Amid a wave of new electric motor patents from Porsche, GM, and Hyundai all focusing on different aspects of rotor design to improve power and efficiency, Mercedes-Benz’s latest patent filing with the European Patent Office proposes a clever two-disc rotor. The concept varies the relative speed of concentric discs to finely tune the magnetic field, delivering a more compact, efficient motor layout without sacrificing performance.
Compact Power, Less Wear
Various factors affect the output and efficiency of an electric motor, and the rotor is a central part of the equation, with its own set of variables, such as the arrangement of wire and rod conductors and the iron loss that usually accompanies a rotor with an iron core. Mercedes-Benz’s focus with this patent is a more compact motor size and a reduction in the axial force exerted by the motor through a two-disc rotor design. Excessive axial force places additional strain on motor components and causes wear. So dialing it back means a longer-lasting, more reliable electric motor.
Key System Components
- Driveshaft & Sleeve Assembly: A driveshaft carries torque, while an axially movable sleeve rides over it.
- Helical Gear Pair: These gears mesh the driveshaft and sleeve, converting sleeve movement into relative disc rotation.
- Actuator Mechanism: Precisely shifts the sleeve along the shaft to control gear engagement.
- Dual Rotor Discs: Two concentric discs—one fixed axially, the other driven by the shaft—form the heart of the variable-field rotor.
Dynamic Field Control
The inner rotor disc is locked in place axially on its shaft, while the outer disc is driven by the rotating driveshaft. When the actuator slides the sleeve, it changes how the helical gears bind the two discs, altering their relative speeds. By tweaking that speed differential, the motor’s control unit can reshape the magnetic field in real time—modulating torque, power, and efficiency on demand. Various actuator designs (electric, hydraulic, or magnetic) can be used to suit different performance and packaging requirements.
Unique Selling Points
Beyond its gains in power and efficiency, this two-disc rotor’s primary advantage is its ultra-compact packaging. This makes it particularly suitable for in-wheel hub motors and in slashing axial thrust. By reducing the inward force on bearings and components, it minimizes wear and maximizes motor lifespan.
