Flow rate control valve for construction machine

Abstract

Disclosed is a flow rate control valve for a construction machine. A flow rate control valve for a construction machine comprises: a valve body having a pump channel for receiving operating oil from a hydraulic pump, a supply channel connected to the pump channel, and an actuator port connected to a hydraulic actuator; a spool installed inside the valve body to be switchable such that, when switched in response to application of signal pressure, the spool selectively causes the supply channel and the actuator port to communicate with each other; a tank channel installed inside the valve body and connected to an operating oil tank; and an orifice formed in the spool to have an inlet formed on an end and an outlet communicating with the tank channel, wherein, when the spool is initially actuated, a part of the signal pressure is discharged to the operating oil tank via the orifice.

1 . A flow rate control valve for a construction machine comprising:
 a valve body including a pump path to which hydraulic fluid from a hydraulic pump is supplied, a supply path connected to the pump path, and actuator ports connected to a hydraulic actuator;   a spool installed in the valve body and shifted in response to a signal pressure applied thereto to cause the supply path and the actuator port to fluidically communicate with each other selectively;   a tank path installed in the valve body and connected to a hydraulic fluid tank; and   an orifice formed in the spool, the orifice including an inlet formed at an end portion to which the signal pressure is applied and an outlet formed to fluidically communicate with the tank path,   wherein part of the signal pressure is discharged to the hydraulic fluid tank through the orifice at an initial stage of the operation of the spool.   
     
     
         2 . The flow rate control valve according to  claim 1 , wherein the hydraulic actuator comprises at least one of a boom cylinder, an arm cylinder, and a bucket cylinder. 
     
     
         3 . The flow rate control valve according to  claim 1 , wherein the outlet of the orifice is formed at a position that is spaced apart by a predetermined distance from the end portion of the spool to which the signal pressure is applied so that the orifice is closed after the spool is moved over a predetermined distance in response to the signal pressure applied thereto. 
     
     
         4 . The flow rate control valve according to  claim 1 , wherein the orifice is formed at at least one of both ends of the spool.