Combine having a temporary retention unit and a shutter

A combine comprising:

• a grain tank that retains grain conveyed from a threshing device;
• a discharge auger that is provided on the bottom of the grain tank, and discharges the grain retained in the grain tank to the outside;
• a temporary retention unit that is provided within the grain tank, has a take-in port, and temporarily retains part of the grain conveyed from the threshing device, the part of the grain being taken in from the take-in port;
• a quality measurement unit that detects quality of the grain retained in the temporary retention unit;
• a discharge port that is formed in the temporary retention unit and is capable of discharging the retained grain into the grain tank;
• a shutter whose position can be changed between an open position at which the discharge port is opened and a closed position at which the discharge port is closed;
• a control unit that performs opening/closing control in which the shutter is moved to the open position when the measurement by the quality measurement unit is completed, and the shutter is moved to the closed position when all of the grain in the temporary retention unit is discharged into the grain tank;
• a volume measurement unit that detects the retention volume of the grain retained in the grain tank;
• and
• a determination unit that determines whether the retention volume of the grain retained in the grain tank exceeds a predetermined value,
• wherein if it is determined by the determination unit that the retention volume exceeds the predetermined value, the control unit stops the opening/closing control.