Wide-node electro-mechanical drive unit for hybrid propulsion efficiency
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Solution Overview
Problem
Hybrid vehicle powertrains face inefficiencies in torque and speed management due to the need for the internal combustion engine to operate in conjunction with the electric motor, limiting the ability to achieve optimal vehicle propulsion efficiency.
Innovation Solution
A wide-node electro-mechanical drive unit with a compound planetary gear arrangement and dual motor/generators, allowing independent control of torques and speeds, and featuring a torque-transmitting device for selective engagement and disengagement to optimize gear ratios and reduce energy losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single electric motor is used in combination with the engine, then the device complexity is reduced, but the ability to independently control torque and speed is limited
Solution Approach 1:
The powertrain is segmented into two separate electric motors (first motor/generator and second motor/generator) that can independently control different aspects of torque and speed. This segmentation allows each motor to be optimized for specific functions, thereby achieving independent torque and speed control while maintaining manageable system complexity
Solution Approach 2:
The dual motor/generator system provides multi-functionality by enabling the vehicle to operate in multiple modes: series hybrid mode, parallel hybrid mode, and purely electric mode. This universality allows the powertrain to adapt to different driving conditions and efficiently manage torque and speed across a wide range of operational scenarios
2Power
If the engine operates in conjunction with the electric motor, then the power output is increased, but the propulsion efficiency is reduced due to limited torque and speed management
Solution Approach 1:
The system dynamically switches between series hybrid mode and parallel hybrid mode based on real-time driving conditions and power demands. In series mode, the engine operates at optimal efficiency points while the first motor/generator handles variable speed requirements. In parallel mode, both motors work together to deliver high power output. This dynamic operation allows the system to maintain high propulsion efficiency across varying power levels
Solution Approach 2:
The compound planetary gear arrangement enables continuous variation of gear ratios, allowing the system to optimize the operating parameters of the engine and electric motors. By changing the gear ratio parameters, the system can maintain the engine in its optimal efficiency range while meeting varying power and speed demands, thereby improving overall propulsion efficiency
3Productivity
If a wide-node gear ratio spread is achieved, then the distance traveled per engine revolution is increased, but the mechanical complexity of the gear arrangement is increased
Solution Approach 1:
The compound planetary gear arrangement uses a nested structure where multiple planetary gear sets are combined within a single mechanism. The first planetary gear set and second planetary gear set are interconnected, with shared components such as the carrier structure and ring gear structure. This nesting allows the system to achieve a wide gear ratio spread (approximately 0.7 to 1 to 4 to 1) without proportionally increasing the overall size or complexity of the mechanism
Solution Approach 2:
The patent merges the functions of multiple planetary gear sets into a single integrated compound planetary gear arrangement. By combining the first planetary gear set and second planetary gear set with shared components, the system achieves a wide-node gear ratio spread while minimizing the number of separate mechanisms required, thereby reducing mechanical complexity
4Loss of energy
If the torque-transmitting device is selectively engaged and disengaged, then the energy losses are reduced, but the control system complexity is increased
Solution Approach 1:
The torque-transmitting device is selectively engaged and disengaged in periodic cycles based on the operating mode requirements. In series hybrid mode, the device is disengaged to allow the first motor/generator to operate independently. In parallel hybrid mode, the device is engaged to transmit torque from both motors to the output shaft. This periodic engagement and disengagement minimizes mechanical energy losses associated with continuous torque transmission while using straightforward control logic
Data Source
AI summary
An electro-mechanical drive unit connectable with first and second motor/generators includes an output member, a stationary member, a gear-train, and a torque-transmitting device. The drive unit also includes a compound planetary gear arrangement having a ring gear structure, first and second sun gears, and a carrier structure. The gear arrangement includes first, second, third, and fourth junction points and has a double-pinion assembly having a first pinion gear in mesh with the first sun gear member and a second pinion gear in mesh with the first pinion gear and with the ring gear structure. The gear arrangement is operatively connected to the second motor/generator at the first junction point via the gear-train and to the first motor/generator at the fourth junction point. The output member is operatively connected to the second junction point. Furthermore, the torque-transmitting device is engageable to ground the third junction point to the stationary member.