Dynamic AC Bias Control for Toner Transfer on Coated Media
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Solution Overview
Problem
Image forming apparatuses face challenges in transferring toner evenly onto recording media with coarse surfaces, leading to patterns of light and dark patches due to inadequate control of transfer conditions such as temperature, humidity, and surface recesses, resulting in insufficient image density and potential electric discharge.
Innovation Solution
An image forming apparatus with a transfer bias output device that adjusts the peak-to-peak voltage of the AC bias based on received information about transfer conditions, including temperature, humidity, and surface characteristics, while reducing the target output value of the DC bias to enhance toner transfer onto recessed portions of the recording medium.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a superimposed bias including AC bias and DC bias is applied to the secondary transfer roller, then transfer of toner to recessed portions is enhanced, but electric discharge occurs in low-temperature low-humidity environments causing reverse charging of toner particles
Solution Approach 1:
The patent implements dynamic control of the AC bias peak-to-peak voltage based on detected transfer conditions (temperature, humidity, paper thickness, recess depth, toner amount). The control unit adjusts the AC bias voltage dynamically to match actual transfer conditions, preventing electric discharge in low-temperature low-humidity environments while ensuring adequate toner transfer to recessed portions under various conditions.
Solution Approach 2:
The patent changes the voltage parameters of the AC bias component based on detected transfer conditions. Specifically, the peak-to-peak voltage of the AC bias is adjusted according to temperature, humidity, paper thickness, recess depth, and toner amount, allowing optimal toner transfer without causing electric discharge under different environmental conditions.
2Manufacturing precision
If the peak-to-peak voltage of AC component is increased to improve toner transfer to recessed portions, then image density at recessed portions improves, but toner voids or missing images occur due to reverse charging
Solution Approach 1:
The patent employs feedback control by detecting transfer conditions (temperature, humidity, paper thickness, recess depth, toner amount) and using this information to adjust the AC bias peak-to-peak voltage. This closed-loop control ensures that the AC bias voltage is optimized for each specific condition, achieving complete toner transfer to recessed portions without causing reverse charging or toner voids.
3Ease of operation
If constant voltage control or constant current control is used for AC bias, then control simplicity is maintained, but desirable image density is difficult to obtain in low-temperature low-humidity environments
Solution Approach 1:
The patent transitions from static constant voltage or constant current control to dynamic control where the AC bias peak-to-peak voltage is adjusted based on detected transfer conditions. The control unit modifies the AC bias voltage in response to temperature, humidity, paper thickness, recess depth, and toner amount, achieving desirable image density in low-temperature low-humidity environments while maintaining reasonable control complexity.
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 ensures improved image density on recessed portions of the recording medium, preventing patterns of light and dark patches and reducing the occurrence of toner voids or missing images, thereby producing higher-quality output images.
Implementation Method 1
a transfer bias to form a transfer electric field including an alternating electric field in the transfer nip to transfer the toner image from the image bearing member onto a recording medium
Data Source
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AI summary
An image forming apparatus includes a transfer bias output device and an information receiving device (51; 52; 50). The transfer bias output device (39) outputs a transfer bias including a superimposed bias composed of an AC bias superimposed on a DC bias to form a transfer electric field in a transfer nip between an image bearing member (31) bearing a toner image and a nip forming member (36), to transfer the toner image onto a recording medium in the transfer nip. A controller operatively connected to the information receiving device (51; 52; 50) and the transfer bias output device causes the transfer bias output device to change a target output of a peak-to-peak voltage of the AC bias based on information received by the information receiving device (51; 52; 50) that affects transfer of the toner image and to reduce a target output of the DC bias as the target output value of the peak-to-peak voltage of the AC bias increases.