DE102021109989A1 - FUEL CELL DEVICE AND FUEL CELL ARRANGEMENT - Google Patents

Abstract

The invention relates to a fuel cell device (28) with a large number of fuel cells (10) stacked on top of one another in a stacking direction (30), each of which is delimited by an upper bipolar plate (12) and a lower bipolar plate (12), with at least one of the bipolar plates (12) of the respective fuel cell (10) connects an electrically conductive connecting lug (32), which is bent relative to the bipolar plate (12), it being possible to measure a voltage of the respective fuel cell (10) via the connecting lug (32).

Description

The invention relates to a fuel cell device, in particular for a motor vehicle, and a fuel cell arrangement.

In order to monitor the individual fuel cells of a fuel cell stack, usually made up of several galvanic fuel cells connected in series, with regard to their optimum functionality, their operating state and their aging condition, it is necessary to precisely monitor the electrical voltage of each individual fuel cell in the fuel cell stack. These voltages can be tapped off and measured on the electrically conductive bipolar plates of the fuel cell stack.

In 1 The drawings show an assembly of a fuel cell 10, which may be part of a fuel cell stack. The fuel cell 10 is delimited by two bipolar plates 12 . In this case, the fuel cell 10 is delimited by an upper bipolar plate 12 and a lower bipolar plate 12 . These electrically conductive bipolar plates 12 are sealed against a plastic layer 16, often referred to as a sub-gasket, with the aid of at least one, in the present case four, seals 14. In the present case, this plastic layer 16 is a masked laminating film. In the case of a metal design, the bipolar plates 12 are often very thin compared to the layers enclosed by them and generally consist of two metal sheets welded to one another, between which a cooling medium is guided within meandering channels. As an alternative to meandering, the channels can have other geometries, such as a star-shaped geometry. Alternatively, the metal sheets can be connected to one another by pressing or gluing. There are also meandering channels on both outer sides of the bipolar plates 12, which carry hydrogen and therefore H ₂ on one side of the bipolar plate and oxygen and therefore O ₂ on the other side of the bipolar plate, often in the form of oxygen-containing air. The sub-gasket laminates a layer, often referred to as a catalyst coated membrane (CCM), consisting of an anode-side catalyst layer 18, a membrane 20 on which the actual chemical reaction takes place, and a cathode-side catalyst layer 22. The anode-side catalyst layer 18 is around that side of the Catalyst Coated Membrane where hydrogen is supplied. The cathode-side catalyst layer 22 is the side of the catalyst coated membrane to which oxygen is supplied in the form of air. In order to achieve a good chemical reaction at the CCM, hydrogen and oxygen must be fed to the CCM as homogeneously as possible. A hydrogen gas diffusion layer 24 and an oxygen gas diffusion layer 26 can be provided for this purpose. A first distribution of the media thus takes place via the meandering channels on the respective bipolar plates 12 and further homogenization of the media distribution is ensured by the gas diffusion layers 24, 26.

A total electrical voltage of a fuel cell stack results from the sum of the individual cell voltages of the fuel cells 10 of the fuel cell stack. The respective cell voltages allow conclusions to be drawn about the state of the respective fuel cell 10 and are therefore a fundamentally important component for ensuring safe operation of a fuel cell system.

From the WO 99/66339 A1 a device for voltage measurement on more than two similar voltage source units, in particular fuel cells, with contacting means for voltage tapping and an evaluation unit connected to the contacting means is known, with at least several contacting means being structurally combined in one contacting unit. The contacting means of the contacting unit of voltage source units to be contacted have detachable electrical spring contacts. The contacting unit is designed as a flat plate on which spring contacts are arranged approximately parallel to one another and protruding essentially perpendicularly from the longitudinal axis of the plate, with the spring contacts each being electrically conductively connected at one end to the associated electrical contact surface and at their free end are movable at least in the direction of the longitudinal axis. The contacting unit is electrically connected, at least indirectly, to the evaluation unit or to an intermediate unit connected between the contacting unit and the evaluation unit by means of a ribbon cable.

Furthermore, from the U.S. 9,620,800 B2 a fuel cell stack and cell voltage monitor transducer assembly is known. This assembly includes a gasket disposed against a fuel cell plate in the fuel cell stack, the gasket having a tab extending therefrom and having first and second openings that receive first and second nonconductive pins thereon. Furthermore, the assembly comprises a contact wire with a first end and a second end, a loop arranged between the ends and a contact area arranged between the loop and the second end. The loop attaches to the first pin, attaching the first end to the fuel cell plate is arranged, whereby an electrical contact is maintained. The second end is disposed on the second pin whereby the second end faces away from the fuel cell plate and is part of the contact area of a contact surface between the second end and the second pin, the contact wire being a resilient member.

Since the bipolar plates 12 of a fuel cell stack with metallic bipolar plates 12 are very close together, a very high level of mechanical complexity and high precision are required both when manufacturing a voltage tapping system and when installing it on the fuel cell stack in order to tap cell voltages in the prior art. In addition, there can be a great deal of effort involved in wiring the respective cell voltage taps. When wiring, for each bipolar plate 12 a cable must be routed from cell voltage tapping points to evaluation electronics. The number of cables represents a high additional effort in terms of space, installation, costs and weight. Measuring lines are also potential receiving antennas for electromagnetic radiation, which are superimposed on the electrical voltages on the respective lines and can falsify them. The voltages of the bipolar plates 12 measured by the evaluation electronics thus become increasingly inaccurate the longer the measuring lines are.

It is therefore the object of the present invention to provide a solution by means of which cell voltages of respective fuel cells in a fuel cell stack can be determined in a particularly simple and precise manner.

This object is achieved according to the invention by the subject matter of the independent patent claim. Further possible developments of the invention are listed in the dependent claims.

The invention relates to a fuel cell device, which can in particular be part of a vehicle battery of a motor vehicle or part of a so-called range extender, with a large number of fuel cells stacked on top of one another in a stacking direction.

These fuel cells are each delimited by an upper and a lower bipolar plate, with an electrically conductive connection lug being connected to at least one of the bipolar plates of the respective fuel cell. When the fuel cells are arranged in a fuel stack, a bipolar plate can delimit two fuel cells that are adjacent to one another. The electrically conductive connecting lug is bent relative to the bipolar plate to which the connecting lug is connected, it being possible to measure a voltage of the respective fuel cell via the connecting lug. In particular, each fuel cell has a connection lug, via which the voltage prevailing in the respective fuel cell can be tapped. To determine the voltage in the respective fuel cell, the voltages present at the respective fuel cells can thus be tapped off by means of a voltage measuring device via the respective connection lugs. Due to the bent design of the connecting lug, a contacting surface of the connecting lug, on which the connecting lug is to be contacted with the voltage measuring device for measuring the voltage, extends at least essentially in the stacking direction. This means that the contacting surface of the connection lug extends at least essentially obliquely, in particular perpendicularly, to a main plane of extension of the associated bipolar plate. In this case, the main extension plane of the respective bipolar plates runs at least essentially perpendicularly to the stacking direction of the fuel cells. Due to the bending of the connecting lug, at least the contacting surface of the connecting lug thus extends in the stacking direction, as a result of which the contacting surface can be provided with a particularly large extent, which in turn makes it possible to provide electrical contact between the voltage measuring device and the connecting lug on the contacting surface in a particularly simple manner. The respective connection lugs thus overhang laterally in some areas over the respective associated bipolar plate, as a result of which the voltage measuring device can be electrically contacted with the respective fuel cells via their connection lugs in a particularly simple manner. As a result, a particularly simple determination of the respective voltage present in the fuel cell is made possible. In order to enable the voltage of each fuel cell in a fuel stack to be tapped particularly easily, it can be provided that a connecting lug is connected to each bipolar plate in the fuel cell stack.

In a further embodiment of the invention, it is provided that the connection lug of the respective fuel cell is arranged along the stacking direction, covering at least one further fuel cell laterally in a covering direction. In this case, the overlapping direction runs at least essentially perpendicularly to the stacking direction of the fuel cells in the fuel cell device. In particular, the overlapping direction can run parallel to the main extension plane of the bipolar plates. In particular, the contact surface provided by the respective connection lug runs transversely, in particular perpendicularly, to the Main extension plane of the bipolar plates. Provision is therefore made for the at least one further fuel cell to be covered laterally in the covering direction by the contact surface of the connection lug. As a result, the contact surface of the connection lug can be provided with a particularly large extent. As a result, it is particularly easy to provide electrical contact between the voltage measuring device and the respective terminal lugs. The voltage measuring device can be easily brought into electrical contact with the connecting lug and via the connecting lug with the bipolar plate adjacent to the connecting lug for measuring the voltage in the respective fuel cell via the contact surface of the respective connecting lug, which has a particularly large extent.

In a further embodiment of the invention, it is provided that the connecting lugs of all fuel cells of the fuel cell device are arranged without overlapping one another in the overlapping direction. This means that the connection lugs are arranged at a respective distance from one another in an adjacent direction running perpendicularly to the overlapping direction and parallel to the main extension plane of the respective bipolar plates. This means that the respective contact surfaces of the terminal lugs are arranged next to one another in the juxtaposition direction, the terminal lugs being arranged at a distance from one another to avoid electrical contact between the respective terminal lugs. The adjacency direction runs, in particular, perpendicularly to the stacking direction of the fuel cells. A respective fuel cell of the fuel cell device can be covered by at least one, in particular at least two, connection lugs in the covering direction. In this case, the respective fuel cell can be covered laterally in the covering direction by connection lugs which are adjacent to one another in the direction of adjacency. Because the connection lugs are arranged without overlap in the direction of overlap, direct electrical contact between the connection lugs and, as a result, a short circuit can be avoided.

In a further embodiment of the invention, at least one electrically insulating insulating element is arranged in the overlapping direction between the connecting lugs and the respective fuel cells laterally covered by the connecting lugs. This insulating element can in particular rest on at least one fuel cell on a first side and on a second side opposite the first side on a connecting lug that covers these fuel cells in the overlapping direction. The at least one fuel cell laterally covered by the connecting lug in the covering direction is thus electrically insulated from this connecting lug via the insulating element. In this way, a short circuit between the connection lug, in particular the fuel cell assigned to the connection lug, and the fuel cell laterally covered by the connection lug in the overlapping direction can be avoided.

In a further embodiment of the invention, it is provided that the at least one insulating element is designed as an insulating strip, which extends between a plurality of connection lugs and fuel cells. As a result, at least two connection lugs can be insulated from respective fuel cells by means of the same insulating element. The at least one insulating strip can be attached particularly easily to the plurality of stacked fuel cells and avoids the time-consuming attachment of an individual insulating element for each of the connecting lugs. In particular, all of the insulating strips, by means of which the connecting lugs of the fuel cell device are insulated from the respective fuel cells, can be connected to one another. All the insulating strips can be connected to one another laterally, for example, so that the insulating strips can be arranged together on the fuel cells and the connection lugs. By laterally connecting the respective isolating strips, the isolating strips can be designed with several fingers corresponding to the letter E. A particularly large number of connecting lugs can thus be insulated simultaneously from the fuel cells via the at least one insulating strip, as a result of which the fuel cell device can be provided in particularly short cycle times.

In a further embodiment of the invention, it is provided that the connection lugs are designed as an extension of the respective associated bipolar plate. This means that the connection lugs are each formed in one piece with the associated bipolar plate. The formation of the connection lugs as an extension of the respective associated bipolar plate enables a particularly reliable electrical contacting of the bipolar plates via a respective electrical contact of the voltage measuring device with the contact surface provided by the respective connection lug.

In a further embodiment of the invention, it is provided that at least one of the connection lugs covers at least one fuel cell in the overlapping direction, which is arranged in the stacking direction above the bipolar plate assigned to the connection lug. Furthermore is it is provided that at least one of the connection lugs covers at least one fuel cell in the overlapping direction, which is arranged in the stacking direction under the bipolar plate associated with the connection lug. This means that at least one of the connecting lugs is bent along the stacking direction in a first direction, in particular upwards, and at least one further connecting lug is bent along the stacking direction in a second direction opposite the first direction, in particular downwards. The respective direction in which the respective connecting lugs are bent along the stacking direction can be selected such that protruding respective connecting lugs beyond respective bipolar plates delimiting a fuel stack formed by stacking all of the fuel cells is avoided. In particular, all of the terminal lugs arranged in a common area can be bent over in the same direction along the stacking direction. The respective contact surface of the connecting lugs is provided by a respective outer side of the respective connecting lug facing away from the covered fuel cells in the covering direction. The risk of damage to the connection lugs can be kept particularly low by avoiding the protrusion of the respective connection lugs beyond the bipolar plates that close off the fuel cell stack.

The invention also relates to a fuel cell arrangement with a fuel cell device as has already been described in connection with the fuel cell device according to the invention. Furthermore, the fuel cell arrangement includes a voltage measuring device, by means of which the respective connection lugs of the fuel cells of the fuel cell device can be contacted, as a result of which a respective voltage of the fuel cells can be determined. This means that the voltage measuring device is in electrical contact with all connection lugs of the fuel cell device, as a result of which the voltage in all fuel cells of the fuel cell device can be determined. Advantages and advantageous developments of the fuel cell device according to the invention are to be regarded as advantages and advantageous developments of the fuel cell arrangement according to the invention and vice versa.

In a further embodiment of the invention, it is provided that the voltage measuring device comprises a contact element for each connecting lug, which is electrically contacted with the respective associated connecting lug, the contact elements being fixed relative to one another. Due to the relative fixing of the contact elements to one another, all of the contact elements can be placed simultaneously on the respective associated connection lugs and electrically contacted with them. As a result, the fuel cell arrangement can be provided in a particularly simple manner. For example, the contact element can be designed as a contact spring or as a contact clip, which is provided by an electrically conductive sheet metal. As a result, the electrical contact between the respective contact element and the associated connection lug can be provided in a particularly simple and reliable manner.

In a further embodiment of the invention, it is provided that the contact elements are held on a printed circuit board device and are electrically contacted via this printed circuit board device. The circuit board device comprises at least one circuit board. In particular, the contact elements can be fixed in their orientation relative to one another via the printed circuit board device. This means that the contact elements can be held rigidly on the circuit board device in order to be fixed relative to one another. Furthermore, the printed circuit board device is particularly robust against electromagnetic radiation, as a result of which measurement signals transmitted via the printed circuit board device can be transported to an evaluation unit of the voltage measuring device in a particularly uncorrupted manner. As a result, the voltage in the respective fuel cells can be determined with particularly high accuracy using the voltage measuring device. The high level of robustness of the circuit board device with respect to electromagnetic radiation can result from the particularly short signal paths. Furthermore, the at least one printed circuit board of the printed circuit board device can have a multilayer design, with shielding surfaces being provided within the printed circuit board, which are made of copper layers, for example, so that electromagnetic shielding of the signal paths can take place.

It is provided in a further embodiment of the invention that the contact elements comprise a spring device, via which the respective contact element is acted upon by a spring force and is supported against the associated connection lug. For example, the contact element can be designed as a spring-loaded pin, with a free end of the spring-loaded pin being pressed against the contact surface of the connecting element via the spring force provided by the spring device. Tolerances can thus be compensated for by means of the spring device, in particular along the overlapping direction, as a result of which reliable electrical contact can be ensured between the respective contact element and the associated connecting lug. Above the spring device can thus press a first end of the contact element against the printed circuit board and a second end opposite the first end can be pressed against the contact surface of the connecting lug.

In a further embodiment of the invention, it is provided that the fuel cell arrangement comprises at least one support element, by means of which the printed circuit board device is supported against the fuel cells in the overlapping direction. The support element can thus be supported with a first side against the circuit board device, in particular by the support element resting with its first side on the circuit board device, and with its second side opposite the first side against the fuel cells, in particular by the support element with its second side laterally applied to at least one of the fuel cells. This support element is designed in particular to be electrically insulating and allows a distance to be maintained between the printed circuit board device and the fuel cells. As a result, the risk of a short circuit can be kept particularly low. In particular, the support element prevents direct electrical contact between the printed circuit board device and the fuel cells, bypassing the contact elements. As a result, the risk of damage to the fuel cell arrangement can be kept particularly low.

In a further embodiment of the invention, provision is made for the circuit board device to be arranged in the overlapping direction so as to overlap with the fuel cells. The circuit board device thus extends obliquely to the main extension plane of the respective bipolar plates of the fuel cells. In particular, the printed circuit board device extends at least essentially in a plane spanned by the overlapping direction and the adjoining direction. In this case, the at least one circuit board of the circuit board device can extend with its main extension plane, in particular at least essentially parallel to a side surface of the fuel cell device. As a result, the voltage measuring device can rest laterally on the fuel cell device, as a result of which the voltage measuring device covers the fuel cell device at least in regions in the overlapping direction. The printed circuit board device of the voltage measuring device can be designed so that it can be fastened to either side of the fuel cell device. Due to the lateral arrangement of the printed circuit board device on the fuel cell stack, the fuel cell arrangement is of particularly compact design. In particular, a respective shortest distance between the contact surfaces of the connecting lugs to the printed circuit board device can be at least essentially the same over the entire printed circuit board device. As a result, the fuel cell arrangement can be provided with a particularly small installation space requirement.

In a further embodiment of the invention, it is provided that the voltage measuring device includes an evaluation unit, which is arranged on the printed circuit board device. In this case, the evaluation unit can in particular comprise evaluation electronics which are arranged on the printed circuit board device. As a result, the respective signal paths from the connection lugs to the evaluation unit can be kept particularly short, as a result of which the risk of falsification of measured values, for example due to electromagnetic radiation, can be kept particularly low.

In a further embodiment of the invention, it is provided that the printed circuit board device comprises at least two printed circuit boards. These several printed circuit boards can be electrically and/or signal-connected to one another. For example, the multiple printed circuit boards can be connected to one another via respective ribbon cables. At least one of these multiple printed circuit boards can be connected to the evaluation unit in order to provide the measured voltages for the evaluation unit. For example, all printed circuit boards of the printed circuit board device can be connected to the evaluation unit via one of the printed circuit boards. Alternatively, each of the printed circuit boards can be connected directly to the evaluation unit. By providing the printed circuit board device with a plurality of printed circuit boards, the printed circuit board device can be set up to contact a particularly large fuel cell device and/or to depict complicated geometries.

Further features of the invention can result from the following description of the figures and from the drawing. The features and feature combinations mentioned above in the description and the features and feature combinations shown below in the description of the figures and/or in the figures alone can be used not only in the combination specified in each case, but also in other combinations or on their own, without going beyond the scope of the invention to leave.

• 1 eine schematische Schnittansicht einer Brennstoffzelle, welche durch eine obere Bipolarplatte und eine untere Bipolarplatte begrenzt ist und welche dazu eingerichtet ist, elektrische Energie durch Reaktion von Wasserstoff mit Sauerstoff bereitzustellen;
• 2 eine schematische Schnittansicht eines Brennstoffzellenstapels, welcher mehrere in einer Stapelrichtung aufeinandergestapelte Brennstoffzellen umfasst, wobei vorliegend eine Bipolarplatte einer Brennstoffzelle durch eine Anschlusslasche verlängert gezeigt ist, wobei die Anschlusslasche relativ zu einer Haupterstreckungsebene der Bipolarplatten umgebogen ist, wodurch eine von der Anschlusslasche bereitgestellte Kontaktfläche, an welcher die Anschlusslasche von einer Spannungsmesseinrichtung elektrisch zu kontaktieren ist, sich parallel zu der Stapelrichtung der Brennstoffzellen erstreckt, wodurch die Kontaktfläche mit einer besonders großen Erstreckung bereitgestellt ist;
• 3 eine schematische Seitenansicht eines Ausschnitts einer Brennstoffzelleneinrichtung mit dem Brennstoffzellenstapel aus den mehreren in der Stapelrichtung aufeinandergestapelten Brennstoffzellen, wobei jeweilige Bipolarplatten des Brennstoffzellenstapels durch Anschlusslaschen verlängert sind, welche entlang der Stapelrichtung jeweilige Brennstoffzellen seitlich überdecken;
• 4 eine schematische Seitenansicht der Brennstoffzelleneinrichtung, wobei für jede Brennstoffzelle wenigstens eine Anschlusslasche vorgesehen ist, über welche die jeweilige Brennstoffzelle elektrisch kontaktierbar ist, wodurch wiederum für jede Brennstoffzelle die in der Brennstoffzelle anliegende Spannung ermittelbar ist, wobei ein Teil der Anschlusslaschen nach oben umgebogen ist und ein weiterer Teil der Anschlusslaschen nach unten umgebogen ist, wodurch ein Überstehen jeweiliger Anschlusslaschen über eine Hauptertreckungsebene einer obersten Bipolarplatte sowie über eine Hauptertreckungsebene einer untersten Bipolarplatte der Brennstoffzelleneinrichtung hinaus vermieden werden kann;
• 5 eine schematische Schnittansicht eines Ausschnitts einer Brennstoffzellenanordnung mit der Brennstoffzelleneinrichtung sowie einer mit der Brennstoffzelleneinrichtung in elektrischem Kontakt stehenden Spannungsmesseinrichtung, über welche die jeweilige in den Brennstoffzellen der Brennstoffzelleneinrichtung anliegende Spannung ermittelbar ist, wobei die Spannungsmesseinrichtung für jede Anschlusslasche ein Kontaktelement aufweist, welches vorliegend als gefederter Stift ausgebildet ist, dessen Basis fest an einer Leiterplatteneinrichtung der Spannungsmesseinrichtung gehalten ist und dessen Spitze über eine Federeinrichtung gegen dessen Basis abgestützt ist und mit der Kontaktfläche der zugeordneten Anschlusslasche kontaktiert ist;
• 6 eine schematische Seitenansicht der Brennstoffzellenanordnung, bei welcher die Leiterplatteneinrichtung die Brennstoffzellen in der Überdeckungsrichtung seitlich überdeckend angeordnet ist und für jede Anschlusslasche der Brennstoffzelleneinrichtung ein Kontaktelement der Spannungsmesseinrichtung vorgesehen ist, welches mit der jeweiligen zugeordneten Anschlusslasche in Kontakt steht, wodurch für jede Brennstoffzelle die in der Brennstoffzelle anliegende Spannung ermittelbar ist;
• 7 eine schematische Schnittansicht des Ausschnitts der Brennstoffzellenanordnung mit der Brennstoffzelleneinrichtung sowie einer mit der Brennstoffzelleneinrichtung in elektrischem Kontakt stehenden Spannungsmesseinrichtung, über welche die jeweilige in den Brennstoffzellen der Brennstoffzelleneinrichtung anliegende Spannung ermittelbar ist, wobei die Spannungsmesseinrichtung für jede Anschlusslasche ein Kontaktelement aufweist, welches vorliegend als Kontaktfeder ausgebildet ist, welche einenends an der Leiterplatteneinrichtung der Spannungsmesseinrichtung gehalten ist und deren Kontaktbereich gefedert gegen die Kontaktfläche der zugeordneten Anschlusslasche abgestützt ist;
• 8 eine schematische Ansicht von Isolierelementen der Brennstoffzelleneinrichtung gemäß 6, wobei über die Isolierelemente die Anschlusslaschen gegen jeweilige Bipolarplatten der Brennstoffzellen elektrisch isoliert sind,
• 9 eine schematische Darstellung einer Anordnung jeweiliger Anschlusslaschen relativ zueinander als Basis für eine Berechnung einer optimalen Länge der jeweiligen Anschlusslaschen; und
• 10 eine schematische Darstellung einer Anordnung jeweiliger Bipolarplatten der Brennstoffzelleneinrichtung relativ zueinander, welche für die Berechnung der optimalen Länge der Anschlusslaschen herangezogen werden kann.

The drawing shows in:

• 1 a schematic sectional view of a fuel cell, which is delimited by an upper bipolar plate and a lower bipolar plate and which is adapted to electrical to provide energy by reacting hydrogen with oxygen;
• 2 a schematic sectional view of a fuel cell stack, which comprises a plurality of fuel cells stacked one on top of the other in a stacking direction, in the present case a bipolar plate of a fuel cell is shown extended by a connecting lug, the connecting lug being bent relative to a main extension plane of the bipolar plates, whereby a contact surface provided by the connecting lug, on which the terminal lug is to be electrically contacted by a voltage measuring device, extends parallel to the stacking direction of the fuel cells, as a result of which the contact surface is provided with a particularly large extent;
• 3 a schematic side view of a detail of a fuel cell device with the fuel cell stack made up of the several fuel cells stacked one on top of the other in the stacking direction, wherein respective bipolar plates of the fuel cell stack are extended by connection lugs which laterally cover respective fuel cells along the stacking direction;
• 4 a schematic side view of the fuel cell device, wherein at least one connecting lug is provided for each fuel cell, via which the respective fuel cell can be electrically contacted, whereby in turn the voltage present in the fuel cell can be determined for each fuel cell, with part of the connecting lugs being bent upwards and another part of the connection lugs is bent downwards, as a result of which the respective connection lugs can be prevented from protruding beyond a main extension plane of an uppermost bipolar plate and beyond a main extension plane of a lowermost bipolar plate of the fuel cell device;
• 5 a schematic sectional view of a section of a fuel cell arrangement with the fuel cell device and a voltage measuring device which is in electrical contact with the fuel cell device and via which the respective voltage present in the fuel cells of the fuel cell device can be determined, the voltage measuring device having a contact element for each connecting lug, which is present as a spring-loaded pin is formed, the base of which is held firmly on a printed circuit board device of the voltage measuring device and the tip of which is supported by a spring device against its base and makes contact with the contact surface of the associated connecting lug;
• 6 a schematic side view of the fuel cell arrangement, in which the printed circuit board device is arranged laterally covering the fuel cells in the overlapping direction and a contact element of the voltage measuring device is provided for each connecting lug of the fuel cell device, which is in contact with the respective associated connecting lug, whereby for each fuel cell the in the fuel cell applied voltage can be determined;
• 7 a schematic sectional view of the section of the fuel cell arrangement with the fuel cell device and a voltage measuring device which is in electrical contact with the fuel cell device and via which the respective voltage present in the fuel cells of the fuel cell device can be determined, the voltage measuring device having a contact element for each connecting lug, which is in the present case designed as a contact spring which is held at one end on the printed circuit board device of the voltage measuring device and the contact area of which is supported in a spring-loaded manner against the contact surface of the associated connecting lug;
• 8th a schematic view of insulating elements of the fuel cell device according to FIG 6 , the connection lugs being electrically insulated from the respective bipolar plates of the fuel cells via the insulating elements,
• 9 a schematic representation of an arrangement of respective connection lugs relative to one another as a basis for calculating an optimum length of the respective connection lugs; and
• 10 a schematic representation of an arrangement of respective bipolar plates of the fuel cell device relative to one another, which can be used to calculate the optimal length of the connection lugs.

Elements that are the same or have the same function are provided with the same reference symbols in the figures. For reasons of clarity, the reference numbers are sometimes only shown in the figures for individual elements of a respective identical group of elements.

As already explained, in 1 a fuel cell 10 delimited at the top and bottom by respective bipolar plates 12 is shown. In 2 is a fuel cell stack of a fuel cell device 28 with a multiplicity of fuel stacked on top of one another in a stacking direction 30 fabric cells 10 shown. In the present case, the stacking direction 30 runs at least essentially perpendicularly to a main extension plane of the respective bipolar plates 12, via which the fuel cells 10 are delimited from one another. In order to be able to determine the respective voltages occurring in the fuel cells 10, the bipolar plates 12 delimiting the respective fuel cells 10 must be electrically contacted.

In order to enable particularly simple electrical contacting of the respective bipolar plates 12 of the fuel cell stack, it is provided that each of the bipolar plates 12 is extended laterally by a connecting lug 32 . The respective connection lug 32 is bent over starting from the main extension plane of the respective associated bipolar plate 12 . This means that a main extension plane of the respective connection lugs 32 runs obliquely to the respective main extension plane of the bipolar plates 12 . In the present case, a connection lug 32 is provided for each bipolar plate 12 . Each connecting lug 32 has a contact surface 34 via which the respective connecting lug 32 can be contacted with a voltage measuring device 36 . In the present case, the respective contact surface 34 runs at least essentially parallel to the stacking direction 30. As a result, the connection lug 32 covers at least one fuel cell 10 with its contact surface 34 along the stacking direction 30 in a covering direction 38. The covering direction 38 runs in particular perpendicularly to the stacking direction 30. In this case, the covering direction 38 run parallel to the main plane of extension of the bipolar plates 12, while the stacking direction 30 runs perpendicular to the main planes of extension of the bipolar plates 12. The respective connection lug 32 thus extends laterally along the fuel cell stack.

As in 3 can be recognized, the respective connection lugs 32 are arranged in the overlapping direction 38 without overlapping one another. This means that the respective connection lugs 32 do not overlap one another in the overlapping direction 38 . As a result, the risk of a short circuit can be kept particularly low by avoiding direct contact between the respective connection lugs 32 . Furthermore, the non-overlapping arrangement of the terminal lugs 32 relative to one another in the overlapping direction 38 enables particularly good accessibility of the respective contact surfaces 34 of the terminal lugs 32 for the voltage measuring device 36 a distance from each other. As a result, the risk of a short circuit as a result of direct contact between the respective connection lugs 32 can be kept particularly low. In particular, respective connection lugs 32 which are adjacent to one another in the adjacent direction 40 are assigned to respective fuel cells 10 which are adjacent in the stacking direction 30 . In the 3 The view shown is relative to the one in 2 shown rotated by 90°.

In 4 the entire fuel cell device 28 is shown schematically. As in 4 can be recognized, a connecting lug 32 is provided for each fuel cell 10, which provides a contact surface 34. As in 4 As can also be seen, the fuel cell device 28 has a first region 42 in which the respective arranged connection lugs 32 cover at least one fuel cell 10 in the overlapping direction 38, which is arranged in the stacking direction 30 under the fuel cell 10 assigned to the connection lug 32. Furthermore, the fuel cell device 28 has a second area 44, wherein respective connection lugs 32 arranged in the second area 44 cover at least one fuel cell 10 in the overlapping direction 38, which is arranged in the stacking direction 30 above the fuel cell 10 assigned to the connection lug 32. This means that the connecting lugs 32, which are arranged in the first area 42 of the fuel cell device 28, are bent downwards in the stacking direction 30, whereas the connecting lugs 32 arranged in the second area 44 of the fuel cell device 28 are bent upwards in the stacking direction 30 . As a result, as in 4 is shown, it can be avoided that respective connection lugs 32 protrude beyond an upper side or an underside of the fuel cell device 28 due to their bending.

In 5 a section of a fuel cell arrangement 46 is shown, which includes the fuel cell device 28 and the voltage measuring device 36 . In order to avoid direct contact between the respective bipolar plates 12 via the connection lugs 32, as in 5 is shown, at least one insulating element 48 may be provided, which is arranged in the overlapping direction 38 between the connection lug 32, in particular the contact surface 34, and the respective bipolar plates 12 that are not assigned to the connection lug 32. In this case, the insulating element 48 can be designed as an insulating strip, by means of which a plurality of connection lugs 32 can be electrically insulated from the respective bipolar plates 12 .

In order to be able to contact the respective connection lugs 32 via the contact surfaces 34 particularly easily, the voltage measuring device 36 comprises a contact element 50 for each connection lug 32. In the fuel cell arrangement 46 provided, all contact elements 50 of the voltage measuring device 36 are in electrical contact with the respectively associated connection lugs 32. In the present case, the respective contact elements 50 are designed as spring-loaded pins. This means that each of the contact elements 50 has a spring device 52 via which a respective contact tip 54 of the respective contact element 50 can be pressed against the associated contact surface 34 of the respective connection lug 32 when subjected to a spring force. Tolerances of the connecting lugs 32 can thus be compensated for by means of the spring device 52 in order to ensure reliable contacting of each of the connecting lugs 32 by the voltage measuring device 36 . The voltage measuring device 36 also includes a printed circuit board device 56 on which each contact element 50 is held. The printed circuit board device 56 can comprise at least one printed circuit board, in particular at least two printed circuit boards. The respective circuit board can also be referred to as a so-called circuit board. In the present case, each of the contact elements 50 protrudes from the circuit board device 56 . Each contact element 50 is held on the circuit board device 56 . As a result, by bringing the printed circuit board device 56 closer to the fuel cell device 28 , all of the contact elements 50 can be contacted at once with the respective associated connection lugs 32 of the fuel cell device 28 .

In the present case, the circuit board device 56 is aligned with its main extension plane at least essentially parallel to the contact surface 34 . The direct attachment of the respective contact elements 50 to the printed circuit board unit 56 allows measurement signals to be evaluated directly on the printed circuit board unit 56 if an evaluation unit 60, in particular at least one electronic evaluation unit of the evaluation unit 60, is also placed directly on the printed circuit board unit 56. In this case, the evaluation electronics can be arranged in particular on a rear side of the printed circuit board device 56 which is remote from the fuel cell device 28 . Alternatively, the evaluation electronics can be arranged in particular on a front side of the circuit board device 56 facing towards the fuel cell device 28 . The contact elements 50 are held on the printed circuit board device 56 on the front side of the printed circuit board device 56 facing the fuel cell device 28 . Due to the use of the printed circuit board device 56, the respective cables from the respective bipolar plates 12 to evaluation electronics can be saved. As a result, the voltage measuring device 36 described enables savings in cables, space required for the cables and weight. Furthermore, the printed circuit board device 56 makes it possible for the influence of electromagnetic interference signals on measured values to be kept particularly low.

In 6 the fuel cell arrangement 46 is shown in a side view, in particular a view of the rear side of the printed circuit board device 56 . In this case, the circuit board device 56 is shown translucent in order to enable the arrangement of the further components of the fuel cell arrangement 46 to be recognized. In 6 it can be seen particularly well that in the present case the at least one insulating element 48 is designed as an insulating strip. The respective insulating elements 48 can be made of an electrically non-conductive plastic, which is intended to prevent the connecting lug 32 from being pressed by the pin prestressed by the spring device 52 against the bipolar plates 12 located behind the connecting lug 32 in the overlapping direction 38 and short-circuiting them. Furthermore, in 6 the respective contact elements 50 are recognized as points which are in contact with the respective contact surfaces 34 of the associated connection lugs 32 .

In 6 respective supporting elements 58 are additionally shown, via which the printed circuit board device 56 can be supported against the fuel cell device 28 . These support elements 58 are designed to be electrically insulating and are designed to avoid direct electrical contact between the printed circuit board device 56 and the fuel cell device 28 , bypassing the contact elements 50 . This can ensure that the respective measured values determined by means of the voltage measuring device 36 come from the terminal lugs 32 permanently assigned to the respective contact elements 50 . A mix-up or falsification of measured values can hereby be at least essentially avoided.

7 shows a fuel cell device 28, as already in connection with 5 has been described. The voltage measuring device 36 is connected to this fuel cell device 28 and can be used to determine the voltages in the respective fuel cells 10 . In this case, the respective contact elements 50 of the voltage measuring device 36 are designed as contact springs, which are held at one end on the printed circuit board device 56 and the other end of which is arranged freely. The contact springs are resilient, whereby a contact area of the respective contact spring by means of spring force to the associated contact surface 34 of the associated connection lug 32 can be pressed when the voltage measuring device 36 is applied to the fuel cell device 28. The contact springs enable a particularly simple configuration of the respective contact elements 50.

In 8th the insulating elements 48 of the fuel cell device 28 are shown separately. It can be recognized here that the insulating elements 48 can be designed as insulating strips. In this case, a plurality of insulating elements 48 can be connected to one another for a particularly simple arrangement of the insulating elements 48 on the fuel cells 10 . In the present case, the connection of the multiple insulating strips results in respective insulating fingers, which can be pushed simultaneously between the respective connection lugs 32 and the plastic layer 16 referred to as the sub-gasket.

The solution described for the particularly simple contacting of the respective bipolar plates 12 by means of the voltage measuring device 36 already begins during the production of the respective bipolar plates 12 . It can be provided for each bipolar plate 12 that during its cutting process a metal strip, in this case the connection lug 32, is formed, which is bent over when the respective fuel cells 10 are arranged in the fuel cell stack. The respective metal strip providing the connecting lug 32, which is attached to one of the bipolar plates 12 or extends the respective bipolar plate 12, protrudes beyond a plurality of fuel cells 10 of the fuel cell stack in the stacking direction 30. Each bipolar plate 12 of the fuel cell stack is provided with a connecting lug 32. In this case, the respective connection lugs 32 are positioned spatially offset in relation to one another in the adjoining direction 40 in order to prevent the connection lugs 32 from overlapping.

the inside 4 and 6 The fuel cell stack shown comprises 120 fuel cells 10 stacked one on top of the other in the stacking direction 30. In the present case, the provision and bending of the respective connection lugs 32, as in FIG 4 and 6 can be seen, six horizontal rows, each with offset positions for the terminal lugs 32 along the adjacent direction 40. The respective widths and lengths of the terminal lugs 32, in particular the contact surfaces 34 of the respective terminal lugs 32, are dimensioned such that a particularly large extension of the contact surface 34 is achieved, whereby a particularly simple positioning of the contact elements 50 on the respective associated contact surfaces 34 is achieved. The respective contact elements 50 can also be referred to as voltage measuring probes. As in 4 As can be seen particularly well, in the present case there is a reversal of a folding direction of the connecting lugs 32 from about half a length of the fuel cell device 28 along the adjacent direction 40. This reversal of the folding direction allows an available side surface of the fuel cell stack to be optimally used, which means that particularly large extensions of the Contact surfaces 34 of the terminal lugs 32 can be reached. The angled and surface-maximized connection lugs 32 serve to tap off electrical voltages on each bipolar plate 12 . To realize such a voltage tap, the contact elements 50 , which are prestressed by means of the spring devices 52 and are designed as pins, in particular metal pins, are used, which can be soldered to the printed circuit board device 56 . The electrical voltage of the bipolar plate 12 tapped off by means of the contact element 50 on the connection lug 32 is forwarded to the printed circuit board device 56 on which conductor tracks are located. The voltage can be passed on to the evaluation electronics, which can be located on the printed circuit board device 56, via these conductor tracks.

The printed circuit board device 56 is positioned on the fuel cell stack as part of an assembly process in such a way that the pins, in this case the contact elements 50, press centrally onto the contact surfaces 34 of the connection lugs 32 and thus tap off the respective cell voltage of the fuel cells 10. When the fuel cell arrangement 46 is assembled, the insulating strips can be pushed between the fuel cells 10 and the respective connection lugs 32 in order to prevent the bipolar plates 12 from short-circuiting.

As in 6 As can be seen, the respective support elements 58 can be arranged in the adjacent direction 40 between the connection lugs 32, which are designed as an electrically non-conductive pin, in particular as a plastic screw or a plastic mandrel, in order to brace the circuit board device 56 with the insulating elements 48 in a suitable manner. As a result, a particularly high mechanical strength of the fuel cell arrangement 46 can be achieved.

The calculation of an optimal length B of the connecting lugs 32 for a given horizontal distance a _h and a given width A of the connecting lugs 32 and for a given width b of the longest side of a bipolar plate 12 is described below. Here, a _v denotes a vertical distance between the terminal lugs 32 in the stacking direction 30. a _h represents a horizontal distance and thus a distance along the adjacency direction 40 between the Terminal lugs 32. A designates a width of a respective terminal lug 32, whereas B represents a length of the respective terminal lug 32. b represents a width of a longest side of the bipolar plates (BPP) 12. H stands for a height of the fuel cell stack and d describes a pitch of the bipolar plates 12. A number of the bipolar plates 12 is denoted by z. n designates a number of terminal lugs 32 in a horizontal row, and thus in the adjacency direction 40, a number of terminal lugs 32 being described here which fit next to one another in a row. m _h describes a number of horizontal gaps of width a _h . k describes a number of necessary connecting lugs 32 in a row in order to accommodate all z connecting lugs 32 for a given number n. In 9 three connection lugs 32 are shown as an example, which are provided with the relevant dimensions. The dimension a _h is the horizontal distance to be specified between two connection lugs 32 and a _v is the automatically resulting vertical distance. In 10 a long side of the fuel cell stack can be seen, with its bipolar plates 12 of length b and number z, labeled BPP. The bipolar plates 12 have a distance d and the fuel cell stack has an overall height H.

Formula (1) applies to the width b. $$b=m_H\cdot a_H+n\cdot A$$

Formula (2) applies to the number of horizontal gaps. $$m_H=n-1$$

Inserting formula (2) into (1), converted to formula (3), results in the number n of connection lugs 32 in a horizontal line. $$n=\left[\frac{b+a_H}{A+a_H}\right]$$

The necessary number of connecting lugs 32 in a horizontal row is calculated from formula (4). $$k=\left[\frac{\mathrm{e.g}}{n}\right]$$

$$H=2kB-d$$

Formulas (5) and (6) describe the overall height of the fuel cell stack. $$H=\mathrm{e.g}\cdot \mathrm{i.e}$$

$$H=2kB-\mathrm{i.e}$$

Equating formulas (5) and (6) and rearranging according to the optimal length B of the connection lugs 32 results in formula (7). $$B=\frac{\left(\mathrm{e.g}+1\right)\cdot \mathrm{i.e}}{2k}$$

Finally, substituting formula (4) into formula (7) gives formula (8). $$B=\frac{(\mathrm{e.g}+\cdot \mathrm{i.e}}{2\cdot \left[\frac{\mathrm{e.g}}{n}\right]}$$

The fuel cell device 28 described and the fuel cell arrangement 46 described make it possible to minimize the outlay on manufacturing a cell voltage tap. Furthermore, no long cables are necessary, which lead the tapped voltages to the evaluation electronics. An analog-to-digital conversion of measured analog voltages can take place directly on the circuit board device 56 on which the contact elements 50 are located. In particular, a three-wire CAN bus cable can be connected from there, the digital signals of which are immune to interference. Another advantage is that there is no cabling required when assembling the cell voltage taps. The prestressed, spring-loaded contact pins, in this case the contact elements 50, which each press on a surface-optimized connection lug 32, the contact surface 34 of which is relatively large, result in particularly large free spaces with regard to manufacturing tolerances and with regard to possible stacking movements in comparison to voltage tap mechanisms of other methods, which have to be aligned with high precision. The fuel cell arrangement 46 also has a particularly high level of immunity to interference with regard to electromagnetic compatibility, due to the fact that the analog/digital conversion of the measured analog voltages can take place directly on the printed circuit board device 56 on which the contact elements 50 are located.

Reference List

10

fuel cell

12

bipolar plate

14

poetry

16

masked laminating film

18

anode-side catalyst layer

20

membrane

22

cathode-side catalyst layer

24

hydrogen gas diffusion layer

26

oxygen gas diffusion layer

28

fuel cell device

30

stacking direction

32

connection tab

34

contact surface

36

voltage measuring device

38

coverage direction

40

adjacency direction

42

first area

44

second area

46

fuel cell assembly

48

insulating element

50

contact element

52

spring device

54

contact tip

56

circuit board setup

58

support element

60

evaluation unit

QUOTES INCLUDED IN DESCRIPTION

This list of documents cited by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent Literature Cited

• WO 9966339 A1 [0005]
• US9620800B2 [0006]

Claims (15)

Fuel cell device (28), with a large number of fuel cells (10) stacked on top of one another in a stacking direction (30), which are each delimited by an upper bipolar plate (12) and a lower bipolar plate (12), wherein at least one of the bipolar plates (12) the respective fuel cell (10) connects an electrically conductive connecting lug (32), which is bent relative to the bipolar plate (12), it being possible to measure a voltage of the respective fuel cell (10) via the connecting lug (32). Fuel cell device (28) after claim 1 , characterized in that the connection lug (32) of the respective fuel cell (10) along the stacking direction (30) is arranged laterally covering at least one further fuel cell (10) in a covering direction (38). Fuel cell device (28) after claim 1 or 2 , characterized in that the connection lugs (32) of all fuel cells (10) of the fuel cell device (28) in the overlapping direction (38) are arranged without overlapping one another. Fuel cell device (28) after claim 2 or 3 , characterized in that at least one electrically insulating insulating element (48) is arranged in the overlapping direction (38) between the connecting lugs (32) and the respective fuel cells (10) laterally covered by the connecting lugs (32). Fuel cell device (28) after claim 4 , characterized in that the at least one insulating element (48) is designed as an insulating strip which extends between a plurality of connection lugs (32) and fuel cells (10). Fuel cell device (28) according to one of the preceding claims, characterized in that the connection lugs (32) are designed as an extension of the respective associated bipolar plate (12). Fuel cell device (28) according to one of the preceding claims, characterized in that at least one of the connection lugs (32) covers at least one fuel cell (10) in the overlapping direction (38), which in the stacking direction (30) above the bipolar plate assigned to the connection lug (32). (12) is arranged, and at least one of the connecting lugs (32) covers at least one fuel cell (10) in the overlapping direction (38), which is arranged in the stacking direction (30) under the bipolar plate (12) assigned to the connecting lug (32). Fuel cell arrangement (46), with a fuel cell device (28) according to one of the preceding claims, and with a voltage measuring device (36), by means of which the respective connection lugs (32) of the fuel cells (10) can be contacted, whereby a respective voltage of the fuel cells (10 ) can be determined. Fuel cell arrangement (46) after claim 8 , characterized in that the voltage measuring device (36) for each connecting lug (32) comprises a contact element (50) which is electrically contacted with the respective associated connecting lug (32), the contact elements (50) being fixed relative to one another. Fuel cell arrangement (46) after claim 9 , characterized in that the contact elements (50) are held on a printed circuit board device (56) and electrically contacted via the printed circuit board device (56). Fuel cell arrangement (46) after claim 9 or 10 , characterized in that the contact elements (50) comprise a spring device (52) via which the respective contact element (50) is acted upon by a spring force and supported against the associated connecting lug (32). Fuel cell arrangement (46) after claim 10 or 11 , characterized in that at least one support element (58) is provided, by means of which the printed circuit board device (56) is supported in the overlapping direction (38) against the fuel cells (10). Fuel cell arrangement (46) according to one of Claims 10 until 12 , characterized in that the printed circuit board device (56) is arranged in the overlapping direction (38) in overlap with the fuel cells (10). Fuel cell arrangement (46) according to one of Claims 10 until 13 , characterized in that the voltage measuring device (36) comprises an evaluation unit which is arranged on the circuit board device (56). Fuel cell arrangement (46) according to one of Claims 10 until 14 , characterized in that the printed circuit board means (56) comprises at least two printed circuit boards.

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