Image Forming Apparatus With Transfer-Fixing Nip Load Control
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Solution Overview
Problem
In electrophotographic image forming apparatuses, the leading end of a paper sheet entering the fixing nip can cause impact, leading to image quality defects on the portion positioned at the transfer nip.
Innovation Solution
The apparatus includes mechanisms to variably control the transfer and fixing nip loads by adjusting the pressure contact states between the image carrier, transfer member, and fixing members, using a control unit to increase the transfer nip load and decrease the fixing nip load before the paper sheet enters the fixing nip, and subsequently return to normal loads.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the leading end of the paper sheet enters the fixing nip with normal fixing nip load, then the fixing process can be performed, but an image quality defect occurs on the portion positioned at the transfer nip due to impact
Solution Approach 1:
The control unit performs preliminary action by decreasing the fixing nip load before the leading end of the paper sheet enters the fixing nip, and increases the transfer nip load at the same timing. This preparatory adjustment of loads prevents the impact that would otherwise cause image quality defects when the paper sheet enters the fixing nip.
Solution Approach 2:
The invention changes the operational parameters (fixing nip load and transfer nip load) dynamically based on the position of the paper sheet. By varying these parameters in response to the paper sheet's entry into the fixing nip, the system maintains fixing process stability while preventing image quality defects.
2Manufacturing precision
If the fixing nip load is decreased before the paper sheet enters the fixing nip, then image quality defects are suppressed, but the fixing process effectiveness may be reduced
Solution Approach 1:
The control unit applies periodic action by temporarily decreasing the fixing nip load only during the brief period when the leading end of the paper sheet is about to enter the fixing nip. After this critical moment passes, the fixing nip load is restored to its normal level, ensuring that the fixing process remains effective for the rest of the paper sheet passage.
Solution Approach 2:
The decrease in fixing nip load is applied as a preliminary measure just before the paper sheet enters the fixing nip, preventing the impact that causes image quality defects. The load is then restored to normal levels to ensure proper fixing effectiveness during the main fixing process.
3Manufacturing precision
If the transfer nip load is increased before the paper sheet enters the fixing nip, then slip and speed variations at the nip interfaces are minimized, but the energy consumption increases
Solution Approach 1:
The control unit applies periodic action by temporarily increasing the transfer nip load only during the brief period when the leading end of the paper sheet is about to enter the fixing nip. After this critical moment passes, the transfer nip load is restored to its normal level, minimizing energy consumption while maintaining image quality consistency during the critical transition phase.
Data Source
AI summary
An image forming apparatus includes: an image carrier configured to carry an image on a surface of the image carrier; a transfer member configured to come into pressure contact with the image carrier to form a transfer nip and configured to transfer the image on the image carrier onto a paper sheet; a pair of fixing members disposed downstream from the transfer member in a transport path of the paper sheet, configured to come into pressure contact with each other to form a fixing nip, and configured to perform a fixing process on the paper sheet; a transfer change mechanism configured to move at least one of the image carrier and the transfer member to change a pressure contact state between the image carrier and the transfer member; a fixing change mechanism configured to move at least one of the pair of fixing members to change a pressure contact state between the pair of fixing members; and a control unit configured to variably control a transfer nip load at the transfer nip by controlling the transfer change mechanism and variably control a fixing nip load at the fixing nip by controlling the fixing change mechanism. The control unit, before a leading end of the paper sheet enters the fixing nip, increases the transfer nip load from a first transfer nip load to a second transfer nip load larger than the first transfer nip load and decreases the fixing nip load from a first fixing nip load to a second fixing nip load smaller than the first fixing nip load.