阅读说明：本技术 具有夹紧装置的燃料电池堆 (Fuel cell stack with clamping device ) 是由 A.吉拉尼 S.桑卡武萨尼克里什纳 于 2019-01-18 设计创作，主要内容包括：本发明涉及一种燃料电池堆(10),其具有第一端板(51)和第二端板(52)以及多个布置在端板(51、52)之间的燃料电池(11)。至少一个弹性夹紧元件(55)沿堆叠方向(S)在端板(51、52)之间夹紧。此外,再夹紧元件(60)布置在夹紧元件(55)与燃料电池堆(10)的表面部分(70)之间。再夹紧元件(60)具有夹紧体(61)和至少一个布置在夹紧体(61)与表面部分(70)之间的调整元件(62)。在夹紧体(61)与表面部分(70)之间的距离能借助于该至少一个调整元件(62)来可变地被调整和固定。(The 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).)

1. A fuel cell stack (10) having:

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) in a 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),

it is characterized in that the preparation method is characterized in that,

the distance between the clamping body (61) and the surface portion (70) can be variably adjusted and fixed by means of at least one adjusting element (62).

2. The fuel cell stack (10) according to claim 1, wherein at least one clamping element (55) rests at least partially flat against a surface of the fuel cell stack (10), and at least one re-clamping element (60) is arranged in a recess (71) of the surface.

3. 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 in such a way that it can be sunk into the recess (71).

4. The fuel cell stack (10) according to any one of the preceding claims, wherein the at least one adjusting element (62) is configured in such a way that it can be removed from the clamping body (61).

5. The fuel cell stack (10) according to any of the preceding claims, wherein the at least one adjustment element (62) is configured in an expandable manner.

6. The fuel cell stack (10) of any of the preceding claims, wherein the at least one adjustment element (62) has a thread that engages into a threaded hole of the surface portion (70).

7. The fuel cell stack (10) according to any one of claims 2 to 6,

wherein the recess (71) is arranged in an edge (72) of the first end plate (51) or the second end plate (52) which is external in the stacking direction (S),

wherein the distance between the clamping body (61) and a first surface portion (73) of the end plate (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/or a second surface portion (74) of the end plate (51, 52) can be variably adjusted and fixed by means of at least one second adjusting element (64).

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

9. The fuel cell stack (10) according to claim 7 or 8, wherein the first surface portion (73) is plane-parallel to an outwardly directed surface (76) of the end plate (51, 52) and the second surface portion (74) is plane-parallel to a side surface (75) of the end plate (51, 52).

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

Technical Field

The invention relates to a fuel cell stack which enables a reclamping, in particular a reclamping by adapting a compressive tensile force acting on the fuel cell stack due to at least one clamping element. The invention also relates to a vehicle having such a fuel cell stack.

Background

Fuel cells utilize the chemical conversion of fuel and oxygen into water to produce electrical energy. For this purpose, the fuel cell has a Membrane Electrode Assembly (MEA) having a membrane electrode unit.

The membrane electrode unit is formed by a proton-conducting membrane, i.e. a PEM, on both sides of which catalytic electrodes are arranged. Here, the membrane separates the anode region assigned to the anode and the cathode region assigned to the cathode from one another and electrically insulates them. Furthermore, a gas diffusion layer may be arranged on the side of the electrode not facing the membrane.

During operation of the fuel cell, a hydrogen-containing fuel is supplied to the anode, where it is released from H with electrons₂Electrochemical oxidation to H⁺. Passing hydrogen ions H through the electrolytic membrane⁺Transported from the anode region to the cathode region either in a water-laden or water-free manner. The electrons provided on the anode are directed to the cathode through the wire.

The oxygen-containing working medium is fed to the cathode, where it is separated from O by the absorption of electrons₂By oxidation to O₂ ^-. These oxygen ions react in the cathode region with the formation of water with the hydrogen ions transported through the membrane.

A fuel cell stack is generally formed by a large number of MEAs arranged in a stack (stack) in a stacked direction with their electric powers added up. Between these membrane electrode assemblies, bipolar plates are usually arranged, which ensure the supply of the reactants and coolant to the individual MEAs and serve as electrically conductive contacts with these membrane electrode assemblies.

Seals are arranged between the mea and the bipolar plates in order to seal the anode and cathode regions from the outside and to prevent working medium from escaping from the stack. These seals are provided on the membrane electrode unit, the bipolar plate, or both.

In order to seal the stack permanently and to ensure electrical contact between the bipolar plates and the mea, the fuel cell stack is compressed prior to commissioning. Tensioning elements are also used in order to also compress the fuel cell stack during operation.

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

It is also known to use clamping, strip-or band-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). With regard to the design and fastening paths of such elastic clamping elements (tensioning elements), reference is made, for example, to EP 1870952 a2, whereby reference is made in full to the contents of EP 1870952 a 2.

In particular, operational height variations, which may vary, for example, with the temperature and humidity of the fuel cell stack, may occur in the active area of the fuel cell stack or MEA. This is also known as stack breathing. In the case of elastic clamping elements, the elasticity of these clamping elements may also decrease over time. In particular in the case of metallic clamping elements which surround the fuel cell stack in a ring shape and thus have a plurality of 90 ° bends, an elongation of the clamping element occurs in particular in the region of these bends.

Irrespective of the height variations of the fuel cell stack and the aging of the clamping elements, a sufficient compression of the stack must always be ensured, in particular in order to ensure the sealing effect of the seals used. Therefore, devices which are intended to be used in an attempt to permanently ensure the compression of the fuel cell stack are already known from the prior art.

DE 102006028498 a1 discloses a clamping device for a fuel cell stack, which has at least one tensioning element for tensioning the fuel cell stack and at least one length compensation element which is integrated into the tensioning element or connects two tensioning elements to one another.

DE 102004027694 a1 discloses a fuel cell stack having a plurality of fuel cells arranged between end plates. A clamping system, in particular a disk spring, is arranged between the end plate and the tensioning device. In the unclamped state, the disk spring has a bulge which opens in the direction of the clamping device, while in the clamped state the disk spring rests approximately flat against the end plate.

According to the aforementioned publication, stress peaks due to the stretching of the stack should be avoided by means of the elastic element. It should also be possible to avoid to some extent height variations of the stack by initially tensioning the elastic element too tightly. However, the elastic element itself is subject to ageing and at least the possible adjustment of the compression force is therefore imprecise and passive.

DE 102010007981 a1 discloses a fuel cell stack having fuel cells arranged between two end plates and at least one tensioning device connecting the end plates for applying a tensile force. A fastening element, which is designed as an eccentric element or comprises an eccentric element, is arranged between the tensioning device and at least one of the end plates. The distance between the end plates and thus the tension between the end plates should be adapted by rotating the fastening element.

The aforementioned publications disclose a compression system of complex construction that requires specially adapted end plates and/or tensioning devices. Furthermore, the compression system is not suitable for use with wrap-around clamping elements.

Disclosure of Invention

The invention is based on the following tasks: the disadvantages of the prior art are overcome and a solution for reclamping a fuel cell stack is provided, which can be integrated without major adaptation into existing fuel cell stacks, in particular into such fuel cell stacks having circumferential band-shaped or strip-shaped clamping elements.

This object is achieved by a fuel cell stack having a first end plate and a second end plate and a plurality of fuel cells arranged between the two end plates in a stacking direction. The fuel cell stack also has at least one elastic clamping element clamped between the end plates in the stacking direction. At least one re-clamping element is arranged between a clamping element, preferably a clamped clamping element (clamping element in the clamped state), and a surface portion of the fuel cell stack, preferably a surface portion of one of the end plates. The re-clamping element has a clamping body and at least one adjusting element arranged between the clamping body and the surface portion. Preferably, the clamping body and the adjusting element are connected to one another, wherein the connection can be realized purely force-fitting.

According to the invention, the distance between the clamping body and the surface section, preferably in the direction of the normal to the surface section, can be variably adjusted by means of at least one adjusting element. In other words, the at least one adjusting element is designed to variably adjust the distance between the clamping body and the surface portion. It is particularly preferred that the distance between a point of the re-clamping element, preferably the point which is furthest away from the surface portion in the normal direction, and the surface portion is variably adjustable by means of the at least one adjusting device.

Furthermore, the clamping body can be fixed (positioned) according to the invention at a selected distance from the surface portion, preferably at a selected distance from the surface portion in the direction of the normal of the surface portion, by means of the at least one adjusting element. In other words, the at least one adjusting device is also designed to fix (position) the clamping body at a variable distance from the surface portion. Preferably, by fixing or positioning the adjusting element, further unwanted displacement of the clamping body due to the force exerted by the adjusting element or the clamping element is avoided.

The fuel cell stack according to the invention is thus able to achieve a reclamping of the at least one clamping element by increasing the fixed distance between the clamping body of the reclamping element and the surface portion of the fuel cell stack by means of the at least one adjusting element. This causes an 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 resilient clamping elements of the fuel cell stack clamp in the hooke range. It is also preferred that the re-clamping element according to the invention enables a re-clamping of the clamping element in the stacking direction (S) of the fuel cell stack and/or transversely to the stacking direction (S) of the fuel cell stack.

Preferably, the clamping elements are elastic clamping elements known from the prior art which are respectively fixed to the end plates of the fuel cell stack or which substantially completely (in other words annularly) surround the fuel cell stack in the stacking direction in at least one cross section. The clamping element rests at least partially flat against a surface of the fuel cell stack. The re-clamping element preferably replaces part of such a surface and/or is preferably arranged in a recess of such a surface.

Preferably, the clamping element is configured as a band-shaped or strip-shaped flexible and/or elastic clamping element, such as is known from EP 1870952 a 2. Preferably, the clamping element consists of an elastic plastic, an elastic polymer (e.g. nylon) or an elastic metal and has an elastic modulus of >1GPa and particularly preferably >5GPa in the clamping direction under standard conditions.

The clamping element is preferably also fastened to at least one stack end plate in a material-fit manner and/or by means of at least one clamping device. In order to ensure simple disassembly of the fuel cell stack, the clamping element is preferably releasably fixed to at least one end plate of the stack. Particularly preferably, the clamping element is suspended from the end plate. For this purpose, the end plate preferably has at least one hook for hooking the clamping element on one of its sides or on its surface pointing outwards in the stacking direction. It is also preferred that the clamping element has at least one hanging hole for hanging on a hook.

Alternatively, the at least one clamping element extends at least substantially around the circumference of the fuel cell stack in the stacking direction in a cross section. In this case, the clamping element is fastened at least one of its end regions to the other end region of the same clamping element or to another clamping element. I.e. the clamping element can be designed to be closed in a ring shape.

In particular, it is preferred that the end region of the at least one clamping element is positively connected to the other end region of the same clamping element, for example by a crimp connection. It is also preferred that the end region of the at least one clamping element is fixed to the other end region of the same clamping element or to the other end region of the other clamping element by means of a fastening device. In particular, it is preferred that the end region of the at least one clamping element is welded to the other end region of the same clamping element or to the other end region of the other clamping element.

Particularly preferably, the fuel cell stack has a plurality of clamping elements which clamp between the end plates in the stacking direction. Here, the re-clamping elements are arranged between one or more, preferably all, of the clamping elements and a plurality of surface portions of the fuel cell stack.

The clamping body of the re-clamping element is preferably adapted to the shape and material of the clamping element. When band-shaped or strip-shaped clamping elements are used, the clamping body preferably has a width adapted to the width of the clamping element. The clamping body preferably also has at least one rounded edge, which comes into contact with the clamping device. In this way, the force exerted on the clamping means as a result of the displacement of the clamping body by means of the at least one adjusting device is advantageously distributed evenly over the clamping means.

In a preferred embodiment, at least one clamping element rests at least partially flat against a surface of the fuel cell stack. Particularly preferably, the surface has the mentioned surface portion, the re-clamping element being arranged between the surface portion and the clamping means. And also preferably to a surface or surface portion of the first or second end plate. According to this preferred embodiment, the re-clamping element is arranged in a recess of the surface. In this case, the clamping body is particularly preferably adapted to the dimensions of the recess. In particular, the re-clamping element, in particular the clamping body, is preferably designed such that it can be lowered into the recess. If the re-clamping element is arranged in a recess of the surface, the mentioned surface part is preferably located in the recess.

The foregoing embodiments can advantageously achieve: the re-clamping element is fully sunk into the recess in the first configuration. The clamping element thus rests flat and flat against this surface. The re-clamping element also has a second configuration in which it protrudes from the recess and beyond the surface. The clamping device thus rests only partially flat and flat against the surface and is stretched (stretched or stretched) in the direction of the normal to the 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.

It is also preferred that the re-clamping element does not sink completely into the recess when the clamping device is clamping. Thus, by lowering 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.

In a preferred embodiment of the fuel cell stack, the at least one adjusting element is designed such that it can be removed from the clamping body. In other words, the adjusting element is at least partially immersed in the clamping body in the first configuration and protrudes further out of the clamping body in the second configuration than in the first configuration. Particularly preferably, the at least one adjusting element is a screw which can be moved into and out of the clamping body by means of a microactuator. It is also preferred that the at least one adjusting element can be pneumatically or hydraulically removed from the clamping body. Particularly preferably, the at least one adjusting element is a threaded rod which can be moved into and out of the clamping body. Preferably, the threaded rod is rotatable in a magnetic manner. Alternatively, the adjusting element, in particular the threaded rod, can preferably be removed, in particular rotated out, from the clamping body by means of a suitable tool.

Alternatively or additionally, the at least one adjusting element is configured in an expandable manner. For example, the adjusting element is designed as a scissors drive or has a scissors drive. It is also preferred that the actuating element is hollow and can be expanded by means of a filling fluid. It is also preferred that the at least one adjusting element is configured in a manner that can be remotely controlled. Thus, a variable adjustment of the fixed distance between the clamping body and the surface portion is achieved by means of a remote control, for example by means of a radio remote control.

In an equally preferred embodiment, the at least one adjusting element has a thread which engages in a threaded hole in the surface section. In this embodiment, the distance between the clamping body and the surface portion is variably adjustable by means of a rotation of the threaded rod in the threaded bore. It is also preferred that the at least one adjusting element is connected in this embodiment only in a force-fitting manner to the clamping body, particularly preferably that the at least one adjusting element is arranged between the clamping body and the surface portion with a force fit. Rotation of the threaded rod is preferably achieved by intervention with a suitable tool. For this purpose, threaded holes are preferably arranged in the protruding part of the end plate in order to enable tool interventions. Alternatively, the rotation of the threaded rod is also effected here by means of a remote control.

The mentioned surface portions may be arranged at different locations of the fuel cell stack. If the at least one clamping element is fixed on one side of the first and second end plate, respectively, by means of the clamping means, the surface portion is preferably located between the clamping means on the side of the first or second end plate. Subsequently, the re-clamping of the clamping element by means of the at least one re-clamping element preferably takes place in a direction transverse to the stacking direction (S) of the fuel cell stack. If the clamping element is fixed to the surface of the first and second end plate, respectively, which is directed outward in the stacking direction, or is designed to be closed in a ring shape, the clamping element extends beyond the edge and the side of the end plate to the opposite end plate. The surface portion is then preferably on the outwardly directed surface of the first or second end plate and/or on the side of the first or second end plate. If the surface portion is on an outwardly directed surface of the first and/or second end plate, the re-clamping of the clamping element by means of the re-clamping element preferably takes place in a direction parallel to the stacking direction (S).

In a particularly preferred embodiment, the recess is arranged in an edge of the first or second end plate which is external in the stacking direction. In other words, the mentioned surface portions extend along the outwardly directed surface and along the side of the end plate from the edge of the end plate which is at the outside in the stacking direction. According to this embodiment, the distance between the clamping body and the first surface section in the direction of the normal of the first surface section can be variably adjusted and fixed by means of at least one first adjusting element, while the distance between the clamping body and the second surface section in the direction of the normal of the second surface section can be variably adjusted and fixed by means of at least one second adjusting element. The clamping body can thus advantageously be displaced in two directions, and thus also the elongation of the clamping device, preferably in multiple directions, can be controlled. Thus, the compressive tensile force, which is substantially opposite to the elongation, can also be readjusted in two different directions.

In this particularly preferred embodiment, the re-clamping element therefore has at least one first adjusting element and at least one second adjusting element. It is also preferred that the re-clamping element has a plurality of first and second adjustment elements.

Particularly preferably, the first surface portion is parallel to the outwardly directed surface plane and the second surface portion is parallel to the side plane of the first or second end plate. The clamping body can thus be displaced in a direction perpendicular to the outwardly directed surface of the end plate 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 face of the fuel cell stack can be elongated in a targeted manner. Thus, the compressive tension applied to the fuel cell stack along or perpendicular to the end plates can be readjusted. Preferably, the first surface portion is perpendicular to the second surface portion. It is therefore particularly preferred that a re-clamping of the clamping element in the stacking direction (S) as well as a re-clamping transverse to the stacking direction (S) is possible.

It is also preferred that the end plate, in the outer edge of which the recess is arranged in the stacking direction, projects beyond the fuel cell stack in the lateral direction, that is to say in a direction parallel to the outwardly directed surface of the end plate. It is also preferred that the first adjustment means is configured as a threaded rod which engages with a threaded hole arranged in the protruding portion of the end plate. The distance of the clamping body perpendicular to the end plate can thus be adjusted by rotating the threaded rod, also by means of a tool intervention. Preferably, the second adjusting device is configured in such a way that it can be removed from the clamping body or expanded.

The subject matter of the invention is also a vehicle, in particular an electric motor-driven vehicle, having a fuel cell stack according to the invention, as described above. The fuel cell stack is used in particular for feeding an electric motor of the vehicle.

Further preferred embodiments of the invention result from the further features mentioned in the dependent claims. The different embodiments of the invention mentioned in the present application can advantageously be combined with one another as long as they are not explained otherwise in individual cases.

Drawings

The invention is subsequently explained in embodiments in accordance with the attached figures. Wherein:

fig. 1 shows a schematic diagram of a fuel cell system according to the prior art;

FIG. 2 illustrates a fuel cell stack having a plurality of clamping elements to compress the stack and a re-clamping element in accordance with an embodiment;

FIG. 3 shows the fuel cell stack of FIG. 2 with the re-clamping elements exposed;

FIG. 4 shows a detailed view of the bare re-clamping element of FIG. 3; and

fig. 5 shows an isolated view of the re-clamping element of fig. 3.

Detailed Description

Fig. 1 shows a fuel cell system, indicated as a whole with 100, according to the prior art. The fuel cell system 100 is part of a vehicle, in particular an electric vehicle, not shown in detail, which has a traction motor, which is supplied with electrical energy by the fuel cell system 100.

The fuel cell system 100 includes, as a core component, a fuel cell stack 10 having a plurality of unit cells 11 arranged in a stack shape, which are constructed by alternately stacking Membrane Electrode Assemblies (MEAs) 14 and bipolar plates 15 (see detailed sections). Each cell 11 therefore comprises an MEA 14, in each case, which has an ion-conducting polymer electrolyte membrane, not shown in detail here, and catalytic electrodes arranged on both sides of the polymer electrolyte membrane. These electrodes catalyze the corresponding sub-reactions of fuel conversion. Both the anode electrode and the cathode electrode are constructed as a coating on the membrane and have a catalytic material, such as platinum, which is supportingly present on a large, specific surface of an electrically conductive support material, such as a carbon-based material.

As shown in the detail of fig. 1, an anode region 12 is formed between a bipolar plate 15 and the anode and a cathode region 13 is formed between the cathode and the next bipolar plate 15. The bipolar plates 15 serve to feed the working medium into the anode and cathode regions 12, 13 and also to establish an electrical connection between the individual fuel cells 11. Alternatively, a gas diffusion layer may be disposed between the membrane electrode assembly 14 and the bipolar plate 15.

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

The anode supply arrangement 20 of the fuel cell system 100 shown in fig. 1 comprises an anode supply path 21 for supplying an anode working medium (fuel), for example hydrogen, into the anode region 12 of the fuel cell stack 10. For this purpose, the anode supply path 21 connects the fuel tank 23 with 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 regulated by a metering valve 27.1. The anode supply 20 also includes an anode exhaust gas path 22 that discharges anode exhaust gas from the anode region 12 through an anode outlet of the fuel cell stack 10.

Furthermore, the anode supply device 20 of the fuel cell system 100 shown in fig. 1 has a recirculation duct 24 which connects the anode off-gas path 22 with the anode supply path 21. Recirculation of fuel is common to return over-stoichiometrically used fuel to the fuel cell stack 10. In the recirculation conduit 24 are arranged: a recirculation conveyor 25, preferably a recirculation fan; and a check valve 27.2.

In the anode supply device 22 of the fuel cell system, a water separator 26 is also built in order to discharge the product water formed by the fuel cell reaction. The water outlet of the water separator may be connected to the cathode exhaust gas line 32, a water tank or an exhaust.

The cathode supply 30 of the fuel cell system 100 shown in fig. 1 comprises a cathode supply path 31 which supplies an oxygen-containing cathode working medium, in particular air, which is drawn in from the surroundings, to the cathode region 13 of the fuel cell stack 10. The cathode supply 30 also comprises a cathode exhaust gas line 32 which discharges cathode exhaust gas (in particular exhaust air) from the cathode region 13 of the fuel cell stack 10 and optionally feeds it to a not shown exhaust.

For conveying and compressing the cathode working medium, a compressor 33 is arranged in the cathode supply path 31. In the exemplary embodiment shown, the compressor 33 is designed as a predominantly motor-driven compressor 33, the drive of which is effected by means of an electric motor 34 equipped with corresponding power electronics 35.

The fuel cell system 100 shown in fig. 1 also has a wetting module 39 arranged upstream of the compressor 33 in the cathode supply line 31. On the one hand, a wetting module 39 is arranged in the cathode supply path 31, so that the cathode working gas can flow through the wetting module. On the other hand, the wetting module is arranged in the cathode off-gas path 32 so that the cathode off-gas can flow through the wetting module. The moisteners 39 generally have a plurality of water-vapor-permeable membranes, which are constructed flat or in the form of hollow fibers. Here, relatively dry cathode working gas (air) flows out from one side of the membranes and relatively humid cathode exhaust gas (exhaust gas) flows out from the other side. Driven by the higher partial pressure on the water vapour in the cathode off-gas, a transfer of water vapour through the membrane into the cathode working gas takes place, which is humidified in this way.

The fuel cell system 100 also has a dampener bypass 37 connecting the cathode supply conduits upstream and downstream of the dampener 39 to each other, which has a check valve arranged therein as a bypass adjustment device 38. Furthermore, check valves 27.3 and 27.4 are arranged in the anode supply line 31 upstream of the fuel cell stack 10 or in the anode exhaust line 32 downstream of the fuel cell stack 10.

Further different details of the anode and cathode supply means 20, 30 are not shown in fig. 1 for reasons of clarity. For example, the anode exhaust gas conduit 22 may lead to the cathode exhaust gas conduit 32 such that the anode exhaust gas and the cathode exhaust gas are exhausted through a common exhaust.

Fig. 2 shows a detailed view of the fuel cell stack 10 shown in fig. 1. The fuel cell stack 10 has a plurality of fuel cells stacked flat on one another in the stacking direction S. In the stacking direction, the fuel cell stack 10 is bounded by a first end plate 51 and an opposing second end plate 52. In a first direction transverse to the stacking direction S, the fuel cell 10 is bordered by side lining plates 53, 54. In a second direction transverse to the first direction and transverse to the stacking direction S, the fuel cell 10 is bordered by side liner plates 56.

The fuel cell stack 10 shown in fig. 2 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, wherein it overlaps the end plates 51, 52 and the lateral lining plates 56. In this case, the clamping elements 55 bear at least against the end plates 51, 52, and each clamping element 55 is welded to itself in the region of the upper end plate 51.

As shown in fig. 2, 3 and 4, a further clamping element 60 according to an embodiment of the invention is arranged below one of the clamping elements 55. An isolated view of the re-clamping element 60 is given in fig. 5. As shown in fig. 2, the outside of the re-clamping element 60 is represented 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.

As shown in particular in fig. 3 and 4, each clamping element 55 is arranged in an associated concave surface portion 70 of the first (upper) end plate 51. A corresponding recessed surface portion is also located on the second (lower) end plate 52 of the fuel cell stack 10. Thus, each gripping element 55 is fixed against lateral sliding.

As is shown in particular in fig. 3 and 4, a recess 71 is arranged in the region of the outer edge 72 of the first end plate 51. The recess 71 extends in an outwardly directed surface 76 of the end plate 51 and in a side 75 of the end plate 51 and has a first surface portion 73 and a second surface portion 74.

The re-clamping element 60 is arranged in the recess 71 and, as shown in fig. 4, lies flat on the first surface portion 73 of the recess 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 recess 71 and has a smaller flat extent and height than the recess 71.

The second adjusting element 64 is designed in such a way that it can be removed from the clamping body 61, and in particular can be removed from the clamping body 61 by means of a remote control. As can be seen from fig. 4, the second adjusting element 64 is not completely immersed in the clamping body 61 in the neutral configuration of the re-clamping element 61. In addition, the second adjusting element 64 can also be moved further into the clamping body 61, if necessary. By moving the second adjusting element 64 in or out, the clamping body 61 can be displaced in a first direction parallel to the outwardly directed surface 76 and perpendicular to the side surface 75.

If the second adjusting element 64 is removed from the clamping body 61, the clamping body is moved outward in the first direction, so that the clamping element 55 extending over the clamping body 61 is re-clamped in the first direction. Therefore, the compressive tension in the first direction increases. If the second adjusting element 64 is moved further into the clamping body 61, the latter is displaced counter to the first direction by the stress of the clamping element 55, and the compressive tension of the clamping element 55 is thereby reduced.

As can also be seen from fig. 3 and 4, the end plate 51 projects laterally beyond the fuel cell stack 10. Thus, at least a portion of the first surface portion 73 also projects laterally beyond the side liner plate 56 of the fuel cell stack 10. In this protruding portion of the first surface portion 73 two threaded holes are arranged, which engage with two first adjustment means 63 of the re-clamping element 60.

The first adjusting devices 63 are each designed as a threaded rod and are accessible from the outside due to the projection of the first end plate 51. The first adjusting device 63 is arranged between the first surface portion 73 and the clamping body 61 by means of a press fit and is not fixedly connected with the clamping body 61. The first adjusting device 63 extends flat on the side facing the clamping body 61 and bears with the press surfaces (not shown) against the first clamping body 61.

If the first adjustment means 63 are rotated with a suitable tool, these first adjustment means are displaced in or against the stacking direction S due to engagement with threaded holes (not shown) in the protruding portion of the first end plate 61. As a result, either more pressure or less pressure is exerted on the clamping body 61 by means of a pressure surface (not shown) which bears against the clamping body 61.

If the first adjustment means 63 are rotated with a suitable tool such that they are displaced upwards, for example into threaded holes of the first end plate 51, the clamping body 61 is displaced in a second direction parallel to the side face 75 and perpendicular to the outwardly directed surface 76. Thus, the clamping element 55 extending through the clamping body 61 is re-clamped in the second direction and the compressive tension in the second direction increases.

If the first adjustment means 63 are rotated with a suitable tool such that they are displaced downwards, for example out of threaded holes in 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 it and the compressive tension is reduced.

Thus, the compressive tension of clamping element 55 in the first and/or second directions may be increased or decreased using re-clamping element 60. The re-clamping element 60 thus allows re-clamping of the aged resilient clamping element 55. The re-clamping element 60 also allows for the relaxation of the resilient clamping element 55 in response to the stack height being raised.