Developing Device Circular Portion Fills Immobile Area
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Solution Overview
Problem
In electrophotographic image forming apparatuses, the existing method of automatically replacing the developer leads to the generation of aggregation toner in immobile areas around the returning screw, causing unstable discharging and resulting in a decrease in the developer amount, which affects image formation, and can lead to toner stain images due to increased temperature and vibration.
Innovation Solution
A developing device design that includes a rotating shaft with a spiral first blade portion, a spiral second blade portion, a disk portion, and a circular portion on the shaft to prevent the formation of immobile areas, ensuring stable developer discharge and reducing the likelihood of aggregation toner generation by filling the clearance between the disk portion and the discharge passage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a returning screw is disposed on the downstream side of the conveying screw to discharge excess developer, then the charging performance is maintained by automatic developer replacement, but aggregation toner is generated in the immobile area between the disk portion and discharge passage
Solution Approach 1:
The invention introduces a new spatial dimension by forming a circular portion on the rotating shaft that extends into the radial direction, filling the immobile area between the disk portion and discharge passage. This dimensional addition eliminates the harmful space where aggregation toner forms, while preserving the developer replacement function for maintaining charging performance.
Solution Approach 2:
The invention converts the previously harmful immobile area into a beneficial filled space by introducing the circular portion. The space that formerly caused aggregation toner generation is now occupied by the circular portion structure, transforming a harmful condition into a solution that prevents aggregation while maintaining developer circulation.
2Productivity
If the end portion of the conveying screw rotates against the bearing, then the conveying screw conveys the developer effectively, but the temperature of the end portion increases causing aggregation toner generation
Solution Approach 1:
The invention extracts the problematic immobile area where temperature-induced aggregation occurs and replaces it with the circular portion structure. By removing the harmful space through extraction and replacement, the temperature-related aggregation toner generation is prevented while preserving effective developer conveyance.
3Ease of operation
If vibration causes aggregation toner to enter the developer circulation path, then the developing device operates normally, but toner stain images are formed
Solution Approach 1:
The invention performs preliminary action by filling the immobile area with the circular portion before vibration can cause aggregation toner to enter the circulation path. This preventive measure eliminates the source of aggregation toner, so that even when vibration occurs during normal operation, there is no aggregation toner available to cause stain images.
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 effectively suppresses the generation of aggregation toner, maintaining the developer amount and ensuring stable image formation over a long period by preventing excessive discharge and toner stain images, thereby maintaining image quality.
Implementation Method 1
a conveying screw that conveys the developer and includes a rotating shaft rotatably disposed in the developer container, a spiral first blade portion that conveys the developer in a first direction of the rotating shaft
Implementation Method 2
a circular portion that is disposed on the rotating shaft at an end portion of the disk portion distal from the second blade portion in an axial direction and whose end portion distal from the disk portion has an outer diameter larger than an outer diameter of the rotating shaft and smaller than an outer diameter of the disk portion
Data Source
AI summary
In the present invention, an image forming apparatus using a method of replacing a developer is configured such that an immobile area in which the heights of a discharge passage and a conveyance passage are changed on the upstream side of a returning screw is filled. This causes the immobile area of the developer to be unlikely to occur and accordingly suppresses formation of a toner stain image due to an aggregation toner, enabling stable image formation over a long period of time.