AGMA 05FTM11-2005 pdf free download.Low LOSS Gears.
These equations were set up for usual spur gear geometries (1 < r. < 2 and £ < Pet) and produce acceptable results in these cases. Extreme gear shapes, however, may result in calculated power losses which deviate significantly from actual power losses. By more detailed considerations a better approximation to the real distribution of the load along the path of contact can be obtained by using sophisticated calculation methods as FEM or the FVA-programme RIKOR. This is proven by expenmental investigations [14]. Gear loss factors based on such methods are called local gear loss factors H1. Differences between H and Hv1 are significant for high contact ratio, helical or gears with profile corrections, see Figure 4.
The gear loss factors Hv [9], or HVL [14] respectively, comprise the integral of the product of the sliding speed and the load distribution. Here, for the calculation of load dependent power losses of gears the local gear loss factor HVL with the more realistic load distribution according to the FVA-programme RIKOR [10] is used.
For gear design power losses are often of subordinate interest compared to load capacity and excitation level. So, if gears are to be optimised in terms of efficiency, load capacity and excitation must not be neglected. For the  evaluation of single gear geometry parameters their influence on power loss, load capacity, and excitation is investigated by the means of FVA-programmes according to Figure 5.Excitation is evaluated by the tooth force level which represents the dynamic load in the tooth contact without respect to the further environment. This load dynamics is cause of,but not equal to, real load dynamics, vibration and noise.
Lubricant properties affect the power losses via the cofficient of friction μ and are not subject to this investigation. Their influence is supposed to be constant here.
5 INFLUENCE OF GEARING GEOMETRY ON LOAD DEPENDENT POWER LOSSES
Figure 6 to Figure 13 show the influences of gear geometry parameters on the gear load dependent power losses compared to the reference gears given in Figure 1. The influence of these parameters on the coefficient of friction is included. For these parameter variations also the pitting and tooth fracture capacities are given referring to the reference gearing with capacities of 100%. In best case, hence, power loss and tooth force level is low while the safety factors of load capacities are high.
Most important geometric parameters are transverse contact ratio (Figure 6) and module size (Figure 7) whose influence on power losses is almost proportional. Less strong is the influence of the pressure angle (Figure 8), but its importance comes from the advantage that in the given range a higher pressure angle has only advantageous effects both on power loss reduction and higher load capacities and no unfavourable effects on excitation.
With helix angle (Figure 9) power losses increase generally, but to a limited extent. For minimum power losses with small transverse contact ratio there has to be a significant overlap contact ratio (E > 1) for proper load capacity and noise excitation.
The influence of surface roughness (Figure 10) shows also only positive effects if it is reduced. Unfortunately, an improvement is usually subject to cost rise. Recent investigations show that this effect is limited. Below a certain roughness there is no further improvement. Moreover, there are other effects of surface structure such as roughness orientation which are not expressed by surface roughness but can affect the power loss to a substantial extent.
The parameters gear ratio and face width (at constant load per face width) are usually constraints which hardly can be changed. Their effect on power loss, capacities, and excitation is shown in Figure 11 and Figure 13, respectively.AGMA 05FTM11 pdf download.