Blade control device for work machinery

Abstract

A blade operation control part of a blade control device controls operation of a blade such that when a blade load is equal to or less than a first load threshold value and a position deviation is equal to or greater than a position threshold value, the blade is lowered to make the position deviation approach zero. The blade operation control part controls operation of the blade such that the blade is raised regardless of the position deviation when the blade load is equal to or greater than a second load threshold value.

1 . A blade control device which is provided in a work machine including a machine body and a blade attached to the machine body so as to be raised and lowered and which controls raising and lowering operation of the blade, the blade control device comprising:
 a target design surface setting part which sets a target design surface that specifies a target shape of an object to be dug by the blade;   a position information acquiring part which acquires position information related to the work machine;   a blade position calculating part which calculates a blade position as a position of the blade on the basis of the position information acquired by the position information acquiring part;   a deviation calculating part which calculates a position deviation as a deviation between the blade position and the target design surface;   a blade load acquiring part which acquires a blade load as a load applied on the blade;   a storage part which stores a first load threshold value as a threshold value of the blade load, a second load threshold value which is a threshold value of the blade load and greater than the first load threshold value, and a position threshold value as a threshold value of the position deviation; and   a blade operation control part which controls operation of the blade, wherein   the blade operation control part controls operation of the blade such that the blade is lowered to make the position deviation approach zero when the blade load is equal to or less than the first load threshold value and the position deviation is equal to or greater than the position threshold value, and   the blade operation control part controls operation of the blade such that the blade is raised regardless of the position deviation when the blade load is equal to or greater than the second load threshold value.   
     
     
         2 . The blade control device according to  claim 1 , wherein
 in a case where the blade load is greater than the first load threshold value and smaller than the second load threshold value, and the position deviation is equal to or greater than the position threshold value, a relative position of the blade with respect to the machine body is maintained.   
     
     
         3 . The blade control device according to  claim 1 , wherein
 in a case where the blade load is greater than the first load threshold value and smaller than the second load threshold value, and the position deviation is smaller than the position threshold value, the blade operation control part controls operation of the blade such that the position deviation approaches zero.   
     
     
         4 . The blade control device according to claim  claims 1 , wherein
 the position threshold value is a first position threshold value,   the storage part further stores a second position threshold value which is a threshold value of the position deviation and is smaller than the first position threshold value, and   the blade operation control part controls operation of the blade such that the blade is raised to make the position deviation approach zero in a case where the blade load is equal to or less than the first load threshold value and the position deviation is equal to or less than the second position threshold value.