The technique for calculating the strength of a globoid worm gear

Worm gears are widely used in mechanical engineering. Recently, worm gears with a globoid worm attract a considerable interest. To improve the quality characteristics of globoid gears, their geometric dimensions and parameters, as well as the production technologies are being improved. It is also important to have a methodology for calculating the strength, which is, however, currently unavailable, and the state standards cover the issue of determining and calculating only the transmission geometry. In this regard, the development of the technique for calculating the contact and bending strength of a globoid worm gear appears relevant. The basic areas of the research are gear enhancement, production technology improvement, the gearing pattern study, working surfaces mathematical simulation, 3-D modeling, and the transmission calculation. The contact strength calculation is based on the Hertz’s formula taking into account the geometric features of globoid worm gears. The authors developed the calculation of the bending strength of the worm gear teeth based on the helical gear calculation method. The paper presents data on the influence of the mechanical properties of the materials of a worm and a worm gear wheel on the gear contact strength, gives the computed coefficients estimated values. The authors note that the dynamic load factor can increase significantly with the wear of the gear working surfaces. The research findings can be used to develop the design calculation technique, as well as to improve it to take into account the effect of transmission wear and working temperature on the operation duration.