Developing Device Helical Blade Pitch Gradient for Toner Uniformity
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Solution Overview
Problem
Image forming apparatuses using two-component developers with toner and magnetic carriers face issues with uneven image density due to toner concentration imbalances and reduced flowability, leading to locally decreased toner concentrations and increased image density in the axial direction of the developing roller.
Innovation Solution
A developing device with multiple conveyance paths and adjustable helical blades, along with a developer surface adjustment window, is implemented to stabilize toner distribution and prevent toner concentration imbalances by gradually decreasing conveyance speed and guiding excess developer away from the main conveyance path, ensuring consistent toner supply to the photoconductor drum.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the developer is conveyed in a circulative manner to quickly disperse supplementary toner, then the charging speed is improved, but the toner concentration becomes uneven causing uneven image density
Solution Approach 1:
The developer conveyance path is divided into multiple separate paths (first conveyance path and second conveyance path) instead of a single circulative path. The developer is conveyed through these multiple paths before reaching the developing roller, which prevents local toner concentration depletion while maintaining rapid mixing and charging capabilities.
Solution Approach 2:
Different regions of the developer conveyance system are designed with different functions: the first conveyance path focuses on rapid toner dispersion and charging, while the second conveyance path ensures uniform toner distribution. This local functional differentiation allows simultaneous achievement of fast charging and uniform image density.
2Stability of the object's composition
If the helical blade pitches are decreased toward the downstream side to stabilize developer surface level, then the surface stability is improved, but the conveyance complexity increases
Solution Approach 1:
The helical blade pitches are designed to vary dynamically along the conveyance direction rather than being uniform. The pitches are decreased toward the downstream side, creating a gradual transition that stabilizes the developer surface level while maintaining a relatively simple single-path conveyance structure.
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 prevents uneven image density by maintaining stable toner concentration and surface levels, ensuring consistent image quality over time by stabilizing the developer surface and reducing toner concentration variations.
Implementation Method 1
a first conveyance member being provided in the first developer conveyance path in a freely rotatable manner and having a helical blade for conveying the two-component developer in one direction
Implementation Method 2
the helical blade having helical pitches decreasing toward a downstream side from an upstream side of a developer conveyance direction to stabilize the level of the surface of the developer
Implementation Method 3
a developer surface adjustment window being provided between the first developer conveyance path and the developer collection path and having a predetermined level for allowing excess developer exceeding the level of the window to be guided from the first developer conveyance path to the developer collection path
Implementation Method 4
The toner and the carrier are agitated in a developing device to generate friction between the toner and the magnetic carrier, and the friction allows the toner to be appropriately charged
Implementation Method 5
The charged toner is supplied to a surface of a developer holder such as a developing roller. The toner supplied to the developing roller is transferred to an electrostatic latent image formed on a photoconductor drum by electrostatic attraction
Data Source
AI summary
A developing device comprises a first and a second developer conveyance path. A first conveyance member is provided in the first developer conveyance path in a freely rotatable manner and has a helical blade. A developing roller supplies the developer in the first developer conveyance path to a photoconductor drum. A developer collection path guides two-component developer left on a surface of the developing roller from the first developer conveyance path. A developer surface adjustment window comprises a predetermined level for allowing excess developer exceeding the level of the window to be guided from the first developer conveyance path to the developer collection path.