JP2020170628A - Fuel cell system - Google Patents

Abstract

To provide a technology that can make braking force more stable in a fuel cell system.SOLUTION: In a scavenging process execution unit of a fuel cell system, an operation of a compressor is controlled to change the supply flow rate of oxidizing gas to a cathode such that the rate of a change in regenerative braking torque calculated from an estimated power generation output during a period of braking a fuel cell vehicle is slower than the rate of a change in friction braking torque which is braking torque using a friction brake.SELECTED DRAWING: Figure 6

Description

The present invention relates to a fuel cell system technology.

Conventionally, there is known a technique of coordinating a regenerative braking torque and a friction braking torque to realize a braking force required by a driver (Patent Document 1). In the conventional technique, the regenerative braking torque limit value is corrected in order to keep the braking torque fluctuation due to the stepping operation of the brake pedal within an allowable range.

Japanese Unexamined Patent Publication No. 2015-105075

Here, in a fuel cell vehicle powered by a fuel cell, during a period in which the regenerative braking torque and the friction braking torque are coordinated, the fuel cell suddenly generates electricity without the driver's operation, that is, due to the scavenging process. Power generation may occur. When the fuel cell generates power, the amount of regenerative power that can be stored may decrease and the regenerative braking torque may decrease because the power storage device recovers the generated power. In this case, a technique for making the braking force more stable is desired.

The present invention can be realized as the following forms.

According to one embodiment of the present invention, a fuel cell system mounted on a fuel cell vehicle is provided. This fuel cell system has a drive motor that is capable of regenerative operation and drives the fuel cell vehicle, a fuel cell that has a cathode and an anode and can supply power to the drive motor, and an oxide gas at the cathode. A predetermined upper limit value of the compressor that feeds the fuel cell, the friction brake that brakes the fuel cell vehicle, the power supply to the drive motor, the generated power generated by the fuel cell, and the regenerated power generated by the regenerative operation. The fuel cell system includes a power storage device capable of storing electricity in the following range and a control device that controls the operation of the compressor to control the supply flow rate of the oxide gas to the cathode. During the period of braking the battery vehicle, as the power generation output of the fuel cell increases, the regenerative braking torque generated by the regenerative operation of the drive motor is configured to decrease, and the control device moves to the cathode. A power generation output estimation unit that estimates the power generation output of the fuel cell with respect to the supply flow rate of the oxide gas, a stagnant water estimation unit that estimates the amount of stagnant water that stays in the fuel cell, and an estimated amount of the stagnant water. However, when the value exceeds a predetermined threshold value, the scavenging process execution unit that executes the scavenging process for discharging the accumulated water to the outside of the fuel cell by supplying the oxidation gas to the cathode by the compressor, and the fuel. When the voltage of the battery reaches a predetermined upper limit voltage, the fuel cell is provided with a voltage maintenance unit that maintains the voltage below the upper limit voltage by generating power, and the scavenging processing execution unit is described. During the period, the operation of the compressor is controlled so that the change speed of the regenerative braking torque calculated from the estimated power generation output becomes slower than the change speed of the friction braking torque, which is the braking torque using the friction brake. The supply flow rate of the oxide gas to the cathode is changed. According to this form, the amount of change in the regenerative braking torque is changed by changing the supply flow rate of the oxide gas so that the change speed of the regenerative braking torque due to the power generation of the fuel cell becomes slower than the change speed of the friction braking torque. Can be supplemented with friction braking torque. As a result, the braking force can be made more stable.
The present invention can be realized in various forms, and in addition to the above-mentioned fuel cell system, for example, a fuel cell vehicle equipped with a fuel cell system, a control method of the fuel cell system, and a control method thereof are realized. It can be realized in the form of a computer program, a non-temporary recording medium on which the computer program is recorded, or the like.

The explanatory view which shows the schematic structure of the fuel cell vehicle in an embodiment. Functional block diagram of the control device. The figure for exemplifying the change of the braking torque at the time of regenerative cooperative braking. The figure for demonstrating the charge amount of a power storage device. A reference diagram schematically showing a change in braking torque during regenerative cooperative braking. A flowchart of the process executed by the control device during the coordinated braking period. An example of a timing chart of the brake depression amount, the oxide gas supply flow rate, and the braking torque in this embodiment. Reference example timing chart.

A. Embodiment:
FIG. 1 is an explanatory diagram showing a schematic configuration of the fuel cell vehicle 20 in the embodiment. The fuel cell vehicle 20 includes a fuel cell system 30, front wheel FW, and rear wheel RW. The fuel cell system 30 includes a fuel cell 100, a power storage device 421, a drive motor 40, a friction brake 50, an accelerator pedal 70, a brake pedal 72, a vehicle speed detection unit 60, and a control device 80. There is.

The fuel cell vehicle 20 is driven or braked according to the operation of the accelerator pedal 70 and the brake pedal 72. The drive motor 40 of the present embodiment is capable of regenerative operation and drives the fuel cell vehicle 20. That is, the drive motor 40 can operate in the power running mode for driving the fuel cell vehicle 20 and the regenerative mode for braking the fuel cell vehicle 20. The drive motor 40 in the power running mode drives the fuel cell vehicle 20 by receiving electric power from the fuel cell system 30 and rotating at least one of the front wheel FW and the rear wheel RW. The drive motor 40 in the regenerative mode brakes the fuel cell vehicle 20 by converting the kinetic energy of the fuel cell vehicle 20 into electric power. Braking by the drive motor 40 in the regenerative mode is also called regenerative braking. The fuel cell vehicle 20 of the present embodiment is braked by a regenerative cooperative brake in which a regenerative brake and a friction brake 50 are used in combination. The braking torque due to the friction brake is also called the friction braking torque, the braking torque due to the regenerative braking is also called the regenerative braking torque, and the braking torque due to the regenerative cooperative braking is also called the regenerative cooperative braking torque.

The fuel cell system 30 of the present embodiment includes a hydrogen supply / exhaust system 200, an air supply / exhaust system 300, and a power supply system 400 in addition to the fuel cell 100. The fuel cell 100 of the present embodiment is a polymer electrolyte fuel cell. The fuel cell 100 generates an electromotive force by an electrochemical reaction. The fuel cell 100 has an anode and a cathode. As the reaction gas of the fuel cell 100, hydrogen gas is used as the fuel gas, and air is used as the oxidation gas. The fuel cell 100 has a stack structure in which a plurality of single cells are stacked, and each single cell is connected in series. Each single cell includes a membrane electrode assembly having electrode catalyst layers on both sides of the electrolyte membrane, and a pair of separators sandwiching the membrane electrode assembly. An anode flow path through which hydrogen gas can flow is formed between the membrane electrode assembly and the separator on the anode side. A cathode flow path through which air can flow is formed between the membrane electrode assembly and the separator on the cathode side. The fuel cell 100 can supply electric power to the drive motor 40.

The hydrogen supply / discharge system 200 includes a hydrogen supply unit 210, a hydrogen circulation unit 220, and a hydrogen discharge unit 230. The hydrogen supply unit 210 includes a hydrogen tank 211, a hydrogen supply flow path 212, a main check valve 213, a pressure reducing valve 214, and an injector 215. The hydrogen tank 211 stores hydrogen gas for supplying to the fuel cell 100 in a high pressure state. The hydrogen supply flow path 212 is a flow path that connects the hydrogen tank 211 and the anode flow path of the fuel cell 100. The hydrogen supply flow path 212 is provided with a main stop valve 213 and a pressure reducing valve 214 in this order from the upstream side. When the main check valve 213 is opened, the high-pressure hydrogen gas stored in the hydrogen tank 211 flows into the hydrogen supply flow path 212. The high-pressure hydrogen gas is depressurized to a predetermined pressure by the pressure reducing valve 214, and then supplied from the injector 215 to the fuel cell 100 in response to the power generation request of the fuel cell 100.

The hydrogen circulation unit 220 includes a hydrogen circulation flow path 221 and a hydrogen circulation pump 222. The hydrogen circulation flow path 221 is a flow path that connects the anode flow path of the fuel cell 100 and the downstream side of the hydrogen supply flow path 212 with respect to the injector 215. A hydrogen circulation pump 222 is provided in the hydrogen circulation flow path 221. The unconsumed hydrogen gas contained in the anode off gas discharged from the fuel cell 100 is circulated to the hydrogen supply flow path 212 by the circulation pump. In addition to the unconsumed hydrogen gas, the anode off gas includes generated water and nitrogen gas generated by the power generation of the fuel cell 100. Therefore, the unconsumed hydrogen gas and the generated water or nitrogen gas are separated by a gas-liquid separator (not shown) provided between the fuel cell 100 and the circulation pump in the hydrogen circulation flow path 221.

The hydrogen discharge unit 230 includes a hydrogen discharge flow path 231 and an exhaust drain valve 232. The hydrogen discharge flow path 231 is a flow path connecting the fuel cell 100 and the hydrogen circulation pump 222 in the hydrogen circulation flow path 221 and the air discharge flow path 321 described later. An exhaust drain valve 232 is provided in the hydrogen discharge flow path 231. When the exhaust drain valve 232 is opened, the anode off gas is discharged to the atmosphere through the air discharge flow path 321.

The air supply / exhaust system 300 includes an air supply unit 310 and an air discharge unit 320. The air supply unit 310 includes an air introduction flow path 311, an air flow meter 312, a compressor 313, a flow dividing valve 314, an air supply flow path 315, and an air bypass flow path 316. The air introduction flow path 311 is a flow path communicating with the atmosphere, and is connected to the air supply flow path 315 and the air bypass flow path 316 by a flow dividing valve 314. The air introduction flow path 311 is provided with an air flow meter 312, a compressor 313, and a flow dividing valve 314 in this order from the upstream side. The air flow meter 312 is a sensor that detects the flow rate of the air introduced into the air introduction flow path 311. The compressor 313 is a compressor for introducing air into the air introduction flow path 311 and sending the introduced air to the fuel cell 100. The compressor 313 of this embodiment is a turbo compressor. The compressor 313 is not limited to the turbo compressor, and may be a positive displacement compressor. The shunt valve 314 can adjust the flow rate of the air flowing into the air supply flow and the flow rate of the air flowing into the air bypass flow path 316 according to the opening degree. The air supply flow path 315 is a flow path that connects the flow dividing valve 314 and the cathode flow path of the fuel cell 100. The air bypass flow path 316 is a flow path that connects the flow dividing valve 314 and the air discharge flow path 321 described later. The air bypass flow path 316 may communicate with the atmosphere without being connected to the air discharge flow path 321.

The air discharge unit 320 includes an air discharge flow path 321 and a pressure regulating valve 322. The air discharge flow path 321 is a flow path that is connected to the cathode flow path of the fuel cell 100 and communicates with the atmosphere. A pressure regulating valve 322 is provided in the air discharge flow path 321. By adjusting the opening degree of the pressure regulating valve 322, the pressure of the air in the cathode flow path of the fuel cell 100 and the flow rate of the air discharged by the compressor 313 are adjusted. On the downstream side of the pressure regulating valve 322 in the air discharge flow path 321, the above-mentioned air bypass flow path 316 and the hydrogen discharge flow path 231 are connected in order from the upstream side. The cathode off gas discharged from the cathode of the fuel cell 100 flows through the air discharge flow path 321 together with the air flowing in from the air bypass flow path 316 and the anode off gas flowing in from the hydrogen discharge flow path 231 and is discharged to the atmosphere. To.

The fuel cell system 30 further includes a refrigerant circulation system (not shown) for adjusting the temperature of the fuel cell 100. The refrigerant circulation system is configured such that the refrigerant that has cooled the fuel cell 100 circulates to the fuel cell 100 via a radiator that dissipates the refrigerant.

The power supply system 400 includes a boost converter 411, an inverter 412, a power storage device 421, a buck-boost converter 422, a first wiring 431, and a second wiring 432. The fuel cell 100, the boost converter 411, and the inverter 412 are electrically connected in this order by the first wiring 431. The power storage device 421, the buck-boost converter 422, and the boost converter 411 and the inverter 412 in the first wiring 431 are electrically connected in this order by the second wiring 432. The DC power generated by the fuel cell 100 is boosted by the boost converter 411, then converted into three-phase AC power by the inverter 412, and supplied to the drive motor 40. The DC power stored by the power storage device 421 is boosted by the buck-boost converter 422, then converted into three-phase AC power by the inverter 412, and supplied to the drive motor 40. The buck-boost converter 422 is configured not only to be able to boost the power stored in the power storage device 421, but also to be able to step down the power generated by the fuel cell 100 and the power generated by the drive motor 40 in the regeneration mode. ing. The inverter 412 is not only configured to be convertible from DC power to AC power, but is also configured to be convertible from AC power to DC power.

The power storage device 421 can store the generated power generated by the fuel cell 100 and the regenerative power generated by the regenerative operation of the drive motor 40 in the regenerative mode. When the total power of the generated power and the regenerated power exceeds the power consumed by the auxiliary equipment of the fuel cell system 30 including the compressor 313 and the hydrogen circulation pump 222, the excess amount of power is transferred to the power storage device 421. It is stored. The power storage device 421 is stored in a range of a power storage amount equal to or less than a predetermined upper limit value. The electric power stored in the power storage device 421 can be supplied to the drive motor 40 and the auxiliary equipment of the fuel cell system 30. As the power storage device 421, for example, a lithium ion battery, a nickel hydrogen battery, or the like can be used. The power storage device 421 may be a capacitor instead of a secondary battery.

The friction brake 50 is a speed reducing device for braking the fuel cell vehicle 20 by converting the kinetic energy of the fuel cell vehicle 20 into thermal energy due to friction. The friction brake 50 of the present embodiment is a hydraulic disc brake driven by an actuator. The fuel cell vehicle 20 has a hydraulic pressure sensor 52 that detects the brake hydraulic pressure, which is the master cylinder pressure of the friction brake 50. The friction brake 50 may be a drum brake driven by an actuator.

The vehicle speed detection unit 60 detects the vehicle speed of the fuel cell vehicle 20. The vehicle speed detection unit 60 of the present embodiment detects the vehicle speed by using the rotation speed of each wheel of the fuel cell vehicle 20 obtained by the wheel speed sensor. The vehicle speed detection unit 60 may detect the vehicle speed by using the acceleration of the fuel cell vehicle 20 obtained by the acceleration sensor, or may use the position information obtained by GNSS (Global Navigation Satellite System) to determine the vehicle speed. It may be detected.

The control device 80 controls the operation of the fuel cell vehicle 20. The control device 80 controls, for example, the operation of the compressor 313 to control the supply flow rate of the oxidizing gas to the cathode.

FIG. 2 is a functional block diagram of the control device 80. The control device 80 is configured as a computer including a CPU 81, a storage unit 89, and an interface circuit to which each component is connected. The storage unit 89 is composed of a ROM, a ROM, or the like, and stores various programs for controlling the fuel cell vehicle 20 and various data. For example, a regenerative braking torque map (not shown) is stored in the storage unit 89. The regenerative braking torque map is a map that defines the regenerative braking torque determined by the power generation output of the fuel cell 100 and the rotation speed of the drive motor 40 determined by the vehicle speed during the regenerative cooperative braking. By executing various programs stored in the storage unit 89, the CPU 81 serves as a power generation output estimation unit 82, a stagnant water estimation unit 83, a scavenging processing execution unit 84, a voltage maintenance unit 86, and a power control unit 87. Function.

The power generation output estimation unit 82 estimates the power generation output [kW] of the fuel cell 100 with respect to the supply flow rate of the oxidizing gas to the cathode of the fuel cell 100. The power generation output estimation unit 82 estimates the power generation output by using, for example, a map stored in the storage unit 89 showing the relationship between the supply flow rate of the oxide gas and the power generation output. In another embodiment, the power generation output estimation unit 82 uses a voltage sensor (not shown) for detecting the voltage of the fuel cell 100 and a current sensor (not shown) for detecting the current of the fuel cell 100. It may be estimated as the power generation output of the fuel cell 100.

The stagnant water estimation unit 83 estimates the amount of stagnant water staying in the fuel cell 100. Specifically, the stagnant water estimation unit 83 estimates the amount of increase in stagnant water per unit time, estimates the amount of increase in stagnant water per estimated unit time, and per unit time estimated with respect to the initial value. The amount of stagnant water is estimated by integrating the amount of increase in stagnant water. The initial value is set to, for example, zero. Further, the stagnant water estimation unit 83 returns the amount of stagnant water to the initial value when the scavenging treatment described later is completed.

The stagnant water estimation unit 83 determines the difference between the amount of generated water generated by the power generation of the fuel cell 100 per unit time and the amount of water discharged from the fuel cell 100 together with the cathode off gas per unit time. Estimated as the amount of increase in accumulated water per hit. The amount of generated water generated by the power generation of the fuel cell 100 per unit time can be calculated by using the current output from the fuel cell 100, the molecular weight of water, and the like. The amount of water discharged from the fuel cell 100 together with the cathode off gas per unit time can be calculated by using the amount of saturated water vapor at the temperature inside the fuel cell 100, the flow rate of air supplied into the fuel cell 100, and the like. The current output from the fuel cell 100 can be measured using a current sensor. As the temperature inside the fuel cell 100, the temperature of the refrigerant in the vicinity of the refrigerant outlet of the fuel cell 100 can be used. The temperature of the refrigerant in the vicinity of the refrigerant outlet of the fuel cell 100 can be measured using a temperature sensor.

The scavenging process execution unit 84 executes the scavenging process when the amount of stagnant water estimated by the stagnant water estimation unit 83 exceeds a predetermined threshold value. The scavenging process is a process of discharging the accumulated water in the fuel cell 100 to the outside of the fuel cell 100 by supplying the cathode with an oxidation gas having a predetermined target flow rate by the compressor 313, regardless of the power required from the fuel cell vehicle 20. Is. During the execution of the scavenging process, the anode gas of the fuel cell 100 is supplied with a predetermined flow rate of the anode gas.

When the voltage of the fuel cell 100 reaches a predetermined upper limit voltage, the voltage maintenance unit 86 adjusts the current drawn from the fuel cell 100 to generate the fuel cell 100, thereby setting the voltage of the fuel cell 100 to the upper limit voltage. Keep below. Specifically, the voltage maintenance unit 86 controls the boost converter 411 when the detection value of the voltage sensor of the fuel cell 100 (not shown) reaches the upper limit voltage, and draws a current from the fuel cell 100 to draw a current from the fuel cell 100. 100 is generated to maintain the voltage below the upper limit voltage. Deterioration of the fuel cell 100 can be suppressed by maintaining the voltage of the fuel cell 100 to be equal to or lower than a predetermined upper limit voltage. Deterioration of the fuel cell 100 can occur due to elution of a catalyst such as platinum contained in the fuel cell 100. The power control unit 87 controls the ratio between the friction braking torque and the regenerative braking torque.

FIG. 3 is a diagram for schematically explaining a change in braking torque during regenerative cooperative braking. The horizontal axis represents the time from the start of braking by the regenerative cooperative brake until the fuel cell vehicle 20 stops. The vertical axis represents the regenerative cooperative braking torque. Generally, the regenerative braking torque decreases in a low speed range in which the torque from the drive wheels for generating the regenerative power of the drive motor 40 is not sufficiently obtained. Therefore, the control device 80 of the present embodiment reduces the ratio of the regenerative braking torque as the fuel cell vehicle 20 becomes slower in order to secure a stable regenerative cooperative braking torque.

FIG. 4 is a diagram for explaining the charge amount of the power storage device 421. The power storage device 421 is controlled by the control device 80 so that power can be stored in a range of Cu or less, which is a predetermined upper limit value. When the power generation of the fuel cell 100 is stopped during the coordinated braking period in which the regenerative cooperative braking is executed, more regenerative electric power can be stored in the power storage device 421. On the other hand, in the coordinated braking period, when the scavenging process is executed and the fuel cell 100 is generated to maintain the voltage below the upper limit voltage, the generated power exceeding the power required for the running of the fuel cell vehicle 20 is generated. It may occur. Therefore, since the surplus generated power is stored in the power storage device 421, the regenerative power that can be stored decreases.

FIG. 5 is a reference diagram schematically showing a change in braking torque during regenerative cooperative braking. FIG. 5 shows a change in the regenerative cooperative braking torque when the scavenging process is executed in a state where the regenerative braking torque is generated. When the scavenging process is executed, the amount of regenerative power stored in the power storage device 421 decreases (FIG. 4). As a result, when the charge amount of the power storage device 421 reaches the upper limit value Cu, there is no storage or consumption destination of the regenerative power, and the current from the drive motor 40 does not flow. Therefore, in the fuel cell system 30, as the power generation output of the fuel cell 100 increases, the magnetic force for the drive motor 40 to brake the rotation of the drive wheels decreases, and the regenerative braking torque decreases. When the regenerative braking torque decreases, the friction braking torque of the friction brake 50 is increased to supplement the braking torque intended by the driver.

The scavenging process execution unit 84 of the present embodiment adjusts the supply flow rate of the oxide gas in the scavenging process according to the responsiveness of the friction brake 50 so that the regenerative braking torque reduced by the scavenging process can be compensated by the friction braking torque by the friction brake 50. Change. Specifically, in the scavenging process execution unit 84, the change speed of the regenerative braking torque of the drive motor 40 calculated from the estimated power generation output in the scavenging process during the coordinated braking period is the change speed of the friction braking torque using the friction brake 50. The operation of the compressor 313 is controlled to change the supply flow rate of the oxide gas to the cathode so as to be slower than the above.

In the present embodiment, the responsiveness of the friction brake 50 changes depending on the level of the brake hydraulic pressure. That is, when the brake hydraulic pressure is high, the responsiveness of the friction brake 50 is fast, and when the brake hydraulic pressure is low, the responsiveness of the friction brake 50 is low.

FIG. 6 is a flowchart of processing executed by the control device 80 during the cooperative braking period. The control device 80 determines whether or not there is a scavenging process request (step S10). Specifically, the scavenging treatment execution unit 84 determines that there is a scavenging treatment request when the amount of stagnant water estimated by the stagnant water estimation unit 83 exceeds a predetermined threshold value. On the other hand, the scavenging treatment execution unit 84 determines that there is no scavenging treatment request when the amount of stagnant water estimated by the stagnant water estimation unit 83 is equal to or less than a predetermined threshold value, and repeatedly executes the determination in step S10. ..

When the determination of "Yes" is made in step S10, the scavenging processing execution unit 84 determines whether or not the friction brake 50 is in the ready state (step S12). Specifically, the scavenging process execution unit 84 determines whether or not the detected pressure of the hydraulic pressure sensor 52 is equal to or higher than a predetermined reference pressure. In step S12, when the detected pressure is equal to or higher than the reference pressure, it can be determined that the responsiveness of the friction brake 50 is fast.

When the determination of "Yes" is made in step S12, the scavenging process execution unit 84 sets the ascending speed of the supply flow rate of the oxidizing gas supplied to the cathode until the target flow rate in the scavenging process is reached. Is set to (step S14). On the other hand, when the determination of "No" is made in step S14, the scavenging process execution unit 84 increases the rate of increase in the supply flow rate of the oxidizing gas supplied to the cathode until the target flow rate in the scavenging process is reached. It is set to the second value (step S16). The second value is a value smaller than the first value. The first and second values are such that the change speed of the regenerative braking torque of the drive motor 40 calculated from the estimated power generation output in the scavenging process during the coordinated braking period is higher than the change speed of the friction braking torque using the friction brake 50. It is set within the range that satisfies the condition of being slow.

After setting the ascending speed in step S14 or step S16, the scavenging processing execution unit 84 controls the rotation speed of the compressor 313 so as to have the set ascending speed, and executes the scavenging processing (step S18). The scavenging process ends, for example, when the total amount of cathode gas supplied to the cathode reaches a predetermined value.

FIG. 7 is an example of a timing chart of the brake depression amount, the oxide gas supply flow rate, and the braking torque in the present embodiment. When the brake pedal 72 is depressed, the target braking torque, that is, the braking torque intended by the driver is determined according to the amount of depression. When the depression of the brake pedal 72 is started at time t0, the power control unit 87 generates a target braking torque by the regenerative cooperative braking.

When there is a scavenging process request and the scavenging process is started at time t1 in the coordinated braking period, the scavenging process execution unit 84 becomes the rate of increase in the supply flow rate of the oxide gas set in step S14 or step S16 shown in FIG. As described above, the operation of the compressor 313 is controlled. As a result, the rate of increase in the supply flow rate until the target oxidation gas flow rate is reached becomes the first value or the second value. In FIG. 7, the dotted line L1 is a line indicating the ascending speed when the ascending speed is the first value, and the line L2 is a line indicating the ascending speed when the ascending speed is the second value. In the timing chart shown in FIG. 7, the scavenging process is stopped at time t2. In the present embodiment, the scavenging process execution unit 84 adjusts the descending speed of the supply flow rate of the oxide gas so that the braking torque does not significantly exceed the target braking torque when the scavenging process is stopped. There is.

FIG. 8 is a timing chart of a reference example. FIG. 8 is a timing chart in the case where the rate of increase of the supply flow rate up to the target supply flow rate of the oxidizing gas is faster than that of the embodiment after the time t1 when the scavenging process is started. When the scavenging process is disclosed, the power generation output of the fuel cell 100 rises sharply, so that the amount of electricity stored in the power storage device 421 rises sharply. As a result, there is no storage or consumption destination of the regenerative power, and the regenerative braking torque drops sharply. Further, when the scavenging process is stopped and the rate of decrease in the supply flow rate of the oxidizing gas is abruptly increased, the regenerative braking torque is abruptly increased.

On the other hand, according to the above embodiment, the scavenging processing execution unit 84 supplies the oxide gas so that the rate of change of the regenerative braking torque accompanying the power generation of the fuel cell 100 is slower than the rate of change of the friction braking torque. Is changed (step S14 or step S16 in FIG. 6). As a result, the amount of change in the regenerative braking torque can be supplemented by the friction braking torque, so that the braking force can be made more stable. As a result, it is possible to prevent the drivability of the fuel cell vehicle 20 from being lowered.

Further, according to the above embodiment, when the friction brake 50 is in the ready state and the responsiveness of the friction brake 50 is relatively fast, the rate of increase in the supply flow rate of the oxidizing gas is higher than the second value. It is set to a value (step S14 in FIG. 6). As a result, the time for the scavenging process can be shortened, so that the driving time of the compressor 313 can be shortened. Therefore, the power consumption of the compressor 313 can be reduced. Further, as a result, the residence time of the accumulated water in the fuel cell 100 can be shortened, so that the durability of the fuel cell 100 can be suppressed from being lowered.

B. Other embodiments:
B-1. Other Embodiment 1:
In the above embodiment, the scavenging processing execution unit 84 first increases the rate of increase in the supply flow rate of the oxide gas so that the rate of change of the regenerative braking torque accompanying the power generation of the fuel cell 100 is slower than the rate of change of the friction braking torque. Set to a value or a second value. However, the scavenging process execution unit 84 is not limited to the above embodiment. For example, the scavenging processing execution unit 84 determines that the rate of change of the regenerative braking torque accompanying the power generation of the fuel cell 100 is slower than the rate of change of the friction braking torque according to the value of the brake oil of the friction brake 50. The rate of increase in the supply flow rate may be changed. Specifically, the scavenging processing execution unit 84 may set the rate of increase in the supply flow rate of the oxidizing gas to a higher value as the brake hydraulic pressure increases.

The present invention is not limited to the above-described embodiment, and includes various modifications. For example, the above-described embodiment has been described in detail in order to explain the present invention in an easy-to-understand manner, and is not necessarily limited to the one including all the described configurations. Further, it is possible to replace a part of the configuration of one embodiment with the configuration of another modification, and it is also possible to add the configuration of another modification to the configuration of one embodiment. Further, it is possible to add / delete / replace a part of the configuration of each embodiment with another configuration. Further, the embodiment, the modified mode, and the modified example may be combined.

20 ... Fuel cell vehicle, 30 ... Fuel cell system, 40 ... Drive motor, 50 ... Friction brake, 52 ... Hydraulic pressure sensor, 60 ... Vehicle speed detector, 70 ... Accelerator pedal, 72 ... Brake pedal, 80 ... Control device, 81 ... CPU, 82 ... Power generation output estimation unit, 83 ... Retained water estimation unit, 84 ... Scavenging processing execution unit, 86 ... Voltage maintenance unit, 87 ... Power control unit, 89 ... Storage unit, 100 ... Fuel cell, 200 ... Hydrogen supply Exhaust system, 210 ... Hydrogen supply unit, 211 ... Hydrogen tank, 212 ... Hydrogen supply flow path, 213 ... Main stop valve, 214 ... Pressure reducing valve, 215 ... Inverter, 220 ... Hydrogen circulation unit, 221 ... Hydrogen circulation flow path, 222 ... Hydrogen circulation pump, 230 ... Hydrogen discharge section, 231 ... Hydrogen discharge flow path, 232 ... Exhaust drain valve, 300 ... Air supply / exhaust system, 310 ... Air supply section, 311 ... Air introduction flow path, 312 ... Air flow meter, 313 ... Compressor, 314 ... Divergence valve, 315 ... Air supply flow path, 316 ... Air bypass flow path, 320 ... Air discharge section, 321 ... Air discharge flow path, 322 ... Pressure regulating valve, 400 ... Power supply system, 411 ... Boost converter 412 ... Inverter, 421 ... Power storage device, 422 ... Buck-boost converter, 431 ... 1st wiring, 432 ... 2nd wiring, Cu ... Upper limit value, FW ... Front wheel, RW ... Rear wheel

Claims (1)

Fuel cell A fuel cell system installed in a vehicle.
A drive motor that is capable of regenerative operation and drives the fuel cell vehicle,
A fuel cell having a cathode and an anode and capable of supplying electric power to the drive motor,
A compressor that sends an oxidizing gas to the cathode,
The friction brake that brakes the fuel cell vehicle and
A power storage device capable of supplying power to the drive motor and storing the generated power generated by the fuel cell and the regenerative power generated by the regenerative operation within a predetermined upper limit or less.
A control device for controlling the operation of the compressor and controlling the supply flow rate of the oxidizing gas to the cathode is provided.
The fuel cell system is configured to reduce the regenerative braking torque generated by the regenerative operation of the drive motor as the power generation output of the fuel cell increases during the period of braking the fuel cell vehicle.
The control device is
A power generation output estimation unit that estimates the power generation output of the fuel cell with respect to the supply flow rate of the oxidation gas to the cathode, and
A stagnant water estimation unit that estimates the amount of stagnant water that stays in the fuel cell,
When the estimated amount of stagnant water exceeds a predetermined threshold value, scavenging is performed by supplying the oxidized gas to the cathode by the compressor to discharge the stagnant water to the outside of the fuel cell. Processing execution part and
A voltage maintenance unit that maintains the voltage below the upper limit voltage by generating electricity when the voltage of the fuel cell reaches a predetermined upper limit voltage is provided.
In the period, the scavenging processing execution unit makes the change speed of the regenerative braking torque calculated from the estimated power generation output slower than the change speed of the friction braking torque which is the braking torque using the friction brake. , A fuel cell system that controls the operation of the compressor to change the supply flow rate of the oxide gas to the cathode.

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