JP4940541B2 - Fuel cell system - Google Patents

Description

  The present invention relates to a fuel cell system, and more specifically, a technique for accurately controlling a hydrogen circulation flow rate to a required hydrogen circulation flow rate even when the gas density in the hydrogen circulation path changes without deteriorating efficiency and fuel consumption. Related to.

  Conventionally, a fuel cell system that circulates hydrogen discharged from a fuel electrode of a fuel cell to a fuel electrode using a circulation pump is known. According to such a fuel cell system, unused hydrogen can be reused at the fuel electrode, and the fuel efficiency of the fuel cell system can be improved.

  By the way, the conventional fuel cell system circulates hydrogen using a circulation pump of a volume type or a scroll type in which the circulation performance does not change depending on the gas density in the hydrogen circulation path (for example, see Patent Document 1). reference). However, when a large amount of hydrogen is circulated by using a circulation pump of a volume type or a scroll type, the circulation pump becomes large.

From such a background, a method of circulating hydrogen using a circulation pump of a type called a speed type or an overflow type that can circulate a large amount of hydrogen without increasing the size is considered. However, in a circulation pump of a type called a speed type or an overflow type, when the gas density is lowered, the circulation performance is lowered, and the circulation performance is affected by the gas density. For this reason, recently, a control method has been proposed in which the circulation pump is operated at the maximum number of rotations (fully open) so that the necessary circulation performance can be ensured even when the gas density changes.
JP 2003-157874 A

  However, according to the above-described control method, hydrogen is circulated excessively in most operating states, so that the efficiency and fuel consumption of the fuel cell system are deteriorated when the circulation pump wastes power.

  The present invention has been made to solve the above-described problems, and its purpose is to require a hydrogen circulation flow rate even when the gas density in the hydrogen circulation path changes without deteriorating efficiency and fuel consumption. An object of the present invention is to provide a fuel cell system capable of accurately controlling the flow rate.

A fuel cell system according to the present invention is a fuel cell system that circulates hydrogen discharged from a fuel electrode of a fuel cell to a fuel electrode through a hydrogen circulation path using a circulation pump, and is supplied to the hydrogen circulation path. A flow rate detection unit for detecting a flow rate of hydrogen, and a required hydrogen circulation flow rate calculated from the flow rate detected by the flow rate detection unit and a required hydrogen circulation flow rate calculated from the hydrogen consumption of the fuel electrode. Of these, the larger value is set as the required hydrogen circulation flow rate, the actual hydrogen circulation flow rate in the hydrogen circulation path is calculated based on the control state and gas density of the circulation pump in the hydrogen circulation path, and the hydrogen circulation A control unit is provided for controlling the actual hydrogen circulation flow rate in the passage so as to be the set required hydrogen circulation flow rate.

  According to the fuel cell system of the present invention, since the actual hydrogen circulation amount in the hydrogen circulation path is calculated based on the gas density in the hydrogen circulation path, the gas in the hydrogen circulation path does not deteriorate efficiency and fuel consumption. Even when the density changes, the hydrogen circulation flow rate can be accurately controlled to the required hydrogen circulation flow rate.

  Hereinafter, a configuration of a fuel cell system according to an embodiment of the present invention will be described with reference to the drawings.

[Configuration of fuel cell system]
A fuel cell system according to an embodiment of the present invention includes a fuel cell that generates power by receiving supply of hydrogen and air to a fuel electrode (anode) and an oxidant electrode (cathode), respectively. In this embodiment, the fuel cell is composed of a polymer electrolyte fuel cell, and the electrochemical reaction at the anode and the cathode and the electrochemical reaction as the whole fuel cell are represented by chemical reaction formulas (1) to (3) shown below. )by.

[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)
[Configuration of anode system]
As shown in FIG. 1, the fuel cell system includes a hydrogen (H ₂ ) storage device 1 and a pressure adjustment valve 2, and the pressure of the hydrogen stored in the hydrogen storage device 1 is adjusted by the pressure adjustment valve 2. Then, hydrogen is supplied to the anode of the fuel cell through the hydrogen circulation path 3a. Further, the hydrogen discharged from the anode of the fuel cell is circulated to the circulation pump 4 via the hydrogen circulation path 3b, and is supplied to the anode of the fuel cell by the circulation pump 4 via the hydrogen circulation path 3a. In this fuel cell system, the circulation pump 4 is constituted by a circulation pump of a type called a speed type or an overflow type in which the circulation performance changes depending on the gas density.

  In the hydrogen circulation paths 3a and 3b, impurity gas such as nitrogen or argon in the air leaking from the cathode, or liquid water in which excessive moisture is liquefied may accumulate. These impurity gases lower the partial pressure of hydrogen to reduce power generation efficiency, or increase the average molecular weight of the circulating gas, making it difficult to circulate hydrogen. Liquid water also hinders hydrogen circulation. For this reason, in this fuel cell system, the purge valve 5 is provided in the hydrogen circulation path 3b. When the impurity gas or liquid water is accumulated, the purge valve 5 is opened for a short time in response to an instruction from the ECU 12 to perform a purge for discharging the impurity gas or liquid water out of the system. Thereby, the hydrogen partial pressure and circulation performance in the hydrogen circulation paths 3a and 3b including the anode can be recovered.

[Cathode configuration]
Although not shown, the fuel cell system includes a compressor that compresses and supplies air, and the compressor supplies the compressed air to the cathode of the fuel cell via an air supply path. Then, the unused air at the cathode of the fuel cell is pressure-adjusted by the air pressure regulating valve, and then discharged out of the system from the air discharge path.

[Control system configuration]
As shown in FIG. 1, the control system in the fuel cell system includes a flow meter 6 that measures the flow rate of hydrogen supplied to the hydrogen circulation path 3a, and a temperature that detects the temperature and pressure of the gas in the hydrogen circulation path 3a. Meter 7 and pressure gauge 8, a gas concentration sensor 9 for detecting the hydrogen concentration in the hydrogen circulation path 3b, a pressure gauge 10 and a thermometer 11 for detecting the pressure and temperature of the gas in the hydrogen circulation path 3b, and a fuel cell ECU12 which controls operation | movement of the whole system. The ECU 12 is constituted by a microprocessor having a CPU, a program ROM, a working RAM, and an input / output interface.

  In the fuel cell system having such a configuration, the ECU 12 executes the hydrogen flow rate control process described below, so that the gas density in the hydrogen circulation paths 3a and 3b has changed without deteriorating efficiency and fuel consumption. Even in this case, the hydrogen circulation flow rate is accurately controlled to the required hydrogen circulation flow rate. Hereinafter, the operation of the ECU 12 when executing the hydrogen flow rate control process according to the first to third embodiments of the present invention will be described with reference to the drawings.

  First, the flow of the hydrogen flow rate control process according to the first embodiment of the present invention will be described with reference to FIGS.

  The flowchart shown in FIG. 2 starts as the fuel cell system is activated, and the hydrogen flow rate control process proceeds to step S1.

  In the process of step S1, the ECU 12 detects the pressure and temperature of the gas in the hydrogen circulation paths 3a and 3b (hereinafter referred to as the anode system) using the pressure gauges 8 and 10 and the thermometers 7 and 11, From the map data showing the pressure and temperature of the gas in the anode system and the amount of nitrogen, hydrogen, and water vapor present in the anode system at that time, the nitrogen, hydrogen, and By reading out the amount of water vapor, the gas density ρ in the anode system is calculated.

  The ECU 12 detects the hydrogen concentration in the hydrogen circulation path 3b using the gas concentration sensor 9 in order to increase the calculation accuracy of the gas density ρ, and the detected values of the pressure gauges 8 and 10 and the thermometers 7 and 11 are detected. Is used to calculate the water vapor concentration, the nitrogen concentration is calculated by subtracting the hydrogen concentration and the water vapor concentration from 100%, and the volume of each gas is calculated from the hydrogen concentration, the water vapor concentration, and the nitrogen concentration. The gas density ρ may be calculated. Thereby, the process of step S1 is completed, and the hydrogen flow rate control process proceeds from the process of step S1 to the process of step S2.

  In the process of step S2, the ECU 12 causes the stack output current value, the calculated amount of discharged hydrogen accompanying purging by the purge valve 5, the detected values of the pressure gauges 8 and 10 and the thermometers 7 and 11, cross leak from the anode side to the cathode side. The hydrogen consumption at the anode is calculated from the estimated hydrogen amount. Thereby, the process of step S2 is completed, and the hydrogen flow rate control process proceeds from the process of step S2 to the process of step S3.

  In step S3, the ECU 12 multiplies the hydrogen consumption amount by a value obtained by subtracting 1 from the hydrogen demand stoichiometry set according to the operating conditions of the fuel cell system, thereby obtaining the required hydrogen circulation flow rate Q of the fuel cell. 'Is calculated. The ECU 12 may calculate the required hydrogen circulation flow rate Q ′ by multiplying the value obtained by subtracting 1 from the required hydrogen stoichiometry by the detection value of the flow meter 6.

  Further, the ECU 12 calculates the required hydrogen circulation flow rate by two methods: a method of multiplying the value obtained by subtracting 1 from the required stoichiometric value by the hydrogen consumption and a method of multiplying the value obtained by subtracting 1 from the required stoichiometric value by the detection value of the flow meter 6. And the larger calculated value may be selected as the required hydrogen circulation flow rate Q ′. According to such processing, the reliability of the calculated required hydrogen circulation flow rate Q ′ can be improved. Thereby, the process of step S3 is completed, and the hydrogen flow rate control process proceeds from the process of step S3 to the process of step S4.

  In the process of step S4, the ECU 12 calculates the differential pressure P of the circulation pump 4 using the detected values of the pressure gauges 8 and 10, and the actual hydrogen circulation flow rate in the anode system using the calculated differential pressure P. Q is calculated. Specifically, first, the ECU 12 determines the inclination of the rotational speed of the circulation pump 4 and the differential pressure (P) -hydrogen circulation flow rate (Q) diagram (hereinafter referred to as a PQ diagram) of the circulation pump 4 and Map data (see FIG. 3) showing a curve indicating the relationship between the intercept (deadline pressure) for each gas density in the anode system is prepared for each gas pressure and temperature in the anode system, and the gas in the current anode system is prepared. Map data corresponding to or close to the pressure and temperature is extracted.

  Next, the ECU 12 reads out data of a curve corresponding to the gas density ρ calculated by the process of step S1 from the extracted map data, and calculates by the process of step S1 as shown in FIG. 4 using the read data. A PQ diagram corresponding to the gas density ρ is created. Then, the ECU 12 reads the hydrogen circulation flow rate Q corresponding to the differential pressure P of the circulation pump 4 from the created PQ diagram, thereby calculating the actual hydrogen circulation flow rate Q in the anode system. Thereby, the process of step S4 is completed, and the hydrogen flow rate control process proceeds from the process of step S4 to the process of step S5.

  In the process of step S5, the ECU 12 compares the required hydrogen circulation flow rate Q ′ calculated by the process of step S3 with the actual hydrogen circulation flow rate Q calculated by the process of step S4, thereby obtaining the required hydrogen circulation flow rate Q ′. The necessary rotation speed of the circulation pump 4 for realizing is determined, and the circulation pump 4 is controlled to operate at the determined necessary rotation speed. Thereby, the process of step S5 is completed, and the hydrogen flow rate control process returns from the process of step S5 to the process of step S1.

  As is apparent from the above description, according to the hydrogen flow rate control process according to the first embodiment of the present invention, the ECU 12 calculates the required hydrogen circulation flow rate Q ′ based on the operating state of the fuel cell system, and the anode Based on the gas density ρ in the system, the actual hydrogen circulation amount Q in the anode system is calculated, and the actual hydrogen circulation flow rate Q in the anode system is controlled to the required hydrogen circulation flow rate Q ′. That is, according to the hydrogen flow rate control process according to the first embodiment of the present invention, the actual hydrogen circulation amount Q in the anode system is calculated based on the gas density in the anode system, so that the circulation flow rate of the circulation pump 4 is The hydrogen circulation flow rate Q can be controlled to the required hydrogen circulation flow rate Q ′ even when the gas density ρ is changed without deteriorating the efficiency and fuel consumption even under circumstances that are not directly understood. In addition, it is possible to prevent the fuel cell from deteriorating due to being lower than the required hydrogen circulation flow rate Q ′.

  The ECU 12 may control the actual hydrogen circulation flow rate Q in the anode system to the required hydrogen circulation flow rate Q ′ by controlling the opening degree of the purge valve 5. According to such a configuration, the opening degree of the purge valve 5 is determined according to the control performed to ensure the required hydrogen circulation flow rate Q ′, so that it is compared with a system that periodically purges. Thus, the amount of hydrogen exhausted from the purge valve 5 can be reduced.

  Next, the flow of the hydrogen flow rate control process according to the second embodiment of the present invention will be described with reference to FIGS.

  In general, as shown in FIG. 5, the state where the gas density ρ in the anode system is the lowest is when 100% hydrogen is in a state where only hydrogen is present in the anode system, and conversely, the gas density ρ is the highest. The condition is when 0% hydrogen where only nitrogen and water vapor are present in the anode system. Further, when the rotation speed of the circulation pump 4 is constant, the total circulation flow rate of the circulation pump 4 increases as the gas density ρ in the anode system increases, so that the hydrogen circulation flow rate in the anode system gradually increases and reaches a maximum. It becomes maximum at the value density ρmax.

  Due to the characteristics of the circulation pump 4, the total circulation flow rate further increases as the gas density ρ in the anode system increases. However, the hydrogen circulation flow rate decreases due to the decrease in the hydrogen concentration accompanying the increase in the gas density ρ. Decrease from the maximum value (hereinafter referred to as the maximum hydrogen circulation flow rate). Further, even when the circulation pump 4 is operating at the maximum number of revolutions, the density at which only the hydrogen circulation amount that is less than the maximum value in the required hydrogen circulation amount region can be circulated (hereinafter referred to as the performance guarantee minimum density) ρmin There is.

  More specifically, the gas density ρ in the anode system increases with time due to the penetration of nitrogen from the cathode side into the anode system and the increase in the amount of water vapor accompanying a temperature change. This is because in the anode system, the concentration of nitrogen or water vapor having a higher molecular weight than hydrogen is high. As the gas density ρ in the anode system increases, the total circulation flow rate in the anode system increases as shown by the straight line L2 in FIG. 6, but the hydrogen concentration gradually decreases as the gas density increases. As shown in the straight line L3 in FIG. 6, the hydrogen circulation flow rate becomes insufficient.

  Further, even if the hydrogen circulation flow rate is not insufficient, the system efficiency is deteriorated because the hydrogen circulation flow rate is small for a large total circulation flow rate. On the other hand, when the gas density ρ in the anode system is low, it means that the hydrogen concentration is high. However, due to the characteristics of the circulation pump 4, when the gas density ρ decreases, the total circulation flow rate also decreases. Therefore, the straight line L1 shown in FIG. Thus, even if the circulation pump 4 is operated at the maximum rotational speed, a necessary hydrogen circulation flow rate may not be ensured.

  Therefore, in the hydrogen flow rate control process according to the second embodiment of the present invention, the ECU 12 operates as described below to suppress the circulation pump 4 from consuming electric power wastefully. Hereinafter, the hydrogen flow rate control process according to the second embodiment of the present invention will be described with reference to FIGS.

  In the hydrogen flow rate control process according to the second embodiment of the present invention, first, the ECU 12 sets an upper limit threshold value ρth2 and a lower limit threshold value ρth1 for the gas density ρ in the anode system as shown in FIGS. When the gas density ρ in the anode system is equal to or higher than the upper limit threshold ρth2, a large amount of gas is circulated, resulting in wasteful power consumption of the circulation pump 4. Further, a state where the gas density ρ exceeds the upper threshold ρth2 means that the hydrogen circulation flow rate will soon exceed the maximum value of the hydrogen circulation flow rate.

In addition, the total circulation flow rate by the circulation pump 4 increases as the gas density ρ increases, but the maximum density ρmax is higher than the rate of increase in the hydrogen circulation amount of the pump due to the density increase. Since the reduction rate is higher, when the hydrogen circulation flow rate exceeds the maximum value of the hydrogen circulation flow rate, the circulation pump 4 circulates the heavy gas due to the low hydrogen ratio, in other words , the amount of nitrogen. As a result, the power consumption of the circulation pump 4 increases. Therefore, it is not desirable that the hydrogen circulation flow rate exceed the maximum value of the hydrogen circulation flow rate.

  Next, the ECU 12 determines whether or not the gas density ρ in the anode system is not less than the upper limit threshold ρth2 or not more than the lower limit threshold ρth1, and the gas density ρ is as indicated by points P1 and P6 shown in FIGS. When the upper limit threshold ρth2 or more, after decreasing the hydrogen circulation flow rate to points P2 and P7 where the gas density ρ becomes equal to or lower than the upper limit threshold ρth2 by increasing the purge amount with the rotation speed of the circulation pump 4 being constant, The hydrogen circulation flow rate is corrected to the required values Q5 and Q10 by correcting the rotation speed of the circulation pump 4 to the required rotation speed. On the other hand, when the gas density ρ is equal to or lower than the lower limit threshold ρth1 as indicated by points P4 and P9 shown in FIGS. 7 and 8, the ECU 12 stops the purge and increases the rotational speed of the circulation pump 4 to increase the hydrogen circulation flow rate. Is corrected to the required values Q5 and Q10.

  When the gas density is lower than the lower limit threshold ρth1, the reason for correcting the hydrogen circulation flow rate Q by controlling the rotation speed of the circulation pump 4 is that the hydrogen circulation flow rate Q decreases the gas density ρ by increasing the purge amount. However, if the gas density ρ is lowered to the performance guarantee minimum density ρmin or less, even if the full output command is issued and the rotation speed of the circulation pump 4 is maximized, the hydrogen density is reduced by the decrease in the gas density ρ. This is because the required hydrogen circulation flow rate Q ′ cannot be ensured because the flow rate Q is also lowered, and the fuel cell is deteriorated due to the output being limited or the lack of hydrogen stoichiometry. Further, after the gas density ρ reaches the lower limit threshold ρth1, the hydrogen circulation flow rate Q cannot be increased suddenly to increase the hydrogen circulation flow rate Q just because the hydrogen circulation flow rate Q is insufficient to the required value (gas In order to increase the density ρ, it is sufficient to increase the nitrogen concentration, but since nitrogen penetrates from the cathode side, it cannot be increased suddenly).

  As is apparent from the above description, according to the hydrogen flow rate control process according to the second embodiment of the present invention, when the gas density ρ in the anode system is equal to or higher than the upper threshold ρth2, the ECU 12 The hydrogen circulation flow rate Q in the anode system is controlled by controlling the number of revolutions of the circulation pump 4 after the gas density ρ is lowered to the upper limit threshold value ρth2 or less by controlling the opening of the purge valve 5 that discharges gas to the outside. Therefore, the hydrogen circulation flow rate Q can be corrected while reducing the load on the circulation pump 4 and lowering the gas density ρ in the anode system.

  Further, according to the hydrogen flow rate control process according to the second embodiment of the present invention, when the gas density ρ in the anode system is equal to or lower than the lower limit threshold ρth1, the ECU 12 controls the number of rotations of the circulation pump 4. Since the hydrogen circulation flow rate Q in the anode system is controlled to the required hydrogen circulation flow rate Q ′, the hydrogen circulation flow rate Q is increased while increasing the gas density ρ in the anode system while keeping the load of the circulation pump 4 small. It can be corrected. Further, since the hydrogen circulation flow rate Q can be corrected while increasing the gas density ρ in the anode system, it is possible to suppress the gas density ρ from decreasing to the minimum performance guaranteed minimum density ρmin and to ensure the reliability of the system. it can.

  Finally, with reference to FIGS. 9 and 10, the flow of the hydrogen flow rate control process according to the third embodiment of the present invention will be described.

  In the hydrogen flow rate control process according to the third embodiment of the present invention, the ECU 12 changes the lower limit threshold value ρth1 and the upper limit threshold value ρth2 according to the operation mode of the vehicle on which the fuel cell system is mounted. Specifically, when the driver detects that the vehicle speed with respect to the switching operation intentionally performed on the mountain road or the like and the vehicle drive motor torque is continuously low for a certain period of time, the ECU 12 As a mode, the gas density range R1 is changed in the direction of the maximum hydrogen circulation flow rate as shown in FIG. As a result, the gas density in the anode system is controlled to be higher than normal, and the maximum hydrogen circulation flow rate is higher than normal (change from the hydrogen circulation flow rate Q12 shown in FIG. 9 to the hydrogen circulation flow rate Q13). Therefore, high-power operation can be performed.

  On the other hand, when it is detected that the amount of decrease in the power generation amount of the fuel cell has become a predetermined value or less, the ECU 12 determines that the fuel cell has deteriorated and sets the gas density range as the stack deterioration protection mode. Change in the direction of maximum hydrogen circulation flow rate. As a result, the gas density in the anode system is controlled to be higher than in the normal state, and more hydrogen is circulated than in the normal state. Deterioration can be suppressed.

  Further, when importance is placed on energy efficiency, such as during normal driving or highway driving, the ECU 12 executes the following energy efficiency-oriented operation mode. In general, the state where the gas density ρ in the anode system is high is a result of reducing the purge amount, and indicates a state where the amount of exhausted hydrogen to the outside of the system is small. In other words, the state where the gas density in the anode system is low is a result of frequent purging, and the energy loss is large. From this, the energy loss due to the purge is expressed as a curve L6 shown in FIG. Further, the power consumption of the circulation pump 4 is large when a high-density gas is circulated as shown by a curve L5 shown in FIG. 10, and is small when a low-density gas is circulated. Therefore, by calculating the sum of the curve L6 and the curve L5, the change in energy loss accompanying the change in gas density is expressed as the curve L4 shown in FIG.

  Therefore, when emphasizing energy efficiency, the ECU 12 operates in the density region (region B shown in FIG. 10) where the curve L4 shown in FIG. Control for good driving. More specifically, the intentional switching operation by the driver and the fluctuation range of the torque of the vehicle drive motor are within a specified value for a certain period of time (= no signal waiting because there is no sudden acceleration, high speed ECU 12 determines that the vehicle is traveling on the road), and the ECU 12 sets the gas density range so as to sandwich the minimum value of the curve L4 as the energy efficiency-oriented operation mode. Control to do.

  As described above, when the anode gas density width is changed in the direction of the maximum value of the hydrogen circulation flow rate, the gas density in the anode system is controlled to be higher than normal, so that the rotation of the circulation pump 4 Even if the number is decreased, the required hydrogen circulation flow rate Q ′ can be secured. Accordingly, when detecting an idle stop state where the sound and vibration of the circulation pump 4 are conspicuous, or when the driver performs an intentional switch operation, the ECU 12 sets the gas density range as a hydrogen vibration reduction mode. By changing the circulating flow rate in the maximum value direction, the number of rotations of the circulating pump 4 may be reduced, and sound and vibration of the circulating pump 4 may be suppressed. Further, the gas density range may be narrowed, or the upper limit threshold ρth2 and the lower limit threshold ρth1 may be matched. Thereby, the characteristic of each above-mentioned operation mode can be taken out more largely. Further, it is possible to operate with high accuracy near the target operating gas density.

  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. That is, it should be added that other embodiments, examples, operation techniques, and the like made by those skilled in the art based on the above embodiments are all 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 flowchart figure which shows the flow of the hydrogen flow control process used as the 1st Embodiment of this invention. It is a figure which shows the inclination and intercept of the rotation speed of a circulation pump, and the differential pressure of a circulation pump-hydrogen circulation flow rate diagram for every gas density in an anode system. It is a differential pressure-hydrogen circulation flow rate diagram of a circulation pump. It is a figure which shows the relationship between the hydrogen circulation flow rate in an anode system for every rotation speed of a circulation pump, and gas density. It is a figure which shows the relationship between the hydrogen circulation flow volume in an anode system, total circulation flow volume, and gas density. It is a figure for demonstrating the hydrogen flow control process used as the 2nd Embodiment of this invention. It is a figure for demonstrating the hydrogen flow control process used as the 2nd Embodiment of this invention. It is a figure for demonstrating the hydrogen flow control process used as the 3rd Embodiment of this invention. It is a figure for demonstrating the hydrogen flow control process used as the 3rd Embodiment of this invention.

Explanation of symbols

1: Hydrogen (H ₂ ) storage device 2: Pressure adjustment valves 3a, 3b: Hydrogen circulation path 4: Circulation pump 5: Purge valve 6: Flow meter 7, 11: Thermometer 8, 10: Pressure gauge 9: Gas concentration sensor 12: ECU

Claims (9)

A fuel cell system that circulates hydrogen discharged from a fuel electrode of a fuel cell using a circulation pump to the fuel electrode via a hydrogen circulation path,
A flow rate detection unit for detecting the flow rate of hydrogen supplied to the hydrogen circulation path;
Of the required hydrogen circulation flow rate calculated from the flow rate detected by the flow rate detection unit and the required hydrogen circulation flow rate calculated from the hydrogen consumption of the fuel electrode, the larger value is set as the required hydrogen circulation flow rate,
Calculate the actual hydrogen circulation flow rate in the hydrogen circulation path based on the control state and gas density of the circulation pump in the hydrogen circulation path,
Fuel cell system in which the actual hydrogen circulation rate in the hydrogen circulation path, characterized in that a control unit for controlling such that the required hydrogen circulation rate was the setting. The fuel cell system according to claim 1,
The control unit controls the actual hydrogen circulation flow rate in the hydrogen circulation path to the set required hydrogen circulation flow rate by controlling the rotation speed of the circulation pump . The fuel cell system of the placing serial to claim 1,
The control unit controls the actual hydrogen circulation flow rate in the hydrogen circulation path to the set required hydrogen circulation flow rate by controlling the opening degree of the purge valve that discharges the gas in the hydrogen circulation path to the outside of the system. A fuel cell system. The fuel cell system according to claim 3 ,
The controller is
A lower limit threshold and an upper limit threshold for the gas density are set, a range between the lower limit threshold and the upper limit threshold is a gas density range, and a relative relationship between the gas density in the hydrogen circulation path and the gas density range is set. Based on the above, when the gas density in the hydrogen circulation path is less than or equal to the lower limit threshold, the number of revolutions of the circulation pump is adjusted, and when the gas density in the hydrogen circulation path is greater than or equal to the upper limit threshold, A fuel cell system , wherein an actual hydrogen circulation flow rate in the hydrogen circulation path is controlled by adjusting a purge amount by the purge valve . The fuel cell system according to claim 4 , wherein
When the gas density in the hydrogen circulation path is equal to or higher than the upper threshold, the control unit reduces the gas density in the hydrogen circulation path below the upper threshold by controlling the opening of the purge valve. And then controlling the number of revolutions of the circulation pump so that the actual hydrogen circulation flow rate in the hydrogen circulation path becomes the required hydrogen circulation flow rate . The fuel cell system according to claim 4 or 5 , wherein
When the gas density in the hydrogen circulation path is equal to or lower than the lower limit threshold, the control unit controls the number of revolutions of the circulation pump so that the actual hydrogen circulation flow rate in the hydrogen circulation path A fuel cell system that is controlled to have a circulating flow rate . The fuel cell system according to any one of claims 4 to 6 ,
The said control part changes the said gas density range according to the driving | running state of a fuel cell system, The fuel cell system characterized by the above-mentioned . The fuel cell system according to 請 Motomeko 7,
When the output of the fuel cell is increased, the control unit changes the gas density range so that the hydrogen circulation flow rate in the hydrogen circulation path is increased . The fuel cell system according to claim 7 or 8 , wherein
In order to increase the energy efficiency of the fuel cell system, the control unit uses the gas density that minimizes the sum of the energy loss due to the discharge of hydrogen by the purge valve and the power consumption of the circulation pump as a reference. A fuel cell system, wherein the gas density range is changed .

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