Variable Transfer Nip and Bias Duty for Image Density
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Solution Overview
Problem
Image forming apparatuses face transfer failures due to unevenness in recording sheets, as existing techniques for controlling transfer bias are inadequate in maintaining image density and productivity, especially at high speeds.
Innovation Solution
The apparatus includes a controller that switches between modes to adjust the duty and width of the transfer nip, using a power source with an alternating-current (AC) component to optimize toner transfer based on the type of recording sheet, with a duty of greater than 50% for plain sheets and less than 50% for uneven sheets, and adjusts the linear velocity and nip width to prevent productivity loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the transfer bias duty is increased to maintain image density, then image quality is improved, but transfer failures occur on uneven sheets
Solution Approach 1:
The patent applies dynamics by making the transfer bias duty variable rather than fixed. The controller dynamically adjusts the duty between a first duty (greater than 50%) for plain sheets and a second duty (less than 50%) for uneven sheets, allowing the system to adapt to different sheet conditions and resolve the contradiction between maintaining image density and preventing transfer failures
Solution Approach 2:
The patent changes the parameter of transfer bias duty based on sheet type detection. By switching between different duty values (first duty >50% and second duty <50%), the system optimizes transfer performance for different sheet conditions, achieving both high image density on plain sheets and reliable transfer on uneven sheets
2Manufacturing precision
If the transfer nip width is reduced to improve image density, then image quality is improved, but productivity decreases
Solution Approach 1:
The patent applies dynamics by making the transfer nip width variable. The nip width changing device adjusts the width between a first width (narrower) for plain sheets and a second width (wider) for uneven sheets, enabling the system to optimize both image density and productivity based on sheet type
Solution Approach 2:
The patent changes the parameter of transfer nip width according to sheet conditions. By switching between different width values, the system achieves high image density on plain sheets while maintaining productivity on uneven sheets, resolving the contradiction between quality and speed
3Reliability
If the transfer bias duty is decreased to prevent transfer failures on uneven sheets, then reliability is improved, but image density decreases
Solution Approach 1:
The patent uses dynamics to switch the transfer bias duty based on detected sheet type. For uneven sheets, it uses a lower second duty to ensure reliable transfer, while for plain sheets, it uses a higher first duty to maximize image density, thus resolving the contradiction through conditional adaptation
4Productivity
If the linear velocity of the image bearer is increased to improve productivity, then output speed is improved, but transfer failures occur on uneven sheets
Solution Approach 1:
The patent applies dynamics by making the linear velocity variable. The controller adjusts velocity between a first velocity for plain sheets and a second velocity for uneven sheets, allowing high-speed operation on plain sheets while ensuring reliable transfer on uneven sheets through reduced velocity
Solution Approach 2:
The patent changes the parameter of linear velocity based on sheet type. By switching between different velocity values, the system achieves high productivity on plain sheets while maintaining transfer reliability on uneven sheets, resolving the contradiction between speed and reliability
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 solution effectively prevents transfer failures and maintains image quality by adapting the transfer bias and nip conditions to the sheet type, ensuring consistent image density and high-speed performance.
Implementation Method 1
The power source outputs a transfer bias including an alternating-current (AC) component to transfer a toner image from the image bearer to a recording sheet in the transfer nip
Data Source
AI summary
An image forming apparatus including an image bearer; a nip forming member, a nip width changing device, a power source; and a controller. The controller switches between a first mode and a second mode according to a predetermined condition. In the first mode, a duty of the transfer bias is a first duty and a width of a transfer nip is a first width. In the second mode, the duty of the transfer bias is a second duty lower than the first duty and the width of the transfer nip is a second width greater than the first width. The duty is (T−Tt)/T×100% where T denotes one cycle of the transfer bias, and Tt denotes a time period, in which the transfer bias is on a transfer-directional side relative to a time-averaged value of the transfer bias, in the one cycle.