Abstract:
Device and method for controlling a drain motor, in which a drain valve is driven with reference to a position of drain valve, for optimal control of the drain motor, the device including a drain motor cam connected to a shaft of the drain motor having a detecting point for detecting a bottom dead center of a drain valve marked on one region of a circumference thereof, a switching unit for detecting a position of detecting point of the drain motor cam when the drain motor cam is rotated to provide a position detecting signal, and a microcomputer for receiving the position detecting signal from the switching unit, to identify a position of the drain valve, and controlling operation of the drain motor according to a result of the identification.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to device and method for controlling a drain motor in a fully automatic washing machine, and more particularly, to device and method for controlling a drain motor, in which a drain valve is driven with reference to a position of drain valve, for optimal control of the drain motor. 
     2. Background of the Invention 
     Though the dirt on clothes is removed by chemical reaction of detergent in the washing water once the clothes is put into the washing water, the washing machine for removing dirt stuck on clothes exerts mechanical action, such as friction or vibration, to the clothes for accelerating removal of the dirt, because the removal of dirt from the clothes only by the action of the detergent takes a long time. 
     In operating the washing machine, first, a washing mode is conducted, in which a quantity of laundry, such as clothes, introduced into a washing tub is detected to determine the quantity of laundry, water flow, detergent, and a total washing time period are set according to the quantity of laundry, and the pulsator is pulsated according to the total washing time period, to circulate the washing water for removing the dirt on the clothes through friction with the laundry. Then, upon completion of the washing mode, a rinsing mode is conducted, in which dirt water in the washing tub is discharged, fresh water is supplied to the washing tub, rinsing is carried out for a preset time set in the system already. Upon completion of the rinsing mode, a spinning mode is conducted, in which the water in the washing tub is discharged, and the induction motor is rotated at a preset high speed, for removing water from the laundry by centrifugal force. During the washing and rinsing modes, a drain vale is held closed, and during the spinning mode, the drain valve is held open. 
     FIG. 1 illustrates a bottom view showing a related art drain motor and drain valve. 
     During the washing and rinsing modes of the washing machine, the drain motor  30  is held turned off, and the drain valve  33  is kept closed, for not draining the washing water. In this state, a brake lever  32  interlocked with a connection link  31  transmitting an action of the drain motor  30  to the drain valve  33  is disposed at a position where a brake band (not shown) fixes a drain shaft (not shown) according to a position of the connection link, and since a fore end of a clutch lever  12  is to pull an end of a clutch spring  16 , to bring the spring into a state in which a diameter of the clutch spring  16  becomes greater than an original diameter, that releases the clutch  20 , the washing shaft connected to the pulsator is free from the spinning shaft connected to the washing tub. In the spinning mode, the drain motor  30  is put into operation, to retract the connection link  31  backward, and to open the drain valve  33 , leaving the washing water in a state to be drained, and on the same time, the retraction of the connection link  31  moves the brake lever  32  also to release the spinning shaft from the brake band, and the backward movement of the brake band pushes a connecting screw, to release the clutch lever  12  having the connecting screw fastened thereto to restore the clutch spring  16  into an original state, thereby permitting the washing shaft and the spinning shaft engaged. There are washing machines provided with two step drain valve and drain motor as the case requires. That is, during draining, a voltage is provided to the drain motor  30 , to drive the brake lever  32  of the clutch  20  and the drain valve  33  on the same time, and upon finish of the draining, the voltage to the drain motor  30  is cut off, to restore the drain valve  33  automatically by the clutch spring  16  attached to the drain valve  33 . However, the large sized motor coming from a high power required for driving the brake lever  32  and the drain valve  33  on the same time in draining in the related art costs high and occupies a large space. 
     SUMMARY OF THE INVENTION 
     Accordingly, the present invention is directed to device and method for controlling a drain motor that substantially obviates one or more of the problems due to limitations and disadvantages of the related art. 
     An object of the present invention is to provide device and method for controlling a drain motor, in which a drain motor is adapted to be controlled in an optimal condition to permit a small sized motor, for reducing cost and a space occupied by the drain motor. 
     Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will 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 and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, the device for controlling a drain motor includes a drain motor cam connected to a shaft of the drain motor having a detecting point for detecting a bottom dead center of a drain valve marked on one region of a circumference thereof, a switching unit for detecting a position of detecting point of the drain motor cam when the drain motor cam is rotated to provide a position detecting signal, and a microcomputer for receiving the position detecting signal from the switching unit, to identify a position of the drain valve, and controlling operation of the drain motor according to a result of the identification. 
     In other aspect of the present invention, there is provided a method for controlling a drain motor, including the steps of (1) initializing the drain motor for detecting a bottom dead center of a drain valve, (2) measuring a time period while operating the drain motor once the bottom dead center of the drain valve is detected, (3) stopping the drain motor and carrying out drain operation if the time period measured in the step (2) is the same with a preset motor stop time period, and (4) returning the drain valve to an original state to the bottom dead center of the drain valve upon completion of the rain operation in the step (3). 
     It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed. 
    
    
     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 part 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 illustrates a bottom view showing a related art drain motor and drain valve; 
     FIG. 2 illustrates a device for controlling a drain motor in accordance with a first preferred embodiment of the present invention; 
     FIG. 3 illustrates an enlarged view of the drain motor cam and the switch shown in FIG. 2; 
     FIG. 4 illustrates a circuit for controlling a drain motor in accordance with a preferred embodiment of the present invention; 
     FIG. 5 illustrates a device for controlling a drain motor in accordance with a second preferred embodiment of the present invention; 
     FIG. 6 illustrates an enlarged view of the drain motor cam and the switch shown in FIG. 5; 
     FIG. 7 illustrates a flow chart showing the steps of a method for controlling a drain motor in accordance with a preferred embodiment of the present invention; 
     FIG. 8 illustrates a flow chart showing the steps of a method for initializing a drain motor in accordance with a preferred embodiment of the present invention; and, 
     FIG. 9 illustrates a flow chart showing the steps of a method for initializing a drain motor in accordance with a preferred embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. 
     First Embodiment 
     FIG. 2 illustrates a device for controlling a drain motor in accordance with a first preferred embodiment of the present invention, FIG. 3 illustrates an enlarged view of the drain motor cam and the switch shown in FIG. 2, and FIG. 4 illustrates a circuit for controlling a drain motor in accordance with a preferred embodiment of the present invention. 
     Referring to FIGS. 2 to  4 , the device for controlling a drain motor in accordance with a first preferred embodiment of the present invention includes a drain motor  50  for being rotated in response to an external control signal, a rod  45  for transmission of a power of the drain motor  50  to a drain valve  40 , a drain motor cam  51  fitted to the drain motor  50  having a projection  51   a  for identifying a position (bottom dead center) of the drain valve  40 , a position detecting switch  52  adapted to be turned on/off by the projection  51   a  on the drain motor cam  51  for generating a position detecting signal that permits to identify a state of the drain motor cam  51 , and a microcomputer  53  for receiving the position detecting signal from the position detecting switch  52 , and controlling operation of the drain motor  50  according to a result of the identification. Particularly, the position detecting switch  52  includes two pieces, of which one piece has one side with a convex portion  52   a  for contact with the projection  51   a  on the drain motor cam  51 , and both pieces have insides with first and second contact portions  52   b  and  52   c  at opposite positions. That is, the position detecting switch  52  includes a first piece having a convex portion for contact with the projection on the drain motor cam, and a second piece opposite to the first piece, with contact portions formed insides of the first and second pieces, respectively. Therefore, when the convex portion  52   a  of the position detecting switch  52  is brought into contact with the projection  51   a  on the drain motor cam  51 , the first and second contact portions  52   b  and  52   c  come into contact, to turn on the position detecting switch  52 . 
     The microcomputer  53  controls operation of the drain motor  50  depending on a position of an operation point OP of the drain valve a state of which is determined according to rotation of the drain motor cam  51  according to rotation of the drain motor  50 . 
     That is, referring to FIG. 3, the operation point OP of the drain valve  40  is positioned between R 1  point and R 2  point. And, there are ‘A’ point and ‘B’ point along a direction of rotation of the drain motor  50  next to the RI point, wherein ‘A’ point denotes a motor stop point, informing that the drain valve  40  is put into operation and the drain motor  50  is stopped, and the B point next to the ‘A’ point denotes a drain valve  40  top dead center informing that the drain valve  40  is fully opened. When a system power is turned on again after being turned off for a while in the middle of operation of the drain motor  50 , since the operation point OP is always reset to a reset point between the R 1  and R 2  points, the operation point OP is positioned at the reset point in an initial operation of the drain motor  60 . If the operation point OP is positioned between the R 2  point˜reset point˜R 1  point, the first and second contact points  52   b  and  52   c  of the position detecting switch  52  are under a state of contact to each other, which denotes a contact point turn on section, and, if the operation point OP is positioned between the R 1  point ˜A point˜B point˜R 2  point, the first and second contact points  52   b  and  52   c  of the position detecting switch  52  are in a state spaced apart from each other, which denotes a contact point turn off section. 
     Referring to FIG. 4, in order to detect the present position of the drain motor cam  51 , a photocoupler ‘P’ is used. The unexplained reference symbol SW 1  in FIG. 4 represents a power switch, and the reference symbol SW 2  represents the position detecting switch  52  explained above. And, the references symbols RS 1  and RS 2  and C denote resisters and a condenser. 
     The operation of the device for controlling a drain motor in accordance with a first embodiment of the present invention will be explained. 
     In an initial operation of the drain motor  50 , the operation point OP is positioned at the reset point (a bottom dead center of the drain valve), and the position detecting switch  52  is positioned within the contact point turn on section. As the drain motor  50  is operated, the operation point OP passes through the R 1  point along the direction ‘R’ of rotation of the drain motor  50  when the first and second contact points  52   b  and  52   c  come apart, to turn off the position detecting switch  52 . Then, the position detecting switch  52  generates a position detecting signal for identifying the present position of the operation point OP and provides to the microcomputer  53 , and the microcomputer  53  measures a moving time period of the operation point OP for controlling the operation of the drain motor  50 , and compares to a motor stop duration ΔT set already in the system. If the measured time period and the motor stop time period is identical, the microcomputer  53 , determining that the operation point OP is positioned at the ‘A’ point at the present time, stops the drain motor  50  and, on the same time, starts draining of the water through the drain valve  40 . After conducting the draining operation for a preset time period, determining that the draining operation is completed, the microcomputer  53  puts the drain motor  50  into operation again, to restore the drain valve  40  to an original state again, as well as to bring the operation point OP to the initial position, i.e., to the reset point, too. 
     A method for controlling the aforementioned device for controlling a drain motor in accordance with a first preferred embodiment of the present invention will be explained. FIG. 7 illustrates a flow chart showing the steps of a method for controlling a drain motor in accordance with a first preferred embodiment of the present invention, and FIG. 9 illustrates a flow chart showing the steps of a method for initializing a drain motor in accordance with a preferred embodiment of the present invention. 
     Referring to FIG. 7, method for controlling a drain motor in accordance with a preferred embodiment of the present invention starts with determining a first and a second contact portions  52   b  and  52   c  of the position detecting switch  52  of being spaced apart from each other (see S 11  and S 12 ) as an operation point OP of the drain valve  40  passes through the R 1  point after the drain motor  50  is put into operation initially, to bring the drain valve to a bottom dead center (S 11 ). If it is determined in the step S 12  that the first and the second contact portions  52   b  and  52   c  of the position detecting switch  52  are spaced apart from each other, the position detecting switch  52  provides a contact point turn off signal. Accordingly, the microcomputer  53  measures a moving time period of the operation point OP (see S 13 ). Then, the moving time period of the operation point OP measured at the step S 13  is determined of being identical to the motor stop time period ΔT set already in the system (see S 14 ). That is, if the moving time period of the operation point OP is shorter than the motor stop time period ΔT set already in the system, the motor is operated until identical, to bring the moving time period of the operation point OP to be identical to the motor stop time period. Therefore, when the moving time period of the operation point OP is identical to the motor stop time period ΔT set already in the system, the operation point OP is determined to be positioned at the ‘A’ point at the present time, the water is drained through the drain valve  40 , and the drain motor  50  is stopped. (see S 15 ). Finally, after elapse of a preset time period, it is determined that the draining operation is completed, to restore the drain valve  40  into an original state as well as to return the operation point OP of the drain motor cam  51  to an initial position. (see S 16 ) Of the steps in the method for controlling a drain motor, the system should be initialized for operating the drain motor  50  in the step S 11 . As shown in FIG. 9, in order to do this, the system is turned off, and, after for a while, turned on in the middle of operation of the drain motor  50  in the steps  1  and  2 . (see S 21  and S 22 ) And, in the step  3 , a state of the position detecting switch  52  is detected, for determining a position of the operation point OP at the present time; if the position detecting switch  52  is in operation, the operation point OP is determined to be on a position of the contact point turn on section (R 2  point ˜reset point˜R 1  point), and if the position detecting switch  52  is not in operation, it is determined that the operation point OP is positioned on a position of the contact turn off section (R 1  point˜A point˜B point˜R 2  point). (see S 23 ) Thereafter, in the step  4 , according to a result of determination in the step  3 (S 23 ), the operation point OP is made to be positioned at the reset point. (see S 24 ) 
     Second Embodiment 
     FIG. 5 illustrates a device for controlling a drain motor in accordance with a second preferred embodiment of the present invention, and FIG. 6 illustrates an enlarged view of the drain motor cam and the switch shown in FIG.  5 . 
     Referring to FIGS. 5 and 6, the device for controlling a drain motor in accordance with a second preferred embodiment of the present invention, in which a recess  61   a  is formed in a drain motor cam  61 , includes a drain motor  60  for being rotated in response to an external control signal, a rod  65  for transmission of a power of the drain motor  60  to a drain valve  70 , a drain motor cam  61  fitted to the drain motor  60  having a recess  61   a  for identifying a position (a bottom dead center) of the drain valve  70 , and a position detecting switch  62  adapted to be turned on/off by the recess  61   a  in the drain motor cam  61  for generating a position detecting signal that permits to identify a state of the drain motor cam  61 . Particularly, the position detecting switch  62  includes two pieces, of which one piece has one side with a convex portion  62   a  for contact with the recess  61   a  in the drain motor cam  61 , and both pieces have insides with first and second contact portions  62   b  and  62   c  at opposite positions. Therefore, when the convex portion  62   a  on the position detecting switch  62  is brought into contact with the recess  61   a  in the drain motor cam  61 , the first and second contact portions  62   b  and  62   c  are spaced apart, to turn off the position detecting switch  62 . Alike the first preferred embodiment of the present invention, the position detecting signal from the position detecting switch  62  is provided to the microcomputer  53  shown in FIG.  4 . Therefore, the microcomputer  53  controls operation of the drain motor  60  depending on a position of an operation point OP of the drain valve  70  a state of which is determined according to rotation of the drain motor cam  61  according to rotation of the drain motor  60 . 
     That is, referring to FIG. 6, the operation point OP of the drain valve  70  is positioned between R 1  point and R 2  point. And, there are ‘A’ point and ‘B’ point along a direction of rotation of the drain motor  60  next to the R 1  point, wherein ‘A’ point denotes a motor stop point, informing that the drain valve  70  is put into operation and the drain motor  60  is stopped, and the B point next to the ‘A’ point denotes a drain valve  70  top dead center, informing that the drain valve  70  is fully opened. When a system power is turned on again after being turned off for a while in the middle of operation of the drain motor  60 , since the operation point OP is always reset to a reset point between the R 1  and R 2  points, the operation point OP is positioned at the reset point in an initial operation of the drain motor  60 . If the operation point OP is positioned between the R 2  point˜reset point˜R 1  point, the first and second contact points  62   b  and  62   c  of the position detecting switch  62  are under a state spaced apart from each other, which denotes a contact point turn off section, and, if the operation point OP is positioned between the R 1  point ˜A point˜B point˜R 2  point, the first and second contact points  62   b  and  62   c  of the position detecting switch  62  are in a state of contact to each other, which denotes a contact point turn on section. 
     The operation of the device for controlling a drain motor in accordance with a second embodiment of the present invention will be explained. 
     In an initial operation of the drain motor  60 , the operation point OP is positioned at the reset point, and the position detecting switch  62  is positioned within the contact point turn off section. As the drain motor  60  is operated, the operation point OP passes through the R 1  point along the direction of rotation of the drain motor  60  when the first and second contact points  62   b  and  62   c  come apart, to turn on the position detecting switch  62 . Then, the position detecting switch  62  generates a position detecting signal for identifying the present position of the operation point OP and provides to the microcomputer  53 , and the microcomputer  53  measures a moving time period of the operation point OP for controlling the operation of the drain motor  60 , and compares to a motor stop duration ΔT set already in the system. If the measured time period and the motor stop time period is identical, the microcomputer  53 , determining that the operation point OP is positioned at the ‘A’ point at the present time, stops the drain motor  60  and, on the same time, starts draining of the water through the drain valve  70 . After conducting the draining operation for a preset time period, determining that the draining operation is completed, the microcomputer  53  puts the drain motor  60  into operation again, to restore the drain valve  70  to an original state again, as well as to bring the operation point OP to the initial position, i.e., to the reset point, too. 
     A method for controlling the aforementioned device for controlling a drain motor in accordance with a second preferred embodiment of the present invention will be explained. FIG. 8 illustrates a flow chart showing the steps of a method for controlling a drain motor in accordance with a second preferred embodiment of the present invention. 
     Referring to FIG. 8, a method for controlling a drain motor in accordance with a second preferred embodiment of the present invention starts with determining a first and a second contact portions  62   b  and  62   c  of the position detecting switch  62  of being in contact with each other (see S 32 ) as an operation point OP of the drain valve  70  passes through the R 1  point after the drain motor  60  is put into operation initially (S 31 ). If it is determined in the step S 32  that the first and the second contact portions  62   b  and  62   c  of the position detecting switch  62  are spaced apart from each other, the position detecting switch  62  provides a contact point turn on signal. Accordingly, the microcomputer  53  measures a moving time period of the operation point OP (see S 33 ). Then, the moving time period of the operation point OP measured at the step S 33  is determined of being identical to the motor stop time period ΔT set already in the system (see S 34 ). That is, if the moving time period of the operation point OP is shorter than the motor stop time period ΔT set already in the system, the motor is operated until identical, to bring the moving time period of the operation point OP to be identical to the motor stop time period. Therefore, when the moving time period of the operation point OP is identical to the motor stop time period ΔT set already in the system, the operation point OP is determined to be positioned at the ‘A’ point at the present time, the water is drained through the drain valve  70 , and the drain motor  60  is stopped. (see S 35 ). Finally, after elapse of a preset time period, it is determined that the draining operation is completed, to restore the drain valve  70  into an original state as well as to return the operation point OP of the drain motor cam  61  to an initial position. (see S 36 ) Of the steps in the method for controlling a drain motor in accordance with a second preferred embodiment of the present invention, the system should be initialized for operating the drain motor  60  in the step S 31 , which is identical to the method explained in connection with FIG.  9 . That is, the system is turned off, and, after for a while, turned on again in the middle of operation of the drain motor  60 . (see S 21  and S 22 ) And, a state of the position detecting switch  62  is detected, for determining a position of the operation point OP at the present time; if the position detecting switch  62  is in a turn off state, the operation point OP is determined to be on a position of the contact point turn on section (R 2  point˜reset point˜R 1  point), and if the position detecting switch  62  is in a turn on state, it is determined that the operation point OP is positioned on a position of the contact turn on section (R 1  point˜A point˜B point˜R 2  point). (see S 23 ) Thereafter, in the step  4 , according to a result of determination in the step  3  (S 23 ), the operation point OP is made to be positioned at the reset point. (see S 24 ) 
     As has been explained, the device and method for controlling a drain motor of the present invention have the following advantages. 
     First, the optimal control of the drain motor by detecting a position of the drain valve in operation of the drain valve by the drain motor permits to use a small sized motor. 
     Second, the permitted use of a small sized motor permits to reduce cost and a space occupied by the motor. 
     It will be apparent to those skilled in the art that various modifications and variations can be made in the device and method for controlling a drain motor of the present invention without departing from the spirit or scope of the invention. Thus, it is intended that the present invention cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.