AGMA 04FTM1-2004 pdf free.Gear Noise – Challenge and Success Based on Optimized Gear Geometries.
A main power transmission gear is subjected to various external influences, such as reaction loads from adjoined external couplings, foundation distorhon. dynamic mass forces due to heavy sea states or transient wind forces, and, not lastly, heat expansion due to the power loss generated by gear teeth and bearings.
In view of all these impacts, and also respecting in most marine field cases low noise generation requirements, the tooth design is to be focused on in particular, as pinions and gears represent ‘the heart” of a gearbox. First priority, the decision on the basic type of gear teeth is of importance, where principally spur gears, single helical or double helical gears are available.
Figure 1 shows the principle coherence between tooth mesh noise excitation and overlap ratio, With spur gears, t equals zero, with low single helices, c values up to 2 are achievable. High helices are in practical sense realized only with double helical gears, achieving > 3. Apart from significant noise reduction at increased c, excitation appears to be minimum with integer value of overlap ratio. The fundamental results as depicted in Figure 1 are considered as state of the art and have been confirmed throughout the past 25 years with numerous research programs, supported by experience with countless applications in service.
Involute gears theoretically mesh without periodical angular deviation in rotation and without dynamic excitation. However, due to manufacturing deviations, misalignment and elastic deformations under load, this theoretical optimum is not achieved in reality. Manufacturing and alignment can be addressed by optimum quality with regard to gear grinding, assembly and commissioning. Deformahon under load cannot be avoided but addressed properly by smart design and appropriate flank modification. Above all, the macro geometry still is the decisive criterion on noise excitation. That means that only optimized macro geometry allows for optimum noise behavior. The basic background will be described in the following paragraphs.
Gears will change their geometric position under load due to the following influences:
●Deflection due to Hertzian pressure,
●bending of teeth,
●elastic deflection of gear bulks and shafts.AGMA 04FTM1 pdf download.