U.S. patent application number 10/565420 was filed with the patent office on 2006-11-02 for electric fluid pump.
Invention is credited to Dean Bajlon, Malcolm J. Clough, Michael C. Lacroix.
Application Number | 20060245956 10/565420 |
Document ID | / |
Family ID | 34102904 |
Filed Date | 2006-11-02 |
United States Patent
Application |
20060245956 |
Kind Code |
A1 |
Lacroix; Michael C. ; et
al. |
November 2, 2006 |
Electric fluid pump
Abstract
An electric fluid pump includes an upper housing having a fluid
inlet and outlet. An impeller is seated within the upper housing
for pumping fluid between the inlet and the outlet. The impeller
includes at least one magnet secured thereto. A lower housing mates
with the upper housing. The lower housing has an upper wall for
closing the upper housing and a shaft extending from the upper wall
for rotatably supporting the impeller. A stator is seated within
the lower housing and spaced from the impeller by the upper wall.
The stator includes a plurality of pillars supporting a winding of
coils for producing a magnetic field to energize the magnet and
rotate the impeller, and a plurality of top plates covering each of
the coils and spaced apart by a predetermined gap for maintaining
the magnetic field between the stator and the impeller. An end cap
closes the stator within the lower housing.
Inventors: |
Lacroix; Michael C.;
(Hamilton, CA) ; Bajlon; Dean; (Toronto, CA)
; Clough; Malcolm J.; (Toronto, CA) |
Correspondence
Address: |
CLARK HILL, P.C.
500 WOODWARD AVENUE, SUITE 3500
DETROIT
MI
48226
US
|
Family ID: |
34102904 |
Appl. No.: |
10/565420 |
Filed: |
July 26, 2004 |
PCT Filed: |
July 26, 2004 |
PCT NO: |
PCT/CA04/01407 |
371 Date: |
January 24, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60489606 |
Jul 24, 2003 |
|
|
|
Current U.S.
Class: |
417/423.1 |
Current CPC
Class: |
H02K 5/1282 20130101;
F04D 13/064 20130101; H02K 7/14 20130101; F04D 13/0666
20130101 |
Class at
Publication: |
417/423.1 |
International
Class: |
F04B 17/00 20060101
F04B017/00 |
Claims
1. An electric fluid pump comprising: an upper housing having a
fluid inlet and outlet; an impeller seated within said upper
housing for pumping fluid between said inlet and said outlet, said
impeller including at least one magnet secured thereto; a lower
housing for mating with said upper housing, said lower housing
having an upper wall for closing said upper housing and a shaft
extending from said upper wall for rotatably supporting said
impeller; a stator seated within said lower housing and spaced from
said impeller by said upper wall, said stator including a plurality
of pillars supporting a winding of coils for producing a magnetic
field to energize said magnet and rotate said impeller, and a
plurality of top plates covering each of said coils and spaced
apart by a predetermined gap for maintaining the magnetic field
between said stator and said impeller; and an end cap for closing
said stator within said lower housing.
2. An electric fluid pump as set forth in claim 2 wherein each of
said top plates of said stator includes bevelled ends for defining
tapered gaps between adjacent top plates to control said magnetic
field between said stator and said impeller.
3. An electric fluid pump as set forth in claim 3 wherein said
stator includes a toroid plate for supporting each of said
pillars.
4. An electric fluid pump as set forth in claim 3 further including
an electronic control assembly seated between said stator and said
end cap for selectively energizing each of said coils to produce a
magnetic field and control said rotation of said impeller.
5. An electric fluid pump as set forth in claim 4 wherein said
impeller includes a plurality of vanes for directing fluid within
said upper housing between said inlet and said outlet.
6. An electric fluid pump as set forth in claim 5 wherein said
lower housing is molded of polymeric material with said upper wall
formed integrally therewith for dissipating heat generated from
said stator.
7. An electric fluid pump as set forth in claim 6 further including
a sealing gasket seated between said upper housing and said lower
housing for sealing fluid therebetween.
8. An electric fluid pump as set forth in claim 7 further including
an o-ring seated between said stator and said end cap for sealing
said lower housing.
9. An electric fluid pump as set forth in claim 1 wherein said end
cap includes a hollow channel extending therethrough.
10. An electric fluid pump as set forth in claim 9 further
including a first flow tube extending between said end cap and said
upper housing in fluid communication with said inlet for passing
fluid through said end cap.
11. An electric fluid pump as set forth in claim 10 further
including a second flow tube extending between said end cap and
said upper housing and in fluid communication with said outlet for
receiving fluid flowing from said end cap.
12. An electric fluid pump as set forth in claim 8 wherein said
impeller is formed from injection molded plastic and integrally
formed with said magnet encapsulated within said impeller facing
said upper wall of said lower housing.
Description
FIELD OF THE INVENTION
[0001] The invention relates to a pump driven by a brushless direct
current (DC) motor. More particularly, the invention relates to any
fluid pump system using DC brushless motor technology to drive
coolant (for water pumps) or oil (for engine and transmission
pumps).
BACKGROUND OF THE INVENTION
[0002] The most common pump accessory arrangement found in
automobiles utilizes the engine rotation to drive a shaft via a
belt connection between a driving pulley (connected to the
crankshaft) and a driven pulley. These belts and pulleys are
cumbersome, bulky, noisy, and transfer power (torque)
inefficiently. Another disadvantage is that these pumps have their
output dictated by the rotational speed of the engine. Certain
accessories that are coupled to the engine, such as the coolant and
oil pumps, must be over-sized, because the pump output must deliver
a minimum flow amount of fluid at low engine speeds. At higher
engine speeds, such as those experienced under normal highway
driving conditions, the flow amount becomes excessive because it is
directly proportional to engine speed, which is up to an order of
magnitude greater. This leads to poor efficiencies and increased
power losses due to the requirement for a bypass.
[0003] Therefore, it is desirable to have the pump output to be
independent of the engine speed, and to be adjustable to match the
operating conditions. This object can be fulfilled by utilizing an
electrically driven pump for supplying coolant or oil to an
internal combustion engine.
[0004] An early example is disclosed in British patent GB 1482411,
which discloses a coolant pump driven by a brush-type electric
motor. Later examples of brush type electric motors include U.S.
Pat. No. 5,540,567.
[0005] In general, for any DC motor to operate, the electric
current to the motor coils must be continually switched relative to
the field magnets. For commutation to occur, power is applied to
the motor's windings to produce torque. In a brush-type motor,
carbon brushes contact a slotted commutator cylinder, which has
each motor coil connected to a corresponding bar of the commutator.
Brushless motors differ in that the windings are located on the
stator and do not move, while the magnets are on the rotor. The
position of the rotor is sensed and continually fed back to an
electronic commutation control to provide for appropriate
switching. Advantages of brushless motors include improved
efficiencies, reduced noise, weight and size, and improved
durability.
[0006] Therefore, the preferred method of driving a fluid pump
employs DC brushless electric motors. Known prior art examples
include U.S. Pat. Nos. 5,158,440, 5,269,663 and 6,213,734, all of
which utilize a basic design wherein the magnets are mounted
radially around the impeller, with the stator (coils and core) also
located around the impeller.
[0007] A more compact brushless motor design, sometimes referred to
as a "flat style", utilizes an axial arrangement wherein the magnet
with multiple poles is mounted axially to the impeller, with the
stator being mounted axially to the impeller (facing the magnet
face with the poles). A recent example of this design is U.S. Pat.
No. 6,034,465, which utilizes a flat style magnet with multiple
poles on its face, a "back-iron" component to enhance the magnetic
field, and an enclosed electronic control for the motor.
[0008] This brushless design type, and other known variations in
the prior art, employ an aluminum plate to prevent the fluid in the
pump from reaching the stator, as well as separating the stator
from the rotor. Another function of the aluminum plate is to
transmit heat generated in the stator to the liquid coolant flowing
in the pump chamber. However, while aluminum has excellent heat
transfer characteristics, it also decreases motor efficiency. Eddy
currents generated in the aluminum by the spinning magnets in the
rotor create reverse magnetic fields which retard the rotation of
the rotor. This results in a loss of efficiency when converting
electrical energy to mechanical power.
[0009] Current prior art designs also utilize a stator that
comprises a core with a plurality of coils. These coils are located
around a post on the core. These posts are limited in size
resulting in a "cogging" effect in which the rotor wants to rest in
specific positions. This limited size sets restrictions regarding
the strength of the permanent magnets and thus limits the maximum
output power of the motor for any given motor size.
[0010] In light of the deficiencies indicated above, there
continues to be a need for pumps driven by brushless electric
motors, in particular, for pumping liquids such as coolant or oil
in vehicular applications.
SUMMARY OF THE INVENTION
[0011] The present invention relates to a pump or other accessory
whose output is adjustable and is driven independently of the
engine. An electric motor replaces the traditional belt and pulley
combination.
[0012] In a broad aspect, the invention relates to the integration
of a brushless DC motor wherein the mechanism to be driven is
integral with the motor and not driven through some sort of
mechanical coupling. The brushless motor is the actual driving
mechanism.
[0013] One of the general objects of the invention is to apply
brushless DC motors for pump systems for use in automobiles,
although the invention has utility in more general use. More
particularly, the invention relates to any fluid pump system using
DC brushless motor technology to drive coolant (for water pumps) or
oil (for engine and transmission pumps).
[0014] In a particular embodiment, the fluid pump comprises a
housing that includes a plurality of components fastened together,
an impeller, a rotor, and a stator with associated windings. The
impeller is rotatably mounted within the pump housing for rotation
about a rotary axis, in order to force fluid to flow through an
outlet of the housing. The rotor is permanently coupled to and
rotatable with the impeller, and includes a permanent magnet and
"backing iron". The stator is spaced apart from and generally faces
the permanent magnetic poles on the rotor. A plurality of magnetic
windings is positioned on the stator and serves to effect rotation
of the rotor and impeller upon energization.
[0015] In an alternate embodiment, the motor housing is a matrix of
a polymer and filling compound that gives the polymer good thermal
characteristics to allow heat generated in the stator to be
transferred through the housing to the coolant or fluid being
pumped.
[0016] One embodiment implements a stator design in which the core
has expanded top surfaces with tapered or bevelled ends. The
tapered ends provide a method to increase the "effective" gap
between the stator poles. This allows the stator phases to be
closer together resulting in a dramatically reduced physical gap
and greatly reducing the "cogging" effect. This feature allows
stronger magnets to be used resulting in greater output power for a
given size.
[0017] In yet another alternate embodiment, the positional feedback
mechanism is removed and the motor is operated in "open loop"
control mode. This mode is called "open loop" because feedback is
not used to control the rotation of the rotor. In this mode, the
control circuit turns the stator coils "on" and "off" in a manner
that creates a rotating electromagnetic field. This rotating field
interacts with the field of the permanent magnet on the rotor,
forcing the permanent magnet to rotate and follow the
electromagnetic field. Regardless of the position of the rotor, the
electromagnetic field will continue to rotate at the predetermined
rate.
[0018] In an alternate embodiment, the rotor and impeller form a
unitary body, in order to reduce the number of parts.
[0019] All embodiments eliminate the need for the conventional
aluminum plate, resulting in the minimization of drag created by
eddy currents generated by the rotating magnets. This results in
greater efficiency in converting electrical energy into mechanical
power. Furthermore, the removal of the aluminum plate allows the
motor housing to be molded as a single unit.
[0020] In a further alternate embodiment, the housing is molded in
such a way as to create channels for fluid to pass from the high
pressure side of the pump to the low pressure side. These channels
would allow the fluid to traverse the back of the housing to allow
heat generated by the control electronics to be transferred through
the back of the housing to the fluid and thus cool the control
electronics.
[0021] Further aspects of the invention are hereinafter described
in the following description and drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] In drawings which illustrate the embodiments of the
invention,
[0023] FIG. 1 is a cut-away view of the pump in accordance with the
preferred embodiment of the present invention;
[0024] FIG. 2 is an exploded perspective view of the pump shown in
FIG. 1;
[0025] FIG. 3 is a top perspective view of the upper housing of the
pump;
[0026] FIG. 4 is a bottom perspective view of the upper housing of
the pump;
[0027] FIG. 5 is a bottom perspective view of the lower housing of
the pump;
[0028] FIG. 6 is a top perspective view of the lower housing of the
pump;
[0029] FIG. 7 is a top perspective view of the impeller and magnet
assembly;
[0030] FIG. 8 is a bottom perspective view of the impeller and
magnet assembly;
[0031] FIG. 9 is a top view of the core with the top plates
removed;
[0032] FIG. 10 is a top view of the top plates of the core;
[0033] FIG. 11 is a cross-section view taken along line 11-11 of
FIG. 10;
[0034] FIG. 12 is an electrical schematic of the motor and control
circuit;
[0035] FIG. 13 is a top view of a pump assembly according to an
alternative embodiment;
[0036] FIG. 14 is a bottom view of the pump assembly of FIG.
13;
[0037] FIG. 15 is a cross-sectional view taken along line 15-15 of
FIG. 13;
[0038] FIG. 16 is a sectional view of the impeller and magnet
assembly of FIG. 15; and
[0039] FIG. 17 is a top view of the circuit board of the pump of
FIG. 15.
DETAILED DESCRIPTION OF THE INVENTION
[0040] Referring to FIGS. 1-8, a pump assembly 100 is shown
including an upper housing 12 with a fluid inlet 10 and outlet 11
and a lower housing 15. The upper 12 and lower 15 housing are
preferably molded of polymeric material to provide good thermal
characteristics and allow heat to dissipate into fluid within the
housing. An impeller 20, preferably formed from injection-molded
plastic, is seated within the interior volume of the upper housing
12. The impeller 20 is integrally formed with a permanent magnet
and "back iron" assembly 8, which also serves as the rotor of a DC
motor, to be described shortly. In one embodiment, the plastic
impeller 20 encapsulates the magnet and "back iron" assembly 8 due
to an overmolding or insert molding operation. Both the impeller 20
and rotor 8 include a central opening to accommodate both a bushing
13 and low friction shaft or spindle 14. The impeller 20 rotates
around the shaft 14 that is fixed to the lower housing 15. The
impeller/magnet assembly 20, 8 is separated from the core by an
intervening upper wall 45 of non-metallic material which is formed
as part of the lower housing 15 and which may or may not have high
thermal conductivity characteristics.
[0041] Optionally, the impeller bore for the shaft 14 is coated
with a mono-crystalline material with extremely low friction
characteristics. In this case, a bushing in the impeller is not
required and is removed.
[0042] The upper housing 12 has non-threaded inserts 51-55 that
align with corresponding threaded inserts 61-65 in the lower
housing 15 and which accept bolts 71-75 during assembly and
attachment of the upper and lower housings 12, 15. A simple gasket
26 serves to seal the upper housing 12 from the lower motor housing
15, which includes a DC motor of the brushless type, with a stator
or core 7 surrounded by windings 820, as discussed below.
[0043] As illustrated in FIGS. 1, 2, and 9-11, the pump 100 has a
core 7 comprising a toroid plate 80, three pillars 810 and three
top plates 310. Around each pillar 810, a coil of copper or other
suitable wire 820 is wound for the purpose of generating a magnetic
field, whose polarity is dependant upon the direct of the flow of
current within the coil. Assembled into, and thus part of the pump
100, is an electronic control assembly 300 including a printed
circuit board 70 which switches the coils 820 on and off
independently. The core 7, coils 820 and electronics 300 are held
in place by an end plate 28 that mates to the back of the lower
housing 15. Alternatively, the core plates 310 may be embedded into
the lower housing 15. This feature allows the gap between the
magnet 8 and the core plates 310 to be precisely maintained from
part to part.
[0044] Between the printed circuit board 70 and the end plate 28 is
a sealing o-ring 27 that provides the necessary tension to ensure
the coils 820, core 7 and electronics 300 do not move after
assembly. The end plate 28 can be made of any suitable material
such as aluminum, steel, copper and polymers, either thermally
conductive or not. The core 7 is made of a soft magnetic material
such as HyMu 80 or other suitable material. The top plates 310 of
the core 7 are designed and arranged to provide a maximum surface
area ratio between the face of the magnet 8 and the face of the
core 7. This surface area ratio is a key feature in increasing
efficiency. As shown in FIG. 10 the arrangement of the plates 310
is such that there is a small gap 320 between them, which is
necessary to reduce or eliminate motor "cogging". As the gap 320
becomes smaller, the degree of cogging decreases.
[0045] In one embodiment as shown in FIG. 11, the core plates 310
have bevelled ends 330 on the face of the plate away from the
magnet 8 and the edge of the plate adjacent to the plate beside it
defining tapered gaps 320 between adjacent top plates 310. This
bevelled end 330 increases the "effective gap" for better
efficiency in the magnetic circuit while allowing the physical gap
320 to be as small as possible for better efficiency due to reduced
cogging.
[0046] The DC motor includes components (not shown) such as Hall
Effect sensors. The sensors determine the angular position of the
magnetic field of the rotor magnet 8. Signals from the sensors are
passed through to the circuit board 70, which is part of the
electronic assembly 300 located in the distal end of the pump
housing. Other methods in which the sensors are not required to
control the rotation of the motor, can also be used with this motor
type with the sensorless "back electromotive force" (back EMF) type
being the preferred embodiment. The control circuit, illustrated
schematically in FIG. 12, also includes a driving transistor (not
shown) for controlling a driving current to be supplied to the
stator windings 820, so that the rotor magnet 8 may be rotated
under the control of the circuit.
[0047] In a slight variation of the above arrangement, the impeller
and rotor are present as a single member. In this case, a suitable
construction material would be plasto-ferrite. In this structure, a
thermoplastic such as polypropylene serves as the matrix, with
strontium ferrite or other suitable magnetic material embedded
within. The advantages provided by a single impeller-rotor assembly
include easier manufacturing and assembly, and fewer parts.
[0048] In operation, the power source is connected to the terminals
1, 2 of the electronic assembly 300 (FIG. 12). Upon application of
an appropriate voltage, the electronic circuit of the electronic
assembly 300 energizes the windings 820 in a predetermined pattern.
This switching pattern causes the windings to generate a rotating
magnetic field within the stator core 7. This rotating magnetic
field interacts with the magnetic field generated by the permanent
rotor magnet 8, causing the rotor 8 to rotate.
[0049] Since the rotor 8 is either embedded within the impeller 20,
or is the same part, the impeller 20 rotates in direct response to
the rotation of the rotor 8 with no coupling or power transfer
assembly required. The number of components and physical size of
the pump are thus reduced. The impeller 20 includes curved vanes
400, as shown in FIGS. 2, 7 and 8, that impart centrifugal energy
to the fluid passing through inlet 10, urging the fluid to flow
under pressure through outlet 11. When the power source is removed
the magnetic field in the core 7 collapses and the impeller 20
stops rotating.
[0050] In an alternative embodiment shown in FIGS. 13-17, the pump
200 includes a first flow tube 30 on the low pressure side of the
pump 200 extending between the upper housing 12 in fluid
communication with the inlet 10 and hollow channelled end cap 40
which closes the end of the lower housing 15. A second flow tube 50
on the high pressure side of the pump 200 extends between the upper
housing 12 in fluid communication with the outlet 11 and the hollow
end cap 40. This allows a small amount of coolant to flow through
the end plate 40 and provide a constant temperature heat sink that
can be used to withdraw heat from heat generating components within
the pump. The pressure differential between the inlet 10 and outlet
11 of the pump 200 causes coolant to flow through the coolant tubes
(30 and 50). The flow direction is as indicated by the arrows 500
and 510 in FIG. 15. The material used for the end plate 40 can be
any suitable thermally conductive material, such as aluminum,
copper, etc.
[0051] Although the invention has been described in detail with
reference to a specific preferred embodiment, variations and
modifications exist within the scope and spirit of the invention as
described and defined in the following claims.
* * * * *