| 摘要 |
PROBLEM TO BE SOLVED: To provide a counter balance valve capable of omitting a check valve and simplifying the usual design constitution. SOLUTION: An hydraulic operation structure is provided with a counter balance valve controlling the opening degree of a flow against a pressure control flow flowing from the first port to the second port by the displacement of the main control spool by transmitting a force from a pilot valve body operated by a hydraulic pressure or an electromagnetic force with respect to the axially movable main control spool in a sliding hole formed in the valve body, through a spring. The structure is also provided with: a piston coaxially arranged to be slidable opposite to the front end face of the main control speed in the counter side to the spring in order to move the main control spool against the spring to open the flow passage for the free flow flowing to the first port from the second port; a first oil chamber formed between the mutually facing end faces of the main control spool and the piston; a second oil chamber formed in the valve body at the other end side of piston; a first passage connecting the first port and the first oil chamber; and second passage connecting the second port and the second oil chamber, and the structure is built in the valve body.
|
