Cantilever Inertial Sensor Layout for Resonance and Sensitivity Balance
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Solution Overview
Problem
Inertial sensors face issues of output abnormality, destruction, and increased vibration rectification error due to resonance when external vibrations with frequencies close to the resonance frequency of the cantilever occur, and reducing the mass of the movable part to increase resonance frequency leads to decreased sensitivity.
Innovation Solution
A physical quantity sensor design with a cantilever having a hinge part and movable part where the movable part is longer than the hinge part in a specific direction, and the free end of the movable part coincides with or is closer to the detection element, allowing for increased resonance frequency and sensitivity without significant mass reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the mass of the movable part is reduced to increase the resonance frequency of the cantilever, then the resonance frequency increases, but the sensitivity of the inertial sensor decreases
Solution Approach 1:
The patent extends the movable part in the Y-axis direction (width direction) rather than reducing mass along the X-axis. This dimensional change allows the resonance frequency to be increased by making the movable part longer in the intersecting direction, while maintaining sufficient mass for sensitivity. The free end of the movable part coincides with or is closer to the hinge part than the end of the detection element, achieving the desired frequency-sensitivity balance through geometric reconfiguration in multiple dimensions.
2Reliability
If the resonance frequency of the cantilever is increased to prevent resonance-induced problems, then output abnormality and destruction are reduced, but the sensitivity decreases due to mass reduction
Solution Approach 1:
The patent resolves this contradiction by extending the movable part in the Y-axis direction (width direction perpendicular to the arrangement direction of hinge part and movable part). This allows the resonance frequency to be increased through geometric configuration without reducing mass, thereby maintaining sensitivity while improving reliability. The specific configuration where the free end of the movable part coincides with or is closer to the hinge part than the end of the detection element achieves both high resonance frequency and adequate mass.
Data Source
AI summary
A physical quantity sensor includes: a base part; a plate-shaped cantilever including a hinge part and a movable part coupled to the base part via the hinge part, the movable part being displaced in relation to the base part with the hinge part serving as a fulcrum; and a physical quantity detection element fixed to the base part and the movable part over the hinge part. The movable part is longer than the hinge part in a second direction intersecting a first direction in which the hinge part and the movable part are arranged when viewed in a plan view of the cantilever, and a free end of the movable part located on a side opposite to the hinge part coincides with an end of the physical quantity detection element on the free end side or is located closer to the hinge part side than the end when viewed in a plan view of the cantilever.