Tractor

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 the control information includes a control function set for obtaining the target machine body level value by using the draft load value as a parameter;
• and
• when the slip ratio acquired by the means for acquiring the slip ratio exceeds a threshold value, said means for changing the control information increases a gradient of the control function.

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 the control information includes a control function set for obtaining the target machine body level value by using the draft load value as a parameter;
• and
• wherein when the slip ratio acquired by the means for acquiring the slip ratio exceeds a threshold value, said means for changing the control information sets a new control function in place of the control function previously set during the draft control, the new control function having a higher target machine body level value than the previously set control function with respect to a same draft load value;
• and
• wherein when the slip ratio exceeds a special threshold value of the slip ration greater than the threshold value, said means for changing the control information increases gradient of the set control function.