Fixing Roller Speed Control for Sheet Loop Detection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional image forming apparatuses face issues with sheet conveying speed control, leading to loop formation between the secondary transfer unit and the fixing unit, which can result in image defects and quality deterioration due to temperature fluctuations and curling of sheets, especially in high-humidity environments, causing reverse loops that are not accurately detected and leading to increased loop sizes and defective images.
Innovation Solution
An image forming apparatus with a loop detecting unit and a control unit that adjusts the sheet conveying speed of the fixing roller pair based on loop detection, reducing the loop size when a reverse loop is presumed, thereby preventing image defects and maintaining loop stability without increasing apparatus size or costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the sheet conveying speed of the fixing roller pair is set slightly lower than that of the secondary transfer unit to prevent transfer noises, then transfer noises are prevented, but a loop is formed in the conveying path between the secondary transfer unit and the fixing roller pair
Solution Approach 1:
The patent applies dynamics by making the fixing roller pair's rotational speed variable rather than fixed. The control unit dynamically adjusts the rotational speed based on real-time loop detection feedback, allowing the system to transition between different speed states (lower than secondary transfer unit when loop is appropriate size, higher than secondary transfer unit when loop becomes too large) to resolve the contradiction between preventing transfer noises and controlling loop size.
Solution Approach 2:
The patent implements feedback control through the loop detecting unit that continuously monitors the loop size in the conveying path. The detection result is fed back to the control unit, which then adjusts the fixing roller pair's rotational speed accordingly. This closed-loop feedback mechanism enables the system to automatically maintain the loop within an appropriate size range while preventing transfer noises.
2Temperature
If the heater capacitance is increased to maintain surface temperature of the fixing roller, then temperature stability is improved, but the apparatus complexity and cost increase
Solution Approach 1:
The patent applies self-service by enabling the fixing roller pair to self-regulate its rotational speed based on loop detection feedback, rather than requiring complex external control systems or oversized heaters. The system uses the existing loop detection capability and control unit to automatically adjust operating parameters, making the system self-correcting and reducing the need for additional temperature control capacity.
Solution Approach 2:
The patent changes the operational parameter (rotational speed) of the fixing roller pair dynamically based on loop size detection. Instead of increasing heater capacitance to maintain temperature stability, the system maintains a standard heater configuration and compensates for temperature variations by adjusting the rotational speed to control loop size, thereby preventing the conditions that would require larger heater capacity.
3Measurement precision
If a flag and sensor are used to detect loop formation, then loop detection is enabled, but the detection may not accurately distinguish between normal loops and reverse loops in high-humidity environments causing defective images
Solution Approach 1:
The patent applies dynamics by making the fixing roller pair's rotational speed variable rather than fixed. The control unit dynamically adjusts the rotational speed based on real-time loop detection feedback, allowing the system to transition between different speed states (lower than secondary transfer unit when loop is appropriate size, higher than secondary transfer unit when loop becomes too large) to resolve the contradiction between preventing transfer noises and controlling loop size.
Solution Approach 2:
The patent implements feedback control through the loop detecting unit that continuously monitors the loop size in the conveying path. The detection result is fed back to the control unit, which then adjusts the fixing roller pair's rotational speed accordingly. This closed-loop feedback mechanism enables the system to automatically maintain the loop within an appropriate size range while preventing transfer noises.
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
The solution effectively conveys curled sheets without causing defective images, maintains loop stability, and reduces the risk of image rubbing, while avoiding the need for large attracting forces or complex apparatus layouts, thus ensuring consistent image quality and cost-effectiveness.
Implementation Method 1
a heater 153 is provided in the fixing roller 152. Temperature control is made by the heater 153 so that a surface temperature of the fixing roller 152 is equal to a predetermined fixing temperature.
Implementation Method 2
Toner of respective colors is heated and pressed by the fixing roller pair 150, so that the toner is fused, color-mixed, and fixed as a full-color image onto the sheet P.
Data Source
AI summary
A sheet which entered between a first sheet conveying unit and a second sheet conveying unit is detected by a sheet detecting unit. A loop of the sheet formed with a difference of sheet conveying speeds between the first and second sheet conveying units is detected by a loop detecting sensor. After the sheet detecting unit detected the sheet, if the loop detecting sensor does not detect the loop, a control unit which controls the sheet conveying speed of at least one of the first and second sheet conveying units controls the sheet conveying speed of at least one of the first and second sheet conveying units, thereby reducing an amount of the formed loop.