Research On Key Problems Of Dynamics Of Helicopter Tail-Drive Transmission System

During the developing process of the helicopter industry, the research work has been almoststopped because of the dynamics of the tail drive system. In general, it could help to detect thevibration characteristics of both the tail drive system and the whole drive system of the helicopterthrough investigating the dynamics of the tail drive system. In order to solve the problem of theconventional method in the engineering application and develop a new method with practical value,the dynamics problem of helicopter tail drive has been researched, including dynamic characteristicsof bevel gear drive, load distribution of ball bearing, modeling and analysis of flexural vibration andtorsion vibration for helicopter tail drive system. The mail contents are as follows:(1) Three-dimensional dynamics model of bending-torsion-axial movement coupled vibrationwith multiple degrees of freedom is established for bevel gear transmission with elastic web plate. Theinfluence of the web damping on the amplitude-frequency characteristics of the bevel geartransmission system is analyzed. Accordingly, it is proposed to select a reasonable range of webdamping coefficient. At the same time, the influence of both the meshing damping coefficient and theweb damping coefficient of gear pairs on the bifurcation characteristics of the system movement werediscussed.(2) The mechanical model is established with the low-speed and high-speed ball bearing. Thecalculation method and processes of load distribution are determined. The influence of load and radialinternal clearance on the load distribution of the low-speed bear is analyzed. Meanwhile, the effect ofloading, rotational speed and materials on the load distribution of high-speed bear is studied.(3) The bending vibration model of helicopter tail drive system is founded based on the analyticmethod. The influence of shaft sections and stiffness on the natural frequency of the helicopter taildrive system is studied, which could provide a reference for designing the drive shafts. An analysis iscarried out for detecting the natural frequency, vibration mode and bending vibration harmonicresponse characteristics of helicopter tail drive system. A proof-testing experiment is conducted toresearch the flexural vibration of helicopter tail drive system.(4) The torsion vibration model of helicopter tail drive system is founded, and the torsiondynamic behavior of shaft is analyzed with main parameters. The influence of shaft torsion stiffnessand gear meshing stiffness on the torsion vibration dynamic characteristics of tail drive system isstudied using finite element analysis. The method in this investigation has been utilized successfullyto solve the vibration problem of the testing platform of tail drive system of helicopters, which indicates the certain engineering value of the method.