Continuously Variable Transmission Axial Dimension Reduction
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Solution Overview
Problem
Conventional continuously variable transmissions with toroidal-type speed change units and planetary gear mechanisms have a long axial dimension, leading to bearing diameter reduction, increased load fluctuation, and reduced precision due to pinion shaft bending, which affects the reliability and compactness of the transmission.
Innovation Solution
A continuously variable transmission design incorporating a main planetary gear mechanism with a two-step pinion and a simple planetary gear unit, along with a double pinion planetary gear unit for the counter gear mechanism, which reduces the axial dimension, supports pinions with larger diameter bearings, and cancels out thrust forces, enhancing precision and reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If the axial dimension of the planetary gear mechanism is reduced, then the bearing diameter can be increased to improve service life, but the pinion shaft bending and load fluctuation increase which reduces precision
Solution Approach 1:
The planetary gear mechanism is divided into two separate mechanisms: a main planetary gear mechanism and a counter planetary gear mechanism. Each mechanism has its own pinion shaft and bearings, allowing the bearing diameter to be increased in each individual mechanism while maintaining pinion shaft rigidity and support precision.
Solution Approach 2:
The two planetary gear mechanisms are arranged in parallel configurations rather than in series along the axial direction. This spatial arrangement reduces the overall axial dimension while allowing each mechanism to have optimized bearing sizes and pinion shaft configurations that maintain precision.
2Length of stationary object
If the axial dimension of the planetary gear mechanism is reduced, then the transmission becomes more compact, but the bearing diameter is reduced which decreases service life
Solution Approach 1:
The planetary gear mechanism is segmented into two separate mechanisms with independent bearing arrangements. This allows the bearing diameter in each mechanism to be optimized for service life while the overall axial dimension is reduced through parallel configuration.
Solution Approach 2:
Two planetary gear mechanisms are combined in a parallel configuration to achieve both compactness and long bearing service life. The merging of these mechanisms allows for optimized bearing sizes in each while maintaining a reduced overall axial dimension.
3Length of stationary object
If the axial dimension of the planetary gear mechanism is reduced, then the transmission is more compact, but pinion shaft bending increases which reduces precision
Solution Approach 1:
The planetary gear mechanism is divided into two separate mechanisms, each with its own pinion shaft. This segmentation allows each pinion shaft to be shorter and stiffer, reducing bending while the parallel arrangement maintains compact overall dimensions.
4Length of stationary object
If the axial dimension of the planetary gear mechanism is reduced, then the transmission becomes more compact, but load fluctuation on bearings increases which reduces reliability
Solution Approach 1:
The planetary gear mechanism is segmented into two separate mechanisms with independent bearing supports. This segmentation distributes and reduces load fluctuation on each bearing while maintaining compact overall dimensions through parallel configuration.
Solution Approach 2:
Two planetary gear mechanisms are merged in parallel to share the load, reducing load fluctuation on individual bearings and improving reliability while maintaining a compact axial dimension.
Data Source
AI summary
Rotation of an input shaft is directly transmitted to a front carrier of a planetary gear mechanism, and rotation, which is speed-changed and reversed by a toroidal-type continuously variable speed change unit, is transmitted to a first sun gear. When a Low clutch is applied, rotation of an output carrier of a simple planetary gear unit is transitted to a counter gear mechanism via a common carrier, and then output at an output shaft. When a High clutch H is applied, rotation of a second sun gear is transmitted to the output shaft. Thus, the pinion shaft is shortened and the service life span of a supporting bearing is increased as compared with a planetary gear mechanism that has a three-step pinion.