JP5596744B2 - Fuel cell system - Google Patents

Description

  The present invention relates to a fuel cell system including an on-off valve such as an injector in a fuel supply path.

  Patent Document 1 describes that the fuel gas is started in a state where the pressure value of the fuel gas upstream of the injector is lower than the pressure value during normal operation of the fuel cell.

JP 2007-323873 A

  However, in the fuel cell system described in Patent Document 1, when the anode flow path of the fuel cell is replaced with air, and activation is performed in a state where air exists in each of the anode flow path and the cathode flow path, the upstream of the injector When the pressure on the side is lowered, the injection amount of the injector is reduced, and it takes time to replace the anode passage with air from hydrogen, and there is a problem that the fuel cell is exposed to a high potential state for a long time. .

  The present invention solves the above-mentioned conventional problems, and an object of the present invention is to provide a fuel cell system capable of preventing the fuel cell from being exposed to a high potential state for a long time during startup.

The present invention includes a fuel cell having an anode channel for supplying fuel gas to the anode and a cathode channel for supplying oxidant gas to the cathode, a fuel gas introduction channel for introducing fuel gas into the fuel cell, and the fuel Provided in the fuel gas introduction flow path, a fuel off gas extraction flow path for deriving the fuel off gas from the battery, a return flow path for returning the fuel off gas discharged to the fuel off gas discharge flow path to the fuel gas introduction flow path, An ejector that sucks the fuel off-gas through the return channel and mixes it with the fuel gas, and an electron that is provided upstream of the ejector in the fuel gas introduction channel and regulates and supplies the fuel gas to the anode channel A control-type first injector, a fuel gas introduction passage upstream from the first injector, and a fuel gas introduction passage downstream from the ejector are connected to the fuel gas introduction passage. A path flow path, an electronically controlled second injector that is provided in the bypass flow path and supplies fuel gas to the anode flow path, and whether or not the anode flow path has been replaced with an oxidant gas. Anode injector replacement determining means for determining when the fuel cell is activated, and the first injector and the second injector when the anode channel replacement determining means determines that the anode channel has been replaced with an oxidant gas. The target pressure of the fuel gas supplied to the anode flow path is set higher than when the anode flow path is not replaced with the oxidant gas, and the pressure increase range of the fuel gas to the anode flow path is set. It is set to be smaller than the normal power generation, and a fuel gas pressure supply control means for supplying a fuel gas to the anode channel, the fuel gas pressure supply control hand At startup of the fuel cell, open in the reference period is the interval from the previous SL opening start of the first injector as the injection amount of the first injector is larger than the normal power generation to the next open-starting The valve time is made longer than that during normal power generation, and the valve opening time in a reference period that is an interval from the start of opening of the second injector to the start of the next valve opening is limited .

  By the way, when power generation of the fuel cell is stopped, the anode channel is replaced with the oxidant gas, and the fuel cell is started with the oxidant gas present in the anode channel and the cathode channel, the inlet of the anode channel When the fuel gas is supplied from the fuel cell, the difference in the concentration of the fuel gas increases between the inlet side and the outlet side of the anode flow path, and this large concentration difference continues for a long time. The knowledge that the fuel cell has deteriorated for a long time has been obtained.

Therefore, in the present invention, when starting the fuel cell in a state where the anode flow path is replaced with the oxidant gas, the target pressure (supply pressure) of the fuel gas supplied to the anode flow path is set higher than that during normal startup. This facilitates the mixing of the oxidant gas and the fuel gas in the anode flow path, eliminates the difference in fuel gas concentration between the inlet side and the outlet side of the anode flow path at an early stage, and makes the fuel cell have a high potential for a long time. It becomes possible to prevent exposure to the state.
By the way, if the pressure of the fuel gas immediately reaches the target pressure when the fuel cell is started, the supply of the fuel gas is stopped, and the mixing of the oxidant gas and the fuel gas is not promoted. Therefore, by setting a limit on the pressure increase range, it is possible to prevent the fuel gas from being supplied halfway, and the mixing of the oxidant gas and the fuel gas is further promoted, so that the fuel cell is kept in a high potential state for a long time. It is possible to prevent exposure more reliably.
Further, by adopting the electronically controlled first injector and the second injector as the fuel gas pressure supply means, finer control can be performed.

  The state in which the anode flow path is replaced with the oxidant gas when the fuel cell power generation is stopped means that when the fuel gas is supplied to the anode flow path at the next startup of the fuel cell, the inlet side and the outlet side of the anode flow path. This means that there is a difference in fuel gas concentration (high on the inlet side and low on the outlet side).

  The anode flow path replacement determination means determines that the anode flow path has been replaced with an oxidant gas when the power generation stop time before starting the fuel cell is a predetermined time or more, and the fuel gas high pressure supply control The means sets the target pressure higher than the case where the power generation stop time is less than a predetermined time when the anode flow path replacement determination means determines that the anode flow path is replaced with an oxidant gas. And

  According to this, when the power generation stop time is long (when it is longer than the predetermined time), the anode flow path is replaced with the oxidant gas, so that the oxidant gas is in each of the anode flow path and the cathode flow path. By setting the target pressure (supply pressure) of the fuel gas supplied to the anode flow path when starting in the existing state higher than that during normal power generation, the oxidant gas and the fuel gas are mixed in the anode flow path. Mixing is promoted, and it becomes possible to prevent the fuel cell from being exposed to a high potential state for a long time.

  The fuel gas high-pressure supply control means sets the target pressure higher as the power generation stop time of the fuel cell becomes longer.

  According to this, the longer the power generation stop time, the longer it takes to mix the oxidant gas and the fuel gas in the anode flow path, so the target pressure needs to be set higher. Therefore, it is not necessary to set the target pressure unnecessarily (uselessly) by appropriately setting the target pressure.

A connection path that connects the fuel gas introduction flow path downstream from the connection point downstream of the bypass flow path and the fuel off-gas discharge flow path upstream of the connection point upstream of the return flow path; A circulation device that is provided in the connection path and returns the fuel off-gas discharged from the outlet of the anode flow path to the inlet of the anode flow path, and the circulation before the fuel gas is supplied by the fuel gas high-pressure supply control means And a circulation device operation start means for starting the operation of the device.

  According to this, the circulation device is operated prior to the fuel gas pressure supply means to form a gas flow in the anode circulation system (connection path, fuel gas introduction path, fuel off-gas lead-out path), and then a new one is created. By starting the supply of the fuel gas, the mixing of the oxidant gas and the fuel gas can be further promoted.

The fuel gas high-pressure supply control means maintains the valve open state of the first injector .

According to this, mixing the oxidant gas and the fuel gas can be promoted by maintaining the valve opening state of the first injector and continuously supplying the fuel gas, rather than intermittently supplying (intermittently supplying) the fuel gas. .

  ADVANTAGE OF THE INVENTION According to this invention, the fuel cell system which can prevent that a fuel cell is exposed to a high potential state for a long time can be provided.

1 is an overall configuration diagram of a fuel cell system according to an embodiment. (A) is a wave form diagram which shows the relationship between the interval at the time of high voltage | pressure start-up, and valve opening time, (b) is a wave form diagram which shows the relationship between the interval at the time of normal electric power generation, and valve opening time. (A) is a graph which shows the operation example of the anode pressure at the time of high pressure starting, (b) is a graph which shows the operation example of the anode pressure at the time of normal starting. (A) is a map showing the relationship between the anode pressure at start-up and the power generation stop time, and (b) is a relationship map between the differential pressure at the start and power generation stop time. It is a flowchart which shows operation | movement of the fuel cell system which concerns on this embodiment. (A) is a graph showing the relationship between the target pressure at high pressure startup, the valve opening time of the injector, and the anode pressure, and (b) shows the relationship between the target pressure at normal power generation, the valve opening time of the injector, and the anode pressure. It is a graph. It is a time chart which shows the operation example of the fuel cell system which concerns on this embodiment. It is a schematic diagram for demonstrating the high electric potential state at the time of starting in a fuel cell.

  An embodiment of the present invention will be described with reference to FIGS. The fuel cell system 1 according to the present embodiment is mounted on, for example, a fuel cell vehicle (vehicle, moving body) (not shown). The fuel cell vehicle is, for example, an automobile, a tricycle, a motorcycle, a unicycle, a train, or the like. However, the structure mounted in the other mobile body, for example, a ship, an aircraft, may be sufficient. Alternatively, it may be applied to a stationary type for home use or business use.

  As shown in FIG. 1, the fuel cell system 1 includes a fuel cell stack 10, an anode system that supplies and discharges hydrogen (fuel gas and reactive gas) to and from the anode of the fuel cell stack 10, and a cathode of the fuel cell stack 10. A cathode system that supplies / discharges oxygen-containing air (oxidant gas, reactive gas), a power control system that controls power generation of the fuel cell stack 10, and an ECU 60 (Electronic Control Unit, electronic control) that electronically controls them. Device).

  The fuel cell stack 10 is a stack formed by stacking a plurality of solid polymer type single cells 11, and the plurality of single cells 11 are electrically connected in series. The single cell 11 includes an MEA (Membrane Electrode Assembly) and two conductive separators sandwiching the MEA. The MEA includes an electrolyte membrane (solid polymer membrane) made of a monovalent cation exchange membrane and the like, and an anode and a cathode (electrode) that sandwich the membrane.

  The anode and the cathode include a porous body having conductivity such as carbon paper, and a catalyst (Pt or the like) that is supported on the porous body and causes an electrode reaction in the anode and the cathode.

  Each separator is formed with a groove for supplying hydrogen or air to the entire surface of each MEA and a through hole for supplying or discharging hydrogen or air to or from all the single cells 11. It functions as a channel 12 (fuel gas channel) and a cathode channel 13 (oxidant gas channel).

  When hydrogen is supplied to each anode via the anode flow channel 12 and air is supplied to each cathode via the cathode flow channel 13, a potential difference (OCV (Open Circuit Voltage), open circuit) is generated in each single cell 11. Voltage) is generated. Next, when the fuel cell stack 10 and an external circuit such as the motor 41 are electrically connected and current is taken out, the fuel cell stack 10 generates power.

  The cell voltage monitor 15 is a device that detects a cell voltage for each of the plurality of single cells 11 constituting the fuel cell stack 10, and includes a monitor main body and a wire harness that connects the monitor main body and each single cell. .

  The monitor body scans all the single cells 11 at a predetermined period, detects the cell voltage of each single cell 11, and calculates the average cell voltage and the lowest cell voltage. The monitor body (cell voltage monitor 15) outputs an average cell voltage and a minimum cell voltage to the ECU 60.

  The anode system includes a hydrogen tank 21 (fuel gas supply source), a normally closed shut-off valve 22, a first injector 23A (fuel gas pressure supply means: expressed as INJA in FIGS. 1 and 5 to 7), second An injector 23B (fuel gas pressure supply means: expressed as INJBP in FIGS. 1 and 5 to 7), an ejector 24, a check valve 25, a purge valve 26, a hydrogen pump 27, a pressure sensor 28, and the like are provided.

  The first injector 23A and the second injector 23B may be the same type (having the same performance), for example, or the first injector 23A injects hydrogen at a larger flow rate than the second injector 23B. What can be used may be used, or the second injector 23B may be capable of injecting a larger flow rate of hydrogen than the first injector 23A, and can be appropriately changed.

  The hydrogen tank 21 is connected to the inlet 12a of the anode flow path 12 via a pipe 21a, a shutoff valve 22, a pipe 22a, a first injector 23A, a pipe 23a, an ejector 24, and a pipe 24a. The pipe 22a is connected to the pipe 24a via the pipe 22b, the second injector 23B, and the pipe 23b. Then, when the first injector 23A and / or the second injector 23B injects hydrogen with the shut-off valve 22 open, the hydrogen in the hydrogen tank 21 is supplied to the anode flow path 12 through the pipe 21a and the like. It has become.

  A pressure reducing valve (regulator) (not shown) for reducing the hydrogen pressure is provided in the piping 22a upstream from the connection point of the piping 22b. This pressure reducing valve may operate using the cathode system pressure as a pilot pressure, or may be electrically controlled.

  Here, the fuel gas introduction flow path through which the hydrogen supplied to the anode flow path 12 is connected to the inlet 12a of the anode flow path 12 includes a pipe 21a, a pipe 22a, a pipe 23a, a pipe 24a, A pipe 22b and a pipe 23b are provided. The ejector 24 is provided at a connection point between the fuel gas introduction channel and a pipe 25b (connection channel) described later.

  The first injector 23A is provided in the fuel gas introduction flow channel upstream of the connection point (ejector 24). Further, the fuel gas introduction flow path upstream from the first injector 23A and the fuel gas introduction flow path downstream from the ejector 24 are connected, and hydrogen from the hydrogen tank 21 connects the first injector 23A and the ejector 24 with each other. The bypass flow path for bypassing includes a pipe 22b and a pipe 23b. And the 2nd injector 23B is provided in the said bypass flow path.

The hydrogen tank 21 is a tank in which hydrogen is sealed at a high pressure.
The shut-off valve 22 is, for example, an electromagnetically actuated type, and opens and closes according to a command from the ECU 60.

  The first injector 23A and the second injector 23B are electronically controlled by the ECU 60 to inject hydrogen intermittently (intermittently) at normal times, and inject hydrogen continuously for a short time at high pressure startup. Is something that can be done.

  The first injector 23A, the second injector 23B, the shutoff valve 22, the hydrogen pump 27, the air pump 31 and the back pressure valve 33 described later are powered by the fuel cell stack 10 and / or the battery 44 described later.

  The first injector 23A and the second injector 23B are configured by combining known parts such as a housing, a solenoid, a plunger, a compression coil spring, and a nozzle. Since the first injector 23A and the second injector 23B are electronically controlled by the ECU 60, the responsiveness to the command (open command / close command) from the ECU 60 is good, and the controllability is good.

  The ejector 24 injects hydrogen (hydrogen from the first injector 23A) to generate a negative pressure, a nozzle 24b that generates negative pressure, and the hydrogen off and the anode off-gas (fuel off-gas) of the pipe 25a and the pipe 25b sucked at the negative pressure. And a diffuser 24c that mixes and supplies the pipe 24a (the anode flow path 12).

  The outlet 12b of the anode channel 12 is connected to the intake port of the ejector 24 via a pipe 26a, a pipe 25a, a check valve 25, and a pipe 25b. Then, anode offgas (fuel offgas) containing unconsumed hydrogen discharged from the anode channel 12 is returned to the ejector 24 (fuel gas introduction channel).

  The check valve 25 is a valve that prevents the backflow of the anode off gas. The pipe 26a is provided with a gas-liquid separator (not shown) that separates liquid water accompanying the anode off gas.

  The pipe 26a is connected to a diluter 34 described later via a purge valve 26 and a pipe 26b. The purge valve 26 discharges (purges) impurities (water vapor, nitrogen, etc.) contained in the anode off-gas that circulates in the circulation flow path (the anode flow path 12, the pipes 26a, 25a, 25b, 24a) when the fuel cell stack 10 generates power. ), Or when the anode flow path 12 is replaced with hydrogen when the system is started up, the ECU 60 opens it. In the present embodiment, the pipes 26a and 26b correspond to fuel off-gas outlet channels.

  The hydrogen pump 27 is a circulation device that circulates the anode off gas (fuel off gas) discharged from the outlet 12 b of the anode flow path 12 back to the inlet 12 a of the anode flow path 12, and is controlled by a command from the ECU 60.

  The introduction port of the hydrogen pump 27 is connected to the pipe 26a via the pipe 27a, and the pipe 27a is connected upstream of the connection point of the pipe 26a with the pipe 25a. The outlet of the hydrogen pump 27 is connected to the pipe 24a via the pipe 27b, and the pipe 27b is connected to the downstream side of the connection point between the pipe 24a and the pipe 23b.

  The pressure sensor 28 is attached to a pipe 24 a in the vicinity of the inlet 12 a of the anode channel 12. The pressure sensor 28 detects the pressure Pa (substantially equal to the pressure in the anode flow path 12) in the pipe 24a and outputs it to the ECU 60. The pressure sensor 28 may be a pipe 26a in the vicinity of the outlet 12b of the anode channel 12.

  The cathode system includes an air pump 31, a humidifier 32, a back pressure valve 33, a diluter 34, a pressure sensor 35, and the like.

  The discharge port of the air pump 31 is connected to the inlet of the cathode channel 13 via a pipe 31a, a humidifier 32, and a pipe 32a. The air pump 31 is driven by a motor (not shown). When operated according to a command from the ECU 60, the air pump 31 takes in oxygen-containing air and supplies it to the cathode flow path 13.

  The outlet of the cathode channel 13 is connected to a diluter 34 via a pipe 32b, a humidifier 32, a pipe 33a, a back pressure valve 33, and a pipe 33b. Cathode off-gas (oxidant off-gas) from the cathode channel 13 is discharged toward the diluter 34.

  The humidifier 32 includes a hollow fiber membrane (not shown) that is permeable to moisture, and through this hollow fiber membrane, new air from the air pump 31 and a humid cathode off gas from the outlet of the cathode channel 13 Water is exchanged between the two to humidify the new air.

  The back pressure valve 33 is configured by a normally open butterfly valve or the like, and controls the back pressure (the pressure of the cathode channel 13) in accordance with a command from the ECU 60. Incidentally, the cathode pressure Pc can be increased / decreased by controlling the back pressure valve 33 so that the differential pressure between the anode and the cathode does not become too large.

  The diluter 34 is a container that mixes the anode off-gas and the cathode off-gas, and dilutes the hydrogen in the anode off-gas with the cathode off-gas (dilution gas), and has a dilution space therein. The diluted gas is discharged out of the vehicle through the pipe 34a.

  The pressure sensor 35 is attached to a pipe 32 a in the vicinity of the inlet of the cathode channel 13. The pressure sensor 35 detects the pressure Pc in the pipe 32 a (substantially equal to the pressure in the cathode flow path 13) and outputs it to the ECU 60. The pressure sensor 35 may be a pipe 32b in the vicinity of the outlet of the cathode channel 13.

  The power control system includes a motor 41, a PDU 42 (Power Drive Unit), a power controller 43, a battery 44, a contactor 45, and the like. The motor 41 is connected to an output terminal (not shown) of the fuel cell stack 10 via the PDU 42, the power controller 43, and the contactor 45, and the battery 44 is connected to the power controller 43. That is, the motor 41 and the battery 44 are connected in parallel to the power controller 43 (fuel cell stack 10).

  The motor 41 is an electric motor that generates a driving force for running the fuel cell vehicle.

  The PDU 42 is an inverter that converts DC power from the power controller 43 into three-phase AC power and supplies it to the motor 41 in accordance with a command from the ECU 60.

  The power controller 43 has a function of controlling the output (generated power, current value, voltage value) of the fuel cell stack 10 and a function of controlling charging / discharging of the battery 44 in accordance with a command from the ECU 60. Such a power controller 43 includes various electronic circuits such as a DC-DC chopper circuit.

  The battery 44 is a power storage device that charges / discharges electric power, and includes, for example, an assembled battery formed by combining a plurality of lithium ion type cells.

  The contactor 45 is provided between the fuel cell stack 10 and the power controller 43 and includes a switch that connects / disconnects the fuel cell stack 10 and an external load (motor 41, battery 44, etc.). The ECU 60 is opened and closed.

  The IG 51 is a start switch of the fuel cell system 1 (fuel cell vehicle), and is provided around the driver's seat. The IG 51 is connected to the ECU 60, and the ECU 60 detects an ON signal (system start signal) and an OFF signal (system stop signal) of the IG 51.

  The timer 52 measures the power generation stop time of the fuel cell stack 10 from when the OFF signal of the IG 51 is detected to when the ON signal is detected, and outputs the measured power generation stop time to the ECU 60. .

  The ECU 60 is a control device that electronically controls the fuel cell system 1 and includes a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), various interfaces, an electronic circuit, and the like. In accordance with a program stored therein, various devices are controlled and various processes are executed.

  The ECU 60 has a function of controlling the first injector 23A and the second injector 23B by PWM (Pulse Width Modulation). That is, as shown in FIGS. 2A and 2B, the ECU 60 outputs to the first injector 23A and the second injector 23B with respect to an interval (interval from the start of valve opening to the next valve opening start, reference cycle). By changing the ratio of the opening command (valve opening time [Ti value], ON duty), the hydrogen injection amount (flow rate) from the first injector 23A and the second injector 23B and the anode flow path 12 are supplied. It has a function to control the flow rate (total flow rate) of hydrogen.

  FIG. 2 (a) shows the control of the first injector 23A at the time of high-pressure startup of the fuel cell stack 10, which will be described later, and shows a case where the Ti value (valve opening time) is matched with the interval. In this case, hydrogen can be continuously supplied. This state corresponds to maintaining the valve open state of the first injector 23A. In addition, about 2nd injector 23B, opening / closing control is performed by setting Ti value (valve opening time) shorter than an interval, and hydrogen is supplied intermittently. Incidentally, in the present embodiment, the reason why the second injector 23B is not continuously opened is to prevent the anode pressure from excessively increasing.

  FIG. 2B shows the control of the first injector 23A and the second injector 23B during normal power generation, and shows a case where the interval is longer than the Ti value (valve opening time). In this case, hydrogen is intermittently supplied.

  Further, the ECU 60 measures the power generation stop time T of the fuel cell stack 10 after detecting the ON signal of the IG 51 (activation of the fuel cell stack 10), and determines that the power generation stop time T is equal to or longer than a predetermined time. (Anode channel replacement determination means) controls the first injector 23A and the second injector 23B to set the anode pressure Pa (target pressure) higher than when the power generation stop time T is less than the predetermined time (fuel) Gas high pressure supply control means).

  That is, as shown in FIG. 3 (a), when the power generation stop time T is equal to or longer than the predetermined time, the injection amount from the first injector 23A and the second injector 23B is increased, and the target pressure (at the time of high-pressure startup) Is set higher than the operating pressure at the time of normal startup shown in FIG. 3B (when the power generation stop time T is less than the predetermined time). For example, the anode pressure Pa (target pressure) is increased by setting the Ti value (valve opening time, injection amount) of the first injector 23A and the second injector 23B larger than those during normal power generation shown in FIG. be able to.

  Further, as shown in FIG. 4A, the target pressure (anode pressure Pa) at the start-up when the power generation stop time T is equal to or longer than the predetermined time is higher than that when the power generation stop time T is less than the predetermined time. Set. When the power generation stop time T is equal to or longer than a predetermined time, the fuel cell stack 10 is activated and the inlet of the anode flow path 12 in a state where air exists in the anode flow path 12 and the cathode flow path 13 respectively. When hydrogen is supplied from 12a, a difference in hydrogen concentration occurs between the inlet 12a side and the outlet 12b side of the anode flow path 12 (the state where the inlet 12a side is high and the outlet 12b side is low), and the fuel cell stack 10 becomes high. It means a state that becomes a potential. The target pressure may be a fixed value, or the target pressure (anode pressure) at startup may be set higher as the power generation stop time becomes longer.

  As shown in FIG. 4B, when setting the target pressure (anode pressure), if the power generation stop time T is equal to or longer than a predetermined time, the inter-electrode differential pressure at the time of startup may be considered. The inter-electrode differential pressure is a pressure difference between the anode pressure Pa on the inlet 12a side of the anode channel 12 obtained from the pressure sensor 28 and the cathode pressure Pc on the inlet 13a side of the cathode channel 13 obtained from the pressure sensor 35. (Pa-Pc). Also in this case, when the power generation stop time T is equal to or longer than the predetermined time, the inter-electrode differential pressure may be set higher as the power generation stop time T becomes longer. Further, it may be set in consideration of the upper limit value of the pressure difference between the electrodes (pressure difference that does not damage the electrolyte membrane).

Next, the operation of the fuel cell system 1 will be described with reference to FIGS.
When the operation of the fuel cell system 1 is stopped (IG-OFF), the supply of hydrogen and air to the fuel cell stack 10 is stopped, and the power generation of the fuel cell stack 10 is stopped. When the power generation is stopped, the purge valve 26 is closed and the back pressure valve 33 is opened. Thus, for example, when power generation is stopped, the flow path including the anode flow path 12 is sealed, and the air in the cathode flow path 13 permeates the anode flow path 12 through the electrolyte membrane, so that the anode flow path 12 Will be gradually replaced with air.

  As shown in FIG. 5, when the ECU 60 detects an ON signal (system activation signal) of the IG 51, the ECU 60 determines whether or not the power generation stop time T measured by the timer 52 is equal to or longer than a predetermined time in step S101. . Note that the predetermined time or longer means that the anode flow path 12 is replaced with air, the next time the fuel cell stack 10 is started and hydrogen is supplied to the anode flow path 12, A difference in hydrogen concentration occurs between the outlet 12b and the fuel cell stack 10 is at a high potential.

  In step S101, if the ECU 60 determines that the power generation stop time T is greater than or equal to the predetermined time (Yes), the ECU 60 proceeds to step S102, and if it determines that the power generation stop time T is less than the predetermined time (No) ), The process proceeds to step S109.

  In step S <b> 102, the ECU 60 opens the shutoff valve 22 and operates (ON) the air pump 31 to supply air to the cathode flow path 13. At this time, since the first injector 23A and the second injector 23B are closed, the hydrogen in the hydrogen tank 21 is depressurized by a pressure reducing valve (not shown) and then upstream of the first injector 23A and the second injector 23B. Stop at the side position.

  In step S102, the air pump 31 is driven at a rotational speed that is equal to or higher than a predetermined rotational speed (higher than that during normal power generation). Thus, the air is increased in order to dilute the hydrogen contained in the anode off-gas discharged from the anode flow path 12 when the purge valve 26 is opened in step S106 described later.

  In step S102, the ECU 60 starts (ON) the drive of the hydrogen pump 27 (circulator operation starting means). By driving the hydrogen pump 27, gas (mainly air) circulates in the anode circulation system (the anode flow path 12, a part of the pipe 26a, the pipes 27a and 27b, and a part of the pipe 24a).

  In step S103, the ECU 60 determines whether or not the predetermined time T1 has elapsed. The predetermined time T1 may be a time when the gas in the anode circulation system (the anode channel 12, the channels 26a, 27a, 27b, and 24a) is in a circulating state. In other words, when hydrogen is supplied from the first injector 23A and the second injector 23B in step S104, which will be described later, the time is set so that hydrogen can be immediately circulated in the anode circulation system. The predetermined time is determined based on a preliminary test or the like.

  If it is determined in step S103 that the predetermined time has elapsed (Yes), the ECU 60 proceeds to step S104. If it is determined that the predetermined time has not elapsed (No), the ECU 60 repeats the process in step S103. .

  In step S104, the ECU 60 opens the first injector 23A and the second injector 23B, respectively. At this time, the Ti value of the first injector 23A is increased so that the injection amount is larger than that during normal power generation (see FIG. 3A). Thereby, the target pressure (anode pressure Pa) of hydrogen supplied to the anode flow path 12 can be increased more than that during normal power generation.

  In step S104, the ECU 60 continuously opens the first injector 23A by matching the Ti value (valve opening time) of the first injector 23A with the interval (see FIG. 2A). Further, the ECU 60 intermittently opens the second injector 23B by making the Ti value (valve opening time) shorter than the interval for the second injector 23B. As will be described later, for the second injector 23B, when the pressure increase width is too large, the injection amount (Ti value) is appropriately limited. Further, the first injector 23A is not limited to the continuous valve opening, and may be any valve opening time that is longer than the valve opening time during normal power generation (see FIG. 2B).

  Here, the reason for limiting the injection amount (Ti value) of the second injector 23B will be described with reference to FIG. FIG. 6A is a graph (this embodiment) showing the relationship between the target pressure at the time of high pressure startup and the valve opening time of the injector, and FIG. 6B is a graph showing the relationship between the target pressure at the time of normal power generation and the valve opening time of the injector. It is a graph (comparative example) which shows a relationship.

  That is, as shown in FIG. 6B, when each of the first injector 23A (INJA) and the second injector 23B (INJBP) is used until they are fully opened, the increase width of the anode pressure Pa (the increase width per unit time). ) Becomes too large, the anode pressure immediately reaches the target pressure, and the supply of hydrogen from the first injector 23A and the second injector 23B stops early. By stopping the supply of hydrogen, a difference in hydrogen concentration occurs between the inlet 12a side and the outlet 12b side of the anode flow path 12 until hydrogen injection from the first injector 23A and the second injector 23B is resumed. Therefore, the high potential state of the fuel cell stack 10 is maintained until the operation is resumed.

  Incidentally, during normal power generation, it is better that the increase width of the anode pressure Pa is large as shown in FIG. This is because by increasing the range of rise, for example, when the fuel cell vehicle is accelerated, the responsiveness can be increased.

  Therefore, in the present embodiment, as shown in FIG. 6A, by limiting the Ti value (valve opening time, injection amount) of the second injector 23B (INJBP), the increase width (unit time) of the anode pressure Pa. The increase range of hit [ΔP / t]) can be suppressed, and the operation of the first injector 23A and the second injector 23B can be prevented from stopping early and hydrogen supply being intermittent. Therefore, hydrogen can be continuously supplied to the anode flow path 12, and the difference in hydrogen concentration generated between the inlet 12a side and the outlet 12b side of the anode flow path 12 can be eliminated at an early stage.

Next, the mechanism by which the high potential state of the fuel cell stack 10 continues due to the difference in hydrogen concentration between the inlet 12a side and the outlet 12b side of the anode channel 12 will be described with reference to FIG.
As shown in FIG. 8, when the fuel cell stack 10 is started in a state where air exists in each of the anode channel 12 and the cathode channel 13 (power generation stop time is a predetermined time or more), the inlet of the anode channel 12 When hydrogen is supplied from 12a, the hydrogen concentration on the inlet 12a side of the anode channel 12 is increased and the hydrogen concentration on the outlet 12b side of the anode channel 12 is decreased in the initial stage of hydrogen supply.

  Thereby, as shown in the equation (1), electrons are separated from hydrogen on the inlet 12a side of the anode flow path 12, and hydrogen ions permeate to the inlet side of the cathode flow path 13 through the electrolyte membrane. Moves to the outlet 12b side of the anode channel 12. At this time, the potential on the inlet 12a side of the anode channel 12 becomes 0 volt with respect to DHE (Dynamic Hydrogen Electrode).

  Further, as shown in the equation (2), on the inlet side of the cathode channel 13, hydrogen ions and electrons react with oxygen in the air on the inlet side to generate water. At this time, a potential of about 1 volt is generated with respect to DHE on the inlet side of the cathode channel 13.

  Further, as shown in the equation (3), on the outlet 12b side of the anode channel 12, the hydrogen ions that permeate the electrolyte membrane from the outlet side of the cathode channel 13 and the electrons received from the inlet 12a of the anode channel 12 The oxygen on the outlet 12b side of the anode channel 12 reacts to generate water. At this time, on the outlet 12b side of the anode channel 12, a potential of about 1 volt is generated with respect to DHE.

  Further, as shown in the equation (4), on the outlet side of the cathode flow path 13, electrons are separated from the catalyst (platinum) used for the cathode (electrode) to generate platinum ions. Further, as shown in the equation (5), the carbon contained in the cathode (electrode) passes through the electrolyte membrane from the outlet 12b side of the anode channel 12 or the generated water from the inlet side of the cathode channel 13 By reacting, carbon dioxide and hydrogen ions are generated, and the electrons at this time move to the inlet side of the cathode channel 13.

  As described above, a potential difference of 1 volt is generated on the inlet side of the fuel cell stack 10, so that a potential difference of 1 volt is also generated on the outlet side of the fuel cell stack 10, so that 2 volt is provided on the outlet side of the cathode flow path 13. Potential is generated. As a result, the fuel cell stack 10 enters a high potential state. At this time, the reaction shown in the formula (4) (the reaction that corrodes the catalyst) and the reaction shown in the formula (5) are continued for a long time, in other words, hydrogen at the inlet 12a side and the outlet 12b side of the anode channel 12 When the state in which the concentration difference occurs continues for a long time, the state in which the fuel cell stack 10 is at a high potential continues, which causes the fuel cell stack 10 to deteriorate. Based on such knowledge, it is important how quickly the difference in hydrogen concentration between the inlet 12a side and the outlet 12b side of the anode channel 12 can be resolved.

Returning to FIG. 5 , the process proceeds to step S <b> 105, where the ECU 60 determines whether or not the anode pressure Pa detected by the pressure sensor 28 is equal to or higher than a predetermined value. The predetermined value (target pressure) is set to a pressure required to eliminate the difference in hydrogen concentration between the inlet 12a side and the outlet 12b side of the anode channel 12. The predetermined value is determined based on a prior test or the like. In addition, it is not limited to the structure determined by the detection value of the pressure sensor 28, You may determine based on time (t2-t3) required to raise to a predetermined value.

  In step S105, when the ECU 60 determines that the anode pressure Pa is less than the predetermined value (No), the ECU 60 repeats the process of step S105, and when it determines that the anode pressure Pa is equal to or higher than the predetermined value (Yes). ), The process proceeds to step S106.

  In step S106, the ECU 60 starts the opening / closing control of the purge valve 26. The opening / closing control is started after the purge valve 26 is delayed from the start of the operation of the first injector 23A and the second injector 23B by increasing the anode pressure Pa in the anode flow path 12 early. This is because the difference in hydrogen concentration between the inlet 12a side and the outlet 12b side is eliminated at an early stage. Even if the purge valve 26 is opened here, the operating pressure of the air pump 31 is higher than that during normal power generation (see S102), so that high-concentration hydrogen is not discharged outside the vehicle.

  In step S106, the ECU 60 switches the first injector 23A from the continuous valve opening to the valve opening control corresponding to the opening operation of the purge valve 26, and closes the second injector 23B. That is, the ECU 60 performs opening / closing control (controls the Ti value) so as to supply from the first injector 23A the amount (amount) discharged by opening the purge valve 26.

  And it progresses to step S107 and ECU60 determines whether starting was completed. The case where the start is completed is a case where it is determined that a predetermined amount of gas has been purged (discharged) after the purge valve 26 is opened (opened / closed). Whether or not a predetermined amount of gas has been purged can be determined based on, for example, the opening time of the purge valve 26 or the like.

  In step S107, the ECU 60 returns to the process of step S104 when determining that the activation is not completed (No), and proceeds to step S108 when determining that the activation is completed (Yes).

  In step S108, the ECU 60 turns on the contactor 45 (connects the fuel cell stack 10 and the external load), starts taking out the generated current from the fuel cell stack 10, and requires the air pump 31 during normal power generation. Reduce to the correct rotation speed. The generated current taken out from the fuel cell stack 10 is supplied to external loads such as the motor 41 and the air pump 31. Further, the ECU 60 controls the opening and closing (controls the Ti value) of the first injector 23 </ b> A according to the magnitude of the generated current extracted from the fuel cell stack 10.

  In step S101, if the ECU 60 determines that the power generation stop time T is less than the predetermined time (No), the ECU 60 proceeds to step S109, opens the shut-off valve 22, and turns on the air pump 31 (rotation during normal startup). Speed).

  And it progresses to step S110 and ECU60 opens the 1st injector 23A and the 2nd injector 23B, respectively. The injection amount (Ti value) from the first injector 23A and the second injector 23B at this time is set to be smaller (smaller) than in the case of step S104.

  In step S110, the ECU 60 intermittently opens the first injector 23A so that the Ti value (valve opening time) of the first injector 23A is shorter than the interval. The ECU 60 also intermittently opens the second injector 23B so that the Ti value (valve opening time) is shorter than the interval for the second injector 23B.

  Then, the process proceeds to step S111, and the ECU 60 starts the opening / closing control of the purge valve 26 as in step S106 described above. In this case, without waiting for the anode pressure to exceed a predetermined value, the opening / closing control of the purge valve 26 is started immediately after the opening of the first injector 23A and the second injector 23B, and the anode flow path 12 The inside is replaced with hydrogen.

  And it progresses to step S112 and ECU60 determines whether starting was completed. In step S112, the ECU 60 returns to the process of step S110 when determining that the activation is not completed (No), and proceeds to step S113 when determining that the activation is completed (Yes).

  In step S113, the ECU 60 turns on the contactor 45 (connects the fuel cell stack 10 and the external load), and starts taking out the generated current from the fuel cell stack 10.

  Further, with reference to the time chart shown in FIG. 7, when a start signal (ON signal) of the IG 51 is detected at time t1, it is determined that the power generation stop time T is equal to or longer than a predetermined time (S101, Yes), the shutoff valve 22 is opened, and driving of the air pump 31 and the hydrogen pump 27 is started (S102).

  The first injector 23A (INJA) is continuously opened and the second injector 23B (INJBP) is intermittently opened at time t2 after a predetermined time T1 has elapsed from time t1. Thereby, anode pressure Pa rises and the voltage (FC voltage) of the fuel cell stack 10 rises.

  Then, at time t3 when the anode pressure Pa reaches a predetermined value (target pressure), the opening / closing control of the purge valve 26 is started (Yes in S105, S106). Even if the purge valve 26 is opened after the start of the opening of the first injector 23A and the second injector 23B, the rotational speed of the air pump 31 is set to be higher than that at the time of normal startup. High concentration (predetermined concentration) of hydrogen is not discharged.

  In addition, after time t3, by opening and closing the purge valve 26 to replace the air in the anode flow path 12 with hydrogen, the gas is discharged from the anode circulation system including the anode flow path 12, and thus the gas was discharged. Depending on the amount, the first injector 23 </ b> A is opened and closed, and hydrogen is intermittently supplied toward the anode flow path 12. At time t3, the second injector 23B is closed and the supply of hydrogen from the second injector 23B is stopped.

  When it is determined that the start-up is completed at time t4 when a predetermined time has elapsed since the start of the opening / closing control of the purge valve 26 (S107, Yes), the contactor 45 is turned on and the fuel cell stack 10 generates power. The process proceeds to normal power generation from which current is extracted (S108). During normal power generation after completion of startup, the opening / closing control is performed according to the generated current to be extracted, so that hydrogen is intermittently supplied.

  As described above, in the fuel cell system 1 according to the present embodiment, when the ECU 60 determines that the power generation stop time T is equal to or longer than the predetermined time, the target when the fuel cell stack 10 is started (IG-ON) By supplying the pressure (anode pressure Pa) higher than when the power generation stop time T is less than the predetermined time (see FIG. 3B) (see FIG. 3A), Mixing of air (oxidant gas) and hydrogen (fuel gas) is promoted, so that the fuel cell stack 10 can be prevented from being exposed to a high potential state for a long time, and the fuel cell stack 10 is deteriorated. Can be suppressed.

  That is, by making the target pressure (anode pressure) higher than during normal startup, the difference in hydrogen concentration between the inlet 12a side and the outlet 12b side of the anode flow path 12 can be eliminated at an early stage. It is possible to prevent exposure to a high potential state.

  In the present embodiment, the target pressure is set higher as the power generation stop time T of the fuel cell stack 10 becomes longer, so that it is not necessary to set the target pressure unnecessarily (unnecessarily). As a result, it is not necessary to operate the first injector 23A and the second injector 23B unnecessarily (unnecessarily), so that power consumption can be reduced.

  Further, in this embodiment, by setting the pressure increase width of the anode pressure Pa to be smaller than that during normal power generation (see FIG. 6B) (see FIG. 6A), hydrogen is generated when the fuel cell stack 10 is started. Can be prevented from becoming intermittent, and mixing of hydrogen and air can be promoted. By promoting the mixing of air and hydrogen, that is, by eliminating the difference in hydrogen concentration between the inlet 12a side and the outlet 12b side of the anode channel 12 at an early stage, the fuel cell is exposed to a high potential state for a long time. Can be prevented.

  Further, in the present embodiment, the ECU 60 starts the operation of the hydrogen pump 27 (circulation device) before operating the first injector 23A and the second injector 23B (before execution of processing by the fuel gas high-pressure supply control means). Thus, the supply of hydrogen is started after the flow of gas (mainly air) is formed in the anode circulation system (connection paths 27a, 27b, pipes 24a, 26a), so that the mixing of air and hydrogen is further increased. Promoted. Accordingly, the difference in hydrogen concentration between the inlet 12a side and the outlet 12b side of the anode channel 12 can be eliminated earlier, so that the fuel cell can be more reliably prevented from being exposed to a high potential state for a long time.

  Further, in the present embodiment, finer control can be performed by using an electronically controlled injector as the fuel gas pressure supply means.

  Further, in the present embodiment, the ECU 60 maintains the first injector 23A and the second injector 23B in the valve-opened state (see FIG. 2B), so that hydrogen can be continuously supplied to further mix air into hydrogen. Can be promoted. Accordingly, the difference in hydrogen concentration between the inlet 12a side and the outlet 12b side of the anode channel 12 can be eliminated earlier, so that the fuel cell can be more reliably prevented from being exposed to a high potential state for a long time.

  The present invention is not limited to the above-described embodiment, and can be modified as appropriate without departing from the spirit of the present invention. For example, in the present embodiment, the case where it is determined that the power generation stop time T is equal to or longer than a predetermined time as a condition for executing the process of increasing the target pressure when the fuel cell stack 10 is started has been described. However, the determination may be made based on whether or not the anode flow path 12 is scavenged with air (oxidant gas) when power generation is stopped (IG-OFF).

  In other words, although not shown in the drawings, the pipe 31a and the pipe 24a are connected to each other to include an introduction pipe for introducing air (oxidant gas) and an introduction cutoff valve for shutting off the introduction pipe. Even when the introduction shutoff valve and the purge valve 26 are opened and the air from the air pump 31 is introduced into the flow path including the anode flow path 12 and the like through the introduction pipe, the anode flow path 12 is still air. It will be replaced. Therefore, even when the anode flow path is scavenged in this way, the fuel cell stack 10 is kept in a high potential state for a long time by executing a process for increasing the target pressure (anode pressure Pa) when the fuel cell stack 10 is started. It can prevent exposure.

  In the present embodiment, the case where the first injector 23A and the second injector 23B are provided has been described as an example, but a fuel cell system including a single injector may be used. Further, the second injector 23B may be replaced with a valve that can flow at a constant flow rate for a fixed time.

  In the present embodiment, the case where both the first injector 23A and the second injector 23B are operated in step S104 has been described as an example. However, one of the first injector 23A and the second injector 23B is operated, The structure which stops the other may be sufficient.

  Further, in the present embodiment, in the control of the first injector 23A and the second injector 23B, the case where the interval is constant and the Ti value (valve opening time) is varied is described as an example, but the present invention is not limited thereto. Instead of this, the Ti value (valve opening time) may be constant and the interval may be varied.

1 Fuel Cell System 10 Fuel Cell Stack (Fuel Cell)
12 Anode channel 12a Inlet 12b Outlet 13 Cathode channel 23A First injector (fuel gas pressure adjusting means)
23B Second injector (fuel gas pressure supply means)
26 Purge valve 27 Hydrogen pump (circulator)
27a, 27b Piping (connection path)
60 ECU (Anode channel replacement determination means, fuel gas high pressure supply control means, circulation device operation start means)

Claims (5)

A fuel cell having an anode channel for supplying fuel gas to the anode and a cathode channel for supplying oxidant gas to the cathode;
A fuel gas introduction channel for introducing fuel gas into the fuel cell;
A fuel off-gas outlet flow path for extracting fuel off-gas from the fuel cell;
A return passage for returning the fuel off-gas discharged to the fuel off-gas outlet passage to the fuel gas introduction passage;
An ejector that is provided in the fuel gas introduction flow path and sucks the fuel off gas through the return flow path and mixes with the fuel gas;
An electronically controlled first injector that is provided upstream of the ejector in the fuel gas introduction channel and that regulates and supplies fuel gas to the anode channel;
A bypass passage connecting the fuel gas introduction passage upstream of the first injector and the fuel gas introduction passage downstream of the ejector;
An electronically controlled second injector that is provided in the bypass flow path and supplies fuel gas to the anode flow path after being regulated;
Anode passage replacement determination means for determining at the time of startup of the fuel cell whether or not the anode passage is replaced with an oxidant gas;
When it is determined by the anode flow path replacement determination means that the anode flow path has been replaced with an oxidant gas, the target pressure of the fuel gas supplied to the anode flow path by the first injector and the second injector is set as follows: The anode channel is set to be higher than when the oxidant gas is not replaced, and the pressure increase width of the fuel gas to the anode channel is set to be smaller than that during normal power generation. A fuel gas high pressure supply control means for supplying
The fuel gas pressure supply control means, upon activation of the fuel cell, from the previous SL opening start of the first injector as the injection amount of the first injector is larger than the normal power generation to the next open-starting The valve opening time in the reference cycle that is the interval is made longer than that during normal power generation, and the valve opening time in the reference cycle that is the interval from the start of opening of the second injector to the start of the next valve opening is limited. A fuel cell system. The anode flow path replacement determination means determines that the anode flow path has been replaced with an oxidant gas when the power generation stop time before the start of the fuel cell is a predetermined time or more,
The fuel gas high-pressure supply control means determines that the target pressure is less than a predetermined time when the anode flow path replacement determination means determines that the anode flow path is replaced with an oxidant gas. The fuel cell system according to claim 1, wherein the fuel cell system is set high.   3. The fuel cell system according to claim 2, wherein the fuel gas high-pressure supply control unit sets the target pressure higher as the power generation stop time of the fuel cell becomes longer. A connection path connecting the fuel gas introduction flow path downstream from the connection point on the downstream side of the bypass flow path and the fuel off-gas outlet flow path upstream from the connection point upstream of the return flow path;
A circulation device that is provided in the connection path and returns the fuel off-gas discharged from the outlet of the anode channel to the inlet of the anode channel;
4. The circulator operation starting means for starting the operation of the circulator before the fuel gas is supplied by the fuel gas high-pressure supply control means. 5. The fuel cell system described.   The fuel cell system according to any one of claims 1 to 4, wherein the fuel gas high-pressure supply control means maintains the valve open state of the first injector.

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