JP5215582B2 - Fuel cell system - Google Patents

Description

  The present invention relates to a fuel cell system. In detail, it is related with the fuel cell system mounted in a motor vehicle.

  In recent years, fuel cell systems have attracted attention as a new power source for automobiles. The fuel cell system includes, for example, a fuel cell that generates power by chemically reacting a reaction gas, a reaction gas supply device that supplies the reaction gas to the fuel cell via a reaction gas flow path, and a control that controls the reaction gas supply device. An apparatus.

  The fuel cell has, for example, a stack structure in which several tens to several hundreds of cells are stacked. Here, each cell is configured by sandwiching a membrane electrode structure (MEA) between a pair of separators. The membrane electrode structure includes two electrodes, an anode electrode (anode) and a cathode electrode (cathode), and these electrodes. And a solid polymer electrolyte membrane sandwiched between the two.

  When hydrogen gas as a reaction gas is supplied to the anode electrode of the fuel cell and air containing oxygen as a reaction gas is supplied to the cathode electrode, power is generated by an electrochemical reaction. Since only harmless water is generated at the time of power generation, fuel cells are attracting attention from the viewpoint of environmental impact and utilization efficiency.

  By the way, since the said electrochemical reaction is accompanied by the heat_generation | fever according to the electric power generation amount, if an electric power generation is continued, an electrolyte membrane may be damaged by this heat | fever. For this reason, the fuel cell system is provided with a cooling means for allowing the refrigerant to flow through the fuel cell, and the temperature of the fuel cell is adjusted so as not to exceed a preset protection temperature in order to protect the electrolyte membrane. .

  As a fuel cell system including such a cooling means, Patent Document 1 discloses a fuel cell system that estimates the cooling capacity of the cooling means and performs control for limiting the power generation amount of the fuel cell based on the cooling capacity. Has been. Specifically, in this fuel cell system, if the heat generation amount of the fuel cell exceeds the threshold value with the estimated value of the cooling capacity as a threshold value, the power generation amount of the fuel cell is limited within a coolable range, When the amount of heat generated by the fuel cell is below the threshold value, the restriction on the power generation amount is released.

  FIG. 6 is a timing chart showing the temperature change of the refrigerant in the vicinity of the outlet of the refrigerant flow path of the fuel cell. Specifically, FIG. 6 is a timing chart showing the temperature change of the refrigerant when the restriction control of the current taken out from the fuel cell is performed based on the threshold as disclosed in Patent Document 1. Here, the threshold value is set to a value lower than the protection temperature for protecting the fuel cell.

As shown in FIG. 6, when the temperature of the refrigerant exceeds the threshold value, limit control is performed to gradually reduce the current limit value so that the refrigerant temperature does not reach the protection temperature. When restriction control is performed, the temperature of the refrigerant once rises and then gradually starts to fall and falls below the threshold value. Next, when the value falls below the threshold value, limit release control is performed so that the current limit value gradually increases. When the restriction release control is performed, the temperature of the refrigerant once decreases, then gradually increases, and again exceeds the threshold value. By performing the current limit control as described above, power generation by the fuel cell can be continued in a state where the temperature of the fuel cell is equal to or lower than the protection temperature.
JP 2002-83622 A

  By the way, the catalyst for the membrane electrode of the fuel cell has an activation temperature at which the electrochemical reaction is promoted. By generating power at such a temperature, power can be generated efficiently. For this reason, when power generation is continuously performed, it is preferable that the fuel cell be maintained in the vicinity of the activation temperature.

  However, for example, in an operating situation in which the amount of power generated by the fuel cell increases rapidly, the temperature of the fuel cell also changes abruptly. Therefore, when current limiting control is performed as shown in FIG. And the decision to remove the restriction are frequently switched. For this reason, the limit value of the current taken out from the fuel cell is hunted, and power generation cannot be stably performed in the vicinity of a temperature preferable for power generation as described above.

  An object of the present invention is to provide a fuel cell system capable of generating power efficiently while keeping the temperature of the fuel cell below the protection temperature.

  The fuel cell system of the present invention includes a fuel cell (for example, a fuel cell 10 described later) that generates power by a reaction of a reaction gas (for example, hydrogen gas described later) and an oxidizing gas (for example, air described later), and the inside of the fuel cell. A cooling means (for example, a cooling system 30 described later) for circulating the refrigerant through the refrigerant, a refrigerant temperature detecting means (for example, an outlet thermometer 44 described later) for detecting the temperature of the refrigerant, and the fuel cell. Current limiting means (for example, a current limiter 12 to be described later) for limiting the current taken out from the current, and a change amount per unit time of a current limit value (for example, a current limit value to be described later) by the current limiting means As a quantity, a fuel cell system (for example, a fuel cell described later) including a current limit rate adjusting means (for example, a current limit rate adjusting unit 47 described later) for adjusting the limit rate amount. The system 1) further includes refrigerant temperature change amount calculation means (for example, a refrigerant temperature change amount calculation unit 46 described later) for calculating the change amount per unit time of the refrigerant temperature detected by the refrigerant temperature detection means. And the current limit rate adjusting means has a temperature lower than the first threshold when the temperature detected by the refrigerant temperature detecting means is equal to or higher than a first threshold lower than a predetermined fuel cell protection temperature. The limit rate amount is set to a negative value until it becomes equal to or lower than a second threshold value. In particular, when the temperature detected by the refrigerant temperature detection unit becomes higher than the first threshold value, the refrigerant temperature change amount calculation unit If the detected temperature change amount is equal to or greater than a predetermined convergence determination value, the limit rate amount is set to a negative predetermined value, and the temperature detected by the refrigerant temperature detecting means is higher than the first threshold value. When the temperature change amount detected by the refrigerant temperature change amount calculating means is smaller than the convergence determination value, the limit rate amount is set to a value larger than the negative predetermined value. And

  According to the present invention, when the temperature of the refrigerant becomes higher than the first threshold, and the amount of change in the temperature of the refrigerant is equal to or greater than the predetermined convergence determination value, the limit rate amount is set to a negative predetermined value, When the temperature change amount is smaller than a predetermined convergence determination value, a current limit rate adjusting means is provided for setting the limit rate amount to a value larger than the negative predetermined value. Thereby, the hunting of the current limit value can be converged as the temperature change amount of the fuel cell becomes smaller. Accordingly, power generation can be continued while the temperature of the fuel cell is converged between the first threshold value and the second threshold value. Here, for example, by setting the first threshold value and the second threshold value in the vicinity of the fuel cell protection temperature, power generation is efficiently performed while maintaining the temperature of the fuel cell at a temperature preferable for power generation as described above. be able to.

  In this case, when the temperature detected by the refrigerant temperature detecting means is larger than the second threshold and smaller than the first threshold, the current limit rate adjusting means sets the value of the limit rate amount to approximately 0. It is preferable to make it.

  According to the present invention, the limit value of the current extracted from the fuel cell is substantially constant between the first threshold value and the second threshold value. Thereby, it is possible to prevent the temperature of the fuel cell from changing rapidly. Further, by making the limit rate amount substantially zero, for example, even when the required output to the fuel cell changes drastically in the vicinity of the set current limit value, the response to this request is stabilized. be able to. Here, for example, when the fuel cell system of the present invention is applied as a motive power source of a vehicle, it is possible to reduce a sense of incongruity felt by the driver by stabilizing the response to the output request by the driver.

  According to the present invention, the hunting of the current limit value can be converged as the temperature change amount of the fuel cell becomes smaller. Accordingly, power generation can be continued while the temperature of the fuel cell is converged between the first threshold value and the second threshold value. Here, for example, by setting the first threshold value and the second threshold value in the vicinity of the fuel cell protection temperature, it is possible to efficiently generate power while maintaining the temperature of the fuel cell at a temperature preferable for power generation.

<First Embodiment>
FIG. 1 is a block diagram of a fuel cell system 1 according to the first embodiment of the present invention.
The fuel cell system 1 includes a fuel cell 10, a supply device 20 that supplies hydrogen gas as a reaction gas and air as an oxidizing gas to the fuel cell 10, and cooling as cooling means for circulating a refrigerant in the fuel cell 10. It has the system 30 and the control apparatus 40 which controls these.

  The fuel cell 10 has a stack structure in which, for example, several tens to several hundreds of cells are stacked. Each cell is configured by sandwiching a membrane electrode structure (MEA) between a pair of separators. The membrane electrode structure is composed of two electrodes, an anode electrode (anode) and a cathode electrode (cathode), and a solid polymer electrolyte membrane sandwiched between these electrodes. Usually, both electrodes are formed of a catalyst layer that performs an oxidation / reduction reaction in contact with the solid polymer electrolyte membrane and a gas diffusion layer in contact with the catalyst layer.

  Such a fuel cell 10 generates electric power by these electrochemical reactions when hydrogen gas is supplied to the anode electrode (anode) side and air containing oxygen is supplied to the cathode electrode (cathode) side. Between each separator of the fuel cell 10, a fuel cell internal flow path 101 through which the refrigerant of the cooling system 30 flows is formed, whereby the fuel cell 10 that has generated heat by the electrochemical reaction is cooled.

  The supply device 20 includes a compressor 21 that supplies air to the cathode electrode side of the fuel cell 10, and a hydrogen tank 22 and an ejector 28 that supply hydrogen gas to the anode electrode side.

  The compressor 21 is connected to the cathode electrode side of the fuel cell 10 via the air supply path 23. An air discharge path 24 is connected to the cathode electrode side of the fuel cell 10, and a back pressure valve 241 is provided at the front end side of the air discharge path 24.

  The hydrogen tank 22 is connected to the anode electrode side of the fuel cell 10 through a hydrogen supply path 25. An ejector 28 is provided in the hydrogen supply path 25. A shutoff valve 251 is provided between the hydrogen tank 22 and the ejector 28 in the hydrogen supply path 25. Further, a hydrogen discharge path 26 is connected to the anode electrode side of the fuel cell 10, and a purge valve 261 is provided on the front end side of the hydrogen discharge path 26. In the hydrogen discharge path 26, on the anode electrode side of the purge valve 261, the hydrogen discharge path 26 is branched and connected to the above-described ejector 28. The ejector 28 collects the hydrogen gas that has flowed into the hydrogen discharge path 26 through the branch path of the hydrogen discharge path 26 and returns it to the hydrogen supply path 25.

  The cooling system 30 includes a refrigerant circulation path 31 through which the refrigerant circulates through the fuel cell internal flow path 101 of the fuel cell 10, and a radiator 33 connected to the refrigerant circulation path 31. The refrigerant circulation path 31 includes a fuel cell inflow path 311 through which refrigerant flows from the radiator 33 to the fuel cell 10, a fuel cell internal channel 101 formed in the fuel cell 10, and a fuel cell through which refrigerant flows from the fuel cell 10 to the radiator 33. An outflow path 312 and a radiator internal flow path 331 formed in the radiator 33 are configured.

  The radiator 33 is provided with a radiator internal flow path 331 connected to the fuel cell outflow path 312 and the fuel cell inflow path 311. By flowing the refrigerant through the radiator internal flow path 331, the radiator 33 exchanges heat with the refrigerant to cool the refrigerant.

  A water pump 32 is provided in the fuel cell inflow passage 311. The water pump 32 circulates the refrigerant in the refrigerant circulation path 31 by pumping the refrigerant in the refrigerant circulation path 31. The water pump 32 can control the rotation speed by the control device 40. Further, an outlet thermometer 44 as a refrigerant temperature detecting means for detecting the temperature of the refrigerant in the fuel cell outflow passage 312 is provided on the fuel cell outflow passage 312 on the fuel cell 10 side. The outlet thermometer 44 measures the temperature T of the refrigerant flowing through the fuel cell outflow passage 312 and outputs it to the control device 40.

  The fuel cell 10 is connected to a high voltage battery 11 and a drive motor 13 via a current limiter (VCU) 12 as current limiting means. The electric power generated by the fuel cell 10 is supplied to the high voltage battery 11 and the drive motor 13. Based on the current limit value output from the control device 40, the current limiter 12 limits the current extracted from the fuel cell 10 within the range of the current limit value, and supplies the electric power of the fuel cell 10 to the high-voltage battery 11 and This is supplied to the drive motor 13.

  The high voltage battery 11 stores the electric power generated by the fuel cell 10 when the voltage of the high voltage battery 11 is lower than the output voltage of the fuel cell 10. On the other hand, power is supplied to the drive motor 13 as needed to assist the drive of the drive motor 13. The high voltage battery 11 is constituted by, for example, a secondary battery such as a lithium ion battery, a capacitor, or the like.

  The control device 40 is connected to the compressor 21, the back pressure valve 241, the shutoff valve 251, the purge valve 261, the water pump 32, and the current limiter 12.

  The control device 40 includes a supply device drive unit 45 that drives the supply device 20, a refrigerant temperature change amount calculation unit 46 as a refrigerant temperature change amount calculation unit, and a current limit rate adjustment unit 47 as a current limit rate adjustment unit. In addition to driving the supply device 20 to generate the fuel cell 10, the limit value of the current taken out from the fuel cell 10 is adjusted.

  Further, an ignition switch (not shown) is connected to the control device 40. This ignition switch is provided in the driver's seat of the fuel cell vehicle, and transmits an on / off signal to the control device 40 in accordance with the operation of the driver. The control device 40 generates power from the fuel cell 10 in accordance with ON / OFF of the ignition switch.

Here, on the basis of the ignition switch being turned on, the procedure for generating power in the fuel cell 10 by the supply device driving unit 45 is as follows.
That is, hydrogen gas is supplied from the hydrogen tank 22 to the anode side of the fuel cell 10 through the hydrogen supply path 25. Further, by driving the compressor 21, air is supplied to the cathode side of the fuel cell 10 through the air supply path 23.
The hydrogen gas and air supplied to the fuel cell 10 are supplied to the power generation system, and then flow into the hydrogen discharge path 26 and the air discharge path 24 together with residual water such as produced water on the anode side from the fuel cell 10. These hydrogen gas and air are processed by an exhaust gas processing device (not shown) and discharged to the outside.

  The refrigerant temperature change amount calculation unit 46 calculates the change amount of the refrigerant temperature per unit time. Specifically, the refrigerant temperature change amount calculation unit 46 calculates the change amount per unit time of the refrigerant temperature based on the refrigerant temperature T in the fuel cell outflow passage 312 detected by the outlet thermometer 44. calculate.

  The current limit rate adjusting unit 47 adjusts the limit rate amount based on the refrigerant temperature and the amount of change thereof, and outputs a current limit value determined based on the limit rate amount to the current limiter 12. Here, the limit rate amount is the amount of change per unit time of the limit value (current limit value) of the generated current extracted from the fuel cell 10. The current limit rate adjusting unit 47 includes a control map for setting the limit rate amount, and can thereby set an appropriate limit rate amount according to the state of the fuel cell system 1.

  The current limit rate adjustment unit 47 limits the output of the fuel cell 10 by setting the limit rate amount to a negative value and gradually decreasing the current limit amount, or setting the limit rate amount to a positive value to limit the current. The limit of the output of the fuel cell 10 is released by increasing the value gradually.

The operation of the current limit rate adjusting unit 47 will be described with reference to the flowchart of FIG.
First, in ST1, it is determined whether or not the refrigerant temperature T detected by the outlet thermometer 44 is equal to or higher than a first threshold value lower than a predetermined fuel cell protection temperature, and this determination is “YES”. If this is the case, the process proceeds to ST2. If this determination is “NO”, the process proceeds to ST5. Here, the fuel cell protection temperature is the upper limit temperature of the refrigerant set to protect the membrane electrode of the fuel cell 10, and is set to 100 ° C., for example, in the present embodiment. Further, the first threshold is set to a temperature lower than the fuel cell protection temperature, for example, 95 ° C. in this embodiment.

  In ST2, a current limiting process is performed, and the process proceeds to ST3. Specifically, in this current limiting process, the current limiting value is set by setting the limiting rate amount of the current limiting value to a predetermined negative value in response to the refrigerant temperature becoming higher than the first threshold value. The power generation current of the fuel cell 10 is limited by gradually decreasing it. Further, the value of the limit rate amount is changed according to the change amount of the refrigerant temperature calculated by the refrigerant temperature change amount calculation unit 46 in the limit rate amount change process of ST6 described later. .

  In ST3, it is determined whether or not the refrigerant temperature T detected by the outlet thermometer 44 is equal to or lower than the second threshold value. If this determination is “YES”, the process proceeds to ST4, and this determination is “ If “NO”, the process proceeds to ST2. Here, the second threshold value is a temperature lower than the first threshold value, and is set to 90 ° C., for example, in the present embodiment. Thus, in ST1 to ST3, when the refrigerant temperature T is equal to or higher than the first threshold value, the limit rate amount is set to be negative until the refrigerant temperature T becomes equal to or lower than the second threshold value.

  In ST4, current limit release processing is performed, and the process proceeds to ST5. Specifically, in the current limit release processing, the current limit value is gradually changed by setting the limit rate amount of the current limit value to a positive value in response to the refrigerant temperature becoming lower than the second threshold value. The limit of the generated current of the fuel cell 10 is released by increasing it. Here, the value of the limiting rate amount is, for example, a value obtained by multiplying the negative limiting rate amount set in the current limiting process of ST2 described above by −1 to be positive.

  In ST5, it is determined whether or not the absolute value of the change amount of the refrigerant temperature calculated by the refrigerant temperature change amount calculation unit 46 is smaller than a predetermined convergence determination value. If this determination is “YES”, ST6 is determined. If this determination is “NO”, the process proceeds to ST1.

  In ST6, limit rate amount change processing is performed, and the process proceeds to ST1. Specifically, in the limit rate amount changing process, the limit rate amount value is set in the current limit process of ST2 described above in response to the refrigerant temperature change amount becoming smaller than a predetermined convergence determination value. The value is larger than the negative limit rate amount. Thereby, in ST5 and ST6, in response to the absolute value of the refrigerant temperature change amount becoming smaller than the predetermined convergence determination value, that is, in response to the refrigerant temperature change starting to converge, Control is performed to converge the current limit value.

The operation of the current limit rate adjusting unit 47 will be described with reference to the timing chart of FIG.
At times t _{1 to} t ₂ , t _{3 to} t ₄ , t _{5 to} t ₆ , and t _{7 to} t ₈ , the current limit value is decreased by setting the limit rate amount of the current limit value to a predetermined negative value. A current limiting process (ST2 process of FIG. 2) is performed. As shown in FIG. 3, the current limiting process is performed until the temperature of the refrigerant becomes equal to or higher than the first threshold value and becomes equal to or lower than the second threshold value.

From time t _{2 to} t ₃ , t _{4 to} t ₅ , t _{6 to} t ₇ , and t _{8 and} later, the current limit is released by increasing the current limit value by setting the limit rate amount of the current limit value to a positive value. Processing (ST4 in FIG. 2) is performed. As shown in FIG. 3, the current limit release processing is performed until the temperature of the refrigerant becomes equal to or higher than the first threshold after being lower than the second threshold.

Here, at time t _5, the temperature variation of the refrigerant absolute value of (the slope of the graph of refrigerant temperature in FIG. 3), is determined to be smaller than the predetermined convergence criterion value (determined in ST5 in FIG. 2), The protection control is switched to the convergence control based on the fact that the limit rate amount changing process (the process of ST6 in FIG. 2) has been performed. That is, the absolute value of the rate limit amount in after time t ₅ of the convergence control section (the slope of the graph of the current limit value in FIG. 3) is a value smaller than the limit rate volume in the protection control section up to time t ₅ . In this manner, the temperature of the refrigerant, that is, the temperature of the fuel cell 10 can be converged between the first threshold value and the second threshold value by switching the limit rate amount.

According to this embodiment, there are the following effects.
(1) According to the fuel cell system 1 of the present embodiment, when the temperature of the refrigerant is higher than the first threshold value, the amount of change in the limit rate when the temperature change amount of the refrigerant is equal to or greater than a predetermined convergence determination value. Is set to a negative predetermined value, and when the amount of change in the temperature of the refrigerant is smaller than a predetermined convergence determination value, a current limiting rate adjusting means is provided that sets the limiting rate amount to a value larger than the negative predetermined value. Thereby, the hunting of the current limit value can be converged as the temperature change amount of the fuel cell becomes smaller. Accordingly, power generation can be continued while the temperature of the fuel cell 10 is converged between the first threshold value and the second threshold value. Here, for example, by setting the first threshold value and the second threshold value in the vicinity of the fuel cell protection temperature, it is possible to efficiently generate power while maintaining the temperature of the fuel cell 10 at a temperature preferable for power generation. .

Second Embodiment
In the following description of the second embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted or simplified. The fuel cell system according to the second embodiment is different from the fuel cell system 1 according to the first embodiment described above in the configuration of the current limit rate adjusting unit of the control device.

The operation of the current limit rate adjustment unit of the present embodiment will be described with reference to the flowchart of FIG.
First, in ST11, it is determined whether or not the refrigerant temperature T detected by the outlet thermometer 44 is equal to or higher than the first threshold value. If this determination is “YES”, the process proceeds to ST12. If “NO”, the process proceeds to ST19.
In ST12, a current limiting process is performed, and the process proceeds to ST13. Specifically, in this current limiting process, the current limiting value is set by setting the limiting rate amount of the current limiting value to a predetermined negative value in response to the refrigerant temperature becoming higher than the first threshold value. The power generation current of the fuel cell 10 is limited by gradually decreasing it. Further, the value of the limit rate amount is changed in accordance with the change amount of the refrigerant temperature calculated by the refrigerant temperature change amount calculation unit 46 in the limit rate amount change process of ST20 described later. .

In ST13, it is determined whether or not the refrigerant temperature T detected by the outlet thermometer 44 is equal to or lower than the first threshold value. If this determination is “YES”, the process proceeds to ST14, where the determination is “ If “NO”, the process proceeds to ST12.
In ST14, a current limit value hold process is performed, and the process proceeds to ST15. Specifically, in this current limit value hold process, the current limit value is made constant by setting the value of the limit rate amount to approximately zero.

In ST15, it is determined whether or not the refrigerant temperature T detected by the outlet thermometer 44 is equal to or lower than the second threshold (90 ° C.). If this determination is “YES”, the process proceeds to ST16. If this determination is “NO”, the process proceeds to ST14.
In ST16, current limit release processing is performed, and the process proceeds to ST17. Specifically, in the current limit release processing, the current limit value is gradually changed by setting the limit rate amount of the current limit value to a positive value in response to the refrigerant temperature becoming lower than the second threshold value. The limit of the generated current of the fuel cell 10 is released by increasing it. Here, as the value of the limit rate amount, for example, a value obtained by multiplying the negative limit rate amount set in the current limit process of ST12 described above by -1 is used.

In ST17, it is determined whether or not the refrigerant temperature T detected by the outlet thermometer 44 is equal to or higher than the second threshold value. If this determination is “YES”, the process proceeds to ST18, and this determination is “ If “NO”, the process proceeds to ST17.
In ST18, a current limit value hold process is performed, and the process proceeds to ST19. Specifically, in this current limit value hold process, the current limit value is made constant by setting the value of the limit rate amount to approximately zero.

  In ST19, it is determined whether or not the absolute value of the change amount of the refrigerant temperature calculated by the refrigerant temperature change amount calculation unit 46 is smaller than a predetermined convergence determination value. If this determination is “YES”, ST20 is performed. If this determination is “NO”, the process moves to ST11.

  In ST20, limit rate amount change processing is performed, and the process proceeds to ST1. Specifically, in this limit rate amount change process, the limit rate amount value is set in the current limit process of ST12 described above in response to the refrigerant temperature change amount becoming smaller than the predetermined convergence determination value. The value is larger than the negative limit rate amount. Thereby, in ST19 and ST20, in response to the absolute value of the refrigerant temperature change amount becoming smaller than the predetermined convergence determination value, that is, in response to the refrigerant temperature change starting to converge, Control is performed to converge the current limit value.

The operation of the current limit rate adjustment unit of the present embodiment will be described with reference to the timing chart of FIG.
At times t _{1 to} t ₂ , t _{5 to} t ₆ , and t _{9 to} t ₁₀ , a current limiting process for reducing the current limiting value by setting the limiting rate amount of the current limiting value to a predetermined negative value (FIG. 4). ST12) is performed. As shown in FIG. 5, the current limiting process is performed until the temperature of the refrigerant becomes equal to or higher than the first threshold value and becomes equal to or lower than the first threshold value.

At times t _{3 to} t ₄ , t _{7 to} t ₈ , and t _{11 to} t ₁₂ , a current limit release process for increasing the current limit value by setting the limit rate amount of the current limit value to a positive value (FIG. 4). ST16) is performed. As shown in FIG. 5, the current limit release processing is performed until the temperature of the refrigerant becomes equal to or higher than the second threshold after being lower than the second threshold.

In addition, at times t _{2 to} t ₃ , t _{4 to} t ₅ , t _{8 to} t ₉ , and t _{10 to} t ₁₁ , the current limit value is kept constant by setting the limit rate amount of the current limit value to substantially zero. Current limit value hold processing (ST14 or ST18 processing in FIG. 4) is performed. As shown in FIG. 5, the current limit value hold processing is performed until the refrigerant temperature falls below the first threshold until it falls below the second threshold, or after the refrigerant temperature rises above the second threshold. This is performed until the threshold value is 1 or more. In the period in which the current limit value hold process is performed, by making the current limit value constant, the amount of change in the temperature of the refrigerant becomes gentle compared to other periods.

At time t _9, the absolute value, is determined to be smaller than the predetermined convergence criterion value (ST19 of the determination in FIG. 4) of the temperature variation of the refrigerant (the slope of the graph of refrigerant temperature in FIG. 5), limit Based on the fact that the rate amount changing process (the process of ST20 in FIG. 4) has been performed, the protection control is switched to the convergence control. That is, the absolute value of the limiting rate volume at time t ₉ after the convergence control section (the slope of the graph of the current limit in FIG. 5) becomes a value smaller than the limit rate volume in the protection control section up to the time t ₉ . In this manner, the temperature of the refrigerant, that is, the temperature of the fuel cell 10 can be converged between the first threshold value and the second threshold value by switching the limit rate amount.

According to the present embodiment, in addition to the above-described effect (1), the following effect can be obtained.
(2) According to the fuel cell system of the present embodiment, the limit value of the current extracted from the fuel cell 10 is substantially constant between the first threshold value and the second threshold value. Thereby, it is possible to prevent the temperature of the fuel cell 10 from rapidly changing. Further, by making the limit rate amount substantially zero, for example, even when the required output to the fuel cell 10 changes drastically in the vicinity of the set current limit value, the response to this request can be stabilized. can do. Here, for example, when the fuel cell system of the present embodiment is applied as a power source for a vehicle, it is possible to reduce a sense of incongruity felt by the driver by stabilizing the response to the output request by the driver.

  It should be noted that the present invention is not limited to the above-described embodiment, and modifications, improvements, etc. within a scope that can achieve the object of the present invention are included in the present invention.

  In the fuel cell systems of the first and second embodiments described above, the limit rate amount of the current limit value is set based on the refrigerant temperature detected by the outlet thermometer 44, but is not limited thereto. For example, the limit rate amount of the current limit value may be set based on the temperature of the gas in the hydrogen discharge path, the temperature of the air in the air discharge path, or the temperature of the fuel cell.

1 is a block diagram of a fuel cell system according to a first embodiment of the present invention. 4 is a flowchart showing an operation of a current limiting rate adjustment unit of the fuel cell system according to the embodiment. 4 is a timing chart showing an operation of a current limiting rate adjustment unit of the fuel cell system according to the embodiment. It is a flowchart which shows operation | movement of the current limiting rate adjustment part of the fuel cell system which concerns on 2nd Embodiment of this invention. 4 is a timing chart showing an operation of a current limiting rate adjustment unit of the fuel cell system according to the embodiment. It is a timing chart which shows the temperature change of a refrigerant | coolant.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fuel cell system 10 Fuel cell 11 High voltage battery 12 Current limiter (current limiting means)
20 Supply device 30 Cooling system (cooling means)
44 Outlet thermometer (refrigerant temperature detection means)
40 Control Device 45 Supply Device Drive Unit 46 Refrigerant Temperature Change Calculation Unit (Refrigerant Temperature Change Calculation Unit)
47 Current Limit Rate Adjustment Unit (Current Limit Rate Adjustment Unit)

Claims (2)

A fuel cell that generates electricity by reaction of the reaction gas and the oxidizing gas;
Cooling means for circulating a refrigerant in the fuel cell and cooling the fuel cell;
Refrigerant temperature detecting means for detecting the temperature of the refrigerant;
Current limiting means for limiting the current drawn from the fuel cell;
A fuel cell system comprising: current limit rate adjusting means for adjusting the amount of limit rate, with the amount of change per unit time of the current limit value by the current limit means as a limit rate amount,
A refrigerant temperature change amount calculating means for calculating a change amount per unit time of the temperature of the refrigerant detected by the refrigerant temperature detecting means;
The current limit rate adjusting means includes
When the temperature detected by the refrigerant temperature detecting means is equal to or higher than a first threshold value lower than a predetermined fuel cell protection temperature, the limiting rate until the temperature becomes equal to or lower than a second threshold value lower than the first threshold value. The quantity is negative,
In particular, when the temperature detected by the refrigerant temperature detecting means becomes higher than the first threshold value , the absolute value of the temperature change detected by the refrigerant temperature change calculating means converges the temperature change of the refrigerant. If it is equal to or greater than the convergence determination value for determining that it has started, the limit rate amount is set to a negative predetermined value,
When the absolute value of the temperature change amount detected by the refrigerant temperature change amount calculating means is smaller than the convergence determination value when the temperature detected by the refrigerant temperature detecting means is higher than the first threshold value. The fuel cell system is characterized in that the limit rate amount is set to a value larger than the negative predetermined value. A fuel cell that generates electricity by reaction of the reaction gas and the oxidizing gas;
Cooling means for circulating a refrigerant in the fuel cell and cooling the fuel cell;
Refrigerant temperature detecting means for detecting the temperature of the refrigerant;
Current limiting means for limiting the current drawn from the fuel cell;
A fuel cell system comprising: current limit rate adjusting means for adjusting the amount of limit rate with a change amount per unit time of a current limit value by the current limit means as a limit rate amount,
A refrigerant temperature change amount calculating means for calculating a change amount per unit time of the temperature of the refrigerant detected by the refrigerant temperature detecting means;
The current limit rate adjusting means includes
When a first threshold value lower than a predetermined fuel cell protection temperature and a second threshold value lower than the first threshold value are set, and the temperature detected by the refrigerant temperature detecting means is equal to or higher than the first threshold value, The limit rate amount is set to a negative value until the temperature becomes equal to or lower than the first threshold value. When the temperature is higher than the second threshold value and equal to or lower than the first threshold value, the value of the limit rate amount is substantially omitted. 0 ,
In particular, when the temperature detected by the refrigerant temperature detecting means becomes higher than the first threshold value, the absolute value of the temperature change detected by the refrigerant temperature change calculating means converges the temperature change of the refrigerant. If it is equal to or greater than the convergence determination value for determining that it has started, the limit rate amount is set to a negative predetermined value,
When the absolute value of the temperature change amount detected by the refrigerant temperature change amount calculating means is smaller than the convergence determination value when the temperature detected by the refrigerant temperature detecting means is higher than the first threshold value. The fuel cell system is characterized in that the limit rate amount is set to a value larger than the negative predetermined value.

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