Liquid Ejection Head Pressure Control for Ink Refilling
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Solution Overview
Problem
Inkjet printing systems face issues with pressure fluctuations and inadequate refilling during high-duty printing, leading to quality deterioration in printed images due to uneven ink distribution and clogging, especially with a large number of ejection ports.
Innovation Solution
A liquid ejection apparatus with a pressure control mechanism that refills the ejection head based on pressure conditions, using a common configuration for multiple flow passages to stabilize ink ejection and prevent clogging, while maintaining efficient circulation and refilling performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If refilling is performed through only the upstream flow passage during high-duty printing, then the pump can prevent backflow through the downstream flow passage, but the ejection head is refilled insufficiently leading to significant pressure changes and negative pressure increase
Solution Approach 1:
The refilling function is segmented between two flow passages: the upstream flow passage (first flow passage) is used for refilling during high-duty printing, while the downstream flow passage (second flow passage) is used for circulation during normal printing. This segmentation allows optimized performance for each function without interference.
Solution Approach 2:
The system dynamically switches between different flow passage configurations based on printing conditions. During high-duty printing, the first flow passage is activated for refilling while the second flow passage is closed. During normal printing, the second flow passage is opened for circulation. This dynamic switching optimizes refilling performance when needed while maintaining circulation during normal operation.
2Productivity
If the number of ejection ports is increased to handle larger printing areas, then printing capacity is improved, but negative pressure increases significantly at latter ejection ports complicating proper ejection
Solution Approach 1:
The flow passage system is segmented into multiple independent pathways (first and second flow passages) that can be selectively activated. This allows better distribution of ink flow to multiple ejection ports, preventing excessive negative pressure buildup at downstream ports while maintaining printing capacity.
3Measurement precision
If a complex pressure control system with separate control mechanisms for multiple flow passages is implemented, then pressure control precision is improved, but the number of components increases and costs rise
Solution Approach 1:
A single pressure control mechanism is designed to perform multiple functions: it controls pressure in both the first flow passage (during high-duty printing) and the second flow passage (during normal printing). This multi-functional design achieves precise pressure control for different operating conditions without requiring separate control mechanisms, thereby reducing component count and system complexity.
Data Source
Figure 1A~1B
Figure 2
Figure 3
AI summary
A liquid ejection apparatus(1) includes an ejection port ejecting a liquid, a pressure chamber(123) storing the liquid, an element(115) generating energy for ejecting the liquid in the pressure chamber(123), first and second tanks(21, 22) which can store the liquid, a flow passage establishing communication between the first and second tanks(21,22) through the pressure chamber(123), a switching unit(4) switching a flowing direction of the liquid in the flow passage between a first direction from the first tank(21) to the second tank(22) and a second direction being opposite to the first direction, and a pressure compensation unit(37). When a pressure in a downstream side flow passage portion downstream of the pressure chamber(123) has a predetermined pressure or below, the pressure compensation unit(37) compensates for reduction in pressure in the downstream side flow passage portion by supplying the liquid to the downstream side flow passage portion.