The excavator hydraulic pump is the "heart" of the excavator's hydraulic system, and its performance directly determines the operating efficiency and stability of the excavator. Its core principle is to change the volume of the sealed working chamber through mechanical movement, thereby realizing the suction and discharge of liquid, converting the mechanical energy of the engine into hydraulic energy, and providing a power source for the entire hydraulic system.

The pistons are connected to the drive shaft via ball-and-socket joints. As the drive shaft rotates, the angular offset forces the pistons to move in and out of their cylinder bores as the distance between the drive flange and cylinder block face changes cyclically. This reciprocation performs the suction and discharge functions against a stationary port plate, similar to the swashplate design.

Structurally, it comprises the drive shaft with a flange, the cylinder block, pistons with connecting rods/balls, a stationary port plate, and a housing incorporating the angle-setting mechanism. For variable displacement versions, the angle of bend between the drive shaft and cylinder block is adjusted (often hydraulically), changing the piston stroke and hence displacement. Fixed displacement versions have a rigidly fixed angle. Bent-axis pumps are renowned for very high mechanical efficiency, smooth operation, and tolerance to high speeds and pressures.