Physical Quantity Detection Device Stress Reduction
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Solution Overview
Problem
Existing physical quantity detection devices face reduced sensitivity due to stress transmission from the difference in the coefficient of linear expansion between the support structure and the package, which affects the resonance frequency of the detection element.
Innovation Solution
A physical quantity detection device design with a shorter distance between the first and second fixing portions, and bended support members to reduce stress transmission, incorporating a connection body with clearances and strategically placed masses to stabilize the device and prevent distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the distance between the first and second fixing portions is reduced to minimize stress transmission, then the detection sensitivity is improved, but the device complexity increases due to the constrained layout requirements
Solution Approach 1:
The patent positions the first and second fixing portions in a direction substantially perpendicular to the detection axis, utilizing spatial arrangement in multiple dimensions to achieve short distance fixation while maintaining proper detector orientation and functionality
2Measurement precision
If bended support members are used to reduce stress transmission, then the detection sensitivity is improved, but the manufacturing precision requirements increase due to the need for precise bended portion geometry
Solution Approach 1:
The patent specifies that the bended portions should have a curvature radius of 0.5 mm to 2.0 mm, transforming the design constraint into a quantifiable parameter range that balances stress reduction effectiveness with manufacturing feasibility
3Reliability
If the fixing portions are positioned close together to reduce thermal expansion stress, then the reliability is improved, but the ease of manufacture decreases due to tighter tolerances
Solution Approach 1:
The patent applies different design characteristics to different regions: the support members have bended portions for stress relief while the connection body has a specific shape to distribute loads, and the fixing portions are strategically positioned to minimize thermal stress concentration
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 reduces stress on the detection element, enhancing detection sensitivity and reliability by minimizing the impact of thermal expansion and assembly inaccuracies, allowing for stable fixation and improved acceleration detection.
Implementation Method 1
detect a force (acceleration) applied to the physical quantity detection device based on a change of the resonance frequency of the physical quantity detection element produced by a force acting in the direction of the detection axis
Implementation Method 2
a stress produced between plural fixing portions of the support structure when the support structure is fixed to a package, for example, due to the difference in the coefficient of linear expansion between the support structure and the package
Data Source
AI summary
A physical quantity detection device includes: a base portion; a movable portion supported by the base portion via a joint and shifting in accordance with a change of a physical quantity; a physical quantity detection element extending over the base portion and the movable portion; a first support member extending from the base portion and having a first fixing portion; and a second support member extending from the base portion and having a second fixing portion. The distance between the first fixing portion and the second fixing portion is shorter than the distance between the root of the first support member at the junction with the base portion and the root of the second support member at the junction with the base portion.