BREAKTHROUGH e-bike rim electromotor

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Motor with magnets directly on the wheel rim

The motor is an integrated part of the rear wheel. The wheel is formed directly by the rotor of the motor, which has magnets installed around its circumference. The arc-shaped stator is part of the rear structure of the frame. The stator magnetic flux is oriented axially. The solution offers key advantages over current engines

  • power/weight ratio
  • low cost of production
  • it does not contain any gearbox or moving component

Direct rim drive for an electric bike

The transmission of the driving power of the drive is gearless, where the power is transmitted directly to the wheel circumference, thus the electric motor is efficient and provides a large torque. The drive does not contain any gearbox, planetary gearbox or friction gear. The driving force is transferred to the rotor with permanent magnets based on the rotating magnetic field generated by the stator of the electric motor. The design enables low-cost production. It is suitable for extreme conditions of dust, mud, rain, snow and large temperature changes and has a low weight. There is no risk of wear, corrosion and water ingress into electric motor elements or transmission components, because it does not contain them.

The drive is based on the principles of a PMSM synchronous electric motor with permanent magnets on the rotor. The stator and rotor are effectively and cooled by naturally flowing air, therefore the permanent magnets never heat up (>80°) so that there is a risk of losing the magnetic ability of the permanent magnets, also the stator coils of the stator are effectively cooled. This aspect increases the overall efficiency and stability of the motor, and at the same time has an advantage over the commonly used closed motors.

Recovery: The stator winding of the motor can be switched to electric energy recovery mode when braking the electric bicycle. During braking, permanent magnets can induce an electromotive voltage in the coils, which in the reverse connection of the power supply circuit, the induced current recharges the battery.

Permanent magnets are located on the circumference of the wheel (open rotor). The stator bodies are not covered on the entire circumference of the rotor, but are placed on the fork on both sides and form only an arc (open stator). Stator bodies contain a stator winding that can be powered by alternating current from the e-bike source. Alternating current is generated using a microprocessor-controlled conversion of the direct current of the battery in the electric bicycle. There are different variants of synchronous motors that use different current waveforms, sinusoidal, trapezoidal, triangular, square or otherwise modified direct current. The implementation in this case is a power supply using a 3-phase current with a sinusoidal waveform where each phase is shifted by 120 degrees. The 3-phase sinusoidal waveform has the best efficiency in driving power transmission and a good effect on engine traction. The video in 3D presentation shows the rotating magnetic field and its intensity due to the action of a 3-phase sinusoidal current in the stator winding. l​

The first working prototype, the only one in the world

Presented at the EUROBIKE international exhibition 2019

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