Planetary Carrier Crack Arresting Features
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Solution Overview
Problem
Carrier units in power transfer systems for motor vehicles are prone to crack formation and propagation due to high tooth stresses, leading to reduced service life under cyclical loading conditions.
Innovation Solution
Incorporating crack arresting features such as throughbores and partial depth indentations, specifically designed as crack mitigating apertures, in close proximity to load-bearing features like spline and clutch teeth within the carrier unit to inhibit stress crack propagation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the carrier unit is designed with load-bearing features like spline and clutch teeth to transmit torque, then the power transfer capability is improved, but stress crack formation and propagation occur under cyclical loading conditions
Solution Approach 1:
The patent introduces apertures (holes) into the carrier unit, which are stress concentration points that would normally be harmful. However, these apertures are strategically positioned to intercept and arrest crack propagation before it reaches critical load-bearing features like spline and clutch teeth. By converting the harmful effect of stress concentration into a beneficial crack-arresting mechanism, the patent maintains torque transmission capability while improving crack resistance.
2Reliability
If the carrier unit material and structure are strengthened to prevent crack propagation, then crack resistance is improved, but the structural complexity and manufacturing difficulty increase
Solution Approach 1:
The patent divides the carrier unit structure by introducing apertures that segment the material continuity. These apertures create discrete zones that can independently manage stress distribution and crack propagation paths. This segmentation approach allows the carrier to maintain overall structural integrity while providing localized crack-arresting functionality, avoiding the need for complex reinforcement structures.
3Duration of action of stationary object
If crack arresting features are added to the carrier unit, then service life is extended, but the manufacturing process becomes more complex
Solution Approach 1:
The patent modifies the geometric parameters of the carrier unit by introducing apertures with specific dimensions, shapes, and positions. These parameter changes are optimized to provide effective crack arrestment while considering manufacturing constraints. The apertures can be formed using standard manufacturing processes like drilling or molding, minimizing the increase in manufacturing complexity while achieving the desired service life extension.
Data Source
AI summary
A two-speed transfer case for a four-wheel drive vehicle is provided. The transfer case has a two-speed planetary gearset, a range clutch, and a range shift mechanism. The planetary gearset includes a carrier unit having at least one crack arresting feature configured to limit propagation of a stress crack. The carrier unit includes a plurality of mounting holes for securing planet gears for rotation relative to the carrier unit. The gearset includes a sun gear configured for and a ring gear, with the planet gears in meshed engagement with the sun gear and the ring gear. The crack arresting feature extends at least partially through a portion of the carrier unit and is configured to receive a crack propagating from a central aperture of the carrier unit. The crack arresting feature is disposed radially between the central aperture and the mounting holes.