Tank for storing operating fluids and motor vehicle

Abstract

Tank (1) for storing a liquid operating fluid (2) for a motor vehicle (3), comprising a tank wall (18) and an interior space (8) bounded by the tank wall (18), and at least one heating device (7) mounted externally through the tank wall (18) and extending into the interior space (8), the heating device (7) forming a heated cage (12) around a conveying device (6), characterized in that the heating device (7) is arranged in a cage-like manner around the conveying device (6) in the manner of a plate, wherein the cage (12) is semicircular, and wherein the heating device (7) comprises openings.

Description

[0001] The invention relates to a tank for storing operating fluids for a motor vehicle. Operating a motor vehicle typically requires several liquid operating fluids, which can freeze in their tanks at low temperatures. Such operating fluids include, for example, fuel for operating an internal combustion engine, windshield washer fluid for cleaning the vehicle's windows, coolant for operating the internal combustion engine, or reducing agents for reducing harmful components in the exhaust gas of an internal combustion engine.

[0002] The use of reducing agents for cleaning exhaust gases from internal combustion engines has recently gained considerable importance in the automotive sector. A commonly used exhaust gas purification method that requires a reducing agent as an additional operating fluid is selective catalytic reduction (SCR). In this process, a reducing agent is added to the exhaust gas from the internal combustion engine, effectively reducing nitrogen oxide (NOx) compounds within the exhaust system. Selective catalytic reduction is particularly common in the exhaust systems of lean-burn internal combustion engines, such as diesel engines, which emit higher levels of nitrogen oxide compounds.

[0003] For the conversion of nitrogen oxides in the SCR process, ammonia is primarily used as a reducing agent. Ammonia is not typically stored directly in the vehicle itself, but rather in the form of a so-called reducing agent precursor, a substance that is first (chemically) converted into ammonia (as needed). A commonly used reducing agent precursor is urea-water solution. A 32.5% urea-water solution is available for this purpose under the trade name AdBlue and is widely used.

[0004] German patent application DE 20 2006 013 535 U1 discloses a container for fluids, in particular a tank for trucks, consisting of modules attached to one another, in the form of one or more intermediate modules with a circumferential wall and preferably a baffle wall molded onto one side, a first end module with a circumferential wall and a closed bottom wall, and a second end module with a circumferential wall and a closed bottom wall, wherein at least one of the modules has an opening for arranging a tank filling nozzle and at least one of the modules has an opening for arranging a fluid line, characterized in that at least one of the end modules has a cap-like additional module attached, which is intended for filling with a reduction solution, in particular aqueous uric acid, wherein the additional module has at least one opening for arranging a filling element, in particular a filling nozzle.as well as a heating coil through which the heating medium flows, with a first connection nozzle penetrating the wall of the additional module and sealed, and a second connection nozzle penetrating the wall and sealed for draining and returning the reduction solution.

[0005] German patent application DE 20 2007 018 408 U1 discloses a thermally insulating container for carrying liquid in a mobile device, in particular in a vehicle, wherein the container has a container wall surrounding the liquid on all sides, wherein the container wall comprises at least two integrally connected layers made of the same material, wherein the layers have different densities.

[0006] German patent application DE 10 2009 009 676 A1 discloses a container arrangement for a vehicle, comprising a fuel tank and an auxiliary container, wherein the auxiliary container is arranged inside the fuel tank and wherein the container arrangement includes a heating device for heating the auxiliary container. Furthermore, the invention relates to a container arrangement for a vehicle, comprising a fuel tank and an auxiliary container, wherein the auxiliary container is arranged at least partially outside the fuel tank.

[0007] German patent application DE 10 2008 023 073 A1 discloses a container for operating fluids of motor vehicles, with a supporting structure on the inside of which a sintered plastic layer is formed to create a receiving space for the operating fluid. The sintered plastic layer is to be made of polyurethane.

[0008] The document DE 10 2007 061 808 A1 discloses a tank extraction device with a cold start heater for frozen liquids from a motor vehicle tank system with at least one main tank, with at least one heat dissipation element which is thermally connected to at least one heating element and which conducts the heat generated in the heating element into the frozen liquid, thereby melting a cold start volume.

[0009] German patent application DE 88 03 323 U1 discloses a device for supplying an internal combustion engine with fuel, in particular a diesel engine with diesel fuel. The device is equipped with an insulated tank, which is closed by a lid and into which a heat exchanger is inserted. Heating water flows in this heat exchanger. A probe measures the temperature of the diesel fuel and acts on a thermostat.

[0010] The publication DE 85 23 335 U1 discloses a thermotank with a tank insert and a fuel filter for storing, conveying and filtering fuel for a diesel engine while simultaneously preheating it by an electrically operated heating device.

[0011] German patent application DE 10 2006 027 487 A1 discloses a vehicle tank for an aqueous urea solution for reducing nitrogen oxides in the exhaust gas of internal combustion engines, made of plastic. The vehicle tank advantageously comprises a functional unit including at least one pump, at least one pressure regulating valve, at least one inner container with integrated electric heating, and at least one suction line.

[0012] Document WO 2010 / 000 827 A1 discloses a level sensor. The sensor comprises a basic unit having a cavity. A first axial end of the cavity is configured for hydraulic communication with a fluid reservoir. A second axial end of the cavity is configured for hydraulic coupling with a fluid accumulator. A heating element is arranged in a wall of the cavity. A first electrode and a second electrode are arranged on the basic unit such that the electrical capacitance formed between the first and second electrodes is representative of the level in the fluid reservoir.

[0013] The publication EP 2 161 422 A2 discloses improved systems and methods for supplying a urea solution to an exhaust gas treatment system. The system comprises a urea tank assembly that includes a reservoir with a fluid inlet opening for receiving the urea solution and a fluid outlet opening for discharging the urea solution. The urea tank further includes a vented hollow element located within the reservoir. The vented hollow element defines an inner cavity and a plurality of openings to allow fluid flow between the reservoir and the inner cavity. The urea tank further includes a heating device arranged along the vented hollow element to heat the urea solution within the inner cavity and the reservoir.

[0014] A problem with storing urea-water solution in a tank is that it freezes at temperatures of approximately -11°C. Such temperatures can occur during the operation of a motor vehicle, especially during extended periods of inactivity in winter. A tank for a reducing agent must therefore be designed so that it is not damaged if the reducing agent stored in the tank freezes. Furthermore, it is necessary that liquid reducing agent is available in the tank as quickly as possible after the vehicle is started. For this reason, it is known to incorporate heating devices in a tank for storing a reducing agent, by means of which frozen reducing agent can be thawed.

[0015] A problem with such heating devices is that they often represent a significant cost factor, both during installation and operation. Furthermore, these devices require intensive maintenance. It has also been observed that the freezing and thawing behavior is highly dependent on the tank's application and position within the vehicle. To meet the aforementioned criteria, existing heating devices are typically designed to be considerably larger than necessary for many applications, further increasing energy consumption and costs. Consequently, a concept for supplying these heating devices with only the precise amount of energy required to thaw the frozen reducing agent is lacking.

[0016] Based on this, the object of the present invention is to at least alleviate the technical problems described in connection with the prior art. In particular, it aims to provide a particularly cost-effective and easy-to-install fuel tank for a motor vehicle, incorporating an effective heating device.

[0017] This problem is solved by a tank according to the features of claim 1 and a motor vehicle according to the features of dependent claim 5. Further advantageous embodiments of the tank are specified in the dependent claims. The features listed individually in the claims can be combined with one another in any technologically meaningful way and can be supplemented by explanatory details from the description, thereby showing further embodiments of the invention.

[0018] The invention therefore relates to a tank for storing a liquid operating fluid for a motor vehicle, comprising a tank wall and an interior space bounded by the tank wall, and at least one heating device which is mounted externally through the tank wall and extends into the interior space, wherein the at least one heating device forms a heated cage around the conveying device, wherein the heating device is arranged around the conveying device in a cage-like manner in the form of a plate, wherein the cage is semicircular, and wherein the heating device comprises openings.

[0019] The tank preferably has a tank wall made of plastic, and in particular, the tank forms a single, enclosed tank wall. The liquid operating fluid (at normal operating conditions or room temperature) can be permanently stored inside the tank. The liquid operating fluid is preferably a reducing agent or a reducing agent precursor for reducing pollutants in the exhaust gas of an internal combustion engine. For example, the operating fluid can be a urea-water solution. For mounting the at least one heating device from the outside through the tank wall, the tank wall preferably has a corresponding (second) mounting opening through which the at least one heating device is installed.

[0020] In addition to at least one heating device, the tank may preferably also be equipped with a conveying device for the liquid operating fluid. The conveying device may, for example, be housed in a metallic casing on the tank wall, which is positioned in a (separate or primary) mounting opening of the tank specifically designated for this purpose.

[0021] The at least one heating device is preferably an electrically operated or controllable heating device, which has at least one PTC heating element (PTC = positive temperature coefficient). Such a heating element is able to regulate its heating power itself over a temperature range defined by the heating element and is therefore particularly advantageous when only the energy required for defrosting is to be introduced into the operating medium.

[0022] In another embodiment of the heating device, it can also be designed as a liquid heating system, in which a hot fluid flows through a heating coil. The cooling water from the internal combustion engine of a motor vehicle, for example, can be used as the heating fluid.

[0023] It is also possible that at least one heating device includes a so-called heat pipe. Heat pipes essentially contain a hermetically sealed volume, usually in the form of a tube. This volume is filled with a working fluid (e.g., water), which occupies a small portion of the volume in a liquid state and the majority in a vapor state. Within the heat pipe are a heat transfer surface for a heat source (near the tank wall or outside the tank wall) and a heat sink (inside the tank or opposite the heat source). When heat is applied, the working fluid begins to evaporate. This locally increases the pressure in the vapor space above the liquid level, resulting in a slight pressure gradient within the heat pipe. The resulting vapor flows towards the heat sink, where it condenses due to the lower temperature of, for example, the frozen reducing agent (heat sink).The previously absorbed latent heat is then released. The now liquid working fluid then returns to the evaporator (heat source) by gravity or capillary action.

[0024] This at least one heating device is, in other words, a local, retrofitted heat source positioned at a predetermined location through the tank wall for the targeted and effective thawing of frozen operating fluid inside the tank. This specifically excludes a surface heating system extending along the tank wall, which would also form a large interface with the surroundings (and which may additionally be provided). Rather, the heating power is directed deep into the tank's interior by means of the at least one heating device. Several such heating devices can be used to achieve a predetermined distribution of heat deep within the tank's interior. The heating devices can also vary in design, particularly with regard to their type, length, orientation, heating capacity, etc.

[0025] This design of the tank allows, in particular, for retrofitting with demand-oriented, efficient heating devices.

[0026] It has been found that heating devices designed in this way can be installed in the tank according to the invention particularly easily and quickly. For heating devices designed in this way, appropriately shaped (second) mounting openings in the tank or a tank wall are advantageous, through which the heating devices can be mounted from the outside. A heating device designed in the form of a rod has a significantly greater length in one direction compared to the other two spatial directions. A heating device designed in the form of a plate has a significantly greater length in two directions compared to a third direction. Preferably, the at least one heating device has a cross-sectional shape and a length perpendicular to this cross-sectional shape. The cross-sectional shape essentially corresponds to the shape of the second mounting opening through which the at least one heating device can be mounted.

[0027] The device according to the invention is further advantageous if the at least one heating device is detachably and fluid-tightly connected to the tank wall. It is particularly advantageous to insert the heating device into the tank through the second mounting opening, or to mount it in the tank, if the second mounting opening is located in the tank wall at the bottom of the tank. In this case, it is particularly important that the heating device seals fluid-tightly against the tank wall in the second mounting opening to prevent any leakage of operating fluid from the tank. Such a detachable integration of the at least one heating device facilitates repair work or the integration of other heating devices if the freezing or thawing behavior of the vehicle subsequently changes.

[0028] According to a further development, it is also proposed that the tank has a height and the at least one heating device a length, with the length extending over at least 40% of the height. Preferably, the length extends over at least 70% or even over 100% of the tank's height. When liquid fuel freezes in a tank, a continuous layer of frozen fuel typically forms on the surface of the formerly liquid fuel. When the vehicle is started, a fuel pump normally begins to draw the fuel out of the tank. This can then create a vacuum below the continuous layer of frozen fuel in the tank. This vacuum prevents further fuel from being drawn out of the tank.A heating device extending over a large proportion of the tank's height is capable of melting an opening in such a closed ceiling, regardless of the height at which the closed ceiling is located within the tank. If, for stability reasons (for example, in off-road vehicles), such a long heating device is not desired, it could, for instance, be implemented at various points within the tank (side, top, bottom) with a shorter length, preferably extending together over at least 70% or even 90% of the tank's height.

[0029] The tank according to the invention is further advantageous if the at least one heating device is at least partially permeable to liquid operating fluid. For this purpose, openings, pores, channels, or similar features can be provided, which may also allow liquid operating fluid to flow through the heating device. In particular, a heating device designed in the form of a plate presents a considerable flow resistance for operating fluid in the tank. For this reason, it is advantageous to design the heating device to be at least partially permeable to liquid operating fluid.

[0030] Furthermore, it is also considered advantageous if at least one heating device forms a heated cage around the conveying device. In the case of a heating device designed as a self-contained or surrounding cage, or as a self-contained or surrounding wall around a conveying device, the heating device separates the conveying device from the rest of the tank's interior. Partial permeability of the heating device to liquid operating fluid is then necessary so that operating fluid from the rest of the tank's interior can reach the conveying device.

[0031] With such a device, a method for positioning a heating device in a tank for storing a liquid operating fluid can be carried out, comprising at least the following steps: a) filling the tank with the operating fluid; b) freezing the filled tank under operating conditions; c) recording the freezing behavior of the filled tank; d) creating a second mounting opening in the tank wall; and e) mounting the heating device at the second mounting opening through the tank wall, so that the heating device extends into an interior space of the tank.

[0032] The term "operating conditions" here refers specifically to the conditions that can actually occur during the operation of the motor vehicle. These conditions can include, for example, the installation position of the tank, the distribution of the operating fluid within the tank, the temperature distribution in the tank's vicinity, and similar factors. Therefore, preferably, to carry out step b), a tank is temporarily installed in a motor vehicle and exposed to appropriate cold temperatures for a predetermined period (possibly repeatedly with different fill levels and / or after different operating states of the motor vehicle, such as long / short / repeated engine operation). This ensures that actual operating conditions are present. The tank's environment within the motor vehicle can significantly influence its freezing behavior.

[0033] The "freezing behavior" describes, for example, where the operating fluid first freezes or how ice formation occurs in the tank, particularly until the operating fluid is completely frozen. This analysis allows for the identification of critical areas that can be mitigated by the subsequent installation of heating devices. In particular, this can keep the dispensing point and / or a vent free of ice for longer periods during (repeated) freezing. The tank's freezing behavior is preferably monitored using appropriate monitoring methods.

[0034] Monitoring can be carried out, for example, using temperature sensors at critical points within the tank. These sensors can be positioned at locations where particularly rapid freezing of the operating fluid is expected. It is also possible to install multiple temperature sensors. For instance, these can be arranged in a predefined pattern in the immediate vicinity of a location where rapid freezing is anticipated. Furthermore, a three-dimensional grid of temperature sensors can be used to monitor freezing behavior throughout the entire tank. Temperature sensors located outside the tank and / or on a pumping module for transferring operating fluid from the tank can also be included in the monitoring of freezing behavior. Additional information, such as vehicle speed and / or fill level, can also be incorporated.All this information can be processed in a suitable model of the tank's freezing behavior with operating fluid to determine the actual freezing behavior of the tank in a specific application. Such a model can, in particular, be an energy model that takes into account the thermal energy stored in the operating fluid and / or the heat flows into and out of the tank.

[0035] Of course, the “thawing behavior” can also be analyzed in order to determine positions for steps d) and e) in advance to achieve an effective heating system.

[0036] The second mounting opening in the tank wall can be created, for example, using a saw or by drilling a hole into the tank wall. Furthermore, preparation of the tank wall may be necessary in the area of ​​the second mounting opening so that at least one heating device can be installed and, in particular, a fluid-tight connection can be created between the tank wall and the heating device.

[0037] The method is particularly advantageous if the second mounting opening in step d) is prepared at the point where particularly rapid freezing of the tank was determined in step c). It is precisely at this point that the reducing agent is first frozen within the tank. Since complete freezing of the operating fluid within the tank will only occur very rarely, frozen operating fluid is often found only at this point. For this reason, a heating device installed there can be operated with particularly high energy efficiency.

[0038] The advantages and special features described for the method can be transferred analogously to the tank according to the invention. The same applies to the special advantages and features described for the tank according to the invention, which are applicable and transferable to the method.

[0039] The method is particularly suitable for manufacturing a test tank according to the invention. With such a test tank, the freezing behavior of the tank can be investigated with and without a heating device, and a particularly advantageous position for a heating device within the tank can be determined. Different installation positions of the heating device(s) in the tank can be investigated without having to manufacture the tank directly with the corresponding mounting openings. For the series production of tanks according to the invention, the ideal installation position for a heating device determined by the method for a specific tank geometry can be adopted, and the tanks can be manufactured directly with the corresponding mounting opening at the determined position, without having to first freeze each individual tank under operating conditions.

[0040] The method for manufacturing a tank according to the invention can also be adapted to a specific type of motor vehicle. Depending on the vehicle type, the installation position of the tank according to the invention, its immediate surroundings within the vehicle, and the operating conditions may differ. Therefore, the same tank may exhibit different freezing behavior in different vehicles. The method makes it possible to identify these differences and take them into account when positioning a heating device within the tank.

[0041] The invention is particularly applicable in a motor vehicle comprising an internal combustion engine and an exhaust gas treatment device for cleaning the exhaust gases of the internal combustion engine, as well as a tank according to the invention with a heating device and a control unit, wherein the exhaust gas treatment device has an addition device for an operating fluid which is stored in the tank and the control unit is configured to control the heating device of the tank. Preferably, a liquid urea-water solution is added to the exhaust gas as the operating fluid.

[0042] The invention and its technical context are explained in more detail below with reference to the figures. The figures show particularly preferred embodiments, to which, however, the invention is not limited. It should be noted in particular that the figures, and especially the depicted dimensions, are only schematic. They show: Fig. 1: A first design variant of a tank in a vertical sectional view, Fig. 2: a second design variant of a tank in a vertical sectional view, Fig. 3: a third design variant of a tank in a vertical sectional view, Fig. 4: a fourth design variant of a tank in a horizontal sectional view, Fig. 5: a fifth embodiment of a tank according to the invention in a horizontal sectional view, and Fig. 6: a motor vehicle comprising a tank according to the invention.

[0043] The Fig. 1, the Fig. 2 and the Fig. Figure 3 shows three different embodiments of a tank 1 for a liquid operating fluid 2 (in particular, a urea-water solution), in which a conveying device 6 for the operating fluid 2 is mounted in a first mounting opening 4. Furthermore, a heating device 7 is mounted in a second mounting opening 5. The heating device 7 extends with a length 10 over a significant portion of the height 11 of the tank 1. The heating device 7 is designed in the form of a rod 26. The heating device 7 has a PTC heating element 23 for converting electrical energy into heat energy and has an electrical connection 22 through which it can be supplied with electrical energy.The conveying device 6 has at least one system heater 20 (for heating the components in the conveying device and / or for heating the operating fluid located in the external environment) and has a line connection 21 through which the operating fluid 2 can be conveyed out of the tank. The tank wall 18 of the tank 1 delimits the interior 8 of the tank 1. In the interior 8, the operating fluid 2 (in the illustrated figures) is mostly in frozen form. Along the heating device 7, the heating device 7 has melted open a channel 25 through which pressure equalization can occur between the environment and a cavity 29 that has melted open around the conveying device 6.

[0044] In the first version of the tank according to Fig. 1 Both the heating device 7 and the conveying device 6 are mounted in a base 9 of the tank.

[0045] In the second version of tank 1 according to Fig. 2. The conveying device 6 extends from the bottom 9 of the tank 1 into the interior 8 of the tank 1, while the heating device 7 extends from the top (the ceiling of the tank) into the interior 8 of the tank 1. The heating device 7 according to Fig. Section 2 is angled. This allows the heating device 7 to reach areas of the interior 8 of the tank 1 that are far removed from the second mounting opening 5. The heating device 7 is preferably designed so that it can be inserted into the tank 1 through the second mounting opening 5 despite the bend 30. The heating device 7 can also have multiple bends 8 or other shapes.

[0046] In the third version of tank 1 according to Fig. 3. The conveying device 6 extends through the bottom 9 into the interior 8 of the tank 1, while the heating device 7 extends from above into the interior 8 of the tank 1. The conveying device 6 has a first coupling part 13, and the heating device 7 has a second coupling part 14. The first coupling part 13 and the second coupling part 14 can be coupled together, creating a rigid connection between the heating device 7 and the conveying device 6. This increases the stability of the tank 1 because the conveying device 6 and the heating device 7 stabilize the tank 1.

[0047] The Fig. Figure 4 shows a fourth design variant and the Fig. Figure 5 shows an embodiment of a tank 1 according to the invention. A horizontal sectional view through the tank 1 is illustrated in each figure. In both embodiments, the tank 1 is visible. The tank wall 18, which defines the interior 8, is cut away. The viewer sees the bottom 9 of the tank 1 from above. Also visible are the conveying device 6 with its housing 19, which is inserted into a first mounting opening 4, and heating devices 7, each comprising a PTC heating element 23, which are inserted into second mounting openings 5.

[0048] In Fig. 4 One heating device 7 is designed in the form of a plate 27. The other heating device 7 is designed in the form of a rod 26.

[0049] A special feature in Fig. Figure 5 shows a heating device 7 arranged in a cage-like manner around the conveying device 6, similar to a plate 27. The cage 12 is semicircular in shape around the conveying device 6. The heating device 7 has openings 24 through which operating fluid can flow from the interior 8 of the tank 1 to the conveying device 6.

[0050] Fig. Figure 6 shows a motor vehicle 3 comprising an internal combustion engine 15 and an exhaust gas treatment device 16 for cleaning the exhaust gases of the internal combustion engine 15. The exhaust gas treatment device 16 has an injection device 17, which is supplied with operating fluid from a tank 1 according to the invention by a conveying device 6. The tank 1 according to the invention has a heating device 7, which can be controlled by a control unit 28. Reference symbol list 1 tank 2 Fuel 3 Motor vehicle 4 first mounting opening 5 second mounting opening 6 Conveyor device 7 Heating device 8 Interior 9 Floor 10 Length 11 Height 12 cage 13 first clutch part 14 second clutch part 15 Internal combustion engine 16 Exhaust gas treatment device 17 Addition device 18 Tank wall 19" enclosure 20 System heating 21 Line connection 22 electrical connection 23 PTC heating element 24-hour opening 25 Channel 26 Staff 27 plate 28 Control unit 29 Cave 30 kink

Claims

[1] Tank (1) for storing a liquid operating fluid (2) for a motor vehicle (3), comprising a tank wall (18) and an interior space (8) bounded by the tank wall (18), and at least one heating device (7) mounted externally through the tank wall (18) and extending into the interior space (8), which forms at least one heating device (7) a heated cage (12) around a conveying device (6), characterized by , that the heating device (7) is arranged in a cage-like manner around the conveying device (6) in the manner of a plate, wherein the cage (12) is semicircular in shape, and wherein the heating device (7) comprises openings. [2] Tank (1) according to claim 1, wherein the at least one heating device (7) is detachably and fluid-tight connected to the tank wall (18). [3] Tank (1) according to one of the preceding claims, wherein the tank (1) has a height (11) and the at least one heating device (7) has a length (10), and the length (10) extends over at least 40% of the height (11). [4] Tank (1) according to one of the preceding claims, wherein the at least one heating device (7) is at least partially permeable to liquid operating fluid (2). [5] Motor vehicle (3) comprising an internal combustion engine (15) and an exhaust gas treatment device (16) for cleaning the exhaust gases of the internal combustion engine (15) and a tank (1) with a heating device (7) according to one of claims 1 to 4, and a control unit (28), wherein the exhaust gas treatment device (16) has an addition device (17) for an operating fluid (2) which is stored in the tank (1) and the control unit (28) is configured to control the heating device (7) of the tank (1).

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