Magnetically-damped supercritical transmission system
A mechanical transmission system for a rotorcraft, including a supercritical transmission shaft and an active magnetic damper secured to the structure of the rotorcraft via a mechanical damper is provided.
1. A transmission system for rotorcraft, said rotorcraft having a structure, said transmission system comprising:
a shaft; and
at least an active magnetic damper extending around the shaft, wherein the magnetic damper is secured to the structure of the rotorcraft via at least a non-magnetic damper that is arranged to limit radial oscillations of the shaft and of the magnetic damper,
the shaft having a ferromagnetic ring secured to the shaft,
the active magnetic damper comprising a mechanical damper holding four contact connections, each connection enabling pivoting about an axis orthogonal to the axis of the shaft, and also sliding in a plane perpendicular to the axis, with dry friction,
said each connection also enabling pivoting about two mutually-perpendicular transverse axes that intersect on the longitudinal axis of the shaft,
the active magnetic damper including four identical electromagnets having cores with respective inside faces, said four identical electromagnets being rigidly connected to one another by a structure secured to the structure of the rotorcraft via the mechanical damper, the axes of the connections coinciding substantially with the longitudinal axes of the electromagnets, and
the respective inside faces of said electromagnet cores having a concave cylindrical shape of a radius equal to the outside radius of the ferromagnetic ring secured to the shaft, plus the value of an airgap, and of axis parallel to a theoretical axis of the shaft.
2. A transmission system according to claim 1 , wherein the non-magnetic damper is a mechanical damper that acts by friction.
3. A transmission system according to claim 1 , wherein the non-magnetic damper acts by at least one of compression and traction.
4. A transmission system according to claim 1 , wherein the non-magnetic damper includes a return member conferring mechanical stiffness to the non-magnetic damper.
5. A transmission system according to claim 1 , wherein the non-magnetic damper includes a plurality of connections, each enabling pivoting about an axis.
6. A transmission system according to claim 1 , wherein the non-magnetic damper includes a plurality of connections, each enabling sliding in a plane perpendicular to an axis.
7. A rotorcraft including a transmission system according to claim 1 .