Charging Roller Speed Switching to Prevent Drum Black Spots
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Solution Overview
Problem
Conventional electrophotographic image forming apparatuses suffer from image defects due to foreign substances adhering to the charging roller, which repeatedly damage the photosensitive drum at specific circumferential lengths, especially when connected via a gear train, leading to issues like black spot images.
Innovation Solution
The apparatus includes a control unit that controls the rotational speed of the photosensitive drum and charging member, switching between a first and second rotational speed to remove foreign substances from the charging roller during non-image forming operations, enhancing cleaning efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the photosensitive drum and charging roller are connected by a gear train, then the charging roller can be driven at a different circumferential speed to prevent excessive toner adhesion, but foreign substances on the charging roller repeatedly damage the photosensitive drum at specific circumferential lengths, causing image defects
Solution Approach 1:
The patent applies dynamics by making the circumferential speed relationship between the photosensitive drum and charging roller variable rather than fixed. The control unit dynamically adjusts the charging roller's rotational speed during non-image forming operations to create speed variations that prevent foreign substances from repeatedly contacting the same position on the photosensitive drum, thereby eliminating periodic image defects while maintaining reliable charging uniformity
Solution Approach 2:
The patent changes the operational parameters of the charging roller by varying its circumferential speed relative to the photosensitive drum. During non-image forming operations, the charging roller is rotated at different speeds to alter the contact pattern between foreign substances on the charging roller and the photosensitive drum surface, preventing repeated damage at specific circumferential lengths and thus preventing image defects
2Stability of the object's composition
If the charging roller rotates at a fixed speed, then the image forming operation is stable, but foreign substances adhering to the charging roller repeatedly damage the photosensitive drum, causing black spot images
Solution Approach 1:
The patent implements periodic action by introducing periodic speed variations of the charging roller during non-image forming operations. This periodic change in rotational speed creates varying contact patterns between foreign substances on the charging roller and the photosensitive drum, preventing the formation of stationary black spots while maintaining overall image forming stability through controlled operational cycles
3Productivity
If the photosensitive drum is continuously rotated at a constant speed, then image formation is efficient, but foreign substances on the charging roller have sufficient time to adhere and damage the photosensitive drum surface
Solution Approach 1:
The patent applies preliminary action by performing preventive speed variation of the charging roller during non-image forming operations before foreign substances can cause damage during image formation. This preliminary adjustment of rotational speed eliminates foreign substances from the charging roller surface in advance, ensuring photosensitive drum integrity is maintained during subsequent high-efficiency image formation operations
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 approach effectively prevents image defects by quickly removing foreign substances, reducing the occurrence of black spots and maintaining image quality.
Implementation Method 1
a charging member configured to form a charging portion by having contact with the photosensitive drum, and to charge a surface of the photosensitive drum at the charging portion
Implementation Method 2
the control unit performs control in such a manner as to perform a switch operation of stopping the photosensitive drum in a state in which the photosensitive drum is driven, while a non-image forming operation to be executed after the image forming operation is executed, and rotationally driving the photosensitive drum again at a second rotational speed faster than the first rotational speed
Data Source
AI summary
An image forming apparatus includes a photosensitive drum, a charging member, a developing member, a transfer member, first and second gears, a drive source, and a control unit. The charging member contacts the photosensitive drum and forms a charging portion to charge a surface of the photosensitive drum. The control unit performs control in such a manner that an image forming operation of performing image formation by rotating the photosensitive drum at a first rotational speed is executable. Where the control unit executes the image forming operation, the control unit performs a switch operation of stopping the photosensitive drum in a state in which the photosensitive drum is driven, while a non-image forming operation to be executed after the image forming operation is executed, and rotationally driving the photosensitive drum again at a second rotational speed faster than the first rotational speed, a plurality of times.