Image Forming Apparatus Sheet Speed Control for Switchback Discharge
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Solution Overview
Problem
The existing image forming apparatuses face challenges in matching discharge productivity between straight and switchback discharge modes, leading to excessive motor load and decreased productivity due to the need for accelerating and decelerating sheets during the switchback process, which affects the decurler unit's operation and sheet handling.
Innovation Solution
The apparatus includes a control unit that manages the rotational speeds of conveyance rollers to perform specific conveyance processes, such as accelerating the sheet after image formation, switching directions, and decelerating before the decurler unit, ensuring consistent productivity and reducing motor load by setting distinct speeds for different phases of sheet handling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the sheet is accelerated after inversion in the switchback discharge mode to equalize discharge productivity, then the discharge productivity is improved, but the motor driving the decurler unit is applied with excessive load and falls out of step
Solution Approach 1:
The system dynamically adjusts sheet conveyance speed through multiple phases: initial acceleration to high speed after inversion, then deceleration to a lower speed before the decurler unit, and final acceleration to discharge speed. This dynamic speed control ensures the decurler motor operates within its torque capacity while maintaining overall productivity
Solution Approach 2:
The sheet conveyance is divided into periodic phases with different speed requirements: a first conveyance phase at high speed, a second conveyance phase at reduced speed through the decurler, and a third conveyance phase at discharge speed. This periodic speed variation resolves the contradiction between productivity and motor reliability
2Reliability
If the sheet is decelerated to a low discharge speed before reaching the decurler unit to reduce motor load, then the motor load is reduced, but sheet discharge productivity is decreased
Solution Approach 1:
The system maintains high productivity by accelerating the sheet to a third (high) speed after it passes through the decurler unit. The speed is dynamically adjusted based on position: low speed through the decurler for reliability, then high speed for the remaining conveyance to maintain overall productivity
3Productivity
If the sheet is conveyed at high speed through the decurler unit to maintain productivity, then the discharge productivity is improved, but the motor driving the decurler unit is applied with excessive load and falls out of step
Solution Approach 1:
The system performs preliminary deceleration before the sheet reaches the decurler unit, reducing the speed to a second (lower) speed in advance. This preliminary action ensures the motor operates within its capacity when the sheet actually passes through the decurler, preventing motor failure while maintaining overall productivity through subsequent acceleration
Data Source
AI summary
An image forming apparatus includes a control unit to perform a first conveyance process in which a sheet is conveyed in a second direction opposite to a first direction at a first speed by a reverse conveyance roller pair, a second conveyance process in which the sheet is conveyed at a second speed by a decurler, and a third conveyance process in which the sheet is conveyed to an inlet roller pair at a third speed by a conveyance roller pair, with the second speed being slower than the first speed, and the third speed being different from the first and second speeds. An image forming unit conveys the sheet at a fourth speed while transferring the image onto the sheet, the fourth speed being slower than the first speed, the second speed, and the third speed.