Cooling body with fibers based on carbon nanostructures

Abstract

The invention relates to a cooling body (1) having a matrix (2) and a plurality of fibers based on a carbon nanostructure (CNB, 3), in particular carbon nanotubes (CNT, 4) or graphite fibers, at least some of which are fixed to the matrix (2). It is provided that the fibers (3, 4) form a bulk structure (12), in particular in the form of cotton wool, felt or yarn, due to their mutual adhesion or support, or that the fibers (3, 4) form loops (6) or a three-dimensional fabric.

Description

Technical Field

[0001] The invention relates to a cooling element having a matrix and a plurality of fibers based on carbon nanostructures (CNB), in particular carbon nanotubes or carbon nanotube bodies (CNT) or graphite fibers, of which some fibers are initially fixed to the matrix for heat conduction. Background Art

[0002] A cooling body of the type mentioned at the outset is known from US 2007158584. The known cooling body has a matrix, with carbon nanostructured fibers being arranged parallel to each other and starting from the matrix. The cooling body is used to cool an object connected to the matrix, wherein the carbon nanostructured fibers are passed through by a cooling medium. Thus, the heat of the object reaches the matrix, from there to the carbon nanostructured fibers and subsequently to the cooling medium.

[0003] Such a heat sink can be used in electronics, in particular in power electronics, for example to dissipate heat generated in power semiconductors. In the field of power electronics in particular, for modern inverters, a heat sink with high efficiency in a small design is required. The present invention relates to a heat sink which, despite being simple to manufacture and in a small design, provides a structure with a large surface, so that large amounts of heat can be dissipated without problems. Summary of the invention

[0004] The cooling body according to the invention comprises a base body and a plurality of cooling bodies based on carbon nanostructured fibers (CNB), in particular carbon nanotubes (CNT) or graphite fibers, at least some of which are fixed to the base body for heat dissipation, wherein the fibers form a bulk structure (volumengefuge) in particular in the form of cotton wool, felt or yarn due to their mutual adhesion or support, or wherein the fibers form loops or three-dimensional fabrics. The invention utilizes the special properties of carbon nanostructured fibers (CNB), in particular carbon nanotubes (CNT) or graphite fibers, which are very good thermal conductivity. Due to the large surface provided by the bulk structure of the fibers, the loops of the fibers or the three-dimensional fabric, the fibers can very effectively dissipate heat to a preferably flowing cooling medium, wherein the cooling medium surrounds or flows through the fibers. In particular, the cooling medium can be a cooling liquid. For the bulk structure, the fibers are in contact with each other, so that there is a kind of adhesion or support, which not only provides the large surface mentioned above, but also produces a relatively strong mechanical structure at the same time, so that even the flowing cooling medium does not deform the fibers or only slightly. More precisely, due to the mentioned structure, a good vortex of the flow of the cooling medium is caused, which leads to better heat dissipation. The "adhesion" mentioned between the fibers does not refer to bonding, etc. in principle, but to a friction resistance, which exists, for example, between two contacting fibers. According to another design, the "mentioned adhesion" still also refers to the bonding of two contacting fibers, for example, by means of an additional substance, such as an adhesive, etc. Soldering points can also be considered. The matrix is ​​connected to the object to be cooled, preferably at least one power semiconductor, by thermal technology.

[0005] According to a further development of the invention, it is provided that the fibers at least partially form an ordered structure and / or at least partially form a disordered structure. In the case of a cotton-like bulk structure, a disordered structure is present. The same applies to felts or yarns. For fibers extending in a ring shape, an ordered structure is rather the starting point. The same applies to the aforementioned fabrics, since there the specific mesh pattern is always repeated.

[0006] A further development of the invention provides a counterpart body which is spaced apart from the matrix and to which at least some of the fibers are fastened. Due to the fastening of the fibers to the matrix and the counterpart body, the entire fiber structure is mechanically particularly well held, so that undesirable deformations due to the flowing cooling medium are not possible. The cooling medium then flows between the matrix and the counterpart body, thereby dissipating heat from the fibers located therebetween. Preferably, the counterpart body is also capable of dissipating heat.

[0007] Preferably, the fixing on the base body and / or on the counterpart is designed as a soldering point, an adhesive point and / or an injection point. The base body and / or the counterpart can be designed, for example, in the form of plates, wherein the aforementioned fixing of the fibers takes place on these plates or sections of the fibers are injected into the base body and / or the counterpart by a casting process during the production of the base body and / or the counterpart.

[0008] In particular, it can be provided that the ring has end regions and at least some of the end regions of the ring are fixed to / in the base body and / or the counterpart. The end regions can be the beginning and / or end of the ring or can also be the turning region of the ring.

[0009] Preferably, the fibers are at least partially compressed relative to one another. During manufacture, for example, a cotton-like structure of the fibers is produced and then compressed in this way, thereby producing a more solid structure, but wherein the compression is not performed so violently that the flow path for the cooling medium is closed too much.

[0010] In order to provide a special resistance to the flowing medium, it can be provided that at least some of the fibers are provided with a mechanically stabilizing coating. For the same reason, according to another development of the invention, at least one support structure, which is composed in particular of metal and / or preferably other carbon nanostructured fibers (CNB), in particular carbon nanotube bodies (CNT) or graphite fibers, can be provided, which supports the fibers. The support structure is therefore in particular a metal structure or a fiber structure, wherein this fiber structure in turn is composed of (in particular other) carbon nanostructured fibers or carbon nanotubes.

[0011] One development provides that the at least one supporting structure is embodied in a grid-like manner and serves for fastening to the base body and / or the counterpart body, wherein provision may in particular be made for the supporting structure to be injected into the base body and / or the counterpart body.

[0012] Preferably, the three-dimensional fabric is mechanically stabilized by the type of mesh and / or the mesh width of the fabric. Through this stabilizing effect produced from the mesh, the fibers based on the carbon nanostructure, especially the carbon nanotubes, are also mechanically protected to prevent deformation.

[0013] It can be provided that at least some of the fibers are based on a fiber matrix, in particular a planar fiber matrix, formed from fibers and / or other fibers based on carbon nanostructures (CNB), in particular carbon nanotubes (CNT) or graphite fibers. Such a fiber matrix can in particular be fixed to a matrix and / or a counterpart or be injected into a matrix and / or a counterpart.

[0014] In particular, it is possible for the mentioned fiber matrix to be configured as a woven fabric.

[0015] A further development of the invention provides that at least some of the fibers extend from the base body to the counterpart body at an angle not equal to 90° in order to achieve the greatest possible fiber length between the two bodies and / or extend at an angle of 90°. The greater the fiber length between the base body and the counterpart body, the more heat the individual fibers can dissipate. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The drawings illustrate the invention with the aid of exemplary embodiments and more precisely:

[0017] Figure 1 A region of a cooling body having donut-shaped carbon nanostructure-based fibers is shown;

[0018] Figure 2 Shows Figure 1 The area of ​​the cooling body together with the area of ​​the matching body;

[0019] Figure 3 shows a region of a cooling body having fibers based on a carbon nanostructure in the form of filaments and in the form of loops;

[0020] Figure 4 A region of a cooling body having a fiber matrix and carbon nanostructured fiber-based in the form of a bulk structure, for example in the form of batt or felt or yarn, is shown;

[0021] Figure 5 shows regions of two variants of cooling bodies with filaments extending essentially at right angles to the fiber base or obliquely to the fiber base; and

[0022] Figure 6 A region of the cooling body is shown having a grid-like supporting structure and fibers running in annular shapes. DETAILED DESCRIPTION

[0023] Figure 1A cooling body 1 is shown, which has a base body 2 and fibers 3 based on a carbon nanostructure, in particular carbon nanotubes 4, also referred to as carbon nanotube bodies or carbon nanotubes, or alternatively graphite fibers. A power electronic component is thermally connected to the cooling body 1 (not shown), which must be cooled during operation. A cooling medium, such as a coolant, outlined by an arrow 5, flows along the cooling body 1, in particular transversely to the direction of the carbon nanotubes 4. The heat of the power electronic component is transferred to the base body 2, from which it is conducted to the carbon nanotubes 4 and discharged by the cooling medium. The carbon nanotubes 4 are extended as loops 6, which, for example, form a meander-shaped structure, wherein the end regions 7 of the loops 6 are embedded in the base body 2. The embedding process is preferably carried out by injection during the production of the base body 2. The base body 2 is preferably composed of a material with good thermal conductivity, in particular a metal. Due to the loop structure of the carbon nanotubes 4, the carbon nanotubes have good mechanical stability relative to the flowing cooling medium, so that they are not deformed by the flow. Furthermore, the annular shape leads to very good heat conduction since a large surface is created.

[0024] exist Figure 2 and all other subsequent figures, for and in Figure 1 The same components are provided with the same reference numerals, so that a detailed explanation does not need to be repeated. Rather, the corresponding explanations apply. Figure 2 The area of ​​the cooling body 1 is also like in Figure 1 2, but the counter-body 8 is additionally arranged at a distance from the base body 2 so that the end region 9 of the ring 6 is fixed to this counter-body 8, preferably injected into this counter-body. As a result, the ring 6 is held at both ends, which results in an even better mechanical stability. The carbon nanotubes 4 can also be fixed to the base body 2 and / or to the counter-body 8 by other means and methods, for example in the form of soldering points or adhesive points.

[0025] Figure 3 A region of a cooling body 1 is shown which has both filaments 10 and loops 6 relative to the carbon nanotubes 4. As an alternative, a cooling body 1 is also possible which has only filaments 10 or only loops 6. The filaments 10 each have a rod-shaped design. Figure 3 In the exemplary embodiment of the present invention, the carbon nanotubes 4 are based on a fiber matrix 11, which is fixed to the matrix 2 or embedded in this matrix (not shown). Preferably, the carbon nanotubes 4 form both the fiber matrix 11 and the filaments 10 or loops 6. The fiber matrix 11 can preferably be formed in the form of a tangled or interwoven region of the carbon nanotubes 4.

[0026] Figure 4 The region of the cooling element 1 is shown, for which a fiber matrix 11 is also present, which is preferably designed as a substantially planar fabric. Figure 3 As in the embodiment of FIG. 1 , the fiber matrix 11 is embedded in the matrix 2 or fixed to the matrix (not shown). Figure 4 The cooling body 1 has fibers 3 based on a carbon nanostructure, in particular carbon nanotubes 4 or graphite fibers, which in this embodiment form a bulk structure 12, wherein the fibers are in contact due to their adhesion or support to one another, so that in particular the bulk structure 12 is present in the form of cotton wool, felt or yarn. This bulk structure 12 results in a large surface of the carbon nanotubes 4 and also in a stable mechanical structure. According to a special embodiment, it can be provided that the fibers 3 based on a carbon nanostructure are at least partially compressed with respect to one another in order to obtain an even more compact and thus more stable structure, which of course allows sufficient flow paths to be opened for the cooling medium.

[0027] exist Figure 5 In the embodiment, the left side shows a method just like that already obtained from Figure 3 The same structure as that shown on the left side of FIG. 1 , namely a structure with filaments 10, which are preferably partially incorporated into the fiber matrix 11, but are then in the flow path of the cooling medium with a "free area", wherein Figure 5 Relative to Figure 3 The difference is that on the side opposite to the fiber matrix 11 there is also another fiber matrix 13 which is formed by the end regions of the carbon nanostructure-based fibers 3, so that overall the free fiber regions are supported at both ends and are therefore not deformed by the flow of the cooling medium. Figure 5 The right side shows that Figure 5 1 , but the difference between the two variants is that on the left the free fiber region is particularly perpendicular to the flow of the coolant 5 and thus essentially at right angles to the two fiber bases 11 or 13; however, on the Figure 5 The free fiber areas on the right side extend obliquely to the flow of the cooling medium, that is, they form an angle of not equal to 90° with the corresponding fiber base 11 or 13. Figure 5 The right side of the embodiment results in a longer free fiber length compared to the left side, thereby providing a larger surface in the flow of the cooling medium.

[0028] Figure 6An embodiment of a region of a cooling body 1 is described, in which a base body 2 and a counterpart body 8 are also present, but these two components are not shown, but only a grid-like support structure 14 or 15 is shown, wherein the support structures 14, 15 can preferably be formed by fibers 3 based on carbon nanostructures, in particular carbon nanotubes 4. The two support structures 14, 15 are fixed to the base body 2 and / or the counterpart body 8 or injected therein and receive the end regions 7 and 9 of the fibers 3 based on carbon nanostructures, in particular carbon nanotubes 4, extending between them. The support structures 14 and 15 have a stabilizing effect. They improve the fixing or injection in particular. The two support grids 14 and 15 can also be connected to each other. This is done by means of corresponding connections 16, in which the end regions 7 and 9 of the fibers 3 based on carbon nanostructures, in particular carbon nanotubes 4, are connected to each other. Figure 6 , only one connection is shown by way of example. Thus, the two support structures 14 and 15 remain separated. The two support structures 14 and 15 can also be formed from metal, that is, a metal grid.

[0029] It should also be mentioned with respect to all the exemplary embodiments that often only one carbon nanostructured fiber 3 or only a few carbon nanostructured fibers 3 are shown there. For a complete corresponding heat sink 1, a large number of carbon nanostructured fibers 3 are of course provided, in particular in a three-dimensional arrangement, in order to obtain a large surface.

[0030] exist Figure 5 In the embodiments of FIG. 1 (both the left and the right), there is an ordered structure of fibers 3 based on a carbon nanostructure, which in this case run essentially parallel to one another. Figure 4 In the embodiment of , there is a completely different structure, that is, a disordered structure.

[0031] Furthermore, in various embodiments, it can be provided that at least some of the carbon nanostructure-based fibers 3 are provided with a mechanically stabilizing coating. This also has the result that the carbon nanostructure-based fibers 3 remain relatively stable in the cooling medium flow and do not bend too much. For example, a coating made of copper or another metal can be provided.

[0032] Especially in Figure 4 In the embodiment of the invention, it is also possible to provide, instead of the bulk structure 12 in the form of cotton wool, felt or yarn, a three-dimensional fabric, that is, the bulk structure 12 is woven with the aid of fibers 3 based on a carbon nanostructure and then embedded in the matrix 2 at least on one side or fixed there, wherein as an alternative this can also be as in Figure 4 As shown in FIG. 1 , this is done with the aid of a fiber matrix 11 which is preferably also produced as a woven structure from fibers 3 based on a carbon nanostructure.

Claims

1. A cooling body (1) comprising a matrix (2) and a plurality of fibers based on a carbon nanostructure, at least some of the fibers being fixed to the matrix (2) for heat conduction, characterized in that: The fibers (3, 4) form a bulk structure (12) due to their mutual adhesion or support, or the fibers (3, 4) form loops (6) or a three-dimensional fabric, and the cooling body (1) also has: a counterpart (8) separated from the substrate (2), at least some of the fibers (3, 4) being fixed on the counterpart; and at least one supporting structure (14, 15) supporting the fibers (3, 4), wherein the at least one supporting structure (14, 15) is constructed in a grid shape and is used to be fixed on the substrate (2) and / or the counterpart (8).

2. The cooling body according to claim 1, characterized in that The fibers (3, 4) at least partially form an ordered structure and / or at least partially form a disordered structure.

3. The cooling body according to claim 1 or 2, characterized in that: The fastening on the base body (2) and / or on the counter body (8) is designed as a soldering point, a bonding point and / or an injection point.

4. The cooling body according to claim 1 or 2, characterized in that: The eyelet (6) has end regions (7, 9) and at least some of the end regions (7, 9) of the eyelet (6) are fixed at / in the base body (2) and / or the counterpart body (8).

5. The cooling body according to claim 1 or 2, characterized in that: The fibers (3, 4) are at least partially compressed against one another.

6. The cooling body according to claim 1 or 2, characterized in that: At least some of the fibers (3, 4) are provided with a mechanically stabilizing coating.

7. The cooling body according to claim 1 or 2, characterized in that: The at least one supporting structure (14, 15) consists of metal and / or of additional fibers based on carbon nanostructures.

8. The cooling body according to claim 1 or 2, characterized in that: The at least one supporting structure (14, 15) is injected into the base body (2) and / or the counterpart body (8).

9. The cooling body according to claim 1 or 2, characterized in that: The three-dimensional fabric is mechanically stabilized by the type of mesh of the fabric and / or the mesh width of the fabric.

10. The cooling body according to claim 1 or 2, characterized in that: At least some of the fibers (3, 4) start from a fiber matrix (11, 13) formed by fibers and / or further fibers based on carbon nanostructures.

11. The cooling body according to claim 10, characterized in that The fiber matrix (11, 13) is fixed at / in the matrix (2) and / or the counterpart (8).

12. The cooling body according to claim 10, characterized in that The fiber matrix (11, 13) is configured as a woven fabric.

13. The cooling body according to claim 1 or 2, characterized in that: At least some of the fibers (3, 4) extend from the base body (2) to the counterpart body (8) at an angle different from 90 degrees in order to obtain the greatest possible fiber length between the two bodies and / or extend at an angle of 90 degrees.

14. The cooling body according to claim 1, characterized in that The carbon nanostructure-based fibers are carbon nanotubes or graphite fibers.

15. The cooling body according to claim 1, characterized in that The fibers (3, 4) form a bulk structure (12) in the form of cotton wool, felt or yarn due to their mutual attachment or support.

16. The cooling body according to claim 10, characterized in that At least some of the fibers (3, 4) start from a planar fiber matrix (11, 13) formed from fibers (3, 4) and / or further fibers based on a carbon nanostructure.

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