Numerical and experimental study of the loaded transmission error of a spiral bevel gear

The design of spiral bevel gears in aeronautical gear boxes requires very precise and realistic numerical simulations. One important criteria is the loaded transmission error (LTE) that gear designers attempt to reduce at the nominal torque. This paper presents a numerical tool that simulates the loaded meshing of spiral bevel gears and experimental tests carried out on a real helicopter gear box. Tooth profile is defined by the Gleason cutting process and tooth bending effects and contact deformations are both taken into account. The bending effect computation uses a three-dimensional finite element model, while the contact deformations are obtained by using Boussinesq's theory. Experimental measurements of the LTE were performed using magnetic and optical encoders rigidly connected with the pinion and gear shafts, giving access to the records of the instantaneous angular positions. The numerical simulations fit quite well the experimental results.