JP6222191B2 - Fuel cell system - Google Patents

Description

  The present invention relates to a fuel cell system.

  A gas-liquid separator that separates and stores moisture from the fuel gas discharged from the fuel cell; and a discharge valve that is connected to the gas-liquid separator and discharges the fuel gas together with the stored water in the gas-liquid separator. A fuel cell system provided is known. For example, Patent Document 1 discloses a technique for estimating the amount of fuel gas discharged by opening a discharge valve.

Japanese Patent Laying-Open No. 2005-302708

  In order to estimate the exhaust amount of the fuel gas, for example, it may be estimated based on the differential pressure between the upstream side and the downstream side of the exhaust valve during the period when the exhaust valve is open. However, the present inventors have found that when the amount of exhaust of fuel gas is estimated by the above method, an error between the estimated amount of exhaust and the actual amount of exhaust may increase depending on the load state of the fuel cell. did.

  Therefore, an object of the present invention is to provide a fuel cell system in which a decrease in accuracy of estimating the amount of exhaust of fuel gas is suppressed in a wide load region of the fuel cell.

  The object is to provide a fuel cell, a fuel supply source for supplying fuel gas to the fuel cell, a supply flow path for flowing the fuel gas supplied from the fuel supply source to the fuel cell, and an exhaust from the fuel cell. A circulation passage for flowing the fuel gas to the supply passage; a gas-liquid separator disposed on the circulation passage for separating and storing moisture from the fuel gas; and the gas-liquid separator connected to the gas-liquid separator. A discharge flow path for discharging the stored water and the fuel gas in the liquid separator to the outside, a discharge valve provided in the discharge flow path, a current detection unit for detecting a load current value of the fuel cell, and the supply A pressure detection unit that detects a pressure in the flow path; a pressure in the discharge flow path upstream of the supply flow path, the circulation flow path, the gas-liquid separator, or the discharge valve; and the discharge valve A differential pressure detection unit for detecting a differential pressure with respect to a pressure on the downstream side, and A control unit that estimates an exhaust amount of the fuel gas discharged by opening the valve, and when the load current value is equal to or less than a reference value, the control unit opens the discharge valve. Based on the amount of disappearance of the fuel gas calculated from the rate of decrease in the pressure in the supply flow path and the amount of consumption of the fuel gas by power generation of the fuel cell calculated from the load current value during the valve opening period A fuel gas exhaust amount, and when the load current value exceeds the reference value, a fuel gas exhaust amount is estimated based on the differential pressure during the valve opening period. Can be achieved by battery system.

  When the load current value is less than or equal to the reference value, the control unit estimates the fuel gas exhaust amount based on a value obtained by subtracting the fuel gas consumption from the fuel gas disappearance amount. It may be.

  The object is to provide a fuel cell, a fuel supply source for supplying fuel gas to the fuel cell, a supply flow path for flowing the fuel gas supplied from the fuel supply source to the fuel cell, and an exhaust from the fuel cell. A circulation passage for flowing the fuel gas to the supply passage; a gas-liquid separator disposed on the circulation passage for separating and storing moisture from the fuel gas; and the gas-liquid separator connected to the gas-liquid separator. A discharge flow path for discharging the stored water and the fuel gas in the liquid separator to the outside, a discharge valve provided in the discharge flow path, a current detection unit for detecting a load current value of the fuel cell, and the circulation From a pressure detection unit that detects any pressure in the flow path and in the gas-liquid separator, and the supply valve, the circulation flow path, the gas-liquid separator, or the discharge valve in the discharge flow path The differential pressure between the pressure on the upstream side and the pressure on the downstream side of the discharge valve A differential pressure detection unit for detecting, and a control unit for estimating an exhaust amount of the fuel gas discharged by opening the discharge valve, wherein the control unit is configured when the load current value is equal to or less than a reference value. Is the amount of disappearance of the fuel gas calculated from the rate of decrease in pressure in either the circulation channel or the gas-liquid separator during the valve opening period of the exhaust valve and the load current during the valve opening period When the fuel gas exhaust amount is estimated based on the amount of fuel gas consumed by power generation of the fuel cell calculated from the value, and the load current value exceeds the reference value, the valve opening period This can also be achieved by a fuel cell system that estimates the exhaust amount of the fuel gas based on the differential pressure at the same time.

  The object is to provide a fuel cell, a fuel supply source for supplying fuel gas to the fuel cell, a supply flow path for flowing the fuel gas supplied from the fuel supply source to the fuel cell, and an exhaust from the fuel cell. A gas-liquid separator that separates and stores water from the fuel gas, a first discharge passage that supplies the fuel gas discharged from the fuel cell to the gas-liquid separator, and the gas-liquid separator. A second discharge passage for discharging the stored water and the fuel gas in the gas-liquid separator to the outside, a discharge valve provided in the second discharge passage, and a load current of the fuel cell A current detection unit for detecting a value; a pressure detection unit for detecting any pressure in the supply flow channel, the first discharge flow channel, and the gas-liquid separator; the supply flow channel; The exhaust in the first discharge channel, the gas-liquid separator, or the second discharge channel A differential pressure detector for detecting a differential pressure between a pressure upstream of the valve and a pressure downstream of the discharge valve; and estimating an exhaust amount of the fuel gas discharged by opening the discharge valve A non-circulating anode fuel cell system that does not return the fuel gas discharged from the fuel cell to the supply flow path, and the control unit has a load current value that is less than or equal to a reference value In this case, the fuel gas calculated from the rate of decrease in pressure in the supply flow path, the first discharge flow path, and the gas-liquid separator during the opening period of the discharge valve The fuel gas exhaust amount is estimated on the basis of the disappearance amount of the fuel gas and the consumption amount of the fuel gas generated by the power generation of the fuel cell calculated from the load current value in the valve opening period, and the load current value is the reference value If it exceeds the value, it is based on the differential pressure during the valve opening period. There estimating the amount of exhaust of the fuel gas can also be achieved by a fuel cell system.

  It is possible to provide a fuel cell system in which a decrease in the estimation accuracy of the exhaust amount of fuel gas is suppressed in a wide load region of the fuel cell.

It is a schematic block diagram of a fuel cell system. 6 is a timing chart showing the operation of the discharge valve, the change in pressure in the supply flow path, and the change in pressure difference between the pressure in the circulation flow path and the pressure in the discharge flow path downstream of the discharge valve. . It is a flowchart of the opening / closing control of the discharge valve performed by ECU. It is a graph of the experimental result which showed the actual exhaust_gas | exhaustion in the case of controlling so that the exhaust_gas | exhaustion estimated by each of the estimation methods A and B corresponds with a target exhaust gas. 3 is a flowchart of an exhaust amount estimation control by an estimation method A. It is the map which prescribed | regulated the relationship between a pressure fall rate and the fuel gas loss | disappearance amount per unit time. It is the map which prescribed | regulated the relationship between a load electric current value and the fuel gas consumption per unit time. It is the figure which showed the relationship between the accumulated fuel gas loss amount Q1, the accumulated fuel gas consumption amount Q2, and the estimated displacement Q of the fuel gas. 7 is a flowchart of an exhaust amount estimation control by an estimation method B. It is the map which prescribed | regulated the relationship between differential pressure | voltage (DELTA) Pb and waste water flow volume. 6 is a map that defines a relationship between a differential pressure ΔPb and an exhaust flow rate. It is a schematic block diagram of the fuel cell system which concerns on a 1st modification. It is a schematic block diagram of the fuel cell system which concerns on a 2nd modification.

  Hereinafter, a fuel cell system 1 (hereinafter referred to as a system) of this embodiment will be described with reference to the drawings. The system 1 can be applied to a vehicle system mounted on a vehicle, for example. However, you may apply to the system of another use. FIG. 1 is a schematic configuration diagram of a system 1. The system 1 includes a fuel cell 2 as power supply means. The fuel cell 2 is configured such that an electrolyte membrane such as a solid polymer electrolyte membrane is sandwiched between an anode and a cathode that are catalyst electrodes (in the drawing, illustration of the electrolyte membrane, the anode, and the cathode is omitted), and to the anode. Power is generated by supplying a fuel gas containing hydrogen and an oxidizing gas containing oxygen such as air to the cathode.

  The tank 3 is a fuel supply source that supplies fuel gas to the fuel cell 2. The supply channel 4 is connected to the anode inlet of the fuel cell 2 and allows the fuel gas supplied from the tank 3 to flow to the fuel cell 2. A pressure regulating valve 6 is arranged in the supply flow path 4, and the fuel gas supplied from the tank 3 is decompressed by the pressure regulating valve 6 and adjusted to a desired pressure before being supplied to the fuel cell 2. In addition, an injector 10 is disposed downstream of the pressure regulating valve 6 in the supply flow path 4. The injector 10 is an electromagnetically driven on-off valve capable of adjusting a gas flow rate and a gas pressure by driving a valve body directly at a predetermined driving cycle with an electromagnetic driving force and separating it from a valve seat. The injector 10 and the pressure regulating valve 6 are controlled by an ECU (Electronic Control Unit) 20.

  Connected to the anode outlet of the fuel cell 2 is a circulation channel 8 through which the fuel gas (fuel offgas) discharged from the fuel cell 2 flows to the supply channel 4. Specifically, the downstream end of the circulation channel 8 is connected to the supply channel 4. In addition, a circulation pump 9 for pressurizing the fuel gas discharged from the fuel cell 2 and sending it to the supply channel 4 is installed in the circulation channel 8. Thus, in the fuel cell system, the fuel gas circulates through the supply flow path 4 and the circulation flow path 8 when the fuel cell 2 is operated.

  A gas-liquid separator 12 is disposed in the middle of the circulation flow path 8 and has a storage tank 12a that separates moisture from the fuel gas and stores the separated water. In the system 1, water generated by the power generation of the fuel cell 2 permeates the electrolyte membrane from the cathode side and leaks to the anode side. The water that has moved to the anode side is discharged together with the fuel gas to the circulation channel 8 and is collected by the gas-liquid separator 12.

  A discharge channel 14 that discharges the stored water and fuel gas in the gas-liquid separator 12 to the outside is connected to the bottom of the storage tank 12 a of the gas-liquid separator 12. The downstream end of the discharge channel 14 is exposed to the outside air. A discharge valve 16 is disposed in the discharge channel 14. The discharge valve 16 is normally closed and is opened by the ECU 20 as necessary. The discharge valve 16 may be any valve that can control the discharge state, such as a shut-off valve or a flow rate adjustment valve. In the present embodiment, the discharge valve 16 is a shutoff valve. The drain valve 16 opens and drains before the stored water overflows from the storage tank 12a, so that liquid water can be prevented from being supplied to the fuel cell 2 via the circulation path 8 and the supply path 4.

  The supply flow path 4 is provided with a pressure sensor 21 that detects the pressure in the supply flow path 4 on the downstream side of the injector 10. The pressure sensor 21 mainly detects the pressure of the fuel gas supplied to the fuel cell 2. The circulation channel 8 is provided with a pressure sensor 22 that detects the pressure in the circulation channel 8 upstream of the gas-liquid separator 12. The pressure sensor 22 mainly detects the pressure of the fuel gas discharged from the fuel cell 2 and can detect the pressure upstream of the discharge valve 16. The discharge flow path 14 is provided with a pressure sensor 23 that detects the pressure in the discharge flow path 14 on the downstream side of the discharge valve 16, and can detect the pressure on the downstream side of the discharge valve 16. The detection value of the pressure sensor 23 indicates substantially atmospheric pressure. The pressure sensors 21 to 23 are connected to the input side of the ECU 20 and input a signal corresponding to the detected pressure to the ECU 20. The pressure sensor 21 is an example of a pressure detection unit that detects the pressure in the supply flow path 4. The pressure sensors 22, 23 are pressures in the supply flow path 4, the circulation flow path 8, the gas-liquid separator 12, or the discharge flow path 14 upstream of the discharge valve 16, and pressures downstream of the discharge valve 16. It is an example of the differential pressure | voltage detection part which detects the differential pressure | voltage.

  A load device 30 is connected to the fuel cell 2. The load device 30 is a device for measuring the electrical characteristics of the fuel cell 2 and can be configured to include, for example, an electrochemical general-purpose potentio galvanostat. The load device 30 is electrically connected to the anode side separator and the cathode side separator of the fuel cell 2 by wiring. The load device 30 can measure the load current flowing through the fuel cell 2 during power generation of the fuel cell 2 and the load voltage (cell voltage) of the fuel cell 2. The load device 30 is an example of a current detection unit that detects a load current value.

  The ECU 20 includes a microcomputer including a CPU (Central Processing Unit), a ROM (Read Only Memory), and a RAM (Random Access Memory). The ECU 20 is electrically connected to each component of the system 1 and controls the operation of each component based on information received from each component. The ECU 20 is an example of a control unit that executes control for estimating the exhaust amount of fuel gas, which will be described in detail later.

  A flow path for supplying oxidizing gas is connected to the cathode inlet of the fuel cell 2, and a flow path for discharging oxidizing off gas is connected to the cathode outlet, but this is omitted in FIG. .

  As described above, the stored water in the gas-liquid separator 12 can be discharged to the outside by opening the discharge valve 16. At this time, part of the fuel gas is discharged to the outside together with the stored water. Here, it is required to control so that the actual exhaust amount of the fuel gas discharged from the discharge valve 16 becomes the target exhaust amount. This is because if the actual exhaust amount is too large with respect to the target exhaust amount, the fuel gas is consumed wastefully and the fuel consumption may be deteriorated. Conversely, if the actual displacement is too small relative to the target displacement, for example, if the actual displacement is zero, the stored water may not be completely discharged. Therefore, in the present system 1, the exhaust amount of the fuel gas exhausted while the exhaust valve 16 is opened is estimated by a method described later, and the exhaust valve 16 is closed when the estimated exhaust amount reaches the target exhaust amount.

  Next, changes in pressure due to the operation of the discharge valve 16 will be described. FIG. 2 shows the differential pressure between the operation of the discharge valve 16, the change in pressure in the supply flow path 4, and the pressure in the circulation flow path 8 and the pressure in the discharge flow path 14 on the downstream side of the discharge valve 16. 6 is a timing chart showing changes. FIG. 2 is a timing chart in a state where fuel gas is not supplied from the injector 10. As described above, the pressure in the supply flow path 4 is detected by the pressure sensor 21. The pressure difference between the pressure in the circulation flow path 8 and the pressure in the discharge flow path 14 on the downstream side of the discharge valve 16 (hereinafter simply referred to as differential pressure) is based on the output values from the pressure sensors 22 and 23. Detected. In FIG. 2, the discharge valve 16 is closed at the time t0, the discharge valve 16 is opened at the time t1, the discharge of the stored water in the gas-liquid separator 12 is completed between the time t1 and t2, and between the time t2 and t3. The fuel gas is discharged.

  As shown in FIG. 2, the pressure in the supply flow path 4 slightly decreases before the discharge valve 16 is opened, and immediately after the discharge valve 16 is opened, the pressure in the supply flow path 4 does not change immediately. However, the pressure drops greatly after a while from the opening of the discharge valve 16. The pressure drop in the supply flow path 4 between the time points t0 and t2 when the drainage of the stored water is completed before the discharge valve 16 is opened is due to the consumption of the fuel gas by the power generation of the fuel cell 2. For the same reason, the differential pressure between time points t0 and t2 also decreases. The reason why the pressure in the supply channel 4 between the time points t1 and t2 does not substantially change from the pressure in the supply channel 4 between the time points t0 and t1 is that the drainage of the stored water is between the time points t1 and t2. This is because the fuel gas is not exhausted.

  When the drainage is completed and the gas-liquid separator 12 and the discharge passage 14 communicate with the atmosphere, the fuel gas is exhausted through the discharge passage 14. Thereby, the pressure in the supply flow path 4 and a differential pressure | voltage fall between time t2-t3. This is because the pressure in the supply flow path 4 communicating with the circulation flow path 8 is also reduced by exhausting the fuel gas. Therefore, the decrease in the pressure in the supply flow path 4 between the time points t2 and t3 is caused by the consumption amount of the fuel gas due to the power generation of the fuel cell 2 and the exhaust amount of the fuel gas. The reason why the differential pressure decreases between time points t2 and t3 is detected by the pressure sensor 23 while the pressure in the circulation flow path 8 detected by the pressure sensor 22 decreases as the fuel gas is exhausted. This is because the atmospheric pressure is not substantially changed. Further, when it is determined that the exhaust amount estimated by the estimation method described later has reached the target exhaust amount, the discharge valve 16 is closed.

  FIG. 3 is a flowchart of the opening / closing control of the discharge valve 16 executed by the ECU 20. The ECU 20 determines whether or not the system 1 is in operation (step 1). This is because the wastewater treatment of the stored water is performed during operation of the system. When the system 1 is in operation, the ECU 20 executes the processing from step 1 onward, and when the system 1 is not in operation, this control ends.

  Next, the ECU 20 determines whether or not the opening condition of the discharge valve 16 is satisfied (step S2). The opening condition of the discharge valve 16 is, for example, when the elapsed time from the previous opening of the discharge valve 16 reaches a predetermined time, but is not limited thereto. If the valve opening condition is not satisfied, this control is terminated. When the valve opening condition of the discharge valve 16 is satisfied, the ECU 20 determines whether or not the load current value of the fuel cell 2 detected by the load device 30 is equal to or less than a reference value (step S3). The reference value will be described later in detail. When the load current value is less than or equal to the reference value, the ECU 20 opens the discharge valve 16 (step S4a), and executes an estimation method A for estimating the amount of fuel gas discharged by opening the discharge valve 16 (step S5a). The ECU 20 determines whether or not the estimated displacement is equal to or greater than the target displacement (step S6a), and continues to estimate the displacement until the estimated displacement is equal to or greater than the target displacement. When the estimated exhaust amount is equal to or greater than the target exhaust amount, the ECU 20 closes the exhaust valve 16 (step S7) and ends this control. The target exhaust amount may be a fixed value set in advance or may be set according to the operating state of the system 1.

  On the other hand, if the determination in step S3 is negative, that is, if the load current value exceeds the reference value, the ECU 20 opens the discharge valve 16 (step S4b), and exhausts the fuel gas by opening the discharge valve 16. The estimation method B for estimating the quantity is executed (step S5b). The ECU 20 determines whether or not the estimated displacement is equal to or greater than the target displacement (step S6b), and continues to estimate the displacement until the estimated displacement is equal to or greater than the target displacement. When the estimated exhaust amount is equal to or greater than the target exhaust amount, the ECU 20 closes the exhaust valve 16 (step S7) and ends this control. By the above control, the stored water in the gas-liquid separator 12 is drained, and the fuel gas is exhausted by a desired amount.

  Next, the reason why the estimation methods A and B are switched according to the load current value will be described. FIG. 4 is a graph of an experimental result showing an actual exhaust amount when the exhaust amount estimated by each of the estimation methods A and B is controlled so as to coincide with the target exhaust amount. The vertical axis of the graph represents the displacement, and the horizontal axis represents the load current value. Line segments CA and CB indicate the actual exhaust amount when the exhaust amount is estimated by the estimation methods A and B under the condition that the target exhaust amount is constant and the load current value is different. Therefore, FIG. 4 shows the degree of error between the estimated displacement and the actual displacement.

  As indicated by the line segment CA, the error between the target displacement, that is, the estimated displacement and the actual displacement is small in the region where the load current value is low, but the error is large in the region where the load current value is high. On the other hand, as indicated by the line segment CB, the error is large in the region where the load current value is low, but the error is small in the region where the load current value is high. In this system 1, the load current value near the intersection of the line segments CA and CB is adopted as the reference value. Thereby, as described above, the exhaust amount is estimated using the estimation method A with less error in the region where the load current value is lower than the reference value, and the estimation method with less error in the region where the load current value is higher than the reference value. B is used to estimate the displacement.

  Next, the estimation method A will be described with reference to FIGS. FIG. 5 is a flowchart of the exhaust amount estimation control by the estimation method A. In the estimation method A, it is calculated from the disappearance amount of the fuel gas calculated from the rate of decrease in the pressure in the supply flow path 4 during the valve opening period when the discharge valve 16 is open and the load current value of the fuel cell 2 during the valve opening period. The exhaust amount of the fuel gas is estimated based on the consumption amount of the fuel gas generated by the generated power of the fuel cell.

  The ECU 20 calculates the accumulated fuel gas disappearance amount Q1 from the pressure drop rate ΔPa in the supply flow path 4 from the time t1 when the discharge valve 16 is opened (step S11). FIG. 6 is a map defining the relationship between the pressure drop rate ΔPa and the amount of fuel gas lost per unit time. Based on this map, the ECU 20 calculates the fuel gas disappearance amount per unit time at the pressure drop rate ΔPa, integrates the time from the time point t1 to the present time, and calculates the integrated fuel gas loss amount Q1. The fuel gas disappearance amount per unit time may be calculated by a calculation formula using the pressure drop rate ΔPa. Further, the ECU 20 calculates a value obtained by subtracting the current pressure value from the previous pressure value detected by the pressure sensor 21 as the pressure decrease rate ΔP.

  Next, the ECU 20 calculates an integrated fuel gas consumption Q2 resulting from the power generation of the fuel cell 2 from the load current value (step S12). FIG. 7 is a map that defines the relationship between the load current value and the fuel gas consumption per unit time. Based on this map, the ECU 20 calculates the fuel gas consumption per unit time corresponding to the load current value, calculates the time integral from time t1 to the current time, and calculates the integrated fuel gas consumption Q2. . 6 and 7 are defined in advance based on experiments and the like, and are recorded in the ROM of the ECU 20. The fuel gas consumption per unit time may be calculated by a calculation formula using a load current value.

  Here, the above-mentioned accumulated fuel gas consumption Q2 indicates the total amount of fuel gas consumed by the power generation of the fuel cell 2. The accumulated fuel gas disappearance amount Q1 indicates the total amount of fuel gas that has disappeared from the supply path 4, the circulation path 8, and the fuel cell 2 regardless of the reason. Therefore, the accumulated fuel gas disappearance amount Q1 includes the accumulated fuel gas consumption amount Q2 and the exhaust amount Q of the fuel gas due to the opening of the discharge valve 16. FIG. 8 is a diagram showing the relationship between the accumulated fuel gas disappearance amount Q1, the accumulated fuel gas consumption amount Q2, and the estimated displacement Q of the fuel gas. Note that when the drainage of the stored water is not completed, the accumulated fuel gas loss Q1 and the accumulated fuel gas consumption Q2 consumed by the power generation are substantially the same value, so the exhaust amount Q of the fuel gas is substantially zero. It becomes.

  Next, the ECU 20 calculates an exhaust amount Q obtained by subtracting the integrated fuel gas consumption amount Q2 from the integrated fuel gas disappearance amount Q1 as an estimated exhaust amount (step S13). Steps S11 to S13 are repeated until the estimated exhaust amount reaches the target exhaust amount as shown in FIG. 3 (No in step S6a), and when the estimated exhaust amount reaches the target exhaust amount ( In step S6a, Yes), the discharge valve 16 is closed (step S7). The exhaust amount is estimated as described above. Note that a value obtained by subtracting the accumulated fuel gas consumption amount Q2 from the accumulated fuel gas loss amount Q1 and a correction coefficient or the like may be calculated as the estimated exhaust amount.

  Next, as shown in FIG. 4, the reason why the error becomes large in the region where the load current is high in the estimation method A will be described. In the estimation method A, when the load current of the fuel cell 2 is large, in other words, when the amount of fuel gas consumed by the power generation of the fuel cell 2 is large, the inside of the supply channel 4 between the time points t1 and t2 shown in FIG. The rate of decrease in pressure increases. In other words, the line segment indicating the pressure in the supply flow path 4 has a steep slope. For this reason, there is a possibility that the pressure drop rate in the supply flow path 4 due to power generation and the pressure drop rate in the supply flow path 4 due to the exhaust of fuel gas substantially coincide. In this case, the accumulated fuel gas disappearance amount Q1 and the accumulated fuel gas consumption amount Q2 calculated by the above method substantially coincide with each other, and the exhaust amount Q may be calculated to be smaller than the actual exhaust amount. As a result, the exhaust valve 16 may be closed after the actual exhaust amount becomes larger than the target exhaust amount. For this reason, it is considered that the error in the estimation method A increases in a region where the load current value is high.

  Next, the estimation method B will be described with reference to FIGS. FIG. 9 is a flowchart of the exhaust amount estimation control by the estimation method B. In the estimation method B, the exhaust amount of the fuel gas is estimated based on the differential pressure during the valve opening period of the discharge valve 16.

  The ECU 20 calculates a storage amount in the gas-liquid separator 12 immediately before the discharge valve 16 is opened (step S21). Specifically, the ECU 20 uses the relational expression in which the generated water amount generated according to the amount of power generated by the fuel cell 2 since the last drainage is associated with the load current of the fuel cell 2 and the generated water amount. The amount of water stored in the gas-liquid separator 12 is calculated using a map or the like. The power generation amount of the fuel cell 2 is calculated from the load current. Next, the ECU 20 estimates the amount of drainage after the discharge valve 16 is opened from the differential pressure ΔPb between the pressure in the circulation flow path 8 and the pressure downstream of the discharge valve 16 (step S22). FIG. 10 is a map that defines the relationship between the differential pressure ΔPb and the drainage flow rate. Based on this map, the ECU 20 calculates the drainage flow rate corresponding to the differential pressure ΔPb, calculates the time integral from the time point t1 when the discharge valve 16 opens to the current time point, and estimates the drainage amount. Note that the map of FIG. 10 is defined in advance based on experiments and the like and recorded in the ROM of the ECU 20. The map in FIG. 10 indicates that the greater the differential pressure ΔPb, that is, the greater the pressure in the circulation channel 8 relative to the pressure downstream of the discharge valve 16, the greater the amount of drainage per unit time. This is because drainage to the outside is promoted as the differential pressure ΔPb increases.

  Next, the ECU 20 determines whether or not the estimated drainage amount is equal to or greater than the calculated stored water amount (step S23). The ECU 20 continues to estimate the drainage amount until the estimated drainage amount becomes equal to or greater than the stored water amount.

  When the estimated amount of drainage reaches the amount of stored water, it is determined that drainage has been completed, and the ECU 20 estimates the exhaust amount from the differential pressure ΔPb upstream and downstream of the discharge valve 16 (step S24). FIG. 11 is a map that defines the relationship between the differential pressure ΔPb and the exhaust gas flow rate. The ECU 20 calculates the exhaust amount of the fuel gas corresponding to the differential pressure ΔPb based on this map, calculates the time integral from the time t2 when the drainage of the stored water is completed to the current time point, and calculates the exhaust amount Q. calculate. Note that the map of FIG. 11 is defined in advance based on experiments and the like and recorded in the ROM of the ECU 20. The map of FIG. 11 indicates that the exhaust flow rate per unit time increases as the differential pressure ΔPb increases, as in the map of FIG. This is because the larger the differential pressure ΔPb, the more the exhaust to the outside is promoted. Note that the drainage amount and the exhaust amount may be estimated by a calculation formula using the differential pressure ΔPb without using the maps of FIGS.

  Steps S21 to S24 are repeated until the estimated exhaust amount reaches the target exhaust amount as shown in FIG. 3 (No in step S6b), and when the estimated exhaust amount reaches the target exhaust amount ( In step S6b, Yes), the discharge valve 16 is closed (step S7). The exhaust amount is estimated as described above.

  As shown in FIG. 4, in the region where the load current value is low, the error of the estimation method B is larger than the error of the estimation method A for some reason. Possible reasons are as follows: In the region where the load current value is low, the pressure in the circulation channel 8 is lower than in the high region, and the differential pressure between the pressure in the circulation channel 8 and the pressure downstream of the discharge valve 16 is also small. When the differential pressure is thus reduced, the detected differential pressure ΔPb may be smaller than the actual differential pressure due to detection errors of the pressure sensors 22 and 23. Therefore, an exhaust flow rate smaller than the actual exhaust flow rate is calculated, and as a result, an exhaust amount smaller than the actual exhaust amount is estimated. As a result, there is a possibility that the actual exhaust amount is larger than the estimated exhaust amount.

  In addition, the following reasons can be considered. Since the amount of water generated by power generation is small in the region where the load current value is low, the amount of water stored in step S21 may be calculated more than the actual amount of water stored in the gas-liquid separator 12. For this reason, it is determined that the drainage is in progress even though the drainage is actually completed, and it is considered that the closing timing of the discharge valve 16 is delayed from the original timing. As a result, the actual displacement may be larger than the target displacement.

  As described above, the ECU 20 of the present system 1 estimates the displacement by the estimation method A with less error in the region where the load current value is lower than the reference value, and estimates with less error in the region where the load current value is higher than the reference value. The displacement is estimated by method B. As a result, a decrease in the estimation accuracy of the exhaust amount of the fuel gas is suppressed in a wide load region of the fuel cell 2.

  Moreover, in the said Example, although the estimation method B detected the differential pressure (DELTA) Pb based on the pressure sensor 22 which detects the pressure in the circulation flow path 8, it is not limited to this. For example, instead of the pressure sensor 22, the detection value of the pressure sensor that detects the pressure in the supply flow path 4, the gas-liquid separator 12, or the discharge flow path 14 upstream of the discharge valve 16 may be used.

  Further, although the differential pressure ΔPb is detected based on the pressure sensor 23 that detects the pressure in the discharge flow path 14 on the downstream side of the discharge valve 16, the present invention is not limited to this. For example, instead of the pressure sensor 23, a pressure sensor provided in a location other than the discharge flow path 14 and provided at a position where atmospheric pressure can be detected may be used. Since the exhaust is discharged to the atmosphere by opening the discharge valve 16, even such a pressure sensor detects the pressure on the downstream side of the discharge valve 16.

  In the above embodiment, the pressure drop rate ΔP in the supply flow path 4 is acquired based on the detection value from the pressure sensor 21, and the integrated fuel gas disappearance amount Q1 is calculated from the pressure drop rate ΔP. However, the present invention is not limited to this. For example, the ECU 20 acquires the pressure decrease rate in the circulation channel 8 based on the detection value from the pressure sensor 22 that detects the pressure in the circulation channel 8, and integrates it from the pressure decrease rate in the circulation channel 8. The fuel gas disappearance amount Q1 may be calculated. This is because when the fuel gas is consumed by the power generation of the fuel cell 2, the pressure in the circulation channel 8 also decreases, and when the discharge valve 16 opens, the pressure in the circulation channel 8 also decreases. In this case, the pressure sensor 22 is an example of a pressure detection unit that detects the pressure in the circulation flow path 8. The pressure sensor 22 may be provided in the circulation channel 8 on the upstream side of the gas-liquid separator 12 or may be provided in the circulation channel 8 on the downstream side of the gas-liquid separator 12. Good.

  Next, a modified example of the system will be described. FIG. 12 is a schematic configuration diagram of a system 1a according to the first modification. In addition, about the structure same as the system 1 mentioned above, the overlapping description is abbreviate | omitted by attaching | subjecting the same code | symbol. In the system 1a, a pressure sensor 24 for detecting the pressure in the gas-liquid separator 12 is provided. The pressure sensor 24 is provided at a high position so that the stored water in the gas-liquid separator 12 is not covered. In the system 1a, the ECU 20 acquires the pressure decrease rate in the gas-liquid separator 12 based on the detection value from the pressure sensor 24, and calculates the accumulated fuel gas loss amount Q1 from the pressure decrease rate in the gas-liquid separator 12. calculate. This is because when the fuel gas is consumed by the power generation of the fuel cell 2, the pressure in the gas-liquid separator 12 also decreases, and when the discharge valve 16 opens, the pressure in the gas-liquid separator 12 also decreases. In this case, the pressure sensor 24 is an example of a pressure detection unit that detects the pressure in the gas-liquid separator 12.

  FIG. 13 is a schematic configuration diagram of a system 1b according to the second modification. Unlike the systems 1 and 1a, the system 1b is an anode non-circulation type, and the circulation channel 8 and the circulation pump 9 are not provided. The fuel gas discharged from the fuel cell 2 is supplied again to the supply channel 4 and the fuel cell. There is no return to 2. The system 1b also includes a first discharge channel 14a for supplying the fuel gas discharged from the fuel cell 2 to the gas-liquid separator 12, and the stored water in the gas-liquid separator 12 connected to the gas-liquid separator 12. And a second discharge channel 14b for discharging the fuel gas to the outside. The discharge valve 16 is disposed in the second discharge flow path 14b. Accordingly, the fuel gas discharged from the fuel cell 2 is discharged to the outside when the discharge valve 16 is opened. The pressure sensor 22 is provided in the first discharge channel 14a and detects the pressure in the first discharge channel 14a. The pressure sensor 23 is provided in the second discharge channel 14 b and detects the pressure in the second discharge channel 14 b on the downstream side of the discharge valve 16.

  Similarly to the systems 1 and 1a, the system 1b can calculate the exhaust amount Q obtained by subtracting the cumulative fuel gas consumption amount Q2 from the cumulative fuel gas disappearance amount Q1 as the estimated exhaust amount. Further, the ECU 20 may acquire the pressure decrease rate ΔP in the supply flow path 4 based on the detection value from the pressure sensor 21, and calculate the integrated fuel gas disappearance amount Q1 from the pressure decrease rate ΔP. Based on the detection value from the sensor 22, the pressure drop rate in the first discharge flow path 14a may be acquired to calculate the accumulated fuel gas lost amount Q1. Further, the ECU 20 obtains the pressure decrease rate in the gas-liquid separator 12 based on the detection value from the pressure sensor 24 that detects the pressure in the gas-liquid separator 12, and calculates the accumulated fuel gas disappearance amount Q1. May be. The pressure sensors 21, 22, and 24 are examples of pressure detection units that detect any pressure in the supply flow path 4, the first discharge flow path 14 a, and the gas-liquid separator 12, respectively.

  Regarding the system 1b, the ECU 20 detects the differential pressure ΔPb based on the detection value of the pressure sensor 22 that detects the pressure in the first discharge flow path 14a, but is not limited thereto. For example, the ECU 20 detects the detection value of the pressure sensor 21 that detects the pressure in the supply flow path 4, the detection value of the pressure sensor 24 that detects the pressure in the gas-liquid separator 12, or the second discharge flow path 14b. The differential pressure ΔPb may be detected based on a detection value of a pressure sensor that detects a pressure upstream of the discharge valve 16.

  Although the preferred embodiments of the present invention have been described in detail above, the present invention is not limited to the specific embodiments, and various modifications and changes can be made within the scope of the gist of the present invention described in the claims. It can be changed.

1 Fuel Cell System 2 Fuel Cell 3 Tank (Fuel Supply Source)
4 Supply flow path 8 Circulation flow path 12 Gas-liquid separator 16 Discharge valve 20 ECU (control part)
21 Pressure sensor (pressure detector)
22, 23 Pressure sensor (differential pressure detector)
30 Load device (current detector)

Claims (4)

A fuel cell;
A fuel supply source for supplying fuel gas to the fuel cell;
A supply flow path for flowing the fuel gas supplied from the fuel supply source to the fuel cell;
A circulation channel for flowing the fuel gas discharged from the fuel cell to the supply channel;
A gas-liquid separator disposed on the circulation flow path for separating and storing water from the fuel gas;
A discharge passage connected to the gas-liquid separator and discharging the stored water in the gas-liquid separator and the fuel gas to the outside;
A discharge valve provided in the discharge flow path;
A current detector for detecting a load current value of the fuel cell;
A pressure detector for detecting the pressure in the supply channel;
Detects a differential pressure between the pressure in the discharge flow channel upstream of the supply flow channel, the circulation flow channel, the gas-liquid separator, or the discharge valve and the pressure downstream of the discharge valve. A differential pressure detector;
A control unit that estimates an exhaust amount of the fuel gas discharged by opening the discharge valve,
When the load current value is less than or equal to a reference value, the control unit determines the amount of fuel gas lost and the valve opening calculated from the rate of decrease in pressure in the supply flow path during the valve opening period of the discharge valve. When the fuel gas exhaust amount is estimated based on the consumption amount of the fuel gas generated by the power generation of the fuel cell calculated from the load current value in a period, and the load current value exceeds the reference value Is a fuel cell system that estimates the displacement of the fuel gas based on the differential pressure during the valve opening period.   The control unit estimates the exhaust amount of the fuel gas based on a value obtained by subtracting the consumption amount of the fuel gas from the disappearance amount of the fuel gas when the load current value is equal to or less than the reference value. Item 2. The fuel cell system according to Item 1. A fuel cell;
A fuel supply source for supplying fuel gas to the fuel cell;
A supply flow path for flowing the fuel gas supplied from the fuel supply source to the fuel cell;
A circulation channel for flowing the fuel gas discharged from the fuel cell to the supply channel;
A gas-liquid separator disposed on the circulation flow path for separating and storing water from the fuel gas;
A discharge passage connected to the gas-liquid separator and discharging the stored water in the gas-liquid separator and the fuel gas to the outside;
A discharge valve provided in the discharge flow path;
A current detector for detecting a load current value of the fuel cell;
A pressure detector for detecting any pressure in the circulation channel and the gas-liquid separator;
A differential pressure between a pressure upstream of the discharge valve in the supply flow path, the circulation flow path, the gas-liquid separator, or the discharge flow path and a pressure downstream of the discharge valve is detected. A differential pressure detector;
A control unit that estimates an exhaust amount of the fuel gas discharged by opening the discharge valve,
When the load current value is less than or equal to a reference value, the control unit calculates from the rate of decrease in pressure in either the circulation channel or the gas-liquid separator during the valve opening period of the discharge valve. Estimating the exhaust amount of the fuel gas based on the consumption amount of the fuel gas by power generation of the fuel cell calculated from the disappearance amount of the fuel gas and the load current value in the valve opening period, and the load current value When the fuel cell system exceeds the reference value, the fuel cell system estimates the exhaust amount of the fuel gas based on the differential pressure during the valve opening period. A fuel cell;
A fuel supply source for supplying fuel gas to the fuel cell;
A supply flow path for flowing the fuel gas supplied from the fuel supply source to the fuel cell;
A gas-liquid separator that separates and stores moisture from the fuel gas discharged from the fuel cell;
A first discharge flow path for supplying the fuel gas discharged from the fuel cell to the gas-liquid separator;
A second discharge passage connected to the gas-liquid separator and discharging the stored water and the fuel gas in the gas-liquid separator to the outside;
A discharge valve provided in the second discharge flow path;
A current detector for detecting a load current value of the fuel cell;
A pressure detection unit that detects any pressure in the supply flow channel, the first discharge flow channel, and the gas-liquid separator;
A pressure upstream of the discharge valve and a pressure downstream of the discharge valve in the supply flow path, the first discharge flow path, the gas-liquid separator, or the second discharge flow path; A differential pressure detector for detecting the differential pressure of
A control unit that estimates an exhaust amount of the fuel gas discharged by opening the discharge valve,
An anode non-circulating fuel cell system that does not return the fuel gas discharged from the fuel cell to the supply flow path,
When the load current value is less than or equal to a reference value, the control unit is provided in the supply flow channel, the first discharge flow channel, and the gas-liquid separator in a valve opening period of the discharge valve. Based on the amount of disappearance of the fuel gas calculated from the rate of decrease of any pressure and the amount of consumption of the fuel gas by power generation of the fuel cell calculated from the load current value during the valve opening period, A fuel cell system that estimates an exhaust amount and estimates an exhaust amount of the fuel gas based on the differential pressure during the valve opening period when the load current value exceeds the reference value.

Images