Crimped Piezoelectric Load Sensor for Stable Low-Profile Preload
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing load sensors using piezoelectric resonators face issues such as breakage of crystal resonator elements due to excessive preloading and poor detection performance over extended periods, along with increased profile due to the incorporation of thrust bearings.
Innovation Solution
A load sensor design featuring an upper housing with a protruding portion and a lateral face, a less elastically deformable lower housing, and a piezoelectric resonator with excitation electrodes extending in the thickness direction. The upper and lower housings are crimped together to apply a preload to the piezoelectric resonator, reducing the sensor's profile and long-term fluctuations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If a screw member is used to apply preload to the piezoelectric resonator, then the resonator can be preloaded, but the profile of the load sensor increases due to the need for a thrust bearing
Solution Approach 1:
The upper housing serves dual functions: it provides structural support and simultaneously applies preload to the piezoelectric resonator through its weight. This eliminates the need for separate preload application mechanisms like screw members and thrust bearings, thereby reducing the overall profile of the load sensor while maintaining effective preload application.
Solution Approach 2:
The upper housing's own weight is utilized to apply the necessary preload to the piezoelectric resonator. This self-weight preloading mechanism eliminates the need for additional active preload application components, simplifying the structure and reducing the sensor's profile without compromising the preload function.
2Force
If a screw member is used to apply preload, then the resonator can be preloaded, but long-term stability deteriorates due to excessive preloading and preload changes over time
Solution Approach 1:
The upper housing's own weight is utilized to apply the necessary preload to the piezoelectric resonator. This self-weight preloading mechanism eliminates the need for additional active preload application components, simplifying the structure and reducing the sensor's profile without compromising the preload function.
Solution Approach 2:
The design changes the preload application method from active mechanical adjustment (screw member) to passive gravitational loading (upper housing weight). This parameter change in the preload mechanism provides more stable long-term performance by eliminating wear, loosening, and over-tightening issues associated with screw-based systems.
3Strength
If a thrust bearing is incorporated to mitigate torsional force, then the resonator is protected from torsional stress, but the profile of the load sensor increases
Solution Approach 1:
The upper housing serves dual functions: it provides structural support and simultaneously applies preload to the piezoelectric resonator through its weight. This eliminates the need for separate preload application mechanisms like screw members and thrust bearings, thereby reducing the overall profile of the load sensor while maintaining effective preload application.
4Force
If a screw member and thrust bearing are used for preload application, then the resonator can be preloaded with force control, but the device complexity increases
Solution Approach 1:
The upper housing serves dual functions: it provides structural support and simultaneously applies preload to the piezoelectric resonator through its weight. This eliminates the need for separate preload application mechanisms like screw members and thrust bearings, thereby reducing the overall profile of the load sensor while maintaining effective preload application.
Solution Approach 2:
The upper housing performs multiple functions: it serves as the structural enclosure for the piezoelectric resonator, provides mechanical support, and simultaneously acts as the preload application mechanism through its weight. This multi-functionality reduces the total number of components needed in the system.
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 proposed load sensor achieves reduced profile and long-term stability, improving detection accuracy and reducing the risk of crystal resonator breakage, while maintaining good loading characteristics.
Implementation Method 1
an end portion of the upper housing and an end portion of the lower housing are fixed to each other with a crimp such that the upper housing is elastically deformed and causes a preload to be applied by the upper housing to the piezoelectric resonator
Implementation Method 2
application of a load to a piezoelectric resonator causes the resonant frequency of the piezoelectric resonator to change in accordance with the applied load
Data Source
AI summary
A load sensor that includes: an upper housing having an upper face portion, and a lateral face portion that extends in the thickness direction from an outer periphery of the upper face portion; a lower housing having a lower face portion that faces the upper face portion in the thickness direction, the lower housing being less elastically deformable than the upper housing; and a piezoelectric resonator in a space between the upper housing and the lower housing, wherein an end portion of the upper housing and an end portion of the lower housing are fixed to each other with a crimp such that the upper housing is elastically deformed and causes a preload to be applied by the upper housing to the piezoelectric resonator in the thickness direction.