Physical Quantity Sensor Protrusion Positioning for Stress Reduction
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Solution Overview
Problem
Existing physical quantity sensors configured according to the rocker lever principle face breakage risks due to excessive acceleration, as the protrusion at the end portion generates high stress in the coupling portion when the movable body contacts the substrate.
Innovation Solution
The physical quantity sensor design includes a movable body with a rotation shaft and a coupling portion connected in an intersecting direction, featuring protrusions that protrude from the support substrate towards the mass portion, positioned within a specific distance range (0.18L to 0.88L) to reduce bending stress and prevent breakage, along with symmetrical and lattice-shaped configurations for enhanced impact resistance and manufacturing efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the protrusion is disposed at the end portion of the mass portion, then the movable body is prevented from contacting the substrate, but large stress is generated in the coupling portion causing breakage risk
Solution Approach 1:
The protrusion is positioned at a specific location (0.18L to 0.88L from the end portion) rather than uniformly at the end, creating localized stress distribution that prevents both substrate contact and excessive stress concentration in the coupling portion
Solution Approach 2:
The position parameter of the protrusion is optimized within a specific range (0.18L to 0.88L) to balance two opposing requirements: preventing substrate contact while minimizing stress on the coupling portion, thereby resolving the contradiction between reliability and strength
2Strength
If the protrusion is positioned to prevent breakage, then coupling portion stress is reduced, but the movable body may contact the substrate
Solution Approach 1:
The protrusion is strategically positioned within the 0.18L to 0.88L range to create localized support that simultaneously achieves stress reduction and substrate contact prevention
Solution Approach 2:
By optimizing the protrusion position parameter within a specific range, the design achieves a balance point where both coupling portion strength and substrate contact prevention are satisfied, resolving the contradiction between these two requirements
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 significantly reduces bending stress on the coupling portion, enhancing the sensor's impact resistance and reliability by distributing the impact and stabilizing the movable body's attitude, while also improving manufacturing efficiency by using protrusions of equal height.
Implementation Method 1
a physical quantity sensor that is configured according to a rocker lever principle and measures the acceleration from electrostatic capacitance that changes according to the acceleration applied in a vertical direction
Data Source
AI summary
A physical quantity sensor includes a movable body that includes a beam portion, a coupling portion that is connected with the beam portion at connection positions and is provided in a direction intersecting with the beam portion, and a first and second mass portions that are connected with the coupling portion; a first and second fixed electrodes that are provided on a support substrate and are opposed to the first and second mass portions; and a protrusion is provided and protrude from the support substrate toward the first and second mass portions. In the intersecting direction, in a case where a distance from connection positions to end portions opposite to the beam portion is L, and a distance from the protrusions to end portions opposite to the beam portion is L1, the distance L1 is 0.18 L or longer and 0.88 L or shorter.