Centrifugal Pump Magnetic Element Segmentation for Axial Force Control
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Solution Overview
Problem
Centrifugal pumps with canned motors face challenges in increasing torque and efficiency due to large gaps between stator and rotor, leading to low radial rigidity and high axial attractive forces, making it difficult to rotate the impeller at high speeds without contacting the housing, especially in small motor designs.
Innovation Solution
A centrifugal pump design with a housing having first and second chambers partitioned by a dividing wall, featuring an impeller with magnetic elements arranged to balance attractive forces and hydrodynamic forces, using coils and magnetic elements to generate a rotating magnetic field, and incorporating grooves for hydrodynamic bearing to reduce axial attractive force while maintaining required torque.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the gap between stator and rotor is reduced to increase torque, then torque increases, but radial rigidity decreases and axial attractive forces increase
Solution Approach 1:
The patent divides the magnetic interaction into two independent segments: one set of magnetic elements generates torque while another set generates axial attractive force. This segmentation allows the torque-generating gap to be small for high torque, while the axial force-generating gap can be larger to maintain radial rigidity, resolving the contradiction between torque and radial rigidity.
Solution Approach 2:
The patent introduces an intermediary mechanism using separate magnetic element sets with different gap configurations. The first magnetic elements (in rotor) and second magnetic elements (in stator) create torque through a small gap, while third magnetic elements create axial attractive force through a different gap configuration, acting as intermediaries that decouple the torque and rigidity requirements.
2Power
If the gap between stator and rotor is reduced to increase torque, then torque increases, but axial attractive forces increase making it difficult to rotate impeller at high speeds
Solution Approach 1:
The patent segments the magnetic element functions: first and second magnetic elements are dedicated to torque generation with small gaps, while third magnetic elements are dedicated to axial positioning with controlled gaps. This allows high torque without excessive axial attractive force, enabling high-speed rotation.
Solution Approach 2:
The patent changes the gap parameter differently for different magnetic element sets: small gaps for torque-generating elements, and optimized gaps for axial force-generating elements. This parameter differentiation allows simultaneous achievement of high torque and high rotation speed.
3Force
If magnetic elements are added to balance attractive forces, then axial attractive force is reduced, but device complexity increases
Solution Approach 1:
The patent makes magnetic elements multi-functional: the first and second magnetic elements serve dual purposes of torque generation and axial force balance. This universality reduces the need for entirely separate components, limiting the increase in device complexity while achieving force balance.
Solution Approach 2:
The patent merges the torque generation function and axial force balance function into integrated magnetic element configurations. The first magnetic elements in the rotor and second magnetic elements in the stator simultaneously provide torque and contribute to axial force balance, reducing overall system complexity.
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 allows for high-speed rotation of the impeller with reduced axial attractive force, enhanced energy efficiency, and stable operation, preventing contact with the housing and minimizing power consumption.
Implementation Method 1
first attractive force between the first and second magnetic elements and second attractive force between the plurality of third magnetic elements and the drive unit are balanced with each other
Implementation Method 2
a plurality of coils provided to face the plurality of third magnetic elements, for generating rotating magnetic field
Implementation Method 3
a first groove for hydrodynamic bearing is formed in one surface of the impeller or in the inner wall of the first chamber facing the one surface, and a second groove for hydrodynamic bearing is formed in the other surface of the impeller or in the dividing wall facing the other surface
Implementation Method 4
an impeller rotatably provided in the first chamber along the dividing wall, for delivering fluid by centrifugal force during rotation
Data Source
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AI summary
A centrifugal blood pump apparatus includes a plurality of permanent magnets (17) in an impeller (10) in a blood chamber (7), a plurality of coils (20) in a motor chamber (8), and a magnetic element (18) in each of the coils (20). The magnetic elements (18) are made shorter than the coils (20) to lower attractive force between the magnetic elements (18) and the permanent magnets (17) in the impeller (10), to set a large gap between the magnetic elements (18) and the permanent magnets (17). As a result, axial attractive force and negative rigidity can be lowered while required torque is satisfied.