Fuser Upper Frame Rib Configuration for Duplex Print Stain Prevention
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Solution Overview
Problem
During duplex printing, water droplets adhering to the ribs of the fuser in an image forming apparatus can be wiped off by the sheet and transferred back to the photosensitive drum, leading to a decrease in the surface potential of the drum and potential toner adhesion to unexposed areas, resulting in stains on the sheet.
Innovation Solution
The image forming apparatus incorporates an upper frame with specific rib configurations, including an upper first rib with a guide surface and a separation surface, and an upper second rib with a guide surface, designed to guide the sheet and reduce moisture adherence, thereby minimizing the transfer of water droplets to the photosensitive drum.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the sheet is conveyed through the fuser to fix the toner image, then the toner image is fixed onto the sheet, but water droplets adhere to the ribs of the frame due to water vapor generated from the heated sheet
Solution Approach 1:
The harmful function of water droplet adhesion is extracted from the rib structure by adding a hydrophobic coating layer. This coating selectively removes the harmful property (water attraction) while preserving the rib's original functions of structural support and sheet guidance.
Solution Approach 2:
A hydrophobic coating layer is introduced as an intermediary substance between the rib surface and water vapor. This intermediate layer prevents direct interaction between water droplets and the rib, causing water to bead up and fall off rather than adhere to the rib structure.
2Productivity
If the sheet wipes off water droplets adhered to the ribs during duplex printing, then the sheet can be reused for the other side printing, but the water droplets may transfer to the photosensitive drum and cause stains
Solution Approach 1:
The hydrophobic coating acts as an intermediary that prevents water droplets from adhering to the rib in the first place. By making the rib surface water-repellent, the coating eliminates the source of water droplets that would otherwise be transferred to the photosensitive drum during duplex printing operations.
Solution Approach 2:
The water vapor that originally caused harm by condensing into stains is converted into a beneficial effect. The hydrophobic coating causes water vapor to condense into discrete droplets that bead up and fall off the rib surface, preventing both rib adhesion and subsequent transfer to the photosensitive drum.
3Ease of operation
If water droplets adhere to the photosensitive drum, then the drum can convey the sheet, but the surface potential of the photosensitive drum decreases causing toner adhesion to unexposed areas
Solution Approach 1:
The harmful effect of water droplet adhesion to the photosensitive drum is extracted by preventing water droplet formation on the rib. The hydrophobic coating removes the intermediate step of water accumulation on the rib, eliminating the source that would otherwise transfer to the drum and affect surface potential.
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
The rib configurations effectively reduce the amount of moisture adhering to the sheet, thereby suppressing the occurrence of stains on the sheet and maintaining the surface potential of the photosensitive drum.
Implementation Method 1
a heating rotating member... When the toner image transferred to the sheet is thermally fixed with the fuser, water vapor is generated from the heated sheet
Implementation Method 2
The upper first rib includes a first guide surface configured to guide an upper surface of the conveyed sheet... The upper second rib includes a second guide surface configured to guide the upper surface of the conveyed sheet
Data Source
AI summary
An image forming apparatus includes a photosensitive drum and a fuser. The fuser includes an upper frame. The upper frame includes an upper first rib downstream of a heating rotating member in a sheet conveying direction, an upper second rib adjacent to the upper first rib in a width direction perpendicular to the sheet conveying direction, and first and second conveying rollers. The upper first rib includes a first guide surface, and a separation surface. The upper second rib includes a second guide surface. The second guide surface is located downstream of the first guide surface in the sheet conveying direction. A distance between a nip point between the first and second conveying rollers and the second guide surface in a direction perpendicular to the sheet conveying direction and the width direction is smaller than a distance between the nip point and the separation surface.