Worm Wheel Rim Fixation Structure for High-Torque Steering
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Solution Overview
Problem
Conventional worm wheels in electric power steering systems face challenges in increasing the coupling strength between the metal core and the synthetic resin rim portion, particularly under high assistant torque conditions, leading to potential mechanical failures.
Innovation Solution
The worm wheel design incorporates additional annular recesses on the core, specifically a second and third annular recess, which enhances the fixation of the rim portion through injection molding, preventing weld lines and improving resin flow, thereby increasing the coupling strength between the core and the rim.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a conventional worm wheel structure with a single first annular recess is used, then the manufacturing process is simple, but the coupling strength between the core and rim portion is insufficient under high assistant torque conditions
Solution Approach 1:
The single first annular recess is segmented into multiple annular recesses (first, second, and third annular recesses) positioned at different locations on the core. This segmentation allows the rim portion to be fixed at multiple points, significantly increasing the coupling strength between the core and rim portion while maintaining a relatively simple overall structure.
Solution Approach 2:
The fixation structure transitions from a single-plane annular recess to a multi-dimensional arrangement with recesses at different axial positions and radial depths. The first annular recess is positioned at one axial end, the second at the other axial end, and the third at a radially outer region, creating a three-dimensional fixation pattern that enhances coupling strength without excessive complexity.
2Reliability
If the rim portion is fixed only at the first annular recess, then the manufacturing process is simple, but the resin flow during injection molding may form weld lines that weaken the structure
Solution Approach 1:
The multiple annular recesses are pre-positioned on the core before injection molding, establishing predetermined flow paths for the resin. This preliminary structural arrangement guides the resin flow to converge at multiple fixed points rather than forming weld lines, ensuring reliable fixation while maintaining manufacturability through standard injection molding processes.
3Reliability
If additional annular recesses are added to enhance coupling strength, then the fixation reliability improves, but the manufacturing precision requirements increase
Solution Approach 1:
Each annular recess is designed with specific local characteristics: the first and second recesses are positioned at axial ends to provide endpoint fixation, while the third recess at the radially outer region provides additional support. This local quality differentiation ensures that each recess serves its specific fixation function, improving overall reliability without requiring uniform high precision across all features.
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 enhanced design significantly increases the coupling strength between the core and the rim portion, improving the mechanical integrity and reducing the likelihood of mechanical failures under high torque conditions.
Implementation Method 1
The rim portion 201 is integrally formed with the core 101 by synthetic resin injection molding
Data Source
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AI summary
A core of a worm wheel has an axial end surface formed with a first annular recess, another axial end surface formed with a second annular recess, and a third annular recess formed in a radially outer region of the first annular recess. A rim portion has a first inner circumferential portion fixed to the first annular recess, a second inner circumferential portion fixed to the second annular recess, and a protrusion engaged with the third annular recess.