JP2009140658A - Fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve accuracy of gas leakage detection while adopting comparatively simple control in a fuel cell system having an opening and closing valve for adjusting supply pressure of a fuel gas and a discharge valve for discharging impurities in the system to the outside. <P>SOLUTION: The fuel cell system 1 includes: a fuel cell 2; a supply passage 22 for flowing the fuel gas supplied from a fuel supply source 21 to the fuel cell 2; a discharge passage 23 for flowing the gas discharged from the fuel cell 2; the discharge valve 31 for discharging the gas in the discharge passage 23 to the outside; and the opening and closing valve 28 driven and controlled at designated driving intervals so as to supply at a downstream side by adjusting a gas condition at an upstream side of the supply passage 22. The fuel cell system 1 further includes a gas leakage detection means for detecting gas leakage of the discharge valve 31 based on the gas condition at a downstream side of the opening and closing valve at one driving interval period of the opening and closing valve 28. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a fuel cell system.

  2. Description of the Related Art Conventionally, a fuel cell system including a fuel cell that generates power by receiving a supply of reaction gas (fuel gas and oxidizing gas) has been proposed and put into practical use. Impurities such as nitrogen and carbon monoxide accumulate over time in the fuel cell of such a fuel cell system and in the circulation path of the fuel off gas with power generation. In order to discharge such impurities to the outside, a discharge valve connected to the circulation flow path is provided with a discharge valve, and by opening and closing the discharge valve, the gas in the circulation flow path is discharged at regular intervals. A technique for purging (purge technique) has been proposed.

At present, various techniques for detecting a gas leak in a discharge valve (or a flow path including the discharge valve) have been proposed. For example, in recent years, based on the amount of fuel gas supplied to the fuel cell, the amount of fuel gas consumed in the fuel cell, and the pressure change of the fuel gas in the detection target flow path (flow path including the discharge valve) A technique for detecting leakage has been proposed (see Patent Document 1).
JP 2006-179469 A

  By the way, in a fuel cell system equipped with an electromagnetic on-off valve for adjusting the supply pressure of fuel gas, in order to reduce noise caused by the on-off operation of the on-off valve, the driving cycle of the on-off valve during low load operation is set. There is a case where control is set to be longer than the drive cycle during normal operation. If the drive cycle of the on-off valve is set to be long in this way, the change in the pressure of the fuel gas in the flow path becomes large. Therefore, even if the conventional technique as described in Patent Document 1 is adopted, highly accurate gas leak detection May be difficult to achieve.

  In addition, if the above-described conventional technology is used to achieve highly accurate gas leak detection, it is necessary to constantly monitor the power generation current of the fuel cell and the gas pressure change in the flow path, which makes the control extremely complicated. There was a problem of becoming.

  The present invention has been made in view of such circumstances, and in a fuel cell system comprising an on-off valve for adjusting the supply pressure of fuel gas and a discharge valve for discharging impurities in the system to the outside An object of the present invention is to improve the accuracy of gas leak detection of the discharge valve while adopting relatively simple control.

  In order to achieve the above object, a fuel cell system according to the present invention comprises a fuel cell, a supply channel for flowing fuel gas supplied from a fuel supply source to the fuel cell, and a gas discharged from the fuel cell. A discharge channel for flowing, a discharge valve for discharging the gas in the discharge channel to the outside, and a predetermined driving cycle so as to adjust the gas state on the upstream side of the supply channel and supply it to the downstream side A fuel cell system comprising a gas leakage detection means for detecting gas leakage from the discharge valve based on a gas state downstream of the on-off valve during one drive cycle of the on-off valve It is.

  When such a configuration is adopted, it is possible to detect a gas leak from the discharge valve based on the gas state downstream of the opening / closing valve during one driving cycle of the opening / closing valve. Since the gas state necessary for gas leak detection can be detected (calculated) with high accuracy during one drive cycle of the on-off valve, the gas leak detection accuracy can be increased with relatively simple control. . The “gas state” means a gas state represented by a flow rate, pressure, temperature, molar concentration, or the like. The “gas state downstream of the on-off valve” includes the amount of gas supplied from the on-off valve to the fuel cell, the amount of gas consumed in the fuel cell, the gas pressure value on the downstream side of the on-off valve of the supply channel, etc. To do.

  The fuel cell system includes a control unit that controls driving of the on-off valve by sending a drive permission command for each drive cycle, and employs a gas leak detection unit that starts gas leak detection from the time when the drive permission command is sent. can do.

  In the fuel cell system, the gas supply amount (gas supply amount from the on-off valve to the fuel cell) during one driving cycle, the gas consumption amount (gas consumption amount in the fuel cell) during one driving cycle, and the gas pressure The gas leakage amount is calculated by subtracting the gas remaining amount in the flow path calculated from the value (the gas pressure value downstream of the on-off valve of the supply flow path), and the calculated gas leakage amount reaches a predetermined threshold value. A gas leak detection means that determines that a gas leak has occurred when the value exceeds the limit can be employed.

  Further, in the fuel cell system, when the gas pressure value (the gas pressure value on the downstream side of the on-off valve of the supply channel) does not reach the predetermined pressure value when the predetermined time has elapsed from the gas leak detection start time, It is also possible to employ a gas leak detection means that determines that the gas has occurred.

  When this configuration is adopted, the gas leak amount from the discharge valve opens and closes when the gas pressure value on the downstream side of the on-off valve does not increase (not reach the predetermined pressure value) even after a predetermined time has elapsed since the start of gas leak detection. It is estimated that the amount of gas supplied from the valve is exceeded, and it can be determined that a gas leak has occurred.

  In the fuel cell system, an injector can be employed as an on-off valve.

  An injector is an electromagnetically driven opening and closing that can adjust the gas state (gas flow rate and gas pressure) by driving the valve body directly with a predetermined driving cycle with electromagnetic driving force and separating it from the valve seat It is a valve. The predetermined control unit drives the valve body of the injector to control the fuel gas injection timing and injection time, whereby the flow rate and pressure of the fuel gas can be controlled with high accuracy.

  According to the present invention, a relatively simple control is employed in a fuel cell system including an on-off valve for adjusting the supply pressure of fuel gas and a discharge valve for discharging impurities in the system to the outside. However, it is possible to improve the gas leak detection accuracy of the discharge valve.

  Hereinafter, a fuel cell system 1 according to an embodiment of the present invention will be described with reference to the drawings. In the present embodiment, an example in which the present invention is applied to an on-vehicle power generation system of a fuel cell vehicle (moving body) will be described.

  First, the structure of the fuel cell system 1 according to the embodiment of the present invention will be described with reference to FIGS. As shown in FIG. 1, the fuel cell system 1 according to the present embodiment includes a fuel cell 2 that generates electric power upon receiving supply of reaction gases (oxidizing gas and fuel gas), and air as oxidizing gas to the fuel cell 2. Supplying oxidant gas piping system 3, fuel gas piping system 4 for supplying hydrogen gas as fuel gas to the fuel cell 2, refrigerant piping system 5 for supplying the refrigerant to the fuel cell 2 and cooling the fuel cell 2, and system power Power system 6 for charging / discharging, and a control unit 7 for controlling the entire system.

  The fuel cell 2 is formed of, for example, a solid polymer electrolyte type and has a stack structure in which a large number of single cells are stacked. The unit cell of the fuel cell 2 has a pair of separators having an air electrode on one surface of an electrolyte made of an ion exchange membrane, a fuel electrode on the other surface, and further sandwiching the air electrode and the fuel electrode from both sides. have. The fuel gas is supplied to the fuel gas flow path of one separator and the oxidizing gas is supplied to the oxidizing gas flow path of the other separator, and the fuel cell 2 generates electric power by this gas supply. The fuel cell 2 is provided with a current sensor 2a for detecting a current during power generation.

  The oxidizing gas piping system 3 has an air supply passage 11 through which oxidizing gas supplied to the fuel cell 2 flows, and an exhaust passage 12 through which oxidizing off-gas discharged from the fuel cell 2 flows. The air supply flow path 11 is provided with a compressor 14 that takes in the oxidizing gas via the filter 13 and a humidifier 15 that humidifies the oxidizing gas fed by the compressor 14. The oxidizing off-gas flowing through the exhaust passage 12 is subjected to moisture exchange by the humidifier 15 through the back pressure adjusting valve 16, and is finally exhausted into the atmosphere outside the system as exhaust gas. The compressor 14 takes in the oxidizing gas in the atmosphere by driving a motor (not shown).

  The fuel gas piping system 4 includes a hydrogen supply source 21, a hydrogen supply passage 22 through which hydrogen gas supplied from the hydrogen supply source 21 to the fuel cell 2 flows, and a gas discharged from the fuel cell 2 through the hydrogen supply passage 22. A circulation flow path 23 for returning to the confluence point A1, a hydrogen pump 24 for pumping the gas in the circulation flow path 23 to the hydrogen supply flow path 22, and an exhaust / drain flow path 25 branched and connected to the circulation flow path 23. ,have.

  The hydrogen supply source 21 corresponds to the fuel supply source in the present invention, and is constituted by, for example, a high-pressure tank or a hydrogen storage alloy, and is configured to store high-pressure hydrogen gas. When a shut-off valve 26 described later is opened, hydrogen gas flows out from the hydrogen supply source 21 into the hydrogen supply flow path 22. The hydrogen gas is finally depressurized to a predetermined low pressure by a regulator 27 and an injector 28 described later, and is supplied to the fuel cell 2. The hydrogen supply source 21 is composed of a reformer that generates a hydrogen-rich reformed gas from a hydrocarbon-based fuel and a high-pressure gas tank that stores the reformed gas generated by the reformer in a high-pressure state. May be. In addition, a tank having a hydrogen storage alloy can be employed as the hydrogen supply source 21.

  The hydrogen supply flow path 22 is provided with a shutoff valve 26 that shuts off or allows the supply of hydrogen gas from the hydrogen supply source 21, a regulator 27 that adjusts the pressure of the hydrogen gas, and an injector 28. A pressure sensor 29 that detects the pressure and temperature of the hydrogen gas in the hydrogen supply channel 22 is located downstream of the injector 28 and upstream of the junction A1 between the hydrogen supply channel 22 and the circulation channel 23. A temperature sensor (not shown) is provided. Further, on the upstream side of the injector 28, a pressure sensor and a temperature sensor (not shown) for detecting the pressure and temperature of the hydrogen gas in the hydrogen supply flow path 22 are provided. Information relating to the gas state (pressure, temperature) of the hydrogen gas detected by the pressure sensor 29 or the like is used for various controls.

  The regulator 27 is a device that regulates the upstream pressure (primary pressure) to a preset secondary pressure. In this embodiment, a mechanical pressure reducing valve that reduces the primary pressure is employed as the regulator 27. The mechanical pressure reducing valve has a structure in which a back pressure chamber and a pressure adjusting chamber are formed with a diaphragm therebetween, and the primary pressure is reduced to a predetermined pressure in the pressure adjusting chamber by the back pressure in the back pressure chamber. Thus, a publicly known configuration for the secondary pressure can be employed. In the present embodiment, as shown in FIG. 1, the upstream pressure of the injector 28 can be effectively reduced by arranging two regulators 27 on the upstream side of the injector 28. For this reason, the design freedom of the mechanical structure (a valve body, a housing, a flow path, a drive device, etc.) of the injector 28 can be increased. In addition, since the upstream pressure of the injector 28 can be reduced, it is possible to prevent the valve body of the injector 28 from becoming difficult to move due to an increase in the differential pressure between the upstream pressure and the downstream pressure of the injector 28. be able to. Therefore, it is possible to widen the adjustable pressure width of the downstream pressure of the injector 28 and to suppress a decrease in responsiveness of the injector 28.

  The injector 28 is an electromagnetically driven on-off valve capable of adjusting the gas flow rate and gas pressure by driving the valve body directly with a predetermined driving cycle with an electromagnetic driving force and separating it from the valve seat. The injector 28 includes a valve seat having an injection hole for injecting gaseous fuel such as hydrogen gas, a nozzle body for supplying and guiding the gaseous fuel to the injection hole, and an axial direction (gas flow direction) with respect to the nozzle body. And a valve body that is movably accommodated and opens and closes the injection hole. In the present embodiment, the valve body of the injector 28 is driven by a solenoid that is an electromagnetic drive device, and the opening area of the injection hole is made two or more stages by turning on and off the pulsed excitation current supplied to the solenoid. It can be switched. By controlling the gas injection time and gas injection timing of the injector 28 by the control signal output from the control unit 7, the flow rate and pressure of the hydrogen gas are controlled with high accuracy. The injector 28 directly opens and closes the valve (valve body and valve seat) with an electromagnetic driving force, and has a high responsiveness because its driving cycle can be controlled to a highly responsive region.

  Injector 28 changes downstream by changing at least one of the opening area (opening) and opening time of the valve provided in the gas flow path of injector 28 in order to supply the required gas flow rate downstream. The gas flow rate (or hydrogen molar concentration) supplied to the side (fuel cell 2 side) is adjusted. Since the gas flow rate is adjusted by opening and closing the valve body of the injector 28 and the gas pressure supplied downstream of the injector 28 is reduced from the gas pressure upstream of the injector 28, the injector 28 is controlled by a pressure regulating valve (pressure reducing valve, regulator). ). Further, in the present embodiment, a variable pressure control valve capable of changing the pressure adjustment amount (pressure reduction amount) of the upstream gas pressure of the injector 28 so as to match the required pressure within a predetermined pressure range according to the gas requirement. Can also be interpreted.

  In the present embodiment, as shown in FIG. 1, the injector 28 is disposed upstream of the junction A <b> 1 between the hydrogen supply channel 22 and the circulation channel 23. Further, as shown by a broken line in FIG. 1, when a plurality of hydrogen supply sources 21 are employed as the fuel supply source, a portion where the hydrogen gas supplied from each hydrogen supply source 21 merges (hydrogen gas merge portion A2). In addition, the injector 28 is arranged on the downstream side.

  An exhaust / drain channel 25 is connected to the circulation channel 23 via a gas / liquid separator 30 and an exhaust / drain valve 31. The gas-liquid separator 30 collects moisture from the hydrogen off gas. The exhaust / drain valve 31 is operated according to a command from the control unit 7 to discharge (purge) the moisture collected by the gas-liquid separator 30 and the gas containing impurities in the circulation passage 23 to the outside. It is. By opening the exhaust / drain valve 31, the concentration of impurities in the gas in the circulation passage 23 decreases, and the concentration of hydrogen in the circulated gas increases. The circulation flow path 23 is an embodiment of the discharge flow path in the present invention, and the exhaust / drain valve 31 is an embodiment of the discharge valve in the present invention.

  The gas discharged through the exhaust / drain valve 31 and the exhaust / drain passage 25 is diluted by a diluter (not shown) and merges with the gas in the exhaust passage 12. The hydrogen pump 24 circulates and supplies the hydrogen gas in the circulation system to the fuel cell 2 by driving a motor (not shown). The hydrogen gas circulation system is constituted by a downstream channel of the junction A1 of the hydrogen supply channel 22, a fuel gas channel formed in the separator of the fuel cell 2, and a circulation channel 23. Become.

  The refrigerant piping system 5 includes a refrigerant channel 41 communicating with the cooling channel in the fuel cell 2, a cooling pump 42 provided in the refrigerant channel 41, and a radiator 43 that cools the refrigerant discharged from the fuel cell 2. ,have. The cooling pump 42 circulates and supplies the refrigerant in the refrigerant channel 41 to the fuel cell 2 by driving a motor (not shown).

  The power system 6 includes a high-voltage DC / DC converter 61, a battery 62, a traction inverter 63, a traction motor 64, various auxiliary machine inverters not shown, and the like. The high-voltage DC / DC converter 61 is a direct-current voltage converter that adjusts the direct-current voltage input from the battery 62 and outputs it to the traction inverter 63 side, and the direct-current input from the fuel cell 2 or the traction motor 64. And a function of adjusting the voltage and outputting it to the battery 62. The charge / discharge of the battery 62 is realized by these functions of the high-voltage DC / DC converter 61. Further, the output voltage of the fuel cell 2 is controlled by the high voltage DC / DC converter 61.

  The battery 62 is configured such that battery cells are stacked and a constant high voltage is used as a terminal voltage, and surplus power can be charged or power can be supplementarily supplied under the control of a battery computer (not shown). The traction inverter 63 converts a direct current into a three-phase alternating current and supplies it to the traction motor 64. The traction motor 64 is a three-phase AC motor, for example, and constitutes a main power source of a vehicle on which the fuel cell system 1 is mounted. The auxiliary inverter is an electric motor control unit that controls driving of each motor, converts a direct current into a three-phase alternating current, and supplies the three-phase alternating current to each motor. The auxiliary inverter is, for example, a pulse width modulation type PWM inverter, which converts the DC voltage output from the fuel cell 2 or the battery 62 into a three-phase AC voltage in accordance with a control command from the control unit 7 and is generated by each motor. To control the rotational torque.

  The control unit 7 detects an operation amount of an operation member (accelerator or the like) for acceleration provided in the vehicle, and receives control information such as an acceleration request value (for example, a required power generation amount from a load device such as the traction motor 64). To control the operation of various devices in the system. In addition to the traction motor 64, the load device is an auxiliary device necessary for operating the fuel cell 2 (for example, each motor of the compressor 14, the hydrogen pump 24, the cooling pump 42, etc.), and is involved in traveling of the vehicle. It is a collective term for power consumption devices including actuators used in various devices (transmissions, wheel control units, steering devices, suspension devices, etc.), air conditioners (air conditioners) for passenger spaces, lighting, audio, and the like.

  The control unit 7 is configured by a computer system (not shown). Such a computer system includes a CPU, a ROM, a RAM, an HDD, an input / output interface, a display, and the like. When the CPU reads various control programs recorded in the ROM and executes desired calculations, various processes are performed. And do control.

  Specifically, as shown in FIG. 2, the control unit 7 determines the flow rate of hydrogen gas consumed by the fuel cell 2 (hereinafter referred to as “hydrogen consumption”) based on the generated current value of the fuel cell 2 detected by the current sensor 2a. (Referred to as “amount”) (fuel consumption calculation function: B1). In the present embodiment, the hydrogen consumption is calculated and updated every calculation cycle of the control unit 7 using a specific calculation expression representing the relationship between the generated current value and the hydrogen consumption.

  The control unit 7 calculates a target pressure value at a downstream position of the injector 28 of hydrogen gas supplied to the fuel cell 2 based on the generated current value of the fuel cell 2 (target pressure value calculation function: B2). The target purge amount (target discharge amount of hydrogen off-gas from the exhaust / drain valve 31) is calculated. In the present embodiment, the target pressure value and the target purge amount are calculated for each calculation cycle of the control unit 7 using a specific map representing the relationship between the generated current value, the target pressure value, and the target purge amount.

  The control unit 7 calculates a deviation between the calculated target pressure value and the pressure value (detected pressure value) at the downstream position of the injector 28 detected by the pressure sensor 29 (pressure difference calculation function: B3). And the control part 7 calculates the hydrogen gas flow volume (feedback correction flow volume) added to hydrogen consumption in order to reduce the calculated deviation (correction flow volume calculation function: B4). The control unit 7 calculates the injection flow rate of the injector 28 by adding the hydrogen consumption amount and the feedback correction flow rate (injection flow rate calculation function: B5).

Then, the control unit 7 calculates the injection time of the injector 28 based on the calculated injection flow rate and drive cycle, and outputs a control signal for realizing this injection time, whereby the gas injection time and gas of the injector 28 are output. The injection timing is controlled to adjust the flow rate and pressure of the hydrogen gas supplied to the fuel cell 2. At this time, the control unit 7 controls driving of the injector 28 by sending a drive permission command (valve opening command) for each drive cycle. That is, the control unit 7 functions as a control unit in the present invention. Here, the drive cycle, as shown in FIG. 3 (A), means the period t ₀ of the stepped (on-off) waveform representing the open or closed state of the injection hole of the injector 28. In the present embodiment, the drive cycle is calculated and updated for each calculation cycle of the control unit 7 using a specific map representing the relationship between the operation state of the system and the drive cycle.

Further, the control unit 7 performs the feedback control of the injector 28 described above and simultaneously controls the opening / closing of the exhaust / drain valve 31 to discharge moisture and gas in the circulation passage 23 from the exhaust / drain valve 31 to the outside. . At this time, the control unit 7 calculates the purge amount (total discharge amount) Q of the gas from the exhaust / drain valve 31 based on the change in the gas supply state from the injector 28 (purge amount calculation function: B6), and calculates it. It is determined whether or not the purge amount Q is equal to or greater than a predetermined target purge amount Q ₀ (purge amount deviation determination function: B7). The control unit 7 opens the exhaust drain valve 31 when the calculated purge amount Q is less than the target purge amount Q ₀ , and exhausts when the calculated purge amount Q is equal to or greater than the target purge amount Q _0. The drain valve 31 is closed (purge control function: B8).

Further, the control unit 7 detects a gas leak from the exhaust / drain valve 31 based on the gas state downstream of the injector 28. Specifically, the control unit 7 determines the hydrogen gas in the fuel cell 2 within the predetermined detection time t from the total injection amount (gas supply amount Q _INJ ) of hydrogen gas from the injector 28 to the fuel cell 2 within the predetermined detection time t. The gas leakage amount Q _{L is} obtained by subtracting the total consumption amount of gas (gas consumption amount Q _FC ) from the residual gas amount QΔ _P in the circulation system flow path calculated from the pressure value of the hydrogen gas downstream of the injector 28. Is calculated, and it is determined that a gas leak has occurred when the calculated gas leak amount Q _L exceeds a predetermined threshold (gas leak detection function: B9). That is, the control unit 7 also functions as a gas leak detection unit in the present invention.

Here, the gas supply amount Q _INJ (NL / min), the gas consumption amount Q _FC (NL / min), and the residual gas amount QΔ _P (NL / min) within the predetermined detection time t (s) are as follows: It is calculated by formula (A) to formula (C). Further, the gas leakage amount Q _L (NL / min) within the predetermined detection time t (s) is calculated by the equation (D).

In the formula (A), N means the number of injections of the injector 28, and V _INJ (NL / injection) means the injection amount at each injection (each drive cycle) of the injector 28. Wherein in _{(B), t C (s} ) control cycle of the controller 7 (t _C <t _{0) means, V FC (NL / t C} ) each control cycle of the control unit 7 t _C (s) Means the consumption of hydrogen gas in In the formula (C), k (= 1 / 101.3) means a unit conversion coefficient, and V (L) is the volume of the circulation system channel (the downstream channel of the confluence A1 of the hydrogen supply channel 22 and the fuel). Means the volume of the flow path formed by the fuel gas flow path formed in the separator of the battery 2 and the circulation flow path 23, and T (° C.) is hydrogen on the downstream side of the injector 28 of the hydrogen supply flow path 22. It means the temperature of the gas. In the formula (C), P ₁ (kPa.abs) means the pressure value of the hydrogen gas downstream of the injector 28 detected by the pressure sensor 29 at the start of the predetermined detection time t, and P ₂ (kPa.abs ) Means the pressure value of the hydrogen gas downstream of the injector 28 detected by the pressure sensor 29 at the end of the predetermined detection time t.

The control unit 7 in the present embodiment starts gas leak detection from the time when the drive permission command for the injector 28 is sent, and detects gas leak from the exhaust / drain valve 31 during one drive cycle t ₀ of the injector 28. Specifically, the control unit 7, as shown in FIG. 3 (A) ~ (C) , from the time when the driving permission command of the injector 28 has been sent (the beginning of the driving period t ₀₎ of the driving period t ₀ The gas supply amount Q _INJ and the gas consumption amount Q _FC are calculated until the end. The control unit 7, as shown in FIG. 3 (A) and FIG. 3 (D), the a time when the drive permission command of the injector 28 has been sent (the beginning of the driving period t _0), the driving period t ₀ and end, both to detect the downstream pressure P _1, P ₂ of the injector 28 in the, to calculate the gas residual amount Qderuta _P of circulation flow path by using these values. Then, a gas leak determination is performed by calculating the gas leak amount Q _L in the drive cycle t ₀ .

As shown in FIG. 3D, since the downstream pressures P ₁ and P ₂ of the injector 28 at the start time and end time of the driving cycle t ₀ are substantially the same value, the values (C the value of gas residual amount Qderuta _P calculated based on) is substantially zero. Therefore, the calculation error of the gas leakage amount Q _L due to the deviation of the downstream pressure of the injector 28 at the start time and end time of the detection time can be suppressed as much as possible. Control unit 7, thus to detect a gas leakage from the water discharge valve 31 in between first drive period t ₀ of the injector 28, it is possible to accurately calculate the amount of gas leakage Q _L, a gas leakage determination accuracy Can be improved.

  In addition, when the pressure value on the downstream side of the injector 28 does not reach the predetermined pressure value when a predetermined time (for example, several seconds) has elapsed since the gas leak detection start time, the control unit 7 It is estimated that the amount of leakage exceeds the amount of gas supplied from the injector 28, and it is determined that a gas leak has occurred.

  Next, an operation method of the fuel cell system 1 according to the present embodiment will be described using the flowchart of FIG.

  During normal operation of the fuel cell system 1, hydrogen gas is supplied from the hydrogen supply source 21 to the fuel electrode of the fuel cell 2 through the hydrogen supply channel 22, and the air whose humidity has been adjusted is supplied to the air supply channel 11. Is supplied to the oxidation electrode of the fuel cell 2 through the electric power to generate electricity. At this time, electric power (required electric power) to be drawn from the fuel cell 2 is calculated by the control unit 7, and hydrogen gas and air in amounts corresponding to the amount of power generation are supplied into the fuel cell 2. In the present embodiment, during such normal operation, feedback control of the injector 28 is performed, and gas leakage from the exhaust / drain valve 31 is detected.

  First, as shown in the flowchart of FIG. 4, the control unit 7 of the fuel cell system 1 detects a current value during power generation of the fuel cell 2 using the current sensor 2a (current detection step: S1). Next, the control unit 7 calculates the hydrogen consumption in the fuel cell 2 based on the detected current value (hydrogen consumption calculation step: S2), and downstream of the injector 28 for the hydrogen gas supplied to the fuel cell 2. A target pressure value at the position is calculated (target pressure value calculating step: S3).

  Next, the control unit 7 detects the pressure value on the downstream side of the injector 28 using the pressure sensor 29 (pressure value detection step: S4). Next, the control unit 7 adds to the hydrogen consumption in order to reduce the deviation between the target pressure value calculated in the target pressure value calculation step S3 and the pressure value (detected pressure value) detected in the pressure value detection step S4. The hydrogen gas flow rate (feedback correction flow rate) is calculated, and the hydrogen consumption amount and the feedback correction flow rate are added to calculate the injection flow rate of the injector 28 (injection flow rate calculation step: S5). And the control part 7 calculates the injection time of the injector 28 based on this injection flow rate and a drive period, and outputs the control signal for implement | achieving this injection time, The gas injection time and gas injection of the injector 28 are output. The timing is controlled to adjust the flow rate and pressure of the hydrogen gas supplied to the fuel cell 2 (feedback control step: S6).

The control unit 7 detects a gas leak from the exhaust / drain valve 31 while realizing the feedback control step S6 described above. The controller 7 determines whether or not gas leak detection is possible (leak detection permission determination step: S7). In the present embodiment, a drive permission command for the injector 28 is sent, and the hydrogen gas pressure value downstream of the injector 28 continues a predetermined reference pressure value (for example, P ₀ in FIG. _3D ) for a predetermined time. If it falls below, it is determined that gas leak detection is possible.

When it is determined that the leak detection is not possible in the leak detection permission determination step S7, the control unit 7 ends the control operation without passing through the subsequent steps. On the other hand, when it is determined that the gas leakage detection is possible in the leakage detection permission determination step S7, the control unit 7 starts the gas leakage detection from the time when the drive permission command for the injector 28 is sent. A gas leakage amount Q _L (gas supply amount Q _INJ , gas consumption amount Q _FC , gas residual amount QΔ _P ) is calculated during one drive cycle t ₀ (gas leakage amount calculation step: S8). Then, the control unit 7 detects whether or not the calculated gas leakage amount Q _L exceeds a predetermined threshold value, or the state where the downstream pressure value of the injector 28 does not reach the predetermined pressure value (pressure drop state). It is determined whether or not the predetermined time has elapsed from the start time (gas leak determination step: S9).

When the control unit 7 determines in the gas leak determination step S9 that the gas leak amount Q _L exceeds a predetermined threshold (or the pressure drop state continues for a predetermined time from the start of gas leak detection), the exhaust drainage It is determined that a gas leak has occurred in the valve 31, a predetermined process is performed (gas leak process step: S10), and the control operation is terminated. On the other hand, when the control unit 7 determines in the gas leakage determination step S9 that the gas leakage amount Q _L is less than or equal to a predetermined threshold and the pressure drop state has not continued for a predetermined time from the start of gas leakage detection. In this case, it is determined that no gas leakage has occurred in the exhaust / drain valve 31, and the control operation is terminated as it is.

  In the fuel cell system 1 according to the embodiment described above, it is possible to detect a gas leak from the exhaust / drain valve 31 based on the gas state downstream of the injector 28 during one drive cycle of the injector 28. Since the gas state necessary for gas leak detection can be detected (calculated) with high accuracy during one drive cycle of the injector 28, the gas leak detection accuracy can be increased with relatively simple control. .

  Further, in the fuel cell system 1 according to the embodiment described above, when the gas pressure value on the downstream side of the injector 28 does not increase (does not reach the predetermined pressure value) even if a predetermined time elapses from the gas leak detection start time. The gas leakage from the exhaust drain valve 31 can be estimated to exceed the gas supply from the injector 28, and it can be determined that a gas leak has occurred.

  In the above embodiment, an example in which the hydrogen pump 24 is provided in the circulation flow path 23 has been described. However, an ejector may be employed instead of the hydrogen pump 24. Moreover, in the above embodiment, although the example which provided the exhaust drainage valve 31 which implement | achieves both exhaust_gas | exhaustion and waste_water | drain in the circulation flow path 23 was shown, the water | moisture content collect | recovered with the gas-liquid separator 30 is discharged | emitted outside. A drain valve and an exhaust valve for discharging the gas in the circulation channel 23 to the outside can be provided separately, and the drain valve and the exhaust valve can be controlled separately by the control unit 7.

  In the above embodiment, the example in which the shutoff valve 26 and the regulator 27 are provided in the hydrogen supply flow path 22 has been described. However, the injector 28 functions as a variable pressure control valve and shuts off the supply of hydrogen gas. Therefore, it is not always necessary to provide the shut-off valve 26 and the regulator 27. Therefore, when the injector 28 is employed, the shutoff valve 26 and the regulator 27 can be omitted, and the system can be reduced in size and cost.

  Moreover, in the above embodiment, although the example which set the hydrogen consumption and the target pressure value based on the electric power generation current value of the fuel cell 2 was shown, the other physical quantity (fuel cell 2 which shows the driving | running state of the fuel cell 2 was shown. The generated voltage value, the generated power value, the temperature of the fuel cell 2, etc.) may be detected, and the hydrogen consumption amount or the target pressure value may be set according to the detected physical quantity. Further, whether the fuel cell 2 is in a stopped state, in an operating state at the time of startup, in an operating state immediately before entering an intermittent operation, in an operating state immediately after recovering from an intermittent operation, or in a normal operating state It is also possible for the control unit to determine whether or not there is an operating state, and to set a hydrogen consumption amount or the like according to these operating states.

  Further, in each of the above embodiments, an example in which the fuel cell system according to the present invention is mounted on a fuel cell vehicle has been shown. Such a fuel cell system can also be mounted. Further, the fuel cell system according to the present invention may be applied to a stationary power generation system used as a power generation facility for a building (house, building, etc.).

1 is a configuration diagram of a fuel cell system according to an embodiment of the present invention. It is a control block diagram for demonstrating the control aspect of the control part of the fuel cell system shown in FIG. 2 is a time chart for explaining a gas leakage determination function of a control unit of the fuel cell system shown in FIG. 1, wherein (A) shows a time history of an injector drive permission command, and (B) shows a gas supply amount from the injector. (C) shows the time history of gas consumption in the fuel cell, and (D) shows the time history of the pressure downstream of the injector. 2 is a flowchart for explaining a gas leak determination method for an exhaust / drain valve of the fuel cell system shown in FIG. 1.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Fuel cell system, 2 ... Fuel cell, 7 ... Control part (control means, gas leak detection means), 21 ... Hydrogen supply source (fuel supply source), 22 ... Hydrogen supply flow path (supply flow path), 23 ... Circulating flow path (discharge flow path), 28... Injector (open / close valve), 31... Exhaust drain valve (discharge valve).

Claims (5)

A fuel cell; a supply channel for flowing fuel gas supplied from a fuel supply source to the fuel cell; a discharge channel for flowing gas discharged from the fuel cell; A fuel cell comprising: a discharge valve for discharging gas to the outside; and an on-off valve that is driven and controlled at a predetermined drive cycle so as to adjust the gas state upstream of the supply flow path and supply the gas downstream. In the system,
Gas leak detection means for detecting a gas leak from the discharge valve based on a gas state downstream of the on-off valve during one drive cycle of the on-off valve,
Fuel cell system. A control means for driving and controlling the on-off valve by sending a drive permission command for each drive cycle;
The gas leak detection means starts gas leak detection from the time when the drive permission command is sent.
The fuel cell system according to claim 1. The gas state downstream of the on-off valve includes a gas supply amount from the on-off valve to the fuel cell, a gas consumption amount in the fuel cell, and a gas pressure value on the downstream side of the on-off valve of the supply passage. Including
The gas leak detection means subtracts the gas consumption amount during the one driving cycle and the residual gas amount in the flow path calculated from the gas pressure value from the gas supply amount during the one driving cycle. Calculating the amount of gas leakage, and determining that a gas leakage has occurred when the calculated amount of gas leakage exceeds a predetermined threshold,
The fuel cell system according to claim 1 or 2. The gas leak detection means determines that a gas leak has occurred when the gas pressure value at the time when a predetermined time has elapsed from the gas leak detection start time does not reach the predetermined pressure value.
The fuel cell system according to claim 3. The on-off valve is an injector;
The fuel cell system according to any one of claims 1 to 4.

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