| 摘要 |
PROBLEM TO BE SOLVED: To improve the working efficiency of a two-piece boom working machine by constructing the machine such that the speed of vertical movement of a second boom is progressively increased or progressively decreased depending on the position of dynamic behavior of a two-piece boom structural mechanism when an ascending motion switch or a descending motion switch is activated. SOLUTION: First and second boom sensors 41, 42 and an arm angle sensor 43 output detection signals indicative of a first boom ground angleα, a second boom hoisting angleβ, and an arm hoisting angleγ, respectively, to a controller 31. Then, the controller executes computation of a height position of the front end of an arm of a two-piece boom mechanism with respect to the ground, based on the anglesα,β, andγ, and lengths of first and second booms and the arm, respectively. The controller 31 progressively accelerates the speed of the second boom in response to operation of a second boom ascending switch 23 when the front end of the arm is in a position of dynamic behavior in the vertical range between upper and lower set heights with respect to the ground. Further, the controller 31 progressively decelerates the speed of the second boom in response to operation of a second boom descending switch 24. Thus, the working efficiency of the machine can be enhanced.
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