Development Device Buffer Area for Toner Concentration Uniformity

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Solution Overview

Problem

In image forming apparatuses, the uneven distribution of developer concentration in the supply channel leads to variations in image density due to the decrease in toner concentration downstream, causing substandard image quality.

Innovation Solution

A development device with a supply channel and a collecting channel, where the supply channel includes a conveyance area and a buffer area, with the buffer area positioned midway and inclined to prevent direct conveyance force, ensuring consistent developer supply to the development roller.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If multiple developer conveyance channels are used to maintain toner concentration, then toner concentration uniformity is improved, but developer amount uniformity deteriorates due to lack of collection in supply channel

Engineering Contradiction:

Improvetoner concentration uniformityVSAvoiddeveloper amount uniformity

Core Design Contradiction:

Manufacturing precisionVSQuantity of substance

Solution Approach 1:

The development device is divided into multiple functional channels: a supply channel for transporting fresh developer, a collection channel for collecting used developer, and a buffer area within the supply channel. This segmentation allows independent optimization of each channel's function to resolve the contradiction between concentration uniformity and amount uniformity.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The buffer area is positioned midway in the supply channel to temporarily store developer before it reaches the development roller. This preliminary storage action ensures that even if developer transport velocity varies, the development roller receives a consistent amount of developer, preventing amount uniformity issues while maintaining the multi-channel structure for concentration uniformity.

Inventive Principle:

Principle #10Preliminary action

2Quantity of substance

If developer conveyance velocity is increased in supply channel, then developer amount supplied is improved, but developer aggregation occurs causing uneven supply

Engineering Contradiction:

Improvedeveloper amount suppliedVSAvoiddeveloper distribution uniformity

Core Design Contradiction:

Quantity of substanceVSStability of the object's composition

Solution Approach 1:

The buffer area serves as a preliminary storage zone where developer is temporarily held before being supplied to the development roller. This preliminary action decouples the high-velocity transport from the actual supply point, allowing fast conveyance without causing aggregation at the supply interface.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The buffer area acts as an intermediary between the high-velocity conveyance system and the development roller. It mediates the transition by providing a transition zone where developer velocity is reduced and distribution is equalized, preventing aggregation while maintaining efficient transport.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Speed

If blade pitch of supply screw is reduced downstream, then developer conveyance velocity is improved upstream, but developer aggregation occurs

Engineering Contradiction:

Improvedeveloper conveyance velocityVSAvoiddeveloper distribution uniformity

Core Design Contradiction:

SpeedVSStability of the object's composition

Solution Approach 1:

The buffer area provides a preliminary deceleration zone where developer velocity is reduced before reaching the supply point. This preliminary action allows the use of aggressive blade pitch reduction upstream for high conveyance velocity without causing aggregation at the supply interface, as the buffer area serves as a velocity transition zone.

Inventive Principle:

Principle #10Preliminary action

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 maintains consistent toner concentration and prevents developer aggregation, resulting in improved image density and quality by separating and re-agitating the developer before re-supplying it to the development roller.

Implementation Method 1

an upstream end face defining an upstream end of the buffer area is inclined relative to the axial direction of the first developer conveyance member so as to draw away from the conveyance area downstream in the developer conveyance direction

Methodology Applied

Scientific EffectGravity: Gravitation

Data Source

PatentEP2560051B1Development device, and process cartridge and image forming apparatus including same

Publication Date: 2021.04.07 RICOH CO LTD

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Figure 2~3
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AI summary

A development device (3) includes a development casing (301), a developer bearer (302), a first developer conveyance member (304) to supply developer to the developer bearer (302), a second developer conveyance member (305) to transport developer axially, and a partition (306) dividing separating a supply channel (340) from a collecting channel (350). The supply channel (340) includes a conveyance area (341) and a buffer area (342) disposed adjacent to the conveyance area (341) in a direction perpendicular to an axial direction to temporarily retain developer and midway in the developer conveyance direction inside the supply channel (340), and an upstream end face (342f) defining an upstream end of the buffer area (342) is inclined relative to the axial direction to draw away from the conveyance area (341) downstream in the developer conveyance direction.