U.S. patent application number 13/392682 was filed with the patent office on 2012-06-21 for control method of laundry machine.
Invention is credited to Jae Hyuk Jang, Bon Kwon Koo.
Application Number | 20120151693 13/392682 |
Document ID | / |
Family ID | 43628638 |
Filed Date | 2012-06-21 |
United States Patent
Application |
20120151693 |
Kind Code |
A1 |
Jang; Jae Hyuk ; et
al. |
June 21, 2012 |
CONTROL METHOD OF LAUNDRY MACHINE
Abstract
A control method of a laundry machine is disclosed. The control
method of laundry machine having a drum, a front balancer provided
with a front portion of the drum and a rear balancer provided with
a rear portion of the drum includes accelerating the drum and
rotating the drum at a constant speed of a predetermined rotation
speed for a predetermined time period, the predetermined rotation
speed allowing that perpendicular displacement at the front portion
of the drum is different from that at the rear portion of the
drum.
Inventors: |
Jang; Jae Hyuk; (Seoul,
KR) ; Koo; Bon Kwon; (Seoul, KR) |
Family ID: |
43628638 |
Appl. No.: |
13/392682 |
Filed: |
August 27, 2010 |
PCT Filed: |
August 27, 2010 |
PCT NO: |
PCT/KR10/05816 |
371 Date: |
February 27, 2012 |
Current U.S.
Class: |
8/137 |
Current CPC
Class: |
D06F 33/00 20130101;
D06F 2204/065 20130101; D06F 2222/00 20130101; D06F 37/225
20130101; D06F 2202/065 20130101; D06F 37/203 20130101 |
Class at
Publication: |
8/137 |
International
Class: |
D06L 1/20 20060101
D06L001/20 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 27, 2009 |
KR |
10-2009-0079912 |
Aug 27, 2009 |
KR |
10-2009-0079922 |
Aug 27, 2009 |
KR |
10-2009-0079923 |
Claims
1. A control method of laundry machine having a drum, a front
balancer provided with a front portion of the drum and a rear
balancer provided with a rear portion of the drum, the control
method comprising: accelerating the drum and rotating the drum at a
constant speed of a predetermined rotation speed for a
predetermined time period, the predetermined rotation speed
allowing that perpendicular displacement at the front portion of
the drum is different from that at the rear portion of the
drum.
2. The control method as claimed in claim 1, wherein the
predetermined rotation speed is included in the transient
region.
3. The control method as claimed in claim 1, wherein perpendicular
displacement at the front portion of the drum with respect to a
rotational shaft of a transient region is contrary to that at the
rear portion of the drum at the predetermined rotation speed.
4. The control method as claimed in claim 1, wherein the control
method further comprising: a first transient region step for
entering a transient region by accelerating the drum; a third
constant speed rotation step for rotating the drum at a constant
speed of a third rotation speed for a first predetermined time, the
third rotation speed allowing that perpendicular displacement at
the front portion of the drum with respect to a rotational shaft of
the transient region is contrary to that at the rear portion of the
drum; and a second transient region step for straying from the
transient region by accelerating the drum at the third rotation
speed or more.
5. The control method as claimed in claim 4, wherein the second
transient region step includes a rotation speed allowing a natural
vibration mode where perpendicular displacement to the rotational
shaft of the drum at the front portion of the drum is contrary to
that at the rear portion of the drum.
6. The control method as claimed in claim 5, wherein the first
predetermined time of the third constant speed rotation step is
determined such that an angle between the front balls and front
unbalance of the drum is 90.degree. or more and an angle between
the rear balls and rear unbalance of the drum is 90.degree. or
more.
7. The control method as claimed in claim 6, wherein the first
predetermined time of the third constant speed rotation step is
determined such that an angle between a centrifugal force center of
the front balls and the front unbalance is 180.degree. and an angle
between a centrifugal force center of the rear balls and the rear
unbalance is 180.degree..
8. The control method as claimed in claim 7, wherein the first
predetermined time of the third constant speed rotation step is
determined such that the angle between the centrifugal force center
of the front balls and the front unbalance and the angle between a
centrifugal force center of the rear balls and the rear unbalance
are uniformly maintained, respectively.
9. The control method as claimed in claim 6, wherein, at the second
transient region step, an angle between the centrifugal force
center of the front balls and the centrifugal force center of the
rear balls is 90.degree. or more when viewed at the front portion
of the drum.
10. The control method as claimed in claim 6, wherein the third
rotation speed of the third constant speed rotation step is
maintained in the range of 250 rpm to 290 rpm.
11. The control method as claimed in claim 10, wherein the third
rotation speed of the third constant speed rotation step is
maintained at 270 rpm.
12. The control method as claimed in claim 6, wherein the third
rotation speed allows the front balancer and the rear balancer to
be subjected to balancing.
13. The control method as claimed in claim 12, wherein the second
transient region step has an acceleration inclination greater than
that of the first transient region step.
14. The control method as claimed in claim 4, further comprising
the step of a fourth constant speed rotation step for rotating the
drum at a constant speed of a fourth rotation speed for a second
predetermined time after the second transient region step.
15. The control method as claimed in claim 14, wherein the fourth
rotation speed allows the drum to be vibrated such that
perpendicular displacement to the rotational shaft of the drum at
the front portion of the drum is equal to that at the rear portion
of the drum.
16. The control method as claimed in claim 4, wherein the first
transient region step includes a rotation speed allowing a natural
vibration mode where perpendicular displacement to the rotational
shaft of the drum at the front portion of the drum is equal to that
at the rear portion of the drum.
17. The control method as claimed in claim 16, wherein, at the
first transient region step, an angle between the centrifugal force
center of the front balls and the centrifugal force center of the
rear balls is within 90.degree. when viewed at the front portion of
the drum.
18. The control method as claimed in claim 4, further comprising: a
first constant speed rotation step for rotating the drum at a
constant speed of a first rotation speed, sensing a first
unbalance, and comparing the sensed first unbalance with a first
allowable unbalance; and a second constant speed rotation step for
sensing a second unbalance at a second rotation speed of the drum
greater than the first rotation speed and comparing the sensed
second balance with a second allowable balance.
19. A control method of a laundry machine having a drum, a front
balancer provided with a front portion of the drum, and a rear
balancer provided with a rear portions of the drum, the control
method comprising: a first transient region step for passing
through a rotation speed allowing a natural vibration mode where
perpendicular displacement to a rotational shaft of the drum at the
front portion of the drum is equal to that at the rear portion of
the drum; a constant speed rotation step for rotating the drum at a
constant speed for a predetermined time after the first transient
region step; and a second transient region step for passing through
a rotation speed allowing a natural vibration mode where
perpendicular displacement to a rotational shaft of the drum at the
front portion of the drum is contrary to that at the rear portion
of the drum.
20. The control method as claimed in claim 1, wherein the laundry
machine comprises a driving unit comprising a shaft connected to a
drum, a bearing housing to rotatably support the shaft, and a motor
to rotate the shaft, and a suspension assembly is connected to the
driving unit.
21. The control method as claimed in claim 1, wherein the laundry
machine comprises a rear gasket for sealing to prevent washing
water from leaking from a space between a driving unit and a tub,
and enabling the driving unit movable relative to the tub.
22. The control method as claimed in claim 1, wherein a tub is
supported rigidly more than a drum being supported by a suspension
assembly.
23. The control method as claimed in claims 20, wherein the front
balancer and the rear balancer have 14 balls, respectively, each of
the balls has a diameter of 18.55 mm to 19.55 mm, a race for
receiving the balls includes a ball space portion having a
sectional area in the range of 410 mm .sup.2 to 413 mm .sup.2, and
a center diameter of the sectional area of the ball space portion
is in the range of 500 mm to 510 mm.
24. The control method as claimed in claim 20, wherein each of the
ball space portions of the front balancer and the rear balancer is
filled with oil having viscosity of 300 cs at a filling level of
340 cc to 360 cc.
25. The control method as claimed in claim 7, wherein the third
rotation speed of the third constant speed rotation step is
maintained in the range of 250 rpm to 290 rpm.
26. The control method as claimed in claim 8, wherein the third
rotation speed of the third constant speed rotation step is
maintained in the range of 250 rpm to 290 rpm.
27. The control method as claimed in claim 9, wherein the third
rotation speed of the third constant speed rotation step is
maintained in the range of 250 rpm to 290 rpm.
28. The control method as claimed in claim 7, wherein the third
rotation speed allows the front balancer and the rear balancer to
be subjected to balancing.
29. The control method as claimed in claim 8, wherein the third
rotation speed allows the front balancer and the rear balancer to
be subjected to balancing.
30. The control method as claimed in claim 9, wherein the third
rotation speed allows the front balancer and the rear balancer to
be subjected to balancing.
31. The control method as claimed in claim 21, wherein the front
balancer and the rear balancer have 14 balls, respectively, each of
the balls has a diameter of 18.55 mm to 19.55 mm, a race for
receiving the balls includes a ball space portion having a
sectional area in the range of 410 mm .sup.2 to 413 mm .sup.2, and
a center diameter of the sectional area of the ball space portion
is in the range of 500 mm to 510 mm.
32. The control method as claimed in claim 22, wherein the front
balancer and the rear balancer have 14 balls, respectively, each of
the balls has a diameter of 18.55 mm to 19.55 mm, a race for
receiving the balls includes a ball space portion having a
sectional area in the range of 410 mm .sup.2 to 413 mm .sup.2, and
a center diameter of the sectional area of the ball space portion
is in the range of 500 mm to 510 mm.
33. The control method as claimed in claim 21, wherein each of the
ball space portions of the front balancer and the rear balancer is
filled with oil having viscosity of 300 cs at a filling level of
340 cc to 360 cc.
34. The control method as claimed in claim 22, wherein each of the
ball space portions of the front balancer and the rear balancer is
filled with oil having viscosity of 300 cs at a filling level of
340 cc to 360 cc.
Description
TECHNICAL FIELD
[0001] The present invention relates to a control method of a
laundry machine.
BACKGROUND ART
[0002] A drum laundry machine includes a drum arranged in a
horizontal direction and a drum also arranged in a horizontal
direction inside the tub. Laundry is located inside the drum and is
washed with tumbling in accordance with rotation of the drum.
[0003] The tub serves to receive washing water therein, and the
drum serves to carry out washing of the laundry.
[0004] The drum is rotatably installed inside the tub.
[0005] A rotational shaft is connected with a rear portion of the
drum, and a rotational force is forwarded from a motor to the
rotational shaft. The rotational force is forwarded to the drum
through the rotational shaft by rotation of the motor, whereby the
drum is rotated.
[0006] The drum is rotated during rinsing and spinning cycles as
well as a washing cycle. The drum is vibrated with rotating.
[0007] The rotational shaft is projected outside the tub while
passing through a rear wall of the tub. In case of a laundry
machine according to the related art, a bearing housing may be
inserted into the rear wall of the tub by insert molding.
Alternatively, the bearing housing may be fixed to the rear wall of
the tub.
[0008] The rotational shaft is supported by the bearing housing,
and vibration of the drum is forwarded to the bearing housing and
the tub through the rotational shaft.
[0009] Accordingly, the tub is vibrated together with the drum. In
order to damp such vibration, a damping support member is connected
with the tub.
[0010] In other words, in the laundry machine according to the
related art, vibration is forwarded to the tub, and is supported
through the damping support member connected with the tub.
DISCLOSURE OF INVENTION
Technical Problem
[0011] Accordingly, the present invention is directed to a control
method of a laundry machine.
[0012] An object of the present invention is to provide a control
method of a laundry machine which can solve the above problem.
Solution to Problem
[0013] To solve the problems, an object of the present invention is
to provide a method for passing through a transient region while
reducing vibration of a drum when the drum is rotated at a speed
more than the transient region in a laundry machine.
[0014] Another object of the present invention is to provide a
method for controlling positions of balls of a balancer by
considering characteristics of a vibration mode at a transient
region.
Advantageous Effects of Invention
[0015] When a drum is rotated at a speed more than a transient
region in a laundry machine, its vibration can be reduced and at
the same time a rotation speed of the drum can pass through the
transient region effectively.
[0016] In particular, as positions of balls of a balancer are
controlled considering characteristics of a vibration mode at the
transient region, unbalance is compensated to conform to the
vibration mode, whereby vibration of the drum can be reduced
effectively.
[0017] Moreover, vibration of the drum can be reduced effectively
even in a vibration mode, i.e., a diagonal vibration mode where
displacement at a front portion of the drum with respect to a
rotational shaft is contrary to displacement at a rear portion of
the drum.
BRIEF DESCRIPTION OF DRAWINGS
[0018] The accompanying drawings, which are included to provide
further understanding of the disclosure and are incorporated in and
constitute a part of this application, illustrate embodiments of
the disclosure and together with the description serve to explain
the principle of the disclosure.
[0019] In the drawings:
[0020] FIG. 1 is a diagram illustrating a laundry machine according
to one embodiment of the present invention;
[0021] FIG. 2 is a partial sectional view illustrating a laundry
machine of FIG. 1;
[0022] FIG. 3 is a sectional view illustrating a front
balancer;
[0023] FIG. 4 is a diagram illustrating the relation between mass
and natural vibration;
[0024] FIG. 5 is a diagram illustrating the position relation
between balls and unbalance based on rotation of a drum;
[0025] FIG. 6 is a diagram illustrating a spinning method according
to one embodiment of the present invention;
[0026] FIG. 7 is a graph showing a relation of mass vs. a natural
frequency; and
[0027] FIG. 8 is a graph illustrating vibration characteristics of
the laundry machine of FIG. 2.
BEST MODE FOR CARRYING OUT THE INVENTION
[0028] FIG. 1 is a partial exploded perspective view illustrating a
laundry machine according to one embodiment of the present
invention.
[0029] According to a laundry machine according to an embodiment,
the tub may be fixedly supported to the cabinet or it may be
supplied to the cabinet by a flexible supporting structure such as
a suspension unit which will be described later. Also, the
supporting of the tub may be between the supporting of the
suspension unit and the completely fixed supporting.
[0030] That is, the tub may be flexibly supported by the suspension
unit which will be described later or it may be complete-fixedly
supported to be movable more rigidly. Although not shown in the
drawings, the cabinet may not be provided unlike embodiments which
will be described later. For example, in case of a built-in type
laundry machine, a predetermined space in which the built-in type
laundry machine will be installed may be formed by a wall structure
and the like, instead of the cabinet. In other words, the built-in
type laundry machine may not include a cabinet configured to define
an exterior appearance thereof independently.
[0031] The laundry machine according to this embodiment of the
present invention includes a tub fixedly supported to a cabinet.
The tub includes a tub front 100 configured to define a front part
thereof and a tub rear 120 configured to define a rear part
thereof. The tub front 100 and the tub rear 120 are assembled to
each other by screws and a predetermined space is formed in the
assembled structure to accommodate a drum. The tub rear 120 may
include an opening formed in a rear surface thereof and an inner
circumference of the rear surface of the tub rear 120 is connected
with an outer circumference of a rear gasket 250. An inner
circumference of the rear gasket 250 is connected with a tub back
130. The tub back 130 includes a through-hole formed in a center
thereof and a shaft passes the through-hole. The rear gasket 250
may be made of flexible material not to transmit the vibration of
the tub back 130 to the tub rear 120.
[0032] The tub rear 120 includes a rear surface 128. The rear
surface 128 of the tub rear 120, the tub back 130 and the rear
gasket 250 define a rear wall of the tub. The rear gasket 250 is
sealingly connected with the tub back 130 and the tub rear 120 and
it prevents wash water held in the tub from leaking out. The tub
back 130 is vibrated together with the drum during the rotation of
the drum. At this time, the tub back 130 is spaced apart from the
tub rear 120 at a predetermined distance enough not to interfere
with the tub rear 120. Since the rear gasket 250 is made of a
flexible material, it allows the tub back 130 to relative-move
without interfering with the tub rear 120. The rear gasket 250 may
include a corrugation part 252 extendible enough to allow such a
relative movement of the tub back 130.
[0033] A foreign-substance-preventing member 200 is connected with
a front portion of the tub front 100 to prevent foreign substances
from coming between the tub and the drum. The
foreign-substance-preventing member 200 is made of a flexible
material and it is fixedly installed to the tub front 100. The
foreign-substance-preventing member 200 may be made of the same
material as that used to make the rear gasket 250 and it will be
referenced to as front gasket for convenience sake.
[0034] The drum includes a drum front 300, a drum center 320 and a
drum back 340. Balancers 310 and 330 are installed in front and
rear portions of the drum, respectively. The drum back 340 is
connected with a spider 350, and the spider 350 is connected with a
rotational shaft 351. The drum 32 is rotated in the tub by the
rotational force transmitted via the rotational shaft 351.
[0035] The rotational shaft 351 is directly connected with a motor
by passing through the tub back 130. Specifically, the rotational
shaft 351 is directly connected with a rotor of the motor. A
bearing housing 400 is coupled to a rear surface of the tub back
130. The bearing housing 400 is located between the motor and the
tub back 130 to rotatably support the rotational shaft 351.
[0036] A stator is fixedly installed to the bearing housing 400 and
the rotor is located around the stator. As mentioned above, the
rotor is directly connected with the rotational shaft 351. The
motor is an outer rotor type motor and it is directly connected
with the rotational shaft 351.
[0037] The bearing housing 400 is supported from a cabinet base 600
through a suspension unit. The suspension unit includes three
perpendicular supporting suspensions and two oblique-supporting
suspensions configured to support the bearing housing obliquely in
a forward and rearward direction.
[0038] The suspension unit may include a first cylinder spring 520,
a second cylinder spring 510, a third cylinder spring 500, a first
cylinder damper, and a second cylinder damper 530, wherein the
first cylinder damper, although not shown, is symmetrically
installed to be opposite to the second cylinder damper.
[0039] The first cylinder spring 520 is connected between a first
suspension bracket 450 and the cabinet base 600, and the second
cylinder spring 510 is connected between a second suspension
bracket 440 and the cabinet base 600.
[0040] The third cylinder spring 500 is directly connected between
the bearing housing 400 and the cabinet base 600.
[0041] The first cylinder damper 540 is obliquely installed between
the first suspension bracket 450 and a rear portion of the cabinet
base. The second cylinder damper 530 is obliquely installed between
the second suspension bracket 440 and the rear portion of the
cabinet base.
[0042] The cylinder springs 520, 510 and 500 of the suspension unit
may be connected to the cabinet base 600 flexibly enough to allow
the drum to move in a forward-and-rearward direction and a
rightward-and-leftward direction, not completely fixed to the
cabinet base 600. That is, the cylinder springs 520, 510 and 500
elastically support the drum to allow the drum to rotate vertically
and horizontally with respect to the connected point with the
cabinet base.
[0043] The perpendicular ones of the suspensions suspend the
vibration of the drum elastically and the oblique ones dampen the
vibration. That is, out of the vibration system that includes
springs and damping means, the perpendicularly installed ones are
employed as springs and the obliquely installed ones are employed
as damping means.
[0044] The tub front and the tub rear are fixedly secured to the
cabinet and the vibration of the drum is suspendingly supported by
the suspension unit. Substantially, the structure of the tub and
the drum may be separate. Even when the drum is vibrated, the tub
may not be vibrated structurally.
[0045] The bearing housing and the suspension brackets are
connected by first and second weights 431 and 430.
[0046] Hereinafter, a balancer will be described in more
detail.
[0047] First of all, if the drum is rotated in a state that laundry
is placed in the drum, unbalance may be generated by the laundry.
Since such unbalance may cause high vibration of the drum during a
spinning cycle, it is preferably required to reduce such unbalance
(UB). In particular, as the rotation speed of the drum is
increased, it reaches a natural vibration region of the laundry
machine. In this case, a problem may occur in that the vibration
becomes great if unbalance is too great.
[0048] Since it is impossible to uniformly distribute the laundry
inside the drum, it is important to reduce unbalance if possible.
An allowable unbalance rate may be required for the laundry machine
considering characteristics of the laundry machine. In this
respect, it is required to sense unbalance and compare the sensed
unbalance with allowable unbalance to control rotation of the
drum.
[0049] In order to reduce unbalance, several solutions may be
provided. One of the several solutions is laundry distribution or
uniform laundry distribution for varying the position of the
laundry inside the drum.
[0050] Also, in order to reduce unbalance, a fluid may be located
in an opposite position of an unbalanced position of the laundry to
compensate for unbalance of the laundry. In other words, a balancer
may be used.
[0051] In this embodiment, a ball balancer is used as the balancer.
The balancer is respectively used at the front and rear portions of
the drum.
[0052] In this embodiment, as shown in FIG. 2, the front balancer
310 is provided at the front portion of the drum, and the rear
balancer 330 is provided at the rear portion of the drum. In more
detail, the front balancer 310 is mounted on a front surface of the
drum front 300, and the rear balancer 330 is mounted on a rear
surface of the drum back 340. To this end, the drum front 300 may
have a front recess recessed in a rearward direction on the front
surface, and the drum back 340 may have a rear recess recessed in a
forward direction.
[0053] In this embodiment, although not necessarily required, it is
preferably required that the front balancer 310 is structurally the
same as the rear balancer 330.
[0054] FIG. 3 illustrates a sectional structure of the front
balancer 310.
[0055] First of all, the front balancer 310 includes a race 31, a
ball 32, and an oil 33. The race 31 may have a ring shaped ball
space portion 31a where the ball 32 can move therein. The ball
space portion 31a may have a square shape roughly as shown.
[0056] A plurality of balls 32 are received in the ball space
portion 31a. The number of balls received in the ball space portion
31a and a diameter of the ball are defined considering the
unbalance rate, together with vibration characteristics of the
laundry machine.
[0057] Also, since the ball space portion 31a is filled with the
oil 33, the number and diameter of balls received in the ball space
portion 31a are preferably defined considering the amount and
viscosity of the oil 33, which affect movement of the ball 32. The
amount and viscosity of the oil 33 may be determined such that the
ball 32 of the balancer may have required movement. Also, the
amount and viscosity of the oil 33 may be determined considering
vibration characteristics of the laundry machine.
[0058] In this embodiment, 14 balls 32 are received in the ball
space portion 31a, and each of the balls has a diameter of 18.55 mm
to 19.55 mm, preferably 19.05 mm. The ball space portion 31a of the
race has a sectional area in the range of 410 mm .sup.2 to 413 mm
.sup.2, preferably 412 mm .sup.2. A center diameter of the
sectional area of the ball space portion 31a is in the range of 500
mm to 510 mm, preferably 505 mm. Silicon based oil such as Poly
Dimethylsiloxane (PDMS) is used as the oil 33. Preferably, the oil
33 has viscosity of 300 cs at a room temperature, and has a filling
level of 340 cc to 360 cc, preferably 350 cc. It is to be
understood that the present invention is not limited to the
aforementioned characteristic values of the balancer.
[0059] Hereinafter, a method of using movement of the ball inside
the balancer when the drum is rotated with unbalance will be
described. Since the balancer is mounted on the drum and then
rotated together with the drum, movement of the ball inside the
balancer can be controlled finally by rotation control of the
drum.
[0060] In particular, if the rotation speed of the drum is close to
natural vibration of the laundry machine, the vibration of the drum
may occur seriously. In this case, it is important how the ball is
controlled.
[0061] In the laundry machine according to the related art, a
natural vibration mode occurs in the range of 200 rpm to 270 rpm.
Such a period where the natural vibration mode occurs may be
referred to as a transient region. In this transient region, a
plurality of natural vibration modes may exist. If the drum should
be rotated at a rotation speed more than the transient region, it
is important to control the ball such that the vibration of the
drum becomes low.
[0062] FIG. 7 illustrates a graph showing a relation of mass vs. a
natural frequency. It is assumed that, in vibration systems of two
laundry machines, the two laundry machines have mass of m0 and m1
respectively and maximum holding laundry amounts are .DELTA.m,
respectively. Then, the transition regions of the two laundry
machines can be determined taking .DELTA.nf0 and .DELTA.nf1 into
account, respectively. In this instance, amounts of water contained
in the laundry will not be taken into account, for the time
being.
[0063] In the meantime, referring to FIG. 7, the laundry machine
with smaller mass m1 has a range of the transition region greater
than the laundry machine with greater mass m0. That is, the range
of the transition region having variation of the laundry amount
taken into account becomes the greater as the mass of the vibration
system becomes the smaller.
[0064] The ranges of the transition regions will be reviewed on the
related art laundry machine and the laundry machine of the
embodiment.
[0065] The related art laundry machine has a structure in which
vibration is transmitted from the drum to the tub as it is, causing
the tub to vibrate. Therefore, in taking the vibration of the
related art laundry machine into account, the tub is indispensible.
However, in general, the tub has, not only a weight of its own, but
also substantial weights at a front, a rear or a circumferential
surface thereof for balancing. Accordingly, the related art laundry
machine has great mass of the vibration system.
[0066] Opposite to this, in the laundry machine of the embodiment,
since the tub, not only has no weight, but also is separated from
the drum in view of a supporting structure, the tub may not be put
into account in consideration of the vibration of the drum.
Therefore, the laundry machine of the embodiment may have
relatively small mass of the vibration system.
[0067] Then, referring to FIG. 7, the related art laundry machine
has mass m0 and the laundry machine of the embodiment has mass m1,
leading the laundry machine of the embodiment to have a greater
transition region, at the end.
[0068] Moreover, if the amounts of water contained in the laundry
are taken into account simply, .DELTA.m in FIG. 7 will become
greater, making a range difference of the transition regions even
greater. And, since, in the related art laundry machine, the water
drops into the tub from the drum even if the water escapes from the
laundry as the drum rotates, an amount of water mass reduction come
from the spinning is small. Since the laundry machine of the
embodiment has the tub and the drum separated from each other in
view of vibration, the water escaped from the drum influences the
vibration of the drum, instantly. That is, the influence of a mass
change of the water in the laundry is greater in the laundry
machine of the embodiment than the related art laundry machine.
[0069] Under above reason, though the related art laundry machine
has the transition region of about 200-270 rpm, A start RPM of the
transient region of the laundry machine according to this
embodiment may be similar to a start RPM of the transient region of
the conventional laundry machine. An end RPM of the transient
region of the laundry machine according to this embodiment may
increase more than a RPM calculated by adding a value of
approximately 30 % of the start RPM to the start RPM. For example,
the transient region finishes at an RPM calculated by adding a
value of approximately 80 % of the start RPM to the start RPM.
According to this embodiment, the transient region may include a
RPM band of approximately 200 to 350 rpm.
[0070] In the meantime, by reducing intensity of the vibration of
the drum, unbalance may be reduced. For this, even laundry
spreading is performed for spreading the laundry in the drum as far
as possible before the rotation speed of the drum enters into the
transition region.
[0071] In a case, a balancer is used, a method may be put into
account, in which the rotation speed of the drum passes through the
transition region while movable bodies provided in the balancer are
positioned on an opposite side of an unbalance of the laundry. In
this instance, it is preferable that the movable bodies are
positioned at exact opposite of the unbalance in middle of the
transition region.
[0072] However, as described above, the transient region of the
laundry machine according to this embodiment is relatively wide in
comparison to that of the conventional laundry machine. Because of
that, even if the laundry even-spreading step or ball balancing is
implemented in a RPM band lower than the transient region, the
laundry might be in disorder or balancing might be failed with the
drum speed passing the transient region.
[0073] As a result, balancing may be implemented at least one time
in the laundry machine according to this embodiment before and
while the drum speed passing the transient region. Here, the
balancing may be defined as rotation of the drum at a
constant-speed for a predetermined time period. Such the balancing
allows the movable body of the balancer to the opposite positions
of the laundry, only to reduce the unbalance amount. By extension,
the effect of the laundry even-spreading. Eventually, the balancing
is implemented while the drum speed passing the transient region
and the noise and vibration generated by the expansion of the
transient region may be prevented.
[0074] Here, when the balancing is implemented before the drum
speed passing the transient region, the balancing may be
implemented in a different RPM band from the RPM of the
conventional laundry machine. For example, if the transient region
starts at 200 RPM, the balancing is implemented in the RPM band
lower than approximately 150 RPM. Since the conventional laundry
machine has a relatively less wide transient region, it is not so
difficult for the drum speed to pass the transient region even with
the balancing implemented at the RPM lower than approximately 150
RPM. However, the laundry machine according to this embodiment has
the relatively wide expanded transient region as described above.
if the balancing is implemented at the such the low RPM like in the
conventional laundry machine, the positions of the movable bodies
might be in disorder by the balancing implemented with the drum
speed passing the transient region. Because of that, the laundry
machine according to this embodiment may increase the balancing RPM
in comparison to the conventional balancing RPM, when the balancing
is implemented before the drum speed enters the transient region.
That is, if the start RPM of the transient region is determined,
the balancing is implemented in a RPM band higher than a RPM
calculated by subtracting a value of approximately 25 % of the
start RPM from the start RPM. For example, the start RPM of the
transient region is approximately 200 RPM, the balancing may be
implemented in a RPM band higher than 150 RPm lower than 200
RPM.
[0075] Moreover, the unbalance amount may be measured during the
balancing. That is, the control method may further include a step
to measure the unbalance amount during the balancing and to compare
the measured unbalance amount with an allowable unbalance amount
allowing the acceleration of the drum speed. If the measured
unbalance amount is less than the allowable unbalance amount, the
drum speed is accelerated after the balancing to be out of the
transient region. In contrast, if the measured unbalance amount is
the allowable unbalance amount or more, the laundry even-spreading
step may be re-implemented, in this case, the allowable unbalance
amount may be different from an allowable unbalance amount allowing
the initial accelerating.
[0076] Generally, the transient region may be defined as a rotation
speed range of the drum. As described above, the transient region
may be defined as a region that includes natural vibration. In the
vibration system, natural vibration is determined by mass and
rigidity (for example, spring constant). Since mass may be varied
depending on the amount of laundry in the laundry machine, the
transient region is preferably controlled considering mass.
[0077] In order to reduce the vibration of the drum at the
transient region, the unbalance rate may be reduced. In this case,
uniform laundry distribution for uniformly distributing the laundry
inside the drum is carried out before the rotation speed of the
drum enters the transient region.
[0078] If the balancer is used, the rotation speed of the drum may
quickly pass through the transient region while the balls are being
located at an opposite position of the unbalanced position of the
laundry. At this time, in the middle of the transient region, the
balls are preferably located at the opposite position of the
unbalanced position. In this case, the relation between the
position of the balls and the unbalanced position can be defined by
an angle (hereinafter, referred to as `nearest ball angle`) of the
ball located nearest to unbalance with respect to the centrifugal
force center of the unbalance.
[0079] FIG. 4 illustrates the position relation between unbalance
(UB) and the balls. In FIG. 4, the position relation between the
balls and unbalance illustrate that the nearest ball angle is
.theta.1 and a centrifugal force center angle is .theta.2. For
convenience' sake, the angle between the ball and unbalance will
mean .theta.1 or .theta.2.
[0080] A steel ball can be used as the ball. If the sizes of the
balls are uniformly provided and the balls are arranged in parallel
to adjoin one another, the centrifugal force center is P1 as shown
in FIG. 4.
[0081] The ball is rotated by a friction force generated when the
drum is rotated. When the drum is rotated, the ball is not kept in
the drum and it is rotated at a different speed from that of the
drum. Here, unbalance means the laundry being in close contact with
an inner wall of the drum and it can be rotated at almost the same
speed as that of the drum because of an enough friction force and
the lift of the inner wall. As a result, the rotation speed of the
unbalance is different from that of the ball. Since the balls are
rotated by rotation of the drum, the rotation speed of the
unbalance is faster than that of the balls. Precisely, an angular
velocity of the unbalance is faster than that of the balls.
[0082] If the rotation speed of the drum is getting faster, the
balls will be in close contact with an outer circumferential
surface of the ball space portion of the racer because of a
centrifugal force. If the friction force between the
circumferential surface and the balls is a predetermined value or
more, the balls will be rotated with the same rotation speed as
that of the drum. In this case, the balls are located at a
predetermined position with respect to the drum in the same manner
as the unbalance. In this specification, the case of the ball being
rotated at the predetermined position with respect to the drum will
be referenced to as `balancing position` or `balancing` for
convenience' sake.
[0083] For the ball balanced rotation speed, the minimum rotation
speed may be varied depending on the balancer. Also, the minimum
rotation speed may be varied depending on whether the balancer is
installed perpendicularly or horizontally. If the balancer is
installed perpendicularly, the positions of the balls being in
contact with the outer circumferential surface of the ball space
portion of the race may be varied by gravity. The balls maintained
at constant speed rotation of the ball balanced rotation speed may
be located at the opposite position of the unbalanced position.
Referring to FIG. 4, the balls may be located at P2.
[0084] In the mean time, balancing may not be carried out at a
rotation speed lower than the transient region due to a low
centrifugal force. Accordingly, when the rotation speed of the drum
passes through the transient region, instead of carrying out
balancing, the position of the balls is checked while the drum is
being rotated at a constant speed, whereby the balls can be located
at the opposite position of the unbalanced position when the
rotation speed of the drum passes through the transient region. In
other words, even though balancing is not carried out, it can be
controlled such that the rotation speed of the drum passes through
the transient region while the balls are being located at the
opposite position of the unbalanced position. For example,
referring to FIG. 4, it can be controlled such that the rotation
speed of the drum passes through the transient region when the
angle .theta.1 or .theta.2 between the ball and unbalance is more
than 90.degree.. At this time, in the middle of the transient
region, it may be preferable that the angle is 180.degree..
[0085] When the drum is rotated at a constant speed more than the
transient region as above, the vibration of the drum may occur such
that displacement at the front portion of the drum is equal to that
at the rear portion of the drum. Accordingly, as shown in FIG. 5,
an angle .theta.3 between the front balls 32f and the rear balls
32e may be within 90.degree.. FIG. 5 is a diagram illustrating the
position relation between the front balls 32f and the rear balls
32e when viewed through the drum in a forward direction.
[0086] At the transient region, a vibration mode where front
displacement of the vibration of the drum is different from rear
displacement thereof may occur. For example, a vibration mode where
front displacement of the vibration of the drum is opposite to rear
displacement thereof may occur. For convenience' sake, this
vibration mode will be referred to as a diagonal vibration mode.
Meanwhile, the transient region of the laundry machine of this
embodiment may expand compared to the conventional laundry machine.
Therefore, the vibration mode of the drum may be changed due to the
expanded transient region, for example, the diagonal vibration mode
can be generated. In this diagonal vibration mode, if the rear
balls 32f and the rear balls 32e are maintained at an angle within
the range of 90.degree. as described above, unbalance to the
diagonal vibration mode may not be compensated normally, whereby
the vibration of the drum may become severe.
[0087] The aforementioned diagonal vibration mode may start to
occur as the vibration of the drum becomes close to natural
vibration of the natural vibration mode corresponding to the
diagonal vibration mode.
[0088] Accordingly, in order to reduce the vibration of the drum,
the positions of the front balls 32f and the rear balls 32e should
be corrected before the vibration of the drum reaches the natural
vibration of the diagonal vibration mode.
[0089] To this end, before the vibration of the drum reaches the
natural vibration, the drum is preferably subjected to constant
speed rotation for a predetermined time at a rotation speed where
the diagonal vibration mode occurs, whereby the positions of the
front balls 32f and the rear balls 32e are corrected to compensate
for unbalance.
[0090] In particular, the aforementioned laundry machine of this
embodiment has a different structure from that of the related art.
Since the natural vibration mode corresponding to the diagonal
vibration mode may occur at the transient region, it is preferably
required to correct the positions of the balls as described
above.
[0091] Hereinafter, a control method for passing through the
transient region to carry out a spinning cycle in the
aforementioned laundry machine will be described using a rotation
speed graph of the drum based on the passage of time with reference
to FIG. 6. In FIG. 6, period `a` denotes a first constant speed
rotation step, period `b` a second constant speed rotation step,
period `c1` a first transient region step, period `c2` third
constant speed rotation step, period `c3` a second transient region
step, and period `d` fourth constant speed rotation step.
[0092] First of all, at the period `a`, laundry distribution or
laundry disentangling is carried out, and a first unbalance value
is sensed while the drum is rotated at a constant speed of a first
rotation speed, and then the sensed first unbalance value is
compared with a first allowable unbalance value.
[0093] At this time, if the sensed first unbalance value is less
than the first allowable unbalance value, the drum is accelerated
to reach a second rotation speed and then rotated at a constant
speed (period `b`). At the period `b`, a second unbalance value is
sensed and then the sensed second unbalance value is compared with
a second allowable unbalance value. If the sensed second unbalance
value is less than the second allowable unbalance value, the drum
is subjected to warming-up for passing through the transient region
period `c`.
[0094] In this case, as shown in A of FIG. 6, at the first
transient region period `c1`, the natural vibration mode where
vibration displacement at the front portion of the drum is equal to
that at the rear portion of the drum occurs. As shown in B of FIG.
6, at the second transient region period `c3` the natural vibration
mode corresponding to the diagonal vibration mode where vibration
displacement at the front portion of the drum is contrary to that
at the rear portion of the drum occurs.
[0095] First of all, in order to pass through the period `c1`the
drum is rotated at a constant speed at the period `b` to check the
position of the ball, whereby an acceleration timing t1 is
determined. At the period `c1`, t1 and its acceleration inclination
are determined such that the angle between the unbalance and the
ball is in the range of 90.degree. or more. At this time, in the
middle of the period `c1`, t1 and its acceleration inclination can
be determined such that the angle between the unbalance and the
ball is in the range of 180.degree.. At the period `c1`, the
centrifugal force center of the front balls 32f and the centrifugal
force center of the rear balls 32e can define an angle within the
range of 90.degree. based on the rotation center of the drum when
viewed in a forward direction. Preferably, the front balls 32f and
the rear balls 32e are located within the range of 90.degree. to
reduce the vibration of the vibration mode where displacement at
the front portion of the drum and displacement at the rear portion
of the drum are equal to each other in a perpendicular direction
with respect to the rotational shaft.
[0096] If the rotation speed of the drum reaches the third rotation
speed via the period `c1`, the drum is rotated at a constant speed
for a predetermined time (period `c2`). The period `c2`may be
regarded as a warming-up period for passing through the natural
vibration mode corresponding to diagonal vibration that may occur
at the period `c3`. At the period `c2`, the drum may be vibrated in
the diagonal vibration mode as it is rotated at a rotation speed
near the natural vibration of the natural vibration mode
corresponding to the diagonal vibration. At this time, as the drum
is rotated at a constant speed for a predetermined time, the
position of the balls of the front balancer and the rear balancer
is varied depending on the corresponding vibration mode.
[0097] After passing through the period `c2`, the rotation speed of
the drum passes through the transient region at the period `c3` in
a state that the angle between the front balls 32f and the front
unbalance and the angle between the rear balls 32e and the rear
unbalance are 90.degree. or more, respectively. At this time, when
viewed from the drum in a forward direction, the angle between the
front balls 32f and the rear balls 32e may be 90.degree. or more.
In order to reduce vibration of the diagonal vibration mode, it is
preferable that the angle between the front balls 32f and the rear
balls 32e is 90.degree. or more.
[0098] The third rotation speed and the predetermined time can be
determined considering that the front balancer and the rear
balancer are subjected to balancing. In other words, as the drum is
rotated at the third rotation speed for the predetermined time, the
third rotation speed and the predetermined time can be determined
in such a manner that the front balls 32f and the rear balls 32e
are moved to a position for compensating front unbalance and a
position for compensating rear unbalance, respectively, at angles
of 180.degree., respectively, and then are maintained at their
positions, respectively.
[0099] In this embodiment, the third rotation speed is preferably
set in the range of 250 rpm to 290 rpm. If the rotation speed of
the drum is too low, a vibration level of the diagonal vibration
mode becomes weak, whereby the period `c2` becomes longer or
balancing may not be carried out preferably. Also, if the rotation
speed of the drum is too high, severe vibration occurs and movement
of the balls becomes unstable, whereby the positions of the balls
may not be varied normally. Preferably, the third rotation speed of
the drum is set in the range of 270 rpm. The period `c2` is
preferably maintained for 30 seconds, approximately.
[0100] The rotations speed of the drum strays from the transient
region while it is passing through the period `c3` where the
natural vibration mode corresponding to diagonal vibration occurs.
Afterwards, the rotation speed of the drum enters the period for
rotating the drum at high speed to carry out the spinning cycle. At
this time, it is necessary to vary the positions of the balls
before the rotation speed of the drum enters the main spinning
step.
[0101] At the period `c2`, since the front balls and the rear balls
are located to be suitable for compensating the unbalance to
diagonal vibration, they may not be suitable for the main spinning
step having a vibration mode different from the diagonal vibration
mode.
[0102] Accordingly, the period `d` for realigning the positions of
the balls while the rotation speed of the drum is maintained at a
constant speed rotation of a fourth rotation speed after passing
through the transient region will be required. In other words, it
is preferably required to realign the balls to be suitable for
compensating the unbalance to the vibration mode of the main
spinning step.
[0103] As the balls are moved at the main spinning step, unbalance
may occur severely. Accordingly, balancing is preferably carried
out at the period `d`. In other words, the rotation speed of the
drum is preferably maintained at the fourth rotation speed suitable
for the corresponding vibration mode such that the balls are
located to compensate for unbalance.
[0104] The fourth rotation speed is preferably determined at a
rotation speed that does not allow the diagonal vibration mode if
possible. For example, the fourth rotation speed is preferably
determined at a rotation speed different from the natural vibration
of the diagonal vibration mode as much as a predetermined rate,
whereby the fourth rotation speed is not affected by the diagonal
vibration mode.
[0105] At the period `d` the rotation speed of the drum can
maintained in the range of 370 rpm to 390 rpm for 50 seconds to 70
seconds, preferably 60 seconds.
[0106] In the mean time, it is preferable that the acceleration
inclination at the period `c1` is smaller than that at the period
`c3`. If the balancing is carried out at the third rotation speed,
since the balls may little be moved, the rotation speed of the drum
can quickly pass through the period `c3`. However, the balls
continue to move without being balanced at the period `cl` and
considering such a movement of the balls, the rotation speed for
passing through the period `cl` is determined.
[0107] Finally, after passing through the period `d` the main
spinning step is carried out at 1000 rpm or more to spin the
laundry.
[0108] Although the spinning cycle is carried out for example in
this embodiment, this embodiment may be applied to any other case
where the drum is rotated at a speed more than the transient
region.
[0109] First, vibration characteristics of the laundry machine
according to the embodiment of the present invention will now be
described with reference to FIG. 8.
[0110] As the rotation speed of the drum is increased, a region
(hereinafter, referred to as"transient vibration region") where
irregular transient vibration with high amplitude occurs is
generated. The transient vibration region irregularly occurs with
high amplitude before vibration is transited to a steady-state
vibration region (hereinafter, referred to as"steady-state
region"), and has vibration characteristics determined if a
vibration system (laundry machine) is designed. Though the
transient vibration region is different according to the type of
the laundry machine, transient vibration occurs approximately in
the range of 200 rpm to 270 rpm. It is regarded that transient
vibration is caused by resonance. Accordingly, it is necessary to
design the balancer by considering effective balancing at the
transient vibration region.
[0111] In the mean time, as described above, in the laundry machine
according to the embodiment of the present invention, the vibration
source, i.e., the motor and the drum connected with the motor are
connected with the tub 12 through the rear gasket 250. Accordingly,
vibration occurring in the drum is little forwarded to the tub, and
the drum is supported by a damping means and the suspension unit
180 via a bearing housing 400. As a result, the tub 12 can directly
be fixed to a cabinet 110 without any damping means.
[0112] As a result of studies of the inventor of the present
invention, vibration characteristics not observed generally have
been found in the laundry machine according to the present
invention. According to the general laundry machine, vibration
(displacement) becomes steady after passing through the transient
vibration region. However, in the laundry machine according to the
embodiment of the present invention, a region (hereinafter,
referred to as"irregular vibration") where vibration becomes steady
after passing through the transient vibration region and again
becomes great may be generated. For example, if the maximum drum
displacement or more generated in an RPM band lower than the
transient region or the maximum drum displacement or more of steady
state step in a RPM band higher than the transient region is
generated, it is determined that irregular vibration is generated.
Alternatively, if an average drum displacement in the transient
region, +20 % to -20 % of the average drum displacement in the
transient region or 1/3 or more of the maximum drum displacement in
the natural frequency of the transient region are generated, it may
be determined that the irregular vibration is generated.
[0113] However, as a result of the studies, irregular vibration has
occurred in a RPM band higher than the transient region, for
example has occurred at a region (hereinafter, referred to
as"irregular vibration region") in the range of 350 rpm to 1000
rpm, approximately. Irregular vibration may be generated due to use
of the balancer, the damping system, and the rear gasket.
Accordingly, in this laundry machine, it is necessary to design the
balancer by considering the irregular vibration region as well as
the transient vibration region.
[0114] For example, the balancer is provide with a ball balancer,
it is preferable that the structure of the balancer, i.e., the size
of the ball, the number of balls, a shape of the race, viscosity of
oil, and a filling level of oil are selected by considering the
irregular vibration region as well as the transient vibration
region. When considering the transient vibration region and/or the
irregular vibration region, especially considering the irregular
vibration region, the ball balancer has a greater diameter of 255.8
mm and a smaller diameter of 249.2. A space of the race, in which
the ball is contained, has a sectional area of 411.93 mm .sup.2.
The number of balls is 14 at the front and the rear, respectively,
and the ball has a size of 19.05 mm. Silicon based oil such as Poly
Dimethylsiloxane (PDMS) is used as the oil. Preferably, oil has
viscosity of 300 CS at a room temperature, and has a filling level
of 350 cc.
[0115] In addition to the structure of the balancer, in view of
control, it is preferable that the irregular vibration region as
well as the transient vibration region is considered. For example,
to prevent the irregular vibration, if the irregular vibration
region is determined, the balancing may be implemented at least one
time before, while and after the drum speed passes the irregular
vibration region. Here, if the rotation speed of the drum is
relatively high, the balancing of the balancer may not be
implemented properly and the balancing may be implemented with
decreasing the rotation speed of the drum, however, if the rotation
speed of the drum is decreased to be lower than the transient
region to implement the balancing, it has to pass the transient
region again. In decreasing the rotation speed of the drum to
implement the balancing, the decreased rotation speed may be higher
than the transient region.
[0116] It will be apparent to those skilled in the art that various
modifications and variations can be made in the present invention
without departing from the spirit or scope of the invention. Thus,
it is intended that the present invention cover the modifications
and variations of this invention provided they come within the
scope of the appended claims and their equivalents.
* * * * *