MEMS Vibration Sensor Layout for Low-Height Skull Vibration Detection
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Solution Overview
Problem
Existing micro-electromechanical transducers in vibration sensors, such as those used in hearing devices, suffer from significant height and compromise sensitivity due to their design.
Innovation Solution
A compact vibration sensor design incorporating a pressure detecting arrangement with a MEMS die and signal processor, a pressure generating arrangement with a frame structure and suspension member, and a housing that minimizes height while maintaining sensitivity by optimizing the acoustical connections and volumes within the sensor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If a traditional micro-electromechanical transducer design is used, then the vibration sensor can detect pressure variations, but the height becomes significantly large
Solution Approach 1:
The patent transitions from a traditional three-dimensional stacked arrangement to a planar two-dimensional layout where the MEMS die and pressure generating arrangement are arranged side-by-side on the same substrate level. This dimensional change allows the sensor to achieve compact height while maintaining the necessary acoustic coupling volume for sensitivity.
Solution Approach 2:
The patent embeds the pressure generating arrangement within the acoustic coupling volume of the MEMS die structure. The frame structure with indentation and suspension member are integrated into the existing MEMS cartridge architecture, allowing nested placement of functional elements without increasing overall height.
2Area of stationary object
If the vibration sensor dimensions are reduced to achieve compact footprint, then the sensor becomes smaller, but the sensitivity may be compromised
Solution Approach 1:
The patent applies local quality optimization by creating a specific indentation in the frame structure that forms a localized acoustic coupling volume. This localized volume is acoustically connected to the MEMS cartridge through a dedicated opening, concentrating the acoustic energy in a specific region to maintain sensitivity despite the overall compact footprint.
Solution Approach 2:
The patent introduces an acoustic coupling volume as an intermediary structure between the pressure generating arrangement and the MEMS cartridge. This intermediate acoustic chamber ensures efficient pressure transmission while allowing the components to be arranged in a compact planar configuration rather than requiring direct vertical stacking.
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 achieves a compact footprint of 3 mm x 4 mm x 2 mm with high sensitivity and reduced resonance peaks, effectively detecting voice-induced vibrations in the skull for applications like hearing aids.
Implementation Method 1
the pressure detecting arrangement comprises a MEMS die and a signal processor, wherein the MEMS die comprises a front volume and a MEMS cartridge
Implementation Method 2
a pressure generating arrangement for generating pressure variations in a coupling volume in response to vibrations of the vibration sensor
Implementation Method 3
the coupling volume is acoustically connected to the MEMS cartridge of the MEMS die via an acoustical opening in the frame structure
Data Source
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AI summary
The present invention relates to vibration sensor comprising a pressure detecting arrangement for detecting generated pressure variations, wherein the pressure detecting arrangement comprises a MEMS die and a signal processor, wherein the MEMS die comprises a front volume and a MEMS cartridge, and wherein the MEMS die comprises oppositely arranged first and second surfaces; a pressure generating arrangement for generating pressure variations in a coupling volume in response to vibrations of the vibration sensor, wherein the pressure generating arrangement comprises a frame structure comprising an indentation, a suspension member comprising first and second surfaces and a moveable mass secured to at least part of the first or second surfaces of the suspension member; and a PCB comprising a first surface, and a housing secured to the first surface of the PCB using an adhesive, wherein the housing and the first surface of the PCB define, in combination, a volume within which volume the pressure detecting arrangement and the pressure generating arrangement are arranged, wherein the coupling volume is defined by the indentation of the frame structure and at least part of the second surface of the suspension member, and wherein said coupling volume is acoustically connected to the MEMS cartridge of the MEMS die via an acoustical opening in the frame structure, and wherein the first surface of the MEMS die is secured to at least part of the frame structure, and wherein at least part of the second surface of the MEMS die is secured to the first surface of the PCB. The present invention further relates to a hearing device comprising such a vibration sensor, and to use of such a vibration sensor for detecting voice induced vibrations in the skull of a user of a hearing device.