Water separator for a fuel cell and method for operating a water separator

Abstract

The present invention relates to a water separator (10) for a fuel cell in a vehicle. 1. The water separator comprises a housing having an inlet (15) for supplying an exhaust gas from an outlet of a stack of the fuel cell (1) and an outlet (16) for returning hydrogen gas to the fuel cell (1). A discharge valve (12) is used to discharge liquid water, and a venting valve (13) is used to discharge gas. A filling level sensor (30) arranged in the housing is used to capacitively measure the filling level of liquid water in the water separator (10). The filling level sensor (30) outputs a measurement signal that is proportional to the filling level. The filling level sensor (30) also comprises a slosh damping and splash guarding device (31) as protection against sloshing waves and water splashes.

Description

[0001] Description

[0002] title

[0003] Water separator for fuel cell and method for operating a water separator

[0004] State of the art

[0005] The present invention relates to a water separator for a fuel cell in a vehicle and a method for operating a water separator.

[0006] As combustion engines are increasingly replaced in vehicle technology, especially in the commercial vehicle sector, fuel cells are becoming increasingly important, as battery-electric drives can lead to high vehicle weight and a relatively short range.

[0007] A fuel cell comprises an anode path (Fh path) and a cathode path (Ch path). In the anode path, hydrogen H2, which is carried in a high-pressure tank in the vehicle, is expanded to a medium pressure and fed via a proportional valve at the desired pressure and in the required quantity to a fuel cell stack to generate electrical current to drive the vehicle's electric motor. The generally known reactions involved in the stack will not be discussed in detail here.

[0008] Unused or excess hydrogen is fed to a water separator via an outlet in the stack, along with unwanted harmful gases such as nitrogen (N2), as well as water droplets or water vapor. The water separator's job is to separate liquid water from the mixture of hydrogen, nitrogen, water vapor, and water droplets, and to temporarily store it in a sump at the bottom of the water separator. At regular intervals, when a predetermined liquid volume is reached, a drain valve is opened to remove liquid water from the water separator, thereby preventing water from overflowing or flowing back into the stack. Furthermore, a vent valve can be opened at regular intervals to remove the harmful gas N2 from the water separator, allowing only the lighter hydrogen to be fed back into the stack via a recirculator, in the dryest and purest state possible.

[0009] Reaching the specified fluid level can be detected by a level sensor, which then triggers the opening of the drain valve. Such level sensors are typically mounted on a side wall of the water separator to act as a switch in a so-called horizontal single-point triggering system, detecting an upper limit of the fluid level to open the drain valve.

[0010] For example, DE 10 2016 115 012 A1 discloses a water separator for a fuel cell system comprising a housing with a supply line from an anode exhaust line and a discharge line to the anode exhaust line. Arranged in a bottom region of the water separator are a first discharge line with a throttle and a second discharge line with an overflow pipe extending upward into the water separator and a valve. The water separator can have a fill level sensor for determining or detecting a water level in the water separator.

[0011] EP 3 097 978 A1 discloses a liquid container with an anti-slosh device. The anti-slosh device consists of a tube arranged inside the liquid container perpendicular to the bottom of the liquid container, which has the same base shape as the liquid container. Openings are provided in the tube wall at the top and bottom ends of the tube.

[0012] Common level sensor arrangements in water separators can have the disadvantage that they typically only detect an upper level limit, triggering only the opening of the drain valve. A lower level limit for closing the drain valve would require an additional sensor with conventional horizontal measurement, resulting in additional costs and requiring additional installation space.

[0013] Fluctuations in the inclination and / or orientation of the water separator, for example due to the movement of the vehicle, can cause the water surface in the water separator to move relative to the level sensor, so that the measurement of the level becomes inaccurate or can deviate significantly from the desired level limit or filling volume of a non-inclined or non-moving water separator, which can cause frequent and possibly undesired switching.

[0014] Water sloshing caused by a change in vehicle movement, and possibly additional water splashes resulting from this, e.g., during acceleration, braking, cornering, etc., can lead to large wave amplitudes and splashes on the wall where the sensor is located, resulting in significant inaccuracies and even overflow of the water separator toward the stack. Furthermore, the sensor may be unprotected from the sloshing and splashes, potentially causing inaccurate measurements.

[0015] Disclosure of the invention

[0016] With the present invention, a self-protection function of a capacitive level sensor can be integrated into a water separator, which can prevent or reduce sloshing waves and / or splashes on a signal electrode of the level sensor. This improves both the measurement accuracy and reliability of the level sensor, and establishes a more precise relationship between the measured level and the volume of water that can be extracted in the water separator, thus ensuring safe operation of the fuel cell.

[0017] According to the invention, a water separator for a fuel cell in a vehicle is provided, having the features of patent claim 1, and a method for operating the water separator, having the features of patent claim 13. The water separator comprises a housing with an inlet for supplying an exhaust gas from an outlet of a fuel cell stack and an outlet for returning hydrogen gas to the fuel cell. As described in the introduction, the exhaust gas can contain hydrogen, water vapor, water droplets, and nitrogen. In the water separator, liquid water and harmful gases such as nitrogen are separated from the residual hydrogen so that pure and dry hydrogen can be returned to the fuel cell.

[0018] The water separator includes a drain valve for draining liquid water and a vent valve for venting gas. The drain valve and vent valve can be controlled electrically or electronically, for example, by a control device.

[0019] A level sensor for measuring the liquid water level in the water separator is arranged in the housing. The level sensor is configured to output a measurement signal proportional to the level. This allows the actual level in the water separator to be measured at any time. In particular, an upper and a lower limit value can be measured or detected, enabling the drain valve to be controlled depending on two or more limit values.

[0020] According to the invention, the level sensor has an intrinsic, sensor-integrated slosh damping and splash protection device that can protect a measuring electrode of the level sensor from extremely fluctuating slosh waves on the water surface and / or water splashes. This can prevent incorrect measurements. Furthermore, the slosh damping and splash protection device can dampen wave motion on the water surface in the water separator, thus achieving greater accuracy in level measurement.

[0021] Due to the proportional or continuous measuring signal, intelligent control strategies can be implemented within the measuring range, for example to dampen sloshing movements and thus avoid constant opening and closing of the drain valve at short intervals due to wave amplitudes.

[0022] A method for operating a water separator for a fuel cell in a vehicle comprises a step of measuring a fill level of liquid water in the water separator along a vertical measuring axis. In a further step, a measurement signal proportional to the fill level is generated. The method further comprises a step of opening a drain valve to drain liquid water when the measurement signal is equal to or greater than a first limit value, and a step of closing the drain valve when the measurement signal is equal to or less than a second limit value, wherein the first limit value is greater than the second limit value.

[0023] Advantageous embodiments and further developments emerge from the further subclaims and from the description with reference to the figures.

[0024] A measuring axis of the level sensor can preferably be arranged vertically. Vertically arranged means that the measuring axis runs essentially parallel to the direction of gravity when the water separator is installed. If the vehicle is moving, slight deviations in the inclination or orientation of the measuring axis may occur.

[0025] The level sensor can preferably comprise a capacitive cylindrical capacitor or a capacitive polygonal capacitor. The measuring principle of the cylindrical capacitor or polygonal capacitor is advantageous in terms of immunity to electrical interference due to the external arrangement of the shield electrode. Furthermore, the outer, preferably tubular, shield electrode simultaneously serves as a slosh damper and splash guard for the measuring electrode arranged inside the shield electrode.

[0026] According to a preferred embodiment, an electrically conductive shielding electrode of the fill level sensor is integrated into the slosh damping and splash protection device. The slosh damping and splash protection device can, for example, be designed as a so-called sensor dome. The slosh damping and splash protection device can, in particular, be designed as a substantially cylindrical tube made of a plastic, with the shielding electrode embedded in the tube. The shielding electrode can simultaneously serve as the ground electrode for the capacitive fill level measurement and for shielding against capacitive external interference. According to an alternative embodiment, the shielding electrode can also be arranged as a conductive foil on a surface of the slosh damping and splash protection device. To protect this foil from the effects of water in the fill level sensor, the conductive foil can be coated with an insulating and sealing protective layer.

[0027] An electrically conductive measuring electrode, insulated and sealed towards the outside of the water separator, is arranged within the sensor dome (slosh dampening and splash protection device) or within the shield electrode as a signal electrode. The shield electrode is preferably tubular with a circular or polygonal cross-section. As a capacitive sensor, the level sensor measures the capacitance between the shield electrode and the measuring electrode. This allows for continuous level measurement over the widest possible measuring range.

[0028] The shielding electrode as well as the slosh damping and splash protection device preferably have openings at the lower end of the measuring range or below in order to create a flow connection between a volume inside the shielding electrode (or slosh damping and splash protection device) and a volume outside the shielding electrode (or slosh damping and splash protection device). The openings can preferably run radially through the shielding electrode or the slosh damping and splash protection device. This makes it possible to fulfill the principle of communicating tubes required for measuring the fill level, which enables fluid exchange between a respective water volume inside and outside the shielding electrode or the slosh damping and splash protection device. In other words, water in the water separator penetrates through the openings into the sensor dome at the bottom, the slosh damping and splash protection device orthe shield electrode so that a level that can be measured together with the signal electrode is established in the level sensor due to the measuring principle.

[0029] Particularly preferably, the measuring axis of the level sensor runs vertically through a center of mass of the liquid, extractable water in the water separator. This minimizes the disruptive influence of an inclination and / or orientation of the inclination of the water separator on the level measurement. Furthermore, the amplitude of waves on the surface of the water during sloshing movements can be minimized and the accuracy of level measurement can be improved. This allows, in particular, limit values ​​of the level to be reliably detected with high accuracy, so that an excessively high level and overflow of the water separator towards the stack can be avoided. On the other hand, at low fill levels, an unintentional escape of hydrogen through the outlet can be prevented, since the lower limit value is also reliably detected. This ensures a minimum fill level.

[0030] A preferred embodiment of the housing comprises a support and a cover, which are connected to each other via a gas-tight interface. Gas-tight here means that the escape of hydrogen gas is suppressed to such an extent that no safety-relevant defects occur.

[0031] The support essentially forms a floor element that surrounds a volume in which a sump is formed for temporarily accommodating the liquid water. The support can, for example, have a substantially rectangular cross-section, wherein the sump formed therein can have a circular cross-section. The valves and other parts or components of the water separator and / or the fuel cell can preferably be arranged on the support. The support can thus also serve as a mechanical platform for attaching other components, as well as for attaching the water separator in a vehicle installation space. The support can essentially be a housing half that is open at the top and has side walls and a floor.

[0032] The cover can be a housing half that opens downwards, similar to the support. Attaching the cover to the support creates a gas-tight interior space in which the level sensor is located. Other components of the water separator can also be arranged on the cover. The inlet and / or outlet are preferably formed on the cover.

[0033] According to a preferred embodiment, the carrier and the cover are each formed as a one-piece plastic injection-molded part. This allows these components to be manufactured cost-effectively in large quantities. A sealing interface required between the carrier and the cover is preferably located in a horizontal plane. This horizontal interface between the carrier and the cover can be designed in such a way that it does not conflict with the installation space of a likewise horizontal interface of the level sensor located lower on the base of the carrier, and is therefore suitable for implementing the level sensor even in small installation spaces.

[0034] Preferably, the fill level sensor is arranged on a horizontal base of the support. This allows a space-saving implementation of a fill level sensor for continuously measuring the fill level in the water separator.

[0035] A level sensor located at the bottom of the carrier with a vertical measuring axis, e.g., along a sensor dome of the level sensor, is suitable for generating a continuous water level measurement signal over a wide measuring range. This allows the water separator to be used across platforms for a wide variety of vehicles.

[0036] Placing the level sensor at the bottom and inside the base of the water separator support allows for robust and integral welding processes to seal the interface between the support and the level sensor. This allows for optimal utilization of the maximum extractable water volume relative to the available space in the water separator. A flat design of the level sensor housing below the measuring section, which is defined by the sensor dome, also allows for the detection of low levels as a shutdown threshold for the drain valve.

[0037] A central arrangement of the level sensor on the floor and on the inside of the water separator with a measuring axis pointing vertically upwards in the sensor dome enables optimal use of the available installation space in the horizontal direction and maximizes the available volume inside the water separator.

[0038] The openings in the slosh dampening and splash guard device are preferably formed at the bottom. This ensures a corresponding fill level inside the level sensor even at a low fill level, allowing the largest possible measuring range to be achieved. For example, one opening or two, three, or four or more round or rectangular openings can be formed near the bottom in the wall of the slosh dampening and splash guard device. Furthermore, additional openings can be formed above the openings near the bottom in the slosh dampening and splash guard device.

[0039] Sliding movements of the water and the resulting additional water splashes can occur, for example, during acceleration, braking, or cornering. These sloshing movements and water splashes can be dampened or prevented by the sloshing and splash protection device. In particular, the centrally located measuring electrode can be protected from splashes. This increases the measuring accuracy and reliability of the level sensor.

[0040] The level sensor is preferably connected to the support via a circumferential welded interface. By welding the level sensor, preferably from the inside into the support of the water separator, there is no direct external interface between the level sensor and the environment. This leads to significantly reduced requirements regarding the hydrogen-tightness of this welded interface. Therefore, it is not a safety-relevant feature, which can reduce testing effort and lower process costs.

[0041] According to a preferred embodiment, the water separator comprises an electrical interface, in particular an external plug interface, for electrically connecting the fill level sensor to an external device, wherein the electrical interface comprises a metallic and overmolded lead frame integrated in the carrier. Particularly preferably, the electrical interface can have space-saving ram contacts. This embodiment makes it possible to realize, for example, additional degrees of freedom, such as arranging the electrical interface to a wiring harness of the vehicle in a position that is advantageous in terms of space requirements and / or remote from the sensor. In addition, further electrical interfaces, such as a heater to prevent water from freezing in the water separator or in the valves, can be integrated into a common lead frame and a common electrical interface.This allows for further cost and space savings. For example, a shared 5-pin connector for the heater and level sensor requires less space than a 3-pin connector for the level sensor and a separate 2-pin connector for the heater. The electrical interface can be used, in particular, to read the measurement signals from the level sensor. Furthermore, the electrical interface can be used to apply the voltages or potentials required for measuring and operating the level sensor to the measuring electrode and / or the shield electrode.

[0042] According to a preferred embodiment, the water separator is configured to open the drain valve when the level sensor detects a first level (first limit value) and to close the drain valve when the level sensor detects a second level (second limit value). The first level is higher than the second level. The first limit value corresponds to a maximum level that should not be exceeded. The limit values ​​can be selected or set depending on requirements and application in order to open and close the drain valve. The complete measuring range of the level sensor can also be used for other control strategies without incurring additional costs or a multitude of different variants or without the need for multiple sensors to detect different limits. Control signals for opening or closingClosing of the drain valve and / or the vent valve can preferably be generated and output by an internal electronics of the water separator or by an external control device.

[0043] The present invention is explained in more detail below with reference to the exemplary embodiments shown in the schematic figures. They show:

[0044] Fig. 1 is a schematic representation of an anode path of a fuel cell;

[0045] Fig. 2 is a perspective view of a water separator according to an embodiment;

[0046] Fig. 3 is a sectional view through a support of the water separator from Fig. 2 with level sensor;

[0047] Fig. 4 is a plan view of the carrier from Fig. 3.

[0048] The accompanying figures are intended to provide a further understanding of embodiments of the invention. They illustrate embodiments and, in conjunction with the description, serve to explain principles and concepts of the invention. Other embodiments and many of the noted advantages will become apparent upon review of the drawings. Elements of the drawings are not necessarily shown to scale relative to one another.

[0049] In the figures of the drawing, identical, functionally identical and acting elements, features and components are provided with the same reference symbols, unless otherwise stated.

[0050] Fig. 1 shows a schematic representation of an anode path of a fuel cell 1 in a vehicle. In the anode path, hydrogen, which is carried in a high-pressure container in the vehicle, is depressurized to a medium pressure via a pressure reducer 3 and fed to a stack 2 via a proportional valve 4 at the desired pressure and in the required quantity to generate electricity to power the vehicle. The illustrated anode path further includes a shutoff valve 5 for disconnecting the hydrogen supply and sensors 6 for measuring pressure and temperature.

[0051] A filter 7 for trapping impurities is also arranged upstream of the inlet to stack 2. Exhaust gases are directed via an outlet of stack 2 into a water separator 10, which has a fill level sensor 30. The water separator 10 also includes a drain valve 12 and a vent valve 13, with a filter 11 arranged upstream of the drain valve 12. Dry and pure hydrogen can be returned to the anode path via an outlet 16. A further pressure sensor can be arranged at the outlet 16.

[0052] Fig. 2 shows a perspective view of a water separator 10 according to an embodiment. The water separator 10 comprises a housing with an inlet 15 for supplying the exhaust gas from the outlet of the stack 2 of the fuel cell 1 and the outlet 16 for returning hydrogen gas to the fuel cell 1.

[0053] The housing here comprises a support 22, which is essentially a housing half open at the top, and a cover 20, which is essentially a housing half open at the bottom. Support 22 and cover 20 are connected to one another via a gas-tight interface 21. The cover 20 and support 22 are screwed together at four corners, see also Fig. 3. An electrically controllable drain valve 12 for draining liquid water and an electrically controllable vent valve 13 for draining gas are arranged on the outside of the support 22. Furthermore, the support comprises an electrical interface 17 for establishing an electrical connection between a fill level sensor 30 arranged in the housing and an external control device (not shown).

[0054] Furthermore, a heating device 18 is arranged on the support 22, which can prevent the valves 12, 13 from freezing. The heating device 18 can be connected to the external control device or a voltage source via an electrical interface 19 (not shown). An outlet 14 is arranged on the outlet valve 13, through which water can flow out of the water separator 10 when the outlet valve 13 is open.

[0055] The carrier 22 and the cover 20 are each designed as a one-piece plastic injection-molded part, which can be manufactured cost-effectively in large quantities.

[0056] Fig. 3 shows a sectional view through the support 22 of the water separator 10 from Fig. 2 with the fill level sensor 30. Approximately centrally at the bottom of the support 22 in the housing, the fill level sensor 30 is arranged for capacitively measuring a fill level of liquid water in the water separator 10. A measuring axis 35 of the fill level sensor 30 is arranged vertically, and the fill level sensor 30 is configured to output a measurement signal proportional to the fill level. The measurement signal can, for example, be a voltage signal between 0 and 5 V or 0 and 24 V. In particular, the measuring axis 35 of the fill level sensor 30 runs through a center of mass of liquid and extractable water in the water separator 10 or at least very close to the center of mass.

[0057] In Fig. 3, W indicates an example water level. M denotes a measuring range of the level sensor 30. S indicates the current fill level. The level sensor 30 thus outputs a measurement signal corresponding to the fill level S via the interface 17.

[0058] The fill level sensor 30 shown in Fig. 3 comprises a capacitive cylindrical capacitor having a so-called sensor dome as a slosh damping and splash protection device 31. An electrically conductive shielding electrode 33 is integrated into the essentially tubular slosh damping and splash protection device 31. An electrically conductive measuring electrode 32 is arranged centrally and concentrically to the shielding electrode 33 within the slosh damping and splash protection device 31. The shielding electrode 33 serves, on the one hand, as a ground electrode for the capacitive measurement and, on the other hand, to shield against capacitive external interference. The fill level sensor 30 is arranged centrally on a horizontally formed base of the carrier 22.

[0059] The slosh damping and splash protection device 31 arranged concentrically around the measuring electrode 32 reduces the surface of the water in the level sensor 30. This can prevent any splashing caused by movements or

[0060] The formation of waves and / or splashes on the water surface and the formation of bubbles in the water caused by incoming air can be significantly reduced by accelerating the water separator 10.

[0061] The shielding electrode 33 and the slosh damping and splash protection device 31 as well as the slosh damping and splash protection device 31 have windows 34, through whose openings a flow connection is established between a volume inside and outside the slosh damping and splash protection device 31. The window openings also serve to dampen slosh and calm the liquid level inside the sensor dome 31. This also applies to a reduction or shielding against bubble formation in the water inside the slosh damping and splash protection device 31 compared to outside. The bubble formation in the water is caused by the inflowing gas volume flow into the water separator 10. The windows or openings 34 establish a flow connection between a volume inside the slosh damping and splash protection device 31 and a volume outside the slosh damping and splash protection device 31.The openings 34 are formed at the lower end of the slosh dampening and splash guard device 31. The sectional view of Fig. 3 shows two opposing pairs of openings 34 in the slosh dampening and splash guard device 31, each formed at the lower end of the slosh dampening and splash guard device 31. The height of the openings 34 can extend up to approximately one-third or approximately half the height of the slosh dampening and splash guard device 31.

[0062] The fill level sensor 30 is connected to the carrier 22 via a circumferential welded interface 29. This allows a secure, gas-tight seal to be created between the fill level sensor 30 and the carrier 22. The fill level sensor 30 comprises an electrical interface 17 (see Fig. 2) formed externally on the carrier 22 as a plug connection for electrically connecting the fill level sensor 30 to an external device (not shown), which is used, for example, to read out the measured values ​​and / or to control the water separator 10. The electrical interface 17 is connected to a metallic and overmolded stamped grid 37 integrated in the carrier 22. The stamped grid 37 serves as an electrical line between the three electrical contacts 36 of the fill level sensor 30 and the external electrical interface 17 to the cable harness connector.

[0063] Fig. 4 shows a top view of the opening of the support 22. Here, the rectangular cross-section of the support 22 can be seen, with the volume for holding water having a substantially circular cross-section. At the four corners of the support 22, screw interfaces 23 for screwing the support 22 to the cover 20 can be seen. During screwing, a seal is used to seal the housing at the interface 21 between the support 22 and the cover 20.

[0064] In the top view of Fig. 4, the three electrical contacts 36 of the level sensor 30 can be seen, which are connected to the electrical interface 17 via the lead frame 37.

[0065] A vent channel 25 is arranged at an upper edge of the support 22, through which undesired gas, such as nitrogen, can be discharged from the water separator 10. The vent valve 13 is used for this purpose.

[0066] Reference numeral 24 denotes the drain channel for draining water from the water separator 10 via the drain valve 12. The drain channel 24 is arranged near the bottom of the support 22. A filter 11 is arranged upstream of the drain valve 12 to prevent dirt from entering the drain valve 12.

[0067] The water separator 10 is configured to open the drain valve 12 when the fill level sensor 30 detects a first fill level as the first upper limit, and to close the drain valve 12 when the fill level sensor 30 detects a second fill level as the second lower limit. The first fill level (first limit) is higher than the second fill level (second limit). This reliably prevents water from overflowing from the water separator 10 into the stack 2. Furthermore, unintentional escape of hydrogen from the water separator at a low fill level can be prevented.

[0068] The present invention, described with reference to the figures, integrates a slosh dampening and splash protection device 31 into a fill level sensor 30 of a water separator 10 of a fuel cell. The fill level sensor 30 is installed in the water separator 10 as a capacitive cylindrical capacitor or polygonal capacitor. The fill level sensor 30 thus has an integrated self-protection function with respect to excessive slosh waves, bubble formation, or splashes onto the central measuring electrode 32 of the fill level sensor 30. The slosh dampening and splash protection device 31 according to the invention utilizes the geometric features of a capacitive fill level sensor 30, which essentially has the shape of a tube with a circular or polygonal base.

[0069] The compensation of the fill level between the medium (here water) outside the fill level sensor 30 with the medium inside the fill level sensor 30 during sloshing events with different wave amplitudes occurs independently of the fill level of the medium within the measuring range provided by the fill level sensor 30.

[0070] Furthermore, the level compensation can be performed independently of the design inclination of the water separator or level sensor 30 relative to the horizon. Typically, fuel cell water separators are required to have an inclination of ±18°.

[0071] The water separator 10 according to the invention ensures correct level measurement regardless of the orientation of the inclination of the water separator or level sensor between 0° and 360° relative to a horizontal plane. Since the level is measured within the level sensor 30, the internal level must correspond to the external level outside the level sensor 30 and within the water separator 10. For this purpose, the level sensor has a plurality of openings 34 in the slosh dampening and splash protection device 31 and in the outer shield electrode 33. Furthermore, complete emptying of the level sensor 30 can be ensured in the event that the connection between the media surface inside and outside the level sensor 30 is interrupted.In the present embodiment, this is achieved by an arrangement of four openings 34, each arranged in pairs opposite one another, in the slosh dampening and splash protection device 31 at the lower end of the slosh dampening and splash protection device 31. This also ensures that the fill level sensor 30 can be refilled, in particular after emptying in an inclined position and in the event of the residual water in the water separator 10 freezing and a subsequent freezing start with refilling while frozen medium (ice) is still present in the lower part of the fill level sensor 30. With several, in particular four, openings 34 evenly distributed around the circumference of the slosh dampening and splash protection device 31, at least one opening 34 advantageously always remains ice-free.

[0072] The outer shield electrode 33 is used here not only as a ground electrode, but also as electrical shielding against capacitive interference from the measuring electrode 32, thus reducing susceptibility to interference and improving measurement accuracy. In this case, the slosh dampening and splash protection device 31 can be designed, for example, as a plastic injection-molded part with an embedded (integrated) metallic shield electrode 33.

[0073] The water separator 10 according to the invention can be operated in various orientation positions between 0° and 360° relative to an inclination to the horizontal plane, so that the spatial distance between a power supply of the level sensor and a power supply of other components of the water separator 10 (such as heater 18, drain valve 12 and vent valve 13) can be maximized without having to accept any other functional losses of the level sensor 30.

[0074] The filling and emptying of the level sensor 30 can be optimized by adjusting the number, width, shape, and height of the opening cross-section of the openings 34, as well as the radii at the openings 34 in the lower area of ​​the slosh dampening and splash protection device 31, in order to utilize the usable measuring range of the level sensor 30 as far down as possible with good accuracy and a sensor characteristic that is as linear as possible. Specifically, several openings 34 with a width of, for example, 4 mm and a height of, for example, 16.5 mm can be formed in the lower area of ​​the level sensor 30.

[0075] In the present invention, several features have been designated "first" and "second." These designations serve only to clearly distinguish the individual features. In particular, they are not intended to imply any spatial or functional arrangement or prioritization.

[0076] When a list of alternatives in this application is marked with the designation “or”, this should be understood to mean both the listed alternatives taken individually and, where appropriate, a combination of several or all of the listed alternatives.

Claims

Claims 1. A water separator (10) for a fuel cell (1) in a vehicle, comprising: a housing with an inlet (15) for supplying an exhaust gas from an outlet of a stack of the fuel cell (1) and an outlet (16) for returning hydrogen gas to the fuel cell (1); a drain valve (12) for draining liquid water; a vent valve (13) for draining gas; and a fill level sensor (30) arranged in the housing for capacitively measuring the fill level of liquid water in the water separator (10), wherein the fill level sensor (30) is configured to output a measurement signal proportional to the fill level, and the fill level sensor (30) has a slosh dampening and splash protection device (31).

2. Water separator (10) according to claim 1, wherein: the level sensor (30) comprises a capacitive cylindrical capacitor or a capacitive polygon capacitor.

3. Water separator (10) according to claim 2, wherein: an electrically conductive shielding electrode (33) of the fill level sensor (30) is integrated into the slosh damping and splash protection device (31) and an electrically conductive measuring electrode (32) is arranged within the slosh damping and splash protection device (31).

4. Water separator (10) according to one of the preceding claims, wherein: the slosh dampening and splash protection device (31) has at least one opening (34) to establish a flow connection between a volume inside the slosh dampening and splash protection device (31) and a volume outside the slosh dampening and splash protection device (31).

5. Water separator (10) according to one of the preceding claims, wherein: the housing comprises a carrier (22) and a cover (20) which are connected to one another via a gas-tight sealed interface (21).

6. Water separator (10) according to claim 4 or 5, wherein: the openings (34) are arranged distributed around the circumference of the slosh dampening and splash protection device (31).

7. Water separator (10) according to claim 6, wherein: the fill level sensor (30) is connected to the carrier (22) via a circumferential welding interface (29).

8. Water separator (10) according to one of claims 4 to 7, wherein: the openings (34) are formed at a lower end of the slosh damping and splash protection device (31) at the bottom of the level sensor (30).

9. Water separator (10) according to one of claims 5 to 8, wherein the carrier (22) and the cover (21) are each formed as a one-piece plastic injection-molded part.

10. Water separator (10) according to one of claims 5 to 9, further comprising: an electrical interface (17) for electrically connecting the fill level sensor (30) to an external device, wherein the electrical interface (17) is connected to a metallic and overmolded lead frame (37) integrated in the carrier (22).

11. The water separator (10) according to any one of the preceding claims, wherein the water separator (10) is configured to: open the drain valve (12) when the level sensor (30) detects a first level; and close the drain valve (12) when the level sensor (30) detects a second level, wherein the first level is higher than the second level.

12. Water separator (10) according to one of the preceding claims, wherein the slosh dampening and splash protection device (31) is tubular.

13. A method for operating a water separator (10) for a fuel cell (1) in a vehicle, comprising: Measuring a level of liquid water in the water separator (10) along a measuring axis; Generating a measuring signal proportional to the fill level; Opening a drain valve (12) to drain liquid water when the measurement signal is equal to or greater than a first limit value; and closing the drain valve (12) when the measurement signal is equal to or less than a second limit value, wherein the first limit value is greater than the second limit value.

14. A method for operating a water separator (10) according to claim 13, wherein the measuring axis is vertical or inclined to the vertical.

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