CN114175235A

CN114175235A - Cooling device

Info

Publication number: CN114175235A
Application number: CN202080047913.2A
Authority: CN
Inventors: A·海泽
Original assignee: Continental Automotive GmbH
Current assignee: Continental Automotive Technologies GmbH
Priority date: 2019-07-02
Filing date: 2020-06-09
Publication date: 2022-03-11
Also published as: DE102019209657A1; EP3994724A1; WO2021001001A1

Abstract

The invention relates to a cooling device, comprising a heat sink (1, 11) with a cooling surface (3) and a component to be cooled with a cooling surface (5), wherein the cooling surface (3) of the heat sink (1, 11) and the cooling surface (5) of the component to be cooled are arranged in close proximity to one another, at least a capillary gap (14) is formed between the cooling surfaces (3, 5) by the arrangement of the cooling surfaces (3, 5), and a capillary filling medium is provided which fills the capillary gap (14).

Description

Cooling device

Technical Field

The invention relates to a cooling device, a method for producing a cooling device according to the invention, and the use of a matrix with paraffin oil, in particular white oil and/or vaseline, as a capillary filling medium in a cooling device according to the invention or in a method according to the invention.

Background

Modern vehicles, such as motor vehicles or motorcycles, are increasingly equipped with driver assistance systems which detect the surroundings by means of sensor systems, recognize traffic situations and provide support for the driver by, for example, braking or steering interventions or by outputting visual or audio warnings. As a sensor system for detecting the surrounding environment, an ultrasonic sensor, a camera sensor, a panoramic looking-around camera, a radar sensor, a laser radar sensor, or the like is generally used. From the sensor data measured by the sensors, conclusions can then be drawn about the surroundings, which enables an assistance function for supporting the driver during parking and/or driving maneuvers. The control of such sensors and the further processing of the generated sensor data is nowadays carried out by means of complex electronic control devices.

The common control devices often generate a large amount of waste heat, i.e. power losses, wherein the power losses of the control devices can be dissipated in different ways depending on the ambient conditions, for example by means of cooling devices. Different forms of cooling are known, for example by natural convection, in which hot air, lighter than cold air, rises, the subsequently inflowing air is heated and then also rises. Furthermore, forced convection may be provided, in which, for example by means of a fan, an air flow is blown or sucked through the component to be cooled, thereby taking hot air away. There are also liquid cooling systems in which the component to be cooled is cooled by a cooling liquid (for example by actively driving the cooling liquid past the component to be cooled by means of a pump). Furthermore, numerous hybrid forms and variants of the illustrated system are known, as well as other cooling possibilities, such as conducting heat to colder points, etc.

Furthermore, the heat dissipation of the electronic control unit can also be dissipated to the outside via a housing of the control unit which is well thermally conductive, for example a metal housing. On the housing surface or at least on one side of the housing, for example, the challenge of dissipating heat as well as possible at higher power consumption is faced in order to protect the components in the housing from overheating. For this purpose, for example, an air cooler with cooling fins or a closed coolant circuit can be connected to the control device housing. In this case, for example, the installation and removal of the device requires the cooling circuit to be interrupted and shorter service intervals (replenishment and refilling of the coolant) are required. Furthermore, it is very complicated to manufacture the flow-through radiator as a housing component, for example as a base housing of a control device.

Starting from the described scenario, therefore, a design is already created which comprises a housing region made of metal, at least in the main cooling region, to which the heat sink is flange-connected, preferably by means of a thermally conductive paste (or a thermally conductive adhesive) or a thermally conductive mat (or a thermally conductive foil or a thermally conductive mat). Such thermal pastes and pads may be manufactured on the basis of so-called Thermal Interface Materials (TIM). In this case, the heat conducting mat or the heat conducting paste is inserted between the heat sink and the housing as far as possible without any air bubbles, so that a good thermal bonding is achieved. However, in the conventional manufacturing process, there is inevitably a case where the surface of the heat sink or the surface of the case is uneven. To compensate for such uneven, uneven surfaces and dirt particles between the housing and the heat sink, the thermal pad is typically one to several millimeters thick and must typically be compressed to ensure acceptable thermal conductivity. Furthermore, the thermal paste must also be distributed very precisely on the surface in order to avoid any air pockets.

In contrast, attempts are usually made to make the thermal pad and the thermal paste very thin, since they are generally much less thermally conductive than metals (e.g., aluminum or copper). However, this is limited by the described balance compensation function and the desired compression value or moderate flow characteristics of the material. In cooling devices as small as a few square centimeters, the degree to which the thermally conductive paste or pad functions is generally acceptable. Larger areas, for example from 1 or 2 square decimeters or from the size of the paper in DIN A5 or DIN A4, result in less and less effective thermal pastes or pads.

Furthermore, the heat sinks can also be designed to be resilient so that they "cling" to the housing. Due to the requirements for the material properties of the heat sink, such designs, if achievable, are often subject to considerable effort, since the gap between the housing and the heat sink is often contaminated with dirt particles or the liquid that is introduced can cause corrosion (crevice corrosion). Due to this problem, such cooling structures should also be moisture and liquid proof to prevent damage, e.g. by condensation or wetting of the liquid with moisture or water.

A power semiconductor device is known from DE 102011083224 a1, in which a thermally conductive paste having a thermochromic color component and a matrix material is provided between the power semiconductor module and the heat sink. The matrix material in which the one or more thermally conductive fillers are embedded may be, for example, an oil, a resin or a fat, or an oil, resin or fat-based paste having at least, for example, an epoxy resin, petrolatum, silicone oil-based paste, or polypropylene glycol-based paste. As the thermally conductive filler, for example, a powder having one or more of the following materials may be used: diamond, copper, aluminum, silver, zinc oxide, beryllium oxide, boron nitride, aluminum nitride, silicon nitride, and aluminum oxide. The thermally conductive paste serves here to compensate for the inevitable unevenness of the contact surfaces of the power semiconductor module and the heat sink and to determine whether the module has exceeded its upper temperature limit after a possible failure of the power semiconductor module. This determination is achieved by a thermochromic color component, the color of which changes continuously or abruptly with a change in temperature of the thermal paste at a certain transition temperature.

Disclosure of Invention

The present invention now has for its object to provide a cooling device and a method, by means of which a good heat transfer between the heat sink and the housing is achieved and the disadvantages resulting from the prior art are overcome in a simple and economical manner.

The above-mentioned object is solved by the general teaching of claim 1 and the independent claims. Advantageous embodiments of the invention are claimed in the dependent claims.

The cooling device according to the invention comprises a heat sink with a cooling surface and a component to be cooled (e.g. a control device, a component, a housing, etc.) with a cooling surface, wherein the cooling surface of the heat sink and the cooling surface of the component to be cooled abut against each other. Due to this arrangement of the cooling surfaces, at least unavoidable capillary gaps are formed between the cooling surfaces, for example by irregularities in the structure of the cooling surfaces. In this case, according to the invention, a capillary filling medium is provided which can fill the capillary gap in particular automatically (for example by "peristaltic movement"). Such capillary filling media can be processed or attached, applied or introduced, i.e. easily applied, particularly easily during initial assembly and/or maintenance/servicing. Furthermore, unevenness of the surface of the cooling surface between the heat sink and the case or a gap between the heat sink and the case due to foreign matter can be compensated/filled in balance, so that good heat transfer can be established between the heat sink and the case. Furthermore, such an arrangement requires little space and can be implemented and retrofitted particularly economically and rationally. In this way, the cooling surfaces can be simply pressed against one another without the use of large mechanical pressing forces, as are required in particular when using heat-conducting mats, which in particular reduces the risk of damage to components. Furthermore, corrosion protection in the capillary gap can be significantly improved by the introduced medium and the air removal associated therewith, for example even with corrosive particles in the electrochemical series (e.g. copper particles in an aluminum housing/heat sink), since the capillary filling makes the penetration of corrosive liquids, moisture, particles, air or materials particularly difficult or prevented.

The capillary filling medium is preferably arranged between the cooling surfaces during assembly, installation, maintenance or production (i.e. in the region of the capillary gap that subsequently occurs), in the heat sink reservoir and/or in the reservoir of the component to be cooled. Here, recesses or explicitly embodied depressions in the housing and/or the heat sink, which recesses are dependent on the production conditions, can be predetermined as reservoirs. Alternatively or additionally, the housing and/or the heat sink can also have a storage region on the edge side, which can be filled in a simple manner from the outside, for example, and can be arranged such that it is in contact with the later-formed capillary gap or is open to the latter or is in fluid connection with the latter. Furthermore, as long as the control device and/or the heat sink are not disassembled, a maintenance-free service life of the thermal connection can be achieved by predetermining one or more reservoirs, for example, to match the service life of the thermal connection to the service life of the vehicle or to exceed the service life of the vehicle.

Depending on the purpose of use, a particularly specifiable operating temperature of the component to be cooled can be predefined, for example as a component to be cooled a minimum, average or maximum operating temperature which is permissible for a control device (for example an electronic control unit ECU or an autopilot control unit ADCU of a vehicle) and for a predefined control device. The capillary filling medium can be arranged in such a way that the capillary gap is filled at a predetermined operating temperature, i.e. at a temperature which is most favorable for the capillary action.

The capillary filling medium is preferably liquid at the operating temperature, i.e. it can also be present in another substance state than at the operating temperature. For example, the capillary filling medium can be easily applied and removed again at room temperature. This results in a permanent, for example, long-lasting thermal connection which can be removed very well after many years. The capillary filling medium is selected or modified in such a way that it can always be kept (significantly) below the boiling point of the medium at the highest operating temperature of the control device/plant and the radiator.

Capillary filling media in the sense of the present invention means media which fill capillary gaps by capillary action and/or capillary effect. This is because the respective medium is a liquid at the operating temperature and fills or has a capillary gap when in contact with the capillary tube or gap by surface tension of the liquid itself and interfacial tension between the liquid or medium and the capillary gap-securing surface (i.e., the "vessel wall", e.g., the metal of the housing or heat sink).

Paraffin wax or paraffin oil such as white oil can surprisingly be used as the capillary filling medium. In particular, white oils of medical quality (liquid paraffin), such as those used in the pharmaceutical or cosmetic industry, can be used, these products meeting very high requirements in terms of purity and tolerability. Such medicinal white oils are generally colorless, odorless and tasteless and are usually purified to exclude other additives such as fragrances or sulfur compounds. Here, the general white oils are characterized by being harmless to humans, so they are also used in the food industry.

Alternatively or additionally, vaseline or similar materials can also be intended as capillary filling medium. A mixture of a liquid component, for example 70% to 90% of highly branched isoparaffins and olefins, and a solid or crystalline component, for example 10% to 30% of long-chain components, such as n-paraffins and small-branched isoparaffins, is referred to herein as petrolatum, wherein the liquid component penetrates the (crystalline) structure of the solid component. Petrolatum is also characterized by excellent human and environmental compatibility, so that the application according to the present invention is convenient to install or media application to a certain extent.

Depending on the purpose of use, the capillary fill medium may contain materials useful for inhibiting corrosion materials (e.g., finely distributed chromates) and/or for promoting drainage or drainage. Thereby, even additionally improved protection against corrosion can be achieved. Paraffin or paraffin oil and vaseline have excellent water-repellent properties and thus already provide a good protection against corrosion.

According to a preferred embodiment, a pressure equalization channel can be predefined, which preferably has a larger dimension (e.g. a larger diameter) than the capillary gap and is connected to the capillary gap or to a groove/recess connected to the capillary gap, for pressure equalization. Thereby, by means of the pressure equalization channel suppressing/reducing the suction/suction process and acting as a reservoir for excess medium, the connection safety can be further improved and/or leakage phenomena of the medium during the filling phase or during operation (e.g. at operating temperature) can be prevented/avoided.

The invention also comprises, as independent or dependent claims, a method for manufacturing a cooling device, in which a cooling surface of a heat sink and a cooling surface of a component to be cooled are placed against each other, wherein by the arrangement of the cooling surfaces at least (usually unavoidable) capillary gaps are formed between the cooling surfaces. In this case, the capillary filling medium can be arranged between the cooling surfaces, in the reservoir of the heat sink and/or in the reservoir of the component to be cooled, for example, in order to fill the capillary gap in the operating state (during operation of the component, for example at operating temperature).

Furthermore, the invention claims the use of paraffin oil, in particular white oil and/or vaseline, as a matrix for the capillary filling medium in a common cooling device, in particular in a cooling device according to the invention or in a method according to the invention.

Drawings

The present invention is explained in more detail below with reference to examples which are intended to be illustrative. Wherein:

fig. 1 shows a simplified cross-sectional view of a first embodiment of a cooling device according to the invention in a disassembled state;

FIG. 2 shows a simplified cross-sectional view of a coolant radiator design of a cooling device according to the invention;

FIG. 3 shows a simplified cross-sectional view of a further embodiment of the cooling device according to the invention, an

Fig. 4 shows a diagrammatic representation of the design of the housing of (a part of) the component to be cooled of the cooling device according to the invention, in which a top view (lower) of the housing and an associated sectional view (upper) along the cutting line a-a are shown.

Detailed Description

Reference numeral 1 in fig. 1 denotes a heat sink for air cooling with a plurality of fins 2 and a flange surface or heat dissipation surface 3 arranged opposite the fins 2. The heat sink 1 serves here to cool the control device 4 or its components by arranging the cooling surface 3 of the heat sink 1 on the cooling surface 5 of the housing 6 of the control device 4, wherein the operating heat is dissipated into the surroundings. Here, the heat sink 1 may also be attachably fixed to the housing 6 (in a similar manner by gluing, riveting, screwing, clamping, etc.). Furthermore, the control device 4 can comprise a housing cover 7 in order to access the interior of the housing 6 and thus the electronic components in a simple manner. As electronic components, for example, a circuit carrier or a printed circuit board 8,

electronic components

9a, 9b (for example, power electronic components and the like are also included) thermally connected to the cooled outer surface, or an electronic component 10 not thermally connected to the cooled outer surface may be provided. The method according to the invention is based on the fact that the components (heat sink 1 and housing 6) which are arranged in close proximity to one another over a large area are brought into close proximity to one another by introducing a capillary filling medium (not shown in the figures for the sake of clarity) which is well-creeping, wherein the medium is water-tight, so that it fills the (unavoidable) gaps, i.e. completely or largely excludes air from the air gaps or capillary gaps, and thus compensates for irregularities in a balanced manner.

Fig. 2 shows a further embodiment of a heat sink, wherein the heat sink 11 has a coolant cooling device with a plurality of cooling channels 12, through which a coolant can flow. Like the radiator 1, the radiator 11 can cool the control device 4 by being provided on the control device 4 cooling surface 5 with a flange surface or cooling surface 13.

By combining the heat sink 1 and the housing 6 now directly with each other, i.e. without a thermal pad or thermal paste in between, as shown in fig. 3, a metallic contact can thus be made directly at one or usually at several places. However, as shown in the enlarged view in fig. 3, at other location(s), the metal or

cooling surfaces

3, 5 have a separation of one thousandth or one hundredth of a millimeter, and sometimes possibly a few tenths of a millimeter. This results in a gap (capillary gap 14) or gaps which are easily filled by the medium on the basis of capillary action. Accordingly, the capillary filling medium fills the capillary gap 14 completely or partially during operation (e.g., at operating temperature). It is surprising here that the thermal conductivity of the medium may be many times poorer than that of a conventional thermal pad or thermal paste, since the medium has only a small proportion of its strength or thickness, and there may also be local direct metallic contact between the cooling

surfaces

3, 5.

Due to the design, it may be necessary to predetermine a cavity or recess 15 in the housing part of the housing base, which is of practically flat design, on which the heat sink is arranged, in order to avoid material accumulations in the region of the housing inner base which has to be locally arched in order to guide the components to be cooled in the housing 6 close to them (for example, housing aluminum components for internal heat dissipation). If these air pockets are enclosed over the entire cooling surface by the medium in the gap between the heat sink and the housing, such air pockets can constitute a blowing or suction effect during expansion or contraction, i.e. during heating or cooling. If such cavitation cannot be avoided, a pressure equalization channel 16 may be predetermined as shown in FIG. 4. The pressure compensation channel 16 has a (capillary) gap which is significantly thicker than the capillary gap 14 between the housing 6 and the heat sink 1. Thus, air or media can be delivered or released with less resistance (i.e., a pressure equalization compensation is implemented to reduce or prevent the suction or blow-out effect).

The capillary filling medium can be applied or introduced in liquid or solid form, for example by spraying (aerosols, sprays and the like), vapor deposition, spraying or application of liquid or paste-like media (for example by means of a brush or a cotton swab), etc. Furthermore, the solid medium may be applied or introduced at room/process temperature to prevent melting of the medium when the control device is warmed (e.g., from normal conditions at room temperature to operating temperatures such as 30 degrees celsius, 40 degrees celsius, 50 degrees celsius, etc.) and subsequently acting on the capillary filling. Here, the medium allows the control device 4 to prevent or not significantly evaporate the medium in the hottest (permissible) conditions (use and standby or shut-down). In practice, the recess 15 or the pressure equalization channel 16 may also be filled with medium during normal operation and/or partly serve as a medium reservoir. It is provided here that the grooves 15 and/or the pressure equalization channels 16 receive the medium from the capillary gap 14 in order to prevent leakage of the medium or loosening or weakening of the connection between the cooling

surfaces

3, 5.

The application or introduction of the capillary filling medium is carried out in practice on one or both contact surfaces of the housing 6 and the heat sink 1, i.e. in the region of the cooling surfaces 3, 5 or by introducing a medium which is liquid, pasty or solid at the processing temperature into recesses 15 on the housing 6 and/or the heat sink 1, which preferably can contact the capillary gap 14.

It is possible to envisage using, for example, paraffin oil or white oil or vaseline, which can also be used in skin protection agents or medical products, as a capillary filling medium, so that there is no risk of use for the human body. In particular, use in the interior of motor vehicles, for example, is not problematic, so that the media used is harmless to humans and the environment, even in the case of maintenance services. The medium does not have to be used as a pure material here. But materials can be mixed which are advantageous for corrosion protection or, for example, for drainage. Alternatively, waxes, such as candle wax, may also be used. In the temperature range in which electronic devices typically operate, the medium should be kept away from the boiling point to ensure no or little evaporation at all. The change of the state of mass of the medium from liquid to solid in the operating temperature range of the control device 4 is not a problem if the fluidity is restored at a higher temperature.

In this way, the medium is or must be liquid at least in the hot or hot operating state of the control device 4, so that in order to fill the capillary gap 4 continuously, there can or should be an additional reservoir or

reservoir region

17a, 17b which can accommodate or supply a larger amount of medium again. The

reservoir regions

17a, 17b may, for example, be placed where less cooling (less heat transfer) is required between the housing 6 and the heat sink 1 and be constructed, for example, in the form of a slightly thicker capillary gap, since the capillary effect is greater in a narrow gap than in a wide gap, i.e. liquid or medium is drawn into a narrower gap. Furthermore, the

storage regions

17a, 17b provided on the edge side or edge sections can be used to apply or introduce a capillary filling medium (similar to the introduction by means of the recesses 15) in the region of the cooling surfaces 3, 5, wherein the medium preferably penetrates into the capillary gap 14 during the production or test process when the control device 4 or the

heat sink

1, 11 is heated.

The invention also explicitly comprises a temperature regulation (i.e. cooling or heating) device and a method, wherein for example heating means, such as heating means, are intended at the component to be cooled (heat sink 1, 11). The invention also comprises combinations of features of the individual embodiment examples and the dependent claims (independent and dependent claims) which are not explicitly mentioned.

List of reference numerals

1 heating radiator (for air cooling)

2 Heat sink

3 Cooling surface

4 control device

5 Cooling surface

6 casing

7 casing cover

8 printed circuit board

9a electronic part (or component)

9b electronic component (or parts)

10 electronic component (or component)

11 heating radiator (for coolant cooling)

12 cooling channel

13 Cooling surface

14 capillary gap

15 groove

16 pressure balance channel

17a reservoir area

17b reservoir zone A-A cut line

Claims

1. A cooling device, comprising:

a radiator (1, 11) with a cooling surface (3),

a component to be cooled having a cooling surface (5), wherein,

the cooling surfaces (3) of the heat sinks (1, 11) and the cooling surfaces (5) of the components to be cooled are arranged in close proximity to one another, at least capillary gaps (14) are formed between the cooling surfaces (3, 5) by the arrangement of the cooling surfaces (3, 5), and

a capillary filling medium is provided which fills the capillary gap (14).

2. A cooling device according to claim 1, characterised in that the capillary filling medium is arranged between the cooling surfaces (3, 5), in a reservoir of the heat sink (1, 11) and/or in a reservoir of the component to be cooled.

3. A cooling device according to claim 1 or 2, characterised in that the operating temperature of the component can be specified, at which operating temperature the capillary gap (14) is filled with the capillary filling medium.

4. A cooling device according to claim 3, characterised in that the capillary filling medium is liquid at the operating temperature.

5. Cooling device according to at least one of the preceding claims, characterized in that a medium based on paraffin oil, in particular white oil, is predetermined as a capillary filling medium.

6. Cooling device according to at least one of the preceding claims, characterized in that a vaseline based medium is foreseen as capillary filling medium.

7. Cooling unit according to at least one of the preceding claims, characterized in that the capillary filling medium contains a material which is advantageous for corrosion and/or drainage inhibition.

8. Cooling unit according to at least one of the preceding claims, characterized in that a predetermined pressure equalization channel (16) is provided which has a larger size than the capillary gap (14) and is connected to the capillary gap for pressure equalization compensation.

9. Method for manufacturing a cooling device, in particular according to at least one of the preceding claims,

the cooling surfaces (3) of the radiators (1, 11) and the cooling surfaces (5) of the components to be cooled are arranged in close proximity to each other, wherein,

at least a capillary gap (14) is formed between the cooling surfaces (3, 5) by the arrangement of the cooling surfaces (3, 5), and a capillary filling medium for filling the capillary gap (14) is provided.

10. Use of paraffin oil, in particular white oil and/or vaseline, as a matrix for capillary filling media in a cooling device or method, in particular according to at least one of the preceding claims.