| 摘要 |
<p>An unloading valve, wherein a spool (33) having a flange part (39) formed thereon is inserted into a spool bore (32) and a pressing force by a spring (52) is always added, through the flange part (39), to the spool (33) in a second pressure chamber (35), and an oil groove (60) is provided in the inner peripheral surface of the spool bore (32) near a contact surface (51) and a pressure oil with the same pressure (P2) as in the second pressure chamber (35) is led into the oil groove (60) through an oil path (61) provided in a valve main body (31), whereby, because the pressure oil invades through the oil groove (60) into a clearance between the flange part (39) and the contact surface (51) when the flange part is fitted closely to the contact surface, a cracking pressure due to a close fitting can be prevented from rising without lowering the strength of the flange part (39) so as to provide the stable opening and closing characteristics of the spool (33).</p> |
