Image Forming Apparatus Registration Roller Nip Pressure Control
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Solution Overview
Problem
Image defects occur due to slack in sheets between the transfer nip and the registration roller pair in image forming apparatuses, particularly when the conveyance speed is increased or when forming long sheets, leading to issues like shock noise and increased conveyance amount differences.
Innovation Solution
An image forming apparatus with a hardware processor that controls the conveyance roller pair to maintain a predetermined nip pressure and reduce it according to the conveyance amount, causing slack in the sheet between the transfer nip and the conveyance nip to prevent image defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the conveyance speed at the registration roller pair is increased to a speed higher than a desired conveyance speed due to a difference in roller diameter and/or to abrasion of the roller, then the conveyance amount of the sheet at the registration roller pair is increased, but the slack amount of the sheet in the registration transfer area is undesirably increased, causing image defects
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the nip pressure of the registration roller pair based on the conveyance amount of the sheet. When the conveyance amount exceeds a predetermined value, the nip pressure is reduced to decrease the conveyance amount, thereby maintaining appropriate slack in the registration transfer area and preventing image defects. This dynamic parameter adjustment resolves the contradiction between maintaining high conveyance speed and preventing excessive slack.
2Productivity
If the conveyance speed at the registration roller pair is increased, then the productivity is improved, but the returning amount of the sheet might be increased, causing shock noise and image defects in the transfer nip
Solution Approach 1:
The patent implements feedback control by monitoring the conveyance amount of the sheet at the registration roller pair and adjusting the nip pressure accordingly. When the conveyance amount exceeds a predetermined threshold, the system reduces the nip pressure to decrease the conveyance amount, preventing excessive returning of the sheet and the associated shock noise and image defects. This feedback mechanism allows the system to maintain high productivity while preventing harmful effects.
3Adaptability or versatility
If an image is formed on a long sheet having a sheet length greater than that of an A3 sheet, then the versatility is improved, but the difference in sheet conveyance amount between the secondary transfer nip and registration roller pair is increased, significantly causing image defects
Solution Approach 1:
The patent applies dynamics by making the nip pressure of the registration roller pair variable rather than fixed. The system dynamically adjusts the nip pressure based on the conveyance amount, which varies with sheet length. For long sheets, the nip pressure is reduced to decrease the conveyance amount at the registration roller pair, thereby reducing the difference in conveyance amount between the secondary transfer nip and registration roller pair and preventing image defects. This dynamic adjustment enables the system to maintain image quality across different sheet lengths.
Data Source
AI summary
An image forming apparatus includes: a transferer that forms a transfer nip for transferring an image to a sheet; a conveyance roller pair disposed on an upstream side relative to the transfer nip in a conveyance direction of the sheet; and a hardware processor that controls the conveyance roller pair such that the sheet conveyed to a conveyance nip formed by the conveyance roller pair is conveyed with a predetermined nip pressure so as to cause slack in the sheet between the transfer nip and the conveyance nip in which the hardware processor controls the conveyance roller pair so as to reduce the nip pressure at the conveyance nip in accordance with an increase in a conveyance amount of the sheet at the conveyance nip.