Water cooled inverter

Details Water cooled inverter Water cooled inverter

2002-07-16

2003-09-16

Thompson, Gregory (Department: 2835)

Electricity: electrical systems and devices

Housing or mounting assemblies with diverse electrical...

For electronic systems and devices

C165S080400, C361S707000, C361S719000, C361S715000, C363S141000, C257S723000

Reexamination Certificate

active

06621701

ABSTRACT:

CROSS REFERENCE TO RELATED APPLICATIONS
The present application is a continuation of patent application Ser. No. 10/100,012, filed Mar. 19, 2002, the entire disclosure of which is incorporated herein by reference. Priority is claimed based on Japanese patent application no. 2001-311562, filed Oct. 9, 2001.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a water cooled inverter provided with a high heat generating power device such as an insulated gate bipolar transistor (hereinafter referred to as “IGBT”).
2. Description of the Prior Art
An inverter for controlling a high output motor such as a motor for a hybrid electric vehicle generally has a structure as shown in sectional schematic diagrams of
FIGS. 2
,
23
,
25
and
26
.
FIG. 23
shows a conventional example of an indirect cooling structure in which a power module is fixed to a water cooled heat sink via thermal conductive grease, and
FIG. 2
shows a conventional example of a direct cooling structure in which cooling water directly contacts a base plate of a power module.
FIGS. 25 and 26
show improved examples of the direct cooling structure.
In the indirect cooling structure shown in
FIG. 23
, a metal base plate
231
of a power module
230
is fixed to an inverter case
233
integrated with a cooling fin
235
via thermal conductive grease
232
, which inverter case is made of metal such as aluminum die casting.
A water channel
236
is formed by attaching a water channel cover
234
so as to cover the lower part of the inverter case
233
with. A printed circuit board (hereinafter referred to as “PCB”)
15
which is a control circuit board including circuit devices such as a microcontroller
16
, a gate driver
17
, a transformer
18
and an electrolytic capacitor
19
is placed above two power modules
230
which are placed side by side and is fixed to an inverter housing
233
. A supply water channel and a drain channel to supply or drain the cooling water to/from the water channel
236
are placed at appropriate locations (not shown).
The PCB
15
is directly fixed to the inverter housing
233
, but also may be attached to a support plate made of metal such as aluminum die casting and then fixed to the inverter housing
233
. The upper surface of the inverter is covered with a metal cover
14
.
The heat generated by a power semiconductor chip inside the power module
230
is transmitted through the base plate
231
and thermal conductive grease
232
to the fin
235
, which is cooled with cooling water, and dissipated thereby. On the other hand, the heat of the circuit devices mounted on the PCB
15
is dissipated by natural convection and at the same time dissipated from through mounting section and the inverter housing
233
, which inverter housing
233
is cooled with cooling water.
In the direct cooling structure shown in
FIG. 2
, as described in JP-A-9-207583, there are provided a water cooling opening
23
for a module in the inverter housing
21
, and a metallic base
11
of a power module
10
, which base is fixed to the inverter housing
21
so as to cover the opening
23
.
A water channel
20
is formed by covering the bottom face of the inverter housing
21
with a water channel cover
22
. In this structure, the cooling water directly contacts the metallic bases
11
. By the way, the metallic base
11
is a flat plate, but may be provided with a fin. The other configurations including that of the control board are the same as those in
FIG. 23
, and the same reference numerals denote the same components.
The greatest advantage of the direct cooling structure over the indirect cooling structure in
FIG. 23
is that it is possible to remove the grease
232
which has low thermal conductivity. This makes it possible to drastically reduce the thermal resistance from the junction of the power semiconductor chip to cooling water, namely Rth(j-w).
If thermal resistance can be reduced, it is possible to reduce a temperature amplitude &Dgr;T due to repetition of heating and cooling of the power semiconductor chip during operation of the inverter. This reduces distortion in the interface between the aluminum wire and power semiconductor chip electrode and distortion in the solder, and thus improves the reliability, wire life and solder life.
Furthermore, FIG.
25
and
FIG. 26
show the structure of a conventional example improved in performance in comparison with the direct cooling structure in
FIG. 2
, by two sections orthogonal to each other. In order to improve the heat dissipation efficiency by cooling water, that is, increase thermal conductivity “h”, it is known to increase the flow velocity of the cooling water.
However, increasing the flow velocity causes an increase in the amount of cooling water, which increases the burden on the pump circulating the cooling water. As a result, the pump capacity needs to be increased.
This leads to an increase in size of the pump, which is fatal if there are strict restrictions on the installation space and weight as in the case of an electric vehicle. Thus, it is preferable to minimize the increase in the amount of cooling water while increasing the flow velocity. This conventional example addresses this problem.
In the water channel structure
250
having an opening
252
where the power module
10
is mounted, a convex section
251
is fixed and a shallow water channel area
254
is provided in the water channel
253
. Since the convex section
251
is provided only under the power module
10
, a high flow velocity section only exists locally under the power module
10
and thereby can prevent an increase of pressure loss. An example similar to this conventional example is described in JP-A-4-2156, etc.
BRIEF SUMMARY OF THE INVENTION
However, the conventional example shown in
FIGS. 25 and 26
, in which the increase of the flow velocity of cooling water is taken into account, has the following problems in the aspects of the system configuration and the cooling performance.
The depth
256
of the shallow water channel which implements high flow velocity is finally restricted by the thickness
257
of the water channel structure
250
. When taking the processing accuracy of components into account, it is practically difficult to allow the convex section
251
to extend into the opening
252
.
It is difficult to reduce the thickness
257
to, for example, 1 to 2 mm from the standpoint of its strength. This becomes more conspicuous in the case of an inverter having a large shape such as a high capacity inverter. Therefore, the conventional structure does not allow the flow velocity to be increased drastically while suppressing the increase of the flow rate.
Furthermore, when the height of the convex section
251
is small, the flow velocity in the area on the power module base plate
11
side in the shallow water channel area
254
is lower than that in the area on the water channel structure
250
side, and therefore the cooling water becomes easily stagnant to prevent efficient heat dissipation and to increase the temperature of the cooling water.
This adversely affects the effect of providing the convex section
251
. Moreover, when the water channel structure
250
has a one-body structure as shown in
FIGS. 25 and 26
, the shape of the convex section
251
shown in
FIG. 26
can hardly be realized in a practical sense.
When consideration is given to inserting the convex section
251
from the opening
252
and fixing there, the convex section
251
must be smaller than the opening
252
. Therefore, it is impossible to significantly increase the flow velocity in the shallow water channel area
254
.
Furthermore, in the case of the above-described conventional example, no consideration is given to mounting a plurality of power modules. In the case of a large capacity inverter, it is hardly imaginable to construct a system only with a single power module. This is because there is a limit to increasing the size of the module when inner stress and yield of the power module are taken into account.
In the above, heat dissi

Affiliated with

Also associated with

Rating

Water cooled inverter does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Water cooled inverter, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Water cooled inverter will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3024085