Researchon Improvement Design Of The Dry Running For A Civil Main Gear Box

The transmission system is the one of three helicopter critical assemblies.The main gearbox(abbreviation is ‘MGB’)is an important assembly of the transmission system.It transfers power from engines output and speed to main rotor,tail drive and helicopter accessory,provides installation interfaces for helicopter accessory and servo bracket.IF failure happens in the lubrication system of MGB,the running surface of gears and bearings is heated under the over loading condition.MGB will quickly into dry running,so that it was severely damaged in a short period of running,completely lost the ability to transfer power and result in a catastrophic accident.In order to guarantee of the helicopter and the crew,CCAR specifies that the helicopter can continue to flight safely at least thirty minutes after failure happens in the lubrication system of MGB,under the inherent requirements of the torque and speed.In other words,civil helicopter transmission system gearbox can continue to work for thirty minute safter failure happens in the lubrication system of MGB.Through analyze the failure mode,failure mechanism and influencing factors of the dry running of the gearbox,calculate gearbox efficiency,carry out diagnostic test of the prototype of the MGB,weak link of the MGB----gear are found.Research on surface modification technologies of gears,which implanting ion Ti/N into the surface of the gear and coating the lubricant thin-film,can improve the ability of gears dry-running.Through the parts test and the test of the MGB,it obtained 30 minutes of dry running ability.It lays the foundation obtaining qualification of civil aviation for the helicopter,and provides technical reserves for the design of the helicopter transmission system.