SMA Actuator Valve with Linear Plunger Motion
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Solution Overview
Problem
Existing valve technologies using shape memory alloy (SMA) wires face challenges such as complex designs, large dimensions, and difficulty in protecting against overstress, particularly in normally-open valves, which can lead to bulky and noisy implementations.
Innovation Solution
A valve design that incorporates an SMA actuator extending along the displacement direction for at least 50% of its length, with a Nickel-Titanium alloy and stress operation of not less than 160 MPa, and a compact linear geometry to efficiently actuate a plunger, reducing the need for complex lever-type mechanisms and enabling tight sealing without excessive load on the SMA actuator.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a lever-type mechanism is employed to translate the length change of the SMA wire into plunger displacement, then the valve can be actuated, but the valve becomes comparably complex and requires many parts
Solution Approach 1:
The patent extracts and eliminates the complex lever-type mechanism from the system. Instead of using a lever to translate SMA wire movement, the invention directly couples the SMA actuator to the plunger, allowing the plunger to move linearly along the displacement direction. This extraction of the intermediate lever mechanism simplifies the overall device structure while maintaining the core actuation function.
Solution Approach 2:
The patent inverts the traditional approach by making the SMA actuator extend along the displacement direction for at least 50% of its length, rather than using it perpendicular to the displacement as in lever mechanisms. This inversion allows direct linear actuation of the plunger, eliminating the need for complex mechanical translation mechanisms.
2Ease of operation
If a lever-type mechanism is employed to translate the length change of the SMA wire into plunger displacement, then the valve can be actuated, but the housing dimensions become large making integration difficult
Solution Approach 1:
The patent removes the lever-type mechanism that would require large housing dimensions. By directly coupling the SMA actuator to the plunger with the actuator extending along the displacement direction, the housing can be designed with compact dimensions suitable for integration into automotive seats, while still achieving full plunger actuation range.
Solution Approach 2:
Instead of using a lever mechanism that requires large spatial dimensions for rotation and movement translation, the patent inverts to a direct linear actuation approach where the SMA actuator aligns with the displacement direction. This inversion dramatically reduces the required housing dimensions while maintaining actuation effectiveness.
3Device complexity
If a normally-open valve design is used with SMA wire, then the valve structure is simpler, but it becomes difficult to protect the SMA wire against overstress once the plunger seals the fluid port
Solution Approach 1:
The patent inverts the traditional normally-open design by implementing a normally-closed valve where the plunger seals the fluid port in the rest position without SMA wire tension. The SMA actuator only engages to open the valve, which eliminates overstress risks during the closed position. This inversion of the default state resolves the overstress protection issue while maintaining structural simplicity.
Solution Approach 2:
The patent applies preliminary anti-action by designing the valve to be normally closed, preventing the condition that would lead to overstress. By establishing the closed position as the default state where the plunger seals without SMA wire engagement, the design proactively prevents overstress scenarios before they can occur, rather than adding complex protection mechanisms.
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 solution provides a compact, efficient, and reliable valve system that minimizes noise and complexity, ensuring effective actuation and protection against overstress while maintaining high sealing performance.
Implementation Method 1
at least one SMA actuator which extends along the displacement direction for at least 50% of its length. The SMA actuator is configured to exert an actuation force on the plunger to displace the plunger from the first position towards the second position
Data Source
AI summary
A valve (100) includes a housing (111) and the fluid port (121). A plunger (125) is configured to seal the fluid port (121) in a first position (91) and to unseal the fluid port (121) in a second position and to displace along a displacement direction (259) from its first position (91) towards its second position. The valve (100) also includes at least one shape memory alloy, SMA, actuator (151, 152) extending along the displacement direction (259) for at least 50% of its length and configured to exert an actuation force (155) on the plunger (125) to displace the plunger (125) from the first position (91) towards the second position.