| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To simplify a hydraulic circuit for a hydraulic device to be mounted on a tunnel excavator. <P>SOLUTION: The hydraulic circuit is provided with a supply passage 5 to supply hydraulic fluid from an oil tank 2 to the hydraulic device 1, a return passage 6 to return hydraulic fluid from the hydraulic device 1 to the oil tank 2, a relief passage 7 branched from the supply passage 5, a relief valve 16 provided on the relief passage 7 to send hydraulic fluid in the supply passage 5 through the relief passage 7 to be released when hydraulic pressure in the relief passages 7 exceeds prescribed relief pressure, and a pressure control valve 17 provided on the return passage 6. With the relief valve 16, the relief pressure is adjustable. The pressure control valve 17 is changeable between a first function to open for releasing hydraulic fluid in the return passage when the hydraulic pressure in the return passage 6 exceeds a prescribed pressure that is lower than the relief pressure of the relief valve 16 and a second function to close for closing the return passage 6 regardless of the hydraulic pressure in the return passage 6. When the hydraulic device 1 is run, it is changed to the first function, and when the relief pressure of the relief valve is adjusted, it is changed to the second function. <P>COPYRIGHT: (C)2009,JPO&INPIT</p> |
