Centrifugal Blood Pump Groove Design for Impeller Stability
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Solution Overview
Problem
Centrifugal blood pumps with hydrodynamic bearings face issues of impeller position variability with rotation speed and liquid viscosity, leading to frictional damage and potential thrombus or hemolysis, and existing solutions increase pump size and component count, reducing reliability.
Innovation Solution
A centrifugal pump design with a housing and impeller configuration that balances magnetic forces and utilizes differently shaped and sized grooves for hydrodynamic bearing to generate varying hydrodynamic pressures, allowing smooth impeller rotation without increasing component count, and includes a drive unit with magnetic elements and coils to manage levitation and rotation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If hydrodynamic bearing grooves are formed in the impeller or housing to reduce friction during rotation, then the impeller can rotate smoothly without contact, but the impeller position varies with rotation speed and liquid viscosity, causing frictional damage and potential thrombus or hemolysis
Solution Approach 1:
The patent applies parameter changes by varying the depth of hydrodynamic bearing grooves at different radial positions. Specifically, grooves have different depths (first depth at inner radius, second depth at outer radius) to optimize hydrodynamic pressure distribution across the impeller surface, maintaining stable positioning while enabling smooth rotation.
Solution Approach 2:
The patent implements local quality by creating non-uniform groove characteristics across the impeller surface. Different radial zones have grooves with different depths, allowing each region to contribute differently to hydrodynamic bearing, thereby stabilizing impeller position while preventing contact friction.
2Stability of the object's composition
If additional components such as electromagnets or magnetic force adjustment coils are added to control impeller position, then impeller positioning can be improved, but pump size increases and component count increases, reducing reliability
Solution Approach 1:
The patent applies self-service by designing the hydrodynamic bearing grooves to automatically generate the necessary hydrodynamic pressure and magnetic forces during impeller rotation. The groove geometry itself provides the positioning control function, eliminating the need for separate electromagnets or control coils, thus maintaining simplicity while achieving stable impeller positioning.
Solution Approach 2:
The patent replaces complex mechanical or electromagnetic control systems with a hydrodynamic-magnetic bearing system where grooves in the impeller or housing work together with magnetic forces to achieve automatic positioning. This substitution eliminates additional control components while maintaining positioning stability.
3Reliability
If magnetic forces are used to levitate the impeller away from the housing, then contact friction is reduced, but the impeller may become unstable or contact the housing when magnetic forces are insufficient, causing damage
Solution Approach 1:
The patent applies parameter changes by optimizing the depth and geometry of hydrodynamic bearing grooves to generate sufficient hydrodynamic pressure that complements magnetic levitation forces. This ensures stable impeller suspension without excessive reliance on magnetic forces alone, preventing contact while maintaining force balance.
Solution Approach 2:
The patent employs a composite bearing system combining hydrodynamic bearing (through grooves) and magnetic bearing (through permanent magnets or electromagnets). This composite approach provides both contactless operation and stable force balance, preventing impeller contact with the housing while maintaining reliability.
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
The design enables smooth impeller rotation and prevents hemolysis by maintaining a stable distance between the impeller and housing, reducing friction and the risk of thrombus formation, while maintaining a compact component count for improved reliability.
Implementation Method 1
attractive force acting on the one surface of the impeller from the electromagnet, attractive force acting on the other surface of the impeller from the permanent magnet in the rotor
Implementation Method 2
a groove for hydrodynamic bearing is formed in a surface of the second diaphragm facing the other surface of the impeller. Owing to attractive force acting on the one surface of the impeller from the electromagnet, attractive force acting on the other surface of the impeller from the permanent magnet in the rotor, and a hydrodynamic bearing effect of the grooves for hydrodynamic bearing, the impeller moves away from an inner surface of the second chamber and rotates without contacting
Data Source
AI summary
A centrifugal blood pump apparatus includes an impeller provided in a blood chamber, first and second permanent magnets provided in one surface and the other surface of the impeller respectively, a third permanent magnet provided in an inner wall of the blood chamber, and a magnetic element and a coil for driving the impeller to rotate with a diaphragm being interposed. First and second grooves for hydrodynamic bearing different in shape and depth from each other are formed in the inner wall of the blood chamber facing the impeller, and third and fourth grooves for hydrodynamic bearing different in shape and depth from each other are formed in the diaphragm facing the impeller. The second and fourth grooves for hydrodynamic bearing generate high hydrodynamic pressure when the impeller is activated to rotate, while the first and third grooves for hydrodynamic bearing generate high hydrodynamic pressure when the impeller steadily rotates.