Inkjet Printhead Resistance Sensor Dynamic Current Detection
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Solution Overview
Problem
Conventional inkjet printing apparatuses face challenges in accurately detecting nozzle discharge failures due to small signal changes in temperature drop rate change points, which are often buried in noise, making it difficult to determine the discharge state and maintain image quality.
Innovation Solution
The apparatus includes a printhead with a heater and a resistance sensor, utilizing a current source to supply constant currents of different values to detect resistance value changes, allowing for high-accuracy temperature change detection by switching current values after ink droplet discharge.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the entire temperature waveform is designed to fall within the input range of the A/D converter, then the temperature detection range is improved, but the small signal change at the temperature drop rate change point becomes smaller and is buried in noise
Solution Approach 1:
The patent applies dynamics by making the current supply to the sensor dynamic rather than static. The current source switches between a first current value and a second current value (larger than the first) at predetermined timing after heater driving. This dynamic current adjustment amplifies the temperature drop rate change point signal during specific time windows, making it detectable above noise while maintaining adequate temperature range coverage through adaptive measurement timing.
Solution Approach 2:
The patent implements periodic action by supplying current to the sensor in periodic pulses synchronized with the heater driving cycle. Current is supplied at specific intervals after heater activation, creating periodic measurement windows that capture the temperature drop rate change point. This periodic current supply pattern enables consistent detection of the transient signal while maintaining system stability.
2Device complexity
If a constant current is supplied to the resistance sensor, then the detection system is simple, but the small signal change at the temperature drop rate change point cannot be distinguished from noise
Solution Approach 1:
The patent transitions from a static constant current system to a dynamic current system that adjusts amplitude based on measurement timing. The current source provides a first current value during certain periods and a second, larger current value during critical measurement windows. This dynamic adjustment amplifies the signal at the temperature drop rate change point without requiring complex additional hardware, maintaining relative system simplicity while dramatically improving measurement precision.
3Measurement precision
If the current value supplied to the resistance sensor is increased, then the signal change at the temperature drop rate change point becomes larger, but the temperature range that can be detected decreases
Solution Approach 1:
The patent resolves this contradiction through periodic current supply synchronized with the thermal cycle. High current (second current value) is supplied only during specific time windows after heater driving when the temperature drop rate change point occurs, amplifying the signal when needed. During other periods, lower current (first current value) is supplied, preserving the ability to detect broader temperature ranges. This time-multiplexed approach allows both high signal magnitude and broad temperature coverage.
Solution Approach 2:
The system dynamically adjusts current amplitude based on the thermal state and measurement timing. By switching between two current values at predetermined timing, the system optimizes signal-to-noise ratio during critical measurement periods while maintaining adequate dynamic range for overall temperature monitoring. This dynamic adaptation allows the system to achieve high measurement precision without permanently sacrificing temperature detection range.
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 method enables precise detection of temperature changes, improving the accuracy of determining nozzle discharge states and preventing image quality degradation by effectively distinguishing between normal and failed discharges.
Implementation Method 1
a resistance sensor whose resistance value changes upon a temperature change of the heater
Implementation Method 2
An electrothermal transducer which generates heat in accordance with energization
Data Source
AI summary
An inkjet printing apparatus includes a current source configured to be able to supply, to a resistance sensor, a constant current of the first constant current value and a constant current of the second constant current value larger than the first constant current value. A change of the resistance value of the resistance sensor is detected by switching the value of the constant current to be supplied to the resistance sensor between the first constant current value and the second constant current value a predetermined time after driving a heater to discharge an ink droplet.