The unloading valve is a valve that can unload the hydraulic pump under certain conditions. The unloading valve is usually a relief valve with a two-position two-way valve (usually a solenoid valve). Its function is to use it to set the main pressure of the system (oil pump) when it is not unloaded. Through valve action conversion) the pressure oil is directly returned to the oil tank, and the oil pump pressure drops to approximately zero to achieve some loop control and improve the life of the oil pump and reduce power consumption. The circuit belongs to the merged circuit. The pressure-reducing valve is used to adjust the pressure required by the actuator. It is connected in series in the circuit and generally cannot be used interchangeably.
The unloading relief valve consists of a relief valve and a one-way valve. When the system pressure reaches the opening pressure of the relief valve, the relief valve opens and the pump is unloaded; when the system pressure drops to the closing pressure of the relief valve, the relief valve closes and the pump loads the system. The pressure at which the pump is unloaded is called the unloading pressure, and the pressure at which the pump is loaded is called the loading pressure.
The main function of the unloading relief valve is to automatically control the unloading or loading of the pump. In view of the function of the unloading relief valve, there is a certain difference between the unloading pressure and the loading pressure. If the difference is too small, the unloading and loading actions of the pump are too frequent; if the difference is too large, the system pressure changes too much.
The difference between the loading pressure and the unloading pressure is an important performance index of the unloading relief valve. Generally, the loading pressure is about 85% of the unloading pressure. Its performance is the same as the relief valve.
The main purpose of unloading relief valve:
a. Automatic unloading and loading of the pump in the accumulator system;
b. Unloading of large flow and low pressure pump in combination of high and low-pressure pumps
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