Magnetic SMA Actuator Subassembly for Fluid-Isolated Valve Motion
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Solution Overview
Problem
Existing actuator systems using shape memory alloy (SMA) wires face limitations in achieving balanced and efficient movement, particularly in fluidic applications, due to asymmetrical forces and restricted thermal management, which hinders miniaturization and proportional control.
Innovation Solution
An actuator subassembly comprising a SMA wire and permanent magnets for reciprocating elements, with magnetic coupling providing both actuation and return mechanisms, and a biasing means to ensure balanced forces, allowing for a V-shape or U-shape configuration of the SMA wire, enhancing design flexibility and thermal management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If SMA wire is used directly in fluidic applications, then actuation function is achieved, but the SMA wire is exposed to damaging fluids which affects reliability
Solution Approach 1:
A magnetic coupling mechanism acts as an intermediary between the SMA wire and the fluidic environment. The SMA wire remains isolated in a non-fluidic chamber while magnetically actuating a movable element that controls the fluidic valve, preventing direct exposure to damaging fluids while maintaining actuation functionality
Solution Approach 2:
The actuator is divided into separate chambers: a non-fluidic chamber containing the SMA wire and a fluidic chamber containing the movable element. This segmentation isolates the SMA wire from harmful fluids while allowing functional interaction through magnetic coupling across a barrier
2Ease of operation
If conventional actuator configuration is used, then actuation is achieved, but asymmetrical forces result in unbalanced movement
Solution Approach 1:
A biasing element (spring or elastic element) is introduced to provide a counterbalancing force that opposes the SMA wire's actuation force. This creates a balanced force system where the movable element experiences symmetrical forces during actuation and return, resulting in smoother movement without asymmetrical imbalances
3Temperature
If SMA wire is exposed to fluidic environment, then direct actuation is possible, but thermal management is restricted
Solution Approach 1:
The actuator separates thermal management functions from fluidic operations by placing the SMA wire in a dedicated non-fluidic chamber with controlled thermal environment, while the fluidic valve operates in a separate chamber. This allows independent optimization of thermal management without compromising fluidic application versatility
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 configuration enables smoother, balanced actuation with faster return to rest positions, supports miniaturization, and ensures proportional control in fluidic applications by maintaining the SMA wire in a fluid-tight environment, avoiding exposure to damaging fluids.
Implementation Method 1
the SMA material property of being characterized by a structural transition between two phases, namely the so-called Martensite phase, which is stable at a lower temperature, and the so-called Austenite phase which is stable at a higher temperature
Implementation Method 2
The shape memory alloy wire controlled shortening, usually by heating through current passage (Joule effect), is used to displace one or more elements in the actuator
Implementation Method 3
the first and second movable elements being magnetically coupled via magnetic responsive elements comprising one or more set of permanent magnets and a corresponding magnetic responsive element
Implementation Method 4
a biasing means connected to the second stationary surface and to one of the movable elements acting in opposition to the driving force exerted by the shape memory alloy wire
Data Source
Figure 1A~1B
Figure 2A~2B
Figure 3A~3B
AI summary
The present invention relates in a first aspect to an actuator subassembly comprising a shape memory alloy wire (15), a biasing spring (16) and magnetic responsive elements (17, 17') to couple the movement of a first movable element (13) and a second movable element (14) provided with a terminal (18), and in a second aspect to a fluidic valve comprising a plunger whose terminal part controls its opening and closing and where the plunger movement is controlled by the action of a shape memory alloy wire, a biasing element and magnetic responsive elements.