Parallel Planetary Gear Train for 9-Speed Transmission Mountability
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Solution Overview
Problem
Existing planetary gear trains face challenges in achieving a high number of shift speeds, which increases the number of components, affecting mountability, cost, weight, and power delivery efficiency, particularly in front-wheel drive vehicles, where minimizing components is crucial.
Innovation Solution
A planetary gear train design with two planetary gear sets disposed on input and output shafts in parallel, connected through externally-meshed gears, and frictional elements like clutches and brakes, allowing for nine forward speeds and one reverse speed, improving gear ratio optimization and power delivery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the number of shift speeds is increased to improve fuel economy, then fuel economy is improved, but the number of components increases leading to deteriorated mountability and power delivery efficiency
Solution Approach 1:
The planetary gear train is divided into two separate planetary gear sets (first and second planetary gear sets) disposed on different shafts (input shaft and output shaft). Each planetary gear set can independently provide speed changes, allowing the system to achieve multiple forward speeds (1st through 9th speeds) and reverse speed without requiring a single complex gear train with excessive components
Solution Approach 2:
The patent transitions from a conventional single-shaft planetary gear arrangement to a dual-shaft configuration where the first planetary gear set is disposed on the input shaft and the second planetary gear set is disposed on the output shaft. This spatial reorganization in another dimension (from single-shaft to dual-shaft architecture) enables more efficient component utilization and reduces the overall number of components needed to achieve 9-speed operation
2Device complexity
If the number of components is reduced to improve mountability, then mountability is improved, but achieving a high number of shift speeds becomes more difficult
Solution Approach 1:
Each planetary gear set is designed to perform multiple functions: the first planetary gear set can provide various speed reductions when engaged with different clutches (1st through 5th speeds), while the second planetary gear set provides additional speed stages (6th through 9th speeds and reverse). This multi-functionality allows each component to contribute to multiple speed ratios, achieving 9 forward speeds and 1 reverse speed with a reduced total component count
Solution Approach 2:
The patent combines the functions of two planetary gear sets working in series, where the output of the first planetary gear set feeds into the input of the second planetary gear set. By merging these two gear sets with shared components (such as common clutches and brakes controlling multiple elements), the system achieves high adaptability (9-speed capability) while minimizing the total number of components compared to using separate gear trains for each speed range
3Device complexity
If traditionally designed planetary gear trains are used, then structural simplicity is maintained, but power delivery efficiency and gear ratio optimization are limited
Solution Approach 1:
The patent implements a dynamic control system using multiple clutches (first clutch, second clutch, third clutch, fourth clutch) and brakes (first brake, second brake) that can selectively engage and disengage different planetary gear elements based on driving conditions. This dynamic reconfiguration allows the system to optimize gear ratios for different operating scenarios (acceleration, cruising, deceleration, reverse), maximizing power delivery efficiency across the entire operating range while maintaining a relatively simple structural foundation
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This design enhances mountability, power delivery performance, and fuel economy by reducing the number of components and enabling flexible gear ratio adjustments, potentially replacing the torque converter with a start-up clutch for improved performance.
Implementation Method 1
frictional elements including clutches connecting the input shaft and the rotation elements of the first and second planetary gear sets and brakes connecting the rotation elements of the first and second planetary gear sets and a transmission housing
Data Source
AI summary
A planetary gear train of an automatic transmission for a vehicle may include: an input; an output; a first planetary gear set on the input including a first rotation element selectively connected to the input and selectively operated as a fixed element, a second rotation element selectively connected to the input and a third rotation element; a second planetary gear set on the output including a fourth rotation element connected to the second rotation element and selectively operated as a fixed element, a fifth rotation element connected to the third rotation element and directly connected to the output, and a sixth rotation element selectively connected to the input; four transfer gears; and frictional elements including clutches connecting the input and the rotation elements of the first and second planetary gear sets, and brakes connecting the rotation elements of the first and second planetary gear sets and a transmission housing.