U.S. patent application number 10/488538 was filed with the patent office on 2005-01-27 for washing machine.
Invention is credited to Hosoito, Tsuyoshi, Ito, Michiaki, Kawabata, Shinichiro, Okazaki, Yoji, Tanaka, Toshimasa.
Application Number | 20050016226 10/488538 |
Document ID | / |
Family ID | 19094762 |
Filed Date | 2005-01-27 |
United States Patent
Application |
20050016226 |
Kind Code |
A1 |
Okazaki, Yoji ; et
al. |
January 27, 2005 |
Washing machine
Abstract
A direct drive washing machine is disclosed which is capable of
performing a washing operation by efficiently converting electric
energy supplied into an electric motor (10) into mechanical energy
or with less vibration and noise. When a washing operation is
carried out with efficient energy conversion, an acceleration time
and a deceleration time of an agitator (8) rotated by the motor
(10) are controlled on the basis of a measured value of a vibration
sensor (25) or a measured value of clothes weight so that vibration
of a water-receiving tub (4) becomes maximum. On the other hand,
when a quiet washing operation with less vibration is carried out,
the acceleration time and the deceleration time of an agitator (8)
rotated by the motor (10) are controlled on the basis of the
measured value of the vibration sensor (25) or the measured value
of clothes weight so that vibration of the water-receiving tub (4)
becomes minimum.
Inventors: |
Okazaki, Yoji; (Yokohama,
JP) ; Kawabata, Shinichiro; (Seto, JP) ;
Hosoito, Tsuyoshi; (Seto, JP) ; Ito, Michiaki;
(Seto, JP) ; Tanaka, Toshimasa; (Seto,
JP) |
Correspondence
Address: |
PILLSBURY WINTHROP, LLP
P.O. BOX 10500
MCLEAN
VA
22102
US
|
Family ID: |
19094762 |
Appl. No.: |
10/488538 |
Filed: |
March 4, 2004 |
PCT Filed: |
September 4, 2002 |
PCT NO: |
PCT/JP02/09007 |
Current U.S.
Class: |
68/12.04 ;
68/12.02; 68/12.06; 68/23.1; 68/23.3 |
Current CPC
Class: |
D06F 2103/04 20200201;
D06F 2103/38 20200201; D06F 2103/26 20200201; D06F 37/304 20130101;
D06F 33/48 20200201; D06F 2105/46 20200201; Y02B 40/00
20130101 |
Class at
Publication: |
068/012.04 ;
068/012.02; 068/012.06; 068/023.1; 068/023.3 |
International
Class: |
D06F 033/02 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 5, 2001 |
JP |
2001-268834 |
Claims
1. A washing machine which comprises: a water-receiving tub
elastically suspended in an outer cabinet; a rotating tub provided
in the water-receiving tub; an agitator provided in the rotating
tub; an electric motor provided on an underside of the
water-receiving tub for direct driving the agitator; and a control
device controlling the motor and the overall washing machine,
characterized in that the control device controls either one or
both of an acceleration time and a deceleration time of the motor
in a washing operation so that vibration of the water-receiving tub
becomes maximum.
2. A washing machine according to claim 1, characterized in that
the control device detects a weight of clothes put into the
rotating tub prior to the washing operation and subsequently reads
an acceleration time corresponding to a detected weight value from
a chart storing relationship between weight of clothes and an
acceleration time required for the vibration of the water-receiving
tub to become maximum corresponding to the weight of clothes, and
that the control device controls either one or both of the
acceleration time and the deceleration time of the motor in the
washing operation so that the acceleration time and/or the
deceleration time corresponds to the read time.
3. A washing machine which comprises: a water-receiving tub
elastically suspended in an outer cabinet; a rotating tub provided
in the water-receiving tub; an agitator provided in the rotating
tub; a vibration sensor detecting vibration of the water-receiving
tub; an electric motor provided on an underside of the
water-receiving tub for direct driving the agitator; and a control
device controlling the motor and the overall washing machine,
characterized in that the control device controls either one or
both of an acceleration time and a deceleration time of the motor
in a washing operation so that a value of vibration detected by the
vibration sensor during the wash operation becomes maximum.
4. A washing machine which comprises: a water-receiving tub
elastically suspended in an outer cabinet; a rotating tub provided
in the water-receiving tub; an agitator provided in the rotating
tub; an electric motor provided on an underside of the
water-receiving tub for direct driving the agitator; and a control
device controlling the motor and the overall washing machine,
characterized in that the control device controls either one or
both of an acceleration time and a deceleration time of the motor
in a washing operation so that vibration of the water-receiving tub
becomes minimum.
5. A washing machine according to claim 4, characterized in that
the control device detects a weight of clothes put into the
rotating tub prior to the washing operation and subsequently reads
an acceleration time corresponding to a detected weight value from
a chart storing relationship between weight of clothes and an
acceleration time required for the vibration of the water-receiving
tub to become maximum corresponding to the weight of clothes, and
that the control device controls either one or both of the
acceleration time and the deceleration time of the motor in the
washing operation so that the acceleration time and/or the
deceleration time corresponds to the read time.
6. A washing machine which comprises: a water-receiving tub
elastically suspended in an outer cabinet; a rotating tub provided
in the water-receiving tub; an agitator provided in the rotating
tub; a vibration sensor detecting vibration of the water-receiving
tub; an electric motor provided on an underside of the
water-receiving tub for direct driving the agitator; and a control
device controlling the motor and the overall washing machine,
characterized in that the control device controls either one or
both of an acceleration time and a deceleration time of the motor
in a washing operation so that a value of vibration detected by the
vibration sensor during the wash operation becomes minimum.
Description
TECHNICAL FIELD
[0001] The present invention relates to a washing machine with a
construction that an agitator and a rotating tub are rotated
directly by a brushless motor.
BACKGROUND ART
[0002] Full automatic washing machines have conventionally been
used as means for removing soil adherent to clothes at home. The
full automatic washing machine is provided with mechanisms for
automatically carrying out sequential steps of wash, rinse and
dehydration in the same tub.
[0003] An agitator is turned alternately in the positive and
negative directions in each of the wash and rinse steps, whereas
the agitator and the rotating tub serving as a wash tub and a
dehydration tub are rotated at high speeds in the same direction.
In order that these two driving manners may be carried out, recent
full automatic washing machines employ a direct drive system
transmitting torque developed by a motor rotor only via a clutch
mechanism directly to the agitator or rotating tub without
provision of reduction gears. No reduction gears are provided
between the motor and the agitator or between the motor and the
rotating tub in the direct drive system. Accordingly, the motor
necessitates the performance of driving the agitator and the motor
rotor at low speeds in the wash step thereby to develop a large
torque. Further, the motor also necessitates, in the dehydration
step, the performance of driving the agitator and the rotating tub
at lower speeds than those by a drive system provided with a
reduction mechanism so that a larger torque is developed than that
developed by the drive system with the reduction mechanism.
Different rotational speeds are required in the wash, rinse and
dehydration steps.
[0004] Thus, the motor for the washing machine of the direct drive
system needs to meet the conditions of low speeds, large torque and
variable speed. In order that the conditions may be met, a large
size brushless DC motor has recently been employed and a control
system has been employed to control torque developed by the
brushless DC motor by means of inverter control such as a vector
control system.
[0005] However, in the conventional washing machine employing the
direct drive system, vibrating characteristics of various
mechanisms of the washing machine are not sufficiently considered
for the wash step. In most cases, only a maximum rotational speed
and a rotating time of the motor are controlled according to
clothes. Accordingly, torque developed by the motor is not
efficiently transmitted to rotating objects including the motor
rotor, the agitator, wash liquid and clothes. Thus, electric energy
supplied to the motor is not effectively used in many cases.
Further, even when a quiet operation with less vibration is
desired, for example, an outer or water-receiving tub resonates to
produce noise, resulting in problems concerning noise in many
cases.
[0006] The present invention was made in view of the foregoing
circumstances and an object thereof is to provide a washing machine
which can perform an operation in which torque developed by the
motor is efficiently transmitted to wash liquid and clothes when an
efficient washing operation is desired, and which can perform an
operation resulting in low vibration and low noise when a quiet
operation with less vibration is desired, for example, in the
night.
DISCLOSURE OF THE INVENTION
[0007] A washing machine of the present invention which comprises a
water-receiving tub elastically suspended in an outer cabinet, a
rotating tub provided in the water-receiving tub, an agitator
provided in the rotating tub, an electric motor provided on an
underside of the water-receiving tub for direct driving the
agitator, and a control device controlling the motor and the
overall washing machine, is characterized in that the control
device controls either one or both of an acceleration time and a
deceleration time of the motor in a washing operation so that
vibration of the water-receiving tub becomes maximum. Consequently,
electric energy supplied to the motor can efficiently be converted
to mechanical energy for the wash liquid and clothes in the washing
operation.
[0008] Further, a washing machine of the present invention is
characterized in that the control device detects a weight of
clothes put into the rotating tub prior to the washing operation
and subsequently reads an acceleration time corresponding to a
detected weight value from a chart storing relationship between
weight of clothes and an acceleration time required for the
vibration of the water-receiving tub to become maximum
corresponding to the weight of clothes and that the control device
controls either one or both of the acceleration time and the
deceleration time of the motor in the washing operation so that the
acceleration time and/or the deceleration time corresponds to the
read time. Consequently, electric energy supplied to the motor can
efficiently be converted to mechanical energy for the wash liquid
and clothes in the washing operation.
[0009] Further, a washing machine of the present invention which
comprises a water-receiving tub elastically suspended in an outer
cabinet, a rotating tub provided in the water-receiving tub, an
agitator provided in the rotating tub, a vibration sensor detecting
vibration of the water-receiving tub, an electric motor provided on
an underside of the water-receiving tub for direct driving the
agitator, and a control device controlling the motor and the
overall washing machine, is characterized in that the control
device controls either one or both of an acceleration time and a
deceleration time of the motor in a washing operation so that a
value of vibration detected by the vibration sensor during the wash
operation becomes maximum. Consequently, electric energy supplied
to the motor can efficiently be converted to mechanical energy for
the wash liquid and clothes in the washing operation.
[0010] Further, a washing machine of the present invention which
comprises a water-receiving tub elastically suspended on an outer
cabinet, a rotating tub provided in the water-receiving tub, an
agitator provided in the rotating tub, an electric motor provided
on an underside of the water-receiving tub for direct driving the
agitator, and a control device controlling the motor and the
overall washing machine, is characterized in that the control
device controls either one or both of an acceleration time and a
deceleration time of the motor in a washing operation so that
vibration of the water-receiving tub becomes minimum. Consequently,
a noise-reduced operation with less vibration can be realized in
the washing operation.
[0011] Further, a washing machine of the present invention is
characterized in that the control device detects a weight of
clothes put into the rotating tub prior to the washing operation
and subsequently reads an acceleration time corresponding to a
detected weight value from a chart storing relationship between
weight of clothes and an acceleration time required for the
vibration of the water-receiving tub to become maximum
corresponding to the weight of clothes and that the control device
controlling either one or both of the acceleration time and the
deceleration time of the motor in the washing operation so that the
acceleration time and/or the deceleration time corresponds to the
read time. Consequently, a noise-reduced operation with less
vibration can be realized in the washing operation.
[0012] Further, a washing machine of the present invention which
comprises a water-receiving tub elastically suspended in an outer
cabinet, a rotating tub provided in the water-receiving tub, an
agitator provided in the rotating tub, a vibration sensor detecting
vibration of the water-receiving tub, an electric motor provided on
an underside of the water-receiving tub for direct driving the
agitator, and a control device controlling the motor and the
overall washing machine, is characterized in that the control
device controls either one or both of an acceleration time and a
deceleration time of the motor in a washing operation so that a
value of vibration detected by the vibration sensor during the
washing operation becomes minimum. Consequently, a noise-reduced
operation with less vibration can be realized in the washing
operation.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] FIG. 1 is a longitudinal section of the washing machine in
accordance with the present invention;
[0014] FIG. 2 is an example of electric circuit arrangement
applicable to a manner in which no vibration sensor is used in the
present invention;
[0015] FIG. 3 illustrates changes in the motor speed in the washing
operation with lapse of time;
[0016] FIG. 4 shows a simplified model of washing machine for the
purpose of analyzing vibration;
[0017] FIG. 5 shows a model of vibration system to set up an
equation of motion of the vibration;
[0018] FIG. 6 shows an equation of motion of the vibration in the
case where the washing machine is divided into three portions;
[0019] FIG. 7 shows an example of frequency characteristics of the
amplitude of the vibration caused by the water-receiving tub;
[0020] FIG. 8 shows waveforms of torque developed by the motor in
the washing operation;
[0021] FIG. 9 illustrates magnitude of amplitude corresponding to
frequency component contained in the torque waveform in the
acceleration;
[0022] FIG. 10 is a longitudinal section of the washing machine in
which the vibration sensor is mounted on the water-receiving tub in
accordance with the present invention;
[0023] FIG. 11 is an electric circuit arrangement applicable to a
manner in which the vibration sensor is mounted on the
water-receiving tub in the present invention;
[0024] FIG. 12 is a chart showing an example of optimum
acceleration time t1 corresponding to put clothes weight when HARD
WASHING COURSE has been selected; and
[0025] FIG. 13 is a chart showing an example of optimum
acceleration time t1 corresponding to put clothes weight when QUIET
WASHING COURSE has been selected.
BEST MODE FOR CARRYING OUT THE INVENTION
[0026] The present invention will be described with reference to
the accompanying drawings in order to be disclosed in more
detail.
[0027] FIG. 1 is a longitudinal section of the overall washing
machine comprising a rotating tub serving as a wash tub and a
dehydration tub and directly driven by an inverter-controlled
brushless motor. A washing machine body 1 in FIG. 1 roughly
comprises a rectangular box-shaped outer cabinet 2 and a top cover
3 provided on the top of the outer cabinet 2. An outer tub or
water-receiving tub 4 receiving dehydrated water is elastically
supported by an elastic suspension mechanism 5 in the outer cabinet
2. A rotating tub 6 serving as a wash tub and a dehydration tub is
rotatably provided in the water-receiving tub 4. The rotating tub 6
has a circumferential wall formed with a number of dehydration
holes 6a. Water dehydrated from clothes is discharged through the
dehydration holes 6a into the water-receiving tub 4 in the
dehydration. Further, a balancing ring 7 is provided along an upper
end of the rotating tub 6 in order to maintain the rotating tub 6
in the balanced state during the dehydration. Further, an agitator
8 is rotatably provided on a bottom of the rotating tub 6.
[0028] A driving mechanism section 9 is provided on an underside of
the water-receiving tub 4. The driving mechanism section 9 includes
a brushless motor 10 of the outer rotor type and a clutch mechanism
(not shown). The motor 10 includes a stator 10a fixed to the
water-receiving tub 4 with a driving mechanism section base 9a
interposed therebetween and a rotor 10b coupled directly to the
agitator 8. Only the agitator 8 is rotated alternately in the
normal and reverse directions by the motor 10 in wash and rinse
steps. The rotating tub 6 is coupled to the rotor 10b by a clutch
so as to be rotated at high speeds together with the agitator 8
only in one direction.
[0029] The water-receiving tub 4 has a bottom formed with a drain
hole 11. A drain valve 12 is mounted in the drain hole 11 and has
an outlet to which a drain hose 13 is connected. An air trap 14 is
further provided to be adjacent to the drain hole 11. Pressure in
the air trap 14 is introduced via an air tube 15 to a water level
sensor 16 (shown in FIG. 2). The water level sensor 16 detects a
water level in the water-receiving tub 4 and is disposed inside the
top cover 3.
[0030] A lid 17 is mounted on the top of the top cover 3 and an
operation panel 18 is mounted on the upper front of the top cover
3. A control device 19 is mounted on the inside of the top cover 3.
Further, a water supply valve 22 (shown in FIG. 2) is mounted on
the rear inside of the top cover 3 for controlling water supply
into the rotating tub 6.
[0031] An electrical arrangement of the aforesaid washing machine
will be described with reference to FIG. 2. A control device 19 is
principally comprised of a microcomputer. The control device 19
includes a memory storing a control program required to control the
operation of the overall washing machine. The control device 19
also has a function of executing control computation required for
inverter control of the motor 10. The results of control
computation for the control of torque developed by the motor 10 or
rotational speed thereof are delivered to a motor drive circuit 23
comprising a PWM forming circuit and a PWM inverter circuit. Output
of the PWM inverter circuit is supplied to the motor 10 so that the
latter is driven. A brushless motor is used as the motor 10. A
rotational position of the rotor 10b is detected by a Hall IC 10c.
Pulse signals detected by the Hall IC 10c are supplied to the
control device 19 and the motor drive circuit 23. The rotational
position of the rotor 10b may be detected and the motor 10 may be
controlled by a sensorless vector control system, instead of
detection using the Hall IC 10c.
[0032] To the control device 19 are supplied ON/OFF signals from
switches 20 mounted on the operation panel 18, a water level signal
from the water level sensor 16, and rotational position signal
pulses from the Hall IC 10c. Further, output signals include
signals supplied to the valve drive circuit 21 for opening and
closing the drain valve 12 and water supply valve 22 and display
signals supplied to the displays 20 mounted on the operation panel
24 as well as a control signal supplied to the motor drive circuit
23.
[0033] The following describes the controlling operation in a wash
step under the foregoing electrical arrangement and mechanical
construction. Clothes to be washed are put into the rotating tub 6
which has not been filled with water, and the lid 17 is then
closed. Thereafter, the wash step starts when a start switch of the
switches 20 is depressed.
[0034] When the washing machine 1 is a full automatic washing
machine, the weight of clothes is generally detected first. The
control device 19 delivers a predetermined speed command signal to
the motor drive circuit 23 so that the rotational speeds of the
rotating tub 6 and the agitator 8 are increased to respective
predetermined values. Thereafter, electric supply to the motor 10
is interrupted so that the drive torque of the motor 10 is
decreased to zero or is under the condition of free running. The
speed of the motor 10 is then reduced by the mechanical friction
and air resistance such that the motor 10 is stopped. The reduction
ratio of the motor 10 is influenced by the weight of clothes to be
washed. Accordingly, the weight of clothes is obtained by
predetermined calculation from changes in the frequency of the
rotational position pulses detected by the Hall IC 10c or the
results of rotor rotational position detection by the sensorless
vector control.
[0035] Upon completion of detection of clothes weight, an "OPEN"
signal is supplied to the water supply valve 22 so that water
supply starts. An amount of water supplied is a predetermined
amount of water determined according to the weight of clothes and
is supplied to the rotating tub 6 also serving as the wash tub.
[0036] Upon completion of water supply, the washing operation
starts. In the washing operation, the rotating tub 6 is fixed to
the drive mechanism section base 9a serving as a stationary portion
by the operation of the clutch, whereupon the rotating tub 6 is not
rotated by the operation of the clutch. The agitator 8 directly
connected to the rotor 10b is rotated alternately in the normal and
reverse directions by the motor 10, so that washing liquid and
clothes in the rotating tub 6 are rotated alternately in the normal
and reverse directions, whereby the washing operation is carried
out.
[0037] The agitator 8 is rotated along a speed curve as shown in
FIG. 3 during the washing operation. More specifically, in the
normal rotation, the motor 10 applies constant torque to the rotor
10b during an acceleration time t1, so that the rotational speed of
the rotor 10b and agitator 8 is increased approximately at constant
acceleration, thereby reaching a predetermined revolution N.
Thereafter, torque developed by the motor is adjusted so that the
predetermined revolution N is maintained.
[0038] The acceleration time t1 is usually set to an
extraordinarily short time so that a time required for the wash
step is shortened. In order that the rotational speed of the rotor
10b and agitator 8 may be increased to the predetermined revolution
N within the short acceleration time t1, the motor 10 is required
to develop an extraordinarily large torque. On the other hand,
torque required to maintain the predetermined revolution N takes a
smaller value as compared with torque required to maintain the
predetermined revolution N. Further, a time period for which the
predetermined revolution N is maintained is extraordinarily longer
than the acceleration time t1. When thus rotated, the agitator 8
results in complex rotational motion of wash liquid and clothes,
whereupon soil is removed from the clothes.
[0039] After the predetermined revolution N is maintained for a
predetermined time, the agitator 8 is transferred to a deceleration
stage and then stopped. Torque developed by the motor 10 is
controlled so that the deceleration time becomes equal to the
acceleration time t1. The torque developed by the motor 10 in the
deceleration stage has a waveform which has the same magnitude as
and the reverse polarity to the torque in the acceleration
stage.
[0040] The agitator 8 is stopped for a predetermined time and
thereafter rotated in the reverse direction. The motor 10 is
controlled so that the agitator 8 is rotated along the same speed
curve as but in the opposite direction to that for the normal
rotation.
[0041] Analysis is carried out for vibration at various sections of
the washing machine. For the purpose of simplification in vibration
analysis calculation, it is assumed that the washing machine is
composed of three separate portions as shown in FIG. 4. The first
portion is stationary and includes the water-receiving tub 4,
rotating tub 6 and stator 10a of the motor. The second portion is
directly rotated by the motor 10 and includes the rotor lob of the
motor and agitator 8. The third portion is driven by rotation of
the agitator 8 and includes wash liquid and clothes. Torque
developed by the motor acts between the first and second
portions.
[0042] FIG. 5 shows a model of rotational vibration system
concerning the foregoing three portions in order that motion of the
rotational vibration system may be represented by an equation of
motion. FIG. 6 shows the equation of motion representative of the
rotational vibration system. In FIGS. 5 and 6, reference symbol m1
designates a total moment of inertia of the first portion, namely,
the water-receiving tub 4, rotating tub 6 and stator 10a of the
motor. Reference symbol m2 designates a total moment of inertia of
the second portion, namely, the rotor 10b of the motor and agitator
8. Reference symbol m3 designates a total moment of inertia of the
third portion, namely, the wash liquid and clothes. Reference
symbols K1 and K2 designate spring constants. Reference symbols c1
to c4 designate damping constants. Reference symbols x1 to x3
designate rotation angles of the first, second and third portions
respectively. Reference symbol T designates torque developed by the
motor. Sinusoidal torque changing at frequency f is considered as
torque T and the equation of motion of FIG. 6 is solved for x1.
FIG. 7 shows the frequency characteristic of the magnitude
(amplitude) of the rotation angle x1. The axis of abscissas
represents frequency f and the axis of ordinates represents a ratio
of amplitude of rotation angle at the frequency to a reference
frequency in dB in FIG. 7. The rotation angle x1 has resonant
frequencies f1 and f3 and an antiresonant frequency f2 as shown in
FIG. 7. The amplitude at the lowest resonant frequency is taken as
the reference amplitude for the divisions of the axis of
ordinates.
[0043] On the other hand, FIG. 8 shows rough waveform of torque
developed by the motor 10 only in the normal rotation in order that
the agitator 8 may be driven along the speed curve as shown in FIG.
3. The axis of abscissas represents time and the axis of ordinates
represents developed torque. Usually, the time period for which the
motor 10 maintains the constant speed N is sufficiently longer than
the accelerating and deceleration times t1. Further, torque
required for the rotation at the constant speed N is sufficiently
smaller than torque in each of acceleration and deceleration.
Accordingly, assume the case where torque with the waveform as
shown in FIG. 8 is applied as the drive torque T in the equation of
FIG. 6. In this case, it is considered that relatively large
vibration of each portion produced during the acceleration time is
damped thereby to become smaller during rotation at the constant
speed N. Constant torque T is applied when the motor is in rotation
at the constant rotational speed N. As stated in the last part of
the description of BACKGROUND ART, the present invention resides in
provision of the washing machine which can perform an operation in
which torque developed by the motor is efficiently transmitted to
wash liquid and clothes when an efficient washing operation is
desired, and which can perform an operation resulting in low
vibration and low noise when a quiet operation with less vibration
is desired, for example, in the night. Accordingly, when the motor
10 is under rotation for a long time with the constant rotational
speed N maintained, this state does not so much relate to the
torque transmission efficiency and noise production. What affects
the object of the invention most is considered to be an operation
of the vibration system in the acceleration and deceleration.
Consequently, analysis can be carried out with attention only to
the behavior of the vibration system in the case where the torque
at the time of acceleration as shown in FIG. 8 is applied thereto.
The same behavior can also be seen at the time of deceleration with
rotational direction reversed.
[0044] In order that the aforesaid behavior may be examined,
consider the case where the torque waveform as shown in FIG. 8,
namely, the torque waveform with constant amplitude and duration t1
is applied once in a single-shot manner. The single-shot waveform
is transformed by means of the Fourier transform to be graphed in
order that the frequency characteristic of the torque component
contained in the single-shot pulse may be examined. FIG. 9 shows
the resultant graph. The axis of abscissas represents the frequency
component contained in the single-shot pulse and the axis of
ordinates represents a relative value in dB representative of
magnitude (amplitude) of the torque corresponding to the frequency
relative to the value in the case where the frequency is at zero.
The frequency component of torque contains a frequency at which the
torque component becomes a minimum. When symbols f4 and f5
designate two lower frequencies of the frequency at which the
torque component becomes a minimum, it is known that there is the
following relationship between the values f4 and f5 and the
acceleration (or deceleration) time t1 in FIG. 3 or 8:
f4=1/t1 and
f5=2/t1.
[0045] Examination by the inventors shows that when the
acceleration time t1 is controlled so that the frequency f4 at
which the torque component becomes a minimum corresponds to the
antiresonant frequency f2 in FIG. 7, electric energy supplied to
the motor 10 is efficiently converted to kinetic energy of wash
liquid and clothes. Further, the examination also shows that
vibration of the water-receiving tub 4 in the rotation direction is
increased when the frequency f4 at which the torque component
becomes a minimum corresponds to the antiresonant frequency f2. The
reason for this is that when the frequency f4 at which developed
torque component becomes a minimum corresponds to the antiresonant
frequency f2 in FIG. 7, namely, the frequency f2 at which vibration
scarcely occurs, the vibration system is vibrated to a large degree
by the torque component due to the frequency other than f4,
whereupon torque developed by the motor 10 is efficiently converted
to mechanical energy or, first of all, the mechanical energy of
wash liquid and clothes.
[0046] On the other hand, when a quiet operation with less
vibration is desired, the acceleration time t1 is controlled so
that the frequency f4 at which the minimum torque component in FIG.
9 is reached corresponds to the resonant frequency f1 of the lowest
order in FIG. 7. Consequently, it is found that a quiet operation
can be carried out even when torque developed by the motor 10 is
relatively large. The reason for this is that it is hard to cause
resonance since drive torque component (torque component of
frequency f4) corresponding to frequency f2 causing resonance is a
minimum value.
[0047] Thus, it is proved that the object is achieved when the
acceleration or deceleration time t1 is controlled so that the
frequency f4 corresponds to the resonant frequency f2 when energy
conversion efficiency is of much importance and the frequency f4
corresponds to the resonant frequency f1 of the lowest order.
[0048] Next, the following is the description of manners of
controlling the acceleration or deceleration time t1 so that the
frequency f4 (=1/t1 ) corresponds to the resonant frequency f1 or
the antiresonant frequency f2. Changing the acceleration or
deceleration time t1 is achieved by delivering, as a target value,
constant torque developing time t1 in the waveform of a torque
command value supplied from the control device 11 to the motor
drive circuit 23. However, how the acceleration time t1
corresponding the frequency f4 to frequency f1 or f2 can be found
is a problem. The inventors have found the following two
manners.
[0049] In the first manner, a vibration sensor 25 is mounted on the
water-receiving tub 4 to detect its vibration as shown in FIGS. 10
and 11. The vibration of the water-receiving tub 4 contains a
number of frequency components. Accordingly, in order that the
magnitude of the vibration may be determined, for example, voltage
signal indicative of the vibratory waveform during the acceleration
time t1 is rectified and then converted to DC voltage, so that the
magnitude of vibration is determined by the magnitude of obtained
DC voltage. In this arrangement, the acceleration time t1 is
changed at the intervals of 0.2 to 1.0 sec., for example, 0.1 sec.
and the magnitude of vibration at the time of change of the
acceleration time t1 is measured in an initial stage of the washing
operation. When the washing operation is carried out with the
priority given to energy transmission efficiency, the acceleration
time t1 is determined so that the measured vibration becomes
maximum. On the other hand, when a quiet operation with less
vibration is carried out, the acceleration time t1 is determined so
that the measured vibration becomes minimum. Consequently, the
washing operation can be carried out so that each purpose is
achieved.
[0050] In the second manner, the acceleration times t1 at which
maximum transmission efficiency and minimum vibration are reached
are obtained. The obtained acceleration times t1 correspond to the
weight of clothes put into the rotating tub and an amount of water
supplied are obtained. A correspondence table is previously stored
in a memory of the control device 19. The weight of clothes is
measured and the acceleration or deceleration time t1 are read from
the correspondence table to be used for the control.
[0051] As described above, the weight of clothes put into the
rotating tub is detected at an initial stage of wash step in the
full automatic washing machines. An amount of water to be supplied
is previously determined for every combination of the measured
weight of clothes and a washing course selected by the switches 20,
for example, "careful washing course" or "quiet washing course."
Water supply is carried out according to the combination of the
clothes weight and the washing course. More specifically, a total
mass of the weight of clothes and amount of washing liquid can be
grasped by the control device 10. Accordingly, previous calculation
or experiment is carried out so that the acceleration time t1
corresponding to the total mass and provides maximum energy
efficiency is grasped and so that the acceleration time t1 at which
minimum vibration and noise are reached is grasped. Correspondence
tables are formed and stored in a memory. Consequently, a
purposeful washing operation can be carried out. FIGS. 12 and 13
illustrate examples of such correspondence charts. FIG. 12 is an
example of chart showing the relationship between optimum
acceleration or deceleration time t1 corresponding to the weight of
clothes and the antiresonant frequency f2 in the case where the
careful washing course (efficient washing course) has been
selected. FIG. 13 is an example of chart showing the relationship
between optimum acceleration or deceleration time t1 corresponding
to the weight of clothes and the resonant frequency f1 of the
lowest order in the case where the quiet washing course (washing
course with less vibration) has been selected.
[0052] In the foregoing description, the acceleration time and the
deceleration time are equal to each other. The reason for this is
that effect corresponding to the purpose most is obtained. When the
effect may be sacrificed more or less, either one of the
acceleration or deceleration time may be controlled in the
aforesaid manner and the other of the acceleration and deceleration
time may be set to a different value.
INDUSTRIAL APPLICABILITY
[0053] As described above, the washing machine in accordance with
the invention is suitable for the execution of the washing
operation according to the purpose when the washing operation most
efficiently converting electric energy to the mechanical energy of
wash liquid and clothes. Further, the washing machine is suitable
for the execution of the washing operation according to the purpose
when a quiet washing operation with less vibration is desired.
* * * * *