Patent Description:
<CIT> discloses a power supply system for an electric vehicle, and the power supply system is capable of driving an electric motor based on electricity of at least one of a fuel cell and a secondary battery. In this power supply system, when the system is stopped, the secondary battery is charged by the fuel cell during a period before a remaining capacity of the secondary battery reaches a predetermined quantity, and the system is stopped after the charging is completed. A similar arrangement is disclosed in the patent application <CIT> (Nissan Motor).

In the system described above, when the system is stopped, it is determined whether the electricity generation of the fuel cell is continued by considering only the remaining capacity of the secondary battery, and execution of a system stop control does not consider an energy cost associated with the electricity generation of the fuel cell, an energy cost from a stop to a restart of the system, and the like. Therefore, depending on a timing from the system stop control to the restart, a waste may occur from the viewpoint of the energy costs.

Therefore, an object of the present invention is to provide a technique for realizing a system control, which can reduce energy costs as much as possible in consideration of an energy cost from a system stop to a next vehicle operation start and an energy cost associated with electricity generation of a fuel cell when a system stop request is received.

The invention is defined by method claim <NUM> and a corresponding system claim <NUM>.

According to the present invetion, a control method for a fuel cell system for a vehicle is provided, the fuel cell system including a fuel cell, and a heater configured to warm up the fuel cell, and capable of executing a stop control when an operation stop request of the fuel cell system is received. The control method includes acquiring the operation stop request of the fuel cell system, acquiring a next vehicle operation start timing, and calculating a first energy cost and a second energy cost at a predetermined timing after acquiring the operation stop request and the next vehicle operation start timing. The first energy cost is an energy cost required from the predetermined timing to completion of warming up of the fuel cell when a warm-up control is executed using the heater in accordance with the next vehicle operation start timing after the stop control is executed. The second energy cost is an energy cost required when an operation of the fuel cell is continued so as to maintain a temperature of the fuel cell at a warm-up temperature from the predetermined timing to the next vehicle operation start timing. The control method also includes continuing the operation of the fuel cell such that the temperature of the fuel cell is maintained at the warm-up temperature while the first energy cost is larger than the second energy cost after the operation stop request is acquired.

Hereinafter, embodiments of the present invention are described with reference to the drawings.

<FIG> is a schematic configuration diagram of a fuel cell system <NUM> according to a first embodiment of the present invention.

The fuel cell system <NUM> shown in <FIG> is, for example, a system mounted on a series hybrid vehicle. The fuel cell system <NUM> includes a fuel cell stack <NUM> as a solid oxide fuel cell (SOFC), a fuel tank <NUM> that stores a liquid fuel used for electricity generation of the fuel cell stack <NUM>, a controller <NUM> that integrally controls the fuel cell system <NUM>, and the like.

The fuel cell stack <NUM> is a fuel cell laminate that generates electricity by receiving an anode gas and a cathode gas. The generated electricity of the fuel cell stack <NUM> is used to charge a battery (see <FIG>) mounted on the hybrid vehicle. The fuel cell stack <NUM> is configured by laminating a plurality of fuel cells, and each fuel cell as an electricity generation source is, for example, a solid oxide fuel cell.

The fuel tank <NUM> stores the liquid fuel necessary for generating the anode gas to be supplied to the fuel cell stack <NUM> or generating a combustion gas used for warming up system components and the like. The liquid fuel is, for example, a fuel consisting of water and ethanol (for example, hydrous ethanol containing <NUM>% by volume of ethanol). The liquid fuel is not limited to hydrous ethanol, and may be a liquid fuel containing gasoline, methanol, or the like.

The fuel cell stack <NUM> and the fuel tank <NUM> are connected to each other through an anode gas passage <NUM>. The anode gas passage <NUM> is provided with an evaporator <NUM>, a fuel heat exchanger <NUM>, and a reformer <NUM> in the order from an upstream side in a flow direction. The evaporator <NUM>, the fuel heat exchanger <NUM>, and the reformer <NUM> are auxiliary machines necessary for supplying the anode gas to the fuel cell stack <NUM>.

On an upstream side of the evaporator <NUM>, a fuel supply path <NUM> branches from the anode gas passage <NUM>, and the fuel supply path <NUM> connects the anode gas passage <NUM> and a catalyst combustor <NUM>.

A first injector 2A is provided on the anode gas passage <NUM> between a branch point of the fuel supply path <NUM> and the evaporator <NUM>, and a second injector 2B is provided on the fuel supply path <NUM>. The first injector 2A is configured to operate in response to a command signal from the controller <NUM> to supply the liquid fuel by injection to the evaporator <NUM>. Further, the second injector 2B is configured to operate in response to a command signal from the controller <NUM> to supply the liquid fuel by injection to the catalyst combustor <NUM>.

The evaporator <NUM> heats the liquid fuel supplied from the first injector 2A to generate a vaporized fuel. The evaporator <NUM> heats the liquid fuel by heat exchange with a high-temperature combustion gas supplied from the catalyst combustor <NUM> through a combustion gas passage <NUM>.

The fuel heat exchanger <NUM> receives the heat of the combustion gas generated by the combustion in the catalyst combustor <NUM> and further heats the vaporized fuel.

The reformer <NUM> has a built-in reforming catalyst, and reforms the vaporized fuel supplied from the fuel heat exchanger <NUM> to generate an anode gas containing hydrogen, carbon monoxide, or the like. The anode gas generated by the reformer <NUM> is supplied to the fuel cell stack <NUM>.

Meanwhile, the fuel cell system <NUM> includes a cathode gas passage <NUM> for supplying air (cathode gas) to the fuel cell stack <NUM>. The cathode gas passage <NUM> is provided with an air heat exchanger <NUM>.

The air heat exchanger <NUM> heats the cathode gas flowing through the cathode gas passage <NUM> by heat exchange with the combustion gas supplied from the catalyst combustor <NUM> through the combustion gas passage <NUM>. In the present embodiment, an air compressor <NUM> is disposed near an open end of the cathode gas passage <NUM>, and air as the cathode gas is suctioned into the cathode gas passage <NUM> through the air compressor <NUM>. The cathode gas is heated when passing through the air heat exchanger <NUM>, and is supplied to the fuel cell stack <NUM>. The air heat exchanger <NUM> is an auxiliary machine necessary for the fuel cell stack <NUM> to generate electricity. As a device for suctioning air, a blower may be used instead of the air compressor <NUM>.

An air supply path <NUM> branches from the cathode gas passage <NUM> between the air compressor <NUM> and the air heat exchanger <NUM>, and the air supply path <NUM> connects the cathode gas passage <NUM> and the catalyst combustor <NUM>. A flow rate control valve <NUM> for adjusting a flow rate of the air supplied to the catalyst combustor <NUM> is disposed in the air supply path <NUM>.

The catalyst combustor <NUM> has a built-in combustion catalyst containing platinum (Pt), palladium (Pd), or the like. The catalyst combustor <NUM> generates a combustion gas by combusting the liquid fuel and the air supplied through the fuel supply path <NUM> and the air supply path <NUM>.

In the fuel cell system <NUM>, the catalyst combustor <NUM> is connected to the air heat exchanger <NUM> and the evaporator <NUM> via the combustion gas passage <NUM>, and heats the air heat exchanger <NUM> and the evaporator <NUM> by the heat of the combustion gas. Meanwhile, the fuel heat exchanger <NUM> and the reformer <NUM> are housed in a case shared with the catalyst combustor <NUM> (one-dot chain line L in <FIG>), and inside the case L, the heat of the catalyst combustor <NUM> is transferred to the fuel heat exchanger <NUM> and the reformer <NUM>.

Further, in the fuel cell system <NUM>, the fuel cell stack <NUM> and the catalyst combustor <NUM> are connected by an anode off-gas passage <NUM> and a cathode off-gas passage <NUM>. The catalyst combustor <NUM> generates a combustion gas by catalytically combusting an anode off-gas and a cathode off-gas discharged from the fuel cell stack <NUM>. The combustion gas generated by the catalyst combustor <NUM> is discharged to the outside through the combustion gas passage <NUM>.

The controller <NUM> is an electronic control unit implemented by a microcomputer provided with a central processing unit (CPU), various storage devices such as ROM and RAM, and an input and output interface and the like, and executes various pre-programmed controls. The controller <NUM> is programmed to control operations of the first injector 2A, the second injector 2B, the air compressor <NUM>, and the flow rate control valve <NUM>, for example, according to a traveling state of the vehicle and an operating state of the fuel cell system <NUM>.

The controller <NUM> detects the operating state of the fuel cell system <NUM> or the like by acquiring detection signals from various sensors or the like. The fuel cell system <NUM> includes, as various sensors, a temperature sensor 50A that detects a temperature of the fuel cell stack <NUM>, a timer 50B that outputs a current time, a start switch 50C for instructing the start and stop of the vehicle, and the like.

Next, an electricity system of the fuel cell system <NUM> is described with reference to <FIG>.

The fuel cell system <NUM> is mounted on the series hybrid vehicle, and the fuel cell stack <NUM> is electrically connected to a battery <NUM> of the vehicle as shown in <FIG>. In the fuel cell system <NUM>, the electricity generated by the fuel cell stack <NUM> is basically charged to the battery <NUM>, but the battery <NUM> may also be charged by using electricity from an external charger <NUM>. The external charger <NUM> is a quick charging device disposed in a facility such as a charging stand, or a household power supply having smaller output electricity than the quick charging device.

As shown in <FIG>, the electricity system of the fuel cell system <NUM> includes the battery <NUM> as a vehicle power supply, a drive device <NUM> as a vehicle driving source, a first wiring <NUM> provided between the drive device <NUM> and the battery <NUM>, a second wiring <NUM> connecting the first wiring <NUM> and the fuel cell stack <NUM>, a relay <NUM> provided on the first wiring <NUM>, a converter <NUM> provided on the second wiring, and a charging connector <NUM> configured to be connected to the external charger <NUM>. Various devices constituting the electricity system are also controlled by the controller <NUM> described above.

The drive device <NUM> is a load connected to the battery <NUM> and the fuel cell stack <NUM>, and drives the vehicle by receiving electricity of at least one of the battery <NUM> and the fuel cell stack <NUM>. The drive device <NUM> includes an electric motor <NUM> as a drive source, and an inverter <NUM> that converts DC electricity of at least one of the battery <NUM> and the fuel cell <NUM> into AC electricity to be supplied to the electric motor <NUM>.

The first wiring <NUM> is a power supply line that connects the battery <NUM> and the inverter <NUM>. The battery <NUM> is a power supply for supplying electricity to the drive device <NUM>, and is a lithium ion battery, a lead battery, or the like. The battery <NUM> is provided with a voltage sensor 50D for detecting an output voltage of the battery <NUM>, and a detection signal of the voltage sensor 50D is output to the controller <NUM>.

The relay <NUM> is disposed on the first wiring <NUM>, and the relay <NUM> is a breaker that switches a state between the battery <NUM> and the drive device <NUM> to a connected state or a disconnected state. The relay <NUM> is also a breaker capable of switching a state between the converter <NUM> and the battery <NUM> in the first wiring <NUM> from a connected state to a disconnected state.

The second wiring <NUM> is a power supply line that branches from the first wiring <NUM> and is connected to the fuel cell stack <NUM>. The second wiring <NUM> is provided with the converter <NUM>.

The converter <NUM> is a DC/DC converter, which is an electricity converter that converts a voltage (primary voltage) of the fuel cell stack <NUM> such that an output voltage (secondary voltage) to the first wiring <NUM> is a predetermined voltage at which electricity of the fuel cell stack <NUM> can be output. The converter <NUM> transmits the electricity of the fuel cell stack <NUM> to the battery <NUM> and the drive device <NUM> via the first wiring <NUM>.

The first wiring <NUM> is provided with a charging connector <NUM> capable of being connected to a charging gun <NUM> disposed in the external charger <NUM>. The charging connector <NUM> is an electric connection device, which is disposed in a charging port provided on a vehicle body, and receives electricity from the charging gun <NUM> when charging by the external charger <NUM>. By connecting a tip end portion of the charging gun <NUM> to the charging connector <NUM>, the electricity can be supplied from the external charger <NUM> to the battery <NUM>. The charging connector <NUM> is provided with a connection state detection sensor that detects whether the tip end portion of the charging gun <NUM> is connected, a current sensor that detects a current flowing from the charging connector <NUM> to the battery <NUM>, or the like. The controller <NUM> determines whether the battery <NUM> is charged by the external charger <NUM> based on detection signals of these sensors.

Operations of various devices such as the relay <NUM>, the inverter <NUM>, and the converter <NUM> that constitute the electricity system of the fuel cell system <NUM> is controlled by the controller <NUM>.

In the fuel cell system <NUM> as described above, a warm-up control that warms up the fuel cell stack <NUM> is executed at the time of starting the system, and a system stop control is executed when a system stop request is received.

For example, in the fuel cell system <NUM> shown in <FIG>, when it is necessary to warm up the fuel cell stack <NUM> at the time of starting the system, the second injector 2B supplies the liquid fuel to the catalyst combustor <NUM>, and the air compressor <NUM> is operated to open the flow rate control valve <NUM> to supply the air to the catalyst combustor <NUM>. Thus, the fuel heat exchanger <NUM> and the like can be heated by the combustion gas generated by the combustion of the liquid fuel. As a result, the anode gas and the cathode gas that are heated by these heat exchangers are supplied to the fuel cell stack <NUM>, and the fuel cell stack <NUM> is warmed up. In this way, the catalyst combustor <NUM> functions as a heater for warming up the fuel cell stack <NUM>.

Here, the term "at the time of starting the system" refers to a period during which a process (warm-up operation for starting the fuel cell system <NUM>) of increasing temperatures of elements in the fuel cell system <NUM> such as the fuel cell stack <NUM> to desired temperatures suitable for respective operations is executed triggered by detection of a system start command from the controller <NUM>, in a state where an operation of the fuel cell system <NUM> is stopped (a state where an operation of each element in the fuel cell system <NUM> including the fuel cell stack <NUM> is stopped).

Further, in the fuel cell system <NUM>, the stop control is executed in response to a system stop request or the like based on a key-off operation of a driver. In the fuel cell system <NUM>, since an operation temperature of the fuel cell stack <NUM> is high, cooling processing of the fuel cell stack <NUM> is executed before the operation of each element of the fuel cell system <NUM> is completely stopped in the stop control. In the cooling processing of the stop control, the air compressor <NUM> is driven to continue supplying the cathode gas, and the fuel cell stack <NUM> is cooled by the cathode gas. At this time, the first injector 2A is also controlled to supply a small quantity of fuel, and a small quantity of anode gas is supplied to the fuel cell stack <NUM>. In this way, by supplying the anode gas to the fuel cell stack <NUM>, the cathode gas (air) can be prevented from flowing back from the catalyst combustor <NUM> into the fuel cell stack <NUM>, and oxidative deterioration of an anode electrode of the fuel cell stack <NUM> can be prevented. Such a stop control starts from a timing when the system stop request is received (stop request acquisition timing), and ends when, for example, the temperature of the fuel cell stack <NUM> reaches a temperature at which the oxidative deterioration of the anode electrode can be suppressed or prevented.

In the fuel cell system <NUM>, the stop control and the warm-up control are generally executed as described above. Once the system is stopped, it is necessary to warm up the fuel cell stack <NUM> to the operation temperature before a next vehicle operation starts. The solid oxide fuel cell stack <NUM> used in the fuel cell system <NUM> has a high operation temperature of about <NUM>, and consumes a large quantity of liquid fuel when the warm-up control is executed. In particular, when the fuel cell system <NUM> is configured to combust the fuel in the catalyst combustor <NUM> to warm up the fuel cell stack <NUM>, the fuel combusted here is not used for electricity generation, but is mainly used for heating the fuel cell stack <NUM> and the like.

Therefore, when the fuel cell system <NUM> is stopped and then restarted, depending on a timing at which the next vehicle operation starts, a case of maintaining the temperature of the fuel cell stack <NUM> by continuing the operation (electricity generation) of the fuel cell stack <NUM> even when the system stop request is issued may be able to reduce the loss of energy costs as compared with a case of executing the stop control immediately when the stop request is issued and then executing the warm-up control.

<FIG> is a diagram illustrating a control method when the system stop request is issued and a change in a fuel quantity consumed at that time. Lines L1 to L4 in <FIG> show a time change of an integrated value of the fuel quantity.

As shown in <FIG>, for example, when the stop control is executed immediately at a time point (time t<NUM>) at which a start switch 50C of the vehicle is operated and a system stop request is output, the supply of the cathode gas and the anode gas to the fuel cell stack <NUM> is continued during a period before a stack temperature decreases to a predetermined temperature TL. Thereafter, when a system restart request is issued at a time t2, the warm-up control is started, and the fuel cell stack <NUM> is warmed up using the combustion heat of the fuel supplied to the catalyst combustor <NUM>. In the stop control, the fuel is not used for electricity generation, and thus almost all of the consumed fuel is a fuel that is not recovered as generated electricity, and also in the warm-up control, the fuel is used as a heat source for warming up, and thus most of the consumed fuel is not recovered as generated electricity. In this way, when the fuel cell system <NUM> is stopped and restarted, as shown in the line L1 of <FIG>, a large quantity of fuel is consumed, and as shown in the line L2, most of the fuel does not contribute to the generated electricity.

On the other hand, when a time from when the system stop request is issued to when the system is restarted is relatively short or the like, as shown in <FIG>, continuing electricity generation to the extent that the temperature of the fuel cell stack <NUM> is maintained even if the system stop request is issued at a time t11 may be more efficient from the viewpoint of overall energy cost. That is, during a period from when the stop request is issued to when a next vehicle operation is started (from the time t11 to a time t13), the fuel is supplied to the fuel cell stack <NUM>, and the electricity generation is continued to the extent that the temperature of the fuel cell stack <NUM> is maintained, and thus the fuel cell stack <NUM> can be normally operated at the same time as a vehicle operation start timing. A fuel quantity (line L3) consumed at the timing t13 when a normal operation can be started is less than a fuel quantity (line L1) consumed during a period from when the stop request is issued to when the warming up is completed (from the time t1 to a time t3) in <FIG>. In this way, depending on a timing of restarting the fuel cell system <NUM>, electricity generation is continued during a period before the vehicle operation is restarted, and thus it can be said that a fuel quantity that is not recovered as generated electricity can be reduced, and the energy generated from the fuel is efficiently used for electricity generation.

Therefore, in the fuel cell system <NUM> according to the present embodiment, when a system stop request is detected, the continuation of electricity generation or the stop control is executed so as to reduce the energy loss as much as possible, considering the energy cost in the case of stopping and restarting the system, the energy cost in the case of continuing the electricity generation with the fuel cell stack <NUM>, and the like.

Hereinafter, the processing executed by the fuel cell system <NUM> when a system stop request is detected is described with reference to <FIG> is a flowchart illustrating a flow of the processing executed when the system stop request is issued. The controller <NUM> of the fuel cell system <NUM> is programmed to perform the processing in <FIG>.

As shown in <FIG>, in step S101, the controller <NUM> determines whether a system stop request is issued. The vehicle is configured to output a stop request for the fuel cell system <NUM> in order to stop the vehicle when the start switch 50C is operated by a driver or the like. When a system stop request based on the operation of the start switch 50C is detected (acquired), the controller <NUM> determines that a system stop request is issued, and then executes processing of step S102. On the other hand, the controller <NUM> repeatedly executes the processing of step S101 when no system stop request is issued while no system stop request is detected.

In step S102, the controller <NUM> determines whether a next operation start time (next vehicle operation start timing) is set and registered. The vehicle equipped with the fuel cell system <NUM> according to the present embodiment is a vehicle capable of storing a vehicle operation plan and the like of a driver in a ROM or the like of the controller <NUM>, and is configured such that a driver or the like can set and register date and time when the vehicle is to be used next or the like via a car navigation device or a smartphone owned by the driver. Further, when the vehicle is a vehicle used for car sharing, a next vehicle operation start timing may be set based on a use status of car sharing. This next operation start time means a timing at which a vehicle operation can be restarted after the fuel cell system <NUM> is warmed up.

When a next vehicle operation start timing is acquired in step S102, the controller <NUM> executes processing of step S103. On the other hand, when no next vehicle operation start timing is set and registered, and the time cannot be acquired, the controller <NUM> executes processing of step S108, starts a stop control without considering various energy costs, and ends the operation of the fuel cell system <NUM> after decreasing the temperature of the fuel cell stack <NUM> to a predetermined temperature.

In step S103, the controller <NUM> determines whether the fuel cell system <NUM> is connected to the external charger <NUM>. This determination is performed, for example, based on an output signal of the connection state detection sensor that detects whether the charging gun <NUM> of the external charger <NUM> is connected to the charging connector <NUM>. When the external charger <NUM> is not connected, the controller <NUM> executes processing of step S104 and subsequent steps. On the other hand, when the external charger <NUM> is connected, the controller <NUM> determines that the battery <NUM> needs to be charged to a target charge quantity when the system is stopped, and executes processing of step S109 and subsequent steps.

When the external charger <NUM> is not connected, the controller <NUM> calculates, in step S104, an energy cost (hereinafter, referred to as a "stop and start energy cost") when the stop and start is executed. The stop and start energy cost calculated in step S104 is an energy cost (first energy cost) required from a current time (cost calculation timing) to completion of warming up of the fuel cell stack <NUM> when a warm-up control is executed using the catalyst combustor <NUM> in accordance with a next vehicle operation start timing after a stop control for stopping the fuel cell system <NUM> is executed. This stop and start energy cost is calculated, for example, as shown in <FIG>.

<FIG> is a diagram illustrating a stop and start energy cost calculation unit <NUM> of the controller <NUM>. As shown in <FIG>, the stop and start energy cost calculation unit <NUM> includes a stop time calculation unit 51A, a pre-start stack temperature calculation unit 51B, a stop energy calculation unit 51C, a start energy calculation unit 51D, an addition unit 51E, and a cost calculation unit 51F.

The stop time calculation unit 51A calculates a stop time, during which the vehicle and the fuel cell system <NUM> is in a stopped state, by subtracting a current time (current cost calculation timing) from a restart timing of the fuel cell stack <NUM> obtained based on a next vehicle operation start timing. The current cost calculation timing is a time from acquisition of a stop request of the fuel cell system <NUM> to a current time, and is also an electricity generation duration time of the fuel cell stack <NUM> from a system stop request timing.

The restart timing of the fuel cell stack <NUM> is calculated as shown in <FIG> based on the next vehicle operation start timing acquired in step S102. As shown in <FIG>, the controller <NUM> acquires a current stack temperature, and calculates, based on the stack temperature, a temperature decrease characteristic line La when the stop control is executed. This characteristic line La may be stored in advance as map data for each current stack temperature, or may be acquired from a heat dissipation simulation obtained based on a heat dissipation quantity of the fuel cell stack <NUM>. The controller <NUM> calculates the restart timing of the fuel cell stack <NUM>, at which the warming up of the fuel cell stack <NUM> is completed when a vehicle operation starts, based on the temperature decrease characteristic line La, a stack temperature-warm-up time characteristic line Lb, and the acquired next vehicle operation start timing. That is, the controller <NUM> sets, as the restart timing (warm-up start timing) of the fuel cell stack <NUM>, an intersection of the decrease characteristic line La, which indicates the decrease in the stack temperature from the current time, and the stack temperature-warm-up time characteristic line Lb, which indicates that the warm-up temperature is reached when a next vehicle operation starts. The stack temperature-warm-up time characteristic line Lb is data obtained by conducting experiments in advance about a relationship between a time for performing the warm-up control and a degree of increase in the stack temperature. This characteristic line Lb may be obtained from a temperature increase simulation obtained based on a stack heat capacity and a heat quantity that can be supplied to the fuel cell stack <NUM>.

As shown in <FIG>, after the stop time calculation unit 51A calculates a stop time, the pre-start stack temperature calculation unit 51B calculates a stack temperature (pre-start stack temperature) at the restart timing (warm-up start timing) of the fuel cell system <NUM> based on the stop time and the current stack temperature. The current stack temperature may be one acquired by the temperature sensor 50A provided on the fuel cell stack <NUM>, or may be estimated based on a temperature of an off-gas discharged from the fuel cell stack <NUM>. As shown in <FIG>, a characteristic line showing a relationship between the stop time and the pre-start stack temperature has a characteristic that as the stop time increases, the pre-start stack temperature decreases. Further, this characteristic line is set for each predetermined stack temperature.

The stop energy calculation unit 51C calculates a stop energy based on the pre-start stack temperature. This stop energy is an energy (fuel quantity or the like) required when the stop control is executed in the fuel cell system <NUM> and the system <NUM> is in a stopped state until the restart timing. As the pre-start stack temperature decreases, the stop energy is calculated to be smaller. Further, this stop energy is calculated so as to be a constant value at a temperature equal to or lower than the predetermined temperature. This is because when the temperature of the fuel cell stack <NUM> is equal to or lower than the predetermined temperature, cooling by a gas or the like is not performed, and a state of natural cooling is realized, and therefore the energy such as the fuel is not consumed.

The start energy calculation unit 51D calculates a start energy based on the pre-start stack temperature. This start energy is an energy (fuel quantity or the like) required from the restart timing to the completion of the warming up of the fuel cell stack <NUM> after the warm-up control is started. As the pre-start stack temperature decreases, the start energy increases.

The addition unit 51E adds the stop energy and the start energy to calculate a stop and start energy. The stop and start energy calculated in this way is input to the cost calculation unit 51F. The cost calculation unit 51F calculates a stop and start energy cost by integrating a cost per unit energy with respect to the stop and start energy. The cost per unit energy is, for example, a fuel cost per unit liter, and may be a value stored in the controller <NUM> in advance or a value appropriately received from an external information terminal or the like.

After calculating the stop and start energy cost in S104 in <FIG>, in S105, the controller <NUM> calculates an energy cost (hereinafter, referred to as an "electricity generation continuation energy cost") when electricity generation is continued as it is in the fuel cell stack <NUM> until a next vehicle operation start timing. The electricity generation continuation energy cost calculated in S105 is an energy cost (second energy cost) required when the electricity generation is continued in a state in which the temperature of the fuel cell stack <NUM> can be maintained at the warm-up temperature from the current time point (cost calculation timing) to the next vehicle operation start timing. This electricity generation continuation energy cost is calculated, for example, as shown in <FIG>.

<FIG> is a diagram illustrating an electricity generation continuation energy cost calculation unit <NUM> and an external charge energy cost calculation unit <NUM> of the controller <NUM>. As shown in <FIG>, the electricity generation continuation energy cost calculation unit <NUM> includes an electricity quantity calculation unit 52A, a system efficiency calculation unit 52B, a subtraction unit 52C, a non-recovery energy calculation unit 52D, an electricity generation energy calculation unit 52E, a selection unit 52F, and a cost calculation unit <NUM>.

The electricity quantity calculation unit 52A calculates a stack electricity quantity by multiplying an electricity generation output of the fuel cell stack <NUM> by a duration (duration time), which is a difference between a next operation time (next vehicle operation start timing) and a current time (current cost calculation timing). During the continuation of electricity generation, the fuel cell stack <NUM> generates electricity in a state where the stack temperature is maintained at the warm-up temperature, so that the electricity generation output is stored in the ROM or the like of the controller <NUM> as a predetermined value set in advance. The electricity generation output is calculated based on an output current and an output voltage at the current time, and an electricity generation output value calculated in this way may be used as the electricity generation output used in the electricity quantity calculation unit 52A.

The system efficiency calculation unit 52B refers to a system efficiency table, and calculates, based on the electricity generation output, electricity conversion efficiency of the entire system in consideration of the electricity loss or the like in various components of the fuel cell system <NUM>. The electricity conversion efficiency is a value of <NUM> or more and <NUM> or less.

The subtraction unit 52C calculates a value obtained by subtracting the electricity conversion efficiency from <NUM>, and the non-recovery energy calculation unit 52D calculates a non-recovery energy by multiplying the value calculated by the subtraction unit 52C and the stack electricity quantity. This non-recovery energy is an energy (fuel quantity or the like) that is not recovered as electricity, among the energy consumed during the continuation of electricity generation.

The electricity generation energy calculation unit 52E calculates, by dividing the stack electricity quantity by the electricity conversion efficiency of the entire system, a total electricity generation energy (fuel quantity or the like) required to generate the stack electricity quantity by using the fuel cell stack <NUM>.

The selection unit 52F outputs one of the non-recovery energy and the total electricity generation energy as the electricity generation continuation energy depending on whether a target charge electricity quantity for the battery <NUM> is set. In the fuel cell system <NUM>, a minimum battery charge quantity when the system is stopped is set, and a target charge electricity quantity is set so as to satisfy this minimum battery charge quantity. The target charge electricity quantity may be set such that a charge quantity of the battery <NUM> is an allowable upper limit charge quantity. The fuel cell system <NUM> may be configured to notify the driver or the like of charging the battery <NUM> by the external charger <NUM> when the target charge electricity quantity is set. Therefore, the selection unit 52F may determine that the target charge electricity quantity is set when the fuel cell system <NUM> is connected to the external charger <NUM>. The selection unit 52F outputs the non-recovery energy as the electricity generation continuation energy when the target charge electricity quantity is not set, and outputs the total electricity generation energy as the electricity generation continuation energy when the target charge electricity quantity is set.

The cost calculation unit <NUM> calculates the electricity generation continuation energy cost by integrating a cost per unit energy with respect to the electricity generation continuation energy (fuel quantity or the like). The cost per unit energy is, for example, a fuel cost per unit liter, and may be a value stored in the controller <NUM> in advance or a value appropriately received from an external information terminal or the like.

After calculating the stop and start energy cost and the electricity generation continuation energy cost in steps S104 and S105 in <FIG>, the controller <NUM> executes processing of S106. In S106, the controller <NUM> compares the electricity generation continuation energy cost required in a case where electricity generation is continued as it is until the next vehicle operation start timing with the stop and start energy cost required in a case where the warm-up control is performed until the vehicle operation starts after the stop control is performed from the current time.

When the stop and start energy cost is larger than the electricity generation continuation energy cost, the controller <NUM> determines that the energy loss is smaller when electricity generation in the fuel cell stack <NUM> is continued, and executes processing of step S107. On the other hand, when the stop and start energy cost is equal to or less than the electricity generation continuation energy cost, the controller <NUM> determines that the energy loss is smaller when the stop control is started at this stage, and executes processing of step S108.

In step S107, the controller <NUM> continues to supply the anode gas and the cathode gas to the fuel cell stack <NUM>, and continues to generate electricity in the fuel cell stack <NUM> in an electricity generation state in which the temperature of the fuel cell stack <NUM> is maintained at the warm-up temperature. After executing the processing of step S107, the controller <NUM> executes the processing of step S103.

In step S108, the controller <NUM> ends the electricity generation of the fuel cell stack <NUM>, and starts the stop control. In this stop control, the temperature of the fuel cell stack <NUM> is decreased to a predetermined temperature by mainly supplying the cathode gas to the fuel cell stack <NUM>, and the operation of the fuel cell system <NUM> is ended. In the fuel cell system <NUM> whose operation is stopped in this way, the operation is stopped until the restart timing of the fuel cell stack <NUM>, and the warm-up control is started at the restart timing.

On the other hand, when the target charge electricity quantity of the battery <NUM> is set by connecting the external charger <NUM> or the like, the controller <NUM> calculates a stop and start energy cost in step S109, and calculates an electricity generation continuation energy cost in step S110. The calculation of the stop and start energy cost in step S109 is the same as the calculation of the stop and start energy cost in step S104, and the calculation of the electricity generation continuation energy cost in step S110 is the same as the calculation of the electricity generation continuation energy cost in step S105.

After the processing of step S110, in step S111, the controller <NUM> calculates an energy cost (hereinafter, referred to as an "external charge energy cost") required when the battery <NUM> is charged to the target charge quantity from the current time by the external charger <NUM>. The external charge energy cost calculated in step S111 is an energy cost (third energy cost) required when the battery <NUM> is charged by the external charger <NUM> from the current cost calculation timing to when the target charge quantity is reached. This external charge energy cost is calculated, for example, as shown in <FIG>.

As shown in <FIG>, the external charge energy cost calculation unit <NUM> includes an external charge energy calculation unit 53A and a cost calculation unit 53B.

The external charge energy calculation unit 53A calculates an external charge energy (electricity quantity or the like) by subtracting the stack electricity quantity (electricity quantity charged from the fuel cell stack <NUM> to the battery <NUM>) calculated by the electricity generation continuation energy cost calculation unit <NUM> from the target charge quantity required for charging to the target charge electricity quantity. When the battery charge quantity is less than a minimum charge quantity predetermined considering the electricity required at the time of starting the system, the target charge electricity quantity is calculated based on a difference between the minimum charge quantity (target charge quantity) and a current battery charge quantity. The controller <NUM> calculates the current battery charge quantity based on a detected value of the voltage sensor 50D or the like.

The cost calculation unit 53B calculates the external charge energy cost by integrating an electricity cost per unit energy with respect to the external charge energy (electricity quantity or the like). The electricity cost per unit energy is, for example, an electricity charge per unit electricity quantity, and may be a value stored in the controller <NUM> in advance or a value appropriately received from an external information terminal or the like.

After calculating the stop and start energy cost, the electricity generation continuation energy cost, and the external charge energy cost in steps S109 to S111 in <FIG>, the controller <NUM> executes processing of step S112. In step S112, the controller <NUM> compares the electricity generation continuation energy cost with a sum of the stop and start energy cost and the external charge energy cost.

When the sum of the stop and start energy cost and the external charge energy cost is larger than the electricity generation continuation energy cost, the controller <NUM> determines that the energy loss is smaller when the electricity generation of the fuel cell stack <NUM> is continued, and executes processing of step S113.

In step S113, the controller <NUM> continues to supply the anode gas and the cathode gas to the fuel cell stack <NUM>, and continues to generate electricity in the fuel cell stack <NUM> in an electricity generation state in which the temperature of the fuel cell stack <NUM> is maintained at the warm-up temperature. At this time, the battery charging by the external charger <NUM> is also continued. After executing the processing of step S113, the controller <NUM> executes the processing of step S103.

On the other hand, when it is determined in step S112 that the sum of the stop and start energy cost and the external charge energy cost is equal to or less than the electricity generation continuation energy cost, the controller <NUM> determines that the energy loss is smaller when the system stop control is executed at this stage, and executes the processing of step S108. In S108, the controller <NUM> ends the electricity generation of the fuel cell stack <NUM>, and starts the system stop control. Although the electricity generation of the fuel cell stack <NUM> is stopped by the system stop control, the battery charging by the external charger <NUM> is continued.

According to the fuel cell system <NUM> in the present embodiment, the following effects can be obtained.

The fuel cell system <NUM> includes the fuel cell stack <NUM>, and the catalyst combustor <NUM> for warming up the fuel cell stack <NUM>, and is configured to execute the stop control when the system operation stop request from the driver or the like is received. The controller <NUM> of the fuel cell system <NUM> acquires the operation stop request of the fuel cell system <NUM>, acquires the next vehicle operation start timing, and calculates the stop and start energy cost and the electricity generation continuation energy cost at a predetermined timing (current cost calculation timing) after acquiring the operation stop request and the next operation start timing. The stop and start energy cost is an energy cost required from the predetermined timing to the completion of warming up of the fuel cell stack <NUM> when the warm-up control is executed using the catalyst combustor <NUM> in accordance with the next vehicle operation start timing after the stop control is executed. The electricity generation continuation energy cost is an energy cost required when the operation of the fuel cell stack <NUM> is continued so as to maintain the temperature of the fuel cell stack <NUM> at the warm-up temperature from the predetermined timing to the next vehicle operation start timing. After acquiring the operation stop request, the controller <NUM> continues operation of the fuel cell stack <NUM> so as to maintain the temperature of the fuel cell stack <NUM> at the warm-up temperature while the stop and start energy cost is larger than the electricity generation continuation energy cost.

In this way, the fuel cell system <NUM> continues the operation of the fuel cell stack <NUM> while the stop and start energy cost is larger than the electricity generation continuation energy cost after the system stop request is acquired, and therefore, the energy loss after the system stop request can be prevented. In this way, it is possible to realize the control of the fuel cell system <NUM>, which can reduced the energy costs in consideration of the energy cost from the system stop to the next vehicle operation start and the energy cost associated with the electricity generation of the fuel cell when the system stop request is received.

Further, after acquiring the operation stop request, the controller <NUM> starts the stop control when the stop and start energy cost is equal to or less than the electricity generation continuation energy cost. In this way, by executing the stop control when the stop and start energy cost is equal to or less than the electricity generation continuation energy cost, the energy loss after the system stop request can be prevented.

Further, the controller <NUM> calculates, based on the stop time from the predetermined timing (cost calculation timing) to the restart timing (warm-up start timing) of the fuel cell stack <NUM> and the stack temperature at the predetermined timing, the pre-start stack temperature after executing the stop control, and calculates the stop and start energy cost based on the calculated pre-start stack temperature. In this way, by using the pre-start stack temperature, the energy costs related to the stop control and the warm-up control can be accurately calculated.

Further, the controller <NUM> of the fuel cell system <NUM> calculates the stack electricity quantity based on a duration (duration time) from the predetermined timing (cost calculation timing) to the next vehicle operation start timing and the electricity generation output of the fuel cell stack <NUM>, and calculates the electricity generation continuation energy cost based on the calculated stack electricity quantity and the electricity conversion efficiency of the fuel cell system <NUM>. In this way, by using the stack electricity quantity that can be generated by the fuel cell stack <NUM> and the electricity conversion efficiency determined in consideration of the entire system, the energy costs can be accurately calculated when the electricity generation is continued in the fuel cell stack <NUM>.

Further, the fuel cell system <NUM> further includes the battery <NUM> as the vehicle power supply, and the charging connector <NUM> that can be connected to the charging unit <NUM> of the external charger <NUM>, and the battery <NUM> is configured to be charged by at least one of the fuel cell stack <NUM> and the external charger <NUM>. The controller <NUM> calculates the external charge energy cost required to charge the battery <NUM> to the target charge quantity by the external charger <NUM>, when the fuel cell system <NUM> is connected to the external charger <NUM>. After acquiring the operation stop request, the controller <NUM> continues the operation of the fuel cell stack <NUM> so as to maintain the temperature of the fuel cell stack <NUM> at the warm-up temperature while the sum of the stop and start energy cost and the external charge energy cost is larger than the electricity generation continuation energy cost, and starts the stop control when the sum of the stop and start energy cost and the external charge energy cost is equal to or less than the electricity generation continuation energy cost.

In the fuel cell system <NUM>, when the battery is charged by the external charger <NUM>, it is possible to determine whether to continue the operation of the fuel cell stack <NUM> or to execute the stop control in consideration of not only the stop and start energy cost and the electricity generation continuation energy cost but also the external charge energy cost. As a result, even when the fuel cell system <NUM> is connected to the external charger <NUM>, the energy loss after the system stop request can be prevented.

The controller <NUM> of the fuel cell system <NUM> calculates the stack electricity quantity based on the duration from the predetermined timing (cost calculation timing) to the next vehicle operation start timing and the electricity generation output of the fuel cell stack <NUM>, and calculates the external charge energy cost based on the target charge electricity quantity of the battery <NUM> and the stack electricity quantity. In this way, by using the target charge electricity quantity of the battery <NUM> and the stack electricity quantity, the energy costs when the battery <NUM> is charged by the external charger <NUM> can be accurately calculated.

Next, the fuel cell system <NUM> according to a second embodiment of the present invention is described with reference to <FIG>. In the following embodiment, the same reference numerals are used for configurations and the like that perform the same functions as those in the first embodiment, and duplicate descriptions are omitted as appropriate.

The fuel cell system <NUM> according to the second embodiment is configured to set the electricity generation duration of the fuel cell stack <NUM> such that the energy loss after the system stop request is minimized when the system is connected to the external charger <NUM> or the like.

Processing executed by the fuel cell system <NUM> according to the second embodiment when a system stop request is detected is described with reference to <FIG> is a flowchart illustrating a flow of the processing executed when the system stop request is issued. Since the processing other than that of steps S201 to S208 in <FIG> is the same as the processing described in <FIG>, the processing of steps S201 to S208 is described here.

In step S103 of <FIG>, when the external charger <NUM> is connected and a target electricity quantity of the battery <NUM> is set, the controller <NUM> executes the processing of step S201.

In step S201, the controller <NUM> calculates a maximum electricity generation duration TMAX as a maximum value of a time during which the electricity generation of the fuel cell stack <NUM> can be continued, for example, by subtracting a time (stop request acquisition timing) when the stop request is acquired from a restart timing of the fuel cell stack <NUM> that is obtained based on a next operation start time.

In step S202, the controller <NUM> determines an electricity generation duration Tk (for example, k = <NUM> to <NUM>) obtained by dividing the maximum electricity generation duration TMAX by a predetermined number of times k. The electricity generation duration Tk indicates an elapsed time from the stop request acquisition timing, and for example, when the maximum electricity generation duration TMAX is <NUM> minutes, values of electricity generation durations are T<NUM> = <NUM> minutes, T<NUM> = <NUM> minute, T<NUM> = <NUM> minutes,. , T<NUM> = <NUM> minutes.

In step S203, the controller <NUM> calculates an energy cost (second stop and start energy cost) required when the stop and start control is executed after electricity is generated only in the electricity generation duration Tk from the stop request acquisition timing. As shown in <FIG>, the controller <NUM> (stop and start energy cost calculation unit <NUM>) calculates a stop time based on the restart timing and the electricity generation duration Tk, and calculates the second stop and start energy cost (fourth energy cost) by inputting this stop time into the pre-start stack temperature calculation unit 51B. The second stop and start energy cost is an energy cost required from the stop request timing to the completion of warming up of the fuel cell when the stop control is executed after the set electricity generation duration is elapsed, and the warm-up control is executed using the heater according to the next vehicle operation start timing. Unlike the first embodiment, the electricity generation duration Tk calculated in step S202 is input to the stop time calculation unit 51A in <FIG> instead of an actual cost calculation timing (current time).

After calculating the second stop and start energy cost in step S203, in step S204, the controller <NUM> calculates an energy cost (second electricity generation continuation energy cost) required when electricity is generated only in the electricity generation duration Tk from the stop request acquisition timing. As shown in <FIG>, the controller <NUM> (electricity generation continuation energy cost calculation unit <NUM>) calculates a stack electricity quantity in the electricity generation duration based on the electricity generation output of the fuel cell stack <NUM> and the electricity generation duration Tk, and calculates the second electricity generation continuation energy cost (fifth energy cost) by inputting this stack electricity quantity to the electricity generation energy calculation unit 52E. Unlike the first embodiment, the electricity generation duration Tk calculated in step S202 is input to the electricity quantity calculation unit 52A in <FIG> instead of a stop time.

After calculating the second electricity generation continuation energy cost in step S204, in step S205, the controller <NUM> calculates an energy cost (second external charge energy cost) required when the battery <NUM> is charged to the target charge quantity by the external charger <NUM>. As shown in <FIG>, the controller <NUM> (external charge energy cost calculation unit <NUM>) calculates the second external charge energy cost (sixth energy cost) based on the target charge electricity quantity, and the stack electricity quantity calculated based on the electricity generation output and the electricity generation duration Tk.

After calculating the external charge energy cost as described above, in step S206 of <FIG>, the controller <NUM> calculates a total energy cost Ck by adding the stop and start energy cost, the electricity generation continuation energy cost, and the external charge energy cost in the electricity generation duration Tk. This total energy cost Ck is temporarily stored in a storage medium such as the RAM of the controller <NUM>.

In step S207, the controller <NUM> determines whether the total energy costs C<NUM> to C<NUM> are calculated for all the electricity generation durations T<NUM> to T<NUM>, and counts up a variable k and repeats processing of step S203 and subsequent steps when not all the calculations are completed. When the total energy costs C<NUM> to C<NUM> are calculated for all the electricity generation durations T<NUM> to T<NUM>, the controller <NUM> executes processing of step S208.

In step S208, the controller <NUM> selects an electricity generation duration with a smallest total energy cost among the total energy costs C<NUM> to C<NUM> in the electricity generation durations T<NUM> to T<NUM>, and continues the operation (electricity generation) of the fuel cell stack <NUM> in an electricity generation state in which the temperature of the fuel cell stack <NUM> is maintained at the warm-up temperature until the selected electricity generation duration elapses from the stop request acquisition timing. At a timing when the electricity generation duration elapses, the controller <NUM> ends the electricity generation of the fuel cell stack <NUM>, and starts the stop control.

According to the fuel cell system <NUM> in the present embodiment described above, as shown in <FIG>, when a system stop request is issued by the driver or the like, a sum (total energy cost) of the second stop and start energy cost, the second electricity generation continuation energy cost, and the second external charge energy cost is calculated for each of the electricity generation durations T<NUM> to T<NUM> obtained by dividing the maximum electricity generation duration. The controller <NUM> selects the electricity generation duration with the smallest total energy cost among the total energy costs in the electricity generation durations T<NUM> to T<NUM>. For example, as shown in <FIG>, when a total energy cost in an electricity generation duration T<NUM> is the smallest, the operation (electricity generation) of the fuel cell stack <NUM> is continued from the stop request acquisition timing until the electricity generation duration T<NUM> elapses, and then the stop control is executed. Since the fuel cell system <NUM> has a configuration in which the operation (electricity generation) of the fuel cell stack <NUM> is continued only in the electricity generation duration which minimizes the total energy cost, the energy loss after the system stop request can be prevented more reliably.

In the second embodiment, the controller <NUM> selects an electricity generation duration Tk with the smallest energy cost as the electricity generation duration, but a method for selecting the electricity generation duration is not limited thereto. For example, in the electricity generation duration Tk, two times including a time with a lowest energy cost and a time with a next lowest energy cost, are extracted, and an average time is calculated from these two times. Then, a total energy cost in this average time is calculated, and a total energy cost in the average time is compared with a minimum total energy cost in the electricity generation duration Tk, and thereby one with a smaller energy cost may be selected as the electricity generation duration.

As described above, the embodiments of the present invention are described, but the above embodiments merely show a part of application examples of the present invention, and do not intend to limit the technical scope of the present invention to the specific configurations of the above embodiments. Various changes and modifications can be made on the above embodiments within the scope of matters described in claims. Further, the technical idea described in the above first embodiment and second embodiment may be combined as appropriate.

The fuel cell system <NUM> according to the above embodiments has a configuration in which the fuel cell stack <NUM> is warmed up by utilizing the combustion heat of the catalyst combustor <NUM>, but may have a configuration in which the fuel cell stack <NUM> is warmed up by using an electric temperature regulator capable of adjusting the temperature of the fuel cell stack <NUM> itself. In this way, when the electric temperature regulator is used, the start energy and the like are calculated based on electricity consumed by the regulator.

Claim 1:
A control method for a fuel cell system (<NUM>) for a vehicle including a fuel cell and a heater configured to warm up the fuel cell, the method executing a stop control of the fuel cell system (<NUM>) when an operation stop request thereof is received (S101), wherein the method further comprises:
determining, after the operation stop request is received, if a next operation start time of the vehicle has been set (S102);
calculating a first energy cost and a second energy cost at predetermined intervals, if the next operation start time of the vehicle has been set (S104, S105), wherein
the first energy cost is an energy cost required from a present time when the stop control is started until when warm-up of the fuel cell using the heater is completed prior to the next operation start time of the vehicle, and
the second energy cost is an energy cost required if an operation of the fuel cell is continued to maintain a temperature of the fuel cell at a warm-up temperature from the present time until the next operation start time of the vehicle; and
continuing the operation of the fuel cell to maintain the temperature of the fuel cell at the warm-up temperature as long as the first energy cost is larger than the second energy cost (S106, S107).