Compact MEMS Vibration Sensor With Coupling Volume for Low Height
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Solution Overview
Problem
Existing micro-electromechanical transducers in hearing devices suffer from significant height, compromising their compactness and sensitivity.
Innovation Solution
A vibration sensor design featuring a MEMS die, pressure generating arrangement, and signal processor, with a frame structure and suspension member, arranged in a space-saving manner to minimize height while maintaining sensitivity, utilizing a compliant adhesive and acoustical connections for efficient pressure variation detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a stand-alone MEMS microphone and sub-assembly are used for vibration detection, then the vibration sensor can detect pressure variations, but the height of the device becomes significantly increased
Solution Approach 1:
The patent combines the MEMS microphone and pressure generating arrangement into a single integrated housing structure. The MEMS die is mounted on the PCB within the same housing that contains the pressure generating arrangement, eliminating the need for separate sub-assemblies and reducing overall device height while maintaining vibration detection functionality
Solution Approach 2:
The patent nests the MEMS die within the housing structure that also contains the pressure generating arrangement. The MEMS cartridge is positioned within the housing, and the coupling volume is formed by the indentation in the frame structure, creating a nested configuration that saves space and reduces height
2Length of stationary object
If the vibration sensor is compacted to reduce height, then the device becomes more suitable for hearing devices, but the sensitivity and performance may be compromised
Solution Approach 1:
The patent creates a localized coupling volume through the indentation in the frame structure, concentrating the pressure variations in a specific region where the MEMS die is positioned. This localized approach ensures that pressure variations are effectively transmitted to the MEMS cartridge while maintaining overall device compactness
Solution Approach 2:
The patent introduces a coupling volume as an intermediary between the pressure generating arrangement and the MEMS die. This coupling volume, defined by the indentation and suspension member, effectively transmits pressure variations from the moving mass to the MEMS cartridge, maintaining sensitivity despite the compact configuration
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, capable of detecting voice-induced vibrations for voice recognition, and withstands severe mechanical shocks with reduced resonance peaks and self-noise.
Implementation Method 1
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 generating pressure variations in a coupling volume in response to vibrations of the vibration sensor
Implementation Method 2
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 is adapted to detect and convert detected pressure variations to an electrical output signal
Data Source
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.