A relief valve is a hydraulic pressure control valve, which mainly plays the role of constant pressure overflow, pressure regulation, system unloading, and safety protection in hydraulic equipment.
The relief valve uses the pressure of the spring to adjust and control the pressure of the hydraulic oil. When the pressure of the hydraulic oil at the oil inlet is less than the set pressure of the relief valve, the spool is pressed by the spring at the inflow port of the hydraulic oil, and the oil inlet of the relief valve is in a closed state, and the hydraulic oil cannot enter the valve body or flow to the tank from the oil outlet.
As the pressure of the hydraulic system rises, when the pressure of the hydraulic oil exceeds its set pressure, that is, the force generated by the hydraulic oil acting on the spool is greater than the spring pressure, the spool is lifted by the hydraulic oil, the relief valve is opened, and the hydraulic oil flows from the oil inlet to the oil outlet to the oil tank. The greater the pressure of hydraulic oil at the oil inlet, the higher the spool is pushed up by hydraulic oil, the larger the opening area of the oil outlet of the relief valve, and the greater the flow of hydraulic oil back to the tank through the relief valve. If the pressure of the hydraulic oil is less than or equal to the spring pressure, the spool is reset under the action of the spring force to seal the hydraulic oil inlet, and the relief valve is closed again.
Pilot relief valve: The pilot relief valve is composed of the pilot valve and main valve, pilot valve is a direct action relief valve.
The pilot relief valve is used to adjust the pressure of the pilot valve and control the pressure of the hydraulic oil in the system.
As can be seen from the figure: When the system hydraulic oil enters the oil inlet of the pilot relief valve, it will enter the oil inlet of the pilot valve through the throttle hole, which is very important. At the same time, the hydraulic oil also enters the upper chamber of the main valve spool. When the pressure of the hydraulic oil inlet is less than the set pressure of the pilot valve, the pilot valve spool is pressed by the spring on the inlet port of the pilot valve, and the oil inlet of the pilot valve is closed.
At this time, there is no hydraulic oil flow in the orifice, the hydraulic oil pressure on both sides of the orifice is equal, and the hydraulic oil pressure acting on the main valve core is equal. The main valve core is under the action of the main valve spring, and the hydraulic oil can not flow from the oil inlet to the oil outlet.
