Research On Dynamic Characteristics Of Helicopter Variable Speed Drive Friction Clutch And Transmission System

As the key technology in the future helicopter transmission field,variable speed transmission system has complex internal structure and many excitation components.In this paper,a certain variable speed helicopter transmission system is taken as the research object.Firstly,the friction torque characteristics of wet clutch are analyzed.Secondly,the clutch friction judder phenomenon during the system engagement process is studied.Finally,the overall dynamics model of the variable speed helicopter transmission system is established and its dynamic characteristics are studied.Combined with the wet clutch engagement characteristics,the corresponding contact models of different joint stages are established.According to the calculation model,the calculation formulas of oil film thickness,relative rotational speed,friction torque and sliding friction power are derived.The friction torque response characteristics of wet clutch engagement were analyzed and The effects of different parameters on the joint properties were studied.The equivalent torsional vibration model of the system during wet clutch engagement is established.The Stribeck friction coefficient and Karnopp friction torque are introduced into the model,and the vibration differential equations of the system before and after the wet clutch engagement are derived.Using Lyapunov's first approximation theory,the critical conditions of clutch judder are obtained.The effects of friction coefficient,clutch engagement parameters,shafting parameters and engagement oil pressure on clutch engagement stability were analyzed.With reference to the foreign two-stage variable speed transmission configuration,a two-stage variable speed helicopter transmission system was designed.The dynamic model of the system is established by the lumped mass method,taking into account the factors such as time-varying mesh stiffness,tooth surface friction,meshing phase of planetary gear trains and comprehensive transmission error.The vibration differential equations in the high-speed and low-speed paths of the system are derived.The Longe Kutta method is used to simulate the above dynamic equations.The inherent characteristics,dynamic load and uniform load of the high-speed and low-speed transmission paths of the system are analyzed.The effects of input power,input speed and friction coefficient on the dynamic characteristics of the system are studied.