Fuel cell system

Abstract

To provide a technology for improving an accuracy of a flow rate control of a fuel gas.SOLUTION: A fuel cell system comprises: a fuel gas supply path having a solenoid valve and an injector in parallel, and having an ejector on a downstream side thereof; a first pressure sensor that detects a pressure in an upstream supply path on an upstream side with respect to the solenoid valve and the injector; a second pressure sensor that detects a pressure in a downstream supply path on a downstream side with respect to the ejector of the fuel gas supply path; and a control apparatus, wherein the control apparatus carries out a flow characteristic learning process for learning a flow characteristic of the injector by, under a predetermined learning condition, calculating a consumption flow rate of a fuel gas from a current value of a fuel cell, calculating a duty ratio of the injector, calculating a maximum supply flow rate of the fuel gas from the injector to the ejector using the calculated consumption flow rate and the calculated duty ratio, and storing the calculated maximum supply flow rate in association with a first pressure detected by the first pressure sensor.SELECTED DRAWING: Figure 2A

Description

[Technical Field]

[0001] The technology disclosed in this specification relates to a fuel cell system. [Background technology]

[0002] Patent Document 1 discloses a configuration in which a fuel gas supply path in a fuel cell is provided with a linear solenoid valve, an injector, and an ejector. The path disclosed in Patent Document 1 is provided with a linear solenoid valve and an injector in parallel as a flow rate control valve. This allows a switching operation to be performed so that the flow rate control valve and injector are used in the small flow rate range, and the solenoid valve or the solenoid valve and injector are used together in the large flow rate range. This allows the flow rate of the fuel gas to be adjusted over a range from small to large flow rates. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2024-12922 Summary of the Invention [Problem to be solved by the invention]

[0004] For example, in Patent Document 1, the flow rate capacity of the injector is calculated based on the pressure value detected by a pressure sensor upstream of the injector. However, due to individual differences in injector parts, it can be difficult to accurately calculate the flow rate of the injector based solely on the upstream pressure. As a result, there is a problem in that the operation cannot be switched at the appropriate time. This makes it difficult to achieve highly accurate flow rate control.

[0005] The technology disclosed in this specification provides a technology for improving the accuracy of fuel gas flow rate control in the fuel cell system described above. [Means for solving the problem]

[0006] The technology disclosed in this specification is embodied in a fuel cell system. The fuel cell system includes a fuel cell, a fuel gas supply path for supplying fuel gas to the fuel cell, the fuel gas supply path including a solenoid valve and an injector arranged in parallel and an ejector downstream of the solenoid valve and the injector, a first pressure sensor for detecting a pressure in an upstream supply path of the fuel gas supply path upstream of the solenoid valve and the injector, a second pressure sensor for detecting a pressure in a downstream supply path of the fuel gas supply path downstream of the ejector, and a control device. The control device is capable of executing a flow characteristic learning process under predetermined learning conditions, including the steps of: calculating a fuel gas consumption flow rate from a current value of the fuel cell; calculating a duty ratio of the injector; calculating a maximum supply flow rate of the fuel gas from the injector to the ejector using the calculated consumption flow rate and the calculated duty ratio; and learning the flow characteristic of the injector by associating the calculated maximum supply flow rate with a first pressure detected by the first pressure sensor and storing the calculated maximum supply flow rate. The predetermined learning conditions include at least that the current value of the fuel cell is constant, that the target pressure for the downstream supply passage is constant, and that the fuel gas is not being discharged to the outside.

[0007] According to this fuel cell system, the flow characteristic of the injector is learned by storing the maximum supply flow rate of the ejector in association with the first pressure through the flow characteristic learning process. The maximum supply flow rate of the injector is accurately calculated using the first pressure, so that operation switching such as starting and stopping of the injector and starting and stopping of the solenoid valve can be appropriately performed. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a diagram showing an outline of an example of the configuration of a fuel cell system. [Figure 2A]FIG. 10 is a diagram illustrating an example of a fuel gas flow rate characteristic learning process. [Figure 2B] FIG. 10 is a diagram showing an example of an operation switching process of an injector / linear solenoid valve using the learning results of the fuel gas flow rate characteristics. [Figure 3A] FIG. 10 is a diagram showing the flow rate characteristics of an injector learned by the fuel cell system. [Figure 3B] FIG. 4 is a diagram showing a time chart of each part of the fuel cell system related to the flow rate characteristics of the injector. [Figure 4A] FIG. 10 is a diagram illustrating an example of a correction process for a current value used in a flow rate characteristic learning process. [Figure 4B] FIG. 10 is a diagram illustrating an example of a process for using a corrected current value in flow rate characteristic learning. [Figure 5] FIG. 10 is a diagram showing the relationship between the duty ratio of the injector and the average supply flow rate via the injector when there is a volume between the injector and the ejector in the hydrogen supply path. [Figure 6] FIG. 10 is a diagram illustrating an example of a fuel gas flow rate characteristic learning process when the above-mentioned volume exists. DETAILED DESCRIPTION OF THE INVENTION

[0009] One embodiment of a fuel cell system of the present disclosure includes a fuel cell; a fuel gas supply path for supplying fuel gas to the fuel cell, the fuel gas supply path including a solenoid valve and an injector arranged in parallel and an ejector downstream thereof; a first pressure sensor for detecting a pressure in an upstream supply path of the fuel gas supply path upstream of the solenoid valve and the injector; a second pressure sensor for detecting a pressure in a downstream supply path of the fuel gas supply path downstream of the ejector; and a control device, wherein the control device is capable of executing a flow characteristic learning process under predetermined learning conditions, the process including: calculating a consumption flow rate of fuel gas from a current value of the fuel cell; calculating a duty ratio of the injector; calculating a maximum supply flow rate of the fuel gas from the injector to the ejector using the calculated consumption flow rate and the calculated duty ratio; and learning the flow characteristic of the injector by associating the calculated maximum supply flow rate with a first pressure detected by the first pressure sensor and storing the calculated maximum supply flow rate; The predetermined learning conditions may include at least that the current value of the fuel cell is constant, that the target pressure for the downstream supply channel is constant, and that the fuel gas is not discharged to the outside.Furthermore, for example, in a polymer electrolyte fuel cell, since it is known that gas permeates through a proton exchange membrane, the predetermined learning conditions may also include that hydrogen cross-leakage from the anode to the cathode is sufficiently small.

[0010] In another embodiment of the fuel cell system, the control device is further capable of executing a correction coefficient calculation process under the predetermined learning conditions, the correction coefficient calculation process including the steps of: calculating an actual fuel gas consumption flow rate based on a time rate of change of a second pressure drop ΔP detected by the second pressure sensor during an off time (Δt-off) when the injector is closed; calculating the fuel gas consumption flow rate from a current value of the fuel cell during the off time (Δt-off) when the injector is closed; and calculating a correction coefficient by dividing the actual consumption flow rate by the consumption flow rate, and the control device includes correcting the fuel cell current value using the correction coefficient in the step of calculating the fuel gas consumption flow rate in the flow characteristic learning process. This makes it possible to correct the current value and calculate a correct consumption flow rate from the corrected current value even when there is a detection error or variation in the fuel cell current value.

[0011] In another embodiment of the fuel cell system, the step of calculating the duty ratio includes the control device incrementally correcting the actual duty ratio of the injector using a pre-stored predetermined relationship. For example, if a volume exists between the injector and the ejector, the fuel gas flow rate increases based on this volume, thereby increasing the fuel cell consumption flow rate based on the current value. As a result, if the increased consumption flow rate is divided by the calculated duty ratio as is, the maximum supply flow rate of the injector becomes larger than the actual maximum supply flow rate. According to another embodiment, an appropriate duty ratio is obtained by incremental correction using the pre-stored predetermined relationship, thereby making it possible to accurately calculate the maximum supply current amount.

[0012] In another embodiment of the fuel cell system, the control device executes the flow characteristic learning process multiple times and learns the flow characteristic of the injector using the obtained representative values ​​of the maximum supply flow rate. This avoids calculation of the maximum supply flow rate based on a specific detection value due to sensor noise or the like, thereby obtaining a more accurate maximum supply flow rate and accurately learning the flow characteristic.

[0013] In another embodiment of the fuel cell system, the control device is further capable of executing an operation switching process while the injector is in operation, and the operation switching execution process includes a step of calculating a required flow rate of the fuel cell, a step of calculating a maximum supply flow rate of the injector at a first pressure detected by the first pressure sensor based on the flow rate characteristics of the injector obtained by the flow rate characteristics learning process, and a step of comparing the required flow rate with the maximum supply flow rate. (a) when the required flow rate exceeds the maximum supply flow rate in the injector's standalone operating state, switching from the injector's standalone operating state to the solenoid valve's standalone operating state or to a co-operation state of the solenoid valve and the injector; (b) when the maximum supply flow rate is equal to or greater than the required flow rate in the solenoid valve's standalone operation state or the solenoid valve's collaborative operation state with the injector, switching from the solenoid valve's standalone operation state or the solenoid valve's collaborative operation state with the injector to the injector's standalone operation state. This makes it possible to switch between the injector's standalone operation state and the solenoid valve's standalone operation state or the solenoid valve's collaborative operation state with the injector at an appropriate timing.

[0014] In this specification, the terms "exceed" and "below" with respect to the required flow rate and the maximum supply flow rate are set in relation to numerical values, and are expressed as "not less than" and "not less than," respectively, depending on the numerical value of the set threshold. That is, in this specification, "exceed" may include the meaning of "not less than," and "not more than" may also mean "below."

[0015] Hereinafter, the flow rate control of hydrogen as fuel gas by switching the operation of the injector and the solenoid valve in the fuel cell system disclosed in this specification will be described with reference to the drawings as appropriate.

[0016] The fuel cell system described below includes a stack in which a large number of fuel cells are stacked in series, a hydrogen supply channel, and a control device. The fuel cell system also includes an air supply channel for supplying air, which is an oxidant gas, and a water-cooled cooling system including a cooling water pump and a cooling water channel. Note that an air-cooled cooling system may be used instead of the water-cooled cooling system. Fuel cell systems are well known in the art and may include various fuel cells, including polymer electrolyte fuel cells (PEFCs). The use of the fuel cell system is not particularly limited. For example, the system may be a mobile fuel cell system mounted on a mobile object such as a vehicle or a ship, or a stationary fuel cell system used in stationary power generation facilities.

[0017] (First embodiment) An outline of the configuration of a fuel cell system 2 according to a first embodiment disclosed in this specification is shown in Fig. 1. The fuel cell system 2 includes a fuel cell 4, a hydrogen supply path 6 to which hydrogen as a fuel gas is supplied and circulated, an air supply path (not shown) to which air as an oxidizing gas is supplied, and a control device 10. In addition, the fuel cell system 2 includes a cooling water circulation path for cooling the fuel cell 4, although this is not shown.

[0018] The hydrogen supply path 6 includes a supply flow path 12 that supplies hydrogen to the hydrogen inlet 4a of the fuel cell 4, and a circulation flow path 16 that discharges fuel off-gas (hereinafter simply referred to as off-gas), which is exhaust gas discharged from the hydrogen outlet 4b of the fuel cell 4, and circulates it back to the fuel cell 4.

[0019] The fuel cell system 2 further includes a linear solenoid valve 20, an injector 30, and an ejector 40. The linear solenoid valve 20 and the injector 30 are arranged in parallel in the supply flow path 12. The linear solenoid valve 20 and the injector 30 adjust the flow rate of hydrogen supplied to the hydrogen inlet 4a of the fuel cell 4. The ejector 40 is arranged downstream of these two flow rate adjustment elements. The linear solenoid valve 20 is an example of a solenoid valve disclosed in this specification.

[0020] The linear solenoid valve 20 is provided on a branch flow path 12a that branches off from a supply flow path 12 that has a hydrogen tank (not shown) as its base end. The linear solenoid valve 20 adjusts the flow rate of hydrogen passing through the linear solenoid valve 20 depending on the opening of a plunger (not shown). The linear solenoid valve 20 is used when a relatively large hydrogen flow rate is required in the fuel cell system 2. The structure of the linear solenoid valve 20 is not particularly limited, and any known linear solenoid valve structure can be used. The branch flow path 12a downstream of the linear solenoid valve 20 is connected to an ejector 40.

[0021] The injector 30 is provided on a branch flow path 12b that branches off from the supply flow path 12 separately from the branch flow path 12a. The injector 30 is opened and closed by a valve element (not shown) driven at a predetermined drive cycle by an electromagnetic driving force or the like. The flow rate of hydrogen is adjusted by the ratio of the time the valve element is opened and closed (open time / total time of open time and closed time, duty ratio). The injector 30 is used when the required flow rate of hydrogen is relatively small in the fuel cell system 2. The structure of the injector 30 is not particularly limited, and any known structure of the injector 30 can be adopted. The branch flow path 12b downstream of the injector 30 is connected to an ejector 40.

[0022] The ejector 40 is equipped with a nozzle (not shown), and sucks in off-gas from the circulation flow path 16 by the injection pressure of hydrogen from the nozzle. As a result, the off-gas is merged with the hydrogen injected from the nozzle and is supplied again to the fuel cell 4. Note that the ejector 40 may be equipped with a plurality of nozzles. Also, a plurality of ejectors 40 may be provided.

[0023] A pressure sensor 50 is provided on the supply flow path 12 between a hydrogen tank (not shown) and the branch point of the branch flow paths 12a and 12b. The pressure sensor 50 detects the pressure in the flow path 14a upstream of the linear solenoid valve 20 and the injector 30 from the tank of the supply flow path 12.

[0024] A pressure sensor 60 is provided on the supply flow path 12 between the ejector 40 and the hydrogen inlet 4a of the fuel cell 4. The pressure sensor 60 detects the pressure in the flow path 14b on the supply flow path 12 downstream of the ejector 40.

[0025] The circulation flow path 16 is provided with a gas-liquid separator 70 and an exhaust / drain valve 80 that allows the off-gas exhausted from the hydrogen outlet 4b to be discharged as needed, and the off-gas is exhausted by opening and closing the valve.

[0026] The control device 10 is configured as a computer equipped with a processor and memories such as RAM and ROM. In accordance with a program stored in the ROM or the like, the control device 10 controls the operation of each part of the fuel cell system 2. The control device 10 is equipped with an executable program that outputs control signals to the linear solenoid valve 20 and the injector 30 to control the supply flow rate of hydrogen.

[0027] The control device 10 is also connected to pressure sensors 50 and 60, and acquires pressure signals and the like from these sensors and stores them in memory as appropriate. The control device 10 also acquires the value of the current flowing through the fuel cell 4 and stores it in memory as appropriate.

[0028] Next, we will explain the learning process for learning the flow rate characteristics of the injector 30 with respect to the supply flow rate of hydrogen in the fuel cell system 2, and the process for switching the operation of the linear solenoid valve 20 and the injector 30 using the learning results. Note that the learning process is an example of the flow rate characteristics learning process disclosed in this specification, and the operation switching process is an example of the operation switching process disclosed in this specification.

[0029] 2A and 2B show an example flow of these processes.

[0030] 3A shows the flow path characteristic that the process shown in FIG. 2A is intended to learn. The flow path characteristic to be learned is the maximum supply flow rate by the injector 30, more specifically, the relationship between the pressure in the upstream flow path 14a detected by the pressure sensor 50 and the maximum supply flow rate by the injector 30 and the ejector 40. The supply flow rate on the vertical axis is the maximum supply flow rate. The higher the pressure in the upstream flow path 14, the larger the maximum supply flow rate.

[0031] 3B shows an overview of learning the flow rate characteristics (maximum supply flow rate) of the injector and a time chart explaining the learning of the maximum supply flow rate of the injector 30. The time chart shows the relationship between the current value of the fuel cell 4, the pressure value of the pressure sensor 60, the duty ratio of the injector 30, and the supply flow rate, which are detected in the learning process.

[0032] 2A, in this learning process, step S10 is executed to determine whether learning conditions are met. The learning conditions determined in step S10 include (1) that the current value of the fuel cell 4 is constant, (2) that the target pressure downstream of the ejector 40 is constant, and (3) that hydrogen is not being discharged outside the fuel cell system 2. Note that (4) because it is known that gas permeates through the proton exchange membrane in a PEFC, the learning conditions may also include that hydrogen cross-leakage from the anode to the cathode is sufficiently small.

[0033] When this learning condition is met, it can be assumed that the injector 30 is opening and closing so that the hydrogen consumed by the fuel cell 4 and the hydrogen supplied from the injector 30 are balanced. That is, the following equation (1) is met, and at the same time, equation (2) is also met. Therefore, the relationship below can be used. As a result, as will be described later, the average supply flow rate and maximum supply flow rate via the injector 30, i.e., via the injector 30 and the ejector 40, can be calculated. Maximum supply flow rate of hydrogen from the injector × duty ratio of the injector 30 = Average hydrogen supply flow rate... Equation (1) Average hydrogen supply flow rate = Hydrogen consumption flow rate (2)

[0034] The control device 10 acquires the current value of the fuel cell 4 in condition (1) from a current sensor or the like provided in the fuel cell system 2. This is a pressure set by the control device 10 itself, and for example, the control device 10 acquires the target pressure in condition (2) as an upper limit command value and a lower limit command value. The control device 10 acquires the state of condition (3) by detecting that the exhaust drain valve 80 is closed.

[0035] If the control device 10 determines that the learning conditions are not met, it ends this process, and if it determines that the learning conditions are met, it executes step S20.

[0036] Next, the control device 10 executes step S20 of calculating the hydrogen consumption flow rate from the current value of the fuel cell 4. The hydrogen consumption rate is calculated using the following equation (3). The hydrogen consumption flow rate can be obtained by appropriately converting this into a rate per hour. Hydrogen consumption = (current value of fuel cell 4 x number of cells constituting the stack) / 2 × Faraday constant (3)

[0037] The control device 10 executes step S30 of calculating the duty ratio of the injector 30 in the fuel cell 4. The duty ratio is calculated based on an injection flag set by the control device 10 based on the lower limit command value and the upper limit command value detected by the pressure sensor 60, for example, as shown in FIG.

[0038] Next, the control device 10 executes step S40, which calculates the maximum supply flow rate of hydrogen via the injector 30. In step S40, the maximum supply flow rate of hydrogen via the injector 30 is obtained using the above formulas (1) to (3), since the maximum supply flow rate of hydrogen from the injector multiplied by the duty ratio of the injector 30 corresponds to the hydrogen consumption flow rate. At the same time, the average supply flow rate is also obtained. As shown in FIG. 3A, the maximum supply flow rate is the flow rate when the valve element of the injector 30 is open.

[0039] 3A, the average supply flow rate or maximum supply flow rate obtained here can be regarded as an actual measurement value or a numerical value approximate to the actual measurement value obtained from the current value of the fuel cell 4 and the duty ratio of the injector 30. In other words, the maximum supply flow rate calculated here is a numerical value that includes the component tolerances and variations in the injector 30, ejector 40, and their nozzles.

[0040] Furthermore, the control device 10 executes step S50 of associating this maximum supply flow rate with the pressure value detected by the pressure sensor 50. That is, the control device 10 associates the maximum supply flow rate with the pressure value of the upstream flow path 14a detected by the pressure sensor 50 when the learning condition is satisfied. As a result, a more specific maximum supply flow rate that takes into account the component tolerances of the injector 30 and the ejector 40 is associated with the upstream pressure value (see FIG. 3A).

[0041] The control device 10 executes step S60 of storing information relating to this association in memory. The control device 10 learns the flow rate characteristics of the injector 30 and the ejector 40 by storing information relating to this association in memory.

[0042] The control device 10 can learn the flow rate characteristics with higher accuracy by repeating this learning process. For example, by repeatedly executing the learning process in a range where the upstream pressure detected by the pressure sensor 50 is high or in a range near the upper limit of the capacity (duty ratio) of the injector 30, a more accurate characteristic curve can be obtained near the maximum supply flow rate.

[0043] For example, if the maximum supply flow rate obtained by this learning is greater than the maximum supply flow rate via the injector 30 that was previously calculated from the pressure value detected by the pressure sensor 50, it is possible to reduce unnecessary operation of the linear solenoid valve 20. On the other hand, if the learned maximum supply flow rate is smaller than the previous maximum supply flow rate, the linear solenoid valve 20 is driven at an appropriate timing to prevent a shortage of hydrogen supply.

[0044] It is possible to obtain multiple average supply flow rates by repeatedly executing the learning process at a specific upstream pressure or capacity (duty ratio) of the injector 30. This allows for more appropriate switching during the operation switching process described below.

[0045] The control device 10 further uses the learning results to execute the process of switching the operations of the injector 30 and the linear solenoid valve 20. This process will be described with reference to Fig. 2B.

[0046] The control device 10 first executes step S70 to determine whether the injector 30 of the fuel cell system 2 is operating independently. Whether the injector 30 is operating independently can be determined based on the pressure value detected by the pressure sensor 60 and the valve opening estimated from the command value for the current applied to the linear solenoid valve 20 or the current value of the linear solenoid valve 20. If the injector 30 is not operating, this process ends.

[0047] When the injector 30 is operating, the control device 10 executes step S80, which calculates the required flow rate of hydrogen from the accelerator opening degree, etc. Furthermore, the control device 10 executes step S90, which calculates the maximum supply flow rate of the injector 30 based on the learning results from the upstream pressure, which is the pressure value detected by the pressure sensor 50. Next, the control device 10 executes step S100, which compares the required flow rate with the maximum supply flow rate, and determines whether the required flow rate exceeds the maximum supply flow rate or whether the maximum supply flow rate is equal to or less than the required flow rate.

[0048] The control device 10 executes the operation switching step S110. That is, when the required flow rate exceeds the maximum supply flow rate, the control device 10 switches the operation from the independent operation of the injector 30 to the independent operation of the linear solenoid valve 20 or the cooperative operation of the injector 30 and the linear solenoid valve 20, and ends this process. On the other hand, when the required flow rate does not exceed the maximum supply flow rate, the operation of the injector 30 continues as is, and therefore ends this process.

[0049] As described above, with the fuel cell system 2, the maximum supply flow rate of hydrogen supplied via the injector 30, i.e., via the injector 30 and the ejector 40, can be calculated based on the pressure value detected by the pressure sensor 50, taking into account the tolerances of the components of the injector 30 and the ejector 40, and is closer to the actual measured value. Because switching is performed based on the calculated maximum supply flow rate, the injector 30 is used appropriately based on its supply capacity. As a result, hydrogen is supplied without excess or deficiency, and a decrease in power generation performance due to a lack of hydrogen can be suppressed. Furthermore, the durability of the injector 30 is improved.

[0050] The above operation switching process is based on the assumption that the injector 30 is in operation, but the learning results can also be used while the linear solenoid valve 20 is in operation. For example, first, it is determined whether the linear solenoid valve 20 of the fuel cell system 2 is in operation. Whether the linear solenoid valve 20 is in operation can be determined based on the pressure value detected by the pressure sensor 60 and the valve opening degree of the linear solenoid valve 20. If the linear solenoid valve 20 is not in operation, this process is terminated.

[0051] The control device 10 determines the operation of the linear solenoid valve 20, and when the operation is affirmative, calculates the required flow rate of hydrogen, then calculates the maximum supply flow rate of the injector 30 from the sensor value of the pressure sensor 50, and when the required flow rate is equal to or less than the maximum supply flow rate, switches to standalone operation of the injector 30. Note that this operation switching process may also be such that the linear solenoid valve 20 and the injector 30 switch to standalone operation while they are operating in cooperation with each other.

[0052] As described above, the fuel cell system 2 can appropriately determine whether to operate the injector 30 in accordance with the flow rate required by the fuel cell 4, based on the learning results obtained through the learning process of the flow rate characteristics of the injector 30. As a result, it is possible to switch between the injector 30 and the linear solenoid valve 20 without excess or deficiency of hydrogen, and to avoid placing an excessive burden on the injector 30 or the linear solenoid valve 20. The fuel cell system 2 can improve the controllability of the hydrogen flow rate.

[0053] (Second embodiment) This embodiment relates to a correction process for correcting a current value used in a learning process executed by the fuel cell system 2. This embodiment is intended to avoid erroneous learning of the maximum supply flow rate of the injector 30 due to variations in the current value acquired from a current sensor of the fuel cell 4 or the like.

[0054] The fuel cell system 2 of this embodiment differs from the first embodiment only in that it performs a correction process to calculate a correction coefficient for the current value and corrects the current value with the correction coefficient obtained by the correction process. Therefore, in the following explanation, only the correction process executed by the control device 10 and the learning process of the flow rate characteristics based on the correction coefficient will be explained, and the fuel cell system 2 will not be shown in the drawings, and the elements will be explained using the same reference numerals as appropriate.

[0055] 4A shows an example of a correction process for the current value used in the flow characteristic learning process, and FIG. 4B shows an example of a learning process using the corrected current value in the flow characteristic learning. The correction process shown in FIG. 4A is also executed when the above-described learning conditions are met. The current value correction process is an example of the correction coefficient calculation process disclosed in this specification.

[0056] The correction process calculates the off time (Δt-off) and the pressure drop (ΔP) at the pressure sensor 60 during this off time from the sensor value of the pressure sensor 60 of the injector 30, the injection flag, etc. Then, the hydrogen consumption flow rate during this off time is calculated based on the following equation. Equation (4) is the gas state equation, and equation (5) is an equation for finding the hydrogen consumption rate (dn / dt) over a certain period of time based on equation (4). PV=nRT (4) dn / dt=(V / RT)dP / dt (5)

[0057] Here, n represents the amount of substance (moles), V represents the total volume (L) of the ejector 40 in the fuel cell system 2, the piping after the ejector 40 leading back to the ejector 40, the fuel cell 4, and the gas-liquid separator 00, R represents the gas constant, and T represents the temperature of hydrogen (K).

[0058] 4A, in step S210, the control device 10 first calculates the off time (Δt-off) of the injector 30 from the injection flag of the pressure sensor 60. Furthermore, in step S220, the control device 10 calculates the amount of drop in the pressure sensor 60 during the off time of the injector 30. In step S230, the control device 10 calculates the actual hydrogen consumption flow rate (actual consumption flow rate) based on the above equation (4), in step S240, calculates the consumption flow rate based on the current value of the fuel cell 4, and in step S250, calculates the ratio of the actual consumption flow rate to the consumption flow rate based on the current value (actual consumption flow rate / consumption flow rate), stores this as a correction coefficient for the current value, and ends the correction process.

[0059] 4B shows an example of a learning process when a current correction coefficient is used. This learning process differs from FIG. 1 only in that step S22 is performed instead of step S20. As shown in FIG. 4B, when the learning conditions are met (step S10), the control device 10 calculates the consumption flow rate based on the current value corrected with the current correction coefficient in step S22. The subsequent steps S30 to S60 prevent erroneous learning due to variations in the current value, and allow the correct maximum supply flow rate and flow rate characteristics of the injector 30 to be learned.

[0060] (Third embodiment) This embodiment relates to a correction process for optimizing the maximum supply flow rate when there is a section between the injector 30 and the ejector 40 where hydrogen can be filled. As shown in FIG. 5, hydrogen filled in this section continues to flow toward the ejector 40 even after the injector 30 is closed, causing an increase in the supply flow rate, which can result in a decrease in the duty ratio detected by the pressure sensor 60. This embodiment aims to optimize the duty ratio and avoid erroneous learning of the maximum supply flow rate of the injector 30. Note that this correction process relates to incremental correction of the duty ratio in this specification.

[0061] The fuel cell system 2 of this embodiment differs from the first embodiment only in that a correction process is carried out in which a correction table for the duty ratio is prepared in advance, and the duty ratio is corrected using the table obtained by the correction process. Therefore, in the following explanation, only the correction process executed by the control device 10 and the learning process of the flow rate characteristics based on the correction table will be explained, and the fuel cell system 2 will not be shown in the drawings, and the elements will be explained using the same reference numerals as appropriate.

[0062] As shown in FIG. 5, by previously acquiring the relationship between the calculated duty ratio and the duty ratio when there is no influence of the volume, it is possible to learn the correct maximum supply flow rate when passing through the injector 30 regardless of the volume.

[0063] For example, under learning conditions, the control device 10 calculates the increase in the amount of fuel that will flow when the injector 30 is off, based on the volume and the pressure values ​​of the pressure sensors 50 and 60. Next, the control device 10 pre-calculates the decrease in the duty ratio based on the calculated increase. Furthermore, the control device 10 pre-creates a correction table that corrects the decrease in the duty ratio calculated in the learning process and stores the correction table in memory. An example of such a correction table is shown in FIG. 5.

[0064] A modified example of the learning process executed in the fuel cell system 2 having such a volume is shown in Figure 6. As shown in Figure 6, in the learning process, after calculating the duty ratio of the injector 30 in step S30, the duty ratio is corrected in step S32 by referring to this correction table, and the correct maximum supply flow rate via the injector 30 can be learned by executing the subsequent step S40 using the duty ratio corrected in step S32.

[0065] In this way, the correct maximum supply flow rate is learned through the learning process, and the appropriate injector / linear solenoid valve operation switching process is performed based on that.

[0066] Although there is no particular mention of repeating the learning process in the second and third embodiments, similarly to the first embodiment, in order to avoid or suppress the effects of sensor noise and variation and improve the accuracy of learning, the learning process may be performed multiple times under the same or a certain range of learning conditions, and a representative value of the maximum supply flow rate thus obtained (for example, an average or median value) may be used as the learning value. Furthermore, by repeating the correction process, it is possible to obtain correction coefficients and correction tables that enable more accurate correction.

[0067] Specific examples of the technology disclosed in this specification have been described in detail above, but these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and variations of the specific examples exemplified above, such as a fuel cell control method. The technical elements described in this specification or in the drawings exhibit technical utility either alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. The technology exemplified in this specification or in the drawings can achieve multiple objectives simultaneously, and achieving one of these objectives itself has technical utility. [Explanation of symbols]

[0068] 2. Fuel cell system 4 fuel cell 6 Hydrogen circulation system 8 Control Device 12 Supply channel 14 Discharge flow path 20 Linear solenoid valve 30 injectors 40 Ejector 50 Pressure Sensor 60 Pressure Sensor 70 Gas-liquid separator 80 Exhaust drain valve

Claims

1. 1. A fuel cell system, comprising: A fuel cell; a fuel gas supply path for supplying fuel gas to the fuel cell, the fuel gas supply path including a solenoid valve and an injector arranged in parallel and an ejector downstream thereof; a first pressure sensor that detects a pressure in an upstream supply passage of the fuel gas supply passage, the upstream supply passage being located upstream of the solenoid valve and the injector; a second pressure sensor that detects a pressure in a downstream supply passage of the fuel gas supply passage that is downstream of the ejector; a control device; The control device, under a predetermined learning condition, calculating a consumption flow rate of fuel gas from the current value of the fuel cell; calculating a duty ratio of the injector; calculating a maximum supply flow rate of the fuel gas from the injector to the ejector using the calculated consumption flow rate and the calculated duty ratio; a step of learning the flow characteristics of the injector by storing the calculated maximum supply flow rate in association with the first pressure detected by the first pressure sensor, the predetermined learning conditions include at least that the current value of the fuel cell is constant, that the target pressure for the downstream supply path is constant, and that the fuel gas is not discharged to the outside. Fuel cell system.

2. The control device is further capable of executing a correction coefficient calculation process under the predetermined learning condition, The correction coefficient calculation process calculating an actual consumption flow rate of the fuel gas based on a time change rate of a decrease ΔP in the second pressure detected by the second pressure sensor during an off time (Δt-off) during which the injector is closed; calculating a consumption flow rate of the fuel gas from a current value of the fuel cell during the off time (Δt-off) when the injector is closed; and calculating a correction coefficient by dividing the actual consumption flow rate by the consumption flow rate, the control device corrects a current value of the fuel cell using the correction coefficient in the step of calculating the consumed flow rate of the fuel gas in the flow rate characteristics learning process; The fuel cell system according to claim 1 .

3. 2. The fuel cell system according to claim 1, wherein in the step of calculating the duty ratio, the control device incrementally corrects the actual duty ratio of the injector using a predetermined relationship that is stored in advance.

4. 2. The fuel cell system according to claim 1, wherein the control device executes the flow characteristic learning process a plurality of times and learns the flow characteristic of the injector using a plurality of representative values ​​of the maximum supply flow rate obtained by executing the flow characteristic learning process a plurality of times.

5. The control device is further capable of executing an operation switching process under the predetermined learning condition, The operation switching execution process includes, during operation of the injector: calculating a required flow rate of the fuel cell; calculating a maximum supply flow rate of the injector at the first pressure detected by the first pressure sensor based on the flow rate characteristics of the injector obtained by the flow rate characteristics learning process; Comparing the required flow rate with the maximum supply flow rate, (a) when the required flow rate exceeds the maximum supply flow rate in the injector's standalone operation state, switching of the injector's standalone operation state to the solenoid valve's standalone operation state or the solenoid valve and the injector's collaborative operation state is executed; (b) an operation switching step of switching an operation from the solenoid valve's independent operation state or the solenoid and the injector's cooperative operation state to the injector's independent operation state when the maximum supply flow rate is equal to or greater than the required flow rate in the solenoid valve's independent operation state or the solenoid and the injector's cooperative operation state; 5. The fuel cell system according to claim 1, comprising:

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