| 摘要 |
A frequency selective damper for damping the low frequency natural lead-lag vibrations of an articulated helicopter rotor blade while leaving essentially unaffected the induced one per revolution frequency motion when the rotor is subjected to the combination of these motions. The damper comprises a hydraulic cylinder, a metering-type load valve connected via flow paths to either side of the cylinder piston, a three-way spool valve connected via flow paths to the load valve and to the flow paths connecting the load valve and the hydraulic cylinder, and a control cylinder connected mechanically to the piston rod of the hydraulic cylinder and via flow paths with the spool valve. The displacement of the valve spool is proportional to the time integral of the displacement of the hydraulic cylinder piston. Consequently, when the hydraulic piston rod velocity and the valve spool displacement are both in the extended or retracted mode or sense, the fluid displaced by the hydraulic piston is forced across the load valve. If, however, the piston rod velocity and valve spool displacement are in the opposite sense, the spool valve provides a low resistance bypass around the load valve. This selective bypass provides improved low frequency damping when the damper is subjected to the combined natural and forced vibratory motion.
|
