Sheet Conveyance Speed Control for Skew Correction
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Solution Overview
Problem
Existing sheet conveyance apparatuses in image forming devices face instability in sheet conveyance due to excessive or insufficient warping reduction, leading to potential buckling or disorder in conveyance speed and position, when using techniques like temporarily stopping or decelerating the sheet conveyance roller for skew correction.
Innovation Solution
A control unit determines specific speeds for each sheet based on detection timing, executing a conveyance operation where the leading edge is abutted against a registration roller in a stopped state, and then the registration roller is driven at a target speed while the pre-registration roller continues to operate, with speed changes to prevent excessive warping, ensuring stable conveyance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If the sheet conveyance roller is temporarily stopped or decelerated to reduce warping for skew correction, then the warping amount is reduced, but the stability of sheet conveyance is deteriorated
Solution Approach 1:
The patent applies dynamics by making the conveyance roller's speed variable rather than fixed. The control unit dynamically adjusts the rotational speed of the conveyance roller during sheet conveyance, transitioning from a stopped state to a rotating state at optimized timing. This dynamic speed adjustment allows the system to reduce warping while maintaining conveyance stability, resolving the contradiction between shape control and conveyance stability.
Solution Approach 2:
The patent applies preliminary action by pre-calculating and optimizing the timing for starting the conveyance roller's rotation before the sheet actually reaches the registration roller. The control unit determines the optimal start timing based on sheet detection timing and conveyance distance, allowing the roller to begin rotating at the precise moment needed to maintain stability while achieving proper warping reduction. This preliminary timing optimization prevents both excessive warping and conveyance instability.
2Manufacturing precision
If the sheet conveyance roller is stopped to abut the leading edge of the sheet, then skew correction is achieved, but the conveyance speed fluctuates causing instability
Solution Approach 1:
The patent applies feedback by using the sheet detection unit's timing information to control the conveyance roller's rotation start timing. The control unit receives feedback about when the sheet is detected upstream and uses this information to calculate the optimal moment to start rotating the conveyance roller. This closed-loop feedback control ensures that the roller begins rotating at the precise timing needed to maintain stable conveyance speed while achieving accurate skew correction through controlled warping.
3Manufacturing precision
If the warping reduction amount is excessive, then skew correction is improved, but the sheet is tensioned causing conveyance disorder
Solution Approach 1:
The patent applies parameter changes by optimizing the rotational speed parameter of the conveyance roller during different phases of sheet conveyance. The control unit adjusts the roller's rotational speed from zero (stopped) to a specific rotational speed at the optimized start timing, creating controlled warping that achieves skew correction without excessive tension. This parameter optimization ensures the warping amount remains within the range needed for skew correction while preventing sheet tension and conveyance position disorder.
Data Source
AI summary
In a conveyance operation, a leading edge of a sheet in a sheet conveyance direction is abutted against a second conveyance member in a stopped state while a first drive source is driving a first conveyance member at the first speed, and then a second drive source starts to drive the second conveyance member with a target of a second speed while the first drive source is continuously driving the first conveyance member. A speed change processing is executed during the conveyance operation, such that the first drive source changes the first conveyance member from the first speed to a third speed that is smaller than the second speed before the second conveyance member reaches the second speed, and then changes the first conveyance member from the third speed to the second speed.