Fluid pressure control device
A fluid pressure control device includes a first control valve that switches to supply a working fluid to the pressure chamber of a cylinder on which a load pressure by the load acts so as to control the extension operation of the cylinder, a second control valve that switches to discharge the working fluid in the pressure chamber so as to control the contraction operation of the cylinder, an operate check valve that is interposed between the pressure chamber and the second control valve and that interrupts the discharge of the working fluid from the pressure chamber when the operate check valve is switched to a closed state and a pilot valve that performs, with a pilot pressure, a pilot operation on the second control valve and that switches, with the pilot pressure, the operate check valve to an opened state.
1. A fluid pressure control device
which makes a cylinder expand and contract with a working fluid supplied from a pump to be able to drive a load and
in which the cylinder includes a pressure chamber on which a load pressure by the load acts in a state where supply and discharge of the working fluid are interrupted,
the fluid pressure control device comprising:
a first control valve that is configured to switch to supply the working fluid to the pressure chamber so as to control an extension operation of the cylinder;
a second control valve that is configured to switch to discharge the working fluid in the pressure chamber so as to control a contraction operation of the cylinder;
an operate check valve that is interposed between the pressure chamber and the second control valve and that interrupts the discharge of the working fluid from the pressure chamber when the operate check valve is switched to a closed state; and
a pilot valve that is configured to perform, with a pilot pressure, a pilot operation on the second control valve and that is configured to switch, with the pilot pressure, the operate check valve to an opened state,
wherein the operate check valve includes:
a valve member that interrupts the discharge of the working fluid from the pressure chamber when the valve member is switched to a closed state;
a spool that is provided to face a back surface of the valve member and that can be moved by the pilot pressure guided through the pilot valve;
a back pressure chamber which is defined between an end of the spool and the back surface of the valve member and to which the working fluid from the pressure chamber is guided through an aperture formed in the valve member; and
a switch pressure chamber which is defined to face the other end of the spool and to which the pilot pressure is guided through the pilot valve, and
when the pilot pressure guided to the switch pressure chamber exceeds a set pressure, the valve member is switched to an opened state by movement of the spool to discharge the working fluid in the back pressure chamber.
2. The fluid pressure control device according to claim 1 , further comprising:
a check valve that is interposed between the first control valve and the pressure chamber and that is configured to allow only passage of the working fluid supplied from the pump to the pressure chamber.
3. The fluid pressure control device according to claim 1 ,
wherein the set pressure is set lower than a pressure at which the pilot operation on the second control valve is operated.
4. The fluid pressure control device according to claim 1 , wherein
the spool and the back pressure chamber are provided on a same side facing the back surface of the valve member.
5. A fluid pressure control device
which makes a cylinder expand and contract with a working fluid supplied from a pump to be able to drive a load, and
in which the cylinder includes a pressure chamber on which a load pressure by the load acts in a state where supply and discharge of the working fluid are interrupted,
the fluid pressure control device comprising:
a first control valve that is configured to switch to supply the working fluid to the pressure chamber so as to control an extension operation of the cylinder;
a second control valve that is configured to switch to discharge the working fluid in the pressure chamber so as to control a contraction operation of the cylinder;
an operate check valve that is interposed between the pressure chamber and the second control valve and that interrupts the discharge of the working fluid from the pressure chamber when the operate check valve is switched to a closed state;
a pilot valve that is configured to perform, with a pilot pressure, a pilot operation on the second control valve and that is configured to switch, with the pilot pressure, the operate check valve to an opened state; and
a shuttle valve that is configured to select a higher one of a pressure of the working fluid supplied from the pump and a pressure of a working oil in the pressure chamber, as the pilot pressure guided through the pilot valve.