| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To provide a hydraulic drive system of a traveling utility machine which can automatically change a characteristic curve of traveling load pressure to utility machine load pressure corresponding to a type of work, is excellent in operability, also is small in the number of part items, and simple in structure. <P>SOLUTION: An HST traveling hydraulic circuit 2 comprises a traveling drive circuit 11 and a traveling control circuit 12 wherein the traveling control circuit 12 includes a hydraulic opening and closing valve 38 and a hydraulic switching valve 41, the hydraulic opening and closing valve 38 includes a first pressure receiving part 38c by which the traveling load pressure is introduced, a second pressure receiving part 38d by which regular utility machine load pressure is introduced and a third pressure receiving part 38e by which the utility machine load pressure is selectively introduced via the hydraulic switching valve 41, and the hydraulic switching valve 41 includes a pressure receiving part 41c by which the utility machine load pressure is introduced. When the utility machine load pressure exceeds a predetermined value Pfa, the hydraulic switching valve 41 is switched, thereby introducing the utility machine load pressure also to the third pressure receiving part 38e. <P>COPYRIGHT: (C)2010,JPO&INPIT</p> |
