FLUID PRESSURE CONTROL APPARATUS

摘要

A fluid pressure control apparatus includes a pilot control valve configured to control a pilot pressure guided from a pilot pump to the control valve and a load retaining mechanism installed in the main passage. The load retaining mechanism includes an operated check valve configured to permit a flow of the working fluid from the load-side pressure chamber to the control valve in accordance with a back pressure and a switch valve configured to switch an action of the operated check valve. The switch valve has a discharge position configured to discharge the working fluid in a back pressure chamber when the pilot pressure has been guided from the pilot control valve. When the switch valve is set to the discharge position, the working fluid in the back pressure chamber is discharged to a tank via a drain port of the pilot control valve.

主权项

1. A fluid pressure control apparatus configured to control extension and retraction operations of a load-driving cylinder, the fluid pressure control apparatus comprising:
a pump configured to supply a working fluid to the cylinder; a control valve configured to control the extension and retraction operations of the cylinder by switching between supply and discharge of the working fluid supplied from the pump to the cylinder; a pilot control valve configured to control a pilot pressure guided from a pilot pump to the control valve; a main passage that connects the control valve and a load-side pressure chamber of the cylinder, the load-side pressure chamber being configured to be subjected to a load pressure attributed to a load when the control valve is maintained in a neutral position; and a load retaining mechanism installed in the main passage, the load retaining mechanism comprising:
an operated check valve configured to permit a flow of the working fluid from the control valve to the load-side pressure chamber, and to permit a flow of the working fluid from the load-side pressure chamber to the control valve in accordance with a back pressure; anda switch valve configured to operate in coordination with the control valve due to the pilot pressure guided via the pilot control valve, so as to switch an action of the operated check valve, wherein the switch valve has a discharge position configured to discharge the working fluid in a back pressure chamber of the operated check valve when the pilot pressure has been guided from the pilot control valve, and when the switch valve is set to the discharge position, the working fluid in the back pressure chamber is discharged to a tank via a drain port of the pilot control valve.