Planetary Gear Train With Shared Ring Gears For Ten Speed Transmission
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Solution Overview
Problem
Current automatic transmissions with more than eight speeds face challenges in achieving efficient fuel consumption and drivability due to increased complexity, weight, and power flow inefficiencies, often requiring multiple planetary gear sets and control elements that complicate installability and shift feel.
Innovation Solution
A planetary gear train configuration with four single pinion planetary gear sets and six control elements, including clutches and brakes, is designed to achieve ten forward speeds and one reverse speed, minimizing parts while enhancing power delivery and fuel efficiency by optimizing torque transmission through a low engine rotation speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the number of planetary gear sets is increased to achieve more shift stages, then fuel consumption and drivability are improved, but device complexity and total length are increased
Solution Approach 1:
The patent merges multiple planetary gear sets into a integrated structure where gear sets share common components. Specifically, the first and second planetary gear sets share a common ring gear, and the third and fourth planetary gear sets share another common ring gear, reducing the total number of independent parts while maintaining ten forward shift stages
Solution Approach 2:
Control elements are designed to perform multiple functions across different gear sets. For example, a single clutch can control torque transmission to multiple planetary gear sets simultaneously, and brakes can lock multiple rotational elements across different gear sets, reducing the number of dedicated control elements from five to seven
2Ease of operation
If the number of control elements is increased to achieve more shift stages, then drivability is improved, but device complexity and installability are worsened
Solution Approach 1:
Each control element is designed to control multiple rotational elements across different planetary gear sets. For instance, the first clutch controls both the first and second planetary gear sets, and the second clutch controls the third and fourth planetary gear sets, allowing seven control elements to manage ten forward shifts effectively
3Productivity
If total length of transmission is increased to accommodate more planetary gear sets, then more shift stages are achieved, but power flow efficiency is reduced
Solution Approach 1:
Planetary gear sets are arranged in a compact configuration where they share common ring gears and rotational elements. This merging reduces the axial length of the transmission while maintaining ten forward shift stages, thereby improving power flow efficiency by minimizing torque transmission path length
Data Source
AI summary
A planetary gear train of an automatic transmission for a vehicle is disclosed. The planetary gear train includes an input shaft for receiving an engine torque, an output shaft for outputting a torque, four planetary gear sets each having three rotational elements. The planetary gear train further comprises a plurality of additional shafts, each of which is selectively connected to the transmission housing and fixedly connected to a rotation element of the first, second, third, and fourth planetary gear set that is not fixedly connected with any of the first to fifth shafts.