Drum type washing machine and its control method

Abstract

The present invention provides a drum-type washing machine which features suppression of vibrations and noises during dehydration. To this end, an unbalanced load occurring around a rotation axis of the drum due to uneven distribution of laundry is canceled. More specifically, a plurality of water tanks ( 20 ) each having an opening on the inner periphery thereof are provided around the rotation axis on the back side of the drum ( 3 ). Where an eccentric load occurring due to the uneven distribution of the laundry is greater than an allowable level, a water supply valve ( 14 ) is opened to introduce water into the respective water tanks ( 20 ) with the drum 3 kept rotated, and the water is kept retained in the water tanks by a centrifugal force. Thereafter, the rotation speed of the drum ( 3 ) is temporarily reduced at a time point according to the position of the eccentric load to cause the water to fall only from water tanks ( 20 ) located at the same position as the position of the eccentric load or adjacent the position of the eccentric load for reduction of the weight of the water retained therein. The eccentric load occurring due to the uneven distribution of the laundry is canceled by an eccentric load generated by the water tanks not fully filled with the water and the other water tanks fully filled with the water, whereby the unbalanced load exerted on the entire drum ( 3 ) can be eliminated.

What is claimed is:  
     
         1 . A washing machine comprising: 
 a drum which is rotated for washing and dehydrating laundry retained therein;    a plurality of liquid chambers provided circumferentially equidistantly about a rotation axis of the drum and rotatable in synchronization with the drum to retain a liquid therein with a centrifugal force;    eccentric load detecting means for detecting a magnitude and a position of an eccentric load occurring due to uneven distribution of the laundry in the drum;    comparing means for comparing the magnitude of the eccentric load detected by the eccentric load detecting means with a reference value;    liquid filling means for filling the liquid substantially evenly in the respective liquid chambers; and    liquid discharge controlling means for temporarily reducing a rotation speed of the drum on the basis of the position of the eccentric load detected by the eccentric load detecting means so that the liquid is discharged from a liquid chamber located at or adjacent the position of the eccentric load for reduction of a liquid amount therein.    
     
     
         2 . A washing machine as set forth in  claim 1 , wherein the liquid discharge controlling means temporarily reduces the rotation speed of the drum to a level at which a centrifugal force acting on the liquid retained in the liquid chambers is smaller than gravity.  
     
     
         3 . A washing machine as set forth in  claim 1  or  2 , further comprising: 
 liquid supplying means for supplying the liquid into the plurality of liquid chambers in a non-contact manner,  
 wherein the liquid filling means fills the respective liquid chambers substantially evenly with the liquid supplied from the liquid supplying means with the drum being rotated at a predetermined rotation speed.  
 
     
     
         4 . A washing machine as set forth in  claim 1  or  2 , wherein the plurality of liquid chambers are provided by partitioning a sealed annular container containing the liquid therein so as to permit the liquid retained in the respective liquid chambers to move within the container.  
     
     
         5 . A washing machine as set forth in any of  claims 1  to  4 , wherein the liquid discharge from the liquid chamber by them liquid discharge controlling means, and the comparison of the magnitude of the eccentric load with the reference value by the comparing means are repeated a predetermined number of times.  
     
     
         6 . A washing machine as set forth in  claim 5 , wherein the liquid discharge from the liquid chamber by the liquid discharge controlling means is intermittently effected when the drum assumes a rotational position corresponding to the position of the eccentric load in each turn of the drum, and a duration of the liquid discharge is set longer for a subsequent turn of the drum than for a precedent turn of the drum.  
     
     
         7 . A washing machine as set forth in  claim 5  or  6 , further comprising a display section for displaying an error sign if the magnitude of the eccentric load is greater than the reference value after the liquid discharge from the liquid chamber by the liquid discharge controlling means and the comparison of the magnitude of the eccentric load with the reference value by the comparing means are repeated the predetermined number of times.  
     
     
         8 . A washing machine as set forth in any of  claims 1  to  7 , further comprising: 
 dehydration driving means for changing the rotation speed of the drum to increase a dehydration rotation speed stepwise to a plurality of dehydration rotation speed levels,  
 wherein the comparing means compares the magnitude of the eccentric load with the reference value whenever the dehydration rotation speed is changed.  
 
     
     
         9 . A washing machine as set forth in  claim 8 , wherein different reference values are defined as the reference value for the respective dehydration rotation speed levels.  
     
     
         10 . A washing machine as set forth in  claim 8  or  9 , wherein the dehydration driving means changes the dehydration rotation speed to four dehydration rotation speed levels including about ⅓, about ½ and about ⅔ of a final dehydration rotation speed, and the final dehydration rotation speed for the stepwise increase of the dehydration rotation speed.  
     
     
         11 . A washing machine as set forth in any of  claims 1  to  10 , further comprising preliminary dehydration driving means for rotating the drum at a preliminary dehydration rotation speed for preliminary dehydration prior to the comparison of the magnitude of the eccentric load with the reference value by the comparing means.  
     
     
         12 . A washing machine as set forth in any of  claims 1  to  11 , further comprising: 
 second comparing means for comparing the magnitude of the eccentric load detected by the eccentric load detecting means with a second reference value; and  
 G-balancing means for temporarily reducing the rotation speed of the drum to a level at which the centrifugal force acting on the laundry is smaller than the gravity from a level at which the centrifugal force acting on the laundry is greater than the gravity at a time point according to the position of the eccentric load detected by the eccentric load detecting means on the basis of a comparison result provided by the second comparing means.  
 
     
     
         13 . A washing machine as set forth in  claim 12 , wherein the comparison of the magnitude of the eccentric load with the second reference value by the second comparing means precedes the comparison of the magnitude of the eccentric load with the reference value by the comparing means.  
     
     
         14 . A washing machine as set forth in  claim 12 , wherein the comparison of the magnitude of the eccentric load with the second reference value by the second comparing means precedes the preliminary dehydration by the preliminary dehydration driving means.  
     
     
         15 . A washing machine as set forth in any of  claims 1  to  14 , wherein the eccentric load detecting means detects an angular position of the eccentric load exerted on the drum due to the uneven distribution of the laundry on the basis of a fluctuation of an acceleration or a weight exerted on a support portion of the drum due to the rotation of the drum.  
     
     
         16 . A washing machine as set forth in any of claims  1  to  14 , wherein the eccentric load detecting means detects the angular position of the eccentric load exerted on the drum due to the uneven distribution of the laundry on the basis of a fluctuation of a torque current of a motor which rotates the drum.  
     
     
         17 . A washing machine as set forth in any of  claims 1  to  16 , wherein the liquid chambers each have an opening which opens toward a rotation center, and are constructed so that, when the drum is rotated at a rotation speed not lower than a predetermined level, the liquid is retained in the liquid chambers by a centrifugal force generated by the rotation of the drum and, when the rotation speed of the drum is lower than the predetermined level, the liquid is spilled down from the liquid chambers in accordance with a change in rotational phase of the drum.  
     
     
         18 . A washing machine as set forth in  claim 17 , wherein the liquid chambers are provided by equidistantly partitioning the annular container along a direction of the rotation by a plurality of partition plates.  
     
     
         19 . A washing machine as set forth in  claim 17  or  18 , wherein the plurality of liquid chambers are each provided with a separation plate covering about ½ to about ⅔ of the opening, and the separation plate covers a forward portion of the opening with respect to the direction of the rotation of the liquid chambers which rotate together with the drum.  
     
     
         20 . A washing machine as set forth in  claim 19 , wherein the separation plate is inclined downward toward an edge thereof which faces the opening to guide the liquid into the liquid chamber through the opening.  
     
     
         21 . A washing machine as set forth in any of  claims 17  to  20 , wherein a liquid supply port for supplying the liquid into the liquid chambers is provided below the rotation axis.  
     
     
         22 . A washing machine as set forth in any of  claims 17  to  21 , wherein the liquid chambers are provided on a rear side of the drum.  
     
     
         23 . A washing machine as set forth in any of  claims 17  to  21 , wherein the liquid chambers are provided on a front side of the drum.  
     
     
         24 . A washing machine as set forth in  claim 22  or  23 , wherein the liquid chambers are arranged with bottoms thereof being offset from the inner circumferential surface of the drum toward the center of the drum.  
     
     
         25 . A washing machine as set forth in any of  claims 1  to  24 , wherein the rotation axis about which the drum is rotated is inclined at an angle of not greater than 30 degrees with respect to a horizontal line.  
     
     
         26 . A washing machine as set forth in  claim 25 , wherein the drum has a closed back and a front opening for loading therein and unloading therefrom the laundry, and the rotation axis is inclined so that the front opening of the drum is directed diagonally upward.  
     
     
         27 . A control method for a drum-type washing machine having a drum which is rotated for washing and dehydrating laundry retained therein, and a plurality of liquid chambers provided circumferentially equidistantly about a rotation axis of the drum and rotatable in synchronization with the drum, the liquid chambers each having an opening which opens toward a rotation center and being constructed so that, when the drum is rotated at a rotation speed not lower than a predetermined level, a liquid is retained in the liquid chambers by a centrifugal force generated by the rotation of the drum and, when the rotation speed of the drum is lower than the predetermined level, the liquid is spilled down from the liquid chambers in accordance with a change in rotational phase of the drum, the drum-type washing machine control method comprising the steps of: 
 performing a liquid filling operation to fill the liquid in the respective liquid chambers while rotating the drum at a rotation speed not lower than the predetermined level; and    performing a liquid discharging operation to spill the liquid selectively from the liquid chambers so as to cancel an eccentric load occurring due to uneven distribution of the laundry retained in the drum by reducing the rotation speed of the drum to lower than the predetermined level at a predetermined time point for a short time.    
     
     
         28 . A drum-type washing machine control method as set forth in  claim 27 , further comprising the step of: 
 performing a comparing operation to compare a magnitude of the eccentric load exerted on the drum when the drum is rotated at a predetermined rotation speed with a predetermined reference value,    wherein the liquid discharging step is performed on the basis of a result provided in the comparing step.    
     
     
         29 . A drum-type washing machine control method as set forth in  claim 27  or  28 , wherein the liquid discharging step and the comparing step are repeated a predetermined number of times.  
     
     
         30 . A drum-type washing machine control method as set forth in  claim 29 , wherein a duration of the liquid discharging step is set longer for a subsequent turn of the drum than for a precedent turn of the drum.  
     
     
         31 . A drum-type washing machine control method as set forth in any of  claims 27  to  30 , wherein the rotation speed of the drum is increased stepwise to a plurality of dehydration rotation speed levels, and the comparing step is performed for each of the dehydration rotation speed levels.  
     
     
         32 . A drum-type washing machine control method as set forth in any of  claims 27  to  31 , further comprising the step of performing a preliminary dehydration operation by rotating the drum at a preliminary dehydration rotation speed prior to the comparing step.  
     
     
         33 . A drum-type washing machine control method as set forth in any of  claims 27  to  32 , further comprising the steps of: 
 performing a second comparing operation to compare the magnitude of the eccentric load exerted on the drum when the drum is rotated at the predetermined rotation speed with a second reference value; and  
 performing a speed reducing operation to temporarily reduce the rotation speed of the drum to a level at which the centrifugal force acting on the laundry is smaller than gravity from a level at which the centrifugal force acting on the laundry is greater than the gravity at a time point according to a position of the eccentric load on the basis of a result provided in the second comparing step.