I wasn't actually ...positive....so I looked it up on Wikipedia:
A
gerotor is a
positive displacement pump. The name
gerotor is derived from "generated
rotor". A gerotor unit consists of an inner and outer rotor. The inner rotor has
n teeth, while the outer rotor has
n+1 teeth; with
n defined as a
natural number greater than or equal to 2. The axis of the inner rotor is offset from the axis of the outer rotor and both rotors rotate on their respective axes. The geometry of the two rotors partitions the volume between them into
n different dynamically-changing volumes. During the assembly's rotation cycle, each of these volumes changes continuously, so any given volume first increases, and then decreases. An increase creates a
vacuum. This vacuum creates
suction, and hence, this part of the cycle is where the inlet is located. As a volume decreases
compression occurs. During this compression period,
fluids can be pumped, or, if they are gaseous fluids, compressed.
