SMA Wire Autofocus Actuator with Acute Angle Arrangement
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Solution Overview
Problem
Existing autofocus camera module actuators using shape memory alloy wires face challenges with limited movement due to fractional length change, high frictional forces, stress concentration, and complexity, leading to reliability and cost issues.
Innovation Solution
A camera module autofocus actuator design that utilizes SMA wires arranged at acute angles to maximize movement along the optical axis without generating off-axis forces, featuring a sliding coupling system with guide posts and carefully selected materials for low friction and stress reduction, eliminating the need for rolling members and reducing component complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If SMA wires are arranged parallel to the optical axis, then the structure is simple, but the degree of movement of the lens carrier is insufficient
Solution Approach 1:
The patent transitions from arranging SMA wires parallel to the optical axis (one-dimensional arrangement) to arranging them at acute angles relative to the optical axis (introducing angular dimension). This dimensional change enables the wires to generate both axial movement and off-axis forces, resolving the contradiction between movement degree and structural simplicity.
2Length of moving object
If SMA wires are arranged at acute angles to the optical axis, then the degree of movement along the optical axis is increased, but off-axis forces cause lateral displacement or tilt of the lens carrier
Solution Approach 1:
The patent employs multiple pairs of SMA wires arranged symmetrically at acute angles, where the off-axis force components from wires in each pair counterbalance each other. This counterweight approach eliminates net lateral displacement or tilt of the lens carrier while preserving the enhanced axial movement benefit.
3Force
If a bearing suspension system is used to resist off-axis forces, then lateral displacement is prevented, but frictional forces increase and size increases
Solution Approach 1:
The patent extracts and eliminates the bearing suspension system from the design by using symmetrical SMA wire arrangements that inherently counterbalance off-axis forces. This removal of the bearing component eliminates the associated frictional losses and reduces the overall actuator size.
4Loss of energy
If rolling members are used to reduce friction, then movement smoothness improves, but device complexity and manufacturing cost increase
Solution Approach 1:
The patent removes rolling members from the suspension system by relying on the symmetrical counterbalancing of off-axis forces through SMA wire arrangement. This extraction eliminates the need for additional rolling components, reducing complexity and manufacturing cost while maintaining low friction through proper material selection and surface finish.
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 achieves significant movement with minimal off-axis forces, reducing friction and stress, enhancing reliability and manufacturing simplicity while maintaining a compact structure, thus improving the actuator's operational life and cost-effectiveness.
Implementation Method 1
The controlled heating via Joule effect of the shape memory alloy wire causes its contraction and consequently the movement of the lens carrier with respect to the housing
Implementation Method 2
the controlled heating via Joule effect of the shape memory alloy wire causes its contraction
Data Source
AI summary
Camera module autofocus actuator comprising a movable lens carrier, one or more shape memory alloy wires, a first return elastic element, a second return elastic element substantially identical to the and symmetric to the first return elastic element, wherein one end of the one or more shape memory alloy is mounted to the first return elastic element and the other end to another return elastic element.