Note: Descriptions are shown in the official language in which they were submitted.
CA 02591191 2008-01-25
Water Pump Especially for Ponds, Aquariums, Fountains or the Like
The invention concerns a water pump especially for ponds, aquariums, fountains
or the like. The pump is to be configured for a power range between
approximately 100 and 900 Watt. Such already relatively large pumps for use in
ponds have in practice asynchronous motors that require a high material
expenditure and are therefore relatively expensive. Also, their efficiency is
often
not satisfactory.
Small pumps are partially already driven by synchronous motors but must be
connected to complex control devices. In this case, the sealing of the
electrical
parts and connections is sometimes difficult.
The invention concerns therefore the problem of providing a water pump whose
efficiency in comparison to conventional pumps of the same power class is
increased and that can be manufactured less expensively and can be operated
comfortably.
According to an aspect of the present invention there is provided a water pump
having a housing, the water pump comprising a pump housing part, provided
with an intake opening and an exit opening and in which an impeller with a
shaft
is rotatably arranged, and further comprising a motor housing part, in which
an
electric motor with a stator with several coils arranged on a plurality stator
poles
and a rotor rotating therein is received, wherein the motor is an
electronically
communicated motor; the stator is comprised of a pack of unitary laminations,
respectively; control electronics for the motor are arranged in the motor
housing
part; and the stator with the coils and the control electronics is water-
tightly
encapsulated.
By using an electronically commuted motor, the efficiency of the pump can be
significantly increased within a power range of approximately 100 to 900 Watt
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wherein the manufacture of the pump motor with a stator comprised of a pack of
unitary sheet metal laminations can be effected in a material-saving and
cost-reducing way. By incorporating control electronics for the motor control
directly into the pump and arranging them within the motor housing part and
encapsulating them together with the stator and the coils in a water-tight
way, the
risk of repairs of the pump can be minimized because all essential electric
and
electronic components are combined and perfectly protected from water by
means of encapsulation.
With regard to efficiency and cost, the pump can be optimized when a two-pole
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permanent magnet is used as a rotor and a stator with six stator poles and
therefore six coils received thereon is used. The two-pole permanent magnet
rotor can be substantially comprised of a unitary two-pole magnet ring that is
diametrically magnetized. It can be produced in a simple and thus inexpensive
way.
The stator is comprised according to the invention of a plurality of stacked
stator
sheet metal laminations that are stamped as unitary parts. This reduces the
assembly costs in comparison to multi-part stators in which the stator poles
are
individually inserted.
In one aspect, the invention provides a water pump, having a body which
comprises a pump-body portion having an intake opening and an outlet opening,
in which pump-body portion an impeller having a shaft is rotatably arranged,
and
which comprises a motor-housing portion in which is held an electronically
commutated electric motor, which electronically commutated electric motor has
a
stator having a plurality of windings arranged on stator poles and has a rotor
rotating in the said windings, the stator comprising a set of laminations
which are
each in one piece, and the stator and the rotor, which takes the form of a two-
pole permanent magnet, being separated from one another by a gap-creating
tube, wherein the stator poles, which are each formed on the inside, to be
substantially free of any widening, have windings which are slid on from the
interior of the stator, these components, together with an electronic control
system for the motor, are arranged in the motor-housing portion, and the
stator,
together with the windings and the electronic control system, is encapsulated
in
the said motor-housing portion to be sealed against water, in such a way that
the
interior of the entire motor-housing portion is provided with an encapsulating
material which fills all the open spaces.
Further advantages and details result from the dependent claims and an
embodiment illustrated in the drawings which will be described in the
following. It
is shown in:
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Fig. 1 a perspective external view of a pump according to the invention;
Fig. 2 a longitudinal section of the pump of Fig. 1;
Fig. 3 a cross-section of the stator of the pump motor in the plane III of
Fig. 2
when mounting the coils;
Fig. 4 the object of Fig. 3 with completely mounted coils; and
Fig-.
u a perspective illustration of the object of Fig. 4 without windings on the
coils.
The pump illustrated in Fig. 1 has a housing 1 that is substantially comprised
of a
pump housing part 2 and a motor housing part 3. The pump housing part 2 has
an intake opening 4 and an exit opening 5 for water to be pumped. The two
housing parts 2, 3 are connected in a simple way with one another, for
example,
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CA 02591191 2008-01-25
as illustrated, by a bayonet closure 6 with additional screw connection 7.
The interior of the pump is illustrated in section in Fig. 2. Between the
intake
opening 4 and the exit opening 5, an impeller 8 is arranged in the pump
housing
part 2 on the shaft 9; the shaft is preferably made of ceramic material. The
impeller and the shaft 9 are driven in rotation by means of an electronically
commutated motor (EC motor) that is arranged in the motor housing 3. The shaft
9 extends from the pump hdusing part 2 into the motor housing part 3 wherein
the motor is shielded from the impeller 8 mechanically by a bearing bracket
10.
The motor is comprised substantially of a stationary stator lamination pack 12
on
which coils 13 that are also stationary gre provided as well as a rotor 14
which in
the illustrated embodiment is advantageously formed as a two-pole permanent
magnet. Between rotor 14 and shaft 9 there is a solid, closed iron ring 15
that is
fixedly connected to both rotor and shaft and increases the magnetic flux of
the
motor significantly.
On the back of the motor a circuit board 16 is arranged that comprises the
entire
control electronics. Finally, the motor has a ground 17 at the stator 12 and a
ground plate 18 at the back of the motor housing part 3.
For sealing the housing part 2 through which the water flows relative to the
housing part 3 that receives the electric components, the rotor 14 with all
movable parts and the stator 12 with all parts through which current flows are
separated from one another by a can 19 surrounding the rotor 14. Toward the
pump housing part 2 the can 19 widens into a large color-shaped flange 19' for
completely separating the pump housing part 2 and the motor housing part 3.
The interior of the entire motor housing part 3 is encapsulated so that all
free
spaces are filled, for example, with a synthetic resin. The encapsulating
compound 20 thus embeds also the entire control electronics 16 so that the
latter
are not only protected from moisture but also protected mechanically against
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CA 02591191 2008-01-25
vibrations. At the same time, the encapsulating compound 20 also supports the
can 19 so that it can be manufactured inexpensively of plastic material that
is not
reinforced externally.
The control electronics 16 may comprise a signal evaluation unit, not
illustrated in
detail, by which the received signals are used for speed regulation of the
pump
motor. The control signals can be modulated directly by the mains voltage that
is
supplied to the motor. In this way, it is not necessary to provide a complex
phase
cutting control for speed regulation of the pump as it has been used up to now
for
conventional motors. The operation for speed regulation can be realized in
particular by means of an intermediate switch that can be remote-controlled
and
is 'arranged between the mains supply and the current supply cable for the
pump.
This intermediate switch comprises a receiving module that receives the
signals
emitted by the remote control for changing the motor speed. In the
intermediate
switch element these signals are modulated onto the mains current and in this
way transmitted to the control electronics of the pump. The intermediate
switch
thus takes on only the task of signal transfer so that no power electronics
are
required.
In the illustrated embodiment the stator 12 and the correlated coils 13 are
preferably configured such that the coils 13 when being mounted can be slipped
onto stator poles 22 of the stator 12 from the interior. This and the
configuration
of the stator 12 with the coils 13 is illustrated in more detail in Figs. 3
through 5.
By being able to simply slip on the coil bodies 13, there is no need for using
expensive threading machines for winding the coils as is needed in regard to
other unitary laminations with pole shoes formed on the inner side. The stator
poles 22 of the stator 12 of the pump according to the invention are therefore
to
be configured at their inner side substantially without widened portions so
that
slipping on the coils is possible.
The geometric conditions that enable that the coils 13 can be slipped onto the
stator poles 22 are illustrated substantially in Fig. 3. For this purpose, the
length a
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of the coils 13 must be smaller than the minimal spacing A1 of two opposed
inner
. pole sides as well as smaller than the length A2 of the individual stator
poles 22.
Moreover, the width b of the coils 13 must be less than the minimal spacing B1
of
an inner pole edge 42 to the inner pole edge 42 of the second to next stator
pole
22, respectively; i.e., between the two stator poles in question precisely one
additional stator pole 22 is located. The width b of the coils 13 must also be
smaller than the minimal spacing B2 of two outer edges of the coils in the
mounted state between which again a further coil 13 or a further stator pole
22 is
located. Finally, the width c of the stator poles 22 is to be selected smaller
than
the inner width C of the coils 13.
The pump according to the invention is optimized in that, on the one hand, its
dimensions are to be kept as small as possible and, on the other hand, its
efficiency should be as high as possible; this should be achieved while the
assembly should be improved. For increasing the efficiency at predetermined
maximum dimensions, the geometric conditions must be selected such that the
coils 13 on the one hand can still be slipped on and, on the other hand, as
many
windings as possible can be arranged on the coils 13. For this purpose, an arc
length BL of the stator poles 22 must be defined. If in the interior of the
stator 12
in which the rotor 14 rotates an imaginary circle of maximum size were
positioned that contacts the inner sides 32 of the stator poles precisely, the
sum
of the arc length BL of all poles 22 could be precisely half of the
circumference of
the defined circle. For the benefit of the copper quantity to be arranged in
the coil
windings and for preventing flux scattering, the arc length BL of each stator
pole
22 is however reduced preferably by approximately 11 percent to 12 percent
relative to the above defined initial length.
Advantageously, an angle V can be defined between two straight lines 50 that
extend from the stator center and touch the inner pole edges 42 of the stator
poles; the angle is between 0.88 times 360 degrees divided by the number n of
the stator poles 22 and approximately 0.89 times 360 degrees divided by the
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CA 02591191 2007-06-07
number n of the stator poles 22. For conditions optimized in this way, the
coils
13 are inserted into the opening ds illustrated in Fig. 3 and are then slipped
onto
the stator poles 22 until they meet the stop.
The stator 12 of the illustrated embodiment has precisely six stator poles 22.
Depending on the requirements, it is also possible to provide the motor with a
stator 12 having three, nine, twelve, fifteen stator poles. However, for more
than
six poles 22 the spacings for the windings of the coils 13 are very narrow so
that
the mounting expenditure and cost expenditure will be increased. However, a
motor that has only three poles has a reduced efficiency.
The pump according to the invention is characterized by high mounting comfort,
minimal manufacturing costs, a high efficiency, and an optimized operating
comfort. It is not prone to failure and therefore can be used without
requiring
much maintenance. Because of its high efficiency and the reduced material
expenditure, the energy demand of such a pump in regard to manufacture as
well as operation is minimized.
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