1. A water detection device (10a, 10b, 70) is provided in a power generation unit (12, 74), the power generation unit (12, 74) having a reactant gas flow path (38, 40) through which a reactant gas flows along a membrane electrode assembly (22),

the water detection device is characterized in that,

has a pair of electrodes (52, 72), a voltage applying section (54), a current measuring section (56), and a determining section (58),

the pair of electrodes (52, 72) are provided so as to be separated from each other at positions facing the reactant gas flow paths,

the voltage applying section (54) applies a voltage to the pair of electrodes,

the current measuring unit (56) is capable of measuring a current flowing between the pair of electrodes,

the determination unit (58) determines whether or not liquid water (W) is present in the reactant gas flow path based on the measurement result of the current measurement unit,

the voltage applying unit is capable of changing a voltage applied to the pair of electrodes within an application range including a1 st voltage and a2 nd voltage, wherein the 1 st voltage is a voltage smaller than an electrolysis voltage of the water, and the 2 nd voltage is a voltage larger than the electrolysis voltage of the water,

the determination unit determines the presence or absence of water based on a change in the current measured by the current measurement unit when the voltage applied to the pair of electrodes is changed within the application range.

2. The water detecting device according to claim 1,

the measurement limit of the current measurement unit is set to be smaller than a current flowing between the pair of electrodes to which the 1 st voltage and the 2 nd voltage are applied when the pair of electrodes are short-circuited,

the determination unit determines that the water is present between the pair of electrodes when a2 nd current measured by the current measurement unit when the 2 nd voltage is applied to the pair of electrodes is larger than a1 st current measured by the current measurement unit when the 1 st voltage is applied to the pair of electrodes.

3. The water detecting device according to claim 1,

the determination unit determines that the water is present between the pair of electrodes when a voltage applied to the pair of electrodes within the application range and at least a part of the current measured by the current measurement unit are in an exponential function relationship.

4. The water detecting device according to claim 1,

the voltage applying unit is capable of applying a plurality of voltages selected from a1 st voltage range smaller than the electrolysis voltage of the water and a plurality of voltages selected from a2 nd voltage range larger than the electrolysis voltage of the water to the pair of electrodes,

the determination unit compares a1 st ratio with a2 nd ratio, and determines that the water is present between the pair of electrodes when the 2 nd ratio is larger than the 1 st ratio, wherein the 1 st ratio is a ratio at which a current flowing between the pair of electrodes changes when a plurality of voltages selected from the 1 st voltage range are applied, and the 2 nd ratio is a ratio at which a current flowing between the pair of electrodes changes when a plurality of voltages selected from the 2 nd voltage range are applied.

5. The water detecting device according to any one of claims 1 to 4,

the voltage applying unit is capable of applying a detection voltage larger than an electrolysis voltage of the water to the pair of electrodes,

the current measuring section is capable of detecting a detection current flowing between the pair of electrodes when the detection voltage is applied,

when the current measuring unit detects the detection current, the voltage applying unit changes the voltage applied to the pair of electrodes within the application range, and the determining unit determines the presence or absence of water.

6. A water detection method detects the presence or absence of liquid water (W) in a reactant gas flow path (38, 40) through which a reactant gas flows along a membrane electrode assembly (22) of a power generation cell (12, 74),

the water detection method is characterized by comprising:

a determination voltage application step of applying a voltage that changes within an application range including a1 st voltage and a2 nd voltage to a pair of electrodes (52, 72) that are provided apart from each other, at a position facing the reactant gas flow path, wherein the 1 st voltage is a voltage smaller than an electrolysis voltage of the water, and the 2 nd voltage is a voltage larger than the electrolysis voltage of the water; and

and a determination step of determining whether or not water is present in the reaction gas flow path based on a change in the current flowing between the pair of electrodes measured by a current measurement unit (56) when a voltage that changes within the application range is applied to the pair of electrodes.

7. The water detection method according to claim 6,

the measurement limit of the current measuring unit is set to be smaller than a current flowing between the pair of electrodes to which a voltage within the application range is applied when the pair of electrodes are short-circuited,

in the determining step, when a2 nd current measured by the current measuring unit when the 2 nd voltage is applied to the pair of electrodes is larger than a1 st current measured by the current measuring unit when the 1 st voltage is applied to the pair of electrodes, it is determined that the water is present between the pair of electrodes.

8. The water detection method according to claim 6,

in the determining step, it is determined that the water is present between the pair of electrodes when the voltage applied to the pair of electrodes within the application range and at least a part of the current measured by the current measuring unit are in an exponential function relationship.

9. The water detection method according to claim 6,

in the determination voltage application step, a plurality of voltages selected from a1 st voltage range smaller than the electrolysis voltage of the water and a plurality of voltages selected from a2 nd voltage range larger than the electrolysis voltage of the water are applied to the pair of electrodes,

in the determination step, a1 st ratio, which is a ratio at which a current flowing between the pair of electrodes changes when a plurality of voltages selected from the 1 st voltage range are applied, and a2 nd ratio, which is a ratio at which a current flowing between the pair of electrodes changes when a plurality of voltages selected from the 2 nd voltage range are applied, are compared, and when the 2 nd ratio is larger than the 1 st ratio, it is determined that the water is present between the pair of electrodes.

10. The water detecting method according to any one of claims 6 to 9,

comprises a detection voltage application step of applying a detection voltage larger than the electrolysis voltage of the water to the pair of electrodes before the determination voltage application step,

the determination voltage applying step and the determination step are performed when the detection current flowing between the pair of electrodes is detected when the detection voltage is applied.

Background

In general, a polymer electrolyte fuel cell has a Membrane Electrode Assembly (MEA) in which a polymer electrolyte membrane is sandwiched between an anode electrode and a cathode electrode. A power generation unit (single fuel cell) is constructed by further sandwiching the membrane electrode assembly with a separator member (bipolar plate). The power generation unit is stacked in a predetermined number and used as, for example, a fuel cell stack for a vehicle.

Between the cathode electrode of the power generating cell and the separator, an oxidant gas channel for flowing an oxidant gas along the cathode electrode is formed as a reactant gas channel. Between the anode electrode of the power generation cell and the separator, a fuel gas flow path through which the fuel gas flows along the anode electrode is formed as a reactant gas flow path. The oxidant gas and the fuel gas (reactant gas) supplied through these reactant gas flow paths are consumed by the electrochemical reaction (power generation reaction) in the membrane electrode assembly, and power is generated.

In such a power generation cell, liquid water such as generated water generated by a power generation reaction and condensed water generated by condensation of water vapor in a reaction gas may be retained in the reaction gas flow path. If water in a liquid state is present in the reaction gas flow path, there is a fear that the flow of the reaction gas in the reaction gas flow path may be obstructed to lower the power generation stability of the power generation unit.

Therefore, for example, as disclosed in Japanese patent application laid-open No. 2019-220414, a water detection device for detecting the presence or absence of liquid water in a reaction gas flow path has been proposed. By detecting the presence or absence of liquid water in the reaction gas flow path by the water detection device, some measure for discharging liquid water can be taken as necessary at an appropriate timing.

Disclosure of Invention

The present invention has been made in view of the above-described technology, and an object thereof is to provide a water detection device and a water detection method capable of improving the detection accuracy of liquid water in a reaction gas flow path.

In one aspect of the present invention, there is provided a water detection device provided in a power generation unit having a reaction gas flow path through which a reaction gas flows along a membrane electrode assembly, the water detection device including a pair of electrodes provided apart from each other at positions facing the reaction gas flow path, a voltage application unit that applies a voltage to the pair of electrodes, a current measurement unit that is capable of measuring a current flowing between the pair of electrodes, a current measurement unit that determines whether or not liquid water is present in the reaction gas flow path based on a measurement result of the current measurement unit, and a determination unit that is capable of changing a voltage applied to the pair of electrodes within an application range including a1 st voltage and a2 nd voltage, wherein the 1 st voltage is a voltage smaller than an electrolytic voltage of the water, the 2 nd voltage is a voltage larger than the electrolysis voltage of the water, and the determination unit determines the presence or absence of the water based on a change in the current measured by the current measurement unit when the voltage applied to the pair of electrodes is changed within the application range.

Another aspect of the present invention is a water detection method for detecting presence or absence of liquid water in a reactant gas flow path through which a reactant gas flows along a membrane electrode assembly of a power generation unit, the water detection method including: a determination voltage application step of applying a voltage that changes within an application range including a1 st voltage and a2 nd voltage to a pair of electrodes provided apart from each other at a position facing the reaction gas flow path, wherein the 1 st voltage is a voltage smaller than an electrolysis voltage of the water, and the 2 nd voltage is a voltage larger than the electrolysis voltage of the water; and a determination step of determining whether or not water is present in the reactant gas flow path based on a change in the current flowing between the pair of electrodes measured by the current measurement unit when a voltage that changes within the application range is applied to the pair of electrodes.

When no current is detected between a pair of electrodes to which a voltage is applied, the electrodes are electrically insulated from each other, and it can be determined that liquid water is not present between the electrodes. On the other hand, when a current is detected between the electrodes to which a voltage is applied, one reason for this is that the current flows through liquid water present between the electrodes. However, as another reason for detecting the current, a short circuit may occur due to electrical contact between a component of the power generation cell and the electrode. That is, even when liquid water is not present between the electrodes, a current may flow between the electrodes. Therefore, it is found that the presence or absence of liquid water between the electrodes may not be detected with high accuracy simply by detecting the current between the electrodes.

In the present invention, a voltage varying within an application range including a1 st voltage smaller than an electrolysis voltage of water and a2 nd voltage larger than the electrolysis voltage of water is applied to the pair of electrodes. When a voltage varying within the application range is applied to the pair of electrodes, the presence or absence of liquid water is determined based on the variation in the current measured by the current measuring unit. In the case where liquid water is present between the electrodes, the current changes in different manners before and after the voltage applied to the pair of electrodes exceeds the electrolysis voltage of water. On the other hand, when a short circuit occurs between the electrodes, the manner of change in the current does not change particularly until the voltage applied to the pair of electrodes exceeds the electrolysis voltage of water and after the voltage exceeds the electrolysis voltage of water.

Therefore, by detecting the change in the current, it is possible to avoid erroneous detection of a short circuit or the like between the electrodes as the presence of liquid water between the electrodes. As a result, the detection accuracy of the liquid water in the reactant gas flow field can be improved.

The above objects, features and advantages will be readily understood by the following description of the embodiments with reference to the accompanying drawings.

Drawings

Fig. 1 is a view of a2 nd partition member in which a water detection device according to an embodiment of the present invention is disposed, as viewed from an oxidizing gas flow path side.

Fig. 2 is an exploded perspective view of a power generation unit having the 1 st partition member of fig. 1.

Fig. 3 is a sectional view of the power generation unit in fig. 2 including a section of the water detection device of fig. 1 viewed from the III-III direction.

Fig. 4 is an enlarged view of a main portion of the water detecting device of fig. 1.

Fig. 5 is an enlarged sectional view taken along line V-V of fig. 1.

Fig. 6 is a graph showing the relationship between the voltage applied between the electrodes and the current flowing between the electrodes in the case where water is present between the electrodes, in the case where a short circuit is present between the electrodes, and in the case where water is not present between the electrodes and in the case where no short circuit is present between the electrodes.

Fig. 7 is a flowchart illustrating a water detection method according to an embodiment of the present invention.

Fig. 8 is a view of the 2 nd partition member incorporating the electrode of the water detection device according to the modification, as viewed from the oxidant gas flow field side.

Fig. 9 is an exploded perspective view of a power generation unit having the 2 nd partition member of fig. 8.

Fig. 10 is a cross-sectional view taken along line X-X of the 2 nd partition member of fig. 8.

Detailed Description

The water detection device and the water detection method according to the present invention will be described in detail below with reference to the drawings, which illustrate preferred embodiments. In the following drawings, the same reference numerals are used for the same components or components that exhibit the same functions and effects, and redundant description thereof may be omitted.

As an example of the power generation unit provided with the water detection devices 10a and 10b according to the present embodiment shown in fig. 1, a power generation unit 12 shown in fig. 2 can be mentioned. Therefore, first, the structure of the power generation unit 12 will be briefly described with reference mainly to fig. 1 to 3. The power generation unit in which the water detection devices 10a and 10b can be installed is not limited to the power generation unit 12 in fig. 2, and can be similarly applied to various power generation units in which liquid water may remain in the reactant gas flow path, as will be described later.

The power generation cells 12 are stacked in plural in the direction of arrows a1 and a2 (horizontal direction) or in the direction of arrows C1 and C2 (gravity direction) in fig. 2, for example, and a fastening load (compression load) is applied in the stacking direction, whereby an unillustrated fuel cell stack can be configured. The fuel cell stack can be mounted on a fuel cell electric vehicle, not shown, or used as a stationary type.

As shown in fig. 2, the power generation cell 12 is configured by stacking the 1 st partition member 14, the resin framed MEA16a, the 2 nd partition member 18, the resin framed MEA16b, and the 3 rd partition member 20 in this order. The 1 st partition member 14, the 2 nd partition member 18, and the 3 rd partition member 20 are each a metal partition member composed of, for example, a steel plate, a stainless steel plate, an aluminum plate, a plated steel plate, or the like. Hereinafter, the 1 st partition member 14, the 2 nd partition member 18, and the 3 rd partition member 20 will be collectively referred to as "partition members" only, unless they are particularly distinguished. The partition member has a rectangular shape when viewed in the direction of arrows a1, a2, and is formed into a cross-sectional concavo-convex shape by press working or the like. Further, the partition member may be a carbon partition member.

The resin framed MEAs 16a, 16b are each configured by joining a resin frame member 24 to the outer periphery of a Membrane Electrode Assembly (MEA) 22. As shown in fig. 3, the membrane electrode assembly 22 has an electrolyte membrane 26, an anode electrode 28 and a cathode electrode 30 sandwiching the electrolyte membrane 26. As the electrolyte membrane 26, for example, a solid polymer electrolyte membrane (cation exchange membrane) such as a thin membrane of perfluorosulfonic acid containing moisture, or an HC (hydrocarbon) based electrolyte membrane can be used.

The cathode electrode 30 has: a cathode electrode catalyst layer 30a joined to the surface of the electrolyte membrane 26 on the arrow a1 side; and a cathode gas diffusion layer 30b laminated on the cathode electrode catalyst layer 30 a. The anode electrode 28 has: an anode electrode catalyst layer 28a joined to the surface of the electrolyte membrane 26 on the arrow a2 side; and an anode gas diffusion layer 28b laminated on the anode electrode catalyst layer 28 a.

The cathode electrode catalyst layer 30a is formed by uniformly applying porous carbon particles having a platinum alloy supported on the surface thereof to the surface of the cathode gas diffusion layer 30b together with an ion-conductive polymer binder, for example. The anode electrode catalyst layer 28a is formed by uniformly applying porous carbon particles having a platinum alloy supported on the surface thereof to the surface of the anode gas diffusion layer 28b together with an ion-conductive polymer binder, for example.

The cathode gas diffusion layer 30b and the anode gas diffusion layer 28b are formed of an electrically conductive porous sheet such as carbon paper or carbon cloth. The resin frame member 24 of fig. 2 is formed of a decorative frame-shaped film, and has an inner peripheral edge portion sandwiched between an outer peripheral edge portion of the cathode gas diffusion layer 30b and an outer peripheral edge portion of the anode gas diffusion layer 28b of fig. 3, for example. The electrolyte membrane 26 may be protruded outward without using the resin frame member 24. Further, frame-shaped thin films may be provided on both sides of the electrolyte membrane 26 protruding outward.

As shown in fig. 2, at one end (the end indicated by the arrow B2) in the longitudinal direction of the rectangular power generation cell 12, an oxygen-containing gas supply passage 32a, a coolant supply passage 34a, and a fuel gas discharge passage 36B, which communicate with each other in the stacking direction (the direction indicated by the arrows a1 and a 2), are provided in a row in the vertical direction (the direction indicated by the arrow C). An oxygen-containing gas is supplied as the oxygen-containing gas to the oxygen-containing gas supply passage 32 a. At least one of pure water, ethylene glycol, oil, and the like is supplied as the coolant to the coolant supply passage 34 a. The hydrogen-containing gas is discharged as the fuel gas from, for example, the fuel gas discharge passage 36 b. Hereinafter, the oxidant gas and the fuel gas are also collectively referred to as "reaction gas".

At the other end (the end on the arrow B1 side) in the longitudinal direction of the power generation cell 12, a fuel gas supply passage 36a, a coolant discharge passage 34B, and an oxygen-containing gas discharge passage 32B are provided in the vertical direction (the arrow C direction) so as to communicate with each other in the stacking direction to supply the fuel gas.

Hereinafter, the oxygen-containing gas supply passage 32a, the coolant supply passage 34a, the fuel gas discharge passage 36b, the fuel gas supply passage 36a, the coolant discharge passage 34b, and the oxygen-containing gas discharge passage 32b will be collectively referred to as "passages" only.

An oxygen-containing gas flow field 38 that communicates with the oxygen-containing gas supply passage 32a and the oxygen-containing gas discharge passage 32b in fig. 1 is provided between the 1 st partition member 14 in fig. 2 and the cathode gas diffusion layer 30b of the resin frame-equipped MEA16 a.

A fuel gas flow field 40 is provided between the 2 nd partition member 18 in fig. 2 and the anode gas diffusion layer 28b of the resin framed MEA16a, and the fuel gas flow field 40 communicates with the fuel gas supply passage 36a and the fuel gas discharge passage 36 b. An oxygen-containing gas flow field 38 is provided between the 2 nd partition member 18 in fig. 2 and the cathode gas diffusion layer 30b of the resin framed MEA16b, and the oxygen-containing gas flow field 38 communicates with the oxygen-containing gas supply passage 32a and the oxygen-containing gas discharge passage 32b in fig. 1.

A fuel gas flow field 40 is provided between the 3 rd partition member 20 in fig. 2 and the anode gas diffusion layer 28b of the resin frame-attached MEA16b, and the fuel gas flow field 40 communicates with the fuel gas supply passage 36a and the fuel gas discharge passage 36 b.

The oxidizing gas channel 38 and the fuel gas channel 40 are also collectively referred to as "reactant gas channels" hereinafter. A plurality of corrugated flow grooves 42 (or straight flow grooves) are formed in the partition members in parallel in the directions indicated by the arrows C1 and C2, and reactant gas flow paths are formed in the corrugated flow grooves 42. Each of the corrugated flow grooves 42 extends in a corrugated shape in the directions indicated by arrows B1 and B2.

In the power generation cells 12 adjacent to each other, the surface on the arrow a1 side of the 1 st partition member 14 constituting one power generation cell 12 and the surface on the arrow a2 side of the 3 rd partition member 20 constituting the other power generation cell 12 face each other. A coolant flow field 44 that connects the coolant supply passage 34a and the coolant discharge passage 34b is provided between the 1 st partition member 14 and the 3 rd partition member 20.

Sealing members 46 are provided along the outer peripheral edges of both surfaces of each partition member. The seal member 46 seals the inside and outside of the partition member in the surface direction surrounded by the seal member 46. As shown in fig. 1 and 2, wavy edges (floats) 48 are provided on both ends of the outer peripheral edge portion of each partition member in the short direction (the direction of arrows C1 and C2) and on both sides of the outer peripheral edge portion in the long direction (the direction of arrows B1 and B2), respectively, at positions closer to the center side than the communication holes. The wavy side 48 is set to protrude from the partition member to a height higher than that of the seal member 46. Such a wavy edge 48 can be used, for example, for positioning when stacking the separators or the resin framed MEAs 16a, 16 b.

As shown in fig. 1 and 2, the seal member 50a is provided on the surface of the 1 st partition member 14 on the arrow a2 side and the surface of the 2 nd partition member 18 on the arrow a2 side, respectively, and the seal member 50a integrally surrounds the oxygen-containing gas supply passage 32a, the oxygen-containing gas discharge passage 32b, and the oxygen-containing gas flow field 38 and seals the inside thereof from the outside in the planar direction.

As shown in fig. 2, the sealing member 50b is provided on the surface of the 2 nd partition member 18 on the arrow a1 side and on the surface of the 3 rd partition member 20 on the arrow a1 side, and the sealing member 50b integrally surrounds the fuel gas supply passage 36a, the fuel gas discharge passage 36b, and the fuel gas flow field 40 and seals the inside thereof from the outside in the planar direction.

A seal member 50c is provided on the surface of the 1 st partition member 14 on the arrow a1 side in fig. 2 and on the surface of the 3 rd partition member 20 on the arrow a2 side, not shown, and the seal member 50c integrally surrounds the coolant supply passage 34a, the coolant discharge passage 34b, and the coolant flow field 44 and seals the inside thereof from the outside in the planar direction. The sealing members 46, 50a, 50b, and 50c are each formed of an elastic body such as rubber or resin having elasticity.

When a power generating operation is performed by a fuel cell stack in which a plurality of power generating cells 12 configured as described above are stacked, the fuel gas is supplied to the fuel gas supply passage 36a, the oxygen-containing gas is supplied to the oxygen-containing gas supply passage 32a, and the coolant is supplied to the coolant supply passage 34a in fig. 2. The fuel gas supplied to the fuel gas supply passage 36a is introduced into the fuel gas flow field 40 and flows along the anode 28. The oxygen-containing gas supplied to the oxygen-containing gas supply passage 32a is introduced into the oxygen-containing gas flow field 38 and flows along the cathode electrode 30.

In the membrane electrode assembly 22, the fuel gas supplied to the anode electrode 28 and the oxidant gas supplied to the cathode electrode 30 are consumed by an electrochemical reaction (power generation reaction) in the anode electrode catalyst layer 28a and the cathode electrode catalyst layer 30a, and power generation is performed. The surplus fuel gas that is not consumed in the power generation reaction is discharged from the fuel gas discharge passage 36b, and the surplus oxygen-containing gas is discharged from the oxygen-containing gas discharge passage 32 b. On the other hand, the coolant supplied to the coolant supply passage 34a flows through the coolant flow field 44 to cool the mea 22, and then is discharged from the coolant discharge passage 34 b.

In the above-described power generation reaction, protons generated by ionization of hydrogen in the fuel gas, electrons after energization to an external load, and oxygen in the oxidant gas are combined with each other, thereby generating liquid water (generated water).

In order for the electrolyte membrane 26 to exhibit good proton conductivity, the electrolyte membrane 26 needs to be maintained in a wet state or the like, and therefore the reaction gas usually contains water vapor. Liquid water (condensed water) is also produced by the condensation of the water vapor. Liquid water such as the produced water or condensed water may be retained in the reactant gas flow field.

The water detection devices 10a and 10b according to the present embodiment of fig. 1 are provided in the power generation unit 12 to detect the presence or absence of liquid water W in the reactant gas flow field. In the following, unless otherwise specified, "water W" is liquid water. The water detection devices 10a and 10b will be described with reference to fig. 4 to 6.

The water detection devices 10a and 10b detect the presence or absence of water W in the oxidizing gas channel 38 between the 2 nd partition member 18 and the cathode gas diffusion layer 30b of the resin framed MEA16 b. However, the water detection devices 10a and 10b can also detect the presence or absence of water W in the oxygen-containing gas channel 38 between the 1 st partition member 14 and the cathode gas diffusion layer 30b of the resin frame-attached MEA16 a.

The water detection devices 10a and 10b can also detect the presence or absence of water W in each of the fuel gas flow path 40 between the 2 nd partition member 18 and the anode gas diffusion layer 28b of the resin-framed MEA16a and the fuel gas flow path 40 between the 3 rd partition member 20 and the anode gas diffusion layer 28b of the resin-framed MEA16 b.

Fig. 1 illustrates two water detection devices 10a and 10b provided in the oxidizing gas channel 38 between the 2 nd partition member 18 and the cathode gas diffusion layer 30b of fig. 3. However, the number of the water detection devices 10a and 10b provided in the reactant gas flow field is not particularly limited. Further, the water detection device 10a may not be provided and only one or a plurality of water detection devices 10b may be provided, or the water detection device 10b may not be provided and only one or a plurality of water detection devices 10a may be provided.

The water detection devices 10a and 10b each include a pair of electrodes 52, a voltage application unit 54, a current measurement unit 56, and a determination unit 58. As shown in fig. 3 and 4, the pair of electrodes 52 is provided at the tip end portions of the two conductive members 60. Each conductive member 60 is, for example, a substantially cylindrical shape formed of a metal wire or the like, and the outer periphery except for the tip end portion thereof is covered with a substantially cylindrical insulating coating 62.

The insulating coating 62 is made of an insulating material capable of electrically insulating a portion of the conductive member 60 other than the tip end portion thereof from the outside of the conductive member 60. An opening 62a is provided at the axial distal end of the insulating film 62. Therefore, the distal end of the conductive member 60 faces the outside of the insulating film 62 through the opening 62a of the insulating film 62. In this way, the electrode 52 is constituted by the distal end portion of the conductive member 60 facing the outside of the insulating coating 62. Further, the conductive member 60 and the insulating coating 62 may be in a band shape (film shape).

In the present embodiment, the axial length (length in the extending direction) of the distal end side of the insulating coating 62 is set to be slightly longer than the axial length (length in the extending direction) of the distal end side of the conductive member 60. Therefore, the distal end portion of the conductive member 60 constituting the electrode 52 faces the outside of the insulating coating 62 through the opening 62a at a position slightly recessed from the distal end of the insulating coating 62 toward the proximal end side. Therefore, as shown in fig. 3, the water W enters the inside of the insulating coating 62 from the opening 62a at the tip end of the insulating coating 62, so that the electrode 52 and the water W can come into contact. In this case, for example, since the electrode 52 is disposed inside the insulating coating 62, it is possible to suppress contact between the components (components other than the water W) of the power generation unit 12 and the electrode 52. As a result, the accuracy of detection of the water W by the electrode 52 can be improved.

As shown in fig. 1 and 4, the pair of electrodes 52 are provided at positions facing the oxidant gas channel 38 (reactant gas channel) apart from each other. As in the present embodiment, when the reaction gas flow paths are formed in each of the plurality of corrugated flow grooves 42, the pair of electrodes 52 are disposed in the same corrugated flow groove 42 at intervals in the extending direction of the corrugated flow groove 42.

As shown in fig. 1, the pair of electrodes 52 is preferably disposed in a downstream region of the oxygen-containing gas flow field 38 where the generated water is likely to accumulate (on the side of the oxygen-containing gas flow field 38 closer to the oxygen-containing gas discharge passage 32 b). However, the pair of electrodes 52 is not particularly limited to this, and may be disposed in an upstream region of the oxygen-containing gas flow field 38 (on the side of the oxygen-containing gas flow field 38 closer to the oxygen-containing gas supply passage 32 a) or between the upstream region and the downstream region.

The conductive member 60 (hereinafter also referred to as a wiring portion 63) covered with the insulating coating 62 is disposed between the 2 nd partition member 18 of the power generation cell 12 and the resin framed MEA16 b. In the water detection device 10a according to the present embodiment, the two wiring portions 63 are inserted from the outside of the power generation cell 12 to between the 2 nd partition member 18 and the resin framed MEA16b via one long side of the power generation cell 12.

In the water detection device 10b according to the present embodiment, one of the two wiring portions 63 is inserted from the outside of the power generation cell 12 to between the 2 nd partition member 18 and the resin framed MEA16b via the long side of the power generation cell 12 on the side of the arrow C1. The other of the two wiring portions 63 is inserted from the outside of the power generation cell 12 through the long side of the power generation cell 12 on the arrow C2 side between the 2 nd partition member 18 and the resin framed MEA16 b.

The water detection device 10a and the water detection device 10b are configured substantially similarly, except that the insertion direction of the wiring portion 63 with respect to the power generation unit 12 is different as described above. The two wiring portions 63 may be inserted between the 2 nd partition member 18 and the resin framed MEA16b from any direction. Each wiring portion 63 may be fixed in position by being bonded to at least one of the 2 nd partition member 18 and the resin framed MEA16b with an adhesive not shown.

As described above, in the fuel cell stack, a fastening load is applied in the stacking direction. Therefore, as shown in fig. 3, the power generation cell 12 in which the wiring portion 63 is inserted between the 2 nd partition member 18 and the resin framed MEA16b is bent by an amount corresponding to the thickness of the wiring portion 63. As a result, the 2 nd partition member 18 and the resin framed MEA16b are in contact with each other in the stacking direction at locations where the wiring portions 63 are not disposed.

As shown in fig. 1, the end of the wiring portion 63 opposite to the electrode 52 is exposed from the power generation cell 12. That is, the wiring portion 63 is disposed so as to cross the outer peripheral edge of the power generation unit 12. In the case where the wiring portion 63 is disposed on the sealing member 46 provided on the outer peripheral edge portion of the partition member so as to intersect the extending direction of the sealing member 46, an adhesive agent, not shown, is preferably provided between the wiring portion 63 and the sealing member 46. Thus, even if the wiring portion 63 is inserted into the power generation cell 12, the inside and outside of the outer peripheral edge portion of the power generation cell 12 can be maintained in a well sealed state.

When the wiring portion 63 crosses the portion of the partition member where the wavy side 48 is provided, it is preferable to form a notch portion 48a in the wavy side 48 as shown in fig. 5. The notch 48a is formed by cutting out a part of the wavy side 48 in the protruding direction in the direction in which the wiring portion 63 crosses. A part of the wiring portion 63 is housed inside the notch portion 48 a. In the present embodiment, two notches 48a are formed in the wavy side 48 corresponding to the two wiring portions 63. The wiring portion 63 is accommodated in each of the two notches 48 a. Further, the adhesive 64 is preferably filled between the inner wall of the notch portion 48a and the wiring portion 63. By providing the notch 48a and the adhesive 64 in this manner, the inside and outside of the outer peripheral edge of the power generation unit 12 can be maintained in a well-sealed state.

Further, a short circuit may occur between the pair of electrodes 52. As an example of the reason, an exposed portion exposed from the insulating film 62 is generated in the conductive member 60 in the wiring portion 63, and the exposed portion is in contact with the partition member, the membrane electrode assembly 22, and the like.

As described above, the wiring portion 63 is inserted between the 2 nd partition member 18 and the resin framed MEA16 b. At this time, the wiring portion 63 abuts the cathode gas diffusion layer 30b of the resin framed MEA16 b. The cathode gas diffusion layer 30b is formed of a structure having fibers such as carbon paper. Therefore, the fibers of the cathode gas diffusion layer 30b come into contact with the insulating coating 62 of the wiring portion 63, so that the insulating coating 62 may be damaged, and the insulating coating 62 may peel off from the conductive member 60 to produce an exposed portion.

The electrolyte membrane 26 expands when its water content increases, and contracts when its water content decreases. When the electrolyte membrane 26 repeats expansion and contraction in accordance with the power generating operation of the fuel cell stack, a load is also repeatedly applied to the wiring portion 63 interposed between the 2 nd partition member 18 and the resin framed MEA16 b. This may cause the insulating coating 62 to peel off from the conductive member 60, thereby generating an exposed portion.

As shown in fig. 1, the voltage application unit 54 and the current measurement unit 56 are electrically connected to the end of the wiring unit 63 disposed outside the power generation cell 12 via a connection terminal 66. The voltage applying unit 54 is configured by a power supply or the like capable of applying a voltage to the pair of electrodes 52. The voltage applying unit 54 can apply a voltage to the pair of electrodes 52, which varies within an application range including the 1 st voltage smaller than the electrolysis voltage of the water W and the 2 nd voltage larger than the electrolysis voltage of the water W.

As shown in fig. 4, the electrolysis voltage of the water W is a voltage at which electrolysis actually occurs in the water W between the pair of electrodes 52 in the reactant gas flow field. The electrolytic voltage of the water W can be obtained in advance by an experiment or the like, and is not particularly limited, and may be set, for example, in a range of 1.23 to 1.5V. Further, 1.23V is a theoretical value of the electrolytic voltage of water W, and 1.5V is a value in consideration of the influence of ions contained in water W and overvoltage. Therefore, for example, the 1 st voltage is preferably a voltage less than 1.23V, and the 2 nd voltage is preferably a voltage greater than 1.5V. In the present embodiment, the 1 st voltage is set to 0.5V and the 2 nd voltage is set to 2.0V, but the present invention is not particularly limited thereto.

The voltage applying section 54 may apply, for example, step voltages of 0V, 0.1V, 0.2V, 0.3V, 0.4V, 0.5V, 1.0V, 1.5V, 2.0V, 3.0V, 4.0V as voltages varying within an application range.

The voltage applying unit 54 may be capable of applying the 1 st selection voltage and the 2 nd selection voltage to the pair of electrodes 52. The 1 st selected voltage is a plurality of voltages selected from a1 st voltage range smaller than the electrolysis voltage of the water W. The 1 st voltage is included in the 1 st select voltage. The 2 nd selection voltage is a plurality of voltages selected from a2 nd voltage range larger than the electrolysis voltage of the water W. The 2 nd voltage is included in the 2 nd selection voltage.

For example, when the electrolysis voltage of the water W is set to 1.5V and the above-described step voltage is applied by the voltage applying unit 54, the 1 st selection voltage may be at least two selected from 0.1V, 0.2V, 0.3V, 0.4V, 0.5V, and 1.0V. Further, in this case, the 2 nd selection voltage may be at least two selected from 2.0V, 3.0V, 4.0V.

The voltage applying unit 54 may apply a detection voltage larger than the electrolysis voltage of the water W to the pair of electrodes 52. The detection voltage is preferably 2.0V, for example. The voltage values of the detection voltage and the 2 nd voltage may be the same.

The current measuring unit 56 is configured by an ammeter or the like capable of detecting a current between the electrodes 52 and measuring a current value when a current is passed between the pair of electrodes 52 to which a voltage is applied by the voltage applying unit 54.

The determination unit 58 is configured as a computer having a CPU, a memory, and the like, which are not shown. The determination unit 58 receives a signal from the current measurement unit 56, and determines the presence or absence of water W in the reactant gas flow path based on the measurement result of the current measurement unit 56.

Here, when there is water W between the pair of electrodes 52, as shown by a solid line L1 in fig. 6, an exponential function relationship is established at least in part between the voltage applied to the pair of electrodes 52 (applied voltage) and the current flowing between the pair of electrodes 52 (current between the electrodes 52). In this case, the current changes in different manners between the electrodes 52 before and after the voltage exceeding the electrolysis voltage of the water W is applied. That is, by increasing the applied voltage, the proportion of the increase in the current between the electrodes 52 after the applied voltage reaches the electrolysis voltage of the water W is larger than that before it reaches the electrolysis voltage of the water W.

On the other hand, when a short circuit occurs between the pair of electrodes 52, a relationship of a proportional function is established between the applied voltage and the current between the electrodes 52 according to ohm's law. When the electrodes 52 are short-circuited, the resistance between the electrodes 52 decreases, and the current between the electrodes 52 increases accordingly. In the present embodiment, as shown by a broken line L2 in fig. 6, when the pair of electrodes 52 is short-circuited, the current between the electrodes 52 exceeds the measurement limit of the current measuring unit 56 when the 1 st voltage and the 2 nd voltage are applied. In other words, the measurement limit of the current measuring section 56 is set to be smaller than the current flowing between the pair of electrodes 52 to which the 1 st voltage and the 2 nd voltage are applied when the pair of electrodes 52 are short-circuited.

Hereinafter, the current measured by the current measuring unit 56 when the 1 st voltage is applied to the pair of electrodes 52 by the voltage applying unit 54 will also be referred to as the 1 st current. The current measured by the current measuring unit 56 when the voltage applying unit 54 applies the 2 nd voltage to the pair of electrodes 52 is also referred to as the 2 nd current. That is, when the pair of electrodes 52 is short-circuited, the 1 st current and the 2 nd current are the measurement limits of the current measuring section 56.

Thus, when a short circuit occurs between the electrodes 52, the relationship of the exponential function between the applied voltage and the current between the electrodes 52 does not hold. In this case, the manner of change in the current between the electrodes 52 is not particularly changed before and after the voltage exceeding the electrolysis voltage of the water W is applied. Therefore, the ratio of the increase in the current between the electrodes 52 by increasing the applied voltage does not particularly change before the applied voltage reaches the electrolysis voltage of the water W and after the applied voltage reaches the electrolysis voltage of the water W.

Therefore, the determination unit 58 determines the presence or absence of water W based on the change in the current measured by the current measurement unit 56 when the voltage applied to the pair of electrodes 52 is changed within the application range. Specifically, as shown by the one-dot chain line L3 in fig. 6, when the current between the electrodes 52 is not detected by the current measuring unit 56, the determination unit 58 determines that no water W is present between the pair of electrodes 52 in the reactant gas flow path and that no short circuit between the electrodes 52 has occurred.

As described above, when the measurement limit of the current measuring unit 56 is set to be smaller than the current between the electrodes 52 at the time of short circuit, and the 2 nd current is larger than the 1 st current, the determining unit 58 may determine that water W is present between the pair of electrodes 52 in the reactant gas flow path. On the other hand, the determination unit 58 may determine that the pair of electrodes 52 is short-circuited when both the 1 st current and the 2 nd current reach the measurement limit of the current measurement unit 56.

In addition, when the voltage applied to the pair of electrodes 52 within the application range and at least a part of the current measured by the current measuring unit 56 are in an exponential function relationship as shown by a solid line L1 in fig. 6, the determining unit 58 may determine that water W is present between the pair of electrodes 52 in the reactant gas flow path. On the other hand, the determination unit 58 may determine that a short circuit occurs in the pair of electrodes 52 when the voltage applied to the pair of electrodes 52 in the application range and the current measured by the current measurement unit 56 are not in an exponential function relationship as shown by a broken line L2 in fig. 6.

As described above, when the 1 st selection voltage and the 2 nd selection voltage are applied to the pair of electrodes 52 by the voltage applying unit 54, the determining unit 58 may compare the 1 st ratio and the 2 nd ratio. The 1 st ratio is a ratio at which a current flowing between the pair of electrodes 52 changes when the 1 st selection voltage is applied. The 2 nd ratio is a ratio at which a current flowing between the pair of electrodes 52 changes when the 2 nd selection voltage is applied.

In the case where water W is present between the pair of electrodes 52, the 2 nd ratio is larger than the 1 st ratio. Therefore, when the 2 nd ratio is larger than the 1 st ratio, the determination unit 58 may determine that water W is present between the pair of electrodes 52.

On the other hand, when a proportional function relationship between the applied current and the current between the electrodes 52 is established, or when the current between the electrodes 52 is constant within the measurement limit of the current measuring unit 56, the 1 st ratio and the 2 nd ratio have the same magnitude. Therefore, when the 2 nd ratio is not more than the 1 st ratio, the determination section 58 can determine that a short circuit occurs between the pair of electrodes 52.

The determination unit 58 may perform the determination of the presence or absence of water W as described above under the following conditions. That is, the voltage applying unit 54 applies the detection voltage before applying the voltage varying within the application range to the pair of electrodes 52. When the current measuring unit 56 detects the detection current flowing between the pair of electrodes 52 when the detection voltage is applied, the voltage applying unit 54 applies a voltage varying within the application range to the pair of electrodes 52 instead of the detection voltage. The determination unit 58 determines the presence or absence of water W in the reactant gas flow path based on the change in the current measured by the current measurement unit 56.

Next, referring to fig. 7 together, the water detection method according to the present embodiment will be described by taking as an example a case where each step of the water detection method according to the present embodiment is performed using the water detection device 10a described above. In the water detection method, a detection voltage application step of applying a detection voltage to the pair of electrodes 52 by the voltage application unit 54 is performed (step S1 in fig. 7). Next, the process proceeds to step S2, and the determination unit 58 determines whether or not the current measurement unit 56 has detected the detection current.

When it is determined in step S2 that the detection current is not detected (no in step S2), the determination unit 58 determines that no water W is present between the pair of electrodes 52 in the reactant gas flow field and that no short circuit occurs between the electrodes 52. Then, the process of step S2 is repeated until the detection current is detected.

When it is determined in step S2 that the detection current is detected (yes in step S2 of fig. 7), the determination unit 58 performs the determination voltage application step of step S3. In the determination voltage application step, a voltage varying within an application range is applied to the pair of electrodes 52 by the voltage application unit 54.

Subsequently, the determination step of step S4 is performed. In the determination step, as described above, the presence or absence of water W in the reactant gas flow path is determined based on the change in the current measured by the current measurement unit 56. After the process of step S4, the flow according to the present embodiment ends.

As described above, in the water detection devices 10a and 10b and the water detection method according to the present embodiment, when a voltage varying within an application range is applied to the pair of electrodes 52, the presence or absence of water W is determined based on a change in current measured by the current measurement unit 56. This can prevent erroneous detection of a short circuit or the like of the electrodes 52 as the presence of the water W between the electrodes 52. As a result, the detection accuracy of the water W in the reactant gas flow field can be improved.

In the water detection devices 10a and 10b according to the above-described embodiments, the determination unit 58 may determine that water W is present between the pair of electrodes 52 when the measurement limit of the current measurement unit 56 is set to be smaller than the current flowing between the pair of electrodes 52 to which the 1 st voltage and the 2 nd voltage are applied when the pair of electrodes 52 are short-circuited, and when the 2 nd current measured by the current measurement unit 56 when the 2 nd voltage is applied to the pair of electrodes 52 is larger than the 1 st current measured by the current measurement unit 56 when the 1 st voltage is applied to the pair of electrodes 52.

In the water detection method according to the above embodiment, the measurement limit of the current measurement unit 56 is set to be smaller than the current flowing between the pair of electrodes 52 to which the 1 st voltage and the 2 nd voltage are applied when the pair of electrodes 52 are short-circuited, and in the determination step, when the 2 nd current measured by the current measurement unit 56 when the 2 nd voltage is applied to the pair of electrodes 52 is larger than the 1 st current measured by the current measurement unit 56 when the 1 st voltage is applied to the pair of electrodes 52, it can be determined that water W is present between the pair of electrodes 52.

In these cases, the presence or absence of water W in the reactant gas flow field can be easily and efficiently determined by comparing the 1 st current with the 2 nd current and confirming whether or not the 2 nd current is larger than the 1 st current.

In the water detection devices 10a and 10b according to the above-described embodiments, the determination unit 58 may determine that water W is present between the pair of electrodes 52 when the voltage applied to the pair of electrodes 52 within the application range and at least a part of the current measured by the current measurement unit 56 are in an exponential function relationship. In the determination step of the water detection method according to the above embodiment, it may be determined that water W is present between the pair of electrodes 52 when at least a part of the current measured by the current measurement unit 56 and the voltage within the application range applied to the pair of electrodes 52 are in an exponential relationship.

In these cases, the presence or absence of water W in the reactant gas flow field can be determined with high accuracy by checking whether or not the voltage in the applied range and at least a part of the current measured by the current measuring unit 56 are in an exponential function relationship. Further, the voltage within the applied range and the current measured by the current measuring unit 56 may be in an exponential function relationship as a whole.

In the water detection devices 10a and 10b according to the above-described embodiments, the voltage applying unit 54 may apply a plurality of voltages (1 st selection voltage) selected from a1 st voltage range smaller than the electrolysis voltage of the water W and a plurality of voltages (2 nd selection voltage) selected from a2 nd voltage range larger than the electrolysis voltage of the water W to the pair of electrodes 52, and the determination unit 58 may compare a1 st ratio at which the current flowing between the pair of electrodes 52 changes when the 1 st selection voltage is applied and a2 nd ratio at which the current flowing between the pair of electrodes 52 changes when the 2 nd selection voltage is applied, and determine that the water W is present between the pair of electrodes 52 when the 2 nd ratio is larger than the 1 st ratio.

In the determination voltage applying step of the water detection method according to the above embodiment, a plurality of voltages (1 st selection voltage) selected from a1 st voltage range smaller than the electrolysis voltage of the water W and a plurality of voltages (2 nd selection voltage) selected from a2 nd voltage range larger than the electrolysis voltage of the water W are applied to the pair of electrodes 52, and in the determination step, a1 st ratio at which the current flowing between the pair of electrodes 52 changes when the 1 st selection voltage is applied and a2 nd ratio at which the current flowing between the pair of electrodes 52 changes when the 2 nd selection voltage is applied are compared, and when the 2 nd ratio is larger than the 1 st ratio, it is determined that the water W is present between the pair of electrodes 52.

In these cases, whether or not the 2 nd ratio is larger than the 1 st ratio can be confirmed by comparing the 1 st ratio and the 2 nd ratio, and the presence or absence of water W in the reactant gas flow field can be easily and accurately determined.

In the water detection devices 10a and 10b according to the above embodiments, the voltage application unit 54 can apply a detection voltage larger than the electrolytic voltage of the water W to the pair of electrodes 52, the current measurement unit 56 can detect a detection current flowing between the pair of electrodes 52 when the detection voltage is applied, and when the detection current is detected by the current measurement unit 56, the voltage application unit 54 changes the voltage applied to the pair of electrodes 52 within the application range, and the determination unit 58 determines the presence or absence of the water W.

In the water detection method according to the above embodiment, the detection voltage application step of applying a detection voltage larger than the electrolytic voltage of the water W to the pair of electrodes 52 is provided before the determination voltage application step, and the determination voltage application step and the determination step are performed when a detection current flowing between the pair of electrodes 52 is detected when the detection voltage is applied.

In these cases, only when current is passed between the pair of electrodes 52, it is sufficient to determine whether the current is caused by the water W interposed between the electrodes 52 or by a short circuit between the electrodes 52. Therefore, the presence or absence of water W in the reaction gas flow path can be detected easily and efficiently.

In the water detection devices 10a and 10b according to the present embodiment, the application of the detection voltage by the voltage application unit 54 is not an essential component. In the water detection method according to the present embodiment, it is not essential to perform the detection voltage application step before the determination voltage application step.

The present invention is not limited to the above-described embodiments, and various changes can be made without departing from the scope of the present invention.

For example, as in the water detection device 70 according to the modification of fig. 8 and 10, an electrode 72 shown in fig. 8 and 10 may be provided instead of the electrode 52 shown in fig. 1, 3, and 4. The electrode 72 of fig. 8 and 10 is integrally assembled to the 2 nd partition member 76 of the electricity generating cell 74 shown in fig. 9. The 2 nd partition member 76 in fig. 9 may be used as a member constituting the power generation cell 74 instead of the 2 nd partition member 18 in fig. 2 only in performance tests of the fuel cell stack and the like. The No. 2 partition member 76 of fig. 9 may be used as a member constituting the power generation unit 74 in actual use of the fuel cell stack.

As shown in fig. 10, the 2 nd partition member 76 has an anode-side plate 78, a cathode-side plate 80, and an intermediate plate 82 sandwiched between the anode-side plate 78 and the cathode-side plate 80. Silver paste 84 is provided between the anode-side plate 78 and the intermediate plate 82, and between the intermediate plate 82 and the cathode-side plate 80, respectively. The anode side plate 78, the intermediate plate 82, and the cathode side plate 80 are integrally bonded by the silver paste 84. The anode-side plate 78 and the cathode-side plate 80 may be composed of the same material as the 2 nd partition member 18 of fig. 2. The intermediate plate 82 may be made of a conductive material such as metal.

The fuel gas flow field 40 is provided on the surface of the anode-side plate 78 on the arrow a1 side, similarly to the surface of the 2 nd partition member 18 on the arrow a1 side in fig. 2. The surface of the cathode-side plate 80 on the arrow a2 side is provided with the oxygen-containing gas flow field 38 in the same manner as the surface of the 2 nd partition member 18 on the arrow a2 side in fig. 2.

As shown in fig. 8 and 10, a plurality of sets of the pair of electrodes 72 that are provided separately from each other are provided on the anode side plate 78 at positions facing the fuel gas flow field 40. A plurality of sets of the pair of electrodes 72, which are provided separately from each other, are provided on the cathode-side plate 80 at positions facing the oxidizing gas flow field 38. Each electrode 72 faces the reactant gas flow field through a through hole 86 that penetrates the anode-side plate 78 and the cathode-side plate 80 in the thickness direction (the direction of arrows a1 and a 2). The number (number of groups) and arrangement of the electrodes 72 are not particularly limited. The electrode 72 may be provided only in one of the fuel gas channel 40 and the oxygen-containing gas channel 38.

A conductive member 88a and a conductive member 88b are disposed in the intermediate plate 82, wherein the conductive member 88a is connected to the electrode 72 facing the oxidant gas channel 38; the conductive member 88b is connected to the electrode 72 facing the fuel gas flow path 40. The voltage applying unit 54 and the current measuring unit 56 of fig. 1 provided outside the power generating unit 74 and the pair of electrodes 72 are electrically connected via a conductive material. These conductive members 88a, 88b are wired such that each of the sets of electrodes 72 can be individually electrically conductive. Accordingly, it is possible to know at which portion of the fuel gas channel 40 and the oxygen-containing gas channel 38 the liquid water W is present.

In the water detection device 70 having the electrodes 72 configured as described above, the presence or absence of water W between the electrodes 72 in the reactant gas flow paths can be detected in the same manner as in the water detection devices 10a and 10b of fig. 1, and the same operational effects as in the water detection devices 10a and 10b of fig. 1 can be obtained. That is, when a voltage varying within the application range is applied to the pair of electrodes 72, the presence or absence of the liquid water W is determined based on the variation in the current measured by the current measuring unit 56.

This prevents erroneous detection of a short circuit or the like of the electrodes 72 as the presence of the liquid water W between the electrodes 72. As a result, the detection accuracy of the liquid water W in the reactant gas flow field can be improved.