Method for determining a quality property of an operating liquid in an operating liquid container for a motor vehicle, and operating liquid container for carrying out the method

Abstract

Methods for determining an electrical conductivity of an operating liquid in an operating liquid container for a motor vehicle. The operating liquid container includes at least one capacitor which is fastened to a container wall of the operating liquid container and has a first electrode and a second electrode opposite said first electrode. A first method determines the electrical conductivity of the operating liquid by means of a frequency-dependent phase progression of the impedance of the at least one capacitor. Another method determines the electrical conductivity of the operating liquid by means of a frequency-dependent capacitance profile of the at least one capacitor. An operating liquid container which is designed for carrying out the methods.

Claims

1. A method for determining an electrical conductivity of an operating liquid in an operating liquid container for a motor vehicle, wherein the operating liquid container comprises at least one capacitor fastened on a container wall of the operating liquid container having a first electrode and a second electrode opposite thereto, the method comprising: applying at least three different AC voltages to the at least one capacitor, wherein a first frequency of a first AC voltage corresponds to a lower limiting frequency (fmin), a second frequency of a second AC voltage corresponds to a frequency between the lower limiting frequency (fmin) and an upper limiting frequency (fmax), and a third frequency of a third AC voltage corresponds to the upper limiting frequency (fmax); determining and storing a first impedance of the at least one capacitor for the first frequency, a second impedance of the at least one capacitor for the second frequency, and a third impedance of the at least one capacitor for the third frequency; determining 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 that an operating liquid located in the operating liquid container meets a quality requirement if the second phase angle (φ2) is greater than the first phase angle (φ1) and is greater than the third phase angle (φ3).

2. The method as claimed in claim 1, further comprising: outputting 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. The method as claimed in claim 1, further comprising: outputting 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. The method as claimed in claim 1, further comprising: outputting a stop signal if a difference between the third phase angle (φ3) and the first phase angle (φ1) is less than a predetermined minimum loss angle (δs).

5. An operating liquid container comprising: an operating liquid container interior is delimited by a ceiling wall, a bottom wall, and a side wall connecting the bottom wall to the ceiling wall; the operating liquid container comprises at least one capacitor fastened to a container wall of the operating liquid container having a first electrode and a second electrode; and the operating liquid container comprises an electronic evaluation unit, which is electrically connected to the first electrode and to the second electrode, wherein the electronic evaluation unit is designed to execute the method as claimed in claim 1.

6. The operating liquid container as claimed in claim 5, wherein the at least one capacitor is embedded in the container wall.

7. The operating liquid container as claimed in claim 5, further comprising the following features: the bottom wall comprises a protrusion extending into the operating liquid container interior; and the first electrode and the second electrode of the at least one capacitor are embedded in the protrusion.

8. The operating liquid container as claimed in claim 5, further comprising the following features: the container wall comprises an outer layer, an inner layer facing toward the operating liquid container interior, and an adhesive layer arranged therebetween; and the first electrode and the second electrode of the at least one capacitor are arranged between the outer layer and the adhesive layer.

9. The operating liquid container as claimed in claim 8, further comprising the following steps: the container wall comprises a shielding layer and an insulation layer; the shielding layer is arranged between the outer layer and the first electrode and the second electrode; and the insulation layer is arranged between the shielding layer and the first electrode and the second electrode.

10. The operating liquid container as claimed in claim 9, wherein the insulation layer has a same dielectric conductivity as the inner layer and/or the outer layer.

11. The operating liquid container as claimed in claim 5, wherein a distance of the first electrode and the second electrode to the operating liquid container interior is between 1.5 mm and 3.5 mm.

12. The operating liquid container as claimed in claim 5, wherein at least one of the first electrode and the second electrode of the at least one capacitor has a nonuniform width extension (B) along a length extension (L) thereof.

13. The operating liquid container as claimed in claim 5, wherein at least one of the first electrode and the second electrode of the at least one capacitor has a width extension (B) increasing in a direction of the bottom wall along a length extension (L) thereof.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Further advantages, details, and features of the invention result hereinafter from the explained exemplary embodiments. In the specific figures:

(2) FIG. 1: shows a flow chart diagram of a method for determining a quality property of an operating liquid according to a first embodiment of the present disclosure, wherein the quality property is an electrical conductivity of the operating liquid;

(3) FIG. 2: shows frequency-dependent phase curves of the impedance of a capacitor for three different operating liquids, which each have different electrical conductivities;

(4) FIG. 3: shows a flow chart diagram of a method for determining a quality property of an operating liquid according to a second embodiment of the present disclosure, wherein the quality property is an electrical conductivity of the operating liquid;

(5) FIG. 4: shows frequency-dependent capacitance curves of a capacitor for three different operating liquids, which each have different electrical conductivities;

(6) FIG. 5: shows a greatly simplified three-dimensional illustration of an operating liquid container according to the disclosure;

(7) FIG. 6: shows a greatly simplified illustration of a layer structure of the bottom wall and/or the side wall of the operating liquid container according to a further embodiment of the present disclosure; and

(8) FIGS. 7A to 7C: show examples of measurement capacitors alone in a lateral top view of operating liquid containers of different embodiments of the present disclosure.

DETAILED DESCRIPTION

(9) In the following description, identical reference signs identify identical components or identical features, so that a description with respect to a component carried out with reference to one figure also applies to the other figures, so that a repeated description is avoided. Furthermore, individual features which were described in conjunction with one embodiment are also usable separately in other embodiments.

(10) FIG. 1 shows a flow chart diagram of a method for determining a quality property of an operating liquid according to a first embodiment of the present disclosure, wherein the quality property is an electrical conductivity of the operating liquid. The method according to the flow chart diagram illustrated in FIG. 1 is executed by an operating liquid container 1 illustrated in FIG. 5.

(11) FIG. 5 shows a greatly simplified three-dimensional illustration of an operating liquid container 1 according to the disclosure. An operating liquid container interior 2 is delimited by a ceiling wall 30, a bottom wall 10, and a side wall 20, which connects the bottom wall 10 to the ceiling wall 30. It is apparent from FIG. 5 that the side wall 20 is formed circumferentially.

(12) The operating liquid container 1 illustrated in FIG. 5 comprises a first capacitor 60 and a second capacitor 70. However, according to the present disclosure, the operating liquid container 1 can also comprise only the first capacitor 60 or only the second capacitor 70. Furthermore, the operating liquid container 1 can also comprise further capacitors, which are not shown in FIG. 5.

(13) The first capacitor 60 comprises a first electrode 61 and a second electrode 62. Both the first electrode 61 and also the second electrode 62 each have a length extension L, a width extension B, and a depth extension (see FIGS. 7A to 7C). The first electrode 61 and the second electrode 62 are each arranged extending in parallel to the side wall 20 in this case such that the length extensions L of the first electrode 61 and the second electrode 62 extend from the bottom wall 10 in the direction of the ceiling wall 30. In this case, depth extensions of the first electrode 61 and the second electrode 62 are arranged opposite to one another.

(14) The first capacitor 60 is embedded in the side wall 20, so that the first electrode 61 and the second electrode 62 of the first capacitor 60 are embedded in the side wall 20. The first capacitor 60 is therefore enclosed by the side wall 20. The first electrode 61 and the second electrode 62 of the first capacitor 60 are therefore not in direct contact with an operating liquid 50 (see FIG. 6). Furthermore, the first electrode 61 and the second electrode 62 of the first capacitor 60 are also not in direct contact with the surroundings of the operating liquid container 1. Reference is made to FIG. 4, which is described hereinafter, with respect to the embedding of the first capacitor 60 in the side wall 20.

(15) However, the present disclosure is not restricted to the first capacitor 60 being embedded in the side wall 20. In the operating liquid container 1 according to the disclosure, the first capacitor 60 can also be arranged on an outer surface of the side wall 20.

(16) Is apparent from FIG. 5 that the first electrode 61 and the second electrode 62 of the first capacitor 60 each comprise two wings 63, which extend in parallel to the width extension B of the electrodes 61, 62. The respective wings 63 are formed in this case at different heights of the first and second electrodes 61, 62, so that the wings 63 are arranged at different heights of the operating liquid container 1. The first and second electrodes 61, 62 of the first capacitor 60 therefore have a nonuniform width extension B along the length extension L thereof. However, the present disclosure is not restricted to a corresponding design 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 comprise a uniform width extension B over the length extensions L thereof.

(17) The second capacitor 70 comprises a first electrode 71 and a second electrode 72. The first electrode 71 and the second electrode 72 extend in parallel to the bottom wall 10. The first electrode 71 and the second electrode 72 are each arranged extending in parallel to the bottom wall 10 here in such a way that the length extensions and the width extensions of the first electrode 71 and the second electrode 72 extend in the plane of the bottom wall 10, so that the depth extensions of the first electrode 71 and the second electrode 72 are arranged opposite to one another.

(18) As is apparent from FIG. 5, the bottom wall 10 comprises a protrusion 11 extending into the operating liquid container interior 2. The second capacitor 70 is embedded in the bottom wall 10 in such a way that the first electrode 71 and the second electrode 72 of the second capacitor 70 are embedded in the protrusion 11 of the bottom wall 10. The first electrode 71 and the second electrode 72 of the second capacitor 70 are therefore not in direct contact with the operating liquid 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 liquid container 1. Due to the embedding of the first electrode 71 and the second electrode 72 in the protrusion 11 of the bottom wall 10, possible deposits on the bottom wall 10 have a reduced effect on the determination of the electrical conductivity of the operating liquid 50 located in the operating liquid container interior 2.

(19) Reference is made to FIG. 6, which is described hereinafter, with respect to the embedding of the second capacitor 70 in the bottom wall 10 or in the protrusion 11 of the bottom wall 10.

(20) However, the present disclosure is not restricted to the second capacitor 70 being embedded in the bottom wall 10. In an operating liquid container 1 according to the disclosure, the second capacitor 70 can also be fastened on an outer surface of the bottom wall 10.

(21) The operating liquid container 1 furthermore 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 produced via electrical lines (not shown in FIG. 5).

(22) The evaluation unit 80 is designed to execute the method according to the flow chart diagram illustrated in FIG. 1, which is described hereinafter.

(23) In a method step A, at least three different AC voltages having different frequencies are applied to the first capacitor 60 and/or to the second capacitor 70. In this case, a first frequency of a first AC voltage corresponds to a lower limiting frequency fmin, for example, 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, wherein the upper limiting frequency is, for example, 100 kHz. A third frequency of a third AC voltage corresponds to the upper limiting frequency fmax.

(24) In a method step B, a first impedance of the first capacitor 60 and/or of 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.

(25) Subsequently, in a method step C, a first phase angle φ1 is determined from the first impedance, a second phase angle φ2 is determined from the second impedance, and a third phase angle φ3 is determined from the third impedance.

(26) Three different frequency-dependent phase curves of impedances of the first capacitor 60 and/or the second capacitor 70 are illustrated for three different operating liquids in FIG. 2.

(27) In this case, the curve 91 shows a phase curve of the impedance for deionized water. The curve 92 shows the frequency-dependent curve of the phase angle of the impedance for a mixture of 50% deionized water and 50% tap water, and the curve 93 shows the frequency-dependent curve of the phase angle of the impedance for tap water. The deionized water has an electrical conductivity between 1-50 μS/cm. The mixture of 50% deionized water and 50% tap water has an electrical conductivity between 50-200 μS/cm. The tap water has an electrical conductivity of greater than 200 μS/cm.

(28) It is apparent from FIG. 2 that the curve 91 of the phase angle of the impedance of the capacitor 60, 70 in the case of deionized water has a maximum between a lower limiting frequency fmin of 10 kHz and an upper limiting frequency fmax of 100 kHz. In contrast, it is furthermore apparent from FIG. 2 that the curve 92 of the phase angle of the impedance of the capacitor 60, 70 for the mixture of deionized water and tap water rises continuously between the lower limiting frequency fmin and the upper limiting frequency fmax. This is also true for the curve 93 of the phase angle of the impedance of the capacitor 60, 70 for tap water. It is apparent in this case that at the upper limiting frequency fmax of 100 kHz, the curve 93 rises more slowly than the curve 92.

(29) Returning to the method according to the flow chart diagram illustrated in FIG. 1, it is checked after method step C whether the second phase angle φ2 is greater than the first phase angle φ1 and is also greater than the third phase angle φ3. If this condition is met, the curve of the phase angle then has a maximum between the lower limiting frequency fmin and the upper limiting frequency fmax. If the curve of the phase angle has a maximum, it is then determined or established in a method step D that the operating liquid located in the operating liquid container 1 meets a predetermined quality requirement.

(30) In the described exemplary embodiment, it is determined upon ascertainment of a maximum of the curve of the phase angle that the electrical conductivity of the operating liquid located in the operating liquid container interior 2 has an electrical conductivity between 1-50 μS/cm. it can be inferred therefrom that the water located in the operating liquid container interior 2 is deionized water and is suitable for the operation of a water injection unit. In this case, a release signal is output in a method step D1. However, step D1 is optional and not obligatory.

(31) If it is ascertained that the second phase angle φ2 is not greater than the third phase angle φ3, it is checked whether a difference between the third phase angle φ3 and the first phase angle φ1 is less than a predetermined minimum loss angle δs. The minimum loss angle δs in the illustrated exemplary embodiment is 1°. It is apparent from the frequency-dependent curve 93 illustrated in FIG. 2 that the loss angle for the upper limiting frequency fmax is less than 1° and is thus less than the minimum loss angle δs. A stop signal is thus output in a method step F. By means of the stop signal, a water injection system (not shown in the figures) can thus be signaled that the water located in the operating liquid container interior 2 is not suitable for the water injection, since the water has an electrical conductivity of greater than 200 μS/cm. The water located in the operating liquid container interior 2 is thus, for example, tap water.

(32) If the difference between the third phase angle φ3 and the first phase angle φ1 is not less than the predetermined minimum loss angle δs, it is checked whether the third phase angle φ3 is greater than the second phase angle φ2. If this condition is met, it is then concluded that the water located in the operating liquid container interior 2 has an electrical conductivity between 50-200 μS/cm. The quality properties of this water are still sufficient for the water injection. However, a warning signal is output in a method step E, so that the user of the motor vehicle in which the operating liquid container 1 according to the disclosure is installed can be made aware that the water located in the operating liquid container interior 2 does meet the requirements but comprises contaminants.

(33) The evaluation unit 80 of the operating liquid container 1 illustrated in FIG. 5 is furthermore designed to execute the method according to the flow chart diagram illustrated in FIG. 3, which is described hereafter.

(34) In a method step G, at least two different AC voltages having different frequencies are applied to the first capacitor 60 and/or to the second capacitor 70. In this case, a first frequency of a first AC voltage corresponds to a lower limiting frequency fmin. A second frequency of a second AC voltage corresponds to an upper limiting frequency fmax.

(35) Subsequently, in a method step H, a first capacitance C1 of the first capacitor and/or the second capacitor 70 for the first frequency is determined and stored. Furthermore, in method step H, a second capacitance C2 of the first capacitor 60 and/or of the second capacitor 70 for the second frequency is determined and stored.

(36) Subsequently, in a method step I, a relative deviation of the second capacitance C2 from the first capacitance C1 is ascertained. It is therefore ascertained in method step I by how many percent the second capacitance C2 deviates from the first capacitance C1.

(37) Three different frequency-dependent capacitance curves of the first capacitor 60 and/or the second capacitor 70 for three different operating liquids are illustrated in FIG. 4. In this case, the curve 101 shows a frequency-dependent capacitance curve of the first capacitor 60 and/or the second capacitor 70 for deionized water. The 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 the curve 103 shows the frequency-dependent capacitance curve of the first capacitor 60 and/or the second capacitor 70 for tap water. The deionized water has an electrical conductivity between 1-50 μS/cm. The mixture of 50% deionized water and 50% tap water has an electrical conductivity between 50-200 μS/cm. The tap water has an electrical conductivity of greater than 200 μS/cm.

(38) It is apparent from FIG. 4 that the curve 101 of the frequency-dependent capacitance of the capacitor 60, 70 in the case of deionized water as the operating liquid drops from the first capacitance C1 to the second capacitance C2. In this case, the capacitor 60, 70 has the first capacitance C1 of approximately 3.2 pF at the lower limiting frequency fmin, which is 10 kHz in the illustrated exemplary embodiments, and has the second capacitance C2 of approximately 2.4 pF at the upper limiting frequency fmax, which is 1 MHz in the illustrated exemplary embodiment. Therefore, the relative deviation from C1 to C2 in the case of deionized water as the operating liquid is approximately 25%.

(39) It is furthermore apparent from FIG. 4 that the frequency-dependent capacitance of the capacitor 60, 70 in the case of the mixture of 50% deionized water and 50% tap water as the operating liquid drops from the first capacitance C1 to the second capacitance C2. In this case, the capacitor 60, 70 has the first capacitance C1 of approximately 3.6 pF at the lower limiting frequency fmin, which is 10 kHz in the illustrated exemplary embodiment, and has the second capacitance C2 of approximately 3.4 pF at the upper limiting frequency fmax, which is 1 MHz in the illustrated exemplary embodiment. The relative deviation from C1 to C2 in the case of the mixture of 50% deionized water and 50% tap water as the operating liquid is therefore approximately 6%.

(40) It is furthermore apparent that the frequency-dependent capacitance of the capacitor 60, 70 drops from the first capacitance C1 to the second capacitance C2 in the case of tap water as the operating liquid. In this case, the capacitor 60, 70 has the first capacitance C1 of approximately 3.4 pF at the lower limiting frequency fmin, which is 10 kHz in the illustrated exemplary embodiment, and has the second capacitance C2 of approximately 3.35 pF at the upper limiting frequency fmax, which is 1 MHz in the illustrated exemplary embodiment. The relative deviation from C1 to C2 in the case of tap water as the operating liquid is therefore approximately 1.5%.

(41) Returning to the method according to the flow chart diagram illustrated in FIG. 3, it is checked after method step I whether the relative deviation of the second capacitance C2 from the first capacitance C1 is greater than a first minimum deviation Δ1. More specifically, it is determined whether the following condition is met:

(42) $\frac{.Math.C1-C2.Math.}{C1}>\Delta 1$

(43) If this condition is met, it is determined in a method step J that the operating liquid located in the operating liquid container 1 meets a predetermined quality requirement, since the electrical conductivity of the operating liquid has a value between 1 to 50 μS/cm.

(44) In the described exemplary embodiment, the minimum deviation Δ1 has a value of 0.2. It is thus determined for deionized water as the operating liquid in method step J that the deionized water meets the predetermined quality requirement, since the relative deviation of the second capacitance C2 from the first capacitance C1 is 25% and thus 0.25.

(45) Subsequently, in a method step J1, a release signal is output if the relative deviation of the second capacitance C2 from the first capacitance C1 is greater than the first minimum deviation Δ1. However, method step J1 is solely optional for the present invention and is not obligatory.

(46) In contrast, if the condition

(47) $\frac{.Math.C1-C2.Math.}{C1}>\Delta 1$

(48) is not met, it is checked whether the following condition is met:

(49) $\mathrm{\Delta 1}>\frac{.Math.C1-C2.Math.}{C1}>\mathrm{\Delta 2}$

(50) If this condition is met, it is concluded that the water located in the operating liquid container interior 2 has an electrical conductivity between 50-200 μS/cm. The quality properties of this water are still sufficient for the water injection. However, a warning signal is output in a method step K, so that the user of the motor vehicle in which the operating liquid container 1 according to the invention is installed can be made aware that the water located in the operating liquid container interior 2 does meet the requirements but comprises contaminants. Therefore, in method step K, a warning signal is output if the relative deviation of the second capacitance C2 from the first capacitance C1 has a value between the first minimum deviation Δ1 and a second minimum deviation Δ2, wherein the second minimum deviation Δ2 is less than the first minimum deviation Δ1.

(51) In the described exemplary embodiment, Δ2 has a value of 0.05. Therefore, for a mixture made up of 50% deionized water and 50% tap water as the operating liquid, in the case of which |C1−C2|/C1 results in a value of 0.06, the condition 0.2>0.06>0.05 is met, so that a warning signal is output in method step K.

(52) In contrast, if the condition

(53) $\mathrm{\Delta 1}>\frac{.Math.C1-C2.Math.}{C1}>\mathrm{\Delta 2}$

(54) is not met, it is checked whether the following condition is met:

(55) $\Delta 2>\frac{.Math.C1-\mathrm{C2}.Math.}{C1}$

(56) If this condition is met, it is concluded that the water located in the operating liquid container interior 2 has an electrical conductivity of greater than 200 μS/cm. The quality properties of this water are inadequate for the water injection. Therefore, a stop signal is output in a method step L. By means of the stop signal, a water injection system (not shown in the figures) can be signaled that the water located in the operating liquid container interior 2 is not suitable for the water injection, since the water has an electrical conductivity of greater than 200 μS/cm. The water located in the operating liquid container interior 2 is therefore, for example, tap water.

(57) Therefore, a stop signal is output in method step L if the relative deviation of the second capacitance C2 from the first capacitance C1 is less than the second minimum deviation Δ2.

(58) In the described exemplary embodiment, Δ2 has a value of 0.05. Therefore, for tap water as an operating liquid, in the case of which |C1−C2|/C1 results in a value of 0.015, the condition 0.05>0.015 is met, so that a stop signal is output in method step L.

(59) FIG. 6 shows a greatly simplified illustration of a layer structure of a container wall 10, 20, 30 of the operating liquid container 1. The container wall can be the bottom wall 10 and/or the side wall 20 and/or the ceiling wall 30. It is apparent that the container wall 10 is constructed in multiple layers.

(60) The layer structure of the container wall 10, 20, 30 is described hereinafter with reference to the side wall 20 and with reference to the first capacitor 60. However, the bottom wall 10 and/or the ceiling wall 30 can also have a corresponding layer structure. Furthermore, the second capacitor 70 can also be embedded in the same manner in the container wall 10, 20, 30.

(61) It is apparent that the side wall 20 comprises an outer layer 41, an inner layer 45 facing toward the operating liquid container interior 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 furthermore comprises a shielding layer 42 and an insulation layer 43, wherein the shielding layer 42 is arranged between the outer layer 41 and the first electrode 61 and the second electrode 62 of the first capacitor 60. The insulation layer 43 is in turn arranged between the shielding layer 42 and the first and second electrodes 61, 62 of the first capacitor 60.

(62) It is furthermore apparent that the side wall 20 comprises an outer layer 41, an inner layer 45 facing toward the operating liquid container interior 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 furthermore comprises a shielding layer 42 and an insulation layer 43, wherein the shielding layer 42 is arranged between the outer layer 41 and the first and second electrodes 61, 62 of the first capacitor 60. The insulation layer 43 is in turn arranged between the shielding layer 42 and the first and second electrodes 61, 62 of the first capacitor 60.

(63) FIG. 7A shows a first capacitor 60 alone in a lateral top view. In the illustrated exemplary embodiment, it is apparent that the first electrode 61 of the first capacitor 60 has a uniform width extension B along its length extension L. The second electrode 62 of the first capacitor 60, in contrast, has a changed width extension B along the length extension of the second electrode 62. It is apparent that the width of the second electrode 62 along its length extension L has a width extension B increasing in the direction of the bottom wall 10.

(64) FIG. 7B shows a further example of a first capacitor 60 according to a further embodiment of the operating liquid container 1. It is apparent that both the first electrode 61 and also the second electrode 62 each comprise two wings 63 at different heights, i.e., in different positions with respect to the length extension L of the first and second electrodes 61, 62, which wings extend along the width extension B of the first and second electrodes 61, 62. It is apparent that the respective wings 63 are rounded.

(65) FIG. 7C in turn shows a first capacitor 60 of an operating liquid container 1 according to a further embodiment. The first capacitor 60 shown in FIG. 7C is also designed such that both the first electrode 61 and also the second electrode 62 each comprise two wings 63, which extend in the width extension B of the respective electrodes 61, 62. The respective wings 63 are arranged here at different heights of the respective electrodes 61, 62.

(66) The present disclosure is not restricted to the designs of the first capacitor 60 illustrated in FIGS. 7A to 7C, however, as long as an electrical field is generated by means of the first capacitor 60 which extends into the operating liquid container interior 2, so that the electrical conductivity of the operating liquid 50 can be ascertained by means of the evaluation unit 80.

LIST OF REFERENCE SIGNS

(67) 1 operating liquid container 2 operating liquid container interior 10 bottom wall (of the operating liquid container) 11 protrusion (of the bottom wall) 20 side wall of the operating liquid container) 30 ceiling 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 liquid 60 first capacitor 61 first electrode (of the first capacitor) 62 second electrode (of the first capacitor) 63 wings (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 curve for deionized water 92 frequency-dependent phase curve for a mixture of 50% deionized water and 50% top water 93 frequency-dependent phase curve for tap 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 length extension (of the electrodes of the measurement capacitor) B width extension (of the electrodes of the measurement capacitor) C1 first capacitance (of the capacitor) C2 second capacitance (of the capacitor) fmin lower limiting frequency fmax upper limiting 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