Piezoelectric Oscillator Segmentation for Ultrasonic Motor Efficiency
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Solution Overview
Problem
Existing ultrasonic motors using discoid piezoelectric elements require complex forming and polarizing processes, leading to high costs and reduced efficiency due to the need for multiple divided and polarized areas to generate B (1, n) mode travelling waves.
Innovation Solution
A piezoelectric oscillator with (4/3)n piezoelectric elements distributed circumferentially on a plate-shaped oscillating body, generating n-wave travelling waves by combining two B (1, n) mode standing waves out of phase by 90°, with each element polarized in one direction and alternating for every two elements, simplifying the forming, polarizing, and electrode processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a discoid piezoelectric element is divided into multiple areas and each area is polarized in opposite directions to generate B (1, n) mode travelling waves, then the travelling wave generation capability is improved, but the forming process and polarizing process become complex and costly
Solution Approach 1:
The piezoelectric element is divided into (4/3)n segments arranged circumferentially, with each segment polarized in the same direction. This segmentation allows the generation of B (1, n) mode travelling waves while simplifying the polarizing process compared to dividing into 4n areas with opposite polarizations.
Solution Approach 2:
Adjacent piezoelectric elements are alternately polarized in opposite thickness directions, creating local quality variations that generate the required standing waves. This local alternation pattern simplifies the overall polarizing process while maintaining travelling wave generation capability.
2Reliability
If the piezoelectric element is divided into 4n areas with opposite polarizations to obtain n-wave travelling waves, then the travelling wave mode is achieved, but the manufacturing cost increases
Solution Approach 1:
The piezoelectric element is divided into (4/3)n segments rather than 4n areas, reducing the number of polarizing operations required. Each segment is polarized uniformly, simplifying the manufacturing process while achieving the desired n-wave travelling wave mode.
Solution Approach 2:
The polarization direction parameter is changed from alternating at each boundary (4n areas) to alternating every two adjacent elements ((4/3)n segments). This parameter change reduces manufacturing complexity and cost while maintaining the travelling wave generation capability.
3Productivity
If two B (1, 3) mode standing waves out of phase by 90° are combined to generate travelling waves, then rotation efficiency is improved, but the piezoelectric element requires complex division and polarization
Solution Approach 1:
The piezoelectric element is segmented into (4/3)n elements arranged circumferentially, enabling the generation of two B (1, n) mode standing waves out of phase by 90°. This segmentation achieves high rotation efficiency while avoiding the complexity of dividing into 4n areas with opposite polarizations.
Solution Approach 2:
The piezoelectric elements are driven in a periodic sequence with 90° phase difference between adjacent pairs, generating the required standing waves and their combination into travelling waves. This periodic driving pattern achieves high rotation efficiency with simplified element structure.
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 configuration enhances oscillation energy and reduces costs by simplifying the manufacturing process while maintaining high rotation efficiency for the rotor, allowing for efficient use of various B (1, n) modes.
Implementation Method 1
two B (1, n) mode standing waves that are out of phase with each other by 90° are generated, and a travelling wave is generated by combining the two standing waves... By applying an alternating voltage to the piezoelectric element 106, areas indicated by the '+' sign and areas indicated by the '-' sign as described above oscillate with phases opposite to each other
Data Source
Figure 1(a)~1(c)
Figure 2(a)~2(b)
Figure 3~4
AI summary
A piezoelectric oscillator that generates a traveling wave using two B (1, n) mode (n is a natural number) standing waves that are out of phase with each other by 90°. The piezoelectric oscillator achieves a structure that allows a forming process, a polarizing process and a electrode forming process of piezoelectric elements to be simplified, and the cost to be reduced, On a lower surface of an oscillating body 4, (4/3)n piezoelectric elements 5 to 16 are provided in order to generate an n-wave traveling wave by combining the two B (1, n) mode standing waves that are out of phase with each other by 90°. When a wavelength of the travelling wave is given by λ, each of the piezoelectric elements 5 to 16 has a dimension in a circumferential direction occupying a central angle corresponding to (1/2)λθ, and a plurality of piezoelectric elements 5 to 16 are spaced apart from each other at intervals each occupies a central angle corresponding to (1/4)λθ. Each piezoelectric element includes a piezoelectric body polarized in a thickness direction and a pair of electrodes formed on two opposite surfaces of the piezoelectric element The piezoelectric bodies of the piezoelectric elements are polarized in one or the other thickness direction so as to alternate for every two piezoelectric elements in the circumferential direction.