Method and apparatus for reducing wash tub displacement during spin cycle ramp-up

A washing machine comprising:

• a) a wash basket that is rotatable about an axis relative to the washing machine;
• b) a drive motor for rotating the wash basket;
• c) a balancing ring mounted to the wash basket in a plane that is generally perpendicular to the rotation axis, the balancing ring having a balancing mass that is movable relative to the balancing ring;
• and
• d) a suspension structure mounted to the washing machine and supporting the wash basket, the suspension structure having,
• i) two resonant critical frequencies for two transnational degrees of freedom of the suspension structure that are generally perpendicular to the axis of rotation that each occur at or below a critical first motor speed, and
• ii) three other resonance frequencies for three rotational degrees of freedom of the suspension structure that each occur at or above a second motor speed that is higher than the first speed.

A method of reducing displacement of a wash basket that is rotatable about an axis of rotation within a washing machine, the washing machine having a drive motor for rotating the wash basket, the method comprising:

• mounting a balancing ring to the wash basket in a plane that is generally perpendicular to the axis of rotation, the balancing ring having a balancing mass that is movable relative to the balancing ring;
• supporting the wash basket by suspension structure to the washing machine;
• determining two resonant critical frequencies for two translational degrees of freedom of the suspension structure that are generally in the plane of the balancing ring;
• and
• initially ramping up the drive motor to the initial spin speed that is above a first motor speed at or below which each of the critical frequencies occurs;
• dwelling the drive motor at the initial spin speed for a time period that permits the balancing mass to move relative to the balancing ring and to lock up with the balancing ring;
• and
• subsequently ramping-up at the drive motor to a final steady state spin speed at a rate that permits the balancing mass to remain generally stationary relative to the balancing ring while ramping up as well as after reaching the steady state final spin speed.