Fixing Device Guide Member Geometry for Sheet Posture Control
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Solution Overview
Problem
Image forming apparatuses with height-direction conveyance paths face issues with curling and waving of recording sheets due to unstable posture after passing through the fixing device, leading to undesirable appearances and potential jams, and conventional solutions require additional components increasing costs and complexity.
Innovation Solution
A fixing device with a specific geometric configuration of guiding members, including a heating rotary member, a pressurizing rotary member, and guiding members that control the recording sheet's posture by adjusting the distance and angle of guiding surfaces to prevent curling and waving, eliminating the need for intermediate rollers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If intermediate rollers are added to correct recording sheet posture after fixing, then curling and waving are suppressed, but device complexity and cost increase
Solution Approach 1:
The patent removes the intermediate rollers (extraction of unnecessary components) and replaces them with a specifically designed guide member structure. The guide member includes a guide surface with specific geometric parameters (distance D between 1.6-2.4 times the heating roller diameter, and angle α between 2.2°-6.5°) that passively corrects recording sheet posture through its shape alone, eliminating the need for active intervention by intermediate rollers.
Solution Approach 2:
The patent changes the geometric parameters of the guide member (distance D and angle α) to optimize recording sheet posture control. By carefully selecting these parameters within specific ranges, the guide member can effectively suppress curling and waving without requiring additional rollers, thus resolving the contradiction between reliability and device complexity.
2Manufacturing precision
If intermediate rollers are added to suppress curling and waving, then recording sheet appearance quality improves, but manufacturing cost increases
Solution Approach 1:
The patent extracts the intermediate rollers from the fixing device structure and replaces them with a guide member that has built-in posture correction capability through its geometric design. This reduction in component count directly lowers manufacturing cost while maintaining or improving recording sheet flatness through the optimized guide surface parameters.
Solution Approach 2:
The guide member with specific geometric parameters serves as a simple, cost-effective solution compared to complex mechanical systems involving multiple rollers. The guide member's shape alone provides the necessary posture correction, making it a cheaper and more manufacturable solution.
3Volume of moving object
If the recording sheet is conveyed upward after fixing, then compact apparatus design is achieved, but recording sheet posture becomes unstable causing curling and waving
Solution Approach 1:
The patent changes the geometric parameters of the guide member (distance D and angle α) to compensate for the instability caused by upward conveyance. The specific parameter ranges (D: 1.6-2.4 times heating roller diameter, α: 2.2°-6.5°) are optimized to maintain recording sheet posture stability in the compact vertical configuration without requiring additional rollers.
Solution Approach 2:
The patent uses the guide surface's three-dimensional geometry (distance and angle parameters) to control recording sheet posture in the vertical conveyance direction. By designing the guide member's shape in multiple dimensions, it can effectively counteract the instability caused by upward conveyance while maintaining compact apparatus design.
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
Effectively suppresses curling and waving of recording sheets by optimizing the guiding members' position and geometry, maintaining a compact design while reducing costs and improving sheet alignment and discharge efficiency.
Implementation Method 1
a heating rotary member; a pressurizing rotary member that forms a nip by coming in contact with the heating rotary member
Implementation Method 2
the recording sheet is corrected in posture by the pair of intermediate rollers 504 applying suitable tension to the recording sheet
Data Source
AI summary
A fixing device comprises: a heating rotary member and a pressurizing rotary member, which form a nip, and guiding members for guiding a recording sheet that has passed through the nip. In a cross-section perpendicular to a rotation axis of the heating rotary member, La connects axial centers of two rotary members, Lb is perpendicular to La, P is on a guiding surface of one of the guiding members and horizontally closer to the pressurizing rotary member than any other points thereon, said one of the guiding members being closer to the heating rotary member than the other, Lc passes through P and is tangent to an outer circumference of the heating rotary member near the nip, and D is a P-La distance. Here, heating rotary member diameter×1.6≦D<heating rotary member diameter×2.4. Above the nip, Lc leans further toward the heating rotary member than Lb, and 2.2°≦angle between Lc and Lb<6.5°.