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EP-4223356-B1 - MAGNETIC SUSPENSION MOTOR AND MAGNETIC SUSPENSION BLOOD PUMP

EP4223356B1EP 4223356 B1EP4223356 B1EP 4223356B1EP-4223356-B1

Inventors

  • LOGAN, THOMAS GEORGE
  • CLIFTON, PETER COLTON JAMES
  • HSU, CHIAHAO

Dates

Publication Date
20260506
Application Date
20210621

Claims (15)

  1. A magnetic suspension motor (10) for use in a blood pump, comprising a stator assembly (11) and a rotor assembly (12) that is disposed above the stator assembly along a vertical central axis (A-A) of the magnetic suspension motor (10), wherein a distance-adjustable axial gap (13) is provided between the stator assembly (11) and the rotor assembly (12); characterized in that the stator assembly (11) comprises a stator base (111), a plurality of stator teeth (112) distributed along a circumference of the stator base (111) and extending upward towards the gap (13) from an upper surface of the stator base (111), and a stator thrust body (114) provided in an internal cavity enclosed by the plurality of stator teeth (112), and the stator teeth are wound with stator coils (113) serving as actuators; wherein the rotor assembly (12) comprises a rotor ring (121) in the form of a circular ring, a rotor driving magnet (122) disposed on a lower surface of the rotor ring (121), and a rotor thrust magnet (124) disposed in an inner cavity of the rotor ring (121); wherein the stator thrust body (114) and the rotor thrust magnet (124) are configured to generate axial magnetic lines and generate an axial repulsive force between the stator thrust body (114) and the rotor thrust magnet (124); wherein the rotor driving magnet (122) comprises a plurality of portions (123), each portion being magnetized along an axial direction and adjacent portions having opposite magnetization directions, so that the rotor driving magnet (122) has a plurality of alternating magnetic poles; and wherein the stator coils (113) are configured to generate: a direct-axis component magnetic field that is aligned with a magnetic field of each portion (123) of the rotor driving magnet (122), for adjusting an axial position of the rotor assembly (12); and a quadrature-axis component magnetic field that is away from the magnetic field of each portion (123) of the rotor driving magnet (122) by half a length of one portion and thus is not aligned with the magnetic field of each portion (123)of the rotor driving magnet (122), for driving the rotor assembly (12) to rotate and adjusting a rotational speed of the rotor assembly (12).
  2. The magnetic suspension motor (10) according to claim 1, characterized in that each portion (123) of the rotor driving magnet (122) has an arc shape, so that each portion (123) is capable of being disposed on the lower surface of the rotor ring (121) following a shape of the rotor ring (121); preferably, the rotor driving magnet (122) comprises four portions (123) and the stator assembly (11) comprises eight stator teeth (112); and preferably, each of the portions (123) comprises one or more magnet segments.
  3. The magnetic suspension motor (10) according to claim 2, characterized in that ends of the plurality of portions (123) are abutted to each other, so that the rotor driving magnet (122) constructed of the plurality of portions (123) has a closed ring shape; or wherein ends of the plurality of portions (123) are spaced apart from each other, so that spacings are presented between corresponding portions.
  4. The magnetic suspension motor (10) according to claim 1, characterized in that the plurality of stator teeth (112) are configured to extend substantially vertically or substantially spirally upward from the upper surface of the stator base (111) towards the gap (13), preferably, the plurality of stator teeth (112) are configured such that a spacing between adjacent stator teeth gradually decreases when the stator teeth (112) extend substantially spirally upward towards the gap (13).
  5. The magnetic suspension motor (10) according to claim 1, characterized in that the rotor thrust magnet (124) and the stator thrust body (114) are both configured as solid cylindrical magnets, and wherein a center of the rotor thrust magnet (124) and a center of the stator thrust body (114) are both coincident with the vertical central axis (A-A) of the magnetic suspension motor (10) in an ideal state, preferably, the rotor thrust magnet (124) has an external diameter larger than that of the stator thrust body (114).
  6. The magnetic suspension motor (10) according to claim 1, characterized in that the rotor thrust magnet (124) is configured as an annular magnet with an internal cavity and the stator thrust body (114) is configured as a solid cylindrical magnet, and wherein a center of the rotor thrust magnet (124) and a center of the stator thrust body (114) are both coincident with the vertical central axis (A-A) of the magnetic suspension motor (10) in an ideal state, preferably, the rotor thrust magnet (124) has an internal diameter of a first size and an external diameter of a second size, and the stator thrust body (114) has an external diameter of a size between the first size and the second size of the rotor thrust magnet (124).
  7. The magnetic suspension motor (10) according to claim 1, characterized in that the stator base (111) is in an annular shape or a round pie shape.
  8. The magnetic suspension motor (10) according to claim 1, characterized in that the stator thrust body (114) is located at a position above the stator coils (113) and close to heads of the stator teeth (112), preferably, the stator thrust body (114) is made of permanent magnet materials or is formed of electromagnetic coils or electromagnets, and preferably the rotor thrust magnet (124) and the rotor driving magnet (122) are both made of permanent magnet materials.
  9. The magnetic suspension motor (10) according to claim 1, characterized in that the stator base (111) is made of magnetic conductive materials for providing magnetically conductive connection between roots of the plurality of stator teeth (112); and/or wherein the rotor ring is made of magnetic conductive materials for providing magnetically conductive connection between corresponding portions of the rotor driving magnet (122).
  10. The magnetic suspension motor (10) according to claim 1, characterized in that each of the stator teeth (112) is wound with a stator coil (113), and each of the stator coils (113) is located between a root and a head of a corresponding stator tooth (112) and extends a portion of a length of the corresponding stator tooth (112), preferably, the stator coils (113) are interconnected in groups to form a plurality of independently controllable stator coil groups, preferably, each stator coil group is connected to an amplifier to allow currents to flow into stator coils (113) in the stator coil group, and preferably, each amplifier is independently controllable to allow currents of different magnitudes to flow into stator coils (113) in the stator coil group that is connected to the amplifier.
  11. The magnetic suspension motor (10) according to claim 10, characterized in that the magnetic suspension motor (10) comprises a controller configured to control a value of current sent to each amplifier, so that the current in each stator coil group conforms to a preset current value for this stator coil group, thereby controlling at least one of an axial movement, a tilting movement, and a rotating movement of the rotor assembly (12).
  12. The magnetic suspension motor (10) according to claim 11, characterized in that the controller is configured to implement at least one of following operations: i) the controller adjusts the direct-axis component magnetic field by adjusting and controlling the value of current sent to the amplifier, thereby adjusting and controlling an axial force generated on the rotor assembly (12) to ensure that the axial gap (13) between the rotor assembly (12) and the stator assembly (11) conforms to a preset distance value; ii) the controller adjusts the quadrature-axis component magnetic field by adjusting and controlling the value of current sent to the amplifier, thereby adjusting and controlling a rotational torque generated on the rotor assembly (12) to ensure that the rotational speed of the rotor assembly (12) conforms to a preset rotational speed value; and iii) the controller adjusts and controls the value of current sent to the stator coils (113) that corresponds to two of the portions opposing each other, thereby adjusting and controlling a tilting moment generated on the rotor assembly (12) to ensure that a tilt angle of the rotor assembly (12) conforms to a preset tilt angle value.
  13. The magnetic suspension motor (10) according to claim 11, characterized in that the magnetic suspension motor (10) comprises one or more sensors for measuring at least one of the axial position, a tilt angle and an angular position of the rotor assembly (12) relative to the stator assembly (11), preferably, the controller is configured to receive measured values from the one or more sensors and adjust the value of current sent to the stator coil group based on the measured values to implement control, and preferably, the sensors are eddy current-based sensors or Hall effect sensors.
  14. The magnetic suspension motor (10) according to claim 1, characterized in that a head of each stator tooth (112) has a size larger than that of other portions of the stator tooth (112), preferably, the head of the stator tooth (112) is provided with a chamfered or inclined surface, such that the head of the stator tooth (112) is wedge-shaped.
  15. A magnetic suspension blood pump, characterized in that the magnetic suspension blood pump comprises an impeller and a magnetic suspension motor (10) according to any one of claims 1 to 14, wherein the magnetic suspension motor (10) is used for driving the impeller.

Description

TECHNICAL FIELD The present disclosure generally relates to the field of medical instruments. More particularly, the present disclosure relates to a magnetic suspension motor for use in a blood pump and a magnetic suspension blood pump including the same. BACKGROUND ART Heart failure is an epidemic and life-threatening disease with 1-year mortality of about 75% once deteriorating into advanced stage. In the light of limited heart donors for advanced heart failure, ventricular assist device (VAD) technology has been a viable therapeutic option to bridge the patients to transplantation or as an alternative therapy. However, adverse events (AEs) incurred by current technology still restrict these devices being used for critically ill patients. Among all, blood damage associated AEs, such as hemolysis, neurological events, stroke, and in-blood pump thrombosis, account for 20% occurrence. Hemolysis and thrombosis are primarily attributed to hyper-physiological stress and flow stagnation in rotary blood pumps (RBPs). Although hemocompatibility could be improved by hydraulic design optimization, such optimization has been extremely challenging for the RBPs with blood-immersed bearings where direct contact between rotating and stationary components is not avoidable. Third generation VADs utilizing non-contacting bearings with hydrodynamic suspension and/or magnetic suspension technology has been developed to address the issues. Hydrodynamic bearings eliminate the direct mechanical contact between the rotor and the stator by creating a thin blood film, normally the secondary flow gap, using blood as the lubricant. The suspension force is directly related to the rotational speed and the blood film geometry between the rotating and stationary components, which changes dynamically following changes of blood pump working conditions. A strict constraint exists for hydrodynamic bearing design because of the strong interlink between the film geometry and the suspension force. On the other hand, active magnetic bearings can keep the secondary gap constant and thus decouples the interlink between the film geometry and the suspension force. This allows more freedom for blood pump designers to optimize the flow field in the blood pump cavity as well as the flow-related hemocompatibility, which is known relevant to the shear stress, exposure time (the time interval which the blood is exposed to the shear stress), and wash-out in the secondary flow path. Therefore, magnetic suspension RBPs has gradually re-gained attention since 2015 because the newest magnetic suspension blood pump design renders a significant reduction in the size of the blood pump to be implanted in thorax and a superior performance in terms of zero occurrence of in-blood pump thrombosis. Therefore, during the designing of magnetic suspension RBPs, it is very important to allow enough freedom in hydraulic optimization while keeping the magnetic suspension bearing performance. The critical performance indicators for magnetic suspension bearing are the numbers of the active controlled degrees-of-freedom (DoFs) and bearing stiffness in each DoF. In order to gain strong stiffness in a DoF, it is natural to control the DoF actively by electromagnetic coils. This requires to place a pair or a set of winding coils along said DoF (orientation), thus complicating the design of the secondary flow path and limiting the space for mechanical structure (for example, the secondary flow path) for the blood flow. In addition, there are two mechanics in a magnetic suspension blood pump: (1) rotational one which is to drive the impeller; and (2) translational one which is to keep the impeller/rotor levitating. To perform these two mechanics, there are two sets of actuators in the motor to provide moving forces for the impeller/rotor. The two sets of actuators, actually two sets of winding coils or actuators in other forms, are either configured to be completely separated from each other or to be arranged more closely adjacent to each other. In either configuration, two sets of components are required, and the two sets of components need to be controlled separately (i.e., two sets of independent control circuits are required), increasing the mechanical structure complexity as well as the failure risk. WO2017033570A1 discloses a magnetic levitation attitude control device. In order to control the attitude of a levitated rotor, a secondary coil is wound on the surface of a levitated rotor facing an electromagnetic induction stator, and the secondary coil is wound such that conductive wire parts extend from the rotation-center-axis side of the levitated rotor toward the outer circumference of the rotor, conductive wire parts extend in the circumferential direction of the levitated rotor, and conductive wire parts extend from the outer-circumferential side of the levitated rotor toward the rotation center axis. WO2020187862A1 discloses an intravascular blood pump for percutaneous in