使得主阀芯打开，P到T实现溢流。该类型的阀一般具有较高的启闭

率，内泄漏小，适用于高压力、大流量的液压系统。

When the pressure at "p"reaches the valvesetting,the

pilot spool starts toopen ,Next themain spool opening

because of the pressure dropbetween inside and outside

of main spool, Realizeoverflow from P to T.This type of

valve canwithstand a certain amount of back pressure,has

high opening and closing rate Suitable for thehydraulic

system of high pressure and large flow.