Capacitive Acceleration Sensor Asymmetric Mass Design
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Solution Overview
Problem
Existing capacitive acceleration sensors for multi-axis measurements face challenges in minimizing height and optimizing space usage while maintaining structural rigidity and performance, often resulting in inefficiencies due to deformation and null shift errors.
Innovation Solution
A capacitive acceleration sensor design featuring a movable electrode supported by symmetrically positioned torsion springs and asymmetrically located lightening features, with measuring electrodes positioned symmetrically relative to the springs, allowing for efficient area utilization and deformation tolerance through machining or etching methods, and utilizing SOI wafers with silicon-glass insulation for thin sealing wafers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If measuring electrodes are positioned in two different planes on both sides of the mass to achieve efficient area utilization, then area usage is improved, but the height of the sensor component increases and structural rigidity deteriorates
Solution Approach 1:
The patent transitions from a two-plane electrode arrangement to a single-plane configuration by utilizing the thickness direction of the mass for asymmetric lightening feature placement. This dimensional reorganization allows the center of gravity to be shifted without increasing height, resolving the contradiction between area utilization and height reduction.
Solution Approach 2:
The patent employs asymmetric lightening features positioned in the thickness direction of the mass to shift the center of gravity. This asymmetric mass distribution achieves the desired sensitivity adjustment and area utilization without requiring electrodes to be placed in multiple planes, thereby reducing overall height while maintaining performance.
2Productivity
If measuring electrodes are positioned in two different planes to optimize space usage, then space efficiency is improved, but structural rigidity worsens due to requirements for great rigidity
Solution Approach 1:
The patent moves the mass adjustment mechanism from the lateral plane to the thickness dimension by introducing asymmetric lightening features. This allows space optimization through center of gravity adjustment without compromising structural rigidity, as the mass distribution is modified within the existing single-plane electrode structure.
3Adaptability or versatility
If torsion springs are positioned off-center to achieve asymmetric support for multi-axis measurement, then measurement capability is improved, but deformation sensitivity increases causing null shift errors
Solution Approach 1:
The patent uses asymmetric lightening features to shift the center of gravity, creating the necessary asymmetry for multi-axis measurement capability. Unlike off-center torsion spring positioning, this asymmetric mass distribution achieves the desired measurement versatility without increasing deformation sensitivity, as the support structure remains symmetric and stable.
Solution Approach 2:
The patent applies local mass modification through lightening features specifically positioned to shift the center of gravity in the thickness direction. This localized change achieves the required asymmetric mass distribution for multi-axis measurement while maintaining overall structural symmetry and minimizing deformation-induced null shift errors.
4Area of stationary object
If the mass is made thicker to increase area utilization, then area efficiency is improved, but height increases which is incompatible with miniaturization requirements
Solution Approach 1:
The patent achieves area efficiency not by increasing the thickness of the mass uniformly, but by strategically placing asymmetric lightening features within the existing thickness. This approach optimizes area utilization through center of gravity adjustment without increasing the overall height, maintaining compatibility with miniaturization 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 design achieves significant height savings on circuit board components, maintains performance and stability, and allows for independent sensitivity adjustment across axes, while tolerating mechanical deformations without generating measuring inaccuracies, thus enhancing the efficiency and reliability of small capacitive acceleration sensors.
Implementation Method 1
Capacitive measuring is based on a change in the gap between the two surfaces of a pair of electrodes of the sensor. The capacitance between the surfaces, i.e. the capacity for storing electric charge, depends on the area of the surfaces and the distance between them.
Implementation Method 2
an inertia mass forming a movable electrode supported by torsion springs symmetrically in the longitudinal direction of the mass and asymmetrically in relation to the thickness direction of the mass
Data Source
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AI summary
The present invention relates to measuring devices used in measuring acceleration and, more precisely, to capacitive acceleration sensors. The object of the invention is to provide an improved method of manufacturing a capacitive acceleration sensor, and to provide a capacitive acceleration sensor, which is applicable for use in small capacitive acceleration sensor solutions, and which, in particular, is applicable for use in small and extremely thin capacitive acceleration sensor solutions measuring acceleration in relation to several axes.