Patent Publication Number: US-2022235514-A1

Title: Washing machine

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority to and the benefit of Korean Patent Application No. 10-2021-0010328, filed on Jan. 25, 2021, the disclosure of which is incorporated herein by reference in its entirety. 
     TECHNICAL FIELD 
     The present disclosure relates to a washing machine, and more particularly to a washing machine for performing laundry treatment using carbon dioxide (CO 2 ). 
     BACKGROUND 
     In a washing procedure and a rinsing procedure of a conventional washing machine designed to use carbon dioxide (CO 2 ), a washing tub of the washing machine is filled with gaseous carbon dioxide (CO 2 ) and liquid carbon dioxide (CO 2 ). In order to wash laundry using carbon dioxide (CO 2 ), carbon dioxide (CO 2 ) flows from a storage tub into the washing machine so that the inside of the washing machine can be filled with the carbon dioxide (CO 2 ). After completion of the washing procedure, carbon dioxide (CO 2 ) is drained from the washing tub to a distillation tub and then flows from the distillation tub into the storage tub, so that the carbon dioxide (CO 2 ) can be reused. In addition, the washing tub is generally designed in a manner that a pulley is connected to a drive shaft, and a motor pulley is connected to a drum pulley through a belt, so that a drum can rotate by the washing tub. 
     A conventional washing machine defines a washing space in which laundry is disposed and a motor space in which a motor is installed that are used together without distinction therebetween, so that the motor space is unavoidably filled with carbon dioxide (CO 2 ). As a result, the amount of carbon dioxide (CO 2 ) to be used in the washing procedure of laundry unavoidably increases. Also, due to the large amount of carbon dioxide (CO 2 ), pressure vessels related to carbon dioxide (CO 2 ) unnecessarily increase in size, and the system becomes very large in size and very heavy in weight, so that there are many restrictions on the space in which the system is to be installed. In addition, for the conventional washing machine, the drum cannot be taken out of the washing space, so that it is impossible to provide an operator (or a repairman) with an easy repair environment in which the drum can be easily repaired. 
     In association with constituent components of the conventional washing machine using carbon dioxide (CO 2 ), there is a great difficulty in easily maintaining/repairing the conventional washing machine. For example, in order for a user such as a repairman to disassemble a flange due to occurrence of a problem in a washing tub, the outer frame of the washing machine should be opened, pipes for interfering with horizontal movement of the flange, a stovepipe for discharging contaminants, and various sensors, etc. should then be removed. In addition, when the user such as a repairman disassembles dozens of bolts of the flange, the user must disassemble such bolts while avoiding interference of significant peripheral components. In addition, even when the user repairs only one component (e.g., a compressor, etc.), carbon dioxide (CO 2 ) of the entire system should be completely exhausted and the system should be recharged with new carbon dioxide (CO 2 ) after being completely repaired, resulting in consumption of unnecessary resources. The above-described situations may unavoidably cause an increase in equipment maintenance costs. 
     SUMMARY 
     The present disclosure is directed to a washing machine in which constituent elements are arranged to facilitate a task for each constituent element. In addition, the present disclosure is directed to a washing machine in which constituent elements are compactly arranged to reduce the overall size of the washing machine. 
     The present disclosure is also directed to a washing machine capable of reducing environmental pollution by reducing the amount of carbon dioxide (CO 2 ) used for laundry treatment such as washing. 
     The present disclosure is also directed to a washing machine capable of reducing the size of a pressure vessel designed to use carbon dioxide (CO 2 ) by reducing the amount of the carbon dioxide (CO 2 ) to be used. 
     The present disclosure is also directed to a washing machine capable of providing the environment in which an operator (or a repairman) can repair the drum that rotates while accommodating laundry. 
     The present disclosure is also directed to a washing machine capable of reducing the size of a space to be occupied by a motor assembly rotating the drum, thereby reducing the size of an overall space to be occupied by the washing machine. 
     The present disclosure is also directed to a washing machine capable of stably operating by allowing a washing space including the drum and a motor space including the motor to be kept at the same pressure. 
     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. 
     The present disclosure is directed to a washing machine, maintenance of which can be easily performed. Whereas it is difficult to maintain/repair the conventional washing machine because it has a complex system structure and heavy high-pressure components and causes difficult handling of high-pressure gas, the washing machine is designed to be easily maintained/repaired by a user such as a repairman. 
     The washing machine can allow an electronic panel to rotate by 180° with respect to one axis of a back surface of the washing machine, so that self-inspection of various sensors mounted in the washing machine, program update, signal system inspection, etc. can be performed. 
     In addition, a compressor, an oil separator, pipes, etc. of the washing machine are modularized in a manner that each component of the washing machine can be independently separated from the system, so that exhausting, vacuuming, and charging of carbon dioxide (CO 2 ) can be performed independently. 
     According to one aspect of the subject matter described in this application, a washing machine can include a frame defining an appearance of the washing machine, a drum configured to receive laundry, a washing chamber including a first housing defining an opening and a space into which the drum is inserted, a barrier that surrounds the opening and that is coupled to the first housing, and a second housing that surrounds a first surface of the barrier and that is coupled to the first housing, a storage tank configured to receive carbon dioxide to be supplied to the drum, a distillation chamber configured to separate contaminants dissolved in liquid carbon dioxide, an electronic circuit configured to control operations of the washing machine, and a configuration unit including a pipe configured to move the carbon dioxide, a first compressor and a second compressor that are configured to compresses the carbon dioxide discharged after washing is completed in the drum and that are configured to move the compressed carbon dioxide into the storage tank, and an oil separator configured to separate oil from the carbon dioxide compressed in the first compressor and the second compressor. The frame can include a front panel provided on a front surface of the frame, a bottom panel provided on a bottom surface of the frame, and a column coupled to the bottom panel and extending from the bottom panel in a vertical direction. 
     Implementations according to this aspect can include one or more of the following features. For example, the electronic unit can be rotatably coupled to the column. 
     In some implementations, the column can includes a front column, and a rear column located opposite to the front panel with respect to the front column. A distance from the front column to the front panel can be less than a distance from the rear column to the front panel, and the rear column can include a first rear column and a second rear column. 
     In some examples, the electronic unit can be rotatably coupled to the second rear column and can be detachably coupled to the first rear column. In some implementations, the storage tank can be supported by the front column and the rear column. In some implementations, components of the configuration unit can be respectively disposed at an upper side and a lower side of the electronic unit. 
     In some implementations, the washing machine can further include a door through which the laundry is introduced into the washing chamber and coupled to the front panel. In some implementations, each of the distillation chamber, the storage tank, and the washing chamber can have a cylindrical shape, and a vertical cross-section of each of the distillation chamber, the storage tank, and the washing chamber can have a circular shape. 
     In some examples, the washing chamber can have a largest radius among the distillation chamber, the storage tank, and the washing chamber. In some examples, the washing chamber can be disposed at a center portion of the front panel with respect to a width direction of the washing machine. 
     In some implementations, a position of each of the storage tank and the distillation chamber can be biased toward one side with respect to a width direction of the washing machine. In some examples, the position of each of the storage tank and the distillation chamber can be biased in a same direction with respect to the width direction of the washing chamber. 
     In some implementations, the washing chamber can be disposed between the distillation chamber and the storage tank. In some examples, the distillation chamber can be disposed at a lowest position among the distillation chamber, the storage tank, and the washing chamber. 
     In some implementations, the storage tank can be disposed at a highest position among the distillation chamber, the storage tank, and the washing chamber. In some implementations, the barrier can be configured to block liquid carbon dioxide injected into a first space provided by the first housing and the barrier from moving into a second space provided by the second housing and the barrier. 
     In some implementations, at least a portion of the configuration unit can be disposed forward to the electronic unit. In some implementations, the first compressor and the second compressor can be disposed below the electronic unit. 
     In some implementations, at least a portion of the storage tank can be disposed above the electronic unit. In some implementations, revolutions per minute (RPM) of the first compressor and RPM of the second compressor can be different from each other in a predetermined pressure range of the washing chamber. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a conceptual diagram illustrating an exemplary washing machine. 
         FIG. 2  is a diagram illustrating an appearance of an exemplary washing chamber. 
         FIG. 3  is a diagram illustrating a front view of the structure shown in  FIG. 2 . 
         FIG. 4  is a diagram illustrating a cross-sectional view of the structure shown in  FIG. 2 . 
         FIG. 5  is a diagram illustrating a second housing separated from the structure shown in  FIG. 2 . 
         FIG. 6  is a diagram illustrating components of an exemplary drum shown in  FIG. 5  detached rearward. 
         FIG. 7  is a diagram illustrating the exemplary drum and some constituent elements included in the exemplary drum. 
         FIG. 8  is a diagram illustrating a cross-sectional view of the structure shown in  FIG. 7 . 
         FIG. 9  is a diagram illustrating an exploded perspective view of the structure shown in  FIG. 7 . 
         FIG. 10  is a diagram illustrating an exploded perspective view of the main constituent elements of the structure shown in  FIG. 7 . 
         FIGS. 11A and 11B  are diagrams illustrating a barrier. 
         FIG. 12  is a diagram illustrating a function of a second through-hole. 
         FIG. 13  is a diagram illustrating a structure in which a heat exchanger is coupled to a barrier. 
         FIG. 14  is a diagram illustrating an O-ring and an O-ring cover mounted to the barrier. 
         FIG. 15  is a diagram illustrating an exemplary state in which the structure of  FIG. 14  is coupled to other constituent elements. 
         FIG. 16  is a diagram illustrating a rotary shaft. 
         FIG. 17  is a diagram illustrating an exemplary state in which the rotary shaft of  FIG. 16  is coupled to other constituent elements. 
         FIG. 18  is a diagram illustrating a concept of operations of the washing machine. 
         FIG. 19  is a flowchart illustrating an operation process of the washing machine. 
         FIGS. 20 and 21  are diagrams illustrating exemplary features in which two compressors are operated in parallel. 
         FIGS. 22 and 23  are diagrams illustrating exemplary features in which two compressors are operated in series. 
         FIG. 24  is a diagram illustrating a path through which oil trapped in a storage tank or a washing chamber flows. 
         FIG. 25  is a diagram illustrating a front view of an exemplary washing machine. 
         FIGS. 26 and 27  are diagrams illustrating rear views of the exemplary washing machine shown in  FIG. 25 . 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  is a conceptual diagram illustrating an exemplary washing machine. 
     Referring to  FIG. 1 , since the washing machine performs various laundry treatments (such as washing, rinsing, etc. of laundry) using carbon dioxide (CO 2 ), the washing machine can include constituent elements capable of storing or processing such carbon dioxide (CO 2 ). 
     The washing machine can include a supply unit for supplying carbon dioxide, a washing unit for processing laundry, and a recycling unit for processing used carbon dioxide. The supply unit can include a tank for storing liquid carbon dioxide therein, and a compressor for liquefying gaseous carbon dioxide. The tank may include a supplementary tank and a storage tank. The washing unit may include a washing chamber into which carbon dioxide and laundry can be put together. The recycling unit may include a filter for separating contaminants dissolved in liquid carbon dioxide after completion of the washing procedure, a cooler for liquefying gaseous carbon dioxide, a distillation chamber for separating contaminants dissolved in the liquid carbon dioxide, and a contamination chamber for storing the separated contaminants after distillation. 
     The supplementary tank  20  can store carbon dioxide to be supplied to the washing chamber  10 . In some implementations, the supplementary tank  20  can be a storage tank that can be used when replenishment of carbon dioxide is required, and the supplementary tank  20  may not be installed in the washing machine in a situation where replenishment of such carbon dioxide is not required. The supplementary tank may not be provided in a normal situation, the supplementary tank can be coupled to supplement carbon dioxide as needed, so that replenishment of carbon dioxide can be performed. In some implementations, when such replenishment of carbon dioxide is completed, the supplementary tank can be separated from the washing machine. 
     The storage tank  30  can supply carbon dioxide to the washing chamber  10 , and can store the carbon dioxide recovered through the distillation chamber  50 . 
     The cooler  40  can re-liquefy gaseous carbon dioxide, and can store the liquid carbon dioxide in the storage tank  30 . 
     The distillation chamber  50  can distill liquid carbon dioxide used in the washing chamber  10 . The distillation chamber  50  can separate contaminants by vaporizing the carbon dioxide through the distillation process, and can remove the separated contaminants. 
     The compressor unit  80  can reduce pressure of the inside of the pressurized washing chamber  10  to approximately 1.5 bar. 
     The contamination chamber  60  can store contaminants filtered through distillation by the distillation chamber  50 . 
     The filter unit  70  can filter out contaminants in the process of discharging liquid carbon dioxide used in the washing chamber  10  into the distillation chamber  50 . The filter unit  70  can include a filter having a plurality of fine holes. 
     Laundry is received in the washing chamber  10 , so that washing or rinsing of the laundry can be performed. When a valve of the storage tank  30  connected to the washing chamber  10  opens a flow passage, air pressure in the washing chamber  10  can become similar to air pressure in the storage tank  30 . In some implementations, gaseous carbon dioxide can be injected first, and then the inside of the washing chamber  10  can be pressurized through equipment such as a pump, so that the inside of the washing chamber  10  can be filled with liquid carbon dioxide. In a situation in which the inside of the washing chamber  10  is maintained at approximately 45˜51 bar and 10˜15° C., washing can be performed for 10˜15 minutes, and rinsing can be performed for 3˜4 minutes. When washing or rinsing is completed, liquid carbon dioxide can be discharged from the washing chamber  10  to the distillation chamber  50 . 
     The valve  90  can remove internal air of the washing chamber  10  before starting the washing procedure, thereby preventing moisture from freezing in the washing chamber  10 . Because washing performance is deteriorated when moisture in the washing chamber  10  is frozen, moisture in the washing chamber  10  can be prevented from being frozen. 
       FIG. 2  is a diagram illustrating the appearance of the washing chamber.  FIG. 3  is a diagram illustrating a front view of the structure shown in  FIG. 2 .  FIG. 4  is a diagram illustrating a cross-sectional view of the structure shown in  FIG. 2 . 
     Referring to  FIGS. 2 to 4 , the washing chamber  10  can include a door  300 , a first housing  100 , and a second housing. In some implementations, the washing chamber  10  can refer to a space in which laundry is received and various laundry treatments such as washing, rinsing, etc. of laundry can be performed. In addition, the washing chamber  10  can be provided with a motor assembly that supplies driving force capable of rotating the drum to the washing chamber  10 . 
     The door  300  can be provided at one side of the first housing  100  to open and close the inlet  102  provided in the first housing  100 . When the door  300  opens the inlet  102 , the user can put laundry to be treated into the first housing  100  or can take the completed laundry out of the first housing  100 . 
     The first housing  100  can define a space in which the drum  350  accommodating laundry is inserted. The drum  350  can be rotatably provided so that liquid carbon dioxide and laundry are mixed together in a state in which laundry is disposed in the drum  350 . 
     The first housing  100  can be provided with an opening  104  in addition to the inlet  102 . The opening  104  can be located opposite to the inlet  102 , and can have a size larger than a size of the inlet  102 . 
     The first housing  100  can have a cylindrical shape, the inlet  102  having a circular shape can be provided at one side of the first housing  100 , and the opening  104  having a circular shape can be provided at the other side of the first housing  100 . 
     The drum  350  can have a cylindrical shape similar to the shape of the inner space of the first housing  100 , so that the drum  350  can rotate clockwise or counterclockwise in the first housing  100 . 
     The opening  104  can have a size larger than a size of the cross-section of the drum  350 , so that the operator or user can repair the drum by removing the drum  350  through the opening  104 . In some implementations, the opening  104  can have a size larger than a maximum cross-section of the drum  350 . Therefore, the operator or the user can open the opening  104  to remove the drum  350 . It is also possible to install the drum  350  in the first housing  100  through the opening  104 . 
     The opening  104  can have a size larger than a size of the maximum cross-section of the space of the first housing  100 . In addition, the opening  104  can be maintained at the same size while extending to the center portion of the first housing  100 . Thus, when the operator or the user removes the drum  350  from the first housing  100  or inserts the drum  350  into the first housing  100 , a space that is sufficient to not interfere with movement of the drum  350  can be guaranteed. 
     In some implementations, the user can put laundry into the first housing  100  using the inlet  102 , and maintenance or assembly of the drum  350  can be achieved using the opening  104 . The inlet  102  and the opening  104  can be located opposite to each other in the first housing  100 . 
     The first housing  100  can be provided with an inlet pipe  110  through which carbon dioxide flows into the first housing  100 . The inlet pipe  110  can be a pipe that is exposed to an outside of the first housing  100 , so that the pipe through which carbon dioxide flows can be coupled to the constituent elements described in  FIG. 1 . 
     The first housing  100  can be provided with the filter fixing part  130  capable of fixing the filter unit  70  to the first housing  100 . The filter fixing part  130  can be formed to radially protrude from the cylindrical shape of the first housing  100 , resulting in formation of a space in which the filter can be inserted. The filter fixing part  130  can be provided with a discharge pipe  132  through which carbon dioxide filtered through the filter unit  70  can be discharged from the first housing  100 . The carbon dioxide used in the first housing  100  can be discharged to an outside of the first housing  100  through the discharge pipe  132 . 
     The first housing  100  can include a first flange  120  provided along the opening  104 . The first flange  120  can extend in a radial direction along the outer circumferential surface of the first housing  100  in a similar way to the cylindrical shape of the first housing  100 . The first flange  120  can be evenly disposed along the circumference of the first housing  100  in a direction in which the radius of the first housing  100  increases. 
     The second housing  200  can be coupled to the first housing  100  to form one washing chamber. In some implementations, the washing chamber can provide a space in which laundry treatment is performed and a space in which a motor assembly for providing driving force required to rotate the drum is installed. 
     The second housing  200  can include a second flange  220  coupled to the first flange  120 . The second housing  200  can have a size similar to the cross-section of the first housing  100 , and can be disposed at a rear side of the first housing  100 . 
     The second flange  220  can be coupled to the first flange  120  by a plurality of bolts, so that the internal pressure of the washing chamber can be maintained at pressure greater than the external atmospheric pressure in a state in which the second housing  200  is fixed to the first housing  100 . 
     The first fixing part  130  provided in the first housing  100  can be provided with a filter  140  for filtering foreign substances. The filter  140  can include a plurality of small holes blocking foreign substances from entering the first housing, but liquid carbon dioxide can pass through the small holes, so that the liquid carbon dioxide can be discharged to the outside of the first housing  100  through the discharge pipe  132 . 
     In some implementations, a barrier  400  for sealing the opening  104  while coupling to the first housing  100  can be provided. The second housing  200  can seal one surface of the barrier  400 . 
     The drum  350  can be disposed in a space provided on left of the barrier  400  as depicted in  FIG. 4 , so that laundry and liquid carbon dioxide can be mixed together and laundry treatment such as washing or rising can be performed in the drum  350 . In some implementations, the motor assembly  500  can be disposed in a space provided on right of the barrier  400  as depicted in  FIG. 4 , thereby providing driving force capable of rotating the drum  350 . In some implementations, a portion of the motor assembly  500  can be coupled to the drum  350  after passing through the barrier  400 . 
     The barrier  400  can have a size larger than a size of the opening  104 , and can be disposed to be in contact with the opening  104 , thereby sealing the opening  104 . The barrier  400  and the opening  104  can be formed to have a substantially circular shape similar to the shape of the first housing  100 , and the diameter L of the opening  104  can be smaller than the diameter of the barrier  400 . The diameter L of the opening  104  can be greater than the diameter of the drum  350 . Therefore, the cross-section of the drum  350  can be formed to have the smallest size among the drum  350 , the opening  104 , and the barrier  400 , the cross-section of the opening  104  can be formed to have a medium size among the drum  350 , the opening  104 , and the barrier  400 , and the barrier  400  can be formed to have the largest size among the drum  350 , the opening  104 , and the barrier  400 . 
     The barrier  400  can be arranged to have a plurality of steps, thereby guaranteeing sufficient strength. 
     The first flange  120  can be provided with a seating groove  122  coupled to the barrier  400  so that the seating groove  122  can be formed along the opening  104 . For example, the seating groove  122  can be provided at a portion extending in a radial direction from the opening  104 . The seating groove  122  can be recessed by a thickness of the barrier  400  so that the first flange  120  and the second flange  220  are provided to contact each other. The seating groove  122  can be formed to have the same shape as the outer circumferential surface of the barrier  400 . Thus, when the barrier  400  is seated in the seating groove  122 , the surface of the first flange  120  can become flat. 
     The first flange  120  can include the first seating surface  124  extending farther in a radial direction than the circumference of the seating groove  122 , and the second flange  220  can include a second seating surface  224  coupled to the first seating surface  124  in surface contact with the first seating surface  124 . The first seating surface  124  and the second seating surface  224  can be disposed to be in contact with each other, so that carbon dioxide injected into the inner space of the first housing  100  can be blocked from being disposed outside the first housing  100 . The first seating surface  124  and the second seating surface  224  can be in surface contact with each other while being disposed at the outer circumferential surfaces of the first housing  100  and the second housing  200 , and can provide a coupling surface where two housings can be bolted to each other. 
     A heat exchanger  600  in which refrigerant flows can be disposed at the barrier  400 . The heat exchanger  600  can be disposed in a space provided by the first housing  100  and the barrier  400 . The heat exchanger  600  can be configured to change a temperature of the space provided by the first housing  100 . The temperature of the space provided by the first housing  100  can be reduced so that humidity of the inner space of the first housing  100  can be lowered. 
     A heat insulation member (i.e., an insulation member)  650  can be disposed between the heat exchanger  600  and the barrier  400 . The heat insulation member  650  can block the temperature of the heat exchanger  600  from being directly transferred to the barrier  400 . The heat insulation member  650  can allow the barrier  400  to be less affected by temperature change of the heat exchanger  600 . The heat insulation member  650  can be formed similar to the shape of the heat exchanger, thereby covering the entire surface of the heat exchanger  600 . 
       FIG. 5  is a diagram illustrating the second housing  200  separated from the structure shown in  FIG. 2 .  FIG. 6  is a diagram illustrating components of the drum shown in  FIG. 5  detached rearward. 
     Referring to  FIGS. 5 and 6 , when the second housing  200  is separated from the first housing  100 , the barrier  400  can be exposed outside. Since the barrier  400  is coupled to the seating groove of the first housing  100 , the inner space of the first housing is not exposed outside even when the second housing  200  is separated from the first housing  100 . The barrier  400  can be coupled to the second housing  200  by a plurality of bolts or the like. 
     A motor assembly  500  can be coupled to the center portion of the barrier  400 , and a second through-hole  420  can be defined at an upper side of the motor assembly  500 . A refrigerant pipe  610  for circulating a refrigerant in the heat exchanger  600  can pass through the second through-hole  420 . 
     When the barrier  400  is separated from the first housing  100 , the opening  104  can be exposed outside. In some implementations, the drum  350  can be withdrawn to the outside through the opening  104 . As the opening  104  is larger in size than the drum  350 , maintenance of the drum  350  can be performed through the opening  104 . 
     A gasket  320  can be disposed between the barrier  400  and the seating groove  122 . In some implementations, when the barrier  400  is coupled to the first housing  100 , carbon dioxide can be blocked from leaking between the barrier  400  and the first housing  100 . When the barrier  400  is seated in the seating groove  122 , the barrier  400  can be coupled to the first housing  100  by the plurality of bolts while compressing the gasket  320 . A plurality of coupling holes through which the barrier  400  is coupled to the first housing  100  can be evenly disposed along the outer circumferential surface of the barrier  400 . 
       FIG. 7  is a diagram illustrating a drum and some constituent elements of the drum.  FIG. 8  is a diagram illustrating a cross-sectional view of the structure shown in  FIG. 7 .  FIG. 9  is a diagram illustrating an exploded perspective view of the structure shown in  FIG. 7 .  FIG. 10  is a diagram illustrating an exploded perspective view of the main constituent elements of the structure shown in  FIG. 7 . 
     As depicted in  FIGS. 7 and 8 , the first housing  100  can be removed so that the drum  350  is exposed outside. The drum  350  can have a cylindrical shape such that laundry received by the drum  350  through the inlet  102  is movable into the drum  350 . 
     The drum  350 , the heat exchanger  600 , and the heat insulation member  650  can be disposed in a left side of the barrier  400  as depicted in  FIGS. 7 and 8 . The motor assembly  500  can be disposed in a right side of the barrier  400  as depicted in  FIGS. 7 and 8 . 
       FIG. 9  is a diagram illustrating an exploded perspective view of the drum  350  and the barrier  400  separated from each other. Referring to  FIG. 9 , the rotary shaft  510  of the motor assembly  500  can be coupled to the drum  350  at the rear of the drum  350 . Therefore, when the rotary shaft  510  rotates, the drum  350  can also be rotated thereby. In addition, when the rotational direction of the rotary shaft  510  is changed, the rotational direction of the drum  350  can also be changed. 
     Since the motor assembly  500  is coupled to the barrier  400 , the driving force required to rotate the drum  350  is not transmitted to the drum  350  through a separate belt or the like. As a result, rotational force of the motor can be directly transmitted to the drum  350 , so that loss of force or occurrence of noise can be reduced. 
       FIG. 10  is a diagram illustrating an exploded perspective view of constituent elements installed at the barrier shown in  FIG. 9 . 
     Referring to  FIG. 10 , the heat exchanger  600  can be formed in a doughnut shape similar to the shape of the opening  104 . A circular through-hole  602  can be defined at the center of the heat exchanger  600  so that the rotary shaft  510  of the motor can pass through the through-hole  602 . 
     The heat insulation member  650  can have a shape corresponding to the heat exchanger  600 , and can block the temperature change generated in the heat exchanger  600  from being transferred to the barrier  400 . The heat insulation member  650  can be made of a material having low thermal conductivity, and can be disposed between the heat exchanger  600  and the barrier  400 . A circular through-hole  652  can be defined at the center of the heat insulation member  650  so that the rotary shaft  510  of the motor can pass through the through-hole  652 . 
     The circular shape of the through-hole  602  of the heat exchanger  600  can be similar in size to the circular shape of the through-hole  652  of the heat insulation member  650 . In some implementations, the through-hole  652  can be formed with a through-groove  654  through which the refrigerant pipe  610  for supplying refrigerant to the heat exchanger  600  can pass. 
     The heat exchanger  600  can include a bracket  620  coupled to the barrier  400 . The bracket  620  can be fixed to the barrier  400  by both a bolt  624  penetrating the barrier  400  and a cap nut  626  coupled to the bolt  624 . 
     The bracket  620  can be formed in a three-dimensionally stepped shape such that the bracket  620  is disposed at a surface where the heat exchanger  600  has a thin thickness. The bolt  624  can be disposed at the stepped groove portion, and can be coupled to the cap nut  626 . 
     The plurality of brackets  620  can be provided, so that the heat exchanger  600  and the heat insulation member  650  can be coupled to the barrier  400  at a plurality of points. Although  FIG. 10  illustrates three brackets  620  for convenience of description, a greater number of brackets or a less number of brackets compared to the three brackets can also be used as necessary. The plurality of brackets can be evenly disposed at various positions of the heat exchanger  600 , so that the heat exchanger  600  can be more stably fixed. 
     The motor assembly  500  can be coupled to the barrier  400 . The motor assembly  500  can include a stator  570 , a rotor  550 , and a bearing housing  520 . The bearing housing  520  can include the rotary shaft  510 . One end of the rotary shaft  510  can be coupled to the rotor  550 , and the other end of the rotary shaft  510  can be coupled to the drum  350 . Therefore, as the rotor  550  rotates around the stator  570 , the rotary shaft  510  is also rotated. 
     The stator  570  is fixed to a bearing housing  520 , thereby providing the environment in which the rotor  550  can rotate. 
     When the bearing housing  520  is coupled to the barrier  400 , an O-ring  450  can be disposed between the bearing housing  520  and the barrier  400 , so that liquid carbon dioxide injected into the first housing  100  is blocked from flowing into a gap between the barrier  400  and the bearing housing  520 . In some implementations, an O-ring cover  460  can be disposed to improve the coupling force of the O-ring  450 . The O-ring cover  460  can be formed similar in shape to the O-ring  450 . The O-ring cover  460  can reduce the size of one surface where the O-ring  450  is exposed to one side of the barrier  400 , thereby more strongly sealing the gap. 
       FIGS. 11A and 11B  are diagrams illustrating the barrier  400 .  FIG. 11A  is a diagram illustrating a front view of the barrier  400 , and  FIG. 11B  is a diagram illustrating a side cross-sectional view of the center portion of the barrier  400 . 
     As depicted in the side cross-sectional view of the barrier  400 , since the barrier  400  includes a plurality of step differences, the barrier  400  can provide sufficient strength by which the heat exchanger  600  can be fixed to one side of the barrier  400  and the motor assembly  500  can be fixed to the other side of the barrier  400 . 
     A first through-hole  410  through which the rotary shaft  510  of the motor passes can be defined at the center of the barrier  400 . The first through-hole  410  can have a circular shape, so that no contact occurs at the rotary shaft  510  passing through the first through-hole  410 . 
     The barrier  400  can include a second through-hole  420  through which gaseous carbon dioxide moves. The second through-hole  420  can be disposed at a higher position than the first through-hole  410 . The second through-hole  420  can be disposed to allow the refrigerant pipe  610  to pass therethrough. The second through-hole  420  can have a size larger than a size of the first through-hole  410 . 
     In some implementations, the second through-hole  420  can be implemented as two separate holes. The second through-holes  420  can be disposed symmetrical to each other with respect to the center point of the barrier  400 . 
     The barrier  400  can be a single component capable of being separated from the first housing  100  or the second housing  200 , and can provide a coupling structure between the heat exchanger  600  and the motor assembly  500 . 
     In addition, when the barrier  400  is separated from the first housing  100 , the environment in which the user or operator can separate the drum  350  from the first housing  100  can be provided. 
     The barrier  400  can be formed to have a plurality of step differences in a forward or backward direction, and can sufficiently increase the strength. In addition or alternatively, the barrier  400  can be formed to have a curved surface within some sections, so that the barrier  400  can be formed to withstand force generated in various directions. The outermost portion of the barrier  400  can be coupled to the seating groove  122  of the first housing  100 . 
     Referring to the direction from the outermost part of the barrier  400  to the center part of the barrier  400  as depicted in  FIG. 11B , the barrier  400  can be formed to have step differences in various directions (e.g., the barrier first protrudes to the left side, protrudes to the right side, and again protrudes to the left side) by various lengths, thereby increasing strength. 
       FIG. 12  is a diagram illustrating a function of the second through-hole. 
     Referring to  FIG. 12 , carbon dioxide may be injected into the drum  350  to perform washing of laundry. In some implementations, the carbon dioxide can be a mixture of liquid carbon dioxide and gaseous carbon dioxide. Since the liquid carbon dioxide is heavier than the gaseous carbon dioxide, the liquid carbon dioxide may be located below the gaseous carbon dioxide, and the gaseous carbon dioxide may be present in the empty space located over the liquid carbon dioxide. 
     By rotation of the drum  350 , laundry disposed in the drum  350  can be mixed with liquid carbon dioxide. 
     The barrier  400  can block liquid carbon dioxide injected into the space provided by both the first housing  100  and the barrier  400  from flowing into the other space defined by both the second housing  200  and the barrier  400 . For example, since the barrier  400  seals the opening  104 , liquid carbon dioxide cannot move to the opposite side of the barrier  400 . 
     During laundry treatment such as washing, the space provided by the first housing  100  and the barrier  400  is separated from the space provided by the second housing  200  and the barrier  400 . In some implementations, the space provided by the first housing  100  and the barrier  400  may be filled with liquid carbon dioxide and gaseous carbon dioxide at a higher pressure than atmospheric pressure. Therefore, in order to stably maintain the pressure of the washing chamber, only gaseous carbon dioxide rather than liquid carbon dioxide may move into the space formed by the second housing  200  and the barrier  400 , resulting in implementation of pressure equilibrium. 
     In some implementations, gaseous carbon dioxide may pass through the barrier  400  through the second through-hole  420  provided at the barrier  400 . However, since the second through-hole  420  is located higher in height than the liquid carbon dioxide, the gaseous carbon dioxide cannot move through the second through-hole  420 . 
     Typically, the amount of liquid carbon dioxide used in washing or rising of laundry may not exceed half of the total capacity of the drum  350 . For example, the amount of liquid carbon dioxide does not exceed the height of the rotary shaft  510  coupled to the drum  350 . 
     Therefore, if the second through-hole  420  is located higher than the rotary shaft  510 , gaseous carbon dioxide may not move through the second through-hole  420 . However, since the space provided by the first housing  100  and the barrier  400  is filled with gaseous carbon dioxide, the gaseous carbon dioxide can freely flow into the space provided by the second housing  200  and the barrier  400 , resulting in implementation of pressure equilibrium. 
     For example, during laundry treatment such as washing or rinsing, gaseous carbon dioxide and liquid carbon dioxide may be mixed with each other in the space partitioned by the first housing  100  and the barrier  400 . On the other hand, whereas liquid carbon dioxide is not present in the space partitioned by the second housing  200  and the barrier  400 , only gaseous carbon dioxide may be present in the space partitioned by the second housing  200  and the barrier  400 . Since two spaces are in a pressure equilibrium state therebetween, liquid carbon dioxide need not be present in the space provided by the second housing  200  and the barrier  400 , and the amount of used liquid carbon dioxide may be reduced in the space provided by the second housing  200  and the barrier  400 . Therefore, the total amount of carbon dioxide to be used in washing or rinsing of laundry can be reduced, so that the amount of carbon dioxide to be used can be greatly reduced compared to the conventional washing machine. As a result, the amount of carbon dioxide to be reprocessed after use can also be reduced. As described above, the amount of carbon dioxide to be used can be reduced, so that a storage capacity of the tank configured to store carbon dioxide and the overall size of the washing machine configured to use carbon dioxide can also be reduced. In addition, since the amount of carbon dioxide to be reprocessed after use is reduced, the time required to perform washing or rinsing can also be reduced. 
       FIG. 13  is a diagram illustrating a structure in which the heat exchanger is coupled to the barrier. 
       FIG. 13  is a diagram illustrating a cross-sectional view of a portion in which the bracket  620  is in contact with the heat exchanger  600 . 
     The bracket  620  can have a stepped shape, and the stepped portion is in contact with the heat exchanger  600 , so that the heat exchanger  600  can be fixed. The protruding portion can be disposed to contact the heat insulation member  650 . 
     The bolt  624  can be fixed to the protruding portion, and the bolt  624  can pass through the heat insulation member  650  and the barrier  400 . A cap nut  626  can be provided at the opposite side of the bolt  624 , so that the bolt  624  can be fixed by the cap nut  626 . The cap nut  626  can be in contact with the plurality of points of the barrier  400 , so that the fixing force at the barrier  400  can be guaranteed. 
     The cap nut  626  can have a rectangular parallelepiped shape, and a coupling groove can be provided at a portion contacting the barrier  400 . A sealing  627  can be disposed in the coupling groove to seal a gap when the cap nut  626  is coupled to the barrier  400 . For example, when the cap nut  626  is coupled to the bolt  624 , the sealing  627  is pressed so that the bolt  624  can be fixed while being strongly pressurized by the cap nut  626 . In some implementations, the barrier  400  can also be pressed together, a hole through which the bolt  624  passes can be sealed. 
     The bracket  620  can be implemented as a plurality of brackets, so that the heat exchanger  600  can be fixed at various positions. Although the shape of the brackets  620  may be changed when viewed from each direction, the same method for coupling the bracket  620  by the bolt and the cap nut can be applied to the brackets  620 . 
       FIG. 14  is a diagram illustrating the O-ring and the O-ring cover mounted to the barrier.  FIG. 15  is a diagram illustrating an exemplary state in which the structure of  FIG. 14  is coupled to other constituent elements. 
     The O-ring  450  can be disposed at a portion where the bearing housing  520  is coupled to the barrier  400 . The O-ring  450  can block liquid carbon dioxide from flowing into the space opposite to the barrier  400 . 
     For example, since the rotary shaft  510  is disposed to pass through the first through-hole  410  of the barrier  400 , the gap may exist in the first through-hole  410 . Since the rotary shaft  510  rotates, the rotary shaft  510  may be spaced apart from the through-hole  410  by a predetermined gap, and this predetermined gap cannot be sealed. Therefore, the bearing housing  520  is coupled to the barrier  400 , and the gap between the bearing housing  520  and the barrier  400  is sealed by the O-ring  450 , so that carbon dioxide can be blocked from moving through the gap sealed by the O-ring  450 . 
     The O-ring  450  can be coupled to the O-ring cover  460  blocking separation of the O-ring  450 . The O-ring cover  460  can surround one surface of the O-ring  450 , so that the O-ring cover  460  can block the O-ring  450  from being exposed to a space provided by the first housing  100 . Therefore, the O-ring cover  460  can block the O-ring  450  from being separated by back pressure. 
       FIG. 16  is a diagram illustrating the rotary shaft.  FIG. 17  is a diagram illustrating an exemplary state in which the rotary shaft of  FIG. 16  is coupled to other constituent elements. 
     A rotary shaft  510  having one side coupled to the drum  350  and the other side coupled to the rotor  550  can be provided at the center of the bearing housing  520 . The rotary shaft  510  can be disposed to pass through the center of the bearing housing  520 . 
     The rotary shaft  510  can be supported by the bearing housing  520  through the first bearing  521  and the second bearing  522 . The rotary shaft  510  can be supported to be rotatable by the two bearings. In some implementations, the two bearings may be implemented as various shapes of bearings as long as they are rotatably supported components. 
     In some implementations, the first bearing  521  and the second bearing  522  may have different sizes, so that the first bearing  521  and the second bearing  522  can stably support the rotary shaft  510 . In some implementations, the shape of the rotary shaft  510  corresponding to a portion supported by the first bearing  521  may be formed differently from the shape of the rotary shaft  510  corresponding to a portion supported by the second bearing  522  as needed. 
     A sealing portion  540  can be provided at one side of the first bearing  521 . The sealing portion  540  can be disposed along the circumferential surface of the rotary shaft  510 . The sealing portion  540  can be disposed to be exposed to the space provided by the first housing  100  and the barrier  400 , so that carbon dioxide can be blocked from moving through a gap between the rotary shaft  510  and the bearing housing  520 . Specifically, the sealing portion  540  can block liquid carbon dioxide from moving into the space opposite to the barrier  400 . 
     The sealing portion  540  can include a shaft-seal housing  542  that is disposed between the rotary shaft  510  and a hole through which the rotary shaft  510  passes, so that the shaft-seal housing  542  can seal a gap between the rotary shaft  510  and the hole. A shaft seal  544  can be disposed at a portion where the shaft-seal housing  542  and the rotary shaft  510  meet each other, thereby improving sealing force. The shaft seal  544  can be disposed to surround the circumferential surface of the rotary shaft  510 . 
     The bearing housing  520  can define a communication hole  526  through which inflow or outflow of external air is provided. The communication hole  526  of the bearing housing  520  can be exposed to the space partitioned by the second housing  200  and the barrier  400 . 
     The rotary shaft  510  can be provided with a first flow passage  512  and a second flow passage  514  spaced apart from each other such that inflow or outflow of air is provided through the first flow passage  512  and the second flow passage  514 . In some implementations, the first flow passage  512  and the second flow passage  514  can be provided in a radial direction from the center of the rotary shaft  510 . 
     Air in the space partitioned by the second housing  200  and the barrier  400  may flow into the rotary shaft  510  through the first flow passage  512  and the second flow passage  514 . 
     For example, a connection flow passage  516  for connecting the first flow passage  512  to the second flow passage  514  can be provided. The connection flow passage  516  can be disposed at the center of rotation of the rotary shaft  510 , and can be vertically connected to each of the first flow passage  512  and the second flow passage  514 . 
     If the connection flow passage  516  does not exist, each of the first flow passage  512  and the second flow passage  514  is perforated on the outer surface of the rotary shaft  510 , but the opposite side of each of the first flow passage  512  and the second flow passage  514  is closed. Therefore, it is difficult for air to substantially flow into the first flow passage  512  or the second flow passage  514 . To this end, the connection flow passage  516  for interconnecting two flow passages may be formed. Thus, when the internal pressure of the rotary shaft  510  is changed, air can more easily flow into the first flow passage  512 , the second flow passage  514 , and the connection flow passage  516 , so that pressure of the rotary shaft  510  can be maintained in the same manner as the external pressure change. 
     The rotary shaft  510  can rotate in a state in which one side of the rotary shaft  510  is fixed to the drum  350  and the other side of the rotary shaft  510  is fixed to the rotor  550 . Therefore, noise or vibration may occur in the rotary shaft  510 . If the rotary shaft  510  rotates at a place where there occurs a pressure deviation, noise or vibration may unavoidably increase. Therefore, the rotary shaft  510  can include a communication hole  526  through which air can flow into the bearing housing  520 . The bearing housing  520  is a relatively large component and has a space for allowing air to enter and circulate therein, so that air can be introduced without distinction between the air inlet and the air outlet. In some implementations, the rotary shaft  510  can be made of a material having high rigidity, but the strength of the rotary shaft  510  is reduced so that it is difficult to secure the space in which air can easily flow, thereby increasing the size of the air passage. Therefore, the plurality of flow passages can be coupled to each other, resulting in formation of a path through which the introduced air can be discharged through the opposite flow passage. 
     In some implementations, the washing chamber  10  can be coupled to the first housing  100  and the second housing  200 , resulting in formation of a sealed space. In some implementations, the sealed space can be divided into two spaces by the barrier  400 . Based on the barrier  400 , one space may be a space for laundry treatment, and the other space may be a space for installation of the motor or the like. 
       FIG. 18  is a diagram illustrating a concept of operations of the washing machine. 
     Referring to  FIG. 18 , the compressor unit  80  can include two compressors. The compressor unit  80  can include a first compressor  82  and a second compressor  84 , each of which compresses carbon dioxide (CO 2 ) discharged after completion of washing in the drum so that the compressed carbon dioxide (CO 2 ) flows into the storage tank  30 . The carbon dioxide (CO 2 ) generated after completion of washing in the washing chamber  10  can be guided to the storage tank  30  by the first compressor  82  and the second compressor  84 . In an initial stage, a parallel operation in which carbon dioxide (CO 2 ) is compressed by each of the two compressors is performed. In the latter stage, a serial operation in which two compressors compress carbon dioxide (CO 2 ) through multistage compression so that carbon dioxide (CO 2 ) flows into the storage tank  30  is performed. 
     When a current pressure of the washing tub reaches a preset pressure during a recovery mode operation of the washing tub of the washing machine in which a reciprocating compressor (based on the piston˜cylinder volume compression scheme) compressor is used in two stages, after a parallel operation mode transitions to a serial operation mode by switching of the system-side valve, the RPM (revolutions per minute) of each compressor is adjusted after lapse of a predetermined time (Δt), so that a serial operation mode of a high-pressure ratio region can be implemented. 
     However, when the system is operated as described above, there are three kinds of vulnerabilities. In the first vulnerability, a (low-speed+serial) operation is performed for a preset time (Δt) so that there occurs a section where the recovery flow rate decreases, resulting in an increase in the total washing time. In the second vulnerability, a mechanical behavior (=RPM) of the compressor is changed after high load caused by chemical change of carbon dioxide (CO 2 ) fluid has occurred, so that sudden RPM change generated in the high-pressure ratio operation may reduce durability of a frictional surface of the compressor unit. In this case, when technology (e.g., hardening of frictional material, heat treatment of a bearing, etc.) for preventing degradation of the durability of the compressor is used, the cost of materials may unavoidably increase. In the third vulnerability, since the design (fixed) compression ratio of the compressor should be considered, the mode conversion pressure setting range is limited, load may be inevitably concentrated on a specific compression stage (1-stage or 2-stage) without accurate load distribution. Accordingly, the system for use in the washing machine can be implemented in other ways in consideration of the above-described technical disadvantages. 
       FIG. 19  is a flowchart illustrating an operation process of the washing machine. 
     In the implementation of  FIG. 19 , when using a plurality of compressors (or multistage compressors) with the same capacity is used, it is assumed that total load is divided equally into the compressors (compression stages). In this case, load of a single compressor is represented by shaft torque. In addition, if the same amount of fluid passes through the respective compressors during the serial operation mode, torque may be proportional to the compressor pressure ratio (=discharge pressure/inlet pressure). For example, in order to maximize the operation efficiency of the compressor in the system designed to use a volumetric compressor, it is very important for the compression ratio of the first compressor and the compression ratio of the second compressor to be implemented in the same operation condition. However, it is practically impossible for the compressor having a fixed design compression ratio to have the same compression ratio in real time under all available situations. Therefore, from the viewpoint of compressor protection, the use of the first criterion in which the pressure ratio is equally selected as the worst condition, and the use of the second criterion in which the compressor pressure ratio designed to increase to a higher-temperature level is set to a lower pressure ratio may be considered advantageous in terms of durability guarantee. In other words, lowering the pressure ratio of the compressor located at a high-pressure stage may be considered advantageous in terms of durability lifespan. 
     In most of washing machines each having a limited intercooler size, a discharge temperature of the high-pressure stage compressor (i.e., second compressor  84 ) in a two-stage compression mode is higher than the discharge temperature of the low-pressure stage compressor (i.e., first compressor  82 ) in the two-stage compression mode. For example, the pressure ratio of the second compressor  84  is set to 4.9 and the second compressor  84  is driven at the pressure ratio of 4.9, and the pressure ratio of the first compressor  82  is set to 5.2 and the first compressor  82  is driven at the pressure ratio of 5.2. As a result, a relatively smaller load is applied to the second compressor  84  located at the high-pressure stage, so that durability of the compressor can be guaranteed. 
     Referring to  FIG. 19 , when washing is finished, the first compressor  82  and the second compressor  84  are arranged in parallel to compress carbon dioxide, so that the compressed carbon dioxide can be guided to the storage tank  30  (S 10 ). In some implementations, two compressors have the same capacity, and the compression efficiency is high, so that a time taken to perform such compression can be shortened. 
     
       
         
           
               
               
               
               
             
               
                 TABLE 1 
               
               
                   
               
               
                 Washing chamber 
                   
                 RPM of First 
                 RPM of Second 
               
               
                 pressure 
                 Operation 
                 Compressor 
                 Compressor 
               
               
                 (barA) 
                 mode 
                 [rpm] 
                 [rpm] 
               
               
                   
               
             
            
               
                 40 → 14(=P1(First 
                 Parallel 
                 6500 
                 6500 
               
               
                 setting pressure)) 
               
               
                 14 → 
                 Parallel 
                 6500 
                 2500 
               
               
                 13(=P2(Second 
               
               
                 setting pressure) 
               
               
                 13 → 2.5 
                 Serial 
                 6500 
                 2500 
               
               
                   
               
            
           
         
       
     
     Since the washing chamber pressure is the same as the internal pressure of the drum, the terms “washing chamber pressure” and “drum internal pressure” will be used interchangeably. The drum is disposed in the washing chamber because portions where the two components are disposed have the same pressure. 
     When the washing chamber pressure, i.e., the drum internal pressure, is lowered by a first setting pressure P 1 , the rpm of the second compressor  84  can be changed (S 20 , S 30 ). Two compressors can be operated in parallel until the drum internal pressure drops to the first setting pressure (e.g., 14), but the two compressors may be kept at the same rpm. 
     Since the carbon dioxide of the washing chamber  10  is continuously compressed during operation of the two compressors, the internal pressure of the washing chamber can be continuously reduced. 
     When the drum internal pressure is reduced by a second setting pressure (P 2 , for example 13), the first compressor  82  and the second compressor  84  can be arranged in series to compress carbon dioxide (S 40 , S 50 ). In some implementations, whereas the rpm of the first compressor  82  is identical to the initial rpm, the rpm of the first compressor  82  can be kept low. 
     For example, the two compressors can be operated in parallel at the same rpm until the drum internal pressure drops to the first setting pressure. 
     When the drum internal pressure reaches the first setting pressure, the rpm of the second compressor  84  can be lowered compared to the conventional rpm in a situation where the parallel operation is maintained. 
     When the drum internal pressure reaches a second setting pressure, the parallel mode can switch to the serial operation. In some implementations, the rpm of the first compressor  82  and the rpm of the second compressor  84  can be maintained at previous rpms of the first compressor  82  and the second compressor  84 , so that each of the first compressor  82  and the second compressor  84  can be prevented from being overloaded when the parallel operation switches to the serial operation. 
     The first setting pressure P 1  may be greater than the second setting pressure P 2 . This is because, as the compressor is driven, carbon dioxide of the washing chamber moves from one place to another place, so that the internal pressure of the washing chamber can also be reduced. 
     In some implementations, during the process of moving the carbon dioxide from the washing chamber to the storage tank after completion of laundry washing, the rpm of the first compressor  82  from among two compressors is maintained at the same rpm, so that operation stability can be guaranteed in the process of driving the first compressor  82 . 
     Until the drum internal pressure is reduced by the second setting pressure P 2 , the first compressor and the second compressor can be operated in parallel to prevent the amount of compression of carbon dioxide from decreasing. For reference, when two compressors are operated in series, whereas carbon dioxide can be compressed at a high pressure, but the amount of compressed carbon dioxide can decrease. 
     When the drum internal pressure is reduced by the first setting pressure P 1 , the rpm of the second compressor can be reduced so that the risk of high load generated by serial arrangement of two compressors can be reduced. 
       FIGS. 20 and 21  are diagrams illustrating exemplary features in which two compressors are operated in parallel.  FIGS. 22 and 23  are diagrams illustrating exemplary features in which two compressors are operated in series. 
       FIGS. 20 and 22  are conceptual diagrams illustrating a path through which carbon dioxide flows, and  FIGS. 21 and 23  are diagrams illustrating actual implementation states. 
     The two compressors  82  and  84  are disposed separately from each other, and manual valves (also called hand valves)  802 ,  810 ,  818 ,  820  are disposed. The manual valves may allow the user to open or close a flow passage. 
     Valves  804 ,  806 ,  808 ,  814 , and  816  capable of opening or closing the flow passage according to a system state can be installed. Oil separators  830  and  840  and the oil reservoir can be installed on the path through which carbon dioxide flows. The oil separators and the oil reservoir can separate oil to be discharged with carbon dioxide from the compressor, and can store the separated oil. 
     In some implementations, when the valve  818  installed in the flow passage through which oil is drained from the oil reservoir is opened, or when the valves  814  and  816  installed in the flow passage through which oil is drained within the oil separators are opened, the stored oil can return to the compressor. In some implementations, the stored oil can also pass through a metering valve  812  as needed. 
     The flow passage through which carbon dioxide compressed by the first compressor  82  and the second compressor  84  is discharged can include a flow passage  815  in which a safety valve is installed, so that the carbon dioxide is prevented from being excessively compressed and excessive increase of such pressure can also be prevented. 
     In addition, the intercooler  86  can be disposed to lower a temperature of the compressed carbon dioxide when a multistage compression mode is performed. In addition, when the parallel operation is performed, the temperature of carbon dioxide introduced into the second compressor  84  can be lowered, so that the second compressor  84  can be prevented from heating up to a high temperature. 
     A method for performing the parallel operation will hereinafter be described with reference to  FIGS. 20 and 21 . Carbon dioxide of the washing chamber  10  can be provided after passing through the manual valve  802 . In some implementations, the flow passage through which carbon dioxide is supplied based on the manual valve  802  and the other flow passage formed to pass through the manual valve  802  can be separated from each other. 
     In some implementations, carbon dioxide passing through the manual valve  802  is guided to the suction passage of the first compressor  82 , and is discharged to the outlet passage. Since the valve  802  is in a state where the flow passage is opened, carbon dioxide having penetrated the manual valve  802  passes through the intercooler  86  and is compressed by the second compressor  84 , so that the compressed carbon dioxide can be discharged. 
     Since the valve  808  is in a state where the flow passage is opened, carbon dioxide compressed by the first compressor  82  and carbon dioxide compressed by the second compressor  84  can simultaneously move toward the flow passage opened by the valve  818 . 
     In some implementations, the valve  806  is in a state where the flow passage is closed, so that carbon dioxide cannot move after passing through the valve  806 . 
     Carbon dioxide having penetrated the manual valve  810  can sequentially pass through the first oil separator  830 , the second oil separator  840 , and the oil reservoir  850 , so that oil mixed with the carbon dioxide can be separated (or isolated). 
     During the compression process by the compressors  82  and  84 , oil used in the compressors  82  and  84  may be mixed with carbon dioxide. If the oil is mixed with carbon dioxide, there is a possibility that laundry is contaminated with oil during washing of the laundry, so that there is a need for oil to be separated from carbon dioxide to be reused. 
     The carbon dioxide having passed through both the oil separator and the oil reservoir can flow into the storage tank  30  after passing through the manual valve  820 , so that the resultant carbon dioxide can be stored in the storage tank  30 . In some implementations, the upper side and the lower side of the washing machine can be separated from each other based on the manual valve  820 , so that the upper portion and the lower portion of the washing machine can be separated from each other based on the manual valve  820  for facilitation of user manipulation. 
     The oil stored in the oil reservoir  850  can return to the compressor when the flow passage is opened by the manual valve  818 . 
     In addition, oil separated by the first oil separator  830  can open the flow passage in the valve  814 , and oil separated by the second oil separator  840  can flow into two compressors when the flow passage is opened by the valve  816 . 
     In  FIGS. 20 and 21 , whereas each of the valve  804  and the valve  808  opens the flow passage, the valve  806  can block the flow passage through which carbon dioxide moves, so that two compressors can be operated in parallel. 
     Exemplary features for operating two compressors in series will hereinafter be described with reference to  FIGS. 22 and 23 . 
     Whereas the valve  804  and the valve  808  shown in  FIGS. 20 and 21  block the flow passage, the valve  806  opens the flow passage through which carbon dioxide moves, so that two compressors can be operated in series. 
     Carbon dioxide guided from the washing chamber is compressed by the first compressor  82  after passing through the valve  802 . In some implementations, since the valve  804  blocks the flow passage, all carbon dioxide can be guided to the first compressor  82  without passing through the valve  804 . 
     Since the valve  808  blocks the flow passage and the valve  806  opens the flow passage, the carbon dioxide compressed in the first compressor  82  can flow into the flow passage passing through the valve  806  and can be cooled after passing through the intercooler  86 . Subsequently, after the carbon dioxide is compressed by the second compressor  84 , the carbon dioxide can move after passing through the manual valve  818 . 
     The process for controlling two compressors to switch from the parallel operation to the serial operation can be implemented by opening/closing the flow passage in the valves  804 ,  806 , and  808 . When the operation condition is changed, the serial operation can switch to the parallel operation and the parallel operation can then switch to the serial operation by activation of the flow passage that is opened or closed by the respective valves. When the drum internal pressure is lowered by the second setting pressure P 2 , the flow passage of the carbon dioxide can be adjusted in a manner that the first compressor and the second compressor are arranged in series. 
     A process for returning oil from the oil separator and the oil reservoir will hereinafter be described with reference to  FIGS. 20 to 23 . 
     The present disclosure relates to a method for separating oil having leaked from the compressor and mixed with a washing solvent from the compressor and re-supplying the separated oil to the compressor, when the oil-supply-type compressor is used as a fluid machine capable of recovering and regenerating the carbon dioxide after completion of the washing course in the washing machine in which the carbon dioxide is used as a washing solvent. Also, the present disclosure relates to a method for completely removing oil mixed with the washing solvent so that laundry can be washed only using the washing solvent formed of pure carbon dioxide. 
     When recovery of the carbon dioxide is performed, one or more compressors can be operated in parallel or in series so as to form a high flow rate and a differential pressure. In some implementations, the oil can be smoothly supplied to the respective compressors through oil return valve control. In addition, the oil accumulated in the storage tank is bypassed without being separated from the oil separator, so that the oil can be removed from the washing solvent. 
     The present disclosure provides the oil-supply-type scroll compressor for implementation of a compact and economical carbon dioxide (CO 2 ) washing machine. For example, in order to form a high flow rate and differential pressure, one or more oil-supply-type scroll compressors are operated in series or in parallel. In some implementations, one or more oil separators can be used to increase separation efficiency of oil having leaked from the compressor. 
     In some implementations, the oil-supply-type scroll compressor is used so that volume can be reduced by about 60% as compared to the other case in which the oil-less compressor is used. 
     In some implementations, in order to supply oil to one or more compressors, a plurality of oil separators is installed, and the separated oil is recirculated using the compressor(s). The plurality of oil separators can be arranged in series, and carbon dioxide including the oil can sequentially pass through the plurality of oil separators, resulting in an increase in oil separation efficiency. 
     In some implementations, the oil filtered by the respective oil separators is collected into a reservoir so that the collected oil can then be returned to the compressor. In some implementations, the amount of returned oil can be measured by calculating the flow rate using oil flowmeter installation or pressure sensing. The amount of oil leakage in the compressor can be measured by the OCR meter or the L-CO 2  extraction method. The amount of returned oil can also be determined in a manner that the appropriate amount of oil can be maintained in the oil separator (or the oil reservoir). 
     The oil separated in the oil separator is supplied to the carbon dioxide suction line of each compressor through a valve. In order to uniformly supply oil to the respective compressors in the system to which one or more compressors are applied, an oil return pipe can be connected to an inlet of a main pipe through which carbon dioxide flows or can be disposed among the compressor, the washing tub, and a distillation tank. In some implementations, the oil supply line can also be installed in each compressor as needed. 
     When the plurality of compressors is operated in parallel, only the oil stored in the first oil separator  830  can be returned as needed. Since the first oil separator  830  is an oil separator at which oil having passed through the compressor first arrives, there are a large amount of flowing carbon dioxide, so that the large amount of oil leakage may also occur. 
     When the plurality of compressors is operated in series, only oil stored in the second oil separator  840  can be returned as needed. A serial operation time is shorter than a parallel operation time, so that the use of the oil of the second oil separator  840  is considered sufficient. 
     In addition, after several washing processes are completed, the oil accumulated in the oil reservoir  850  can be returned through the third valve  818 . Unlike the first valve  814  or the second valve  816 , the third valve  818  can be designed in a manner that the flow passage is not opened or closed according to a specific condition, the flow passage is opened or closed by the user so that the stored oil can return to the compressor. 
     The first oil separator  830  can separate the oil from the carbon dioxide compressed by the first compressor and the second compressor. The oil separated by the oil separator  830  may flow into the compressor through the first valve  814  for opening or closing the flow passage through which the oil is guided to the first compressor or the second compressor. 
     The second oil separator  840  can separate oil from the carbon dioxide having passed through the first oil separator  830 . The oil separated by the second oil separator  840  can be guided to the compressor through the second valve  818  for opening/closing the flow passage through which the separated oil is guided to the first compressor or the second compressor. 
     The oil reservoir  850  can separate oil from the carbon dioxide having passed through the second oil separator  840 , and may store the separated oil therein. The oil stored in the oil reservoir  850  may be returned to the compressor through the third valve  818  that opens and closes a flow path through which the oil stored in the oil reservoir  850  is guided to the first compressor or the second compressor. 
     In some implementations, the first valve  814  can open the flow passage while the first compressor and the second compressor are operated in parallel, so that the oil can return to the compressor. In some implementations, the first valve  814  can close the flow passage while the first compressor and the second compressor are operated in series, so that the oil is not returned to the compressor. 
     While the first compressor and the second compressor are operated in parallel, the second valve  816  can close the flow passage to block returning of the oil. In contrast, while the first compressor and the second compressor are operated in series, the second valve  816  can open the flow passage so that the oil can be returned to the compressor. 
     The amount of oil filtered by the first oil separator  830  is greater than that of the second oil separator  840 . This is because the carbon dioxide having passed through the compressor passes through the first oil separator before being guided to the second oil separator. 
     Therefore, since parallel operation is conducted for a longer period of time than serial operation, the oil filtered by the first oil separator  830  is guided to the compressor, so that the sufficient amount of oil can be supplied to the compressor. 
     In some implementations, the oil separators to be used for oil returning are used in different ways according to the serial operation and the parallel operation, so that the oil can be relatively evenly returned. 
     The third valve  818  can be constructed in a manner that the washing cycle is continuously performed two or more times and the flow passage is opened after completion of such washing cycle so that the oil can be returned to the compressor. 
     When each of the first valve, the second valve, and the third valve opens the flow passage, the other valves may not open the flow passage so that the oil can be individually supplied to each of the compressors. For example, when oil is returned from the first valve, the second valve and the third valve can block returning of the oil. As the other valves operate similarly, the oil can be evenly returned to the compressors. 
       FIG. 24  is a diagram illustrating a path through which oil trapped in the storage tank or the washing chamber flows. 
     The storage tank can store carbon dioxide. As the storage time increases, oil having a relatively large specific gravity may sink. Therefore, the oil accumulated at the bottom may be guided to a gap between the first oil separator  830  and the second oil separator  840 , so that the oil can be filtered through the second oil separator  840 . 
     In some implementations, the valve  864  is provided, so that the flow passage can be opened by the valve  864  only when there is a need to filter the oil stored in the storage tank  30 . 
     In some implementations, the valve  864  and the valve  862  are simultaneously used to open the flow passage, so that the oil stored in the washing chamber  10  can be filtered by the second oil separator  840 . 
     The oil collected in the storage tank  30  sinks under the storage tank  30  due to a specific gravity (density) difference and is then bypassed to a third space rather than the washing chamber during a short period of time. Thus, the oil mixed with the carbon dioxide washing solvent supplied to the washing chamber can be recovered. 
     In some implementations, the storage tank  30  is disposed to be inclined toward one side, so that the oil stored in the storage tank  30  may be collected at the inclined lower portion. The oil moved in a relatively downward direction is separated from the carbon dioxide, so that laundry can be blocked from being contaminated by the oil during washing. 
       FIG. 25  is a diagram illustrating a front view of the exemplary washing machine.  FIGS. 26 and 27  are diagrams illustrating rear views of the exemplary washing machine shown in  FIG. 25 . 
     The present disclosure provides technology for enabling the electronic module to be rotatably mounted to the washing machine so that a separate operation can be performed as needed. The compressor oil separator, the intercooler, the pipes, etc. are modularized, so that the corresponding component can be maintained and repaired alone, and exhausting, filling, and vacuuming of the carbon dioxide can be performed. In addition, in a situation where each of the storage tank storing the large amount of carbon dioxide, the distillation chamber, the washing chamber, etc. is kept in a fully filled state, each of the storage tank, the distillation chamber, the washing chamber, etc. can be maintained and repaired. 
     The present disclosure provides a washing machine in which carbon dioxide is used as a washing solvent. In this washing machine, the electronic panel may rotate by 180° with respect to one axis of a back surface of the washing machine, so that self-inspection of various sensors mounted in the washing machine, program update, signal system inspection, etc. can be performed. 
     In addition, the compressor, the oil separator, pipes, etc. of the washing machine are modularized in a manner that each component of the washing machine can be independently separated from the system, so that exhausting, vacuuming, and charging of carbon dioxide can be performed independently. 
     In the present embodiment, the overall appearance of the washing machine will be described. The washing machine can include a frame forming an appearance thereof, a washing chamber  10  installed in the frame, a storage tank  30  for storing carbon dioxide to be supplied to the drum, a distillation chamber  50  for separating contaminants dissolved in liquid carbon dioxide, an electronic unit  1100  in which the electric devices are installed, and a configuration unit  1200 . 
     The configuration unit  1200  may refer to a configuration shown in  FIGS. 22 to 24 , and a redundant description thereof will herein be omitted for convenience of description. 
     In contrast, the configuration unit  1200  can include one or more pipes through which carbon dioxide moves; first and second compressors  82  and  84 , each of which compresses the carbon dioxide discharged from the drum after completion of laundry washing and allowing the compressed carbon dioxide to flow into the storage tank; and oil separators  830  and  840  for separating the oil from carbon dioxide compressed in each of the first and second compressors. 
     The electronic unit  1100  can include a printed circuit board (PCB) substrate, can generate a control signal for driving each valve, and can perform various commands according to a user input. The electronic unit  1100  can receive external power, so that the electronic unit  1100  can be powered on. 
     All components of the washing machine can be installed in the frame. Accordingly, if only a space in which the frame can be installed is guaranteed, the washing machine can be installed in the space. 
     The frame can include a front panel  1002  provided on the front side, a bottom panel  1006  provided on the floor, and columns  1014 ,  1013 , and  1010  vertically coupled to the bottom panel  1006 . 
     The column can include a front column  1010  located adjacent to the front panel  1002 , and a rear column located opposite to the front panel  1002 . The rear column can include a first rear column  1013  and a second rear column  1014 . The first rear column  1913  and the second rear column  1014  are spaced apart from each other, so that the first rear column  1913  and the second rear column  1014  can be located at a rear vertex side of the bottom panel. 
     The front panel  1002  can be disposed perpendicular to the bottom panel  1006 , and can be arranged in a rectangular shape at the front edge of the bottom panel  1006 . 
     An opening can be provided in the front panel  1002 , and the door  300  can be disposed in the opening. As the door  300  is opened, the user can put laundry into the washing chamber  10  or can take laundry out of the washing chamber  10 . The door  300  is coupled to the front panel  1002 , so that the user can handle the door  300  without approaching the side surface of the washing chamber  10 . 
     The bottom panel  1006  can have a rectangular shape so that various components can be supported. In addition, a plurality of ribs can be disposed at a lower portion of the bottom panel  1006 , thereby reinforcing the bottom panel  1006 . The plurality of columns can be spaced apart from each other with respect to the bottom panel  1006 , so that various components can be supported by the columns. 
     The electronic unit  1100  can be rotatably coupled to the second rear column  1014 . As shown in  FIG. 27 , the electronic unit  1100  can rotate with respect to the second rear column  1014 , and can be selectively coupled to the first rear column  1013  as shown in  FIG. 26 . Therefore, when maintenance is required for the electronic unit  1100 , the electronic unit  1100  can be separated from the first rear column  1013  as shown in  FIG. 27 , so that the separated electronic unit rotates. After such maintenance is completed, the electronic unit  1100  can be rotated to be coupled to the first rear column  1013 . 
     The configuration unit  1200  can be constructed in a manner that the respective components are disposed on the upper side and the lower side of the electronic unit  1100 . For example, among the components included in the configuration unit  1200 , the oil separator can be disposed at the upper side of the electronic unit  1100 , and the compressor is disposed at the lower side of the electronic unit  1100 . Therefore, if maintenance of the configuration unit  1200  is required, the electronic unit  1100  can rotate so that a working space can be guaranteed. 
     In some implementations, a portion corresponding to the manual valve from among the components included in the configuration unit  1200  can be separated from the washing machine by modularizing the manual valve separated by the user. A detailed description thereof will herein be omitted as previously described. 
     Each of the distillation chamber  50 , the storage tank  30 , and the washing chamber  10  can have a cylindrical shape, and can be placed in a lying state so that a vertical cross-section of each of the distillation chamber  50 , the storage tank  30 , and the washing chamber  10  can have a circular shape. Therefore, the space occupied by the washing machine can be reduced in size by the chamber and the tank, resulting in reduction in overall size of the washing machine. 
     Among the distillation chamber  50 , the storage tank  30 , and the washing chamber  10 , the washing chamber  10  can be formed to have the largest radius. The washing chamber  10  can be designed in a manner that the drum disposed therein rotates and laundry is accommodated in the drum, so that the washing chamber  10  can occupy a relatively large space. 
     The washing chamber  10  is disposed at the center of the front panel  1002  in the width direction. For example, the washing chamber  10  is disposed at the center of the front panel  1002  in a horizontal direction when viewed from  FIG. 25 . Since the washing chamber  10  has the largest radius, it is preferable that the washing chamber  10  be first disposed at the center of the front panel  1002 , and arrangement of other components be then determined, resulting in an increase in space use efficiency. In addition, vibration occurs in the washing chamber  10  due to rotation of the motor, so that the washing chamber  10  can be disposed at the center of the frame, resulting in prevention of resonance or the like. 
     The storage tank  30  and the distillation chamber  50  can be disposed to be biased toward one side with respect to a width direction. In particular, the storage tank and the distillation chamber can be arranged to be biased in the same direction with respect to the washing chamber. Referring to  FIG. 25 , the storage tank and the distillation chamber can be disposed on the right side with respect to the washing chamber  10 . 
     The washing chamber  10  can be disposed between the distillation chamber  50  and the storage tank  30 . The distillation chamber  50  can be disposed at the lowest position among the distillation chamber, the storage tank, and the washing chamber. The storage tank  30  can be disposed at the highest position among the distillation chamber, the storage tank, and the washing chamber. 
     For example, the storage tank  30  is disposed at the highest position with respect to the front panel  1002 , and the washing chamber  10  is disposed below the storage tank  30 , and the distillation chamber  50  is then disposed below the washing chamber  10 . 
     The carbon dioxide used in the washing chamber  10  may be disposed at a lower portion of the washing chamber  10 , so that the carbon dioxide can move toward the distillation chamber  50  due to gravity and can then be filtered in the distillation chamber  50 . 
     The storage tank  30  can be supported by the front column  1010  and the rear column  1013 . 
     In some implementations, the washing chamber can have a cylindrical shape having a shorter length than the storage tank  30  or the distillation chamber  50 , so that the electronic unit  1100  can be located at a height where the washing chamber  10  is located. The electronic unit  1100  can include a plurality of components such as a PCB, a space capable of including the plurality of components is required. Since the length of the washing chamber  10  is short, the space for enabling the electronic unit  1100  to be disposed in the frame can be guaranteed. In some implementations, the electronic unit  1100  is formed in an approximately rectangular parallelepiped shape, and the components are arranged in the corresponding rectangular parallelepiped space, and there occurs no interference with other components in the frame. 
     In some implementations, when maintenance is required for the washing chamber  10 , the electronic unit  1100  rotates as shown in  FIG. 27  so that a work (or task) space for the washing chamber  10  can be guaranteed. In addition, after completion of the task or work, the electronic unit  1100  returns to its original position as shown in  FIG. 26 , so that the space occupied by the washing machine can be reduced in size. 
     Since the washing chamber  10  is disposed between the distillation chamber  50  and the storage tank  30 , the side surface and the back surface of the washing chamber  10  may be exposed to the user. Therefore, when maintenance is required for the distillation chamber or the storage tank, the user can access the distillation chamber  50  or the storage tank  30  without the necessity of removing other components from the washing machine. 
     As is apparent from the above description, the washing machine can include constituent elements arranged for easy maintenance. Thus, when maintenance is required for a specific constituent element, inconvenience of a user who has to attach/detach other constituent elements can be eliminated. In addition, a tank or chamber having a relatively large volume can be stably distributed to reduce noise or vibration generated in the washing machine. 
     The washing machine can reduce the amount of carbon dioxide to be used so that the amount of residual carbon dioxide to be reprocessed after use can also be reduced, resulting in improvement in energy efficiency of the entire system. In addition, since the amount of carbon dioxide to be used is reduced, the size of a storage tank that should store carbon dioxide before use can also be reduced, so that the overall size of the washing machine can be reduced. 
     For example, the amount of carbon dioxide to be used in the washing machine can be reduced as compared to the conventional washing machine, so that the amount of carbon dioxide to be reprocessed after use can also be reduced. As the amount of carbon dioxide to be used is reduced, the overall size of the washing machine for using carbon dioxide as well as the capacity of a storage tank storing carbon dioxide can be reduced. In addition, since the amount of carbon dioxide to be reprocessed after use is reduced, the time required to perform washing or rinsing can also be reduced. 
     The washing machine can be constructed in a manner that various constituent elements can be separated from the washing machine so that an operator (or a repairman) can easily access and repair a necessary constituent component from among the constituent elements. In addition, the washing machine provides a structure in which various constituent elements can be combined to produce an actual product, so that the operator can easily manufacture the washing machine designed to use carbon dioxide. 
     The washing machine can include a stator and a rotor disposed together around a rotary shaft configured to rotate the drum, and the space to be occupied by a motor assembly is reduced in size, so that the overall size of the washing machine can also be reduced. In addition, the coupling relationship of the constituent elements for rotating the drum is simplified, so that noise generated by rotation of the drum can be reduced and the efficiency of power transmission can increase. 
     In some implementations, whereas liquid carbon dioxide is not introduced into the driving space in which the motor is disposed, gaseous carbon dioxide can flow into the driving space, and the drum can be rotated in a state in which pressure equilibrium between the washing space and the driving space is maintained. Therefore, when the washing machine operates, the drum can stably rotate. In addition, since the driving space is filled with gaseous carbon dioxide, the amount of carbon dioxide to be used for laundry treatment such as washing can be reduced. 
     In some implementations, liquid carbon dioxide discharged into the storage tank does not generate a large change in the storage level of liquid carbon dioxide stored in the storage tank, so that the storage level of the liquid carbon dioxide stored in the storage tank can be accurately detected.