Thermal Printer Sensor Placement for Accurate Energy Correction
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Solution Overview
Problem
Existing thermal printers face challenges in accurately correcting the amount of energy applied to the heating elements due to deviations in temperature detection between the thermal head and the printing medium, leading to potential printing defects such as faint or blurred characters.
Innovation Solution
A printing apparatus is designed with a first temperature sensor placed near the thermal head and a second temperature sensor on the opposite side of the conveyance path, allowing the processor to accurately correct the energy application based on both temperatures, minimizing heat interference and improving temperature accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a single ambient temperature sensor is provided near the thermal head, then the temperature detection is convenient, but the detection accuracy deteriorates due to heat interference from the thermal head
Solution Approach 1:
The single temperature sensor is divided into two separate temperature sensors positioned at different locations. The first temperature sensor is placed near the thermal head to detect thermal head temperature, while the second temperature sensor is placed away from the thermal head to detect ambient temperature. This segmentation allows independent measurement of different temperature zones, resolving the contradiction between detection convenience and accuracy.
Solution Approach 2:
The processor acts as an intermediary that receives temperature data from both sensors and calculates the corrected applying energy. By using the temperature difference between the two sensors as an intermediate parameter, the system can compensate for heat interference effects and determine accurate energy correction without requiring a single perfect sensor location.
2Device complexity
If the ambient temperature sensor is placed close to the thermal head, then the device structure is simplified, but the temperature measurement accuracy deteriorates due to substantial heat effect from the thermal head
Solution Approach 1:
Instead of using one sensor close to the thermal head, the system segments the measurement function into two sensors at different locations. This segmentation increases device complexity slightly but dramatically improves measurement accuracy by separating the measurement points from each other's thermal interference zones.
Solution Approach 2:
Different regions of the device are assigned different measurement qualities. The first sensor region near the thermal head is optimized for detecting thermal head temperature, while the second sensor region away from the thermal head is optimized for detecting ambient temperature. This local quality differentiation allows each sensor to perform its specific measurement function with high accuracy.
3Reliability
If the amount of applying energy is increased to prevent faint printing, then printing quality improves, but character blurring occurs due to excessive heat
Solution Approach 1:
The system implements feedback control by continuously monitoring temperatures from both sensors and using this information to dynamically adjust the applying energy. The processor calculates the temperature difference and uses it as feedback to determine the precise energy correction needed, preventing both faint printing and character blurring by maintaining optimal energy levels based on real-time thermal conditions.
Solution Approach 2:
The system changes the parameter of applying energy based on detected temperature conditions. By adjusting the energy parameter according to the temperature difference between the thermal head and ambient environment, the system optimizes printing quality and prevents harmful effects like blurring while ensuring sufficient ink transfer for clear characters.
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 configuration enables high-accuracy correction of energy application, reducing printing defects by effectively accounting for the temperature changes of both the thermal head and the printing medium, resulting in clearer and more consistent prints.
Implementation Method 1
an energy is applied to a heating element of a thermal head, and printing is carried out by imparting heat to a printing medium by the heating element that has generated heat
Implementation Method 2
since the first temperature sensor is provided in the first space on the side of the thermal head with respect to the conveyance path, an effect of heat from the thermal head on the first temperature sensor becomes large
Implementation Method 3
since the second temperature sensor is provided in the second space on a side opposite to the thermal head with respect to the conveyance path, an effect of heat from the thermal head on the second temperature sensor becomes small
Data Source
AI summary
A printing apparatus includes: a main-body having a space therein; a thermal head arranged on a substrate provided in the space, the thermal head having heating elements arranged along a predetermined arrangement direction; a conveyor which conveys a thermal paper along a conveyance path provided in the space and intersecting with the arrangement direction; a first temperature sensor provided in a first space in the space on a side of the thermal head with respect to the conveyance path; a second temperature sensor provided in a second space in the space on a side opposite to the thermal head with respect to the conveyance path; and a processor configured to: correct an amount of applying energy to be applied to the heating elements, based on first and second temperatures detected by the first and second temperature sensors; and apply corrected amount of the applying energy selectively to the heating elements.