Valve apparatus and hydraulic circuit system

A valve apparatus comprising at least one directional control valve having a supply passage communicating with a hydraulic fluid supply source, a pair of load passages communicating with an actuator, a pair of variable restricting sections disposed between said supply passage and said pair of load passages and formed in an axially movable valve spool in such a manner as to continuously vary opening areas from a closed state dependent on an amount of movement of said valve spool, and a first passage located between said pair of variable restricting sections and said pair of load passages;

• pressure regulating means for holding a differential pressure across said variable restricting sections at a predetermined value;
• a detection line branched from said first passage for receiving a load pressure produced upon operation of said actuator;
• and a control line for introducing the load pressure led through said detection line, as a control pressure, to said pressure regulating means, said valve apparatus further comprising:
• first flow control means disposed downstream of a point where said detection line is branched from said first passage, for allowing a flow of hydraulic fluid proceeding from said first passage toward the load passage corresponding to one of said variable restricting sections, but blocking off a flow of the hydraulic fluid in a reverse direction when said one variable restricting section is opened;
• and said pressure regulating means being a pressure compensating valve disposed between said supply passage and said pair of variable restricting sections so that an outlet pressure of said one variable restricting section and a supply pressure from said hydraulic fluid supply source are applied in a valve-opening direction, while an input pressure of said one variable restricting section and said control pressure are applied in a valve-closing direction, and said first flow control means communicating an outlet side of said one variable restricting section with said corresponding load passage directly.