Multi-speed countershaft transmission with planetary gear set
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Solution Overview
Problem
Traditional multi-speed transmissions require a large number of gears and clutches to achieve a wide range of speed ratios, leading to increased complexity, length, and fuel inefficiency, particularly in automatic transmissions.
Innovation Solution
A combination countershaft and planetary gear set transmission that achieves nine forward and at least one reverse speed ratio using only eight torque-transmitting mechanisms, minimizing the number of gears on the countershafts and incorporating a two-way dog clutch and rotating clutches to reduce overall length and enhance fuel efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If traditional multi-speed transmissions use a large number of gears and clutches to achieve wide speed ratios, then the speed ratio coverage is improved, but the device complexity and length increase
Solution Approach 1:
The patent combines a planetary gear set with a countershaft transmission system into a single integrated transmission unit. The planetary gear set provides multiple speed ratios through its inherent mechanism, while the countershaft transmission adds additional ratios through gear pairs. This merging of two transmission systems allows achieving nine forward speed ratios and reverse capability with only eight torque-transmitting mechanisms, rather than requiring separate transmission systems or numerous individual gears and clutches.
Solution Approach 2:
The planetary gear set serves multiple functions within the transmission system: it provides direct drive ratio, overdrive ratio, and intermediate ratios, while also enabling reverse operation when combined with the countershaft system. The countershaft gears similarly serve multiple ratio achievement functions. This multi-functionality reduces the need for dedicated components for each speed ratio, thereby reducing overall device complexity.
2Ease of operation
If traditional transmissions increase the number of gears to reduce ratio step size, then the shift quality is improved, but the device length and fuel efficiency worsen
Solution Approach 1:
By merging the planetary gear set with the countershaft transmission, the patent achieves nine forward speed ratios within a compact configuration. The planetary gear set inherently provides closely spaced ratios through its sun gear, ring gear, and carrier combinations, while the countershaft adds complementary ratios. This combination achieves small ratio steps (improving shift quality) without requiring a long sequence of individual gears, thus controlling transmission length.
3Extent of automation
If automatic transmissions use multiple friction clutches and dog clutches for dynamic shifts, then the automation level is improved, but the device complexity and fuel consumption increase
Solution Approach 1:
The patent integrates the planetary gear set with the countershaft transmission system, allowing automatic shifting to be achieved with fewer torque-transmitting mechanisms (eight total). The planetary gear set's inherent design allows for smooth ratio transitions with reduced clutching requirements compared to traditional multi-gear countershaft systems, thereby reducing both device complexity and associated fuel consumption.
Data Source
AI summary
A transmission is provided that combines first and second countershafts with a planetary gear set, and uses first and second head gear sets to provide ratio. Each of the countershafts supports gears in no more than five co-planar, intermeshing gear sets (and in most embodiments no more than four co-planar, intermeshing gear sets), thus minimizing the overall length of the countershafts. The transmission provides at least nine forward speed ratios and a reverse speed ratio and utilizes only eight torque-transmitting mechanisms.