US20120241135A1

US20120241135A1 - Heat exchanger for cooling interior of housing

Info

Publication number: US20120241135A1
Application number: US13/289,360
Authority: US
Inventors: Hiroshi Takigawa; Yoshiki Hashimoto; Yoshikiyo Tanabe
Original assignee: Fanuc Corp
Current assignee: Fanuc Corp
Priority date: 2011-03-22
Filing date: 2011-11-04
Publication date: 2012-09-27
Also published as: JP5053447B1; DE102012102195A1; CN102695402B; JP2012199412A; CN102695402A

Abstract

The air inside a housing containing heat generating parts is forced by an inside air fan to flow in a heat exchanger case through an inside air inlet, flow partially upward and partially downward in an inside air passage while being cooled by inner fins, between the inner fins, installed in the inside air passage, that form a heat exchanger heat sink, and discharge from the inside air passage through an upper, first inside air outlet and a lower, second inside air outlet. The air discharged through the two inside air outlets flows over the surfaces of the heat generating parts in the housing, taking heat from them.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention
The present invention relates to a heat exchanger for cooling the interior of a housing, installable in a small housing and capable of achieving a high heat exchange efficiency and a high flow rate of inside air.
2. Description of the Related Art
In machining factories and the like, electronic parts and electric wiring parts are often contained and used in a sealed housing to prevent them from being contaminated or damaged by dust, cutting fluid, or the like. If the electronic parts contained in the housing generate a large amount of heat and enough heat cannot be dissipated from the surface of the housing, the air temperature inside the housing rises and the temperature of the heat generating parts also rises exceeding their permissible limits, resulting in a shorter life, malfunctioning, or other problems of the electronic parts. Since outside air cannot be taken directly into the housing for ventilation to avoid such problems, an alternative method being used is to use a heat exchanger to exchange heat between the air inside the housing and the air outside the housing.
An example of a prior art heat exchanger for cooling the interior of a housing by exchanging heat between the air inside the housing and the air outside the housing will be described with reference to FIG. 14.
An inside air passage 19 through which the air inside a housing 2 containing heat generating parts flows and an outside air passage 20 through which the air outside the housing 2 flows are separated by a heat exchanger heat sink 12 (see FIG. 3) having fins mounted on both sides of a base plate or corrugated fins 18 (see FIG. 4). An inside air fan 5 forces the air inside the housing 2 to flow in and flow through the inside air passage 19. On the other hand, an outside air fan 6 forces the air outside the housing 2 to flow in and flow through the outside air passage 20. With this, heat is exchanged between the air inside the housing 2 and the air outside the housing 2.
Another example of a prior art heat exchanger for cooling the interior of a housing by exchanging heat between the air inside the housing and the air outside the housing will be described with reference to FIG. 15.
In this heat exchanger, inner fins 14 and outer fins 16 are thermally connected by heat pipes 31 having an extremely high heat conductivity. This heat exchanger has a relatively complicated structure and involves a higher assembly cost.
Japanese Patent Application Laid-Open No. 2005-150667 discloses a heat exchanger for cooling the interior of a housing, which is a cooling device to be retrofitted to the housing and has a double structure formed of an inner air conduit through which the air inside the housing flows and an outer air conduit through which the air outside the housing flows. In this double structure, heat is exchanged between the air inside the housing and the air outside the housing and the heat generated inside the housing is thus dissipated to outside the housing.
As a technical trend in recent years, there are demands for downsizing of the housings containing heat generating parts, similarly to other electronic devices. Downsizing the housing reduces the amount of heat dissipated from its surface, so it is necessary to increase the amount of heat dissipated by a heat exchanger. Consequently, a small-sized heat exchanger having a high heat exchange efficiency is required. A heat exchanger with a high heat exchange efficiency lowers the temperature of the air inside the housing, but does not always lower the temperature of the heat generating parts. This is because the amount of heat dissipated by heat transfer from the heat generating parts to the air inside the housing is proportional to the difference between the temperature of the heat generating parts and the temperature of the air inside the housing, and is also proportional to the square root of the velocity of the air flowing over the surfaces of the heat generating parts.
The use of a stirring fan is also contemplated to increase the velocity of the air flowing inside the housing, but it requires its installation space inside the housing and inevitably enlarges the housing. To increase the velocity of the air flowing inside the housing without using a stirring fan, it suffices to increase the flow rate of the air flowing through the inside air outlets of the heat exchanger. To increase the heat exchange efficiency of a small-sized heat exchanger, heat absorbing fins installed in the inside air passage of the heat exchanger has to be finely pitched to increase their surface areas, but such finely pitched fins would cause a significant pressure drop of the air flowing between them and reduce the flow rate as shown in FIG. 13 according to the pressure-flow rate characteristics (P-Q characteristics) of the inside air fan that forces the air to flow through the inside air passage.
As the technique disclosed in Japanese Patent Application Laid-Open No. 2005-150667 mentioned above employs a special structure in which a single motor is used to rotate both the inner air fan and the outer air fan, a plurality of heat exchanger sections, a cooler (heat exchanger) of which case has an irregular structure, and a partition plate having a complicated shape, parts cost and assembly cost becomes high, and it is difficult to obtain a high flow rate if a centrifugal fan which can easily obtain a high static pressure, is used. Even if an axial fan is used, it is usually difficult to obtain a high flow rate because a partition plate is disposed as a shielding obstacle closely facing the inlet or outlet side of an axial fan in its axial direction.

SUMMARY OF THE INVENTION

In view of prevailing demands for inexpensive heat exchangers for small housings, the above problems should be solved with a heat exchanger with a simple structure by minimizing the number of additional parts, the use of expensive parts, and the increase in assembly cost. With the foregoing circumstances in mind, an object of the present invention is to provide an inexpensive heat exchanger that is installable in a small housing and capable of achieving both a high heat exchange efficiency and a high flow rate of inside air.
A heat exchanger for cooling the interior of a housing according to the present invention includes a heat exchanger case mounted on a wall of a housing containing heat generating parts, the heat exchanger case having an inside air inlet through which an air flows into the housing and an inside air outlet through which an air flows back to the housing formed therein, a single heat exchanger heat sink including a first partitioning member for separating the inside of the heat exchanger case into an inside air passage through which the air from inside the housing flows and an outside air passage through which the air from outside the housing flows, inner fins provided on a surface of the first partitioning member facing the inside air passage, and outer fins provided on a surface of the first partitioning member facing the outside air passage, an inside air fan for forcing the air inside the housing to flow in the inside air passage having the inner fins provided therein through the inside air inlet and discharging the air flowing in the inside air passage through the inside air outlet, and an outside air fan for forcing the air outside the housing to flow in the outside air passage having the outer fins provided therein through an outside air inlet formed in the housing and discharging the air flowing in the outside air passage through an outside air outlet formed in the housing. In this heat exchanger, the first partitioning member, inner fins and outer fins, which form the heat exchanger heat sink, respectively extend in the same longitudinal direction. The inside air outlets include at least one first inside air outlet formed in the heat exchanger case at a portion near one longitudinal end of the heat exchanger heat sink, and at least one second inside air outlet formed in the heat exchanger case at a portion near another longitudinal end of the heat exchanger heat sink. The inside air inlet is formed in the heat exchanger case between the first inside air outlet and the second inside air outlet. The inside air fan is an axial fan disposed facing front edges of the inner fins. The inside air fan forces the air inside the housing to flow in the inside air passage through the inside air inlet and discharge the air flowing through the inside air passage through both of the first inside air outlet and the second inside air outlet.
The inside air inlet and the inside air fan may be installed at a position where the temperature of the air discharged from the first inside air outlet and the temperature of the air discharged from the second inside air outlet become substantially equal to each other.
The heat exchanger case may be a substantially rectangular parallelepiped structure made of a sheet metal, equipped with a flange for attaching the structure to a wall of the housing and having the first inside air outlet and the second inside air outlet formed therein.
The heat exchanger heat sink may be an aluminum or aluminum alloy molded product manufactured by extrusion from a die and cut to a specific dimension in the longitudinal direction without any other cutting process.
A first filling member may be installed between front edges of the inner fins and an inner surface of the heat exchanger case between the inside air inlet and the first inside air outlet, and a second filling member may be installed between the front edges of the inner fins and an inner surface of the heat exchanger case between the inside air inlet and the second inside air outlet.
A second partitioning member having no fins formed on the surface thereof and having substantially the same width as the first partitioning member may be connected to one or both longitudinal ends of the first partitioning member forming the heat exchanger heat sink to separate the one or both longitudinal ends of the heat exchanger heat sink from the heat exchanger case.
The present invention can provide an inexpensive heat exchanger that is installable in a small housing and capable of achieving both a high heat exchange efficiency and a high flow rate of inside air.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects and features of the present invention will be apparent from the following description of embodiments with reference to the appended drawings, in which:

FIG. 1 is a perspective view of a heat exchanger for cooling the interior of a housing according to the first embodiment of the present invention;

FIG. 2 is a schematic sectional view showing the structure of the heat exchanger in FIG. 1;

FIG. 3 is a perspective view of a heat exchanger heat sink used in the heat exchanger in FIG. 1;

FIG. 4 is a perspective view of corrugated fins used in the heat exchanger in FIG. 1;

FIG. 5 is a perspective view of a first variation of the heat exchanger in FIG. 1, with a heat exchanger case having a different structure from that in FIG. 1;

FIG. 6 is a schematic sectional view showing the structure of the heat exchanger in FIG. 5;

FIG. 7 is a schematic sectional view showing a second variation of the heat exchanger in FIG. 1, with an outside air fan and outside air outlets mounted at different positions from those in FIG. 1;

FIG. 8 is a schematic sectional view showing the structure of a heat exchanger for cooling the interior of a housing according to the second embodiment of the present invention;

FIG. 9 is a schematic sectional view showing the structure of a heat exchanger for cooling the interior of a housing according to the third embodiment of the present invention;

FIG. 10A is a schematic sectional view showing the structure of a heat exchanger for cooling the interior of a housing according to the fourth embodiment of the present invention;

FIG. 10B shows the heat exchanger in FIG. 10A, wherein the panel having an outside air fan attached thereto is removed from the housing containing heat generating parts;

FIG. 11A is a schematic sectional view showing the structure of a heat exchanger for cooling the interior of a housing according to the fifth embodiment of the present invention;

FIG. 11B is an external view, as viewed from an inside air fan mounting surface, of the heat exchanger case of the heat exchanger in FIG. 11A from which an inside air fan is removed;

FIG. 12 is a schematic sectional view showing the structure of a heat exchanger for cooling the interior of a housing according to the sixth embodiment of the present invention;

FIG. 13 is a graph schematically showing the pressure-flow rate characteristics (P-Q characteristics) of the axial fan and centrifugal fan;

FIG. 14 is a schematic sectional view of a first example of structure of a prior art heat exchanger for cooling the interior of a housing; and

FIG. 15 is a schematic sectional view of a second example of structure of a prior art heat exchanger for cooling the interior of a housing.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

First Embodiment

A heat exchanger for cooling the interior of a housing according to the first embodiment of the present invention will now be described with reference to FIGS. 1-4.
As shown in FIG. 2, an air inside a housing 2 containing hermetically heat generating parts such as electronic parts and electric wiring parts is forced by an inside air fan 5, which is attached to an outer surface of a heat exchanger case 3 and connected to an inside air inlet 7 and is arranged to face front edges 15 of inner fins 14 (see FIG. 3), to flow in the heat exchanger case 3 through an inside air inlet 7 formed therein and flow into an inside air passage 19. In the inside air passage 19, the air flows partially upward and partially downward, losing heat as it flows between the inner fins 14 installed in the inside air passage 19, and is discharged through the first, or upper, inside air outlet 8 and second, or lower, inside air outlet 9.
The temperature of the air drops because its heat is removed by the inner fins 14. The low temperature air discharged through the first and second inside air outlets 8, 9 flows over the surfaces of the heat generating parts (not shown), taking heat from them and decreasing their temperature. The air inside the heat-generating-part containing housing 2, which circulates within the housing 2 and takes heat from the heat generating parts so that temperature of the air is raised, is forced again by the inside air fan 5 back to the heat exchanger 1.
To keep low the temperature of the heat generating parts, it is required that the difference between the temperature of the heat generating parts and the air temperature inside the housing 2 should be large and that a large volume of air should flow through the first and second inside air outlets 8, 9 and flow over the surfaces of the heat generating parts at high velocity.
In this embodiment, as shown in FIG. 2, the first inside air outlet 8 is formed in the upper section of the inside air passage 19, the second inside air outlet 9 is formed in the lower section of the inside air passage 19, and the inside air fan 5 and inside air inlet 7 are located between the first inside air outlet 8 and the second inside air outlet 9. The heat exchanger heat sink 12 can therefore use long and fine-pitched (i.e., a large number of) fins 14, 16 having a large surface area, as shown in FIG. 3. The fins with a large surface area provide a high heat exchange efficiency.
Since the distance from the inside air inlet 7 to the first and second inside air outlets 8, 9 is shortened and the cross section of the inside air passage 19 through which the air flows upward and downward is enlarged, the pressure drop of the air flow in the inside air passage 19 from the inside air inlet 7 to the first and second inside air outlets 8, 9 is reduced and accordingly a large volume of air can be discharged through the first and second inside air outlets 8, 9.
With the inside air fan 5 and inside air inlet 7 located at a position where the temperature of the air discharged through the first inside air outlet 8 and the temperature of the air discharged through the second inside air outlet 9 become substantially equal to each other, it is possible to avoid a circumstance where an air of insufficient heat dissipation, maintaining high heat, is caused to flow back to the heat-generating-part containing housing 2 through either the first inside air outlet 8 or the second inside air outlet 9. The phenomenon that an air of insufficient heat dissipation, maintaining high heat, is caused to flow back to the heat-generating-part containing housing 2 through only one of the first inside air outlet 8 and the second inside air outlet 9 indicates that the inner fins 14 are only partially used and therefore the heat exchange efficiency is lowered.
The heat exchanger case 3 is a substantially rectangular parallelepiped structure equipped with a flange 4 (see FIG. 5) for attaching the heat exchanger case 3 to an inner wall of the heat-generating-part containing housing 2, as well as openings for the inside air inlet 7 and inside air outlets 8, 9. The heat exchanger case 3 with such a structure can be easily made at low cost by sheet metal working.
The heat exchanger heat sink 12 shown in FIG. 3 is an aluminum or aluminum alloy product molded by extrusion using a die and has identical cross sections at any level in the longitudinal (height) direction. The heat exchanger heat sink 12 can be manufactured at low cost by simply cutting the molded product extruded from the die to a predetermined length without any other cutting process. This heat exchanger heat sink 12 can be manufactured at the lowest cost if it can be manufactured only by cutting the aluminum or aluminum alloy product molded by extrusion from a die to a predetermined length. The parts cost and assembly cost required for the heat exchanger heat sink 12 can be reduced by using a single heat exchanger heat sink 12 for the plurality of inside air outlets 8, 9.
Since the heat exchanger case 3 is a simple rectangular parallelepiped structure that can be manufactured easily only by cutting, bending, and bonding a sheet metal, without any machining or molding process that would increase the manufacturing cost or the thickness of the heat exchanger case 3 and make its downsizing difficult, a thin and lightweight heat exchanger case 3 can be obtained at low cost.
Increasing the width of the heat exchanger heat sink 12 or the height of the fins in order to increase the surface area of the fins would generally require a large and expensive extrusion die. In this embodiment, as can be seen from the shape of the heat exchanger heat sink 12 shown in FIG. 3, since the first partitioning member 13, inner fins 14, and outer fins 16 have their longitudinal directions (height direction in FIG. 3) coincident with the direction of extrusion from the extrusion die, the surface area of the fins can be increased by increasing the length (height) of the heat exchanger heat sink 12 without the need to enlarge the extrusion die. When such a heat exchanger heat sink 12 having its height (longitudinal dimension) larger than its width (lateral dimension) is used, the structure having the inside air inlet 7 disposed between the first inside air outlet 8 and second inside air outlet 9 is particularly effective to increase the flow rate of the inside air. In this first embodiment, corrugated fins 18 shown in FIG. 4 may be used instead of the heat exchanger heat sink 12 shown in FIG. 3 formed of the first partitioning member 13, inner fins 14, and outer fins 16.
In the example shown in FIG. 2, the first and second inside air outlets 8, 9 disposed in the upper and lower sections of the inside air passage 19 are formed in the side of the heat exchanger case 3 to which the inside air fan 5 is attached. Alternatively, at least one of the first and second inside air outlets 8, 9 disposed in the upper and lower sections of the inside air passage 19 may be formed in a side of the heat exchanger case 3 that is perpendicular to the side to which the inside air fan 5 is attached, as shown in FIGS. 5 and 6. FIG. 5 shows an example in which the first inside air outlet 8 is formed in the top of the heat exchanger case 3, while FIG. 6 shows an example in which the first and second inside air outlets 8, 9 are formed in the top and bottom of the heat exchanger case 3.
The first and second inside air outlets 8, 9 formed in the top and/or bottom of the heat exchanger case 3 as shown in FIG. 5 or 6 prevent air accumulation spots from being created in the first corners 25, 25 (see FIG. 2) formed by the first partitioning member 13 and inner fins 14 forming the heat exchanger heat sink 12 and the heat exchanger case 3, so the air can flow smoothly between the inner fins 14 to both longitudinal ends of the heat exchanger heat sink 12. This enables the surfaces of the inner fins 14 to be efficiently utilized for heat exchange and can provide a high heat exchange efficiency. In case where the first and second inside air outlets 8, 9 formed in the top and bottom of the heat exchanger case 3, the low temperature air discharged through the first and second inside air outlets 8, 9 may sometimes become difficult to flow easily toward the heat generating parts, but such a problem may be solved by attaching a deflection plate 27 to at least one of the first and second inside air outlets 8, 9 to deflect the air flow discharged therethrough as shown in FIG. 6.
Furthermore, to suppress the temperature rise of the heat generating parts that generate a particularly large amount of heat, deflection plates (not shown) may be attached to the first and second inside air outlets 8, 9 to selectively direct the air from the outlets 8, 9 toward those heat generating parts.
On the other hand, the air outside the heat-generating-part containing housing 2 is forced by the outside air fan (axial fan) 6 disposed facing front edges 17 of the outer fins 16 to flow in the housing 2 through the outside air inlet 10 formed in the wall of the housing 2. After passing through the outside air fan 6, the air flows into the outside air passage 20, takes heat from the outer fins 16 installed in the outside air passage 20 as it flows between the outer fins 16, and is discharged through the outside air outlet 11. In this embodiment, a baffle plate 28 (see FIG. 2) is provided to prevent the air outside the heat-generating-part containing housing 2 forced by the outside air fan 6 to flow in the outside air passage 20 through the outside air inlet 10 from exiting through the outside air outlet 11 without flowing between the outer fins 16.
In this embodiment, the outside air fan 6 is located near the lower end of the heat exchanger heat sink 12 and the outside air outlet 11 is formed in the housing 2 at a portion near the upper end of the heat exchanger heat sink 12, as shown in FIG. 2. Alternatively, the outside air fan 6 may be located near the upper end of the heat exchanger heat sink 12 and the outside air outlet 11 may be formed in the housing 2 at a portion near the lower end of the heat exchanger heat sink 12. Alternatively, the outside air fan 6 may be located near the middle in the longitudinal direction of the heat exchanger heat sink 12 and one of the outside air outlets may be formed in the housing 2 at a portion near the lower end of the heat exchanger heat sink 12 and the other one of the outside air outlets may be formed in the housing 2 at a portion near the upper end of the heat exchanger heat sink 12, as shown in FIG. 7.
In this embodiment, the heat exchanger heat sink 12 is vertically oriented in the heat exchanger case 3 with the first inside air outlet 8 and second inside air outlet 9 being located near the upper and lower ends, respectively, of the heat exchanger heat sink 12 as shown in FIGS. 2 and 3. Alternatively, the heat exchanger heat sink 12 may be horizontally oriented in the heat exchanger case 3 with the first inside air outlet 8 and second inside air outlet 9 being located near the left and right ends, respectively, of the heat exchanger heat sink 12.
For safety reasons, a fan guard may be provided outside the outside air fan 6 and the outside air outlet 11 may have punched slits to prevent the entrance of foreign matters.
As described above, the heat exchanger according to the first embodiment of the present invention is the same as those of the prior art in that it employs a single heat exchanger heat sink longitudinally extending in the air flow direction and an axial fan advantageous in obtaining a large air flow rate so as to force the air to flow from one end of the heat exchanger heat sink to the other end thereof.
In the heat exchanger according to this embodiment, however, the distance through which the air flows between the inner fins 14 from the inside air inlet 7 to the first and second inside air outlets 8, 9 is approximately one half the distance of the prior art described above and the cross-sectional area of the inside air passage 19 through which the air flows between the inner fins 14 is approximately double that of the prior art. In this embodiment, accordingly, even if the inner fins 14 has the same surface area and the same heat exchange capacity as those of the prior art, the pressure drop of the air flow caused by the inner fins 14 is significantly reduced and the flow rate of the air discharged through the first inside air outlet 8 and second inside air outlet 9 is significantly increased according to the P-Q characteristics of the inside air fan 5, so that the temperature of the air inside the housing as well as the temperature of the heat generating parts can be kept low without using a stirring fan.
Furthermore, according to this embodiment, since the pressure drop of the air flow caused by the inner fins 14 is reduced as described above, fine-pitched inner fins 14 causing a high pressure drop can be used. Consequently, since the volume of the heat exchanger heat sink 12 can be reduced while the surface area of the inner fins 14 can be kept to the same degree, the entire size of the heat exchanger can be reduced. The arrangement of this embodiment is also applicable to a heat-generating-part containing housing 2 of small size. This embodiment is also advantageous in downsizing the entire size of the heat exchanger, because the pressure drop is reduced as described above and a necessary air flow rate can be obtained with a relatively small fan.
The inside air inlet 7 and inside air fan 5 are installed at a position where the amount of heat dissipation per unit flow rate of the inside air from the inside air inlet 7 to the first inside air outlet 8 and the amount of heat dissipation per unit flow rate of the inside air from the inside air inlet 7 to the second inside air outlet 9 become substantially equal to each other. With this, the temperature of the air discharged from the first inside air outlet 8 and the temperature of the air discharged from the second inside air outlet 9 become substantially equal to each other. Consequently, according to this embodiment, it is possible to avoid the reduction of heat exchange efficiency due to partial use of the inner fins as in the case where an air of insufficient heat dissipation, maintaining high temperature, is caused to flow back to the heat-generating-part containing housing 2 through only one inside air outlet and thus a high heat exchange efficiency can be achieved.
From the structural viewpoint, the heat exchanger according to this embodiment only differs from the prior art heat exchanger (illustrated in FIG. 14) in the positions of the inside air inlet and inside air fan and the number of openings for the inside air outlets formed in the heat exchanger case. This means that the heat exchanger according to this embodiment can be manufactured at low cost because there are no additional parts, no replacement with expensive parts, no additional assembling steps, and little factors that increase the cost, as compared with the prior art heat exchanger.
The structure of the heat exchanger shown in FIG. 2 may be modified by attaching both the inside air fan 5 and the outside air fan 6 such that the air is sent in the directions opposite to the directions shown in FIG. 2, replacing accordingly the first and second inside air outlets 8, 9 with the first and second inside air inlets, replacing the inside air inlet 7 and outside air inlet 10 with the inside air outlet and outside air outlet, and replacing the outside air outlet 11 with the outside air inlet.
In this modified structure of the heat exchanger, when an axial fan is used as the inside air fan (and as the outside air fan), the flow rate is not affected much by obstacles (fins in the case of the example in FIG. 2) located on the outlet side, but is significantly reduced by those located on the inlet side, deviating from the P-Q characteristics. The reduction in flow rate of the inside air is against the object of the present invention and the reduction in flow rate of the outside air is also undesirable. On the other hand, increasing the distance between the intake side of the fan and the obstacles to the extent that the flow rate is not affected would unavoidably result in a larger heat exchanger. Although the structure of the heat exchanger according to the first embodiment (FIG. 2) could be modified as described above, the resultant structure would not be desirable to achieve the object of the present invention.

Second Embodiment

A heat exchanger for cooling the interior of a housing according to the second embodiment of the present invention will now be described with reference to FIG. 8.
In the first embodiment described above, the outside air fan 6 is mounted inside the housing 2 containing heat generating parts as shown in FIG. 2. In the second embodiment, the outside air fan 6 is mounted outside the housing 2. With this arrangement, the outside air fan 6 protrudes out of the housing 2.
In the heat exchanger according to this embodiment, if there are no restrictions in aesthetic terms or in terms of the installation location of the housing 2, no baffle plate 28 (see FIG. 6) is required to prevent the air outside the housing 2 forced by the outside air fan 6 to flow in the outside air passage 20 through the outside air inlet 10 from exiting through the outside air outlet 11 without passing through the outer fins 16. Accordingly, in this embodiment, since the space occupied by the baffle plate 28 is not required, the size (in this case, the thickness (i.e., depth)) of the heat exchanger 1 can be reduced, in addition to the reduction in the number of parts, parts cost, and assembly cost.

Third Embodiment

A heat exchanger for cooling the interior of a housing according to the third embodiment of the present invention will now be described with reference to FIG. 9.
In the first embodiment described above, the outside air fan 6 is disposed facing the front edges of the outer fins 16, as shown in FIG. 2.
On the other hand, in the third embodiment, the outside air fan 6 is installed in a space extended in the longitudinal direction from the heat exchanger heat sink 12 (right above the heat exchanger heat sink 12 in FIG. 9) and a third partitioning member 24 is connected to the first partitioning member 13 forming the heat exchanger heat sink 12. With this arrangement, the air forced by the outside air fan 6 to flow in the outside air passage 20 from outside the housing 2 through the outside air inlet 10 flows between the outer fins 16 forming the heat exchanger heat sink 12 without being mixed with the air coming from inside the housing 2 and is discharged through the outside air outlet 11.
In the heat exchanger according to this embodiment, the vertical dimension (height) of the heat exchanger 1 is increased, but its thickness (depth) can be reduced, although the outside air fan 6 does not protrude out of the housing 2 in its depth direction. Consequently, the heat exchanger according to this embodiment is applicable to small housings that have enough height but not enough depth.

Fourth Embodiment

A heat exchanger for cooling the interior of a housing according to fourth embodiment of the present invention will now described with reference to FIGS. 10A and 10B.
In the first embodiment described above, the outside air inlet 10 and outside air outlet 11 are formed in the wall of the heat-generating-part containing housing 2 and the outside air fan 6 is mounted on the inner wall of the housing 2 so as to be connected to the outside air inlet 10, as shown in FIG. 2. On the other hand, in the fourth embodiment, an opening larger than the outside air inlet 10 and outside air outlet 11 is formed in the wall of the heat-generating-part containing housing 2 and is covered by a panel 29 mounted outside the housing 2. This panel 29 has an outside air inlet 10 and an outside air outlet 11 formed as shown in FIG. 10B. The outside air fan 6 is mounted on the side of the panel 29 facing the housing 2 so as to be connected to the outside air inlet 10.
By removing the panel 29 thus arranged from the outside of the housing 2, the outer fins 16 can be exposed easily. The heat exchanger according to this embodiment, therefore, facilitates the cleaning of the outer fins 16 contaminated or clogged by dusts, cutting fluid, etc., sucked from outside the housing 2, as well as the cleaning, replacement, or other maintenance of the outside air fan 6 without the need to open the door of the housing 2 and thus also prevents the interior of the heat-generating-part containing housing 2 from being contaminated by opening the door.

Fifth Embodiment

A heat exchanger for cooling the interior of a housing according to the fifth embodiment of the present invention will now described with reference to FIGS. 11A and 11B.
In the first embodiment described above, the gap between the inside air fan 5 and the front edges of the inner fins 14 is limited to the thickness of a thin metal plate forming the heat exchanger case 3 as shown in FIG. 2. On the other hand, in the fifth embodiment, as shown in FIG. 11A, a first filling member 21 is installed between the front edges 15 of the inner fins 14 and the inner surface of the heat exchanger case 3 between the inside air inlet 7 and the first inside air outlet 8, and a second filling member 22 is installed between the front edges 15 of the inner fins 14 and the inner surface of the heat exchanger case 3 between the inside air inlet 7 and the second inside air outlet 9. The first filling member 21 and the second filling member 22 have the same thickness.
By installing the first filling member 21 and second filling member 22, a gap is formed between the front edges of the inner fins 14 and the inner surface of the heat exchanger case 3 adjacent to the inside air fan 5. With this arrangement, as shown in FIG. 11B, even if the width of the heat exchanger heat sink 12 is larger than the diameter of the inside air fan 5, the air drawn in by the inside air fan 5 reliably flows between the inner fins of the heat exchanger heat sink 12 extending around the inside air fan 5, so a small-sized inside air fan 5 having a small diameter can be incorporated into the heat exchanger 1. Preferably, the first and second filling members 21, 22 have a thickness in the range of several millimeters to a dozen or so millimeters. Increasing the thickness thereof more than necessary is meaningless and would inhibit downsizing of the heat exchanger 1.

Sixth Embodiment

A heat exchanger for cooling the interior of a housing according to the sixth embodiment of the present invention will now be described with reference to FIG. 12.
In the first embodiment described above, the longitudinal (upper and lower) ends of the heat exchanger heat sink 12 are in contact with the heat exchanger case 3 as shown in FIG. 2. On the other hand, in the sixth embodiment, second partitioning members 23, 23 having substantially the same width as the first partitioning member 13 and having no fins on the surface thereof are connected to the longitudinal (upper and lower) ends of the first partitioning member 13 forming the heat exchanger heat sink 12 to separate the longitudinal ends of the heat exchanger heat sink 12 from the heat exchanger case 3. The second partitioning member 23 may be attached to only one end (e.g., only upper end) of the first partitioning member 13 of the heat exchanger heat sink 12 for dimensional reasons.
The second partitioning members 23 thus arranged prevent air accumulation spots from being created in the first corner 25 formed by the first partitioning member 13 and inner fins 14 forming the heat exchanger heat sink 12 and the heat exchanger case 3 and in the second corner 26 formed by the first partitioning member 13, outer fins 16, and heat exchanger case 3. As described above, according to this embodiment, although the second partitioning members 23 slightly increase the cost of the heat exchanger 1, they enhance the heat exchange efficiency by helping the air pass smoothly between the inner fins 14 or outer fins 16 to the upper and lower ends of the heat exchanger heat sink 12 and thus the surfaces of the inner fins 14 and/or outer fins 16 forming the heat exchanger heat sink 12 be used efficiently.
Instead of connecting the second partitioning members 23, 23 to the upper and lower ends of the first partitioning member 13 forming the heat exchanger heat sink 12, the upper and lower sections of the inner fins 14 and/or outer fins 16 forming the heat exchanger heat sink 12 may be partially removed by cutting to separate the longitudinal ends of the heat exchanger heat sink 12 from the heat exchanger case 3.
Adding the cutting process for removing partially the inner fins 14 and/or outer fins 16 of the heat exchanger heat sink 12 molded by extrusion is not desirable, however, because it significantly increases the manufacturing cost of the heat exchanger.
The first and second inside air outlets 8, 9 formed in the top and bottom, instead of being formed in the side wall, of the heat exchanger case 3 as in FIG. 5 or 6 can prevent the air accumulation spots from being created, but make it difficult to direct the cool air discharged through the first and second inside air outlets 8, 9 toward the heat generating parts. In addition, the outside air outlet 11 cannot be formed in the top or bottom of the heat exchanger case 3; it can be formed only in the side wall of the housing 2.
Preferably, the gap between the longitudinal ends of the heat exchanger heat sink 12 and the inner surface of the heat exchanger case 3 is in a range of several millimeters to dozen or so millimeters, because an unnecessarily wide gap between the longitudinal ends of the heat exchanger heat sink 12 and the inner surface of the heat exchanger case 3 could not noticeably increase the heat exchange efficiency.
As described above, according to the present invention, an inexpensive, small-sized heat exchanger 1 can be implemented that is capable of achieving both a high heat exchange efficiency and a high flow rate of inside air and is applicable to a small housing containing parts that generate a large amount of heat. It should be appreciated that the heat exchange efficiency as used herein is a value obtained by dividing the difference between the amount of heat generated inside the housing 2 and the amount of heat dissipated from the surface of the housing 2 by the difference (ΔT (K)) between the air temperature inside the housing 2 and the air temperature outside the housing 2. The amount of heat dissipated from the surface of the housing 2 is a function of ΔT (=the air temperature inside the housing 2 minus the air temperature outside the housing 2) and increases substantially linearly as ΔT increases.

Claims

1. A heat exchanger for cooling the interior of a housing comprising:

a heat exchanger case mounted on a wall of a housing containing heat generating parts, the heat exchanger case having an inside air inlet through which an air flows into the housing and an inside air outlet through which an air flows back to the housing formed therein;

a single heat exchanger heat sink including a first partitioning member for separating the inside of the heat exchanger case into an inside air passage through which the air from inside the housing flows and an outside air passage through which the air from outside the housing flows, inner fins provided on a surface of the first partitioning member facing the inside air passage, and outer fins provided on a surface of the first partitioning member facing the outside air passage;

an inside air fan for forcing the air inside the housing to flow in the inside air passage having the inner fins provided therein through the inside air inlet and discharging the air flowing in the inside air passage through the inside air outlet; and

an outside air fan for forcing the air outside the housing to flow in the outside air passage having the outer fins provided therein through an outside air inlet formed in the housing and discharging the air flowing in the outside air passage through an outside air outlet formed in the housing;

wherein the first partitioning member, inner fins and outer fins, which form the heat exchanger heat sink, respectively extend in the same longitudinal direction;

the inside air outlets include at least one first inside air outlet formed in the heat exchanger case at a portion near one longitudinal end of the heat exchanger heat sink, and at least one second inside air outlet formed in the heat exchanger case at a portion near another longitudinal end of the heat exchanger heat sink;

the inside air inlet is formed in the heat exchanger case between the first inside air outlet and the second inside air outlet;

the inside air fan is an axial fan disposed facing front edges of the inner fins;

the inside air fan forces the air inside the housing to flow in the inside air passage through the inside air inlet and discharge the air flowing through the inside air passage through both of the first inside air outlet and the second inside air outlet.

2. The heat exchanger according to claim 1, wherein the inside air inlet and the inside air fan are installed at a position where the temperature of the air discharged from the first inside air outlet and the temperature of the air discharged from the second inside air outlet become substantially equal to each other.

3. The heat exchanger according to claim 1, wherein the heat exchanger case is a substantially rectangular parallelepiped structure made of a sheet metal, equipped with a flange for attaching the structure to a wall of the housing and having the first inside air outlet and the second inside air outlet formed therein.

4. The heat exchanger according to claim 1, wherein the heat exchanger heat sink is an aluminum or aluminum alloy molded product manufactured by extrusion from a die and cut to a specific dimension in the longitudinal direction without any other cutting process.

5. The heat exchanger according to claim 1, wherein a first filling member is installed between front edges of the inner fins and an inner surface of the heat exchanger case between the inside air inlet and the first inside air outlet, and a second filling member is installed between the front edges of the inner fins and an inner surface of the heat exchanger case between the inside air inlet and the second inside air outlet.

6. The heat exchanger according to claim 1, wherein a second partitioning member having no fins formed on the surface thereof and having substantially the same width as the first partitioning member is connected to one or both longitudinal ends of the first partitioning member forming the heat exchanger heat sink to separate the one or both longitudinal ends of the heat exchanger heat sink from the heat exchanger case.