Pump with two or more gear wheels with teeth on the outside that rotate engaged in each other. As a result the hydraulic fluid is pressed out of the gaps between the teeth on the outlet side, while the necessary vacuum is produced on the suction side.
External gear pumps are the simplest and most economical hydraulic pumps and are very suitable for simple low-pressure drives. They operate with high reliability and are also robust in operation. They have a large permissible viscosity range and a good intake characteristic.
Higher pressures (approx. >100 bar) necessitate higher requirements (axial and radial gap reduction). Due to the heavy pulsations they are then also so noisy that for pressures above 200 bar they are often replaced with internal gear pumps .