Fuel cell stack manufacturing method, fuel cell stack, and vehicle

Abstract

The application relates to a fuel cell stack manufacturing method, a fuel cell stack and a vehicle. The fuel cell stack manufacturing method comprises the following steps: obtaining a stack size parameter, an initial pressing force, a stack mechanical property parameter and a spring mechanical property parameter; calculating a spring size parameter according to the stack size parameter, the initial pressing force, the stack mechanical property parameter and the spring mechanical property parameter; selecting a target spring according to the spring size parameter; stacking a plurality of cells along a first direction to form a core; abutting the target spring against one side of the core along the first direction, and fixing the target spring and the core. The method can solve the problem that the buffering and compensation effect of the current technology is poor.

Description

Technical Field

[0001] This application relates to the field of vehicle technology, and in particular to a method for manufacturing a fuel cell stack, a fuel cell stack, and a vehicle. Background Technology

[0002] A proton exchange membrane fuel cell (PEMFC) is an electrochemical device that converts the chemical energy of fuel into electrical energy. It has advantages such as high energy conversion efficiency, low emissions, low pollution, low noise, and convenient maintenance, and is therefore widely used in fuel cell stacks in vehicles.

[0003] A fuel cell stack typically consists of multiple individual cells connected in series. These cells are clamped together by end plates at both ends and secured with bolts or cable ties. Because the stack expands and contracts internally, it usually requires components such as springs for cushioning and compensation. However, current technology suffers from inadequate cushioning and compensation in fuel cell stacks. Summary of the Invention

[0004] Therefore, it is necessary to provide a fuel cell stack manufacturing method, a fuel cell stack, and a vehicle to address the problem of poor buffering and compensation effects of fuel cell stacks.

[0005] According to one aspect of this application, a method for manufacturing a fuel cell stack is provided, comprising the following steps: obtaining stack size parameters, initial pressing force, stack mechanical performance parameters, and spring mechanical performance parameters; calculating spring size parameters based on the stack size parameters, the initial pressing force, the stack mechanical performance parameters, and the spring mechanical performance parameters; selecting a target spring based on the spring size parameters; stacking multiple cells along a first direction to form a stack core; and abutting the target spring against one side of the stack core along the first direction and fixing the target spring to the stack core.

[0006] In some embodiments, the stack size parameters include stack length and stack width; wherein the length extension direction of the stack is perpendicular to the width extension direction of the stack, and both the length extension direction and the width extension direction of the stack are perpendicular to the first direction.

[0007] In some embodiments, calculating the spring size parameters based on the fuel cell stack size parameters, the initial pressing force, the fuel cell stack mechanical performance parameters, and the spring mechanical performance parameters includes: pre-selecting a preset spring outer diameter, the number of spring columns, and the number of spring rows based on the fuel cell stack length and the fuel cell stack width; and pre-selecting a preset spring cross-sectional circle diameter based on the preset spring outer diameter; wherein the spring row direction is parallel to the length extension direction of the fuel cell stack, and the spring column direction is parallel to the width extension direction of the fuel cell stack.

[0008] In some embodiments, obtaining the mechanical performance parameters of the spring includes: selecting the material of the spring; and obtaining the tensile strength of the spring based on the spring material properties and the preset spring cross-sectional circle diameter.

[0009] In some embodiments, the mechanical performance parameters of the fuel cell stack include the fuel cell stack force retention rate; obtaining the mechanical performance parameters of the spring includes: calculating the maximum load and minimum load of the spring based on the initial pressing force, the number of spring columns, and the number of spring rows; and calculating the allowable shear stress of the spring based on the maximum load, minimum load, fuel cell stack force retention rate, and tensile strength of the spring.

[0010] In some embodiments, calculating the spring size parameters based on the fuel cell stack size parameters, the initial pressing force, the fuel cell stack mechanical performance parameters, and the spring mechanical performance parameters includes: determining the preset spring mean diameter and the preset spring inner diameter based on the preset spring outer diameter; calculating the preset spring helix ratio based on the preset spring mean diameter and the preset spring cross-sectional circle diameter; calculating the reference spring cross-sectional circle diameter based on the spring maximum load, the spring allowable shear stress, the preset spring helix ratio, and the preset spring mean diameter, and rounding the reference spring cross-sectional circle diameter to an integer to obtain the modified spring cross-sectional circle diameter; and determining the modified spring mean diameter, the modified spring outer diameter, and the modified spring inner diameter based on the modified spring cross-sectional circle diameter.

[0011] In some embodiments, the fuel cell stack mechanical performance parameters include the fuel cell stack expansion rate; calculating the spring size parameters based on the fuel cell stack size parameters, the initial pressing force, the fuel cell stack mechanical performance parameters, and the spring mechanical performance parameters includes: determining the spring stiffness coefficient based on the spring maximum load, the spring minimum load, and the fuel cell stack expansion rate; calculating the effective number of spring coils based on the spring stiffness coefficient, the modified spring outer diameter, and the spring material shear modulus; calculating the modified spring pitch and the modified spring helix angle based on the modified spring outer diameter; and calculating the spring free height based on the modified spring outer diameter, the modified spring cross-sectional circle diameter, the effective number of spring coils, and the modified spring pitch.

[0012] In some embodiments, the fuel cell stack manufacturing method further includes: calculating a spring safety factor based on the allowable shear stress of the spring, and calculating a spring stability factor based on the spring free height and the modified spring outer diameter; comparing the spring safety factor with a safety factor range, and comparing the spring stability factor with a stability factor range; confirming whether the spring safety factor falls within the safety factor range and whether the spring stability factor falls within the stability factor range; if so, selecting a target spring based on the modified spring mean diameter, the modified spring outer diameter, the modified spring inner diameter, the effective number of spring coils, and the spring free height; if not, recalculating the spring size parameters.

[0013] According to another aspect of this application, a fuel cell stack is provided, comprising: a stack core formed by stacking a plurality of cells along a first direction; and a plurality of springs abutting against one side of the stack core along the first direction, wherein the dimensional parameters of the springs are obtained using the fuel cell stack manufacturing method described above.

[0014] According to another aspect of this application, a vehicle is provided, including a fuel cell stack as described above.

[0015] The fuel cell stack manufacturing method provided in this application obtains the stack's dimensional and mechanical performance parameters, and calculates parameters such as the spring's free height and outer diameter by combining the initial pressing force of the stack and the mechanical performance parameters of the spring. Then, based on the calculation results, a suitable target spring is selected and placed against the stack core along the stacking direction, thereby utilizing the spring to buffer and compensate for the multiple stacked cells. Because the spring selection matches the stack's requirements, the spring can better meet the stack's buffering and compensation needs. Attached Figure Description

[0016] Figure 1 A perspective view of a fuel cell stack according to an embodiment of this application is shown;

[0017] Figure 2 It shows Figure 1 A schematic diagram of the split structure of a fuel cell stack.

[0018] Explanation of icon numbers:

[0019] 1. Fuel cell stack;

[0020] 10. Core; 20. Spring; 30. Inlet end plate; 40. Inlet end manifold; 50. Blind end manifold; 60. Blind end plate; 70. Blind end pressure plate; 71. Guide post; 80. Fastener;

[0021] X, the first direction. Detailed Implementation

[0022] To make the above-mentioned objectives, features, and advantages of this application more apparent and understandable, the specific embodiments of this application are described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of this application. However, this application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of this application. Therefore, this application is not limited to the specific embodiments disclosed below.

[0023] In the description of this application, it should be understood that if terms such as "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential" appear, these terms indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application.

[0024] Furthermore, where the terms "first" and "second" appear, these terms are for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined with "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, where the term "multiple" appears, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0025] In this application, unless otherwise expressly specified and limited, the terms "installation," "connection," "joining," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise expressly limited. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0026] In this application, unless otherwise expressly specified and limited, the use of descriptions such as "above" or "below" the second feature indicates that the first and second features are in direct contact or indirect contact via an intermediate medium. Furthermore, "above," "on top of," and "over" the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. Similarly, "below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0027] It should be noted that if an element is referred to as being "fixed to" or "set on" another element, it can be directly on the other element or there may be an intervening element. If an element is considered to be "connected to" another element, it can be directly connected to the other element or there may be an intervening element. If so, the terms "vertical," "horizontal," "upper," "lower," "left," "right," and similar expressions used in this application are for illustrative purposes only and do not represent the only possible implementation.

[0028] A fuel cell stack comprises multiple cells connected in series. Each cell includes a bipolar plate and a membrane electrode assembly (MEA). The bipolar plates and MEAs of the multiple cells are arranged alternately, and sealant is embedded between the cells. The stack is then secured by pressing together front and rear plates. The MEA consists of a gas diffusion layer, a catalyst layer, and a proton exchange membrane (PEM). These components are bonded together using a hot-pressing process. The bipolar plates have gas flow channels. To improve fuel cell performance, the contact resistance between the bipolar plates and the MEA needs to be minimized. Therefore, a certain force needs to be applied to the stack to compress the gas diffusion layer and simultaneously compress the sealing adhesive lines to achieve a seal.

[0029] Throughout the entire lifecycle of a fuel cell stack, operating temperatures can reach as high as 80°C, while cryogenic storage temperatures can drop as low as -40°C. With these temperature changes, the stack's internal structure expands and contracts. Additionally, aerodynamic loads exist during operation. Both temperature variations and aerodynamic loads alter the stack's assembly forces, potentially leading to loosening of the membrane electrode assembly (MEA) and seals. This, in turn, increases the contact resistance between the gas diffusion layer and the electrode plates, reduces sealing reliability, and ultimately lowers stack performance and lifespan.

[0030] Therefore, related technologies incorporate springs to buffer and compensate for the expansion and contraction within the fuel cell stack. However, in practical applications, it has been found that different fuel cell stacks have varying requirements for buffering and compensation effects. Thus, while current technologies can buffer and compensate for the expansion and contraction within the stack to some extent, their buffering and compensation effects are not ideal.

[0031] To address the aforementioned issues, this application provides a method for manufacturing a fuel cell stack. First, by obtaining the stack's dimensional and mechanical performance parameters, and combining these with the initial pressing force of the stack and the mechanical performance parameters of the springs, parameters such as the spring's free height and outer diameter are calculated. Then, based on the calculation results, a suitable spring is selected for use during the fuel cell stack fastening process, and the spring is used to adjust the stack's length. In this way, the spring selection matches the stack's requirements, enabling the spring to better meet the stack's buffering and compensation needs.

[0032] An embodiment of this application provides a method for manufacturing a fuel cell stack, comprising the following steps:

[0033] Obtain the fuel cell stack dimensional parameters, initial pressing force, fuel cell stack mechanical performance parameters, and spring mechanical performance parameters;

[0034] Calculate the spring dimensions based on the fuel cell stack size parameters, initial pressing force, fuel cell stack mechanical performance parameters, and spring mechanical performance parameters;

[0035] Select the target spring based on its size parameters;

[0036] Multiple batteries are stacked along a first direction to form a core;

[0037] The target spring is placed against one side of the reactor core along the first direction, and the target spring is fixed to the reactor core.

[0038] It is understandable that during the fuel cell stack manufacturing process, multiple cells need to be stacked. Two end plates, such as a front plate and a rear plate, are placed on the outside of the stacked cells, and an initial pressing force is applied to the stacked cells to maintain a relatively stable relative position after the fuel cell stack is manufactured. Factors affecting the selection of the initial pressing force include the fuel cell stack operating pressure, the material properties of the fuel cell stack sealing strip, the design of the fuel cell stack cross-sectional dimensions, and the operating characteristics of the fuel cell stack module membrane electrode gas diffusion layer.

[0039] Specifically, when using the fuel cell stack cross-sectional dimensions as the basis for selecting the initial pressing force, the force can be selected based on the planar dimensions of the bipolar plates. Fuel cell stacks with larger planar dimensions require a greater pressing force. When using the operating characteristics of the membrane electrode gas diffusion layer of the fuel cell stack assembly as the basis for selecting the initial pressing force, the initial pressing force corresponding to the compression characteristics and compression amount of the gas diffusion layer can be selected based on compression characteristic test data. For example, when the bipolar plate dimensions of the fuel cell stack are 400mm × 100mm and the inlet end plate dimensions are 430mm × 130mm, an initial pressing force of 40000N can be selected.

[0040] The fuel cell stack manufacturing method provided in this embodiment obtains the stack's dimensional and mechanical performance parameters, and calculates parameters such as the spring's free height and outer diameter by combining the initial pressing force of the stack and the spring's mechanical performance parameters. Then, based on the calculation results, a suitable target spring is selected and placed against the stack core along the stacking direction. This utilizes the spring to buffer and compensate for the multiple stacked cells. Because the spring selection matches the stack's requirements, the spring can better meet the stack's buffering and compensation needs.

[0041] Optionally, the spring is a helical spring. Therefore, the use of helical springs offers a significant weight reduction advantage compared to traditional disc springs. Specifically, the helical spring can be a single-strand helical spring or a multi-strand helical spring. The cross-sectional shape of the helical spring can be circular, rectangular, or square. The material of the helical spring can be carbon spring steel wire, high-performance spring steel wire, alloy spring steel wire, or spring steel. Based on the selected material of the helical spring, the mechanical properties of the material, such as Young's modulus and tensile strength, can be determined.

[0042] Furthermore, the surface of the spring is treated with electroplating, oxidation, or phosphating to protect it from corrosion.

[0043] In some embodiments, the dimensional parameters of the battery stack include the length and width of the battery stack; wherein the length extension direction of the battery stack is perpendicular to the width extension direction of the battery stack, and both the length extension direction and the width extension direction of the battery stack are perpendicular to a first direction. Based on this, the area available for arranging the spring can be determined by the battery stack length and width. Further, the battery stack length and width can be determined based on the bipolar plate length and width. For example, the battery stack length is greater than or equal to the bipolar plate length, and the battery stack width is greater than or equal to the bipolar plate width.

[0044] In some embodiments, calculating the spring size parameters based on the fuel cell stack size parameters, initial pressing force, fuel cell stack mechanical performance parameters, and spring mechanical performance parameters includes: pre-selecting the preset spring outer diameter, number of spring rows, and number of spring columns based on the fuel cell stack length and width; and pre-selecting the preset spring cross-sectional circle diameter based on the preset spring outer diameter. The row direction of the spring is parallel to the length extension direction of the fuel cell stack, and the column direction of the spring is parallel to the width extension direction of the fuel cell stack. Taking a bipolar plate size of 400mm × 100mm and an inlet end plate size of 430mm × 130mm as an example, considering the bipolar plate size and inlet end plate size, and taking into account clearance and load-bearing capacity, based on existing experience, the preset spring outer diameter is selected as 50mm, and the preset spring cross-sectional circle diameter is selected as 8.5mm. Two rows of springs are arranged along the width direction of the bipolar plate, and six rows are arranged along the length direction of the bipolar plate, for a total of 12 sets of springs. The multiple springs in the width direction are evenly spaced, and the multiple springs in the length direction are evenly spaced to ensure uniform spring distribution and thus uniform force transmission.

[0045] Understandably, in practical applications, although the springs currently used in this technology do not provide ideal buffering and compensation for the fuel cell stack, the outer diameter of the springs can be preliminarily selected based on current technological practices. The number of springs that can be arranged in the length and width directions can then be determined based on this outer diameter. Then, the spring stability coefficient and safety factor are verified using the spring size parameter calculation method of this application to determine if they are acceptable. If not, springs with larger or smaller outer diameters are selected based on the spring stability coefficient and safety factor, and the acceptance of the reselected springs is further verified until the selected springs are acceptable. This reduces the number of verification steps. Alternatively, without relying on existing experience, springs with different outer diameters can be selected sequentially, and the spring stability coefficient and safety factor of each selected spring can be verified one by one using the spring size parameter calculation method of this application.

[0046] In some embodiments, obtaining the mechanical performance parameters of the spring includes: selecting the spring material; and obtaining the tensile strength of the spring based on the spring material properties. For example, oil-quenched spring steel wire is selected, and its tensile strength is approximately 1400 MPa, which can be obtained by referring to a table.

[0047] Optionally, the fuel cell stack mechanical performance parameters include the stack force retention rate. This force retention rate is obtained based on existing experimental and simulation data. Considering that the elongation and contraction of the fuel cell stack will affect the contact resistance of its components, its airtightness, and its external electrical performance, the force retention rate needs to be selected. For example, a force retention rate of 50%-70% requires that the initial pressing force be maintained at 50%-70% under the action of the spring, so that the contact resistance and airtightness of the fuel cell stack components meet design requirements, and the external electrical performance meets the initial design requirements. Since factors affecting the force retention rate include the geometry of the spring, such as the helix ratio and the number of coils, this application obtains the required spring mechanical performance parameters based on the force retention rate requirements and calculates the spring size parameters based on these parameters to select a suitable spring. In other words, this application takes the stack force retention rate as one of the factors to consider when selecting springs, so that the contact resistance of each component of the stack, the stack airtightness, and the stack's external electrical performance, which are affected by the stack force retention rate, become factors to consider when selecting springs, thereby making the selection of springs more reasonable.

[0048] Furthermore, obtaining the mechanical performance parameters of the spring includes: calculating the maximum and minimum loads of the spring based on the initial pressing force, the number of spring rows, and the number of spring columns; and calculating the allowable shear stress of the spring based on the maximum and minimum loads, the stack force retention rate, and the tensile strength of the spring. Specifically, the allowable shear stress of the helical spring is determined based on the ratio of the maximum to minimum load that the helical spring may bear during use and the load characteristics of the spring during stack operation. For example, if the initial pressing force of the stack is 40,000 N, oil-quenched spring steel wire is selected, and its tensile strength is approximately 1400 MPa according to a table, with 2 rows of springs arranged along the width of the bipolar plates and 6 rows along the length of the bipolar plates, totaling 12 sets of springs, and the stack force retention rate is 60%, the maximum load of each set of springs is 3333 N, and the minimum load is 2000 N. Based on this, the allowable shear stress of the spring is approximately 650 MPa.

[0049] Optionally, the spring size parameters are calculated based on the fuel cell stack size parameters, initial pressing force, fuel cell stack mechanical performance parameters, and spring mechanical performance parameters, including: determining the preset spring mean diameter and preset spring inner diameter based on the preset spring outer diameter; calculating the preset spring helix ratio based on the preset spring mean diameter and preset spring cross-sectional circle diameter; calculating the reference spring cross-sectional circle diameter based on the spring maximum load, spring allowable shear stress, preset spring helix ratio, and preset spring mean diameter, and rounding the reference spring cross-sectional circle diameter to an integer to obtain the modified spring cross-sectional circle diameter; and determining the modified spring mean diameter, modified spring outer diameter, and modified spring inner diameter based on the modified spring cross-sectional circle diameter. Optionally, the preset spring helix ratio C is 4-16, and further, the preset spring helix ratio C is 5-8.

[0050] Taking a bipolar plate size of 400mm × 100mm and an inlet end plate size of 430mm × 130mm as an example, based on a preset outer diameter of 50mm for the spring, a preset spring cross-sectional circle diameter of 8.5mm can be selected. The difference between the preset outer diameter and the preset spring cross-sectional circle diameter is the preset spring mean diameter. In this case, the preset spring mean diameter is 41.5mm, and the preset spring inner diameter is 33mm. The preset spring helix ratio is calculated to be 4.9 based on the preset spring helix ratio and the preset spring cross-sectional circle diameter. The curvature coefficient K of the spring is then calculated according to the formula. The calculated preset spring curvature coefficient is 1.3. Based on this, the reference spring cross-sectional circle diameter is further calculated according to the spring's maximum load, allowable shear stress, preset spring helix ratio, and preset spring mean diameter. The reference spring cross-sectional circle diameter is then rounded to the nearest integer, resulting in a corrected spring cross-sectional circle diameter of 9 mm. Based on this corrected spring cross-sectional circle diameter, the spring dimensions are verified, yielding a corrected spring mean diameter of 41 mm, a corrected spring outer diameter of 50 mm, and a corrected spring inner diameter of 32 mm.

[0051] Optionally, the fuel cell stack mechanical performance parameters include the stack's operational expansion rate. Based on the fuel cell stack size parameters, initial pressing force, fuel cell stack mechanical performance parameters, and spring mechanical performance parameters, the spring size parameters are calculated as follows: The spring stiffness coefficient is determined based on the spring's maximum load, minimum load, and the fuel cell stack's operational expansion rate; the effective number of spring coils is calculated based on the spring stiffness coefficient, the modified spring outer diameter, and the spring material shear modulus; the modified spring pitch and helix angle are calculated based on the modified spring outer diameter; and the spring free height is calculated based on the modified spring outer diameter, the modified spring cross-sectional circle diameter, the effective number of spring coils, and the modified spring pitch. It is understood that during fuel cell stack operation, pressure changes, temperature changes, permanent compression deformation of the sealing strip, and creep of the membrane electrode gas diffusion layer all affect the overall size changes of the fuel cell stack. Specifically, increased temperature and operating pressure lead to material expansion; decreased temperature leads to material contraction. This size change of the fuel cell stack can be characterized by the fuel cell stack's operational expansion rate, reflecting the length adjustment requirements of the fuel cell stack. For example, during use, springs are affected by factors such as temperature changes, operating pressure changes, and material creep, resulting in a total elongation and contraction of approximately 10 mm. This application incorporates the fuel cell stack's expansion and contraction rate, a key mechanical performance parameter, as one of the factors to consider when selecting springs, thereby enabling a higher degree of spring matching.

[0052] This application determines the required stiffness coefficient of the spring based on the difference between the maximum and minimum loads of the spring, the sum of the absolute values ​​of elongation and contraction along the stacking direction during the use of the fuel cell stack, and the ratio of this difference to the sum. The required number of effective spring coils is calculated based on the spring stiffness coefficient, the shear modulus of the spring material, and the modified spring outer diameter. Optionally, both ends of the spring are ground flat, and 1-5 coils, preferably 2-3 coils, are retained as support coils. The total number of spring coils is the sum of the effective spring coils and the number of support coils. For example, the effective spring coils are 7, both ends are fixed and ground flat, with 1 coil retained at each end as a support coil, resulting in a total of 9 coils. Based on the modified spring outer diameter, considering the spring load and the gap between coils, a modified spring outer diameter of 0.1 to 1 times is selected as the modified spring pitch, preferably 0.25 to 0.65 times the modified spring outer diameter. For example, the modified spring pitch is 12.5 mm. The corrected spring helix angle is calculated based on the corrected spring outer diameter and corrected spring pitch, and the range of the corrected spring helix angle is 4° to 10°. Based on the corrected spring outer diameter, corrected spring cross-sectional circle diameter, effective number of spring coils, and corrected spring pitch, the spring free height is calculated to be 126mm, and the corrected spring helix angle is 5.5°, which meets the requirements of the preferred range.

[0053] Optionally, the fuel cell stack manufacturing method further includes: calculating the spring safety factor based on the allowable shear stress of the spring, and calculating the spring stability coefficient based on the spring free height and the modified spring outer diameter; comparing the spring safety factor with the safety factor range, and comparing the spring stability coefficient with the stability coefficient range; confirming whether the spring safety factor falls within the safety factor range and the spring stability coefficient falls within the stability coefficient range; if so, selecting a target spring based on the modified spring mean diameter, modified spring outer diameter, modified spring inner diameter, effective number of spring coils, and spring free height; if not, recalculating the spring size parameters. For example, the spring safety factor ranges from 1.1 to 1.4, and the stability coefficient is less than 5.5. In one embodiment of this application, the spring has a safety factor of 1.12, which meets the usage requirements, and a stability coefficient of 3.0, theoretically preventing any deviation during use.

[0054] This application calculates the spring stability coefficient and compares it with a specified range to determine the spring safety factor. This safety factor is then compared with a specified range to ensure that both the spring safety factor and stability coefficient fall within the safe range before the spring is used as the target spring in the fuel cell stack. If the spring safety factor or stability coefficient does not fall within the safe range, the spring dimensions are recalculated. The spring selected in this way provides excellent supplementary adjustment throughout the fuel cell stack's entire lifecycle. Based on the spring's dimensions and compressed characteristics, and by matching it with blind-end plates, blind-end pressure plates, and other structural designs, a compact and highly reliable fuel cell stack is formed.

[0055] In one exemplary embodiment, a method for manufacturing a fuel cell stack with bipolar plates measuring 400mm × 100mm and an inlet end plate measuring 430mm × 130mm includes the following steps:

[0056] Choose the type of spring, specifically a single-strand helical spring with a circular cross-section, and the spring material is oil-quenched spring steel wire; based on the material properties, its shear modulus and Young's modulus can be obtained by querying the material parameters;

[0057] Based on the bipolar plate size and other fuel cell stack size parameters, the initial pressing force of the fuel cell stack is selected as 40000N;

[0058] Based on the fuel cell stack dimensions, the preset spring outer diameter is 50mm, the number of spring columns is 2, and the number of spring rows is 6. Since the force borne by a single spring is equal to the ratio of the initial pressing force to the total number of springs, the maximum load of each group of springs can be determined to be 3333N based on the initial pressing force and the number of springs. Combining this with the fuel cell stack force retention rate of 60%, the minimum load of each group of springs can be determined to be 2000N. Based on this, the allowable shear stress of the springs is further determined to be approximately 650MPa.

[0059] Based on the preset outer diameter of the spring, the preset diameter of the spring cross-section circle is determined to be 8.5mm. By referring to the table, its tensile strength can be obtained as approximately 1400MPa.

[0060] Based on the preset outer diameter of the spring, the preset middle diameter of the spring is determined to be 41.5mm and the preset inner diameter of the spring is 33mm.

[0061] Based on the preset spring mean diameter and preset spring cross-sectional circle diameter, the preset spring helix ratio is calculated to be 4.9;

[0062] Based on the preset spring helix ratio, the preset spring curvature coefficient is calculated to be 1.3;

[0063] Based on the maximum load of the spring, the allowable shear stress of the spring, the preset spring helix ratio, and the preset spring mean diameter, after recalculation and rounding, the corrected spring cross-section circle diameter is obtained as 9mm.

[0064] Based on the rounded spring, the corrected spring mean diameter is 41mm, the corrected spring outer diameter is 50mm, and the corrected spring inner diameter is 32mm.

[0065] Based on the maximum load of the spring, the minimum load of the spring, the expansion rate of the fuel cell, the corrected mean diameter of the spring, the corrected diameter of the spring section circle, and the tangential modulus of the spring material, the effective number of coils of the spring is calculated to be 7. This spring is fixed at both ends, and the ends are ground flat. One coil is retained on each side as a support coil, so the total number of coils of the spring is 9.

[0066] The spring pitch is tentatively set at 12.5mm. If this is satisfied, the calculated free height of the spring is 126mm, and the helix angle of the spring is 5.5°, which meets the requirements of the preferred range.

[0067] After verification, the safety factor of the spring is 1.12, which meets the usage requirements; its stability factor is 3.0, and theoretically, it will not deflect during use.

[0068] Based on the dimensions of this spring and its characteristics after compression, and by matching the structural design of blind end plates, blind end pressure plates, and other components, a compact and highly reliable fuel cell stack was fabricated.

[0069] See Figure 1 and Figure 2 , Figure 1 A perspective view of a fuel cell stack according to one embodiment of this application is shown. Figure 2 It shows Figure 1A schematic diagram of the split structure of a fuel cell stack. Based on the same inventive purpose, this application provides a fuel cell stack. In one embodiment of this application, the fuel cell stack 1 includes a core 10 and a plurality of springs 20. The core 10 includes a plurality of cells stacked along a first direction X. Each spring 20 abuts against one side of the core 10 along the first direction X, and the dimensional parameters of the spring 20 are obtained using the fuel cell stack manufacturing method described in the above embodiment.

[0070] Furthermore, the fuel cell stack 1 also includes an inlet end plate 30, an inlet end manifold 40, a blind end manifold 50, a blind end plate 60, a blind end pressure plate 70, and fasteners 80. The stack core 10 is located between the inlet end manifold 40 and the blind end manifold 50. The inlet end plate 30 is located on the side of the inlet end manifold 40 away from the blind end manifold 50, the blind end plate 60 is located on the side of the blind end manifold 50 away from the inlet end manifold 40, and the blind end pressure plate 70 is located on the side of the blind end plate 60 away from the blind end manifold 50. A spring 20 is located between the blind end plate 60 and the blind end pressure plate 70. Fasteners 80 fix the inlet end plate 30, the inlet end manifold 40, the blind end manifold 50, the blind end plate 60, and the blind end pressure plate 70 of the stack core 10.

[0071] Optionally, the intake end plate 30 and the blind end plate 60 are made of engineering plastics, such as polyphenylene sulfide (PPS), polyamide (PA), polyphenylene ether (PPO), high-temperature resistant nylon (PPA), etc., filled with glass fiber, wherein the filling ratio of glass fiber ranges from 30% to 55%.

[0072] Optionally, the materials for the intake manifold 40 and the blind manifold 50 can be high-purity copper such as electrolytic copper as the base material, with nickel, silver or gold plated on the surface of the base material, and the plating thickness less than or equal to 10μm.

[0073] Optionally, the blind end pressure plate 70 is made of aluminum alloy, and its surface has guide posts 71 that are adapted to the spring 20. The end of the spring 20 away from the blind end plate 60 can be sleeved on the guide post 71, and there is a gap between the spring 20 and the guide post 71, for example, a gap of 0.1mm to 1mm, so as to facilitate the cooperation between the spring 20 and the guide post 71, while preventing the spring 20 from shaking.

[0074] Optionally, the fastening method can be a pull rod, bolt, or strap, with the corresponding fasteners 80 being a pull rod, a long bolt rod, or a steel strap, respectively. Furthermore, to ensure electrical insulation safety and structural compactness, the surface of the fastener 80 is covered with an insulating layer with a thickness of 1mm to 3mm.

[0075] In one exemplary embodiment, the fastener 80 is a fully wound steel strip, and four steel strips are arranged at intervals along the length of the bipolar plate. This achieves a good fastening effect.

[0076] This application establishes a relationship between the fuel cell stack size and the size limit of the helical spring 20, establishes a principle for the retention rate of the fuel cell stack force based on the needs of fuel cell stack assembly and use, and further correlates it with the size and structural characteristics of the helical spring 20. Based on the actual size and working characteristics of the helical spring 20, an evaluation criterion for the helical spring 20 is formed, and this is used as the evaluation basis to ensure the reliability of the fuel cell stack. Based on the design of the helical spring 20 and other fuel cell stack components, as well as the materials and structures, such as insulation design, grooves, guide posts 71, etc., the reliability and compactness of the fuel cell stack are further improved.

[0077] Based on the same inventive purpose, this application provides a vehicle that includes the fuel cell stack described in the above embodiments.

[0078] It should be noted that the spring terminology mentioned in this case, such as shear modulus, Young's modulus, helix ratio, curvature coefficient, stability coefficient, mean diameter, and outer diameter, all use industry-standard expressions. Readers can obtain the relevant calculation methods by consulting relevant design documents.

[0079] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0080] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A method for manufacturing a fuel cell stack, characterized in that, Includes the following steps: Obtain the fuel cell stack dimensional parameters, initial pressing force, fuel cell stack mechanical performance parameters, and spring mechanical performance parameters; Calculate the spring size parameters based on the fuel cell stack size parameters, the initial pressing force, the fuel cell stack mechanical performance parameters, and the spring mechanical performance parameters; Select the target spring based on the spring size parameters; Multiple batteries are stacked along a first direction to form a core; The target spring is placed against one side of the core along the first direction, and the target spring is fixed to the core. The fuel cell stack dimensions include the fuel cell stack length and the fuel cell stack width; Wherein, the length extension direction of the fuel cell stack is perpendicular to the width extension direction of the fuel cell stack, and both the length extension direction and the width extension direction of the fuel cell stack are perpendicular to the first direction. The calculation of the spring size parameters based on the fuel cell stack size parameters, the initial pressing force, the fuel cell stack mechanical performance parameters, and the spring mechanical performance parameters includes: Based on the length and width of the fuel cell stack, a preset outer diameter of the spring, the number of spring columns, and the number of spring rows are selected. Pre-select the diameter of the preset spring cross-section circle based on the preset spring outer diameter; The row direction of the springs is parallel to the length extension direction of the fuel cell, and the column direction of the springs is parallel to the width extension direction of the fuel cell. The acquisition of spring mechanical performance parameters includes: Choose the material for the spring; The tensile strength of the spring is determined based on the properties of the spring material. The mechanical performance parameters of the fuel cell stack include the fuel cell stack force retention rate; The acquisition of spring mechanical performance parameters includes: Calculate the maximum spring load and the minimum spring load based on the initial pressing force, the number of spring columns, and the number of spring rows; Calculate the allowable shear stress of the spring based on the maximum load of the spring, the minimum load of the spring, the charge retention rate of the fuel cell, and the tensile strength of the spring; The calculation of the spring size parameters based on the fuel cell stack size parameters, the initial pressing force, the fuel cell stack mechanical performance parameters, and the spring mechanical performance parameters includes: Based on the preset outer diameter of the spring, determine the preset middle diameter and the preset inner diameter of the spring; Calculate the preset spring helix ratio based on the preset spring mean diameter and the preset spring cross-sectional circle diameter; Based on the maximum load of the spring, the allowable shear stress of the spring, the preset spring helix ratio, and the preset spring mean diameter, calculate the diameter of the reference spring section circle, and round the diameter of the reference spring section circle to an integer to obtain the diameter of the modified spring section circle; Based on the diameter of the modified spring cross-section circle, determine the modified spring mean diameter, modified spring outer diameter, and modified spring inner diameter; The mechanical performance parameters of the fuel cell stack include the fuel cell stack's scaling ratio; The calculation of the spring size parameters based on the fuel cell stack size parameters, the initial pressing force, the fuel cell stack mechanical performance parameters, and the spring mechanical performance parameters includes: The spring stiffness coefficient is determined based on the maximum load of the spring, the minimum load of the spring, and the expansion and contraction rate of the fuel cell stack. Calculate the effective number of spring coils based on the spring stiffness coefficient, the modified spring outer diameter, and the spring material shear modulus; Based on the corrected spring outer diameter, calculate the corrected spring pitch and the corrected spring helix angle; The free height of the spring is calculated based on the outer diameter of the modified spring, the diameter of the cross-sectional circle of the modified spring, the effective number of spring coils, and the pitch of the modified spring.

2. The method for manufacturing a fuel cell stack according to claim 1, characterized in that, The method for manufacturing the fuel cell stack also includes: Calculate the spring safety factor based on the spring's allowable shear stress, and calculate the spring stability coefficient based on the spring's free height and the corrected spring outer diameter. The spring safety factor is compared with the safety factor range, and the spring stability factor is compared with the stability factor range; Confirm whether the spring safety factor falls within the safety factor range and whether the spring stability factor falls within the stability factor range; If so, then select the target spring based on the mean diameter of the corrected spring, the outer diameter of the corrected spring, the inner diameter of the corrected spring, the effective number of spring coils, and the free height of the spring; If not, then recalculate the spring size parameters.

3. A fuel cell stack, characterized in that, include: A core is formed by stacking multiple batteries along a first direction; A plurality of springs are provided, the springs abutting against one side of the stack core along the first direction, and the dimensional parameters of the springs are obtained using the fuel cell stack manufacturing method as described in claim 1 or 2.

4. A vehicle, characterized in that, Including the fuel cell stack as described in claim 3.

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