The valve including a main body having an inlet and an outlet, a support hole and a gate on upper and lower portions of a support part connected to the inlet between an operating chamber and a compression chamber; a cover provided to an outer upper part of the operating chamber of the body and having a control screw in a control pipe; an inserting part inserted into a support hole at a disk balancer's center; a gate rubber for opening and closing the gate at a lower portion of a stem inserted into a guide hole with a spring; a depressuring check part with an operating groove guiding a head of the stem at a lower portion of the stem bolt coupled to an upper portion of the disk balancer; and a control portion having a control spring between the control screw and the disk balancer to protect the control screw with a cap.
