Physical Quantity Sensor Beam Structure Impact Resistance

Solution Overview

Problem

Existing physical quantity sensors, such as acceleration sensors, are prone to breaking when subjected to strong impacts due to stress concentration on beams, particularly in the Z-axis direction.

Innovation Solution

The design incorporates a support structure with first and second fixed plates, first and second beams, and third and fourth beams that are torsionally deformable, reducing stress concentration by allowing the beams to bend and dispersing stress, and includes stoppers to prevent collision and potential breakage.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If a simple beam structure is used to support the movable electrode, then the device complexity is reduced, but the reliability deteriorates due to stress concentration and beam breakage under strong impact

Engineering Contradiction:

Improvebeam structureVSAvoidbeam breakage resistance

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The support structure is divided into multiple beams (first beam, second beam, third beam, fourth beam) arranged in a grid pattern between the fixed electrode and movable electrode. This segmentation distributes the mechanical stress across multiple independent beam elements, preventing stress concentration at single critical points and reducing the likelihood of complete structure failure under impact loads.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The beam structure is designed with specific geometric characteristics including width W1 for the first and second beams, and width W2 for the third and fourth beams. These localized dimensional variations optimize the stress distribution and torsional deformation characteristics of each beam segment, enhancing overall impact resistance while maintaining structural functionality.

Inventive Principle:

Principle #3Local quality

2Stability of the object's composition

If the beam is made rigid to maintain structural stability, then the stability is improved, but the manufacturing precision deteriorates due to difficulty in forming rigid beams with precise dimensions

Engineering Contradiction:

Improvestructural stabilityVSAvoidbeam formation accuracy

Core Design Contradiction:

Stability of the object's compositionVSManufacturing precision

Solution Approach 1:

The beam dimensions are optimized with specific width parameters (W1 for first and second beams, W2 for third and fourth beams) that balance structural stability with manufacturability. These parameter choices enable the beams to achieve adequate rigidity for structural stability while remaining formable through standard semiconductor manufacturing processes like ICP etching, thereby improving manufacturing precision.

Inventive Principle:

Principle #35Parameter changes

3Reliability

If the beam is made flexible to absorb impact energy, then the reliability is improved, but the manufacturing precision deteriorates due to difficulty in controlling beam deformation characteristics

Engineering Contradiction:

Improveimpact resistanceVSAvoidbeam deformation control

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The support structure is divided into multiple beams (first beam, second beam, third beam, fourth beam) arranged in a grid pattern between the fixed electrode and movable electrode. This segmentation distributes the mechanical stress across multiple independent beam elements, preventing stress concentration at single critical points and reducing the likelihood of complete structure failure under impact loads.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The beam structure is designed with specific geometric characteristics including width W1 for the first and second beams, and width W2 for the third and fourth beams. These localized dimensional variations optimize the stress distribution and torsional deformation characteristics of each beam segment, enhancing overall impact resistance while maintaining structural functionality.

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

This design enhances impact resistance and reduces the likelihood of beam breakage by dispersing stress and preventing collisions, while also enabling high-precision etching and accurate formation of beams, thereby improving the sensor's durability and accuracy.

Implementation Method 1

in a case where a strong impact is applied in the Z-axis direction, the first beam and the second beam can be torsionally deformed

Methodology Applied

Scientific EffectTorsional deformation: Torsion Spring

Implementation Method 2

in the case of forming the movable body and the support by etching using inductive coupling method (ICP), the etching rate to form the third beam can be reduced

Methodology Applied

Scientific EffectEtching: Ablation

Data Source

PatentUS11181546B2Physical quantity sensor, electronic device, and vehicle

Publication Date: 2021.11.23 SEIKO EPSON CORP

AI summary

A physical quantity sensor includes a substrate; a movable body that is displaceable about a support axis according to a physical quantity and includes an opening; a support that is provided on the substrate and is located in the opening, and the support includes a first fixed plate and a second fixed plate that are fixed to the substrate and provided so as to sandwich the support axis in plan view; a first beam and a second beam that each connect the first fixed plate with the second fixed plate and are spaced apart from each other; a third beam extending in a direction of the support axis and connecting the first beam with the movable body; and a fourth beam extending in a direction of the support axis and connecting the second beam with the movable body.