DC Motor Drive Current Control for Thermal Printer Tension
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In printing apparatuses using thermal heads, maintaining consistent tension in film-shaped media is challenging due to variations in DC motor torque caused by environmental temperature and age deterioration, leading to deteriorated image quality.
Innovation Solution
A printing apparatus with a controller that calculates and adjusts the drive current for the DC motor to maintain a consistent rotation velocity, independent of media tension, using a rotation amount detector and motor driver to ensure proper tension correction, and incorporates a temperature detector for temperature compensation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If DC motor is controlled to compensate for roll diameter variation, then media tension is improved, but image quality deteriorates due to incorrect rotation velocity measurement under tension
Solution Approach 1:
The system performs preliminary calibration by measuring the rotation velocity of the DC motor when no media tension is applied (during initialization or maintenance mode). This pre-measured velocity characteristic is stored and later used to calculate corrected drive currents during actual printing operations, avoiding the problem of measuring under tension conditions.
Solution Approach 2:
The system implements a feedback mechanism where the measured rotation velocity (from tension-free conditions) and the actual drive current are used to calculate a correction factor. This correction factor is fed back to adjust the drive current in real-time, ensuring that the motor maintains accurate rotation velocity despite changes in media tension or motor characteristics due to temperature and aging.
2Measurement precision
If DC motor torque varies with temperature and age, then media tension consistency deteriorates, but rotation velocity measurement remains accurate
Solution Approach 1:
The system compensates for changes in motor characteristics (torque variations due to temperature and age) by dynamically adjusting the drive current parameters. The correction calculation modifies the supply current based on the relationship between measured rotation velocity and reference rotation velocity, effectively compensating for motor degradation and environmental factors to maintain consistent media tension.
3Manufacturing precision
If correction is made based on rotation velocity measured under tension, then roll diameter compensation is improved, but motor control accuracy deteriorates
Solution Approach 1:
The invention extracts the media tension effect from the rotation velocity measurement process by performing measurements under tension-free conditions. This separates the motor's intrinsic velocity characteristics from the external tension influence, allowing accurate motor characterization that can then be applied during tensioned printing operations without the confounding tension effect.
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 effectively prevents image quality deterioration by accurately correcting the supply current to the DC motor, ensuring consistent media tension and improved printing performance.
Implementation Method 1
DC motor that rotates at least one of the supply spool and the wind-up spool
Implementation Method 2
rotation amount detector that detects a rotation amount of the DC motor
Data Source
AI summary
The printing apparatus includes a ribbon laid between spools, and DC motors for rotating these spools. A CPU drives the motor without tension, calculates the rotation velocity of the motor based on the rotation amount of the motor, applies the calculated rotation velocity and supplies current in driving the motor, by calculating a drive current for providing the DC motor with a same rotation velocity as a rotation velocity of a reference DC motor based on a difference between a rotation speed of the DC motor in driving the DC motor at a predetermined supply current in a state in which the ribbon is broken, or the ribbon is separated from the supply spool, and a rotational speed of the reference DC motor in driving the reference DC motor at the predetermined supply current, and controls the motor driver to supply the calculated drive current.