Multi-speed Transmission with Four Planetary Gear Sets
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Solution Overview
Problem
Current multi-speed automatic transmissions face challenges in achieving a sufficient number of forward gears with a large overall transmission ratio spread while minimizing construction costs and avoiding group gearshifts, which are complex and costly to implement.
Innovation Solution
The proposed solution involves a multi-speed transmission with four planetary gear sets and six or seven shift elements, allowing for the shifting of ten or eleven forward gears and one reverse gear without group gearshifts, utilizing a specific arrangement of planetary gear sets and shift elements to achieve independent kinematics and efficient gear shifting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the number of forward gears is increased to achieve a large overall transmission ratio spread, then the transmission ratio spread is improved, but the number of shift elements and device complexity increases
Solution Approach 1:
The transmission is divided into four separate planetary gear sets, each capable of independent operation. This segmentation allows the transmission to achieve a wide overall ratio spread (up to 11 forward gears) by selectively engaging different planetary gear sets and their various gear ratios, rather than requiring a single complex gear train with many shift elements.
Solution Approach 2:
Each planetary gear set is designed with multiple elements (sun gear, planet gears, ring gear, carrier) that can serve multiple functions. By selectively fixing different elements and changing power flow paths, each planetary gear set can provide multiple gear ratios, reducing the need for additional dedicated shift elements for each gear.
2Adaptability or versatility
If more planetary gear sets are added to increase the number of forward gears, then the number of forward gears is improved, but construction costs and device complexity increase
Solution Approach 1:
The transmission uses four modular planetary gear sets that can be manufactured as standardized units. This segmentation into identical or similar modules simplifies manufacturing processes and reduces construction costs compared to designing a completely different gear train for each gear ratio.
Solution Approach 2:
The invention achieves different gear ratios by changing the engagement state of shift elements (clutches and brakes) rather than physically changing the gear set configuration. This allows the same hardware to provide multiple gear ratios, reducing construction costs.
3Productivity
If sequential shifting is implemented to avoid group gearshifts, then shifting efficiency is improved, but the kinematic complexity of the transmission increases
Solution Approach 1:
The transmission employs dynamic engagement and disengagement of clutches and brakes to achieve sequential gear shifts. By controlling the timing and sequence of shift element engagement, the transmission can shift gears one at a time without requiring complex group gearshift mechanisms, maintaining relatively simple kinematics while achieving high shifting efficiency.
Data Source
AI summary
An automatic transmission includes a housing, a plurality of rotatable shafts, a plurality of planetary gear sets and a plurality of shift elements. A second element of a fourth planetary gear set forms a drive shaft, and a second element of a third planetary gear set forms an output shaft. A first element of the fourth planetary gear set forms a third shaft, and a fifth shaft is constantly connected to at least two shift elements of the plurality of shift elements. A third element of the third planetary gear set forms a sixth shaft, and a seventh shaft constantly connects a first element of a second planetary gear set to a third element of the fourth planetary gear set. A second element of the second planetary gear set forms an eighth shaft.