Study On Survival Life Of Spiral Bevel Gear Transmission System Of A Helicopter In Case Of Loss Of Lubrication

The attack helicopter was damaged by various weapons from ground to sky, such as antiaircraft artillery and the attack aircraft. The gear meshing backlash or rolling bearing normal clearance are eliminated by the key parts deformation due to the large frictional heat in conditions of lubrication loss, which would lead the spiral bevel gear transmission system failure. In this paper, the survival lifetime of the spiral bevel gear transmission system was studied under above extreme conditions in a helicopter tail reducer. the friction power loss, temperature field, thermal deformation and survival lifetime of the spiral bevel gear transmission system were studied on the basis theories of mechanics, tribology and thermo-elasticity etc. The main jobs and are listed as follows:1. The survival lifetime of spiral bevel gear transmission system in conditions of lubrication loss is studied for the first time systematically. The total research procedure contain frictional heat, temperature field, thermal deformation, and survival lifetime.2. A computational model of friction power loss for spiral bevel gear was established. The influence of pressure angle, mean spiral angle, transverse module, tooth width, input rotate speed and input power on friction power loss of spiral bevel gear and the influence of above factors were analyzed using the orthogonal experiment method. And the optimum parameters were also determined in the common parameter ranges for the lowest friction power loss of spiral bevel gear.3. The spiral bevel gear can be equivalent to the spur gear on the basis of equivalent gear theory. A simple and convenient computational method of gear meshing backlash was then presented. The influence of thermal deformation of the transmission system on the gear backlash and bearing radial clearance was analyzed under normal lubrication condition based on thermo-elasticity theory.4. The transient temperature field of the spiral bevel gear transmission system was calculated in the condition of lubrication loss using thermal network method. The time of the meshing backlash and bearing radial clearance disappearing due to thermal deformation was then calculated on the basis of thermo-elasticity theory. Finally, the survival lifetime of the spiral bevel gear transmission system was gotten under lubrication loss condition.5. Considering the requirement of 30 minutes survival ability of a helicopter tail reducer in conditions of lubrication loss, the integrated design of the smallest spiral bevel gear meshing backlash and bearing radial clearance were proposed for spiral bevel gear transmission system.