Tool-free fuel cell short stack structure and assembly method thereof

Abstract

The invention provides a tool-free fuel cell short stack structure and an assembly method thereof. The tool-free fuel cell short stack structure comprises a first end plate, a second end plate, a reactor core, a positioning pin and a fastening bolt, the first end plate and the second end plate are respectively positioned at two ends of the tool-free fuel cell short stack structure; the reactor core is arranged between the first end plate and the second end plate and comprises a plurality of bipolar plates and membrane electrode assemblies which are sequentially and alternately stacked along the stacking direction; the at least three positioning pins are arranged along the stacking direction, penetrate through the first end plate and the second end plate and are used for carrying out plane positioning on the reactor core in the stacking process; the projections of the at least three positioning pins on a plane perpendicular to the stacking direction are asymmetrically arranged; a plurality of fastening bolts extend in the stacking direction and penetrate through the first end plate and the second end plate, and the fastening bolts are used for applying pressure at least in the stacking direction to the first end plate and the second end plate by being in threaded fit with the nuts so as to compress the reactor core to a preset compression size.

Description

Technical Field

[0001] This application relates to the field of fuel cell technology, and in particular to a tooling-free fuel cell short stack structure and its assembly method. Background Technology

[0002] A fuel cell is a power generation device that directly converts the chemical energy of fuel into electrical energy through an electrochemical reaction. Due to its high energy conversion efficiency and zero or low emissions, it is considered an important future direction for clean energy technology. The fuel cell stack is the core of a fuel cell system, typically composed of dozens to hundreds of individual cells (mainly including bipolar plates and membrane electrode assemblies), which are encapsulated and compressed using structural components such as end plates, current collectors, and fasteners. The assembly quality of the stack, especially the alignment accuracy of each component and the uniformity and magnitude of the pressure applied to the core, directly determines the stack's performance, sealing, and lifespan.

[0003] In existing fuel cell stack manufacturing processes, a typical assembly process includes three main steps: stacking, pressing, and final assembly. First, in the stacking step, operators use high-precision external stacking fixtures to stack thin-film components such as bipolar plates and membrane electrode assemblies in a predetermined order. These external fixtures are typically large and complex, requiring extremely high rigidity and positioning accuracy to ensure the alignment and repeatability of the entire stack during the stacking process, preventing gas leakage or uneven cell performance due to component misalignment. After stacking, the semi-finished product, including the stack core and external fixtures, is transferred to a large hydraulic or electric press for pressing. The press applies a large, precisely controlled preload force along the axial direction of the stack (i.e., the stacking direction). The preload has two main purposes: first, to compress the gas diffusion layer (GDL) in the membrane electrode assembly, achieving optimal porosity and thickness to ensure good gas transmission while forming good electrical contact with the bipolar plate flow field ribs, thus reducing contact resistance; second, to compress the sealing adhesive lines or gaskets between the bipolar plates, ensuring reliable sealing between different fluid channels (such as hydrogen, oxygen / air, and coolant) within the fuel cell stack. After the press compresses the fuel cell stack to the preset size or pressure value, the end plates at both ends are locked using fasteners such as tie rods, bolts, or straps to maintain the compressed state of the fuel cell stack. Finally, the press is removed, and the external stacking fixtures are dismantled, completing the assembly of the fuel cell stack.

[0004] However, with the rapid development of fuel cell technology, especially proton exchange membrane fuel cells (PEMFCs), towards higher power density and larger single-stack power, the traditional assembly scheme of "external tooling + large press" has gradually exposed its inherent limitations and technical problems. First, the design and manufacturing costs of high-precision stacking tooling and large-stroke presses capable of providing pressures of nearly 100 kilonewtons are extremely high, making it uneconomical for short stacks in small-batch trial production or R&D stages. Second, during manual stacking and press compaction, components within the stack, especially bipolar plates and membrane electrode assemblies, are prone to misalignment and slippage due to uneven stress or inaccurate positioning. This affects the uniformity of the flow field and current distribution within the stack, and in severe cases, may even lead to fuel leakage, posing safety hazards, or causing battery damage and shortened lifespan. Therefore, simplifying the assembly process, reducing reliance on expensive specialized equipment, and ensuring assembly accuracy and pressure uniformity have become urgent technical problems to be solved in the fuel cell manufacturing field. Summary of the Invention

[0005] To address the problems in the prior art, this application provides a tooling-free fuel cell short stack structure and its assembly method.

[0006] This application provides a tooling-free fuel cell short stack structure, including a first end plate, a second end plate, a core, locating pins, and fastening bolts. The first end plate and the second end plate are located at opposite ends of the tooling-free fuel cell short stack structure. The core is disposed between the first end plate and the second end plate, and the core includes multiple bipolar plates and membrane electrode assemblies that are alternately stacked along the stacking direction. At least three locating pins are disposed along the stacking direction, passing through the first end plate and the second end plate, and are used for planar positioning of the core during stacking. The projections of the at least three locating pins on a plane perpendicular to the stacking direction are asymmetrically arranged. Multiple fastening bolts extend along the stacking direction and pass through the first end plate and the second end plate. The fastening bolts, through threaded engagement with nuts, are used to apply pressure to the first end plate and the second end plate at least along the stacking direction to compress the core to a predetermined compression size.

[0007] Understandably, this application achieves tooling-free and press-free fuel cell stack assembly by integrating positioning and clamping functions into the structure. Specifically, the built-in positioning pins replace expensive external stacking tooling. Their asymmetrical layout provides a stable and unconstrained positioning reference for the core, solving the problem of core misalignment and slippage during stacking and ensuring assembly accuracy. Simultaneously, multiple fastening bolts directly apply pressure to the first and second end plates, replacing the function of a large press, significantly reducing equipment costs and space requirements. This solves the problems of existing technologies relying on expensive equipment, complex processes, and difficulty in guaranteeing accuracy, making it particularly suitable for R&D and small-batch production scenarios.

[0008] In one embodiment, in a projection plane perpendicular to the stacking direction, the outer contour of the core is a quadrilateral, including a first long side, a second long side, a first short side, and a second short side; wherein two positioning pins are spaced apart along the first long side; the number of positioning pins is four, and the four positioning pins are arranged around the outer periphery of the core; two positioning pins are spaced apart corresponding to the first long side, another positioning pin is arranged corresponding to the second long side, and another positioning pin is arranged corresponding to the first short side.

[0009] Understandably, by setting locating pins on both long sides and supplementing them with locating pins on the short sides, a stable constraint framework is formed, which can more effectively resist misalignment forces from the long side direction and prevent the core from rotating in a plane. Compared with a general asymmetrical layout, the positioning effect is more targeted and reliable, further improving the assembly accuracy.

[0010] In one embodiment, two positioning pins are respectively set at one-third and two-thirds of the first long side, another positioning pin is set at the midpoint of the second long side, and another positioning pin is set at the first short side and is closer to the first long side than the second long side.

[0011] Understandably, placing locating pins at the three-thirds points of the long side distributes the constraint force more evenly, effectively preventing deformation in the middle of the long side; placing them at the midpoint of the other long side provides stable single-point support, ensuring the stability of the reactor core's position and attitude throughout the assembly process, and achieving a higher level of assembly precision control. Meanwhile, among the first and second short sides, locating pins are only placed on the first short side to ensure that positioning can be achieved.

[0012] In one embodiment, the number of fastening bolts is ten; wherein, four fastening bolts are evenly spaced along the first long side, four fastening bolts are evenly spaced along the second long side, one fastening bolt is positioned at the midpoint of the first short side, and one fastening bolt is positioned at the midpoint of the second short side.

[0013] Understandably, by setting ten evenly distributed bolts, a uniformly distributed pressure field can be formed. By forming a complete pressure ring around the core, it is possible to ensure that the sealing lines inside the core are uniformly compressed, thereby guaranteeing the sealing reliability of the fuel cell stack and good electrical contact between individual cells, achieving pressure uniformity comparable to the pressing effect of a large press.

[0014] In one embodiment, both the locating pin and the fastening bolt are arranged around the outer periphery of the core; the projections of the locating pin and the fastening bolt on a plane perpendicular to the stacking direction are located between the outer contour of the core and the outer contours of the first end plate and the second end plate.

[0015] Understandably, placing the locating pins and fastening bolts in the non-active area forms a retainer around the core, which not only avoids encroachment on the effective reaction area of ​​the core and increases the power density of the fuel cell stack, achieving a compact structure, but also facilitates stacking and bolt tightening operations during assembly, improving operability.

[0016] This application also provides an assembly method for a tooling-free fuel cell short stack structure, including the following steps: Step S1: Fix the first end plate and install at least three locating pins and multiple fastening bolts on the first end plate; Step S2: Using at least three locating pins as a reference, stack multiple bipolar plates and membrane electrode assemblies of the reactor core sequentially on the first end plate; Step S3: Place the second end plate onto the locating pin and fastening bolt, and install the nut that mates with the fastening bolt, so that the nut contacts the surface of the second end plate away from the first end plate along the stacking direction; Step S4: Tighten all nuts initially so that the first end plate is roughly parallel to the second end plate, and apply an initial preload. Step S5: Gradually increase the pressure applied to the reactor core by tightening the nuts in stages, in a predetermined sequence and step amount, until the reactor core is compressed to the predetermined compression size.

[0017] Understandably, this assembly method provides a complete tooling-free and press-free operation process. By stacking components based on the structure's built-in locating pins, high-precision self-guided assembly is achieved, replacing external tooling. A precisely controlled pressurization process is provided through staged, sequential, and incremental nut tightening, avoiding component slippage caused by uneven force. This method ensures low-cost, high-precision assembly from a process perspective.

[0018] In one embodiment, in a projection plane perpendicular to the stacking direction, the outer contour of the core is a quadrilateral, including a first long side, a second long side, a first short side, and a second short side; in step S5, the predetermined order is in a diagonal sequence, first tightening the nut that mates with a fastening bolt corresponding to the middle of the first long side, then tightening the nut that mates with another fastening bolt that is set on the second long side and is diagonally set to the first fastening bolt, and finally tightening the nuts that mate with the two fastening bolts corresponding to the first and second short sides respectively.

[0019] Understandably, by alternately tightening the nuts at opposite corners, the pressure can be balanced around the core center, thus effectively maintaining the parallelism of the end plates at each pressurization step. This effectively suppresses end plate tilting and core misalignment caused by excessive force on one side, improving the stability of the manual clamping process and the assembly success rate.

[0020] In one embodiment, the number of fastening bolts is ten, and the number of nuts is correspondingly ten. Four nuts are evenly spaced along the first long side, and from the first short side to the second short side, they are arranged in the following order: seventh nut, first nut, third nut, and fifth nut. Another four nuts are evenly spaced along the second long side, and from the first short side to the second short side, they are arranged in the following order: sixth nut, fourth nut, second nut, and eighth nut. Another nut is positioned at the midpoint of the first short side and is designated as the ninth nut. Another nut is positioned at the midpoint of the second short side and is designated as the tenth nut. Step S5 includes sequentially alternating forward and reverse operations. The tightening order of the forward operation is the same as that of the first, second, third, fourth, fifth, sixth, seventh, eighth, ninth, and tenth nuts. The tightening order of the reverse operation is completely opposite to that of the forward operation.

[0021] Understandably, on the one hand, the alternating tightening sequence from the center outwards diagonally ensures roughly uniform pressure while achieving manual reactor compaction, preventing endplate tilting and core misalignment caused by excessive force on one side. On the other hand, by introducing alternating tightening methods of forward and reverse sequence operations, the cumulative errors or residual torsional stress that may occur during unidirectional tightening can be effectively offset and homogenized, resulting in a higher level of uniformity in the pressure distribution applied to the reactor core, further improving the reactor's sealing reliability and performance uniformity.

[0022] In one embodiment, the segmented clamping in step S5 means that the clamping process in step S5 includes an early clamping stage, a middle clamping stage, and a late clamping stage in chronological order; the predetermined step amount in step S5 means that the rotation angle step amount of the nut in the early clamping stage is greater than the rotation angle step amount of the nut in the middle clamping stage, and the rotation angle step amount of the nut in the middle clamping stage is greater than the rotation angle step amount of the nut in the late clamping stage.

[0023] Understandably, large step sizes are used in the early stages to improve efficiency, while the step size is gradually reduced in the middle and later stages to achieve a smooth transition and precise control. This ensures assembly efficiency and allows for fine adjustments when approaching the target size, avoiding the risk of overpressure damage to internal components (especially membrane electrode assemblies) and improving the safety of the pressing process and the accuracy of the final dimensions.

[0024] In one embodiment, the method further includes performing a leveling step S6 at the end of at least one stage of the phased pressing process and after the pressing is completed; step S6 includes measuring and adjusting the distance between the first end plate and the second end plate at each fastening bolt position using a feeler block and feeler gauge, and correcting the parallelism of the first end plate and the second end plate.

[0025] Understandably, by actively measuring and correcting the parallelism of the end plates during and after the compaction process, accumulated errors can be effectively eliminated, ensuring that the two end plates achieve extremely high parallelism in the final state. This fundamentally guarantees that the pressure applied to the entire plane of the core is highly uniform, which is the ultimate guarantee for achieving optimal battery performance, reliable sealing, and long service life. Attached Figure Description

[0026] Figure 1 This is a three-dimensional schematic diagram of the tooling-free fuel cell short stack structure provided in the embodiments of this application from one angle.

[0027] Figure 2 This is a three-dimensional schematic diagram of the tooling-free fuel cell short stack structure provided in the embodiments of this application from another angle.

[0028] Figure 3 This is a three-dimensional exploded view of the tooling-free fuel cell short stack structure provided in the embodiments of this application.

[0029] Figure 4 This is a three-dimensional exploded view of the tooling-free fuel cell short stack structure provided in the embodiments of this application.

[0030] Figure 5 This is a schematic flowchart of the assembly method for the tooling-free fuel cell short stack structure provided in the embodiments of this application.

[0031] Figure 6 This is a schematic diagram of the stacking sequence of the assembly method for the tooling-free fuel cell short stack structure provided in the embodiments of this application.

[0032] Explanation of reference numerals in the attached drawings: 11. First end plate; 12. Second end plate; 121. Blind end plate; 122. Blind end insulating plate; 13. Core; 131. First long side; 132. Second long side; 133. First short side; 134. Second short side; 14. Locating pin; 15. Fastening bolt; 16. Nut; 1601. First sequence nut; 1602. Second sequence nut; 1603. Third sequence nut; 1604. Fourth sequence nut; 1605. Fifth sequence nut; 1606. Sixth sequence nut; 1607. Seventh sequence nut; 1608. Eighth sequence nut; 1609. Ninth sequence nut; 1610. Tenth sequence nut; 17. Current collector plate. Detailed Implementation

[0033] The following is in conjunction with the appendix Figures 1 to 6 This application will be described in further detail below.

[0034] The technical solutions in the embodiments of this application will be further described in detail below with reference to the accompanying drawings. The described embodiments are only possible technical implementations of this application, but are not limited thereto. Other embodiments obtained by those skilled in the art in conjunction with the embodiments of this application without creative effort are also within the protection scope of this application.

[0035] like Figures 1 to 4 As shown in the embodiment of this application, a tooling-free fuel cell short stack structure mainly consists of a first end plate 11 and a second end plate 12 disposed at both ends in the stacking direction, a core 13 located between the two end plates, and positioning pins 14 and fastening bolts 15 for positioning and clamping. The first end plate 11 can be a gas port end plate, integrating inlet and outlet manifolds for fuel, oxidant, and coolant. The second end plate 12 can be formed by stacking a blind end plate 121 and a blind end insulating plate 122, providing support and electrical insulation. The core 13 is the core functional part of the fuel cell, consisting of multiple bipolar plates and membrane electrode assemblies stacked alternately along the stacking direction. A current collector 17 is typically disposed between the core 13 and the two end plates for collecting and conducting electrical energy. The positioning and clamping of the core 13 during assembly are achieved through the built-in positioning pins 14 and fastening bolts 15, eliminating the reliance on external large stacking tooling and presses.

[0036] In one embodiment, the first end plate 11 and the second end plate 12 are located at opposite ends of the tooling-free fuel cell short stack structure, respectively; the core 13 is disposed between the first end plate 11 and the second end plate 12, and the core 13 includes a plurality of bipolar plates and membrane electrode assemblies that are alternately stacked along the stacking direction; at least three positioning pins 14 are disposed along the stacking direction, passing through the first end plate 11 and the second end plate 12, and are used to perform planar positioning of the core 13 during stacking; the projections of the at least three positioning pins 14 on a plane perpendicular to the stacking direction are asymmetrically arranged; a plurality of fastening bolts 15 extend along the stacking direction and pass through the first end plate 11 and the second end plate 12, and the fastening bolts 15, through thread engagement with nuts 16, are used to apply pressure to the first end plate 11 and the second end plate 12 at least along the stacking direction to compress the core 13 to a predetermined compression size.

[0037] Understandably, this application achieves tooling-free and press-free fuel cell stack assembly by integrating positioning and clamping functions into the structure. Specifically, the built-in positioning pin 14 replaces expensive external stacking tooling. Its asymmetrical layout provides a stable and unconstrained positioning reference for the core 13, solving the problem of misalignment and slippage of the core 13 during stacking and ensuring assembly accuracy. Simultaneously, multiple fastening bolts 15 directly apply pressure to the first end plate 11 and the second end plate 12, replacing the function of a large press. This significantly reduces equipment costs and space requirements, solving the problems of existing technologies relying on expensive equipment, complex processes, and difficulty in guaranteeing accuracy. It is particularly suitable for R&D and small-batch production scenarios.

[0038] It should be explained that the asymmetric layout of the locating pins 14 enables precise positioning without over-constraints. Over-constraints refer to repeated constraints on the same degree of freedom of an object, which can lead to assembly difficulties or internal stress. Through the asymmetric layout, the position and orientation (translation in the X and Y directions and rotation about the Z axis) of each sheet component (such as bipolar plates and membrane electrode assemblies) in the core 13 can be uniquely determined, avoiding the multiple positioning possibilities or installation interference that may be caused by the symmetric layout. The fastening bolts 15 and nuts 16 constitute a miniature press system integrated on the stack body. By manually tightening the nuts 16, uniform and controllable axial pressure can be applied to the core 13 to complete the stack pressing process.

[0039] In this embodiment, the first end plate 11 and the second end plate 12 are arranged substantially parallel to each other, and the lengths and widths of the first end plate 11 and the second end plate 12 are approximately equal. Both ends of the locating pin 14 and the fastening bolt 15 are respectively connected to the first end plate 11 and the second end plate 12. The locating pin 14 and the fastening bolt 15 are both arranged substantially vertically along the interval direction (Z direction) between the first end plate 11 and the second end plate 12, and are substantially parallel to each other. One end of the locating pin 14 is inserted into the first end plate 11, and the other end of the locating pin 14 is movably inserted into the through hole of the second end plate 12. Both ends of the fastening bolt 15 are respectively locked to the first end plate 11 and the second end plate 12, wherein one end of the fastening bolt 15 protrudes from the second end plate 12 through the through hole, and the nut 16 abuts against the surface of the second end plate 12 away from the first end plate 11. A current collector 17 is provided between the core 13 and the first end plate 11, and another current collector 17 is provided between the core 13 and the second end plate 12.

[0040] In one embodiment, in a projection plane perpendicular to the stacking direction, the outer contour of the core 13 is a quadrilateral, including a first long side 131, a second long side 132, a first short side 133, and a second short side 134; wherein two positioning pins 14 are spaced apart along the first long side 131; the number of positioning pins 14 is four, and the four positioning pins 14 are arranged around the outer periphery of the core 13; two positioning pins 14 are spaced apart corresponding to the first long side 131, another positioning pin 14 is arranged corresponding to the second long side 132, and another positioning pin 14 is arranged corresponding to the first short side 133.

[0041] Understandably, by setting locating pins 14 on both long sides and supplementing them with locating pins 14 on the short side, a stable constraint frame is formed, which can more effectively resist the misalignment force from the long side direction and prevent the core 13 from rotating in the plane. Compared with the general asymmetrical layout, the positioning effect is more targeted and reliable, further improving the assembly accuracy.

[0042] In this embodiment, a layout of four locating pins 14 is adopted, which can more stably constrain the reactor core 13. In the top view, the two locating pins 14 set along the first long side 131 together constitute the main positioning reference of the reactor core 13 in the Y direction (perpendicular to the long side), effectively limiting its translation in the Y direction. The one locating pin 14 set along the first short side 133 serves as the main positioning reference in the X direction (parallel to the long side). These three locating pins 14 together determine the planar position of the reactor core 13. The fourth locating pin 14, located on the second long side 132, plays an auxiliary positioning and anti-rotation role. It cooperates with the aforementioned three locating pins 14 to prevent the reactor core 13 from rotating around the stacking axis. In particular, it provides strong constraint on the tendency of the rectangular reactor core 13 to slip along the long side due to the deformation of the sealing glue line under pressure during the compaction process, ensuring the stability of the compaction process.

[0043] In one embodiment, two positioning pins 14 are respectively set at one-third and two-thirds of the first long side 131, another positioning pin 14 is set at the midpoint of the second long side 132, and another positioning pin 14 is set at the first short side 133 and is closer to the first long side 131 than the second long side 132.

[0044] Understandably, placing the locating pin 14 at one-third of the long side can distribute the constraint force more evenly and effectively prevent deformation in the middle of the long side; placing it at the midpoint of the other long side provides a stable single-point support, ensuring the positional stability of the core 13 throughout the assembly process and achieving a higher level of assembly precision control. Meanwhile, among the first short side 133 and the second short side 134, the locating pin 14 is only placed on the first short side 133 to ensure that positioning can be achieved.

[0045] In this embodiment, the two locating pins 14 on the first long side 131 are positioned at approximately one-third and two-thirds of the length, rather than at both ends, which more effectively supports the long side and prevents it from warping outwards in the middle during stacking or compression. The locating pin 14 on the second long side 132 is positioned at the midpoint to provide stable Y-direction constraint. The locating pin 14 on the first short side 133 is offset to allow space for the fastening bolt 15 at the midpoint of this short side, reflecting the integration of the structural design and the rationality of space utilization. In one embodiment, the number of fastening bolts 15 is ten. Four fastening bolts 15 are evenly spaced along the first long side 131, four fastening bolts 15 are evenly spaced along the second long side 132, one fastening bolt 15 is positioned at the midpoint of the first short side 133, and one fastening bolt 15 is positioned at the midpoint of the second short side 134.

[0046] Understandably, by setting ten evenly distributed bolts, a uniformly distributed pressure field can be formed. By forming a complete pressure ring around the outer periphery of the core 13, it is possible to ensure that the sealing adhesive lines inside the core 13 are uniformly compressed, thereby ensuring the sealing reliability of the fuel cell stack and good electrical contact between individual cells, achieving pressure uniformity comparable to the pressing effect of a large press.

[0047] In this embodiment, ten fastening bolts 15 form a densely distributed pressure ring around the core 13. Four evenly spaced fastening bolts 15 are positioned corresponding to each of the first long side 131 and the second long side 132, and one fastening bolt 15 is positioned at the midpoint of each of the first short side 133 and the second short side 134. This bolt array, evenly distributed along the outer contour of the core 13, ensures that the pressure applied by tightening the nuts 16 is transmitted relatively evenly to the first end plate 11 and the second end plate 12, and ultimately acts on the entire sealing surface of the core 13. Uniform pressure is crucial for ensuring that all sealing lines inside the core 13 are compressed to design requirements, forming a reliable seal, and for ensuring that the gas diffusion layer is appropriately compressed and forms good electrical contact with the bipolar plate flow field ribs.

[0048] In one embodiment, the positioning pin 14 and the fastening bolt 15 are both arranged around the outer periphery of the core 13; the projection of the positioning pin 14 and the fastening bolt 15 on a plane perpendicular to the stacking direction is located between the outer contour of the core 13 and the outer contour of the first end plate 11 and the second end plate 12.

[0049] Understandably, placing the locating pin 14 and fastening bolt 15 in the non-active area forms an enclosed structure surrounding the core 13. This avoids encroachment on the effective reaction area of ​​the core 13, increases the power density of the fuel cell stack, and achieves a compact structure. It also facilitates stacking and bolt tightening operations during assembly, improving operability.

[0050] In this embodiment, the planar dimensions of the first end plate 11 and the second end plate 12 are larger than the planar dimensions of the core 13, forming a flange region. All the locating pins 14 and fastening bolts 15 are located within this flange region, surrounding the core 13 but not penetrating or encroaching upon the effective reaction zone of the core 13. Spatially separating the auxiliary functional structures such as locating and fastening from the power generation functional area ensures the integrity and uniformity of the internal flow field and current density distribution of the core 13, maximizing the effective area and power density of the fuel cell stack. It also provides ample operating space for the heads of the fastening bolts 15 and the nuts 16, facilitating assembly operations using tools such as torque wrenches.

[0051] Further integration Figure 5 and Figure 6 As shown in the embodiments of this application, an assembly method for a tooling-free fuel cell short stack structure is also provided, including the following steps: Step S1: Fix the first end plate 11 and install at least three locating pins 14 and multiple fastening bolts 15 onto the first end plate 11.

[0052] Step S2: Using at least three positioning pins 14 as a reference, stack multiple bipolar plates and membrane electrode assemblies of the core 13 sequentially on the first end plate 11.

[0053] Step S3: Place the second end plate 12 onto the positioning pin 14 and the fastening bolt 15, and install the nut 16 that mates with the fastening bolt 15, so that the nut 16 contacts the surface of the second end plate 12 away from the first end plate 11 along the stacking direction.

[0054] Step S4: Tighten all nuts 16 initially so that the first end plate 11 is approximately parallel to the second end plate 12, and apply an initial preload.

[0055] Step S5: By tightening the nuts 16 in stages, in a predetermined sequence and step amount, the pressure applied to the reactor core 13 is gradually increased until the reactor core 13 is compressed to a predetermined compression size.

[0056] Understandably, this assembly method provides a complete tooling-free and press-free operation process. By stacking components using the built-in locating pins 14 as a reference, high-precision self-guided assembly is achieved, replacing external tooling. A precisely controlled pressurization process is provided through staged, sequential, and incremental tightening of the nuts 16, avoiding component slippage caused by uneven force. This method ensures low-cost, high-precision assembly from a process perspective.

[0057] Specifically, phased, step-by-step operations can balance assembly efficiency and yield, avoiding inefficiency due to excessively slow assembly speed, and preventing damage to the diaphragm in core 13 due to excessively fast assembly speed. Sequential operations can avoid the accumulation of stress or deviations, ensuring relatively uniform compaction of the reactor core.

[0058] It should be explained that this method internalizes the two independent processes of traditional tooling positioning and press clamping into a self-positioning stacking and bolt pressurization process based on the product's own structure. The initial tightening in step S4, also known as pre-leveling, aims to eliminate initial gaps between components, making the entire stack a pre-joined whole. The operator can use simple tools such as a steel ruler to measure the spacing between the end plates and bolts, and fine-tune each nut 16 to ensure the spacing is basically consistent, while applying a small initial torque, such as 3 ± 0.5 Nm, to ensure that each bolt is under tension. Step S5 achieves the effect of manually stabilizing the stack through phased, sequential, and controlled-step operations.

[0059] In one embodiment, in a projection plane perpendicular to the stacking direction, the outer contour of the core 13 is a quadrilateral, including a first long side 131, a second long side 132, a first short side 133, and a second short side 134. In step S5, the predetermined order is to tighten the nut 16 that mates with one fastening bolt 15 in the middle of the first long side 131, then tighten the nut 16 that mates with another fastening bolt 15 that is located on the second long side 132 and is diagonally located to the first bolt, and finally tighten the nuts 16 that mate with the two fastening bolts 15 that mate with the first short side 133 and the second short side 134 respectively.

[0060] In this embodiment, the tightening sequence of the diagonal bolts is as follows: first tighten the diagonal bolts on the inner side of the long side, then tighten the diagonal bolts on the outer side of the long side, and finally tighten the diagonal bolts on the short side, thereby gradually and stably completing the compaction of the entire plane. By alternately tightening the nuts 16 on the diagonals, it can be ensured that the pressure is evenly diffused from the central area of ​​the core 13 to the surrounding area, preventing the end plate from tilting due to premature tightening on one side or in a localized area, which could lead to misalignment and slippage of the internal components of the core 13.

[0061] Understandably, by alternately tightening the nuts 16 at opposite corners, the pressure can always be applied in a balanced manner around the center of the core 13, thereby effectively maintaining the parallel state of the end plates at each step of pressurization, effectively suppressing the tilting of the end plates and the misalignment of the core 13 caused by excessive force on one side, and improving the stability of the manual pressing process and the assembly success rate.

[0062] In this embodiment, there are ten fastening bolts 15 and ten nuts 16. Four nuts 16 are evenly spaced along the first long side 131, and from the first short side 133 to the second short side 134, they are arranged in the following order: seventh nut 1607, first nut 1601, third nut 1603, and fifth nut 1605. Another four nuts 16 are evenly spaced along the second long side 132, and from the first short side 133 to the second short side 134, they are arranged in the following order: sixth nut 1606, fourth nut 1604, second nut 1602, and eighth nut 1608. Another nut 16 is located at the midpoint of the first short side 133 and is the ninth nut 1609. Another nut 16 is located at the midpoint of the second short side 134 and is the tenth nut 1610. Step S5, in a predetermined order, includes alternating forward and reverse operations. The screwing sequence of the forward operation is as follows: first nut 1601, second nut 1602, third nut 1603, fourth nut 1604, fifth nut 1605, sixth nut 1606, seventh nut 1607, eighth nut 1608, ninth nut 1609, and tenth nut 1610. The screwing sequence of the reverse operation is completely opposite to that of the forward operation.

[0063] In this embodiment, the forward sequence operation is from the first sequential nut 1601 to the tenth sequential nut 1610, which is actually a combination of a series of diagonal operations: first tighten the first sequential nut 1601, then the second sequential nut 1602 (one set of inner diagonal), then tighten the third sequential nut 1603, then the fourth sequential nut 1604 (another set of inner diagonal), then the fifth sequential nut 1605, then the sixth sequential nut 1606, then the seventh sequential nut 1607, then the eighth sequential nut 1608 (two sets of outer diagonal), and finally the ninth sequential nut 1609, then the tenth sequential nut 1610 (short side diagonal). After completing one round of forward-sequence operations, the next round uses the completely opposite reverse-sequence operations, in the following order: tenth nut 1610, ninth nut 1609, eighth nut 1608, seventh nut 1607, sixth nut 1606, fifth nut 1605, fourth nut 1604, third nut 1603, second nut 1602, and first nut 1601. This alternation of forward and reverse-sequence operations not only ensures even pressure application but also effectively releases and homogenizes torsional stress that may accumulate in the bolts and end plates during unidirectional tightening, resulting in a more uniform final pressure distribution and further eliminating potential cumulative errors.

[0064] Understandably, on the one hand, the alternating tightening sequence from the center outwards diagonally ensures roughly uniform pressure while achieving manual pressurization, avoiding endplate tilting and core 13 misalignment caused by excessive force on one side. On the other hand, by introducing alternating tightening methods of forward and reverse sequence operations, the cumulative errors or residual torsional stress that may be generated during unidirectional tightening can be effectively offset and homogenized, resulting in a higher level of uniformity in the pressure distribution finally applied to core 13, further improving the sealing reliability and performance uniformity of the fuel cell stack.

[0065] In one embodiment, the segmented clamping in step S5 refers to the clamping process in step S5 including an early clamping stage, a middle clamping stage, and a late clamping stage in chronological order; the predetermined stepping amount in step S5 means that the rotation angle stepping amount of the nut 16 in the early clamping stage is greater than that in the middle clamping stage, and the rotation angle stepping amount of the nut 16 in the middle clamping stage is greater than that in the late clamping stage. The model and size of the nut 16 are known (a suitable nut 16 is selected according to the actual situation), and the corresponding pitch is also known. Combining the rotation angle and the pitch, the linear motion (compression value) of the nut 16 along the screw 15 after rotating the nut 16 by the corresponding angle can be calculated.

[0066] In this embodiment, during the initial compression stage (e.g., before compressing to 60% of the target value), the internal gap of the core 13 is large and the compression resistance is low. A larger step size can be used, for example, lowering the end plate by 2 mm each time the core is tightened, to improve assembly efficiency. During the intermediate compression stage (e.g., compressing to 60% to 80% of the target value), the gas diffusion layer and seals begin to deform significantly, and the compression resistance increases rapidly. At this point, the step size should be reduced, for example, lowering by 1 mm each time, to ensure a smooth transition. During the later compression stage (compressing to 80% to 100% of the target value), the compression resistance is very high, and even small displacement changes can cause huge pressure changes. At this point, a more refined angle control method is used, for example, gradually reducing the step angle from 70 degrees each time to 60 degrees, 50 degrees, 40 degrees, and finally 30 degrees, to achieve precise control over the final compression size.

[0067] Understandably, the dimensional changes of core 13 during compression vary depending on the stress level, and this change is not linear. Large step increments are used initially to improve efficiency, while the step increments are gradually reduced in the later stages to achieve a smooth transition and precise control. This ensures assembly efficiency while allowing for fine adjustments as the dimensions approach the target size, avoiding the risk of overpressure damage to internal components (especially the membrane electrode assembly), and improving the safety of the compression process and the accuracy of the final dimensions.

[0068] It should be explained that the membrane electrode assembly (MEA) of core 13 typically includes a proton exchange membrane, a catalyst layer, and a gas diffusion layer. The gas diffusion layer is usually made of carbon fiber and needs to be compressed to adjust resistance and efficiency. Based on the objective material properties of the gas diffusion layer, a suitable compression ratio (typically 15%) can be selected by referring to a table comparing its material properties (resistance, power generation efficiency, etc.) with the compression amount (this varies depending on the supplied raw materials and will not be elaborated here). This is then combined with the design requirements of the fuel cell to calculate the corresponding final compression size. This process and calculation method are well-known to those skilled in the art and will not be elaborated here. The size boundary points between the early, middle, and late compression stages are then determined based on this compression size.

[0069] In one embodiment, the assembly method of the tooling-free fuel cell short stack structure further includes a leveling step S6 at the end of at least one stage of the staged compaction process and after the compaction is completed; step S6 includes measuring and adjusting the distance between the first end plate 11 and the second end plate 12 at the positions of each fastening bolt 15 using a stopper and a feeler gauge, and correcting the parallelism of the first end plate 11 and the second end plate 12.

[0070] In this embodiment, the leveling step is a closed-loop feedback control link throughout the entire compression process. For example, after the initial compression stage, a pre-prepared plug with a size of 80% of the target compression size is used to measure the spacing between each bolt position on the end plates, and the corresponding nuts 16 are fine-tuned until the plug can be inserted with similar tightness at all points. After the intermediate stage, this process is repeated using a plug with a size of 60% of the target compression size. In the later compression stage and after final completion, a more precise plug (e.g., a plug 2 mm smaller than the final size) is used with feeler gauges for high-precision measurement and adjustment. This proactive measurement and correction at critical nodes effectively eliminates the cumulative parallelism deviation caused by factors such as material inhomogeneity and operational errors, and is an important guarantee for achieving high-precision pressure uniformity in manual compression.

[0071] Understandably, by actively measuring and correcting the parallelism of the end plates during and after the compression process, accumulated errors can be effectively eliminated, ensuring that the two end plates achieve extremely high parallelism in the final state. This fundamentally guarantees that the pressure applied to the entire plane of the core 13 is highly uniform, which is the ultimate guarantee for achieving optimal battery performance, reliable sealing, and long service life.

[0072] The embodiments described herein are preferred embodiments and are not intended to limit the scope of protection of this application. Identical components are represented by the same reference numerals. All equivalent changes made to the structure, shape, and principle of this application should be included within the scope of protection of this application.

Claims

1. A tooling-free fuel cell short stack structure, characterized in that, include: The first end plate (11) and the second end plate (12) are located at the two ends of the tooling-free fuel cell short stack structure, respectively. The core (13) is disposed between the first end plate (11) and the second end plate (12). The core (13) includes a plurality of bipolar plates and membrane electrode assemblies that are stacked alternately along the stacking direction. At least three positioning pins (14) are arranged along the stacking direction, the positioning pins (14) passing through the first end plate (11) and the second end plate (12), for planar positioning of the core (13) during stacking; the projections of the at least three positioning pins (14) on a plane perpendicular to the stacking direction are asymmetrically arranged. Multiple fastening bolts (15) extend along the stacking direction and pass through the first end plate (11) and the second end plate (12). The fastening bolts (15) are threadedly engaged with nuts (16) to apply pressure to the first end plate (11) and the second end plate (12) at least along the stacking direction, thereby compressing the core (13) to a predetermined compression size.

2. The tooling-free fuel cell short stack structure according to claim 1, characterized in that: In a projection plane perpendicular to the stacking direction, the outer contour of the core (13) is a quadrilateral, including a first long side (131), a second long side (132), a first short side (133), and a second short side (134); wherein two positioning pins (14) are spaced apart along the first long side (131); the number of positioning pins (14) is four, and the four positioning pins (14) are arranged around the outer periphery of the core (13); two positioning pins (14) are spaced apart corresponding to the first long side (131), another positioning pin (14) is arranged corresponding to the second long side (132), and another positioning pin (14) is arranged corresponding to the first short side (133).

3. The tooling-free fuel cell short stack structure according to claim 2, characterized in that: Two of the positioning pins (14) are set at one-third and two-thirds of the first long side (131), respectively. Another positioning pin (14) is set at the midpoint of the second long side (132). Another positioning pin (14) is set at the first short side (133) and is closer to the first long side (131) than the second long side (132).

4. The tooling-free fuel cell short stack structure according to claim 2, characterized in that: The number of the plurality of fastening bolts (15) is ten; wherein, four of the fastening bolts (15) are evenly spaced along the first long side (131), four of the fastening bolts (15) are evenly spaced along the second long side (132), one of the fastening bolts (15) is set at the midpoint of the first short side (133), and one of the fastening bolts (15) is set at the midpoint of the second short side (134).

5. The tooling-free fuel cell short stack structure according to claim 1, characterized in that: The positioning pin (14) and the fastening bolt (15) are both arranged around the outer periphery of the core (13); the projection of the positioning pin (14) and the fastening bolt (15) on a plane perpendicular to the stacking direction is located between the outer contour of the core (13) and the outer contours of the first end plate (11) and the second end plate (12).

6. A method for assembling a tooling-free fuel cell short stack structure as described in any one of claims 1 to 5, characterized in that, Includes the following steps: Step S1: Fix the first end plate (11) and install the at least three positioning pins (14) and the plurality of fastening bolts (15) on the first end plate (11). Step S2: Using the at least three positioning pins (14) as a reference, stack the multiple bipolar plates and membrane electrode assemblies of the core (13) sequentially on the first end plate (11); Step S3: Sleeve the second end plate (12) onto the positioning pin (14) and the fastening bolt (15), and install the nut (16) that mates with the fastening bolt (15), so that the nut (16) contacts the surface of the second end plate (12) away from the first end plate (11) along the stacking direction; Step S4: Tighten all nuts (16) initially so that the first end plate (11) is approximately parallel to the second end plate (12), and apply an initial preload. Step S5: By tightening the nuts (16) in stages, in a predetermined sequence and step amount, the pressure applied to the core (13) is gradually increased until the core (13) is compressed to a predetermined compression size.

7. The assembly method for the tooling-free fuel cell short stack structure according to claim 6, characterized in that: In a projection plane perpendicular to the stacking direction, the outer contour of the core (13) is a quadrilateral, including a first long side (131), a second long side (132), a first short side (133), and a second short side (134). In step S5, the predetermined order is to tighten the nut (16) that is engaged with one of the fastening bolts (15) in the middle of the first long side (131) in a diagonal order. Then, tighten the nut (16) that is engaged with another fastening bolt (15) that is set on the second long side (132) and is diagonally set with the previous bolt. Finally, tighten the nuts (16) that are engaged with the two fastening bolts (15) that are engaged with the first short side (133) and the second short side (134) respectively.

8. The assembly method of the tooling-free fuel cell short stack structure according to claim 7, characterized in that: The number of fastening bolts (15) is ten, and the number of nuts (16) is correspondingly ten; four of the nuts (16) are evenly spaced along the first long side (131), and from the first short side (133) to the second short side (134), they are, in order, the seventh nut (1607), the first nut (1601), the third nut (1603), and the fifth nut (1605); the other four nuts (16) are evenly spaced along the second long side (132), and from the first short side (133) to the second short side (134), they are, in order, the sixth nut (1606), the fourth nut (1604), the second nut (1602), and the eighth nut (1608); the other nut (16) corresponds to the... The midpoint of the first short side (133) is set as the ninth sequential nut (1609); the other nut (16) is set as the midpoint of the second short side (134) as the tenth sequential nut (1610); the predetermined sequence in step S5 includes sequential and reverse operations performed alternately. The screwing sequence of the sequential operation is as follows: first sequential nut (1601), second sequential nut (1602), third sequential nut (1603), fourth sequential nut (1604), fifth sequential nut (1605), sixth sequential nut (1606), seventh sequential nut (1607), eighth sequential nut (1608), ninth sequential nut (1609), and tenth sequential nut (1610). The screwing sequence of the reverse operation is completely opposite to that of the sequential operation.

9. The assembly method of the tooling-free fuel cell short stack structure according to claim 6, characterized in that: The segmented tightening in step S5 refers to the tightening process in step S5 including an early tightening stage, a middle tightening stage, and a late tightening stage in chronological order; the predetermined step amount in step S5 means that the rotation angle step amount of the nut (16) in the early tightening stage is greater than the rotation angle step amount of the nut (16) in the middle tightening stage, and the rotation angle step amount of the nut (16) in the middle tightening stage is greater than the rotation angle step amount of the nut (16) in the late tightening stage.

10. The assembly method of the tooling-free fuel cell short stack structure according to claim 9, characterized in that: It also includes a step S6 for leveling at the end of at least one stage of the phased pressing process and after the pressing is completed; step S6 includes measuring and adjusting the distance between the first end plate (11) and the second end plate (12) at the respective fastening bolt (15) positions using a feeler block and feeler gauge, and correcting the parallelism of the first end plate (11) and the second end plate (12).

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