Liquid Ejection Head Current Sensing for Heater Deterioration
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Solution Overview
Problem
Existing liquid ejection heads struggle to accurately detect the deterioration state of heaters due to limitations in current measurement methods, particularly in detecting minute changes in current flow, leading to potential disconnection or damage.
Innovation Solution
A liquid ejection head design that includes a current measurement element connected to the heater, with exclusive switching elements for ejection and measurement operations, allowing direct current measurement and detection of resistance value changes to assess heater condition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If indirect measurement using electrostatic induction is used, then device complexity is reduced, but measurement precision deteriorates because minute changes in current cannot be detected
Solution Approach 1:
The patent introduces a current measurement element as an intermediary component that directly measures the current flowing through the heater. This mediator element enables precise measurement of minute current changes without requiring complex indirect measurement systems, thus improving measurement precision while maintaining reasonable device complexity
Solution Approach 2:
The patent replaces the electrostatic induction-based indirect measurement system with a direct electrical measurement approach using a current measurement element. This substitution enables accurate detection of minute current changes by directly measuring the electrical parameter rather than inferring it through electromagnetic induction
2Productivity
If heaters are driven continuously without liquid, then productivity is maintained, but reliability deteriorates due to excessive heat causing disconnection or damage
Solution Approach 1:
The patent implements a feedback mechanism where the current measurement element continuously monitors the current flowing through the heater. When no liquid is detected or the heater temperature becomes excessive, the system provides feedback to stop or reduce heating, thus preventing disconnection or damage while maintaining productivity when liquid is present
Solution Approach 2:
The patent makes the heater operation dynamic by adjusting the driving conditions based on real-time current measurements. The system can switch between different operating states (normal ejection, idle, error condition) based on the measured current values, allowing continuous productivity when needed while preventing damage when liquid is absent
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
Enables precise detection of heater deterioration by measuring minute changes in current flow, facilitating effective reuse assessment and preventing damage during recycling processes.
Implementation Method 1
a heater configured to generate energy for ejecting liquid from the ejection port
Implementation Method 2
Because parasitic capacitance is present between the wiring of the heater and the sense wiring, the voltage value at terminal of the resistor changes via the parasitic capacitance due to electrostatic induction in accordance with a change in the value of the current flowing through the wiring of the heater
Data Source
AI summary
A liquid ejection head includes an ejection port configured to eject liquid, a heater configured to generate energy for ejecting liquid from the ejection port, an ejection switching element configured to be connected to the heater and to energize the heater, a current measurement element configured to have one end connected to a wiring that connects the heater and the ejection switching element and to measure a current flowing through the heater, and a measurement switching element configured to be connected to another end of the current measurement element and to energize the heater and the current measurement element, wherein switching of the ejection switching element to a conducting state and switching of the measurement switching element to a conducting state are performed mutually exclusively.