JPS6441681U - - Google Patents

Description

[Brief explanation of the drawing]

FIG. 1 is a hydraulic circuit diagram showing the configuration of a variable displacement pump according to one embodiment of this invention, and FIGS. 2, 3, and 4 are hydraulic circuit diagrams showing different embodiments. 1: Pump element, 2: Discharge rate variable element, 3: Spring, 4: Operation piston, 5: Proportional electromagnetic three-way control valve, 6: Safety valve, 7: Displacement detector, 8: Pressure sensor, 9a, 9b: Setting input Terminal, 10: Control amplifier device, 11: Additional pump, 12: Pressure control valve, 1
3, 14: Check valve, 15: Bias piston.

Claims (1)

[Claims for Utility Model Registration] 1. Increasing the pilot pressure oil pressure in the pressure chamber of the operating piston for applying operating force to the discharge amount variable element by introducing a part of the discharge pressure oil through the pilot line or into the tank. A single proportional electromagnetic three-way control valve is used to control the discharge rate variable element using a closed-loop feedback control based on the measured electrical quantity of the discharge pressure and discharge flow rate so as to reduce the pressure by deriving the spring force via the piston. When the discharge pressure is below the set pressure, the discharge flow rate is maintained at the set value, and when the discharge pressure reaches the set pressure, the variable element is displaced to a cut-off position where the discharge flow rate is the minimum necessary. The pump is a variable displacement pump, and the operating piston is in a cut-off control position through a bleed hole through which a portion of pilot pressure oil flows from the pressure chamber to a drain at least for a flow rate necessary to stably hold the variable element in a control position. The pressure chamber is provided at a predetermined position on the peripheral wall of the pressure chamber so as to be opened at a certain time, and is provided with an additional pump means for supplementing the pilot pressure oil when the pressure of the discharge line to the load is below a predetermined pressure value. A variable displacement pump featuring: 2. An auxiliary pump in which the additional pump means is driven in common with the pump element controlled by the variable element;
The variable displacement pump according to claim 1, which includes a pressure control valve device that replenishes the pressure oil discharged from the auxiliary pump into the pilot line only when the pressure oil discharged from the auxiliary pump falls below the predetermined discharge pressure. .