Developing Device Magnetic Flux Distribution for Carrier Deposition
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Solution Overview
Problem
Conventional image forming apparatuses using two-component developers face a challenge in maintaining developing efficiency while extending the developing region, as excessive electric field strength can lead to carrier deposition on the photosensitive drum, causing white dropout and impaired development.
Innovation Solution
The solution involves a developing device with a developing magnetic pole having a single peak of magnetic flux density, where the 80%-value-width is broader than the half peak width, ensuring linear extension of magnetic lines of force towards the photosensitive drum, preventing free ends of magnetic chains from extending along its surface and maintaining a high magnetic attraction force.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the electric field strength is enhanced to increase toner development amount, then developing efficiency is improved, but carrier deposition on the photosensitive drum occurs causing white dropout
Solution Approach 1:
The patent changes the magnetic flux density distribution parameters by making the 80%-value-width broader than the half peak width, which modifies the magnetic field characteristics to improve developing efficiency without increasing electric field strength, thereby avoiding carrier deposition
2Area of stationary object
If the developing region is extended by increasing the half peak width of the developing magnetic pole, then the developing region is expanded, but the magnetic lines of force become curved causing free ends of magnetic chains to contact the photosensitive drum along its surface
Solution Approach 1:
The patent applies local quality by creating a specific magnetic flux density distribution where the 80%-value-width is broader than the half peak width, ensuring that in the critical developing region the magnetic lines of force extend linearly while allowing the overall pole width to be increased for expanded developing region
3Area of stationary object
If the half peak width of the developing magnetic pole is made large to extend the developing region, then the developing region is increased, but developing efficiency decreases due to curved magnetic lines of force
Solution Approach 1:
The patent resolves this contradiction by changing the magnetic flux density distribution parameters to satisfy the relationship where 80%-value-width is broader than half peak width, which maintains linear magnetic lines of force in the developing region even with increased pole width, thereby preserving developing efficiency while extending the developing region
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 lowering of developing efficiency by ensuring proper contact and adherence of magnetic chains, allowing for an expanded developing region without toner impairment, thereby enhancing image formation quality.
Implementation Method 1
the developer is carried on a developing sleeve by a magnet (magnetic field generating means) fixedly provided in the developing sleeve and the magnetic carrier forms magnetic chains along magnetic lines of force of the magnetic field generating means
Implementation Method 2
the toner is deposited on the electrostatic latent image by a force of an electric field generated by a potential difference between the developing sleeve and the electrostatic latent image on the photosensitive drum
Implementation Method 3
charged toner is brought near to a photosensitive drum and is electrostatically deposited on an electrostatic latent image on the photosensitive drum
Data Source
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AI summary
The present invention relates to an image forming apparatus comprising: an image bearing member; an exposure device configured to expose said image bearing member to form an electrostatic latent image thereon; and a developing device including a rotatable developing member configured to carry and feed a developer containing toner and a carrier to develop the electrostatic latent image formed on said image bearing member, and a magnet provided non-rotatably and stationarily inside said rotatable developing member. Magnetic chains formed by the carrier, on said rotatable developing member, magnetized by said magnet contact the electrostatic latent image formed on said image bearing member in a developing region of said rotatable developing member. Said magnet includes a developing magnetic pole, an upstream magnetic pole arranged upstream of the developing magnetic pole with respect to a rotational direction of said rotatable developing member and adjacent to the developing magnetic pole, and a downstream magnetic pole arranged downstream of the developing magnetic pole with respect to the rotational direction of said rotatable developing member and adjacent to the developing magnetic pole. A magnetic flux peak, where a magnetic flux of the developing magnetic pole is maximum with respect to a normal direction of said rotatable developing member within a region, between the upstream magnetic pole and the downstream magnetic pole with respect to the rotational direction of said rotatable developing member and sandwiched by reverse positions where the polarity of the magnetic flux density with respect to the normal direction of said rotatable developing member is reversed, is only one, and a position of the magnetic flux peak exists within the developing region with respect to the rotational direction of said rotatable developing member. A ratio of an 80 %-value-width which is a width of a portion where the magnetic flux density of the developing magnetic pole with respect to the normal direction of said rotatable developing member is 80 % of the maximum of the magnetic flux density of the developing magnetic pole with respect to the normal direction of said rotatable developing member to a half peak width which is a width of a portion where the magnetic flux density of the developing magnetic pole with respect to the normal direction of said rotatable developing member is half of the maximum of the magnetic flux density of the developing magnetic pole with respect to the normal direction of said rotatable developing member is 0.65 or more.