Apparatus and method for welding half sheets to a bipolar plate
The apparatus and method for welding bipolar plates using a multi-component tool with complementary openings address the challenge of gap formation in thin metal sheets, achieving high-quality, high-speed production of bipolar plates with airtight joints.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2024-04-17
- Publication Date
- 2026-04-14
AI Technical Summary
Existing welding technologies struggle to produce defect-free bipolar plates with thin metal sheets due to gaps forming during the welding process, especially as sheets become thinner, leading to issues like hole formation and reduced process reliability.
An apparatus and method using a multi-component upper tool component with complementary openings for pressurized gas and joining energy, allowing precise alignment and sequential welding of thin half-sheets to form bipolar plates, reducing thermal stress and gaps, and enabling high-quality, continuous production.
The solution ensures high process reliability and precision, reducing welding defects and enabling high-speed production of bipolar plates with airtight joints, even with sheets as thin as 100 μm or less, by minimizing gaps and thermal stress.
Smart Images
Figure 2026512102000001_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to a method for forming a bipolar plate for a stack of electrochemical cells by welding half sheets. Further, the present invention relates to an apparatus suitable for carrying out such a method.
Background Art
[0002] Chinese Patent Application Publication No. 112388166 discloses various apparatuses capable of fixing a bipolar plate during laser welding. Here, a tool system combining a lower tool part and an upper tool part is considered known. In this context, the welding process is carried out from both sides of the bipolar plate through openings in the lower tool part and the upper tool part by two laser units.
[0003] The apparatus described in Chinese Patent No. 113967805 is intended to enable holding a very thin sheet in place during laser welding. This apparatus includes a bottom plate and a plurality of other plates, and the individual components of the apparatus are movably coupled to each other.
[0004] A laser welding apparatus for a separator of a fuel cell made of half sheets is known from Korean Registered Patent No. 10-2241379, but the apparatus has a main block with a recess as a fastening contour. Here, two or more so-called island-shaped blocks are attached to the main block. The main block, i.e., the lower tool part, has an opening leading to the region of the media through-flow openings in the half sheet to be welded. During welding, an inert gas can be fed through these openings. The inert gas is used to reduce or prevent oxidation of the weld seam.
[0005] Korean Patent Publication No. 2013-0025527 describes an apparatus and a method for holding a separator plate for a fuel cell in place during welding, and in this apparatus, a vacuum is used to fix the components.
[0006] Chinese Patent Application Publication No. 108838240 discloses the automated formation and welding of metal bipolar plates constructed according to a "two-plate, three-field" scheme. In this case, resistance welding is proposed as the welding method. Shielding gas is also used.
[0007] When welding metal sheets together during the manufacturing of bipolar plates, the clamping technique employed to press the sheets together without gaps is crucial. A defect-free welding process is only possible when the metal sheets are directly overlapping each other, i.e., there are no gaps between the sheets. Otherwise, if a gap exceeding approximately 10% of the sheet thickness exists between the metal sheets, the molten metal formed during welding will sag, creating holes. Due to weight considerations, the trend in technological development is toward making the sheets thinner, in which case this effect becomes even more pronounced. [Overview of the project] [Problems that the invention aims to solve]
[0008] The present invention is based on providing a possibility for welding bipolar plates for electrochemical systems, which is an advancement compared to the prior art described above, and is characterized in particular by high process reliability and precision. [Means for solving the problem]
[0009] This objective is achieved according to the present invention by an apparatus configured according to claim 1 for welding half sheets of bipolar plates. This objective is also achieved by a method for welding half sheets of bipolar plates as described in claim 7.
[0010] The apparatus for welding half sheets to form a bipolar plate according to the present invention comprises at least three tool components, namely a lower tool component and a multi-component upper tool component, wherein the half sheets to be welded together can be inserted between the lower tool component and the multi-component upper tool component. The multi-component upper tool component comprises a plurality of individual components, which can be arranged sequentially and alternately on the lower tool component, and each individual component of the multi-component upper tool component is formed with both at least one first opening for introducing pressurized gas that can press the half sheets together through it, and at least one second opening for introducing joining energy during the welding process for welding the half sheets. The shapes of the second openings in the individual components of the multi-component upper tool component are configured such that, when viewed perpendicular to the plane of the half sheet, they are largely complementary to each other and overlap only within a region, thereby allowing only a portion of the overall weld to be formed to be generated in each case using the individual components of the multi-component upper tool component.
[0011] Here, "half-sheet" is understood to refer specifically to a thin metal foil having a thickness of 100 μm or less. In its undeformed state or in a three-dimensionally undeformed region, such metal foil is flexible and difficult to handle. Multiple such half-sheets can be welded together to form a bipolar plate, and in particular, two half-sheets can be welded together. However, multiple half-sheets, for example, three half-sheets, can also exist.
[0012] By applying a time delay to the weld seam on a half-sheet, achieved by replacing different individual parts of the upper tool components of multiple parts, thermal stress on the thin half-sheet is locally reduced, improving the overall quality of the weld seam and bipolar plate. The apparatus according to the present invention reduces the occurrence of welding defects such as hole formation and enables the continuous production of large quantities of bipolar plates.
[0013] Lower tool components, which do not have openings, have a relatively simple shape, while upper tool components, which consist of multiple parts, have a much more complex configuration.
[0014] The individual parts of the upper tool component of the multi-parts are located on various first and second openings that serve different purposes.
[0015] Preferably, there are multiple first openings distributed on each individual part to ensure that the half-sheets are pressed together over a wide area.
[0016] The second opening in each individual component allows for the formation of only a portion of the weld seams necessary to form the bipolar plate. This allows the half-sheet configuration to cool again while the individual components are being replaced before the next welding process begins.
[0017] Interchangeable upper tool components of multiple parts can be assigned to a single lower tool component. In this context, the upper tool components of multiple parts are configured such that only the entire set of individual components of each upper tool component, combined with the lower tool component, rather than the individual components of the upper tool component alone, identifies the location of all weld seams connecting the half-sheets to each other.
[0018] In particular, the second opening of the individual parts of the upper tool part of a multi-part system has a V-shaped cross-section that widens away from the lower tool part. This facilitates the welding process.
[0019] In particular, the first individual part and the second individual part together form the upper tool part of a multi-part assembly. However, three or more individual parts can also form the corresponding upper tool part of a multi-part assembly.
[0020] Preferably, the individual upper tool parts of a multi-part system have a second opening and a plurality of raised pressure stamps adjacent to them on the side facing the lower tool part. This creates particularly good contact pressure between the half-sheets, allowing for the formation of a continuous, strong weld seam during the welding process.
[0021] Depending on the geometric configuration of the bipolar plate, one half-sheet or each half-sheet may have a three-dimensional structural modification. The three-dimensional structural modification of the half-sheet is preferably introduced by embossing before the welding process. In this regard, the half-sheets are not necessarily formed to be perfectly mirror-symmetric to one another. This structural modification increases the rigidity of the formed areas of the half-sheet, and therefore makes them easier to handle. Nevertheless, the undeformed areas remain flexible, and the deformed areas are still easily deformable, so these areas can be pressed together by a gas flow.
[0022] The method according to the present invention for welding half sheets to form a bipolar plate using the apparatus according to the present invention assumes that the configuration of half sheets lying on top of each other is welded together by inserting half sheets between a lower tool part and a first individual part of a multi-part upper tool part. Pressurized gas is passed through at least one first opening in the first individual part, thereby pressing the half sheets together, and at the same time, joining energy for welding the half sheets is introduced through at least one second opening located in the first individual part, forming a first portion of the weld seam. The first individual part is then replaced with at least one second individual part of the multi-part upper tool part so as to pass pressurized gas through at least one first opening in at least one second individual part, thereby pressing the half sheets together. At the same time, joining energy for welding the half sheets is introduced through at least one second opening located in the second individual part, forming a further portion of the weld seam.
[0023] This method enables the high-speed and high-quality continuous production of bipolar plates.
[0024] As the pressurized gas, compressed air or an inert gas can be used.
[0025] During the execution of this method, each individual part of the upper tool part of the plurality of parts is pressed against the half sheet and the lower tool part. In particular, the optional pressure stamps of the first individual part and at least one second individual part press the half sheet against the lower tool part.
[0026] This enables the gas flow from at least one first opening to flow along between the individual part and the half sheet adjacent thereto, and in particular to press the existing flexible regions of the half sheet against each other without gaps.
[0027] As the welding method, laser welding can be particularly selected. Depending on the material from which the half sheet is made, different welding methods such as electron beam welding can also be considered.
[0028] Regardless of the material selection and the welding method, the lower tool part can be arranged either on a rigid lower structure or on a rotating table. In the latter case, since the individual parts of the upper tool part of each of the plurality of parts have relatively little mobility, they are provided as substantially stationary components. It is precisely this quasi-static configuration of the individual parts of the upper tool part of the plurality of parts that facilitates the supply of compressed air or gas to these individual parts. The first opening through which the pressurized gas is supplied can be located in any region of the bipolar plate, for example, in the active field and / or the port region.
[0029] The device according to the invention for welding half sheets to form a bipolar plate is suitable for generating an airtight joint between thin half sheets. Such metal sheets are preferably made of steel, preferably stainless steel, or titanium. Here, the sheet thickness, i.e., the thickness of the half sheet, can be 100 μm or less, for example 75 μm or even less. Thus, such half sheets are closer to metal foils. An optional coating can be applied to the half sheets at any time, either before or after welding.
[0030] In either case, by exposing one of the half sheets to compressed air or another pressurized gas, particularly an inert gas, geometric inaccuracies are compensated, whereby during the welding process, the regions of the thin half sheets to be welded together are positioned on top of each other in a state substantially free of gaps.
[0031] According to one possible method variant, a leak test is carried out following welding, and for this test, the same pressurized gas source previously used to press the half sheets against each other can be used.
[0032] Hereinafter, exemplary embodiments of the invention will be described based on the drawings.
Brief Description of the Drawings
[0033] [Figure 1] Shows a device for welding half sheets to form a bipolar plate. [Figure 2] Shows a top view of the shape of the welding seam of a bipolar plate manufactured by the device according to FIGS. 1, 3, and 4. [Figure 3] Shows individual parts of an upper tool part of a plurality of parts each combined with a lower tool part of the device according to FIG. 1. [Figure 4] Shows individual parts of an upper tool part of a plurality of parts each combined with a lower tool part of the device according to FIG. 1.
Embodiments for Carrying out the Invention
[0034] The overall manufacturing system, indicated by reference no. 12, comprises apparatus 5 used for welding half sheets 2 and 3 of bipolar plate 1. Manufacturing system 12 comprises apparatus 5, as well as welding apparatus 13 suitable for welding metal sheets, in the form of a laser of a type known in itself.
[0035] The apparatus 5 comprises a lower tool component 6a and a multi-component upper tool component 6b, which in this case comprises a first individual component 7 and a second individual component 8. During the operation of the manufacturing system 12, the lower tool component 6a is located on a substructure 14, which in this case is a rotary table.
[0036] Even before the half-sheets 2 and 3, made of steel plates, particularly stainless steel, are inserted into the tool or apparatus 5, three-dimensional structural processing 4 is generated on the half-sheets 2 and 3 in an upstream manufacturing process. The structural processing 4 of the half-sheets 2 and 3, in this case embossing, can be carried out using any continuous and / or discontinuous method known in itself. Alternatively, at least part of the formation of the half-sheets 2 and 3 can be carried out using the tool or apparatus 5.
[0037] Structural processing 4 creates a cavity between the half-sheets 2 and 3, through which a coolant—more generally, a heat transfer medium—can flow into the subsequent cell stack, which comprises multiple bipolar plates 1 of the outlined type. Depending on the operating stage of the electrochemical cell stack and ambient conditions, the cell stack may also be heated by the heat transfer medium. In this case, the electrochemical cell stack is, in particular, a fuel cell stack. Alternatively, the electrochemical cell stack can be configured, for example, as an electrolytic cell for producing hydrogen. The working medium of the electrochemical cell flows on the outer surface of the bipolar plates 1 in the subsequent final product, i.e., outside the half-sheets 2 and 3.
[0038] As shown in Figure 1, the lower tool part 6a has a simple shape with no openings intended for supplying pressurized gas or inputting energy during welding. The absence of openings does not apply to holes that may exist, for example, for positioning pins or screw connections. In contrast to the lower tool part 6a, there are multiple first openings 9 in the upper tool part 6b or in the first individual part 7 and the second individual part 8 that can be used for introducing pressurized gas, and multiple second openings 10, 10' of various shapes (see also Figures 3 and 4) that can be used for welding.
[0039] At various positions on individual components 7 and 8 are first openings 9, i.e., holes intended for supplying pressurized gas. The holes located in the central regions of individual components 7 and 8, and thus of the half-sheets 2 and 3, allow for the introduction of pressurized gas, such as compressed air, to form an airflow LS into the active field region behind the bipolar plate 1. On the other hand, holes located further out on individual components 7 and 8 (see Figures 3 and 4) are used to supply pressurized gas to the port region of the bipolar plate 1.
[0040] Overall, the upper half-sheet 2 is pressed against the lower half-sheet 3 by pressurized gas supplied through the first opening 9 into the volume between the respective individual parts 7, 8 and the half-sheet 2, thereby completely or nearly completely eliminating any gaps between the half-sheets 2 and 3 in the area where they are welded together. The pressure on the airflow LS must be selected so as not to cause any undesirable plastic deformation in the half-sheets 2 and 3.
[0041] Each of the individual parts 7, 8 of the upper tool part 6b of the multi-parts has a second opening 10, 10' spatially separated from the described first opening 9, which serves to supply gas, and these openings allow welding of the half sheets 2, 3. In Figure 1, the laser 13 used for welding is directed towards one of the second openings 10 of the first individual part 7 to generate a weld seam 11. Also as can be seen from Figure 1, the second opening 10 that enables welding has a V-shaped cross-section that widens upward, i.e., in the direction of the laser 13. This V-shape is adjusted so that the laser beam is incident obliquely on the workpiece, i.e., the bipolar plate 1, and can converge conically toward a point defined in a focused manner.
[0042] All second openings 10, 10' have a linear slot shape in the simplified example shown in the top view (see Figures 3 and 4), and the subsequent weld seam 11 also has a linear shape. In practice, more complex shapes of weld seam 11 exist. In particular, sections of the weld seam 11 may be curved or oriented at an angle to the outer contours of the half-sheets 2 and 3.
[0043] Figure 2 shows the overall shape of the weld seam 11 connecting the half sheets 2 and 3. Part of this overall shape is predetermined by the shape of the slotted second opening 10 of the first individual part 7, outlined in Figure 3. After a portion of the weld seam 11 has been generated using the first individual part 7, the first individual part is replaced with the second individual part 8. This is achieved by rotating a rotary table having the half sheets 2 and 3 already partially welded beneath the lower tool part 6a and the second individual part 8.
[0044] As the comparison of Figures 3 and 4 shows, the shape of the opening 10' of the second individual part 8 is primarily complementary to the opening 10 of the first individual part 7. The openings 10 and 10' partially overlap. Overall, the continuous application of the two individual parts 7 and 8 results in the overall shape of the weld seam 11, which is recognizable in Figure 2. When replacing individual parts 7 and 8, there are optional fixing means (not shown) that serve to prevent any changes in the position of the half-sheets 2 and 3 or the partially completed bipolar plate 1 during manufacturing.
[0045] Furthermore, a variation of the method can be realized using apparatus 5, in which multiple half-sheets 2, 3 of the same configuration are initially partially welded using the first individual part 6b. After processing a batch of such half-sheets 2, 3, the first individual part 7 is replaced with a different second individual part 8 to complete the welding process. In this case, a positioning contour must be provided on the lower tool part 6a and at least one of the half-sheets 2, 3, to ensure that the half-sheets 2, 3 are positioned in precisely defined locations during each welding process.
[0046] A variation of the method can also be realized in which multiple half-sheets 2, 3 of the same configuration are initially partially welded using the upper tool part 6b of the first multi-part. After processing such a batch, the upper tool part 6b of the first multi-part is replaced with the upper tool part 6b of a different second multi-part, and multiple half-sheets 2, 3 of the same but different configuration are welded using the upper tool part 6b of the second multi-part. In this case, a positioning contour must also be provided on the lower tool part 6a and at least one of the half-sheets 2, 3, to ensure that during each welding process, the half-sheets 2, 3 are positioned at precisely defined locations where different bipolar plates 1 should be formed. [Explanation of Symbols]
[0047] 1 bipolar plate 2 half seats 3 Half Seats 4 Structural processing 5 Equipment 6a Lower tool part 6b Upper tool part of multiple components 7. Individual parts of the upper tool part of multiple parts 8. Individual parts of the upper tool part of multiple parts 9. Air supply opening 10 Welding openings 10' Welding opening 11 Weld seam 12 Manufacturing Systems 13 Welding equipment, laser 14 Undercarriage 15 Side view 16 pressure stamps LS gas flow
Claims
1. An apparatus (5) for welding half sheets (2, 3) to form a bipolar plate (1), comprising at least three tool parts (6, 7, 8), namely a lower tool part (6a) and a multi-part upper tool part (6b), wherein the half sheets (2, 3) to be welded together can be inserted between the lower tool part (6a) and the multi-part upper tool part (6b), the multi-part upper tool part (6b) comprises a plurality of individual parts (7, 8), the plurality of individual parts (7, 8) can be arranged sequentially and alternately on the lower tool part (6a), and each of the individual parts (7, 8) of the multi-part upper tool part (6a) is provided with a mechanism for pushing the half sheets (2, 3) through each other. Apparatus (5) having both at least one first opening (9) for introducing pressurized gas and at least one second opening (10, 10') for introducing joining energy during the welding process for welding the half sheets (2, 3), wherein the shapes of the second openings (10, 10') in the individual parts (7, 8) of the upper tool part (6a) of the plurality of parts are configured to be largely complementary to each other and overlap only within a region when viewed perpendicular to the plane of the half sheets (2, 3), thereby allowing the individual parts (7, 8) of the upper tool part (6a) of the plurality of parts to generate, in each case, only a portion of the overall weld to be formed.
2. The apparatus (5) according to claim 1, characterized in that the second opening (10, 10') has a V-shaped cross-section that widens in the direction away from the lower tool part (6a).
3. The apparatus (5) according to claim 1 or 2, characterized in that multiple interchangeable upper tool parts (6b) can be combined with the lower tool part (6a).
4. The apparatus (5) according to claim 3, characterized in that the entirety of the second opening (10, 10') in the individual parts (7, 8) of the upper tool part (6b) of the plurality of parts identifies the location of all the welding seams (11) for joining the half sheets (2, 3).
5. The apparatus (5) according to any one of claims 1 to 4, characterized in that a first individual part (7) and at least one second individual part (8) together form an upper tool part (6a) of the plurality of parts.
6. The apparatus (5) according to any one of claims 1 to 5, characterized in that the individual parts (7, 8) of the upper tool part (6b) of the plurality of parts have a plurality of raised pressure stamps (16) adjacent to the second opening (10, 10') on the side facing the lower tool part (6a).
7. A method for forming a bipolar plate (1) by welding half sheets (2, 3) using the apparatus (5) according to any one of claims 1 to 6, wherein the configurations of the half sheets (2, 3) lying on each other are welded together, the half sheets (2, 3) are inserted between the lower tool component (6a) and the first individual component (7) of the upper tool component (6b) of the plurality of components, pressurized gas passes through the at least one first opening (9) of the first individual component (7), thereby pressing the half sheets (2, 3) together, and at the same time, the joining energy for welding the half sheets (2, 3) is located at least the first individual component (7) A method wherein pressurized gas is introduced through one second opening (10) to form a first portion of the weld seam (11), and subsequently the first individual part (7) is replaced with at least one second individual part (8) of the upper tool part (6b) of the plurality of parts, pressurized gas is introduced through the at least one first opening (9') of the at least one second individual part (8) to press the half sheets (2, 3) together, and at the same time, joining energy for welding the half sheets (2, 3) is introduced through at least one second opening (10') located in the second individual part (8) to form a further portion of the weld seam (11).
8. The method according to claim 7, characterized in that pressure stamps (16) on the first individual component (7) and the at least one second individual component (8) press the half-sheets (2, 3) against the lower tool component (6a).
9. The method according to claim 8, characterized in that the welding is performed by laser welding.
10. The method according to claim 8, characterized in that the welding is performed by electron beam welding.