Patent ID: 8849521

Claim:
A tractor including a ground work implement liftably mounted to a traveling machine body which is caused to travel with a traveling apparatus, the tractor comprising: a draft load sensor for detecting a draft load value during a work by the ground work implement; means for changing control information, the means for changing control information setting, as predetermined control information, one of a plurality of control information based on the draft load value detected by the draft load sensor to obtain a target machine body value; means for controlling draft by executing lifting up/down control of the ground work implement so as to achieve agreement between the target machine body level value obtained by using the predetermined control information which is set based on the draft load value detected by the draft load sensor, and a machine body level value detected by a level sensor; and means for acquiring a slip ratio of the traveling apparatus relative to the ground surface; wherein when the slip ratio acquired by the means for acquiring the slip ratio exceeds a threshold value, (i) said means for changing the control information newly sets, as the predetermined control information, control information which obtains a higher target machine body value relative to a same draft load value, in place of the predetermined control information which has been already used during the draft control, or (ii) said means for changing the control information newly sets, as the predetermined control information, control information which obtains a value which renders an amount of change of the target machine body level value greater than an amount of change of the draft load value, in place of the predetermined control information which has been already used during the draft control.