Washing machine and method for controlling the same

This application claims the benefit of Korean Application Nos. P2004-013268, and P2004-013269, both filed on Feb. 27, 2004, which are hereby incorporated by reference as if fully set forth herein.

1. Field of the Invention

The present invention relates to washing machines, and more particularly, to method and device for preventing resonance from occurring in spinning of a washing machine.

2. Discussion of the Related Art

In general, the washing machine washes laundry by softening action of detergent, and friction of the laundry with water circulation caused by rotation of a pulsator or drum. Recently, demands for drum type washing machines increases day by day, which can reduce an entire height compared to a pulsator type washing machine, and prevent wrinkles from forming.

FIG. 1 illustrates a section of a related art drum type washing machine.

Referring to FIG. 1, the related art drum type washing machine is provided with a tub 3 inside of a cabinet 5 which forms an outer appearance of the drum type washing machine, and a drum 9 rotatably mounted on an inside of the tub 3. The cabinet 5 has a door 1 on a front for introduction of laundry, with a gasket 2 between the door 1 and the tub 3.

The tub 3 has springs 4 each with one end secured to an upper outside circumference thereof and the other end secured to the cabinet 5, and a friction damper 10 thereunder for damping vibration.

On a rear of the tub 3, there is a motor 6 directly coupled to the drum 9 with a rotation shaft 13. On front and rear portion of the rotation shaft 13, there are bearings 12 provided thereto, and on a rear surface of the tub 3, there is a bearing housing for supporting the bearing 12.

The motor 6 is provided with a stator 7 and a rotor 8, wherein the stator 7 is mounted to the rear surface of the tub 3, and the rotor 8 is fixed to the rotation shaft 13. Therefore, when the rotor 8 rotates, the drum 9 connected to the rotor 8 rotates at the same time.

There is a sensor (not shown) at one side of the motor 6 for detecting a rotation speed of the rotor 8, and on an upper portion of a front surface of the cabinet 5, there is a control panel having various buttons for controlling operation of the washing machine.

In the meantime, upon introduction of the laundry into the drum 9, and selecting a washing course, a washing cycle and a rinsing cycle are performed, and a spinning cycle is performed after above cycles are finished.

In the spinning cycle of the laundry, the rotation speed of the motor 6 is increased gradually until the rotation speed reaches to a preset speed when the preset speed is maintained for a preset time period. In this instance, even though a water extraction performance is proportional to the rotation speed of the motor 6, the rotation speed may vary with an extent of eccentricity of the laundry. That is, if the eccentricity of the laundry is great, the rotation speed of the drum 9 drops, or the rotation shaft 13 suffers from damage. Therefore, it is required to measure the eccentricity before the spinning of the washing machine starts.

In the meantime, during the spinning, there can be resonance occurred at the washing machine installed on a floor at a particular rotation speed of the motor 6. That is, if the rotation speed of the motor and the drum approaches close to a natural frequency of the frame, such as the cabinet and the like, the resonance occurs, and once the resonance occurs, vibration and noise become very heavy.

The heavy vibration and noise gives a feeling of inconvenience significantly in measuring the eccentricity of the laundry or in spinning the laundry, or damages the laundry. Moreover, the heavy vibration and noise drops reliability of user on the product.

Accordingly, the present invention is directed to a washing machine, and a method for controlling the same that substantially obviates one or more problems due to limitations and disadvantages of the related art.

An object of the present invention is to provide a washing machine for preventing resonance from occurring during spinning of the washing machine, and a method for controlling the same.

Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objectives and other advantages of the invention may be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.

To achieve these objects and other advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, a method for controlling a washing machine having a drum of which rotation speed is adjustable includes a first step for rotating the drum at a first rotation speed set at control unit, a second step for detecting whether resonance occurs or not at the drum rotating at the first rotation speed, and a third step for changing the rotation speed of the drum if the resonance is detected at the drum.

The third step includes the step of storing the changed rotation speed in the control unit. The drum is rotated at the changed rotation speed when the washing machine is put into operation again after the washing machine is stopped.