Three-Planetary Automatic Transmission Layout for Compact 8-Speed Gearing
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Solution Overview
Problem
Current eight-speed automatic transmissions in passenger cars face issues with compactness and lightweight design due to complex structures and increased number of planetary rows and clutches, which affect fuel efficiency and overall transmission efficiency.
Innovation Solution
An automatic transmission system utilizing three planetary rows with three single planetary gearsets, three clutches, and three brakes to achieve eight forward gears and one reverse gear, simplifying the structure and improving compactness and lightweight design by selectively engaging operating elements to achieve multiple speed ratios.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the number of planetary rows and clutches is increased to achieve more gears, then the fuel consumption decreases and economy improves, but the device complexity and number of elements increase
Solution Approach 1:
The patent combines multiple planetary rows (first, second, and third planetary rows with sun gears, planetary gear sets, and ring gears) into a single integrated transmission system where they work cooperatively to achieve eight-speed transmission. This merging approach reduces the need for separate clutch assemblies for each gear, thereby decreasing overall device complexity while maintaining multiple gear ratios for fuel efficiency.
Solution Approach 2:
The transmission system employs three clutches (first, second, and third clutches) that serve multiple functions across different gear ratios. Each clutch can engage with different planetary rows to achieve various forward gears and reverse gear, making the clutches multi-functional. This universality reduces the total number of clutches needed compared to traditional designs where each gear requires a dedicated clutch.
2Productivity
If the Lavina structure and double planetary gearsets are adopted to achieve eight-speed transmission, then the gear ratios are achieved, but the structure becomes too complicated which is not conducive to lightweight design
Solution Approach 1:
The patent divides the transmission system into three distinct planetary rows, each with its own sun gear, planetary gear set, and ring gear. This segmentation allows for a more organized and potentially lighter structure compared to the integrated Lavina structure, as each segment can be optimized independently and assembled in a distributed manner, reducing overall complexity and weight.
Solution Approach 2:
Instead of using the traditional Lavina structure with double planetary gearsets, the patent inverts the approach by using three separate single planetary gear rows. This inversion simplifies the structural design, making it more conducive to lightweight construction while still achieving the required eight-speed transmission capability through clever engagement of the three clutches and three brakes.
3Productivity
If four pairs of fixed-shaft constant meshing gears are added on the intermediate shaft to achieve eight-speed transmission, then the gear ratios are achieved, but the elements of the transmission increase which is not conducive to compactness
Solution Approach 1:
The patent employs a nested arrangement where the three planetary rows are concentrically positioned around a common input shaft, with each planetary row containing sun gears, planetary gears, and ring gears that are nested within each other. This nesting eliminates the need for separate fixed-shaft constant meshing gears on an intermediate shaft, as the planetary gears themselves provide the constant meshing function. The result is a more compact transmission volume while maintaining eight-speed capability.
Data Source
AI summary
An automatic transmission having three planetary rows, which includes an input element and an output element. The input element is fixedly connected to the second sun gear, the output element is fixedly connected to the third planetary carrier, the second planetary carrier is fixedly connected to the third gear ring, the first gear ring is fixedly connected to the third planetary carrier. When the brake is engaged, the elements connected with the brake are braked accordingly. The first rear sun gear is connected to the input element, the second planetary carrier is connected to the third gear ring, and the second clutch is selectively engaged to connect with any two of the second sun gear, the second gear ring and the second planetary carrier, so as to make the second planetary row rotate overall.