JP2006164781A - Fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell system quickly and smoothly starting up even in a low temperature environment. <P>SOLUTION: When a temperature of air supplied to a fuel cell 1 is lower than a prescribed value, in compressing the air to set pressure to increase a fuel cell entrance air temperature up to a target temperature by an air supply device 6 and an air-pressure regulating valve 7, a control unit controls the supply device 6 and the regulating valve 7 so that all of an exit air temperature of the supply device 6, an entrance air temperature of a humidifier 26, and an entrance air temperature of the fuel sell 1 do not exceed respective upper limit temperatures. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a fuel cell system having improved system startability in a low temperature environment.

Conventionally, as this type of technology, for example, those described in the following documents are known (see Patent Document 1). The technology described in this document reduces the power generation efficiency at low temperature startup by lowering the supply pressure of hydrogen gas supplied to the fuel cell at low temperature startup than during steady operation, and increases the self-heating amount of the fuel cell Thus, the warm-up time of the fuel cell is shortened.
JP 2002-313388 A

  In the above conventional fuel cell system, the temperature of the fuel cell itself is increased by increasing the self-heating value by inefficient power generation at low temperature startup. However, in a low temperature environment, hydrogen gas or air supplied to the fuel cell is used. The gas reaction gas is also cold. In particular, when starting in a low-temperature environment below freezing, if the fuel cell power generation is not sufficient, for example, if subzero air gas is introduced into the cathode of the fuel cell at the beginning, the water generated on the cathode side due to power generation will freeze. However, there is a risk that power generation cannot be performed.

  In order to avoid such a problem, a method has been adopted in which the temperature of the air gas is raised and then supplied to the fuel cell when the system is started below freezing. In order to raise the temperature of the air gas, since the power generation of the fuel cell is not sufficient at the time of starting below freezing point, the compressor that supplies the compressed air to the fuel cell using the battery power is operated at a high pressure.

  However, if the air temperature at the fuel cell inlet is to be raised above the specified temperature only by adjusting the air flow rate and pressure, the upper limit temperature of the aftercooler that cools and adjusts the air discharge temperature of the compressor and the temperature of the air discharged from the compressor. In addition, there is a risk of exceeding the upper limit temperature of the humidifier that humidifies the air supplied to the fuel cell. For this reason, there existed a possibility of damaging the structure of an air supply system.

  Also, if the air temperature rise time is shortened, the air temperature may exceed the discharge temperature or the upper limit temperature described above, so it is difficult to shorten the temperature rise time and quickly obtain stable power. The problem of becoming was invited.

  The present invention has been made in view of the above, and an object of the present invention is to provide a fuel cell system capable of smoothly starting the system in a short time even in a low temperature environment.

In order to achieve the above object, the means for solving the problems of the present invention includes a fuel cell that generates power by a chemical reaction between a fuel gas and an oxidant gas, and the oxidant gas at a set flow rate and pressure. An oxidant gas supply means for supplying to the fuel cell, a humidifying means for humidifying the oxidant gas compressed by the oxidant gas supply means, and a target air flow rate of the oxidant gas supplied to the fuel cell when the system is started. A fuel cell system having a control means for calculating a target air pressure and controlling the oxidant gas supply means so that an oxidant gas is supplied to the fuel cell at the calculated target air flow rate and target air pressure; The control means compresses the oxidant gas to a set pressure by the oxidant gas supply means when the temperature of the oxidant gas supplied to the fuel cell is a low temperature equal to or lower than a predetermined value. When the gas temperature is raised to the target temperature, the outlet oxidant gas temperature of the oxidant supply means, the humidifier inlet oxidant gas temperature, and the fuel cell inlet oxidant gas temperature all do not exceed the respective upper limit temperatures. The oxidant gas supply means is controlled as described above.

  According to the present invention, when the temperature of the oxidant gas supplied to the fuel cell is raised during the low temperature startup of the system, the upper limit temperature of the fuel cell inlet temperature, the humidifier inlet temperature, and the oxidant gas supply device outlet temperature is not exceeded. Thus, it becomes possible to raise the temperature of the oxidant gas. As a result, the system can be started up smoothly in a short time without damaging the configuration of the air supply system.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS The best embodiment for carrying out the present invention will be described below with reference to the drawings.

  FIG. 1 is a diagram showing a configuration of a fuel cell system according to Embodiment 1 of the present invention. The system of Embodiment 1 shown in FIG. 1 includes a fuel cell 1, a hydrogen supply tank 2, a hydrogen pressure regulator 3, a purge adjustment valve 4 and a hydrogen circulation pump 5 as a fuel gas system configuration, and an oxidant gas system configuration. As an air supply device 6, an aftercooler (A / C) 25, a humidifier 26 and an air pressure regulating valve 7, and a cooling water pump 8.

  The fuel cell 1 generates electricity by chemically reacting the hydrogen of the supplied fuel gas and the air of the oxidant gas, and the heat generated by the electricity generation is removed by the cooling water circulated through the fuel cell 1 by the cooling water pump 8. Is done. Hydrogen supplied to the fuel cell 1 is stored in the hydrogen supply tank 2, and the hydrogen stored in the hydrogen supply tank 2 is pressure-adjusted by the hydrogen pressure regulator 3 and supplied to the fuel cell 1. A portion of the unused hydrogen discharged from the fuel cell 1 is exhausted via a purge adjustment valve 4 that purges nitrogen accumulated in the circulating hydrogen system, while the remaining hydrogen is passed through a hydrogen circulation pump 5. It is returned to the hydrogen inlet side of the fuel cell 1 and circulated. The circulated circulating hydrogen is mixed with hydrogen derived from the hydrogen supply tank 2 and supplied to the fuel cell 1 as mixed hydrogen. The circulating hydrogen circulating in the circulating hydrogen system contains a lot of water vapor, and is mixed with dry hydrogen derived from the hydrogen supply tank 2 so that the hydrogen supplied to the anode electrode of the fuel cell 1 is humidified. Yes.

  On the other hand, the oxidant gas air that has been discharged from the air supply device 6, adjusted in temperature by the aftercooler 25, and humidified by the humidifier 26 is supplied to the fuel cell 1, and is unused from the fuel cell 1. The air is pressure-adjusted via an air pressure regulating valve 7 that adjusts the pressure of the air introduced into the cathode electrode of the fuel cell 1 and exhausted. The air supply device 6 includes a compressor that compresses air, and the air compressed by the compressor is supplied to the fuel cell 1. Therefore, the pressure and flow rate of the air supplied to the fuel cell 1 are set and adjusted based on the rotational speed of the compressor and the valve opening degree of the air pressure regulating valve 7. Moreover, since the air supplied to the fuel cell 1 is compressed by the compressor of the air supply device 6, it generates heat by the compression. Therefore, since the temperature of the air supplied to the fuel cell 1 is raised by the air supply device 6 and the air pressure regulating valve 7, the air supply device 6 and the air pressure regulating valve 7 function as a temperature raising means for raising the temperature of the air. Since the calorific value of air varies depending on the pressure and flow rate of air, the temperature rise of air is controlled based on the pressure and flow rate.

  The fuel cell system further includes a power conversion device 9, a load device 10, a battery 11, a battery controller 12, and various sensors.

  The electric power obtained by the power generation of the fuel cell 1 is converted into electric power corresponding to the specifications of the load device 10 or the battery 11 by the power conversion device 9 and given to the load device 10 and / or the battery 11. The load device 10 is composed of, for example, an inverter or a drive motor that consumes power obtained by power generation. When the load device 10 is configured by an inverter, a load such as a drive motor that consumes power obtained by power generation is connected to the inverter. The The load device 10 sets a power generation value and takes out a load current from the fuel cell 1 in accordance with the set power generation value.

  The power converted by the power conversion device 9 and applied to the battery 11 is stored in the battery 11, and the stored power is supplied to the air supply device 6 that is an auxiliary machine when the system is started, for example, to drive the compressor It bears a part of electric power. The battery controller 12 is connected to the battery 11, measures the SOC (State of charge) of the battery 11, and the SOC measured by the battery controller 12 is used to estimate the power that can be supplied from the battery 11. .

  As various sensors, the hydrogen inlet of the fuel cell 1 is provided with a pressure sensor 13 for measuring the pressure of hydrogen introduced into the fuel cell 1 and a temperature sensor 14 for measuring the temperature. A temperature sensor 15 that measures the temperature of the cooling water discharged from the fuel cell 1 is provided at the cooling water flow path outlet of the fuel cell 1. The fuel cell 1 is provided with a voltage sensor 16 that measures the voltage of the fuel cell constituting the fuel cell 1.

  A temperature sensor 17 that measures the temperature of the air sucked into the air supply device 6 is provided on the upstream side of the air supply device 6. Downstream of the air supply device 6, a flow sensor 27 that measures the flow rate of the air discharged from the air supply device 6 and a temperature sensor 28 that measures the temperature of the air are provided. A temperature sensor 29 that measures the temperature of the air discharged from the aftercooler 25 and the temperature of the air introduced into the humidifier 26 is provided on the downstream side of the aftercooler 25. At the air inlet of the fuel cell 1, a pressure sensor 18 that measures the pressure of air introduced into the fuel cell 1 and a temperature sensor 19 that measures temperature are provided.

  Between the fuel cell 1 and the power converter 9, a current sensor 20 that measures a load current flowing from the fuel cell 1 to the power converter 9 and a voltage that measures a voltage applied from the fuel cell 1 to the power converter 9. A sensor 21 is provided. Between the fuel cell 1 and the battery 11, there are provided a voltage sensor 22 for measuring a voltage applied from the power converter 9 to the battery 11 and a current sensor 23 for measuring a current. In the vicinity of the battery 11, a temperature sensor 24 that measures the temperature near the battery 11 that approximates the temperature of the battery 11 is provided.

  Although not shown, the fuel cell system includes a control unit. The control unit functions as a control center for controlling the operation of the system, and is provided with resources such as a CPU, a storage device, and an input / output device necessary for a computer that controls various operation processes based on a program, for example, a microcomputer Etc. The control unit reads signals from all the sensors (not shown) in this system including the various sensors shown in FIG. 1, and based on the read various signals and the control logic (program) stored in advance in advance. Commands are sent to each component of the system including the air supply device 6 and the air pressure regulating valve 7, and all necessary for operating / stopping the system including the temperature rising process at startup and calculation of the power balance described below are described. Control and control the overall operation.

  Next, with reference to the flowchart shown in FIG. 2, the procedure of the temperature raising control process for the air supplied to the fuel cell 1 when the system is started will be described.

  In FIG. 2, first, the system is started as usual. In the first embodiment, since the hydrogen supply is configured as a pressure regulator, hydrogen is supplied to the fuel cell 1 in accordance with the pressure difference from the fuel cell inlet. When the system is started, the purge adjustment valve 4 is opened to generate a pressure difference so that hydrogen is supplied. Further, the target flow rate and the target pressure are input to the control unit, the compressor rotation speed and the pressure adjustment valve opening are calculated by the control unit, and output to the compressor of the air supply device 6 and the air pressure regulating valve 7. The flow rate and pressure of the air supplied to the are controlled (step S200). In the first embodiment, in consideration of interference between the flow rate of air and pressure, a non-interference control method for flow rate and pressure known in control theory is adopted.

  Subsequently, it is determined whether or not the system is activated in the low temperature mode (step S201). In the first embodiment, it is determined whether or not to start in the low temperature mode based on the intake air temperature of the air supply device 6 and the fuel cell outlet cooling water temperature.

  This determination is made according to the procedure shown in the flowchart of FIG. In FIG. 3, it is first determined whether or not the intake air temperature <the threshold value Th1 or the fuel cell outlet cooling water temperature <the threshold value Th2 (step S300). If any one of the requirements is satisfied, the operation is started in the low temperature mode. If neither requirement is satisfied, the operation is started in the normal mode (steps S301 and S202). Here, the threshold values Th1 and Th2 are variables set in advance through experiments and desk studies. In Example 1, for example, Th1 = 0 ° C. and Th2 = 0 ° C. are set.

  Returning to FIG. 2, when starting in the low temperature mode, the heated air is supplied to the fuel cell 1. First, in order to determine the temperature of the fuel cell inlet air temperature, The target temperature is set (step S203). In the first embodiment, target temperatures for the fuel cell inlet air temperature, the compressor discharge temperature, and the humidifier inlet temperature are set. In Example 1, each target temperature was set as the upper limit temperature of each constituent member.

  Next, the target flow rate and the target pressure calculated in the previous step S200 are temperature-corrected so that the fuel cell inlet air temperature becomes the target temperature (step S204). This temperature correction is executed as shown in the control block diagram of FIG. 4A. Based on the fuel cell inlet air temperature, the compressor discharge temperature, and the humidifier inlet temperature, the temperature correction is performed using a known PI controller. This is done by adopting a control method that predicts the characteristics.

  In the control method for predicting the temperature dynamic characteristic using this known PI controller, an experiment for acquiring the temperature dynamic characteristic is performed in advance, and the relationship between the compressor rotation speed and the temperature of each part, the pressure adjustment valve opening degree is obtained from the experimental result. And obtain the relationship data of temperature change. Such an experiment is called a step response experiment and is a well-known method and will not be described. Coefficients K1, K2, L1, L2, M1, and M2 of the following relational expression (Equation 1) are obtained from such experimental data. Each of these coefficients is a vector coefficient aligned in time series (only the prediction time). This is called a system identification or multivariate analysis method, and is a known method, so that the description thereof is omitted.

(Equation 1)
Fuel cell inlet air temperature y1 = K1 × compressor rotational speed u1 + K2 × pressure adjusting valve opening u2
Compressor discharge temperature y2 = L1 × compressor rotational speed u1 + L2 × pressure adjusting valve opening u2
Humidifier inlet temperature change y3 = M1 × compressor rotational speed u1 + M2 × pressure adjusting valve opening u2
For example, when the fuel cell inlet air temperature changes as shown in FIG. 5 when the compressor rotational speed u1 is step-changed from a certain rotational speed to a certain rotational speed, for example, each time point (time t1) , T2...) Is a coefficient. Furthermore, data standardization such as subtracting the average value is performed to create a coefficient. Details are well known in the system identification theory and will be omitted. It is possible to predict future temperature dynamic characteristics by inputting the compressor rotation speed and the pressure adjustment valve opening into the following model equation (Equation 2) having such time-series coefficients.

(Equation 2)
If t is time and a, b, c, d, e, f are coefficients,
y1 (y) = a1 * y1 (t-1) + a2 * y1 (t-2) + K11 * u1 (t-1) + K12 * u1 (t-2)
+ b1 * y1 (t-1) + b2 * y1 (t-2) + K21 * u2 (t-1) + K22 * u2 (t-2)
y2 (y) = c1 * y2 (t-1) + c2 * y2 (t-2) + L11 * u1 (t-1) + L12 * u1 (t-2)
+ d1 * y2 (t-1) + d2 * y2 (t-2) + L21 * u2 (t-1) + L22 * u2 (t-2)
y3 (y) = e1 * y3 (t-1) + e2 * y3 (t-2) + M11 * u1 (t-1) + M12 * u1 (t-2)
+ f1 * y3 (t-1) + f2 * y3 (t-2) + M21 * u2 (t-1) + M22 * u2 (t-2)
In Example 1, fuel cell inlet air temperature predicted value and upper limit value, compressor discharge temperature predicted value and upper limit value, humidifier inlet temperature predicted value and deviation of upper limit value are calculated respectively, and (upper limit value−predicted value) The one with the positive deviation and the smallest absolute value was selected and used for calculating the correction amount. On the other hand, when the deviation of (upper limit value−predicted value) is negative, the one having the largest absolute value is selected and used for the calculation of the correction amount. Moreover, in this Example 1, since each target temperature was made into each upper limit temperature, the deviation of target temperature and estimated temperature was made to become a deviation with upper limit temperature.

  For example, when the deviation between the fuel cell inlet air temperature predicted value and the upper limit temperature (upper limit value−predicted value) is positive and the absolute value is the smallest compared to the others, based on the deviation between the fuel cell inlet air temperature and the target temperature. The correction amount is calculated by the PI controller. This is to prevent the maximum temperature from being deviated by controlling what is most likely to exceed the maximum temperature. When the deviation between the fuel cell inlet air temperature predicted value and the upper limit temperature (upper limit−predicted value) is negative and the absolute value is the largest, the PI controller is based on the deviation between the fuel cell inlet air temperature and the target temperature. The correction amount was calculated with. This is to prevent the upper limit temperature from being deviated by controlling the one having the largest amount of excess upper limit temperature. In addition, when the deviation is positive (not yet overshooted but likely), and when the deviation is negative (already overrun), the negative deviation is selected with priority.

  On the other hand, when there are a plurality of the above conditions and one cannot be selected, the fuel cell inlet air temperature, the compressor discharge temperature, and the humidifier inlet temperature are preferentially selected. This priority order was determined according to whether or not it could withstand to some extent even if the upper limit value was exceeded, based on the temperature tolerance test result of a single component. The above priority order is the order in which the ability to hold when the upper limit is exceeded is weak.

  In addition, the fuel cell air inlet temperature described above is the temperature in the immediate vicinity of the connecting portion between the fuel cell 1 and the air pipe, but may be the temperature of the fuel cell inlet pipe portion or the temperature of the fuel cell manifold portion. . In the first embodiment, since the temperature sensor 19 is easier to attach to the fuel cell inlet piping, this temperature is used for control. The temperature of the fuel cell manifold can be estimated using the material and thickness of the manifold.

  Following the correction of the air flow rate and the air pressure, when the fuel cell inlet temperature is low, the air flow rate correction and the air pressure correction are further corrected (step S205). When the fuel cell inlet temperature is equal to or lower than a predetermined temperature set in advance, the correction of the air pressure is prioritized and the correction of the air flow rate is not performed. That is, when the fuel cell inlet temperature is equal to or lower than the predetermined temperature, only the correction for the air pressure is executed, and the air flow rate is decreased so as to increase the air pressure. On the other hand, when the fuel cell inlet temperature is equal to or higher than a predetermined temperature, both the air pressure and the air flow rate are corrected.

  This temperature correction is performed by setting correction coefficients for the air pressure and the air flow rate in the control block shown in FIG. As shown in FIG. 4B, the correction coefficient for the air pressure is always set to 1 with respect to the fuel cell inlet air temperature, and temperature correction is performed. On the other hand, as shown in FIG. 4C, the correction coefficient for the air flow rate is set to 0 when the temperature is equal to or lower than a predetermined temperature with respect to the fuel cell inlet air temperature, and temperature correction is not performed. On the other hand, if the temperature is equal to or higher than the predetermined temperature, the temperature correction is performed as 1.

  Finally, as shown in the flowchart shown in FIG. 6, it is determined whether or not the fuel cell inlet temperature has reached the target value (= upper limit value), and whether or not to end the series of air temperature raising operations in the low temperature mode. Is determined (step S206). As a result of the determination, when the fuel cell inlet temperature has reached the target value (= upper limit value), the system startup in the low temperature mode is terminated, whereas when it has not reached, the process returns to the previous step S203.

  As described above, in the first embodiment, the air supplied to the fuel cell at the low temperature is targeted by correcting the compressor rotational speed and the pressure adjustment valve opening so that the air temperature at the fuel cell inlet is raised to the target temperature. The temperature can be raised to a temperature, and water generated by power generation in the fuel cell can be prevented from freezing. In this correction, the upper limit temperatures of the fuel cell inlet temperature, the humidifier inlet temperature, and the compressor outlet temperature are not exceeded, so that the air can be heated so as not to exceed the respective upper limit temperatures.

  When correcting the air target flow rate and target pressure, the temperature dynamic characteristics are predicted and the correction amount is calculated, so that delay in temperature control can be prevented, thereby avoiding exceeding the set temperature. can do.

  When the upper limit temperature is not exceeded, correction is made so that the difference between the upper limit temperature of the compressor outlet temperature, humidifier inlet temperature, and fuel cell inlet temperature and the predicted value is the smallest so that the upper limit temperature is not exceeded. It is possible to prevent the compressor outlet temperature, the humidifier inlet temperature, and the fuel cell inlet temperature from exceeding the upper limit temperature.

  On the other hand, when the upper limit temperature is exceeded, correction is performed so that the difference between the upper limit temperature of the compressor outlet temperature, the humidifier inlet temperature, and the fuel cell inlet temperature and the predicted value is the maximum temperature or less. As a result, the temperature exceeding the upper limit temperature can be quickly brought to the upper limit temperature or less.

  When the fuel cell inlet air temperature is equal to or lower than a predetermined value, the correction is made so that only the air pressure is increased. Therefore, the flow rate of the air supplied to the fuel cell 1 is reduced, and the cooled air becomes the fuel. The fuel cell 1 is cooled by being supplied to the battery 1, and the generated water generated by power generation can be prevented from freezing.

  FIG. 7 is a diagram showing a configuration of a fuel cell system according to Embodiment 2 of the present invention. The feature of the first embodiment shown in FIG. 7 is that, compared to the system of the first embodiment, an air bypass unit for leading the air discharged from the air supply device 6 to the air inlet of the fuel cell 1 to the outside. A bypass valve 31 that is controlled to be opened and closed by the control unit is provided in the bypass unit, a temperature sensor 30 that measures the temperature of the air bypass unit is provided, and the opening and closing of the bypass valve 31 is controlled under the control of the control unit. The temperature rise of the air supplied to the battery 1 is controlled, and the others are the same as in the first embodiment.

  Next, with reference to the flowchart shown in FIG. 8, the procedure of the temperature raising control process for the air supplied to the fuel cell 1 when the system is started will be described. In the following description, the description of the operation similar to the processing procedure shown in FIG. 2 is omitted, and only different parts are described.

  In FIG. 8, first, in addition to step S200 of FIG. 2, the bypass valve 31 is opened (step S800).

  Subsequently, after performing the same processing as steps S201 and S202 shown in FIG. 2 (steps S801 and S802), the target temperature is set to what temperature the fuel cell inlet air temperature is to be raised (step S803). . In the second embodiment, the target temperature of the fuel cell inlet air bypass section temperature, the compressor discharge temperature, and the humidifier inlet temperature detected by the temperature sensor 30 is set. The target temperature of the compressor discharge temperature and the humidifier inlet temperature was set to the respective upper limit temperature. As shown in FIG. 9, the target temperature of the air bypass unit is set so that the fuel cell inlet air temperature upper limit value becomes a value that overshoots (overshoots) a predetermined amount. Later, the overshoot amount was set to 0%.

  Next, in the first embodiment, the coefficients K1, K2, L1, L2, M1, and M2 shown in the above (Equation 1) were obtained. In this second embodiment, instead of the fuel cell inlet air temperature, the fuel Similar to the prediction of the battery inlet air temperature, the air bypass section temperature is predicted as shown below, and the air flow rate and the air pressure are corrected as in the first embodiment (step S804).

(Equation 3)
Air bypass section temperature = KK1 × compressor rotation speed + KK2 × pressure adjustment valve opening The coefficients KK1 and KK2 in the above equation are obtained to predict the air bypass section temperature.

The order of priority for correction was the order of compressor, humidifier, and air bypass section temperature.

  Next, as in the first embodiment, correction is further performed on the correction of the air flow rate and the correction of the air pressure (step S805). In the second embodiment, the air bypass section temperature measured by the temperature sensor 30 is used instead of the fuel cell inlet temperature, and temperature correction is performed in the same manner as in the first embodiment, and the air bypass section temperature is a predetermined value. In the following cases, correction is made so that the air flow rate decreases.

  Finally, in addition to the system start completion determination performed in step S206 of the first embodiment, it is determined whether the bypass valve 31 is closed and the supply of air to the fuel cell 1 is started (step S806). This determination is executed according to the procedure shown in the flowchart of FIG. In FIG. 10, first, it is determined whether or not the air temperature of the air bypass section detected by the temperature sensor 30 is equal to or higher than a predetermined temperature Th2 set in advance, and the fuel cell inlet air temperature upper limit is exceeded as shown in FIG. (Step S1000).

  If it goes too far, then, as shown in FIG. 9, it is determined whether or not the air temperature has decreased to the fuel cell inlet air temperature upper limit (step S1001). The determination as to whether or not the settling was made was whether or not the deviation between the upper limit value and the target temperature of the air bypass portion was within a predetermined value, for example, within about 5%. As a result of the determination, when the set value is settled, the bypass valve 31 is closed (step S1002), and the activation of the system is ended.

  Thus, in the second embodiment, in addition to being able to obtain the same effect as the first embodiment, when the fuel cell inlet air temperature is low and below a predetermined value, the air bypasses the fuel cell 1. Therefore, it is possible to prevent cold air from being supplied to the fuel cell 1 and cooling the fuel cell 1 to freeze the generated water.

  Since the temperature of the air bypass section is corrected so as to exceed the upper limit temperature of the fuel cell inlet, the temperature raising time of the air can be shortened.

  Since the overshoot of the temperature of the air bypass section is settled and the air bypass section temperature becomes equal to or lower than the fuel cell inlet temperature upper limit value, the bypass valve 31 is closed and the supply of air to the fuel cell 1 is started. It is possible to prevent the battery 1 from being supplied with air that exceeds the upper limit temperature.

It is a figure which shows the structure of the fuel cell system which concerns on Example 1 of this invention. It is a flowchart which shows the procedure of the processing operation which concerns on Example 1 of this invention. It is a flowchart which shows the procedure which judges whether a system is started by low temperature mode. It is a control block diagram explaining temperature correction of an air flow rate and air pressure. It is a figure which shows the coefficient in the relationship between the rotation speed of a compressor, and air temperature. It is a flowchart which shows the procedure which judges whether the fuel cell inlet_port | entrance temperature became target value. It is a figure which shows the structure of the fuel cell system which concerns on Example 2 of this invention. It is a flowchart which shows the procedure of the processing operation which concerns on Example 2 of this invention. It is a figure which shows the change of the target temperature of an air bypass part. It is a flowchart which shows the procedure which judges whether the completion | finish judgment of system starting and air supply start to a fuel cell are started.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Fuel cell 2 ... Hydrogen supply tank 3 ... Hydrogen pressure regulator 4 ... Purge adjustment valve 5 ... Hydrogen circulation pump 6 ... Air supply device 7 ... Air pressure control valve 8 ... Cooling water pump 9 ... Power converter 10 ... Load device 11 ... Battery 12 ... Battery controller 13, 18 ... Pressure sensor 14, 15, 17, 19, 24, 28, 29, 30 ... Temperature sensor 16, 21, 22 ... Voltage sensor 20, 23 ... Current sensor 25 ... After cooler 26 ... Humidification 27 ... Flow sensor 31 ... Bypass valve

Claims (4)

A fuel cell that generates electricity by a chemical reaction between the fuel gas and the oxidant gas;
Oxidant gas supply means for supplying oxidant gas to the fuel cell at a set flow rate and pressure;
Humidifying means for humidifying the oxidant gas compressed by the oxidant gas supply means;
At the time of starting the system, the target air flow rate and the target air pressure of the oxidant gas supplied to the fuel cell are calculated, and the oxidant gas is supplied to the fuel cell with the calculated target air flow rate and target air pressure. A fuel cell system having control means for controlling the oxidant gas supply means;
When the temperature of the oxidant gas supplied to the fuel cell is a low temperature below a predetermined value, the control means compresses the pressure set by the oxidant gas supply means to compress the oxidant gas at the fuel cell inlet When raising the temperature to the target temperature, the outlet oxidant gas temperature of the oxidant supply means, the humidifier inlet oxidant gas temperature, and the fuel cell inlet oxidant gas temperature should not exceed the respective upper limit temperatures. And controlling the oxidant gas supply means. The control means predicts temperature dynamic characteristics of the outlet oxidant gas temperature, the humidifier inlet oxidant gas temperature, and the fuel cell inlet oxidant gas temperature of the oxidant supply means, and an upper limit temperature corresponding to each of the predicted temperatures. When the predicted temperature is equal to or lower than the upper limit temperature, the oxidant gas supply means is controlled so that the one with the smallest difference from the upper limit temperature does not exceed the upper limit temperature. 2. The fuel cell system according to claim 1, wherein the oxidant gas supply means is controlled so that the difference between the predicted temperature and the upper limit temperature is not more than the upper limit temperature when the temperature exceeds the upper limit temperature. When the fuel cell inlet oxidant gas temperature is equal to or lower than a predetermined value, the control means controls the oxidant gas supply means so that the pressure of the oxidant gas is prioritized over the flow rate and only the pressure is increased. The fuel cell system according to claim 1 or 2, characterized in that An oxidant gas bypass means for selectively branching the oxidant gas derived from the oxidant gas supply means;
When the fuel cell inlet oxidant gas temperature is equal to or lower than a predetermined value, the control means causes the oxidant gas bypass means to branch the oxidant gas so that the temperature of the branched oxidant gas exceeds the fuel cell inlet upper limit temperature. The oxidant gas bypass means when the temperature of the branched oxidant gas becomes equal to or lower than the upper limit temperature of the fuel cell inlet when the excess of the temperature of the oxidant gas branched thereafter is settled. The fuel cell system according to any one of claims 1, 2, and 3, wherein branching of the oxidant gas by the gas is stopped.

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