During the meshing process of a pair of internal hypocycloid gears, all of the mating teeth are in contact to their counterparts. In order to apply in designing rotary positive displacement pumps, one has used the variation of the tooth space to trap fluid and force it around the outer periphery. The variation of the tooth space generates suction and discharge effects. During the meshing process, there is profile sliding between the teeth in each mating pair, which results in tooth wear unequally. Therefore, practitioners have to select two parameters R1 and rcl for the rotor tooth profile. Up to date, the optimal combinations of these two parameters in order to achieve equal wearing rates have not yet been established. This paper presents a method for finding this relationship.
