Fuel cell stack and fuel cell system including the fuel cell stack

Abstract

The invention relates to a fuel cell stack (3) comprising a number of individual cells (24), each of which has a common cathode region (5) and a common anode region (4) separated from said common cathode region (5). The fuel cell stack according to the invention is characterized in that it is integrally equipped with at least one valve device (20, 21) for blocking the flow paths leading to and / or from said cathode region (5).

Description

[Technical Field]

[0001] The present invention relates to a fuel cell stack including a number of unit cells having a common cathode region and a common anode region, and a fuel cell system including the fuel cell stack, and more particularly to a fuel cell stack including a number of unit cells having a common cathode region and a common anode region separated from the common cathode region, and a fuel cell system including the fuel cell stack. [Background technology]

[0002] Fuel cell stacks consisting of a large number of individual cells are known in the prior art. These cells are typically clamped between two end plates and have a common cathode region and a common anode region for all the individual cells of the same fuel cell stack. The inlet / outlet regions typically extend along the entire length of the stack. These inlet / outlet regions are formed by a number of through-holes in each individual cell, which allow the various gaseous reactants to flow parallel to one another through all the cells of the fuel cell stack.

[0003] Fuel cell stacks are now being implemented in fuel cell systems. In these stacks, consisting of multiple PEM-based cells—those with proton-conducting or polymer electrolyte membranes—the various gases present in the fuel cell system are metered in during startup, scavenging the system through the fuel cell stack. This is particularly critical in the anode region. After a fuel cell stack has ceased operation, air is often present in the anode region if the hydrogen present in the anode region has evaporated or been consumed by oxygen from the air that flows in later. If additional hydrogen is then added, the air / hydrogen interface flows parallel to all the cells in the fuel cell stack. This, combined with the air in the cathode region, creates a dangerous potential difference at this interface that can damage the fuel cell catalyst. This type of startup, also known as air / air startup, adversely affects the lifespan of a fuel cell stack.

[0004] To address this issue, hydrogen can be stored in the anode region, ideally so that it is not consumed throughout the entire shutdown period of the fuel cell stack. One mechanism for this is to prevent the subsequent inflow of air into the cathode region. In various fuel cell systems known from the prior art, various valve devices are often implemented to isolate the cathode region of the fuel cell stack when the fuel cell system is shut down. These components, also known as cathode block valves, are often large valves or flaps installed around the fuel cell stack. They are heavy, prone to failure, and have poor sealing properties, which can be quite costly, at least if they are designed to provide adequate sealing. Furthermore, their control electronics and the actuators that control the valves open and close require a considerable amount of installation space. Summary of the Invention [Problem to be solved by the invention]

[0005] In light of the above, the problem that the present invention aims to solve is to further improve the type of fuel cell stack described in the preamble of claim 1 to enable a longer lifespan, and to provide an improved fuel cell system equipped with such a fuel cell stack. [Means for solving the problem]

[0006] According to the invention, this problem is solved by a fuel cell stack having the features set forth in claim 1, and in particular by a fuel cell system having the features set forth in claim 15. Advantageous configurations and developments emerge from the dependent claims.

[0007] The fuel cell stack according to the present invention is designed to have integrated therein at least one valve device for blocking a flow path, particularly preferably for blocking the flow path of air in and / or from the cathode region, particularly the air-containing cathode gas flowing into and / or out of the cathode region. By incorporating a valve device into the fuel cell stack in this way, it is possible to reduce the number of valve devices located in the region of the fuel cell system, particularly outside the fuel cell stack, which contributes significantly to reducing installation space, particularly for fuel cell systems. Since the valve device alone can already block the flow path through the cathode region, a throughflow through the cathode region is no longer possible. This alone has a very positive effect, since air can still only be exchanged in the cathode region by convection processes from one side of the valve, particularly the valve device, and the other side.

[0008] In a particularly advantageous development of the fuel cell stack according to the present invention, the at least one valve device is integrated into at least one end plate. As already mentioned above, the individual cells of the fuel cell stack are typically clamped together between two end plates. In this case, there is sufficient mounting space in the area of ​​these end plates, which are typically thicker than the individual cells of the fuel cell stack, to allow for the integration of any valve device as described above. The valve device may be integrated into the intake and / or exhaust ports, for example, by screwing it into the end plate from the connection port side of the intake and / or exhaust lines routed around the fuel cell stack.

[0009] The at least one valve device may be configured as a normally closed valve device, which ensures a constant sealing of the flow path through the cathode region of the fuel cell stack without the need for active operation and without the need for permanent energy consumption. Active opening may be achieved, for example, by various electromagnetic forces, i.e., switching of the valve device must be performed intentionally.

[0010] Alternatively, it may be possible to construct a structure that does not require control by incorporating a permanent magnet in combination with a magnetizable valve body and / or valve seat to provide a magnetic force that counteracts the spring pressure and / or magnetic force, particularly a permanent magnetic force.

[0011] These magnetic forces in particular then have a very important advantage, since they allow the creation of a passive, magnetically degressive valve device, meaning that the valve device is normally held closed by its respective magnets, and the force used to hold it closed is high, but the force that tries to close it again after it has opened, also known as the closing force, decreases with increasing valve position, in contrast to a spring-loaded valve, whose closing force increases with increasing valve position.

[0012] In particular, the valve body is held within the valve seat without a flow of a significant pressure and / or a significant flow velocity impinging on the valve seat under normal conditions, and the arrangement is sealed in this non-operating state and is adapted to utilize one or more seals or one or more sealing elements, which are preferably arranged downstream of the valve body to provide a good seal and to avoid unnecessary pressure losses during flow through.

[0013] It is worth noting that when a passive magnetically degressive valve device is used, the resulting blocking function of this valve device is that by combining one or more (permanent) magnets with one or more other (permanent) magnets and / or multiple magnetizable areas on the valve body and / or multiple magnetizable areas on the valve seat, the valve body of the valve device is held very securely and sealingly within the valve seat, thereby reducing the number of harmful air / air starts that contribute to fuel cell stack degradation and extending the hydrogen protection time.

[0014] If the cathode area is then actively subjected to a flow of air or cathode gas supplied via an air supply line and an air supply device, such as one or more flow compressors, compressors or the like, the pressure and flow velocity of the supplied air will lift the valve body from the valve seat against spring force and / or, very preferably, against magnetic force, so that the valve device automatically allows flow through the cathode area when the air supply is switched on. In this case, in particular, the various magnetic forces of permanent magnets, which may be located in or spaced from the valve seat in combination with a magnetizable valve body, can result in a reliable flow through the valve device regardless of the volumetric flow rate. The overall structure is lightweight and robust, and the introduction of magnets and the typical progressive behavior of their force-stroke characteristics allow smooth, unimpeded flow, whether at the minimum volumetric flow rate just sufficient to open the valve device or at the maximum volumetric flow rate. The progressive force-stroke characteristic curve of each magnet is ideal for both of these cases of flow, resulting in a constant flow in both cases without the valve or valve device constantly switching between open and closed states. This therefore reliably prevents pressure pulsations in the cathode area and allows the valve or valves or valve devices to operate efficiently and quietly. This is also known as "play-free" operation.

[0015] Furthermore, by using at least one passive magnetically degressive valve device, the required installation space can be further reduced, since this valve device does not require any additional installation space for wiring and / or controls.

[0016] The valve body itself may preferably be configured as a soft magnetic part, in particular as a soft magnetic rotating part, or may incorporate either soft magnetic, in particular magnetizable material and / or permanent magnets, and may preferably have a shape optimized with respect to flow.

[0017] According to a particularly advantageous development configuration of the fuel cell stack according to the invention, the valve body has an end facing the inlet of at least one valve device, which in one embodiment has an annular recess or trough, while in another embodiment this end of the valve body points upwards when used as specified.

[0018] In yet another embodiment, liquid, such as water, which may possibly overflow from the cathode region may thereby be collected using this recess or trough.

[0019] According to yet another particularly advantageous development of the fuel cell stack according to the invention, the at least one valve device has a guide device with one or more guide surfaces that are arranged to guide the opening and closing movement of the valve body, the guide device having a cylindrical part, the valve body having at least one protrusion extending in the direction of the outlet of the at least one valve device, in one embodiment, particularly a central protrusion of the at least one protrusion extending into the interior of the cavity formed by the cylindrical part of the guide device and / or one of the at least one protrusions surrounding the end of the cylindrical part of the guide device facing the inlet of the at least one valve device.

[0020] This allows, in one embodiment, to reliably prevent the movement of the valve body from being restricted and / or blocked, for example by tilting.

[0021] According to yet another particularly advantageous development configuration of the fuel cell stack according to the invention, the end of the cylindrical part of the guide device opposite the inlet of the at least one valve device is closed or has a passage.

[0022] Thereby, in one embodiment in which the cylindrical portion of the guide device has a passageway, any liquid present, such as water, can flow through this passageway and subsequently through the outlet of the valve and out of the valve device.

[0023] According to yet another particularly advantageous development of the fuel cell stack according to the invention, the at least one valve device has a fixed magnet, in one embodiment attached to the guide device, and a magnet attached to the valve body and movable together with the valve body, such that a magnetic force acts between the fixed magnet and the magnet movable together with the valve body, causing the fixed magnet and the magnet movable together with the valve body to attract each other.

[0024] In one embodiment, this advantageously achieves a further reduction in the closing force with increasing cathode block valve opening.

[0025] In the area where the valve body contacts the valve seat during subsequent operation, or in areas where only a small flow cross section remains between the valve body and the surrounding material, several hydrophobic surfaces may be provided. These hydrophobic surfaces may be realized, for example, by any suitable surface treatment or coating scheme. Preferably, additionally, several hydrophilic surfaces may be provided inside the valve device to prevent water from accumulating in various areas important for the operation of the valve device and, at the same time, to provide various areas where water can accumulate without danger. This allows for targeted redirection of any unavoidable water accumulation in the cathode area of ​​the fuel cell stack, and here especially in the area of ​​the outflow medium, to various locations where freezing of the water does not pose a danger.

[0026] In this case, the at least one valve device may have an area with a particularly hydrophobic surface; in one embodiment, the valve seat and / or the surface of a sealing element arranged in the area of ​​the valve seat and / or the surface of the valve body facing the surface of the valve body are configured hydrophobically, and / or the guide surface of the guide device and / or the front surface of the guide device facing the inlet of the valve device and / or the respective surface part of the valve body facing the guide device are configured hydrophobically.

[0027] In one embodiment, this can at least largely prevent liquids, in particular water, from collecting in those areas provided with a hydrophobic surface.

[0028] Furthermore, the at least one valve device may have a region with a particularly hydrophilic surface, and in one embodiment, in particular the surface of the recess and / or the surface of an undercut provided in the lateral part of the valve body of the fuel cell stack in which the valve device is integrated, which surface points towards the outlet of the valve device, is configured to be hydrophilic.

[0029] In one embodiment, this can be achieved such that any liquid, such as water, possibly contained in the cathode gas, accumulates in these areas with hydrophilic surfaces and is thereby at least temporarily removed from the rest of the fuel cell stack or fuel cell system. Even if this accumulation of water in these areas leads to ice formation due to the low temperature, it will have no or only a very slight effect on the operation of the valve device, since it will not restrict the mobility of the valve body in particular, as would be the case, for example, if the valve body were to freeze onto the valve seat or sealing element.

[0030] According to yet another particularly advantageous development of the fuel cell stack according to the invention, it can be provided that one valve device is provided on the inlet side and one on the outlet side of the cathode region, i.e. in this very advantageous development of the fuel cell stack according to the invention, the fuel cell stack has two separate valve devices that can shut off the fuel cell stack on the inlet side and on the outlet side when not in operation, thereby reliably and reliably preventing any subsequent inflow of air, whether due to convection effects, wind effects or the like.

[0031] According to a further very advantageous development of the fuel cell stack according to the invention, it is further contemplated that both valve devices are implemented as the same component. Therefore, both valve devices may be implemented as the same component, which leads to lower costs for the overall structure, since all valve devices can be manufactured in high batch quantities, thereby providing scaling effects. Each valve device is then inverted and assembled inside the fuel cell stack so that the flow through the fuel cell stack is in the same direction on both the inlet and outlet sides.

[0032] A fuel cell system according to the present invention comprises a fuel cell stack as described above, the fuel cell stack being arranged downstream of the outlet of the cathode region and having a valve device integrated therein, in one embodiment configured as a passive magnetically degressive valve device, the fuel cell system further comprising an (active) multi-way valve arranged upstream of the inlet of the cathode region, and a gas jet pump having at least one suction inlet port and one actuation inlet port, the inlet of the multi-way valve being connected to the supply line of the cathode region, a first outlet of the multi-way valve being connected to the inlet of the cathode region, and a second multi-way valve being connected to the supply line of the cathode region. a second outlet of the at least one suction inlet port of the gas jet pump is connected to the drive inlet port of the gas jet pump, and a suction inlet port of at least one suction inlet port of the gas jet pump is switchably connected to an outlet of the cathode region, in one embodiment upstream of a valve device, in one embodiment by means of a cathode purge valve, and / or another suction inlet port of the at least one suction inlet port of the gas jet pump is switchably connected to an outlet of the anode region, in one embodiment via a recirculation line connected to the outlet of the anode region, in one embodiment by means of a purge / drain valve.

[0033] This allows various liquids, such as water, which may be present, to be sucked out of the volume occupied by the anode region by evaporation under low pressure or after evaporation, and various gases, such as air, to be sucked out spontaneously at low temperatures, in a manner similar to that of the volume occupied by the cathode region, which, in the ideal case, is relatively uniform so that high pressure differences between the cathode and anode regions are avoided, thereby ensuring gentle treatment of the membrane.

[0034] In this case, the disadvantage of requiring wiring to control the operation of this active multi-way valve is accepted, but in exchange for this, if two passive valve devices are placed on the inlet and outlet sides of the cathode region, the pressing force will always be applied to one of the valve devices, resulting in an advantage that would be thought impossible: the fuel cell stack can be placed under negative pressure.

[0035] According to a further very advantageous development of the fuel cell system according to the invention, the second outlet of this multi-way valve is connected to the exhaust line of the cathode region via a cathode bypass line in which a gas jet pump is arranged.

[0036] According to a further very advantageous development of the fuel cell system according to the invention, the multi-way valve is integrated into a component of the fuel cell system.

[0037] This, in one embodiment, allows for a reduction in the installation space required for the fuel cell system.

[0038] According to a further very advantageous development configuration example of the fuel cell system according to the invention, the fuel cell system further comprises as a component a gas / gas humidifier arranged upstream of the inlet of the cathode region and a gas / gas humidifier bypass line connected to the supply air line upstream of the gas / gas humidifier and connected to the exhaust line of the cathode region upstream of the gas / gas humidifier, wherein a multi-way valve is integrated in the gas / gas humidifier, in one embodiment together with a humidifier bypass flap of the gas / gas humidifier, and / or a gas jet pump is arranged in the gas / gas humidifier bypass line such that the second outlet of the multi-way valve is connected to the drive inlet port of the gas jet pump.

[0039] Further advantageous configurations of the fuel cell stack according to the invention will become apparent from the examples which will be described in detail below with reference to the drawings. [Brief explanation of the drawings]

[0040] [Figure 1] 1 shows an example of a fuel cell system according to the prior art; [Figure 2] 1 shows a possible embodiment of a fuel cell stack according to the present invention; [Figure 3] 1 shows a valve device used in a possible embodiment of a fuel cell stack according to the present invention. [Figure 4] FIG. 4 is a top view of a portion of the valve device shown in FIG. 3, viewed from above in the direction of flow. [Figure 5] 1 is a graph showing the relationship between the closing force of a valve device and the opening degree of the valve device. [Figure 6] 1 is a schematic diagram illustrating a portion of a possible embodiment of a fuel cell system according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0041] 1 shows, in a highly schematic representation, a fuel cell system 1, which may be mounted, for example, on a vehicle 2 to provide electric drive power. A fuel cell stack 3, often referred to as a fuel cell or fuel cell stack, forms the core of the fuel cell system 1. It typically comprises a stack of multiple individual cells 24 (see FIG. 2). Illustratively, a common anode chamber or region 4 and a common cathode chamber or region 5 are shown, separated from each other by a proton-conducting membrane 6. The fuel cell stack 3 is thus a PEM fuel cell stack.

[0042] The anode chamber 4 is supplied with hydrogen from a hydrogen source 7, for example a compressed gas accumulator or a cryogenic accumulator. This hydrogen enters the anode chamber 4 of each single cell via a pressure control and metering unit 8. Unconsumed hydrogen can be returned via a recirculation line 9 equipped with a recirculation delivery device 10, here by way of example only a recirculation blower. Water and hydrogen are periodically discharged from a water trap 11 and may be vented via a purge and drain valve 12.

[0043] The cathode area 5 of the fuel cell system 1 is supplied with air as an oxygen source via an air supply line 13. The exhaust air leaves the fuel cell system 1 via an exhaust line 14. A flow compressor 15 is arranged here to deliver the required air. The hot, dry air downstream of this flow compressor 15 passes through a gas / gas humidifier 16 and, if necessary, an intercooler (not shown) before entering the cathode area 5. The humidified exhaust air leaving the cathode area 5 passes through the exhaust line 14 again to the gas / gas humidifier 16, where it releases moisture into the dry, hot intake air before flowing to the surroundings via an exhaust turbine 19 in the embodiment shown. This exhaust turbine 19 and the flow compressor 15 are connected to each other via a common shaft 17 and an electric machine 18, so that the energy stored in the area of ​​the exhaust turbine 19 can be used to help drive the air delivery device 15 or, if it does not require any drive power, to drive the electric machine 18 as a generator.

[0044] Now, this fuel cell system 1 according to the prior art has, by way of example only, two cathode block valves 20, 21, one in the supply line 13 located between the gas / gas humidifier and the fuel cell stack 3, and one in the exhaust line 14. These cathode block valves 20, 21 are typically configured as flaps that are actively controlled to open and close, which require a relatively large installation space inside the fuel cell system 1, are accordingly expensive, and are complex and time-consuming to assemble and control.

[0045] Nevertheless, such cathode block valves 20, 21 have a positive effect on the lifespan of the fuel cell stack 3, since they prevent fresh air from flowing into the cathode region 5 at a later time, ultimately resulting in the ideal case that only nitrogen is still present after the fuel cell system 1 has been shut down for an extended period of time, and the hydrogen passing through the fuel cell stack 3 and leaving the anode region 4 during shut down is no longer consumed, thereby preventing air / air starts, which are critical for the lifespan of the fuel cell stack 3, when restarting the fuel cell system 1 or the fuel cell stack 3.

[0046] FIG. 2 shows a schematic diagram of one possible embodiment of a fuel cell stack 3 according to the present invention. A number of individual cells 24 are clamped between two end plates 22, 23. Each cell, only some of which are labeled with reference numerals, has a cathode region 5 or chamber 5, an anode region 4 or chamber 4, and a membrane 6. The individual anode and cathode regions 4 and 5 are connected to each other via through-holes formed in each cell 24, forming a coolant flow area within the fuel cell stack 3, similar to a heat exchanger. Hydrogen is supplied to the anode region 4 via a hydrogen supply line 25 in the area of ​​the first end plate 22 and flows out to a recirculation line 9 in the area of ​​the other end plate 23. Also visible in FIG. 2 is a coolant supply 26 in the area of ​​the first end plate 22 and a coolant discharge 27 in the area of ​​the other end plate 23.

[0047] The intake line 13 is connected to a first end plate 22, and the exhaust line 14 to a second end plate 23. Instead of being arranged within the confines of the fuel cell system 1, the cathode block valves 20, 21 are now integrally integrated into the fuel cell stack 3, preferably into the respective end plates 22, 23 as shown diagrammatically here. That is, the end plate 22 carries integrally therein the intake side cathode block valve 20, which is a valve device within the meaning of the present application, and the other end plate 23 carries integrally therein the exhaust side cathode block valve 21, which is also a valve device within the meaning of the present application. These cathode block valves 22, 21, which are integrated into each end plate 22, 23 of the fuel cell stack 3, are ideally configured to be passive, i.e., normally closed, but when the incoming supply air or exhaust air impinges on them, they are pressed accordingly, allowing them to be easily and efficiently switched from the closed state while minimizing the installation space required inside the fuel cell system 1.

[0048] Now, in the diagram of Figure 3, it is possible to see cathode block valves 20, 21 incorporated into a portion of the fuel cell stack 3 shown in Figure 2 in a possible implementation variant according to the present invention.

[0049] The cathode block valve 20, 21 or valve device 20, 21 has a valve body 101 disposed within a cavity of a portion of the fuel cell stack 3. The valve body 101 is disposed, at least in part, within the cavity of the portion of the fuel cell stack 3 so as to be movable, particularly linearly movable, both along the direction of a constant flow of (cathode) gas or (cathode) fluid into or out of the cathode region 5, which is present in normal use and is specifically indicated by arrow P1 in FIG. 3 , and also opposite to the direction of this flow of cathode gas. Any cross-section of the cavity of the portion of the fuel cell stack 3, or of any cross-section of the region surrounding the cavity of the fuel cell stack 3, tapers in the direction opposite to the direction of cathode gas flow, so that movement of the valve body 101 opposite to the direction of cathode gas flow is limited by this tapered cross-section. This portion of the fuel cell stack 3 that is tapered in cross section forms the valve seat 120 for the cathode block valves 20,21.

[0050] When the valve body 101 abuts against the valve seat 120, which in one embodiment is abutted against a sealing element 102 configured as, for example, an O-ring arranged in the area of ​​the valve seat 120 as specifically shown in FIG. 3, the cathode block valves 20, 21 are in a fixed closed position, whereas when the valve body 101 is not abutting against the valve seat 120 or the valve body 101 is not abutting against the sealing element 102, the cathode block valves 20, 21 are in a fixed open position.

[0051] In order to guide the movement of the valve body 101 inside the fuel cell stack 3, in particular the opening and closing movement, the cathode block valves 20, 21 further have a guide device 112 provided with one or more guide surfaces that are arranged to guide the movement of the valve body 101, in particular by causing the valve body 101 to slide along the one or more guide surfaces during its movement.

[0052] The guide device 112 is attached to the inner surface of the part of the fuel cell stack 1 surrounding this gap by means of one or more, preferably three, fixing elements 106, in particular fin-shaped fixing elements 106, so that the guide device 112 is fixed in its position inside the fuel cell stack 1. Figure 4 shows a top view of the guide device 112 together with the fixing elements 106 when viewed from above in the direction of the cathode gas flow.

[0053] The guide device 112 preferably has a cylindrical portion extending parallel to the direction of cathode gas flow, the end of which opposite the inlet of the cathode block valves 20, 21 may be closed in one embodiment, or in another embodiment as shown in Figure 3 may be provided with a passage 105 through which any liquid, such as water, present may flow out.

[0054] The valve body 101 has one or more protrusions extending toward the outlets of the cathode block valves 20, 21, with one of these protrusions, particularly the central protrusion, extending into the cavity formed by the cylindrical portion of the guide device 112, and another of these protrusions surrounding the end of the cylindrical portion of the guide device 112 facing the inlets of the cathode block valves 20, 21.

[0055] The cathode block valves 20, 21 are configured as magnetically degressive valves that are normally held in a closed position by various magnetic forces, particularly when the pressure difference between the inlet and outlet sides of the cathode block valves 20, 21 is below a predetermined threshold. The force used to hold the cathode block valves 20, 21 in the closed position is relatively large, but the closing force F required to return the cathode block valves 20, 21 to the closed position after opening decreases with increasing valve position, i.e., with increasing distance D from the valve seat 120 or sealing element 102 to the valve body 101, as shown in the graph of FIG. 5, unlike a spring-loaded valve in which the closing force decreases with increasing valve position.

[0056] For this purpose, the cathode block valves 20, 21 have one or more magnets 104, preferably permanent magnets, with north and south poles 104-1, 104-2, located in the region of the valve seat 120 or at a distance from the valve seat 120, and the valve body 101 at least partially has magnetizable material and / or (permanent) magnets of the same polarity as the magnets 104, particularly in one or more regions facing the magnets 104 and / or in one or more regions 116 located in the vicinity of the magnets 104. The valve body 101 is thereby moved toward the inlet of the cathode block valves 20, 21 by the magnetic forces generated between the respective magnets 104 and the magnetizable material and / or (permanent) magnets of the valve body 101.

[0057] In another embodiment, a fixed (permanent) magnet 108 having north and south poles 108-1, 108-2 is preferably provided inside the cylindrical portion of the guide device 112 and a (permanent) magnet 107 having north and south poles 107-1, 107-2 is provided attached to the valve body 101 and movable therewith, with the magnets having the same polarity as the magnet 104, so that the attractive force between the magnets 107, 108 and therefore the valve closing force is further reduced as the cathode block valves 20, 21 are opened to an increased degree.

[0058] The valve body 101 has, in its surface at the end facing the inlets of the cathode block valves 20, 21, a recess or trough 110, particularly an annular recess, which can be used to collect liquid, such as water, that may overflow from the cathode region 5, particularly in cases where the cathode block valves 20, 21 are integrally incorporated into the outlet side of the cathode region 5. For this purpose, the cathode block valves 20, 21 or the valve body 101 are preferably mounted inside the fuel cell stack 3 so that the exposed surface of the trough 110 points upward when used as intended, thereby allowing any liquid that falls from above and hits the surface of the valve body 101 to be collected in the trough 110.

[0059] In one embodiment, the surface of the trough 110 is configured to be hydrophilic, as specifically shown by the dashed line labeled 103 in Figure 3. In another embodiment, the surfaces of a plurality of undercuts 113 provided in the portion of the valve body 101 of the fuel cell stack 3 on the side where the valve devices 20, 21 are integrally integrated, and pointing toward the outlets of the cathode block valves 20, 21, are also configured to be hydrophilic, as specifically shown by dashed line 114.

[0060] By configuring the surface of the trough 110 and / or the surface of each undercut 113 to be hydrophilic, any liquid, such as water, possibly contained in the cathode gas, will collect at these points and thereby be at least temporarily removed from the rest of the fuel cell stack 3 or fuel cell system 1. Even if this accumulation of water at these points leads to ice formation due to low temperatures, this will have no or only a very slight effect on the operation of the cathode block valves 20, 21, since it will not restrict the mobility of the valve body 101 in particular, as would be the case, for example, due to freezing of the valve body 101 onto the valve seat 120 or sealing element 102.

[0061] In order to sufficiently prevent freezing of the valve body 101 onto the valve seat 120 or the sealing element 102, furthermore, the surfaces of the valve seat 120 and / or the sealing element 102 and / or the surface of the valve body 101, which surfaces of the valve seat 120 and / or the sealing element 102 facing this surface of the valve body 101, as specifically indicated by the dashed line marked with the reference numeral 111, and / or the above-mentioned guide surfaces and / or the end face of the guide device 112 facing the inlet of the cathode block valve 20, 21 and / or parts of the valve body 101 facing the guide device 112, as specifically indicated by the dashed line marked with the reference numeral 109, are configured to be hydrophobic, so that liquids, in particular water, can be at least sufficiently prevented from accumulating at these points.

[0062] The hydrophobic / hydrophilic treatment of each of the above-mentioned regions or surfaces may be carried out, for example, by a) selecting any suitable hydrophobic / hydrophilic material, b) polishing each surface for hydrophobic treatment or roughening each surface for hydrophilic treatment, c) treating each surface with plasma, and d) generating capillary forces by shaping, for example by forming a lamellar structure on each surface.

[0063] Now, in the diagram of FIG. 6, one can see a schematic diagram of a portion of a fuel cell system in one example of a possible embodiment of a fuel cell system according to the present invention.

[0064] In this embodiment, the fuel cell system 1 has only one cathode block valve 20, 21 integrated into the fuel cell stack 3, in particular a passive magnetically degressive cathode block valve 21 as specifically shown in FIG. 3, which is located near the outlet of the cathode region 5.

[0065] On the other hand, on the inlet side of the cathode region 5, a multi-way valve 204, in particular a 3 / 2-way valve, which functions as an active or actively controlled cathode block valve, is preferably arranged in the air supply line 13 or is integrally incorporated into any other component of the fuel cell system 1.

[0066] In another embodiment, not shown, the multi-way valve 204 is integrated into an air purification unit (APU) or humidifier unit, such as the gas-to-gas humidifier 16, and is further integrated with or integrated within a commonly provided humidifier bypass flap or humidifier bypass control function.

[0067] An inlet of the multi-way valve 204 is connected to the air supply line 13. A first outlet of the multi-way valve 204 is connected to the inlet of the cathode region 5, where closing the first outlet of the multi-way valve 204 blocks the flow path into the cathode region. A second outlet of the multi-way valve 204 is connected to the exhaust line 14 of the cathode region 5 downstream of the cathode block valve 21 via a cathode bypass line 208, which may optionally be provided with a catalyst 206 as specifically shown in FIG. 6 .

[0068] The cathode block valve 21 and the multi-way valve 204 incorporated inside the fuel cell stack 3 are connected to each other, particularly via a gas jet pump, ejector pump, or jet pump 203, which may incorporate or consist of a Venturi nozzle, for example, and is driven by a propulsive jet flow of cathode gas flowing through a cathode bypass line 208 and adapted to flow into a driving inlet port of the gas jet pump 203. Here, an exhaust line 209 connected to a recirculation line 9, particularly to the outlet of a water trap 205 arranged in the recirculation line 9, is connected to the suction inlet port of the gas jet pump 203 via a blow-off valve, purge valve 202, or purge / drain valve 202. In addition, a cathode branch line 207 connected to the outlet of the cathode region 5 upstream of the cathode block valve 21 is connected to another suction inlet port of the gas jet pump 203 via the cathode purge valve 201.

[0069] By doing so, on the one hand, the cathode region 5 can be placed under negative pressure by switching the multi-way valve 204 to the second outlet to connect the air supply line 13 to the exhaust line 14 via the gas jet pump 203 and switching the cathode purge valve 201 to any open position, and on the other hand, the anode region 4 can be placed under negative pressure by switching the multi-way valve 204 to the second outlet to connect the air supply line 13 to the exhaust line 14 via the gas jet pump 203 and switching the purge / drain valve 202 to any open position.

[0070] Thus, various liquids, such as water, which may be present, can be sucked out of the volume occupied by the anode region 4 or the anode circuit by vaporization under low pressure, or various gases, such as air, spontaneously at low temperatures, in a manner similar to that of the volume occupied by the cathode region 5. This sucking out takes place relatively uniformly, in the ideal case, so that high pressure differences between the cathode region 5 and the anode region 4 are avoided, thereby ensuring gentle handling of the membrane. It would be impossible to achieve this function (sucking out and vaporization) in a fuel cell system 1 equipped with two passive cathode block valves 20, 21 at the inlet and outlet sides of the cathode region 5, since one of the cathode block valves 20, 21, especially the inlet cathode block valve 20, would be repeatedly opened by the sucking process.

[0071] In another embodiment (not shown), the gas jet pump 203 may be integrated into the bypass of the air purifying unit (LAE) or a humidifier unit, e.g., the gas-gas humidifier 16, instead of, or preferably together with, the multi-way valve 204, and may then be integrated into or integrated with a commonly provided humidifier bypass flap or humidifier bypass control. In this case, the gas jet pump 203 may be driven using the gas flowing through the bypass as a propulsion jet, and may further be switchably connected on the suction side to the cathode region 5 or the anode region 4 via the cathode purge valve 201 or the purge / drain valve 202 and the respective lines, thereby enabling suction to be performed to empty these regions.

Claims

1. A fuel cell stack (3) comprising a plurality of unit cells (24), each unit cell (24) having a common cathode region (5) and a common anode region (4) separated from the common cathode region (5), At least one valve device (20, 21) is incorporated to block the flow paths into and / or out of said cathode region (5), the at least one valve device (20, 21) is configured as a normally closed valve device (20, 21); when the volumetric flow rate through the cathode region (5) is sufficient, the valve body (101) of the at least one valve device (20, 21) is held open against the pressure of a spring and / or against the force of a magnet, the valve body (101) is made of a soft magnetic material or comprises a soft magnetic material and / or a permanent magnet, and at least one permanent magnet (104) connected to it in direct or indirect magnetic cooperation is arranged in the region of the valve seat, The fuel cell stack (3), wherein the at least one valve device (20, 21) has a fixed magnet (108) and a magnet (107) attached to the valve body (101) and movable together with the valve body (101), a magnetic force acts between the fixed magnet (108) and the magnet (107) movable together with the valve body (101), and the fixed magnet (108) and the magnet (107) movable together with the valve body (101) attract each other.

2. 2. The fuel cell stack (3) according to claim 1, characterized in that the at least one valve device (20, 21) is adapted to be integrated into at least one end plate (22, 23).

3. 3. The fuel cell stack (3) according to claim 1 or 2, characterized in that the valve body (101) has an end facing the inlet of the at least one valve device (20, 21), the end having an annular recess (110), the end of the valve body (101) facing upwards when in normal use.

4. 4. The fuel cell stack (3) according to claim 3, characterized in that the at least one valve device (20, 21) has a guide device (112) with one or more guide surfaces arranged to guide a certain opening and closing movement of the valve body (101), the guide device (112) has a cylindrical portion, the valve body (101) has at least one protrusion extending in the direction of the outlet of the at least one valve device (20, 21), a central protrusion of the at least one protrusion extending into a cavity formed by the cylindrical portion of the guide device (112) and / or one protrusion of the at least one protrusion surrounding an end of the cylindrical portion of the guide device (112) facing the inlet of the at least one valve device (20, 21).

5. 5. The fuel cell stack (3) according to claim 4, characterized in that the end of the cylindrical portion of the guide device (112) opposite the inlet of the at least one valve device (20, 21) is closed or has a passage (105).

6. said at least one valve device (20, 21) having an area (103, 111) with a hydrophobic surface; the valve seat (120) and / or the surface of the sealing element (102) arranged in the area of ​​the valve seat (120) and / or the surface of the valve body (101) are hydrophobic, and the surfaces of the valve seat (120) and / or the sealing element (102) face the surface of the valve body (101); and / or 5. The fuel cell stack (3) according to claim 4, characterized in that the guide surfaces of the guide devices (112) and / or the end faces of the guide devices (112) facing the inlets of the valve devices (20, 21) and / or the surface portions of the valve bodies (101) facing the guide devices (112) are configured to be hydrophobic.

7. 5. The fuel cell stack (3) according to claim 4, characterized in that the at least one valve device (20, 21) has an area (103) with a hydrophilic surface, and the surface of the recess (110) and / or the surface of an undercut (113) provided in the part of the side of the valve body (101) of the fuel cell stack (3) in which the valve device (20, 21) is incorporated, which surface points toward the outlet of the valve device (20, 21), are configured to be hydrophilic.

8. 3. The fuel cell stack (3) according to claim 1 or 2, characterized in that the downstream sealing element (102) is arranged in the region of the valve seat.

9. 3. The fuel cell stack (3) according to claim 1 or 2, characterized in that at least one valve device (20, 21) is arranged on the inlet and outlet sides of the cathode region (5).

10. 10. The fuel cell stack (3) according to claim 9, characterized in that the two valve devices (20, 21) are embodied as one and the same part.

11. A fuel cell system (1) comprising a fuel cell stack (3) according to claim 1 or 2, the fuel cell stack (3) has a valve device (21), the valve device (21) being located downstream of the outlet of the cathode region (5), integrated into the fuel cell stack (3) and configured as a passive magnetically degressive valve device; and The fuel cell system (1) further comprises: a multi-way valve (204) arranged upstream of the inlet of the cathode region (5), and a gas jet pump (203) having at least one suction inlet port and one drive inlet port; an inlet of the multi-way valve (204) connected to the supply line (13) of the cathode region (5), a first outlet of the multi-way valve (204) connected to the inlet of the cathode region (5), and a second outlet of the multi-way valve (204) connected to the drive inlet port of the gas jet pump (203); a cathode purge valve (201) connected upstream of the valve device (21) to an outlet of the cathode region (5); and / or a purge / drain valve (202) connected upstream of the valve device (21) to an outlet of the anode region (4).

12. 12. The fuel cell system (1) according to claim 11, wherein the second outlet of the multi-way valve (204) is connected to an exhaust line (14) of the cathode region (5) via a cathode bypass line (208) in which the gas jet pump (203) is arranged.

13. The fuel cell system (1) of claim 11, wherein the multi-way valve (204) is integrated into a component of the fuel cell system (1).

14. a gas / gas humidifier (16) located upstream of the inlet of the cathode region (5); and a gas / gas humidifier bypass line connected to the gas supply line (13) upstream of the gas / gas humidifier (16) and to an exhaust line (14) of the cathode region (5) upstream of the gas / gas humidifier (16); 14. The fuel cell system (1) of claim 13, wherein the multi-way valve (204) is integrated into the gas / gas humidifier (16) together with a humidifier bypass flap of the gas / gas humidifier (16), and / or the gas jet pump (203) is arranged in the gas / gas humidifier bypass line such that the second outlet of the multi-way valve (204) is connected to the drive inlet port of the gas jet pump (203).

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