Developing Device Gap Retainer Sealing for Toner Leakage
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Solution Overview
Problem
Existing developing devices in image forming apparatuses face challenges in preventing developer scattering and electrical discharge, which affect image quality due to inadequate sealing and potential for toner accumulation, especially when using alternating current (AC) bias for developer transfer.
Innovation Solution
A developing device with a casing containing a developer container and a gap retainer that secures a predetermined gap to prevent developer scattering, combined with a sealing system including an end face seal, a contact portion, and a lateral end seal to inhibit leakage and electrical discharge, while using a conductive developer container to manage electrical charges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a gap retainer is used to secure a predetermined gap between the developer bearer and the casing, then developer scattering is prevented, but developer leakage may occur at the ends of the gap retainer
Solution Approach 1:
A flexible seal member is introduced at the end portion of the gap retainer to prevent developer leakage. The seal member comprises a seal portion made of elastic material that elastically contacts the casing, creating a flexible sealing barrier that prevents developer from leaking at the ends of the gap retainer while maintaining the predetermined gap functionality.
2Manufacturing precision
If high-voltage AC bias is applied for developer transfer, then image density is improved, but electrical discharge occurs causing operational issues
Solution Approach 1:
A ground electrode is introduced as an intermediary between the high-voltage AC bias system and the casing to prevent electrical discharge. The ground electrode is electrically connected to the casing through a grounding mechanism, acting as a discharge path that prevents electrical discharge while allowing high-voltage AC bias to be applied for improved image density.
3Reliability
If the gap retainer extends fully to prevent leakage, then developer containment is improved, but the structure becomes more complex and harder to assemble
Solution Approach 1:
The sealing function is segmented from the gap retainer structure by introducing a separate seal member. The seal member is a distinct component that can be independently manufactured and assembled, allowing the gap retainer to maintain its simple structural form while the seal member provides the necessary sealing function at the end portions.
4Reliability
If sealing structures are added to prevent developer leakage, then developer containment is improved, but the device complexity increases
Solution Approach 1:
A simple flexible seal member made of elastic material is used instead of complex rigid sealing structures. The seal member can be a simple ring or strip that elastically contacts the casing, providing effective sealing through material flexibility rather than complex geometric features, thereby maintaining simplicity while improving developer containment.
Data Source
AI summary
A developing device includes a developer bearer to carry, by rotation, developer to a developing range, a casing including a developer container to contain the developer and housing the developer bearer, a gap retainer adjacent to the developer container and downstream from the developing range in a rotation direction of the developer bearer, an opposing wall opposing an end face of the gap retainer in an axial direction of the developer bearer, a first seal disposed between the end face of the gap retainer and the opposing wall, and a contact portion disposed adjacent to an end portion of the gap retainer in the axial direction of the developer bearer. The gap retainer secures a predetermined gap between the developer bearer and the gap retainer. The contact portion contacts, via a second seal, the gap retainer in a direction intersecting the axial direction of the developer bearer.