Fixing Belt Grounding With Protective Resistor for AC Banding
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Solution Overview
Problem
Existing image forming apparatuses suffer from AC banding, a density unevenness issue caused by AC voltage transmission from the fixing nip to the transfer nip, which complicates the configuration and increases manufacturing costs, and are susceptible to lightning surges due to low fixing grounding resistance.
Innovation Solution
The image forming apparatus includes a fixing device with a rotatable fixing belt grounded via a first grounding path and a transfer device with a transferor grounded via a third grounding path, where the transfer resistance satisfies the expression Rf / (jXs + Rp + Rt) / (jXh + Rf / (jXs + Rp + Rt) < 0.3, to prevent AC banding without increasing costs and protect against lightning surges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If AC voltage is applied to the heater without rectification, then manufacturing cost is reduced by eliminating the rectifier circuit, but AC banding occurs causing density unevenness in the image
Solution Approach 1:
A protective resistor is introduced as an intermediary component in the grounding path of the fixing belt. This resistor acts as a mediator to suppress the AC voltage transmitted from the fixing nip to the transfer nip, thereby preventing AC banding while allowing the use of unrectified AC voltage for heating, thus maintaining cost effectiveness
Solution Approach 2:
The invention changes the electrical parameter (resistance) in the grounding path by adding a protective resistor with a specific resistance value. This parameter change suppresses the AC voltage transmission to the transfer nip, preventing image density unevenness while maintaining the heating function
2Manufacturing precision
If fixing grounding resistance is decreased to reduce AC voltage transmission, then AC banding is prevented, but the apparatus becomes susceptible to lightning surges
Solution Approach 1:
The protective resistor is designed with a specific resistance value that optimally balances two opposing requirements: it is low enough to suppress AC voltage transmission and prevent AC banding, but high enough to limit lightning surge current and protect the apparatus from electrical damage
3Manufacturing precision
If a heating roller is added to form a heating nip, then AC banding is prevented, but device complexity and manufacturing cost increase
Solution Approach 1:
The invention extracts the AC voltage suppression function from the heating system and relocates it to the grounding path of the fixing belt. By removing the need for a separate heating roller and its associated heating nip, the invention simplifies the device configuration while maintaining the ability to prevent AC banding through the protective resistor
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 configuration effectively prevents AC banding and reduces the risk of lightning damage, maintaining image quality and apparatus integrity while avoiding cost increases.
Implementation Method 1
The fixing belt is grounded via a first grounding path from the fixing belt to a ground. The first grounding path includes a protective resistor.
Implementation Method 2
an alternating current (AC) voltage of a commercial power supply or a direct current (DC) voltage converted by rectifying the AC voltage is applied to a resistive heat generator in a fixing device
Implementation Method 3
The transferor has a transfer resistance satisfying a following expression, where Rt is a resistance value of the transferor resistance
Data Source
Figure 1~2
Figure 3
Figure 4
AI summary
An image forming apparatus includes a fixing device, a power supply, and a transfer device. The fixing device includes a fixing belt grounded via a protective resistor, a heater contacting the fixing belt, and a pressure rotator grounded and facing the fixing belt to form a nip. The power supply applies an alternating current voltage to the heater. The transfer device includes a transferor grounded and an opposed rotator facing the transferor to form a nip. The transferor has a transfer resistance Rt satisfying a following expression, (I) where Rf is a resistance value of the protective resistor, Rp is a resistance value of a recording medium, jXs is an impedance of the fixing belt, and jXh is an impedance of the heater.