Patent Application
20150357687
This application claims priority to German Patent Application No. 10 2014 210 572.2, filed Jun. 4, 2014, the contents of which are hereby incorporated by reference in its entirety.
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.
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.
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.
Temperature control devices with heat exchangers are known from the prior art, for example cooling plates or collector/tube systems with fluid ducts 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 a heat transmission element, for example a 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.
In such temperature control devices, it proves to be significant that both for the heat transmission elements, for example 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 heat transmission medium. Furthermore, however, frequently also a mechanical compensation must also be performed by the so-called interface material, in order to compensate manufacturing and installation tolerances in the cell module manufacture. If this compensation cannot take place, or can only take place partially, this leads to air inclusions in the region between cooler and cell module base, whereby a poor or respectively non-homogeneous cooling of the module takes place. It is, however, an essential task not only to maintain the specified temperature range, but also to keep the temperature differential between the cells of a battery as small as possible.
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.
It is further known from the prior art to arrange thermally highly conductive materials with elastic characteristics between the individual battery cells and a heat exchanger, e.g. a cooling plate of the temperature control device, e.g. so-called heat-conducting foils. These are able partially 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 heat transmission element.
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 owing to their only limited elastic deformability they can only partially compensate variations in the dimensions of the intermediate spaces between the heat exchanger, e.g. cooling plate, and the individual battery cells according to permissible surface pressure.
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.
The said problems are solved by the subject of the independent claims. Preferred embodiments are the subject of the dependent claims.
The basic idea of the invention is, accordingly, to provide in sections on a heat transmission element of the temperature control device an elastic, mechanical compensation layer, which has a low thermal resistance and is applied by means of screen printing and/or stencil printing. The application of a plastic onto the heat transmission element permits the formation of almost any desired print pattern by suitable selection of the print layout which is to be used. Thereby, it becomes possible to adapt the compensation layer e.g. to the geometry of the individual battery cells, whereby in turn an improved compression behaviour or respectively an improved elastic deformability of the compensation layer can be achieved. As a result, an improved thermal coupling of all battery cells to the heat transmission element can be achieved, and a low differential temperature of all cells of a battery can be ensured.
It is essential to the invention here that the effective area of the heat transmission element is not completely covered by said compensation layer, but rather that at least a region of the effective area of the heat transmission element exists in which no such layer is present. In other words, the compensation layer according to the invention comprises on the heat transmission element at least two layer sections arranged at a distance from one another. This permits the compensation layer, formed only in sections on the heat transmission element, to also extend laterally on the heat transmission element, when battery cells of the battery are arranged on the compensation layer. As a result, a particularly reliable mechanical and also thermal contact of the fluid flowing through the fluid duct to all battery cells arranged on the compensation layer is guaranteed, even when only a small surface pressure is permissible. This applies expressly also for those battery cells which due to manufacture or installation have a differing, increased distance from the effective area of the heat transmission element; this increased distance is completely filled by the plastic of the compensation layer which is applied by means of screen printing and/or stencil printing. Undesired intermediate spaces, because they reduce the thermal coupling between individual battery cells and the heat transmission element, are therefore avoided.
Furthermore, compared with conventional interface layers based on heat-conducting paste or a heat-conducting foil, on the basis of the compensation layer according to the invention, the same degree of thermal coupling with respect to the thermal homogeneity of the cells can already be achieved with reduced layer thickness, i.e. with reduced use of material. In addition, cost advantages 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 layers.
A temperature control device according to the invention for controlling the temperature of a battery has a fluid duct, able to be flowed through by a fluid, in particular by a coolant, which as heat transmission element in turn has at least one duct wall. On at least one effective area of the heat transmission element at least one elastic compensation layer of plastic, applied by means of screen printing and/or stencil printing, is provided. The compensation layer has at least two layer sections, which are arranged at a distance from one another on the outer side of the heat transmission element.
In a preferred embodiment, the plastic of the compensation layer is an elastomer. Elastomers are able to deform under compressive stress and tensile stress, which means that the layer formed from an elastomer, owing to its elastic characteristics, can adapt to varying distances between individual battery cells and the effective area of the heat transmission element. Therefore, it can be ensured that, if desired, each individual intermediate space between a particular battery cell and the heat transmission element is filled by the compensation layer. Silicone, rubber and polyurethane (PU) prove to be particularly suited to use as elastomer in the compensation layer. These basic substances can preferably have an increased thermal conductivity, which can be achieved by filling with suitable substances such as e.g. alu-oxide or copper. The material of the compensation layer can therefore be electrically insulating or electrically conductive, according to the requirements.
In another preferred embodiment, the compensation layer essential to the invention can have not only two, but a plurality of layer sections, which are all provided at a distance from one another on the heat transmission element. It is conceivable, for instance, that a separate layer section is associated with each of the battery cells of the battery which are to be cooled. The intermediate spaces formed between the individual layer sections then permit the individual layer sections to nestle against the battery cells, when the latter are pressed against the compensation layer in the course of their installation.
In an advantageous further development of the invention, the compensation layer, in a top view onto the heat transmission element, can have a plurality of layer sections with a respectively identical marginal contour. The resulting pattern-like construction of the compensation layer can be produced in a simple manner by means of the screen printing and/or stencil printing according to the invention by the use of a correspondingly configured screen or respectively a stencil. With suitable configuration of the geometry of the individual layer sections, these bring about a further improvement to the compression characteristics of the entire compensation layer.
Experimental investigations have shown that different distances between the different battery cells and the heat transmission element, which are not known beforehand on their installation on the heat transmission element, can be compensated particularly well when the layer section has in top view with the marginal contour of a polygon, preferably a quadrilateral, a hexagon, most preferably a rectangle or a regular hexagon.
In an advantageous further development, said layer sections are arranged in top view in a grid-like manner with at least two grid lines and at least two grid gaps on the effective area of the heat transmission element. In the intermediate spaces formed between the individual layer sections of the grid, no compensation layer is provided on the heat transmission element.
If, in addition, an electrical insulation is necessary, the partial layer essential to the invention can be applied onto an already present covering electrical insulation layer.
In a particularly preferred embodiment, it is proposed to dimension a first distance between two adjacent grid lines to be greater than a second distance between two adjacent grid gaps or vice versa. Such a geometry proves to be particularly advantageous when an individual battery cell extends along a grid line. The possibility presents itself to select the distance of two adjacent layer sections along a grid line to be smaller than along a grid gap, i.e. between two adjacent grid lines, so that the forming intermediate space is available as a compensation space for a lateral extending of the compensation layer along the grid line, when the respective battery cell is brought to abut against the compensation layer in the course of installation. In the optimum case, the intermediate spaces under a cell are completely closed in the course of tensioning. Reverse considerations apply when a battery cell is to be placed along a grid gap on the compensation layer.
For example, the first distance can be at least ten times, preferably twenty times the second distance, or vice versa. In such an embodiment, the first distance can be at least 0.4 mm and the second distance can be at most 8 mm, or vice versa.
In another preferred embodiment, the compensation layer can comprise at least two layers, preferably a plurality of layers, which are stacked on one another along a stacking direction. Said stacking direction is established here by the plane defined by the heat transmission element and runs orthogonally to this wall plane. The individual layers can be produced from respectively different plastics and/or can have individual layer thicknesses. It is also conceivable that the compensation layer on different sections of the heat transmission element is formed by a different number of individual layers. In this way, the elastic characteristics and therefore the compression behaviour of the compensation layer can be adapted to different requirements in a manner specific to the application.
In a further preferred embodiment, at least two layer sections of the compensation layer can have a different layer thickness. It is conceivable, for instance, to reduce the layer thickness in those regions in which the battery cells are to be brought to abutment against the heat transmission element or respectively compensation layer. This leads to an improved contact behaviour of the compensation layer. It is likewise conceivable to increase the partial coating in these regions, in order to also contact offset cells with an increased distance from the heat transmission element in every case and therefore to avoid thermally insulating air inclusions.
An embodiment proves to be particularly expedient, in which the at least two layer sections have a layer thickness between 100 and 2000 μm, depending on the cell offset which is to be compensated and the permissible surface pressure on tensioning.
The fluid duct can preferably be constructed as a flat tube, wherein the heat transmission element, equipped with the compensation layer according to the invention, forms a part of such a flat tube. Likewise, a so-called cover plate can additionally be applied onto the flat tube(s), which cover plate then constitutes the heat transmission element.
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.
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.
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.
There are shown, respectively diagrammatically
As
From the illustration of
The plastic of the compensation layer 9 is preferably an elastomer. Suitable elastomers are, for example, silicone or polyurethane (PU). To reduce the thermal resistance, these materials preferably have an increased thermal conductivity, which can be achieved for example by mixing/filling with readily thermally conductive materials. Owing to the spring-elastic characteristics of elastomers, the compensation layer 9 can be adapted to varying distances between the individual battery cells 3a-3c and the effective area 8 of the heat transmission element 5. Such varying distances can occur owing to installation or can be brought about by tolerances in the outer dimensions of individual battery cells. This is shown in
The use of a screen printing and/or stencil printing process for the production of the compensation 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 heat transmission element 5 have a respectively identical marginal contour 17, but alternatively also may have different marginal contours 17.
Examples of a pattern-like construction of the compensation layer resulting therefrom are illustrated by the examples of
Such a scenario is shown by the battery arrangement 20 of
As
The desired marginal contours 17 of the layer sections 16 can be produced by the layer sections 16 forming the marginal contour 17 of a polygon being equipped with an increased or reduced layer thickness compared with the remaining regions of the compensation layer 9. Alternatively or additionally, the layer sections 16 can also be realized by one or more additional individual layers of the compensation layer 9 with respect to the remaining regions of the compensation layer 9.
a shows a variant of the example of
In a variant of the example of
| Number | Date | Country | Kind |
|---|---|---|---|
| 102014210572.2 | Jun 2014 | DE | national |
