| 摘要 |
PROBLEM TO BE SOLVED: To make it possible for traction force to be fully used in digging even if a boom is raised during digging in a work tool controller applied on a work vehicle such as a wheel loader. SOLUTION: This work tool controller consists of a boom cylinder 2, a work tool cylinder 3, a boom main valve 4, a work tool main valve 5, a detector 6, a bypass passage 7, and a bypass valve 8. The detector 6 detecting a predetermined scope of elevation movementθfrom the lowermost position of a boom 82 to a predetermined height position is provided, and the bypass passage 7 for conducting a part of fluid supplied to an elevation movement pilot port Pb2 of the boom main valve 4 into a depression movement pilot port Pa1 of the work tool main valve 5 is provided. Furthermore, the bypass valve 8 which is opened only in the predetermined scope of elevation movementθof the boom 82 by the detector 6 and lets a work tool perform depression movement in accordance with the elevation movement of the boom 82 to hold the work tool in substantially horizontal condition is provided in the bypass passage 7.
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