Thermal Head Current Timing Control for Printing Speed and Concentration Uniformity
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Solution Overview
Problem
In printing apparatuses using thermal heads, reducing the time difference in current passage start timing to increase printing speed leads to unevenness in image concentration due to voltage drops, causing energy loss disparities between different heater elements.
Innovation Solution
Implementing a current passage control mechanism that synchronizes the timing of current passage through different heater elements, ensuring that the integrated current values for odd and even-numbered printing lines are balanced across both sets of elements, with overlapping current passage times and distinct start and end timings for each set.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the time difference in current passage start timing is decreased to increase printing speed, then printing speed is improved, but unevenness in image concentration occurs due to voltage drops
Solution Approach 1:
The heater elements are divided into two groups (first and second sets) with different current passage timing. The first set includes heater elements at positions where voltage drop has less influence, while the second set includes heater elements at positions where voltage drop has more influence. This segmentation allows differential timing control to compensate for voltage drop effects across different spatial positions.
Solution Approach 2:
Different current passage start timings are applied asymmetrically to different groups of heater elements based on their positional characteristics. The first strobe signal and second strobe signal are configured with different timing offsets from the reference timing, creating an asymmetric timing pattern that compensates for the asymmetric voltage drop effects across the heater element array.
2Reliability
If current passage timing is staggered to reduce power supply voltage capacity, then power supply stability is improved, but printing speed decreases
Solution Approach 1:
The system uses periodic strobe signals to control current passage through heater elements. By configuring the first and second strobe signals with different timing relative to a reference timing, the system creates a periodic pattern where current passage is distributed in time, reducing peak power demands while maintaining continuous printing operation.
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 approach enhances printing speed while minimizing the unevenness in image concentration by stabilizing the energy distribution across heater elements, reducing the impact of voltage drops.
Implementation Method 1
Each heater element of the thermal head is comprised of a resistor, and the current (energy amount) passing through each heater resistor is of I(current)=V(voltage)/R(resistance).
Data Source
AI summary
To provide a printing apparatus for enabling printing speed to be increased, while enabling the unevenness of concentration to be reduced, a printing apparatus is provided with a thermal head having a plurality of heater elements lined up in the main scanning direction and a CPU for switching current passage timing of the plurality of heater elements, and the CPU switches the current passage timing for the plurality of heater elements so that a second strobe signal STB2 is switched to an ON state after switching a first strobe signal STB1 to an ON state, after switching the STB2 to the ON state the STB1 is switched to an OFF state, the STB2 is switched to an OFF state, then the STB1 is switched to the ON state after switching the STB2 to the ON state, after switching the STB1 to the ON state the STB2 is switched to the OFF state, and that the STB1 is switched to the OFF state.