JP2006309974A - Fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress the generation of hunting that increases and decreases cooling liquid flow rate, caused by transitionally increasing of the temperature difference between cooling liquid temperature on the inlet side and that on the outlet side of a fuel cell, when the cooling liquid flow rate is decreased. <P>SOLUTION: A heat quantity estimation means 15 estimates the heat quantity of a fuel cell stack, and a cooling liquid flow rate decreasing amount control means 17 limits the decreasing amount of the cooling liquid flow rate so that the decreasing amount of the cooling liquid flow rate is decreased with the increase in the estimated heat quantity, when the cooling liquid flow rate is decreased. Thereby, when the cooling liquid flow rate is decreased, transitional increase of the temperature difference between cooling liquid temperature on the inlet side and that on the outlet side of the fuel cell stack, due to the influence of the heat capacity or the like is prevented, and generation of increasing and decreasing of hunting in the cooling liquid flow rate can be suppressed. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a fuel cell system having a cooling system for cooling a fuel cell.

In general, a fuel cell that generates electricity by receiving supply of fuel gas and oxidant gas has a temperature suitable for operation. By keeping the temperature of the fuel cell at this temperature, the fuel cell can efficiently generate power. . Against this background, the conventional fuel cell system supplies the coolant to the fuel cell so that the temperature of the fuel cell is suitable for operation, and the temperature of the coolant supplied to the fuel cell and the fuel cell When the temperature difference ΔT of the temperature of the coolant discharged from the fuel cell exceeds a predetermined value, the fuel cell is maintained at a temperature suitable for operation by increasing the flow rate of the coolant and reducing the temperature difference ΔT. (See, for example, Patent Document 1). Further, in the conventional fuel cell system, in order to suppress the power consumption of the coolant supply device that supplies the coolant to the fuel cell, when the generated power of the fuel cell is small, a device for reducing the coolant flow rate is devised. .
JP 10-340734 A

  However, when the flow rate of the coolant is reduced as the generated power of the fuel cell decreases as in the conventional fuel cell system, noise and vibration are generated by repeatedly increasing and decreasing the flow rate of the coolant. The power consumption of the coolant supply device increases. That is, in general, the temperature change of the coolant has a delay time with respect to the change in the generated power of the fuel cell and the change in the flow rate of the coolant due to the influence of the heat capacity of the fuel cell, etc. When the flow rate of the coolant is decreased in accordance with the above, the temperature difference ΔT becomes transiently excessive because the temperature change of the coolant occurs later than the decrease in the flow rate. When the temperature difference ΔT becomes excessive, the flow rate of the coolant must be increased in order to reduce the temperature difference ΔT. As a result, the flow rate of the coolant is repeatedly increased and decreased.

  The present invention has been made in order to solve the above-described problems. The purpose of the present invention is to provide a transiently large temperature difference between the coolant temperatures on the inlet side and the outlet side of the fuel cell when reducing the coolant flow rate. Thus, an object of the present invention is to provide a fuel cell system capable of suppressing the occurrence of hunting in which the coolant flow rate increases or decreases.

  In order to solve the above-described problem, when the fuel cell system according to the present invention estimates the heat amount of the fuel cell and decreases the coolant flow rate, the greater the estimated heat amount of the fuel cell, the more the coolant flow rate decreases. The amount of decrease in the coolant flow rate is limited so as to reduce the amount.

  According to the fuel cell system of the present invention, when the coolant flow rate is decreased, the temperature difference between the coolant temperature on the inlet side and the outlet side of the fuel cell becomes transiently large, and the coolant flow rate causes hunting. This can be suppressed. As a result, the entire fuel cell can be controlled to a temperature suitable for operation, and the efficiency of the fuel cell can be increased.

  Hereinafter, the configuration and operation of a fuel cell system according to first to fifth embodiments of the present invention will be described with reference to the drawings.

[Configuration of fuel cell system]
As shown in FIG. 1, the fuel cell system according to the first embodiment of the present invention includes a plurality of stacked fuel cells that generate power by supplying hydrogen and air as fuel gas and oxidant gas to the anode and the cathode, respectively. The fuel cell stack 1 is provided. A gas supply system that supplies hydrogen and air to the fuel cell stack 1 is not shown. The electrochemical reaction at the anode and cathode of each fuel cell constituting the fuel cell stack 1 and the electrochemical reaction of the fuel cell stack 1 as a whole are based on the following formulas (1) to (3).

[Anode] H ₂ → 2H ⁺ + 2e ⁻ (1)
[Cathode] 1/2 O ₂ + 2H ⁺ + 2e ⁻ → H ₂ O (2)
[Overall] H ₂ +1/2 O ₂ → H ₂ O (3)
The fuel cell system includes a coolant supply pump 3 that pumps a coolant for cooling the fuel cell stack 1 to the fuel cell stack 1 through the coolant circulation path 2, and discharges the fuel cell stack 1 from the fuel cell stack 1. And a radiator fan 5 for adjusting the cooling capacity of the radiator 4 by sending air to the radiator 4. The fuel cell system is supplied to the fuel cell as a control system, a current sensor 6 that detects the generated current of the fuel cell stack 1, a voltage sensor 7 that detects the generated voltage of the fuel cell (single cell), and the fuel cell. A temperature sensor 8 that detects the temperature of the coolant, a temperature sensor 9 that detects the temperature of the coolant discharged from the fuel cell stack 1, and a controller that controls the operation of the entire fuel cell system based on the detection results of each sensor. 10.

  The controller 10 generates a command value of the PWM signal so as to have a predetermined duty ratio according to the rotational speed of the radiator fan 5, and outputs the generated command value to the radiator fan 5, thereby cooling liquid The temperature can be controlled. Similarly, the controller 10 generates a command value of the PWM signal so as to have a duty ratio determined in advance according to the coolant flow rate in the coolant circulation path 2, and uses the generated command value as the coolant supply pump. 3 is configured so that the coolant flow rate can be controlled. The controller 10 is constituted by a microprocessor including an I / O interface, a program ROM, a work RAM, and a CPU.

  In this embodiment, when the CPU in the controller 10 executes a control program stored in the program ROM, the controller 10 detects the fuel cell inlet temperature detection means 11 and the fuel cell outlet temperature detection shown in FIG. The functions of the means 12, the coolant temperature difference calculating means 13, the fuel cell heat generation amount calculating means 14, the heat amount estimating means 15, the pre-change rate limiting target coolant flow rate calculating means 16, and the coolant flow rate reduction amount limiting means 17 are realized. To do. The functions of these means will be described later. In the present embodiment, the coolant flow rate reduction amount limiting means 17 includes a change rate upper limit value calculating means 21 due to temperature difference, a change rate upper limit value calculating means 22 due to outlet temperature, a change rate limit calculating means 23 due to heat, and a change. A rate minimum value determining unit 24 and a target coolant flow rate calculating unit 25 after the change rate limiting process.

  In the fuel cell system having such a configuration, when the coolant flow rate is decreased by the controller 10 performing the following coolant flow rate control process, the cooling on the inlet side and the outlet side of the fuel cell stack 1 is performed. The temperature difference of the liquid temperature becomes transiently large, and the occurrence of hunting that increases or decreases the coolant flow rate is suppressed. Hereinafter, the operation of the controller 10 when the coolant flow rate control process is executed will be described with reference to the flowchart shown in FIG.

[Cooling liquid flow control processing]
The flowchart shown in FIG. 3 starts in response to the start of the fuel cell system, and the coolant flow rate control process proceeds to step S1. In addition, this control process shall be repeatedly performed for every control period (for example, 10 [msec]) of the controller 10. FIG.

  In the process of step S1, the fuel cell heat generation amount calculation means 14 multiplies the current value I detected by the current sensor 6 by the voltage value V detected by the voltage sensor 7, thereby generating the power generation amount W of the fuel cell stack 1. [Kw] is calculated. Thereby, the process of step S1 is completed and this control process progresses to the process of step S2.

In the process of step S <b> 2, the fuel cell inlet temperature detection means 11 detects the coolant temperature T _in [° C.] on the inlet side of the fuel cell stack 1 using the temperature sensor 8. Thereby, the process of step S2 is completed and this control process progresses to the process of step S3.

In the process of step S _<b > 3, the fuel cell outlet temperature detecting means 12 detects the coolant temperature T _out [° C.] on the outlet side of the fuel cell stack 1 using the temperature sensor 9. Thereby, the process of step S3 is completed and this control process progresses to the process of step S4.

In the process of step S4, the coolant temperature difference calculating means 13 detects the fuel cell detected by the process of step S2 from the coolant temperature T _out [° C.] on the outlet side of the fuel cell stack 1 detected by the process of step S3. The coolant temperature T _in [° C.] on the inlet side of the stack 1 is subtracted, and the absolute value of the subtracted value is calculated as the coolant temperature difference ΔT [° C.]. Thereby, the process of step S4 is completed, and the control process proceeds to the process of step S5.

In the process of step S5, the fuel cell heat generation amount calculation means 14 substitutes the current value I and the voltage value V detected by the process of step S1 into the following formula 1, thereby generating the heat generation amount Q _fc of the fuel cell stack 1. _{, K} [kw]. The parameters ΔH, F, and N in Formula 1 constitute the enthalpy change amount [kJ / mol], the Faraday constant [C / mol], and the fuel cell stack 1 when hydrogen 1 [mol] reacts, respectively. Indicates the number of fuel cells (cells). Thereby, the process of step S5 is completed, and the control process proceeds to the process of step S6.

In step S6, the pre-change rate limiting target coolant flow rate calculation means 16 refers to the table data indicating the relationship between the pre-change rate target coolant flow rate and the calorific value of the fuel cell as shown in FIG. Then, the target coolant flow rate corresponding to the calorific value Q _{fc, k} [kw] calculated by the process of step S5 is calculated as the target coolant flow rate Q _{t, n} [L / min] before the change rate restriction. The table data shown in FIG. 4 has a tendency that the target coolant flow rate Q _{t, n} [L / min] increases as the calorific value Q _{fc, k} [kw] of the fuel cell stack 1 increases. The flow rate value is set to a value at which the temperature difference ΔT is not excessive based on the experimental results using an actual machine. Thereby, the process of step S6 is completed and this control process progresses to the process of step S7.

In the process of step S7, the fuel cell heat generation amount calculation means 14 uses the following formula 2 to calculate the moving average value of the integrated values of the history of the heat generation amount Q _{fc, k} [kw] calculated by the process of step S5. The average calorific value Q _{fc, ave} [kw] of the fuel cell stack 1 is calculated. Note that the history of the calorific value Q _{fc, k} [kw] is updated every predetermined control cycle, and the history update cycle and the history sample number j used for the moving average are the actual averages based on experiments using actual machines. The difference between the calorific value [kw] and the average calorific value Q _{fc, ave} [kw] calculated by this processing is set to a value that does not become excessive. Thereby, the process of step S7 is completed, and the control process proceeds to the process of step S8.

In the process of step S8, the heat quantity estimation means 15 uses the table data indicating the relationship between the estimated heat quantity Q _fc [J] of the fuel cell stack 1 and the average calorific value Q _{fc, ave} [kw] as shown in FIG. With reference to this, an estimated value Q _fc [J] of the heat quantity of the fuel cell stack 1 corresponding to the average calorific value Q _{fc, ave} [kw] calculated by the process of step S7 is calculated. The table data shown in FIG. 5 has a tendency that as the average calorific value Q _{fc, ave} [kw] increases, the estimated value Q _fc [J] of the calorie increases, and each estimated value uses an actual machine. It is determined by measuring the relationship between the heat capacity and the average calorific value of the fuel cell stack 1 and the temperature by experiment, and calculating the relationship between the average calorific value and the calorific value from the measurement result. Thereby, the process of step S8 is completed, and the control process proceeds to the process of step S9.

In the process of step S9, the change rate upper limit value calculation means 22 according to the outlet temperature performs the upper limit value V _tout [L / min / 1 control cycle] of the change rate of the coolant flow rate as shown in FIG. by referring to the table data showing the relationship between coolant temperature T _out of the outlet side _[° C.], corresponding to the coolant temperature T _{out [°} C.] of the outlet side of the fuel cell stack 1 detected by the processing in step S3 cooling The upper limit value V _tout [L / min / 1 control cycle] of the change rate of the liquid flow rate is calculated. Note that the table data shown in FIG. 6 indicates that the higher the coolant temperature T _out [° C.] on the outlet side of the fuel cell stack 1, the upper limit value V _tout [L / min / 1 control cycle] of the change rate of the coolant flow rate. The upper limit value is an electrolyte membrane that constitutes the fuel cell when the coolant temperature T _out [° C.] on the outlet side of the fuel cell stack 1 becomes excessive based on an experiment using an actual machine. The value is set so that drying is not a problem. Thereby, the process of step S9 is completed and this control process progresses to the process of step S10.

In the process of step S10, the change rate upper limit value calculation means 21 due to the temperature difference has an upper limit value V _ΔT [L / min / 1 control period] of the change rate of the coolant flow rate and the coolant temperature difference ΔT as shown in FIG. With reference to the table data indicating the relationship of [° C.], the upper limit value V _ΔT [L / min / 1] of the change rate of the coolant flow rate corresponding to the coolant temperature difference ΔT [° C.] calculated by the process of step S4. Control cycle] is calculated. The table data shown in FIG. 7 has a tendency that the larger the coolant temperature difference ΔT [° C.] is, the smaller the upper limit value V _ΔT [L / min / 1 control cycle] of the change rate of the coolant flow rate is. Each upper limit value is set to a value that does not cause a decrease in power generation efficiency due to an excessive coolant temperature difference ΔT [° C.] based on an experiment using an actual machine. Thereby, the process of step S10 is completed, and the control process proceeds to the process of step S11.

In the process of step S11, the change rate restriction calculation means 23 according to the amount of heat has a limit value V _Qfc [L / min / 1 control period] of the change rate of the coolant flow rate and an estimated value Q _{fc of} heat amount as shown in FIG. J] with reference to the table data indicating the relationship of J], the limit value V _Qfc of the change rate of the coolant flow rate corresponding to the estimated value Q _fc [J] of the heat quantity calculated by the process of step S8 [L / min / 1 Control cycle] is calculated. The table data shown in FIG. 8 has a tendency that the limit value V _Qfc [L / min / 1 control cycle] of the rate of change decreases as the estimated value Q _fc [J] of the heat quantity increases. Is determined to be a value that does not increase the coolant temperature difference ΔT [° C.] and the temperature T _out [° C.] of the coolant on the outlet side of the fuel cell stack 1 based on experiments using actual machines. Thereby, the process of step S11 is completed and this control process progresses to the process of step S12.

In the process of step S12, the change rate minimum value determining means 24 uses the upper limit value V _tout [L / min / 1 control cycle] calculated by the process of step S9, and the upper limit value V _ΔT [ L / min / 1 control cycle] and the smallest value V _min [L / min / 1 control cycle] among the limit values V _Qfc [L / min / 1 control cycle] calculated by the process of step S11 ]. Thereby, the process of step S12 is completed and this control process progresses to the process of step S13.

In the process of step S13, the post-change rate limiting target coolant flow rate calculating means 25 is one control cycle before the pre-change rate target coolant flow rate Q _{t, n} [L / min] calculated by the process of step S6. By subtracting the target coolant flow rate Q _{lim, n−1} [L / min] after limiting the change rate of the coolant, the change rate V _t [L / min / 1 control period] of the coolant flow rate before the change rate limit is calculated. To do. Thereby, the process of step S13 is completed and this control process progresses to the process of step S14.

In the process of step S14, the target coolant flow rate calculating means 25 after the change rate limiting process determines whether or not the change rate V _t [L / min / 1 control cycle] calculated by the process of step S13 is 0 or more. Determine. If the result of determination is not greater than 0, that is, the coolant flow rate has decreased, the post-change rate limiting process target coolant flow rate calculation means 25 advances this control process to step S15. On the other hand, if it is 0 or more, that is, if the coolant flow rate is increasing, the post-change rate limiting process target coolant flow rate calculation means 25 advances this control process to the process of step S16.

In the process of step S15, the target coolant flow rate calculation means 25 after the change rate limiting process determines that the absolute value of the change rate V _t [L / min / 1 control cycle] calculated by the process of step S13 is the result of the process of step S12. It is determined whether or not it is less than the calculated minimum value V _min [L / min / 1 control cycle]. As a result of the determination, the absolute value of the rate of change V _t [L / min / 1 control cycle] is less than the minimum value V _min [L / min / 1 control cycle], that is, the rate of change V where the flow rate is less than the minimum value V _{min. When} it is decreased at _t , the target coolant flow rate calculation means 25 after the change rate limiting process advances this control process to the process of step S16. On the other hand, the absolute value of the change rate V _t [L / min / 1 control cycle] is not less than the minimum value V _min [L / min / 1 control cycle], that is, the flow rate decreases with the change rate V _t less than the minimum value V _min. If not, the target coolant flow rate calculation means 25 after the change rate limiting process advances this control process to the process of step S17.

In the process of step S16, the target coolant flow rate calculation means 25 after the change rate restriction process uses the target coolant flow rate Q _{t, n} [L / min] before the change rate restriction calculated by the process of step S6 as the target coolant flow rate. Set to Q _{lim, n} [L / min]. Thereby, the process of step S16 is completed and this control process progresses to the process of step S18.

In the process of step S17, the target coolant flow rate calculation means 25 after the change rate limiting process starts from the target coolant flow rate Q _{lim, n-1} [L / min] after the change rate limit of one control cycle before the process of step S12. Is subtracted from the minimum value V _min [L / min / 1 control cycle], and the subtraction value is set to the target coolant flow rate Q _{lim, n} [L / min]. Thereby, the process of step S17 is completed and this control process progresses to the process of step S18.

In the process of step S18, the target coolant flow rate calculation unit 25 after the change rate limiting process and the command rotation speed N _pmp [rpm] of the coolant supply pump 3 as shown in FIG. Q _lim, by referring to the table data showing a relationship between n [L / min], the step S16 or the target coolant set in the processing in step S17 the flow rate _Q lim, coolant supply corresponding to n [L / min] The command rotational speed N _pmp [rpm] of the pump 3 is calculated. In the table data shown in FIG. 9, the command rotational speed N _pmp [rpm] of the coolant supply pump 3 tends to increase as the target coolant flow rate Q _{lim, n} [L / min] after the change rate restriction increases. Each rotational numerical value is determined by measuring the relationship between the coolant flow rate and the rotational speed of the coolant pump 3 based on an experiment using an actual machine. Thereby, the process of step S18 is completed, and the control process proceeds to the process of step S19.

In the process of step S19, a drive signal is sent to the coolant supply pump 3 so that the target coolant flow rate calculation means 25 after the change rate limiting process operates at the command rotational speed N _pmp [rpm] calculated by the process of step S18. And the coolant flow rate is controlled to the target coolant flow rate Q _{lim, n} [L / min]. Thereby, the process of step S19 is completed and a series of coolant flow rate control processes are completed.

  In the conventional fuel cell system, as shown in FIGS. 10 (a) and 10 (b), the coolant flow rate is reduced as the generated power of the fuel cell is reduced, in other words, the amount of heat of the fuel cell is large. 10 (c), (d), the coolant temperature difference between the outlet side and the inlet side of the fuel cell becomes transiently greater than or equal to the flow rate increase threshold, as shown in FIGS. As a result, as shown in FIG. 10B, the flow rate of the coolant is repeatedly increased and decreased.

In contrast, in the fuel cell system according to the first embodiment of the present invention, as described above, the heat quantity estimation means 15 estimates the heat quantity Q _fc [J] of the fuel cell stack 1 and decreases the coolant flow rate. When reducing the coolant flow rate, the amount limiting means 17 limits the amount of decrease in the coolant flow rate so that the amount of decrease in the coolant flow rate decreases as the estimated heat quantity Q _fc [J] increases. According to such a configuration, when the coolant flow rate is decreased, the coolant on the inlet side and the outlet side of the fuel cell stack 1 is affected by the influence of the heat capacity of the fuel cell, as shown in FIG. The temperature difference between the temperatures does not increase transiently, and as shown in FIG. 11B, it is possible to suppress the occurrence of hunting in which the coolant flow rate increases or decreases. As a result, the entire fuel cell stack 1 can be controlled to a predetermined temperature, and the efficiency of the fuel cell stack 1 can be increased.

In the fuel cell system according to the first embodiment of the present invention, the coolant flow rate reduction amount limiting means 17 decreases the rate of decrease in the coolant flow rate as the estimated heat quantity Q _fc [J] increases. Thus, since the amount of decrease in the flow rate of the coolant is limited, the power consumption of the cooling system can be suppressed, and the temperature difference between the coolant on the inlet side and the outlet side of the fuel cell stack 1 can be reduced. As a result, it is possible to increase the efficiency of the fuel cell system by controlling the fuel cell stack 1 to a predetermined temperature while preventing the power consumption of the cooling system from increasing.

In the fuel cell system according to the first embodiment of the present invention, the coolant flow rate decrease amount limiting means 17 changes with time when the coolant flow rate decreases as the estimated heat quantity Q _fc [J] increases. Since the amount of decrease in the coolant flow rate is limited so as to reduce the rate, the power consumption of the cooling system can be reduced by a simpler method and the temperature difference between the coolant on the inlet side and the outlet side of the fuel cell stack 1 can be reduced. can do. As a result, it is possible to increase the efficiency of the fuel cell system by controlling the fuel cell stack 1 to a predetermined temperature while preventing the power consumption of the cooling system from increasing.

  Further, in the fuel cell system according to the first embodiment of the present invention, the coolant flow rate reduction amount limiting means 17 is configured to reduce the coolant flow rate so that the coolant temperature on the outlet side of the fuel cell stack 1 becomes a predetermined value or less. An upper limit value is set for the amount of decrease of the fuel cell, and the higher the coolant temperature on the outlet side of the fuel cell stack 1, the smaller the upper limit value, so that the outlet temperature of the fuel cell stack 1 can be prevented from becoming excessive. . As a result, the electrolyte membrane constituting the fuel cell can be prevented from drying, and the efficiency of the fuel cell stack 1 can be increased.

  Further, in the fuel cell system according to the first embodiment of the present invention, the coolant flow rate reduction amount limiting means 17 is such that the temperature difference between the coolant temperatures on the inlet side and the outlet side of the fuel cell stack 1 is not more than a predetermined value. Thus, the upper limit value is set for the amount of decrease in the coolant flow rate, and the larger the temperature difference, the smaller the upper limit value. Therefore, the temperature difference between the coolant temperature on the inlet side and the outlet side of the fuel cell stack 1 becomes excessive. Can be prevented. As a result, the entire fuel cell stack 1 can be more reliably controlled to a predetermined temperature, and the efficiency of the fuel cell stack 1 can be increased.

Further, in the first embodiment become the fuel cell system of the present invention, heat estimating means 15, the calorific value Q _fc of the fuel cell _{stack, k} heat Q _fc of the fuel cell stack 1 based on _{[kw] [J]} Therefore, the heat quantity Q _fc [J] of the fuel cell stack 1 can be accurately estimated. As a result, the entire fuel cell stack 1 can be accurately controlled to a predetermined temperature, and the efficiency of the fuel cell stack 1 can be increased. Note that the heat quantity estimating means 15 may estimate the heat quantity Q _fc [J] in consideration of the heat radiation quantity of the fuel cell stack 1.

[Configuration of fuel cell system]
In the fuel cell system according to the second embodiment of the present invention, the configuration of the controller 10 is different from that of the fuel cell system according to the first embodiment, and the CPU inside the controller 10 is stored in the program ROM. By executing the control program, the fuel cell inlet temperature detection means 11, the fuel cell outlet temperature detection means 12, the coolant temperature difference calculation means 13, the fuel cell heat generation amount calculation means 14, the heat quantity estimation means 15, and the waste shown in FIG. The functions of the pre-time processing target coolant flow rate calculation means 31 and the coolant flow rate decrease amount restriction means 17 are realized. In the present embodiment, the coolant flow rate decrease amount limiting means 17 includes a dead time lower limit value calculating means 32 due to a temperature difference, a dead time lower limit value calculating means 33 due to an outlet temperature, a dead time calculating means 34 due to heat, and a dead time. It has a maximum value judging means 35 and a target coolant flow rate calculating means 36 after dead time processing. In the fuel cell system having such a configuration, when the coolant flow rate is decreased by the controller 10 performing the following coolant flow rate control process, the cooling on the inlet side and the outlet side of the fuel cell stack 1 is performed. The temperature difference of the liquid temperature becomes transiently large, and the occurrence of hunting that increases or decreases the coolant flow rate is suppressed. Hereinafter, the operation of the controller 10 when the coolant flow rate control process is executed will be described with reference to the flowchart shown in FIG.

[Cooling liquid flow control processing]
The flowchart shown in FIG. 13 starts as the fuel cell system is activated, and the coolant flow rate control process proceeds to the process of step S21. 13 is the same as the process from step S1 to step S8 shown in FIG. 3, and therefore, only the process after step S29 will be described below.

In the process of step S29, the dead time lower limit value calculation means 33 based on the outlet temperature has the lower dead time V _tout [sec] as shown in FIG. 14 and the coolant temperature T _out [° C.] on the outlet side of the fuel cell stack 1. ], The lower limit value V _tout [sec] of the dead time corresponding to the coolant temperature T _out [° C.] on the outlet side of the fuel cell stack 1 detected by the process of step S23. calculate. The table data shown in FIG. 14 has a tendency that the lower limit value V _tout [sec] of the dead time increases as the coolant temperature T _out [° C.] on the outlet side of the fuel cell stack 1 increases. The value is set to such a value that drying of the electrolyte membrane constituting the fuel cell does not become a problem when the coolant temperature T _out [° C.] on the outlet side of the fuel cell stack 1 becomes excessive based on an experiment using an actual machine. ing. Thereby, the process of step S29 is completed, and the control process proceeds to the process of step S30.

In the process of step S30, the dead time lower limit value calculation means 32 due to the temperature difference generates table data indicating the relationship between the lower dead time value V _ΔT [sec] and the coolant temperature difference ΔT [° C.] as shown in FIG. Referring to FIG. 8, a dead time lower limit value V _ΔT [sec] corresponding to the coolant temperature difference ΔT [° C.] calculated by the process of step S24 is calculated. The table data shown in FIG. 15 has a tendency that the lower limit value V _ΔT [sec] of the dead time increases as the coolant temperature difference ΔT [° C.] increases, and each lower limit value is an experiment using an actual machine. Is set to a value that does not cause a decrease in power generation efficiency due to an excessively large coolant temperature difference ΔT [° C.]. Thereby, the process of step S30 is completed, and the control process proceeds to the process of step S31.

In the process of step S31, the dead time calculation means 34 based on the amount of heat refers to the table data showing the relationship between the dead time V _Qfc [sec] and the estimated amount of heat Q _fc [J] as shown in FIG. A dead time V _Qfc [sec] corresponding to the estimated value Q _fc [J] of the heat quantity calculated by the process of S28 is calculated. Note that the table data shown in FIG. 16 has a tendency that the dead time V _Qfc [sec] becomes larger as the estimated value Q _fc [J] of the heat quantity is larger, and each dead time is based on an experiment using an actual machine. Thus, it is determined that the coolant temperature difference ΔT [° C.] and the temperature T _out [° C.] of the coolant on the outlet side of the fuel cell stack 1 do not increase. Thereby, the process of step S31 is completed and this control process progresses to the process of step S32.

In the process of step S32, the dead time maximum value determining means 35 uses the lower limit value V _tout [sec] calculated by the process of step S29, the lower limit value V _ΔT [sec] calculated by the process of step S30, and step S31. The largest value in the dead time V _Qfc [sec] calculated by the process is calculated as the maximum value V _max [sec]. Thereby, the process of step S32 is completed, and the control process proceeds to the process of step S33.

In the process of step S33, the target coolant flow rate calculation means 36 after the dead time process is set to the target coolant flow rate one control cycle before from the target coolant flow rate Q _{t, n} [L / min] calculated by the process of step S26. By subtracting Q _{lim, n−1} [L / min], the change rate V _t [L / min / 1 control period] of the coolant flow rate before the dead time processing is calculated. Thereby, the process of step S33 is completed, and the control process proceeds to the process of step S34.

In the process of step S34, the target coolant flow rate calculation means 36 after the dead time process determines whether or not the rate of change V _t [L / min / 1 control cycle] calculated by the process of step S33 is 0 or more. To do. If the result of determination is not greater than 0, that is, the coolant flow rate is decreasing, the post-dead-time target coolant flow rate calculation means 36 advances this control processing to step S36. On the other hand, when it is 0 or more, that is, when the coolant flow rate is increasing, the target coolant flow rate calculation means 36 after the dead time processing advances this control processing to the processing of step S35.

In the process of step S35, the target coolant flow rate calculation means 36 after the dead time process sets the dead time as the maximum value V _max [sec], and the target coolant flow rate Q _{t, n} [L / min calculated by the process of step S26. ] Is subjected to a dead time process, and a target coolant flow rate Q _{lim, n} [L / min] after the dead time process is calculated. In this specification, the dead time processing means processing for translating and delaying the signal before the dead time processing by the dead time [sec] on the time axis. In this case, _assuming that the target coolant flow rate Q _{t, n} ) and the dead time are X (s) and L, respectively, this means a process of calculating the output signal Y (s) by the following Equation 3. Thereby, the process of step S35 is completed and this control process progresses to the process of step S37.

In the process of step S36, the target coolant flow rate calculation means 36 after the dead time process has processed the target coolant flow rate Qt _{, n} [L / min] calculated by the process of step S26 after the dead time process. Set to Q _{lim, n} [L / min]. Thereby, the process of step S36 is completed and this control process progresses to the process of step S37.

In the process of step S37, the target coolant flow rate calculation means 36 after the dead time process corresponds to the target coolant flow rate Q _{lim, n} [L / min] after the dead time process set by the process of step S35 or step S36. The command rotation speed N _pmp [rpm] of the coolant supply pump 3 to be calculated is calculated. Thereby, the process of step S37 is completed, and the control process proceeds to the process of step S38.

In the process of step S38, the target coolant flow rate calculation means 36 after the dead time process outputs a drive signal to the coolant supply pump 3 so as to operate at the command rotational speed N _pmp [rpm] calculated by the process of step S37. Then, the coolant flow rate is controlled to the target coolant flow rate Q _{lim, n} [L / min]. Thereby, the process of step S38 is completed and a series of coolant flow control processes are complete | finished.

As is clear from the above description, in the fuel cell system according to the second embodiment of the present invention, the coolant flow rate reduction amount limiting means 17 increases the estimated heat quantity Q _fc [J] and the coolant flow rate. Therefore, the amount of heat of the fuel cell stack 1 can be quickly reduced. As a result, it is possible to increase the efficiency of the fuel cell stack 1 by controlling the entire fuel cell stack 1 to a predetermined temperature while preventing the amount of heat of the fuel cell stack 1 from becoming excessive.

Further, in the fuel cell system according to the second embodiment of the present invention, when the coolant flow rate is decreased, the dead time processing is performed on the target coolant flow rate Q _{t, n} [L / min] to reduce the coolant flow rate decrease amount. The limiting means 17 increases the dead time of the dead time process as the estimated heat quantity Q _fc [J] is larger, so that the heat quantity of the fuel cell stack 1 can be quickly reduced by a simpler method. As a result, it is possible to increase the efficiency of the fuel cell stack 1 by controlling the entire fuel cell stack 1 to a predetermined temperature while preventing the amount of heat of the fuel cell stack 1 from becoming excessive.

[Configuration of fuel cell system]
In the fuel cell system according to the third embodiment of the present invention, the configuration of the controller 10 is different from that in the fuel cell systems according to the first and second embodiments, and the CPU inside the controller 10 is stored in the program ROM. By executing the control program, the fuel cell inlet temperature detecting means 11, the fuel cell outlet temperature detecting means 12, the coolant temperature difference calculating means 13, the fuel cell heat generation amount calculating means 14, and the heat amount estimating means shown in FIG. 15. The functions of the target coolant flow rate calculation means 41 before the first-order lag processing and the coolant flow rate reduction amount restriction means 17 are realized. In the present embodiment, the coolant flow rate reduction amount limiting means 17 includes the time constant lower limit value calculating means 42 based on the temperature difference, the time constant lower limit value calculating means 43 based on the outlet temperature, the time constant calculating means 44 based on the heat amount, and the time constant. It has a maximum value judging means 45 and a target coolant flow rate calculating means 46 after the first-order lag processing. In the fuel cell system having such a configuration, when the coolant flow rate is decreased by the controller 10 performing the following coolant flow rate control process, the cooling on the inlet side and the outlet side of the fuel cell stack 1 is performed. The temperature difference of the liquid temperature becomes transiently large, and the occurrence of hunting that increases or decreases the coolant flow rate is suppressed. Hereinafter, the operation of the controller 10 when the coolant flow rate control process is executed will be described with reference to the flowchart shown in FIG.

[Cooling liquid flow control processing]
The flowchart shown in FIG. 18 starts as the fuel cell system is activated, and the coolant flow rate control process proceeds to the process of step S41. 18 is the same as the process from step S1 to step S8 shown in FIG. 3, only the process after step S49 will be described below.

In the process of step S49, the time constant lower limit value calculation means 43 based on the outlet temperature uses the time constant lower limit value V _tout [msec] as shown in FIG. 19 and the coolant temperature T _out [° C.] on the outlet side of the fuel cell stack 1. ], The lower limit value V _tout [msec] of the time constant corresponding to the coolant temperature T _out [° C.] on the outlet side of the fuel cell stack 1 detected by the process of step S43. calculate. The table data shown in FIG. 19 has a tendency that the lower limit value V _tout [msec] of the time constant increases as the temperature T _out [° C.] of the coolant on the outlet side of the fuel cell stack 1 increases. The lower limit value is set to a value that does not cause the problem of drying of the electrolyte membrane constituting the fuel cell when the coolant temperature T _out [° C.] on the outlet side of the fuel cell stack 1 becomes excessive based on an experiment using an actual device. Has been. Thereby, the process of step S49 is completed, and the control process proceeds to the process of step S50.

In the process of step S50, the time constant lower limit value calculation means 42 based on the temperature difference generates table data indicating the relationship between the time constant lower limit value V _ΔT [msec] and the coolant temperature difference ΔT [° C.] as shown in FIG. Referring to FIG. 4, a lower limit value V _ΔT [msec] of a time constant corresponding to the coolant temperature difference ΔT [° C.] calculated by the process of step S44 is calculated. The table data shown in FIG. 20 has a tendency that the lower limit value V _ΔT [msec] of the time constant increases as the coolant temperature difference ΔT [° C.] increases, and each lower limit value is an experiment using an actual machine. Is set to a value that does not cause a decrease in power generation efficiency due to an excessively large coolant temperature difference ΔT [° C.]. Thereby, the process of step S50 is completed, and the control process proceeds to the process of step S51.

In the process of step S51, the time constant calculation unit 44 based on the amount of heat refers to the table data indicating the relationship between the time constant V _Qfc [msec] and the estimated amount of heat Q _fc [J] as shown in FIG. A time constant V _Qfc [msec] corresponding to the estimated value Q _fc [J] of the heat quantity calculated by the processing of S28 is calculated. The table data shown in FIG. 21 has a tendency that the time constant V _Qfc [msec] becomes larger as the estimated value Q _fc [J] of the heat quantity is larger, and each time constant is based on an experiment using an actual machine. Thus, the coolant temperature difference ΔT [° C.] and the temperature T _out [° C.] of the coolant on the outlet side of the fuel cell stack 1 are set to values that do not increase. Thereby, the process of step S51 is completed, and the control process proceeds to the process of step S52.

In the process of step S52, the time constant maximum value determination means 35 uses the lower limit value V _tout [msec] calculated by the process of step S49, the lower limit value V _ΔT [msec] calculated by the process of step S50, and step S51. The largest value of the _hourly time V _Qfc [msec] calculated by the process is calculated as the maximum value V _max [msec]. Thereby, the process of step S52 is completed, and the control process proceeds to the process of step S53.

In the process of step S53, the target coolant flow rate calculation means 46 after the first-order lag process is one control cycle before the target coolant flow rate Q _{t, n} [L / min] before the first-order lag process calculated by the process of step S46. By subtracting the target coolant flow rate Q _{lim, n-1} [L / min] after the first-order lag process, the change rate V _t [L / min / 1 control period] of the coolant flow rate before the first-order lag process is calculated. . Thereby, the process of step S53 is completed, and the control process proceeds to the process of step S54.

In the process of step S54, the target coolant flow rate calculation means 46 after the first-order lag process determines whether or not the rate of change V _t [L / min / 1 control cycle] calculated by the process of step S53 is 0 or more. To do. If the result of determination is not greater than or equal to 0, that is, the coolant flow rate is decreasing, the target coolant flow rate calculation means 46 after the first-order lag process advances this control process to step S56. On the other hand, when it is 0 or more, that is, when the coolant flow rate is increasing, the post-first-order-lag target coolant flow rate calculation means 46 advances this control process to the process of step S55.

In the process of step S55, the target coolant flow rate calculation means 46 after the first-order lag process sets the time constant to the maximum value V _max [sec], and the target coolant flow rate Q _{t, n} [L / min calculated by the process of step S46. ], The target coolant flow rate Q _{lim, n} [L / min] after the first-order lag process is calculated. In this specification, the first-order lag process is the addition of the output value in the previous control process and the output value in the current control process at a predetermined ratio determined from the time constant [sec] and the control cycle [sec]. Specifically, when the input signal (in this case, the target coolant flow rate Q _{t, n} ), the control gain, and the time constant are X (s), K, and T, respectively, 4 represents the process of calculating the output signal Y (s). In this embodiment, the first-order lag process using only the output value in the previous control process is performed. However, the N-th order lag process may be performed using the output value before the N (> 1) control process. Good. In this specification, the process including the first-order lag process and the N-th order lag process is defined as a filter process having a delay element. Thereby, the process of step S55 is completed, and the control process proceeds to the process of step S57.

In the process of step S56, the target coolant flow rate calculation means 46 after the first-order lag process uses the target coolant flow rate Q _{t, n} [L / min] calculated by the process of step S46 as the target coolant-flow rate after the first-order lag process. Set to Q _{lim, n} [L / min]. Thereby, the process of step S56 is completed, and the control process proceeds to the process of step S57.

In the process of step S57, the target coolant flow rate calculation unit 46 after the first-order lag process sets the target coolant flow rate Q _{lim, n-1} [L / min] after the first-order lag process set by the process of step S55 or step S56. The command rotation speed N _pmp [rpm] of the coolant supply pump 3 corresponding to is calculated. Thereby, the process of step S57 is completed, and the control process proceeds to the process of step S58.

In the process of step S58, the target coolant flow rate calculation means 46 after the first-order lag process outputs a drive signal to the coolant supply pump 3 so as to operate at the command rotational speed N _pmp [rpm] calculated by the process of step S57. Then, the coolant flow rate is controlled to the target coolant flow rate Q _{lim, n} [L / min]. Thereby, the process of step S58 is completed and a series of coolant flow rate control processes are completed.

As is clear from the above description, in the fuel cell system according to the third embodiment of the present invention, when the coolant flow rate is decreased, the first-order lag processing is performed on the target coolant flow rate _{Qt, n} , and the coolant flow rate is reduced. Since the reduction amount limiting means 17 increases the time constant of the first-order lag process as the estimated heat quantity Q _fc [J] is larger, the dynamic characteristics of the temperature change of the fuel cell system can be taken into consideration. As a result, the entire fuel cell stack 1 can be more accurately controlled to a predetermined temperature, and the efficiency of the fuel cell stack 1 can be increased.

As mentioned above, although the embodiment to which the invention made by the present inventor is applied has been described, the present invention is not limited by the description and the drawings that form part of the disclosure of the present invention according to this embodiment. For example, in the fuel cell system according to the embodiment described above, table data indicating the relationship between the estimated value Q _fc [J] of the fuel cell heat quantity and the average calorific value Q _{fc, ave} [kw] of the fuel cell as shown in FIG. The estimated value Q _fc [J] of the heat quantity of the fuel cell is calculated with reference to FIG. 22. For example, as shown in FIG. 22, the fuel cell system is configured and the temperature of the coolant on the inlet side and outlet side of the fuel cell stack 1 is calculated. The estimated value Q _fc [J] of the heat quantity of the fuel cell stack 1 may be calculated using T _in , T _out [° C.]. That is, in this case, the heat quantity estimation means 15 uses the following Equation 5 to calculate the temperature T _{fc of the} fuel cell stack 1 from the coolant temperatures T _in and T _out [° C.] on the inlet side and the outlet side of the fuel cell stack 1. And the estimated temperature Q _fc [J] of the fuel cell stack 1 is calculated by substituting the calculated temperature T _fc into the following Equation 6. Note that the parameters m and C in Equation 6 indicate the mass [kg] and specific heat [J / (kg · K), respectively, of the fuel cell. Further, the heat quantity estimation means 13 calculates the temperature T _fc of the fuel cell stack 1 using only one of the coolant temperatures T _in and T _out [° C.] on the inlet side and the outlet side of the fuel cell stack 1. May be.

According to such a configuration, the heat quantity estimation means 15 is configured so that the heat quantity Q _fc [J] of the fuel cell stack 1 increases as the temperature T _fc of the fuel cell stack 1 increases. Since Q _fc [J] is estimated, the heat quantity Q _fc [J] can be estimated by a simpler method. As a result, since the entire fuel cell stack 1 can be controlled to a predetermined temperature by a simpler method, the efficiency of the fuel cell stack 1 can be increased. Also, since by using at least one of the coolant temperature at the inlet side and the outlet side of the fuel cell stack 1 is estimated temperature T _fc of the fuel cell stack 1, even when the temperature T _fc of the fuel cell can not be measured, The amount of heat Q _fc [J] of the fuel cell stack 1 can be estimated. As a result, even if the temperature T _{fc of the} fuel cell cannot be measured, the entire fuel cell stack 1 can be controlled to a predetermined temperature, so that the fuel cell system can be simplified.

Of the hydrogen temperature on the inlet side of the fuel cell stack 1, the hydrogen temperature on the outlet side of the fuel cell stack 1, the air temperature on the inlet side of the fuel cell stack 1, and the air temperature on the outlet side of the fuel cell stack 1 The estimated value Q _fc [J] of the heat quantity of the fuel cell stack 1 may be calculated using at least one of the following. When calculating the estimated value Q _fc [J] of the heat quantity of the fuel cell stack 1 using the oxidant gas temperature T _Ox on the outlet side of the fuel cell stack 1, for example, a fuel cell system is configured as shown in FIG. Then, the calorific value estimation means 15 substitutes the oxidant gas temperature T _Ox on the outlet side of the fuel cell stack 1 detected by the fuel cell outlet oxidant gas temperature detection means 51 into the following equation 7 to thereby calculate the fuel cell stack 1. calculating the temperature T _fc, and calculates the estimated value Q _fc of heat of the fuel cell stack 1 by substituting the temperature T _fc of the calculated fuel cell stack 1 in the formula 6 above _[J].

According to such a configuration, the hydrogen temperature on the inlet side of the fuel cell stack 1, the hydrogen temperature on the outlet side of the fuel cell stack 1, the air temperature on the inlet side of the fuel cell stack 1, and the fuel cell stack 1 Since the temperature T _fc of the fuel cell stack 1 is estimated using at least one of the air temperatures on the outlet side of the fuel cell stack 1, even if the temperature of the fuel cell stack 1 cannot be measured, the heat quantity of the fuel cell stack 1 is Can be estimated. As a result, even if the temperature of the fuel cell stack 1 cannot be measured, the entire fuel cell stack 1 can be controlled to a predetermined temperature, so that the fuel cell system can be simplified.

  As described above, it is a matter of course that all other embodiments, examples, operation techniques, and the like made by those skilled in the art based on the above embodiments are included in the scope of the present invention.

It is a schematic diagram which shows the structure of the fuel cell system used as embodiment of this invention. It is a block diagram which shows the internal structure of the controller used as the 1st Embodiment of this invention. It is a flowchart figure which shows the flow of the coolant flow rate control process used as the 1st Embodiment of this invention. It is a map figure which shows the relationship between the target coolant flow rate before change rate restriction | limiting, and the emitted-heat amount of a fuel cell. It is a map figure which shows the relationship between the estimated value of the calorie | heat amount of a fuel cell, and an average calorific value. It is a map figure which shows the relationship between the upper limit of the change rate of a coolant flow rate, and the coolant temperature on the exit side of a fuel cell. It is a map figure which shows the relationship between the upper limit of the change rate of a coolant flow rate, and the temperature difference of the coolant temperature on the inlet side and outlet side of a fuel cell. It is a map figure which shows the relationship between the limiting value of the change rate of a coolant flow rate, and the estimated value of the calorie | heat amount of a fuel cell. It is a map figure which shows the relationship between the rotation speed of a cooling fluid supply pump, and the target cooling fluid flow rate after the rate of change restriction | limiting of a cooling fluid flow rate. It is a figure which shows the relationship of the temperature difference of the generated electric power at the time of decreasing the coolant flow volume in the conventional fuel cell system, a coolant flow volume, coolant temperature, and the coolant temperature of the inlet side of a fuel cell, and an exit side. Temperature difference between generated power, coolant flow rate, coolant temperature, and coolant temperature on the inlet side and outlet side of the fuel cell when the coolant flow rate is decreased in the fuel cell system according to the first embodiment of the present invention. It is a figure which shows the relationship. It is a block diagram which shows the internal structure of the controller used as the 2nd Embodiment of this invention. It is a flowchart figure which shows the flow of the coolant flow rate control process used as the 2nd Embodiment of this invention. It is a map figure which shows the relationship between the lower limit of dead time, and the coolant temperature on the exit side of a fuel cell. It is a map figure which shows the relationship between the lower limit of dead time, and the temperature difference of the coolant temperature of the inlet side of a fuel cell, and an exit side. It is a map figure which shows the relationship between dead time and the estimated value of the calorie | heat amount of a fuel cell. It is a block diagram which shows the internal structure of the controller used as the 3rd Embodiment of this invention. It is a flowchart figure which shows the flow of the coolant flow rate control process used as the 4th Embodiment of this invention. It is a map figure which shows the relationship between the lower limit of a time constant, and the coolant temperature on the exit side of a fuel cell. It is a map figure which shows the relationship between the lower limit of a time constant and the temperature difference of the coolant temperature of the inlet side of a fuel cell, and an exit side. It is a map figure which shows the relationship between the time constant and the estimated value of the calorie | heat amount of a fuel cell. It is a block diagram which shows the internal structure of the controller used as the application example of this invention. It is a block diagram which shows the internal structure of the controller used as the application example of this invention.

Explanation of symbols

1: Fuel cell stack 2: Coolant circulation path 3: Coolant supply pump 4: Radiator 5: Radiator fan 6: Current sensor 7: Voltage sensor 8, 9: Temperature sensor 10: Controller 11: Fuel cell inlet temperature detection means 12 : Fuel cell outlet temperature detection means 13: Coolant temperature difference calculation means 14: Fuel cell heat generation amount calculation means 15: Heat quantity estimation means 16: Target coolant flow rate calculation means before change rate restriction processing 17: Coolant flow rate decrease amount restriction means

Claims (12)

A fuel cell that generates power by receiving supply of fuel gas and oxidant gas;
A coolant supply means for supplying a coolant for cooling the fuel cell to the fuel cell;
A calorific value estimating means for estimating a calorific value of the fuel cell;
A coolant flow rate reduction means for reducing the coolant flow rate according to the heat quantity of the fuel cell estimated by the heat quantity estimation means;
Cooling fluid flow rate reduction amount limiting means for limiting the amount of decrease in the coolant flow rate so that the amount of decrease in the coolant flow rate decreases as the amount of heat of the fuel cell estimated by the heat amount estimation unit increases. Fuel cell system. The fuel cell system according to claim 1,
The coolant flow rate reduction amount limiting means limits the amount of decrease in the coolant flow rate so that the rate of decrease in the coolant flow rate decreases as the heat quantity of the fuel cell estimated by the heat quantity estimation unit increases. Fuel cell system. The fuel cell system according to claim 1 or 2, wherein
The coolant flow rate reduction amount limiting means limits the amount of decrease in the coolant flow rate so that the time rate of change of the coolant flow rate decreases as the heat quantity of the fuel cell estimated by the heat quantity estimation unit increases. A fuel cell system. The fuel cell system according to claim 1,
The coolant flow rate reduction amount limiting means delays the coolant flow rate decrease with time as the heat quantity of the fuel cell estimated by the heat quantity estimation means increases. The fuel cell system according to claim 1 or 4, wherein
The cooling liquid flow rate reduction amount limiting means performs dead time processing on the cooling liquid flow rate when the cooling liquid flow rate is reduced, and the dead time of the dead time processing is increased as the heat quantity of the fuel cell estimated by the heat quantity estimation means is larger. A fuel cell system characterized by being enlarged. The fuel cell system according to any one of claims 1, 2, and 4,
The cooling liquid flow rate reduction amount limiting means performs a filtering process having a delay element with respect to the cooling liquid flow rate when the cooling liquid flow rate decreases, and the larger the heat quantity of the fuel cell estimated by the heat quantity estimation means, the longer the filtering process delays. A fuel cell system characterized by increasing the size of the fuel cell system. The fuel cell system according to any one of claims 1 to 6, wherein
An outlet side coolant temperature detecting means for detecting a coolant temperature on the outlet side of the fuel cell is provided, and the coolant flow rate reduction amount limiting means is configured so that the coolant temperature on the outlet side of the fuel cell becomes a predetermined value or less. A fuel cell system, wherein an upper limit value is provided for a decrease amount of the coolant flow rate, and the upper limit value is decreased as the coolant temperature on the outlet side of the fuel cell is higher. The fuel cell system according to any one of claims 1 to 6, wherein
An inlet side coolant temperature detecting means for detecting a coolant temperature on the inlet side of the fuel cell; and an outlet side coolant temperature detecting means for detecting a coolant temperature on the outlet side of the fuel cell, wherein the coolant flow rate decrease The amount limiting means sets an upper limit value for the amount of decrease in the coolant flow rate so that the temperature difference between the coolant temperature on the inlet side and the coolant temperature on the outlet side of the fuel cell is not more than a predetermined value. A fuel cell system characterized in that the upper limit value is reduced. The fuel cell system according to any one of claims 1 to 8, wherein
The fuel cell temperature estimation means for estimating the temperature of the fuel cell, wherein the heat quantity estimation means estimates the heat quantity of the fuel cell so that the heat quantity of the fuel cell increases as the temperature of the fuel cell increases. Fuel cell system. The fuel cell system according to claim 9, wherein
At least one of inlet side coolant temperature detecting means for detecting the coolant temperature on the inlet side of the fuel cell and outlet side coolant temperature detecting means for detecting the coolant temperature on the outlet side of the fuel cell; The temperature estimation means estimates the temperature of the fuel cell using at least one of the coolant temperature on the inlet side and the coolant temperature on the outlet side of the fuel cell. The fuel cell system according to claim 9, wherein
Inlet fuel gas temperature detecting means for detecting the fuel gas temperature on the inlet side of the fuel cell, outlet fuel gas temperature detecting means for detecting the fuel gas temperature on the outlet side of the fuel cell, and oxidation on the inlet side of the fuel cell At least one of an inlet-side oxidant gas temperature detecting means for detecting an oxidant gas temperature and an outlet-side oxidant gas temperature detecting means for detecting an oxidant gas temperature on the outlet side of the fuel cell, the fuel cell temperature The estimation means includes a fuel gas temperature on the fuel cell inlet side, a fuel gas temperature on the fuel cell outlet side, an oxidant gas temperature on the fuel cell inlet side, and an oxidant gas temperature on the fuel cell outlet side. A fuel cell system that estimates the temperature of the fuel cell using at least one of the above. The fuel cell system according to any one of claims 1 to 8, wherein
A calorific value calculating means for calculating the calorific value of the fuel cell, and a heat dissipation amount estimating means for estimating the heat dissipation amount of the fuel cell, wherein the calorific value estimating means is based on the calorific value and the heat dissipation amount of the fuel cell. A fuel cell system characterized by estimating the amount of heat.

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