Physical Quantity Sensor Stress Distortion Absorption

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Solution Overview

Problem

Existing acceleration measurement devices face issues with stress distortion due to thermal expansion coefficient differences between dissimilar materials, leading to reduced measurement accuracy and reliability when mounted on printed circuit boards.

Innovation Solution

A physical quantity sensor design featuring a base, movable portion, and arm portions with strategically positioned fixed regions that absorb stress distortion through localized deformation, preventing transmission of stress to the measurement element, and including a constricted portion acting as a fulcrum for the movable portion.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the outer circumference of the acceleration measurement device is all fixed to the printed circuit board, then the device is securely mounted, but stress distortion due to thermal expansion coefficient differences is transmitted to the measurement element, reducing measurement accuracy

Engineering Contradiction:

Improvemounting stabilityVSAvoidmeasurement accuracy

Core Design Contradiction:

ReliabilityVSMeasurement precision

Solution Approach 1:

The fixed region is divided into multiple discrete locations rather than continuous fixation. The arm portion has fixed regions at specific positions (first fixed region on the base side, second fixed region on the movable portion side) while leaving other regions free to deform, segmenting the stress transmission path

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different regions of the arm portion have different fixation properties. The first fixed region and second fixed region provide localized support while other regions maintain flexibility. This local differentiation allows the structure to be rigid where needed and flexible where needed to absorb thermal stress

Inventive Principle:

Principle #3Local quality

2Stability of the object's composition

If the arm portion is made more rigid to improve structural stability, then mounting stability improves, but stress distortion from thermal expansion is more strongly transmitted to the measurement element

Engineering Contradiction:

Improvestructural stabilityVSAvoidmeasurement accuracy

Core Design Contradiction:

Stability of the object's compositionVSMeasurement precision

Solution Approach 1:

The arm portion exhibits local quality with rigid fixed regions for stability and flexible non-fixed regions for stress absorption. The fixed regions provide structural support while the non-fixed portions allow thermal expansion/contraction without transmitting stress to the measurement element

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The non-fixed portions of the arm portion act as intermediaries that absorb and isolate thermal stress between the rigid structure and the measurement element, preventing direct stress transmission while maintaining structural integrity

Inventive Principle:

Principle #24Intermediary (Mediator)

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 reduces stress distortion, enhancing measurement accuracy and reliability by allowing localized deformation of arm portions, maintaining peak temperature stability and improving reproducibility and hysteresis characteristics compared to traditional designs.

Implementation Method 1

a constricted portion serving as a fulcrum for the movable portion

Methodology Applied

Scientific EffectFulcrum mechanism: Lever

Implementation Method 2

fixed regions that absorb stress distortion through localized deformation

Methodology Applied

Scientific EffectStress distortion absorption: Deformation

Data Source

PatentUS11630122B2Physical quantity sensor, physical quantity sensor device, and inclinometer, inertia measurement device, structure monitoring device, and vehicle using physical quantity sensor device

Publication Date: 2023.04.18 SEIKO EPSON CORP

AI summary

A physical quantity sensor includes a base, at least two arms, a movable plate, a hinge, and a physical quantity measurement element. Four quadrants of the sensor are defined by first and second orthogonal lines. The first line passes through the center of the sensor and crosses the hinge. The second line extends along the hinge. Fixed regions of the sensor are located in the first and second quadrants. No fixed regions are located in at least one of the third and fourth quadrants. The third and fourth quadrants are closer to the base than the first and second quadrants in a plan view.