Hitachi Excavator Pump System

Why does the Hitachi Excavator Pump System require extra attention?

Hitachi excavators have the ability to control the pump displacement dependent on inputs from the machine control system. The regulator also automatically adjusts the output displacement depending on the system pressure, this assists in maintaining the total horsepower requirements to a defined window.

This system optimises hydraulic output to the horsepower available from the engine.

On top of these functions, the regulator also has auxiliary inputs to increase or decrease pump displacement from control outputs from the machine control system to give increased dig performance when the engine horsepower is available or conversely reduce output to prevent engine overload conditions.

In order to achieve these various functions the regulator is made up of a complex mechanical linkage system operating on control spools, all working in unison to continuously vary pump displacement depending on the system conditions.

The downside to this complexity is the regulators are prone to increased wear in the linkage system and require periodical adjustment to maintain correct control.

Blown up diagram of a Hitachi pump regulator.