Six-Speed Automatic Transmission Three Planetary Gearsets
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Solution Overview
Problem
Conventional automatic transmissions face difficulties in achieving an overdrive ratio of 0.75 or greater while maintaining numerically higher gear ratios in lower gears, which affects vehicle drivability, performance, and fuel economy.
Innovation Solution
The automatic transmission incorporates three planetary gearsets with specific coupling arrangements between the planetary carriers, sun gears, and annulus gears, along with clutch and brake assemblies to achieve improved gear ratio spacing, including a permanently coupled first planetary carrier with the second sun gear and annulus gears, and an output member connected to the annulus gear and planetary carrier of the third gearset, allowing for selective engagement to achieve underdrive and overdrive ratios.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional planetary gearset design is used, then the transmission can provide various torque ratios, but it becomes difficult to achieve an overdrive ratio of 0.75 or greater while maintaining numerically higher gear ratios in lower gears
Solution Approach 1:
The transmission system is divided into three separate planetary gearsets (first, second, and third planetary gearsets) with distinct functions. The first planetary gearset handles lower gear ratios, the second planetary gearset enables overdrive ratios, and the third planetary gearset provides additional ratio steps. This segmentation allows each gearset to be optimized for specific ratio ranges, resolving the contradiction between achieving high overdrive ratios and maintaining proper lower gear ratios for drivability.
2Adaptability or versatility
If complex planetary gearset arrangements are used to achieve improved ratio spacing, then overdrive ratio of 0.82 in fifth gear and 0.63 in sixth gear is achieved, but the device complexity increases
Solution Approach 1:
The patent merges three planetary gearsets into a single integrated transmission system where the gearsets share common components and are controlled by a unified clutch and brake assembly system. The permanent couplings between planetary carriers and sun gears create a consolidated structure that achieves complex ratio spacing (0.82 in fifth gear, 0.63 in sixth gear) without requiring separate transmission units, thereby managing device complexity while maintaining versatile gear ratios.
3Adaptability or versatility
If multiple clutch and brake assemblies are used to selectively engage planetary gearsets, then various gear ratios including reverse are achieved, but the device complexity increases
Solution Approach 1:
The clutch and brake assemblies are designed with multi-functionality to control multiple planetary gearsets simultaneously. The same clutch assemblies (first, second, and third clutch assemblies) and brake assemblies (first, second, and third brake assemblies) can engage different combinations of planetary gearsets to achieve various forward gears, reverse gear, and overdrive ratios. This universal control system reduces the need for dedicated actuators for each gear ratio, managing device complexity while maintaining versatile gear selection capability.
Data Source
AI summary
A six-speed automatic transmission for a vehicle includes a transmission housing, an input member, an output member, three planetary gearsets for changing a ratio of torque between the input member and the output member, clutch assemblies to selectively couple the input member to predetermined members of the planetary gearsets, and brake assemblies to selectively couple predetermined members of the planetary gearsets to the transmission housing. The transmission achieves an improved gear ratio spacing and, correlatively, enhanced vehicle drivability, performance, and fuel economy, by respectively permanently coupling the planetary carrier of the first gearset with the sun gear of the second gearset, the annulus gears of the first and third gearsets with the planetary carrier of the second gearset, and the output member with both the annulus gear of the second gearset and the planetary carrier of the third gearset.