Image-Forming Gear Spacer Structure for Sink Mark and Wear Reduction
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Solution Overview
Problem
Existing image forming apparatuses face challenges in maintaining gear accuracy and strength while minimizing sink marks and abrasion due to the direct support of large-diameter gears, leading to increased noise and material costs.
Innovation Solution
The image forming apparatus employs a dual-component gear structure where a gear member is supported by a shaft member through a spacer, utilizing a retaining structure with a snap-fit and a rotation-preventing structure to restrict relative movement, ensuring stable support and preventing gear slippage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a large-diameter gear is made as a single resin-molded member and directly supported by a shaft member, then the gear structure is simple and manufacturing is easy, but sink marks occur reducing molding accuracy and gear strength declines due to required thinning
Solution Approach 1:
The gear assembly is segmented into multiple components: a gear member (first member) with gear teeth, a reinforcement member (second member) inserted into a hole in the gear member, and a shaft member. The reinforcement member is engaged with the gear member through engaging portions and engaged portions, creating a segmented structure that eliminates sink marks while maintaining manufacturing simplicity.
Solution Approach 2:
The reinforcement member acts as an intermediary component between the gear member and the shaft member. It is inserted into the gear member's hole and engaged with both the gear member (via engaging portions) and the shaft member (via engaged portions), serving as a mediator that transmits rotational force while preventing relative movement and eliminating the need for direct gear-shaft engagement that causes sink marks.
2Device complexity
If the gear is directly supported by the shaft member, then the support structure is simple, but abrasion occurs between the gear and shaft leading to increased noise and reduced service life
Solution Approach 1:
The reinforcement member serves as an intermediary that prevents direct contact between the gear member and shaft member. The engaged portions of the reinforcement member engage with the shaft member, creating a controlled support interface that eliminates abrasive wear between the gear and shaft, reducing noise, and extending service life while maintaining structural simplicity.
Solution Approach 2:
The harmful direct contact interface between the gear member and shaft member is extracted and replaced by the reinforcement member. The reinforcement member is taken out as a separate component that mediates the interaction, removing the source of abrasion while maintaining the necessary support and force transmission functions.
3Reliability
If engaging portions and engaged portions are provided in overlapping axial ranges, then relative movement is effectively restricted in both axial and circumferential directions, but the structure becomes more complex
Solution Approach 1:
The first restricting structure (engaging portion and engaged portion for axial direction) and the second restricting structure (engaging portion and engaged portion for circumferential direction) are merged into a single reinforcement member component. This integration achieves effective restriction of relative movement in both axial and circumferential directions while avoiding the complexity of separate independent restricting mechanisms.
Solution Approach 2:
The reinforcement member is designed as a universal component that simultaneously performs multiple functions: it reinforces the gear member structure, prevents axial movement through first engaging portions, prevents circumferential movement through second engaging portions, and transmits rotational force from the shaft member. This multi-functionality reduces overall structural complexity while achieving reliable movement restriction.
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 gear accuracy, reduces noise, and minimizes material costs by preventing sink marks and abrasion, while ensuring stable gear operation and extended service life.
Implementation Method 1
an inner circumferential surface slidably coming into contact with an outer circumferential surface of the shaft member
Data Source
AI summary
A first gear includes a gear member and a spacer provided inside the gear member with respect to a direction that is perpendicular to an axial direction, and the first gear is rotatably supported by a shaft member by having the spacer slidably come into contact with the shaft member. As a retaining structure, the gear member and the spacer include a snap-fit and a first engaging portion that engages with the snap-fit, and, as a rotation-preventing structure, include a slit and a second engaging portion that engages with the slit. In the first gear, a range, in the axial direction, of a portion provided with the retaining structure and a range, in the axial direction, of a portion provided with the rotation-preventing structure at least partially overlap with each other in the axial direction.