JP7616138B2 - Cleaning Equipment - Google Patents

Description

The technology disclosed in this specification relates to a cleaning device, and in particular to a cleaning device that cleans conveying sheets used in the manufacture of fuel cells.

In the manufacture of fuel cells, a method is known in which a catalyst ink is applied to a transfer sheet, dried, and then transferred to a solid electrolyte membrane to produce a membrane electrode assembly (MEA). In order to reuse the transfer sheet, it is necessary to remove any deposits remaining on the surface of the transfer sheet after the fuel cell is manufactured.

In regard to the above point, Patent Document 1 describes a device for removing deposits remaining on the surface of a sheet member. This removal device includes a support mechanism for supporting the sheet member, and an air injection mechanism for injecting high-pressure air toward the surface of the sheet member. Therefore, any deposits remaining on the surface of the sheet member are removed by being blown away by the air.

JP 2003-047922 A

The catalyst ink used in the manufacture of fuel cells may contain sulfo groups. In this case, it is believed that a deposit containing sulfo groups remains on the surface of the conveying sheet after the fuel cell is manufactured. This deposit is firmly attached to the conveying sheet by the sulfo groups, and cannot be removed by the above-mentioned air cleaning. Alternatively, it is possible to peel the deposit from the conveying sheet using adhesive tape or the like, but this can lead to problems such as the deposit not being completely removed and damage being caused to the surface of the conveying sheet.

In view of the above situation, this specification provides a technique for removing any remaining adhesions on the surface of a conveying sheet without causing any damage to the surface of the conveying sheet.

The technology disclosed in this specification is embodied in a cleaning device for cleaning a conveying sheet used in the manufacture of fuel cells. This cleaning device includes a cleaning tank that stores a cleaning liquid containing N-methyl-2-pyrrolidone, a support mechanism that supports the conveying sheet in the cleaning liquid parallel to the liquid surface of the cleaning liquid, and an ultrasonic irradiation mechanism that is disposed below the support mechanism and irradiates ultrasonic waves toward the liquid surface of the cleaning liquid. The support mechanism is configured to support the conveying sheet at the position of the antinode of an ultrasonic standing wave formed between the ultrasonic irradiation mechanism and the liquid surface.

In the above-mentioned cleaning device, a solvent containing N-methyl-2-pyrrolidone (hereinafter referred to as NMP), which can dissolve sulfo groups, is used as the cleaning liquid. However, since NMP is highly hydrophobic, NMP can only penetrate from the edge of the deposit, and it takes a relatively long time to penetrate into the deposit. Therefore, in this technology, an ultrasonic irradiation mechanism is further used to irradiate ultrasonic waves toward the liquid surface of the cleaning liquid, thereby forming an ultrasonic standing wave between the ultrasonic irradiation mechanism and the liquid surface. Then, a conveying sheet is supported at the position of the antinode of the ultrasonic standing wave. Since the sound pressure is maximized at the antinode position of the ultrasonic standing wave, NMP can be penetrated into the deposit, and the time required for cleaning the conveying sheet can be shortened. In addition, since NMP does not contain elements (e.g., sulfur, silicon, and chlorine) that significantly reduce the power generation performance of a fuel cell, it is considered that even if a fuel cell is manufactured using a conveying sheet on which NMP remains, the power generation performance will not be significantly affected.

FIG. 1 is a diagram illustrating a schematic configuration of a cleaning device 10. 5 is a diagram for explaining the relationship between ultrasonic standing waves SW and the position at which a conveying sheet 100 is disposed. FIG. FIG. 11 is a comparative example of the present embodiment, showing the behavior of cleaning liquid CS when ultrasonic waves are not applied during cleaning of conveying sheet 100. 6A and 6B are diagrams showing the behavior of cleaning liquid CS when ultrasonic waves are applied to the conveying sheet 100 during cleaning.

In one embodiment of the present technology, the cleaning device may further include a filtering mechanism having an inlet connected to the bottom surface of the cleaning tank and an outlet connected to the side surface of the cleaning tank. In this case, the bottom surface of the cleaning tank may be inclined downward toward the inlet of the filtering mechanism. With this configuration, it is possible to prevent or suppress adhesions removed from the conveying sheet from remaining on the bottom surface of the cleaning tank. Furthermore, since the filtering mechanism can remove adhesions contained in the cleaning liquid, it is possible to reuse the cleaning liquid. Furthermore, precious metals can be recovered from the adhesions removed by the filtering mechanism.

The cleaning device 10 of the embodiment and the conveying sheet 100, which is the object to be cleaned, will be described with reference to the drawings. The conveying sheet 100 is used to manufacture a membrane electrode assembly (MEA) in the fuel cell manufacturing process. The conveying sheet 100 is a long sheet member. Although not limited to this, the conveying sheet 100 is made of a material containing polytetrafluoroethylene (PTFE), such as VALFLON (registered trademark) glass cloth.

As shown in FIG. 1, the cleaning device 10 includes a cleaning tank 12. The cleaning tank 12 is a container with an opening at the top, and stores cleaning liquid CS inside. Although not limited to this, the cleaning tank 12 includes an intermediate wall 12a. The intermediate wall 12a is a plate-shaped member with multiple through holes, and is provided at the bottom of the cleaning tank 12.

As shown in FIG. 1, the cleaning device 10 further includes a payout roller 14, a plurality of conveying rollers 16, and a winding roller 18. A roll 102 on which a conveying sheet 100 having an attachment AD on its surface (i.e., a conveying sheet 100 before cleaning) is wound in a ring shape is set on the payout roller 14, and the conveying sheet 100 before cleaning can be sent out. The plurality of conveying rollers 16 are provided between the payout roller 14 and the winding roller 18, and define a conveying path along which the conveying sheet 100 is conveyed. As will be described in detail later, when passing through this conveying path, cleaning of the conveying sheet 100 is performed, and the attachment AD remaining on the surface of the conveying sheet 100 is removed. The winding roller 18 can wind up the conveying sheet 100 (i.e., the conveying sheet 100 after cleaning) that has passed through the conveying path. For this reason, a roll 104 on which the conveying sheet 100 after cleaning is wound in a ring shape is set on the winding roller 18. Although not limited thereto, the payout roller 14, the multiple transport rollers 16, and the take-up roller 18 are communicatively connected to a controller (not shown), and their operation is controlled and monitored by the controller.

The plurality of conveying rollers 16 include a first conveying roller 16a, a second conveying roller 16b, a third conveying roller 16c, and a fourth conveying roller 16d. The first conveying roller 16a is provided between the unwinding roller 14 and the second conveying roller 16b, the second conveying roller 16b is provided between the first conveying roller 16a and the third conveying roller 16c, the third conveying roller 16c is provided between the second conveying roller 16b and the fourth conveying roller 16d, and the fourth conveying roller 16d is provided between the third conveying roller 16c and the winding roller 18. The first conveying roller 16a and the fourth conveying roller 16d are provided outside the cleaning tank 12. The second conveying roller 16b and the third conveying roller 16c are provided below the liquid level LS of the cleaning liquid CS and above the intermediate wall 12a of the cleaning tank 12. Furthermore, the second transport roller 16b is provided at the same height as the third transport roller 16c, spaced a predetermined distance apart.

As a result, the conveying sheet 100 sent out by the payout roller 14 is conveyed by passing through the first conveying roller 16a, the second conveying roller 16b, the third conveying roller 16c, and the fourth conveying roller 16d in order, and is wound up by the winding roller 18 (see the arrow in FIG. 1). In detail, the conveying sheet 100 passes through the first conveying roller 16a, and then enters the cleaning liquid CS. Then, in the cleaning liquid CS, the conveying sheet 100 passes through the second conveying roller 16b and the third conveying roller 16c. At this time, the conveying sheet 100 located between the second conveying roller 16b and the third conveying roller 16c is supported by the two conveying rollers 16b and 16c in parallel with the liquid surface LS of the cleaning liquid CS. After that, the conveying sheet 100 leaves the cleaning liquid CS, passes through the fourth conveying roller 16d, and is wound up by the winding roller 18.

1, the cleaning device 10 further includes an ultrasonic transducer 20. The ultrasonic transducer 20 is disposed below the second conveyor roller 16b and the third conveyor roller 16c in the cleaning tank 12. As an example, the ultrasonic transducer 20 is disposed on the intermediate wall 12a of the cleaning tank 12. The ultrasonic transducer 20 irradiates ultrasonic waves to the cleaning liquid CS in the cleaning tank 12 toward the liquid surface LS of the cleaning liquid CS. Although not particularly limited, the operation of the ultrasonic transducer 20 is controlled and monitored by a controller (not shown). Here, the ultrasonic transducer 20 in this specification is an example of an ultrasonic irradiation mechanism in the present technology. Note that the ultrasonic transducer 20 does not necessarily need to be disposed on the intermediate wall 12a of the cleaning tank 12. For example, as another embodiment, the ultrasonic transducer 20 may be supported by a support member or the like provided on the side surface 12c of the cleaning tank 12. In this case, regardless of the method of support, the ultrasonic transducer 20 only needs to be positioned below the second transport roller 16b and the third transport roller 16c within the cleaning tank 12.

2, the ultrasonic waves emitted from the ultrasonic transducer 20 are transmitted toward the liquid surface LS of the cleaning liquid CS (i.e., upward). The ultrasonic waves that reach the liquid surface LS of the cleaning liquid CS are reflected by the liquid surface LS. The ultrasonic waves emitted from the ultrasonic transducer 20 and the reflected waves of the ultrasonic waves reflected by the liquid surface LS interfere with each other, forming an ultrasonic standing wave SW between the ultrasonic transducer 20 and the liquid surface LS of the cleaning liquid CS. This ultrasonic standing wave SW has three nodes S1, S2, and S3 and two antinodes A1 and A2. In this embodiment, the conveying sheet 100 is supported by the second conveying roller 16b and the third conveying roller 16c at a height position equal to the position of the antinode A1 of the ultrasonic standing wave SW. The second conveying roller 16b and the third conveying roller 16c in this specification are an example of a support mechanism in this technology. The number and positions of the multiple conveying rollers 16 are not particularly limited, and as long as the conveying sheet 100 is supported in the cleaning liquid CS at a height position equal to the position of the antinode A1 of the ultrasonic standing wave SW, the number and arrangement may be any number necessary to support the conveying sheet 100 parallel to the liquid surface LS of the cleaning liquid CS. Also, as in this embodiment, when there are multiple positions of the antinodes A1 and A2 of the ultrasonic standing wave SW, the conveying sheet 100 may be supported at a height position equal to the position of one of the antinodes A1 and A2.

In the above-mentioned cleaning device 10, a solvent containing NMP capable of dissolving sulfo groups is used as the cleaning liquid CS. However, since NMP is highly hydrophobic, as shown in FIG. 3, NMP can only penetrate from the end of the deposit AD, and it takes a relatively long time to penetrate into the deposit AD. Therefore, in this technology, an ultrasonic vibrator 20 is further used to irradiate ultrasonic waves toward the liquid surface LS of the cleaning liquid CS, thereby forming an ultrasonic standing wave SW between the ultrasonic vibrator 20 and the liquid surface LS. Then, the conveying sheet 100 is supported at the position of the antinode A1 of the ultrasonic standing wave SW. Since the sound pressure is maximized at the position of the antinode A1 of the ultrasonic standing wave SW, as shown in FIG. 4, NMP can be penetrated into the deposit AD, and the time required for cleaning the conveying sheet 100 can be shortened. In addition, since NMP does not contain elements (e.g., sulfur, silicon, chlorine) that significantly reduce the power generation performance of a fuel cell, it is believed that even if a fuel cell is produced using a conveying sheet 100 in which NMP remains, the power generation performance will not be significantly affected.

1, the cleaning device 10 further includes a filtration unit 22. The filtration unit 22 includes a circulation path 24, a pump 26, and a filter device 28. The circulation path 24 is a path through which the cleaning liquid CS flows. The suction port 24a of the circulation path 24 is connected to the bottom surface 12b of the cleaning tank 12, and the discharge port 24b of the circulation path 24 is connected to the side surface 12c of the cleaning tank 12. Furthermore, the bottom surface 12b of the cleaning tank 12 is provided with a downward inclination toward the suction port 24a of the filtration unit 22. The pump 26 is provided in the circulation path 24 and can adjust the flow rate of the cleaning liquid CS flowing through the circulation path 24. The filter device 28 has a filter therein. The filter device 28 is provided in the circulation path 24 and can remove adhesions AD contained in the cleaning liquid CS flowing through the filter device 28. Although not particularly limited, the filter of the filter device 28 is a replaceable filter and is replaced at predetermined intervals. Note that the filtration unit 22 in this specification is an example of a filtration mechanism in the present technology.

The above configuration makes it possible to prevent or suppress the adhesion AD removed from the conveying sheet 100 from remaining on the bottom surface 12b of the cleaning tank 12. Furthermore, since the filtration unit 22 can remove the adhesion AD contained in the cleaning liquid CS, the cleaning liquid CS can be reused. In addition, precious metals can be recovered from the adhesion AD removed by the filtration unit 22.

Although several specific examples have been described in detail above, these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and variations of the specific examples given above. The technical elements described in this specification or drawings have technical utility either alone or in combination.

10: cleaning device 12: cleaning tank 12a: intermediate wall 12b: bottom surface 12c: side surface 14: pay-out rollers 16a-16d: transport rollers 18: take-up roller 20: ultrasonic vibrator 22: filtration unit 24: circulation path 24a: suction port 24b: discharge port 26: pump 28: filter device 100: transport sheet 102: roll AD: deposit CS: cleaning liquid LS: liquid surface

Claims (2)

A cleaning device for cleaning a conveying sheet used in the manufacture of a fuel cell, comprising:
A cleaning tank storing a cleaning solution containing N-methyl-2-pyrrolidone;
a support mechanism that supports the conveying sheet in the cleaning liquid so as to be parallel to a liquid surface of the cleaning liquid;
an ultrasonic irradiation mechanism disposed below the support mechanism and configured to irradiate ultrasonic waves toward the liquid surface of the cleaning liquid;
Equipped with
the support mechanism is configured to support the conveying sheet at a position of an antinode of an ultrasonic standing wave formed between the ultrasonic irradiation mechanism and the liquid surface.
Cleaning equipment. The cleaning tank further includes a filtration mechanism having a suction port connected to a bottom surface of the cleaning tank and a discharge port connected to a side surface of the cleaning tank,
The cleaning device according to claim 1 , wherein the bottom surface of the cleaning tank is inclined downward toward the suction port of the filtering mechanism.

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