Washing machine and method for measuring water level

Abstract

The washing machine according to an embodiment of the present invention comprises: a washing tub in which laundry, and gaseous and liquid carbon dioxide are inserted for the laundry to be washed; a liquid pipe connected to the washing tube to supply liquid carbon dioxide; a gas pipe connected to the washing tub to supply gaseous carbon dioxide; a cylinder, the lower end of which is connected to a pipe branched from the liquid pipe and the upper end of which is connected to the gas pipe, the cylinder being upright to be filled with liquid carbon dioxide while maintaining the same water level as the level of the liquid carbon dioxide supplied to the inside of the washing tub; a first level sensor mounted inside the cylinder to measure the level of the liquid carbon dioxide injected into the washing tub; and a second level sensor installed at a point adjacent to the lower end of the cylinder to detect the level of the liquid carbon dioxide filled inside the cylinder, wherein the second level sensor is a sensor which is not affected by changes in permittivity of the liquid carbon dioxide.

Description

Washing Machine and Water Level Measurement Method

[0001] The present invention relates to a washing machine and a water level measuring method, and more particularly, to a washing machine and a water level measuring method capable of improving the reliability of water level measurement for carbon dioxide levels by performing an automatic correction process before measuring the level of liquid carbon dioxide contained in a washing tub after washing.

[0002] In general, a carbon dioxide washing machine, which is an anhydrous washing machine, is a washing machine that uses carbon dioxide as a detergent to wash laundry.

[0003] Washing machines that use carbon dioxide as a detergent fill the entire washing tub with both gaseous and liquid carbon dioxide during the wash and rinse cycle. To use carbon dioxide as a detergent, the carbon dioxide is supplied from a carbon dioxide storage tank to the washing tub. Once the wash cycle is complete, the carbon dioxide is discharged from the washing tub to a distillation tank. The carbon dioxide collected in the distillation tank is then returned to the storage tank for reuse in the next wash cycle. During this process, pollutants released from the washing tub to the distillation tank along with the carbon dioxide are discharged to the outside.

[0004] After the wash cycle is complete, high-pressure gaseous carbon dioxide remains in the washing machine. To remove the laundry, a compressor is used to suck the gaseous carbon dioxide and send it to a cooler. The gaseous carbon dioxide sent to the cooler is then liquefied into liquid carbon dioxide and returned to the storage tank. This liquid carbon dioxide can then be re-introduced to the washing machine for use in the next laundry process.

[0005] In the case of conventional carbon dioxide washing machines, a capacitive water level sensor is installed around the washing tub to measure the level of liquid carbon dioxide in the washing tub.

[0006] The capacitive water level sensor is installed on the outer wall of the washing tank, applies a constant voltage between two electrodes, and measures the capacitance that changes as the level of liquid carbon dioxide with a specific permittivity changes.

[0007] Water level measurement using a capacitive water level sensor is performed through a sequence control method in which the pneumatic valve of the washing machine is opened through on signal control until the liquid carbon dioxide reaches the set target water level, and the pneumatic valve is closed through off signal control when the carbon dioxide reaches the target water level.

[0008] Capacitive level sensors have the advantage of being able to perform continuous measurements, but they can only be used after inputting and calibrating the dielectric constant value of the liquid carbon dioxide, which is the fluid to be measured.

[0009] However, when measuring the carbon dioxide level using a capacitive level sensor, a difference in permittivity between pure liquid carbon dioxide and the actual measured liquid carbon dioxide occurs due to impurities and laundry additives caused by contaminants accompanying the washing process. This difference in capacitance makes it difficult to accurately measure the water level, which in turn leads to instability in the washing system.

[0010] The purpose of the present invention is to provide a washing machine and a level measurement method capable of improving the reliability of level measurement for the level of carbon dioxide by performing an automatic correction process before measuring the level of liquid carbon dioxide.

[0011] In order to achieve the above object, a washing machine according to an embodiment of the present invention comprises: a washing tub into which laundry and gaseous and liquid carbon dioxide are introduced to treat the laundry; a liquid pipe connected to the washing tub for supplying liquid carbon dioxide; an organ connected to the washing tub for supplying gaseous carbon dioxide; a cylinder vertically erected so as to be filled with liquid carbon dioxide while maintaining a water level equal to the water level of liquid carbon dioxide supplied into the washing tub; a first water level sensor mounted inside the cylinder and measuring the water level of the liquid carbon dioxide introduced into the washing tub; and a second water level sensor installed at a point adjacent to the lower end of the cylinder and detecting the water level of the liquid carbon dioxide filled into the cylinder, wherein the second water level sensor is characterized in that it is a sensor that is not affected by a change in the permittivity of the liquid carbon dioxide.

[0012] The above first water level sensor is characterized in that it is a capacitance sensor.

[0013] The second water level sensor includes one of an ultrasonic sensor and an optoelectronic sensor.

[0014] The above second water level sensor includes a sensor to which a switch capable of outputting an on / off signal is applied.

[0015] The actual measurement section of the liquid carbon dioxide level by the first water level sensor is defined as the section from the lower end to the upper end of the inner surface of the drum, and the dielectric constant correction section by the second water level sensor is characterized in that it is defined as the section between the lowest end of the first water level sensor and the lower end of the inner surface of the drum.

[0016] The lowermost portion of the first water level sensor is characterized in that it corresponds to the lower end of the cylinder.

[0017] The second water level sensor is installed at a point within the correction section, and the liquid carbon dioxide level measured by the first water level sensor is calculated based on an initial permittivity value until the liquid carbon dioxide level supplied into the washing tub is detected by the second water level sensor, and when the water level detected by the first water level sensor and the height of the second water level sensor are different, the initial permittivity value is corrected so that the water level detected by the first water level sensor and the height of the second water level sensor become the same, and after the permittivity value is corrected, the supply of the liquid carbon dioxide is resumed, and when the water level detected by the first water level sensor reaches a set level, the supply of the liquid carbon dioxide is stopped.

[0018] A method for measuring a water level of a washing machine according to an embodiment of the present invention comprises the steps of: opening a pneumatic valve of the washing machine and supplying liquid carbon dioxide into a washing tub before a process of actually measuring a liquid carbon dioxide level by a first water level sensor; detecting a level of the liquid carbon dioxide supplied into the washing tub by the first water level sensor based on a preset initial permittivity value; detecting the level of the liquid carbon dioxide by a second water level sensor that is not affected by the permittivity of a fluid, and closing the pneumatic valve; and, at the time when the pneumatic valve is closed, if the level of the liquid carbon dioxide detected by the first water level sensor is different from a height of the second water level sensor, correcting the initial permittivity value to a new permittivity value so that the water level value detected by the first water level sensor becomes equal to the height of the second water level sensor.

[0019] When the correction of the dielectric constant value is completed, the pneumatic valve is reopened, and the liquid carbon dioxide is supplied to the washing tank.

[0020] The above set level is characterized in that it is the level of the liquid carbon dioxide calculated based on the corrected dielectric constant value.

[0021] The reopening state of the above pneumatic valve is characterized in that it is maintained until the level of the liquid carbon dioxide reaches a set level.

[0022] When the correction of the dielectric constant value is completed, the height of the second water level sensor is changed to zero water level, and the set water level is characterized in that it is a water level calculated from the zero water level.

[0023] According to the washing machine and water level measuring method according to the present invention having the configuration described above, an automatic correction process for correcting the permittivity deviation of the water level sensor is performed before measuring the level of liquid carbon dioxide stored in the washing tub, so that the reliability of the measured value can be improved when measuring the level of liquid carbon dioxide.

[0024] According to the washing machine and water level measuring method according to the present invention, continuous measurement of the water level sensor is possible, and measurement error of the water level sensor due to dielectric constant fluctuations is improved, thereby improving the system stability of the washing machine.

[0025] Fig. 1 is a drawing showing the configuration of a washing machine according to an embodiment of the present invention.

[0026] Figure 2 is a drawing illustrating a washing tub and a water level sensor of a washing machine according to an embodiment of the present invention.

[0027] Figure 3 is a flowchart explaining the dielectric constant correction of a water level sensor according to an embodiment of the present invention.

[0028] Hereinafter, a washing machine according to an embodiment of the present invention will be described in detail with reference to the attached drawings.

[0029] FIG. 1 is a drawing showing the configuration of a washing machine according to an embodiment of the present invention.

[0030] Since the washing machine according to an embodiment of the present invention washes laundry through processes such as washing and rinsing using carbon dioxide as a detergent, it may include a component capable of storing or processing carbon dioxide.

[0031] Specifically, the washing machine includes a supply unit that supplies carbon dioxide, a washing unit that processes laundry, and a regeneration unit that processes used carbon dioxide.

[0032] Referring to FIG. 1, the supply unit may include a storage tank for storing liquid carbon dioxide. The storage tank may include at least a portion of a distillation tank (120), a storage tank (150), and a replenishment tank (160).

[0033] The washing machine may include a washing tub (110) into which carbon dioxide and laundry can be injected together.

[0034] The regeneration unit may include a contaminant separator for separating contaminants dissolved in liquid carbon dioxide after washing, a cooler (140) for changing the phase of gaseous carbon dioxide into a liquid state, a distillation tank (120) for storing liquid carbon dioxide from which contaminants have been separated, and a contaminant storage tank (170) for storing contaminants separated after distillation in the distillation tank (120). As described above, the distillation tank (120) may not only function as a supply unit for supplying carbon dioxide to the washing tank, but also function as a regeneration unit for separating carbon dioxide and contaminants.

[0035] The replenishment tank (160) of the supply unit can store excess carbon dioxide to be supplied to the washing tank (110). Of course, the replenishment tank (160) is a storage tank that can be selectively used only when carbon dioxide replenishment is required, and may not be provided in situations where carbon dioxide replenishment is not required. Accordingly, in general situations, the replenishment tank (160) is not provided, but when the replenishment tank (160) is connected as needed, carbon dioxide replenishment is performed, and when replenishment is completed, the replenishment tank (160) can be separated from the washing machine.

[0036] In the embodiment of the present invention, since the carbon dioxide supplied to the washing tank (110) can be recovered and reused, the need for a supplementary tank (160) is not present or is low, and therefore it is not an essential component.

[0037] Below, we will describe a washing machine that processes laundry using carbon dioxide.

[0038] A washing machine according to an embodiment of the present invention can perform at least one laundry treatment process among washing, rinsing, dehydration, and drying to remove contaminants from laundry stored in a washing tub (110). Furthermore, a process for treating laundry using carbon dioxide instead of water as a detergent can be performed.

[0039] A washing machine according to an embodiment of the present invention may include, as described above, a washing tank (110), a distillation tank (120), a compressor (130), a cooler (140), and a storage tank (150), and may optionally further include a supplementary tank (160).

[0040] The washing machine's washing tub (110) can perform laundry treatment operations on laundry received using carbon dioxide.

[0041] The washing tub (110) may include a sensor for measuring the amount of liquid carbon dioxide stored within the washing tub (110). If the sensor determines that a liquid carbon dioxide exceeding a reference value has been supplied to the washing tub (110), the control unit (not shown) of the washing machine may control the supply of carbon dioxide to be stopped. Specifically, the reference value for measuring the amount of liquid carbon dioxide may be determined based on the amount of laundry washed by the washing machine and may be proportional to the amount of laundry.

[0042] In addition, the washing tub (110) may include a washing tub heat exchanger (111) for maintaining the temperature inside the washing tub (110) at a set temperature. The washing tub heat exchanger (111) may supply heat inside the washing tub (110) to prevent laundry from hardening or being damaged due to a rapid drop in the temperature inside the washing tub when discharging liquid carbon dioxide or gaseous carbon dioxide inside the washing tub (110).

[0043] In addition, during the laundry treatment operation, the washing tank heat exchanger (111) is required to maintain the required amount of carbon dioxide in a liquid state during the washing and rinsing operations.

[0044] In order to maximize the contact area with the carbon dioxide contained in the washing tank (110), the flow pipe through which the carbon dioxide flows may be extended in a zigzag shape in the washing tank heat exchanger (111).

[0045] The distillation tank (120) can distill the liquid carbon dioxide used in the washing and rinsing steps to separate foreign substances from the liquid carbon dioxide and then reuse the carbon dioxide. Specifically, the liquid carbon dioxide discharged to the distillation tank (120) can be vaporized through heat exchange with the high-temperature, high-pressure gaseous carbon dioxide discharged from the compressor (130), thereby separating contaminants from the carbon dioxide. The contaminants include sludge separated from the laundry during the washing or rinsing process.

[0046] Carbon dioxide vaporized during the distillation process for regeneration is located at the upper part of the distillation tank (120), and contaminants settle at the lower part of the distillation tank (120). Contaminants settled at the lower part of the distillation tank (120) can be temporarily stored by being discharged to the contaminant storage tank (170) by the contaminant separator.

[0047] The interior of the distillation tank (120) may include a heat exchanger (121) that only performs heat exchange without mixing with liquid carbon dioxide containing contaminants. The heat exchanger (121) refers to a flow pipe that extends from the outlet of the compressor (130) and is inserted into the tank. The heat exchanger (121) may be defined as a distillation tank heat exchanger, and like the washing tank heat exchanger (111), it may form a meander line that is rounded multiple times to increase heat exchange efficiency.

[0048] The distillation tank heat exchanger (121) may be connected to a cooler (140). Accordingly, the high-temperature, high-pressure gaseous carbon dioxide discharged from the compressor (130) is first cooled while exchanging heat with the liquid carbon dioxide inside the distillation tank (120) as it passes through the distillation tank heat exchanger (121), and then is secondarily cooled while passing through the cooler (140) and changes into liquid carbon dioxide.

[0049] The distillation tank (120) may be positioned at the bottom of the washing tank (110) so that it can receive liquid carbon dioxide inside the washing tank (110) by gravity. In addition, a pipe connecting the upper surface of the distillation tank (120) and the lower surface of the washing tank (110) may be installed. Accordingly, the liquid carbon dioxide inside the washing tank (110) is discharged to the distillation tank (120) by gravity through the pipe.

[0050] Meanwhile, after the laundry is put in and the washing tub is turned into a vacuum state, the gaseous carbon dioxide in the distillation tank (120) is first supplied to the washing tub (110), and then the liquid carbon dioxide stored in the storage tank (150) is supplied to the washing tub (110). In addition, the gaseous carbon dioxide in the distillation tank (120) is supplied to the washing tub (110) through the pipe, and can be supplied until the pressure inside the washing tub (110) reaches the set pressure.

[0051] The compressor (130) can suck in carbon dioxide in a gaseous state stored inside the distillation tank (120), compress it at high temperature and high pressure, and then discharge it to the washing tank heat exchanger (111) or the distillation tank heat exchanger (121).

[0052] In Fig. 1, a flow path is illustrated in which carbon dioxide discharged from a compressor is selectively supplied to the washing tank heat exchanger (111) or the distillation tank heat exchanger (121), but this is not limited thereto. That is, it is to be noted that a flow path configuration in which the outlet of the washing tank heat exchanger (111) and the inlet of the distillation tank heat exchanger (121) are connected, and the washing tank heat exchanger (111) and the distillation tank heat exchanger (121) are connected in series is also possible.

[0053] Accordingly, the gaseous carbon dioxide discharged from the compressor (130) can be delivered to the cooler (140) after passing through the washing tank heat exchanger (111) and / or the distillation tank (120).

[0054] The above cooler (140) can be understood as a condenser that condenses and liquefies gaseous carbon dioxide discharged from the compressor (130) and passed through the washing tank heat exchanger (111) and / or the distillation tank heat exchanger (121).

[0055] The condensed liquid carbon dioxide passing through the cooler (140) is supplied to and stored in the storage tank (150), and the liquid carbon dioxide stored in the storage tank (150) is supplied to the washing tank (110) for washing or rinsing operations. In order to ensure that the liquid carbon dioxide stored in the storage tank (150) is supplied to the washing tank (110) by gravity, the storage tank (150) may be installed at a higher location than the washing tank (110).

[0056] FIG. 2 is a drawing illustrating a washing tub and a water level sensor of a washing machine according to an embodiment of the present invention.

[0057] Referring to Fig. 2, a first water level sensor (200) is installed on one side of the washing tank (110) filled with both gaseous carbon dioxide and liquid carbon dioxide. Then, the level of the liquid carbon dioxide supplied to the washing tank (100) is measured by the first water level sensor (200).

[0058] The above first water level sensor (200) is a capacitance sensor that applies a constant voltage between two electrodes designed at a constant interval and measures the capacitance accumulated according to the change in the water level of liquid carbon dioxide having a specific permittivity.

[0059] The first water level sensor (200) may be installed inside a cylinder (112) that is vertically erected and connects a pipe branching from a liquid carbon dioxide supply pipe connected to the washing tub (110) and a gaseous carbon dioxide flow pipe connected to the washing tub (110). Then, the internal pressure of the cylinder (112) and the internal pressure of the washing tub (110) become the same, and the internal water level of the washing tub (110) and the internal water level of the cylinder (112) become the same.

[0060] Of course, it may be possible to detect the level of stored liquid carbon dioxide using other types of level sensors, but it must be a level sensor that can measure the capacitance accumulated according to the change in the level of liquid carbon dioxide with a specific permittivity.

[0061] The present invention proposes a method for preventing a decrease in the measurement accuracy of a first water level sensor (200) due to a change in the dielectric constant of liquid carbon dioxide used in a washing process caused by impurities and laundry additives accompanying the carbon dioxide washing process.

[0062] To this end, the present invention is characterized in that a second water level sensor (300) is added that can correct the dielectric constant deviation of the first water level sensor (200) by adding a calibration section before the actual measurement section of the first water level sensor (200).

[0063] The actual measurement section that can be measured by the first water level sensor (200) can be defined as the inner diameter of the washing tub (110). That is, the section from the lowest to the highest point of the inner surface of the horizontally placed cylindrical washing tub (110) can be defined as the actual measurement section.

[0064] The correction section can be defined as the section from the lowest part of the first water level sensor (200), that is, the lowest part of the cylinder (112), to the inner surface floor of the washing tub (110).

[0065] The second water level sensor (300) may be understood as a sensor that corrects the deviation between the permittivity of pure liquid carbon dioxide and the permittivity of the liquid carbon dioxide actually measured by the first water level sensor (200). The second water level sensor (300) is a sensor that is not affected by changes in the permittivity of the liquid carbon dioxide due to impurities added to the liquid carbon dioxide. For example, the second water level sensor (300) may be any one of an ultrasonic sensor and an optoelectronic sensor that do not have concerns about a decrease in accuracy due to a deviation in the permittivity of the liquid carbon dioxide, and may be a sensor to which a switching means capable of controlling an on / off signal output is applied.

[0066] In the present invention, the second water level sensor (300) may be an ultrasonic sensor or an optoelectronic sensor, but is not necessarily limited thereto, and various sensors capable of controlling on / off signal output may be adopted.

[0067] Since the second water level sensor (300) is installed within the calibration section, the height of the second water level sensor (300) can be set within the calibration section.

[0068] Until the level of the liquid carbon dioxide filled inside the washing tank (110) reaches the height at which the second water level sensor (300) is installed from the lowest end of the first water level sensor (200), the first water level sensor (200) continuously outputs and measures the water level as the value of the initial dielectric constant.

[0069] And when the level of the liquid carbon dioxide reaches the height of the second level sensor (300), the second level sensor (300) operates through on signal control.

[0070] When the liquid carbon dioxide reaches a fixed height of the second level sensor (300), the second level sensor (300) is activated to perform control logic for comparing the level measurement value of the first level sensor (200) with the height of the second level sensor (300).

[0071] At this time, if the water level output to the first water level sensor (200) is not the same as the height of the second water level sensor (300), this means that there is a deviation between the permittivity of the liquid carbon dioxide actually measured by the first water level sensor (200) and the permittivity of the pure liquid carbon dioxide, and thus the reliability of the actually measured liquid carbon dioxide level may be reduced.

[0072] The operating principles of the first water level sensor (200) and the second water level sensor (300) are as follows.

[0073] The size of the electrostatic capacitance (C) of the first water level sensor (200) with two parallel electrodes is proportional to the area (A) of the electrodes and inversely proportional to the spacing (d) between the electrodes.

[0074] When there is a dielectric constant (ε) between the electrodes, the capacitance (C) is It becomes.

[0075] Therefore, the larger the surface area (A) of the electrode, the narrower the gap (d), and the larger the permittivity (ε) of the liquid carbon dioxide, the larger the electrostatic capacitance (C).

[0076] The dielectric constant (ε) of the liquid carbon dioxide actually measured by the first water level sensor (200) can be calibrated to a value at which the water level output by the first water level sensor (200) and the height of the second water level sensor (300) become the same.

[0077] That is, the initial input dielectric constant (ε0) to the first water level sensor (200) _ ini ) based on the water level (h) output from the first water level sensor (200) cap ), the electrostatic capacity (C) of the first water level sensor (200) cap ) is C cap = ε 0_ini wh cap / d (w: width of electrode)

[0078] And the water level (h) output from the first water level sensor (200) cap) is the height value (h) of the second water level sensor (300). ref ) and the dielectric constant (ε) derived by correction 0 mod )silver,

[0079] ε0 mod = ε0 _ ini * (h cap / h ref ) becomes.

[0080] In this way, the water level value (h) output from the first water level sensor (200) cap ) is the height value (h) of the second water level sensor (300). ref ) and the dielectric constant (ε0) derived by correction mod ) is the water level value (h) output to the first water level sensor (200). cap ) and the initial input dielectric constant (ε0) to the first water level sensor (200) _ ini ) is proportional to the height value (h) of the second water level sensor (300). ref ) can be inversely proportional.

[0081] Therefore, the initial input dielectric constant (ε0) to the first water level sensor (200) _ ini ) is the corrected dielectric constant (ε0 mod ), the water level output from the first water level sensor (200) can be corrected to the height of the second water level sensor (300).

[0082] Figure 3 is a flowchart for dielectric constant correction of a water level sensor according to an embodiment of the present invention.

[0083] Referring to Fig. 3, the pneumatic valve of the washing machine is opened by on signal control (S110).

[0084] In detail, when the pneumatic valve of the washing machine is opened by the on signal control, liquid carbon dioxide is supplied to the washing tub (110) of the washing machine, causing the carbon dioxide level to rise.

[0085] Then, it is determined whether the second water level sensor (300) is operating through on signal control (S120). If the second water level sensor (300) is operating through on signal control, the pneumatic valve of the washing machine stops the supply of carbon dioxide through off signal control (S130).

[0086] Next, the water level value (h) output to the first water level sensor (200) cap ) and the height value (h) of the second water level sensor (300) ref ) to determine whether the two values ​​are the same (S140).

[0087] If the water level value (h) output to the first water level sensor (200) cap ) and the height value (h) of the second water level sensor (300) ref ) is compared, and if the two values ​​are not the same, a process of correcting the water level output signal of the first water level sensor (200) is performed through logic that corrects the value of the initial dielectric constant so that the two values ​​match (S150).

[0088] Through the calibration process, the water level value (h) output from the first water level sensor (200) cap ) and the height value (h) of the second water level sensor (300) ref ) is corrected to the dielectric constant so that the height value (h) of the liquid carbon dioxide, i.e. the water level value (h) output to the first water level sensor (200) cap ) and the height value (h) of the second water level sensor (300) ref ) of the difference (h) cap - h ref ) is reset to ‘0’ and determined as ‘0 level’ (S160).

[0089] In this way, an automatic calibration process for correcting the dielectric constant deviation of the first water level sensor (200) can be performed prior to the actual measurement section of the first water level sensor (200). This calibration process can improve measurement reliability when measuring the level of liquid carbon dioxide.

[0090] When the above automatic correction process is completed, the pneumatic valve of the washing machine is opened again by the on signal control (S210), so that the supply of liquid carbon dioxide to the washing tub (110) of the washing machine is resumed, and the carbon dioxide level rises.

[0091] Next, the first water level sensor (200) determines whether the height of the liquid carbon dioxide reaches the target level (S220).

[0092] If, in the first water level sensor (200), the height of the liquid carbon dioxide reaches the target level, the pneumatic valve of the washing machine is closed by off signal control (S230).

[0093] At this point, the level of the liquid carbon dioxide measured by the first water level sensor (200) is output as the actual measured level (S240).

[0094] By correcting the dielectric constant deviation before the actual measurement section for each washing cycle through the control logic of the flow chart as described above, the accuracy of the water level measurement of the first water level sensor (200) can be improved, thereby improving the reliability of the measurement of the carbon dioxide level in the drum of the washing tub (110).

[0095] In addition, the system stability of the washing machine can be improved by improving the measurement error of the first water level sensor (200) due to dielectric constant fluctuation while enabling continuous measurement of the first water level sensor (200).

Claims

1. A washing tub in which laundry and gaseous and liquid carbon dioxide are injected to treat the laundry; A liquid pipe for supplying liquid carbon dioxide, connected to the above washing tank; An organ for supplying carbon dioxide gas, connected to the above washing tank; A cylinder having the lower end connected to a pipe branching from the liquid pipe, the upper end connected to the organ, and being vertically erected to be filled with liquid carbon dioxide while maintaining the same level as the level of liquid carbon dioxide supplied into the washing tank; A first water level sensor mounted inside the cylinder and measuring the level of the liquid carbon dioxide injected into the washing tank; and A second level sensor is installed at a point adjacent to the bottom of the cylinder and detects the level of liquid carbon dioxide filled inside the cylinder, The above second water level sensor, A washing machine characterized by being a sensor that is not affected by changes in the dielectric constant of the liquid carbon dioxide.

2. In paragraph 1, A washing machine, characterized in that the first water level sensor is a capacitance sensor.

3. In paragraph 1, The above second water level sensor, A washing machine comprising either an ultrasonic sensor or an optoelectronic sensor.

4. In paragraph 3, The above second water level sensor, A washing machine including a sensor having a switch capable of outputting an on / off signal.

5. In paragraph 1, The actual measurement section of the liquid carbon dioxide level by the above first water level sensor is defined as the section from the bottom to the top of the inner surface of the drum, A washing machine characterized in that the dielectric constant correction section by the second water level sensor is defined as the section between the lowest end of the first water level sensor and the lower end of the inner surface of the drum.

6. In paragraph 5, A washing machine, characterized in that the lowest end of the first water level sensor corresponds to the bottom of the cylinder.

7. In paragraph 5, The above second water level sensor is installed at any point within the above calibration section, Until the level of the liquid carbon dioxide supplied into the washing tank is detected by the second level sensor, the level of the liquid carbon dioxide measured by the first level sensor is calculated based on the initial dielectric constant value, If the water level detected by the first water level sensor and the height of the second water level sensor are different, the initial dielectric constant value is corrected so that the water level detected by the first water level sensor and the height of the second water level sensor become the same. After the dielectric constant value is corrected, the supply of the liquid carbon dioxide is resumed, A washing machine characterized in that the supply of the liquid carbon dioxide is stopped when the water level detected by the first water level sensor reaches a set level.

8. Before the actual measurement of the liquid carbon dioxide level by the first water level sensor, the pneumatic valve of the washing machine is opened to supply the liquid carbon dioxide into the washing tub; A step in which the level of the liquid carbon dioxide supplied into the washing tank is detected by the first water level sensor based on a preset initial dielectric constant value; A step in which the level of the liquid carbon dioxide is detected by a second level sensor that is not affected by the dielectric constant of the fluid, and the pneumatic valve is closed; and A method for measuring water level in a washing machine, comprising a step of correcting the initial permittivity value to a new permittivity value so that the water level value detected by the first water level sensor becomes the same as the height of the second water level sensor when the pneumatic valve is closed, if the liquid carbon dioxide level detected by the first water level sensor is different from the height of the second water level sensor.

9. In paragraph 8, A method for measuring water level in a washing machine, characterized in that when the correction of the dielectric constant value is completed, the pneumatic valve is reopened and the liquid carbon dioxide is supplied to the washing tub.

10. In paragraph 9, A method for measuring the water level of a washing machine, characterized in that the above-mentioned set water level is the water level of the liquid carbon dioxide calculated based on the above-mentioned corrected dielectric constant value.

11. In paragraph 10, A method for measuring the water level of a washing machine, characterized in that the reopening state of the pneumatic valve is maintained until the level of the liquid carbon dioxide reaches a set level.

12. In paragraph 9, When the correction of the above dielectric constant value is completed, the height of the second water level sensor is changed to zero water level, A method for measuring water level of a washing machine, characterized in that the above set water level is a water level calculated from the zero water level.

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