Ultrasonic Motor Segmented Piezoelectric Stator
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Solution Overview
Problem
Existing ultrasonic motors face challenges in manufacturing efficiency, high production costs, and complex holding structures due to the need for precise circular ring-shaped piezoelectric members and limited rotor contact surfaces, which hinder efficient excitation and rotation.
Innovation Solution
The ultrasonic motor employs a stator with a circular or polygonal vibrating member and 4n rectangular piezoelectric elements disposed in a circumferential direction, each polarized in alternating thickness directions, generating a 3n or (2k + 1)n traveling wave, allowing for efficient wave excitation and simplified holding structures with multiple contact surfaces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a circular ring-shaped piezoelectric member is used to generate traveling waves, then the ultrasonic motor can achieve rotation, but the manufacturing precision requirement becomes extremely high and costs increase
Solution Approach 1:
The patent divides the continuous circular ring-shaped piezoelectric member into multiple discrete piezoelectric elements arranged circumferentially. Each element can be independently manufactured with standard precision, and collectively they generate the required traveling wave through phased excitation. This segmentation eliminates the need for high-precision circular ring fabrication while maintaining the rotational functionality.
Solution Approach 2:
Multiple piezoelectric elements are combined to form a distributed array around the rotating member. By applying phase-shifted voltages to adjacent elements, the system merges their individual vibrations to create a traveling wave pattern that circulates around the ring, achieving rotation without requiring any single element to be precisely circular.
2Reliability
If the entire surface of the elastic member is covered by the piezoelectric vibrator, then the rotor contact surface is limited to one side, but design flexibility is reduced
Solution Approach 1:
Instead of covering the entire elastic member surface with piezoelectric material, the patent applies piezoelectric elements only at specific locations where they are needed to generate the traveling wave. This localized approach leaves other surfaces of the elastic member free for rotor contact, enabling multi-sided rotor configurations and improved design flexibility while maintaining effective vibration generation.
3Reliability
If piezoelectric ceramics are polished with high precision to align centers, then the traveling wave can be properly generated, but manufacturing complexity and costs increase
Solution Approach 1:
By segmenting the piezoelectric structure into multiple discrete elements, the patent eliminates the need to polish and align a single large piezoelectric ceramic piece. Each element can be manufactured independently using standard piezoelectric fabrication processes without requiring precision alignment of centers, significantly reducing manufacturing complexity.
Solution Approach 2:
The patent uses multiple identical or similar piezoelectric elements that can be manufactured using the same standard process. Instead of requiring a unique, precisely-polished circular ring, the system copies the same element design multiple times around the structure, allowing standardization and simplification of the manufacturing process.
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 manufacturing efficiency, reduces costs, and simplifies the holding structure, enabling stable and efficient rotation of the rotor with increased excitation efficiency and flexibility in surface contact.
Implementation Method 1
a plurality of piezoelectric elements are disposed so as to be dispersed in the form of a ring... generating a traveling wave of a 3n wave (n is a natural number) traveling in a circulating manner by vibrating the vibrating member
Data Source
Figure 1~2
Figure 3
Figure 4(a)~4(b)
AI summary
An ultrasonic motor which is easy to manufacture, which has high efficiency, which has few restrictions in a portion that drives a rotor, and which makes it possible to simplify a holding structure is provided. An ultrasonic motor includes a stator 1 and a rotor. In the stator 1, an n number of piezoelectric elements 3 to 6 (n is a natural number) are affixed to one surface of a vibrating member 2, whose outer circumferential edge is circular or polygonal, along a direction in which the outer circumferential edge extends. If the wavelength of a traveling wave that is generated is λθ, each of the piezoelectric elements 3 to 6 has a size corresponding to λθ/2 in terms of center angle, and the piezoelectric elements that are adjacent to each other are disposed so as to be separated by an interval corresponding to λθ/4 in terms of the center angle along the circumferential direction. The piezoelectric elements 3 to 6 are polarized in opposite directions in thickness directions. The rotor is disposed so as to contact the stator 1, and is rotated by receiving vibration resulting from a 3n-wave traveling wave generated by the stator 1.