Ball Planetary CVT Axle Egression Prevention
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Solution Overview
Problem
Existing continuously variable transmissions (CVTs) face challenges with axial force generation systems that add complexity, cost, and parasitic losses, particularly in toroidal-type CVTs, and there is a need for improved performance and operational control.
Innovation Solution
The implementation of a ball planetary type CVT with a plurality of planets arranged angularly about a sun assembly, utilizing a tiltable axis of rotation and a control system that adjusts the skew angle to balance forces and prevent binding, along with modified stator slots and a timing plate to inhibit axle egression and ensure efficient power transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If toroidal-type CVT is used to achieve continuous variable ratios, then power transmission capability is improved, but axial force generation system complexity and parasitic losses increase
Solution Approach 1:
The patent extracts and eliminates the complex axial force generation system from the toroidal-type CVT by adopting a ball planetary type design where planets naturally self-align through geometric constraints, removing the need for additional axial force generation components while maintaining power transmission capability
Solution Approach 2:
The patent replaces the mechanical axial force generation system with a geometrically-constrained ball planetary mechanism where the tiltable planet axles self-adjust through inherent mechanical geometry, substituting complex active force generation with passive geometric self-alignment
2Reliability
If robust axial force generation system is added to toroidal-type CVT to handle force variation, then reliability is improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The ball planetary planets self-adjust their tilt angles through inherent geometric constraints and force balances, automatically handling force variations without requiring external axial force generation systems, making the system self-regulating and eliminating additional complexity
3Adaptability or versatility
If planet axles are allowed to tilt freely to adjust speed ratio, then adaptability is improved, but risk of axle egression and binding increases
Solution Approach 1:
The patent incorporates preliminary anti-action by designing guide slots with radial inward surfaces that proactively prevent axle egression before it can occur, and by positioning axles in a skewed state that pre-balances forces to prevent binding, addressing potential failures before they happen
Solution Approach 2:
The guide slots are pre-configured with specific geometries (radial inward surfaces, width variations) that establish force balances and axial position limits before operation, ensuring axles remain properly positioned throughout the speed ratio adjustment range without requiring active control
4Ease of operation
If guide slots are designed with wide clearance to accommodate axle movement, then ease of operation is improved, but manufacturing precision requirements increase
Solution Approach 1:
The guide slots exhibit local quality variations with different widths at different locations - wider at the entrance for easy assembly, narrower in the middle for precise positioning, and with radial inward surfaces for force balancing - optimizing both ease of operation and manufacturing precision at different locations
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 solution allows for a compact, lightweight CVT with improved performance and reduced risk of binding, maintaining power capacity and range while preventing axle egression and damage, enabling efficient operation across a wide range of speed ratios.
Implementation Method 1
The planets may receive or transmit power via direct contact with the input or output disc
Implementation Method 2
via contact with any of a type of fluid capable of transmitting power
Data Source
Figure 1~2B
Figure 3
Figure 4A
AI summary
Components, subassemblies, systems, and/or methods for improving the performance and increasing the life of continuously variable transmissions (CVT). A first stator may be formed with an outer diameter greater than an outer diameter of a second stator. A stator may have radial slots formed to extend farther radially inward than slots on the other stator. The larger outer diameter of a stator or the formation of guide slots on a first stator extending farther radially inward of guide slots on a second stator may prevent egress of a planet axle from a radial slot, increase range of the CVT, allow for larger tolerances to reduce losses, and other advantages, Slots on a timing plate may be formed having a width greater than a width of guide slots formed on either stator to allow the stators to control adjustments while the timing plate avoids runaway axles. The shape, including junction between surfaces on a timing plate or stator may also prevent an axle from egressing. Any one or a combination of these features allow a CVT to be formed smaller and lighter to allow for clearance in smaller environments and for reduced inertia.