The pump is a variable displacement plunger pump that discharges two of the same flow rate from a cylinder. Although it has a dual pump structure, the 3 pump and the pilot pump are connected on the same axis through a coupling sleeve, but the structure is very compact. Because this pump has only one swash plate, the tilt angle is the same. The tilt angle of the pump can change the total flow Q1 + Q2. The output power is a constant value, so the product of outlet pressure and flow rate is constant, that is (Q1 + Q2) × p = P (constant).
Pump control function
The angle of the swash plate is determined by the discharge pressure of the Pl pump and the P2 pump, and the acting force of the power spring is opposite to the direction of the discharge pressure. When the pressure is less than the set load of the power spring A, the swash plate is at the maximum tilt angle position. When the pressure exceeds the set load of the power spring A, the inclination angle of the swash plate will change to a small angle and be fixed at a position in a state of equilibrium under the hydraulic oil pressure and the force of the power spring A. When the inclination angle of the swash plate continues to decrease due to the increase of the pressure of the hydraulic oil, the spring B, which has not been functioning, begins to function. If the elastic force of the two spring forces is to be overcome, the maximum bottom dead center of the oil pressure must be reached. When the p3 hydraulic oil pushing the servo piston flows in, the control displacement curve will be changed.
