Image Transfer Conveyance Control for Thick Paper Contact
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Solution Overview
Problem
Existing image forming apparatuses face issues such as image defects due to gaps forming between sheets and intermediate transfer belts, leading to discharge and toner image rubbing, and require complex configurations that increase size and cost.
Innovation Solution
The apparatus includes a control unit that performs specific conveyance operations involving first, second, and third conveyance processes, using a reverse conveyance unit and dual conveyance paths to ensure sheets are properly aligned with the intermediate transfer belt, and employs a pressure roller with a foamed silicone rubber elastic layer to manage heat and curl the sheets for optimal contact.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a sheet guide member with pressing spring is provided to press the sheet against the intermediate transfer belt, then image defects due to discharge are suppressed, but the apparatus size and cost increase due to complicated configuration
Solution Approach 1:
The invention changes the conveyance speed parameter of the standby conveyance roller pair, setting it higher than the conveyance speed at the transfer nip. This speed difference creates sheet bending that naturally presses the sheet against the intermediate transfer belt, eliminating the need for additional pressing mechanisms while maintaining image quality
Solution Approach 2:
The invention extracts the pressing function from a separate mechanical component (sheet guide member with spring) and integrates it into the conveyance speed control of the standby conveyance roller pair. By controlling the speed difference between rollers, the pressing action is achieved through motion control rather than mechanical force application
2Reliability
If the sheet conveyance speed of standby conveyance roller pair is set higher than at transfer nip to bend the sheet, then the sheet contacts the intermediate transfer belt properly, but the intermediate transfer belt and sheet slide against each other causing toner image rubbing
Solution Approach 1:
The invention dynamically adjusts the conveyance speed of different roller pairs at different stages. The standby conveyance roller pair operates at a higher speed to create bending and contact, while the transfer nip area maintains coordinated speeds to prevent sliding. This dynamic speed variation resolves the contradiction between achieving contact and preventing image damage
Solution Approach 2:
The standby conveyance roller pair performs preliminary sheet bending and positioning at a higher speed before the sheet reaches the transfer nip. This preliminary action ensures the sheet is properly aligned and contacted with the intermediate transfer belt, preparing it for the subsequent transfer operation without causing rubbing
3Object-affected harmful factors
If a large sheet guide member is provided to change pressing force, then discharge is suppressed, but the apparatus size increases
Solution Approach 1:
The invention replaces the mechanical pressing system (large sheet guide member with spring mechanism) with a motion-based control system. By adjusting the conveyance speed of the standby roller pair, the sheet is naturally pressed against the intermediate transfer belt through centrifugal force and bending, eliminating the need for large mechanical pressing components
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 effectively suppresses image defects, particularly with thick papers, by ensuring consistent contact with the intermediate transfer belt, reducing discharge-related issues, and maintaining image quality without increasing apparatus size or cost.
Implementation Method 1
a fixing unit including a heating unit, and a pressure roller including an elastic layer including a foam and configured to form a fixing nip portion together with the heating unit
Data Source
AI summary
An image forming apparatus includes an image forming unit including an image bearing member, an intermediate transfer member, and a transfer roller, a conveyance rotary member pair, a fixing unit, a first conveyance path, a second conveyance path, a reverse conveyance unit, and a control unit. The control unit is configured to perform a conveyance operation of conveying the sheet, the conveyance operation including (i) a first conveyance processing of conveying the sheet toward the reverse conveyance, (ii) a second conveyance processing of conveying the sheet toward the second conveyance path by the reverse conveyance unit, and (iii) a third conveyance processing of transferring the toner image to the sheet at the transfer nip portion. A surface, of the sheet, that faces the pressure roller in the first conveyance processing is configured to face the intermediate transfer member in the third conveyance processing.