Fixing Roller Speed Control for Reliable Short-Sheet Jam Detection
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Solution Overview
Problem
In large fixing devices, when a sheet jams around the fixing roller and emergency stop occurs, the sheet may not be detected by sensors due to inertial overrun, leading to undetected jams.
Innovation Solution
The image forming apparatus adjusts the conveyance speed of the fixing rotatable member based on sheet length and type, using different speeds for sheets of varying lengths to ensure timely detection by sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the fixing roller is stopped emergently when a sheet jam occurs, then the sheet winding around the fixing roller can be prevented, but the sheet may not be detected by upstream sensors due to inertial overrun
Solution Approach 1:
The control portion performs preliminary action by detecting sheet length before conveyance and pre-adjusting the conveyance speed of the fixing roller accordingly. For short sheets, a lower speed is selected in advance to ensure the sheet will be detected by upstream sensors before the fixing roller stops, preventing undetected sheet jams while maintaining reliable detection capability.
2Productivity
If the fixing roller conveys short sheets at high speed, then productivity is improved, but the sheet may not be detected by sensors before the fixing roller stops
Solution Approach 1:
The conveyance speed of the fixing roller is made dynamic rather than fixed. The control portion adjusts the conveyance speed based on sheet length: high speed for long sheets to maintain productivity, and low speed for short sheets to ensure detection reliability. This dynamic speed adjustment resolves the contradiction between productivity and detection reliability.
Solution Approach 2:
The conveyance speed parameter of the fixing roller is changed based on sheet length conditions. By changing this operational parameter dynamically according to the detected sheet length, the system achieves both high productivity for long sheets and reliable detection for short sheets, resolving the contradiction between these two objectives.
3Adaptability or versatility
If the fixing device size is increased to handle larger sheets, then versatility is improved, but inertial overrun increases making sheet detection more difficult
Solution Approach 1:
The control portion performs preliminary detection of sheet length and pre-adjusts the conveyance speed before the fixing roller conveys the sheet. For short sheets conveyed in larger fixing devices, the speed is reduced in advance to compensate for increased inertial overrun, ensuring the sheet will be detected by upstream sensors before the fixing roller stops, thus maintaining detection reliability despite increased device size.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach allows for reliable detection of sheet jams, preventing undetected winding issues and maintaining productivity by adjusting conveyance speeds accordingly.
Implementation Method 1
a fixing rotatable member configured to fix the image by heating the sheet on which the image is transferred
Data Source
AI summary
An image forming apparatus includes a fixing roller to fix an image by heating a sheet on which the image is transferred and to convey the sheet. In a case in which a first plain paper of which a sheet length in a sheet conveyance direction is equal to or more than a predetermined length is conveyed, the fixing roller conveys the first plain paper at a first speed. In a case in which a second plain paper of which the sheet length is less than the predetermined length is conveyed, the fixing roller conveys the second plain paper at a second speed less than the first speed. In a case in which an envelope of which the sheet length is less than the predetermined length is conveyed, the fixing roller conveys the second envelope at the first speed.