Electrode Finger Collision Prevention in Acceleration Sensors
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing acceleration sensors face damage and reduced mechanical strength due to large impacts, as the movable unit's displacement can cause electrode fingers to collide, leading to damage and compromised detection accuracy.
Innovation Solution
A physical quantity sensor design with shorter electrode fingers and a symmetrical configuration that reduces collision risk, incorporates springs for displacement, and cancels noise by changing electrostatic capacitance phases, enhancing impact resistance and detection accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the movable unit is allowed to displace freely to detect acceleration, then detection sensitivity is improved, but the electrode fingers may collide and cause damage during large impacts
Solution Approach 1:
The patent introduces a stopper structure that prevents the movable unit from displacing beyond a safe range during large impacts. The stopper includes a stopper protrusion on the movable unit and a stopper groove on the fixed substrate, creating a mechanical limit that cushions against excessive displacement and prevents electrode finger collision damage before it can occur.
2Measurement precision
If the electrode fingers are made longer to increase detection sensitivity, then measurement precision improves, but mechanical strength and impact resistance deteriorate
Solution Approach 1:
The patent extends the electrode fingers in the Y-axis direction (width) rather than increasing their length in the X-axis direction (displacement direction). This dimensional change allows the electrode fingers to have sufficient surface area for accurate electrostatic capacitance detection while maintaining shorter lengths that prevent collision damage during impacts.
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 sensor achieves improved mechanical strength and detection accuracy with reduced electrode finger damage and noise cancellation, even with shorter lengths, effectively handling impacts and maintaining sensitivity.
Implementation Method 1
electrostatic capacitance is formed between the first movable electrode finger and the first fixed electrode finger... the electrostatic capacitance between the first movable electrode finger and the first fixed electrode finger and the electrostatic capacitance between the second movable electrode finger and the second fixed electrode finger change, and thus the received acceleration can be detected based on the change of the electrostatic capacitance
Data Source
AI summary
A physical quantity sensor includes a substrate, a support portion fixed to the substrate, a movable body which is displaceable in a first direction with respect to the support portion and has a movable electrode provided therein, and a fixed electrode fixed to the substrate. The fixed electrode includes first and second fixed electrode fingers positioned on one side of the support portion, third and fourth fixed electrode fingers positioned on the other side thereof. The movable electrode includes first to fourth movable electrode fingers which face the first to fourth fixed electrode fingers in the first direction, respectively.