Patent ID: 7175155

Claim:
A control valve apparatus comprising an inlet chamber and an outlet chamber both formed in a housing, a seat valve member slidably disposed in said housing and controlling the amount of an opening between said inlet chamber and said outlet chamber, a control pressure chamber formed in said housing at the backside of said seat valve member and biasing said seat valve member in a valve closing direction, a variable throttle formed in said seat valve member and having an opening which is communicated with said control pressure chamber and of which amount is changed depending on a displacement of said seat valve member, a first passage for communicating said inlet chamber and said variable throttle with each other, a pilot passage for communicating said control pressure chamber and said outlet chamber with each other, and a pilot control valve member disposed in said pilot passage, wherein said control valve apparatus further comprises: a first valve unit disposed in said first passage and allowing a flow only in a direction from said inlet chamber toward said variable throttle; a second passage communicating with said control pressure chamber; a third passage communicating with said outlet chamber; and a second valve unit disposed between said second passage and said third passage and allowing a flow only in a direction from said outlet chamber toward said control pressure chamber.