Spiral Shaft Coupling Surface Roughness for Stable Rotation
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Solution Overview
Problem
Existing image forming apparatuses face instability in transmitting driving force due to inclination of drive transmitting surfaces during forward and reverse rotations of shaft couplings, leading to inefficient power transmission.
Innovation Solution
The apparatus employs a detachable unit with a driven side shaft coupling featuring spiral-shaped receiving surfaces and a drive side shaft coupling with spiral-shaped transmitting surfaces, where the second transmitting and receiving surfaces are rougher than the first, ensuring stable power transmission during both rotational directions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If shaft couplings are manufactured by resin injection molding with undercut processing to achieve twisted shape, then manufacturing productivity and ease of manufacture are improved, but the drive transmitting surfaces develop inclination that causes force separation during rotation
Solution Approach 1:
The shaft coupling is divided into two distinct functional surfaces: a first drive transmitting surface for forward rotation and a second drive transmitting surface for reverse rotation. Each surface is optimized independently - the first surface has a smooth finish for efficient power transmission, while the second surface has a rough finish to prevent separation during reverse rotation, resolving the contradiction between manufacturing ease and transmission reliability
Solution Approach 2:
Different surface qualities are applied to different regions of the shaft coupling. The first drive transmitting surface is manufactured with a smooth finish (low roughness) for efficient power transmission during forward rotation, while the second drive transmitting surface is manufactured with a rough finish (high roughness) to prevent separation during reverse rotation. This local differentiation resolves the contradiction by optimizing each surface for its specific functional requirement
2Loss of energy
If shaft coupling surfaces are made smooth for efficient power transmission, then power transmission efficiency is improved, but stability during reverse rotation deteriorates due to separation forces
Solution Approach 1:
The shaft coupling employs different surface roughness values at different locations: the first drive transmitting surface has a smooth finish (Ra ≤ 0.8 μm) to minimize energy loss during forward rotation, while the second drive transmitting surface has a rough finish (Ra ≥ 1.6 μm) to prevent separation and ensure reliability during reverse rotation. This local quality differentiation simultaneously achieves low energy loss and high reliability
3Ease of operation
If the shaft coupling is designed to rotate in opposite direction for cleaning, then cleaning effectiveness is improved, but stable power transmission deteriorates due to force separation on the drive surfaces
Solution Approach 1:
The shaft coupling is segmented into two functional surfaces optimized for opposite rotation directions. The first surface (smooth) handles forward rotation for image formation, while the second surface (rough) handles reverse rotation for cleaning. This segmentation allows the cleaning function to operate reliably without compromising power transmission stability in either direction
Solution Approach 2:
The surface roughness parameter is changed between the two drive transmitting surfaces. The first surface has low roughness for efficient forward rotation, while the second surface has high roughness to prevent separation during reverse rotation. This parameter change enables the shaft coupling to maintain reliable power transmission during both forward rotation (image formation) and reverse rotation (cleaning operation)
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 enables stable drive force transmission during both forward and reverse rotations, preventing separation of surfaces and maintaining efficient operation even when forces act in directions that would otherwise cause disengagement.
Implementation Method 1
the second transmitting surface and the second receiving surface are rougher than the first transmitting surface and the first receiving surface
Data Source
AI summary
Disclosed is an image forming apparatus including a detachable unit having a rotator with a driven shaft coupling and a drive unit having a drive shaft coupling to engage with the driven shaft coupling and providing a force to the rotator via the drive shaft coupling. The driven shaft coupling includes spiral first and second receiving surfaces. The drive side shaft coupling includes a spiral first transmitting surface, which contacts the first receiving surface and provides a rotational force in a first rotational direction to the driven shaft coupling, and a spiral second transmitting surface, which contacts the second receiving surface and provides a force in the second rotational direction opposite to the first rotational direction to the driven shaft coupling when the drive shaft coupling rotates in the second rotating direction. The second transmitting and receiving surfaces are rougher than the first transmitting and receiving surfaces.