Worm Gear Hub Assembly With Molded Ring Torque Retention
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Solution Overview
Problem
The existing methods for manufacturing worm gear hubs for electric power steering systems are costly due to the expensive machining required for creating knurled surfaces and the use of solid steel or powdered metal hubs, which are inefficient for torque transfer.
Innovation Solution
A worm gear hub assembly featuring a gear hub blank with bent tabs and lugs that facilitate the molding of a polymeric ring, allowing for the formation of a gear blank with improved retention and torque transfer capabilities, reducing material costs and complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If solid steel or powdered metal hubs are used with knurled surfaces for bonding plastic rings, then torque transfer capability is achieved, but manufacturing cost increases due to expensive machining operations
Solution Approach 1:
The invention changes the manufacturing method from expensive precision machining of knurled surfaces to cost-effective stamping and forming operations. The hub uses a smooth inner surface with externally formed lugs and tabs, eliminating the need for complex knurling machinery while maintaining torque transfer capability through the plastic ring bonding to these formed features.
Solution Approach 2:
The invention replaces expensive solid steel or powdered metal hubs with a cheaper stamped metal hub that achieves the same function. The hub uses a simpler construction with a smooth bore and externally formed lugs that are stamped or formed rather than machined, significantly reducing manufacturing cost while maintaining reliability.
2Reliability
If knurled surfaces are machined on metal hubs for plastic bonding, then bonding surface area is increased, but manufacturing complexity and cost increase
Solution Approach 1:
Instead of creating surface complexity on the inner hub surface (knurling), the invention inverts the approach by creating external lugs and tabs on the outer surface of the hub that extend into the plastic ring. This external formation method is simpler to manufacture while achieving the same bonding objective.
Solution Approach 2:
The invention moves the bonding feature from the radial dimension (knurled surface texture) to the axial dimension (external lugs and tabs extending outward). This dimensional shift allows bonding to occur through the plastic ring encapsulating these external features rather than through surface texture, simplifying the manufacturing process.
3Reliability
If plastic rings are molded onto machined knurled hubs, then torque transfer is enabled, but production time and cost increase
Solution Approach 1:
The hub is prepared in advance with externally formed lugs and tabs through stamping or forming operations before the plastic ring is molded. This preliminary formation of bonding features eliminates the need for time-consuming knurling operations during hub production, allowing faster manufacturing cycles and improved productivity.
Data Source
AI summary
A method of making a worm gear. The method includes forming a gear blank having a plurality of individual lugs formed about an outer circumferential edge of said blank to facilitate a uniform flow of a material around said plurality of individual lugs. The method also includes molding said material around said plurality of individual lugs to form a ring.