Fuel cell flexible graphite composite bipolar plate mold

Abstract

The application relates to a fuel cell flexible graphite composite bipolar plate mold, and belongs to the technical field of mold devices. In order to solve the problem that the existing graphite composite bipolar plate preparation mold cannot independently control the tablet thickness during use, leading to a single product category and being unsuitable for scientific research adjustment, the application comprises an upper mold unit of a compression mold device, a lower mold unit of the compression mold device and a gasket unit. The upper mold unit of the compression mold device is inserted into the lower mold unit of the compression mold device. The gasket unit is arranged between the top of the upper mold unit of the compression mold device and the lower mold unit of the compression mold device. The gasket unit is a multi-layer split structure, and the thickness of each layer of gaskets in the gasket unit can be the same or different. The application is mainly used as a mold structure for the compression process of a fuel cell flexible graphite composite bipolar plate.

Description

Technical Field

[0001] This utility model belongs to the field of mold device technology, specifically relating to a mold for a flexible graphite composite bipolar plate for fuel cells. Background Technology

[0002] Fuel cells are a new type of environmentally friendly energy source, possessing advantages such as cleanliness, high efficiency, no pollution, and good stability. Among them, proton exchange membrane fuel cells (PEMFCs) are the most widely used devices. The bipolar plate is a crucial component, and its performance directly affects the use of the fuel cell. Expanded graphite-based composite bipolar plates possess excellent corrosion resistance, electrical and thermal conductivity, and airtightness, integrating the advantages of traditional graphite and metal bipolar plates, making them a current research focus for PEMFC bipolar plates. However, current graphite bipolar plates for fuel cells suffer from poor sealing performance, high gas permeability, and difficulty in processing. Currently, high-purity expanded graphite prepared by electrochemical methods is used as the conductive substrate, and optimized polymer resin is selected as the binder. Flexible graphite composite bipolar plates are prepared using a vacuum impregnation-molding method. However, during the preparation of flexible graphite composite bipolar plates using the vacuum impregnation-molding method, it was found that the thickness of the pressed plates cannot be independently controlled, resulting in a relatively limited variety of finished products, unsuitable for research adjustments. To overcome this deficiency, developing a mold for flexible graphite composite bipolar plates for fuel cells is highly necessary. Utility Model Content

[0003] This invention aims to address the problem that existing graphite composite bipolar plate preparation molds cannot independently adjust the pressing thickness during use, resulting in a relatively limited range of finished products and making them unsuitable for research adjustments. Therefore, this invention provides a flexible graphite composite bipolar plate mold for fuel cells.

[0004] A flexible graphite composite bipolar plate mold for fuel cells includes an upper mold unit, a lower mold unit, and a gasket unit. The upper mold unit is inserted into the lower mold unit, and the gasket unit is arranged between the tops of the upper mold unit and the lower mold unit. The gasket unit has a multi-layer split structure, and the thickness of each layer of gasket in the gasket unit can be the same or different.

[0005] Furthermore, the gasket unit has a three-layer split structure, with the thickness of the three gaskets increasing sequentially from top to bottom. The thickness of the first gasket is 1mm, the thickness of the second gasket is 2mm, and the thickness of the third gasket is 3mm.

[0006] Furthermore, the upper mold unit of the molding device includes an upper top cover of the molding device, and a molding inner core that cooperates with the lower mold unit of the molding device is fixedly connected to the bottom center of the upper top cover of the molding device.

[0007] Furthermore, the lower mold unit of the molding tool includes a molding base, and a lower mold outer sleeve that mates with the inner core of the molding is detachably connected to the top of the molding base;

[0008] Furthermore, the top of the lower mold outer sleeve is provided with an outer sleeve boss along the circumferential direction;

[0009] Furthermore, a limiting boss is provided at the top center of the molding base;

[0010] Furthermore, the mold also includes a channel template, which is placed on top of the limiting boss. The edge of the channel template is provided with an upwardly extending side enclosure. The top of the channel template is machined with a bipolar plate channel. A limiting post is erected at both ends of the bipolar plate channel, and the bottom of each limiting post is fixedly connected to the top of the channel template.

[0011] Furthermore, the mold also includes an outer sleeve limiting unit, which includes a bottom support plate. The bottom support plate integrates multiple base positioning components. The positioning end of each base positioning component extends to the top of the bottom support plate, and the adjustment end of each base positioning component extends to the outside of the bottom support plate. Multiple side limiting components are detachably connected to the top of the bottom support plate. The lower mold unit of the pressing tool is arranged at the top center of the bottom support plate. The pressing base is positioned by the base positioning components, and the outer sleeve eliminates external expansion tension by multiple side limiting components.

[0012] Furthermore, the base positioning assembly includes a No. 1 push bolt and a base positioning block. The top of the bottom support plate is machined with a groove for accommodating the base positioning block. The base positioning block is placed in the groove and is movably connected to the bottom support plate. The No. 1 push bolt is inserted into the bottom support plate from the side and is threadedly connected to the bottom support plate. The screwing part of the No. 1 push bolt is located on the outside of the bottom support plate. The threaded end of the No. 1 push bolt extends into the groove and is correspondingly set with the base positioning block embedded in the bottom support plate.

[0013] Furthermore, the side limiting assembly includes a mounting base, which is detachably connected to the top of the bottom support plate. A connecting plate is mounted on the top of the mounting base, and a threaded sleeve is provided on the top of the connecting plate. A second push bolt is inserted into the threaded sleeve and is threadedly connected to the threaded sleeve. The screwing part of the second push bolt is located away from the lower mold outer sleeve. A side pressure plate is rotatably connected to the threaded end of the second push bolt through a rotating part. The side pressure plate provides thrust through the second push bolt to eliminate the external expansion tension experienced by the lower mold outer sleeve during operation.

[0014] The beneficial effects of this application compared to the prior art are:

[0015] This utility model provides a flexible graphite composite bipolar plate mold for fuel cells. By optimizing the mold structure, it can produce the following beneficial effects compared with the prior art:

[0016] 1. The gasket structure provided in this application is a multi-layer gasket structure, which is suitable for different thickness requirements and meets the pressing requirements of different thicknesses. It is beneficial to control the pressing thickness during preparation. When the multi-layer gaskets are arranged from top to bottom, they follow the arrangement from thin to thick. This setting can precisely adjust the installation gap and is easier to adapt to actual size deviations than using a single thick gasket, reducing the installation difficulty. At the same time, the transition from thin to thick can avoid local stress concentration, reduce extrusion damage during operation, and extend the service life of the mold.

[0017] 2. The lower mold unit of the molding tool provided in this application consists of a base and an outer sleeve. It adopts a split molding tool lower mold unit design, which facilitates product demolding.

[0018] 3. During the research and development of this application, it was considered that the graphite material, after being squeezed by the core of the die, would exert an extrusive force from the inside out on the lower die outer sleeve. This pressure would directly act on the lower die outer sleeve, causing it to deform under stress, thereby affecting the precision and service life of the die itself. In order to overcome this drawback, this application added a side limiting component to the traditional die. The side limiting component can provide thrust from the outside when the lower die outer sleeve is working, which can effectively suppress the external expansion tension on the lower die outer sleeve during operation, thereby improving the service life of the lower die outer sleeve. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the structure of a flexible graphite composite bipolar plate mold for a fuel cell as described in this application;

[0020] Figure 2 This is an exploded view of a flexible graphite composite bipolar plate mold for a fuel cell as described in this application;

[0021] Figure 3 This is a schematic diagram of the composition of a flexible graphite composite bipolar plate mold for a fuel cell as described in this application;

[0022] Figure 4 This is a schematic diagram of the channel template in a flexible graphite composite bipolar plate mold for fuel cells as described in this application;

[0023] Figure 5 This is a top view of the channel template in a flexible graphite composite bipolar plate mold for a fuel cell described in this application;

[0024] Figure 6 A front view schematic diagram of a flexible graphite composite bipolar plate mold for fuel cells with an added outer jacket limiting unit as described in this application;

[0025] Figure 7 A top view schematic diagram of adding an outer jacket limiting unit to a mold for a flexible graphite composite bipolar plate for a fuel cell as described in this application;

[0026] In the diagram: 1. Top cover of the molding tool; 2. Inner core of the molding tool; 3. Gasket; 4. Outer jacket of the lower mold; 41. Outer jacket boss; 5. Mold base; 51. Limiting boss; 6. Side enclosure; 7. Bipolar plate channel; 8. Limiting post; 9. Bottom support plate; 10. No. 1 push bolt; 11. Base positioning block; 12. Mounting seat; 13. Connecting plate; 14. Threaded sleeve; 15. No. 2 push bolt; 16. Rotating part; 17. Side pressure plate. Detailed Implementation

[0027] Specific implementation method one: Combining Figures 1 to 7 This embodiment provides a flexible graphite composite bipolar plate mold for fuel cells. The mold includes an upper mold unit, a lower mold unit, and a gasket unit. The upper mold unit is inserted into the lower mold unit, and the gasket unit is arranged between the tops of the upper mold unit and the lower mold unit. The gasket unit has a multi-layer split structure, and the thickness of each layer of gasket 3 in the gasket unit can be the same or different.

[0028] The upper mold unit of the molding tool includes an upper top cover 1 of the molding tool, and a molding inner core 2 that cooperates with the lower mold unit of the molding tool is fixedly connected to the bottom center of the upper top cover 1 of the molding tool.

[0029] The lower mold unit of the molding tool includes a molding base 5, and a lower mold outer sleeve 4 that mates with the inner core 2 is detachably connected to the top of the molding base 5;

[0030] The top of the lower mold jacket 4 is provided with a jacket boss 41 along the circumferential direction;

[0031] A limiting boss 51 is provided at the top center of the molding base 5.

[0032] This embodiment provides a flexible graphite composite bipolar plate mold for fuel cells. The mold's gasket unit has a multi-layer structure. By stacking different gaskets, various thicknesses can be selected. The thickness of the multi-layer gasket structure increases sequentially from the top to the bottom. The thickness of a single gasket 3 is between 0.5mm and 5mm, achieving a wide range of thickness control. The lower mold unit of the molding tool adopts a split design. The detachable connection between the lower mold outer sleeve 4 and the molding base 5 facilitates demolding after product preparation. To ensure the accuracy of the positioning between the lower mold outer sleeve 4 and the molding base 5, a limiting boss 51 with a thickness of 5mm is provided on the top of the molding base 5. The lower mold outer sleeve 4 is positioned by the limiting boss 51. At the same time, the limiting boss 51 also restricts the position of the outer wall of the mold to prevent the outer wall from sliding during the molding process, which would lead to leakage of the molding material. The outer sleeve boss 41 added to the top of the lower mold outer sleeve 4 buffers the impact between the upper cover 1 of the molding tool and the lower mold outer sleeve 4, creating a gap between the two to facilitate the separation of the upper cover 1 of the molding tool and the lower mold outer sleeve 4. At the same time, the outer sleeve boss 41 can also guide and position the multi-layer gasket structure. The shape of the mold in this application is not fixed. Generally, the inner core 2 of the molding tool, the lower mold outer sleeve 4 and the molding base 5 are all rectangular structures, but they can be replaced with circular or other regular polygonal structures according to the needs of the product.

[0033] When pressing graphite bipolar plates, it was found that the existing mold has poor venting function. During the extrusion molding process, the gas in the cavity formed by the lower mold outer sleeve 4, the mold base 5, and the mold inner core 2 cannot be discharged, resulting in uneven stress on the raw material during the pressing process. To avoid this situation, venting holes can be machined on the side wall of the mold inner core 2. The venting holes are L-shaped, with one end connected to the side wall of the mold inner core 2, and the other end passing through the top cover 1 of the mold and connected to the outer top of the top cover 1. To ensure the stability of venting, the vertical part of the venting hole should not be too far from the side wall of the mold inner core 2. The spacing between them should not exceed 12mm, and the height of the vent should not be too low. It should be at least 20mm away from the bottom of the inner core 2 of the mold. The vent is connected to the gap between the lower mold outer sleeve 4 and the inner core 2 of the mold. During the pressing process, the gas in the cavity enters the vent through the gap between the lower mold outer sleeve 4 and the inner core 2 of the mold and is discharged to the outside of the mold along the vent. Since the gap between the lower mold outer sleeve 4 and the inner core 2 of the mold is small, the raw material of the product will not overflow from the gap between the lower mold outer sleeve 4 and the inner core 2 of the mold during extrusion. This method has been verified in actual tests and will not affect the finished product of the plate.

[0034] Specific Implementation Method Two: Combining Figures 1 to 7This embodiment differs from Specific Embodiment Two in that the mold further includes a channel template, which is placed on top of the limiting boss 51. The channel template has upwardly extending side guards 6 at its edge. A bipolar plate channel 7 is machined on the top of the channel template, and a limiting post 8 is erected at each end of the bipolar plate channel 7. The bottom of each limiting post 8 is fixedly connected to the top of the channel template. Other components and connection methods are the same as in Specific Embodiment One.

[0035] This embodiment takes into account that some bipolar plate structures require the processing of channel structures. In this way, the bipolar plate containing channels can be directly pressed out during the bipolar plate pressing process through the channel template. At the same time, the design of the external channel mold can be replaced to be applied to different channel requirements. The limiting post 8 is used to drill the required limiting holes in the bipolar plate during the preparation of the bipolar plate, so as to connect the bipolar plate with other components in the fuel cell. The size can be designed to be different according to the needs of different bipolar plates, and various cylindrical surfaces can also be added as needed for use in different fuel cells. The side enclosure 6 is used to fix the shape of the bipolar plate, and the thickness can be adjusted according to the needs.

[0036] Specific implementation method three: Combining Figures 1 to 7 This embodiment differs from specific embodiment one in that the mold also includes an outer sleeve limiting unit. The outer sleeve limiting unit includes a bottom support plate 9, which integrates multiple base positioning components. The positioning end of each base positioning component extends to the top of the bottom support plate 9, and the adjustment end of each base positioning component extends to the outside of the bottom support plate 9. Multiple side limiting components are detachably connected to the top of the bottom support plate 9. The lower mold unit of the pressing tool is arranged at the top center of the bottom support plate 9. The pressing base 5 is positioned by the base positioning components, and the outer sleeve 4 eliminates external expansion tension through multiple side limiting components.

[0037] The base positioning assembly includes a first push bolt 10 and a base positioning block 11. The top of the bottom support plate 9 is machined with a groove for accommodating the base positioning block 11. The base positioning block 11 is placed in the groove and is movably connected to the bottom support plate 9. The first push bolt 10 is inserted into the bottom support plate 9 from the side and is threadedly connected to the bottom support plate 9. The screwing part of the first push bolt 10 is located on the outside of the bottom support plate 9. The threaded end of the first push bolt 10 extends into the groove and is correspondingly set with the base positioning block 11 embedded in the bottom support plate 9.

[0038] The side limiting assembly includes a mounting base 12, which is detachably connected to the top of the bottom support plate 9. A connecting plate 13 is mounted on the top of the mounting base 12, and a threaded sleeve 14 is provided on the top of the connecting plate 13. A second push bolt 15 is inserted into the threaded sleeve 14 and is threadedly connected to the threaded sleeve 14. The screwing part of the second push bolt 15 is located away from the lower mold outer sleeve 4. A side pressure plate 17 is rotatably connected to the threaded end of the second push bolt 15 through a rotating part 16. The side pressure plate 17 provides thrust through the second push bolt 15 to eliminate the external expansion tension experienced by the lower mold outer sleeve 4 during operation. Other components and connection methods are the same as in specific embodiment one.

[0039] During the research and development of this application, it was considered that the graphite material, after being squeezed by the inner core 2 of the mold, would exert an outward compressive force on the outer casing 4 of the lower mold. This pressure would directly act on the outer casing of the lower mold, causing it to deform under stress (outward expansion), thus affecting the precision and service life of the mold itself. To address this issue, this application added an outer casing limiting unit to the traditional mold. The outer casing limiting unit consists of two parts. One part is a base positioning component for positioning and clamping the mold base 5. When the mold base 5 is placed on the bottom support plate 9, the base positioning block 11 can be pushed towards the mold base 5 by turning the first push bolt 10. When multiple base positioning blocks 11 are simultaneously pressed against the mold base 5, the positioning and fixing of the mold base 5 are achieved. The other part of the outer casing limiting unit is a side limiting component. The working principle of the side limiting component is similar to that of the base positioning component, both providing a driving force through the push bolt. The difference lies in the power source. The side pressure plate 17 is mounted on the end of the second push bolt 15 via a rotating part 16, and can move synchronously with the forward or backward movement of the second push bolt 15. The rotating part 16 is a rotating bearing, which is fitted onto the end of the second push bolt 15. The side pressure plate 17 includes an extension rod and a pressure plate body. One end of the extension rod is machined with a fitting hole, and the extension rod is fitted onto the rotating part 16 through the fitting hole. The pressure plate body is fixed to the other end of the extension rod. In order to increase the support strength between the extension rod and the pressure plate body, multiple reinforcing ribs are arranged circumferentially between the pressure plate body and the extension rod. One end of each reinforcing rib is fixedly connected to the pressure plate body, and one end of each reinforcing rib is fixedly connected to the extension rod. Since the side pressure plate 17 has a certain weight, when the second push bolt 15 is tightened, the side pressure plate 17 will not rotate synchronously with the second push bolt 15 due to gravity, but will only move axially with the second push bolt 15.

[0040] It is worth noting that the side limiting component is detachably connected to the bottom support plate 9. It is only used when pressing tablets with a large thickness. When preparing tablets with a thickness of less than 5mm, the side limiting component can be omitted to provide side clamping force. Instead, a base positioning block 11 with a higher height can be selected. The base positioning block 11 extends to the area at the bottom of the lower mold jacket 4 to assist in side limiting and prevent the lower part of the lower mold jacket 4 from deforming due to external expansion force.

[0041] The present invention has been disclosed above with reference to preferred embodiments, but it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed structure and technical content to create equivalent embodiments without departing from the scope of the present invention. However, any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

[0042] Working principle

[0043] The working principle of this application is illustrated by taking the fabrication of a channeled bipolar plate as an example:

[0044] First, place the mold base 5 on the press, then place the channel template on the limiting boss 51, then place the lower mold jacket 4 on the mold base 5 and fix the lower mold jacket 4 by the limiting boss 51. Then, add expanded graphite to the center blank position of the lower mold jacket 4. After the material is added, place the multi-layer gasket 3 on the top of the lower mold jacket 4 and limit it by the jacket boss 41. Then, the top cover 1 of the mold tool and the mold inner core 2 are slowly slid into the hollow part of the lower mold jacket 4 to ensure that the air in the cavity can be discharged through the gap between the mold inner core 2 and the lower mold jacket 4. Finally, apply pressure to the top cover 1 of the mold tool to make the molding process go smoothly.

[0045] If an outer sleeve limiting unit is added, the bottom support plate 9 needs to be placed on the press, and the mold base 5 is arranged at the top center of the bottom support plate 9 and positioned and clamped by multiple base positioning components. Then, the channel template, lower mold outer sleeve 4, expanded graphite, multi-layer gasket 3 and upper cover 1 of the mold tool are arranged in sequence according to the above process. Before the press applies pressure, the lower mold outer sleeve 4 is supported by the outside of the multiple side limiting components, and then pressure is applied to the upper cover 1 of the mold tool. In this way, the external expansion deformation of the lower mold outer sleeve 4 during operation can be effectively avoided under the action of the side limiting components.

Claims

1. A mold for a flexible graphite composite bipolar plate for a fuel cell, the mold comprising an upper mold unit, a lower mold unit, and a gasket unit, wherein the upper mold unit is inserted into the lower mold unit, and the gasket unit is arranged between the tops of the upper mold unit and the lower mold unit, characterized in that: The gasket unit is a multi-layered split structure, and the thickness of each gasket (3) in the gasket unit can be the same or different.

2. The flexible graphite composite bipolar plate mold for fuel cells according to claim 1, characterized in that: The gasket unit is a three-layer split structure. The thickness of the three gaskets (3) increases from top to bottom. The thickness of the first gasket is 1mm, the thickness of the second gasket is 2mm, and the thickness of the third gasket is 3mm.

3. The flexible graphite composite bipolar plate mold for fuel cells according to claim 2, characterized in that: The upper mold unit of the molding tool includes an upper top cover (1) of the molding tool, and a molding core (2) that cooperates with the lower mold unit of the molding tool is fixed at the bottom center of the upper top cover (1).

4. The flexible graphite composite bipolar plate mold for fuel cells according to claim 3, characterized in that: The lower mold unit of the molding tool includes a molding base (5), and the top of the molding base (5) is detachably connected to a lower mold outer sleeve (4) that cooperates with the inner core (2) of the molding tool.

5. A flexible graphite composite bipolar plate mold for fuel cells according to claim 4, characterized in that: The top of the lower mold outer jacket (4) is provided with an outer jacket boss (41) along the circumferential direction.

6. A flexible graphite composite bipolar plate mold for fuel cells according to claim 5, characterized in that: A limiting boss (51) is provided at the top center of the molding base (5).

7. A flexible graphite composite bipolar plate mold for fuel cells according to claim 6, characterized in that: The mold also includes a channel template, which is placed on top of the limiting boss (51). The edge of the channel template is provided with an upwardly extending side enclosure (6). The top of the channel template is machined with a bipolar plate channel (7). A limiting post (8) is erected at both ends of the bipolar plate channel (7). The bottom of each limiting post (8) is fixedly connected to the top of the channel template.

8. A flexible graphite composite bipolar plate mold for fuel cells according to claim 7, characterized in that: The mold also includes an outer sleeve limiting unit, which includes a bottom support plate (9). The bottom support plate (9) integrates multiple base positioning components. The positioning end of each base positioning component extends to the top of the bottom support plate (9), and the adjustment end of each base positioning component extends to the outside of the bottom support plate (9). Multiple side limiting components are detachably connected to the top of the bottom support plate (9). The lower mold unit of the molding tool is arranged at the top center of the bottom support plate (9). The molding base (5) is positioned by the base positioning components, and the outer sleeve (4) eliminates the external expansion tension by multiple side limiting components.

9. A flexible graphite composite bipolar plate mold for fuel cells according to claim 8, characterized in that: The base positioning assembly includes a first push bolt (10) and a base positioning block (11). The top of the bottom support plate (9) is machined with a groove for accommodating the base positioning block (11). The base positioning block (11) is placed in the groove and is movably connected to the bottom support plate (9). The first push bolt (10) is inserted into the bottom support plate (9) from the side and is threadedly connected to the bottom support plate (9). The screwing part of the first push bolt (10) is located outside the bottom support plate (9). The threaded end of the first push bolt (10) extends into the groove and is correspondingly set with the base positioning block (11) embedded in the bottom support plate (9).

10. A flexible graphite composite bipolar plate mold for a fuel cell according to claim 9, characterized in that: The side limiting assembly includes a mounting base (12), which is detachably connected to the top of the bottom support plate (9). A connecting plate (13) is installed on the top of the mounting base (12). A threaded sleeve (14) is provided on the top of the connecting plate (13). A second push bolt (15) is inserted into the threaded sleeve (14), and the second push bolt (15) is threadedly connected to the threaded sleeve (14). The screwing part of the second push bolt (15) is located away from the lower mold outer sleeve (4). A side pressure plate (17) is rotatably connected to the threaded end of the second push bolt (15) through a rotating part (16). The side pressure plate (17) provides thrust through the second push bolt (15) to eliminate the external expansion tension of the lower mold outer sleeve (4) during operation.

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