Photosensitive Drum Speed Control for Image Density Uniformity
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Solution Overview
Problem
Image forming apparatuses face issues with image expansion and contraction due to changes in external forces affecting the recording material, leading to density non-uniformity, especially in high-resolution printing where precise control of the peripheral speed of the photosensitive drum and the moving speed of the recording material is crucial.
Innovation Solution
The apparatus adjusts the surface movement speed of the photosensitive drum and the exposure interval prior to changes in the recording material's moving speed at the transfer portion, ensuring that the image forming apparatus maintains consistent image magnification and density by anticipating and compensating for external forces such as frictional and tensile forces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the photosensitive drum rotates at a constant speed, then the scanning interval of the polygon mirror is maintained at a constant level, but the image contracts or expands when the recording material moving speed changes due to external forces
Solution Approach 1:
The photosensitive drum rotation speed is changed from constant to variable, dynamically adjusting the peripheral speed to match changes in recording material moving speed caused by external forces, thereby maintaining consistent image magnification despite speed variations
Solution Approach 2:
The system detects changes in recording material moving speed (caused by external forces like friction and tension) and uses this information to adjust the photosensitive drum rotation speed, creating a feedback loop that maintains synchronization between drum surface speed and material speed
2Adaptability or versatility
If the recording material moving speed changes due to external forces, then the frictional and tensile forces affect the speed, but this causes image expansion and contraction leading to density non-uniformity
Solution Approach 1:
The system anticipates the effect of external forces (friction and tension) on recording material speed by detecting speed changes and preemptively adjusting the photosensitive drum rotation speed to compensate, preventing image expansion or contraction before they occur
Solution Approach 2:
The peripheral speed of the photosensitive drum is changed as a variable parameter in response to detected changes in recording material speed, allowing the system to adapt to external forces while maintaining constant image magnification and density uniformity
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 suppresses image expansion and contraction, resulting in output images that are free from density non-uniformity, even at high resolutions, by synchronizing the speeds and intervals to match the external forces' impact on the recording material.
Implementation Method 1
an exposure portion (3) configured to expose the photosensitive member to light depending on image information to form a latent image on the photosensitive member
Implementation Method 2
a developing portion (4) configured to develop the latent image into a toner image with toner
Implementation Method 3
a transfer portion configured to transfer the toner image from the photosensitive member onto a recording material
Data Source
AI summary
An image forming apparatus includes a photosensitive member; an exposure portion configured to expose the photosensitive member to light depending on image information to form a latent image on the photosensitive member; a developing portion configured to develop the latent image into a toner image with toner; and a transfer portion configured to transfer the toner image from the photosensitive member onto a recording material. The image forming apparatus changes a surface movement speed of the photosensitive member at timing prior to predetermined timing, when a moving speed of a recording material at the transfer portion changes, by a predetermined time.