Fixing Nip Width Measurement via Nip Image Formation
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Solution Overview
Problem
Existing image forming apparatuses face challenges in accurately measuring the width of the fixing nip due to the obscuration of the toner trace boundary, especially when using monochromatic black images, which affects the precision of temperature control and leads to potential image defects.
Innovation Solution
The apparatus includes a control system that forms a nip image on the sheet corresponding to the shape of the fixing nip, allowing for precise measurement by stopping the sheet conveyance and adjusting the heating portion's temperature to maintain the smoothness of the nip image, thereby enhancing the accuracy of the fixing nip width measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the measurement sheet passes through the fixing unit again to form the nip image, then the trace of the nip can be formed on the black image, but the toner at the trace of the nip is melted again by heat and the boundary becomes obscure
Solution Approach 1:
The patent applies preliminary action by forming the nip image on the measurement sheet before it passes through the fixing unit for the second time. The measurement sheet is prepared with a black image that will receive the nip trace, and the conveyance is stopped at the appropriate position to allow the nip trace to form clearly before the sheet undergoes another fixing process that could blur the boundaries.
Solution Approach 2:
The patent employs dynamics by controlling the conveyance speed of the measurement sheet through the fixing unit. The conveyance is stopped temporarily at the position where the nip image should be formed, allowing the fixing nip to create a clear trace on the black image. This dynamic control of conveyance timing and speed ensures that the nip trace boundary remains sharp while still allowing the sheet to pass through the fixing unit.
2Ease of operation
If the boundary of the trace of the nip becomes obscure, then the measurement can be performed, but the accuracy in measuring the width of the fixing nip drops
Solution Approach 1:
The patent implements feedback by using the reading unit to read the nip image that has been formed on the measurement sheet. The control portion then processes this read information to calculate the width of the fixing nip. This feedback loop ensures that even if the nip trace boundary becomes slightly obscure, the system can still accurately determine the fixing nip width by analyzing the optical density distribution of the nip image.
Solution Approach 2:
The patent replaces mechanical measurement methods (such as using a caliper to physically measure the nip trace) with an optical reading system. The reading unit optically scans the nip image on the measurement sheet, and the control portion processes the optical density data to calculate the fixing nip width. This substitution allows for more precise measurements even when the physical boundary is not perfectly sharp.
3Duration of action of stationary object
If the pressure roller durability deteriorates, then the width of the fixing nip increases, but the heat application consistency deteriorates
Solution Approach 1:
The patent applies self-service by automatically measuring the fixing nip width using the reading unit and control portion, and then automatically adjusting the fixing temperature based on the measured value. This self-adjusting mechanism compensates for changes in fixing nip width caused by pressure roller deterioration, maintaining consistent heat application without requiring manual intervention or replacement of the pressure roller.
Solution Approach 2:
The patent employs parameter changes by adjusting the fixing temperature based on the measured fixing nip width. When the fixing nip width increases due to pressure roller deterioration, the control portion modifies the fixing temperature parameter to compensate, ensuring that the heat application remains consistent and appropriate for achieving proper image fixation.
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 improves the accuracy of fixing nip width measurement, ensuring consistent heat application and reducing the likelihood of image defects by maintaining the clarity of the nip image boundary, even as the durability of the pressure roller deteriorates.
Implementation Method 1
a heating portion configured to heat the first rotary member, the fixing portion being configured to fix the non-fixed toner image which has been transferred onto the sheet to the sheet as a fixed toner image by heat and pressure at the fixing nip
Implementation Method 2
the control portion sets the heating portion to a second temperature which is lower than the first temperature in a case where the nip image passes through the fixing nip from when the nip image has been formed on the sheet until when the reading unit reads the nip image
Data Source
AI summary
An image forming apparatus includes an image bearing member configured to bear a non-fixed toner image, a transfer portion configured to transfer the non-fixed toner image onto a sheet at a transfer nip, a fixing portion including a first rotary member, a second rotary member and a heating portion configured to heat the first rotary member, a control portion configured to execute a nip image forming process of forming a nip image, on the sheet, corresponding to a shape of the fixing nip, and a reading unit configured to read the nip image, wherein the control portion sets the heating portion to a first temperature in a case where the non-fixed toner image passes through the fixing nip and sets the heating portion to a second temperature which is lower than the first temperature in a case where the nip image passes through the fixing nip.