Work vehicle and method for controlling work vehicle

A work vehicle comprising:

• a vehicle body having a first side surface and a second side surface facing the first side surface;
• a first traveling device provided on the first side surface of the vehicle body;
• a second traveling device provided on the second side surface of the vehicle body;
• a first hydraulic motor to drive the first traveling device;
• a second hydraulic motor to drive the second traveling device;
• a first hydraulic pump connected to a first hydraulic motor via a first hydraulic circuit and having a first port and a second port, the first hydraulic pump being configured to supply hydraulic fluid to the first hydraulic motor via the first hydraulic circuit to drive the first traveling device forward when the pressure applied to the first port is higher than the pressure applied to the second port, the first hydraulic pump being configured to supply hydraulic fluid to the first hydraulic motor via the first hydraulic circuit to drive the first traveling device backward when the pressure applied to the second port is higher than the pressure applied to the first port;
• a second hydraulic pump connected to a second hydraulic motor via a second hydraulic circuit and having a third port and a fourth port, the second hydraulic pump being configured to supply hydraulic fluid to the second hydraulic motor via the second hydraulic circuit to drive the second traveling device forward when the pressure applied to the third port is higher than the pressure applied to the fourth port, the second hydraulic pump being configured to supply hydraulic fluid to the second hydraulic motor via the second hydraulic circuit to drive the second traveling device backward when the pressure applied to the fourth port is higher than the pressure applied to the third port;
• a pilot pump configured to supply pilot oil to the first hydraulic pump and the second hydraulic pump;
• an engine configured to drive the first hydraulic pump, the second hydraulic pump, and the pilot pump;
• at least one pilot oil passage connecting the pilot pump and the first hydraulic pump and connecting the pilot pump and the second hydraulic pump;
• a hydraulic pressure adjustment mechanism provided in the at least one pilot oil passage and configured to adjust the pilot pressure of each of the at least one pilot oil passages to a target pilot pressure;
• a direction input device configured to operate a traveling direction of the work vehicle by instructing forward or backward movement of at least one of the first traveling device and the second traveling device;
• a sensor to detect operation of the direction input device;
• and
• a controller configured to determine whether or not the traveling state of the work vehicle is a turning state based on the operation of the direction input device, to output a rotation command to reduce the target rotational speed of the engine from a first rotational speed to a second rotational speed, and to control the hydraulic pressure adjustment mechanism such that the displacement volume of each of the first hydraulic pump and the second hydraulic pump to which the target pilot pressure is applied is maximized when substantially no load is applied to the first hydraulic motor and the second hydraulic motor.