Three-Planetary Automatic Transmission Layout for Compact 8-Speed Gearing
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Solution Overview
Problem
Current eight-speed automatic transmissions face challenges in compactness and lightweight design due to complex structures and increased components, such as multiple planetary rows and clutches, which affect fuel efficiency and structural complexity.
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 enhancing compactness and lightweight design by selectively engaging operating elements to establish multiple speed ratios.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the number of gears in the automatic transmission is increased to improve fuel consumption, then the fuel economy is improved, but the number of planetary rows and clutches increases making the structure more complex
Solution Approach 1:
The patent combines multiple planetary gearsets into a shared structure where three planetary rows share common components including the input element, output element, and housing. This merging approach allows eight-speed transmission capability while reducing the total number of independent planetary rows and clutches compared to conventional designs, thereby maintaining fuel efficiency without proportionally increasing structural complexity
Solution Approach 2:
The planetary gearsets are designed with multi-functional elements that serve multiple purposes across different gear ratios. The same planetary components participate in different gear formation combinations, allowing a single planetary row to contribute to multiple speed ratios. This universality reduces the need for additional dedicated components for each gear, balancing the complexity increase from higher gear count
2Adaptability or versatility
If more planetary rows and clutches are added to achieve more gears, then the gear ratio range is improved, but the volume and weight of the transmission increase
Solution Approach 1:
The patent employs a nested arrangement where planetary gearsets are positioned concentrically around a common rotation axis. The planetary rows are arranged in series along the rotation axis with compact spacing, and components are nested within the housing structure. This nesting allows multiple planetary rows to occupy minimal space while providing a wide gear ratio range through their combined operation
Solution Approach 2:
Instead of arranging planetary rows in a linear sequence that increases volume, the patent utilizes the axial dimension by ordering planetary rows along the rotation axis. This dimensional arrangement allows gear ratio changes to be achieved through axial positioning and selective engagement rather than radial expansion, maintaining compact transmission volume while achieving versatile gear ratios
3Adaptability or versatility
If more planetary rows and clutches are added to achieve more gears, then the gear ratio range is improved, but the weight of the transmission increases
Solution Approach 1:
The patent merges multiple planetary gearsets into a shared structure where three planetary rows share common components including the input element, output element, and housing. This merging approach allows eight-speed transmission capability while reducing the total number of independent planetary rows and clutches compared to conventional designs, thereby maintaining fuel efficiency without proportionally increasing structural complexity
Solution Approach 2:
The patent employs composite construction methods where planetary gearsets and housing are designed as integrated composite structures. The housing serves multiple functions as both structural support and component mounting platform, reducing the need for separate weightly components. This composite approach achieves wide gear ratio range while controlling transmission weight
4Productivity
If conventional planetary row structures are used to achieve eight-speed transmission, then the gear shifting capability is improved, but the manufacturing complexity and cost increase
Solution Approach 1:
The patent segments the transmission into three distinct planetary rows that can be manufactured and assembled as modular units. Each planetary row is designed as a separate assembly that can be produced independently using standardized manufacturing processes, then integrated into the complete transmission. This segmentation simplifies manufacturing compared to monolithic designs while maintaining eight-speed capability through the combined operation of segmented planetary rows
Data Source
AI summary
The input element of the automatic transmission 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, and the third sun gear is stationary. The first brake is engaged to brake the first rear sun gear, the second brake is engaged to brake the first front sun gear, and the third brake is engaged to simultaneously brake the first planetary carrier and the second gear ring; the first rear sun gear is connected to the input element via the first clutch, the first planetary carrier is connected to the second sun gear via the second clutch, and the first planetary carrier is connected to the second gear ring via the third clutch.