Actuator Flexure Tapering for Stress Reduction
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Solution Overview
Problem
Conventional distributed mode actuators (DMAs) and electromagnetic (EM) actuators are susceptible to mechanical stress due to bending, leading to decreased performance and lifetime, especially those with flexible components of fixed widths and right-angle bends.
Innovation Solution
The actuators feature flexible components with strategically increased dimensions in high-stress regions, including a rigid frame with an elongate flexure that tapers in width and is attached to a magnetic circuit with a voice coil, allowing for stress distribution and reduced volume occupation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional DMAs and EM actuators use flexible components with fixed widths and right-angle bends, then the device complexity is reduced and ease of manufacture is improved, but the reliability decreases due to mechanical stress from bending
Solution Approach 1:
The flexure width is varied locally along its length, with increased width at high-stress regions (attachment points and bend areas) and reduced width in low-stress regions. This local variation in geometry optimizes stress distribution and prevents failure without requiring complex overall structure
Solution Approach 2:
The flexure transitions from a uniform width design to a non-uniform width design, changing the geometric parameter (width) along the length of the flexure to match the stress distribution pattern, with wider sections at high-stress locations
2Strength
If the flexure width is increased in high-stress regions, then the strength and reliability are improved, but the volume occupied by the actuator increases
Solution Approach 1:
Instead of uniformly increasing flexure width throughout, the design applies increased width only at specific high-stress locations while maintaining or reducing width in low-stress regions, optimizing strength-to-volume ratio
Solution Approach 2:
The flexure uses out-of-plane bending (right-angle bends) to achieve compact spatial arrangement, allowing the actuator to fit within constrained volumes while maintaining sufficient flexure length for functionality
3Adaptability or versatility
If the flexible component is subjected to repeated bending during operation, then the actuator can accommodate displacement, but the mechanical stress decreases performance and lifetime
Solution Approach 1:
The flexure design concentrates structural reinforcement at the bend locations and attachment points where stress is highest, while maintaining flexibility in the intermediate regions, allowing repeated displacement cycles without failure
Solution Approach 2:
The increased width at high-stress regions acts as a preventive measure against stress concentration and fatigue failure, cushioning the structure against the harmful effects of repeated bending before damage can occur
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 design reduces the likelihood of actuator failure from mechanical stress while maintaining performance and fitting within constrained volumes, suitable for integration in electronic devices like mobile devices.
Implementation Method 1
an electromechanical module attached to a portion of the flexure unattached to the frame, the electromechanical module being configured to displace an end of the flexure that is free of the frame in a direction perpendicular to the surface of the panel during operation of the actuator
Data Source
Figure 1~2
Figure 3A~3B
Figure 4A~4B
AI summary
A device comprising: an actuator (500) attached to a panel (106) and configured to couple vibrations to the panel to cause the panel to emit audio waves, the panel (106) extending in a plane, the actuator (500) comprising: a frame (520) comprising one or more pillars extending perpendicular to the panel's plane; a magnetic circuit assembly (A, B, 542, 544, 548) comprising a magnet (A, B, 542, 544) and a voice coil (548), the magnet and voice coil being moveable relative to each other during operation of the actuator along an axis perpendicular to the panel's plane (106); and one or more suspension members (530a-530d) attaching the frame (520) to the magnetic circuit assembly (A, B, 542, 544, 548). Each suspension member (530a-530d) comprises: a segment (630) attaching the suspension member (530a-530d) to a pillar of the frame (520), a first arm (601) extending away from the segment (630) to a first end attached to the magnetic circuit assembly (A, B, 542, 544, 548), and a second arm (602) extending away from the segment (630) to a second end attached to the magnetic circuit assembly (A, B, 542, 544, 548), the first and second ends being respectively attached to opposite sides of the magnetic assembly. During operation of the actuator the first arm (601) and the second arm (602) of the one or more suspension members (530a-530d) flex to accommodate axial displacements of the magnet assembly (A, B, 542, 544, 548) relative to the voice coil (548).