The variable plunger pump is the driving force for the motor and other actuators, which highly pressurizes and delivers hydraulic oil from the tank. The pump is composed of a casing, shaft, cylinder block, plunger, swash plate, valve plate, and other components. As the shaft rotates, the plunger strokes along the swash plate, sucking and delivering hydraulic oil. The delivery flow can be adjusted by altering the inclination of the swash plate. The delivery flow is controlled by the regulator. The regulator controls the pump output to correspond with the engine output by adjusting the delivery flow. Next, we will explain how the regulator decreases the flow rate. When the delivery pressure of the pump P1 or of a companion pump P2 increases, the pressure moves the compensating piston pushing it against the compensating rod. As the compensating rod is pushed, the lever rotates, moving the feedback lever, which in turn moves the spool. Also, the delivery pressure of P1 passes through the spool and pushes against the larger side of the servo piston. As the servo piston moves, the inclination of the swash plate decreases, reducing the delivery flow. Next, we will explain how the regulator increases the flow rate. When the delivery pressure of the pump P1 or of a companion pump P2 decreases or when the pilot pressure is released by the power increase and control system. The compensation rod and piston are pushed back by their springs. As the compensating rod moves, the lever rotates, moving the feedback lever, which in turn moves the spool. As a result, the pressure within the larger side of the servo piston is released through the tank port, which then moves the servo piston. As the servo piston moves, the inclination of the swash plate increases, increasing the delivery flow.