Transfer Belt Wrinkle Control via Crowned Stretching Rollers
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Solution Overview
Problem
In image forming apparatuses using electrophotographic methods, low-stiffness recording materials like thin paper can experience image deterioration due to wrinkles forming in the transfer portion, leading to electrical discharges and uneven toner transfer.
Innovation Solution
The apparatus includes a configuration with a first belt and a second belt, where the first stretching roller has a crown shape with smaller diameters at the ends and the second stretching roller has an inverted crown shape with larger diameters at the ends, ensuring the secondary transfer belt is stretched evenly and reduces tension, thereby minimizing wrinkle formation and improving belt durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a separating roller with a relatively large crown amount is used to obtain a sufficient wrinkle stretching effect, then the wrinkle stretching effect is improved, but the service life of the transfer belt becomes shorter due to large tension and concentrated stress
Solution Approach 1:
The invention applies local quality by providing regulating ribs only at specific positions (both ends in the widthwise direction) of the transfer belt rather than uniformly across the entire belt. This localized structure provides necessary tension control and wrinkle prevention only where needed, reducing overall stress on the belt and extending its service life while maintaining effective wrinkle stretching.
Solution Approach 2:
The transfer belt is constructed as a composite structure with a base material and regulating ribs integrated into it. This composite design allows the belt to have different mechanical properties in different regions - the ribs provide structural support and tension control at critical areas while the base material maintains flexibility for wrinkle stretching, achieving both reliability and durability.
2Reliability
If large tension is imparted to the transfer belt to deform it along the peripheral surface of the crown shape, then the wrinkle stretching effect is improved, but the service life of the transfer belt becomes shorter due to concentrated stress
Solution Approach 1:
The regulating ribs are positioned only at both ends in the widthwise direction of the transfer belt, providing localized tension control. This creates a gradient in tension distribution across the belt width, with higher tension at the ends where wrinkles are most problematic and lower tension in the central area, reducing overall stress accumulation and extending belt life while maintaining wrinkle stretching effectiveness.
Solution Approach 2:
Instead of applying uniform tension across the entire transfer belt, the invention applies tension partially only at the end regions where regulating ribs are located. This partial action is sufficient to prevent wrinkles at the critical areas without subjecting the entire belt to excessive stress, thereby extending service life while achieving the necessary wrinkle stretching effect.
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 stretches wrinkles on low-stiffness recording materials, reducing image deterioration and extending the service life of the transfer belt by reducing the high tension that leads to premature wear.
Implementation Method 1
The toner image on the image bearing member is electrostatically transferred onto the recording material by nipping the recording material between the image bearing member and a transfer device in a transfer portion and forming a transfer electric field in the transfer portion
Implementation Method 2
ensuring the secondary transfer belt is stretched evenly and reduces tension, thereby minimizing wrinkle formation and improving belt durability
Data Source
AI summary
An image forming apparatus includes an image bearing member, a first belt to which a toner image is transferred, a first transfer roller in contact with an inner surface of the first belt, a second belt in contact with an outer surface of the first belt, and a second transfer roller to form a nip portion between itself and the first transfer roller through the second belt. First and second stretching roller are provided upstream and downstream of the second transfer roller in a rotational direction of the second belt, respectively. The first stretching roller includes a part, at both end portions in a rotational axis direction, of which a diameter is smaller than that of a central portion. The second stretching roller includes a part, at both end portions in the rotational axis direction, of which a diameter is larger than that of a central portion.