Developing Device Overflow Discharge Screw Pitch Ratio
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Solution Overview
Problem
In developing devices of the function-separation type, it is challenging to stabilize the discharge of developers through a discharge opening without causing unintended overflow, especially when the flow path area is reduced and the opening area is decreased, leading to developer stagnation and insufficient circulation.
Innovation Solution
The developing device incorporates a first screw member with a reduced or absent screw blade in a specific region near the discharge opening, and a rib is used to stabilize developer flow, ensuring that the ratio of developer feeding speed in this region to the upstream and downstream regions, combined with optimized cross-sectional areas and rotational speeds, prevents stagnation and allows controlled discharge.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the flow path area of the second feeding path and the opening area of the second opening are reduced to downsize the developing device, then the device size is reduced, but the developer stagnates at the second opening and is temporarily discharged through the discharge opening in an unintended amount
Solution Approach 1:
The first screw member is divided into multiple regions (first region near discharge opening, second region upstream, third region downstream) with different screw blade configurations. This segmentation allows each region to perform its specific function: the first region prevents stagnation, while the other regions maintain feeding efficiency, thus resolving the contradiction between downsizing and reliable developer circulation.
Solution Approach 2:
The screw blade diameter is made locally smaller in the first region compared to the second and third regions. This local quality change creates a velocity difference that prevents developer stagnation at the second opening, allowing the device to be downsized without compromising circulation stability.
2Reliability
If the discharge opening is disposed at a downstream position of the developer carrying region to enable stable discharge, then the discharge is stabilized, but the flow amount of the developer becomes smaller as it moves toward the downstream end
Solution Approach 1:
The first screw member in the first region preliminarily accelerates the developer flow before it reaches the discharge opening. This preliminary action compensates for the natural flow reduction at downstream positions, ensuring both stable discharge and sufficient flow amount.
Solution Approach 2:
The screw blade diameter varies dynamically across different regions of the first screw member. The smaller diameter in the first region creates a dynamic velocity profile that maintains adequate flow amount while enabling stable discharge at the downstream position.
3Reliability
If the screw blade diameter is reduced in the first region to prevent developer stagnation, then the discharge control is improved, but the feeding efficiency may be reduced
Solution Approach 1:
The screw blade diameter is optimized locally in each region: smaller in the first region for discharge control, and larger in the second and third regions for feeding efficiency. This local differentiation resolves the contradiction by ensuring each region performs its primary function effectively.
Solution Approach 2:
The first screw member is segmented into regions with different screw blade diameters. The segmentation allows the first region to focus on discharge control while the second and third regions maintain feeding efficiency, thus resolving the contradiction between discharge control and feeding efficiency.
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 enables stable and controlled discharge of developers, preventing unintended overflow and maintaining sufficient circulation, while allowing for the downsizing of the developing device without compromising performance.
Implementation Method 1
a first screw member, including a screw blade, for supplying the developer to the developer carrying member while feeding the developer delivered from the second feeding path through the first opening by being rotated in the first feeding path
Implementation Method 2
a second screw member, including a screw blade, for feeding the developer delivered from the first feeding path through the second opening and the developer collected from the carrying region by being rotated in the second feeding path
Implementation Method 3
a discharging portion capable of discharging a part of the developer in the first feeding path through a discharge opening, provided in a first region between the carrying region and the second opening in the first feeding path, by causing the part of the developer to overflow the first feeding path
Data Source
AI summary
A developing device includes: a developer carrying member; first and second feeding paths; a first screw member; a second screw member; and a discharge portion. When a ratio of a developer feeding speed in a first region to a developer feeding speed in the second region is α, a screw blade pitch of the first screw member in the second region is p1, a screw blade pitch of the first screw member in the third region is p1′, a rotational speed of the first screw member is ω1, a maximum of a cross-sectional area of a flow path lower than a lower end of the discharge opening in an axially vertical cross section including the discharge opening of the first feeding path is R″, and an opening area of an opening is S′, the following relationship is satisfied: R″αp1/p1′≦S′≦R″p1/p1′.