Roll Media Tension Control via Reverse Rotation
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Solution Overview
Problem
Existing image forming apparatuses face challenges in maintaining stable tension for roll-type media, leading to skew and paper jam issues, which affect printing quality, and require complex and costly configurations to control medium conveyance effectively.
Innovation Solution
The apparatus incorporates a medium supplier, conveyor, winder, and rotation controller to manage tension by rotating the medium supplier in both winding and reverse directions, allowing for intermittent conveyance and slack control to maintain consistent tension and reduce positional deviations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a tension bar is used to apply tension to the print medium, then conveyance reliability is improved, but device size and cost increase
Solution Approach 1:
The patent removes the tension bar from the system entirely and replaces it with a sheet feed motor that directly applies torque to the roll-type medium. This extraction of the unnecessary component simplifies the device structure while maintaining the essential function of applying tension through direct rotational force.
Solution Approach 2:
The patent replaces the mechanical tension bar system with a motor-driven system. The sheet feed motor provides rotational force directly to the roll-type medium, substituting a complex mechanical tension application mechanism with a simpler electromechanical system that achieves the same conveyance control.
2Measurement precision
If a current detection circuit and CPU are added for coordinate control of conveyance roller speed and medium feed roller torque, then conveyance control precision is improved, but device cost and complexity increase
Solution Approach 1:
The patent makes the sheet feed motor self-regulating by using the torque limiter's inherent mechanical properties. The system leverages the natural characteristics of the torque limiter to automatically maintain appropriate torque levels without requiring external sensing or complex control algorithms, thereby achieving precise control through passive mechanical means.
Solution Approach 2:
The patent changes the control approach from active electronic control to passive mechanical parameter-based control. By utilizing the torque limiter's predetermined torque characteristics and the motor's inherent torque-speed curves, the system achieves precise conveyance control through parameter matching rather than active feedback control.
3Device complexity
If torque is applied in the sheet winding direction without reverse rotation, then medium winding is simplified, but tension stability deteriorates due to outer diameter variations
Solution Approach 1:
The patent implements periodic alternation between forward rotation (winding) and reverse rotation (loosening) of the medium supplier. This periodic action compensates for tension fluctuations caused by changing outer diameter, maintaining stable tension throughout the printing process by dynamically adjusting the medium supply characteristics.
Solution Approach 2:
The patent introduces reverse rotation as the opposite of the normal winding rotation. By periodically rotating the medium supplier in reverse, the system counteracts the natural tension increase that occurs as the outer diameter decreases, thereby stabilizing tension through inverse compensation.
Data Source
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AI summary
An image forming apparatus (100) includes a medium supplier (52, 64) configured to supply a print medium (M) wound in a roll shape, a medium conveyor (63) configured to intermittently convey the print medium (M) supplied by the medium supplier (52, 64) by a predetermined supply amount, a medium winder (44, 65) configured to wind the print medium (M) conveyed by the medium conveyor (63), a printer (6, 25) configured to print on the print medium (M) conveyed by the medium conveyor (63), and a rotation controller (61) configured to cause the medium supplier (52, 64) to rotate in a medium winding direction at a predetermined timing after the medium conveyor (63) has started to intermittently convey the print medium (M), and cause the medium supplier (52, 64) to rotate in a reverse direction opposite the medium winding direction to loosen the print medium (M).