JP3572455B2 - Fuel cell system - Google Patents

Fuel cell system Download PDF

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Publication number
JP3572455B2
JP3572455B2 JP2001162177A JP2001162177A JP3572455B2 JP 3572455 B2 JP3572455 B2 JP 3572455B2 JP 2001162177 A JP2001162177 A JP 2001162177A JP 2001162177 A JP2001162177 A JP 2001162177A JP 3572455 B2 JP3572455 B2 JP 3572455B2
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Japan
Prior art keywords
fuel cell
gas
cell system
control device
power generation
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JP2002352824A (en
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博史 宮窪
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日産自動車株式会社
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    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02EREDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00Enabling technologies or technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/50Fuel cells
    • Y02E60/52Fuel cells characterised by type or design
    • Y02E60/521Proton Exchange Membrane Fuel Cells [PEMFC]

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a fuel cell system.
[0002]
[Prior art]
The fuel cell directly generates power by supplying hydrogen to the fuel electrode as a fuel gas and supplying oxygen-containing air to the air electrode to electrochemically react hydrogen and oxygen. High power generation efficiency can be obtained even on a small scale, and the environment is excellent. In recent years, by using a solid polymer ion exchange membrane as an electrolyte, miniaturization and high output can be achieved, and an acid aqueous solution becomes unnecessary. For these reasons, polymer electrolyte fuel cells have attracted attention as a fuel cell system using hydrogen gas.
[0003]
Hydrogen gas, which is a fuel gas, has a small molecular weight and thus easily leaks and is highly ignitable. Therefore, in order to prevent ignition, a method of detecting a leak of hydrogen gas has been conventionally proposed. For example, in the technique disclosed in Japanese Patent Application Laid-Open No. 4-220955 (referred to as a first conventional example), a fuel cell body is housed in a container. Then, hydrogen contained in the inert gas supplied into the container is detected by a sensor to detect leakage.
[0004]
As a method for detecting a leak in a hydrogen pipe, there is a technique disclosed in Japanese Patent Application Laid-Open No. 9-22711 (referred to as a second conventional example). First, an on-off valve is interposed in the middle of the pipe so that a closed space can be formed. At the time of detection, the on-off valve is closed to form a closed space, and the pressure in the closed space is observed by a pressure sensor. By detecting the occurrence of a pressure drop, the presence or absence of a leak is determined.
[0005]
As described above, it is possible to detect hydrogen leakage using the first conventional example and the second conventional example. However, in the first conventional example, it is necessary to store the fuel cell body in a container. This not only causes an increase in the weight and volume of the unit, but also causes a problem that leakage outside the container cannot be detected.
[0006]
The second conventional example also has a drawback that only leakage of a closed space defined by an on-off valve can be confirmed, and the detection site is limited. Furthermore, it is necessary to stop the supply of hydrogen to the fuel cell when a leak is detected. Therefore, it is difficult to detect leakage during operation of the fuel cell.
[0007]
As a method that does not have such a defect, a technique disclosed in Japanese Patent Application Laid-Open No. 63-51061 (referred to as a third conventional example) has been proposed. In the third conventional example, the fuel cell is operated, and a calculated surplus amount of discharged hydrogen obtained using the amount of supplied hydrogen and the value of the direct current is provided at the hydrogen gas outlet of the fuel cell. The actual amount of discharged hydrogen calculated from the measured value of the hydrogen concentration sensor is compared. Then, the amount of hydrogen leakage is calculated from this deviation.
[0008]
[Problems to be solved by the invention]
In the third conventional example, it is possible to detect a leak during operation of the fuel cell. However, there is a problem that the measurement items required for calculating the deviation between the hydrogen supply amount and the usage amount are diversified, and a large number of sensors are required.
[0009]
The present invention has been made to solve the above problems, and an object of the present invention is to provide a fuel cell system capable of detecting gas leakage during operation with few detection devices.
[0010]
[Means for Solving the Problems]
A first invention is a flow control device that controls a volume flow rate of a gas supplied as fuel to a fuel cell body, a state measurement device that measures a thermodynamic state of the gas upstream of the flow control device, A power generation amount measuring device that measures the power generation amount of the fuel cell body, a supply amount of the gas calculated based on the flow rate and the thermodynamic state, and a consumption amount of the gas calculated based on the power generation amount. A control device for comparing the flow rate of the gas with the downstream pressure of the flow rate control device in a state where the upstream pressure with respect to the downstream side of the flow control device is equal to or higher than the critical pressure. Calculated by ignoring the general state.
[0011]
In a second aspect, in the state in which the upstream pressure of the flow control device of the first aspect with respect to the downstream side is equal to or higher than the critical pressure, a steady state in which the power generation amount is steady for a predetermined period is realized. ing.
[0012]
According to a third aspect, in the second aspect, an auxiliary battery that supplies power generated by the fuel cell main body to a load whose power consumption fluctuates, absorbs surplus power of the fuel cell main body, and compensates for the insufficient power. The control device determines the gas leakage in a state where the operation of the fuel cell main body is forcibly stabilized by associating the auxiliary battery with the fluctuation of the power consumption of the load. .
[0013]
A fourth invention further comprises a charge amount measuring device for measuring the charge amount of the auxiliary battery according to the third invention, wherein the control device absorbs surplus power in the auxiliary battery from a measurement result of the charge amount measurement device. When it is determined that there is room to make up for the insufficient power, the operation of the fuel cell main body is forcibly made steady.
[0014]
In a fifth aspect, the gas according to any one of the first to fourth aspects is a gas containing hydrogen, and the fuel cell main body performs the power generation by reacting the hydrogen with oxygen. .
[0015]
According to a sixth aspect, in the fifth aspect, a humidifier for humidifying the gas before the gas is supplied to the fuel cell body is further added to the fifth aspect. Before judging the leakage of the fuel cell, preventive measures for preventing water clogging in the fuel cell body are taken.
[0016]
According to a seventh aspect of the present invention, in any one of the first to sixth aspects, the gas is circulated in a circulation path including the fuel cell main body, and the gas is circulated before being used for the power generation. A circulation mechanism for mixing the gas with the used gas and supplying the mixed gas to the fuel cell body is further added.
[0017]
In an eighth aspect, the control device according to any one of the first to seventh aspects changes a degree of suppression of a power generation amount of the fuel cell body according to a degree of the gas leakage. .
[0018]
Function and Effect of the Invention
According to the first invention, the determination of gas leakage is made in a state where the upstream pressure with respect to the downstream side of the flow control device is equal to or higher than the critical pressure. Thus, it is not necessary to consider the thermodynamic state of the gas in the downstream in the calculation, and it is possible to omit the detection means on the downstream side. Costs are reduced by reducing the number of components for leak detection.
[0019]
According to the second aspect, a steady state in which the power generation amount is steady for a predetermined period is realized, so that the gas supply amount can be calculated easily and accurately.
[0020]
According to the third aspect, even when the power consumption of the load fluctuates, it is possible to determine the leakage while keeping the operation of the fuel cell main body stationary. This makes it possible to maintain the steady state for the time required for the determination, and improves the reliability of the leak determination.
[0021]
According to the fourth aspect, the operation of the fuel cell main body is stabilized when the auxiliary battery has a margin for absorbing the surplus power and making up for the insufficient power. As a result, the steady state can be reliably maintained, and the leakage can be reliably determined.
[0022]
According to the fifth aspect, the leakage of hydrogen is determined during the operation of the fuel cell, and it is possible to avoid ignition.
[0023]
According to the sixth aspect, the fuel cell main body is prevented from being clogged by the liquid water generated by the aggregation of the humidification water, and the leakage can be reliably determined.
[0024]
According to the seventh aspect, by supplying the gas not consumed by the fuel cell to the fuel cell main body again, the gas can be efficiently used.
[0025]
According to the eighth aspect, the operation of the fuel cell main body is restricted according to the degree of leakage. This can avoid the inconvenience caused by suddenly stopping the power generation when the leakage is slight.
[0026]
BEST MODE FOR CARRYING OUT THE INVENTION
The configuration of the present embodiment controls the hydrogen gas so that the state of the hydrogen gas on the upstream side of the hydrogen flow control valve 5 can be observed to determine the supply amount of the hydrogen gas supplied on the downstream side. Then, the leakage of hydrogen during operation is detected by comparing the supply amount of hydrogen gas to the fuel cell unit 20 during operation and the consumption amount of hydrogen gas used for power generation. First, the overall configuration of the fuel cell unit 20 will be described.
[0027]
FIG. 1 is a schematic view illustrating the configuration of the fuel cell unit 20. The fuel cell stack (main body) 1 has a fuel electrode 2 and an air electrode 10 to which hydrogen gas and air are supplied, respectively. Although only the gas system is shown in the figure, cooling water piping is actually incorporated in the fuel cell stack 1. The fuel electrode 2 and the air electrode 10 are joined in the stack 1 with a solid polymer film (not shown) interposed therebetween. Then, hydrogen ions move through the solid polymer membrane using water as a medium and come into contact with oxygen molecules to generate power.
[0028]
The configuration shown in FIG. 1 is a type in which the hydrogen fuel itself is directly stored in the hydrogen storage tank 4, and the hydrogen gas is compressed and stored in a high pressure state. A two-stage pressure reducing mechanism including a pressure adjusting mechanism 9 and a hydrogen flow adjusting valve 5 so that the hydrogen gas sent from the tank 4 is supplied to the fuel cell stack 1 at a stable pressure by opening the supply cutoff valve 17. Pass through. The first-stage pressure adjusting mechanism 9 reduces the pressure of the hydrogen gas to a predetermined value so that the second-stage hydrogen flow adjusting valve 5 operates properly. The throttle area of the hydrogen flow control valve 5 is controlled by the fuel cell unit controller 21a shown in FIG. Therefore, the hydrogen gas decompressed by the pressure adjusting mechanism 9 is set to a predetermined volume flow according to the throttle area of the hydrogen flow adjusting valve 5 and sent to the circulation path including the stack 1.
[0029]
A pressure sensor 14 and a temperature sensor 15 are interposed between the pressure control mechanism 9 and the hydrogen flow control valve 5, and detect the pressure and temperature of the thermodynamic state of the hydrogen gas flowing into the hydrogen flow control valve 5. By detecting it.
[0030]
The hydrogen gas that has passed through the hydrogen flow control valve 5 flows into the recirculation device 6. The recirculation device 6 mixes the new hydrogen gas sent from the hydrogen tank 4 with the used hydrogen gas that has passed through the fuel electrode 2 of the stack 1 and sends it out to a certain downstream of the stack 1. . The mixed hydrogen gas is humidified in the humidifier 3 to a substantially saturated state, and then flows into the stack 1. The hydrogen gas is used for power generation at the fuel electrode 2 of the stack 1. The value of the current generated by the power generation is measured by an ammeter 18 attached to the stack 1. By knowing this current value, it is possible to grasp the amount of power generation and the amount of hydrogen gas actually used for this.
[0031]
The residual hydrogen gas that has not been used in the power generation is discharged from the stack 1 together with the condensed water generated due to the decrease in the hydrogen concentration due to the power generation. These are passed through the water recovery device 7 and the condensed water is recovered as water. Thereafter, the residual hydrogen gas is sent to the recirculation device 6 and circulates again in the circulation path. As a result, hydrogen gas can be used without waste, and fuel efficiency is improved. In the configuration of FIG. 1, a pressure sensor 16 is attached to a pipe that connects the humidifier 3 and the stack 1, and the detected value is input to a fuel cell unit controller 21a (not shown). The fuel cell unit controller 21a reflects the detected value, determines the throttle area, adjusts the opening of the flow control valve 5, and supplies a predetermined pressure of hydrogen gas to a required load. To
[0032]
In order to react hydrogen gas and oxygen in the fuel cell stack 1, it is necessary to supply water to the solid polymer membrane, and a humidifier 3 is provided for this purpose. However, in an operation state in which the circulation amount of the hydrogen gas is small, the condensed water generated in the fuel electrode 2 stagnates as it is, and the water clogging may lower the power generation efficiency of the stack 1. Therefore, in order to eliminate water clogging of the fuel electrode 2, the purge valve 8 provided downstream of the stack 1 is periodically opened. Then, the condensed water is discharged to the outside together with the discharged hydrogen gas by utilizing the pressure of the hydrogen gas in the circulation pipe.
[0033]
Next, an air system for supplying air to the air electrode 10 will be described. At the uppermost stream of the air system, a compressor 11 that takes in the air, compresses the air, and sends the compressed air to the air line is installed. The air compressed by the compressor 11 also flows into the stack 1 after being humidified to a substantially saturated state in the humidifier 3 similarly to the hydrogen gas. Then, the remaining air in which oxygen has been consumed in the air electrode 10 of the stack 1 is sent to the water recovery device 12 together with moisture generated by power generation in the stack 1. Here, moisture is collected, and the exhaust air passes through a pressure control valve 13 attached to an air line and is discharged to the atmosphere. The pressure of the air is controlled by the degree of opening of the pressure control valve 13 so as to have a predetermined value according to the load requirement. This control is performed by the above-described controller not shown. Also in the air system, purging using air is performed to prevent clogging with condensed water.
[0034]
The water recovered by the water recovery device 7 and the water recovery device 12 is supplied to the humidifier 3 by a pressurized pump (not shown) or used as cooling water for the stack 1 to be effectively reused. .
[0035]
Next, the calculation principle of this embodiment for detecting hydrogen leakage will be described. The hydrogen flow control valve 5 has a valve body whose throttle area A is variable depending on the holding position, between the inlet and the outlet. By adjusting the throttle area A, it is possible to set the volume flow rate of hydrogen gas passing through the adjustment valve 5 per unit time. The change of the holding position of the valve body can be performed using the magnetic force generated by the electromagnetic coil in response to the command from the fuel cell unit controller 21a described above, for example. When the pressure P0 on the upstream side of the hydrogen flow control valve 5 is equal to or higher than the critical pressure "P0 *" with respect to the pressure P1 on the downstream side, the hydrogen gas flow passing through the throttle area always becomes a sonic flow. Here, the critical pressure P0 * with respect to the downstream pressure P1 is about 1.9 times with hydrogen. At this time, since the velocity is always sonic without being directly affected by the upstream pressure P0 and the downstream pressure P1, the volume flow rate of the hydrogen gas depends on the throttle area A. Then, the mass flow rate of hydrogen gas M HIN Is given by the following equation:
[0036]
(Equation 1)
Here, k: the specific heat ratio of the fluid (in this case, the ratio of the constant pressure specific heat to the constant volume specific heat of hydrogen gas), T0: the upstream temperature of the hydrogen gas, and R: the gas constant. As represented by the equation (1), when the hydrogen gas passing through the throttle portion of the flow control valve 5 is a sonic flow, the mass flow rate M HIN Does not depend on the downstream pressure P1. Specifically, the mass flow rate M HIN Are only the upstream pressure P0, the upstream temperature T0, and the throttle area A (related to the volume of hydrogen gas supplied per unit time). Therefore, the value of the throttle area A corresponding to the command value of the fuel cell unit controller 21a is stored in advance in the fuel cell unit controller 21a, and the measured value of the upstream pressure P0 is sent to the pressure sensor 14 and the temperature sensor 15 is sent to the temperature sensor 15. By providing a measurement of the upstream temperature T0, the mass flow rate of hydrogen gas M HIN Can be calculated.
[0037]
Of course, for example, when the passage area is reduced by the condensed water in the fuel electrode 2 of the stack 1 and the downstream pressure P1 rises, the upstream pressure P0 becomes insufficient from the critical pressure P0 *. Then, the supplied hydrogen gas does not become a sonic flow, and the mass flow rate M HIN Cannot be obtained accurately, and it becomes necessary to consider the downstream pressure P1. However, occurrence of such an abnormal situation can be sufficiently avoided by taking measures such as purging. Furthermore, if the upstream pressure P0 is set to be sufficiently larger than the downstream pressure P1, the supplied hydrogen gas has a sonic flow even if the downstream pressure P1 fluctuates somewhat.
[0038]
Therefore, when the upstream pressure of the flow control valve 5 is equal to or higher than the critical pressure, the mass flow rate M does not take into account the behavior of the downstream pressure P1, that is, the thermodynamic state of the hydrogen gas downstream of the control valve 5. HIN It is possible to calculate By reducing the number of parameters required for the calculation, the calculation is simplified and the load on the calculation means is reduced. Further, a sensor for measuring the pressure P1 of the hydrogen gas before being humidified by the humidifier 3 becomes unnecessary. That is, since the number of sensors required for calculation is reduced, the cost of equipment required for detecting hydrogen leakage is reduced.
[0039]
Next, a method of knowing the amount of hydrogen consumed in the fuel cell stack 1 will be described. Here, the current when the fuel cell stack 1 is generating power is due to electric charges generated according to the following chemical formula.
[0040]
Embedded image
Therefore, the mass M of hydrogen gas consumed for power generation per unit time HCON Is proportional to the current generated at the time of power generation of the stack 1 and is expressed as in the following Expression 2.
[0041]
(Equation 2)
Here, I: current value, F: Faraday constant, m H2 : Represents a hydrogen molecular weight. By measuring the value of the current generated in the stack 1 using the ammeter 18 and substituting it into the equation 2, the mass M of the consumed hydrogen is obtained. HCON Can be calculated.
[0042]
Here, when the hydrogen gas supplied to the fuel cell stack 1 is not used for 100% power generation, the flow rate of the hydrogen gas corresponding to the amount of power generation required by the load is set to a flow rate with a margin for the exhausted hydrogen gas. There is a need. Therefore, if there is a leak, "the supplied mass flow rate M HIN = Mass consumed M HCON + Mass of exhausted hydrogen gas + mass of leaked hydrogen "holds. This can be rewritten as "mass of leaked hydrogen = supplied mass flow rate M HIN -(Consumed mass M HCON + Mass of exhaust hydrogen gas) ". Therefore, it is necessary to attach a sensor for detecting the flow rate of the exhausted hydrogen gas as in Conventional Example 3. On the other hand, when all the hydrogen gas is used for power generation, “the mass of the leaked hydrogen = the supplied mass flow rate M HIN The mass M consumed HCON And a sensor for detecting the flow rate of the exhaust hydrogen gas is unnecessary.
[0043]
As such an example, when the hydrogen system is configured so that the exhaust hydrogen gas is circulated as illustrated in FIG. 1, the hydrogen gas supplied to the circulation path is used for power generation except during purge. All of the supplied hydrogen is used for power generation because it stays in the circuit until it is used.
[0044]
By the way, when the power generation amount of the fuel cell unit 20 fluctuates, that is, when the fuel cell unit 20 is not in the steady operation state, the supply amount of the hydrogen gas must be changed in accordance with the fluctuation of the amount of the consumed hydrogen gas. In the unsteady operation state, even if the upstream pressure of the flow control valve 5 continues to be equal to or higher than the critical pressure, the throttle area A changes with time, and the thermodynamic state of the gas also changes. In equation (1), the time change of all parameters must be grasped and used for the flow rate calculation, and the detection of leakage is possible but troublesome.
[0045]
On the other hand, when the fuel cell unit 20 is in a steady operation state, it is not necessary to consider variations in various parameters. That is, if the supply amount and the consumption amount of the hydrogen gas are kept constant, the discharge amount of the discharged hydrogen gas discharged from the fuel cell stack 1 is also constant, and the discharged hydrogen gas circulating in the circulation path is reduced in the required power generation amount. Is always maintained substantially as a marginal amount of hydrogen gas for achieving the above. In such a state, all the parameters are constant, and the flow rate calculation can be easily performed.
[0046]
Therefore, when the circulation type fuel cell unit 20 is in the steady operation state, the unit time “the mass of the hydrogen leaking constantly = the mass flow rate M that is constantly supplied” HIN The mass M consumed constantly HCON Is established. Therefore, the mass flow rate M HIN And mass M HCON If the difference is obtained, the amount of leakage can be grasped. Further, in the steady state, the values of the respective parameters are stable, the time required for reading the values is shortened, and the time required for detecting a leak is shortened. Further, leakage of hydrogen gas in a relatively wide circulation path including the recirculation device 6, the humidifier 3, the stack 1, and the water recovery device 7 is captured.
[0047]
As described above, in order to simplify the grasp of the amount of leakage, it is desirable that the fuel cell stack 1 be in a steady operation state when leakage is detected. However, when the fuel cell unit 20 is used for an object whose required load fluctuates, such as a vehicle, it is difficult to always maintain a steady operation state. Therefore, by using the fuel cell unit 20 in combination with a secondary battery to form a hybrid system, it is possible to forcibly realize a steady state.
[0048]
FIG. 2 is a schematic view illustrating the configuration of a vehicle equipped with a hybrid fuel cell system having a fuel cell unit 20 and a secondary battery 24. In the hybrid system having the configuration in which the secondary battery 24 is mounted, even if the power generation amount of the fuel cell stack 1 in FIG. It is possible to absorb or supplement by charging and discharging the secondary battery 24.
[0049]
The integrated control device 21 includes the fuel cell unit controller 21a, the motor controller 21b, the secondary battery controller 21c, and the arithmetic unit 21d for performing various calculations. The fuel cell unit controller 21a receives outputs from various sensors disposed in the fuel cell unit 20, outputs drive commands to various actuators in the fuel cell unit 20 according to the load required by the vehicle, and outputs a fuel command. The unit 20 is controlled.
[0050]
On the other hand, the motor controller 21b gives a command to the power conversion device 22 to supply the power generated by the fuel cell unit 20 or the power discharged from the secondary battery 24 to the drive motor 23, or to generate the regenerative power Control for charging the battery 24 is performed. Further, the secondary battery controller 21c receives a signal from the storage capacity sensor 25 disposed on the secondary battery 24, and detects the state of charge of the secondary battery 24. Then, it instructs the power converter 22 to charge and discharge the secondary battery 24 as needed. The operation unit 21d performs an operation on the above-described mathematical expression.
[0051]
As described above, the operating state of the fuel cell unit 20 can be stabilized by the secondary battery 24. However, it takes a certain amount of time to detect a leak, and if the secondary battery 24 cannot cover all the fluctuations, it may hinder the detection. Therefore, it is preferable to perform the leak detection in a state where the target on which the fuel cell unit 20 is mounted operates for a certain period of time and almost constantly. For example, when the object to be mounted is a vehicle, when the vehicle is traveling on a highway, or when idling while waiting for a traffic light or the like, it is preferable to detect leakage.
[0052]
Here, the leakage of hydrogen gas is likely to occur at the joint of each member or at the stack layer of the fuel cell stack 1. Therefore, the leakage of the hydrogen gas becomes more remarkable as the pressure of the hydrogen gas becomes higher, and the detection becomes easier. Therefore, it is more efficient to perform the detection in an operating state where the load is high, such as when driving on a highway, that is, in a state where the set pressure of the fuel electrode 2 is high.
[0053]
The detection of the hydrogen gas leak may be performed, for example, at predetermined intervals determined by the driving time, the running distance, and the like. Before the detection, the purge valve 8 and the purge valve 13 are controlled so as to be temporarily opened to prevent water clogging between the air electrode 10 and the fuel electrode 2 in particular. This can reduce the possibility that the detection of hydrogen gas leakage must be interrupted due to deterioration of the power generation state of the stack 1 due to water clogging, and reliable implementation is possible.
[0054]
Next, a processing procedure of the integrated control device 21 will be described. FIG. 3 is a flowchart illustrating a control procedure of the integrated control device 21 of the present embodiment. First, in step 70, it is determined whether the load condition required by the vehicle is appropriate for detecting hydrogen gas leakage. This is a step to avoid performing detection in a state that is not suitable for detecting hydrogen gas leakage, such as when the load fluctuation is large or the load is too low, as described above. is there. Whether the load is too low may be determined by comparing the preset threshold value and the load value with the integrated control device 21. Similarly, the load variation can be determined by comparing the variation with a predetermined threshold value of the variation width.
[0055]
If the load is too low or the fluctuation amount is too large, “NO” is determined in the step 70, and the processing of the step 70 is repeated until it is determined that the load state is appropriate. Not done. On the other hand, if it is determined in step 70 that the load is not too low and the variation is within the allowable range (YES), the process of step 71 is performed.
[0056]
In this step 71, the state of charge of the secondary battery 24 is determined by the secondary battery controller 21c based on the output value of the storage capacity sensor 25. In order to cope with the fluctuation of the load, it is desirable that a sufficient chargeable capacity is left in the secondary battery 24 and that the charge amount is sufficient. The secondary battery controller 21c compares the amount of charge of the secondary battery 24 with a total of two thresholds, which are preset upper (expiration side of charging) and lower (empty side of charging). When the charge amount is between the two thresholds, the charge amount is appropriate, and the secondary battery has sufficient discharge and charge margins. In this case, the determination is “YES” and the process proceeds to step 72. On the other hand, if the charged amount does not exist in the range between the two thresholds, “NO” is determined, the process returns to step S70, and the leak is not detected.
[0057]
In step 72, control for setting the operation of the fuel cell unit 20 of FIG. 2 to a steady state is started by the fuel cell unit controller 21a. The change in load required by the vehicle is handled by charging or discharging the secondary battery 24 under the control of the motor controller 21b and the secondary battery controller 21c. The steady state of the operation of the fuel cell unit 20 is determined by confirming that the output value of the pressure sensor 16 in FIG. 1 is constant or that the detected value of the current generated by power generation is constant. 21a. When the operation becomes steady, the routine proceeds to step 73.
[0058]
Next, in step 73, the throttle area A is obtained from the command value of the fuel cell unit controller 21a, and the measurement of the pressure P0 and the temperature T0 upstream of the flow control valve 5 and the current value I of the stack 1 is performed as shown in FIG. The pressure sensor 14, the temperature sensor 15, and the ammeter 18 are used. In the next step 74, the mass flow rate of the supplied hydrogen gas M HIN Using Equation 1, the mass M of the hydrogen gas consumed HCON Is calculated by the arithmetic unit 21d using Equation 2. Then, these values are subtracted, and the absolute value DM of the difference is calculated.
[0059]
The absolute value DM of the difference obtained as described above is classified into three ranges in the following processing. That is, a range in which it is determined that hydrogen has not been leaked, a range in which hydrogen has been leaked but at a relatively low level that may allow time to stop the fuel cell unit 20, and a relatively high level. This is the range where the system 20 must be shut down immediately to handle a hydrogen leak. The classification is performed based on the magnitude relationship obtained by comparing the absolute value DM of the difference with two preset values.
[0060]
First, in step 75, it is determined whether or not hydrogen has leaked. Here, each sensor has a measurement error. Further, a deviation may occur in the throttle area A of the flow control valve 5. This is because the position of the valve body of the adjustment valve 5 set according to the opening command value from the integrated control device 21 in FIG. 2 is affected by hysteresis. Therefore, in order to increase the reliability of the detection of hydrogen gas leakage, a tolerance DMstd is set in consideration of variations in the aperture area A and measurement errors of various sensors, and is stored in the integrated control device 21 in advance.
[0061]
Note that the absolute value DM = | M HIN -M HCON │, but in an ideal situation where there is no measurement error etc., M HIN -M HCON It must always hold that ≧ 0. Therefore, M HIN -M HCON If <0, it is considered to be due to the influence of measurement error and hysteresis. Such an effect is unique to each fuel cell unit 20. So, M HIN -M HCON For example, a plurality of absolute values DM when <0 may be stored, an average may be taken, and the integrated control device 21 may be set to update the tolerance DMstd by reflecting the average. With such a learning function, it is possible to improve the reliability of the leak determination.
[0062]
Specifically, in step S75, the absolute value DM and the allowable value DMstd are compared. If the absolute value DM is less than the allowable value DMstd (YES), it is regarded that hydrogen gas has not leaked, the detection of the leak is terminated, and the maintenance of the steady state of the fuel cell unit 20 is cancelled. Return to control. On the other hand, if it is determined that DM ≧ DMstd (NO), the process proceeds to step 76 in order to proceed to a process for dealing with hydrogen leakage.
[0063]
In step 76, it is determined whether the degree of hydrogen leakage is minor or serious. Specifically, the degree of leakage is classified by comparing the absolute value DM of the difference with the allowable amount DMca. Here, the allowable amount DMca is the amount of hydrogen that can be discharged per unit time depending on the ventilation capacity of the fuel cell unit 20. If the absolute value DM of the difference is less than the permissible amount DMca (YES), a problem that may occur due to hydrogen leakage is temporarily avoided by ventilation.
[0064]
Therefore, when it is determined that the leakage is minor, the emergency stop of the fuel cell unit 20 is not performed so as not to hinder the traveling performance of the vehicle, and the traveling performance of the vehicle is ensured. Then, the process proceeds to a step 77, in which a fuel leakage warning lamp is turned on to notify the driver of the abnormality and to call attention and to prompt an inspection. In the following step 78, processing for suppressing an increase in the amount of leakage of hydrogen gas is performed. Specifically, the fuel cell unit controller 21a prohibits the output of the fuel cell unit 20 from increasing beyond the current value or a preset reference value.
[0065]
On the other hand, if it is determined in step 76 that DM ≧ DMca (NO), the amount of hydrogen gas leakage exceeds the ventilation capacity of the fuel cell unit 20, and the operation of the fuel cell unit 20 is immediately stopped. There is a need. Therefore, the process proceeds to step 79 in order to deal with a relatively high level of hydrogen gas leakage.
[0066]
In step 79, the system stop warning light is turned on to notify the driver of the emergency stop of the fuel cell unit 20. At this time, it is effective to call attention together with voice. Next, in step 80, the fuel cell unit controller 21a performs control to close the shutoff valve 17, which is the main plug for supplying hydrogen gas. As a result, the supply of hydrogen gas from the hydrogen tank 4 is stopped. Then, in step 81, the operation of the fuel cell unit 20 is stopped immediately.
[0067]
Through the series of processes described above, vehicle safety is ensured. When the driver stops the operation of the fuel cell unit 20 after moving the vehicle to a safe place using the electric power charged in the secondary battery of FIG. 2 or the inertia of the vehicle when the operation of the fuel cell unit 20 is stopped, good.
[0068]
While the steady state of the fuel cell unit 20 is maintained, the state of charge of the secondary battery 24 is constantly detected by the storage capacity sensor 25 of FIG. It is preferable to constantly monitor whether an excess or deficiency occurs in the range. This is because if the charge amount deviates from the allowable range, comfortable running of the vehicle may be hindered. Therefore, when the occurrence of excess or deficiency is detected, the processing routine of FIG. 3 may be interrupted to return to the normal control.
[0069]
By performing the configuration and control processing described above, it is possible to reduce the number of sensors that must be attached to the fuel cell unit 20 for detecting hydrogen gas leakage, Leakage in the hydrogen system during operation can be quickly detected. Further, by changing the suppression of the power generation amount of the fuel cell unit 20 in accordance with the degree of leakage of the hydrogen gas, when the leakage is slight, for example, the traveling ability of the vehicle remains within a certain range. Thereby, the usability of the mounting target of the fuel cell unit 20 is improved.
[Brief description of the drawings]
FIG. 1 is a schematic view illustrating the configuration of a fuel cell unit 20.
FIG. 2 is a schematic view illustrating the configuration of an object on which the fuel cell unit 20 is mounted.
FIG. 3 is a flowchart illustrating a processing procedure of the integrated control device 21;
[Explanation of symbols]
1 Fuel cell stack
2 Fuel electrode
3 Humidifier
5 Flow control valve
8,13 Purge valve
10 air electrode
14 Pressure sensor
15 Temperature sensor
18 Ammeter
20 Fuel cell unit
21 Integrated control device
23 Drive motor
24 Secondary batteries
25 Storage capacity sensor

Claims (8)

  1. A flow control device that controls a volume flow rate of a gas supplied as fuel to the fuel cell body,
    A state measurement device that measures the thermodynamic state of the gas upstream of the flow control device,
    A power generation amount measuring device for measuring the power generation amount of the fuel cell body,
    A control device for comparing the supply amount of the gas calculated based on the flow rate and the thermodynamic state with the consumption amount of the gas calculated based on the power generation amount and determining a leakage of the gas. ,
    The fuel cell according to claim 1, wherein the supply amount of the gas is calculated in a state where an upstream pressure with respect to a downstream side of the flow control device is equal to or higher than a critical pressure, and ignoring a thermodynamic state in the downstream. system.
  2. The fuel cell system according to claim 1, wherein
    In the fuel cell system, in the state where the upstream pressure with respect to the downstream side of the flow control device is equal to or higher than the critical pressure, a steady state in which the power generation amount is steady for a predetermined period is realized.
  3. The fuel cell system according to claim 2, wherein
    To the load whose power consumption fluctuates, supply the power generated by the fuel cell body,
    An auxiliary battery that absorbs the surplus power of the fuel cell body and compensates for the insufficient power is used in combination,
    The fuel cell system, wherein the control device determines the gas leakage in a state where the operation of the fuel cell main body is forcibly stabilized by causing the auxiliary battery to correspond to the fluctuation of the power consumption of the load.
  4. The fuel cell system according to claim 3, wherein
    Further comprising a charge amount measuring device for measuring the charge amount of the auxiliary battery,
    The control device forcibly stabilizes the operation of the fuel cell main body when the auxiliary battery absorbs surplus power from the measurement result of the charge amount measuring device and determines that there is room to compensate for the insufficient power. Fuel cell system.
  5. The fuel cell system according to any one of claims 1 to 4, wherein
    The gas is a gas containing hydrogen, and the fuel cell body performs the power generation by reacting the hydrogen with oxygen.
  6. The fuel cell system according to claim 5, wherein
    A humidifier that humidifies the gas before the gas is supplied to the fuel cell body;
    The fuel cell system, wherein the control device performs a preventive measure for preventing water clogging in the fuel cell main body before determining the gas leakage.
  7. The fuel cell system according to any one of claims 1 to 6, wherein:
    A circulation mechanism for circulating the gas in a circulation path including the fuel cell main body, mixing the gas before being used for the power generation and the gas after being used, and supplying the mixed gas to the fuel cell main body; Equipped fuel cell system.
  8. The fuel cell system according to any one of claims 1 to 7, wherein:
    The fuel cell system, wherein the control device changes a degree of suppression of a power generation amount of the fuel cell body according to a degree of the gas leakage.
JP2001162177A 2001-05-30 2001-05-30 Fuel cell system Expired - Fee Related JP3572455B2 (en)

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JP4886161B2 (en) * 2003-03-03 2012-02-29 本田技研工業株式会社 Fuel cell system
JP4529387B2 (en) * 2003-07-10 2010-08-25 トヨタ自動車株式会社 Fuel cell system
DE112005001278B4 (en) 2004-06-02 2012-04-19 Toyota Jidosha Kabushiki Kaisha The fuel cell system
FR2872348B1 (en) * 2004-06-29 2006-10-20 Air Liquide System for securing a fuel cell operating in a closed local
JP2006108024A (en) * 2004-10-08 2006-04-20 Toyota Motor Corp High pressure gas feeder and fuel cell system using it
JP2006134647A (en) * 2004-11-04 2006-05-25 Nissan Motor Co Ltd Fuel cell system
JP4730064B2 (en) 2004-11-29 2011-07-20 トヨタ自動車株式会社 Gas leak detection device and fuel cell system
JP4923426B2 (en) * 2005-03-25 2012-04-25 日産自動車株式会社 Fuel cell system
JP4956906B2 (en) * 2005-03-29 2012-06-20 トヨタ自動車株式会社 Fuel cell system and hydrogen leak detection method
JP5151010B2 (en) * 2005-04-05 2013-02-27 トヨタ自動車株式会社 Fuel cell system and gas leak detection method of the fuel cell system
JP5070685B2 (en) * 2005-07-27 2012-11-14 トヨタ自動車株式会社 Fuel cell system, gas leak detection device and gas leak detection method
JP4736612B2 (en) 2005-08-11 2011-07-27 トヨタ自動車株式会社 Moving body
JP5270942B2 (en) * 2008-03-26 2013-08-21 本田技研工業株式会社 Fuel cell vehicle
FR2986109B1 (en) * 2012-01-25 2014-12-05 Air Liquide Fuel cell installation and leak detection method
JP5850769B2 (en) * 2012-03-12 2016-02-03 アイシン精機株式会社 Fuel cell system
JP5957664B2 (en) * 2012-05-25 2016-07-27 本田技研工業株式会社 Fuel cell system and operation method thereof
US20150346007A1 (en) * 2014-05-27 2015-12-03 Microsoft Corporation Detecting Anomalies Based on an Analysis of Input and Output Energies
JP6335967B2 (en) * 2016-05-12 2018-05-30 本田技研工業株式会社 Control method for fuel cell vehicle

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