Image Forming Apparatus Loop Control for Sheet Conveyance
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Solution Overview
Problem
Existing image forming apparatuses face issues with sheet conveying velocity discrepancies between the transfer and fixing portions, leading to image deterioration, instability, and defects due to thermal expansion, individual differences, and environmental variations, despite previous solutions that rely on loop detection and velocity control, which often result in unnecessarily large or small loops and sudden velocity changes.
Innovation Solution
An image forming apparatus with a loop detecting portion and a control mechanism that adjusts the fixing conveying velocity between multiple predefined velocity bands based on detected loop states, allowing for continuous adjustment to maintain an optimal loop size and minimize velocity changes, thereby stabilizing sheet conveyance and image quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the fixing conveying velocity is set to be lower than the transfer conveying velocity to prevent sheet pulling, then image deterioration is prevented, but an unnecessarily large loop is formed causing image scattering and offset
Solution Approach 1:
The patent applies dynamics by making the fixing conveying velocity adjustable rather than fixed. The control unit dynamically changes the fixing conveying velocity based on real-time loop amount detection, allowing the system to adapt between preventing sheet pulling and avoiding excessive loop formation by switching between different velocity levels.
Solution Approach 2:
The patent implements feedback by using the loop amount detection unit to continuously monitor the loop size and feed this information back to the control unit. The control unit then adjusts the fixing conveying velocity based on this feedback, creating a closed-loop control system that automatically maintains optimal conditions.
2Manufacturing precision
If the fixing conveying velocity is set to be higher than the transfer conveying velocity to eliminate loop, then image scattering is prevented, but sheet pulling toward the fixing portion occurs causing image deterioration
Solution Approach 1:
The system dynamically adjusts the fixing conveying velocity based on detected loop conditions. When the loop amount is within a safe range, the control unit increases the fixing conveying velocity to prevent image scattering. When the loop becomes excessively large, the control unit decreases the velocity to prevent sheet pulling, thus adapting to different operational conditions.
Solution Approach 2:
The feedback mechanism allows the control unit to monitor loop amount and adjust fixing conveying velocity accordingly. This closed-loop control ensures that the system prevents both image scattering and sheet pulling by continuously adapting to real-time conditions based on detection feedback.
3Productivity
If multiple velocity combinations are provided and switching is performed based on loop elimination time, then velocity optimization is achieved, but sudden velocity changes cause image scattering and stretching
Solution Approach 1:
The patent applies dynamics by implementing gradual velocity adjustment rather than sudden switching. The control unit changes the fixing conveying velocity in a controlled manner based on loop conditions, avoiding abrupt changes that would cause image scattering or stretching while still optimizing conveyance efficiency.
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 solution effectively maintains a stable loop size between the transfer and fixing portions, reducing image defects and ensuring consistent image quality by finely controlling the fixing conveying velocity, even with variations in roller dimensions and surface properties, and thermal changes.
Implementation Method 1
a pressure roller (50) that rotates in the fixing portion (7)
Implementation Method 2
a heating unit (40) that heats the sheet (P)
Implementation Method 3
a loop detecting portion (20) for detecting a state of a loop of the sheet
Data Source
AI summary
Disclosed is an image forming apparatus, including: a transfer portion configured to convey a sheet and to transfer a toner image to the sheet; a fixing portion configured to convey the sheet at a fixing conveying velocity and to fix the toner image; and a control portion configured to control the fixing portion such that the fixing conveying velocity is changed to a first velocity or to a second velocity which is lower than the first velocity, wherein the control portion can set a plurality of velocity bands each of which is a combination of the first velocity and the second velocity, the control portion can perform a changing of the velocity band a several times based on the state of the loop of the sheet while the transfer portion and the fixing portion are conveying the sheet.