| 摘要 |
PROBLEM TO BE SOLVED: To improve traveling operability by avoiding sudden deceleration, the occurrence of hunting phenomenon due to vibration of a valve element of a traveling brake valve or the occurrence of a shock due to sudden return of the brake valve in deceleration in the case where high load is applied to the traveling hydraulic motor due to a bad road or the like so that a sudden change in pressure is caused in a traveling oil pressure circuit in which the traveling brake valve is disposed between a traveling hydraulic motor and a control valve. SOLUTION: A directional control valve 9 constituting the traveling brake valve 5 is provided with forward and backward pilot ports 9a, 9b where the pilot pressure for displacing the valve element of the directional control valve 9 from the neutral position N to the forward and backward operating positions X, Y is introduced. Although the pressure in first and second main oil passages 7, 8 as a pressure oil supply passage to a traveling hydraulic motor 3 is introduced to the pilot ports 9a, 9b, the pressure in the second and first main oil passages 8, 7 is not introduced thereto. COPYRIGHT: (C)2005,JPO&NCIPI
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