Fixing Device Pad Positioning for Thermal Expansion Gap Control
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Solution Overview
Problem
Existing fixing devices face challenges in enhancing the separation property of recording materials with small basis weights, such as thin paper, from the fixing belt due to thermal expansion of the pad member, which increases the gap between the separation plate and the fixing belt, thereby reducing the effectiveness of separation.
Innovation Solution
A fixing device with a rotatable fixing belt and a pressing pad supported by a metal stay, where one component has a projection and the other a recess or hole to determine the pad's position, reducing the thermal expansion impact by positioning the pad closer to the downstream end, thus minimizing the gap between the separation plate and the belt.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the separation plate is brought closer to the fixing belt to enhance separation property, then separation performance is improved, but thermal expansion of the pad member causes contact between the separation plate and fixing belt
Solution Approach 1:
The pad member is positioned upstream relative to the separation plate, establishing its initial position before thermal expansion occurs. This preliminary positioning allows the downstream end of the pad to naturally curve away from the separation plate during heating, preventing contact while maintaining close proximity for effective separation
Solution Approach 2:
The downstream end of the pad member is designed with a curved surface that naturally forms an arc shape during thermal expansion. This curvature directs the expansion away from the separation plate, allowing the pad to approach closer to the separation plate without causing harmful contact
2Reliability
If the pad member is thermally expanded to improve nip formation, then fixing performance is enhanced, but the gap between separation plate and fixing belt increases
Solution Approach 1:
Different portions of the pad member have different functional characteristics: the upstream portion provides uniform pressing for nip formation, while the downstream curved end provides controlled thermal expansion that curves away from the separation plate. This local differentiation allows fixing performance enhancement without increasing the gap
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 reduces the thermal expansion-induced gap, improving the separation performance of thin papers and other lightweight recording materials by maintaining a stable separation distance, even under thermal expansion, thereby enhancing the separation efficiency.
Implementation Method 1
a heating roller including a heater, wherein the belt is entrained around the heating roller to heat the belt
Implementation Method 2
the pad member is heated and thus is thermally expanded
Data Source
AI summary
A toner image fixing device include a fixing belt; a heating roller training the belt around; a pressing pad of resin material provided inside the belt; a rotatable pressing member contacting the belt and pressing against the pad through the belt to form a nip for nipping and feeding the sheet; a supporting stay supporting the pad and including a surface contacting the pad, one of the pad and the stay being provided with a projection, and the other being provided with a recess engaged with the projection at an engaging position; and a separation plate provided without contact to the belt at a position opposed to the pad downstream of the nip in the sheet feeding direction. A distance between the engaging position and a downstream end of the pad is 0-35% of a length of the pad measured along the feeding direction.