JP2019046740A - Coating device - Google Patents

Abstract

To provide a coating device capable of suppressing variation in coating thickness of a catalyst ink and suppressing deterioration in yield.SOLUTION: The coating thickness of a catalyst ink 6a on a web 60 is estimated in real time from the shear stress detected by a strain gauge 57 provided on the web 60 side of a downstream lip head portion 56b of a die head 56, the transport speed of the web 60 to the die head 56, and the viscosity of the catalyst ink 6a, and a relative distance between the downstream lip head portion 56b of the die head 56 and the web 60 (that is, application clearance) is adjusted based on the estimated coating thickness.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a coating apparatus that coats a web with a catalyst ink that constitutes a fuel cell electrode.

  For example, a cell of a polymer electrolyte fuel cell (sometimes referred to as a fuel cell, a single cell, or a single cell) includes an ion permeable electrolyte membrane, an anode catalyst layer (electrode layer) sandwiching the electrolyte membrane, and A membrane electrode assembly (MEA: Membrane Electrode Assembly) comprising a cathode side catalyst layer (electrode layer) is provided. On both sides of the MEA, a gas diffusion layer (GDL: Gas Diffusion Layer) is formed to provide fuel gas or oxidant gas and to collect electricity generated by the electrochemical reaction. The MEA in which GDLs are arranged on both sides is referred to as MEGA (Membrane Electrode & Gas Diffusion Layer Assembly), and the MEGA is sandwiched by a pair of separators. Here, the MEGA is a power generation unit of the fuel cell, and when there is no gas diffusion layer, the MEA is a power generation unit of the fuel cell.

  The anode-side catalyst layer (electrode layer) and the cathode-side catalyst layer (electrode layer) constituting the membrane electrode assembly (MEA) have carbon particles supporting a catalyst metal that proceeds with an electrochemical reaction, and proton conductivity. For example, platinum (Pt) or a platinum alloy composed of platinum (Pt) and another metal such as ruthenium (Ru) is used as a catalyst metal. The anode side catalyst layer (electrode layer) and the cathode side catalyst layer (electrode layer) are usually coated on the surface of the electrolyte membrane with a catalyst ink in which carbon particles carrying a catalyst metal or a polymer electrolyte is dispersed. After the catalyst layer is formed on the transfer film, the catalyst layer is formed on the surface of the electrolyte membrane by pressure transfer or the like.

JP, 2014-079669, A Unexamined-Japanese-Patent No. 2017-054580

  By the way, the Pt basis weight (Pt weight per unit area) of the catalyst layer, which is a component member of a fuel cell electrode, is an important characteristic directly linked to the power generation performance of the fuel cell, but the web during processing (coating) The coating thickness of the catalyst ink varies due to the thickness variation of the electrolyte membrane or the transfer film as a base material, etc., and there is a possibility that the deviation of the standard of Pt basis weight occurs and the yield is deteriorated.

  Also, in order to guarantee the Pt weight per unit area of the catalyst layer described above, usually, the film thickness after coating and drying of the catalyst layer is measured by a sampling inspection in the catalyst layer manufacturing process. Specifically, as shown in FIG. 6, the web as a substrate is unrolled from the unwinding roll, and the catalyst ink for forming the catalyst layer is discharged from the die head, and is continuously carried out by the conveying roller. The catalyst ink is applied to the surface of the transported web and then dried to form a catalyst layer. Then, the web after catalyst layer formation is taken up on a take-up roll, and after processing is completed for each roll, a part of the formed catalyst layer is pulled out from the roll and the DRY film thickness (Pt weight) of the catalyst layer is measured I am examining it.

  Therefore, in the conventional sampling inspection as described above, when the inspection result in the sampling inspection for each roll is NG (Pt weight deviation standard deviation), the entire roll must be discarded, and the yield may be further deteriorated. There was a sex.

  This invention is made in view of the said subject, and the place made as the objective is providing the coating apparatus which can suppress the dispersion | variation in the coating thickness of a catalyst ink, and can suppress the deterioration of a yield. is there.

  In order to solve the above-mentioned subject, a coating device by the present invention is a coating device which discharges a catalyst ink which constitutes a fuel cell electrode to a web from a die head, and coats it, and the downstream side lip of the die head A strain detection device is provided on the web side of a head unit, and the catalyst ink to the web is obtained from the shear stress detected by the strain detection device, the transport speed of the web to the die head, and the viscosity of the catalyst ink The coating thickness of the die head is estimated, and the relative distance between the downstream lip head portion of the die head and the web is adjusted based on the estimated coating thickness.

  According to the present invention, the catalyst ink for the web is obtained from the shear stress detected by the strain detection device provided on the web side of the downstream lip head portion of the die head, the transport speed of the web to the die head, and the viscosity of the catalyst ink. Of the coating thickness of the die head in real time, and based on the estimated coating thickness, the relative distance between the downstream lip head portion of the die head and the web (that is, the distance between the downstream lip head portion of the die head and the web surface) By adjusting the application clearance, it is possible to suppress the variation of the coating thickness of the catalyst ink due to the variation of the thickness of the web, etc., prevent the deviation of the standard of the Pt basis weight beforehand, and suppress the deterioration of the yield. .

FIG. 2 is a cross-sectional view of main parts of a fuel cell stack. It is a flowchart which shows the outline of the catalyst layer manufacturing process in the manufacturing process of a fuel cell stack. (A) is a principal part expanded sectional view which expands and shows the principal part of the die head used at a catalyst layer manufacturing process, (B) is a sectional view according to the UU arrow line of (A). The principal part expanded sectional view which expands and shows the principal part of other examples of the die head used at a catalyst layer manufacturing process. It is a flow figure showing an outline of control processing by a control device used at a catalyst bed manufacturing process. It is a flowchart which shows the outline of the catalyst layer manufacturing process in the manufacturing process of the conventional fuel cell stack.

  Hereinafter, the configuration of the present invention will be described in detail based on an example of an embodiment shown in the drawings. The following description exemplifies a case where the present invention is applied to a fuel cell mounted on a fuel cell vehicle or a fuel cell system including the same as an example, but the scope of application is not limited to such an example. .

[Fuel cell stack configuration]
First, referring to FIG. 1, the structure of a polymer electrolyte fuel cell will be outlined as an example of a fuel cell stack (fuel cell) to which the present invention is applied.

  FIG. 1 is a cross-sectional view of the main part of a fuel cell stack (fuel cell) 10. As shown in FIG. 1, in the fuel cell stack 10, a plurality of cells (unit cells) 1 as a basic unit are stacked (cell stack 9). Each cell 1 is a polymer electrolyte fuel cell that generates an electromotive force by an electrochemical reaction of an oxidant gas (for example, air) and a fuel gas (for example, hydrogen). The cell 1 includes the MEGA 2 and a separator 3 in contact with the MEGA 2 so as to partition the MEGA 2. In the present embodiment, the MEGA 2 is sandwiched by the pair of separators 3, 3.

  MEGA 2 is one in which a membrane electrode assembly (MEA) 4 and gas diffusion layers (GDL) 7 and 7 disposed on both sides thereof are integrated. The membrane electrode assembly 4 includes an electrolyte membrane 5 and a pair of electrodes 6 and 6 joined so as to sandwich the electrolyte membrane 5. The electrolyte membrane 5 is formed of a proton conductive ion exchange membrane formed of a solid polymer material, and the electrode 6 is formed of, for example, a porous carbon material supporting a catalyst such as platinum (Pt). The electrode (anode catalyst layer (electrode layer)) 6 disposed on one side of the electrolyte membrane 5 is an anode, and the other electrode (cathode catalyst layer (electrode layer)) 6 is a cathode. The gas diffusion layer 7 is formed of a conductive member having gas permeability such as a carbon porous body such as carbon paper or carbon cloth, or a metal porous body such as a metal mesh or a foam metal.

  In the present embodiment, the MEGA 2 is a power generation unit of the fuel cell 10, and the separator 3 is in contact with the gas diffusion layer 7 of the MEGA 2. When the gas diffusion layer 7 is omitted, the membrane electrode assembly 4 is a power generation unit, and in this case, the separator 3 is in contact with the membrane electrode assembly 4. Therefore, the power generation unit of the fuel cell 10 includes the membrane electrode assembly 4 and is in contact with the separator 3.

  The separator 3 is a plate-like member whose base material is a metal excellent in conductivity, gas impermeability, etc., and one of the separators is in contact with the gas diffusion layer 7 of the MEGA 2 and the other separator is adjacent. 3 is in contact with the other side.

  In the present embodiment, each separator 3 is formed in a wave shape or a concavo-convex shape. The shape of the separator 3 is in the shape of an isosceles trapezoid, and the top of the wave is flat, and both ends of the top are angular at equal angles. That is, the respective separators 3 have substantially the same shape as viewed from the front side or viewed from the back side. The top of the separator 3 is in surface contact with one gas diffusion layer 7 of the MEGA 2, and the top of the separator 3 is in surface contact with the other gas diffusion layer 7 of the MEGA 2.

  A gas passage 21 defined between the gas diffusion layer 7 on one electrode (i.e., anode) 6 side and the separator 3 is a passage through which fuel gas flows, and the other electrode (i.e., cathode) 6 side The gas flow path 22 defined between the gas diffusion layer 7 and the separator 3 is a flow path through which the oxidant gas flows. When the fuel gas is supplied to one of the opposing gas flow paths 21 via the cell 1 and the oxidant gas is supplied to the gas flow path 22, an electrochemical reaction occurs in the cell 1 to generate an electromotive force.

  Further, one cell 1 and another cell 1 adjacent thereto are disposed such that the electrode 6 serving as the anode and the electrode 6 serving as the cathode face each other. Also, the top of the back side of the separator 3 disposed along the electrode 6 serving as the anode of one cell 1 and the top of the back side of the separator 3 disposed along the electrode 6 serving as the cathode of another cell 1 And are in surface contact. Water as a refrigerant for cooling the cells 1 flows in a space 23 defined between the separators 3 and 3 in surface contact between two adjacent cells 1.

[Catalyst layer production process]
Next, referring to FIG. 2 to FIG. 5, the manufacturing process of the fuel cell stack, in particular, the catalyst layer manufacturing process of the anode side to the cathode side thereof, and the coating apparatus of the catalyst ink used in the catalyst layer manufacturing process. The structure of

  FIG. 2 is a flow diagram schematically showing a catalyst layer manufacturing process in the manufacturing process of the fuel cell stack.

  As described above, the anode-side catalyst layer (electrode layer) 6 and the cathode-side catalyst layer (electrode layer) 6 constituting the membrane electrode assembly (MEA) 4 are carbon particles that carry a catalyst metal that promotes an electrochemical reaction. And a polymer electrolyte having proton conductivity. As a catalyst metal, for example, platinum (Pt) or a platinum alloy composed of platinum (Pt) and another metal such as ruthenium (Ru) is used. The anode side catalyst layer (electrode layer) 6 and the cathode side catalyst layer (electrode layer) 6 are coated on the surface of the electrolyte membrane 5 with a catalyst ink in which carbon particles carrying a catalyst metal and a polymer electrolyte are dispersed. After the catalyst layer 6 is formed on the transfer film, the catalyst layer 6 is transferred onto the surface of the electrolyte membrane 5 by pressure bonding or the catalyst ink is coated on the surface of the gas diffusion layer 7 or the like. It is formed.

  In the present embodiment, the anode side catalyst layer (electrode layer) 6 and the cathode side catalyst layer (electrode layer) 6 are attached to a die head 56 on which a strain gauge 57 as a strain detection device is installed and a die head 56 Using a coating device 50 provided with a control device 59 or the like that controls (the driving state of) the servomotor 58 as a device to control the advance / retraction (with respect to the web 60) of the die head 56 The film thickness (coating thickness) immediately after the application of the catalyst ink 6a that forms the catalyst layer 6 is manufactured while adjusting in real time.

  Specifically, as shown in FIG. 2, the web 60 (electrolyte film 5, transfer film, gas diffusion layer 7 etc.) as a substrate is unrolled from the unwinding roll 51a wound in a roll shape. The paste-like catalyst ink 6a stored in the tank 55 is discharged from (the slit-like discharge port 56a of) the die head 56 through the pump 54, continuously transported by the plurality of transport rollers 53, and passed over the back roll 52. The catalyst ink 6 a is applied to the surface of the web 60.

  The rotational speed of the unwinding roll 51a, the rotational speed of the transport roller 53 (that is, the transport speed of the web 60), the discharge flow rate of catalyst ink 6a from the die head 56 (the discharge port 56a thereof) The pressure of the pump 54 and the like, the rotational speed of the take-up roll 51b described later, and the like are controlled by the control device 59 and the like provided in the coating device 50.

  Here, in the present embodiment, as shown in FIGS. 3A and 3B, the downstream lip head portion (the coating thickness of the catalyst ink 6a (the coating thickness of the catalyst ink 6a is positioned downstream of the discharge port 56a of the die head 56). (A part defining the application clearance)) a strain gauge 57 is embedded on the web 60 side of 56b.

  In the present embodiment, the strain gauge 57 is provided inside the downstream lip head portion 56b of the die head 56. However, for example, as shown in FIG. Of course, the strain gauge 57 may be disposed at the rear (downstream side) of the downstream side lip head 56 b of 56.

  The control device 59 is constituted by a microcomputer provided with a central processing unit (CPU), a storage device and the like, and as described above, the catalyst ink 6a is discharged from the die head 56 and coated on the web 60. The information (detection value) detected by the strain gauge 57 provided in the die head 56 is acquired, and the control process shown in FIG. 5 is executed.

That is, the control device 59 is acquired by the strain gauge 57 based on the idea that the catalyst ink 6a flowing between the downstream lip head 56b of the die head 56 and the web 60 can be approximated as "a fluid sandwiched between parallel plates". From the shear stress (τ) to be transferred, the transport speed of the web 60 to the die head 56 (δu) (corresponding to the shear rate), and the viscosity coefficient (viscosity) (μ) of the catalyst ink 6a, The coating thickness (δy) of the catalyst ink 6a on the web 60 is calculated (estimated) using (1) (S51).

  Further, the control device 59 compares the coating thickness calculated in S51 with a predetermined reference value (reference range) (S52), and the coating thickness calculated in S51 is larger than the reference value Operates the servomotor 58 provided on the die head 56 to advance the die head 56 relative to the web 60, and the relative distance between the downstream lip head portion 56 b of the die head 56 and the web 60 passing over the back roll 52 ( That is, the application clearance is narrowed to reduce the coating thickness of the catalyst ink 6a on the web 60 (S53). On the other hand, when the coating thickness calculated in S51 is smaller than the reference value, the servomotor 58 provided on the die head 56 is operated to retract the die head 56 relative to the web 60, and the downstream lip head portion of the die head 56 The relative distance (that is, the application clearance) between the web 56 passing over the back roll 52 and the web 56 b is increased, and the coating thickness of the catalyst ink 6 a on the web 60 is increased (S 54).

  As described above, the control device 59 uses the information obtained from the strain gauges 57 installed on the downstream side of the discharge port 56 a of the die head 56, and the WET film thickness immediately after the application of the catalyst ink 6 a to the web 60 (coating Desired thickness (for example, standard) by calculating (estimating) the thickness in real time and applying feedback to coating conditions (coating clearance and discharge flow rate of catalyst ink 6a) (specifically, automatically adjusting coating clearance) The catalyst ink 6 a can be coated on the surface of the web 60 at a constant thickness within the range.

  Next, as shown in FIG. 2, the web 60 coated with the catalyst ink 6 a having a desired thickness is continuously transported to the drying furnace 49, and the catalyst ink 6 a on the surface of the web 60 is dried by the drying furnace 49. Is dried to form a catalyst layer 6, and then the web 60 after forming the catalyst layer 6 is wound on a take-up roll 51b. As a result, the above-mentioned anode catalyst layer (electrode layer) 6 and cathode catalyst layer (electrode layer) 6 are produced.

  As described above, in the present embodiment, the shear stress detected by the strain gauge 57 provided on the web 60 side of the downstream lip head portion 56 b of the die head 56, and the transport speed of the web 60 with respect to the die head 56 The coating thickness of the catalyst ink 6a on the web 60 is estimated in real time from the viscosity of the catalyst ink 6a, and the relative distance between the downstream lip head 56b of the die head 56 and the web 60 based on the estimated coating thickness That is, by adjusting the application clearance), the variation in the coating thickness of the catalyst ink 6a caused by the thickness variation of the web 60 and the like is suppressed, and the deviation of the Pt basis weight is prevented in advance, thereby deteriorating the yield. It can be suppressed.

  Further, in the present embodiment, adjusting the thickness of the catalyst layer in real time eliminates the need for a conventional inspection for removal, and thus has the advantage of shortening the process lead time.

  In the above embodiment, the application clearance is automatically adjusted by controlling the servomotor 58 provided on the die head 56 by the control device 59 and advancing or retracting the die head 56 with respect to the web 60. The side of the web 60 transported onto the roll 52 may be moved relative to the die head 56, and it is needless to say that the die head 56 and the web 60 may both be moved.

  As mentioned above, although the embodiment of the present invention has been described in detail with reference to the drawings, the specific configuration is not limited to this embodiment, and there are design changes and the like within the scope of the present invention. Also, they are included in the present invention.

DESCRIPTION OF SYMBOLS 1 ... cell (fuel cell), 2 ... MEGA, 3 ... separator, 4 ... membrane electrode assembly (MEA), 5 ... electrolyte membrane, 6 ... electrode (anode side catalyst layer (electrode layer), cathode side catalyst layer ( Electrode layer)) 6a catalyst ink 7 gas diffusion layer (GDL) 9 cell stack 10 fuel cell stack (fuel cell) 21 22 gas flow path 23 space in which water flows , 49: drying oven, 50: coating device, 51a: unwinding roll, 51b: winding roll, 52: back roll, 53: conveying roller, 54: pump, 55: tank, 56: die head, 56a: discharge port 56b: downstream lip head portion 57: strain gauge (strain detection device) 58: servomotor (moving device) 59: control device 60: web

Claims (1)

It is a coating apparatus which discharges the catalyst ink which comprises the electrode for fuel cells from a die head with respect to a web, and coats,
A strain detection device is provided on the web side of the downstream lip head portion of the die head;
The coating thickness of the catalyst ink on the web is estimated from the shear stress detected by the strain detection device, the transport speed of the web to the die head, and the viscosity of the catalyst ink, and the coating thickness estimated The coating apparatus which adjusts the relative distance of the downstream lip head part of the said die head, and the said web based on (4).

Images