Cooling apparatus and cooling method for heating elements

Abstract

A cooling liquid 28 with a boiling temperature lower than the maximum allowed temperature for the operating atmosphere of switching elements 42 and which is highly insulative is used to liquid seal the switching elements 42. This cooling liquid 28 is cooled by a liquid cooler 50. The cooling liquid 28 vaporizes and removes the heat generated by the switching elements 42 to cool the switching elements 42. Vaporized cooling liquid 28 is cooled by the liquid cooler 50 and is liquefied. The switching elements 42 can be efficiently cooled and the size of the apparatus can be reduced.

Description

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a cooling apparatus and a cooling method for heating elements.

[0003] 2. Description of the Related Art

[0004] A type of cooling apparatus for heating elements has been proposed in which IGBT elements (switching elements) used as heating elements are cooled by an inverter constituted from the IGBT elements mounted on an opening of a liquid cooling heat sink. This is described in, for example, Japanese Patent Laid-Open Publication No. Hei 9-121557. In this apparatus, the heat generated by the IGBT elements is transferred to the liquid cooling heat sink by heat conduction and removed by a cooling medium, such as water, flowing through a path formed at the opening of the liquid cooling heat sink. Thereby, the IGBT elements are cooled.

[0005] Another cooling apparatus for heating elements is proposed in which semiconductor elements are liquid sealed by Freon and partitions are provided between the semiconductor elements (for example, Japanese Patent Laid-Open Publication No. Sho 57-141945). In this apparatus, the semiconductor elements are cooled by removing the heat of vaporization of Freon from the semiconductor elements. In this apparatus, decrease in cooling effect due to generation of film of bubbles between the semiconductors is prevented by providing partitions.

[0006] However, in this type of apparatus for cooling IGBT elements using a liquid cooling heat sink, there is a problem that the IGBT elements cannot be effectively or sufficiently cooled. Especially in recent years, there is a strong demand for reducing the size of all devices including the inverter etc., and to fulfill this demand, the switching elements of the inverter are closely packed. Therefore, although sufficient cooling of these switching elements remains a requirement, the amount of heat which can be removed by cooling using heat conduction is not sufficient.

[0007] In the apparatus in which the semiconductor elements are liquid sealed by Freon, some of the semiconductor elements are released from the liquid sealing when the apparatus is tilted, thereby causing a problem where the semiconductor elements are not sufficiently cooled. Moreover, when the semiconductor elements are used for long period of time, the temperature of Freon reaches its boiling temperature causing intense vaporization, generating a vaporization film around the semiconductor elements, and again causing a problem that the semiconductor elements are not sufficiently cooled.

SUMMARY OF THE INVENTION

[0008] One object of a cooling apparatus of heating elements according to the present invention is to efficiently and sufficiently cool the heating elements. Another object of the cooling apparatus of heating elements of the present invention is to sufficiently cool the heating elements, even when the apparatus is tilted. A further object of the cooling apparatus of the heating elements of the present invention is a reduction in size of the apparatus. One object of a cooling method of heating elements according to the present invention is to provide a method for efficiently and sufficiently cooling the heating elements.

[0009] In order to solve the objects mentioned above, the cooling apparatus and cooling method of the heating elements according to the present invention are configured as described below.

[0010] The heating element cooling apparatus according to the present invention is a cooling apparatus for cooling heating elements comprising a liquid sealing container for liquid sealing said heating elements using a cooling liquid having a boiling temperature lower than the allowed temperature of operating atmosphere of said heating elements, and a cooling mechanism for cooling said cooling liquid.

[0011] With the heating element cooling apparatus of the present invention, the heating elements are cooled by removing the heat of vaporization of the cooling liquid having a boiling temperature lower than the allowed temperature of operating atmosphere of the heating elements directly or indirectly from the heating elements, thereby increasing the cooling efficiency. Furthermore, the vaporized gas of the cooling liquid can be liquefied by cooling the gas with the cooling mechanism. The reliquefied gas can be re-used for cooling the heating elements, placing the temperature of the operating atmosphere of the heating elements within the allowed temperature range.

[0012] In accordance with one aspect of the heating element cooling apparatus of the present invention, said liquid sealing container can be means for removing fluids other than said cooling liquid and for liquid sealing said heating elements using said cooling liquid. With this configuration, the heating elements do not expose themselves out of the cooling liquid even when the apparatus is tilted, and the heating elements can be cooled even in such a case.

[0013] In accordance with another aspect of the heating element cooling apparatus of the present invention, said liquid sealing container can be means having a flow path for the cooling medium used by said cooling mechanism. In this manner, the cooling liquid used for liquid sealing can be cooled using the cooling medium.

[0014] In accordance with further aspect of the heating element cooling apparatus of the present invention, said heating elements can be switching elements and said cooling liquid can be an insulator. With this configuration, electric short-circuiting by liquid sealing can be prevented. In the cooling apparatus of the heating elements of this aspect of the present invention, said cooling liquid can be perfluoro carbon.

[0015] A heating element cooling method according to the present invention is a cooling method for cooling heating elements, comprising the steps of cooling said heating elements using the heat of vaporization of a cooling liquid having a boiling temperature lower than the allowed temperature of the operating atmosphere of said heating elements and contacting with at least some of said heating elements, and cooling said cooling liquid using a cooling medium different from said cooling liquid.

[0016] With the heating element cooling method of the present invention, cooling can be efficiently performed because the heating elements are cooled by directly or indirectly removing the heat of vaporization of the cooling liquid having a boiling temperature lower than the allowed temperature of the operating atmosphere of the heating elements from the heating elements. Moreover, by cooling the cooling liquid using a cooling medium other than the cooling liquid, vaporized gas of the cooling liquid can be liquefied and the liquefied gas can be re-used for cooling the heating elements, thereby maintaining the temperature of the operating atmosphere of the heating elements within the allowed temperature range.

[0017] In accordance with one aspect of the cooling method of the heating elements of the present invention, said heating elements can be switching elements and said cooling liquid can be an insulator. In this manner, electric short-circuiting by the liquid sealing can be prevented. In the cooling method of heating elements of this aspect of the present invention, said cooling liquid can be perfluoro carbon.

BRIEF DESCRIPTION OF THE DRAWING

[0018] FIG. 1 is a structural diagram schematically showing an example structure of a cooling apparatus according to the preferred embodiment of the present invention.

DESCRIPTION OF PREFERRED EMBODIMENT

[0019] The preferred embodiment of the present invention is described next. FIG. 1 is a structural diagram schematically showing the structure of a cooling apparatus 20 for cooling switching elements 42 which are heating elements according to one embodiment of the present invention. As shown in the figure, the cooling apparatus 20 of this embodiment comprises a box-shaped case 22 for storing a plurality of switching elements 42 in a storage section 23, cooling liquid 28 filled into the storage section 23 of the case 22, and a liquid cooler 50 for cooling the cooling liquid 28.

[0020] The case 22 is provided with a flow path 26 in the outer wall for a cooling medium such as water. A flow-in end 24 and a flow-out end 25 of the cooling medium are connected to a circulation tube 52 of the liquid cooler 50. The storage section 23 inside the case 22 is sealed and switching elements 42 are placed on a plate 40 by wire bonding 44 at the bottom of the storage section 23. In this example, IGBT (Insulated Gate Bipolar Transistor) elements are used as the heating elements. Because the mounting substrate and electric wiring of the switching elements 42 do not constitute the main section of the present invention, they are neither shown nor explained.

[0021] The cooling liquid 28 to be filled in the storage section 23 of the case 22 has a boiling temperature within the range of operating atmosphere temperatures in which the switching elements can comfortably operate. This cooling liquid 28 also is highly insulative. In the present embodiment, perfluoro carbon (such as Frorinate manufactured by Sumitomo 3M, Co.) which is highly insulative and the boiling temperature of which is lower than the allowed temperature of the operating atmosphere of IGBT. The cooling liquid 28 cools the switching elements 42 by removing the heat generated by the switching elements 42 through vaporization.

[0022] The liquid cooler 50 comprises a circulation tube 52 which is connected to the flow-in end 24 and the flow-out end 25 of the case 22 and which forms a circulation path with the flow path 26 of the case 22, a circulation pump 54 mounted on this circulation tube 52 for circulating the cooling medium through the circulation tube 52, and a radiator 56 also mounted on the circulation tube 52 for cooling the cooling medium using the outside air. The liquid cooler 50 cools the cooling liquid 28 filling the storage section 23 of the case 22 by circulating the liquid medium cooled by the outside air through the circulation tube 52 using the circulation pump 54. Thus, the cooling liquid 28 which is vaporized by the heat of the switching elements 42 is cooled and liquefied by the liquid cooler 50.

[0023] With the heating element cooling apparatus 20 as described above, the switching elements 42 can be cooled by directly or indirectly removing the heat of vaporization of the cooling liquid 28 having a boiling temperature lower than the allowed temperature of the operating atmosphere from the switching elements 42. Moreover, because the cooling liquid 28 is cooled by the liquid cooler 50, vaporized cooling liquid 28 can be liquefied and re-used for cooling the switching elements 42. As a result, the cooling efficiency can be improved and, at the same time, the size of the apparatus can be reduced. Furthermore, because the cooling liquid 28 is highly insulative, electric short circuiting does not occur. The temperature of the operating atmosphere of the switching elements 42 can be placed within the allowed temperature range.

[0024] In the heating element cooling apparatus 20 as described, because the storage section 23 of the case 22 is formed to have a sealed structure and is filled with the cooling liquid 28, the switching elements 42 are not exposed out of the cooling liquid 28, even when the cooling apparatus 20 is tilted, enabling efficient cooling of the switching elements 42 even under such conditions.

[0025] Even though the cooling apparatus 20 of heating elements of the present embodiment is constructed to cool the switching elements 42 which are IGBT used as the heating elements, it can also be constructed to cool switching elements other than IGBT or to cool heating elements other than switching elements.

[0026] In the heating element cooling apparatus 20 described above, perfluoro carbon is used as the cooling liquid 28 to fill the storage section 23 of the case 22, but other liquid coolants can also be used as long as they are sufficiently insulative and have a boiling temperature within the allowed range of temperatures for the operating atmosphere of the switching elements 42. When it is not necessary to consider electrical short-circuiting for the heating elements, the liquid need not be highly insulative.

[0027] In the cooling apparatus 20 of heating elements of the embodiment, the flow path 26 for the cooling medium is provided on the outer wall of the case 22, but a tube can also be provided inside the storage section 23 to form the flow path for the cooling medium.

[0028] The preferred embodiment of the present invention has been described, but this description is not intended to limit the scope of the invention, and variations and modifications can be realized within the spirit and scope of the invention.

Claims

What is claimed is:

1. A cooling apparatus for cooling heating elements, comprising, a liquid sealing container for liquid sealing heating elements using a cooling liquid having a boiling temperature within the allowed temperature range for the operating atmosphere of said heating elements, and a cooling mechanism for cooling said cooling liquid.

2. A cooling apparatus of claim 1, wherein, said heating elements are switching elements and said cooling liquid is an insulator.

3. A cooling apparatus of claim 2, wherein, said cooling liquid is perfluoro carbon.

4. A cooling apparatus of claim 1, wherein, said liquid sealing container removes fluids other than said cooling liquid and liquid seals said heating elements using said cooling liquid.

5. A cooling apparatus of claim 4, wherein, said heating elements are switching elements and said cooling liquid is an insulator.

6. A cooling apparatus of claim 5, wherein, said cooling liquid is perfluoro carbon.

7. A cooling apparatus of claim 1, wherein, said liquid sealing container has a flow path for a cooling medium used by said cooling mechanism.

8. A cooling apparatus of claim 7, wherein, said heating elements are switching elements and said cooling liquid is an insulator.

9. A cooling apparatus of claim 8, wherein, said cooling liquid is perfluoro carbon.

10. A cooling method for cooling heating elements, comprising the steps of, cooling heating elements using the heat of vaporization of a cooling liquid having a boiling temperature within the allowed temperature range for the operating atmosphere of said heating elements and contacting with one or more of said heating elements, and cooling said cooling liquid using a cooling medium other than said cooling liquid.

11. A cooling method of claim 10, wherein, said heating elements are switching elements and said cooling liquid is an insulator.

12. A cooling method of claim 11, wherein, said cooling liquid is perfluoro carbon.