MEMS Transducer Variable Vent Flap High Pressure Protection

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Solution Overview

Problem

Conventional MEMS transducers, such as capacitive microphones, are vulnerable to damage from high pressure impulses, which can occur during handling or accidental drops, and existing variable vent structures often compromise between pressure relief and acoustic performance.

Innovation Solution

A MEMS transducer with a variable vent structure featuring a moveable vent cover comprising at least two flap sections, where the first flap section is hingedly coupled to the side of the vent hole and the second flap section is articulated to the first, allowing for a varying flow path size in response to pressure differentials, ensuring minimal impact on normal operating pressures while providing adequate relief during high-pressure events.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a variable vent structure with a moveable vent cover is used to relieve high pressure impulses, then the transducer's ability to withstand high pressure impulses is improved, but the acoustic performance may be compromised due to the vent opening at normal operating pressures

Engineering Contradiction:

Improveability to withstand high pressure impulsesVSAvoidacoustic performance degradation

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The vent cover is made moveable and responsive to pressure differentials, transitioning from a static vent structure to a dynamic one. The cover opens only when the pressure differential exceeds a threshold, allowing the system to adapt its venting behavior based on operating conditions, thus protecting against high pressure impulses while maintaining acoustic performance during normal operation

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The flow path size is changed dynamically in response to pressure differentials. At normal operating pressures, the vent cover remains closed maintaining a small flow path size and preserving acoustic performance. During high pressure events, the cover opens to increase the flow path size, enabling rapid pressure equalization and protection of the transducer

Inventive Principle:

Principle #35Parameter changes

2Reliability

If the vent hole is kept open to provide rapid pressure equalization during high pressure events, then the protection against high pressure impulses is improved, but the sensitivity and acoustic performance during normal operation deteriorates

Engineering Contradiction:

Improveprotection against high pressure impulsesVSAvoidsensitivity during normal operation

Core Design Contradiction:

ReliabilityVSMeasurement precision

Solution Approach 1:

The vent structure transitions from a permanently open state to a dynamically controlled state. The moveable vent cover responds to pressure differentials, remaining closed during normal operation to preserve sensitivity and acoustic performance, and opening only during high pressure events to provide rapid pressure equalization and protection

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The vent cover is positioned to preliminarily block the vent hole before high pressure events occur. This preliminary blocking action prevents acoustic performance degradation during normal operation, while the cover's moveable nature allows it to yield and open when high pressure impulses occur, providing protection when needed

Inventive Principle:

Principle #9Preliminary anti-action

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 enhances the transducer's ability to withstand high pressure impulses without compromising acoustic performance, maintaining sensitivity within the normal operating range and ensuring rapid pressure equalization during high-pressure events, thus protecting the membrane from damage.

Implementation Method 1

the vent cover is moveable from said equilibrium position in response to a pressure differential across the vent cover so as to vary the size of a flow path through the vent hole

Methodology Applied

Scientific EffectPressure differential: Pressure Gradient

Implementation Method 2

a flexible membrane which is free to move in response to pressure differences generated by sound waves

Methodology Applied

Scientific EffectPressure difference: Pressure Gradient

Implementation Method 3

the membrane is moved by electrostatic forces generated by varying a potential difference applied across the electrodes

Methodology Applied

Scientific EffectElectrostatic forces: Electrostatics

Data Source

PatentUS10301174B2MEMS device and processes

Publication Date: 2019.05.28 CIRRUS LOGIC INC

AI summary

This application relates to MEMS transducer having a membrane layer (101) and at least one variable vent structure (301). The variable vent structure has a vent hole for venting fluid so as to reduce a pressure differential across the membrane layer and a moveable vent cover (302a, 302b) which, at an equilibrium position, at least partly blocks the vent hole. The vent cover is moveable from its equilibrium position in response to a pressure differential across the vent cover so as to vary the size of a flow path through the vent hole. In various embodiments the vent cover comprises at least a first flap section (302a) and a second flap section (302b), the first flap section being hingedly coupled to the side of the vent hole and the second flap section being hingedly coupled to the first flap section so as to be moveable with respect to the first flap section. In some embodiments the second flap section (302b) may be configured so that it deflects away from the first section (302a) more readily than the first section deflects away from its equilibrium position.