Image Forming Apparatus Curl Correction via Variable Conveyance Speed
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Solution Overview
Problem
Existing image forming apparatuses, such as laser beam printers, face challenges in correcting curl in sheets of paper during double-sided printing mode, as the curvature of curls on the first and second surfaces differ, requiring a different approach than single-sided printing.
Innovation Solution
The apparatus employs a control system to adjust conveyance speeds, setting the downstream conveyance speed higher than the upstream speed for the first surface and reducing the speed difference between upstream and downstream conveyance speeds for the second surface to effectively correct curls, matching the curvature of each surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the sheet of paper is pressed against the guide member with the same pressing force in both first surface and second surface printing, then the curl correction mechanism remains simple, but the curl of the sheet of paper cannot be appropriately corrected in double-sided printing mode
Solution Approach 1:
The patent applies dynamics by making the conveyance speeds of the first and second conveyance rollers variable rather than fixed. The control unit dynamically adjusts the rotational speeds based on the printing side (first or second surface) to achieve appropriate pressing forces against the guide member. This resolves the contradiction by enabling effective curl correction for both surfaces while using a single guide member structure, avoiding the need for complex mechanical adjustments.
Solution Approach 2:
The patent changes the parameter of conveyance speed to resolve the curl correction problem. By setting different conveyance speeds for the first and second conveyance rollers, the system creates different pressing forces against the guide member. Specifically, when printing the first surface, the second conveyance roller rotates faster to press the paper against the guide member, while when printing the second surface, the speed difference is reduced to match the gentler curvature. This parameter change enables effective curl correction without increasing device complexity.
2Manufacturing precision
If the downstream conveyance speed is set higher than upstream speed for first surface printing, then curl correction is effective for the first surface, but excessive pressing force may be applied to the second surface with gentler curvature
Solution Approach 1:
The patent applies local quality by providing different conveyance speeds for different printing surfaces. The control unit determines which surface is being printed and adjusts the speed difference between the first and second conveyance rollers accordingly. For the first surface with greater curvature, a larger speed difference creates stronger pressing force. For the second surface with gentler curvature, a smaller speed difference creates milder pressing force. This localized adaptation of pressing force resolves the contradiction between effective curl correction and avoiding excessive force.
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 method allows for appropriate curl correction in double-sided printing by adjusting the conveyance speed differences, ensuring proper alignment and minimizing excessive curl correction on the second surface, which has a gentler curvature.
Implementation Method 1
the sheet of paper is heated and pressed by the fixing part and a curl thereby appears in the sheet of paper
Implementation Method 2
a first conveyance roller is provided on the downstream side of the fixing part and a second conveyance roller is provided on the further downstream side
Implementation Method 3
The sheet of paper is conveyed while being pressed against the guide member which is curved in a direction opposite to a direction of a curl of the sheet of paper
Data Source
AI summary
An image forming apparatus comprises a fixing part for fixing a toner image on a transfer material to the transfer material, a conveying part provided on the downstream side of the fixing part, a correcting member provided in a conveyance path leading from the fixing part to the conveying part, for correcting a curl of the transfer material, and a control part for controlling an upstream-side conveyance speed which is a conveyance speed at which the fixing part provided on the upstream side of the correcting member conveys the transfer material and a downstream-side conveyance speed which is a conveyance speed at which the conveying part provided on the downstream side of the correcting member conveys the transfer material. In printing of a first surface in a double-sided printing mode, the control part sets the downstream-side conveyance speed to be larger than the upstream-side conveyance speed. In printing of a second surface in the double-sided printing mode, the control part sets the upstream-side conveyance speed and the downstream-side conveyance speed so that a difference between the upstream-side conveyance speed and the downstream-side conveyance speed is smaller than a difference between the upstream-side conveyance speed and the downstream-side conveyance speed in printing of the first surface.