Planetary Variator Fork Layout for Wider Ratio Range
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Solution Overview
Problem
The design of planet forks in existing planetary variators faces conflicting requirements, such as avoiding interference and withstanding forces, due to the need for a complex geometric link between the ring wheel, sun wheel, and planet wheels, which limits the range of torque and speed ratios and complicates the construction of the forks.
Innovation Solution
The planetary variator design features a ring wheel and sun wheel with axisymmetric bodies positioned around a common central symmetry axis, where the planet wheels have a shaft and wheel portion that rotate about a hinge axis perpendicular to the central axis, allowing for a non-circular rolling surface shape that ensures a drill-free rolling motion, with the hinge axis positioned externally to the central axis, enabling a more straightforward and optimized fork construction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the hinge axis intersects the common central axis to achieve geometric link between ring wheel, sun wheel, and planet wheels, then the transmission ratio can be varied, but the planet forks interfere with each other at certain inclination angles and contact with ring wheel or sun wheel occurs at extreme ratios
Solution Approach 1:
The hinge axis is positioned asymmetrically relative to the common central axis, specifically offset by a distance e. This asymmetric positioning eliminates the interference problems that occur with symmetric (intersecting) hinge axis configurations, allowing planet forks to operate without mutual interference across the full range of inclination angles while avoiding contact with ring wheel or sun wheel at extreme transmission ratios.
2Reliability
If the planet fork design is made lighter to avoid contact between components, then component interference is reduced, but the forks cannot withstand the forces acting on them
Solution Approach 1:
The asymmetric hinge axis positioning creates sufficient clearance between planet forks and other components throughout the operating range, eliminating the need for overly conservative (heavy) fork designs. The forks can be optimized for strength-to-weight ratio without compromising interference avoidance, as the geometric configuration inherently prevents contact.
3Power
If multiple planet forks are used with hinge axes intersecting the common central axis, then torque transmission is improved, but the forks must be designed to avoid interference at all inclination angles which complicates the construction
Solution Approach 1:
By positioning hinge axes asymmetrically (offset by distance e from the common central axis), the patent simplifies the fork construction. The asymmetric configuration naturally provides clearance between multiple planet forks operating simultaneously, eliminating the complex geometric constraints that would otherwise be required to prevent interference, thus reducing manufacturing and design complexity.
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 design allows for a wider range of torque and speed ratios while simplifying the construction of the forks, enabling them to withstand greater loads and cover increased inclination angles, thus enhancing the mechanical characteristics and efficiency of the variator.
Implementation Method 1
interaction between the ring wheel, the at least two planet wheels, and the sun wheel takes place through a rolling motion of a rolling surface provided on each of the planet wheels' wheel portions, on rolling surfaces provided on the ring wheel and the sun wheel
Implementation Method 2
The rolling surfaces are designed so as to obtain a so-called drill-free rolling motion, i.e. a rolling without sliding of the rolling surfaces in the contact area
Data Source
AI summary
A planetary variator applicable in a variable transmission for realizing a variable speed and torque ratio includes: a ring wheel; at least two planet wheels, the at least two planet wheels including a shaft portion and a wheel portion that is rotatable about the shaft portion, the shaft portion having a longitudinal central axis, the longitudinal central axis also being the rotation axis of the wheel portion, each planet wheel being freely rotatable about a hinge axis that is oriented essentially perpendicularly with respect to a plane defined by the common central axis and the rotation axis of the wheel portion of the planet wheel; and a sun wheel. The ring wheel and the sun wheel are axisymmetric bodies positioned with respect to a common central symmetry axis. Interaction between the ring wheel, the at least two planet wheels, and the sun wheel takes place through a rolling motion.