Composite Gear Wheel Hub Geometry to Prevent Shrinkage Cracks
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Solution Overview
Problem
Composite wheels, particularly composite gear wheels, suffer from premature failure due to stress concentrations and shrinkage issues at sharp edges, leading to undesirable noises, play, and reduced service life, especially when metal hubs are overmolded with plastic rings.
Innovation Solution
A hub body design with a convex outer lateral surface featuring a progression of root diameters and engagement teeth that minimizes sharp edges, allowing for a durable and reliable connection between the metal hub and plastic ring, enhancing stress distribution and reducing manufacturing complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If shoulders and/or grooves with sharp edges are arranged on the hub body to transmit axial forces, then axial force transmission is achieved, but stress concentrations occur leading to shrinkage stress cracks and premature failure
Solution Approach 1:
The invention replaces sharp-edged shoulders and grooves with a convex outer lateral surface featuring a progression of root diameters. This curved geometry eliminates stress concentration points while maintaining axial force transmission capability through the crowned surface that allows the plastic ring body to shrink onto the metal hub body during cooling.
2Force
If engagement gearing is applied to the hub body using gear hobbing, then torque transmission is achieved, but additional sharp edges are created promoting crack formation
Solution Approach 1:
The invention modifies the local geometry at the root of engagement teeth by implementing a progression of root diameters along the tooth height. This creates a convex root section that eliminates sharp edges at the tooth root while maintaining the engagement gearing's torque transmission function, thereby preventing crack initiation at this critical location.
3Stability of the object's composition
If grooves are applied to the hub body for ring body engagement, then the connection is established, but grooves shrink to become free during cooling causing noise and play
Solution Approach 1:
The invention replaces conventional grooves with a convex outer lateral surface that features a progression of root diameters. This crowned geometry allows the plastic ring body to shrink onto the hub body during cooling, maintaining continuous contact and eliminating play and noise, while still providing stable connection through the convex surface engagement.
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 provides a durable, reliable, and cost-effective composite wheel with improved stress distribution, reducing noise and play, and extending the service life while maintaining manufacturing ease.
Implementation Method 1
When the plastic-injected ring body cools down, the sharp edges regularly lead to shrinkage stress cracks due to stress concentrations
Data Source
AI summary
Hub body (16) for a composite wheel (10), in particular a composite gear wheel (12), comprisingan axis of rotation (14),a first front side of the hub (20),a second front side of the hub (22),an outer lateral surface (24) arranged along the axis of rotation (14) between the first front side of the hub (20) and the second front side of the hub (22),wherein the outer lateral surface (24) has an engagement gearing (28) with at least one engagement tooth (30) as well as a convex outer lateral section (64),as well as a composite wheel (10), in particular a composite gear wheel (12), with such a hub body (16),as well as a steering unit for a motor vehicle with such a composite wheel.