Dual Electric Machine Powertrain with Segmented Torque Paths
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Solution Overview
Problem
Existing electric vehicle powertrains face challenges in increasing tractive torque and power while minimizing torque interruption during gear shifts, particularly in heavy-duty applications.
Innovation Solution
A powertrain configuration featuring two electric machines connected to a transmission with distinct gear ratios, where one torque path has a fixed gear ratio and the other has two selectable gear ratios, allowing for converged power flow to a common output shaft, enhancing tractive torque and power output while optimizing energy efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If two electric machines are used with converged power flow to increase tractive torque and power, then the total power output increases, but the transmission complexity increases due to multiple torque paths and gear ratios
Solution Approach 1:
The transmission is segmented into two independent torque paths: a first torque path with a fixed gear ratio for continuous torque transmission, and a second torque path with two selectable gear ratios for optimized performance. This segmentation allows each path to be optimized independently while maintaining overall system manageability despite the increased complexity from dual electric machines
Solution Approach 2:
The transmission system performs multiple functions through its dual torque path architecture: it provides continuous torque transmission via the first path, enables gear ratio selection for optimized performance via the second path, and allows seamless transitions during gear shifts. The first torque path serves as a universal backup and continuous operation path while the second path provides specialized optimized ratios
2Use of energy by moving object
If gear shifts are performed in the second torque path, then optimal working points are achieved for electric machines, but torque interruption occurs during the shift process
Solution Approach 1:
The first torque path is pre-configured with a fixed gear ratio that enables continuous torque transmission. Before a gear shift is initiated in the second torque path, the first torque path is already prepared to immediately take over torque transmission, ensuring no interruption occurs. This preliminary preparation of the alternative torque path eliminates torque gaps during transitions
Solution Approach 2:
The first torque path acts as an intermediary during gear shifts in the second torque path. When the second path is shifting between its two gear ratios, the first torque path mediates by providing continuous torque transmission to the output shaft, bridging the temporary disconnection in the second path and maintaining overall torque continuity
3Adaptability or versatility
If three different gear ratios are used across two torque paths, then better working points are obtained for electric machines, but the device complexity increases with more gear selection mechanisms
Solution Approach 1:
The three gear ratios are segmented across two torque paths: one fixed ratio in the first path and two selectable ratios in the second path. This segmentation simplifies the selection mechanism compared to having three selectable ratios in a single path, as the first path requires no selection mechanism and provides a continuous baseline option
Solution Approach 2:
The system dynamically selects between the first torque path with its fixed gear ratio and the second torque path with its two selectable gear ratios based on operating conditions. This dynamic selection allows the system to adapt to different working points and optimize electric machine performance without requiring a complex fixed mechanism for all three ratios
Data Source
AI summary
A vehicle powertrain includes a first electric machine and a second electric machine, a transmission arranged to transmit torque from the electric machines to a pair of driven wheels of a vehicle, where the first electric machine is drivingly connected to a first input shaft of the transmission and a second electric machine is drivingly connected to a second input shaft of the transmission, a first torque path for transmitting torque includes only one gear ratio between the first input shaft and an output shaft of the transmission, and a second torque path for transmitting torque includes two selectable and separately engageable gear ratios between the second input shaft and the output shaft of the transmission, and where the three gear ratios of the first and second torque paths are different from each other.