Load Transfer Among Spur Gear Teeth with Tip Relief Under Non-nominal Loading Conditions

Profile modifications are often used on gear teeth to ensure a smooth start of contact, avoiding noise, vibrations and dynamic loads induced by a sooner contact outside the pressure line which occurs due to unavoidable tooth deflections under load. A suitable tip relief on the driven gear teeth delays the start of contact, locating it at the appropriate point of the pressure line. However, the amount of relief depends on the deflection, and consequently on the load, which means that it should be calculated for a specific load, obviously coincident with the nominal load, which may be non-suitable for non-nominal, overloaded or underloaded operating conditions. In this paper, the behaviour of gear teeth with profile modifications under non-nominal loading conditions is studied. The load transfer between couples of teeth is simulated and described by analytic, approximate equations. The influence of the non-nominal load on the effective contact ratio is also presented.