METHOD FOR MANUFACTURING A COOLING DEVICE

Description

[0001] The invention is based on a method for producing a cooling device according to the preamble of independent patent claim 1. The present invention also relates to precursors for the production of a cooling device.

[0002] According to the prior art, the casting of tube inserts is a common process, even for automotive assemblies, such as a cooling coil in a die-cast radiator, an oil line in a transmission, etc. Particularly in the production of aluminum die-cast parts into which aluminum tubes are inserted, the stability of the aluminum tube inserts must be maintained during the casting process. The high melting temperature and pressure of the aluminum die-cast melt can be particularly critical for the aluminum tube inserts. Therefore, it is known from the prior art to fill the aluminum tube inserts with a salt or sand core to ensure tube stability during the casting process. After the insert has been cast, the salt or sand core filling is removed by an additional rinsing process to ensure the patency of the tube.

[0003] DE 10 2008 039 208 A1 discloses the production of aluminum die-cast components with cores intended to form a cavity in the aluminum component and having a surface layer made of a metal or metal alloy, in particular copper, nickel, zinc, tin, bismuth (or bismuth), silicon, copper-tin-based alloy, copper-nickel-based alloy, or copper-zinc-based alloy, which, for economic reasons, remain in the casting after the casting process. The surface coating acts as a bonding layer between the melt and the core shell and specifically influences the functionality of the core shell portion remaining in the casting, particularly with regard to the thermal conductivity between the casting wall of the finished component and the subsequent cavity of the casting, which is filled with a cooling medium.

[0004] DE 10 2011 076 312 A1 discloses a cooling device for a housing in which at least one component of a power electronics system is housed. A hollow cooling structure to be overmolded represents a cooling surface for the housing. During the manufacture of the housing, the cooling structure to be overmolded is supported by a medium acting on the cooling structure to be overmolded. The cooling structure to be overmolded is made of aluminum or an aluminum alloy and extends in a meandering or U-shaped manner from a medium inlet to a medium outlet.

[0005] DE 10 2008 016 994 A1 discloses a method for producing a housing component with an internal channel. The housing component is manufactured in a die-casting mold using a die-casting process, and the channel is formed by at least one tube embedded in the housing component. A light metal tube, e.g., aluminum or an aluminum alloy, is overmolded with aluminum or an aluminum alloy in the die-casting mold.

[0006] DE 10 2015 001 190 A1 discloses a cooling element for metallurgical furnaces and a method for manufacturing such a cooling element. The cooling element is made of cast copper and is intended particularly for use in the walls of melting and reduction furnaces subject to high thermal stress. Coolant channels are arranged inside the cooling element. These channels consist of copper tubes that are specially galvanically or chemically coated on both sides before being encased in liquid copper. These enable waterless cooling with low-melting organic molten salts and protect the cooling element from corrosion damage.The method for producing a cooling element provided with copper channels formed from copper tubes in its interior, in particular for use in ceilings and / or walls of thermally highly stressed melting and reduction furnaces, comprises the steps: a) manufacturing the tube bundle including all desired bends, lines and connections, b) pretreatment and chemical coating of the tubes of the tube bundle on the inside, c) pretreatment and galvanic coating of the tubes of the tube bundle on the outside, d) placing the tube bundle in the casting mold, pouring molten copper or copper alloy around the tube bundle within the casting mold with simultaneous, preferably waterless, cooling of the inner walls of the tubes with low-melting organic molten salts, e) cooling the copper melt under defined cooling gradients and cooling times to achieve certain material properties.

[0007] DE 1 119 469 B discloses a core for creating cavities in metal die-cast parts. The die-cast part comprises a hollow body made of a steel sheet with good thermal conductivity and a base body made of a cast metal with good thermal conductivity. To produce the die-cast part, the hollow body is filled internally with a molten substance which has a lower melting point than the cast metal and the hollow body. The filling fills the hollow body and is then cooled. The filled hollow body is placed in a die-casting mold, and the cast metal is introduced into the die-casting mold as a die-casting at a first temperature and flows at least partially around the hollow body. The die-casting melts the steel sheet of the hollow body, so that a material-to-material bond is created, at least in some regions, between the die-casting forming the base body and the steel sheet of the hollow body.The die casting solidifies and becomes solid. During the solidification phase, the die cast heats the molten material inside the hollow body until it reaches its melting temperature, and the molten material is removed from the hollow body. The molten material used is a plastic produced by the polymerization of crystalline aromatic hydrocarbons.

[0008] From JP H10 152767 A a cooling device with aluminum tubes is known, which have a zinc coating on their inside.

[0009] Published patent application US2015 / 0151385 A1 shows a solder wire for forming a soldered connection between two joining partners. A variant of the solder wire with a round cross-section has a core made of a tin wire, which in turn is coated with a sequence of Al, Cu, possibly additional material layers, and finally, in one embodiment, with a tin layer. The coatings on the tin wire core are applied using a sputtering or vapor deposition process. The coating thicknesses are only a few nanometers in each case. Disclosure of the invention

[0010] The method for producing a cooling device with the features of independent patent claim 1 has the advantage that the coating and filling of the at least one hollow body are combined in a single process, and no additional transport is required. Instead of an additional rinsing process, the filling of the third material is advantageously removed quickly and cost-effectively directly after pouring due to the material properties in the hot and liquid state. Since the coating material is used simultaneously to fill the hollow body, the number of materials in the assembly can be reduced, since no additional filling material, such as salt or sand, is required to ensure the stability of the hollow body during the casting process. In addition, the surface coating made of the third material protects the surface of the hollow body from oxidation before the hollow body is further processed.The surface coating is advantageously melted due to the high temperature of the die casting of the second material, which is higher than the melting temperature of the third material, and washed away from the first material of the hollow body, so that at least in some areas a material-to-material connection is made possible between the first material of the hollow body and the second material of the die casting or the base body.

[0011] Embodiments of the present invention provide a method for producing a cooling device comprising at least one tubular hollow body made of a first material with good thermal conductivity and a base body made of a second material with good thermal conductivity. The hollow body is coated externally with a third material with good thermal conductivity and filled and coated internally with the third material, which has a lower melting temperature than the first and second materials. The filling fills the hollow body and is then cooled. The filled hollow body is placed in a die-casting mold.The second material is then introduced into the die-casting mold as a die-casting at a first temperature and flows at least partially around the hollow body, wherein the die-casting melts the third material of the surface coating and melts the first material of the hollow body, so that at least in some regions a material-to-material connection is created between the die-casting of the second material forming the base body and the first material of the hollow body. The die-casting of the second material then solidifies and becomes solid, wherein during the solidification phase the die-casting of the second material heats the filling of the third material inside the hollow body until it reaches the melting temperature, and wherein the molten third material is removed from the hollow body under pressure.

[0012] Furthermore, a precursor product with the features of independent claim 7 is proposed for the production of a cooling device. In a first alternative, the precursor product comprises a tubular hollow body made of a first material with good thermal conductivity. The unbent hollow body has a surface coating made of a third material with good thermal conductivity on its exterior and a filling made of the third material with good thermal conductivity, which has a lower melting point than the first material. The filling completely fills the hollow body. Handling an unbent hollow body during coating and filling is easier than with an already bent hollow body.

[0013] In a second alternative, the tubular hollow body is bent and cut to a desired shape and has a surface coating made of a third material with good thermal conductivity on its outer surface and a filling made of the third material with good thermal conductivity, which has a lower melting point than the first material, with the filling completely filling the hollow body. The coated and filled tubular hollow body can be bent and cut to a desired shape immediately after cooling.

[0014] Such a cooling device comprises at least one hollow body made of a first material with good thermal conductivity, which is embedded in a base body made of a second material with good thermal conductivity. A material-to-material connection is formed between the first material of the at least one hollow body and the second material of the base body, at least in some regions, on the outer side of the at least one hollow body. Furthermore, the hollow body has a surface coating on its inner side made of a third material with good thermal conductivity, which has a lower melting point than the first material of the hollow body with good thermal conductivity and the second material of the base body with good thermal conductivity.The integral connection and integration of the hollow body into the base body allows for a low thermal resistance between the base body and the hollow body, advantageously eliminating the need for additional measures, such as applying a thermally conductive adhesive, to improve thermal conductivity between the base body and the hollow body. Furthermore, the surface coating on the inside of the hollow body has the advantage of preventing oxidation of the surface of the hollow body, thus enabling good heat transfer between the hollow body and a cooling medium flowing through the hollow body.

[0015] Such a cooling device can be used in an electrical assembly to cool at least one electrical power component.

[0016] The measures and further developments listed in the dependent claims enable advantageous improvements to the method for producing a cooling device specified in independent patent claim 1.

[0017] According to the invention, the first material of the hollow body is aluminum or an aluminum alloy. The second material of the base body is also aluminum or an aluminum alloy. By using aluminum or an aluminum alloy, the lightweight construction concept and good thermal conductivity can be implemented cost-effectively and easily, since proven methods and processes can be used during production. According to the invention, the third material for the surface coating of the hollow body is zinc or a zinc alloy, or tin or a tin alloy.

[0018] Tin or zinc materials have significantly higher thermal conductivity values ​​than salt or sand, meaning they support the hollow body not only mechanically but also thermally during the casting process. In addition, the low melting temperatures of tin (231°C) and zinc (419°C) enable simple and rapid coating or filling of the hollow body made of aluminum, which has a much higher melting temperature (660°C). The maximum temperature of the viscous aluminum die casting is in the range of approximately 560 to 580°C. Using various alloys, the melting point of the surface coating could be reduced even further to assist the melting of the surface coating of the hollow body by the aluminum die casting. During casting, the tin or zinc material of the filling in the hollow body is still solid, meaning the hollow body remains stable. After a very short time (approx. 1 second), the die casting solidifies and becomes solid.At the same time, the tin or zinc material in the hollow body is heated until it reaches or exceeds its melting point. At this point, the molten tin or zinc material can be removed from the hollow body under high pressure, for example, via gas injection. The tin or zinc material removed from the hollow body can be collected and reused (recycling).

[0019] In an advantageous embodiment of the process, the hollow body can be treated with a zincate process before coating and filling. This allows, when aluminum is used as the first material, an oxide layer on the hollow body surface to be removed before the surface of the hollow body is protected from further oxidation by a surface coating, preferably made of a tin or zinc material.

[0020] In a further advantageous embodiment of the method, the hollow body can be coated and filled with the third material in a coating bath. Such a coating bath allows the coating and filling of the hollow body with the third material to be carried out in a single process step. Furthermore, filling the hollow body with the molten liquid third material is faster and more cost-effective than filling it with salt or sand.

[0021] In a further advantageous embodiment of the process, the filled and cooled hollow body can be cut and bent into a desired shape. It is significantly easier to bend and cut a pre-product comprising a filled and coated hollow body than to first bend and cut the hollow body and then coat and fill it.

[0022] In a further advantageous embodiment of the method, the temperature of the filling can be determined at the ends of the hollow body during the solidification phase. This allows pressure to be applied to the hollow body to remove the filling when the temperature of the filling reaches and / or exceeds a predetermined threshold. The predetermined temperature threshold can be selected so that the third material of the filling has exceeded its melting point and is liquid. To optimally detect this time window and independently of the product, temperature sensors can be installed at the ends of the hollow body. The pressure for blowing out the hollow body can then be controlled using the measured values ​​from the temperature sensors.

[0023] Embodiments of the invention are illustrated in the drawings and explained in more detail in the following description. In the drawings, identical reference numerals designate components or elements that perform identical or similar functions. Short description of the drawings

[0024] Fig. 1 shows a longitudinal sectional view of an embodiment of a cooling device for an electrical assembly. Fig. 2 shows a cross-sectional view of the embodiment of a cooling device for an electrical assembly from Fig. 1 . Fig. 3 shows a schematic flow diagram of an embodiment of a method according to the invention for producing the cooling device from Fig. 1 and 2 . Fig. 4 shows a schematic representation of a coating bath with an embodiment of a precursor according to the invention for the production of the cooling device from Fig. 1 and 2 . Fig. 5shows a characteristic diagram showing a first characteristic curve with the temperature profile of a die casting and a second characteristic curve with the temperature profile of a filling of a hollow body during the production of the cooling device for an electrical assembly from Fig. 1 and 2 represents. Embodiments of the invention

[0025] As from Fig. 1 and 2As can be seen, the illustrated embodiment of a cooling device 10 for an electrical assembly comprises at least one hollow body 30 made of the highly thermally conductive first material, which is embedded in a base body 20 made of the highly thermally conductive second material. In this case, a material-to-material connection is formed at least in regions between the first material of the at least one hollow body 30 and the second material of the base body 20 on the outer side 34 of the at least one hollow body 30. In addition, the hollow body 30 has on its inner side 32 a surface coating 36 made of the highly thermally conductive third material, which has a lower melting temperature than the highly thermally conductive first material of the hollow body 30 and the highly thermally conductive second material of the base body 20.

[0026] In the illustrated embodiment of the cooling device 10, the first material of the hollow body 30 is a wrought aluminum alloy and the second material of the base body 20 is a die-cast aluminum. The third material of the surface coating 36 of the hollow body 30 is zinc in the illustrated embodiment. Unlike what is intended for the invention, other material combinations are also conceivable; for example, the hollow body 30 can also be made of copper or a copper alloy or another suitable metal or metal alloy with good heat conduction. According to the invention, the surface coating 36 of the hollow body 30 can also be a zinc alloy or tin or a tin alloy. In the illustrated embodiment, the hollow body 30 is designed as a meandering tube with a round cross-section.Of course, the hollow body 30 can also have other shapes and cross-sections and can be designed, for example, as a U-shaped bent tube with a square cross-section.

[0027] Embodiments of the cooling device 10 are preferably used to cool at least one electrical power component in an electrical assembly (not shown in detail), which is designed, for example, as a control unit. For example, the cooling device 10 can be used as a base plate of the electrical assembly and / or as part of a housing of the control unit. The power components to be cooled can then be arranged on this base plate or the housing part. In this case, the cooling device 10 can be used as a gas cooler, in which a gas is passed through the hollow body 30 for heat dissipation, or as a liquid cooler, in which a liquid is passed through the hollow body 30 for heat dissipation.

[0028] As from Fig. 3 and 4As can be seen, the illustrated embodiment of a method 1 according to the invention for producing the cooling device 10, which comprises at least one hollow body 30 made of the first material with good heat conduction and a base body 20 made of the second material with good heat conduction, comprises the following steps: In a step S100, the hollow body 30 is coated on the outside with the third material and filled on the inside with the third material, which has a lower melting temperature than the first material of the hollow body 30 and the second material of the base body 20. The filling 5 fills the hollow body 30. The filled hollow body is then cooled in step S110 and in step S120 the filled hollow body 30 is placed in a die-casting mold. In a step S130, the second material is introduced into the die-casting mold as a die-casting at a first temperature and flows at least partially around the hollow body 30.In this process, the die casting melts the third material of the surface coating 36 and the first material of the hollow body 30, so that at least in some regions a material-to-material bond is created between the die casting of the second material forming the base body 20 and the first material of the hollow body 30. In step S140, the die casting of the second material solidifies and becomes solid, with the die casting of the second material heating the filling 5 of the third material inside the hollow body 30 during the solidification phase in step S140 until the melting temperature is reached. In step S150, the molten third material is removed from the hollow body 30 under pressure.

[0029] In the illustrated embodiment of the method 1 according to the invention, aluminum or an aluminum alloy is used as the first material for the hollow body 30 and as the second material for the base body 20. Zinc or a zinc alloy is used as the third material for the surface coating 36 and filling 5 of the hollow body 30. Unlike what is provided for in the invention, other material combinations are also conceivable; for example, the hollow body 30 can also be made of copper or a copper alloy or another suitable metal or metal alloy with good heat conduction. According to the invention, the surface coating 36 of the hollow body 30 can also be tin or a tin alloy.

[0030] As from Fig. 3As can be seen further, the hollow body 30 can be treated with a zincate process in an optional step S50 shown in dashed lines before coating and filling in order to remove an oxide layer on the surface of the hollow body 30.

[0031] As from Fig. 4 As can be seen further, the hollow bodies 30 as pre-product 3, unbent, with a length of approximately 6m, are coated with the third material in a coating bath 9 and completely filled according to the zincate process in step S50 in step S100. Fig. 4As can be seen, the hollow body 30 is immersed at an angle into the coating bath 9 and maintains this position during the coating and filling process, so that the hollow body 30 is completely filled with the third material, here zinc, and air 7 can escape from the hollow body 30. When the hollow body 30 is lifted out of the coating bath 9, the lower end of the hollow body 30 is tightly closed. In this state, the hollow body 30 is cooled so that the third material, while still in its liquid state, cannot flow out.

[0032] As from Fig. 3 As can be further seen, the filled and cooled hollow body 30 or the precursor 3 can be bent and cut into a desired shape in an optional step S115 shown in dashed lines. The filling 5 increases the stability of the hollow body 30 during the bending process or mechanical processing.

[0033] In order to identify an optimal time window for removing the filling 5 from the hollow body 30, the temperature of the filling 5 can be determined at the ends of the hollow body 30 during the solidification phase in step S140. In step S150, the pressure for removing the filling 5 can then be applied to the hollow body 30 when the temperature of the filling 5 reaches and / or exceeds a predetermined threshold. The predetermined temperature threshold can be selected such that the third material of the filling 5 has exceeded its melting point and is liquid. In order to identify this time window optimally and independently of the product, temperature sensors can be provided at the ends of the hollow body 30. The pressure for blowing out the hollow body 30 can then be controlled by the measured values ​​of the temperature sensors. If the hollow body 30 is filled with zinc, the pressure could, for example, be activated when the temperature of the filling 5 exceeds 450°C.The pressure could be deactivated again if the temperature drops below 420°C. For example, if the hollow body 30 is filled with tin, the pressure could be activated when the temperature of the filling exceeds 250°C. The pressure could be deactivated again if the temperature drops below 235°C. During this process, the pressure loss can be measured, and thus the permeability of the hollow body 30 can be monitored or tested. For example, temperature sensors can be provided at the ends of the hollow body 30. The third material of the filling, which is removed from the hollow body 30, can be collected and reused (recycling).

[0034] As from Fig. 5As can be seen, the aluminum used in the illustrated embodiment, which is introduced into the die-casting mold as a die-casting in step S130 and whose temperature profile shows a first characteristic curve K1, has a solid first state Z1 up to time t1. During a first time window tF(Al) between time t1 and a second time t2, the introduced aluminum die-casting has a liquid or viscous state Z2 and a temperature in the range from 400 to 580°C. From time t2 onwards, the aluminum die-casting solidifies and again has the solid first state Z1. As the first characteristic curve K1 shows, the aluminum die-casting cools down slowly.

[0035] As from Fig. 5As can be seen further, the filling 5 of the hollow body 30, the temperature profile of which shows a second characteristic curve K2, still has the solid first state Z1 during casting, i.e. the hollow body 30 remains stable. After the first time window tF(Al), which is very short (approx. 1 second), the die casting solidifies and becomes solid. At the same time, the filling 5 in the hollow body 30 is heated up by the hot die casting and the melting temperature of the filling 5 is reached or exceeded. When tin is used, the filling 5 reaches its melting temperature at a third time t3 and changes into the liquid or viscous state Z2 for the duration of a second time window tF(Zn). When zinc is used, the filling 5 reaches its melting temperature at a fourth time t4 and changes into the liquid or viscous state Z2 for the duration of a third time window tF(Sn).From a fifth time t5, the filling 5 solidifies again and returns to the solid first state Z1. Thus, when using tin, the molten filling 5 can be removed from the hollow body 30 at high pressure during the second time window tF(Zn). When using zinc, the molten filling 5 can be removed from the hollow body 30 at high pressure during the third time window tF(Sn), wherein the third time window tF(Sn) is significantly shorter than the second time window tF(Zn), the end of which and the transition to the solid first state are no longer visible due to the scaling of the diagram.

Claims

1. Method (1) for producing a cooling apparatus (10) for an electrical assembly, comprising at least one tubular hollow body (30) made of a first material having good thermal conductivity and a base body (20) made of a second material having good thermal conductivity, wherein the outside of the hollow body (30) is coated with a third material having good thermal conductivity and the inside of the hollow body is filled and coated with the third material having good thermal conductivity, which has a lower melting temperature than the first and second materials, wherein the filling (5) fills the hollow body and is subsequently cooled, wherein the filled hollow body (30) is put into a die casting mould, wherein the second material is introduced as a die casting at a first temperature into the die casting mould and flows around the hollow body (30) at least in part, wherein the die casting melts away the third material of the surface coating (36) and melts onto the first material of the hollow body (30), so that a material bond between the die casting of the second material, forming the base body (20), and the first material of the hollow body (30) is obtained at least in regions, wherein the die casting of the second material sets and becomes solid, wherein during the setting phase the die casting of the second material heats the filling (5) made of the third material inside the hollow body (30) until it reaches the melting temperature, and wherein the molten third material is removed from the hollow body (30) under pressure, and wherein the first material of the hollow body (30) and the second material of the base body (20) are aluminium or an aluminium alloy and the third material of the surface coating (36) of the hollow body (30) is zinc or a zinc alloy or tin or a tin alloy.

2. Method (1) according to Claim, characterized in that the hollow body (30) is treated using a zincate method before coating and filling.

3. Method (1) according to either of Claims 1 and 2, characterized in that the hollow body (30) is coated and filled with the third material in a coating bath (9).

4. Method (1) according to one of Claims 1 to 3, characterized in that the filled and cooled hollow body (30) is bent and cut into a desired shape.

5. Method (1) according to one of Claims 1 to 4, characterized in that during the setting phase the temperature of the filling (5) is ascertained at the ends of the hollow body (30).

6. Method (1) according to Claim 5, characterized in that the pressure to remove the filling (5) is applied to the hollow body (30) when the temperature of the filling (5) reaches and / or exceeds a prescribed threshold value.

7. Precursor (3) for use in a method according to Claims 1 to 6 for producing a cooling apparatus (10) for an electrical assembly, having a tubular hollow body (30) made of a first material having good thermal conductivity, characterized in that the unbent hollow body (30) or the hollow body (30) that has been cut to length and bent into a desired shape has a surface coating (36) made of a third material having good thermal conductivity on its outside (34) and a filling (5) made of the third material having good thermal conductivity, which has a lower melting point than the first material, wherein the filling (5) fills the hollow body (30) completely, and wherein the first material of the hollow body (30) is aluminium or an aluminium alloy, and the third material of the surface coating (36) of the hollow body (30) and of the filling (5) is zinc or a zinc alloy or tin or a tin alloy.