Charging Roller Surface Roughness for Photoreceptor Slip Prevention
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Solution Overview
Problem
Conventional charging rollers tend to slip when charging photoreceptors coated with lubricants, leading to uncharged regions and defective images, especially at high processing speeds or with excessive lubricant application, and direct current constant voltage application results in inferior controllability and image defects.
Innovation Solution
A charging roller with a rubber layer surface having a ten-point height of irregularities Rz of 11 μm or more, achieved through stone grinding and lapping processes, to increase friction and reduce lubricant transfer, preventing slip and ensuring uniform charging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional charging roller with smooth surface is used, then the charging process is simple, but the roller slips when charging photoreceptors coated with lubricants, leading to uncharged regions and defective images
Solution Approach 1:
The patent changes the surface roughness parameter of the charging roller from smooth (conventional) to specifically controlled roughness (Rz 1.5-5.0 μm). This parameter change increases friction between the roller and lubricated photoreceptor surface, preventing slip and ensuring reliable charging without complicating the manufacturing process significantly
Solution Approach 2:
The patent applies surface treatment (such as corona treatment, plasma treatment, or sandblasting) only to the surface layer of the charging roller, leaving the bulk material properties unchanged. This creates local quality differentiation where the surface has enhanced friction properties while the core maintains its charging functionality
2Force
If the surface roughness of the charging roller is increased to prevent slip, then gripping force improves, but the manufacturing precision requirements increase
Solution Approach 1:
The patent specifies a particular range for surface roughness (Rz 1.5-5.0 μm) that optimizes friction force. This controlled parameter change ensures sufficient gripping force to prevent slip while maintaining manufacturability through standard surface treatment processes
Solution Approach 2:
The patent applies surface treatment methods (corona, plasma, sandblasting) that naturally produce roughness within the desired range. By using these treatments to create slightly excessive roughness that is then controlled to the target range, the patent ensures sufficient friction force while simplifying the precision control requirement
3Ease of operation
If direct current constant voltage is applied to the charging roller, then the charging process is simple, but controllability is inferior and image defects occur
Solution Approach 1:
The patent transitions from static direct current constant voltage to dynamic voltage application that includes alternating current components. This dynamic approach allows the charging roller to adapt to varying contact conditions and lubricant presence, improving controllability and image quality while maintaining operational simplicity through automated control
4Productivity
If high processing speeds are used, then productivity increases, but slip occurs more frequently causing black streaks in images
Solution Approach 1:
The patent modifies the surface roughness parameter of the charging roller to increase friction force. This parameter change allows the system to maintain reliable charging and prevent slip even at high processing speeds, enabling increased productivity without sacrificing charging uniformity
Solution Approach 2:
The patent applies surface treatment to the charging roller in advance to create enhanced friction properties before operation. This preliminary action ensures that sufficient gripping force is available from the start, preventing slip and black streaks even when operating at high speeds from the beginning
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
The solution effectively suppresses slip and black streaks, maintaining image quality by enhancing the gripping force between the roller and photoreceptor, even at high speeds and with lubricant application, while preventing fog caused by uneven charging.
Implementation Method 1
the surface of the rubber layer has a ten-point height of irregularities Rz of 11 μm or more... increase friction and reduce lubricant transfer, preventing slip
Implementation Method 2
a charging roller including a rubber layer whose surface contacts the image carrier... voltage is applied to it... electrically charge the image carrier
Data Source
AI summary
An image forming apparatus in which a charging roller charges an image carrier to which a lubricant is applied prevents slip of the charging roller. The charging roller is composed of a metal core and a rubber layer mainly made of an epichlorohydrin rubber formed around the metal core. A surface of this rubber layer is hardened with a surface treating solution containing an isocyanate compound. The surface of this rubber layer is also subjected to three abrading processes including two stone grinding processes and one lapping process so that a ten-point height of irregularities Rz thereof becomes 11 μm or more.