CA2027310A1 - Electric floor cleaner with a soft start function - Google Patents

Abstract

AN ELECTRIC FLOOR CLEANER WITH A SOFT START FUNCTION

ABSTRACT OF THE DISCLOSURE

An electric floor cleaner is of the type arranged to drive a three-phase motor, whose rated voltage is substantially equal to a voltage obtained by voltage doubling and rectifying a single-phase commercial power line and then by converting a voltage doubled d.c. voltage into three-phase a.c. by an inverter. The voltage and frequency of the three-phase a.c.
output from the inverter are controlled for a predetermined period of time after a power switch is put into a turned on state from a turned off state. It is therefore possible to reduce the starting current to a small value enabling the use of a larger rated output motor than a motor in a conventional system within an allowable current limit of a commercial power line.

Description

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A~ ELECr~RIC CLEANER WITH A SO~I` START FUNCTION
BACKGROUND OF TIIE INVENTION
(F':iled of t:he :tnventlorl) 'rhis ;nvelltlon gerlerally relates to electric floor cleaners, alld rnore particulclrly to an electric floor cleaner of the type having a three-phase s~c. motor dr.iven by three-phase s.c. obtained by converting single phase a.c. from a asingle phase power source.
(Description of the Prior Art) In conventional electric floor cleaners or polishers, there is a relationship between a brush-driving mo-tor and power source voltage in theory as follows:
(a) A system in which a two-phase lOO volt driving motor is connected to an output side of an inverter whose input is 100 volts and output is 100 volts. This system is referred to as system A. In this speciEication, the words "inverter system" are used to mean a system which converts an a.c. input into a d.c. by way of a rectifier, and then the d.c. is converted into a desired a.c., and an inverter which simply converts a.c. to d.c. is referred to as "inver-ter".
(b) A system in which a three-phase 100 volt driving motor is connected to an output side of an inverter whose input is 100 volts and output is 100 volts. ~his system is referred to as system B.
(c) A system in which a single-phase lOO volt driving motor is operated through primary voltage control. This system is referred to as system C.
(d) A system in which a single-phase lOO volt driving , .

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motor is driven directly by commercial power source. This system is referred to as system D.
(e) A system in which a d.c. drlving motor is operal:ed wh~re comm~rcial power :is converted into d.c. by utilizincJ tilyristors or the lilce. This system is referred to as system E.
(f) A system in which a three-phase 200 volt driving motor is connected to an output side of an inverter whose input is 200 volts and output is 200 volts where the inverter is connected to an output side of a transformer whose input is 100 volts and output is 200 volts. This system is referred to as system F.
The above mentioned conventional systems A to F have the following advantages and disadvantages.
SYSTEM A
(DISADVANTAGES) Since the motor is of special -type, the required frame is bulky.
Starting current is twice the normal operation current.
Cost is high.
SYSTEM B
(DISADVANTAGES) The inverter system is bulky.
Transistors have control current which are large.
A standard motor is not available.
The size of the motor is large.
Cost is high.

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SYSTEM C
(DISADVANTAGES) The size oE the motor is twice tl~at of a standard motor.
A feedbaclc circuit and a TG (tachometer generator) are required.
A motor of a very special type is required.
The starting current is large.
Efficiency is very poor.
(ADVANTAGES) The required controller is small in size.
SYSTEM D
(DISADVANTAGES) The upper limit of the motor output wi-thin the allowable current limit, which will be described later is low.
The degree of shock on starting is high.
There are considerable magnetic vibrations.
The starting current is large.
Variable speed is not available.
The size of the motor is twice that of a standard motor.
Efficiency is very poor.
(ADVANTAGES) A standard motor and standard parts can be utilized.
Cost is low.
SYSTEM E
(DISADVANTAGES) The maintenance of carbon brushes is troublesome.

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The upper limit of the motor output is low.
The motor is large in size.
Cost is several t.imes.
(~DV~N~AGES) 'l'he rcql~ired contrc)l.ler is smal.l ln size.
SYS'l`~M F

(DIS~DVANTAGES) A large-sized transformer is required.
(ADVANTAGE,S) A standard inverter can be used.
Among the above described systems A to F, systems D
and E are actually used.
Generally, the allowable current which can be taken from a single plug socket or convenience outlet of a commercial power line in a building is 20 amperes, and it is l.imited to disconnecting loads which require current more than the all.owable current.
In recent years since computers or the like are often used in building, it is very important to avoid power supply cut-off resuting fxom excess demand above the allowable current. ~herefore, careful attention must be used to avoid using a polisher where the current is above a given allowable value.
In the above mentioned systems D and E, it rnay be to be dangerous to use a driving motor of 0.75 kilowatt or more.
In systems using a single-phase motor as the system D, strong electromagnetic vibrations are transmitted to the hands of an operator holding a polisher handle, and in the -:: . : , , :. . :

worst cases, operators often suffer from an occupational disease due to long time use of such a polisher.
In order to solve this problem, the present inventors invented, pr:i.or to the presellt .invention, an elect.rlc floo.r c.l.eaner having a three-phase 200 volt dr.iving motor which :i.s dr:iv~ll by ~llree-pl~ase 200 volt a.c. obtained by an inverter s~steln connected to a single-phase 100 volt power source. This electri.c floor cleaner is capable of increasing the upper limit of a motor's output without exceeding the allowable current limit and is al.so capable of reducing the ocuurrence of occupational diseases and undersirable influences both caused from electromagnetic vibra~ions. More specifically, this novel electric floor cleaner according to the prior invention is of a driving method in which a three-phase 200 volt driving motor is connected to an output side of an inverter system with an input of a single-phase 100 volts and an output of three-phase 200 volts.
However, even if a three-phase motor is driven by producing three-phase 200 to 240 volt power using an inverter system having a voltage doubler rectifier connected to a commercial power source of 100 volts to 120 volts, and an inverter, it was only possible to increase motor output as high as 1.0 kilowatt within allowable current of a single plug socket of a single-phase commercial power source line because of the influence of starting current which flows on starting the motor.
SUMMARY OF THE INVENTION
Thus, the present invention is an improvement of the . .
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above-described conventlonal electric floor cleaner of three-pllase motor driving system. It is therefore an object of the prcsent invention to provide a ncw and useE~Il electric ~`:loc)r cLearler wl-l:lcll ls capabl.e of lncreas:ing motor output W:i~h:i.ll all allowl~le current l:imit of a single-pllase commercial power source line.
A further object of the present invention is to provide an electrical Eloor cleaner whose starting current is minimum while the size is small and efficiency and power factor are the best when comparing with the above-mentioned systems A
to F.
A still fruther object of the present invention is to provide an electl-ical floor cleaner which emits less vibrations whose cost is low and which can be manufactured by using a standard motor and standard parts.
To achieve the above objects the present invention provides:
an electrical floor cleaner comprising:
(a) a device for voltage doubling and rectifying a single-phase commercial power source voltage fed through a power switch;
(b) an inverter for converting a voltage doubled d.c.
obtained by the voltage doubling and rectifying device into three-phase a.c.;
(c) a device for controlling timing of conduction of switching elements of said inverter so as to control voltage and frequency of said three-phase a.c. for a predetermined period of time after said power switch is put into on state . . .
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from off state;
(d) a three-phase motor arran~ed to be driven by said t~ree-pl)asc a.c. applied ELOm said invertcr, said three-phase motor hclv:i~lg a ral:ed vo:ltage whlch is substalltially equal to ~:he tloubled voltac~e; antl (e) a Eloor cleaning member arranged to be driven by the three-phase motor.
BRIEF DESCRIPTION OF THE DRAWINGS
The object and features of the present invention will become more readlly apparent from the following detailed description taken in conjunction with the accompanying drawings in which:
Fig. 1 is a perspective view of the electxic floor cleaner according to the present invention;
Fig. 2 is a block diagram showing an electrical circuit of the electric floor cleaner according to the present invention;
Fig. 3 is a waveform diagram for descri~ing the operation of the block diagram of Fig. 2;
Fig. 4 is a block diagram showing the structure of a control power source circuit shown in Fig. 2;
Fig. 5 is a block diagram showing the structure of an over voltage detecting circuit showin in Fig. 2;
Fig. 6 is a block diagram showing the structure of a soft start setting circuit showin in Fig. 2;
Fig. 7 is a flowchart showing the operation of a CPU
in a control circuit show in Fig. 2; and Fig. 8 is a diagram showing patterns giving the ~ :;

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relationshlp between frequencies and voltages which can be selected by the so~t start setting circuit.
The same or corresponding elements or parts are desigllated at lllce reference numerals throughout the drawings.
ILE~ ~ESCRIPTION OF TllE PREF`E~ ED EMBODIMENT
Re~erring to the drawings a preferred embodiment of the electric floor cleaner of the present invention will be described hereinbelow.
Fig. 1 illustrates a perspective view of an ernbodiment of the present invention.
In the illustrated a perspective view of an embodiment of the present invention.
In the illustrated embodiment a supporting truck 2 is attached to a tip portion of a handle shaft 1 and a cover 3 is attached to a front end of the supporting truck 2. On the upper center portion of the cover 3 is mounted a general purpose three-phase 200 volt motor 4. Below the cover 3 a rotary brush 5 is detachably a~tached. A gear box (not shown) for transmitting the rotational force of the three-phase 200 volt motor to the rotary brush 5 is mounted in the cover 3 and a single-phase power source inverter system 6 having a manipulation panel for converting single-phase 100 volts to three-phase 200 volts is fixed to the peripheral wall of the motor 4. The above-mentionted three-phase 200 volt motor 4 is supplied with power via the single-phase power source inverter system 6 from single-phase 100 volt commercial power source cable 7.
The present invention may be implemented as having a ~, , .- . , -, ~,2 ri, S' r' '` ' ,.' vacuum suction function, detergent spraying function, and in such a case, a motor used for vacuum suction or spraying may also be supplled with power via the single--phase power source inve:rtcr. Furthermore, a secondary lli.gh-resistallce special scluirrel-cage s~epless speed-cllarlge induct:ion motor which is ~ellerally callecl a VC motor ll~ay be usecl as tlle three phase 200 vo:Lt motor.
In this embodiment, althou~h it is assumed that the voltage of a cornmercial single-phase power source is 100 volts and the rated voltage of the three-phase motor 4 is 200 volts, if the voltage of a commercial power source is different from 100 volts, for instance in the case of 120 volts, the rated voltage of the three-phase motor 4 is then 240 volts which is twice the rated line voltage. The single-phase power source inverter system 6 has a structure as shown in the block diagram of Fig. 2. A single-phase 100 volt a.c. is input through terminals R and S to be converted into d.c. power of 200 volts by way of a voltage doubling and rectifying circuit 11. The d.c~ power is smoothed by a smoothing capacitor 12, and is converted into an a.c. power of 200 volts by an inverter 13 to output three-phase a.c. of 200 volts through terminals u, v and w. In the drawing, references, C1 and C2 are smoothing capacitors for the voltage doubling and rectifying circuit 11, the references Dl and D2 are rectifier diodes, and the references D3 and D4 are flywheel diodes. The reference R2 is a current-detecting resistor; the reference IM is a three-phase induction motor whose rated voltage is 200 volts; a control circuit power source 14; an overvoltage detecting circuit 15;

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-an undervoltage detecting circuit 16; an overcurrent detecting circuit 17; a soft start setting circuit 18 is provided a manually operable potentiometer 19 is connected between a d.c.
voltaqe IV and groulld. ~n A/D converter 20, a display circuit 21; a base drive circuit 22 are also provided; and an abnormal output signal c.ircui-t 25 are also provided.
Fig. 3 shows waveforms of lnput and output voltages oE the inverter system, and more specifically, it is illustrated how an input of single-phase 100 volts, 50 ~z is converted into an output of three-phase 200 volts, 25Hz.
Conduction timings of transistors which are switching elernents of the inverter 13 are controlled by the base drive circuit 22 to obtain an approximate sinusoidal wave shown in Fig. 3. The output vo]tage and fre~uency can be controlled as will be describved later.
The control circuit 25 receives respective detection signals from the overvoltage detecting circuit 15, undervoltage detecting circuit 16, overcurrent detecting clrcuit 17, a soft start setting signal from the soft start setting circuit 18, a speed setting signal from the A/D converter 20 to feed the base drive circuit 22 with a control signal through a given computation. This control circuit 25 comprises a general-purpose microprocessor (CPU), ROMs, RAMs, interEaces and so on.
The control circuit power source 14 supplies the control circuit 25 with given d.c. power voltage, and as shown in Fig. 4 a d.c. voltage between both terminals (P-N terminals) of the capacitor 12 is input into a switching circuit 30 to l n _ . . , : , ,, . . . :
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forrn a pulse waveform, and then voltage regulation is performed by a pulse transEormer 31 to obtain a d.c. output oE a given voltage by a rectiEier 32.
'I'he overvoltage detectillcl circuit 15 whose block cl:iacJralrl is showrl in l'ig. 5, compares a d.c. voltaye between both terrnlrlals ~P-N terrninals) of tlle capacitor 12 with a reference value using a comparator 34, and is arranged to output an ~l or L level signal obtained through this comparison via a photocoupler 35. In Fig. 5, a filter 33 is a LPF for removing ripple components.
Sinee the undervoltage detecting circuit 16 and the overcurrent de-tecting circuit 17 have substantially the same structure as the overvoltage detecting circuit 15, illustration of these circuits is omitted.
The softstart setting circuit 18 whose structure is shown in Fig. 6 comprises a dip switch 37 having four circuits, and four resistors 38-1 to 38-4, and is arranged to send 4--bit data set in advance to the control cireuit 25. The funetion of this soft start setting circuit 18 will be described in conneetion with a flowehart oE a CPU which will be described later.
The display circuit 21 comprises, for instance, a lamp and its drive cireuit for informing a user of an abnormal state by repeatedly flashing the lamp on an abnormal state such as the increase of the load of the motor IM.
The base drive circuit 22 is arranged to control the timing of turning on and turning off of the power transistors in the inverter 13 on the basis of determined results, and the ' -, ~ '. ~ . '. ' ~

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struc-ture of this base drive circuit 22 may be the same as a general base drive circuit conventionally used.
Fig. 7 is a flowchart showing the operational flow of the CPU whicll :is a main elemelll: oE the control circ~it 25. As is clear Erom ~"ig. 7, wl-ell any one of the detection signals froln the circuits 15 to 17 indicates an abnorrnal state, the display circuit 21 is driven to inform a user of an abnormal state by flashing the lamp or by other methods.
When an abnormal state is not present, 4-bit data from the soft start setting circuit 18 is input, and an address of a ROM within the control circuit 25 is designated by this 4-bit data to read out corresponding data from the ROM. This data is used for determining frequency and voltage of the three-phase power to be fed to the motor IM, and is usad Eor controlling the inverter 13 through the base drive circuit 22.
A next step is for determining whether a predetermined period of time has lapsed or not after an unshown power switch is turned on, More specifically, a starting current flows for this predetermined period of time after the power switch is turned on, and therefore, the voltatge (V) and the frequency (f) of the three-phase power to be applied to the motor IM are controlled on the basis of the data read out of the ROM. For this period, the control of the starting current is performed irrespective of a speed set by the manually operable potentiometer 19.
Fig, 8 is a graph showing the relationship between the voltaghe (V) and frequency (f) of the output power from the inverter 13 on starting resulted from the soft start control.

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In this graph, five different curves are shown, and one of them is selected in advance by manipulating the dip switch 37 shown in ~ . 6. As shown ln the drawin~, it is possi.ble to respectively change th~ frequency between several llz and 120 1l;~, and the voltacJe betweerl .lO or rnore volts and a rated voltaye.
Turning back to the flowchart of Fig. 7, after the above mentioned predetermined period of time has lapsed, the base drive circuit 22 is controlled in the same manner as in conventional circuits to control the inverter 13 so as to obtain a motor rotati.onal speed set by the potentiometer 19.
From the Eoregoing detailed description of the invention, it will be understood that the electric floor cleaner according to the present invention comprises a single-phase power source inverter system oE single-phase lOO
volts input and three-phase 200 volts output, a three-phase 200 volt motor connected to an output side of the single-phase inverter system, where the motor is used for driving a floor cleaning member, such as a rotary brush, and soft start means, thereby proving the followi.ng advantages:
(a) The electric floor cleaner can be manufactured at a low cost utilizing a standard motor and standard parts, such as an inverter.
(b) It is possible to safely use the driving motor up to approximately 1.3 kilowatt even if the above mentioned current limit of 20 A is present, and therefore, motor output can be increased.
(c) The size of the cleaner can be reduced to the ; ..... .
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minimum when compared with the aforementioned system A to F.
(d) The efficiency and power factor are the best when compared with the aEorementioned systems A to F, and therefore, the clealler can contribute to improvemellt of power factor of transfo.L-ming equipment or the like.
(e) Electromagnetic vibrations which give undesirable inEluences to an operator can be drastically reduced.
(f) The starting current can be reduced to the minimum when compared with -the aforementioned systems A to F
and the system disclosed the Japanese patent application provisional publication No. 61-249427.
The above described embodiment is just an example of the invention and therefore, it will be understood for those skilled in the art that various rnodifications and variations may be made without departing from the sprit of the invention.

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Claims (6)

1. An electrical floor cleaner comprising:
voltage doubling and rectifying means for voltage doubling and rectifying a single-phase commercial power source voltage input through a power switch;
an inverter for converting a doubled d.c. voltage from said voltage doubling and rectifying means into three-phase a.c.;
control means for controlling voltage and frequency of said three-phase a.c. for switching elements of said inverter for a predetermined period of time after said power switch is put into an on state from an off state, said control means controlling said voltage and frequency according to a predetermined combimation thereof, said voltage and frequency are different from rated values thereof, therein providing a soft start;
a three-phase motor arranged to be driven by said three-phase a.c. applied from said inverter, said three-phase motor having a rated voltage which is substantially equal to the doubled voltage; and a floor cleaning member arranged to be driven by said three-phase motor.

2. An electric floor cleaner as claimed in Claim 1, wherein said control means comprises a manually operable dip switch having a plurality of circuits, and a memory means for storing a plurality of patterns of relationship between voltages and frequencies which are designated by said manually operable dip switch.

3. An electric floor cleaner as claimed in Claim 1, further comprising manually operable adjustable speed setting means, and means responsive to an output from said speed setting means for controlling conduction timings of switching elements of said inverter so that said motor rotates at a setting speed after said predetermined period of time has lapsed.

4. An electrical floor cleaner as claimed in Claim 1, further comprising detecting means detecting for detecting input voltage of said inverter and alarm means responsive to said detecting means for emitting an alarm.

5. An electrical floor cleaner as claimed in Claim 1, further comprising detecting means for detecting input current of said inverter and alarm means responsive to said detecting means for emitting an alarm.

6. An electrical floor cleaner comprising:
voltage doubling and rectifying means for voltage doubling and rectifying a single-phase commercial power source voltage input through a power switch;
an inverter for converting a doubled d.c. voltage from said voltage doubling and rectifying means into three-phase a.c.;
control means for controlling timing of conduction of switching elements of said inverter so as to control voltage and frequency of said three-phase a.c. for a predetermined period of time after said power switch is put into an on state from an off state, said control means including a manually operable dip switch having a plurality of circuits, and a memory means for storing a plurality of patterns of relationship between voltages and frequencies which are designated by said manually operable dip switch;
a three-phase motor arranged to be driven by said three-phase a.c. applied from said inverter, said three-phase motor having a rated voltage which is substantially equal to the doubled volrtage; and a floor cleaning member arranged to be driven by said three-phase motor.