JP2005243491A - Fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell system capable of correctly controlling the amount of purge. <P>SOLUTION: The fuel cell system discharges anode offgas by opening and closing a purge valve (SV5) connected to an outlet of a fuel cell 10. The fuel cell system has a construction 20 which enables to control the open and close operation of the purge valve (SV5) according to the pressure at the outlet of the fuel cell, when purging. In the case of purging, the pressure at the outlet of the fuel cell is referred and the open and close operation of the purge valve is controlled according to the amount of the pressure at the outlet of the fuel cell, that is, a time duration and a frequency of the purge or the flow rate in the case that the purge valve is a valve controllable in the flow rate is controlled, and thus the gas can be discharged at an estimated flow rate. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a fuel cell system including a purge valve, and more particularly to a technique for controlling purge.

In a system using a fuel cell, in a system that supplies fuel gas to a fuel electrode, nitrogen contained in water and air generated by an electrochemical reaction accumulates as impurities, so a purge that discharges hydrogen gas for a certain period of time is performed. Sometimes. For example, in Japanese Patent Application Laid-Open No. 2002-289237, a shut valve is provided in an exhaust passage branched from a circulation path on the fuel electrode side, and when the concentration in the circulating hydrogen gas increases, the shut valve is opened to circulate. A part of hydrogen gas containing impurities is discharged (Patent Document 1).
JP 2002-289237 A (paragraph number 0064)

  However, the flow rate of the gas passing through the valve is affected by the pressure before and after the valve. Since the above conventional technology does not consider the pressure upstream or downstream of the shut valve, impurities discharged are expected. There was a case where it deviated from the emission amount as it was.

  Therefore, an object of the present invention is to provide a fuel cell system capable of accurately controlling the purge amount.

  In order to solve the above-described problems, the present invention provides a fuel cell system that opens and closes a purge valve connected to an outlet of a fuel cell to discharge anode off gas, and performs purging according to the outlet pressure of the fuel cell. Thus, the open / close state of the purge valve can be controlled.

  The flow rate of the gas passing through the purge valve, that is, the purge amount is affected by the pressure on the primary side of the purge valve corresponding to the upstream side and the pressure on the secondary side of the purge valve corresponding to the downstream side. According to the above configuration, when purging, the outlet pressure of the fuel cell is referred to, and the open / close state of the purge valve is controlled according to the outlet pressure equivalent amount, that is, the purge time length or frequency, or the purge valve When is a valve capable of controlling the flow rate, the flow rate is controlled, so that the gas having a predetermined flow rate can be discharged.

  Here, “the outlet pressure of the fuel cell” is a general term for the pressure of the gas that flows into the fuel cell and is discharged after being subjected to an electrochemical reaction, and is not limited to a specific piping position. . The "outlet pressure" is not only the direct pressure measured by the pressure detection means, but also the value corresponding to the pressure that can be estimated from the power generation amount, load, and other factors of the fuel cell is handled as this "outlet pressure". be able to.

  The “open / closed state” is a concept that includes not only opening / closing of the valve but also valve opening and opening / closing time.

  For example, the outlet pressure of the fuel cell may be the anode outlet pressure. This is because the anode outlet pressure is the pressure on the primary side of the purge valve and is an element that affects the flow rate of the purge valve when the purge valve is opened. Here, the “anode outlet pressure” is a general term for the pressure in the downstream direction from the fuel gas discharge port of the fuel cell, and refers to a pressure that can be detected up to the inlet of the purge valve.

  Further, the outlet pressure of the fuel cell can be set as the cathode outlet pressure. The secondary pressure of the purge valve is also an element that affects the flow rate of the purge valve when the purge valve is opened. The cathode outlet pressure is the pressure of the air outlet, and the secondary side of the purge valve is also the outlet. Therefore, the cathode outlet pressure is correlated with the pressure on the secondary side of the purge valve. Here, the fuel cell system further includes a configuration for merging the anode off-gas and the cathode off-gas. According to this configuration, for example, the cathode off gas is joined to dilute the anode off gas, and the pressure of the cathode off gas corresponds to the pressure on the secondary side of the purge valve. Here, the “cathode outlet pressure” is a general term for the pressure downstream from the air outlet of the fuel cell. The pressure near the junction of the cathode offgas and the anode offgas, or the purge valve retroactively from the junction. This is the pressure on the secondary side of the purge valve up to the outlet.

  Here, it is preferable to control the opening and closing of the purge valve by correcting the outlet pressure of the fuel cell according to the atmospheric pressure. The pressure on the secondary side of the purge valve is often controlled to be close to atmospheric pressure, but if it deviates from atmospheric pressure at low altitudes such as high places, it is preferable to make corrections according to fluctuations in the atmospheric pressure. It is. This is particularly necessary when the pressure on the secondary side of the purge valve is obtained by estimation calculation based on the secondary pressure under atmospheric pressure in the lowland.

  It is also preferable that the outlet pressure of the fuel cell is a differential pressure between the anode outlet pressure and the cathode outlet pressure. This is because the differential pressure between the primary side and the secondary side of the purge valve is also an element that affects the flow rate of the purge valve when the purge valve is opened.

  Further, it is preferable to integrate the purge valve flow rate equivalent value during the period in which the purge valve is open, and to correct the opening and closing of the purge valve according to the integrated flow rate equivalent value. Since the purged anode off-gas may burn if it is at a high concentration, it is necessary to discharge the anode off-gas below a combustible concentration. According to the above configuration, the integrated amount of the anode off-gas that has flowed through the purge valve is monitored, and the open / close state of the purge valve is controlled (for example, closed) before the amount easily burns.

  For example, the opening and closing of the purge valve is controlled so that the flow rate equivalent value has a predetermined reference amount as an upper limit. By setting the reference amount smaller than the combustible flow rate of the anode off gas, it is possible to avoid burning of the anode off gas.

  As described above, according to the present invention, the outlet pressure of the fuel cell is referred to, and the opening and closing of the purge valve is controlled in accordance with the outlet pressure equivalent amount. Therefore, the required amount of anode off-gas can be discharged, and the purge amount can be accurately set. It can be controlled.

  Next, preferred embodiments for carrying out the present invention will be described with reference to the drawings. The following embodiment is merely one embodiment of the present invention, and the present invention is not limited thereto and can be applied.

(Embodiment 1)
In the first embodiment, the purge control method of the present invention is applied to a fuel cell system mounted on a moving body such as an electric vehicle. FIG. 1 shows an overall system diagram of the fuel cell system. As shown in FIG. 1, the fuel cell system cools the fuel cell stack 10, a system for supplying hydrogen gas as a fuel gas to the fuel cell stack 10, a system for supplying air as an oxygen source, and the fuel cell stack 10. And a system for doing so.

The fuel cell stack 10, a hydrogen gas, air, and a separator having a flow path of the cooling water, MEA sandwiched by a pair of separators (M embrane E lectrode A ssembly) and, stacking a plurality of cells composed of a stacked structure It has. The MEA has a structure in which a polymer electrolyte membrane is sandwiched between two electrodes, a fuel electrode and an air electrode. The fuel electrode is provided with a fuel electrode catalyst layer in the form of a porous support layer, and the air electrode is provided with an air electrode catalyst layer on the porous support layer. Since a fuel cell causes a reverse reaction of water electrolysis, hydrogen gas, which is an anode gas, is supplied to a fuel electrode side, which is an anode (cathode), and an air electrode side, which is a cathode (anode). Cathode gas (air) containing oxygen is supplied, and a reaction such as equation (1) is caused on the fuel electrode side, and a reaction such as equation (2) is caused on the air electrode side to circulate electrons and flow current. Is.

H ₂ → 2H ⁺ + 2e− (1)
2H ⁺ + 2e − + (1/2) O ₂ → H ₂ O (2)
The anode gas supply system includes a hydrogen tank 11 as a hydrogen gas supply source, a main valve SV1, a pressure regulating valve RG, a fuel cell inlet shutoff valve SV2, a fuel cell stack 10 and a fuel cell outlet shutoff valve SV3, and a gas-liquid separator 12. And a shutoff valve SV4, a hydrogen pump 13, and a check valve RV. In the fuel cell system of Embodiment 1, the circulation path R is formed by connecting the output of the check valve RV to the upstream side of the pressure regulating valve RG.

  The hydrogen tank 11 is filled with high-pressure hydrogen gas. As a hydrogen supply source, various types such as a hydrogen tank using a hydrogen storage alloy, a hydrogen supply mechanism using a reformed gas, a liquid hydrogen tank, and a liquefied fuel tank can be applied in addition to a high-pressure hydrogen tank. The main valve SV1 controls the supply of hydrogen gas. The pressure regulating valve RG determines the pressure in the circulation path R. The fuel cell inlet shut-off valve SV2 and the outlet shut-off valve SV3 are closed when the fuel cell power generation is stopped.

  The gas-liquid separator 12 removes moisture and other impurities generated by the electrochemical reaction of the fuel cell stack 10 during normal operation from the hydrogen off-gas and discharges them to the outside through the shutoff valve SV4. The hydrogen pump 13 forcibly circulates hydrogen gas in the circulation path R based on a control signal from the control unit 20.

  The hydrogen off-gas flowing from the outlet of the fuel cell outlet shut-off valve SV3 to the downstream circulation path R to the check valve RV corresponds to the anode off-gas of the present invention, and the pressure detected in these paths is the anode of the present invention. Corresponds to outlet pressure.

  Before the check valve RV, a branch is made to the discharge path, and a purge valve SV5 which is a shutoff valve corresponding to the purge valve of the present invention is provided on the discharge path. The primary side (upstream side) of the purge valve SV5 is provided with a pressure sensor p1 for measuring the pressure of the anode off-gas and a temperature sensor t1 for measuring temperature, and the secondary side (downstream side) of the purge valve SV5 is provided with a cathode A pressure sensor p2 for measuring the off-gas pressure is provided. In the following embodiment, the pressure on the secondary side is obtained by estimation without relying on the pressure sensor p2. Each valve is opened and closed in response to a control signal from the control unit 20.

  The cathode gas supply system includes an air cleaner 21, a compressor 22, and a humidifier 23. The air cleaner 21 purifies the outside air and takes it into the fuel electric system. The compressor 22 changes the amount of air and the air pressure supplied to the fuel cell stack 10 by compressing the introduced air based on the control signal of the control unit 20. The humidifier 23 exchanges moisture between the compressed air and the cathode off-gas to add an appropriate humidity. A pressure sensor p3 is provided in the vicinity of the air intake port of the air cleaner 21 so that the external atmospheric pressure (atmospheric pressure) can be detected.

  The cathode offgas discharged from the fuel cell stack 10 is supplied to the diluter 14 and mixed with the anode offgas discharged from the purge valve SV5. That is, the cathode offgas is configured to dilute the combustible anode offgas. For this reason, the anode off-gas and the cathode off-gas have a pressure in the vicinity of atmospheric pressure, and the pressure difference between them is not large. For this reason, the pressure on the secondary side immediately after the purge valve SV5 is almost atmospheric pressure and close to the pressure of the cathode off gas.

  The cooling system for the fuel cell stack 10 includes a radiator 31, a fan 32, and a cooling pump 33, and cooling water is circulated and supplied into the fuel cell stack 10.

The control unit 20 is a known computer system, such as ECU (E lectric C ontrol U nit ), by the CPU (not shown) software program stored in the ROM or the like, not shown (central processing unit) is sequentially executed, the It is possible to cause the system to implement the purge control method of the present invention.

  In the above configuration, when hydrogen gas as the anode gas and air as the cathode gas are supplied to the fuel cell stack 10, the electrochemical reaction shown in the formulas (1) and (2) occurs to generate power. As power generation continues, impurities are generated and accumulated. Since the circulation path of the cathode off gas is not formed, and the cathode off gas is discharged through the diluter 14, there is little adverse effect of impurity accumulation. On the other hand, since the anode off gas circulates in the circulation path R, impurities are accumulated over time. For this reason, it is necessary to periodically perform a purge to open the purge valve SV5 and discharge the cathode off gas containing impurities. In the present embodiment, when purging is performed, the opening and closing of the purge valve SV5 is controlled in accordance with the outlet pressure of the fuel cell stack 10.

  That is, the flow rate q of the gas passing through the purge valve is as follows, assuming that the primary side pressure is P1, the secondary side pressure P2, the differential pressure between the primary side pressure and the secondary side pressure is ΔP, and the primary side gas temperature is T. There is a relationship.

q ∝√ (ΔP * P2) * √ (1 / T) (3)
ΔP = P1-P2
4 shows the relationship between the gas temperature and the gas flow rate when the secondary pressure of the shut-off valve is fixed, and FIG. 5 shows the relationship between the gas temperature and the gas flow rate when the primary pressure of the shut-off valve is fixed. ing. As shown in FIG. 4, when the primary pressure of the shut-off valve is increased, the gas flow rate is increased. Further, as shown in FIG. 5, the flow rate increases when the secondary pressure of the shut-off valve is decreased. In either case, there is some influence of gas temperature. These characteristic diagrams represent the relationship of Expression (3).

  In the present embodiment, in view of the equation (3), the estimated value of the primary pressure P1 of the purge valve SV5 and the secondary pressure P2 of the purge valve SV5 is obtained to obtain the flow rate q of the anode off gas to be purged, and the purge valve SV5 Control the time and frequency of opening.

  Here, impurities accumulate for several reasons. First, there are impurities left over from the previous run. Since this impurity decreases with the lapse of time since the previous shutdown, it can be obtained by referring to the map of this decrease characteristic.

  Next, impurities such as nitrogen leak from the air electrode side through the MEA electrolyte membrane. As shown in FIG. 3, since the impurity concentration due to the cross leak changes in accordance with the elapsed time from the start of operation, it can be obtained by referring to a map of the impurity concentration due to the cross leak.

  Furthermore, impurities contained in hydrogen gas are also accumulated. Since the amount of impurities contained in the anode gas itself corresponds to the amount of anode gas used, and the amount of anode gas used corresponds to the amount of power generation (power amount), reference is made to a relationship map between the amount of power generation and the amount of impurities. Can be obtained.

  When the concentration of impurities accumulated due to the above factors increases, it becomes necessary to purge. Based on the flowchart shown in FIG. 2, the purge control method in the present embodiment will be described more specifically.

  First, when it is a start time (S1: YES), it is necessary to consider the impurity accumulation due to the first factor. The control unit 20 refers to a data map showing the relationship between the standing time since the previous operation stop and the decrease in impurities, and grasps the impurity concentration remaining in the circulation path R at the start of operation (S2).

  Next, in order to grasp the amount of accumulated impurities due to the second factor, the control unit 20 refers to a data map showing the relationship between the elapsed time t after the previous purge and the accumulated impurity concentration C as shown in FIG. The impurity accumulation concentration due to the cross leak is grasped (S3).

  Further, in order to grasp the accumulated amount of impurities due to the third factor, the control unit 20 refers to the total power generation amount after the previous purge, estimates the total usage amount of the anode gas, and is caused by the lack of purity of the hydrogen gas determined based on it. Then, the accumulated impurity concentration is grasped (S4).

  The control unit 20 adds the impurity concentrations determined by the first factor, the second factor, and the third factor, respectively, and calculates the impurity concentration accumulated after the previous purge (S5).

  When the impurity concentration is obtained, the purge flow rate necessary for discharging the impurity of that concentration is determined. Therefore, the control unit 20 refers to the data map of the impurity concentration and the necessary purge flow rate to determine the purge flow rate at a constant temperature. (S6). Here, the temperature of the anode off gas is determined in relation to the number of times purge is executed. The control unit 20 refers to the data map indicating the relationship between the two, and estimates the anode off-gas temperature determined from the number of purges from the start of operation (S8). Of course, the primary pressure may be directly measured by referring to the detection signal from the temperature sensor t1.

  Next, in order to obtain the secondary pressure of the purge valve, the control unit 20 refers to the required load amount of the fuel cell system, and the air amount uniquely determined corresponding to the load amount on the fuel cell stack 10, that is, the required power generation amount. That is, the flow rate of the cathode off gas is calculated (S9). The pressure on the secondary side of the purge valve SV5 corresponds to the flow rate of the cathode off gas. Therefore, the control unit 20 estimates the cathode offgas pressure, that is, the secondary pressure of the purge valve SV5 with reference to the data map of the cathode offgas flow rate and pressure (S10).

  Here, the data map for estimating the pressure of the cathode offgas indicates the relationship at atmospheric pressure, and the electric vehicle is traveling in the highland, and the external atmospheric pressure deviates from the standard atmospheric pressure (for example, 1013 hPa) in the lowland. Needs to be corrected according to the degree of the deviation. Therefore, the control unit 20 refers to the detection signal of the pressure sensor p3 capable of measuring the atmospheric pressure, and determines the secondary side pressure of the purge valve SV5 calculated in step S10 according to the external air pressure obtained from the detection signal. Is corrected (S11).

  When the secondary pressure of the purge valve SV5 can be estimated, the control unit 20 measures the primary pressure of the purge valve SV5 with reference to the detection signal of the pressure sensor p1 (S12). As a result, since the cathode offgas temperature T, the primary pressure P1 and the secondary pressure P2 of the purge valve SV5, which are parameters necessary for the calculation of the expression (3), can be grasped, the control unit 20 The flow rate of the gas that can flow through the purge valve SV5 can be determined by referring to the calculation formula (3) in consideration of the constraints determined from the effective sectional area of SV5 or the data map showing the relationship shown in FIGS. Ask. The valve opening time t1 of the purge valve SV5 is obtained from the flow rate of the purge valve SV5 and the necessary purge flow rate for discharging the impurities obtained in step S5 (S13).

  Here, the anode off gas needs to be diluted with the cathode off gas. This is because if the concentration of the anode off gas is excessively higher than a predetermined reference value, there is a possibility of burning. Therefore, the control unit 20 determines the time t2 during which the purge valve SV5 can be opened to the maximum from the maximum amount of cathode offgas that can be discharged in consideration of the flow rate of the cathode offgas determined in step S9 (S14). If it is the time below the said time t2, the possibility that the off-gas diluted and exhausted will burn can be suppressed.

  Therefore, the control unit 20 compares the valve opening time t1 calculated from the viewpoint of impurity removal with the valve opening time t2 calculated from the viewpoint of combustion prevention (S15), and if the former exceeds the latter ( (S15: YES) The valve opening time t2 is selected as the upper limit value (S16). If the former is less than the latter (S15: NO), the valve opening time t1 is selected (S17).

  In the above embodiment, the secondary side pressure of the purge valve SV5 is obtained by estimation calculation, but it may be directly measured by referring to the detection signal of the pressure sensor p2.

  According to the first embodiment described above, since the flow rate of the purge valve SV5 is accurately obtained from the pressure of the anode offgas and the pressure of the cathode offgas of the fuel cell stack 10 and the purge time length is determined, impurities can be reliably discharged. Can do.

  Further, according to the first embodiment, since the atmospheric pressure is measured and the cathode offgas pressure is corrected according to the measured value, even if the fuel cell system is in a place where the atmospheric pressure such as the high altitude is different from the low altitude. Purge control can be performed accurately.

  Furthermore, according to the first embodiment, the purge control is performed so as not to exceed the maximum purgeable time, so that the possibility of burning off-gas can be reliably suppressed.

(Embodiment 2)
In the first embodiment, the flow rate that can pass through the purge valve is estimated in advance and the valve opening time is determined, but in the second embodiment of the present invention, instead of determining the valve opening time, the flow rate through the purge valve is integrated, The opening and closing of the purge valve is controlled based on whether or not this integrated amount reaches the required purge flow rate.

  The fuel cell system used in the second embodiment is the same as that shown in the first embodiment. In the first embodiment, the purge secondary pressure is obtained by calculation. In the present embodiment, the secondary side pressure may be estimated by the same method, but here, for the sake of simplicity, the detection signal of the pressure sensor p2 that directly measures the secondary side pressure of the purge valve SV5 is used. Shall be used.

  FIG. 6 shows a flowchart for explaining the purge control in the second embodiment. Since the grasp of the required purge flow rate is the same as the processing (S1 to S6) in the first embodiment, the description is omitted. That is, it is assumed that the grasp of the required purge amount has been completed when the process proceeds to the flowchart of FIG.

  When performing the purge process (S21: YES), the control unit 20 first opens the purge valve SV5 (S22). Here, as shown in FIG. 7, a pressure anxiety point region exists immediately after the valve is opened. Therefore, the control unit 20 waits until the pressure is stabilized (S23), and starts integrating the flow rate.

  In order to integrate the flow rate, the controller 20 identifies the primary pressure P1 of the purge valve SV5 with reference to the detection signal of the pressure sensor p1 (S24), and refers to the detection signal of the pressure sensor p2 to detect the purge valve SV5. Secondary side pressure P2 is specified (S25). Then, the pressure difference ΔP of the purge valve is calculated by subtracting the secondary pressure from the primary pressure P1 (S26).

  If the pressure difference ΔP, the primary side pressure P1, and the secondary side pressure P2 are determined, the flow rate q per short time is determined in consideration of the effective sectional area of the purge valve SV5. The control unit 20 calculates the flow rate q (S27), and performs a cumulative calculation of adding the currently calculated flow rate q to the previous integrated value Qn−1 (S28).

  As long as the integrated value Q does not exceed the predetermined value Qth (S29: NO), the integration calculation is repeated (S24 to S28). The predetermined value Qth can be the required purge flow rate calculated in the first embodiment. Also, the upper limit amount of purgeable time may be used to prevent off-gas combustion. That is, the same determination may be made by converting the comparison of the valve opening times performed in steps S15 to S17 of the first embodiment into the comparison of the flow rates.

  When the integrated value Q exceeds the predetermined value Qth (S29: YES), the control unit 20 outputs a control signal for closing the purge valve SV5 and ends the process (S30). At the end of the purge, this integrated value Q is reset to zero.

  As described above, according to the second embodiment, purge control can be performed by integrating the flow rate of the gas that actually passes through the purge valve, and the same effects as those of the first embodiment can be achieved.

  In particular, according to the present embodiment, the purge flow rate can be kept constant even when there is an influence of a change in pressure on the secondary side of the purge valve SV5 (disturbance such as back pressure, atmospheric pressure, and water clogging). The purge amount can be ensured and the fuel cell can be operated stably. Further, it is possible to prevent deterioration in fuel consumption due to excessive purging.

  In the second embodiment, the instantaneous flow rate q passing through the purge valve SV5 is obtained and integrated, but instead the flow rate is uniquely determined even if the pressure difference ΔP of the purge valve is integrated. Alternatively, an integrated flow rate obtained from the pressure difference ΔP may be used.

  In the second embodiment, the secondary side pressure of the purge valve SV5 is measured by a pressure sensor for the sake of simplicity. However, as in the first embodiment, the secondary side pressure is estimated or the secondary side pressure is You may obtain | require by the estimation calculation which considers it as atmospheric pressure, and also adds correction | amendment by an atmospheric pressure sensor.

(Other embodiments)
The present invention is not limited to the above embodiments and can be used with various modifications. For example, the fuel cell system has been applied to a system in which the circulation path R is connected to the upstream side of the pressure regulating valve RV. This form is suitable for the gas leak inspection downstream of the pressure regulating valve RG because the pulsation due to the operation of the hydrogen pump is not transmitted downstream of the pressure regulating valve RG, but is not limited to such a form.

  For example, as shown in FIG. 8, it is also possible to apply the present invention as it is to a fuel cell system in which the circulation path R is connected to the downstream side of the pressure regulating valve RV. According to such a system, since the pressure change of the hydrogen pump 13 in the circulation path R is not transmitted to the upper part of the pressure regulating valve RV, it is advantageous when the gas leak inspection of the main valve SV1 is accurately performed.

  Further, as shown in FIG. 9, the present invention can be applied as it is to a fuel cell system without a circulation path. Furthermore, the present invention may be applied to a system in which the diluter 14 is not provided. In this case, since the cathode off-gas pressure does not directly become the secondary pressure of the purge valve SV5, direct measurement by a pressure sensor or estimation that the secondary pressure is atmospheric pressure is required.

  In addition to controlling the opening and closing time as described above, the purge cutoff valve may be controlled by controlling the valve opening and adjusting the flow rate.

1 is a block diagram of a fuel cell system according to Embodiment 1. FIG. 3 is a flowchart for explaining a purge control method of the fuel cell system according to the first embodiment. The figure which shows the relationship between elapsed time and impurity concentration. The relationship figure of gas temperature when the secondary side pressure is made constant, and valve passage gas flow rate. The relationship figure of gas temperature when the primary side pressure is made constant, and the valve passing gas flow rate. 9 is a flowchart for explaining a purge control method for a fuel cell system according to a second embodiment. The timing chart which shows the relationship between the purge valve opening and closing which concerns on this Embodiment 2, and a primary side pressure, a secondary side pressure, and a pressure loss integrated value. The block diagram of the fuel cell system which concerns on a modification. The block diagram of the fuel cell system which concerns on another modification.

Explanation of symbols

  p1 to p3 ... pressure sensor, t1 ... temperature sensor, RG ... pressure regulating valve, SV1 ... main valve, SV2 ... fuel cell inlet shutoff valve, SV3 ... fuel cell outlet shutoff valve, SV4 ... shutoff valve, SV5 ... purge shutoff valve, RV DESCRIPTION OF SYMBOLS ... Check valve, 10 ... Fuel cell stack, 11 ... High pressure hydrogen tank, 12 ... Gas-liquid separator, 13 ... Hydrogen pump, 14 ... Diluter, 20 ... Control part, 21 ... Air cleaner, 22 ... Compressor, 23 ... Humidification 31 ... Radiator 32 ... Fan 33 ... Cooling water pump

Claims (7)

In the fuel cell system for discharging the anode off gas by opening and closing the purge valve connected to the outlet of the fuel cell,
A fuel cell system configured to be able to control an open / close state of the purge valve in accordance with an outlet pressure of the fuel cell when purging.   The fuel cell system according to claim 1, wherein the outlet pressure of the fuel cell is the anode outlet pressure. The fuel cell system includes a configuration for joining the anode off-gas and the cathode off-gas,
The fuel cell system according to claim 1 or 2, wherein the outlet pressure of the fuel cell is the cathode outlet pressure.   The fuel cell system according to claim 3, wherein opening and closing of the purge valve is controlled by correcting an outlet pressure of the fuel cell according to an atmospheric pressure.   The fuel cell system according to any one of claims 1 to 4, wherein an outlet pressure of the fuel cell is a differential pressure between the anode outlet pressure and the cathode outlet pressure.   The value corresponding to the flow rate of the purge valve in a period during which the purge valve is open is integrated, and the opening and closing of the purge valve is corrected according to the integrated value corresponding to the flow rate. The fuel cell system described in 1. The fuel cell system according to claim 6, wherein opening and closing of the purge valve is controlled such that the flow rate equivalent value has a predetermined reference amount as an upper limit.

Images