Planetary Gear Carrier Spline Optimization
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Solution Overview
Problem
Existing spline connections in truck propulsion drive trains face limitations in strength enhancement while meeting packaging and cost constraints, as increasing spline length has practical and economic boundaries.
Innovation Solution
A carrier design for planet gears in a planetary gear train with splines having a parameter (P) value between 2.5 and 6.0, defined by the equation P=1.155·T+Ls·Db·N[Dr+(Do-Dr)3]2, where T is surface tensile strength, Ls is spline length, Db is base diameter, N is number of splines, Dr is root diameter, and Do is outside diameter, optimizing spline geometry for improved strength and fit within constrained spaces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the axial length of spline teeth is increased to improve spline strength, then the load capacity increases, but the packaging constraints and cost increase
Solution Approach 1:
The patent applies parameter changes by optimizing the spline geometry parameters (axial length, base diameter, root diameter, outside diameter) and material properties (surface tensile strength) to achieve a parameter P value between 2.5 and 6.0. This mathematical optimization allows the spline connection to achieve sufficient strength without requiring excessive axial length, thereby resolving the contradiction between strength improvement and packaging constraints.
2Strength
If the axial length of spline teeth is increased to improve spline strength, then the load capacity increases, but the manufacturing cost increases
Solution Approach 1:
The patent establishes an optimized parameter range (P=2.5 to 6.0) that balances strength requirements with manufacturing economy. By optimizing the combination of geometric parameters and material properties within this range, the design achieves sufficient load capacity without unnecessarily increasing axial length, thereby controlling manufacturing costs while meeting strength requirements.
3Duration of action of stationary object
If the spline geometry is optimized for strength, then component life increases, but the design complexity increases
Solution Approach 1:
The patent simplifies the design process by consolidating multiple geometric and material parameters into a single optimization criterion (parameter P with value 2.5 to 6.0). This unified parameter approach guides the optimization of axial length, base diameter, root diameter, outside diameter, and surface tensile strength simultaneously, making the design process more systematic and manageable while achieving extended component life through optimized strength characteristics.
Data Source
AI summary
A carrier for a planetary gear train includes a hub disposed about an axis of rotation, the hub having an external cylindrical surface including a plurality of splines extending along a longitudinal direction, the longitudinal direction being parallel to the axis of rotation; and a deck extending away from the hub along a radial direction, the radial direction being transverse to the longitudinal direction. The deck defining a plurality of holes therethrough, each hole of the plurality of holes being configured to receive an axle of a planet gear of the plurality of planet gears, the hub being disposed between the plurality of holes and the axis of rotation along the radial direction. The splines have a value of a parameter (P) that is not less than 2.5 and not greater than 6.0.