Piezoelectric Inkjet Switching Circuit Parasitic Diode Charge Release
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Solution Overview
Problem
In ink jet printers, unintended DC voltage applied to piezoelectric elements can cause continuous unintended displacement, leading to stress on the vibration plate, potential cracks, and fluctuations in ink ejection accuracy due to unintended stress and voltage fluctuations.
Innovation Solution
A liquid ejecting apparatus with a piezoelectric element and a switching circuit that includes NMOS and PMOS transistors, with specific modes of operation to control the supply of drive signals and criterion voltage signals, utilizing parasitic diodes to release charges and reduce unintended voltage differences between electrodes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a not-intended DC voltage is supplied to the piezoelectric element, then the piezoelectric element performs displacement, but the vibration plate bends larger than expected and not-intended stress is applied to the vibration plate
Solution Approach 1:
The patent applies preliminary anti-action by introducing a discharge path that actively removes accumulated charges from the piezoelectric element before they can cause harmful unintended displacement. The switching circuit is configured to discharge charges under normal operating conditions, preventing the buildup that would lead to excessive vibration plate bending and stress concentration.
Solution Approach 2:
The switching circuit acts as an intermediary between the piezoelectric element and the voltage supply. It controls charge accumulation and discharge, mediating the electrical interactions to prevent harmful effects while maintaining necessary piezoelectric element operation for ink ejection.
2Reliability
If the piezoelectric element performs not-intended displacement for a long term, then cracks may occur in the vibration plate, but the ejection accuracy is deteriorated due to ink leakage
Solution Approach 1:
The patent implements preliminary action by proactively managing charge accumulation through controlled discharge cycles. The switching circuit is designed to discharge charges before they reach levels that would cause harmful displacement and potential cracks, preventing the chain of events that would lead to both structural failure and ejection accuracy deterioration.
Solution Approach 2:
The switching circuit provides feedback control by monitoring charge accumulation and automatically initiating discharge when necessary. This feedback mechanism maintains the piezoelectric element and vibration plate within safe operating parameters, preventing both long-term damage and immediate ejection errors.
3Reliability
If ink leaked from cracks adheres to the electrodes, then a current path via the ink is formed and the potential of the criterion voltage signal fluctuates, but the ejection accuracy of the entire apparatus is influenced
Solution Approach 1:
The patent applies beforehand cushioning by preventing crack formation through proactive charge management. The switching circuit discharges accumulated charges before they can cause vibration plate stress and cracks, thereby preventing the cascade of failures that would lead to ink leakage and electrical shorting. This preventive approach protects both the mechanical structure and electrical integrity.
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 solution reduces unintended displacement of the piezoelectric element and vibration plate, minimizing stress and maintaining accurate ink ejection by controlling voltage differences and preventing charge accumulation, thereby enhancing the overall ejection accuracy of the ink jet printer.
Implementation Method 1
a piezoelectric element that includes a first electrode to which a drive signal is supplied and a second electrode to which a criterion voltage signal is supplied, and that performs displacement by a potential difference between the first electrode and the second electrode
Implementation Method 2
a first mode in which charges at a first node at which the first electrode and the second terminal are electrically connected to each other are released via a parasitic diode of the first switching circuit
Data Source
AI summary
A liquid ejecting apparatus includes a piezoelectric element that includes a first electrode to which a drive signal is supplied and a second electrode to which a criterion voltage signal is supplied, and performs displacement by a potential difference between the first electrode and the second electrode, a cavity which is filled with a liquid, a vibration plate provided between the cavity and the piezoelectric element, and a first switching circuit that includes a first terminal to which the drive signal is supplied and a second terminal which is electrically connected to the first electrode and controls a supply of the drive signal to the first electrode. The liquid ejecting apparatus has a first mode in which charges at a first node at which the first electrode and the second terminal are electrically connected to each other are released via a parasitic diode of the first switching circuit.