Heating element for controlling the temperature of through-flowing liquid, and liquid circuit with heating element arranged therein
Patent Information
- Authority / Receiving Office
- EP · EP
- Patent Type
- Applications
- Current Assignee / Owner
- GENTHERM GMBH
- Filing Date
- 2024-08-31
- Publication Date
- 2026-07-08
Smart Images
Figure EP2024074383_06032025_PF_FP_ABST
Abstract
Description
[0001] Heating element for tempering flowing liquid and liquid circuit with heating element arranged therein
[0002] The present invention relates to a heating element for forming a flow section for a fluid circuit intended for thermal exchange with a drive battery. Furthermore, the invention relates to a fluid circuit with a heating element arranged therein and through which fluid flows.
[0003] Known drive and energy supply units for electric vehicle drives, in which the electrical energy supply for one or more electric drive motors is ensured by rechargeable battery or accumulator units, generally require more or less comprehensive energy management. This energy management system, which not only controls or regulates the output drive power according to a current driver requirement, but also controls recuperation processes for recovering electrical energy during braking or coasting, sensibly incorporates a thermal component, as accumulators achieve their highest performance in a temperature range that is above 15°C, but not too high, preferably below 30°C.
[0004] Since the battery units used for vehicle propulsion are subject to high levels of stress both during charging and during their intended use as an electrical energy source for the drive motors, their temperature control is generally advisable. Particularly in cold temperatures, the electrical performance and available capacity of the battery cells used in the battery units decrease significantly, so rapid warming before and during a journey is desirable.
[0005] Since the need for rapid cooling in the event of significant heat buildup of battery units generally requires liquid cooling, this cooling circuit is also generally available for controlling the temperature of battery units in cold outside temperatures. Typically, electrical heating elements similar to immersion heaters can be used. These can, for example, be electrically heated metal heating coils, which are surrounded by the circulating liquid and can thus heat the liquid as needed.
[0006] Since such heating devices operate relatively imprecisely and can only be controlled and regulated with a certain inertia, they generally cannot be used to achieve precise and rapid control of the temperature in the liquid.
[0007] An electrically operated heating device, which is said to be particularly suitable for motor vehicles, is disclosed in DE 102007 001 451 A1. This heating device has a structure through which air flows, which structure is formed by an electrically conductive foil that can be electrically heated to heat the air. The foil forms a plurality of channels, each of which is flowed through by the air to be heated. The electrically conductive foil can, in particular, have a wave-like shape, wherein the channels through which the air to be heated flows are formed by the individual waves. It is also proposed to bring the wave-like shape of the electrically conductive foil into a structure that is wound or folded together in certain regions.
[0008] Since the arrangement of DE 102007 001 451 A1 is very sensitive to local changes in the flow velocity, particularly temperature-stable and therefore expensive materials must be used so that such heating devices can be used to heat the cabin air of passengers.
[0009] In contrast, it is desirable to improve the known state of the art and to provide an efficient, safe and cost-effective heating system for a traction battery.
[0010] This object of the invention is achieved by the subject matter of the independent claims. Features of advantageous developments of the invention emerge from the respective dependent claims. To achieve this object, the invention proposes a heating element for forming a flow section for a fluid circuit intended for thermal exchange with a drive battery, wherein the heating element according to the invention comprises at least one electrical heating conductor and a carrier, wherein the at least one electrical heating conductor is arranged on this carrier.
[0011] Such a heating element according to the invention can be manufactured cost-effectively. Its integration into a water circuit ensures safe operation.
[0012] This is because water has a significantly higher heat capacity than air; the heat capacity of water is about four times higher than the heat capacity of air.
[0013] Due to its higher mass, water has greater inertia and is distributed more reliably and homogeneously as it flows through the heating channels.
[0014] In addition, there is a safety buffer in the form of a phase change, which allows for at least some of the additional excess energy to be absorbed. Theoretically, gas would be an additional, easily monitored parameter that could be used for safety purposes alongside a temperature change. And all of these safety buffers exist, even though even small deviations from the target temperature can be reliably detected in a water cycle.
[0015] In addition, critical temperature values cannot occur in any channel because each channel wall is exposed to liquid flow from two sides and the temperature of the wall is therefore automatically limited to the temperature of the surrounding liquid.
[0016] In addition, the heating element is usually only switched on during the initial phase of vehicle operation until the battery has reached its operating temperature.
[0017] In the heating element according to the invention, it can be provided that the carrier is a carrier layer or carrier film which is wound and / or folded several times and thus brought into a spatial structure, wherein one or more flow channels for liquid is or are provided between regions of the carrier layer or carrier film which are spaced apart from one another in the radial direction. Alternatively, however, it can also be provided that the carrier is a carrier layer or carrier film which is wound or wound spirally around a longitudinal central axis of the heating element, at least in sections, wherein one or more flow channels for liquid are or are also provided between regions of the carrier layer or carrier film which are spaced apart from one another in the radial direction.
[0018] According to a further embodiment of the heating element according to the invention, the carrier layer or carrier foil, which forms the carrier for the electrical heating conductor, can be shaped into a non-circular cross-section. The term "cross-section" used here refers to a cutting direction perpendicular to the flow direction of the heating element. This non-circular cross-section can, for example, be a polygonal contour, in particular a quadrangular contour, which can be realized optionally by winding the carrier layer, by folding it, or by a combination of winding and folding.
[0019] The carrier layer or carrier film can thus be folded at least in some areas and / or brought into the described spatial contour by meandering, which can be combined with a winding of sections of the carrier layer or carrier film if required or as appropriate.
[0020] In the case of such a partially folded and / or meandering shape of the carrier layer or carrier film, immediately adjacent surface sections of the carrier layer or carrier film can, for example, be placed on top of one another.
[0021] While a cylindrically or nearly cylindrically wound carrier layer or carrier film can be easily inserted into housing shapes, which are designed, for example, in the form of a tube thickening, cuboid-shaped housing shapes are often easier and more cost-effective to manufacture and also allow easier insertion of the heating element by inserting it into an opening that can be closed by a lid and can extend largely over the entire side surface of such a cuboid housing. To bring the heating element into such a shape, which can be predetermined in particular by a cuboid-shaped housing shape, the carrier layer or carrier film can advantageously be folded several times, in particular with surface sections lying flat against one another between the folds extending over the entire length.
[0022] The entire wound, coiled and / or folded, i.e. multiply folded, carrier layer or carrier film which forms the carrier for the electrical heating conductor can thus form an approximately cuboid-shaped spatial contour and be enclosed by a cuboid-shaped housing or accommodated in a cuboid-shaped housing. The electrical heating conductor can preferably be equipped with a plurality of flow channels through which the liquid to be tempered can flow essentially parallel to the longitudinal center axis of the cuboid-shaped housing or of the heating conductor. The connections for the liquid supply and liquid discharge are expediently located on the opposite end faces of a typically elongated cuboid-shaped housing and can be connected there in a flow-optimized manner, for example by channel extensions.
[0023] However, according to an alternative embodiment, the heating element can also be equipped with a cylindrical housing that accommodates the electrical heating conductor. The electrical heating conductor can preferably be equipped with a plurality of flow channels through which the liquid to be tempered can flow essentially parallel to the longitudinal center axis of the particularly cylindrical housing or the heating conductor.
[0024] The flow channels of the heating element according to the invention can preferably each extend with approximately constant cross-sections through the longitudinal direction of the heating conductor. The heating element is suitable as a rapidly and precisely controllable heating device in that at least sections of the channel walls of the flow channels are designed as heatable surfaces that can ensure rapid and effective heat transfer as the liquid flows past from the heating conductor to the liquid.
[0025] Optionally, the heatable surfaces of the flow channels can extend over the entire length of the respective flow channels.
[0026] However, embodiments of the electric heating element are also conceivable in which the heatable surfaces of the flow channels can have separately controllable regions along their length, which can be separated from one another and subjected to different temperatures. These separately controllable regions can, for example, be formed by separate sections of the flat heating conductors.
[0027] In principle, it is sensible if the numerous channels of the heating element each have similar cross-sections from an inlet face to an outlet face of the heating element, since in this way there are no significant flow influences on the liquid conveyed through the heating element.
[0028] The heating element according to the invention can, for example, comprise a wound and / or folded planar heating conductor which is provided with a corrugated cover layer which is applied in regular line contact to a first planar partial layer and thus forms the regularly spaced flow channels between the two layers.
[0029] Since different terminology often occurs in practice, it should be clarified at this point that the corrugated layer with or without conductor tracks on it can be referred to as a corrugated layer or a corrugated intermediate layer, while the non-corrugated layer on or below the corrugated layer can be referred to as a cover layer. According to a first embodiment of the electrical heating element according to the invention, this non-cover layer has no conductor tracks; according to an alternative embodiment of the heating element, it can also be equipped with conductor tracks that function as heating conductors.
[0030] Optionally, the first flat partial layer (straight or non-corrugated cover layer) as well as the corrugated cover layer or the web, which may also be referred to here as a corrugated intermediate layer, can each be coated with an electrically conductive coating at least on their facing surfaces and designed as a temperature-regulating surface.
[0031] Alternatively, both the first flat partial layer (i.e., the straight or non-corrugated layer or cover layer) and the corrugated cover layer, or the track, which may also be referred to here as the corrugated intermediate layer, can each be coated on both sides with an electrically conductive coating and designed as temperature-regulating surfaces. Furthermore, it is advantageous in the heating element according to the invention if the electrically conductive layers of the partial layers are each equipped with conductor tracks that are closely spaced from one another and distributed over the surfaces of the layers, thereby enabling effective heat transfer to the flowing liquid.
[0032] In the heating element, the winding arrangement of the heating conductor can form a uniform spiral or helical arrangement in cross-section or transversely to the longitudinal center axis of the cylindrical housing, in which the spacing between the superimposed winding layers is largely constant. This particularly applies to a heating element design in which a cylindrical housing is used.
[0033] In the cuboid-shaped housing mentioned as a sensible structural alternative, the folded and / or wound sections can also be irregularly or unevenly spaced from one another or slightly compressed in places to adapt to the shape of the housing, so that uneven spacing of the superimposed winding layers and / or the adjacent folded layers can result, which, however, does not normally have any negative effects on the heat transfer between the heating conductor and the liquid to be tempered.
[0034] Optionally, the heating element can also be equipped with at least one temperature measuring zone, which is advantageously located in the area of the flat and / or wavy sections or sublayers, thus enabling relatively precise temperature detection within the heating element. With at least one conductive track circuit, for example, the change in resistance with temperature could be used as a temperature sensor, allowing the changing temperature coefficient of the metal to be utilized. This would provide a temperature sensor integrated into the heating element that does not alter the flow pattern. If this sensor circuit is distributed across the entire heating surface, it can measure an average temperature. If it is placed only in the outflow area, it can be used to detect the resulting water temperature.
[0035] The heating element forms a type of foil water heater. The wave-shaped and spirally wound and / or multiply folded foil heating element comprises heating conductor tracks that can be heated by applying voltage. The heating conductor tracks can be specially shaped or designed with different coverage densities on the heating foil, so that the heating power density can be locally optimized if necessary. For example, it can be advantageous to heat the part of the heating coil or the area of the folded heating element sections where the cold water or the liquid to be tempered enters first more intensively. In the case of non-uniform flow, the area with a stronger flow can be heated more intensively and areas with a slower flow can be heated less intensively in order to create an even heat distribution in the liquid.It is often easier to adjust the local heating output than to spend extra effort ensuring that the flow is as uniform as possible.
[0036] Another option is to divide the heating elements into several heating circuits. This allows the heating output to be easily increased or decreased by connecting or disconnecting additional circuits. Furthermore, this eliminates the need for expensive power semiconductor components, whose power adjustment requires pulse-width modulation.
[0037] The heating element according to the invention makes it possible to heat all types of water-cooled systems used for battery units, in particular for traction batteries in vehicle drives.
[0038] As already mentioned above, for example, terminology has been established for corrugated cardboard materials that includes a fluted web, i.e. a corrugated intermediate layer, and a cover layer, i.e. a straight and non-corrugated layer on or beneath the fluted web. When speaking of layers, non-corrugated or corrugated layers in the present context, the terms web, fluted web and carrier web could also be used instead. The term web often appears more appropriate than the term layer because the term web can generally be understood as more objective than the term layer, which could often also be understood as a synonym for the term intangible level.
[0039] For this reason, it should be clarified at this point that the term "corrugated track," used here as an alternative to the term "corrugated layer," refers to a corrugated surface element that is provided, in particular, with the conductor tracks described above. Furthermore, it should be clarified that the term "carrier track," used here as an alternative, refers to a surface element that serves to mechanically stabilize the corrugated track, possibly also to mechanically stabilize the corrugated track only in certain sections. Both of these track types can, in turn, be formed from multiple layers. Thus, the track types can each have a carrier layer or cover layer, or multiple carrier layers or cover layers.
[0040] Since a corrugated sheet provided with an upper and lower support sheet generally resists rolling and such a composite would tend to buckle, the composite used here as a rollable and / or foldable structure for the heating element preferably has at least one support sheet and at least one corrugated sheet, wherein the support sheet and the corrugated sheet are arranged to overlap one another. Furthermore, the support sheet and the corrugated sheet are attached to one another at least at certain points, preferably in linear fashion. Finally, the corrugated sheet is preferably attached to a support sheet on only one of its two surfaces to maintain the flexibility of the resulting composite.
[0041] In particular, the composite can comprise exactly one carrier web and exactly one corrugated web, which are arranged overlapping one another and are fastened to one another at least at certain points, preferably in lines.
[0042] Maximum heating performance in the smallest space is achieved with a configuration in which both the carrier track and the corrugated track carry a heating resistor or are provided with conductor tracks and are thus each designed as an electrical heating element.
[0043] However, differently designed composite structures, which also have a high heating density and are therefore practically useful, are easier to manufacture. In such alternatively designed composite structures of the electrical heating element according to the invention, the corrugated track, in particular, can carry a heating resistor and be designed as a heating element, while the carrier track does not carry a heating resistor and thus functions purely as a carrier track without any further heating function. In this variant, the carrier track thus has no electrical conduction or heating function and serves as a purely mechanical support. The cost-benefit ratio can be designed particularly favorably with this variant, even if it does not represent the technically possible optimum with regard to the maximum heating output achievable within a given volume.
[0044] Furthermore, technical solutions are conceivable and also covered by the general inventive definition that do not require the described corrugated assembly. In such a variant, a flat heating element can simply be wound spirally. Since there are no corrugations as spacers to separate the individual windings from each other, linear spacers can be installed at regular intervals to keep the different winding layers spaced apart and to enable a largely unobstructed flow of the fluid to be heated between them.
[0045] It should also be clarified at this point that, in addition to the heating element explained above in various embodiments, the invention can comprise a heating element to be defined as follows. Thus, the invention also relates to a heating element that serves for thermal exchange with a fluid circuit, wherein the heating element comprises at least one heating track, at least one spatial arrangement pattern, at least one spacer element, and at least one channel.
[0046] When at this point we speak of at least one heating track of the heating element, the term heating track refers to a surface structure intended for heating, which converts electrical energy into thermal energy when energized.
[0047] When we speak of at least one spatial arrangement pattern of the heating element at this point, it is defined that this spatial arrangement pattern arranges at least two sections of the heating track in an overlapping zone.
[0048] The above-mentioned spacer element is arranged in the overlap zone between overlapping sections of the heating track.
[0049] Finally, when referring to at least one channel of the heating element, it should be defined that this channel serves to conduct fluid along the heating track. Furthermore, the walls of the at least one channel are formed by two overlapping sections of the heating track and the spacer element.
[0050] Preferably, the spatial planning pattern may comprise at least one of the following structures:
[0051] - spiral winding of the heating track around a central axis,
[0052] - Zig-zag folding to a cuboid stack,
[0053] - Winding the heating track around a central axis into a cuboid shape.
[0054] Preferably, the spacer element is selected from:
[0055] - a wave track that keeps two sections of a heating track at a distance,
[0056] - a carrier track that keeps two corrugated sections of a heating track at a distance,
[0057] - a multitude of elongated webs or strands that keep two sections of a heating track at a distance.
[0058] Preferably, at least the heating track or the corrugated track is multi-layered. In this case, it is preferably at least one of the following layers:
[0059] - a first covering layer, preferably waterproof and electrically non-conductive,
[0060] - an electrical covering layer, preferably with a resistance material,
[0061] - a second covering layer, preferably of the same type as the first covering layer.
[0062] To achieve the above-mentioned objective, the invention proposes, in addition to the electric heating element described in various embodiments, a fluid circuit for controlling the temperature of a liquid-cooled battery unit of a drive and power supply unit of a vehicle drive. The fluid is circulated in the fluid circuit by means of a pump and can thus be pumped through the liquid-cooled battery unit.
[0063] In a defined flow section of the fluid circuit, there is at least one electrically operated heating element equipped with flow channels whose channel walls are designed as flat heating conductors to enable heat transfer to a fluid circulating or flowing through the flow channels, which then enters the battery unit and can heat it. In the fluid circuit according to the invention, the at least one electrical heating element can be designed in particular according to one of the previously described embodiments.
[0064] Furthermore, the liquid circuit according to the invention can advantageously be equipped with a control and / or regulation unit for temperature control, which can supply the electric heating element with a controllable supply voltage according to the respective heating requirement of the liquid.
[0065] The electrical heating element advantageously used in the liquid circuit according to the invention offers, due to its design and structure, a particularly high heating power density of up to 60 kW / m 2 or more. This high heat output density is essentially due to the cooling fluid's ability to absorb and transfer significantly more energy, even at slow flow, than is the case with heated air, for example. While the heat output density of air heat exchangers hardly reaches values of around 8 kW / m 2 achieved, the heating element according to the invention provides values for the heating power density that are many times greater than those of air heaters or air heat exchangers.
[0066] Further differences from air heat exchangers lie in the different materials that can be used. Due to the higher temperatures generated in air heaters and the inherent risk of overheating, carbon and / or PTC materials, i.e., those with a positive temperature coefficient, must be used. For the electric heating element according to the invention, metallic conductors such as suitable aluminum alloys can be used without further restrictions.
[0067] On the other hand, the liquid heat transfer medium used in each case requires the metallic materials used to be resistant to chemically reactive medium, which may contain glycol. The materials should also be resistant to hydrolysis. This applies to both housing components and the foils used as heating conductors. Furthermore, greater effort is required for electrical insulation and sealing of the liquid-carrying system compared to air-based systems. The following exemplary embodiments will explain the invention and its advantages in more detail with reference to the attached figures. The proportions of the individual elements to one another in the figures do not always correspond to the actual proportions, since some shapes are simplified and others are enlarged in relation to other elements for better illustration.
[0068] Fig. 1 shows a schematic diagram of a liquid circuit with an electrical heating element arranged therein, which can be used to control the temperature of a liquid circulating through a battery unit.
[0069] Fig. 2A shows a schematic and perspective view of the heating element according to Fig. 1, through which liquid can be conveyed.
[0070] Fig. 2B shows an internal structure of the heating element according to Fig. 2A with a plurality of flow channels through which the liquid to be heated can flow.
[0071] Fig. 20 shows a layer structure of a heating conductor that can be inserted into the heating element.
[0072] Fig. 2D shows a frontal view of the heating element with its multitude of flow channels.
[0073] Fig. 3A shows a first embodiment of a conductor track structure of a flat heating conductor in a schematic plan view.
[0074] Fig. 3B shows a schematic and perspective view of the conductor track structure according to Fig. 3A in a wound structure, which can be located in the heating element.
[0075] Fig. 30 shows a second embodiment of a conductor track structure of the planar heating conductor in a schematic plan view.
[0076] Fig. 3D shows a schematic and perspective view of the wound structure of the conductor tracks as it can be found in the heating element.
[0077] Fig. 3E shows a third embodiment of a conductor track structure of the planar heating conductor in a schematic top view. Fig. 3F shows a schematic front view of the wound structure of the conductor tracks according to Fig. 3E, as it can be found in the heating element.
[0078] Fig. 4A shows a schematic and perspective view of an alternative design of the heating element in which a wound carrier layer is formed into an approximately cuboid contour.
[0079] Fig. 4B shows the embodiment of the heating element according to Fig. 4A inserted into a cuboid-shaped housing.
[0080] Figures 5A and 5B show a variant of an electrical cable connection which is guided through a wall of the housing of the heat exchanger by means of a sealing element.
[0081] Figures 6A and 6B show, in schematic and perspective representations, a further alternative design of the heating element, in which the carrier layer, provided with an optional support film and folded several times, is brought into an approximately cuboid-shaped contour.
[0082] Fig. 7A shows a first variant of a layer structure of the flat heating conductor.
[0083] Fig. 7B shows a second variant of the layer structure of the flat heating conductor.
[0084] Figures 8A to 8F each show different variants of a further alternative design variant of a heating conductor of the electrical heating element, which do not require the corrugated composite described above and are instead equipped with spacers between heating conductors wound on top of one another.
[0085] Identical reference numerals are used for identical or equivalently functioning elements of the invention. Furthermore, for the sake of clarity, only those reference numerals are shown in the individual figures that are necessary for the description of the respective figure. The illustrated embodiments merely represent examples of how the device according to the invention can be configured and do not represent a definitive limitation.
[0086] The schematic representation of Fig. 1 shows a drive and energy supply unit 10 for an electric vehicle drive 12 with at least one electric drive motor 14, whose electrical energy supply is ensured by a rechargeable battery or accumulator unit 16 with a plurality of battery cells 18. The battery cells 18 together form the battery or accumulator unit 16 and are connected in series in groups in a sensible arrangement in order to be able to provide a desired output voltage. In addition, several such groups of battery cells 18 are generally connected in parallel in order to ensure a desired total electrical output. The structure of such a battery or accumulator unit 16 is not shown in detail here, since it can be assumed to be known to those skilled in the art.
[0087] Between the drive motor 14 and the battery or accumulator unit 16 there is at least one control and regulation unit 20, which not only controls or regulates the output drive power according to a current driver requirement, but also normally ensures the recuperation of electrical energy during braking or coasting of the vehicle. Furthermore, it is essential that the entire energy and charging management system be monitored, controlled, and regulated by this control and regulation unit 20. The complex functional scope of such a control and regulation unit 20 need not be discussed in detail here, but can also be assumed to be sufficiently known to the person skilled in the art.
[0088] Since such battery units 16 or accumulator modules, as shown schematically here and used as part of the drive and energy supply unit 10 for the drive motor 14 of the vehicle drive 12, are subject to relatively high electrical, thermal and, under certain circumstances, also mechanical loads both during charging and during their intended use as an electrical energy source, and since the battery cells 18 usually used for this purpose best develop their electrical properties and develop their maximum capacity within a limited temperature range, it is generally advisable to temperature control the battery cells 18 or the entire battery unit 16.In addition, there is the considerable heat development both during charging operation, particularly during rapid charging with high power, and when the power demand is high due to ferry operation, so that temperature control is often required throughout the entire operation. The drive and energy supply unit 10, shown schematically in Fig. 1, comprises a liquid circuit 22 with at least one pump 24 for circulating a liquid circulating within the liquid circuit 22. This liquid circulated by the pump 24 flows through the battery unit 16 and can optionally flow through a heat exchanger 26, which can be used to cool the circulating liquid and thus also the battery unit 16 as needed when the battery cells 18 heat up considerably due to a charging process or due to high power demands from the drive motor 14 of the vehicle drive 12.
[0089] However, since the temperature range for high performance of the battery cells 18 should not fall significantly below approximately 15 to 20°C, the fluid circuit 22 also contains a controllable and / or adjustable electrical heating element 28, through which the circulating fluid also flows. This electrical heating element 28, which receives a controlled supply voltage 30 from the control and regulation unit 20, is explained in detail below in terms of its structure and function as part of the drive and energy supply unit 10 and as part of the fluid circuit 22 coupled thereto.
[0090] The electrical heating element 28 shown here thus serves to quickly and effectively heat the liquid circulating in the liquid circuit 22, forms a defined flow section 32 within the liquid circuit 22 and can thus ensure a thermal exchange with the battery cells 18 of the battery unit 16.
[0091] The perspective views of Figures 2A and 2B show an embodiment of a fluid-flowing electric heating element 28, which can be used for the targeted and controllable heating of the fluid circulating in the fluid circuit 22 (see Figure 1). The heating element 28 comprises a housing 34 with a cylindrical body 36 and conical outlets 38 on both ends, each of which opens into line connections 40.
[0092] The two conical outlet funnels 38 can, for example, each have a length in the direction of the longitudinal central axis 42 that corresponds approximately to a quarter of the length of the cylindrical body 36. The cylindrical body 36 can, for example, have a diameter that corresponds to half its length. A reasonable cross-section of the two line connections 40, between which the flow section 32 shown in Fig. 1 with the electric heating element 28 arranged therein is located, can be approximately a quarter or less of the outer diameter of the cylindrical body 36.
[0093] In the interest of low flow resistance, the line connections 40 opening into the housing 34 on both sides can be aligned with one another, preferably in simultaneous alignment with a longitudinal center axis 42 of the housing 34 and its cylindrical body 36, as shown by way of example in Fig. 2A.
[0094] Thus, the fluid circulating in the fluid circuit 22 can enter the housing 34 of the heating element 28 at a first line connection 40 and exit the housing 34 again through the opposite second line connection 40. The exiting fluid can be tempered as needed, i.e., heated relative to the inlet side. To achieve this, the fluid flowing through the heating element 28 can be tempered or heated within the cylindrical body section 36 of the housing 34 by means of electrical heating conductors 44 arranged there.
[0095] As can be seen from a comparison of Figures 2B, 2C, and 2D, the actual electrical heating conductors 44 are located within the housing 34 of the electrical heating element 28 (see Figure 2A), forming a conductive layer on the surface of a compactly rolled-up, flat carrier 46. The carrier 46 shown, on which the electrical heating conductors 44 are arranged, is a two-part, flat carrier layer 48 or carrier foil 48, the first partial layer 50 of which is initially aligned flat in order to apply a second partial layer 52 thereto, as illustrated in Figure 2C.
[0096] Both the flat first sub-layer 50, which is located at the bottom in the side view of Fig. 2C, and the second sub-layer 52 arranged above it and attached to the first sub-layer 50 are each equipped with heating conductors 44, described in more detail below, in order to form the heatable flow channels 54. Since the second sub-layer 52 has a corrugated structure with a uniformly meandering surface, it can be placed in linear contact with the first sub-layer 50 and then bonded to the first sub-layer 50, which is also clearly visible in Fig. 2C.
[0097] Since the mutually facing surfaces of the two partial layers 50 and 52 of the carrier 46 are each equipped with heating conductors 44, and since the cavities formed between the joined partial layers 50 and 52 each form flow channels 54, which, as shown in Fig. 2D, all extend parallel to the longitudinal center axis 42 of the heating element 28, the liquid flowing through the flow channels 54 can be brought to a desired elevated temperature depending on the selected application of electrical energy to the heating conductors 44.
[0098] Fig. 2D shows that the two-layer carrier 46 is spirally wound or wound around the longitudinal center axis 42 of the heating element 28, so that between the regions of the flat carrier 46 or the carrier film 48, which are spaced apart from one another in the radial direction, a large number of flow channels 54 are provided for the liquid flowing through the heating element 28. Since the meandering, corrugated second partial layer 52, which is applied to the first partial layer 50 of the carrier 46, defines a certain thickness of the carrier 46 formed in this way, the winding structure shown in Fig. 2D, for example, results from the carrier layer 48 wound up according to the diameter of the housing 34, wherein the wave structure of the second partial layer 52 and the distances between the respective wave troughs or wave crests determine both the opening cross-section of the flow channels 54 and the distance between the successive winding layers in the case of the arrangement according to Fig.2D spiral wound carrier film 48.
[0099] The possible total number of flow channels 54 also results from the number of winding layers of the two-part carrier layer 48, consisting of the two joined partial layers 50 and 52, which fit into the cylindrical housing 34 and form the carrier 46 with the electrical heating conductors 44 applied thereto. As can be seen in Fig. 2D, the interior of the cylindrical housing 34 is thus equipped with the aforementioned plurality of flow channels 54, through which the liquid to be tempered can flow parallel to the longitudinal center axis 42 of the cylindrical housing 34. An alternative embodiment is explained and illustrated below, in which the flow channels 54 run helically due to a differently structured second partial layer 52, which may be desirable for fluidic reasons.
[0100] Since the wave structure of the second partial layer 52 according to Fig. 20 runs regularly over its entire surface, the flow channels 54 formed thereby each extend with approximately constant cross sections through the longitudinal direction of the housing 34 of the heating element 28. The desired heat transfer to the liquid flowing through the flow channels 54, which is used to control the temperature of the battery cells 18 of the drive and energy supply unit 10 (cf. Fig. 1), takes place through the electrical heating conductors 44 explained in detail below, which are formed at least in partial areas of the channel walls.
[0101] Preferably, the flat heating conductors 44 extend over the entire length of the respective flow channels 54 within the housing 34. This requires a complete flat coating of the respective carrier layer 48, preferably on the first partial layer 50 as well as on the corrugated second partial layer 52 attached thereto.
[0102] For the flat heating conductors 44, which are applied as closely spaced conductor tracks 56 with parallel runs and 180° deflections at the ends to the respective carrier layers 48, i.e. on the first partial layer 50 and on the second partial layer 52, various additional functions can be provided as shown in Fig. 3A, Fig. 3C or Fig. 3E. Fig. 3A illustrates a variant in which a narrow section of the conductor tracks 56, namely the section on the right in the plan view of the carrier layer 48 shown on the left, is designed as a temperature measuring area 58, which can supply a corresponding temperature signal to the control and regulation unit 20 shown in Fig. 1, so that temperature regulation of the unit 20 is possible.
[0103] The conductor tracks 56 applied to the carrier foil 48 ensure the desired heating due to their internal resistance when an electric current flows through the conductor tracks 56. Since they cover almost the entire surface of the carrier foil 48, it acts as a flat heating device.
[0104] In the right-hand illustration of Fig. 3A, in which the carrier 46 is shown in the unwound state, this temperature measuring area 58 is located in the right-hand section of the carrier 46, ie in the vicinity of the downstream outlet funnel 38 of the heating element 28 (cf. Fig. 2A), so that the temperature after flowing through the flow channels 54 of the heating element 28 can be effectively recorded and made available as an electrical signal to the control and regulation unit 20 (cf. Fig. 1).
[0105] Furthermore, the schematic top view of Fig. 3C illustrates a variant in which a narrow section of the conductor tracks 56, namely the section located on the left in the top view of the carrier layer 48 shown, is designed as a separately controllable sub-region 60, which preferably enables graduated temperature control. Thus, this separately controllable sub-region 60 of the conductor tracks 56 can be controlled separately from the other regions and, in particular, can be subjected to different temperatures, so that this sub-region 60 can, for example, be heated more intensively.
[0106] In the perspective view of Fig. 3D shown to the right of Fig. 3C, in which the carrier 46 is shown in the wound-up state, this separately controllable partial area 60 is located according to a preferred embodiment of the heating element 28 in the left section of the carrier 46, ie in the vicinity of the upstream mouth funnel 38 of the heating element 28, so that the temperature can initially be increased more strongly after flowing into the flow channels 54 of the heating element 28 and then further increased with a moderate heating effect.
[0107] In addition, the schematic top view of Fig. 3E illustrates a further embodiment variant in which defined longitudinal sections 62 of the carrier layer 46 can be configured as separately controllable sections of the conductor tracks 56, which in turn enables graduated temperature control, but here for channels 54 with uneven flow, so that the liquid passing through them is also heated unevenly. Such separately controllable longitudinal sections 62, which can, for example, be tempered more strongly, allow flow channels 54 with less flow to be heated more intensely, so that a more uniform temperature control of the liquid can be achieved across the entire cross-section of the heating element 28 within the housing 34.
[0108] Such graduated temperature control, however, requires a correspondingly spatially resolved temperature measurement, which can be ensured by appropriately subdivided temperature measurement areas 58 (see Fig. 3A). The different temperatures in different subregions of the flow channels 54 can be visualized, for example, according to the schematic front view of the wound structure of the conductor tracks shown to the right of the top view of Fig. 3E, as shown in Fig. 3F. Thus, Fig. 3F shows a top view of the wound carrier 46 with differently measured temperature profiles (see graphic addition on the right in Fig. 3F) of the liquid flowing through the channels 54.
[0109] The different regions 58, 60 and 62 of the conductor track structures 56 can optionally also be combined with one another, so that different temperature measuring regions 58 (cf. Fig. 3A) can be combined with more strongly temperature-controlled partial regions 60 along the flow direction (cf. Fig. 3B) and / or with more or less strongly temperature-controlled and accordingly separately controllable longitudinal sections 62 of the conductor tracks 56 in any desired and in each case more expedient manner.
[0110] The arrows on the right of Figures 3A, 3C, and 3E, which point to the right toward Figures 3B, 3D, and 3F, respectively, are intended to illustrate the deformation of the initially flat carrier 46, as shown in Figure 2C, in which the two partial layers 50 and 52 are joined together. The carrier 46 is rolled up in the manner shown so that it assumes the barrel-shaped contour shown in Figures 2B and 2D and can be inserted into the interior of the cylindrical housing 34.
[0111] Fig. 4A illustrates, in a schematic and perspective view, an alternative design of the heating element 28, in which the two-layer carrier 46 is not wound or wound in a precise spiral shape around the longitudinal center axis 42 of the heating element 28 as shown in Fig. 2D. The carrier 46 or the carrier foil 48 can, in particular, be designed in the same or comparable manner as shown with reference to Fig. 2C and described above. The distribution of the conductor tracks 56 and / or the temperature measuring region 58 in the carrier foil 48 illustrated in Fig. 4A can, in particular, be designed in accordance with Figures 3A, 3C, and / or 3E.
[0112] According to the variant shown in Fig. 4A, the winding of the carrier 46 can preferably lead to a cuboid-shaped outer contour of the entire electrical heating conductor 44, so that a large number of flow channels 54 for the liquid flowing through the heating element 28 are provided between the regions of the flat carrier 46 or the carrier foil 48, which are spaced apart from one another in the radial direction. However, the flow channels 54 in the successive winding layers of the wound carrier 46 can have different effective cross-sections due to the locally different spacing of the superimposed layers of the carrier layer 48. However, due to the overall small cross-sectional differences, this effect is negligible in its entirety or is technically acceptable.
[0113] Since the meandering, corrugated second partial layer 52, which is applied to the first partial layer 50 of the carrier 46, defines a certain thickness of the carrier 46 formed in this way, the winding structure shown in Fig. 4A, for example, results from the carrier layer 48 wound up according to the dimension of the available cuboid housing 35 (cf. Fig. 4B), wherein the wave structure of the second partial layer 52 and the distances between the respective wave troughs or wave crests specify both the opening cross-section of the flow channels 54 and the distance between the successive winding layers in the carrier film 48 which, according to Fig. 4A, is wound spirally only in the inner region around the longitudinal center axis 42, while the carrier film 48 assumes the approximately cuboid winding contour recognizable in Fig. 4A with increasing radial distance from the longitudinal center axis 42.
[0114] Optionally, the finished wound shape of the heating conductor 44 can be held in the required contour and mechanically stabilized by means of support bands 64 placed or stretched around the outer surface of the heating conductor 44.
[0115] The schematic and perspective view of Fig. 4B illustrates a possible installation situation of an approximately cuboid-shaped wound heating conductor 44 according to Fig. 4A, which is inserted into a cuboid-shaped housing 35. The housing 35 can preferably have a correspondingly dimensioned housing opening 66, which can be approximately the size of an entire side surface of the housing 35, so that the heating conductor 44, formed by the carrier layer 48 wound according to Fig. 4A, can be inserted through this housing opening 66.
[0116] The illustration in Fig. 4B shows the cuboid housing 35 with the housing cover removed (not shown here), thus exposing the housing opening 66 and the heating conductor 44 inserted in the housing 35. The design of the outlet funnels 38 located on the opposite end faces of the cuboid housing 35 and the respective line connections 40 adjoining them can be carried out in a corresponding manner, as described above with reference to Fig. 2A, but adapted to the cuboid housing design with its respective quadrangular or square end faces, to whose contours the outlet funnels 38 are to be adapted expediently.
[0117] The perspective views of Figures 5A and 5B show a conceivable embodiment of an electrical cable connection 68 for supplying electrical power to the electrical heating conductor 44 and for electrical signal transmission. Since the entire electrical heating conductor 44 is located within the fluid-permeable cylindrical housing 34 (see Figure 2A) or cuboid-shaped housing 35 (see Figure 4B), reliable sealing of the cable feedthrough into and out of the housing 34 or 35 must be ensured.
[0118] This can be ensured, for example, by a design of the electrical line connection 68 according to Fig. 5A and / or Fig. 5B, in which the electrical line connection 68 is equipped with an elongated sealing element 70, which can ensure the desired sealing effect when the line connection 68 is mounted and the housing 34 or 35 is closed.
[0119] The schematic and perspective representations of Figures 6A and 6B also illustrate an alternative embodiment of the heating conductor 44, the layers of which are not wound but folded, so that the structure of the heating conductor 44 shown in Figure 6B is created, with the carrier layers 72 of the carrier layer 48 folded by 180° at each of the longitudinal edges and placed one above the other. To stabilize the shape of this layer structure, the support bands according to Figure 4A and / or a supporting covering 74 made of foil (see Figure 6B) or the like can be used.
[0120] Fig. 6A illustrates a preliminary manufacturing stage in which the carrier layer 48 is covered on at least one side, preferably both sides, with a support film 76, which can be glued or otherwise adhered to the carrier layer 48, i.e., to the first and second partial layers 50 and 52 (cf. Fig. 2C). The folds, i.e., the bend edges at which the 180° folds of the carrier film 48 are to occur, can be predetermined by means of longitudinal slits 78 or weakened areas at defined intervals from one another in order to achieve the folded and layered structure of the heating conductor 44 according to Fig. 6B.
[0121] An additional advantage of the design variant of the heating conductor 44 according to Fig. 6A and 6B is the simpler production-technical feasibility compared to a cuboid-shaped winding, as is required in the variant according to Fig. 4A.
[0122] Finally, Figures 7A and 7B illustrate two alternative embodiments. The front view of one end face of the two-layer carrier 46 (Fig. 7A, top) shows that the longitudinal extension directions of the regularly spaced waves and valleys of the corrugated second sub-layer 52, which is connected to the flat lower sub-layer 50 and together with it forms the flow channels 54, run perpendicular to the side edges of the still flat carrier layer 48 (Fig. 7A, bottom).
[0123] In this embodiment, the winding direction is transverse to this, i.e., transverse to the longitudinal directions of the shafts and supports of the second partial layer 52, so that in the wound or rolled state of the support 46 (see Fig. 2B and Fig. 2D), the longitudinal extension directions of all parallel flow channels 54 also run parallel to the longitudinal extension direction 42 of the entire heating element 28 (see Fig. 2A). The temperature control fluid flowing through the flow channels 54 is thus not deflected at an angle.
[0124] In contrast, in the second embodiment according to Fig. 7B, the longitudinal extension directions of the regularly spaced waves and valleys of the corrugated second partial layer 52, which is connected to the flat lower partial layer 50 and together with it forms the flow channels 54, do not run exactly perpendicular to the side edges of the still flat carrier layer 48, but enclose an acute angle of, for example, 10° to approximately 25° with it (cf. Fig. 7B below).
[0125] However, in this embodiment, the winding direction is also transverse to the side edges of the rectangular support 46, so that the same acute angles to the longitudinal directions of the shafts and supports of the second partial layer 52 are maintained. This means that in the wound or rolled state of the support 46 (see Fig. 2B and Fig. 2D), the longitudinal extension directions of all parallel flow channels 54 also run at an acute angle of approximately 10° to 25° to the longitudinal extension direction 42 of the entire heating element 28. The temperature control fluid flowing through the flow channels 54 is thus deflected obliquely and thereby acquires a vortex-like swirl.
[0126] Further design variants are conceivable which may differ from the variants according to Fig. 7A and Fig. 7B, for example those with non-rectilinear longitudinal extension directions of the flow channels 54, but rather moderately wavy or meandering courses or the like.
[0127] At this point, it should be noted that a film material that is permanently resistant to water and / or glycol alcohol is suitable as the carrier layer 48 or as the carrier film 48. For example, a PEN carrier film that has the desired properties can be used as the carrier film 48.
[0128] Furthermore, the conductor tracks 56 and the carrier foil 48 should be capable of operating and functioning permanently at high-voltage ranges (e.g., approximately 300 to 1000 volts, in particular approximately 400 to 900 volts). Furthermore, the selection of suitable materials and suitable dimensions should ensure that short circuits between the heating tracks (i.e., the conductor tracks 56) and the sensor tracks (i.e., the conductor tracks of the temperature measuring area 58), as illustrated by way of example in Figures 3A, 3C, and 3E, can be avoided.
[0129] Furthermore, the schematic representations of Figures 8A to 8F each show different variants of a further alternative design variant of the heating conductor 44 of the electrical heating element 28, which do not require the corrugated connection described above. In the variants shown, a flat heating conductor 44 is simply wound up in a spiral shape. Since there are no corrugations as spacers to distance the individual windings from one another, linear spacers 80 are introduced at regular intervals, which keep the various winding layers at constant distances from one another, whereby the liquid to be heated can flow largely unhindered within the flow channels 54 formed in this way. Electrical connection contacts 82 are each led outwards to provide electrically conductive connections to the conductor tracks 56 (cf.Figures 3A, 3C and 3E) of the heating conductors 44. Figures 8A and 8B each show, in plan views of the wound structure of two superimposed heating conductors 44, a variant of an electrical heating element 28 with a large total flow cross-section, since the heating conductors 44 are wound on top of one another more than five times. Fig. 8A shows a variant with heating conductors 44 ending at one point on the outside, in which the electrical connection contacts 82 are thus located close to one another. Fig. 8B, on the other hand, shows a variant of the electrical heating element 28 in which the heating conductors 44 end at opposite regions of the outer circumference, so that the respective electrical connection contacts 82 are also arranged at opposite regions of the outer circumference of the heating element 28.
[0130] Figures 80 and 8D each show, in plan views of the wound structure of two superimposed heating conductors 44, another variant of an electrical heating element 28 with a medium total flow cross-section, since the heating conductors 44 are wound on top of one another only two or three times. Fig. 8C shows a variant with heating conductors 44 ending at one point on the outside, in which the electrical connection contacts 82 are thus located close to one another. Fig. 8D, on the other hand, shows a variant of the electrical heating element 28 in which the heating conductors 44 end at opposite regions of the outer circumference, so that the respective electrical connection contacts 82 are also arranged at opposite regions of the outer circumference of the heating element 28.
[0131] Finally, Figures 8E and 8F each show plan views of the wound structure of two superimposed heating conductors 44, a further variant of an electrical heating element 28 with a small total flow cross-section, since the heating conductors 44 are only wound on top of one another once. Fig. 8E shows a variant with heating conductors 44 ending at one point on the outside, in which the electrical connection contacts 82 are thus located close to one another. Fig. 8F, on the other hand, shows a variant of the electrical heating element 28 in which the heating conductors 44 end at opposite regions of the outer circumference, so that the respective electrical connection contacts 82 are also arranged at opposite regions of the outer circumference of the heating element 28. As a result, the invention provides an effective surface that can be temperature-controlled, for example.approximately a quarter of a square meter, which can be accommodated within a heating element 28, which may have a housing length of, for example, only about fifteen to twenty centimeters, and this with a practical housing diameter of less than ten centimeters. Such a heating element 28 can be easily integrated into a fluid circuit 22 for controlling the temperature of a battery unit 16, as described above in Fig. 1 using the example of an electric vehicle drive 14.
[0132] An evaluation electronics unit which should preferably be provided - formed in particular by or implemented in particular in the control unit 20 mentioned above (cf. Fig. 1) - could also record the resistance of at least one conductor track circuit and, using the known temperature coefficient of aluminum or the aluminum alloy used in each case, determine the currently prevailing water temperature or the temperature of the tempering liquid or the carrier liquid. In addition, this evaluation electronics unit could be enabled to cause this conductor track circuit to heat up additionally, for example by approximately 5°C, and to determine the electrical energy required for this (calculated from the product of the applied electrical voltage and the electrical current flowing through the conductor track circuit). The faster the water orThe faster the temperature control fluid or carrier fluid flows through the circuit, the more energy is required to maintain the desired temperature difference of, for example, about 5°C.
[0133] Thus, a simply constructed and reliably functioning flow sensor could be realized in the manner described. If this flow sensor were to detect a standstill in the flow or an excessive reduction in the flow velocity, all heating circuits could be shut down to prevent overheating of the heating element 28 and / or the entire fluid-flowing circuit.
[0134] The invention has been described with reference to a preferred embodiment. However, it is conceivable for a person skilled in the art that modifications or changes to the invention can be made without departing from the scope of the following claims.
[0135] 10 Drive and power supply unit
[0136] 12 Vehicle drive
[0137] 14 Drive motor, electric drive motor
[0138] 16 Battery unit, accumulator unit, battery module, accumulator module
[0139] 18 battery cells
[0140] 20 Control unit, regulation unit, control and / or regulation unit
[0141] 22 Fluid circuit
[0142] 24 Pump
[0143] 26 heat exchangers
[0144] 28 Heating element, electric heating element
[0145] 30 Supply voltage
[0146] 32 flow section
[0147] 34 housings
[0148] 35 cuboid housing
[0149] 36 Body, cylindrical body, body section
[0150] 38 estuary funnels
[0151] 40 line connection
[0152] 42 Longitudinal center axis
[0153] 44 heating conductor, electrical heating conductor
[0154] 46 carriers
[0155] 48 Carrier layer, carrier film
[0156] 50 first sub-shift
[0157] 52 second sub-layer, corrugated second sub-layer, corrugated top layer
[0158] 54 flow channel
[0159] 56 conductor tracks
[0160] 58 temperature measuring range
[0161] 60 separately controllable sub-areas
[0162] 62 longitudinal sections, separately controllable longitudinal sections
[0163] 64 support band
[0164] 66 Housing opening
[0165] 68 Electrical cable connection Sealing element Carrier layer Envelope Support film Slotting Spacer Electrical connection contacts
Claims
Claims 1 . Heating element (28) for forming a flow section (32) for a liquid circuit (22) provided for thermal exchange with a drive battery (16), comprising - at least one electrical heating conductor (44) and - a carrier (46) on which the at least one electrical heating conductor (44) is arranged, characterized in that the carrier (46) is a carrier layer or carrier film (48) which is wound and / or folded several times and thus brought into a spatial structure, wherein between regions of the carrier layer or carrier film (48) which are spaced apart from one another in the radial direction, one or more flow channels (54) for liquid are provided.
2. Heating element (28) according to claim 1, the carrier layer or carrier foil (48) of which forms the carrier (46) for the electrical heating conductor (44) is wound at least in regions in a spiral shape around a longitudinal central axis (42) of the heating element (28).
3. Heating elements (28) according to claim 1 or 2, whose carrier layer or carrier foil (48), which forms the carrier (46) for the electrical heating conductor (44), is brought into a contour which is not round in cross-section, in particular into a polygonal, particularly preferably into an approximately square contour, in particular by a winding of the carrier layer or carrier foil (48).
4. Heating element (28) according to claim 1, wherein the carrier layer or carrier film (48) is folded at least in some regions and / or is brought into the spatial structure by meandering shaping.
5. Heating element (28) according to claim 4, wherein immediately adjacent surface sections of the carrier layer or carrier film (48) are placed one on top of the other.
6. Heating element (28) according to one of claims 1 to 5, wherein the entire wound, coiled and / or folded carrier layer or carrier foil (48) which forms the carrier (46) for the electrical heating conductor (44) forms a cuboid spatial structure and is enclosed and / or accommodated by a cuboid housing (34).
7. Heating element (28) according to claim 1 or 2, whose particularly cylindrical housing (34) accommodates the electrical heating conductor (44).
8. Heating element (28) according to one of claims 1 to 7, in which the electrical heating conductor (44) is equipped with a plurality of flow channels (54) through which the liquid to be tempered can flow substantially parallel to a longitudinal central axis (42) of the cuboid-shaped or cylindrical housing (34) or of the heating conductor (44).
9. Heating element (28) according to one of claims 1 to 8, wherein the flow channels (54) each extend with approximately constant cross sections through the longitudinal direction of the heating conductor (44).
10. Heating element (28) according to one of claims 1 to 9, in which at least sections of the channel walls of the flow channels (54) are designed as heatable surfaces which can effect a heat transfer when the liquid flows past from the heating conductor (44) to the liquid.
11. Heating element (28) according to claim 10, wherein the heatable surfaces of the flow channels (54) extend over the entire length of the respective flow channels (54).
12. Heating element (28) according to claim 10 or 11, wherein the heatable surfaces of the flow channels (54) have separately controllable regions over their longitudinal extent, which are separated from one another and which can be subjected to different temperatures.
13. Heating element (28) according to one of claims 1 to 12, which comprises a wound flat heating conductor (44) which is provided with a corrugated cover layer (52) which is applied in regular line contact to a first flat partial layer (50) and between the two layers (50, 52) the regularly spaced flow channels (54) are formed.
14. Heating element (28) according to claim 13, wherein both the first flat partial layer (50) and the corrugated cover layer (52) are each coated with an electrically conductive layer at least on their facing surfaces and are designed as a tempering surface.
15. Heating element (28) according to claim 13, wherein both the first flat partial layer (50) and the corrugated cover layer (52) are each coated on both sides with an electrically conductive coating and are designed as tempering surfaces.
16. Heating element according to claim 14 or 15, wherein the electrically conductive layers of the sub-layers (50, 52) are each provided with conductor tracks (56) which are closely spaced from one another and distributed over the surfaces of the layers (50, 52).
17. Heating element (28) according to one of claims 1 to 16, which is equipped with at least one temperature measuring region (58) which is located in the region of the flat and / or wavy sections or the partial layers (50, 52).
18. Liquid circuit (22) for controlling the temperature of a liquid-cooled battery unit (16) of a drive and energy supply unit (10) of a vehicle drive (14), wherein the liquid in the liquid circuit (22) can be circulated by means of a pump (24) and conveyed through the liquid-cooled battery unit (16), wherein in a defined flow section (32) of the liquid circuit (22) there is at least one electrically operated heating element (28) which is equipped with flow channels (54) whose channel walls are designed as flat heating conductors (44).
19. Liquid circuit (22) according to claim 18, wherein the at least one electrical heating element (28) is designed according to one of claims 1 to 17.
20. Liquid circuit (22) according to claim 18 or 19, which is equipped with a control and / or regulating unit (20) for temperature control, which electrical heating element (28) can be supplied with a controllable supply voltage (30).