JP2006269337A - Fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell system detecting the abnormalities of a fuel cell, while driving, which can be operated without making a driver feel uncomfortable. <P>SOLUTION: On the fuel cell system that generates power by using hydrogen-rich fuel cell and oxidant containing oxygen, an operating pressure difference between fuel gas pressure at a fuel electrode (anode) and oxidant gas pressure at oxidant electrode (cathode) is set up by a pressure control means of a control unit 100 so as to reduce the hydrogen concentration, when the hydrogen concentration exceeds a prescribed hydrogen concentration 1 threshold detected by a hydrogen concentration sensor (hydrogen concentration detection means) 20 for detecting the hydrogen concentration, arranged on an air exhaust flow passage 15 located on the downstream side of the oxidant electrode (cathode) of a fuel cell stack 1, while driving. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a fuel cell system that generates power using a hydrogen-rich fuel gas and an oxidizing gas containing oxygen, and in particular, makes the driver feel uncomfortable by setting the operating pressure and the operating differential pressure between the fuel gas and the oxidizing gas. The present invention relates to a fuel cell system capable of continuing operation without causing it.

  Fuel cell technologies that enable clean exhaust and high energy efficiency are attracting attention as countermeasures against environmental problems in recent years, in particular, air pollution caused by automobile exhaust gas and global warming caused by carbon dioxide. A fuel cell is an energy conversion device that supplies a fuel gas containing hydrogen and an oxidant gas such as air to an electrolyte / electrode catalyst complex, causes an electrochemical reaction, and converts chemical energy into electric energy. Among them, a solid polymer electrolyte fuel cell using a solid polymer membrane as an electrolyte is easy to downsize at low cost and has a high output density, so that it can be used as a power source for mobile objects such as automobiles. Is expected.

By the way, a fuel cell system including such a fuel cell is still under development, and a failure or the like may occur. As a technique for detecting an abnormality of a fuel cell, there is an invention disclosed in Japanese Patent Laid-Open No. 2003-45467, for example. In the fuel cell abnormality detection method described in this conventional example, the abnormality of the fuel cell is detected by detecting the rate of decrease in the cell voltage of the fuel cell when the fuel cell is stopped. Further, when an abnormality of the fuel cell is detected, the operating pressure of the reaction gas at the time of power generation after the next time is limited to be lower than that before the abnormality is detected, thereby reducing the amount of gas leakage.
JP 2003-45467 A

  However, in the technique disclosed in Patent Document 1 described above, an abnormality of the fuel cell is detected from a voltage drop after the fuel cell is stopped. Therefore, if an abnormality occurs during operation, the abnormality detection is delayed. There is a problem of increasing the damage of the gas and a problem of increasing the amount of gas leakage. In addition, when an abnormality is detected, the operation pressure is lowered to operate, so that the output of the fuel cell is lowered and the drivability may be impaired.

  The present invention has been made to solve such a conventional problem, and the object of the present invention is to detect an abnormality of the fuel cell during driving and to drive without causing the driver to feel uncomfortable. It is to provide a fuel cell system capable of continuing.

  In order to solve the above object, the present invention provides a fuel cell that generates power by supplying a hydrogen-rich fuel gas and an oxidant gas containing oxygen, and a fuel gas that supplies fuel gas to the anode (fuel electrode) of the fuel cell. A supply means; an oxidant gas supply means for supplying an oxidant gas to the cathode (oxidant electrode) of the fuel cell; and a hydrogen concentration detector installed in an exhaust pipe downstream of the cathode of the fuel cell to detect a hydrogen concentration. Means, or a hydrogen concentration estimation means for estimating a hydrogen concentration in the exhaust gas downstream of the cathode of the fuel cell based on a predetermined physical quantity, and a hydrogen concentration based on the hydrogen concentration detection means or the hydrogen concentration estimation means during operation When the gas exceeds a predetermined hydrogen concentration first threshold, the difference between the fuel gas pressure at the anode and the oxidant gas pressure at the cathode is reduced so that the hydrogen concentration decreases. A pressure control means for setting the operating pressure difference that, characterized in that it comprises a.

  In the fuel cell system according to the present invention, in a fuel cell system that generates power using a hydrogen-rich fuel gas and an oxidant gas containing oxygen, the pressure control means causes the downstream exhaust pipe on the downstream side of the cathode of the fuel cell during operation. The hydrogen concentration based on the hydrogen concentration detecting means installed to detect the hydrogen concentration or the hydrogen concentration estimating means for estimating the hydrogen concentration in the exhaust gas downstream of the cathode of the fuel cell based on a predetermined physical quantity is a predetermined hydrogen concentration. When the first threshold value is exceeded, the operation differential pressure, which is the difference between the anode fuel gas pressure and the cathode oxidant gas pressure, is set so that the hydrogen concentration becomes small. Even if gas leaks occur without delay, it is possible to remarkably reduce the amount of leaks, and further, the operability is impaired by a decrease in operation output. It is no, it is possible to allow continued operation of seamlessly fuel cell.

  Hereinafter, embodiments of the fuel cell system of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a configuration diagram of a fuel cell system according to Embodiment 1 of the present invention. The fuel cell system of the present embodiment is used as a driving power source of a fuel cell vehicle, for example, and includes a fuel cell stack 1 that generates power by supplying hydrogen and air as shown in FIG.

  The hydrogen supply system includes a hydrogen tank 4, a pressure control valve 5, a hydrogen supply flow path 6, an ejector 7, a pressure sensor 8, a hydrogen circulation flow path 9, a hydrogen exhaust flow path 10, and a purge valve 11, and an air supply system. As a compressor 12, an air supply flow path 13, a filter 14, an air exhaust flow path 15, a pressure control valve 16, a pressure sensor 19 and a hydrogen concentration sensor (hydrogen concentration detection means) 20, and the fuel cell stack 1 A cell voltage sensor 2 and a temperature sensor 3 are additionally provided. Although there is also a cooling mechanism that includes a coolant pump and a radiator to keep the temperature of the fuel cell stack 1 within a predetermined range, it is a component that is not directly related to the present invention, so illustration and description of its function are omitted.

  Further, the fuel cell system of the present embodiment controls the respective components of the hydrogen supply system and the air supply system and the warning lamp 101 based on detection signals from various sensors of the hydrogen supply system and the air supply system and other various sensors. It is the structure provided with the control unit 100 which performs lighting control of.

  The fuel cell stack 1 includes a fuel cell (anode) supplied with hydrogen as a fuel gas and an oxidant electrode (cathode) supplied with air as an oxidant gas with an electrolyte interposed therebetween to form a power generation cell. In addition, it has a stack structure in which a plurality of power generation cells are stacked in multiple stages, and converts chemical energy into electrical energy by an electrochemical reaction based on hydrogen and oxygen in the air. In each power generation cell of this fuel cell stack 1, a reaction occurs in which hydrogen supplied to the fuel electrode (anode) is separated into hydrogen ions and electrons, the hydrogen ions pass through the electrolyte, and the electrons pass through an external circuit to generate power. And move to the oxidant electrode (cathode). At the oxidant electrode (cathode), oxygen in the supplied air reacts with hydrogen ions and electrons that have moved through the electrolyte to produce water, which is discharged to the outside.

  As the electrolyte of the fuel cell stack 1, for example, a solid polymer electrolyte membrane is used in consideration of high energy density, low cost, light weight, and the like. The solid polymer electrolyte membrane is made of an ion (proton) conductive polymer membrane such as a fluororesin ion exchange membrane, and functions as an ion conductive electrolyte when saturated with water.

  The voltage of each power generation cell of the fuel cell stack 1 is monitored by a cell voltage monitor (battery voltage detecting means) 2, and the information is sent to the control unit 100 that controls the operation of the entire fuel cell system. Further, the fuel cell stack 1 is provided with a temperature sensor 3 for detecting the temperature of the fuel cell stack 1, and its output is sent to the control unit 100. The control unit 100 monitors the power generation state and temperature state of the fuel cell stack 1 based on the information from the cell voltage monitor 2 and the output from the temperature sensor 3.

  In order to generate power in the fuel cell stack 1, it is necessary to supply hydrogen as fuel gas or air as oxidant gas to the fuel electrode (anode) or oxidant electrode (cathode) of each power generation cell. Then, a hydrogen supply system and an air supply system are provided as a mechanism for that purpose.

  The hydrogen supply system includes, for example, a hydrogen tank 4, a pressure control valve 5, a hydrogen supply flow path 6, and an ejector 7. Then, the hydrogen supplied from the hydrogen tank 4 which is a hydrogen supply source is decompressed by the pressure control valve 5 and is sent to the fuel electrode (anode) of the fuel cell stack 1 through the hydrogen supply flow path 6 and the ejector 7. It has become. The fuel electrode pressure (the pressure on the anode side) of the fuel cell stack 1 is detected by the pressure sensor 8, and the control unit 100 feeds back the detected value of the pressure sensor 8 to control the operation of the pressure control valve 5. The fuel electrode pressure (the pressure on the anode side) of the stack 1 is maintained at a desired pressure.

  In the fuel cell stack 1, not all of the supplied hydrogen is consumed, and the remaining hydrogen (hydrogen discharged from the fuel electrode of the fuel cell stack 1) is newly supplied from the hydrogen tank 4 and supplied to the hydrogen supply flow. The hydrogen flowing in the path 6 is mixed with the ejector 7 and supplied again to the fuel electrode (anode) of the fuel cell stack 1. Therefore, a hydrogen circulation passage 9 is connected to the fuel electrode outlet side of the fuel cell stack 1, and hydrogen discharged from the fuel electrode of the fuel cell stack 1 flows back to the ejector 7 through the hydrogen circulation passage 9. It has come to be. The ejector 7 uses the fluid energy of hydrogen flowing through the hydrogen supply flow path 6 to circulate the hydrogen flowing through the hydrogen circulation flow path 9.

  Further, a hydrogen exhaust that discharges hydrogen from the fuel electrode (anode) of the fuel cell stack 1 to the outside of the hydrogen circulation system so as to branch from the hydrogen circulation channel 9 to the fuel electrode outlet side of the fuel cell stack 1. A flow path 10 is connected, and a purge valve 11 is provided on the downstream side of the branch position of the hydrogen exhaust flow path 10 and the hydrogen circulation flow path 9. The purge valve 11 has a function of switching the flow path of hydrogen discharged from the fuel electrode of the fuel cell stack 1, and is opened when performing hydrogen purge and discharged from the fuel electrode of the fuel cell stack 1. Hydrogen is discharged to the outside through the hydrogen exhaust passage 10.

  As mentioned above, when hydrogen is circulated and used, impurities such as nitrogen may accumulate in the system as the hydrogen circulates, and the hydrogen partial pressure decreases when the impurities accumulate excessively. As a result, the average mass of the circulating gas increases, leading to a decrease in the efficiency of the fuel cell stack 1, and the hydrogen circulation flow rate in the ejector 7 decreases. In such a case, the purge valve 11 is opened. By purging the hydrogen, the impurity is discharged out of the system from the hydrogen exhaust passage 8 together with the hydrogen.

  On the other hand, the air supply system includes a compressor 12 and an air supply channel 13 for sucking outside air and pumping the air to the oxidant electrode (cathode) of the fuel cell stack 1. Is supplied to the oxidizer electrode (cathode) of the fuel cell stack 1. The air supply flow path 13 is provided with a filter 14 for trapping microdust, sulfur content, oil discharged from the compressor 12, and the like, and this filter 14 is provided at the oxidant electrode (cathode) of the fuel cell stack 1. In this way, the air purified by the above is supplied.

  An air exhaust passage 15 for discharging air from the fuel cell stack 1 is connected to the oxidant electrode outlet side of the fuel cell stack 1, and oxygen and air that have not been consumed in the fuel cell stack 1. Other components therein are discharged out of the system through the air exhaust passage 15. The air exhaust passage 15 is provided with a pressure control valve 16, and the oxidant electrode pressure (cathode side pressure) of the fuel cell stack 1 is detected by the pressure sensor 19. By feeding back the detected value and controlling the operation of the pressure control valve 16, the oxidant electrode pressure (the pressure on the cathode side) of the fuel cell stack 1 is maintained at a desired pressure. Further, the air exhaust passage 15 is provided with a hydrogen concentration sensor 20 as a hydrogen concentration detecting means, and the signal is sent to the controller 100 to monitor the hydrogen concentration value.

  Further, the air supply system is provided with humidifying means for humidifying the air supplied to the oxidant electrode (cathode) of the fuel cell stack 1. In this humidifying means, the moisture generated in the fuel cell stack 1 is collected by the moisture condenser 18 provided in the exhaust pipe 15 path, and the operation is controlled by the control unit 100 via a tank, a valve or the like (not shown). The fuel cell stack 1 is humidified by being pumped to the humidifier 17. For example, a film humidifier is used as the humidifier 17.

  In addition, a cooling mechanism (not shown) is incorporated in the fuel cell system and is controlled so as to keep the temperature of the fuel cell stack 1 within a predetermined range.

  Further, the fuel cell system includes a warning lamp (notification means) 101 that notifies the driver of system abnormality in accordance with a lighting request from the control unit 100.

  The control unit 100 is configured as a microcomputer having, for example, a CPU, a ROM, a RAM, a peripheral interface, etc., and an outside air temperature sensor (not shown) for detecting the outside air temperature or a cell voltage monitor connected to the fuel cell stack 1. 2. The detection values of various sensors such as the temperature sensor 3 are read, and various control signals are output according to the determination and calculation results for the detection values, thereby controlling the operation of each part of the fuel cell system.

  The control unit 100 includes pressure control means as a constituent element, and this pressure control means represents a functional group of programs executed on the CPU, and the oxidant electrode of the fuel cell stack 1. When the hydrogen concentration based on a hydrogen concentration sensor (hydrogen concentration detecting means) 20 installed in the air exhaust flow path 15 of the (cathode) detects a hydrogen concentration exceeds a predetermined hydrogen concentration first threshold value, the hydrogen concentration is The operating differential pressure, which is the difference between the fuel gas pressure at the fuel electrode (anode) and the oxidant gas pressure at the oxidant electrode (cathode), is set to be smaller.

  Further, in the pressure control means, when the operation load is high, the fuel electrode (anode) with respect to the normal set values of the fuel gas pressure of the fuel electrode (anode) and the oxidant gas pressure of the oxidant electrode (cathode). ), The oxidant gas pressure at the oxidant electrode (cathode) is increased when the operation load is low, and the operation differential pressure is increased as the operation load of the fuel cell stack 1 is increased. Set.

  Further, in the pressure control means, when the hydrogen concentration based on the hydrogen concentration sensor (hydrogen concentration detection means) 20 exceeds a predetermined second hydrogen concentration threshold value that is larger than the first hydrogen concentration threshold value, the fuel cell stack 1 And a warning lamp (notification means) 101 to notify the driver of that, and a predetermined third hydrogen concentration threshold value in which the hydrogen concentration is higher than the second hydrogen concentration threshold value. When the value exceeds the value, the fuel cell system is stopped.

  In the pressure control means, the operation differential pressure is set when the steady operation state is determined.

  Next, with respect to the operation at the time of operation of the fuel cell system of the present embodiment configured as described above, the case where the fuel cell system is used as a driving power source of a fuel cell vehicle will be described as an example with reference to FIGS. This will be briefly described with reference to FIG. 2 is an explanatory diagram for explaining the relationship between the operating load and the operating pressure of the fuel cell stack 1, and FIG. 3 is an explanatory diagram for explaining the voltage characteristics of the fuel cell stack 1 with respect to the load when the fuel cell stack 1 is operated. It is.

  During operation of the fuel cell system, the pressure on the fuel electrode (anode) side of the fuel cell stack 1 depends on the amount of hydrogen and the amount of air corresponding to the output (electric power) corresponding to the accelerator opening by the driver's operation. The hydrogen whose pressure is adjusted by the control valve 5 is supplied, and the compressor 12 supplies air to the oxidant electrode (cathode) side of the fuel cell stack 1. Further, the humidifier 17 guides the air from the compressor 12 to the oxidant electrode (cathode) of the fuel cell stack 1 in a humidified state. At this time, the basic operating pressure is set according to the operating load as shown in FIG. 2, and is set low for low load operation and high for high load operation. Detailed operation will be described later.

  In the hydrogen supply system, hydrogen discharged from the fuel electrode (anode) of the fuel cell stack 1 is circulated by the hydrogen circulation passage 9 and the ejector 7. The cell voltage is monitored by the cell voltage monitor 2 because the concentration of impurities such as nitrogen gradually increases due to permeation of the electrolyte membrane or the like, or water is clogged, and the cell voltage is monitored. When the voltage drops below a predetermined value (for example, 0.2V) relative to the average value, or when the average cell voltage drops by a predetermined width (for example, 0.1V) or more, the purge valve 11 is opened to circulate hydrogen. The cell voltage is recovered by discharging impurities together with hydrogen in the flow path 6 and the fuel cell stack 1 to the outside.

  Here, as a method for detecting a decrease in the average cell voltage, as shown in FIG. 3, the voltage characteristic (IV characteristic) of the fuel cell stack 1 with respect to the load during operation is stored in the control unit 100 as table data. In addition, the average cell voltage that should be at a certain temperature according to the operating load of the fuel cell stack 1 is obtained, the change in the cell voltage due to the temperature of the fuel cell stack 1 is corrected, the average cell voltage that is to be obtained is obtained, Determination can be made by comparing the value with the average cell voltage detected during actual operation. Further, in consideration of long-term deterioration of the fuel cell stack 1, when the cell voltage drop in a relatively long cycle is corrected by learning, the fuel cell stack 1 gradually deteriorates and the average cell voltage is lowered. However, the above determination can be made.

  As a result of the normal operation as described above, an output corresponding to the driver's accelerator operation is taken out from the fuel cell system, and the vehicle is driven by a vehicle drive motor (not shown).

  Next, in the fuel cell system of the present embodiment schematically described above, the pressure control operation that is a feature of the present invention will be described along the flowchart of FIG. 4 with reference to FIG. 5 and FIG. Here, FIG. 4 is a flowchart showing the flow of pressure control processing performed during normal operation in the fuel cell system of the first embodiment, and FIG. 5 is an explanatory diagram of pressure loss with respect to the operating load of the first embodiment. FIG. 6 is an explanatory diagram of the hydrogen concentration threshold value of the first embodiment.

  First, the control unit 100 reads the accelerator opening from an accelerator pedal sensor or the like (not shown), and also reads the hydrogen concentration value as a detection result from the hydrogen concentration sensor 20 (step S101).

  Next, it is determined whether it is in a steady operation state (step S102). The method for determining the steady operation can be obtained, for example, by determining whether or not the standard deviation of the accelerator opening exceeds a predetermined threshold value. If it is determined in step S102 that the vehicle is not in a steady operation state, the process ends without performing the following processing.

  If it is determined in step S102 that the vehicle is in a steady operation state, it is next determined whether or not the read hydrogen concentration value is equal to or less than a predetermined hydrogen concentration first threshold value (step S103). Specifically, it is determined whether or not it is equal to or lower than a hydrogen concentration first threshold value Hdt1 (shown by a broken line in the figure) which is the lowest threshold value of hydrogen concentration shown in FIG.

  In step S103, if the hydrogen concentration is equal to or lower than the hydrogen concentration first threshold value Hdt1, the process proceeds to step S104, where the operating pressure of the system is determined as the basic operating pressure (according to the operating load as shown in FIG. 2). The pressure control routine is terminated.

  In step S103, if the hydrogen concentration exceeds the hydrogen concentration first threshold value Hdt1, the process proceeds to step S105, and whether or not the hydrogen concentration value is equal to or less than a predetermined hydrogen concentration second threshold value. Determine. Specifically, in FIG. 6, it is determined whether or not it is equal to or lower than a hydrogen concentration second threshold value Hdt2 (indicated by a solid line in the figure) set higher than the hydrogen concentration first threshold value Hdt1. Yes.

  When the hydrogen concentration is equal to or lower than the hydrogen concentration second threshold value Hdt2 in step S105 (that is, when the hydrogen concentration exceeds the hydrogen concentration first threshold value Hdt1 and falls within the hydrogen concentration second threshold value Hdt2 or less). ), Pressure control (change of operating pressure) is performed according to the case according to the operating load.

  That is, it is determined whether or not the operation load is low (step S106). Specifically, it is determined whether or not the operating load is a predetermined load or less (for example, the ratio of the operating load to the total load is 20% or less). When the operating load is equal to or less than a predetermined load (the ratio of the operating load to the total load is 20% or less), the load is low. When the operating load exceeds the predetermined load, the load is not low.

  If it is determined in step S106 that the operation load is low, the oxidant electrode pressure (cathode oxidant gas pressure) of the fuel cell stack 1 is increased (step S107). For example, as shown in FIG. 5, this pressure increase amount is obtained as an amount corresponding to the operating load, and the control unit 100 controls the operation of the pressure control valve 16 while feeding back the detection value of the pressure sensor 19. The oxidant pole pressure (cathode side pressure) of the fuel cell stack 1 is maintained at a pressure increased by the increased amount.

  If it is determined in step S106 that the operation load is not low, the fuel electrode pressure (the fuel gas pressure of the anode) of the fuel cell stack 1 is reduced (step S108). Similar to step S107, the pressure decrease amount is obtained as an amount corresponding to the operating load (see FIG. 5), and the control unit 100 controls the operation of the pressure control valve 5 while feeding back the detection value of the pressure sensor 8. As a result, the fuel electrode pressure (the pressure on the anode side) of the fuel cell stack 1 is maintained at a pressure reduced by the amount of the reduction.

  On the other hand, if the hydrogen concentration exceeds the hydrogen concentration second threshold value Hdt2 in step S105, the warning lamp 101 is turned on to warn the driver that the state is abnormal (step S109). Moreover, since it is in an abnormal state, the output of the fuel cell stack 1 is limited (step S110). In step S110, the load to be limited is limited to 70% of the total load, for example. In this embodiment, the output limit is fixed, but the limit value may be obtained according to the detected hydrogen concentration.

  Further, when the hydrogen concentration exceeds the hydrogen concentration second threshold value Hdt2, it is determined whether or not the hydrogen concentration value is equal to or less than a predetermined hydrogen concentration third threshold value (step S111). Specifically, in FIG. 6, it is determined whether or not it is equal to or lower than a hydrogen concentration third threshold value Hdt3 (indicated by a one-dot chain line in the drawing) higher than the hydrogen concentration second threshold value Hdt2. ing.

  In step S111, when the hydrogen concentration is equal to or lower than the hydrogen concentration third threshold value Hdt3 (that is, the hydrogen concentration exceeds the hydrogen concentration second threshold value Hdt2 and is within the range of the hydrogen concentration third threshold value Hdt3 or less). If the hydrogen concentration exceeds the hydrogen concentration third threshold value Hdt3, it is determined that the hydrogen concentration has increased and the system cannot be operated continuously. Is stopped (step S112).

  As described above, in the fuel cell system of the present embodiment, in the fuel cell system that generates power using the hydrogen-rich fuel gas and the oxidant gas containing oxygen, the pressure control means of the control unit 100 operates during operation. A hydrogen concentration based on a hydrogen concentration sensor (hydrogen concentration detection means) 20 installed in the air exhaust passage 15 downstream of the oxidant electrode (cathode) of the fuel cell stack 1 and detecting a hydrogen concentration is a predetermined hydrogen concentration first. When the threshold value is exceeded, an operation differential pressure that is the difference between the fuel gas pressure at the fuel electrode (anode) and the oxidant gas pressure at the oxidant electrode (cathode) is set so that the hydrogen concentration becomes smaller.

  As a result, the detection of abnormality is not delayed as in the prior art, and even if gas leakage occurs, the amount of leakage can be remarkably reduced, and the drivability is impaired due to a decrease in driving output. Thus, it is possible to continue the operation of the fuel cell system without a sense of incongruity while reducing the hydrogen concentration. As a result, the practicality of the fuel cell system can be greatly improved.

  Further, in the fuel cell system of this embodiment, when the operation load is high, the pressure control means of the control unit 100 sets the fuel gas pressure at the fuel electrode (anode) and the oxidant gas pressure at the oxidant electrode (cathode). Since the fuel gas pressure at the fuel electrode (anode) is reduced with respect to the normal set value, even if gas leakage occurs without exceeding the preset operating pressure, the amount of leakage is significantly reduced. And the operation of the fuel cell system can be continued.

  Further, in the fuel cell system of this embodiment, when the operation load is low, the pressure control means of the control unit 100 sets the fuel gas pressure at the fuel electrode (anode) and the oxidant gas pressure at the oxidant electrode (cathode). Since the oxidant gas pressure at the oxidant electrode (cathode) is increased with respect to the normal set value, even if a gas leak occurs without lowering the preset operating pressure, the amount of leak is significantly reduced. The fuel cell system can be continuously operated.

  Further, in the fuel cell system of this embodiment, the operating pressure difference of the fuel cell stack 1 is set larger as the operating load of the fuel cell stack 1 is increased by the pressure control means of the control unit 100. Even if leakage occurs, the amount of leakage can be significantly reduced, and the operation of the fuel cell system can be continued.

  In the fuel cell system of the present embodiment, the hydrogen concentration based on the hydrogen concentration sensor (hydrogen concentration detecting means) 20 is higher than the first threshold value by the pressure control means of the control unit 100. When the threshold value is exceeded, the operation load of the fuel cell stack 1 is limited. In other words, if the hydrogen concentration does not fall below the second threshold value even if the operation differential pressure is set, the operation load of the fuel cell is limited, so that when the abnormal state of the fuel cell system is expanded Further, the operation can be continued and the expansion of the abnormal state can be suppressed.

  In the fuel cell system of the present embodiment, the hydrogen concentration based on the hydrogen concentration sensor (hydrogen concentration detecting means) 20 is higher than the first threshold value by the pressure control means of the control unit 100. When the threshold value is exceeded, a warning lamp (notification means) 101 is notified to the driver. In other words, if the hydrogen concentration does not fall below the hydrogen concentration second threshold value even after setting the operation differential pressure, the driver can be made aware of this, so the abnormal state of the fuel cell system is expanded. In this case, it becomes possible to recognize that repair is necessary at an early stage. Moreover, the expansion of the abnormal state can be suppressed.

  In the fuel cell system of the present embodiment, the hydrogen concentration based on the hydrogen concentration sensor (hydrogen concentration detecting means) 20 is higher than the second threshold value by the pressure control means of the control unit 100. When the threshold value is exceeded, the fuel cell system is stopped. That is, even if the operation differential pressure is set, if the hydrogen concentration does not fall below the hydrogen concentration third threshold value, the fuel cell system is stopped. It is possible to detect that a situation has occurred in which the stack 1 is seriously damaged, and at that time, the system can be stopped immediately.

  Furthermore, in the fuel cell system of the present embodiment, the operation differential pressure is set when the pressure control means of the control unit 100 is determined to be in the steady operation state, so that the operation difference can be reliably performed without causing misjudgment or the like. The pressure can be set.

  Next, a fuel cell system according to Example 2 of the present invention will be described. The configuration of the fuel cell system of Example 2 is the same as that of Example 1 (FIG. 1), and a specific description of each component is omitted.

  However, in the pressure control means of the control unit 100, as in the first embodiment, a hydrogen concentration sensor (hydrogen concentration) installed in the air exhaust passage 15 of the oxidant electrode (cathode) of the fuel cell stack 1 to detect the hydrogen concentration. When the hydrogen concentration based on the detection means 20 exceeds a predetermined hydrogen concentration first threshold value, the fuel gas pressure at the fuel electrode (anode) and the oxidant at the oxidant electrode (cathode) are reduced so that the hydrogen concentration decreases. The operating differential pressure, which is the difference from the gas pressure, is set. However, the larger the flow rate of at least one of the fuel gas and the oxidant gas supplied to the fuel cell stack 1, the larger the operating differential pressure is set. The larger the density of the fuel gas supplied to 1, the larger the operating differential pressure is set. The lower the temperature of the oxidant gas supplied to the fuel cell stack 1, the larger the operating differential pressure. Point of Ku setting, as well as the temperature of the fuel gas supplied to the fuel cell stack 1 is high, a point to set a large operating differential pressure different from the first embodiment.

  Further, in the pressure control means of the control unit 100, when the operation differential pressure exceeds a predetermined operation differential pressure first threshold value set according to the operation load, the operation load of the fuel cell stack 1 is limited and a warning is given. The point of notifying the driver via a lamp (notification means) 101, when the driving differential pressure exceeds a predetermined driving differential pressure second threshold value that is larger than the driving differential pressure first threshold value, the fuel The point of stopping the battery system and the point of learning the set operating differential pressure and updating the target operating pressure value are functions unique to the present embodiment that are not in the first embodiment.

  Next, in the fuel cell system of the present embodiment, the pressure control operation that is a feature of the present invention will be described along the flowchart of FIG. 7 with reference to FIGS.

  FIG. 7 is a flowchart showing a flow of pressure control processing performed during normal operation in the fuel cell system of the second embodiment. FIG. 8 is an explanatory diagram of pressure loss with respect to the anode gas flow rate of the second embodiment. FIG. 9 is an explanatory diagram of the pressure loss with respect to the cathode gas flow rate of Example 2, FIG. 10 is an explanatory diagram of the pressure loss correction value with respect to the anode gas density of Example 2, and FIG. 11 is the cathode gas temperature of Example 2. FIG. 12 is an explanatory diagram of a pressure loss correction value with respect to the anode gas temperature of the second embodiment, and FIG. 13 is an explanatory diagram of an operation differential pressure threshold value with respect to the operating load of the second embodiment. FIG. 14 is an explanatory diagram (part 2) of the operating differential pressure threshold value with respect to the operating load of the second embodiment.

  First, the control unit 100 reads the accelerator opening from an accelerator pedal sensor or the like (not shown), and also reads the hydrogen concentration value as a detection result from the hydrogen concentration sensor 20 (step S201).

  Next, it is determined whether it is in a steady operation state (step S202). The method for determining the steady operation is the same as that in the first embodiment. If it is determined in step S202 that the steady operation state is not established, the routine ends without performing the following processing.

  If it is determined in step S202 that the vehicle is in the steady operation state, the read hydrogen concentration value is equal to or less than the first hydrogen concentration threshold value Hdt1 (broken line in FIG. 6), as in the first embodiment. Is determined (step S103).

  In step S203, if the hydrogen concentration is equal to or lower than the hydrogen concentration first threshold value Hdt1, the process proceeds to step S204, where the system operating pressure is determined as the basic operating pressure (according to the operating load as shown in FIG. 2). The pressure control routine is terminated.

  In step S203, if the hydrogen concentration exceeds the hydrogen concentration first threshold value Hdt1, the process proceeds to step S205, where the hydrogen concentration value is set to the hydrogen concentration second threshold value Hdt2 (shown by a solid line in FIG. 6). Determine whether or not:

  In step S205, when the hydrogen concentration is equal to or lower than the hydrogen concentration second threshold value Hdt2 (that is, the hydrogen concentration exceeds the hydrogen concentration first threshold value Hdt1 and falls within the hydrogen concentration second threshold value Hdt2). )), Pressure control (change of operating pressure) is performed according to the case according to the operating load. That is, as in the first embodiment, it is determined whether or not the operation load is low (step S206).

  If it is determined in step S206 that the operation load is low, the oxidant electrode pressure (cathode side pressure) of the fuel cell stack 1 is increased (step S207). The amount of increase in pressure is obtained based on pressure loss and pressure loss correction values obtained in advance through experiments or calculations, and the control unit 100 controls the operation of the pressure control valve 16 while feeding back the detection value of the pressure sensor 19. The oxidant pole pressure (cathode side pressure) of the fuel cell stack 1 is maintained at a pressure increased by the increased amount. The reference operating pressure shown in FIG. 2 is updated using the value of the pressure increase amount as the learning value.

  Further, when it is determined in step S206 that the operation load is not low, the fuel electrode pressure (anode pressure) of the fuel cell stack 1 is decreased (step S208). Similar to step S207, the pressure decrease amount is obtained based on the pressure loss or pressure loss correction value obtained in advance by experiment or calculation, and the control unit 100 feeds back the detection value of the pressure sensor 8 while feeding back the detected value of the pressure control valve 5. By controlling the operation, the fuel electrode pressure (the pressure on the anode side) of the fuel cell stack 1 is maintained at a pressure reduced by the amount of reduction. Note that the reference operating pressure shown in FIG. 2 is updated with the value of the pressure decrease as the learning value.

  Here, the concept of obtaining the pressure increase or decrease based on the pressure loss or the pressure loss correction value will be described with reference to FIGS.

  FIG. 8 and FIG. 9 show that the pressure loss increases as the anode gas flow rate (fuel gas flow rate of the fuel electrode) and the cathode gas flow rate (oxidant gas flow rate of the oxidant electrode) increase, The amount of increase or decrease in pressure so that the set value of the operation differential pressure increases as the flow rate of the anode gas or cathode gas flowing into the fuel electrode (anode) or oxidant electrode (cathode) of the fuel cell stack 1 increases. Is increased, it is possible to absorb fluctuations in pressure loss according to the anode gas flow rate or the cathode gas flow rate.

  FIG. 10 shows that the pressure loss correction value increases as the anode gas density (fuel gas density of the fuel electrode) increases, and is supplied to the fuel electrode (anode) of the fuel cell stack 1. As the anode gas density is increased, the pressure loss correction value according to the anode gas density can be absorbed by increasing the pressure increase or decrease so that the set value of the operation differential pressure increases.

  In addition, FIG. 11 shows that the pressure loss correction value decreases as the cathode gas temperature (oxidant gas temperature of the oxidant electrode) increases, and is applied to the oxidant electrode (cathode) of the fuel cell stack 1. If the amount of increase or decrease in pressure is increased so that the set value of the operating differential pressure increases as the temperature of the supplied cathode gas decreases, fluctuations in the pressure loss correction value according to the cathode gas temperature can be absorbed. it can.

  Further, FIG. 12 shows that the pressure loss correction value increases as the anode gas temperature (fuel gas temperature of the fuel electrode) increases, and is supplied to the fuel electrode (anode) of the fuel cell stack 1. If the amount of increase or decrease in pressure is increased so that the set value of the operation differential pressure increases as the temperature of the anode gas increases, fluctuations in the pressure loss correction value according to the anode gas temperature can be absorbed.

  Thus, by appropriately setting the operating differential pressure to be set according to the flow rate of the anode gas or cathode gas, according to the anode gas density, or according to the temperature of the anode gas or cathode gas, Even when an abnormality occurs in the fuel cell system, stable operation can be continued regardless of the operation load or the like.

  On the other hand, if the hydrogen concentration exceeds the hydrogen concentration second threshold value Hdt2 in step S205, next, the current set value of the operation differential pressure with respect to the operation load is set to a predetermined operation differential pressure level. It is determined whether or not the threshold value is 1 or less (step S209). Specifically, in the relationship of the operation differential pressure according to the operation load shown in FIG. 13, the operation differential pressure first threshold value Pdt1 (shown by a solid line in the figure), which is the lowest threshold value of the operation differential pressure. It is determined whether or not.

  In step S209, when the set value of the operation differential pressure is equal to or less than the operation differential pressure first threshold value Pdt1, the pressure control routine is terminated. If the operating differential pressure set value exceeds the operating differential pressure first threshold value Pdt1, the process proceeds to step S210, where the current operating differential pressure set value for the operating load is the predetermined operating differential pressure level. It is determined whether or not the threshold value is two or less. Specifically, in the relationship of the operation differential pressure corresponding to the operation load shown in FIG. 14, the operation differential pressure second threshold Pdt2 (in the figure, set higher than the operation differential pressure first threshold Pdt1). It is determined whether it is equal to or less than that (indicated by a one-dot chain line).

  In step S210, when the operation differential pressure is equal to or less than the operation differential pressure second threshold value Pdt2 (that is, the operation differential pressure exceeds the operation differential pressure first threshold value Pdt1 and is equal to or less than the operation differential pressure second threshold value Pdt2). In this state, the abnormal state of the fuel cell system is considered to be relatively minor, and the warning lamp 101 is turned on to warn the driver of the abnormal state (step S211). In addition, since the state is abnormal, the output of the fuel cell stack 1 is limited so that the above state of the fuel cell system does not rapidly expand (step S212). In step S212, the load to be limited is limited to 70% of the total load, for example.

  Further, when the operation differential pressure exceeds the operation differential pressure second threshold value Pdt2, it is determined that the fuel cell system cannot be continuously operated, and the system is unavoidably stopped (step S112).

  As described above, in the fuel cell system of the present embodiment, at least one of the fuel gas (anode gas) and the oxidant gas (cathode gas) supplied to the fuel cell stack 1 by the pressure control means of the control unit 100. As the flow rate increases, the operating differential pressure is set larger. Therefore, even if a gas leak occurs when the gas flow rate is changed without changing the operating load, the leakage amount can be significantly reduced. The operation of the fuel cell system can be continued.

  Further, in the fuel cell system of the present embodiment, the operation differential pressure is set larger as the density of the fuel gas (anode gas) supplied to the fuel cell stack 1 is increased by the pressure control means of the control unit 100. When the gas (anode gas) density changes and pressure loss changes, even if a gas leak occurs, the amount of leak can be significantly reduced, and the fuel cell system can continue to operate. Is possible.

  Further, in the fuel cell system of the present embodiment, the operating differential pressure is set larger as the temperature of the oxidant gas (cathode gas) supplied to the fuel cell stack 1 is lowered by the pressure control means of the control unit 100. Even if gas leakage occurs when the water vapor increases and the cathode pressure loss decreases, the amount of leakage can be significantly reduced, and the operation of the fuel cell system can be continued.

  Further, in the fuel cell system of this embodiment, the operation differential pressure is set to be larger as the temperature of the fuel gas (anode gas) supplied to the fuel cell stack 1 is higher by the pressure control means of the control unit 100. When the temperature rises and the water vapor in the gas increases, even if gas leakage occurs when the anode pressure loss increases, the amount of leakage can be significantly reduced, and the operation of the fuel cell system can be reduced. It can be continued.

  Further, in the fuel cell system of the present embodiment, when the operation differential pressure exceeds a predetermined operation differential pressure first threshold value set according to the operation load by the pressure control means of the control unit 100, the fuel cell stack 1 Therefore, even when the abnormal state of the fuel cell system is expanded, the operation can be continued and the expansion of the abnormal state can be suppressed.

  Further, in the fuel cell system of the present embodiment, when the operating differential pressure exceeds a predetermined operating differential pressure first threshold value set according to the operating load by the pressure control means of the control unit 100, a warning lamp (notification Means) Since the fact is notified to the driver via 101, when the abnormal state of the fuel cell system expands, it becomes possible to recognize that repair is necessary at an early stage, and it is also possible to suppress the expansion of the abnormal state it can.

  Further, in the fuel cell system of the present embodiment, when the operating differential pressure exceeds a predetermined operating differential pressure second threshold value that is larger than the operating differential pressure first threshold value by the pressure control means of the control unit 100, Since the fuel cell system is stopped, it is possible to detect that gas leakage or the like is likely to occur and the fuel cell stack 1 is seriously damaged. At that time, the system is immediately You can stop.

  Furthermore, in the fuel cell system of the present embodiment, the target operating pressure value is updated by learning the set operation differential pressure by the pressure control means of the control unit 100, so that the fuel cell system that proceeds at a relatively slow speed is used. It is possible to provide a fuel cell system that can be operated in a state that is always matched to a failure, gas leakage, and the like, and that can be operated without increasing gas damage and increasing damage to the fuel cell stack 1. In addition, by learning the set operating differential pressure and correcting the operating pressure, it is possible to cope with the case where the system is once stopped and then started or when the abnormal state of the fuel cell progresses relatively slowly. .

  In the first and second embodiments described above, the hydrogen concentration sensor (hydrogen concentration detecting means) 20 that is installed in the air exhaust passage 15 of the oxidant electrode (cathode) of the fuel cell stack 1 and detects the hydrogen concentration is provided. Instead of this, a hydrogen concentration estimating means for estimating the hydrogen concentration in the air exhaust passage 15 of the oxidant electrode (cathode) of the fuel cell stack 1 based on a predetermined physical quantity is provided in the control unit 100. It is good also as a structure provided in (it is as a functional unit, ie, a program). Thereby, the effect equivalent to Example 1 and Example 2 mentioned above can be acquired, without installing the hydrogen concentration sensor 20. FIG.

  The hydrogen concentration estimation method is known and is not particularly limited. For example, in “Fuel Cell System” of Japanese Patent Application Laid-Open No. 2001-229941, the output of the reformed gas flow rate detection device and the output of the reformed gas temperature detection device are used. A method of estimating the hydrogen component concentration of the exhaust reformed gas based on the output of the pressure detection device and the output of the generated power detection device has been proposed.

  In the first and second embodiments, when the operating differential pressure exceeds a predetermined operating differential pressure first threshold set according to the operating load, or when the hydrogen concentration is a predetermined hydrogen concentration second. The warning lamp 101 is used as a notification means for notifying the driver when the threshold value is exceeded, and the system is notified to the driver according to the lighting request from the control unit 100. However, the present invention is not limited to this. For example, a warning message may be output on the display panel, a specific mark or specific word on the display panel may be identified and displayed, or a warning voice message to that effect may be output.

  Furthermore, in Example 2, it was set as the structure which learns the set driving | operation differential pressure, and updates a target driving | operation pressure value, but also as a structure which learns the set driving | operation differential pressure and updates a target driving | operation differential pressure value good. This also provides the same effect as that of the second embodiment.

1 is a configuration diagram of a fuel cell system according to an embodiment of the present invention. 3 is an explanatory diagram for explaining a relationship between an operation load of the fuel cell stack 1 and an operation pressure. FIG. It is explanatory drawing explaining the voltage characteristic of the fuel cell stack 1 with respect to the load at the time of fuel cell stack 1 driving | operation. 6 is a flowchart illustrating a flow of pressure control processing performed during normal operation in the fuel cell system according to the first embodiment. It is explanatory drawing of the pressure loss with respect to the driving | running load of Example 1. FIG. FIG. 6 is an explanatory diagram of a hydrogen concentration threshold value in Example 1. 6 is a flowchart illustrating a flow of pressure control processing performed during normal operation in the fuel cell system of Example 2. FIG. It is explanatory drawing of the pressure loss with respect to the anode gas flow volume of Example 2. FIG. It is explanatory drawing of the pressure loss with respect to the cathode gas flow volume of Example 2. FIG. It is explanatory drawing of the pressure loss correction value with respect to the anode gas density of Example 2. FIG. It is explanatory drawing of the pressure loss correction value with respect to the cathode gas temperature of Example 2. FIG. It is explanatory drawing of the pressure loss correction value with respect to the anode gas temperature of Example 2. FIG. It is explanatory drawing of the driving | operation differential pressure | voltage threshold with respect to the driving | running load of Example 2. FIG. It is explanatory drawing (the 2) of the driving | operation differential pressure | voltage threshold value with respect to the driving | running load of Example 2. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fuel cell stack 2 Cell voltage sensor 3 Temperature sensor 4 Hydrogen tank 5,16 Pressure control valve 6 Hydrogen supply flow path 7 Ejector 8, 19 Pressure sensor 9 Hydrogen circulation flow path 10 Hydrogen exhaust flow path 11 Purge valve 12 Compressor 13 Air supply Flow path 14 Filter 15 Air exhaust flow path 17 Humidifier 18 Moisture condensing device 20 Hydrogen concentration sensor (hydrogen concentration detection means)
100 Control unit (control means)
101 Warning lamp (notification means)

Claims (16)

A fuel cell that generates electricity by supplying a hydrogen-rich fuel gas and an oxidant gas containing oxygen;
Fuel gas supply means for supplying fuel gas to the anode (fuel electrode) of the fuel cell;
An oxidant gas supply means for supplying an oxidant gas to the cathode (oxidant electrode) of the fuel cell;
Hydrogen concentration detection means installed in the exhaust pipe downstream of the cathode of the fuel cell to detect the hydrogen concentration, or hydrogen concentration for estimating the hydrogen concentration in the exhaust gas downstream of the cathode of the fuel cell based on a predetermined physical quantity An estimation means;
During operation, when the hydrogen concentration based on the hydrogen concentration detection means or the hydrogen concentration estimation means exceeds a predetermined hydrogen concentration first threshold value, the fuel gas pressure of the anode and the cathode are reduced so that the hydrogen concentration decreases. Pressure control means for setting an operation differential pressure that is a difference from the oxidant gas pressure of
A fuel cell system comprising:   The pressure control means reduces the anode fuel gas pressure with respect to the normal set values of the anode fuel gas pressure and the cathode oxidant gas pressure when the operating load is high. The fuel cell system according to claim 1.   The pressure control means increases the oxidant gas pressure of the cathode with respect to normal set values of the fuel gas pressure of the anode and the oxidant gas pressure of the cathode when the operation load is low. The fuel cell system according to claim 1.   4. The fuel cell system according to claim 1, wherein the pressure control unit sets the operation differential pressure to be larger as the operation load of the fuel cell is larger. 5.   The pressure control means sets the operation differential pressure to be larger as the flow rate of at least one of the fuel gas or the oxidant gas supplied to the fuel cell is larger. The fuel cell system according to any one of the above.   The said pressure control means sets the said operation differential pressure so that the density of the said fuel gas supplied to the said fuel cell is large, The any one of Claims 1-5 characterized by the above-mentioned. Fuel cell system.   7. The pressure control unit according to claim 1, wherein the operating pressure difference is set larger as the temperature of the oxidant gas supplied to the fuel cell is lower. Fuel cell system.   The said pressure control means sets the said operation differential pressure large, so that the temperature of the said fuel gas supplied to the said fuel cell is high, The any one of Claims 1-7 characterized by the above-mentioned. Fuel cell system.   The pressure control means limits the operating load of the fuel cell when the operating differential pressure exceeds a predetermined operating differential pressure first threshold value set in accordance with the operating load. The fuel cell system according to any one of claims 8 to 9.   When the operating differential pressure exceeds a predetermined operating differential pressure first threshold value set according to the operating load, the pressure control means notifies the driver via the predetermined informing means. The fuel cell system according to any one of claims 1 to 9, wherein the fuel cell system is any one of claims 1 to 9.   The pressure control means stops the fuel cell system when the operating differential pressure exceeds a predetermined operating differential pressure second threshold value that is greater than the operating differential pressure first threshold value. Item 11. The fuel cell system according to any one of Items 9 and 10.   When the hydrogen concentration based on the hydrogen concentration detection unit or the hydrogen concentration estimation unit exceeds a predetermined hydrogen concentration second threshold value that is larger than the hydrogen concentration first threshold value, the pressure control unit The fuel cell system according to any one of claims 1 to 11, wherein an operation load is limited.   When the hydrogen concentration based on the hydrogen concentration detection unit or the hydrogen concentration estimation unit exceeds a predetermined hydrogen concentration second threshold value that is larger than the hydrogen concentration first threshold value, the pressure control unit is a predetermined notification unit. The fuel cell system according to any one of claims 1 to 2, wherein the driver is notified of the fact via the control.   When the hydrogen concentration based on the hydrogen concentration detection unit or the hydrogen concentration estimation unit exceeds a predetermined third hydrogen concentration threshold value that is greater than the second hydrogen concentration threshold value, the pressure control unit 14. The fuel cell system according to claim 12, wherein the fuel cell system is stopped.   The fuel cell system according to any one of claims 1 to 14, wherein the pressure control unit sets the operation differential pressure when it is determined as a steady operation state.   The pressure control means learns the set operation differential pressure and updates at least one value of the target operation pressure or the target operation differential pressure. The fuel cell system described in 1.

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