Inkjet Head Cancel Pulse Timing for Piezo Stability
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Solution Overview
Problem
In high-speed ink-jet printing, the short interval between ink discharges leads to pressure wave reverberation, causing unstable ink discharge, and existing methods for stabilizing the discharge, such as using a cancel pulse, risk insulation breakdown in thin-film piezoelectric elements due to high electric fields.
Innovation Solution
An ink-jet head with a drive signal that includes a discharge pulse and a cancel pulse of the same polarity, applied Tc times an even number greater than or equal to 4 after the discharge pulse ends within a one-pixel period, to effectively curb pressure wave reverberation without exceeding the withstand voltage of the thin-film piezoelectric element.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a cancel pulse with opposite polarity is applied to curb pressure wave reverberation, then ink discharge stability is improved, but the thin-film piezoelectric element may experience insulation breakdown due to high electric field
Solution Approach 1:
Instead of applying a cancel pulse with opposite polarity to the discharge pulse, the invention applies a cancel pulse with the same polarity. This inverted approach achieves pressure wave reverberation cancellation through timing-based interference rather than polarity-based cancellation, thereby avoiding insulation breakdown while maintaining ink discharge stability
Solution Approach 2:
The invention utilizes periodic discharge pulses applied at intervals matching the natural vibration period of the pressure chamber. By timing the cancel pulse to occur at specific periodic intervals (when a time equal to Tc times an even number greater than or equal to 4 elapses), the pressure waves interfere destructively to cancel reverberation without requiring high voltage opposite polarity pulses
2Productivity
If discharge pulses are applied at short intervals for high-speed printing, then productivity is improved, but pressure wave reverberation causes unstable ink discharge
Solution Approach 1:
The invention applies discharge pulses periodically at intervals matching the natural vibration period of the pressure chamber (Tc). This periodic timing allows the pressure chamber to complete vibration cycles between pulses, preventing reverberation accumulation and maintaining stable ink discharge even at high printing speeds
Solution Approach 2:
The cancel pulse is applied in advance at a specific timing (when a time equal to Tc times an even number greater than or equal to 4 elapses after the discharge pulse) to preemptively counteract pressure wave reverberation before it can destabilize subsequent ink discharge, enabling high-speed operation without sacrificing reliability
3Manufacturing precision
If multiple discharge pulses are applied within one pixel period for multi-gradation, then image quality is improved, but the timing of cancel pulse becomes complex
Solution Approach 1:
The invention uses a universal cancel pulse timing rule (applying the cancel pulse when a time equal to Tc times an even number greater than or equal to 4 elapses after the discharge pulse) that works consistently regardless of whether one or multiple discharge pulses are applied within a pixel period. This universal timing approach simplifies the drive circuit design while supporting multi-gradation functionality
Solution Approach 2:
The invention controls the timing parameter of the cancel pulse relative to the discharge pulse based on the natural vibration period Tc of the pressure chamber. By expressing the cancel pulse timing as a multiple of Tc (even number ≥ 4), the system adapts to different operating conditions without requiring complex circuitry, enabling multi-gradation with simplified drive electronics
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 approach allows for stable multi-gradation and high-speed drawing while avoiding the complexity of the drive circuit and ensuring the reliability of the thin-film piezoelectric element, maintaining consistent ink discharge speed across pixels.
Implementation Method 1
a piezoelectric thin film sandwiched between a pair of electrodes (upper electrode, lower electrode) and located on a driven film (diaphragm) that composes an upper wall of a pressure chamber. With ink stored in the pressure chamber, by applying a voltage (drive signal) to the pair of electrodes to extend and shrink the piezoelectric thin film and vibrating the diaphragm
Data Source
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AI summary
A drive signal applied to a thin-film piezoelectric element includes the following: at least one discharge pulse that causes a drop of ink to be discharged from a pressure chamber; and a cancellation pulse. Said cancellation pulse has the same polarity as the discharge pulse(s) and serves to suppress reverberations of a pressure wave applied to the pressure chamber when the thin-film piezoelectric element is driven by the application of the discharge pulse(s). Letting Tc represent half of the natural vibration period of the pressure chamber, within the period within which a single pixel is placed, the cancellation pulse is applied once an amount of time equal to Tc times an even integer greater than or equal to 4 has passed since the end of the application of the first discharge pulse.