Abstract
The models of normal force on teeth surface of gears are important to decide the contact ratio factor or the temperature rising on teeth surface. The real contact ratio εR of Plastic/Plastic gears are often above 2, and the distributions of normal force are alike mountain instead of step of steel gears. According to Prof. YELLE' theory and experimental study, a model as ε_R under 2 and 3 models as ε_R above 2 are considered. Using model-based reasoning, the equivalent contact ratio factor Yε' and the temperature rising Δθ are studied. When ε_R under 2, Yε' of plastic gears are as same as steel gears. But ε_R above 2, they are more than them of steel gears. The more ε_R rises the more Δθ. When ε_R under 2, Δθ change rapidly, but ε_R above 2, slowly by any more models.
