Sheet Discharge Control to Prevent Curling in Image Forming
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Solution Overview
Problem
Image forming apparatuses face the issue of medium curling when discharged sheets are held by discharge rollers, especially for longer sheets that can become curled or fall off.
Innovation Solution
An image forming apparatus with a controller that selects between a first discharge mode for holding and a second discharge mode for releasing the medium based on conditions such as material type and length, using a medium holder to manage discharge operations to prevent curling and falling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the discharged medium is held by discharge rollers to prevent falling off, then the medium can be kept secure, but the medium may become curled
Solution Approach 1:
The patent changes the discharge mode parameters based on medium characteristics. When the medium length exceeds a threshold value, the system switches from continuous holding to temporary holding followed by release, preventing curling while still preventing falls for longer media
Solution Approach 2:
The discharge roller's holding action is made dynamic rather than static. The holding state is changed to a temporary state with automatic release timing, allowing the system to adapt to different medium lengths and prevent curling while maintaining fall prevention capability
2Reliability
If the medium holder continues to hold the discharged medium, then the medium is prevented from falling, but the medium is more likely to become curled
Solution Approach 1:
The medium holder performs periodic action by holding the medium for a prescribed period and then releasing it. This periodic holding-release cycle prevents continuous contact that causes curling while still providing sufficient holding time to prevent falls
Solution Approach 2:
The holding time parameter is changed from continuous to a prescribed limited period. This parameter change allows the system to balance fall prevention with curling prevention by releasing the medium after the specified time
Data Source
AI summary
An image forming apparatus includes a medium accommodating part, an image forming engine, a discharge part, a medium conveyer configured to convey a medium from the medium accommodating part to the image forming engine and to the discharge part, a medium holder configured to hold the medium discharged to the discharge part, and a controller. The controller selects a first discharge mode for causing the medium holder to continue to hold the medium when a holding condition is satisfied or a second discharge mode for causing the medium holder not to hold the medium or to hold the medium for a prescribed period and then release the medium. The holding condition includes at least one of a first condition being that material of the medium does not correspond to specific materials and a second condition being that a medium length is less than a first threshold value.