Charging Roller Toner Adhesion Control in Drum Cleanerless Printers
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Solution Overview
Problem
In image forming apparatuses using the drum cleanerless method, excessive residual toner on the photosensitive drum can adhere to the charging member, causing charging failures and image defects due to improper potential differences and toner collection issues.
Innovation Solution
The apparatus includes a control unit that manages the application of charging and development voltages to prevent toner adherence on the charging member. During a cleaning operation, the development voltage is applied with a polarity opposite to the normal polarity, and the charging voltage is set to ensure a potential difference at the charging portion that is lower than or equal to the discharge start voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the drum cleanerless method is used to reduce device complexity, then the structure is simplified by eliminating the dedicated toner cleaning unit, but residual toner accumulates on the photosensitive drum and adheres to the charging member causing charging failures
Solution Approach 1:
The patent applies preliminary action by performing a cleaning operation before the charging operation. The development member is used to remove residual toner from the photosensitive drum surface in advance, preventing toner accumulation that would otherwise adhere to the charging member and cause charging failures during subsequent operations.
Solution Approach 2:
The patent applies universality by making the development member serve dual functions: (1) developing toner images during normal operation, and (2) collecting residual toner during cleaning operation. This eliminates the need for a separate dedicated toner cleaning unit, resolving the contradiction between device complexity and reliability.
2Device complexity
If residual toner is collected by the development unit, then device complexity is reduced, but excessive residual toner adheres to the charging member causing potential difference control failures
Solution Approach 1:
The cleaning operation is performed as a preliminary action before charging. The development member removes residual toner from the photosensitive drum surface in advance, ensuring that when charging occurs, the charging member does not come into contact with excessive residual toner that would cause potential difference control failures.
Solution Approach 2:
The patent maintains continuity of useful action by ensuring the development member continuously performs its dual function of toner development and residual toner collection. The cleaning operation is integrated into the continuous operation sequence, preventing toner accumulation that would disrupt potential difference control.
3Reliability
If the charging voltage is increased to ensure proper charging, then charging effectiveness is improved, but the potential difference becomes too high causing toner discharge and adherence to the charging member
Solution Approach 1:
The cleaning operation is performed as a preliminary action before charging with high voltage. By removing residual toner from the photosensitive drum surface in advance, the system prevents toner discharge and adherence to the charging member when high charging voltage is applied, ensuring reliable charging effectiveness.
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 charging failures and ensures proper collection of residual toner, thereby maintaining image quality and preventing defects caused by toner smears on the charging roller.
Implementation Method 1
a charging member configured to come into contact with the image bearing member to form a charging portion and charge a surface of the image bearing member at the charging portion
Implementation Method 2
a development member configured to be rotatable and to come into contact with the image bearing member to form a development portion and develop a toner image at the development portion by supplying a toner charged to a normal polarity to the surface of the image bearing member
Implementation Method 3
a transfer member configured to form a transfer portion opposed to the image bearing member and transfer the toner image from the image bearing member to a transfer material at the transfer portion
Implementation Method 4
the control unit controls application of the development voltage to apply, to the development member in the cleaning operation, a development voltage having a polarity that is opposite to the normal polarity
Data Source
AI summary
An image forming apparatus includes an image bearing member, a charging member, a development member, a transfer member, a charging voltage application unit, a development voltage application unit, and a control unit. The development member collects toner that remains on a surface of the image bearing member after a toner image is transferred from the image bearing member surface to transfer material. The control unit controls application of a development voltage to apply, to the development member in a cleaning operation, a development voltage having a polarity that is opposite to a normal polarity, and controls application of a charging voltage to apply, to the charging member, a charging voltage having the normal polarity such that a potential difference formed at a charging portion between the applied charging voltage and a surface potential formed at the image bearing member surface is lower than or equal to a discharge start voltage.