Pump with two gear wheels in most cases whose outer (ring gear) has teeth on the inside. The inner sprocket is smaller. The fluid is conveyed in the spaces between the gaps in the teeth of the two gear wheels.
Thanks to a long contact length and a lack of play at the teeth, internal gear pumps are associated with very low delivery flow pulsation and are therefore quiet during operation.
With axial play compensation they can achieve average pressures of up to around 160 bar, while 300 to 320 bar is possible with combined axial and radial play compensation at the sprocket and ring gear (Figure I 11). Their geometric displacement cannot be adjusted (constant pump).
Figure I 11: Internal gear pump with axial and radial play compensation