METHOD FOR DETERMINING A QUALITY PROPERTY OF AN OPERATING FLUID IN AN OPERATING FLUID CONTAINER FOR A MOTOR VEHICLE AND OPERATING FLUID CONTAINER FOR CARRYING OUT THE METHOD

Description

[0001] The present invention relates to a method for determining the electrical conductivity of an operating fluid in an operating fluid reservoir for a motor vehicle. The present invention further relates to an operating fluid reservoir for carrying out the method.

[0002] The following also refers to operating fluid reservoirs designed as water reservoirs for use in motor vehicles. Operating fluid reservoirs within the meaning of the invention include, in particular but not exclusively, water reservoirs for motor vehicles for storing, for example, water to be injected into the intake manifold of an internal combustion engine, windshield washer fluid reservoirs, urea reservoirs, fuel tanks (for gasoline or diesel fuel), oil reservoirs, auxiliary fluid reservoirs, or additive reservoirs for motor vehicles. Reservoirs of the type mentioned above are frequently manufactured by extrusion blow molding, with HDPE (high-density polyethylene) being particularly suitable for the production of extrusion blow-molded reservoirs. Furthermore, it is possible to manufacture corresponding operating fluid reservoirs using an injection molding process.

[0003] Water injection is a method for increasing the performance of internal combustion engines. To prevent exceeding the maximum temperature at peak power, distilled water is injected into the intake manifold of an internal combustion engine. The evaporating liquid has a cooling effect and reduces the work required for compression. Injection during the combustion stroke is also practiced for steam power generation and to reduce exhaust gas temperature, thereby reducing exhaust backpressure. Water injection can reduce pollutant emissions, particularly nitrogen oxides, from internal combustion engines. The water injected into the air intake manifold provides effective charge air cooling through the heat of evaporation, thus also achieving internal engine cooling. The colder combustion air, and therefore its higher density, results in an increase in power output.

[0004] Only distilled or deionized water should be used for water injection to prevent combustion of impurities and deposits in the injection system, thus ensuring that the vehicle's emissions are not increased. Tap water is therefore unsuitable for water injection.

[0005] Consequently, for operating fluid reservoirs in motor vehicles designed as water tanks, the electrical conductivity of the water in the reservoir is a quality property that must be monitored. Distilled or deionized water exhibits significantly reduced conductivity compared to, for example, tap water.

[0006] WO 2017 / 142253 A1 describes a device and a method for determining the concentrations of ingredients within a tank used for IT applications. The device comprises two electrodes electrically connected to a potentiometer. The potentiometer, in turn, is connected to a frequency analyzer.

[0007] The present invention is based on the objective of providing a method for determining the electrical conductivity of an operating fluid in an operating fluid container for a motor vehicle.

[0008] The problem underlying the present invention is solved by a method according to claim 1 of the present invention. Advantageous embodiments of the method are described in the dependent claims.

[0009] More precisely, the problem underlying the present invention is solved by a method for determining the electrical conductivity of an operating fluid in an operating fluid reservoir for a motor vehicle, wherein the operating fluid reservoir has at least one capacitor attached to a reservoir wall of the operating fluid reservoir, with a first electrode and a second electrode opposite it. The method according to the invention is characterized by the following method steps A, B, C and D: A) Applying at least three different alternating voltages to the capacitor, where a first frequency corresponds to a lower cutoff frequency, a second frequency corresponds to a frequency between the lower cutoff frequency and an upper cutoff frequency, and a third frequency corresponds to a third voltage at the upper cutoff frequency; B) Determining and storing a first impedance of the capacitor for the first frequency, a second impedance of the capacitor for the second frequency, and a third impedance of the capacitor for the third frequency; C) Determining a first phase angle from the first impedance, a second phase angle from the second impedance, and a third phase angle from the third impedance;and D) Determine (D) that the operating fluid in the operating fluid reservoir meets a quality requirement if the second phase angle is greater than the first phase angle and greater than the third phase angle.

[0010] The method according to the invention has the advantage that it allows for a reliable determination of whether an operating fluid located in the operating fluid reservoir meets a predetermined quality requirement without direct contact between a measuring device, in this case the capacitor, and the operating fluid. The predetermined quality requirement correlates with the electrical conductivity of the operating fluid. Thus, by determining the electrical conductivity of the operating fluid located inside the operating fluid reservoir, conclusions can be drawn about the quality properties of the operating fluid.

[0011] The frequency-dependent impedance of the capacitor depends on the electrical conductivity of the medium through which the alternating electric field between the first and second electrodes passes. Therefore, the frequency-dependent impedance of the capacitor depends on the material of the container wall and on the operating fluid inside the container.

[0012] The applicant has discovered that the impedance curve of the capacitor as a function of the applied AC voltage allows for unambiguous conclusions to be drawn about the quality characteristics of the operating fluid. Specifically, the applicant found that the phase angle of the impedance between a lower and an upper cutoff frequency exhibits a maximum when the electrical conductivity of the operating fluid is low. The lower and upper cutoff frequencies of the AC voltage applied to the capacitor depend on the capacitor's geometry, the size of the capacitor's electrodes, and the distance between these electrodes.

[0013] The applicant has determined that the frequency-dependent phase response of the capacitor's impedance for deionized water with an electrical conductivity between 1 µS / cm and 50 µS / cm within the operating fluid reservoir exhibits a maximum in a frequency range between 10 kHz and 1 MHz. However, the frequency range can change depending on the size and geometry of the capacitor.

[0014] The operating fluid reservoir is preferably an operating fluid reservoir for a motor vehicle. More preferably, the operating fluid reservoir is designed as a water reservoir for a motor vehicle to hold water intended for injection into the internal combustion engine of the motor vehicle.

[0015] In process step A of applying at least three different alternating voltages to the capacitor, preferably a plurality, i.e. more than three different alternating voltages with different frequencies in a frequency range between the lower cutoff frequency and the upper cutoff frequency, are applied to the capacitor.

[0016] Both the lower and upper cutoff frequencies depend on the geometry and dimensions of the capacitor and can therefore vary. The lower cutoff frequency is 10 kHz and the upper cutoff frequency is 1 MHz or 100 kHz.

[0017] The frequency spacing of the respective adjacent AC voltages is preferably variable and depends on the geometry and dimensions of the capacitor and on the required measurement resolution. In particular, the frequency spacing between the frequencies of the different AC voltages is 1 kHz.

[0018] Procedure step B can also be formulated as follows: Determining and storing the frequency-dependent impedances of the capacitor for the different alternating voltages.

[0019] The phase angle is the angle between the voltage applied to the capacitor and the current flowing through the capacitor.

[0020] Consequently, in process step C, a frequency-dependent phase response between the voltage and the current is determined.

[0021] In process step D, the condition that the second phase angle is larger than the first phase angle and larger than the third phase angle is equivalent to the fact that the phase angle curve has a maximum between the lower cutoff frequency and the upper cutoff frequency.

[0022] Preferably, the method is designed such that it includes a process step D1 of outputting a release signal when the second phase angle is greater than the first phase angle and greater than the third phase angle.

[0023] By issuing a release signal, it is possible in particular to signal to a control unit of the motor vehicle that the operating fluid located inside the operating fluid reservoir meets a specified quality requirement, thus enabling the operation of the motor vehicle.

[0024] Preferably, the method is designed such that it includes a process step E of issuing a warning signal when the third phase angle is greater than or equal to the second phase angle.

[0025] In process step E of issuing a warning signal, this signal is therefore only issued if no maximum of the phase angle can be determined in a frequency-dependent phase angle curve between the lower cutoff frequency and the upper cutoff frequency.

[0026] If no maximum phase angle can be determined between the lower and upper cutoff frequencies, but the difference between the third and first phase angles is greater than a predefined minimum loss angle, then the operating fluid inside the fluid reservoir is of sufficient quality. However, a warning signal is issued so that the user of the vehicle in which the fluid reservoir is installed can be alerted that the operating fluid inside the reservoir is of reduced quality, but still sufficient for the operation of the vehicle.

[0027] A loss angle is defined as the difference between -90° and the phase angle of the impedance.

[0028] Preferably, the method is designed such that it includes a process step F of outputting a stop signal when a difference between the third phase angle and the first phase angle is smaller than a predetermined minimum loss angle.

[0029] If the difference between the third phase angle and the first phase angle is less than a predefined minimum loss angle, then the operating fluid in the fluid reservoir is of a quality insufficient for the operation of the vehicle and could cause damage to the vehicle or its components, such as a water injection system or an internal combustion engine. Therefore, the vehicle can be prevented from operating by issuing a stop signal.

[0030] Furthermore, a method for determining the electrical conductivity of an operating fluid in an operating fluid reservoir for a motor vehicle is described, wherein the operating fluid reservoir has at least one capacitor attached to a reservoir wall, with a first electrode and a second electrode opposite it. The method is not part of the invention. The method is characterized by the following process steps G, H, I, and J: G) Applying at least two different alternating voltages to the capacitor, wherein a first frequency corresponds to a lower cutoff frequency and a second frequency corresponds to an upper cutoff frequency; H) Determining and storing a first capacitance of the capacitor for the first frequency and a second capacitance of the capacitor for the second frequency; I) Determining a relative deviation of the second capacitance from the first capacitance; and J) Determining that the operating fluid in the operating fluid reservoir meets a specified quality requirement if the relative deviation of the second capacitance from the first capacitance is greater than a first minimum deviation.

[0031] This method has the advantage that it allows for the reliable determination of whether a fluid in the fluid reservoir meets a predefined quality requirement without direct contact between a measuring device, in this case a capacitor, and the fluid. The predefined quality requirement correlates with the capacitor's capacitance, which in turn depends on the medium through which the alternating electric field between the capacitor's first and second electrodes passes. Therefore, by determining the frequency-dependent capacitance of the capacitor, conclusions can be drawn about the quality characteristics of the fluid.

[0032] The frequency-dependent capacitance of the capacitor depends on the electrical conductivity of the medium through which the alternating electric field between the first and second electrodes of the capacitor passes. Therefore, the frequency-dependent capacitance of the capacitor depends on the material of the container wall and on the operating fluid inside the container.

[0033] The capacitance curve of a capacitor as a function of the applied AC voltage allows for clear conclusions about the quality characteristics of the operating fluid. The capacitance curve between a lower and upper cutoff frequency must exhibit a certain deviation, for example, a certain drop, if the electrical conductivity of the operating fluid is low. The lower and upper cutoff frequencies of the AC voltage applied to the capacitor depend on the capacitor's geometry, the size of its electrodes, and the distance between them.

[0034] For deionized water with an electrical conductivity between 1 µS / cm and 50 µS / cm within the operating fluid reservoir, the capacitance of the capacitor deviates by at least 20% in a frequency range between 10 kHz and 1 MHz. Thus, the difference between the capacitance of the capacitor at a frequency of 1 MHz and the capacitance of the capacitor at a frequency of 10 kHz is at least 20%. However, the frequency range can vary depending on the size and geometry of the capacitor.

[0035] The operating fluid reservoir is preferably an operating fluid reservoir for a motor vehicle. More preferably, the operating fluid reservoir is designed as a water reservoir for a motor vehicle to hold water intended for injection into the internal combustion engine of the motor vehicle.

[0036] In process step I, determining the relative deviation of the second capacity from the first capacity, the following calculation is performed: delta = Cfmin − Cfmax / Cfmin

[0037] This includes: fmin the lower cutoff frequency fmax the upper cutoff frequency Cfmin the first capacitance of the capacitor at an AC voltage with the lower cutoff frequency fmin Cfmax the second capacitance of the capacitor at an AC voltage with the upper cutoff frequency fmax delta the relative deviation of the second capacitance Cfmax from the first capacitance Cfmin

[0038] The first minimum deviation is preferably more than 0.2.

[0039] For deionized water and a lower cutoff frequency of 10 kHz and an upper cutoff frequency of 100 kHz, the minimum deviation is approximately 0.2, for example, if the electrodes of the capacitor have a length of 100 mm, a width of 50 mm and a distance of 10 mm between the first and second electrodes.

[0040] The specified quality requirement preferably concerns the conductivity of the operating fluid. If the operating fluid reservoir is designed as a water reservoir for holding water intended for injection into an internal combustion engine, the specified quality requirement is, for example, the conductivity of the water and is between 1 µS / cm and 50 µS / cm.

[0041] Preferably, the method is designed such that it includes a process step J1 of outputting a release signal if the relative deviation of the second capacity from the first capacity is greater than the first minimum deviation.

[0042] By issuing a release signal, it is possible in particular to signal to a control unit of the motor vehicle that the operating fluid located inside the operating fluid reservoir meets a specified quality requirement, thus enabling the operation of the motor vehicle.

[0043] Preferably, the method is designed such that it includes a process step K of issuing a warning signal when the relative deviation of the second capacity from the first capacity is a value between the first minimum deviation and a second minimum deviation, wherein the second minimum deviation is smaller than the first minimum deviation.

[0044] If the relative deviation of the second capacity from the first capacity is less than the first minimum deviation but greater than the second minimum deviation, then the operating fluid inside the fluid reservoir is of sufficient quality. However, a warning signal is issued so that a user of the vehicle in which the fluid reservoir is installed can be alerted that the quality of the operating fluid inside the reservoir is reduced, but still sufficient for the operation of the vehicle.

[0045] Preferably, the method is designed such that it includes a process step K of outputting a stop signal when the relative deviation of the second capacity from the first capacity is less than a second minimum deviation, wherein the second minimum deviation is less than the first minimum deviation.

[0046] In this case, the operating fluid inside the fluid reservoir is of a quality that is insufficient for the operation of the vehicle and could cause damage to the vehicle or its components, such as a water injection system or an internal combustion engine. Therefore, the vehicle can be prevented from operating by issuing a stop signal.

[0047] Of course, it is also possible to combine one of the methods according to one of claims 1 to 4 with a method according to one of claims 5 to 8.

[0048] Furthermore, the present invention is based on the objective of providing an operating fluid container which is designed to determine the electrical conductivity of an operating fluid contained therein.

[0049] This problem is solved by a service fluid container with the features of claim 5. Advantageous embodiments of the service fluid container are described in the dependent claims.

[0050] More precisely, the problem underlying the present invention is solved by a fluid reservoir whose interior is bounded by a top wall, a bottom wall, and a side wall connecting the bottom wall to the top wall. The fluid reservoir has at least one capacitor attached to a reservoir wall, with a first electrode and a second electrode. Furthermore, the fluid reservoir has an electronic evaluation unit that is electrically connected to the first electrode and the second electrode. The fluid reservoir according to the invention is characterized in that the evaluation unit is configured to carry out at least one of the methods described above according to any one of claims 1 to 4.

[0051] The at least one capacitor is preferably attached to or in a side wall of the operating fluid container. More preferably, the at least one capacitor is arranged on or in the side wall such that the first electrode and the second electrode, each having a longitudinal extension, a lateral extension, and a lateral extension, each run parallel to the side wall such that the longitudinal extensions of the first electrode and the second electrode extend from the bottom wall towards the top wall.

[0052] According to a further embodiment of the operating fluid container, at least one capacitor is arranged on or in the bottom wall, so that the first electrode and the second electrode each run parallel to the bottom wall.

[0053] The at least one capacitor can be arranged on and connected to the outer surface of the container wall. Alternatively, the at least one capacitor can be integrated or embedded within the container wall. In this case, the first and second electrodes of the capacitor are enclosed by the container wall.

[0054] The operating fluid container is preferably designed such that at least one condenser is embedded in the container wall.

[0055] When the capacitor electrode is embedded in the container wall, the electrodes are enclosed by the container wall, so that only the electrical connections of the electrodes protrude from the container wall.

[0056] The specially designed fluid reservoir offers the advantage that, due to the embedding of at least one capacitor in the reservoir wall, the first and second electrodes of the capacitor are located closer to the reservoir's interior and thus to the fluid inside. Therefore, the electric field between the first and second electrodes of the capacitor interacts less with the reservoir wall material and more with the fluid inside the reservoir. This allows for a more accurate determination of the electrical conductivity of the fluid inside the reservoir.

[0057] Another advantage of embedding the at least one capacitor in the container wall is that both the at least one capacitor is mechanically and chemically protected, so that the operating fluid container according to the invention has increased long-term stability.

[0058] The operating fluid container is specifically designed as an operating fluid container for a motor vehicle.

[0059] Preferably, the operating fluid container is designed such that the bottom wall has a projection extending into the interior of the operating fluid container, wherein the first electrode and the second electrode of the capacitor are embedded in the projection.

[0060] By appropriately designing the operating fluid container, the determination of the electrical conductivity of the operating fluid can be made with even greater accuracy, since any deposits in the area of ​​the bottom wall have a reduced influence on the determination of the electrical conductivity of the operating fluid located inside the operating fluid container.

[0061] The raised bottom wall is preferably designed as an indentation into the interior of the operating fluid container.

[0062] The raised area is preferably between 2mm and 5mm above the surrounding inner surface of the floor wall.

[0063] Preferably, the operating fluid container is designed such that the container wall has an outer layer, an inner layer facing the interior of the operating fluid container and an adhesive layer arranged between them, wherein the first electrode and the second electrode of the at least one capacitor are arranged between the outer layer and the adhesive layer.

[0064] Consequently, at least one capacitor is positioned between the outer layer and the adhesive layer. The inner layer can therefore be brought into direct contact with the operating fluid.

[0065] A suitable design of the operating fluid reservoir allows for a simplified construction and simplified integration of the condenser into the reservoir wall.

[0066] Preferably, the operating fluid container is designed such that the container wall has a shielding layer and an insulating layer, wherein the shielding layer is arranged between the outer layer and the first and second electrodes, and wherein the insulating layer is arranged between the shielding layer and the first and second electrodes.

[0067] The appropriately designed operating fluid reservoir offers the advantage of even greater accuracy in determining the electrical conductivity of the operating fluid inside the reservoir. This is because the shielding layer, preferably a metal layer, protects the electrodes of the at least one capacitor from interference fields. .

[0068] The shielding layer is therefore located between the outer layer and the reference capacitor or the capacitor.

[0069] The shielding layer is preferably in contact with the outer layer.

[0070] The insulating layer is therefore arranged in a sandwich-like fashion between the shielding layer and the capacitor.

[0071] The shielding layer contains a metal, so that at least one capacitor is protected from electrical interference fields.

[0072] The insulating layer is made of a dielectric material, preferably a plastic, so that the first and second electrodes of the at least one capacitor are not in electrical contact with the shielding layer.

[0073] Preferably, the operating fluid container is designed such that the insulating layer has the same dielectric conductivity as the inner layer and / or the outer layer.

[0074] The appropriately designed operating fluid container has the advantage that it offers an even higher accuracy in determining the electrical conductivity of the operating fluid located inside the operating fluid container.

[0075] Preferably, the operating fluid container is designed such that the distance between the first and second electrodes and the interior of the operating fluid container is between 1.5 mm and 3.5 mm.

[0076] The appropriately designed operating fluid container has the advantage that it offers an even higher accuracy in determining the electrical conductivity of the operating fluid inside the operating fluid container, because the distance between the corresponding electrodes and the operating fluid inside the operating fluid container is reduced.

[0077] Preferably, the inner layer therefore has a thickness of 1.5 mm to 3.5 mm.

[0078] Consequently, at least one condenser has a distance of only 1.5 mm to 3.5 mm to the interior of the operating fluid reservoir.

[0079] Preferably, the operating fluid reservoir is designed such that at least one of the first and second electrodes of the capacitor has a non-uniform width extent along its longitudinal extent.

[0080] The wider the electrodes are, the deeper the electric field penetrates into the interior of the operating fluid container and into the operating fluid itself, so that the operating fluid has a greater influence on the determination of the electrical conductivity of the operating fluid.

[0081] Preferably, the operating fluid reservoir is designed such that at least one of the first and second electrodes of the capacitor has a width extension that increases towards the bottom wall along its longitudinal extent.

[0082] The appropriately designed operating fluid container has the advantage that the measurement accuracy of the electrical conductivity is increased by means of the capacitor in the bottom area of ​​the operating fluid container.

[0083] Further advantages, details, and features of the invention will become apparent from the exemplary embodiments described below. Specifically, the following will be shown: Figure 1: A flowchart of a method for determining a quality property of an operating fluid according to a first embodiment of the present invention, wherein the quality property is an electrical conductivity of the operating fluid; Figure 2: Frequency-dependent phase responses of the impedance of a capacitor for three different operating fluids, each exhibiting different electrical conductivities; Figure 3: A flowchart of a method for determining a quality property of an operating fluid according to a second embodiment, which is not part of the invention, wherein the quality property is an electrical conductivity of the operating fluid; Figure 4: Frequency-dependent capacitance responses of a capacitor for three different operating fluids, each exhibiting different electrical conductivities;Figure 5: a highly simplified spatial representation of a working fluid container according to the invention; Figure 6: a highly simplified representation of a layered structure of the bottom wall and / or the side wall of the working fluid container according to a further embodiment of the present invention; and Figures 7A to 7C: examples of measuring capacitors in individual positions in a side view of working fluid containers of different embodiments of the present invention.

[0084] In the following description, identical reference numerals denote identical components or identical features, so that a description of a component in relation to one figure also applies to the other figures, thus avoiding repetitive descriptions. Furthermore, individual features described in connection with one embodiment can also be used separately in other embodiments.

[0085] Figure 1 Figure 1 shows a flowchart of a method for determining a quality property of an operating fluid according to a first embodiment of the present invention, wherein the quality property is an electrical conductivity of the operating fluid. The method according to Figure 2 is described in Figure 3. Figure 1 The flow diagram shown is generated by a Figure 5 The operating fluid container 1 shown is designed.

[0086] Figure 5 Figure 1 shows a highly simplified spatial representation of a working fluid container 1 according to the invention. The interior of the working fluid container 2 is bounded by a ceiling wall 30, a bottom wall 10, and a side wall 20 connecting the bottom wall 10 to the ceiling wall 30. Figure 5 It is evident that the side wall 20 is formed all around.

[0087] The in Figure 5The illustrated operating fluid reservoir 1 has a first capacitor 60 and a second capacitor 70. According to the present invention, however, the operating fluid reservoir 1 can also have only the first capacitor 60 or only the second capacitor 70. Furthermore, the operating fluid reservoir 1 can also have additional capacitors which are arranged in Figure 5 are not shown.

[0088] The first capacitor 60 has a first electrode 61 and a second electrode 62. Both the first electrode 61 and the second electrode 62 each have a longitudinal extent L, a lateral extent B, and a lateral extent (see Figures 7A to 7CThe first electrode 61 and the second electrode 62 are each arranged parallel to the side wall 20 such that the longitudinal extents L of the first electrode 61 and the second electrode 62 extend from the bottom wall 10 towards the ceiling wall 30. The depth extents of the first electrode 61 and the second electrode 62 are arranged opposite each other.

[0089] The first capacitor 60 is embedded in the side wall 20, such that the first electrode 61 and the second electrode 62 of the first capacitor 60 are embedded in the side wall 20. Therefore, the first capacitor 60 is enclosed by the side wall 20. Consequently, the first electrode 61 and the second electrode 62 of the first capacitor 60 are not in contact with an operating fluid 50 (see Figure 6) in direct contact. Furthermore, the first electrode 61 and the second electrode 62 of the first capacitor 60 are also not in direct contact with the environment of the operating fluid reservoir 1. Regarding the embedding of the first capacitor 60 in the side wall 20, see below. Figure 4 referred to, which is described further below.

[0090] However, the present invention is not limited to the first capacitor 60 being embedded in the side wall 20. In an operating fluid container 1 according to the invention, the first capacitor 60 can also be attached to an outer surface of the side wall 20.

[0091] Out of Figure 5It is evident that the first electrode 61 and the second electrode 62 of the first capacitor 60 each have two wings 63 that extend parallel to the width B of the electrodes 61, 62. The respective wings 63 are formed at different heights of the first and second electrodes 61, 62, so that the wings 63 are arranged at different heights of the operating fluid reservoir 1. Thus, the first and second electrodes 61, 62 of the first capacitor 60 have a non-uniform width B along their longitudinal extent L. However, the present invention is not limited to a corresponding configuration of the first and second electrodes 61, 62 of the first capacitor 60. For example, the first and second electrodes 61, 62 of the first capacitor 60 can also have a uniform width B along their longitudinal extent L.

[0092] The second capacitor 70 has a first electrode 71 and a second electrode 72. The first electrode 71 and the second electrode 72 run parallel to the bottom wall 10. The first electrode 71 and the second electrode 72 are each arranged parallel to the bottom wall 10 such that the longitudinal and lateral extents of the first electrode 71 and the second electrode 72 lie in the plane of the bottom wall 10, so that the depth extents of the first electrode 71 and the second electrode 72 are opposite each other.

[0093] As from Figure 5As can be seen, the base wall 10 has a projection 11 extending into the interior of the operating fluid reservoir 2. The second capacitor 70 is embedded in the base wall 10 such that the first electrode 71 and the second electrode 72 of the second capacitor 70 are embedded in the projection 11 of the base wall 10. Consequently, the first electrode 71 and the second electrode 72 of the second capacitor 70 are not in direct contact with the operating fluid 50. Furthermore, the first electrode 71 and the second electrode 72 of the second capacitor 70 are also not in direct contact with the surroundings of the operating fluid reservoir 1. Due to the embedding of the first electrode 71 and the second electrode 72 in the projection 11 of the base wall 10, any deposits on the base wall 10 have a reduced effect on the determination of the electrical conductivity of the operating fluid 50 located in the interior of the operating fluid reservoir 2.

[0094] Regarding the embedding of the second capacitor 70 in the bottom wall 10 or in the elevation 11 of the bottom wall 10, reference is made to Figure 6 referred to, which is described further below.

[0095] However, the present invention is not limited to the second capacitor 70 being embedded in the bottom wall 10. In an operating fluid container 1 according to the invention, the second capacitor 70 can also be attached to an outer surface of the bottom wall 10.

[0096] The operating fluid reservoir 1 further comprises an electronic evaluation unit 80, which is electrically connected to the first capacitor 60 and the second capacitor 70. The electrical connection of the evaluation unit 80 to the first capacitor 60 and the second capacitor 70 is made via in Figure 5 Electrical wiring not shown.

[0097] The evaluation unit 80 is designed to execute the procedure according to the one described in Figure 1 to execute the flowchart shown, which is described below.

[0098] In process step A, at least three different alternating voltages with different frequencies are applied to the first capacitor 60 and / or the second capacitor 70. The first frequency of a first alternating voltage corresponds to a lower cutoff frequency fmin of 10 kHz. The second frequency of a second alternating voltage corresponds to a frequency between the lower cutoff frequency fmin and an upper cutoff frequency fmax, where the upper cutoff frequency is, for example, 100 kHz. The third frequency of a third alternating voltage corresponds to the upper cutoff frequency fmax.

[0099] In a process step B, a first impedance of the first capacitor 60 and / or the second capacitor 70 for the first frequency, a second impedance of the first capacitor 60 and / or the second capacitor 70 for the second frequency and a third impedance of the first capacitor 60 and / or the second capacitor 70 for the third frequency are determined and each stored.

[0100] Subsequently, in a process step C, a first phase angle φ1 is determined from the first impedance, a second phase angle φ2 from the second impedance and a third phase angle φ3 from the third impedance.

[0101] In Figure 2Three different frequency-dependent phase responses of the impedances of the first capacitor 60 and / or the second capacitor 70 are shown for three different operating fluids. Graph 91 shows the phase response of the impedance for deionized water. Graph 92 shows the frequency-dependent phase angle of the impedance for a mixture of 50% deionized water and 50% tap water, and graph 93 shows the frequency-dependent phase angle of the impedance for tap water alone. The deionized water has an electrical conductivity between 1 and 50 µS / cm. The mixture of 50% deionized water and 50% tap water has an electrical conductivity between 50 and 200 µS / cm. The tap water has an electrical conductivity of over 200 µS / cm.

[0102] Out of Figure 2It is evident that the phase angle curve of the impedance of capacitor 60, 70 exhibits a maximum in deionized water between a lower cutoff frequency fmin of 10 kHz and an upper cutoff frequency fmax of 100 kHz. In contrast, it is evident from Figure 2 Furthermore, it is evident that the curve 92 of the phase angle of the impedance of capacitor 60, 70 for the mixture of deionized water and tap water increases steadily between the lower cutoff frequency fmin and the upper cutoff frequency fmax. The same applies to the curve 93 of the phase angle of the impedance of capacitor 60, 70 for pure tap water. It is evident that at the upper cutoff frequency fmax of 100 kHz, curve 93 increases more slowly than curve 92.

[0103] Returning to the procedure according to the in Figure 1According to the flow diagram shown, after process step C, it is checked whether the second phase angle φ2 is greater than the first phase angle φ1 and also greater than the third phase angle φ3. If this condition is met, then the phase angle profile between the lower cutoff frequency fmin and the upper cutoff frequency fmax exhibits a maximum. If the phase angle profile exhibits a maximum, then in process step D it is determined or established that the operating fluid in the operating fluid reservoir 1 meets a predefined quality requirement.

[0104] In the described embodiment, determining a maximum of the phase angle curve reveals that the electrical conductivity of the operating fluid in the interior of the operating fluid reservoir 2 is between 1 and 50 µS / cm. From this, it can be concluded that the water in the interior of the operating fluid reservoir 2 is deionized water and suitable for operating a water injection device. In this case, a release signal is output in process step D1. However, step D1 is optional and not mandatory.

[0105] If it is determined that the second phase angle φ2 is not larger than the third phase angle φ3, it is checked whether the difference between the third phase angle φ3 and the first phase angle φ1 is smaller than a predetermined minimum loss angle δs. The minimum loss angle δs in the illustrated embodiment is 1°. From the in Figure 2As can be seen from the frequency-dependent curve shown in Figure 93, the loss angle for the upper cutoff frequency fmax is less than 1° and therefore less than the minimum loss angle δs. Consequently, a stop signal is output in a process step F. This stop signal can be used to indicate to a water injection system (not shown in the figures) that the water in the interior of the operating fluid reservoir 2 is unsuitable for water injection because it has an electrical conductivity of more than 200 µS / cm. Therefore, the water in the interior of the operating fluid reservoir 2 is, for example, tap water.

[0106] If the difference between the third phase angle φ3 and the first phase angle φ1 is not smaller than the predetermined minimum loss angle δs, it is checked whether the third phase angle φ3 is larger than the second phase angle φ2. If this condition is met, it is concluded that the water inside the operating fluid reservoir 2 has an electrical conductivity between 50 and 200 µS / cm. The quality properties of this water are still sufficient for water injection. However, in a process step E, a warning signal is issued so that the user of the motor vehicle in which the operating fluid reservoir 1 according to the invention is installed can be alerted that the water inside the operating fluid reservoir 2, although meeting the requirements, contains impurities.

[0107] The evaluation unit 80 of the in Figure 5The operating fluid container 1 shown is further designed to carry out the process according to the method described in Figure 3 to execute the flowchart shown, which is described below.

[0108] In process step G, at least two different alternating voltages with different frequencies are applied to the first capacitor 60 and / or to the second capacitor 70. The first frequency of a first alternating voltage corresponds to a lower cutoff frequency fmin. The second frequency of a second alternating voltage corresponds to an upper cutoff frequency fmax.

[0109] Subsequently, in process step H, a first capacitance C1 of the first capacitor and / or the second capacitor 70 is determined and stored for the first frequency. Furthermore, in process step H, a second capacitance C2 of the first capacitor 60 and / or the second capacitor 70 is determined and stored for the second frequency.

[0110] Subsequently, in process step I, the relative deviation of the second capacity C2 from the first capacity C1 is determined. In process step I, therefore, the percentage by which the second capacity C2 deviates from the first capacity C1 is calculated.

[0111] In Figure 4Three different frequency-dependent capacitance curves of the first capacitor 60 and / or the second capacitor 70 are shown for three different operating fluids. Curve 101 shows a frequency-dependent capacitance curve of the first capacitor 60 and / or the second capacitor 70 for deionized water. Curve 102 shows the frequency-dependent capacitance curve of the first capacitor 60 and / or the second capacitor 70 for a mixture of 50% deionized water and 50% tap water, and curve 103 shows the frequency-dependent capacitance curve of the first capacitor 60 and / or the second capacitor 70 for tap water alone. The deionized water has an electrical conductivity between 1 and 50 µS / cm. The mixture of 50% deionized water and 50% tap water has an electrical conductivity between 50 and 200 µS / cm. The tap water has an electrical conductivity of over 200 µS / cm.

[0112] Out of Figure 4 It is evident that the frequency-dependent capacitance curve of capacitor 60, 70, when using deionized water as the operating fluid, drops from the first capacitance C1 to the second capacitance C2. At the lower cutoff frequency fmin, which is 10 kHz in the illustrated embodiment, capacitor 60, 70 has a first capacitance C1 of approximately 3.2 pF, and at the upper cutoff frequency fmax, which is 1 MHz in the illustrated embodiment, it has a second capacitance C2 of approximately 2.4 pF. Consequently, the relative deviation between C1 and C2 is approximately 25% when using deionized water as the operating fluid.

[0113] Out of Figure 4It is further evident that the frequency-dependent capacitance of capacitors 60, 70 decreases from the first capacitance C1 to the second capacitance C2 when using a mixture of 50% deionized water and 50% tap water as the operating fluid. At the lower cutoff frequency fmin, which is 10 kHz in the illustrated embodiment, capacitors 60, 70 have a first capacitance C1 of approximately 3.6 pF, and at the upper cutoff frequency fmax, which is 1 MHz in the illustrated embodiment, they have a second capacitance C2 of approximately 3.4 pF. Consequently, the relative deviation between C1 and C2 is approximately 6% when using a mixture of 50% deionized water and 50% tap water as the operating fluid.

[0114] Out of Figure 4It is further evident that the frequency-dependent capacitance of capacitors 60, 70 decreases from the first capacitance C1 to the second capacitance C2 when tap water is used as the operating fluid. At the lower cutoff frequency fmin, which is 10 kHz in the illustrated embodiment, capacitors 60, 70 have a first capacitance C1 of approximately 3.4 pF, and at the upper cutoff frequency fmax, which is 1 MHz in the illustrated embodiment, they have a second capacitance C2 of approximately 3.35 pF. Consequently, the relative deviation between C1 and C2 is approximately 1.5% when tap water is used as the operating fluid.

[0115] Returning to the procedure according to the in Figure 3 According to the flowchart shown, after process step I, it is checked whether the relative deviation of the second capacity C2 from the first capacity C1 is greater than a first minimum deviation Δ1. More precisely, it is determined whether the following condition is met: C 1 − C 2 C 1 > Δ 1

[0116] If this condition is met, in a process step J it is determined that the operating fluid in the operating fluid container 1 meets a specified quality requirement, since the electrical conductivity of the operating fluid has a value between 1 and 50 µS / cm.

[0117] In the described embodiment, the minimum deviation Δ1 has a value of 0.2. Therefore, for deionized water as the operating fluid in process step J, it is determined that the deionized water meets the specified quality requirements, since the relative deviation of the second capacity C2 from the first capacity C1 is 25%, and thus 0.25.

[0118] Subsequently, in process step J1, a release signal is issued if the relative deviation of the second capacity C2 from the first capacity C1 is greater than the first minimum deviation Δ1. Process step J1 is optional and not mandatory.

[0119] If the condition C 1 − C 2 C 1 > Δ 1 If, however, this condition is not met, it is checked whether the following condition is met: Δ 1 > C 1 − C 2 C 1 > Δ 2

[0120] If this condition is met, it is concluded that the water inside the operating fluid reservoir 2 has an electrical conductivity between 50 and 200 µS / cm. The quality properties of this water are still sufficient for water injection. However, in process step K, a warning signal is issued so that the user of the vehicle in which the operating fluid reservoir 1 is installed can be alerted that the water inside the operating fluid reservoir 2, while meeting the requirements, contains impurities. Consequently, in process step K, a warning signal is issued if the relative deviation of the second capacity C2 from the first capacity C1 has a value between the first minimum deviation Δ1 and a second minimum deviation Δ2, where the second minimum deviation Δ2 is smaller than the first minimum deviation Δ1.

[0121] In the described embodiment, Δ2 has a value of 0.05. Therefore, for a mixture of 50% deionized water and 50% tap water as the operating fluid, where |C1-C2| / C1 has a value of 0.06, the condition 0.2 > 0.06 > 0.05 is met, so that a warning signal is issued in process step K.

[0122] If the condition Δ 1 > C 1 − C 2 C 1 > Δ 2 If, however, this condition is not met, it is checked whether the following condition is met: Δ 2 > C 1 − C 2 C 1

[0123] If this condition is met, it is concluded that the water inside the operating fluid reservoir 2 has an electrical conductivity of more than 200 µS / cm. The quality properties of this water are insufficient for water injection. Therefore, a stop signal is issued in a process step L. This stop signal can be used to indicate to a water injection system (not shown in the figures) that the water inside the operating fluid reservoir 2 is unsuitable for water injection because it has an electrical conductivity of more than 200 µS / cm. Consequently, the water inside the operating fluid reservoir 2 is, for example, tap water.

[0124] Consequently, a stop signal is output in process step L if the relative deviation of the second capacity C2 from the first capacity C1 is less than the second minimum deviation Δ2.

[0125] In the described embodiment, Δ2 has a value of 0.05. Therefore, for tap water as the operating fluid, where |C1-C2| / C1 yields a value of 0.015, the condition 0.05 > 0.015 is met, so that a stop signal is output in process step L.

[0126] Figure 6 Figure 1 shows a highly simplified representation of the layered structure of a container wall 10, 20, 30 of the operating fluid container 1. The container wall can be the bottom wall 10 and / or the side wall 20 and / or the top wall 30. It is evident that the container wall 10 has a multi-layered structure.

[0127] The layered structure of the container wall 10, 20, 30 is described below with reference to the side wall 20 and the first condenser 60. However, the bottom wall 10 and / or the top wall 30 may also have a corresponding layered structure. Furthermore, the second condenser 70 may also be embedded in the container wall 10, 20, 30 in the same manner.

[0128] It can be seen that the side wall 20 has an outer layer 41, an inner layer 45 facing the interior of the operating fluid reservoir 2, and an adhesive layer 44 arranged between the outer layer 41 and the inner layer 45. The first electrode 61 and the second electrode 62 of the first capacitor 60 are arranged between the outer layer 41 and the adhesive layer 44. The side wall 20 also has a shielding layer 42 and an insulating layer 43, the shielding layer 42 being arranged between the outer layer 41 and the first electrodes 61 and the second electrode 62 of the first capacitor 60. The insulating layer 43, in turn, is arranged between the shielding layer 42 and the first and second electrodes 61 and 62 of the first capacitor 60.

[0129] It is further evident that the side wall 20 has an outer layer 41, an inner layer 45 facing the interior of the operating fluid reservoir 2, and an adhesive layer 44 arranged between the outer layer 41 and the inner layer 45. The first electrode 61 and the second electrode 62 of the first capacitor 60 are arranged between the outer layer 41 and the adhesive layer 44. The side wall 20 also has a shielding layer 42 and an insulating layer 43, the shielding layer 42 being arranged between the outer layer 41 and the first and second electrodes 61, 62 of the first capacitor 60. The insulating layer 43, in turn, is arranged between the shielding layer 42 and the first and second electrodes 61, 62 of the first capacitor 60.

[0130] Figure 7AFigure 1 shows a first capacitor 60 in isolation, viewed from the side. In the illustrated embodiment, it is evident that the first electrode 61 of the first capacitor 60 has a uniform width B along its length L. The second electrode 62 of the first capacitor 60, however, has a width B that varies along its length L. It is evident that the width B of the second electrode 62 increases towards the bottom wall 10 along its length L.

[0131] Figure 7B Figure 1 shows another example of a first capacitor 60 according to a further embodiment of the operating fluid reservoir 1. It can be seen that both the first electrode 61 and the second electrode 62 are each at different heights, i.e. .The first and second electrodes 61, 62 each have two wings 63 in different positions with respect to their longitudinal extent L, extending along their lateral extent B. It is evident that the respective wings 63 are rounded.

[0132] Figure 7C Figure 1 again shows a first capacitor 60 of an operating fluid reservoir 1 according to a further embodiment. Also shown in Figure 7C The first capacitor 60 shown is designed such that both the first electrode 61 and the second electrode 62 each have two wings 63 extending across the width B of the respective electrodes 61, 62. The respective wings 63 are arranged at different heights of the respective electrodes 61, 62.

[0133] The present invention relates to the invention described in the Figures 7A to 7CHowever, the illustrated embodiments of the first capacitor 60 are not limited as long as an electric field is generated by means of the first capacitor 60 that extends into the interior of the operating fluid container 2, so that the electrical conductivity of the operating fluid 50 can be determined by means of the evaluation device 80. Reference symbol list

[0134] 1 Operating fluid reservoir 2 Operating fluid reservoir interior 10 Bottom wall (of the operating fluid reservoir) 11 Rise (of the bottom wall) 20 Side wall (of the operating fluid reservoir) 30 Top wall 41 Outer layer (of the bottom wall / the side wall) 42 Shielding layer (of the bottom wall / the side wall) 43 Insulation layer (of the bottom wall / the side wall) 44 Adhesive layer (of the bottom wall / the side wall) 45 Inner layer (of the bottom wall / the side wall) 50 Operating fluid 60 First capacitor 61 First electrode (of the first capacitor) 62 Second electrode (of the first capacitor) 63 Wing (of the first electrode and / or the second electrode) 70 Second capacitor 71 First electrode (of the second capacitor) 72 Second electrode (of the second capacitor) 80 Evaluation unit 91 Frequency-dependent phase response for deionized water 92-frequency-dependent phase response for a mixture of 50% deionized water and 50% tap water; 93-frequency-dependent phase response forTap water 101 Frequency-dependent capacitance curve for deionized water 102 Frequency-dependent capacitance curve for a mixture of 50% deionized water and 50% tap water 103 Frequency-dependent capacitance curve for tap water L Longitudinal extent (of the electrodes of the measuring capacitor) B Width extent (of the electrodes of the measuring capacitor) C1 First capacitance (of the capacitor) C2 Second capacitance (of the capacitor) fmin Lower cutoff frequency fmax Upper cutoff frequency φ1 First phase angle φ2 Second phase angle φ3 Third phase angle δs Minimum loss angle Δ1 First minimum deviation Δ2 Second minimum deviation

Claims

1. Method for determining an electrical conductivity of an operating liquid in an operating liquid container (1) for a motor vehicle, wherein the operating liquid is deionized water, wherein the operating liquid container (1) comprises at least one capacitor (60, 70) fastened on a container wall (10, 20, 30) of the operating liquid container (1) having a first electrode (61, 71) and a second electrode (62, 72) opposite thereto, wherein the method is characterized by the following method steps: - applying (A) at least three different AC voltages to the capacitor (60, 70), wherein a first frequency of a first AC voltage corresponds to a lower limiting frequency (fmin) of 10 kHz, a second frequency of a second AC voltage corresponds to a frequency between the lower limiting frequency (fmin) and an upper limiting frequency (fmax) of 1 MHz or 100 kHz, and a third frequency of a third AC voltage corresponds to the upper limiting frequency (fmax); - determining and storing (B) a first impedance of the capacitor (60, 70) for the first frequency, a second impedance of the capacitor (60, 70) for the second frequency, and a third impedance of the capacitor (60, 70) for the third frequency; - determining (C) a first phase angle (φ1) from the first impedance, a second phase angle (φ2) from the second impedance, and a third phase angle (φ3) from the third impedance; and - determining (D) that an operating liquid (50) located in the operating liquid container (1) meets a quality requirement of electrical conductivity between 1 µS / cm and 50 µS / cm if the second phase angle (φ2) is greater than the first phase angle (φ1) and is greater than the third phase angle (φ3).

2. Method as claimed in claim 1, characterized by the method step: - outputting (D1) a release signal if the second phase angle (φ2) is greater than the first phase angle (φ1) and is greater than the third phase angle (φ3).

3. Method as claimed in one of the preceding claims, characterized by the method step: - outputting (E) a warning signal if the third phase angle (φ3) is greater than the second phase angle (φ2) or is equal to the second phase angle (φ2).

4. Method as claimed in one of the preceding claims, characterized by the method step: - outputting (F) a stop signal if the difference between the third phase angle (φ3) and the first phase angle (φ1) is less than a predetermined minimum loss angle (δs).

5. Operating liquid container (1) having the following features: - an operating liquid container interior (2) is delimited by a ceiling wall (30), a bottom wall (10), and a side wall (20) connecting the bottom wall (10) to the ceiling wall (30); - the operating liquid container (1) comprises at least one capacitor (60, 70) fastened to a container wall (10, 20, 30) of the operating liquid container (1) having a first electrode (61, 71) and a second electrode (62, 72); - the operating liquid container (1) comprises an electronic evaluation unit (80), which is electrically connected to the first electrode (61, 71) and to the second electrode (62, 72), wherein the operating liquid container (1) is characterized in that the evaluation unit (80) is designed to execute a method as claimed in at least one of claims 1 to 4.

6. The operating liquid container (1) as claimed in claim 5, characterized in that the capacitor (60, 70) is embedded in the container wall (10, 20, 30).

7. The operating liquid container (1) as claimed in one of claims 5 to 6, characterized by the following features: - the bottom wall (10) comprises a protrusion (11) extending into the operating liquid container interior (2); and - the first electrode (71) and the second electrode (72) of the capacitor (70) are embedded in the protrusion (11).

8. The operating liquid container (1) as claimed in one of claims 5 to 7, characterized by the following features: - the container wall (10, 20, 30) comprises an outer layer (41), an inner layer (45) facing toward the operating liquid container interior (2), and an adhesive layer (44) arranged between them; - the first electrode (61, 71) and the second electrode (62, 72) of the at least one capacitor (60) are arranged between the outer layer (41) and the adhesive layer (44).

9. The operating liquid container (1) as claimed in one of claims 5 to 8, characterized by the following features: - the container wall (10, 20, 30) comprises a shielding layer (42) and an insulation layer (43); - the shielding layer (42) is arranged between the outer layer (41) and the first and second electrodes (61, 62; 71, 72); and - the insulation layer (43) is arranged between the shielding layer (42) and the first and second electrodes (61, 62; 71, 72).

10. The operating liquid container (1) as claimed in claim 9, characterized in that the insulation layer (43) has the same dielectric conductivity as the inner layer (45) and / or the outer layer (41).

11. The operating liquid container (1) as claimed in one of claims 5 to 10, characterized in that a distance of the first and second electrodes (61, 62; 71, 72) to the operating liquid container interior (2) is between 1.5 mm and 3.5 mm.

12. The operating liquid container (1) as claimed in one of claims 5 to 11, characterized in that at least one of the first and second electrodes (61, 62; 71, 72) of the capacitor (60, 70) has a nonuniform width extension (B) along its length extension (L).

13. The operating liquid container (1) as claimed in one of claims 5 to 12, characterized in that at least one of the first and second electrodes (61, 62, 71, 72) of the capacitor (60) has a width extension (B) increasing in the direction of the bottom wall (10) along its length extension (L).