Variable Sheet Conveyance Speed Control for Duplex Image Formation
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Solution Overview
Problem
Conventional image forming apparatuses face issues in forming images on both surfaces of a sheet due to variations in sheet conveying speeds between the transfer and fixing devices, leading to image deterioration, instability, and defective prints, especially when dealing with moisture-absorbent sheets in high-temperature and high-humidity environments.
Innovation Solution
An image forming apparatus with speed controlling means that adjusts the sheet conveying speed between the transfer and fixing devices based on the loop formed by the difference in conveying speeds, using a loop detecting sensor to maintain a predetermined loop amount, and calculates the average sheet conveying speed for the second surface based on the first surface's speed control to ensure stable image formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the sheet conveying speed of the fixing device is set higher than the transfer device, then the fixing device can process sheets faster, but the sheet bearing an unfixed toner image is pulled toward the fixing device side causing image deterioration
Solution Approach 1:
The fixing device dynamically adjusts its sheet conveying speed based on the detected loop amount. The speed control unit varies the conveying speed within a predetermined range to maintain the loop amount within acceptable limits, allowing the fixing device to operate at higher speeds while preventing sheet pulling and image deterioration.
Solution Approach 2:
A loop detection sensor continuously monitors the loop amount formed between the transfer and fixing devices. This feedback information is used by the speed control unit to adjust the fixing device's conveying speed in real-time, creating a closed-loop control system that maintains image quality while optimizing productivity.
2Productivity
If the sheet conveying speed of the transfer device is set extremely higher than the fixing device, then the transfer device can process sheets faster, but a loop more than necessary is formed causing unstable sheet separation and scattering
Solution Approach 1:
The fixing device dynamically adjusts its sheet conveying speed to match the transfer device's speed while maintaining an appropriate loop amount. This dynamic speed adjustment prevents excessive loop formation and ensures stable sheet separation and conveyance, allowing the transfer device to operate at high speeds without compromising stability.
Solution Approach 2:
The loop detection sensor provides continuous feedback on the loop amount, enabling the speed control unit to adjust the fixing device's conveying speed to prevent excessive loop formation. This feedback mechanism ensures stable sheet separation and prevents scattering while maintaining high productivity.
3Reliability
If a loop is formed in the sheet between transfer device and fixing device to prevent pulling, then sheet pulling is prevented, but the separating direction and angle of incidence become unstable causing scattering and offset
Solution Approach 1:
The system dynamically controls the loop amount within a predetermined range by adjusting the fixing device's conveying speed. This dynamic control prevents sheet pulling while maintaining stable sheet separation direction and angle of incidence, eliminating the scattering and offset problems associated with excessive or uncontrolled loops.
Solution Approach 2:
The speed control unit changes the conveying speed parameter of the fixing device to maintain the loop amount within an optimal range. By controlling this parameter, the system prevents sheet pulling while ensuring stable sheet convection, separating direction, and angle of incidence.
4Manufacturing precision
If the circumferential speed of the fixing device roller is changed during sheet conveyance to control loop amount, then loop control is achieved, but the system complexity increases with speed control means
Solution Approach 1:
The system uses a loop detection sensor to monitor the loop amount and provides feedback to the speed control unit. This feedback mechanism enables precise loop control through speed adjustment without requiring complex mechanical structures, achieving manufacturing precision through intelligent control.
Solution Approach 2:
The patent replaces complex mechanical speed control mechanisms with an electronic control system that adjusts the fixing device's conveying speed based on sensor feedback. This substitution reduces mechanical complexity while achieving precise loop amount control through electronic speed regulation.
Data Source
AI summary
In a construction for forming images on the both surfaces of a sheet, a speed controlling device for effecting the conveyance control of the sheet between a transfer device and a fixing device controls, when the image is to be formed on a first surface, the sheet conveying speed between the transfer device and the fixing device on the basis of loop detection by a loop detecting sensor provided between the transfer device and the fixing device so that a loop formed in the sheet may be maintained within a predetermined range. Also, when the image is to be formed on a second surface, the speed controlling device controls the sheet conveying speed between the transfer device and the fixing device on the basis of the average sheet conveying speed between the transfer device and the fixing device when the image has been formed on the first surface.