JP2016134375A - Fuel battery system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel battery system that is improved in durability of electrolyte membrane without reducing responsibility of output.SOLUTION: A fuel battery system comprises a fuel battery for outputting current upon introduction of oxidant gas and fuel gas thereto, an output prediction part for predicting increase of an output requested to the fuel battery when a predetermined condition concerning the state of the fuel battery is satisfied, and a pressure controller for starting increase control of the pressure of the oxidant gas or the fuel gas (solid line) (time T1) before the requested output is increased (time T2) when the increase of the requested output is predicted (time T1). The pressure controller starts the increase control (solid lines La1, Lb1) at a lower increasing speed than that when the increase control is started (dotted lines La',Lb') after the requested output is increased (time T2) so that the pressure (Pa, Pb) of the oxidant gas or the fuel gas reaches a target value (Pb_rq, Pa_rq) corresponding to the output requested within a predetermined time (Δt) from the increasing timing (T2) of the requested output.SELECTED DRAWING: Figure 6

Description

  The present invention relates to a fuel cell system.

  Recently, the development of fuel cells is progressing, such as the introduction of fuel cell vehicles (FCVs). The fuel cell mounted on the FCV drives the motor by generating electricity by chemically reacting hydrogen of fuel and oxygen in the air.

  The fuel cell includes a membrane electrode assembly (MEA) composed of an anode electrode that is a hydrogen electrode, a cathode electrode that is an oxygen electrode, and an electrolyte membrane sandwiched between the electrodes. The pressure in the hydrogen flow path on the anode electrode side and the pressure in the oxygen flow path on the cathode electrode side are controlled according to the output required for the fuel cell.

  Regarding the fuel cell, for example, in Patent Document 1, in order to avoid deterioration of the electrolyte membrane, the difference between the pressure in the hydrogen flow path and the pressure in the oxygen flow path (hereinafter referred to as “differential pressure between electrodes”) is reduced. Points are listed. For example, Patent Document 2 describes that when an increase in load required for a fuel cell is predicted, the gas pressure supplied to the fuel gas chamber is increased or decreased before the load increases.

JP 2005-267937 A JP 2008-251489 A

  The electrolyte membrane bends due to the differential pressure between the electrodes. For this reason, when the output required for the fuel cell (hereinafter referred to as “required output”) increases rapidly, the pressure in the hydrogen flow path or oxygen flow path also increases rapidly, and the electrolyte membrane is bent. A great stress is caused by.

  Therefore, the electrolyte membrane has a problem of a decrease in durability due to stress. In order to avoid this, even if the pressure increase rate is reduced, the required time until the required output is obtained from the fuel cell is increased, so that the output responsiveness is lowered. Such a problem is not limited to the fuel cell used for FCV, but also exists for fuel cells used for other purposes.

  Accordingly, the present invention has been made in view of the above problems, and an object thereof is to provide a fuel cell system in which the durability of the electrolyte membrane is improved without deteriorating output responsiveness.

  The fuel cell system described in this specification is required for the fuel cell that outputs a current by introducing an oxidant gas or a fuel gas and when the predetermined condition regarding the state of the fuel cell is satisfied. An output predicting unit for predicting an increase in output, and when the required increase in output is predicted by the output predicting unit, before the required output increases, the oxidizing gas or the fuel gas A pressure control unit for starting pressure increase control, wherein the pressure control unit sets the pressure of the oxidizing gas or the fuel gas to the required output within a predetermined time from the required output increase timing. The increase control is started at a lower increase speed than when the increase control is started after the required output increases so as to reach the corresponding target value.

  According to the present invention, the durability of the electrolyte membrane can be improved without deteriorating output responsiveness.

It is a block diagram which shows an example of a fuel cell system. It is sectional drawing of a fuel battery cell. It is a graph which shows the relationship of the target value of the pressure with respect to the output current of a fuel cell. It is a flowchart which shows an example of operation | movement of a fuel cell system. It is a graph which shows an example of the change of the open circuit voltage at the time of a stop of a fuel cell. It is a figure which shows an example of the increase control of a pressure. It is a flowchart which shows the other example of operation | movement of a fuel cell system.

  FIG. 1 is a configuration diagram illustrating an example of a fuel cell system 1. The fuel cell system 1 is mounted on a vehicle such as a fuel cell vehicle and supplies power to a motor M that drives the vehicle.

  The fuel cell system 1 includes a control device 10, an air compressor 11, an inlet side air pressure sensor 14, an outlet side air pressure sensor 13, a hydrogen tank 16, a fuel gas pressure regulating valve 17, a fuel gas pressure sensor 19, and a purge. A valve 22 and a fuel cell 23 are provided. The fuel cell system 1 further includes an impedance measuring unit 24, a voltage sensor V, a temperature sensor T, a DC-DC converter 25, a DC-AC inverter 26, and a recirculation pump 29.

  The control device 10 controls the operation of the fuel cell system 1. The control device 10 has a processor such as a CPU (Central Processing Unit), for example, and operates according to a program read from storage means such as a ROM (Read Only Memory). When the processor in the control device 10 reads the program, the pressure control unit 100 and the output prediction unit 101 are formed as functions, and the target value information 102 is stored in the memory in the control device 10. The pressure control unit 100, the output prediction unit 101, and the target value information 102 will be described later. Note that the control device 10 is not limited to one that operates with a program, and may be one that operates only with hardware.

  The control device 10 outputs control signals S <b> 1 to S <b> 3 to the air compressor 11, the purge valve 22, and the fuel gas pressure regulating valve 17 in accordance with various commands and control processes. Further, the control device 10 includes a pressure Pa measured by the inlet side air pressure sensor 14, a pressure Pa ′ measured by the outlet side air pressure sensor 13, a pressure Pb measured by the fuel gas pressure sensor 19, and a temperature Tw measured by the temperature sensor T. The voltage value E detected by the voltage sensor V and the impedance value Z measured by the impedance measuring unit 24 are input.

  The control device 10 further includes a vehicle travel distance DIS measured by the travel distance measuring unit 40, a vehicle speed Vx detected by the vehicle speed sensor 41, a shift lever position LP detected by the shift lever sensor 42, and a brake sensor 43. The detected brake opening BK and the accelerator opening AC detected by the accelerator sensor 44 are input. Further, route information NV is input to the control device 10 from the navigation device 45 that indicates the route to the destination to the driver of the vehicle.

  A fuel gas supply path 18 for supplying hydrogen gas, which is an example of fuel gas, and a fuel gas discharge path 21 for discharging hydrogen gas used for power generation are connected to the fuel cell 23. A hydrogen tank 16, a fuel gas pressure regulating valve 17, and a fuel gas pressure sensor 19 are connected to the fuel gas supply path 18 in this order.

The hydrogen tank 16 is a hydrogen gas (H ₂ ) supply device, and stores hydrogen gas in a high pressure state. Hydrogen gas is introduced from the hydrogen tank 16 to the anode side of the fuel cell 23 via the fuel gas pressure regulating valve 17 and the fuel gas pressure sensor 19.

  The pressure of the hydrogen gas is adjusted by passing through the fuel gas pressure regulating valve 17. The fuel gas pressure adjusting valve 17 adjusts the pressure of hydrogen gas introduced into the fuel cell 23 by adjusting the opening of the valve based on the control signal S <b> 3 from the control device 10.

  The fuel gas pressure sensor 19 measures the pressure Pb of hydrogen gas introduced into the fuel cell 23. The fuel gas pressure sensor 19 notifies the control device 10 of the measured pressure Pb.

  Hydrogen gas (that is, off-gas) discharged from the fuel cell 23 is guided to the fuel gas discharge path 21. A purge valve 22 is provided in the middle of the fuel gas discharge path 21.

  The purge valve 22 is opened and closed in accordance with a control signal S2 from the control device 10. The purge valve 22 is opened when scavenging hydrogen gas from the fuel cell 23.

  A recirculation path 20 branches from the fuel gas discharge path 21. The branched recirculation path 20 is connected to the fuel gas supply path 18. A recirculation pump 29 is provided in the recirculation path 20, and the recirculation pump 29 guides the hydrogen gas discharged to the fuel gas discharge path 21 to the fuel gas supply path 18 via the recirculation path 20. . The hydrogen gas guided from the recirculation path 20 to the fuel gas supply path 18 is again introduced into the fuel cell 23 via the fuel gas pressure sensor 19.

  The fuel cell 23 is connected to an air supply path 12 for supplying air and an air discharge path 15 for discharging air used for power generation. An air compressor 11 and an inlet side air pressure sensor 14 are connected to the air supply path 12.

The air compressor 11 takes in air containing oxygen (O ₂ ) from the outside of the vehicle, for example, and pumps it to the fuel cell 23. In this embodiment, air is used as an example of the oxidizing gas, but the present invention is not limited to this. The air compressor 11 introduces air to the cathode side of the fuel cell 23 in accordance with the control signal S 1 from the control device 10. For this reason, the pressure of air is controlled based on the control signal S1.

  The air discharged from the fuel cell 23 is guided to the air discharge path 15. An outlet side air pressure sensor 13 is connected to the air discharge path 15.

  The outlet side air pressure sensor 13 measures the pressure Pa ′ of the air discharged from the fuel cell 23. The outlet side air pressure sensor 13 notifies the control device 10 of the measured pressure Pa ′.

  The fuel cell 23 is configured as a stacked body (stack) of a plurality of fuel cells. The fuel cell 23 includes an anode electrode (fuel electrode) to which hydrogen gas that is a fuel gas is supplied, and a cathode electrode (air electrode) to which air is supplied. Hydrogen and oxygen generate water and electricity by chemical reaction. In this way, the fuel cell 23 generates power by introducing hydrogen and oxygen, and outputs a current to the motor M that drives the vehicle.

  Further, the fuel cell 23 is supplied with cooling water (refrigerant) for cooling the fuel cell 23 from a cooling device (not shown) and cooling water used for cooling in the fuel cell 23. A cooling water discharge path 31 for discharging is connected. The cooling water supply path 30 and the cooling water discharge path 31 constitute a circulation path for circulating the cooling water.

  The cooling water discharge path 31 is provided with a temperature sensor T that detects the temperature Tw of the cooling water discharged from the fuel cell 23. The temperature sensor T notifies the control device 10 of the detected temperature Tw.

  The voltage sensor V measures the voltage value E output from the cell of the fuel cell 23. The voltage sensor V notifies the control device 10 of the measured voltage value E.

  The impedance measurement unit 24 measures the impedance Z of the fuel cell 23 from the relationship with the voltage value when the current value is changed by passing a current through the fuel cell 23. The impedance measuring unit 24 notifies the control device 10 of the measured impedance Z.

  The DC-DC converter 25 includes a step-up / step-down chopper circuit, for example, and converts the output voltage of the fuel cell 23. The DC-DC converter 25 converts a voltage by performing on / off control of a plurality of switching elements such as FETs (Field Effect Transistors) provided in the step-up / step-down chopper circuit. The output current of the DC-DC converter 25 is input to the DC-AC inverter 26.

  The DC-AC inverter 26 converts the output current of the DC-DC converter 25 from direct current to three-phase alternating current. The DC-AC inverter 26 converts the current when the switching element is on / off controlled based on, for example, a PWM (Pulse Width Modulation) control method. The output current of the DC-AC inverter 26 is output to the motor M.

  Next, the fuel cell constituting the fuel cell 23 will be described. FIG. 2 is a cross-sectional view of the fuel battery cell.

  The fuel cell 23a includes a cathode side separator 30a, an anode side separator 30b, a frame 38, a cathode side gas diffusion layer (GDL) 31a, an anode side gas diffusion layer (GDL) 31b, and an MEA 35. The MEA 35 includes an anode electrode 33b, a cathode electrode 33a, and an electrolyte membrane 34 sandwiched between the anode electrode 33b and the cathode electrode 33a.

  The cathode side GDL 31a, the MEA 35, and the anode side GDL 31b are stacked in this order, and are sandwiched between the cathode side and anode side separators 30a and 30b. A flow path Ra through which air flows is formed in parallel in the cathode side separator 30a, and a flow path Rb through which hydrogen gas flows is formed in parallel in the anode side separator 30b. The air flow path Ra communicates with the air supply path 12 and the air discharge path 15, and the hydrogen gas flow path Rb communicates with the fuel gas supply path 18 and the fuel gas discharge path 21.

  The GDLs 31a and 31b are made of, for example, carbon fiber, and take in air and hydrogen gas from the flow paths Ra and Rb, respectively, and diffuse them uniformly into the MEA 35. The end of the anode-side GDL 31 b reaches the frame 38, but the end of the cathode-side GDL 31 a does not reach the frame 38. That is, the width of the cathode-side GDL 31a is shorter than the width of the anode-side GDL 31b. For this reason, the end 35a of the MEA 35 is in contact with the anode-side GDL 31b and is not in contact with the cathode-side GDL 31a. Exposed to Ra.

In the MEA 35, oxygen in the air is supplied to the cathode electrode 33a and hydrogen is supplied to the anode electrode 33b, whereby a chemical reaction between hydrogen and oxygen is performed. At this time, the hydrogen ions pass through the electrolyte membrane 34 and move from the anode electrode 33b side to the cathode electrode 33a side. Therefore, the anode electrode 33b, by the hydrogen ions are bonded with oxygen ions, water (H 2 _O) is generated.

  The frame 38 is formed of an insulating material such as resin, for example, and is provided so as to surround the cathode side GDL 31a, the MEA 35, and the anode side GDL 31b. The frame 38 is sandwiched between the cathode side separator 30a and the anode side separator 30b, and is provided at the same height as the MEA 35 and the GDLs 31a and 31b in the stacking direction.

  The pressure Pb in the anode-side flow path Rb and the pressure Pa in the cathode-side flow path Ra are controlled according to the output required for the fuel cell 23. At this time, since the pressure Pb of the hydrogen gas is higher than the pressure Pa of the air, the electrolyte membrane 34 bends due to the inter-electrode differential pressure (Pb-Pa). In particular, the end 35a of the MEA 35 is in contact with the anode-side GDL 31b and is not in contact with the cathode-side GDL 31a. I'll be stuck.

  Therefore, when the output required for the fuel cell 23 suddenly increases, if the pressures Pa and Pb in the flow path Ra or the flow path Rb also increase suddenly, a large stress due to bending occurs in the electrolyte membrane 34. Therefore, the durability is lowered. The degree of the decrease in durability is affected by the humidity of the fuel cell 23a which varies depending on the power generation state. That is, the durability of the electrolyte membrane 34 tends to decrease as the humidity increases. Further, when the thickness of the electrolyte membrane 34 is reduced due to factors such as aging, the durability is likely to be lowered.

  Therefore, the fuel cell system 1 according to the embodiment performs the increase control of the pressure of the air or hydrogen gas at a low increase speed before the required output increases when the increase in the output required for the fuel cell 23 is predicted. Start. Thereby, since the stress which arises in the electrolyte membrane 34 is reduced, durability of the electrolyte membrane 34 is improved. Details of the pressure control will be described below.

  Referring again to FIG. 1, the pressure control unit 100 of the control device 10 controls the hydrogen gas pressure Pb and the air pressure Pa in accordance with the output required for the fuel cell 23. Here, the required output is determined from, for example, the vehicle speed Vx, the shift lever position LP, the brake opening BK, and the accelerator opening AC.

  More specifically, the pressure control unit 100 controls the control signals S1, S3 of the air compressor 11 and the fuel gas pressure regulating valve 17 so that the hydrogen gas pressure Pb and the air pressure Pa become target values according to the required output. Is generated. At this time, the pressure control unit 100 refers to the target value information 102 to determine target values for the pressures Pa and Pb.

  FIG. 3 is a graph showing the relationship between the target values of the pressures Pa and Pb with respect to the output current of the fuel cell 23. In FIG. 3, the horizontal axis indicates the output current, that is, the output required for the fuel cell 23, and the vertical axis indicates the target value Pa_rq of the pressure Pa and the target value Pb_rq of the pressure Pb.

  Imax indicates the maximum value of the output current, and Pa0 and Pb0 indicate the target values of the pressures Pa and Pb when the value is half the maximum value Imax of the output current (Imax / 2). I1 to I4 indicate current values determined by design.

  The target value Pa_rq is proportional to the output current when the output current is in the range of I2 to I4, and is constant when the output current is smaller than I2 or larger than I4. The target value Pb_rq is proportional to the output current when the output current is within the range of I1 to I3, and is constant when the output current is smaller than I1 or larger than I3. Note that I1 to I4 have a relationship of I1 <I2 <I3 <I4.

  The target value information 102 is held, for example, as a table in which the relationship between the output current and the target values Pa_rq and Pb_rq is mapped.

  Further, the output predicting unit 101 shown in FIG. 1 predicts an increase in output required for the fuel cell 23 when a predetermined condition regarding the state of the fuel cell 23 is satisfied. Examples of the predetermined condition relating to the state of the fuel cell 23 include, but are not limited to, a thickness condition and a humidity condition of the electrolyte membrane 34 as described later. The required output predicting means may be, for example, determining whether or not predetermined conditions regarding the vehicle speed Vx, the shift lever position LP, and the brake opening degree BK are satisfied. There are various ways to do this.

  When an increase in the required output is predicted by the output predicting unit 101, the pressure control unit 100 starts increasing control of the air pressure Pa or the hydrogen gas pressure Pb before the required output increases. At this time, as will be described later, the pressure control unit 100 causes the air pressure Pa or the hydrogen gas pressure Pb to reach target values Pa_rq and Pb_rq corresponding to the required output within a predetermined time from the increase timing of the required output. The increase control is started at a lower increase speed than when the increase control is started after the increase in the required output. Details of operations of the pressure control unit 100 and the output prediction unit 101 will be described below.

  FIG. 4 is a flowchart showing an example of the operation of the fuel cell system 1. This operation is executed, for example, at a constant time period.

  First, the output predicting unit 101 determines whether or not the thickness of the electrolyte membrane 34 (hereinafter referred to as “film thickness”) may have decreased (step St1). In this process, the output predicting unit 101 can determine that there is a possibility of a decrease in film thickness, for example, when the traveling distance DIS measured by the traveling distance measuring unit 40 exceeds a predetermined threshold. Further, the output predicting unit 101 may determine that there is a possibility that the film thickness may be reduced when the traveling time exceeds a predetermined threshold instead of the traveling distance DIS.

  Furthermore, the output predicting unit 101 can also determine whether or not there is a possibility of a decrease in film thickness based on an open circuit voltage (OCV) when the fuel cell 23 is started or stopped. Here, the open circuit voltage is obtained from the voltage value E detected by the voltage sensor V.

  More specifically, the output predicting unit 101 can determine that there is a possibility of a decrease in film thickness when the open circuit voltage at the time of starting or stopping is smaller than a predetermined voltage value. Alternatively, the output predicting unit 101 can also make a determination based on the rate of decrease of the open circuit voltage at the time of stop.

  FIG. 5 is a graph showing an example of changes in the open circuit voltage when the fuel cell 23 is stopped. In FIG. 5, the horizontal axis indicates the time elapsed since the fuel cell 23 stopped, and the vertical axis indicates the open circuit voltage (OCV).

  When the film thickness is normal, the open circuit voltage gradually decreases as indicated by a solid line, but when the film thickness is decreased, the open circuit voltage decreases rapidly as indicated by a dotted line. Therefore, the output predicting unit 101 can determine whether or not there is a possibility of film thickness reduction by detecting the decrease rate of the open circuit voltage.

  Referring to FIG. 4 again, when there is no possibility of the film thickness decreasing (No in Step St1), the pressure control unit 100 maintains the current operation state of the fuel cell 23 (Step St5). Further, when there is a possibility that the film thickness is decreased (Yes in Step St1), the output predicting unit 101 determines whether or not the electrolyte membrane 34 is in a high humidity environment (Step St2).

  In this process, the output predicting unit 101 can determine that the electrolyte membrane 34 is in a high humidity environment, for example, when the temperature Tw of the cooling water detected by the temperature sensor T is lower than a predetermined value. The output prediction unit 101 can also determine that the electrolyte membrane 34 is in a high humidity environment when the impedance Z measured by the impedance measurement unit 24 is lower than a predetermined value.

  In the cathode electrode 33a, as described above, water is generated by a chemical reaction between oxygen and hydrogen. The generated water is discharged to the outside of the fuel cell 23 by the air flowing through the flow path Ra. For this reason, it can be estimated that the larger the difference (Pa−Pa ′) between the pressure Pa at the inlet of the channel Ra and the pressure Pa ′ at the outlet of the channel Ra, the more water remains in the channel Ra.

  Therefore, the output predicting unit 101 can determine that the electrolyte membrane 34 is in a high humidity environment when the difference (Pa−Pa ′) is larger than a predetermined value. Note that the determination means related to the humidity of the electrolyte membrane 34 is not limited to the above method, and other logic-based methods can also be employed.

  Referring to FIG. 4 again, when it is determined that the electrolyte membrane 34 is not in a high humidity environment (No in Step St2), the pressure control unit 100 maintains the current operation state of the fuel cell 23 (Step St5). ). Further, when the output predicting unit 101 determines that the electrolyte membrane 34 is in a high humidity environment (Yes in Step St2), the output predicting unit 101 predicts whether or not the required output is increased (Step St3).

  As described above, the output predicting unit 101 predicts an increase in the required output when the condition regarding the fuel cell 23, more specifically, the condition regarding the electrolyte membrane 34 (see Steps St1 and St2) is satisfied.

  For example, the output predicting unit 101 can predict an increase in the required output based on the driving state of the vehicle. For example, the speed Vx detected by the vehicle speed sensor 41 is equal to or lower than a predetermined value, the position LP of the shift lever detected by the shift lever sensor 42 is “D” (drive), and is detected by the brake sensor 43. If the brake opening BK changes to 0, it is predicted that the vehicle will be accelerated in the next driving operation.

  Therefore, the output predicting unit 101 can predict that the required output increases when the speed Vx, the shift lever position LP, and the brake opening degree BK satisfy the above conditions. Further, the output prediction unit 101 may predict an increase in request output from the route information NV input from the navigation device 45. In this case, for example, when it is detected from the route information NV that the vehicle is going uphill from a flat road, it is predicted that the vehicle will be accelerated in the next driving operation. An increase is expected.

  Furthermore, the output predicting unit 101 may predict an increase in the required output based on traffic information obtained from an intelligent transport system (ITS). For example, when it is detected in advance from traffic information that the color of a traffic signal changes from red to blue, it is predicted that the vehicle will be accelerated in the next driving operation. The In addition, when it is detected from the traffic information that the inter-vehicle distance (measured by a millimeter wave radar or the like) with the vehicle ahead is greater than a predetermined value, it is predicted that the vehicle will be accelerated in the next driving operation. Therefore, an increase in required output is predicted.

  As described above, the output predicting unit 101 can predict an increase in the required output using various methods.

  Referring to FIG. 4 again, when an increase in the required output is not predicted (No in Step St3), the pressure control unit 100 maintains the current operating state of the fuel cell 23 (Step St5). When an increase in the required output is predicted (Yes in step St3), the pressure control unit 100 starts increasing control of the air pressure Pa or the hydrogen gas pressure Pb before the required output increases (step St4). In this way, the fuel cell system 1 operates.

  FIG. 6 shows an example of increasing control of the pressures Pa and Pb. In FIG. 6, the horizontal axis indicates time, and the vertical axis indicates air and hydrogen gas pressures Pa and Pb. Further, the solid line shows an example of the increase control of the pressures Pa and Pb in step St4, and the broken line shows an example of the increase control of the pressures Pa and Pb in the operation state of step St5 as a comparative example. In the following description, first, the pressure increase control in step St4 will be described, and then the pressure increase control contents of the comparative example will be described.

  T1 indicates the time when the notification of the increase in request output is received from the output prediction unit 101, and T2 indicates the time when the request output actually increases, that is, the increase timing of the request output. T3 indicates the time at which the pressures Pa and Pb of the air and the hydrogen gas reach the target outputs Pa_rq and Pb_rq according to the required output, that is, the required output current. In this example, the case where both the pressures Pa and Pb of the air and hydrogen gas are controlled is given, but even when one of the pressures Pa and Pb of the air and hydrogen gas is controlled, the same effects as the following contents are obtained. can get.

  As indicated by the solid line, the pressure control unit 100 starts increasing control of the pressures Pa and Pb of the air and hydrogen gas at time T1. At this time, the pressure control unit 100 increases and controls the target values Pa_rq and Pb_rq as, for example, Pa0 and Pb0 shown in FIG.

  Further, the pressure control unit 100 increases the increasing speeds of the pressures Pa and Pb so that the pressures Pa and Pb reach the target values Pa_rq and Pb_rq after a predetermined time Δt has elapsed from the time T2 (time T3 = T2 + Δt). Here, the increase rate refers to an increase amount of the pressures PA and Pb per unit time. The pressure control unit 100 determines that the required output has actually increased based on the accelerator opening degree AC detected by the accelerator sensor 44 at time T2.

  Thereby, the pressures Pa and Pb of the air and hydrogen gas reach the target values Pa_rq and Pb_rq at time T3. Note that the arrival timing of the pressures Pa and Pb to the target values Pa_rq and Pb_rq may be before the predetermined time Δt has elapsed from the time T2.

  On the other hand, in the comparative example (see the broken line), the pressure control unit 100 performs pressure increase control without predicting an increase in the required output by the output prediction unit 101. For this reason, when the pressure control unit 100 determines that the required output has increased at time T2, the pressures Pa and Pb are set such that the pressures Pa and Pb reach the target values Pa_rq and Pb_rq after a predetermined time Δt has elapsed from time T2. Increase control of the pressures Pa and Pb of air and hydrogen gas is started.

  Also in the comparative example, the pressures Pa and Pb of the air and hydrogen gas reach the target values Pa_rq and Pb_rq at time T3. However, in the comparative example, since the increase control of the pressures Pa and Pb is started at the time T2, which is the actual increase timing of the required output, the time for increasing the pressure Pa and Pb is only the predetermined time Δt at most.

  On the other hand, in the pressure increase control (see the solid line) in step St4, the pressure control unit 100 detects the increase in the required output by the output prediction unit 101, that is, the pressure Pa and Pb at time T1 (<T2). Since the increase control is started, it is possible to secure more time for increasing the pressures Pa and Pb than in the comparative example. At this time, the time for increasing control of the pressures Pa and Pb is the sum (T2−T1 + Δt) of T2−T1 which is the difference between the times T1 and T2 and the predetermined time Δt.

  For this reason, in step St4, the pressure control unit 100, at time T1, increases at a speed lower than the speed of increase in the comparative example (refer to the slopes of the straight lines indicated by the signs La ′ and Lb ′) (the straight lines indicated by the signs La1 and Lb1). The increase control of the pressures Pa and Pb can be started. That is, the pressure control unit 100 starts the increase control after increasing the required output so that the pressures Pa and Pb reach the target values Pa_rq and Pb_rq corresponding to the required output within a predetermined time Δt from the time T2 (that is, comparison) Example) Start increasing control at a lower increasing speed.

  In Step St4, the pressure control unit 100 performs the increase control of the pressures Pa and Pb at an increase rate lower than the increase rate in the comparative example (see slopes of straight lines indicated by reference signs La2 and Lb2) after time T2. be able to. That is, the pressure control unit 100 performs the increase control after the increase in the required output so that the pressures Pa and Pb reach the target values Pa_rq and Pb_rq corresponding to the required output within the predetermined time Δt from the time T2 even after the increase in the required output. The increase control is continued until the pressures Pa and Pb reach the target values Pa_rq and Pb_rq at a lower increase speed than when starting (that is, the comparative example).

  Therefore, in step St4, the pressure control unit 100 can gradually increase the pressures Pa and Pb in the flow path Ra or the flow path Rb even when the output required for the fuel cell 23 increases rapidly. .

  Here, the output predicting unit 101 determines that the thickness of the electrolyte membrane 34 has decreased (Yes in step St1), and determines that the electrolyte membrane 34 is in a high humidity environment (in step St2). Yes), a request output increase prediction process (step St3) is performed. That is, the output predicting unit 101 predicts an increase in the required output when the above-described condition regarding the state of the fuel cell 23 is satisfied.

  On the other hand, the output predicting unit 101 does not perform a process for predicting an increase in the required output when the above-described condition regarding the state of the fuel cell 23 is not satisfied (No in Steps St1 and St2). In this case, the pressure control unit 100 performs the pressure increase control shown as the comparative example.

  Therefore, the pressure control unit 100 performs the increase control of the pressures Pa and Pb prior to the increase in the required output only when the electrolyte membrane 34 is easily affected by the increase in the required output (Step St4). That is, the pressure control unit 100 can gradually increase the pressures Pa and Pb according to the state of the fuel cell 23. For this reason, the stress which arises in the electrolyte membrane 34 is suppressed, and durability of the electrolyte membrane 34 is improved. Furthermore, the fuel cell system 1 can operate so that the contradiction to the output and fuel consumption of the fuel cell 23 is minimized.

  Further, when the increase in the required output is predicted by the output predicting unit 101, the pressure control unit 100 starts the increase control of the pressures Pa and Pb before the increase in the required output. Even if it is lower, the pressures Pa and Pb can be controlled so that the pressures Pa and Pb reach the target values Pa_rq and Pb_rq within a predetermined time Δt from the increase timing (time T2) of the required output. Thereby, the responsiveness of the output of the fuel cell 23 is maintained.

  Thus, the fuel cell system of the embodiment can improve the durability of the electrolyte membrane 34 without deteriorating the output responsiveness.

  Next, the operation when each determination process in steps St1 to St3 in FIG. 4 is made more specific will be described. FIG. 7 is a flowchart showing an operation example of the fuel cell system 1 in this case. In FIG. 7, processes that are the same as those in FIG. 4 are given the same reference numerals, and descriptions thereof are omitted.

  First, the output prediction unit 101 compares the open circuit voltage (OCV) when the fuel cell 23 is started up with a predetermined voltage value α (step St1 '). Thereby, it is determined whether or not the thickness of the electrolyte membrane 34 may be decreased. Note that the open circuit voltage is obtained from the voltage value E detected by the voltage sensor V as described above. The predetermined voltage value α is, for example, 0.9 (V), but is not limited to this.

  When the open circuit voltage is equal to or higher than the predetermined voltage value α (No in Step St1 ′), the pressure control unit 100 maintains the current operation state of the fuel cell 23 (Step St5). When the open circuit voltage is smaller than the predetermined voltage value α (Yes in step St1 ′), the output predicting unit 101 compares the coolant temperature Tw detected by the temperature sensor T with the predetermined value β (step St2). '). Thereby, it is determined whether or not the electrolyte membrane 34 is in a high humidity environment. The predetermined value β is, for example, 50 (° C.), but is not limited thereto.

  When the temperature Tw is equal to or higher than the predetermined value β (No in Step St2 ′), the pressure control unit 100 maintains the current operation state of the fuel cell 23 (Step St5). Further, when the temperature Tw is smaller than the predetermined value β (Yes in Step St2 ′), the output predicting unit 101 determines the speed Vx detected by the vehicle speed sensor 41, the position LP of the shift lever detected by the shift lever sensor 42, and It is determined whether or not the brake opening degree BK detected by the brake sensor 43 satisfies a predetermined condition (step St3 ′).

Vx <γ (1)
LP = “D” (drive) (2)
BK = 0 (3)

  More specifically, the output prediction unit 101 determines whether the above formulas (1) to (3) are successful. Note that the predetermined value γ in the equation (1) is, for example, 5 (km / h), but is not limited thereto. When all of the above equations (1) to (3) hold, as described above, it is predicted that the vehicle is accelerated in the next driving operation.

  When at least one of the above formulas (1) to (3) does not hold (No in step St3 '), the pressure control unit 100 maintains the current operation state of the fuel cell 23 (step St5). When all of the above formulas (1) to (3) are satisfied (Yes in step St3 ′), that is, when an increase in the required output is predicted, the pressure control unit 100 increases the pressure as described above. Control is started (step St4). In this way, the fuel cell system 1 operates.

  As described above, the fuel cell system 1 according to the embodiment includes the fuel cell 23, the output prediction unit 101, and the pressure control unit 100. The fuel cell 23 outputs an electric current when air or hydrogen gas is introduced. The output prediction unit 101 predicts an increase in output required for the fuel cell 23 when a predetermined condition regarding the state of the fuel cell 23 is satisfied.

  When the required output increase is predicted by the output predicting unit 101, the pressure control unit 100 starts increasing control of the pressures Pa and Pb of the air or hydrogen gas before the required output increases. The pressure control unit 100 is requested so that the pressures Pa and Pb of the air or hydrogen gas reach the target values Pa_rq and Pb_rq corresponding to the required output within the predetermined time Δt from the required output increase timing T2. The increase control is started at a lower increase speed than when the increase control is started after the output is increased.

  According to the above configuration, when the required output increase is predicted by the output predicting unit 101, the pressure control unit 100 starts the increase control of the pressures Pa and Pb before the required output increases. For this reason, the pressure control unit 100 can secure more time for increasing the pressure Pa and Pb than when starting the increase control of the pressure Pa and Pb after the required increase in output.

  Then, the pressure control unit 100 is configured so that the pressures Pa and Pb of the air or hydrogen gas reach the target values Pa_rq and Pb_rq corresponding to the required output within a predetermined time Δt from the required output increase timing T2. The increase control is started at a lower increase speed than when the increase control is started after the required output increase. Therefore, the pressure control unit 100 can gradually increase the pressures Pa and Pb according to the state of the fuel cell 23 even when the output required for the fuel cell 23 increases rapidly. For this reason, the durability of the electrolyte membrane 34 is improved by suppressing the stress generated in the electrolyte membrane 34 of the fuel cell 23.

  In addition, when the required output increase is predicted by the output prediction unit 101, the pressure control unit 100 starts increasing control of the pressures Pa and Pb before the required output increases. Therefore, the pressure controller 100 controls the pressures Pa and Pb so that the pressures Pa and Pb reach the target values Pa_rq and Pb_rq within a predetermined time Δt from the required output increase timing even when the increase rate is low. it can. Thereby, the responsiveness of the output of the fuel cell 23 is maintained.

  Therefore, the fuel cell system 1 of the embodiment can improve the durability of the electrolyte membrane 34 without lowering the output responsiveness.

  The above-described embodiment is an example of a preferred embodiment of the present invention. However, the present invention is not limited to this, and various modifications can be made without departing from the scope of the present invention.

DESCRIPTION OF SYMBOLS 1 Fuel cell system 10 Control apparatus 11 Air compressor 17 Fuel gas pressure regulating valve 23 Fuel cell 34 Electrolyte membrane 100 Pressure control part 101 Output prediction part

Claims (1)

A fuel cell that generates electricity by introducing an oxidizing gas or a fuel gas; and
An output predicting unit that predicts an increase in output required for the fuel cell when a predetermined condition relating to the state of the fuel cell is satisfied;
A pressure control unit that starts an increase control of the pressure of the oxidizing gas or the fuel gas before the required output increases when the required output increase is predicted by the output prediction unit; ,
The pressure control unit is configured to output the required output so that the pressure of the oxidizing gas or the fuel gas reaches a target value corresponding to the required output within a predetermined time from the increase timing of the required output. A fuel cell system that starts the increase control at a lower increase speed than when the increase control is started after the increase.

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