Image Forming Apparatus Stepwise Voltage Control for Toner Deposition
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Solution Overview
Problem
Existing image forming apparatuses experience image defects due to toner deposition on the charging member when the toner's electric charge is attenuated, and improper collection of toner leads to fog and charging non-uniformity.
Innovation Solution
The image forming apparatus includes a rotatable image bearing member, a charging member, a developing member, a transfer member, an exposure unit, and a controller that controls the charging and developing voltages. During the image forming operation, toner remaining on the image bearing member is collected by the developing member, and a preparatory operation is executed before the image forming operation, where the rotation of the image bearing member is started, and the charging and developing voltages are increased stepwise to ensure proper toner collection and image formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If the image forming apparatus stands by for a long time, then the toner electric charge is attenuated, but this causes non-electrostatic deposition of toner on the image bearing member resulting in fog
Solution Approach 1:
The patent applies preliminary action by executing a preparatory operation before the main image forming operation. This preparatory operation includes rotating the image bearing member and controlling the charging and developing voltages to be increased stepwise, which restores toner charge and prevents fog before actual image formation begins
Solution Approach 2:
The patent changes electrical parameters (charging voltage and developing voltage) during the preparatory operation. By increasing these voltages stepwise before image formation, the toner's electric charge is restored, transforming the toner from a charged state to a properly electrostatic state that prevents non-electrostatic deposition
2Reliability
If the charging voltage is increased stepwise during preparatory operation, then toner collection is improved, but this increases the complexity of voltage control
Solution Approach 1:
The complex voltage control is performed in advance during the preparatory operation before image formation. By executing the stepwise voltage increase beforehand, the main image forming operation can proceed with standard voltage control, reducing the perceived complexity during critical operations
Solution Approach 2:
The voltage control is divided into periodic stages: a preparatory period with stepwise voltage increase, followed by the main image forming period with standard voltage. This periodic structure organizes the complex control into manageable phases
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 suppresses image defects by ensuring proper toner collection and maintaining the back contrast within a proper range, thereby preventing toner deposition on the charging member and ensuring uniform charging.
Implementation Method 1
a charging member configured to electrically charge a surface of the image bearing member at a charging portion where the charging member is provided in contact with the image bearing member
Implementation Method 2
a developing member configured to form a toner image on the image bearing member by supplying a developer to a developing portion where the developing member is provided in contact with the image bearing member
Implementation Method 3
a potential difference (back contrast, fog-removing contrast) between the developing member and the image bearing member in a developing portion where the image bearing member and the developing member oppose each other is controlled to a proper range
Implementation Method 4
the surface of an image bearing member such as a photosensitive drum is electrically charged uniformly by a charging member, and is exposed to light by an exposure unit, so that an electrostatic latent image is formed (written)
Data Source
AI summary
An image forming apparatus includes a rotatable image bearing member, a charging member, a developing member, a transfer member, an exposure unit, and a controller. The controller executes a preparatory operation in which, before an image forming operation, rotation of the image bearing member is started and a charging voltage and a developing voltage are increased stepwisely. In the preparatory operation, the controller carries out control so as to start application of the charging voltage at a voltage value not less than a discharge start voltage of the charging member before a surface region of the image bearing member positioned in a developing portion at a time of a start of the rotation of the image bearing member reaches a charging portion in a state in which a surface of the image bearing member is exposed to light by the exposure unit.