Heat Generating Element Asymmetry in Liquid Ejection Heads
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Solution Overview
Problem
High-density ink jet recording systems face damage to heat generating elements due to cavitation when ejection orifices and flow paths are arranged at 1,200 dpi or more, requiring slender heat generating elements with aspect ratios of 2.5 or more, which increases the risk of cavitation and damage.
Innovation Solution
A liquid ejection head with a rectangular heat generating element having a long-side to short-side ratio of 2.5 or more, where the longitudinal direction of the heat generating element is aligned with the flow path, and the end portion on the downstream side is positioned between the end portions of the ejection orifice on both the downstream and upstream sides, allowing the bubble to communicate with outside air and prevent division and subsequent cavitation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If ejection orifices and flow paths are arranged at high density of 1,200 dpi or more, then recording density is improved, but the heat generating element becomes slender with large aspect ratio which increases cavitation damage
Solution Approach 1:
The patent applies asymmetry by intentionally deviating the center of the ejection orifice from the center of the heat generating element toward the upstream side. This asymmetric arrangement creates a specific bubble communication path that prevents bubble division and reduces cavitation damage to the heat generating element, while maintaining high-density ejection capability of 1,200 dpi or more
2Productivity
If heat generating element aspect ratio is increased to 2.5 or more for high-density ejection, then ejection performance is improved, but cavitation damage to the heat generating element increases
Solution Approach 1:
The patent uses the asymmetric positional relationship between the ejection orifice and heat generating element as an intermediary mechanism. This arrangement mediates the bubble behavior to communicate with air at a site where division is difficult, thereby protecting the heat generating element from cavitation damage while maintaining the required aspect ratio of 2.5 or more for high-density ejection
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 configuration effectively inhibits cavitation and damage to the heat generating element, while maintaining high-density ejection capabilities, reducing mist generation and improving ejection durability by controlling the positional deviation between the ejection orifice and heat generating element.
Implementation Method 1
thermal energy is generated by a heat generating element arranged in a flow path (nozzle) to which an ink is supplied
Implementation Method 2
causing film-boiling of the ink around the heat generating element to generate a bubble
Implementation Method 3
the heat generating element is damaged by cavitation caused by the extinction of the bubble generated on the heat generating element
Data Source
AI summary
A liquid ejection method is effected in a liquid ejection head that includes an ejection orifice for ejecting a liquid, a flow path for supplying the liquid from a liquid supply port to the ejection orifice, and a heat generating element. The heat generating element is rectangular with a long-side to short-side ratio of 2.5 or more for generating thermal energy used to eject the liquid, and a longitudinal direction of the heat generating element is arranged along an extending direction of the flow path. An end portion of the heat generating element on a downstream side with respect to a liquid flowing direction within the flow path is located between an end portion of the ejection orifice on the downstream side and an end portion of the ejection orifice on an upstream side when viewed from a direction in which the liquid is ejected from the ejection orifice.