Work machine and method for controlling work machine

Abstract

A work machine includes a vehicle body, a lift frame supported so as to be rotatable about a lift axis with respect to the vehicle body, a blade supported so as to be rotatable about a pitch axis with respect to the lift frame, a pitch actuator connected to the blade and the lift frame, and a controller. The pitch actuator is configured to cause the blade to perform a pitch motion about the pitch axis in a forward tilt direction and a backward tilt direction. The controller is configured to acquire a traction force of the vehicle body and control the pitch actuator so as to change a pitch angle of the blade based on the traction force.

1 . A work machine comprising:
 a vehicle body;   a lift frame supported so as to be rotatable about a lift axis with respect to the vehicle body;   a blade supported so as to be rotatable about a pitch axis with respect to the lift frame;   a pitch actuator connected to the blade and the lift frame, the pitch actuator being configured to cause the blade to perform a pitch motion about the pitch axis in a forward tilt direction and a backward tilt direction; and   a controller configured to
 acquire a traction force of the vehicle body and 
 control the pitch actuator so as to change a pitch angle of the blade based on the traction force. 
   
     
     
         2 . The work machine according to  claim 1 , wherein
 the controller is configured to
 determine whether the traction force is greater than or equal to a first threshold, and 
 control the pitch actuator so that the blade is tilted backward upon determining that the traction force is greater than or equal to the first threshold. 
   
     
     
         3 . The work machine according to  claim 2 , wherein
 the controller is configured to control the pitch actuator so that the blade is tilted backward as the traction force increases.   
     
     
         4 . The work machine according to  claim 2 , wherein
 the controller is configured to
 determine whether the traction force is greater than or equal to a second threshold that is greater than the first threshold, and 
 control the pitch actuator so that the blade is tilted backward to a limit position in the backward tilt direction when the traction force is greater than or equal to the second threshold. 
   
     
     
         5 . The work machine according to  claim 1 , wherein
 the controller is configured to
 determine whether the work machine is traveling uphill, and 
 control the pitch actuator so as to change the pitch angle of the blade based on the traction force upon determining that the work machine is not traveling uphill. 
   
     
     
         6 . A method for controlling a work machine including a vehicle body, a lift frame supported so as to be rotatable about a lift axis with respect to the vehicle body, a blade supported so as to be rotatable about a pitch axis with respect to the lift frame, and a pitch actuator connected to the blade and the lift frame, the pitch actuator being configured to cause the blade to perform a pitch motion about the pitch axis in a forward tilt direction and a backward tilt direction, the method for controlling the work machine comprising:
 acquiring a traction force of the vehicle body; and   controlling the pitch actuator so as to change a pitch angle of the blade based on the traction force.   
     
     
         7 . The method according to  claim 6 , further comprising:
 determining whether the traction force is greater than or equal to a first threshold; and   controlling the pitch actuator so that the blade is tilted backward upon determining that the traction force is greater than or equal to the first threshold.   
     
     
         8 . The method according to  claim 7 , further comprising:
 controlling the pitch actuator so that the blade is tilted backward as the traction force increases.   
     
     
         9 . The method according to  claim 7 , further comprising:
 determining whether the traction force is greater than or equal to a second threshold that is greater than the first threshold; and   controlling the pitch actuator so that the blade is tilted backward to a limit position in the backward tilt direction when the traction force is greater than or equal to the second threshold.   
     
     
         10 . The method according to  claim 6 , further comprising:
 determining whether the work machine is traveling uphill; and   controlling the pitch actuator so as to change the pitch angle of the blade based on the traction force upon determining that the work machine is not traveling uphill.