Printhead Sensor Plate Impedance Ink Level Detection
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Solution Overview
Problem
Existing ink level sensing techniques for inkjet printers lack accuracy and are costly, leading to premature replacement of ink cartridges and potential low-quality prints due to inadequate ink supply detection.
Innovation Solution
The implementation of a printhead with a MEMS structure and an impedance measurement/sensor circuit that uses a sensor plate to detect the presence of ink by measuring impedance changes, incorporating a biasing algorithm to optimize the circuit's operating point for maximum output difference between wet and dry conditions, and utilizing either a controlled voltage or current source to induce current or voltage responses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional ink level sensing techniques are used, then the system can detect ink levels, but the measurement precision is insufficient and the cost is high
Solution Approach 1:
The patent combines the ink level sensing function with the existing printhead structure by integrating a sensor plate into the printhead's fluidic channel. This merging eliminates the need for separate external sensors and reduces overall system complexity while maintaining measurement precision through direct contact sensing.
Solution Approach 2:
The printhead structure is designed to serve multiple functions: it acts as both the ink ejection device and the ink level sensor. The sensor plate within the fluidic channel enables the printhead to simultaneously perform its primary function of drop generation and the secondary function of ink level detection, reducing component count and cost.
2Measurement precision
If impedance measurement circuit is integrated onto printhead, then the cost is reduced and accuracy is improved, but the device complexity increases
Solution Approach 1:
The impedance measurement circuit utilizes the inherent electrical properties of the ink itself as the sensing medium. The circuit measures the impedance change caused by ink presence or absence in the fluidic channel, allowing the system to self-diagnose ink levels without requiring external reference materials or complex calibration mechanisms.
Solution Approach 2:
The measurement circuit detects ink levels by monitoring changes in electrical impedance parameters. As ink flows into or out of the sensor region, the electrical impedance changes due to the conductive properties of ink versus air, providing a measurable signal for level detection without mechanical movement or complex optical systems.
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 solution provides accurate ink level indications with high tolerance to contamination and cost-effectiveness by integrating the sensor circuitry onto existing thermal inkjet printheads, ensuring reliable ink detection and reducing waste.
Implementation Method 1
measuring the impedance of ink, which will be much lower than that of air, to determine if ink is no longer in contact with the sensor
Data Source
AI summary
In an implementation, a printhead includes a nozzle and a fluid channel. A sensor plate is located within the fluid channel. An impedance measurement circuit is coupled to the sensor plate to measure impedance of fluid within the channel during a fluid movement event that moves fluid past the sensor plate.