Fixing Apparatus Belt Back-Up Member Curvature
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Solution Overview
Problem
Fixing devices with a belt backing member in electrophotographic machines often produce image defects known as 'cracking' due to wrinkling of the fixation belt's surface layer, which causes toner particle displacement and adhesion issues, especially with increased belt thickness for higher speed and image quality demands.
Innovation Solution
A fixing apparatus with a cylindrical belt and a back-up member that forms a first convex surface towards the roller in the upstream region and a second convex surface towards the back-up member in the downstream region within the fixing nip, minimizing belt compression and wrinkling, thereby reducing image defects and facilitating easy separation of the recording material.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a belt backing member is used to form a nip in the fixing device, then the fixing device can maintain structural stability and achieve reliable toner fixation, but the outward surface layer of the fixation belt wrinkles due to compression, causing image defects known as 'cracking'
Solution Approach 1:
The belt backing member is designed with different surface configurations for different regions: a first surface in the upstream region that reduces compression of the outward surface layer, and a second surface in the downstream region that maintains compression to prevent wrinkles. This local differentiation allows the same component to simultaneously prevent image defects in the upstream region while maintaining fixation reliability in the downstream region.
2Productivity
If the fixation belt is made thicker to meet higher speed and image quality demands, then the fixing device can operate at higher speeds and maintain image quality, but the compression of the outward surface layer increases, leading to more severe wrinkling and image defects
Solution Approach 1:
The belt backing member's first surface is specifically designed to reduce compression on the outward surface layer in the upstream region where the belt is thicker. This allows the belt to maintain its thicker construction for high-speed operation and image quality while preventing the excessive compression that would cause wrinkling in the critical upstream region.
3Manufacturing precision
If the outward surface layer of the fixation belt is compressed to form a nip, then toner particles can be effectively fixed to the recording medium, but the compression causes wrinkles in the surface layer that displace toner particles and create image defects
Solution Approach 1:
The belt backing member creates different compression conditions in different regions: reduced compression in the upstream region to prevent wrinkles and toner displacement, and maintained compression in the downstream region to ensure effective toner fixation. This spatial differentiation of compression levels allows the system to achieve both high image quality and effective fixation.
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 image defects caused by belt surface creasing and ensures easy separation of the recording material from the fixation belt, maintaining image quality even at higher speeds.
Implementation Method 1
a recording material carrying an unfixed toner image is nipped and fed through the fixing nip, during which the unfixed toner image on the recording material is heated and fixed thereon by the fixing nip
Implementation Method 2
said roller being provided with an elastic layer, said roller being cooperative with said back-up member to sandwich said belt and form a fixing nip between said belt and said roller
Data Source
AI summary
A fixing apparatus includes a back-up member contacting an inner surface of a cylindrical belt; a roller having an elastic layer and contacting an outer surface of the belt, the roller being cooperative with the back-up member to form a fixing nip between the belt and the roller. A sheet carrying a toner image is nipped and fed through the fixing nip, during which the unfixed toner image is heat-fixed thereon by the fixing nip. The back-up member includes a portion contactable with the inner surface and having such a configuration that the belt forms a first curved surface convex toward the roller in an upstream region in the fixing nip with respect to a moving direction of the belt and that the belt forms a second curved surface convex toward the back-up member in a downstream region in the fixing nip with respect to the moving direction.