Registration Roller Speed Control for Color Misalignment
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Solution Overview
Problem
Image distortion and color misalignment in electrophotographic image forming apparatuses occur due to fluctuations in sheet conveyance speed, particularly at the secondary transfer portion, affecting the transfer of toner images onto sheets.
Innovation Solution
The image forming apparatus employs a controller to adjust the conveyance speed of the registration roller pair, changing from a first speed before the trailing edge of the sheet passes through an upstream conveyance unit to a second, faster speed after the trailing edge has passed, thereby reducing the fluctuation of force acting on the secondary transfer portion and minimizing color misalignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the conveyance speed of the registration roller pair is increased after the trailing edge of the sheet passes through the upstream conveyance unit, then the fluctuation of force acting on the secondary transfer portion is reduced and color misalignment is minimized, but the sheet conveyance speed fluctuation occurs during the transfer process
Solution Approach 1:
The conveyance speed of the registration roller pair is dynamically adjusted based on the position of the sheet. The controller increases the conveyance speed after the trailing edge passes through the upstream conveyance unit, transforming the static speed control into a dynamic response that adapts to the sheet's position and the resulting force fluctuations on the secondary transfer portion.
Solution Approach 2:
The controller anticipates the force fluctuation that occurs when the trailing edge passes through the upstream conveyance unit and applies a counteracting action by increasing the conveyance speed in advance. This preliminary anti-action compensates for the expected disturbance before it fully impacts the secondary transfer portion, thereby reducing color misalignment.
2Manufacturing precision
If the conveyance speed is varied to compensate for sheet distortion, then the image transfer accuracy is improved, but the complexity of the control system increases
Solution Approach 1:
The control system uses feedback from sheet position detection to adjust the conveyance speed of the registration roller pair. By monitoring when the trailing edge passes through the upstream conveyance unit and responding with speed adjustment, the system achieves improved image transfer accuracy through a feedback-based control mechanism.
Data Source
AI summary
An image forming apparatus includes an image bearing member, a transfer member, a conveyance unit arranged upstream of a transfer portion in a sheet conveyance direction, an upstream conveyance unit arranged upstream of the conveyance unit, a drive unit configured to drive the conveyance unit; and a controller to control the drive unit to change a conveyance speed of the conveyance unit. In a case where a trailing edge of the sheet passes through the upstream conveyance unit after a leading edge of the sheet in the sheet conveyance direction has entered the transfer portion, the conveyance unit conveys the sheet by a first speed before the trailing edge of the sheet passes through the upstream conveyance unit, and by a second speed that is faster than the first speed after the trailing edge of the sheet has passed through the upstream conveyance unit.