Piezoelectric Actuator Compressive Stress Mitigation
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Solution Overview
Problem
The existing recording heads with piezoelectric actuators suffer from reduced deformability due to pulling stress in the piezoelectric member, leading to lower displacement volume and increased risk of breakage when voltage is applied.
Innovation Solution
A piezoelectric actuator configuration with a vibration plate having compressive stress and a piezoelectric layer with pulling stress, where the compressive stress mitigates the pulling stress, ensuring compliance and thickness are within threshold values to enhance deformability and prevent buckling-like deformation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the piezoelectric member is formed by the sol-gel method, then the piezoelectric member can be manufactured, but pulling stress remains in the piezoelectric member which lowers deformability
Solution Approach 1:
The patent introduces a thickness parameter for the piezoelectric actuator as a critical control variable. By setting the thickness to not less than a first thickness corresponding to a compliance allowing an extreme point to generate, the patent optimizes the balance between deformability and structural integrity. This parameter change resolves the contradiction by ensuring the piezoelectric actuator can withstand manufacturing-induced pulling stress while maintaining sufficient deformability for effective liquid discharge.
2Productivity
If voltage is applied to the piezoelectric actuator, then liquid discharge is achieved, but the pulling stress reduces deformability and lowers displacement volume
Solution Approach 1:
The patent controls the thickness parameter of the piezoelectric actuator to ensure it meets or exceeds the first thickness threshold. This parameter optimization allows the actuator to achieve adequate deformability when voltage is applied, thereby maintaining high displacement volume and effective liquid discharge capability despite the presence of pulling stress from the sol-gel manufacturing process.
3Strength
If the piezoelectric actuator is made thinner to increase deformability, then compliance increases, but buckling-like deformation may occur
Solution Approach 1:
The patent establishes a minimum thickness parameter (first thickness) for the piezoelectric actuator that corresponds to a compliance allowing an extreme point to generate. By controlling the thickness to not less than this threshold, the patent prevents buckling-like deformation while maintaining sufficient deformability. This parameter-based approach resolves the contradiction between thinness-induced compliance and structural stability.
4Strength
If compressive stress is increased in the vibration plate to mitigate pulling stress, then deformability improves, but excessive compressive stress may cause instability
Solution Approach 1:
The patent optimizes the thickness parameter of the piezoelectric actuator to balance the effects of compressive stress in the vibration plate. By setting the thickness to not less than the first thickness threshold, the patent ensures that the compressive stress effectively mitigates pulling stress and enhances deformability without causing excessive compressive stress that would lead to structural instability or buckling.
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 configuration improves deformability and reduces the risk of breakage by maintaining compressive stress within manageable limits, allowing for higher displacement volume and efficient energy transmission while preventing excessive deformation.
Implementation Method 1
an electromechanical transducing element which is formed on the vibration plate and which is constructed of a lower electrode, a piezoelectric member (piezoelectric layer) and an upper electrode. The electromechanical transducing element of the recording head is formed by a film-forming method using the sol-gel method, and is driven when an electric signal is supplied to the electromechanical transducing element. By mechanical vibration of the vibration plate accompanying with the driving of the electromechanical transducing element, pressure is applied to the liquid
Data Source
AI summary
There is provided a piezoelectric actuator configured to displace to project toward a pressure chamber to apply pressure to a liquid inside the pressure chamber, the piezoelectric actuator including: a vibration plate having a compressive stress; a piezoelectric layer having a pulling stress; and an individual electrode. The compressive stress of the vibration plate has a magnitude which is not less than a threshold value at which an extreme point is generated in a relationship between a compliance of the piezoelectric actuator and a displacement volume of the pressure chamber in a case that an electric voltage is applied to the piezoelectric actuator, the displacement volume converting from increasing to decreasing relative to increase in the compliance at the extreme point; and the thickness of the piezoelectric actuator is not less than a first thickness corresponding to a compliance allowing the extreme point to generate.