Apparatus and method for assembling a cell stack

Abstract

A device for assembling a cell stack (7), in particular a fuel cell stack, comprises a processing device (2), which comprises a gripper (6) and a positioning and pressure system (10), which is designed to compress the partially completed cell stack (7). The positioning and pressing system (10) comprises a lifting device (11) arranged to accommodate the cell stack (7) in any production stage and a transverse fixing device (12) located above the lifting device (11), the transverse fixing device consisting of a plurality of components (13, 14), wherein the components (13, 14) are provided for bearing against the cell stack (7) in vertical and horizontal directions and can be adjusted and fixed in both directions.

Description

Summary of the Invention

[0001] The present invention relates to a method for assembling a cell stack, in particular an electrochemical cell stack, such as a fuel cell stack, and also to a device suitable for carrying out the assembly method. Background Art

[0002] DE 10 2016 220 173 A1 discloses an assembly device for stacking fuel cell stacks. This assembly device is used to vertically stack fuel cell stacks composed of alternating membrane electrode units (MEUs) and bipolar plates. The known assembly device has a generally rectangular assembly space defined by a plurality of vertically oriented support rods. These support rods are horizontally movable and serve to position the MEUs and bipolar plates relative to each other during the stacking process.

[0003] DE 10 2017 100 362 A1 discloses a system for assembling and compressing a fuel cell stack. The system includes a fuel cell stack housing and a press having a plurality of press rods for compressing the fuel cell stack, which is formed by stacking fuel cell components layer by layer in the fuel cell stack housing.

[0004] DE 10 2015 220 399 A1 describes a device for automatically stacking fuel cell stacks. The device includes a rotatable pressure element configured to apply pressure to the stacked fuel cells. The device also aims to detect defective components and test the stack for tightness.

[0005] Different compression systems for fuel cell stacks are described in DE 10 2020 127 917 A1 and DE 10 2021 112 699 A1. In these cases, tensioning straps or strip-shaped holding devices connected to the stack end plates are provided for compressing the fuel cell stack.

[0006] DE 10 2018 119 633 A1 proposes a package for assembling a fuel cell stack, which prestresses and seals the fuel cell components in the stacking direction of the fuel cells.

[0007] The fuel cell stack assembly device described in DE 20 2020 105 427 U1 includes a magnetic assembly component that extends perpendicularly to the base of the assembly device and attracts a plurality of fuel cell units. In this case, the magnetic assembly component engages with notches or grooves of the fuel cell elements.

[0008] A device described in US 2020 / 0091542 A1 uses a robot to handle solar panels. In this case, the aim is to enable the orientation of the battery components to be detected with the help of sensors.

[0009] Other devices and methods for processing components of electrochemical systems are known from documents CN 207265167 U, CN 107706438 A and CN 113036200 A. In the latter case, adhesive elements are provided to hold the compressed cell stack together. Summary of the Invention

[0011] The object of the present invention is to achieve an improvement in the production of cell stacks, in particular fuel cell stacks, compared to the above-mentioned prior art, wherein a particularly favorable balance is sought between assembly effort and process reliability.

[0012] According to the invention, this object is achieved by a device suitable for assembling a cell stack, in particular an electrochemical cell stack, having the features of claim 1. This object is also achieved by a method for assembling a cell stack, in particular a fuel cell stack, in accordance with claim 8. The embodiments and advantages of the invention described below with respect to the assembly method also apply mutatis mutandis to the assembly device, and vice versa.

[0013] The device provided for assembling the battery stack comprises a handling device comprising a gripper suitable for lifting flat objects, for example in the form of a vacuum gripper, or a plurality of such grippers, and a positioning and pressure system cooperating with the gripper or grippers, the positioning and pressure system being designed to compress the partially completed battery stack. In this context, the term compression does not necessarily mean that the vertical dimensions of the battery stack are significantly reduced at any point in time. In any case, the battery stack to be built is aligned vertically, which is equivalent to the horizontal alignment of the flat components of the battery stack to be stacked layer by layer. The horizontal position of the battery components facilitates the high-speed construction of the stack.

[0014] The positioning and pressure system comprises a lifting device designed to accommodate a cell stack at any stage of production, and a transverse securing device located above the lifting device. The transverse securing device is designed to bear against the cell stack in both vertical and horizontal directions and can be adjusted in various ways in these directions and secured as needed. The securing device comprises several components that act on different locations of the cell stack.

[0015] For example, two such assemblies are provided, wherein the first and the second assembly are arranged mirror-symmetrically to one another next to the cell stack, i.e., surround the cell stack from both sides. Designs are also possible in which the fastening device is composed of three, four, or more similar or different assemblies. The at least two assemblies can be adjusted simultaneously or independently of one another, and the two assemblies are preferably positioned in a symmetrical arrangement.

[0016] The battery stack is held in shape by applying pressure during the formation process, rather than after completion, thanks to a fixture consisting of multiple components. This, combined with the horizontal alignment of the battery components, facilitates both high-cadence assembly and high geometric precision. Specifically, compression of the battery stack during assembly prevents the components from sliding within the stack.

[0017] According to a first possible design, each of the two or more components of the integral multi-part fixture of the assembly device includes a plurality of horizontally movable fixture elements, which are configured to support the bipolar plates disposed one above the other and included in the cell stack in both the lateral and vertical directions. In this case, vertical support means introducing vertically acting forces into the cell stack.

[0018] For example, three or more fastening elements arranged one above the other, each intended to contact a bipolar plate, are supported in a shared, horizontally and vertically adjustable receptacle in an individually spring-loaded manner. The adjustable receptacle can be assigned a single clamping device designed to simultaneously tighten or release all fastening elements located in the receptacle when necessary.

[0019] In addition to the horizontally movable fixing elements, a switchable membrane electrode assembly (MEA) holder is optionally also provided. This MEA holder is designed to hold down the top membrane electrode assembly (MEA) in the partially completed cell stack. If a bipolar plate is placed on the MEA, the MEA holder is deactivated.

[0020] According to a second set of possible designs, the transverse components of the fixing device each have an angular circumferential clamp against which the cell stack rests laterally and simultaneously upwards. This significantly simplifies the assembly device compared to the first set of possible designs. This configuration is particularly well-suited to situations where the bipolar plates bend during assembly, as will be explained in more detail below.

[0021] In each of two possible design options, a lifting device for accommodating a cell stack can have three plates arranged parallel to one another: a bottom plate, a middle plate, and an upper plate intended to support the cell stack. In this case, a pressure measurement system can be provided between the bottom plate and the middle plate, while the upper plate is supported vertically displaceably on the middle plate by means of springs. In particular, the two lower plates can be perforated in any manner as long as the intended support function is achieved.

[0022] Optionally, a distance measuring device is provided, which is designed to measure the distance between the upper plate and the middle plate. If the properties of the spring are known, the distance measuring device can also be used for pressure measurement, thus providing redundancy in the force measurement together with the pressure measuring system arranged below on the bottom plate.

[0023] The method for assembling a cell stack is characterized in that the cell stack under construction, comprising bipolar plates and membrane electrode assemblies arranged horizontally and parallel to one another, is subjected to pressure during its formation. This is achieved by applying downward pressure to the cell stack, which is not yet complete at this production stage, after each additional bipolar plate is placed (in addition to the weight of the cell assemblies). The cell stack as a whole is pressed downward by this pressure, wherein the springs supporting the cell stack located below the cell stack are compressed, a process known as over-pressing. After over-pressing has occurred during the assembly of the cell stack, the vertically downward pressure is reduced so that the cell stack is slightly lifted again by the springs. Finally, in the subsequent state in which the springs are at least partially expanded, at least the bipolar plate located at the top is fixed in the vertical and transverse directions while maintaining a component of the downward pressure.

[0024] The springs that are compressed during over-pressing can be arranged in the aforementioned manner between the height-adjustable plates, for example, in the form of coil springs or leaf springs. Pneumatic supports can also be used. In all cases, the lifting system that enables height adjustment of the plates can be used to readjust the force measurement, the length measurement, or a combination of force and geometric measurements.

[0025] A first method variant provides for the bipolar plates and the membrane electrode assemblies to be placed alternately on the cell stack in a completely flat position.

[0026] According to an alternative method variant, at least the bipolar plate is placed in a bent state onto the cell stack while a vertical downward force is applied, wherein first a central area of ​​the bipolar plate is pressed onto the cell stack and then, while maintaining the pressure, the entire bipolar plate is brought into contact with the cell stack while being transformed into its original flat shape.

[0027] One advantage of the present invention is in particular that the cell stack, that is to say the pile, is continuously compressed during its formation. This advantage applies regardless of the type of cell involved, such as a fuel cell or an electrolysis cell. There is no need to tilt the stack during assembly. Depending on the design of the positioning and pressure system, which prevents the stack assembly from sliding during assembly, the stack assembly can be aligned not only with its external geometry, but also with structures located further inside, such as the active fields. Assembling the components in their final alignment is particularly advantageous in cases where the stack assembly can no longer be easily moved for adjustment later. For example, the subsequent adjustability may be limited due to the presence of seals in the cell stack, such as silicone seals. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The following describes several embodiments of the present invention in detail with reference to the accompanying drawings. Herein, they are roughly schematically shown:

[0029] Figure 1 A first embodiment of an apparatus for assembling an electrochemical cell stack is shown.

[0030] Figure 2 A schematic sectional view of a second exemplary embodiment of a device for assembling a cell stack is shown in a first operating state.

[0031] Figure 3 Shown according to Figure 2 The assembly device is in the second operating state. DETAILED DESCRIPTION

[0032] Unless otherwise stated, the following description applies to both exemplary embodiments. Components that correspond to one another or that function in principle in the same manner are denoted by the same reference numerals in all figures.

[0033] The production plant, generally designated by reference numeral 1, is designed as an apparatus for assembling a cell stack 7 (i.e., a fuel cell stack). The production plant 1, i.e., the assembly apparatus, comprises a handling device 2 for lifting and positioning the flat fuel cell assembly to be assembled. The handling device 2 comprises a support element 3 and a movable element 4, wherein the movable element 4 may be the arm of an articulated-arm robot (not further illustrated). The handling device 2 may also, in a manner not illustrated, include a movable element 4 that is only linearly movable.

[0034] The elements 3, 4 support a gripper 6 of a known design in principle, such as a vacuum gripper. Alternatively, the gripper 6 can utilize other physical principles, such as adhesion or magnetism. Figure 1 shown in, but also appears in accordance with Figure 2 and Figure 3 The position detection system 5 in the embodiment of the present invention is designed to detect the positioning of the object relative to the vacuum gripper 6. In a manner not shown, in addition to Figure 1In addition to the position detection system 5 shown, a position detection device installed at a fixed position may be provided.

[0035] A fuel cell stack 7, also referred to simply as a stack, is constructed with the aid of a processing device 2. The flat components of the stack 7 are bipolar plates 8 and membrane electrode assemblies 9. The fuel cell stack 7, which is in the process of being formed, is already under pressure during its construction. For this purpose, a positioning and pressure system is provided, generally designated 10. The positioning and pressure system 10 includes a lifting device 11, on which the partially completed stack 7 rests. In addition, the positioning and pressure system 10 has a transverse fixing device, generally designated 12, which in this case includes exactly two components 13, 14, namely a first component 13 and a second component 14, wherein the components 13, 14 are designed to be mirror-symmetrical to each other. Without limiting the generality, in this case, the first component 13 is referred to as the left component of the fixing device 12, and the second component 14 is referred to as the right component. In an alternative embodiment, for example, there are four components 13, 14, which are located on all four sides of the stack 7, which is rectangular in plan view.

[0036] The stack 7 is constructed vertically, meaning that its various components 8, 9 are always aligned horizontally during its formation. The height of the stack 7 can be adjusted via a lifting system 15, which is part of the lifting device 11. The lifting system 15 is adapted to change the height setting of a base plate 16 located below an intermediate plate 18. A pressure measuring system 17, in the form of a scale, is located between the plates 16, 18. Several springs 19, designed as compression springs, are located on the intermediate plate 18. These support an upper plate 21, also known as a receiving device, which supports the stack 7 to be assembled. If the properties of the springs 19 are known, a distance measuring device 20 acting between the intermediate plate 18 and the upper plate 21 can be used as an additional force measuring device.

[0037] In order to enable a defined linear displacement between the intermediate plate 18 and the receiving device 21, a linear guide 22 is provided. When the receiving device 21 is raised to its maximum height from the intermediate plate 18 and thus also from the base plate 16, the end stops 35 come into play. The bottom contour of the receiving device 21 is adapted to the dimensions of the components 8, 9 of the stack 7.

[0038] In order to hold the various components 8, 9 of the fuel cell stack 7 in their arranged positions during the formation process, and in this case to exert a force F on the stack 7 in the vertical direction, the aforementioned fixing device 12 is provided on the one hand, and an MEA holding device 23 is provided on the other hand. The MEA holding device 23 is provided specifically for contacting the membrane electrode assembly 9 located at the top of the stack 7. Once this membrane electrode assembly 9 is covered by the bipolar plate 8, the MEA holding device 23 is deactivated. The actuating mechanism of the MEA holding device 23 (i.e., the device for holding the membrane electrode assembly 9) is designated by 24.

[0039] exist Figure 1 In the illustrated embodiment, each component 13, 14 of the fixing device 12 has a plurality (in this case, three) of movable fixing elements 25. A spring 26 acts on each fixing element 25, which is designed as a slide, and pushes the corresponding fixing element 25 toward the stack 7. The fixing element 25 and the spring 26 of each component 13, 14 are arranged together in a container 27. The guide device for horizontally moving the container 27 is marked 28. The guide device 28 can be actuated by means of an actuator 29. To lock the fixing element 25 in the container 27, a clamping device 30 including a clamping plate 31 is provided. A spring 32 acts on the clamping plate 31 in a vertical clamping direction. A tension element 33, which can be actuated by an actuator 34, acts in the opposite direction.

[0040] according to Figure 2 and Figure 3 Embodiments and basis Figure 1 The embodiment of FIG. 1 differs in that the components 13 , 14 of the transverse fixing device 12 are designed to be significantly simpler. Figure 2 and Figure 3 In this case, the functions of the components 13, 14 are each assumed by a circumferential clamp 36, which acts both as a lateral stop for the components 8, 9 relative to the fuel cell stack 7 and compresses the stack 7 as a whole. The bipolar plate 8 is initially received by the vacuum clamp 6 in a completely horizontal orientation, as shown in FIG. Figure 2 The corresponding content applies to the accommodation of the membrane electrode assembly 9 by the processing device 2. In this regard, it can be used Figure 2 and Figure 3 The method and use of the device shown Figure 1 There is still no difference between the methods performed by the devices shown. Figure 2 and Figure 3 In the case of FIG, not only one vacuum gripper 6 is provided, but a plurality of vacuum grippers 6 are provided.

[0041] After the bipolar plate 8 is lifted, Figure 2 and Figure 3 The method shown is the same as Figure 1 Compared with the method performed by the production device 1 shown, there is a special feature. Figure 3As shown, the bipolar plate 8, lifted by a clamp 6 (e.g., a vacuum clamp), is bent before placement on the stack 7, with the edges of the bipolar plate 8 curved upward. In this state, the central region of the bipolar plate 8 is first placed on the stack 7. Subsequently, as the force F increases, the bipolar plate 8 returns to its original flat shape. Once this process is complete, two circumferential clamps 36 clamp the stack 7, maintaining its compressed configuration. The circumferential clamps 36 are then temporarily removed from the stack 7 to allow the next initially bent component 8, 9 to be placed on the fuel cell stack 7.

[0042] exist Figure 1 In the embodiment shown, as already mentioned, the bipolar plates 8 are not deformed during the construction of the stack 7. If the bipolar plates 8 are to be placed on the stack 7, the MEA holder 23 is first opened. The correct placement of the bipolar plates 8 is monitored by means of the position detection system 5. After the bipolar plates 8 have been placed, they are initially held fixed in the holder 6. The handling device 2 then presses the bipolar plates 8 onto the stack 7 in such a way that they are over-pressed relative to the springs 19. Compared to the deformation of the springs 19, the deformation of the stack 7 itself is insignificant in this case. The over-pressing in the vertical direction (in millimeters) is equal to the sum of the thickness of the bipolar plates 8 and a defined additional displacement, which is significantly smaller than the thickness of the bipolar plates 8.

[0043] If an additional displacement is achieved due to over-compression, the compressive force is no longer applied to the transverse fixing element 25. Figure 1 As shown, the laterally movable fixing element 25 is designed in such a way that it enables lateral and vertical support of the bipolar plate 8. When no vertical force is acting on the fixing element 25, the fixing element is moved laterally out of the stack 7 with the aid of the guide device 28 and the actuator device 29. The stack 7 is then pressed further downwards using the handling device 2 until the maximum over-pressing amount is reached. In this state, when the clamping device 30 is opened, the fixing element 25 is brought back into contact with the bipolar plate 8, but offset by exactly the amount of one bipolar plate 8. The clamping device 30 can now be closed again. The setting of the lifting device 11 is tracked during the process, with measurement redundancy being provided by different measuring devices 17, 20. If the membrane electrode assembly 9 is placed on the fuel cell stack 7 under construction, the over-pressing does not occur.

[0044] List of Reference Numerals

[0045] 1. Production Equipment

[0046] 2 Processing device

[0047] 3 Support elements

[0048] 4 movable elements

[0049] 5 Position detection system

[0050] 6 Gripper, vacuum gripper

[0051] 7 Fuel cell stacks and stacks

[0052] 8 Bipolar plates

[0053] 9 Membrane Electrode Assembly, MEA

[0054] 10 Positioning and pressure system

[0055] 11 Lifting device

[0056] 12 Horizontal fixing device

[0057] 13. First component of the fixing device

[0058] 14 Second component of the fixing device

[0059] 15 Lifting System

[0060] 16 bottom plate

[0061] 17 Pressure Measurement System

[0062] 18 Middle plate

[0063] 19 Spring

[0064] 20 Distance measuring device

[0065] 21. Loading and accommodating equipment

[0066] 22 Linear Guides

[0067] 23 MEA holding device

[0068] 24 Actuation mechanism of MEA holding device

[0069] 25 Laterally movable fixing element

[0070] 26 Spring acting on the fixing element 25

[0071] 27 Receptacle for fixing element

[0072] 28 Guide for horizontal displacement of the receiving part 27

[0073] 29 Actuating device for guide device 28

[0074] 30 Clamping device

[0075] 31 Clamping plate

[0076] 32 Spring acting on the clamping plate 31

[0077] 33 Tensile element to offset the clamping force

[0078] 34 Actuating device for actuating a tension element

[0079] 35 End Stops

[0080] 36 Circumferential clamp

[0081] F-force

Claims

1. A device for assembling a battery stack (7), comprising: a handling device (2) having a gripper (6) designed to lift a flat object; and a positioning and pressure system (10) designed for compressing a partially completed battery stack (7) and comprising a lifting device (11) arranged to accommodate the battery stack (7) at any production stage and a transverse fixing device (12) located above the lifting device (11), the transverse fixing device consisting of a plurality of components (13, 14), wherein the components (13, 14) are arranged to abut against the battery stack (7) in the vertical and horizontal directions and can be adjusted and fixed in both directions.

2. The device according to claim 1, characterized in that Each of the components (13, 14) of the fixing device (12) comprises a plurality of fixing elements (25) movable in the horizontal direction, and the fixing elements are configured to support the bipolar plates (8) arranged one above the other in the lateral and vertical directions.

3. The device according to claim 2, characterized in that At least three fixing elements (25) arranged one above the other and provided for contacting a bipolar plate (8) in each case are arranged in a common, horizontally and vertically adjustable receptacle (27) in an individually spring-loaded manner.

4. The device according to claim 3, characterized in that A single clamping device (30) is assigned to the receiving part (27), which is designed to simultaneously clamp all fastening elements (25) located in the receiving part (27).

5. The device according to any one of claims 2 to 4, characterized in that In addition to the horizontally movable fixing element (25), a switchable MEA holder (23) is also present, which is designed to press down the membrane electrode assembly (9) located on top in the partially completed cell stack (7).

6. The device according to claim 1, characterized in that The two transverse components (13, 14) of the fixing device (12) each have an angular circumferential clamp (36) against which the cell stack (7) rests laterally and simultaneously upwards.

7. The device according to any one of claims 1 to 6, characterized in that The lifting device (11) has three plates (16, 18, 21) arranged parallel to each other, namely a bottom plate (16), an intermediate plate (18) and an upper plate (21) provided for accommodating the battery stack (7), wherein a pressure measuring system (17) is present between the bottom plate (16) and the intermediate plate (18), and the upper plate (21) is supported on the intermediate plate (18) in a vertically movably manner by means of a spring (19), and wherein a distance measuring device (20) is provided for measuring the distance between the upper plate (21) and the intermediate plate (18).

8. A method of assembling a battery stack (7), wherein: A cell stack (7) under construction comprising bipolar plates (8) and membrane electrode assemblies (9) aligned horizontally and arranged parallel to one another is subjected to pressure during its formation by applying a vertically downward pressure to the cell stack (7) after placement of each additional bipolar plate (8), thereby pressing the cell stack (7) downward as a whole, which represents a transition to an over-pressed state in which a spring (19) supporting the cell stack below the cell stack (7) is compressed, and wherein, after the over-pressing, the vertically downward pressure is reduced so that the cell stack (7) is again lifted by the spring (19) and, in the subsequently expanded state of the spring (19), at least the top bipolar plate (8) is fixed in the vertical and transverse directions while maintaining a component of the downward pressure.

9. The method according to claim 8, characterized in that The bipolar plates (8) and the membrane electrode assemblies (9) are each placed alternately on the battery stack (7) in a completely flat state.

10. The method according to claim 8, characterized in that At least the bipolar plate (8) is placed onto the battery stack (7) in a bent state, wherein the central area of ​​the bipolar plate (8) is first pressed onto the battery stack (7), and then, while maintaining the pressure, the entire bipolar plate (8) is brought into contact with the battery stack (7) while being transformed into its flat shape.

Images