Control valve apparatus and pressure circuit
The control valve apparatus holds a seat valve member in a position seated on a valve seat to thereby prevent a backward flow even if the pressure in the inlet chamber side becomes lower than the pressure in the outlet chamber side. With a pilot control valve member is in a closed state, when the pressure in the inlet chamber is higher, a pressurized medium is introduced to the control pressure chamber via a first valve unit and is cut off from the outlet chamber by a second valve unit. When the pressure in the outlet chamber is higher, the pressurized medium is introduced to the control pressure chamber via the second valve unit and is cut off from the outlet chamber by the first valve unit.
1. 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.
2. The control valve apparatus according to claim 1 , wherein a portion of said seat valve member facing said inlet chamber is positioned at the outer side in the radial direction of a valve seat, and a portion of said seat valve member facing said outlet chamber is positioned at the inner side in the radial direction of said valve seat.
3. The control valve apparatus according to claim 1 , wherein a portion of said seat valve member facing said inlet chamber is positioned at the inner side in the radial direction of a valve seat, and a portion of said seat valve member facing said outlet chamber is positioned at the outer side in the radial direction of said valve seat.
4. The control valve apparatus according to claim 1 , wherein said first valve unit is provided inside said seat valve member.
5. The control valve apparatus according to claim 1 , wherein a part of said first passage and said first valve unit are provided inside said housing.
6. The control valve apparatus according to claim 1 , wherein one or both of said second passage and said third passage are in common with a part of said pilot passage.
7. The control valve apparatus according to claim 1 , wherein said second valve unit and respective parts of said second passage and said third passage are provided inside said pilot control valve member, and the remaining parts of said second passage and said third passage are in common with said pilot passage.
8. The control valve apparatus according to claim 1 , further comprising a resilient member for applying a force to bias said seat valve member in the valve closing direction.
9. A pressure circuit using the control valve apparatus according to claim 1 , wherein said inlet chamber is connected to a pressure source, said outlet chamber is connected to a load holding side port of an actuator, and said pressure circuit includes means for reducing a pressure of said pressure source when said control valve apparatus is closed.