Discharging Roller Deceleration for Uniform Paper Stacking
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Solution Overview
Problem
High-speed image forming apparatuses often result in non-uniform stacking of documents in the discharge tray due to varying curling of trailing edges caused by single-sided or double-sided printing, leading to inconsistent discharging speeds.
Innovation Solution
A discharging roller decelerating unit that adjusts the deceleration timing of discharging rollers based on the type of printing (single-sided or double-sided) by setting a predetermined delay time, sensed by a sensor unit, to ensure uniform stacking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the operating speed of the image forming apparatus is increased to improve productivity, then documents are discharged at a faster rate, but documents become non-uniformly stacked in the discharge tray
Solution Approach 1:
The patent applies dynamics by making the discharging roller speed variable rather than constant. The roller operates at high speed during most of the document discharge process to maintain productivity, then automatically decelerates to a lower speed just before the trailing edge reaches the discharge tray. This dynamic speed adjustment allows the system to achieve both fast discharge and uniform stacking, resolving the contradiction between productivity and stacking precision.
2Manufacturing precision
If the rotation speed of discharging rollers is reduced just before document discharge to improve stacking uniformity, then documents stack uniformly, but the decelerating moment varies when trailing edges curl differently
Solution Approach 1:
The patent implements feedback control by using a sensor to detect the actual position of the document trailing edge and comparing it with the expected position. Based on this feedback, the control unit adjusts the deceleration timing and magnitude dynamically. When trailing edges curl differently, the sensor detects the variation and the control system compensates by modifying the deceleration command, ensuring consistent stacking uniformity regardless of curling variations.
Solution Approach 2:
The system performs preliminary action by predicting when the trailing edge will reach the discharge tray based on document length and discharge speed, then initiates deceleration in advance. The control unit calculates the optimal deceleration start point and applies braking force before the trailing edge actually reaches the discharge position. This preliminary deceleration ensures that documents are slowed down at the right moment for uniform stacking, while the feedback mechanism adjusts this preliminary action based on actual trailing edge position.
Data Source
AI summary
An image forming apparatus includes a discharging roller decelerating unit and a method of decelerating discharging rollers. The image forming apparatus includes a print unit, discharging rollers, a sensor unit that sensing a trailing edge of paper, and the discharging roller decelerating unit. The method includes detecting a trailing edge of paper using a sensor unit and decelerating the discharging rollers after a predetermined period of delay time subsequent to the sensing of the trailing edge of the paper. Accordingly, even when there is a difference between the sensing moments of the trailing edge of the paper, the decelerating moments of the discharging rollers are stabilized, and thus the paper can be uniformly stacked regardless of double-sided printing or single-sided printing, even when the paper is discharged at a high speed.