Traction-Ball CVT with Dynamic Axial Force and Iris Ratio Control
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Solution Overview
Problem
Existing continuously variable gear transmissions face challenges in maintaining efficient torque transfer under varying loads and rapid changes in transmission ratio, with a need for a compact and simple design that adjusts to different load situations.
Innovation Solution
A continuously variable gear transmission design that incorporates a pre-spanning ring with a specific curvature and an axial force generator, which adjusts normal forces on traction balls based on load conditions, combined with a rotatable iris plate system for controlling ball axis tilt and a disengagement mechanism for efficient torque transfer and ratio changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a spring axial force generator is used to provide contact pressure, then the necessary contact pressure between input/output discs and traction balls is ensured, but the design becomes less adaptable to varying loads and rapid transmission ratio changes
Solution Approach 1:
The patent replaces the static spring axial force generator with a dynamic hydraulic axial force generator that can automatically adjust the contact pressure on traction balls according to varying load conditions and transmission ratio changes, thereby maintaining reliable torque transfer while adapting to different operating conditions
Solution Approach 2:
The hydraulic axial force generator changes the axial force parameter dynamically based on load requirements, allowing the system to optimize contact pressure between input/output discs and traction balls for each specific operating condition rather than relying on a fixed spring pressure
2Stress or pressure
If the pre-spanning ring has a larger radius curvature, then the normal forces at contact points are optimized for constant ratio operation, but the acceleration capability for units with greater inertia is reduced
Solution Approach 1:
The patent makes the pre-spanning ring radius dynamically adjustable, allowing the system to optimize the radius for each specific operating condition - using larger radii for constant ratio operation to maximize normal forces, and smaller radii during acceleration phases to improve acceleration capability for high-inertia loads
3Ease of operation
If the iris plate is rotated to control transmission ratio changes, then the ball axis tilt is controlled for ratio variation, but the torque transfer efficiency may be affected during rapid ratio changes
Solution Approach 1:
The hydraulic axial force generator performs preliminary action by increasing the axial force on traction balls before and during rapid transmission ratio changes, ensuring that sufficient contact pressure is maintained throughout the transition period to prevent torque transfer interruptions or inefficiencies
Solution Approach 2:
The system incorporates feedback mechanisms where the hydraulic axial force generator responds to detected transmission ratio changes and load conditions, automatically adjusting the axial force on traction balls to maintain optimal torque transfer efficiency during iris plate rotation and ratio variation
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 enhances torque transfer efficiency by automatically adjusting to load conditions, minimizing external forces and ensuring stable operation under varying loads and rapid ratio changes, while maintaining a compact and efficient structure.
Implementation Method 1
the pre-spanning ring will have contact where the pre-spanning ring has its largest inner diameter
Implementation Method 2
an axial force generator which will increase the normal forces on the traction balls when the torque requirements rise
Implementation Method 3
The iris plate is a disc or plate with spiral grooves, and the iris plate is shaped to fit around the curvature of the traction balls
Implementation Method 4
The exact curvature of the inner surface of the pre-spanning ring can be designed to match the requirements of the specific usage
Data Source
AI summary
A continuously variable gear is described having an input shaft, a plurality of traction balls distributed radially around the axis, each traction ball is mounted on an axle passing there through, the axles are tiltable in the radial grooves in the housing and support plate. To control the position of the traction balls, the axles are guided in curved slots of a turnable iris plate. To control the axial placement of the traction balls, there is a rotatable input disc positioned adjacent to the traction balls, a rotatable output disc positioned adjacent to the traction balls opposite the input disc, and a pre-spanning ring around the traction balls such that each of the traction balls is making three-point contact with the input disc, the output disc and the pre-spanning ring, the contact surface of the pre-spanning ring having a specific curvature larger than the radius of the traction balls.