U.S. patent application number 11/976069 was filed with the patent office on 2008-07-24 for washing machine with balancers and control method thereof.
This patent application is currently assigned to Samsung Electronics Co., Ltd.. Invention is credited to Seung Ju Choi, Hong Seok Ko, Gyu Sung Na.
Application Number | 20080172805 11/976069 |
Document ID | / |
Family ID | 39410355 |
Filed Date | 2008-07-24 |
United States Patent
Application |
20080172805 |
Kind Code |
A1 |
Na; Gyu Sung ; et
al. |
July 24, 2008 |
Washing machine with balancers and control method thereof
Abstract
Disclosed are a washing machine and a control method thereof
capable of reincreasing a number of rotations of a motor after
maintaining the number of rotations at a predetermined number
before excessive vibration of a water tub, braking the motor when
the water tub is vibrated at more than a predetermined vibration
level, and reincreasing the number of rotations, thereby reducing
the excessive vibration of the water tub. The control method
includes detecting the number of rotations, determining whether the
detected number of rotations has reached a predetermined number,
controlling the motor such that the number of rotations is
maintained at the predetermined number of rotations when it is
determined that the detected number of rotations has reached the
predetermined number, counting the time taken to maintain the
number of rotations at the predetermined number of rotations, and
increasing the number of rotations after a predetermined first time
has elapsed.
Inventors: |
Na; Gyu Sung; (Incheon,
KR) ; Ko; Hong Seok; (Yongin-si, KR) ; Choi;
Seung Ju; (Seoul, KR) |
Correspondence
Address: |
STAAS & HALSEY LLP
SUITE 700, 1201 NEW YORK AVENUE, N.W.
WASHINGTON
DC
20005
US
|
Assignee: |
Samsung Electronics Co.,
Ltd.
Suwon-si
KR
|
Family ID: |
39410355 |
Appl. No.: |
11/976069 |
Filed: |
October 19, 2007 |
Current U.S.
Class: |
8/159 ; 68/23.2;
8/158 |
Current CPC
Class: |
D06F 37/225 20130101;
D06F 35/007 20130101; D06F 34/16 20200201; D06F 2103/24 20200201;
D06F 37/203 20130101; D06F 2103/26 20200201; D06F 33/48 20200201;
D06F 2105/56 20200201; D06F 33/40 20200201 |
Class at
Publication: |
8/159 ; 68/23.2;
8/158 |
International
Class: |
D06F 37/20 20060101
D06F037/20 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 24, 2007 |
KR |
2007-7606 |
Claims
1. A control method of controlling a washing machine including a
motor, a water tub, and balancers, the control method comprising:
detecting a number of rotations of the motor during an operation of
the washing machine; determining whether the detected number of
rotations of the motor has reached a predetermined number of
rotations and, when it is determined that the detected number of
rotations of the motor has reached the predetermined number of
rotations, controlling the motor such that the number of rotations
of the motor is maintained at the predetermined number of
rotations; counting a time taken to maintain the number of
rotations of the motor at the predetermined number of rotations;
and increasing the number of rotations of the motor after a
predetermined first time has elapsed.
2. The control method according to claim 1, wherein the
predetermined number of rotations is a number of rotations of the
motor lower than a number of excessive vibration rotations of the
water tub.
3. The control method according to claim 2, wherein the number of
excessive vibration rotations of the water tub is a number of
rotations of the motor at a point where an excessive vibration of
the water tub is generated due to a difference in a rotating speed
between the rotary tub and balls in the balancers before the balls
reach a balancing position.
4. The control method according to claim 1, wherein the
predetermined first time is a time necessary to maintain the number
of rotations of the motor at the predetermined number of rotations
until the balls reach a balancing position.
5. The control method according to claim 4, wherein the increasing
the number of rotations of the motor includes maintaining the
number of rotations of the motor at the predetermined number of
rotations for the predetermined first time until the balls reach
the balancing position and increasing the number of rotations of
the motor to a spin-drying RPM to perform a spin-drying operation
of the washing machine.
6. The control method according to claim 1, wherein the controlling
the motor such that the number of rotations of the motor is
maintained at the predetermined number of rotations includes
maintaining the number of rotations of the motor at a predetermined
number of rotations before an excessive vibration generating point
of the water tub such that the motor passes through the excessive
vibration generating point of the water tub generated during an
operation of the washing machine.
7. The control method according to claim 1, further comprising:
detecting a vibration of the water tub generated as the number of
rotations of the motor is increased; braking the motor to lower the
number of rotations of the motor when the detected vibration of the
water tub exceeds a predetermined vibration level; and counting a
time after the braking of the motor and reincreasing the number of
rotations of the motor after a predetermined second time has
elapsed.
8. The control method according to claim 7, wherein the detecting
the vibration of the water tub includes detecting an excessive
vibration of the water tub generated due to a difference in a
rotating speed between the rotary tub and balls in the balancers
before the balls reach a balancing position during the operation of
the washing machine.
9. The control method according to claim 8, wherein the braking the
motor to lower the number of rotations of the motor includes
lowering the number of rotations of the motor to a predetermined
number of rotations to reduce the excessive vibration of the water
tub generated before the balls reach the balancing position.
10. The control method according to claim 7, wherein the
reincreasing the number of rotations of the motor includes
detecting a lowered number of rotations of the motor and, when the
detected lowered number of rotations of the motor has reached a
predetermined number of rotations, reincreasing the number of
rotations of the motor to perform the operation.
11. The control method according to claim 7, wherein the
predetermined vibration level is reference vibration data as to an
excessive vibration of the water tub.
12. The control method according to claim 7, wherein the
predetermined second time is previously set data used to locate an
excessive vibration passing point of the water tub at a balancing
position.
13. The control method according to claim 12, wherein the
reincreasing the number of rotations of the motor includes
maintaining the number of rotations of the motor for the
predetermined second time such that the excessive vibration passing
point of the water tub is located at the balancing position after
the braking of the motor and increasing the number of rotations of
the motor to a spin-drying RPM to perform a spin-drying operation
of the washing machine.
14. A washing machine including a motor, a water tub, and
balancers, the washing machine comprising: a rotational frequency
detection unit detecting a number of rotations of the motor during
an operation of the washing machine; and a control unit determining
whether the detected number of rotations of the motor has reached a
predetermined number of rotations, controlling the motor such that
the number of rotations of the motor is maintained at the
predetermined number of rotations when it is determined that the
detected number of rotations of the motor has reached the
predetermined number of rotations, counting a time taken to
maintain the number of rotations of the motor at the predetermined
number of rotations, and increasing the number of rotations of the
motor after a predetermined first time has elapsed.
15. The washing machine according to claim 14, further comprising:
a vibration detection unit detecting a vibration of the water tub
generated by the rotation of the motor, wherein the control unit
brakes the motor to lower the number of rotations of the motor when
the detected vibration of the water tub exceeds a predetermined
vibration level, counts a time after the brake of the motor, and
reincreases the number of rotations of the motor after a
predetermined second time has elapsed.
16. The method according to claim 1, wherein the operation is a
spin-drying operation of the washing machine.
17. The washing machine according to claim 14, wherein the
operation is a spin-drying operation of the washing machine.
18. A washing machine having a motor, balancers, balancing balls
fitted within the balancers and a water tub, comprising: a rotation
frequency detection unit detecting a number of rotations of the
motor during an operation of the washing machine; a vibration
detection unit detecting a vibration of the water tub generated by
the rotation of the motor; and a control unit maintaining the
number of rotations of the motor at a predetermined number of
rotations before excessive vibration is generated from the water
tub until the balancing balls reach a balancing position.
19. The washing machine according to claim 18, wherein the control
unit decreases the number of rotations of the motor by braking the
motor when the detected vibration of the water tub exceeds a
predetermined vibration level.
20. The washing machine according to claim 18, wherein the control
unit increases the number of rotations of the motor after a
predetermined time has elapsed after the brake of the motor.
21. A control method of controlling a washing machine having a
motor, balancers, balancing balls fitted within the balancers and a
water tub, comprising: braking the motor after beginning an
operation of the washing machine and after detecting that a
vibration of the water tub exceeds a predetermined vibration level;
and increasing a number of rotations of the motor after a
predetermined time has elapsed in order to reduce excessive
vibration of the water tub until the balancing balls reach a
balancing position.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of Korean Patent
Application No. 2007-007606, filed on Jan. 24, 2007 in the Korean
Intellectual Property Office, the disclosure of which is
incorporated herein by reference.
BACKGROUND
[0002] 1. Field
[0003] The present invention relates to a washing machine with
balancers, and, more particularly, to a washing machine and a
control method thereof that is capable of reducing vibration
generated from a water tub due to eccentricity, i.e., unbalance,
generated during the rotation of the washing machine.
[0004] 2. Description of the Related Art
[0005] Generally, a washing machine (normally, a drum type washing
machine) is a machine that washes laundry by lifting and dropping
the laundry. The washing machine includes a water tub mounted in a
housing forming the appearance of the washing machine to receive
wash water, a rotary tub rotatably mounted in the water tub to
receive laundry, and a motor to generate a driving force necessary
to rotate the rotary tub.
[0006] When the rotary tub is rotated at high speed in an
unbalanced state in which the laundry is not uniformly distributed
in the rotary tub but is concentrated at a specific region of the
rotary tub during a spin-drying operation of the washing machine,
the rotary tub eccentrically rotates with respect to a rotary
shaft. As a result, the rotary tub collides with the water tub,
thereby generating vibration and noise. When this phenomenon
repeatedly occurs, parts of the washing machine, including the
rotary tub and the motor, may break down or the life of the parts
of the washing machine may be shortened.
[0007] In order to solve the problem, there has been proposed a
washing machine including balancers mounted at the front and rear
ends of a rotary tub to reduce vibration generated from a water tub
due to the eccentric rotation of the rotary tub. An example is
disclosed in Korean Patent Application Publication No.
1999-0038279. The balancers of the washing machine disclosed in the
publication include races mounted at the front and rear ends of the
rotary tub to maintain the dynamic balance during the high-speed
rotation of the rotary tub, steel balls disposed in the respective
races to move freely, and viscous fluids filled in the respective
races to control the momentum of the balls. Each race is formed by
welding annular upper and lower plates with each other.
[0008] Consequently, when the rotary tub is rotated while not
maintaining the dynamic balance due to the unbalanced eccentric
structure of the rotary tub and the biased distribution of laundry
in the rotary tub, the steel balls compensate for the eccentricity
of the rotary tub such that the rotary tub is rotated while
maintaining the dynamic balance.
[0009] In the balancers of the conventional washing machine,
however, at least two races, for example an inner race and an outer
race, are provided for each balancer, and viscous fluids having
different viscosities and steel balls having different sizes are
put in the respective races to prevent excessive vibration from
being generated from the water tub before the balls reach the
balancing position. As a result, the manufacturing costs are high.
In addition, the structure of the races is not designed to prevent
the generation of the excessive vibration of the water tub based on
accurate calculation, but to reduce a probability of vibration
generation. For this reason, there is still a possibility that
excessive vibration is generated from the water tub. Consequently,
it is required to use an increased number of races to lower the
probability that excessive vibration is generated from the water
tub.
SUMMARY
[0010] Therefore, it is an aspect of the invention to provide a
washing machine and a control method thereof that is capable of
reincreasing the number of rotations of a motor after maintaining
the number of rotations of the motor at a predetermined number of
rotations before excessive vibration of a water tub is generated
for a predetermined time such that the motor passes through an
excessive vibration generating point of the water tub.
[0011] It is another aspect of the invention to provide a washing
machine and a control method thereof that is capable of braking a
motor, when a water tub is vibrated at more than a predetermined
vibration level after the reincrease of RPM of the motor, to lower
the RPM of the motor to a predetermined number of rotations and
reincreasing the RPM of the motor, thereby reliably reducing the
excessive vibration of the water tub.
[0012] Additional aspects and/or advantages 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
invention.
[0013] The foregoing and/or other aspects are achieved by providing
a control method of a washing machine including a motor, a water
tub, and balancers, the control method including detecting a number
of rotations of the motor during a spin-drying operation of the
washing machine, determining whether the detected number of
rotations of the motor has reached a predetermined number of
rotations, controlling the motor such that the number of rotations
of the motor is maintained at the predetermined number of rotations
when it is determined that the detected number of rotations of the
motor has reached the predetermined number of rotations, counting
the time taken to maintain the number of rotations of the motor at
the predetermined number of rotations, and increasing the number of
rotations of the motor after a predetermined first time has
elapsed.
[0014] The predetermined number of rotations may be a number of
rotations of the motor lower than the number of excessive vibration
rotations of the water tub during the spin-drying operation of the
washing machine.
[0015] The number of excessive vibration rotations of the water tub
may be a number of rotations of the motor at a point where the
excessive vibration of the water tub is generated due to the
difference in rotating speed between the rotary tub and balls in
the balancers before the balls reach a balancing position.
[0016] The predetermined first time may be a time necessary to
maintain the number of rotations of the motor at the predetermined
number of rotations until the balls reach the balancing
position.
[0017] The step of increasing the number of rotations of the motor
includes maintaining the number of rotations of the motor at the
predetermined number of rotations for the predetermined first time
until the balls reach the balancing position and increasing the
number of rotations of the motor to a spin-drying RPM to perform
the spin-drying operation of the washing machine.
[0018] The step of controlling the motor such that the number of
rotations of the motor is maintained at the predetermined number of
rotations includes maintaining the number of rotations of the motor
at a predetermined number of rotations before an excessive
vibration generating point of the water tub such that the motor
passes through the excessive vibration generating point of the
water tub generated during the spin-drying operation of the washing
machine.
[0019] The control method may further include detecting the
vibration of the water tub generated as the number of rotations of
the motor is increased, braking the motor to lower the number of
rotations of the motor when the detected vibration of the water tub
exceeds a predetermined vibration level, counting the time after
the brake of the motor, and reincreasing the number of rotations of
the motor after a predetermined second time has elapsed.
[0020] The detecting the vibration of the water tub may include
detecting the excessive vibration of the water tub generated due to
the difference in rotating speed between the rotary tub and balls
in the balancers before the balls reach a balancing position during
the spin-drying operation of the washing machine.
[0021] The lowering the number of rotations of the motor may
include lowering the number of rotations of the motor to a
predetermined number of rotations to reduce the excessive vibration
of the water tub generated before the balls reach the balancing
position.
[0022] The reincreasing the number of rotations of the motor may
include detecting the lowered number of rotations of the motor and
reincreasing the number of rotations of the motor to perform the
spin-drying operation when the detected number of rotations of the
motor has reached a predetermined number of rotations.
[0023] The predetermined vibration level may be reference vibration
data considered as an excessive vibration of the water tub.
[0024] The predetermined second time may be data previously set
through experiments to locate the excessive vibration passing point
of the water tub at the balancing position.
[0025] The reincreasing the number of rotations of the motor may
include maintaining the predetermined second time such that the
excessive vibration passing point of the water tub is located at
the balancing position after the braking of the motor and
increasing the number of rotations of the motor to a spin-drying
RPM to perform the spin-drying operation of the washing
machine.
[0026] The foregoing and/or other aspects are achieved by providing
a washing machine having a motor, a water tub, and balancers, the
washing machine including a rotational frequency detection unit to
detect a number of rotations of the motor during a spin-drying
operation of the washing machine, and a control unit to determine
whether the detected number of rotations of the motor has reached a
predetermined number of rotations, control the motor such that the
number of rotations of the motor is maintained at the predetermined
number of rotations when it is determined that the detected number
of rotations of the motor has reached the predetermined number of
rotations, count time taken to maintain the number of rotations of
the motor at the predetermined number of rotations, and increase
the number of rotations of the motor after a predetermined first
time has elapsed.
[0027] The washing machine may further include a vibration
detection unit to detect the vibration of the water tub generated
by the rotation of the motor, and the control unit may brake the
motor to lower the number of rotations of the motor when the
detected vibration of the water tub exceeds a predetermined
vibration level, count the time after the brake of the motor, and
reincrease the number of rotations of the motor after a
predetermined second time has elapsed.
[0028] The foregoing and/or other aspects are achieved by providing
a washing machine having a motor, balancers, balancing balls fitted
within the balancers and a water tub, including a rotation
frequency detection unit detecting a number of rotations of the
motor during an operation of the washing machine; a vibration
detection unit detecting a vibration of the water tub generated by
the rotation of the motor; and a control unit maintaining the
number of rotations of the motor at a predetermined number of
rotations before excessive vibration is generated from the water
tub until the balancing balls reach a balancing position.
[0029] The control unit may decrease the number of rotations of the
motor by braking the motor when the detected vibration of the water
tub exceeds a predetermined vibration level.
[0030] The control unit may increase the number of rotations of the
motor after a predetermined time has elapsed after the brake of the
motor.
[0031] The foregoing and/or other aspects are achieved by providing
a control method of controlling a washing machine having a motor,
balancers, balancing balls fitted within the balancers and a water
tub, including: braking the motor after beginning an operation of
the washing machine and after detecting that a vibration of the
water tub exceeds a predetermined vibration level; and increasing a
number of rotations of the motor after a predetermined time has
elapsed in order to reduce excessive vibration of the water tub
until the balancing balls reach a balancing position.
BRIEF DESCRIPTION OF THE DRAWINGS
[0032] These and/or other aspects and advantages will become
apparent and more readily appreciated from the following
description of the embodiments, taken in conjunction with the
accompanying drawings, of which:
[0033] FIG. 1 is a sectional view illustrating the structure of a
washing machine with balancers according to the present
embodiment;
[0034] FIG. 2 is an exploded perspective view of a rotary tub
according to the present embodiment;
[0035] FIG. 3 is an assembled perspective view of the rotary tub
according to the present embodiment;
[0036] FIG. 4 is a control block diagram of the washing machine
with the balancers according to the present embodiment;
[0037] FIG. 5 is a signal waveform graph illustrating vibration
generated from a water tub due to the difference in rotating speed
between the rotary tub and balls in the washing machine with the
balancers according to the present embodiment;
[0038] FIG. 6 is a view illustrating the difference in rotating
speed between the rotary tub and the balls in the washing machine
with the balancers according to the present embodiment;
[0039] FIGS. 7A and 7B are flow charts illustrating a process of
reducing excessive vibration of the water tub in the washing
machine with the balancers according to the present embodiment;
[0040] FIG. 8 is a graph illustrating a ball behavior control
process of reducing the excessive vibration of the water tub in the
washing machine with the balancers according to the present
embodiment;
[0041] FIG. 9 is a graph illustrating a rotational frequency
control process of reducing the excessive vibration of the water
tub in the washing machine with the balancers according to the
present embodiment; and
[0042] FIG. 10 is a graph illustrating a brake control process of
reducing the excessive vibration of the water tub in the washing
machine with the balancers according to the present embodiment.
DETAILED DESCRIPTION OF THE EMBODIMENTS
[0043] Reference will now be made in detail to the embodiment,
examples of which are illustrated in the accompanying drawings,
wherein like reference numerals refer to like elements throughout.
The embodiment is described below to explain the present invention
by referring to the figures.
[0044] FIG. 1 is a sectional view illustrating the structure of a
washing machine with balancers according to the present
embodiment.
[0045] Referring to FIG. 1, the washing machine includes a water
tub 20 mounted in a housing 10 forming the appearance of the
washing machine to receive wash water, a rotary tub 30 rotatably
mounted in the water tub 20 to receive laundry, and a door 40
hingedly coupled to the open front part of the housing 10.
[0046] Above the water tub 20 are mounted a water supply valve 12
and a detergent supply unit 14 to supply wash water and detergent
into the water tub 20. Below the water tub 20 is mounted a drainage
pump 16 to drain the wash water in the water tub 20 out of the
housing 10 after the laundry is washed.
[0047] To the rear of the rotary tub 30 is mounted a rotary shaft
51 that extends through the rear of the water tub 20. At the rear
of the water tub 20 is mounted a motor 50, to which the rotary
shaft 51 is connected. Consequently, when the motor 50 is operated,
the rotary shaft 51 is rotated with the result that the rotary tub
30 is rotated.
[0048] At the circumference of the rotary tub 30 are formed a
plurality of through-holes 30a, through which the water in the
water tub 20 is introduced into the rotary tub such that the
laundry is washed by the water containing detergent during a
washing operation. During a spin-drying operation, the water is
drained out of the housing 10 through the drainage pump 16.
[0049] Inside the rotary tub 30 are mounted a plurality of lifters
30b which are arranged in the longitudinal direction. As the rotary
tub 30 is rotated at low speed during the washing operation, the
lifters 30b lift the laundry wetted by the water from the bottom of
the rotary tub 30 and drop the laundry to the bottom of the rotary
tub 30 such that the laundry is effectively washed.
[0050] During the washing operation, the rotary shaft 51 is rotated
in alternating directions by the motor 50 such that the rotary tub
30 is rotated at low speed to wash the laundry. During the
spin-drying operation, the rotary shaft 51 is rotated in one
direction such that the rotary tub 30 is rotated at high speed to
spin-dry the laundry.
[0051] When the center of gravity of the rotary tub 30 does not
coincide with the center of rotation of the rotary tub 30 or the
laundry is not uniformly distributed in the rotary tub 30, i.e.,
the laundry is concentrated at a specific region of the rotary tub
30, while the rotary tub 30 is rotated at high speed during the
spin-drying operation, the rotary tub 30 eccentrically rotates with
respect to the rotary shaft 51. As a result, the rotary tub 30 does
not maintain the dynamic balance.
[0052] In order to prevent the occurrence of the dynamic unbalance
of the rotary tub 30 such that the rotary tub 30 can be rotated at
high speed while the center of gravity of the rotary tub 30
coincides with the center of rotation of the rotary tub 30,
balancers 60 are mounted at the front and rear ends of the rotary
tub 30 to stabilize the rotation of the rotary tub 30.
[0053] FIG. 2 is an exploded perspective view of the rotary tub
according to the present embodiment, and FIG. 3 is an assembled
perspective view of the rotary tub according to the present
embodiment.
[0054] Referring to FIG. 2, the rotary tub 30 includes a
cylindrical body 31 having open front and rear parts, the
through-holes 30a, and the lifters 30b, a front member 32 coupled
to the open front part of the body 31 and having an opening 34
through which laundry is put into or removed from the body 31, and
a rear member 33 coupled to the open rear part of the body 31 and
the rotary shaft 51 to rotate the rotary tub 30.
[0055] At the edge of the front member 32 is formed an annular
recess 35 which is formed approximately in the sectional shape of a
`[` and is opened forward to receive the corresponding balancer 60.
At the edge of the rear member 33 is also formed an annular recess
(not shown) which is open rearward to receive the corresponding
balancer 60.
[0056] As shown in FIG. 3, the front member 32 and the rear member
33 are fitted in the front edge and the rear edge of the body 31
and fixed to the body 31 by screws or other suitable fixing
members.
[0057] The balancers 60 are mounted in the recesses 35 of the front
and rear members 32 and 33. Each balancer 60 is constructed in the
structure of an annular single race, in which a plurality of steel
balls 61 are disposed and a viscous fluid is filled to control the
moving speed of the balls 61.
[0058] The balls 61 are movable in a circumferential direction such
that, when a dynamic unbalance occurs at the rotary tub 30, the
balls 61 move to a position symmetrical to the position where the
dynamic unbalance occurs to reduce the vibration of the rotary tub
30.
[0059] FIG. 4 is a control block diagram of the washing machine
with the balancers according to the present embodiment. The washing
machine includes a signal input unit 100, a vibration detection
unit 110, a control unit 120, a drive unit 130, and a rotational
frequency detection unit 140.
[0060] The signal input unit 100 inputs operation information, such
as a washing course (for example, a delicate washing course or a
normal washing course), a washing temperature, spin-drying rpm, and
additional rinsing, selected by a user, depending upon material to
be laundered, to the control unit 120.
[0061] The vibration detection unit 110 detects vibration of the
water tub 20 that is changed while the number of rotations of the
motor 50 is maintained at a predetermined number of rotations
(W-RPM: approximately 160 to 270 RPM) before excessive vibration is
generated from the water tub 20 until the balls 61 reach the
balancing position. The number of rotations at which the excessive
vibration is generated (A-RPM) is approximately 270 RPM. The
balancing position is the side opposite to concentrated laundry W
causing the unbalance. Therefore, excessive vibration of the water
tub 20 is prevented from being generated before the balls 61 reach
the balancing position during a spin-drying operation of the
washing machine with the balancers 60. A signal waveform of the
vibration frequency as shown in FIG. 5 is detected by the vibration
detection unit 110.
[0062] The vibration frequency of FIG. 5 is a signal waveform
generated due to a modulation phenomenon caused by the difference
between the rotating speed (RPM1) of the rotary tub 30 and the
rotating speed (RPM2) of the balls 61 as shown in FIG. 6.
[0063] The control unit 120 is a microcomputer to control the
washing machine according to the operation information inputted
from the signal input unit 100. The control unit 120 maintains the
number of rotations of the motor 50 at the predetermined number of
rotations (W-RPM) for a predetermined time (W-T1). W-RPM is the
number of rotations at which the modulation phenomenon is easily
observed while the vibration of the water tub does not exceed a
predetermined value. W-T1 is the time calculated based on time
taken until the number of rotations of the water tub reaches the
number of excessive vibration rotations from the predetermined
number of rotations. The number of rotations of the motor 50 is
maintained at the predetermined time such that the motor 50 passes
through the excessive vibration generating point of the water tub
20 during a spin-drying operation until the balls 61 reach the
balancing position, and the control unit 120 reincreases the number
of rotations of the motor 50 such the rotary tub 30 is rotated at
high speed.
[0064] Also, the control unit 120 checks the vibration of the water
tub 20 when reincreasing the number of rotations of the motor 50,
and, when the vibration of the water tub 20 exceeds a predetermined
vibration level (i.e., a reference vibration level considered as
the excessive vibration of the water tub), brakes the motor 50 such
that the RPM of the motor 50 is lowered to the predetermined number
of rotations (W-RPM). Then the control unit 120 reincreases the RPM
of the motor 50 to reliably reduce the excessive vibration of the
water tub 20 during the spin-drying operation.
[0065] The control unit 120 sets a time (W-T2) necessary to brake
the motor 50 such that the RPM of the motor 50 is lowered to the
predetermined number of rotations (W-RPM) and reincreases the RPM
of the motor 50 such that the excessive vibration passing point is
located at half cycle. Therefore, the balls 61 are located at the
balancing position after the brake of the motor 50. The time may be
derived through experiments.
[0066] The drive unit 130 drives the water supply valve 12, the
drainage pump 16, and the motor 50 according to a drive control
signal of the control unit 120.
[0067] The rotational frequency detection unit 140 detects the
number of rotations of the motor 50 to determine whether the RPM of
the motor 50 is lowered by the brake of the motor 50 and inputs the
detected number of rotations of the motor 50 to the control unit
120.
[0068] Hereinafter, the operation of the washing machine with the
above-stated construction and a control method of the washing
machine will be described.
[0069] FIGS. 7A and 7B are flow charts illustrating a process of
reducing excessive vibration of the water tub in the washing
machine with the balancers according to the present embodiment.
[0070] First, it is determined whether the operation of the washing
machine is a spin-drying operation (S200). When it is determined
that the operation of the washing machine is the spin-drying
operation, the control unit 120 controls the drive unit 130 to
drive the motor 50, and the spin-drying rotation of the rotary tub
30 is initiated by the motor 50 (S202).
[0071] As the spin-drying rotation of the rotary tub 30 is
performed by the motor 50, the rotating speed of the motor 50
increases. In the initial rotation of the rotary tub 30, a viscous
fluid (not shown) filled in the balancers 60 does not push the
balls 61 upward with the result, as shown in FIG. 6, that there is
a difference between the rotating speed (RPM1) of the rotary tub 30
and the rotating speed (RPM2) of the balls 61. Due to the
difference between the rotating speed (RPM1) of the rotary tub 30
and the rotating speed (RPM2) of the balls 61, a resonance point
where the water tub 20 is excessively vibrated is generated before
the balls 61 reach the balancing position, which is the position
where the balls are located at the side opposite to concentrated
laundry W causing the unbalance.
[0072] According to the present embodiment, the control unit 120
controls the motor 50 to be maintained at the predetermined number
of rotations (W-RPM) before the motor 50 passes through the number
of rotations (A-RPM) at the resonance point where the excessive
vibration of the water tub 20 is generated, which is the excessive
vibration generating point, until the balls 61 reach the balancing
position during the spin-drying operation such that the motor 50
passes through the excessive vibration generating point of the
water tub 20.
[0073] More specifically, the rotational frequency detection unit
140 detects the number of rotations of the motor 50, while the
motor 50 performs the spin-drying rotation of the rotary tub 30,
and inputs the detected number of rotations of the motor 50 to the
control unit 120 (S204).
[0074] The control unit 120 compares the number of rotations of the
motor 50 detected by the rotational frequency detection unit 140
with the predetermined number of rotations (W-RPM) to determine
whether the detected number of rotations of the motor 50 has
reached the predetermined number of rotations (W-RPM) (S206).
[0075] When it is determined that the number of rotations of the
motor 50 has reached the predetermined number of rotations (W-RPM),
the number of rotations of the motor 50 is maintained as shown in
FIGS. 8 and 9 (S208). If it is determined that the number of
rotations of the motor 50 has not reached the predetermined number
of rotations (W-RPM), the operation returns to S202.
[0076] FIG. 8 is a graph illustrating a ball behavior control
process of reducing the excessive vibration of the water tub in the
washing machine with the balancers according to the present
embodiment, and FIG. 9 is a graph illustrating a rotational
frequency control process of reducing the excessive vibration of
the water tub in the washing machine with the balancers according
to the present embodiment.
[0077] As shown in FIGS. 8 and 9, the number of rotations of the
motor 50 is maintained at the predetermined number of rotations
(W-RPM) before the excessive vibration (Vmax) of the water tub 20
is generated until the balls 61 reach the balancing position.
[0078] While the number of rotations of the motor 50 is maintained
at the predetermined number of rotations (W-RPM), the signal
waveform shown in FIG. 5 may be obtained by a device to detect the
speed change or vibration of the water tub 20, for example, a
vibration detection unit.
[0079] The vibration frequency of FIG. 5 is a signal waveform
generated due to a modulation phenomenon caused by the difference
between the rotating speed (RPM1) of the rotary tub 30 and the
rotating speed (RPM2) of the balls 61 as shown in FIG. 6. The
signal waveform is used to set the number of rotations of the motor
50 at which the modulation phenomenon caused by the difference
between the rotating speed (RPM1) of the rotary tub 30 and the
rotating speed (RPM2) of the balls is easily observed such that the
spin-drying operation is performed while the vibration of the water
tub 20 does not exceed the predetermined vibration level (Vmax),
the reference vibration level considered as the excessive vibration
of the water tub.
[0080] Also, the control unit 120 counts the time taken to maintain
the number of rotations of the motor 50 at the predetermined number
of rotations (W-RPM) to determine whether a predetermined first
time (W-T1) has elapsed (S210). When it is determined that the
predetermined first time (W-T1) has elapsed, the control unit 120
performs the spin-drying operation while reincreasing the number of
rotations of the motor 50 to a spin-drying RPM as shown in FIGS. 8
and 9 (S212). If it is determined that the predetermined first time
(W-T1) has not elapsed, the operation returns to S208.
[0081] The number of rotations of the motor 50 may be reincreased
after the number of rotations of the motor 50 is maintained at the
predetermined number of rotations (W-RPM) for the predetermined
first time (W-T1) or before the vibration frequency reaches the
minimum level (i.e., the lowest signal point) while the control
unit 120 continuously checks the signal waveform of the vibration
frequency shown in FIG. 5.
[0082] Subsequently, the vibration detection unit 110 detects the
vibration of the water tub 20 changed as the number of rotations of
the motor 50 is reincreased and inputs the detected vibration to
the control unit 120 (S214).
[0083] The control unit 120 compares the vibration of the water tub
20 detected by the vibration detection unit 110 with the
predetermined vibration level (Vmax) to determine whether the
vibration of the water tub 20 exceeds the predetermined vibration
level (Vmax) (S216).
[0084] When it is determined at S216 that the vibration of the
water tub 20 exceeds the predetermined vibration level (Vmax), the
control unit 120 brakes the motor 50 to lower the number of
rotations of the motor 50 (S218). If it is determined that the
vibration of the water tub 20 does not exceed the predetermined
vibration level (Vmax), the operation returns to S212.
[0085] As the number of rotations of the motor 50 is lowered, the
vibration of the water tub 20 decreases. The rotational frequency
detection unit 140 detects the lowered number of rotations of the
motor 50, and inputs the detected number of rotations of the motor
50 to the control unit 120 (S220).
[0086] The control unit 120 determines whether the number of
rotations of the motor 50 detected by the rotational frequency
detection unit 140 has reached the predetermined number of
rotations (W-RPM) (S222). When it is determined that the number of
rotations of the motor 50 has not reached the predetermined number
of rotations (W-RPM), the operation returns to S218 and the control
unit 120 brakes the motor 50 to lower the RPM of the motor 50 until
the number of rotations of the motor 50 reaches the predetermined
number of rotations (W-RPM).
[0087] When it is determined at S222 that the number of rotations
of the motor 50 has reached the predetermined number of rotations
(W-RPM), the control unit 120 determines whether a predetermined
second time (W-T2) has elapsed after the brake of the motor 50
(S224). When it is determined that the predetermined second time
(W-T2) has elapsed, the control unit performs the spin-drying
operation while reincreasing the number of rotations of the motor
50 to the spin-drying RPM as shown in FIG. 10 (S226). If it is
determined that the predetermined second time (W-T2) has not
elapsed, the operation returns to S224.
[0088] The number of rotations of the motor 50 may be reincreased
after the number of rotations of the motor 50 is maintained at the
predetermined number of rotations (W-RPM) for the predetermined
second time (W-T2), or the time point where the number of rotations
of the motor 50 is reincreased may be derived through experiments
such that the excessive vibration (Vmax) passing point is located
at half cycle.
[0089] FIG. 10 is a graph illustrating a brake control process of
reducing the excessive vibration of the water tub in the washing
machine with the balancers according to the present embodiment.
[0090] As shown in FIG. 10, when the vibration of the water tub
exceeds the predetermined vibration level (Vmax), the control unit
brakes the motor 50 such that the RPM of the motor is rapidly
lowered to the predetermined number of rotations (W-RPM) to
reliably reduce the vibrations of the water tub 20, and reincreases
the number of rotations of the motor 50, after the predetermined
second time (W-T2) has elapsed, to reduce the magnitude and
deviation of the excessive vibration of the water tub 20. In
addition, the time necessary for the reincrease of the number of
rotations of the motor 50 is reduced, and thereby the total washing
time is reduced.
[0091] Subsequently, when it is determined that the spin-drying
operation has been completed (S228), the control unit 120 stops the
operation of the motor 50 (S230). If it is not determined that the
spin-drying operation has not been completed, the operation returns
to S228.
[0092] In the above-described embodiment, the process of reducing
the excessive vibration of the water tub 20 generated during the
spin-drying operation was described. However, the present
embodiment is not limited to the spin-drying operation. For
example, the present embodiment may be applied to any operation in
which the vibration of the water tub 20 may be generated before the
balls reach a balancing position in the washing machine with the
balancers 60.
[0093] As apparent from the above description, the present
embodiment provides a washing machine and a control method thereof
that is capable of reincreasing the number of rotations of a motor
after maintaining the number of rotations of the motor at a
predetermined number of rotations before excessive vibration of a
water tub is generated for a predetermined time such that the motor
passes through an excessive vibration generating point of the water
tub. Consequently, the present embodiment has the effect of
reducing the excessive vibration of the water tub generated before
balls reach the balancing position.
[0094] Furthermore, the present embodiment provides a washing
machine and a control method thereof that is capable of braking the
motor, when the water tub is vibrated at more than a predetermined
vibration level after reincreasing the RPM of the motor, to lower
the RPM of the motor to a predetermined number of rotations, and
reincreasing the RPM of the motor, whereby the excessive vibration
of the water tub is prevented based on not the probability but the
control. Consequently, the present embodiment has the effect of
reliably reducing the excessive vibration of the water tub.
[0095] Although a few embodiments have been shown and described, it
would be appreciated by those skilled in the art that changes may
be made in this embodiment without departing from the principles
and spirit of the invention, the scope of which is defined in the
claims and their equivalents.
* * * * *