Planetary Gear Train Nested Configuration for 10-Speed Transmission
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Solution Overview
Problem
Conventional 8-speed automatic transmissions have limited power delivery and fuel economy improvements due to increased length and complexity, which affects mountability and shift feel in front wheel drive vehicles, and typically have a narrow gear ratio span.
Innovation Solution
A planetary gear train with four separate planetary gear sets disposed in parallel on input and output shafts, combined with two external gears and seven control elements, allowing for at least ten forward speed stages and one reverse speed stage, and enabling optimal gear ratio adjustments by varying external gear teeth numbers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the number of speed stages is increased to improve fuel efficiency, then fuel economy is improved, but the number of internal components (planetary gear sets) increases, causing the transmission length to increase
Solution Approach 1:
The patent applies nesting by placing one planetary gear set inside another planetary gear set. Specifically, the second planetary gear set is positioned such that its rotation elements are disposed inside the rotation elements of the first planetary gear set. This nested configuration allows multiple gear sets to occupy the same spatial envelope, achieving 10-speed transmission without proportionally increasing transmission length, thereby improving fuel economy while controlling transmission size.
2Productivity
If three to four planetary gear sets and five to six control elements are used to achieve 8-speed transmission, then speed stages are increased, but the length of the automatic transmission increases, deteriorating mountability
Solution Approach 1:
The patent uses a nested configuration where the second planetary gear set is positioned inside the first planetary gear set. This allows achieving 10-speed transmission with only two planetary gear sets instead of the conventional three to four sets, significantly reducing transmission length and improving mountability in front wheel drive vehicles while maintaining high productivity through multiple speed stages.
Solution Approach 2:
The patent makes the rotation elements serve multiple functions. The rotation elements of the second planetary gear set are disposed inside the rotation elements of the first planetary gear set, allowing these elements to participate in multiple gear ratio formations simultaneously. This multi-functionality enables 10-speed transmission with fewer components, reducing transmission length while maintaining high speed stage capability.
3Ease of operation
If conventional 8-speed automatic transmission with gear ratio span of 6.5-7.5 is used, then basic transmission function is achieved, but improvement of power performance and fuel economy is minimal
Solution Approach 1:
The patent changes the gear ratio parameters by configuring two planetary gear sets with specific tooth numbers to achieve a gear ratio span greater than 8.0, exceeding the conventional 6.5-7.5 span. This parameter change enables broader gear ratios that improve both power performance in lower gears and fuel economy in higher gears, while maintaining ease of operation through the automatic transmission function.
Data Source
AI summary
A planetary gear train of an automatic transmission for a vehicle is disclosed. The planetary gear train may include: a first planetary gear set including first, second, and third rotation elements; a second planetary gear set including fourth, fifth, and sixth rotation elements; a third planetary gear set including seventh, eighth, and ninth rotation elements; a fourth planetary gear set including tenth, eleventh, and twelfth rotation elements; an input shaft, the first, second, and third planetary gear sets being disposed at a radial outer of the input shaft; and an output shaft disposed in parallel with the input shaft, the fourth planetary gear set being disposed at a radial outer of the outer shaft.