MEMS Inertial Sensor Flexible Protrusion Impact Protection

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Solution Overview

Problem

Inertial sensors using MEMS technology face issues with damage and operation failure due to excessive seesaw swinging and stiction when subjected to strong vibrations or impacts, as the movable body collides with protrusions, leading to potential short circuits and mechanical damage.

Innovation Solution

The design incorporates a substrate with a first movable body that swings around a first rotation axis, supported by a first support beam, and includes a second and third movable body that swing around intersecting axes, with protrusions on the substrate or lid to prevent excessive swinging and absorb impact energy, utilizing insulating layers to prevent short circuits and enhance damping through optimized through-hole arrangements.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a protrusion is provided to prevent excessive swinging of the movable body, then the movable body is protected from contacting fixed electrodes, but the movable body and protrusion collide as rigid bodies under strong vibration or impact, causing damage or stiction

Engineering Contradiction:

Improveprevention of short circuitVSAvoiddamage to movable body or protrusion

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

The patent replaces the rigid protrusion with a flexible movable body that can bend and deform. The movable body is designed with flexible portions that allow it to elastically deform during impact, preventing rigid body collision while still providing the stopping function to prevent excessive swinging and short circuits.

Inventive Principle:

Principle #30Flexible shells and thin films

Solution Approach 2:

The patent changes the mechanical parameters of the movable body by introducing flexible portions with specific rigidity characteristics. The movable body is designed to have different rigidity in different regions, allowing it to be rigid enough to prevent excessive swinging but flexible enough to deform during impact, thereby resolving the contradiction between protection and damage.

Inventive Principle:

Principle #35Parameter changes

2Adaptability or versatility

If the movable body swings excessively to detect strong acceleration, then detection range is improved, but the movable body collides with the protrusion causing operation failure due to stiction

Engineering Contradiction:

Improvedetection rangeVSAvoidoperation failure due to stiction

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The flexible movable body can elastically deform during excessive swinging, allowing the sensor to detect strong acceleration signals without causing rigid body collision. The flexibility prevents the sticking phenomenon while maintaining the ability to swing extensively for detection purposes.

Inventive Principle:

Principle #30Flexible shells and thin films

Solution Approach 2:

The movable body is designed with built-in flexibility that acts as a cushion before collision occurs. This prior cushioning through elastic deformation prevents the rigid body impact that would cause stiction, while still allowing the full range of motion needed for detecting strong acceleration.

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

This configuration effectively reduces damage and stiction by absorbing impact energy and preventing excessive swinging, ensuring accurate detection of acceleration while maintaining sensor integrity under varying conditions.

Implementation Method 1

capable of detecting an acceleration in a vertical direction based on a change in electrostatic capacitance between the first and second mass members

Methodology Applied

Scientific EffectElectrostatic capacitance: Capacitance

Implementation Method 2

a second insulating layer covering a surface of the lid or the substrate, the second insulating layer having a different coefficient of thermal expansion than that of the first insulating layer

Methodology Applied

Scientific EffectElectrical insulation: Electrical Resistance

Implementation Method 3

the movable body and the protrusion collide with each other due to excessive seesaw swinging... the movable body or a contact portion of the protrusion may be broken

Methodology Applied

Scientific EffectElastic deformation: Elasticity

Data Source

PatentUS11693023B2Inertial sensor and inertial measurement unit

Publication Date: 2023.07.04 SEIKO EPSON CORP

AI summary

In an inertial sensor, a first movable body configured to swing around a first rotation axisrotation axis along a first direction has an opening; the opening includes a second movable body configured to swing around a second rotation axisrotation axis along a second direction, a second support beam supporting the second movable body as the second rotation axisrotation axis, a third movable body configured to swing around a third rotation axisrotation axis along the second direction, and a third support beam supporting the third movable body as the third rotation axisrotation axis; and a protrusion is provided at a surface facing the second movable body and the third movable body, or at the second movable body and the third movable body, the protrusion protruding toward the second movable body and the third movable body or the surface.