Soft Mechanical Stops for Piezoelectric Cantilever Over-Travel

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Solution Overview

Problem

Piezoelectric cantilever devices are prone to failure due to excessive force, which can cause the piezoelectric material to break or crack, leading to device malfunction or failure, especially when subjected to impacts like drops.

Innovation Solution

Incorporating a flexible cantilever stop spring and landing pads within the device to absorb excessive force and prevent over-bending, using flexible electrodes and piezoelectric materials, and strategically placing proof masses to distribute stress, thereby providing a soft stop mechanism that absorbs shock and protects the device.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a rigid stop mechanism is used to limit over-travel of the proof mass, then the device structure is simple, but the piezoelectric material may break or crack due to excessive force

Engineering Contradiction:

Improveprotection against excessive forceVSAvoidpiezoelectric material integrity

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

The patent applies beforehand cushioning by incorporating a compliant stop mechanism that absorbs excessive force before it can damage the piezoelectric material. The compliant stop acts as a pre-positioned protective element that engages during over-travel events, cushioning the impact and preventing direct transmission of damaging forces to the piezoelectric cantilever and proof mass assembly.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

2Reliability

If proof masses are attached to increase flex strain, then the sensitivity and output of the device is improved, but the risk of breaking from excessive force increases

Engineering Contradiction:

Improvedevice sensitivityVSAvoidvulnerability to impact damage

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The compliant stop serves as a beforehand cushioning mechanism that protects the proof mass and piezoelectric material from impact damage. By positioning the stop in advance along the over-travel path, it absorbs excessive forces before they can cause damage, allowing the proof mass to be sized for optimal sensitivity without compromising reliability.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

3Power

If the cantilever arm is made more flexible to increase strain, then the piezoelectric output is improved, but the cantilever becomes more susceptible to breaking

Engineering Contradiction:

Improvepiezoelectric voltage outputVSAvoidcantilever resistance to breaking

Core Design Contradiction:

PowerVSStrength

Solution Approach 1:

The compliant stop provides beforehand cushioning that protects the flexible cantilever from excessive bending forces. This allows the cantilever to be designed with higher flexibility for maximum piezoelectric output while the stop acts as a safety mechanism that engages during extreme events, preventing the cantilever from bending beyond its elastic limit and breaking.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

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 effectively prevents damage from excessive stress, enhancing the reliability and durability of piezoelectric devices by absorbing shock and reducing the risk of material failure, while maintaining manufacturing simplicity and cost-effectiveness.

Implementation Method 1

Piezoelectric materials may be used to generate electrical energy when strain is applied to the piezoelectric material by external forces or vibrations

Methodology Applied

Scientific EffectPiezoelectric effect: Piezoelectric Effect