DE102005050500A1 - Device for determining the voltage of a fuel cell stack comprises a contact foil on which are arranged strip conductors having contact surface for electrically contacting with the electrode of a single cell assigned to the strip conductors - Google Patents

Abstract

Device for determining the voltage of a fuel cell stack comprises a contact foil (1) on which are arranged strip conductors (3) each having a contact surface (5) for electrically contacting with the electrode of a single cell assigned to the strip conductors. Independent claims are also included for the following: (1) Method for determining the voltage of a fuel cell stack using the above device; and (2) Device for determining the temperature of a fuel cell stack.

Description

The The invention relates to an apparatus and method for voltage detection on a fuel cell stack.

It is known, a plurality of fuel cells to a fuel cell stack ("Stack") in layers and put together to provide a voltage in the desired height in series. fuel cell stack can both a rather small and a relatively large number, i.e. from about five up to several hundred, single cells exist. The tap of the produced by the fuel cell stack (or its single cells) electrical voltage and / or temperature, and in particular prepare a secure contact of the voltage taps in the Practice, however, regularly difficulties. As is known, For example, in fuel cell stacks, which in particular composed of proton exchange membrane fuel cells (PEMFC) could be, spring wires or resilient pins or resilient contact needles using a retaining strip pressed perpendicular to the bipolar plates of the fuel cell stack. signals are transferred with plugs and cables to an evaluation unit. However, this method is costly and the assembly as well as the fine adjustment The taps are usually difficult, especially at a bad dimensional stability of the fuel cell stack. In addition, the known constructions take considerable Space of the fuel cell stack and are quite prone to failure. are also the electrodes or the bipolar plates of the fuel cell stack made of graphite, as is usually the case with PEMFCs is obtained in the known from the prior art and devices further difficulties due to the anisotropic Properties of the graphite and its brittleness.

Of the The invention is therefore based on the technical problem, an improved Device and an improved method for voltage detection to create a fuel cell stack.

The solution the technical problem results according to the invention by things the claims 1, 17, 21 and 37. Further advantageous embodiments of the inventions emerge from the dependent claims.

Of the The invention is based on the recognition that essential less space is needed and also a much more flexible design variety possible is when to he version of the voltage on a fuel cell stack instead of the known devices and methods for tapping the Tension a contact foil is used. This is inventively achieved by a device and method for voltage detection on a Fuel cell stack is proposed, wherein the fuel cell stack comprises a plurality of individual cells and wherein each individual cell is formed with at least two electrodes, via which the voltage of the respective Single cell can be tapped, and provided at least one contact foil is on the tapping the voltage of the respective single cell at least two conductor tracks are provided, which in each case at least have a contact surface, which is assigned to the electrical contacting of the conductor track Electrode of the single cell is provided. Due to the fact, that - constructive conditionally depending on the embodiment fuel cells - adjacent Single cells also interconnected or common electrodes can have is also conceivable that for tapping the voltage a trace is assigned to two individual cells. Under the "electrode" is any kind of electrical Chief to mediate the transition to understand the electric current in another conductor medium. In the exemplary case of a proton exchange membrane fuel cell it is thus both the catalyst coated with a catalyst Electrode layers on the membrane of a single cell as well as around which are arranged between the membranes of two or more individual cells Bipolar plates act on which tapped the generated voltage can be. Under the tension of a single cell is the electrical potential between the opposite and facing each other Pages of two adjacent electrodes or bipolar plates to understand. The contact film has a relatively low in the rule Thickness and is also lightweight, flexible and flexible. By the The use of such a contact foil therefore becomes a simple, affordable compact, versatile and suitable for mass production solution created for tapping the voltage on a fuel cell stack.

In an advantageous embodiment, the conductor tracks are printed on the contact foil. In this case, the contact foil itself preferably consists of an electrically nonconductive material, while the side of the contact foil printed on at least one side of the contact foil is at least partially capped by the printed conductors printed on one side of the contact foil. This corresponds to a particularly simple, inexpensive and production-ready solution for tapping the voltages at a reduced weight. Further advantages are that the printed circuit traces represent a uniform and transition-free means for contacting, signal measurements and forwarding and also automa easily can be made tisiert.

In a further advantageous embodiment, the contact foil on at least one side tabs, each on each tab a conductor is at least partially arranged. The contact surface of the each conductor is on the surface of the tab and preferably arranged at the free-standing end. The track then runs each preferably from the tab over the contact foil to a at the other end of the contact foil arranged connection unit, for example, a power strip. The tabs can then be used as "fingers" for contacting serve the respective electrodes of the fuel cell stack. Out a, for example, rectangular piece of contact foil can thus by simple cutting and possibly folding for each Fuel cell stack to be built a matching Kontaktiermodul.

In a further advantageous embodiment, the tabs each a different length on. Thus, you can the various electrodes of the fuel cell stack in a simple manner be reached and contacted by means of the tabs. It is preferable a long tab for contacting a more distant single cell of Fuel cell stack provided while a shorter tab for one closer Single cell is provided.

In In another advantageous embodiment, the tabs are for contacting the at least one electrode of a single cell each bendable and fixable to the electrode. The tabs then press preferably with the conductively backed side, i. the one end the conductor track, on the electrode or bipolar plates to these to contact. Thus, you can the electrodes of the individual cells of a fuel cell stack in particularly simple manner contacted and the mounting of the contact foil be relieved. Series applications can be achieved, for example, by automatically "snapping in" the respective tabs be easily mounted and contacted.

In In another advantageous embodiment, the fixation takes place the tabs on the electrode by clamping between two adjacent Single cells. Thus, must the contact foil or its tabs not separately to the respective Single cells become trapped as they pass through the single cells itself (or possibly their bipolar plates) in their interstices during Compressing the fuel cell stack are trapped. On this way you can additional Saving fasteners are saved.

In In another advantageous embodiment, the fixation takes place the tabs on the electrode of the single cell by clamping means at least one retaining clip. The retaining clip may be a conventional one Standard component, which is often used in electronic applications place. That way you can additional costs for complex Custom made to be avoided. The retaining clip is included itself preferably flexible and more preferably from an electrical formed non-conductive material. It is also conceivable that several retaining clips into one unit, for example as a flexible wavy bar, put together are to several pieces of contact film to fix at the same time.

In a further advantageous embodiment, the electrode at least one contact nose on which the retaining clip can be latched is. Before latching the retaining clip is preferably the contact foil postpone on the contact nose and with the contact surfaces of the To bring conductor tracks into electrical contact. Further preferably at least one groove is attached to the contact nose, while the Retaining clip corresponding to the shape of the groove section has to fix the retaining clip and the contact foil to engage in the groove. The contact nose is preferably as partially protruding Part of the electrode to be contacted formed at which the Retaining clip can be attached. This corresponds to a structurally simple and extremely affordable solution for safe contacting of the individual cells.

In a further advantageous embodiment, the contact foil is at least partially rolled up and can be introduced with its rolled-up part into an opening provided in the fuel cell stack, wherein in the rolled-up part the conductor tracks of the contact foil can be brought into contact with one electrode of a single cell. The opening in the fuel cell stack is preferably a bore extending transversely to the individual cells. This embodiment offers the advantage that the contact foil does not have to be clamped separately, since it is pressed by its tendency to self-roll with a certain uniform force against the inner wall of the bore, ie to the electrodes. The contact pressure is dependent on the flexibility and / or the restoring force of the film against bending and the bore diameter in the fuel cell stack and structurally arbitrary. To increase the contact pressure, ie for improved pressing of the rolled contact surfaces to the electrodes of the fuel cell stack, it is also conceivable to additionally introduce an elongated flexible body in compressed form in the rolled-up part of the contact foil, which follows with some delay, as it were according to the principle an "ear plug", in particular in the radial direction expands or ver. Ver volume enlarges. This may preferably be a flexible body made of foamed material, for example polyurethane, silicone or other foam. However, it is also conceivable that an elongated or rod-shaped balloon is used to increase the contact pressure instead of a flexible body of foam, which is introduced in at least partially emptied form in the rolled-up part of the contact foil and after inflation with a fluid, such as air , exerts a radial pressure on the inside of the rolled-up part. Both in the embodiment of foam and in the balloon variant is also conceivable that the flexible body not after the final assembly of the rolled-up portion of the contact foil, ie after insertion into the opening in the fuel cell stack, there introduced nachträg Lich and put into position is, but that the rolled-up part of the contact foil is already wrapped around the flexible body before the final assembly of the contact foil in the fuel cell stack. The arrangement of the conductor tracks, ie in particular their distance, is largely structurally arbitrary. Preferably, the contact foil is rolled up such that the conductor tracks run on the outer winding transversely to the roll axis and are arranged next to one another at a distance which corresponds to the distances of the electrodes of the individual cells, so that after the introduction of the rolled-up part into the opening of the fuel cell stack a contact surface of a conductor touches an electrode of a single cell. Thus, for example, from a rectangular piece of contact foil by simply rolling up and pushing into the opening to each fuel cell stack a suitable, suitable for mass production contact module can be built. Furthermore, the production and assembly is facilitated by the fact that the rolled contact sheets can be easily inserted after the compression of the fuel cell stack in the designated opening.

In a further advantageous embodiment, the conductor tracks on the contact foil an angled and / or hook-shaped and / or J-shaped Course on. Thus lets can easily achieve that the traces on the outer winding of the rolled-up part transverse to the roll axis while they are already deflected at the non-rolled part of the contact foil and parallel to the roll axis, where they are particularly compact and space-saving manner a connection part, such as a Plug connector, supplied can be. Preferably, the conductor tracks describe an example, for example 90 ° curved or angled curve. The deflection of the tracks is constructive freely selectable. Further preferably, the conductor tracks run on the outer winding the rolled-up part is not exactly perpendicular to the roll axis, so that the contact surfaces of the tracks on the outer surface of the Winding at an imprecise Positioning the contact foil in the opening of the fuel cell stack can not be located exactly between the anodes and cathodes, causing the Contact would be prevented. However, it is important to ensure that each of the contact surfaces at least once touched an electrode, without simultaneously touching two electrodes and in this way one Short circuit.

In Another advantageous embodiment is in the contact foil in at least one space between the tracks in parallel provided for these at least one incision. Through these intermediate cuts can compensate the positional tolerances of the fuel cell stack be improved, which is preferably to a "concertina-like" unfolding the contact foil leads, if the fuel cell stack with the introduced into the opening contact foil moved so that, despite the movement, the contacts between the contact surfaces of the tracks and the electrodes can be maintained. To that the parallel cuts between the tracks facilitate the transition from the small rolling radius of the rolled-up part to the unrolled part Part of the contact foil.

In Another advantageous embodiment is in the contact foil between the rolled up and the unrolled part across the tracks provided extending cuts. These cuts enable a slight rolling up or facilitate the handling of the rolled up Part of the contact foil and ensure at the same time that the unrolled part is its desired shape maintains. They favor thus in particular the shaping of the transition between the rolled up and the unrolled portion of the contact sheet. It is, however to make sure that the running transversely to the tracks Do not cut cuts in the tracks.

In a further advantageous embodiment, in each case at least one thermocouple is arranged between the contact surfaces of at least two adjacent conductor tracks. Since the signals of the individual cell voltages are forwarded via the contact foil from the electrodes to a terminal unit by means of the conductor tracks anyway, a temperature measurement via the additionally arranged on the contact foil thermocouples can be performed in this way simultaneously, ie integrated with the voltage measurement. In this way, a mass-production-suitable temperature measurement within the fuel cell stack can preferably take place without requiring additional space. The temperature measurement offers the general advantage that unevenness in the temperature image ei Fuel cell stack can be detected. The reaction media and coolant pass through all single cells quasi parallel and thus ensure a fairly similar temperature of the various individual cells, which is usually measured at the coolant entrances and exits. However, this temperature balance is merely a highly integrated measurement that can not represent the problems of particular single cells. There is the danger that either either weak individual cells remain cold or in their coolant flow disabled cells may not be sufficiently cooled and burn. However, with the aid of the local temperature measurement according to the invention on the contact foil, individual cells which do not operate satisfactorily can be identified quickly, since they have a temperature which does not correspond to the general temperature of the fuel cell stack. Preferably, the contact surfaces of the conductor tracks or the thermocouples arranged between them are as close as possible to the active surface of the individual cells. In this way, both the electrical potential and the contact temperature can then be measured at the respective contact point. This can be realized particularly advantageously with the aid of the partially rolled-up variant of the contact foil for introduction into an opening of the fuel cell stack, since a local temperature measurement within the fuel cell stack can then take place there. However, it is also conceivable that the temperature measurement by means of at least one thermal element in the mounting variant of the contact foil, which preferably has on one side tabs for clamping between the bipolar plates of the fuel cell stack is used. In this case, the temperature measurement is then preferably outside of the fuel cell stack. Further preferably, the thermocouples are so small that they can be easily accommodated including their leads between the voltage taps serving conductor tracks on the contact foil. However, it is also conceivable that for accommodating the thermocouples widened portions of the contact foil, for example, tabs or the like, may be provided. Under a "thermocouple" can be understood both an electrical component for generating a thermoelectric voltage and, for example, a temperature-dependent NTC or PTC resistor.

In a further advantageous embodiment, the at least a thermocouple printed on the contact foil. This matches with a simple, inexpensive, production-ready and problem-free manufacturing solution that can be automated with ease Attaching a local temperature measurement option on the fuel cell stack at low weight. In addition, thus, the contact foil as a anyway to be manufactured and installed part without much effort added to another feature become.

In In a further advantageous embodiment, the individual cells of the fuel cell stack as PEM fuel cells with proton exchange membrane educated. PEM fuel cells (PEMFC) do without an electrolyte fluid as a replacement medium for the ions of the reduced fuel between anode and cathode and instead use only a thin membrane film on both sides Electrodes are applied with a catalyst. On both sides The membrane is pressed in each case a bipolar plate, preferably graphite or a graphite fiber fabric. These bipolar plates serve as possible optimal approach and distribution of the two reaction gases to the entire active electrode surface as well for deriving the generated electrical charge and for regulation the removal of the resulting water. Because of its universal Applicability and the simple technique are PEM fuel cells for one industrial use also in the context of mass production preferred.

In In another advantageous embodiment, the single-cell voltages are the fuel cell stack continuously measurable. In this way Thus, the current drain of the fuel cell stack can be controlled be that no harmful Umpoleffekt occurs at any of the individual cells, which, if necessary, fuel shortage at the anode in individual cells a fuel cell stack arise and the wear of membranes and catalyst layers and their carriers can lead.

Usually the measurement of the temperature at the fuel cell stack or at the individual cells in connection with a voltage measurement. However, cases are equally conceivable in which only the temperature should be measured. The measurement of the temperature takes place then alone or separately from any voltage measurement, i.e. independently from the fact whether a voltage measurement is made on the single cells will or not. In these cases can in particular with regard to the design of the contact foil and the other elements used for this purpose on all described inventive principles the voltage measurement used which are then mutatis mutandis for a sole Temperature measurement can be used.

The Invention will be described below with reference to a preferred embodiment explained in more detail. In the associated Drawings show

1 a schematic representation of a preferred embodiment of the device according to the invention in plan view,

2 a schematic representation of the same preferred embodiment of the device according to the invention in the mounted state in a cross-sectional view,

3 a schematic representation of another preferred embodiment of the device according to the invention in plan view,

4 a schematic representation of the same preferred embodiment of the device according to the invention in the mounted state in a cross-sectional view,

5 a schematic representation of another preferred embodiment of the device according to the invention in plan view,

6 a schematic representation of another preferred embodiment of the device according to the invention in plan view,

7 a circuit diagram of a device according to the invention with integrated temperature measurement,

8th a mounting variant of another preferred embodiment of the device according to the invention in an exploded cross-sectional view,

9 a schematic representation of the same preferred embodiment of the device according to the invention in the mounted state in a cross-sectional view,

10 a schematic representation of the same preferred embodiment of the device according to the invention in the assembled state in plan view,

11 a mounting variant of another preferred embodiment of the device according to the invention in an exploded cross-sectional view,

12 a schematic representation of the same preferred embodiment of the device according to the invention in the assembled state in a cross-sectional view and

13 a schematic representation of the same preferred embodiment of the device according to the invention in the assembled state in plan view.

1 schematically shows in plan view a preferred embodiment of a device according to the invention for detecting voltage in a fuel cell stack. This has a contact foil 1 on, for tapping the voltage of the respective single cell of the fuel cell stack (see 2 ) a plurality of conductor tracks 3 are provided, which each have a contact surface 5 having, for electrical contacting of the conductor track 3 associated electrode of the single cell (s. 2 ) is provided. The contact foil has a relatively small thickness (eg, preferably <1 mm) and is also light, flexible and flexible. The tracks 3 are on the contact foil 1 printed. There is the contact foil 1 itself from an electrically non-conductive material, while passing through on one side of the contact foil 1 Printed circuit traces 3 the relevant side of the contact foil 1 partially laminated conductive. The contact foil 1 has stepped tabs on one of its two narrower sides 8th on, taking on each tab 8th one track each 3 at least partially arranged. The tabs 8th arise from the fact that transversely to the outer edge of the contact foil 1 slots 9 are mounted at a defined distance from each other. The contact surface 5 the respective track 3 is on the surface of the tab 8th arranged at the free-standing end. The tracks 3 then run each of the tabs 8th in the longitudinal direction over the contact foil 1 to one at the other end of the contact foil 1 arranged as a connector strip 7 trained connection unit, preferably a fine plug. However, it is also conceivable that on the contact foil 1 instead of the power strip 7 an active logic unit (not shown), for example, an integrated circuit is mounted, through which the measured voltages evaluated and, for example, to a vehicle electronics in already processed form, eg as a CAN signal, passed. In principle, it is also conceivable that the active logic is a multiplexer, from which only one signal output (at n signal inputs) is led out, and the voltage measurement of the individual cells then takes place discretely and in addressed form. The tabs 8th each have a different length and serve as a "finger" for contacting the respective electrodes of the fuel cell stack.The width of a "finger" can be very small, for example, preferably <1 mm. Thus, a large number of interconnects can be 3 or contact surfaces 5 on the contact foil to the various electrodes of the fuel cell stack in a simple manner by means of the tabs 8th to reach and contact. This is schematically in the assembled state in 2 shown. It is preferably a long tab 8th for contacting a more distant (ie in 2 located further above) single cell of the fuel cell stack, while a shorter tab for a closer (ie in 2 further down) cell is provided. In 2 is a partial section of a sandwich-like stacked single cells existing Brennstoffzel lenstapels shown in a cross-sectional view. The individual cells of the fuel cell stack are formed as PEM fuel cells with proton exchange Mebran. These have a membrane membrane formed as a thin membrane membrane 20 on, on the two-sided electrodes, namely one anode each 12 and one cathode each 14 , are applied with a catalyst. On both sides of the electrode-membrane unit 20 each is a bipolar plate 10 pressed, which preferably consists of a graphite fiber fabric. The bipolar plates 10 serve as optimal as possible pre-supply and distribution of the two reaction gases, hydrogen and oxygen, to the entire active electrode surface and to dissipate the generated electrical charge and to regulate the removal of the resulting water. The tabs 8th the contact foil 1 are for contacting the electrode or bipolar plate 10 a single cell each kinkable and on the bipolar plate 10 fixable. The fixation of the tabs 8th at the bipolar plate 10 is done by clamping between two adjacent single cells. Thus, the contact foil must 1 or their tabs 8th are not separately clamped to the individual cells, as they pass through the bipolar plates 10 the individual cells themselves are trapped in their interstices during compression of the fuel cell stack. The tabs 8th Then press with the conductive laminated side, ie the one end of the conductor 3 , on the respective bipolar plate 10 to contact them. The contact foil 1 and with it the tabs 8th have a known thickness, which is the stratification of the bipolar plates 10 and the electrode-membrane units 20 and in particular of possibly in the bipolar plates 10 introduced seals 16 can affect. Preferably, therefore, in the spaces between the bipolar plates 10 protruding tabs 8th the contact foil 1 each in a designated groove 15 inserted, which further preferably with the formed of a flexible mass seal 16 can be completed. The locally increased pressure of the seal 16 in the stack compression then leads to a low and uniform contact resistance of the contact surfaces 5 the tabs 8th to graphite. Preferably, as in the case of the other embodiments illustrated in the figures, the individual cell voltages of the fuel cell stack are continuously measured. Because of fuel dynamics at PEM fuel cells due to their dynamical properties at the anode 12 Under certain circumstances, can come to umpolung individual cells of a stack can be controlled by the continuous single cell voltage measurement, the current drain of the stack so that none of the individual cells in a harmful polarity reversal. Thus, it is attempted not to allow such harmful Umpoleffekte even at first, which otherwise lead to unwanted wear of membranes and the catalyst layers and their carriers.

3 schematically shows a further preferred embodiment of the device according to the invention. in the plan view. This is an embodiment of the contact foil 1 for mounting on the fuel cell stack (see 4 ) does not need to be clamped separately, but only partially rolled up and into a hole 19 (S. 4 ) of the fuel cell stack is introduced and then pressed by their tendency to self-roll with a certain uniform force to the inner wall of the bore and thus to the electrodes of the individual cells. The tracks 3 on the contact foil 1 lead in curved or angled paths from a long side of the contact foil 1 to the power strip 7 , which is located at a preferably arranged at a 90 ° angle to the long side narrow side of the contact foil. The tracks 3 for this purpose have a J-shaped course. In the contact foil 1 are also in the spaces between the tracks 3 provided parallel to these cuts (not shown). By these intermediate cuts, a compensation of the positional tolerances of the fuel cell stack can be improved, which is preferably to a "accordion-like" unfolding of the contact foil 1 leads when the fuel cell stack with the in the hole 19 introduced rolled-up contact foil 1 (S. 4 ) so that, despite the movement, the contacts between the contact surfaces 5 the tracks 3 and the electrodes or bipolar plates 10 can be maintained. In addition, the parallel cuts between the tracks facilitate 3 the transition from the small, in the rolled state inside rolling radius of the rolled-up part 24 on the unrolled part 23 the contact foil 1 (S. 4 ). Furthermore, in the contact foil 1 between the rolled-up part 24 and the unrolled part 23 transverse to the tracks 3 running cuts 22 intended. These cuts 22 allow easy rolling or facilitate the handling of the rolled-up part 24 the contact sheets 1 while ensuring that the unrolled part 23 maintains its desired shape. This is in 4 to recognize in which this embodiment of the device according to the invention in the assembled state is shown schematically in a cross-sectional view. In this case, the individual cells of the fuel cell stack are in turn formed as PEM fuel cells with proton exchange membrane, which is designed as a thin membrane membrane electrode membrane unit 20 have, on the both sides each have an anode 12 and one cathode each 14 with a catalyst and in each case a bipolar plate 10 made of graphite are applied. Furthermore, in the bipolar plates 10 cooling levels 18 be provided. The contact foil 1 is in the 4 shown assembled state partially rolled up and with her rolled up part 24 in the space provided as running transversely to the individual cells bore 19 trained opening introduced in the fuel cell stack, wherein in the rolled-up part 24 the tracks 3 the contact foil 1 with one of the electrodes or one of the bipolar plates 10 a single cell are brought into contact. The contact foil 1 is rolled up so that the tracks 3 on the outer winding transverse to the roll axis 25 run and at a distance corresponding to the distances of the electrodes of the individual cells, are arranged side by side, so that after the introduction of the rolled-up part 24 into the hole 19 of the fuel cell stack each have a contact surface 5 a trace 3 an electrode or bipolar plate 10 touched a single cell. The contact surfaces 5 Then press the conductive coated side of the contact foil 1 , ie the one end of the respective conductor track 3 , on the appropriate bipolar plate 10 to contact them. The contact pressure of the contact surfaces 5 on the bipolar plates 10 is the flexibility and / or the restoring force of the contact foil 1 against bending and the diameter of the hole 19 in the fuel cell stack dependent and constructive freely selectable. The tracks 3 run on the outer winding of the rolled-up part 24 transverse to the roll axis 25 while at the unrolled part 23 the contact foil 1 are already deflected due to their J-shaped course and parallel to the roll axis 25 run where they are the power strip 7 be supplied. Here describe the tracks 3 an approximately 90 ° curved or angled curve. On the outer winding of the rolled-up part 24 run the tracks 3 but not exactly perpendicular to the roll axis 25 , This has the purpose of making the contact surfaces 5 the tracks 3 on the outer surface of the winding with an imprecise positioning of the rolled-up part 24 the contact foil 1 in the hole 19 the fuel cell stack is not exactly between the respective anode 12 and the adjacent cathode 14 can be located, whereby the contact would be prevented. On the other hand, the "slope" of the conductors located in a winding may 3 just be so big that every contact surface 5 or conductor track 3 does not touch two electrodes at the same time and thus generates a short circuit, but if possible only touches an electrode once.

5 schematically shows a further preferred embodiment of the device according to the invention in plan view. It is between the contact surfaces 5 two adjacent tracks 3 a thermocouple 30 arranged. The thermocouple 30 is on the contact foil 1 printed. Since the signals of the single cell voltages anyway on the contact foil 1 from the electrodes by means of the conductor tracks 3 to the power strip 7 and from there possibly to a connection unit (not shown) can be forwarded, in this way simultaneously, ie, integrated with the voltage measurement, a temperature measurement on the additional on the contact foil 1 arranged thermocouple 30 be performed. Preferably, the contact surfaces are in the assembled state (not shown) 5 the tracks 3 or the interposed thermocouple 30 as close as possible to the active area of the single cell (s). In this way, both the electrical potential and the contact temperature can then be measured at the respective contact point. This can be particularly advantageous with the aid of the illustrated variant of the contact foil 1 partially rolled up for assembly and into the hole 19 (see. 4 ) of the fuel cell stack is implemented realize, since there then a local temperature measurement can take place within the fuel cell stack. However, it is equally conceivable that the temperature measurement by means of at least one thermocouple in the mounting variant of the contact foil 1 which latches on one side 3 for clamping between the bipolar plates 10 of the fuel cell stack is applied as shown in FIG 6 is shown. In this case, the temperature measurement is then preferably outside of the fuel cell stack. The thermocouple 30 can be both in one ( 5 ) as well as in the other ( 6 ) Embodiment of the device be designed so small that it, including its leads easily between the tapes serving for voltage tap 3 on the contact foil 1 can be accommodated. In the present case, however, it is shown (by way of example only) that for accommodating the thermocouple 30 widened sections of the contact foil 1 , For example, a greater distance between the tracks 3 ( 5 ) or a widened tab 8a ( 6 ) are provided. 7 shows a contrast diagram of a device according to the invention with integrated temperature measurement, if instead of a thermocouple 30 to generate a thermoelectric voltage several series-connected temperature-dependent resistors 31 (as well as a temperature independent resistor 32 ) can be used to carry out the temperature measurement at the individual measuring points, for example between the potentials of the individual cells, in the process of voltage measurement.

8th . 9 and 10 show schematically a mounting variant of another preferred embodiment of the device according to the invention, both in unmounted ( 8th ) as well as in the assembled state ( 9 and 10 ). At first, there is a retaining clip 35 provided on a contact nose 37 can be postponed and fastened there latching. The retaining clip 35 is doing so flexible and made of an electrically non-conductive material. The contact nose 37 on which the retaining clip 35 can be latched, is part of one of the electrodes or bipolar plates 10 one of the single cells. By snapping the retaining clip 35 on the contact nose 37 the fixation of the contact foil takes place 1 at the electrode of the single cell by clamping. Preferably, the contact film 1 for attaching to the contact nose 37 tabs 8th on. Before snapping on the retaining clip 35 is the contact foil 1 on the contact nose 37 defer and with the contact surfaces 5 the tracks 3 to bring into electrical contact (s. 10 ). At the contact nose 37 is a groove on two opposite sides 38 attached while the retaining clip 35 one with the shape of the groove 38 has corresponding portion to fix the retaining clip 35 and the contact foil 1 in the groove 38 the contact nose 37 to be able to engage. The contact nose 37 is here as at least partially projecting part of the bipolar plate to be contacted 10 formed, on which the retaining clip 35 can be attached.

11 . 12 and 13 schematically show a further mounting variant of a device according to the invention for voltage detection on a fuel cell stack, both in unassembled ( 8th ) as well as in the assembled state ( 9 and 10 ). In this case, a retaining clip which can be clamped to the electrode of one of the individual cells is provided 35 provided, on which, for example, as a conductor 3 trained line is attached to tap the voltage of the single cell.

The retaining clip 35 can on a contact nose 37 be pushed and fastened there latching. The retaining clip 35 is itself flexible and preferably formed of an electrically conductive material or has at least one electrically conductive surface, whereby the electrical contact between the retaining clip 35 and the contact nose 37 can be produced. The contact nose 37 on which the retaining clip 35 can be latched, is part of one of the electrodes or bipolar plates 10 the associated single cell. By snapping the retaining clip 35 on the contact nose 37 the fixation of the retaining clip takes place 35 and thus the electrical contacting of the conductor track 3 at the electrode of the single cell by clamping. It is also conceivable that on the retaining clip 35 for example by means of a solder joint 39 not just a track 3 but a circuit board 40 is attached (s. 12 ). Also the track 3 For example, by means of the solder joint 39 on the retaining clip 35 be attached (s. 13 ). At the contact nose 37 is a groove on two opposite sides 38 attached while the retaining clip 35 one with the shape of the groove 38 has corresponding portion to fix the retaining clip 35 and the associated track 3 and / or circuit board 40 in the groove 38 the contact nose 37 to be able to engage. The contact nose 37 is here as at least partially projecting part of the bipolar plate to be contacted 10 formed, on which the retaining clip 35 can be attached.

1

Contact sheet

3

conductor path

5

contact area

7

power strip

8th, 8a

flap

9

slot

10

bipolar

12

anode

14

cathode

15

groove

16

poetry

18

cooling plane

19

drilling

20

Electrode-membrane unit

22

incision

23

Not rolled up part

24

coiled part

25

roll axis

30

thermocouple

31

temperature-dependent resistance

32

temperature independent resistance

35

retaining clip

37

Contact nose

38

groove

39

soldered point

40

circuit board

Claims (37)

Device for voltage detection on a fuel cell stack, wherein the fuel cell stack comprises a plurality of individual cells and wherein each individual cell is formed with at least two electrodes, via which the voltage of the respective individual cell can be tapped off, characterized in that at least one contact foil ( 1 ) is provided, on which for tapping the voltage of the respective single cell at least two tracks ( 3 ) are provided, which in each case at least one contact surface ( 5 ), which for electrical contacting of the conductor track ( 3 ) associated electrode of the single cell is provided. Apparatus according to claim 1, characterized in that the conductor tracks ( 3 ) on the contact foil ( 1 ) are printed. Device according to one of the preceding claims, characterized in that the contact foil ( 1 ) on at least one side tabs ( 8th ), wherein on each tab ( 8th ) one ladder each train ( 3 ) is at least partially arranged. Device according to claim 3, characterized in that the tabs ( 8th ) each have a different length. Device according to one of claims 3 or 4, characterized in that the tabs ( 8th ) for contacting the at least one electrode of a single cell are each kinkable and fixable to the electrode. Apparatus according to claim 5, characterized in that the fixation of the tabs ( 8th ) takes place at the electrode by clamping between two adjacent single cells. Device according to one of claims 3 to 6, characterized in that the fixation of the tabs ( 8th ) at the electrode of the single cell by clamping by means of at least one retaining clip ( 35 ) he follows. Device according to claim 7, characterized in that the electrode has at least one contact nose ( 37 ), to which the retaining clip ( 35 ) is latched. Device according to one of claims 1 or 2, characterized in that the contact foil ( 1 ) is at least partially rolled up and can be introduced with its rolled-up part into an opening provided for this purpose in the fuel cell stack, wherein in the rolled-up part ( 24 ) the conductor tracks ( 3 ) of the contact foil ( 1 ) can be brought into contact with one electrode of a single cell in each case. Apparatus according to claim 9, characterized in that the conductor tracks ( 3 ) on the contact foil ( 1 ) have an angled and / or hook-shaped and / or J-shaped course. Device according to one of claims 9 or 10, characterized in that in the contact foil ( 1 ) in at least one space between the tracks ( 3 ) is provided parallel to these at least one incision. Device according to one of claims 9 to 11, characterized in that in the contact foil ( 1 ) between the rolled up ( 24 ) and the unrolled part ( 23 ) across the tracks ( 3 ) incisions ( 22 ) are provided. Device according to one of the preceding claims, characterized in that between the contact surfaces ( 5 ) at least two adjacent interconnects ( 3 ) at least one thermocouple ( 30 ) is arranged. Apparatus according to claim 13, characterized in that the at least one thermocouple ( 30 ) on the contact foil ( 1 ) is printed. Device according to one of the claims, characterized characterized in that the individual cells of the fuel cell stack formed as PEM fuel cell with proton exchange Mebran are. Device according to one of the claims, characterized characterized in that the single-cell voltages of the fuel cell stack are continuously measurable. Device, in particular device according to one of claims 1 to 7, for detecting voltage on a fuel cell stack, wherein the fuel cell stack comprises a plurality of individual cells and the voltage tap on at least one individual cell, characterized in that at least one clampable to the electrode of the single cell retaining clip ( 35 ) is provided, to which a line for tapping the voltage of the at least one individual cell is attached. Device according to Claim 17, characterized in that the electrode has at least one contact nose ( 37 ), to which the retaining clip ( 35 ) is latched. Device according to one of claims 17 or 18, characterized that the single cells of the fuel cell stack as PEM fuel cells are formed with proton exchange Mebran. Device according to one of claims 17 to 19, characterized that the single cell voltages of the fuel cell stack continuously are measurable. A method for voltage detection on a fuel cell stack, wherein the fuel cell stack comprises a plurality of individual cells and wherein each individual cell is formed with at least two electrodes, via which the voltage of the respective individual cell is tapped, characterized in that at least one contact foil ( 1 ) is provided, on which for tapping the voltage of the respective single cell at least two tracks ( 3 ) are provided, which in each case at least one contact surface ( 5 ), which for electrical contacting of the conductor track ( 3 ) associated electrode of the single cell is provided. A method according to claim 21, characterized in that the conductor tracks ( 3 ) on the contact foil ( 1 ) are printed. Method according to one of claims 21 or 22, characterized in that the contact foil ( 1 ) on at least one side tabs ( 8th ), wherein on each tab ( 8th ) each a conductor track ( 3 ) is at least partially arranged. Method according to claim 23, characterized in that the tabs ( 8th ) each have a different length. Method according to one of claims 23 or 24, characterized in that the tabs ( 8th ) are each bent for contacting the at least one electrode of a single cell and fixed to the electrode. A method according to claim 25, characterized in that the fixation of the tabs ( 8th ) takes place at the electrode by clamping between two adjacent single cells. Method according to one of claims 23 to 26, characterized in that the fixation of the tabs ( 8th ) at the electrode of the single cell by clamping by means of at least one retaining clip ( 35 ) he follows. Method according to claim 27, characterized in that the electrode has at least one contact nose ( 37 ), to which the retaining clip ( 35 ) is locked. Method according to one of claims 21 or 22, characterized in that the contact foil ( 1 ) at least partially rolled up and with its rolled-up part ( 24 ) is introduced into an opening provided in the fuel cell stack, wherein in the rolled-up part ( 24 ) the conductor tracks ( 3 ) of the contact foil ( 1 ) are brought into contact with one electrode of a single cell. A method according to claim 29, characterized in that the conductor tracks ( 3 ) on the contact foil ( 1 ) have an angled and / or hook-shaped and / or J-shaped course. Method according to one of claims 29 or 30, characterized in that in the contact foil ( 1 ) in at least one space between the tracks ( 3 ) is provided parallel to these at least one incision. Method according to one of claims 29 to 31, characterized in that in the contact foil ( 1 ) between the rolled up ( 24 ) and the unrolled part ( 23 ) across the tracks ( 3 ) incisions ( 22 ) are provided. Method according to one of claims 21 to 32, characterized in that between the contact surfaces ( 5 ) at least two adjacent interconnects ( 3 ) at least one thermocouple ( 30 ) is arranged. A method according to claim 33, characterized in that the at least one thermocouple ( 30 ) on the contact foil ( 1 ) is printed. Method according to one of Claims 21 to 34, characterized that the single cells of the fuel cell stack as PEM fuel cells with proton exchange S are formed. Method according to one of claims 21 to 35, characterized that the single cell voltages of the fuel cell stack continuously be measured. Device for detecting temperature at a fuel cell stack, wherein the fuel cell stack comprises a plurality of individual cells and the temperature is measured on at least one individual cell, characterized in that at least one contact foil ( 1 ) is provided on the at least one thermocouple for measuring the temperature of the respective individual cell ( 30 ) is provided, which is provided for thermal contacting of the single cell.