Down Angle Gearboxes – Calculation and Manufacturing Innovation for Low Noise Beveloid Gears

Conical involute gears, also known as beveloid gears, are used in marine gearboxes to provide an angle between the drive shaft and the output shaft. The axes of the beveloid gear meshes reviewed can be intersecting or skewed. Beveloid gears are a general case of spur gears with their virtual generating rack cutter tilted in the direction of feed. An appropriate variable addendum modification along the face width leads to conjugate flanks and therefore to tooth line contact. The elasticity of the gear mesh itself, the shafts, bearings and the gear housing cause deformations and deflections. Thus a tip relief at the generating tool in combination with flank modifications is applied to improve strength and transmission characteristics. Noise emission is reduced by comparing the level of dynamic excitation of different profile corrections. Strength calculations are done with local stresses, since there is no standardized nominal stress assessment. Theoretical evaluations are confirmed by prototype testing. This integrated designing procedure allows for an efficient planning and engineering for special beveloid gears. Several examples of application will be shown.