Abstract:
A temperature control device for a battery may include a fluid duct being flowable at least one of through and around by a fluid. The fluid duct may be delimited by at least one duct wall composed of an electrically conductive material. An outer side of the duct wall facing away from the fluid may include at least one electrically insulating insulation layer disposed thereon via at least one of a screen printing process and a stencil printing process. The at least one insulation layer may be composed of a plastic material.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority to German Patent Application No. 10 2014 210 570.6, filed Jun. 4, 2014, the contents of which are hereby incorporated by reference in its entirety. 
       TECHNICAL FIELD 
       [0002]    The invention relates to a temperature control device for controlling the temperature, in particular a cooling device for the cooling and/or a heating device for the heating, of a battery, and a battery arrangement with such a temperature control device. The invention also relates to a motor vehicle with such a battery arrangement. Finally, the invention relates to a method for producing such a temperature control device. 
       BACKGROUND 
       [0003]    Rechargeable battery systems for electric vehicles with a purely electric drive and for hybrid vehicles and vehicles with fuel cell drive are the subject of current research. At present, in the said types of vehicle, lithium-ion batteries are preferably used, which are distinguished by a high energy density and an only slightly marked, undesired memory effect. The capability of a rechargeable battery to reliably supply various electric consumers installed in motor vehicles with electrical energy depends to a considerable extent on the thermal conditions prevailing in the environment of the battery. This is because both the electrochemical processes occurring in the battery in the provision and also in the receiving of electrical energy—in the sense of recharging—are dependent to a not insignificant extent on the operating temperature of the battery. Extensive investigations of various lithium-ion-based battery systems have shown, for instance, that below a critical temperature, for instance in the region of approximately 0° C., the electrical energy density made available by the battery decreases greatly compared with higher operating temperatures. Below this temperature, in addition damage to the Li-ion cell can occur during charging. 
         [0004]    The provision of thermally well-defined environmental conditions is therefore crucial for a reliable and interference-free operation of said batteries—this applies not only for said lithium-ion-based batteries, but generally for any rechargeable battery systems. With regard to the considerable temperature fluctuations occurring under normal operating conditions for instance in a motor vehicle, this means that these must be compensated by suitable temperature control devices coupled thermally with the battery, in order to keep the environmental temperature of the battery—and hence also the temperature of the battery itself—within a temperature interval specified, for example, by the manufacturer. 
         [0005]    Temperature control devices with heat exchangers are known from the prior art, which are based for example on fluid ducts in the form of cooling plates or collector/tube systems which form a cooling channel, which is flowed through by a heat transmission medium, for example a coolant. The battery cells which are to be temperature-controlled are brought to lie respectively flat against at least one duct wall of the heat exchanger of the temperature control device. In this way, a thermal contact is produced between the battery and the coolant, so that the coolant can extract heat from the battery cells and their temperature can consequently be kept below a maximum permissible threshold value. 
         [0006]    In such temperature control devices, it proves to be significant, however, that both for the duct walls of the fluid ducts, and also for the housing, a material with high thermal conductivity must be selected, if a highly effective thermal coupling is to be achieved between battery and coolant. Metals which have the desired characteristics with regard to the thermal conductivity therefore come into consideration to a particular extent. If, however, a metal is selected as material for a heat exchanger of the temperature control device cooperating with the battery or respectively for the battery housing, then an electrically conducting connection also occurs between the heat exchanger and the battery,—which connection is undesired for safety considerations —, when these two components are brought mechanically in contact with one another. Such an electrical connection could be avoided if the heat exchanger were arranged at a sufficient distance from the battery. However, owing to the air gap then present, this would lead to an unacceptable reduction of the thermal coupling between battery and heat exchanger. 
         [0007]    For an effective thermal coupling between battery cells and heat exchanger with simultaneous electrical insulation of the two components with respect to one another, it is therefore usual to provide a thermal interface with electrically insulating characteristics between these two components. From DE 10 2008 059 952 B4 a battery with several battery cells and a generic temperature control device constructed as a cooling device for cooling the battery cells is known. A metallic base body of the temperature control device is equipped with an electrically insulating insulation layer. This is an injection moulded layer of a plastic injected onto the base body. 
         [0008]    It is further known from the prior art to arrange thermally highly conductive materials with elastic characteristics between the individual battery cells and the temperature control device. These are able to compensate the formation of undesired intermediate spaces between individual battery cells and the duct walls of the fluid duct, caused for instance owing to manufacturing or installation tolerances. Heat-conducting foils, heat-conducting pastes or heat-conducting adhesives are used for use as a conventional thermal interface between the battery cells and the duct wall. 
         [0009]    It proves to be a problem in the said heat-conducting pastes that their function in the practical operation of the temperature control device, typically in a motor vehicle, cannot be guaranteed for instance owing to regularly occurring vibrations. The mentioned heat-conducting foils, on the other hand, have the disadvantage that they are expensive to purchase and their bubble-free application on the temperature control device is complex with regard to the technical process. In addition, owing to their only limited elastic deformability they can only compensate to a limited extent variations in the dimensions of the intermediate spaces between the temperature control device and the individual battery cells. 
         [0010]    It is therefore an object of the present invention to provide an improved embodiment for a temperature control device, in which the problems discussed above no longer occur. 
         [0011]    The said object is solved by the subject of the independent claims. Preferred embodiments are the subject of the dependent claims. 
       SUMMARY 
       [0012]    The basic idea of the invention is, accordingly, to provide on an electrically conductive duct wall of a fluid duct of the temperature control device an electrically insulating insulation layer of a plastic, which is applied by means of screen printing and/or stencil printing. The application of a plastic onto the metallic duct wall permits the formation of almost any desired print patterns to be realized in the electrical insulation layer by suitable selection of the print layout which is to be used. Thereby, it becomes possible to adapt the insulation layer to the geometry of the individual battery cells of the battery and to only use material where this is actually required. 
         [0013]    Compared with conventional insulation layers which are based on heat-conducting paste or a heat-conducting foil, on the basis of the insulation layer according to the invention in addition the same degree of thermal coupling can be achieved with reduced layer thickness. In addition to the not insignificant saving on material, cost advantages also occur, because the applying of a plastic by means of screen printing and/or stencil printing involves considerably reduced manufacturing costs compared with conventionally produced insulation layers. 
         [0014]    A temperature control device according to the invention for cooling a battery having at least one battery cell comprises a fluid duct, able to be flowed through by a fluid, in particular by a heat transmission medium, e.g. coolant, which has at least one electrically conducting duct wall, e.g. of a metal. On an outer side of the duct wall at least electrically insulating insulation layer, applied by means of screen printing and/or stencil printing, is provided. 
         [0015]    In a preferred embodiment, the plastic of the electrically insulating insulation layer is an elastomer. Elastomers are able to deform under compressive stress or tensile stress, which means that the insulation layer formed from an elastomer, owing to its elastic characteristics, can adapt to varying distances between individual battery cells and the outer side of the duct wall. It is therefore ensured that each individual intermediate space between a particular battery cell and the duct wall is filled by the insulation layer. Silicone and polyurethane (PU) prove to be particularly suited to use as elastomer in the insulation layer. 
         [0016]    These basic materials can be used in a further preferred embodiment to increase the thermal conductivity, provided with fillers, e.g. aluminium oxide, boron nitride, or similar. 
         [0017]    The use of the printing method essential to the invention makes it possible to produce the electrically insulating insulation layer in a preferred embodiment with a uniform layer thickness. In this way, it can be ensured that individual regions of the insulation layer are not formed with a layer thickness which is too small. Experimental investigations have shown that depending on the cell distance, values between 50 and 1000 μm with corresponding materials result in a compressibility of the insulation layer which brings about a particularly good mechanical and thermal contact of the layer both with all battery cells and also with the duct wall of the fluid duct. 
         [0018]    By comparison, in another preferred embodiment, it can be advantageous to provide different regions of the insulation layer—designated below as layer sections—with different layer thicknesses. It is conceivable, for instance, to provide local regions on the duct wall, in which no battery cells are to be arranged, with an insulation layer of reduced layer thickness. Alternatively thereto, however, it is also conceivable to increase the layer thickness in this region, so that the insulation layer for the respective battery cell forms a recess in which the battery cells can be partially received. 
         [0019]    In a further preferred embodiment, the electrically insulating insulation layer comprises at least two individual layers, preferably a plurality of individual layers, which are stacked on one another along a stacking direction, running orthogonally to the wall plane defined by the duct wall, on the outer side of the duct wall. In this way, the compressibility of the electrically insulating insulation wall can be adjusted. 
         [0020]    In an advantageous further development of the invention, at least one individual layer extends completely over the duct wall, whereas at least one further individual layer is arranged only in sections on the duct wall. In this way, it can be ensured that the duct wall is completely insulated electrically with respect to the battery cells. 
         [0021]    Particularly expediently, the fluid duct can be constructed as a flat tube, wherein duct wall, equipped with the insulation layer according to the invention, forms a part of the flat tube. 
         [0022]    The invention also relates to a battery arrangement, in particular for a motor vehicle, with a temperature control device with one or more of the above-mentioned features. The battery arrangement has a battery which is thermally coupled with the duct wall, which battery in turn comprises at least one battery cell. The electrically insulating insulation layer is arranged here in a sandwich-like manner between the duct wall and the at least one battery cell. The invention also relates to a motor vehicle with such a battery arrangement. 
         [0023]    Finally, the invention also relates to a method for the production of a temperature control device. In a first step a) of the method, an electrically insulating insulation layer of plastic is applied by means of screen printing and/or stencil printing onto an outer side of a duct wall, which is part of a fluid duct. In a second step b), a battery with at least one battery cell is applied on the insulation layer. The cross-linking or respectively hardening of the insulation layer, if applicable with the use of an active activation, e.g. by temperature increase or irradiation e.g. with UV light, can take place either before or after step b), preferably before step b), so that the temperature control device and the battery are not permanently stuck to one another. 
         [0024]    Further important features and advantages of the invention will emerge from the subclaims, from the drawings and from the associated figure description with the aid of the drawings. 
         [0025]    It shall be understood that the features mentioned above and to be further explained below are able to be used not only in the respectively indicated combination, but also in other combinations or in isolation, without departing from the scope of the present invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0026]    Preferred example embodiments of the invention are represented in the drawings and are explained in further detail in the following description, wherein the same reference numbers refer to identical or similar or functionally identical components. 
           [0027]    There are shown, respectively diagrammatically 
           [0028]      FIG. 1  an example of a temperature control device according to the invention in a rough diagrammatic and partial illustration, 
           [0029]      FIG. 2  a rough diagrammatic and partial illustration of the temperature control device of  FIG. 1  according to another example, 
           [0030]      FIG. 3  a rough diagrammatic and partial illustration of the temperature control device of  FIG. 1  according to another example, 
           [0031]      FIG. 4  a rough diagrammatic and partial illustration of the temperature control device of  FIG. 1  according to another example, 
           [0032]      FIG. 5  a rough diagrammatic and partial illustration of the temperature control device of  FIG. 1  according to another example, 
           [0033]      FIG. 6  a rough diagrammatic and partial illustration of the temperature control device of  FIG. 1  according to another example 
           [0034]      FIG. 7A  an elevated view of the temperature control device of  FIG. 1  according to another example, 
           [0035]      FIG. 7B  a rough diagrammatic and partial illustration of the temperature control device of  FIG. 7A  along the section line X-X, 
           [0036]      FIG. 8A  an elevated view of the temperature control device of  FIG. 1  according to another example, and 
           [0037]      FIG. 8B  a rough diagrammatic and partial illustration of the temperature control device of  FIG. 8A  along the section line X-X. 
       
    
    
     DETAILED DESCRIPTION 
       [0038]      FIG. 1  illustrates in a rough diagrammatic schematic illustration an example of a temperature control device  1  according to the invention for cooling a battery  2  with a plurality of battery cells, of which in  FIG. 1  by way of example three battery cells  3   a - 3   c  are shown. A heat exchanger  4  of the temperature control device  1 , which is flowed though by a fluid F serving as coolant, comprises a fluid duct  5 , of which in  FIG. 1  only a single duct wall  6 , for example of a metal, is shown. The fluid duct  5  delimits a fluid channel  7 , in which the fluid F flows. By thermal interaction of the battery cells  3   a - 3   c  with the fluid F through the duct wall  6 , these deliver waste heat to the fluid F for cooling purposes. For this, the battery cells  3   a - 3   c  are arranged on an outer side  8  of the duct wall  6  of the fluid duct  5 . 
         [0039]    As  FIG. 1  shows, an electrically insulating insulation layer  9  of a plastic is applied by means of screen printing and/or stencil printing on an outer side  8  of the duct wall  6  facing away from the fluid duct  7 . The battery cells  3   a - 3   c  of the battery  2  can be mounted on this insulation layer  9  of the temperature control device  1 . After completed mounting of the battery cells  3   a - 3   c  which are to be cooled, the insulation layer  9  is therefore arranged in a sandwich-like manner between the duct wall  6  and the battery cells  3   a - 3   c . Particularly expediently, the fluid duct  5  can be constructed as a flat tube, wherein the duct wall  6 , coated with the insulation layer  9  according to the invention, forms a part of such a flat tube. 
         [0040]    The plastic of the electrically insulating insulation layer  9  is preferably an elastomer. Elastomers coming into consideration are, in particular, silicone or polyurethane (PU). Owing to the spring-elastic characteristics of elastomers, the insulation layer  9  can be adapted to varying distances a between the individual battery cells  3   a - 3   d  and the outer side  8  of the duct wall  6 . Such a variation of the distances of individual battery cells  3   a - 3   c  can occur, for instance, owing to installation. This is shown in  FIG. 1  by way of example by means of the central battery cell  3   b , the distance of which to the duct wall  6  is greater than that of the two adjacent battery cells  3   a ,  3   c . It can therefore be ensured that each individual intermediate space  10   a - 10   c  between the respective battery cell  3   a - 3   c  and the duct wall  6  is filled completely by the insulation layer  9 . In this way, the desired thermal coupling of all battery cells  3   a - 3   c , in particular of the battery cell  3   b  with increased distance, to the duct wall  6  and therefore also to the fluid F, is ensured, which for example would not be the case if after the mounting of the battery cells  3   a - 3   c  a cavity remained between the battery cell  3   b  and the duct wall  6 . 
         [0041]    The same applies to the example shown in  FIG. 2 , which differs from that of  FIG. 1  in that the increased distance a between the central battery  3   b  and the duct wall  6  does not come about due to installation, but rather owing to reduced external dimensions of the central battery cell  3   b  compared with the remaining battery cells  3   a ,  3   c , due to manufacture. 
         [0042]    The duct wall  6  with the electrically insulating insulation layer  9  and the battery cells  3   a - 3   d  arranged thereon form a battery arrangement  20 . The use of a screen printing and/or stencil printing process for applying the insulation layer  9  on the duct wall  6  makes it possible to provide the insulation layer  9 , before the mounting of the battery cells  3   a - 3   d  of the battery  2 , both in the example of  FIG. 1  and also in the example of  FIG. 2 , with a uniform layer thickness. In this way, it can be ensured that individual regions of the insulation layer  9  are not produced with a layer thickness which is too small. Experimental investigations have shown that, depending on material characteristic and cell offset, values between 50 and 1000 μm result in a compressibility of the insulation layer  9 , on arranging of the battery cells  3   a - 3   d  on the duct wall  6 , which brings about a particularly good mechanical or respectively thermal contact of the insulation layer  9  both with the battery cells  3   a - 3   d  and also with the duct wall  6  of the fluid duct  5 . Layer thicknesses between 30 and 500 μm are sufficient for the electrical insulation—according to dielectric strength of the material and insulation requirement. If applicable (not shown here), a further electrically non-insulating layer can be applied for compensating the offset and/or different dimensions of the various battery cells  3   a - 3   d  onto the insulation layer  9 , which electrically non-insulating layer serves for a more homogeneous heat transmission between the duct wall  6  and the battery cells  3   a - 3   d.    
         [0043]    In a variant of the example of  FIGS. 1 and 2 , the electrically insulating insulation layer  9  can be provided in a targeted manner with a variable layer thickness. Such a scenario is shown by the example of  FIG. 3 , in which the battery cells  3   a - 3   c , which are still to be mounted on the insulation layer  9 , are shown in a dashed representation. It can be seen that the insulation layer  9 , in the regions  11  on the outer side  8  of the duct wall  6 , in which no battery cells  3   a - 3   c  are to be arranged, is provided with a reduced layer thickness compared with the regions  12 , in which the battery cells  3   a - 3   c  are to be in contact mechanically with the insulation layer. Alternatively thereto, however, it is also conceivable to increase the layer thickness precisely in these regions, so that the insulation layer for the respective battery cell forms a virtual “trough-like” recess, in which it can be partially received. Such a scenario is shown, by way of example, by  FIG. 4 . It shall be understood that the variants shown in  FIGS. 3 and 4  can be both combined with each other and also with the example scenarios shown in  FIGS. 1  and two. 
         [0044]      FIG. 5  shows a further variant, which is able to be combined with the examples shown in  FIGS. 1 to 4 . Accordingly, the electrically insulating insulation layer  9  can be formed not only from a single layer of uniform or varying layer thickness, but from at least two individual layers of different layer material. These can be stacked on one another along a stacking direction S, as illustrated in  FIG. 5 . Said stacking direction S extends orthogonally to a wall plane E defined by the duct wall  6 . In the example of  FIG. 5 , the insulation layer  9  comprises three individual layers  9   a ,  9   b ,  9   c , but in variants a different number of individual layers is also possible. The individual layers  9   a - 9   c  are produced from different plastics and can have individual layer thicknesses. On the mounting of the battery cells  3   b , the individual layers  9   b ,  9   c  are typically compressed, as shown in  FIG. 5 . 
         [0045]      FIG. 6  illustrates a further example of a temperature control device  1  according to the invention, in which the electrically insulating insulation layer  9  is formed on different sections of the duct wall  6  by a different number of individual layers  9   a ,  9   b ,  9   c . In this way, the elastic characteristics and therefore the compression behaviour of the insulation layers can be adapted in an application-specific manner to different requirements. In the example of  FIG. 6 , the insulation layer  9  has two individual layers  9   a ,  9   b  with respectively different layer material in lateral regions  13  in which battery cells  3   a - 3   d  are arranged thereon. In lateral regions  14 , on the other hand, in which no battery cells are provided—the regions  14  are therefore lateral intermediate spaces between adjacent battery cells  3   a ,  3   b  or respectively  3   b ,  3   c —the insulation layer  9  has, on the other hand, three individual layers  9   a - 9   c , stacked on one another, respectively of different layer material. The trough-like recesses  15   a - 15   c , shown in  FIG. 6 , are produced, for receiving the battery cells  3   a - 3   c . The individual layers  9   a ,  9   b  therefore extend completely over the duct wall  6 , whereas the individual layer  9   c  is only arranged in sections on the duct wall  6 . By means of the individual layers  9   a ,  9   b , it is ensured that the duct wall  6  is completely insulated electrically with respect to the battery cells  3   a - 3   c.    
         [0046]    The use of a screen printing and/or stencil printing process according to the invention for the production of the electrically insulating insulation layer  9  also makes it possible to produce this with a plurality of layer sections  16 , which with respect to a top view onto the duct wall  6  have a respectively identical or different marginal contour  17 . In this connection, experimental investigations have shown that different distances between the individual battery cells  3   a - 3   c  and the duct wall  6 , which are not known on mounting of the battery cells  3   a - 3   c  on the electrically insulating insulation layer  9 , can be compensated particularly well when the layer sections  16  in top view onto the duct wall  6  are provided with the marginal contour  17  of a polygon, preferably a quadrilateral or a hexagon, most preferably a rectangle or a hexagon. The desired marginal contours  17  can be formed by the layer sections  16  respectively forming a polygon being equipped with an increased or reduced layer thickness with respect to the remaining regions of the electrically insulating insulation layer  9 , as was already explained with the aid of  FIGS. 3 and 4 . Alternatively or additionally, the layer sections  16  can also be formed by an additional or absent individual layer  9   a ,  9   b ,  9   c  of the insulation layer  9 . 
         [0047]    Particularly advantageous elastic characteristics of the electrically insulating insulation layer  9  are produced when the previously discussed layer sections  16  with identical marginal contour  17  in top view are arranged in a grid-like manner with at least two grid lines  18   a  and at least two grid gaps  18   b  on the outer side  8  of the duct wall  6 . Such a scenario is shown by way of example in  FIG. 7   a , in which the layer sections  16  respectively have the marginal contour  17  of a rectangle and are arranged in a grid-like manner with respect to one another. A particular battery cell  3   a - 3   c  can be arranged on each grid gap  18   b . The number of layer sections  16  shown by way of example in  FIG. 7  can vary in variants of the example. In the regions or respectively intermediate spaces formed between the individual layer sections  16  of the grid, which constitute a base layer  19 , the layer thickness of the electrical insulation layer  9  is reduced. This can be seen with the aid of  FIG. 7   b , which shows the electrical insulation layer  9  in a longitudinal section along the section line X-X of  FIG. 7   a . The distance between two adjacent grid gaps  18   b  here, as shown, can be greater than that between two adjacent grid lines  18   a , or vice versa. 
         [0048]    Finally,  FIGS. 8   a  and  8   b  show a variant of the example of  FIG. 7   a  or respectively  7   b , in which the marginal contours  17  of the layer sections  16  have respectively the shape of a regular hexagon. The distance between two adjacent grid gaps  18   b  in the example of  FIGS. 8   a ,  8   b , just as in the example of  FIGS. 7   a ,  7   b , is greater than that between two adjacent grid lines  18   a . As  FIG. 8   b  shows, on the outer side  8  of the duct wall  6  between two adjacent grid gaps  18   a ,  18   b  or respectively two adjacent grid lines  18   a ,  18   b , regions or respectively intermediate spaces, which form a base layer  19 , are present, in which the layer thickness of the electrical insulation layer  9  is lower compared with the layer thickness of the layer sections  16 . This is illustrated by  FIG. 8   b , which in an analogous manner to  FIG. 7   b  shows a longitudinal section through the electrical insulation layer  9  along the section line X-X of  FIG. 8   a.