JP5326220B2 - Fuel cell system and hybrid vehicle system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent or eliminate a flooding state by elevating a temperature of a fuel cell. <P>SOLUTION: A fuel cell system 30 includes a fuel cell system body 40 and a control part 70 equipped with a fuel cell stack 42. The control part 70 includes a temperature elevation halfway-stop determination module 72 to determine whether or not the shutdown of the fuel cell system 30 is temperature elevation halfway-stop which is a stop before reaching a prescribed temperature, and includes a start-up power generation control module 76 to carry out low efficiency power generation control at the time of the next start-up of the fuel cell system 30 in the case that it is determined as the temperature elevation halfway-stop. Moreover, in place of the temperature elevation halfway-stop determination module 72, the system can include a flooding estimation module 74 to estimate whether or not the fuel cell at the start-up time is in a flooding state based on an elapse history before starting the fuel cell system 30. <P>COPYRIGHT: (C)2009,JPO&amp;INPIT

Description

  The present invention relates to a fuel cell system and a hybrid vehicle system equipped with the fuel cell.

  Since there is little impact on the environment, fuel cells are installed in vehicles. In the fuel cell, for example, a fuel gas such as hydrogen is supplied to the anode side of the fuel cell stack, an oxidizing gas containing oxygen such as air is supplied to the cathode side, and necessary electric power is taken out by an electrochemical reaction through the electrolyte membrane. This electrochemical reaction requires appropriate humidity. For example, if the oxidizing gas is too dry and the humidity is too low, sufficient electrochemical reaction does not proceed. Conversely, if the oxidizing gas is too humid, so-called flooding occurs and the progress of the electrochemical reaction decreases.

  In the narrow sense, flooding here often means that the gas diffusion layer constituting the fuel cell is covered with water, but in a broad sense, in addition to the gas diffusion layer, it includes a catalyst layer, a separator, etc. It means that the gas flow path is covered with water on at least one of the cathode side and the anode side. In the flooding state, the gas flow path is covered with water, so that the oxidizing gas or fuel gas is not sufficiently supplied to the electrolyte membrane and the like, the electrochemical reaction is lowered, and the terminal voltage in the single cell of the fuel cell is lowered. To do. Therefore, for example, it is possible to determine whether or not the flooding state is based on the fact that the terminal voltage of the single cell is equal to or lower than a predetermined value.

  When flooding occurs in this manner, the electrochemical reaction of the fuel cell is not sufficiently performed. Therefore, in order to prevent the flooding state or to remove the flooding state, the humidity of the fuel cell is managed.

  For example, Patent Document 1 discloses that gas is supplied to the fuel cell by the moisture adjusting means in accordance with the history of progress before the start of the fuel cell to adjust the moisture inside the fuel cell. The progress history before the start of startup includes a wet state during a period from when the fuel cell is operated, when the operation is completed, until the next operation is resumed. The determination of the wet state of the fuel cell is performed based on the dimensional change, weight change, humidity sensor, cell voltage statistical processing, atmospheric temperature, and the like of the fuel cell stack. The moisture adjustment is performed by a gas flow rate, a heat exchanger using combustion exhaust gas, heat of cooling water, and the like.

JP 2005-276663 A

  According to Patent Document 1, when the operation of the fuel cell is stopped in the flooding state, the humidity of the fuel cell is adjusted by gas supply at the next start-up or by heating with heat exchanger, heat of cooling water, etc. Can do. However, although it is possible to blow off moisture by the gas supply method, the temperature of the fuel cell cannot be raised. In the method using the heat of the cooling water, it is insufficient to raise the temperature of the fuel cell when the temperature of the cooling water is low.

  In Patent Document 1, power is consumed for driving an air compressor or the like for gas supply, heating in a heat exchanger, etc., but the power is consumed from a secondary battery or the like other than the fuel cell. It will be. Therefore, the state of charge of the secondary battery is not sufficient for these processes, and for example, power for operating the drive motor may be insufficient when the vehicle travels next time.

  As described above, in the prior art, in order to eliminate the flooding state, gas supply without power generation of the fuel cell is performed, and in order to perform gas supply without power generation of the fuel cell, the secondary battery power is used. Drive gas transport sources such as blowers, fans and compressors. Therefore, the state of charge of the secondary battery, which is the power storage device, is lowered due to the driving of the gas conveyance source such as the blower, the fan, and the compressor, which may cause trouble when the vehicle is started next time.

  An object of the present invention is to provide a fuel cell system capable of suppressing or eliminating a flooding state by raising the temperature of the fuel cell and a hybrid vehicle system equipped with the fuel cell. Another object of the present invention is to provide a fuel cell system and a hybrid vehicle system equipped with the fuel cell that can generate power from the fuel cell immediately after starting while suppressing flooding. Another object is to provide a hybrid vehicle system that enables the vehicle to be driven by the electric power of the fuel cell thus generated. The following means contribute to at least one of these purposes.

In the fuel cell system according to the present invention, the fuel cell current I _fc that maximizes the output power is I _fcmax , the fuel cell voltage V _fc is V _fcmax , and the operating point of normal operation is I _fc ≦ I _fcmax , V _fc ≧ A fuel cell having V _fcmax and I _fc > I _fcmax , V _fc <V _fcmax as an operating point for low-efficiency power generation, and a control unit for controlling the operation of the fuel cell,
The control unit
As the progress history before the fuel cell shuts down, whether the fuel cell shuts down before it reaches the warm-up threshold temperature, which is the temperature when the fuel cell is fully warmed up. Based on the determination means for determining whether or not the fuel cell at the time of the next start when the operation is stopped is estimated based on the determination result of the determination means, and when it is estimated that the fuel cell is in the flooding state Estimating means for setting a flag indicating that the temperature rise is stopped and recording the data, and the estimating means is estimated to be in a flooding state at the start, and at the next start when the fuel cell is shut down, And a start-time power generation control means for performing low-efficiency power generation control at the time of starting when a flag indicating that the temperature rise is stopped is set. Here, the low-efficiency power generation control is a fuel cell operation control capable of increasing the heat generation amount of the fuel cell itself and quickly increasing the temperature of the fuel cell itself at the expense of the power generation efficiency of the fuel cell. .

The hybrid vehicle system according to the present invention, and a control unit for controlling the operation of the drive motor and the fuel cell and the fuel cell and the charge reservoir voltage converter, the drive motor between the power storage device and the fuel cell A hybrid vehicle system is provided, in which a drive motor is driven by at least one of a power storage device and a fuel cell, and a voltage converter is connected between the power storage device and the drive motor. The fuel cell current I _{fc at} which the power is maximized is I _fcmax , the fuel cell voltage V _fc is V _fcmax , the operating points for normal operation are I _fc ≦ I _fcmax , V _fc ≧ V _fcmax, and I _fc > I _fcmax , the V _fc <V _fcmax the operating point of the low-efficiency power generation, control unit, as the elapsed history fuel cell is in the state before the shutdown, when the operation stop of the fuel cell is a fuel cell is sufficiently warmed up Temperature Determining means for determining whether temperature increase developing stop whether you stopped before reaching the machine threshold temperature, based on a determination result of the determination means, whether the fuel cell at the time of next start when the stop operation is flooded The estimation means for setting a flag indicating that the temperature rise is stopped when the estimation is made, and the data is recorded, and the estimation means is estimated to be in the flooding state at start- up. When the flag indicating that the fuel cell is stopped during the temperature rise is set at the next start when the fuel cell is shut down, low-efficiency power generation control is performed at a voltage higher than the voltage that can drive the drive motor at the start. Power generation control means for starting.

In the hybrid vehicle system according to the present invention, the fuel cell current I _{fc at} which the output power is maximized is I _fcmax , the fuel cell voltage V _fc is V _fcmax , and the operating point of normal operation is I _fc ≦ I _fcmax , V _fc ≧ V _fcmax , I _fc > I _fcmax , V _fc <V _fcmax is a fuel cell having a low-efficiency power generation operating point, and a control unit that controls the operation of the fuel cell, as an interim history is the state before stopping the operation, the operation stop of the fuel cell whether heating developing stop has stopped before the fuel cell reaches the warm-up threshold temperature is a temperature when it is sufficiently warmed up Based on the judgment means for judgment and the judgment result of the judgment means, it is estimated whether or not the fuel cell at the next start when the operation is stopped is in the flooding state, and the temperature rises when it is estimated that the fuel cell is in the flooding state Flag indicating that the stop is halfway Vertical and estimating means for recording the data, it is estimated to be flooded at start-up by the estimating means, at the next start-up when the fuel cell is stopped operating, a flag indicating that it is a heating developing stopped And a power generation control means at start-up that performs low-efficiency power generation control at a voltage higher than the voltage that can drive the drive motor at the time of start-up, and by the low-efficiency power generation control at the next start-up when the operation is stopped The vehicle is driven using the generated electric power.

  According to at least one of the above-described configurations, the fuel cell system has estimation means for estimating whether or not the fuel cell at the start is in a flooding state based on a history of the fuel cell before the start. When it is sometimes estimated that the vehicle is flooded, low-efficiency power generation control is performed at the next start of the fuel cell. Therefore, the flooding state can be resolved by raising the temperature of the fuel cell. In addition, power can be generated immediately after the next power generation of the fuel cell.

  Further, according to at least one of the above-described configurations, the fuel cell system includes a determination unit that determines whether or not the stop of the fuel cell operation stopped before reaching a predetermined temperature, and the estimation unit includes: As the progress history before starting the fuel cell, it is estimated whether or not the fuel cell at the start is in a flooding state based on the determination result of the determining means. When the temperature rise is stopped, the fuel cell may be flooded. According to the above configuration, the flooding state can be prevented or eliminated by raising the temperature of the fuel cell. In addition, power can be generated immediately after the next power generation of the fuel cell.

  According to at least one of the above-described configurations, the hybrid vehicle system includes a fuel cell, and estimates whether or not the fuel cell at the start is in a flooding state based on a history of the fuel cell before the start. When the estimation unit estimates that the flooding state is established at the time of starting, low-efficiency power generation control is performed at a voltage higher than a voltage capable of driving the drive motor at the next start of the fuel cell. As a result, for example, even when the state of charge of the power storage device is lowered, the drive motor can be driven using the power generated by the low-efficiency power generation control of the fuel cell at the time of startup. In addition, compared to driving the drive motor by supplying power from the power storage device via the voltage converter, the use of power from the power storage device can be suppressed and energy loss can be suppressed.

  Further, according to at least one of the above configurations, the hybrid vehicle system estimates whether or not the fuel cell at the start is in a flooding state based on a history of the fuel cell before starting, and the flooding state at the start When the fuel cell is estimated to be low, the low-efficiency power generation control is performed at a voltage higher than the voltage at which the drive motor can be driven at the next start of the fuel cell, and the vehicle is driven using the electric power generated thereby. Therefore, the vehicle can be driven by generating electricity immediately after starting while suppressing flooding.

  Hereinafter, an embodiment according to the present invention will be described in detail with reference to the drawings. In the following, as a configuration of the fuel cell system, a voltage converter is provided as a device for performing voltage conversion in order to exchange power between the fuel cell stack and the secondary battery pack, but a voltage converter is provided. Instead, an element having a power distribution function may be provided between the fuel cell stack and the secondary battery pack, and power may be supplied from the power distributor having the power distribution function to the load. As such a power distributor, based on the power generation state of the fuel cell stack and the charging state of the secondary battery pack, whether the power required for the load is supplied from the fuel cell stack side or the secondary battery pack side, Alternatively, it is possible to use a power circuit or the like having a power supply source switching function such as compensating for power shortage by only one side with power from the other side.

  The secondary battery pack is described as using a lithium ion assembled battery or a nickel hydride assembled battery. However, any other configuration may be used as long as it can be charged and discharged. For example, a capacitor can be used as the power storage device. Note that values such as voltages described below are examples for explanation, and can be appropriately changed depending on the application.

  In the following description, the power supply system of the hybrid vehicle will be described as having a secondary battery pack, a smoothing capacitor, a voltage converter, a fuel cell stack, and an inverter circuit. However, in addition to these, a low-voltage DC / DC converter, A voltage battery, a system main relay, or the like may be included.

  FIG. 1 is a configuration diagram of a hybrid vehicle system 10. The hybrid vehicle system 10 is a power supply system in a hybrid vehicle that can travel with a fuel cell. The hybrid vehicle system 10 includes a secondary battery 12, a secondary battery side smoothing capacitor 14, a voltage converter 16, a fuel cell side smoothing capacitor 18, a fuel cell system 30, and an inverter circuit 20. . The inverter circuit 20 is connected to a motor / generator (M / G) 22 for traveling the vehicle.

  The secondary battery 12 is a secondary battery pack in which a combination of a plurality of lithium ion cells or a combination of nickel hydride cells is used as a high voltage battery of about 200V to 400V, for example, about 288V.

  The secondary battery side smoothing capacitor 14 is a large-capacity capacitor having a function of absorbing fluctuations such as a voltage between the positive electrode bus and the negative electrode bus on the secondary battery 12 side and suppressing pulsation as DC power.

  The voltage converter 16 has a function of performing voltage conversion between the power on the secondary battery 12 side and the high voltage power on the fuel cell system 30 side to exchange power. For example, the DC / DC converter A bidirectional voltage converter capable of stepping up and down using a reactor can be used. As described above, the power converter 16 has a function of boosting the voltage of the secondary battery 12 to convert it to a high voltage, and inputting the high voltage to the inverter circuit 20 using the positive and negative buses.

  The fuel cell-side smoothing capacitor 18 is a large-capacity capacitor that has a function of absorbing fluctuations in the voltage between the positive and negative electrode buses on the fuel cell side and suppressing pulsation as DC power.

  The inverter circuit 20 is a circuit that is connected between a high-voltage positive electrode bus and a negative electrode bus and has a function of performing power conversion between DC power and three-phase AC power. As shown in FIG. 1, the inverter circuit 20 is connected between the high voltage positive electrode bus and the negative electrode bus between the voltage converter 16 and the fuel cell stack 30. That is, the motor / generator 22 is arranged to be connected between the voltage converter 16 and the fuel cell stack 30 via the inverter circuit 20. When the motor / generator 22 is driven, the inverter circuit 20 converts the DC power from the secondary battery 12 or the fuel cell system 30 into three-phase AC power and supplies it to the motor / generator 22 functioning as a drive motor. At the time of braking of the generator 22, the regenerative power from the motor / generator 22 functioning as a generator is converted into DC power, and the secondary battery 12 is charged via the voltage converter 16.

  The motor / generator 22 is an electric rotating machine that functions as an electric motor by a high-voltage three-phase AC drive signal. As described above, the vehicle functions as a generator when braking. The motor / generator 22 consumes a different amount of electric power when the vehicle is traveling at a low speed and when the vehicle is traveling at a high speed. For example, the electric power consumed differs by two to three times when traveling at a low speed such as the traveling speed of a bicycle and when overtaking another vehicle. To illustrate this in terms of the magnitude of the AC voltage, the drive voltage for starting the motor / generator 22 to drive the vehicle is about 220V to about 260V, and is about 330V to about 380V during normal driving.

  The fuel cell system 30 includes a fuel cell stack that generates electricity by an electrochemical reaction, a gas source, auxiliary equipment, and other devices necessary for the operation of the fuel cell stack, and a control device that controls the operation of these elements as a whole. It is a system including. FIG. 2 shows the configuration of the fuel cell system 30. The fuel cell system 30 includes a fuel cell system main body 40 and a control unit 70.

  The fuel cell system main body 40 includes a fuel cell main body called a fuel cell stack 42 in which a plurality of fuel cells are stacked, elements for supplying hydrogen gas arranged on the anode side of the fuel cell stack 42, and a cathode side It is comprised including each element for the air supply arrange | positioned in.

  The fuel cell stack 42 is formed by laminating a plurality of unit cells each having a separator disposed between both sides of an MEA (Membrane Electrode Assembly) in which catalyst electrode layers are disposed on both sides of the electrolyte membrane. The fuel cell stack 42 supplies a fuel gas such as hydrogen to the anode side, supplies an oxidizing gas containing oxygen, for example, air, to the cathode side, generates power by an electrochemical reaction through the electrolyte membrane, takes out necessary power, It has a function of supplying to the load 24. In the example of FIG. 1, the load 24 is an inverter circuit 20, a motor / generator 22, or the like. Note that the voltage of the generated power is detected by the voltage detection unit 64, and data of the detected generated voltage is transmitted to the control unit 70.

  The anode-side hydrogen gas source 44 is a tank that supplies hydrogen as a fuel gas. The regulator 46 connected to the hydrogen gas source 44 has a function of adjusting the gas from the hydrogen gas source 44 to an appropriate pressure and flow rate under the control of the control unit 70. The output port of the regulator 46 is connected to the anode side inlet of the fuel cell stack 42, and the fuel gas adjusted to an appropriate pressure and flow rate is supplied to the fuel cell stack 42.

  The exhaust valve 50 provided at the anode side outlet of the fuel cell stack 42 is for flowing into the diluter 58 when the impurity gas concentration of the exhaust gas from the anode side outlet increases. The exhaust gas at this time is a hydrogen gas containing reaction product water in addition to nitrogen. In addition, the circulation booster 48 provided between the anode side outlet and the anode side inlet increases the hydrogen partial pressure of the gas returning from the anode side outlet and returns to the anode side inlet for reuse again. It is.

  The cathode-side oxidizing gas source 52 can actually use the atmosphere. The atmospheric air as the oxidizing gas source 52 is supplied to the cathode side after passing through the filter. An air compressor (ACP) 54 provided after the filter is a gas booster that increases the pressure by compressing the volume of oxidizing gas by a motor (not shown). Further, the ACP 54 has a function of providing a predetermined amount of oxidizing gas by changing the rotation speed (the number of rotations per minute) under the control of the control unit 70. That is, when the required flow rate of the oxidizing gas is large, the rotational speed of the motor is increased. Conversely, when the required flow rate of the oxidizing gas is small, the rotational speed of the motor is decreased.

  The humidifier 56 has a function of appropriately moistening the oxidizing gas and efficiently performing the fuel cell reaction in the fuel cell stack 42. The oxidizing gas appropriately moistened by the humidifier 56 is supplied to the cathode side inlet of the fuel cell stack 42 and exhausted from the cathode side outlet. At this time, water as a reaction product is also discharged together with the exhaust. Since the fuel cell stack 42 is heated to a high temperature by the reaction, the discharged water is water vapor, and this water vapor is supplied to the humidifier 56 to appropriately wet the oxidizing gas. Thus, the humidifier 56 has a function of appropriately giving moisture of water vapor to the oxidizing gas, and a gas exchanger using a so-called hollow fiber can be used.

  Here, the flow path connecting the oxidizing gas source 52 and the cathode side inlet of the fuel cell stack 42 can be referred to as an inlet side flow path. Correspondingly, the flow path connected from the cathode side outlet of the fuel cell stack 42 to the exhaust side can be called an outlet side flow path. An oxidizing gas path 55 that is an oxidizing gas path enters the fuel cell stack 42 from the inlet side channel through the humidifier 56 from the oxidizing gas source 52, and passes through the humidifier 56 from the outlet side channel. Extends to the open air.

  The diluter 58 mixes the anode side exhaust discharged from the anode side exhaust valve 50 and the cathode side exhaust exhausted from the cathode side, dilutes to an appropriate hydrogen concentration, and discharges it to the outside. It is.

  The fuel cell stack 42 is provided with a circulating cooling water channel 60, for example, by circulating an appropriate refrigerant such as LLC (Long Life Coolant), so that the temperature of the fuel cell stack 42 can be within an appropriate range. The circulating cooling water channel 60 is provided with a cooling water temperature detection unit 62 that detects the temperature of the cooling water and transmits the data to the control unit 70.

  The control unit 70 controls the above-described elements of the fuel cell system main body 40 as a whole system, and is sometimes called a so-called fuel cell CPU. For example, the control unit 70 has a function of performing the rotational speed control of the ACP 54 and the opening degree control of the regulator 46 based on the required power generation amount and the generated power data transmitted from the voltage detection unit 64 and the like. Have.

  In particular, here, in relation to the ignition switch on / off (IG ON / OFF) 66, the fuel cell system 30 has a function of performing flooding prevention or removal control when the fuel cell system 30 is started and stopped. Specifically, it is determined that the temperature increase stoppage determination module 72 determines whether or not the operation stop of the fuel cell system 30 is stopped before reaching a predetermined temperature, and the temperature increase stoppage determination module 72. The start-up power generation control module 76 that performs low-efficiency power generation control at the next start-up of the fuel cell system 30.

  Further, in place of the temperature rising stop determination module 72, a configuration including a flooding estimation module 74 for estimating whether or not the fuel cell at the start is in a flooding state based on the history of the fuel cell system 30 before starting. It can also be. These functions can be realized by software, specifically, by executing a corresponding fuel cell system control program or the like. Some of these functions can also be realized by hardware.

  The storage device 80 that is communicably connected to the control unit 70 has a function of storing a fuel cell system control program and the like and storing necessary data. In particular, here, there is a function of storing information on whether or not the temperature rise is stopped when the fuel cell system 30 is stopped as data of the flag 82 at least until the next start of the fuel cell system 30. Since the data of the flag 82 is stored even while the fuel cell system 30 is stopped, a nonvolatile rewritable memory is used for storing the flag 82. Alternatively, a memory that operates with an appropriate backup power source may be used.

  The operations of the hybrid vehicle system 10 and the fuel cell system 30 configured as described above, particularly the functions of the control unit 70, will be described in detail with reference to the flowchart of FIG. The flowchart of FIG. 3 shows a procedure relating to flooding prevention or removal control at the start and stop of the fuel cell system 30, and each procedure corresponds to each processing procedure of the fuel cell system control program. In the following description, the reference numerals in FIGS. 1 and 2 are used.

  FIG. 3 shows a procedure when the operation is stopped from the state in which the fuel cell system 30 is in operation and is started again. Here, the operation stop and start of the fuel cell system 30 are instructed by (IG ON / OFF) 66 described in FIG. That is, when the ignition switch is turned on, the fuel cell system 30 starts, and when the ignition switch is turned off, the fuel cell system 30 stops. Of course, the fuel cell system 30 may be instructed to be turned on / off by an operator other than the ignition switch.

  The procedure from S 10 to S 16 is a procedure for stopping the fuel cell stack 42, and these processes are executed by the function of the temperature raising stop determination module 72 of the control unit 70.

In the fuel cell system 30, the (IG ON / OFF) state is constantly monitored under an appropriate sampling interval or the like. That is, while the fuel cell system 30 is in operation, it is always determined whether or not IG is OFF (S10). If it is determined that IG is OFF, then whether or not the fuel cell temperature is lower than a predetermined threshold temperature θ ₀ is determined. It is judged (S12). In FIG. 3, FC is an abbreviation for Fuel Cell, and refers to the fuel cell stack 42 here. In the example of FIG. 2, the temperature of the fuel cell stack 42 is determined based on data detected by the coolant temperature detection unit 62. For example, the correlation between the cooling water temperature and the temperature of an appropriate portion of the fuel cell stack 42 is obtained in advance, and the temperature of the fuel cell stack 42 can be obtained based on the cooling water temperature. Of course, the temperature of the fuel cell stack 42 can be determined by an appropriate means other than detecting the coolant temperature. For example, a fuel cell thermometer directly attached to the fuel cell stack 42 is used, or an outside air thermometer installed in the vicinity of the fuel cell stack 42 is used, and the fuel cell temperature is set to a predetermined threshold temperature based on these detection data. or as to determine whether less than theta _0.

The threshold temperature θ ₀ is set from the viewpoint of whether or not the fuel cell stack 42 has been warmed up to an appropriate temperature as viewed from the operation. That is, the threshold temperature θ ₀ is the warm-up threshold temperature of the fuel cell stack 42. For example, θ ₀ can be about 65 ° C. Above this sufficiently warmed-up temperature, the fuel cell stack 42 can properly perform an electrochemical reaction, and therefore no flooding occurs in the fuel cell stack 42. In a state where the temperature is lower than the threshold temperature θ ₀ , there is a possibility that a flooding state occurs. In that sense, the determination of whether or not the FC temperature in S12 is less than θ ₀ is made from the viewpoint of flooding, whether the fuel cell stack 42 is IG OFF when it is still in the process of being heated, or has already been sufficiently warmed up. It is also determined whether the IG is turned off after that.

If it is determined that the FC temperature is less than θ _0, it is assumed that IG OFF has been performed during the temperature increase, and the temperature increase stop flag is set to “1”. Note that the temperature rising stop flag is normally set to “0”. Further, as described above, the data of the temperature rising stop flag is stored as the flag 82 of the storage device 80 even while the fuel cell system 30 is stopped.

  In S12, the temperature rising stoppage is determined based on the FC temperature, and in the case of the temperature rising stoppage, the temperature rising stop flag is set to “1”. You can also. For example, when the FC operation time is less than a predetermined time, it is determined that the temperature raising is stopped, and the temperature raising stop flag may be set to “1”. Further, instead of the FC operation time, when the continuous travel distance of the vehicle is less than a predetermined distance, it may be determined that the temperature rising is stopped and the temperature rising middle stop flag is set to “1”.

  After the process of S14, the process proceeds to S16 and a normal end process is executed. If the determination in S12 is negative, the process of S14 is not performed, that is, the temperature rising stop flag is not set to “1”, but remains “0” and the process proceeds to S16, and a normal end process is executed. . The normal termination process is, for example, instructing the ACP 54 or the like to stop the supply of the oxidizing gas, or instructing the regulator 46 or the like to stop the supply of the fuel gas.

  In this way, the stop process of the fuel cell system 30 is executed. The procedures from S18 to S26 indicate procedures for restarting the fuel cell stack 42, and these procedures are executed by the function of the start-time power generation control module 76 of the control unit 70.

  As described above, since the fuel cell system 30 constantly monitors the state of (IG ON / OFF), after the stop process, it is always determined whether or not IG is ON (S18), and the IG is ON. Next, the flag 82 of the storage device 80 is searched, and it is determined whether or not the state of the temperature rising stop flag is “1” (S20).

When it is determined that the temperature rising stop flag is “1”, low-efficiency power generation control is executed (S22). Here, low efficiency power generation will be described. FIG. 4 shows a common relationship between the output power P _fc of the fuel cell and the fuel cell current (FC current) I _{fc and} the relationship between the fuel cell current (FC current I _fc and fuel cell voltage (FC voltage) V _fc ). The horizontal axis of the _graph indicates the FC current I _fc , where the operating point during the operation of the fuel cell moves on the IV line, which is the relationship between the FC current and the FC voltage.

As shown in FIG. 4, in general, the output power characteristic of the fuel cell shows a characteristic similar to a quadratic curve with respect to the FC current, and the maximum output power can be obtained at a certain FC current. This will be described with respect to the FC voltage of the IV line. The center of the maximum output operation operating point (I _fcmax , V _fcmax ) at which the maximum output electric power P _fcmax is obtained is the center at the operation operating point on the IV line shown on the left side of FIG. Although the output power P _fc with a decrease in voltage V _fc increases, the output power P _fc with the decrease of the FC voltage V _fc in operation point on the IV line shown on the right side in FIG. 4 decreases.

In general, it is known that the power loss in the fuel cell increases as the FC voltage V _fc decreases. Therefore, even when the fuel cell is operated to output the same output power, the operation point on the IV line shown on the right side of the maximum output operation point, for example, the operation point (I _fc2 , V _fc2 ), The power loss is larger than the operation at the operation point on the IV line shown on the left side of the maximum output operation point, for example, the operation point (I _fc1 , V _fc1 ). Therefore, the operation output point on the IV line where the output power P _fc increases with the decrease in the FC voltage V _fc , which is the same output power and with less power loss, and is the same output power. Thus, the operation point on the IV line where the output power P _fc decreases as the power loss is larger, that is, the output power P _fc decreases as the FC voltage V _fc decreases, can be set as the low efficiency operation point.

That is, the normal operation operating point (I _fc , V _fc ) is expressed by the following equation.
I _fc ≤ I _fcmax
V _fcmax ≤ V _fc
Similarly, the low-efficiency operation point (I _fc , V _fc ) is expressed by the following equation.
I _fcmax <I _fc
V _fc <V _fcmax
Low-efficiency power generation is to operate at this low-efficiency operation point.

  Here, the low-efficiency power generation control may be any control as long as the temperature of the fuel cell stack 42 is raised at the expense of power generation efficiency. For example, the ACP 54 is assumed to make the oxidant gas flow rate different from the optimum flow rate. Can give instructions. In addition, for example, it is possible to give an instruction to a control valve or the like not shown in FIG. In addition to the oxidizing gas condition control, the fuel gas condition control may be performed. As described above, since the low-efficiency power generation control changes the conditions of normal fuel cell power generation control, the temperature of the fuel cell stack 42 can be increased.

The low-efficiency power generation control is preferably continued until, for example, the temperature of the fuel cell stack 42 reaches a predetermined temperature based on data from the coolant temperature detection unit 62. The predetermined temperature in this case may be the same as the threshold temperature θ ₀ , or may be a temperature obtained by increasing / decreasing an appropriate temperature difference to θ ₀ .

  It is also possible to determine whether or not the flooding state has been eliminated in the fuel cell stack 42 and continue the low-efficiency power generation control until the flooding state is eliminated. The determination of elimination of the flooding state can be made, for example, based on the measurement of the membrane resistance of the single cells constituting the fuel cell stack 42. That is, it can be determined that the flooding state has been eliminated by keeping the value of the membrane resistance within a predetermined range. Further, it may be determined that the flooding state has been eliminated by continuing the low-efficiency power generation control for a predetermined time. As for the predetermined time in this case, several initial conditions are assumed in advance based on the configuration of the target fuel cell stack 42 and the content of the low-efficiency power generation control, and the time necessary for eliminating the flooding state is obtained. It is preferable to set according to the result.

  Further, as the low-efficiency power generation control, it is preferable to set conditions so that the generated voltage is equal to or higher than the minimum threshold voltage that can drive the motor / generator 22. The threshold voltage at which the motor / generator 22 can be driven is a voltage that allows the motor / generator 22 to travel at a low speed, and is lower than the voltage required for normal travel. The threshold voltage can be set according to the application. For example, the threshold voltage can be set to a voltage corresponding to a traveling speed at which the traveling speed of a bicycle is low on a flat ground but cannot be overtaken by other vehicles. Can do. In the above example, when the drive voltage for starting the motor / generator 22 to drive the vehicle is about 220V to about 260V, the threshold voltage is set as a value between about 220V and about 260V. be able to.

  Thus, at the time of starting, the motor / generator 22 can be driven by the electric power generated by the low-efficiency power generation of the fuel cell stack 42. For example, when the SOC (State Of Charge) indicating the charged state of the secondary battery 12 is lowered, the motor generator 22 can be driven by making up for the shortage by the electric power generated by the fuel cell stack 42. Even when the SOC is sufficient, the power consumption of the secondary battery 12 can be suppressed by using the power generated by the fuel cell stack 42 without using the power of the secondary battery 12.

  Returning to FIG. 3 again, when it is determined that the low-efficiency power generation control is sufficiently performed and the temperature of the fuel cell stack 42 has sufficiently increased or the flooding state has been sufficiently eliminated, the routine shifts to normal operation control ( S26). The normal operation control is a control for operating at an optimum efficiency while supplying the oxidizing gas and the fuel gas according to the required power generation amount and monitoring the data of the voltage detection unit 64. When it is determined in S20 that the temperature rising stop flag is “0”, the low-efficiency power generation control is not executed, and the normal power generation control in S26 is performed as it is.

  In this way, when the stop of the fuel cell stack 42 is a stop during the temperature rise, the operation is stopped in a state where the warm-up is not sufficient, and there is a possibility of being in a flooding state at the time of restart. Low-efficiency power generation control is executed to prevent or eliminate the flooding state.

In the above description, the temperature rising stop flag is set to “1” in accordance with the determination of whether the FC temperature is lower than the threshold temperature θ ₀ in S12. Instead, based on the history before starting the fuel cell stack 42, it is estimated whether or not the fuel cell stack 42 at the time of starting is in a flooding state, and when it is estimated that the fuel cell stack 42 is in a flooding state at the time of starting. Alternatively, low-efficiency power generation control may be performed.

  Specifically, at the time of restart, it is estimated whether or not the fuel cell stack 42 at the time of start-up is in a flooding state based on the history of the fuel cell stack 42 before the start-up. Therefore, as a processing procedure, it is determined whether or not IG is OFF. When IG is OFF, the termination process is performed as usual. Next, whether or not IG is ON is determined. When IG is ON, the fuel cell stack is determined. Whether or not the fuel cell stack 42 at the start is in a flooding state is estimated based on the history of the start 42 before starting. When the estimation result is in the flooding state, the low efficiency power generation control is executed. The continuation condition for the low-efficiency power generation control can be the same as that described in relation to S22 of FIG. 3, and the transition to the normal operation control after the low-efficiency power generation control is also described in relation to S24. It is the same as what I did.

  The history before the start of the fuel cell stack 42 used for estimating whether or not the fuel cell stack 42 at the time of restarting is in a flooding state is the state when the fuel cell stack 42 stopped operating last time. And at least one of the states in which the operation is stopped before the fuel cell is started. The former state when the operation is stopped can include the temperature of the fuel cell stack 42, the humidity of the oxidizing gas, the membrane resistance of the unit cell, and the like. The state in which the operation is stopped before starting in the latter can include the operation stop time, the outside air temperature, and the like.

FIG. 5 illustrates a state in which it is estimated whether or not the fuel cell stack at the time of restart is in a flooding state based on the initial temperature θ ₁ of the fuel cell stack when the operation is stopped and the operation stop time T. FIG. Below, it demonstrates using the code | symbol in FIG. 1, FIG. FIG. 5 shows the elapsed time calculated from when the fuel cell stack 42 is stopped on the horizontal axis and the temperature θ of the fuel cell stack 42 on the vertical axis, and the temperature θ of the fuel cell stack 42 over time. It is a figure which shows the change characteristic 92. FIG. The temperature θ of the fuel cell stack 42 can be determined based on the data of the coolant temperature detection unit 62 as described above. Since the temperature change characteristic 92 is affected by the outside air temperature or the like, the state of the influence is indicated by a broken line. As shown in FIG. 5, the characteristic of the temperature change characteristic 92 can be obtained in advance by giving the configuration of the fuel cell stack 42, the initial temperature θ ₁ , the outside air temperature, and the like.

FIG. 5 shows the threshold temperature θ ₀ described in S12 of FIG. In the temperature change characteristic 92, the initial temperature θ ₁ decreases as time passes, but the time when the threshold temperature θ ₀ is reached is indicated as t ₀ . If the elapsed time from the stop of the operation of the fuel cell stack 42 exceeds t ₀ and is restarted thereafter, the temperature of the fuel cell stack 42 becomes less than the threshold temperature θ _0. There is a possibility. A hatched area in FIG. 5 is an area 94 that is estimated to be in a flooding state at the time of restart. Thus, if restart is performed in a time exceeding time t ₀ , it is estimated that a flooding state is in effect at the time of restart. For example, in FIG. 5, if the restart is performed at the time indicated as the operation stop time T, the operation stop time T is included in the region 94, so that it is estimated that the vehicle is flooded at the time of restart.

  Thus, by using at least one of the state when the fuel cell stack 42 stopped operating last time and the state where the fuel cell stack 42 is stopped before starting the fuel cell, the fact that the fuel cell stack 42 is in the flooding state at the time of restarting Estimation can be performed.

  As an example of using at least one of a state when the fuel cell stack 42 stopped operating last time and a state where the fuel cell stack 42 is stopped before the fuel cell is started in order to estimate whether or not the flooding state occurs at the time of restart. In addition to this, the following can be used. In other words, when the shutdown time is long, or when the outside air temperature is high, the electrolyte membrane or the like may dry out, and the flooding state may not occur even at the next start when the temperature rise is stopped. is there. Therefore, in order to estimate whether or not the long-time operation stop time, high outside air temperature, etc. are flooded at the time of restart, the state when the fuel cell stack 42 was last stopped and before the fuel cell was started It is possible to use an example in which at least one of the states during the operation stop at is used.

In embodiment which concerns on this invention, it is a block diagram of the hybrid vehicle system carrying a fuel cell. In embodiment which concerns on this invention, it is a figure which shows the structure of a fuel cell system. 5 is a flowchart showing a procedure for preventing flooding or removing control when starting and stopping a fuel cell system in an embodiment according to the present invention. In embodiment which concerns on this invention, it is a figure explaining low efficiency electric power generation. In embodiment which concerns on this invention, it is a figure explaining a mode that it is estimated whether the fuel cell stack at the time of restart is a flooding state.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 Hybrid vehicle system, 12 Secondary battery, 14 Secondary battery side smoothing capacitor, 16 Voltage converter, 18 Fuel cell side smoothing capacitor, 20 Inverter circuit, 22 Motor generator, 24 Load, 30 Fuel cell system, 40 Fuel cell System body, 42 Fuel cell stack, 44 Hydrogen gas source, 46 Regulator, 48 Circulating pressure booster, 50 Exhaust valve, 52 Oxidizing gas source, 54 ACP, 55 Oxidizing gas path, 56 Humidifier, 58 Diluter, 60 Circulating cooling Water channel, 62 Cooling water temperature detection unit, 64 Voltage detection unit, 66 IG ON / OFF, 70 control unit, 72 Temperature rising stop determination module, 74 Flooding estimation module, 76 Start-up power generation control module, 80 storage device, 82 flag , 92 Temperature change characteristics, 94 regions

Claims (3)

The fuel cell current I _{fc at} which the output power is maximum is I _fcmax , the fuel cell voltage V _fc is V _fcmax , the operating points for normal operation are I _fc ≦ I _fcmax , V _fc ≧ V _fcmax, and I _fc > I _fcmax , V _fc <V _fcmax as an operating point for low-efficiency power generation, and a control unit for controlling the operation of the fuel cell,
The control unit
As an interim history fuel cell is in the state before the shutdown, warm developing or stopped died before reaching the warm-up threshold temperature is a temperature at which the operation stop of the fuel cell is a fuel cell is sufficiently warmed up A determination means for determining whether or not,
Based on the determination result of the determination means, it is estimated whether or not the fuel cell at the time of the next start when the operation is stopped is in a flooding state, and when it is estimated that the fuel cell is in a flooding state, An estimation means for setting a flag indicating and recording the data ;
When the estimation means estimates that the fuel cell is flooded at the start and the flag indicating that the fuel cell is stopped during the next start when the fuel cell is shut down, Power generation control means at start-up for performing power generation control;
A fuel cell system comprising: A power storage device, a voltage converter, a drive motor, a fuel cell, and a control unit that controls the operation of the fuel cell. The drive motor is provided between the power storage device and the fuel cell and is driven by at least one of the power storage device and the fuel cell. A hybrid vehicle system in which a drive motor is driven and a voltage converter is connected between the power storage device and the drive motor.
In the fuel cell, the fuel cell current I _{fc at} which the output power is maximum is I _fcmax , the fuel cell voltage V _fc is V _fcmax , the operating points of normal operation are I _fc ≦ I _fcmax , V _fc ≧ V _fcmax , _{Let fc} > I _fcmax and V _fc <V _{fcmax be} the operating point for low-efficiency power generation,
The control unit
As the progress history before the fuel cell shuts down, whether the fuel cell shuts down before it reaches the warm-up threshold temperature, which is the temperature when the fuel cell is fully warmed up . A determination means for determining whether or not ,
Based on the judgment result of the judgment means, that the fuel cell at the time of next start when the shutdown is estimated whether a flooded state, is heated developing stopped when estimated to be flooded An estimation means for setting a flag indicating and recording the data;
When the estimation means estimates that the vehicle is in a flooding state at the start, and a flag indicating that the fuel cell is stopped during the next start when the fuel cell is shut down, the drive motor at the start Power generation control means at start-up that performs low-efficiency power generation control at a voltage higher than the voltage capable of driving
Hybrid vehicle system which comprises a. The fuel cell current I _{fc at} which the output power is maximum is I _fcmax , the fuel cell voltage V _fc is V _fcmax , the operating points for normal operation are I _fc ≦ I _fcmax , V _fc ≧ V _fcmax, and I _fc > I _fcmax , V _fc <V _fcmax as an operating point for low-efficiency power generation, and a control unit for controlling the operation of the fuel cell,
The control unit
As the progress history of the state before the fuel cell was shut down, the fuel cell shutdown stopped before reaching the predetermined warm-up threshold temperature, which is the temperature when the fuel cell was fully warmed up A judging means for judging whether or not,
Based on the determination result of the determination means, it is estimated whether or not the fuel cell at the time of the next start when the operation is stopped is in a flooding state, and when it is estimated that the fuel cell is in a flooding state, An estimation means for setting a flag indicating and recording the data;
When the estimation means estimates that the vehicle is in a flooding state at the start, and a flag indicating that the fuel cell is stopped during the next start when the fuel cell is shut down, the drive motor at the start Power generation control means at start-up that performs low-efficiency power generation control at a voltage higher than the voltage capable of driving
Including
Hybrid vehicle system vehicle is characterized Rukoto is driven using the electric power generated by the low-efficiency power generation control during the next start-up when the shutdown.

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