Toner Conveyance Screw With Oversized Insertion Part
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Solution Overview
Problem
Toner leakage occurs in toner conveyance devices due to gaps between screws and bearings, leading to increased complexity and manufacturing costs when sealing members are used to mitigate this issue.
Innovation Solution
A toner conveyance device with a screw featuring a spiral fin and a downstream insertion part with a larger outer diameter than the fin's end portion, which is inserted into a bearing, shifting the gap radially outward to prevent toner leakage, while maintaining a simple configuration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a gap is provided between the screw and bearing to enable smooth rotation, then rotational smoothness is improved, but toner leakage increases
Solution Approach 1:
The invention shifts the gap from the radial dimension (where it causes toner leakage) to the axial dimension by making the insertion part longer than the fin width. This dimensional transformation allows the gap to exist without compromising sealing performance.
Solution Approach 2:
The screw shaft is segmented into two functional zones: the fin portion for toner conveyance and the longer insertion part for bearing support. This segmentation allows each zone to optimize its function independently without interfering with the other.
2Object-generated harmful factors
If a sealing member is added to prevent toner leakage, then toner leakage is suppressed, but device complexity and manufacturing cost increase
Solution Approach 1:
The screw shaft itself provides the sealing function through its extended insertion part, eliminating the need for separate sealing components. The structure serves multiple functions: support, rotation enablement, and toner leakage prevention.
Solution Approach 2:
The insertion part performs multiple functions simultaneously: it supports the bearing for smooth rotation and acts as a seal to prevent toner leakage. This multi-functionality reduces the overall component count and simplifies the device structure.
3Object-generated harmful factors
If the insertion part outer diameter is made larger than the fin end portion, then toner leakage is prevented, but screw dimensions change
Solution Approach 1:
The screw shaft has different diameters at different locations: the fin portion maintains its original diameter for toner conveyance, while the insertion part has a larger diameter for bearing support and sealing. This local variation optimizes each section's function.
Solution Approach 2:
The extended insertion part is designed in advance to protrude beyond the fin width, creating a built-in seal before toner leakage can occur. This preliminary structural arrangement prevents the problem rather than correcting it.
Data Source
AI summary
An image forming apparatus (1) includes a casing (21) having a toner conveyance path (34); a screw (24) conveying a toner in the toner conveyance path (34) in a predetermined conveyance direction; and a downstream side bearing (25) rotatably supporting a downstream side end portion of the screw (24) in the conveyance direction, wherein the screw (24) includes: a shaft (51) extending in the conveyance direction; and a spiral fin (52) provided around an outer circumferential face of the shaft (51), the shaft (51) has a downstream side insertion part (54) inserted into the downstream side bearing (25), and the downstream side insertion part (54) has an outer diameter larger than an outer diameter of a downstream side end portion of the fin (52) in the conveyance direction.