DE102010048761B4 - A method of fabricating a bipolar plate for a fuel cell stack and bipolar plate - Google Patents

Abstract

Method for manufacturing a bipolar plate for a fuel cell stack, in which a semifinished product is formed into an inner part (3) to be coupled to a frame part (2) of the bipolar plate, wherein a plurality of channels (4) are introduced into the inner part (3) which an electrode of a membrane electrode assembly of the fuel cell can be acted upon by a reactant, characterized in that the frame part (2), which surrounds the inner part (3) on the outer peripheral side, and the inner part (3) of the bipolar plate by forming each of a metallic Semi-finished are formed, wherein for forming the frame part (2) and the inner part (3) from the respective semi-finished different forming processes (10, 17) are used, wherein the frame part (2) with the inner part (3) for forming a cathode side plate (1) the bipolar plate is connected, wherein an anode-side sub-plate with the cathode-side sub-plate (1) of the bipolar plate ver is bound, and wherein a frame portion and an inner portion of the anode-side sub-plate are formed in the same forming process of a semifinished product.

Description

The invention relates to a method for manufacturing a bipolar plate for a fuel cell stack, in which a semifinished product is formed into an inner part to be coupled to a frame part of the bipolar plate. In the inner part, a plurality of channels is introduced in the forming process, via which an electrode of a membrane electrode assembly of the fuel cell can be acted upon by a reactant. Furthermore, the invention relates to a bipolar plate for a fuel cell stack.

From the generic DE 102 61 482 A1 a bipolar plate is known which comprises an inner part designed as a metal insert. Channels are formed by the metal insert part, via which, during operation of the fuel cell, a cathode or an anode of a membrane-electrode arrangement is charged with the respective reaction gas. An edge region of the metal insert has no channels and is enclosed in a frame of the bipolar plate, which is formed as an injection molded part. In the formed of a metal sheet with a corrosion-protective coating metal insert the necessary for the gas distribution and cooling structures are produced by a non-cutting forming of the steel sheet.

A disadvantage of such a multipart, namely a frame part and an inner part having bipolar plate is the fact that the production of this bipolar plate is relatively complex.

The US 5 981 098 A describes a flow field plate having a first part and a second part in which respective flow channels for reactants are formed. A surface having straight sections of the flow channels and two strips having end regions of the flow channels may be formed by separate components of the respective part.

Object of the present invention is therefore to provide a method of the type mentioned, which allows a particularly simple and inexpensive production of a bipolar plate, and a corresponding bipolar plate.

This object is achieved by a method having the features of patent claim 1 and by a bipolar plate having the features of patent claim 8. Advantageous embodiments with expedient developments of the invention are specified in the dependent claims.

In the method according to the invention for manufacturing a bipolar plate for a fuel cell stack, a semifinished product is formed into an inner part, which can be coupled to a frame part of the bipolar plate. During forming, a plurality of channels are introduced into the inner part, which serve to act upon an electrode of a membrane electrode assembly of the fuel cell with a reactant. Here, the frame part, which surrounds the inner part on the outer peripheral side, and the inner part of the bipolar plate are formed by forming from a respective metallic semifinished product, and for forming the frame part and the inner part of the respective semi-finished different forming processes are used. In a method known from the prior art, in which the frame part and the inner part are integrally formed and formed in a common forming process, namely the shaping process limits are set. In the present case, however, for the respective part of the bipolar plate to the shaping that forming method can be used, which is particularly well matched to the function to be performed by the part in the bipolar plate. In particular, in the shaping of the channels of the inner part, a forming process can be used, which is solely focused on the optimal design of the channels and does not need to take into account the shape of the frame part at the same time. As a result, it is possible, for example, to produce particularly deep and particularly narrow channels, which would not be obtainable from the same metallic semi-finished product while simultaneously forming structures in the region of the frame part.

The frame part is connected to the inner part to form a cathode-side partial plate of the bipolar plate. In the case of the cathode-side partial plate, it is advantageous to provide particularly deep and narrow channels in the inner part, and this can be achieved particularly well if the inner part is formed separately from the frame part in a shaping process adapted to the desired shaping from the semifinished product.

To form the bipolar plate, an anode-side partial plate is connected to the cathode-side partial plate of the bipolar plate. In this case, it is advantageous that a frame region and an inner region of the anode-side partial plate are formed from a semifinished product in the same forming process. In the case of the one-piece anode-side sub-panel, only channels of lesser depth need to be provided in the interior, so that one and the same forming method can also be used both for forming the channels in the interior region of the anode-side sub-panel and for reshaping the frame area.

Characterized in that for forming the frame part and the inner part of the metallic semifinished product In each case different forming methods are used, the functionalities of these parts can be exploited to a large extent. In addition, the production is particularly simple and inexpensive. By using specific forming processes for the frame part and the inner part, a particularly efficient bipolar plate can thus be produced. This leads to a particularly high efficiency of the fuel cell stack. Internal parts with a channel structure which is particularly favorable for the distribution of the fuel or of the oxidizing agent namely allow a particularly favorable distribution of the reactants in the region of the membrane-electrode arrangement of the fuel cell having the bipolar plate. Due to the high efficiency of the fuel cell stack, a lightweight construction can be realized, which is particularly advantageous when the fuel cell stack is to be used in a vehicle.

Cost savings also result from the fact that leading to a high efficiency of the fuel cell individual components bring high energy densities of the respective fuel cell with it. Since each forming process needs to be adapted to the shape of only a part of the bipolar plate, a respective simple and thus robust process technology can be used in the respective forming process, which also leads to cost savings. In addition, conventionally available process techniques can be used in the shaping of the frame part and the inner part, whereby highly complex designs, in particular of the inner part, can also be realized. In addition, the forming processes selected for the functionality of each part allow short cycle times to be achieved during production.

In an advantageous embodiment of the invention, the channels are introduced into the at least one inner part by bending the associated semifinished product. Such a deformation of the semifinished product for the inner part allows the introduction of channels in the same, without a local weakening of the inner part is to be feared at a comparatively large channel depth.

It has been found to be advantageous if the channels are introduced into the at least one inner part by roll forming or forming rolls of the associated semi-finished product. During roll forming, the semifinished product passes through a series of forming stations in which respective pairs of rolls gradually bend the semifinished product into the desired profile shape. In the form of rolling the semi-finished product is conveyed between two counter-rotating rollers, wherein intermeshing outer contours of the rollers determine the shape of the semifinished product to be achieved. These forming processes make it possible to form deeper and narrower channels in the inner part than would be possible by a stamping process. Such deep and narrow channels are particularly advantageous with regard to the electrochemical conversion of the reactants of the membrane-electrode assembly.

In a further advantageous embodiment of the invention, the frame part is formed in a progressive compound process from the associated semi-finished product. In the progressive compound process at least two tool modules are arranged in a tool, which each provide for a processing step of the semifinished product. For example, through a first tool module in the semi-finished viewfinder holes are introduced, which allow the subsequent recording of the frame part. In a further step of the follow-on composite process, a cutout of a basic shape can take place from the semifinished product, in which the later frame part is only connected to the remaining semifinished product at a few connection regions. Then impressions can be made, for example to form bulges of the frame part in the area later applied to this seals. Further, passages for media, such as the reactants or a coolant, can be formed in the frame member in the progressive compound process. Such a progressive compound process allows a particularly favorable and rapid manufacturing of the frame part.

It is also advantageous if the semifinished product for the inner part and / or the frame part is unrolled from a roll and provided for the respective forming process. Thus, a particularly efficient production of the bipolar plate can be realized. The reshaping of the inner part and of the frame part can be preceded by a straightening process in which the rolled semi-finished product is straightened. Then it can be reshaped with a particularly great precision.

In a further advantageous embodiment of the invention, the reshaped inner part and / or the frame part are separated out of the respective semi-finished product. Then the two, their final shape having parts available for a joining process in which they can be clamped together, glued, welded or soldered. In particular, the jamming to form a frictional connection and / or a positive connection of the two parts with each other allows a particularly rapid, cost-effective production of the bipolar plate.

An advantageous embodiment of the method with regard to the handling of remainders of the semifinished product can be achieved if a waste of the semifinished product for the inner part and / or for the frame part is wound onto a roll. It then no container or the like needs to be provided to receive the waste, but after manufacturing the inner part and the frame part, it is located on a respective roll that can be easily returned to a supplier.

Advantageously, the frame region, which corresponds to the frame part in the case of the two-part partial plate, and the inner region, which corresponds to the inner part in the case of the two-part partial plate, are formed from the semifinished product in the case of the anode-side partial plate in a progressive composite process.

In the bipolar plate according to the invention for a fuel cell stack, a frame part of the bipolar plate is mechanically coupled to an inner part. The inner part has a plurality of channels, via which an electrode of a membrane electrode assembly of the fuel cell can be acted upon by a reactant. In this case, the frame part, which surrounds the inner part on the outer peripheral side, and the inner part of the bipolar plate are formed from the respective metallic semi-finished product by mutually different forming methods. The frame part is connected to the inner part for forming a cathode-side partial plate of the bipolar plate. An anode-side partial plate is connected to the cathode-side partial plate of the bipolar plate. A frame region and an inner region of the anode-side sub-plate are formed from a semi-finished product in the same forming process.

The advantages and preferred embodiments described for the method according to the invention also apply to the bipolar plate according to the invention.

• 1 in einer schematischen Draufsicht eine kathodenseitige Teilplatte einer Bipolarplatte für einen Brennstoffzellenstapel, bei welcher ein Kanäle für das Oxidationsmittel aufweisendes Innenteil separat von einem Rahmenteil der Teilplatte gefertigt ist;
• 2 schematisch in einer Draufsicht einen Ausschnitt des noch nicht mit dem Innenteil versehenen Rahmenteils gemäß 1;
• 3 schematisch in einer Draufsicht einen Ausschnitt des Innenteils gemäß 1; und
• 4 Verfahrensschritte beim Fertigen der kathodenseitigen Teilplatte.

Further advantages, features and details of the invention will become apparent from the claims, the following description of preferred embodiments and from the drawings. Showing:

• 1 in a schematic plan view of a cathode-side partial plate of a bipolar plate for a fuel cell stack, in which a channels for the oxidant exhibiting inner part is made separately from a frame part of the partial plate;
• 2 schematically in a plan view a section of not yet provided with the inner part frame part according to 1 ;
• 3 schematically in a plan view of a section of the inner part according to 1 ; and
• 4 Process steps in the manufacture of the cathode-side partial plate.

1 shows schematically and in a plan view of a cathode-side partial plate 1 a bipolar plate for a fuel cell stack. The partial plate 1 is composed of two parts, namely a frame part 2 which is an interior part 3 Outside circumference surrounds, and the inner part 3 , In alternative embodiments, in such a multipart sub-plate 1 also the frame part 2 and the inner part 3 be formed of several individual parts.

The inner part 3 the cathode-side partial plate 1 has channels 4 on, through which during operation of the fuel cell, the oxidizing agent, for example, air or oxygen, flows. The channels 4 form a channel structure, which is also referred to as a flow field, and ensure a uniform distribution of the oxidizing agent in the region of a cathode (not shown) of a membrane electrode assembly of the fuel cell. In the frame part 2 are passages 5 . 5 ' . 6 . 6 ' . 7 . 7 ' provided via which the supply and removal of media takes place. This is how the passage is used 5 supplying a fuel, such as hydrogen, to the flow field of the inner part of an anode-side sub-plate (not shown) and the opposite passage 5 ' the removal of unused fuel. The passage 6 serves to supply the oxidizing agent to the channels 4 the cathode-side inner part 3 and the passage 6 ' the removal of the oxidizing agent.

To form a bipolar plate, the cathode-side sub-plate 1 and the complementary, anode-side sub-plate coupled to each other, so that a cavity is formed on the respectively mutually facing surfaces of the sub-plates. Due to the structure of the flow field, this consists of a system of several interconnected tunnels. The cavity or system of the tunnels is essentially through the partial plates 1 in the edge region circumferential edge liquid-tight edged, passing over the passage 7 Coolant introduced into the cavity and over the passage 7 ' the coolant is removed.

In peripheral areas 8th . 9 of the inner part 3 are the inner part 3 and the frame part 2 connected with each other. Preferably, the joining of the two parts takes place by jamming of the inner part 3 with the frame part 2 , In addition, by applying an adhesive, the fixing of the inner part 3 on the frame part 2 get supported. The inner part 3 can on the frame part 2 be held positively and / or positively.

2 shows part of the frame part 2 before its joining with the in 3 shown inner part 3 , In the present case are the frame part 2 and the inner part 3 each formed from a metallic semi-finished, wherein the shape of the frame part 2 another forming method is used than for shaping the inner part 3 , In the inner part 3 namely the channels 4 introduced by bending of the metallic semifinished product. Especially deep and narrow channels 4 can be in the inner part 3 the cathode-side partial plate 1 bring in, when the associated semi-finished by molding 10 (see. 4 ) is transformed. However, the desired channels can be left 4 Roll form also in a shape which ensures a particularly efficient loading of the cathode with the oxidizing agent.

Based on 4 should finish 11 of the inner part 3 and finishing 12 of the frame part 2 be illustrated. In a first step 13 becomes a respective role of the semifinished product for the frame part 2 and the inner part 3 provided. In one step 14 the semi-finished product is unwound from the respective role and straightened in a straightening process. Then the actual forming of the functional areas of the inner part takes place 3 or the forming of the frame part 2 , In the inner part 3 become the channels 4 introduced by the semifinished the forming process of the form rolling 10 is subjected. Here, a feed of the directed semi-finished product between at least two counter-rotating rollers, which have outer peripheral side structures, whose shape is the later shape of the channels 4 in the inner part 3 pretends. The structures of the counter-rotating rollers engage each other and thus provide a bending load of the directed and rolled from the roll semifinished product.

Alternatively, the introduction of the channels 4 in the at least one inner part 3 done by roll forming the associated semifinished product. In a next step 15 a reshaped portion of the semifinished product is cut out of this, so that the channels 4 having inner part 3 for a subsequent joining process 16 is available. The waste of the semifinished product is wound up on a roll so that it can be disposed of in a particularly easy way.

When finished 12 of the frame part 2 takes place after the step 14 the unrolling and straightening of the semi-finished product, the mechanical forming in a follow-on composite process 17 , Here, a tool, namely a so-called progressive tool, a plurality of tool modules, which make different processing steps on the semifinished product. First, finder holes are introduced into the semifinished product, which accommodates the finished frame part 2 enable. In another tool module, a free cut of the future frame part takes place 2 , which is then only in a few narrow areas with the waste of unused semi-finished product in connection. In the cut semi-finished structures are introduced or cut in other tool modules structures. So can in a border area 18 of the frame part 2 (see. 2 ) a bead are impressed, by which a bearing surface is provided for a sealing element. Furthermore, in the follow-on composite process 17 the passages 5 . 6 . 7 created as well as the central area of the frame part 2 for the following picture of the inner part 3 designed. Subsequently, when finished 12 of the frame part 2 a cut out 19 of the frame part 2 , which then for the joining process 16 is available. Also when finished 12 of the frame part 2 For example, the waste of the semifinished product is preferably wound onto a roll.

The cathode-side partial plate 1 is thus constructed in two parts, and in this two-part construction, the inner part 3 separately from the frame part 2 and in one on the design of the channels 4 transformed forming process. On the other hand, in the manufacture of the anode-side partial plate, an inner region having the channels and an edge region having the passages can be shaped together, for example in a progressive compound process 17 , in which when impressing the structures in the frame area and the impressing of the channels 4 takes place in the interior. The channels 4 namely, in the interior of the anode-side sub-plate may have a smaller depth than the channels 4 the cathode-side inner part 3 ,

However, in alternative embodiments, also in the anode-side sub-plate, a separate manufacturing of the inner part 3 and the frame part 2 be provided, especially if the design of the channels 4 a forming process which is particularly suitable for the desired shaping can be considered meaningful.

Claims (8)

Method for manufacturing a bipolar plate for a fuel cell stack, in which a semifinished product is formed into an inner part (3) to be coupled to a frame part (2) of the bipolar plate, wherein a plurality of channels (4) are introduced into the inner part (3) which an electrode of a membrane electrode assembly of the fuel cell can be acted upon by a reactant, characterized in that the frame part (2), which surrounds the inner part (3) on the outer peripheral side, and the inner part (3) of the bipolar plate by forming each of a metallic Semi-finished are formed, wherein for forming the frame part (2) and the inner part (3) from the respective semi-finished different forming processes (10, 17) are used, wherein the frame part (2) with the inner part (3) for forming a cathode side plate (1) the bipolar plate wherein an anode-side sub-plate is connected to the cathode-side sub-plate (1) of the bipolar plate, and wherein a frame portion and an inner portion of the anode-side sub-plate are formed from a semifinished product in the same forming method. Method according to Claim 1 , characterized in that the channels (4) are introduced into the at least one inner part (3) by bending load (10) of the associated semi-finished product. Method according to Claim 2 , characterized in that the channels (4) are introduced into the at least one inner part (3) by roll forming or forming rollers (10) of the associated semi-finished product. Method according to one of Claims 1 to 3 , characterized in that the frame part (2) is formed in a progressive compound process (17) from the associated semi-finished product. Method according to one of Claims 1 to 4 , characterized in that the semifinished product for the inner part (3) and / or the frame part (2) is unrolled from a roll and, in particular after a straightening process (14), for the respective forming process (10, 17) is provided. Method according to one of Claims 1 to 5 , characterized in that the formed inner part (3) and / or frame part (2) are separated out of the respective semi-finished product. Method according to one of Claims 1 to 6 , characterized in that a waste of the semifinished product for the inner part (3) and / or for the frame part (2) is wound up on a roll. A bipolar plate for a fuel cell stack, wherein a frame part (2) of the bipolar plate is coupled to an inner part (3), the inner part (3) having a plurality of channels (4) over which an electrode of a membrane electrode assembly of the fuel cell can be acted upon with a reactant, characterized in that the frame part (2), which surrounds the inner part (3) on the outer peripheral side, and the inner part (3) of the bipolar plate from a respective metallic semifinished product by different forming processes (10, 17) are formed, wherein the frame part (2) is connected to the inner part (3) for forming a cathode-side sub-plate (1) of the bipolar plate, wherein an anode-side sub-plate is connected to the cathode-side sub-plate (1) of the bipolar plate, and wherein a frame portion and an inner portion of the anode-side Partial plate in the same forming process are formed from a semi-finished product.

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