Maintenance Pulse Waveform for Liquid Ejecting Apparatus
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Solution Overview
Problem
Liquid ejecting apparatuses face instability in ejecting ink during maintenance due to increased viscosity of ink near nozzles, leading to air bubbles being trapped and causing ejection defects.
Innovation Solution
A maintenance pulse with specific timing and voltage conditions is applied to the pressure generation unit, including an expansion element, contraction element, and reexpansion element, to minimize meniscus movement and prevent air bubble mixing, along with a microvibration pulse to improve ink flowability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional flushing operation is performed after ink viscosity increases near nozzles, then air bubbles and thickened ink should be ejected, but the ejection becomes unstable due to trapped air bubbles
Solution Approach 1:
The patent applies a preliminary action by performing a microvibration pulse before the main maintenance pulse. This microvibration pulse preliminarily agitates the thickened ink and prevents air bubbles from becoming trapped, creating favorable conditions for the subsequent main ejection pulse to operate stably without air bubble interference
Solution Approach 2:
The patent employs periodic action through the use of a maintenance pulse with a specific periodic waveform that includes expansion, contraction, and reexpansion phases. This periodic action creates controlled pressure fluctuations that systematically work through the thickened ink and expelled air bubbles in a rhythmic manner, improving ejection stability
2Productivity
If the pressure chamber is rapidly contracted to eject ink droplets, then ink ejection occurs, but residual vibrations cause the meniscus to move back and forth creating air bubble entrapment
Solution Approach 1:
The patent applies preliminary anti-action by introducing a microvibration pulse that counteracts the harmful residual vibrations before they can cause air bubble entrapment. This preliminary vibration pulse agitates the liquid and prevents the meniscus from settling into positions that would trap air bubbles during the subsequent main ejection pulse
Solution Approach 2:
The patent utilizes parameter changes by modifying the pressure chamber's volume parameters through a controlled sequence of expansion and contraction phases in the maintenance pulse. These parameter changes create pressure gradients that systematically move the meniscus and expelled air bubbles in a controlled manner, improving ejection stability
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 allows for stable ink ejection during maintenance by reducing air bubble entrapment and improving ink flow, even when the ink has thickened, thereby preventing ejection defects and reducing ink consumption.
Implementation Method 1
a pressure generation unit that brings about a pressure fluctuation in a liquid inside the pressure chamber, and that is capable of ejecting the liquid from the nozzle through actuation of the pressure generation unit
Implementation Method 2
a piezoelectric element that changes its length in response to a change in voltage applied thereto, and that is capable of causing a pressure chamber to expand and contract
Implementation Method 3
a microvibration pulse that brings about a pressure fluctuation in the liquid inside the pressure chamber to an extent at which liquid is not ejected from the nozzle
Data Source
AI summary
A maintenance pulse is a pulsed waveform that includes an expansion element that causes a pressure chamber to expand, a contraction element that causes the pressure chamber that is expanded by the expansion element to contract, and a reexpansion element that causes the pressure chamber that is contracted by the contraction element to expand again, and satisfies the following condition (1) when a time from the beginning of the contraction element to the beginning of the reexpansion element is given the term T1, and a specific vibration period that is caused in the liquid inside the pressure chamber is given the term Tc.1.2×Tc≦T1<1.5×Tc (1)