Alternating Transfer Bias Control for Embossed Media

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Solution Overview

Problem

Image forming apparatuses using electrophotographic methods face challenges in transferring toner onto recording media with coarse or embossed surfaces, resulting in uneven image density due to inadequate toner transfer in recessed portions.

Innovation Solution

The apparatus employs a transfer bias power source that alternates between a transfer-directional voltage and a return-directional voltage, with the controller adjusting the frequency of the output voltage as the ratio of the return-directional voltage time period to the total cycle time decreases, improving toner transfer on uneven surfaces.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a superimposed voltage with DC and AC components is applied to improve toner transfer in recessed portions, then transferability on embossed surfaces is improved, but image density uniformity deteriorates due to light and dark patterns appearing in the output image

Engineering Contradiction:

Improvetransferability on embossed surfacesVSAvoidimage density uniformity

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The patent applies periodic alternating voltage with varying duty cycles to the transfer device. By periodically switching between positive and negative voltages with different time ratios, the system achieves both improved toner transfer into recessed portions and reduced light-dark patterns, resolving the contradiction between transferability and image density uniformity

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

The patent changes the voltage parameters by adjusting the duty cycle ratio of alternating voltages applied to the transfer device. By varying the time ratio between positive and negative voltage periods, the system optimizes both transferability into recesses and image density uniformity, addressing the technical contradiction

Inventive Principle:

Principle #35Parameter changes

2Reliability

If the time period of return-directional voltage is increased to improve transfer into recessed portions, then toner transferability is enhanced, but the frequency of voltage alternation decreases which may affect transfer efficiency

Engineering Contradiction:

Improvetoner transferabilityVSAvoidtransfer efficiency

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The patent employs periodic alternating voltage with optimized duty cycles, where the ratio of negative voltage time to total cycle time is controlled within specific ranges (5-50% or 50-95%). This periodic action with optimized timing improves toner transfer into recessed portions while maintaining adequate transfer frequency to ensure overall transfer efficiency

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

The patent optimizes voltage parameters by controlling the duty cycle ratio and frequency of alternating voltages. By adjusting these parameters within specific ranges, the system achieves both improved transferability into recesses and maintained transfer efficiency, resolving the contradiction between these two factors

Inventive Principle:

Principle #35Parameter changes

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 enhances toner transferability on recording media with uneven surfaces, reducing the occurrence of transfer failures and ensuring consistent image quality by optimizing the voltage waveform.

Implementation Method 1

a belt type image bearer bearing an image contacts a transfer device opposed to the image bearer to form a transfer nip, thereby transferring a toner image onto a recording medium in the transfer nip

Methodology Applied

Scientific EffectElectrostatic transfer: Electrostatic Deposition

Implementation Method 2

The transfer bias power source outputs the voltage that alternates between a transfer-directional voltage and a return-directional voltage... The controller reduces a frequency of the output voltage as a ratio of A to B decreases

Methodology Applied

Scientific EffectAlternating voltage application: Alternating Magnetic Field

Data Source

PatentUS9541865B2Image forming apparatus with a controller to control an alternating transfer bias

Publication Date: 2017.01.10 RICOH CO LTD

AI summary

An image forming apparatus includes an image bearer; a transfer device; a transfer bias power source; and a controller to control the transfer bias power source. The transfer bias power source outputs the voltage that alternates between a transfer-directional voltage and a return-directional voltage. The transfer-directional voltage having a polarity transfers the toner image from a side of the image bearer to a side of the recording medium. The return-directional voltage has an opposite polarity to the polarity of the transfer-directional voltage. The controller reduces a frequency of the output voltage as a value of a ratio of A to B decreases while changing the value of the ratio of A to B. In this case, A is a time period of application of the return-directional voltage within one cycle of the output voltage, and B is a time period of the one cycle of the output voltage.