U.S. patent application number 10/679921 was filed with the patent office on 2004-06-03 for pump.
Invention is credited to Black, David Thomas, Williams, David John.
Application Number | 20040105767 10/679921 |
Document ID | / |
Family ID | 9945627 |
Filed Date | 2004-06-03 |
United States Patent
Application |
20040105767 |
Kind Code |
A1 |
Black, David Thomas ; et
al. |
June 3, 2004 |
Pump
Abstract
A pump including a driving part and a pumping part, the pumping
part including a plurality of generally parallel planar elements
all mounted for rotation about a first axis, wherein the driving
part is coupled to the pumping part by means of a magnetic coupling
device such that rotation of the driving part may cause rotation of
the pumping part about the first axis.
Inventors: |
Black, David Thomas;
(Birmingham, GB) ; Williams, David John; (Warwick,
GB) |
Correspondence
Address: |
DYKEMA GOSSETT PLLC
39577 WOODWARD AVENUE
SUITE 300
BLOOMFIELD HILLS
MI
48304-5086
US
|
Family ID: |
9945627 |
Appl. No.: |
10/679921 |
Filed: |
October 6, 2003 |
Current U.S.
Class: |
417/420 |
Current CPC
Class: |
F01D 1/36 20130101; F04D
5/001 20130101; F04D 13/024 20130101 |
Class at
Publication: |
417/420 |
International
Class: |
F04B 017/00 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 10, 2002 |
GB |
0223516.6 |
Claims
1. A pump including a driving part and a pumping part, the pumping
part including a plurality of generally parallel planar elements
all mounted for rotation about a first axis, wherein the driving
part is coupled to the pumping part by means of a magnetic coupling
device such that rotation of the driving part causes rotation of
the pumping part about the first axis.
2. A pump according to claim 1 wherein the magnetic coupling
includes a first coupling part which is connected to the driving
part for rotation with the driving part, and a second coupling part
which is connected to the pumping part for rotation with the
pumping part, one of the first or second parts including a magnet,
and the other of the first or second parts including an
electrically conductive part.
3. A pump according to claim 2 wherein the first coupling part and
second coupling part are mounted for rotation about the first
axis.
4. A pump according to claim 2 wherein the magnet is a permanent
magnet.
5. A pump according to claim 2 wherein the magnet has a side wall
which encloses a generally cylindrical space, and the electrically
conductive part is generally cylindrical and is located at least
partly within the wall of the magnet.
6. A pump according to claim 5 wherein the electrically conductive
part of the magnetic coupling includes a plurality of elongate
copper elements arranged in a generally circular array around an
axis of rotation of the first part of the magnetic coupling, a
longitudinal axis of each copper element being generally parallel
to the axis of rotation.
7. A pump according to claim 6 wherein the electrically conductive
part includes two generally annular copper plates which are mounted
on either side of the copper elements in contact with end portions
of all the copper elements.
8. A pump according to claim 6 wherein the electrically conductive
part includes a soft iron core.
9. A pump according to claim 2 wherein the second coupling part is,
in use, immersed in the liquid to be pumped, and a sealing part is
provided between the first and second coupling parts, the sealing
part substantially preventing pumped liquid from contacting the
first coupling part and the motor.
10. A pump according to claim 1 wherein the pumping part includes a
plurality of generally parallel, co-axial discs.
11. An engine including a lubricant pump, the pump including a
driving part and a pumping part, the pumping part including a
plurality of generally parallel planar elements all mounted for
rotation about a first axis, wherein the driving part is coupled to
the pumping part by means of a magnetic coupling device such that
rotation of the driving part causes rotation of the pumping part
about the first axis.
12. A lubrication system for an engine including two lubricant
pumps, one of which is a pump including a driving part and a
pumping part, the pumping part including a plurality of generally
parallel planar elements all mounted for rotation about a first
axis, wherein the driving part is coupled to the pumping part by
means of a magnetic coupling device such that rotation of the
driving part causes rotation of the pumping part about the first
axis, the pump being adapted to pump lubricant on start-up of the
engine.
Description
[0001] This application claims priority to United Kingdom Patent
Application No. 0223516.6 filed Oct. 10, 2002, the entire
disclosure of which is incorporated herein by reference.
FIELD OF THE INVENTION
[0002] The present invention relates to a pump, particularly, but
not exclusively for use in pumping lubricant such as oil into an
engine.
DESCRIPTION OF THE PRIOR ART
[0003] Conventionally, a positive displacement pump such as a gear
pump or gerotor is used to pump a liquid lubricant such as oil in
an engine. When the engine is cold, on start-up for example, the
oil is relatively viscous, and pumping oil of such high viscosity
with a conventional positive displacement pump is not only
inefficient, but when the pump is electrically driven, this can put
the pump motor under undesirable strain.
SUMMARY OF THE INVENTION
[0004] According to a first aspect of the invention we provide a
pump including a driving part and a pumping part, the pumping part
including a plurality of generally parallel planar elements mounted
for rotation about a first axis, wherein the driving part is
coupled to the pumping part by means of a magnetic coupling device
such that rotation of the driving part causes rotation of the
pumping part about the first axis.
[0005] A pump in which liquid to be pumped is moved by a plurality
of generally parallel planar elements such as discs or annular
plates will hereinafter be referred to as a disc pump. An advantage
of a disc pump is that the efficiency of such a pump is greater
when the viscosity of the pumped liquid is greater. Thus, a disc
pump most advantageously may be used in the invention to pump high
viscosity liquid such as cold oil.
[0006] Moreover, by virtue of coupling the driving part to the
pumping part by means of a magnetic coupling device, slip may occur
between the driving part and pumping part if the torque necessary
to rotate the pumping part exceeds a threshold value. Thus, where
the driving part is motor driven, the possibility of the motor
being damaged as a result of it being placed under strain when
pumping high viscosity liquid is reduced.
[0007] Preferably, the magnetic coupling includes a first coupling
part which is connected to the driving part for rotation with the
driving part, and a second coupling part which is connected to the
pumping part for rotation with the pumping part, one of the first
or second parts including a magnet, and the other of the first or
second parts including an electrically conductive part.
[0008] Preferably the first coupling part and second coupling part
are mounted for rotation about the first axis.
[0009] Preferably, the magnet is a permanent magnet.
[0010] The magnet may have a side wall which encloses a generally
cylindrical space, and the electrically conductive part may be
generally cylindrical and may be located at least partly within the
wall of the magnet.
[0011] The electrically conductive part of the magnetic coupling
may include a plurality of elongate copper elements arranged in a
generally circular array around an axis of rotation of the first
part of the magnetic coupling, a longitudinal axis of each copper
element being generally parallel to the axis of rotation. The
electrically conductive part may also include two generally annular
copper plates which are mounted on either side of the copper
elements in contact with end portions of all the copper elements.
The electrically conductive part may also include a soft iron
core.
[0012] Preferably the second coupling part is, in use, immersed in
the liquid to be pumped, and a sealing part is provided between the
first and second coupling parts, the sealing part substantially
preventing pumped liquid from contacting the first coupling part
and the motor.
[0013] Preferably the pumping part includes a plurality of
generally parallel, co-axial discs.
[0014] According to a second aspect of the invention we provide an
engine including a lubricant pump according to the first aspect of
the invention.
[0015] According to a third aspect of the invention we provide a
lubrication system for an engine including two lubricant pumps, one
of which is a pump according to the first aspect of the invention
which is adapted to pump lubricant on start-up of the engine.
[0016] By virtue of the viscosity of lubricant such as oil
decreasing with increasing temperature, the pump of the invention
lends itself particularly for use pumping lubricant in an engine.
Whereas the efficiency of the disc pump decreases as temperature
rises to a usual working temperature, the amount of slip of the
magnetic coupling alone will decrease as less torque is imposed on
the driving part.
DESCRIPTION OF THE DRAWINGS
[0017] The invention will now be described with reference to the
accompanying drawings of which,
[0018] FIG. 1 illustrates a cross-section through a pump according
to the invention, and
[0019] FIG. 2 illustrates an exploded perspective view of the
magnetic coupling and sealing part of the pump of FIG. 1,
[0020] FIG. 3 is a schematic illustration of a lubrication system
according to the third aspect of the invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION
[0021] Referring to the figures, there is shown a pump 10,
typically for use in pumping lubricating oil in an automotive
engine. The pump 10 includes a driving part 12, which in this case
is the output shaft 12 of an electric motor 18, and a pumping part
14, hereinafter referred to as a disc pack 14, the disc pack 14
including a plurality of co-axial, generally parallel discs 16.
Typically, the motor 18 is an electric motor, but any other type of
motor 18 may be used. The output shaft 12 of the motor 18 is
coupled to the disc pack 14 by means of a magnetic coupling 20.
[0022] The magnetic coupling 20 includes a first coupling part 22
which is connected to the motor output shaft 12 and which is
mounted for rotation with the output shaft 18 about an axis A, and
a second coupling part 24 which is connected to the disc pack 14
and mounted for rotation with the disc pack 14.
[0023] The first coupling part 22 includes a magnet 26, in this
case a permanent magnet, with a circular base 26a and a side wall
26b which encloses a generally cylindrical space. The motor output
shaft 12 is connected to the base 26a generally at the centre of
the base 26a such that the side wall 26b extends axially away from
and generally parallel to the output shaft 18.
[0024] The second coupling part 24 is generally cylindrical and
includes an electrically conductive part with plurality of copper
bars 28a arranged in a generally circular array around the axis of
rotation A. The bars are spaced from one another with a
longitudinal axis of each of the bars 28a parallel to the axis of
rotation A. The copper bars 28a are mounted between two annular
copper plates 28b such that both ends of each copper bar 28a are in
contact with a copper plate 28b. The copper plates 28b are normal
to and centred around the axis of rotation A, and provide an
electrical connection between the copper bars 28a. The bars 28a and
plates 28b are supported on a soft iron core 28c.
[0025] The second coupling part 24 is mounted around a cylindrical
bearing shaft 30 for rotation about the bearing shaft 30. The
bearing shaft 30 extends along the axis A, and the second coupling
part 24 is rigidly connected to the disc pack 14 such that the
second coupling part 24 and disc pack 14 may rotate together about
axis A. In this example, the disc nearest the coupling 20 is bolted
to the second coupling part 24, but the second coupling part 24,
may alternatively be welded to the disc pack 14, or moulded as an
integral part of the disc pack 14.
[0026] The motor output shaft 12 and magnetic coupling 20 are
contained within a generally cylindrical housing 32 which extends
from a casing 18a of the motor 18. The housing 32 has four wings
32a which extend radially outwardly from the housing 32 to which
are bolted, at an end of the housing 32 opposite the motor 18, a
volute 34 with an inlet port 34a and an outlet port 34b, the disc
pack 14 being contained within the volute 34. The volute 34 is of a
conventional spiral configuration with the inlet port 34a located
generally centrally of the volute 34 and extending generally along
the axis of rotation A of the second coupling part 24 and the disc
pack 14, and the outlet port 34b extending tangentially outwardly
from the periphery of the volute 34.
[0027] There is also provided a sealing part 36 which has a
circular base 36a, a side wall 36b enclosing a generally
cylindrical space, and a lip 36c which extends outwardly from an
end of the side wall 36b opposite to the base 36a. The sealing part
36 is located between the first coupling part 22 and the second
coupling part 24, the base 36a being adjacent to the base 26a of
the first coupling part 22. The second coupling part 24 extends
into the space enclosed by the side wall 36b of the sealing part
36, and the sealing part 36 extends into the space enclosed by the
side wall 26b of the first coupling part 22. Thus the side wall 26b
of the first coupling part 26 encloses the second coupling part 24,
but the two are separated by the sealing part 36.
[0028] The base 36a of the sealing part 36 includes a generally
central recess in which the bearing shaft 30 is located. The
bearing shaft 30 may also be supported at its end nearest the disc
pack 14.
[0029] The lip 36c of the sealing part 36 is sandwiched between the
housing 32 and the volute 34, and provides a substantially liquid
tight seal between the first and second coupling parts 22, 24. The
sealing part 36 is made from an electrically non-conductive
material, and is typically polymeric.
[0030] In use, pumped fluid may flow from the volute 34 into part
of the housing 32, and may flow around the second coupling part 24.
The sealing part 36 substantially prevents the fluid from flowing
around the first coupling part 22 and the motor output shaft 12,
and hence pumped fluid does not come into contact with the motor
18.
[0031] The oil pump 10 operates as follows.
[0032] Activation of the motor 18 causes the motor output shaft 12
and hence the first coupling part 22 to rotate about axis A.
Rotation of the magnet 26 induces eddy currents in the copper bars
28a and plates 28b of the second coupling part 24, and the eddy
currents produce a magnetic field. The magnetic field produced by
the eddy currents interacts with that of the magnet 26, and as a
result of this interaction, the second coupling part 24 rotates
with the first coupling part 22.
[0033] Rotation of the second coupling part 24 causes the disc pack
14 to rotate, and shear forces in the oil between the discs of the
disc pack cause the oil to be pulled around the volute 34 and
pumped out of the outlet port 34b. As transfer of rotational energy
from the disc pack 16 to the oil arises due to viscous drag, the
efficiency of pumping decreases with decreasing oil viscosity.
Thus, the efficiency of pumping decreases as the engine warms up,
and the pump is particularly useful for pumping oil when the oil is
cold.
[0034] If, however, the fluid is so viscous that the torque
required to rotate the disc pack 14 exceeds a threshold value, the
magnetic coupling 20 will slip such that the second coupling part
24 rotates at a lower speed than the first coupling part 22. This
is possible because the first coupling part 22 is not mechanically
connected to the second coupling part 24. Slip may occur, for
example, when pumping cold oil on engine start-up.
[0035] The threshold value of the torque before slip occurs can be
determined by providing the first coupling part 22 with a magnet 26
of an appropriate strength. The stronger the magnetic field
produced by the magnet 26, the higher the maximum value of torque
transferred. Slip of the magnetic coupling 20 assists in protecting
the motor 18 from damage through turning against excessive
torque.
[0036] When the pump 10 is used for pumping lubricating oil into an
automotive engine, as the engine warms up, the viscosity of the oil
decreases, and hence the efficiency of the disc pack 14 in pumping
the oil decreases. The torque required to rotate the disc pack 14
decreases, however, and thus slip between the first and second
coupling parts 22, 24 is reduced if not eliminated. Thus as the
efficiency of the disc pack 14 in pumping fluid decreases, the
efficiency of the coupling 20 in transferring motive power from the
motor 18 to the disc pack 16 increases.
[0037] A pump 10 according to the first aspect of invention may be
used instead of a conventional oil pump in an engine such as an
automotive engine, or may be used in a lubrication system as a
supplementary pump to pump oil when the engine is cold. An example
of such an engine lubrication system is illustrated in FIG. 3, and
includes a supplementary pump 10 according to the first aspect of
the invention, and a main pump 40 which is a conventional engine
lubrication pump such as a positive displacement pump, both of
which are adapted to pump lubricant, such as oil, from a lubricant
reservoir 42 into the engine 44.
[0038] A control device 48 is also provided, the control device 48
being adapted to select which pump 10, 40 is to be used to pump
lubricant into the engine 44. On engine start-up, when the engine
is cold, the control device 48 is adapted to select the
supplementary pump 10, and when the engine approaches its usual
working temperature, the control device 48 is adapted to switch to
select the main pump 40 instead of or in addition to the
supplementary pump 10. The control device 48 may be adapted to
switch between pumps 10, 40, or the pumps 10, 40 may operate
simultaneously, for example during a transition period, as desired.
The control device 48 may be adapted to control flow of power to
the pumps 10, 40 and/or flow of lubricant to the pumps 10, 40.
[0039] The pump 10 need not be driven by a motor 18. It may instead
by driven by means of a power take-off from the engine for which
the pump is providing lubrication.
* * * * *