Eccentric Planetary Traction Drive Wedge Gap Design
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Eccentric cylindrical traction drive designs are limited to speed ratios less than 8:1 due to increased contact stress and reduced service life as the speed ratio increases, which restricts the application of torque-actuated loading mechanisms.
Innovation Solution
The design incorporates an outer ring and sun roller with offset eccentricity, featuring support and loading rollers with raceways of different diameters to create a wedge gap, allowing for extended speed ratios by optimizing the contact geometry and using a pin shaft assembly with elastic bearing seats for flexible mounting of loading rollers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the speed ratio of eccentric cylindrical planetary traction drive is increased beyond conventional limits, then the loading capacity and power transmission capability are improved, but the contact stress increases significantly and service life is reduced
Solution Approach 1:
The patent divides the planetary carrier into multiple segments or supports multiple planetary rollers independently. This segmentation allows the load to be distributed across multiple contact points, reducing the contact stress on any single roller while maintaining the high speed ratio. The modular approach enables better stress management and extended service life.
Solution Approach 2:
The patent introduces a novel geometric configuration by offsetting the eccentricity of the planetary carrier from the standard arrangement. This dimensional change in the eccentric offset creates a more favorable contact geometry that reduces contact stress while maintaining the high speed ratio, effectively solving the contradiction between power capacity and reliability.
2Adaptability or versatility
If the speed ratio is extended beyond 8:1, then the application range and versatility are improved, but the effective contact radius becomes undesirable leading to increased contact stress
Solution Approach 1:
The patent optimizes the local geometric properties of the contact surfaces by adjusting the eccentric offset and raceway profiles. This local quality enhancement ensures that the contact stress is distributed more favorably across the contact area, enabling high speed ratios beyond 8:1 without excessive stress concentrations, thus expanding the application range.
Solution Approach 2:
The patent changes key geometric parameters including the eccentric offset distance, roller diameter, and raceway curvature. By optimizing these parameters, the contact stress is reduced while maintaining the extended speed ratio, allowing the transmission to operate reliably in applications requiring high gear ratios.
3Ease of manufacture
If conventional eccentric cylindrical design is used, then the structure is simple and manufacturing is easy, but the speed ratio is limited to less than 8:1
Solution Approach 1:
The patent introduces a dynamically adjustable eccentric offset mechanism that allows the transmission to adapt to different operating conditions. This dynamic feature enables the system to maintain optimal contact geometry across a wider range of speed ratios while keeping the overall structure relatively simple and manufacturable.
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 effectively extends the speed ratio beyond conventional limits, reducing contact stress and enhancing the service life of the traction drive while maintaining torque-actuated loading, enabling higher efficiency and reliability.
Implementation Method 1
When a planetary roller is in the converged wedge gap, frictional forces at the contacts tend to pull the planetary roller towards the smaller end of the gap, wedging the roller against the outer ring and the sun roller. An appreciable amount of normal load is thus generated at the frictional contacts.
Implementation Method 2
By offsetting the outer ring eccentric to the sun roller, a convergent wedge gap is created along the annular space between the outer ring and the sun roller.
Data Source
AI summary
A traction drive transmission has an outer ring 40, a sun roller 10, support rollers 30, and one or more loading rollers 20. The outer ring 40 includes a raceway 42 presented inwardly. The sun roller 10 includes a raceway 12 presented outwardly toward the raceway 42 of the outer ring 40. The sun roller 10 is offset eccentrically with respect to the outer ring 40 so that a wedge gap 112 exists between the raceways 42, 12 of the outer ring 40 and sun roller 10. The support rollers 30 are located between the outer ring 40 and sun roller 10. Each support roller 30 has first and second raceways 36, 38 that have different diameters and contacts the raceway 12 of the sun roller 10 along its first raceway 36 and the raceway 42 of the outer ring 40 along its second raceway 38. Each loading roller 20 is located at the wedge gap 112 between the raceway 42 of the outer ring 40 and the raceway 12 of the sun roller 10. Each loading roller 20 has first and second circular raceways 22, 26 that have different diameters and contacts the raceway 12 of the sun roller 10 along its first raceway 22 and the raceway 42 of the outer ring 40 along its second raceway 26.