Hydrodynamic Bearing Blood Pump for Torque and Startup Balance
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Solution Overview
Problem
Existing centrifugal blood pumps face challenges in achieving high torque on the impeller while maintaining axial and radial centering without mechanical bearings, and in reducing frictional forces during startup.
Innovation Solution
The centrifugal blood pump design features a pump casing with a central axis, a blood flow inlet along the central axis, and a blood flow outlet on the pump casing's circumference. The impeller is freely movable axially and radially within limited clearances and is equipped with permanent magnets cooperating with an electromagnetic drive. A hydrodynamic radial bearing is created with a radial clearance of 100 μm or less between the impeller and the circular wall, and the electromagnetic drive coils are designed without ferromagnetic cores to reduce axial attraction forces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the strength of impeller magnets is increased to increase torque, then torque on the impeller is improved, but the pump becomes harder to start due to increased magnetic attraction forces
Solution Approach 1:
The patent applies dynamic control of magnetic fields by using electromagnets in the drive means that can be activated and deactivated. During startup, the electromagnets are deactivated to reduce magnetic attraction forces, allowing easy initiation of rotation. Once the impeller is rotating, the electromagnets are activated to provide the necessary torque for operation. This dynamic switching resolves the contradiction between needing strong magnets for torque and avoiding strong magnetic attraction during startup.
2Use of energy by moving object
If the distance between electromagnets and impeller magnets is increased to achieve maximum efficiency, then energy efficiency is improved, but radial self-centering effect is reduced
Solution Approach 1:
The patent introduces a hydrodynamic bearing as an intermediary mechanism to provide radial self-centering. Instead of relying solely on magnetic forces for centering, the patent uses fluid dynamic forces generated by the relative motion between the impeller and pump housing to maintain radial positioning. This allows the electromagnets to be positioned at an optimal distance for energy efficiency while the hydrodynamic bearing compensates for the reduced magnetic centering effect.
3Reliability
If mechanical bearings are omitted to prevent thrombosis and contamination, then blood safety is improved, but axial and radial centering of the impeller becomes difficult to achieve
Solution Approach 1:
The patent replaces mechanical bearings with a hydrodynamic bearing system that uses fluid dynamic forces to achieve impeller centering. The relative rotation between the impeller and pump housing generates hydrodynamic pressure that automatically centers the impeller both radially and axially. This substitution eliminates mechanical contact with blood, preventing thrombosis and contamination while providing the necessary centering function through non-mechanical means.
4Stability of the object's composition
If the radial clearance is reduced to create hydrodynamic radial bearing, then impeller centering is improved, but manufacturing precision requirements increase
Solution Approach 1:
The patent specifies a radial clearance of 100 μm or less to establish hydrodynamic radial bearing conditions. This precise parameter control enables the generation of sufficient hydrodynamic pressure for impeller centering while balancing manufacturing feasibility. The patent combines this dimensional parameter control with the hydrodynamic mechanism to achieve reliable centering without requiring excessively tight tolerances that would be difficult to manufacture.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This design allows for high torque on the impeller while maintaining axial and radial centering without mechanical bearings, reducing frictional forces during startup, and ensuring long-term reliability and efficiency.
Implementation Method 1
The impeller is rotated by means of an external electromagnetic drive cooperating with magnets provided on the blades of the impeller
Implementation Method 2
the impeller blades comprise supporting surfaces which hydrodynamically lift the impeller during rotation such that the impeller slides on a fluid cushion, i.e. a blood cushion
Implementation Method 3
A hydrodynamic radial bearing is created with a radial clearance of 100 μm or less between the impeller and the circular wall
Data Source
AI summary
A centrifugal blood pump without a mechanical bearing comprises a pump casing (1), an impeller (9) arranged in the pump casing rotatably about the central axis and freely movable axially and radially within a limited clearance. The impeller has per-manent magnets or permanently magnetized magnetic regions (N/S) which cooperate with an electromagnetic drive to set the impeller rotating. A circular wall (12) or circularly arranged wall sections are provided within the pump casing, their inner surfaces defining a radial clearance together with the outer circumference of the impeller to form a hydrodynamic radial bearing for the impeller.