Resin Toothed Pulley Flange Structure to Prevent Core Slip
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Solution Overview
Problem
Existing toothed pulleys with a cylindrical metallic core and resin teeth face challenges in preventing relative rotation in the circumferential direction while maintaining accuracy and avoiding increased manufacturing costs, as methods like insert molding and knurling lead to thickness discrepancies and burrs, affecting weight and accuracy specifications.
Innovation Solution
A toothed pulley design featuring a cylindrical metallic core with an outward flange having a radially inward-displaced surface, covered by a resin portion, which prevents relative rotation without the need for post-processing like knurling, reducing weight and ensuring accuracy by minimizing resin thickness and differential shrinkage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If rectangular openings are formed on the outer periphery of the metal attachment member to prevent relative rotation, then the relative rotation is prevented, but burrs are generated requiring additional post-processing steps
Solution Approach 1:
The invention forms protrusions on the outer periphery of the metal attachment member before the insert molding process. These pre-formed protrusions serve as rotation prevention features during the subsequent resin injection, eliminating the need for post-processing to create rotation prevention features through rectangular openings.
Solution Approach 2:
The invention extracts the rotation prevention function from the insert molding process itself and implements it separately through pre-formed protrusions on the metal attachment member. This separation allows the protrusions to be formed independently, avoiding burr generation that would occur with rectangular openings.
2Stability of the object's composition
If the resin pulley body thickness is increased to prevent relative rotation, then the rotation prevention is improved, but the differential shrinkage increases reducing tooth accuracy
Solution Approach 1:
The invention applies local quality by forming protrusions only at specific locations on the outer periphery of the metal attachment member rather than increasing the overall resin pulley body thickness. This localized approach prevents relative rotation without increasing the radial thickness of the resin portion, thereby maintaining tooth accuracy and minimizing differential shrinkage.
3Stability of the object's composition
If the metal attachment member thickness is increased to prevent relative rotation, then the rotation prevention is improved, but the weight of the toothed pulley increases
Solution Approach 1:
The invention forms protrusions on the metal attachment member before the insert molding process to provide rotation prevention. These protrusions enable the use of a thinner metal attachment member compared to designs requiring increased thickness for rotation prevention, thereby reducing the overall weight of the toothed pulley while maintaining structural integrity.
4Stability of the object's composition
If knurling is applied on the outer peripheral surface of the metallic core to prevent relative rotation, then the relative rotation is prevented, but the manufacturing cost increases due to additional machining steps
Solution Approach 1:
The invention forms protrusions on the outer periphery of the metal attachment member as a preliminary action before the insert molding process. These protrusions provide rotation prevention functionality without requiring subsequent knurling or other post-molding machining operations, thereby reducing manufacturing complexity and cost.
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
The solution effectively prevents circumferential rotation of the metallic and resin components, reduces manufacturing costs, and maintains the required accuracy specifications for toothed pulleys in power transmission mechanisms.
Implementation Method 1
the resin pulley body 22 is formed by insert molding onto the radially outside of the metal attachment member 21 with the metal attachment member 21 as an insert article
Implementation Method 2
the molten resin enters the openings 21c and is solidified to prevent the metal attachment member 21 from turning in the circumferential direction
Data Source
Figure 1
Figure 2
Figure 3A~3B
AI summary
To prevent, in a toothed pulley including a cylindrical metallic core and a resin portion with teeth, the metallic core and the resin portion from relatively rotating in the circumferential direction, while securing the accuracy in the teeth and preventing the manufacturing cost from increasing. A toothed pulley A includes a cylindrical metallic core B and a resin portion C including teeth T. The metallic core B has, at one end thereof in the axial direction, an outward flange 1C projecting outward in the radial direction. The outward flange 1C has a radially outer peripheral surface M serving as a rotation prevention shape X including a plurality of parts displaced inward in the radial direction from the radially outer peripheral surface having a cylindrical shape. The radially outer peripheral surface M of the outward flange 1C is covered by the resin portion C.