U.S. patent application number 11/604876 was filed with the patent office on 2007-06-07 for core structure of housingless-type oil cooler.
This patent application is currently assigned to CALSONIC KANSEI CORPORATION. Invention is credited to Norimitsu Matsudaira.
Application Number | 20070125529 11/604876 |
Document ID | / |
Family ID | 37814299 |
Filed Date | 2007-06-07 |
United States Patent
Application |
20070125529 |
Kind Code |
A1 |
Matsudaira; Norimitsu |
June 7, 2007 |
Core structure of housingless-type oil cooler
Abstract
A housingless-type oil cooler includes cooling elements having
first and second plates coupled with together, an oil return tube
vertically arranged through a core portion, and a heat-transfer
suppressing means. The cooling elements are piled up in a vertical
direction of the core portion to alternately form cooling water
chambers and oil chambers so that the adjacent cooling water
chambers are fluidically connected through a cooling water passage
and the adjacent oil chambers are fluidically connected through an
oil passage. The oil return tube discharges oil introduced from one
side of the core portion toward its other side through the oil
chambers and the oil passages. The heat-transfer suppressing means
is arranged between the oil chambers and the oil return tube to
suppress heat transfer between the oil flowing in the oil chambers
and the oil flowing in the oil return tube.
Inventors: |
Matsudaira; Norimitsu;
(Tokyo, JP) |
Correspondence
Address: |
FOLEY AND LARDNER LLP;SUITE 500
3000 K STREET NW
WASHINGTON
DC
20007
US
|
Assignee: |
CALSONIC KANSEI CORPORATION
|
Family ID: |
37814299 |
Appl. No.: |
11/604876 |
Filed: |
November 28, 2006 |
Current U.S.
Class: |
165/167 ;
165/916 |
Current CPC
Class: |
F28D 9/0012 20130101;
F28D 9/005 20130101; F28F 13/00 20130101 |
Class at
Publication: |
165/167 ;
165/916 |
International
Class: |
F28F 3/08 20060101
F28F003/08 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 29, 2005 |
JP |
2005-343871 |
Claims
1. A core structure of a housingless-type oil cooler comprising: a
plurality of cooling elements, each of the cooling elements
including a first plate and a second plate that are coupled with
each other, the cooling elements being piled up in a vertical
direction of a core portion to alternately form cooling water
chambers and oil chambers so that the adjacent cooling water
chambers are fluidically connected with each other through a
cooling water passage and the adjacent oil chambers are fluidically
connected with each other through an oil passage; an oil return
tube that is arranged in the vertical direction through the core
portion to discharge oil introduced from one side of the core
portion toward the other side of the core portion through the oil
chambers and the oil passages; and a heat-transfer suppressing
means that is arranged between the oil chambers and the oil return
tube to suppress heat transfer between the oil flowing in the oil
chambers and the oil flowing in the oil return tube.
2. The core structure according to claim 1, wherein the
heat-transfer suppressing means is a heat-transfer suppressing
chambers that are arranged between the oil chambers and the oil
return tube and are fluidically connected with the cooling water
chambers.
3. The core structure according to claim 1, wherein the
heat-transfer suppressing means is a heat-transfer suppressing
chambers that are arranged between the oil chambers and the oil
return tube and are filled with air.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a core structure of a
housingless-type oil cooler which has a plurality of plates piled
up to form cooling water chambers and oil chambers therebetween
without an additional housing so as to cool oil flowing through the
oil chambers.
[0003] 2. Description of the Related Art
[0004] Conventional oil coolers are used for and attached to, for
example, automatic transmissions to cool oil thereof. Some of the
conventional ones are constructed to have an oil tube forming an
oil chamber and arranged in a cooling water chamber formed between
a housing of the oil cooler and the oil tube. The other
conventional ones are, what is called, a housingless-type oil
cooler, which is constructed to have a plurality of plates to
alternately form cooling water chambers and oil chambers
therebetween for removing a housing, thereby decreasing its
manufacturing costs and dimensions.
[0005] Specifically, such the housingless-type oil cooler has a
core portion where a plurality of first plates and a plurality of
second plates are piled up alternately with each other in a
vertical direction of the core portion to alternately form cooling
water chambers and oil chambers. The adjacent cooling water
chambers are fluidically connected with each other through a
cooling water passage, and the adjacent oil chambers are
fluidically connected with each other through an oil passage. An
oil return tube is provided to penetrate the core portion to allow
oil to flow from the one side of the core portion toward the other
side thereof. Such conventional oil coolers are disclosed in
Japanese patents laid-open publication No. (Tokkaihei) 7-286786,
No. (Tokkaihei) 11-351778, and No. 2002-277177.
[0006] The above known conventional core structures of the
housingless-type oil coolers, however, encounter a problem in that
coolability of the oil cooler deteriorates because the
low-temperature oil, which is cooled by the cooling water in the
cooling water chamber while it flows in the oil chambers, is
reheated due to heat transfer from high-temperature oil in the oil
chamber through a wall of the oil return tube while it flows
through the oil return tube.
[0007] It is, therefore, an object of the present invention to
provide a core structure of a housingless-type oil cooler which
overcomes the foregoing drawbacks and can improve coolability of
oil in the oil cooler.
SUMMARY OF THE INVENTION
[0008] According to a first aspect of the present invention there
is provided a core structure of a housingless-type oil cooler
including a plurality of first plates, a plurality of second
plates, an oil return tube, and a heat-transfer suppressing means.
The first plates are arranged alternately with the second plates so
that the first plates and the second plates are piled up in a
vertical direction of a core portion to alternately form cooling
water chambers and oil chambers. The adjacent cooling water
chambers are fluidically connected with each other through a
cooling water passage, and the adjacent oil chambers are
fluidically connected with each other through an oil passage. The
oil return tube is arranged in the vertical direction through the
core portion to discharge oil introduced from one side of the core
portion toward the other side of the core portion through the oil
chambers and the oil passages. The heat-transfer suppressing means
is arranged between the oil chambers and the oil return tube to
suppress heat transfer between the oil flowing in the oil chambers
and the oil flowing in the oil return tube.
[0009] Therefore, the heat-transfer suppressing means suppresses
the heat transfer from high-temperature oil in the oil chamber to
the oil in the return oil tube through a wall of the oil return
tube while it flows through the oil return tube. This can suppress
rise in heat of the oil in the oil return tube and keep it be at
the low temperature, thereby improving coolability of the oil
cooler.
[0010] Preferably, the heat-transfer suppressing means is a
heat-transfer suppressing chambers that are arranged between the
oil chambers and the oil return tube and are fluidically connected
with the cooling water chambers.
[0011] Therefore, the heat-transfer chambers suppress heat transfer
between the oil flowing in the oil return tube and the oil flowing
in the oil chambers, thereby improving coolability of the oil
cooler. In addition, the cooling water in the heat-transfer cools
the oil flowing through the oil return tube, further improving the
coolability.
[0012] Preferably, the cooling water in the heat-transfer
suppressing means is a heat-transfer suppressing chambers that are
arranged between the oil chambers and the oil return tube and are
filled with air.
[0013] Therefore, the air, having a low heat-transfer coefficient,
in the heat-transfer chambers suppresses heat transfer between the
oil flowing in the oil return tube and the oil flowing in the oil
chambers, thereby improving coolability of the oil cooler.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] The objects, features and advantages of the present
invention will become apparent as the description proceeds when
taken in conjunction with the accompanying drawings, in which:
[0015] FIG. 1 is a view showing a housingless-type oil cooler
having a core structure of a first embodiment according to the
present invention;
[0016] FIG. 2 is a cross-sectional side view of the
housingless-type oil cooler having the core structure of the first
embodiment shown in FIG. 1;
[0017] FIG. 3 is another cross-sectional side view of the
housingless-type oil cooler having the core structure of the first
embodiment, taken along a line S3-S3 in FIG. 2;
[0018] FIG. 4A is an enlarged and exploded cross-sectional view
showing a first plate, a second plate, and an inner fin, which
constitute a core portion of the housingless-type oil cooler shown
in FIGS. 1 to 3, and FIG. 4B is an enlarged cross-sectional view of
the core structure of the first embodiment, both figures being
shown from the same side as shown in FIG. 2;
[0019] FIG. 5A is an enlarged and exploded cross-sectional view
showing the first plate, the second plate, and the inner fin, which
constitute the core portion of the housingless-type oil cooler
shown in FIGS. 1 to 3, and FIG. 5B is an enlarged cross-sectional
view of the core structure of the first embodiment, both figures
being shown from the same side as shown in FIG. 3;
[0020] FIG. 6 is an enlarged cross-sectional view of a left half
part of the core portion shown in FIG. 2;
[0021] FIG. 7 is a cross-sectional view illustrating oil in the oil
cooler shown in FIG. 3;
[0022] FIG. 8 is a cross-sectional view illustrating the oil in the
oil cooler shown in FIG. 2;
[0023] FIG. 9A is a cross-sectional view of a first plate, a second
plate, and an inner fin, which constitute a core structure of a
second embodiment according to the present invention, and FIG. 9B
is a cross-sectional view of the core portion of the second
embodiment;
[0024] FIG. 10 is a cross-sectional view showing an oil cooler,
shown from the same side as shown in FIG. 9B, having the core
structure of the second embodiment;
[0025] FIG. 11 is a cross-sectional view showing the oil cooler
having the core structure of the second embodiment, taken along a
line S11-S11 in FIG. 10;
[0026] FIG. 12 is an enlarged cross-sectional view of a left half
part of the core portion shown in FIG. 10;
[0027] FIG. 13 is a cross-sectional view showing a left half part
of a core structure of a third embodiment according to the present
invention; and
[0028] FIG. 14 is a cross-sectional view of a first plate which is
used in a core portion and obtained by modifying the first plates
used in the core structures of the first to third embodiments.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0029] Throughout the following detailed description, similar
reference characters and numbers refer to similar elements in all
figures of the drawings, and their descriptions are omitted for
eliminating duplication.
[0030] Referring to FIG. 1 and FIG. 2, there is shown a core
structure of a housingless-type oil cooler AA of a first preferred
embodiment according to the present invention.
[0031] The housingless-type oil cooler AA includes a core portion
1, an upper cover 4 covering a top portion of the core portion 1
sandwiched between an upper casing 2, a lower casing 3, and a oil
return tube 6 fixed to the core portion and penetrating through a
center axis thereof.
[0032] As shown in FIG. 2 and FIG. 3, the core portion 1 is formed
in a circular cylinder shape. The upper casing 2 is placed on a top
surface of the core portion 1, and the lower casing 3 is placed on
a bottom surface of the core portion 1.
[0033] The upper cover 4 is formed like a dish, and covers a top
portion of the upper casing 2 to form an oil tank chamber 5 defined
between the upper cover 4 and the upper casing 2. The upper cover 4
is formed at its center position with a fixing hole 4c in a
circular cross-section, as shown in FIG. 3, and an adapter member
10, which will be later described, is fixed to a wall portion
forming the fixing hole 4c.
[0034] As shown in FIG. 2, the upper casing 2 is formed like a
disc, and is provided with an oil discharge port 2a at a position
away from its center position, and also with a fixing hole 2b at
the center position. The oil discharge port 2a is formed to have a
circular cross-section, and fluidically communicates between the
oil tank chamber 5 and oil passages 16a and 16b of the core portion
1.
[0035] The lower casing 3 is formed like a disc, and is provided
with an oil introducing port 3a at a position away from its center
position, and also with a fixing hole 3b at the center position.
The oil introducing port 3a is formed to have a circular
cross-section, and fluidically communicates between the oil passage
16a and a not shown automatic transmission. The lower casing 3 is
formed with an O-ring groove 3c, for receiving a not shown O ring,
at its bottom surface so as to ensure a gap between the lower
casing 3 and the automatic transmission to be liquid-tight when
they are assembled with each other.
[0036] The oil return tube 6 is formed in a circular cylinder
shape, and is inserted in the fixing holes 2b and 3b of the upper
and lower casings 2 and 3, respectively, to be fixed to wall
portions forming the fixing holes 2b and 3b so that its upper
opening is located in the oil tank chamber 5 and its lower opening
is located inside the automatic transmission.
[0037] On the other hand, as shown in FIG. 3, the upper cover
member 4 is further formed with two fixing holes 4a and 4b at
positions which are away from its center position and opposite to
each other. The upper casing 2 is further formed with two
projecting portions, which are formed in a circular cylinder to
project upward and have fixing holes 2c and 2d at positions which
are away from both of its center position and the fixing holes 2b
and 2b and opposite to each other, respectively. A cooling-water
introducing pipe 7 is inserted in the fixing hole 4a of the upper
cover 4 and the fixing hole 2c of the upper casing 2, and fixed to
walls thereof. A cooling-water discharging pipe 8 is inserted in
the fixing hole 4b of the upper cover 4 and the fixing hole 2d of
the upper casing 2, and fixed to walls thereof.
[0038] The core portion 1 is constructed so that a plurality of
cooling elements are piled up in the vertical direction between the
upper casing 2 and the lower casing 3. Each cooling elements has a
first plate 11, a second plate 12 coupled with the first plate 11,
and an inner fin 13 arranged between the first and second plates 11
and 12.
[0039] As shown in FIGS. 4A and 4B, the first plate 11 is formed
like a rectangular box having an opening at its bottom side. The
first plate 11 has a first cylindrical portion 11a projecting
downward and shaped in a large circular cylinder at its center
position, and second and third cylindrical portions 11b and 11c
projecting upward and shaped in a small circular cylinder at
symmetric positions with respect to the first cylindrical portion
11a.
[0040] In addition, as shown in FIGS. 5A and 5B, the first plate 11
further has fourth and fifth cylindrical portions 11d and 11e
projecting upward and shaped in a small circular cylinder at
positions where they are located on a line perpendicular to a line
connecting the second and third cylindrical portions 11b and 11c
and are in symmetric with respect to the first cylindrical portion
11a.
[0041] The second plate 12 is, as shown in FIGS. 4a and 4B, formed
like a rectangular box having an opening at its bottom side. The
second plate 12 has a first cylindrical portion 12a projecting
upward and shaped in a large circular cylinder at its center
position, and second and third cylindrical portions 12b and 12c
projecting downward and shaped in a small circular cylinder at
symmetric positions with respect to the first cylindrical portion
12a. The first cylindrical portion 12a has a bending portion 14, at
an upper end portion thereof, narrowing its opening as a position
of the first cylindrical portion 12a becomes higher.
[0042] In addition, as shown in FIGS. 5A and 5B, the second plate
12 further has fourth and fifth cylindrical portions 12d and 12e
projecting upward and shaped in a small circular cylinder at
positions where they are located on a line perpendicular to a line
connecting the second and third cylindrical portions 12b and 12c
and are in symmetric with respect to the first cylindrical portion
12a.
[0043] The first to fifth cylindrical portions 12a to 12e of the
second plate 12 are arranged to correspond with the first to fifth
cylindrical portions 11a to 11e of the first plate 11,
respectively.
[0044] The inner fin 13 is an offset fin in the first embodiment,
but may be used another type one. The inner fin 13 is formed with
first to fifth through-holes 13a to 13e corresponding to the first
to fifth cylindrical portions 11a to 11e of the first plate 11 and
to the first to fifth cylindrical portions 12a to 12e of the second
plate 12.
[0045] The first plate 11 and the second plate 12 are coupled with
each other, containing the inner fin 13 therein, to form an inner
space therebetween for containing the inner fin 13, thereby forming
the cooling element. The inner space forms an oil chamber 15 as
shown in FIGS. 4B and 5B.
[0046] The second and third cylindrical portions 11b and 11c of the
first plate 11 and the second and third cylindrical portions of the
next second plate 12 are fitted with each other, as shown in FIG.
4B, to form a pair of oil passages 16a and 16b for fluidically
connecting with the adjacent oil chambers 15.
[0047] On the other hand, the second plate 12 and its adjacent
first plate 11 are also coupled with each other to form a cooling
water chamber 17 therebetween as shown in FIGS. 4B and 5B.
Therefore, in the core portion 1 of the oil cooler AA, the oil
chambers 15 and the cooling water chambers 17 are arranged
alternately with each other. The fourth and fifth cylindrical
portions 11d and 11e of the first plate 11 and the fourth and fifth
cylindrical portions 12d and 12e are fitted with each other to form
a pair of cooling water passages 18a and 18b as shown in FIG.
5B.
[0048] Incidentally, the second plate 12 is provided with a
plurality of dimples 12f, four dimples 12f in the first embodiment,
near the first cylindrical portion 12a on its bottom surface. The
dimples 12f are not indispensable in the invention.
[0049] The second plate 12 and the next first plate 11 are kept
predetermined-interval away from each other in the vertical
direction by contacting the bending portion 14 with the bottom
surface of the first plate 11 and connecting the dimples 12f with
the upper surface of the next first plate 12.
[0050] As shown in FIGS. 2 and 6, a cylindrical portion 11f,
corresponding to the second cylindrical portion 11b, of an
upper-most first plate 11 is inserted into the oil discharging port
2a to fluidically communicate the oil passage 16a and the oil tank
chamber 5 with each other, while the upper-most first plate 11 is
not formed with a cylindrical portion corresponding to the third
cylindrical portion 11c to be blocked off.
[0051] In addition, instead of the first plates 11 arranged at
predetermined columns, the core portion 1 is provided between the
adjacent first plates 11 with blocking-off plates 19, which has a
blocking-off portion 19a at positions corresponding one of the
second and third cylindrical portions 11b and 11c of the first
plate 11. The block-off portions 19a contact on the upper surface
of the next first plate 11 so that the first and second plates 11
and 12 are keep away from each other.
[0052] As shown in FIG. 3, a cylindrical portion 11h, corresponding
to the fourth cylindrical portion 11d, of the upper-most first
plate 11 fluidically communicates the cooling water passage 17a and
the cooling-water introducing pipe 7 with each other, and a
cylindrical portion 11i, corresponding to the fifth cylindrical
portion 11e, of the upper-most first plate 11 fluidically
communicates the cooling water passage 17b and the cooling-water
discharging pipe 8 with each other.
[0053] The lower-most first plate 11 has no cylindrical portions,
and is formed at its center position with a hole through which the
oil return tube 6 can pass.
[0054] As shown in FIG. 6, an outer peripheral surface of the oil
return tube 6 liquid-tightly contacts on inner surfaces of the
first cylindrical portions 11a of the first plates 11. The bending
portions 14 of the second plates 12 contact with the inner surfaces
of the first cylindrical portions 11a of the first plates 11 to
form heat-transfer suppressing chambers 20 that are arranged around
the oil return tube 6 and fluidically communicating with the
cooling-water chambers 17. The heat-transfer suppressing chamber 20
corresponds to a heat-transfer suppressing means of the present
invention.
[0055] Incidentally, each part of the housingless-type oil cooler
AA is made of aluminum, and at least one side part of jointing
parts is provided with a clad layer (a blazing sheet) thereon.
Then, this temporarily assembled oil cooler AA is conveyed into a
not-shown heating furnace to be heat-treated so as to be integrally
formed by blazing the jointing parts. Thus assembled oil cooler AA
is attached to the automatic transmission by using a bolt 9. The
bolt 9 has a head to be pressed on an upper surface of the adapter
member 10 at its top, and a screw portion 9a to be screwed into a
screw hole of the automatic transmission at its bottom. The bolt 9
passes through a fixing hole 10a of the adapter member 10 and the
oil return tube 6 in a state where there is formed a space as an
oil return passage 6a for fluidically communicating the oil tank
chamber 5 and a not-shown oil inlet port of the automatic
transmission between the inner surface of the oil return tube 6 and
the outer peripheral surface of the bolt 9.
[0056] Incidentally, the oil cooler AA may be attached to the
automatic transmission by using bolts screwed into screw holes of
flange portions radially projecting from the lower casing 3. In
this case, the adapter member 10 is removed and the fixing hole 4c
of the upper casing 4 is blocked off.
[0057] The operation of the housingless-type oil cooler AA having
the core structure of the first embodiment will be described.
[0058] The cooling water is introduced into the cooling-water
passage 18a through the cooling-water introducing pipe 7, and fills
up each cooling-water chamber 17, then flowing out through the
cooling-water passage 18b, where its flow direction is indicated by
arrows in FIG. 7.
[0059] On the other hand, high-temperature oil is introduced into
the oil passage 16a through oil introducing port 3a, and then is
changed its flow direction by the block-off plates 19, winding its
way as indicated by arrows in FIG. 8. The oil is cooled down due to
heat transfer between the oil in each oil chamber 15 and the
cooling water in the adjacent cooling-water chambers 17 while it
flows through the core portion 1. After cooling, the oil flows into
the oil tank chamber 5 through the oil discharging port 2a.
Low-temperature oil in the oil tank 5 flows to the automatic
transmission through the oil return passage 6a. Thus, the oil is
circulated between the oil cooler AA and the automatic
transmission. Incidentally, the oil introducing port 3a and the oil
discharging port 2a may be replaced by each other, and the
cooling-water introducing pipe 7 and the cooling-water discharging
pipe 8 may be replaced by each other.
[0060] In the first embodiment, the oil flowing through the oil
return tube 8 is prevented from receiving heat from the high
temperature oil flowing in the oil passages 16a and 16b, because
the heat-transfer suppressing chambers 20 filled with the cooling
water are located therebetween to block off the heat transfer
therebetween. This improves coolability of the oil cooler AA.
[0061] In addition, the cooling water in the heat-transfer
suppressing chambers 20 cools the oil flowing through the oil
return passage 6a, further improving the coolability of the oil
cooler AA.
[0062] Next, a core structure of a housingless-type oil cooler of a
second embodiment according to the present invention will be
described with reference to the accompanying drawings.
[0063] As shown in FIG. 9A, in the core structure of the
housingless-type oil cooler BB of the second embodiment, a first
plate 11 has a first cylindrical portion 11a projecting downward
and shaped in a large circular cylinder at it center position. The
first cylindrical portion 11a has a bending portion 21, at an upper
end portion thereof, narrowing its opening as a position of the
first cylindrical portion 11a becomes lower.
[0064] On the other hand, a second plate 12 has a first cylindrical
portion 12a projecting downward, not having a bending portion like
the first embodiment.
[0065] The first plate 11 and the second plate 12 are coupled with
each other, containing an inner fin 13 therebetween, to form a
cooling element. A plurality of the cooling elements are piled up
in a vertical direction to form a core portion 1 of the oil cooler
BB as shown in FIGS. 9B to 12.
[0066] In the assembled core portion 1, the bending portions 21
formed on the first cylindrical portions 11a of the first plates 1
and an outer surface of the oil return tube 6 are contacted with
each other to form rooms as heat-transfer suppressing chambers 22
between the first cylindrical portions 11a and the outer surface of
the oil return tube 6. The heat-transfer suppressing chambers 22
are arranged around the oil return tube 6 and are filled with the
air for suppressing the heat transfer between the oil flowing in
the oil return tube 6 and high-temperature oil flowing in oil
chambers 15. The heat-transfer suppressing chamber 22 corresponds
to a heat-transfer suppressing means of the present invention.
[0067] The other parts of the second embodiment are similar to
those of the first embodiment, and their descriptions are omitted.
The operation of the oil cooler BB having the core structure of the
second embodiment is also similar to that of the first embodiment,
and its description is omitted.
[0068] The air in the heat-transfer suppressing chambers 22
suppresses the heat transfer between the oil flowing in the oil
return tube 6 and high-temperature oil flowing in oil chambers 15,
because a heat transfer coefficient is low, thereby improving
coolability of the oil cooler BB.
[0069] While there have been particularly shown and described with
reference to preferred embodiments thereof, it will be understood
that various modifications may be made therein, and it is intended
to cover in the appended claims all such modifications as fall
within the true spirit and scope of the invention.
[0070] The number of the cooling elements may be set arbitrarily,
and positions and the numbers of the block-off plates 19 may be set
arbitrarily according to need.
[0071] The heat-transfer chambers 22 filled with the air are formed
by inwardly bending a peripheral portion of the end portion of the
first cylindrical portion 11a formed on the first plate 11 to
contact the peripheral portion on the outer surface of the oil
return tube 6 in the second embodiment. Instead of the bending
portion 21 of the first cylindrical portion 11a, as shown in FIG.
13, a projecting portion 23, formed in an annular shape and
inwardly projecting from an inner surface of the first cylindrical
portion 11a, may be used for forming a space, as a heat-transfer
suppressing chamber 24 filled with the air, between the inner
surface of the first cylindrical portion 11a and the outer surface
of the oil return tube 6. This modification can provide advantages
similar to those of the second embodiment. The heat-transfer
suppressing chamber 24 corresponds to a heat-transfer suppressing
means of the present invention.
[0072] Instead of the annular projecting portion 23, as shown in
FIG. 14, a plurality of inwardly projecting portions, formed by
partially cutting off the end portion of the first cylinder portion
11a of the first plate 11, may be formed on the inner surface of
the first cylindrical portion 11a so as to fluidically communicate
between the adjacent heat-transfer suppressing chambers 24. This
modification can provide advantages similar to those of the second
embodiment.
[0073] As described above, configurations of the first and second
plates 11 and 12 and the oil return tube 6 may be set arbitrarily
as long as they can form a heat-transfer suppressing chamber.
[0074] The entire contents of Japanese Patent Application No.
2005-343871 filed Nov. 29, 2005 are incorporated herein by
reference.
* * * * *