Asymmetric Nip Gap for DC Development Density Uniformity
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Solution Overview
Problem
Image forming apparatuses using the DC development method are prone to toner image density unevenness due to fluctuations in the gap between the developer support member and the image support member, as they require lower voltages and result in less toner contribution during the development process.
Innovation Solution
The apparatus incorporates a developing device with a developer support member that uses a magnetic field to hold toner and carriers, and a voltage applying device that applies a DC voltage to develop electrostatic latent images, with a control member that adjusts the packing density by varying the gap between the developer support member and the image support member to ensure consistent toner distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If DC development method is used, then structure of image forming apparatus can be simple, but toner images have density unevenness
Solution Approach 1:
The patent applies local quality by creating asymmetric gap distribution in the nip area. Specifically, the gap between the developer support member and image support member is made smaller in the first region (upstream from closest point) than in the second region (downstream from closest point). This local variation in gap size ensures sufficient toner contribution while preventing density unevenness, resolving the contradiction between simple structure and image quality.
2Power
If low voltage is applied in DC development, then development process is simpler, but toner contribution is insufficient leading to density unevenness
Solution Approach 1:
The patent applies parameter changes by optimizing the gap distance parameter in the nip area. By controlling the gap to be smaller in the first region and larger in the second region, the system compensates for the low voltage condition. This parameter optimization ensures sufficient toner contribution and prevents density unevenness while maintaining the simplicity of DC development.
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 density unevenness in toner images by increasing the packing density and ensuring a consistent amount of toner contributes to development, even with non-uniform rotations, and also suppresses stripe noise by controlling the magnetic flux direction.
Implementation Method 1
a developing device comprising a developer support member having a second peripheral surface for supporting the developer thereon, the second peripheral surface traveling in a direction opposite to the first peripheral surface at a point where the second peripheral surface faces to the first peripheral surface, the developing device attracting the carriers of the developer by an effect of a magnetic field so as to hold the developer on the second peripheral surface
Implementation Method 2
a voltage applying device for applying a DC voltage to the second peripheral surface such that the electrostatic latent image supported on the first peripheral surface is developed with the developer supported on the second peripheral surface
Data Source
AI summary
An image forming apparatus for forming a toner image on a print medium with a developer composed of toner and carriers, wherein when the first distance is longer than the second distance, an average gap between the first peripheral surface and a member that faces to the first peripheral surface in an area with a length of the first distance extending upstream from the closest point with respect to the specified direction is smaller than an average gap between the first peripheral surface and a member that faces to the first peripheral surface in an area with a length of the first distance extending downstream from the closest point with respect to the specified direction.