1. Based on whether the flow rate is adjustable, pumps can be divided into: variable displacement pumps and fixed displacement pumps. Pumps whose output flow rate can be adjusted as needed are called variable displacement pumps, while those whose flow rate cannot be adjusted are called fixed displacement pumps.
2. Based on the pump structure commonly used in hydraulic systems, pumps can be divided into: gear pumps, vane pumps, and piston pumps.
Gear pumps: Smaller in size, simpler in structure, less demanding on oil cleanliness, and cheaper; however, the pump shaft is subjected to unbalanced forces, resulting in severe wear and significant leakage.
Vane pumps: Divided into double-acting vane pumps and single-acting vane pumps. These pumps offer uniform flow, smooth operation, low noise, higher working pressure and volumetric efficiency than gear pumps, but have a more complex structure.
Piston pumps: High volumetric efficiency, low leakage, can operate under high pressure, and are mostly used in high-power hydraulic systems; however, they have a complex structure, require high-precision materials and machining, are expensive, and have high requirements for oil cleanliness.
Piston pumps are generally used when gear pumps and vane pumps cannot meet the requirements. There are other types of hydraulic pumps, such as screw pumps, but their application is not as widespread as the three types mentioned above.
