Ball Planetary CVT Skew Control for Precise Speed Ratio Adjustment
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Solution Overview
Problem
Current ball planetary continuously variable transmission systems lack improved performance and operational control, particularly in achieving precise speed ratios and torque transmission.
Innovation Solution
The system incorporates a skew-based control mechanism with radially offset guide slots and a stator driver assembly to rotate the stators relative to each other, allowing for angular misalignment of traction planets, thereby adjusting the speed ratio and torque transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a ball planetary continuously variable transmission system uses conventional guide slots configuration, then the structure is simpler, but the speed ratio precision and torque transmission performance are insufficient
Solution Approach 1:
The patent employs asymmetric guide slots configuration where the first and second guide slots are positioned at different angular locations relative to the traction planet axle. This asymmetric arrangement creates differential guidance that enables precise control of the traction planet's angular misalignment, thereby achieving accurate speed ratio adjustment while maintaining a relatively simple structural implementation.
2Adaptability or versatility
If the stators are fixed relative to each other, then the structure is more stable, but the speed ratio adjustment capability is limited
Solution Approach 1:
The patent implements a dynamic stator configuration where the stators are permitted to rotate relative to each other about the main axle. This dynamic arrangement allows the guide slots to maintain stable geometric relationships while enabling continuous adjustment of the traction planet axles' angular positions, thus providing versatile speed ratio control without compromising the structural stability of the stator assembly.
3Productivity
If traction planets are perfectly aligned with the main axle, then the torque transmission path is more direct, but the speed ratio variability is reduced
Solution Approach 1:
The patent utilizes angular misalignment of the traction planet axles relative to the main axle as a controllable parameter for speed ratio adjustment. By varying the angular position of the traction planets through the asymmetric guide slots mechanism, the system achieves continuous speed ratio variability while maintaining sufficient torque transmission efficiency through optimized contact geometry and force distribution.
Data Source
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AI summary
A skew control system in a ball planetary continuously variable transmission, CVT, having a plurality of traction planets distributed radially about a main axle defining a longitudinal axis, each traction planet rotatable about a tiltable axle, a first traction ring and a second traction ring being in contact with the plurality of traction planets, the plurality of traction planets being interposed between the first traction ring and the second traction ring, and an idler assembly positioned radially inward of and in contact with each of the traction planets of the plurality of traction planets, the system comprising: a first stator having a plurality of radial guide slots for engaging a first end of each tiltable axle of the plurality of traction planets; a second stator having a plurality of radially offset guide slots for engaging a second end of each tiltable axle of the plurality of traction planets, the plurality of radially offset slots formed at an angle relative to the plurality of radial guide slots; a stator driver assembly configured to rotate the first stator relative to the second stator to move each tiltable axle of the plurality of traction planets to a particular skew angle; and a timing plate having a plurality of helical grooves for further engagement with one of the first end or the second end of each tiltable axle of the plurality of traction planets.A stator assembly for a continuously variable transmission (CVT) having a plurality of traction planet assemblies (142), the stator assembly comprising: a first stator (160) having a plurality of radial guide slots (161); a second stator (64) coaxial with the first stator (160), the first and second stators (160,164) configured to rotate relative to each other, the second stator (164) having a plurality of radially off-set guide slots (165); characterized in that the stator assembly further comprises: a reaction plate (162) coaxial with the first and second stators (160,164); a plurality of eccentric gears (168) coupled to the plate (162) and the first stator (160); and a stator driver (166) coupled to each of the eccentric gears (168), wherein the eccentric gears (168) are provided with a cam lobe (170) adapted to couple to the reaction plate (162); and wherein each eccentric gear (168) is provided with a reaction lobe (172) that is adapted to couple to the second stator (164); and wherein the cam lobe (170) is provided with a rotational center that is off-set from a rotational center of the reaction lobe (172).