U.S. patent application number 10/659495 was filed with the patent office on 2005-05-12 for electric vacuum cleaner.
This patent application is currently assigned to Toshiba Tec Kabushiki Kaisha. Invention is credited to Kushida, Hiroyuki, Sakurai, Osamu.
Application Number | 20050097701 10/659495 |
Document ID | / |
Family ID | 32040829 |
Filed Date | 2005-05-12 |
United States Patent
Application |
20050097701 |
Kind Code |
A1 |
Kushida, Hiroyuki ; et
al. |
May 12, 2005 |
Electric vacuum cleaner
Abstract
The present invention provides an electric vacuum cleaner
equipped with a step-up converter circuit with a DC power supply as
a drive source, which drives and controls the step-up converter
circuit so as to refer to such a relationship as to decrease a
variation in dust suction capability, determine an output voltage
to be boosted according to the state of a load on a motor-driven
blower, boost the output voltage, based on the result of
determination and supply power to the motor-driven blower, thereby
activating the step-up converter circuit with satisfactory
efficiency. Thus, the dust suction performance of the electric
vacuum cleaner is enhanced and the usage time of a battery per
charge is lengthened.
Inventors: |
Kushida, Hiroyuki;
(Odawara-shi, JP) ; Sakurai, Osamu; (Isehara-shi,
JP) |
Correspondence
Address: |
FRISHAUF, HOLTZ, GOODMAN & CHICK, PC
767 THIRD AVENUE
25TH FLOOR
NEW YORK
NY
10017-2023
US
|
Assignee: |
Toshiba Tec Kabushiki
Kaisha
Tokyo
JP
|
Family ID: |
32040829 |
Appl. No.: |
10/659495 |
Filed: |
September 10, 2003 |
Current U.S.
Class: |
15/319 ;
15/327.1 |
Current CPC
Class: |
A47L 9/2821 20130101;
A47L 9/2857 20130101; A47L 9/2884 20130101; A47L 9/2842 20130101;
A47L 9/2831 20130101 |
Class at
Publication: |
015/319 ;
015/327.1 |
International
Class: |
A47L 005/00; A47L
009/00 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 17, 2002 |
JP |
2002-302682 |
Claims
What is claimed is:
1. An electric vacuum cleaner, comprising: a motor-driven blower
driven with a DC power supply as a drive source; voltage converting
means which boosts a voltage outputted from the DC power supply and
supplies power to the motor-driven blower; load detecting means
which detects a state of a load applied to the motor-driven blower;
memory means which stores therein such a relation as to reduce a
variation in dust suction capability with respect to a relationship
between the state of the load on the motor-driven blower and the
output voltage to be boosted by the voltage converting means; and
electric vacuum cleaner control means which refers to the relation
stored in the memory means, determines an output voltage to be
boosted by the voltage converting means from the state of the load
on the motor-driven blower and controls the output voltage of the
voltage converting means based on the result of said
determination.
2. The electric vacuum cleaner according to claim 1, wherein the
load detecting means detects the state of a load on the
motor-driven blower by detecting an airflow in the electric vacuum
cleaner.
3. The electric vacuum cleaner according to claim 1, wherein the
load detecting means detects the state of a load on the
motor-driven blower by detecting a current that flows through the
motor-driven blower.
4. The electric vacuum cleaner according to claim 1, further
comprising: an inlet body capable of communicating with a space
brought to negative pressure by driving of the motor-driven blower
and capable of being in contact with a surface to be cleaned; and
cleaned surface detecting means which determines contact or
non-contact of the inlet body with the cleaned surface; wherein
when the cleaned surface detecting means determines that the inlet
body is in contact with the cleaned surface, the electric vacuum
cleaner control means increases a boost rate corresponding to a
rate of an output voltage to an input voltage.
5. The electric vacuum cleaner according to claim 1, further
comprising: an inlet body capable of communicating with a space
brought to negative pressure by driving of the motor-driven blower
and capable of being in contact with a surface to be cleaned; and
cleaned surface detecting means which determines contact or
non-contact of the inlet body with the cleaned surface; wherein
when the cleaned surface detecting means determines that the inlet
body is not in contact with the cleaned surface, the electric
vacuum cleaner control means deactivates the voltage converting
means.
6. The electric vacuum cleaner according to claim 1, further
comprising: an inlet body capable of detachably communicating with
a space brought to negative pressure by driving of the motor-driven
blower and capable of being in contact with a surface to be
cleaned; and attachment/detachment detecting means which determines
attachment or detachment of the inlet body from a main body of the
electric vacuum cleaner; wherein when the attachment/detachment
detecting means determines that the inlet body has been detached
from the space, the electric vacuum cleaner control means increases
the output voltage of the DC power supply by means of the voltage
converting means to thereby increase a boost rate corresponding to
a rate of an output voltage to an input voltage.
7. The electric vacuum cleaner according to claim 6, wherein when
the attachment/detachment detecting means determines that the inlet
body has been detached from the space, the electric vacuum cleaner
control means fixes a proportion of a rise in the boost rate
corresponding to a rate of an output voltage to an input
voltage.
8. The electric vacuum cleaner according to claim 1, further
comprising: switching means which performs switching between a
step-up operation mode for bringing the voltage converting means to
an active state and a non step-up operation mode for bringing the
voltage converting means to an inactive state; and an operation
mode switching controller which accepts an operation for selecting
the operation modes for the electric vacuum cleaner; wherein the
electric vacuum cleaner control means controls the switching means
in accordance with the operation accepted by the operation mode
switching controller to thereby realize an operation mode
associated with the operation of the operation mode switching
controller.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] The present application is based on Japanese Priority
Document JP2002-302682 filed on Oct. 17, 2003, the content of which
is incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to an electric vacuum cleaner,
and particularly to a battery-operated electric vacuum cleaner.
[0004] 2. Discussion of the Background
[0005] In a battery-operated electric vacuum cleaner provided with
a motor-driven blower, a method for increasing an input to the
motor-driven blower is generally known as a method for increasing
the output of the motor-driven blower to enhance dust suction
capability. As a specific example, there is known a method for
changing windings of a motor-driven blower, increasing current
inputted to the motor-driven blower, and boosting or stepping up a
power supply voltage to thereby increase an input to the
motor-driven blower.
[0006] When an attempt is made to increase an input current where
the motor-driven blower is made up of a commutator motor, a carbon
of a brush portion that makes contact with a commutator is worn,
and the brush portion becomes apt to be damaged due to sparks or
the like at the commutator. It is therefore hard to ensure
reliability.
[0007] As a method for boosting the power supply voltage in the
case of the battery-operated electric vacuum cleaner, a method for
increasing the number of batteries is the simplest. However, in a
case of requiring a high voltage, when only the batteries are used,
each of the batteries becomes large-sized.
[0008] Therefore, there has heretofore been proposed a method for
obtaining a high voltage by use of a step-up converter circuit to
solve such an imperfection or trouble (For example, JP7-322971 and
JP8-224198).
[0009] For example, JP8-224198 discloses a technology for providing
a switching means for switching a power supply for supplying power
to a motor-driven blower to any one of a commercial power source
and a secondary battery and gradually raising a boosted voltage
from a low voltage to a predetermined voltage upon boosting.
[0010] Meanwhile, a technology for coordinating use states of a
step-up converter circuit and an electric vacuum cleaner equipped
with the step-up converter circuit to thereby enhance dust suction
performance is extremely important to the electric vacuum
cleaner.
[0011] It is known that the load on the motor-driven blower greatly
varies depending on the relationship between, for example, an inlet
of the electric vacuum cleaner and a target to be cleaned.
[0012] It is known that the electric vacuum cleaner equipped with
the step-up converter circuit has a drawback that in a voltage
boosting or step-up process at the operation of the step-up
converter circuit, a power loss occurs due to a switching element
or the like of a booster or step-up circuit.
[0013] Therefore, there has been a demand for an effective
operation of the step-up converter circuit according to the state
of a load on the electric vacuum cleaner to cover the drawback such
as the power loss with a view toward enhancing dust suction
performance and lengthening the usage time of a battery per
charge.
[0014] However, the technology described in JP8-224198 referred to
above describes only that there is provided the switching means for
switching the power supply for supplying power to the motor-driven
blower to any one of the commercial power source and the secondary
battery and the boosted voltage is gradually raised from the low
voltage to the predetermined voltage upon boosting. Thus, the
present technology does not disclose the state of a load and the
operation of the step-up converter circuit. No suggestion thereof
is provided either.
SUMMARY OF THE INVENTION
[0015] Accordingly, an object of the present invention is to
provide an electric vacuum cleaner equipped with a step-up
converter circuit with a DC power supply as a drive source, wherein
the step-up converter circuit is operated with satisfactory
efficiency based on the state of a load on the electric vacuum
cleaner to thereby enhance dust suction performance of the electric
vacuum cleaner and lengthen the usage time of a battery per
charge.
[0016] The object of the present invention is achieved by a novel
electric vacuum cleaner of the present invention.
[0017] Thus, according to the novel electric vacuum cleaner of the
present invention, such an electric vacuum cleaner equipped with a
step-up converter circuit with a DC power supply as a drive source
drives and controls the step-up converter circuit so as to refer to
such a relationship inputted in advance to a memory means as to
decrease a variation in dust suction capability, determine an
output voltage to be boosted according to the state of a load on a
motor-driven blower, boost the output voltage, based on the result
of determination and supply power to the motor-driven blower,
thereby activating the step-up converter circuit with satisfactory
efficiency.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] A more complete appreciation of the present invention and
many of the attendant advantages thereof will be readily obtained
as the same becomes better understood by reference to the following
detailed description when considered in connection with the
accompanying drawings, wherein:
[0019] FIG. 1 is a perspective view showing an outward appearance
of an electric vacuum cleaner illustrated as one embodiment of the
present invention;
[0020] FIG. 2 is a circuit diagram illustrating one example of a
control circuit of the electric vacuum cleaner shown in FIG. 1;
[0021] FIG. 3 is a circuit diagram depicting a circuit for a
voltage converting means or the electric vacuum cleaner shown in
FIG. 1;
[0022] FIG. 4 is a circuit diagram showing a configurational
example of a voltage conversion control means of the electric
vacuum cleaner shown in FIG. 1;
[0023] FIG. 5 is a timing chart illustrating a pulse signal and a
triangular wave;
[0024] FIG. 6 is an explanatory view depicting one example of
operation control of the electric vacuum cleaner shown in FIG.
1;
[0025] FIG. 7 is a graph showing the characteristic of the electric
vacuum cleaner shown in FIG. 1;
[0026] FIG. 8 is a vertical sectional side view illustrating an
internal configuration of the electric vacuum cleaner shown in FIG.
1;
[0027] FIG. 9 is a typical diagram for describing a data table
stored in a storage means;
[0028] FIG. 10 is a typical diagram for describing a data table
stored in the storage means;
[0029] FIG. 11 is a flowchart illustrating one example of boost
rate control of the electric vacuum cleaner shown in FIG. 1;
[0030] FIG. 12 is a typical diagram for describing a data table
stored in the storage means;
[0031] FIG. 13 is a flowchart showing one example of boost rate
control of the electric vacuum cleaner shown in FIG. 1;
[0032] FIG. 14 shows an inlet body, wherein FIG. 14(a) is a bottom
view thereof, and FIG. 14(b) is a circuit diagram for detecting its
attachment/detachment;
[0033] FIG. 15 shows an inlet body, wherein FIG. 15(a) is a bottom
view thereof, and FIG. 15(b),is a circuit diagram for detecting its
attachment/detachment;
[0034] FIG. 16 is a perspective view showing a crevice tool and a
brush attached to the inlet body; and
[0035] FIG. 17 is a circuit diagram illustrating another example of
the voltage converting means of the electric vacuum cleaner shown
in FIG. 1.
DETAILED DESCRIPTION OF THE INVENTION
[0036] A first embodiment of the present invention will be
described with reference to FIGS. 1 through 17.
[0037] [External Configuration]
[0038] FIG. 1 is a perspective view showing an external
configuration of an electric vacuum cleaner according to the
embodiment of the present invention. As shown in FIG. 1, the
electric vacuum cleaner 1 according to the present embodiment
includes a hose body 4 detachably mounted to an inlet 3 attached to
a case 2.
[0039] A dust cup 5 used as a dust chamber, a motor-driven blower
6, and a DC power supply (see FIG. 2) are provided within the case
2. A plurality of exhaust ports 8, which communicate with the
motor-driven blower 6 and are open in substantially front side
directions, are defined in side plate portions of the case 2. A
handle 9 used as a knob means is provided on its corresponding
upper surface of the case 2. The handle 9 is formed so as to take a
substantially Y-shape as seen in a plane surface. A display means
10 provided with a plurality of light-emitting diodes is disposed
in the vicinity of the handle 9.
[0040] Also charge terminals (not shown) set to a charging bed or
base for thereby supplying power to the DC power supply 7 to charge
the DC power supply 7 are provided at a substantially central
portion of the rear face of the case 2.
[0041] The hose body 4 has an inlet body 11 provided at its leading
end, and an extension pipe 12 that causes the inlet body 11 and the
inlet 3 to communicate with each other. The hose body 4 is
detachably connected to the inlet 3 such that the base end of the
hose body 4 communicates with the suction side of the motor-driven
blower 6 through the dust cup 5 used as the dust chamber. The
extension pipe 12 is a flexible connecting pipe. Thus, the hose
body 4 has flexibility. The inlet body 11 is provided with an
unillustrated rotating cleaning body (rotating brush) rotated under
an electric operation or the flow of air.
[0042] The hose body 4 is provided with a hand control 13 used as
an operation means having a bent shape The hand control 13 is
provided with an operation mode switching controller 14 that
functions as a controller at a position where it can be operated by
the operator's fingers.
[0043] The operation mode switching controller 14 shares the use of
a power switch of the motor-driven blower 6 and is configured so as
to be able to select a plurality of types of operation modes for
respectively bringing the motor-driven blower 6 to different driven
states. Described specifically, as shown in FIG. 2, a control
button (switch for stop) 14a for stop setting corresponding to an
operation mode, a control button 14b for low operation setting
corresponding to an operation mode, and a control button 14c for
high-operation setting corresponding to an operation mode are
sequentially arranged side by side in a line within the operation
mode switching controller 14 in the direction of the extension pipe
12 as viewed from the hose body 4.
[0044] In the present embodiment, the interior of the case 2,the
interior of the extension pipe 12 and the interior the hose body 4
are constituted as a space that assumes negative pressure or vacuum
according to the operation of the motor-driven blower 6. Therefore,
the inlet body 11 is in communication with the space that assumes
the negative pressure according to the operation of the
motor-driven blower 6.
[0045] [Control Circuit]
[0046] A configuration of a control circuit with respect to the
motor-driven blower 6 employed in the electric vacuum cleaner 1,
and its operation will next be explained with reference to FIGS. 2
through 6.
[0047] The motor-driven blower 6 provided within the case 2 is
connected to a power supply circuit comprising the DC power supply
7 and a voltage converting means 33. The DC power-supply 7 is
chargeable via the charge terminals (not shown) referred to above.
The voltage converting means 33 boosts or steps up a voltage
outputted from the DC power supply 7 and outputs the stepped-up or
boosted voltage to the motor-driven blower 6.
[0048] A switching part (A) 24 is connected between the DC power
supply 7 and a main circuit 33a for the voltage converting means
33. The switching part (A) 24 is an electromagnetic relay or a
semiconductor switching element such as a bipolar transistor or the
like. The switching part (A) 24 is controlled by an electric vacuum
cleaner control means 25.
[0049] The electric vacuum cleaner control means 25 comprises a
motor-driven blower control means 30, a voltage conversion control
means 28, a DC power supply monitoring means 27, a memory or
storage means 26, a load detecting means 29, a voltage reading
means 31, and an AD converter 32, and the like. The electric vacuum
cleaner control means 25 controls the whole electric vacuum cleaner
1. The operation mode switching controller 14, the display means
10, a thermistor 21 for measuring the temperature of the DC power
supply 7, a rechargeable battery identifying means 34, a section 22
(corresponding to a section for detecting an output voltage of a
rechargeable battery) for detecting a voltage inputted to the
voltage converting means 33, a section 23 (corresponding to a
section for detecting a voltage inputted to the motor-driven blower
6) for detecting a voltage outputted from the voltage converting
means 33, a current detecting section 37, and a negative pressure
detecting section 39 (see FIG. 8) that functions as the load
detecting means 29, and the like are connected to the electric
vacuum cleaner control means 25. The negative pressure detecting
section 39 will be described later.
[0050] The electric vacuum cleaner control means 25 may be made up
of a plurality of circuit components and a plurality of
microcomputers, or may be configured with a one-chip microcomputer
as the center.
[0051] Although described later, the DC power supply 7 includes a
rechargeable battery 7a. A series circuit of a resistor R1 and a
resistor R2 is connected to the rechargeable battery 7a. The
electric vacuum cleaner control means 25 is connected to the
voltage converting means input-voltage detecting section 22
provided between these resistors R1 and R2. A voltage divided by
the resistors R1 and R2 is inputted to the electric vacuum cleaner
control means 25.
[0052] Similarly, a series circuit of a resistor R3 and a resistor
R4 is connected between both ends of the motor-driven blower 6. The
electric vacuum cleaner control means 25 is connected to the
voltage converting means output-voltage detecting section 23
provided between these resistors R3 and R4. Thus, a voltage divided
by the resistors R3 and R4 is inputted to the electric vacuum
cleaner control means 25.
[0053] The motor-driven blower control means 30 performs switching
to the switching part 24 in accordance with the operation of each
control button of the operation mode switching controller 14 to
thereby control the output of the motor-driven blower 6.
[0054] [Description of DC Power Supply]
[0055] The DC power supply 7 will next be described. The DC power
supply 7 for supplying power comprises the--rechargeable battery 7a
in which batteries such as nickel cadmium batteries, nickel
hydrogen batteries, lithium ion batteries are connected in series
in plural form, the thermistor 21, a resistor R0 used as the
rechargeable battery identifying means 34, and a thermostat 35, and
the like.
[0056] A plus terminal of the rechargeable battery 7a is connected
to one end of the thermostat 35. The other end of the thermostat 35
is connected to one end of the resistor R0.
[0057] [Description of Operation Mode Switching Controller]
[0058] A specific configuration of the operation mode switching
controller 14 and its operation will next be explained.
[0059] In the electric vacuum cleaner control means 25, a
voltage-divided value of a reference voltage V1 changes according
to the state of operation of the operation mode switching
controller 14. In the electric vacuum cleaner control means 25, the
voltage-divided value varied according to the operation state is
converted into a digital signal by the ADC 32 corresponding to an
analog/digital converter, followed by being read by the voltage
reading means 31.
[0060] A circuit configuration (voltage variable circuit) for
allowing the voltage-divided value of the reference voltage VI to
change according to the operation state of the operation mode
switching controller 14, will be described below. The
voltage-divided value of resistors R5 and R6 is first inputted to
the ADC 32. Then, switches 35a, 36b and 36c are provided which are
switched by operating the respective control buttons 14a, 14b and
14c of the operation mode switching controller 14. Resistors R7, R8
and R9 respectively different in resistance value, which are
respectively connected to the switches 36a, 36b and 36c, are
parallel-connected to the resistor R6. Accordingly, the
voltage-divided value of the reference voltage V1 changes according
to the operation of each of the control buttons 14a, 14b and 14c of
the operation mode switching controller 14.
[0061] A control program or a control value or the like associated
with each voltage value read by the voltage reading means 31 has
been stored in the storage means 26 provided in the electric vacuum
cleaner control means 25. Thus, the electric vacuum cleaner 1 is
operated in accordance with the respective control buttons of the
operation mode switching controller 14.
[0062] Thus, the operation mode switching controller 14 is capable
of selecting and setting a plurality of voltages. The voltage
reading means 31 reads each of the voltages set by the operation
mode switching controller 14. A plurality of electric vacuum
cleaner operation modes are switched in accordance with the read
voltages respectively. Therefore, the addition of each operation
mode can be realized at low cost without increasing signal lines
for the operation mode switching controller 14 and the ADC 32.
[0063] [Description of Voltage Converting Means]
[0064] Next, a configurational example of the voltage converting
means 33 with respect to the motor-driven blower 6 in the electric
vacuum cleaner 1 is shown in FIG. 3. The voltage converting means
33 comprises a magnetic part 40 such as a reactor that assumes the
role of storage and emission of energy, a switching part (Q) 41
using a semiconductor switching element such as a MOSFET, a bipolar
transistor or an IGBT, a backflow or reverse-current prevention
part 42 (diode) for preventing a back-flow of the energy, a
capacitor 43 used as a capacitive impedance part element, and the
voltage conversion control means 28, etc.
[0065] The reactor used as the magnetic part 40 is composed
principally of a winding (coil) and a core made of a magnetic
material. The core is inserted into the wiring. The switching part
(Q) 41 is turned on and off to control current that flows through
the wiring. The reactor performs the storage and emission of the
energy in accordance with this operation. The core material of the
reactor is a magnetic material such as ferrite, Sendust, Permalloy,
an amorphous, alloy. As the shape of the core, may be mentioned, a
solenoid shape, a toroid shape or the like.
[0066] The voltage conversion control means 28 controls the
operation of the switching part (Q) 41 for increasing or boosting a
voltage outputted from the rechargeable battery 7a. That is, the
voltage conversion control means 28 has the function of setting the
frequency of an on/off pulse signal, and duty defined by an on
time/(on time+off time) of the on/off pulse signal and outputting
the pulse signal.
[0067] A voltage outputted from the main circuit 33a for the
voltage converting means is adjusted according to the frequency or
duty of the pulse signal outputted from the voltage conversion
control means 28. Incidentally, the ratio of the output voltage
boosted or stepped up by the voltage converting means 33 to the
voltage (voltage inputted to) outputted from the DC power supply 7
is called a step-up or boost rate. That is, the boost rate is
expressed in (boost rate)=(output voltage boosted by the voltage
converting means 33)/(output voltage of the DC power supply 7).
Here, the output voltage from the DC power supply 7 results in the
input voltage as viewed from the voltage converting means 33.
Therefore, the boost rate may also be represented by (the output
voltage boosted by the voltage converting means 33)/(the voltage
inputted to the voltage converting means 33).
[0068] Described more specifically, the voltage converting means 33
has an input terminal Pa connected to the DC power supply 7 side, a
common terminal Pb, and an output terminal Pc connected to the
motor-driven blower 6 side. The input terminal Pa is connected to
one terminal of the magnetic part (reactor) 40. The other terminal
of the magnetic part (reactor) 40 and a drain terminal of the
switching part (Q) 41 are connected to each other. A source
terminal of the switching part (Q) 41 and the common terminal Pb
are connected to each other. The voltage conversion control means
28 is connected to a gate terminal of the switching part (Q) 41. A
point where the reactor 40 and the switching part (Q) 41 are
connected to each other, and an anode terminal of the diode 42 are
connected to each other. A cathode terminal of the diode 42 and one
terminal of the capacitor 43 are connected to each other. The other
terminal of the capacitor 43 and the common terminal Pb are
connected to each other. A point where the diode 42 and the
capacitor 43 are connected to each other, is connected to the
output terminal Pc. The boosted voltage of the DC power supply 7 is
outputted between the output terminal Pc and the common terminal
Pb.
[0069] The boosting or step-up operation of the voltage converting
means 33 will now be explained. When the switching part (Q) 41 is
turned on in response to the pulse signal outputted from the
voltage conversion control means 28, a current Is flows so that
energy is stored in the reactor 40 by a current IL. Next, when the
switching part (Q) 41 is turned off by the voltage conversion
control means 28, the energy stored in the reactor 40 flows into
the motor-driven blower 6 through the diode 42 as a current Id,
followed by being charged into the capacitor 43. By allowing the
voltage conversion control means 28 to continuously turn on and off
the switching part (Q) 41 in this way, the repetition of the
storage of the energy in the reactor 40 and the emission of the
energy from the reactor 40 is realized.
[0070] The energy stored in the capacitor 43 is not fed back or
returned to the reactor 40 owing to the diode 42. The capacitor 43
is charged with a voltage higher than that of the DC power supply
7, and the charged voltage of the capacitor 43 is supplied to the
motor-driven blower 6.
[0071] A specific method for adjusting the frequency and duty of
the pulse signal outputted from the voltage conversion control
means 28 will next be explained with reference to FIG. 4.
[0072] In FIG. 4, the operation mode switching controller 14 is
operated to activate the voltage conversion control means 28. In
the voltage conversion control means 28, signals are inputted to an
error amplifier 51 from a reference voltage section 52 and an input
voltage section 53 respectively. A signal outputted from the error
amplifier 51 and a triangular wave signal oscillated from an
oscillation section 54 are inputted to a signal comparator 55. The
oscillation section 54, which allows the triangular wave signal to
oscillate, is a method conventionally known per se. A pulse signal
is outputted from the signal comparator 55 to control the turning
on and off of the switching part (Q) 41.
[0073] Now, the frequency of the triangular wave signal oscillated
from the oscillation section 54 is suitably set to thereby make it
possible to control the frequency of the pulse signal. Also the
switching part 56 is suitably switched to vary the value of the
voltage at the input voltage section 53. It is thus possible to
control the duty of the pulse signal outputted from the signal
comparator 55. A switching method of the switching part 56 is
stored in the storage means 26.
[0074] The method of controlling the frequency and duty of the
pulse signal inputted to the switching part (Q) 41 can be realized
even by a programming process of a microcomputer. The relationship
between the frequencies and duties of the triangular wave signal
and pulse signal is illustrated as a timing chart in FIG. 5. The
triangular wave signal is digitally generated through the use of a
timer counter. In the case of an up/down counter mode, for example,
the maximum value TCp1 of a counter value is set to thereby obtain
a period Tp(k) of the pulse signal as follows:
Tp(k)-2.times.TCp1.times.timer counter clock [sec]
[0075] Thus, the frequency fp(k) of the pulse signal is given as
follows:
fp(k)-1/2(2.times.TCp1.times.timer counter clock) [Hz]
[0076] Further, a set value S(k) stored in the storage means 26 and
the value of the timer counter are compared. When the timer
counter's value (triangular wave signal) reaches greater than or
equal to the set value S(k), the pulse signal is set so as to
assume ON. Consequently, a pulse width PW(k)[sec] is determined and
hence a duty Du(k) is represented as follows:
Du(k)=PW(k)/(2.times.TCp1.times.timer counter clock) [% ]
[0077] The maximum value TCp1 of the timer counter value and the
set value S(k) are changed to control the frequency fp(k) and duty
Du(k) of the pulse signal. A method of changing these set values is
stored in the storage means 26.
[0078] Thus, as shown in FIGS. 4 and 5, at least one of the
frequency and duty of the pulse signal is controlled to make it
possible to control the boost rate of the voltage converting means
33. For instance, the duty is raised to increase the boost rate,
and the duty is reduced in reverse to decrease the boost rate.
[0079] [Description of Operation]
[0080] The operations of the electric vacuum cleaner 1 and voltage
converting means 22 where the low control button 14b, high control
button 14c and stop control button 14a are operated in the
operation mode switching controller 14 of the control circuit shown
in FIG. 2 to which the voltage converting means shown in FIG. 3 is
applied, will now be described in detail with reference to FIG. 6
together with the operations of the switching part (Q) 41 and
switching part (A) 24.
[0081] When the low control button 14b is first operated in the
electric vacuum cleaner 1 in a halt state, an on signal is
outputted from the motor-driven blower control means 30. The
switching part (A) 24 performs an on operation, based on the
signal, so that the motor-driven blower 6 starts to rotate. Thus,
the output of the motor-driven blower 6 rises from a zero output to
a pre-set low operation mode output P1.
[0082] When the high control button 14c is operated from this
state, the voltage conversion control means 28 outputs a pulse
signal to the switching part (Q) 41. The voltage converting means
main circuit 33a is operated in response to the pulse signal, so
that the output voltage of the rechargeable battery 7a is stepped
up, followed by being applied to the motor-driven blower 6. Then,
the output of the motor-driven blower 6 is raised up to a pre-set
high operation mode output P2.
[0083] When the stop control button 14a is operated from this
condition, the voltage conversion control means 28 stops the output
of the pulse signal. Then, the switching part (Q) 41 is turned off
so that the voltage converting means main circuit 33a is
deactivated. Further, the switching part (A) 24 s turned off by the
motor-driven blower control means 30 so that the motor-driven
blower 6 is deactivated.
[0084] As illustrated in the present operation example, a process
for controlling the switching operation of the switching part (Q)
41 constitutes a switching means for selecting any one of the
output voltage of the DC power supply 7 and the output voltage
boosted by the voltage converting means 33 together with the
switching part (Q) 41.
[0085] However, according to the present embodiment, when the high
control button 14c is operated, the output voltage boosted by the
voltage converting means 33 is supplied to the motor-driven blower
6. Therefore, a deboost or non step-up operation mode is set in a
low operation mode of "low" and "high" operation modes of the
electric vacuum cleaner 1. On the other hand, a boost or step-up
operation mode is set in the high operation mode of the low and
high operation mode of the electric vacuum cleaner 1. In this
sense, the control button 9 for low operation setting functions as
a control section for selecting the non step-up operation mode. On
the other hand, the control button 14c for high operation setting
functions as a control section for selecting the step-up operation
mode. In addition, the stop button 14a functions as a stop control
section for stopping the rotation and driving of the motor-driven
blower 6.
[0086] Although not illustrated in particular, a bypass path for
directly supplying the voltage of the DC power supply 7 to the
motor-driven blower 6 may be provided without using the path of the
voltage converting means main circuit 33a in the non step-up
operation mode. In this case, it is possible to eliminate losses in
the reactor 40 and diode 42 of such a voltage converting means main
circuit 33a as shown in FIG. 3.
[0087] An example of a method for controlling the voltage
converting means 33 in a step-up operation mode shown in FIG. 6
will next be described. A user uses the electric vacuum cleaner
under various circumstances. For example, the user cleans above a
carpet, a mat, and a floor, or detaches the inlet body 11 and the
extension pipe 12 for their cleaning. Due to the differences among
targets to be cleaned, the state of a load applied to the electric
vacuum cleaner 1 changes and the state of output of the electric
vacuum cleaner 1 also changes.
[0088] FIG. 7 shows an airflow Q vs. negative pressure H
characteristic of the electric vacuum cleaner 1 and an airflow Q
vs. power P characteristic thereof where the boost rate of the
voltage converting means 33 is changed. The power P of the electric
vacuum cleaner 1 can be calculated from the airflow Q and the
negative pressure H. The suction force of the electric vacuum
cleaner 1 that a user feels, significantly depends on the power P.
Since the airflow of the electric vacuum cleaner 1 (the loaded
state thereof) is determined due to the difference between targets
to be cleaned, operating points H1 and P1 in FIG. 7, for example,
result in an operating point at a certain target (airflow Q1) to be
cleaned in the case of the boost rate e. Thus, this operating point
is also shifted if the target to be cleaned is changed.
[0089] Also as shown in FIG. 7, the characteristic of the electric
vacuum cleaner 1 varies for each boost rate of the voltage
converting means 33. Thus, in the present invention, the state of a
load is detected by the load detecting means 29, and the boost rate
of the load detecting means 33 is changed based on the detected
value to thereby shift the operating point of the electric vacuum
cleaner 1 onto the characteristic at another boost rate.
[0090] As one example of control on the above, such a control
example that when the airflow Q changes and the power P of the
electric vacuum cleaner 1 is reduced, the boost rate is raised and
the power P of the electric vacuum cleaner 1 is maintained at a
certain constant level, is illustrated in FIG. 7. The
characteristics at five types of boost rates are shown in the
figure. As a matter of course, drawn trajectories of operating
points become smooth by finely changing the boost rates.
[0091] When the electric vacuum cleaner 1 is in use, the inlet body
11 and the extension pipe 12 are pressed against a surface to be
cleaned or spaced away therefrom. The airflow Q changes depending
on this operation. Thus, it is so effective for the load detecting
means 29 to determine the airflow Q and automatically increase or
decrease the boost rate of the voltage converting means 33
according to the determined airflow Q to thereby control the power
P of the electric vacuum cleaner 1, from the viewpoint that a high
suction force is acquired when necessary. Since the motor-driven
blower 6 is not operated all the time at a high boost rate, the
consumption of battery energy is suppressed and the continuous use
time per charge can also be rendered long.
[0092] As a method for detecting the state of a load applied to the
electric vacuum cleaner 1 by the load detecting means 29, there is
known, for example, a method for detecting the airflow Q and the
negative pressure H in the electric vacuum cleaner 1 or a method
for detecting current that flows through the motor-driven blower 6.
For example, the negative pressure detecting section 39, which
functions as the load detecting means 29, is installed within an
upstream air path of the motor-driven blower 6. Described more
specifically, as shown in FIG. 8, a negative pressure detecting
section 39 (39a) is provided in an air path between the inlet 3 and
the dust cup 5. Alternatively, a negative pressure detecting
section 39 (39b) is provided in an air path between the dust cup 5
and the motor-driven blower 6. The negative pressure detecting
section 39 can be realized by a pressure sensor, for example.
Incidentally, although the dust cup 5 of cyclone dust collection
type is illustrated in the present embodiment, a method such as a
paper bag type may be adopted as the dust collection type.
[0093] And as an another method for detecting the state of a load,
an airflow detecting section which provided at the same part of the
negative pressure detecting section 39a, 39b detects each flow
velocity (m/s). And, the airflow detecting section calculates
airflow from a cross section (m.sup.2) of an air path which is
provided at the negative pressure detecting section 39a, 39b. And,
the airflow detecting section detects the state of a load applied
to the electric vacuum cleaner 1.
[0094] A data table showing the relationship of correspondence
between the negative pressure and the airflow set every boost rates
such as shown in FIG. 9 is prepared in the storage means 26 in
advance on the basis of such a relation as shown in FIG. 7. By
referring to the data table, the airflow can be grasped based on
the negative pressure detected by the negative pressure detecting
section 39. In addition to such a data table as shown in FIG. 9,
the relationship between the negative pressure and the airflow may
be defined using a relational expression. Data about such a table
or relational expressions have bee stored in the storage means
26.
[0095] Now, an example of a data table descriptive of input
voltages, boost rates, and values for an airflow range employed in
the voltage converting means 33 is shown in FIG. 10. In the present
data table, the boost rates are respectively set according to the
input voltages of the voltage converting means 33. When the
rechargeable battery 7a is used as the DC power supply 7, the
voltage of the battery is reduced with the use of the electric
vacuum cleaner 1 after its charge. Therefore, the boost rates are
set every input voltages of the voltage converting means 33 so that
operation modes of various specs can easily be realized.
[0096] In the case of, for example, an operation mode in which the
continuous use time per charge is long, the boost rate is also
changed small each time the input voltage of the voltage converting
means 3 drops.
[0097] Also in the case of, for example, an operation mode in which
emphasis is placed on the magnitude of a suction force, the boost
rate is-not changed small even if the input voltage of the voltage
converting means 33 is reduced.
[0098] FIG. 11 shows one example of a control flow for changing the
boost rate of the voltage converting means 33 according to the
state of a load on the electric vacuum cleaner 1 through the use of
the data tables shown in FIGS. 9 and 10.
[0099] The maximum negative pressure Hmax is first set (Step S101).
Next, the maximum output voltage Voutmax of the voltage converting
means 33 is set (Step S102), and an input voltage Vin of the
voltage converting means 33 is detected (Step S103) If the input
voltage Vin of the voltage converting means 33 is larger than a
lower limit voltage from the result of its detection (Y in step
S104), then the data table is retrieved in accordance with the its
detected value (Step S105) and a boost rate (duty) and an airflow
ranges Qdwn and Qup are set (Step S106). Thereafter, a step-up
operation is started (Step S107).
[0100] Then, an output voltage Vout of the voltage converting means
33 is detected (Step S108). It the output voltage Vout is greater
than an upper limit voltage Voutmax (Y in step 5109), then the
negative pressure H1 is detected (Step S110). When the detected
value of the negative pressure H1 is larger than the previously set
Hmax (N in step S111), the step-up operation is stopped (Step
S115). Described more specifically, this operation is supposed to
be taken in abnormal conditions such as a case in which the air
path of the electric vacuum cleaner 1 is blocked off by a large
refuse or the like. When the air path of the electric vacuum
cleaner 1 is blocked off by the large refuse or the like, the
negative pressure in the electric vacuum cleaner 1 rises. Thus,
needless power consumption can be suppressed owing to this
operation.
[0101] On the other hand, when the negative pressure H1 is detected
(Step S110) and its detected value is smaller than the previously
set Hmax (Y in step S111), the airflow Q1 is estimated from its
detected value H1 and such a data table as shown in FIG. 9 (Step
S112).
[0102] If the estimated airflow Q1 is larger than the airflow range
value Qdwn and smaller than Qup (Y in step S113), then the boost
rate is not changed.
[0103] On the other hand, if the estimated airflow. Q is smaller
than the airflow range value Qdwn or larger than Qup (N in step
3113), then the boost rate is changed to a large value (Step S114),
and the control flow is returned to Step S106. By increasing the
boost rate in this way, the power P of the electric vacuum cleaner
1 is enhanced and the suction force increases. Increasing the value
of the boost rate is performed by, for example, increasing the duty
of a pulse signal outputted from the voltage conversion control
means 28. Such a control flow is repeatedly executed.
[0104] It is so effective from the viewpoint that a high suction
force is acquired when necessary, to automatically increase or
decrease the boost rate of the voltage converting means 33
according to the state of a load to thereby control the power P of
the electric vacuum cleaner 1.
[0105] Since the motor-driven blower 6 is not activated all the
time with a high boost rate, the consumption of battery energy is
suppressed and the continuous use time per charge can also be
lengthened.
[0106] Here, the state of pressing of the inlet body 11 against a
surface to be cleaned, of use forms of the electric vacuum cleaner
is a well-known circumstance. In the state in which the inlet body
11 is being pressed against the surface to be cleaned, the airflow
Q1 is reduced and the negative pressure H increases, as compared
with the state in which the inlet body 11 is being spaced away from
the surface to be cleaned.
[0107] Accordingly, the magnitude of the suction force at this time
is one performance so important to a user. Thus, it is so effective
for a sweeper to automatically increase the boost rate of the
voltage converting means 33 and enhance the power P where the inlet
body 11 is pressed against the surface to be cleaned so that the
quality of air Q is reduced.
[0108] As another control example, it may be feasible to detect a
current that flows through the motor-driven blower 6 to thereby
grasp the state of a load and control the output voltage of the
voltage converting means 33 according to the value of the detected
current. An example of a data table descriptive of input voltages,
boost rates and values for current ranges of the voltage conversion
means 33, which are used in this control, is shown in FIG. 12. Data
about such a table or relational expressions are stored in the
storage means 26.
[0109] Incidentally, the current that flows through the
motor-driven blower 6 is detected by the current detecting section
37 constituted of, for example, a current transformer and a shunt
resistor as shown in FIG. 2.
[0110] FIG. 13 shows another example of the control flow for
varying the boost rate of the voltage converting means 33 according
to the state of a load applied to the electric vacuum cleaner 1
through the use of the data table illustrated in FIG. 12.
[0111] First of all, the minimum current Imin, the maximum current
Imax, and the maximum output voltage Voutmax of the voltage
converting means 33 are set (Steps S201 and S202). Next, an input
voltage Vin of the voltage converting means 33 is detected (Step
S203). If the input voltage Vin is greater than a lower limit
voltage Vd (Y in step S204), then a boost rate (duty) and current
ranges Idwn and Iup are set according to the value of the detected
voltage vin (Step S206). Afterwards, a step-up operation is started
(Step S207). Then, an output voltage vout of the voltage converting
means 33 is detected (Step S208). If the value of the detected
voltage is smaller than the maximum output voltage Voutmax (Y in
step S209), then a current I1 is detected (Step S21). When the
detected value I1 is smaller than the previously set Imin or larger
than the previously set Imax (N in step S211), the step-up
operation is stopped (Step S214). This is supposed to be taken
where the electric vacuum cleaner 1 lapses into an abnormal
state.
[0112] On the other hand, when the current value I1 is detected and
the value of the detected current is larger than the previously set
Imin and smaller than the previously set Imax (Y in step S211), it
is next compared with the current range values (Step S212).
[0113] If the detected value of current I1 is larger than the range
value Idwn and smaller than the range value Iup (Y in step S212),
then the boost rate is not changed.
[0114] On the other hand, when the detected current value I1 is
-smaller than the range value Idwn or larger than Iup (N in step
S212), the boost rate is changed to a large value (Step S213).
[0115] By increasing the boost rate in this way, the power P of the
electric vacuum cleaner 1 is enhanced and the suction force
increases.
[0116] As described above, it is so effective from the viewpoint
that a high suction force is acquired when necessary, to
automatically increase or decrease the boost rate of the voltage
converting means 33 according to the state of the load to thereby
control the power P of the electric vacuum cleaner 1.
[0117] Since the motor-driven blower 6 is not activated all the
time with a high boost rate, the consumption of battery energy is
suppressed and the continuous use time per charge can also be
lengthened.
[0118] Incidentally, as shown in FIG. 14, a cleaned surface
detecting means 80 may be provided on the suction side of the inlet
body 11 mounted to a leading end of an air path. When, for example,
the cleaned surface detecting means 80 is made up of a mechanical
switch and the inlet body 11 is pressed against the surface to be
swept, the switch is turned on so that a signal is inputted to the
electric vacuum cleaner control means 25. The voltage conversion
control means 28 controls the boost rate according to the input
signal.
[0119] One example of its control is described. When the signal is
inputted from the cleaned surface detecting means 80 during
cleaning, the electric vacuum cleaner control means 25 judges that
the airflow Q is reduced and the negative pressure H is increasing,
and controls the boost rate to increase it.
[0120] Consequently, the electric vacuum cleaner control means 25
is capable of indirectly grasping the state of a load in accordance
with the signal of the cleaned surface detecting means 80.
[0121] Incidentally, the cleaned surface detecting means 80 can be
realized even by another type of switch such as an optical
switch.
[0122] As described above, the state of pressing of the inlet body
11 mounted to the leading end of the air path against the surface
to be cleaned, of the use forms of the electric vacuum cleaner is a
well-known circumstance.
[0123] The magnitude of the suction force in the state in which the
inlet body 11 is pressed against the surface to be cleaned, is one
performance so important to a user.
[0124] Therefore, it is so effective for a sweeper to automatically
increase the boost rate of the voltage converting means 33 when the
inlet body 11 is being pressed against the surface to be
cleaned.
[0125] Since the boost rate is not increased at random when the
inlet body 11 is not brought into contact with the surface to be
cleaned, the continuous use time per charge can be lengthened.
[0126] Here, the rate of increase in the boost rate may be fixed,
i.e., the boost rate may be increased at a predetermined
proportion. The rate at which the boost rate is raised according to
the input voltage of the voltage converting means 33, may be
changed. When the rate of increase in the boost rate is fixed, that
is, the boost rate is increased at the predetermined proportion,
control on the boost rate can be simplified.
[0127] Incidentally, when the inlet body 11 is not in contact with
the cleaned surface, the electric vacuum cleaner control means 25
may control the step-up operation of the voltage converting means
33 so as to avoid its step-up operation. Described specifically,
when the inlet body 11 is spaced away from the surface to be
cleaned, and the mechanical switch is turned off, the electric
vacuum cleaner control means 25 automatically stops the step-up
operation.
[0128] The continuous use time per charge can be lengthened by
performing the step-up operation only when necessary without always
performing the step-up operation.
[0129] Detection is made as to whether such an inlet body 11 as
shown in FIG. 15 is connected to the extension pipe 12, the hose
body 4 or the case 2 or the like, whereby the state of a load can
be indirectly grasped and hence the boost rate can be controlled.
Described specifically, when a connecting plug 81 mounted to the
inlet body 11 is detached from the extension pipe 12, the hose body
4 or the like, the resistance of wiring changes. The change in the
resistance thereof is detected by the electric vacuum cleaner
control means 25. It is thus possible to detect whether the inlet
body 11 is connected to the extension pipe 12, the hose body 4 or
the case 2 or the like. Here, the function of an
attachment/detachment detecting means is executed.
[0130] Thus, owing to the provision of the attachment/detachment
detecting means for detecting the presence or absence of the state
of attachment/detachment of the inlet body 11 at the tip of the air
path, the electric vacuum cleaner control means 25 changes the
boost rate according to a signal outputted from the
attachment/detachment detecting means.
[0131] When the inlet body 11 is detached, for example, the
electric vacuum cleaner control means 25 controls the boost rate of
the voltage converting means 33 so as to increase it of use forms
of the electric vacuum cleaner, the state in which as shown in FIG.
16, the inlet body 11 is detached, and a crevice tool 60 or a brush
91 is attached to the tip of an air path of the extension pipe 12
or the hose body 4 or the like to thereby perform cleaning, is a
well-known circumstance. The magnitude of a suction force at this
time is one performance so important to a user. Thus, it is so
effective to automatically increase the boost rate of the voltage
converting means 33 when the user has detached the inlet body 11
(the inlet body 11 is detached). The rate at which the boost rate
increases, may be fixed. Alternatively, the rate at which the boost
rate increases, may be changed according to the input voltage of
the voltage converting means 33. In the case of its fixing, control
on the boost rate can be simplified.
[0132] The above embodiment shows an example in which the low
control button 14b and a high control button 9d are sequentially
operated from a halt state, based on FIG. 6. That is, it
illustrates an example in which a non step-up operation mode is
switched to a step-up operation mode. As a matter of course, the
high control button 9d may directly be operated at the halt state.
In this case, the operation mode is switched to the step-up
operation mode directly from the halt state.
[0133] Thus, the non step-up operation mode for supplying a voltage
outputted from the DC power supply 7 to the motor-driven blower 6
and the step-up operation mode for supplying an output voltage
obtained by boosting the output voltage of the DC power supply 7 to
the motor-driven blower 6 are prepared in advance. Further, a
switching means for selecting these operation modes and an
operation mode switching control section for operating the
switching means are provided. Consequently, the user is able to
carry out direct switching in person.
[0134] On the other hand, when the power supply voltage is boosted
by the voltage converting means 33, a loss in power by each circuit
part or component or the like that constitutes a voltage converter
occurs. Therefore, a drawback arises in that needless power is
inevitably used as compared with a case in which the electric
vacuum cleaner is directly driven by the battery.
[0135] However, there is provided a feature that a power supply
unit can be significantly made small-sized and lightened as
compared with a case in which the capacity of the battery is
increased in size.
[0136] Where the voltage of the battery is boosted by the voltage
converting means, the user makes use of the voltage converting
means even under the condition in which dust suction capability is
not required, when the voltage converting means is always operated,
thus causing a loss in power due to the use of the voltage
converting means and shortening the service or usage time of the
battery. When the battery is of a rechargeable battery, the usage
time per charge becomes short.
[0137] On the other hand, as in the present embodiment, a (non
step-up operation mode) means for driving the motor-driven blower
by an output voltage of a battery alone, which is applied to a case
in which the dust suction capability is not so required or it is
desired to make long the usage time (usage time per charge in the
case of a rechargeable battery) of the battery, and a (step-up
operation mode) means for driving the motor-driven blower by an
output voltage boosted by the voltage converting means, which is
applied to a case in which high dust suction capability is needed,
are provided as means for controlling the output of the
motor-driven blower. Further, there is provided a switching means
capable of selecting these output control means whenever necessary.
Consequently, the user is able to select the corresponding
operation mode according to user's various circumstances.
[0138] As a matter of course, such a configuration that the step-up
operation mode is selected, may be adopted even if any one of the
low control button 14b and the high control button 14c is operated.
In this case, such table data as shown in FIGS. 9, 10 or 12 is
provided for the respective control buttons. Alternatively, when
any one of the control buttons is operated, the boost rate is
fixed.
[0139] [Another Configurational Example of Voltage Converting
Means]
[0140] Another configurational example of the voltage converting
means with respect to the motor-driven blower 6 in the electric
vacuum cleaner 1 will next be described with reference to FIG. 17.
In a voltage converting means 60 employed in the present
embodiment, a transformer 61 having a primary winding 61a and a
secondary winding 61b is used as a magnetic part. The primary
winding 61a and the secondary winding 61b of the transformer 61 are
reversely connected.
[0141] Described more specifically, the voltage converting means 60
has an input terminal Pa and an input-side common terminal Pd
connected to the DC power supply 7, and an output terminal Pc and
an output-side common terminal Pe connected to the motor-driven
blower 6. The voltage converting means 60 is configured as follows:
The input terminal Pa and one terminal of the primary winding 61a
of the transformer 61 are connected to each other. The other
terminal of the primary winding 61a of the transformer 61 and a
drain terminal of a switching part (Q) 41 are connected to each
other. A source terminal of the switching part (Q) 41 and the
input-side common terminal Pd are connected to each other. The
output side of a voltage conversion control means 28 is connected
to a control terminal of the switching part (Q) 41. One terminal of
the secondary winding 61b of the transformer 61 is connected to an
anode terminal of a diode 42. A cathode terminal of the diode 42
and one terminal of a capacitor 43 are connected to each other. The
other terminal of the capacitor 43 and the other terminal of the
secondary winding 61b of the transformer 61 are connected to each
other. A point where the diode 42 and the capacitor 43 are
connected, is connected to the output terminal Pc. A connecting
point of the capacitor 43 and the secondary winding 61b of the
transformer 61 is connected to the output-side common terminal Pe.
A voltage obtained by boosting the output voltage of the DC power
supply 7 is outputted between the output terminal Pc and the
output-side common terminal Pe.
[0142] A boost or step-up operation of such a voltage converting
means 60 will be explained. When the switching part (Q) 41 is
turned on in response to a pulse signal outputted from the voltage
conversion control means 28, a current IT1 flows so that energy is
stored or accumulated in the transformer 61. Since, at this time,
the primary winding 61a and the secondary winding 61b of the
transformer 61 are reversely connected, no current flows into the
secondary side owing to the diode 42.
[0143] Next, when the switching part (Q) 41 is turned off by the
voltage conversion control means 28, a back electromotive voltage
occurs in the corresponding winding of the transformer 61 so that
the potential is inverted. Therefore, the energy stored in the
transformer 61 is discharged into the secondary winding 61b side
(motor-driven blower 6 side) through the diode 42 as a current IT2.
A voltage higher than the DC power supply 7 is charged into the
capacitor 43 and then supplied to the motor-driven blower 6.
[0144] Obviously, numerous modifications and variations of the
present invention are possible in light of the above teachings. It
is therefore to be understood that within the scope of the appended
claims, the invention may be practiced otherwise than as
specifically described herein.
* * * * *