Control system for cooling fan, work machine, and method of controlling cooling fan

Abstract

A control system for a cooling fan that can ensure cooling capability of the cooling fan is provided. The control system includes an engine, a work implement driven by the engine, a cooling fan configured such that the number of rotations thereof is controllable independently of the number of rotations of the engine, and a controller that controls the cooling fan. The controller controls the cooling fan to make a difference in frequency between the cooling fan and the engine larger than the difference at a time point when the controller obtains the frequency of the cooling fan, by changing the frequency of the cooling fan when the number of rotations of the engine is larger than a threshold value and the frequency of the cooling fan is within a prescribed range from a frequency of the engine while the work implement is in a standstill.

1 . A control system for a cooling fan, the control system comprising:
 an engine;   a work implement driven by the engine;   a cooling fan configured such that the number of rotations is controllable independently of the number of rotations of the engine; and   a controller that controls the cooling fan, wherein   the controller obtains a frequency of the engine and a frequency of the cooling fan, and   the controller controls the cooling fan to make a difference in frequency between the cooling fan and the engine larger than the difference at a time point when the controller obtains the frequency of the cooling fan, by changing the frequency of the cooling fan when the number of rotations of the engine is larger than a threshold value and the frequency of the cooling fan is within a prescribed range from the frequency of the engine while the work implement is in a standstill.   
     
     
         2 . The control system for a cooling fan according to  claim 1 , wherein
 the controller changes the frequency of the cooling fan to be equal to or lower than a lower limit of the prescribed range.   
     
     
         3 . The control system for a cooling fan according to  claim 2 , wherein
 the controller changes the frequency of the cooling fan to the lower limit of the prescribed range.   
     
     
         4 . The control system for a cooling fan according to  claim 1 , wherein
 when the number of rotations of the engine becomes equal to or smaller than a second threshold value smaller than the threshold value, the controller cancels control to change the frequency of the cooling fan.   
     
     
         5 . The control system for a cooling fan according to  claim 1 , wherein
 the cooling fan is mounted on a work machine, and   the controller cancels control to change the frequency of the cooling fan when the controller receives a command from an operator for activating the work machine.   
     
     
         6 . A work machine comprising:
 an engine;   a work implement driven by the engine;   a cooling fan configured such that the number of rotations is controllable independently of the number of rotations of the engine; and   a controller that controls the cooling fan, wherein   the controller obtains a frequency of the engine and a frequency of the cooling fan, and   the controller controls the cooling fan to make a difference in frequency between the cooling fan and the engine larger than the difference at a time point when the controller obtains the frequency of the cooling fan, by changing the frequency of the cooling fan when the number of rotations of the engine is larger than a threshold value and the frequency of the cooling fan is within a prescribed range from the frequency of the engine while the work implement is in a standstill.   
     
     
         7 . A method of controlling a cooling fan in a work machine, the work machine including an engine, a work implement driven by the engine, and a cooling fan configured such that the number of rotations is controllable independently of the number of rotations of the engine, the method comprising:
 determining whether the work implement is operating;   obtaining a frequency of the engine;   obtaining a frequency of the cooling fan; and   controlling the cooling fan to make a difference in frequency between the cooling fan and the engine larger than the difference at a time point when the frequency of the cooling fan is obtained, by changing the frequency of the cooling fan when the number of rotations of the engine is larger than a threshold value and the frequency of the cooling fan is within a prescribed range from the frequency of the engine while the work implement is in a standstill.