Patent ID: 7921816

Claim:
A control device for a hydraulically driven fan, comprising: a cooling fan rotated by a hydraulic motor and carrying out a ventilation for cooling a working fluid that is involved in an operation of an engine; first detecting means for detecting a temperature of the working fluid; adjusting means for adjusting a rotating speed of the hydraulic motor in correspondence to a result of detection of the first detecting means; second detecting means for detecting whether a working mechanism actuated by the engine is in a stopped state by determining whether a working machine lever has been operated; and control means for controlling an operation of the adjusting means in correspondence to a result of detection by the second detecting means thereby adjusting the rotating speed of the hydraulic motor in such a manner that a resonance between the cooling fan and the engine is suppressed, wherein if the working machine lever has not been operated and a temperature of the working fluid is lower than a predetermined value, the control means causes the adjusting means to operate in such a manner that a rotating speed of the cooling fan is lowered; wherein, when all the working machine levers are switched to a neutral position from an operating position, the control means controls the operations of the engine and the hydraulic motor in such a manner that the rotating speeds of the engine and the cooling fan are lowered from a normal range to a predetermined low rotating speed range after a predetermined delay time has elapsed.