 5 is a schematic cross-sectional view of a pump including the rotor shown in FIG. 1 according to an embodiment of the present disclosure;

FIG. 6 is a perspective view of a rotor according to another embodiment of the present disclosure;

FIG. 7 is an exploded view of the rotor shown in FIG. 6; and

FIG. 8 is a partial schematic view of a rotor according to another embodiment of the present disclosure.

Detailed description of the invention

As used in this disclosure, the term "generally helical" refers to a feature that extends in a direction parallel to the axis and bends in a circumferential direction about the axis in a direction along the axis over a range of at least 50% thereof. Furthermore, as used herein, the terms "about" and "substantially" are intended to mean that a slight deviation from the absolute value is included within the scope of the term so modified.

Referring now to the drawings, in which like reference numerals refer to like elements, there is shown in fig. 1-4 a rotor or impeller 10 constructed in accordance with one embodiment of the present disclosure. Rotor 10 includes a hub 20, a plurality of rotor blades 30, and a magnet 40. The hub 20 defines a central body of the rotor 10 and also defines the rotor 10 or a rotor axis or main longitudinal axis 14 about which axis 14 the rotor 10 rotates. The hub 20 includes end portions 24, 26 and an intermediate portion 22 disposed between the end portions 24 and 26. The end portions 24, 26 are rotating tapered solids, while the intermediate portion 22 is substantially in the form of a solid body of revolution, which intermediate portion 22 may have a uniform cross-sectional dimension along its length, or may have a varying cross-sectional dimension. In this regard, as shown, the intermediate portion 22 may be cylindrical and the end portions 24 and 26 may be conical. The intermediate portion 22 is hollow and comprises a side wall 21, which side wall 21 defines an inner space surrounded by a wall surface 29, which wall surface 29 is in the form of a surface rotating about the axis 14. As best shown in fig. 3B, such interior space is sized to receive and house magnet 40.

A plurality of rotor blades 30 protrude from hub 20. In the particular embodiment shown, the plurality of blades 30 includes exactly three rotor blades 30 a-c. Each blade 30 extends outwardly from hub 20 away from hub axis 14 to an outer end thereof that is remote from hub 20. More specifically, each blade 30 extends out of the hub 20 in an outward radial or "spanwise" direction perpendicular to the axis 14. Each blade 30 also extends lengthwise or in the axial direction over a portion of the axial extent of hub 20 such that blades 30a-c are coextensive with each other in the axial direction. In the particular embodiment shown, each blade 30 extends along the length of the intermediate portion 22 and terminates at the adjacent end portions 24 and 26 of the hub 20. In other words, the lobes 30a-c project outwardly from the intermediate portion 22. However, in some embodiments, the vanes 30a-c may partially protrude outward from the end portions 24 and 26 and from the intermediate portion 22.

Each blade 30 defines a generally helical surface 36, 38, and these generally helical surfaces 36, 38 intersect the outer or bottom surface 23 of the intermediate portion 22 of the hub 20. As shown in fig. 3C, these helical surfaces 36, 38 are referred to as pressure surfaces 36 and suction surfaces 38. The pressure surface 36 and the suction surface 38 are arranged at opposite sides of each blade 30 and converge towards each other at an inflow edge 37 and an outflow edge 39, which inflow edge 37 and outflow edge 39 are arranged at the inflow and outflow ends of the blades 30 a-c. The pressure surface 36 faces forward, i.e. in the circumferential direction, indicated by arrow F in fig. 1, along which the rotor rotates, while the suction surface 38 faces rearward, i.e. in the circumferential direction opposite to the forward direction. Arrow D in the drawing indicates the flow direction from upstream to downstream.

The rotor blades 30a-c are evenly spaced from one another about the axis 14 in both the forward and aft circumferential directions. Thus, the vanes 30a-c define a plurality of flow channels 12 that extend in an axial direction between the vanes 30a-c and likewise along the rotor axis 14. Such a channel 12 is delimited by the outer surface 23 of the intermediate portion 22 and the pressure and suction surfaces 36, 38 of adjacent blades 30. In this regard, the flow passage 12 is generally helical to correspond to the helical contour of the pressure and suction surfaces 36, 38.

Each blade 30 has a tip surface 35 that intersects with and extends between a pressure surface 36 and a suction surface 38. Each end surface 35 faces outwardly away from the axis 14 and defines the outermost end or periphery of both the blade 30 and the rotor 10 itself. These end surfaces 35 define a total surface area that is greater than the total surface area defined by the flow channels 12 at the outer periphery of the rotor 10. In other words, each tip surface 35 of the blades 30a-c is larger than the free space of the flow channel 12, such that in general the surface area defined by the tip surfaces 35 is larger than the total area of the flow channel 12 taken at the periphery of the rotor 10. In this regard, the rotor 10 is characterized by a wide blade or a large area rotor. The previously cited' 586 patent; U.S. patent No. 7,972,122; 8,007,254 No; other exemplary wide vane rotors are described in 8,419,609 and U.S. publication 2015/0051438, all of which are incorporated herein by reference in their entirety. The wide blade configuration of the rotor 10 allows the rotor blades 30a-c to have hydrodynamic bearing surfaces at the blade tips 35 that enable the rotor 10 to be suspended within the pump housing during operation without the need for mechanical support. Moreover, this wide blade configuration of the rotor 10, in particular in combination with the hydrodynamic bearing at the blade tip 35, allows the rotor 10 to be extremely compact. For example, the maximum diameter of the rotor 10 at the blades 30a-c may be about 0.5 inches (12.7 millimeters) and have an overall length of about 0.86 inches (21.8 millimeters).

In the configuration shown in FIGS. 1 and 2, each tip surface 35 of the rotor blades 30a-c includes a land surface 33, an upstream hydrodynamic bearing surface 34, and a downstream hydrodynamic bearing surface 32. The surface 33 is then in the form of a portion of a surface of rotation about the central axis 14. In the particular embodiment shown, the surface of rotation is cylindrical such that the radius from the axis 14 to the following surface 33 is uniform over the entire extent of the rotor 10 and such that the radius is half the maximum diameter of the rotor 10 at the blades 30.

Each hydrodynamic bearing surface 32, 34 extends in a rearward circumferential direction from a pressure surface 36 of its respective blade 30, and is bounded by the trailing surface 33 and is radially recessed relative to the trailing surface 33. The concavity of the bearing surfaces 32, 34 is greatest at the leading edge of such surfaces, where the bearing surfaces 32, 34 meet the pressure surface 36 of the blade 30. The recess of each bearing surface 32, 34 is gradually reduced in the rear circumferential direction so that each bearing surface 32, 34 smoothly merges into the following surface 33 at the rear edge of each bearing surface 32, 34.

Referring now to fig. 3 and 4, in one configuration, the magnet 40 is a permanent magnet and is a rotating one-piece solid body. In this regard, as shown, the magnet 40 may be a solid cylinder, wherein the magnet 40 is completely solid throughout its thickness. However, the magnet 40 may also be an elongated tube having a hollow interior. The magnet 40 is sized to fit and be retained within the interior space of the hub 20. In addition, the magnet 40 is magnetized to have a magnetic field direction transverse to its axis and ideally perpendicular to its axis so as to have a plurality of radial poles. The magnets have sufficient magnetic flux to rotate the rotor 10 when a moving magnetic field is applied to such poles. In one configuration, the magnet 40 is the only component within the rotor 10 having ferromagnetic properties, which simplifies the construction of the rotor 10. The magnet 40 may be made of any magnetic material including non-biocompatible and biocompatible materials. For example, the magnet 40 may be made of neodymium and its alloy, or an aluminum-cobalt-nickel alloy.

As best shown in fig. 3B, the magnet 40 is disposed within the intermediate portion 22 of the hub 20 and is fixed to the intermediate portion 22 such that the axis of the magnet 40, and therefore its center of mass, is aligned with the axis 14 of the rotor 10. The magnets 40 also extend from one end of the intermediate portion 22 to the other and terminate just short of the end portions 24 and 26. However, in some embodiments, the magnet 40 may extend into the ends 24, 26. Further, magnets 40 are disposed within hub 20 such that magnets 40 are aligned with rotor blades 30a-c in an axial direction and are substantially coaxial with axis 14.

Magnet 40 is a permanent magnet made of a ferromagnetic material that may or may not be biocompatible. However, the biocompatibility of the magnet 40 is not important when implanted in a patient, as such a magnet 40 is embedded within the rotor 10, whereas the rotor 10 itself has a biocompatible exterior. In addition to having a biocompatible exterior, the rotor 10 is non-ferromagnetic. As described above, the magnet 40 may be the only magnetic component within the rotor 10. In other words, the hub 20 and the rotor blades 30a-c are made of a non-ferromagnetic material, or of a biocompatible material, or of a non-biocompatible material with a biocompatible coating. For example, the rotor 10 may be made of a biocompatible polymeric material such as a silicone polymer, a fluoroalkylsiloxane polymer, or a polyphosphazene. Such a polymer material may be molded over the magnet 40. Alternatively, the polymer rotor 10 may be molded separately from the magnets 40 and machined to form the interior space for the magnets 40 within the hub 20. The separately molded end portions 24, such as shown in fig. 4, may then be welded, such as by friction welding, to the intermediate portion 22, or otherwise secured to the intermediate portion 22 to seal the magnet 40 therein.

The rotor 10 may also be made of a non-ferromagnetic metal such as non-magnetic stainless steel or titanium, or a non-ferromagnetic ceramic such as pyrolytic carbon, alumina, and zirconia. Furthermore, the rotor 10 may have a biocompatible coating, such as a parylene, silicone, chromium nitride, or titanium nitride coating. The rotor 10 may be made of a combination of the above materials, but in general, the rotor itself is non-ferromagnetic regardless of which material is selected. In this regard, the choice of materials is varied and can be selected to control cost and/or optimize performance without additional consideration to providing magnetization that is itself provided by the central magnet 40.

The pump 50 according to one embodiment of the present invention includes a pump housing 60, a motor stator 70, and a rotor 10, as discussed above with reference to fig. 1-4. The housing 60 defines an interior bore or flow passage 62. The rotor 10 is disposed within the flow channel 62, and the inner surface 64 of the housing 60 surrounds the tip surface 35 of the rotor 10. The motor stator 70 is disposed around the outside of the housing 60. The rotor blades 30a-c are disposed directly between the motor stator 70 and the magnet 40. The motor stator 70 includes a set of coils 72, the set of coils 72 being arranged around the exterior of the housing 60. The coil 72 may be of conventional construction. By way of example, the coils 72 may be provided as three sets of diametrically opposed coils disposed at equal intervals around the circumference of the housing 60. The motor stator 70 also includes a ferromagnetic component called a back iron that is associated with the stator coils 72.

In operation, for example, with the pump 50 implanted in a mammal and the housing 60 connected to the circulatory system, for example in a conventional manner for a VAD, the coils 72 are actuated to provide a magnetic field oriented transverse to the rotor axis 14 to cause such a magnetic field to rotate rapidly about the axis 14. This magnetic field interacts with the radial poles of the magnets 40 disposed within the rotor 10 to cause the magnets 40, and thus the rotor 10 itself, to rotate with the magnetic field.

The rotor 10 also passively interacts with the back iron 74 of the motor stator 70. In this regard, the permanent magnets of the back iron 74 and the center magnet 40 result in a magnetic attraction force that resists axial displacement of the rotor 10 within the flow channel 62, which may be caused by the head weight or both. Also, as the rotor 10 rotates, a thin film of blood forms between the hydrodynamic bearing surfaces 32, 34 and the inner surface 64 of the housing 60, which keeps the rotor 10 coaxial with the housing 60 such that the rotor 10 does not contact the inner surface 64 due to radial movement transverse to the axis 14 of the rotor 10 or due to the axis 14 being inclined relative to the housing 60. Thus, the hydrodynamic bearings 32, 34 of the blades 30a-c, in combination with the axial alignment provided by the attractive forces of the central magnet 40 and back iron 74, eliminate the need for a mechanical suspension system to stabilize the rotor 70 during operation. This allows the flow channel 62 to be free from obstructions other than the rotor 10 itself.

The rotor 10 as described above has significant advantages. For example, since the blades 30 of the rotor 10 are formed of a non-ferromagnetic material, the blades 30 do not introduce unbalanced magnetic force, and the rotor 10 can stably operate using three blades 30. A rotor 10 with three vanes 30 and three channels of a given overall cross-sectional area provides better flow conditions than a four-vane rotor with four channels of the same overall cross-sectional area. Precise alignment between the axis of the magnet 40 and the axis 14 of the rotor is achieved in conventional manufacturing techniques. For example, the magnets may be formed into precisely dimensioned rotating bodies by techniques such as machining or centerless grinding. The inner surface 29 of the wall surrounding the inner space can be formed as a surface of revolution having precise dimensions and being precisely coaxial with the axis and the following surface 33 of the blade by machining or moulding the inner surface.

Other alternative embodiments of the foregoing apparatus are contemplated. For example, fig. 6 and 7 depict alternative embodiments of rotor 110. Such a rotor 110 is similar to the rotor 10 in the following respects: rotor 110 includes a hub 120, a central magnet 140 disposed within a mid-portion 122 of hub 120, and a plurality of wide blades 130 defining hydrodynamic bearing surfaces 132, 134, and flow channels 112 between blades 130. Furthermore, as with rotor 10, the only magnetic component in rotor 110 is central magnet 140. However, rotor 110 differs in that rotor 110 includes four rotor blades 130a-d instead of three. In this regard, the central magnets, such as magnets 40 and 140, in combination with non-ferromagnetic vanes, such as vanes 30 or 130, allow for the use of any number of rotor vanes without fear that the number of vanes selected will affect the magnetic balance.

Another rotor 210 according to further embodiments of the present disclosure is shown in fig. 8. The rotor 210 is similar to the rotor 10 in the following respects: rotor 210 includes a hub 220, rotor blades 230 (shown in phantom) extending from hub 220, and a center magnet 240. As described above, such rotor blades 230 may be non-ferromagnetic and also have hydrodynamic bearing surfaces at their tips. As shown, the hub 220 has a hollow middle portion 222 disposed between end portions 224 and 226. The intermediate portion 222 includes a first section 222a and a second section 222b that each partially define an interior space of the hub 220. In this regard, the first section 222a includes a first wall surface 229a in the form of a surface of rotation about the rotor axis 214, and the second section 222b includes a second wall surface 229b also in the form of a surface of rotation about the rotor axis 214. These surfaces 229a-b surround and define an interior space. In the particular embodiment shown, the first wall surface 229a and the second wall surface 229b define an interior space such that the interior space has a uniform cross-sectional dimension along the first wall surface 229a and a tapered cross-sectional dimension along the second wall surface 229 b. However, in other embodiments, the first wall surface 229a and the second wall surface 229b may define an interior space such that the interior space has a one-piece cross-sectional dimension along both the first wall surface 229a and the second wall surface 229b, but wherein the cross-section of the interior space tapers at a greater rate along the second wall surface 229b than the first wall surface 229 a. It is also contemplated that the intermediate portion 222 of the hub 220 may have a single rotating wall surface defining an interior space that tapers along its entire length to form, for example, a frustoconical space.

In the rotor embodiment shown in fig. 8, magnet 240 may have a smaller but proportional size relative to the size of intermediate portion 222, such that magnet 240 may be disposed in the interior space defined by surfaces 229a-b, and such that the axis defined by magnet 240 is coaxial with axis 214. Thus, the magnet 240 may be a one-piece solid of revolution with its first section 242a having a first cross-sectional dimension proportional to the first section 222a of the hub 220 and its second section 242b having a second cross-sectional dimension proportional to the second section 222b of the hub 220.

In the embodiments discussed above, the axial movement of the rotor relative to the pump chamber is limited by magnetic attraction between the magnets and back iron incorporated in the stator. In other embodiments, the hydrodynamic bearing surface of the rotor may comprise a hydrodynamic bearing surface arranged to provide axial thrust and thereby constrain the rotor against axial movement relative to the pump chamber and the stator. For example, as disclosed in U.S. published patent application No. 2011/0311383, a hydrodynamic bearing surface facing in a direction oblique to the axis may be provided on the blade to provide axial thrust in the blade, which is incorporated herein by reference in its entirety for the purpose of providing full axial constraint, the oblique surface may comprise an oblique surface facing in the opposite axial direction.

Certain embodiments of the invention include:

embodiment 1. a pump rotor, comprising:

a hub having a major longitudinal axis;

a magnet disposed within the hub along the major longitudinal axis; and

a plurality of rotor blades projecting outwardly from the hub away from the axis and spaced apart from one another in a circumferential direction about the axis, each of the plurality of rotor blades defining a hydrodynamic bearing at an outer end thereof remote from the hub, the plurality of rotor blades defining a plurality of flow channels, and each of the plurality of rotor blades being configured to drive fluid through the flow channels as the rotor rotates about the axis.