Translatable Rotor Hub for Variable Torque Electric Machines
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Solution Overview
Problem
Permanent magnet-type electric machines experience efficiency decreases at high-speed/low-torque operating conditions, compromising their energy efficiency advantages compared to internal combustion engines.
Innovation Solution
The electric machine features a translatable rotor hub with varying magnetic field strengths and reluctance characteristics along its axial length, allowing continuous variation of magnetic and reluctance torque contributions by adjusting its position relative to the stator assembly, enabled by an actuator or self-actuation via flux-weakening currents, to optimize torque distribution based on speed and load.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the electric machine operates at high speed, then the rotational speed increases, but the torque decreases and energy efficiency deteriorates
Solution Approach 1:
The rotor hub is made dynamically adjustable along the axial direction, allowing it to change position between a first position (for high torque) and a second position (for high speed). This dynamic reconfiguration enables the electric machine to adapt its magnetic characteristics to different operating conditions, maintaining energy efficiency across both high-speed/low-torque and low-speed/high-torque regimes.
Solution Approach 2:
The invention changes the magnetic reluctance parameter by adjusting the rotor hub position. At the first axial position, the rotor hub provides high magnetic reluctance for high torque output, while at the second axial position, it provides low magnetic reluctance optimized for high speed operation. This parameter adjustment resolves the contradiction between speed and energy efficiency.
2Force
If the magnetic field strength is increased to improve torque output, then the torque increases, but the complexity of the magnetic field distribution increases
Solution Approach 1:
The rotor hub is segmented into different axial regions with distinct magnetic field characteristics. The first end of the rotor hub has magnetic field characteristics optimized for high torque, while the second end is optimized for low torque/high speed operation. By translating the rotor hub axially, the appropriate segment is positioned to interact with the stator windings, simplifying the magnetic field distribution control.
Solution Approach 2:
The invention extracts the torque optimization function from a complex distributed magnetic field system and concentrates it in the translatable rotor hub structure. By moving the rotor hub to different positions, the system selectively engages different magnetic field strength regions, achieving variable torque output without requiring complex real-time magnetic field distribution control.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration enhances efficiency by dynamically adjusting torque contributions, maintaining high efficiency across varying operating conditions without compromising structural integrity or packaging, thereby improving performance in high-speed/low-torque scenarios.
Implementation Method 1
the electric machine has continuously-variable magnetic reluctance characteristics that are selected in response to the current rotational speed and torque of the electric machine
Implementation Method 2
The rotating electromagnetic field then interacts in a push-pull manner with the permanent magnetic field of the rotor hub, with the resultant forces rotating the rotor shaft
Implementation Method 3
self-actuation via flux-weakening currents, with the resultant field changes caused by introduction of the stator current serving to attract or repel the rotor hub as needed
Data Source
AI summary
An electric machine produces motor torque having continuously variable magnetic and reluctance torque components. The electric machine includes stator and rotor assemblies. Different ends of the rotor hub have different average magnetic field strengths, with the second field strength at one end being weaker than the other. The rotor hub translates along the rotor shaft to vary the magnetic and reluctance torque components at different speed and torque operating points of the electric machine. A vehicle includes the machine, a transmission, a load, and a controller executing a method for controlling the axial position of the rotor hub. The method may include determining the speed and a torque of the electric machine, determining a corresponding desired axial position of a rotor hub, and translating the rotor hub to the desired axial position.