Patent Publication Number: US-2005115006-A1

Title: Method for controlling dewatering operation of washing machine

Description:
RELATED APPLICATION  
      The present disclosure relates to subject matter contained in Korean Application No. 10-2003-0085274, filed on Nov. 27, 2003, which is herein expressly incorporated by reference in its entirety.  
     BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The present invention relates to a washing machine, and particularly, to a method for controlling dewatering operation of the washing machine.  
      2. Description of the Conventional Art  
      In general a washing machine is a machine for washing laundry by performing a washing process, a rinsing process and a dewatering process. The washing machine is divided into a pulsator type, an agitation type, a drum type or the like according to a washing method. Hereinafter, a drum type washing machine will now be described with reference to  FIG. 1 .  
       FIG. 1  is a sectional view showing a construction of a drum type washing machine in accordance with a conventional art.  
      As shown therein, the drum type washing machine includes a casing  12 ; a tub  17  installed inside the casing  12 ; and a drum  15  rotatably disposed inside the tub  17 .  
      Hereinafter, a construction of a drum type washing machine in accordance with the conventional art will now be described.  
      First, the casing  12  has a rectangular parallelepiped shape, and an aperture  22  is formed at a front plate of the casing  12  in order to put in/take out the laundry therethrough. A door  23  for opening/closing the aperture  22  is installed at a side surface of the aperture  22 . In addition, a tub  17  for receiving washing water is installed in the casing  12 , and a support spring  11  and a damper  18  are respectively installed at upper and lower sides of the tub  17  in order to support and damp the tub  17 .  
      A spider  13  is coupled to the rear of the tub  17  in order to rotatably support the drum  15 , and a drum driving motor  14  for rotating the drum  15  is integrally coupled to a rear side surface of the spider  13 .  
      A water supply pipe (not shown) and a water supply valve (not shown) are installed at an upper region of the tub  17  in order to supply washing water into the tub  17 . A drain pump  19  is installed at a lower region of the tub  17  in order to discharge washing water through a drain pipe  16 .  
      A cyclic water pipe  20  is installed at one side of the drain pipe  16  in order to draw washing water out of the tub  17  and circulate the washing water, which has been drawn out, to an upper region of the tub  17 . A circulation pump  21  for pumping the washing water is installed at the cyclic water pipe  20 .  
      Accordingly, when laundry is received in the drum  15  and detergent and washing water is supplied thereto, a control unit (not shown) controls the drum driving motor  14  to rotate the drum  15  and drives the circulation pump  21  to circulate the washing water, performing a washing process.  
      Thereafter, when the washing process is completed, the control unit controls the drain pump  19  and the drum driving motor  14  to perform a draining process and a dewatering process in order, and supplies washing water into the tub  17  to perform a rinsing process a few times. Herein, whenever the rinsing process is performed, the draining process and the dewatering process are respectively performed once.  
      Hereinafter, a method for controlling dewatering operation of the washing machine will now be described in detail with reference to  FIGS. 2, 3 .  
       FIG. 2  is an operation flow chart of a dewatering operation control method of a drum type washing machine in accordance with the conventional art.  
       FIG. 3  is a graph showing a process for detecting the amount of eccentricity and performing dewatering after detecting the amount of eccentricity at a low speed.  
      First, when a mode of the drum type washing machine is converted into a dewatering mode (S 1 ), the amount of eccentricity of the drum in the drum type washing machine is detected. For example, when a dewatering process is performed in a state that the laundry is eccentrically disposed in the drum  15 , the eccentricity of the laundry causes damage and forced abrasion of the drum  15 , the tub  17  and a support element (not shown) of the drum  15 . Accordingly, in order to prevent the damage and the forced abrasion, the amount of eccentricity of the drum is detected before dewatering process (S 2 ).  
      After detecting the amount of eccentricity of the drum  15 , when the detected amount of eccentricity is smaller than a preset reference value, the drum  15  is rotated at a high speed, performing dewatering (S 3 , S 5 , S 6 ).  
      On the other hand, when the detected amount of eccentricity of the drum  15  is larger than the preset reference value, the drum  15  is stopped and the dewatering operation is not performed. That is, when the detected amount of eccentricity is larger than the preset reference value (standard value of the amount of eccentricity of drum), operation for stopping and then driving the drum  15  is repeatedly performed a few times at the minimum and tens of times at the maximum and then it returns to the step of detecting the amount of eccentricity (S 3 , S 4 ).  
      However, in the drum type washing machine in accordance with the conventional art, when a mode of the drum type washing machine is converted to a dewatering mode, and the amount of eccentricity of the drum  15  is smaller than a preset reference value, the drum  15  is rotated at a high speed, performing dewatering operation. Then, the amount of drained moisture becomes different depending on the kind of laundry in the drum. That is, a drum  15  having laundry of low moisture content and laundry of high moisture content is rotated at a high speed (e.g., 600 rpm), increasing the amount of eccentricity. If the amount of eccentricity is increased while the drum  15  is rotated at a high speed, vibration and noise of the washing machine are increased.  
      Detailed descriptions of a washing machine in accordance with the conventional art is disclosed in U.S. Pat. No. 6,615,619, and No. 6,612,138,  
     SUMMARY OF THE INVENTION  
      Therefore, an object of the present invention is to provide a method for controlling dewatering operation of a washing machine capable of reducing excessive vibration and noise generated during a dewatering process, by detecting an initial reference eccentric position of a drum and an initial amount of eccentricity while the drum of a washing machine is rotated at a low speed, detecting a current eccentric position and a current amount of eccentricity of a drum while a drum is rotated at a low speed again after being rotated at a high speed, and controlling dewatering operation based on the detected initial reference eccentric position, the initial amount of eccentricity, the current eccentric position and the current amount of eccentricity  
      To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described herein, there is provided a method for controlling dewatering operation of a washing machine including detecting an initial amount of eccentricity of a drum and an initial reference eccentric position in the drum while the drum is rotated at a low speed; detecting a current amount of eccentricity of the drum and a current eccentric position in the drum while the drum is rotated at a low speed again after being rotated at a high speed; and controlling dewatering operation based on the detected initial amount of eccentricity, the initial reference eccentric position, the current amount of the eccentricity and the current eccentric position.  
      To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described herein, there is provided a method for controlling dewatering operation of a washing machine including detecting the initial amount of eccentricity of a drum while the drum of a washing machine is rotated at a low speed; determining a drum eccentric position as an initial reference eccentric position at a maximum speed of a range of the low speed that the drum is operated at; detecting the current amount of eccentricity while the drum is rotated at the low speed after being rotated at the high speed for a preset time; determining a drum eccentric position as a current eccentric position at a maximum speed of a range of the low speed that comes after a rotation at the high speed for the preset time; and controlling dewatering operation of a washing machine based on the initial amount of eccentricity, the initial reference eccentric position, the current amount of eccentricity and the current eccentric position.  
      The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a unit of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention.  
      In the drawings:  
       FIG. 1  is a sectional view showing a construction of a drum type washing machine in accordance with the conventional art;  
       FIG. 2  is an operation flow chart of a method for controlling dewatering operation of a drum type washing machine in accordance with the conventional art;  
       FIG. 3  is a graph showing a process for performing dewatering after detecting the amount of eccentricity at a low speed;  
       FIG. 4  is an operation flow chart of a method for controlling dewatering operation of a washing machine in accordance with an embodiment of the present invention;  
       FIG. 5  is a graph showing a process for detecting the initial amount of eccentricity, an initial reference eccentric position, the current amount of eccentricity, and a current eccentric position and performing dewatering based on the detected result;  
       FIG. 6A  depicts a drum having laundry of both low and high moisture content; and  
       FIG. 6B  is a graph showing processes that an initial reference eccentric position is changed by laundry of low moisture content and laundry of high moisture content and detecting the changed eccentric position through a phase difference. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
      Hereinafter, a preferred embodiment of a method for controlling dewatering operation of a washing machine configured to reduce excessive vibration and noise generated during a dewatering process, by detecting an initial reference eccentric position of a drum and the initial amount of eccentricity while a drum of a washing machine is rotated at a low speed, detecting a current eccentric position and the current amount of eccentricity of a drum while the drum is rotated at a low speed again after being rotated at a high speed, and controlling dewatering operation based on the detected initial reference eccentric position, the initial amount of eccentricity, current eccentric position and the current amount of eccentricity, will now be described with reference to  FIGS. 4 through 6 .  
       FIG. 4  is an operation flow chart of a method for controlling dewatering operation of a washing machine in accordance with an embodiment of the present invention.  
      As shown therein, the method for controlling dewatering operation of a washing machine in accordance with the present invention includes: a step (S 11 ) in which when a mode of the washing machine is converted to a dewatering mode, a step (S 12 ) in which the initial amount of eccentricity of a drum is detected while a drum of a washing machine is rotated at a low speed; a step (S 13 ) in which a drum eccentric position is determined as an initial reference eccentric position when the drum is rotated at a maximum speed and while the drum of the washing machine is rotated at a low speed; a step (S 14  and S 15 ) in which the current amount of eccentricity is detected while the drum is rotated at a low speed again after being rotated at a high speed for predetermined time, and a drum eccentric position when a speed of the drum is maximum is determined as a current eccentric position (S 16 ); a step (S 17 ) in which it is determined whether a difference value between the current amount of eccentricity and the initial amount of eccentricity is larger than a first preset reference value a; when the difference value is smaller than the first preset reference value a, dewatering is performed (S 20 ), and when the difference value is larger than the first preset reference value, a phase difference, a difference value between the current eccentric position and the initial reference eccentric position is detected (S 18 ) and it is determined whether the phase difference is larger than a second preset reference value β; and a step in which when the phase difference is smaller than the second preset reference value β, dewatering is performed (S 20 ), and when the phase difference is larger than the second preset reference value, it returns to the step (S 12 ) in which the initial amount of eccentricity of the drum is detected after operation of stopping and then rotating the drum is performed predetermined times.  
      Hereinafter, a method for controlling dewatering operation of a washing machine in accordance with the present invention will now be described in detail with reference to  FIG. 5 .  
       FIG. 5  is a graph showing a process for detecting the initial amount of eccentricity, an initial reference eccentric position, the current amount of eccentricity and a current eccentric position and performing dewatering based on the detected result. That is,  FIG. 5  is a graph showing a process for detecting the amount of eccentricity and initial reference eccentric position while a drum is rotated at a low speed, and detecting the current amount of eccentricity and a current eccentric position while the drum is rotated at a low speed again after being rotated at a high speed for a preset time.  
      First, when a mode of a washing machine is converted from a washing mode to a dewatering mode (S 11 ), as shown in  FIG. 5 , the drum of the washing machine is rotated at a low speed (e.g., 200 rpm (revolution per minute)), and during this rotation, the initial amount of eccentricity of the drum is detected (S 12 ).  
      In addition, a drum eccentric position is set as an initial reference eccentric position when a speed of a drum becomes maximum while the drum is rotated at a low speed (e.g., 200 rpm (revolution per minute). That is, as shown in  FIG. 5 , in case that the amount of eccentricity of the drum is detected while the drum is rotated at a low speed, the speed of the drum is changed by the amount of eccentricity of the drum. At this time, a drum eccentric position when the drum is rotated at a maximum speed is set as an initial reference eccentric position. For example, in case that the speed of the drum is changed by the amount of eccentricity of the drum, when the set initial reference eccentric position is the nearest to a ground, the speed of the drum becomes maximum by gravity, and when the set initial reference eccentric position is at a position of a 180-degree rotation on the basis of a ground, the speed of the drum becomes minimum (S 13 ).  
      Thereafter, the drum of the washing machine is rotated at a high speed (e.g., over 400 rpm) for preset time (e.g., 20˜30 seconds). That is, the drum of the washing machine is rotated at a high speed after being rotated at a low speed, so that the laundry is dewatered for 20˜30 seconds.  
      Thereafter, as shown in  FIG. 5 , after being rotated at a high speed for the preset time (e.g., 20˜30 seconds), the drum is rotated at a low speed again, and the current amount of eccentricity is detected while the drum is rotated at a low speed (S 14 , S 15 ). In addition, a drum eccentric position is determined as a current eccentric position when a speed of the drum becomes maximum while the drum is rotated at a low speed again after being rotated at a high speed for the preset time (e.g., 20˜30 seconds) (S 16 ).  
      Thereafter, a difference value between the detected current amount of eccentricity and the initial amount of eccentricity is detected, and it is determined whether the detected difference value is larger than a preset reference value (α) (S 17 ). At this time, the preset reference value (α) is preset by an experiment.  
      When the difference value is smaller than the preset reference value (α), the drum of the washing machine is rotated at a high speed (e.g., 600 rpm) performing dewatering (S 20 ). On the contrary, when the difference value is larger than the preset reference value (α), a phase difference, a difference value between the current eccentric position and the initial eccentric position is detected, and it is determined whether the detected phase difference is larger than a preset reference value (β) (S 18 ). Herein, the preset reference value (β) is preset by an experiment. A process for detecting the phase difference will now be described with reference to FIGS.  6  A&amp;B.  
       FIG. 6A  depicts a drum having laundry of both low and high moisture content.  FIG. 6B  is a graph showing a process that an initial reference eccentric position is changed by laundry of low moisture content and laundry of high moisture content and the changed eccentric position is detected through a phase difference. That is,  FIG. 6B  is a graph showing a process that an eccentric position is changed when the drum having laundry of low moisture content and that of high moisture content is rotated at a low speed again after being rotated at a high speed for 20˜30 seconds after being rotated at a low speed, and then the changed eccentric position is detected.  
      As shown in  FIG. 6B , by detecting the phase difference, change of an eccentric position can be detected. For example, when a rotation angle from an initial reference eccentric position is measured and the measured rotation angle is 1000 degree (rotation of 2.7 times), it is determined that the eccentric position is moved by a 280-degree (1000 degree−360 degree*2=280 degree). That is, it can be known that a current eccentric position has been made since the initial eccentric position is moved by a 280-degree.  
      Thereafter, when a phase difference, a difference value between the current eccentric position and an initial eccentric position is smaller than the preset reference value (β), the drum of the washing machine is rotated at a high speed performing dewatering. On the contrary, when a phase difference, a difference value between the current eccentric position and an initial eccentric position is larger than the preset reference value (β), operation of stopping and then driving the drum is performed a preset number of times (e.g., three times) so that the phase difference becomes smaller than the preset reference value (β), and it returns to the step of detecting the initial amount of eccentricity (S 12 ), (S 19 ).  
      As so far described, the present invention can reduce vibration and noise generated in dewatering, by detecting an initial reference eccentric position of a drum and the initial amount of eccentricity while a drum of a washing machine is rotated at a low speed, detecting a current eccentric position and the current amount of eccentricity of a drum while the drum is rotated at a low speed again after being rotated at a high speed, and controlling dewatering operation based on the detected initial reference eccentric position, the initial amount of eccentricity, current eccentric position and the current amount of eccentricity.  
      As the present invention may be embodied in several forms without departing from the spirit or essential characteristics thereof, it should also be understood that the above-described embodiments are not limited by any of the details of the foregoing description, unless otherwise specified, but rather should be construed broadly within its spirit and scope as defined in the appended claims, and therefore all changes and modifications that fall within the metes and bounds of the claims, or equivalence of such metes and bounds are therefore intended to be embraced by the appended claims.