WASHING MACHINE AND A METHOD OF CONTROLLING THE SAME

Abstract

Provided are a washing machine and a method of controlling the washing machine. The method includes measuring a time required for an amount of washing water supplied to a washing tub to reach a predetermined reference amount, determining a water pressure of the washing water in accordance with the measured time, and varying a water supply time in accordance with the determined water pressure. The water supply time can be adjusted according to the water pressure, it can be prevented that the washing performance is varied whenever the wash water is varied. Thus, the washing performance can be improved regardless of the water pressure.

Description

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority from Korean Patent Application No. 10-2009-0118525 filed on Dec. 2, 2009 in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a washing machine and a method of controlling the same, and more particularly, to a washing machine and a method of controlling the same, which can prevent washing performance from varying in accordance with a water pressure at a place where the washing machine is disposed.

2. Description of the Related Art

In general, a washing machine is a machine that removes foreign substances from laundry by treating the laundry.

A process for treating the laundry by the washing machine includes a process for washing the laundry using washing water in which detergent is dissolved, a process for rinsing the laundry by supplying the washing water, which does not contain the detergent, from an outer side to a washing tub, and a process for removing the washing water out of the laundry that is washed. The process for treating the laundry may further include a process for drying the laundry and a process for discharging the laundry after ironing the laundry. However, the process for treating the laundry includes a detergent mixing process, a washing process, a rinsing process, and a spinning process for removing the water out of the laundry.

All of the detergent mixing process, washing process, rinsing process, and spinning process require a process for wetting the laundry by supplying the washing water into the washing tub. Generally, the washing water is supplied in a direction from a cover side toward the washing tub to wet the laundry.

However, when wetting the laundry by supplying the washing water in the direction from the cover side toward the washing tub, it is difficult to evenly wet the laundry in the washing tub. In order to overcome this limitation, a nozzle method for spraying high-pressured washing water from the cover side using a nozzle has been proposed. The nozzle method evenly wets the laundry by spraying the washing water to the laundry through a narrow water outlet. However, when spraying the washing water through the nozzle, an amount of the washing water supplied into the washing tub varies in accordance with an intensity of the pressure applied to the nozzle and thus an amount of the washing water sprayed to the laundry varies. That is, water pressure of a place where the washing machine is installed is not considered.

In addition, when the water pressure of the washing water is high, the washing water sprayed through the nozzle is not directed toward the laundry but scattered toward an inner surface of the washing tub. When the water pressure of the washing water is low, the washing water may not be properly sprayed through the nozzle.

Accordingly, a method for constantly maintaining washing performance by adjusting an amount of the washing water sprayed from the nozzle and a spraying time considering the water pressure of the place where the washing machine is installed is required.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a washing machine and a method of controlling the same, which determine a time for which washing water is sprayed into a washing tub in accordance with water pressure of a place where the washing machine is disposed.

According to an aspect of the present invention, a method of controlling a washing machine includes measuring a time required for an amount of washing water supplied to a washing tub to reach a predetermined reference amount; determining a water pressure of the washing water in accordance with the measured time; and varying a water supply time in accordance with the determined water pressure.

According to another aspect of the present invention, a method of controlling a washing machine includes filling washing water by a predetermined reference amount; measuring a time required for the washing water to be filled; determining water pressure of the washing water in accordance with the measured time; determining a spraying time of the washing water in accordance with the determined water pressure; perform a wash cycle by spraying the washing water for the determined spraying time; and perform a rinse cycle by spraying the washing water for the determined spraying time.

According to still another aspect of the present invention, a washing machine includes a memory including a reference table storing data on a time required for washing water to be filled in a washing tub by a predetermined reference amount and a water pressure determined according to the time; and a control unit for determining the water pressure of the washing water with reference to the reference table and varying a spraying time of the washing time sprayed into the washing tub in accordance with the determined water pressure.

According to the aspects of the present invention, since the time for spraying the washing water is properly adjusted in accordance with a water pressure of the washing water supplied to the washing machine, it is possible to sufficiently wet the laundry even when the water pressure of the washing water is lowered, thereby providing a proper washing state for the laundry.

BRIEF DESCRIPTION OF THE DRAWINGS

The features and advantages of the present invention will become more apparent from reading the Detailed Description of the Invention which makes reference to the attached drawings in which:

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

FIG. 2 is a reference view illustrating a method of controlling the washing machine of FIG. 1;

FIG. 3 is a reference view illustrating a control flow of the washing machine according to an embodiment of the present invention;

FIG. 4 is a reference view illustrating an example of the spray-time table stored in the memory;

FIG. 5 is a flowchart illustrating a method of controlling the washing machine according to an embodiment of the present invention;

FIG. 6 is a reference view illustrating an example of a method of detecting a laundry load;

FIG. 7 is a reference view illustrating an example of a spraying unit formed between a cover and a case; and

FIG. 8 is a reference view illustrating a method of controlling a washing machine according to another embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The invention is described more fully hereinafter with reference to the accompanying drawings, in which exemplary embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the exemplary embodiments set forth herein. Rather, these exemplary embodiments are provided so that this disclosure is thorough, and will fully convey the scope of the invention to those skilled in the art. Like reference numerals in the drawings denote like elements.

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

Referring to FIG. 1, a washing machine includes a cabinet 10, a top cover 200 that is disposed above the cabinet 10 and provided with a laundry loading/unloading opening which the laundry can be loaded and unloaded, a lid assembly 100 that is rotatably coupled to the top cover to open and close the laundry loading/unloading opening, and a control panel that provides an interface so that a user can manipulate the washing machine.

An outer tub 31 that is hung by a supporting member 20 is disposed in the cabinet 10 and an inner tub 35 is rotatably disposed in the outer tub 31.

In the present invention, when there is no need to distinguish the outer tub 31 from the inner tub 35 as different things, the inner and outer tubs 35 and 31 will be referred to as “washing tub 30” hereinafter. In the present invention, when describing a wash cycle in which a liquid detergent that is formed by mixing a detergent with washing water is sprayed, the outer and inner tubs 31 and 35 will not be described as separate things.

A damper 25 for absorbing shaking of the outer tub 31, which is caused by vibration that is generated during rotation of the inner tub 35, is disposed on a lower end of the supporting member 20. A pulsator 40 for forming a rotational water stream is disposed on a bottom of the inner 35.

In addition, a motor 50 that is a driving unit for rotating the inner tub 35 and the pulsator 40 is disposed under the outer tub 31. The motor 50 is connected to the inner tub 35 through a rotational shaft 55 to rotate the inner tub 35. A clutch (not shown) for selectively transmitting torque of the motor 50 to the inner tub 35 and the pulsator 40 may be disposed between the inner tub 35 and the pulsator 40. Accordingly, depending on the operation of the clutch, only one of the inner tube 35 and the pulsator 40 may rotate or both of the inner tube 35 and the pulsator 40 may simultaneously rotate.

Meanwhile, a detergent box 15 for storing the detergent is detachably disposed on the top cover 200. A water supply hose 70 that is connected to an outer water source to supply washing water to the detergent box 60 and a water supply valve 75 for controlling the washing water introduced through the water supply hose 70 are disposed. When the water supply valve 75 is opened and thus the washing water is supplied from the outer water source, the washing water is directed to the detergent box 60, after which the washing water is supplied to the inner tub 35. The washing water that is supplied from the detergent box 60 to the inner tub 35 is filled in the outer tub 31 through a plurality of water holes 36 formed on the inner tub 35 and the laundry is received in the inner tub 35.

Further, a drain hose 80 for draining the washing water in the outer tub 31 to an external side and a drain adjusting valve 85 for controlling the washing water that is being drained through the drain hose 80, and a drain pump 86 are provided on a lower end of the outer tub 31.

FIG. 2 is a reference view illustrating a method of controlling the washing machine of FIG. 1.

Referring to FIG. 2, a method of controlling the washing machine according to an embodiment of the present invention adjust a time for spraying the washing water toward the laundry with reference to a water pressure of the washing water introduced into the washing machine.

A method of controlling the washing machine according to an embodiment of the present invention uses a property where, as the time for introducing a reference amount D-th of the washing water into the washing tub 30 increases, the water pressure is reduced and, as the time for introducing the reference amount D-th of the washing water into the washing tub 30 is reduced, the water pressure increases.

Here, the reference amount D-th is determined depending on an amount of the laundry loaded in the washing tub. If a large amount of the laundry is loaded in the washing tub 30, the reference amount D-th of the washing water introduced into the washing tub 30 increases. On the other hand, when a small amount of the laundry is loaded in the washing tub 30, the reference amount D-th of the washing water introduced into the washing tub 30 is reduced. The reference amount D-th to the amount of the laundry is defined by a data file provided in the form of a reference table. The reference table may be recorded in a control unit 210 to be reprogrammable or may be stored in an external memory (not shown) connected to the controlled unit 210.

The control unit 210 measures time required for the amount of the washing water introduced into the washing tub 30 to reach the reference amount D-th and determines the water pressure of the washing water introduced into the washing tub 30 with reference to the measured time. The water pressure is reduced as the time required for the amount of the washing water to reach the reference amount D-th increases. In addition, the water pressure of the washing water introduced into the washing tub 30 is determined by an amount of the water supplied to the washing tub 30 per a predetermined time (e.g., about 10 seconds).

When the amount of the washing water introduced into the washing tub 30 reaches the reference amount D-th, the control unit 210 calculates the water pressure of the washing water and determines the spraying time for spraying the washing water toward the laundry loaded in the washing tube 30 in accordance with the calculated water pressure.

Meanwhile, the memory (not shown) further contains a spray-time table defining the spraying time of the washing water into the washing tub 30 in accordance with the amount of the laundry.

The control unit 210 renews the time information recorded in the spray-time table with reference to the water pressure that is calculated based on the time required for the amount of the washing water to reach the reference amount D-th. For example, when it is assumed that the spraying time for spraying the washing water for about 1 Kg laundry is about 80 sec, the substantial spraying time may be 90 sec when the water pressure is low and the spraying time recorded in the spray-time table is renewed from about 80 sec to about 90 sec to adjust the spraying time of the washing water toward the laundry in response to the water pressure of the place where the washing machine is installed.

FIG. 3 is a block diagram illustrating a control flow of the washing machine according to an embodiment of the present invention.

Referring to FIG. 3, when a user set a washing course and a washing time by manipulating the control panel 230 after loading the laundry in the washing tub 30, the control unit 210 determines, in accordance with the washing course, an amount of the washing water, an amount of the detergent, a time for rotating the washing tub 30, and a rotational pattern. According to the determined conditions, the control unit 210 supplies the detergent into the washing tub 30, after which the control unit 210 controls a water supply driving unit 250 to primarily supply the washing water into the washing tub 30. At this point, the amount of the washing water supplied to the washing tub 30 is controlled with reference to an amount detected by a sensor 220. Here, the water supply driving unit 250 may include a water supply valve.

The memory 270 has the spray-time table that defines the time for spraying the washing water into the washing tub 30 according to the amount of the washing water and the amount of the laundry and the reference table for calculating the water pressure of the washing water supplied through the water supply driving unit 250.

The spray-time table defines, in accordance with the amount of the laundry loaded in the washing tub 30, an amount of the water that will be supplied to the washing tub 30 and the time for spraying the washing water to the washing tub 30.

The reference table indicates a table having the time required for filling the washing tub with the washing water to the reference amount according to the amount of the laundry and data on the water pressure of the washing water or an equation for calculating the water pressure.

The control unit 210 determines the amount of the washing water introduced into the washing tub 30 depending on the amount of the laundry. Hereinafter, the amount of the washing water, which is determined depending on the amount of the laundry, will be referred to as “reference amount.” The reference amount is determined when the laundry is loaded in the washing tub 30.

The control unit 210 measures time required for the amount of the washing water introduced into the washing tub 30 to reach the reference amount and calculates the water pressure based on the measured time. When the time required for the washing water to reach the reference amount is short, the water pressure is high. On the other hand, when the time required for the washing water to reach the reference amount is long, the water pressure is low. The reference amount and the water pressure data in accordance with the time required for the water amount to reach the reference amount are recorded on the reference table stored in the memory 270. The control unit determines the water pressure of the washing water introduced through the water supply driving unit 250 with reference to the time and water pressure data that are recorded on the reference table. At this point, the control unit 210 identifies a time point at which the amount of the washing water reaches the reference amount through the sensor 220 and applies the identified time point to the water pressure calculation. Here, the reference table is recorded on the memory 270 when a manufacturer designs and manufactures the washing machine.

The control unit 210 determines the spraying time of the washing water sprayed into the washing tub 30 with reference to the water pressure of the washing water introduced into the washing tub 30 through the water supply driving unit 250. The spraying time of the washing water is determined by varying the time written on the spray-time table recorded on the memory 270.

For example, when the water pressure of the washing water introduced into the washing tub 30 is reduced by 10% and thus the time for introducing the washing water into the washing tub 30 is retarded by about 10%. The control unit 210 may increase the time for spraying the washing water into the washing tub 30 by 10% in reverse proportion to the reduction of the water pressure by 10%. At this point, the control unit 210 may renew the spraying time written on the spray-time table by increasing the spraying time by about 10%.

In general, when it is consumed that the water pressure of the washing water introduced into the washing machine is constant, the control unit 210 may spray the washing water into the washing tub 30 and performs the wash cycle using the renewed spray-time table.

Needless to say, when the washing machine is installed at a place where the water pressure frequently varies, the control unit 210 determined the water pressure of the washing water and renews the spray-time table whenever a laundry treating cycle is performed.

Next, the control unit 210 rotates the washing tub 30 or the pulsator 40 by driving the IPM driver in accordance with the washing course and washes the laundry using frictional force generated by the washing tub 30 or the pulsator 40. The IPM driver is a driver for driving the motor 50. The IPM driver 240 rotates the motor 50 clockwise or counterclockwise by controlling a voltage and current applied to the motor 50.

When the control unit 210 drives the motor 50 by controlling the IPM driver 240, the control unit 210 drives the motor 50 such that the motor alternately repeats the clockwise rotation and the counterclockwise rotation, whereby the washing tub 30 or the pulsator 40 can alternately repeat the clockwise rotation and the counterclockwise rotation. As a result, the washing efficiency can be improved.

At this point, the control unit 10 may form a rising water stream in the washing tub 30 by rotating the washing tub 30 or the pulsator 40 and allows the washing water containing the detergent to be well mixed with the laundry using the rising water stream.

Finally, after the wash cycle by the washing course set by the user is performed, the control unit 210 drains the washing water that is fully filled in the washing tub 30 by driving the drain adjusting valve 85 and the drain pump 86 through the drain driving unit 250 and supplies new washing water to the washing tub 30 through the water supply driving unit 260, after which the control unit 210 performs the spinning cycle for the laundry using the new washing water.

FIG. 4 is a reference view illustrating an example of the spray-time table stored in the memory.

Referring to FIG. 4, the spray-time table has 10 water amount sections in accordance with the amount (kg) of the laundry loaded in the washing tub 30. In each section, the amount of the laundry corresponds to the spraying time of the washing water sprayed toward the laundry.

In FIG. 4, the first water amount section is a section corresponding to the laundry of about 0.3-1.3 kg. In addition, the spraying time of the washing water in the first water amount section is set to be about 80 seconds. If the laundry of about 1 kg is loaded in the washing tub 30, the control unit 210 sprays the washing water toward the laundry for about 80 seconds.

The second water amount section corresponds to the laundry of about 1.6-2.6 kg. Like in the first water amount section, the spraying time of the washing water in the second water amount section is about 80 seconds. This is for simplify the algorithm by applying an identical spraying time for the sections (e.g., the first and second water amount sections) having similar amount of the laundry. However, different spraying times may be applied for the first and second water amount sections and the spray-time table also defines different spraying times for the respective water amount sections. In addition, although the water amount sections includes the first to tenth water amount sections in this embodiment, the present invention is not limited to this. For example, the number of the water amount sections may be increased or reduced in accordance with the maximum amount of the washing water.

As described above, the control unit 210 renews the time information recorded on the spray-time table considering the water pressure.

When the water pressure is low, a predetermined time is added to the time recorded on the spray-time table and the spray-time table is renewed with the added time.

FIG. 5 is a flowchart illustrating a control method of the washing machine according to an embodiment of the present invention.

First, the control unit 210 detects the amount of the laundry loaded in the washing tub 30 using the rotation of the washing tub 30 or the pulsator 40. When the laundry is dry laundry that is relatively light, the control unit 201 accelerates the pulsator 40 in a direction at about 200 RPM, after which the control unit 201 determines the amount of the laundry with reference to a speed reduction time of the washing tub or a speed reduction gradient. At this point, when the amount of the laundry loaded in the washing tub 30 is relatively small, the speed of the pulsator 40 is steeply reduced. On the other hand, when the amount of the laundry loaded in the washing tub 30 is relatively large, the speed of the pulsator 40 is slowly reduced.

If the laundry is wet laundry that is relatively heavy, the control unit 210 accelerates the washing tub 30 instead of the pulsator 40 at about 40-60 RPM, after which the control unit 210 determines the amount of the laundry with reference to a speed reduction gradient attained when the washing tub puts on the brakes with reserve power. (S301).

The control unit 210 may detect the amount of the laundry using the wet or dry laundry. Alternatively, the control unit 210 may detect the amount of the laundry using firstly the dry laundry and detect using secondly the wet laundry. When both of the method for detecting the amount of the laundry using the dry laundry and the method for detecting the amount of the laundry using the wet laundry are used, the control unit 210 may determines a mean value of the detected amount for the dry laundry and the detected amount for the wet laundry as the amount of the laundry. Alternatively, when the dry laundry is detected and it is determined that the amount of the laundry is light, the detected amount for the dry laundry may be determined as the amount of the laundry. Alternatively, when the detected amount for the dry laundry deviates a predetermined amount (e.g., about 6 kg), the detected amount for the wet laundry may be determined as the amount of the laundry (S302).

Next, the control unit 210 determines the water amount section and spraying time that correspond to the amount of the laundry with reference to the spray-time table stored in the memory 270. At this point, the control unit 210 determines a reference amount to be supplied to the washing tub 30. When the reference amount is determined, the control unit 210 sprays the washing water into the washing tub 30 through a spraying hole provided near the cover 150 by controlling the water supply driving unit 250 (S303). Next, the control 210 determines if the amount of the washing water sprayed into the washing tub 30 reaches the reference amount (S304), measures the time required for the amount of the washing water reaches the reference amount (S305), and determines the water pressure of the washing water with reference to the reference table stored in the memory 270 (S306). After this, the control unit 210 increases and reduces the spraying time recorded on the spray-time table with reference to the water pressure of the washing water and sprays the washing water to the washing tub 30 for the increased or reduced time.

Finally, the control unit 210 performs the remaining cycles such as the wash, rinse, and spinning cycles when the washing water sprayed toward the laundry evenly wets the laundry (S309)

FIG. 6 is a reference view illustrating an example of a method of detecting a laundry load.

Referring to FIG. 6, in a laundry load table, gradient values are listed in each of laundry load sections //3, //14, //5, //6, and //7. The laundry load table is a table corresponding to a gradient of rotational reduction section and a laundry load of dry laundry or wet laundry and is provided in the form of a data table in the memory 270.

In FIG. 6, the laundry load table is provided for the respective laundry load sections //3, //4, //5, //6, and //7. Gradient values (135, 129, 122 . . . , and the like) corresponding to the respective laundry load sections are written on the laundry load table. For example, if the speed reduction gradient value of the motor 50 is about 183, it may be determined that the weight corresponds to the laundry load section “//4.”

Although not shown in the drawings, a weight value range of the laundry may be assigned to each of the laundry load sections. For example, a weight value range of about 3 Kg to about 4 Kg may be assigned to the laundry load section //3.

FIG. 7 is a reference view illustrating an example of a spraying unit formed between the cover and the case.

The washing machine of an embodiment of the present invention sprays the washing water toward the laundry to evenly wet the laundry. The washing machine uses a spraying unit provided in the form of a nozzle having a narrow outlet to spray the washing water.

The spraying unit 120 is a unit for spraying the circulation water into the inner tub 31. The spraying unit 120. The spraying unit 120 has a plurality of nozzle holes (not shown) that are relatively small to spray the washing water into the inner tub 31 through a shower manner. Since the spraying unit 120 directly sprays the washing water toward the laundry loaded in the inner tub 31, it can evenly effectively wet the laundry. This method has an advantage of reducing an amount of the washing water that is necessary to wet the laundry as compared with a typical method where the washing water is supplied into the inner tub 31 up to a predetermined water level so that the laundry can be sunk under the washing water. Particularly, the spraying unit 120 may be set such that a spraying direction thereof is set toward a sidewall of the inner tub 31 to effectively wet the laundry adhered to the sidewall.

FIG. 8 is s a reference view illustrating a method of controlling the washing machine according to another embodiment of the present invention.

Referring to FIG. 8, the control unit 210 loads and drives a driving pattern for each of the wash courses stored in the memory in accordance with a wash course set by a user. The control unit 210 determines if a treatment cycle of the washing machine is a wash cycle with reference to the driving pattern of each of the wash courses (S401). When the treatment cycle is the wash cycle, the control unit 210 supplies the washing water to the washing tub 30 by controlling the water supply driving unit 250. At this point, the control unit 210 determines the water pressure of the washing water with reference to a time for which the washing water is supplied to the washing tub 30 (S403). The determination of the water pressure is realized with reference to a reference amount and a reference table corresponding to the reference amount, which are stored in the memory 270. After determining the water pressure of the control unit 210, the control unit 210 stores the determined water pressure in the memory 270 and performs the wash cycle for the laundry (S404).

Next, the control unit 210 determines if it is time to perform the rinse cycle for the laundry with reference to the driving pattern stored in the memory (S405). When it is determined that it is time to perform the rinse cycle for the laundry, the control unit 210 determines the time for which the washing water will be sprayed into the washing tub 30 with reference to water pressure information stored in the memory 270 (S406) and sprays the washing water into the washing tub 30 for the determined time (S407).

However, the present invention is not limited to the above. For example, when the water pressure is determined, the spraying time is preset according to the determined water pressure and the water pressure and spraying time are stored in the memory 270, after which the water spraying is performed in accordance with the spraying time that is stored in the spinning cycle.

Finally, the control unit 210 finishes all cycles with respect to the laundry by spinning the washing tub 30 for the rinse and spin cycles with respect to the laundry (S408).

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the following claims.

Claims

1. A method of controlling a washing machine, the method comprises:

measuring a time required for an amount of washing water supplied to a washing tub to reach a predetermined reference amount;

determining a water pressure of the washing water in accordance with the measured time; and

varying a water supply time in accordance with the determined water pressure.

2. The method of claim 1, wherein data on a spraying time required for an amount of washing water to reach the predetermined reference amount and a water pressure of the washing water are stored in a reference table in advance.

3. The method of claim 1, in the determining of the present water pressure, a water pressure of washing water supplied in the present compares with the water pressure stored in the reference table.

4. The method of claim 1, wherein the water supply time is increased when the determined water pressure is less than a predetermined reference water pressure.

5. The method of claim 1, wherein the water supply time is reduced when the determined pressure is greater than a predetermined reference water pressure.

6. The method of claim 1, wherein the water supply time is set to be in reverse proportion to the water pressure.

7. The method of claim 1, wherein a washing water level corresponding to an amount of the laundry loaded in the washing tub is preset, wherein the water supply time is set in accordance with the washing water level.

8. The method of claim 7, wherein the water supply time is set by increasing or reducing the water supply, which is preset in accordance with the washing water level, according to variation of the determined water pressure.

9. The method of claim 7, wherein the water supply time set in accordance with the washing water level varies and renewed according to the determined water pressure.

10. The method of claim 1, wherein the predetermined reference amount is in proportion to an amount of the laundry loaded in the washing tub.

11. The method of claim 1, wherein the predetermined reference amount is increased or reduced in accordance with a wash course selected.

12. A method of controlling a washing machine, the method comprising:

filling washing water by a predetermined reference amount;

measuring a time required for the washing water to be filled;

determining water pressure of the washing water in accordance with the measured time;

determining a spraying time of the washing water in accordance with the determined water pressure;

perform a wash cycle by spraying the washing water for the determined spraying time; and

perform a rinse cycle by spraying the washing water for the determined spraying time.

13. A washing machine comprises:

a memory comprising a reference table storing data on a time required for washing water to be filled in a washing tub by a predetermined reference amount and a water pressure determined according to the time; and

a control unit for determining the present water pressure of the washing water with reference to the reference table and varying a spraying time of the washing time sprayed into the washing tub in accordance with the determined water pressure.

14. The washing machine of claim 13, wherein the memory further comprises a spray-time table storing a spraying time of the washing water according to an amount of laundry.

15. The washing machine of claim 14, wherein the control unit measures a time required for the washing water to reach a reference amount and determines the present water pressure by comparing the measured time with data that is preset in the reference table.

16. The washing machine of claim 14, wherein the control unit reduces the spraying time stored in the spray-time table as the water pressure increases.

17. The washing machine of claim 14, wherein the control unit increases the spraying time stored in the spray-time table as the water pressure reduces

18. The washing machine of claim 14, wherein the control unit renews the spray-time table in accordance with the newly determined water pressure.

19. The washing machine of claim 14, wherein the reference amount is in proportion to the amount of the laundry loaded in the washing tub.

20. The washing machine of claim 13, further comprising a water supply driving unit for supplying the washing water for the spraying time set by the control unit and a spraying unit for spraying the washing water into the washing tub according to operation of the water supply driving unit.