U.S. patent application number 09/784117 was filed with the patent office on 2001-08-16 for power inverter.
Invention is credited to Hombu, Mitsuyuki, Kuwabara, Heikichi, Obara, Sanshirou, Sasaki, Kaname, Suzuki, Osamu, Yamamura, Hirohisa, Yasukawa, Akio.
Application Number | 20010014029 09/784117 |
Document ID | / |
Family ID | 18566425 |
Filed Date | 2001-08-16 |
United States Patent
Application |
20010014029 |
Kind Code |
A1 |
Suzuki, Osamu ; et
al. |
August 16, 2001 |
Power inverter
Abstract
A heat sink or cooling case has a cooling channel and at least
one opening formed to face part of the channel. A first seal is
provided outside the at least one opening. A cooling case has a
groove located outside the first seal. Holes are discretely formed
in the groove and leads from the groove to an exterior of the
cooling case. A second seal is provided outside the groove. A
radiating plate constituting a circuit case is mounted on the heat
sink by using a clamping device inn or outside the second seal.
Inventors: |
Suzuki, Osamu; (Chiyoda,
JP) ; Kuwabara, Heikichi; (Tsuchiura, JP) ;
Yasukawa, Akio; (Kashiwa, JP) ; Hombu, Mitsuyuki;
(Hitachinaka, JP) ; Yamamura, Hirohisa;
(Hitachioota, JP) ; Obara, Sanshirou; (Toukai,
JP) ; Sasaki, Kaname; (Hitachinaka, JP) |
Correspondence
Address: |
ANTONELLI TERRY STOUT AND KRAUS
SUITE 1800
1300 NORTH SEVENTEENTH STREET
ARLINGTON
VA
22209
|
Family ID: |
18566425 |
Appl. No.: |
09/784117 |
Filed: |
February 16, 2001 |
Current U.S.
Class: |
363/141 |
Current CPC
Class: |
H05K 7/20927 20130101;
H01L 2924/0002 20130101; H02M 7/003 20130101; H01L 2924/0002
20130101; H01L 2924/00 20130101 |
Class at
Publication: |
363/141 |
International
Class: |
H02M 001/00 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 16, 2000 |
JP |
2000-43519 |
Claims
What is claimed is:
1. A power inverter, comprising: at least one semiconductor module
having a plurality of power inverting semiconductor elements
mounted therein; and a cooling case containing a cooling liquid for
cooling said at least one semiconductor module, wherein said at
least one semiconductor module comprises a semiconductor element
and an electric circuit on a radiating plate, and an upper case
containing said semiconductor elements and electric circuits is
provided on said radiating plate, and said cooling case has a
cooling channel in which the cooling liquid flows and at least one
opening for bring said radiating plate in contact with the cooling
liquid flowing in said cooling channel, and a first seal portion is
provided at a circumference of said at least one opening, and an
annular groove is formed at a circumference of said first seal
portion, and at least one liquid relieving hole is formed in said
annular groove, said hole leading from said groove to a surface of
the cooling case other than the surface of the cooling case in
contact with said radiating plate.
2. The power inverter according to claim 1, wherein means for
clamping said radiating plate and said cooling case together is
provided outside said groove and outside said upper case.
3. The power inverter according to claim 2, wherein a second seal
portion is provided outside said groove, and said clamping means is
provided in or outside said second seal portion.
4. The power inverter according to claim 2, wherein said clamping
means comprises a bolt and a threaded bolt hole provided in said
radiating plate at said first seal portion, and said threaded bolt
hole has a length not extending through said radiating plate.
5. The power inverter according to claim 1, wherein means for
detecting leakage of the cooling liquid is provided in said
groove.
6. A power inverter, comprising: at least one semiconductor module
having a plurality of power inverting semiconductor elements
mounted therein; and a heat sink for cooling said at least one
semiconductor module, wherein said heat sink includes a cooling
channel and at least one opening in communication with said
channel, and a seal portion is provided outside said at least one
opening to maintain liquid tightness against a cooling liquid, and
a liquid relieving gap is formed outside said seal portion and on a
member forming the heat sink, said gap leading to a surface of the
heat sink other than the surface of the heat sink on which said at
least one semiconductor module is mounted.
7. A power inverter, comprising: a circuit case accommodating at
least one semiconductor module; and a cooling case including at
least one opening at a position corresponding to an inner surface
of said circuit case so that a surface of the cooling case which is
located opposite a semiconductor module mounting surface is in
contact with a cooling liquid, wherein a clamping section is
provided outside said circuit case and used to clamp said cooling
case with bolts.
8. The power inverter according to claim 7, wherein an annular
groove that is not in communication with said at least one opening
is formed on an outer peripheral side of said at least one opening
in said cooling case.
9. The power inverter according to claim 8, wherein a seal portion
is provided between said at least one opening in said cooling case
and said groove.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to a power inverter and in
particular, to a power inverter for electric vehicles or hybrid
cars equipped with a plurality of components such as an engine, a
revolving apparatus and the like, which are required to be small
and light.
[0002] A conventional power inverter is disclosed, for example, in
JP-A-11-163572 specification. In this power inverter, a circuit
case for accommodating a substrate having circuit elements mounted
thereon is formed with a window for exposing the substrate, and an
opening of a cooling case (opening for contact cooling) is closed
by a surface portion of the substrate which is exposed from the
window and is the reverse of the substrate surface on which the
circuit elements are mounted. This specification further discloses
a configuration in which a contact area (circuit-case-side contact
area) between the circuit case surrounding the substrate exposing
window and the reverse surface of the substrate is arranged in such
a manner that a liquid releasing gap in communication with an
exterior is located between the above contact area and a contact
area (cooling-case-side contact area) between the cooling case
surrounding the opening for contact cooling and the reverse surface
of the substrate. The gap in communication with the exterior is
used to release a liquid if a seal is damaged.
[0003] The power inverter uses a configuration in which the cooling
case and the circuit substrate are clamped together by bolts
extending from the circuit substrate side. Thus, disadvantageously,
the individual bolts must be sealed and if the sealed portions of
the bolts are degraded, the liquid may leak to the circuit
substrate side from the degraded sealed portions.
[0004] To solve this disadvantage, the circuit substrate and the
cooling case (a heat sink) may be joined or integrated with each
other. In this case, however, if the circuit is to be replaced due
to defect thereof, it must be disassembled and dismantled together
with the cooling case (heat sink). Thus, a new problem arises
particularly with a power inverter for a hybrid vehicle using one
enclosure to house a plurality of circuits; that is, maintenance
for such a power inverter is difficult.
OBJECT AND SUMMARY OF THE INVENTION
[0005] It is an object of the present invention to provide a power
inverter that has an excellent cooling performance, prevents
leakage, and allows size reduction of the apparatus and easy
maintenance.
[0006] The above object is attained by a power inverter in which a
plurality of power inverting semiconductor elements and exothermic
electric parts are provided on insulated substrates, the insulated
substrates are joined to a cooling plate (cooling substrate)
constituting a lower lid of a case for accommodating the insulated
substrates, an upper lid of the case is fixed to the cooling plate
with screws or the like to constitute a power module, a heat sink
having an opening is arranged in contact with a bottom surface of
the cooling plate, a first seal portion is provided outside the
opening and a groove is formed outside the first seal portion and
in an outer wall of the heat sink, holes are formed in the groove
at a plurality of locations so as to communicate with an outer
surface side of the heat sink, and the heat sink and the cooling
plate are clamped together outside the upper lid of the case and
outside the groove formed in the heat sink.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] FIG. 1 is a view showing a configuration of a cooling
section of a power inverter module according to a first embodiment
of the present invention;
[0008] FIG. 2 is a sectional view taken along a line II-II in FIG.
1;
[0009] FIG. 3 is a sectional view taken along a line III-III in
FIG. 2;
[0010] FIG. 4 is a sectional view taken along a line IV-IV in FIG.
2;
[0011] FIG. 5 is a view showing a configuration of a cooling
section of a power inverter module according to a second embodiment
of the present invention;
[0012] FIG. 6 is a view showing a configuration of a cooling
section of a power inverter module according to a third embodiment
of the present invention;
[0013] FIG. 7 is a view showing a configuration of a cooling
section of a power inverter module according to a fourth embodiment
of the present invention;
[0014] FIG. 8 is a view showing a configuration of a cooling
section of a power inverter module according to a fifth embodiment
of the present invention;
[0015] FIG. 9 is a view showing a configuration of a cooling
section of a power inverter module according to a sixth embodiment
of the present invention;
[0016] FIG. 10 is a view showing a configuration of a cooling
section of a power inverter module according to a seventh
embodiment of the present invention; and
[0017] FIG. 11 is a main circuit diagram of a drive system to which
the present invention is applied.
DESCRIPTION OF THE EMBODIMENTS
[0018] Embodiments of the present invention will be described
hereinafter with reference to FIGS. 1 to 11.
[0019] First, functions of a power inverter according to the
present invention will be described with reference to FIG. 11. FIG.
11 shows the configuration of a drive system of an electric car in
a circuit diagram principally showing the power inverter.
[0020] The power inverter of this embodiment uses an inverter
circuit to invert a DC current from a battery 302 into an alternate
current of variable voltage and frequency to control a three-phase
AC electric motor 305 to thereby drive wheels of the vehicle (not
shown). The inverter circuit has a filter capacitor 303 connected
to a DC side thereof to remove ripple components from a DC current
from the battery 302. Additionally, the inverter circuit comprises
power semiconductor elements such as a semiconductor switching
element 301a, for example, an IGBT, and an inverse parallel diode
301b. The inverter circuit outputs a PWM-modulated three-phase
alternate current of variable voltage and frequency from an input
direct current by outputting a pulse having three levels, that is,
positive, negative, and neutral levels. The electric motor 305 has
its rotation controlled when an alternate current of variable
voltage and frequency is input thereto and the rotation is
transmitted to the wheels for power running of the automobile.
Additionally, during a regeneration period when the electric motor
305 is operated as a generator, contrary to the power running,
energy flows to the battery 302.
[0021] A microcomputer control circuit 308 PWM controls a power
supply to the electric motor 305 by using a current sensor 304 and
an encoder 306 to detect an output torque from the electric motor
305 and a rotation speed thereof and calculating these values to
control a gate circuit 307 for an IGBT 301. In the PWM control of
this embodiment, a carrier frequency is set at about 10 kHz to
prevent operational sounds of the inverter from becoming noise.
[0022] In the above described power inverter, main exothermic
electric parts are the semiconductor switching element 301a and the
inverse parallel diode 301b, the sizes of which depend chiefly on
the cooling performance. That is, semiconductor elements and
modules must be maintained at a fixed temperature or lower in order
to ensure operations of the elements or make them reliable by, for
example, preventing module structures from being destroyed due to
thermal fatigue. Thus, a liquid cooling structure which has a high
cooling performance is employed to increase an amount of power that
can be processed by the semiconductor elements. That is, an amount
of power processed by the semiconductor elements per unit volume
increases to correspondingly allow the size of the semiconductor
elements to be reduced.
[0023] On the other hand, in a case where a power inverter of such
liquid cooling type is mounted in the vehicle, if electric parts in
the power inverter get wet with a leaking liquid, not only the
apparatus may be hindered from functioning but its components may
also be destroyed or made inoperative due to a short circuit or an
improper insulation. As a result, the parts must be replaced with
new ones or large costs are required for repairs. Furthermore, from
the view point of the safety of occupants in the vehicle, the
possibility of giving an electric shock to the occupants must
sufficiently be excluded. Therefore, the electric parts of the
power inverter of liquid cooling type must each employ a structure
that is as unlikely to get wet as possible.
[0024] The power inverter according to embodiments of the invention
described hereinafter can meet these requirements.
[0025] A first embodiment of the power inverter of the present
invention will be described with reference to FIGS. 1 to 4. FIG. 1
is a view showing a configuration of a cooling section of a power
inverter module according to a first embodiment of the present
invention. FIG. 2 is a sectional view taken along a line II-II in
FIG. 1. FIG. 3 is a sectional view taken along a line III-III in
FIG. 2. FIG. 4 is a sectional view taken along a line IV-IV in FIG.
2.
[0026] This embodiment shows a power inverter for a hybrid vehicle
and shows an example of a case where two respectively independent
inverter circuits are mounted to control two revolving electric
apparatus. These drawings principally show semiconductor modules
and heat sinks (cooling cases or substrates) for cooling the
semiconductor modules and omit description of other electric parts
such as a capacitor and a microcomputer control circuit, wiring,
and others.
[0027] First, the configuration of this embodiment will be
described. The semiconductor module comprises semiconductor
elements 102 and other electric-circuit parts mounted on insulated
substrates 103. Furthermore, the insulated substrates 103 are
attached on a radiating plate 104. An upper lid 101 of a circuit
case for accommodating the insulated substrates 103 on which the
semiconductor elements 102 and the like are mounted is fixed to the
radiating plate 104 (radiating plate) with bolts or the like. That
is, the upper lid 101 and the radiating plate 104 form the circuit
case. The radiating plate 104 has a plurality of through holes for
bolt clamping formed in a frame portion thereof (that is, on the
radiating plate and outside the upper lid). Bolts 106 are inserted
into the through holes to clamp the semiconductor modules and a
heat sink 1 (cooling case) together through seals, described later.
In addition, the radiating plate 104 has radiating fins 105
arranged in parallel with a flowing direction of a cooling liquid
to increase a contact area against the cooling liquid to improve
the cooling capability. Further, electrodes 107 used to connect the
semiconductor modules to other electric parts are provided on the
upper lid 101. In these drawings, the wiring between the
semiconductor elements and these electrodes is omitted.
[0028] The heat sink 1 of this embodiment has two of the above
described semiconductor modules mounted thereon (not only two but
also one or two or more semiconductor modules may of course be
mounted thereon). Each module constitutes an independent inverter
circuit. Such a configuration is also applicable to, for example, a
case where two modules constitute one inverter circuit to control
one large-capacity revolving apparatus. Although not shown, the
present heat sink has other electric parts such as a capacitor 303,
for example, mounted thereon.
[0029] The heat sink 1 of this embodiment has a cooling channel 2
formed therein for passing cooling liquid within one substrate to
cool the semiconductor modules. The cooling channel 2 is formed
with openings 5 such that the cooling liquid can come into direct
contact with the radiating plate 104 for the semiconductor modules
or with the plurality of radiating fins 105 provided along the
flowing direction of the cooling liquid. The openings 5 are sized
to be smaller than dimension of the radiating plate 104 so that the
openings 5 are covered by the radiating plate 104 when the
radiating plate 104 is mounted on the heat sink 1. In addition, an
inlet 3a and an outlet 3b are formed at opposite ends of the
cooling channel 2 on a rear surface of the heat sink 1 opposite to
the openings 5 to introduce and discharge the cooling liquid from
and to an exterior of the heat sink 1. The inlet 3a and outlet 3b
for the cooling liquid may of course be formed at end surface of
the heat sink 1. Furthermore, the heat sink 1 has a plurality of
bolt holes 8 arranged outside the openings 5 so as to surround
them, in order to fix the radiating plate with the semiconductor
modules mounted thereon.
[0030] The heat sink also has annular grooves 6 formed in an area
of an outer surface thereof (opening side surface) between the
openings 5 of the cooling channel and the bolt holes 8. The annular
grooves are sized such that the cooling liquid can flow
therethrough and are hindered from communicating with the cooling
channel 2. Further, the groove 6 has a plurality of holes 7
discretely formed in a bottom surface thereof in communication with
a rear surface of the heat sink 1, that is, the surface located
opposite the surface on which the semiconductor modules are
mounted. In the illustrated embodiment, four of these holes 7 are
formed on one side of the groove 6; that is, a total of eight holes
7 are formed in each groove. When the grooves 6 are thus formed,
the contact area between the radiating plate 104 for the
semiconductor modules and the heat sink 1 is divided into an inner
contact area from the opening 5 to an inner periphery of the groove
6, and an outer contact area from an outer periphery of the groove
6 to an outer periphery of the radiating plate 104.
[0031] Seals for maintaining liquid tightness are respectively
interposed between the radiating plates 104 and the heat sink 1.
Specifically, a first seal is disposed in the inner contact area
from the opening 5 and the inner periphery of the groove 6, so that
a first seal portion 9 is formed. A second seal is disposed in the
outer contact area from the outer periphery of the groove 6 and the
outer periphery of the radiating plate 104, so that a second seal
portion 10 is formed. These seals may comprise, for example, solid
or liquid gaskets composed of laminated or combined rubber,
compounds, metal, or O rings. In addition, for easy installation,
these two seals may be partly coupled together into one gasket,
which may then be inserted between the heat sink 1 and the
radiating plate 104.
[0032] In this embodiment, the radiating plate of the semiconductor
module is clamped, outside the circuit case, to the heat sink
having the channel for cooling liquid, without providing any
clamping means inside the circuit case accommodating the
semiconductor elements and others.
[0033] Next, the operation of the above-described configuration of
this embodiment will be described. It is in the inner contact areas
that liquid tightness is most difficult to obtain. Thus, the first
seal is disposed in the inner contact areas and is forcedly brought
into contact therewith to obtain liquid tightness. If, however, a
pressure larger than a permissible design value is effected on the
heat sink and the semiconductor modules due to degradation of the
durability of the seals, a decrease in the urging force of the
bolts caused by their loosening, or external factors, the liquid
may leak from the first seal portions.
[0034] Thus, the behavior of the cooling liquid leaking effected if
the first seal portion can no longer maintain liquid tightness for
any reason will be described. The cooling liquid having leaked to
an outside of the first seal portion 9 first flows into the annular
groove 6 located outside the first seal. The groove 6 has the holes
7 formed therein and the holes 7 lead to an exterior of the heat
sink 1 and are opened to atmospheric pressure. Accordingly, even if
a large amount of cooling liquid leaks out of the first seal
portion 9, the pressure of the leaked liquid is lower than that can
be permitted (sealed) by the second seal portion 10. Therefore, the
cooling liquid having flowed into the groove 6 is finally
discharged via the holes 7 to an exterior of the heat sink 1,
specifically, from the surface of the radiating plate 104 which is
located opposite its semiconductor element mounting surface. Thus,
portions of the semiconductor modules other than the radiating
plates do not get with the liquid. That is, the electric parts
mounted on the surfaces of the radiating plates of the
semiconductor modules cannot get wet.
[0035] The most important points of the configuration and operation
of this embodiment are that the outside of the semiconductor
modules has the function of keeping the cooling channel liquid
tight and the function of fixing the semiconductor modules to the
heat sink 1 without providing any means for fixing to the heat sink
1 inside the circuit case of the semiconductor modules.
Accordingly, the possibility that the cooling liquid leaks into the
circuit cases of the semiconductor modules through the bolt holes
are perfectly diminished. Furthermore, since the holes 7 leading to
the outside of the heat sink 1 are discretely formed in the bottom
of the groove 6, rigidity of the heat sink is not reduced, so that
the essential sealing performance is not reduced. Moreover, the
holes 7 are formed only in the flowing direction of the cooling
channel 2 to eliminate the need to provide in the cooling channel
pillars required to form liquid relieving holes, which may hinder
the flow. Accordingly, the resistance in the cooling channel is not
increased, so that it is possible to increase the flow rate of the
cooling liquid, thereby contributing to improving the cooling
performance.
[0036] Next, a second embodiment of the power inverter of the
present invention will be described with reference to FIG. 5. FIG.
5 is a sectional view of cooling structure for the semiconductor
modules.
[0037] This embodiment differs from the first embodiment in that
clamping bolts 106b are provided in the pressure contact areas of
the first seal portion 9. It should be noted that for the clamping
bolts in the first seal portion 9, through-holes are formed in the
heat sink 1, while internal thread holes are formed in the
radiating plate 104 but processed so as not to penetrate through
the substrate into the case for the semiconductor modules. These
bolts chiefly serve to obtain an appropriate surface pressure in
the pressure contact areas of the first seal portion and to improve
the distribution of surface pressure, thereby further improving the
sealing performance. In addition, since the internal thread holes
do not penetrate the radiating plate 104, the possibility that the
liquid will leak into the semiconductor modules is eliminated.
[0038] A third embodiment of the power inverter of the present
invention will be described with reference to FIG. 6. FIG. 6 is a
sectional view of cooling structure for the semiconductor
module.
[0039] This embodiment differs from the first embodiment in that
leakage sensors 11 are provided in each groove 6. The leakage
sensors 11 detect leakage to issue, for example, an alarm signal to
a driver or stop the operation of the power inverter. Also in this
case, in order to prevent the pressure of the liquid from being
applied to the second seal portion, the groove 6 also has the holes
7 discretely provided at the bottom of the grooves 6, which are in
communication with an atmosphere outside the apparatus. With this
configuration, it is possible to protect the power inverter before
the adverse effects of a failure or the like resulting from the
leakage propagate to other parts.
[0040] Next, a fourth embodiment of the power inverter of the
present invention will be described with reference to FIG. 7. FIG.
7 is a sectional view of cooling section for semiconductor
module.
[0041] In this embodiment, a heat sink cover 12 having a cooling
channel constructed therein is provided. A space corresponding to
an area surrounded by the outer peripheries of the grooves in the
first embodiment is formed in the heat sink 1. The heat sink cover
12 is inserted in the space so as to form grooves corresponding to
the grooves 6 of the first embodiment between the heat sink 1 and
the heat sink cover 12. Additionally, the holes corresponding to
the holes 7 of the first embodiment are discretely formed at the
heat sink cover 12. Alternatively, the function of the holes 7 can
be achieved without providing any special liquid-tightness
maintaining means in a contact surface between the heat sink 1 and
the heat sink cover 12. The heat sink cover 12, constituting the
cooling channel, is fixed on the heat sink 1 by means of clamping
means such as bolts from the rear side of the heat sink cover, and
bolt holes therefor are formed so as not to penetrate the radiating
plate 104. This configuration has advantages to eliminate the
possibility of causing the mounting surface of the semiconductor
module to get wet and to omit working for forming the grooves. In
addition, in this embodiment, the radiating plate is clamped to the
heat sink 1 outside the circuit case for housing the semiconductor
modules, as in the first embodiment.
[0042] Next, a fifth embodiment of the power inverter of the
present invention will be described with reference to FIG. 8. FIG.
8 is a sectional view of cooling section for semiconductor
module.
[0043] The fifth embodiment differs from the first embodiment in
that that surface of the radiating plate 104 for the semiconductor
modules, which comes into contact with the cooling liquid is
smoothed. That is, the embodiment is suitable for a case in which a
direct liquid cooling is used for conventional semiconductor
modules of a type mounted on the heat sink via grease or the like.
In general, a method for mounting such semiconductor modules
comprises forming bolt holes in an outer edge of each module as in
this embodiment. Accordingly, the sealing manner according to the
present invention functions effectively if such conventional
semiconductor modules are directly cooled with a liquid. That is,
the cooling performance can be improved without specializing the
semiconductor modules for the direct liquid cooling type, thereby
contributing to reducing module costs.
[0044] A sixth embodiment of the power inverter of the present
invention will be described with reference to FIG. 9. FIG. 9 is a
sectional view of cooling section for semiconductor module.
[0045] In the embodiment shown in FIG. 9, in addition to the
structure of the embodiment shown in FIG. 8 in which the liquid
contact section is smoothed, a bottom surface of the opening in the
heat sink is located closer to the radiating plate to increase a
flow velocity of the cooling liquid in order to further improve the
cooling performance. That is, in the embodiment shown in FIG. 8,
the opening must have a fixed thickness to allow the groove 6 to be
formed in the heat sink 1, so that a flow passage cross section of
the opening may increase to reduce the flow velocity to thereby
locally degrade the cooling performance. To solve this problem, in
the embodiment shown in FIG. 9, a spacer 13 is provided for
smoothly reducing the flow passage cross section so that the flow
passage cross section directly below the openings 5 can decrease
gradually to increase the flow velocity while minimizing an
increase in pressure loss, thereby further improving the cooling
performance.
[0046] A seventh embodiment of the power inverter of the present
invention will be described with reference to FIG. 10. FIG. 10 is a
sectional view of cooling section for semiconductor module.
[0047] In the embodiment shown in FIG. 10, in addition to the
embodiment shown in FIG. 8, a plurality of projections are provided
in the heat sink near the openings. The projections disturb the
flow of the cooling liquid immediately below the openings 5 to
facilitate heat transmission. That is, the projections are
disturbance facilitator. This disturbance facilitator may comprise
an object such as a group of cylinders or prisms or a wing-shaped
spacer, for example, which disturb a boundary phase formed on the
surface of the radiating plate 104. This has an effect of enabling
the cooling performance to be further improved without using
semiconductor modules specialized for the direct liquid cooling
method, thereby contributing to reducing module costs.
[0048] In the above embodiments, the grooves 6 are respectively
provided so as to surround respective semiconductor modules. The
invention, however, is not limited to this structure. The following
structure may be used. A plurality of semiconductor modules are
mounted on one radiating plate, and openings 5 are provided in a
heat sink 1 at locations corresponding to the plurality of
semiconductor modules. The one radiating plate is fixed to the heat
sink by means of fastener such as bolts at outer periphery portions
(frame) thereof. One annular groove is formed in the heat sink so
as to surround all of the semiconductor modules.
[0049] According to the power inverter of the present invention,
the radiating plate for the semiconductor modules can be brought
into direct contact with the cooling liquid and the possibility of
causing the electric parts mounted in the semiconductor modules to
get wet can be eliminated, thereby providing a very reliable power
inverter having a high cooling performance.
* * * * *