Sheet Cassette Detection for Transfer-Roller Image Defect Control
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Solution Overview
Problem
Existing image forming apparatuses face issues where removing a sheet cassette during image formation can cause the transfer roller to pull out sheets from a stopped conveyance roller, leading to image defects and sheets being discharged improperly.
Innovation Solution
An image forming apparatus with a detection unit to identify the attached or detached state of the cassette, a drive unit to control motor force transmission based on the cassette state, and a determination unit to detect image defects during a monitoring period, ensuring proper operation and preventing image defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the cassette is removed during image formation, then the conveyance roller stops driving, but the transfer roller continues to drive causing image defects
Solution Approach 1:
The control unit stops the conveyance roller before the transfer roller completes its image transfer operation by detecting cassette removal during a monitoring period. This preliminary stopping action prevents the transfer roller from pulling sheets off the conveyance roller, thereby avoiding image defects while maintaining system simplicity
Solution Approach 2:
The system uses feedback from the cassette detection unit to monitor whether the cassette is properly attached during image formation. When the cassette is detected as removed during the monitoring period, the control unit adjusts the conveyance roller's operation accordingly, creating a closed-loop control system that prevents image defects
2Ease of operation
If the transfer roller continues to drive after conveyance roller stops, then sheet may be pulled out from conveyance roller, but this causes sheet discharge to outside of apparatus
Solution Approach 1:
The control unit stops the conveyance roller in advance before the transfer roller completes its operation when cassette removal is detected during the monitoring period. This preliminary action ensures that the sheet remains properly positioned on the conveyance roller, preventing it from being pulled out and discharged improperly to the outside of the apparatus
Solution Approach 2:
The system applies a counter-action by stopping the conveyance roller before the harmful effect (transfer roller pulling sheet off) can occur. This preliminary anti-action prevents the sheet from being discharged to the outside of the apparatus, thereby eliminating the harmful effect while maintaining normal operation
Data Source
AI summary
An image forming apparatus includes: a detection unit configured to detect whether a cassette accommodating a sheet is in an attached state or in a non-attached state; a transfer roller configured to transfer an image to the sheet in a transfer region; a conveyance roller configured to convey, to the transfer region, a first sheet; a drive unit configured not to transmit the driving force to the conveyance roller in the non-attached state; and a determination unit configured to determine that an image defect has occurred when the detection unit detects that a state of the cassette has transitioned to the non-attached state, in a monitoring period including a period from a first timing at which the first sheet starts to be conveyed by the transfer roller, to a second timing.