AUTOMATIC PUMP AND OPERATION CONTROL METHOD FOR THE SAME
BACKGROUND OF THE INVENTION
1. Field of the invention
The present invention relates to an automatic pump
and an operation control method of the automatic pump.
2. Description of the Prior Art
As generally known in the art, a pump refers to an
apparatus for transferring fluid by the action of
pressure, and an automatic pump refers to a pump that
automatically rotates or stops an impeller for forcedly
discharging introduced fluid according to preset
conditions.
An automatic pump has a housing which forms a flow
path for a fluid. In addition, a motor-driven impeller is
installed within the housing, and a pressure sensor for
sensing the internal pressure of the housing or a flow
switch for sensing the quantity of fluid discharged out of
the housing is provided at one side of the housing.
Thus, in the automatic pump, the internal pressure of
the housing turns the drive motor to operate or stop, or
the fluid discharge out of the housing causes the motor to
run or pause, which in turn rotates or suspends the
impeller.
Since the conventional automatic pumps have the motor
driven in constant speed, the impeller is always rotated
constantly. The resultant inability to control the speed
of rotation of the impeller depending on the desired fluid
discharge rate causes a deterioration of the pump
efficiency.
In addition, as for an automatic pump with a pressure
switch installed, the frequent changes of the internal
pressure in the housing trigger the motor on and off too
often, resulting in a problem of wasted energy. Moreover,
in the case of the automatic pump with the flow switch
installed, a slow reaction rate and insufficient fluid
discharge would leave the motor difficult to control.
To solve the above-mentioned problems, there has been
an automatic pump developed to have a pressure sensor for
sensing an internal pressure of a housing and an inverter
for carrying out DC to AC conversion responsive to the
pressure sensed by the pressure sensor and changing the
frequency and voltage, so as to control the rotation speed
of the motor according to the internal pressure of the
housing or an internal pressure of a discharge pipe
communicating with the housing.
However, the inverter-installed automatic pumps have a
drawback in that they require a high priced inverter, which
increases the manufacturing cost of the automatic pumps and
also undesirably adds to the bulkiness of the automatic
pumps.
SUMMARY OF THE INVENTION
Accordingly, the present invention has been made to
solve the above-mentioned problems occurring in the prior
art, and an object of the present invention is to provide
an automatic pump and a method for controlling the
operation thereof whereby reducing the manufacturing cost
thereof as well as the volume of the automatic pump
In order to accomplish this object, there is provided
an automatic pump including: a housing having an inlet
formed at one side for a fluid to enter and an outlet
formed at another side for discharging the fluid; an
impeller installed inside of the housing for forcefully
drawing the fluid through the inlet into the housing and
then forcefully discharging the fluid through the outlet; a
motor being capable of shifting the impeller through multi-
stage rotational speeds or into a stop; a control unit for
controlling the motor; a pressure sensor for sensing an
internal pressure of the housing and transmitting the
internal pressure to the control unit; and a switching unit
responsive to a signal corresponding to the internal
pressure of the housing transmitted from the pressure
sensor to the control unit for selectively changing winding
counts of a stator coil of the motor and thereby running
the motor at one of set multi-stage rotational speeds or
stopping the motor.
In accordance with another aspect of the present
invention, there is provided a method for controlling
operation of an automatic pump provided with a housing, an
impeller installed inside of the housing for forcefully
drawing and discharging a fluid into and out of the
housing, a motor being capable of shifting the impeller
through multi-stage rotational speeds or into a stop, and a
pressure sensor for sensing an internal pressure of the
housing, the method including: comparing an internal
pressure of the nouslng after sensing the internal pressure
with a set pressure; continuously sensing the internal
pressure of the housing if the internal pressure is greater
than the set pressure, and driving the motor if the
internal pressure is equal to or less than the set
pressure; and sensing a change in the internal pressure of
the housing while the motor is running, and if the change
is sensed, accelerating or decelerating rotational speeds
of the motor by selectively switching winding counts of a
stator coil of the motor.
The automatic pump and its operation control method
according to the present invention are responsive to the
internal pressure of the housing which forms a flow path
within the automatic pump for making selective switching
connections with variable winding counts of a stator coil
of a pump motor, and thereby shift the rotational speed of
the motor to an appropriate one of multi-stage rotational
speeds or stops the same. This eliminates the need for
employing the inverters as in the conventional automatic
pumps to provide a substantial cost reduction as well as
enabling compactness of the pump.
BRIEF DESCRIPTION OF THE DRAWINGS
The above and other objects, features and advantages
of the present invention will be more apparent from the
following detailed description taken in conjunction with
the accompanying drawings, in which:
FIG. 1 is a perspective view of an automatic pump
according to an embodiment of the present invention;
FIG. 2 is a cross-sectional view taken along line A-A
of FIG. 1;
FIG. 3 is a wiring diagram of a stator coil
functioning as a switching unit for shifting the motor
speed of an automatic pump according to an embodiment of
the present invention;
FIG. 4 is a cross-sectional view of a pressure sensor
of an automatic pump according to an embodiment of the
present invention;
FIG. 5 is a flowchart for illustrating a drive control
method of an automatic pump according to an embodiment of
the present invention; and
FIG. 6 is a flowchart, connected to the flow chart of
FIG. 5, for further illustrating a stop control method of
an automatic pump according to an embodiment of the present
invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Hereinafter, a preferred embodiment of an automatic
pump and its operation control method according to the
present invention will be described with reference to the
accompanying drawings.
FIG. 1 is a perspective view of an automatic pump
according to an embodiment of the present invention, and
FIG. 2 is a cross-sectional view taken along line A-A of
FIG. 1.
As shown, in accordance with the present embodiment,
the automatic pump includes a housing 110 having a first
housing part 111 and a second housing part 115 which are
interconnected.
Formed respectively at opposite sides of the housing
110 are an inlet 111a for communicating with a fluid source
of, for example, water and an outlet 115a communicating
with an application site such as a faucet. More
specifically, the inlet 111a is formed on the first housing
part 111, and the outlet 115a is formed on the second
housing part 115.
Within the housing 110, impellers 120 are installed
near the inlet 111a and a motor 130 is mounted near the
outlet 115a. Rotated by the motor 130, the impellers 120
forcedly introduce a fluid through the inlet 111a into the
housing 110 and forcedly discharge the same through the
outlet 115a out of the housing 110.
According to the present embodiment, the automatic
pump has two impellers 120 installed with a dif f user 125
interposed between the impellers 120. The diffuser 125
guides the fluid discharged from one the impeller 120
located closer to the inlet 111a to the other the impeller
120 farther from the inlet 111a without loss of energy.
The impeller 120 may be installed either singularly or
plurally. In the latter case, a diffuser 125 is interposed
between the impellers 120. In addition, a check valve 117
for preventing the fluid within housing 110 from flowing
back toward the fluid source when the impeller 120 is
stopped is installed at the side of the inlet 111a.
In addition, the motor 130 according to the present
embodiment can shift through multiple stages of the
rotational speed, such as a low-speed, medium-speed, high-
speed. Accordingly, the speed of the impeller 120 also
changes through the multiple stages, such as the low-speed,
medium-speed, high-speed.
Motor 130 may be installed on the outside of the
housing 110.
At one side, the housing 110 has a control unit 140
mounted for controlling the motor 130 and other components,
and a pressure sensor 150 installed at a portion of the
housing 110 near the control unit 140.
The pressure sensor 150 is installed at a portion of
the housing 110 between the outlet 115a and the impeller
120 and detects the internal pressure of the housing 110
and transmits the detected pressure to the control unit
140. Then, the control unit 140 compares a signal
corresponding to the internal pressure of the housing 110
transmitted from the pressure sensor 150, with a preset
pressure. As a result of the comparison, when there is a
pressure change, the control unit 140 stops or drives motor
130 to one of the set multi-stage rotational speeds under a
set condition.
At this time, the control unit 140 may compare a
predetermined value ± the value of the signal corresponding
to the internal pressure of the housing 110 transmitted
from the pressure sensor 150, with the preset pressure. As
a result of the comparison, when there is a pressure
change, the control unit 140 may suspend or drive the motor
130 at one of the set multi-stage rotational speeds.
A switching unit for shifting the rotational speed of
motor 130' varies the electric forces of a stator coil 131
by varying the winding counts of the stator coil 131 of the
motor 130. Changes of the electric forces of the stator
coil 131 vary the electromagnetic force established between
the stator coil 131 and the rotor 137 of the motor 130 to
cause the rotational speed of the motor 130 to change.
The switching unit will be described with reference to
FIGs. 2 and 3. FIG. 3 is a wiring diagram of a stator coil
functioning as a switching unit for shifting the motor
speed of an automatic pump according to an embodiment of
the present invention.
As shown, the switching unit has a main coil 131a
constituting the stator coil 131, multiple sub-coils 131b
which constitutes the stator coil 131 and are
interconnected in series, and a selector switch 133.
One end of the main coil 131a is connected with one
end of the serially connected sub-coils 131b, and the other
end of the main coil 131a is connected to a portion of the
serially connected sub-coils 131b opposite to said one end
of the serially connected sub-coils 131b. Said portion of
the serially connected sub-coils 131b connected with the
other end of main coil 131a is selectively controlled. In
other words, one portion is selected from a plurality of
portions of the serially connected sub-coils 131b opposite
to said one end thereof and is connected via the selector
switch 133 to the other end of the main coil 131a.
Depending on the portion of the sub-coils 131b into
which the selector switch 133 comes into contact, the
stator coil 131 provides variable winding counts so as to
shift the rotational speed of the motor 130.
In addition, the main coil 131a is provided with a
shut-off switsh: 135 for interrupting the power supply when
the motor 130 is stopped. The selector switch 133 and the
shut-off switch 135 are controlled by the control unit 140.
The pressure sensor 150 will be described with
reference to FIGs. 1, 2 and 4. FIG. 4 is a cross-sectional
view of a pressure sensor of an automatic pump according to
an embodiment of the present invention.
As shown, the pressure sensor 150 has a body 151, a
deformable plate 153, and connecting terminals 155.
The body 151 is installed on the housing 110. The
body 151 is formed with a fluid path 151a having one end
which communicates with the interior of the housing 110
where the fluid is introduced and flows. Thus, the fluid
is introduced from the housing 110 into the fluid path
151a. At this time, the fluid path 151a and the housing
110 may internally communicate with each other through a
connecting pipe 157.
The deformable plate 153 is installed on the body 151
in the fluid path 151a to close the opposite end of the
fluid path 151a and comes into contact with the fluid
introduced in the fluid path 151a. Fluctuations in the
internal pressure of the housing 110 causes the fluid path
151a to correspondingly change its internal pressure, which
deforms the deformable plate 153 in varying degrees.
More specifically, the deformable plate 153 is formed
of a ceramic materials Thus, when deformation occurs in
the deformable plate 153, the resistance value of the
deformable plate 153 changes in proportion with the degree
of deformation.
The connecting terminals 155 have first end- connected
to the deformable plate 153 and second ends connected to
the control unit 140 to deliver the resistance value
corresponding to the degree of deformation of the
deformable plate 153 to the control unit 140.
With the impeller 120 discharging the fluid toward the
outlet 115a, if the internal pressure of the fluid path
151a ascends over a set pressure, which implies that the
amount of the fluid discharged toward the outlet 115a is
exceeded by the amount of the fluid supplied by the
impeller 120, the motor 130 is shifted down to a lower
rotational speed.
In addition, if the internal pressure of the fluid
path 151a descends under the set pressure, which implies
that the amount of the fluid discharged toward the outlet
115a is larger than the amount of the fluid supplied by the
impeller 120, the motor 130 is shifted up to a higher
rotational speed.
The pressure sensor 150 may be mounted on the housing
110 through one-touch fitting (not shown). The one-touch
tube fittings are usual connectors for connecting tubes
with each other or connecting a tube and a filter with each
other.
As shown in FIG. 2, the motor 130 has a frame 138
which is in contact with the fluid flowing into the
interior of the housing 110 and has a temperature sensor
160 installed to detect the temperature of the motor 130
and sends the detected temperature to the control unit 140.
The control unit 140 may stop or drive the motor 130 in
response to the signals received from the temperature
sensor 160.
To be more specific, there may be abnormal conditions
where the motor 130 in normal operation finds no fluid
being discharged to the outlet 115a or no fluid entering
the inlet 111a. Then, the motor 130 may be overheated and
damaged. To prevent this failure, when the temperature
detected by the temperature sensor 160 is greater than the
set temperature while the motor 130 is driven, the control
unit 140 stops the motor 130.
Cold weather may also damage the pump by freezing the
fluid within the housing 110.
As a preventive measure, when the temperature detected
by the temperature sensor 160 is lower than a first set
temperature in a state in which the motor 130 is in a
stationary state, the motor 130 is driven. In addition,
after the motor 130 is driven, when the temperature
detected by the temperature sensor 100 becomes higher than
a second set temperature, which is higher than the first
set temperature, the motor 130 is stopped again.
A driving control method for such a construction of
the automatic pump of the present embodiment will be
described.
First, the automatic pump driving control method
according to the present embodiment will be described with
reference to FIGs. 1, 2, and 5. FIG. 5 is a flow chart
for illustrating a drive control method of an automatic
pump according to an embodiment of the present invention.
It is assumed that the motor 130 is stationary in the
initial state.
As shown, in the initial state, the power is turned on
at step S10. With the power turned on, a standby state is
established to allow driving of the motor 130, and the
pressure sensor 150 senses the internal pressure of the
housing 110 at step S30.
In addition, at step S50 where the motor 130 is in the
standby state, the internal pressure of the housing 110 is
compared with the set pressure for driving the motor 130.
In such an event where no fluid is present in the
housing 110 as the automatic pump is installed for the
first time, there will be no changes in the internal
pressure of the housing 110 even with the faucet connected
and opened. Additionally, in such a case whero the housing
110 has a fluid already introduced but the faucet is at a
higher level than the housing 110, opening of the faucet
makes no change in the internal pressure of the housing
110.
Thus, at step S50, for driving the motor 130, the
internal pressure of the housing 110 is compared with the
set pressure. In this case, the set pressure is
appropriately provided depending on the characteristics of
the automatic pump.
Therefore, if the sensed internal pressure of the
housing 110 is higher than the set pressure, the pressure
sensing at step S30 is continued, and if the internal
pressure of the housing 110 becomes equal to or lower than
the set pressure, the motor 130 is driven at step S70.
Assuming the rotational speed of the motor 130
consists of, for example, three optional stepped rotations
of slow, medium and high-speeds, the motor 130 may be
driven at a proper rotational speed according to the
conditions applied.
Driving the motor 130 is performed by turning on the
cut-off switch 135 for shutting off standby electric power.
Then, the stator coil 131 of the motor 130 is powered to
drive the motor 130. Once the motor 130 is driven, the
impeller 120 is rotated, which forcedly draws and
discharges the fluid into and then out of the interior of
the housing 110.
Next, while the motor 130 is in a driving condition,
the internal pressure of the housing 110 is sensed at step
S90, and then it is determined whether the housing 110 has
fluctuations or not in the internal pressure (step S110).
The changes of the internal pressure of the housing
110 occur due to the differences between the amount of
fluid discharged through the outlet 115a and the amount of
fluid introduced into the housing 110 by the impeller 120.
In other words, the internal pressure of the housing
110 drops if the amount of fluid discharged through the
outlet 115a exceeds the amount of fluid drawn into the
housing 110, and the internal pressure of the housing 110
rises if the amount of fluid discharged through the outlet
115a falls under the amount of fluid drawn into the housing
110.
In addition, the amount of fluid discharged through
the outlet 115a changes by the degree of opening and
closing the faucet, and the amount of fluid drawn into the
housing 110 changes depending on the rotational speed of
the impeller 120. It is natural that the rotational speed
of the impeller 120 corresponds to the rotational speed of
the motor 130.
The degree of opening and closing the faucet may
represent how much a faucet opens if the outlet 115a has a
single faucet in communication, and may represent the
number of opened faucets if the outlet 115a has a plurality
of faucets communicating therewith.
Pressure fluctuation at step S110 implies that the
amount of fluid discharged through the outlet 115a and the
amount of fluid drawn into the housing 110 are not in
balance.
For example, with the motor 130 running at a low,
medium and high-speed rotations respectively, repeated
experiments are performed to find such an internal pressure
of the housing 110 that establishes an equilibrium between
the amount of fluid discharged through the outlet 115a and
the amount of fluid drawn into the housing 110 to set the
internal pressure respectively as a±a (kgf/cm2) for the low
speed, a±ß (kgf/cm2) for the medium speed, and a±? (kgf/cm2)
for the high speed. In addition, at the low running speed
of the motor 130, it is determined that there is no
pressure fluctuation if the internal pressure of the
housing 110 sensed at step S90 is within the range of a±a
(kgf/cm2), and if it is out of the range, it is determined
that a pressure fluctuation is present. In addition, at
the medium running speed of the motor 130, it is determined
that there is no pressure fluctuation if the internal
pressure of the housing 110 sensed at step S90 is within
the range of a±p (kgf/cm2) , and if it is out of the range, it
is determined that a pressure fluctuation is present. In
addition, at the high running speed of the motor 130, it is
determined that there is no pressure fluctuation if the
internal pressure of the housing 110 sensed at step S90 is
within the range of a±Y (kgf/cm2), and if it is out of the
range, it is determined that a pressure fluctuation is
present. In this way, the fluctuations in pressure are
determined.
Conversely, with the motor 130 running at a low,
medium and high-speed rotations respectively, repeated
experiments are performed to find such a reference pressure
of the housing 110 that establishes an equilibrium between
the amount of fluid discharged through the outlet 115a and
the amount of fluid drawn into the housing 110 to set the
reference pressure respectively as a kgf/cnf, b kgf/CTO2 and c
kgf/cnf. In addition, at the low running speed of the motor
130, it is determined that there is no pressure fluctuation
if the internal pressure of the housing 110 sensed at step
S90 is a±a (kgf/cm2), and if not, it is determined that a
pressure fluctuation is present. In addition, at the
medium running speed of the motor 130, it is determined
that there is no pressure fluctuation if the internal
pressure of the housing 110 sensed at step S90 is b±a
(kgf/Cm2) , and if not, it is determined that a pressure
fluctuation is present. In addition, at the high running
speed of the motor 130, it is determined that there is no
pressure fluctuation if the internal pressure of the
housing 110 sensed at step S90 is c±a (kgf/cm2) , and if not,
it is determined that a pressure fluctuation is present.
In this way, the fluctuations in pressure are determined.
In the present embodiment, the rotational speed of the
motor 130 is shifted appropriately depending on changes in
internal pressure of the housing 110.
According to the determination on the pressure
fluctuations at S110, there are three possible events with
the internal pressure of the housing 110 including no
fluctuations, pressure descending, and pressure ascending.
No changes in the internal pressure of the housing 110
means an approximate equilibrium maintained between the
amount of fluid drawn into the housing 110 and the amount
of fluid discharged through the outlet 115a, so the motor
130 is kept driven at the current speed and a continued
pressure sensing at step S90 is performed.
In addition, if the internal pressure of the housing
110 shows a descending change, which implies the amount of
fluid discharged through the outlet 115a exceeding the
amount of fluid drawn into the housing 110, then the
rotational speed of the motor 130 is increased at step S130
followed by the pressure sensing at step S90 again.
In addition, an ascending change of the internal
pressure of the housing 110 represents that the fluid
discharged through the outlet 115a is not present at all or
decreased. Therefore, if the internal pressure of the
housing 110 shows an ascending change, it is determined
whether the internal pressure of the housing 110 is a
minimum set speed (step S150).
If internal pressure of the housing 110 is not the
minimum set speed, which represents that the fluid
discharged through the outlet 115a is decreased, the motor
130 is decelerated (step S170) and the pressure is then
sensed (step S90).
The driving control method of the automatic pump of
the present embodiment constantly carries out the above
process to appropriately control the rotational speed of
the motor 130 depending on the amount of fluid discharged
to the application site. The rotational speed of the motor
130 is controlled by selectively switching the winding
counts of the stator coil 131 of the motor 130.
It is preferable that shifting the cpeed of the motor
130 in the driving state is done in step-by-step
acceleration or deceleration. This is to save the motor
130 from being damaged by preventing an abrupt change in
the rotational speed and reduce energy consumption.
If it is determined at step S150 that the rotational
speed of the motor 130 is the lowest speed, which
represents that no fluid is discharged out through the
outlet 115a, the motor 130 is stopped at step S190. A
method of stopping control of the motor 130 will be
described with reference to FIGs. 1, 2 and 6.
As shown, if the rotational speed of the motor 130 is
the lowest speed, changes in internal pressure of the
housing 110 is determined again (step S181). Step S181 is
to more accurately determine the condition to stop the
motor 130.
While the motor 130 is at the minimum rotational
speed, if there is a change in the internal pressure of the
housing 110, which represents a change occurring in the
amount of fluid discharged through the outlet 115a, then
the pressure sensing at step S90 is performed. The
reference value of changes in internal pressure at step
S181 at the minimum rotational speed of the motor 130 can
be appropriately set to a range over a proper pressure
considering the characteristics of the automatic pump.
Automatic pumps often encounter performance
degradation due to aging or inappropriately low voltage
supplies to Si-ow underperformance as compared to their
designed specifications.
For example, when the motor is driven at a minimum
speed with the faucet completely closed, it is assumed that
the internal pressure of the housing ascends to 1 kgf/cm2
normally. However, with the performance degradation of the
automatic pump considered due to aging or low voltage
supplies, the stopping control is carried out by setting
that the motor running at the minimum speed and accompanied
with the internal housing pressure of 0.8 Jcgf/cnf represents
a case of no pressure fluctuation. Therefore, in the
actual operation of the automatic pump, there exist such
cases where the internal pressure of the housing is 0.8-1
(kgf/cm2) despite the fact that the faucet has not been
closed.
According to the present embodiment of driving control
method of the automatic pump, when the motor 130 is running
at the minimum speed and it is determined that no
fluctuations are present in the internal pressure of the
housing 110, it is checked whether a complete closure of
the faucet causes the no fluctuation or whether this occurs
despite the fact that the faucet is not completely closed,
and then the motor 130 is stopped (step S190) .
No fluctuations in the internal pressure of the
housing 110 while the motor 130 is at the minimum
rotational speed imply no fluid discharged through the
outlet 115a. However, in the present embodiment of driving
control method of the automatic pump, in accordance with a
safe performance criterion set lower than the maximum
performance specification in consideration of factors
including the performance degradation of the automatic pump
considered, it is determined if there is no fluid
discharged through the outlet 115a. To this end, if there
is no fluctuations in the internal pressure (step S181),
the motor 130 is accelerated from the low speed to the
medium speed (step S183), the internal pressure of the
housing 110 is detected at the accelerated speed (step
S184), and the detected pressure is saved. Further, the
motor 130 accelerated to the medium speed is decelerated to
the low speed {step S185), the internal pressure of the
housing 110 is then detected at the decelerated speed (step
S186), and the detected pressure is then saved.
Then, at step S188, the internal pressure of the
housing 110 after the accelerating of the motor 130 at step
S183 is compared with the internal pressure of the housing
110 after the decelerating of the motor 130 at step S185 to
make the comparative determination.
At this time, if the pressure after the acceleration
and the pressure after the deceleration are not different
within a certain range, which represents no fluid
discharged through the outlet 115a, then the motor 130 is
stopped at step S190. After the motor 130 is stopped, the
standby power supply to the motor 130 is cut off by control
unit 140.
In addition, if the difference between the pressure
after the acceleration and the pressure after the
deceleration is beyond the certain range, which implies
that it has been determined that there is no fluctuations
in the internal pressure of the housing 110 based on the
aforementioned performance criterion set lower than the
peak performance specification in consideration of the
factors including the performance degradation of the
automatic pump, then the fluid is discharged toward the
outlet 115a. Thus, the pressure sensing at step S90 is
performed.
Since the internal pressure after accelerating the
motor 130 is higher than the internal pressure after
decelerating the motor 130, a certain level or more of the
pressure after the deceleration as compared to the pressure
after the acceleration is determined as equality of the two
pressures, and the pressure after the deceleration under
the certain level is determined as inequality of the two
pressures.
The driving control method of the automatic pump of
the present embodiment may include stopping the motor 130
by sensing the temperature of the motor 130.
Specifically, with the motor 130 in the driving
condition, if a sensed temperature of the motor 130 is
greater than a set temperature, the motor 130 is stopped.
This is to safeguard the motor 130 from running in an
abnormal condition despite no fluid being discharged or no
fluid being introduced and thereby prevent the motor 130
from being damaged.
In addition, when the motor 130 is in the quiescent
state, if the sensed temperature of the motor 130 is equal
to or lower than a first set temperature, the motor 130 is
driven, and if the motor 130 after driving reaches a second
set temperature or above, the motor 130 is stopped. This
is to prevent cold weather from breaking the pump with
frozen fluid.
The driving control method of the automatic pump of
the present embodiment is responsive to the internal
pressure of the housing 110 for making selective switching
connections with variable winding counts of the stator coil
131 of the motor 130, and thereby shifting the rotational
speed of the motor 130 to one of the multi-step rotational
speeds which have been set. Thus, this obviates the
inverters used in the conventional automatic pumps towards
a cost reduction and pump compactness.
Although a preferred embodiment of the present
invention has been described for illustrative purposes,
those skilled in the art will appreciate that various
modifications, additions and substitutions are possible,
without departing from the scope and spirit of the
invention as disclosed in the accompanying claims.
We Claim:
1. An automatic pump comprising:
a housing having an inlet formed at one side for a
fluid to enter and an outlet formed at another side for
discharging the fluid;
an impeller installed inside of the housing for
forcefully drawing the fluid through the inlet into the
housing and then forcefully discharging the fluid through
the outlet;
a motor capable of shifting the impeller through
multi-stage rotational speeds or into a stop;
a control unit for controlling the motor;
a pressure sensor for sensing an internal pressure of
the housing and transmitting the internal pressure to the
control unit; and
a switching unit responsive to a signal corresponding
to the internal pressure of the housing transmitted from
the pressure sensor to the control unit for selectively
changing winding counts of a stator coil of the motor and
thereby running the motor at one of set multi-stage
rotational speeds or stopping the motor.
2. The automatic pump as claimed in claim 1, wherein
the switching unit includes a main coil for forming the
stator coil of the motor, a plurality of sub-coils
interconnected in series for forming the stator coil of the
motor, and a selector switch,
wherein the main coil has one end connected to one end
of the sub-coils interconnected in series and another end
connected to a portion of the sub-coils, said portion of
the sub-coils being selected from a plurality of portions
of the sub-coils interconnected in series by the selector
switch, said portions of the sub-coils being opposite to
said one end of the sub-coils.
3. The automatic pump as claimed in claim 2, wherein
the main coil is provided with a shut-off switch for
blocking a standby electric power.
4. The automatic pump as claimed in claim 3, wherein
the pressure sensor comprises:
a body installed in the housing and formed with a
fluid path having one end communicating with the interior
of the housing;
a deformable plate installed on the body in the fluid
path for closing the other end of the fluid path and
deforming in response to a change in the internal pressure
of the housing; and
a connecting terminal installed on the body for
delivering the degree of deformation of the deformable
plate to the control unit.
5. The automatic pump as claimed in claim 4, wherein
the motor has a temperature sensor installed for sensing a
temperature of the motor and transmitting the temperature
to the control unit, and
the control unit is responsive to a signal received
from the temperature sensor for stopping or driving the
motor.
6. A method for controlling operation of an automatic
pump provided with a housing, an impeller installed inside
of the housing for forcefully drawing and discharging a
fluid into and out of the housing, a motor being capable of
shifting the impeller through multi-stage rotational speeds
or into a stop, and a pressure sensor for sensing an
internal pressure of the housing, the method comprising the
steps of:
comparing an internal pressure of the housing after
sensing the internal pressure with a set pressure;
continuously sensing the internal pressure of the
housing if the internal pressure is greater than the set
pressure, and driving the motor if the internal pressure is
equal to or less than the set pressure; and
sensing a change in the internal pressure of the
housing while the motor is running, and if the change is
sensed, accelerating or decelerating rotational speeds of
the motor by selectively switching winding counts of a
stator coil of the motor.
7. The method as claimed in claim 6, further
comprising:
accelerating the rotational speed of the motor if the
internal pressure of the housing is determined to be
descending while the motor is running;
determining whether the rotational speed of the motor
is a minimum speed or not if the internal pressure of the
housing is determined to be ascending while the motor is
running; and
decelerating the rotational speed of the motor when
the rotational speed is not the minimum speed and stopping
the motor when the rotational speed is the minimum speed.
8. The method as claimed in claim 7, further
comprising:
accelerating the rotational speed of the motor running
at the minimum speed and then sensing the internal pressure
of the housing;
decelerating an accelerated rotational speed of the
motor followed by sensing the internal pressure of the
housing; and
when internal pressures of the housing sensed after
the accelerating and the decelerating are equal to each
other, stopping the motor.
9. The method as claimed in claim 8, wherein the
stator coil is provided by a main coil and a plurality of
sub-coils interconnected in series,
the sub-coils interconnected in series has one end
connected to one end of the main coil and a portion
selectively connected to another end of the main coil, said
portion of the sub-coils being selected from a plurality of
portions of the sub-coils opposite to said one end of the
sub-coils, and
the rotational speed of the motor is shifted through a
selective switching connection between said another end of
the main coil and one portion among said portions of the
sub-coils.
10. The method as claimed in claim 9, wherein a
standby electric power supplied to the motor is blocked
when the motor is at rest.
11. The method as claimed in claim 9, further
comprising:
providing a temperature sensor for sensing a
temperature of the motor;
stopping the motor in running condition if the
temperature of the motor is sensed to be greater than a set
temperature;
driving the motor at rest if the temperature of the
motor is sensed to be equal to or less than a first set
temperature; and
stopping the motor after the driving if the
temperature of the motor is sensed to be ascending from the
first set temperature to a second set temperature.

ABSTRACT

An automatic pump and an operation control method for
the same are disclosed. The disclosed pump and method
operate in response to fluctuations in the internal
pressure of a housing forming a fluid path inside the
automatic pump for making selective switching connections
with variable winding counts of a stator coil of the pump
motor and thereby shifting the rotational speed of the
motor to an appropriate one of multi-stage rotational
speeds or stop the motor. Such a consequently obviated
inverter used in conventional automatic pumps offers cost
reduction and pump compactness.