Development Sleeve Oval Recesses for Uniform Image Density
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Solution Overview
Problem
Existing electrophotographic development devices face issues with uneven image density due to differences in developer properties between upstream and downstream portions, leading to reduced image quality and increased device size, as well as carry-over of developer at axial end portions, which affects image density and requires larger device sizes or costly materials.
Innovation Solution
A development device with a development sleeve featuring regularly arranged oval recesses on its surface, which balances developer conveyance ability and image density uniformity, and a unidirectional circulation system that reduces rotational frequency and stress on the developer, preventing carry-over by adjusting the angle and distribution of recesses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If grooves are formed on the development sleeve surface to improve developer conveyance, then developer transport reliability is improved, but image density uniformity deteriorates due to uneven developer distribution in groove portions
Solution Approach 1:
The development sleeve surface is segmented into multiple recesses distributed in the axial direction. Each recess independently conveys developer, and the segmented structure prevents localized developer accumulation that would occur with continuous grooves, thereby maintaining image density uniformity while ensuring reliable developer conveyance.
Solution Approach 2:
The recesses are strategically positioned and dimensioned to create localized developer storage zones. The depth, width, and axial spacing of each recess are optimized to control the amount of developer held in each location, ensuring uniform developer distribution across the development width while maintaining effective conveyance to the development zone.
2Manufacturing precision
If developer circulation speed is increased to maintain uniform charge amount, then developer uniformity is improved, but stress on developer increases causing toner degradation
Solution Approach 1:
The recesses pre-position and pre-distribute developer in controlled quantities before it reaches the development zone. This preliminary action ensures uniform charge distribution without requiring high-speed circulation, thereby reducing mechanical stress on the developer and preventing toner degradation from repeated doctor blade contact.
Solution Approach 2:
The development sleeve rotation speed is optimized to balance developer uniformity and stress reduction. The dynamic system allows the recesses to effectively distribute developer at moderate speeds, avoiding the need for high-speed circulation that would increase stress on the developer material.
3Strength
If development sleeve diameter is increased to reduce rotational frequency and stress, then device size increases, but developer stress is reduced
Solution Approach 1:
The segmented recess structure enhances developer distribution efficiency, allowing effective operation at larger diameters with lower rotational frequencies. The multiple recesses ensure adequate developer conveyance even at reduced speeds, enabling the use of larger development sleeves that reduce stress on the developer while maintaining compact overall device dimensions.
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
The solution achieves consistent image density and reduced device size by enhancing developer conveyance and reducing stress, while maintaining high image quality and extending the life of the development sleeve.
Implementation Method 1
a magnet roller (133) provided outside an outer circumferential surface of the metal core (134) and having a plurality of fixed magnetic poles
Implementation Method 2
The magnetic field generator generates a magnetic force for pumping up the developer from the developer container onto the surface of the development sleeve
Implementation Method 3
multiple recesses (139) formed in an outer surface of the development sleeve (132)
Data Source
Figure 1
Figure 2
Figure 3A~4
AI summary
A development device (113) including a developer container (121), a developer bearer (132), a magnetic field generator (133), a developer agitator (118a) to supply the developer to the developer bearer (132), and a developer regulator (116) to adjust a layer thickness of the developer carried on the developer bearer (132). Multiple oval recesses (139) oblique to the axial direction of the developer bearer (132) are formed in the outer circumferential surface of the developer bearer (132) and arranged in a circumferential direction and the axial direction thereof. An upstream inner wall (139a) of the recess (139) in the rotational direction of the developer bearer (132) applies a force to the developer as the developer bearer (132) rotates, and an angle between a long axis of the recess (139) and the axial direction is set so that the force applied by the upstream inner wall (139a) of the recess (139) has a component in a direction substantially identical to the developer conveyance direction of the developer agitator (118a).