Acceleration Sensor with 45-Degree Vibrating Beam
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Solution Overview
Problem
Existing acceleration sensors lack high detection sensitivity, particularly in detecting acceleration in the Z-axis direction, due to limitations in design that result in reduced sensitivity and increased undesired vibrations.
Innovation Solution
The acceleration sensor design includes a fixation member, a weight member with a cutout, and a vibrating beam aligned at a 45° angle, with the connected position between the vibrating beam and weight member optimized near the barycentric position to enhance sensitivity and reduce undesired vibrations, utilizing a driver and detector on the vibrating beam to output a detection signal based on deformation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the vibrating beam is positioned at 45 degrees relative to the X and Y axes with the connected position near the barycentric position of the weight member, then detection sensitivity for Z-axis acceleration is improved, but device complexity increases due to precise positioning requirements
Solution Approach 1:
The vibrating beam is positioned asymmetrically at a 45-degree angle relative to the X and Y axes, with its connected position specifically located near the barycentric position of the weight member. This asymmetric configuration optimizes the detection sensitivity for Z-axis acceleration by creating a favorable geometric relationship between the vibrating beam and the weight member, while the cutout in the weight member further enhances this effect by reducing undesired vibrations.
Solution Approach 2:
The invention introduces a specific spatial dimension by positioning the vibrating beam at a 45-degree angle in the X-Y plane, creating a three-dimensional geometric relationship that optimizes Z-axis acceleration detection. This angular positioning, combined with the vertical Z-axis detection direction, creates a multi-dimensional configuration that enhances sensitivity while the cutout in the weight member adds another dimensional feature to control vibration characteristics.
2Measurement precision
If the lengthwise size of the vibrating beam is increased to improve detection sensitivity, then sensitivity for Z-axis acceleration is enhanced, but the device area increases
Solution Approach 1:
The invention specifies that the lengthwise size of the vibrating beam should be between 0.6 to 1.2 times the reference size (which is defined as the distance from the fixation member to the barycentric position of the weight member). This parameter optimization ensures that the vibrating beam is sufficiently long to provide good detection sensitivity for Z-axis acceleration, while avoiding excessive length that would unnecessarily increase the device area. The cutout in the weight member further optimizes the system by reducing undesired vibrations, allowing for efficient use of the vibrating beam length.
3Strength
If the weight member is made larger to improve impact resistance, then impact resistance is enhanced, but undesired vibrations increase
Solution Approach 1:
The invention introduces a cutout in the weight member that extracts or removes material from specific regions of the weight member. This cutout is strategically positioned to reduce undesired vibrations while maintaining the overall mass and impact resistance of the weight member. By removing material from areas that would otherwise contribute to undesired vibrations, the cutout optimizes the vibration characteristics without significantly compromising the impact resistance provided by the weight member's overall mass.
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 significantly increases detection sensitivity for acceleration in the Z-axis direction, with sensitivity improvements noted when the vibrating beam's lengthwise size is between 0.6 to 1.2 times the reference size, and further enhances impact resistance with the inclusion of holding beams, resulting in improved performance compared to comparative examples.
Implementation Method 1
detect, in a state where a weight member is connected to a distal end of a vibrating portion of a cantilever beam and the vibrating portion is vibrated at a resonant frequency of the natural vibration thereof, a magnitude of acceleration from a change in a resonant frequency of the natural vibration of the vibrating portion
Implementation Method 2
a piezoelectric thin film layer 114 formed on the lower electrode layer 113... pressure is exerted on a portion of the piezoelectric thin film layer 114... thereby generating electric charges
Data Source
AI summary
An acceleration sensor includes a fixation member, a weight member including a plate with two opposing sides parallel or substantially parallel to an X-direction and two opposing sides parallel to a Y-axis direction in a plan view, the weight member including a cutout extending in a direction about 45° relative to the X and Y axis directions, a vibrating beam linearly extending in the direction about 45° relative to the X and Y axis directions in the plan view, and one end portion is connected to the fixation member and the other end portion is connected to the weight member, the vibrating beam is partly arranged within the cutout and supporting the weight member to be displaceable in a Z-axis direction, a driver disposed on the vibrating beam and vibrating the vibrating beam, and a detector disposed on the vibrating beam and outputting a detection signal that is changed depending on deformation of the vibrating beam.