Toothed Pulley Flange Geometry to Prevent Core-Resin Slip
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Solution Overview
Problem
Existing toothed pulleys with a cylindrical metallic core and a resin portion with teeth face challenges in preventing relative rotation in the circumferential direction while maintaining high accuracy and avoiding increased manufacturing costs.
Innovation Solution
A toothed pulley design featuring a cylindrical metallic core with an outward flange having a radially outer peripheral surface with inwardly displaced parts, which is covered by the resin portion, preventing relative rotation and reducing manufacturing costs by eliminating the need for post-processing like knurling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If rectangular openings are formed in the metal attachment member and resin is inserted to prevent rotation, then relative rotation is prevented, but burrs are generated requiring additional post-processing steps
Solution Approach 1:
The outward flange is formed with a radially outer peripheral surface having parts displaced inward from the cylindrical shape before resin insertion. This preliminary shaping creates mechanical interlocking features that prevent rotation during the molding process itself, eliminating the need for post-processing to remove burrs from rectangular openings.
Solution Approach 2:
The radially outer peripheral surface is divided into multiple parts, with some parts displaced inward from the cylindrical shape. This segmentation creates multiple contact points and mechanical interlocking features between the metal attachment member and resin, providing effective rotation prevention without requiring rectangular openings and subsequent burr removal.
2Reliability
If thickness of the resin pulley body is increased to prevent rotation, then relative rotation is prevented, but differential shrinkage increases reducing teeth accuracy
Solution Approach 1:
Instead of uniformly increasing the thickness of the entire resin pulley body, the invention locally modifies the metal attachment member by displacing specific parts of the radially outer peripheral surface inward. This localized geometric modification creates rotation prevention features without increasing overall resin thickness, thereby maintaining teeth accuracy while preventing relative rotation.
3Reliability
If knurling is applied to the metallic core to prevent rotation, then relative rotation is prevented, but manufacturing cost increases due to additional processing steps
Solution Approach 1:
The desired geometric features for rotation prevention are incorporated into the outward flange during the initial forming process of the metal attachment member. This preliminary action eliminates the need for subsequent knurling operations, reducing manufacturing steps and costs while achieving the same rotation prevention function.
Solution Approach 2:
The invention extracts the rotation prevention function from the resin portion and transfers it to the metal attachment member through the geometrically modified outward flange. By forming parts of the radially outer peripheral surface with inward displacements, the metal component itself provides rotation prevention, eliminating the need for additional knurling processing on the metallic core.
Data Source
AI summary
A toothed pulley includes a cylindrical metallic core and a resin portion including teeth. The metallic core has, at one end thereof in the axial direction, an outward flange projecting outward in the radial direction. The outward flange has a radially outer peripheral surface that is a rotation prevention shape having a plurality of parts displaced inward in the radial direction from a cylindrical surface of the radially outer peripheral surface. The radially outer peripheral surface of the outward flange is covered by the resin portion.