DE102015224126B4 - Manufacturing process for a separator plate and a fuel cell system - Google Patents

Abstract

Method for producing a separator plate (14, 14', 14'') for a fuel cell (101, 102, 103, 104), comprising the step: attaching at least one contact element (15, 15', 15'') to the separator plate (14, 14', 14''), the fastening taking place by plastic deformation, at least one crimping area (140, 140', 140'') of the separator plate (14, 14', 14'') being plastically deformed.

Description

The technology disclosed here relates to a manufacturing method of a separator plate and a manufacturing method of a fuel cell system. The technology disclosed here relates in particular to the electrical connection of separator plates of a fuel cell system to a system for monitoring multiple fuel cells.

Such a cell voltage monitoring system (CVM system) usually monitors a large number of fuel cells. The individual fuel cells are usually connected to the CVM system by a cable. There is also a plug out of the DE102007003506 B4 known, which contacts individual separator plates of the fuel cells. The DE 10 2004 028 424 A1 and the GB 2 521 401 A are previously known solutions.

There is a need to connect the many fuel cells to a CVM system in a way that is as cost-effective, fail-safe, fail-safe and/or as space-saving as possible.

It is an object of the technology disclosed here to reduce or eliminate the disadvantages of the previously known solutions. Further tasks arise from the beneficial effects of the technology disclosed here. The task(s) is/are solved by the subject matter of the independent patent claims. The dependent claims represent preferred embodiments.

The technology disclosed herein relates to a manufacturing method for a fuel cell system and a fuel cell system. The fuel cell system includes several fuel cells. The fuel cell system is intended, for example, for mobile applications such as motor vehicles, in particular to provide the energy for the at least one drive machine for moving the motor vehicle. In its simplest form, a fuel cell is an electrochemical energy converter that converts fuel and oxidizers into reaction products, producing electricity and heat. The fuel cell includes an anode and a cathode separated by an ion-selective or ion-permeable separator. The anode has a supply for a fuel to the anode. Preferred fuels are: hydrogen, low molecular weight alcohol, biofuels, or liquefied natural gas. The cathode has, for example, a supply for oxidizing agents. Preferred oxidizing agents include, for example, air, oxygen and peroxides. The ion-selective separator can be designed, for example, as a proton exchange membrane (PEM). A cation-selective polymer electrolyte membrane is preferably used. Examples of materials for such a membrane are: Nation®, Flemion® and Aciplex®. A fuel cell system includes at least one fuel cell and peripheral system components (BOP components) that can be used when operating the at least one fuel cell. As a rule, several fuel cells are combined to form a fuel cell stack. The fuel cell system further includes the separator plate disclosed herein.

The fuel cells of the fuel cell system usually include two separator plates. The ion-selective separator of a fuel cell is usually arranged between two separator plates. One separator plate forms the anode together with the ion-selective separator. The further separator plate arranged on the opposite side of the ion-selective separator forms the cathode together with the ion-selective separator. Gas channels for fuel or oxidizing agents are preferably provided in the separator plates.

The separator plates can be designed as monopolar plates and/or bipolar plates. In other words, a separator plate expediently has two sides, one side forming an anode together with an ion-selective separator and the second side forming a cathode together with a further ion-selective separator of an adjacent fuel cell.

So-called gas diffusion layers or gas diffusion layers (GDL) are usually provided between the ion-selective separators and the separator plates.

The technology disclosed herein includes a method for producing a separator plate for a fuel cell and a separator plate. Further, the technology disclosed herein includes a method of manufacturing the multiple fuel cell fuel cell system disclosed herein. The method for producing a fuel cell system includes the step of producing a plurality of separator plates using the method for producing a separator plate disclosed herein.

The method expediently includes the step: fastening at least one contact element to or on the separator plate, the fastening being carried out by plastic deformation. Fastening is expediently done before assembling the fuel cell or the fuel cell stack.

The contact element is therefore expediently a separate component that is mounted on the separator plate in a further step. The contact element can be attached to the separator plate in particular by crimping.

The person skilled in the art understands crimping as a joining process in which two components are connected to one another through plastic deformation, for example through flanging, squeezing, curling or folding. A crimp connection is usually a non-detachable connection. The requirements for crimp connections are specified in international standards and regulations, for example in DIN EN 60352-2 (issue date 2014-04): solderless connections - Part 2: Crimp connections - general requirements, test methods and application notes, 2) MIL-DTL-22520 (issue date 1997): Crimping Tools, Wire Termination, General Specification, and 3) ECSS-Q- ST-70-26C (issue date 2007-08): Crimping of high-reliability electrical connections.

The separator plate can have at least one crimping area. The crimping area is in particular the plastically deformable area or the plastically deformable component of the separator plate intended for crimping. The method disclosed herein may include the step of plastically deforming the at least one crimp region. Preferably, the at least one crimping region is designed to completely enclose the contact element at least in a partial region of the contact element after crimping.

Furthermore, the method disclosed here can include the step: forming the at least one crimping area, for example by embossing, punching and/or welding. The crimping area is preferably produced at the same time as the media channels. For example, a crimping area can be provided in the original geometry of the separator plate.

The method disclosed here may include the step whereby the at least one crimping region has adjacent partial regions in the plastically deformed state (i.e. after crimping). The adjacent subregions can preferably be connected to one another in a materially bonded manner. Adjacent subareas are expediently designed to be immediately adjacent. For example, there can be partial areas that directly adjoin one another, with a maximum gap being formed between them, which can be closed at least in areas by the cohesive connection. The neighboring subareas can also overlap. Cohesive connections are all connections in which the connection partners are held together by atomic or molecular forces. In particular, they are non-detachable connections that can only be separated by destroying the connecting means. The cohesive connection methods include, for example, soldering, welding and/or gluing. The term “cohesive connection” does not include configurations in which the contact elements are made simultaneously with the separator plate from the same material or from the semi-finished separator plate by forming (e.g. a “separator plate bead”).

The adjacent partial areas are preferably connected to one another in a materially bonded manner using the same tool with which various components of a separator plate are also connected to one another in a materially bonded manner. The different components can in particular be different layers or different separator sheets (usually metal plates with a plate material thickness of less than 5 mm, preferably less than 3 or 1 mm), which are connected to one another in order to form the different media channels. The adjacent partial areas can preferably be connected to one another in a materially bonded manner in the same process step in which the various components of a separator plate are also connected to one another in a materially bonded manner

The fuel cell separator plate disclosed herein may include: at least one contact element and at least one crimp area. The crimping area can be plastically deformed and fix the contact element to the separator plate. The separator plate can also have a cohesive connection, wherein the cohesive connection can connect adjacent portions of the crimp area to one another in the plastically deformed state. Furthermore, the separator plate disclosed here can also include features that are described in more detail in connection with the methods disclosed here.

• a. Ausbilden von mindestens einem Crimpbereich in mindestens einem Separatorblech einer Separatorplatte;
• b. Einlegen und Fixieren der Separatorbleche in einem Werkzeug; und
• c. Verschweißen der Separatorbleche und Verschweißen von elastisch verformten Teilbereichen des Crimpbereiches.

The method disclosed here for producing a separator plate particularly preferably comprises the steps:

• a. Forming at least one crimping area in at least one separator sheet of a separator plate;
• b. Inserting and fixing the separator sheets in a tool; and
• c. Welding of the separator sheets and welding of elastically deformed parts of the crimping area.

Steps a are preferred. to c. in the order shown, with the steps in step c. summarized steps can take place simultaneously or sequentially, preferably with the same Welding device. Furthermore, the method preferably includes the step after which the crimping areas after method step b. are plastically deformed, whereby the contact element is fixed to the separator sheets.

The at least one contact element can be designed as a contact pin or as an electrical line. It is therefore preferably an element that conducts the electrical current well or conducts it better than the other material of the separator plate. The separator plate and the contact element are preferably made from different materials. The contact element can be made, for example, from copper or its alloys. In particular, the contact element can be provided on the separator plate in such a way that the contact element increases the rigidity of the separator plate at least in some areas. The separator plate is preferably made from a metal sheet.

An electrical line can also be referred to as an electrical cable, in particular as a single- or multi-core assembly of wires (individual lines) coated with insulating materials and used to transmit energy and/or information. An electrical line embedded in a flex conductor or flex cable can also be included.

The at least one contact element can have a free end. The free end of the contact element is the end of the contact element that is not attached to the separator plate. In particular, a phase and/or a curve can be provided at the free end. Such a phase and/or rounding can make a plug easier to put on. Furthermore, the risk of the contact pin being deformed when installing a plug can be reduced. It can therefore advantageously be installed more reliably and quickly.

According to the technology disclosed here, the at least one contact element can be attached before assembling the fuel cell, in particular before assembling the fuel cell stack. In other words, first the contact elements are attached to the separator plates and then the components of the fuel cell stack are stacked. The fuel cells can first be created individually and then the individual cells can be layered. The individual fuel cells are preferably only created when the components of the fuel cell stack are brought together. The separator plates and the other components are put together to form a fuel cell stack after the contact element has been fastened to the separator plate. However, bipolar plates are expediently used.

The at least one contact element can in particular be arranged and designed in such a way that the contact element can be connected directly or indirectly to a cell monitoring system. The cell monitoring system (en.: cell voltage monitoring system or CVM system) can be designed to monitor the state of at least one cell. It usually monitors the condition of a large number of fuel cells. In this context, monitoring means that the system can directly or indirectly determine the status of the monitored cells. This means that any degradation or cell failure that occurs can advantageously be detected early on and appropriate countermeasures can be initiated. This can potentially increase the service life to a certain extent and/or increase the performance of the cell as a whole through suitable countermeasures.

Advantageously, at least one measurement variable can be recorded directly or indirectly. The measured variable can in particular be the electrical voltage of the monitored cell. The individual cell voltages of several or all cells as well as the total voltage are advantageously determined. The current flowing through the fuel cell stack is also preferably determined. From the measured voltages, the CVM system can, for example, determine one of the following values: minimum, maximum and average value of the individual cell voltage. Voltage deviations between the individual cells or from an average of the individual cell voltages can thus advantageously be detected. Further single cell analysis methods are preferably carried out, such as an impedance calculation (e.g.: electrochemical impedance spectroscopy).

In particular, the individual, several or all contact elements can be connected to the cell monitoring system after the components have been assembled to form a fuel cell stack. The contact elements make it easier to contact the separator plates. The contact elements can be designed as electrical lines. The free ends of the electrical cables can be held after assembly. A positioning device, for example a type of comb, can be designed to grip or precisely position the individual lines (in particular their free ends). The retained free ends can then be connected directly or indirectly to a cell monitoring system. This means that a simple, fail-safe and cost-effective installation of a CVM system can be advantageously realized. The contact elements can, for example, have a plug element can be connected to the cell monitoring system, the plug element being designed to contact contact elements of different separator plates.

The at least one separator plate preferably has at least one recess. The at least one recess can be arranged and designed in such a way that the at least one recess leaves out an area in which at least one contact element of at least one adjacent separator plate is arranged. At least one contact element of at least one adjacent separator plate can in particular be designed and arranged such that the at least one contact element or the at least one crimping area projects at least partially into the recess. In this context, a recess can also be considered if the separator plate is shortened overall (i.e. recessed over the entire side). The space for contacting the contact pins using a plug element can thus advantageously be increased and/or the required installation space for the fuel cell stack can be reduced.

In other words, the technology disclosed here relates to a method in which, in particular, an edge region of a bipolar plate can be designed as a crimping element. The cable for cell voltage monitoring can be attached directly to this crimping element. This can be designed either at the edge of the bipolar plate structure or in a structure set back from the side edge of the bipolar plate. During production, the crimp contour can be pre-embossed when inserted into the welding tools. The overall closure of the crimp can preferably be done with laser point reinforcement, for example by closing the tool during welding and at the same time adding the cable. The technology disclosed here allows more defined and fail-safe contacts and thus better measurement results. Furthermore, with the method disclosed here, the number of plugs and plug housings (cf. DE102007003506 B4 ) can be significantly reduced. This is accompanied by a significant reduction in the required installation space and weight. In addition, better insulation of the individual components can be achieved.

• 1 eine schematische Seitenansicht des Brennstoffzellenstapels 100;
• 2 eine schematische Draufsicht auf eine Bipolarplatte 14;
• 3 eine schematische Detailansicht einer Bipolarplatte 14;
• 4 eine schematische Detailansicht einer Bipolarplatte 14;
• 5 eine schematische Detailansicht eines Crimpbereichs 140;
• 6 eine schematische Detailansicht eines Crimpbereichs 140; und
• 7 bis 9 verschiedene Ausgestaltungen in einer schematischen Seitenansicht eines Brennstoffzellenstapels 100.

The technology disclosed here will now be explained using the figures. Show it:

• 1 a schematic side view of the fuel cell stack 100;
• 2 a schematic top view of a bipolar plate 14;
• 3 a schematic detailed view of a bipolar plate 14;
• 4 a schematic detailed view of a bipolar plate 14;
• 5 a schematic detailed view of a crimping area 140;
• 6 a schematic detailed view of a crimping area 140; and
• 7 to 9 various embodiments in a schematic side view of a fuel cell stack 100.

The 1 shows schematically a fuel cell stack 100 with a large number of individual cells, of which the individual cells 10 ₁ , 10 ₂ , 10 ₃ , 10 ₄ are shown here as an example. The individual cells are held and biased by two end plates 30. Current collectors 20 are provided adjacent to the end plates 30. The separator plates are designed here as bipolar plates 14, 14 ', 14''. One half of each of two adjacent bipolar plates 14, 14', 14", together with a membrane electrode assembly (MEA) 12, 12', 12" arranged between them, form a single cell 10 ₁ , 10 ₂ , 10 ₃ , 10 ₄ . The bipolar plates shown are connected to a cell monitoring system 400 that is designed to monitor the condition of the individual cells. The contact elements 15, 15 ', 15'' are fastened here to the bipolar plates 14, 14', 14'' and protrude laterally from the plug element 40 shown here in dashed lines. The plug element 40 connects the plug element 40 to a control device 400, for example via a data bus. Instead of one plug element 40, several plug elements 40 can also be provided. For example, clamping elements 42 can be arranged in the plug element 40. The clamping elements 42 can in particular be arranged and designed in such a way that the contact pins 15, 15 ', 15'' can be inserted into these clamping elements, and that the clamping elements 42 clamp the contact pins 15, 15', 15'', thereby creating an electrical contact . In particular, the clamping elements 42 can be designed to be elastically resilient (cf. 6 ). It is also conceivable that the contact elements are connected directly to electronic components of the CVM system. For example, the contact elements could be designed as contact pins that directly contact a circuit board of the CVM system. Contact pins are primarily shown in the figures. The teaching disclosed in connection with these figures is also applicable to designs with electrical lines and should be considered disclosed.

The 2 shows a top view of an anode side of the bipolar plate 14. The fuel supply channel 130, the fuel discharge channel 150, the oxidation supply channel 160, the oxidation discharge channel 180, the coolant supply channel 170 and the coolant discharge channel 190 run perpendicular to the plane of the drawing. These channels could be in the bipolar Plate 14 can also be arranged differently. The seal 17 surrounds the media channels and the flow field and seals the fuel cell from the environment. The contact element 15 protrudes here from the immediately adjacent edge regions R ₁₅ and from the remaining edge R of the bipolar plate 14.

The 3 shows a schematic detailed view of a bipolar plate 14. The bipolar plate 14 includes a crimping area 140. The crimping area 140 is here a part of the sheet metal from which the bipolar plate 14 is formed. The bipolar plate 14 has an immediately adjacent (side) edge R ₁₅ . The crimping area 140 is designed to protrude or protrude relative to both the immediately adjacent edge R ₁₅ and relative to the entire edge R of the bipolar plate side. In particular, the crimping area 140 includes a neck area or web area 144, which extends outwards from the immediately adjacent edge R ₁₅ . However, this neck area does not have to be provided. At the front end of the neck region 144, two laterally extending arms 142, 142 are provided. These arms 142, 142 serve as plastically deformable partial areas 142. These plastically deformable partial areas 142, 142 can be placed around the contact element 15, 15 ', 15'' (cf. 6 and 7 ). However, the crimping area 140 does not have to be designed to protrude relative to the entire side edge of the bipolar plate 14.

The 4 shows a further schematic detailed view of a bipolar plate 14. In the exemplary embodiment shown here, the crimping area 140 is arranged set back. The crimping area 140 is here projecting relative to the immediately adjacent edge R ₁₅ and not projecting relative to the entire edge R of the bipolar plate side. The crimping area 140 is therefore arranged to be mechanically protected before and after the plastic deformation.

The 5 shows an enlarged view of the clamping element 42, which here makes electrically conductive contact with a contact element 15 designed as a contact pin. A curve is provided here at the free end 152 of the contact element 15, which makes it easier to slide on the clamping element 42. The partial areas 142, 142 firmly enclose the contact element 15 and fix it. The partial areas 142, 142 are arranged overlapping here. These overlapping partial areas 142, 142 are particularly preferably connected to one another by a spot weld. A particularly stable connection between the contact element 15 and the bipolar plate 14 can thus advantageously be achieved.

The 6 shows an enlarged view of a contact element 15 designed as an electrical line. The electrical line includes a fixed end 156 which is attached directly to the bipolar plate 14. Furthermore, the electrical line also includes a free end 154 that is not attached to the bipolar plate. The free end 154 is spaced from the fixed end 156 and from the bipolar plate 14 via an insulated line section. This line, which is attached to the bipolar plate 14 before stacking, increases the flexibility in designing the electrical connection to the CVM system 400. After stacking, the individual electrical lines 15 of the individual bipolar plates can be moved into a defined position using an automated positioning device. for example, by placing an isolating element (here a comb K) of the positioning device on the electrical lines immediately adjacent to the edge R of the bipolar plates (the position of the individual electrical lines is defined in this area) and then moving the isolating element K away from the edge R until the free end 154 of the lines is arranged in or immediately adjacent to the separating element K. In this second position, the individual positions of the free ends 152 are well defined. The positioning device can then further fix these free ends 152 to establish an electrical connection to the CVM system, for example by placing a plug element 40 on the free ends 152. Like with that 6 A crimping area 140 with elastically deformed partial areas 142, 142 is also provided here, which fix the electrical line.

The 7 shows schematically a detailed view of an embodiment according to 1 and 2 . Simplifying things have been done with the 7 to 9 the seals 17 are omitted. The contact elements 15, 15', 15'' are dimensioned here such that they can be arranged in the space between two immediately adjacent bipolar plates 14, 14', 14'' without these contact elements causing an electrical short circuit between two immediately adjacent bipolar plates arises. No recesses 18, 18', 18'' are provided here.

The 8th shows schematically a detailed view of a further exemplary embodiment. The recesses 18, 18', 18'' enable the use of larger crimp areas 140 or larger contact elements 15 with approximately the same package. The individual crimping areas 140, 140', 140'' and preferably also the recesses 18, 18', 18'' are arranged offset here in a direction perpendicular to the fuel cell stack longitudinal axis or to the stacking direction Z. The bipolar plate 14 includes a recess 18. This recess 18 can have a certain depth in the Y direction. Furthermore, the recess 18 can also extend over the entire side edge in the Y direction. In other words it is Bipolar plate 18 is then shortened in the X direction compared to the separator plate 14''. Here, the contact elements 15, 15', 15'' and/or the crimping areas 140, 140', 140'' can advantageously protrude into the recesses 18, 18', 18''. Not shown is a further bipolar plate 14'' with the recess 18'' into which the contact element 15' engages. This recess 18'' is not arranged on the edge of the bipolar plate here, but is spaced from the edge between the flow field and the edge.

9 shows a further embodiment in which the contact elements 15, 15" or crimp areas 140, 140" of two immediately adjacent bipolar plates 14, 14" point towards each other and in recesses 18, 18" of the immediately adjacent bipolar plates 14, 14'' intervene. This configuration also enables a compact structure.

The figures above show examples of the technology disclosed here. However, the technology disclosed here is not limited to the specific embodiments shown in the figures. For example, monopolar plates can also be used instead of bipolar plates. The disclosure regarding a bipolar plate is therefore also applicable to a monopolar plate. These two types of plates can be generally referred to as separator plates. If we are talking about a separator plate, this should always include a monopolar plate and also a bipolar plate. In particular, the exemplary embodiments shown can all also be designed with electrical lines. The contact element, the crimping area and the recess can also not be arranged in a corner area, but in a central area of a bipolar plate side. Furthermore, an insulator can be arranged between a contact element and an immediately adjacent separator plate, which is preferably part of a subframe (=means for holding the MEA).

The foregoing description of the present invention is for illustrative purposes only and not for the purpose of limiting the invention. Various changes and modifications are possible within the scope of the invention without departing from the scope of the invention and its equivalents.

Reference symbol list

101, 102, 103, 104

Fuel cell

12, 12', 12''

MEA

14, 14', 14''

Separator plate

15, 15', 15''

Contact element

17

poetry

18, 18', 18''

recess

20

pantograph

30

End plates

40

Connector element

42

Clamping element

100

Fuel cell stack

130

Fuel supply channel

140, 140', 140''

crimping area

142

Sub-area

144

Jetty area

150

Fuel discharge channel

160

Oxidation feed channel

170

Coolant supply channel

180

Oxidation removal channel

190

Coolant discharge channel

152, 154

free ending

156

fixed end

400

Cell monitoring system

R

edge

K

Comb

Claims (11)

Method for producing a separator plate (14, 14', 14'') for a fuel cell (10 ₁ , 10 ₂ , 10 ₃ , 10 ₄ ), comprising the step: attaching at least one contact element (15, 15', 15'' ) on the separator plate (14, 14', 14''), the fastening taking place by plastic deformation, with at least one crimping area (140, 140', 140'') of the separator plate (14, 14', 14'') being plastic is deformed. Procedure according to Claim 1 , further comprising the step: forming the at least one crimping area (140, 140', 140'') by stamping, punching and/or welding. Procedure according to Claim 1 or 2 , wherein the at least one crimping area (140, 140', 140'') has adjacent partial areas (142), and wherein the adjacent partial areas (142) are connected to one another in a materially bonded manner. Procedure according to Claim 3 , wherein the adjacent subregions (142) are materially connected to one another using the same tool with which various components of a separator plate (14, 14 ', 14'') are also materially connected to one another; and/or wherein the adjacent subregions (142) are materially connected to one another in the same process step in which various components of a separator plate (14, 14', 14'') are also materially connected to one another. Method according to one of the preceding claims, wherein the at least one contact element (15, 15', 15'') is a contact pin or an electrical line. Method for producing a fuel cell system with multiple fuel cells, comprising the steps: - Producing a plurality of separator plates (14, 14 ', 14'') using a method according to one of the preceding claims, and - Assembling the separator plates (14, 14', 14'') and other components to form a fuel cell stack (100). Procedure according to Claim 6 , wherein the contact elements (15, 15 ', 15'') are designed as electrical lines, free ends (154) of the electrical lines being held after assembly, and wherein the free ends (154) are directly or indirectly connected to a cell monitoring system ( 400). Procedure according to Claim 6 or 7 , wherein at least one separator plate (14, 14', 14'') has at least one recess (18, 18', 18''), wherein the at least one recess (18, 18', 18'') is arranged and designed in such a way in that the at least one recess (18, 18', 18'') leaves out an area of the separator plate (14, 14', 14'') in which at least one contact element (15, 15', 15'') is at least one adjacent Separator plate (14, 14 ', 14'') is arranged. Procedure according to Claim 8 , wherein the at least one contact element (15, 15', 15'') of the at least one adjacent separator plate (14, 14', 14'') is designed and arranged such that the at least one contact element (15, 15', 15'') at least partially protrudes into the at least one recess (18, 18', 18''). Separator plate (14, 14', 14'') for a fuel cell (10 ₁ , 10 ₂ , 10 ₃ , 10 ₄ ), comprising: - at least one contact element (15, 15', 15''); and - at least one crimping area (140, 140', 140''), wherein the crimping area (140, 140', 140'') is plastically deformed and the contact element (15, 15', 15'') is attached to the separator plate ( 14, 14', 14'') fixed. Separator plate (14, 14 ', 14'') after Claim 10 , further comprising a cohesive connection, wherein the cohesive connection connects adjacent portions (142) of the crimping area (140, 140', 140'') to one another in the plastically deformed state.

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