The idea behind this pump is different pressure zones (caused by constant volume changes) .
In this pump there are only 2 moving parts, the orange rotor in the middle, which spins by the engine power, moves the passive outer yellow rotor.
The active rotor is driven either by a little metal chain like in some scooters, or sprockets in motorcycles and cars.
The CONSTANT VOLUME CHANGES create different pressure zones in certain areas of the pump.
At the left you can see the empty space (which is shown as stripes) always expanding – exactly there, you will find the oil entrance to the pump.
On the right side you will see the space is constantly getting smaller – there is the oil exit pipe located.
The oil is pumped in on the left, it is then carried in the space between the two rotors, and then finally being squeezed out on the right side exit.
This pump is very popular in motorcycles, scooters and even cars. This pump has 4/5 rotors. There are other pumps with 8/9 rotors and even more.