Charging Roll Axial Positioning Support Member
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Solution Overview
Problem
In contact-type charging devices of image forming apparatuses, the frictional drive force from the rotating photosensitive drum causes the charging member to shift axially, leading to nip nonuniformity, load nonuniformity, and eventual image density unevenness due to abrasion of the photosensitive drum.
Innovation Solution
A support member, such as a cleaning member, is positioned on the downstream side of the nip portion between the image carrier and the charging roll, in contact with the charging roll on an upstream plane perpendicular to the axis of the image carrier, to prevent movement of the charging roll and maintain stable rotation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the charging member is elastically supported with a spring to press against the photosensitive drum, then the charging member can rotate with the photosensitive drum, but the frictional drive force causes the charging member to shift axially from its predetermined position
Solution Approach 1:
A support member is introduced as an intermediary component between the charging member and the photosensitive drum. This support member prevents axial displacement of the charging member while allowing it to rotate with the drum, thus resolving the contradiction between rotation following capability and axial position stability.
Solution Approach 2:
The support member applies a preliminary constraint force to prevent axial displacement before the frictional drive force can cause the charging member to shift position. This preliminary anti-action counteracts the harmful axial movement while preserving the beneficial rotational following function.
2Productivity
If the charging member shifts axially due to frictional drive force, then the charging member can follow the rotation of the photosensitive drum, but nip nonuniformity and load nonuniformity occur in the pressure-contact portion
Solution Approach 1:
The support member acts as a mediator that maintains proper axial positioning of the charging member during rotation. By preventing axial shift, it ensures uniform pressure contact between the charging member and photosensitive drum throughout the rotation cycle, eliminating nip nonuniformity while preserving charging functionality.
3Ease of operation
If the charging member varies its axial position relative to the photosensitive drum, then the charging member can rotate with the drum, but abrasion unevenness of the photosensitive drum occurs with time
Solution Approach 1:
The support member provides preliminary axial constraint to prevent the charging member from shifting position during rotation. This prevents uneven wear and abrasion on the photosensitive drum by maintaining consistent contact pressure, thereby extending the service life of the photosensitive drum while allowing the charging member to rotate with it.
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 prevents axial position variation of the charging roll, reducing nip and load nonuniformity, and minimizing image defects and abrasion of the photosensitive drum, while also simplifying the apparatus design and reducing costs by minimizing the number of components.
Implementation Method 1
The charging member rotates with following rotation of the photosensitive drum, using a contact frictional force in a pressure-contact part
Implementation Method 2
a charging member to which a charge voltage is applied is elastically supported with a spring so as to press the charging member against a photosensitive drum
Data Source
AI summary
An image forming apparatus includes a rotatable image carrier, a charging roll and a support member. The image carrier has a surface on which an electrostatic latent image is to be formed. The charging roll follows rotation of the image carrier. The charging roll charges the surface of the image carrier at a predetermined potential. The support member is in contact with the charging roll at a contact point. The contact point is on a downstream of a nip portion between the image carrier and the charging roll in a rotation direction of the charging roll. The contact point is on an upstream of a plane, which contains an axis line of the charging roll and is perpendicular to a plane defined by an axis line of the image carrier and the axis line of the charging roll.