Planetary Gear Train Using Nested Sets for 10-Speed Transmission
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Solution Overview
Problem
Conventional 8-speed automatic transmissions face challenges with increased length, mountability issues, and reduced shift feel due to the number of planetary gear sets and control elements, which affect fuel economy and drivability.
Innovation Solution
A planetary gear train configuration using four simple planetary gear sets and six control elements to achieve at least ten forward speed stages and one reverse speed stage, with shaft connections and clutches that allow for efficient torque transmission and silent driving by utilizing a low rotational speed region of the engine.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the number of speed stages is increased to enhance fuel economy and drivability, then fuel economy and drivability are improved, but the number of internal components (planetary gear sets) increases, causing the transmission length to increase
Solution Approach 1:
The patent employs nested planetary gear sets where the ring gear of one planetary gear set serves as the sun gear of the next planetary gear set. This nesting arrangement allows multiple speed stages to be achieved within a compact structure, reducing the overall transmission length while maintaining the capability for enhanced fuel economy through multiple speed stages
2Adaptability or versatility
If the number of planetary gear sets is increased to achieve more speed stages, then speed stages are increased, but mountability deteriorates due to increased length
Solution Approach 1:
By nesting planetary gear sets where the ring gear of one set becomes the sun gear of the next, the patent achieves multiple speed stages (10 forward and 1 reverse) within a compact arrangement that improves mountability while maintaining versatility
3Adaptability or versatility
If conventional 8-speed automatic transmission is implemented with three to four planetary gear sets and five to seven control elements, then speed stages are achieved, but the length of the automatic transmission increases
Solution Approach 1:
The patent uses four nested planetary gear sets with six control elements to achieve 10 forward and 1 reverse speed stage, reducing the transmission length compared to conventional designs that use three to four planetary gear sets with five to seven control elements for 8-speed transmissions
Solution Approach 2:
The nested planetary gear sets serve multiple functions simultaneously, where each gear set contributes to multiple speed stages, reducing the overall number of components needed while achieving the same or better speed range
Data Source
AI summary
The present disclosure provides a planetary gear train of an automatic transmission for a vehicle. The planetary gear train may include: an input shaft receiving torque of an engine; an output shaft outputting torque; 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; and a fourth planetary gear set including tenth, eleventh, and twelfth rotation elements. The planetary gear train provides advantages of improving power delivery performance and fuel economy by achieving at least ten forward speed stages and one reverse speed stage.