Tuning-Fork Piezoelectric Vibrator Head Geometry for Low CI
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Solution Overview
Problem
The reduction in size of tuning-fork type piezoelectric vibrating pieces leads to a decrease in vibration efficiency and an increase in crystal impedance (CI) value, affecting frequency stability.
Innovation Solution
The design includes a base portion with vibrating arm portions, where the head portion has a width larger than the arm portion, and specific dimensional constraints are applied to the head and arm lengths to maintain vibration efficiency and reduce CI, such as 0.13×10^12 ≤ Vh(Lh^2 + Wh^2) ≤ 0.39×10^12, and 0.24 ≤ Lh/La ≤ 0.35, to limit inertia moment and frequency change.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the size of the piezoelectric vibrating piece is reduced, then the device becomes more compact, but the vibration efficiency decreases and the crystal impedance value increases
Solution Approach 1:
The patent applies parameter changes by precisely controlling the dimensions of the head portion (Lh, Wh, Vh) and their relationships (Lh/La ratio, Vh(Lh²+Wh²) product) to optimize vibration efficiency. By adjusting these parameters within specific ranges, the invention achieves compact size while preventing excessive increase in crystal impedance and maintaining vibration efficiency.
2Volume of moving object
If the size of the piezoelectric vibrating piece is reduced, then the device becomes more compact, but the crystal impedance (CI) value increases
Solution Approach 1:
The patent controls the crystal impedance by establishing specific parameter relationships for the head portion dimensions. The constraints on Vh(Lh²+Wh²) ≤ 0.39×10^12 μm⁵ and Lh/La within 0.24-0.35 ensure that the CI value increase is limited to within 5%, achieving compact size while minimizing the harmful impedance effect.
3Measurement precision
If the head portion size is increased for frequency adjustment, then the frequency can be adjusted, but the vibration efficiency of the vibrating arm portion decreases
Solution Approach 1:
The patent optimizes the head portion dimensions (Lh, Wh, Vh) and their relationships to achieve frequency adjustment while preventing excessive reduction in vibration efficiency. By controlling Lh/La within 0.24-0.35 and Vh(Lh²+Wh²) within 0.13-0.39×10^12 μm⁵, the invention balances frequency tuning capability with maintained vibration efficiency.
Solution Approach 2:
The patent applies local quality by creating a head portion with specific dimensional characteristics (wider than the arm portion) at the distal end, concentrating the mass adjustment function in this localized region while maintaining the overall structural integrity and vibration characteristics of the vibrating arm portions.
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 approach prevents a decrease in vibration efficiency and reduces the CI value by about 5%, maintaining frequency stability within 5% of the original value, enabling a small and high-quality piezoelectric vibrator and oscillator.
Implementation Method 1
tuning-fork type piezoelectric vibrating piece
Data Source
AI summary
A decrease in vibration efficiency due to size reduction of a tuning-fork type piezoelectric vibrating piece is prevented. A piezoelectric vibrating piece includes a base portion, and a pair of vibrating arm portions extending in parallel from the base portion. Each of the vibrating arm portions includes an arm portion extending from the base portion, and a head portion connected to a distal end of the arm portion and having a width larger than that of the arm portion. The piezoelectric vibrating piece satisfies the following relation: 0.13×1012≤Vh(Lh2+Wh2)≤0.39×1012, where Lh [μm] is a length of the head portion, Wh [μm] is a width of the head portion, and Vh [μm3] is a volume of the head portion.