Liquid Ejecting Head Filling to Reduce Air Bubble Adhesion
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Solution Overview
Problem
Air bubbles are likely to be generated in a liquid ejecting apparatus when a liquid with high surface tension is introduced, leading to their adhesion to the inner surfaces of the head, which can hinder proper ejection.
Innovation Solution
A method involving a first initial introduction process where the negative pressure pump is stopped, followed by driving the positive pressure pump to fill the head channels with the liquid, and then activating both pumps to circulate the liquid, minimizing bubble generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the negative pressure pump is driven to circulate the inspection liquid, then the liquid can be circulated between the ink tank and the ejecting head, but air bubbles are generated in the inspection liquid by air entering the ejecting head through nozzles
Solution Approach 1:
The patent applies preliminary action by first driving only the positive pressure pump to fill the head channels with inspection liquid before subsequently driving both pumps for circulation. This preliminary filling step prevents air bubbles from entering the head channels through nozzles when the negative pressure pump operates, as the channels are already filled with liquid.
2Productivity
If the positive pressure pump and negative pressure pump are driven simultaneously to circulate the inspection liquid, then the liquid flows continuously, but air bubbles adhere to the inner surface of the ejecting head and are not discharged
Solution Approach 1:
The patent applies preliminary action by first driving only the positive pressure pump to fill the head channels with inspection liquid before subsequently driving both pumps for circulation. This preliminary filling step prevents air bubbles from entering the head channels through nozzles when the negative pressure pump operates, as the channels are already filled with liquid.
Solution Approach 2:
The patent applies segmentation by dividing the pump operation into two distinct phases: a first phase where only the positive pressure pump operates to fill the head channels, and a second phase where both pumps operate for circulation. This segmentation separates the filling function from the circulation function, preventing air bubble generation during the circulation phase.
3Ease of operation
If the inspection liquid with high surface tension is introduced into the head, then the liquid can be supplied from the tank, but air bubbles are likely to be generated and adhere to the inner surface of the head
Solution Approach 1:
The patent applies preliminary action by first driving only the positive pressure pump to fill the head channels with inspection liquid before subsequently driving both pumps for circulation. This preliminary filling step prevents air bubbles from entering the head channels through nozzles when the negative pressure pump operates, as the channels are already filled with liquid.
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 effectively reduces the likelihood of air bubbles remaining in the head channels, ensuring smooth liquid ejection.
Implementation Method 1
a positive pressure pump configured to apply positive pressure to supply the liquid from the tank to the head through the liquid supply channel
Implementation Method 2
a negative pressure pump configured to apply negative pressure to discharge the liquid from the head to the tank through the liquid return channel
Implementation Method 3
the first liquid flows in order from the liquid supply channel to the supply manifold, the head channel, the return manifold, and the liquid return channel, and gas will be discharged to the tank through the liquid return channel with the flow of the first liquid
Implementation Method 4
In a case where an air bubble is generated in the first liquid having the surface tension of 30 mN/m or greater, the air bubble adheres to an inner surface of the head channel or the return manifold
Data Source
AI summary
A liquid ejecting apparatus including: a tank; a head including a nozzle, a head channel, a supply manifold, and a return manifold; a liquid supply channel; a liquid return channel; a positive pressure pump; a negative pressure pump; and a controller configured to execute a first initial introduction process depending on acceptance of a first command indicating an initial introduction of a first liquid. The first initial introduction process includes: a first step of driving the positive pressure pump in a state that the negative pressure pump is stopped; and a second step of driving the positive pressure pump and the negative pressure pump after the first step. Surface tension of the first liquid stored in the tank in the first initial introduction process is 30 mN/m or greater.