Patent ID: 8341787

Claim:
A controlling method of a drum type washing machine having a rotary tub to receive laundry and ball balancers installed on the rotary tub to maintain a dynamic balance, the control method comprising: accelerating the rotary tub to a first rotation speed configured to detect eccentricity amount of laundry, when a spin-drying operation is performed; maintaining the rotation speed of the rotary tub at the first rotation speed for a predetermined period of time; detecting the eccentricity amount of the laundry, when the rotation speed of the rotary tub reaches the first rotation speed; accelerating the rotary tub to a second rotation speed larger than the first rotation speed, configured to perform a drainage process when the detected eccentricity amount is less than a predetermined eccentricity amount; when the detected eccentricity amount is not less than the predetermined eccentricity amount, accelerating the rotary tub to the first rotation speed, maintaining the rotation speed of the rotary tub at the first rotation speed for the predetermined period of time, and detecting the eccentricity amount of the laundry, when the rotation speed of the rotary tub reaches the first rotation speed; decelerating the rotary tub to a third rotation speed configured to estimate positions of balls, when the rotation speed of the rotary tub reaches to the second rotation speed; maintaining the rotation speed of the rotary tub at the third rotation speed for a predetermined period of time such that the balls move to a balancing position to estimate the positions of the balls when the rotation speed of the rotary tub reaches to the third rotation speed; and determining a point of time for spin-drying acceleration using the estimated positions of the balls; accelerating the rotary tub to a rotation speed at the determined point of time for the spin-drying acceleration, wherein the third rotation speed is larger than the first rotation speed that is maintained to detect the eccentricity amount of the laundry for the predetermined period of time.