In the internal gear pump, the inner rotor is the driving wheel, the outer rotor is driven theory, and the ratio of the inner and the outer rotor is i = Z1 / Z2. Due to a tooth difference between the number of teeth inside and outside the rotor, there is "secondary meshing" exists during the meshing process. Therefore, several independent closed package liquid chambers can be formed. With the rotation of the inner and outer rotors, the volumes of the liquid chambers vary with each other. When the volume of the liquid chamber changes from small to large, a partial vacuum is generated in the liquid chamber. Under atmospheric pressure, the liquid flows through the inlet pipe and the pump Cover the annular groove, into the pump chamber began absorbing liquid. When the volume of the liquid chamber reaches its maximum, the liquid absorption process is completed. When the volume of the fluid chamber changes from large to small, the fluid in the fluid chamber is pushed out of the other annular groove, which is the discharge process of the pump. Pump in the process of work, a tooth of the inner rotor turned a week, there is a working cycle, that is, to complete the pump liquid to the drainage process. A rotor pump rotor has a tooth, which every one revolution, there must be a cavity with the same working cycle, the pump will continue to work out through a continuous infusion, so inside and outside the rotor around the two axes parallel to each other to do different Speed ​​of the same direction of operation, there will be relative movement, the movement of the rotor inside and outside to produce ever-changing space, and connected with the liquid suction drainage in order to achieve the purpose of suction and drainage.