Resin Gear Drive Member with Metal Insert for Torsional Rigidity
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Solution Overview
Problem
In image forming apparatuses, drive transmitting members made from resin experience rotation non-uniformity due to residual strain from differences in linear expansion coefficients and internal stress, leading to deformation and potential slip, which affects image quality.
Innovation Solution
A drive transmitting member is designed with a gear portion made of one resin and a flange portion made of another resin, where the flange portion includes a shaft portion and a rotation stopper that is larger than the shaft portion, and they are integrally molded, with the gear portion covering the rotation stopper and not overlapping with the shaft portion, to minimize axial displacement and stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a gear is made from resin to reduce weight and simplify manufacturing, then ease of manufacture is improved, but torsional rigidity deteriorates leading to rotation non-uniformity
Solution Approach 1:
The patent employs composite materials by integrating a metal insert within the resin gear body. The metal portion provides high torsional rigidity to prevent deformation under load, while the resin portion maintains ease of manufacture and weight reduction benefits. This composite structure resolves the contradiction between manufacturing simplicity and mechanical strength.
Solution Approach 2:
The gear is segmented into distinct functional zones: a resin body for manufacturing ease and weight, and a metal insert for torsional rigidity. The metal insert is positioned specifically at the core where it provides maximum structural support without interfering with gear tooth engagement, allowing each material to perform its optimal function.
2Strength
If a metal shaft is used to ensure torsional rigidity, then strength is improved, but residual strain and deformation occur due to differential thermal expansion with resin components
Solution Approach 1:
The patent addresses thermal expansion mismatch by designing the metal insert with specific geometric parameters and positioning it within the resin gear in a way that accommodates differential expansion. The insert's cross-sectional area and location are optimized to minimize stress concentration and prevent deformation during temperature variations and crystallization processes.
Solution Approach 2:
The metal insert acts as an intermediary element between the resin gear body and the drive shaft. It provides a stable interface that compensates for thermal expansion differences, preventing direct stress transmission from the resin to the shaft that would cause misalignment and rotation non-uniformity.
3Ease of manufacture
If the gear shrinks relative to the shaft due to residual strain, then manufacturing is simplified, but rotation non-uniformity increases affecting image quality
Solution Approach 1:
The composite structure of resin gear with metal insert prevents differential shrinkage between components. The metal insert maintains dimensional stability during cooling and crystallization, ensuring that the gear teeth remain properly aligned with the drive shaft throughout the manufacturing process and subsequent operation, thereby maintaining rotation uniformity.
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 reduces deformation and slip of the drive transmitting member, ensuring high torsional rigidity and sliding characteristics, thereby maintaining excellent image quality and endurance.
Implementation Method 1
residual strain is caused when a resin temperature at the time of molding is reduced to a normal temperature to cause shrinkage due to a difference between linear expansion coefficients of the resin
Implementation Method 2
since polyacetal resin is crystalline resin, the shrinkage further advances in a process where internal crystallization advances
Implementation Method 3
residual strain is caused when a resin temperature at the time of molding is reduced to a normal temperature
Implementation Method 4
ensuring high torsional rigidity and sliding characteristics
Data Source
AI summary
A drive transmitting member including: a gear portion that is formed of a first resin and has gear teeth; and a flange portion that is formed of a second resin, in which the flange portion includes a shaft portion that transmits driving force from the gear teeth to a drive transmitted member, and a rotation stopper (i) that stops rotation of the gear portion with respect to the flange portion at an outer periphery of the flange portion and (ii) that is larger than an external form of the shaft portion, so that the shaft portion and the rotation stopper are integrally molded in the flange portion, and the gear portion has a shape that covers the rotation stopper and is not overlapped with the shaft portion as viewed in an axial direction of the shaft portion.