Fixing Device Thrust Mechanism for Crease Reduction
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Solution Overview
Problem
Existing fixing devices in electrophotographic image forming apparatuses face challenges in effectively fixing toner images on recording media without causing creases or deformations, particularly when handling diverse media types like paper and resin sheets.
Innovation Solution
A fixing device comprising a cylinder member, a circulating member, and a pressing member with a nip forming portion and a thrusting portion, where the circulating member is pressed against the cylinder member to form a nip region, and the thrusting portion applies varying pressure to reduce bending deformation and crease formation by offsetting the deformation occurring in the nip region.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional fixing device nips the recording medium between the cylinder member and circulating member, then toner fixation is achieved, but creases and deformations occur on the recording medium
Solution Approach 1:
The thrusting portion applies a preliminary thrusting force to the circulating member at the thrusting position, which is upstream of the nip region. This preliminary action counteracts the bending deformation that would otherwise occur when the medium enters the nip region, thereby preventing crease formation while maintaining effective toner fixation
Solution Approach 2:
The pressing member is designed with different functional portions: a thrusting portion that applies force at the thrusting position and a nip forming portion that creates the nip region. This local differentiation allows the device to apply different types of forces at different locations, preventing creases while maintaining fixation quality
2Productivity
If the circulating member is pressed against the cylinder member to form a nip region, then toner fixation efficiency is improved, but bending deformation occurs in the nip region
Solution Approach 1:
The thrusting portion applies a counter-thrust force to the circulating member before it enters the nip region. This preliminary anti-action compensates for the bending deformation that occurs during nipping, allowing efficient toner fixation without permanent shape distortion
Solution Approach 2:
The thrusting portion acts as a counterbalancing mechanism that applies force in opposition to the deforming force generated in the nip region. By positioning the thrusting portion upstream and applying force in the opposite direction, the system neutralizes the harmful bending effects while preserving the beneficial fixation effects
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 ensures efficient toner fixation on various media types while minimizing crease formation and tension in the sheet, maintaining a flat profile and reducing the likelihood of deformation, thus enhancing the overall printing quality and media handling.
Implementation Method 1
a heat source, which heats a recording medium which holds an unfixed toner image on a surface
Implementation Method 2
a cylinder member, which has a shape of a cylinder and is elastically deformed in a direction of crushing the cylinder
Data Source
AI summary
A fixing device includes: a cylinder member that rotates in a circumferential direction thereof; a circulating member that circularly moves in a circumferential direction thereof and is pressed against the cylinder member; a heat source that heats a recording medium holding an unfixed toner image and nipped between the cylinder member and the circulating member; and a pressing member provided inside the circulating member, and including a nip forming portion that presses the circulating member against the cylinder member to form a nip region therebetween, and a thrusting portion that thrusts, upstream of the nip forming portion in a moving direction of the circulating member, and from inside the circulating member toward the cylinder member, the circulating member before being pressed against the cylinder member such that the thrust is greater in end portions of the circulating member than in a central portion of the circulating member.