Separating tool for separating bipolar plates and membrane-electrode assemblies

Abstract

The invention relates to a separating tool (10) for separating bipolar plates (101) and membrane-electrode assemblies in fuel cells of a fuel cell stack (100), the separating tool comprising: a blade body (12) which has a longitudinal axis (16); two blade sections (18, 20) which are arranged opposite one another with respect to the longitudinal axis (16), each blade section (18, 20) having, on the side facing away from the longitudinal axis (16), a boundary edge (24, 26) having at least one edge section (28, 30, 32, 34); and a blade tip (22), wherein the edge sections (28, 30) of the two blade sections (18, 20) that face the blade tip (22) intersect the longitudinal axis (16).

Description

[0001] R. 413779

[0002] - 1 -

[0003] Description

[0004] Separation tool for separating bipolar plates and membrane electrode assemblies

[0005] Technical field

[0006] The invention relates to a separation tool for separating bipolar plates and membrane electrode assemblies in fuel cells of a fuel cell stack, which is characterized in particular in connection with an automated separation of the fuel cells by a particularly safe separation process in which damage to the bipolar plates and the membrane electrode assemblies is avoided.

[0007] State of the art

[0008] Within the framework of alternative drive concepts, hydrogen drives are known, for example, for commercial vehicles that use fuel cell stacks as part of an energy conversion system from chemical to electrical energy. Such fuel cell stacks typically consist of a large number of fuel cells stacked on top of each other. Each fuel cell, in turn, consists of two bipolar plates and a foil-like membrane electrode assembly arranged between the bipolar plates. Flat sealing elements are arranged between the membrane electrode assembly and the bipolar plates, mechanically connecting and sealing these components.

[0009] To be able to replace or recycle the components or parts contained in such fuel cell stacks, for example, at the end of their service life or if individual fuel cells of the stack are damaged, it is necessary to separate the components of the fuel cell stack, which are arranged one above the other and connected to each other in the area of ​​the sealing elements. For this reason, corresponding devices are already known from the prior art. For example, EP 1 478043 A1 and R. 413779

[0010] - 2 -

[0011] On opposite sides of the fuel cell stack, a strip-shaped, wedge-shaped separating tool is inserted, which engages in a gap between two superimposed bipolar plates and separates the bipolar plates by moving the two separating tools against each other. The known separating tool has a length that extends across the entire width of the fuel cells or the aforementioned gap between the bipolar plates.

[0012] Furthermore, US patent 2020 / 0373590 A1 discloses cutting tools acting on opposite sides of the fuel cell stack, which, in plan view, are fork-shaped with two projections or prongs spaced apart from each other.

[0013] Disclosure of the invention

[0014] The separation tool according to the invention for separating cell layers of a cell stack, in particular bipolar plates and membrane electrode assemblies of a cell stack of an electrochemical cell, preferably of a fuel cell stack of a fuel cell, with the features of claim 1, has the advantage that, in particular within the framework of an automated separation of the bipolar plates and membrane electrode assemblies, preferably in conjunction with an image processing system, it enables a particularly safe operation, which avoids damage to the bipolar plates and the membrane electrode assemblies during separation and enables effective, process-reliable and simple separation.

[0015] Furthermore, the invention relates to a separating device for separating cell layers of a cell stack, in particular bipolar plates and membrane electrode units of a cell stack of an electrochemical cell, preferably a fuel cell stack of a fuel cell, with a separating tool according to the type described above and an optical detection unit, in particular a camera system for position detection of the separating tool.

[0016] The invention also relates to the use of a separation tool of the type described above for separating cell layers of a cell stack, in particular bipolar plates and membrane electrode assemblies R. 413779

[0017] - 3 -

[0018] of a cell stack of an electrochemical cell, preferably of a fuel cell stack of a fuel cell.

[0019] The cell layers are preferably bipolar plates and / or membrane electrode assemblies. The cell stack is preferably a cell stack or a fuel cell stack. Within the scope of the present invention, an electrochemical cell comprises, in particular, a fuel cell and / or an electrolysis cell and / or a battery cell. It should be noted that the cell stack can also be that of a cooler or heat exchanger without departing from the scope of the present invention.

[0020] The invention is based on the idea of ​​using an elongated cutting tool, shaped like a knife, to penetrate with its blade body longitudinally at a defined point in a gap between two superimposed bipolar plates of a fuel cell, a gap which is enlarged due to the design of the bipolar plates, and to initially separate them only across a portion of their width. By moving the tool transversely to a longitudinal axis, the resulting gap between the bipolar plates can then be widened and formed across their entire width. The cutting tool thus initially creates a locally confined gap relative to the transverse extent of the bipolar plates. A blade tip formed at an acute angle facilitates the precise penetration of the blade body into the gap between the bipolar plates.

[0021] In light of the above explanations, a separating tool according to the invention for separating bipolar plates and membrane electrode assemblies in fuel cells of a fuel cell stack, comprising the features of claim 1, therefore has a blade body having a longitudinal axis. Two blade sections are provided opposite the longitudinal axis, each blade section having a boundary edge with at least one edge section on the side facing away from the longitudinal axis. Furthermore, a blade tip is provided, wherein the edge sections of the two blade sections facing the blade tip intersect the longitudinal axis and the points of intersection are arranged at a distance from one another, such that one point of intersection forms the blade tip. R. 413779

[0022] - 4 -

[0023] forms, and wherein an acute first angle is formed between the longitudinal axis and the edge section bounding the blade tip.

[0024] Advantageous further developments of the separation tool according to the invention for separating cell layers of a cell stack, in particular bipolar plates and membrane electrode units of a cell stack of an electrochemical cell, preferably of a fuel cell stack of a fuel cell, are listed in the dependent claims.

[0025] To prevent the cutting tool from snagging on the bipolar plates and their membrane electrode assemblies when entering the gap between them, and to allow for a smooth increase in force on the bipolar plates, the aforementioned acute first angle in the area of ​​the blade tip should be as small as possible. In particular, acute first angles between 10° and 30°, preferably 20°, have proven advantageous. This results in the smoothest possible transition between the blade tip area and the area of ​​the blade body adjacent to the blade tip.If, on the other hand, an angle of less than 10° is chosen, there is a risk that the blade tip will be bent perpendicular to the plane of the bipolar plates during the later stages of the separation process as the gap between the two bipolar plates widens due to the movement of the separation tool, because the thickness in the area of ​​the blade tip is too small. If an angle greater than 30° is chosen, precise penetration of the blade tip at the intended location in the fuel cell is only possible with increased force, which would bend and destroy the bipolar plates.

[0026] To enable reliable position detection of the cutting tool using a camera system, it has proven advantageous to design the blade body such that it has a boundary edge aligned with the longitudinal axis between the two intersection points where the edge sections intersect the longitudinal axis. The rationale for this is that when the blade body moves into the cutting gap between the bipolar plates, the cutting tool moves in alignment with the longitudinal axis, and this movement is detected by the aforementioned image processing system in the area of ​​the boundary edge. The edge of the cutting tool is thus designed so that the camera of the R. 413779

[0027] - 5 -

[0028] The image processing system can detect the cutting tool as effectively as possible on the surface composed of the cutting edge and the material thickness of the cutting tool. The edge design of the cutting tool specifically prevents interfering reflections from the surface to be detected, ensuring that the cutting tool is optimally displayed in the camera images and can be detected as effectively as possible by the image processing algorithm.

[0029] Another preferred geometric embodiment of the blade body provides that an acute second angle is formed between the longitudinal axis and the edge section intersecting the longitudinal axis, which is arranged at a distance from the blade tip. This second angle is preferably equal in size to the first acute angle at the blade tip. To prevent the cutting tool from snagging on the bipolar plates and membrane electrode assemblies as it penetrates deeper into the gap between the bipolar plates, and to allow for a smooth increase in force on the bipolar plates, the aforementioned acute second angle in the region of the blade tip is as small as possible. Acute second angles between 10° and 30° have proven particularly advantageous in this regard. This results in the smoothest possible transition between the blade tip region and the rest of the blade body.Additionally, after the cutting blade penetrates the gap while separating the transverse side of a bipolar plate, no additional transverse forces are generated on the blade tip; instead, the transverse forces are introduced onto the more stable construction of the blade body, since the thickness of the cutting tool is significantly greater here than in the area of ​​the blade tip.

[0030] From the two edge sections mentioned so far, which are arranged at acute angles, the blade body transitions into a rectangular sub-area, which is formed or bounded by a further edge section, wherein the further edge sections are arranged parallel to each other, and in particular also parallel to the longitudinal axis.

[0031] To achieve the most optimal force transmission in a direction perpendicular to the plane of the bipolar plates, and to ensure the largest possible tolerances in the (automated) positioning or alignment of the blade body to the gap between the superimposed bipolar plates, see R. 413779.

[0032] - 6 -

[0033] Furthermore, to permit this, it is stipulated that the blade tip, at least in the area of ​​the edge section, must have chamfers extending at an angle to a central plane of the blade body. In particular, the chamfers are symmetrical to the central plane.

[0034] Regarding the dimensioning of the blade body in relation to its thickness, it has proven advantageous if the blade body has a length that is between five and ten times the width of the blade body, wherein the blade body has a thickness between 1mm and 3mm, preferably between 1.5mm and 2mm.

[0035] To achieve the longest possible service life of the blade body or cutting tool, while simultaneously allowing for relatively simple manufacturing, it is advantageous for the blade body to be made from a sheet of steel. This sheet of steel can, for example, be cut from a sheet of metal using a laser cutting process.

[0036] Particularly in connection with camera-based scanning of the area around the cutting edge of the blade body and the surface of the cutting tool, it is advantageous to design the cutting tool with high contrast to the surrounding (illuminated) environment at the bipolar plate disassembly point in the areas relevant for image processing. Therefore, it is planned that at least the aforementioned areas will be darkened through a surface treatment. This can be achieved, for example, with black paint or a similar material.

[0037] To prevent color fading over time, it is particularly advantageous for the blade body to be coated with carbon, which provides the desired black or dark color and thus contrasts with the light surroundings. The carbon coating also ensures exceptional hardness and therefore robustness of the blade body.

[0038] To attach the blade body to a suitable device for moving the cutting tool, it has two through-holes, in particular bores, which are spaced apart from each other when viewed along the longitudinal axis. The cutting tool can be fastened to these two through-holes by screws or similar fasteners. R. 413779

[0039] - 7 -

[0040] They can be shifted and secured against twisting so that forces acting on the cutting tool from different directions can be absorbed.

[0041] Further advantages, features and details of the invention will become apparent from the following description of preferred embodiments of the invention and from the drawings.

[0042] Brief description of the drawings

[0043] Fig. 1 shows a top view of a blade body of a cutting tool,

[0044] Fig. 2 is a perspective view of the blade body according to Fig. 1,

[0045] Fig. 3 shows a section through the blade body in the plane III-III of Fig. 1 and

[0046] Fig. 4 shows a perspective view of a fuel cell stack with fuel cells arranged one above the other, each consisting of two bipolar plates, during the separation of the uppermost bipolar plate using a separation tool designed according to the invention.

[0047] Embodiments of the invention

[0048] Identical elements or elements with the same function are provided with the same reference numbers in the figures.

[0049] Figures 1 and 2 show a separating tool 10 for separating bipolar plates 101 (shown only in Figure 4) and membrane electrode assemblies (not shown in detail in Figure 4) in fuel cells of a fuel cell stack 100. As is known from the prior art, such a fuel cell consists of two bipolar plates 101 with a film-like membrane electrode assembly arranged between them. The membrane electrode assembly is mechanically connected to the respective bipolar plate 101 on both sides via sealing elements and sealed against the bipolar plate 101. R. 413779

[0050] - 8 -

[0051] The cutting tool 10 has a blade body 12 made of metal, in particular steel, which is cut from a sheet metal plate, particularly by means of a laser device. Because the blade body 12 is cut from a sheet metal plate, it typically has a relatively low roughness. Preferably, the entire surface of the blade body 12 is provided with a carbon coating 14, so that the blade body 12 appears dark or black.

[0052] The blade body 12 has a longitudinal axis 16, from which a blade section 18, 20 projects on each side. On the side facing the bipolar plates 101, the blade body 12 has a blade tip 22. The two blade sections 18, 20 each have a boundary edge 24, 26 on the side facing away from the longitudinal axis 16, each with an obliquely arranged edge section 28, 30 and each with a further edge section 32, 34, wherein the two further edge sections 32, 34 are arranged parallel to each other and merge into the edge section 28, 30 on the side facing the blade tip 22.

[0053] Edge section 28 has an acute first angle α with respect to the longitudinal axis 16, and edge section 30 has an acute second angle β with respect to the longitudinal axis 16. Preferably, the two acute angles α and β are of equal size and each measure between 10° and 30°, preferably approximately 20°.

[0054] The two edge sections 28, 30 intersect the longitudinal axis 16 at points 36, 38. These two points of intersection 36, 38 are spaced a distance a apart, which is, for example, approximately 15 mm. Furthermore, the blade section 18 between the point of intersection 38 of the edge section 30, viewed in the direction of the longitudinal axis 16, forms or limits the actual blade tip 22. Between the two points of intersection 36, 38, the blade body 12 has a boundary edge 39 that runs parallel to the longitudinal axis 16 and perpendicular to the plane of Fig. 1.

[0055] As can be seen from Fig. 3, at least the edge section 28, and preferably also the edge section 30 of the blade body 12, is provided with chamfers 40, 42 on both sides, which extend symmetrically to a central plane 43 of the blade body 12. R. 413779

[0056] - 9 -

[0057] The blade body 12 has a length L of, for example, 145 mm and a width B of, for example, 20 mm. Preferably, the length L of the blade body 12 is between five and ten times the width B of the blade body 12. Furthermore, the blade body 12 has a thickness d between 1.0 mm and 3.0 mm, preferably between approximately 1.5 mm and 2.0 mm.

[0058] In the area of ​​the further edge sections 32, 34, the blade body 12 has two through-holes 44, 46 arranged at a distance from each other, aligned with the longitudinal axis 16. These through-holes serve to attach the blade body 12 or the cutting tool 10 to a device (not shown) that allows the blade body 12 to be fed forward along the longitudinal axis 16, i.e., in the direction of feed as indicated by arrow 48, during the separation of the bipolar plates 101, and also enables height adjustment relative to the bipolar plates 101. The feed direction is aligned with the plane of the blade body 12.

[0059] Fig. 4 shows the fuel cell stack 100 with the plurality of bipolar plates 101 arranged one above the other and connected to each other by sealing elements with the membrane electrode unit in between.

[0060] In particular, a semicircular indentation 103 can be seen in an edge region 102 of the bipolar plates 101 facing the blade body 12. In the area of ​​this indentation 103, the two superimposed bipolar plates 101 of a fuel cell have a separation gap 105 of, for example, approximately 3.0 mm, which makes it possible to insert the separation tool 10 into the separation gap 105 and, when inserted in the direction of arrow 48, to partially separate the connected bipolar plates 101 from each other. Further separation of the bipolar plates 101 occurs when the separation tool 10, after being inserted between the bipolar plates 101, is moved back and forth in a transverse direction perpendicular to the direction of arrow 48, as indicated by the double arrow 50. Simultaneously, the membrane electrode assembly of the fuel cell located below the upper bipolar plate 101 is also separated from the upper bipolar plate 101.After the upper bipolar plate 101 has been separated or removed, the separation process between the membrane electrode assembly remaining on the lower bipolar plate 101 and the lower bipolar plate 101 of the fuel cell is repeated using the separation tool 10 to separate the membrane electrode assembly of the fuel cell. R. 413779.

[0061] - 10 -

[0062] The separation processes are then repeated, so that a bipolar plate 101 and a membrane electrode unit are separated alternately.

[0063] The separating tool 10 described so far can be modified or adapted in a variety of ways without deviating from the inventive concept.

Claims

R. 413779 - 11 - Claims 1. Separating tool (10) for separating cell layers (101) of a cell stack (100), in particular bipolar plates (101) and membrane electrode assemblies of a cell stack (100) of an electrochemical cell, preferably of a fuel cell stack (100) of a fuel cell, comprising a blade body (12) having a longitudinal axis (16), with two blade sections (18, 20) arranged opposite the longitudinal axis (16), wherein each blade section (18, 20) has a boundary edge (24, 26) on the side facing away from the longitudinal axis (16), each with at least one edge section (28, 30, 32, 34), with a blade tip (22), wherein the edge sections (28, 30) of the two blade sections (18, 20) facing the blade tip (22) intersect the longitudinal axis (16) and the points of intersection (36, 38) have a distance (a) from each other, such that one intersection point (36) limits the blade tip (22),and wherein an acute first angle (a) is formed between the longitudinal axis (16) and the edge section (28) bounding the blade tip (22).

2. T cutting tool according to claim 1 , characterized by that the acute first angle (a) is between 10° and 30°.

3. Separating tool according to claim 1 or 2, characterized by that the blade body (12) has a boundary edge (39) that runs in alignment with the longitudinal axis (16) between the two points of intersection (36, 38).

4. Separating tool according to one of claims 1 to 3, characterized by that an acute second angle (ß) is formed between the longitudinal axis (16) and the edge section (30) which is arranged at a distance from the blade tip (22) and which intersects the longitudinal axis (16), and which is preferably equal in size to the acute first angle (a). R. 413779 - 12 - 5. Separating tool according to one of claims 1 to 4, characterized by that the two blade sections (18, 20) each have a further edge section (32, 34) on the side facing away from the blade tip (22), wherein the two further edge sections (32, 34) are arranged parallel to each other, in particular also parallel to the longitudinal axis (16).

6. Separating tool according to one of claims 1 to 5, characterized by that the blade tip (22) has chamfers (40, 42) extending at an angle to a central plane (43) of the blade body (12), at least in the area of ​​the edge section (28).

7. T cutting tool according to claim 6, characterized by that the chamfers (40, 42) are symmetrical to the median plane (43).

8. Separating tool according to one of claims 1 to 7, characterized by that the blade body (12) has a length (L) which is between five and ten times the width (B) of the blade body (12), and that the blade body (12) has a thickness (d) between greater than or equal to 1 mm and less than or equal to 3 mm, preferably between greater than or equal to 1.5 mm and less than or equal to 2 mm.

9. Separating tool according to one of claims 1 to 8, characterized by that the blade body (12) is made of a sheet of steel.

10. Separating tool according to one of claims 1 to 9, characterized by that the blade body (12) is dark at least in some areas, especially in the area of ​​the blade tip (22). R. 413779 - 13 - 11. T cutting tool according to claim 9 or 10, characterized by that the blade body (12) is provided with a carbon coating (14).

12. Separating tool according to one of claims 1 to 11, characterized by that the blade body (12) has two through openings (44, 46), in particular bores, which are arranged at a distance from each other when viewed in the direction of the longitudinal axis (16).

13. Separation device for separating cell layers (101) of a cell stack (100), in particular bipolar plates (101) and membrane electrode units of a cell stack (100) of an electrochemical cell, preferably of a fuel cell stack (100) of a fuel cell, comprising a separation tool (10) according to one of claims 1 to 12 and an optical detection unit, in particular a camera system for position detection of the separation tool (10).

14. Use of a separation tool (10) according to one of claims 1 to 12 for separating cell layers (101) of a cell stack (100), in particular bipolar plates (101) and membrane electrode assemblies of a cell stack (100) of an electrochemical cell, preferably of a fuel cell stack (100) of a fuel cell.

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