U.S. patent application number 13/581718 was filed with the patent office on 2013-01-31 for cooler.
This patent application is currently assigned to TOYOTA JIDOSHA KABUSHIKI KAISHA. The applicant listed for this patent is Tomohiro Takenaga. Invention is credited to Tomohiro Takenaga.
Application Number | 20130025837 13/581718 |
Document ID | / |
Family ID | 47295619 |
Filed Date | 2013-01-31 |
United States Patent
Application |
20130025837 |
Kind Code |
A1 |
Takenaga; Tomohiro |
January 31, 2013 |
COOLER
Abstract
A cooler includes a plate, a cooling case having a coolant
flowing therein, and a plurality of wavy fins having a raised
curved portion and a lowered curved portion formed alternately on a
side face in a flow direction of the coolant. In this cooler, the
coolant flows through between the raised curved portion and the
lowered curved portion opposite to each other in a meandering
manner. The raised curved portion is provided with a bank creating
a flow of coolant from the raised curved portion toward the
opposite lowered curved portion. With this bank, a part of a main
stream of the coolant can be mixed with the coolant stagnating near
the lowered curved portion, whereby the heat transfer coefficient
of the wavy fins can be improved. Thus, stagnation of the coolant
near the lowered curved portion can be prevented, so that the
cooler can have enhanced cooling performance.
Inventors: |
Takenaga; Tomohiro;
(Toyota-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Takenaga; Tomohiro |
Toyota-shi |
|
JP |
|
|
Assignee: |
TOYOTA JIDOSHA KABUSHIKI
KAISHA
Toyota-shi
JP
|
Family ID: |
47295619 |
Appl. No.: |
13/581718 |
Filed: |
June 7, 2011 |
PCT Filed: |
June 7, 2011 |
PCT NO: |
PCT/JP2011/063048 |
371 Date: |
August 29, 2012 |
Current U.S.
Class: |
165/168 |
Current CPC
Class: |
H01L 23/473 20130101;
H01L 2924/0002 20130101; H01L 2924/00 20130101; H01L 2924/0002
20130101 |
Class at
Publication: |
165/168 |
International
Class: |
F28F 3/02 20060101
F28F003/02; F28F 3/12 20060101 F28F003/12 |
Claims
1. A cooler including: a plate connected to a semiconductor device;
a cooling case covered with the plate and having a coolant flowing
therein; and wavy fins connected to the plate, each wavy fin having
a raised curved portion and a lowered curved portion formed
alternately on a side face of the wavy fin in a flow direction of
the coolant, the coolant flowing through between the raised curved
portion and the lowered curved portion of the adjacent wavy fins
opposite to each other in a meandering manner, wherein the raised
curved portion is provided with a stagnation preventing member for
creating a flow of coolant from the raised curved portion toward
the opposite lowered curved portion, the stagnation preventing
member being provided at a base portion of the raised curved
portion on a semiconductor device side in a thickness direction of
the wavy fins.
2. (canceled)
3. The cooler according to claim 1, wherein the stagnation
preventing member is a tapered bank tapering toward a bottom wall
of the cooling case.
4. The cooler according to claim 1, the stagnation preventing
member is a protrusion protruding from the raised curved portion
toward the opposite lowered curved portion.
5. The cooler according to claim 1, wherein a second stagnation
preventing member for creating a flow of coolant from the raised
curved portion toward the opposite lowered curved portion is
provided, the second stagnation preventing member being positioned
at a distal portion of the raised curved portion on a side of the
bottom wall of the cooling case in a thickness direction of the
wavy fins.
6. The cooler according to claim 3, wherein a second stagnation
preventing member for creating a flow of coolant from the raised
curved portion toward the opposite lowered curved portion is
provided, the second stagnation preventing member being positioned
at a distal portion of the raised curved portion on a side of the
bottom wall of the cooling case in a thickness direction of the
wavy fins.
7. The cooler according to claim 4, wherein a second stagnation
preventing member for creating a flow of coolant from the raised
curved portion toward the opposite lowered curved portion is
provided, the second stagnation preventing member being positioned
at a distal portion of the raised curved portion on a side of the
bottom wall of the cooling case in a thickness direction of the
wavy fins.
Description
TECHNICAL FIELD
[0001] The present invention relates to a cooler in which a coolant
flows along wavy fins arranged between a plate and a cooling case,
and more particularly to a cooler with improved cooling
performance.
BACKGROUND ART
[0002] In hybrid electric vehicles or the like, an inverter device
(power conversion device) performs power conversion. The inverter
device having a semiconductor device mounted therein is equipped
with a cooler for cooling the heat generated by switching the
semiconductor device. The amount of heat the semiconductor device
generates has been increasing since such an inverter device is
required to be small and lightweight and yet to provide high power
output. Accordingly, a cooler with improved cooling performance
(heat transfer coefficient) to keep stable operation of the
inverter device is being sought after.
[0003] Patent Literature 1 specified below, for example, describes
a cooler with improved cooling performance. The cooler described in
Patent Literature 1 specified below includes a plate connected to a
semiconductor device and a cooling case covered with the plate and
containing a coolant flowing therein. To the plate are connected,
as shown in FIG. 19, a plurality of wavy fins 130 extending in a
flow direction (direction indicated by an arrow in FIG. 19) in
which coolant 140 flows, the wavy fins 130 each having raised
curved portions 131 and lowered curved portions 132 formed
alternately in the flow direction on both sides thereof. The
coolant 140 thus flows through between the raised curved portions
131 and lowered curved portions 132 opposite to each other in a
meandering manner. This helps to create turbulence more easily and
results in improved cooling performance.
Citation List
Patent Literature
[0004] [Patent Literature 1] JP 2008-186820 A
SUMMARY OF INVENTION
Technical Problem
[0005] The cooler described above had the following problem.
Namely, the coolant 140 generally tends to flow straight, because
of which the coolant 140 does not flow smoothly near the lowered
curved portions 132 (parts Q indicated by imaginary lines in FIG.
19) when the coolant 140 passes through between the raised curved
portions 131 and the lowered curved portions 132 opposite to each
other as shown in FIG. 19. In other words, the flow of coolant 140
can hardly bend along the lowered curved portion 132. This led to
stagnation (stagnation points) of the coolant 140 near the lowered
curved portions 132, resulting in the cooling function of the
coolant 140 not being fully exploited.
[0006] The present invention has been devised to solve the
above-described problem and it is an object of the invention to
provide a cooler that prevents stagnation of coolant near lowered
curved portions to improve the cooling performance.
Solution to Problem
[0007] (1) A cooler according to an aspect of the present invention
includes a plate connected to a semiconductor device, a cooling
case covered with the plate and having a coolant flowing therein,
and wavy fins connected to the plate, each wavy fin having a raised
curved portion and a lowered curved portion formed alternately on a
side face of the wavy fin in a flow direction of the coolant, the
coolant flowing through between the raised curved portion and
lowered curved portion opposite to each other in a meandering
manner, wherein the raised curved portion is provided with a
stagnation preventing member for creating a flow of coolant from
the raised curved portion toward an opposite lowered curved
portion.
[0008] (2) In the cooler according to the above-described aspect of
the present invention, the stagnation preventing member is provided
preferably at a base portion of the raised curved portion on a
semiconductor device side in a thickness direction of the wavy
fins.
[0009] (3) In the cooler according to the above-described aspect of
the present invention, the stagnation preventing member is
preferably a tapered bank tapering toward a bottom wall of the
cooling case.
[0010] (4) In the cooler according to the above-described aspect of
the present invention, the stagnation preventing member may be a
protrusion protruding from the raised curved portion toward the
opposite lowered curved portion.
[0011] (5) In the cooler according to the above-described aspect of
the present invention, a second stagnation preventing member for
creating a flow of coolant from the raised curved portion toward
the opposite lowered curved portion may be provided, the second
stagnation preventing member being positioned at a distal portion
of the raised curved portion on a side of the bottom wall of the
cooling case in a thickness direction of the wavy fins.
Advantageous Effects of Invention
[0012] The advantageous effects of the cooler will be
described.
[0013] With the configuration (1), the stagnation preventing member
creates a flow of coolant from the raised curved portion toward an
opposite lowered curved portion. Thereby, the main stream of the
coolant that tends to flow straight can be mixed with the coolant
stagnating near the lowered curved portion, whereby the heat
transfer coefficient of the wavy fins can be improved. Thus,
stagnation of the coolant near the lowered curved portion can be
prevented, so that the cooler can have enhanced cooling
performance.
[0014] With the configuration (2), there is created a flow of the
coolant from the base portion of the raised curved portion on the
semiconductor device side toward the opposite lowered curved
portion. Thereby, the coolant is disturbed near the base portions
of the wavy fins where the temperature is relatively high.
Therefore, the heat transfer coefficient of the wavy fins can be
effectively improved. Moreover, by providing the stagnation
preventing member only at the base portion, pressure fluctuations
of the coolant caused by the stagnation preventing member can be
reduced and pressure loss increase of the cooler can be kept
small.
[0015] With the configuration (3), the tapered bank creates a flow
of the coolant from the bank toward the bottom wall of the cooling
case in addition to the flow of coolant from the bank toward the
lowered curved portion. Therefore, the coolant can be disturbed
largely near the bank, so that the heat exchange rate of the wavy
fins can be effectively improved.
[0016] With the configuration (4), the stagnation preventing member
is a protrusion, i.e., the stagnation preventing member can be
provided with a very simple configuration. The protrusion can be
configured small, so that pressure fluctuations of the coolant
caused by the protrusion are reduced, and there will be almost no
increase in the pressure loss in the cooler.
[0017] With the configuration (5), the stagnation preventing member
and the second stagnation preventing member create flow of the
coolant from the raised curved portion toward the opposite lowered
curved portion. Thereby, the main stream of the coolant that tends
to flow straight can be mixed substantially with the coolant
stagnating near the lowered curved portion, whereby the heat
transfer coefficient of the wavy fins can be largely improved.
BRIEF DESCRIPTION OF DRAWINGS
[0018] FIG. 1 shows an overall configuration diagram of an inverter
device;
[0019] FIG. 2 shows a longitudinal end view of a cooler in FIG.
1;
[0020] FIG. 3 shows a perspective view of wavy fins in FIG. 2;
[0021] FIG. 4 shows a plan view of the wavy fins in FIG. 3;
[0022] FIG. 5 shows an end view of the cooler taken along a line
V-V in FIG. 4;
[0023] FIG. 6 shows an end view of the cooler taken along a line
W-W in FIG. 4;
[0024] FIG. 7 shows an enlarged view of a part X in FIG. 5;
[0025] FIG. 8 shows a schematic view illustrating flow of coolant
when there are no banks provided on a raised curved portion;
[0026] FIG. 9 shows a schematic view illustrating the flow of the
coolant when there are banks provided on the raised curved
portion;
[0027] FIG. 10 is a schematic graph showing a relationship between
a distance from a base portion and a temperature of the wavy fins
and the coolant when there are no banks provided on a base
portion;
[0028] FIG. 11 is a schematic graph showing a relationship between
the distance from the base portion and the temperature of the wavy
fins and the coolant when there are banks provided on the base
portion;
[0029] FIG. 12 is a diagram indicating measured values of the heat
transfer coefficient of the wavy fins and the pressure loss of the
cooler when the coolant flows in the cooler;
[0030] FIG. 13 is an end view of the cooler corresponding to FIG. 2
in a case where a sheet member is interposed between an end portion
of the wavy fins and a bottom wall of the cooling case;
[0031] FIG. 14 is a schematic view illustrating the flow of the
coolant when there are protrusions provided on the raised curved
portion in a second embodiment;
[0032] FIG. 15 is an enlarged view of a part Yin FIG. 14;
[0033] FIG. 16 is an end view corresponding to FIG. 5, illustrating
a second bank is provided on a bottom wall of a cooling case in a
third embodiment;
[0034] FIG. 17 is an enlarged view of a part Z in FIG. 16;
[0035] FIG. 18 is an end view corresponding to FIG. 5, illustrating
a second bank is provided on a sheet member in a forth embodiment;
and
[0036] FIG. 19 is an explanatory view explaining how stagnation of
coolant is created near a lowered curved portion of a wavy fin in a
prior art.
DESCRIPTION OF EMBODIMENTS
[0037] The cooler according to the present invention will be
hereinafter described with reference to the drawings. FIG. 1 is an
overall configuration diagram schematically illustrating an
inverter device 1 to which a cooler 4 is applied. This inverter
device 1 is mounted in hybrid electric vehicles or electric
vehicles, for example, and includes a semiconductor device 2, an
insulating substrate 3, and the cooler 4, as shown in FIG. 1.
[0038] The semiconductor device 2 is an electronic component that
forms an inverter circuit. This semiconductor device 2 is, for
example, an IGBT or a diode and it is a heat generating element
that generates heat by its switching operation. The semiconductor
device 2 is joined onto the insulating substrate 3 by
soldering.
[0039] The insulating substrate 3 provides electrical insulation
between the semiconductor device 2 and the cooler 4. This
insulating substrate 3 is, for example, a DBA substrate. The
insulating substrate 3 is joined onto the cooler 4 by brazing.
Here, although the cooler 4 includes one each semiconductor device
2 and insulating substrate 3 mounted thereon, there may be provided
a plurality of them.
[0040] The cooler 4 cools the heat generated by switching the
semiconductor device 2 with a coolant 40 flowing inside. FIG. 2 is
a longitudinal end view of the cooler 4 shown in FIG. 1; it is
viewed in a direction in which the coolant flows. The cooler 4
includes a plate 10, a cooling case 20, and a plurality of wavy
fins 30 as shown in FIG. 2.
[0041] The plate 10 functions as a lid member to the cooling case
20. The plate 10 is formed of aluminum, for example, which has good
thermal conductivity. This plate 10 is planar, and the wavy fins 30
are each integrally connected to the plate 10 at one side facing
the cooling case 20. The plate 10 is connected to the semiconductor
device 2 via the insulating substrate 3.
[0042] The cooling case 20 is a case for the coolant 40 to flow
inside. The cooling case 20 is formed of aluminum, for example,
which has good thermal conductivity. This cooling case 20 is an
open-end box as shown in FIG. 2 and includes a rectangular bottom
wall 21 and side walls 22 extending vertically upwards in FIG. 2
from peripheral edges of this bottom wall 21.
[0043] The side walls 22 are formed with a recess 22a for an O-ring
50 to be fitted in, and insertion holes 22b for bolts 51 to be
threaded in as shown in FIG. 2. Thus, with the O-rings 50 fitted
into the recesses 22a in the side walls 22, the plate 10 is
assembled to the side walls 22 of the cooling case 20 by the bolts
51. The plate 10 and the cooling case 20 may be assembled together
by welding instead.
[0044] An inlet pipe 61 is connected to the side wall 22 on the
front side in FIG. 1, while an outlet pipe 62 is connected to the
side wall 22 on the back side in FIG. 1. The inlet pipe 61 is
connected to a discharge pump 63 via a discharge flow path 71. The
outlet pipe 62 is connected to a heat exchanger 64 via a return
flow path 72. The discharge pump 63 and the heat exchanger 64 are
connected to each other via an intake flow path 73.
[0045] Thus the coolant 40 flows into the cooler 4 through the
inlet pipe 61 after being discharged from the discharge pump 63.
The coolant 40 then flows inside the cooling case 20 as being in
contact with respective wavy fins 30. At this time, the heat from
the respective wavy fins 30 is absorbed by the coolant 40 and warms
up the coolant 40. After that, the coolant 40 is sent out through
the outlet pipe 62 to the heat exchanger 64. Thereby, the coolant
40 is cooled down by heat dissipation to the air in the heat
exchanger 64, and the cooled coolant 40 is returned to the
discharge pump 63.
[0046] The coolant 40 circulates through the cooler 4 in this way
to cool down the heat conducted from the semiconductor device 2 to
the wavy fins 30. The coolant 40 may be, as in this embodiment, a
liquid such as LLC, but not limited to liquids and may be gas such
as air. FIG. 3 is a perspective view of the wavy fins 30 shown in
FIG. 2. FIG. 4 is a plan view of the wavy fins 30 shown in FIG.
3.
[0047] As shown in FIGS. 3 and 4, the wavy fins 30 extend in a flow
direction in which the coolant 40 flows (direction indicated by an
arrow in FIGS. 3 and 4), and there are five such fins formed on the
underside of the plate 10. The number of the wavy fins 30 is not
limited to five and may be changed as required. These wavy fins 30
are integrally molded on the plate 10 by casting. Each wavy fin 30
winds in a meandering shape so as to increase the contact area with
the coolant 40 and is spaced apart by about 1 mm from an adjacent
wavy fin 30 in a direction orthogonal to the flow direction.
Dimension h in the thickness direction (see FIG. 7) of each wavy
fin 30 is about 3 mm which is slightly smaller than the dimension
in the height direction of the side walls 22. Flow paths for the
coolant 40 are thus formed inside the cooling case 20, so that the
coolant 40 flows along the flow direction, meandering through
between the adjacent wavy fins 30.
[0048] In this embodiment, the distance (flow path width) d between
adjacent wavy fins 30 is constant (about 1 mm) at any point in the
flow direction as shown in FIG. 4. This is for reducing a
difference in pressure of the coolant 40 at an inlet side (left
side in FIG. 4) of the wavy fins 30 and an outlet side (right side
in FIG. 4) of the wavy fins 30 so as to reduce pressure loss of the
cooler 4. Namely, if the distance d between adjacent wavy fins 30
varied in the flow direction, there would be large fluctuations in
the coolant 40 pressure at the inlet and outlet sides of the wavy
fins 30, which would increase pressure loss of the cooler 4. A
large pressure loss in the cooler 4 would necessitate large driving
force to drive the discharge pump 63, and such driving energy would
be wasted.
[0049] Here, the five wavy fins 30 in FIGS. 3 and 4 will be denoted
by 30A, 30B, 30C, 30D, and 30E in order in the direction orthogonal
to the flow direction. The wavy fins 30A and 30E at both ends have
a flat surface formed on one side. This is because one side of the
wavy fins 30A and 30E faces the side wall 22 of the cooling case
20. The other side of the wavy fins 30A and 30E, on the other hand,
is formed with raised curved portions 31 and lowered curved
portions 32 alternately in the flow direction. The wavy fins 30B,
30C, and 30E are also formed on both sides with the raised curved
portions 31 and lowered curved portions 32 alternately in the flow
direction. Thus the raised curved portions 31 and lowered curved
portions 32 of the adjacent wavy fins 30 face each other with
spaced apart by about 1 mm.
[0050] In this embodiment, as shown in FIGS. 3 and 4, the raised
curved portions 31 of each wavy fin 30 are each formed with a bank
31x. Each bank 31x prevents creation of stagnation (stagnation
points) of the coolant 40 in vicinity of each lowered curved
portion 32. These banks 31x are integrally formed with the
respective raised curved portions 31 by casting. This bank 31x is
the stagnation preventing member of the present invention.
Hereinafter the bank 31x will be described in detail. FIG. 5 is an
end view of the cooler 4 taken along a line V-V shown in FIG. 4.
FIG. 6 is an end view of the cooler 4 taken along a line W-W shown
in FIG. 4.
[0051] The bank 31x has a shape like a generally vertical half of a
taper as shown in FIGS. 5 and 6, tapering toward the bottom wall 21
of the cooling case 20. The tip portion of this bank 31 is not
pointed but has a flat surface parallel to the bottom wall 21. The
tip shape of the bank 31 is not limited to the flat shape and may
be changed as required, and it may be pointed.
[0052] FIG. 7 is an enlarged view of a part X shown in FIG. 5. As
shown in FIG. 7, the dimension s in the width direction (vertical
direction in FIG. 7) of the bank 31x is about 0.7 mm, and the
dimension t in the height direction (lateral direction in FIG. 7)
of the bank 31x is about 0.5 mm. This bank 31x thus generates flows
of the coolant 40 as indicated by arrows in FIG. 7. Namely, there
are created flows of the coolant 40 from the raised curved portion
31 toward the opposite lowered curved portion 32.
[0053] Next, the advantageous effects of the bank 31x will be
explained using FIGS. 8 and 9. FIG. 8 is a schematic diagram
illustrating flow of the coolant 40 when there are no banks 31x
provided on the raised curved portions 31. FIG. 9 is a schematic
diagram illustrating the flow of the coolant 40 when there are
banks 31x provided on the raised curved portions 31. FIG. 9 is an
enlarged view of a part R shown in FIG. 4.
[0054] When there are no banks 31x as shown in FIG. 8, the coolant
40 does not flow smoothly near the lowered curved portions 32
(parts Q indicated by imaginary lines in FIG. 8) when the coolant
40 passes through between the raised curved portions 31 and the
lowered curved portions 32 opposite to each other. In other words,
since the coolant 40 generally flows straight, the main stream MS
that tends to flow straight does not easily bend along the lowered
curved portions 32. For this reason, there are created some
stagnation (stagnation points) of the coolant 40 near the lowered
curved portions 32, and the cooling function of the coolant 40
cannot be fully exploited.
[0055] On the other hand, when there are banks 31x provided as
shown in FIG. 9, part MS1 of the main stream MS flows toward the
lowered curved portions 32 when the coolant 40 passes through
between the raised curved portions 31 and the lowered curved
portions 32 opposite to each other. Therefore, the part MS1 of the
main stream MS mixes with the coolant 40 located near the lowered
curved portions 32. As a result, no stagnation of the coolant 40
occurs near the lowered curved portions 32, so that the cooling
function of the coolant 40 is fully exploited.
[0056] The bank 31x of this embodiment is provided at a base
portion 31a on the semiconductor device 2 side (left side in FIG. 5
to FIG. 7) of the raised curved portion 31 in the thickness
direction (lateral direction in FIGS. 5 to 7) of the wavy fin 30,
as shown in FIGS. 5 to 7. The reason why the bank 31x is provided
at the base portion 31a will be explained using FIGS. 10 and
11.
[0057] FIG. 10 is a schematic graph showing the relationship
between the distance from the base portion 31a and the temperature
of the wavy fins 30 and the coolant 40 when there are no banks 31x
provided on the base portions 31a. On the other hand, FIG. 11 is a
schematic graph showing the relationship between the distance from
the base portion 31a and the temperature of the wavy fins 30 and
the coolant 40 when there are banks 31x provided on the base
portions 31a. Here, in FIGS. 10 and 11, the solid line represents
the temperature of the wavy fins 30, while the broken line
represents the temperature of the coolant 40. A portion of the
raised curved portion 31 located on the side of the bottom wall 21
(right side in FIGS. 10 and 11) of the cooling case 20 in the
thickness direction of the wavy fin 30 will be referred to as a
distal portion 31b.
[0058] As shown in FIG. 10, when there are no banks 31x provided on
the base portions 31a, the temperature difference .DELTA.T1 between
the base portions 31a and the coolant 40 is large, while the
temperature difference .DELTA.T2 between the distal portions 31b
and the coolant 40 is small. This is because the base portions 31a
are formed closer to the semiconductor device 2 as a heat
generating element than the distal portions 31b and tend to be hot,
because of which the coolant 40 located near the base portions 31a
cannot sufficiently absorb the heat of the hot base portions 31a.
Thus the temperature difference .DELTA.T1 is large, resulting in a
low heat transfer coefficient of the wavy fins 30.
[0059] In contrast, as shown in FIG. 11, when there are banks 31x
provided on the base portions 31a, the temperature difference
.DELTA.T1 is small. This is because the coolant 40 located near the
base portions 31a is disturbed because of the banks 31x and absorbs
the heat of the hot base portions 31a sufficiently. Thus, by
providing banks 31x on the base portions 31a, the temperature
difference .DELTA.T1 is made small, leading to a high heat transfer
coefficient of the wavy fins 30. Namely, when the banks 31x are
provided on the base portions 31a, the temperature difference
between the wavy fins 30 and the coolant 40 is made smaller than
when the banks 31x are provided on other portions than the base
portions 31a, whereby the heat transfer coefficient of the wavy
fins 30 can be effectively improved.
[0060] In this embodiment, the banks 31x are provided only on the
base portions 31a as shown in FIGS. 5 to 7, and not on other
portions than the base portions 31a. This is based on the following
reason. If the banks 31x are also provided on portions than the
base portions 31a, the main stream MS (see FIG. 9) of the coolant
40 would be largely obstructed. This would result in large
fluctuations in the coolant 40 pressure at the inlet and outlet
sides of the wavy fins 30, which would increase pressure loss of
the cooler 4. Thus, providing the banks 31x only on the base
portions 31a will improve the heat transfer coefficient of the wavy
fins 30 as well as reduce an increase in pressure loss of the
cooler 4.
[0061] Next, test results of the heat transfer coefficient of the
wavy fins and the pressure loss of the cooler will be described
using FIG. 12. FIG. 12 is a diagram showing actual measurements
(measured values) of the heat transfer coefficient of the wavy fins
and the pressure loss of the cooler when the coolant is flowing
inside the cooler. The measurements were obtained in this test
under conditions that the coolant 40 is discharged from the
discharge pump 63 at a predetermined constant rate (L/min) and
there is a small gap SM formed between end portions 30a (see FIG.
2) of the wavy fins 30 and the bottom wall 21 of the cooling case
20.
[0062] In FIG. 12, the circle indicates the measurement when there
are banks 31x provided as in this embodiment (see FIG. 9) while the
square indicates the measurement when there are no banks 31x (see
FIG. 8). At the point indicated by the circle in FIG. 12, the heat
transfer coefficient is U1 and the pressure loss is .DELTA.P1. At
the point indicated by the square in FIG. 12, the heat transfer
coefficient is U2 and the pressure loss is .DELTA.P2. U1 is higher
than U2 by about 9%, indicating that the heat transfer coefficient
is increased by providing the banks 31x. .DELTA.P1 is larger than
.DELTA.P2, indicating that the pressure loss is increased by
providing the banks 31x.
[0063] Here, the heat transfer coefficient and the pressure loss
are proportional to the flow rate and speed of the coolant 40.
Namely, the flow rate and speed of the coolant 40 have a
relationship to the heat transfer coefficient and the pressure loss
such that the larger the former, the larger the latter. Therefore,
a comparison of the level of the heat transfer coefficient between
a case where there are banks 31x provided and another case where
there are no banks 31x needs to be made under a condition that the
pressure loss is the same. The double square in FIG. 12 indicates
the measurement when the pressure loss is made to .DELTA.P1 by
increasing the flow rate and speed of the coolant 40 when there are
no banks 31x based on the assumption above. The solid line shown in
FIG. 12 indicates changes in the heat transfer coefficient and the
pressure loss with the change in the flow rate and speed of the
coolant 40 when there are no banks 31x provided.
[0064] As is clear from a comparison between the circle and the
double square indicated in FIG. 12, when the pressure loss is
.DELTA.P1, the heat transfer coefficient when there are banks 31x
provided is higher than the heat transfer coefficient when there
are no banks 31x provided. Accordingly, it can be considered that
while providing the banks 31x increases the pressure loss, it can
also largely improve the heat transfer coefficient. More
specifically, it was confirmed that the temperature at the base
portions 31a of the wavy fins 30 was reduced by about 5.degree. C.
by providing the banks 31x.
[0065] In this embodiment, as shown in FIG. 2, there is a small gap
SM formed between the end portions 30a of the wavy fins 30 and the
bottom wall 21 of the cooling case 20. This gap SM is about 0.3 mm,
for example, which is shown exaggerated in FIG. 2. If the coolant
40 flows into this gap SM, the flow speed of the main stream MS of
the coolant 40 reduces, which in turn reduces the heat transfer
coefficient of the wavy fins 30. However, in the cooler 4 of this
embodiment, since the heat transfer coefficient of the wavy fins 30
is effectively improved by providing the banks 31x at the base
portions 31a as described above, this reduction in the heat
transfer coefficient of the wavy fins 30 caused by the formation of
the gap SM does not become a problem.
[0066] One possibility here would be to interpose a sheet member 80
made of an elastic material (such as rubber or resin) between the
end portions 30a of the wavy fins 30 and the bottom wall 21 of the
cooling case 20 as shown in FIG. 13 in order to prevent the coolant
40 from flowing into the gap SM. The cost, however, would be higher
with the cooler 4A shown in FIG. 13 because of the sheet member 80
being added as another component, as compared to the cooler 4 of
this embodiment.
[0067] Moreover, with the cooler 4A shown in FIG. 13, there is a
risk that the end portions 30a of the wavy fins 30 are pressed to
the sheet member 80 when the plate 10 with the wavy fins 30 is
assembled to the cooling case 20, so that the sheet member 80 may
enter in a space between adjacent wavy fins 30 as indicated by the
imaginary lines KS in FIG. 13. In this case, the pressure loss
increases as compared to the cooler 4 of this embodiment since the
space for the coolant 40 to flow in is reduced.
[0068] In short, even without the sheet member 80 to be fitted in
the gap SM, the heat transfer coefficient of the wavy fins 30 can
be effectively improved by providing the banks 31x at the base
portions 31a according to the cooler 4 of the present embodiment.
By not providing the sheet member 80, the cooler 4 can be
configured less expensively, and pressure loss increase in the
cooler 4 is reduced.
[0069] The advantageous effects of the cooler 4 of the first
embodiment will be described. In this cooler 4, as shown in FIG. 9,
the banks 31x create flows of the coolant 40 from the raised curved
portions 31 toward the opposite lowered curved portions 32.
Thereby, the part MS1 of the main stream MS of the coolant 40 can
be mixed with the coolant 40 stagnating near the lowered curved
portions 32, whereby the heat transfer coefficient of the wavy fins
30 can be improved. Thus, stagnation of the coolant 40 near the
lowered curved portions 32 can be prevented, so that the cooler 4
can have enhanced cooling performance.
[0070] In the cooler 4 of the first embodiment, as shown in FIG. 7,
the banks 31x provided at the base portions 31a create flows of
coolant from the base portions 31a of the raised curved portions 31
toward the opposite lowered curved portions 32. Thereby, the
coolant 40 is disturbed near the base portions 31a of the wavy fins
30 where the temperature is relatively high. Therefore the heat
transfer coefficient of the wavy fins 30 can be effectively
improved. Moreover, since the banks 31x are provided only at the
base portions 31a, pressure fluctuations of the coolant 40 caused
by the banks 31x can be reduced and pressure loss increase in the
cooler 4 can be kept small.
[0071] In the cooler 4 of the first embodiment, as shown in FIG. 7,
the tapered banks 31x also create flows of the coolant 40 from the
banks 31x toward the bottom wall 21 of the cooling case 20, in
addition to the flows of the coolant 40 from the banks 31x toward
the lowered curved portions 32. Therefore, the coolant 40 is
disturbed largely near the banks 31x, so that the heat exchange
rate of the wavy fins 30 can be effectively improved.
[0072] Next, a second embodiment will be described using FIGS. 14
and 15. In the second embodiment, protrusions 31y are provided in
the raised curved portions 31 instead of the banks 31x of the first
embodiment. FIG. 14 is a schematic view illustrating the flow of
the coolant 40 when there are protrusions 31y provided on the
raised curved portions 31.
[0073] The protrusions 31y prevent creation of stagnation
(stagnation point) of the coolant 40 near the lowered curved
portions 32. This protrusion 31y is in a triangular column shape as
shown in FIG. 14 and protrudes from the raised curved portion 31
toward the opposite lowered curved portion 32. This protrusion 31y
is provided at the base portion 31a of the raised curved portion 31
and integrally formed with the raised curved portion 31 by casting.
Alternately, the protrusions 31y may be separate members from the
wavy fins 30 and may be joined to the raised curved portions 31 by
welding or bonding.
[0074] When the coolant 40 passes through between the raised curved
portion 31 and the lowered curved portion 32 opposite to each
other, as shown in FIG. 14, the protrusion 31y changes the
direction of the part MS1 of the main stream MS, and thereby the
part MS1 of the main stream MS flows toward the lowered curved
portion 32. Thus, the part MS1 of the main stream MS is mixed with
the coolant 40 located near the lowered curved portion 32 (part Q).
As a result, no stagnation of the coolant 40 occurs near the
lowered curved portions 32, so that the cooling function of the
coolant 40 is fully exploited.
[0075] FIG. 15 is an enlarged view of a part Y shown in FIG. 14. As
shown in FIG. 15, the dimension e in the width direction (lateral
direction in FIG. 15) of the protrusion 31y is about 0.1 mm, and
the dimension f of the protruding distance of the protrusion 31y
from the surface of the raised curved portion 31 is about 0.1 mm.
The dimension in the height direction (direction orthogonal to the
paper plane of FIG. 15) of the protrusion 31y is about 0.1 mm. That
is, the protrusions 31y are substantially smaller than the banks
31x of the first embodiment. Since other configurations of the
second embodiment are similar to the configurations of the first
embodiment, the description will be omitted.
[0076] Since the protrusions 31y are very small as described above,
the main stream MS of the coolant 40 is unlikely to be obstructed
largely by the protrusions 31y. Therefore, the pressure
fluctuations of the coolant 40 are smaller than that in the first
embodiment and the pressure loss of the cooler can be made small.
However, the amount of the coolant 40 made to flow toward the
lowered curved portions 32 by the protrusions 31y is smaller than
that of the coolant 40 made to flow toward the lowered curved
portions 32 by the banks 31x in the first embodiment. Accordingly,
the amount of the coolant 40 mixed near the lowered curved portions
32 is smaller than that in the first embodiment, because of which
an increase in the heat transfer coefficient of the wavy fins 30 is
accordingly small.
[0077] The triangle shown in FIG. 12 indicates the measurement in a
test in which the protrusions 31y are provided. The measurement
indicated by the triangle was obtained in the test under the same
conditions as the tests in which the measurements were made when
the banks 31x of the first embodiment are provided (circle in FIG.
12) and when the banks 31x are not provided (square in FIG.
12).
[0078] At the triangle in FIG. 12, the heat transfer coefficient is
U3, which is higher than U2 by about 5%. This indicates that
providing the protrusions 31y improves the heat transfer
coefficient. However, it also indicates that, with the protrusions
31y, the increase in the heat transfer coefficient is smaller than
when the banks 31x are provided.
[0079] At the triangle in FIG. 12, the pressure loss is .DELTA.P3,
which is slightly larger than .DELTA.P2. This indicates that the
pressure loss increase caused by the protrusions 31y is very small.
It also indicates that, with the protrusions 31y, the pressure loss
increase is sufficiently smaller than that of the case where the
banks 31x are provided.
[0080] The advantageous effects of the second embodiment will be
described. In the second embodiment, the stagnation preventing
member is the protrusions 31y, i.e., the stagnation preventing
member can be provided with a very simple configuration. Since the
protrusions 31y are configured very small as shown in FIG. 15,
pressure fluctuations of the coolant 40 caused by the protrusions
31y are reduced, so that there will be almost no increase in the
pressure loss in the cooler. Since other advantageous effects of
the second embodiment are similar to the advantageous effects of
the first embodiment, the description will be omitted.
[0081] Next, a third embodiment will be described using FIGS. 16
and 17. In the third embodiment, second banks 21x are provided on
the bottom wall 21 of the cooling case 20.
[0082] FIG. 16 is an end view corresponding to FIG. 5 illustrating
the second banks 21x provided on the bottom wall 21 of the cooling
case 20.
[0083] As shown in FIG. 16, the banks 31x are each provided at the
base portions 31a of the respective raised curved portions 31, as
with the first embodiment. In the third embodiment, the second
banks 21x are each located closer to distal portions 31b of
respective raised curved portions 31 on the bottom wall 21 side
(right side in FIG. 16) of the cooling case 20 in the thickness
direction of the wavy fins 30, these second banks 21x being
integrally formed to the bottom wall 21 of the cooling case 20. The
second banks 21x prevent creation of stagnation (stagnation points)
of the coolant 40 near the lowered curved portions 32, and
correspond to the second stagnation preventing member of the
present invention. FIG. 17 is an enlarged view of a part Z shown in
FIG. 16.
[0084] The second bank 21x has a shape like a generally vertical
half of a taper as shown in FIG. 17, tapering toward the plate 10
(left side of FIG. 17). A tip portion of this second bank 21x is
not pointed but has a flat surface parallel to the bottom wall 21.
The tip shape of the second bank 21x is not limited to the flat
shape and may be changed as required, and it may be pointed.
[0085] The dimension j in the width direction (vertical direction
in FIG. 17) of the second bank 21x is about 0.7 mm, and the
dimension g in the height direction (lateral direction in FIG. 17)
of the bank 21x is about 0.5 mm. This second bank 21x thus
generates flows of the coolant 40 as indicated by arrows in FIG.
17. Namely, there are created flows of coolant from the distal
portions 31b of the raised curved portions 31 toward the opposite
lowered curved portions 32. Since other configurations of the third
embodiment are similar to the configurations of the first
embodiment, the description will be omitted.
[0086] The advantageous effects of the third embodiment will be
described. In the third embodiment, as shown in FIG. 17, the banks
31x and the second banks 21x create flows of the coolant 40 from
the raised curved portions 31 toward the opposite lowered curved
portions 32. Thereby, the main stream MS of the coolant 40 that
tends to flow straight can be mixed substantially with the coolant
40 stagnating near the lowered curved portions 32, whereby the heat
transfer coefficient of the wavy fins 30 can be largely improved.
Namely, the heat transfer coefficient of the wavy fins 30 can be
increased more than the first embodiment.
[0087] However, the pressure fluctuations of the coolant 40 are
large in the third embodiment since the space for the coolant 40 to
flow in is reduced due to the second banks 21x. The pressure loss
in the cooler 4B of the third embodiment is therefore larger than
the pressure loss of the cooler 4 of the first embodiment. Since
other advantageous effects of the third embodiment are similar to
the advantageous effects of the first embodiment, the description
will be omitted.
[0088] Next, a fourth embodiment will be described using FIG. 18.
In the fourth embodiment, a sheet member 90 is fitted in the gap SM
between the end portions 30a of the wavy fins 30 and the bottom
wall 21 of the cooling case 20, and second banks 90x are provided
to this sheet member 90. FIG. 18 is an end view corresponding to
FIG. 5 illustrating the second banks 90x provided on the sheet
member 90.
[0089] The flat plate-like sheet member 90 fills up the gap SM as
shown in FIG. 18. This sheet member 90 prevents the coolant 40 from
flowing into the gap SM. The sheet member 90 is made of an elastic
material (such as rubber or resin) and bonded to the bottom wall 21
of the cooling case 20 before the plate 10 and the wavy fins 30 are
assembled to the cooling case 20. The gap SM is about 0.3 mm, for
example, and the sheet member 90 also has a thickness of about 0.3
mm, for example.
[0090] In the fourth embodiment, the second banks 90x are each
located at the distal portions 31b of the respective raised curved
portions 31, and formed integrally with the sheet member 90. The
second banks 90x prevent creation of stagnation (stagnation points)
of the coolant 40 near the respective lowered curved portions 32,
and correspond to the second stagnation preventing member of the
present invention. The second bank 90x has a shape like a generally
vertical half of a taper, tapering toward the plate 10 (left side
in FIG. 18). Since other configurations of the fourth embodiment
are similar to the configurations of the first embodiment, the
description will be omitted.
[0091] The advantageous effects of the fourth embodiment will be
described. In the fourth embodiment, since the gap SM is filled up
with the sheet member 90 as shown in FIG. 18, the coolant 40 can be
prevented from flowing into the gap SM. This prevents the main
stream MS of the coolant 40 from slowing down, whereby the heat
transfer coefficient of the wavy fins 30 can be improved. Moreover,
the banks 31x and the second banks 90x create flows of the coolant
40 from the raised curved portions 31 toward the opposite lowered
curved portions 32. Thereby, the main stream MS of the coolant 40
that tends to flow straight can be mixed substantially with the
coolant 40 stagnating near the lowered curved portions 32, whereby
the heat transfer coefficient of the wavy fins 30 can be largely
improved.
[0092] The cost, however, is higher with the cooler 4C of the
fourth embodiment because of the sheet member 90 being added as
another component, as compared to the cooler 4 of the first
embodiment. The pressure fluctuations of the coolant 40 are larger
since the space for the coolant 40 to flow in is reduced by the
second banks 90. The pressure loss of the cooler 4C of the fourth
embodiment is, therefore, larger than that of the cooler 4 of the
first embodiment. Since other advantageous effects of the fourth
embodiment are similar to the advantageous effects of the first
embodiment, the description will be omitted.
[0093] While coolers according to the present invention have been
described above, the present invention is not limited to these and
can be modified in various manners without departing from the
subject matter. In the first embodiment, for example, the banks 31x
are integrally formed to the respective raised curved portions 31
by casting. Alternately, the banks 31x may be separate from the
plate 10 and may be joined to the raised curved portions 31 by
welding or bonding. In the first embodiment, the banks 31x are
provided at the base portions 31a of the raised curved portions 31.
Alternately, the banks 31x may be provided at other portions than
the base portions 31a of the raised curved portions 31, for example
at the distal portions 31b of the raised curved portions 31. The
shape and the size of the banks 31x may be changed as required.
[0094] In the second embodiment, one protrusion 31y is provided on
each raised curved portion 31. Alternately, a plurality of
protrusions 31y may be provided on each raised curved portion 31.
For example, two protrusions 31y may be provided at the base
portion 31a of the raised curved portion 31. Alternatively, one
protrusion 31y may be provided at the base portion 31a of the
raised curved portion 31, and another protrusion 31y may be
provided at the distal portion 31b of the raised curved portion 31.
The shape and the size of the protrusions 31y can be changed as
required.
[0095] In the third embodiment, the banks 31x are provided at the
base portions 31a of the raised curved portions 31, while the
second banks 21x are provided at the distal portions 31b of the
raised curved portions 31. Alternately, protrusions may be provided
at the base portions 31a of the raised curved portions 31 instead
of the banks 31x. Alternatively, protrusions may be provided at the
distal portions 31b of the raised curved portions 31 instead of the
second banks 21x.
[0096] In the forth embodiment, the second banks 90x are provided
on the sheet member 90. Alternately, protrusions may be provided on
the sheet member 90.
[0097] In each embodiment mentioned above, the distance (flow path
width) of the adjacent wavy fins 30 is made constant at any points
in the flowing direction, but it may be changed at any points in
the flowing direction.
REFERENCE SIGNS LIST
[0098] 1 Inverter device [0099] 2 Semiconductor device [0100] 3
Insulating substrate [0101] 4, 4A, 4B, 4C Cooler [0102] 10 Plate
[0103] 20 Cooling case [0104] 21 Bottom wall [0105] 21x Second bank
[0106] 30 Wavy fin [0107] 31 Raised curved portion [0108] 31a Base
portion [0109] 31b Distal portion [0110] 31x Bank [0111] 31y
Protrusion [0112] 32 Lowered curved portion [0113] 40 Coolant
[0114] 90 Sheet member [0115] 90x Second bank
* * * * *