Pyörrevaihde

Pyörrevaihde, a Finnish term often translated as "vortex gear" or "swirl gear," is a type of mechanical transmission that operates on a principle of fluid dynamics rather than traditional meshing gears. Unlike conventional gearboxes that rely on the physical interlocking of teeth, a pyörrevaihde utilizes the viscous drag of a fluid to transfer rotational power.

The core component of a pyörrevaihde is typically a housing containing a rotor or impeller connected to the input shaft and a second rotor or runner connected to the output shaft. The space between these components is filled with a special fluid, often oil. When the input shaft rotates, the rotor within the housing spins, imparting its kinetic energy to the fluid. This energized fluid then flows, creating a vortex or swirling motion, which in turn exerts force on the second rotor, causing it to rotate and drive the output shaft.

The speed ratio in a pyörrevaihde is not fixed but can vary dynamically based on the load and input speed. This can lead to a smooth, stepless acceleration and a degree of damping, absorbing shocks and vibrations from the drivetrain. However, there is inherent slippage in this type of transmission, meaning that the output shaft will always rotate slightly slower than the input shaft, leading to some energy loss and reduced efficiency compared to mechanical gears. Pyörrevaihde technology is most commonly found in torque converters used in automatic transmissions of vehicles, where its ability to multiply torque at low speeds and provide smooth engagement is advantageous.