Lead-Free Vibration Actuator Structure for Symmetric Bidirectional Motion
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Solution Overview
Problem
Existing vibration-type actuators using lead-free piezoelectric ceramics experience temperature distribution and in-plane distribution of piezoelectric properties, leading to inequivalent vibration characteristics in forward and reverse directions.
Innovation Solution
A vibration-type actuator design with a rectangular-shaped elastic body and piezoelectric element, featuring protruding portions with space portions and specific temperature bonding processes, ensures a round-trip speed difference of less than 0.178, enhancing vibration symmetry and uniformity of piezoelectric properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If lead-free piezoelectric ceramics are used to reduce environmental impact, then the piezoelectric element can be manufactured with low lead content, but temperature distribution and in-plane distribution of piezoelectric properties occur during polarization treatment, leading to inequivalent vibration characteristics in forward and reverse directions
Solution Approach 1:
The patent introduces asymmetric space portions within the elastic body that create intentional thermal asymmetry during polarization treatment. This asymmetric structure compensates for the inherent symmetries in the piezoelectric element, allowing controlled temperature distribution that corrects in-plane piezoelectric property variations and achieves equivalent vibration characteristics in both directions while maintaining lead-free composition
2Reliability
If polarization treatment is performed on piezoelectric ceramics to activate piezoelectric properties, then the piezoelectric element becomes functional, but temperature distribution occurs within the plane of the piezoelectric element causing in-plane distribution of piezoelectric properties
Solution Approach 1:
The patent implements local quality modification by incorporating space portions with specific geometric characteristics (area ratios between 0.178-0.684) at predetermined locations within the elastic body. These localized structural features create specific thermal zones during polarization treatment that compensate for regional piezoelectric property variations, achieving uniform overall performance through non-uniform local treatment
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 actuator achieves reduced round-trip speed difference and improved vibration symmetry, ensuring equivalent vibration characteristics in both directions and minimizing environmental impact through reduced lead content.
Implementation Method 1
a vibration body configured such that, when an alternating voltage is applied to an electro-mechanical energy conversion element such as a piezoelectric element, a vibration is excited in an elastic body joined to the piezoelectric element
Implementation Method 2
The vibration-type actuator is utilized as an ultrasonic motor that utilizes a driving force of vibration excited in the vibration body, so as to relatively move a contact body that is brought into pressure contact with the vibration body, and the vibration body
Data Source
Figure 1A~1C
Figure 2A~2B
Figure 3
AI summary
A vibration-type actuator in which the content of lead included in a piezoelectric material is 1000 ppm or less has an elastic body that includes a protruding portion and a flat portion. The protruding portion includes a top portion that contacts a contact body. The protruding portion is provided with a space portion therein, and includes an outer surface and an inner surface. The top portion is arranged at a position crossing a nodal line of out-of-plane vibration of the elastic body in plan view. A value obtained by dividing a total area of a portion surrounded by the outer surface when a base portion of the protruding portion is viewed in cross-section in a direction parallel to the flat portion by a product of a length of a short side and a length of a long side of a principal surface of the piezoelectric element is smaller than 0.178.