Coolant heating device and method for configuring a coolant heating device

Abstract

The invention relates to a coolant heating device (10) having at least one inflow region and at least one outflow region, via which coolant to be heated can flow in and out as required. An insulating element is also provided, which is functionally connected to at least one electrical heating element in the form of an electrical conductor (16), wherein the conductor is functionally connected to an energy source in such a way that electrical current flows through the conductor (16) when the energy source is activated in order to output heating power. The conductor (16) has a first portion having a first electrical partial resistance and at least one second portion having a second electrical partial resistance, wherein the first electrical partial resistance and the second electrical partial resistance differ.

Description

[0001] Description

[0002] Coolant heating device and method for the design of a coolant heating device

[0003] The invention relates to a coolant heating device and a method for designing a coolant heating device. Reference is also made to motor vehicles with such coolant heating devices, in particular to motor vehicles with an electric drive energy storage system, also known as Battery Electric Vehicles (BEVs).

[0004] In particular, the invention relates to a coolant heating device with at least one inlet area and at least one outlet area through which coolant to be heated can flow in and out as required, and with at least one electrical heating element that is functionally connected via a power source. The heating element is in particular a resistance heating element with an electrical conductor.

[0005] Specifically, the invention relates to coolant heating devices, also known as high-voltage heaters, in particular coolant heating devices that operate with an input voltage of 60 volts or 120 volts or higher. Reference is made in particular to coolant heating devices that operate with voltages of more than 250 V, more than 300 V, or more than 400 V, for example, 270 V to 1,600 V, in particular 270 V to 1,000 V, 270 V to 940 V, or 300 V to 900 V.

[0006] The invention relates to both thick-film heating elements and heating films.

[0007] With regard to thick-film heating elements, particular reference is made to screen-printed thick-film heating elements, which are essentially resistance circuits screen-printed onto a substrate, allowing current to generate heat as it passes through the circuit. This property forms the integrated circuit for screen-printed thick-film heating elements (referred to as a thick-film circuit). Available substrates include stainless steel, aluminum, or ceramic. The substrate can also be flat or tubular. A dielectric layer, a resistance layer, and a protective layer are applied to the substrate. With regard to heating films, particular reference is made to the arrangement and / or configuration of one or more electrical conductors in the form of a conductor track, positioned between two insulating films. Adhesive is typically used to bond the two insulating films.The adhesive is applied particularly on the outside and between spaced conductor tracks or conductor track sections.

[0008] In vehicles with electric drive energy storage, high-voltage heaters are used, especially in cold temperatures, to quickly heat the coolant. This coolant is then used to heat the battery and, in some cases, the vehicle's interior to the desired temperature.

[0009] From EP 0 837 381 A2, an electric heater with at least two electrical heating elements is known, the heating power of which is set by a control device comprising a plurality of controllers, each assigned to one of the electrical heating elements. The control range of the control device is divided among the controllers, and each controller is assigned a different control range. Reference is made to its application for heating media connected to a circuit in a motor vehicle, such as preheating coolant. The detailed design of the heating elements is not discussed.

[0010] German patent DE 102011 002 144 A1 discloses a method for controlling an electric heater and an electric heater with which overheating can be reliably prevented when using a resistance heating element. This is achieved, in particular, with the aid of power electronics by determining the actual resistance and comparing it with the stored cut-off resistance, by switching off the resistance heating element or reducing the power consumption when the actual resistance reaches the cut-off resistance. Design details of the resistance heating element are not discussed.

[0011] From DE 19946 339 C1, a method for controlling an automatic heating and / or air conditioning system is known, wherein the automatic heating and / or air conditioning system has an auxiliary heater comprising various heating elements, and the heating elements can be controlled independently of one another. The generator output is intended to be used as heating power. According to this method, to improve the utilization of the heating power, the generator output available for heating is determined, a flow profile of the coolant in the auxiliary heater is determined, a location of maximum coolant flow is identified, and the heating element located at this location is activated. Design details of the heating elements are not discussed.

[0012] The invention is based on the objective of providing a coolant heating device and a method for designing a coolant heating device that enables safe and efficient heating of coolant.

[0013] The problem is solved according to the invention by the features of the independent claims. Further practical embodiments and advantages of the invention are described in connection with the dependent claims.

[0014] A coolant heating device according to the invention has at least one inlet area and at least one outlet area through which coolant to be heated can flow into and out of the device as required. Furthermore, an insulating element is provided which is functionally connected to at least one electrical heating element in the form of an electrical conductor. The conductor is functionally connected to an energy source—which is controllable, in particular with regard to the power output—such that when the energy source is activated, the conductor is energized by an electric current to deliver heating power.Furthermore, the conductor has a first subsection with a first partial electrical resistance and at least a second subsection with a second partial electrical resistance, wherein the first and second partial electrical resistances differ, in particular due to their cross-sectional area (in the case of rectangular profiles, especially thickness and width) and / or due to their specific resistance due to the conductor material used. Such a very simple design with only two subsections can be particularly useful when a flow path between an inlet area and an outlet area is to be divided into only two sections, for example, because the coolant can and should be heated more in a first subsection and less in a second subsection because it already has a higher temperature.According to this basic principle, by dividing the electrical conductor and the corresponding coolant flow path into several subsections, the power density between the inlet and outlet sections can be reduced to achieve a more favorable heat distribution. In this context, a favorable heat distribution is understood in particular as an optimization such that...

[0015] Application scenario in which the conductor reaches a certain temperature, the temperature across the entire conductor is approximately the same to achieve a uniform material load.

[0016] In a practical embodiment of a coolant heating device according to the invention, the conductor exhibits varying partial electrical resistances along its length, resulting at least in part from locally differing cross-sectional areas of the conductor. This means, in particular, that the conductor is made of the same material along its length, but has different cross-sectional areas and, consequently, different electrical resistances depending on the size of the cross-section. The smaller the cross-section, the greater the electrical resistance and the greater the heating power delivered to that section. Preferably, the varying partial electrical resistances are adjusted solely by changing the size of the cross-section. This is relatively simple and cost-effective to implement.

[0017] The realization of different conductor cross-sections can be achieved particularly easily and cost-effectively by creating different conductor widths, while keeping the height of the cross-section constant.

[0018] The conductor thickness is preferably between 5 pm and 50 pm, particularly between 9 pm and 18 pm. The conductor width is preferably selected depending on the desired resistance, particularly between approximately 0.5 mm and 2 mm.

[0019] In another practical embodiment of a coolant heating device according to the invention, the insulating element is an electrically non-conductive film and / or the heating element is realized by a conductor track produced from an electrically conductive film or printed onto the insulating element made of an electrically conductive material.

[0020] Particularly in the case of a heating element made from an electrically conductive film, different cross-sections and widths can be produced by milling or laser cutting paths from a single film, using a simple film of constant thickness as the starting material. The width can then be adjusted as needed by controlling a milling or laser tool.

[0021] Alternatively, a plastic film can be used as the starting material for an electrically non-conductive film, which is printed with (at least) one conductor track with a changing cross-section using a 3D printing process. It is advantageous if a coolant heating device according to the invention has a film with several heating circuits in the form of conductors (resistive tracks) as an insulating element. If the resistive tracks are also formed from a film, the uniform film thickness results in a constant thickness. Films designed as insulating elements with three heating circuits have proven particularly advantageous, especially such that each heating circuit has the same total resistance. This has the advantage that the three heating circuits can be controlled symmetrically, and the same amplitudes and spectra occur in an interleaf circuit of the power switches.

[0022] If three heating elements are provided, preferably one heating element is provided for the inlet area, one for the middle area, and one for the outlet area. This results in heating zones of varying sizes.

[0023] In another practical embodiment of a coolant heating device according to the invention, the conductor exhibits varying partial electrical resistances along its length due to the use of different materials. This means that the conductor, for example, a conductor produced using a 3D printing process, can be made of different materials in order to vary the partial electrical resistance of one section relative to another. Thus, by selecting suitable materials, varying electrical resistances can be achieved independently of the cross-sectional variation.

[0024] In a coolant heating device according to the invention, the electrical resistance of the conductor can be continuously and steplessly adjusted, at least over a portion of its length. For example, a conductor can be divided into a multitude of small (even infinitesimally small) sub-sections, and an individual electrical resistance can be determined for each sub-section, which can then be implemented structurally as the respective partial resistance. This allows for a very precise structural adjustment of the conductor with respect to the required heating power.

[0025] In another practical embodiment of a coolant heating device according to the invention, the electrical resistance of the conductor is at least partially adjusted in steps. For example, stepwise adjustment can be achieved by defining limits for the power input (e.g., for "jumps" of 5 W or 10 W power input). Such stepwise adjustment allows for a simpler and less complex conductor geometry, achieving similarly positive results as continuously and steplessly adjusted embodiments. However, due to the simpler geometry, the continuously and steplessly adjusted embodiments can be manufactured more quickly and therefore more cost-effectively, for example, because the width only varies in the area of ​​the jumps.

[0026] Regardless of the embodiments described above, it has proven advantageous and beneficial for the service life of a coolant heating device according to the invention if the electrical resistance of the heating element in the direction of coolant flow is designed such that the power output in the coolant inlet area is greater than in the outlet area. This takes into account the fact that the incoming coolant heats up increasingly due to the action of the heating element as it flows through the coolant heating device. By progressively reducing the heat input along the flow path from the inlet area, it is best ensured that overheating of the heating element and / or the coolant does not occur.

[0027] The invention also relates to a method for designing the electrical resistance of a heating element in the form of a conductor in a coolant heating device as described above, which comprises the following method steps: a) The length of the conductor is divided into a discrete number of segments, b) a maximum load condition of the coolant heating device is determined; this is in particular the operating condition in which the smallest volume flow rate flows through the coolant heating device while the power output is maximum (e.g., smallest volume flow rate (10 l / min) at maximum power output (6000 W)), c) the segment of the conductor is determined in which (assuming a conductor with a constant cross-section and constant resistance over its length) the highest local heating temperature occurs, or the segment which is first exposed to the incoming coolant is selected as the first segment.next, d) the electrical resistance in the determined section is adjusted so that in the determined maximum load condition the maximum permissible insulating element temperature (if the insulating element is a film, this is the.

[0028] e) sets the foil temperature and e) repeat steps c) and d) with the remaining segments until the electrical resistance for each segment is determined.

[0029] This method allows for the design of a coolant heating device with uniform power input, achieving efficient power distribution and a consistent load along the pipe path through the heating device. The goal here is to design a heating element that, after optimization, maximizes the utilization of the heating surface (more heating power can be transferred over the same area, or the area can be reduced while maintaining the same heating power). As a result, the area of ​​a foil serving as an insulating element can be reduced.

[0030] Preferably, the electrical resistance and the required width of a conductor are adjusted section by section from an entry side, while maintaining the same height and material, so that the same foil temperature of an insulating element designed as a foil results over the entire conductor in the maximum operating state.

[0031] In a further practical embodiment of a method for designing the electrical resistance of a heating element in the form of a conductor in a coolant heating device as described above, or for further designing a coolant heating device designed according to the method described above, the following method steps are carried out: a) Determining the expected usage-related failure point of the insulating element (in particular an electrically non-conductive film used as an insulating element) and b) Reducing the electrical resistance in the area of ​​the usage-related failure point to such an extent that a different usage-related failure point results.

[0032] The aforementioned step a) can be carried out in particular by simulation, testing and / or analytical analysis. Optionally, the aforementioned process steps a) and b) can be repeated once or multiple times to further improve the durability of a coolant heating device and, in particular, to achieve the most uniform aging of the insulating element possible. In this case, the design is carried out according to operating conditions such that uniform aging of the heating element results.

[0033] Further practical embodiments of the invention are described below in connection with the drawings. They show:

[0034] Fig. 1 shows a schematic representation of a first embodiment of a section of a coolant heating device according to the invention with a conductor whose width is continuously and steplessly adjusted and

[0035] Fig. 2 shows a schematic representation of a second embodiment of a section of a coolant heating device according to the invention, with a conductor which is divided into five sections and whose width is adjusted stepwise in each section.

[0036] Figures 1 and 2 each show a section of a coolant heating device 10 according to the invention, depicting only the elements essential for understanding the invention. Each figure shows an insulating element 12 in the form of an electrically non-conductive film 14, which, in the schematic representation, has a rectangular shape. A conductor 16 is arranged on the electrically non-conductive film 14, extending in a U-shape from left to right, then downwards, and then back to the left. In the embodiment shown in Figure 1, the conductor is printed onto the film 14 using a 3D printing process.

[0037] In the embodiment shown in Figure 2, the conductor 16 is formed by an electrically conductive film 18. This can be achieved, in particular, by applying an electrically conductive film with a larger area to the film 14 and then removing it, for example by laser irradiation, so that the stepwise adjustment of the width shown in Figure 2 is obtained.

[0038] In both embodiments, a first electrical connection 22 and a second electrical connection 24 for connecting the conductor to a voltage source (not shown) are located in the areas of the conductor 16 that extend to the left edge 20 of the foil 14. Current flows through the conductor 16 in the direction of arrow s. Coolant flows in the direction of arrow K.

[0039] For the sake of completeness, it should be noted that the illustration is not to scale, but rather significantly exaggerated for easier understanding. This applies particularly to the geometry and, specifically, the width of each ladder 16. In practice, the actual width usually varies only slightly. However, the exaggerated representation was chosen to make the variation in width clearly visible.

[0040] In Figure 1, the width bi varies continuously depending on the respective length position L of the conductor. Starting from the first electrical terminal 22, it initially decreases continuously to the opposite end, then remains constant, and subsequently increases again on the way to the second electrical terminal 24, until it reaches the same width in the region of the left edge 20 as it did starting from the first electrical terminal 22 in the region of the left edge 20.

[0041] In Figure 2, the width varies in steps. Starting from the first electrical connection 22, it is initially bi, then decreases abruptly to width b2 and subsequently to width b3 in the region of the opposite end. The width then remains constant and, on the way to the second electrical connection 24, increases again in steps from width b2 to width bi in the region of the left edge 20.

[0042] The width profiles shown are only exemplary. The invention relates in particular to coolant heating devices 10 with continuously changing widths, which are adapted to the heat output that the insulating element 12 used, in particular an electrically non-conductive carrier film 14, can permanently absorb in the application case in which the greatest heat output is transferred to it.

[0043] The features of the invention disclosed in the present description, the drawings, and the claims can be essential for realizing the invention in its various embodiments, both individually and in any combination. The invention can be varied within the scope of the claims and taking into account the knowledge of a person skilled in the art. Reference numerals: Coolant heating device, Insulating element, Electrically non-conductive film, Conductor, Electrically conductive film, Left edge, First electrical connection, Second electrical connection

Claims

Claims 1. Coolant heating device (10) with at least one inlet area and at least one outlet area through which coolant to be heated can flow in and out as required, with an insulating element which is functionally connected to at least one electrical heating element in the form of an electrical conductor (16), wherein the conductor is functionally connected to an energy source such that the conductor (16) is energized by electric current when the energy source is activated in order to deliver heating power, characterized in that the conductor (16) has a first sub-area with a first partial electrical resistance and at least a second sub-area with a second partial electrical resistance, wherein the first partial electrical resistance and the second partial electrical resistance are different.

2. Coolant heating device (10) according to the preceding claim, characterized in that the conductor (16) has different electrical partial resistances along its length, which result at least partially from locally different cross-sectional areas of the conductor (16).

3. Coolant heating device (10) according to the preceding claim, characterized in that the different cross-sections of the conductor (16) are at least partially formed by different widths of the conductor (16).

4. Coolant heating device (10) according to one of the preceding claims, characterized in that the insulating element is an electrically non-conductive film (14) and / or the heating element is realized by a conductor track produced from an electrically conductive film (18) or printed onto the insulating element made of an electrically conductive material.

5. Coolant heating device (10) according to one of the preceding claims, characterized in that the conductor (16) has different partial electrical resistances along its length due to different materials.

6. Coolant heating device (10) according to one of the preceding claims, characterized in that the electrical resistance of the conductor (16) is continuously and steplessly adjusted at least over part of its length.

7. Coolant heating device (10) according to one of the preceding claims, characterized in that the electrical resistance of the conductor (16) is at least partially adjusted in stages.

8. Coolant heating device (10) according to one of the preceding claims, characterized in that the electrical resistance of the heating element in the flow direction of the coolant is designed such that the power output in the inlet area of ​​the coolant is greater than in the outlet area.

9. Method for designing the electrical resistance of a heating element in the form of a conductor (16) in a coolant heating device (10) according to one of claims 1 to 8 within the coolant heating device (10), characterized in that a) the length of the conductor (16) is divided into a discrete number of segments, b) the maximum load state of the coolant heating device (10) is determined, c) the segment of the conductor (16) is determined in which the highest local heating temperature occurs, or the segment which is first exposed to the inflowing coolant is selected as the first segment.next, d) the electrical resistance in the determined section is adjusted so that the maximum permissible insulating element temperature is reached in the determined maximum load condition, and e) steps c) and d) are repeated with the remaining sections until the electrical resistance for each section is determined.

0. Method for designing the electrical resistance of a heating element in the form of a conductor (16) in a coolant heating device (10) according to any one of claims 1 to 8 or method according to the preceding claim, which is carried out for further design, wherein the following steps are carried out: a) determining the expected usage-related failure point of the insulating element and b) reducing the electrical resistance in the area of ​​the usage-related failure point to such an extent that a different usage-related failure point results.

Images