Liquid Ejection Head Pressure Control via Dual Circulation
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Solution Overview
Problem
Conventional liquid ejection apparatuses face challenges in preventing the precipitation of color material and stagnation of foreign matters in the liquid flow channel, leading to waste inks and downtime, especially with high-speed printing, and instability in ejection properties due to negative pressure variations during reciprocal scanning of the liquid ejection head.
Innovation Solution
A liquid ejection apparatus with a configuration that includes a pressure control unit, a first circulation unit for circulating ink between the liquid ejection unit and the pressure control unit, and a second circulation unit for circulating ink between the liquid storing unit and the pressure control unit, using a piezoelectric type diaphragm pump and differential pressure valve to maintain stable ink pressure and reduce pressure variations, thereby preventing ink precipitation and ensuring stable ejection properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a circulation pump is mounted above the liquid ejection head to circulate liquid, then liquid circulation is achieved, but the device complexity increases and pressure control stability deteriorates
Solution Approach 1:
A circulation pump is introduced as an intermediary component between the liquid storage unit and the liquid ejection head. The pump includes a suction port connected to the liquid storage unit and a discharge port connected to the liquid supply flow channel, serving as a mediator to drive liquid circulation without direct mounting on the ejection head, thus reducing complexity while maintaining circulation capability
Solution Approach 2:
The circulation system is segmented into distinct functional components: the circulation pump as a separate unit, the liquid storage unit, the liquid supply flow channel, and the liquid ejection head. This segmentation allows each component to be optimized independently and simplifies the overall system configuration compared to integrated designs
2Productivity
If liquid is circulated at high speed, then productivity increases, but pressure variations cause ejection property instability
Solution Approach 1:
A pressure sensor is installed in the liquid supply flow channel to detect liquid pressure in real-time. The control unit receives pressure information from the sensor and adjusts the circulation pump operation accordingly, creating a feedback loop that maintains stable liquid pressure even during high-speed circulation, thereby ensuring consistent ejection properties
Solution Approach 2:
The circulation pump operation is made dynamic and adjustable based on real-time pressure conditions. The control unit varies the pump speed or operation mode according to the detected pressure and printing requirements, allowing the system to adapt to different printing speeds and maintain stability across varying operational conditions
3Device complexity
If circulation is performed without pressure control, then device complexity is reduced, but color material precipitation occurs
Solution Approach 1:
The pressure sensor continuously monitors liquid pressure in the supply flow channel and provides feedback to the control unit. This feedback mechanism ensures that liquid pressure remains within an optimal range that prevents color material precipitation while maintaining a relatively simple circulation system without complex pressure control mechanisms
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 enables productive liquid ejection operations with reduced waste inks and downtime, maintaining high image quality and stability even at high scanning speeds by suppressing ink precipitation and stabilizing ejection properties, eliminating the need for preliminary suction recovery operations.
Implementation Method 1
using a piezoelectric type diaphragm pump and differential pressure valve to maintain stable ink pressure
Data Source
AI summary
A liquid ejection apparatus includes a liquid storing unit capable of storing liquid, a liquid ejection unit including an ejection port that is capable of ejecting the liquid, and a pressure control unit that receives the liquid from the liquid storing unit and allows the liquid having a pressure controlled to be within a predetermined pressure range to be supplied to the liquid ejection unit. Additionally, the liquid ejection apparatus includes a first circulation unit that supplies the liquid having the pressure controlled by the pressure control unit to the ejection port while circulating the liquid between the liquid ejection unit and the pressure control unit, and a second circulation unit that circulates the liquid between the liquid storing unit and the pressure control unit.