Variable Displacement Hydraulic Main Pump AP2D36 Hydraulic Pump

Rexroth Excavator AP2D36 Hydraulic Pump Variable Displacement Main Pump Excavator Swash Plate Pump Assembly

Core Function

Driven by the engine, the hydraulic pump rotates and converts mechanical energy from the engine into hydraulic oil pressure energy. High‑pressure oil is supplied to hydraulic cylinders and motors to realize boom lifting, arm telescoping, bucket opening/closing, machine traveling and upper‑structure slewing. No hydraulic pump means zero movement for the excavator.

High‑speed rotation of the hydraulic pump’s internal parts, driven by the engine, draws hydraulic oil in and pressurizes it. Pressurized oil runs through piping to cylinders and motors to drive boom, arm, bucket, travel and slew functions. Upon releasing operation controls, oil flows back to the hydraulic tank for circulation.

Power Input: The excavator engine spins the hydraulic pump’s main shaft and piston cylinder block at high speed by means of a coupling.

Oil Suction (Low‑Pressure)

Multiple pistons inside the cylinder block rotate alongside it. The swash plate drives pistons in reciprocating motion. Retraction of pistons enlarges internal pump volume, creating vacuum pressure to intake oil from the hydraulic tank.

Oil Discharge (High‑Pressure)

Piston extension reduces internal volume, squeezing oil into high‑pressure hydraulic fluid. It is then transmitted via the valve plate and oil outlet to the main control valve.

Automatic Flow Regulation (Variable Displacement Core Function)

For heavy‑duty tasks including excavation and heavy lifting, the pump boosts displacement and flow automatically for enhanced power output. Under light‑load or idle conditions, it lowers displacement to save fuel. Internal servo valves and regulators adjust swash plate angles to modify piston strokes for this function.

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