JP2006086117A - Fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To estimate the hydrogen concentration of discharging hydrogen which flows in a hydrogen circulating path, without using a hydrogen concentration sensor and to control the power generation of a fuel cell system by using the estimated hydrogen concentration. <P>SOLUTION: The fuel cell system has the discharged hydrogen pressurized, after it has been circulated through the anode 2 of a fuel cell 1 by a hydrogen circulating pump 11, provided in a hydrogen circulating path 9 and recirculates it to a hydrogen supply path 5 for supplying the supply hydrogen of a hydrogen supply source 3 to the anode 2 of the fuel cell. The fuel cell system includes data detecting means 12, 13 for detecting the physical data, caused by the drive of the hydrogen circulating pump 11 caused by the viscosity difference of the hydrogen changing, in response to the operating state of the fuel cell 1, and a hydrogen concentration presuming calculating means for estimating the hydrogen concentration, by converting into hydrogen concentration, based on the physical data detected by the data detecting means 12, 13. Moreover, the data detecting means detects the amount of the pressure rise of the discharged hydrogen as the physical data by the drive of the hydrogen circulating pump 11. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a fuel cell system that controls the power generation capability of a fuel cell by estimating and grasping the fuel gas concentration without using a fuel gas sensor.

  In a polymer electrolyte fuel cell, an electrolyte membrane is sandwiched between an anode electrode (fuel electrode) and a cathode electrode (air electrode), hydrogen (fuel gas) is placed on the anode electrode side, and air (oxidizing gas) is placed on the cathode electrode side. ) Is generated by an electrochemical reaction, but with the passage of time, nitrogen gas and moisture tend to leak from the cathode side to the anode side through the electrolyte membrane. For this reason, when the power generation mode is stopped for a long time, or when the exhaust hydrogen passage freezes and the exhaust valve operation is defective, the amount of nitrogen, moisture, etc. leaking from the cathode side to the anode side increases more and more. The hydrogen concentration is greatly reduced. Therefore, in power generation control of a fuel cell system that reuses exhaust hydrogen, it is necessary to grasp the hydrogen concentration of exhaust hydrogen after passing through the anode from the viewpoint of improving power generation efficiency.

  A hydrogen concentration sensor (gas concentration meter) is used to detect the hydrogen concentration. Since the hydrogen concentration sensor usually reacts with components other than hydrogen, the presence of components other than hydrogen tends to reduce the measurement accuracy. It is expensive because expensive materials such as platinum are used. Further, since the hydrogen concentration sensor has a certain size (physique), there are restrictions on the installation location in the fuel cell system. Therefore, it is not easy to measure the hydrogen concentration of a mass-produced fuel cell system that is greatly limited in cost, size, and the like.

Thus, for example, in the fuel cell system described in Japanese Patent Application Laid-Open No. 2003-197232, the fuel cell is operated on the basis of the voltage between the terminals of the fuel cell and the voltage between the terminals at the optimum hydrogen utilization rate. It is unnecessary. That is, when the ratio of the amount of hydrogen consumed in the fuel cell to the amount of hydrogen supplied to the fuel cell is defined as the hydrogen utilization rate, the hydrogen utilization rate at the point where the voltage between the terminals of the fuel cell suddenly drops, that is, the optimum hydrogen utilization rate is obtained. Based on this, the fuel cell is operated.
JP 2003-197232 A

  However, in the above-mentioned Japanese Patent Application Laid-Open No. 2003-197232, the voltage between the terminals of the fuel cell is measured to determine the hydrogen utilization rate, and the power generation is controlled, and it varies depending on the operating state such as nitrogen gas leak from the cathode side. It is difficult to figure out the possible hydrogen concentration. For this reason, although power generation control is performed without using a hydrogen concentration sensor, there is a problem that cannot be applied to power generation control of a fuel cell system including a hydrogen circulation path in which discharged hydrogen after passing through the anode is recirculated.

  Therefore, an object of the present invention is to provide a fuel cell system capable of estimating the hydrogen concentration in the hydrogen circulation path without using a hydrogen concentration sensor.

  In order to solve the above problems, the present invention provides a fuel gas supply path for supplying fuel gas to a fuel cell, a fuel gas circulation path for returning fuel off-gas discharged from the fuel cell to the fuel gas supply path, and the fuel In a fuel cell system including a fuel gas circulation pump that is provided in a gas circulation path and boosts the fuel off-gas and recirculates the fuel off-gas to the fuel gas supply path, the physics related to the fuel off-gas that varies depending on the operating state of the fuel cell Data detection means for detecting the target data, and fuel gas concentration estimation calculation means for estimating the fuel gas concentration or impurity concentration on the fuel electrode side based on the physical data detected by the data detection means.

  In the present invention, attention is paid to the difference in physical characteristics (pressure, density, viscosity) of each gas in detecting the concentration of the fuel gas or impurity gas in the fuel off-gas discharged from the fuel cell. For example, the viscosity coefficient (viscosity) differs between hydrogen gas corresponding to fuel gas and nitrogen gas corresponding to impurity gas. A fluid in which fuel gas and impurities are mixed (for example, fuel off-gas) exhibits physical characteristics (viscosity and the like) corresponding to the quantitative ratio (concentration) of the fuel gas and impurity gas.

  According to the configuration of the above invention, physical data induced in the fuel gas circulation path or the like by the fuel gas circulation pump drive is detected according to the viscosity of the fuel off gas. Changes in physical data that change in accordance with the operating state of the fuel cell are detected by the data detection means, and the detection result is input to the fuel gas concentration estimation calculation means for calculation processing. Convert to estimate the fuel gas concentration.

  Thus, without using a sensor such as a fuel gas concentration sensor or a fuel gas sensor, the fuel gas concentration can be ascertained based on physical data such as viscosity, that is, according to the operating state of the fuel cell. It becomes possible to efficiently perform power generation control.

  Here, viscosity (viscosity) μ is internal friction between fluids (gases) with different flow velocities, and τ is the shearing stress per unit area, and the fluid velocity gradient is du / dy. Then, it is expressed as μ = τ / (du / dy) [Pa · s]. For example, the viscosity (viscosity resistance) of nitrogen gas or moisture, which is an impurity gas, is higher than that of hydrogen gas as a fuel gas.

  Preferably, the data detection unit detects the pressure increase amount of the fuel off-gas driven by the fuel gas circulation pump as the physical data.

  A pressure increase (pressure difference) occurs between the pressure of the fuel off-gas upstream (pump inlet side) of the fuel gas circulation pump and the pressure of the fuel off-gas downstream (pump outlet side) of the fuel gas circulation pump. Therefore, the pressure increase amount is detected as physical data by the data detection means, and the detection result is calculated by the fuel gas concentration estimation calculation means to estimate the fuel gas concentration. The fuel gas concentration can be estimated and grasped only by measuring the pressure increase by the pump.

  Preferably, the data detection means is formed by pressure sensors respectively arranged upstream and downstream of the fuel gas circulation pump as the physical data, and the pressure increase amount of the fuel off gas by the fuel gas circulation pump is determined by the both pressure sensors. It is detected as the physical data.

  Since the pressure sensors are arranged upstream and downstream of the fuel gas circulation pump, the pressure increase amount of the fuel off gas by the fuel gas circulation pump can be measured. Even at the same gas flow rate, when the viscosity of the fuel off-gas is high, the output difference between the upstream and downstream pressure sensors becomes large, and when the viscosity is low, the output difference between both pressure sensors becomes small. From the output difference, the fuel gas concentration estimation calculation means estimates the viscosity of the fuel off gas, and the concentration of the fuel gas (or impurity gas) of the fuel off gas is estimated from the viscosity.

  Preferably, a check valve is provided in the fuel gas circulation path between the fuel gas circulation pump and the fuel gas supply path, while the data detection means is arranged upstream or downstream of the fuel gas circulation pump. Formed by the pressure sensor.

  A pressure sensor is disposed upstream or downstream of the fuel gas circulation pump in the fuel gas circulation path for returning the fuel off-gas discharged from the fuel cell to the outside to the fuel gas supply path.

  In a mode in which a pressure sensor is disposed upstream of the fuel gas circulation pump, that is, between the fuel gas circulation pump and the anode outlet of the fuel cell, a constant pressure fuel gas is received by the pressure regulating valve on the inlet side. The gas pressure is measured at the outlet side of the fuel cell stack. The fuel cell stack has a large pressure loss (pressure loss), and a pressure smaller than the constant pressure is detected in the fuel off-gas on the outlet side. At this time, the viscosity of the refluxed fuel off gas and the impurity gas permeating from the cathode side affects the pressure loss. As the ratio of the impurity gas with high viscosity (for example, nitrogen gas or water vapor) to the fuel off-gas increases, the pressure loss due to the fluid resistance coefficient increases. Since the gas pressure on the outlet side is detected as a relatively low pressure value at the same flow rate when the impurity gas concentration in the fuel off-gas increases (or the fuel gas concentration decreases), the fuel gas concentration can be estimated. . Water vapor can be removed by a gas-liquid separator.

  Moreover, in the aspect which has arrange | positioned the pressure sensor downstream from the fuel gas circulation pump, ie, the fuel circulation path between the fuel gas circulation pump and the check valve, it depends on the fluid resistance coefficient when the fuel off-gas passes through the check valve. A pressure loss occurs, and the pressure (the pressure is higher than the pressure in the fuel gas supply path) is detected as physical data by the pressure sensor also in this mode. As described above, the pressure of the fuel off-gas detected in this manner becomes smaller as the low-viscosity fuel gas (hydrogen gas) is mixed, so that the fuel gas concentration can be estimated.

  Preferably, the data detection means detects power consumption consumed by driving the fuel gas circulation pump as the physical data.

  Since the power consumption of the fuel gas circulation pump is measured, an impurity having a viscosity different from that of the fuel gas (for example, hydrogen) when the circulation amount (pump rotation speed) of a certain fuel off gas is set as a control target value When the ratio of gas (for example, a gas component such as nitrogen) in the fuel off-gas increases, the power consumption in the fuel gas circulation pump becomes different from the predicted value. In addition, the higher the viscosity of the gas, the more electric power is consumed, so the fuel gas concentration (or impurity gas concentration) can be estimated.

  Preferably, when the estimated calculation value of the fuel gas concentration is calculated by the fuel gas concentration estimation calculating means, based on the calculated calculation value of the fuel gas concentration, open / close control of the fuel gas exhaust valve provided in the fuel gas circulation path, the fuel gas circulation pump Control means for performing at least one of the control of the rotational speed of the engine and the opening / closing control of the pressure regulating valve having a pressure reducing function provided in the fuel gas supply path.

  When the estimated calculation value of the fuel gas concentration is calculated by the fuel gas concentration estimation calculating means, the opening / closing control of the fuel gas exhaust valve, the rotation speed control of the fuel gas circulation pump, or the opening / closing control of the pressure control valve is smoothly performed based on the calculated calculation value. It is possible to perform the power generation control of the fuel cell efficiently.

  Preferably, the physical data relating to the fuel off-gas is data resulting from the viscosity of the fuel off-gas. The viscosity of the fuel off gas can be detected as a pressure loss due to a fluid resistance coefficient when the fuel off gas passes through a portion of the passage.

  Preferably, the fuel gas concentration estimation calculation means estimates the fuel gas concentration (or impurity gas concentration) in the fuel off-gas when the operating state of the fuel cell is constant. By performing data detection under the same operating condition or in a stable operating condition, the fuel gas concentration in the fuel off-gas can be measured more accurately.

  Preferably, the fuel gas concentration estimation calculation means estimates the concentration of the fuel off gas in consideration of the gas temperature. The fuel cell stack is provided with a cooling mechanism so that it can be operated at a constant temperature. However, the fuel gas concentration can be estimated more accurately by considering the temperature of the fuel off-gas related to the viscosity and the fuel cell stack can be more It is possible to accurately estimate the fuel gas concentration.

  Preferably, the data detection means detects the pressure of the fuel off gas or the fuel gas by providing a throttle in the fuel gas circulation path or the fuel gas supply path. Thereby, it is possible to perform pressure detection more easily or at a more appropriate portion (location), which is favorable.

  Preferably, the data detection means estimates the fuel gas concentration from the pump rotation value at a constant value of the upstream / downstream differential pressure of the rotary pump (fuel gas circulation pump). It is also possible to estimate the fuel gas concentration (or impurity gas concentration) from the difference in the rotational speed that obtains a certain differential pressure.

  According to the present invention, it is possible to grasp the fuel gas concentration according to the operating state of the fuel cell without using hydrogen sensors. Further, the power generation control of the fuel cell can be performed efficiently based on the estimated fuel gas concentration.

  Embodiments of a fuel cell system according to the present invention will be described below with reference to the drawings.

  FIG. 1 is a block diagram of a fuel cell system. As shown in the figure, the fuel cell system generally includes a polymer electrolyte fuel cell 1 (sometimes referred to as a “fuel cell stack”), a high-pressure tank 3 that stores hydrogen gas as a fuel gas, A pressure regulating valve (pressure reducing valve) 4 for regulating hydrogen from the high-pressure hydrogen tank 3, a hydrogen supply passage 5 as a fuel gas supply passage for supplying regulated hydrogen to the inlet of the anode 2 of the fuel cell 1, and not shown A humidification module 7 for adding moisture to the air as the oxidizing gas supplied from the air pump, an air supply path 8a for supplying the humidified air to the inlet of the cathode 6 of the fuel cell 1, and the air that has passed through the cathode 6 of the fuel cell 1 Returning hydrogen 8 as a fuel off-gas that passes through the return path 8b that discharges to the outside of the fuel cell 1 and the anode 2 of the fuel cell 1 and is discharged to the outside from the outlet thereof is recirculated to the hydrogen supply path 5 Thereby comprising a hydrogen circulation path 9 as a fuel gas circulation path, and the electronic control unit 10 for controlling the entire system, the. The air supply path 8 a and the return path 8 b constitute an air flow path 8. In the humidification module 7, heat exchange between the exhaust air and the supply air is performed.

  The hydrogen circulation path 9 includes a fixed-volume hydrogen circulation pump 11 as a fuel gas circulation pump for boosting the discharged hydrogen, and data detection for detecting the pressure (physical data) of the discharged hydrogen upstream (on the pump inlet side). A first pressure sensor (pressure gauge) 12 as a means, a second pressure sensor (pressure gauge) 13 for detecting the discharge pressure downstream (pump outlet side), a hydrogen exhaust valve 14 for releasing discharged hydrogen to the outside, A check valve 15 for preventing a back flow of hydrogen from the hydrogen supply path 5 to the hydrogen circulation path 9 is disposed.

  The hydrogen supply path 5 described above reduces high-pressure hydrogen having a concentration of 100% to a pressure of about 100 KPa (1 atm), for example, by the pressure control valve 4, and then supplies hydrogen to the anode 2 at the constant pressure. The pressure control valve 4 and the hydrogen exhaust valve 14 are, for example, normally open solenoid valves that are controlled to open and close based on command signals from an electronic control unit 10 to be described later. The pressure regulating valve 4 may be a mechanical pressure regulating valve or a combination of a mechanical pressure regulating structure and an electromagnetic on-off valve.

  Next, the electronic control unit 10 will be described. The electronic control unit 10 includes a CPU 10a that executes predetermined arithmetic processing according to a preset control program, and a ROM 10b and CPU 10a that store control programs and control data necessary for executing various arithmetic processing in the CPU 10a. Receives signals from each part of the fuel cell system such as the RAM 10c, the first pressure sensor 12 and the second pressure sensor 13 for temporarily reading and writing data necessary for executing various arithmetic processes, and the pressure control valve 4 , The hydrogen circulation pump 11, the hydrogen exhaust valve 14, and the like are provided with an input / output port 10 d for transmitting signals to each part. The timer 10e measures, for example, the open time of the hydrogen exhaust valve 14. The electronic control unit 10 also includes a fuel cell stack and a temperature detector (not shown) that detects the temperature of the exhausted hydrogen.

  The CPU 10a stores a calculation control program as hydrogen (fuel gas) concentration calculation estimation means for estimating the hydrogen concentration. The hydrogen concentration calculation estimating means calculates, for example, the pressure increase amount of the discharged hydrogen by the hydrogen circulation pump 11 from the pressures detected by the first and second pressure sensors 12 and 13, and estimates the hydrogen concentration based on the pressure increase amount. The calculated value is calculated to estimate the hydrogen concentration (or nitrogen concentration). The hydrogen concentration calculation estimating means estimates the hydrogen concentration by other modes described later.

  The electronic control unit 10 further includes an opening / closing control of the pressure control valve 4 and the hydrogen exhaust valve 14 when the CPU 10a determines that the hydrogen concentration in the hydrogen discharged from the hydrogen circulation path 9 has reached a certain estimated calculation value. Alternatively, a control means (control program) for executing increase / decrease control of the rotation speed of the hydrogen circulation pump 11 is provided. As a result, control is performed to increase the hydrogen concentration by increasing the amount of circulating hydrogen by increasing the amount of exhaust hydrogen to the outside of the hydrogen circulation path 9 or increasing the amount of new hydrogen introduced.

Example 1
Next, in the fuel cell system configured as described above, a first embodiment of the procedure for estimating the hydrogen concentration will be described based on the power generation control flowcharts shown in FIGS.

  In the fuel cell system, standby current flows from a battery power source (not shown), but when a main switch (not shown) for operating the fuel cell system is turned on (step S1; YES), the electronic control unit 10 operates. It is determined whether or not the mode is selected (step S2). If it is not the operation mode in step S2 (step S2; NO), the process returns to step S1.

  In step S1, when the main switch is OFF (NO), it is determined that the fuel cell is not operated, the pressure control valve 4 is closed, and the hydrogen circulation pump 11 is stopped (steps S10 and S11). ) The fuel cell does not generate electricity.

  When the electronic control unit 10 determines that the fuel cell 1 is in the operation mode (step S2; YES), the pressure control valve 4 that has been closed is opened (step S3). Hydrogen is depressurized from the high-pressure hydrogen tank 3 and supplied to the anode 2 through the hydrogen supply path 5.

  The electronic control unit 10 operates an air pump (not shown) to supply a predetermined amount of air to the cathode 6 via the humidification module 7 to cause the fuel cell 1 to generate power.

  In the operation mode state, in step S4, the electronic control unit 10 gives a command signal to start the operation of the hydrogen circulation pump 11, and controls the hydrogen circulation pump 11 to operate at a predetermined rotational speed N1.

  For example, when certain operating conditions such as stable operation of the pumps are established, the pressures P1 and P2 (physical offgas) of the discharged hydrogen (fuel offgas) in the hydrogen circulation path 9 are detected by the first pressure sensor 12 and the second pressure sensor 13. Data) are measured (steps S5 and S6), and these measurement data are input to the electronic control unit 10.

  In the electronic control unit 10, the CPU 10a storing the calculation control program for estimating the hydrogen concentration calculates the amount of pressure increase (pressure difference ΔP = P2-P1) generated by driving the hydrogen circulation pump 11 (step S7). A hydrogen concentration corresponding to the pressure increase amount ΔPx is estimated (step S8).

  FIG. 4 shows an example of a map (graph) provided in advance in the electronic control unit 10 for hydrogen concentration estimation. A characteristic map of the temperature parameter Ta corresponding to the current temperature t of the fuel cell stack is selected from the plurality of maps. As shown in the figure, the pressure difference ΔP increases with an increase in the number of revolutions (exhaust hydrogen amount) of the hydrogen circulation pump 11, and further, with a decrease in hydrogen concentration in the exhaust hydrogen (nitrogen concentration increases). The pressure difference ΔP tends to increase. The CPU 10a (hydrogen concentration calculation estimating means) obtains the hydrogen concentration Hx% (or nitrogen concentration Nx%) of the graph passing through the x point corresponding to the rotation speed N1 and the pressure increase amount ΔPx of the hydrogen circulation pump 11 from this map.

In step S9, a comparison determination is made as to whether or not the estimated hydrogen concentration value Hx% obtained in step S8, that is, the estimated hydrogen concentration is equal to or less than the target hydrogen concentration value (target value) Hs%.
If the hydrogen concentration has not decreased (step S9; NO), steps S1 to S9 are repeated, and the discharged hydrogen flowing through the anode 2 and flowing into the hydrogen circulation path 9 is again boosted by the hydrogen circulation pump 11 as it is. Then, it is recirculated to the hydrogen supply path 5 to perform normal operation.

  If it is determined in step S9 that the hydrogen concentration has dropped below the target hydrogen concentration value Hs (step S9; YES), the opening / closing control of the hydrogen exhaust valve 14 and the rotation of the hydrogen circulation pump 11 are performed as shown in FIG. Number increase / decrease control and pressure control valve 4 opening / closing control are selectively executed by the control means of the electronic control unit 10.

  That is, in step S12, the CPU 10a determines whether to control the hydrogen exhaust valve 14 with reference to various condition flags in a fuel cell system (not shown). If it is determined that control is to be performed (step S12; YES), a drive signal is given to the hydrogen exhaust valve 14 for a predetermined time to control it to be in an open state (step S13). Thereby, the amount of hydrogen discharged from the anode 2 to the hydrogen circulation path 9 increases. The discharged hydrogen is sent together with nitrogen (impurities) through a hydrogen exhaust valve 14 to a combustor or a diluter (not shown) for processing. At the same time, new hydrogen is supplied from the pressure control valve 4 to the anode 2. The hydrogen concentration in the fuel cell 1 is increased and the power generation amount is increased (or recovered). Thereafter, the process proceeds to step S14.

  If NO is determined in step S12, the CPU 10a determines whether or not to control the hydrogen circulation pump 11 with reference to various condition flags in a fuel cell system (not shown) (step S15). In the case of YES, the rotation speed of the hydrogen circulation pump 11 is increased (step S16), control for increasing the amount of circulating hydrogen is started, and the process proceeds to step S14. By increasing the amount of circulating hydrogen, drainage of produced water in the anode can be promoted.

  If NO is determined in step S15, the CPU 10a determines whether or not to control the pressure control valve 4 with reference to various condition flags in a fuel cell system (not shown) (step S17). In the case of YES, the pressure control valve 4 is greatly opened (step S18), control for increasing the amount of circulating hydrogen is performed, and the process proceeds to step S14. If NO is determined in step S17, the process proceeds to step S14.

  In steps S14 to S22, the CPU 10a estimates the hydrogen concentration again in the same procedure as in steps S5 to S8 described above.

  That is, the pressure P1 downstream of the circulation pump 11 is detected by the first pressure sensor 12 (step S14), and then the pressure P2 upstream of the pump is detected by the second pressure sensor 13 (step S19). The pressure increase amount ΔP (= P2−P1) is calculated (step S20), and the hydrogen concentration is estimated based on the pressure increase amount ΔP and the rotational speed of the circulation pump 11 (step S21). In step S22, it is determined whether or not the estimated calculation value obtained in step S21, that is, the estimated hydrogen concentration Hx% has reached the target hydrogen concentration (target value) Hs%.

  If the CPU 10a determines in step S22 that the hydrogen concentration of the discharged hydrogen has reached the target value (step S22; YES), that is, if the concentration of the discharged hydrogen in the hydrogen circulation path 9 has increased (step S22; YES), step S23 Corresponding to the control of each control means (steps S12 to S17), the hydrogen exhaust valve 14 is closed, or the rotational speed of the hydrogen circulation pump 11 is reduced to the original rotational speed, or in the case of the pressure regulating valve 4, Return control is performed so that the opening becomes smaller.

  After passing through step S23, it returns to step S1 again, and electric power generation control is performed in continuous operation mode according to each subsequent step.

  On the other hand, if it is determined in step S22 that the estimated hydrogen concentration has not reached the target value (step S22; NO), the process returns to step S1, and the routine is repeated until the target value is reached in step S22.

  As described above, in the embodiment, the map shown in FIG. 4 is provided for each temperature of the discharged hydrogen. By providing a temperature detector in the fuel cell stack or the hydrogen circulation path 9, it is possible to estimate the hydrogen concentration more suitable for the current operation state by detecting the temperature of the discharged hydrogen and selecting a map of the temperature. Become. For example, the fuel cell system includes a cooling device (not shown) and operates at a constant temperature, but the temperature of the device may be lowered when the fuel cell system is started. In such a case, it is possible to improve the accuracy of hydrogen concentration estimation by selecting a map corresponding to the current temperature Ta. Of course, it is also possible to use one standard map that is corrected at the current temperature. More simply, one standard map may be used as it is.

  Further, when the hydrogen circulation path 9 (exhaust hydrogen line) has become defective in valve operation due to freezing or the like, the control means as described above is not controlled to increase the hydrogen concentration, and the command from the electronic control unit 10 is not performed. This activates the abnormality notifying means such as a buzzer and an alarm lamp to stop the operation of the fuel cell.

  According to the above embodiment, since the hydrogen concentration is estimated by converting into the hydrogen concentration based on the pressure increase amount ΔP of the discharged hydrogen by the hydrogen circulation pump 11, the fuel cell 1 of the fuel cell 1 is used without using a hydrogen sensor as in the conventional case. Since the hydrogen concentration according to the operating state can be grasped and the pressure is detected by the pressure sensors 12 and 13 arranged in both the upper and lower flows of the hydrogen circulation pump 11, the hydrogen concentration can be estimated accurately. Further, in order to optimally control the opening / closing control of the hydrogen exhaust valve 14, the hydrogen exhaust amount by the control of the hydrogen exhaust valve 14 and the increase / decrease control of the hydrogen circulation amount by the control of the hydrogen circulation pump 11 or the pressure control valve 4 can be accurately performed. In addition, there is an advantage that it is possible to obtain a fuel cell system that can suppress waste of discharged hydrogen and that is low in cost.

(Example 2)
In the first embodiment described above, the first pressure sensor 12 and the second pressure sensor 13 are arranged in both the upper and lower flows of the hydrogen circulation pump 11 to measure the pressure. Instead, the second pressure sensor 13 is eliminated. Thus, only the first pressure sensor 12 may be used.

  In such a second embodiment, the hydrogen supply path 5 is at a constant pressure (for example, 100 KPa), whereas in the hydrogen circulation path 9 between the anode 2 and the hydrogen circulation pump 11, the fuel cell stack Under the influence of the viscosity of the hydrogen that has passed through 1 (and the recirculated exhaust hydrogen is also mixed), a pressure P1 smaller than the above-mentioned constant pressure is detected. The pressure P1 detected in this manner is such that a smaller pressure value is detected as the degree of high-viscosity nitrogen (impurity gas) mixed into the supplied hydrogen increases. Therefore, the pressure loss ΔP by the fuel cell stack, for example, ΔP = 100 KPa. -Detect P1. Then, the hydrogen concentration can be estimated by referring to a map of ΔP, the rotation speed of the hydrogen circulation pump 11 (discharged hydrogen flow rate), and the concentration curve as shown in FIG.

(Example 3)
In the first embodiment described above, the first pressure sensor 12 and the second pressure sensor 13 are arranged in both the upper and lower flows of the hydrogen circulation pump 11 and the pressure is measured. Instead, the first pressure sensor 12 is eliminated. Thus, only the second pressure sensor 13 may be used.

  In the case of the third embodiment, a pressure loss occurs due to the fluid resistance coefficient when the discharged hydrogen passes through the check valve 15, so in this third embodiment also the pressure P2 (the pressure is , Higher than the pressure of the hydrogen supply path) is detected as physical data. Since the pressure P2 detected in this manner increases as the highly viscous nitrogen gas is mixed in, the pressure loss ΔP (= P2−100 KPa) is detected to map the same as in the second embodiment (see FIG. 4). It is possible to estimate the hydrogen concentration using

Example 4
FIG. 5 shows a fourth embodiment. This figure shows only the portion of the hydrogen circulation path 9 in the overall configuration shown in FIG. In the figure, parts corresponding to those in FIG. 1 are denoted by the same reference numerals, and description thereof is omitted.

  In this embodiment, an orifice (throttle) 9 a is inserted in the hydrogen circulation path 9. The fluid pressure is detected by the pressure sensor 13 upstream of the orifice 9a. Since the fluid pressure changes depending on the viscosity due to the hydrogen concentration of the discharged hydrogen passing through the orifice 9a, referring to the map at each temperature as shown in FIG. 4, the rotation speed of the hydrogen circulation pump 11 (discharged hydrogen flow rate) and the detected pressure are used. The hydrogen concentration x% can be estimated by selecting the curve Gx of the corresponding hydrogen concentration.

(Example 5)
FIG. 6 shows a fifth embodiment. This figure also shows only the hydrogen circulation path 9 in the overall configuration shown in FIG. 1, and the other configurations are the same as those in FIG. In the figure, parts corresponding to those in FIG. 1 are denoted by the same reference numerals, and description thereof is omitted.

In this embodiment, an orifice (throttle) 9 a is inserted in a bypass provided in parallel with the hydrogen circulation path 9. The fluid pressure is detected by the pressure sensor 13 upstream of the bypass orifice 9a. Further, the hydrogen circulation path 9 is provided with a bypass control valve 9 b whose opening and closing is controlled by the electronic control unit 10.
In such a configuration, the bypass control valve 9b is closed only when the fluid pressure of the discharged hydrogen is detected by the pressure sensor 13, and otherwise the bypass control valve 9b is opened. Thereby, an increase in loss in the hydrogen circulation path 9 due to the provision of the orifice 9a is avoided.

Even in the configuration of this embodiment, the fluid pressure varies depending on the hydrogen concentration of the discharged hydrogen passing through the orifice 9a, so the rotation speed of the hydrogen circulation pump 11 (discharged hydrogen flow rate) with reference to the map at each temperature as shown in FIG. ) And the detected pressure, the hydrogen concentration x% can be estimated by selecting the curve Gx of the corresponding hydrogen concentration.
The orifice can be provided not only in the fuel gas circulation path 9 but also in the fuel gas supply path 5. Thereby, the pressure of the fuel off gas and the fuel gas can be detected.

(Example 6)
In each of the above-described embodiments, the pressure of discharged hydrogen in the hydrogen circulation path 9 caused by the hydrogen circulation pump 11 is detected as physical data in each case, and the hydrogen concentration is estimated based on the detected pressure. It is also possible to measure the power consumption consumed by the hydrogen circulation pump 11 as physical data.
In this embodiment, the electronic control unit 10 has a function of detecting the power consumption of the hydrogen circulation pump 11, but does not require the pressure sensors 12 and 13.

FIG. 7 is a graph showing the relationship between the rotation speed of the hydrogen circulation pump (constant volume type) and the pump power consumption. This graph is prepared for each temperature and stored in the electronic control unit 10 as a map.
As shown, the graph for 100% hydrogen is indicated by G1. A graph of hydrogen in which the hydrogen concentration is reduced due to nitrogen mixing is shown by an exponential curve like G2. Here, assuming that the hydrogen circulation gas amount (gas flow rate), that is, the pump rotation speed in the fuel cell system is set at, for example, the rotation speed of the hydrogen circulation pump 11 at 1000 rpm, the operation is performed in a highly viscous gas with a reduced hydrogen concentration. Since the power consumption W2 of the hydrogen circulation pump 11 is larger than the power consumption W1 of the 100% hydrogen concentration, the power consumption difference (W2-W1) is calculated, and the hydrogen concentration is estimated by converting to the hydrogen concentration based on the result. It becomes possible.

  Further, referring to the map of the rotation speed versus power consumption characteristic curve group of the hydrogen circulation pump using the hydrogen concentration measured in advance for each temperature as a parameter as shown in FIG. 9, the hydrogen circulation pump at the current fluid temperature The hydrogen concentration can be estimated from the rotation speed (gas flow rate) of 11 and the power consumption of the pump at the rotation speed.

  10 and 11 show the procedure for estimating the hydrogen concentration in the present embodiment, and the same reference numerals are given to the portions common to the flowcharts shown in FIGS. 2 and 3 in the first embodiment.

  That is, FIG. 10 corresponds to the flowchart of FIG. 2, and FIG. 11 corresponds to the flowchart of FIG. 2 differs from FIG. 2 in that step S5 to step S7 in FIG. 2 are replaced with step S31, and FIG. 11 differs from FIG. 3 in that step S14 to step S20 in FIG. ing. Steps S31 and 32 are steps for calculating the power consumption (W2-W1) of the hydrogen circulation pump. Since the other steps are common, detailed description of the procedure is omitted.

  In step S31, the CPU 10a refers to the map shown in FIG. 7 corresponding to the current exhaust hydrogen temperature. The CPU 10a detects the current rotation speed (for example, 1000 rpm) of the hydrogen circulation pump 11 and the current power consumption W2 of the hydrogen circulation pump 11. The electric power W1 at the current rotational speed (for example, 1000 rpm) is read from the characteristic curve G1 of 100 percent hydrogen stored in advance in the map. The power consumption difference ΔW (= W2−W1) is calculated.

  Further, the hydrogen concentration is read from the map of the hydrogen concentration versus the power consumption difference ΔW at a predetermined rotational speed (for example, 1000 rpm) shown in FIG. The same applies to step S32.

  As another method, the CPU 10a can refer to the map shown in FIG. 9 corresponding to the current exhaust hydrogen temperature. In this case, the CPU 10a detects the current rotation speed of the hydrogen circulation pump 11 (corresponding to the hydrogen flow rate) and the current power consumption W2 of the hydrogen circulation pump 11. The hydrogen concentration is read from the hydrogen concentration parameter of the characteristic curve at the position x where the number of revolutions of the pump and the power consumption W2 intersect. The same applies to step S32.

  Therefore, also in this embodiment, the fuel cell system can be operated by estimating the hydrogen concentration without using a hydrogen sensor as in the above-described embodiments.

  In the above-described embodiment and the first to third modifications, 100% concentration of hydrogen is used for the hydrogen supply path 5, but the present invention can also be applied to a mode of supplying reformed hydrogen.

(Example 7)
12 and 13 show a seventh embodiment of the present invention. FIG. 12 is a flowchart showing the control procedure, and FIG. 13 is a graph for explaining the operation.
In this embodiment, the fact that the rotation speed of the hydrogen circulation pump 11 that generates a predetermined pressure loss ΔP (= P2−P1) in the hydrogen circulation path 9 is reduced when the hydrogen concentration of the discharged hydrogen is lowered is utilized.

  As shown in FIG. 12, when this control mode is started (step S50), the CPU 10a gives a drive signal to the hydrogen circulation pump 11 to operate at a predetermined rotational speed (step S52). When the rotational speed of the hydrogen circulation pump 11 reaches a predetermined rotational speed (step S54), the detected values P1 and P2 of the pressure sensors 12 and 13 are read, and the current differential pressure ΔP (= P2−P1) is calculated (step S56). ).

  The CPU 10a determines whether or not this differential pressure ΔP is equal to the differential pressure ΔPs set in advance as a detection reference (within an allowable range) (step S58). If the deviation is larger than the specified value (step S58; NO), the number of revolutions of the hydrogen circulation pump 11 is increased or decreased to adjust the current differential pressure ΔP to the differential pressure ΔPs (steps S52 to S58). .

  When the differential pressure ΔP becomes equal to the reference differential pressure ΔPs (step S58; YES), the CPU 10a reads the rotational speed Nx of the hydrogen circulation pump 11 at this time (step S60). The CPU 10a refers to the map shown in FIG. 13 and selects a curve corresponding to the rotational speed Nx and the differential pressure ΔPs. The hydrogen concentration of the discharged hydrogen is read from the parameters of this curve (step S62).

When the hydrogen concentration is lower than the reference value, processing such as anode purge for opening the hydrogen exhaust valve 14 (see Steps S12 to S18) is performed (Step S64).
Thus, the fuel gas concentration can be estimated from the pump rotation value when the upstream / downstream differential pressure is constant.

  As described above, the fuel cell system according to the embodiment of the present invention includes a hydrogen supply path that supplies hydrogen supplied from a hydrogen supply source to the anode of the fuel cell, and a hydrogen supply path that supplies hydrogen off-gas discharged from the anode of the fuel cell. And a hydrogen circulation pump that is provided in the hydrogen circulation path and pressurizes the hydrogen off-gas and recirculates the hydrogen off-gas to the hydrogen supply path, according to the operating state of the fuel cell. Data detection means for detecting physical data relating to the fluctuating hydrogen offgas, and hydrogen concentration estimation calculation means for estimating the hydrogen concentration of the hydrogen offgas based on the physical data detected by the data detection means. Prepare.

The data detection means detects the amount of pressure increase of the hydrogen off gas by driving the hydrogen circulation pump as the physical data.
The data detection means is formed by pressure sensors disposed upstream and downstream of the hydrogen circulation pump as the physical data, and the pressure increase amount of hydrogen off-gas by the hydrogen circulation pump is determined by the both pressure sensors. Detected as

The data detection means detects power consumption consumed by driving the hydrogen circulation pump as the physical data.
The physical data related to the hydrogen off gas is data resulting from the viscosity of the hydrogen off gas.

  In addition, a check valve is provided in the hydrogen circulation path between the hydrogen circulation pump and the hydrogen supply path, while the data detection means is formed by a pressure sensor arranged upstream or downstream of the hydrogen circulation pump. is doing.

  When the hydrogen concentration estimation calculation means calculates the hydrogen concentration estimation calculation value, on the basis of this, the hydrogen exhaust valve opening / closing control provided in the hydrogen circulation path, the hydrogen circulation pump rotation speed control, or the above Control means for performing at least any one of opening / closing control of a pressure regulating valve having a pressure reducing function provided in the hydrogen supply path is provided.

  As described above, according to the embodiment of the present invention, since the physical concentration detected by the data detecting means is processed by the hydrogen concentration estimating calculating means to estimate the hydrogen concentration, the hydrogen sensors are not used. The hydrogen concentration according to the operating state of the fuel cell can be grasped, and the power generation control of the fuel cell can be efficiently performed.

  In addition, since the hydrogen concentration is estimated based on the pressure increase of the discharged hydrogen by the hydrogen circulation pump, it is possible to grasp the hydrogen concentration according to the operation state without using hydrogen sensors, and smooth operation control. In addition, the fuel cell system can be realized at a low cost.

  In addition, since the pressure sensors are arranged upstream and downstream of the hydrogen circulation pump, the hydrogen concentration can be accurately estimated.

  In addition, by arranging a pressure sensor upstream or downstream of the hydrogen circulation pump, it is possible to estimate and grasp the hydrogen concentration and detect a decrease in the hydrogen concentration.

  It is also advantageous to estimate the hydrogen concentration by measuring the power consumption of the hydrogen circulation pump, thereby detecting a decrease in the hydrogen concentration.

  In addition, when the hydrogen concentration estimation calculation value is calculated by the hydrogen concentration estimation calculation means, it is possible to smoothly perform the opening / closing control of the hydrogen exhaust valve, the rotation speed control of the hydrogen circulation pump, or the opening / closing control of the pressure control valve based on the calculated value. There is an advantage that the power generation control of the fuel cell can be executed efficiently.

  Also, a plurality of types of hydrogen concentration estimation methods can be combined.

1 is a block diagram of a fuel cell system in an embodiment of the present invention. 3 is a flowchart illustrating a power generation control procedure of the fuel cell system according to the first embodiment. 3 is a flowchart illustrating a power generation control procedure of the fuel cell system according to the first embodiment. It is a graph explaining the rotation speed versus differential pressure characteristic which uses hydrogen concentration as a parameter. It is explanatory drawing explaining the example which provided the orifice in the hydrogen circulation path. It is explanatory drawing explaining the example which provided the orifice in the bypass of a hydrogen circulation path. It is a graph explaining the rotation speed versus power consumption characteristic of the hydrogen circulation pump as a hydrogen concentration parameter. It is a graph explaining the power consumption characteristic of the hydrogen concentration of discharged hydrogen versus the hydrogen circulation pump. It is a graph explaining the rotation speed versus power consumption characteristic of the hydrogen circulation pump which uses hydrogen concentration as a parameter. It is a flowchart which shows the electric power generation control procedure of a fuel cell system. Similarly, it is a flowchart which shows the electric power generation control procedure of the fuel cell system in a 3rd modification. 14 is a flowchart illustrating a control procedure according to the seventh embodiment. It is a graph explaining the rotation speed versus differential pressure characteristic of the hydrogen circulation pump which uses hydrogen concentration as a parameter.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fuel cell (fuel cell stack), 2 Anode, 3 High pressure hydrogen tank, 4 Pressure control valve, 5 Hydrogen supply path, 6 Cathode, 7 Humidification module, 8 Air flow path, 9 Hydrogen circulation path, 10 Electronic control unit, 11 Hydrogen circulation pump, 12 1st pressure sensor, 13 2nd pressure sensor, 14 Hydrogen exhaust valve, 15 Check valve

Claims (11)

A fuel gas supply path for supplying fuel gas to the fuel cell;
A fuel gas circulation path for returning the fuel off-gas discharged from the fuel cell to the fuel gas supply path;
A fuel cell system including a fuel gas circulation pump provided in the fuel gas circulation path for boosting the fuel off-gas and returning it to the fuel gas supply path;
Data detection means for detecting physical data relating to the fuel off-gas, which varies according to the operating state of the fuel cell;
Fuel gas concentration estimation calculation means for estimating the fuel gas concentration on the fuel electrode side based on the physical data detected by the data detection means;
A fuel cell system comprising:   2. The fuel cell system according to claim 1, wherein the data detection unit detects a pressure increase amount of the fuel off gas by driving the fuel gas circulation pump as the physical data.   The data detection means is formed by pressure sensors arranged upstream and downstream of the fuel gas circulation pump as the physical data, and the pressure increase amount of the fuel off-gas by the fuel gas circulation pump is determined by the both pressure sensors. The fuel cell system according to claim 2, detected as:   A pressure sensor in which a check valve is provided in the fuel gas circulation path between the fuel gas circulation pump and the fuel gas supply path, and the data detection means is disposed upstream or downstream of the fuel gas circulation pump. The fuel cell system according to claim 1, formed by:   2. The fuel cell system according to claim 1, wherein the data detection unit detects power consumption consumed by driving the fuel gas circulation pump as the physical data.   When the estimated calculation value of the fuel gas concentration is calculated by the fuel gas concentration estimation calculation means, the opening / closing control of the fuel gas exhaust valve provided in the fuel gas circulation path based on the calculated calculation value of the fuel gas concentration, the rotation speed of the fuel gas circulation pump 6. The control device according to claim 1, further comprising: a control unit that performs at least one of control and open / close control of a pressure regulating valve having a pressure reducing function provided in the fuel gas supply path. A fuel cell system according to claim 1.   The fuel cell system according to any one of claims 1 to 5, wherein the physical data related to the fuel off-gas is data resulting from a viscosity of the fuel off-gas.   2. The fuel cell system according to claim 1, wherein the fuel gas concentration estimation calculating means estimates the concentration of the fuel off gas when the operating state of the fuel cell is constant.   The fuel cell system according to claim 1, wherein the fuel gas concentration estimation calculation means estimates the concentration of the fuel off gas in consideration of the gas temperature.   2. The fuel cell system according to claim 1, wherein the data detection unit detects a pressure of the fuel off gas or the fuel gas by providing a throttle in the fuel gas circulation path or the fuel gas supply path.   2. The fuel cell system according to claim 1, wherein the data detection unit estimates a fuel gas concentration from a numerical value of pump rotation at a time when the upstream / downstream differential pressure of the fuel gas circulation pump is constant.

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