Spherical Roller CVT Shifting for Precise Ratio Control
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Solution Overview
Problem
Existing continuously variable transmissions (CVTs) face challenges in efficiently adjusting input to output speed ratios due to limitations in variator mechanisms, particularly in belt-type and toroidal-type CVTs, which lack the flexibility and efficiency of spherical-type variators with tiltable axes of rotation.
Innovation Solution
The implementation of a spherical-type CVT using spherical power rollers with tiltable axes of rotation, distributed in a plane about the longitudinal axis of the CVT, and a shift rod mechanism to adjust the speed ratio by tilting the rollers, allowing for three-point contact with traction rings and an idler, enhancing torque transmission and speed adjustment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If belt-type or toroidal-type variator mechanisms are used in CVT, then the transmission can achieve continuous speed ratio variation, but the flexibility and efficiency of speed ratio adjustment are limited
Solution Approach 1:
The patent employs spherical power rollers instead of traditional belt or toroidal disc mechanisms. The spherical geometry allows the rollers to tilt and roll between input and output discs, creating a more flexible and efficient continuous variable transmission mechanism that overcomes the limitations of conventional variator designs.
2Measurement precision
If spherical power rollers with tiltable axes are used, then precise control over speed ratios is achieved, but the device complexity increases
Solution Approach 1:
The patent implements dynamically adjustable spherical rollers whose axes of rotation can tilt to vary the speed ratio. This dynamic configuration allows precise control of transmission ratios while maintaining a relatively simple overall structure through the natural rolling and tilting motion of the spherical elements.
Solution Approach 2:
The invention introduces an additional degree of freedom by allowing the spherical rollers to tilt their axes of rotation. This dimensional change from fixed-axis to tilting-axis rollers enables precise speed ratio control without proportionally increasing structural complexity.
3Power
If multiple power rollers are distributed in a plane about the longitudinal axis, then torque transmission efficiency is enhanced, but the manufacturing complexity increases
Solution Approach 1:
The patent divides the power transmission function across multiple spherical rollers distributed in a plane about the longitudinal axis. This segmentation of the transmission function among several identical spherical elements enhances torque transmission efficiency while allowing for standardized manufacturing and assembly of each roller unit.
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 configuration enables precise control over input to output speed ratios, improving the efficiency and flexibility of the CVT by allowing continuous variation of the speed ratio through tilting the spherical rollers, thus enhancing the transmission's performance and adaptability.
Implementation Method 1
The rollers are contacted on one side by an input disc and on the other side by an output disc, one or both of which apply a clamping contact force to the rollers for transmission of torque
Implementation Method 2
a shift rod nut operationally coupled to actuate a tilt in said axis, and a shift rod coupled to the shift rod nut, wherein a rotation of the shift rod causes the shift rod nut to translate axially
Data Source
AI summary
Inventive embodiments are directed to components, subassemblies, systems, and/or methods for continuously variable transmissions (CVT). In one embodiment, a main axle is adapted to receive a shift rod that cooperates with a shift rod nut to actuate a ratio change in a CVT. In another embodiment, an axial force generating mechanism can include a torsion spring, a traction ring adapted to receive the torsion spring, and a roller cage retainer configured to cooperate with the traction ring to house the torsion spring. Various inventive idler-and-shift-cam assemblies can be used to facilitate shifting the ratio of a CVT. Embodiments of a hub shell and a hub cover are adapted to house components of a CVT and, in some embodiments, to cooperate with other components of the CVT to support operation and/or functionality of the CVT. Among other things, shift control interfaces and braking features for a CVT are disclosed.