JP5205986B2 - Fuel cell system - Google Patents

Description

  The present invention relates to a fuel cell system.

  In recent years, a fuel cell has attracted attention as a power source excellent in operating efficiency and environmental performance. A fuel cell generates power by an electrochemical reaction between a fuel gas and an oxidizing gas. The electrochemical reaction between the fuel gas and the oxidizing gas is performed in a fuel battery cell that supports a catalyst. When the fuel gas and the oxidizing gas react, water is generated. If the produced water adheres to the fuel battery cell, it affects the gas reaction. Therefore, in order to perform stable power generation, it is necessary to grasp the state of the produced water and perform appropriate water management.

As a technique for measuring the water content of a fuel cell, a technique for detecting the impedance between an anode and a cathode and calculating the water content from a map or a characteristic equation is known (see, for example, Patent Documents 1 to 3). . In addition, as a technique for measuring the impedance of the fuel cell, a technique for detecting the resistance of a monitor cell provided in the reaction gas flow path and estimating the impedance of the fuel cell main body (see, for example, Patent Document 4), A technique is known in which an alternating electrical signal is applied between an anode and a cathode of a battery and impedance is estimated from changes in voltage and current (see, for example, Patent Document 5).
JP 2007-179833 A JP 2007-157414 A JP 2007-149572 A Japanese Unexamined Patent Publication No. 62-31957 JP-T-2001-519081

  A fuel cell stack in which fuel cells are stacked is configured such that cells at both ends are sandwiched in order to prevent a gap from being formed between the cells. By the way, the stacked fuel cells expand and contract in the stacking direction due to changes in water content and temperature. Therefore, for example, when a fixed fastening structure that restrains expansion and contraction in the stacking direction is adopted to simplify the holding member, the fuel cell stack can be reduced in size, but each cell can be changed depending on changes in water content and temperature. The clamping force applied to the lens is likely to change greatly. When the force applied to the cell stack changes, the force acting between the structural members changes, so the conductivity of the entire stack changes. If the electrical characteristics of the fuel cell stack are not stable, it becomes extremely difficult to calculate the water content necessary for water management from the electrical characteristics of the cell. This invention is made | formed in view of the problem which concerns, and makes it a subject to provide the fuel cell system which can improve the estimation precision of the moisture content of a fuel cell.

  In order to solve the above-described problems, the present invention has been made to estimate the water content in consideration of the amount of change in the conductivity of the fuel cell stack that changes in accordance with the force applied to the fuel cell.

Specifically, the fuel cell system generates power by an electrochemical reaction between a fuel gas and an oxidizing gas, and includes a stacked portion in which a plurality of fuel cell units each having a membrane electrode assembly are stacked, and both ends of the stacked portion in the stacking direction. A fuel cell stack having a clamping part; a first detection means for detecting an impedance of the fuel cell stack; and a change amount of conductivity of the fuel cell stack for changing the impedance, wherein the clamping A second detecting means for detecting a change in conductivity of the fuel cell stack due to a change in clamping force applied to the stacked part by the part, the impedance detected by the first detecting means, and the second detection Estimation means for estimating the water content based on the conductivity change amount detected by the means.

  The fuel cell system according to the present invention is premised on the use of a fuel cell stack in which a plurality of fuel cell cells each having a membrane electrode assembly that generates electricity by causing an electrochemical reaction between a fuel gas and an oxidizing gas. In addition, this fuel cell stack is premised on the fact that the fuel cells are fastened together by sandwiching both ends of the fuel cell stack in the stacking direction.

  A fuel cell stack configured by combining conductive members such as fuel cells has a component component conductivity that varies due to factors other than a change in water content. Here, when the fuel cell is fastened by being clamped at both ends in the stacking direction, the value of the conductivity of the fuel cell stack can be changed according to the change in the fastening force between the members. In particular, in the case of a fuel cell stack that does not have a means for keeping the fastening force applied to the cells substantially constant, the change in fastening force is particularly significant due to the body size variation of the laminate due to the change in cell temperature and the change in water content. In this application, the water content may indicate the physical amount (absolute amount) of water contained in the electrolyte membrane of the membrane electrode assembly, or the amount of water contained in the electrolyte membrane may be the power generation of the fuel cell stack. It may indicate whether or not the problem is caused.

  When the moisture content in the stack is detected by measuring the impedance of the fuel cell stack, the impedance of the stack largely fluctuates due to the change in conductivity, so the first detection means detects the fuel cell stack. In addition to the amount of change caused by the change in the amount of water in the stack, the impedance also includes a change amount caused by the change in conductivity. Here, since the change in the conductivity of the stack due to the change in the clamping force is a simple DC resistance component, the change in the conductivity and the change in the electrolyte membrane resistance due to the change in the water content are also distinguished by impedance measurement. Is difficult. Therefore, in the fuel cell system according to the present invention, the conductivity of the fuel cell stack caused by the change in the clamping force is specified in order to identify the component caused by the change in the conductivity from the amount of change in the impedance detected by the first detection means. Second detection means for detecting the amount of change is provided. By specifying the amount of change in conductivity caused by the change in the clamping force, it is possible to estimate the water content in consideration of such a fluctuation component. Therefore, it is possible to improve the accuracy of the estimated water content of the fuel cell stack. In addition, in this application, the impedance of a fuel cell stack is a parameter which shows the electrical internal resistance of a fuel cell stack, for example, is a parameter which changes according to the fluctuation | variation of the moisture content contained in a membrane electrode assembly. In addition, the change in the conductivity of the fuel cell stack due to the change in the clamping force is a parameter indicating the change in the electrical internal resistance of the fuel cell stack caused by the change in the clamping force applied to the stack, and This is a parameter of the amount of change in the electrical internal resistance of the fuel cell stack that is detected so as not to be affected even if the moisture content contained in the membrane electrode assembly varies.

  Further, the estimating means corrects the impedance detected by the first detecting means with the change in conductivity detected by the second detecting means, and estimates the water content based on the corrected impedance. You may do it. As a result, it is possible to obtain the estimated water content of the fuel cell stack from which the fluctuation component due to the change in the clamping force has been removed.

  In addition, the stacked unit includes a simulated fuel cell that does not cause the electrochemical reaction, and the second detection unit detects the amount of change in conductivity of the simulated fuel cell, thereby May detect the amount of change in the conductivity of the fuel cell stack due to a change in clamping force applied to the stacked portion.

In order to remove the fluctuation component due to the change in conductivity from the impedance of the fuel cell stack, it is only necessary to know the parameter from which the fluctuation component due to the change in water content has been removed and perform division processing. Therefore, a simulated fuel cell that does not contain water and can acquire only a change in conductivity due to a change in clamping force is arranged, and the change in conductivity is measured. As a result, it is possible to specify the amount of the variation factor resulting from the change in the clamping force and remove this amount from the impedance detected by the first detection means.

  The fuel cell stack further includes third detection means for detecting a temperature change amount of the fuel cell stack, and the estimation means includes the second detection means based on the temperature change amount detected by the third detection means. The detected change in conductivity is corrected, the impedance detected by the first detection means is corrected based on the corrected change in conductivity, and the moisture content is estimated based on the corrected impedance. It may be.

  The conductivity of the fuel cell stack can also vary due to changes in the electrical properties of the stack components as the temperature changes. Here, if the conductivity change amount detected by the second detection means does not take into account such a temperature change, an error may be given to the estimation result of the generated water amount. Thus, by detecting the temperature change amount of the fuel cell stack and correcting the detection result of the second detection means, it is possible to improve the accuracy of the moisture content estimation result.

  The conductivity change amount detected by the second detection unit may be a physical amount resulting from a change in contact resistance between a plurality of conductive members constituting the stacked portion. As a factor of the amount of change in the conductivity of the stack due to the change in the holding force applied to the stacked portion by the holding portion, there is a change in the conductivity that occurs between the conductive members constituting the stack. This is because the contact resistance is caused by the roughness of the surface of the constituent member, etc., and the degree of adhesion between the members greatly changes due to the change in the clamping force, and the resistance value largely fluctuates. Therefore, paying attention to such a contact resistance as a physical quantity detected by the second detection means, a change in the contact resistance is detected. As a result, it is possible to remove fluctuation factors other than the change in the water content included in the impedance detected by the first detection means, and to increase the accuracy of the estimation result of the water content.

  Also, a fuel cell system that generates electric power by an electrochemical reaction between a fuel gas and an oxidant gas, wherein a stacked portion in which a plurality of fuel battery cells each having a membrane electrode assembly are stacked, and both ends in the stacking direction of the stacked portion are sandwiched A fuel cell stack having a sandwiching portion; first detection means for sensing an impedance of the fuel cell stack; and a change amount of the conductivity of the fuel cell stack that changes the impedance. And a second detection means for detecting a change in conductivity of the fuel cell stack caused by a change in clamping force applied to the stacked portion, and the impedance detected by the first detection means and the second Control for adjusting the water content of the film may be performed based on the conductivity change amount detected by the detection means. That is, the water content of the membrane is adjusted without specifying the state of the water content of the membrane electrode assembly.

  Here, the adjustment of the moisture content is a control to increase or decrease the moisture content of the membrane electrode assembly. All the controls that can change the water content of the membrane electrode assembly, such as adjustment of the above, are included. The adjustment of the moisture content based on the impedance and the change in conductivity is to adjust the moisture content according to the change in the parameters of the impedance and the conductivity change. When the predetermined value is exceeded, the water content is increased, or the water content is increased or decreased in proportion to the change in impedance or conductivity. Here, the predetermined value is a threshold value for impedance and conductivity change when determining whether or not to adjust the water content, for example, a value allowed for the fuel cell stack to generate power. And a value determined in advance from experiments or the like from the viewpoint of preventing dry-up of the electrolyte membrane.

The present invention may be an invention of a method for executing any one of the above functions. Further, the present invention may be a computer program that causes the control means of the fuel cell system to execute any of the above functions, or a computer-readable recording medium that records such a program.

  According to the fuel cell system of the present invention, it is possible to improve the estimation accuracy of the water content of the fuel cell.

  An embodiment of a fuel cell system 1 according to the present invention will be described in detail based on the drawings. The fuel cell system 1 according to this embodiment is based on the premise that power is supplied to a drive motor that is a drive source of a vehicle, but for a moving object such as a ship or a robot or a thing installed on the ground. Is also applicable.

<Configuration>
FIG. 1 is a diagram showing a schematic configuration of a fuel cell system 1 according to the present embodiment. As shown in FIG. 1, the fuel cell system 1 includes a water content detection device 2 and a fuel cell stack 3. FIG. 1 shows the fuel cell stack 3 in an electrical equivalent circuit diagram.

  The water content detection device 2 includes an impedance measurement device 4 (corresponding to a first detection unit in the present invention), a contact resistance measurement device 5 (corresponding to a second detection unit in the present invention), and A water amount estimation device 6 (corresponding to an estimation unit in the present invention) is provided.

  The impedance measuring device 4 is provided for the purpose of measuring the water content of the fuel cell stack 3 and detects the water content by measuring the impedance of the fuel cell stack 3. The impedance measuring device 4 measures an AC load device 7 that applies AC electricity between an anode and a cathode of an output terminal that outputs generated power of the fuel cell stack 3, a voltmeter 8 that measures a potential difference, and a current value. Are connected to the ammeters 9 respectively. When measuring the impedance of the fuel cell stack 3, the impedance measuring device 4 controls the AC load device 7 to generate AC electricity necessary for measuring the impedance of the fuel cell stack 3, and the generated AC electricity is used as fuel. While being applied to the battery stack 3, the voltage and current of the fuel cell stack 3 are measured by the voltmeter 8 and the ammeter 9. Then, the impedance measuring device 4 specifies the impedance of the fuel cell stack 3 from the relationship between the voltage and current of the fuel cell stack 3 when AC electricity is applied to the fuel cell stack 3.

  The contact resistance measuring device 5 measures the resistance value (contact resistance) of the contact resistance detection module 12 obtained by supplying a measurement current to the simulated fuel cell of the fuel cell stack 3. That is, the contact resistance measuring device 5 measures the resistance value of the simulated fuel cell, and estimates the contact resistance of the entire fuel cell constituting the fuel cell stack 3 by multiplying the measured value by a predetermined coefficient. Specifically, the coefficient multiplication process multiplies the resistance value of the simulated fuel cell by a value obtained by dividing the number of fuel cells 10 by the number of simulated fuel cells. Further, the resistance value of the simulated fuel cell is multiplied by a value obtained by dividing the area of the simulated fuel cell by the area of the fuel cell 10. By calculating the resistance value of the measured simulated fuel cell in this way, it is possible to obtain the contact resistance inside the fuel cell stack 3 (that is, the total contact resistance between the fuel cells constituting the stack). become.

  The water content estimation device 6 estimates the water content of the fuel cell stack 3 based on parameters obtained from the impedance measurement device 4 and the contact resistance measurement device 5. The moisture content estimation device 6 notifies the control means (not shown) of the moisture content estimation result. The notified moisture content estimation result is utilized as a control parameter for each device constituting the fuel cell system 1.

FIG. 2 is a configuration diagram of the fuel cell stack 3. The fuel cell stack 3 is a polymer electrolyte fuel cell (PEFC) suitable for a moving medium such as a fuel cell automobile, and includes a stacked body 11 in which a plurality of fuel battery cells 10 are stacked, and both ends of the stacked body 11 in the stacking direction. A stack fastening case 13 for clamping is provided. The fuel cell stack 3 includes an insulating spacer 14 that electrically insulates between the stacked body 11 and the stack fastening case 13.

  The fuel cell 10 includes a membrane electrode assembly (MEA) in which a polymer electrolyte membrane is joined so as to be sandwiched between an anode catalyst electrode and a cathode catalyst electrode. Further, the fuel cell 10 includes a conductive gas diffusion layer film and a separator that are arranged so as to sandwich the membrane electrode assembly. The polymer electrolyte membrane is composed of a conductive material having ion exchange ability with a solid polymer such as polyfluorocarbon as a main chain and a side chain such as a sulfone group or a carboxylic acid group attached to carry a charge. . The catalyst electrode is made of carbon black or the like carrying platinum (Pt). The membrane electrode assembly causes an electrochemical reaction when fuel gas and oxidizing gas are passed through the gas diffusion layer, and generates a potential difference between the electrodes.

  The fuel cell stack 3 has a contact resistance detection module 12 for measuring the conductivity of the fuel cell stack 3 in addition to the fuel cell 10 that generates power by receiving supply of hydrogen as a fuel gas and oxygen as an oxidizing gas. (Corresponding to the simulated fuel cell in the present invention). The contact resistance detection module 12 is composed of the same members as the fuel cell 10, but is configured not to be supplied with fuel gas and oxidant gas, and does not cause an electrochemical reaction even when the fuel cell 10 is generating power. It is configured as follows. The contact resistance detection module 12 is disposed adjacent to the stacked body 11 of the fuel cells 10 that generate power, and is disposed so as to be sandwiched between the stack fastening case 13 and the stacked body 11. In the contact resistance detection module 12, an insulating spacer 14 is disposed between the stack fastening case 13 and the fuel cell 10 and is electrically insulated.

  Here, when both ends in the stacking direction of the stacked body in which the fuel cells 10 are stacked are pressed with a constant load, the fuel cell stack 3 is generated between the catalyst electrode, the electrolyte membrane, the gas diffusion layer film, and the separator constituting the fuel cell stack 3. The contact resistance is almost constant. However, the contact resistance acting between the conductive members is generated due to the roughness of the surface of each conductive member. Therefore, when the contact force acting between the conductive members changes, the resistance The value also changes. In particular, like the fuel cell stack 3 according to the present embodiment, a member that absorbs the displacement between the constituent members, such as a spring, is disposed between both ends of the stack of fuel cells and the stack fastening case 13. Otherwise, the fastening force applied from the stack fastening case 13 to the fuel battery cell 10 varies greatly due to the expansion and contraction of the laminate due to the heat and water generated by the fuel battery cell 10 generating power. When the contact resistance between the conductive members constituting the fuel cell stack 3 varies greatly due to the change in the fastening force, the impedance of the fuel cell stack 3 varies greatly. Since the impedance is a value determined by three elements of a resistance component (resistance), an inductive component (reactance), and a capacitance component (capacitance), when the contact resistance of the members constituting the fuel cell stack 3 changes, the impedance measuring device The impedance of the fuel cell stack 3 measured by 4 varies greatly. Therefore, when the impedance change caused by the change in the contact resistance of the fuel cell stack 3 is mixed with the measured value of the impedance measuring device 4 provided for the purpose of measuring the water content of the fuel cell stack 3, the change in the moisture content is caused. The impedance change caused by the impedance change and the contact resistance change is a change amount of the direct current component and cannot be distinguished from each other. The contact resistance measuring device 5 is provided to separate such a change amount of the contact resistance among the impedance changes.

<Estimation of water content>
Next, the correlation between the impedance of the fuel cell stack 3 and the water content is specified. That is, fuel gas and oxidant gas are supplied to the fuel cell stack 3 to generate power, and generated water or the like accompanying an electrochemical reaction is generated. The amount of water generated in the fuel cell stack 3 is measured by the amount of generated power, the humidification amount of the supply gas, the weight of the stack, or the like. The amount of generated water in the fuel cell stack 3 is changed by adjusting the supply amounts of the fuel gas and the oxidizing gas, and the relationship between the generated water amount and the impedance is examined. The impedance of the fuel cell stack 3 is a parameter measured by the impedance measuring device 4, and the alternating current load device 7 supplies high frequency AC power to the fuel cell stack 3 (in order to separate reaction resistance components due to voltage application, for example, several It is specified from the relationship between the voltage and current of the fuel cell stack 3 when a voltage of 100 Hz or more is applied. FIG. 3 is a map showing the relationship between the water content specified by changing the water content of the fuel cell stack 3 and the impedance. As shown in FIG. 3, when the water content is high, electrons easily pass through the conductive member constituting the fuel cell stack 3, so that the resistance component (resistance) is reduced and the impedance is reduced. On the other hand, when the water content is small, electrons are difficult to pass through the conductive members constituting the fuel cell stack 3, so that the resistance component increases and the impedance increases. The contact resistance between the constituent members of the fuel cell stack 3 at this time is set to the standard state.

  Next, the content of the process of correcting the estimated water content according to the contact resistance will be described. FIG. 4 is a map showing the relationship between the water content and the impedance when the impedance is corrected according to the actual measurement value of the contact resistance. When the contact resistance of the fuel cell stack 3 measured by the contact resistance measurement device 5 using the contact resistance detection module 12 is lower than the contact resistance in the standard state described above, the fuel cell stack 3 measured by the impedance measurement device 4 The measured value of is lower by the amount corresponding to the decrease in contact resistance. Therefore, if the water content is estimated from the map of FIG. 3 based on this measured value, the estimated water content will be larger than the actual water content. Therefore, as shown in FIG. 4, when the contact resistance of the fuel cell stack 3 measured by the contact resistance measuring device 5 is lower than the contact resistance in the standard state described above, the fuel cell stack 3 measured by the impedance measuring device 4. The contact resistance is added from the measured value and corrected. Thereby, the difference between the estimated water content and the actual water content can be reduced.

  FIG. 5 is a configuration diagram of the fuel cell stack 3 in a state containing generated water. When water is generated in the fuel cell 10, the laminate 11 expands. Therefore, when both ends of the laminate in the stacking direction are fixed so as to be sandwiched between stack fastening cases as shown in FIG. The clamping force applied to the cell 10 changes. For this reason, the contact resistance between conductive members such as catalyst electrodes and separators, gas diffusion layer films, and electrolyte films constituting the fuel cell 10 changes. FIG. 6 is a graph showing the correlation between the impedance before and after correction and the water content. The correlation between the impedance and the water content becomes a graph as shown by a broken line when the change in the contact resistance is not corrected. Moreover, when it correct | amends, it becomes a graph as shown with a continuous line. As shown in FIG. 6, when the water content is small, in other words, when the clamping force applied to the fuel cell 10 is small, the contact resistance is close to the standard state, so the correction amount is small. On the other hand, when the water content is high, in other words, when the holding force applied to the fuel cell 10 is large, the contact resistance is much smaller than that in the standard state, and thus the correction amount is large.

<Effect>
In a fuel cell system that employs a fuel cell stack with a fixed-size fastening structure that is used to reduce the size of the fuel cell stack, the change in the impedance of the fuel cell stack due to a change in external force applied to the fuel cell, etc. It becomes possible to remove and improve the estimation accuracy of generated water. And it becomes possible to control appropriately which adjusts the moisture content of a membrane electrode assembly by controlling each device which does not constitute a fuel cell system using a parameter whose estimation accuracy was improved. For example, if the water content is estimated to be low, the water content is increased. Therefore, the cooling device is controlled to lower the cooling temperature of the fuel cell stack, or the humidification amount in the humidifier is increased. Prevent ups. It should be noted that the water content adjustment of the membrane electrode assembly may be executed based on whether or not the estimated water content satisfies a predetermined threshold, or the control of the system in proportion to the fluctuation of the estimated water content. The parameter may be adjusted steplessly.

<Modification 1>
Hereinafter, modifications of the embodiment will be described. In the embodiment described above, the contact resistance detection module 12 detects a change in contact resistance caused by a change in the clamping force applied to the fuel battery cell 10 and corrects the impedance. By the way, the contact resistance generated between the conductive members is a resistance due to the roughness of the surface of the contact surface, etc., so the hardness of the material changes due to temperature change, and the contact resistance generated between the materials changes. . Here, as described above, the contact resistance detection module 12 of the above embodiment does not cause an electrochemical reaction. Therefore, the temperature of the contact resistance detection module 12 that does not cause an electrochemical reaction is lower by an amount that does not generate reaction heat than the fuel cell 10 that is actually causing an electrochemical reaction. In other words, it can be said that the amount of change in contact resistance detected by the contact resistance detection module 12 does not take into account a physical quantity resulting from a temperature change compared to the amount of change in contact resistance of the fuel cell 10. Therefore, in the present modification, the accuracy of the estimated value is improved by performing impedance correction that also takes into account the amount of change in contact resistance caused by a temperature change.

  Specifically, a temperature sensor is provided in the fuel battery cell 10. FIG. 7 is a configuration diagram of a fuel cell stack 3 ′ according to this modification. As shown in FIG. 7, in the fuel cell stack 3 ′ according to this modification, the temperature detection module 15 is disposed in the fuel cell 10. The temperature detection module 15 is a so-called thermistor having a large change in electrical resistance with respect to a temperature change, and detects a temperature change in the fuel cell 10. For convenience of explanation, the same reference numerals are given to the same components as those in the above-described embodiment, and detailed description thereof is omitted.

  FIG. 8 is a diagram showing a schematic configuration of a fuel cell system 1 ′ according to this modification. As shown in FIG. 8, the fuel cell system 1 ′ includes a water content detection device 2 ′ and a fuel cell stack 3 ′, as in the above embodiment. Since the fuel cell stack 3 ′ is the same as the fuel cell stack 3 according to the above-described embodiment except that the temperature detection module 15 is disposed, the description thereof is omitted.

  The moisture content detection device 2 ′ according to the present modified example and the moisture content detection device 2 according to the above-described embodiment are different in the contact resistance detection circuit used for impedance correction. That is, in the above-described embodiment, only the measured contact resistance of the simulated fuel cell 10 is used as the impedance correction parameter. In this modification, the temperature of the fuel cell 10 is also used as the impedance correction parameter. Specifically, the water content detection device 2 ′ includes a temperature measurement device 16, a fastening pressure measurement device 17, and a contact resistance map unit 18 instead of the contact resistance measurement device 5.

  The fastening pressure measuring device 17 measures the resistance value of the contact resistance detection module 12 obtained by applying a measurement current to the contact resistance detection module 12 as a fastening pressure value. Then, the measured value is notified to the contact resistance map unit 18. Further, the temperature measuring device 16 measures the temperature of the fuel cell 10 obtained by measuring the change in the resistance value of the temperature detection module 15. Then, the measured value is notified to the contact resistance map unit 18. The contact resistance map unit 18 measures the contact resistance of the fuel cell stack 3 based on the fastening force notified from the fastening pressure measuring device 17 and the temperature notified from the temperature measuring device 16. FIG. 9 is a map showing the relationship between the fastening pressure held by the contact resistance map unit 18 and the contact resistance. As shown in FIG. 9, the contact resistance map unit 18 holds a map indicating the correspondence between the fastening pressure and the contact resistance for each temperature, and the fastening pressure notified from the fastening pressure measuring device 17 and the temperature measuring device 16. Then, the contact resistance of the fuel cell stack 3 is obtained from the temperature parameter. The vertical axis of the map in FIG. 9 indicates the contact resistance per unit area, but as with the contact resistance measuring device 5 according to the above-described embodiment, a coefficient is appropriately multiplied according to the cell area and the number of stacked layers. To do. Unlike the case of the above-described embodiment, the water content estimation device 6 includes the water content of the fuel cell stack 3 based on the value obtained by correcting the impedance with the contact resistance of the fuel cell stack 3 acquired by the contact resistance map unit 18. Is estimated.

  FIG. 10 is a configuration diagram of the fuel cell stack 3 ′ including generated water. When water is generated in the fuel cell 10 ′, the stacked body of the fuel cell 10 ′ expands, and the clamping force applied to the cell changes. In addition, the temperature of the fuel cell 10 'rises due to an electrochemical reaction that occurs in the fuel cell 10'. Thereby, the contact resistance between the conductive members constituting the fuel cell stack 3 ′ changes. FIG. 11 is a map showing the relationship between the water content held by the water content estimation device 6 and the resistance value. The water content estimation device 6 estimates the water content of the fuel cell stack 3 based on the contact resistance notified from the contact resistance map unit 18 and the map shown in FIG. As a result, it is possible to remove the change in the impedance of the fuel cell stack due to the change in the external force applied to the fuel cell, the temperature change of the cell, etc., and to increase the estimation accuracy of the generated water.

<Modification 2>
Moreover, in the said embodiment and modification, the impedance measured by the impedance measuring device 4 was correct | amended based on the parameter which the contact resistance measuring device 5 measured, and the moisture content was estimated based on the corrected impedance. However, the embodiment and the modification may estimate the water content of the membrane electrode assembly based on the uncorrected impedance and contact resistance. That is, the impedance measuring device 4 and the contact resistance measuring device 5 are directly connected to the water content estimating device 6 respectively. Further, the water content estimation device 6 stores in advance a map that specifies the state of the water content from the relationship between the impedance and the resistance value as shown in FIG. The moisture content estimation device 6 estimates the moisture content state of the membrane electrode assembly based on the parameters notified from the impedance measurement device 4 and the resistance measurement device 5.

  In the map shown in FIG. 12, the water content state is defined based on the following concept. That is, when the impedance notified from the impedance measuring device 4 increases, it can be estimated that the water content is usually reduced in proportion to this, but the contact resistance notified from the resistance measuring device 5 also increases. If so, the actual decrease in water content is small. Therefore, the map shown in FIG. 12 is defined so that it is determined that the greater the impedance, the smaller the moisture content, while the greater the contact resistance, the greater the moisture content.

  According to this modification, it is possible to estimate the water content state of the membrane electrode assembly without performing an impedance correction process. In addition, although the map shown in FIG. 12 is defined so that the state of water content is specified from the relationship between impedance and contact resistance, the present invention is not limited to this, and for example, FIG. You may make it perform the water content state determination by formulating the conditions defined by the map.

The schematic block diagram of a fuel cell system. The block diagram of a fuel cell stack. A map showing the relationship between water content and impedance. A map showing the relationship between water content and impedance. The block diagram of a fuel cell stack. The graph which shows the correlation of an impedance and moisture content. The block diagram of the fuel cell stack which concerns on a modification. The schematic block diagram of the fuel cell system which concerns on a modification. The map which shows the relationship between fastening pressure and contact resistance. The block diagram of a fuel cell stack. A map showing the relationship between water content and resistance value. A map that identifies the moisture content from the relationship between impedance and resistance.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Fuel cell system 2 ... Water content detection apparatus 3 ... Fuel cell stack 4 ... Impedance measurement device 5 ... Contact resistance measurement device 6 ... Water content estimation apparatus

Claims (6)

A fuel cell system that generates electricity by an electrochemical reaction between a fuel gas and an oxidizing gas,
A fuel cell stack having a stacked portion in which a plurality of fuel cells each having a membrane electrode assembly are stacked, and a sandwiching portion that sandwiches both ends of the stacked portion in the stacking direction;
First detection means for detecting the impedance of the fuel cell stack;
A conductivity of the fuel cell stack for changing the impedance, a second detecting means for detecting the conductivity of the fuel cell stack the clamping portion due to the clamping force applied to the laminated portion,
And a estimation unit that estimates the water content on the basis of said conductivity, wherein the said impedance first detection unit detects the second detection unit detects,
Fuel cell system. Said estimating means, said the impedance first detection unit detects the second detection means is corrected by the conductivity detected to estimate the water content based on the corrected said impedance,
The fuel cell system according to claim 1. The stacked portion has a simulated fuel cell that does not cause the electrochemical reaction,
It said second detection means, by detecting the conductivity of the simulated fuel cell, for detecting the conductivity of said fuel cell stack the clamping portion due to the clamping force applied to the laminated portion,
The fuel cell system according to claim 1 or 2. Further comprising third detection means for detecting a temperature change amount of the fuel cell stack,
Said estimating means, said third of said second detecting means corrects the conductivity detected on the basis of the temperature change amount is detected sensing means, said first detection based on the corrected conductive rate Correcting the impedance detected by the means, and estimating the water content based on the corrected impedance;
The fuel cell system according to any one of claims 1 to 3. The conductivity of the second detection means is detected, a physical quantity due to contact resistance between the plurality of conductive members constituting the laminate unit,
The fuel cell system according to any one of claims 1 to 4. A fuel cell system that generates electricity by an electrochemical reaction between a fuel gas and an oxidizing gas,
A fuel cell stack having a stacked portion in which a plurality of fuel cells each having a membrane electrode assembly are stacked, and a sandwiching portion that sandwiches both ends of the stacked portion in the stacking direction;
First detection means for detecting the impedance of the fuel cell stack;
A conductivity of the fuel cell stack for changing the impedance, and a second detecting means for detecting the conductivity of the fuel cell stack due to the clamping force applied the clamping unit in the stacking unit,
Performs control for adjusting the water content of the film on the basis of said conductivity, wherein the said impedance first detection unit detects the second detection unit detects,
Fuel cell system.

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