WASHING MACHINE AND CONTROL METHOD THEREOF

Abstract

A washing machine having a boiling washing course function to perform washing by heating water to increase a washing effect, and a control method thereof. In the washing machine and control method, it is possible to increase a washing effect by heating water for a predetermined time according to the temperature of the initially supplied water, draining the water if the temperature of the heated water is less than the set temperature, and maintaining the amount of the initially supplied water without draining the water if the temperature of the water is equal to or greater than the set temperature. Further, by allowing the water to reach the target temperature of a high temperature within a predetermined washing time while maintaining the amount of the initially supplied water, it is possible to maintain a washing effect due to a washing temperature thereof.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of Korean Patent Application No. 10-2013-0108819, filed on Sep. 11, 2013 in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference.

BACKGROUND

1. Field

Embodiments of the present disclosure relate to a washing machine having a boiling washing course function to perform washing by heating water in order to increase a washing effect, and a control method thereof.

2. Description of the Related Art

In general, a washing machine (e.g., fully automatic washing machine) includes a tub to accommodate water (washing water or rinsing water), a washing tub rotatably installed inside the tub to accommodate the laundry and a pulsator rotatably installed inside the washing tub to generate a water flow, and a motor to generate driving force for rotating the washing tub and the pulsator. The washing machine is an apparatus for removing stains from laundry by surface activity of a detergent and a water flow.

This washing machine performs washing by a series of operations such as a washing process to separate stains from the laundry using water (specifically, washing water) in which a detergent is dissolved, a rinsing process to rinse a residual detergent or bubbles out of the laundry using water (specifically, rinsing water) which does not contain a detergent, and a spin-dry process to remove water contained in the laundry by high speed rotation.

Among the above-mentioned processes, the washing process has a boiling washing course function to perform washing by heating supplied water in order to increase a washing effect of contaminated laundry.

In a conventional boiling washing course, initially supplied water is heated and the water is unconditionally drained when the temperature (water temperature) of the water reaches a set temperature. Then, after the water level is reduced to be lower than the level of the initially supplied water, the water is heated up to a target temperature. This is intended to reduce electrical energy consumed for heating the water because plenty of water is used due to the nature of the fully automatic washing machine.

However, in the conventional boiling washing course, since the water is unconditionally drained although the level of the initially supplied water is the amount of washing water suitable for the laundry, the amount of the detergent and the initially supplied water for washing the contaminated laundry decreases, and the washing effect may be reduced.

SUMMARY

Therefore, it is an aspect of the present disclosure to provide a washing machine capable of increasing a washing effect by heating initially supplied water for a predetermined time, determining whether to drain water according to the temperature of the water, and maintaining the amount of the initially supplied water without unconditionally draining the water, and a control method thereof.

Additional aspects of the disclosure will be set forth in part in the description which follows and, in part, will be apparent from the description, or may be learned by practice of the disclosure.

In accordance with one aspect of the present disclosure, a control method of a washing machine including a tub to accommodate water and a heater installed inside the tub to heat the water includes determining whether a currently washing course is a boiling washing course, supplying water into the tub if the currently washing course is the boiling washing course, performing primary heating washing to heat the supplied water for a predetermined time, detecting a temperature of the primarily heated water, and controlling a level of water in the tub for secondary heating washing according to the detected temperature of the water. The controlling the water level includes varying the level of water in the tub according to the temperature of the primarily heated water.

The controlling the water level may include comparing the temperature of the primarily heated water with a set temperature, and maintaining a current water level without draining the primarily heated water if the temperature of the primarily heated water is greater than the set temperature.

Further, if the temperature of the primarily heated water is equal to or less than the set temperature, the primarily heated water may be drained to lower the water level.

The supplying the water into the tub may include supplying water up to a predetermined water level for the boiling washing course.

The supplied water may be cold water or hot water.

The performing the primary heating washing may include detecting a temperature of the water supplied into the tub, determining a primary heating time according to the detected temperature of the water, and driving the heater according to the determined primary heating time.

The draining the water may include draining the water down to a water level lower by one level than the predetermined water level.

Further, the control method may further include performing secondary heating washing to heat the primarily heated water up to a target temperature after controlling the water level.

The set temperature may be a temperature of the water supplied up to the predetermined water level, which may reach the target temperature within a secondary heating time, and the set temperature may be about 45° C.

The target temperature may be equal to or greater than 70° C. which may provide a boiling effect.

Further, the control method may further include performing washing for a set time after the secondary heating washing.

Further, the control method may further include performing a cooling process by supplying cold water after performing the washing.

Further, the control method may further include performing a washing and cooling process by supplying cold water after performing the secondary heating washing.

In accordance with another aspect of the present disclosure, a control method of a washing machine includes a tub to accommodate water and a heater installed inside the tub to heat the water determining whether a currently washing course is a boiling washing course, supplying water into the tub if the currently washing course is the boiling washing course, detecting a temperature of the supplied water, determining a primary heating time according to the detected temperature of the water, performing primary heating washing by driving the heater according to the determined primary heating time, and controlling a level of water in the tub for secondary heating washing according to the detected temperature of the water. The controlling the water level includes varying the level of water in the tub according to the temperature of the supplied water.

The controlling the water level may include comparing the temperature of the supplied water with a set temperature, and maintaining a current water level without draining the primarily heated water if the temperature of the supplied water is greater than the set temperature.

Further, the controlling the water level may include comparing the temperature of the supplied water with a set temperature, and lowering the water level by draining the primarily heated water if the temperature of the supplied water is equal to or less than the set temperature.

Further, the control method may further include, after controlling the water level, performing secondary heating washing to heat the primarily heated water up to a target temperature.

In accordance with one aspect of the present disclosure, a washing machine includes a tub to accommodate water, a heater installed inside the tub to heat the water, an input unit through which a boiling washing course is selected, a control unit to, if the boiling washing course is selected, perform primary heating washing for a predetermined time after supplying water into the tub, detect a temperature of the primarily heated water, and control a level of water in the tub for secondary heating washing. The control unit may vary the level of water in the tub according to the temperature of the primarily heated water.

The control unit may compare the temperature of the supplied water with a set temperature, and maintain a current water level without draining the primarily heated water if the temperature of the supplied water is greater than the set temperature.

Further, the control unit may compare the temperature of the supplied water with a set temperature, and lower the water level by draining the primarily heated water if the temperature of the supplied water is equal to or less than the set temperature.

Further, after controlling the water level, the control unit may perform secondary heating washing to heat the primarily heated water up to a target temperature.

In accordance with another aspect of the present disclosure, a washing machine includes a tub to accommodate water, a heater installed inside the tub to heat the water, an input unit through which a boiling washing course is selected, a control unit to, if the boiling washing course is selected, supply water into the tub, detect a temperature of the supplied water, perform primary heating washing to drive the heater for a primary heating time determined according to the detected temperature of the water, and control a level of water in the tub for secondary heating washing according to the detected temperature of the water. The control unit may vary the level of water in the tub according to the temperature of the supplied water.

The control unit may compare the temperature of the supplied water with a set temperature, and maintain a current water level without draining the primarily heated water if the temperature of the supplied water is greater than the set temperature.

The control unit may compare the temperature of the supplied water with a set temperature, and lower the water level by draining the primarily heated water if the temperature of the supplied water is equal to or less than the set temperature.

According to the proposed washing machine and control method thereof, it is possible to increase a washing effect by heating water for a predetermined time according to the temperature of the initially supplied water, draining the water if the temperature of the heated water is less than the set temperature, and maintaining the amount of the initially supplied water without draining the water if the temperature of the water is equal to or greater than the set temperature. Further, by allowing the water to reach the target temperature of a high temperature within a predetermined washing time while maintaining the amount of the initially supplied water, it is possible to maintain a washing effect due to a washing temperature.

BRIEF DESCRIPTION OF THE DRAWINGS

These and/or other aspects of the disclosure will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:

FIG. 1 is a cross-sectional view showing a configuration of a washing machine according to an embodiment of the present disclosure;

FIG. 2 is a control block diagram of the washing machine according to the embodiment of the present disclosure;

FIG. 3 is a diagram showing the water levels of the washing machine according to the embodiment of the present disclosure;

FIGS. 4A and 4B illustrate an operation flowchart showing a first control algorithm for boiling washing in the washing machine according to the embodiment of the present disclosure;

FIGS. 5A and 5B illustrate an operation flowchart showing a second control algorithm for boiling washing in the washing machine according to the embodiment of the present disclosure;

FIGS. 6A and 6B illustrate an operation flowchart showing a third control algorithm for boiling washing in the washing machine according to the embodiment of the present disclosure; and

FIGS. 7A and 7B illustrate an operation flowchart showing a fourth control algorithm for boiling washing in the washing machine according to the embodiment of the present disclosure.

DETAILED DESCRIPTION

Reference will now be made in detail to the embodiments of the present disclosure, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to like elements throughout.

FIG. 1 is a cross-sectional view showing a configuration of a washing machine according to an embodiment of the present disclosure.

Referring to FIG. 1, a washing machine 1 according to the embodiment of the present disclosure includes a substantially box-shaped cabinet 10 forming an external appearance of the washing machine 1, a tub 11 installed inside the cabinet 10 to accommodate water (washing water or rinsing water), a washing tub 12 rotatably installed inside the tub 11 to accommodate the laundry and a pulsator 13 rotatably installed inside the washing tub 12 to rotate clockwise or counterclockwise (forward or backward) and generate a water flow. The washing machine has a vertical axis.

The washing tub 12 is formed in a cylindrical shape to have an open top portion. On the side surface of the washing tub 12, plural water-extracting holes 12a are formed. A balancer 12b may be installed in an upper portion of the washing tub 12 such that the washing tub 12 may be rotated stably during high-speed rotation.

On the lower outside of the tub 11, there are installed a washing motor 14 to generate a driving force for rotating the washing tub 12 and the pulsator 13, and a power switching device 15 to simultaneously or selectively transfer the driving force generated from the washing motor 14 to the washing tub 12 and the pulsator 13.

A hollow water-extracting shaft 16 is coupled to the washing tub 12. A washing shaft 17 is installed in the hollow portion of the water-extracting shaft 16. The washing shaft 17 may be coupled to the pulsator 13 through a washing shaft coupling part 18.

The washing motor 14 is a direct drive (DD) motor having a variable speed function. The washing motor 14 may selectively transfer driving force to the washing tub 12 or the pulsator 13 according to vertical movements.

Further, as the washing motor 14, a universal motor including a field coil and an armature, a brushless direct current (BLDC) motor including a stator and a rotor, or the like may be used. In addition, any motor which is applicable to the washing machine 1 may be used. Alternatively, the washing motor 14 may be configured in a belt manner.

A water outlet port 20 is formed at the bottom of the tub 11 to discharge water to the outside, and a first drain pipe 21 is connected to the water outlet port 20. A drain motor 22 is installed in the first drain pipe 21 to regulate drainage. A second drain pipe 23 for discharging water to the outside is connected to the outlet of the drain motor 22.

Further, on the lower inside of the tub 11, there are installed a heater 30 to heat the water in the tub 11, a temperature sensor 32 to detect the temperature of the water in the tub 11, and a water level sensor 34 to detect a frequency varying according to the water level in order to detect the amount of water (water level) in the tub 11.

On the upper side of the cabinet 10, there are installed a door 40 which is opened/closed to load laundry into the washing tub 12 or unload the laundry from the washing tub 12, and a top cover 42 which the door 40 is separated from or seated on according to whether the door 40 is opened or closed.

At the top cover 42, there is formed a laundry input port 46 through which the laundry is loaded into the washing tub 12 or the laundry is unloaded from the washing tub 12. The laundry input port 46 may be opened and closed by the door 40.

Further, a detergent box 48 for supplying a detergent and softening agent and a water supply device 50 for supplying water (washing water or rinsing water) are installed in the upper part of the cabinet 10.

The water supply device 50 includes first and second water supply pipes 51 and 52 which connect an external water supply pipe to the detergent box 48 to supply water (washing water or rinsing water) into the tub 11, and first and second water supply valves 53 and 54 which are installed in the first and second water supply pipes 51 and 52 to control the supply of hot or cold water. This configuration enables the water supplied into the tub 11 to pass through the detergent box 48 so that the detergent may be supplied together with the water into the tub 11.

FIG. 2 is a control block diagram of the washing machine according to the embodiment of the present disclosure.

Referring to FIG. 2, the washing machine 1 according to the embodiment of the present disclosure is configured to include an input unit 70, a control unit 72, a memory 74, a driving unit 76 and a display unit 78.

The input unit 70 enables the user to input a command for performing a washing process, a rinsing process, a spin-dry process and the like of the washing machine 1. The input unit 70 may be configured as keys, buttons, switches, touch pads and the like, and includes all devices to generate predetermined input data by an operation (e.g., pressing, touching, pressure and rotation).

Further, the input unit 70 includes a plurality of buttons (power, reservation, washing, rinsing, water-extraction, water level selection, etc.) for entering a user command related to operation of the washing machine 1. Among the plurality of buttons, there are provided course selection buttons for selecting a washing course (standard course, wool course, boiling course, etc.) depending on the type of laundry loaded in the washing machine 1.

The course selection buttons provided in the input unit 70 include a boiling course button 71 to select a boiling washing course for performing washing by heating the supplied water in order to increase a washing effect on the contaminated laundry.

The boiling course button 71 is provided to perform washing by heating the supplied water in the case of requiring a sterilization effect as well as removal of stains and odors from laundry such as baby clothes and underwear. The boiling course does not require the water to be heated to a boiling point, i.e. 100° C.

The control unit 72 is a microcomputer for controlling the overall operations of the washing machine 1 such as washing, rinsing and spin-dry operations according to the operating information inputted from the input unit 70. The control unit 72 sets the amount of water for washing and rinsing, a target RPM, a motor operation rate (washing motor on-off time), washing and rinsing time and the like according to the weight (load) of the laundry in the selected washing course.

Further, the control unit 72 controls a driving timing and driving time of a heater 30 to maximize washing effects by heating the supplied water during boiling washing.

Accordingly, if a boiling washing course is selected, the control unit 72 performs primary heating washing for a predetermined washing time by driving the washing motor 14 and the heater 30 after supplying water up to a second water level (middle water level) determined for a boiling washing course. The primary heating time varies depending on the temperature (water temperature) of primarily heated water. As the water temperature is higher, the primary heating time is shorter. When the primary heating time has elapsed, the primary heating washing is stopped by stopping the washing motor 14 and the heater 30.

Then, the control unit 72 determines whether to drain water according to the temperature of the primarily heated water. That is, the control unit 72 determines whether the temperature of the primarily heated water is a water temperature (third temperature; about 45° C.) that may reach a target temperature Ts within a secondary heating time, and determines whether to drain water.

For example, if the temperature of the primarily heated water is equal to or less than the third temperature, the control unit 72 performs secondary heating washing to heat the water up to the target temperature by driving the washing motor 14 and the heater 30 again after draining water down to a first water level (low water level).

On the other hand, if the temperature of the primarily heated water is greater than the third temperature, the control unit 72 performs secondary heating washing to heat the water up to the target temperature Ts by driving the washing motor 14 and the heater 30 again while maintaining the second water level of the primarily heated water without draining the water.

Thus, the control unit 72 performs a boiling course process to increase the washing effect by determining whether to drain water according to the water temperature after heating the primarily heated water for boiling washing, and maintaining the amount of the primarily heated water without unconditionally draining the water.

The memory 74 may store control data for controlling the operation of the washing machine 1, reference data used during the control of the operation of the washing machine 1, operation data generated while the washing machine 1 performs a predetermined operation, setting information such as setting data inputted via the input unit 70 to enable the washing machine 1 to perform a predetermined operation, use information including the number of times the washing machine 1 performs a specific operation and model information of the washing machine 1, and failure information including the cause or location of the malfunction when the washing machine 1 malfunctions.

The driving unit 76 drives the washing motor 14, the drain motor 22, the heater 30, the first water supply valve 53, the second water supply valve 54 and the like relating to the operation of the washing machine 1 according to a driving control signal of the control unit 72.

The display unit 78 displays the operating state of the washing machine 1 and the operation status of the user according to a display control signal of the control unit 72.

Hereinafter, an operation process and operational effects of the washing machine and control method thereof according to the embodiment of the present disclosure will be described.

When the user intends to wash baby clothes and underwear, the user desires to perform boiling washing such that bacteria in the laundry may be sterilized while removing stains and odors from the laundry. Accordingly, in the present disclosure, a boiling washing course capable of further increasing the washing effect compared to conventional cases while satisfying user demands will be described with reference to FIGS. 3 to 7.

FIG. 3 is a diagram showing the water levels of the washing machine according to the embodiment of the present disclosure.

In FIG. 3, the levels of water supplied into the tub 11 are represented as three water levels. The first water level is the lowest water level of 12 L, the second water level is the middle water level of 18 L, and the third water level is the highest water level of 27 L.

FIGS. 4A and 4B illustrate an operation flowchart showing a first control algorithm for boiling washing in the washing machine according to the embodiment of the present disclosure.

Referring to FIGS. 4A and 4B, if the user loads the laundry (specifically, baby clothes) into the washing tub 12 and selects the boiling course button 71 provided in the input unit 70 (operation 100), the operation information selected by the user is inputted to the control unit 72 through the input unit 70.

Accordingly, the control unit 72 operates the first water supply valve 53 or the second water supply valve 54 through the driving unit 76 in order to supply water (washing water) required for the boiling washing process. In this case, the operation of the first water supply valve 53 or the second water supply valve 54 varies according to the water supply of hot water or cold water selected by the user.

For example, the first water supply valve 53 is operated if the user selects hot water, and the second water supply valve 54 is operated if the user selects cold water. If the user selects hot and cold water, the first water supply valve 53 and the second water supply valve 54 are operated.

If the first water supply valve 53 or the second water supply valve 54 is operated, the first water supply valve 53 or the second water supply valve 54 is opened, and the water (washing water) supplied through the external water supply pipe passes through the first water supply pipe 51 or the second water supply pipe 52 and the detergent box 48 and is supplied into the tub 11 together with the detergent (operation 102).

Accordingly, the control unit 72 detects the level of the water supplied into the tub 11 through the water level sensor 34 and determines whether the water level is the second water level (middle water level when the water levels in the washing machine are divided into three water levels; about 18 L) shown in FIG. 3 (operation 104). The control unit 72 continues a water supply operation until the level of the water supplied into the tub 11 reaches the second water level.

If the level of the water supplied into the tub 11 reaches the second water level through the water supply operation, the control unit 72 stops the water supply operation by stopping the first water supply valve 53 or the second water supply valve 54.

Upon completion of the water supply up to the second water level, the control unit 72 detects the temperature (water temperature T) of the water in the tub 11 through the temperature sensor 32 (operation 106).

The control unit 72 determines whether the water temperature T detected through the temperature sensor 32 is greater than 0° C. (T0) and equal to or less than a first temperature T1 (about 10° C.) (operation 108).

As the determination result of operation 108, if it is determined that the water temperature T is greater than 0° C. (T0) and equal to or less than the first temperature T1 (about 10° C.), the control unit 72 determines that the water temperature T is a water temperature in winter, and performs the primary heating washing by driving the washing motor 14 and the heater 30 (operation 110).

In this case, the control unit 72 determines, as a first time period (about 25 minutes), a time period during which the water must be heated to determine whether to drain water after the primary heating washing under the winter water temperature conditions. Then, the control unit 72 counts the time passed since the start of the primary heating washing, and determines whether the predetermined first time period (about 25 minutes) has elapsed (operation 112).

As the determination result of operation 112, if the first time period has not elapsed, the control unit 72 returns to operation 110, and performs the primary heating washing until the first time period has elapsed.

On the other hand, as the determination result of operation 112, if the first time period has elapsed, the control unit 72 stops the primary heating washing by stopping the washing motor 14 and the heater 30 (operation 114).

On the other hand, as the determination result of operation 108, if it is not determined that the water temperature T is greater than 0° C. (T0) and equal to or less than the first temperature T1 (about 10° C.), the control unit 72 determines whether the water temperature T detected through the temperature sensor 32 is greater than the first temperature T1 (about 10° C.) and equal to or less than a second temperature T2 (about 20° C.) (operation 140).

As the determination result of operation 140, if it is determined that the water temperature T is greater than the first temperature T1 (about 10° C.) and equal to or less than the second temperature T2 (about 20° C.), the control unit 72 determines that the water temperature T is a water temperature in spring/fall, and performs the primary heating washing by driving the washing motor 14 and the heater 30 (operation 142).

In this case, the control unit 72 determines, as a second time period (about 20 minutes), a time period during which the water must be heated to determine whether to drain water after the primary heating washing under the spring/fall water temperature conditions. Then, the control unit 72 counts the time passed since the start of the primary heating washing, and determines whether the predetermined second time period (about 20 minutes) has elapsed (operation 144).

As the determination result of operation 144, if the second time period has not elapsed, the control unit 72 returns to operation 142, and performs the primary heating washing until the second time period has elapsed.

On the other hand, as the determination result of operation 144, if the second time period has elapsed, the control unit 72 proceeds to operation 114 and stops the primary heating washing by stopping the washing motor 14 and the heater 30.

On the other hand, as the determination result of operation 140, if it is not determined that the water temperature T is greater than the first temperature T1 (about 10° C.) and equal to or less than the second temperature T2 (about 20° C.), the control unit 72 determines whether the water temperature T detected through the temperature sensor 32 is greater than the second temperature T2 (about 20° C.) (operation 150).

As the determination result of operation 150, if it is determined that the water temperature T is greater than the second temperature T2 (about 20° C.), the control unit 72 determines that the water temperature T is a water temperature in summer, and performs the primary heating washing by driving the washing motor 14 and the heater 30 (operation 152).

In this case, the control unit 72 determines, as a third time period (about 15 minutes), a time period during which the water must be heated to determine whether to drain water after the primary heating washing under the summer water temperature conditions. Then, the control unit 72 counts the time passed since the start of the primary heating washing, and determines whether the predetermined third time period (about 15 minutes) has elapsed (operation 154).

As the determination result of operation 154, if the third time period has not elapsed, the control unit 72 returns to operation 152, and performs the primary heating washing until the third time period has elapsed.

On the other hand, as the determination result of operation 154, if the third time period has elapsed, the control unit 72 proceeds to operation 114 and stops the primary heating washing by stopping the washing motor 14 and the heater 30.

Thus, the primary heating washing is performed to heat the water for the first time period, the second time period, or the third time period according to the temperature of the primarily heated water. Then, after the primary heating washing, whether to drain water is determined according to the water temperature.

Accordingly, the control unit 72 detects the water temperature T of the primarily heated water through the temperature sensor 32 in order to determine whether to drain water according to the temperature of the primarily heated water, and determines whether the detected water temperature T is equal to or less than a predetermined third temperature T3 (water temperature which may reach the target temperature within the secondary heating time; about 45° C.) (operation 116).

As the determination result of operation 116, if the water temperature T is equal to or less than the third temperature T3 (about 45° C.), the control unit 72 determines that the temperature of the primarily heated water is not a water temperature which may reach the target temperature Ts within the second heating time (about 35 minutes), and operates the drain motor 22 to drain the primarily heated water (washing water) (operation 118).

Accordingly, the control unit 72 detects the level of the water remaining in the tub 11 according to the drain operation through the water level sensor 34, determines whether the water level is the first water level (the lowest water level when the water levels in the washing machine are divided into three water levels; about 12 L) shown in FIG. 3 (operation 120), and continues the drain operation until the water level reaches the first water level.

When the level of the water remaining in the tub 11 through the drain operation reaches the first water level, the control unit 72 stops the drain operation of the drain motor 22.

Subsequently, the control unit 72 drives the washing motor 14 and the heater 30 again and performs secondary heating washing to heat the water up to the target temperature Ts (final target temperature capable of providing a boiling effect; about 90° C.) (operation 122).

On the other hand, as the determination result of operation 116, if the water temperature T is greater than the third temperature T3 (about 45° C.), the control unit 72 determines that the temperature of the primarily heated water is a water temperature which may reach the target temperature Ts within the second heating time (about 35 minutes), and does not drain the primarily heated water.

Accordingly, the control unit 72 proceeds to operation 122 while maintaining the second water level of the primarily heated water, and performs the secondary heating washing to heat the water up to the target temperature Ts by driving the washing motor 14 and the heater 30 again.

Thus, if the water temperature increases according to the secondary heating washing, the control unit 72 detects the water temperature T of the secondarily heated water through the temperature sensor 32, and determines whether the detected water temperature T is equal to or greater than the predetermined target temperature Ts (operation 124).

As the determination result of operation 124, if the water temperature T is less than the target temperature Ts, the control unit 72 returns to operation 122, and continues the secondary heating washing until the water temperature T reaches the target temperature Ts.

On the other hand, as the determination result of operation 124, if the water temperature T is equal to or greater than the target temperature Ts, the control unit 72 stops the secondary heating washing by stopping the washing motor 14 and the heater 30 (operation 125).

Then, the control unit 72 performs washing by using high-temperature water (washing water) after the water temperature T reaches the target temperature Ts (operation 126). In this case, washing is performed for a set time using high-temperature water without additional consumption of electricity by driving only the washing motor 14 without driving the heater 30, thereby providing a more or less boiling washing effect.

The control unit 72 counts the washing progress time in the state of the first water level (or second water level) in which cold water is not supplied after the water temperature T reaches the target temperature Ts, and determines whether a fifth time period (time period during which washing is additionally performed after the water temperature T reaches the target temperature Ts to increase the washing effect, about 10 to 15 minutes) has elapsed (operation 128).

As the determination result of operation 128, if the fifth time period has not elapsed, the control unit 72 returns to operation 126, and performs the subsequent operations.

On the other hand, as the determination result of operation 128, if the fifth time period has elapsed, the control unit 72 operates the second water supply valve 54 to supply cold water (operation 130). When high-temperature water is drained after the boiling washing is completed, there is a possibility that the user may get burned. Taking this possibility into consideration, a cooling process is performed by supplying cold water in the final stage of the boiling washing.

Thus, the control unit 72 detects the water level, at which cold water is supplied into the tub 11, through the water level sensor 34, and determines whether the water level is the third water level (the highest water level when the water levels in the washing machine are divided into three water levels; about 27 L) shown in FIG. 3 (operation 132). Then, the control unit 72 continues a water supply operation until the level of the water supplied into the tub 11 reaches the third water level. That is, in order to reduce the temperature of the water to a temperature (about 55 to 60° C.) suitable for drainage at which there is no risk of burns when water is drained after the boiling washing, cold water is supplied up to the third water level.

If the level of the water supplied into the tub 11 reaches the third water level through the water supply operation, the control unit 72 stops the cold water supply operation by closing the second water supply valve 54.

Upon completion of the supply of cold water up to the third water level, the control unit 72 performs a separate cooling process by driving the washing motor 14 for a set time (about 2 minutes) (operation 134), and completes the washing process.

Meanwhile, in the embodiment of the present disclosure, a case of performing washing for a set time (about 10 to 15 minutes) using high-temperature water by driving only the washing motor 14 without driving the heater 30 after the water temperature T reaches the target temperature Ts has been described as an example, but the present disclosure is not limited thereto. That is, washing may be performed for a set time while maintaining the target temperature Ts by driving the heater 30 as well as the washing motor 14.

Next, a method of providing a cooling effect while performing the washing for the remaining time by supplying cold water after the water temperature T reaches the target temperature Ts will be described with reference to FIGS. 5A and 5B.

FIGS. 5A and 5B illustrate an operation flowchart showing a second control algorithm for boiling washing in the washing machine according to the embodiment of the present disclosure. A repeated description of the same configurations as those of FIGS. 4A and 4B will be omitted.

Referring to FIGS. 5A and 5B, if the user loads the laundry (specifically, baby clothes) into the washing tub 12 and selects the boiling course button 71 provided in the input unit 70 (operation 200), the operation information selected by the user is inputted to the control unit 72 through the input unit 70.

Accordingly, the control unit 72 operates the first water supply valve 53 or the second water supply valve 54 through the driving unit 76 in order to supply water (washing water) required for the boiling washing process.

If the first water supply valve 53 or the second water supply valve 54 is operated, the first water supply valve 53 or the second water supply valve 54 is opened, and the water (washing water) supplied through the external water supply pipe passes through the first water supply pipe 51 or the second water supply pipe 52 and the detergent box 48 and is supplied into the tub 11 together with the detergent (operation 202).

Accordingly, the control unit 72 detects the level of the water supplied into the tub 11 through the water level sensor 34 and determines whether the water level is the second water level (operation 204). The control unit 72 continues a water supply operation until the level of the water supplied into the tub 11 reaches the second water level.

Upon completion of the water supply up to the second water level, the control unit 72 detects the temperature (water temperature T) of the water in the tub 11 through the temperature sensor 32 (operation 206).

The control unit 72 determines whether the water temperature T detected through the temperature sensor 32 is greater than 0° C. (T0) and equal to or less than a first temperature T1 (about 10° C.) (operation 208).

As the determination result of operation 208, if it is determined that the water temperature T is greater than 0° C. (T0) and equal to or less than the first temperature T1 (about 10° C.), the control unit 72 determines that the water temperature T is a water temperature in winter, and performs the primary heating washing by driving the washing motor 14 and the heater 30 (operation 210).

Then, the control unit 72 counts the time passed since the start of the primary heating washing, and determines whether a predetermined first time period (about 25 minutes) has elapsed (operation 212).

As the determination result of operation 212, if the first time period has not elapsed, the control unit 72 performs the primary heating washing until the first time period has elapsed.

On the other hand, as the determination result of operation 212, if the first time period has elapsed, the control unit 72 stops the primary heating washing by stopping the washing motor 14 and the heater 30 (operation 214).

On the other hand, as the determination result of operation 208, if it is not determined that the water temperature T is greater than 0° C. (T0) and equal to or less than the first temperature T1 (about 10° C.), the control unit 72 determines whether the water temperature T detected through the temperature sensor 32 is greater than the first temperature T1 (about 10° C.) and equal to or less than a second temperature T2 (about 20° C.) (operation 240).

As the determination result of operation 240, if it is determined that the water temperature T is greater than the first temperature T1 (about 10° C.) and equal to or less than the second temperature T2 (about 20° C.), the control unit 72 determines that the water temperature T is a water temperature in spring/fall, and performs the primary heating washing by driving the washing motor 14 and the heater 30 (operation 242).

In this case, the control unit 72 determines, as a second time period (about 20 minutes), a time period during which the water must be heated to determine whether to drain water after the primary heating washing under the spring/fall water temperature conditions. Then, the control unit 72 counts the time passed since the start of the primary heating washing, and determines whether the predetermined second time period (about 20 minutes) has elapsed (operation 244).

As the determination result of operation 244, if the second time period has not elapsed, the control unit 72 performs the primary heating washing until the second time period has elapsed.

On the other hand, as the determination result of operation 244, if the second time period has elapsed, the control unit 72 proceeds to operation 214 and stops the primary heating washing by stopping the washing motor 14 and the heater 30.

On the other hand, as the determination result of operation 240, if it is not determined that the water temperature T is greater than the first temperature T1 (about 10° C.) and equal to or less than the second temperature T2 (about 20° C.), the control unit 72 determines whether the water temperature T detected through the temperature sensor 32 is greater than the second temperature T2 (about 20° C.) (operation 250).

As the determination result of operation 250, if it is determined that the water temperature T is greater than the second temperature T2 (about 20° C.), the control unit 72 determines that the water temperature T is a water temperature in summer, and performs the primary heating washing by driving the washing motor 14 and the heater 30 (operation 252).

In this case, the control unit 72 determines, as a third time period (about 15 minutes), a time period during which the water must be heated to determine whether to drain water after the primary heating washing under the summer water temperature conditions. Then, the control unit 72 counts the time passed since the start of the primary heating washing, and determines whether the predetermined third time period (about 15 minutes) has elapsed (operation 254).

As the determination result of operation 254, if the third time period has not elapsed, the control unit 72 returns to operation 152, and performs the primary heating washing until the third time period has elapsed.

On the other hand, as the determination result of operation 254, if the third time period has elapsed, the control unit 72 proceeds to operation 214 and stops the primary heating washing by stopping the washing motor 14 and the heater 30.

Thus, the primary heating washing is performed to heat the water for the first time period, the second time period, or the third time period according to the temperature of the primarily heated water. Then, after the primary heating washing, whether to drain water is determined according to the water temperature.

Accordingly, the control unit 72 detects the water temperature T of the primarily heated water through the temperature sensor 32 in order to determine whether to drain water according to the temperature of the primarily heated water, and determines whether the detected water temperature T is equal to or less than a predetermined third temperature T3 (about 45° C.) (operation 216).

As the determination result of operation 216, if the water temperature T is equal to or less than the third temperature T3 (about 45° C.), the control unit 72 determines that the temperature of the primarily heated water is not a water temperature which may reach the target temperature Ts within the second heating time (about 35 minutes), and operates the drain motor 22 to drain the primarily heated water (washing water) (operation 218).

Accordingly, the control unit 72 detects the level of the water remaining in the tub 11 according to the drain operation through the water level sensor 34, determines whether the water level is the first water level (operation 220), and continues the drain operation until the water level reaches the first water level.

When the level of the water remaining in the tub 11 through the drain operation reaches the first water level, the control unit 72 drives the washing motor 14 and the heater 30 again and performs secondary heating washing to heat the water up to the target temperature Ts (about 90° C.) (operation 222).

On the other hand, as the determination result of operation 216, if the water temperature T is greater than the third temperature T3 (about 45° C.), the control unit 72 determines that the temperature of the primarily heated water is a water temperature which may reach the target temperature Ts within the second heating time (about 35 minutes), and does not drain the primarily heated water.

Accordingly, the control unit 72 proceeds to operation 222 while maintaining the second water level of the primarily heated water, and performs the secondary heating washing to heat the water up to the target temperature Ts by driving the washing motor 14 and the heater 30 again.

Thus, if the water temperature increases according to the secondary heating washing, the control unit 72 detects the water temperature T of the secondarily heated water using the temperature sensor 32, and determines whether the detected water temperature T is equal to or greater than the predetermined target temperature Ts (operation 224).

As the determination result of operation 224, if the water temperature T is less than the target temperature Ts, the control unit 72 returns to operation 222, and continues the secondary heating washing until the water temperature T reaches the target temperature Ts.

On the other hand, as the determination result of operation 224, if the water temperature T is equal to or greater than the target temperature Ts, the control unit 72 stops the secondary heating washing by stopping the washing motor 14 and the heater 30 (operation 225).

If the water temperature T reaches the target temperature Ts, the control unit 72 operates the second water supply valve 54 to supply cold water (operation 226). When high-temperature water is drained after the boiling washing is completed, there is a possibility that the user may get burned. Taking this possibility into consideration, a cooling process is performed by supplying cold water in the final stage of the boiling washing

Thus, the control unit 72 detects the water level, at which cold water is supplied into the tub 11, through the water level sensor 34, and determines whether the water level is the third water level (operation 228). Then, the control unit 72 continues a water supply operation until the level of the water supplied into the tub 11 reaches the third water level.

Upon completion of the supply of cold water up to the third water level, the control unit 72 performs the process to provide a washing and cooling effect by driving the washing motor 14 for the remaining time (about 10 to 15 minutes) (operation 230), and completes the washing process.

Next, a method of performing a separate cooling process by supplying cold water after washing is performed for a set time after the water temperature T reaches the target temperature Ts will be described with reference to FIGS. 6A and 6B.

FIGS. 6A and 6B illustrate an operation flowchart showing a third control algorithm for boiling washing in the washing machine according to the embodiment of the present disclosure. A repeated description of the same configuration as that of FIGS. 4A and 4B will be omitted.

Referring to FIGS. 6A and 6B, if the user loads the laundry (specifically, baby clothes) into the washing tub 12 and selects the boiling course button 71 provided in the input unit 70 (operation 300), the operation information selected by the user is inputted to the control unit 72 through the input unit 70.

Accordingly, the control unit 72 operates the first water supply valve 53 or the second water supply valve 54 through the driving unit 76 in order to supply water (washing water) required for the boiling washing process.

If the first water supply valve 53 or the second water supply valve 54 is operated, the first water supply valve 53 or the second water supply valve 54 is opened, and the water (washing water) supplied through the external water supply pipe passes through the first water supply pipe 51 or the second water supply pipe 52 and the detergent box 48 and is supplied into the tub 11 together with the detergent (operation 302).

Accordingly, the control unit 72 detects the level of the water supplied into the tub 11 through the water level sensor 34 and determines whether the water level is the second water level (operation 304). The control unit 72 continues a water supply operation until the level of the water supplied into the tub 11 reaches the second water level.

Upon completion of the water supply up to the second water level, the control unit 72 detects the temperature (water temperature T) of the water in the tub 11 through the temperature sensor 32 (operation 306).

The control unit 72 determines whether the water temperature T detected through the temperature sensor 32 is greater than 0° C. (T0) and equal to or less than a first temperature T1 (about 10° C.) (operation 308).

As the determination result of operation 308, if it is determined that the water temperature T is greater than 0° C. (T0) and equal to or less than the first temperature T1 (about 10° C.), the control unit 72 determines that the water temperature T is a water temperature in winter, and performs the primary heating washing by driving the washing motor 14 and the heater 30 (operation 310).

Then, the control unit 72 counts the time passed since the start of the primary heating washing, and determines whether a predetermined first time period (about 25 minutes) has elapsed (operation 312).

As the determination result of operation 312, if the first time period has elapsed, the control unit 72 stops the primary heating washing by stopping the washing motor 14 and the heater 30 (operation 314).

On the other hand, as the determination result of operation 308, if it is not determined that the water temperature T is greater than 0° C. (T0) and equal to or less than the first temperature T1 (about 10° C.), the control unit 72 determines whether the water temperature T detected through the temperature sensor 32 is greater than the first temperature T1 (about 10° C.) and equal to or less than a second temperature T2 (about 20° C.) (operation 340).

As the determination result of operation 340, if it is determined that the water temperature T is greater than the first temperature T1 (about 10° C.) and equal to or less than the second temperature T2 (about 20° C.), the control unit 72 determines that the water temperature T is a water temperature in spring/fall, and performs the primary heating washing by driving the washing motor 14 and the heater 30 (operation 342).

Then, the control unit 72 counts the time passed since the start of the primary heating washing, and determines whether a predetermined second time period (about 20 minutes) has elapsed (operation 344).

As the determination result of operation 344, if the second time period has elapsed, the control unit 72 proceeds to operation 314 and stops the primary heating washing by stopping the washing motor 14 and the heater 30.

On the other hand, as the determination result of operation 340, if it is not determined that the water temperature T is greater than the first temperature T1 (about 10° C.) and equal to or less than the second temperature T2 (about 20° C.), the control unit 72 determines whether the water temperature T detected through the temperature sensor 32 is greater than the second temperature T2 (about 20° C.) and equal to or less than a third temperature T3 (about 45° C.) (operation 350).

As the determination result of operation 350, if it is determined that the water temperature T is greater than the second temperature T2 (about 20° C.) and equal to or less than the third temperature T3 (about 45° C.), the control unit 72 determines that the water temperature T is a water temperature in summer, and performs the primary heating washing by driving the washing motor 14 and the heater 30 (operation 352).

Then, the control unit 72 counts the time passed since the start of the primary heating washing, and determines whether a predetermined third time period (about 15 minutes) has elapsed (operation 354).

As the determination result of operation 354, if the third time period has elapsed, the control unit 72 proceeds to operation 314 and stops the primary heating washing by stopping the washing motor 14 and the heater 30.

Thus, the primary heating washing is performed to heat the water for the first time period, the second time period, or the third time period according to the temperature of the primarily heated water. The control unit 72 determines that the temperature of the primarily heated water is not a water temperature which may reach the target temperature Ts within the second heating time (about 35 minutes), and operates the drain motor 22 to drain the primarily heated water (washing water) (operation 318).

Accordingly, the control unit 72 detects the level of the water remaining in the tub 11 according to the drain operation through the water level sensor 34, determines whether the water level is the first water level (operation 320), and continues the drain operation until the water level reaches the first water level.

Subsequently, the control unit 72 drives the washing motor 14 and the heater 30 again and performs secondary heating washing to heat the water up to the target temperature Ts (about 90° C.) (operation 322).

On the other hand, as the determination result of operation 150, if it is not determined that the water temperature T is greater than the second temperature T2 (about 20° C.) and equal to or less than the third temperature T3 (about 45° C.), the control unit 72 determines whether the water temperature T detected through the temperature sensor 32 is greater than the third temperature T3 (about 45° C.) (operation 360).

As the determination result of operation 360, if the water temperature T is greater than the third temperature T3 (about 20° C.), the control unit 72 determines that the water temperature T is a water temperature which may reach the target temperature Ts within the second heating time, and performs the primary heating washing by driving the washing motor 14 and the heater 30 (operation 362).

Then, the control unit 72 counts the time passed since the start of the primary heating washing, and determines whether a predetermined fourth time period (about 15 minutes) has elapsed (operation 364).

As the determination result of operation 364, if the fourth time period has elapsed, the control unit 72 proceeds to operation 366 and stops the primary heating washing by stopping the washing motor 14 and the heater 30.

Thus, the primary heating washing is performed to heat the water for the fourth time period according to the temperature of the primarily heated water. The control unit 72 determines that the temperature of the primarily heated water is a water temperature which may reach the target temperature Ts within the second heating time (about 35 minutes), and does not drain the primarily heated water.

Accordingly, the control unit 72 proceeds to operation 322 while maintaining the second water level of the primarily heated water, and performs the secondary heating washing to heat the water up to the target temperature Ts by driving the washing motor 14 and the heater 30 again.

Thus, if the water temperature increases according to the secondary heating washing, the control unit 72 detects the water temperature T of the secondarily heated water using the temperature sensor 32, and determines whether the detected water temperature T is equal to or greater than the predetermined target temperature Ts (operation 324).

As the determination result of operation 324, if the water temperature T is less than the target temperature Ts, the control unit 72 returns to operation 322, and continues the secondary heating washing until the water temperature T reaches the target temperature Ts.

On the other hand, as the determination result of operation 324, if the water temperature T is equal to or greater than the target temperature Ts, the control unit 72 stops the secondary heating washing by stopping the washing motor 14 and the heater 30 (operation 325).

Then, the control unit 72 performs washing by using high-temperature water (washing water) after the water temperature T reaches the target temperature Ts (operation 326). In this case, washing is performed for a set time using high-temperature water without additional consumption of electric energy by driving only the washing motor 14 without driving the heater 30, thereby providing a boiling washing effect to some extent.

The control unit 72 counts the washing progress time in the state of the first water level (or second water level) in which cold water is not supplied after the water temperature T reaches the target temperature Ts, and determines whether a fifth time period (time period during which washing is additionally performed after the water temperature T reaches the target temperature Ts to increase the washing effect, about 10 to 15 minutes) has elapsed (operation 328).

As the determination result of operation 328, if the fifth time period has not elapsed, the control unit 72 returns to operation 326, and performs subsequent operations.

On the other hand, as the determination result of operation 328, if the fifth time period has elapsed, the control unit 72 operates the second water supply valve 54 to supply cold water (operation 330). When high-temperature water is drained after the boiling washing is completed, there is a possibility that the user may get burned. Taking this possibility into consideration, a cooling process is performed by supplying cold water in the final stage of the boiling washing

Thus, the control unit 72 detects the water level, at which cold water is supplied into the tub 11, through the water level sensor 34, and determines whether the water level is the third water level (operation 332). Then, the control unit 72 continues a water supply operation until the level of the water supplied into the tub 11 reaches the third water level. That is, in order to reduce the temperature of the water to a temperature (about 55 to 60° C.) suitable for drainage at which there is no risk of burns when water is drained after the boiling washing, cold water is supplied up to the third water level.

Upon completion of the supply of cold water up to the third water level, the control unit 72 performs a separate cooling process by driving the washing motor 14 for a set time (about 2 minutes) (operation 334), and completes the washing process.

Next, a method of providing a cooling effect while performing the washing for the remaining time by supplying cold water after the water temperature T reaches the target temperature Ts will be described with reference to FIGS. 7A and 7B.

FIGS. 7A and 7B illustrate an operation flowchart showing a fourth control algorithm for boiling washing in the washing machine according to the embodiment of the present disclosure. A repeated description of the same configurations as those of FIGS. 6A and 6B will be omitted.

Referring to FIGS. 7A and 7B, if the user loads the laundry (specifically, baby clothes) into the washing tub 12 and selects the boiling course button 71 provided in the input unit 70 (operation 400), the operation information selected by the user is inputted to the control unit 72 through the input unit 70.

Accordingly, the control unit 72 operates the first water supply valve 53 or the second water supply valve 54 through the driving unit 76 in order to supply water (washing water) required for the boiling washing process.

If the first water supply valve 53 or the second water supply valve 54 is operated, the first water supply valve 53 or the second water supply valve 54 is opened, and the water (washing water) supplied through the external water supply pipe passes through the first water supply pipe 51 or the second water supply pipe 52 and the detergent box 48 and is supplied into the tub 11 together with the detergent (operation 402).

Accordingly, the control unit 72 detects the level of the water supplied into the tub 11 through the water level sensor 34 and determines whether the water level is the second water level (operation 404). The control unit 72 continues a water supply operation until the level of the water supplied into the tub 11 reaches the second water level.

Upon completion of the water supply up to the second water level, the control unit 72 detects the temperature (water temperature T) of the water in the tub 11 through the temperature sensor 32 (operation 406).

The control unit 72 determines whether the water temperature T detected through the temperature sensor 32 is greater than 0° C. (T0) and equal to or less than a first temperature T1 (about 10° C.) (operation 408).

As the determination result of operation 408, if it is determined that the water temperature T is greater than 0° C. (T0) and equal to or less than the first temperature T1 (about 10° C.), the control unit 72 determines that the water temperature T is a water temperature in winter, and performs the primary heating washing by driving the washing motor 14 and the heater 30 (operation 410).

Then, the control unit 72 counts the time passed since the start of the primary heating washing, and determines whether a predetermined first time period (about 25 minutes) has elapsed (operation 412).

As the determination result of operation 412, if the first time period has elapsed, the control unit 72 stops the primary heating washing by stopping the washing motor 14 and the heater 30 (operation 414).

On the other hand, as the determination result of operation 408, if it is not determined that the water temperature T is greater than 0° C. (T0) and equal to or less than the first temperature T1 (about 10° C.), the control unit 72 determines whether the water temperature T detected through the temperature sensor 32 is greater than the first temperature T1 (about 10° C.) and equal to or less than a second temperature T2 (about 20° C.) (operation 440).

As the determination result of operation 440, if it is determined that the water temperature T is greater than the first temperature T1 (about 10° C.) and equal to or less than the second temperature T2 (about 20° C.), the control unit 72 determines that the water temperature T is a water temperature in spring/fall, and performs the primary heating washing by driving the washing motor 14 and the heater 30 (operation 442).

Then, the control unit 72 counts the time passed since the start of the primary heating washing, and determines whether a predetermined second time period (about 20 minutes) has elapsed (operation 444).

As the determination result of operation 444, if the second time period has elapsed, the control unit 72 proceeds to operation 414 and stops the primary heating washing by stopping the washing motor 14 and the heater 30.

On the other hand, as the determination result of operation 440, if it is not determined that the water temperature T is greater than the first temperature T1 (about 10° C.) and equal to or less than the second temperature T2 (about 20° C.), the control unit 72 determines whether the water temperature T detected through the temperature sensor 32 is greater than the second temperature T2 (about 20° C.) and equal to or less than a third temperature T3 (about 45° C.) (operation 450).

As the determination result of operation 450, if it is determined that the water temperature T is greater than the second temperature T2 (about 20° C.) and equal to or less than the third temperature T3 (about 45° C.), the control unit 72 determines that the water temperature T is a water temperature in summer, and performs the primary heating washing by driving the washing motor 14 and the heater 30 (operation 452).

Then, the control unit 72 counts the time passed since the start of the primary heating washing, and determines whether a predetermined third time period (about 15 minutes) has elapsed (operation 454).

As the determination result of operation 454, if the third time period has elapsed, the control unit 72 proceeds to operation 414 and stops the primary heating washing by stopping the washing motor 14 and the heater 30.

Thus, the primary heating washing is performed to heat the water for the first time period, the second time period, or the third time period according to the temperature of the primarily heated water. The control unit 72 determines that the temperature of the primarily heated water is not a water temperature which may reach the target temperature Ts within the second heating time (about 35 minutes), and operates the drain motor 22 to drain the primarily heated water (washing water) (operation 418).

Accordingly, the control unit 72 detects the level of the water remaining in the tub 11 according to the drain operation through the water level sensor 34, determines whether the water level is the first water level (operation 420), and continues the drain operation until the water level reaches the first water level.

Subsequently, the control unit 72 drives the washing motor 14 and the heater 30 again and performs secondary heating washing to heat the water up to the target temperature Ts (about 90° C.) (operation 422).

On the other hand, as the determination result of operation 450, if it is not determined that the water temperature T is greater than the second temperature T2 (about 20° C.) and equal to or less than the third temperature T3 (about 45° C.), the control unit 72 determines whether the water temperature T detected through the temperature sensor 32 is greater than the third temperature T3 (about 45° C.) (operation 460).

As the determination result of operation 460, if the water temperature T is greater than the third temperature T3 (about 20° C.), the control unit 72 determines that the water temperature T is a water temperature which may reach the target temperature Ts within the second heating time, and performs the primary heating washing by driving the washing motor 14 and the heater 30 (operation 462).

Then, the control unit 72 counts the time passed since the start of the primary heating washing, and determines whether a predetermined fourth time period (about 15 minutes) has elapsed (operation 464).

As the determination result of operation 464, if the fourth time period has elapsed, the control unit 72 stops the primary heating washing by stopping the washing motor 14 and the heater 30 (operation 466).

Thus, the primary heating washing is performed to heat the water for the fourth time period according to the temperature of the primarily heated water. The control unit 72 determines that the temperature of the primarily heated water is a water temperature which may reach the target temperature Ts within the second heating time (about 35 minutes), and does not drain the primarily heated water.

Accordingly, the control unit 72 proceeds to operation 422 while maintaining the second water level of the primarily heated water, and performs the secondary heating washing to heat the water up to the target temperature Ts by driving the washing motor 14 and the heater 30 again.

Thus, if the water temperature increases according to the secondary heating washing, the control unit 72 detects the water temperature T of the secondarily heated water through the temperature sensor 32, and determines whether the detected water temperature T is equal to or greater than the predetermined target temperature Ts (operation 424).

As the determination result of operation 424, if the water temperature T is less than the target temperature Ts, the control unit 72 returns to operation 422, and continues the secondary heating washing until the water temperature T reaches the target temperature Ts.

On the other hand, as the determination result of operation 424, if the water temperature T is equal to or greater than the target temperature Ts, the control unit 72 stops the secondary heating washing by stopping the washing motor 14 and the heater 30 (operation 425).

If the water temperature T reaches the target temperature Ts, the control unit 72 operates the second water supply valve 54 to supply cold water (operation 426). When high-temperature water is drained after the boiling washing is completed, there is a possibility that the user may get burned. Taking this possibility into consideration, a cooling process is performed by supplying cold water in the final stage of the boiling washing.

Thus, the control unit 72 detects the water level, at which cold water is supplied into the tub 11, through the water level sensor 34, and determines whether the water level is the third water level (operation 428). Then, the control unit 72 continues a water supply operation until the level of the water supplied into the tub 11 reaches the third water level.

Upon completion of the supply of cold water up to the third water level, the control unit 72 performs the process to provide a washing and cooling effect by driving the washing motor 14 for the remaining time (about 10 to 15 minutes) (operation 430), and completes the washing process.

Although, in the embodiment of the present disclosure, a case of setting the target temperature Ts to 90° C. has been described as an example, the present disclosure is not limited thereto. That is, even if the target temperature Ts is set to equal to or greater than 70° C. at which the sterilizing effect begins to appear, the same object and effect as those of the present disclosure may be achieved.

Although a few embodiments of the present disclosure have been shown and described, it would be appreciated by those skilled in the art that changes may be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the claims and their equivalents.

Claims

1. A control method of a washing machine including a tub to accommodate water and a heater installed inside the tub to heat the water, the method comprising:

determining whether a currently washing course is a boiling washing course;

supplying water into the tub if the currently washing course is the boiling washing course;

performing primary heating washing to heat the supplied water for a predetermined time;

detecting a temperature of the primarily heated water; and

controlling a level of water in the tub for secondary heating washing according to the detected temperature of the water,

wherein the controlling the water level comprises varying the level of water in the tub according to the temperature of the primarily heated water.

2. The control method according to claim 1, wherein the controlling the water level comprises:

comparing the temperature of the primarily heated water with a set temperature; and

maintaining a current water level without draining the primarily heated water if the temperature of the primarily heated water is greater than the set temperature.

3. The control method according to claim 2, wherein if the temperature of the primarily heated water is equal to or less than the set temperature, the primarily heated water is drained to lower the water level.

4. The control method according to claim 3, wherein the supplying the water into the tub comprises supplying water up to a predetermined water level for the boiling washing course.

5. The control method according to claim 4, wherein the supplied water is cold water or hot water.

6. The control method according to claim 4, wherein the performing the primary heating washing comprises:

detecting a temperature of the water supplied into the tub;

determining a primary heating time according to the detected temperature of the water; and

driving the heater according to the determined primary heating time.

7. The control method according to claim 4, wherein the draining the water comprises draining the water down to a water level lower by one level than the predetermined water level.

8. The control method according to claim 4, further comprising performing secondary heating washing to heat the primarily heated water up to a target temperature after controlling the water level.

9. The control method according to claim 8, wherein the set temperature is a temperature of the water supplied up to the predetermined water level, which may reach the target temperature within a secondary heating time.

10. The control method according to claim 9, wherein the set temperature is about 45° C.

11. The control method according to claim 9, wherein the target temperature is equal to or greater than 70° C. which may provide a boiling effect.

12. The control method according to claim 8, further comprising performing washing for a set time after the secondary heating washing.

13. The control method according to claim 12, further comprising performing a cooling process by supplying cold water after performing the washing.

14. The control method according to claim 8, further comprising performing a washing and cooling process by supplying cold water after performing the secondary heating washing.

15. A control method of a washing machine including a tub to accommodate water and a heater installed inside the tub to heat the water, the method comprising:

determining whether a currently washing course is a boiling washing course;

supplying water into the tub if the currently washing course is the boiling washing course;

detecting a temperature of the supplied water;

determining a primary heating time according to the detected temperature of the water;

performing primary heating washing by driving the heater according to the determined primary heating time; and

controlling a level of water in the tub for secondary heating washing according to the detected temperature of the water,

wherein the controlling the water level comprises varying the level of water in the tub according to the temperature of the supplied water.

16. The control method according to claim 15, wherein the controlling the water level comprises:

comparing the temperature of the supplied water with a set temperature; and

maintaining a current water level without draining the primarily heated water if the temperature of the supplied water is greater than the set temperature.

17. The control method according to claim 15, wherein the controlling the water level comprises:

comparing the temperature of the supplied water with a set temperature; and

lowering the water level by draining the primarily heated water if the temperature of the supplied water is equal to or less than the set temperature.

18. The control method according to claim 15, further comprising, after controlling the water level, performing secondary heating washing to heat the primarily heated water up to a target temperature.

19. A washing machine comprising:

a tub to accommodate water;

a heater installed inside the tub to heat the water;

an input unit through which a boiling washing course is selected;

a control unit to, if the boiling washing course is selected, perform primary heating washing for a predetermined time after supplying water into the tub, detect a temperature of the primarily heated water, and control a level of water in the tub for secondary heating washing,

wherein the control unit varies the level of water in the tub according to the temperature of the primarily heated water.

20. The washing machine according to claim 19, wherein the control unit compares the temperature of the supplied water with a set temperature, and maintains a current water level without draining the primarily heated water if the temperature of the supplied water is greater than the set temperature.

21. The washing machine according to claim 19, wherein the control unit compares the temperature of the supplied water with a set temperature, and lowers the water level by draining the primarily heated water if the temperature of the supplied water is equal to or less than the set temperature.

22. The washing machine according to claim 19, wherein the control unit determines a primary heating time by detecting a temperature of the water supplied into the tub, and performs primary heating washing by driving the heater according to the determined primary heating time.

23. The washing machine according to claim 19, wherein after controlling the water level, the control unit performs secondary heating washing to heat the primarily heated water up to a target temperature.

24. The washing machine according to claim 23, wherein the control unit additionally performs washing for a set time after the secondary heating washing.

25. The washing machine according to claim 24, wherein the control unit performs a cooling process by supplying cold water after the washing.

26. The washing machine according to claim 23, wherein the control unit performs a washing and cooling process by supplying cold water after the secondary heating washing.

27. A washing machine comprising:

a tub to accommodate water;

a heater installed inside the tub to heat the water;

an input unit through which a boiling washing course is selected;

a control unit to, if the boiling washing course is selected, supply water into the tub, detect a temperature of the supplied water, perform primary heating washing to drive the heater for a primary heating time determined according to the detected temperature of the water, and control a level of water in the tub for secondary heating washing according to the detected temperature of the water,

wherein the control unit varies the level of water in the tub according to the temperature of the supplied water.

28. The washing machine according to claim 27, wherein the control unit compares the temperature of the supplied water with a set temperature, and maintains a current water level without draining the primarily heated water if the temperature of the supplied water is greater than the set temperature.

29. The washing machine according to claim 27, wherein the control unit compares the temperature of the supplied water with a set temperature, and lowers the water level by draining the primarily heated water if the temperature of the supplied water is equal to or less than the set temperature.