Elastomer Pressure Roll Nip Width Uniformity in Fixing Devices
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Solution Overview
Problem
Conventional fixing devices in image forming apparatuses face issues with uneven nip width distribution, leading to nonuniform heat supply and potential creases on recording media, especially when increasing speed, as methods to widen the nip often result in shape deflection and longer warm-up times.
Innovation Solution
A fixing device with a rotatable member and a tubular member that applies pressure using an elastomer pressure pad, where the end position of one elastomer surface is positioned further upstream in the transport direction than the other, ensuring consistent pressure distribution and reducing crease generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If the load between the fixing roll and the pressure roll is increased to increase the nip width, then the nip width increases, but the shape of the nip width becomes nonuniform along the roll axis due to roll deflection, causing uneven fixing and creases
Solution Approach 1:
The pressure roll is constructed with a flexible elastomer layer (5-15 mm thickness) over a core, allowing the roll surface to conform and distribute pressure uniformly without rigid deflection. This flexible structure maintains consistent nip width across the roll axis while accommodating the increased load required for high-speed fixing.
2Length of stationary object
If the thickness of the elastomer layer of the fixing roll is increased to increase the nip width, then the nip width increases, but the shape of the nip width becomes nonuniform along the roll axis, causing uneven fixing and creases
Solution Approach 1:
The pressure roll utilizes a carefully engineered elastomer layer thickness (5-15 mm) that provides sufficient flexibility for uniform pressure distribution while preventing excessive deflection. This optimized thickness ensures consistent nip width morphology along the entire roll axis during high-speed operation.
3Length of stationary object
If the diameter of the rolls is increased to increase the nip width, then the nip width increases, but the apparatus size is enlarged and the warm-up time from room temperature to fixable temperature becomes long
Solution Approach 1:
Instead of increasing roll diameter to widen the nip, the invention increases the elastomer layer thickness in the radial dimension. This allows achieving the required nip width (15-30 mm) without proportionally increasing the overall roll diameter, thereby maintaining compact apparatus size and reducing thermal mass for faster warm-up.
Solution Approach 2:
The flexible elastomer layer provides the necessary nip width through its compressible thickness rather than through large roll diameter, enabling high-speed fixing with reduced thermal mass and shorter warm-up time while maintaining uniform pressure distribution.
4Productivity
If the speed is increased in the heating roll type fixing device, then the productivity increases, but the nip width must be increased in proportion to maintain sufficient heat supply, which causes nonuniform nip shape and creases
Solution Approach 1:
The elastomer layer in the pressure roll provides compliant pressure distribution that maintains uniform nip width even at high fixing speeds. The flexibility allows the roll to adapt to speed variations without creating the nonuniform deflection patterns that cause creases, enabling productivity increase without sacrificing image quality.
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 maintains consistent pressure distribution across the nip width, improving image quality and reducing crease formation while allowing for increased speed without elongating warm-up times.
Implementation Method 1
the pressure member is made of an elastomer
Implementation Method 2
a fixing roll 110 that includes a heating source 113 inside a cylindrical core
Data Source
AI summary
Provided is a fixing device including a rotatable rotating member, a tubular member that is movable while coming into contact with the rotating member, a pressure member that is arranged inside the tubular member and nips a recording medium holding an unfixed toner image at a nip portion formed between the rotating member and the tubular member by bringing the tubular member into pressure contact with the rotating member, to apply pressure for fixing the unfixed toner image on the recording medium, and a holding member that holds the pressure member, wherein the pressure member is made of an elastomer, and the end position of one surface of the elastomer that comes into contact with the tubular member is located further toward the upstream side in the transport direction of the recording medium than the end position of the other surface of the elastomer held by the holding member.