JP5825839B2 - Fuel cell vehicle - Google Patents

Description

  The present invention relates to a fuel cell vehicle including a fuel cell, a power storage device capable of storing power from the fuel cell, and a load supplied with power from at least one of the fuel cell or the power storage device.

  Conventionally, in order to suppress deterioration of a fuel cell used in a fuel cell vehicle or the like, a fuel cell system that generates power by avoiding an oxidation-reduction potential has been proposed (Patent Document 1). In the fuel cell system of Patent Document 1, even when the system required power (Wreq) gradually increases, the output voltage (Vfc) of the fuel cell is once limited by the oxidation-reduction potential (Voxpt), and the limited voltage The power corresponding to is controlled to be supplemented by a battery. After that, even if the fuel cell power generation is no longer necessary due to a decrease in the accelerator opening, etc., the fuel cell output voltage is maintained below the oxidation-reduction potential and power generation is continued until the remaining battery capacity exceeds a predetermined value. Continue power generation (summary).

JP 2007-005038 A

  As described above, in the control of Patent Document 1, the output voltage of the fuel cell is maintained below the oxidation-reduction potential, but in order to keep avoiding the oxidation-reduction potential, the electric power required by the load such as the travel motor is required. It is necessary to increase the output power of the fuel cell. In that case, the surplus power of the fuel cell is charged into the battery. For this reason, in order to continue to avoid the oxidation-reduction potential, the frequency of charging and discharging of the battery increases. When the frequency of charging / discharging of the battery increases, the power loss accompanying charging / discharging increases, and the output efficiency of the entire fuel cell system decreases.

  The present invention has been made in view of such problems, and provides a fuel cell vehicle capable of improving the output efficiency of the entire fuel cell vehicle while suppressing deterioration of the fuel cell stack. Objective.

The fuel cell vehicle according to the present invention includes a fuel cell, a power storage device that stores power from the fuel cell, a load that is supplied with power from at least one of the fuel cell or the power storage device, and a voltage of the fuel cell. A control device for controlling the power supplied to the load by the fuel cell and the power storage device based on power required by the load, and a reaction gas supply device for supplying a reaction gas to the fuel cell When the target voltage of the fuel cell is equal to or lower than a first voltage lower than the oxidation-reduction progress voltage range of platinum, the control device converts the actual voltage of the fuel cell to the output voltage of the converter. a first mode to follow adjusted to the target fuel cell voltage than the first mode with reducing stoichiometric ratio than the first mode is used when a relatively low load, before The actual voltage is adjusted by the output voltage of the converter and maintained at a voltage equal to the first voltage, and the reaction gas supply device is controlled to adjust the supply amount of the reaction gas to the fuel cell to adjust the current of the fuel cell. Switching control is performed between a second mode in which voltage characteristics are changed and the fuel cell outputs the power required by the load, and the fuel cell vehicle is in at least an uphill state and an acceleration state during the second mode. If it is determined that the target voltage is maintained at a voltage equal to the first voltage, the stoichiometric ratio of the reaction gas is changed from the stoichiometric ratio of the second mode to the stoichiometric ratio of the first mode. The power generation current of the fuel cell is increased to increase the power generation current.

  According to the present invention, it is possible to improve the efficiency of the entire fuel cell vehicle while suppressing deterioration of the fuel cell.

  That is, mainly in the first mode that can be used at a relatively high load, the target voltage of the fuel cell is set lower than the oxidation-reduction progress voltage range of platinum, so that the oxidation reaction and the reduction reaction of the catalyst occur at the same time. Therefore, it is possible to prevent the fuel cell from being deteriorated frequently. In addition, by adjusting the actual voltage of the fuel cell with the output voltage of the converter to follow the target fuel cell voltage, it becomes possible to meet the required load of the fuel cell system, so the output of the fuel cell can be made more efficient It becomes.

  In the second mode that can be used mainly at a relatively low load, the actual voltage of the fuel cell is maintained at the first voltage (that is, a value lower than the oxidation-reduction progress voltage range). The oxidation reaction and the reduction reaction are prevented from being repeated frequently at the same time, and the deterioration of the fuel cell can be prevented. In addition, since the fuel cell outputs the electric power required by the load by changing the current-voltage characteristics of the fuel cell by adjusting the amount of reactant gas supplied to the fuel cell, By reducing the frequency, power loss in the power storage device can be reduced.

  As described above, according to the present invention, it is possible to improve the efficiency of the entire fuel cell system while suppressing deterioration of the fuel cell.

  In addition, according to the present invention, when it is determined that the fuel cell vehicle is in a high load state during the second mode, the stoichiometric ratio of the reaction gas is increased. Thus, when the fuel cell vehicle is in a high load state, the stoichiometric ratio is increased in the second mode, so that the fuel cell has a higher output and can maintain drivability at a high load.

When the control device determines that the fuel cell vehicle is at least one of an uphill state and an accelerated state during the second mode, the stoichiometric ratio equivalent value set in the first mode is set as the stoichiometric ratio of the reactive gas. May be raised.
When the control device determines that the fuel cell vehicle is at least one of an acceleration state and a climbing state during the second mode, the actual voltage of the fuel cell is set outside the oxidation-reduction progress voltage range. The second voltage may be maintained. As a result, even when the stoichiometric ratio is increased in a high load state, it is possible to prevent the actual voltage of the fuel cell from being within the platinum oxidation-reduction progress voltage range and to suppress deterioration of the fuel cell. It becomes possible. The second voltage may be the same value as the first voltage.

When the fuel cell vehicle is climbing in the first mode, the stoichiometric ratio of the reactive gas may be increased from the normal stoichiometric ratio in the first mode. Thereby, the electric power supplied to drive sources, such as a travel motor, increases, and it becomes possible to enlarge the output of the drive source. Therefore, the output when climbing is increased and drivability is improved.

  According to the present invention, it is possible to improve the efficiency of the entire fuel cell vehicle while suppressing deterioration of the fuel cell.

1 is a schematic overall configuration diagram of a fuel cell vehicle according to an embodiment of the present invention. It is a block diagram of the electric power system of the said fuel cell vehicle. It is a schematic block diagram of the fuel cell unit in the said embodiment. It is a figure which shows the detail of the DC / DC converter in the said embodiment. It is a flowchart of basic control in an electronic control unit (ECU). It is a flowchart which calculates a system load. It is a figure which shows the relationship between the present motor rotation speed and motor expected power consumption. It is a figure which shows the relationship of SOC of a battery, a charge / discharge coefficient, and average regenerative electric power. It is a figure which shows an example of the relationship between the electric potential of the fuel cell which comprises a fuel cell, and the amount of degradation of a cell. It is a cyclic voltammetry figure which shows the example of the mode of progress of oxidation and the progress of reduction | restoration when the fluctuation speeds of the electric potential of a fuel cell differ. It is explanatory drawing of the several electric power supply mode in the said embodiment. 4 is a flowchart in which the ECU performs energy management of the fuel cell system. It is a flowchart of uphill running determination. It is a flowchart of acceleration determination. It is a figure which shows the relationship between an air stoichiometric ratio and a cell current. It is a figure which shows the relationship between a motor voltage and the motor efficiency at the time of high torque rotation. It is a flowchart of a normal second mode. It is a figure which shows the relationship between target FC electric current and target oxygen concentration. It is a figure which shows the relationship between target oxygen concentration and target FC electric current, target air pump rotation speed, and target water pump rotation speed. It is a figure which shows the relationship between target oxygen concentration, target FC electric current, and target back pressure valve opening. It is a figure which shows the relationship between target FC electric current and an air flow rate. It is a figure which shows the relationship between the opening degree of a circulation valve, and a circulating gas flow rate. It is a figure which shows the relationship between the electric power generated of a fuel cell, and electric power generation efficiency. It is a flowchart of torque control of a motor. It is a 1st example of the time chart at the time of using the various control which concerns on the said embodiment. It is a 2nd example of the time chart at the time of using the various control in the said embodiment. It is a 3rd example of the time chart at the time of using the various control in the said embodiment. It is a block diagram which shows schematic structure of the 1st modification of the fuel cell system which concerns on the said embodiment. It is a block diagram which shows schematic structure of the 2nd modification of the fuel cell system which concerns on the said embodiment. It is a block diagram which shows schematic structure of the 3rd modification of the fuel cell system which concerns on the said embodiment.

1. Explanation of overall configuration [1-1. overall structure]
FIG. 1 is a schematic overall configuration diagram of a fuel cell vehicle 10 (hereinafter referred to as “FC vehicle 10” or “vehicle 10”) according to an embodiment of the present invention. FIG. 2 is a block diagram of the power system of the FC vehicle 10. As shown in FIGS. 1 and 2, the FC vehicle 10 includes a fuel cell system 12 (hereinafter referred to as “FC system 12”), a motor 14 for traveling, and an inverter 16.

  The FC system 12 includes a fuel cell unit 18 (hereinafter referred to as “FC unit 18”), a high voltage battery 20 (hereinafter also referred to as “battery 20”) (power storage device), a DC / DC converter 22, and electronic control. And a device 24 (hereinafter referred to as “ECU 24”).

[1-2. Drive system]
The motor 14 generates a driving force based on the electric power supplied from the FC unit 18 and the battery 20, and rotates the wheels 28 through the transmission 26 by the driving force. Further, the motor 14 outputs electric power (regenerative power Preg) [W] generated by performing regeneration to the battery 20 or the like (see FIG. 2).

  The inverter 16 has a three-phase full-bridge configuration, performs DC / AC conversion, converts DC to three-phase AC, and supplies it to the motor 14. On the other hand, the inverter 16 receives DC after AC / DC conversion accompanying the regenerative operation. Is supplied to the battery 20 or the like through the DC / DC converter 22.

  The motor 14 and the inverter 16 are collectively referred to as a load 30. The load 30 can also include components such as an air pump 60, a water pump 80, and an air conditioner 90 described later.

[1-3. FC system]
(1-3-1. Overall configuration)
FIG. 3 is a schematic configuration diagram of the FC unit 18. The FC unit 18 includes a fuel cell stack 40 (hereinafter referred to as “FC stack 40” or “FC40”), an anode system that supplies and discharges hydrogen (fuel gas) to and from the anode of the FC stack 40, A cathode system that supplies and discharges oxygen-containing air (oxidant gas) to the cathode, a cooling system that circulates cooling water (refrigerant) that cools the FC stack 40, and a cell voltage monitor 42 are provided.

(1-3-2. FC stack 40)
The FC stack 40 has, for example, a structure in which fuel cell cells (hereinafter referred to as “FC cells”) formed by sandwiching a solid polymer electrolyte membrane from both sides between an anode electrode and a cathode electrode are stacked.

(1-3-3. Anode system)
The anode system has a hydrogen tank 44, a regulator 46, an ejector 48, and a normally closed purge valve 50. The hydrogen tank 44 stores hydrogen as a fuel gas, and is connected to the inlet of the anode flow path 52 through a pipe 44a, a regulator 46, a pipe 46a, an ejector 48, and a pipe 48a. Thereby, the hydrogen in the hydrogen tank 44 can be supplied to the anode flow path 52 via the pipe 44a and the like. Note that a shutoff valve (not shown) is provided in the pipe 44a, and the shutoff valve is opened by the ECU 24 when the FC stack 40 generates power.

  The regulator 46 adjusts the pressure of the introduced hydrogen to a predetermined value and discharges it. That is, the regulator 46 controls the downstream pressure (anode hydrogen pressure) in accordance with the cathode pressure (pilot pressure) input via the pipe 46b. Accordingly, the hydrogen pressure on the anode side is linked to the air pressure on the cathode side. As will be described later, when the rotation speed of the air pump 60 is changed to change the oxygen concentration, the hydrogen pressure on the anode side also changes. To do.

  The ejector 48 generates a negative pressure by injecting hydrogen from the hydrogen tank 44 with a nozzle, and the negative off-pressure of the pipe 48b can be sucked by this negative pressure.

  The outlet of the anode flow path 52 is connected to the intake port of the ejector 48 through the pipe 48b. Then, the anode off gas discharged from the anode flow path 52 is introduced again into the ejector 48 through the pipe 48b, whereby the anode off gas (hydrogen) circulates.

  The anode off gas contains hydrogen that has not been consumed by the electrode reaction at the anode and water vapor. The pipe 48b is provided with a gas-liquid separator (not shown) that separates and collects moisture {condensed water (liquid), water vapor (gas)} contained in the anode off gas.

  A part of the pipe 48b is connected to a diluter (not shown) provided in the pipe 64b described later via the pipe 50a, the purge valve 50, and the pipe 50b. When it is determined that the power generation of the FC stack 40 is not stable, the purge valve 50 is opened for a predetermined time based on a command from the ECU 24. The diluter dilutes hydrogen in the anode off gas from the purge valve 50 with the cathode off gas.

(1-3-4. Cathode system)
The cathode system includes an air pump 60, a humidifier 62, a normally open type back pressure valve 64, a normally open type circulation valve 66, flow rate sensors 68 and 70, and a temperature sensor 72.

  The air pump 60 compresses the outside air (air) and sends it to the cathode side, and the intake port thereof communicates with the outside of the vehicle (outside) via a pipe 60a. The discharge port of the air pump 60 is connected to the inlet of the cathode channel 74 through the pipe 60b, the humidifier 62, and the pipe 62a. When the air pump 60 operates in accordance with a command from the ECU 24, the air pump 60 sucks and compresses air outside the vehicle via the pipe 60a, and the compressed air is pumped to the cathode channel 74 through the pipe 60b and the like.

  The humidifier 62 includes a plurality of hollow fiber membranes 62e having moisture permeability. The humidifier 62 exchanges moisture between the air toward the cathode channel 74 and the humid cathode offgas discharged from the cathode channel 74 via the hollow fiber membrane 62e, and the air toward the cathode channel 74 Humidify.

  On the outlet side of the cathode channel 74, a pipe 62b, a humidifier 62, a pipe 64a, a back pressure valve 64, and a pipe 64b are arranged. The cathode off gas (oxidant off gas) discharged from the cathode channel 74 is discharged outside the vehicle through the pipe 62b and the like. The pipe 64b is provided with the above-described diluter (not shown).

  The back pressure valve 64 is configured by, for example, a butterfly valve, and the air pressure in the cathode channel 74 is controlled by controlling the opening degree of the back pressure valve 64 by the ECU 24. More specifically, when the opening degree of the back pressure valve 64 is reduced, the air pressure in the cathode flow path 74 is increased, and the oxygen concentration (volume concentration) per volume flow rate is increased. On the contrary, when the opening degree of the back pressure valve 64 increases, the pressure of the air in the cathode flow path 74 decreases, and the oxygen concentration (volume concentration) per volume flow rate decreases.

  A pipe 64b on the downstream side of the diluter is connected to the pipe 60a via a pipe 66a, a circulation valve 66, and a pipe 66b. As a result, a part of the exhaust gas (cathode off-gas) is supplied as circulation gas to the pipe 60a through the pipe 66a, the circulation valve 66, and the pipe 66b, merges with new air from the outside of the vehicle, and is taken into the air pump 60. Is done.

  The circulation valve 66 is constituted by, for example, a butterfly valve, and the flow rate of the circulation gas is controlled by controlling the opening degree of the circulation valve 66 by the ECU 24.

  The flow rate sensor 68 is attached to the pipe 60b, detects the flow rate [g / s] of the air flowing toward the cathode flow path 74, and outputs it to the ECU 24. The flow rate sensor 70 is attached to the pipe 66b, detects the flow rate Qc [g / s] of the circulating gas toward the pipe 60a, and outputs it to the ECU 24.

  The temperature sensor 72 is attached to the pipe 64a, detects the temperature of the cathode off gas, and outputs it to the ECU 24. Here, since the temperature of the circulating gas is substantially equal to the temperature of the cathode off gas, the temperature of the circulating gas can be detected based on the temperature of the cathode off gas detected by the temperature sensor 72.

(1-3-5. Cooling system)
The cooling system includes a water pump 80 and a radiator 82 (heat radiator). The water pump 80 circulates cooling water (refrigerant), and its discharge port is connected to the suction port of the water pump 80 through the pipe 80a, the refrigerant flow path 84, the pipe 82a, the radiator 82, and the pipe 82b in this order. It is connected. When the water pump 80 is operated in accordance with a command from the ECU 24, the cooling water circulates between the refrigerant flow path 84 and the radiator 82 to cool the FC stack 40.

(1-3-6. Cell voltage monitor)
The cell voltage monitor 42 is a device that detects a cell voltage Vcell for each of a plurality of single cells constituting the FC stack 40, and includes a monitor main body and a wire harness that connects the monitor main body and each single cell. The monitor main body scans all the single cells at a predetermined period, detects the cell voltage Vcell of each single cell, and calculates the average cell voltage and the lowest cell voltage. Then, the average cell voltage and the lowest cell voltage are output to the ECU 24.

(1-3-7. Power system)
As shown in FIG. 2, the power from the FC 40 (hereinafter referred to as “FC power Pfc”) is added to the inverter 16 and the motor 14 (during power running), the DC / DC converter 22 and the high voltage battery 20 (during charging). , The air pump 60, the water pump 80, the air conditioner 90, the downverter 92, the low voltage battery 94, the accessory 96, and the ECU 24. As shown in FIG. 1, a backflow prevention diode 98 is disposed between the FC unit 18 (FC 40), the inverter 16, and the DC / DC converter 22. Further, the power generation voltage of FC 40 (hereinafter referred to as “FC voltage Vfc”) is detected by voltage sensor 100 (FIG. 4), and the power generation current of FC 40 (hereinafter referred to as “FC current Ifc”) is detected by current sensor 102. Both are output to the ECU 24.

[1-4. High voltage battery 20]
The battery 20 is a power storage device (energy storage) including a plurality of battery cells. For example, a lithium ion secondary battery or a capacitor can be used. In this embodiment, a lithium ion secondary battery is used. The output voltage (hereinafter referred to as “battery voltage Vbat”) [V] of the battery 20 is detected by a voltage sensor (not shown), and the output current (hereinafter referred to as “battery current Ibat”) [A] of the battery 20 is not shown. It is detected by the current sensor and output to the ECU 24, respectively. Further, the remaining capacity (hereinafter referred to as “SOC”) [%] of the battery 20 is detected by the SOC sensor 104 (FIG. 2) and output to the ECU 24.

[1-5. DC / DC converter 22]
The DC / DC converter 22 supplies FC power Pfc from the FC unit 18, power supplied from the battery 20 (hereinafter referred to as “battery power Pbat”) [W], and regenerative power Preg from the motor 14. To control.

  FIG. 4 shows details of the DC / DC converter 22 in the present embodiment. As shown in FIG. 4, one of the DC / DC converters 22 is connected to the primary side 1 </ b> S where the battery 20 is located, and the other is connected to the secondary side 2 </ b> S which is a connection point between the load 30 and the FC 40.

  The DC / DC converter 22 boosts the voltage on the primary side 1S (primary voltage V1) [V] to the voltage (secondary voltage V2) [V] (V1 ≦ V2) on the secondary side 2S and secondary voltage This is a step-up / step-down and chopper-type voltage converter that steps down the voltage V2 to the primary voltage V1.

  As shown in FIG. 4, the DC / DC converter 22 includes a phase arm UA disposed between the primary side 1S and the secondary side 2S, and a reactor 110.

  The phase arm UA includes an upper arm element (upper arm switching element 112 and diode 114) and a lower arm element (lower arm switching element 116 and diode 118). As the upper arm switching element 112 and the lower arm switching element 116, for example, a MOSFET or an IGBT is employed.

  Reactor 110 is inserted between the middle point (common connection point) of phase arm UA and the positive electrode of battery 20, and converts voltage between primary voltage V <b> 1 and secondary voltage V <b> 2 by DC / DC converter 22. In particular, it has the function of releasing and storing energy.

  The upper arm switching element 112 is turned on by the high level of the gate drive signal (drive voltage) UH output from the ECU 24, and the lower arm switching element 116 is turned on by the high level of the gate drive signal (drive voltage) UL. Is done.

  The ECU 24 detects the primary voltage V1 with the voltage sensor 120 provided in parallel with the primary-side smoothing capacitor 122, and detects the primary-side current (primary current I1) [A] with the current sensor 124. To do. Further, the ECU 24 detects the secondary voltage V2 by the voltage sensor 126 provided in parallel with the secondary-side smoothing capacitor 128, and detects the secondary-side current (secondary current I2) [A] by the current sensor 130. To do.

[1-6. ECU 24]
The ECU 24 controls the motor 14, the inverter 16, the FC unit 18, the battery 20, and the DC / DC converter 22 via the communication line 140 (FIG. 1 and the like). In the control, a program stored in a memory (ROM) is executed, and the cell voltage monitor 42, the flow rate sensors 68 and 70, the temperature sensor 72, the voltage sensors 100, 120, and 126, and the current sensors 102, 124, and 130 are executed. The detection values of various sensors such as the SOC sensor 104 are used.

  The various sensors here include an opening sensor 150, a motor rotation number sensor 152, and a vehicle speed sensor 154 (FIG. 1) in addition to the above sensors. The opening sensor 150 detects the opening θp [degree] of the accelerator pedal 156. The rotation speed sensor 152 detects the rotation speed Nm [rpm] of the motor 14. The vehicle speed sensor 154 detects the vehicle speed V [km / h] of the FC vehicle 10. Further, a main switch 158 (hereinafter referred to as “main SW 158”) is connected to the ECU 24. The main SW 158 switches whether power can be supplied from the FC unit 18 and the battery 20 to the motor 14, and can be operated by the user.

  The ECU 24 includes a microcomputer and has an input / output interface such as a timer, an A / D converter, and a D / A converter as necessary. Note that the ECU 24 is not limited to only one ECU, but can be composed of a plurality of ECUs for each of the motor 14, the FC unit 18, the battery 20, and the DC / DC converter 22.

  The ECU 24 is required for the FC system 12 as a whole of the FC vehicle 10 determined based on the input (load request) from various switches and various sensors in addition to the state of the FC stack 40, the state of the battery 20, and the state of the motor 14. From the load, the load to be borne by the FC stack 40, the load to be borne by the battery 20, and the distribution (sharing) of the load to be borne by the regenerative power source (motor 14) are determined while arbitrating. , Sends a command to the FC unit 18, the battery 20 and the DC / DC converter 22.

2. Control of this Embodiment Next, the control in ECU24 is demonstrated.

[2-1. Basic control]
FIG. 5 shows a flowchart of basic control in the ECU 24. In step S1, the ECU 24 determines whether or not the main SW 158 is on. If the main SW 158 is not on (S1: NO), step S1 is repeated. If the main SW 158 is on (S1: YES), the process proceeds to step S2. In step S2, the ECU 24 calculates a load (system load Psys) [W] required for the FC system 12.

  In step S3, the ECU 24 performs energy management of the FC system 12. The energy management here is intended to make the output of the entire FC system 12 more efficient while suppressing the deterioration of the FC stack 40.

  In step S4, the ECU 24 controls peripheral devices of the FC stack 40, that is, the air pump 60, the back pressure valve 64, the circulation valve 66, and the water pump 80 (FC power generation control). In step S <b> 5, the ECU 24 performs torque control of the motor 14.

  In step S6, the ECU 24 determines whether or not the main SW 158 is off. If the main SW 158 is not off (S6: NO), the process returns to step S2. If the main SW 158 is off (S6: YES), the current process is terminated.

[2-2. Calculation of system load Psys]
FIG. 6 shows a flowchart for calculating the system load Psys. In step S <b> 11, the ECU 24 reads the opening degree θp of the accelerator pedal 156 from the opening degree sensor 150. In step S <b> 12, the ECU 24 reads the rotational speed Nm [rpm] of the motor 14 from the rotational speed sensor 152.

  In step S13, the ECU 24 calculates the expected power consumption Pm [W] of the motor 14 based on the opening degree θp and the rotational speed Nm. Specifically, in the map shown in FIG. 7, the relationship between the rotational speed Nm and the predicted power consumption Pm is stored for each opening θp. For example, when the opening degree θp is θp1, the characteristic 120 is used. Similarly, when the opening degree θp is θp2, θp3, θp4, θp5, and θp6, the characteristics 122, 124, 126, 128, and 130 are used, respectively. And after specifying the characteristic which shows the relationship between the rotation speed Nm and estimated power consumption Pm based on opening degree (theta) p, the expected power consumption Pm according to rotation speed Nm is specified.

  In step S14, the ECU 24 reads the current operation status from each auxiliary machine. The auxiliary machine here includes, for example, a high-voltage auxiliary machine including the air pump 60, the water pump 80 and the air conditioner 90, and a low-voltage auxiliary machine including the low-voltage battery 94, the accessory 96 and the ECU 24. It is. For example, in the case of the air pump 60 and the water pump 80, the rotation speed Nap and Nwp [rpm] are read. If it is the air conditioner 90, the output setting is read.

  In step S15, the ECU 24 calculates the power consumption Pa [W] of the auxiliary machine according to the current operation status of each auxiliary machine. In step S16, the ECU 24 calculates a charge / discharge coefficient α. The charge / discharge coefficient α is a coefficient that is multiplied by the sum (provisional system load) of the predicted power consumption Pm and the auxiliary machine power consumption Pa, and is the average value of the SOC of the battery 20 and the regenerative power Preg of the motor 14 (hereinafter referred to as “average regeneration” "Power Pregave"). The average regenerative power Pregave is an average value of the regenerative power Preg obtained within a predetermined period.

  FIG. 8 is a map showing the relationship among the SOC, the charge / discharge coefficient α, and the average regenerative power Pregave. In the example of FIG. 8, the target SOC is set to 50%, and when the SOC exceeds 50% (when in a sufficiently charged state), the charge / discharge coefficient α is set to less than 1. As a result, the system load Psys can be reduced by multiplying the temporary system load by a multiplier less than 1, and excess SOC of the battery 20 can be consumed. Further, when the SOC is less than 50% (when charging is required), the charge / discharge coefficient α is made larger than 1. As a result, the system load Psys can be increased by multiplying the temporary system load by a multiplier exceeding 1, and the shortage of the SOC can be compensated.

  In the example of FIG. 8, the relationship between the SOC and the charge / discharge coefficient α is switched according to the average regenerative power Pregave. That is, as shown in FIG. 8, when the average regenerative power Pregave is low (when it is difficult to obtain the regenerative power Preg), the charge / discharge coefficient α is set in the range where the SOC exceeds 50% because the regenerative power Preg cannot be expected so much. The charge / discharge coefficient α is set to a value close to 1 in the range where the SOC is less than 50%. On the other hand, when the average regenerative power Pregave is high (when the regenerative power Preg is easy to obtain), the charge / discharge coefficient α is reduced in the range where the SOC exceeds 50%, and the SOC is 50 as much as the regenerative power Preg can be expected. In the range below%, the charge / discharge coefficient α is greatly separated from 1. The target SOC may be set to a value other than 50%. Further, for example, measured values and simulation values can be used in the map of FIG.

  Returning to FIG. 6, in step S <b> 17, the ECU 24 multiplies the sum of the expected power consumption Pm of the motor 14 and the power consumption Pa of the auxiliary machine (temporary system load) by the charge / discharge coefficient α to estimate the expected consumption of the entire FC vehicle 10. The power (that is, the system load Psys) is calculated.

[2-3. Energy management]
As described above, the energy management in the present embodiment intends to improve the efficiency of the output of the entire FC system 12 while suppressing the deterioration of the FC stack 40.

(2-3-1. Assumptions)
FIG. 9 shows an example of the relationship between the potential (cell voltage Vcell) [V] of the FC cells constituting the FC stack 40 and the amount of cell degradation D. That is, the curve 160 in FIG. 9 shows the relationship between the cell voltage Vcell and the deterioration amount D.

  In FIG. 9, in the region below potential v1 (for example, 0.5 V) (hereinafter referred to as “platinum aggregation increasing region R1” or “aggregation increasing region R1”), the reduction reaction of platinum (platinum oxide) contained in the FC cell. Proceeds violently and platinum aggregates excessively. The potential v1 to the potential v2 (for example, 0.8 V) is a region where the reduction reaction proceeds stably (hereinafter referred to as “platinum reduction region R2” or “reduction region R2”).

  The potential v2 to the potential v3 (for example, 0.9 V) is a region where the redox reaction proceeds with respect to platinum (hereinafter referred to as “platinum redox progress region R3” or “redox region R3”). The potential v3 to the potential v4 (for example, 0.95 V) is a region where the oxidation reaction of platinum proceeds stably (hereinafter referred to as “platinum oxidation stable region R4” or “oxidation region R4”). The potential v4 to OCV (open circuit voltage) is a region where the oxidation of carbon contained in the cell proceeds (hereinafter referred to as “carbon oxidation region R5”).

  As described above, in FIG. 9, if the cell voltage Vcell is in the platinum reduction region R2 or the platinum oxidation stable region R4, the progress degree of deterioration of the FC cell is small. On the other hand, if the cell voltage Vcell is in the platinum aggregation increase region R1, the platinum oxidation-reduction progress region R3, or the carbon oxidation region R5, the progress degree of deterioration of the FC cell is large.

  In FIG. 9, the curve 160 is uniquely expressed, but in actuality, the curve 160 changes according to the amount of fluctuation (fluctuation speed Acell) [V / sec] of the cell voltage Vcell per unit time. .

  FIG. 10 is a cyclic voltammetry diagram showing an example of the progress of oxidation and the progress of reduction when the fluctuation rates Acell are different. In FIG. 10, a curve 170 shows a case where the fluctuation speed Acell is high, and a curve 172 shows a case where the fluctuation speed Acell is low. As can be seen from FIG. 10, since the degree of progress of oxidation or reduction varies depending on the fluctuation speed Acell, the potentials v1 to v4 are not necessarily uniquely specified. In addition, the potentials v1 to v4 can change depending on individual differences of FC cells. For this reason, it is preferable to set the potentials v1 to v4 as those in which an error is reflected in the theoretical value, the simulation value, or the actual measurement value.

  Further, in the current-voltage (IV) characteristics of the FC cell, the cell current Icell [A] increases as the cell voltage Vcell decreases (see FIG. 11), as in a general fuel cell. In addition, the power generation voltage (FC voltage Vfc) of the FC stack 40 is obtained by multiplying the cell voltage Vcell by the number Nfc of serial connections in the FC stack 40. The serial connection number Nfc is the number of FC cells connected in series in the FC stack 40, and is also simply referred to as “cell number” hereinafter.

  Based on the above, in the present embodiment, when the DC / DC converter 22 is performing the voltage conversion operation, the target voltage (target FC voltage Vfctgt) [V] of the FC stack 40 is mainly set in the platinum reduction region R2. While setting, it is set in the platinum oxidation stable region R4 as necessary (a specific example will be described with reference to FIG. 12 and the like). By switching the target FC voltage Vfctgt in this way, the time during which the FC voltage Vfc is within the regions R1, R3, R5 (particularly, the platinum oxidation-reduction progress region R3) is shortened as much as possible, and the FC stack 40 is deteriorated. Can be prevented.

  In the above processing, there is a case where the power supplied to the FC stack 40 (FC power Pfc) and the system load Psys are not equal. In this regard, when the FC power Pfc is below the system load Psys, the shortage is supplied from the battery 20. Further, when the FC power Pfc exceeds the system load Psys, the excess is charged in the battery 20.

  In FIG. 9, the potentials v <b> 1 to v <b> 4 are specified as specific numerical values, but this is for performing control to be described later, and the numerical values are determined in consideration of control convenience. In other words, as can be seen from the curve 160, the deterioration amount D changes continuously, so that the potentials v1 to v4 can be appropriately set according to the control specifications.

  However, the platinum reduction region R2 includes the minimum value of the curve 160 (first minimum value Vlmi1). In the platinum oxidation-reduction progress region R3, the maximum value (maximum value Vlmx) of the curve 160 is included. The platinum oxidation stable region R4 includes another minimum value (second minimum value Vlmi2) of the curve 160.

(2-3-2. Power supply mode used in energy management)
FIG. 11 is an explanatory diagram of a plurality of power supply modes in the present embodiment. In the present embodiment, two control methods (power control mode) are used as a power supply control method (power supply mode) used in energy management. That is, in the present embodiment, voltage variable / current variable control (first mode) in which both the target FC voltage Vfctgt and the FC current Ifc are variable, and a voltage in which the target FC voltage Vfctgt is constant and the FC current Ifc is variable. Switching between fixed and variable current control (second mode) is used.

  The first mode (variable voltage / current variable control) is mainly used when the system load Psys is relatively high, and the target oxygen concentration Cotgt is fixed (or oxygen is maintained in a rich state). Thus, the FC current Ifc is controlled by adjusting the target FC voltage Vfctgt. Thus, basically, the system load Psys can be covered by the FC power Pfc. The first mode is divided into a normal first mode used during normal travel (during travel other than climbing) and a first climbing mode used during climbing.

  The second mode (voltage fixed / current variable control) is mainly used when the system load Psys is relatively low, and the target cell voltage Vcelltgt (= target FC voltage Vfctgt / number of cells) is changed to the redox region. The FC current Ifc is made variable by fixing the reference potential {potential v2 (= 0.8 V) in this embodiment} set at a potential lower than R3 and making the target oxygen concentration Cotgt variable. . Thus, basically, the system load Psys can be covered by the FC power Pfc (details will be described later). The shortage of the FC power Pfc is assisted from the battery 20. The second mode is divided into a normal second mode used during normal traveling (during traveling other than climbing and acceleration) and a second climbing / acceleration second mode used during climbing or acceleration.

(2-3-3. Overall flow of energy management)
FIG. 12 shows a flowchart in which the ECU 24 performs energy management of the FC system 12 (S3 in FIG. 5). In step S21, the ECU 24 determines whether or not the system load Psys calculated in step S2 exceeds a threshold value THPsys1 for determining a high load. When the system load Psys exceeds the threshold value THPsys1 (S21: YES), in step S22, the ECU 24 performs an uphill running determination that determines whether or not the vehicle 10 is going uphill. If the vehicle 10 is not climbing up (S23: NO), in step S24, the ECU 24 executes the normal first mode (voltage variable / current variable control). When the vehicle 10 is climbing up (S23: YES), in step S25, the ECU 24 executes the first mode during climbing (variable voltage / current variable control).

  When the system load Psys does not exceed the threshold value THPsys1 in step S21 (S21: NO), in step S26, the same uphill running determination as in step S22 is performed. In subsequent step S27, the ECU 24 performs acceleration determination for determining whether or not the vehicle 10 is accelerating. When the vehicle 10 is neither climbing up nor accelerating (S28: NO), in step S29, the ECU 24 normally selects the second mode (voltage fixed / current variable control). If the vehicle 10 is either climbing or accelerating (S28: YES), in step S30, the ECU 24 executes the second mode (voltage fixed / current variable control) during climbing / acceleration.

(2-3-4. Climbing judgment)
FIG. 13 is a flowchart of uphill determination. In step S41, the ECU 24 calculates an average value (average motor torque Tmave) of the torque Tm of the motor 14, and the average motor torque Tmave is greater than or equal to a threshold value THTmave1 for determining whether or not the vehicle 10 is climbing up. It is determined whether or not there is.

  If the average motor torque Tmave is equal to or greater than the threshold value THTmave1 (S41: YES), in step S42, the ECU 24 calculates an average value (average motor rotation speed Nmave) of the rotation speed Nm of the motor 14, and the average motor rotation speed Nmave is calculated. Then, it is determined whether or not the vehicle 10 is not less than a threshold value THNmave1 for determining whether or not the vehicle 10 is climbing up.

  When the average motor rotation speed Nmave is equal to or greater than the threshold THNmave1 (S42: YES), in step S43, the ECU 24 sets the climbing flag FLG1 indicating whether the vehicle 10 is climbing or not, and the vehicle 10 is climbing. Is set to “1”.

  When the average motor torque Tmave is not equal to or greater than the threshold value THTmave1 (S41: NO) or when the average motor speed Nmave is not equal to or greater than the threshold value THNmave1 (S42: NO), in step S44, the ECU 24 sets the acceleration flag FLG1 and the vehicle 10 climbs the slope. It is set to “0” indicating that there is no medium.

(2-3-5. Acceleration judgment)
FIG. 14 is a flowchart of acceleration determination. In step S51, the ECU 24 calculates the output of the motor 14 (motor output Pmot), and determines whether or not the motor output Pmot is greater than or equal to a threshold value THPmot1 for determining whether or not the vehicle 10 is accelerating. To do.

  When the motor output Pmot is greater than or equal to the threshold value THPmot1 (S51: YES), in step S52, the ECU 24 determines that the opening degree θp of the accelerator pedal 156 is greater than or equal to a threshold value THθp1 for determining whether or not the vehicle 10 is accelerating. It is determined whether or not.

  When the opening degree θp is equal to or greater than the threshold value THθp1 (S52: YES), in step S53, the ECU 24 indicates an acceleration flag FLG2 indicating whether or not the vehicle 10 is accelerating, and indicates that the vehicle 10 is accelerating. Set to “1”.

  When the motor output Pmot is not greater than or equal to the threshold value THPmot1 (S51: NO) or when the opening degree θp of the accelerator pedal 156 is not greater than or equal to the threshold value THθp1 (S52: NO), in step S54, the ECU 24 sets the acceleration flag FLG2 and the vehicle 10 Set to “0” to indicate that acceleration is not in progress.

(2-3-6. First mode)
As described above, the first mode is mainly used when the system load Psys is relatively high. In the state where the target oxygen concentration Cotgt is fixed (or oxygen is maintained in a rich state), The FC current Ifc is controlled by adjusting the FC voltage Vfctgt. The first mode is divided into a normal first mode that is used when the vehicle 10 is traveling normally on an uphill (during travel other than when climbing), and a first mode that is used when climbing uphill.

  That is, as shown in FIG. 11, in the normal first mode, the current-voltage characteristic (IV characteristic) of the FC 40 is normal (represented by a solid line in FIG. 11). In the first mode when climbing, the IV characteristics of FC40 with an increased air stoichiometric ratio are used.

  As in the case of a normal fuel cell, in the IV characteristics of FC40, the cell current Icell (FC current Ifc) increases as the cell voltage Vcell (FC voltage Vfc) decreases. For this reason, in the normal first mode and the first mode when climbing, the target FC current Ifctgt is calculated according to the system load Psys, and the target FC voltage Vfctgt corresponding to the target FC current Ifctgt is calculated. Then, the ECU 24 controls the DC / DC converter 22 so that the FC voltage Vfc becomes the target FC voltage Vfctgt. That is, the primary voltage V1 is boosted by the DC / DC converter 22 so that the secondary voltage V2 becomes the target FC voltage Vfctgt, thereby controlling the FC voltage Vfc and controlling the FC current Ifc.

  Note that the oxygen-rich state means that, for example, as shown in FIG. 15, even if the air stoichiometric ratio is increased, the cell current Icell becomes substantially constant and exceeds the normal stoichiometric ratio that is substantially saturated. Means oxygen in the region. The same applies when hydrogen is rich. The air stoichiometric ratio is adjusted by controlling the oxygen concentration, for example.

  According to the first mode as described above (normal first mode and first mode when climbing), even when the system load Psys is relatively high, basically all of the system load Psys is obtained by the FC power Pfc. It is possible to cover.

  In particular, according to the first mode when climbing, even when the vehicle 10 is climbing, all of the system load Psys can be covered by the FC power Pfc. That is, in the first mode when climbing, the FC voltage Vfc is increased because the IV characteristic of the FC 40 in which the air stoichiometric ratio is increased is used. When the FC voltage Vfc increases, the voltage at which the inverter 16 drives the motor 14 (motor voltage Vmot) increases. As shown in FIG. 16, the motor efficiency during high-torque rotation increases in proportion to the increase in motor voltage Vmot. As a result, even when the vehicle 10 is climbing up, all of the system load Psys can be covered by the FC power Pfc, and drivability can be maintained by higher output.

(2-3-7. Second mode)
As described above, the second mode is mainly used when the system load Psys is relatively low, and the target cell voltage Vcelltgt (= target FC voltage Vfctgt / number of cells) is set higher than that in the redox region R3. The FC current Ifc is made variable by fixing the reference potential {in this embodiment, the potential v2 (= 0.8V)} set below a low potential and making the target oxygen concentration Cotgt (air stoichiometric ratio) variable. To do. The second mode is divided into a normal second mode used during normal traveling (during traveling other than climbing and acceleration) and a second climbing / acceleration second mode used during climbing or acceleration.

  That is, as shown in FIG. 11, in the normal second mode, the oxygen concentration Co is lowered by lowering the target oxygen concentration Cotgt while keeping the cell voltage Vcell constant. As shown in FIG. 15, when the air stoichiometric ratio (oxygen concentration Co) decreases, the cell current Icell (FC current Ifc) also decreases. For this reason, it is possible to control the cell current Icell (FC current Ifc) and the FC power Pfc by increasing or decreasing the target oxygen concentration Cotgt while keeping the cell voltage Vcell constant. Note that the shortage of the FC power Pfc is assisted from the battery 20.

  In the second mode during uphill / acceleration, the air stoichiometric ratio is increased and returned to the same level as in the normal first mode. Therefore, the second mode is a mode in which the FC current Ifc is made variable by fixing the target cell voltage Vcelltgt (target FC voltage Vfctgt) and making the target oxygen concentration Cotgt variable. In the second mode, since the target oxygen concentration Cotgt is fixed, the target cell voltage Vcelltgt (target FC voltage Vfctgt) and the FC current Ifc are substantially constant.

  FIG. 17 shows a flowchart of the second mode (second mode during normal time and second mode during uphill / acceleration). In step S61, the ECU 24 adjusts the step-up rate of the DC / DC converter 22 to thereby set a reference potential that is set at a potential lower than the oxidation-reduction region R3 (in this embodiment, the potential v2 (= 0.8 V)). }, The target FC voltage Vfctgt is fixed. In step S62, the ECU 24 calculates a target FC current Ifctgt corresponding to the system load Psys. In the second mode during uphill / acceleration, the target FC current Ifctgt here is constant.

  In step S63, the ECU 24 calculates the target oxygen concentration Cotgt corresponding to the target FC current Ifctgt on the assumption that the target FC voltage Vfctgt is the reference potential (see FIGS. 11 and 18). FIG. 18 shows the relationship between the target FC current Ifctgt and the target oxygen concentration Cotgt when the FC voltage Vfc is the reference potential. In the second mode during uphill / acceleration, since the target FC current Ifctgt is constant, the target oxygen concentration Cotgt is also constant.

  In step S64, the ECU 24 calculates and transmits a command value to each unit in accordance with the target oxygen concentration Cotgt. The command value calculated here includes the rotational speed of the air pump 60 (hereinafter referred to as “air pump rotational speed Nap” or “rotational speed Nap”), and the rotational speed of the water pump 80 (hereinafter referred to as “water pump rotational speed Nwp” or “ ), The opening of the back pressure valve 64 (hereinafter referred to as “back pressure valve opening θbp” or “opening θbp”), and the opening of the circulation valve 66 (hereinafter referred to as “circulation valve opening θc” or “ "Opening angle θc").

  That is, as shown in FIGS. 19 and 20, the target air pump speed Naptgt, the target water pump speed Nwptgt, and the target back pressure valve opening degree θbptgt are set according to the target oxygen concentration Cotgt. Moreover, the target opening degree θctgt of the circulation valve 66 is set to an initial value (for example, an opening degree at which the circulating gas becomes zero).

  In step S65, the ECU 24 determines whether power generation by the FC 40 is stable. As the determination, when the lowest cell voltage input from the cell voltage monitor 42 is lower than the voltage obtained by subtracting the predetermined voltage from the average cell voltage {lowest cell voltage <(average cell voltage−predetermined voltage)}, the FC 40 Is determined to be unstable. As the predetermined voltage, for example, an experimental value, a simulation value, or the like can be used.

  If the power generation is stable (S65: YES), the current process is terminated. When power generation is not stable (S65: NO), in step S66, the ECU 24 increases the opening degree θc of the circulation valve 66 while monitoring the flow rate Qc [g / s] of the circulation gas via the flow rate sensor 70. Then, the flow rate Qc is increased by one step (see FIG. 21). FIG. 21 illustrates the case where the flow rate Qc is increased in the fourth stage and the maximum flow rate is obtained when the circulation valve 66 is fully opened.

  However, when the opening degree θc of the circulation valve 66 increases, the ratio of the circulation gas in the intake gas sucked into the air pump 60 increases. That is, the intake gas changes such that the ratio of the circulating gas increases in the ratio of new air (air taken from outside the vehicle) and the circulating gas. Therefore, the ability to distribute oxygen to all single cells is improved. Here, the oxygen concentration of the circulating gas (cathode off-gas) is lower than the oxygen concentration of the new air. For this reason, before and after the control of the opening degree θc of the circulation valve 66, if the rotation speed Nap of the air pump 60 and the opening degree θbp of the back pressure valve 64 are the same, the oxygen concentration of the gas flowing through the cathode channel 74 decreases. It will be.

  Therefore, in step S66, the rotation speed Nap of the air pump 60 is increased and the opening θbp of the back pressure valve 64 is interlocked with the increase in the circulation gas flow rate Qc so that the target oxygen concentration Cotgt calculated in step S63 is maintained. Preferably, at least one of the reductions is performed.

  For example, when the flow rate Qc of the circulating gas is increased, it is preferable to increase the rotational speed Nap of the air pump 60 and increase the flow rate of new air. In this way, the flow rate of the entire gas (mixed gas of new air and circulating gas) toward the cathode flow path 74 increases, so that the ability to distribute oxygen to all single cells is further improved, and the FC 40 The power generation performance is easily recovered.

  Thus, since the circulating gas is merged with the new air while maintaining the target oxygen concentration Cotgt, the volume flow rate [L / s] of the gas flowing through the cathode channel 74 is increased. As a result, the gas whose volume flow rate has increased while the target oxygen concentration Cotgt is maintained can easily reach the entire cathode channel 74 formed in a complex manner in the FC 40. Accordingly, the gas is easily supplied to each single cell as well, and the unstable power generation of the FC 40 is easily resolved. In addition, water droplets (condensed water, etc.) adhering to the surface of the MEA (membrane electrode assembly) and the wall surface surrounding the cathode channel 74 are easily removed.

  In step S <b> 67, the ECU 24 determines whether or not the circulating gas flow rate Qc detected via the flow rate sensor 70 is equal to or higher than the upper limit value. The upper limit value serving as the determination criterion is set to a value at which the opening degree θc of the circulation valve 66 is fully opened.

  In this case, even if the circulation valve opening degree θc is the same, if the rotation speed Nap of the air pump 60 increases, the flow rate Qc of the circulating gas detected by the flow sensor 70 increases. In association with the number Nap, that is, when the rotation speed Nap of the air pump 60 is increased, the upper limit value is preferably set to be increased.

  When it is determined that the flow rate Qc of the circulating gas is not equal to or higher than the upper limit value (S67: NO), the process returns to step S65. When it is determined that the flow rate Qc of the circulating gas is equal to or higher than the upper limit value (S67: YES), the process proceeds to step S68.

  Here, in steps S66 and S67, the process is executed based on the circulation gas flow rate Qc directly detected by the flow sensor 70, but the process may be executed based on the circulation valve opening θc. That is, in step S66, the circulation valve opening degree θc is increased in one step (for example, 30 °) in the opening direction. If the circulation valve 66 is fully open in step S67 (S67: YES), the process proceeds to step S68. It is good also as a structure to advance.

  In this case, the circulation gas flow rate Qc [g / s] can also be calculated based on the degree of opening θc of the circulation valve 66, the temperature of the circulation gas, and the map of FIG. As shown in FIG. 22, since the density decreases as the temperature of the circulating gas increases, the flow rate Qc [g / s] decreases.

  In step S68, the ECU 24 determines whether or not power generation is stable, similarly to step S65. If the power generation is stable (S68: YES), the current process ends. If the power generation is not stable (S68: NO), in step S69, the ECU 24 increases the target oxygen concentration Cotgt by one step (approaches the normal concentration). Specifically, at least one of increasing the rotation speed Nap of the air pump 60 and decreasing the opening θbp of the back pressure valve 64 is performed in one step.

  In step S70, the ECU 24 determines whether or not the target oxygen concentration Cotgt is equal to or lower than the target oxygen concentration (normal oxygen concentration Conml) in the normal IV characteristics. When the target oxygen concentration Cotgt is less than or equal to the normal oxygen concentration Conml (S70: YES), the process returns to step S68. If the target oxygen concentration Cotgt is not less than or equal to the normal oxygen concentration Conml (S70: NO), the ECU 24 stops the FC unit 18 in step S71. That is, the ECU 24 stops the supply of hydrogen and air to the FC 40 and stops the power generation of the FC 40. Then, the ECU 24 turns on a warning lamp (not shown) to notify the driver that the FC 40 is abnormal. Note that the ECU 24 supplies electric power from the battery 20 to the motor 14 and continues running of the FC vehicle 10.

  According to the second mode as described above, when the second mode is normally selected, when the system load Psys is relatively low, the cell voltage Vcell is lowered from the potential v2, and basically the system load. All of Psys can be covered by the FC power Pfc. Further, when the second mode during climbing / acceleration is selected, even when the vehicle 10 is climbing or accelerating, all of the system load Psys can be covered by the FC power Pfc, and higher output is achieved. As a result, drivability can be maintained.

(2-3-8. Overall efficiency of FC system 12)
FIG. 23 shows the relationship among each power supply mode, FC power Pfc, and power generation efficiency of FC 40 in the present embodiment. As can be seen from FIG. 23, in the normal first mode, basically, the power generation efficiency of the FC 40 can be kept high while all the system load Psys is covered with the FC power Pfc. In the first mode when climbing, basically all of the system load Psys can be covered by the FC power Pfc, but the power generation efficiency of the FC 40 is lower than that in the first mode. However, as described above, the motor efficiency is improved. This is because when the target oxygen concentration Cotgt (air stoichiometric ratio) increases, the FC voltage Vfc increases and the FC current Ifc decreases due to the characteristics of the FC 40, so that the current passing through the inverter 16 decreases. Therefore, the output efficiency may increase when viewed with the FC vehicle 10 as a whole.

  Normally, in the second mode, the power generation efficiency of the FC 40 is low, but basically, all the system load Psys is covered by the FC power Pfc, so that the frequency of charging / discharging of the battery 20 is suppressed, and the output of the entire FC system 12 is output. It is possible to increase the efficiency. In the second mode during uphill / acceleration, the output efficiency of the vehicle 10 as a whole decreases as the FC 40 generates surplus power. On the other hand, while the power generation efficiency of the FC 40 is improved, the motor efficiency is improved as described above. improves.

[2-4. FC power generation control]
As described above, as the FC power generation control (S4 in FIG. 5), the ECU 24 controls peripheral devices of the FC stack 40, that is, the air pump 60, the back pressure valve 64, the circulation valve 66, and the water pump 80. Specifically, ECU24 controls these apparatuses using the command value (for example, S64 of FIG. 17) of these apparatuses calculated by energy management (S3 of FIG. 5).

[2-5. Torque control of motor 14]
FIG. 24 shows a flowchart of torque control of the motor 14. In step S81, the ECU 24 reads the vehicle speed V from the vehicle speed sensor 154. In step S <b> 82, the ECU 24 reads the opening degree θp of the accelerator pedal 156 from the opening degree sensor 150.

  In step S83, the ECU 24 calculates a temporary target torque Ttgt_p [N · m] of the motor 14 based on the vehicle speed V and the opening degree θp. Specifically, a map that associates the vehicle speed V, the opening degree θp, and the temporary target torque Ttgt_p is stored in a storage unit (not shown), and the temporary target torque Ttgt_p is determined based on the map, the vehicle speed V, and the opening degree θp. calculate.

  In step S84, the ECU 24 calculates a limit output (motor limit output Pm_lim) [W] of the motor 14 equal to a limit value (limit supply power Ps_lim) [W] of power that can be supplied from the FC system 12 to the motor 14. Specifically, the limit supply power Ps_lim and the motor limit output Pm_lim are calculated from the sum of the FC power Pfc from the FC stack 40 and the limit value of the power that can be supplied from the battery 20 (limit output Pbat_lim) [W]. The power consumption Pa is subtracted (Pm_lim = Ps_lim ← Pfc + Pbat_lim−Pa).

  In step S85, the ECU 24 calculates a torque limit value Tlim [N · m] of the motor 14. More specifically, the torque limit value Tlim is obtained by dividing the motor limit output Pm_lim by the vehicle speed V (Tlim ← Pm_lim / V).

  In step S86, the ECU 24 calculates a target torque Ttgt [N · m]. Specifically, the ECU 24 sets the provisional target torque Ttgt_p, which is limited by the torque limit value Tlim, as the target torque Ttgt. For example, when the temporary target torque Ttgt_p is equal to or less than the torque limit value Tlim (Ttgt_p ≦ Tlim), the temporary target torque Ttgt_p is set as the target torque Ttgt as it is (Ttgt ← Ttgt_p). On the other hand, when the temporary target torque Ttgt_p exceeds the torque limit value Tlim (Ttgt_p> Tlim), the torque limit value Tlim is set as the target torque Ttgt (Ttgt ← Tlim).

  Then, the motor 14 is controlled using the calculated target torque Ttgt.

3. Examples of various controls [3-1. Example when climbing]
FIG. 25 shows a first example of a time chart (when climbing) when various controls according to the present embodiment are used. Since the system load Psys exceeds the threshold value THPsys1 from the time point t1 to the time point t3 (S21: YES in FIG. 12), the first mode is selected. Also, from the time point t1 to the time point t2, since the average motor rotation speed Nmave is less than the threshold value THNmave1 (S42: NO in FIG. 13), the vehicle is not climbing (not being accelerated). For this reason, the first mode is normally executed.

  At the time point t2, the average motor torque Tmave is equal to or greater than the threshold value THTmave (S41 in FIG. 13: YES) and the average motor rotational speed Nmave is equal to or greater than the threshold value THNmave1 (S42: YES). Determine (S43). For this reason, the first mode is shifted to the first mode during climbing, and the air stoichiometric ratio (here, the oxygen concentration Co) is made larger than usual (FIG. 11). As a result, the cell voltage Vcell increases and the power generation efficiency of the FC 40 decreases, but the efficiency of the motor 14 increases.

  FIG. 26 shows a second example of a time chart (when climbing) when various controls according to the present embodiment are used. From time t11 to time t13, since the system load Psys is not more than the threshold value THPsys1 (S21: NO in FIG. 12), the second mode is selected. Further, during the same period, since the average motor rotation speed Nmave is less than the threshold value THNmave1 (S42: NO in FIG. 13), the vehicle is not climbing (not being accelerated). For this reason, the second mode is normally executed.

  At time t12, the average motor torque Tmave is equal to or greater than the threshold value THTmave (S41 in FIG. 13: YES) and the average motor speed Nmave is equal to or greater than the threshold value THNmave1 (S42: YES). Determine (S43). For this reason, the second mode is shifted to the second mode during climbing / acceleration, and the air stoichiometric ratio (here, oxygen concentration Co) is returned to normal (FIG. 11). As a result, the power generation efficiency of the FC 40 is increased, and the excess is charged in the battery 20.

  At time t13, the system load Psys exceeds the threshold value THPsys1 (S21 in FIG. 12: YES), so the mode is shifted from the second mode to the first mode. In addition, since the average motor torque T is greater than or equal to the threshold value THTmave1 (S41 in FIG. 13: YES) and the average motor speed Nmave is greater than or equal to the threshold value THNmave1 (S42: YES), the ECU 24 determines that the vehicle 10 is climbing up. (S43). For this reason, the first mode is shifted to the first mode during climbing, and the air stoichiometric ratio (here, the oxygen concentration Co) is made larger than usual (FIG. 11). As a result, the cell voltage Vcell increases and the power generation efficiency of the FC 40 decreases, but the efficiency of the motor 14 increases.

  In the example of FIG. 26, the second mode during uphill / acceleration is sandwiched between the normal second mode and the first mode during uphill. For this reason, when a response delay (decrease in climbing force) from the second mode to the first mode when climbing normally occurs, the response delay is compensated by using the second mode during climbing / acceleration to improve drivability. It becomes possible to improve.

[3-2. Example of acceleration]
FIG. 27 shows a third example (at the time of acceleration) of a time chart when various controls according to the present embodiment are used. In the example of FIG. 27, the second mode is selected from time t21 to time t23.

  From time t21 to time t22, the motor output Pmot is less than the threshold value THPmot1 (S51: NO in FIG. 14). For this reason, the second mode is normally executed.

  At time t22, when the motor output Pmot is equal to or greater than the threshold value THPmot1 (S51: YES in FIG. 14) and the opening degree θp of the accelerator pedal 156 is equal to or greater than the threshold value THθp1 (S52: YES), the ECU 24 indicates that the vehicle 10 is accelerating. Determine (S53). For this reason, the normal second mode is shifted to the second mode during uphill / acceleration, and the air stoichiometric ratio (here, the oxygen concentration Co) is returned to the normal state (FIG. 11). As a result, the power generation efficiency of the FC 40 is increased, and the excess is charged in the battery 20.

  At time t23, since the system load Psys exceeds the threshold value THPsys1 (S21 in FIG. 12: YES), the mode is shifted from the second mode to the first mode. In the first mode of the present embodiment, there is no mode for acceleration, so here, the first mode is shifted to the normal first mode, and the FC power Pfc using the target FC voltage Vfctgt and the target FC current Ifctgt is used. Is controlled (FIG. 11). Thus, the FC 40 can generate power with high output and high power generation efficiency.

  In the example of FIG. 27, the second mode during uphill / acceleration is sandwiched between the normal second mode and the normal first mode. For this reason, when a response delay (decrease in acceleration force) from the normal second mode to the normal first mode occurs, the response delay is compensated through the second mode during uphill / acceleration to improve drivability. It becomes possible to do.

4). Effects of this Embodiment As described above, according to this embodiment, it is possible to improve the efficiency of the FC vehicle 10 while suppressing the deterioration of the FC 40.

  That is, mainly in the first mode that can be used when the system load Psys is relatively high, the target FC voltage Vfctgt is set to a value lower than the oxidation-reduction region R3. It is possible to prevent the FC 40 from being deteriorated by being frequently repeated at the same time. In addition, the FC voltage Vfc is adjusted by the output voltage (secondary voltage V2) of the DC / DC converter 22 so as to follow the target FC voltage Vfctgt. This makes it possible to cope with the system load Psys. It becomes possible to do.

  In the second mode that can be used mainly when the system load Psys is relatively low, the FC voltage Vfc is maintained at the potential v2 (that is, a value lower than the oxidation-reduction region R3). It is possible to prevent the reaction and the reduction reaction from being repeated frequently at the same time, thereby preventing the deterioration of FC40. In addition, the air stoichiometric ratio (target oxygen concentration Cotgt) of the FC 40 is adjusted to change the IV characteristic of the FC 40, and the system load Psys is output by the FC 40. Therefore, the amount and frequency of discharge and charge in the battery 20 are reduced. It becomes possible to reduce the power loss in the battery 20.

  As described above, according to this embodiment, it is possible to improve the efficiency of the entire FC system 40 while suppressing deterioration of the FC 40.

  In addition, according to the present embodiment, the air stoichiometric ratio (target oxygen concentration Cotgt) is increased when it is determined that the vehicle 10 is in a high load state (during climbing or accelerating) during the second mode. Thus, when the vehicle 10 is in a high load state, the air stoichiometric ratio is increased in the second mode, so that the FC 40 has a higher output and can maintain drivability at the time of high load.

  In the present embodiment, the ECU 24 maintains the FC voltage Vfc at the potential V2 (= 0.8 V) outside the redox region R3 when it is determined that the vehicle 10 is in the acceleration state or the uphill state during the second mode. . As a result, even when the air stoichiometric ratio is increased in a high load state, the FC voltage Vfc is prevented from entering the oxidation-reduction region R3, and deterioration of the FC 40 can be suppressed.

  In the present embodiment, when the vehicle 10 is going uphill, the air stoichiometric ratio (target oxygen concentration Cotgt) is increased from the air stoichiometric ratio in the normal first mode (see FIG. 11). Thereby, the electric power supplied to the motor 14 increases, and the output of the motor 14 can be increased. Therefore, the output when climbing is increased and drivability is improved.

  In the present embodiment, the FC system 12 is mounted on the FC vehicle 10. Thereby, it is possible to realize the FC vehicle 10 having high durability, high efficiency, and high drivability.

5. Modifications It should be noted that the present invention is not limited to the above-described embodiment, and it is needless to say that various configurations can be adopted based on the contents described in this specification. For example, the following configuration can be adopted.

[5-1. Installation target]
In the said embodiment, although FC system 12 was mounted in FC vehicle 10, you may mount not only in this but in another object. For example, the FC system 12 can be used for a moving body such as a ship or an aircraft. Alternatively, the FC system 12 may be applied to a household power system.

[5-2. Configuration of FC system 12]
In the above embodiment, the FC 40 and the high voltage battery 20 are arranged in parallel, and the DC / DC converter 22 is arranged in front of the battery 20, but this is not restrictive. For example, as shown in FIG. 28, the FC 40 and the battery 20 may be arranged in parallel, and the step-up, step-down or step-up / step-down DC / DC converter 22 may be arranged in front of the FC 40. Alternatively, as shown in FIG. 29, the FC 40 and the battery 20 are arranged in parallel. The structure to arrange | position may be sufficient. Alternatively, as shown in FIG. 30, the FC 40 and the battery 20 may be arranged in series, and the DC / DC converter 22 may be arranged between the battery 20 and the motor 14.

[5-3. Stoichi ratio]
In the above embodiment, the means or method for adjusting the stoichiometric ratio is one that adjusts the target oxygen concentration Cotgt. However, the present invention is not limited to this, and the target hydrogen concentration can also be adjusted. Further, instead of the target concentration, the target flow rate or both the target concentration and the target flow rate can be used.

  In the said embodiment, although the structure provided with the air pump 60 which supplies the air containing oxygen was illustrated, it is good also as a structure provided with the hydrogen pump which supplies hydrogen instead of or in addition to this.

  In the above-described embodiment, the configuration including the merging flow path (piping 66a, 66b) for merging the cathode off gas with the new air and the circulation valve 66 is illustrated, but instead of or in addition to this, the anode side is similarly configured. May be. For example, a circulation valve may be provided in the pipe 48b, and the flow rate of the anode off gas that joins the new hydrogen may be controlled by this circulation valve.

[5-4. Power supply mode]
In the above embodiment, the first mode is divided into when climbing (first mode when climbing) and other (normally first mode), but the first mode is switched in a high load state of the motor 14 (drive source). If there is, it is not limited to this. For example, the first mode may be provided with acceleration (first mode during acceleration or first mode during uphill / acceleration). Alternatively, when the average motor torque Tmave increases, when the average motor rotation speed Nmave increases, when the motor output Pmot increases, or when the opening θp of the accelerator pedal 156 increases, One mode may be provided.

  In the above-described embodiment, the second mode is divided into when climbing and accelerating (second mode when climbing / accelerating) and other (normally second mode). If it changes a mode, it will not be restricted to this. For example, the second mode may be provided only for one of climbing and acceleration. Alternatively, when the average motor torque Tmave increases, when the average motor rotation speed Nmave increases, when the motor output Pmot increases, or when the opening θp of the accelerator pedal 156 increases, Two modes may be provided.

  In the above embodiment, both the average motor torque Tmave and the average motor rotation speed Nmave are used for the uphill determination, but only one of them may be used. Further, instead of the average motor torque Tmave, the average current of the motor 14 or the average value of the FC current Ifc may be used. Further, instead of the average motor rotation speed Nmave, a change amount of the motor rotation speed, a vehicle speed or an acceleration may be used. Alternatively, the climbing determination may be performed by comparing the output of a gradient sensor (not shown) with a threshold value for determining whether or not the vehicle is climbing. Alternatively, the climbing determination may be performed using road information (for example, at least one information of a slope, a slope, and an altitude) stored in a car navigation device (not shown).

  In the above embodiment, both the motor output Pmot and the opening degree θp of the accelerator pedal 156 are used for the acceleration determination, but only one of them may be used. Moreover, the input current to the motor 14 or the generated current Ifc of the FC 40 may be used instead of the motor output Pmot. Furthermore, instead of the opening degree θp of the accelerator pedal 156, a change amount of the opening degree θp in a predetermined time may be used.

  In the above embodiment, the target FC voltage Vfctgt in the second mode is set to the potential v2 × the number of cells, but this is not restrictive. For example, the target FC voltage Vfctgt in the second mode may be set to another potential in the reduction region R2 or the oxidation region R4.

DESCRIPTION OF SYMBOLS 10 ... Fuel cell vehicle 12 ... Fuel cell system 14 ... Traveling motor (load) 16 ... Inverter (load)
18 ... Fuel cell unit (reactive gas supply unit)
DESCRIPTION OF SYMBOLS 20 ... High voltage battery (power storage device) 22 ... DC / DC converter 24 ... ECU (control device) 30 ... Load 40 ... FC 60 ... Air pump (load)
80 ... Water pump (load) 90 ... Air conditioner (load)

Claims (4)

A fuel cell;
A power storage device for storing power from the fuel cell;
A load supplied with power from at least one of the fuel cell or the power storage device;
A converter for adjusting the voltage of the fuel cell;
A control device for controlling power supplied to the load by the fuel cell and the power storage device based on power required by the load;
A fuel cell vehicle comprising a reaction gas supply device for supplying a reaction gas to the fuel cell,
The controller is
A first mode in which when the target voltage of the fuel cell is equal to or lower than a first voltage lower than the platinum oxidation-reduction voltage range, the actual voltage of the fuel cell is adjusted by the output voltage of the converter to follow the target fuel cell voltage; ,
While maintaining the than the first mode than the first mode with reducing stoichiometric ratio used during relatively low load, before SL adjusts the first voltage and a voltage equal to the actual voltage at the converter output voltage And controlling the reactive gas supply device to adjust the reactive gas supply amount to the fuel cell to change the current-voltage characteristic of the fuel cell so that the fuel cell outputs the power required by the load. To switch between the second mode and
When it is determined that the fuel cell vehicle is at least one of an uphill state and an acceleration state during the second mode, the stoichiometric ratio of the reaction gas is maintained with the target voltage maintained at a voltage equal to the first voltage. The fuel cell vehicle, wherein the power generation current of the fuel cell is increased by increasing the stoichiometric ratio of the second mode toward the stoichiometric ratio of the first mode . The fuel cell vehicle according to claim 1, wherein
When the control device determines that the fuel cell vehicle is at least one of an uphill state and an accelerated state during the second mode, the stoichiometric ratio equivalent value set in the first mode is set as the stoichiometric ratio of the reactive gas. A fuel cell vehicle characterized by being raised to a maximum. The fuel cell vehicle according to claim 1 or 2,
When the control device determines that the fuel cell vehicle is at least one of an acceleration state and a climbing state during the second mode, the actual voltage of the fuel cell is set outside the oxidation-reduction progress voltage range. A fuel cell vehicle characterized by maintaining the second voltage. The fuel cell vehicle according to claim 1, wherein
When the fuel cell vehicle is climbing in the first mode, the stoichiometric ratio of the reaction gas is increased from the normal stoichiometric ratio in the first mode.

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