Liquid Ejection Head Filling Pressure Control

The patent applies parameter changes by dynamically adjusting the pressure in the recovery tank during different phases of the filling process. Specifically, the pressure is controlled to be less than atmospheric pressure during the initial filling phase to improve filling efficiency, then switched to greater than atmospheric pressure when the meniscus breaks to prevent air bubble ingestion. This temporal variation of pressure parameters resolves the contradiction between filling efficiency and air bubble prevention.

The patent implements periodic action by dividing the filling process into distinct periods with different pressure conditions. The first period uses depressurization to fill the flow path efficiently, while the second period uses pressurization to prevent air bubble entry. This periodic switching between different pressure states allows the system to achieve both high filling efficiency and reliable operation without air bubbles.

The patent applies preliminary action by breaking the meniscus in advance during the first period when the liquid level is sufficient, before the liquid reaches the recovery flow path. This preliminary meniscus breaking allows the liquid to fill the recovery flow path without creating a pressure differential that would draw air bubbles in during the subsequent ejection phase.

The patent implements beforehand cushioning by establishing a cushion of liquid in the recovery flow path before the ejection process begins. By ensuring the liquid reaches the recovery flow path during the filling period and maintaining appropriate pressure conditions, the system creates a protective liquid cushion that prevents air bubbles from being drawn into the flow path during operation.