Cycloid pin gear planetary reducer as an important mechanical transmission parts with small volume, light weight, high transmission efficiency features. In order to accurately describe the cycloid formation and classification, we introduce the circle inside the domain and round outland this concept. Round within the domain refers to the tolerance range of internal arc line, round outland is outside the scope of the tolerance area. According to the division of the internal and outside the domain, the epicycloid are defined as follows: epicycloid: rolling in the base circle and outland base circle tangent and along the base circle for pure roll, rolling on the designated track is outside cycloid. Cutting epicycloid: rolling in the round outland and base circle circumscribed form epicycloid (The base circle are rounded outlands)。 In cutting epicycloid: rolling in the base circle of outland and cut inside base circle formation epicycloid (The base circle inside the rounded domain)。 Short of epicycloid: cutting epicycloid forming process, the rolling inside domain with rounded some point trajectory of the relatively fixed; Cut inside or outside cycloid formation process, rolling and rolling outland relatively fixed point of a track. Long epicycloid: in contrast to the short of epicycloid, relatively fixed some point for foreign cutting epicycloid outland in rolling; In terms of internal cutting epicycloid relatively fixed within a certain point in the rolling field. Short of epicycloid with amplitude transformer epicycloid epicycloid known as long. Amplitude outer cycloid luffing degree coefficient of amplitude is used to describe, respectively the amplitude coefficient or short length coefficient. Outside cutting epicycloid amplitude coefficient is defined as the swinging rod length and the ratio of the rolling radius. Swinging rod length refers to the rounded inside domain or rounded a relatively fixed point outland and round up to the distance of the center of the circle. For cutting epicycloid inside, the amplitude coefficient, on the other hand, it is expressed as the rolling radius and the ratio of swinging rod length.
