JP4973060B2 - Humidity determination device for fuel cell - Google Patents

Description

  The present invention relates to an apparatus for determining a humidified state of a fuel cell from a change in voltage of a single cell unit constituting the fuel cell.

  As a method for determining the humidified state of the fuel cell, the technique of Patent Document 1 is disclosed. That is, the voltage of the single cells constituting the fuel cell is measured, and when the voltage falls below a predetermined value, the stack position of the single cells where the voltage drop has occurred is determined, and the stack position is near the edge of the stack. For example, it is determined that the humidified state of the stack is excessively humidified, and if it is near the center, it is determined that humidification is insufficient.

Furthermore, the voltage is memorized over time when the voltage of the single cell becomes a predetermined value or less, and it is judged that humidification is insufficient when the voltage is decreasing with time. The technology of judging that it is excessive is disclosed.
JP 2002-184438 A

  However, even if the stack position of the single cell is in the central part, the voltage drop of the single cell may occur due to excessive humidification, and even if the stack position is near the end, the humidification is insufficient. A voltage drop may occur. Therefore, the technique of Patent Document 1 cannot accurately determine the humidified state of the fuel cell.

  In addition, since the voltage changes with time during operation of the fuel cell, the technique of Patent Document 1 has a problem that it takes time to determine the humidified state, and the electrolyte membrane constituting the single cell is broken due to insufficient error. .

  The present invention relates to a humidifying state determination device for a fuel cell, comprising a voltage measuring means for measuring a voltage of a single cell unit constituting the fuel cell, and a control unit, and the control unit is a single cell having a predetermined voltage or less. When the unit is present, a humidification state determination unit is provided that determines the humidification state of the fuel cell from the voltage of the unit cell unit in the vicinity of the unit cell unit.

  According to the present invention, the humidified state of the fuel cell can be accurately and quickly determined with a simple configuration.

  Embodiments of the present invention will be described below with reference to the drawings. In the description of the drawings, the same or similar parts are denoted by the same or similar reference numerals.

(First embodiment)
With reference to FIG. 1, a humidified state determination device for a fuel cell according to a first embodiment of the present invention will be described.

  FIG. 1 shows an overall configuration of a fuel cell system including a humidification state determination device for a fuel cell according to the first embodiment.

  The fuel cell system according to the first embodiment includes a fuel cell 1 that generates power by a reaction between a fuel gas containing hydrogen and an oxidant gas containing oxygen, a fuel gas supply device 2 that supplies the fuel gas, and an oxidant gas. Controlling the operation of each member constituting the fuel cell system, the oxidant gas supply device 3 for supplying air (for example, air), the cooling water circulation unit 11 for circulating the cooling water, the voltage measuring device (voltage sensor) 22 A control unit (control unit) 20 for controlling the power generation of the fuel cell 1 is provided.

  The fuel gas supply device 2 may be, for example, a storage tank that stores a fuel gas containing hydrogen at a high pressure. The oxidant gas supply device 3 may be a compressor that supplies air, for example.

  The fuel gas inlet of the fuel cell 1 and the fuel gas supply device 2 are connected by a fuel gas supply pipe 4, and the oxidant gas inlet of the fuel cell 1 and the oxidant gas supply device 3 are connected by an oxidant gas supply pipe 5. The Further, anode exhaust gas is discharged from the fuel gas discharge pipe 6 connected to the fuel gas outlet of the fuel cell 1, and cathode exhaust gas is discharged from the oxidant gas discharge pipe 7 connected to the oxidant gas outlet of the fuel cell 1. .

  A fuel gas pressure adjustment valve 8 is disposed in the fuel gas pipe 4 to adjust the pressure of the fuel gas supplied to the fuel cell 1. A purge valve 9 is disposed in the fuel gas discharge pipe 6. Although the purge valve 9 is normally closed, when the fuel cell 1 generates power at a constant power or for a certain time, the purge valve 9 is opened and water and nitrogen gas are discharged together with the fuel gas. An oxidant gas pressure adjusting valve 10 is disposed in the oxidant gas discharge pipe 7 to adjust the pressure of the oxidant gas.

  The cooling water circulation unit 11 includes a cooling water supply pipe 13 connected to a cooling water inlet / outlet of the fuel cell 1 and a circulation pump 12 that is disposed in the cooling water supply pipe 13 and circulates the cooling water.

  The control unit 20 includes a humidified state determination unit 21 that determines the humidified state of the fuel cell 1.

  The fuel cell 1 has a structure in which a plurality of unit cell units 30 each composed of a single cell are stacked as shown in FIG.

  That is, the fuel cell 1 includes all the unit cell units 30 (1) to 30 (n) constituting the fuel cell 1, and the voltages V (a 1) to V (V) at the end a of each unit cell unit 30. voltage sensor 22 (b1) -22 (an) which detects voltage sensor 22 (a1) -22 (an) which detects an), and voltage V (b1) -V (bn) of the edge part b of each cell unit 30 bn) are provided (FIG. 2). Here, the value of the constant n corresponds to the number of stacked battery cell units, and for example, n = 100 in the present embodiment.

  The voltage sensor 22 is desirably installed at a portion where the unit cell unit 30 is likely to be excessively humidified or insufficiently humidified, and is preferably disposed at the outlet of the oxidant gas or the fuel gas as a measurement portion. This is because, for example, since the humidity generally increases from the inlet to the outlet due to the generation of water accompanying power generation on the oxidant gas side, there is a high possibility of excessive humidification on the outlet side. Further, on the fuel gas side, the relative humidity increases from the inlet to the outlet due to consumption of the fuel gas, and water is diffused from the oxidant gas to the fuel gas side, so that excessive humidification occurs on the outlet side. The possibility of falling is increased.

  Therefore, as shown in FIG. 2, if the flows of the fuel gas and the oxidant gas are supplied in opposite directions, the fuel gas outlet (oxidant gas inlet) and the oxidant gas outlet (fuel gas outlet) By installing the voltage sensors 22 on both sides of the inlet), it can be determined whether the oxidant gas side is excessively humidified or the fuel gas side is excessively humidified.

  FIG. 3 is a view showing a cross section A-A ′ of the fuel cell 1 of FIG. 2. The unit cell unit 30 includes a solid electrolyte membrane 31 having proton conductivity, an oxidant electrode layer (cathode) 32, a fuel electrode layer (anode) 33, an oxidant gas separator 34, and a fuel gas separator 35. . The solid electrolyte membrane 31 is sandwiched between the cathode 32 and the anode 33. The oxidant gas separator 34 is disposed on the opposite side of the cathode 32 with respect to the solid electrolyte membrane 31, and the fuel gas separator 35 is disposed on the opposite side of the anode 33 with respect to the solid electrolyte membrane 31.

  The cathode 32 and the anode 33 include an oxidant gas diffusion layer 32a and a fuel gas diffusion layer 33a made of a porous material such as carbon fiber, and a cathode catalyst layer 32b and an anode catalyst layer made of a carbon carrier supporting platinum as a catalyst. 33b.

  The oxidant separator 34 has an oxidant gas flow path 36 on the cathode 32 side, the fuel gas separator 35 has a fuel gas flow path 37 on the anode side, and a cooling water flow path between the adjacent cathode 32 and anode 33. 38 is provided.

  Next, the operation of the fuel cell humidification state determination apparatus according to the first embodiment will be described with reference to the flowchart of FIG.

  (A) First, in S100, the voltages V (a1) to V (an) and V (b1) to V (bn) of the cell units 30 (1) to 30 (n) are measured.

  (B) In S101, there is a unit cell unit 30 that is equal to or lower than a predetermined voltage among the voltages V (a1) to V (an) and V (b1) to V (bn) of the unit cell unit 30 measured in S100. To detect. When unit cell unit 30 (first unit cell unit) having a predetermined voltage or less is present (YES in S101), the process proceeds to S102. If there is a single cell unit 30 that is equal to or lower than the predetermined voltage (NO in S101), the process returns to S100 and the operation is continued. Note that the “predetermined voltage” is a part of the condition for determining whether humidification is insufficient or excessive, but is a parameter that varies depending on the mode of implementation of the present invention, so it is difficult to clearly specify the setting range.

  (C) In S102, the voltage of the unit cell unit (second unit cell unit) in the vicinity of the unit cell unit whose voltage is equal to or lower than the predetermined voltage is compared with the insufficient humidification determination voltage. When the voltage of the second unit cell unit is equal to or lower than the humidification shortage determination voltage (YES in S102), humidification state determination unit 21 determines that fuel cell 1 is insufficiently humidified (S103), and proceeds to S104. 20 increases the flow rate of the cooling water. On the other hand, when the voltage of the second unit cell unit is larger than the humidification deficiency determination voltage (NO in S102), the process proceeds to S105. “Near” is a concept that includes not only a single battery unit adjacent to the first single battery unit but also a single battery unit that is separated from the first single battery unit by a plurality. That is, the second single battery unit in the vicinity of the first single battery unit includes a plurality of single battery units. However, it is not necessary for all of the plurality of unit cell units to satisfy the above condition (S102), and it is sufficient that at least any one unit cell unit is satisfied.

  (D) In S105, the voltage of the second unit cell unit is compared with the humidification excess determination voltage. When the voltage of the second unit cell unit is equal to or higher than the excessive humidification determination voltage (YES in S105), humidification state determination unit 21 determines that fuel cell 1 is excessively humidified (S106), and proceeds to S107. 20 reduces the flow rate of the cooling water. On the other hand, when the voltage of the second unit cell unit is smaller than the humidification excess determination voltage (NO in S105), the process returns to S100 and the operation is continued.

  In S104, when the voltage of the second unit cell unit is equal to or lower than the humidification insufficient determination voltage, it is determined that the fuel cell 1 is insufficiently humidified. The reason will be described below.

  That is, when the unit cell unit 30 is insufficiently humidified, the solid electrolyte membrane is dried, and the resistance of the solid electrolyte membrane is increased. On the other hand, the voltage V of the unit cell unit 30 can be expressed by equation (1), where E is the electromotive force of the unit cell unit 30, I is the current, and R is the resistance of the unit cell unit 30.

V = EI × R (1)
Therefore, the voltage of the unit cell 30 with insufficient humidification decreases as the resistance R increases. Further, heat corresponding to the increase in resistance R is released. Therefore, the voltage decreases due to insufficient humidification, and the temperature rises in the vicinity of the first unit cell unit, so that the second unit cell unit also moves in the drying direction. As a result, the vicinity of the first unit cell unit is also insufficiently humidified, causing a voltage drop in the second unit cell unit.

  Furthermore, in S106, when the voltage of the second unit cell unit is larger than the excessive humidification determination voltage, it is determined that the fuel cell 1 is excessively humidified. The reason will be described below.

  When the unit cell unit 30 becomes excessively humidified, the supply gas flow path is blocked by the condensed water. Accordingly, since the reaction between the fuel gas and the oxidant gas is hindered, power generation does not occur and the voltage is reduced. However, in order for the current to show a constant value regardless of the portion where power is not generated, the current needs to bypass the portion where power is not generated, resulting in a current density distribution. FIG. 5 shows a conceptual diagram thereof. Arrows indicate current flow. For example, even if the cell unit 30 has a current density of 1 (A / cm 2), if a portion 60 is generated that is not excessively humidified and does not generate power, the portion indicated by 61 is 0.6 (A / cm 2), 62 In the portion shown, a distribution occurs in the current density as 1.1 (A / cm 2). On the other hand, the relationship between the current density and voltage of the unit cell unit 30 is generally a performance curve shown in FIG. As shown in FIG. 6, the voltage increases as the current density decreases.

  Therefore, when there is a portion 60 in the first unit cell unit that is not humidified and does not generate power, the portion indicated by 61 in the second unit cell unit has a lower current density and a higher voltage.

  On the other hand, in this embodiment, the insufficient humidification determination voltage and the excessive humidification determination voltage are set as follows. In the fuel cell, the voltage varies due to the distribution variation. For this reason, even when the battery is operating normally, there are single battery units that are lower or higher than the average voltage. Therefore, as shown in FIG. 7, the humidification shortage determination voltage is set to a value lower than the average voltage, and as shown in FIG. 8, the humidification excess determination voltage is set to a value higher than the average voltage.

  From the above, in the first embodiment, the humidification state of the fuel cell can be determined by measuring the voltage of the second unit cell unit, so the determination of the humidification state can be made instantaneously.

  In addition, the predetermined value for determining insufficient humidification of the fuel cell 1 and the predetermined value for determining excessive humidification are set to different values, so that the determination of the humidified state can be performed more accurately even when the voltage varies. it can.

  Furthermore, since the single battery unit 30 consists of a single cell and measures the voltage of all the single cells, the voltage measurement accuracy is good and the humidified state can be accurately determined.

  Further, after determining that the fuel cell 1 is insufficiently humidified in S103, the flow rate of the cooling water is increased in S104, so that the heat accompanying the power generation of the fuel cell is absorbed by the cooling water and the temperature inside the fuel cell is lowered. Therefore, the humidity can be increased, so that the fuel cell 1 can be brought into an appropriate operating state. Similarly, after determining that the fuel cell 1 is excessively humidified in S106, the flow rate of the cooling water is decreased in S107, whereby the fuel cell 1 can be brought into an appropriate operation state.

(Modification of the first embodiment)
In the first embodiment, the single battery unit 30 is a single cell and the voltage is measured for each single cell. However, the single battery unit 30 may be composed of a plurality of single cells 40 as shown in FIG. Thereby, the humidification state determination apparatus of a fuel cell can be simplified.

  In the first embodiment, when it is determined that the fuel cell 1 is insufficiently humidified, (1) the flow rate of the cooling water is increased, but (2) the flow rate of at least one of the fuel gas and the oxidant gas is increased. (3) The pressure of at least one of the fuel gas and the oxidant gas may be increased, or (4) the humidity of at least one of the fuel gas and the oxidant gas may be increased. Alternatively, the operations of (1), (2), (3) and (4) may be combined.

  As an effect as described above, by reducing the flow rate of at least one of the fuel gas and the oxidant gas, moisture taken out from the unit cell unit 30 can be suppressed and the humidified state can be set in the wet direction. By increasing the pressure of at least one of the fuel gas and the oxidant gas, the amount of moisture that can be brought into the stack in the gas whose pressure has been increased increases, so that the humidified state can be set in the wet direction. Naturally, by increasing the humidity of at least one of the fuel gas and the oxidant gas, the water vapor is easily condensed, so that the humidified state can be set in the wet direction. Therefore, the fuel cell can be brought into an appropriate operation state.

  Even when it is determined that the fuel cell 1 is excessively humidified, in the first embodiment, (1) the flow rate of the cooling water is decreased, but (2) the flow rate of at least one of the fuel gas and the oxidant gas. (3) reduce the pressure of at least one of the fuel gas and the oxidant gas, or (4) reduce the humidity of at least one of the fuel gas and the oxidant gas, or (1) The operations of (2), (3) and (4) may be combined. Since the effect is reverse to the operation in the case of insufficient humidification, the description is omitted.

  In the first embodiment, the insufficient humidification determination voltage and the excessive humidification determination voltage are different values, but may be the same value. For example, the voltage of the second unit cell unit is lower than the average voltage when the humidification is insufficient, and is higher than the average voltage when the humidification is excessive. Therefore, the insufficient humidification determination voltage and the excessive humidification determination voltage may be the same value as the average voltage of the unit cell units 30 constituting the fuel cell 1. Since the average voltage can be easily calculated, the humidification state determination device for the fuel cell can be simplified.

(Second Embodiment)
In the first embodiment, in the determination of insufficient humidification (S102 in FIG. 4), the voltage of the second single battery unit is only compared with the insufficient humidification determination voltage. However, in the second embodiment, the second single unit is compared. The change of the battery unit voltage over time is measured to determine whether the humidification is insufficient.

  The configuration of the fuel cell humidified state determination apparatus in the second embodiment is the same as that shown in FIG.

  Next, the operation of the fuel cell humidification state determination apparatus according to the second embodiment will be described with reference to the flowchart of FIG.

  Steps S200 to S202 are the same as steps S100 to S102 in FIG.

  In S203, it is determined whether the voltage of the second unit cell unit has decreased with the passage of time. If it decreases with the passage of time (YES in S203), the process proceeds to S204, and the humidification state determination unit 21 determines that the fuel cell 1 is insufficiently humidified. If it has not decreased with the passage of time (NO in S203), the process returns to S200 and the operation is continued.

  Steps S205 to S208 are the same as steps S104 to S107 in FIG.

  As described above, in the second embodiment, when the unit cell unit 30 is insufficiently humidified, if the operation is continued, the drying proceeds and the voltage continues to decrease. Therefore, it is determined that the humidification is insufficient by observing the change with time of the voltage. I can do it.

(Third embodiment)
In the first embodiment, in the determination of excessive humidification (S105 in FIG. 4), the voltage of the second single battery unit is only compared with the excessive humidification determination voltage. However, in the third embodiment, the second single cell unit is compared. When the voltage of the battery unit exceeds the excessive humidification determination voltage twice or more, the excessive humidification determination is made.

  The configuration of the fuel cell humidification state determination apparatus according to the third embodiment is the same as that shown in FIG.

  Next, the operation of the fuel cell humidification state determination apparatus according to the third embodiment will be described with reference to the flowchart of FIG.

  S300 to S305 are the same as S100 to S105 in FIG.

  In S306, it is determined whether the voltage of the second unit cell unit exceeds the humidification excess determination voltage at least twice. If the humidification excess determination voltage is exceeded twice or more (YES in S306), the process proceeds to S307, and humidification state determination unit 21 determines that fuel cell 1 is excessively humidified. In step S308, the flow rate of the cooling water is decreased. On the other hand, if the humidification excess determination voltage is not exceeded twice or more (NO in S306), the process returns to S300 and the operation is continued.

  As described above, in the third embodiment, when the unit cell unit 30 is excessively humidified, the location of water clogging changes. Therefore, the voltage drops due to the clogging of the gas flow path and the elimination of the clogging at the position where the voltage is measured. And voltage recovery may occur, and the voltage of the second cell unit may rise and return to the normal voltage value accordingly. Can be judged.

  Moreover, in this embodiment, you may combine the operation | movement of the humidification insufficient determination in 2nd Embodiment. Thereby, not only the determination of excessive humidification but also the determination of insufficient humidification can be determined with higher accuracy.

(Fourth embodiment)
In the first embodiment, after the determination of insufficient humidification (S102 in FIG. 4), the operation has been shifted to the operation of eliminating the insufficient humidification. However, in the fourth embodiment, whether the cause of insufficient humidification is the clogging of the cooling water flow path 38. Judgment.

  FIG. 12 shows an overall configuration of a fuel cell system including a humidified state determination device for a fuel cell according to the fourth embodiment. In the fourth embodiment, the control unit 20 further includes a water clogging determination unit 23. The water clogging determination unit 23 determines whether the cause of insufficient humidification of the fuel cell is clogging of the cooling water passage 38.

  Next, the operation of the fuel cell humidification state determination apparatus according to the fourth embodiment will be described with reference to the flowchart of FIG.

  S400 to S403 are the same as S100 to S103 in FIG.

  (Ii) In S404, the control unit 20 increases the ejection pressure of the cooling water circulation pump 12.

  (B) Next, in S405, the voltage of the first unit cell unit is compared with a predetermined voltage. If the voltage remains below the predetermined voltage (YES in S405), the process proceeds to S406, and control unit 20 increases the flow rate of the cooling water. On the other hand, when the voltage is greater than the predetermined voltage (NO in S405), water clogging determination unit 23 determines that the cause of insufficient humidification is clogging of cooling water flow path 38 (S410).

  Steps S407 to S409 are the same as steps S105 to S107 in FIG.

  In S405, when the voltage of the first unit cell unit becomes higher than the predetermined voltage by increasing the jet pressure of the cooling water circulation pump 12, it is determined that the cause of insufficient humidification is clogging of the cooling water flow path 38. The reason will be described below.

  Air or the like clogged in the cooling water passage 38 is forcibly removed by increasing the pressure of the cooling water. Therefore, the heat that could not be dissipated because the cooling water did not flow can be released to the cooling water, so that the temperature of the unit cell unit 30 decreases, the humidity in the fuel cell increases, and the resistance R of the solid electrolyte membrane decreases. This is because the voltage of the unit cell unit 30 rises from the formula (1) because it becomes smaller.

  As mentioned above, in 4th Embodiment, when the voltage of the 1st single cell unit in which the voltage was falling by raising the pressure of cooling water rises, the cause of insufficient humidification is clogging of the cooling water flow path 38. Judgment can be made.

(Modification of the fourth embodiment)
FIG. 14 shows an overall configuration of a fuel cell system including a fuel cell humidification state determination device according to a modification of the fourth embodiment. In the present embodiment, the fuel cell humidification state determination apparatus of FIG. 1 further includes a first valve 40, a second valve 41, a first bypass flow path 42, and a second bypass flow path 43 in the coolant circulation section 11. .

  The first valve 40 is arranged in the cooling water supply pipe 13 between the circulation pump 12 and the fuel cell 1, and the second valve 41 is arranged in the cooling water supply pipe 13 between the circulation pump 12 and the fuel cell 1. .

  The first bypass channel 42 branches from between the circulation pump 12 and the second valve 41 and is connected to the cooling water supply pipe 13 between the first valve 40 and the fuel cell 1. The second bypass flow path 43 branches from between the circulation pump 12 and the first valve 40, and is connected to the cooling water supply pipe 13 between the second valve 41 and the fuel cell 1.

  In the fourth embodiment, the ejection pressure of the cooling water circulation pump 12 is increased in S405, but the circulation direction of the cooling water may be reversed by closing the first valve 40 and the second valve 41. As a result, it is possible to remove foreign matters and the like that cannot be collected by the foreign matter filter or the like and are stuck in the cooling water flow path. Therefore, since the heat that could not be dissipated because the cooling water was not flowing can be released to the cooling water, the temperature of the unit cell unit 30 is lowered, so that the same effect as in the fourth embodiment can be obtained.

(Fifth embodiment)
In 5th Embodiment, the voltage sensor 22 is each arrange | positioned in two or more site | parts (for example, the edge part a and the edge part b of FIG. 2) of each cell unit 30, and a humidification state determination part is measured in each site | part. A method for determining the humidified state of the fuel cell 1 from the voltage distribution of the single cell unit 30 will be described.

  The overall configuration of the fuel cell system including the humidified state determination device for a fuel cell according to the fifth embodiment is the same as that shown in FIG. In addition, as shown in FIG. 2, the voltage V (a1) ˜ at the end a of each unit cell unit 30 is added to each of all the unit cell units 30 (1) ˜30 (n) constituting the fuel cell 1. Voltage sensors 22 (a1) to 22 (an) for detecting V (an), and voltage sensors 22 (b1) to 22 (b1) for detecting voltages V (b1) to V (bn) at the end b of each unit cell unit 30 22 (bn). Since the flow of the fuel gas and the oxidant gas are supplied in opposite directions, the end a and the end b are the part on the inlet side and the part on the outlet side of the oxidant gas of the unit cell unit, It is also the part on the exit side and the part on the inlet side of the fuel gas. Moreover, these end part a and end part b are equivalent to the both-ends part in the longitudinal direction of this unit on the structure of a cell unit.

  Next, the operation of the fuel cell humidification state determination apparatus according to the fifth embodiment will be described with reference to the flowchart of FIG.

  (A) First, in S500, the voltages V (a1) to V (an) and V (b1) to V (bn) of the cell units 30 (1) to 30 (n) are measured.

  (B) In S501, there is a unit cell unit 30 that is equal to or lower than a predetermined voltage among the voltages V (a1) to V (an) and V (b1) to V (bn) of the unit cell unit 30 measured in S500. To detect. When unit cell unit 30 (first unit cell unit) having a predetermined voltage or less exists (YES in S501), the process proceeds to S502. If there is a single cell unit 30 that is equal to or lower than the predetermined voltage (NO in S501), the process returns to S500 and the operation is continued.

  (C) In S502, the voltage of the unit cell unit (second unit cell unit) in the vicinity of the unit cell unit whose voltage is equal to or lower than the predetermined voltage is compared with the insufficient humidification determination voltage. If the voltage of the second cell unit is equal to or lower than the humidification deficiency determination voltage (YES in S502), the process proceeds to S503, and the voltage of the second cell unit is greater than the dampness deficiency determination voltage (NO in S502). , The process proceeds to S506.

  (D) In S503, the voltage at the farthest in-plane portion of the unit cell unit where the voltage is equal to or lower than the predetermined voltage is measured. That is, when the voltage sensor 22 (a) that measures a voltage that is equal to or lower than the predetermined voltage is installed at the end a, the voltage sensor disposed at the end b located at the farthest part in the same unit cell unit surface. 22 (b) is used to measure the farthest in-plane voltage.

  (E) Proceeding to S504, it is determined whether or not the voltage at the farthest portion in the plane is equal to or lower than a predetermined voltage. If the voltage is lower than the predetermined voltage (YES in S504), the process proceeds to S505. If the voltage is not lower than the predetermined voltage (NO in S504), the process proceeds to S509.

  (F) In S505, the voltage at the farthest in-plane portion of the unit cell unit (second unit cell unit) in the vicinity of the unit cell unit whose voltage is equal to or lower than the predetermined voltage is compared with the excessive humidification determination voltage. If the voltage at the farthest in-plane portion of the second cell unit is equal to or higher than the excessive humidification determination voltage (YES in S505), the process proceeds to S507, and the voltage at the farthest in-plane portion of the second cell unit is excessively humidified. If it is less than the determination voltage (NO in S505), the process proceeds to S509.

  (G) In S509, the humidification state determination unit 21 determines that the fuel cell 1 is insufficiently humidified, proceeds to S510, and the control unit 20 increases the flow rate of the cooling water.

  (H) On the other hand, when the voltage of the second unit cell unit is higher than the humidification deficiency determination voltage in S502 (NO in S502), the process proceeds to S506 and the voltage of the second unit cell unit is compared with the humidification excess determination voltage. . When the voltage of the second unit cell unit is equal to or higher than the excessive humidification determination voltage (YES in S506), humidification state determination unit 21 determines that fuel cell 1 is excessively humidified (S507), and proceeds to S508 to control unit 20 reduces the flow rate of the cooling water. On the other hand, when the voltage of the second unit cell unit is smaller than the humidification excess determination voltage (NO in S506), the process returns to S500 and the operation is continued.

  In this way, the voltage of the unit cell unit (second unit cell unit) in the vicinity of the unit cell unit that is equal to or lower than the predetermined voltage is humidified at one part (end part a or end part b) of the unit cell unit 30. The voltage of the second cell unit is lower than the insufficient determination voltage (YES in S502), and the voltage of the second cell unit is higher than the excessive humidification determination voltage in the other part (end b or end a) of the unit cell (S505). In the case of YES), the humidification state determination unit 21 determines that the fuel cell 1 is excessively humidified. That is, even if one part of the unit cell unit 30 exhibits a behavior of insufficient humidification (FIG. 7), if the other part exhibits a behavior of excessive humidification (FIG. 8), excessive humidification occurs. By determining that there is, it is possible to avoid erroneous determination and avoid perforation of the electrolyte membrane and the vehicle falling into a failure.

  In one part (end part a or end part b) of the unit cell unit 30, the voltage of the unit cell unit (second unit cell unit) in the vicinity of the unit cell unit that is equal to or lower than the predetermined voltage is equal to or lower than the insufficient humidification determination voltage. (YES in S502), and if the voltage of the second unit cell unit is equal to or lower than the excessive humidification determination voltage in the other part (end b or end a) of the unit cell unit (NO in S505) ), The humidification state determination unit determines that the fuel cell 1 is insufficiently humidified. In other words, it is a case where one part of the unit cell unit 30 exhibits an insufficiently humidified behavior, and if the other part does not exhibit an excessively humidified behavior, an erroneous determination is made by determining that the humidification is insufficient. Thus, it is possible to avoid the perforation of the electrolyte membrane and the vehicle from falling into a failure.

  By installing voltage sensors at the inlet side portion and the outlet side portion of the oxidant gas, flooding caused by the oxidant gas can be detected.

  By installing voltage sensors at the inlet side portion and the outlet side portion of the fuel gas, flooding caused by the fuel gas can be detected.

  The determination method at the time of excessive humidification in the fifth embodiment will be described in more detail. First, the behavior of the voltage distribution in the stacking direction in the vicinity of the voltage measurement site when the humidification is excessive will be described. As shown in FIG. 5, when an excessively humidified state occurs in a specific cell (single cell unit), the excessively humidified portion 60 of the single cell unit does not generate power. Precisely, excessive humidification may cause gas to not reach or be difficult to reach the power generation surface, and power generation is hindered and voltage drops. Therefore, the load current inside the stack flows so as to avoid the non-power generation and the power generation performance lowering portion 60, but cannot flow avoiding only the non-power generation portion. This is because the current flowing in the plane direction (the -X direction in FIG. 5) flows through the separator, and therefore flows only in the plane direction about several A. Therefore, the current starts to decrease from a cell several cells away from the power generation performance degradation portion 60. Then, although the cell adjacent to the power generation performance degradation portion 60 can generate power, the amount of load current decreases, so the voltage rises from the IV characteristic shown in FIG. Therefore, in the distribution of the voltage measured by the voltage sensor on the excessively humidified portion 60 side, as the voltage of the excessively humidified portion 60 decreases, the voltage of the surrounding cells increases as shown in FIG.

  However, at this time, the current is concentrated on the opposite side in the same cell plane, that is, the farthest in-plane portion of the same cell, because it does not include the excessively humidified portion. Therefore, the current increases and the voltage decreases on the side opposite to the excessively humidified portion 60. The voltage distribution on the opposite side of the excessively humidified portion 60 exhibits a behavior similar to insufficient humidification, as shown in FIG.

  As described above, when the humidification is excessive, the current density is increased and the voltage is decreased at a portion other than the excessive humidification portion (flooding occurrence portion) 60 in the unit cell unit 30 (particularly, the farthest in-plane portion). The voltage distribution similar to that at the time of insufficient humidification shown in FIG. 7 is shown. For this reason, if the humidification state is determined based only on the voltage distribution of the part other than the excessively humidified part 60, it may be erroneously determined that the humidification is insufficient (dry out) although it is actually flooded. .

  In particular, there is a high possibility of misjudgment when a short stack (single cell unit) in the longitudinal direction that is easily affected by the current distribution or severe flooding occurs. The following shows cases where there is a possibility of misjudgment.

  (1) When only one voltage measurement part is provided in the surface of one unit cell unit 30 and the behavior such as insufficient humidification is shown, there is a possibility that the humidification is actually excessive on the opposite surface of the voltage measurement part. is there.

  (2) Although a plurality of voltage measurement parts are attached to the surface of one unit cell unit 30, when each of them is judged independently, it does not have a function of judging by comparing a plurality of parts. This makes a decision that contradicts the situation, resulting in a false decision. Or there is a possibility that the judgment is impossible.

  (3) If the stack is short in the longitudinal direction, that is, if it is short in the Y direction in FIG. 2, the influence of the current distribution is likely to occur in the opposite direction in the plane with respect to the flooding part. The voltage distribution at becomes easy to show the behavior of insufficient humidification.

  (4) In the case of remarkably intense flooding, the area of power generation failure is increased as in (3), so the area through which current flows when the current distribution is applied is reduced, so it is short in the longitudinal direction. Behaves like a stack.

  On the other hand, the determination method at the time of insufficient humidification (dry out) is demonstrated.

  At the time of dryout, the solid electrolyte membrane is dried, the resistance of the solid electrolyte membrane is increased, the unit cell insufficiently humidified causes a voltage drop for the IR loss, and heat for the IR loss is released. Therefore, the temperature around the unit cell unit 30 whose voltage has dropped due to insufficient humidification rises, and the unit cell unit 30 around the unit also moves in the drying direction. Therefore, the surrounding single cell unit 30 is also insufficiently humidified, causing a voltage drop. For this reason, not only the humidified portion but also the voltage in the vicinity is lowered. Therefore, it does not show a behavior in which the voltage of the nearby unit cell unit 30 is increased as in the case of excessive humidification. Further, the potential distribution in the stacking direction of other voltage measurement sites in the plane when the humidification is insufficient is flat or tends to decrease in voltage due to drying due to heat generation. This is because, unlike excessive humidification, it is not affected by the current distribution. Thus, when the voltage drops during dryout, the voltage does not rise anywhere due to the influence of the current distribution.

  Therefore, if a voltage increase is confirmed as shown in FIG. 8 by looking at the voltage behavior of the cell unit 30 adjacent to the voltage drop site when the voltage drop unit cell 30 is detected (YES in S506), in-plane Even if the voltage behavior of the other voltage measurement parts attached to a plurality of is not seen (without comparison), it is determined as flooding (S507). On the other hand, if the voltage behavior of the unit cell unit 30 that is close to the voltage reduction part is detected when the unit cell unit 30 that has dropped the voltage is detected, as shown in FIG. 7 (YES in S502), Whether it is dryout or flooding is determined by looking at the voltage behavior of other voltage measurement parts installed in the plane. Specifically, if the voltage behavior of other voltage measurement parts indicates excessive humidification, it is determined as flooding, and if the voltage behavior of other voltage measurement parts does not indicate excessive humidification, it is determined as dryout. To do.

  As described above, according to the fifth embodiment, voltage measurement parts are provided at two or more places in the same unit cell unit 30, and the voltage distribution during power generation is distributed not only in the stacking direction but also in the in-plane direction. Taking into consideration the dry and wet judgment. As a result, the determination system is improved, and it is possible to avoid perforation of the electrolyte membrane and decrease in output due to insufficient humidification.

  In addition, when the voltage measurement part of three or more places (for example, the central part in addition to the both end parts in the longitudinal direction of the unit cell unit) is installed, if one of the three places shows the behavior during flooding, If it is determined that flooding has occurred and all three locations exhibit behavior during dryout, it may be determined as dryout.

  The control unit 20 may further include a water clogging determination unit 23 that determines whether or not the cooling water passage is clogged. When the humidification state determination unit 21 determines that the fuel cell 1 is insufficiently humidified, it executes at least one of processing for increasing the pressure of the cooling water and processing for reversing the direction in which the cooling water flows. Then, after these processes, when the voltage of the unit cell unit whose voltage is equal to or lower than the predetermined voltage increases, the water clogging determination unit 23 determines that the cooling water flow path is clogged with water.

  Further, when the humidification state determination unit 21 determines that the fuel cell 1 is insufficiently humidified, the control unit 20 performs a process of increasing the flow rate of the cooling water for cooling the unit cell unit 30, the fuel gas and the oxidant gas. At least one of a process for reducing the flow rate of at least one, a process for increasing the pressure of at least one of the fuel gas and the oxidant gas, and a process for increasing the humidity of at least one of the fuel gas and the oxidant gas May be executed.

  Further, when the humidification state determination unit 21 determines that the fuel cell 1 is excessively humidified, the control unit 20 performs a process of reducing the flow rate of the cooling water for cooling the unit cell unit 30, the fuel gas and the oxidant gas. At least one of a process for increasing the flow rate of at least one, a process for reducing the pressure of at least one of the fuel gas and the oxidant gas, and a process for reducing the humidity of at least one of the fuel gas and the oxidant gas May be executed.

  In the first to fifth embodiments and the modifications thereof, the humidified state determination unit 21 determines that the voltage measurement site in the unit cell unit having a predetermined voltage or less is the oxidant gas outlet side site. May be determined that the fuel cell is excessively humidified on the cathode side. According to this configuration, flooding caused by the oxidant gas can be detected.

  Further, the humidification state determination unit 21 determines that the fuel cell is excessively humidified on the anode side when the voltage measurement part of the unit cell unit that is equal to or lower than the predetermined voltage is the fuel gas outlet side part. Also good. According to such a configuration, flooding caused by the oxidant gas can be detected.

  Furthermore, the humidification state determination unit 21 sets a second humidification excess determination voltage that is greater than the humidification excess determination voltage, and the voltage of the cell unit in the vicinity of the cell unit that is equal to or lower than a predetermined voltage is the second excessive humidification voltage. If it is greater than the determination voltage, it may be determined that the fuel cell is excessively humidified and the degree thereof is severe. According to such a configuration, it is possible to determine the degree of excess at the time of excessive humidification. Further, in this case, the control unit 20 performs a process for reducing the flow rate of the cooling water for cooling the unit cell unit 30, a process for increasing the flow rate of at least one of the fuel gas and the oxidant gas, and the fuel gas and the oxidant gas. At least one of the process of reducing the pressure of at least one of the above and the process of lowering the humidity of at least one of the fuel gas and the oxidant gas may be performed while being increased from the normal time.

  As described above, the present invention has been described with reference to the first to fifth embodiments and modifications thereof. However, it should be understood that the description and drawings constituting a part of this disclosure limit the present invention. is not. From this disclosure, various alternative embodiments, examples and operational techniques will be apparent to those skilled in the art. That is, it should be understood that the present invention includes various embodiments not described herein. Therefore, the present invention is limited only by the invention specifying matters according to the scope of claims reasonable from this disclosure.

It is a block diagram showing the outline of the fuel cell system containing the humidification state determination apparatus of the fuel cell concerning 1st Embodiment. 2 shows an arrangement of voltage sensors that measure the voltage of a single cell unit constituting the fuel cell of FIG. It is sectional drawing showing the structure of the single cell unit which comprises the fuel cell of FIG. It is a flowchart showing operation | movement of the humidification state determination apparatus of the fuel cell of FIG. It is a conceptual diagram showing the density distribution of the electric current which flows through a fuel cell when a fuel cell is excessive humidification. It is a graph showing the relationship between the current density of the current flowing through the fuel cell and the voltage of the fuel cell. It is a graph showing the relationship between the humidification excess determination voltage concerning 1st Embodiment, and an average voltage. It is a graph showing the relationship between the humidification excess determination voltage concerning 1st Embodiment, and an average voltage. The arrangement | positioning of the voltage sensor which measures the voltage of the cell unit concerning the modification of 1st Embodiment is represented. It is a flowchart showing operation | movement of the humidification state determination apparatus of the fuel cell concerning 2nd Embodiment. It is a flowchart showing operation | movement of the humidification state determination apparatus of the fuel cell concerning 3rd Embodiment. It is a block diagram showing the outline of the fuel cell system containing the humidification state determination apparatus of the fuel cell concerning 4th Embodiment. It is a flowchart showing operation | movement of the humidification state determination apparatus of the fuel cell in FIG. It is a block diagram showing the outline of the fuel cell system containing the humidification state determination apparatus of the fuel cell concerning the modification of 4th Embodiment. It is a flowchart showing operation | movement of the humidification state determination apparatus of the fuel cell concerning 5th Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fuel cell 2 Fuel gas supply apparatus 3 Oxidant gas supply apparatus 4 Fuel gas supply pipe 5 Oxidant gas supply pipe 6 Fuel gas discharge pipe 7 Oxidant gas discharge pipe 8 Fuel gas pressure regulating valve 9 Purge valve 10 Oxidant gas pressure Adjustment valve 11 Cooling water circulation part 12 Circulation pump 13 Cooling water supply pipe 20 Control part 21 Humidity determination part 22 Voltage sensor (voltage measurement means)
23 Water Clogging Determination Unit 30 Cell Unit 31 Solid Electrolyte Membrane 32 Oxidant Electrode Layer (Cathode)
32a Oxidant gas diffusion layer 32b Oxidant catalyst layer 33 Fuel electrode layer (anode)
33a Fuel gas diffusion layer 33b Fuel agent catalyst layer 34 Oxidant gas separator 35 Fuel gas separator 36 Oxidant gas channel 37 Fuel gas channel 38 Cooling water channel

Claims (22)

A fuel cell humidification state determination device in which a plurality of unit cell units that generate electricity by reacting fuel gas and oxidant gas are stacked,
Voltage measuring means for measuring the voltage of the unit cell unit;
With a control unit,
When the voltage measuring unit detects a voltage that is equal to or lower than a predetermined voltage among the plurality of single cell units, the control unit detects the voltage of the single battery unit in the vicinity of the single cell unit that is equal to or lower than the predetermined voltage. A humidification state determination device for a fuel cell, comprising: a humidification state determination unit that determines a humidification state of the fuel cell. The humidified state determination unit
When the voltage of the unit cell unit in the vicinity of the unit cell unit that is equal to or less than the predetermined voltage is equal to or less than the insufficient humidification determination voltage greater than the predetermined voltage, it is determined that the fuel cell is insufficiently humidified,
The fuel cell is determined to be excessively humidified when a voltage of a single cell unit in the vicinity of the single cell unit that is equal to or lower than the predetermined voltage is greater than an excessive humidification determination voltage that is equal to or higher than the insufficient humidification determination voltage. The humidifying state determination device for a fuel cell according to claim 1. The humidification state determination device for a fuel cell according to claim 2, wherein the humidification shortage determination voltage and the humidification excess determination voltage are equal. The control unit further includes an average voltage calculation unit, and the average voltage calculation unit calculates an average voltage of the plurality of unit cell units,
The humidification shortage determination voltage is equal to or lower than the average voltage,
4. The humidification state determination device for a fuel cell according to claim 2, wherein the humidification excess determination voltage is equal to or higher than the average voltage.   The humidification state determination unit determines that the fuel cell is insufficiently humidified when the voltage of the unit cell unit in the vicinity of the unit cell unit whose voltage is equal to or lower than the predetermined voltage decreases with time. The humidified state determination device for a fuel cell according to any one of claims 1 to 4, wherein the device is a humidified state determination device.   The humidification state determination unit determines that the fuel cell is excessively humid when the voltage of a single cell unit in the vicinity of the single cell unit whose voltage is equal to or lower than the predetermined voltage exceeds the excessive humidification determination voltage multiple times. The humidified state determination device for a fuel cell according to any one of claims 2 to 5, wherein: The control unit further includes a water clogging determination unit that determines whether the cooling water passage is clogged,
When the humidification state determination unit determines that the fuel cell is insufficiently humidified,
Treatment for increasing the pressure of the cooling water;
Performing at least one of the processes of reversing the flow direction of the cooling water;
After the process, when the voltage of the unit cell that the voltage is equal to or lower than the predetermined voltage,
The humidified state determination device for a fuel cell according to any one of claims 2 to 6, wherein the water clogging determination unit determines that the cooling water passage is clogged with water. When the humidification state determination unit determines that the fuel cell is insufficiently humidified,
The controller is configured to increase a flow rate of cooling water for cooling the unit cell unit;
A process for reducing the flow rate of at least one of the fuel gas and the oxidant gas;
A process of pressurizing at least one of the fuel gas and the oxidant gas; and
The humidification state determination of a fuel cell according to any one of claims 2 to 7, wherein at least one of the processes of increasing the humidity of at least one of the fuel gas and the oxidant gas is performed. apparatus. When the humidification state determination unit determines that the fuel cell is excessively humidified,
The controller is configured to reduce a flow rate of cooling water for cooling the unit cell unit;
A process for increasing the flow rate of at least one of the fuel gas and the oxidant gas;
A process of reducing the pressure of at least one of the fuel gas and the oxidant gas; and
The humidification state determination of a fuel cell according to any one of claims 2 to 7, wherein at least one of the processes of reducing the humidity of at least one of the fuel gas and the oxidant gas is performed. apparatus.   The humidifying state determination device for a fuel cell according to any one of claims 1 to 9, wherein the single cell unit is a single cell.   The humidifying state determination device for a fuel cell according to any one of claims 1 to 9, wherein the single cell unit includes a plurality of single cells. The voltage measuring means is respectively disposed at two or more parts of the unit cell unit,
2. The fuel cell humidification state determination device according to claim 1, wherein the humidification state determination unit determines a humidification state of the fuel cell from a voltage distribution of the unit cell unit measured at each part. 3. The humidified state determination unit
In one part of the unit cell unit, the voltage of the unit cell unit in the vicinity of the unit cell unit that is equal to or lower than the predetermined voltage is equal to or lower than the humidification shortage determination voltage that is greater than the predetermined voltage, and the other side of the unit cell unit If the voltage of the single cell unit in the vicinity of the single cell unit that is equal to or lower than the predetermined voltage is greater than the excessive humidification determination voltage that is equal to or higher than the insufficient humidification determination voltage, it is determined that the fuel cell is excessively humidified. The humidified state determination device for a fuel cell according to claim 12. The humidified state determination unit
In one part of the unit cell unit, the voltage of the unit cell unit in the vicinity of the unit cell unit that is equal to or lower than the predetermined voltage is equal to or lower than the humidification shortage determination voltage that is greater than the predetermined voltage, and the other side of the unit cell unit When the voltage of the single cell unit in the vicinity of the single cell unit that is equal to or lower than the predetermined voltage is equal to or lower than the excessive humidification determination voltage that is equal to or higher than the insufficient humidification determination voltage, the fuel cell is determined to be insufficiently humidified. 14. The fuel cell humidification state determination device according to claim 12 or 13,   The humidified state determination device for a fuel cell according to any one of claims 12 to 14, wherein the two or more parts of the unit cell unit include an inlet side part and an outlet side part of the oxidant gas.   The humidified state determination device for a fuel cell according to any one of claims 12 to 14, wherein the two or more parts of the unit cell unit include an inlet side part and an outlet side part of the fuel gas.   The humidified state determination device for a fuel cell according to any one of claims 12 to 14, wherein the two or more portions of the unit cell unit include both end portions in the longitudinal direction of the unit.   The humidified state determination device for a fuel cell according to claim 17, wherein the two or more parts of the unit cell unit further include a central part in the longitudinal direction of the unit. The humidified state determination unit
The fuel cell is determined to be excessively humidified on the cathode side when the voltage measurement site in the unit cell unit having the predetermined voltage or less is the outlet side site of the oxidant gas. Item 14. The fuel cell humidification state determination device according to Item 2 or 13. The humidified state determination unit
The fuel cell is determined to be excessively humidified on the anode side when a voltage measurement site in the unit cell unit that is equal to or lower than the predetermined voltage is the fuel gas outlet side site. 14. A humidifying state determination device for a fuel cell according to 2 or 13. The humidified state determination unit
When the voltage of the unit cell unit in the vicinity of the unit cell unit that is equal to or lower than the predetermined voltage is larger than the second humidification excess determination voltage that is larger than the humidification excess determination voltage, the fuel cell is excessively humidified, and to the extent The humidified state determination device for a fuel cell according to claim 2, wherein the determination is that the fuel is intense. The humidified state determination unit
In the other part of the unit cell unit, when the voltage of the unit cell unit in the vicinity of the unit cell unit that is equal to or lower than the predetermined voltage is greater than a second humidification excess determination voltage greater than the humidification excess determination voltage, the fuel cell The humidification state determination device for a fuel cell according to claim 13, wherein is determined to be excessive and humid.

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