Rectangular Piezoelectric Actuator Multilayer Structure
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Solution Overview
Problem
Existing piezoelectric actuators for ultrasonic motors have large dimensions, high manufacturing costs, require high excitation voltages, and lack thermal stability due to complex structures and low electromechanical coupling coefficients, making them inefficient and costly to produce and operate.
Innovation Solution
A piezoelectric actuator with a rectangular acoustic oscillation resonator and a multilayer structure featuring alternating layers of excitation and common electrodes, along with a control unit that allows self-excitation based on mechanical parameters, reducing dimensions, excitation voltage, and manufacturing complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If piezoelectric elements are connected as thin lamellae packets to the metallic resonator, then the actuator can be constructed, but the dimensions become large and manufacturing costs increase
Solution Approach 1:
The invention merges the piezoelectric element and metallic resonator into a single integrated component where the piezoelectric element serves as both the active element and the resonator structure, eliminating the need for separate components and reducing overall dimensions
Solution Approach 2:
The piezoelectric element is designed with a nested multilayer structure where alternating layers of piezoelectric material and electrode material are integrated within each other, allowing compact packaging of functional components
2Power
If lamellar piezoelectric elements are used with metallic resonator, then the actuator can operate, but the electromechanical coupling coefficient decreases and excitation voltage increases
Solution Approach 1:
The invention changes the geometric parameters of the piezoelectric element, specifically using a compact multilayer structure with increased surface area to volume ratio, which enhances the electromechanical coupling coefficient and reduces the required excitation voltage
Solution Approach 2:
The actuator uses a composite structure combining piezoelectric material with metallic electrode layers in a multilayer configuration, creating optimized electromagnetic coupling properties that reduce excitation voltage requirements
3Ease of manufacture
If bending resonance with low electromechanical coupling coefficient is used, then the actuator can be constructed, but excitation voltage reaches high values of 300 Veff
Solution Approach 1:
The invention utilizes longitudinal mechanical vibration resonance instead of bending resonance, which provides higher electromechanical coupling and significantly reduces the excitation voltage required for actuator operation
Solution Approach 2:
The resonator geometry is optimized with specific length-to-diameter ratios and multilayer configurations that enhance longitudinal vibration modes, maximizing the electromechanical coupling coefficient and minimizing excitation voltage requirements
4Ease of operation
If second longitudinal resonance is present within bending resonance range, then the actuator can operate, but control becomes difficult and thermal stability reduces
Solution Approach 1:
The piezoelectric element is designed with non-uniform electrode distribution and varying layer thicknesses in different regions, creating localized stress concentrations that enhance the desired resonance mode while suppressing unwanted longitudinal resonances
Solution Approach 2:
The actuator incorporates adjustable compliance elements that allow dynamic tuning of the resonance characteristics, enabling the system to adapt to changing operating conditions and maintain stable operation across temperature variations
5Volume of stationary object
If multilayer piezoelectric element is pressed into metallic resonator body, then dimensions are reduced, but excitation circuit complexity increases and operating stability reduces
Solution Approach 1:
The piezoelectric element is designed with self-contained electrode connections and integrated wiring paths that eliminate the need for complex external excitation circuits, allowing the actuator to self-generate the required excitation signals
Solution Approach 2:
The metallic resonator structure is designed to serve multiple functions simultaneously: it acts as the resonator body, provides structural support, serves as an electrode connection path, and functions as part of the excitation circuit, thereby simplifying the overall system architecture
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 results in a more compact, cost-effective, and stable actuator with lower excitation voltages, improved operating stability, and simplified control, enabling efficient operation over a wide temperature and mechanical stress range.
Implementation Method 1
a piezoelectric actuator for an ultrasonic motor with a control unit for this actuator (27), wherein the acoustic oscillation resonator (2) is formed as a rectangular piezoelectric plate (3) with two main surfaces (4), two side surfaces (5) and two end faces (6), with a multilayer structure in its interior
Implementation Method 2
The multilayer structure represents layers of excitation electrodes (7) taking turns with the layers of the common electrodes (8) and the layers of polarized ceramic provided therebetween
Implementation Method 3
which is comprised of an acoustic oscillation resonator (2) with a multilayer generator (17, 18) for an acoustic standing wave
Data Source
AI summary
A piezoelectric actuator, especially for an ultrasonic motor, includes an acoustic oscillation resonator, wherein the acoustic oscillation resonator is substantially formed as a rectangular piezoelectric plate with two main surfaces, two side surfaces and two end faces and has a multilayer structure in its interior which represents a layer of excitation electrodes taking turns with the layers of the common electrodes and the layers of polarized ceramic provided therebetween, with the polarization vector extending perpendicularly with respect to the surface of the electrodes, wherein all excitation electrodes are divided into two groups not connected to each other, which are disposed symmetrically with respect to the symmetry surface of the aforementioned plate, wherein this symmetry surface extends perpendicularly with respect to the main and side surfaces of the plate, namely through the center thereof.