The typical structure of a cycloidal pinwheel planetary reducer is mainly composed of four parts:

(1) The planetary carrier consists of an input shaft and a double eccentric sleeve, with the two eccentric directions on the sleeve forming 180 degrees with each other.

(2) Planetary gears, also known as cycloidal gears, typically have teeth that are equidistant from the inner side of a short epicycloid. According to motion requirements, a planetary gear can be used for transmission, but in order to achieve static balance of the input shaft and improve bearing capacity, for a one tooth difference needle pendulum transmission, two identical odd teeth planetary gears (two tooth difference needle pendulum transmission is not limited to this) are often used, installed on a double eccentric sleeve, and the positions of the two wheels are exactly 180 degrees different. A roller bearing (called a rotary arm bearing) is installed between the planetary gear (cycloidal gear) and the eccentric sleeve to reduce friction. In order to save radial space, roller bearings usually use roller bearings without outer race, and the inner hole surface of the cycloidal needle gear reducer is directly used as the raceway. In recent years, the optimized design of the structure often combines the double eccentric sleeve with the bearing as a whole, known as the integrated double eccentric bearing.

(3) The center wheel, also known as the cycloidal needle wheel, is equipped with a set of needle teeth pins on the needle tooth housing, and usually there is also a needle tooth sleeve on the needle tooth pin.

(4) The output mechanism often uses a pin type output mechanism.