Voltage Control for Toner Transfer Suppression in Contact Development
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Solution Overview
Problem
In electrophotographic image forming apparatuses using a contact development system without a contact and separation mechanism, toner transfer occurs from the development roller to the photosensitive drum during preliminary and subsequent rotation operations, leading to 'development fogging' and toner consumption, especially when the system is idle for extended periods.
Innovation Solution
The apparatus includes a control unit that manages voltage application to the developer bearing member and supply member to maintain appropriate charge polarity and layer thickness, adjusting the supply contrast during preliminary and subsequent rotation operations to prevent toner transfer, by setting the supply voltage to be less than or reversed from the developing voltage, ensuring efficient triboelectric charging and reduced toner supply.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the development roller and photosensitive drum are constantly in contact without a contact and separation mechanism, then the device complexity is reduced, but toner transfer occurs during idle periods causing development fogging
Solution Approach 1:
The patent applies voltage parameter changes to the supply roller to control toner supply. During preliminary rotation operations, the supply voltage is set to a specific polarity and magnitude to prevent excessive toner transfer to the photosensitive drum, while during image forming operations, the voltage is adjusted to enable normal toner supply. This dynamic parameter adjustment resolves the contradiction by maintaining simple constant contact structure while preventing development fogging through electrical control.
Solution Approach 2:
The patent implements periodic voltage adjustment to the supply roller based on operational phases. Different voltage conditions are applied periodically: one condition during preliminary rotation (to suppress toner transfer) and another during image forming (to enable toner supply). This periodic control allows the system to operate with constant contact between rollers without causing development fogging during idle periods.
2Object-generated harmful factors
If voltage is applied to prevent toner transfer during idle periods, then development fogging is suppressed, but toner charging may be insufficient during image forming operations
Solution Approach 1:
The patent employs dynamic voltage control of the supply roller that adapts to different operational states. The supply voltage is dynamically adjusted between two main states: a first voltage condition during preliminary rotation that suppresses toner transfer, and a second voltage condition during image forming that enables adequate toner supply and charging. This dynamic adjustment ensures both development fogging suppression and sufficient toner charging at appropriate times.
Solution Approach 2:
The patent applies preliminary voltage control to the supply roller during the preliminary rotation operation before image forming begins. This preliminary action sets the toner supply and charging conditions in advance, ensuring that when image forming starts, the toner is properly charged and ready for transfer. The preliminary voltage application prevents development fogging while preparing adequate toner charge for subsequent image formation.
3Quantity of substance
If the supply voltage contrast is high during preliminary rotation, then toner supply is sufficient, but excessive toner transfers to the photosensitive drum
Solution Approach 1:
The patent changes the voltage parameter of the supply roller based on operational phase. During preliminary rotation, the supply voltage is set to a specific value that limits toner transfer to the photosensitive drum. During image forming operations, the supply voltage is changed to a different value that ensures sufficient toner supply. This parameter change resolves the contradiction by controlling toner supply quantity and transfer amount according to operational needs.
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 effectively suppresses toner transfer during idle periods, reducing development fogging and toner consumption, and maintains image quality by ensuring sufficient toner charging and density during image forming operations.
Implementation Method 1
a regulation member configured to triboelectrically charge the developer borne on the surface of the developer bearing member
Implementation Method 2
a first voltage application unit configured to apply a voltage to the developer bearing member, a second voltage application unit configured to apply a voltage to the supply member
Data Source
AI summary
An image forming apparatus includes a developer bearing member, a supply member, first and second voltage application units, and a control unit. Assuming that a difference between a voltage to be applied to the developer bearing member by the first voltage application unit and a voltage to be applied to the supply member by the second voltage application unit in the image forming operation is defined as a first supply contrast, and a difference between the voltage to be applied to the developer bearing member by the first voltage application unit and the voltage to be applied to the supply member by the second voltage application unit in the preliminary rotation operation is defined as a second supply contrast, the control unit controls the second supply contrast to be less than the first supply contrast or to have polarity reversed from polarity of the first supply contrast.