Thermal Head Control for High-Speed Printing Sharpness

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Solution Overview

Problem

Conventional methods of controlling thermal heads in high-speed printing result in impaired image sharpness at borders due to the thermal head's inability to follow speed, leading to reduced sharpness in transitions from black to white and white to black.

Innovation Solution

The method involves reversing the energizing and non-energizing periods in each line, where a relatively long non-energizing period is initially set to eliminate heat, followed by a short energizing period to maintain heat for subsequent dark images, and a short non-energizing period is used for white images to prevent color generation, ensuring high image sharpness.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If the conventional method of controlling a thermal head is used (energizing period from line-start, non-energizing period after energizing period), then it is possible to represent an image with a predetermined gradation on each line, but when the moving speed becomes high, the thermal response does not follow the speed and image sharpness is impaired

Engineering Contradiction:

Improveprinting speedVSAvoidimage sharpness

Core Design Contradiction:

ProductivityVSManufacturing precision

Solution Approach 1:

The patent inverts the conventional sequence of energizing and non-energizing periods. Instead of energizing from line-start followed by non-energizing, the patent applies non-energizing period first from line-start followed by energizing period. This inversion allows the thermal head to eliminate heat before printing, preventing heat accumulation that degrades image sharpness at high speeds.

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The patent applies a preliminary non-energizing period at the start of each line to eliminate heat before the actual printing process. This preliminary action ensures that the thermal head is in an optimal thermal state for high-speed printing, allowing the thermal response to follow the printing speed without degrading image sharpness.

Inventive Principle:

Principle #10Preliminary action

2Manufacturing precision

If a relatively long non-energizing period is provided at the start of one line, then it is possible to eliminate heat of the resistors and prevent reduction in image sharpness in change from white to black, but the energizing period must be shortened

Engineering Contradiction:

Improveimage sharpness in white to black transitionVSAvoidenergizing period duration

Core Design Contradiction:

Manufacturing precisionVSDuration of action of moving object

Solution Approach 1:

The patent changes the timing parameters of energizing and non-energizing periods. By setting the non-energizing period to start from line-start and extending it through part of the line, the patent creates a time window for heat elimination. The energizing period is then applied within the remaining time, optimizing both heat management and printing efficiency for high-speed operation.

Inventive Principle:

Principle #35Parameter changes

3Manufacturing precision

If a relatively short energizing period is provided after the non-energizing period, then it is possible to provide resistors with remaining heat and prevent generation of color, but the non-energizing period must be extended

Engineering Contradiction:

Improveimage sharpness in black to white transitionVSAvoidnon-energizing period duration

Core Design Contradiction:

Manufacturing precisionVSLoss of time

Solution Approach 1:

The patent applies periodic action by alternating between non-energizing and energizing periods in a structured sequence. The non-energizing period starts from line-start and the energizing period follows, creating a rhythmic thermal cycle that manages heat effectively. This periodic pattern ensures proper thermal response at high speeds while maintaining image sharpness in both white-to-black and black-to-white transitions.

Inventive Principle:

Principle #19Periodic action

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 maintains high image sharpness even at high printing speeds by effectively managing heat in the thermal head, preventing reduction in sharpness during transitions from white to black and black to white.

Implementation Method 1

A thermal head, hitherto provided in a printer and the like, includes a plurality of resistors. Based on data for printing, each resistor is selectively energized to execute printing on sheet surface.

Methodology Applied

Scientific EffectJoule heating: Joule Heating

Data Source

PatentUS7683921B2Method of controlling a thermal head

Publication Date: 2010.03.23 MITSUBISHI ELECTRIC CORP

AI summary

The present invention provides a method of controlling a thermal head which is capable of maintaining high image sharpness even in high-speed printing. In the method of controlling a thermal head according to the present invention, resistors constituting the thermal head is energized and non-energized, thereby realizing an image with a predetermined gradation. Further, one line period includes one energizing period in which energization is performed and one non-energizing period in which non-energization is performed, and the resistors are energized during the energizing period after the non-energizing period in the one line period.