| 摘要 |
PROBLEM TO BE SOLVED: To enable hoisting work to be performed in a possible range even if an electric motor of a winch for the hoisting work has heat, while securing the reliability of overload protection and preventing damage of the electric motor.SOLUTION: A crane is equipped with an overload protection device 48. The overload protection device 48 has: a torque limit value setting part 58 setting a torque limit value smaller than a torque rated value when a torque effective value of an electric motor 26 exceeds the torque rated value; a hoisting capacity limit value calculation part 59 calculating a hoisting capacity value corresponding to the set torque limit value; an update part 60, when the calculated hoisting capacity value is smaller than a corresponding set hoisting capacity value in a hoisting capacity data base, updating the set hoisting capacity value to a value equal to the hoisting capacity value; and a control part 63 operating the electric motor 26 when the detected load value of a load detector 44 is equal to or smaller than a newest corresponding set hoisting capacity value, and stopping the operation of the electric motor 26 when the detected load value of the load detector 44 exceeds the newest corresponding set hoisting capacity value.SELECTED DRAWING: Figure 2 |
