Fixing Device Cleaning Mode for Toner Offset Prevention
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Solution Overview
Problem
In image forming apparatuses, particularly in fixing devices of electrophotographic printers, the accumulation of paper powder-rich contaminants on the pressing member surface leads to reduced parting properties, causing toner offset and image defects, and can result in the transfer of contaminants onto the recording material, leading to jamming and image quality issues.
Innovation Solution
An image forming apparatus is designed with a cleaning mode that controls the surface temperatures of the fixing and pressing members within specific ranges (Tf2≦Tp≦Tf3) during idling, where Tf2 is the toner deformation end point and Tf3 is the toner flow start point, allowing a cleaning sheet to be conveyed through the fixing nip to effectively remove paper powder-rich contaminants.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the fixing device operates continuously without cleaning, then productivity is maintained, but contaminants accumulate on the pressing member surface causing image defects and jams
Solution Approach 1:
The invention implements periodic cleaning cycles during which the fixing device temporarily stops image formation operations. A cleaning sheet is fed through the fixing device at predetermined intervals to remove accumulated contaminants from the pressing member surface, thereby maintaining image quality consistency while enabling continuous operation over extended periods
Solution Approach 2:
The cleaning sheet is prepared in advance with surface properties designed to effectively remove contaminants. The cleaning operation is performed before contaminants reach critical levels that would cause image defects or jams, preventing problems rather than reacting to them
2Reliability
If the pressing member surface temperature is kept high to prevent contaminant accumulation, then parting property is maintained, but energy consumption increases and toner may be excessively melted
Solution Approach 1:
The pressing member operates at normal temperature during image formation and only increases temperature during periodic cleaning cycles. This approach maintains parting property when needed without incurring continuous energy consumption, while the cleaning sheet removes contaminants that would otherwise require sustained high temperatures to prevent accumulation
Solution Approach 2:
The system dynamically adjusts the pressing member temperature based on operational mode. During cleaning cycles, temperature is increased to facilitate contaminant removal. During normal image formation, temperature is maintained at the minimum required for proper toner fixation, avoiding excessive melting and reducing energy consumption
3Reliability
If a parting layer is applied to the pressing member surface to prevent toner deposition, then toner parting is improved, but paper powder and calcium carbonate still accumulate reducing effectiveness
Solution Approach 1:
The cleaning sheet acts as an intermediary medium between the pressing member surface and the contaminants. During cleaning cycles, the cleaning sheet contacts the pressing member surface and removes accumulated paper powder, calcium carbonate, and toner through friction and adhesion, restoring the effectiveness of the parting layer without requiring replacement or modification of the layer itself
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 effectively prevents the accumulation of paper powder-rich contaminants on the pressing member surface, maintaining parting properties and preventing toner offset, thereby enhancing image quality and reducing the risk of jamming.
Implementation Method 1
a surface temperature Tp of the second rotatable member immediately after passing through the fixing nip is within a temperature range Tf2≦Tp≦Tf3 wherein Tf2 is a deformation end point of the toner and Tf3 is a flow start point of the toner
Implementation Method 2
the unfixed toner image is heated and melted while nip-conveying the recording material carrying the unfixed toner image, thus being heat-fixed on the recording material
Data Source
AI summary
An image forming apparatus is capable of setting a cleaning mode in which a fixing portion is cleaned by a cleaning sheet while nip-conveying the cleaning sheet in a fixing nip. When the cleaning mode is set, an image forming apparatus provides a period in which a first rotatable member and a second rotatable member are rotated in a state in which a heater is controlled so that a surface temperature Th of the first rotatable member immediately after passing through the fixing nip is kept within a temperature range of Th≦Tf3, wherein Tf3 is a flow start point of a toner and so that a surface temperature Tp of the second rotatable member immediately after passing through the fixing nip is within a temperature range Tf2≦Tp≦Tf3, wherein Tf2 is a deformation end point of the toner.