Duplex Printing Dew Condensation Prevention
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Solution Overview
Problem
In image forming apparatuses, dew condensation on guide members and switchback rollers during duplex printing leads to poor image quality due to water vapor condensation, especially when the apparatus is not sufficiently heated, causing blurring, wrinkles, or roughness in printed sheets.
Innovation Solution
An image forming apparatus with a temperature sensing unit that controls the sheet feed operation timing based on the temperature of the re-transport roller, delaying the start of duplex image formation after one-side image formation to prevent dew condensation, by retarding the sheet feed operation when the temperature is lower.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the apparatus operates in a cold state to perform duplex printing, then productivity is improved by avoiding warm-up time, but image quality deteriorates due to dew condensation on guide members and switchback rollers
Solution Approach 1:
The patent applies preliminary action by detecting the temperature of the re-transport roller before duplex printing and proactively controlling the sheet feed timing. When the temperature is below the dew point, the system retards the sheet feed operation to allow the roller to warm up first, preventing dew condensation before it occurs. This resolves the contradiction by preparing the system in advance rather than reacting after condensation occurs.
2Manufacturing precision
If the sheet feed operation is delayed to prevent dew condensation, then image quality is improved, but productivity deteriorates due to increased waiting time
Solution Approach 1:
The patent applies dynamics by making the sheet feed timing adaptive rather than fixed. The control unit dynamically adjusts the sheet feed operation based on real-time temperature detection of the re-transport roller. When the temperature is sufficient, printing proceeds without delay; when the temperature is below the dew point, the timing is retarded. This dynamic adjustment optimizes both image quality and productivity by avoiding unnecessary delays.
Solution Approach 2:
The patent applies feedback by using a temperature detection unit to continuously monitor the re-transport roller temperature and feeding this information back to the control unit. The control unit then adjusts the sheet feed timing based on this feedback. This closed-loop control ensures that delays are applied only when necessary (when temperature < dew point) and not when the system is already warm, thereby maintaining high productivity while preventing dew condensation.
3Object-affected harmful factors
If the air-tightness of the fixing unit is increased to absorb water vapor, then dew condensation is reduced, but device complexity increases
Solution Approach 1:
The patent applies the taking out principle by removing the water vapor absorption function from the fixing unit and relocating it to the re-transport roller. Instead of modifying the fixing unit to be air-tight and absorb water vapor, the system extracts the condensation prevention function and implements it at the re-transport roller through temperature-based sheet feed control. This simplifies the fixing unit structure while effectively preventing dew condensation.
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 a reduction in image quality due to dew condensation by ensuring the apparatus is sufficiently heated before initiating duplex printing, thereby maintaining image quality and preventing issues like blurring or wrinkles.
Implementation Method 1
a temperature sensing unit which senses a temperature of the re-transport roller
Implementation Method 2
as the temperature of the re-transport roller sensed by the temperature sensing unit is lower, the control unit retards a timing to cause the sheet feed unit to start the sheet feed operation
Implementation Method 3
when the main body of the image forming apparatus is set in a relatively low temperature state, the water vapor may condense within a sheet-transport path. If dew condensation occurs, when the sheet passes through the sheet-transport path, water droplets adhere to the sheet
Data Source
AI summary
An image forming apparatus includes a sheet feed unit which feeds a sheet to an image forming unit forming an image on the sheet, a re-transport roller which reverses the sheet with a toner image fixed on the sheet and re-transports the sheet to the image forming unit, and a control unit which controls a sheet feed operation of the sheet feed unit for feeding the sheet. As the temperature of the re-transport roller sensed by the temperature sensing unit is decreased, the control unit retards the timing at which the sheet feed unit starts the sheet feed operation when a duplex image formation in which the image is formed on both sides of the sheet is performed after a one-side image formation is completed.