JP2007134200A - Fuel cell system and its gas leak detection method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell system capable of performing the detection of gas leak accurately in a short time, and a detection method of gas leak of the fuel cell system. <P>SOLUTION: The fuel cell system is provided with a hydrogen supply source 30, a cut-off valve H100 installed at its downstream, hydrogen pressure control valves H9, H10 installed at further downstream, a pressure sensor P6 installed between the cut-off valve H100 and the hydrogen pressure control valve H9, a pressure sensor P9 which is installed between the hydrogen pressure control valve H9 and the hydrogen pressure control valve H10 and has an upper limit of detection lower than the pressure sensor P6. At the time of start of the fuel cell system, the fuel supply passage 74 is pressurized within the detection range of the pressure sensor P9, and the gas leak in the fuel supply system is detected based on the detection pressure of the pressure sensor P9. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a fuel cell system including a fuel cell that generates power upon receiving gas supply and a gas leak detection method thereof, and more particularly, to a technique for detecting gas leak in a fuel supply system when the system is activated.

  In recent years, a fuel cell system using a fuel cell (cell) that generates power by an electrochemical reaction between a fuel gas and an oxidizing gas (hereinafter referred to as a reactive gas) has attracted attention. In the conventional fuel cell system, when the system is started, the presence or absence of fuel gas leakage is determined as follows.

First, the main stop valve of the fuel gas tank is opened, and the inside of the fuel system pipe is sufficiently pressurized with the fuel gas. Next, the main stop valve is once closed, and the pressure change in the pipe is monitored by a pressure sensor provided upstream of the most upstream pressure adjustment element (pressure adjustment valve). And when a pressure falls, it determines with a gas leak.
JP-A-9-22711

  However, the most upstream pressure sensor has a high detection upper limit and a wide detection range, so the accuracy is low and the error of the pressure sensor itself is very large. For example, if the error is 1% in the detection range of 70 MPa, the error is 7 MPa, and in order to detect a slight pressure change due to gas leakage, the pressure change over the error (7 MPa or more) is detected over time. There is a problem that must be done.

  In view of the above circumstances, an object of the present invention is to provide a fuel cell system and a gas leak detection method for a fuel cell system that can accurately detect a gas leak in a short time.

  In order to achieve the above object, a fuel cell system according to the present invention includes a fuel supply source for supplying fuel to a fuel cell, a main stop valve provided downstream of the fuel supply source, and a downstream of the main stop valve. The first pressure regulating valve, the second pressure regulating valve provided downstream of the first pressure regulating valve, and the first pressure provided between the main stop valve and the first pressure regulating valve. A fuel cell system comprising: a sensor; and a second pressure sensor provided between the first pressure regulating valve and the second pressure regulating valve and having a lower detection upper limit than the first pressure sensor. Then, when the system is started, the gas is pressurized based on the detection result of the second pressure sensor while pressurizing the pressure regulation value of the first pressure regulation valve to be equal to or less than the pressure regulation value of the second pressure regulation valve. Gas leak detection means for performing leak detection is provided.

  In this configuration, the gas leak detection means is configured to detect the detection range of the second pressure sensor (adjustment of the first pressure regulating valve) based on the detection result by the second pressure sensor whose detection upper limit is lower than that of the first pressure sensor. The gas leakage is detected at a pressure value equal to or lower than the pressure value and equal to or higher than the pressure control value of the second pressure control valve. Therefore, it is possible to detect the gas leak with higher accuracy in a shorter time as compared with the case of detecting the gas leak using the first pressure sensor. Note that a plurality of second pressure regulating valves may be provided in the fuel supply system, or a single second pressure regulating valve may be provided.

  The fuel supply source may be a high pressure hydrogen tank.

  A gas leak detection method for a fuel cell system according to the present invention includes a fuel supply source for supplying fuel to a fuel cell, a main stop valve provided downstream of the fuel supply source, and a downstream of the main stop valve. The first pressure regulating valve, the second pressure regulating valve provided downstream of the first pressure regulating valve, and the first pressure sensor provided between the main stop valve and the first pressure regulating valve And a second pressure sensor provided between the first pressure regulating valve and the second pressure regulating valve and having a lower detection upper limit than the first pressure sensor, a gas leak of a fuel cell system In the detection method, when the system is activated, the detection result of the second pressure sensor while pressurizing the pressure regulation value of the first pressure regulation valve to be equal to or less than the pressure regulation value of the second pressure regulation valve. Based on the above, gas leak detection is performed.

  According to such a configuration, by using the second pressure sensor whose detection upper limit is lower than that of the first pressure sensor, the detection range of the second pressure sensor (below the pressure regulation value of the first pressure regulating valve, and Gas leak detection is performed with a pressure regulation value equal to or higher than the pressure regulating value of the second pressure regulating valve), so that gas leak detection is performed in a shorter time and with higher accuracy than when gas leak detection is performed using the first pressure sensor. Is possible.

  According to the present invention, it is possible to accurately detect a gas leak at the time of system startup in a short time.

  Next, an embodiment of a fuel cell system according to the present invention will be described. Hereinafter, the case where this fuel cell system is applied to an in-vehicle power generation system of a fuel cell vehicle will be described. However, the present invention is not limited to such an application example, and is applicable to all moving objects such as ships, airplanes, trains, and walking robots. For example, the present invention can be applied to a stationary power generation system in which a fuel cell is used as a power generation facility for a building (house, building, etc.).

  As shown in FIG. 1, air (outside air) as an oxidizing gas is supplied to an air supply port of the fuel cell 20 via an air supply path 71. The air supply path 71 is provided with an air filter A1 that removes particulates from the air, a compressor A3 that pressurizes the air, a pressure sensor P4 that detects the supply air pressure, and a humidifier A21 that adds required moisture to the air. The compressor A3 is driven by a motor (auxiliary machine). This motor is driven and controlled by a control unit (gas leak detection means) 50 described later. The air filter A1 is provided with an air flow meter (flow meter) (not shown) that detects the air flow rate.

  The air off gas discharged from the fuel cell 20 is discharged to the outside through the exhaust path 72. The exhaust path 72 is provided with a pressure sensor P1 that detects the exhaust pressure, a pressure adjustment valve A4, and a heat exchanger for the humidifier A21. The pressure sensor P <b> 1 is provided in the vicinity of the air exhaust port of the fuel cell 20. The pressure adjustment valve A4 functions as a pressure regulator (pressure reduction) that sets the air pressure supplied to the fuel cell 20.

  Detection signals (not shown) of the pressure sensors P4 and P1 are sent to the control unit 50. The control unit 50 sets the supply air pressure and the supply air flow rate to the fuel cell 20 by adjusting the motor rotation speed of the compressor A3 and the opening area of the pressure adjustment valve A4.

  Hydrogen gas as fuel gas is supplied from a hydrogen supply source (fuel supply source) 30 to a hydrogen supply port of the fuel cell 20 via a fuel supply path (fuel supply system) 74. The hydrogen supply source 30 corresponds to, for example, a high-pressure hydrogen tank, but may be a so-called fuel reformer, a hydrogen storage alloy, or the like.

  A shutoff valve (main stop valve) H100 that supplies or stops supplying hydrogen from the hydrogen supply source 30 and a pressure sensor that detects the supply pressure of hydrogen gas from the hydrogen supply source 30 (first first) Pressure sensor) P6, a first hydrogen pressure regulating valve H9, a second hydrogen pressure regulating valve H10, and a hydrogen pressure regulating valve downstream thereof, which adjust the hydrogen gas supply pressure to the fuel cell 20 by reducing the pressure to a predetermined pressure regulation value. H11, pressure sensors (second pressure sensors) P9 and P10 for detecting the hydrogen gas pressure downstream of the hydrogen pressure regulating valves H9 and H10, respectively, and a shutoff valve H21 for opening and closing between the hydrogen supply port of the fuel cell 20 and the fuel supply path 74 , And a pressure sensor P5 for detecting the inlet pressure of the hydrogen gas fuel cell 20 is provided.

  Among these hydrogen pressure regulating valves H9 to H11, the detection upper limit of the pressure sensor P9 provided between the hydrogen pressure regulating valve H9 provided in the uppermost stream of the fuel supply path 74 and the hydrogen pressure regulating valve H10 provided downstream thereof is It is less than the detection upper limit of the pressure sensor P6 provided between the shutoff valve H100 and the hydrogen pressure regulating valve H9. Further, the pressure regulating values of the hydrogen pressure regulating valves H9 to H11 are set so as to gradually decrease in order from the upstream side of the fuel supply path 74, that is, in order of the hydrogen pressure regulating valves H9, H10, and H11.

  For example, as shown in FIG. 2, the first pressure (for example, 70 MPa, 35 MPa) in the hydrogen supply source 30 is a second pressure (for example, a pressure regulation value of the hydrogen pressure regulation valve H9 by the hydrogen pressure regulation valve H9). 3 MPa). Further, the second pressure is reduced (regulated) by the hydrogen pressure regulating valve H10 to a third pressure (for example, 1 MPa) that is a pressure regulating value of the hydrogen pressure regulating valve H10. Further, the third pressure is reduced (regulated) by the hydrogen pressure regulating valve H11 to a fourth pressure (for example, 200 kPa) that is the pressure regulating value of the hydrogen pressure regulating valve H11.

  When the upstream side pressure (primary pressure) of the hydrogen pressure regulating valve H9 is equal to or lower than the pressure regulating value of the hydrogen pressure regulating valve H9, the opening degree of the hydrogen pressure regulating valve H9 is fully opened, and the same as the hydrogen pressure regulating valve H10 downstream thereof. Pressure. Such valve characteristics are the same for the other hydrogen pressure regulating valves H10 and H11.

  As the hydrogen pressure control valves H9 to H11, for example, pressure control valves that perform mechanical pressure reduction can be used. However, the valve opening degree may be linearly or continuously adjusted by a pulse motor. Detection signals (not shown) of the pressure sensors P5, P6, P9, and P10 are supplied to the control unit 50.

  The hydrogen gas that has not been consumed in the fuel cell 20 is discharged as a hydrogen off-gas to the hydrogen circulation path 75 and returned to the fuel supply path 74 downstream of the hydrogen pressure regulating valve H11. The hydrogen circulation path 75 includes a temperature sensor T31 that detects the temperature of the hydrogen off-gas, a shutoff valve H22 that communicates / blocks the fuel cell 20 and the hydrogen circulation path 75, a gas-liquid separator H42 that collects moisture from the hydrogen off-gas, and a hydrogen A drain valve H41 that collects the generated water in a tank (not shown) outside the hydrogen circulation path 75, a hydrogen pump H50 that pressurizes the hydrogen off-gas, and a backflow prevention valve H52 are provided.

  The shutoff valves H21 and H22 close the anode side of the fuel cell 20. A detection signal (not shown) of the temperature sensor T31 is supplied to the control unit 50. The operation of the hydrogen pump H50 is controlled by the control unit 50.

  The hydrogen off gas merges with the hydrogen gas in the fuel supply path 74 and is supplied to the fuel cell 20 for reuse. The backflow prevention valve H52 prevents the hydrogen gas in the fuel supply path 74 from flowing back to the hydrogen circulation path 75 side. The shutoff valves H100, H21, and H22 are driven by a signal from the control unit 50.

  The hydrogen circulation path 75 is connected to the exhaust path 72 by the purge flow path 76 via the discharge control valve H51. The discharge control valve H51 is an electromagnetic shut-off valve, and discharges (purges) hydrogen off-gas to the outside by operating according to a command from the control unit 50. By intermittently performing this purging operation, it is possible to prevent the cell voltage from decreasing due to an increase in the impurity concentration in the hydrogen off-gas.

  A cooling path 73 for circulating the cooling water is provided at the cooling water inlet / outlet of the fuel cell 20. In the cooling path 73, a temperature sensor T1 that detects the temperature of the cooling water drained from the fuel cell 20, a radiator (heat exchanger) C2 that radiates the heat of the cooling water to the outside, and a pump that pressurizes and circulates the cooling water. C1 and a temperature sensor T2 for detecting the temperature of the cooling water supplied to the fuel cell 20 are provided. The radiator C2 is provided with a cooling fan C13 that is rotationally driven by a motor.

  The fuel cell 20 is configured as a fuel cell stack in which a required number of unit cells that generate power upon receiving supply of fuel gas and oxidizing gas are stacked. The electric power generated by the fuel cell 20 is supplied to a power control unit (not shown). The power control unit consists of an inverter that supplies electric power to the drive motor of the vehicle, an inverter that supplies electric power to various auxiliary devices such as a compressor motor and a motor for a hydrogen pump, and charging of power storage means such as a secondary battery. A DC-DC converter or the like that supplies power to the motors from the power storage means is provided.

  The control unit 50 receives control information from a requested load such as an accelerator signal of a vehicle (not shown) and sensors (pressure sensors, temperature sensors, flow sensors, output ammeters, output voltmeters, etc.) of each part of the fuel cell system. In addition to controlling the operation of the valves and motors, in this embodiment, the fuel system piping (the fuel supply path 74, the gas flow path in the fuel cell 20, and the hydrogen circulation path 75) downstream of the shutoff valve H100. It also functions as a gas leak detection means for performing gas leak detection.

  That is, when performing the pressurizing process of the fuel supply path 74 at the time of starting the system, the control unit 50 has a pressure between the shutoff valve H100 and the hydrogen pressure regulating valve H10 that is equal to or lower than the pressure regulating value of the hydrogen pressure regulating valve H9. By controlling the open / close state of the shutoff valve H100 so that the pressure is equal to or higher than the pressure regulation value of the pressure regulation valve H10, the gas leakage of the fuel system piping is prevented using the pressure sensor P9 having higher detection accuracy than the pressure sensor P6. Detect.

  The control unit 50 is configured by a control computer system (not shown). The control computer system has a known configuration such as a CPU, ROM, RAM, HDD, input / output interface, and display, and is configured by a commercially available control computer system.

  Next, the operation at the time of system startup by the control unit 50 will be described.

  When the control unit 50 determines that a command for starting operation (for example, ignition OFF) or a flag is set (event occurrence) in a main control program (not shown), the control unit 50 first opens the shutoff valve H100 to supply hydrogen. The fuel supply path 74 is pressurized with high-pressure hydrogen from the source 30, and the pressure change in the fuel supply path 74 is monitored by the pressure sensor P5.

  Then, when the pressure of the pressure sensor P5 reaches a predetermined pressure value that is designed for each system, such as the pipe volume, the shutoff valve H100 is closed, so that the upstream pressure of the hydrogen pressure regulating valve H11 is changed to the value of the hydrogen pressure regulating valve H10. A third pressure that is the pressure regulation value and a pressure value that is lower than the second pressure that is the pressure regulation value of the hydrogen pressure regulation valve H9 is set to both upstream side pressures of the hydrogen pressure regulation valves H10 and H9. The pressure value is within the detection range of the pressure sensor P9. The timing for closing the shutoff valve H100 may be determined by the valve opening time of the shutoff valve H100.

  Then, the upstream pressure of the hydrogen pressure regulating valves H9 and H10, that is, the pressure value of the fuel supply path 74 between the shutoff valve H100 and the hydrogen pressure regulating valve H10 at the time of starting the system, as shown in FIG. A value that is equal to or lower than the second pressure that is the pressure regulation value of the pressure valve H9 and that is equal to or greater than the third pressure that is the pressure regulation value of the hydrogen pressure regulation valve H10, for example, the pressure regulation value of the hydrogen pressure regulation valve H9 is 3 MPa. Is 2 MPa.

  Under such a pressurized state, the control unit 50 detects the pressure between the shutoff valve H100 and the hydrogen pressure regulating valve H10 at a predetermined cycle by the pressure sensor P9, and the pressure change amount or the pressure change after a predetermined time has elapsed. When the rate is equal to or greater than a predetermined leakage determination threshold, it is determined that gas leakage has occurred in the fuel system piping downstream of the shutoff valve H100.

  Since the detection accuracy of the pressure sensor P9 used at this time is higher than the detection accuracy of the pressure sensor P6, and the detection upper limit of the pressure sensor P9 is lower than the detection upper limit of the pressure sensor P6, from the shutoff valve H100 to the hydrogen pressure regulating valve H10. It is possible to detect the gas leak during the period of time in a short time with high accuracy, and it is possible to shorten the startup time of the system accompanied by the gas leak determination.

  In the above embodiment, the pressurization value of the fuel supply path 74 at the time of starting the system is controlled based on the pressure control values of the hydrogen pressure control valves H9 and H10. However, the pressure control values of the hydrogen pressure control valves H10 and H11 further downstream are controlled. You may make it control the pressurization value of the fuel supply path 74 on the basis of a pressure value. In this case, gas leak detection is performed using the pressure sensor P10 whose detection upper limit is lower than that of the pressure sensor P9, so that more accurate gas leak detection is possible.

1 is a system configuration diagram schematically illustrating an embodiment of a fuel cell system according to the present invention. It is a figure for demonstrating the pressure control at the time of the gas leak detection by the control part shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Fuel cell system, H9 ... Hydrogen pressure regulation valve (1st pressure regulation valve), H10 ... Hydrogen pressure regulation valve (2nd pressure regulation valve), H100 ... Shut-off valve (main stop valve), P6 ... Pressure sensor (1st Pressure sensor), P9 ... Pressure sensor (second pressure sensor), 20 ... Fuel cell, 30 ... Hydrogen supply source (fuel supply source, high-pressure hydrogen tank), 50 ... Control unit (gas leak detection means), 74 ... Fuel Supply path, 75 ... Hydrogen circulation path

Claims (3)

A fuel supply source for supplying fuel to the fuel cell;
A main stop valve provided downstream of the fuel supply source;
A first pressure regulating valve provided downstream of the main stop valve;
A second pressure regulating valve provided downstream of the first pressure regulating valve;
A first pressure sensor provided between the main stop valve and the first pressure regulating valve;
A fuel cell system comprising: a second pressure sensor provided between the first pressure regulating valve and the second pressure regulating valve and having a lower detection upper limit than the first pressure sensor,
Gas leakage detection based on the detection result of the second pressure sensor while pressurizing to a value equal to or less than the pressure regulation value of the first pressure regulating valve and above the pressure regulation value of the second pressure regulating valve at the time of system startup A fuel cell system comprising gas leak detection means for performing   The fuel cell system according to claim 1, wherein the fuel supply source is a high-pressure hydrogen tank. A fuel supply source for supplying fuel to the fuel cell, a main stop valve provided downstream of the fuel supply source, a first pressure regulating valve provided downstream of the main stop valve, and the first pressure regulating valve A second pressure regulating valve provided downstream, a first pressure sensor provided between the main stop valve and the first pressure regulating valve, the first pressure regulating valve and the second pressure regulating valve. A gas leak detection method for a fuel cell system, comprising: a second pressure sensor provided between a pressure valve and a lower detection upper limit than the first pressure sensor,
Gas leakage detection based on the detection result of the second pressure sensor while pressurizing to a value equal to or less than the pressure regulation value of the first pressure regulating valve and above the pressure regulation value of the second pressure regulating valve at the time of system startup A gas leak detection method for a fuel cell system.

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