Measuring device, measuring table having measuring device, and method for measuring thickness of flat component, in particular gas diffusion layer

Abstract

The invention relates to a measuring device (1) for determining the thickness of a gas diffusion layer (11) of an electrochemical cell (31), comprising a lower pressure plate (3), an upper pressure plate (5) and a test weight (9) guided by a vertical guide (7), during the measurement, a predeterminable test force can be applied to a flat component (10, 11) to be tested by the gravity of the test weight (9), the measuring device further comprises a distance sensor (13), by means of which the distance between the upper pressure plate (5) and the lower pressure plate (3) can be determined as a thickness measurement (H) of the flat component (10, 11) under a predetermined test force (F). The invention further relates to a measuring table (27) having the measuring device (1) and to a method for measuring the thickness of a flat component (10, 11), in particular a gas diffusion layer (11) for an electrochemical cell (31).

Description

Technical Field

[0001] This invention relates to a measuring apparatus for measuring the thickness of a gas diffusion layer in an electrochemical cell, particularly a PEM electrolytic cell. The invention also relates to a measuring stage including the measuring apparatus and a method for measuring the thickness of the gas diffusion layer. Background Technology

[0002] Electrochemical cells are generally known and are classified into galvanic cells and electrolytic cells. An electrolytic cell is a device that uses an electric current to drive a chemical reaction, during which at least some electrical energy is converted into chemical energy. A galvanic cell is a complementary device to an electrolytic cell, used to spontaneously convert chemical energy into electrical energy. A known example of such a galvanic cell is a fuel cell.

[0003] As is well known, water is decomposed to produce hydrogen and oxygen using an electrolytic cell and an electric current. This process is mainly divided into two technical systems: alkaline electrolysis and PEM (Proton-Exchange-Membrane) electrolysis.

[0004] The core of industrial electrolysis equipment is the electrolytic cell, which consists of two electrodes and an electrolyte. In a PEM electrolytic cell, the electrolyte is composed of a proton-conducting membrane, with the electrodes located on either side. The unit consisting of the membrane and electrodes is called a MEA (Membran-Electrode-Assembly in English, Membran-Elektroden-Einheit in German, meaning membrane electrode assembly). In the assembled state of an electrolytic stack consisting of multiple electrolytic cells, so-called bipolar plates contact the electrodes through a gas diffusion layer, separating the individual electrolytic cells in the stack from each other. Here, the O2 side of the electrolytic cell corresponds to the positive electrode, and the H2 side corresponds to the negative electrode, separated by the membrane electrode assembly located between them.

[0005] On the O2 side, the PEM electrolyzer is supplied with fully desalinated water, which is decomposed into oxygen and protons (H2O) at the anode. + Protons pass through the electrolyte membrane and recombine at the cathode (H2 side) to form hydrogen gas. The gas diffusion layer attached to the electrode ensures not only electrode contact but also optimal water distribution (and thus membrane wetting) and the output of product gases. Therefore, a conductive, porous element that maintains good long-term contact with the electrode is required as the gas diffusion layer. Another requirement is that any structural tolerances that may occur in the electrolyzer must be compensated for to ensure uniform contact with the MEA under any tolerance conditions.

[0006] In known electrolytic cells, sintered metal discs are sometimes used as gas diffusion layers. While these discs meet the requirements for conductivity and porosity, they cannot provide additional compensation for the tolerances of the electrolytic cell components on either side of the gas diffusion layer. Furthermore, the manufacturing cost of such discs is relatively high, and the extrusion pressure required during manufacturing imposes dimensional limitations. Additionally, large components exhibit uncontrollable deformation problems.

[0007] For example, the use of gas diffusion electrodes with elastic elements to establish electrical contacts in alkaline electrolyzers is described in documents WO 2007 / 080193 A2 and EP 2436804 A1.

[0008] A flexible plate is known from document EP 1378589 B1, in which the individual flexible elements alternately bend upward and downward. This flexible plate is installed only on the cathode side of an ion exchange electrolyzer, so that the flexible plate is in direct contact with the cathode.

[0009] Document US 2003 / 188966 A1 describes another elastic component for an electrolytic cell, arranged between a partition wall and the cathode. This elastic component comprises multiple sheet-like elastic elements that rest against the cathode for uniform adjustment. Furthermore, gas diffusion electrodes with different structures are described in documents WO 2002035620 A2, DE 10027339 A1, and DE 102004023161 A1.

[0010] Document EP 2 957 659 B1 discloses a gas diffusion layer installed between a bipolar plate and an electrode in an electrochemical cell. This gas diffusion layer comprises at least two layers stacked on top of each other, one of which is an elastic component with a progressive elastic characteristic curve. This progressive elasticity ensures sufficient pressing force at all tolerant locations of the contacting components. The progressive elasticity in the gas diffusion layer is achieved through the geometric design of the elastic component. Therefore, in electrochemical cells, particularly electrolytic cells or galvanic cells, component tolerances, especially those occurring in the bipolar plate region, can be compensated, at least to a certain extent.

[0011] Document WO 2021 / 018459 A1 describes an electrolytic cell with a cell frame and a method for manufacturing the electrolytic cell. The cell frame has a stepped inner profile. This inner profile includes at least one support surface for accommodating planar components within the cell frame. This support surface has a recess for sealing. Due to the stepped inner profile, a first gas diffusion layer protrudes beyond the boundary of a second gas diffusion layer. Therefore, the gap size between the cell frame and the membrane, more specifically the gas diffusion layer, can advantageously be larger. This advantageously simplifies and shortens the assembly process. Furthermore, the outer profile of the membrane and / or the gas diffusion layer can advantageously be chosen with considerable freedom.

[0012] A typical PEM electrolyzer structure includes a first gas diffusion layer and a second gas diffusion layer. A proton exchange membrane is arranged between the gas diffusion layers. All layers are arranged within a cell frame. To manufacture a reliably operating electrolyzer and subsequently stack multiple electrolyzers, the gas diffusion layers within the cell frame must be arranged with high precision. This makes the manufacturing and assembly of components typically very complex.

[0013] Especially when the number of electrolytic cells stacked one after another is large, manufacturing deviations occur due to the inconsistent thickness of the gas diffusion layer of the electrolytic cells. In individual cases, the accumulated thickness tolerance is still within the allowable range, but when a large number of electrolytic cells are fixed in a stack, it will lead to unacceptable mechanical stress.

[0014] Therefore, in pursuit of industrialized mass production, there is an increasing demand for improved accuracy and repeatability of thickness measurement in the manufacturing of the gas diffusion layer of an electrolytic cell. To provide marketable electrolyzers with high production volumes and high electrolytic power, ensuring the manufacturing quality of the electrolytic cell layers is becoming increasingly important. Against this backdrop, an object of the present invention is to provide a measuring device with improved measurement accuracy and repeatability. Furthermore, an object of the present invention is to provide a method for measuring the thickness of a stacked gas diffusion layer, characterized by high accuracy and repeatability. Summary of the Invention

[0015] According to the present invention, this objective is achieved by a measuring device for measuring the thickness of a gas diffusion layer in an electrochemical cell. The measuring device includes a lower pressure plate, an upper pressure plate, and a test weight guided by a vertical guide. During the measurement process, the gravity of the test weight can apply a preset test force to the flat member to be tested, thereby generating a defined surface pressure. In addition, a distance sensor is included, which can determine the distance between the upper and lower pressure plates as the thickness measurement value of the flat member under the preset test force.

[0016] This invention is based on the understanding that the gas diffusion layers of an electrolytic cell have particularly high requirements for their height and thickness distributions. Dimensional accuracy and stability are increasingly important today, especially for large, flat gas diffusion layers, such as those currently being developed and designed for high-power electrolyzer applications. In the installed state, the gas diffusion layer is compressed and must precisely fill the pre-defined installation space within the electrolytic cell under pressure. The gas diffusion layer typically exhibits a spring-like force / displacement characteristic curve within certain limits. Since multiple electrolytic cells are connected in series and stacked in practical applications, thickness tolerances accumulate. This invention recognizes that conventional measuring devices and existing general-purpose testing machines are insufficient to measure the thickness of extended and flat gas diffusion layers with the required measurement uncertainty of <0.01 mm as accurately as possible. Given the increased requirements for measurement accuracy, dimensional stability, and repeatability, high demands are placed on measuring devices and methods to meet the required quality assurance with a reasonable workload while being as easily integrated as possible into the industrial manufacturing process of the electrolytic cell.

[0017] To date, thickness has been determined using conventional general-purpose testing machines. These machines are equipped with pressure plates and operate in a "compression test" mode, where the test force is typically adjusted via an electric actuator and a drive spindle. The problem is that these machines deform under the applied pressure, leading to distorted measurements, sometimes exceeding the required accuracy by one or two orders of magnitude. The common practice is to use a one-time recorded compensation curve to very complexly compensate for the measurements, but this requires regular checking and calibration. When variations occur, the measurements become unusable. If the machine exceeds its force limits, the component involved can suffer irreversible damage, such as being compressed thinner than the minimum thickness dimension. In addition to the time required for continuous monitoring and periodic calibration after each component (typically 2 to 10 times per shift), manufacturing is heavily dependent on external influences such as fluctuations in air humidity and temperature. This measurement principle and its associated drawbacks are the same for all general-purpose testing machines examined. Furthermore, in standard designs, a portion of the test force is used to orient curved, flat components evenly on the table, which is highly disadvantageous.

[0018] The measuring device of the present invention overcomes these shortcomings and meets the high-precision requirements of a measuring device that guarantees quality on an industrial scale. With this measuring device, for example, the thickness of a spring-elastic gas diffusion layer (as a flat member) formed from a metal plate can be determined under a clearly defined test force. This measuring device, thus designed, can advantageously operate on an industrial scale in a manufacturing workshop in three shifts. The measuring device ensures that, during measurement, the test force is introduced into the flat member solely through the preset gravity of the test weight. This allows for a defined surface pressure between the upper and lower pressure plates, thereby providing a distortion-free measurement result as a thickness measurement value, the distance between the pressure plates being provided by a distance sensor. A vertical guide section guides the test weight vertically lowering and raising, and during measurement, ensures that the upper pressure plate flatly contacts and applies pressure to the flat member to be measured.

[0019] This measuring device is particularly advantageous for determining, and is specifically designed for, the gas diffusion layer or gas diffusion layer portion of a flat member based on a metal plate as a measurement. In batch operation of the measuring device, it allows for the rapid, accurate, and repeatable measurement of large-area flat members with a preferred rectangular base, with varying dimensional accuracies. Thus, flat members (e.g., gas diffusion layers) can undergo shape cutting during industrial manufacturing, and the measuring device can be used to measure the same location before and after cutting, ensuring quality. The measuring device is preferably advantageous for measuring the thickness of flat members, for example, having a length of 600-1500 mm, a width of 350-450 mm, and a height of 0-7 mm. The height of the flat member corresponds to the thickness measurement value to be determined, which can be determined with high precision.

[0020] In a particularly preferred design of the measuring device, the measuring device includes a lifting mechanism that can lower the test counterweight, thereby applying a preset test force to the flat component by gravity.

[0021] The preset test force is conveniently applied to the flat component solely by the gravity of the test counterweight, and locally through the contact surface of the upper pressure plate. Therefore, the stiffness of the measuring device and the higher-level mechanical structure integrating it does not affect the measurement accuracy. Furthermore, the test counterweight is a force source with very limited variation and essentially unchanged over time. The test counterweight can be lowered during measurement via a lifting device, generating a preset surface pressure.

[0022] In a preferred design of the measuring device, the lifting mechanism decouples itself from the test counterweight during the measurement process, so that no additional force is applied to the flat member except for the test force generated by the test counterweight.

[0023] Therefore, reducing the test weight only locally introduces the test force into the placed flat member within the defined contact area of ​​the upper and lower pressure plates. The distance between the upper and lower pressure plates can then be measured using a distance sensor under well-defined test conditions. For a flat member configured as a gas diffusion layer, a test force of approximately 1180 N typically produces, for example, 0.6 N / mm². 2 Surface pressure is advantageous. The thickness or height of a flat member is defined as the distance between the upper and lower pressure plates when the upper and lower pressure plates are flat against the flat member and a test force is applied.

[0024] In the complete measurement process using the measuring device, the weight must be removed from the flat component to ensure safe insertion and removal. For this purpose, a lifting mechanism can be used to advantageously raise the test counterweight, creating a gap of, for example, approximately 40 mm between the flat component and the upper pressure plate. The raising and lowering of the counterweight should be performed gently to avoid damaging the flat component being measured. Therefore, the control and design of the lifting mechanism in the measuring device must limit the acceleration and speed of the test counterweight. This limitation is adjustable, for example, by using a pneumatic or hydraulic damping and limiting device for raising and lowering, such as by setting a limiting valve.

[0025] In this configuration, the lifting mechanism is designed such that during the actual measurement phase, only the gravity generated by the test counterweight acts on the flat component. The lifting mechanism itself is completely decoupled during this phase and does not introduce additional gravity, thus ensuring undistorted measurement results. For example, a rope-guided lifting mechanism with corresponding rollers and a drive unit for lifting the test counterweight could be considered.

[0026] Preferably, in this measuring device, the gravity of the test counterweight is adjustable, thereby enabling calibration of the test force.

[0027] The choice of material and volume for the test counterweight ensures that the gravity generated by the structure (including pressure plates, etc.) resting against the flat component matches the required test force. Depending on specific requirements, the preset test force can be determined and adjusted, for example, using a balance. Therefore, the test counterweight can be composed of a combination of various counterweight units.

[0028] This allows for advantageous adjustments and calibrations, such as fine-tuning the test force by selectively adding / removing counterweight units, and making changes as needed.

[0029] Therefore, preferably, the measuring device can achieve a pressure of 950N (surface pressure 0.5N / mm). 2 ) up to 2000N (surface pressure 1N / mm 2The test force can be varied within a certain range, for example, by allowing sufficient space for changes in the test weight. For industrial production and quality control, this provides the measuring device with flexibility, enabling it to adjust the test force flexibly around a preferred value, for example, 1178 ± 10 N.

[0030] In a particularly advantageous design of the measuring device, the vertical guide is fixed and cannot rotate around the vertical axis, thereby ensuring accurate positioning and repeatable reduction of the test counterweight.

[0031] The test counterweight can be precisely guided linearly up and down via a vertical guide, and is simultaneously fixed so as not to rotate about the axis of motion, thus achieving linear guidance of the measuring device mechanically under forced conditions. Therefore, the vertical guide is advantageously constructed as a vertically oriented longitudinal guide with minimal friction, so that the weight of the test counterweight can be transferred to the flat component to be measured with minimal change. For example, a brass bushing can be used here, in which a guide rod or a vertically oriented metal shaft is held.

[0032] In another preferred design, the measuring device is equipped with a calibration device, which can be used to determine the current reference value as the zero point of the distance measurement, and thereby calibrate the distance between the upper and lower pressure plates.

[0033] Therefore, the zero point of the distance measurement between the upper and lower pressure plates is calibrated as needed, periodically, or periodically between measurement processes. Thus, the distance sensor is equipped with a calibration function, thereby enabling accurate thickness measurement. Therefore, the distance and thickness of the flat member introduced into the measuring device are derived from length measurement. For this purpose, an automated length measuring device can be set up, which includes a distance sensor with a calibration function. The advantageous basic function of this length measuring device stems from the fact that the position of the test counterweight can be determined relative to a fixed point, for example, located on the housing of the measuring device. By introducing the force of the test counterweight, the force path of the measurement can be separated from the force path of the lifting mechanism, thereby achieving decoupling and obtaining the best possible measurement results.

[0034] To accurately determine the distance between the upper and lower pressure plates in each measurement, the measuring device must first be placed in a reference position, i.e., "zeroed," before any component to be tested is placed. Preferably, this reference position is checked periodically during the operation of the measuring device, ideally always between the two components. Here, in zero-point measurement, the pressure plates are moved smoothly onto each other without any component, and the output measurement value is determined as the "zero value" of the tool distance. If the absolute value of the measurement is greater than the maximum allowable value, for example, >3 μm, the reference position is automatically reset, and the measuring device is calibrated accordingly. Through this process, time drift, such as due to temperature changes, can be detected and compensated for in the field during the operation of the measuring device. This automation of zero-point calibration is achieved by a control and regulation device advantageously integrated into the measuring device. This control and regulation device can also perform other functions that automate the measurement process.

[0035] In another preferred design of the measuring device, a totgewicht is provided, which is arranged radially on the outside of the vertically guided upper pressure plate, so that when the upper pressure plate is lowered, the flat component to be tested can be flattened on the base under the gravity of the totgewicht.

[0036] The inherent counterweight is an additional counterweight that ensures the flat member rests flat on the base. By arranging the inherent counterweight radially on the outside of the pressure plate, the inherent counterweight is completely decoupled from the measurement process and does not participate in the measurement, i.e., it does not affect the surface pressure under the preset test counterweight. The inherent counterweight is preferably used only to position and place the flat member flat on a flat measuring base, especially at its edges.

[0037] Since flat components often have warping that can affect measurement results due to manufacturing reasons, in a preferred design, a circular inherent counterweight or a radially surrounding ring around the upper pressure plate is integrated into the measuring device. This allows the flat component, particularly the gas diffusion layer made of metal sheets, to be flattened and further fixed to the base, unaffected by the test force. By placing the additional counterweight at a predetermined distance beyond the measuring surface parallel to the planes of the upper and lower pressure plates, the weight of the additional counterweight is not included in the test force. The distance from the inherent counterweight to the measuring surface is preferably at least 15 mm.

[0038] Preferably, for this measuring device, the inherent counterweight is fixed so that it cannot rotate about the vertical axis, wherein the inherent counterweight can be locked and removed as needed.

[0039] Therefore, for example, during maintenance, the upper pressure plate and other functional parts of the measuring device can be accessed. The inherent counterweight is protected against rotation around the vertical axis and can be locked and removed at a point vertically above the measuring device. Locking at the top point is required to adjust the ball head, clean the pressure plate, and perform measurements without the inherent counterweight.

[0040] The corresponding surface of the additional or inherent counterweight on the base of the flat member is preferably also a circular ring (ring), having the same dimensions as the inherent counterweight itself. The support surface of the member, including the pressure plate, preferably protrudes slightly from the base, for example, from a table made of granite slab. To facilitate the introduction of the flat member to be measured into the measurement position, the support surface is provided with a bevel or chamfer, having an angle of, for example, 20°. The following parameters have proven advantageous, for example, for the inherent counterweight: an inner diameter of 110 mm for the additional counterweight ring, an outer diameter of 140 mm for the additional counterweight ring, and a mass of 15 kg for the inherent counterweight. Adjusted diameters may also be used depending on the measurement task and the size of the flat member. The contact surface between the additional counterweight and the flat member to be measured is preferably made of hardened and corrosion-resistant stainless steel, for example, 1.4923 steel or 1.4021 steel.

[0041] In a particularly preferred design of the measuring device, the pressure plates are circular flat plates made of hardened stainless steel, and the pressure plates are oriented in a consistent and planar parallel manner.

[0042] Here, the upper pressure plate is preferably connected to the shaft of the test counterweight via a ball joint, thereby allowing adjustment of the orientation of the parallel planes of the pressure surfaces of the upper and lower pressure plates.

[0043] Here, for example, the movable upper pressure plate and the lower pressure plate fixedly integrated into the base are circular plates made of corrosion-resistant hardened steel (e.g., 1.4923 steel or 1.4021 steel). The diameter of the circle is preferably machined to 50 + / - 0.05 mm, wherein the contact surfaces of the components are ground (Rz < 4) to achieve the best possible planar parallelism of the contact surfaces. To avoid distortion of surface pressure, large chamfers > 0.1 × 45° should be avoided, thereby providing a precisely pre-defined, circular, consistent, and planar parallel standard surface through the pressure plates.

[0044] To ensure the pressure surfaces of the upper and lower pressure plates are precisely parallel to each other, the upper pressure plate is preferably axially connected to the test counterweight via a ball head. During calibration, the ball head is fixed and positioned under the measuring pressure. The ball head can rotate about a vertical axis, and the center point of the ball is preferably located on the contact surface of the upper pressure plate. To allow access to the ball joint's fixing device under the measuring pressure, the inherent counterweight is fixed above it.

[0045] Preferably, the measuring device has multiple plate pairs, each including an upper pressure plate and a lower pressure plate, wherein the plate pairs are arranged such that the thickness of the flat member introduced for measurement can be determined simultaneously at multiple measuring points during the measurement.

[0046] In this way, the thickness of a flat component can be measured simultaneously at multiple different locations. Therefore, for extended flat components such as gas diffusion layers composed of stacked metal sheets, particularly uniform surface pressure and thickness adjustment can be achieved. For example, the thickness of the component can be measured simultaneously at six locations. As an exemplary embodiment, the measuring device is particularly advantageously designed and adjusted to provide a surface pressure of, for example, 0.6 N / mm² between circular pressure plates and has a test counterweight of 1178 N + / - 10 N, wherein each pressure plate has a diameter of 50 mm. The distance between the measuring points relative to each other is preferably constant, although the distance to the edge of the flat component may vary depending on the component. For this purpose, an adjustable stop can be provided in the measuring device for positioning the flat component.

[0047] The thickness or height of a component is defined as the distance between the upper and lower pressure plates when the upper and lower pressure plates are flat against the flat component and a preset test force is applied.

[0048] Therefore, in the measuring device, the plate pairs consisting of the upper and lower pressure plates are preferably arranged regularly on the surface, so that the corresponding local thickness measurements of the flat member introduced for measurement can be determined. It is particularly advantageous for local thickness measurements at multiple measurement points to arrange the plate pairs uniformly in a grid pattern relative to the surface of the flat member and position them as a rectangular or square grid. Since the flat member has fairly repeatable compressive characteristics and an elastic constant of up to 50 kN / mm, it is preferable to uniformly position the measurement points on the flat member. This is especially true for gas diffusion layers made of metal plates used in electrolytic cells.

[0049] According to the invention, the objective is further achieved by a measuring table with a measuring device, the measuring table comprising a platform in which a lower pressure plate is integrated, wherein a support surface is formed on the platform for receiving a flat member to be measured for thickness. The measuring table with the platform is configured such that during the measurement process, the flat member rests only against the support surface with its inherent counterweight and the lower pressure plate protruding relative to the platform. The platform also serves for good guidance and repeatable positioning of the flat member, particularly during the insertion and removal of the flat member during the measurement process.

[0050] In a particularly preferred design, the measuring station includes a control device with an operation panel, which can control and monitor the measurement process, wherein the measurement data from the distance sensor can be read into the processor and processed.

[0051] To control and monitor the process, a computer with an operating device, including an operation panel, is preferably provided. At the operator station, the measurement results can also be visually displayed to the operator, for example, via a monitor or display. Measurements can be triggered by the operator, for example, via a foot switch. A maintenance function, optionally manually operable, is preferably implemented in the control device. In this maintenance function, movement is made toward the lower end of the test weight to, for example, adjust the ball joint and simultaneously secure the test weight.

[0052] Preferably, the measuring table includes a transfer device for loading and unloading flat components.

[0053] Automatic feeding of flat components is particularly advantageous here. The objective is also achieved by a method for measuring the thickness of a gas diffusion layer in an electrochemical cell, the method comprising: providing a measuring device, wherein the gas diffusion layer is placed as a flat component into the measuring device, wherein during the measurement process, a defined surface pressure is generated by lowering a test weight, a preset test force is applied to the gas diffusion layer by means of the gravity of the test weight, and wherein the distance between an upper pressure plate and a lower pressure plate is determined under the action of the preset test force.

[0054] In this method, it is preferable to determine the current reference value as the corresponding zero point, and thereby calibrate the distance between the upper and lower pressure plates.

[0055] The repeatability and accuracy of thickness measurements are crucial and are preferably set to a value of <5 μm. This measuring device can also be compared with existing measuring systems. To check repeatability, a "zero-point measurement process" without any attached components is performed in this method to place the measuring system in a reference position.

[0056] Furthermore, in this method, it is preferable to perform thickness measurements simultaneously at multiple measurement points distributed on the surface of the gas diffusion layer during the measurement process.

[0057] The measurement points can be evenly and grid-like distributed on the surface of the gas diffusion layer. Only the surfaces of the upper and lower pressure plates that are parallel and consistent at each measurement point serve as the functional surfaces for introducing force through the preset test counterweight.

[0058] The advantages of the measurement method according to the invention are consequently derived from the advantages of the measuring device.

[0059] Further advantages, features, and details of the invention will become apparent from the following description and accompanying drawings of preferred embodiments. The features and combinations thereof mentioned above in the specification, as well as the features and combinations thereof shown separately in the description of the drawings and / or in the various drawings, can be used not only in the given combinations, but also in other combinations or individually, without departing from the scope of the invention. Attached Figure Description

[0060] Embodiments of the invention will be explained in more detail with reference to the accompanying drawings. These drawings are schematic and extremely simplified:

[0061] Figure 1 This is an example of the basic structure of an electrochemical cell constructed as a PEM electrolytic cell;

[0062] Figure 2 This is a simplified diagram illustrating the basic measurement principle of the present invention for determining the thickness of a flat component configured as a gas diffusion layer;

[0063] Figure 3 It refers to the arrangement of multiple measurement points on the gas diffusion layer;

[0064] Figure 4 This is a view of the measuring device used for selected measurement points in the gas diffusion layer;

[0065] Figure 5 This is a view of a measuring device with a gas diffusion layer inserted before measurement;

[0066] Figure 6 It is based on Figure 5 A view of the measuring device shown during measurement;

[0067] Figure 7 This is a cross-sectional view of a lower punch with a lower pressure plate;

[0068] Figure 8 It is based on Figure 7 The diagram shows the plan view of the lower punch;

[0069] Figure 9 It is a schematic plan view of a measuring station with measuring devices and an inserted gas diffusion layer. Detailed Implementation

[0070] Figure 1 The structure of an electrochemical cell 31, configured as a PEM electrolyzer, is schematically shown. Electrochemical cell 31 is part of an electrolyzer (not shown in detail here) used to produce hydrogen and oxygen by splitting water with an electric current.

[0071] The electrochemical cell 31 includes an electrolyte composed of a proton-conducting membrane 33 (proton exchange membrane, PEM), with electrodes 35a and 35b located on either side. The unit consisting of the membrane and electrodes is called a membrane electrode assembly (MEA). Here, electrode 35b is called the cathode, and electrode 35a is called the anode. A gas diffusion layer 11 is attached to each of electrodes 35a and 35b, respectively. The gas diffusion layers 11 are contacted by so-called bipolar plates 37, which are separated from each other in the assembled state of an electrolytic stack consisting of multiple individual electrolytic cells 31.

[0072] Water is supplied to electrochemical cell 31, which is decomposed into oxygen (O2) and protons (H) at anode 35a. + Proton H + They migrate through the electrolyte membrane 33 toward the cathode 35b. On the cathode side, they recombine to form hydrogen gas (H2).

[0073] In another embodiment, the electrochemical cell 31 is configured as a galvanic cell, more precisely, a fuel cell, for generating electricity. According to the invention, the gas diffusion layer 11 of such an electrochemical cell 31 is... Figure 1 The electrolytic cell 31 shown is similarly modified. Therefore, without limiting its generality, the following description will take the electrochemical cell 31 configured as an electrolytic cell as an example.

[0074] The gas diffusion layer 11, also known as the gas diffusion layer section, is a flat component 10 and a crucial functional layer for the electrolytic cell 31, performing various tasks during its operation. The gas diffusion layer 11 ensures optimal water distribution and the output of product gases. In the case of a galvanic cell, the gas diffusion layer 11 is used to supply reactants to the respective electrodes. Crucially, the gas diffusion layer 11 must possess sufficient permeability to allow the gaseous products or precipitates to be discharged under all circumstances.

[0075] Especially in the case of an electrolytic cell, the gas diffusion layer 8 also functions as a current distributor. Therefore, the gas diffusion layer 8 is formed of a conductive porous material.

[0076] In the illustrated embodiment, the gas diffusion layer 11 compensates for component tolerances, particularly those of the bipolar plate 37 it abuts against. Therefore, the gas diffusion layer 11 comprises layers stacked upon each other, with the outer layer being an elastic component having a progressive elastic characteristic curve. The gas diffusion layer 11 specifically includes contact components, diffusion components, and elastic components, which differ from each other, particularly in their structure and / or composition.

[0077] The gas diffusion layer 11 of the electrolytic cell 37 comprises multiple layered diffusion layers, the height and thickness of which must meet particularly stringent requirements. Furthermore, the pre-installed space within the cell frame must be precisely designed and manufactured for use in the electrolytic cell 37. Dimensional accuracy and stability within permissible thickness limits are becoming increasingly important, especially for large, flat gas diffusion layers 11, such as those currently being developed and designed for high-power electrolyzer applications. Therefore, quality assurance of the thickness adjustment of the gas diffusion layer 11 is crucial for high-volume industrial manufacturing processes with large effective functional areas. Moreover, permissible thickness tolerances must be monitored during the axial stacking and mechanical fixing of multiple electrolytic cells 31 to form a high-performance electrolyzer.

[0078] Figure 2 The measurement principle is illustrated exemplarily to demonstrate the measurement of the thickness of a prefabricated multilayer gas diffusion layer 11. The gas diffusion layer 11 comprises layers (not shown in detail) stacked on top of each other, wherein the outer layers are elastic components with progressive elastic characteristic curves. The gas diffusion layer 11 specifically includes contact components for power supply, diffusion components for medium transmission, and elastic components for providing the required elastic properties when the gas diffusion layer 11 is mounted into a pool frame. The components and layers of the gas diffusion layer may differ from each other in their structure and / or composition due to function and installation conditions. A circular upper pressure plate 5 and a correspondingly circular lower pressure plate 7 have the same diameter D and are arranged vertically above and below each other, forming an intermediate space. The gas diffusion layer 11, having multiple gas diffusion layers of undetermined thickness, is placed within this intermediate space. The upper pressure plate 5 can move vertically downwards and upwards, while the lower pressure plate 3 is fixedly integrated into a solid base. The upper pressure plate 5 and the lower pressure plate 3 have flat, parallel component contact surfaces 23, which have the same precise diameter D, for example, D = 50 ± 0.05 mm, to generate a predetermined and well-defined surface pressure during measurement using a vertical test force F. The pressure plates 3 and 5 are made of hardened and corrosion-resistant steel, such as 1.4923 steel or 1.4021 steel. The component contact surfaces 23 are ground to achieve the best possible planar parallelism.

[0079] When a test force F is applied to the upper pressure plate 5, a defined surface pressure, for example 0.6 N / mm, is generated at a selected measurement point in the gas diffusion layer 11. 2 Under the defined surface pressure, the thickness measurement value H of the gas diffusion layer 11 is obtained, where the thickness measurement value H is defined as the distance between the upper pressure plate 5 and the lower pressure plate 3. Here, the measuring assembly ensures that the upper pressure plate 5 and the lower pressure plate 3 are in planar contact with the gas diffusion layer through the component contact surface 23 and a test force F is applied. The test force F is set to a fixed value, for example, F = 1178 ± 10 N.

[0080] exist Figure 3 In this diagram, a plan view of the flat member 10 is shown, taking a flat rectangular gas diffusion layer 11 as an example. Multiple measurement points 25 are shown here, uniformly distributed on the flat member 10. Each measurement point 25 is formed by a circular surface region corresponding to... Figure 2The corresponding upper pressure plate 5 or lower pressure plate 3 component contact surface 23. Measuring points 25 are arranged in a grid pattern, with a predetermined grid distance X in the direction of their length extension (i.e., along the x-axis) relative to the component axis of the flat component 10, and a predetermined grid distance Y in the direction of their width extension (i.e., along the y-axis). Currently, six measuring points 25 are given, so an application of, for example, 0.6 N / mm² is applied to each measuring point 25. 2 Under the same surface pressure, the height of the component can be locally determined simultaneously at six measuring points (25). Based on... Figure 3 In the view, the height of the component is determined perpendicularly to the component plane of the flat component defined by the x-axis and y-axis. Typically, a rectangular grid of measurement points can be constructed with constant distances of X = 635 mm and Y = 210 mm. The distance from the measurement point 25 to the edge of the component can vary depending on the flat component 10 and can be adjusted as needed. The gas diffusion layer 11, which is the flat component 10, has particularly good compressibility characteristics. The elastic constant of the gas diffusion layer 11 reaches a maximum of 50 kN / m.

[0081] Figure 4 A view of a measuring device 1 for a selected measurement point 25 of a gas diffusion layer 11 is shown. This measuring device 1 is used to accurately measure the thickness of the gas diffusion layer 11. The measuring device 1 has a lower pressure plate 3, an upper pressure plate 5, and a test weight 9. The test weight 9 can be vertically moved and guided with low friction via a vertical guide 7, and is fixed so as not to rotate about a vertical axis. The lower pressure plate 3 is embedded and fixed in a solid platform 21, for example, made of granite. Here, the lower pressure plate 3 is a specially designed, protruding, but integral component of an all-metal lower punch 41 embedded in the platform 21. The upper pressure plate 5 is mechanically coupled to the test weight 9. Therefore, a preset gravity can be introduced into the upper pressure plate 5 via the test weight 9, and a defined surface pressure is applied to the flat member 10 to be tested. For this purpose, the measuring device 1 has a lifting mechanism 15, by which the test weight 9 can be guided vertically lowered, so that a preset test force F (see [reference]) can be applied solely by the gravity of the test weight 9. Figure 2 The force F is applied to the flat member 10. The lifting mechanism 15 is designed to be completely decoupled from the test weight 9 during the measurement process, so that the test force F generated by the test weight 9 does not exert additional distorting force on the flat member 10. Therefore, the thickness of the gas diffusion layer 11 to be measured can be measured very accurately and repeatably using the measuring device 1. The C-shaped bracket 39 bears the force of the test weight 9 through the lifting mechanism 15. The bracket 39 is very stable and solid. In addition, the bracket 29 is also used to fasten the lifting mechanism 15. Figure 9The guide device 53, shown in detail, is based on a rope traction system, for raising and lowering the test counterweight 9 during the measurement cycle. A distance sensor 13, integrated into the upper-level measurement and calibration device 17, is provided to determine the accurate thickness measurement value H of the gas diffusion layer 11 under specified test conditions and surface pressure. This allows the current reference value to be established as the zero point for distance measurement, and this reference value is continuously checked, thereby periodically recalibrating the distance between the upper pressure plate 5 and the lower pressure plate 3 as needed. Furthermore, an inherent counterweight 19 is provided in the measuring device 1 as an additional counterweight to stabilize the gas diffusion layer 11 under test, primarily ensuring its planar orientation. The inherent counterweight 19 is radially positioned at least 15 mm outside the vertically guided upper pressure plate 5 and does not affect the thickness measurement. When the upper pressure plate 5 is lowered above the test counterweight 9, the placed gas diffusion layer 11 is thus pressed flat against the base under the gravity of the inherent counterweight. The inherent counterweight 19 is also fixed so that it cannot rotate around the vertical axis, and can be locked in the upper position as needed, and can be removed.

[0082] Figure 5 A view of the measuring device 1 is shown, which has a gas diffusion layer 11 that is already inserted into the measuring device 1 before the measurement begins. At this time, the test counterweight 9 and the upper pressure plate 5 are in a vertically upward position. The gas diffusion layer 11 is an extended flat member 10, and is likely warped mainly at the edges due to manufacturing reasons. This is in Figure 5 As shown in the diagram. The inherent counterweight 19 is introduced into the measuring device as an additional counterweight and is arranged radially around the perimeter, concentric with and at a certain distance from the upper pressure plate 5. The inherent counterweight 19 can be a solid hollow metal cylinder with a circular and flat support surface to fulfill its function. Therefore, the inner diameter A of the inherent counterweight 19 is larger than the diameter D of the upper pressure plate 5 and the lower pressure plate 3. The outer diameter B is correspondingly larger than the inner diameter A. The annular design of the inherent counterweight 19 provides a suitable working surface. The lower pressure plate 3 is part of the lower punch 41 and is used to apply a defined surface pressure during measurement. The lower punch 41 is integrated into the platform 21, wherein the circular lower pressure plate 3 protrudes relative to the solid platform 21. Accordingly, the lower punch 41 has a similarly protruding annular support surface, which coincides with the annular working surface of the inherent counterweight 19. The upper pressure plate 5 is connected to the test counterweight 9 via a ball joint 43. With the help of the ball joint 43, the contact surfaces 23 of the upper pressure plate 5 and the lower pressure plate 3 can be precisely adjusted and aligned in a plane.

[0083] and Figure 5 compared to, Figure 6A measuring device 1 is shown during thickness measurement at the introduced gas diffusion layer 11, wherein a preset pressure F, due to the gravity of the test weight, is introduced through an upper pressure plate 5. The test weight 9 is lowered along with the upper pressure plate 5, thereby causing the test force F to induce local surface pressure defined by the gas diffusion layer 11. Furthermore, the inherent weight 19 is also lowered accordingly and rests precisely against the periphery of the opposing annular protrusion support surface relative to the lower punch 41. This achieves a very accurate and repeatable planar orientation of the gas diffusion layer 11 for measurement, and is completely decoupled from the test force F introduced by the test weight 9. Therefore, the measurement can be performed very accurately and conveniently, because the test force F is conveniently provided as the gravity of the solid test weight 9, which therefore has little or no tolerance. Due to the simplicity of the measuring device 1 and the measuring method, cumbersome compensation is not required as with previously known general-purpose testing machines used for this measurement purpose.

[0084] Figure 7 A cross-sectional view of the lower punch 41 with the lower pressure plate 3 is shown, and Figure 8 It shows that according to Figure 7 The corresponding plan view of the lower punch 41. For the lower punch 41, the lower pressure plate 3 is an integral component. The lower pressure plate 3 is cylindrical and has a circular component contact surface 23 with a predetermined diameter D, for example, D=50mm. The component contact surface 23 is flat and surface-treated, for example, polished, and has a low average roughness Rz<4. The total diameter G of the lower punch 41 is typically G=190mm. The inner diameter A can be, for example, A=110mm, and the outer diameter B can be, for example, B=140mm. Thus, equally protruding annular surfaces 45 are formed as support surfaces, which concentrically and radially spaced around the component contact surface 23. The lower punch 41 is a single piece and made of solid stainless steel, preferably made as a machined part and surface-treated. The transition portion from the protruding annular surface 45 in a radially inward direction to the protruding component contact surface 23, and the transition portion in a radially outward direction to the edge of the lower punch 41, is constructed as a ramp 47, which has an angle α typically of α = 20°. This provides a concentric recess around the lower pressure plate 3, which advantageously facilitates the insertion and positioning of the gas diffusion layer 11 for measurement. In this recess around the lower pressure plate 3, a smooth transition region 49 abuts the ramp 47 from the radially inward side.

[0085] Figure 9 A schematic plan view of the measuring stage 27 is shown. This provides a measuring system for measuring the thickness of the gas diffusion layer 11. The measuring stage 27 has a solid platform 21 and integrates the aforementioned measuring device 1. Depending on the number of measuring points 25, a corresponding number of lower punches 41 and corresponding lower pressure plates 3 are integrated into the platform 21, correspondingly compared... Figure 7 and Figure 8 The measuring points 25 are arranged in a regular grid pattern on the platform 21. The desired position and location of the gas diffusion layer 11 can be precisely and flexibly set via variable stops 49, and this setting is adjustable. Depending on the number and arrangement of the measuring points 25 on the measuring platform, each measuring point 25 is equipped with its own C-shaped support 39, which has a corresponding lifting mechanism 15. To raise and lower the test counterweight 9 during a series of measurements, a guide device 53 is mounted on the support 39, which can be activated, for example, by a rope traction system. A safety device 51, such as a light curtain, is also provided to protect the operator 55. Furthermore, a control device with an operation panel 29 is provided, allowing for automatic control and monitoring of the measurement process. Here, measurement data from the distance sensor 13 or calibration device 17 is read into the processor and processed. A transmission device (not shown in detail) can be set up for automatic feeding. A central computer with an operation device is advantageous for controlling and monitoring the process. At the operation station, the results are displayed and saved on the operation panel 29. Operator 55 can trigger the measurement, for example, via a foot switch. Simultaneously, a manual maintenance function is implemented on the measuring platform 27 as needed, in which the platform can be moved towards the lower end of the test counterweight 9 to, for example, adjust the ball joint 43.

[0086] In the process of measuring the thickness of the gas diffusion layer 11, a measuring device 1 is provided, in which the gas diffusion layer 11 is placed as a flat member 10 into the measuring device 1. During the measurement process, a limited surface pressure is generated by lowering the test weight 9, and a preset test force F is applied to the gas diffusion layer by means of the gravity of the test weight 9. The distance between the upper pressure plate 5 and the lower pressure plate 3 is determined under the preset test force F. During this process, the current reference value is determined as the corresponding zero point, and the distance between the upper pressure plate 5 and the lower pressure plate 3 is calibrated accordingly. During the measurement process, thickness measurements are simultaneously performed at multiple measuring points 25 distributed on the surface of the gas diffusion layer 11.

Claims

1. A measuring device (1) for measuring the thickness of a gas diffusion layer (11) of an electrochemical cell (31), the measuring device comprising a lower pressure plate (3), an upper pressure plate (5) and a test weight (9) guided by a vertical guide (7), wherein during the measurement process, the gravity of the test weight (9) can apply a preset test force to the flat member (10, 11) to be tested, thereby generating a limited surface pressure, and the measuring device further comprising a distance sensor (13), wherein the distance sensor can determine the distance between the upper pressure plate (5) and the lower pressure plate (3) under the action of a preset test force (F) as the thickness measurement value (H) of the flat member (10, 11).

2. The measuring device (1) according to claim 1, the measuring device includes a lifting mechanism (15) that can lower the test counterweight (9) and thereby apply a preset test force (F) to the flat member (10, 11) by gravity.

3. The measuring device (1) according to claim 2, wherein, The lifting mechanism (15) is decoupled from the test counterweight (9) during the measurement process, so that no additional force is applied to the flat member (10, 11) except for the test force (F) generated by the test counterweight (9).

4. The measuring device (1) according to any one of the preceding claims, wherein, The gravity of the test counterweight (9) can be adjusted, thereby enabling the calibration of the test force (F).

5. The measuring device (1) according to any one of the preceding claims, wherein, The vertical guide (7) is fixed and does not rotate around the vertical axis, thereby ensuring that the test weight (9) is accurately and repeatably lowered.

6. The measuring device (1) according to any one of the preceding claims, wherein, A calibration device (17) is provided, which can determine the current reference value as the zero point for distance measurement, and thereby calibrate the distance between the upper pressure plate (5) and the lower pressure plate (3).

7. The measuring device (1) according to any one of the preceding claims, wherein, An inherent counterweight (19) is provided, which is arranged radially on the outside of the vertically guided upper pressure plate (5), so that when the upper pressure plate (5) is lowered, the flat member (10, 11) to be tested can be flattened on the base under the gravity of the inherent counterweight (19).

8. The measuring device (1) according to any one of the preceding claims, wherein, The inherent counterweight (19) is fixed and does not rotate about the vertical axis, wherein the inherent counterweight (19) can be locked and removed as needed.

9. The measuring device (1) according to any one of the preceding claims, wherein, The pressure plates (3, 7) are circular flat plates made of hardened and corrosion-resistant steel, and the pressure plates are oriented in a consistent and planar parallel manner.

10. The measuring device (1) according to any one of the preceding claims, wherein, The upper pressure plate (5) is axially connected to the test counterweight (9) via a ball joint (43), thereby enabling adjustment of the plane parallel orientation of the pressure surfaces of the upper pressure plate (5) and the lower pressure plate (3).

11. A measuring device (1), the measuring device having multiple plate pairs, each plate pair including an upper pressure plate (5) and a lower pressure plate (3), wherein, The plates are arranged such that, during measurement, the corresponding thickness measurements (H) of the flat members (10, 11) introduced for the purpose of measurement can be determined simultaneously at multiple measurement points (25).

12. The measuring device (1) according to claim 11, wherein, The plates are regularly arranged on the surface, thereby enabling the determination of the corresponding local thickness measurements (H) of the flat members (10, 11) introduced for measurement.

13. A measuring table (27), the measuring table comprising a measuring device (1) according to any one of the preceding claims, the measuring table comprising a platform (21) in which a lower pressure plate (3) is integrated, wherein, A support surface is formed on the platform (21) for receiving flat members (10, 11) for thickness measurement.

14. The measuring station (27) according to claim 13, wherein the measuring station includes a control device with an operation panel (29) for controlling and monitoring the measurement process, wherein, It can read the measurement data from the distance sensor (13) into the processor and process it.

15. The measuring table (27) according to claim 13 or 14, the measuring table comprising a transfer device for loading and unloading the flat components (10, 11).

16. A method for measuring the thickness of a gas diffusion layer (11) in an electrochemical cell (31), wherein, A measuring device is provided according to any one of claims 1 to 12, wherein a gas diffusion layer (11) is placed in the measuring device (1) as a flat member (10), wherein during the measurement process, a defined surface pressure is generated by reducing the test weight (9), and a preset test force (F) is applied to the gas diffusion layer (11) by means of the gravity of the test weight (9), and wherein the distance between the upper pressure plate (5) and the lower pressure plate (3) is determined under the preset test force (F).

17. The method according to claim 16, wherein, The current reference value is determined as the corresponding zero point, and the distance between the upper pressure plate (5) and the lower pressure plate (3) is calibrated accordingly.

18. The method according to claim 16 or 17, wherein, During the measurement process, thickness measurements are performed simultaneously at multiple measurement points (25) distributed on the surface of the gas diffusion layer (11).

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