Feeding Screw Design for Toner Overflow in Image Forming Apparatus
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Solution Overview
Problem
In image forming apparatuses, the reduced developer feeding power near the discharge opening leads to stagnation and overflow issues, increasing the rotational load on the feeding screw and potentially causing it to lock, due to high flowability and low charge amount of the developer.
Innovation Solution
An image forming apparatus with a feeding screw designed to have a smaller outer diameter in the region opposing the discharge opening, and a controller that adjusts the screw's driving speed based on the developer's charge amount, increasing speed when flowability is high and charge is low to ensure proper discharge.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If the blade of the feeding screw in the opposing region to the discharge opening is removed or made small, then the developer feeding power in this region is reduced, but the developer stagnates and overflows the discharge opening
Solution Approach 1:
The feeding screw is designed with a smaller outer diameter specifically in the first region opposing the discharge opening, while maintaining a larger outer diameter in the second region. This local variation in geometry creates different feeding characteristics in different regions, allowing the screw to reduce developer feeding power near the discharge opening (preventing overflow) while maintaining adequate feeding power in other regions.
2Object-generated harmful factors
If the developer feeding power is reduced near the discharge opening, then the developer stagnation is increased, but the rotational load on the feeding screw becomes high and the screw may lock
Solution Approach 1:
By making the outer diameter of the feeding screw smaller only in the first region opposing the discharge opening, the invention locally reduces feeding power where stagnation causes harm (near the discharge opening), while maintaining the original diameter in the second region to ensure adequate feeding power elsewhere, thus balancing stagnation control with rotational load management.
Solution Approach 2:
The feeding screw's rotational speed is dynamically adjusted based on detected developer charge amount. When charge amount is low (indicating high flowability and potential stagnation), the rotation speed is increased to enhance feeding power and prevent stagnation, while when charge amount is sufficient, the rotation speed is reduced to lower rotational load and prevent screw locking.
3Object-generated harmful factors
If the developer charge amount is low and flowability is high, then the developer does not readily stagnate, but the developer surface does not rise and discharge is insufficient
Solution Approach 1:
A detection device monitors the charge amount of the developer and provides feedback to the control device. Based on this feedback, the control device adjusts the feeding screw's rotational speed to optimize discharge. When charge amount is low (high flowability), the system increases rotation speed to compensate for the lack of natural stagnation and promote sufficient discharge, ensuring proper developer level maintenance regardless of flowability conditions.
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 developer stagnation and overflow by raising the developer surface and ensuring proper discharge, even when flowability is high and charge is low, thereby reducing the risk of screw lock and maintaining apparatus stability.
Implementation Method 1
the toner and the carrier are triboelectrically charged by feeding the developer while stirring the developer by rotating a feeding screw
Implementation Method 2
control so that a driving speed at which the feeding screw is driven by the driving device is faster when the charge amount of the developer corresponds to a second charge amount lower than a first charge amount, than when the charge amount of the developer corresponds to the first charge amount
Data Source
AI summary
An image forming apparatus that continuously carries out image formation on a plurality of recording materials includes an image bearing member and a developing device configured to develop an electrostatic latent image on the image bearing member. A first feeding screw is provided in a developing chamber and includes a first screw portion, a second screw portion and a third screw portion. Each of the second and third screw portions are provided with a blade portion formed helically on an outer peripheral surface of a rotation shaft of the first feeding screw, and the first screw portion is not provided with the blade portion. Based on information on the relative humidity in the developing container and on the amount of toner consumed with the image formation on a plurality of recording materials, a controller controls a driving speed for rotationally driving the first feeding screw by a driving device.