PRESSURE INCREASING DEVICE FOR HIGH LIFT WORK VEHICLE

PROBLEM TO BE SOLVED: To provide a pressure increasing device capable of selecting one mode from a plurality of modes and keeping the maximum pressure of working oil fed to a hydraulic tool constant even if an amount of working oil fed out by a working oil pump varies.SOLUTION: A pressure increasing device 12 for a high lift work vehicle 1 in which a mode selection part 41 is provided, comprises: a pressure sensor 14 for detecting a pressure of working oil fed to a hydraulic tool (100); and a controller 31 for controlling a solenoid changing-over valve 24 while recognizing pressure transition of the working oil on the basis of a signal from the pressure sensor 14. The controller 31 sets a threshold Pa in response to a selection state of the mode selection part 41, controls the solenoid changing-over valve 24 so as to change-over from a state in which the working oil is guided to a pressure increasing oil passage 26 to a state in which the working oil is guided to a pressure decreasing oil passage 25 when determining the pressure of the working oil to exceed the threshold Pa .SELECTED DRAWING: Figure 2 【課題】複数のモードから一のモードを選択でき、かつ作動油ポンプが送り出す作動油量が変化しても油圧工具へ送られる作動油の最大圧力を一定に保つことができる増圧装置を提供する。【解決手段】高所作業車１用の増圧装置１２において、モード選択部４１を設けるとともに、油圧工具（１００）へ送られる作動油の圧力を検出する圧力センサ１４と、圧力センサ１４からの信号に基づいて作動油の圧力推移を認識しつつ電磁切換弁２４を制御するコントローラ３１と、を具備し、コントローラ３１は、モード選択部４１の選択状況に応じて閾値Ｐａを定め、作動油の圧力が閾値Ｐａを超えたと判断したときに電磁切換弁２４を制御して増圧油路２６へ作動油を案内する状態から減圧油路２５へ作動油を案内する状態に切り換える、とした。【選択図】図２