Load sharing model for spur gears with tip relief: An investigation on the influence of profile modifications on the mesh stiffness

摘要

The tooth deflections under load, and consequent relative rotation of the driving gear respect to the driven one, produce a sooner start of contact of the subsequent couples of teeth. This sooner, non-conjugate contact occurs outside the pressure line of the gear pair and results in a shock between both meshing teeth inducing noise, vibrations and dynamic load, which reduce the load capacity and the gears life. To avoid these problems and to ensure a smooth start of contact, the profile modifications are often used. A suitable tip relief on the driven gear teeth delays the start of contact, locating it at the appropriate point of the pressure line. Though the amount of material eliminated at tip relieves is very small, the gear meshing stiffness may be affected due to the different contact conditions, which will have influence on several transmission parameters, as the load sharing or the transmission error. In this paper, the influence on the load sharing is investigated both for standard and high contact ratio spur gears. Equations for the load sharing ratio are provided considering different amounts, lengths and shapes of tip relief. An analytic equation to calculate the advance angle of start of contact as a function of the tooth deflections, for unmodified profiles, is also presented.