Planetary Gear Train for Automatic Transmission with Nested Configuration
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Solution Overview
Problem
Conventional automatic transmissions with increased speed stages face challenges in mountability, cost, weight, and transmission efficiency due to the number of internal components, particularly planetary gear sets, which can deteriorate as the number of speed stages increases, and often result in compromised shift feel when using dog clutches instead of control elements.
Innovation Solution
A planetary gear train for automatic transmissions that achieves at least ten forward and four reverse speed stages using four simple planetary gear sets and six control elements, including clutches and brakes, to optimize power delivery and fuel economy while minimizing component count and improving silent driving by operating at low engine rotational speeds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the number of speed stages in automatic transmission is increased, then fuel economy and drivability are improved, but the number of internal components (planetary gear sets) increases causing transmission length to increase
Solution Approach 1:
The patent applies nesting by placing one planetary gear set inside another planetary gear set. Specifically, the first planetary gear set is disposed inside the second planetary gear set, and the third planetary gear set is disposed inside the fourth planetary gear set. This nested configuration allows multiple gear sets to occupy overlapping spatial volumes, significantly reducing the overall transmission length while maintaining the required number of speed stages for improved fuel economy
Solution Approach 2:
The patent transitions from a linear arrangement of planetary gear sets to a three-dimensional nested structure. By utilizing radial and axial dimensions to position gear sets inside one another rather than end-to-end, the design achieves compactness in the transmission length direction while preserving all necessary speed stages
2Productivity
If the number of speed stages is increased, then fuel economy is improved, but the number of control elements (frictional elements) increases causing device complexity to increase
Solution Approach 1:
The patent achieves multi-functionality by having control elements manage multiple functions across different planetary gear sets. The control elements selectively connect various rotation elements (sun gears, planet carriers, ring gears) from different planetary gear sets to achieve ten forward speed stages and four reverse speed stages, reducing the total number of control elements needed compared to conventional designs
3Adaptability or versatility
If conventional 8-speed automatic transmission is used with three to four planetary gear sets, then speed stages are achieved, but transmission length increases deteriorating mountability
Solution Approach 1:
The patent implements nesting by disposing the first planetary gear set inside the second planetary gear set, and the third planetary gear set inside the fourth planetary gear set. This configuration achieves ten forward speed stages and four reverse speed stages with a compact structure that significantly reduces transmission length compared to conventional linear arrangements, thereby improving mountability
Data Source
AI summary
A planetary gear train of an automatic transmission for a vehicle may include an input shaft configured to receive torque of an engine and an output shaft configured to output torque. The planetary gear train further includes a plurality of planetary gear sets comprising rotation elements, a first plurality of shafts connected to one of the rotation elements of the plurality of planetary gear sets, and a second plurality of shafts. Each of which is selectively connected to a transmission housing and fixedly connected to one of the rotation elements of the plurality of planetary gear sets that is not fixedly connected with any of the first plurality of shafts.