Planetary Transmission Layout for More Forward and Reverse Ratios
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Solution Overview
Problem
Existing multi-speed transmissions face challenges in achieving a sufficient number of forward and reverse speed ratios using conventional planetary gearsets and selective couplers.
Innovation Solution
The proposed multi-speed transmission employs a configuration of five planetary gearsets and seven selective couplers, including clutches and brakes, to achieve at least nine forward and four reverse speed ratios.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional planetary gearsets and selective couplers are used, then the transmission structure is relatively simple, but the number of forward and reverse speed ratios is insufficient
Solution Approach 1:
The transmission is divided into multiple independent planetary gearsets (first, second, third, fourth, and fifth planetary gearsets), each capable of providing different speed ratios. This segmentation allows the system to achieve a greater number of forward and reverse speed ratios by selectively engaging different gearsets, resolving the contradiction between versatility and complexity.
Solution Approach 2:
The planetary gearsets are arranged in a nested configuration where multiple gearsets are integrated within a single transmission housing. The first planetary gearset includes sun gear, planet gears, and ring gear, with subsequent gearsets similarly structured and interconnected through shared components like the input shaft and output shaft. This nesting enables compact arrangement of multiple speed ratio mechanisms.
2Adaptability or versatility
If multiple planetary gearsets and selective couplers are added to increase speed ratios, then the adaptability improves, but the device complexity increases
Solution Approach 1:
The selective couplers (clutches and brakes) serve multiple functions: clutches connect different planetary gearsets to the input shaft, while brakes hold various gear components (sun gears, ring gears, planet carriers) stationary. Each coupler can engage different components to achieve various speed ratios, making the system more versatile without proportionally increasing component count.
Solution Approach 2:
Multiple planetary gearsets are merged into a single integrated transmission system with shared input and output members. The first, second, third, fourth, and fifth planetary gearsets all connect to the common input shaft and output shaft, allowing them to work together or independently to provide multiple speed ratios. This merging reduces overall system complexity compared to having separate transmission units.
3Manufacturing precision
If seven selective couplers are used to achieve nine forward and four reverse speed ratios, then the speed ratio control precision improves, but the manufacturing complexity increases
Solution Approach 1:
Each selective coupler is designed with specific engagement characteristics tailored to its function: clutches are designed to connect rotating components while brakes are designed to hold components stationary. The couplers are distributed throughout the transmission at different locations, with each coupler controlling a specific gear component or connection point, enabling precise local control of speed ratios.
Solution Approach 2:
The planetary gearsets and selective couplers are pre-configured in the transmission housing with predetermined engagement relationships. The clutches and brakes are positioned to engage specific components (sun gears, ring gears, planet carriers) of the planetary gearsets, so that when activated, they immediately establish the desired speed ratio without requiring complex real-time adjustments during operation.
Data Source
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AI summary
A multi-speed transmission may include a plurality of planetary gearsets and a plurality of selective couplers. The plurality of planetary gearsets may include a first planetary gearset, a second planetary gearset, a third planetary gearset, a fourth planetary gearset, and a fifth planetary gearset. The plurality of selective couplers may include a number of clutches and a number of brakes. The multi-speed transmission may have five planetary gearsets and seven selective couplers. The seven selective couplers may include two clutches and five brakes or three clutches and three brakes.