Piezoelectric Actuator Displacement via Coercive Field Control
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Solution Overview
Problem
Conventional piezoelectric actuator drive circuits face limitations in displacement due to small expansion and contraction of piezoelectric films, and complex voltage-dependent characteristics that restrict the usable displacement of actuators.
Innovation Solution
A switching apparatus that utilizes a control section to apply drive voltages exceeding and below coercive electric fields to piezoelectric films, allowing for increased displacement by controlling the expansion and contraction of the films within specific electric field ranges, and includes a support layer to manage the actuator's movement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If conventional bimorph operation is used with piezoelectric films, then the actuator can be driven by applying voltage to expand and contract the films, but the displacement of the actuator is very small relative to the size of the actuator because the expansion and contraction of each piezoelectric film is no greater than approximately 1% of the total length
Solution Approach 1:
The patent applies parameter changes by utilizing different voltage magnitude ranges relative to the coercive electric field. By switching between voltage ranges (below coercive field for expansion, above coercive field for contraction), the piezoelectric film exhibits different displacement characteristics, thereby increasing the overall actuator displacement without requiring complex mechanical structures.
2Length of moving object
If the expansion and contraction characteristic of piezoelectric film is complicated with respect to the sign of applied voltage, then only a portion of the expansion and contraction characteristic can be used, but the displacement amount of the actuator cannot be increased
Solution Approach 1:
The patent resolves the limited usability of piezoelectric characteristics by changing the voltage parameter magnitude relative to the coercive electric field. By applying voltages both below and above the coercive field threshold, the system accesses different operational modes of the piezoelectric material, effectively utilizing a broader range of its expansion and contraction characteristics to increase actuator displacement.
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 solution enhances the displacement of the actuator, increases the usable range of piezoelectric film expansion and contraction, and extends the lifetime of the piezoelectric films by preventing polarity inversion, thus improving the switching apparatus's performance and reliability.
Implementation Method 1
a first piezoelectric film 136 that expands and contracts according to the first drive voltage
Implementation Method 2
causes the first piezoelectric film 136 to contract by causing a change from a voltage that applies an electric field to the first piezoelectric film 136 that is less than a first coercive electric field to a voltage that applies an electric field to the first piezoelectric film 136 that exceeds the first coercive electric field
Data Source
AI summary
Provided is a switching apparatus comprising a contact point section that includes a first contact point; an actuator that includes a second contact point and moves the second contact point to contact or move away from the first contact point; and a control section that controls a first drive voltage. The actuator includes a first piezoelectric film that expands and contracts according to the first drive voltage and a support layer disposed on the first piezoelectric film. The control section causes the first piezoelectric film to contract by causing a change from a voltage that applies an electric field that is less than a first coercive electric field to a voltage that applies an electric field that exceeds the first coercive electric field, and causes the first piezoelectric film to expand by outputting a voltage that applies an electric field that is less than a second coercive electric field.