The inner rotor of the general rotor oil pump has 4 or more than 4 convex teeth, and the number of concave teeth of the outer rotor is one more than the number of convex parts of the inner rotor, so that the inner and outer rotors rotate in the same direction out of sync.The outer contour curve of the rotor is subcycloidal.
The tooth profile of the rotor is designed so that when the rotor rotates to any Angle, the tooth profile of each tooth of the inner and outer rotor can always contact with each other at points.In this way, four working cavities are formed between the inner and outer rotors. With the rotation of the rotor, the volume of the four working cavities is constantly changing.On one side of the inlet cavity, due to the rotor disengagement, the volume gradually increases, resulting in a vacuum, the oil is inhaled, the rotor continues to rotate, the oil is brought to the side of the oil channel, at this time, the rotor just into engagement, so that the empty cavity volume is reduced, the oil pressure is increased, the oil is extruded from the teeth and sent out by the oil outlet pressure.In this way, as the rotor continues to rotate, the oil is constantly being sucked in and pressed out.
Rotor type oil pump has the advantages of compact structure, small size, light weight, large vacuum degree of oil absorption, large amount of oil pump, good uniformity of oil supply and low cost. It is widely used in medium and small engines.Its disadvantage is that the sliding resistance of the meshing surface of the inner and outer rotor is larger than that of the gear pump, so the power consumption is larger.