Mechanism for attenuating torque pulsations between an engine and a rotorcraft rotor driven by the engine
View Patent ↗The invention provides a mechanism for attenuating torque pulsations between an engine ( 2 ) and a rotor ( 1 ) of a rotorcraft. Torsion means ( 5 ) are interposed between the driving and driven shafts and comprise a torsion shaft ( 6 ) axially engaged with the drive shaft ( 3 ) and the driven shaft ( 4 ) an inlet shaft ( 9 ) and an outlet shaft ( 10 ) respectively engaged with the drive and driven shafts ( 3, 4 ) a lever system ( 7 ) that extends radially relative to the torsion shaft ( 6 ) and that has the inlet and outlet shafts ( 9, 10 ) hinged thereto via points ( 11, 12 ) that are spaced apart; and a mass ( 8 ) carried by said lever arm ( 7 ) at its free end ( 13 ) radially farthest away from the axis along which the torsion shaft ( 6 ) extends.
1. A mechanism for attenuating torque pulsations between an engine and a rotorcraft rotor driven in rotation by the engine, the mechanism comprising torsion means interposed in coaxial engagement between a drive shaft and a driven shaft for driving the rotor, wherein said torsion means comprise:
a torsion shaft provided with coaxial engagement means with the drive shaft and with the driven shaft;
an inlet shaft and an outlet shaft provided with coaxial engagement means respectively with the drive shaft and with the driven shaft;
at least one lever system comprising a rigid lever arm extending radially to the torsion shaft and having the inlet and outlet shafts hinged thereto at spaced-apart points; and
at least one mass carried by said lever arm at its free end radially distant from the axis on which the torsion shaft extends and from said hinge points of the inlet and outlet shafts.
2. A mechanism according to claim 1 , wherein one of the inlet and outlet shafts is hinged to an end of the lever arm opposite from its free end carrying the mass, and wherein the other one of the inlet and outlet shafts is hinged between the two ends of the lever arm.
3. A mechanism according to claim 1 , wherein an lever ratio ( r ) defined by the separation distance ( a ) of the hinge point of one of the inlet and outlet shafts and the anchor point of the mass and by the separation distance ( b ) between the hinge points of the inlet and outlet shafts on the lever arm lies in the range 8 to 12.
4. A mechanism according to claim 1 , wherein the shaft that is hinged to the lever arm between its ends has a hinge connection with said lever arm via a link.
5. A mechanism according to claim 1 , wherein each of the inlet and outlet shafts carries at least one tab for receiving a connection finger hinged with the lever arm.
6. A mechanism according to claim 1 , wherein the lever arm forms an angle lying in the range 90° to 180° between its ends.
7. A mechanism according to claim 6 , wherein the lever arm forms an angle of 90° between its ends for a said lever ratio ( r ) less than 10.
8. A mechanism according to claim 1 , wherein the mass is made up of a plurality of flyweights that are uniformly distributed radially about the axis (A) along which the torsion shaft extends, being individually carried by respective individual lever arms to which the inlet and outlet shafts are hinged.
9. A mechanism according to claim 8 , wherein the flyweights and the individual lever arms are three in number and are uniformly distributed at 120° intervals relative to the axis (A) along which the torsion shaft extends.
10. A mechanism according to claim 1 , wherein said coaxial engagements of the inlet and outlet shafts respectively with the drive shaft and the driven shaft are constituted equally well by direct engagements and/or by indirect engagements via the torsion shaft.