Fuel cell stack

Abstract

The present invention relates to a fuel cell stack (10) having a first end plate (51) and a second end plate (52) and a plurality of fuel cells (11) arranged between the end plates (51, 52). At least one elastic clamping element (55) is clamped between the end plates (51, 52) in the stacking direction (S). Furthermore, a re-clamping element (60) is arranged between the clamping element (55) and a surface portion (70) of the fuel cell stack (10). The re-clamping element (60) has a clamping body (61) and at least one adjusting element (62) arranged between the clamping body (61) and the surface portion (70). The distance between the clamping body (61) and the surface portion (70) can be variably adjusted and fixed by means of the at least one adjusting element (62).

Description

Field of the Invention

[0001] The present invention relates to a fuel cell stack which can be reclamped, in particular by adapting the compressive tensile force acting on the fuel cell stack due to at least one clamping element. The present invention also relates to a vehicle having such a fuel cell stack. Background Art

[0002] A fuel cell utilizes the chemical conversion of fuel and oxygen into water to generate electric energy. For this purpose, the fuel cell has a membrane electrode assembly (MEA), and the membrane electrode assembly has a membrane electrode unit.

[0003] The membrane electrode unit is formed by a proton-conducting membrane, i.e., a PEM, and catalytic electrodes are arranged on both sides of the proton-conducting membrane. Here, the membrane isolates the anode region assigned to the anode and the cathode region assigned to the cathode from each other and electrically insulates them. In addition, a gas diffusion layer may be arranged on the side of the electrode that does not face the membrane.

[0004] During the operation of the fuel cell, a hydrogen-containing fuel is supplied to the anode, where it is electrochemically oxidized from H 2 to H + . Through the electrolytic membrane, hydrogen ions H + are transported from the anode region to the cathode region in a water-containing or water-free manner. The electrons provided at the anode are led to the cathode through a wire.

[0005] An oxygen-containing working medium is supplied to the cathode, such that at the cathode, it is oxidized from O 2 to O 2 - . These oxygen ions react with the hydrogen ions transported through the membrane to form water in the cathode region.

[0006] A fuel cell stack is generally formed by a large number of MEAs arranged overlappingly in a stack in the stacking direction, and the electric powers of the MEAs are added together. Generally, bipolar plates are arranged between these membrane electrode assemblies, and the bipolar plates ensure the supply of reactants and coolant to each MEA and serve as a conductive contact portion with these membrane electrode assemblies.

[0007] Seals are arranged between the membrane electrode unit and the bipolar plate to seal the anode and cathode regions from the outside and prevent the working medium from spilling out of the stack. These seals are provided on the membrane electrode unit, the bipolar plate, or both of these components.

[0008] To permanently seal the stack and to ensure electrical contact between the bipolar plates and the membrane electrode assembly, the fuel cell stack is clamped before commissioning. Tensioning elements are also used in order to clamp the fuel cell stack during operation as well.

[0009] Different tensioning elements are known from the prior art. For example, two end plates arranged at the ends of the fuel cell stack can be connected by means of tensioning elements. By introducing the tensile force via these tensioning elements into the end plates, the fuel cell stack is pressed together. For example, threaded rods, tie rods, chains etc. are used as tensioning elements.

[0010] It is also known to use clamped strip-shaped or belt-shaped elastic clamping elements which are either connected to the end caps or at least partially surround the stack in at least one cross-section (in the stacking direction). Regarding the design and fastening means of such elastic clamping elements (tensioning elements), reference is made, for example, to EP 1870952 A2, hereby incorporating the content of EP1870952A2 in its entirety.

[0011] In particular, height changes due to operation can occur in the active area of the fuel cell stack or the MEA, and these height changes can vary, for example, with the temperature and humidity of the fuel cell stack. This is also referred to as stack breathing. In the case of using elastic clamping elements, the elasticity of these clamping elements can also decrease over time. In particular, in the case of metal clamping elements which annularly surround the fuel cell stack and thus have a plurality of 90° bends, elongation of the clamping elements occurs especially in the area of these bends.

[0012] Irrespective of the height changes of the fuel cell stack and the aging of the clamping elements, sufficient compression of the stack must always be ensured, especially in order to guarantee the sealing effect of the seals used. Thus, devices which are supposed to permanently ensure the compression of the fuel cell stack are already known from the prior art.

[0013] DE 102006028498 A1 discloses a clamping device for a fuel cell stack, which clamping device has at least one tensioning element for tensioning the fuel cell stack and at least one length extension compensation element which is integrated into the tensioning element or connects two tensioning elements to one another.

[0014] DE 102004027694 A1 discloses a fuel cell stack which has a plurality of fuel cells arranged between end plates. A clamping system, in particular a disc spring, is arranged between the end plates and the tensioning device. In the unclamped state, the disc spring has an arch which opens in the direction of the clamping device, while in the clamped state, the disc spring lies approximately flat against the end plate.

[0015] According to the previously mentioned published literature, elastic elements should be used to avoid stress peaks due to the stretching of the stack. The change in the height of the stack should also be avoided to a certain extent by initially stretching the elastic elements too tightly. However, the elastic elements themselves are subject to aging and at least the possible adjustment of the compressive force is inaccurate and passive due to this.

[0016] DE 102010007981 A1 discloses a fuel cell stack having fuel cells arranged between two end plates and at least one tensioning device for applying a tensile force that connects these end plates. A fastening element is arranged between the tensioning device and at least one of the end plates, and the fastening element is configured as an eccentric element or includes an eccentric element. The distance between the end plates should be changed by rotating the fastening element and thus the tensile force between the end plates should be adapted.

[0017] The previously mentioned published literature discloses a complex compression system that requires specially adapted end plates and / or tensioning devices. In addition, this compression system is not suitable for use with circumferential clamping elements.

[0018] Other solutions of the prior art for designing a clamping system for a fuel cell stack that can, if necessary, re-clamp the fuel cell stack are disclosed in the published literature JP 2013020740 A, JP 2002063929 A, and WO 2005 / 045981. Unfortunately, these design solutions are not so compact and thus, for example, make it difficult to arrange multiple fuel cell stacks in a complex. Summary of the Invention

[0019] Now, the task on which the present invention is based is to overcome the disadvantages of the prior art and to provide a solution for re-clamping a fuel cell stack that can be integrated into an existing fuel cell stack without major adaptation, in particular into such a fuel cell stack having a circumferential belt-shaped or strip-shaped clamping element without major adaptation.

[0020] This task is solved by a fuel cell stack having a first end plate and a second end plate and a plurality of fuel cells arranged between these two end plates in the stacking direction. The fuel cell stack also has at least one elastic clamping element that clamps between the end plates in the stacking direction. At least one re-clamping element is arranged between the clamping element, preferably the clamped clamping element (the clamping element in the clamped state), and a surface part of the fuel cell stack, preferably a surface part of one of the end plates. The re-clamping element has a clamping body and at least one adjustment element arranged between the clamping body and the surface part. Preferably, the clamping body and the adjustment element are connected to each other, and this connection can be achieved in a purely force-fitting manner.

[0021] According to the present invention, the distance between the clamping body and the surface portion, preferably the distance in the direction of the normal to the surface portion, can be variably adjusted by means of at least one adjusting element. In other words, the at least one adjusting element is configured to variably adjust the distance between the clamping body and the surface portion. Particularly preferably, the distance between the point of the re-clamping element, preferably the point furthest from the surface portion in the direction of the normal, and the surface portion can be variably adjusted by means of the at least one adjusting device.

[0022] Furthermore, the clamping body can be fixedly positioned (positioned) at a selected distance from the surface portion by means of the at least one adjusting element according to the present invention, preferably fixedly positioned (positioned) at a selected distance from the surface portion in the direction of the normal to the surface portion. In other words, the at least one adjusting device is also configured to fixedly position (position) the clamping body at a variable distance from the surface portion. Preferably, by fixing or positioning the adjusting element, other unwanted displacements of the clamping body caused by the forces exerted by the adjusting element or the clamping element are avoided.

[0023] According to the present invention, at least one clamping element at least partially lies flat against the surface of the fuel cell stack. Preferably, the surface has the mentioned surface portion, and the re-clamping element is arranged between the surface portion and the clamping device. Preferably, it relates to the surface or surface portion of the first or second end plate. According to the present invention, the re-clamping element is arranged in a void of the surface. Here, preferably, the dimensions of the clamping body and the void are adapted, and particularly preferably, the re-clamping element, in particular the clamping body, is configured to be able to sink into the void. If the re-clamping element is arranged in the void of the surface, the mentioned surface portion is preferably located in the void.

[0024] Thus, the fuel cell stack according to the present invention can achieve re-clamping of the at least one clamping element by increasing the fixed distance between the clamping body of the re-clamping element and the surface portion of the fuel cell stack by means of at least one adjusting element. This causes elongation of the elastic clamping element, whereby the compressive tensile force exerted by the elastic clamping element on the fuel cell stack increases. Preferably, the elastic clamping element of the fuel cell stack clamps within the Hooke's range. Also preferably, the re-clamping element according to the present invention can achieve re-clamping of the clamping element in the stacking direction (S) of the fuel cell stack and / or transverse to the stacking direction (S) of the fuel cell stack.

[0025] The present invention can also advantageously achieve that the re-clamping element is completely sunk into the recess in the first configuration. Thus, the clamping element lies flat and flush against this surface. The re-clamping element also has a second configuration in which the re-clamping element projects out of the recess and projects beyond this surface. Thus, the clamping device only partly lies flat and flush against this surface and is stretched (extended or elongated) in the direction of the normal to this surface by the re-clamping element in the region of the recess. By the elongation of the clamping device, the compressive tensile force exerted by the clamping device increases as in the case of a spring. Preferably, the re-clamping element is not completely sunk into the recess when the clamping device clamps. Thus, by the sinking of the clamping body, it is also possible to reduce the compressive force, for example in the case of an increase in the stack height due to operation.

[0026] Preferably, the clamping element is an elastic clamping element known from the prior art, which is respectively fixed to the end plate of the fuel cell stack or substantially completely (in other words annularly) surrounds the fuel cell stack in at least one cross-section along the stacking direction. Here, the clamping element lies at least partly flat against the surface of the fuel cell stack. The re-clamping element preferably replaces parts of such a surface and / or is preferably arranged in a recess in such a surface.

[0027] Preferably, the clamping element is configured as a strip-shaped or bar-shaped flexible and / or elastic clamping element, such as is known from EP1870952A2. Preferably, the clamping element consists of an elastic plastic, an elastic polymer (such as nylon) or an elastic metal and has a modulus of elasticity of >1 GPa and particularly preferably >5 GPa along the clamping direction under standard conditions.

[0028] The clamping element is also preferably fixed to at least one stack end plate in a material-locking manner and / or by means of at least one clamping device. To ensure simple disassembly of the fuel cell stack, the clamping element is preferably detachably fixed to at least one end plate of the stack. Particularly preferably, the clamping element is hooked onto the end plate. For this purpose, the end plate preferably has at least one hook for hooking the clamping element onto one of its sides or onto its surface pointing outwards in the stacking direction. Equally preferably, the clamping element has at least one hanging hole for hanging on the hook.

[0029] Alternatively, the at least one clamping element extends at least substantially around the circumference of the fuel cell stack in at least one cross-section along the stacking direction. Here, the clamping element is fixed at at least one end region in its end region to the other end region of the same clamping element or to another clamping element. That is, the clamping element can be configured to be annularly closed.

[0030] Particularly preferably, the end region of the at least one clamping element is in form-fitting connection with the other end region of the same clamping element, for example by hemming for form-fitting connection. Equally preferably, the end region of the at least one clamping element is fixed to the other end region of the same clamping element or the other end region of another clamping element by means of a fastening device. Particularly preferably, the end region of the at least one clamping element is welded to the other end region of the same clamping element or the other end region of another clamping element.

[0031] Particularly preferably, the fuel cell stack has a plurality of clamping elements clamped between these end plates in the stacking direction. Here, a re-clamping element is arranged between one or more of the clamping elements, preferably all of the clamping elements, and a plurality of surface portions of the fuel cell stack.

[0032] The clamping body of the re-clamping element is preferably adapted in shape and material to the clamping element. When using strip-shaped or bar-shaped clamping elements, the clamping body preferably has a width adapted to the width of the clamping element. The clamping body also preferably has at least one rounded edge that comes into contact with the clamping device. In this way, the force exerted on the clamping device due to the displacement of the clamping body by means of the at least one adjusting device is advantageously evenly distributed over the clamping device.

[0033] In a preferred embodiment of the fuel cell stack, the at least one adjusting element is configured to be removable from the clamping body. In other words, the adjusting element is at least partially sunk into the clamping body in a first configuration and protrudes further from the clamping body in a second configuration than in the first configuration. Particularly preferably, the at least one adjusting element is a bolt that can be moved into and out of the clamping body by means of a micro-actuator. Equally preferably, the at least one adjusting element can be removed from the clamping body pneumatically or hydraulically. Particularly preferably, the at least one adjusting element is a threaded rod that can be moved into and out of the clamping body. Preferably, the threaded rod can be rotated magnetically. Alternatively, the adjusting element, in particular the threaded rod, is preferably removable, in particular rotatable, from the clamping body by means of a suitable tool.

[0034] Alternatively or additionally, the at least one adjusting element is configured to be expandable. For example, the adjusting element is configured as a scissor drive or has a scissor drive. Equally preferably, the adjusting element is hollow and can be expanded by filling it with a fluid. Equally preferably, the at least one adjusting element is configured to be remotely controllable. Thus, a variable adjustment of the fixed distance between the clamping body and the surface portion is achieved by means of remote control, for example by radio remote control.

[0035] In a likewise preferred embodiment, the at least one adjusting element has a thread which engages into a threaded bore of the surface part. In this embodiment, the distance between the clamping body and the surface part is variably adjustable by rotation of the threaded rod in the threaded bore. Also preferably, the at least one adjusting element is connected to the clamping body in this embodiment only in a force-fitting manner, particularly preferably the at least one adjusting element is arranged between the clamping body and the surface part in the case of a press fit. The rotation of the threaded rod is preferably effected by intervention using a suitable tool. For this purpose, the threaded bore is preferably arranged in a protruding part of the end plate in order to enable tool intervention. Alternatively, the rotation of the threaded rod is also effected here by means of remote control.

[0036] The surface part mentioned can be arranged at different locations of the fuel cell stack. If the at least one clamping element is fixed to a respective side of the first and second end plates by means of a clamping device, the surface part is preferably located between the clamping devices on the side of the first or second end plate. Then, the reclamping of the clamping element by means of the at least one reclamping element is preferably effected in a direction transverse to the stacking direction (S) of the fuel cell stack. If, however, the clamping elements are fixed to the surfaces of the first and second end plates pointing outwards in the stacking direction or are constructed in a ring-closed manner, the clamping elements extend beyond the edges and sides of the end plates to the opposite end plates. Then, the surface part is preferably located on the surface of the first or second end plate pointing outwards and / or on the side of the first or second end plate. If the surface part is located on the surface of the first and / or second end plate pointing outwards, the reclamping of the clamping element by means of the reclamping element is preferably effected in a direction parallel to the stacking direction (S).

[0037] In a particularly preferred embodiment, a cutout is arranged in the edge of the first or second end plate which is external in the stacking direction. In other words, the surface part mentioned extends from the edge of the end plate which is external in the stacking direction along the surface pointing outwards and along the side of the end plate. According to this embodiment, the distance in the normal direction of the first surface part between the clamping body and the first surface part can be variably adjusted and fixed by means of at least one first adjusting element, and the distance in the normal direction of the second surface part between the clamping body and the second surface part can be variably adjusted and fixed by means of at least one second adjusting element. Thus, the clamping body can advantageously be displaced in two directions, and thus the elongation of the clamping device can also preferably be controlled in a plurality of directions. Thus, the compressive tensile force which is substantially opposite to this elongation can also be readjusted in two different directions.

[0038] Thus, in this particularly preferred embodiment, the reclamping element has at least one first adjusting element and at least one second adjusting element. Also preferably, the reclamping element has a plurality of first and second adjusting elements.

[0039] Particularly preferably, the first surface portion is parallel to the surface plane facing outwards, and the second surface portion is parallel to the side plane of the first end plate or the second end plate. Thus, the clamping body can be displaced in a direction perpendicular to the surface of the end plate facing outwards and in a direction perpendicular to the side of the end plate. Thus, the portion of the clamping device extending along the end plate or the portion of the clamping device extending along the side of the fuel cell stack can be elongated in a targeted manner. Thus, the compressive tensile force acting on the fuel cell stack along or perpendicular to the end plate can be readjusted. Preferably, the first surface portion is perpendicular to the second surface portion. Thus, particularly preferably, reclamping of the clamping element in the stacking direction (S) and reclamping transverse to the stacking direction (S) are both possible.

[0040] Also preferably, the end plate having a void arranged in its outer edge in the stacking direction projects laterally, that is to say in a direction parallel to the surface of the end plate facing outwards, beyond the fuel cell stack. Also preferably, the first adjusting device is configured as a threaded rod that engages with a threaded hole (threaded bore) arranged in the protruding portion of the end plate. Thus, the distance of the clamping body perpendicular to the end plate can be adjusted by rotating the threaded rod, also with the aid of tool intervention. Preferably, the second adjusting device is configured to be removable from or expandable within the clamping body.

[0041] The subject matter of the present invention is also a vehicle, in particular an electrically driven vehicle, having a fuel cell stack according to the present invention, as described above. Here, the fuel cell stack is in particular used to supply power to the electric motor of the vehicle.

[0042] Other preferred embodiments of the present invention are obtained from the remaining description below. As long as no other explanation is made in individual cases, the different embodiments of the present invention mentioned in this application can be advantageously combined with each other. Description of the Drawings

[0043] Subsequently, the present invention will be illustrated in embodiments with reference to the accompanying drawings. Among them:

[0044] Figure 1 A schematic diagram of a fuel cell system according to the prior art is shown;

[0045] Figure 2 A fuel cell stack is shown, which has a plurality of clamping elements for compressing the stack and a reclamping element according to an embodiment;

[0046] Figure 3 Shows Figure 2 The fuel cell stack with the exposed reclamping element;

[0047] Figure 4 ShowsFigure 3 Detailed view of the exposed re-clamping element; and

[0048] Figure 5 shows Figure 3 Isolation diagram of the re-clamping element of Detailed implementation

[0049] Figure 1 Shows a fuel cell system generally designated by 100 according to the prior art. The fuel cell system 100 is part of a vehicle, in particular an electric vehicle, not further shown, which has a traction motor that is supplied with electrical energy by the fuel cell system 100.

[0050] The fuel cell system 100 includes a fuel cell stack 10 as a core component, which has a plurality of single cells 11 arranged in a stack shape. These single cells are constructed by alternately stacked membrane electrode assemblies (MEA) 14 and bipolar plates 15 (see detailed fragment). Thus, each single cell 11 includes an MEA 14, which has an ion-conducting polymer electrolyte membrane not further shown here and catalytic electrodes arranged on both sides of the polymer electrolyte membrane. These electrodes catalyze the corresponding sub-reactions of fuel conversion. The anode electrode and the cathode electrode are both constructed as coatings on the membrane and have a catalytic material, such as platinum, which is supported on a conductive carrier material (such as a carbon-based material) with a large specific surface area.

[0051] As shown in the detailed view of Figure 1 An anode region 12 is constructed between the bipolar plate 15 and the anode, and a cathode region 13 is constructed between the cathode and the next bipolar plate 15. The bipolar plate 15 is used to transport the working medium into the anode and cathode regions 12, 13 and also establish an electrical connection between the individual fuel cells 11. Optionally, a gas diffusion layer can be arranged between the membrane electrode assembly 14 and the bipolar plate 15.

[0052] In order to supply the fuel cell stack 10 with the working medium, the fuel cell system 100 has an anode supply device 20 on the one hand and a cathode supply device 30 on the other hand.

[0053] In Figure 1The anode supply device 20 of the fuel cell system 100 shown in the figure supplies the anode working medium (fuel), such as hydrogen, to the anode region 12 of the fuel cell stack 10 through the anode supply path 21. For this purpose, the anode supply path 21 connects the fuel reservoir 23 to the anode inlet of the fuel cell stack 10. The feed pressure of the anode working medium into the anode region 12 of the fuel cell stack 10 is adjusted by the metering valve 27.1. The anode supply device 20 also includes an anode exhaust gas path 22, which discharges the anode exhaust gas from the anode region 12 through the anode outlet of the fuel cell stack 10.

[0054] In addition, in Figure 1 the anode supply device 20 of the fuel cell system 100 shown in the figure has a recirculation pipeline 24, which connects the anode exhaust gas path 22 to the anode supply path 21. Recycling of the fuel is common in order to return the fuel used in excess of the stoichiometric amount to the fuel cell stack 10. Arranged in the recirculation pipeline 24 are: a recirculation conveying device 25, preferably a recirculation fan; and a check valve 27.2.

[0055] In the anode supply device 22 of this fuel cell system, a water separator 26 is also constructed to discharge the product water formed by the fuel cell reaction. The water outlet of this water separator can be connected to the cathode exhaust gas pipeline 32, a water tank or an exhaust device.

[0056] In Figure 1 the cathode supply device 30 of the fuel cell system 100 shown in the figure includes a cathode supply path 31, which supplies the oxygen-containing cathode working medium, especially air, to the cathode region 13 of the fuel cell stack 10, and the oxygen-containing cathode working medium is inhaled from the surrounding environment. The cathode supply device 30 also includes a cathode exhaust gas path 32, which discharges the cathode exhaust gas (especially the discharged air) from the cathode region 13 of the fuel cell stack 10 and, if necessary, conveys the cathode exhaust gas to an exhaust device (not shown).

[0057] To convey and compress the cathode working medium, a compressor 33 is arranged in the cathode supply path 31. In the illustrated embodiment, the compressor 33 is designed as a mainly motor-driven compressor 33, and the drive of this compressor is realized by a motor 34 equipped with a corresponding power electronic device 35.

[0058] In Figure 1The fuel cell system 100 shown also has a humidification module 39 arranged upstream of the compressor 33 in the cathode supply conduit 31. On the one hand, the humidification module 39 is arranged in the cathode supply path 31 such that the cathode working gas can flow through the humidification module. On the other hand, the humidification module is arranged in the cathode exhaust path 32 such that the cathode exhaust gas can flow through the humidification module. The humidifier 39 generally has a plurality of water vapor permeable membranes, which are configured flat or in the form of hollow fibers. Here, the relatively dry cathode working gas (air) flows out from one side of these membranes and the relatively humid cathode exhaust gas (exhaust gas) flows out from the other side. Driven by the higher partial pressure of the water vapor in the cathode exhaust gas, water vapor transfer through the membrane into the cathode working gas occurs, and the cathode working gas is humidified in this way.

[0059] The fuel cell system 100 also has a humidifier bypass 37 connecting the cathode supply conduits upstream and downstream of the humidifier 39 to each other, and the humidifier bypass has a check valve arranged therein as a bypass regulating device 38. In addition, check valves 27.3 and 27.4 are arranged upstream of the fuel cell stack 10 in the anode supply conduit 31 or downstream of the fuel cell stack 10 in the anode exhaust conduit 32.

[0060] Other different details of the anode and cathode supply devices 20, 30 are not shown in Figure 1 for reasons of clarity. For example, the anode exhaust conduit 22 can lead to the cathode exhaust conduit 32 such that the anode exhaust gas and the cathode exhaust gas are discharged through a common exhaust device.

[0061] Figure 2 Shown in Figure 1 is a detailed view of the fuel cell stack 10 shown in

[0062] In Figure 2 The fuel cell stack 10 shown is compressed by a total of five clamping elements 55. Here, each clamping element 55 completely surrounds the cross-section of the fuel cell stack 10, and the clamping element overlaps with the end plates 51, 52 and the side liners 56. Here, these clamping elements 55 at least abut against the end plates 51, 52, and each clamping element 55 is welded to itself in the region of the upper end plate 51.

[0063] As in Figure 2 、3 As shown in FIGS. 4, a re-clamping element 60 according to an embodiment of the present invention is arranged below one of these clamping elements 55. In Figure 5 an isolated view of the re-clamping element 60 is given. As in Figure 2 shown, the re-clamping element 60 is presented to the outside by a slight deformation of the clamping element 55. The re-clamping element 60 has a clamping body 61 and a total of 4 adjusting elements 62.

[0064] As especially in Figure 3 and 4 shown, each clamping element 55 is arranged in the respective recessed surface portion 70 of the first (upper) end plate 51. A corresponding recessed surface portion is also present on the second (lower) end plate 52 of the fuel cell stack 10. Thus, each clamping element 55 is fixed against lateral sliding.

[0065] As especially in Figure 3 and 4 shown, a void portion 71 is arranged in the region of the outer edge 72 of the first end plate 51. Here, the void portion 71 extends within the outer-facing surface 76 of the end plate 51 and within the side surface 75 of the end plate 51, and has a first surface portion 73 and a second surface portion 74.

[0066] The re-clamping element 60 is arranged in the void portion 71 and, as shown in Figure 4 lies flat on the first surface portion 73 of the void portion 71. The re-clamping element 60 has a clamping body 61 and two second adjusting elements 64 arranged between the clamping body 61 and the second surface portion 74. The clamping body 61 is adapted to the void portion 71 and has a smaller flat extension and height than the void portion 71.

[0067] The second adjusting element 64 is designed to be removable from the clamping body 61, and in particular can be removed from the clamping body 61 by means of remote control. As can be seen from Figure 4 in, the second adjusting element 64 does not completely sink into the clamping body 61 in the neutral configuration of the re-clamping element 61. In addition, the second adjusting element 64 can also be further moved into the clamping body 61 when needed. By moving the second adjusting element 64 in or out, the clamping body 61 can be displaced in a first direction parallel to the outer-facing surface 76 and perpendicular to the side surface 75.

[0068] If the second adjusting element 64 is removed from the clamping body 61, the clamping body moves outwards in the first direction, such that the clamping element 55 extending through the clamping body 61 is re-clamped in the first direction. Accordingly, the compressive tensile force in the first direction increases. If the second adjusting element 64 is further inserted into the clamping body 61, the clamping body is displaced against the first direction due to the stress of the clamping element 55, and the compressive tensile force of the clamping element 55 is thereby reduced.

[0069] As can also be seen from Figure 3 and 4 the end plate 51 laterally protrudes beyond the fuel cell stack 10. Accordingly, at least a part of the first surface portion 73 also laterally protrudes beyond the side lining 56 of the fuel cell stack 10. Two threaded holes are arranged in the protruding portion of the first surface portion 73, and the two threaded holes engage with the two first adjusting devices 63 of the re-clamping element 60.

[0070] The first adjusting devices 63 are each configured as threaded rods and can be accessed from the outside due to the protrusion of the first end plate 51. The first adjusting devices 63 are arranged between the first surface portion 73 and the clamping body 61 by means of a press fit and are not fixedly connected to the clamping body 61. The first adjusting devices 63 extend flatly on the side facing the clamping body 61 and abut against the first clamping body 61 with these pressing surfaces (not shown).

[0071] If the first adjusting devices 63 are rotated using a suitable tool, these first adjusting devices are displaced along or against the stacking direction S due to engagement with threaded holes (not shown) in the protruding portion of the first end plate 61. Thereby, either more pressure is applied to the clamping body 61 or less pressure is applied to the clamping body 61 by means of the pressing surfaces (not shown) abutting against the clamping body 61.

[0072] If the first adjusting devices 63 are rotated using a suitable tool such that these first adjusting devices are displaced upwards, for example, inserted into the threaded holes of the first end plate 51, the clamping body 61 is displaced in a second direction parallel to the side surface 75 and perpendicular to the surface 76 pointing outwards. Accordingly, the clamping element 55 extending through the clamping body 61 is re-clamped in the second direction and the compressive tensile force in the second direction increases.

[0073] If the first adjusting devices 63 are rotated using a suitable tool such that these first adjusting devices are displaced downwards, for example, removed from the threaded holes of the first end plate 51, the clamping body 61 is displaced against the second direction due to the stress of the clamping element 55 extending through the clamping body and the compressive tensile force is reduced.

[0074] Thus, the use of the re-clamping element 60 allows an increase or a decrease in the compressive tensile force of the clamping element 55 in the first and / or second direction. Thus, the re-clamping element 60 allows re-clamping of the aged elastic clamping element 55. The re-clamping element 60 also allows relaxation of the elastic clamping element 55 in response to an increase in the stack height.

Claims

1. A fuel cell stack (10), comprising: a first end plate (51) and a second end plate (52); a plurality of fuel cells (11) arranged between the end plates (51, 52); at least one elastic clamping element (55) clamped between the end plates (51, 52) along the stacking direction (S); at least one re-clamping element (60) arranged between the clamping element (55) and a surface portion (70) of the fuel cell stack (10), the re-clamping element having a clamping body (61) and at least one adjusting element (62) arranged between the clamping body (61) and the surface portion (70), characterized in that the distance between the clamping body (61) and the surface portion (70) can be variably adjusted and fixed by means of the at least one adjusting element (62), wherein the at least one adjusting element (62) is configured to be movable into and out of the clamping body (61), wherein the adjusting element (62) is at least partially sunk into the clamping body (61) in a first configuration and projects further from the clamping body (61) in a second configuration than in the first configuration, and at least one clamping element (55) at least partially lies flat against the surface of the fuel cell stack (10), and at least one re-clamping element (60) is arranged in a clearance portion (71) of the surface.

2. The fuel cell stack (10) according to claim 1, wherein the clamping body (61) of the at least one re-clamping element (60) is configured to be sinkable into the clearance portion (71).

3. The fuel cell stack (10) according to claim 1 or 2, wherein the at least one adjusting element (62) is configured to be removable from the clamping body (61).

4. The fuel cell stack (10) according to claim 1 or 2, wherein the at least one adjusting element (62) is configured to be expandable.

5. The fuel cell stack (10) according to claim 1 or 2, wherein the at least one adjusting element (62) has a thread that engages a threaded hole in the surface portion (70).

6. The fuel cell stack (10) according to claim 1 or 2, wherein the clearance portion (71) is arranged in an outer edge (72) of the first end plate (51) or the second end plate (52) along the stacking direction (S), wherein, the adjusting element (62) comprises at least one first adjusting element (63) and at least one second adjusting element (64), wherein the distance between the clamping body (61) and a first surface portion (73) of the clearance portion (71) of the end plates (51, 52) can be variably adjusted and fixed by means of at least one first adjusting element (63), and the distance between the clamping body (61) and a second surface portion (74) of the clearance portion (71) of the end plates (51, 52) can be variably adjusted and fixed by means of at least one second adjusting element (64).

7. The fuel cell stack (10) according to claim 6, wherein the first surface portion (73) is oriented perpendicular to the second surface portion (74).

8. The fuel cell stack (10) according to claim 6, wherein the first surface portion (73) is parallel to the outward-facing surface (76) of the end plates (51, 52), and the second surface portion (74) is parallel to the side surface (75) of the end plates (51, 52).

9. A vehicle having a fuel cell stack (10) according to any one of claims 1 to 8.

Images