U.S. patent application number 11/368432 was filed with the patent office on 2006-09-14 for electric vacuum cleaner.
Invention is credited to Akihiro Ishizawa, Hiroyuki Kushida.
Application Number | 20060204383 11/368432 |
Document ID | / |
Family ID | 36971135 |
Filed Date | 2006-09-14 |
United States Patent
Application |
20060204383 |
Kind Code |
A1 |
Kushida; Hiroyuki ; et
al. |
September 14, 2006 |
Electric vacuum cleaner
Abstract
An electric vacuum cleaner includes a filter, blower, switching
element for switching current flowing through the blower, current
detecting section, and control section, wherein the control section
includes a first control mode in which an amount of airflow flowing
through the filter and the blower is restrained and a second
control mode in which an applied power to the blower is maintained
to a target value, and selects one of the first and second control
modes according to the applied power.
Inventors: |
Kushida; Hiroyuki; (Tokyo,
JP) ; Ishizawa; Akihiro; (Tokyo, JP) |
Correspondence
Address: |
DLA PIPER RUDNICK GRAY CARY US LLP
P. O. BOX 9271
RESTON
VA
20195
US
|
Family ID: |
36971135 |
Appl. No.: |
11/368432 |
Filed: |
March 7, 2006 |
Current U.S.
Class: |
417/423.2 |
Current CPC
Class: |
A47L 9/2831 20130101;
A47L 9/2821 20130101; A47L 9/2842 20130101; F04D 27/004 20130101;
A47L 9/2857 20130101; A47L 9/2889 20130101; F05D 2270/335 20130101;
Y02B 30/70 20130101 |
Class at
Publication: |
417/423.2 |
International
Class: |
F04B 17/00 20060101
F04B017/00 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 8, 2005 |
JP |
2005-064330 |
Claims
1. An electric vacuum cleaner comprising: a blower for generating
an air flow containing dust; a filter configured to separate dust
from the air flow; a switching element for switching a current
flowing through the blower in response to a control signal; an
air-flow-amount sensing section for sensing an amount of the air
flowing through the filter to output a first value indicating the
sensed result, the air-flow-amount being varied in response to
amount of the dust separated by the filter; a current detecting
section for detecting a current flowing through the blower to
output a second value indicating the detected current value, the
current corresponding to power applied to the blower; and a control
section for selecting, in accordance with power applied to the
blower, one of a first control mode in which a suitable output
timing of the control signal from the control section to the
switching element is determined so that variation in the amount of
the air flow is restrained based on the first value and a second
control mode in which a suitable output timing of the control
signal is determined so that the applied power to the blower is
maintained at a prescribed target value based on the second value
and for controlling the operation of the switching element with the
control signal outputted at the suitable output timing of the
selected mode.
2. The electric vacuum cleaner according to claim 1, wherein the
air-flow-amount sensing section includes a current sensor for
sensing a current flowing through the blower, the current being
varied in response to an amount of the air flowing through the
filter.
3. The electric vacuum cleaner according to claim 1, wherein the
control section selects the first control mode when the power
applied to the blower is equal to or less than a prescribed value
and otherwise selects the second mode.
4. The electric vacuum cleaner according to claim 1, further
comprising a zero-cross detecting section for detecting a
zero-cross point of the applied voltage to the blower, wherein the
control section outputs the control signal every half period of the
applied voltage with reference to the detected zero-cross
point.
5. The electric vacuum cleaner according to claim 1, wherein the
control section includes a PWM (pulse-width-modulation) signal
generation section for outputting a PWM signal to the switching
element as the control signal.
6. The electric vacuum cleaner according to claim 1, further
comprising a memory for storing a plurality of output timing values
and thresholds of the air-flow-amount corresponding to each value
of the output timing values, wherein, in the first control mode,
the control section compares the thresholds with one of the first
value and a value calculated based on the first value, selects one
of the plurality of output timing values in accordance with the
compared result, and outputs the control signal based on the
selected value of the output timing.
7. The electric vacuum cleaner according to claim 6, wherein the
memory stores a first switching threshold, and wherein the control
section switches the first control mode to the second control mode
when the one of the first value and the calculated value exceeds
the first switching threshold.
8. The electric vacuum cleaner according to claim 1, further
comprising a memory for storing value of a target current and a
proportional coefficient, wherein the control section, in the
second control mode, calculates an error between the target current
value and one of the second value and a current value calculated
based on the second value, and determines the suitable output
timing according to a value that is obtained by multiplying the
error by the proportional coefficient.
9. The electric vacuum cleaner according to claim 8, wherein the
memory stores a second switching threshold, and wherein the control
section switches the second control mode to the first control mode
when the error goes smaller than the second switching
threshold.
10. The electric vacuum cleaner according to claim 1, further
comprising an informing section for informing that the blower
operates in the second mode.
Description
CROSS REFERENCE OF THE INVENTION
[0001] This application is based upon and claims the benefit of
priority from the prior Japanese Patent Application No. 2005-064330
filed on Mar. 8, 2005, the contents of which are incorporated
herein by reference.
BACKGROUND OF THE INVENTION
[0002] (1) Field of the Invention
[0003] The present invention relates generally to an electric
vacuum cleaner, and more particularly to a controller controlling
operation of a blower provided to the electric vacuum cleaner.
[0004] (2) Description of the Related Art
[0005] An electric vacuum cleaner has a blower generating an
air-flow containing dust and a filter which separates the dust from
the air-flow and collects the dust. Increasing the amount of
collected dust causes air-flow resistance in an intake side of the
blower to increase and the air-flow to decrease, resulting in
reducing the suction power by the blower in the cleaner if the
applied power is constant. An operator or user generally desires
that an electric vacuum cleaner can have a stable suction power
generating an air-flow irrespective of an amount of collected or
trapped dust in the filter.
[0006] In connection with this, the Japanese Laid-open (Kokai)
Patent No. HEI 08-228978 discloses an electric vacuum cleaner
configured to compare a current varying depending on air-flow
resistance in an intake side of a blower, i.e., current flowing
through the blower, with a prescribed threshold value, and vary in
rise and/or descent the applied power to the blower step by step in
response to the compared result, repeatedly.
[0007] In a household electric vacuum cleaner, an upper limit value
is applied to an input power for the sake of energy saving and it
is occasionally required under some circumstance to have a high
suction power generating air-flow within an input power range not
exceeding the upper limit value.
[0008] Conventionally, an electric vacuum cleaner has been
configured to compare a current flowing through a blower with a
prescribed threshold value and to control the input power to the
blower to be increased or decreased step by step to vary an amount
of air-flow drawing through the blower in response to the compared
result. In case that an applied power is controlled to become a
target value using the conventional method, it is required
beforehand to prepare a lot of current threshold values to smoothly
adjust the applied power to the target value and thus a memory
having a large storage capacity is needed. In addition, a lot of
experiments are also needed to determine such a large amount of
current threshold values and thus, development efficiency of a
controller is deteriorated.
SUMMARY OF THE INVENTION
[0009] Accordingly, an object of the present invention is to
provide an electric vacuum cleaner implementing two different
controls, one of which is to maintain a suitable amount of air flow
irrespective of increasing an amount of collected dust on a filter
and the other is to adjust an applied power to a target value.
[0010] To accomplish the above object, an electric vacuum cleaner
comprising:
[0011] a blower for generating an air flow containing dust;
[0012] a filter configured to separate dust from the air flow;
[0013] a switching element for switching a current flowing through
the blower in response to a control signal;
[0014] an air-flow-amount sensing section for sensing an amount of
the air flowing through the filter to output a first value
indicating the sensed result, the air-flow-amount being varied in
response to amount of the dust separated by the filter;
[0015] a current detecting section for detecting a current flowing
through the blower to output a second value indicating the detected
current value; and
[0016] a control section for selecting, in accordance with power
applied to the blower, one of a first control mode in which a
suitable output timing of the control signal from the control
section to the switching element is determined so that variation of
the amount of the air flow is restrained based on the first value
and a second control mode in which a suitable output timing of the
control signal is determined so that the applied power to the
blower is maintained at a prescribed target value based on the
second value and for controlling the operation of the switching
element with the control signal outputted at the suitable output
timing of the selected mode.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] These and other objects and advantages of this invention
will become apparent and more readily appreciated from the
following detailed description of the presently preferred exemplary
embodiments of the invention taken in conjunction with the
accompanying drawings wherein:
[0018] FIG. 1 is a perspective view showing an electric vacuum
cleaner according to an embodiment of the present invention;
[0019] FIG. 2 is a block diagram illustrating a controller of an
electric vacuum cleaner according to a first embodiment of the
present invention;
[0020] FIG. 3 is a view illustrating a voltage waveform, a current
waveform, and a signal waveform from respective sections according
to the first embodiment;
[0021] FIG. 4 is a block diagram showing function of the respective
sections of a controller in the first embodiment;
[0022] FIG. 5 is a view of a data table for the first
embodiment;
[0023] FIG. 6 is a graph illustrating a relationship between an
intake-air-flow amount and an applied power of a blower when the
electric vacuum cleaner in the first embodiment is driven;
[0024] FIG. 7 is a flow chart illustrating a process in which
control modes are switched by a microprocessor in the first
embodiment;
[0025] FIG. 8 is a block diagram showing function of the respective
sections of a controller in a second embodiment;
[0026] FIG. 9 is a block diagram illustrating a controller of an
electric vacuum cleaner according to a third embodiment;
[0027] FIG. 10 a view illustrating a voltage waveform and a signal
waveform from respective sections according to the third
embodiment;
[0028] FIG. 11 is a block diagram showing function of the
respective sections of a controller in the third embodiment;
[0029] FIG. 12 is a graph illustrating a relationship between both
an intake-air-flow amount and an applied power of a blower when the
electric vacuum cleaner in a fourth embodiment is driven;
[0030] FIG. 13 is a block diagram illustrating a controller of an
electric vacuum cleaner according to a fifth embodiment.
DETAILED DESCRIPTION OF THE INVENTION
[0031] The present invention will now be described in more detail
with reference to the accompanying drawings. However, the same
numerals are applied to the similar elements in the drawings, and
therefore, the detailed descriptions thereof are not repeated.
FIRST EMBODIMENT
[0032] Firstly, structure of a canister type electric vacuum
cleaner 20 (hereinafter referred to as a "cleaner 20") will now be
described with reference to FIG. 1.
[0033] As shown in FIG. 1, a main body 21 of cleaner 20 includes a
lower case 22 whose upper surface is open, an upper case 23, a
bumper 24 and a lid 25. The rear top part of lower case 22 is
closed by upper case 23. Bumper 24 is sandwiched between
circumferential edges of lower case 22 and upper case 23 and is
joined therewith. Lid 25 is swingably provided to the front part of
lower case 22 to open and close the front part. Formed on the lid
25 is an informing section 40, including a light emitting element
or a sounding element, e.g., a light Emitting Diode (LED) or
speaker, to inform an operator of an operational state of the
cleaner 20, e.g., an amount of collected dust, during its
operation.
[0034] A bag-shaped filter 27 (hereinafter referred to as "filter
27") and a blower 26 in a rear side of filter 27 are serially
located in main body of cleaner 20. An airflow generated by blower
26 is led through filter 27 to separate dust from the airflow.
[0035] A caster (not shown) is rotatably provided on a lower part
of front side of main body 21 in a forwarding direction. A pair of
idle wheels each having a large diameter is provided on both sides
of rear side of main body 21.
[0036] An intake opening 29 is formed at a center of the front wall
of main body 21 to draw air from the outside into the inside of
main body 21. One end of a flexible cylindrical hose 30 is
separably connected in fluid communication with intake opening 29
and the other end is fixed in fluid communication with an
operational section 31.
[0037] Operational section 31 includes a plurality of operation
buttons 32 each of which is selectively operated to instruct one of
operation modes of blower 26 including strong, week, and "Off"
modes. Operational section 31 further includes a handhold portion
33 which is grasped by an operator when cleaning. One end of an
extendable pipe 34 is separably connected to a tip of operational
section 31 so that extendable pipe 34 fluidly communicates with
cylindrical hose 30 through operational section 31. Extendable pipe
34 includes a first pipe 34a having a larger diameter and a second
pipe 34b having a smaller diameter which is slidably inserted into
first pipe 34a. Pipe 34 is extended by sliding second pipe 34b
against first pipe 34a. A floor brush 35 having an opening through
which dust on the floor is taken with airflow into cleaner 20 is
separably connected to the other end of extendable pipe 34.
[0038] Serial connection arrangement of floor brush 35, extendable
pipe 34, hose 30 forms a main airflow channel.
[0039] A controller 100 of cleaner 20 including blower 26 and a
control section 10a will now be described with reference to FIG. 2.
In the inside of main body 21, blower 26 and a circuit board 101 on
which a control section 10a is functionally realized to control
blower 26 is mounted.
[0040] Serially connected in controller 100 are a commercial AC
power source 1, a current fuse 4, a motor 5 consisting in blower
26, and a switching element, e.g., bi-directional thyristor 2,
which switches applied power from the AC power source 1 to blower
26.
[0041] Blower 26 essentially comprises motor 5 and a fan 13. Motor
5 is of a universal type, e.g., a commutator motor (brush motor),
which comprises an armature 5a with a commutator and field windings
5b, 5c. Fan 13 is of a centrifugal type fixed to a spindle of motor
5.
[0042] A current detecting section 3 is provided to controller 100.
Current detecting section 3 is comprised of, for example, a
current-transformer or a shunt-resistance to detect a load current
flowing through motor 5. Since current flowing through motor 5
varies in response to an amount of airflow passing through filter
27, the amount of the airflow can be determined indirectly by
detecting the current. In this embodiment, current detecting
section 3 also serves as or is, so to say, an airflow amount
sensing section. A zero-crossing point of AC voltage applied to
motor 5 is detected by a zero-cross detecting section 6.
[0043] Control section 10a includes a microprocessor 7, a memory 8,
and an I/O port 9. I/O port 9 is equipped with an A/D conversion
function. In memory 8, a control program for functionally operating
microprocessor 7 and data including several constants needed to
carry out operations by microprocessor 7 are stored beforehand.
Memory 8 includes a data area for temporarily storing data from
microprocessor 7 and a work area for microprocessor 7.
[0044] A detected current by current detecting section 3 is fed to
I/O port 9 after being full-wave-rectified or half-wave-rectified
by a rectifier 11. I/O port 9 includes analog to digital converter
(A/D converter) converting an analog value into a digital value.
While the rectified detected current is converted by the A/D
converter, I/O port 9 acquires the digital value corresponding to
the rectified detected current. A zero-cross detection signal
generated by zero-cross detecting section 6 is also input to I/O
port 9 when the zero-cross detecting section 6 detects the
zero-cross point of AC voltage.
[0045] Controller 100 also includes operational section 31 from
which an instruction signal 1 is output to I/O port 9.
[0046] Control section 10a provided in controller 100 acquires the
detected current value, i.e., current flowing through motor 5, the
zero-cross detection signal, and the instruction signal, and then
outputs a control signal to a gate terminal (a control terminal) of
bi-directional thyristor 2.
[0047] When a power voltage having a waveform indicated in (a) of
FIG. 3 from a commercial AC power source 1 is applied to controller
100 and the control signal from control section 10a is applied to
the gate terminal of bi-directional thyristor 2 at timings shown in
(c) of FIG. 3, voltage shown in (d) of FIG. 3 is generated between
terminals of motor 5 because bi-directional thyristor 2
short-circuits until a polarity of the power voltage is
inverted.
[0048] At this time, the zero-cross detection signal indicated in
(b) of FIG. 3 is input to I/O port 9 of control section 10a. A
waveform of current flowing through motor 5 which is detected by
current detecting section 3 and full-wave-rectified by rectifier 11
is shown in (e) of FIG. 3. This current waveform is input as a
voltage value to control section 10a as it is or as a flattened
waveform.
[0049] A conducting angle .PHI. (%) of bi-directional thyristor 2
is calculated by the following formula:
.PHI.={(Tv/2)-ta}/(Tv/2).times.100 wherein Tv (sec) is a period of
AC power voltage, and ta (sec) is a time until the control signal
of motor 5 is output after the AC power voltage comes to a
zero-cross point. Hereinafter, the time ta (sec) is referred to as
an output timing.
[0050] Each function implemented by control section 10a is
described with reference to FIG. 4. Control section 10a generally
includes a current acquiring section 71, a control mode selecting
section 73 for selecting one of two control modes, e.g., a first
control mode and a second control mode, and an output timing
determination section 54 for determining the output timing ta.
[0051] Current acquiring section 71 repeatedly acquires a value In
of current flowing through motor 5 (hereinafter referred to as
"current In") detected by current detecting section 3 at a
predetermined period, and transfers the current In to control mode
selecting section 73 and output timing determination section 54.
Since current In against an applied power varies depending on a
characteristic of blower 26 and the conducting angle .PHI., it is
required to experimentally determine the current In at a designing
stage. An applied power under a constant power voltage can be
estimated from current In. Control mode selecting section 73
selects one of the control modes of control section 10a
corresponding to the applied power to blower 26 based on current
In. Output timing determination section 54 determines an output
timing of the control signal to bi-directional thyristor based on
the current In and the selected current mode by control mode
selecting section 73.
[0052] As set forth above, control section 10a selects one of the
predetermined control modes based on the current In of blower 26,
determines the output timing ta, and outputs the control signal
according to this output timing ta. The output timing ta is used as
an instruction value to switch on or off bi-directional thyristor
2.
[0053] The first and second control modes are now described. In the
first control mode, blower 26 is controlled to restrain variation
of an amount of airflow generated by blower 26 passing through
filter 27. In the second control mode, an applied power to blower
26 is controlled to be adjusted to a prescribed target value. The
control section 10a selects one of the above-described first and
second control modes.
[0054] Firstly, the first control mode is described in more detail.
Data table 16 used in the first control mode is stored in memory 8,
previously. Content of data table 16 is shown in FIG. 5. In this
mode, current detecting section 3 functions as airflow amount
sensing section.
[0055] Data table 16 includes n preset values of U1, U2, U3, - - -
, and Un (Un< - - - <U<U2<U1) as respective output
timing values at which a control signal is output to bi-directional
thyristor 2. Data table 16 further includes a lower limited current
threshold Ig1 and a higher limited current threshold Ig2. The lower
limited current threshold Ig1 has n thresholds of X1, X2, X3, - - -
, and Xn, (Xn> - - - >X3>X2>X1) each of which
corresponds to each of the n preset values. The higher limited
current threshold Ig2 also has n-1 thresholds of Y1, Y2, Y3, - - -
, and Yn-1, (Yn-1> - - - >Y3>Y2>Y1) each of which
corresponds to each of the n preset values. As shown in FIG. 6,
each of the lower and higher current thresholds Ig1 and Ig2 is set
to satisfy a relationship of
X1<X2<Y1<X3<Y2<X4<Y3<X5<Y4< - - -
<Xn<Yn-1. Each of the n thresholds X1 to Xn and n-1
thresholds Y1 to Yn-1 further indicates a threshold of an airflow
amount corresponding to each of the output timing values.
[0056] When starting up blower 26, control section 10a operates in
the first control mode. In an initial state that no dust is trapped
on filter 27, the output timing value U1 is set so that an airflow
amount generated by the blower 26 corresponding to an applied power
to blower 26 exceeds a value Q0 indicated on the abscissa axis in
FIG. 6. In this embodiment, for example, the operating state of
blower 26 is indicated by the point A in FIG. 6.
[0057] When cleaning operation is conducted from the initial state,
cleaner 20 starts separating dust from airflow and thus dust is
collected or trapped on filter 27. As the cleaning operation
proceeds, the collected dust is increased, resulting in increase in
the airflow-resistance of the filter 27. Thus, the intake airflow
amount of blower 26 is decreased. In response to these processes,
the applied power to blower 26 gradually decreases from the
operating point A along the line in FIG. 6. This is because that
the load bearing on blower 26 reduces and a current In flowing
through motor 5 also decreases.
[0058] When the current value In goes lower than the threshold X1
of the lower limited current threshold, control section 10a changes
the output timing value from U1 to U2 to shorten the output timing
ta of the control signal to bidirectional thyristor 2 with
reference to the zero-cross point and causes the conducting angle
.PHI. of bi-directional thyristor 2 to increase. Increase of the
conducting angle .PHI. causes the applied power to blower 26 to
increase, resulting in increase of the intake airflow amount of
blower 26.
[0059] After that, as the collected dust increases in the operation
in which the output timing ta is kept U2, the airflow-resistance of
filter 27 further increases and the intake airflow amount of blower
26 further decrease again. In accordance with decrease of the
intake airflow amount, the current value In flowing through motor 5
gradually decreases.
[0060] When the current value In goes lower than the threshold X2
of the lower limited current threshold, control section 10a changes
the output timing value from U2 to U3 to further shorten the output
timing ta with reference to the zero-cross point so that the
conducting angle .PHI. of bidirectional thyristor 2 further
increases. Increase of the conducting angle causes the applied
power to blower 26 to further increase, resulting in increase of
the intake airflow amount of blower 26.
[0061] As aforementioned above, while collection of dust on filter
27 proceeds, control section 10a changes the output timing value in
order of U1, U2, U3, U4, - - - Un every time that the current In
goes smaller than the respective thresholds X1, X2, X3, X4, - - -
Xn of the lower limited current thresholds. Control section 10a
restrains decrease of the intake airflow amount of blower 26 by
changing the output timing value.
[0062] In the control method set forth above, the control is
carried out assuming that, as an amount of dust trapped on filter
27 increases, an airflow-resistance increases resulting in decrease
of the applied power to blower 26. On the other hand, when an
operator actually uses cleaner 20, variation in a positional
relationship a gap between floor brush 35 and floor surface,
variation in a bending angle airflow pass in diameter of a flexible
cylindrical hose 30, or uneven accumulation of a collected dust
within filter 27 may cause an airflow-resistance to tentatively
decrease and an intake airflow amount to unexpectedly increase.
[0063] In case that the intake airflow amount is unexpectedly
changed when the operating point of blower 26 is positioned, for
example, at B in FIG. 6 or the output timing value is being U4,
control section 10a changes the output timing value from U4 to U3
if the current value In exceeds the threshold Y3 of the higher
limited current threshold. Such change of the output timing causes
the conducting angle .PHI. of bi-directional thyristor 2 to
decrease and the applied power to blower 26 to decrease. At this
moment, the applied power to blower 26 is also decreased.
Therefore, control section 10a restrains an abrupt increase of the
intake airflow amount of blower 26.
[0064] Inventors of the present invention experimentally confirmed
the number of values of each item, i.e., output timing value, lower
and higher limited current thresholds Ig1, Ig2, which is required
when the control section 10a carries out the control operation to
restrain the variation in the airflow amount in the first control
mode. For example, in case that the upper limit value of the
applied power of the blower 26 was one (1) kW and the applied power
of the range within 700 W and 950 W was applied to the blower 26,
the number of the output timing values and lower and higher limited
current thresholds Ig1 and Ig2 were at most 10, respectively.
Therefore, a required precise control in the first control mode can
be achieved when 10 of the output timing values, the lower limited
current thresholds Ig1 and the higher limited current thresholds
Ig2 are respectively prepared beforehand.
[0065] Inventors of the present invention further confirmed the
number of values of each item, i.e., output timing value, lower and
higher limited current thresholds Ig1, Ig2, which is additionally
required in order that the control section 10a adjusts the applied
power to the blower 26 to the upper limit value (1 kW) in the first
control mode. The additional number of the output timing values and
lower and higher limited current thresholds Ig1 and Ig2 were 50 to
100, respectively.
[0066] As described above, a memory having a large capacity is
needed to carry out a control operation in the first control mode
alone in which variation in the airflow amount of the blower 26 is
restrained when the applied power to the blower 26 is within a
prescribed range and the applied power is adjusted to the upper
limit value (target value) when the applied power exceeds the
prescribed range. This is because that it is required to narrow the
dividing or sampling intervals of each item, i.e., output timing,
lower and higher limited current thresholds Ig1, Ig2, within a
control range to achieve the above-described control operation,
resulting in such a large amount of values of each item needed.
[0067] Therefore, to dissolve the above-described problem, another
control mode (second control mode) is needed together with the
first control mode. Second control mode which is suitable to
control the blower 26 in the vicinity of the upper limit value of
the applied power to the blower 26 will be described.
[0068] In the second control mode, control section 10a calculates
an error .DELTA.I between a current value In detected by current
detecting section 3 and a targeted current value Is (hereinafter
referred to as "target current Is") by the formula
(.DELTA.I=Is-In). The target current Is indicates a value
determined experimentally based on an higher limited value of an
applied power to blower 26 and is stored in memory 8 previously.
Control section 10a determines an output timing ta of a control
signal to bidirectional thyristor 2 based on the error .DELTA.I. An
instruction value Tp of the output timing ta of the control signal
is calculated by control section 10a, for example, by the following
formula: Tp=Tp'+.alpha..times..DELTA.I (1)
[0069] Wherein Tp' is the last time instruction value and a is a
coefficient.
[0070] The above-described second control mode is a target value
control that exclusively aims at a control operation which adjusts
the current In to the target current Is. Control section 10a
operating in the second mode can adjust the applied power to the
blower 26 to a prescribed target value. The target current Is is
previously set as a value corresponding to the higher limited value
(1 kW) of the applied power to blower 26.
[0071] While operating in the second control mode, if an
airflow-resistance is further increased because of increase of the
amount of collected dust in filter 27 and operation under the
higher limited value of the applied power is continued, motor 5 may
become malfunction. To prevent this, control section 10a changes
the output timing of the control signal to make the applied power
decrease, and outputs an informing signal to informing section 40
so as to call an operator's attention to the filter 27 packed with
dust. Thus, the operator can promptly eliminate dust out of the
filter 27.
[0072] A process for determining output timing ta will be described
with reference to a flowchart shown in FIG. 7. Control section 10a
periodically conducts the process according to a control program
previously installed in memory 8.
[0073] In step S1, current acquiring section 71 acquires a current
value In detected by current detecting section 3. In step S2,
control mode selecting section 73 determines whether the present
control mode is the first control mode. If the present control mode
is the first control mode, step S3 is taken. In step S3, output
timing determination section 54 compares the detected current In to
the lower and higher current thresholds listed in FIG. 5. For
example, when the present output timing value is being set to U4,
control section 10a checks whether or not the detected current In
falls within a range from X4 to Y3 (X4.ltoreq.In<Y3). If the
detected current In falls within the above range, output timing
determination section 54 maintains the present output timing value
U4 in step S5. On the other hand, in step S3, if the detected
current In falls out the above range, step S4 is taken. Output
timing determination section 54 changes the present output timing
value U4 to the upper value U5 or lower value U3 of the table in
FIG. 5 and thus output timing value is determined as U4 or U5 in
step 5. In step S2, if the present control mode is the second
control mode, step S6 is taken and output timing determination
section 54, calculates instruction value Tp by the formula (1).
Following the calculation, output timing value of control signal is
determined as the calculated value in step S5.
[0074] A condition that control section 10a changes its control
mode from the first control mode to the second control mode will be
described. In control section 10a, an output timing value Un shown
in the table in FIG. 5 is previously set as an output timing ta for
switching the first control mode to the second. In an operation
that control section 10a controls blower 26 under an output timing
value Un in the first control mode, control mode selecting section
73 switches the present control mode (the first control mode) to
the second when it is determined that the detected current In goes
smaller than lower limited current threshold Xn (In<Xn). The
lower limited current threshold Xn forms a first switching
threshold to switch the first control mode to the second.
[0075] Next, a method of switching the second control mode to the
first control mode under some switching conditions will be
described. [0076] Switching conditions include:
[0077] Condition 1: Using a detected current In,
[0078] Condition 2: Using an output timing instruction value Tp
and
[0079] Condition 3: Using a detected current value In and an output
timing instruction value Ta.
[0080] In case that condition 1 is adopted as the switching
condition, control section 10a switches the present control mode
(second control mode) to the first control mode when the detected
current In exceeds a prescribed switching threshold previously
stored in memory 8.
[0081] In case that condition 2 is adopted, control section 10a
switches the present control mode (second control mode) to the
first control mode when the output timing instruction value Tp
calculated by the formula (1) exceeds an output timing threshold Tw
previously stored in memory 8.
[0082] Further, in case that condition 3 is adopted, control
section 10a switches the present control mode (second control mode)
to the first control mode when the output timing instruction value
Tp calculated by the formula (1) exceeds an output timing threshold
Tw previously stored in memory 8 and furthermore an error .DELTA.I
between a detected current In and the target current Is goes
smaller than an error threshold .DELTA.Iq (.DELTA.I<.DELTA.Iq )
previously stored in memory 8. Control section 10a may adopt the
above-described conditions alone or in combination.
[0083] As described above, controller 100 of cleaner 20 in this
embodiment can control the operation by switching the control mode
from the first control mode in which a variation of airflow is
restrained irrespective of an amount of collected or trapped dust
by the filter to maintain the suction power of the cleaner, to the
second control mode in which the applied power to blower 26 is
controlled to adjust the applied power to a targeted power, and
vice versa.
[0084] To be more precise, in controller 100 of cleaner 20, control
section 10a operates in the first control mode when an applied
power is equal to or less than a prescribed value, e.g., 950 W, and
in the second control mode when the applied power exceeds 950 W. In
the second control mode, the applied power is to be maintained at 1
kW. Controller 100 as described above operates in the first control
mode to restrain variation in the airflow amount of blower 26 by
regulating the applied power itself to blower 26 in such state that
an amount of collected or trapped dust in filter 27 is small and
thus a sufficient suction power can be achieved even if the applied
power to blower 26 is small. Thus, the cleaner 20 being operated in
the first control mode can maintain a stable cleaning ability
without consuming an excess power. After that, controller 100 then
operates in the second control mode to adjust the applied power to
blower 16 to an upper limit value of the applied power which is
provided by law when an amount of collected dust in filter 27
increases and the applied power to blower 26 approaches to the
upper limit value. Thus, the cleaner 20 can rapidly increase its
suction power with a simple configuration when dust is further
collected or trapped by filter 27.
[0085] In the second control mode, control section 10a controls the
applied power to blower 26 to meet the targeted power value,
calculating the instruction value Tp of output timing of control
signal using the rate .alpha., the detected current value In and
the targeted current value Is. Accordingly, comparing to the
operation in the first control mode, the operation in the second
control mode can adjust the applied power to blower to the targeted
value without requiring the number of constants, e.g. output timing
values, current threshold values and so on, in excess. The
operation in the second control mode is effective.
[0086] The method for switching the first control mode to the
second does not need a lot of process load to microprocessor 7 and
realize high process speed for the switch of the mode, since the
method simply use the detected current In and does not require
newly complicated process to switch the mode.
[0087] The method for changing the second control mode to the first
also does not need a lot of process load to microprocessor 7 and
realize high process speed for the switch of the mode, since the
method simply use the detected current In and the instruction value
Tp calculated by the formula (1).
[0088] Control section 10a conducts its mode selection using the
detected current In and thus blower 26 is instantly controlled even
if a variation of airflow resistance takes place due to increase of
the collected dust in filter 27, variation of positional
relationship between floor brush 35 and floor surface, variation in
bending angle of a flexible cylindrical hose 30, or uneven
accumulation of the collected dust within filter 27. This is
because that the detected current In can be treated to be
equivalent to both the applied power to blower or the intake
airflow amount which are varied by the above-described
incidents.
SECOND EMBODIMENT
[0089] In the first embodiment, the control section 10a controls
blower 26 by using the detected current In as it is. In the second
embodiment, the control section 10b controls blower 26 by using a
calculated current value Ix which results from calculation in a
method that is predetermined taking a relationship between the
detected current In and the applied power into account every time
when the detected current In is acquired. The calculation does not
need a complicated process, and thus not adversely affect the
processing capacity of a microprocessor.
[0090] With reference to FIG. 8, respective functions of control
section 10b controlling blower 26 based on the calculated current
value Ix (hereinafter referred to as "calculated current Ix") are
described. Control section 10b is formed such that a current
calculating section 72 is added to control section 10a shown in
FIG. 4.
[0091] Current acquiring section 71 acquires the detected current
In, which is periodically detected by current detecting section 3
in a predetermined period, flowing through motor 5 and the detected
current In is input to current calculating section 72. Current
calculating section 72 calculates according to a predetermined
method to obtain the calculated current Ix. The calculated current
Ix is set to vary in response to a variation of an applied power to
blower 26. After calculation, current calculating section 71
outputs the calculated current Ix to both control mode selecting
section 73 and output timing determination section 54. Control mode
selecting section 73 checks its present control mode, and changes
the control mode if needed. In accordance with the calculated
current Ix and the checking result of control mode selecting
section 73, the output timing determination section 54 determines
output timing ta of control signal to bidirectional thyristor
2.
[0092] An example in which a calculated current Ix is obtained
based on a detected current In is explained. Current acquiring
section 71 periodically acquires, for example, the detected current
In every 0.2 millisecond on commercial power with 50 Hz. In other
words, the detected current In is acquired 100 times in one period,
i.e., 20 millisecond, on the commercial power. The calculated
current Ix (=.SIGMA. In) is obtained by reiteratedly adding one
detected current In acquired to the calculated result. Where a
period of the .SIGMA. In (calculated current Ix) is made to a
period of the commercial power, 100 times of the detected current
In are added. The calculated current Ix varies in response to a
variation of the applied power to blower 26 according to a
variation in the intake airflow amount.
[0093] Even if noise of the commercial power adversely affects the
detected current In when sampling at a certain timing, calculated
current Ix can still be used because the calculated current Ix is
obtained by addition of the sampled currents and thus such
affection by noise is effectively alleviated. Hence the applied
power to blower 26 can be accurately and reliably controlled.
Alternatively, it can be possible that the detected current In is
modified by multiplying the detected current In by a weighting
ratio (.beta.) every time the detected current In is acquired and
the modified current In is added successively.
[0094] In this embodiment, in place of the detected current In it
is possible to apply the calculated current value Ix obtained
therefrom.
[0095] In these embodiments aforementioned, output timing
determination section 54 acquires both the output timing value at
the present time and the current threshold value Ig1 or Ig2 on the
data table stored in memory 8 as indicated in FIG. 5. The present
invention is not necessarily limited to using the data table.
Instead of the preset data table, output timing determination
section 54 may be configured to calculate lower limited current
threshold of n-th value (Xn) according to the following formula:
Xn=X1+K.times.(n-1).times.(output timing value) (2) wherein X1
indicates lower limited current threshold of the first value and K
indicates a proportional rate experimentally predetermined.
[0096] Intervals (.DELTA.Un) of respective adjacent output timing
values (Un) and (U(n-1)) and intervals (.DELTA.Xn) or (.DELTA.Yn)
of respective adjacent current threshold values (Xn) and (X(n-1))
or (Yn) and (Y(n-1)) are not needed to be constant and may be set
in accordance with intended use of cleaner 20 or characteristic of
blower 26.
THIRD EMBODIMENT
[0097] With reference to FIGS. 9 to 11, controller 110 of cleaner
20 in the third embodiment is now described. A DC power source 61,
e.g., secondary battery, powers controller 110 to rotate motor 5 as
shown in FIG. 9. Motor 5 is connected in series with the applied
power to the motor 5.
[0098] As shown in FIG. 11, control section 10c includes output
timing determination section 64 provided with a PWM signal
generating section 65 generating a pulse width modulation signal.
The PWM signal can be generated by publicly known method. When
power voltage from DC power source 61 is applied to controller 110
and the PWM signal formed with a period having Pc second, as
indicated in FIG. 10(b), is supplied to a gate of MOSFET, motor 5
is periodically switched on for tc second to rotate. Duty factor Du
of the PWM signal is calculated as follows: Du=tc/Pc (3) As can be
understood from the formula, larger the duty factor Du larger the
applied power to blower 26.
[0099] As described above, control section 10c can change the
output timing of the control signal to MOSFET 62, varying the duty
factor Du of PWM signal from the PWM signal generating section 65.
In the controller 110, the duty factor Du is referred as an output
timing and thus, the output timing value shown in FIG. 5 and the
instruction value of output timing calculated by the formula (1)
are needed to be set taking the duty factor Du into
consideration.
[0100] It should be noted that not only a commutator motor but also
a brushless DC motor may be applied to form blower 26 in controller
110.
FOURTH EMBODIMENT
[0101] An electric vacuum cleaner in forth embodiment is now
described. The cleaner of this embodiment includes a fixed type
cleaner installed such as between walls, on a ceiling, on a roof,
or under a floor and a central cleaner having one filter and a
plurality of airflow intakes being in fluid communication with the
filter. A relationship between airflow amount of blower 26 and the
applied power during the operation is, for example, illustrated in
FIG. 12. Comparing to a canister type cleaner, the cleaner of this
type requires larger applied power to blower 26 and is continuously
operated for relatively a long time once the operation is started.
Therefore, an idling operation for the blower is required before
the control operation (ordinary operation) is effected.
[0102] Control section 10c outputs an informing signal to informing
section 40 when the second control mode is effected so that a light
emitting element is flickered to indicate an operational state of
the second control mode to an operator. Flickering of the light
emitting element informs an operator that an amount of dust trapped
on the filter approaches an allowable level before the amount of
dust exceeds the allowable level. No specific threshold value for
informing full of dust on the filter is needed.
FIFTH EMBODIMENT
[0103] Fifth embodiment is now described. Electric vacuum cleaners
described in the above first to fourth embodiments use a current
detecting section to detect an airflow amount. In this embodiment,
however, in lieu of the current detecting section air pressure
detecting section 81 is provided in controller 110 to detect the
airflow amount as illustrated in FIG. 13.
[0104] Air pressure detecting section 81 detects air pressure
generated by airflow that varies in response to the amount of dust
trapped on the filter 27. Specifically the detection of the air
pressure is implemented between an air intake and filter 27.
Control section 10d in this embodiment includes memory 8 storing a
data table similar to the data table illustrated in FIG. 5. In the
data table of this embodiment, a lower and higher limited pressure
thresholds respectively corresponding to output timings are used
instead of a lower and higher limited current thresholds in FIG. 5.
Control of blower 26 in the first control mode and switch from the
first control mode to the second are performed according to an
output from air pressure detecting section 81. Control of blower 26
in the second control mode and switch from the second control mode
to the first control mode as well as other operations are like
operations described in the first to fourth embodiments.
[0105] In the above descriptions of respective control sections
10a, 10b, and 10c, processes of current acquiring section 71,
current calculating section 72, control mode selecting section 73,
and output timing determination section 54 are realized with
software. It may be possible however to realize such processes or
functions with hardware configuration.
[0106] The present invention has been described with respect to
specific embodiments. However, other embodiments based on the
principles of the present invention should be obvious to those of
ordinary skill in the art. Such embodiments are intended to be
covered by the claims.
* * * * *