EP3149796A2

EP3149796A2 - Fuel cell housing

Info

Publication number: EP3149796A2
Application number: EP15722354.6A
Authority: EP
Inventors: Andreas Buchner; Johannes Schmid; Lukas WITTCHEN; Maximilian Zettl
Original assignee: Bayerische Motoren Werke AG
Current assignee: Bayerische Motoren Werke AG
Priority date: 2014-05-28
Filing date: 2015-04-28
Publication date: 2017-04-05
Also published as: CN106104893B; WO2015180914A2; WO2015180914A3; DE102014210262A1; CN106104893A; US20170077542A1

Abstract

The invention relates to a fuel cell housing. Said fuel cell housing comprises at least one portion that has at least three layers, including a first, outward-facing layer designed as an electrically conductive layer, a second layer for absorbing mechanical forces and as a penetration shield, and a third layer designed as a high voltage-insulating, hydrogen-insulating layer.

Description

fuel cell case

description

The present invention relates to a highly functional, space-optimized and weight-reduced fuel cell housing.

A fuel cell housing is used in a fuel cell system to accommodate fuel cells combined to form a stack. Due to safety considerations, the enclosure must be designed to prevent the escape of reactant gases and not crack or otherwise suffer damage under mechanical stress, such as impact or impact, which compromises the functionality or safety of the fuel cell system. As described for example in DE 1 496 1 10, the fuel cell housing is therefore usually formed of metal. Also, a construction of ceramic is possible, which thus additionally acts electrically insulating, so that can be dispensed with a separate layer for electrical insulation, which is achieved in metal housings by providing a large air gap between the fuel cell and the housing. A disadvantage of conventional fuel cell housings is their high weight and a space inefficient design.

Based on this prior art, it is therefore an object of the present invention to provide a fuel cell housing, which is characterized by high functionality with reduced weight and space optimized design.

The object is achieved in a fuel cell housing according to the invention in that it comprises at least one section which is multi-layered and has at least three layers. As such a section, for example, a side surface or a bottom surface is in question, which has the specific multi-layer structure according to the invention. However, it is also possible to characterize a plurality of surfaces of the fuel cell housing or also the entire fuel cell housing by the multilayer structure according to the invention. In any case, at least one section has a layer structure comprising at least three layers, namely, a first outward-facing layer, a second layer, and a third layer, the second layer and the third layer being arranged in relation to the first Layer can vary. The layers fulfill different functions and can each be configured as a single layer or even as a multilayer arrangement.

The first, so the outermost layer of the fuel cell housing, which communicates with an environment of the fuel cell housing is formed as an electrically conductive layer and is used to ground the fuel cell and as electromagnetic compatibility shielding or as a way to detect in case of insulation failure. An intervention in the interior of the fuel cell housing is thereby prevented and errors can be detected. The second layer serves to absorb mechanical forces, for example by deformation, and as penetration protection. The provision of the penetration protection prevents the penetration of objects or other components by manipulation or in the event of a crash, and the formation of a leakage point. The fuel cells thus remain unaffected in form, arrangement and function and the safety of the system is guaranteed. The third layer is designed as a high-voltage insulating and hydrogen-insulating layer. Largely by them, the requirements for electrical safety, in particular a dielectric strength and creepage distance guaranteed. Due to the high-voltage insulation, the individual fuel cells are also insulated from each other and it is also an insulation compared to the housing achieved, so that on insulating air gaps in favor of the smallest possible volume of the fuel cell housing can be dispensed with. The additional, compared to hydrogen insulating function of the third layer, the reliability of the fuel cell is increased. The provision of both functionalities in the third layer can be done very well by different, in particular polymeric coatings.

Due to the multilayer layer structure of at least a portion of the fuel cell housing according to the invention, the required, very complex functionality of the housing is divided into several individual layers, so that an individual adaptation of the layers in shape and function, taking into account a space-saving design and thus a reduced volume of space as possible low weight, takes place. The combination of differently structured functional layers thus also combines the advantageous properties of the individual layers and exploits synergies with each other. The requirements for contact protection, such as e.g. according to ISO 20654, are thus very well met. Likewise, the multi-layer structure fulfills the requirements placed on a housing with high-voltage insulating layer, namely protection against breakdown of e.g. 2500V and thus in particular a sufficient creepage distance (see DIN 60644), an air gap (see DIN 60664) and a conductivity of about 50 Ω. The fuel cell housing offers not least because of its acting as ground first layer high contact protection, protection in case of failure and thus high application security, but is characterized by the hydrogen-insulating function and mechanical stability of the second and third layer generally in the event of a crash by a high reliability ,

The dependent claims contain advantageous developments and refinements of the invention. For further weight reduction with at the same time very good electrical insulating properties, the first layer comprises nets and / or fibers and / or films of conductive materials, such as aluminum or steel or conductive polymers. Due to the very high stability even against corrosion, the use of a copper mesh is particularly preferred. Since connections or transitions should be provided on a housing, which allows an electrical or other connection of the fuel cell housing or the components contained therein, it is further advantageously provided with regard to a further weight reduction and space savings that the first layer and / or the second Layer connections and / or fittings for fixing the fuel cell housing or for fastening other components or components or for media management includes. This is particularly well implemented due to the electrical conductivity of the first layer. Connections and the like can be taken into account, for example, even in the manufacturing process of the fuel cell housing, for example by providing feedthroughs sealed by injection molding or media guides that are integrated directly into the first layer of the housing. In particular, an external manifold can also be imaged by the housing itself via the media tightness. Thus, at least a portion of the housing according to the invention takes on an additional, media-feeding or laxative function and thus increases the overall functionality of the housing with further weight savings for separate components. Further advantageously, the fact that the electrically conductive first layer is present on the outside of the housing, a simple contact, for example, be made by screwing. Also sockets may be integrated into the first layer or connected to the first layer. As a result, the fuel cell housing according to the invention is simple and stable installable.

To an even better stability against mechanical action and in particular against clamping forces, such as those acting in the tension of the fuel cell stack with the housing, operating loads or crash loads, and also to implement a tertiary Explosion protection, the second layer is formed of at least two individual layers, namely a reinforcing layer for receiving mechanical forces and a penetration protection layer for providing the penetration protection. In order to image both functions in one layer, the second layer would have to be very solid, for example made of a metal sheet, whereby a high weight is introduced into the fuel cell system. This can be prevented by the splitting of the second layer into two individual layers with different functional emphasis. Due to the very good mechanical stability with low weight, the reinforcing layer is preferably formed from a fiber composite material. According to the invention, the fiber composite material comprises at least one fiber material and at least one matrix material, it also being possible for mixtures of different fiber materials and also matrix materials to be used. The fibrous material is preferably present as a textile semifinished product, that is to say in particular as a woven fabric, scrim, knitted fabric, knitted fabric, braid and the like. The use of a fiber composite material also has the advantage that due to the manufacturing process of the fiber composite material, the first layer can be partially integrated with the matrix material of the fiber composite material. If, for example, a copper mesh is used in the first layer, the matrix material of the reinforcing layer can flow around the same and stably bind it after curing. The use of carbon fiber material in the fiber composite material has been found to be particularly advantageous in view of a high stability with minimized weight.

Due to the excellent resistance to cracking when exposed to articles, the penetration-resistant layer is preferably formed of Kevlar or metal. Kevlar is particularly well-suited for the production of the penetration protection layer because of its own weight, which is many times lower than that of metal. To further reduce the installation space of the fuel cell housing, the third layer is formed from at least two individual layers, a high-voltage insulation layer and a hydrogen insulation layer. The provision of a high-voltage insulation layer makes it possible to arrange the fuel cell housing directly around the fuel cell stack without providing, as is conventional in the art, an air-isolated space which prevents electrical attack from the fuel cells to the housing. Since hydrogen is a small molecule that penetrates many materials unhindered, the provision of a hydrogen isolation layer separately is advantageous from the standpoint of maximum hydrogen retention capacity with minimal weight input.

The high-voltage insulation layer preferably contains non-conductive polymers and / or glass fibers for reasons of weight reduction. The hydrogen insulation layer advantageously comprises a metal layer and / or a polymer layer. The polymer layer may consist exclusively of one or more polymers or further contain a fibrous material. These materials are characterized by a high density against hydrogen. For reasons of weight and also for reasons of cost, a polymer layer is preferred over a metal layer. On the other hand, metal layers for hydrogen insulation can be easily produced by electroplating.

The further inside the hydrogen insulation layer lies in the housing structure, the fewer layers must be protected against the influence of hydrogen, and here in particular against embrittlement. The hydrogen insulation layer is therefore preferably an innermost layer or a second innermost layer.

Alternatively, the high-voltage insulation layer is preferably a layer which points into the interior of the housing, since a necessary distance between the electrical components and the housing can be further reduced as a result. moreover It is thus very easy to provide connections and / or screw connections for fastening the components of the fuel cell housing or for fastening further components or for guiding the media. The high-voltage insulation layer is preferably formed from a glass fiber layer and / or from a polymer layer.

Due to the advantageous development that the second layer contains conductive materials, in particular conductive polymers, carbon fibers, carbon nanotubes, metal fibers and mixtures thereof, the second layer can support a current dissipation of the first layer, especially in fault currents.

To increase the operational safety of the fuel cell housing, this advantageously comprises at least one further hydrogen-absorbing or hydrogen-converting layer. This further layer can bind hydrogen either physically or chemically or convert it by means of a catalyst.

In order to avoid short circuits inside the fuel cell housing by water condensation drop formation, a surface of the innermost layer is modified so as to substantially prevent dripping of condensed water. This is possible, for example, by hydrophilizing the inner surface. A contact angle of a water droplet formed by condensation is smaller due to the increased hydrophilicity, so that a thin film of water instead of water droplets is formed whose layer thickness is so low that an electric spark skip is prevented. Due to the solutions according to the invention and their developments, the following advantages result:

The fuel cell housing meets with reduced weight all the requirements for a reliable housing.

- The fuel cell housing is space-saving. - Tying functions, connections and transitions can be integrated into the fuel line housing.

- Electrical short circuits are prevented.

- Hydrogen leakage is effectively prevented.

- Explosion protection can be integrated.

Weather details, features and advantages of the invention will become apparent from the following description and the figures. Show it:

FIG. 1 shows a multilayered section of a fuel cell housing according to a first development of the invention,

FIG. 2 shows a multilayer section of a fuel cell housing according to a second development of the invention,

FIG. 3 shows a multilayer section of a fuel cell housing according to a third development of the invention.

FIG. 4 shows a multilayer section of a fuel cell housing according to a fourth development of the invention.

FIG. 5 shows a multilayer section of a fuel line housing according to a fifth development of the invention.

The present invention will be illustrated in detail by way of embodiments. Only the areas of interest of the fuel cell housing according to the invention are shown here. All other components are omitted for clarity, tn the figures number the same reference numerals like layers / components.

FIG. 1 schematically shows a three-layer structure of a section of a fuel cell housing 10. This layer structure thus comprises a minimum number of individual layers. A first, outwardly facing layer 1, is formed as an electrically conductive layer, the grounding of the Fuel cell serves and thus is able to implement also a touch protection and an electromagnetic compatibility shielding. The first layer 1 preferably comprises nets and / or fibers and / or films of conductive materials, and in particular a copper mesh. Advantageously, the first layer may comprise connections and screw connections for fastening the fuel cell housing or for fastening further components.

A second layer 2 shown in FIG. 1 as a middle layer is designed for receiving mechanical forces and as penetration protection and acts as a reinforcing or supporting layer that can absorb tensioning forces, discharge operating loads or crash loads and implement tertiary explosion protection. The second layer 2 advantageously comprises conductive materials, e.g. conductive polymers, carbon fibers, carbon nanotubes, metal fibers, and mixtures thereof.

Furthermore, the section of the fuel cell housing 10 according to the invention shown in FIG. 1 comprises a third layer 3, which points into the interior of the housing 10 and is designed as a high-voltage insulating layer that is insulated from hydrogen.

In particular, a surface of the third layer 3 pointing into the interior of the housing 10 is modified in such a way that it essentially does not permit the formation of droplets of condensed water and is in particular hydrophilized for this purpose.

FIG. 2 shows a second embodiment of the fuel cell housing 20 according to the invention. In contrast to FIG. 1, the third layer is split into two individual layers 3a, 3b. Single layer 3a is formed as a hydrogen insulating layer and is in particular made of a metal layer and / or a polymer layer. The inwardly facing single layer 3b is formed as a high-voltage insulation layer and preferably contains non-conductive polymers and / or glass fibers.

FIG. 3 shows a third embodiment of the invention. The multi-layered section of the fuel cell housing 30 shown in FIG. 3 differs from that of FIG. 1 in that the second layer is split into two individual layers 2 a, 2 b. Single layer 2a is formed as a penetration protection layer and contains in particular Kevlar or metal. Single layer 2b is formed as a reinforcing layer for receiving mechanical forces and in particular comprises at least one fiber material and at least one matrix material. The fiber material is preferably a carbon fiber material and is present in particular in the form of a textile semi-finished fiber product.

Other layers, such as a hydrogen-absorbing or hydrogen-converting layer, may supplement the fuel cell housing structures shown in FIGS. 1 to 3.

Figures 4 and 5 show further preferred embodiments of a multilayer portion of the invention

Fuel cell housing 40, 50. Here, in each case a first layer 1 by a copper mesh, so a mesh-like or reticulated copper layer is formed. Due to the high conductivity of copper, the first layer 1 is very suitable for earthing the housing. The copper mesh is integrated into a reinforcing layer 2b formed in the form of a carbon fiber reinforced plastic (CFRP). The copper mesh has entered into an intimate, cohesive connection with the resin material of the CFRP. This contributes to the stabilization of the reinforcing layer 2b and thus to the reinforcement of the housing.

The second layer 2 further comprises a penetration protection layer 2a formed of Kevlar. According to FIG. 4, the Keviar layer is adjoined by a hydrogen insulation layer 3a formed as a polymer layer, which is surrounded on its exposed side by glass fibers as a high-voltage insulation layer 3b. Due to their liquid-crystal structure, the glass fibers provide a good high-voltage insulation which, depending on the polymer used in the polymer layer, can still be improved.

FIG. 5 differs in the third layer 3 from FIG. 4. According to FIG. 5, this comprises only a polymer layer as the third layer 3, which is designed to be insulating both as a high-voltage insulation layer and against hydrogen. The high-voltage insulation can be improved by increasing the layer thickness of the polymer layer.

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.

LIST OF REFERENCE NUMBERS

1 first shift

2 second layer

3 third layer

2a penetration protection layer

2b reinforcement layer

3a hydrogen isolation layer

3b high-voltage insulation layer

10 fuel cell housing

20 fuel cell housing

30 fuel cell housing

40 fuel cell housing

50 fuel cell housing

Claims

claims:

1. A fuel cell housing comprising at least one at least three-layer section with a first, outwardly facing layer (1), which is formed as an electrically conductive layer, a second layer (2) for receiving mechanical forces and as a penetration protection and a third layer (3) , which is designed as a high-voltage insulating and hydrogen-insulating layer.

2. Fuel cell housing according to claim 1, characterized in that the first layer (1) nets and / or fibers and / or films of conductive materials, and in particular a Kupfermesh comprises.

3. Fuel cell housing according to claim 1 or 2, characterized in that the first layer (1) and / or the second layer (2) connections and / or fittings for fixing the fuel cell housing (10, 20, 30, 40, 50) and for attachment of other components or for media management includes.

4. Fuel cell housing according to one of the preceding claims, characterized in that the second layer (2) is formed from at least two individual layers, a reinforcing layer (2b) for receiving mechanical forces and a penetration protection layer (2a) for providing the penetration protection.

5. Fuel cell housing according to claim 4, characterized in that the reinforcing layer (2b) comprises a fiber composite material, comprising at least one fiber material and at least one matrix material, wherein the fiber material in particular a Carbon fiber material and / or wherein the fiber material is present in particular as a textile semifinished product.

6. Fuel cell housing according to claim 4 or 5, characterized in that the penetration-protection layer (2a) made of Kevlar or metal, in particular Kevlar, is formed.

7. Fuel cell housing according to one of the preceding claims, characterized in that the third layer (3) is formed from at least two individual layers, a high-voltage insulation layer (3b) and a hydrogen insulation layer (3a).

8. Fuel cell housing according to claim 7, characterized in that the hydrogen insulation layer (3a) is formed by a metal layer and / or a polymer layer.

9. Fuel cell housing according to claim 7 or 8, characterized in that the high-voltage insulation layer (3b) contains non-conductive polymers and / or glass fibers.

10. Fuel cell housing according to one of claims 7 to 9, characterized in that the high-voltage insulation layer (3b) is a pointing into the interior of the housing layer.

11. Fuel cell housing according to one of the preceding claims, characterized in that the second layer (2) is capable of conductivity

Contains materials, in particular conductive polymers, carbon fibers, carbon nanotubes, metal fibers and mixtures thereof and / or characterized in that the fuel cell housing comprises at least one further hydrogen-absorbing or hydrogen-converting layer and / or characterized in that a

Surface of the innermost layer is modified so that it allows essentially no dripping of condensation.