Traction apparatus and traction force control method of traction apparatus

A traction apparatus that applies a desired traction force to a body to be pulled, the traction apparatus comprising:

• an operation portion that sets a traction force to be applied to the body to be pulled;
• a traction mechanism that includes a fixture that is attached to the body to be pulled and a wire that is connected to the fixture, and applies traction force to the body to be pulled;
• a drive mechanism that winds up the wire;
• a traction force sensor that detects a traction force acting on the wire;
• and
• a control circuit that fetches a set output of a set traction force that is set by the operation portion and a detected output of the traction force sensor and controls driving of the drive mechanism, the control circuit including
• a first traction control process portion that winds up a slack portion of the wire by the drive mechanism to eliminate slack of the wire connected to the body to be pulled,
• a second traction control process portion that converts the set traction force to a traction amount to calculate a converted value and, by defining a predetermined amount of a traction amount set based on the converted value as an initial target value, winds up the wire continuously by the drive mechanism to the target value, and
• a third traction control process that calculates a drive stop time of the drive mechanism by defining the set traction force as a final target value based on the detected output of the traction force sensor and drives the drive mechanism, and stops driving of the drive mechanism at a point of reaching the drive stop time.