Sheet Conveyance Device with Bent Driving Shaft for Nip Alignment
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Solution Overview
Problem
In image forming apparatuses, the misalignment of nip portions between center and side driven rollers causes creasing and skewing of document sheets, leading to improper image reading due to deformation of foam rubber center rollers and bending of the driving shaft.
Innovation Solution
A sheet conveyance device with driving rollers made of hard material and driven rollers, including center and side rollers with soft and hard materials respectively, where the driving shaft is bent downstream and tilted in a V-like shape to align nip portions, ensuring proper sheet alignment and feeding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the center driven rollers are made of foam rubber to provide soft contact, then the user can sense contact precisely, but the rollers deform under pressure causing misalignment of nip portions
Solution Approach 1:
The driven rollers are segmented into two types: center driven rollers made of foam rubber for soft contact sensing, and side driven rollers made of hard plastic for structural stability. This segmentation allows each component to fulfill its specific function without compromising the other.
Solution Approach 2:
Different materials are applied to different locations of the driven shaft system. The center portion uses soft foam rubber rollers for contact sensing, while the side portions use hard plastic rollers for maintaining precise nip alignment. This local differentiation resolves the contradiction between soft contact and alignment precision.
2Object-affected harmful factors
If the driving shaft is bent downstream to align nip portions, then creasing is reduced, but the sheet may still skew during insertion
Solution Approach 1:
The driving shaft is intentionally designed with an asymmetric bent shape, tilting in a V-like configuration downstream. This asymmetric geometry compensates for the deformation of foam rubber rollers and ensures that all nip portions (center and side) are aligned at the same height, preventing both creasing and skewing during sheet insertion.
Solution Approach 2:
The driving shaft incorporates a curved bent shape rather than a straight configuration. This curvature is specifically designed to offset the compression deformation of the soft center driven rollers, ensuring that the nip portions remain aligned despite the soft material deformation under operating pressure.
3Force
If the center driven rollers are pressed against driving rollers, then sheet conveyance force is provided, but the nip portions become misaligned in sub-scanning direction
Solution Approach 1:
The driving shaft is pre-bent downstream before operation begins. This preliminary geometric adjustment anticipates and compensates for the deformation that will occur when the foam rubber center driven rollers are pressed against the driving rollers during sheet conveyance, ensuring alignment is maintained under load.
Solution Approach 2:
The physical parameters of the driving shaft (its bent shape and tilt angle) are specifically designed to counterbalance the compression deformation of the soft center driven rollers. By adjusting the shaft's geometry, the system maintains proper nip portion alignment even as the roller materials deform under operational pressure.
Data Source
AI summary
In a sheet conveyance device, a plurality of driving rollers opposes a plurality of driven rollers to form nip portions between the plurality of driving rollers and the plurality of driven rollers. A center portion of a driving shaft for supporting the plurality of driving rollers in an axial direction of the driving shaft is bent downstream in a sheet conveyance direction so that the plurality of driving rollers is shifted downstream in the sheet conveyance direction and tilted with respect to the sheet conveyance direction in a V-like shape about a center line in a width direction of a sheet. The plurality of driven rollers is shifted downstream in the sheet conveyance direction by an amount determined by an amount by which the plurality of driving rollers is shifted downstream in the sheet conveyance direction.