Cooling device

Abstract

To provide a cooling device capable of storing a sufficient amount of a heating medium in a reservoir section, enabling the heating medium to open a check valve and flow into a heat reception section by applying appropriate pressure to the check valve from the heating medium and maintaining a cooling state based on circulation of the heating medium.SOLUTION: In a heat reception section 11, a reservoir section 17 is provided in a return flow passage 14 toward which a heating medium 80 is caused to flow, and compared to the case where only the return passage 14 is provided, a larger amount of a liquid-phase heating medium can be temporarily stored in the reservoir section 17. Since pressure based on the weight of the liquid-phase heating medium stored in the reservoir section 17 can be applied to a check valve 16, even if heat reception section internal pressure rises along with an increase in a heat input amount to the heat reception section 11, the pressure from the heating medium 80 opens the check valve 16 to cause the heating medium 80 to flow into the heat reception section 11, and thus circulation of the heating medium 80 can be secured so as to enable cooling of a heat generating body to be maintained. Since it is unnecessary to increase the size of an entire device vertically to secure pressure to be applied to the check valve 16 from the liquid-phase heating medium in the return flow passage 14, this can make the entire device compact.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a cooling device for cooling a heat generating body such as a semiconductor element. [Background technology]

[0002] When semiconductor components such as power semiconductors and microprocessors operate, they generate heat, causing their temperature to rise. In the case of semiconductor components that generate a lot of heat, if the temperature rises too high, it may not only reduce processing power due to the thermal protection function, but may also lead to malfunctions or destruction. For this reason, semiconductor components have long been cooled to prevent excessive temperature rise.

[0003] Air-cooled and water-cooled cooling devices are mainly used to cool semiconductor components. However, these conventional cooling devices may not be able to provide sufficient cooling when the heat generated by the semiconductor components increases, and there has been a demand for cooling devices with higher cooling capacity.

[0004] 2. Description of the Related Art In recent years, a loop-type cooling device has been proposed as a cooling device with high cooling capacity, in which a working fluid is circulated and cooled by changing the phase of the working fluid between a liquid phase and a gas phase. This cooling device comprises a box-shaped heat receiving section (heat receiving unit) that transfers heat from the outer wall where a heating element is located to the inner wall to obtain vapor of working fluid, an inlet pipe for injecting the working fluid into the heat receiving section, an outlet pipe for discharging the vapor of working fluid from the heat receiving section, a radiator that releases heat of the vapor of working fluid that has passed through the outlet pipe, and a check valve provided on the opening side of the inlet pipe.

[0005] In this cooling device, the direction of circulation of the working fluid is determined by the increase in outlet pressure after the check valve. The working fluid liquefied in the radiator is returned to the heat receiving section via the check valve. A slit is provided from the inside to the outside of the surface surrounded by the outer periphery of the opening of the inlet pipe on the inner wall of the heat receiving section, and the pressure inside the inlet pipe increases due to the heat from the heating element on the outer wall, causing bubbles and unevaporated working fluid to form a multiphase flow and be discharged to the outlet pipe. This makes it a cooling device with excellent heat absorption performance without the need for a pump. An example of such a conventional cooling device is described in Japanese Patent No. 4978401. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 4978401 Summary of the Invention [Problem to be solved by the invention]

[0007] In the conventional cooling device described in the above patent document, it is essential to make the working fluid leaving the heat dissipation section reach the inlet pipe and the heat receiving section to continue circulating the working fluid. To achieve this, the working fluid needs to push the check valve open against the biasing force that tries to close the valve in order to maintain the backflow prevention state. Usually, the force that opens the check valve is a pressure based on the weight of the liquid phase working fluid present upstream of the check valve.

[0008] In such conventional cooling devices, when the amount of heat generated by the heating element increases, the amount of heat input to the heat receiving section also increases, and the amount of evaporation of the working fluid per unit time also increases, which tends to increase the internal pressure of the heat receiving section. When the internal pressure of the heat receiving section increases in this way, in order to maintain a backflow prevention state in which the working fluid reaches the introduction pipe through the check valve to the heat receiving section, an additional force is required to push the check valve open from above against the force trying to close the valve. For this reason, the amount of liquid phase working fluid present above the check valve in the upstream pipe of the check valve must be increased, and the pressure based on its weight must be increased.

[0009] In order to increase the amount of liquid-phase working fluid in the pipe upstream of the check valve, it is possible to increase the height of the entire cooling device, enlarge the pipe vertically, and increase the amount of liquid-phase working fluid that can exist in the pipe. However, increasing the height of the entire cooling device leads to an increase in the installation space, which limits the objects in which it can be installed. In other words, it was difficult for conventional cooling devices to both be compact and handle a large amount of heat.

[0010] The present invention has been made to solve the above-mentioned problems, and has an object to provide a cooling device that can store a sufficient amount of heat medium in a storage section and apply an appropriate pressure from the heat medium to a check valve, allowing the heat medium to open the check valve and flow into the heat receiving section, thereby maintaining a cooling state based on the circulation of the heat medium. [Means for solving the problem]

[0011] The cooling device according to the disclosure of the present invention is a loop-type thermosiphon cooling device that continuously transfers heat from a high-temperature heat source to a low-temperature heat source by a heat medium that circulates with a phase change, and includes a hollow heat receiving section that transfers heat from a predetermined heat generating body as the high-temperature heat source to an internal heat medium, a hollow heat dissipation section that is located above the heat receiving section and dissipates heat from the internal heat medium to a predetermined external fluid as the low-temperature heat source, a tubular heat dissipation flow path that connects a heat medium outlet of the heat receiving section to a heat medium inlet of the heat dissipation section, and The system comprises a tubular return flow passage that connects the heat medium outlet of the heat dissipation section to the heat medium inlet of the heat receiving section, and a check valve that is provided on the heat medium inlet side of the heat receiving section in the return flow passage and limits the movement of the heat medium from the heat receiving section to the return flow passage side, and a storage section that is connected to the return flow passage at a predetermined location in the return flow passage or that forms part of the return flow passage and is capable of storing a predetermined amount of heat medium, and the storage section stores at least a weight of heat medium that is sufficient to apply pressure to the check valve to open the check valve.

[0012] According to the disclosure of the present invention, a storage section is provided in the return flow path that directs the heat medium to the heat receiving section, and a larger amount of liquid-phase heat medium can be temporarily stored in the storage section than in the case of only the return flow path, and pressure based on the weight of the liquid-phase heat medium stored in the storage section can be applied to the check valve, so that even if the internal pressure of the heat receiving section rises due to an increase in the amount of heat input to the heat receiving section, the pressure from the heat medium opens the check valve and causes the heat medium to flow into the heat receiving section, ensuring circulation of the heat medium and maintaining cooling of the heat-generating body. Also, by storing the liquid-phase heat medium in the storage section, it is not necessary to make the entire device larger vertically to ensure the pressure applied to the check valve from the liquid-phase heat medium in the return flow path, and the entire device can be made compact while obtaining sufficient cooling performance, thereby reducing restrictions on installation.

[0013] In addition, in the cooling device disclosed in the present invention, as necessary, the storage section stores a predetermined weight of heat medium, which is equal to or greater than a lower limit weight of the heat medium derived from the value of the heat quantity per unit time generated by the heating element and a lower limit weight of the heat medium stored in the storage section, based on the mutual relationship between the value of the heat quantity per unit time generated by the heating element and a lower limit weight of the heat medium stored in the storage section.

[0014] Thus, according to the disclosure of the present invention, the size of the storage section is set so that the heat medium stored therein can be stored up to a weight derived from the amount of heat generated by the heat-generating element or more, and even if the amount of heat generated becomes large, pressure can be applied to the check valve from a heat medium of a weight equal to or greater than the amount of heat, so that the check valve can be opened intermittently to allow the heat medium to flow into the heat receiving section, and the heat medium can be circulated smoothly to continue cooling the heat-generating element.

[0015] Furthermore, as necessary, the cooling device disclosed in the present invention is configured so that the relationship between the value of the heat quantity and the lower limit weight of the heat medium is such that the lower limit weight of the heat medium is expressed by a natural exponential function having the value of the heat quantity as a variable, and the storage section stores a predetermined weight of the heat medium that is equal to or greater than the lower limit weight of the heat medium derived from the natural exponential function having the value of the heat quantity as a variable.

[0016] Thus, according to the disclosure of the present invention, the size of the storage section is set so that the heat medium stored therein can store a weight equal to or greater than the value calculated by a functional equation in which the amount of heat generated by the heating element is a variable, and even if the amount of heat becomes large, pressure is applied to the check valve from a weight of heat medium equal to or greater than the weight estimated to be able to appropriately apply pressure to open the check valve in response to the amount of heat. This makes it possible to intermittently open the check valve to allow the heat medium to flow into the heat receiving section, thereby ensuring that the heat medium circulates and maintaining a cooling state for the heating element.

[0017] In addition, in the cooling device disclosed herein, the storage portion forms a communicating portion with the heat medium outlet of the heat dissipation portion in the return flow path and is arranged so as to overlap the underside of the heat dissipation portion, as necessary.

[0018] According to the disclosure of the present invention, the storage section is disposed at the end of the return flow path so as to overlap the heat dissipation section, and the liquid phase heat transfer medium is stored in the storage section and fills almost the entire return flow path to apply pressure to the check valve, so that the weight of the liquid phase heat transfer medium present in the return flow path can be effectively used to apply pressure to the check valve, and the height of the entire device can be reduced accordingly. In addition, by integrating the storage section with the heat dissipation section, the device can be made compact, installation can be easily performed, and the number of parts can be reduced, resulting in lower costs. [Brief description of the drawings]

[0019] [Figure 1] FIG. 1 is a schematic configuration explanatory diagram of a cooling device according to a first embodiment of the present invention. [Diagram 2] FIG. 4 is an explanatory diagram of an arrangement of a heat receiving portion in another cooling device according to the first embodiment of the present invention. [Diagram 3] FIG. 5 is a schematic configuration explanatory diagram of a cooling device according to a second embodiment of the present invention. [Figure 4] 1 is a first graph showing the relationship between the amount of heat and the weight of the heat medium in an embodiment of the present invention. [Diagram 5] 11 is a second graph showing the relationship between the amount of heat and the weight of the heat medium in the embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] (First embodiment of the present invention) Hereinafter, a cooling device according to a first embodiment of the present invention will be described with reference to FIG. In FIG. 1 , the cooling device 1 according to this embodiment includes a heat receiving section 11 which transfers heat from a predetermined heat generating element to a heat medium 80, a heat dissipation section 12 which dissipates heat from the heat medium 80 to a predetermined external fluid, a heat dissipation flow path 13 which connects a heat medium outlet of the heat receiving section 11 to a heat medium inlet of the heat dissipation section 12, a return flow path 14 which connects the heat medium outlet of the heat dissipation section 12 to the heat medium inlet of the heat receiving section 11, a check valve 16 provided on the heat medium inlet side of the heat receiving section 11 in this return flow path, and a storage section 17 capable of storing a predetermined amount of heat medium 80.

[0021] The heat medium 80 used in the cooling device of this embodiment has temperature characteristics that cause a phase change (evaporation) from a liquid phase to a gas phase due to heat generated from the semiconductor element, while at the same time being a compound having excellent chemical stability and high fluidity, such as hydrofluoroether.

[0022] The heat receiving section 11 includes a heat receiving plate 11a that contacts a semiconductor element 90 serving as a heat generating body to receive heat, and a housing section 11b that is provided so as to cover the surface of the heat receiving plate 11a opposite to the contact surface with the semiconductor element 90. The heat receiving section 11 is formed into a hollow container by the heat receiving plate 11a and the housing section 11b, and the hollow portion between the heat receiving plate 11a and the housing section 11b serves as a heat receiving space 70 through which the heat medium 80 flows in and out.

[0023] The heat receiving section 11 is further configured to include an introduction pipe section 11c that introduces the heat medium 80 that has passed through the check valve 16 to the vicinity of the heat receiving plate 11a. This introduction pipe section 11c protrudes into the heat receiving space 70 from a part of the housing section 11b that forms the heat medium inlet of the heat receiving section 11, and is configured so that its tip is in contact with the heat receiving plate 11a or there is a small gap between it and the heat receiving plate 11a.

[0024] The heat receiving plate 11a is a plate-like body made of a material with low thermal resistance, such as copper, aluminum, etc. On the surface of the heat receiving plate 11a opposite to the contact surface with the semiconductor element 90, i.e., on the surface on the heat receiving space 70 side, a plurality of thin grooves (not shown) are formed from a portion facing the inside of the inlet pipe portion 11c to a portion facing the heat receiving space 70 on the outside of the inlet pipe portion 11c. The portion of the heat receiving plate 11a that faces the inside of the introduction pipe portion 11c is located in the center of the heat receiving plate 11a, and is exactly opposite the portion that comes into contact with the semiconductor element 90.

[0025] The housing 11b is provided with an outlet 11d communicating with the heat dissipation flow path 13 as a heat medium outlet of the heat receiving section 11. The heat receiving section 11 sends out the heat medium 80 from the heat receiving space 70 to the heat dissipation flow path 13 through the outlet 11d. On the other hand, the housing 11b has an introduction pipe 11c integrally attached to an opening portion that forms the heat medium inlet of the heat receiving section 11, and the heat medium 80 attempting to flow from the return flow path 14 through the check valve 16 into the heat receiving space 70 of the heat receiving section 11 is first introduced into the introduction pipe 11c.

[0026] In the heat receiving section 11, the heat medium 80 that has reached the heat receiving section 11 first flows into the inlet pipe section 11c and comes into contact with the portion of the heat receiving plate 11a surface facing the inside of the inlet pipe section 11c that is closest to the semiconductor element 90. Here, the heat medium 80 undergoes a phase change (evaporation) of a part thereof due to the heat transferred from the semiconductor element 90 to the heat receiving plate 11a. The pressure inside the inlet pipe section 11c increases due to the volume expansion caused by this phase change. Then, the grown bubbles and the unevaporated heat medium 80 become a mixed-phase flow, and reach the heat receiving space 70 through a groove (not shown) that runs from the inside to the outside of the outlet pipe section 11c on the surface of the heat receiving plate 11a, or through a small gap between the tip of the inlet pipe section 11c and the heat receiving plate 11a. The heat medium 80 that has become a mixed-phase flow flows out of the heat receiving space 70 further through the outlet 11d to the heat dissipation flow path 13.

[0027] The phase change of the heat medium 80 in the heat receiving portion 11 and the mechanism for cooling the semiconductor element 90 are similar to those of known cooling devices of this type, for example, the one shown in Patent Document 1, and a detailed description thereof will be omitted.

[0028] The heat radiating section 12 is located above the heat receiving section 11 and radiates the heat of the heat medium 80 to a predetermined external fluid serving as a low-temperature heat source. The heat dissipation unit 12 is a heat exchanger that introduces a heat medium 80 from a heat dissipation flow path 13 into a hollow portion that is isolated from the outside by a partition wall that serves as a heat transfer unit, and exchanges heat between the air as an external fluid and the heat medium through the partition wall. A fan 12a is provided outside the heat dissipation unit 12, and the airflow forcibly generated by the fan 12a is directed against the partition wall, thereby promoting heat exchange between the air and the heat medium. The configuration of the heat dissipation unit 12 is similar to that of a known heat exchanger such as a radiator that releases heat from a fluid to be cooled flowing inside to the surrounding air, and a detailed description thereof will be omitted.

[0029] The gas-phase heat medium introduced into the heat dissipation section 12 is cooled by heat exchange with the outside air, and condenses to become a liquid-phase heat medium. The heat medium in the heat dissipation section 12 finally leaves the heat dissipation section 12 and proceeds to the return flow path 14.

[0030] The heat dissipation flow path 13 is formed as a tubular body, and connects a heat medium outlet in the heat receiving portion 11 to a heat medium inlet in the heat dissipation portion 12 . The return flow passage 14 is formed as a tubular body, and connects a heat medium outlet in the heat radiating section 12 to a heat medium inlet in the heat receiving section 11. A reservoir section 17 is provided at a predetermined position of the return flow passage 14.

[0031] The check valve 16 is provided on the heat medium inlet side of the heat receiving section 11 in the return flow path 14, and restricts the movement of the heat medium 80 from the heat receiving section 11 to the return flow path 14. The check valve 16 suppresses the backflow of the heat medium 80, thereby determining the circulation direction of the heat medium 80 in the device.

[0032] The storage portion 17 is in the form of a hollow container, and is provided at a predetermined intermediate position in the return flow path 14 so as to form a part of the return flow path 14, and is capable of storing a predetermined amount of heat medium 80 therein. The storage portion 17 stores at least a heat medium 80 having a weight sufficient to apply pressure to the check valve 16 for intermittently opening the check valve 16 .

[0033] More specifically, the storage section 17 stores a predetermined weight of heat medium, which is equal to or greater than the lower limit weight of the heat medium 80 derived from the value of the heat quantity per unit time generated by the semiconductor element 90 as a heat generating element, based on the relationship between the value of the heat quantity per unit time generated by the semiconductor element 90 as a heat generating element and the lower limit weight of the heat medium 80 stored in the storage section 17.

[0034] The relationship between the value of the amount of heat generated per unit time in the semiconductor element 90 and the lower limit weight of the stored heat medium 80 specifically means that the lower limit weight of the heat medium 80 is expressed by a natural exponential function with the value of the amount of heat as a variable. This relationship was derived from a test (see Examples described later) in which a number of conditions were set under which the amount of heat generated in the semiconductor element was changed, and the heat medium weight at which the circulation of the heat medium was established for each condition was obtained.

[0035] In practice, the storage unit 17 is set to a sufficient storage amount based on the lower weight limit of the heat medium derived using the above-mentioned natural exponential function from the value of the amount of heat generated per unit time in the semiconductor element 90 measured in advance. Then, the storage unit 17 stores heat medium 80 in an amount equal to or greater than the lower weight limit of the heat medium, and circulates through the device.

[0036] By setting the amount of heat medium stored in the storage section so that it is equal to or greater than the lower limit weight of the heat medium obtained based on the maximum amount of heat expected to be generated in the semiconductor element 90 within the range allowable in terms of costs and installation conditions, a stable circulation of the heat medium can be maintained.

[0037] In other words, by storing an appropriate amount of heat medium 80 in the storage section 17, together with the heat medium 80 present in the return flow path 14 below the storage section 17, it is possible to apply pressure to the check valve 16 that enables the check valve 16 to open intermittently, regardless of the internal pressure of the heat receiving section 11 (particularly the pressure in the inner part of the inlet pipe section 11c).

[0038] Next, the heat transfer state in the cooling device based on the above configuration will be described. It is assumed that heat is continuously generated in the semiconductor element 90 due to a large current flowing therethrough, and all of the heat generated in the semiconductor element 90 is transferred to the heat receiving plate 11a of the heat receiving part 11 that is in contact with the semiconductor element 90.

[0039] The heat generated in the semiconductor element 90 and transferred from the semiconductor element 90 to the heat receiving plate 11a increases the temperature of the heat receiving plate 11a. In the heat receiving section 11, the liquid phase heat medium 80 that has flowed into the inlet pipe section 11c from the return flow path 14 reaches the surface of the heat receiving plate 11a and receives heat from the heat receiving plate 11a. As a result, at least a part of the liquid phase heat medium 80 evaporates and changes to a gas phase. Meanwhile, the heat of the heat receiving plate 11a is transferred to the heat medium 80, thereby suppressing a further increase in temperature of the heat receiving plate 11a and the semiconductor element 90 integrated therewith.

[0040] As the heat medium 80 evaporates, the pressure inside the inlet pipe portion 11c increases, and the heat medium 80 becomes a mixed phase flow of gas and liquid phases and flows out from the inside of the inlet pipe portion 11c to the heat receiving space 70 on the outside. The pressure of the heat medium 80 is also high in the heat receiving space 70 outside the inlet pipe portion 11c, so the heat medium 80 flows out of the heat receiving portion 11 through the outlet 11d and proceeds to the heat dissipation flow path 13.

[0041] In the heat receiving section 11, the evaporation of the heat medium 80 increases the pressure in the heat receiving space 70, including the inside of the inlet pipe section 11c, but the check valve 16 prevents the heat medium 80 from moving toward the return flow path 14, ensuring that the heat medium 80 can proceed from the heat receiving section 11 to the heat dissipation flow path 13.

[0042] The pressure inside the heat receiving section 11, the heat dissipation flow path 13, the heat dissipation section 12, and the return flow path 14, through which the heat medium 80 circulates, may be reduced to a pressure (e.g., vacuum) lower than atmospheric pressure, and the heat medium 80 may be evaporated at a temperature lower than the original boiling point of the heat medium 80. In this case, the heat medium 80 in contact with the heat receiving plate 11a whose temperature has increased due to the heat of the semiconductor element 90 can be efficiently evaporated, improving the cooling capacity for the semiconductor element 90. In addition, the heat medium that does not evaporate even when in contact with the heat receiving plate whose temperature has increased under atmospheric pressure can be used as an evaporable medium under reduced pressure conditions without any problems, thereby widening the range of heat medium selection.

[0043] The heat medium 80 further proceeds to the heat dissipation section 12 via the heat dissipation flow path 13, where it exchanges heat with air that has been made into a continuous airflow by the fan 12a. In the heat dissipation section 12, the heat medium 80 in the gas phase condenses and becomes liquid, and the heat of the heat medium 80 is released to the air through heat exchange. The heat medium 80 that has released the heat flows out of the heat dissipation section 12 in a liquid phase and proceeds to the return flow path 14.

[0044] The heat medium 80 that has progressed to the return flow passage 14 flows into the storage section 17 and is stored in the region from the storage section 17 to the return flow passage 14 below. A part of the stored heat medium 80 reaches the upper side of the check valve 16 through the return flow passage 14, and the pressure from the stored heat medium 80 is applied to the check valve 16.

[0045] While the check valve 16 is in a closed state, pressure based on the weight of the liquid-phase heat medium 80 accumulated in the reservoir 17 and the return flow path 14 is applied to the upper side of the check valve 16. This pressure is a force that tends to open the check valve 16. With check valve 16 in a closed state, the amount of liquid phase heat medium 80 stored in reservoir 17 gradually increases, and the pressure applied by heat medium 80 to the upper side of check valve 16 also increases.

[0046] On the other hand, while the check valve 16 is in the closed state, no new heat medium 80 flows into the heat receiving section 11. Therefore, as the heat medium 80 continues to flow out of the heat receiving section 11, the heat medium 80 present in the heat receiving space 70 decreases, and the pressure in the heat receiving space 70 including the inside of the introduction pipe section 11c gradually decreases.

[0047] As the check valve 16 continues to be closed, if the pressure applied from the heat medium 80 to the upper side of the check valve 16 (force trying to open the check valve 16) becomes greater than the forces trying to maintain the check valve 16 closed, including the pressure (internal pressure) pushing up the check valve 16 from the heat receiving space 70 side, the check valve 16 temporarily opens. When the check valve 16 opens, the heat medium 80 in the return flow path 14 flows through the check valve 16 into the heat receiving section 11 and reaches the inside part of the introduction pipe section 11c in the heat receiving space 70.

[0048] Due to the inflow of new heat medium 80 into the heat receiving section 11, the pressure in the heat receiving space 70 is restored, and the liquid phase heat medium 80 accumulated in the reservoir section 17 and the return flow path 14 is reduced, decreasing the pressure applied from the heat medium 80 to the upper side of the check valve 16 in the return flow path 14. As a result, when the pressure applied from the heat medium 80 to the upper side of the check valve 16 becomes smaller than the force trying to maintain the check valve 16 in the closed state, the check valve 16 returns to the closed state. In the heat receiving section 11, the liquid phase heat medium 80 flows into the inlet pipe section 11c, causing the liquid phase heat medium 80 to evaporate, and thereafter, the same process as described above is repeated.

[0049] By circulating the heat medium 80 through the heat receiving section 11, the heat dissipation flow path 13, the heat dissipation section 12, and the return flow path 14 as described above, heat transfer (heat reception) from the semiconductor element 90 to the heat medium 80 and heat transfer (heat dissipation) from the heat medium 80 to the external air continue, resulting in continuous cooling of the semiconductor element 90.

[0050] When the amount of heat generated in the semiconductor element 90, which is a heat generating body, increases, the amount of heat input to the heat receiving plate 11a of the heat receiving section 11 increases, and the heat transfer from the heat receiving plate 11a to the heat medium 80 in the heat receiving section 11 also increases. As a result, the amount of evaporation of the heat medium 80 per unit time also increases, and the internal pressure of the heat receiving section 11 also increases accordingly.

[0051] The increase in the internal pressure of the heat receiving section 11 in this way means a stronger force that tries to keep the check valve 16 closed. Therefore, in order to open the check valve 16 and allow the heat medium 80 to flow into the heat receiving section 11, it is essential that the pressure applied from above to the check valve 16 be increased as necessary so as to be able to respond to the increase in the internal pressure of the heat receiving section 11.

[0052] In this embodiment, the return flow path 14 is provided with the storage section 17 so that an appropriate weight of the heat medium 80 can be stored therein, and therefore, when the circulating heat medium 80 reaches and accumulates in the storage section 17, the pressure applied to the upper side of the check valve 16 through the return flow path 14 can be made sufficiently large. In other words, when a sufficient weight of the heat medium 80 accumulates in the storage section 17 and the pressure applied to the check valve 16 based on the heat medium 80 reaches a level capable of opening the check valve 16, the check valve 16 opens and allows the heat medium 80 in liquid phase to flow into the heat receiving section 11.

[0053] In order to increase the weight of the liquid phase heat transfer medium 80 in the return flow passage 14 and increase the pressure applied to the upper side of the check valve 16, it is possible to make the entire cooling device taller and enlarge the return flow passage vertically so that more liquid phase heat transfer medium can be stored in this return flow passage. However, increasing the height of the entire cooling device leads to an increase in the installation space for the device, which creates the problem that it cannot be easily installed. In contrast, the cooling device according to the present embodiment can reduce the height of the entire device, achieving both miniaturization and the ability to handle a large amount of heat generation, which is extremely useful.

[0054] In this manner, in the cooling device according to this embodiment, the storage section 17 is provided in the return flow path 14 that directs the heat medium 80 to the heat receiving section 11, and a larger amount of the liquid phase heat medium 80 can be temporarily stored in the storage section 17 than in the case where only the return flow path 14 is used. Since pressure based on the weight of the liquid phase heat medium 80 stored in the storage section 17 can be applied to the check valve 16, even if the internal pressure of the heat receiving section increases due to an increase in the amount of heat input to the heat receiving section 11, the pressure from the heat medium 80 opens the check valve 16, causing the heat medium 80 to flow into the heat receiving section 11, thereby ensuring circulation of the heat medium 80 and maintaining cooling of the semiconductor element 90, which is a heat-generating body.

[0055] Furthermore, by storing the liquid phase heat medium 80 in the storage section 17, there is no need to increase the vertical size of the entire device to ensure the pressure applied to the check valve 16 from the liquid phase heat medium 80 in the return flow path 14. This makes it possible to make the entire device compact while obtaining sufficient cooling performance, thereby reducing installation constraints.

[0056] In the cooling device according to the embodiment described above, one heat receiving part is provided to circulate the heat medium and release heat from the heat generating body to the heat medium. However, this is not limited to this. As shown in FIG. 2, it is also possible to provide a plurality of heat receiving parts 11 in parallel and transfer heat to the heat medium in each part to cool the heat generating body (semiconductor element 90).

[0057] If the heat medium 80 is stored in the storage section 17 in an amount equal to or greater than the weight of the heat medium corresponding to the amount of heat generated by the heat generating element in contact with each heat receiving section 11, the heat medium 80 can be made to flow into each heat receiving section 11 and heat can be transferred from the heat generating element to the heat medium 80 in each heat receiving section 11, thereby cooling the heat generating element, even when multiple heat receiving sections 11 are connected in parallel. In the cooling device, if the storage section 17 stores a sufficient amount of heat medium 80, the circulation of the heat medium 80 to the heat receiving section 11 can be said to be robust against fluctuations in the number of heat receiving sections and heat medium flow paths installed, and stable circulation of the heat medium is possible.

[0058] In the cooling device according to the embodiment, the air that exchanges heat with the heat medium 80 is forced to pass through the heat dissipation section 12 by the fan 12a, so that the air that exchanges heat with the heat medium 80 is constantly replaced and the temperature conditions during the heat exchange are kept as constant as possible, but the present invention is not limited to this. For example, the heat dissipation section may be arranged so that natural wind is introduced into the heat dissipation section, or when the cooling device itself is installed in a moving object (such as an electric vehicle), the heat dissipation section may be arranged so that airflow caused by the movement flows in, or new air may be sequentially introduced into the heat dissipation section by natural convection of the warmed air after heat exchange. In this case, the heat dissipation section may be arranged so that natural wind is introduced into the heat dissipation section without using a fan, etc.

[0059] In addition, in the cooling device according to the embodiment, air is used as the external fluid that exchanges heat with the heat medium 80 in the heat dissipation unit 12, but the present invention is not limited to this, and a liquid such as water may be used as the external fluid. In this case, as in the embodiment, the liquid may be forcibly sent to the heat dissipation unit by a pump or the like to exchange heat with the heat medium, or the heat dissipation unit may be provided immersed in liquid in a location (e.g., a river, a lake, the sea, etc.) where a large amount of liquid is present and the liquid that has undergone heat exchange with the heat medium is appropriately replaced, so that the temperature change on the liquid side can be almost ignored, and heat exchange between the liquid and the heat medium may be performed.

[0060] (Second embodiment of the present invention) In the cooling device according to the first embodiment, the storage section 17 is provided in the middle of the return flow path 14, but this is not limited thereto. As a second embodiment, as shown in FIG. 3, the storage section 27 can be provided at the end of the return flow path 24 near the heat dissipation section 22, and integrated with the heat dissipation section 22.

[0061] In this case, the heat dissipation section 22 and the storage section 27 have a structure in which they are connected vertically, and after the heat medium 80 that has entered the heat dissipation section 22 exchanges heat, the liquid phase heat medium flows down into the storage section 27 as it is, and the gas phase heat medium flows down into the liquid phase heat medium after condensing.

[0062] Other than the integrated heat dissipation section 22 and storage section 27, and the return flow path 24 connected to the storage section 27, the heat receiving section 21, the heat dissipation flow path 23, and the check valve 26 that constitute the cooling device 2 are similar to those in the first embodiment, and therefore their description will be omitted.

[0063] In addition, the storage section 27 is provided with a plurality of passages through which the air forcibly ventilated into the heat dissipation section 22 by the fan 22a above the heat dissipation section 22 passes, and it goes without saying that the storage section 27 has a mechanism for smoothly flowing out the air after heat exchange with the heat medium 80 in the heat dissipation section 22, thereby enabling continuous heat exchange in the heat dissipation section 22.

[0064] In this way, the storage section 27 is disposed at the end of the return flow path 24 so as to overlap the heat dissipation section 22, and the liquid phase heat transfer medium 80 is stored in the storage section 27 and fills almost the entire return flow path, applying pressure to the check valve 26. Therefore, the weight of the liquid phase heat transfer medium 80 present in the return flow path 24 can be effectively used to apply pressure to the check valve 26, and the height of the entire apparatus can be reduced accordingly. In addition, by arranging the storage portion 27 integrally with the heat dissipation portion 22, the device can be made more compact and easier to install, and the number of parts can be reduced, resulting in lower costs. EXAMPLES

[0065] We evaluated whether the cooling device according to the disclosure of the present invention can continuously cool the heat generating body by allowing the liquid phase heat medium stored in the storage section to flow into the heat receiving section, realizing circulation of the heat medium within the device. Specifically, we obtained the weight of the heat medium in the storage section when circulation of the heat medium was established in the cooling device while changing the amount of heat generated from the heat generating body, and evaluated and verified the condition of the lower limit value of the heat medium weight required for stable operation of the cooling device corresponding to a predetermined amount of heat.

[0066] As a first example of a cooling device according to the disclosure of the present invention, for the example of a cooling device shown in the above embodiment that circulates a heat medium to cool a heat-generating body, tests were conducted to cool the heat-generating body by changing the conditions of the amount of heat generated by the heat-generating body and the weight of the circulating heat medium stored in the storage section, and the relationship between the amount of heat and the weight of the heat medium was investigated.

[0067] The check valve of the cooling device is subjected to a pressure head equivalent to the liquid level of the liquid-phase heat medium from the check valve to the gas-liquid interface in the return flow path and the reservoir, i.e., a pressure based on the weight of the liquid-phase heat medium. If the liquid-phase heat medium opens the check valve and flows into the heat receiving section, and can circulate through the cooling device, the weight of the liquid-phase heat medium calculated from the liquid level of the liquid-phase heat medium at that time can be said to be the effective weight of the heat medium in the reservoir for the amount of heat received by the heat receiving section. The purpose of the test is to find the lower limit of the heat medium weight in the storage section that allows the cooling device to operate stably for a given amount of heat.

[0068] The cooling device has the same configuration as the above embodiment, and the height of the entire device, i.e., the height from the bottom of the heat receiving part to the top of the heat dissipating part, is 1200 mm. Hydrofluoroether (Novec (registered trademark) 7000) was used as the heat medium. This heat medium was filled into the cooling device after the air in the cooling device was evacuated with a vacuum pump before the start of the test.

[0069] The heat receiving section is made of transparent polycarbonate except for the copper heat receiving plate, so that the inside can be seen. The heat receiving surface area of ​​the heat receiving plate is 400 mm 2 (20mm x 20mm). A brass heating block with three cartridge heaters at the bottom is used as the heating element that comes into contact with this heat receiving part. The heat receiving part is placed on the heating block and receives heat from the heating block, which is heated by the heaters. To determine the amount of heat generated, thermocouples are installed at three locations inside the heating block to measure the temperatures at these three locations. The amount of heat generated is calculated from the measured temperatures at the three locations using Fourier's law.

[0070] On the other hand, the heat dissipation unit is a plate-type heat exchanger in which a heat medium flow path and a cooling water flow path are arranged with a heat transfer plate between them, and exchanges heat between the heat medium and the cooling water. The cooling water flow path of the heat dissipation unit is connected by a pipe to a thermostatic bath that supplies cooling water, and cooling water at 25°C is supplied from the thermostatic bath at 1.5 L / min.

[0071] The heat dissipation flow path and the return flow path are made of semi-transparent resin pipes with an inner diameter of 5.5 mm, allowing the heat transfer medium inside to be observed. The reservoir, which is provided as part of the return flow path, is cylindrical with an inner diameter of 56.0 mm.

[0072] The test is performed by heating the heating block so that heat is transferred to the heat receiving part. The power supplied to the cartridge heater of the heating block was increased stepwise to set five different amounts of heat generated by the heating block as a heating element. The five amounts of heat P generated by the heating block were 100, 200, 310, 380, and 420 (unit: W), respectively.

[0073] In the test, the amount of heat transfer medium stored in the storage section, which appears as the liquid level of the liquid heat transfer medium from the check valve to the gas-liquid interface in the storage section, was changed in several ways for each amount of heat, and the minimum liquid level of the liquid heat transfer medium at which the liquid heat transfer medium flows into the heat receiving section and circulates through the device, enabling stable operation of the cooling device to be maintained, was measured.The weight of the heat transfer medium in the storage section was then calculated from the minimum liquid level, and the minimum condition for the weight of the heat transfer medium required to maintain stable operation of the cooling device for a given amount of heat was found.

[0074] Table 1 shows the minimum liquid level h (unit: mm) at which the heat transfer medium can circulate for each of the five heat quantities P, and the lower limit weight G (unit: g) of the heat transfer medium calculated from this value.

[0075] [Table 1]

[0076] 4 and 5 are graphs in which the weight (lower limit) G of the heat medium is plotted against the five different amounts of heat P. As shown in Figure 5, the distribution of heat medium weight G corresponding to heat amount P is almost linear in a graph with the vertical axis (weight) indicated as a logarithmic scale, and it can be presumed that the relationship between heat amount P and weight (lower limit) G is shown as a natural logarithmic function. In other words, it can be presumed that the lower limit weight of the heat medium corresponding to the increased amount of heat generated by the heat generating element increases significantly.

[0077] When we draw an approximation curve from the values ​​of heat quantity and weight, we find that weight G is a natural logarithm function of heat quantity P, G=86.779e 0.0066P It can be expressed as:

[0078] 4 and 5, the curve or line showing the natural logarithm function can be regarded as the lower limit of the weight of the heat medium corresponding to each amount of heat. In these graphs, if the weight of the heat medium is a value above the curve or line showing the natural logarithm function, that is, if the heat medium is stored in the storage section so that the weight of the heat medium in the storage section is equal to or greater than the lower limit, the heat medium can be made to flow into the heat receiving section without straining it in relation to the amount of heat generated, and the cooling device can be maintained in a stable operation.

[0079] From the above results, it can be clearly said that the cooling device disclosed in the present invention is able to apply pressure to the check valve to open it by storing a predetermined weight of heat medium in a storage section, which is equal to or greater than the lower limit weight of the heat medium derived from the amount of heat generated by the heat generating element per unit time, and is able to circulate the heat medium to cool the heat generating element. [Explanation of symbols]

[0080] 1, 2 Cooling device 11, 21 Heat receiving part 11a Heat receiving plate 11b Housing 11c Inlet pipe section 11d outlet 12, 22 Heat radiation part 12a, 22a Fan 13, 23 Heat radiation channel 14, 24 Return flow path 16, 26 Check valve 17, 27 Reservoir 70 Heat receiving space 80 Heat medium 90 Semiconductor elements

Claims

1. In a loop-type thermosiphon cooling device, heat is continuously transferred from a high-temperature heat source to a low-temperature heat source by a heat medium that circulates with a phase change. a hollow heat receiving portion that transfers heat from a predetermined heating element as the high-temperature heat source to an internal heat medium; a hollow heat dissipation section located above the heat receiving section and dissipating heat from the internal heat medium to a predetermined external fluid as the low-temperature heat source; a tubular heat dissipation flow path that connects a heat medium outlet of the heat receiving portion to a heat medium inlet of the heat dissipation portion; a tubular return flow passage that connects a heat medium outlet of the heat dissipation section to a heat medium inlet of the heat receiving section; a check valve provided on a heat medium inlet side of the heat receiving portion in the return flow path to limit movement of the heat medium from the heat receiving portion to the return flow path side, A reservoir portion is provided in communication with the return flow passage at a predetermined location in the return flow passage or forms a part of the return flow passage and is capable of storing a predetermined amount of heat medium; The storage portion stores at least a heat medium having a weight sufficient to apply pressure to the check valve to open the check valve. A cooling device characterized by:

2. 2. The cooling device according to claim 1, The storage unit stores a predetermined weight of the heat medium, the weight being equal to or greater than a lower limit weight of the heat medium derived from the value of the heat quantity, based on a relationship between the value of the heat quantity per unit time generated by the heat generating element and a lower limit weight of the heat medium stored in the storage unit. A cooling device characterized by:

3. 3. The cooling device according to claim 2, The relationship between the value of the calorific value and the lower limit weight value of the heat medium is expressed by a natural exponential function having the value of the calorific value as a variable, The storage unit stores a predetermined weight of the heat medium, the weight being equal to or greater than a lower limit weight of the heat medium derived from a natural exponential function having the value of the heat quantity as a variable. A cooling device characterized by:

4. 2. The cooling device according to claim 1, The storage portion forms a communication portion with the heat medium outlet of the heat radiating portion in the return flow path, and is provided so as to overlap the lower side of the heat radiating portion. A cooling device characterized by:

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