Fixing Device Nip Forming Member Convex Shape
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Solution Overview
Problem
Conventional fixing devices in image forming apparatuses using electrophotographic technology often cause wrinkles in recording materials due to pressure differences across the width of the belt, leading to uneven toner fixation and image quality issues.
Innovation Solution
A fixing device with a non-rotatable nip forming member that includes a contact area with a convex downstream end portion and thinner end portions in the widthwise direction, which helps to maintain a consistent conveying rate and reduce wrinkles by optimizing the running direction of the belt and the conveying force.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If pressure is applied from both end portions of the belt in the widthwise direction to form the fixing nip portion, then the fixing function is achieved, but the belt wrinkles due to pressure difference in the widthwise direction
Solution Approach 1:
The nip forming member is designed with a convex downstream end portion that creates localized pressure distribution. The convex shape concentrates the pressing force at the downstream end, compensating for the natural pressure gradient along the belt and preventing wrinkles while maintaining effective fixing pressure where needed.
Solution Approach 2:
The nip forming member features an asymmetric convex downstream end portion that protrudes more than the upstream end. This asymmetric design creates a pressure distribution that counteracts the belt's natural tendency to wrinkle under uniform pressure, balancing the pressure across the belt width and preventing deformation.
2Stability of the object's composition
If the nip forming member has a convex downstream end portion, then the conveying rate is maintained consistently and wrinkles are suppressed, but the device complexity increases
Solution Approach 1:
The invention modifies the geometric parameters of the nip forming member by adding a convex downstream end portion. This shape modification changes the pressure distribution parameters and contact area parameters, optimizing the conveying characteristics and preventing belt wrinkles through controlled pressure variation.
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 the occurrence of wrinkles on the recording material, ensuring uniform toner fixation and improved image quality by adjusting the protruding amount of the downstream end portion based on the nip length and pressuring force, thereby maintaining a balanced conveying rate across the belt.
Implementation Method 1
a nip forming member configured to contact an inner peripheral surface of the belt and form the nip portion by being disposed opposite to the rotatable member
Implementation Method 2
fixing the toner image onto the recording material by application of heat and pressure
Implementation Method 3
fixing the toner image onto the recording material by application of heat and pressure
Data Source
AI summary
A fixing device includes a rotatable endless belt, a pressing roller and a fixing pad. The pressing roller contacts an outer peripheral surface of the belt and forms a nip portion in cooperation with the belt. A toner image is formed in the nip portion and fixed onto the recording material by application of heat and pressure. The fixing pad contacts an inner peripheral surface of the belt. The fixing pad includes a contact area in contact with the inner peripheral surface of the belt. The contact area includes a downstream end portion with respect to a conveyance direction of the recording material. The downstream end portion includes a central portion and both end portions with respect to a widthwise direction of the belt. The central portion locates downstream of the both end portions with respect to the conveyance direction.