Liquid Ejecting Head Flow Path Asymmetry for Bubble Removal
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Solution Overview
Problem
Ink jet type recording heads and liquid ejecting heads face issues with discharge defects due to air bubbles and thickened ink causing nozzle clogging and deviation in ink droplet direction, which existing configurations fail to adequately address.
Innovation Solution
A liquid ejecting head design featuring a flow path substrate with a nozzle plate and energy generating element, including a first and second common liquid chamber, and individual flow paths where the nozzle is positioned in a first flow path with a smaller cross-sectional area than the second flow path, facilitating high-speed ink flow to prevent ink thickening and air bubble accumulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a circulation flow path is provided from the first common liquid chamber to the second common liquid chamber, then air bubbles can be removed from the system, but discharge defects occur such as ink thickening near the nozzle, nozzle clogging by infiltrated air bubbles, and deviation in ink droplet flying direction
Solution Approach 1:
The patent applies local quality by creating a specific flow path configuration where the first flow path has a smaller cross-sectional area than the second flow path. This local variation in flow path geometry creates different flow velocities in different regions, causing air bubbles to accumulate in the slower-moving second flow path rather than the nozzle area, thus preventing discharge defects while maintaining air bubble removal capability
Solution Approach 2:
The patent uses the second flow path as an intermediary region with larger cross-sectional area that acts as a buffer zone. Air bubbles are diverted into this intermediary space where they can accumulate safely without affecting the nozzle operation, effectively mediating between the circulation requirement and the discharge quality requirement
2Speed
If the nozzle is disposed in the first flow path with smaller cross-sectional area, then ink flow velocity increases preventing ink thickening, but the flow path complexity increases
Solution Approach 1:
The patent segments the flow path into distinct sections with different cross-sectional areas - the first flow path with smaller area for high-velocity ink delivery to the nozzle, and the second flow path with larger area for air bubble accommodation. This segmentation allows each section to perform its specific function optimally while maintaining overall system manageability
Solution Approach 2:
The patent employs asymmetry by making the cross-sectional area of the first flow path deliberately smaller than that of the second flow path. This asymmetric design creates the necessary velocity differential to achieve both high-speed ink delivery to the nozzle and air bubble separation, resolving the contradiction between speed enhancement and structural simplicity
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
Prevents discharge defects by effectively removing thickened ink and air bubbles from the nozzle area, ensuring consistent ink droplet discharge and direction.
Implementation Method 1
an energy generating element such as a piezoelectric actuator that induces a change in the pressure of the ink in the pressure chamber. If the energy generating element induces a change in the pressure of the ink in the pressure chamber, ink droplets are discharged from the nozzle.
Implementation Method 2
if air bubbles stay in the pressure chamber, the air bubbles absorb the pressure change induced by the energy generating element, and thus it is not possible to normally discharge the ink droplets from the nozzle.
Implementation Method 3
A cross-sectional area of the first flow path is smaller than a cross-sectional area of the second flow path. In this aspect, the nozzle is disposed in the first flow path at a position close to the second flow path.
Data Source
Figure 1
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AI summary
A liquid ejecting head includes a flow path substrate which includes a nozzle plate and in which a flow path is formed; and an energy generating element inducing a change in a pressure of a liquid in the flow path. The flow path includes a first common liquid chamber, a second common liquid chamber, and a plurality of individual flow paths which communicate with the first common liquid chamber and the second common liquid chamber and through which the liquid flows from the first common liquid chamber toward the second common liquid chamber. The individual flow path includes a nozzle communicating with an outside, a first flow path, in the middle of which the nozzle is disposed and which extends in a first direction that is an in-plane direction of a nozzle surface of the nozzle plate in which the nozzle opens, a second flow path coupled to the first flow path and extending in a second direction other than the first direction, a third flow path coupled to the second flow path and extending in the third direction other than the second direction, and a pressure chamber which is disposed in the third flow path and in which a pressure change is induced by the energy generating element. A cross-sectional area of the first flow path is smaller than a cross-sectional area of the second flow path.