The pressure valve is to control the opening and closing of the oil passage on the valve body by the balance of spring force and liquid pressure, the highest pressure of the system is adjusted by the relief valve, and the working pressure of the system is determined by the external load. The working principle of the pressure valve shows that after the oil from the hydraulic pump enters the B cavity, there is no axial thrust on the valve core because the area on both sides is equal. In the indicated position, the spring pushes the spool to isolate the P port from the T port, the oil does not leak, the system pressure rises, the pressure in the A cavity also increases, and the force of the downward compression spring continues to increase until it exceeds the thrust of the spring, so that the valve core moves downward. Because the P port and the T port are connected, the pressure oil is discharged back to the oil tank through the T port, the system pressure drops, the A cavity pressure is also reduced, when the oil pressure is lower than the spring force, the valve core moves up, and cuts off the connection between the P port and the T port, the oil can not leak, the pressure rises, the valve core so constantly alternately action, the system pressure is balanced in the dynamic, stable at a certain value, this is the working principle of the pressure valve.
