Ravigneaux Planetary Gearset Transmission with Electrical Machine
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Solution Overview
Problem
Existing transmissions with Lepelletier gear sets require a large number of clutches and brakes, as well as separate starting devices like hydrodynamic torque converters, which increase complexity and cost.
Innovation Solution
The Ravigneaux planetary gear set is drive-connected to a secondary drive, such as an electrical machine, and a braking device is used to block a sun gear shaft, allowing for a compact design with reduced clutch and brake devices, enabling stepless power-split operation and three gears for combined and electric drive modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a Lepelletier gear set with simple planetary set and Ravigneaux set is used, then transmission functionality is improved, but the number of clutches and brakes increases
Solution Approach 1:
The patent combines the simple planetary set and Ravigneaux set into a unified gear structure where the carrier of the simple planetary set serves as the sun gear of the Ravigneaux set. This merging reduces the number of independent components and their associated control elements (clutches and brakes), while maintaining multiple transmission functions through the integrated structure.
Solution Approach 2:
The integrated planetary gear set is designed to perform multiple functions simultaneously - it can operate in different gear ranges, provide starting torque, and enable power splitting without requiring separate dedicated components for each function. The single gear structure replaces multiple specialized components, reducing overall system complexity.
2Ease of operation
If separate starting devices like hydrodynamic torque converters are used, then starting capability is improved, but device complexity and space requirements increase
Solution Approach 1:
The patent extracts the starting function from separate hydrodynamic torque converters and integrates it directly into the planetary gear set structure. The carrier of the simple planetary set serves as the sun gear of the Ravigneaux set, creating an inherent starting mechanism that eliminates the need for external starting devices.
Solution Approach 2:
The starting capability is merged with the transmission gear structure itself. The integrated planetary sets provide starting torque generation as an intrinsic function rather than requiring a separate hydrodynamic starting device, thereby reducing space requirements and device complexity.
3Adaptability or versatility
If multiple clutches and brakes are used for power splitting, then power-split operation ranges are improved, but manufacturing cost and device complexity increase
Solution Approach 1:
The patent merges multiple power-split functions into a single integrated planetary gear structure. By combining the simple planetary set and Ravigneaux set, the system achieves multiple power-split operation ranges without requiring multiple separate clutch and brake assemblies, thereby reducing manufacturing cost and complexity.
Solution Approach 2:
The integrated gear set is designed to provide multiple power-split operation ranges through its unified structure. The same combined planetary mechanism can operate in different modes (first power-split range, second power-split range, third gear range) without requiring separate dedicated components for each range, reducing overall manufacturing cost.
Data Source
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AI summary
The invention relates to a transmission (1) that comprises a drive train having a primary drive with a primary drive shaft (16), particularly for a vehicle, and that comprises a Ravigneaux planetary gearset (2) which has a double planetary gear with two sun gear shafts (10, 13), one planetary carrier shaft (18) and at least one ring gear shaft (12), as well as an upstream single planetary gearset (3) which is designed as a reduction gearing and comprises the gear elements of sun gear (5a), planetary carrier (8a) and ring gear (6a). A first of said gear elements of the single planetary gear set (2), particularly the sun gear (5a), is designed to be fixed to a housing. According to the invention, at least one first element of said Ravigneaux planetary gear set (2) is drive-connected, preferably permanently, to a secondary drive (21) which is particularly preferred to be in the form of an electrical machine.