Fuel Cell Systems

Abstract

To provide a fuel cell system capable of suppressing voltage fluctuation of a fuel cell caused by switching between an intermittent operation and a load operation.SOLUTION: A fuel cell system 1 is configured to store the history of voltage during a load operation, and when switching an operation from the load operation to an intermittent operation, adjust a voltage limit range Vb during the intermittent operation by referring the history of voltage during the load operation. Specifically, a control device 50 stores in a storage unit 51 a stack voltage immediately before switching from the load operation to the intermittent operation as a last voltage, and sets the voltage limit range Vb during the intermittent operation so as to include at least the last voltage.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to fuel cell systems. [Background technology]

[0002] Conventionally, there is known a fuel cell system that effectively suppresses degradation of the electrode catalyst by taking into consideration the number of times the fuel cell voltage fluctuates during intermittent operation and the amount of electrode catalyst degradation corresponding to the amount of voltage fluctuation of the fuel cell during intermittent operation (see, for example, Patent Document 1). The fuel cell system of Patent Document 1 uses a degradation characteristics map that specifies the relationship between the duration of intermittent operation and the amount of electrode catalyst degradation, and changes the upper and lower limit voltage values ​​of the fuel cell voltage fluctuation during intermittent operation according to the duration of intermittent operation so as to minimize the amount of electrode catalyst degradation. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2013-101774 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, when switching from the normal operation mode of load operation to intermittent operation or from intermittent operation to load operation, the voltage of the fuel cell fluctuates. Such voltage fluctuations are undesirable because they can cause deterioration of the electrode catalyst.

[0005] However, in Patent Document 1, the upper and lower limit voltage values ​​of the fuel cell during intermittent operation are set according to the duration of the intermittent operation, and the voltage of the fuel cell in the normal operation mode is not taken into consideration at all. As a result, the voltage fluctuation of the fuel cell occurs due to switching between intermittent operation and load operation.

[0006] An object of the present disclosure is to provide a fuel cell system capable of suppressing voltage fluctuations in a fuel cell caused by switching between intermittent operation and load operation. [Means for solving the problem]

[0007] The invention described in claim 1 is 1. A fuel cell system comprising: a fuel cell stack (10) formed by stacking a plurality of cells (10a); an operation control unit (50a) that performs a load operation when a required output from a load device (LD) exceeds a predetermined output, and performs an intermittent operation that intermittently supplies air to the fuel cell stack when the required output is equal to or less than the predetermined output; a voltage setting unit (50b) that sets upper and lower limit voltage values ​​of the fuel cell stack during intermittent operation as a voltage limit range; The voltage setting unit stores the voltage of the fuel cell stack immediately before switching from load operation to intermittent operation in a memory unit (51) as a immediately preceding voltage, and sets a voltage limit range during intermittent operation so as to include at least the immediately preceding voltage.

[0008] In this way, by setting the voltage limit range during intermittent operation to include the voltage immediately before switching to intermittent operation, it is possible to suppress the voltage fluctuation of the fuel cell stack when switching from load operation to intermittent operation, and therefore the voltage fluctuation of the fuel cell caused by switching between intermittent operation and load operation can be suppressed.

[0009] The invention described in claim 6 is 1. A fuel cell system comprising: a fuel cell stack (10) including a plurality of cells (10a) stacked together; an operation control unit (50a) that performs a load operation when a required output from a load device (LD) exceeds a predetermined output, and performs an intermittent operation that intermittently supplies air to the fuel cell stack when the required output is equal to or less than the predetermined output; a voltage setting unit (50b) that sets upper and lower limit voltage values ​​of the fuel cell stack during intermittent operation as a voltage limit range; an output prediction unit (50c) that predicts a required output after switching from the intermittent operation to the load operation as a predicted output, and calculates a voltage of the fuel cell stack corresponding to the predicted output as a predicted voltage; When a predetermined condition is satisfied during the intermittent operation, the voltage setting unit sets the voltage limit range before switching from the intermittent operation to the load operation to a range that includes at least the predicted voltage.

[0010] In this way, if the voltage limit range during intermittent operation is set to include the predicted voltage after switching to load operation when a predetermined condition is met during intermittent operation, it is possible to suppress the voltage fluctuation of the fuel cell stack when switching from intermittent operation to load operation, and therefore the voltage fluctuation of the fuel cell caused by switching between intermittent operation and load operation can be suppressed.

[0011] The invention described in claim 7 is 1. A fuel cell system comprising: a fuel cell stack (10) including a plurality of cells (10a) stacked together; an operation control unit (50a) that performs a load operation when a required output from a load device (LD) exceeds a predetermined output, and performs an intermittent operation that intermittently supplies air to the fuel cell stack when the required output is equal to or less than the predetermined output; a voltage setting unit (50b) that sets upper and lower limit voltage values ​​of the fuel cell stack during intermittent operation as a voltage limit range; an output prediction unit (50c) that predicts a required output after switching from the load operation to the intermittent operation as a predicted output and calculates a voltage of the fuel cell stack corresponding to the predicted output as a predicted voltage; When a predetermined condition is satisfied during the load operation, the voltage setting unit sets a voltage limit range after switching from the load operation to the intermittent operation to a range that includes at least the predicted voltage.

[0012] In this way, if the voltage limit range after switching to intermittent operation is set to a range including the predicted voltage when a predetermined condition is met during load operation, it is possible to suppress the voltage fluctuation of the fuel cell stack when switching from load operation to intermittent operation, and therefore the voltage fluctuation of the fuel cell caused by switching between intermittent operation and load operation can be suppressed.

[0013] The reference symbols in parentheses attached to each component indicate an example of the correspondence between the component and specific components described in the embodiments described below. [Brief description of the drawings]

[0014] [Figure 1] FIG. 1 is an explanatory diagram for explaining a moving body on which a fuel cell system according to a first embodiment is mounted. [Diagram 2] 1 is a schematic configuration diagram of a fuel cell system according to a first embodiment. [Diagram 3] FIG. 2 is an explanatory diagram for explaining the relationship between an FC voltage and an FC output. [Figure 4] FIG. 11 is an explanatory diagram for explaining the relationship between the average value of the FC voltage during intermittent operation and the stack voltage during load operation after the intermittent operation. [Diagram 5] 4 is a flowchart showing the flow of a control process executed by a control device of the fuel cell system according to the first embodiment. [Figure 6] 4 is a timing chart for explaining a control process executed by a control device of the fuel cell system according to the first embodiment. [Figure 7] 10 is a flowchart showing the flow of a control process executed by a control device of a fuel cell system according to a second embodiment. [Figure 8] FIG. 11 is a schematic configuration diagram of a fuel cell system according to a third embodiment. [Figure 9] 10 is a flowchart showing the flow of a control process executed by a control device of a fuel cell system according to a third embodiment. [Figure 10]10 is a flowchart showing the flow of an output prediction process executed by a control device of a fuel cell system according to a third embodiment. [Figure 11] FIG. 11 is an explanatory diagram for explaining a predicted voltage acquisition interval. [Figure 12] 13 is a timing chart illustrating a control process executed by a control device of a fuel cell system according to a third embodiment. [Figure 13] 10 is a flowchart showing the flow of a control process executed by a control device of a fuel cell system according to a fourth embodiment. [Figure 14] 13 is a flowchart showing the flow of an output prediction process executed by a control device of a fuel cell system according to a fourth embodiment. [Figure 15] 13 is a timing chart for explaining a control process executed by a control device of a fuel cell system according to a fourth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Hereinafter, the embodiments of the present disclosure will be described with reference to the drawings. In the following embodiments, the same reference numerals are used for parts that are the same as or equivalent to those described in the preceding embodiments, and the description thereof may be omitted. In addition, in the embodiments, when only a part of the components is described, the components described in the preceding embodiments can be applied to the other parts of the components. In the following embodiments, each embodiment can be partially combined with each other, even if not specifically stated, as long as it does not cause any trouble in combination.

[0016] (First embodiment) This embodiment will be described with reference to Figures 1 to 6. As shown in Figure 1, a fuel cell system 1 of the present disclosure is applied to a bus BS, which is a mobile body, and controls the power generation state of a fuel cell stack 10 mounted on the bus BS. The fuel cell system 1 can also be applied to mobile bodies other than the bus BS.

[0017] As shown in Fig. 2, the fuel cell stack 10 is composed of a plurality of cells 10a stacked together. The cells 10a output electric energy through an electrochemical reaction between reactant gases, such as an oxidant gas containing oxygen and a fuel gas containing hydrogen. Although not shown, the cells 10a are composed of solid polymer electrolyte fuel cells equipped with a membrane electrode assembly MEA including an electrolyte membrane. MEA is an abbreviation for Membrane Electrode Assembly.

[0018] Each cell 10a outputs electrical energy through the electrochemical reaction of hydrogen and oxygen as shown below.

[0019] (Fuel electrode side): H2→2H + +2e -

[0020] (Air electrode side): 2H + +1 / 2O2+2e - →H2O The fuel cell stack 10 outputs an integrated voltage of the voltages output by each of the cells 10a to a DC-DC converter CNV through an external circuit (not shown). The fuel cell stack 10 includes a flow path for circulating cooling water, and the temperature of the fuel cell stack 10 is maintained within an appropriate range by the cooling water flowing through the flow path.

[0021] In this disclosure, the voltage output by each cell 10a is defined as the cell voltage, the terminal voltage of the fuel cell stack 10 is defined as the stack voltage, and the stack voltage divided by the number of cells 10a is defined as the FC voltage [V / cell]. The FC voltage is the average voltage of the cell voltages of the cells 10a.

[0022] The fuel cell stack 10 supplies the FC output, which is the output power (DC power) of the fuel cell stack 10, to the battery BT and a load device LD including an electric motor and auxiliary devices for driving the vehicle, via a DC-DC converter CNV. The DC-DC converter CNV supplies at least one of the FC output and the power stored in the battery BT to the load device LD in accordance with the output required by the load device LD. When the FC output includes power that is surplus on the load device LD side, the DC-DC converter CNV supplies the surplus power to the battery BT. The battery BT is a chargeable and dischargeable secondary battery.

[0023] A fuel supply pipe 21 which is a path for supplying fuel to the fuel cell stack 10 and a fuel discharge pipe 22 which is a path for discharging off-fuel discharged from the fuel cell stack 10 are connected to the fuel cell stack 10 .

[0024] A hydrogen tank 23 is provided at the most upstream portion of the fuel supply pipe 21. A hydrogen supply valve 24 is provided downstream of the hydrogen tank 23 in the fuel supply pipe 21. The hydrogen supply valve 24 is an adjustment valve that adjusts the amount of hydrogen supplied from the hydrogen tank 23 to the fuel cell stack 10.

[0025] The fuel discharge pipe 22 is provided with a gas-liquid separator 25 for separating gas and liquid of the off-fuel, and a hydrogen discharge valve 26 is provided downstream of the gas-liquid separator 25. The gas-liquid separator 25 separates water and the like contained in the off-fuel from gas containing unreacted fuel contained in the off-fuel. The gas-liquid separator 25 is connected to a circulation pipe 27 for returning the gas containing unreacted fuel separated by the gas-liquid separator 25 to the fuel supply pipe 21. One end of the circulation pipe 27 is connected to a liquid outlet of the gas-liquid separator 25, and the other end is connected to the fuel supply pipe 21 between the hydrogen supply valve 24 and the fuel cell stack 10. The circulation pipe 27 is provided with a circulation pump 28 for pumping the gas containing unreacted fuel to the fuel supply pipe 21. In addition, the fuel cell system 1 may have an ejector between the circulation pipe 27 and the fuel supply pipe 21 instead of the circulation pump 28.

[0026] An air supply pipe 31 which is a path for supplying air to the fuel cell stack 10 and an air exhaust pipe 32 which is a path for exhausting off-air exhausted from the fuel cell stack 10 are connected to the fuel cell stack 10 .

[0027] The air supply pipe 31 is provided with an air pump 33 that pressurizes and sends air toward the fuel cell stack 10. The air supply pipe 31 is provided with a bypass pipe 34 for causing a portion of the air supplied from the air pump 33 to bypass the fuel cell stack 10 and flow into the air exhaust pipe 32. One end of the bypass pipe 34 is connected to the air supply pipe 31 between the air pump 33 and the fuel cell stack 10, and the other end is connected to the air exhaust pipe 32.

[0028] A diverter valve 35 is provided at the connection between the air supply pipe 31 and the bypass pipe 34. The diverter valve 35 is a flow rate control valve that adjusts the air flow rate from the air pump 33 toward the fuel cell stack 10 and the air flow rate from the air pump 33 toward the bypass pipe 34. The diverter valve 35 may be provided at the connection between the air exhaust pipe 32 and the bypass pipe 34.

[0029] Next, we will explain the electronic control unit of the fuel cell system 1. The fuel cell system 1 includes a control device 50 as an electronic control unit. The control device 50 is configured with an ECU including a processor, a storage unit 51, I / O devices, and other peripheral devices. The storage unit 51 is configured with a non-transient tangible storage medium.

[0030] A DC-DC converter CNV, a battery BT, a voltage sensor 52, and a current sensor 53 are connected to the input side of the control device 50. The control device 50 is connected to the DC-DC converter CNV and the battery BT, and is thereby able to acquire information regarding the storage capacity SOC of the battery BT.

[0031] The control device 50 is connected to a voltage sensor 52, and is therefore able to acquire information including a stack voltage, which is the voltage between the terminals of the fuel cell stack 10, from the voltage sensor 52. In addition, the control device 50 is connected to a current sensor 53, and is therefore able to acquire information including the FC current swept from the fuel cell stack 10, from the current sensor 53.

[0032] In addition, an operation unit 54 including a start switch SW and an accelerator opening sensor 55 are connected to the control device 50. The start switch SW is a switch that is operated by the user.

[0033] When the start switch SW is turned on by the user, it transmits a control signal to the controller 50 to instruct the controller to start the fuel cell stack 10. When the start switch SW is turned off by the user, it transmits a control signal to the controller 50 to instruct the controller to stop the fuel cell stack 10.

[0034] The accelerator opening sensor 55 is a sensor that detects the amount of pedal operation of the accelerator pedal by the user. The accelerator opening sensor 55 periodically or irregularly outputs a signal indicating the amount of pedal operation to the control device 50. The accelerator opening sensor 55 does not need to be directly connected to the control device 50, and may be indirectly connected via another ECU.

[0035] Connected to the output side of the controller 50 are the hydrogen supply valve 24, the hydrogen discharge valve 26, the circulation pump 28, the air pump 33, and the flow dividing valve 35. When the start switch SW is turned on, the controller 50 controls the operation of the various devices connected to the output side of the controller 50 in response to the required output from the load device LD.

[0036] The control device 50 switches the operation mode according to the output required from the load device LD. Specifically, the control device 50 performs a load operation when the output required from the load device LD exceeds a predetermined output, and performs an intermittent operation in which air is intermittently supplied to the fuel cell stack 10 when the output is equal to or less than the predetermined output. In this embodiment, the function of switching the operation mode in the control device 50 constitutes an "operation control unit 50a."

[0037] Load operation is a normal operation mode in which power is generated (i.e., power is output) by the fuel cell stack 10 and the power is used to drive the load device LD. Note that the load operation may be configured to use not only the power of the fuel cell stack 10 but also the power of the battery BT.

[0038] The intermittent operation is an operation mode in which power generation by the fuel cell stack 10 is stopped and the load device LD is driven using the power of the battery BT. Note that the intermittent operation is not limited to a mode in which power generation by the fuel cell stack 10 is completely stopped, but may be an operation mode in which a small amount of power generation continues while limiting power generation.

[0039] Here, the present inventors investigated how fuel cell vehicles equipped with the fuel cell system 1 are used in the market. As a result of this investigation, the following became clear.

[0040] (1) The frequency of intermittent operation when the required output from the load device LD is low tends to increase in proportion to the mileage.

[0041] (2) The output frequency of the fuel cell system 1 tends to be most frequently in the low output range of less than 20% of maximum output. Due to the above (1) and (2), it is estimated that fuel cell vehicles in the market are repeatedly and alternately operated between intermittent operation and low-output load operation. It is estimated that voltage fluctuations in the fuel cell stack 10 are likely to occur when switching from load operation to intermittent operation, or when switching from intermittent operation to load operation. For example, when switching from load operation to intermittent operation, the FC current swept from each cell 10a decreases, causing the FC voltage to rise and voltage fluctuations to occur, as shown in FIG. 3. For this reason, it is estimated that when switching from load operation to intermittent operation, the deterioration of the electrode catalyst in each cell 10a is likely to progress.

[0042] Based on these findings, the present inventors have found that in order to suppress deterioration of the electrode catalyst in each cell 10a, it is necessary to suppress the fluctuation in FC voltage that occurs when switching between load operation and intermittent operation.

[0043] Here, in JP 2013-101774 A, which is cited as background art of this disclosure, the lower limit of the FC voltage during intermittent operation is set to about 0.7 volts.

[0044] The inventors conducted a test to investigate the relationship between the average voltage of the FC voltage during intermittent operation and the stack voltage during load operation after the intermittent operation. The results showed that, as shown in FIG. 4, the lower the average voltage of the FC voltage during intermittent operation, the more likely it is that the stack voltage during load operation after the intermittent operation will increase. In particular, when the average value of the FC voltage during intermittent operation is 0.7 volts or less, the stack voltage during subsequent load operation is higher than when it exceeds 0.7 volts. In other words, it was found that the performance during load operation after intermittent operation is improved when the lower limit value of the FC voltage during intermittent operation is lower than 0.7 volts, which is indicated as the lower limit voltage of the FC voltage in "JP Patent Publication 2013-101774".

[0045] This improvement in performance is thought to be the result of the so-called electrode catalyst refreshing effect, which is the effect of restoring the effective surface area of ​​the electrode catalyst, and can be obtained by lowering the potential on the air electrode side to a reduction voltage to remove the oxide film on the surface of the electrode catalyst.

[0046] In consideration of these, in the fuel cell system 1 of this embodiment, the control device 50 executes a control process for suppressing voltage fluctuations in the fuel cell stack 10 when switching from load operation to intermittent operation. This control process will be described with reference to Fig. 5. The control routine shown in Fig. 5 is executed by the control device 50 periodically or irregularly with the start switch SW turned off.

[0047] 5, the controller 50 determines whether or not the start switch SW is turned on in step S100. The controller 50 waits until the start switch SW is turned on, and when the start switch SW is turned on, the process proceeds to step S105.

[0048] In the fuel cell system 1, the required output from the load device LD is often low for a while after the start switch SW is turned on. For this reason, when the start switch SW is turned on, the control device 50 starts, in step S105, intermittent operation, which also serves as the startup operation of the fuel cell system 1. In intermittent operation, hydrogen and air are supplied to the fuel cell stack 10, and the upper and lower limit voltage values ​​of the fuel cell stack 10 are set to a voltage limit range Va, and the operation of various devices connected to the output side of the control device 50 is controlled so that the stack voltage is maintained within the voltage limit range Va.

[0049] Specifically, in intermittent operation, air is supplied intermittently to the fuel cell stack 10. For example, as shown in Fig. 6, the control device 50 stops the air supply to the fuel cell stack 10 when the stack voltage reaches an upper limit voltage value Vaa of the voltage limit range Va, and resumes the air supply to the fuel cell stack 10 when the stack voltage reaches a lower limit voltage value Vad of the voltage limit range Va. Note that the voltage limit range Va is set to a voltage width that is the difference between the upper limit voltage value Vaa and the lower limit voltage value Vad so that deterioration of the electrode catalyst due to voltage fluctuation during intermittent operation is unlikely to occur. This voltage width is set to, for example, about 0.1.

[0050] Next, in step S110, the control device 50 calculates the required output of the load device LD based on the signal supplied from the accelerator opening sensor 55, and determines whether the calculated required output is equal to or less than a predetermined first output. Note that the first output is set to a required output required of the fuel cell stack 10 during, for example, idling, cruising at a constant speed, regenerative braking, etc.

[0051] The control device 50 continues intermittent operation when the required output of the load device LD is equal to or less than the first output, and proceeds to step S115 to start load operation when the required output of the load device LD exceeds the first output. In this load operation, the operation of various devices connected to the output side of the control device 50 is controlled so that the output of the fuel cell stack 10 becomes the required output of the load device LD.

[0052] Next, in step S120, the control device 50 detects the stack voltage of the fuel cell stack 10 during load operation, and sequentially stores the stack voltage as a load operation voltage in the memory unit 51. Of the load operation voltages, the control device 50 stores the stack voltage immediately before switching from load operation to intermittent operation as the immediately preceding voltage in the memory unit 51. Note that the control device 50 may be configured to sequentially store the FC voltage during load operation in the memory unit 51 as the load operation voltage.

[0053] Next, in step S125, the control device 50 determines whether the required output of the load device LD is equal to or lower than a predetermined second output. This second output may be the same as the first output, but is preferably set to a value lower than the first output so as to suppress control hunting.

[0054] When the required output of the load device LD exceeds the second output, the control device 50 continues the load operation. On the other hand, when the required output of the load device LD becomes equal to or less than the second output, the control device 50 proceeds to step S130.

[0055] In step S130, the control device 50 sets a voltage limit range Vb, which is the upper and lower limit voltages of the fuel cell stack 10 during intermittent operation, so as to include at least the stack voltage immediately before switching to intermittent operation (i.e., the immediately preceding voltage). In this embodiment, the function of the control device 50 that sets the voltage limit range Vb during intermittent operation constitutes the "voltage setting unit 50b." The voltage width of the voltage limit range Vb is set similarly to the voltage limit range Va.

[0056] The control device 50 of this embodiment sets the voltage limit range Vb during intermittent operation based on the load operation voltage stored in the storage unit 51. For example, as shown in the upper part of Fig. 6, the control device 50 sets the average value of the load operation voltage stored in the storage unit 51 to the median value Vbc of the voltage limit range Vb during intermittent operation so that the average value of the load operation voltage stored in the storage unit 51 becomes the average voltage during intermittent operation.

[0057] Here, as described above, if the lower limit value of the FC voltage during intermittent operation is set to less than "0.7", the performance during load operation after intermittent operation is improved. Taking this into consideration, when the FC voltage immediately before switching from load operation to intermittent operation is 0.7 volts or less, the control device 50 sets the voltage limit range Vb during intermittent operation so that the lower limit voltage value Vbd of the voltage limit range Vb is equal to or less than the value obtained by multiplying the number of cells by "0.7". Furthermore, when the FC voltage immediately before switching from load operation to intermittent operation exceeds 0.7 volts, the control device 50 sets the voltage limit range Vb during intermittent operation so that the voltage fluctuation width falls within a predetermined voltage width (for example, about 0.1). Note that the above number of cells is the number of cells 10a that constitute the fuel cell stack 10.

[0058] Next, the control device 50 starts intermittent operation in step S135. In this intermittent operation, the operation of various devices connected to the output side of the control device 50 is controlled so that the stack voltage of the fuel cell stack 10 is maintained within the voltage limit range Vb set in step 130. This suppresses an increase in stack voltage when switching from load operation to intermittent operation. Note that, if the intermittent operation of step S105 is performed in step S135, the stack voltage will increase when switching from load operation to intermittent operation, as shown by the dashed line in the upper part of FIG. 6.

[0059] Here, Fig. 3 shows the relationship between FC output and FC voltage. For example, when the FC current swept from each cell 10a is suddenly decreased at operating point A shown in Fig. 3, the fuel cell stack 10 is in a state rich in both hydrogen and air, so that the FC voltage suddenly rises.

[0060] Taking this into consideration, the control device 50 gradually reduces the FC current and at the same time gradually reduces the air flow rate to the fuel cell stack 10, as shown in Fig. 6. This prevents the performance of each cell 10a from being deteriorated due to a lack of air, resulting in an excessive FC voltage. The air flow rate can be adjusted by adjusting the rotation speed of the air pump 33 and the opening of the flow dividing valve 35.

[0061] Then, when the control device 50 has completed adjusting the stack voltage, it sets the air flow rate lower than at the start of the intermittent operation so that the stack voltage at that time is maintained. Note that the timing of the air supply to the fuel cell stack 10 may be adjusted as necessary.

[0062] Next, in step S140, the control device 50 determines whether the required output of the load device LD is equal to or lower than a predetermined third output. This third output may be the same as the second output, but is preferably set to a value higher than the second output so as to suppress control hunting. The third output may be the same as the first output, or may be different from the first output.

[0063] When the required output of the load device LD exceeds the third output, the control device 50 returns to step S115 and starts the load operation. On the other hand, when the required output of the load device LD is equal to or less than the third output, the control device 50 proceeds to step S145.

[0064] In step S145, the control device 50 determines whether the start switch SW is off. If the start switch SW is on, the control device 50 returns to step S135 to perform intermittent operation, and if the start switch SW is off, the control device 50 exits from this process and executes a power generation stop process (not shown).

[0065] The fuel cell system 1 described above is configured to store the history of the voltage during load operation, and adjust the voltage limit range Vb during intermittent operation by referring to the history of the voltage during load operation when switching from load operation to intermittent operation. Specifically, the control device 50 stores the stack voltage immediately before switching from load operation to intermittent operation in the storage unit 51 as the immediately preceding voltage, and sets the voltage limit range Vb during intermittent operation so as to include at least the immediately preceding voltage. In this way, if the voltage limit range Vb during intermittent operation is set to include the immediately preceding voltage immediately before switching to intermittent operation, it is possible to suppress the voltage fluctuation of the fuel cell stack 10 when switching from load operation to intermittent operation. Therefore, it is possible to suppress the voltage fluctuation of the fuel cell stack 10 caused by switching between intermittent operation and load operation. As a result, it is possible to suppress the deterioration of the electrode catalyst in each cell 10a.

[0066] Moreover, according to this embodiment, the following effects can be obtained.

[0067] (1) The control device 50 sequentially stores the stack voltage during the load operation performed before switching to intermittent operation as the load operation voltage in the memory unit 51. The control device 50 then sets the voltage limit range Vb during intermittent operation based on the load operation voltage stored in the memory unit 51. In this way, by setting the voltage limit range Vb during intermittent operation based not only on the immediately preceding voltage but also on the load operation voltage that is sequentially stored during load operation, it is possible to suppress voltage fluctuations in the fuel cell stack 10 when switching from load operation to intermittent operation.

[0068] (2) The control device 50 sets the voltage limit range Vb during intermittent operation so as to include the average value of the load operation voltage stored in the memory unit 51. In this way, by setting the voltage limit range Vb during intermittent operation so as to include the average value of the load operation voltage, it is possible to suppress the effect of temporary voltage drops and voltage increases due to load fluctuations on the setting of the voltage limit range Vb during intermittent operation. This makes it possible to suppress voltage fluctuations in the fuel cell stack 10 when switching from load operation to intermittent operation.

[0069] In addition, if the voltage limit range Vb is set so that the average value of the load operation voltage stored in the memory unit 51 becomes the average voltage during intermittent operation, it is possible to lower the required accuracy of the air pump 33 and the flow dividing valve 35, which are means for adjusting the air flow rate. This makes it possible to configure at least one of the air pump 33 and the flow dividing valve 35 as a general-purpose component.

[0070] (3) When the FC voltage immediately before switching from load operation to intermittent operation is 0.7 volts or less, the control device 50 sets the voltage limit range Vb during intermittent operation so that the lower limit voltage value Vbd of the voltage limit range Vb is equal to or less than the number of cells multiplied by "0.7." This makes it easier to obtain a refreshing effect on the electrode catalyst built into the cells 10a when the voltage of the load operation is low, thereby improving the performance of the load operation after the intermittent operation.

[0071] In this way, the fuel cell system 1 of this embodiment provides a catalyst refreshing effect during intermittent operation while suppressing voltage fluctuations in the fuel cell stack 10 when switching from load operation to intermittent operation, thereby sufficiently suppressing deterioration of the electrode catalyst of each cell 10a.

[0072] (Modification of the first embodiment) In the first embodiment, the voltage limit range Vb is set so that the average value of the load operation voltage stored in the storage unit 51 becomes the average voltage during intermittent operation, but the present invention is not limited to this. For example, the control device 50 stores the load operation voltage in the storage unit 51 in association with the required output from the load device LD at the time of detection of the load operation voltage. Then, it is preferable that the control device 50 sets the voltage limit range Vb during intermittent operation based on the load operation voltage corresponding to the required output whose frequency of request from the load device LD is equal to or greater than a predetermined value, among the load operation voltages stored in the storage unit 51. This also makes it possible to suppress the temporary voltage drop or voltage rise during load operation from affecting the setting of the voltage limit range Vb during intermittent operation, and therefore it is possible to suppress the voltage fluctuation of the fuel cell stack 10 when switching from load operation to intermittent operation.

[0073] The control device 50 of the first embodiment may be configured to set the voltage limit range Vb so that the immediately preceding voltage stored in the storage unit 51 becomes the average voltage during intermittent operation. The control device 50 may also be configured to set the voltage limit range Vb so that the weighted moving average value of the stack voltage stored in the storage unit 51 becomes the average voltage during intermittent operation.

[0074] As in the first embodiment, when switching from load operation to intermittent operation, the control device 50 desirably adjusts the stack voltage by gradually reducing the FC output and gradually reducing the air flow rate to the fuel cell stack 10, but is not limited to this. For example, the control device 50 may adjust the stack voltage by reducing the FC output after reducing the air flow rate to the fuel cell stack 10.

[0075] As in the first embodiment, it is desirable for the control device 50 to set the voltage limit range Vb so that the lower limit voltage value Vbd of the voltage limit range Vb is equal to or less than the value obtained by multiplying the number of cells by "0.7" when the FC voltage immediately before switching to intermittent operation is equal to or less than 0.7 volts, but is not limited to this. The control device 50 may be configured to set the voltage limit range Vb during intermittent operation so that the lower limit voltage value Vbd of the voltage limit range Vb exceeds the value obtained by multiplying the number of cells by "0.7" even when the FC voltage immediately before switching to intermittent operation is slightly higher than 0.7 volts. In addition, the control device 50 may be configured to set the voltage limit range Vb during intermittent operation so that the lower limit voltage value Vbd of the voltage limit range Vb exceeds the value obtained by multiplying the number of cells by "0.7" when the average value of the load operation voltage is equal to or less than 0.7 volts.

[0076] The control device 50 of the first embodiment is configured to execute intermittent operation that also serves as a startup operation when the start switch SW is turned on, but is not limited to this. For example, the control device 50 may be configured to execute a startup operation that is different from the intermittent operation when the start switch SW is turned on.

[0077] The control device 50 of the first embodiment adjusts the voltage of the fuel cell stack 10 using the stack voltage as a control index during intermittent operation, but is not limited to this, and may also adjust the voltage of the fuel cell stack 10 using the FC voltage as a control index.

[0078] These modifications are applicable not only to the first embodiment but also to the following embodiments.

[0079] Second embodiment Next, a second embodiment will be described with reference to Fig. 7. In this embodiment, a part of the control process executed by the control device 50 is different from that in the first embodiment. In this embodiment, the parts different from the first embodiment will be mainly described.

[0080] The control device 50 executes a control process shown in Fig. 7 in order to suppress voltage fluctuations in the fuel cell stack 10 when switching from load operation to intermittent operation. The control process shown in Fig. 7 corresponds to the control process in Fig. 5 described in the first embodiment.

[0081] Of the control processes shown in FIG. 7, the processes of steps S200, S205, S210, and S215 are similar to the processes of steps S100, S105, S110, and S115 shown in FIG. 5, and therefore description thereof will be omitted.

[0082] 7, after the load operation is started in step S215, the control device 50 determines in step S220 whether the required output of the load device LD is equal to or less than a predetermined second output. If the required output of the load device LD exceeds the second output, the control device 50 continues the load operation. On the other hand, if the required output of the load device LD becomes equal to or less than the second output, the control device 50 proceeds to step S225.

[0083] Here, in the intermittent operation in step S115 of Fig. 5 described in the first embodiment, the FC output is gradually reduced, so surplus power is generated. The amount of this surplus power can be estimated by multiplying the FC output by the time until the FC output becomes zero. Note that since the time until the FC output becomes zero is easily determined by the voltage adjustment means and the volume of the air flow path of the fuel cell stack 10, the predetermined time may be set uniquely.

[0084] If the amount of surplus power is equal to or less than the free capacity of the battery BT, the surplus power can be charged to the battery BT without any problem. On the other hand, if the amount of surplus power exceeds the free capacity of the battery BT, the battery BT will be overcharged by the surplus power.

[0085] Taking these into consideration, the control device 50 determines in step S225 whether or not the surplus power generated during intermittent operation can be charged to the battery BT. In other words, the control device 50 determines whether or not the amount of surplus power generated during intermittent operation exceeds the free capacity of the battery BT.

[0086] For example, the control device 50 calculates the free capacity of the battery BT from a value obtained by subtracting the current SOC of the battery BT from the SOC of the battery BT when fully charged. After that, the control device 50 determines whether or not the battery BT can be charged with surplus power based on the magnitude relationship between the free capacity of the battery BT and the amount of surplus power calculated by the above-mentioned method.

[0087] If the surplus power can be charged to the battery BT, in step S230, the control device 50 detects the stack voltage of the fuel cell stack 10 during load operation, and stores the stack voltage as the load operation voltage in the storage unit 51. Note that the process of step S230 is similar to step S120 shown in Fig. 5, and therefore a detailed description thereof will be omitted.

[0088] Next, in step S235, the control device 50 sets the voltage limit range Vb during intermittent operation, and then proceeds to the process of step S240. Note that the process of step S235 is similar to step S130 shown in FIG. 5, and therefore a detailed description thereof will be omitted.

[0089] On the other hand, if the surplus power cannot be charged to the battery BT, the control device 50 skips the processes of steps S230 and S235 and proceeds to the process of step S240, thereby preventing the battery BT from being overcharged.

[0090] The control device 50 starts intermittent operation in step S240. When the voltage limit range Vb is adjusted in step S235, the control device 50 performs intermittent operation similar to step S135 shown in Fig. 5. On the other hand, when the voltage limit range Vb described in step S235 is not set, the control device 50 performs intermittent operation similar to step S105 shown in Fig. 5.

[0091] Next, in step S245, the control device 50 determines whether the required output of the load device LD is equal to or less than a predetermined third output. If the required output of the load device LD exceeds the third output, the control device 50 returns to step S215 and starts the load operation. On the other hand, if the required output of the load device LD is equal to or less than the third output, the control device 50 proceeds to step S250.

[0092] In step S250, the control device 50 determines whether the start switch SW is off. If the start switch SW is on, the control device 50 returns to step S240 to continue intermittent operation, and if the start switch SW is off, the control device 50 exits from this process and executes a power generation stop process (not shown).

[0093] The rest is the same as in the first embodiment. The fuel cell system 1 of the present embodiment can obtain the same effects as in the first embodiment, which are achieved by a configuration common to the first embodiment or an equivalent configuration.

[0094] (1) The control device 50 determines whether the amount of surplus power generated during intermittent operation is equal to or less than the free capacity of the battery BT. When the amount of surplus power is equal to or less than the free capacity of the battery BT, the control device 50 reduces the FC output over a predetermined time to perform intermittent operation. On the other hand, when the amount of surplus power exceeds the free capacity of the battery BT, the control device 50 reduces the FC output for a time shorter than the predetermined time to perform intermittent operation. Note that a time shorter than the predetermined time is, for example, a time that does not substantially generate surplus power.

[0095] This makes it possible to prevent overcharging of the battery BT and suppress voltage fluctuations in the fuel cell stack 10 caused by switching from load operation to intermittent operation. As a result, it is possible to protect the battery BT and suppress deterioration of the electrode catalyst in each cell 10a.

[0096] (Modification of the second embodiment) In the second embodiment, when switching from load operation to intermittent operation, if the amount of surplus power generated during intermittent operation exceeds the free capacity of the battery BT, the control device 50 reduces the FC output in a time shorter than a predetermined time to perform intermittent operation, but is not limited to this. For example, if the amount of surplus power generated during intermittent operation exceeds the free capacity of the battery BT, the control device 50 may be configured to execute a process of increasing the free capacity of the battery BT during load operation so that the free capacity of the battery BT becomes larger than the amount of surplus power.

[0097] Third embodiment Next, a third embodiment will be described with reference to Fig. 8 to Fig. 12. The fuel cell system 1 of this embodiment suppresses the voltage fluctuation of the fuel cell stack 10 caused by switching from intermittent operation to load operation. In this embodiment, differences from the first embodiment will be mainly described.

[0098] 8, the fuel cell system 1 of this embodiment is connected to an information acquisition unit 56 that acquires location information of the bus BS. The information acquisition unit 56 acquires the location information of the bus BS, for example, via a GPS of a navigation system mounted on the vehicle. The information acquisition unit 56 may also acquire the location information from a system installed outside the vehicle.

[0099] The control device 50 predicts the required output from the load device LD after switching from intermittent operation to load operation as a predicted output, and calculates the stack voltage corresponding to the predicted output as a predicted voltage. Specifically, the control device 50 is configured to refer to a control map that specifies the correspondence between the position of the bus BS and the predicted output, and to obtain the predicted output from the current position of the bus BS. In this embodiment, the function of the control device 50 that predicts the predicted output and predicted voltage constitutes the "output prediction unit 50c." The control map is pre-stored in the memory unit 51.

[0100] In addition, when a predetermined condition is met during intermittent operation, the control device 50 sets the voltage limit range Vb before switching from intermittent operation to load operation to a range that includes at least the predicted voltage in order to suppress voltage fluctuations in the fuel cell stack 10.

[0101] Hereinafter, the control process executed by the control device 50 to suppress voltage fluctuations in the fuel cell stack 10 when switching from intermittent operation to load operation will be described with reference to Fig. 9. The control process shown in Fig. 9 corresponds to the control process shown in Fig. 5 described in the first embodiment. Among the control processes shown in Fig. 9, the processes of steps S300, S305, and S310 are similar to the processes of steps S100, S105, and S110 shown in Fig. 5, and therefore descriptions thereof will be omitted.

[0102] 9, when the required output of the load device LD exceeds the first output in the determination process of step S310, the control device 50 starts the load operation in step S315. Note that the process of step S315 is similar to step S115 shown in FIG. 5, and therefore a detailed description thereof will be omitted.

[0103] Next, in step S320, the control device 50 determines whether the required output of the load device LD is equal to or less than the second output. If the required output of the load device LD exceeds the second output, the control device 50 continues the load operation. On the other hand, if the required output of the load device LD becomes equal to or less than the second output, the control device 50 proceeds to step S335.

[0104] On the other hand, if the required output of the load device LD is equal to or less than the first output in the determination process of step S310, the control device 50 executes an output prediction process for predicting the required output from the load device LD after switching from the intermittent operation to the load operation in step S325. This output prediction process will be described with reference to the flowchart shown in FIG.

[0105] 10, in step S400, the control device 50 acquires position information of the bus BS, which is a moving object, from the information acquisition unit 56. Then, in step S405, the control device 50 determines whether the current position of the bus BS is in a predictable section where the predicted output can be obtained by the output prediction unit 50c. The predictable section is a section in the travel route of the moving object where the position of the moving object and the predicted output are associated in the control map.

[0106] FIG. 11 is an explanatory diagram for explaining an example of a predictable section. As shown in FIG. 11, when a bus BS temporarily stops at a bus stop ST and then departs from the bus stop ST, the required output of the load device LD increases and load operation is performed in order to maintain the vehicle speed until the bus BS approaches the bus stop ST. When the bus BS reaches the bus stop ST, the accelerator pedal is temporarily not depressed, so the required output of the load device LD becomes approximately zero and intermittent operation is performed. Thereafter, when the bus BS departs from the bus stop ST, the accelerator pedal is depressed to accelerate, so the required output of the load device LD increases and load operation is performed.

[0107] The possibility that the above series of operations will be performed is very high near the bus stop ST, and the required output of the load device LD is easy to predict. For this reason, in this embodiment, the bus stop ST and the areas before and after the bus stop ST are set as predictable sections. The required output of the load device LD can be easily predicted based on the required output of the load device LD when the bus actually ran near the bus stop ST in the past.

[0108] Incidentally, the predictable section is not limited to the vicinity of the bus stop ST, but may be set to the vicinity of an ETC gate, a railroad crossing, or a traffic light. This is because there is a high possibility that a series of operations similar to those at the bus stop ST will be performed when the bus BS is at an ETC gate, waiting at a railroad crossing, waiting at a traffic light, etc. For example, when passing through an ETC gate, the required output of the load device LD is increased and load operation is performed in order to maintain the vehicle speed until the bus BS approaches the ETC gate. While the bus BS is passing through the ETC gate, the accelerator pedal is temporarily not depressed, so the required output of the load device LD becomes approximately zero, and intermittent operation is performed. After that, after the bus BS passes through the ETC gate, the accelerator pedal is depressed to accelerate, so the required output of the load device LD is increased and load operation is performed.

[0109] 10, if the current position of the bus BS is within the prediction interval, the control device 50 acquires a predicted output based on the current position of the bus BS in step S410. The control device 50 acquires a predicted output based on the current position of the bus BS, for example, by referring to a control map that defines the correspondence between the position of the bus BS and the predicted output.

[0110] Here, it is desirable that the predicted output is based on a preset predicted output value and an actual value of the required output value requested at that position, and the difference between the predicted output value and the actual value is fed back to update the predicted output value.

[0111] In addition, the control map may have a single required output set for multiple bus stops ST, but it is preferable to set a unique required output for each of the installation locations of multiple bus stops ST. When a unique required output is set for each of the installation locations of multiple bus stops ST, there is an advantage in that the accuracy of the predicted output can be increased. In addition, when a single required output is set for multiple bus stops ST, the control map can be easily generated. In addition, the control map may have installation locations of ETC gates, railroad crossings, signals, etc., other than bus stops ST, and the required output predicted at the locations.

[0112] In step S415, the control device 50 calculates the voltage of the fuel cell stack 10 corresponding to the predicted output as a predicted voltage based on the predicted output. In the calculation process in step S415, the predicted voltage is calculated from the predicted output in step S410 using a relational expression or the like that specifies the correspondence between the predicted output and the predicted voltage. It is desirable to correct the relationship between the predicted output and the predicted voltage in anticipation of a decrease in power generation performance due to deterioration over time, such as the mileage and the accumulated power generation time. The control device 50 stores the predicted output and predicted voltage obtained in the calculation processes in steps S410 and S415 in the memory unit 51.

[0113] Next, in step S420, the control device 50 updates the voltage limit range Vb during intermittent operation based on the predicted voltage, and exits the output prediction process. The control device 50 sets the voltage limit range Vb during intermittent operation so that at least the predicted voltage is included. For example, as shown in the upper part of FIG. 12, the control device 50 sets the predicted voltage stored in the storage unit 51 to the median value Vbc of the voltage limit range Vb during intermittent operation so that the predicted voltage stored in the storage unit 51 becomes the average voltage during intermittent operation. In addition, when the predicted voltage is 0.7 volts or less, the control device 50 sets the voltage limit range Vb during intermittent operation so that the lower limit voltage value Vbd of the voltage limit range Vb is equal to or less than the value obtained by multiplying the number of cells by "0.7". The reason is as described in the first embodiment. In addition, when the predicted voltage exceeds 0.7 volts, the control device 50 sets the voltage limit range Vb during intermittent operation so that the voltage fluctuation width falls within a predetermined voltage width (for example, about 0.1).

[0114] On the other hand, if the current position of the bus BS is not in the prediction-enabled section, the control device 50 skips steps S410, S415, and S420 and exits the output prediction process. That is, the control device 50 exits the output prediction process without predicting the required output during load operation.

[0115] After the output prediction process, the control device 50 determines whether the required output of the load device LD is equal to or less than the third output in step S330 of Fig. 9. If the required output of the load device LD exceeds the third output, the control device 50 proceeds to step S315 and starts load operation.

[0116] In this intermittent operation, when the voltage limit range Vb during intermittent operation is updated to a range including the predicted voltage in step S420 of Fig. 10, the operation of various devices connected to the output side of the control device 50 is controlled so as to maintain the voltage within the voltage limit range Vb. This suppresses the rise in stack voltage when switching from intermittent operation to load operation.

[0117] On the other hand, if the required output of the load device LD is equal to or less than the third output, the control device 50 proceeds to step S335. In step S335, the control device 50 determines whether the start switch SW is off. If the start switch SW is on, the control device 50 returns to step S305 to perform intermittent operation, and if the start switch SW is off, the control device 50 exits from this process and executes a power generation stop process (not shown).

[0118] The rest is the same as in the first embodiment. The fuel cell system 1 of the present embodiment can obtain the same effects as in the first embodiment, which are achieved by a configuration common to the first embodiment or an equivalent configuration.

[0119] (1) When a predetermined condition is satisfied during intermittent operation, the control device 50 changes the voltage limit range Vb before switching from intermittent operation to load operation to a range that includes at least the predicted voltage. This makes it possible to suppress voltage fluctuations in the fuel cell stack 10 when switching from intermittent operation to load operation.

[0120] (2) For example, when the bus BS is located on an uphill slope, the required output from the load device LD tends to be high. Also, when the bus BS is located on a downhill slope or when the bus BS is traveling at a substantially constant speed on a highway or the like, the required output from the load device LD tends to be low. Thus, a correlation is observed between the position of the bus BS and the required output from the load device LD. This correlation is also observed in moving objects other than the bus BS.

[0121] Taking these factors into consideration, the control device 50 of this embodiment is configured to refer to a control map that defines the correspondence between the position of the bus BS and the predicted output, and to obtain the predicted output from the current position of the bus BS. This makes it possible to appropriately predict the required output from the load device LD when switching from intermittent operation to load operation.

[0122] (3) The above-mentioned predetermined condition may be, for example, a condition that is satisfied when the current position of the bus BS is in a predictable section. Note that the predetermined condition is not limited to this, and may be, for example, a condition that is satisfied when the current position of the bus BS is a position registered in the control map together with the predicted output.

[0123] (Modification of the third embodiment) The fuel cell system 1 of the third embodiment is configured to suppress the voltage fluctuation of the fuel cell stack 10 caused by switching from intermittent operation to load operation, but is not limited thereto. The fuel cell system 1 of the third embodiment may be configured to suppress the voltage fluctuation of the fuel cell stack 10 caused by switching from load operation to intermittent operation. For example, the fuel cell system 1 may store the stack voltage immediately before switching from load operation to intermittent operation in the storage unit 51 as the immediately preceding voltage, and set the voltage limit range Vb during intermittent operation so as to include at least the immediately preceding voltage. This makes it possible to obtain the effect of suppressing the voltage fluctuation of the fuel cell stack 10 when switching from intermittent operation to load operation, in addition to the effect of suppressing the voltage fluctuation of the fuel cell stack 10 when switching from load operation to intermittent operation.

[0124] In addition, the control device 50 of the third embodiment is configured to refer to a control map that defines the correspondence between the position of the bus BS and the predicted output, and to obtain the predicted output from the current position of the bus BS, but is not limited to this. For example, the current position of a moving body such as a bus BS can be estimated according to the time. For this reason, the control device 50 may be configured to predict the required output from the load device LD based on the current time. In addition, the control device 50 may be configured to learn the accelerator pedal operation amount and brake pedal operation amount when the vehicle speed increases or decreases, and to predict the required output from the load device LD from the current accelerator pedal operation amount and brake pedal operation amount based on the learning result. These are the same in the following embodiments.

[0125] (Fourth embodiment) Next, a fourth embodiment will be described with reference to Fig. 13 to Fig. 15. The fuel cell system 1 of this embodiment suppresses the voltage fluctuation of the fuel cell stack 10 caused by switching from load operation to intermittent operation. In this embodiment, differences from the first and third embodiments will be mainly described.

[0126] The control device 50 predicts the required output from the load device LD after switching from the load operation to the intermittent operation as a predicted output, and calculates the stack voltage corresponding to the predicted output as a predicted voltage. In this embodiment, the function of predicting the predicted output and the predicted voltage in the control device 50 constitutes the "output prediction unit 50c." The control map is stored in advance in the storage unit 51.

[0127] In addition, when a predetermined condition is met during load operation, the control device 50 sets the voltage limit range Vb after switching from load operation to intermittent operation to a range that includes at least the predicted voltage in order to suppress voltage fluctuations in the fuel cell stack 10.

[0128] The control process executed by the control device 50 to suppress voltage fluctuations in the fuel cell stack 10 when switching from load operation to intermittent operation will be described below with reference to Fig. 13. The control process shown in Fig. 13 corresponds to the control process in Fig. 5 described in the first embodiment. Among the control processes shown in Fig. 13, the processes of steps S500, S505, S510, and S515 are similar to the processes of steps S100, S105, S110, and S115 shown in Fig. 5, and therefore descriptions thereof will be omitted.

[0129] As shown in Fig. 13, after the load operation is started in step S515, the control device 50 executes an output prediction process to obtain a predicted output based on the current position of the bus BS in step S520. This output prediction process will be described with reference to the flowchart shown in Fig. 14.

[0130] 14, in step S600, the control device 50 acquires location information of the bus BS, which is a moving object, from the information acquisition unit 56. Then, in step S605, the control device 50 determines whether the current location of the bus BS is within a predictable section in which the predicted output can be obtained by the output prediction unit 50c.

[0131] If the current position of the bus BS is in the prediction interval, the control device 50 acquires a predicted output based on the current position of the bus BS in step S610. Then, in step S615, the control device 50 calculates the voltage of the fuel cell stack 10 corresponding to the predicted output as a predicted voltage based on the predicted output. These processes are similar to the processes in steps S410 and S415 in Fig. 10, and therefore description thereof will be omitted.

[0132] Next, in step S620, the control device 50 determines whether the required output of the load device LD is equal to or less than the second output. If the required output of the load device LD exceeds the second output, the control device 50 returns to step S515 and continues the load operation. On the other hand, if the required output of the load device LD is equal to or less than the third output, the control device 50 updates the voltage limit range Vb during intermittent operation based on the predicted voltage in step S625 and exits the output prediction process. That is, the control device 50 sets the voltage limit range Vb during intermittent operation so that at least the predicted voltage is included. For example, as shown in the upper part of FIG. 15, the control device 50 sets the predicted voltage stored in the storage unit 51 to the median value Vbc of the voltage limit range Vb during intermittent operation so that the predicted voltage stored in the storage unit 51 becomes the average voltage during intermittent operation.

[0133] On the other hand, if the current position of the bus BS is not in the predictable section, the control device 50 determines in step S630 whether the required output of the load device LD is equal to or less than the third output. This third output may be the same as or different from the second output.

[0134] If the required output of the load device LD exceeds the third output, the control device 50 returns to step S515 and continues the load operation. On the other hand, if the required output of the load device LD is equal to or less than the third output, the control device 50 exits the output prediction process.

[0135] After the output prediction process, the control device 50 starts intermittent operation in step S525 of Fig. 13. In this intermittent operation, when the voltage limit range Vb during intermittent operation is updated to a range including the predicted voltage in step S625 of Fig. 14, the operation of various devices connected to the output side of the control device 50 is controlled so that the voltage limit range Vb is maintained within the voltage limit range Vb. This suppresses the rise in stack voltage when switching from load operation to intermittent operation.

[0136] For example, the control device 50 gradually reduces the air flow rate, as shown in the lower part of Fig. 15. In addition, the control device 50 gradually reduces the air flow rate to the fuel cell stack 10. This prevents the performance of each cell 10a from being deteriorated due to a lack of air, resulting in an excessive FC voltage. The air flow rate can be adjusted by adjusting the rotation speed of the air pump 33 and the opening of the flow dividing valve 35.

[0137] Next, in step S530, the control device 50 determines whether the required output of the load device LD is equal to or less than a predetermined fourth output. If the required output of the load device LD exceeds the fourth output, the control device 50 returns to step S515 and starts the load operation. On the other hand, if the required output of the load device LD is equal to or less than the fourth output, the control device 50 proceeds to step S535.

[0138] In step S535, the control device 50 determines whether the start switch SW is off. If the start switch SW is on, the control device 50 returns to step S505 to perform intermittent operation, and if the start switch SW is off, the control device 50 exits from this process and executes a power generation stop process (not shown).

[0139] The rest of the embodiment is the same as the first and third embodiments. The fuel cell system 1 of the present embodiment can obtain the same effects as the first and third embodiments, which are achieved by the configuration common to the first and third embodiments or the equivalent configuration.

[0140] (1) When a predetermined condition is met during load operation, the control device 50 of this embodiment sets the voltage limit range Vb after switching to intermittent operation to a range that includes the predicted voltage. This makes it possible to suppress voltage fluctuations in the fuel cell stack 10 when switching from load operation to intermittent operation. Therefore, it is possible to suppress voltage fluctuations in the fuel cell stack 10 caused by switching between intermittent operation and load operation.

[0141] (Modification of the fourth embodiment) The fuel cell system 1 of the fourth embodiment is configured to suppress voltage fluctuations in the fuel cell stack 10 caused by switching from load operation to intermittent operation, but is not limited to this. The fuel cell system 1 of the fourth embodiment may be configured to suppress voltage fluctuations in the fuel cell stack 10 caused by switching from intermittent operation to load operation. That is, similar to the third embodiment, the fuel cell system 1 is configured to predict the required output after switching from intermittent operation to load operation as a load predicted output, and calculate the stack voltage corresponding to the load predicted output as a load predicted voltage. In this configuration, when a predetermined condition is met during intermittent operation, the fuel cell system 1 desirably changes the voltage limit range Vb before switching from intermittent operation to load operation to a range that includes at least the load predicted voltage. This makes it possible to obtain an effect of suppressing voltage fluctuations in the fuel cell stack 10 when switching from load operation to intermittent operation, as well as an effect of suppressing voltage fluctuations in the fuel cell stack 10 when switching from intermittent operation to load operation.

[0142] (Other embodiments) Representative embodiments of the present disclosure have been described above, but the present disclosure is not limited to the above-described embodiments and can be modified in various ways, for example, as described below.

[0143] In the above-described embodiment, the detailed configuration and detailed operation of the fuel cell system 1 are described, but the present invention is not limited to these and may have a different configuration or operation than those described above.

[0144] In addition, in the above embodiment, an example was described in which the fuel cell system 1 was applied to a mobile body, but the application of the fuel cell system 1 is not limited to mobile bodies, and it can also be applied to stationary equipment or systems.

[0145] In the above-described embodiments, it goes without saying that the elements constituting the embodiments are not necessarily essential, except in cases where it is particularly expressly stated that they are essential or where they are clearly considered to be essential in principle.

[0146] In the above-described embodiments, when numerical values ​​such as the number, values, amounts, ranges, etc. of components of the embodiments are mentioned, they are not limited to the specific numbers unless it is specifically stated as required or unless it is clearly limited to a specific number in principle.

[0147] In the above-described embodiments, when referring to the shapes, positional relationships, etc. of components, etc., there is no limitation to those shapes, positional relationships, etc., unless specifically stated or in principle limited to a specific shape, positional relationship, etc.

[0148] In the above-described embodiment, when the external environment information of the vehicle is acquired from a sensor, it is also possible to eliminate the sensor and receive the external environment information from a server or cloud outside the vehicle. Alternatively, it is also possible to eliminate the sensor and acquire related information related to the external environment information from a server or cloud outside the vehicle, and estimate the external environment information from the acquired related information. [Explanation of symbols]

[0149] 10. Fuel Cell Stack 10a cell 50a Operation control unit 50b Voltage setting section 51 Storage section LD load device

Claims

1. 1. A fuel cell system comprising: A fuel cell stack (10) formed by stacking a plurality of cells (10a); an operation control unit (50a) that performs a load operation when a required output from a load device (LD) exceeds a predetermined output, and performs an intermittent operation in which air is intermittently supplied to the fuel cell stack when the required output is equal to or less than the predetermined output; a voltage setting unit (50b) that sets upper and lower limit voltage values ​​of the fuel cell stack during the intermittent operation as a voltage limit range; The voltage setting unit stores the voltage of the fuel cell stack immediately before switching from the load operation to the intermittent operation in a memory unit (51) as a immediately preceding voltage, and sets the voltage limit range during the intermittent operation so as to include at least the immediately preceding voltage.

2. The voltage setting unit is The voltage of the fuel cell stack during the load operation performed before the operation is switched to the intermittent operation is sequentially stored in the storage unit as a load operation voltage; 2. The fuel cell system according to claim 1, wherein the voltage limit range during the intermittent operation is set based on the load operation voltage stored in the memory unit.

3. 3. The fuel cell system according to claim 2, wherein the voltage setting unit sets the voltage limit range during the intermittent operation so as to include an average value of the load operation voltage stored in the memory unit.

4. The voltage setting unit stores the load operation voltage in the storage unit in association with the required output at the time of detection of the load operation voltage, 3. The fuel cell system according to claim 2, wherein the voltage limit range during the intermittent operation is set based on the load operation voltage stored in the memory unit, the load operation voltage corresponding to the required output at which a frequency of request from the load device is equal to or higher than a predetermined value.

5. When the total voltage of the fuel cell stack is divided by the number of cells, the FC voltage is:

5. The fuel cell system according to claim 1, wherein the voltage setting unit sets the voltage limit range during the intermittent operation so that, when the FC voltage immediately before switching from the load operation to the intermittent operation is 0.7 volts or less, a lower limit voltage value of the voltage limit range is equal to or less than a value obtained by multiplying the number of the cells constituting the fuel cell stack by 0.

7.

6. an output prediction unit (50c) that predicts the required output after switching from the intermittent operation to the load operation as a predicted output, and calculates a voltage of the fuel cell stack corresponding to the predicted output as a predicted voltage; 6. The fuel cell system according to claim 1, wherein when a predetermined condition is satisfied during the intermittent operation, the voltage setting unit changes the voltage limit range before switching from the intermittent operation to the load operation to a range that includes at least the predicted voltage.

7. 1. A fuel cell system comprising: A fuel cell stack (10) in which a plurality of cells (10a) are stacked; an operation control unit (50a) that performs a load operation when a required output from a load device (LD) exceeds a predetermined output, and performs an intermittent operation in which air is intermittently supplied to the fuel cell stack when the required output is equal to or less than the predetermined output; a voltage setting unit (50b) that sets upper and lower limit voltage values ​​of the fuel cell stack during the intermittent operation as a voltage limit range; an output prediction unit (50c) that predicts the required output after switching from the intermittent operation to the load operation as a predicted output, and calculates a voltage of the fuel cell stack corresponding to the predicted output as a predicted voltage; When a predetermined condition is satisfied during the intermittent operation, the voltage setting unit sets the voltage limit range before switching from the intermittent operation to the load operation to a range that includes at least the predicted voltage.

8. 1. A fuel cell system comprising: A fuel cell stack (10) in which a plurality of cells (10a) are stacked; an operation control unit (50a) that performs a load operation when a required output from a load device (LD) exceeds a predetermined output, and performs an intermittent operation in which air is intermittently supplied to the fuel cell stack when the required output is equal to or less than the predetermined output; a voltage setting unit (50b) that sets upper and lower limit voltage values ​​of the fuel cell stack during the intermittent operation as a voltage limit range; an output prediction unit (50c) that predicts the required output after switching from the load operation to the intermittent operation as a predicted output, and calculates a voltage of the fuel cell stack corresponding to the predicted output as a predicted voltage; When a predetermined condition is satisfied during the load operation, the voltage setting unit sets the voltage limit range after switching from the load operation to the intermittent operation to a range that includes at least the predicted voltage.

9. the output prediction unit predicts the required output after switching from the intermittent operation to the load operation as a load predicted output, and calculates a voltage of the fuel cell stack corresponding to the load predicted output as a load predicted voltage; 9. The fuel cell system according to claim 8, wherein when the predetermined condition is satisfied during the intermittent operation, the voltage setting unit sets the voltage limit range before switching from the intermittent operation to the load operation to a range that includes at least the load predicted voltage.

10. Applied to a moving object, 10. A fuel cell system according to claim 6, wherein the output prediction unit is configured to refer to a control map that defines a correspondence between the position of the moving body and the predicted output, and to determine the predicted output from the current position of the moving body.

11. 11. The fuel cell system according to claim 10, wherein the predetermined condition is met when the current position is within a predictable interval in which the predicted output can be obtained by the output predicting section.

12. When the total voltage of the fuel cell stack is divided by the number of cells, the FC voltage is:

12. The fuel cell system according to claim 7, wherein, when the predicted voltage is 0.7 volts or less, the voltage setting unit sets the voltage limit range during the intermittent operation so that a lower limit voltage value of the voltage limit range is equal to or less than a value obtained by multiplying the number of the cells constituting the fuel cell stack by 0.7.

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