Note: Descriptions are shown in the official language in which they were submitted.
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TITLE
Liquid cooling arrangement for electric machines
FIELD
[0001] The
present invention relates to electric machines. More
specifically, the present invention is concerned with a liquid cooling
arrangement for electric machines and with electric machines provided with
such a liquid cooling arrangement.
BACKGROUND
[0002] Electric
machines, motors or generators, are well known in
the art. It is also widely known that electric machines generate heat as a by-
product and that this heat must be somehow extracted from the machine to
improve the performance of the machine and/or prevent early degradation or
failure thereof.
[0003] Electric
machines are often air-cooled. This is easily done by
providing apertures in the body of the machine to force air therethrough. The
efficiency of such a cooling arrangement is poor since air is a generally low
efficiency cooling fluid. Furthermore, some electric machines operate in
environments that are such that it is not possible to provide an electric
machine
with apertures to allow air therein. Accordingly, fluid cooling arrangements
for
electric machines have also been designed.
[0004] Some
permanent magnet electric machines are provided with
an internal stator and an external rotor generally enclosing the stator. When
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this is the case, the stator has a generally cylindrical body and coils are so
mounted to the cylindrical body as to outwardly produce a magnetic field that
interacts with the externally provided rotor. Since the heat is generally
generated in the stator that is somewhat enclosed by the rotor, it may be
difficult to install a fluid cooling arrangement inside an enclosed stator of
such
an external rotor electric machine.
BRIEF DESCRIPTION OF THE DRAWINGS
[0005] In the appended drawings:
[0006] Figure 1 is a perspective view of a liquid cooling arrangement
according to a first illustrative embodiment;
[0007] Figure 2 is a sectional side elevation view taken along line 2-
2 of Figure 1;
[0008] Figure 3 is a bottom plan view of the liquid cooling
arrangement of Figure 1;
[0009] Figure 4 is a top plan view of the liquid cooling arrangement
of Figure 1;
[0010] Figure 5 is a sectional side elevation view taken along line 5-
of Figure 4;
[0011] Figure 6 is a sectional view of an electric machine provided
with the liquid cooling arrangement of Figure 1;
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[0012] Figure 7 is a perspective view of a liquid cooling arrangement
according to a second illustrative embodiment;
[0013] Figure 8 is a perspective view illustrating a stator provided
with a liquid cooling arrangement according to a third illustrative
embodiment;
[0014] Figure 9 is a sectional view taken along line 9-9 of Figure 8;
[0015] Figure 10 is a perspective view of a liquid cooling
arrangement according to a fourth embodiment; and
[0016] Figure 11 is a perspective view of a liquid cooling
arrangement according to a fifth embodiment.
DETAILED DESCRIPTION
[0017] In accordance with an illustrative embodiment, there is
provided a liquid cooling arrangement to be inserted in the internal stator of
an
electric machine, the internal stator being provided with an internal surface,
the
liquid cooling arrangement comprising:
a tubular body provided first and second longitudinal ends
and an external surface so configured and sized as to be applied to the
internal
surface of the internal stator; the first and second longitudinal ends include
expansion slots allowing deformation of the tubular body; the tubular body
also
includes a cooling path provided with a fluid inlet and a fluid outlet;
a biasing assembly so configured and sized as to bias the
external surface of the tubular body against the internal surface of the
internal
stator.
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[0018] According to another aspect, there is provided an electric machine
comprising:
an internal stator provided with an internal surface;
an external rotor coaxially mounted about the internal stator; and
a liquid cooling arrangement inserted in the internal stator, the liquid
cooling arrangement comprising:
a tubular body provided first and second longitudinal ends and
an external surface so configured and sized as to be applied to the internal
surface of the internal stator; the first and second longitudinal ends include
expansion slots allowing deformation of the tubular body; the tubular body
also includes a cooling path provided with a fluid inlet and a fluid outlet;
and
. a biasing assembly so configured and sized as to bias the
external surface of the tubular body against the internal surface of the
internal stator.
[0019] The present description refers to other documents listed throughout
the present disclosure.
[0020] The use of the word "a" or "an" when used in conjunction with the
term "comprising" in the claims and/or the specification may mean "one", but
it is
also consistent with the meaning of "one or more", "at least one", and "one or
more than one". Similarly, the word "another" may mean at least a second or
more.
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[0021] As used in this specification and claim(s), the words
"comprising" (and any form of comprising, such as "comprise" and
"comprises"), "having" (and any form of having, such as "have" and "has"),
"including" (and any form of including, such as "include" and "includes") or
"containing" (and any form of containing, such as "contain" and "contains"),
are
inclusive or open-ended and do not exclude additional, unrecited elements or
process steps.
[0022] The term "about" is used to indicate that a value includes an
inherent variation of error for the device or the method being employed to
determine the value.
[0023] An object is therefore to provide a liquid cooling arrangement
for electric machines.
[0024] It is to be noted that the expression "electric machine" is to
be
construed herein as encompassing both electric motors and electric generators
disregarding the technology used in these machines.
[0025] Other objects, advantages and features will become more
apparent upon reading of the following non-restrictive description of
illustrative
embodiments thereof, given by way of example only with reference to the
accompanying drawings.
[0026] Generally stated, cooling arrangements according to
illustrative embodiments use a cooling tube associated with a heat storing
element. The cooling tube has a serpentine configuration and the generally
cylindrical heat storing element includes longitudinal slots starting from
both
longitudinal ends of the heat storing element. Accordingly, it is possible to
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slightly deform the heat storing element to properly position it into the
internal
stator of an electric machine. Furthermore, the longitudinal slots allow the
material of the heat storing element to contract and expand at a different
rate
than the material forming the stator of the electric machine without undue
deformation of the stator and without contact loss occurring between these
elements. An adequate heat transfer between the heat storing element and the
stator is therefore possible while allowing the use of different materials
forming
these elements. A biasing assembly may be used to force the external surface
of the heat storing element against the internal surface of the stator.
[0027] Turning now to Figures 1 to 6, a liquid cooling arrangement
according to a first illustrative embodiment will be described.
[0028] The liquid cooling arrangement 10 includes a heat storing
element in the form of a tubular body 12 and a cooling path in the form of a
continuous serpentine cooling tube 14 embedded in the tubular body 12.
[0029] The tubular body 12 is generally C-shaped and includes an
external surface 16 and first and second longitudinal ends 18 and 20. Three
expansion slots 22 are provided from the first longitudinal end 18 and two
expansion slots 24 are provided from the second longitudinal end 20 (see
Figure 2). The expansion slots 22 are open to the first longitudinal end 18
but
do not reach the second longitudinal end 20. Conversely, as can be better
seen from the bottom plan view of Figure 3, the expansion slots 24 are open to
the second longitudinal end 20 but do not reach the first longitudinal end 18.
[0030] The C-shape of the tubular body 12 is defined by a larger slot
25 open to both longitudinal ends 18 and 20.
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[0031] The
serpentine cooling tube 14, shown in dashed lines in
Figure 1, includes a fluid inlet 26 and a fluid outlet 28.
[0032] Figure 2
illustrates the cooling tube 14 embedded in the body
12. Figure 2 also illustrates that each straight portion of the cooling tube
14 is
adjacent to at least one expansion slot 22 or 24.
[0033] Figures
3 and 4 are respectively bottom and top plan views of
the body 12 showing, in dashed lines, the potential deformation for the
insertion
of the body 12 in an internal stator (not shown).
[0034] Figure 5
illustrates, in dashed lines, the cooling tube 14
embedded in the body 12. As can be seen from this figure, the expansion slots
22 and 24 are provided in U-shaped portions of the serpentine cooling tube 14
to allow a continuous cooling tube 14 while providing expansion slots open to
either longitudinal end of the body 12.
[0035] Figure 6
schematically illustrates portions of an electric
machine 50 provided with the liquid cooling arrangement 10. The electric
machine 50 includes a stator 52 provided with coils 54 and a rotor 56 provided
with permanent magnets 58.
[0036] The
stator 52 includes a generally cylindrical inner surface 60
against which a portion of the outer surface 16 of the cooling arrangement 10
is
applied. A bottom shoulder 62 of the stator 52 and a top shoulder 64 of the
body 12 ensure a proper insertion of the cooling arrangement 10 in the stator
52. Of course, the shoulders 62 and 64 could be different than those
illustrated
herein.
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[0037] As can
be seen on the sectional Figure 6, the internal surface
66 of the body 12 includes a central constriction 68 defined by two angled
wall
portions 70 and 72.
[0038] Figure 6
also illustrates an internal biasing assembly 74 used
to bias the external surface 16 of the tubular body 12 against the internal
surface 60 of a stator 52. The biasing assembly 74 is provided with first and
second rings 76, 78 and a plurality of fasteners 80 (two shown in Figure 6)
interconnecting the first ring 76 to the second 78. The outside peripheral
walls
82 of the rings 76 and 78 are so angled as to generally correspond to the
angle
wall portions 70 and 72.
[0039]
Accordingly, once the cooling arrangement 10 is slightly
deformed to be inserted in the stator 12, thanks to the expansion slots 22 and
24 and the slot 25, the fasteners 80 can be tightened (see arrows 84) causing
the rings 76 and 78 to be pulled towards one another (see arrows 86). The
interaction of the angled walls 82, 70 and 72 deforms the body 12 so as to
push
the outer wall 16 of the body 12 onto the inner surface 60 of the stator 52
(see
arrows 88). Accordingly, an adequate heat transfer is realized between the
stator 52 and cooling arrangement 10.
[0040] The
expansions slots 22 and 24 allow the stator 52 and the
cooling arrangement 10, made of dissimilar materials, to thermally expand
and/or contract at different rates without causing non-elastic deformation of
these elements and while keeping an adequate contact therebetween to allow
for an adequate heat transfer.
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[0041] The
rings 76 and 78 can be made of the same material as the
stator 52, typically steel, to thermally expand and contract at the same rate
thereof.
[0042] Of
course, other fastening arrangements could be used. For
example, the fasteners 80 of Figure 6 could be replaced by rivets (not shown),
provided that compressing means (not shown) are used to temporarily maintain
the rings 76 and 78 towards one another while the rivets are installed.
[0043] As will
easily be understood by one skilled in the art, other
mechanisms mounted inside the tubular body and designed to provide an
outwardly directed radial force could be used to bias the external surface of
the
tubular body against the internal surface of the stator.
[0044] It will
easily be understood by those skilled in the art that both
the cooling tube 14 and the body 12 can be made of many adequate heat
transfer material. For example, the cooling tube 14 could be made of stainless
steel while the body 12 could be made of aluminum. Of course, other materials
such as, for example, copper for the tube and cast iron, plastic, zinc or
magnesium for the body could be used. One skilled in the art will be in a
position to select compatible materials for the tube and body.
[0045] Turning
now to Figure 7, a liquid cooling arrangement 100
according to a second illustrative embodiment will be described. It is to be
noted that since the liquid cooling arrangements 10 and 100 are very similar,
and for concision purpose, only the differences between these liquid cooling
arrangements will be described hereinbelow.
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[0046] The main difference between the cooling arrangements 100 and 10
resides in the proportions of the cooling arrangement. Indeed while the
cooling
arrangement 10 was designed for small diameter electric machines, the cooling
arrangement 100 is designed for larger diameter electric machines.
Accordingly,
the tubular body 102 has a larger diameter and is provided with more expansion
slots 104 and 106 from both longitudinal ends 108 and 110 of the body 102.
[0047] Another interesting difference is that the body 102 of the liquid
cooling arrangement 100 is not C-shaped. The increased number of slots allows
a
more substantial deformation of the body 102, allowing it to be inserted in a
stator
and subsequently forced against the internal surface of the stator without
requiring
the body 102 to be C-shaped.
[0048] Turning now to Figures 8 and 9 of the appended drawings, a liquid
cooling arrangement 200 according to a third illustrative embodiment will be
described. The liquid cooling arrangement 200 is very similar to the liquid
cooling
arrangements 10 and 100 illustrated in Figures 1 to 7. Accordingly, only the
differences therebetween will be described hereinbelow.
[0049] As is apparent from Figure 8 the biasing assembly 204 used to apply
the external surface of the cooling assembly 200 onto the internal surface of
the
stator 202 is different from the biasing assembly described hereinabove. The
biasing assembly illustrated in Figure 8 is described in US Patent 6,960,851
entitled "Cooling device including a biasing element" and naming Poulin et al.
as
inventors.
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[0050] The liquid cooling arrangement 200 is not provided with embedded
tubes. As can be seen from Figure 9, the liquid cooling arrangement 200
includes
a plurality of bores that are drilled at an angle to define V-shaped channels,
and
are spaced such that adjacent V-shaped channels intersect.
[0051] More specifically, each angled bore 205 is open to both longitudinal
ends 206 and 208 of the liquid cooling arrangement 200. Adjacent bores are
closed by deformable plugs 210 to form a cooling path from an inlet 212 to an
outlet 214. Expansion slots 216 are provided on both longitudinal ends 206,
208 of
the arrangement 200 between the plugs 210. Accordingly, the cooling path is
not
disturbed by the expansion slots.
[0052] Such a configuration of bores and plugs is described in US Patent
7,474,021 entitled "Cooling assembly for electric machine" and naming Didier
Perrin as inventor.
[0053] Turning now to Figure 10 of the appended drawings, a liquid cooling
arrangement 300 according to a fourth illustrative embodiment will be
described. It
is to be noted that the liquid cooling arrangement 300 is similar to the
liquid cooling
arrangement 100 illustrated in Figure 7. Accordingly, only the differences
therebetween will be described hereinbelow.
[0054] The cooling path of the liquid cooling arrangement 300 is defined by
a cooling tube 302 that is not embedded in the tubular body 304 but is
inserted
and deformed in a serpentine channel 306 provided on the external surface 308
of
the tubular body 304. The serpentine channel 306 has a generally C-shaped
cross-section.
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[0055] The continuous cooling tube 302 is therefore in physical contact
with
both the body 304 and the stator (not shown), when the liquid cooling
arrangement
300 is inserted in a stator.
[0056] Again, the expansion slots 310 are provided between the longitudinal
portions of the cooling tube 302 to prevent interference therebetween.
[0057] Such- a cooling tube configuration described in US Patent 6,992,411,
entitled "Liquid cooling arrangement for electric machines" and naming Houle
etal.
as inventors.
[0058] Finally, turning to Figure 11 of the appended drawings, a liquid
cooling arrangement 400 according to a fifth illustrative embodiment will be
described. Again, since the liquid cooling arrangement 400 is similar to the
liquid
cooling arrangement 100 illustrated in Figure 7, only the differences
therebetween
will be described hereinbelow.
[0059] The cooling path of the liquid cooling arrangement 400 includes
eight
U-shaped cooling tubes 402 each including a fluid inlet 404 and a fluid outlet
406.
Expansion slots 408 are provided either between the U- shaped cooling tubes
402
or between the longitudinal legs thereof so as to not interfere with the
operation of
the cooling tubes 402.
[0060] The cooling path also includes a manifold 410 provided with a fluid
inlet 412 and a fluid outlet 414 and mounted to the inlets 404 and outlets 406
of
the cooling tubes 402 to provide a single inlet and outlet for the liquid
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cooling arrangement 400. It is to
be noted that the manifold 410 is
schematically illustrated in Figure 10.
[0061] Of
course, one skilled in the art will understand that the
number of U-shaped cooling tubes 402 can be changed.
[0062] It is to
be noted that while the external surfaces of the cooling
arrangement bodies is shown herein as having shoulders defining different
body diameters, straight cylindrical outside surfaces could be used. As will
be
easily understood by one skilled in the art the external surface of the body
of
the cooling arrangement generally corresponds to the internal surface of the
stator of the electric machine to provide an adequate contact therebetween.
[0063] While
cylindrical shaped cooling arrangements have been
described above, other shapes, such as polygons, could be used for the outer
surface of the cooling arrangement and for the inner surface of the stator. Of
course, the shape of these surfaces must correspond to provide an adequate
contact and hence heat transfer.
[0064] It is
also to be noted that heat transfer materials such as
adhesive, thermal grease or thermal pads could be provided between the
external surface of the body and the internal surface of the stator to improve
the heat transfer from the stator to the liquid cooling arrangement.
[0065] It is to
be understood that the invention is not limited in its
application to the details of construction and parts illustrated in the
accompanying drawings and described hereinabove. The invention is capable
of other embodiments and of being practiced in various ways. It is also to be
understood that the phraseology or terminology used herein is for the purpose
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of description and not limitation. Hence, the present invention has been
described
hereinabove by way of illustrative embodiments thereof and, accordingly, the
foregoing description is by way of example only and is not intended to be
limiting.
Also, the scope of the claims should not be limited by those embodiments, but
should be given the broadest interpretation consistent with the description as
a
whole.
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