A hydrogen fuel cell membrane electrode coating liquid level automatic control system

Abstract

The utility model relates to hydrogen fuel cell technical field, concretely is a kind of hydrogen fuel cell membrane electrode coating liquid level automatic control system, including main material jar, feed pump, coating material tank, coating roller, coating doctor and coating substrate, slurry is stored in main material jar, main material jar is connected with the import of feed pump by conveying pipe one, the outlet of feed pump is connected with the material tank feed port of coating material tank by conveying pipe two, coating roller sinks and suspends and places float in material tank, coating doctor is equipped in coating roller side, coating doctor and coating roller are tangentially arranged, coating substrate is equipped in coating roller top, coating substrate and coating roller are tangentially arranged, and coating substrate and coating roller make slurry on coating roller transfer to coating substrate to complete coating by relative motion;Compared with prior art, the utility model solves the problem of coating "white" or slurry overflow waste, significantly improves the stability and automation level of coating production line, effectively avoids the uncertainty of manual control.

Description

Technical Field

[0001] This utility model relates to the field of hydrogen fuel cell technology, specifically to an automatic control system for the coating liquid level of a hydrogen fuel cell membrane electrode. Background Technology

[0002] Currently, the main coating methods for the core component of the membrane electrode assembly (MEA) in proton exchange membrane hydrogen fuel cells, the "catalytic layer," include ultrasonic spraying, microgravure coating, and slot extrusion coating. Ultrasonic spraying suffers from low efficiency and poor uniformity, making it unsuitable for mass production. Slot extrusion coating offers high speed and good coating consistency, but its complex coating-feeding system leads to significant slurry loss and requires high consistency in slurry rheological properties between batches, making it suitable for mass production (>5000m / batch), but not the optimal choice for current fuel cell market demands. Microgravure coating has a relatively simple structure and can achieve roll-to-roll continuous coating, making it suitable for both small-batch pilot production and large-scale production, and therefore widely used for coating fuel cell catalyst layers.

[0003] Microgravure coating, due to its relatively simple coating and feeding system, has extremely flexible applications in the field of hydrogen fuel cell coating. However, the simple feeding system also presents a problem: how to precisely control the feeding rate, neither too fast nor too slow. If the feeding speed is too fast, if the operator does not notice and shut off the feeding pump in time, it will lead to slurry overflow, causing slurry contamination or even waste. If the feeding speed is too slow, the liquid level in the slurry tank will continuously decrease as coating progresses, eventually leading to localized material shortages on the coating roller. This manifests in uneven coating density or even localized "white spots" in the coating quality, affecting product performance and consistency, and also representing a huge waste of slurry. Fuel cell slurry is mainly composed of platinum catalyst and Nafion resin solution, so the slurry is very expensive, and it is necessary to maximize the utilization rate of the slurry in actual production. Therefore, how to continuously control the reasonable liquid level range during the coating process, so as to prevent slurry tank overflow and material shortages, has become a very important issue. Currently, the main control method is still to start and stop the feed pump by visually observing the liquid level. However, the observation window is limited, and the traces left by the black slurry on the tank wall greatly interfere with the judgment of the actual liquid level. Therefore, the risk of control failure is very high.

[0004] While other fields offer designs for material supply systems—for example, patent CN103182360A in lithium battery coating utilizes a level sensor to detect and control the supply pump, and patent CN214267071U in ink printing uses a buoyancy switch to control the injection and shut-off of ink in the ink tank—these methods are structurally complex and involve large equipment. However, because the slurries in these two fields are relatively inexpensive, produced in large batches (by the ton), and insensitive to losses, and because the corresponding coating equipment itself is large, the aforementioned control mechanisms can be easily installed. In contrast, proton exchange membrane fuel cells, due to their diverse applications and the need for adaptable slurry formulations, typically require smaller batch sizes. To save costs and achieve coating even with small quantities of slurry, microgravure coating tanks are designed for compact dimensions. The aforementioned control methods, due to their complex structures and poor matching, result in significant slurry waste, difficult cleaning of the coating system, and even the risk of cross-contamination.

[0005] Therefore, in the field of hydrogen fuel cell catalyst coating, it is necessary to develop more suitable methods to achieve stable control of slurry level, so as to solve the problem of coating "whitening" or slurry overflow and waste caused by this, and improve the current situation of relying on operators to observe the liquid level throughout the process. Summary of the Invention

[0006] The purpose of this invention is to address the aforementioned shortcomings by providing an automatic control system for the coating liquid level of hydrogen fuel cell membrane electrode assemblies. This system solves the problems of "white showing" in the coating or slurry overflow and waste, significantly improves the stability and automation level of the coating production line, and effectively avoids the uncertainty of manual control.

[0007] To achieve the above objectives, an automatic control system for the coating liquid level of a hydrogen fuel cell membrane electrode assembly is designed, comprising a main material tank 1, a feed pump 4, a coating trough 5, a coating roller 6, a coating blade 7, and a coating substrate 8. The main material tank 1 contains slurry. The main material tank 1 is connected to the inlet of the feed pump 4 via a feed pipe 31. The outlet of the feed pump 4 is connected to the feed inlet 51 of the coating trough 5 via a feed pipe 32. The coating roller 6 is suspended and floats in the trough 5. A coating blade 7 is provided on one side of the coating roller 6. The coating blade 7 is tangentially arranged to the coating roller 6 at a certain angle. The coating substrate 8 is provided above the coating roller 6. The coating substrate 8 is tangentially arranged to the coating roller 6. The coating substrate 8 and the coating roller 6 move relative to each other, causing the slurry on the coating roller 6 to be transferred to the coating substrate 8 to complete the coating.

[0008] Furthermore, the coating tank 5 is equipped with a high liquid level sensor 52 and a low liquid level sensor 53. The low liquid level sensor 53 is located at a low horizontal position, and the high liquid level sensor 52 is located at a high horizontal position. Both the high liquid level sensor 52 and the low liquid level sensor 53 are connected to a PLC controller. The PLC controller is synchronously connected to the feed pump 4 and controls the opening and closing of the feed pump 4.

[0009] Furthermore, the high liquid level sensor 52 and the low liquid level sensor 53 are respectively installed at the upper liquid level line and the lower liquid level line of the coating material tank 5. The top of the coating material tank 5 is designed with a slurry overflow groove 55. The upper liquid level line is set at 2-4 mm below the horizontal height of the slurry overflow groove 55, and the lower liquid level line is set at 2-4 mm above the bottom horizontal line of the coating roller 6, thereby providing a buffer time for timely start-up of material supply.

[0010] Furthermore, the coating tank 5 has a tank wall 54 made of 316L stainless steel, and the high liquid level sensor 52 and the low liquid level sensor 53 are installed on the inner side of the tank wall 54.

[0011] Furthermore, both the high liquid level sensor 52 and the low liquid level sensor 53 are temperature sensors, preferably miniature sensors, and are tightly installed on the wall 54 of the trough. Both the high liquid level sensor 52 and the low liquid level sensor 53 are installed opposite the feed inlet 51 of the trough, which can reduce signal interference during the feeding process and effectively solve the problems of complex structure and difficulty in cleaning.

[0012] Furthermore, both the high liquid level sensor 52 and the low liquid level sensor 53 are pressure sensors or infrared ranging sensors, and are triggered by high or low liquid level signals.

[0013] Furthermore, the material inlet 51 is designed on the side or bottom of the coating material tank 5, and the material inlet 51 is a single-inlet or multi-inlet feeding port.

[0014] Furthermore, the main material tank 1 is surrounded by cooling circulating water 2, the temperature of which is 0-10℃ and is adjustable.

[0015] Furthermore, the feed pump 4 is selected from any one of a peristaltic pump, a diaphragm pump, or a screw pump.

[0016] Compared with the prior art, this utility model has the following advantages: (1) This utility model achieves accurate liquid level judgment through dual sensors, which can accurately control the start and stop of the feeding pump, so that the liquid level in the coating tank is always kept within the safe range, which improves the degree of automation, solves the risk of coating "white exposure" or leakage, and provides an effective solution for the continuous large-scale production of hydrogen fuel cell membrane electrode catalyst layer. (2) The optimized design of the sensor combined with the material tank structure of this utility model enables the residual tailings of the slurry coating to be ≤20g, and the slurry utilization rate is much higher than the current industry level; (3) This utility model only requires the installation of a micro sensor in the material tank. The corresponding mechanical structure is simple and occupies little space. It is very suitable for micro-gravure coating of hydrogen fuel cells. It is also applicable to the automatic control of slurry supply in other industries and other coating methods. (4) The response speed of the automatic coating liquid level control system of this utility model is adjustable. Based on different coating widths, coating speeds and coating surface densities, different feeding speeds can be adjusted accordingly, which has a strong flexibility. In summary, this invention solves the problems of "white showing" in the coating or waste of slurry overflow, significantly improves the stability and automation level of the coating production line, improves the current situation of relying on operators to observe the liquid level throughout the process, and effectively avoids the uncertainty of manual control. It is worthy of widespread application. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the structure of this utility model; Figure 2 This is a schematic diagram of the coating tank of this utility model; Figure 3 This is a schematic diagram of the working principle of this utility model; In the diagram: 1. Main material tank; 2. Cooling circulating water; 31. Material conveying pipe one; 32. Material conveying pipe two; 4. Feed pump; 5. Coating trough; 6. Coating roller; 7. Coating doctor blade; 8. Coating substrate; 51. Material trough inlet; 52. High liquid level sensor; 53. Low liquid level sensor; 54. Material trough wall; 55. Slurry overflow groove. Detailed Implementation

[0018] As attached Figure 1 and attached Figure 2As shown, this utility model provides an automatic control system for the coating liquid level of a hydrogen fuel cell membrane electrode, including a main material tank 1, a feed pump 4, a coating trough 5, a coating roller 6, a coating blade 7, and a coating substrate 8. The main material tank 1 contains slurry. The main material tank 1 is connected to the inlet of the feed pump 4 through a feed pipe 31, and the outlet of the feed pump 4 is connected to the feed inlet 51 of the coating trough 5 through a feed pipe 32. The coating roller 6 is suspended and floats in the trough 5. A coating blade 7 is provided on one side of the coating roller 6, and the coating blade 7 is at a certain angle to the coating roller 6. The coating roller 6 is tangentially arranged with a coating substrate 8 above it. The coating substrate 8 and the coating roller 6 are arranged tangentially, and the coating substrate 8 and the coating roller 6 move relative to each other, so that the slurry on the coating roller 6 is transferred to the coating substrate 8 to complete the coating. The main material tank 1 is surrounded by cooling circulating water 2, the temperature of which is 0-10℃ and is adjustable. The feed pump 4 is selected from any one of peristaltic pump, diaphragm pump or screw pump. The material tank inlet 51 is designed on the side or bottom of the coating material tank 5, and the material tank inlet 51 can be single-port or multi-port.

[0019] The coating tank 5 is equipped with a high level sensor 52 and a low level sensor 53. The low level sensor 53 is located at a low horizontal position, and the high level sensor 52 is located at a high horizontal position. Both the high level sensor 52 and the low level sensor 53 are connected to the PLC controller. The PLC controller is also connected to the feed pump 4 and controls the opening and closing of the feed pump 4. The high level sensor 52 and the low level sensor 53 are respectively installed at the upper and lower liquid level lines of the coating tank 5. The top of the coating tank 5 is designed with a slurry overflow groove 55. The upper liquid level line is set at 2-4 mm below the horizontal height of the slurry overflow groove 55, and the lower liquid level line is set at 2-4 mm above the bottom horizontal line of the coating roller 6, thereby providing a buffer time for timely start-up of the feeding.

[0020] The coating tank 5's tank wall 54 is made of 316L stainless steel. The high level sensor 52 and low level sensor 53 can be installed on the inner side of the tank wall 54. The high level sensor 52 and low level sensor 53 can be temperature sensors, preferably miniature sensors, and are tightly installed with the tank wall 54. The high level sensor 52 and low level sensor 53 are both installed opposite the tank inlet 51, which can reduce signal interference during the feeding process and effectively solve the problems of complex structure and difficulty in cleaning. The high level sensor 52 and low level sensor 53 can also be pressure sensors or infrared ranging sensors, and are triggered by high and low liquid levels.

[0021] The present invention will be further described below with reference to the accompanying drawings and specific embodiments: As attached Figure 1As shown, this utility model designs an automatic feeding system for micro-gravure coating. Specifically, all the prepared slurry is stored in the main material tank 1. The main material tank 1 is connected to the feeding pump 4 through the first feeding pipe 31, and the feeding pump 4 is connected to the coating trough 5 through the second feeding pipe 32. The coating roller 6 is suspended and floats in the coating trough 5. The coating blade 7 is tangent to the coating roller 6 at a certain angle, and the contact surface pressure is adjustable, thereby ensuring that excess material is scraped off from the roller surface. The coating substrate 8 is tangent to the coating roller 6, and the slurry on the coating roller 6 is transferred to the coating substrate 8 through relative motion to complete the coating. The main material tank 1 is placed in the cooling circulating water 2 for low-temperature storage, preferably at a temperature of 0-10℃; the first and second material conveying pipes are connected by flexible hoses, rigid pipes, or a combination of both. When the rigid pipe is a metal pipe, its material requirement is 316L stainless steel or other materials with better corrosion resistance; the second material conveying pipe 32 is connected to the material tank inlet 51. The coating material tank 5 is designed with a slurry overflow groove 55, so that the distance between the coating roller and the bottom of the material tank can be minimized, with the aim of improving the slurry utilization rate.

[0022] As attached Figure 2 As shown, the feed inlet 51 of the trough can be designed on the side or bottom of the trough, and can be a single-inlet or multi-inlet feed; the trough wall 54 is made of 316L stainless steel or a material with better corrosion resistance; the high liquid level sensor 52 and the low liquid level sensor 53 are respectively installed on the side of the trough, with the low liquid level sensor 53 located at the low horizontal position and the high liquid level sensor 52 located at the high horizontal position. Both the high liquid level sensor 52 and the low liquid level sensor 53 are connected to the PLC control system. The PLC is synchronously connected to the feed pump to control the pump to start and stop.

[0023] In this automatic control system for the coating liquid level of the hydrogen fuel cell membrane electrode, the feed pump of the automatic feeding system can be a peristaltic pump, a diaphragm pump, or a screw pump, etc. The main feed tank 1 of the feeding system is surrounded by cooling circulating water 2, and the temperature of the cooling water is adjustable. The slurry is stored at low temperature in the feed tank, and its temperature differs from the ambient temperature by more than 10°C. Utilizing this characteristic, a temperature sensor is preferred. When the slurry comes into contact with the temperature sensor probe, the temperature signal changes, triggering a signal to the PLC control system when a set threshold is reached. Similarly, when the liquid level drops below the probe, the probe temperature rises rapidly, reaching a set threshold, triggering a signal to the PLC control system to adjust the feed pump. A miniature temperature sensor is preferred and is tightly installed against the feed tank wall. The installation position is preferably opposite the feed inlet of the tank to reduce signal interference during the feeding process. This design effectively solves the problems of complex structure and difficulty in cleaning. The sensor is not limited to a temperature sensor; pressure sensors or infrared ranging sensors, or other sensor devices that can trigger signals based on liquid level changes, can also be used. The sensor installation height is as follows: the high liquid level sensor 52 and the low liquid level sensor 53 are installed at the upper liquid level line and the lower liquid level line of the material tank, respectively. Furthermore, the upper liquid level point is set at 2-4mm below the horizontal height of the slurry overflow groove 55, and the lower liquid level line is the minimum liquid level height to ensure stable coating. The setting benchmark is 2-4mm above the horizontal line of the bottom of the coating roller to provide buffer time for timely start-up of material supply.

[0024] As attached Figure 3 This is a schematic diagram illustrating the working principle of this utility model. Addressing the lack of effective and safe methods for controlling the coating liquid level in micro-grooving processes for hydrogen fuel cells, and the high reliance on manual intervention, this utility model's automatic control device for the coating liquid level of hydrogen fuel cell membrane electrodes utilizes a liquid level detection sensor installed in the micro-grooving coating tank. The sensor is connected to the feed pump via a control system PLC to achieve active control of the liquid level. Furthermore, the sensor includes sensor one and sensor two, where sensor one is a low-level sensor and sensor two is a high-level sensor. The overall automatic feeding control logic is described in detail below: 1) Stage 1: Coating preparation stage. The feed pump starts feeding material, and the slurry in the tank gradually rises until the liquid level reaches the height of sensor two. Sensor two triggers a signal and sends it to the PLC control system. The PLC control system issues a stop feeding command to the feed pump, and feeding stops.

[0025] 2) Stage 2: Coating Stage. As coating progresses, the slurry in the tank is continuously consumed, and the liquid level gradually decreases until it falls below the detection height of sensor 1. Sensor 1 then triggers a signal and sends it to the PLC control system. The PLC control system then issues a start feeding command to the feeding pump, and feeding begins.

[0026] 3) Stage 3: Slurry replenishment stage. After feeding begins, the liquid level will gradually rise until it triggers level sensor two, at which point feeding stops. This completes the closed-loop control of the feeding process.

[0027] More preferably, the feed rate setting value needs to be greater than the consumption rate of the slurry during the coating process, so as to ensure that the liquid level can rise effectively during the slurry replenishment stage of stage 3, thereby preventing a continuous drop in liquid level.

[0028] The contents not described in detail in this specification are existing technologies known to those skilled in the art. The standard parts used can be purchased from the market, and the irregular parts can be customized according to the description and drawings. The specific connection methods of each part adopt conventional methods such as bolts, rivets, and welding that are mature in the existing technology. The machinery, parts and equipment adopt conventional models in the existing technology, and the circuit connection adopts conventional connection methods in the existing technology, which will not be described in detail here.

[0029] This utility model is not limited to the above-described embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of this utility model shall be considered equivalent substitutions and shall be included within the protection scope of this utility model.

Claims

1. An automatic control system for coating liquid level of hydrogen fuel cell membrane electrode assembly, comprising a main material tank (1), a feed pump (4), a coating trough (5), a coating roller (6), a coating blade (7), and a coating substrate (8), wherein the main material tank (1) contains a slurry, characterized in that: The main material tank (1) is connected to the inlet of the feed pump (4) through the first feed pipe (31). The outlet of the feed pump (4) is connected to the feed inlet (51) of the coating trough (5) through the second feed pipe (32). The coating roller (6) is suspended and floats in the trough (5). A coating scraper (7) is provided on one side of the coating roller (6). The coating scraper (7) is tangent to the coating roller (6) at a certain angle. A coating substrate (8) is provided above the coating roller (6). The coating substrate (8) is tangent to the coating roller (6). The coating substrate (8) and the coating roller (6) move relative to each other, so that the slurry on the coating roller (6) is transferred to the coating substrate (8) to complete the coating.

2. The automatic control system for coating liquid level of hydrogen fuel cell membrane electrode as described in claim 1, characterized in that: The coating tank (5) is equipped with a high liquid level sensor (52) and a low liquid level sensor (53). The low liquid level sensor (53) is located at a low horizontal position, and the high liquid level sensor (52) is located at a high horizontal position. Both the high liquid level sensor (52) and the low liquid level sensor (53) are connected to the PLC controller. The PLC controller is connected to the feed pump (4) in a synchronous manner and controls the opening and closing of the feed pump (4).

3. The automatic control system for coating liquid level of hydrogen fuel cell membrane electrode as described in claim 2, characterized in that: The high liquid level sensor (52) and the low liquid level sensor (53) are respectively installed at the upper liquid level line and the lower liquid level line of the coating tank (5). The top of the coating tank (5) is designed with a slurry overflow groove (55). The upper liquid level line is set at 2-4 mm below the horizontal height of the slurry overflow groove (55), and the lower liquid level line is set at 2-4 mm above the bottom horizontal line of the coating roller (6).

4. The automatic control system for coating liquid level of hydrogen fuel cell membrane electrode as described in claim 3, characterized in that: The coating tank (5) wall (54) is made of 316L stainless steel, and the high liquid level sensor (52) and low liquid level sensor (53) are installed on the inner side of the coating tank wall (54).

5. The automatic control system for coating liquid level of hydrogen fuel cell membrane electrode as described in claim 4, characterized in that: Both the high liquid level sensor (52) and the low liquid level sensor (53) are temperature sensors, preferably miniature sensors, and are tightly installed on the wall of the trough (54). Both the high liquid level sensor (52) and the low liquid level sensor (53) are installed opposite the feed inlet (51) of the trough.

6. The automatic control system for coating liquid level of hydrogen fuel cell membrane electrode as described in claim 4, characterized in that: Both the high liquid level sensor (52) and the low liquid level sensor (53) are pressure sensors or infrared ranging sensors, and are triggered by high or low liquid level signals.

7. The automatic control system for coating liquid level of hydrogen fuel cell membrane electrode as described in claim 1, characterized in that: The feed inlet (51) of the material tank is designed on the side or bottom of the coating material tank (5), and the feed inlet (51) is a single-port feed or a multi-port feed.

8. The automatic control system for coating liquid level of hydrogen fuel cell membrane electrode as described in claim 1, characterized in that: The main material tank (1) is surrounded by cooling circulating water (2), the temperature of which is 0-10℃ and is adjustable.

9. The automatic control system for coating liquid level of hydrogen fuel cell membrane electrode as described in claim 1, characterized in that: The feed pump (4) can be any one of a peristaltic pump, a diaphragm pump, or a screw pump.

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