Dual-Motor Electric Powertrain With Selective Torque Sharing
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Solution Overview
Problem
Electrically operated working machines, such as wheel loaders and wheeled excavators, face inefficiencies due to the need for oversized electric motors to handle high propulsion power requirements in certain applications, while hydraulic power demands are often low, leading to suboptimal energy usage and motor sizing.
Innovation Solution
A powertrain configuration with two electric machines and a transmission assembly that allows selective gear engagement and torque transfer between them, enabling efficient use of torque for various applications by tailoring the motor sizing for common use cases and assisting only when necessary, with friction clutches for smooth engagement and a dog clutch for reduced frictional losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a single oversized electric motor is used for propulsion to handle high power requirements in uphill applications, then the machine can provide sufficient propulsion power, but the motor is oversized for common applications leading to suboptimal energy usage
Solution Approach 1:
The single propulsion motor is segmented into two separate electric machines: a first electric machine connected to the propulsion axle and a second electric machine connected to the power take-off. This segmentation allows each machine to be optimally sized for its specific function, with the first machine handling propulsion and the second machine handling hydraulic power, thereby avoiding the energy inefficiency of using an oversized motor for all operations.
Solution Approach 2:
The second electric machine serves dual purposes: it can independently power the hydraulic system through the power take-off, and it can also assist the first electric machine in providing additional propulsion power when needed. This multi-functionality allows the system to handle both common applications efficiently and high-power uphill applications effectively.
2Productivity
If propulsion and working hydraulics are separated in electrically operated working machines to optimize each function, then each function can be optimized, but each function may require an unusually high power in certain applications
Solution Approach 1:
While the propulsion and hydraulic systems are separated into different electric machines, the patent merges their power delivery through the transmission assembly. The transmission assembly includes a first output shaft connected to the propulsion axle and a second output shaft for power take-off, allowing both systems to operate independently yet be integrated when additional power is required.
Solution Approach 2:
The transmission assembly acts as an intermediary between the two electric machines and their respective outputs. It includes selectively engageable gears and clutches that mediate the power flow, allowing torque from either or both electric machines to be transferred to the appropriate output shaft, thereby managing power requirements efficiently.
3Power
If a second electric machine is added to assist the first electric machine for propulsion in torque demanding applications, then torque availability is improved, but the device complexity increases
Solution Approach 1:
The second electric machine is designed with multi-functionality: it primarily powers the hydraulic system through the power take-off but can also assist the first electric machine in propulsion when needed. This universal design justifies the added complexity by providing dual benefits without requiring a third dedicated assistance motor.
Solution Approach 2:
The patent merges the functions of a dedicated hydraulic motor and a propulsion assistance motor into a single second electric machine. This machine can be selectively connected to either the power take-off or the propulsion system through the transmission assembly, reducing overall system complexity compared to having separate machines for each function.
Data Source
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AI summary
An electric powertrain (200) for a working machine, comprising: - a first electric machine (20), - a second electric machine (30), - a propulsion axle (40) for propulsion of the working machine, - a transmission assembly (1) comprising: a first input shaft (2) drivingly connected to the first electric machine; a second input shaft (3) drivingly connected to the second electric machine; a first output shaft (4) drivingly connected to the propulsion axle, the first and the second input shafts being selectively drivingly connectable to the first output shaft; at least one second output shaft (5) for power take-off, to which the second input shaft is drivingly connected; a set of gears (6) comprising at least two selectable gear ratios for transfer of torque, wherein at least the first input shaft is drivingly connectable to the first output shaft via the set of gears.