Worm Gear Hub: Metal-Polymer Composite for Cost Reduction
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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 powdered metal hubs, which hinders efficient torque transfer between the worm shaft and steering shaft.
Innovation Solution
A worm gear hub assembly featuring a metal hub blank with radially extending tabs and a polymeric ring overlay, where the polymeric ring is injection molded around the tabs, and gear teeth are cut using a hobbing process, providing a cost-effective and efficient torque transfer mechanism.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional machining methods are used to create knurled surfaces on solid steel hubs, then torque transfer capability is achieved, but manufacturing cost increases significantly
Solution Approach 1:
The patent applies composite materials by combining a metal hub blank with a polymeric ring overlay. The metal hub provides structural integrity and torque transfer capability, while the polymeric ring is molded onto the hub to form gear teeth. This composite structure eliminates the need for expensive knurling operations on solid steel hubs while maintaining reliable torque transfer from the worm shaft through the gear assembly to the steering shaft.
Solution Approach 2:
The patent changes the material parameter from solid steel to a composite of metal hub blank and polymeric ring. This parameter change allows the gear teeth to be formed by injection molding the polymeric material onto the hub blank, replacing the traditional machining process. The polymeric material's ability to be molded directly onto the metal hub provides a cost-effective manufacturing approach while achieving the required torque transfer capability.
2Productivity
If powdered metal hubs are used for worm gear assembly, then manufacturing efficiency is improved, but manufacturing cost increases
Solution Approach 1:
The patent changes the manufacturing process parameter from powdered metal forming to cold forming followed by injection molding. The metal hub blank is cold-formed and then the polymeric ring is injection molded onto it. This parameter change maintains manufacturing efficiency by using high-volume processes like injection molding while reducing material costs compared to powdered metal hubs.
Solution Approach 2:
The patent uses a cold-formed metal hub blank that can be produced at low cost through stamping or similar processes, replacing expensive powdered metal hubs. The hub blank serves as a cost-effective base that is then overlaid with polymeric material to create the final gear assembly, achieving both productivity and cost reduction.
3Ease of manufacture
If cold forming and injection molding are used to create the hub assembly, then manufacturing cost is reduced, but structural integrity must be maintained
Solution Approach 1:
The patent uses composite materials where a metal hub blank provides the structural backbone and strength, while the polymeric ring overlay provides the gear teeth and functional surfaces. The metal hub blank's inherent strength is preserved through cold forming, and the polymeric ring is securely molded onto it, creating a composite structure that maintains structural integrity while enabling cost-effective manufacturing through injection molding.
Solution Approach 2:
The patent segments the gear hub into two distinct components: a metal hub blank and a polymeric ring overlay. This segmentation allows each component to be optimized for its specific function - the metal hub for structural strength and the polymeric ring for gear engagement - while being manufactured separately and then assembled through injection molding, reducing overall manufacturing 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
This solution reduces manufacturing costs and enhances torque transfer efficiency by utilizing a cold-formed metal hub with a polymeric ring, enabling reliable operation of electric power steering systems while maintaining structural integrity and rigidity.
Implementation Method 1
a polymeric material is injection molded around the tabs to form a polymeric ring
Implementation Method 2
The metal hub blank with the polymeric ring is pressed on a shaft
Implementation Method 3
gear teeth are cut onto an outer surface of the polymeric ring with a hobbing process
Data Source
Figure 1~2
Figure 3
Figure 4~5
AI summary
A gear blank is provided. It comprises a metal hub blank having an outer perimeter. A plurality of individual adjacent tabs extend radially from the outer perimeter of the metal hub blank. A polymeric ring overlaying a portion of the metal hub blank including the tabs is provided.