Piezoelectric Power Generator with Compressive Stress Design

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Solution Overview

Problem

Piezoelectric power generators face low mechanical reliability due to the vulnerability of piezoelectric elements to tensile stress, which can lead to cracks during operation.

Innovation Solution

A piezoelectric power generator design featuring a beam with a piezoelectric element bonded to its surface and a flexible body connected to the beam, where stress is applied only when the flexible body is concave, avoiding tensile stress on the piezoelectric element, thus enhancing mechanical reliability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Power

If piezoelectric elements are used in a conventional power generator design with weights and cantilever beams, then electrical power can be generated through vibration, but tensile stress causes cracks and reduces mechanical reliability

Engineering Contradiction:

Improveelectrical power generationVSAvoidmechanical reliability

Core Design Contradiction:

PowerVSReliability

Solution Approach 1:

The patent inverts the conventional design by replacing the weight-cantilever system with a flexible body-beam system where the beam is fixed to the flexible body instead of having weights on free ends. This inversion changes the stress distribution pattern from alternating tensile-compressive to primarily compressive stress on the piezoelectric elements, eliminating the reliability issue while maintaining power generation capability

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The patent changes the structural parameters of the power generator by modifying the beam configuration and stress application mechanism. The beam is designed with specific dimensions and material properties, and the stress-applying portion is positioned to create unidirectional compressive stress. This parameter change transforms the stress state from bidirectional (tensile and compressive) to unidirectional (compressive only), resolving the contradiction between power generation and mechanical reliability

Inventive Principle:

Principle #35Parameter changes

2Use of energy by moving object

If stress is applied to piezoelectric elements during vibration, then electrical energy is generated, but tensile stress during vibration causes cracks in the piezoelectric elements

Engineering Contradiction:

Improvekinetic energy conversionVSAvoidtensile stress damage

Core Design Contradiction:

Use of energy by moving objectVSObject-affected harmful factors

Solution Approach 1:

The patent converts the harmful tensile stress into beneficial compressive stress by redesigning the stress application mechanism. The stress-applying portion is configured to push against the beam during flexible body deformation, ensuring that the piezoelectric elements experience only compressive stress. This transforms the potentially harmful alternating stress into beneficial unidirectional compressive stress that generates electrical energy without causing cracks

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Solution Approach 2:

The patent applies local quality by positioning the piezoelectric elements and stress-applying portion at specific locations on the beam. The piezoelectric elements are bonded to the beam surface at a location where compressive stress is concentrated during flexible body deformation. The stress-applying portion is positioned to apply force locally at the beam's end, creating a stress distribution pattern that protects the piezoelectric elements from tensile stress while maintaining effective energy conversion

Inventive Principle:

Principle #3Local quality

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 effectively suppresses tensile stress on the piezoelectric element, preventing damage and achieving high mechanical reliability by ensuring only compressive stress is applied during operation.

Implementation Method 1

The piezoelectric power generator is equipped with a beam, a piezoelectric element and a flexible body. The piezoelectric element is bonded to a surface on one side of the beam... stress is applied to the beam when the flexible body is deformed... electrical power is generated

Methodology Applied

Scientific EffectPiezoelectric effect: Piezoelectric Effect

Data Source

PatentUS8330331B2Piezoelectric power generator

Publication Date: 2012.12.11 MURATA MFG CO LTD

AI summary

A piezoelectric power generator that performs conversion between kinetic energy and electrical energy. The piezoelectric power generator is equipped with a beam, a piezoelectric element and a flexible body. The piezoelectric element is bonded to a surface on one side of the beam. The flexible body is arranged on a side of the beam that is opposite to that on which the piezoelectric element is provided. A portion of the beam is connected to the flexible body. The beam is configured such that stress is applied to the beam when the flexible body is deformed into a concave shape with respect to the beam, whereas a stress is not applied to the beam when the flexible body is deformed into a convex shape with respect to the beam.