Washing machine having ball balancers

A washing machine comprising:

• a housing;
• a tub in the housing to contain washing water;
• a drum rotatably disposed in the tub to receive laundry to be washed, the drum including a front cover with an opening provided at a front side of a drum body to receive laundry, an annular recess being formed in the front cover such that the annular recess is located immediately adjacent to a wall of the drum body;
• and
• a ball balancer coupled to the drum to compensate for a dynamic imbalance during rotation of the drum, the ball balancer including a ring-shaped racer constructed of injection molded pieces, the ring-shaped racer having a closed internal space in which a plurality of balls and viscous oil having a viscosity in a range of 100˜380 cSt are accommodated, wherein a width between opposing side walls defining the closed internal space of the racer is greater than a diameter of the balls such that a gap (L1+L2) in a range of 1.0˜2.0 mm is formed between each of the balls and the opposing side walls, and the ball balancer is supported by the annular recess formed in the front cover of the drum.