Physical Quantity Sensor L-Shaped Restricting Unit for Impact Resistance
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Solution Overview
Problem
Existing physical quantity sensors, such as those disclosed in JP-A-2011-247714, are prone to failure due to excessive impacts, which can cause breakage and sticking of movable electrodes with fixed electrodes, especially when stoppers without elastic functions are used to limit displacement.
Innovation Solution
A physical quantity sensor design incorporating a movable body with a restricting unit having an L-shaped configuration, including first and second portions extending in orthogonal directions, and a third portion facing a fixed portion, which absorbs excessive impacts by bending and prevents direct contact between electrodes, thereby enhancing impact resistance and miniaturization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If stoppers without elastic functions are used to limit displacement, then displacement limitation is achieved, but impact resistance deteriorates causing breakage and sticking
Solution Approach 1:
The restricting unit is designed with elastic portions that can deform elastically to absorb impact energy before it reaches the electrodes. This beforehand cushioning mechanism prevents direct transmission of excessive impact forces that would cause breakage or sticking, while still maintaining the displacement limitation function.
Solution Approach 2:
The restricting unit changes its mechanical parameters by incorporating elastic portions with specific elastic moduli and dimensional parameters. These parameter changes allow the structure to transition from a rigid displacement limiter to a compliant impact-absorbing mechanism that maintains both displacement control and impact resistance.
2Reliability
If restricting unit with L-shaped configuration is used, then impact resistance is improved, but device complexity increases
Solution Approach 1:
The restricting unit is segmented into multiple portions (first portion, second portion, third portion) with distinct functions. The first and second portions form the L-shaped configuration for impact absorption, while the third portion provides additional structural support. This segmentation allows each portion to be optimized for its specific function while maintaining overall simplicity.
Solution Approach 2:
The restricting unit serves multiple functions simultaneously: it limits displacement in both first and second directions, absorbs impact energy through elastic deformation, and maintains electrode spacing. This multi-functionality reduces the need for separate components, thereby managing device complexity while improving impact resistance.
3Volume of moving object
If compact sensor size is achieved, then miniaturization is improved, but detection sensitivity may deteriorate
Solution Approach 1:
The restricting unit is integrated into the compact sensor structure with portions arranged in a nested or space-efficient configuration. The L-shaped first and second portions utilize vertical and horizontal spaces efficiently, allowing the restricting unit to occupy minimal volume while maintaining its impact-absorbing and displacement-limiting functions.
Solution Approach 2:
The restricting unit utilizes three-dimensional space by extending in both first and second directions orthogonal to each other. This dimensional approach allows the structure to achieve compact footprint on the substrate while maintaining adequate electrode spacing and detection sensitivity through vertical and lateral arrangement optimization.
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 effectively absorbs excessive impacts, preventing breakage and sticking, while maintaining detection sensitivity and allowing for compact sensor size by distributing stress and ensuring electrode spacing changes for accurate acceleration detection.
Implementation Method 1
a third portion extending in a second direction orthogonal to the first direction from the other end of the second portion; and a fixed portion fixed to the substrate, wherein the third portion faces the fixed portion
Data Source
AI summary
A physical quantity sensor detects a physical quantity in at least one of a first direction and a second direction. The physical quantity sensor includes a fixed electrode unit provided on a substrate, a movable body including a movable electrode unit provided such that movable electrodes face fixed electrodes of the fixed electrode unit, a fixed portion fixed to the substrate, a support beam having one end coupled to the fixed portion and the other end coupled to the movable body, and a restricting unit configured to restrict displacement of the movable body. The restricting unit includes a first portion having one end coupled to the movable body and extending in the first direction, and a second portion having one end coupled to the other end of the first portion and extending in the second direction.