JP2000205769A - Evaporative cooling apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a fluid refrigerant in a refrigerant tank from reversely flowing upon ergent stoppage and traveling on a slope (ascending slope). SOLUTION: A refrigerant tank 3 has an upper end side connected with a lower tank 21 being inclined rearwardly of a vehicle and hence is sharply inclined with respect to the lower tank 21. A reverse flow prevention plate 26 covering a lower side odf a vapor flow outlet 17 over the entire area of the tank in reft and right directions is fixed to an upper end surface of the cooling tank 3 inseted into the lower tank 21 with the aid of a screw and the like. Hereby, the fliid refrigerant reversely flowing toward the vapor flow outlet 17 strikes the reverse flow prevention plate 26 and is repelled, and hence is prevented from scattering from the vapor flowoutlet 17. Further, although upon the vehicle traveling on an ascending slope a refrigerant liquid surface in the refrigeration chamber is relatively raised with repect to the vapor flow outlet 17 becouse the attitude of the cooling tank 3 approches a horizontal one, even if the refrigerant liquid surface moreraises from a lowermost portion of the vapor flow outlet 17, the liquid refrigerant is prevented from scattering from the vapor flow outlet 17 owing to the reverse flow prevention plate 26.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a boiling cooling device for cooling a heating element by repeatedly boiling and condensing a refrigerant.

[0002]

2. Description of the Related Art As a prior art, Japanese Patent Laid-Open No. 9-12661 is known.
A boiling cooling device described in Japanese Patent Publication No. 7-107 is known. This boiling cooling device is used as a heat radiating device for an electric vehicle, and is installed inside a hood. Therefore, in consideration of the mountability inside the bonnet where the installation space in the vertical direction is particularly limited, the radiator 100 and the refrigerant tank 110 are assembled in a substantially right angle direction via the lower tank 120 as shown in FIG. And the refrigerant tank 110 is installed in a greatly inclined posture.

[0003]

However, in the above-mentioned boiling cooling device, since the refrigerant tank 110 is greatly inclined,
For example, when the vehicle suddenly stops or runs on a slope, the refrigerant tank 110
There is a possibility that the liquid refrigerant inside flows back to the radiator 100 side, and it is difficult to stably fill the boiling surface of the refrigerant tank 110 with the liquid refrigerant. In such a case, there is a problem that the boiling surface of the refrigerant tank 110 is apt to cause burnout (rapid rise in temperature) and the heat radiation performance is greatly reduced. In particular, in order to reduce the amount of expensive refrigerant to be charged, there is a demand for cost reduction, and the refrigerant tank 110
As the thickness is reduced, burnout tends to occur on the boiling surface. The present invention has been made based on the above circumstances, and an object of the present invention is to provide a boiling cooling device mounted on a vehicle with a refrigerant tank inclined, so that the liquid refrigerant in the refrigerant tank at the time of a sudden stop or traveling on a slope is used. It is to suppress backflow to the heat radiating part side.

[0004]

The refrigerant tank has an upper end connected to the connecting tank in an inclined posture,
In addition, a part of the upper end opening that opens into the connection tank is covered with the backflow prevention plate. As a result, even when the refrigerant tank is mounted on the vehicle in an inclined position, the liquid refrigerant in the refrigerant tank can be prevented from jumping out of the upper end opening during a sudden stop or traveling on a slope, and the boiling surface of the refrigerant tank can be reduced. Can be stably filled.

The refrigerant tank has a refrigerant chamber for storing the liquid refrigerant corresponding to the mounting surface of the heating element, a vapor outlet from which refrigerant vapor boiling in the refrigerant chamber flows out, and a radiator. A liquid inlet into which the condensed liquid cooled and liquefied by the liquid flows, and a return passage for returning the condensate flowing from the liquid inlet to the refrigerant chamber, wherein the vapor outlet and the liquid inlet are connected to each other as an upper opening. And a part of the steam outlet is covered with a backflow prevention plate. In this case, it is possible to prevent the liquid refrigerant in the refrigerant tank from jumping out of the vapor outlet at the time of a sudden stop or traveling on a slope, and to stably fill the boiling surface of the refrigerant tank with the liquid refrigerant.

(Means of Claim 3) In the boiling cooling device according to Claim 2, the backflow prevention plate covers a lower side of the steam outlet. In this case, the inflow of condensed liquid from the vapor outlet can be prevented by the backflow prevention plate, and the liquid refrigerant in the refrigerant tank can be prevented from jumping out of the vapor outlet during a sudden stop or traveling on a slope (uphill). The effect can also be demonstrated.

According to a fourth aspect of the present invention, in the boiling cooling apparatus according to the second aspect, the backflow prevention plate is formed on the entire surface of the steam outlet by forming a plurality of small holes. Only a part can be covered.

(5) The refrigerant tank has a refrigerant chamber for storing a liquid refrigerant corresponding to the mounting surface of the heating element, a vapor outlet for discharging refrigerant vapor boiling in the refrigerant chamber, and a radiator. A liquid inlet into which the condensed liquid cooled and liquefied by the liquid flows, and a return passage for returning the condensate flowing from the liquid inlet to the refrigerant chamber, wherein the vapor outlet and the liquid inlet are connected to each other as an upper opening. And a part of the liquid inlet is covered with a backflow prevention plate. In this case, the liquid refrigerant in the refrigerant tank can be prevented from jumping out of the liquid inflow port at the time of sudden stop or running on a slope, and the boiling surface of the refrigerant tank can be stably filled with the liquid refrigerant. Further, by providing the backflow prevention plates at both the vapor outlet and the liquid inlet, it is possible to further suppress the liquid refrigerant in the refrigerant tank from jumping out at the time of a sudden stop or traveling on a slope.

(Means of Claim 6) In the boiling cooling device according to claim 5, the backflow prevention plate covers an upper side of the liquid inlet. In this case, the liquid refrigerant in the refrigerant tank can be prevented from jumping out of the liquid inlet when the vehicle is suddenly stopped or traveling on a slope, and the condensate can be recirculated from the lower side of the liquid inlet.

[0010] In the boiling cooling device according to the present invention, the backflow prevention plate may be formed on a whole surface of the liquid inlet by forming a plurality of small holes, so that the backflow preventing plate is provided with the liquid inlet. Only a part can be covered.

(Eighth Means) The heat radiating portion is inclined forward of the vehicle with respect to the connecting tank. In this case, the radiator rises upright when the vehicle travels on a slope (uphill) that requires power, so that a part of the radiator can be prevented from being immersed in the liquid refrigerant, and the required radiating performance can be secured.

[0012]

Next, an embodiment of the present invention will be described with reference to the drawings. (First Embodiment) FIG. 1 is a side view of a boiling cooling device 1.
The boiling cooling device 1 of the present embodiment cools the heating element 2 by repeatedly boiling and condensing the refrigerant, and includes a refrigerant tank 3 for storing a liquid refrigerant therein, and a radiator mounted on the upper part of the refrigerant tank 3. , And manufactured by integral brazing. The heating element 2 is, for example, an IGBT module that forms an inverter circuit of an electric vehicle, and is fixed to the surface of the refrigerant tank 3 with bolts 5 or the like as shown in FIG.

The refrigerant tank 3 comprises a hollow member 6 and an end plate 7, and as shown in FIG. 2, a refrigerant chamber 8, a liquid return passage 9, a heat insulating passage 10, and a communication passage 11 (see FIG. 1).
have. The hollow member 6 is an extruded product made of a metal material having excellent thermal conductivity, such as aluminum, and is shown in FIG.
As shown in FIG. 3, a plurality of ribs (first ribs 1) having different thicknesses are provided in
2, the second rib 13, the third rib 14, and the fourth rib 15). However, as shown in FIG. 3B, the lower ends of the ribs 12 to 15 are deleted by a predetermined length, and the lower ends of the ribs 12 to 15 are higher than the lower end of the hollow member 6. It is located in. Further, the first rib 12 and the third rib 14 are provided with a plurality of screw holes 16 for screwing the bolts 5. The upper end of the hollow member 6 has the left and right third ribs 1.
4 has a height difference between the outer part and the inner part, and the inner part is provided to protrude upward from the outer part,
Further, as shown in FIG. 3 (c), the upper end surface of the inner portion is inclined.

The end plate 7 is made of, for example, the same aluminum as the hollow member 6, is elongated in the left-right direction, and is provided with an inner portion 7b slightly protruding from an outer peripheral edge 7a, as shown in FIG. As shown in FIG. 5, the end plate 7 has an inner portion 7b projecting into the opening at the lower end of the hollow member 6, and an outer peripheral edge 7a is attached to the hollow member 6 as shown in FIG.
The lower end opening of the hollow member 6 is closed by contacting the outer peripheral lower end surface of the hollow member 6. However, a predetermined space is provided between the surface of the inner portion 7b of the end plate 7 fitted into the lower end opening of the hollow member 6 and the lower end surfaces of the ribs 12 to 15 of the hollow member 6.

In FIG. 3B, the refrigerant chamber 8 is provided between the first rib 12 located on the right side of the center of the hollow member 6 and the third ribs 14 on the left and right sides. Are divided into passageways. This refrigerant chamber 8
Defines a space in which the liquid refrigerant stored inside receives the heat of the heating element 2 and boils. In the following description,
The upper opening of the refrigerant chamber 8 that opens at the upper end surface of the hollow member 6 is called a vapor outlet 17. As described above, the vapor outlet 17 projects upward from the upper end opening surface of the liquid return passage 9 and has an inclined opening surface.

The liquid return passage 9 is a passage through which the condensed liquid cooled and liquefied by the radiator 4 flows, and is provided on both left and right sides of the hollow member 6. In the following description, the upper opening of the liquid return passage 9 that opens at the upper end surface of the hollow member 6 is referred to as a liquid inlet 18. The heat insulating passage 10 is a passage for insulating the space between the refrigerant chamber 8 and the liquid return passage 9, and is separated from the refrigerant chamber 8 by the third rib 14, and is separated from the liquid return passage 9 by the fourth rib 15. . The communication passage 11 is connected to the liquid return passage 9.
A passage for supplying the condensed liquid flowing into the refrigerant chamber 8,
It is formed at the lower end of the hollow member 6 closed by the end plate 7 (see FIG. 5), and communicates the liquid return passage 9, the refrigerant chamber 8, and the heat insulating passage 10 with each other.

The radiator 4 is, as shown in FIG.
9, the upper tank 20, the lower tank 21 (the connection tank of the present invention), the refrigerant control plate 22 is installed inside the lower tank 21. The core section 19 is a heat radiating section of the present invention that cools the refrigerant vapor that has boiled by receiving the heat of the heating element 2 by heat exchange with an external fluid (for example, air).
As shown in FIG. 5, the heat radiating tube 23 includes a plurality of heat radiating tubes 23 and heat radiating fins 24 interposed between the heat radiating tubes 23.

The heat radiating tube 23 forms a refrigerant passage through which the refrigerant flows. For example, a flat tube made of aluminum is cut into a predetermined length to form a plurality of tubes between the lower tank 21 and the upper tank 20. The lower tank 21 and the upper tank 20 communicate with each other. The heat radiating fins 24 are formed by alternately bending thin metal plates (for example, aluminum plates) having excellent thermal conductivity to form a wavy shape, and are joined to the surface of the heat radiating tube 23.

The upper tank 20 is constructed by combining a shallow dish-shaped core plate 20A and a deep dish-shaped tank plate 20B, and a plurality of heat radiation tubes are provided in a plurality of long holes (not shown) opened in the core plate 20A. The upper end of 23 is inserted. The lower tank 21 is
Similarly to the above, a shallow dish-shaped core plate 21A and a deep dish-shaped tank plate 21B (see FIG. 6) are combined to radiate heat to a plurality of long holes (not shown) opened in the core plate 21A. The lower end of the tube 23 is inserted, and the upper end of the hollow member 6 is inserted into the opening 25 opened in the tank plate 21B (see FIG. 1). As shown in FIG. 6C, the tank plate 21B has a large inclination angle with respect to the lowest bottom surface (the surface facing the upper opening on which the core plate 21A is covered) in the shape viewed from the longitudinal direction. It has an inclined surface 21a, and the opening 25 is opened in the inclined surface 21a (see FIG. 6).

Therefore, as shown in FIG.
It is attached to the lower tank 21 with a large inclination. When mounted on the vehicle, the refrigerant tank 3 is disposed on the vehicle front side of the radiator 4. That is, the refrigerant tank 3 is connected to the lower tank 21 with the upper end inclined toward the vehicle rear side, and is arranged such that the right side is the vehicle front side and the left side is the vehicle rear side in FIG. The mounting surface of the heating element 2 faces downward so that the vapor outlet 17 faces obliquely upward in the lower tank 21 (accordingly, the heating element 2 is
And is inserted into the lower tank 21 through the opening 25. As shown in FIG. 2, a backflow prevention plate 26 covering the lower side of the steam outlet 17 over the entire region in the left-right direction is fixed to the upper end surface of the hollow member 6 with screws or the like.

The refrigerant control plate 22 is for preventing the condensed liquid cooled and liquefied in the core portion 19 from dropping directly to the vapor outlet 17, as shown in FIG. Both ends of the refrigerant control plate 22 reach the upper part of the heat insulating passage 10, and also cover the vapor outlet 17 and the upper part of the heat insulating passage 10 in the front-rear direction (see FIG. 1). The refrigerant control plate 22 can be attached to the upper end surface of the hollow member 6 inserted into the lower tank 21 with a screw or the like (see FIG. 1). In addition, it is desirable that the refrigerant control plate 22 be mounted in a gently inclined state so that the front end side is slightly higher than the mounting portion side in the front-rear direction shown in FIG.

Next, the operation of this embodiment will be described. The refrigerant vapor boiled by receiving the heat of the heating element 2 in the refrigerant chamber 8 enters the lower tank 21 through the vapor outlet 17, and flows into the lower tank 2.
1 enters each heat radiation tube 23. The refrigerant vapor flowing through the heat radiating tube 23 is cooled by heat exchange with an external fluid passing through the core 19, releases latent heat, and condenses in the heat radiating tube 23. The released latent heat is transmitted from the wall surface of the heat radiating tube 23 to the heat radiating fins 24 and is released to the external fluid via the heat radiating fins 24. On the other hand, the condensed liquid that has condensed into droplets is radiated by the heat radiation tube
And falls down from the heat radiation tube 23 into the lower tank 21.

In the lower tank 21, since the refrigerant control plate 22 covers the upper part of the vapor outlet 17 and the heat insulating passage 10, the condensed liquid dropped from the heat radiation tube 23 flows into the refrigerant chamber 8 from the vapor outlet 17. Can be prevented. The condensed liquid dropped from the heat radiating tube 23 onto the upper surface of the refrigerant control plate 22 flows along the slope of the refrigerant control plate 22 and then passes through the passage formed by the side surface of the lower tank 21 and the refrigerant control plate 22 in the left-right direction It flows into the liquid inlet 18. Lower tank 2
The condensed liquid accumulated at the bottom of the first liquid flows into the liquid inlet 18 when the liquid level exceeds the height of the lowermost part of the liquid inlet 18, and flows from the liquid return passage 9 to the refrigerant chamber 8 through the communication passage 11. Can be refluxed.

Next, the operation when the vehicle stops suddenly and runs on an uphill will be described. a) In the evaporative cooling device 1 of the present embodiment, the refrigerant tank 3 is attached to the radiator 4 with a large inclination toward the rear side of the vehicle. Attempts to jump out of exit 17. On the other hand, since the lower side of the vapor outlet 17 is covered with the backflow prevention plate 26, the liquid refrigerant flowing backward through the refrigerant chamber 8 toward the vapor outlet 17 due to a sudden stop is indicated by an arrow in FIG. As described above, the water is bounced off the backflow prevention plate 26, and is prevented from jumping out from the steam outlet 17.

B) When the vehicle runs uphill, the inclination of the refrigerant tank 3 becomes larger (the attitude of the refrigerant tank 3 becomes closer to a horizontal state). The refrigerant liquid level of 8 rises and approaches the vapor outlet 17. Therefore, the liquid refrigerant in the refrigerant chamber 8 may easily jump out of the vapor outlet 17 while traveling uphill. Even in this case, since the lower side of the vapor outlet 17 is covered with the backflow prevention plate 26, the refrigerant liquid level of the refrigerant chamber 8 temporarily becomes lower than the vapor outlet 17.
7B, the backflow prevention plate 26 prevents the steam from flowing out from the steam outlet 17 as shown in FIG. 7B.

(Effects of the First Embodiment) In this embodiment, the lower side of the steam outlet 17 is covered with the backflow prevention plate 26, so that the vehicle can be stopped suddenly or run uphill. The liquid refrigerant in the refrigerant chamber 8 can be prevented from jumping out from the vapor outlet 17 and the boiling surface of the refrigerant tank 3 (the mounting surface of the heating element).
Can be stably filled with the liquid refrigerant. As a result, it is possible to prevent a decrease in heat radiation performance due to burnout (rapid temperature rise) of the boiling surface. In particular, when the thickness of the refrigerant tank 3 is reduced,
Since the amount of the charged refrigerant is small, when the liquid refrigerant in the refrigerant chamber 8 jumps out of the vapor outlet 17 at the time of a sudden stop or traveling on a slope, burnout tends to occur on the boiling surface. Therefore, in the thinned refrigerant tank 3 of the present embodiment, it can be said that the effect that the backflow prevention plate 26 can prevent the liquid refrigerant from jumping out is extremely large.

Further, by covering the lower side of the steam outlet 17 with the backflow prevention plate 26, the opening of the steam outlet 17 not covered by the backflow prevention plate 26 and the liquid inlet 18 are provided.
Therefore, the condensed liquid stored in the lower tank 21 can flow into the liquid inlet 18 stably. As a result, the refrigerant outlet 8
The condensate flowing into the refrigerant chamber 8 can be reduced, and the effect of preventing the interference between the rising refrigerant vapor and the falling condensate in the refrigerant chamber 8 can be prevented.

(Second Embodiment) FIG. 8 is a side view of the boiling cooling device 1. This embodiment is an example in which the radiator 4 of the boiling cooling device 1 described in the first embodiment is installed to be inclined toward the front of the vehicle. In the boiling cooling device 1, the radiator 4 stands upright when the vehicle travels on a slope (uphill) requiring power, so that a part of the radiator 4 can be prevented from being immersed in the liquid refrigerant, and the required radiant performance can be improved. Can be secured. Of course, also in this embodiment, since the lower side of the steam outlet 17 is covered with the backflow prevention plate 26, it goes without saying that the same effect as in the first embodiment can be obtained.

(Third Embodiment) FIG. 9 is a front view of the boiling cooling device 1. In this embodiment, the liquid inlet 18 and the heat insulating passage 1
This is an example in which the upper side of the upper end opening surface 10a of the No. 0 is covered with a backflow prevention plate 27. In this case, it is possible to prevent the liquid refrigerant in the refrigerant tank 3 from jumping out of the liquid inlet 18 and the upper end opening surface 10a of the heat insulating passage 10 during a sudden stop, traveling on an uphill, or the like. It can be stably filled with liquid refrigerant. Further, since the backflow prevention plate 27 covers the upper side of the liquid inlet 18, it does not hinder the condensate in the lower tank 21 from entering the liquid inlet 18, and from the lower side of the liquid inlet 18. The condensate can be refluxed.

(Fourth Embodiment) FIG. 10 is a front view of the boiling cooling device 1. This embodiment is an example in which a backflow prevention plate 27 having a plurality of small holes 28 is arranged on the entire surface of the liquid inlet 18. Even in this case, the liquid refrigerant in the refrigerant tank 3 can be prevented from jumping out of the liquid inlet 18 at the time of a sudden stop or traveling on an uphill (uphill), and the boiling surface of the refrigerant tank 3 can be stably filled with the liquid refrigerant. Can be. The backflow prevention plate 27 is connected to the heat insulating passage 10.
May be extended to the upper end opening surface 10a of the heat insulating passage 10 like the liquid inlet 18.

(Fifth Embodiment) FIG. 11 is a side view of the boiling cooling device 1. In the present embodiment, the upper end surface of the refrigerant tank 3 is provided at the same height (the vapor outlet 17 and the liquid inlet 18 and the upper end opening surface 10a of the heat insulating passage 10 have the same height). Is an example in which is covered by a backflow prevention plate 26. Even in this case, the liquid refrigerant in the refrigerant chamber 8 can be prevented from jumping out of the vapor outlet 17 at the time of sudden stop or traveling on an uphill (uphill), and the boiling surface of the refrigerant tank 3 can be stably filled with the liquid refrigerant. Can be.

(Sixth Embodiment) FIG. 12 is a side view of the boiling cooling device 1. This embodiment is applied to the evaporative cooling device 1 described in the first embodiment. The lower part of the vapor outlet 17 is covered with the backflow prevention plate 26, and the upper part of the liquid inlet 18 is the backflow prevention plate 27. This is an example covered with. In this case, the liquid refrigerant in the refrigerant tank 3 can be prevented from jumping out of the vapor outlet 17 and the liquid inlet 18 at the time of a sudden stop or traveling on an uphill (uphill) by the two backflow prevention plates 26 and 27. The boiling surface of the refrigerant tank 3 can be more stably filled with the liquid refrigerant.

[Brief description of the drawings]

FIG. 1 is a side view of a boiling cooling device (first embodiment).

FIG. 2 is a front view of a boiling cooling device (first embodiment).

FIG. 3 is a top view (a), a front view (b), and a side view (c) of a hollow member.

FIG. 4 is a side view (a), a plan view (b), and a cross-sectional view (c) of an end plate.

FIG. 5 is a sectional view showing a mounted state of an end plate.

FIG. 6 is a front view (a), a side view (b), and a bottom view (c) of the lower tank.

FIG. 7 is an explanatory diagram at the time of a sudden stop, and FIG. 7B is an explanatory diagram at the time of traveling uphill.

FIG. 8 is a side view of a boiling cooling device (second embodiment).

FIG. 9 is a front view of a boiling cooling device (third embodiment).

FIG. 10 is a front view of a boiling cooling device (fourth embodiment).

FIG. 11 is a side view of a boiling cooling device (fifth embodiment).

FIG. 12 is a side view of a boiling cooling device (sixth embodiment).

FIG. 13 is a sectional view of a boiling cooling device (prior art).

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Boiling cooling device 2 Heating element 3 Refrigerant tank 8 Refrigerant chamber 9 Liquid return passage (Reflux passage) 17 Vapor outlet 18 Liquid inlet 19 Core part (radiator) 21 Lower tank (connection tank) 26 Backflow prevention plate 27 Backflow prevention Board 28 multiple holes

Claims (8)

[Claims] 1. A boiling cooling device mounted on a vehicle, comprising: a refrigerant tank for storing a liquid refrigerant that boils by receiving heat from a heating element; and releasing heat of refrigerant vapor boiling in the refrigerant tank to an external fluid. And a connection tank provided at a lower portion of the heat radiator and connected to an upper end of the refrigerant tank and connecting the refrigerant tub and the heat radiator. The refrigerant tank has an inclined posture. Wherein the upper end is connected to the connection tank, and a part of the upper end opening that opens into the connection tank is covered by a backflow prevention plate. 2. The refrigerant tank has a refrigerant chamber for storing a liquid refrigerant corresponding to a mounting surface of the heating element, a vapor outlet through which refrigerant vapor boiled in the refrigerant chamber flows out, and cooling by the radiator. A liquid inlet into which the condensed liquid that has been liquefied flows, and a reflux passage for returning the condensate flowing from the liquid inlet to the refrigerant chamber. The vapor outlet and the liquid inlet serve as the upper end opening. 2. The boiling cooling device according to claim 1, wherein the device is open in the connection tank, and a part of the steam outlet is covered by the backflow prevention plate. 3. 3. The boiling cooling device according to claim 2, wherein the backflow prevention plate covers a lower side of the steam outlet. 4. The boiling cooling device according to claim 2, wherein the backflow prevention plate has a plurality of small holes and is arranged on the entire surface of the steam outlet. 5. A refrigerant chamber for storing a liquid refrigerant corresponding to a mounting surface of the heating element, a vapor outlet through which refrigerant vapor boiling in the refrigerant chamber flows out, and cooling by the heat radiating portion. A liquid inlet into which the condensed liquid that has been liquefied flows, and a reflux passage for returning the condensate flowing from the liquid inlet to the refrigerant chamber. The vapor outlet and the liquid inlet serve as the upper end opening. 3. The boiling cooling device according to claim 1, wherein the boil cooling device opens in the connection tank, and a part of the liquid inflow port is covered by the backflow prevention plate. 4. 6. The boiling cooling device according to claim 5, wherein the backflow prevention plate covers an upper side of the liquid inlet. 7. The boiling cooling device according to claim 5, wherein the backflow prevention plate has a plurality of small holes and is disposed on the entire surface of the liquid inlet. 8. A boiling cooling device according to claim 1, wherein said heat radiating portion is inclined forward of the vehicle with respect to said connection tank.