JP5434054B2 - Fuel cell system - Google Patents

Description

  The present invention relates to a fuel cell system, and more particularly to control at low temperature startup.

In the fuel cell system, improvement of startability, that is, shortening of start-up time has been an issue. In particular, shortening the warm-up time at the time of start-up in a low-temperature environment (hereinafter referred to as “low-temperature start-up”) is a major issue, and various measures are being studied. For example, by preventing the cooling water from flowing for a predetermined period from the low temperature startup, it is possible to prevent heat generated by self-heating due to power generation from being dissipated to the cooling water and to promote warm-up. 1 is disclosed.
JP 2007-73378 A

  However, in the configuration disclosed in Patent Document 1, since the cooling water does not circulate in the system for a predetermined period from the start, the temperature of the fuel cell rises even after the generated power reaches the target power (power during normal operation). There is a risk of continuing. In this case, the self-heat generation amount is reduced due to the increase in power generation efficiency as the temperature of the fuel cell rises. Then, when the cooling water starts to flow after the predetermined period has passed, the temperature of the fuel cell stack is lowered, so that the generated power is lower than the target power and the self-heat generation amount is further reduced. For this reason, there is a problem that the time until the warm-up ends becomes long.

  Accordingly, an object of the present invention is to shorten the warm-up time of the fuel cell system at the time of low temperature startup.

The fuel cell system according to the present invention detects circulation of a fuel cell cooling medium to the fuel cell, a flow rate control unit for controlling the flow rate of the heat medium to be supplied to the fuel cell, and the generated power of the fuel cell. Power detection means. The flow rate control means increases the flow rate of the heat medium with respect to the flow rate before reaching when the generated power of the fuel cell reaches a preset target generated power before the warm-up of the fuel cell is finished .

  According to the present invention, by increasing the flow rate of the heat medium when the generated power reaches the target generated power, the increase in the fuel cell temperature after reaching the target power can be suppressed. As a result, the warm-up time can be shortened.

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

  FIG. 1 is a configuration diagram of a fuel cell system to which the first embodiment is applied. 1 is a fuel cell stack, 2 is a cathode gas (air) inlet for supplying air containing cathode gas to the fuel cell stack 1, 3 is a compressor for boosting the cathode gas, and 4 is an anode gas supply device (for example, a high-pressure hydrogen cylinder). 5 is a fuel cell inlet anode gas pressure sensor (hereinafter simply referred to as “anode gas pressure sensor”), 6 is a gas-liquid separator, 7 is an anode circulation means, 8 is a control unit as a power detection means, and 9 is an anode. Pressure control valve, 10 is a water level sensor associated with the gas-liquid separator 6, 11 is a drainage control valve, 12 is a purge valve for discharging hydrogen path gas, and 15 is a fuel for heating medium (cooling water in this embodiment). 2 is a heat medium supply device as a circulation means for supplying to the battery stack 1.

  The fuel cell stack 1 is configured by sandwiching a fuel cell in which an anode electrode and a cathode electrode are placed facing each other with a solid polymer electrolyte membrane interposed therebetween, and laminating a plurality of these. Then, anode gas is supplied to the anode electrode and cathode gas is supplied to the cathode electrode, and these are reacted electrochemically to generate electric power. Moreover, it has the voltage detection means 14 (for example, voltage sensor) which detects a fuel cell total voltage, and the current detection means 23 (for example, current sensor) which detects a fuel cell load current.

  The anode gas supply device 4 supplies anode gas to the fuel cell stack 1. An anode pressure control valve 9 is provided in the anode gas supply flow path to control the hydrogen pressure of the fuel cell stack 1 according to the output of the anode gas pressure sensor 5.

  The gas-liquid separator 6 is installed at the fuel cell anode outlet, where the liquid water contained in the anode off-gas is separated. The liquid water separated here is temporarily stored in a storage tank associated with the gas-liquid separator 6, and the anode gas is discharged during drainage by the drainage control valve 11 according to the output of the water level sensor 10 installed in the storage tank. Is controlled more than water that is not discharged.

  Part of oxygen is consumed in the air that has passed through the fuel cell stack 1 and is discharged through the discharge passage 24 together with moisture generated by power generation.

  The discharge flow path 24 is provided with a cathode pressure adjusting valve 13 for adjusting the cathode gas pressure supplied to the fuel cell stack 1, and the opening degree of the cathode pressure adjusting valve 13 is set by the control unit 8. Further, the generated water of the fuel cell stack 1 collected by the gas-liquid separator 6 installed on the anode side is also discharged through the discharge channel 24.

  The heat medium supply device 15 supplies the heat medium to the fuel cell stack 1 so as to keep the temperature of the fuel cell stack 1 appropriately. The supply flow path for this purpose includes flow rate detection means 16 (for example, a flow rate sensor) for detecting the flow rate of the heat medium supplied to the fuel cell stack 1 and temperature detection for detecting the temperature of the heat medium supplied to the fuel cell stack 1. Means 17 (for example, a temperature sensor), temperature detection means 22 (for example, a temperature sensor) for detecting the temperature of the heat medium discharged from the fuel cell stack 1, and heat dissipation for dissipating the heat of the fuel cell stack 1 through the heat medium. , A bypass line L2 that bypasses the radiator 18, a flow dividing adjusting means 19 (for example, a three-way valve) that adjusts a flow rate ratio between the radiator 18 and the bypass line L2, and a pressure in the cooling line of the fuel cell stack 1 are detected. Pressure detecting means 20 (for example, a pressure sensor) that performs temperature detection, and temperature detecting means 21 (for example, a temperature sensor) that detects the temperature of the fuel cell stack 1 are provided.

  The flow adjusting means 19 bypasses the radiator 18 when the temperature of the fuel cell stack 1 is lower than the control temperature, and increases the flow rate to the radiator 18 when the temperature is higher than the control temperature. Is adjusted to a desired temperature.

  The power generation in the fuel cell stack 1 is performed by adjusting the fuel cell power generation current so that the total voltage of the fuel cell stack 1 does not fall below a preset voltage threshold.

  FIG. 2 is a flowchart of control executed by the control unit 8 in the fuel cell system as described above. This control is started in response to an activation command from the driver. For example, it is assumed that a start command is given when the start button is turned ON.

  In step S001, it is determined whether or not low temperature operation is necessary. This determination may be, for example, any one of the fuel cell temperature, the fuel cell heat medium temperature, the outside air temperature, the component temperature of the fuel cell system, or the total voltage of the fuel cell when the fuel gas is supplied to the fuel cell stack 1. Judgment can be made based on conditions or a combination of these conditions. In addition to the above conditions, it is also possible to use characteristics indicating the state of the fuel cell, such as the cell voltage and the total voltage at the time of supplying the reaction gas.

  If it is determined in step S001 that the low temperature operation is not necessary, the process proceeds to step S007, and the heat medium flow control is changed to the normal operation control. If it is determined that the low temperature operation is necessary, the process proceeds to step S002 to determine the fuel cell total voltage target value Vt.

  The fuel cell total voltage target value Vt is, for example, a restriction on the start time of a moving body (for example, a vehicle) on which the fuel cell stack 1 is mounted, prevention of freezing during power generation of the fuel cell stack 1 and the components of the fuel cell system, It is determined in consideration of factors such as deterioration of the fuel cell stack 1.

  The target value set here may be a parameter related to the power generation efficiency of the fuel cell stack 1. For this reason, it is good also as an average cell voltage and fuel cell power generation efficiency not only in a fuel cell total voltage. However, when the average cell voltage or the fuel cell power generation efficiency is used, it is necessary to detect the voltage for each cell or to calculate based on the detection result of the total voltage. Therefore, it is desirable to use the total fuel cell voltage.

  In step S003, the initial value Qf of the heat medium flow rate supplied to the fuel cell stack 1 is determined.

  The initial value Qf of the heat medium flow rate is one of the detection results of the fuel cell stack inlet heat medium temperature detecting means 17, the fuel cell stack outlet heat medium temperature detecting means 22, or the fuel cell stack temperature detecting means 21, or a combination thereof. Determine based on. For example, when the determination is made based on the detection result of the fuel cell stack temperature detection means 21, the sensitivity to the temperature of the IV characteristic as shown in FIG. If the temperature is equal to or higher than the temperature (temperature T2 in FIG. 3) at which the fuel cell total voltage target value Vt can be secured, the flow rate for normal operation is set. If it is less than T2, it is determined based on a table for calculating the heat medium flow initial value Qf from the temperature detection result as shown in FIG.

  In the table of FIG. 4, the initial value Qf of the heat medium flow rate is zero until the detected temperature is 0 ° C., and the initial value Qf of the heat medium flow rate increases as the temperature rises from 0 ° C. to a temperature at which it can be determined that the warm-up is completed. doing. When creating such a table, the initial value Qf of the heat medium flow rate must be determined in consideration of startability at low temperatures and heat damage to the components. It is necessary to determine the heat capacity of the fuel cell stack 1 including the components of the fuel cell system to be used and the coolant and the component allowable temperature together.

  By setting the heat medium flow initial value Qf in this way, it is possible to prevent the IV characteristics from being deteriorated by cooling with the heat medium. As a result, it is possible to prevent the increase in the amount of self-heating without slowing the generated power.

  By the way, since the determination of the heat medium flow initial value Qf can be determined according to the state of the fuel cell stack 1, it can be determined without depending on the detection result of the above-described temperature detection means. From the viewpoint of preventing a significant temperature rise, it is desirable to make a determination based on the detection result of the temperature detecting means described above.

  In step S004, the diversion adjusting device 19 is set so that the entire amount of the heat medium flows into the pipe L2 bypassing the radiator 18. Here, even if the heat medium flowing out from the fuel cell stack 1 does not bypass the radiator 18, the effect of shortening the warm-up time can be obtained. However, by bypassing the radiator 18, heat radiation from the radiator 18 can be prevented, and further, the total heat capacity of the circulation path of the heat medium can be reduced, so that the warm-up time is further shortened by bypassing. be able to.

  In step S005, power generation is performed in the fuel cell stack 1 so that the fuel cell total voltage target value Vt determined in step S002 is reached, and the process proceeds to the flowchart of FIG.

  FIG. 5 is a flowchart of the adjustment control of the flow rate of the heat medium supplied to the fuel cell stack 1.

  In step S007, it is determined whether or not the fuel cell stack 1 has been warmed up. If the warm-up has been completed, the process proceeds to step S006 to shift to normal operation, and if not completed, the process proceeds to step S008. Whether or not the warm-up has been completed is, for example, whether or not the temperature detection means 17 for detecting the temperature of the heat medium flowing into the fuel cell stack 1 is equal to or higher than a predetermined threshold for determination, or when a certain generated current is generated. Whether the difference between the static detection result of the voltage detection means 14 and the ideal voltage (theoretical power generation voltage at the time of the current generation during normal operation) is within a preset threshold value can be determined.

  In step S008, it is determined whether or not the thermal condition assumed when the flow rate of the heat medium supplied to the fuel cell stack 1 is limited is acceptable. The thermal condition is a condition that can prevent damage to the fuel cell stack 1 and the components of the fuel cell system due to a temperature rise in the fuel cell stack 1 due to a decrease in the flow rate of the heat medium, and a thermal stress caused by a temperature difference in the fuel cell. It is determined in consideration of the heat load condition such as the condition that can prevent the fuel cell stack 1 from being damaged by the above. For example, the determination as to whether or not the fuel cell stack 1 is acceptable can be made at the sum of the difference between the self-heat generation amount of the fuel cell stack 1 and the heat amount taken out of the fuel cell stack 1 by the heat medium, and the heat medium inlet and outlet of the fuel cell stack 1. The temperature can be determined based on the temperature detected by the temperature detecting means 17 and 22.

  If it is determined that it is not acceptable, the process proceeds to step S012, and the flow rate of the heat medium is increased. If it is determined that it is acceptable, the process proceeds to step S009.

  In step S009, it is determined whether or not the actual generated power of the fuel cell stack 1 has reached the upper limit power set value Pu. The upper limit power set value Pu is a value set as power that can be consumed by a system using the fuel cell system as an energy source. For example, in the case of a mobile body equipped with a fuel cell, power consumed by components constituting the fuel cell system, power consumed by a system such as an information panel for transmitting air conditioning and operating information of the living space, driving of the mobile body This is the sum of power consumed as a source, power absorbed by a power storage device such as a battery or capacitor, and power consumed by other auxiliary machines. The actual generated power is calculated based on the actual generated voltage and load current.

  The upper limit power setting value Pu may be set to be equal to or less than the maximum value of the total power described above. However, when the maximum value is set to the maximum value, the self-heat generation amount of the fuel cell stack 1 is maximized. It is desirable to do.

  As a result of the determination, if the upper limit power set value Pu has not been reached, the process proceeds to step S010, and the heat medium supply device 15 is operated to reduce the flow rate of the heat medium supplied to the fuel cell stack 1 as will be described later. Thus, steps S007 to S010 are repeated until the actual generated power reaches the upper limit power set value Pu.

  This is because when the actual generated power reaches the upper limit power set value Pu, the power generation efficiency increases with a rise in the temperature of the fuel cell stack 1 and the self-heat generation amount decreases. is there. Here, the fuel cell total voltage is used as the characteristic value of the power generation efficiency. However, the present invention is not limited to this, and the average cell voltage or the power generation efficiency itself may be used as the characteristic value representing the power generation efficiency of the fuel cell.

  On the other hand, when the actual generated power of the fuel cell stack 1 has reached the upper limit power set value Pu, the process proceeds to step S011.

  Note that the process proceeds from step S009 to step S011 not only when the actual generated power reaches the upper limit power set value Pu. For example, when the change rate of the fuel cell power generation load is equal to or higher than a predetermined value, the process may proceed to step S010 when it is predicted that the upper limit power set value Pu will be reached. Further, when the actual generated power is within a predetermined range with reference to the upper limit power set value Pu, the process may proceed to step S010.

  In step S011, it is determined whether or not the difference between the detection result of the total voltage detecting means 14 of the fuel cell stack 1 and the target total voltage Vt is larger than a predetermined value set in advance. If larger than the predetermined value, the process proceeds to step S012, the flow rate of the heat medium supplied to the fuel cell stack 1 is increased as described later, and the process returns to step S007. If it is smaller than the predetermined value, the current heat medium supply amount is maintained, and the process returns to step S007.

  Note that the determination in step S011 only needs to prevent the total voltage of the fuel cell stack 1 from becoming equal to or higher than the target total voltage Vt, and is not limited to the determination based on the amount of deviation from the target total voltage Vt described above. For example, the determination using the change rate of the total voltage of the fuel cell stack 1 may be used.

  Here, the amount of decrease in the heat medium flow rate in step S010 and the amount of increase in the heat medium flow rate in step S012 will be described.

  In step S010, the heat medium flow initial value Qf is set as an initial value, and the amount of power is reduced until the actual generated power of the fuel cell stack 1 reaches the upper limit power set value Pu. As shown in FIG. 6, the amount of decrease in the heat medium flow rate is set such that the amount of decrease in the heat medium flow rate increases as the divergence amount between the actual generated power and the upper limit power set value Pu increases, and the heat medium flow rate decreases as the divergence amount decreases. Set the decrease amount to a small value. Further, the amount of decrease in the heat medium flow rate is reduced as the heat medium temperature at the fuel cell stack inlet is higher, and the amount of decrease is set as the heat medium temperature is lower.

  On the other hand, step S012 performs an increase process using the heat medium flow rate when the actual generated power of the fuel cell stack 1 reaches the upper limit power set value Pu as an initial value. As shown in FIG. 7, the increase amount of the heat medium flow rate is set such that the increase amount increases as the deviation amount between the target total voltage Vt and the actual total voltage increases, and the increase amount decreases as the deviation amount decreases. Further, when the temperature of the heat medium at the fuel cell stack inlet is high, the increase amount is set large, and when it is low, the increase amount is set small.

  FIG. 8 is a time chart when the above-described heat medium flow rate is increased or decreased. Here, the heat medium flow initial value Qf is set to Qf0.

  Power generation is started at t = 0, and the generated power of the fuel cell stack 1 reaches the upper limit power set value Pu at t1. During this time, the heat medium flow rate is reduced in accordance with the difference between the upper limit power set value Pu and the actual power. As a result, it is possible to prevent the IV characteristic from deteriorating due to cooling by the heat medium and slowing the increase in the amount of self-heating.

  The heat medium flow rate after t1 is increased according to the difference between the target voltage and the actual voltage, with the flow rate at t1 as an initial value.

  When the actual generated power reaches the upper limit power set value Pu, the IV voltage increases, and the total voltage increases as shown by the solid line in FIG. Therefore, by increasing the flow rate of the heat medium to promote the cooling of the fuel cell stack 1, an excessive increase in the IV characteristic is suppressed, and the total voltage is converged to the target total voltage. Ideally, it is desirable that the total voltage remain at the target total voltage after t1 as indicated by the broken line in FIG.

  Next, the effect of this embodiment will be described with reference to FIGS. 9 to 11. FIG. 9 shows the self-heat generation amount, the power generation efficiency (voltage) of the fuel cell stack 1, the load current, the generated power, the temperature of the fuel cell stack 1, and the heat medium flow rate when the heat medium flow control of the present embodiment is executed. It is a time chart. FIG. 10 and FIG. 11 are time charts for the case where timer control is performed on the flow rate of the heat medium according to the elapsed time from the startup as a comparative example. FIG. 10 shows that the generated power reaches the upper limit power set value. 11 is a case where the heat medium is periodically passed before reaching the upper limit power set value when the heat medium is allowed to flow after a predetermined time has elapsed.

  Note that the temperature of the fuel cell at the time of startup is assumed to be below zero. For this reason, the initial value of the heat medium flow rate is zero. Further, the chart of the fuel cell efficiency (voltage), load current, and generated power in FIG. 9 shows a case where an ideal change is made by the heat medium flow control described in FIG.

  First, when FIG. 9 and FIG. 10 are compared, since the heat medium flow rate is zero until the generated power reaches the upper limit power set value after the system is started at t = 0, the arrival time (t1) is reached. There is no difference.

  In the present embodiment, as described above, the fuel cell efficiency is kept constant by increasing the heat medium flow rate after t1. Thereby, the load current and the generated power are also maintained constant. Further, although the fuel cell is cooled by starting to flow the heat medium flow rate, the self-heat generation amount is maintained at the heat generation amount at the upper limit power set value Pu by maintaining the fuel cell power generation efficiency constant. Since the heat medium flow rate is increased while maintaining the load current and the generated power constant, the system is warmed up when the heat medium flow rate becomes the normal operation flow rate.

  On the other hand, in FIG. 10, since the heat medium flow rate continues to be zero after t1, the IV characteristic is improved and the fuel cell power generation efficiency is increased. For this reason, in order to maintain the generated power at the upper limit power set value, it is necessary to reduce the load current. In addition, the self-heat generation amount decreases as the fuel cell efficiency increases. When the heat medium starts to flow at t2 in a state where the self-heat generation amount and the load current are thus reduced, the fuel cell temperature is lowered. As a result, the IV characteristic is reduced and the generated power is reduced, so that the generated voltage is reduced and the load current is also limited. Moreover, the amount of self-heating is further reduced due to a decrease in generated power. Therefore, after the heat medium flow rate becomes the normal operation flow rate, it takes time until the generated power reaches the upper limit power set value again. That is, it takes time for the fuel cell stack 1 to be warmed up as compared to the present embodiment.

  Here, the warm-up state refers to a state in which the generated power of the fuel cell stack 1 has reached the upper limit power set value Pu and the heat medium flow rate is a flow rate in the normal operation state.

  Next, FIG. 9 and FIG. 11 are compared. In FIG. 11, the heat medium is periodically passed before the generated power reaches the upper limit power set value Pu. For this reason, the fuel cell temperature rises slowly while the heat medium is flowing, the IV characteristic does not increase, and the current value cannot be increased. Therefore, the rising speed of the generated power becomes moderate, and it takes time to warm up compared to the present embodiment.

  As described above, according to the present embodiment, the following effects can be obtained.

  (1) The heat medium flow initial value Qf is set when the fuel cell system is started, and when the generated power of the fuel cell stack 1 reaches the upper limit power set value Pu, the heat medium flow is set to the heat medium flow initial value Qf. Therefore, the increase in the fuel cell temperature can be suppressed and the decrease in the amount of self-heating can be suppressed, and as a result, the warm-up time can be shortened.

  (2) Since the increase amount of the heat medium flow rate is set so that the total voltage is maintained at the upper limit power setting value Pu, it is possible to suppress a decrease in the amount of self-heating while maintaining the power generation efficiency.

  (3) Since the amount of increase in the heat medium flow rate is set to be larger as the difference between the target value and the actual value of the total voltage is larger and smaller as the difference is smaller, the total voltage can be made closer to the target value.

  (4) Since the amount of increase in the heat medium flow rate is set larger as the temperature of the heat medium is higher and smaller as the temperature of the heat medium is lower, the total voltage can be made closer to the target value.

  (5) Since the heat medium flow initial value Qf is set smaller as the temperature at the start of the fuel cell is lower, excessive cooling by the heat medium at low temperature start is prevented, power generation efficiency is increased, and self-heating value is reduced. Increase can be promoted.

  (6) When the generated power of the fuel cell stack 1 is equal to or lower than the target generated power (upper limit power setting value Pu), the flow rate of the heat medium is decreased with respect to the heat medium flow rate initial value Qf. Increase in efficiency can be promoted, and increase in self-heating value can be promoted.

  (7) Since the amount of decrease in the heat medium flow rate is set larger as the difference between the generated power and the target generated power (upper limit power setting value Pu) is larger and smaller as the difference is smaller, the power increase is promoted and the warm-up time is increased. Can be shortened.

  (8) Since the amount of decrease in the heat medium flow rate is set larger as the temperature of the heat medium is lower and smaller as the temperature of the heat medium is higher, the power increase is promoted and the warm-up time can be shortened.

  A second embodiment will be described.

  FIG. 12 is a configuration diagram of a fuel cell system to which the present embodiment is applied. The difference from FIG. 1 is that a heat medium heating device 25 is provided in front of the fuel cell stack heat medium inlet.

  For example, an electric heater is used as the heat medium heating device 25. FIG. 15 is a diagram illustrating an example of the calorific value characteristic of the heat medium heating device 25. In this way, the maximum heat generation amount is limited by the flow rate of the heat medium passing through the heat medium heating device 25, and the maximum heat generation amount becomes larger as the temperature of the heat medium is lower. Can be prevented.

  The operation of the fuel cell system of this embodiment will be described with reference to FIGS. 13 and 14.

  FIG. 13 is a flowchart of the control executed by the control unit 8. This control is started in response to a start command for the fuel cell system. For example, it is assumed that a start command is given when the start button is turned ON.

  Steps S101 to S106 are the same as steps S001 to S006 in FIG. However, the processing after starting fuel cell power generation in step S105 is different.

  FIG. 14 is a flowchart of control performed after fuel cell power generation is started in step S105.

  In step S107, it is determined whether the power generation capacity of the fuel cell stack 1 is within an allowable range. Specifically, the change rate of the detection result of the current detection means 23 for detecting the fuel cell load current is compared with the assumed change rate Iu. If the change rate is larger than Iu, the I of the fuel cell stack 1 is compared. From the -V characteristic, it is determined that the power generation capacity is within the allowable range, and the process proceeds to the heat medium flow rate adjustment shown in FIG. On the other hand, if the rate of change is equal to or less than Iu, the process proceeds to step S108.

  The determination of the power generation capacity may be made in advance before power generation, for example, by a temperature detection means or the like. However, in order to make a judgment according to the actual condition such as the frozen state inside the fuel cell stack 1, any system that adjusts the generated current so as to keep the total voltage of the fuel cell stack 1 constant as described above. It is desirable to judge based on the change rate of the load current. Moreover, even if it judges from directly generated electric power, the judgment according to the actual condition can be performed.

  In step S108, it is determined that the IV characteristic of the fuel cell stack 1 is low, and the amount of heat medium supplied to the fuel cell stack 1 is set to the heat medium flow rate in the mode in which the heat medium heating device 25 is used. In step S109, heating by the heat medium heating device 25 is started.

  The heat medium flow rate in the mode using the heat medium heating device 25 is determined so that the difference between the heat amount of the heat medium flowing into the fuel cell stack 1 and the heat amount of the heat medium flowing out of the fuel cell stack 1 is maximized. Is the most effective.

  In step S110, it is determined whether or not to continue using the heat medium heating device 25 based on the thermal conditions of the fuel cell stack 1 and the heat medium heating device 25. When it is determined that it cannot be continued, the process proceeds to step S112, and the heat medium heating device 25 is stopped. If it is determined that the process can be continued, the process proceeds to step S111.

  In step S111, it is determined whether the generated power has reached the upper limit power set value Pu. If it is determined that it has been reached, the process proceeds to step S112. If it is determined that it has not been reached, the process returns to step S110. The determination method in step S111 and the concept of setting the upper limit power setting value Pu are the same as those in step S009 in FIG.

  After stopping the heat medium heating device 25 in step S112, the same control as in FIG. 5 of the first embodiment is executed.

  As described above, in the present embodiment, by including the heat medium heating device 25, the warm-up time can be further shortened.

  A third embodiment will be described.

  FIG. 16 is a configuration diagram of a fuel cell system to which the present embodiment is applied. The difference from FIG. 1 is that a fuel cell stack heating line L3 (hereinafter referred to as L3 line) is further provided, a heat medium heating device 25, a circulation device 26 for circulating the heat medium, and a fuel in this L3 line. The temperature detecting means 27 for detecting the temperature of the heat medium flowing into the battery stack 1 and the flow rate detecting means 28 for detecting the heat medium flow rate in the L3 line are provided. The fuel cell stack 1 has a heat exchanger (not shown) having a heat exchange function between the heat medium and the fuel cell stack 1.

  Further, the same control as in the second embodiment is applied to the control at the time of starting the system.

  In this way, the L3 line for heating the heat medium is provided independently, for example, around the end cell in the fuel cell stack 1, a part where the temperature is most unlikely to rise in a low temperature environment and a voltage drop is likely to occur. Is heated, the fuel cell stack 1 can be effectively warmed up.

  The operation of the heat medium heating device 25 in the L3 line and the method for determining the circulation amount of the heat medium are the same as those in the second embodiment, and independent and in parallel with the flow rate control of the bypass line L2 that bypasses the radiator 18. Can be done.

  As a method for warming up the fuel cell stack 1, in addition to transferring heat through the heat medium as described above, the fuel cell stack 1 may be directly heated by a heater such as a heater. Further, the L3 line is not dedicated to heating the fuel cell stack 1, but may be shared with a part having another function such as a heat medium line of an indoor air conditioner.

  As described above, in the present embodiment, the fuel cell system can be warmed up efficiently as in the first or second embodiment.

  The present invention is not limited to the above-described embodiments, and it goes without saying that various modifications can be made within the scope of the technical idea described in the claims.

It is a system configuration figure of a 1st embodiment. It is a control flowchart at the time of fuel cell system starting of a 1st embodiment. It is a figure which shows the sensitivity with respect to the temperature of an IV characteristic. 6 is a table for calculating a heat medium flow initial value Qf. It is a flowchart of adjustment control of the heat carrier flow rate of 1st Embodiment. It is a table for determining the decreasing amount of a heat carrier flow rate. It is a table for determining the increase amount of a heat carrier flow rate. It is a time chart for demonstrating the effect by the increase / decrease in a heat carrier flow rate. It is a time chart at the time of performing the heat medium flow control of 1st Embodiment. It is a time chart (the 1) for a comparison. It is a time chart (the 2) for comparison. It is a system configuration figure of a 2nd embodiment. It is a control flowchart at the time of fuel cell system starting of a 2nd embodiment. It is a control flowchart of a heat carrier heating device. It is a calorific value characteristic view of a heat carrier heating device. It is a system configuration figure of a 3rd embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fuel cell stack 2 Cathode gas (air) inlet 3 Compressor 4 Anode gas supply device 5 Fuel cell inlet anode gas pressure sensor 6 Gas-liquid separation device 7 Anode circulation means 8 Control unit 9 Anode pressure control valve 10 Water level sensor 11 Drainage control Valve 12 Purge valve 14 Voltage detection means 15 Heat medium supply device 16 Flow rate detection means 17 Temperature detection means 18 Radiator 19 Pressure detection means 20 Pressure detection means 21 Temperature detection means 22 Temperature detection means 23 Current detection means 24 Discharge flow path 25 Heat Medium heating device 26 Circulating device 27 Temperature detection means 28 Flow rate detection means

Claims (7)

A circulation means for supplying the fuel cell with a heat medium for cooling the fuel cell;
Flow rate control means for controlling the flow rate of the heat medium supplied to the fuel cell;
Power detection means for detecting the power generated by the fuel cell;
Total voltage detection means for detecting the total voltage of the fuel cell;
With
The flow rate control means is configured to maintain the total voltage of the fuel cell at a predetermined value when the generated power of the fuel cell reaches a preset target generated power before the end of warm-up of the fuel cell. A fuel cell system, wherein the flow rate of the heat medium is increased with respect to the flow rate before reaching.   The flow rate control means increases the amount of increase in the flow rate of the heat medium as the difference between a preset target total voltage and the actual total voltage detected by the total voltage detection means increases, and the target total voltage and the actual total voltage increase. The fuel cell system according to claim 1, wherein the fuel cell system is set to be smaller as the difference from the voltage is smaller. Temperature detecting means for detecting the temperature of the heat medium flowing into the fuel cell;
The flow rate control means sets the increase amount of the flow rate of the heat medium to be larger as the temperature of the heat medium is higher and to be smaller as the temperature of the heat medium is lower. The fuel cell system described. Means for detecting a temperature at the time of starting the fuel cell;
The fuel cell system according to any one of claims 1 to 3, wherein the flow rate control unit sets the initial flow rate to be smaller as the temperature at the time of startup of the fuel cell is lower.   5. The fuel cell according to claim 4, wherein when the generated power of the fuel cell is equal to or lower than the target generated power, the flow rate control unit decreases the flow rate of the heat medium with respect to the initial flow rate. system.   The flow rate control means increases the amount of decrease in the flow rate of the heat medium as the difference between the generated power of the fuel cell and the target generated power increases, and the difference between the generated power of the fuel cell and the target generated power increases. The fuel cell system according to claim 5, wherein the fuel cell system is set to be smaller as it is smaller.   The flow rate control means sets the amount of decrease in the flow rate of the heat medium to be larger as the temperature of the heat medium flowing into the fuel cell is lower and smaller as the temperature of the heat medium flowing into the fuel cell is higher. The fuel cell system according to claim 5 or 6.