Spool type change-over valve.

摘要

In a pilot-driven spool type change-over valve, lateral width (W) of a valve body (4) and sizes of each port and valve hole are efficiently determined in such manner that flow rate of fluid per unit time reaches the highest value without substantially impairing responsiveness in order to increase ability to change over the fluid. Inner diameter (d1) of the valve hole and lateral length (b) of an opening of the port are set to substantially the highest value as determined by lateral width (W) of the valve body, and longitudinal length a of an opening of each port, i.e. length in axial direction in the valve hole, is set to such a size that a characteristic value given by a/W<2> is 1.5 to 2.2 x 10<-><2>.