Multi-mode Hybrid Drive Unit with Planetary Gear Sets
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Solution Overview
Problem
Traditional hybrid transmissions face challenges in providing both optimum low-speed torque and highway speed efficiency, often requiring large and expensive electric machines, leading to inefficiencies and increased complexity and size, which negatively impacts fuel economy and manufacturing costs.
Innovation Solution
A hybrid drive unit with first and second planetary gear sets, electric machines, and clutch mechanisms that allow for selective coupling of electric machines to the output shaft, enabling operation in three modes by activating different clutch mechanisms, reducing complexity and size while improving efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If large and powerful electric machines are used to provide optimum torque during low speed operation, then low speed torque is improved, but device complexity and size increase
Solution Approach 1:
The system dynamically switches between single-mode and multi-mode operations based on driving conditions. The clutch mechanisms enable or disable specific planetary gear sets and electric machine connections, allowing the transmission to adapt its complexity level - using simpler single-mode operation when possible and more complex multi-mode operation when performance demands require it
Solution Approach 2:
The electric machines serve multiple functions across different operating modes - they can operate as motors during low-speed torque demands, as generators during regenerative braking, and can be selectively connected or disconnected via clutch mechanisms. This multi-functionality allows smaller electric machines to replace larger dedicated motors while maintaining performance across various operating conditions
2Adaptability or versatility
If multiple planetary gear sets are used to provide multiple modes of operation, then adaptability is improved, but device complexity and size increase
Solution Approach 1:
The transmission dynamically reconfigures its gear ratios and power flow paths by engaging or disengaging clutch mechanisms connected to different planetary gear sets. This allows the system to switch between single-mode and multi-mode operations, adapting to different driving conditions without permanently maintaining complex multi-gear architecture that would be required in traditional multi-mode transmissions
3Adaptability or versatility
If multiple planetary gear sets rotating at all times are used, then multiple gear ratios are achieved, but energy loss increases
Solution Approach 1:
The system extracts or disconnects unnecessary planetary gear sets and electric machine connections from active operation through clutch mechanisms. During single-mode operation, certain planetary gear sets are disengaged and removed from the power flow path, eliminating their associated friction losses and improving fuel economy while maintaining the capability to engage them when multi-mode operation is required
4Adaptability or versatility
If numerous offset axes of rotation are used to achieve multiple modes, then adaptability is improved, but device complexity and packaging difficulty increase
Solution Approach 1:
The patent merges multiple planetary gear sets and electric machine connections onto a common axis of rotation. The input shaft, electric machine shaft, and output shaft all share a common axis, eliminating the need for numerous offset axes. This consolidation simplifies the transmission architecture, reduces packaging requirements, and lowers manufacturing complexity while maintaining the ability to achieve multiple operating modes through selective clutch engagement
Data Source
AI summary
A hybrid transmission providing multiple modes of operation in a compact arrangement is provided and includes first and second planetary gear sets and first and second electric machines. An electric machine shaft directly couples the first planetary gear set to the second planetary gear set and the second electric machine to the second planetary gear set. The second electric machine is selectively directly coupled to an output shaft via a first clutch mechanism, and indirectly coupled to the output shaft via the second planetary gear set and a drive shaft, which extends parallel to the electric machine shaft and external to the second electric machine. A second clutch mechanism selectively couples the first electric machine to a carrier of the second planetary gear set and a third clutch mechanism selectively couples a ring gear of the second planetary gear set to a hybrid drive unit housing.